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Sample records for single heterostructure ring

  1. Tracking Ultrafast Carrier Dynamics in Single Semiconductor Nanowire Heterostructures

    Directory of Open Access Journals (Sweden)

    Taylor A.J.

    2013-03-01

    Full Text Available An understanding of non-equilibrium carrier dynamics in silicon (Si nanowires (NWs and NW heterostructures is very important due to their many nanophotonic and nanoelectronics applications. Here, we describe the first measurements of ultrafast carrier dynamics and diffusion in single heterostructured Si nanowires, obtained using ultrafast optical microscopy. By isolating individual nanowires, we avoid complications resulting from the broad size and alignment distribution in nanowire ensembles, allowing us to directly probe ultrafast carrier dynamics in these quasi-one-dimensional systems. Spatially-resolved pump-probe spectroscopy demonstrates the influence of surface-mediated mechanisms on carrier dynamics in a single NW, while polarization-resolved femtosecond pump-probe spectroscopy reveals a clear anisotropy in carrier lifetimes measured parallel and perpendicular to the NW axis, due to density-dependent Auger recombination. Furthermore, separating the pump and probe spots along the NW axis enabled us to track space and time dependent carrier diffusion in radial and axial NW heterostructures. These results enable us to reveal the influence of radial and axial interfaces on carrier dynamics and charge transport in these quasi-one-dimensional nanosystems, which can then be used to tailor carrier relaxation in a single nanowire heterostructure for a given application.

  2. Nanoscale heterostructures with molecular-scale single-crystal metal wires.

    Science.gov (United States)

    Kundu, Paromita; Halder, Aditi; Viswanath, B; Kundu, Dipan; Ramanath, Ganpati; Ravishankar, N

    2010-01-13

    Creating nanoscale heterostructures with molecular-scale (synthesis of nanoscale heterostructures with single-crystal molecular-scale Au nanowires attached to different nanostructure substrates. Our method involves the formation of Au nanoparticle seeds by the reduction of rocksalt AuCl nanocubes heterogeneously nucleated on the substrates and subsequent nanowire growth by oriented attachment of Au nanoparticles from the solution phase. Nanoscale heterostructures fabricated by such site-specific nucleation and growth are attractive for many applications including nanoelectronic device wiring, catalysis, and sensing.

  3. Magnetotransport investigations of single- and heterostructure epitaxial films of IV/VI-semiconductors

    International Nuclear Information System (INIS)

    Ambrosch, K.-E.

    1985-01-01

    Lead salts are small gap semiconductors that are used for infrared detectors and lasers. PbMnTe and PbEuTe are semimagnetic semiconductors. Magnetotransport properties of epitaxial films and epitaxial heterostructures (PbTe / PbSnTe) are investigated. Epitaxial films of PbSnTe, PbMnTe and PbEuTe have been used for Shubnikov de Haas - experiments in tilted magnetic fields. This method allows the quantitative determination of the electric carrier distribution with respect to the crystal directions. The nonequal distribution is caused by strain effects that are more important for PbMnTe than for PbSnTe and PbEuTe. Magnetoresistance experiments show a deviation from cubic symmetry that leads to the same results for the carrier distribution as the Shubnikov de Haas effect. Magnetoresistance experiments performed with PbTe / PbSnTe heterostructures show no megnetoresistance if the magnetic field is in plane with the layers. The difference of the magnetoresistance for single films and heterostructures is explained by 'quasitwodimensional' carriers. Shubnikov de Haas experiments performed on heterostructures as a function of the tilt angle of the magnetic field show different behaviour compared to that of single films. Using additional information about effective masses and strain it was possible to distinguish between 'two-' and 'threedimensional' electronic systems. The distribution of carriers in single films and heterostructures has been determined by means of magnetotransport experiments. The results are explained by strain effects of the crystal lattice. In addition heterostructures show a 'quasitwodimensional' behaviour caused by interaction of their layers. (Author)

  4. Single crystalline PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices.

    Science.gov (United States)

    Lin, Yung-Chen; Lu, Kuo-Chang; Wu, Wen-Wei; Bai, Jingwei; Chen, Lih J; Tu, K N; Huang, Yu

    2008-03-01

    We report the formation of PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices from such heterostructures. Scanning electron microscopy studies show that silicon nanowires can be converted into PtSi nanowires through controlled reactions between lithographically defined platinum pads and silicon nanowires. High-resolution transmission electron microscopy studies show that PtSi/Si/PtSi heterostructure has an atomically sharp interface with epitaxial relationships of Si[110]//PtSi[010] and Si(111)//PtSi(101). Electrical measurements show that the pure PtSi nanowires have low resistivities approximately 28.6 microOmega.cm and high breakdown current densities>1x10(8) A/cm2. Furthermore, using single crystal PtSi/Si/PtSi nanowire heterostructures with atomically sharp interfaces, we have fabricated high-performance nanoscale field-effect transistors from intrinsic silicon nanowires, in which the source and drain contacts are defined by the metallic PtSi nanowire regions, and the gate length is defined by the Si nanowire region. Electrical measurements show nearly perfect p-channel enhancement mode transistor behavior with a normalized transconductance of 0.3 mS/microm, field-effect hole mobility of 168 cm2/V.s, and on/off ratio>10(7), demonstrating the best performing device from intrinsic silicon nanowires.

  5. Modelling a singly resonant, intracavity ring optical parametric oscillator

    DEFF Research Database (Denmark)

    Buchhave, Preben; Tidemand-Lichtenberg, Peter; Wei, Hou

    2003-01-01

    We study theoretically and experimentally the dynamics of a single-frequency, unidirectional ring laser with an intracavity nonlinear singly resonant OPO-crystal in a coupled resonator. We find for a range of operating conditions good agreement between model results and measurements of the laser...

  6. Single-crystalline Ni2Ge/Ge/Ni2Ge nanowire heterostructure transistors.

    Science.gov (United States)

    Tang, Jianshi; Wang, Chiu-Yen; Xiu, Faxian; Hong, Augustin J; Chen, Shengyu; Wang, Minsheng; Zeng, Caifu; Yang, Hong-Jie; Tuan, Hsing-Yu; Tsai, Cho-Jen; Chen, Lih Juann; Wang, Kang L

    2010-12-17

    In this study, we report on the formation of a single-crystalline Ni(2)Ge/Ge/Ni(2)Ge nanowire heterostructure and its field effect characteristics by controlled reaction between a supercritical fluid-liquid-solid (SFLS) synthesized Ge nanowire and Ni metal contacts. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies reveal a wide temperature range to convert the Ge nanowire to single-crystalline Ni(2)Ge by a thermal diffusion process. The maximum current density of the fully germanide Ni(2)Ge nanowires exceeds 3.5 × 10(7) A cm(-2), and the resistivity is about 88 μΩ cm. The in situ reaction examined by TEM shows atomically sharp interfaces for the Ni(2)Ge/Ge/Ni(2)Ge heterostructure. The interface epitaxial relationships are determined to be [Formula: see text] and [Formula: see text]. Back-gate field effect transistors (FETs) were also fabricated using this low resistivity Ni(2)Ge as source/drain contacts. Electrical measurements show a good p-type FET behavior with an on/off ratio over 10(3) and a one order of magnitude improvement in hole mobility from that of SFLS-synthesized Ge nanowire.

  7. Synthesis of Freestanding Single-crystal Perovskite Films and Heterostructures by Etching of Sacrificial Water-soluble Layers

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Di; Baek, David J.; Hong, Seung Sae; Kourkoutis, Lena F.; Hikita, Yasuyuki; Hwang, Harold Y.

    2016-08-22

    The ability to create and manipulate materials in two-dimensional (2D) form has repeatedly had transformative impact on science and technology. In parallel with the exfoliation and stacking of intrinsically layered crystals, atomic-scale thin film growth of complex materials has enabled the creation of artificial 2D heterostructures with novel functionality and emergent phenomena, as seen in perovskite heterostructures. However, separation of these layers from the growth substrate has proven challenging, limiting the manipulation capabilities of these heterostructures with respect to exfoliated materials. Here we present a general method to create freestanding perovskite membranes. The key is the epitaxial growth of water-soluble Sr3Al2O6 on perovskite substrates, followed by in situ growth of films and heterostructures. Millimetre-size single-crystalline membranes are produced by etching the Sr3Al2O6 layer in water, providing the opportunity to transfer them to arbitrary substrates and integrate them with heterostructures of semiconductors and layered compounds.

  8. Realization of single and double axial InSb-GaSb heterostructure nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ghalamestani, Sepideh Gorji [Solid State Physics, Lund University, Lund (Sweden); Ek, Martin [Center for Analysis and Synthesis, Lund University, Lund (Sweden); Dick, Kimberly A. [Solid State Physics, Lund University, Lund (Sweden); Center for Analysis and Synthesis, Lund University, Lund (Sweden)

    2014-03-15

    Heteroepitaxial growth of III-Sb nanowires allows for the formation of various interesting complex structures and enables the combination of their remarkable properties. In this Letter, we investigate the heteroepitaxial growth of Au-seeded InSb and GaSb nanowires using metalorganic vapor phase epitaxy. We demonstrate successful single and double axial InSb-GaSb heterostructures in both directions. The formation properties of the grown nanowires including the compositional change of the particle and the interface sharpness are further discussed. In addition, the decomposition of InSb and GaSb segments and their side facet evolution are explained. XEDS compositional line scans overlaid on STEM HAADF image along the InSb-GaSb-InSb nanowire indicating sharp interface from GaSb to InSb segment and graded interface in the opposite direction. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. A radio-frequency single-electron transistor based on an InAs/InP heterostructure nanowire

    DEFF Research Database (Denmark)

    Nilsson, Henrik A.; Duty, Tim; Abay, Simon

    2008-01-01

    We demonstrate radio frequency single-electron transistors fabricated from epitaxially grown InAs/InP heterostructure nanowires. Two sets of double-barrier wires with different barrier thicknesses were grown. The wires were suspended 15 nm above a metal gate electrode. Electrical measurements...... on a high-resistance nanowire showed regularly spaced Coulomb oscillations at a gate voltage from −0.5 to at least 1.8 V. The charge sensitivity was measured to 32 µerms Hz−1/2 at 1.5 K. A low-resistance single-electron transistor showed regularly spaced oscillations only in a small gate-voltage region just...

  10. Fast-Response Single-Nanowire Photodetector Based on ZnO/WS2 Core/Shell Heterostructures.

    Science.gov (United States)

    Butanovs, Edgars; Vlassov, Sergei; Kuzmin, Alexei; Piskunov, Sergei; Butikova, Jelena; Polyakov, Boris

    2018-04-12

    The surface plays an exceptionally important role in nanoscale materials, exerting a strong influence on their properties. Consequently, even a very thin coating can greatly improve the optoelectronic properties of nanostructures by modifying the light absorption and spatial distribution of charge carriers. To use these advantages, 1D/1D heterostructures of ZnO/WS 2 core/shell nanowires with a-few-layers-thick WS 2 shell were fabricated. These heterostructures were thoroughly characterized by scanning and transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Then, a single-nanowire photoresistive device was assembled by mechanically positioning ZnO/WS 2 core/shell nanowires onto gold electrodes inside a scanning electron microscope. The results show that a few layers of WS 2 significantly enhance the photosensitivity in the short wavelength range and drastically (almost 2 orders of magnitude) improve the photoresponse time of pure ZnO nanowires. The fast response time of ZnO/WS 2 core/shell nanowire was explained by electrons and holes sinking from ZnO nanowire into WS 2 shell, which serves as a charge carrier channel in the ZnO/WS 2 heterostructure. First-principles calculations suggest that the interface layer i-WS 2 , bridging ZnO nanowire surface and WS 2 shell, might play a role of energy barrier, preventing the backward diffusion of charge carriers into ZnO nanowire.

  11. Single patent vessel over an embedded ring: a case report.

    Science.gov (United States)

    Awan, Bassim; Samargandi, Osama A; Aljaaly, Hattan A; Makhdom, Asim M

    2013-01-01

    Embedded ring injury is rarely encountered in clinical practice, and most of the few reported cases share common features, including deliberate neglect, mental illness, poor social support, female gender, and adult age group. Ischemia has never been reported in such injuries. Here, we report the case of a 16-year-old girl who presented with a completely embedded ring in the right index finger and a partially embedded ring in the left ring finger. Revascularization after ring embedment probably explains the intact vessel that was observed on the outer aspect of the embedded ring during surgical exploration of the right index finger.

  12. Low-threshold room-temperature AlGaAs/GaAs nanowire/single-quantum-well heterostructure laser

    OpenAIRE

    Yan, Xin; Wei, Wei; Tang, Fengling; Wang, Xi; Li, Luying

    2017-01-01

    Near-infrared nanowire lasers are promising as ultrasmall, low-consumption light emitters in on-chip optical communications and computing systems. Here, we report on a room-temperature near-infrared nanolaser based on an AlGaAs/GaAs nanowire/single-quantum-well heterostructure grown by Au-catalyzed metal organic chemical vapor deposition. When subjects to pulsed optical excitation, the nanowire exhibits lasing, with a low threshold of 600 W/cm2, a narrow linewidth of 0.39 nm, and a high Q fac...

  13. Single photon emission and quantum ring-cavity coupling in InAs/GaAs quantum rings

    Energy Technology Data Exchange (ETDEWEB)

    Gallardo, E; Nowak, A K; Sanvitto, D; Meulen, H P van der; Calleja, J M [Departamento de Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); MartInez, L J; Prieto, I; Alija, A R; Granados, D; Taboada, A G; GarcIa, J M; Postigo, P A [Instituto de Microelectronica de Madrid, Centro Nacional de MicrotecnologIa, CSIC, Isaac Newton 8, PTM Tres Cantos, E-28760 Madrid (Spain); Sarkar, D, E-mail: eva.gallardo@uam.e [Department of Physics and Astronomy, University of Sheffield, S3 7RH (United Kingdom)

    2010-02-01

    Different InAs/GaAs quantum rings embedded in a photonic crystal microcavity are studied by quantum correlation measurements. Single photon emission, with g{sup (2)}(0) values around 0.3, is demonstrated for a quantum ring not coupled to the microcavity. Characteristic rise-times are found to be longer for excitons than for biexcitons, resulting in the time asymmetry of the exciton-biexciton cross-correlation. No antibunching is observed in another quantum ring weakly coupled to the microcavity.

  14. Atomically thin heterostructures based on single-layer tungsten diselenide and graphene.

    Science.gov (United States)

    Lin, Yu-Chuan; Chang, Chih-Yuan S; Ghosh, Ram Krishna; Li, Jie; Zhu, Hui; Addou, Rafik; Diaconescu, Bogdan; Ohta, Taisuke; Peng, Xin; Lu, Ning; Kim, Moon J; Robinson, Jeremy T; Wallace, Robert M; Mayer, Theresa S; Datta, Suman; Li, Lain-Jong; Robinson, Joshua A

    2014-12-10

    Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy, photoluminescence, and scanning tunneling microscopy confirm high-quality WSe2 monolayers, whereas transmission electron microscopy shows an atomically sharp interface, and low energy electron diffraction confirms near perfect orientation between WSe2 and EG. Vertical transport measurements across the WSe2/EG heterostructure provides evidence that an additional barrier to carrier transport beyond the expected WSe2/EG band offset exists due to the interlayer gap, which is supported by theoretical local density of states (LDOS) calculations using self-consistent density functional theory (DFT) and nonequilibrium Green's function (NEGF).

  15. Atomically Thin Heterostructures Based on Single-Layer Tungsten Diselenide and Graphene

    KAUST Repository

    Lin, Yu-Chuan

    2014-11-10

    Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy, photoluminescence, and scanning tunneling microscopy confirm high-quality WSe2 monolayers, whereas transmission electron microscopy shows an atomically sharp interface, and low energy electron diffraction confirms near perfect orientation between WSe2 and EG. Vertical transport measurements across the WSe2/EG heterostructure provides evidence that an additional barrier to carrier transport beyond the expected WSe2/EG band offset exists due to the interlayer gap, which is supported by theoretical local density of states (LDOS) calculations using self-consistent density functional theory (DFT) and nonequilibrium Green\\'s function (NEGF).

  16. Second order single particle dynamics in quasi-isochronous storage rings and its application to the LNLS-UVX ring

    Energy Technology Data Exchange (ETDEWEB)

    Lin Liu (Pro-Reitoria de Pesquisa, Univ. Estadual de Campinas, SP (Brazil) Lab. Nacional de Luz Sincrotron-LNLS, Campinas, SP (Brazil)); Concalves da Silva, C.E.T. (Inst. de Fisica Gleb Wataghin, Univ. Estadual de Campinas, SP (Brazil) Lab. Nacional de Luz Sincrotron-LNLS, Campinas, SP (Brazil))

    1993-05-15

    We analyze the second order single particle longitudinal dynamics in a quasi-isochronous storage ring. We expand the momentum compaction factor to include the effects of second order terms taking sextupoles into account and of transverse betatron oscillations. The introduction of nonlinearities due to higher order terms results in a second stability region for longitudinal phase oscillations, in addition to the well known linear stable operation point. The conditions for this new solution to fall within the energy acceptance of the storage ring are presented. Inclusion of transverse motion coupling may lead to either a reduction or an enhancement of the stable longitudinal phase-space regions. The analysis is applied to the LNLS 1.15 GeV UVX electron storage ring, indicating that it should be possible to operate this ring in a quasi-isochronous mode. (orig.).

  17. A radio frequency single-electron transistor based on an InAs/InP heterostructure nanowire.

    Science.gov (United States)

    Nilsson, Henrik A; Duty, Tim; Abay, Simon; Wilson, Chris; Wagner, Jakob B; Thelander, Claes; Delsing, Per; Samuelson, Lars

    2008-03-01

    We demonstrate radio frequency single-electron transistors fabricated from epitaxially grown InAs/InP heterostructure nanowires. Two sets of double-barrier wires with different barrier thicknesses were grown. The wires were suspended 15 nm above a metal gate electrode. Electrical measurements on a high-resistance nanowire showed regularly spaced Coulomb oscillations at a gate voltage from -0.5 to at least 1.8 V. The charge sensitivity was measured to 32 microe rms Hz(-1/2) at 1.5 K. A low-resistance single-electron transistor showed regularly spaced oscillations only in a small gate-voltage region just before carrier depletion. This device had a charge sensitivity of 2.5 microe rms Hz(-1/2). At low frequencies this device showed a typical 1/f noise behavior, with a level extrapolated to 300 microe rms Hz(-1/2) at 10 Hz.

  18. Fabrication and Characterization of a Single Hole Transistor in p-type GaAs/AlGaAs Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Tracy, Lisa A [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Reno, John L. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Hargett, Terry W. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    Most spin qubit research to date has focused on manipulating single electron spins in quantum dots. However, hole spins are predicted to have some advantages over electron spins, such as reduced coupling to host semiconductor nuclear spins and the ability to control hole spins electrically using the large spin-orbit interaction. Building on recent advances in fabricating high-mobility 2D hole systems in GaAs/AlGaAs heterostructures at Sandia, we fabricate and characterize single hole transistors in GaAs. We demonstrate p-type double quantum dot devices with few-hole occupation, which could be used to study the physics of individual hole spins and control over coupling between hole spins, looking towards eventual applications in quantum computing. Intentionally left blank

  19. Low-threshold room-temperature AlGaAs/GaAs nanowire/single-quantum-well heterostructure laser

    Science.gov (United States)

    Yan, Xin; Wei, Wei; Tang, Fengling; Wang, Xi; Li, Luying; Zhang, Xia; Ren, Xiaomin

    2017-02-01

    Near-infrared nanowire lasers are promising as ultrasmall, low-consumption light emitters in on-chip optical communications and computing systems. Here, we report on a room-temperature near-infrared nanolaser based on an AlGaAs/GaAs nanowire/single-quantum-well heterostructure grown by Au-catalyzed metal organic chemical vapor deposition. When subjects to pulsed optical excitation, the nanowire exhibits lasing, with a low threshold of 600 W/cm2, a narrow linewidth of 0.39 nm, and a high Q factor of 2000 at low temperature. Lasing is observed up to 300 K, with an ultrasmall temperature dependent wavelength shift of 0.045 nm/K. This work paves the way towards ultrasmall, low-consumption, and high-temperature-stability near-infrared nanolasers.

  20. Wavelength-selectable and steady single-mode erbium-doped fiber multiple ring laser

    Science.gov (United States)

    Yeh, Chien-Hung; Yang, Zi-Qing; Huang, Tzu-Jung; Chow, Chi-Wai; Chen, Jing-Heng; Chen, Kun-Huang

    2017-11-01

    To achieve a stable and selectable C-band erbium-doped fiber (EDF) laser with single-longitudinal-mode output, a multiple ring architecture is proposed and demonstrated experimentally. In this work, we design a passively quadruple-ring structure in the cavity of an EDF laser to produce a Vernier effect with a mode filter for suppressing the multimode spikes significantly. In addition, the output performance and stability of the proposed EDF ring laser are discussed.

  1. Evolution between self-assembled single and double ring-like nanostructures

    International Nuclear Information System (INIS)

    Lee, J H; Wang, Zh M; Abuwaar, Z Y; Strom, N W; Salamo, G J

    2006-01-01

    The evolution between lattice-matched GaAs/Al 0.3 Ga 0.7 As single and double ring-like nanostructures is studied, with an emphasis on the construction and destruction of the observed outer ring. Using droplet epitaxy, this was achieved by directly controlling the Ga surface diffusion on GaAs(100). Double ring-like nanostructures were observed at relatively low temperatures under a fixed As 4 flux (beam equivalent pressure (BEP) of 6.4 μTorr) and at a fixed temperature under a high As 4 flux. The construction of the outer ring can be controlled through surface diffusion by varying the substrate temperature or the As 4 flux. Single ring-like nanostructures were realized both at relatively high temperatures under a fixed As 4 flux, and at low temperatures under a relatively low As 4 flux

  2. Controlled switching of single-molecule junctions by mechanical motion of a phenyl ring

    Directory of Open Access Journals (Sweden)

    Yuya Kitaguchi

    2015-10-01

    Full Text Available Mechanical methods for single-molecule control have potential for wide application in nanodevices and machines. Here we demonstrate the operation of a single-molecule switch made functional by the motion of a phenyl ring, analogous to the lever in a conventional toggle switch. The switch can be actuated by dual triggers, either by a voltage pulse or by displacement of the electrode, and electronic manipulation of the ring by chemical substitution enables rational control of the on-state conductance. Owing to its simple mechanics, structural robustness, and chemical accessibility, we propose that phenyl rings are promising components in mechanical molecular devices.

  3. Detection and direction discrimination of single vortex rings by harbour seals (Phoca vitulina).

    Science.gov (United States)

    Krüger, Yvonne; Hanke, Wolf; Miersch, Lars; Dehnhardt, Guido

    2018-02-27

    Harbour seals possess highly sensitive vibrissae that enable them to track hydrodynamic trails left behind by a swimming fish. Most of these trails contain vortex rings as a main hydrodynamic component. They may reveal information about their generator as the trails differ depending on the fish species, the fish's body shape, size, and swimming style. Additionally, fish generate single vortex rings in diverse natural situations. In this study, the ability of blindfolded stationary harbour seals to detect and analyse single vortex rings regarding directional information has been investigated. In three different behavioural experiments, the animals were trained to respond to single artificially generated vortex rings. The results show that harbour seals are able to respond to a variety of different vortex rings upon vibrissal stimulation. The investigation of the minimum hydrodynamically perceivable angle revealed that it is at least as small as 5.7°, which was the smallest adjustable angle. Moreover, harbour seals are capable of analysing the travel direction of a vortex ring perceived by the mystacial pads irrespective of whether the vibrissae were stimulated ipsilaterally or contralaterally. In situations in which no complex hydrodynamic trail is available, it is advantageous for a hunting seal to be able to extract information from a single vortex ring. © 2018. Published by The Company of Biologists Ltd.

  4. Enhanced photocatalytic efficiency in zirconia buffered n-NiO/p-NiO single crystalline heterostructures by nanosecond laser treatment

    Energy Technology Data Exchange (ETDEWEB)

    Molaei, R.; Bayati, M. R.; Alipour, H. M.; Nori, S.; Narayan, J. [Department of Materials Science and Engineering, NC State University, EB-1, Raleigh, North Carolina 27695-7907 (United States)

    2013-06-21

    We report the formation of NiO based single crystalline p-n junctions with enhanced photocatalytic activity induced by pulsed laser irradiation. The NiO epilayers were grown on Si(001) substrates buffered with cubic yttria-stabilized zirconia (c-YSZ) by using pulsed laser deposition. The NiO/c-YSZ/Si heterostructures were subsequently laser treated by 5 pulses of KrF excimer laser (pulse duration = 25 Multiplication-Sign 10{sup -9} s) at lower energies. Microstructural studies, conducted by X-ray diffraction ({theta}-2{theta} and {phi} techniques) and high resolution transmission electron microscope, showed a cube-on-cube epitaxial relationship at the c-YSZ/Si interface; the epitaxial relationship across the NiO/c-YSZ interface was established as NiO<111 > Double-Vertical-Line Double-Vertical-Line c-YSZ<001> and in-plane NiO<110> Double-Vertical-Line Double-Vertical-Line c-YSZ<100>. Electron microscopy studies showed that the interface between the laser annealed and the pristine region as well as the NiO/c-YSZ interface was atomically sharp and crystallographically continuous. The formation of point defects, namely oxygen vacancies and NiO, due to the coupling of the laser photons with the NiO epilayers was confirmed by XPS. The p-type electrical characteristics of the pristine NiO epilayers turned to an n-type behavior and the electrical conductivity was increased by one order of magnitude after laser treatment. Photocatalytic activity of the pristine (p-NiO/c-YSZ/Si) and the laser-annealed (n-NiO/p-NiO/c-YSZ/Si) heterostructures were assessed by measuring the decomposition rate of 4-chlorophenol under UV light. The photocatalytic reaction rate constants were determined to be 0.0059 and 0.0092 min{sup -1} for the as-deposited and the laser-treated samples, respectively. The enhanced photocatalytic efficiency was attributed to the suppressed charge carrier recombination in the NiO based p-n junctions and higher electrical conductivity. Besides, the oxygen vacancies

  5. Planar heterostructures of single-layer transition metal dichalcogenides: Composite structures, Schottky junctions, tunneling barriers, and half metals

    Science.gov (United States)

    Aras, Mehmet; Kılıç, ćetin; Ciraci, S.

    2017-02-01

    Planar composite structures formed from the stripes of transition metal dichalcogenides joined commensurately along their zigzag or armchair edges can attain different states in a two-dimensional (2D), single-layer, such as a half metal, 2D or one-dimensional (1D) nonmagnetic metal and semiconductor. Widening of stripes induces metal-insulator transition through the confinements of electronic states to adjacent stripes, that results in the metal-semiconductor junction with a well-defined band lineup. Linear bending of the band edges of the semiconductor to form a Schottky barrier at the boundary between the metal and semiconductor is revealed. Unexpectedly, strictly 1D metallic states develop in a 2D system along the boundaries between stripes, which pins the Fermi level. Through the δ doping of a narrow metallic stripe one attains a nanowire in the 2D semiconducting sheet or narrow band semiconductor. A diverse combination of constituent stripes in either periodically repeating or finite-size heterostructures can acquire critical fundamental features and offer device capacities, such as Schottky junctions, nanocapacitors, resonant tunneling double barriers, and spin valves. These predictions are obtained from first-principles calculations performed in the framework of density functional theory.

  6. Efficient Nitrogen Doping of Single-Layer Graphene Accompanied by Negligible Defect Generation for Integration into Hybrid Semiconductor Heterostructures.

    Science.gov (United States)

    Sarau, George; Heilmann, Martin; Bashouti, Muhammad; Latzel, Michael; Tessarek, Christian; Christiansen, Silke

    2017-03-22

    While doping enables application-specific tailoring of graphene properties, it can also produce high defect densities that degrade the beneficial features. In this work, we report efficient nitrogen doping of ∼11 atom % without virtually inducing new structural defects in the initial, large-area, low defect, and transferred single-layer graphene. To shed light on this remarkable high-doping-low-disorder relationship, a unique experimental strategy consisting of analyzing the changes in doping, strain, and defect density after each important step during the doping procedure was employed. Complementary micro-Raman mapping, X-ray photoelectron spectroscopy, and optical microscopy revealed that effective cleaning of the graphene surface assists efficient nitrogen incorporation accompanied by mild compressive strain resulting in negligible defect formation in the doped graphene lattice. These original results are achieved by separating the growth of graphene from its doping. Moreover, the high doping level occurred simultaneously with the epitaxial growth of n-GaN micro- and nanorods on top of graphene, leading to the flow of higher currents through the graphene/n-GaN rod interface. Our approach can be extended toward integrating graphene into other technologically relevant hybrid semiconductor heterostructures and obtaining an ohmic contact at their interfaces by adjusting the doping level in graphene.

  7. Utilizing wheel-ring architecture for stable and selectable single-longitudinal-mode erbium fiber laser

    Science.gov (United States)

    Yeh, Chien-Hung; Yang, Zi-Qing; Huang, Tzu-Jung; Chow, Chi-Wai

    2018-03-01

    To achieve a steady single-longitudinal-mode (SLM) erbium-doped fiber (EDF) laser, the wheel-ring architecture is proposed in the laser cavity. According to Vernier effect, the proposed wheel-ring can produce three different free spectrum ranges (FSRs) to serve as the mode-filter for suppressing the densely multi-longitudinal-mode (MLM). Here, to complete wavelength-tunable EDF laser, an optical tunable bandpass filter (OTBF) is utilized inside the cavity for tuning arbitrarily. In addition, the entire output performances of the proposed EDF wheel-ring laser are also discussed and analyzed experimentally.

  8. Experimental evidences of quantum confined 2D indirect excitons in single barrier GaAs/AlAs/GaAs heterostructure using photocapacitance at room temperature

    Science.gov (United States)

    Bhunia, Amit; Singh, Mohit Kumar; Galvão Gobato, Y.; Henini, Mohamed; Datta, Shouvik

    2018-01-01

    We investigated excitonic absorptions in a GaAs/AlAs/GaAs single barrier heterostructure using both photocapacitance and photocurrent spectroscopies at room temperature. Photocapacitance spectra show well defined resonance peaks of indirect excitons formed around the Γ-AlAs barrier. Unlike DC-photocurrent spectra, frequency dependent photocapacitance spectra interestingly red shift, sharpen up, and then decrease with increasing tunneling at higher biases. Such dissimilarities clearly point out that different exciton dynamics govern these two spectral measurements. We also argue why such quantum confined dipoles of indirect excitons can have thermodynamically finite probabilities to survive even at room temperature. Finally, our observations demonstrate that the photocapacitance technique, which was seldom used to detect excitons in the past, is useful for selective detection and experimental tuning of relatively small numbers (˜1011/cm2) of photo-generated indirect excitons having large effective dipole moments in this type of quasi-two dimensional heterostructures.

  9. Embedding the dynamics of a single delay system into a feed-forward ring

    Science.gov (United States)

    Klinshov, Vladimir; Shchapin, Dmitry; Yanchuk, Serhiy; Wolfrum, Matthias; D'Huys, Otti; Nekorkin, Vladimir

    2017-10-01

    We investigate the relation between the dynamics of a single oscillator with delayed self-feedback and a feed-forward ring of such oscillators, where each unit is coupled to its next neighbor in the same way as in the self-feedback case. We show that periodic solutions of the delayed oscillator give rise to families of rotating waves with different wave numbers in the corresponding ring. In particular, if for the single oscillator the periodic solution is resonant to the delay, it can be embedded into a ring with instantaneous couplings. We discover several cases where the stability of a periodic solution for the single unit can be related to the stability of the corresponding rotating wave in the ring. As a specific example, we demonstrate how the complex bifurcation scenario of simultaneously emerging multijittering solutions can be transferred from a single oscillator with delayed pulse feedback to multijittering rotating waves in a sufficiently large ring of oscillators with instantaneous pulse coupling. Finally, we present an experimental realization of this dynamical phenomenon in a system of coupled electronic circuits of FitzHugh-Nagumo type.

  10. Temperature persistent bistability and threshold switching in a single barrier heterostructure hot-electron diode

    DEFF Research Database (Denmark)

    Stasch, R.; Hey, R.; Asche, M.

    1996-01-01

    Bistable current–voltage characteristics caused by competition of tunneling through and field-enhanced thermionic emission across a single barrier are investigated in an n–-GaAs/Al0.34Ga0.66As/n+-GaAs structure. The S-shaped part of the characteristic persists in the whole temperature regime...

  11. Reliability in Single, Double and N2R Ring Network Structures

    DEFF Research Database (Denmark)

    Jørgensen, T.; Pedersen, L.; Pedersen, Jens Myrup

    This paper studies the properties of single, double and N2R ring network structures during link errors. The structure of the network infrastructure must be redesigned in order to fulfil the requirements of services using the Internet in the future; hence, N2R structures have been suggested. N2R s...

  12. Continuous-wave singly resonant optical parametric oscillator placed inside a ring laser.

    Science.gov (United States)

    Abitan, Haim; Buchhave, Preben

    2003-11-20

    A cw singly resonant optical parametric oscillator (SRO) was built and placed inside the cavity of a ring laser. The system consists of a diode-end-pumped Nd:YVO4 ring laser with intracavity periodically poled lithium niobate as the nonlinear gain medium of the SRO. When the laser was operated in a unidirectional mode, we obtained more than 520 mW of signal power in one beam. When the laser was operated in a bidirectional mode, we obtained 600 mW of signal power (300 mW in two separate beams). The power and the spectral features of the laser in the unidirectional and bidirectional modes were measured while the laser was coupled with the SRO. The results show that it is preferable to couple a SRO with a unidirectional ring laser.

  13. Enzymatic formation of carbohydrate rings catalyzed by single-walled carbon nanotubes.

    Science.gov (United States)

    Hyun, Moon Seop; Park, Jong Pil; Seo, Dongkyun; Chang, Sung-Jin; Lee, Seok Jae; Lee, Sang Yup; Kwak, Kyungwon; Park, Tae Jung

    2016-05-01

    Macrocyclic carbohydrate rings were formed via enzymatic reactions around single-walled carbon nanotubes (SWNTs) as a catalyst. Cyclodextrin glucanotransferase, starch substrate and SWNTs were reacted in buffer solution to yield cyclodextrin (CD) rings wrapped around individual SWNTs. Atomic force microscopy showed the resulting complexes to be rings of 12-50 nm in diameter, which were highly soluble and dispersed in aqueous solution. They were further characterized by Raman and Fourier transform infrared spectroscopy and molecular simulation using density functional theory calculation. In the absence of SWNT, hydrogen bonding between glucose units determines the structure of maltose (the precursor of CD) and produces the curvature along the glucose chain. Wrapping SWNT along the short axis was preferred with curvature in the presence of SWNTs and with the hydrophobic interactions between the SWNTs and CD molecules. This synthetic approach may be useful for the functionalization of carbon nanotubes for development of nanostructures.

  14. Continuous-wave singly resonant optical parametric oscillator placed inside a ring laser

    DEFF Research Database (Denmark)

    Abitan, Haim; Buchhave, Preben

    2003-01-01

    in a unidirectional mode, we obtained more than 520 mW of signal power in one beam. When the laser was operated in a bidirectional mode, we obtained 600 mW of signal power (300 mW in two separate beams). The power and the spectral features of the laser in the unidirectional and bidirectional modes were measured while......A cw singly resonant optical parametric oscillator (SRO) was built and placed inside the cavity of a ring laser. The system consists of a diode-end-pumped Nd:YVO4 ring laser with intracavity periodically poled lithium niobate as the nonlinear gain medium of the SRO. When the laser was operated...... the laser was coupled with the SRO. The results show that it is preferable to couple a SRO with a unidirectional ring laser....

  15. Single and multi-band electromagnetic induced transparency-like metamaterials with coupled split ring resonators

    Science.gov (United States)

    Bagci, Fulya; Akaoglu, Baris

    2017-08-01

    We present a metamaterial configuration exhibiting single and multi-band electromagnetic induced transparency (EIT)-like properties. The unit cell of the single band EIT-like metamaterial consists of a multi-split ring resonator surrounded by a split ring resonator. The multi-split ring resonator acts as a quasi-dark or dark resonator, depending on the polarization of the incident wave, and the split ring resonator serves as the bright resonator. Combination of these two resonators results in a single band EIT-like transmission inside the stop band. EIT-like transmission phenomenon is also clearly observed in the measured transmission spectrum at almost the same frequencies for vertical and horizontal polarized waves, and the numerical results are verified for normal incidence. Moreover, multi-band transmission windows are created within a wide band by combining the two slightly different single band EIT-like metamaterial unit cells that exhibit two different coupling strengths inside a supercell configuration. Group indices as high as 123 for single band and 488 for tri-band transmission, accompanying with high transmission rates (over 80%), are achieved, rendering the metamaterial very suitable for multi-band slow light applications. It is shown that the group delay of the propagating wave can be increased and dynamically controlled by changing the polarization angle. Multi-band EIT-like transmission is also verified experimentally, and a good agreement with simulations is obtained. The proposed novel methodology for obtaining multi-band EIT, which takes advantage of a supercell configuration by hosting slightly different configured unit cells, can be utilized for easily formation and manipulation of multi-band transmission windows inside a stop band.

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

    DEFF Research Database (Denmark)

    Poulsen, Christian; Sejka, Milan

    1993-01-01

    A continuous wave (CW) tunable diode-pumped Er3+-doped fiber ring laser, pumped by diode laser at wavelengths around 1480 nm, is discussed. Wavelength tuning range of 42 nm, maximum slope efficiency of 48% and output power of 14.4 mW have been achieved. Single longitudinal mode lasing with a line...... with a linewidth of 6 kHz has been measured. A fast model of erbium-doped fiber laser was developed and used to optimize output parameters of the laser......A continuous wave (CW) tunable diode-pumped Er3+-doped fiber ring laser, pumped by diode laser at wavelengths around 1480 nm, is discussed. Wavelength tuning range of 42 nm, maximum slope efficiency of 48% and output power of 14.4 mW have been achieved. Single longitudinal mode lasing...

  17. Rings and rackets from single-wall carbon nanotubes: manifestations of mesoscale mechanics.

    Science.gov (United States)

    Wang, Yuezhou; Semler, Matthew R; Ostanin, Igor; Hobbie, Erik K; Dumitrică, Traian

    2014-11-21

    We combine experiments and distinct element method simulations to understand the stability of rings and rackets formed by single-walled carbon nanotubes assembled into ropes. Bending remains a soft deformation mode in ropes because intra-rope sliding of the constituent nanotubes occurs with ease. Our simulations indicate that the formation of these aggregates can be attributed to the mesoscopic mechanics of entangled nanotubes and to the sliding at the contacts. Starting from the single-walled carbon nanotubes, the sizes of the rings and rackets' heads increase with the rope diameter, indicating that the stability of the experimental aggregates can be largely explained by the competition between bending and van der Waals adhesion energies. Our results and simulation method should be useful for understanding nanoscale fibers in general.

  18. Experimental Performance of a Single-Mode Ytterbium-doped Fiber Ring Laser with Intracavity Modulator

    Science.gov (United States)

    Numata, Kenji; Camp, Jordan

    2012-01-01

    We have developed a linearly polarized Ytterbium-doped fiber ring laser with a single longitudinal mode output at 1064 run. A fiber-coupled intracavity phase modulator ensured mode-hop free operation and allowed fast frequency tuning. The fiber laser was locked with high stability to an iodine-stabilized laser, showing a frequency noise suppression of a factor approx 10 (exp 5) at 1 mHz

  19. Dynamical aspects on FEL interaction in single passage and storage ring devices

    Energy Technology Data Exchange (ETDEWEB)

    Dattoli, G.; Renieri, A. [ENEA, Frascati (Italy)

    1995-12-31

    The dynamical behaviour of the free-electron lasers is investigated using appropriate scaling relations valid for devices operating in the low and high gain regimes, including saturation. The analysis is applied to both single passage and storage ring configurations. In the latter case the interplay between the interaction of the electron bean with the laser field and with the accelerator environment is investigated. In particular we discuss the effect of FEL interaction on the microwave instability.

  20. Single-Bunch Instability Driven by the Electron Cloud Effect in the Positron Damping Ring of the International Linear Collider

    International Nuclear Information System (INIS)

    Pivi, Mauro; Raubenheimer, Tor O.; Ghalam, Ali; Harkay, Katherine; Ohmi, Kazuhito; Wanzenberg, Rainer; Wolski, Andrzej; Zimmermann, Frank

    2005-01-01

    Collective instabilities caused by the formation of an electron cloud (EC) are a potential limitation to the performances of the damping rings for a future linear collider. In this paper, we present recent simulation results for the electron cloud build-up in damping rings of different circumferences and discuss the single-bunch instabilities driven by the electron cloud

  1. Single-chip ring resonator-based 1 x 8 optical beam forming network in CMOS-compatible waveguide technology

    NARCIS (Netherlands)

    Zhuang, L.; Roeloffzen, C.G.H.; Heideman, Rene; Borreman, A.; Meijerink, Arjan; van Etten, Wim

    2007-01-01

    Optical ring resonators (ORRs) are good candidates to provide continuously tunable delay in optical beam forming networks (OBFNs) for phased array antenna systems. Delay and splitting/combining elements can be integrated on a single optical chip to form an OBFN. A state-of-the-art ring resonator-

  2. Current-Transport Mechanisms in the AlInN/AlN/GaN single-channel and AlInN/AlN/GaN/AlN/GaN double-channel heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Arslan, Engin, E-mail: engina@bilkent.edu.tr [Nanotechnology Research Center, Department of Physics, Department of Electrical and Electronics Engineering, Bilkent University, Bilkent, 06800 Ankara (Turkey); Turan, Sevil; Gökden, Sibel; Teke, Ali [Department of Physics, Faculty of Science and Letters, Balıkesir University, Çağış Kampüsü, 10145 Balıkesir (Turkey); Özbay, Ekmel [Nanotechnology Research Center, Department of Physics, Department of Electrical and Electronics Engineering, Bilkent University, Bilkent, 06800 Ankara (Turkey)

    2013-12-02

    Current-transport mechanisms were investigated in Schottky contacts on AlInN/AlN/GaN single channel (SC) and AlInN/AlN/GaN/AlN/GaN double channel (DC) heterostructures. A simple model was adapted to the current-transport mechanisms in DC heterostructure. In this model, two Schottky diodes are in series: one is a metal–semiconductor barrier layer (AIInN) Schottky diode and the other is an equivalent Schottky diode, which is due to the heterojunction between the AlN and GaN layer. Capacitance–voltage studies show the formation of a two-dimensional electron gas at the AlN/GaN interface in the SC and the first AlN/GaN interface from the substrate direction in the DC. In order to determine the current mechanisms for SC and DC heterostructures, we fit the analytical expressions given for the tunneling current to the experimental current–voltage data over a wide range of applied biases as well as at different temperatures. We observed a weak temperature dependence of the saturation current and a fairly small dependence on the temperature of the tunneling parameters in this temperature range. At both a low and medium forward-bias voltage values for Schottky contacts on AlInN/AlN/GaN/AlN/GaN DC and AlInN/AlN/GaN SC heterostructures, the data are consistent with electron tunneling to deep levels in the vicinity of mixed/screw dislocations in the temperature range of 80–420 K. - Highlights: • Current mechanisms were investigated on single and double channel heterostructures. • A model was adapted to the current mechanisms in double channel heterostructures. • We observed a weak temperature dependence of the saturation current. • And a small dependence of the tunneling parameters in this temperature range.

  3. Current-Transport Mechanisms in the AlInN/AlN/GaN single-channel and AlInN/AlN/GaN/AlN/GaN double-channel heterostructures

    International Nuclear Information System (INIS)

    Arslan, Engin; Turan, Sevil; Gökden, Sibel; Teke, Ali; Özbay, Ekmel

    2013-01-01

    Current-transport mechanisms were investigated in Schottky contacts on AlInN/AlN/GaN single channel (SC) and AlInN/AlN/GaN/AlN/GaN double channel (DC) heterostructures. A simple model was adapted to the current-transport mechanisms in DC heterostructure. In this model, two Schottky diodes are in series: one is a metal–semiconductor barrier layer (AIInN) Schottky diode and the other is an equivalent Schottky diode, which is due to the heterojunction between the AlN and GaN layer. Capacitance–voltage studies show the formation of a two-dimensional electron gas at the AlN/GaN interface in the SC and the first AlN/GaN interface from the substrate direction in the DC. In order to determine the current mechanisms for SC and DC heterostructures, we fit the analytical expressions given for the tunneling current to the experimental current–voltage data over a wide range of applied biases as well as at different temperatures. We observed a weak temperature dependence of the saturation current and a fairly small dependence on the temperature of the tunneling parameters in this temperature range. At both a low and medium forward-bias voltage values for Schottky contacts on AlInN/AlN/GaN/AlN/GaN DC and AlInN/AlN/GaN SC heterostructures, the data are consistent with electron tunneling to deep levels in the vicinity of mixed/screw dislocations in the temperature range of 80–420 K. - Highlights: • Current mechanisms were investigated on single and double channel heterostructures. • A model was adapted to the current mechanisms in double channel heterostructures. • We observed a weak temperature dependence of the saturation current. • And a small dependence of the tunneling parameters in this temperature range

  4. Narrow band wavelength selective filter using grating assisted single ring resonator

    Energy Technology Data Exchange (ETDEWEB)

    Prabhathan, P., E-mail: PPrabhathan@ntu.edu.sg; Murukeshan, V. M. [Centre for Optical and Laser Engineering (COLE), School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2014-09-15

    This paper illustrates a filter configuration which uses a single ring resonator of larger radius connected to a grating resonator at its drop port to achieve single wavelength selectivity and switching property with spectral features suitable for on-chip wavelength selection applications. The proposed configuration is expected to find applications in silicon photonics devices such as, on-chip external cavity lasers and multi analytic label-free biosensors. The grating resonator has been designed for a high Q-factor, high transmittivity, and minimum loss so that the wavelength selectivity of the device is improved. The proof-of-concept device has been demonstrated on a Silicon-on-Insulator (SOI) platform through electron beam lithography and Reactive Ion Etching (RIE) process. The transmission spectrum shows narrow band single wavelength selection and switching property with a high Free Spectral Range (FSR) ∼60 nm and side band rejection ratio >15 dB.

  5. Single-frequency blue light generation by single-pass sum-frequency generation in a coupled ring cavity tapered laser

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Petersen, Paul Michael

    2013-01-01

    A generic approach for generation of tunable single frequency light is presented. 340 mW of near diffraction limited, single-frequency, and tunable blue light around 459 nm is generated by sum-frequency generation (SFG) between two tunable tapered diode lasers. One diode laser is operated in a ring...... cavity and another tapered diode laser is single-passed through a nonlinear crystal which is contained in the coupled ring cavity. Using this method, the single-pass conversion efficiency is more than 25%. In contrast to SFG in an external cavity, the system is entirely self-stabilized with no electronic...

  6. Development of CRID [Cerenkov Ring Imaging Detector] single electron wire detector

    International Nuclear Information System (INIS)

    Aston, D.; Bean, A.; Bienz, T.

    1989-02-01

    We describe the R and D effort to define the design parameters, method of construction and experimental results from the single electron wire detectors. These detectors will be used for particle identification using the Cerenkov Ring Imaging techniques in the SLD experiment at SLAC. We present measurements of pulse heights for several gases as a function of gas gain, charge division performance on a single electron signal using both 7 μm and 33 μm diameter carbon wires, photon feedback in TMAE laden gas, average pulse shape, and its comparison with the predicted shape and cross-talk. In addition, we present results of wire aging tests, and other tests associated with construction of this unusual type of wire chamber. 12 refs., 9 figs

  7. Single frequency 1645 nm Er:YAG nonplanar ring oscillator resonantly pumped by a 1470 nm laser diode.

    Science.gov (United States)

    Zheng, Yan; Gao, Chunqing; Wang, Ran; Gao, Mingwei; Ye, Qing

    2013-03-01

    A 1645 nm Er:YAG nonplanar ring oscillator, resonantly pumped by a 1470 nm laser diode, is reported. By using a 0.5%-doped Er:YAG nonplanar ring resonator, a 0.284 W single-frequency laser output at 1645 nm was obtained with a slope efficiency of 42.1%. The beam quality in x and y directions were 1.064 and 1.039, respectively.

  8. Carbon-Ring Microelectrode Arrays for Electrochemical Imaging of Single Cell Exocytosis: Fabrication and Characterization

    Science.gov (United States)

    Lin, Yuqing; Trouillon, Raphaël; Svensson, Maria I.; Keighron, Jacqueline D.; Cans, Ann-Sofie; Ewing, Andrew G.

    2012-01-01

    Fabrication of carbon microelectrode arrays, with up to 15 electrodes in total tips as small as 10 to 50 μm, is presented. The support structures of microelectrodes were obtained by pulling multiple quartz capillaries together to form hollow capillary arrays before carbon deposition. Carbon ring microelectrodes were deposited by pyrolysis of acetylene in the lumen of these quartz capillary arrays. Each carbon deposited array tip was filled with epoxy, followed by beveling of the tip of the array to form a deposited carbon-ring microelectrode array (CRMA). Both the number of the microelectrodes in the array and the tip size are independently tunable. These CRMAs have been characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, and electrogenerated chemiluminescence. Additionally, the electrochemical properties were investigated with steady-state voltammetry. In order to demonstrate the utility of these fabricated microelectrodes in neurochemistry, CRMAs containing eight microring electrodes were used for electrochemical monitoring of exocytotic events from single PC12 cells. Subcellular temporal heterogeneities in exocytosis (ie. cold spots vs. hot spots) were successfully detected with the CRMAs. PMID:22339586

  9. Effects of topology on the adsorption of singly tethered ring polymers to attractive surfaces.

    Science.gov (United States)

    Li, Bing; Sun, Zhao-Yan; An, Li-Jia

    2015-07-14

    We investigate the effect of topology on the equilibrium behavior of singly tethered ring polymers adsorbed on an attractive surface. We focus on the change of square radius of gyration Rg(2), the perpendicular component Rg⊥(2) and the parallel component Rg‖(2) to the adsorbing surface, the mean contacting number of monomers with the surface , and the monomer distribution along z-direction during transition from desorption to adsorption. We find that both of the critical point of adsorption εc and the crossover exponent ϕ depend on the knot type when the chain length of ring ranges from 48 to 400. The behaviors of Rg(2), Rg⊥(2), and Rg‖(2) are found to be dependent on the topology and the monomer-surface attractive strength. At weak adsorption, the polymer chains with more complex topology are more adsorbable than those with simple topology. However, at strong adsorption, the polymer chains with complex topology are less adsorbable. By analyzing the distribution of monomer along z-direction, we give a possible mechanism for the effect of topology on the adsorption behavior.

  10. Spatial and frequency domain ring source models for the single muscle fiber action potential

    DEFF Research Database (Denmark)

    Henneberg, Kaj-åge; R., Plonsey

    1994-01-01

    In the paper, single-fibre models for the extracellular action potential are developed that will allow the potential to the evaluated at an arbitrary field point in the extracellular space. Fourier-domain models are restricted in that they evaluate potentials at equidistant points along a line...... parallel to the fibre axis. Consequently, they cannot easily evaluate the potential at the boundary nodes of a boundary-element electrode model. The Fourier-domain models employ axial-symmetric ring source models, and thereby provide higher accuracy that the line source model, where the source is lumped...... including anisotropy show that the spatial models require extreme care in the integration procedure owing to the singularity in the weighting functions. With adequate sampling, the spatial models can evaluate extracellular potentials with high accuracy....

  11. Identification of Dewetting Stages and Preparation of Single Chain Gold Nanoparticle Rings by Colloidal Lithography.

    Science.gov (United States)

    Nagy, Norbert; Zámbó, Dániel; Pothorszky, Szilárd; Gergely-Fülöp, Eszter; Deák, András

    2016-02-02

    Massively parallel nanoparticle assembly was carried out by means of colloidal lithographic experiments over a silicon substrate supported (sub)microparticle Langmuir-Blodgett monolayer, using high purity aqueous solution of PEGylated gold nanoparticles. The size of the polystyrene template particles in the monolayer was varied between 608 nm and 2.48 μm, while gold nanoparticles with diameters between 18 and 65 nm were used. Thanks to the PEGylation of the gold nanoparticles, they could be used as tracer objects to follow the drying process. In this way, different dewetting stages could be identified in the confined space between and underneath the template polystyrene spheres. Depending on the concentration of the nanoparticles, the presented approach allows the preparation of single-particle width necklace structures composed of gold particles. At the same time, the high purity of the substrate as well as of the evolved particle rings is preserved and unwanted particle deposition on the substrate surface is minimized.

  12. Dielectronic recombination experiments with tungsten ions at the test storage ring and development of a single-particle detector at the cryogenic storage ring

    International Nuclear Information System (INIS)

    Spruck, Kaija

    2015-05-01

    This work is about electron-ion collision experiments at the ion storage rings of the Max Planck Institute for Nuclear Physics in Heidelberg. Absolute recombination rate coefficients of highly-charged tungsten ions featuring an open 4-f-shell structure have been measured at the heavy-ion storage ring TSR. The resulting plasma rate coefficients have been used to probe the significance of newly developed theoretical approaches. Plasma rate coefficients of highly-charged tungsten ions are in particular interesting for the development of plasma models for nuclear fusion reactors, since tungsten is a foreseeable impurity in the fusion plasma. In the relevant temperature range, the experimental results exceed the theoretical data used so far by up to a factor of 10, showing the need for more reliable theoretical calculations. Furthermore, based on the design of the detectors which have been used in the experiments at TSR, a movable single-particle detector for electron-ion recombination studies at the cryogenic storage ring CSR has been developed and installed within the scope of this work. The device has been designed specifically to meet the requirements of the CSR regarding low ion energies and cryogenic ambient temperature conditions. In a series of experiments, the detector was carefully characterised and successfully tested for its compatibility with these requirements. The detector was part of the infrastructure used for the room-temperature commissioning of CSR (2014) and is currently operated as a single-particle counter during the first cryogenic operation of CSR in 2015.

  13. Ionization of elements in medium power capacitively coupled argon plasma torch with single and double ring electrodes.

    Science.gov (United States)

    Ponta, Michaela; Frentiu, Maria; Frentiu, Tiberiu

    2012-06-01

    A medium power, low Ar consumption capacitively coupled plasma torch (275 W, 0.4 L min-1) with molybdenum tubular electrode and single or two ring electrodes in non-local thermodynamic equilibrium (LTE) was characterized with respect to its ability to achieve element ionization. Ionization degrees of Ca, Mg, Mn and Cd were determined from ionic-to-atomic emission ratio and ionization equilibrium according to Saha's equation. The ionization degrees resulted from the Saha equation were higher by 9-32% than those obtained from spectral lines intensity in LTE regime and closer to reality. A linear decrease of ionization with increase of ionization energy of elements was observed. Plasma torch with two ring electrodes provided higher ionization degrees (85 ± 7% Ca, 79 ± 7% Mn, 80 ± 7% Mg and 73 ± 8% Cd) than those in single ring arrangement (70 ± 6% Ca, 57 ± 7% Mn, 57 ± 8% Mg and 42 ± 9% Cd). The Ca ionization decreased linearly by up to 79 ± 4% and 53 ± 6% in plasma with two ring electrodes and single ring respectively in the presence of up to 400 µg mL-1 Na as interferent. The studied plasma was effective in element ionization and could be a potential ion source in mass spectrometry.

  14. Distribution of Ejecta in Analog Tephra Rings from Discrete Single and Multiple Subsurface Explosions

    Science.gov (United States)

    Graettinger, A. H.; Valentine, G. A.; Sonder, I.; Ross, P. S.; White, J. D. L.

    2015-12-01

    Buried-explosion experiments were used to investigate the spatial and volumetric distribution of extra-crater ejecta resulting from a range of explosion configurations with and without a crater present. Explosion configuration is defined in terms of scaled depth, the relationship between depth of burial and the cube root of explosion energy, where an optimal scaled depth explosion produces the largest crater diameter for a given energy. The multiple explosion experiments provide an analog for the formation of maar-diatreme ejecta deposits and the deposits of discrete explosions through existing conduits and hydrothermal systems. Experiments produced meter-sized craters with ejecta distributed between three major facies based on morphology and distance from the crater center. The proximal deposits form a constructional steep-sided ring that extends no more than two-times the crater radius away from center. The medial deposits form a low-angle continuous blanket that transitions with distance into the isolated clasts of the distal ejecta. Single explosion experiments produce a trend of increasing volume proportion of proximal ejecta as scaled depth increases (from 20-90% vol.). Multiple explosion experiments are dominated by proximal deposits (>90% vol.) for all but optimal scaled depth conditions (40-70% vol.). In addition to scaled depth, the presence of a crater influences jet shape and how the jet collapses, resulting in two end-member depositional mechanisms that produce distinctive facies. The experiments use one well-constrained explosion mechanism and, consequently, the variations in depositional facies and distribution are the result of conditions independent of that mechanism. Previous interpretations have invoked variations in fragmentation as the cause of this variability, but these experiments should help with a more complete reconstruction of the configuration and number of explosions that produce a tephra ring.

  15. Characterization of LP-MOCVD grown (Al, Ga)As/GaAs heterostructures by photoluminescence - Single heterojunction and inadvertent quantum wells

    Science.gov (United States)

    Zemon, S.; Norris, P.; Lee, J.; Lambert, G.; Black, J.

    1984-12-01

    Photoluminescence (PL) was used to detect rapid alloy compositional fluctuations which were found in (Al, Ga)As/GaAs heterostructures grown by low-pressure metal-organic chemical vapor deposition (LP-MOCVD). PL data are employed to estimate the thickness and aluminum composition of the resulting inadvertent quantum well. A way to eliminate these artifacts was found. Using the improved growth procedures, modulation-doped heterostructures showing two-dimensional electron-gas behavior were then achieved.

  16. AMS measurement of C-14 concentration in a single-year ring of a 2500-yr-old tree

    International Nuclear Information System (INIS)

    Sakurai, H.; Gandou, T.; Kato, W.; Sawaki, Y.; Matsumoto, T.; Aoki, T.; Matsuzaki, H.; Gunji, S.; Tokanai, F.

    2004-01-01

    The 14 C concentration in rings of an old tree that date back approximately 2500 yr has been measured at single-year intervals with a highly accurate liquid scintillation counter (LSC) (0.2%) to investigate the 11-yr periodicity of solar activity. To investigate the applicability of AMS to accurate 14 C measurement, 16 graphite samples produced from the cellulose of a single-year tree ring of a 2500-yr-old cedar were measured with the micro analysis laboratory tandem (MALT) accelerator, at The University of Tokyo, and the results were compared with the 14 C age determined using LSC. The average 14 C age of the single-year tree ring calculated from 16 measurements was 2496 ± 23 yr BP, corresponding to the statistical accuracy of 0.26%. This was consistent with the age of 2514 ± 23 yr BP determined using LSC within the acceptable error range, which indicates that accelerator mass spectrometry (AMS) is applicable for accurate 14 C measurement using multi-graphite for the same single-year tree ring

  17. Ring resonator-based single-chip 1x8 optical beam forming network in LPCVD waveguide technology

    NARCIS (Netherlands)

    Zhuang, L.; Roeloffzen, C.G.H.; Heideman, Rene; Borreman, A.; Meijerink, Arjan; van Etten, Wim; Koonen, A.M.J.; Leijtens, X.J.M.; van den Boom, H.P.A.; Verdurmen, E.J.M.; Molina Vázquez, J.

    2006-01-01

    Optical ring resonators (ORRs) are good candidates to provide continuously tunable delay in beam forming networks (BFNs) for phased array antenna systems. Delay and splitting/combining elements can be integrated on a single optical chip to form an OBFN. A state-of-the-art 1×8 OBFN chip has been

  18. A new approach to sum frequency generation of single-frequency blue light in a coupled ring cavity

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Petersen, Paul Michael

    2014-01-01

    We present a generic approach for the generation of tunable single-frequency light and demonstrate generation of more than 300 mW tunable light around 460 nm. One tapered diode laser is operated in a coupled ring cavity containing the nonlinear crystal and another tapered diode laser is sent thro...

  19. Multiphysics Modeling of a Single Channel in a Nuclear Thermal Propulsion Grooved Ring Fuel Element

    Science.gov (United States)

    Kim, Tony; Emrich, William J., Jr.; Barkett, Laura A.; Mathias, Adam D.; Cassibry, Jason T.

    2013-01-01

    In the past, fuel rods have been used in nuclear propulsion applications. A new fuel element concept that reduces weight and increases efficiency uses a stack of grooved discs. Each fuel element is a flat disc with a hole on the interior and grooves across the top. Many grooved ring fuel elements for use in nuclear thermal propulsion systems have been modeled, and a single flow channel for each design has been analyzed. For increased efficiency, a fuel element with a higher surface-area-to-volume ratio is ideal. When grooves are shallower, i.e., they have a lower surface area, the results show that the exit temperature is higher. By coupling the physics of turbulence with those of heat transfer, the effects on the cooler gas flowing through the grooves of the thermally excited solid can be predicted. Parametric studies were done to show how a pressure drop across the axial length of the channels will affect the exit temperatures of the gas. Geometric optimization was done to show the behaviors that result from the manipulation of various parameters. Temperature profiles of the solid and gas showed that more structural optimization is needed to produce the desired results. Keywords: Nuclear Thermal Propulsion, Fuel Element, Heat Transfer, Computational Fluid Dynamics, Coupled Physics Computations, Finite Element Analysis

  20. Size and strain tunable band alignment of black-blue phosphorene lateral heterostructures.

    Science.gov (United States)

    Li, Yan; Ma, Fei

    2017-05-17

    Single-element lateral heterostructures composed of black and blue phosphorene are not only free from lattice mismatch but also exhibit rich physical properties related to the seamlessly stitched interfaces, providing the building blocks for designing atomically thin devices. Using first-principles calculations, we investigate the influence of interface structure, size effect and strain engineering on the electronic structure, effective masses and band alignment of black-blue phosphorene lateral heterostructures. The lateral heterostructure with an octatomic-ring interface presents a strong metallic feature due to the interface states, while a metal-semiconductor transition takes place in the system with a hexatomic-ring interface upon hydrogen passivation. Following a reciprocal scaling law, the band gap is tuned in a wide energy range by synchronously increasing the widths of black and blue phosphorene or by only widening that of black phosphorene. Moreover, type-II band alignment is observed in the width ranges of 2.0-3.1 nm and 3.7-4.2 nm, out of which it is type-I. However, the band gap and effective masses show small changes if only the width of blue phosphorene is altered. When the lateral heterostructure is tensile loaded, the effective mass ratio of hole to electron is enlarged by an order of magnitude at a strain of 4% along the zigzag direction. Meanwhile, the band alignment undergoes a crossover from type-I to type-II at a strain of 2%, facilitating efficient electron-hole separation for light detection and harvesting.

  1. A single-molecular twin rotor: correlated motion of two pyrimidine rings coordinated to copper.

    Science.gov (United States)

    Takara, Yusuke; Kusamoto, Tetsuro; Masui, Tatsuya; Nishikawa, Michihiro; Kume, Shoko; Nishihara, Hiroshi

    2015-02-18

    We describe the two correlated rotational motions of pyrimidine rings in 4,4'-dimethyl-2,2'-bipyrimidine ligated to Cu(i). The two pyrimidine rings delimited by anthryl and phenanthroline groups rotate to afford three isomers. (1)H NMR measurements revealed that the two rotational processes were activated at different temperatures. Cyclic voltammetry gave the kinetic and thermodynamic parameters that provide clear evidence of the correlation between the two rotational steps.

  2. Multifloquet to Single Electronic Channel Transition in the Transport Properties of a Resistive 1D Driven Disordered Ring

    Science.gov (United States)

    Foieri, Federico; Arrachea, Liliana; Sánchez, María José

    2007-12-01

    We investigate the dc response of a 1D disordered ring coupled to a reservoir and driven by a magnetic flux with a linear dependence on time. We identify two regimes: (i) A localized or large length L regime, characterized by a dc conductance, gdc, whose probability distribution P(gdc) is identical to the one exhibited by a 1D wire of the same length L and disorder strength placed in a two terminal Landauer setup and (ii) a multifloquet regime for small L and weak coupling to the reservoir, which exhibits large currents and conductances that can be gdc>1, in spite of the fact that the ring contains spinless electrons and a single electronic transmission channel. The crossover length between the multifloquet to the single-channel transport regime Lc is controlled by the coupling to the reservoir.

  3. Gate-tunable quantum dot in a high quality single layer MoS2 van der Waals heterostructure

    Science.gov (United States)

    Pisoni, Riccardo; Lei, Zijin; Back, Patrick; Eich, Marius; Overweg, Hiske; Lee, Yongjin; Watanabe, Kenji; Taniguchi, Takashi; Ihn, Thomas; Ensslin, Klaus

    2018-03-01

    We have fabricated an encapsulated monolayer MoS2 device with metallic ohmic contacts through a pre-patterned hexagonal boron nitride (hBN) layer. In the bulk, we observe an electron mobility as high as 3000 cm2/Vs at a density of 7 × 1012 cm-2 at a temperature of 1.7 K. Shubnikov-de Haas oscillations start at magnetic fields as low as 3.3 T. By realizing a single quantum dot gate structure on top of hBN, we are able to confine electrons in MoS2 and observe the Coulomb blockade effect. By tuning the middle gate voltage, we reach a double dot regime where we observe the standard honeycomb pattern in the charge stability diagram.

  4. Heterostructured semiconductor single-walled carbon nanotube films for solution-processed high-performance field-effect transistors

    Science.gov (United States)

    Park, Noh-Hwal; Lee, Seung-Hoon; Jeong, Seung-Hyeon; Khim, Dongyoon; Kim, Yun Ho; Yoo, Sungmi; Noh, Yong-Young; Kim, Jang-Joo

    2018-03-01

    In this paper, we report a simple and effective method to simultaneously achieve a high charge-carrier mobility and low off current in conjugated polymer-wrapped semiconducting single-walled carbon nanotube (s-SWNT) transistors by applying a SWNT bilayer. To achieve the high mobility and low off current, highly purified and less purified s-SWNTs are successively coated to form the semiconducting layer consisting of poly (3-dodecylthiophene-2,5-diyl) (P3DDT)-wrapped high-pressure carbon mono oxide (HiPCO) SWNT (P3DDT-HiPCO) and poly (9, 9-di-n-dodecylfluorene) (PFDD)-wrapped plasma discharge (PD) SWNT (PFDD-PD). The SWNT transistors with bilayer SWNT networked film showed highly improved hole field-effect mobility (6.18 ± 0.85 cm2V-1s-1 average), on/off current ratio (107), and off current (˜1 pA). Thus, the combination of less purified PFDD-PD (98%-99%) charge-injection layer and highly purified s-P3DDT-HiPCO (>99%) charge-transport layer as the bi-layered semiconducting film achieved high mobility and low off current simultaneously.

  5. Bidirectional single-longitudinal mode SOA-fiber ring laser based on optical filter assisted gain starvation

    Science.gov (United States)

    Khalil, Kamal; Al-Arifi, Fares; Al-Otaibi, Mohammed; Sabry, Yasser M.; Khalil, Diaa

    2015-03-01

    Generation of a single-longitudinal mode (SLM) in bidirectional ring lasers has direct impact on the laser linewidth and dynamic range of operation, when used in rotation sensing applications. Besides, operating at a specific wavelength helps in optimizing the performance of the system components. In this work, we report a novel method for generating SLM in bidirectional SOA-fiber ring laser using mechanically tunable Fabry-Perot filter with 1-nm bandwidth. The method is based on gain starvation by tuning the central wavelength of the filter in the blue edge of the gain-wavelength response. By adjusting the SOA driving current, the oscillation condition is satisfied mainly for single mode and bidirectional operation can be achieved simultaneously. The SLM operation is verified by monitoring the beating signal between the modes on an RF spectrum analyzer. Using an SOA with a small-signal gain of 20 dB at 300 mA pumping current and a gain bandwidth of 100 nm centered around 1490 nm; the central wavelength of the ring laser could be tuned from 1440 nm to 1480 nm with a side-mode suppression ratio of 25 dB.

  6. Ring-laser optical flip-flop memory with single active element

    NARCIS (Netherlands)

    Zhang, S.; Liu, Y.S.; Lenstra, D.; Hill, M. T.; Ju, H. K.; Khoe, G.D.; Dorren, H.J.S.

    2004-01-01

    We present a novel optical flip-flop configuration that consists of two unidirectional ring lasers with separate cavities but sharing the same active element unidirectionally. We show that in such a configuration light in the lasing cavity can suppress lasing in the other cavity so that this system

  7. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe{sub 3}O{sub 4} nanoparticle rings

    Energy Technology Data Exchange (ETDEWEB)

    Takeno, Yumu [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Murakami, Yasukazu, E-mail: murakami@tagen.tohoku.ac.jp, E-mail: kannanmk@uw.edu; Shindo, Daisuke [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Center for Emergent Matter Science, RIKEN, Wako 351-0198 (Japan); Sato, Takeshi [Hitachi High-Technologies Corporation, 1040 Ichige, Hitachinaka-shi, Ibaraki 312-0033 (Japan); Tanigaki, Toshiaki [Center for Emergent Matter Science, RIKEN, Wako 351-0198 (Japan); Central Research Laboratory, Hitachi, Ltd., Hatoyama 350-0395 (Japan); Park, Hyun Soon [Center for Emergent Matter Science, RIKEN, Wako 351-0198 (Japan); Department of Materials Science and Engineering, Dong-A University, Busan 604-714, Republic of South Korea (Korea, Republic of); Ferguson, R. Matthew [LodeSpin Labs, P.O. Box 95632, Seattle, Washington 91845 (United States); Krishnan, Kannan M., E-mail: murakami@tagen.tohoku.ac.jp, E-mail: kannanmk@uw.edu [Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195-2120 (United States)

    2014-11-03

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe{sub 3}O{sub 4} nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy.

  8. Detecting mode hopping in single-longitudinal-mode fiber ring lasers based on an unbalanced fiber Michelson interferometer.

    Science.gov (United States)

    Ma, Mingxiang; Hu, Zhengliang; Xu, Pan; Wang, Wei; Hu, Yongming

    2012-10-20

    A method of detecting mode hopping for single-longitudinal-mode (SLM) fiber ring lasers has been proposed and experimentally demonstrated. The method that is based on an unbalanced Michelson interferometer (MI) utilizing phase generated carrier modulation instantly transforms mode-hopping dynamics into steep phase changes of the interferometer. Multiform mode hops in an SLM erbium-doped fiber ring laser with an 18.6 MHz mode spacing have been detected exactly in real-time domain and discussed in detail. Numerical results show that the MI-based method has a high testing sensitivity for identifying mode hopping, which will play a significant role in evaluating the output stability of SLM fiber lasers.

  9. Ultrahigh efficiencies in vertical epitaxial heterostructure architectures

    Science.gov (United States)

    Fafard, S.; York, M. C. A.; Proulx, F.; Valdivia, C. E.; Wilkins, M. M.; Arès, R.; Aimez, V.; Hinzer, K.; Masson, D. P.

    2016-02-01

    Optical to electrical power converting semiconductor devices were achieved with breakthrough performance by designing a Vertical Epitaxial Heterostructure Architecture. The devices are featuring modeled and measured conversion efficiencies greater than 65%. The ultrahigh conversion efficiencies were obtained by monolithically integrating several thin GaAs photovoltaic junctions tailored with submicron absorption thicknesses and grown in a single crystal by epitaxy. The heterostructures that were engineered with a number N of such ultrathin junctions yielded an optimal external quantum efficiencies approaching 100%/N. The heterostructures are capable of output voltages that are multiple times larger than the corresponding photovoltage of the input light. The individual nanoscale junctions are each generating up to ˜1.2 V of output voltage when illuminated in the infrared. We compare the optoelectronic properties of phototransducers prepared with designs having 5 to 12 junctions and that are exhibiting voltage outputs between >5 V and >14 V.

  10. Aspects of Lubrication in a Reciprocating Single-ring Test Rig and Further Implementation to Engine Applications

    Directory of Open Access Journals (Sweden)

    P.S. Dellis

    2017-06-01

    Full Text Available A major concern in modern engine design is the issue of the lubrication regime at the piston-liner assembly. To fully understand the complex lubrication phenomena between the piston-rings and cylinder liner in reciprocating engines and at the same time achieve minimal energy losses with the oncoming emission regulations, it is important to characterize the developing oil film. This dynamic process involves many factors, such as piston-ring and piston dynamics, starved lubrication, liner geometry deformation, lubricant - additive degradation and blow-by, which, in turn, enhance the difficulty of interpreting engine experimental results. The simplified test rig is used as a platform to develop oil film measuring techniques and study experimental results from different sensors by means of a robust and solid technique without the engine testing ambiguities, at different lubrication regimes. This paper is focused on experimental findings from the simplified test rig and how these can be applied on specially modified engines, with the respective sensors fitted. A comparison between the single-ring test rig and the engine visualization results is attempted so that similar forms of cavitation identified, be further studied. Moreover, a calibration coefficient for LIF engine experiments can be derived via the simplified test rig arrangement.

  11. Heterostructures and quantum devices

    CERN Document Server

    Einspruch, Norman G

    1994-01-01

    Heterostructure and quantum-mechanical devices promise significant improvement in the performance of electronic and optoelectronic integrated circuits (ICs). Though these devices are the subject of a vigorous research effort, the current literature is often either highly technical or narrowly focused. This book presents heterostructure and quantum devices to the nonspecialist, especially electrical engineers working with high-performance semiconductor devices. It focuses on a broad base of technical applications using semiconductor physics theory to develop the next generation of electrical en

  12. Tunable single-polarization single-longitudinal-mode erbium-doped fiber ring laser employing a CMFBG filter and saturable absorber

    Science.gov (United States)

    Feng, Suchun; Lu, Shaohua; Peng, Wanjing; Li, Qi; Feng, Ting; Jian, Shuisheng

    2013-04-01

    A tunable single-polarization single-longitudinal-mode (SLM) erbium-doped fiber ring laser is proposed and demonstrated. For the first time as we know, a chirped moiré fiber Bragg grating (CMFBG) filter with ultra-narrow transmission band and a uniform fiber Bragg grating (UFBG) are used to select the laser longitudinal mode. The stable SLM operation of the fiber laser is guaranteed by the combination of the CMFBG filter and 3 m unpumped erbium-doped fiber acting as a saturable absorber. The single polarization operation of the fiber laser is obtained by using an inline broadband polarizer. A tuning range of about 0.7 nm with about 0.1 nm step is achieved by stretching the uniform FBG.

  13. Iron-YBCO heterostructures and their application for trapped field superconducting motor

    International Nuclear Information System (INIS)

    Granados, X; Bartolome, E; Obradors, X; Tornes, M; Rodrigues, L; Gawalek, W; McCulloch, M; Hughes, D Dew; Campbell, A; Coombs, T; Ausloos, M; Cloots, R

    2006-01-01

    In this work we report on the magnetic behavior of the heterostructures formed by bulk based YBCO rings and ferromagnetic yoke. The magnetization cycle has been performed by an In-Field Hall Mapping technique. A video-like recording of the magnetization process makes it possible to obtain the magnetization of selected areas. The current flowing through the superconducting rings can be deduced from the magnetic field maps. The displacement of the peak of magnetization due to the flux reversal produced by the magnetization of the yoke is also considered. These hybrid heterostructures formed by ferromagnetic and superconducting material have been applied in the construction of the rotor for a brushless AC motor. The design and construction of this machine was carried out within the framework of the TMR Network SUPERMACHINES. The rotor has been designed in a quadrupolar configuration by cutting large YBCO 'window frames' from seeded melt-textured single domain YBCO pellets. This rotor has been coupled to a conventional stator of copper coils wound on an iron armature. The stator can be excited both in bipolar or quadrupolar mode. We report on the behaviour of the motor after a field cooling process when excited in quadrupolar mode

  14. Screening Test Procedure For Long Life Single Mode Step Index Separate Confinement Heterostructure Single Quantum Well (Sinsch-Sqw) Laser Diodes

    Science.gov (United States)

    Fritz, William J.

    1989-06-01

    An experiment was conducted to establish an effective burn-in and screening procedure for long life SINSCH-SQW laser diodes. The laser diodes were grown by MOCVD and processed with 20μ wide oxide defined stripes. The devices had a high reflective back facet coating with a small etalon bonded to a passivated front facet to ensure single mode operation. The laser diodes were bonded p-side up to copper heat sinks using indium solder. A total of 48 devices were selected prior to burn-in and were operated at 200mA constant current for 2000 hours at an average heat sink temperature of 55°C. The average initial output power was 45mW per device. At the end of the test, the output powers ranged from lmW to 85mW. Most of the devices with the low final power failed catastrophically within 24 hours from the start of the test. Many laser diodes showed very little change in output power while others degraded gradually by varying amounts. Failure analysis showed that failures were facet, bulk, or heat sink related. The temporal output power degradations (i.e., gradual degradation, etc.) can be explained by the identified failure mechanisms. From the test results and failure analysis, a screening strategy based on inspection and burn-in can be devised to reject devices that may fail early. Also, improvements in processing can provide potential yield improvements. After accounting for degradation related to processing, a very long material lifetime is predicted for these SINSCH-SQW laser diodes.

  15. Integration of an Optical Ring Resonator Biosensor into a Self-Contained Microfluidic Cartridge with Active, Single-Shot Micropumps

    Directory of Open Access Journals (Sweden)

    Sascha Geidel

    2016-09-01

    Full Text Available While there have been huge advances in the field of biosensors during the last decade, their integration into a microfluidic environment avoiding external tubing and pumping is still neglected. Herein, we show a new microfluidic design that integrates multiple reservoirs for reagent storage and single-use electrochemical pumps for time-controlled delivery of the liquids. The cartridge has been tested and validated with a silicon nitride-based photonic biosensor incorporating multiple optical ring resonators as sensing elements and an immunoassay as a potential target application. Based on experimental results obtained with a demonstration model, subcomponents were designed and existing protocols were adapted. The newly-designed microfluidic cartridges and photonic sensors were separately characterized on a technical basis and performed well. Afterwards, the sensor was functionalized for a protein detection. The microfluidic cartridge was loaded with the necessary assay reagents. The integrated pumps were programmed to drive the single process steps of an immunoassay. The prototype worked selectively, but only with a low sensitivity. Further work must be carried out to optimize biofunctionalization of the optical ring resonators and to have a more suitable flow velocity progression to enhance the system’s reproducibility.

  16. Visible near-infrared light scattering of single silver split-ring structure made by nanosphere lithography.

    Science.gov (United States)

    Okamoto, Toshihiro; Fukuta, Tetsuya; Sato, Shuji; Haraguchi, Masanobu; Fukui, Masuo

    2011-04-11

    We succeeded in making a silver split-ring (SR) structure of approximately 130 nm in diameter on a glass substrate using a nanosphere lithography technique. The light scattering spectrum in visible near-infrared region of a single, isolated SR was measured using a microscope spectroscopy optical system. The electromagnetic field enhancement spectrum and distribution of the SR structure were simulated by the finite-difference time-domain method, and the excitation modes were clarified. The long wavelength peak in the light scattering spectra corresponded to a fundamental LC resonance mode excited by an incident electric field. It was shown that a single SR structure fabricated as abovementioned can operate as a resonator and generate a magnetic dipole. © 2011 Optical Society of America

  17. Diverse Functionalities of Vertically Stacked Graphene/Single layer n-MoS2/SiO2/p-GaN Heterostructures.

    Science.gov (United States)

    Perumal, Packiyaraj; Karuppiah, Chelladurai; Liao, Wei-Cheng; Liou, Yi-Rou; Liao, Yu-Ming; Chen, Yang-Fang

    2017-08-30

    Integrating different dimentional materials on vertically stacked p-n hetero-junctions have facinated a considerable scrunity and can open up excellent feasibility with various functionalities in opto-electronic devices. Here, we demonstrate that vertically stacked p-GaN/SiO 2 /n-MoS 2 /Graphene heterostructures enable to exhibit prominent dual opto-electronic characteristics, including efficient photo-detection and light emission, which represents the emergence of a new class of devices. The photoresponsivity was found to achieve as high as ~10.4 AW -1 and the detectivity and external quantum efficiency were estimated to be 1.1 × 10 10 Jones and ~30%, respectively. These values are superier than most reported hererojunction devices. In addition, this device exhibits as a self-powered photodetector, showing a high responsivity and fast response speed. Moreover, the device demonstrates the light emission with low turn-on voltage (~1.0 V) which can be realized by electron injection from graphene electrode and holes from GaN film into monolayer MoS 2 layer. These results indicate that with a suitable choice of band alignment, the vertical stacking of materials with different dimentionalities could be significant potential for integration of highly efficient heterostructures and open up feasible pathways towards integrated nanoscale multi-functional optoelectronic devices for a variety of applications.

  18. 1  kHz single-frequency 2.09  μm Ho:YAG ring laser.

    Science.gov (United States)

    Na, Quanxin; Gao, Chunqing; Wang, Qing; Zhang, Yixuan; Gao, Mingwei; Zhang, Meng; Wang, Yujia

    2017-09-01

    In this paper, we report the experimental realization of a high-repetition-rate single-frequency Ho-doped yttrium aluminum garnet (Ho:YAG) ring laser at 2.09 μm. Single-frequency operation of the ring laser is achieved by injection-seeding with a continuous wave (CW) Ho:YAG non-planar ring oscillator (NPRO) laser. The output energy of the ring laser is 6.24 mJ with a pulse width of 172 ns and a repetition rate of 1 kHz. The beam quality M 2 -factor is measured to be ∼1.3 at the maximum output energy. The half-width of the pulse spectrum is measured to be 2.61 MHz by a heterodyne technique.

  19. Direct Production of High $p_T$ Single Photons at the CERN Intersecting Storage Rings

    CERN Document Server

    Diakonou, M; Resvanis, L.K.; Filippas, T.A.; Fokitis, E.; Trakkas, C.; Cnops, A.M.; Cobb, J.H.; Fowler, E.C.; Hood, D.M.; Iwata, S.; Palmer, R.B.; Rahm, D.C.; Rehak, P.; Stumer, I.; Fabjan, C.W.; Fields, T.; Lissauer, D.; Mannelli, I.; Molzon, W.; Mouzourakis, P.; Nakamura, K.; Nappi, A.; Willis, W.J.

    1979-01-01

    Single photon production in pp collisions at 30 < √ s < 62 GeV has been measured with liquid-argon-lead calorimeters at the CERN ISR. This process remains approximately constant with increasing √ s . For fixed √ s , the single photon to π 0 ratio increases strongly with increase in p T . The γ π 0 ratio is about 0.2 for p T above 4.5 GeV/c.

  20. Thon rings from amorphous ice and implications of beam-induced Brownian motion in single particle electron cryo-microscopy.

    Science.gov (United States)

    McMullan, G; Vinothkumar, K R; Henderson, R

    2015-11-01

    We have recorded dose-fractionated electron cryo-microscope images of thin films of pure flash-frozen amorphous ice and pre-irradiated amorphous carbon on a Falcon II direct electron detector using 300 keV electrons. We observe Thon rings [1] in both the power spectrum of the summed frames and the sum of power spectra from the individual frames. The Thon rings from amorphous carbon images are always more visible in the power spectrum of the summed frames whereas those of amorphous ice are more visible in the sum of power spectra from the individual frames. This difference indicates that while pre-irradiated carbon behaves like a solid during the exposure, amorphous ice behaves like a fluid with the individual water molecules undergoing beam-induced motion. Using the measured variation in the power spectra amplitude with number of electrons per image we deduce that water molecules are randomly displaced by a mean squared distance of ∼1.1 Å(2) for every incident 300 keV e(-)/Å(2). The induced motion leads to an optimal exposure with 300 keV electrons of 4.0 e(-)/Å(2) per image with which to observe Thon rings centred around the strong 3.7 Å scattering peak from amorphous ice. The beam-induced movement of the water molecules generates pseudo-Brownian motion of embedded macromolecules. The resulting blurring of single particle images contributes an additional term, on top of that from radiation damage, to the minimum achievable B-factor for macromolecular structure determination. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  1. The development of evaluating tensile property method used the single notched ring test

    International Nuclear Information System (INIS)

    Bae, Bong Kook; Koo, Jae Mean; Seok, Chang Sung

    2003-01-01

    In this study, the single notched specimen which was proposed the previous study was used to evaluate of the transverse tensile property of zircaloy cladding. The single notched specimen has notches which give stress intensity effect, so both FEM and experiment are needed for the same time. Take a coincidence of tensile behavior about both FEM and experiment, then obtain stress and strain from FEM only. The influence of notch was estimated by comparing the result of experimental, FEM. Then the relationship between stress-strain and displacement was evaluated

  2. Generation of broadband mid-IR and UV light in gas-filled single-ring hollow-core PCF.

    Science.gov (United States)

    Cassataro, Marco; Novoa, David; Günendi, Mehmet C; Edavalath, Nitin N; Frosz, Michael H; Travers, John C; Russell, Philip St J

    2017-04-03

    We report generation of an ultrafast supercontinuum extending into the mid- infrared in gas-filled single-ring hollow-core photonic crystal fiber (SR-PCF) pumped by 1.7 µm light from an optical parametric amplifier. The simple fiber structure offers shallow dispersion and flat transmission in the near and mid-infrared, enabling the generation of broadband spectra extending from 270 nm to 3.1 µm, with a total energy of a few µJ. In addition, we demonstrate the emission of ultraviolet dispersive waves whose frequency can be tuned simply by adjusting the pump wavelength. SR-PCF thus constitutes an effective means of compressing and delivering tunable ultrafast pulses in the near and mid-infrared spectral regions.

  3. A tuneable, power efficient and narrow single longitudinal mode fibre ring laser using an inline dual-taper fibre Mach–Zehnder filter

    International Nuclear Information System (INIS)

    Ahmad, H; Dernaika, M; Alimadad, M; Ibrahim, M F; Lim, K S; Harun, S W; Kharraz, O M

    2014-01-01

    A tuneable single longitudinal mode fibre ring laser with dual-taper fibre filter is proposed and experimentally demonstrated in this paper. The single longitudinal mode operation, and power limitations for a Mach–Zehnder interferometer filter generated from a single mode fibre, are verified for the first time. Incorporating an in-line taper fibre Mach–Zehnder interferometer filter inside the laser ring cavity causes a spatial mode beating interference, resulting in a passive narrow band filter with the ability to generate stable single longitudinal modes. The single longitudinal mode achieves a side mode suppression ratio of more than 60 dB using low pump power. The tuneability of the fibre laser ranges from 1525 to 1562 nm using a passive band pass filter. A study of the stability and limitation of the single longitudinal mode in the Mach–Zehnder tapered fibre is also presented. (paper)

  4. Fabry-Pérot microcavity modes observed in the micro-photoluminescence spectra of the single nanowire with InGaAs/GaAs heterostructure.

    Science.gov (United States)

    Yang, Lin; Motohisa, Junichi; Fukui, Takashi; Jia, Lian Xi; Zhang, Lei; Geng, Ming Min; Chen, Pin; Liu, Yu Liang

    2009-05-25

    We report on the fabrication of the nanowires with InGaAs/GaAs heterostructures on the GaAs(111)B substrate using selective-area metal organic vapor phase epitaxy. Fabry-Pérot microcavity modes were observed in the nanowires with perfect end facets dispersed onto the silicon substrate and not observed in the free-standing nanowires. We find that the calculated group refractive indices only considering the material dispersion do not agree with the experimentally determined values although this method was used by some researchers. The calculated group refractive indices considering both the material dispersion and the waveguide dispersion agree with the experimentally determined values well. We also find that Fabry-Pérot microcavity modes are not observable in the nanowires with the width less than about 180 nm, which is mainly caused by their poor reflectivity at the end facets due to their weak confinement to the optical field.

  5. Ring interferometry

    CERN Document Server

    Malykin, Grigorii B; Zhurov, Alexei

    2013-01-01

    This monograph is devoted to the creation of a comprehensive formalism for quantitative description of polarized modes' linear interaction in modern single-mode optic fibers. The theory of random connections between polarized modes, developed in the monograph, allows calculations of the zero shift deviations for a fiber ring interferometer. The monograph addresses also the

  6. Feedback for suppression of single-bunch transverse instability in electron-positron storage rings

    International Nuclear Information System (INIS)

    Smaluk, V; Sukhanov, D; Oreshonok, V; Cherepanov, V; Kiselev, V

    2012-01-01

    Transverse head-tail instability is a severe limitation of a single-bunch beam current in circular accelerators. Applicability and efficiency of feedbacks for suppression of the instability is analyzed. Both chromatic and nonlinear effects have been taken into account to understand the processes of excitation and damping of the instability. Analytical estimations are compared with the results of experiments and numerical simulations. A feedback system has been developed, installed and commissioned at the VEPP-4M electron-positron collider. An original scheme of the kicker powering has been developed to provide the necessary performance with minimal expenses. Real-time digital data processing performed by a code running in an FPGA module provides high efficiency and flexibility of the system. During the system commissioning, a more than threefold increase of intensity of the VEPP-4M single-bunch beam has been achieved.

  7. Magnetic Heterostructures Advances and Perspectives in Spinstructures and Spintransport

    CERN Document Server

    Bader, Samuel D

    2008-01-01

    Magnetic heterostructures constitute an important field in magnetism and nanotechnology, which has developed over the past fifteen years due to important advances in epitaxial- growth techniques and lithographic processes. Magnetic heterostructures combine different physical properties which do not exist in nature. Examples are semiconductors/ferromagnets, superconductors/ferromagnets, and ferromagnets/antiferromagnets. These combinations display rich and novel physical properties different from those that exit in any single one of them. Interlayer exchange coupling, exchange bias, proximity effects, giant magneto-resistance, tunneling magneto-resistance, spininjection and spintransport are examples of new physical phenomena that rely on the combination of different materials layers. Since the literature on magnetic heterostructures is widely spread and highly specialized, the situation calls for a book that provides an overview of the basics and the state of the art of magnetic heterostructures. These contri...

  8. High-power actively Q-switched single-mode 1342 nm Nd:YVO4 ring laser, injection-locked by a cw single-frequency microchip laser.

    Science.gov (United States)

    Koch, Peter; Bartschke, Juergen; L'huillier, Johannes A

    2015-11-30

    In this paper we report on the realization of a single-mode Q-switched Nd:YVO4 ring laser at 1342 nm. Unidirectional and single-mode operation of the ring laser is achieved by injection-locking with a continuous wave Nd:YVO4 microchip laser, emitting a single-frequency power of up to 40 mW. The ring laser provides a single-mode power of 13.9 W at 10 kHz pulse repetition frequency with a pulse duration of 18.2 ns and an excellent beam quality (M2 laser, a power of 8.7 W at 671 nm with a pulse duration of 14.8 ns and a beam propagation factor of M2 < 1.1 is obtained. The 671 nm radiation features a long-term spectral width of 75 MHz.

  9. Characterization of Al{sub x}Ga{sub 1-x}As/GaAs heterostructures for single quantum wells grown by a solid arsenic MOCVD system

    Energy Technology Data Exchange (ETDEWEB)

    Castillo-Ojeda, R. [Universidad Politecnica de Pachuca, Km. 20, Rancho Luna, Ex-Hacienda de Santa Barbara, Municipio de Zempoala, Hidalgo 43830 (Mexico); Diaz-Reyes, J., E-mail: jdiazr2001@yahoo.co [Instituto Politecnico Nacional, Centro de Investigacion en Biotecnologia Aplicada, CIBA-IPN, Ex Hacienda de San Juan Molino, Km. 1.5. Tepetitla, Tlaxcala 90700 (Mexico); Galvan-Arellano, M.; Pena-Sierra, R. [CINVESTAV-IPN, Depto. de Ing. Electrica, SEES. Apdo. 14-740, Mexico, D.F. 07000 (Mexico)

    2011-06-15

    This work presents the results of the growth and characterization of Al{sub x}Ga{sub 1-x}As/GaAs multilayer structures obtained in a metallic-arsenic-based-MOCVD system. The main goal is to explore the ability of the growth system to grow high quality multilayer structures like quantum wells. The use of metallic arsenic could introduce important differences in the growth process due to the absence of the hydride group V precursor (AsH{sub 3}), which manifests in the electrical and optical characteristics of both GaAs and Al{sub x}Ga{sub 1-x}As layers. The characterization of these epilayers and structures was performed using low-temperature photoluminescence, Hall effect measurements, X-ray diffraction, Raman spectroscopy, secondary ion mass spectroscopy (SIMS) and Atomic Force Microscopy (AFM). - Research highlights: {yields} This work is reported the growth of AlxGa1-xAs/GaAs/AlxGa1-xAs heterostructures by a solid arsenic based MOCVD system. {yields} The results obtained with this system are comparable with those obtained with the traditional arsine based growth system. {yields} The main limitation of the alternative MOCVD system is related to the lack of monoatomic hydrogen on the growth surface that acts modifying the surface kinetics and enhancing the carbon incorporation. {yields} The experimental results indicate that it can be grown AlxGa1-xAs using elemental arsenic by MOCVD, which can be used to optoelectronic devices.

  10. Experimental synchronization of chaos in a large ring of mutually coupled single-transistor oscillators: Phase, amplitude, and clustering effects

    Science.gov (United States)

    Minati, Ludovico

    2014-12-01

    In this paper, experimental evidence of multiple synchronization phenomena in a large (n = 30) ring of chaotic oscillators is presented. Each node consists of an elementary circuit, generating spikes of irregular amplitude and comprising one bipolar junction transistor, one capacitor, two inductors, and one biasing resistor. The nodes are mutually coupled to their neighbours via additional variable resistors. As coupling resistance is decreased, phase synchronization followed by complete synchronization is observed, and onset of synchronization is associated with partial synchronization, i.e., emergence of communities (clusters). While component tolerances affect community structure, the general synchronization properties are maintained across three prototypes and in numerical simulations. The clusters are destroyed by adding long distance connections with distant notes, but are otherwise relatively stable with respect to structural connectivity changes. The study provides evidence that several fundamental synchronization phenomena can be reliably observed in a network of elementary single-transistor oscillators, demonstrating their generative potential and opening way to potential applications of this undemanding setup in experimental modelling of the relationship between network structure, synchronization, and dynamical properties.

  11. Heterostructure infrared photovoltaic detectors

    Science.gov (United States)

    Rogalski, Antoni

    2000-08-01

    HgCdTe remains the most important material for infrared (IR) photodetectors despite numerous attempts to replace it with alternative materials such as closely related mercury alloys (HgZnTe, HgMnTe), Schottky barriers on silicon, SiGe heterojunctions, GaAs/AlGaAs multiple quantum wells, InAs/GaInSb strained layer superlattices, high temperature superconductors and especially two types of thermal detectors: pyroelectric detectors and silicon bolometers. It is interesting, however, that none of these competitors can compete in terms of fundamental properties. In addition, HgCdTe exhibits nearly constant lattice parameter which is of extreme importance for new devices based on complex heterostructures. The development of sophisticated controllable vapour phase epitaxial growth methods, such as MBE and MOCVD, has allowed fabrication of almost ideally designed heterojunction photodiodes. In this paper, examples of novel devices based on heterostructures operating in the long wavelength, middle wavelength and short wavelength spectral ranges are presented. Recently, more interest has been focused on p-n junction heterostructures. As infrared technology continues to advance, there is a growing demand for multispectral detectors for advanced IR systems with better target discrimination and identification. HgCdTe heterojunction detectors offer wavelength flexibility from medium wavelength to very long wavelength and multicolour capability in these regions. Recent progress in two-colour HgCdTe detectors is also reviewed.

  12. Data for increase of Lymantria dispar male survival after topical application of single-stranded RING domain fragment of IAP-3 gene of its nuclear polyhedrosis virus

    Science.gov (United States)

    Oberemok, Volodymyr V.; Laikova, Kateryna V.; Zaitsev, Aleksei S.; Gushchin, Vladimir A.; Skorokhod, Oleksii A.

    2016-01-01

    This data article is related to the research article entitled “The RING for gypsy moth control: topical application of fragment of its nuclear polyhedrosis virus anti-apoptosis gene as insecticide” [1]. This article reports on significantly higher survival of gypsy moth Lymantria dispar male individuals in response to topical application of single-stranded DNA, based on RING (really interesting new gene) domain fragment of LdMNPV (L. dispar multicapsid nuclear polyhedrosis virus) IAP-3 (inhibitor of apoptosis) gene and acted as DNA insecticide. PMID:27054151

  13. Electronic properties of graphene-based heterostructures

    Science.gov (United States)

    Skachkova, V. A.; Baranava, M. S.; Hvazdouski, D. C.; Stempitsky, V. R.

    2017-11-01

    Heterostructures based on graphene were investigated by using density function theory (DFT). It is found that energy gap appear in ZnS-graphene heterostructure. Heterostructures graphene-ZnO and graphene-phosphorene have almost zero-band gap. Binding energy between heterostructure layers was determined.

  14. Room temperature single longitudinal mode laser output at 1645 nm from a laser-diode pumped Er:YAG nonplanar ring oscillator.

    Science.gov (United States)

    Yao, B Q; Yu, X; Liu, X L; Duan, X M; Ju, Y L; Wang, Y Z

    2013-04-08

    We report on a monolithic 1645 nm Er:YAG nonplanar ring oscillator (NPRO) resonantly pumped by a fiber-coupled laser diode. In the experiment, an up to 550 mW single frequency laser output at 1645.2 nm was obtained, corresponding to a slope efficiency of 19.1% and an absolute efficiency of 6.0%. The beam quality M2 was measured to be 2.1 at the highest output power.

  15. Future applications of heterostructures

    Science.gov (United States)

    König, Ulf

    1996-01-01

    In this review the status and future of heterostructure devices is discussed. The author concentrates on III/V and Si/SiGe. Performance and applications are folded to the data and expectations of the micro- and opto-electronic market and to the traditional Si-mainstream. New trends, i.e. the SIA-roadmap, are checked how heterodevices can fit in. Only the most attractive candidates for applications are considered, i.e. the heterobipolar-, the hetero field effect-transistors, the resonant tunnel diode and to a less extent, some optoelectronic devices. Considered figures of merit are frequencies, transconductance, noise at high and low frequencies, threshold voltage, power delay, threshold current and quantum efficiencies. It is pointed out how to optimize those by material and design. Extrapolations to the future potential of heterodevices are made, just taking the claimed scaling of lateral dimensions into consideration. Field of applications are presented, where heterodevices offer exclusive qualities, i.e. high frequency transmission and sensors, and new mixed systems. In the case of logic the trend goes to nanoscaled devices and ICs targeting nanoelectronics beyond traditional electronics. Heterostructure layers allow a vertical nanoscaling and thus give an additional degree of freedom for designing and optimation. It is an attractive challenge for scientists and engineers to solve the related technological problems like thin, low thermal budget oxides, like defect free buffer layers etc. Special attention is put on Si/SiGe, which is now on an upswing in electronics and photonics.

  16. Electronic homogeneity of nanowire heterostructure Light Emitting Diodes (LEDs)

    Science.gov (United States)

    Selcu, Camelia; May, Brelon J.; Sarwar, A. T. M. Golam; Myers, Roberto C.

    In addition to low defect densities and great tunability bandgap within a single heterostructure, the possibility of growing (Al, In,_) GaN nanowire heterostructure LEDs on different substrates while maintaining their high electronic and optical properties makes them very attractive. We investigated the electronic homogeneity of the (Al, In,_) GaN nanowire ensemble by acquiring current maps at certain applied biases using conductive AFM. By taken IVs on individual nanowires, we found that different wires have different turn on voltages and that some of the nanowires degrade due to the applied bias.

  17. Monte Carlo simulation of second-generation open-type PET ''single-ring OpenPET'' implemented with DOI detectors

    International Nuclear Information System (INIS)

    Tashima, Hideaki; Yamaya, Taiga; Hirano, Yoshiyuki; Yoshida, Eiji; Kinouch, Shoko; Watanabe, Mitsuo; Tanaka, Eiichi

    2013-01-01

    At the National Institute of Radiological Sciences, we are developing OpenPET, an open-type positron emission tomography (PET) geometry with a physically open space, which allows easy access to the patient during PET studies. Our first-generation OpenPET system, dual-ring OpenPET, which consisted of two detector rings, could provide an extended axial field of view (FOV) including the open space. However, for applications such as in-beam PET to monitor the dose distribution in situ during particle therapy, higher sensitivity concentrated on the irradiation field is required rather than a wide FOV. In this report, we propose a second-generation OpenPET geometry, single-ring OpenPET, which can efficiently improve sensitivity while providing the required open space. When the proposed geometry was realized with block detectors, position-dependent degradation of the spatial resolution was expected because it was necessary to arrange the detector blocks in ellipsoidal rings stacked and shifted relative to one another. However, we found by Monte Carlo simulation that the use of depth-of-interaction (DOI) detectors made it feasible to achieve uniform spatial resolution in the FOV. (author)

  18. Formation and Device Application of Ge Nanowire Heterostructures via Rapid Thermal Annealing

    OpenAIRE

    Tang, Jianshi; Wang, Chiu-Yen; Xiu, Faxian; Zhou, Yi; Chen, Lih-Juann; Wang, Kang L.

    2011-01-01

    We reviewed the formation of Ge nanowire heterostructure and its field-effect characteristics by a controlled reaction between a single-crystalline Ge nanowire and Ni contact pads using a facile rapid thermal annealing process. Scanning electron microscopy and transmission electron microscopy demonstrated a wide temperature range of 400~500°C to convert the Ge nanowire to a single-crystalline Ni2Ge/Ge/Ni2Ge nanowire heterostructure with atomically sharp interfaces. More importantly, we studie...

  19. 1.5 W high efficiency and tunable single-longitudinal-mode Ho:YLF ring laser based on Faraday effect.

    Science.gov (United States)

    Wu, Jing; Ju, Youlun; Dai, Tongyu; Yao, Baoquan; Wang, Yuezhu

    2017-10-30

    We demonstrated an efficient and tunable single-longitudinal-mode Ho:YLF ring laser based on Faraday effect for application to measure atmospheric carbon dioxide (CO 2 ). Single-longitudinal-mode power at 2051.65 nm achieved 528 mW with the slope efficiency of 39.5% and the M 2 factor of 1.07, and the tunable range of about 178 GHz was obtained by inserting a Fabry-Perot (F-P) etalon with the thickness of 0.5 mm. In addition, the maximum single-longitudinal-mode power reached 1.5 W with the injected power of 528 mW at 2051.65 nm by master oscillator power amplifier (MOPA) technique. High efficiency and tunable single-longitudinal-mode based on Faraday effect around 2 μm has not been reported yet to the best of our knowledge.

  20. Resonant pickups for non-destructive single-particle detection in heavy-ion storage rings and first experimental results

    Energy Technology Data Exchange (ETDEWEB)

    Sanjari, Mohammad Shahab

    2013-04-26

    Nuclear astrophysics studies on highly charged radionuclides benefit from accelerator facilities with storage rings, where exotic nuclides produced with small yields can be efficiently investigated. Currently there are two accelerator facilities capable of storing highly charged heavy ions, GSI in Darmstadt and IMP in Lanzhou. Non-destructive detection methods are often used for in-flight measurements based on frequency analysis. The sensitivity of such detection systems are of primary importance specially when number of stored ions is small. Furthermore, since the exotic nuclides of interest are as a rule short-lived, the detectors must be fast. One common form of such detectors are parallel plate SCHOTTKY monitors, on which particles induce a mirror charge at each passage. This method has been successfully used at ESR experimental storage ring of GSI since 1991. In this work we describe a new resonant SCHOTTKY pickup operating as a high sensitive cavity current monitor which was mounted and commissioned in the ESR early 2010. It was successfully used in several storage ring experiments. A very similar pickup was mounted in CSRe at IMP Lanzhou in 2011. First in-ring tests have been performed and new experimental results are pending. The spectral analysis of acquired signals by the new detector has enabled a broad range of new physics experiments. The theory of operation and first experimental results and future perspectives are presented in this thesis.

  1. A 250-Mbit/s ring local computer network using 1.3-microns single-mode optical fibers

    Science.gov (United States)

    Eng, S. T.; Tell, R.; Andersson, T.; Eng, B.

    1985-01-01

    A 250-Mbit/s three-station fiber-optic ring local computer network was built and successfully demonstrated. A conventional token protocol was employed for bus arbitration to maximize the bus efficiency under high loading conditions, and a non-return-to-zero (NRS) data encoding format was selected for simplicity and maximum utilization of the ECL-circuit bandwidth.

  2. Spin Transport in Semiconductor heterostructures

    International Nuclear Information System (INIS)

    Marinescu, Domnita Catalina

    2011-01-01

    The focus of the research performed under this grant has been the investigation of spin transport in magnetic semiconductor heterostructures. The interest in these systems is motivated both by their intriguing physical properties, as the physical embodiment of a spin-polarized Fermi liquid, as well as by their potential applications as spintronics devices. In our work we have analyzed several different problems that affect the spin dynamics in single and bi-layer spin-polarized two-dimensional (2D) systems. The topics of interests ranged from the fundamental aspects of the electron-electron interactions, to collective spin and charge density excitations and spin transport in the presence of the spin-orbit coupling. The common denominator of these subjects is the impact at the macroscopic scale of the spin-dependent electron-electron interaction, which plays a much more subtle role than in unpolarized electron systems. Our calculations of several measurable parameters, such as the excitation frequencies of magneto-plasma modes, the spin mass, and the spin transresistivity, propose realistic theoretical estimates of the opposite-spin many-body effects, in particular opposite-spin correlations, that can be directly connected with experimental measurements.

  3. Single-site laparoscopic percutaneous extraperitoneal closure of the internal ring using an epidural and spinal needle: excellent results in 1464 children with inguinal hernia/hydrocele.

    Science.gov (United States)

    Wang, Furan; Zhong, Hongji; Chen, Yi; Zhao, Junfeng; Li, Yan; Chen, Junxian; Dong, Sheng

    2017-07-01

    Laparoscopic percutaneous extraperitoneal closure (LPEC) of the internal ring is a well-developed procedure for pediatric inguinal hernia and hydrocele. To reduce the skin incisions and improve the cosmesis, single-site LPEC (SLPEC) has been developed with numerous techniques and instruments. In this study, we described our modifications of SLPEC using an epidural and spinal needle in a large pediatric population. From February 2013 to February 2016, 1464 pediatric patients who underwent SLPEC in our hospital were retrospectively reviewed. A 5-mm laparoscope was introduced at the subumbilicus. An 18-gauge epidural needle with a silk suture loop was introduced into the corresponding skin of the internal ring. The needle was advanced extraperitoneally on the medial side of the ring. The suture loop was pushed into peritoneal cavity by the spinal needle. The epidural needle was withdrawn to the roof of the internal ring and then kept advancing along the lateral side. Aided by the spinal needle and laparoscope, a long suture loop was sent into the first loop in peritoneal cavity. The long suture loop was pulled out of the abdominal wall by picking up the first loop, and the internal ring was closed by knotting the suture extracorporeally. The contralateral patent processus vaginalis (CPPV) was simultaneously repaired if present. In total, 981 patients presented with inguinal hernia and 483 with hydrocele. A CPPV was present in 483 patients with unilateral pathology and thus simultaneously repaired. The hydrodissection technique and grasping forceps were used in 290 and 113 patients, respectively. The median operation time was 11 min (7-18 min) and 18 min (10-30 min) for unilateral and bilateral inguinal hernias/hydroceles, respectively. There was no development of intra- or postoperative complications. SLPEC using an epidural and spinal needle can be performed with excellent results in pediatric inguinal hernias and hydroceles.

  4. Little-Parks Oscillations in a Single Ring in the vicinity of the Superconductor-Insulator Transition

    OpenAIRE

    Gurovich, Doron; Tikhonov, Konstantin S.; Mahalu, Diana; Shahar, Dan

    2014-01-01

    We present results of measurements obtained from a mesoscopic ring of a highly disordered superconductor. Superimposed on a smooth magnetoresistance background we find periodic oscillations with a period that is independent of the strength of the magnetic field. The period of the oscillations is consistent with charge transport by Cooper pairs. The oscillations persist unabated for more than 90 periods, through the transition to the insulating phase, up to our highest field of 12 T.

  5. 6.1 W single frequency laser output at 1645 nm from a resonantly pumped Er:YAG nonplanar ring oscillator.

    Science.gov (United States)

    Gao, Chunqing; Zhu, Lingni; Wang, Ran; Gao, Mingwei; Zheng, Yan; Wang, Lei

    2012-06-01

    A monolithic 1645 nm Er:YAG nonplanar ring oscillator (NPRO) resonantly pumped by a 1532 nm fiber laser is demonstrated. For reducing the energy-transfer upconversion effect, a 0.5% doped Er:YAG nonplanar crystal was used. An up to 6.1 W single frequency laser output at 1645 nm was obtained, with a slope efficiency of 55.2% and an optical efficiency of 48.0%. The linewidth of the Er:YAG NPRO was 14.4 kHz.

  6. Brane world black rings

    International Nuclear Information System (INIS)

    Sahay, Anurag; Sengupta, Gautam

    2007-01-01

    Five dimensional neutral rotating black rings are described from a Randall-Sundrum brane world perspective in the bulk black string framework. To this end we consider a rotating black string extension of a five dimensional black ring into the bulk of a six dimensional Randall-Sundrum brane world with a single four brane. The bulk solution intercepts the four brane in a five dimensional black ring with the usual curvature singularity on the brane. The bulk geodesics restricted to the plane of rotation of the black ring are constructed and their projections on the four brane match with the usual black ring geodesics restricted to the same plane. The asymptotic nature of the bulk geodesics are elucidated with reference to a bulk singularity at the AdS horizon. We further discuss the description of a brane world black ring as a limit of a boosted bulk black 2 brane with periodic identification

  7. Terahertz-frequency InN/GaN heterostructure-barrier varactor diodes

    International Nuclear Information System (INIS)

    Reklaitis, A

    2008-01-01

    Frequency multipliers based on the single-barrier and double-barrier InN/GaN heterostructure varactor diodes are suggested. The DC and large-signal AC vertical electron transport in the InN/GaN diodes are investigated by ensemble Monte Carlo simulations. It is found that InN/GaN heterostructure-barrier varactor diodes are able to operate as efficient frequency multipliers in the frequency range up to 1 THz

  8. Fast all-optical multistate flip-flop operation realized by a single self-sustained micro-ring laser memory cell

    International Nuclear Information System (INIS)

    Wang, Zhuoran; Yuan, Guohui

    2013-01-01

    We investigate all-optical multistate flip-flop operation realized by a single self-sustained micro-ring laser memory cell based on a time-domain multi-mode nonlinear model. Each state is written by the corresponding 100 ps-width input non-return-to-zero (NRZ) pulse carrying the directional and wavelength information, and the cell remains in the written state until another trigger arrives. The effects of key parameters including the detuning frequency and injection power ratio on the injection locking and flipping regions of different modes in both directions of the micro-ring device are studied. By optimizing the operation conditions, we simulate the minimal switching speed for each mode. The fast switching speed of less than 20 ps and up to ten mode flip-flop operation indicate that this single optical memory cell can support ten states at a data rate of at least 10 Gbps, which is particularly valuable for the realization of future all-optical networking and functional sub-system technology. (letter)

  9. Thermospin effects in superconducting heterostructures

    Science.gov (United States)

    Bobkova, I. V.; Bobkov, A. M.

    2017-09-01

    Recently, thermally created pure spin currents were predicted for Zeeman-split superconductor/normal-metal heterostructures. Here it is shown that this "thermospin" current can lead to an accumulation of a pure spin imbalance in a system. The thermally induced spin imbalance can reach the value of Zeeman splitting of the superconducting density of states and strongly influences superconductivity in the heterostructure. Depending on the temperature difference between the superconductor and the normal reservoir it can enhance the critical temperature of the superconductor or additionally suppress the zero-temperature superconducting state. The last possibility gives rise to an unusual superconducting state, which starts to develop at finite temperature.

  10. Heterostructures of transition metal dichalcogenides

    KAUST Repository

    Amin, Bin

    2015-08-24

    The structural, electronic, optical, and photocatalytic properties of out-of-plane and in-plane heterostructures of transition metal dichalcogenides are investigated by (hybrid) first principles calculations. The out-of-plane heterostructures are found to be indirect band gap semiconductors with type-II band alignment. Direct band gaps can be achieved by moderate tensile strain in specific cases. The excitonic peaks show blueshifts as compared to the parent monolayer systems, whereas redshifts occur when the chalcogen atoms are exchanged along the series S-Se-Te. Strong absorption from infrared to visible light as well as excellent photocatalytic properties can be achieved.

  11. Vortex rings

    CERN Document Server

    Akhmetov, D G

    2009-01-01

    This text on vortex rings covers their theoretical foundation, systematic investigations, and practical applications such as the extinction of fires at gushing oil wells. It pays special attention to the formation and motion of turbulent vortex rings.

  12. Low temperature magnetic properties and spin dynamics in single crystals of Cr{sub 8}Zn antiferromagnetic molecular rings

    Energy Technology Data Exchange (ETDEWEB)

    Adelnia, Fatemeh [Dipartimento di Fisica, Università degli Studi di Milano and INSTM, I-20133 Milano (Italy); Dipartimento di Fisica, Università degli Studi di Pavia and INSTM, I-27100 Pavia (Italy); Chiesa, Alessandro; Bordignon, Sara; Carretta, Stefano [Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Parma, I-43124 Parma (Italy); Ghirri, Alberto; Candini, Andrea [CNR Institute Nanosciences S3, I- 41125 Modena (Italy); Cervetti, Christian [Dipartimento di Scienze Fisiche, Informatiche, Matematiche, Università di Modena e Reggio Emilia, I-41125 Modena (Italy); Evangelisti, Marco [CNR Institute Nanosciences S3, I- 41125 Modena (Italy); Dipartimento di Scienze Fisiche, Informatiche, Matematiche, Università di Modena e Reggio Emilia, I-41125 Modena (Italy); Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain); Affronte, Marco [CNR Institute Nanosciences S3, I- 41125 Modena (Italy); Dipartimento di Scienze Fisiche, Informatiche, Matematiche, Università di Modena e Reggio Emilia, I-41125 Modena (Italy); Sheikin, Ilya [Grenoble High Magnetic Field Laboratory, CNRS-LNCMI, 25, B.P. 166, 38042 Grenoble Cedex 9 (France); Winpenny, Richard; Timco, Grigore [The Lewis Magnetism Laboratory, The University of Manchester, M13 9PL Manchester (United Kingdom); Borsa, Ferdinando [Dipartimento di Fisica, Università degli Studi di Pavia and INSTM, I-27100 Pavia (Italy); and others

    2015-12-28

    A detailed experimental investigation of the effects giving rise to the magnetic energy level structure in the vicinity of the level crossing (LC) at low temperature is reported for the open antiferromagnetic molecular ring Cr{sub 8}Zn. The study is conducted by means of thermodynamic techniques (torque magnetometry, magnetization and specific heat measurements) and microscopic techniques (nuclear magnetic resonance line width, nuclear spin lattice, and spin-spin relaxation measurements). The experimental results are shown to be in excellent agreement with theoretical calculations based on a minimal spin model Hamiltonian, which includes a Dzyaloshinskii-Moriya interaction. The first ground state level crossing at μ{sub 0}H{sub c1} = 2.15 T is found to be an almost true LC while the second LC at μ{sub 0}H{sub c2} = 6.95 T has an anti-crossing gap of Δ{sub 12} = 0.19 K. In addition, both NMR and specific heat measurements show the presence of a level anti-crossing between excited states at μ{sub 0}H = 4.5 T as predicted by the theory. In all cases, the fit of the experimental data is improved by introducing a distribution of the isotropic exchange couplings (J), i.e., using a J strain model. The peaks at the first and second LCs in the nuclear spin-lattice relaxation rate are dominated by inelastic scattering and a value of Γ ∼ 10{sup 10} rad/s is inferred for the life time broadening of the excited state of the open ring, due to spin phonon interaction. A loss of NMR signal (wipe-out effect) is observed for the first time at LC and is explained by the enhancement of the spin-spin relaxation rate due to the inelastic scattering.

  13. A rare single cytogenetic finding of isochromosome 14q in a female with refractory anemia with ring sideroblasts (RARS)

    Energy Technology Data Exchange (ETDEWEB)

    Haag, M.M.; Sutcliffe, M.J.; Nelson, R.P. [All Children`s Hospital, St. Petersburg, FL (United States)]|[Univ. of South Florida, Tampa, FL (United States)] [and others

    1994-09-01

    Clonal cytogenetic abnormalities occur in 79% of patients with myelodysplastic syndrome (MDS) and can be used to diagnose malignancy. Some of these clonal chromosomal changes have been useful in evaluation of the pathobiological similarity between MDS and acute nonlymphocytic leukemia (ANLL) and can be used to monitor the disease progression. A 44-year-old woman, presenting with normochromic, normocytic anemia was clinically asymptomatic and physical examination revealed no lymphadenopathy or hepatosplenomegaly. Stains for iron demonstrated adequate stores but with numerours ring sideroblasts which constituted approximately 15% of the total erythoblastic population. No increased reticulum or fibrosis was noted. These findings supported a diagnosis of MDS, classification refractory anemia with ring sideroblasts (RARS). Bone marrow cytogentic analysis showed an isochromosome 14q as the sole chromosome abnormality and this was confirmed by molecular cytogenetics using a whole chromosome Coatasome probe for No. 14. A population of 46,XX cells (20%) was also observed. Numerous interphase cells had three isolated fluorescent signals for No. 14. Structural and numerical abnormalities of chromosome No. 14 are reported in many hematological disorders, but few structural abnormalities have been reported for RARS and no extra copies, including i(14q), have been reported for MD or RARS. However, examples of extra copies of No. 14, including the isochromosome form, have been reported for ANLL. Since 15% of RARS patients progress to ANLL, there may be prognostic significance to this chromosome abnormality for his patient. The patient is awaiting a suitable donor for bone marrow transplantation. The presence of isochromosome No. 14 in the malignant cells offers an opportunity to monitor disease progression pre-transplantation and minimal residual disease post-transplantation.

  14. Escher-like quasiperiodic heterostructures

    International Nuclear Information System (INIS)

    Barriuso, A G; Monzon, J J; Sanchez-Soto, L L; Costa, A F

    2009-01-01

    Quasiperiodic heterostructures present unique structural, electronic and vibrational properties, connected to the existence of incommensurate periods. We go beyond previous schemes, such as Fibonacci or Thue-Morse, based on substitutional sequences, by introducing construction rules generated by tessellations of the unit disc by regular polygons. We explore some of the properties exhibited by these systems. (fast track communication)

  15. Escher-like quasiperiodic heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Barriuso, A G; Monzon, J J; Sanchez-Soto, L L [Departamento de Optica, Facultad de Fisica, Universidad Complutense, 28040 Madrid (Spain); Costa, A F [Departamento de Matematicas Fundamentales, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia, Senda del Rey 9, 28040 Madrid (Spain)

    2009-05-15

    Quasiperiodic heterostructures present unique structural, electronic and vibrational properties, connected to the existence of incommensurate periods. We go beyond previous schemes, such as Fibonacci or Thue-Morse, based on substitutional sequences, by introducing construction rules generated by tessellations of the unit disc by regular polygons. We explore some of the properties exhibited by these systems. (fast track communication)

  16. Planetary Rings

    Science.gov (United States)

    Tiscareno, Matthew S.

    Planetary rings are the only nearby astrophysical disks and the only disks that have been investigated by spacecraft (especially the Cassini spacecraft orbiting Saturn). Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 10- 7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close range and in real time in planetary rings.We review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We then review planetary rings by type. The A, B, and C rings of Saturn, plus the Cassini Division, comprise our solar system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are found both at Uranus (where they comprise the main rings entirely) and at Saturn (where they are embedded in the broad disk) and are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally confined arcs at Neptune, Saturn, and Jupiter. Finally, every known ring system includes a substantial component of diffuse dusty rings.Planetary rings have shown themselves to be useful as detectors of planetary processes around them, including the planetary magnetic field and interplanetary impactors as well as the gravity of nearby perturbing moons. Experimental rings science has made great progress in recent decades, especially numerical simulations of self-gravity wakes and other processes but also laboratory investigations of coefficient of restitution and spectroscopic ground truth. The age of self-sustained ring systems is a matter of

  17. Intergrown new zeolite beta polymorphs with interconnected 12-ring channels solved by combining electron crystallography and single-crystal X-ray diffraction

    KAUST Repository

    Yu, Zhengbao

    2012-10-09

    Two new polymorphs of zeolite beta, denoted as SU-78A and SU-78B, were synthesized by employing dicyclohexylammonium hydroxides as organic structure-directing agents. The structure was solved by combining transmission electron microscopy and single-crystal X-ray diffraction. SU-78 is an intergrowth of SU-78A and SU-78B and contains interconnected 12-ring channels in three directions. The two polymorphs are built from the same building layer, similar to that for the zeolite beta family. The layer stacking in SU-78, however, is different from those in zeolite beta polymorph A, B, and C, showing new zeolite framework topologies. SU-78 is thermally stable up to 600 °C. © 2012 American Chemical Society.

  18. Graphyne-graphene (nitride) heterostructure as nanocapacitor

    Science.gov (United States)

    Bhattacharya, Barnali; Sarkar, Utpal

    2016-10-01

    A nanoscale capacitor composed of heterostructure derived from finite size graphyne flake and graphene (nitride) flake has been proposed and investigated using density functional theory (DFT). The exothermic nature of formation process of these heterostructures implies their stability. Significant charge transfer between two flakes generates permanent dipole in this heterostructures. The amount of charge transfer is tunable under the application of external electric field which enhances their applicability in electronics. We have specifically focused on the capacitive properties of different heterostructure composed of graphyne flake and graphene (nitride) flake, i.e., graphyne/graphene, graphyne/h-BN, graphyne/AlN, graphyne/GaN. The charge stored by each flake, energy storage, and capacitance are switchable under external electric field. Thus, our modeled heterostructures are a good candidate as nanoscale capacitor and can be used in nanocircuit. We found that the charge stored by each flake, energy storage, and capacitance value are highest for graphyne/GaN heterostructures.

  19. Generation of localized strain in a thin film piezoelectric to control individual magnetoelectric heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Jizhai; Liang, Cheng-Yen; Sepulveda, Abdon; Carman, Gregory P.; Lynch, Christopher S., E-mail: cslynch@seas.ucla.edu [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095 (United States); Paisley, Elizabeth A.; Ihlefeld, Jon F. [Electronic, Optical, and Nano Materials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    2015-08-31

    Experimental results demonstrate the ability of a surface electrode pattern to produce sufficient in-plane strain in a PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} (PZT) thin film clamped by a Si substrate to control magnetism in a 1000 nm diameter Ni ring. The electrode pattern and the Ni ring/PZT thin film heterostructure were designed using a finite element based micromagnetics code. The magnetoelectric heterostructures were fabricated on the PZT film using e-beam lithography and characterized using magnetic force microscopy. Application of voltage to the electrodes moved one of the “onion” state domain walls. This method enables the development of complex architectures incorporating strain-mediated multiferroic devices.

  20. Storage rings

    Energy Technology Data Exchange (ETDEWEB)

    O' Neill, Gerald K.

    1963-04-15

    The development of storage rings is discussed. Advantages of such devices are pointed out as well as their limits, requirements, and design and fabrication problems. Information gained by the operation of small electron storage rings is included, and three experiments are proposed for colliding-beam facilities. (D.C.W.)

  1. Analysis of crestal bone loss around single piece ball attachment implant placed bilaterally in canine region and wear of O-ring in implant supported overdenture: Three year follow-up.

    Science.gov (United States)

    Raza, Fathima Banu; Vaidyanathan, Anand Kumar; Veeravalli, Padmanabhan T; Ravishankar, Subhiksha; Ali, Aashique S

    2018-03-06

    Single piece implant in fixed prosthesis is widely been evaluated, however, long term evaluation of crestal bone loss and the wear of O-ring in single piece ball attachment implant supported overdenture is yet to be evaluated PURPOSE: The present article evaluates the crestal bone loss around single piece ball attachment implants placed bilaterally in the canine region and the wear of O-ring in implant supported overdenture over a period of three years. Twelve completely edentulous patients between the age group of 55-65 years were selected. Two 3.3 mm × 13 mm myriad snap fit implants were placed in the mandibular interforaminal region. All the implants were conventionally loaded at three months after surgical placement. Intra-oral periapical radiographs were made and crestal bone loss was measured at the end of one year and three years. The elasticity and wear of O-Ring was assessed after three years of usage. The crestal bone loss showed no significant difference between the first and third year after implant placement. The mean bone loss at the end of third year was 1.5 mm. Analysis of O-ring for change in the elasticity showed reduction in displacement and a significant increase in maximum displacement and elongation. The area of O-ring and yield stress did not show any changes from the standard value. Compression set damage was observed in the O-ring at the end of three years. The present study shows that the bilateral single piece implant supported overdenture has a success rate equivalent to the two piece implant supported overdenture and is a viable treatment option. © 2018 Wiley Periodicals, Inc.

  2. Stable single-frequency output at 2.01 microm from a diode-pumped monolithic double diffusion-bonded Tm:YAG nonplanar ring oscillator at room temperature.

    Science.gov (United States)

    Gao, Chunqing; Gao, Mingwei; Zhang, Yunshan; Lin, Zhifeng; Zhu, Lingni

    2009-10-01

    We demonstrate a monolithic double diffusion-bonded monolithic Tm:YAG nonplanar ring laser pumped by a fiber-coupled laser diode. Up to 867 mW single-frequency output at 2.01 microm was obtained from the Tm:YAG system at room temperature, with a slope efficiency and an optical-optical efficiency of 31.6% and 19.2%. The power stability of the single frequency laser was 0.32% within 30 min.

  3. Determinantal rings

    CERN Document Server

    Bruns, Winfried

    1988-01-01

    Determinantal rings and varieties have been a central topic of commutative algebra and algebraic geometry. Their study has attracted many prominent researchers and has motivated the creation of theories which may now be considered part of general commutative ring theory. The book gives a first coherent treatment of the structure of determinantal rings. The main approach is via the theory of algebras with straightening law. This approach suggest (and is simplified by) the simultaneous treatment of the Schubert subvarieties of Grassmannian. Other methods have not been neglected, however. Principal radical systems are discussed in detail, and one section is devoted to each of invariant and representation theory. While the book is primarily a research monograph, it serves also as a reference source and the reader requires only the basics of commutative algebra together with some supplementary material found in the appendix. The text may be useful for seminars following a course in commutative ring theory since a ...

  4. ring system

    African Journals Online (AJOL)

    1,3,2-DIAZABORACYCLOALKANE. RING SYSTEM. Negussie Retta" and Robert H. Neilson. 'Department of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia. Department of Chemistry, Texas Christian University.

  5. Vascular ring

    Science.gov (United States)

    ... trachea) and esophagus can lead to breathing and digestive problems. The more the ring presses down, the more severe the symptoms will be. Breathing problems may include: ... Digestive symptoms are rare, but may include: Choking Difficulty ...

  6. An Innovative 3D Ultrasonic Actuator with Multidegree of Freedom for Machine Vision and Robot Guidance Industrial Applications Using a Single Vibration Ring Transducer

    Directory of Open Access Journals (Sweden)

    M. Shafik

    2013-07-01

    Full Text Available This paper presents an innovative 3D piezoelectric ultrasonic actuator using a single flexural vibration ring transducer, for machine vision and robot guidance industrial applications. The proposed actuator is principally aiming to overcome the visual spotlight focus angle of digital visual data capture transducer, digital cameras and enhance the machine vision system ability to perceive and move in 3D. The actuator Design, structures, working principles and finite element analysis are discussed in this paper. A prototype of the actuator was fabricated. Experimental tests and measurements showed the ability of the developed prototype to provide 3D motions of Multidegree of freedom, with typical speed of movement equal to 35 revolutions per minute, a resolution of less than 5μm and maximum load of 3.5 Newton. These initial characteristics illustrate, the potential of the developed 3D micro actuator to gear the spotlight focus angle issue of digital visual data capture transducers and possible improvement that such technology could bring to the machine vision and robot guidance industrial applications.

  7. Structure and dynamics of ringed galaxies

    International Nuclear Information System (INIS)

    Buta, R.J.

    1984-01-01

    In many spiral and SO galaxies, single or multiple ring structures are visible in the disk. These inner rings (r), outer rings (R), and nuclear rings (nr) were investigated by means of morphology, photometry, and spectroscopy in order to provide basic data on a long neglected phenomenon. The metric properties of each ring are investigated and found to correlate with the structure of the parent galaxy. When properly calibrated, inner rings in barred (SB) systems can be used as geometric extragalactic distance indicators to distances in excess of 100 Mpc. Other statistics are presented that confirm previous indications that the rings have preferred shapes, relative sizes, and orientations with respect to bars. A survey is made of the less homogeneous non-barred (SA) ringed systems, and the causes of the inhomogeneity are isolated. It is shown that rings can be identified in multiple-ring SA systems that are exactly analogous to those in barred spirals

  8. Graphyne–graphene (nitride) heterostructure as nanocapacitor

    International Nuclear Information System (INIS)

    Bhattacharya, Barnali; Sarkar, Utpal

    2016-01-01

    Highlights: • Binding energy of heterostructures indicates the exothermic nature. • Increasing electric field enhances charge and energy stored in the system. • The external electric fields amplify the charge transfer between two flakes. • The capacitance value gets saturated above a certain electric field. - Abstract: A nanoscale capacitor composed of heterostructure derived from finite size graphyne flake and graphene (nitride) flake has been proposed and investigated using density functional theory (DFT). The exothermic nature of formation process of these heterostructures implies their stability. Significant charge transfer between two flakes generates permanent dipole in this heterostructures. The amount of charge transfer is tunable under the application of external electric field which enhances their applicability in electronics. We have specifically focused on the capacitive properties of different heterostructure composed of graphyne flake and graphene (nitride) flake, i.e., graphyne/graphene, graphyne/h-BN, graphyne/AlN, graphyne/GaN. The charge stored by each flake, energy storage, and capacitance are switchable under external electric field. Thus, our modeled heterostructures are a good candidate as nanoscale capacitor and can be used in nanocircuit. We found that the charge stored by each flake, energy storage, and capacitance value are highest for graphyne/GaN heterostructures.

  9. Graphyne–graphene (nitride) heterostructure as nanocapacitor

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, Barnali; Sarkar, Utpal, E-mail: utpalchemiitkgp@yahoo.com

    2016-10-20

    Highlights: • Binding energy of heterostructures indicates the exothermic nature. • Increasing electric field enhances charge and energy stored in the system. • The external electric fields amplify the charge transfer between two flakes. • The capacitance value gets saturated above a certain electric field. - Abstract: A nanoscale capacitor composed of heterostructure derived from finite size graphyne flake and graphene (nitride) flake has been proposed and investigated using density functional theory (DFT). The exothermic nature of formation process of these heterostructures implies their stability. Significant charge transfer between two flakes generates permanent dipole in this heterostructures. The amount of charge transfer is tunable under the application of external electric field which enhances their applicability in electronics. We have specifically focused on the capacitive properties of different heterostructure composed of graphyne flake and graphene (nitride) flake, i.e., graphyne/graphene, graphyne/h-BN, graphyne/AlN, graphyne/GaN. The charge stored by each flake, energy storage, and capacitance are switchable under external electric field. Thus, our modeled heterostructures are a good candidate as nanoscale capacitor and can be used in nanocircuit. We found that the charge stored by each flake, energy storage, and capacitance value are highest for graphyne/GaN heterostructures.

  10. Synthesis of Won-WX2 (n=2.7, 2.9; X=S, Se) Heterostructures for Highly Efficient Green Quantum Dot Light-Emitting Diodes

    KAUST Repository

    Han, Shikui

    2017-07-04

    Preparation of two-dimensional (2D) heterostructures is important not only fundamentally, but also technologically for applications in electronics and optoelectronics. Herein, we report a facile colloidal method for the synthesis of WOn -WX2 (n=2.7, 2.9; X=S, Se) heterostructures by sulfurization or selenization of WOn nanomaterials. The WOn -WX2 heterostructures are composed of WO2.9 nanoparticles (NPs) or WO2.7 nanowires (NWs) grown together with single- or few-layer WX2 nanosheets (NSs). As a proof-of-concept application, the WOn -WX2 heterostructures are used as the anode interfacial buffer layer for green quantum dot light-emitting diodes (QLEDs). The QLED prepared with WO2.9 NP-WSe2 NS heterostructures achieves external quantum efficiency (EQE) of 8.53 %. To our knowledge, this is the highest efficiency in the reported green QLEDs using inorganic materials as the hole injection layer.

  11. Stabilized thin film heterostructure for electrochemical applications

    DEFF Research Database (Denmark)

    2015-01-01

    The invention provides a method for the formation of a thin film multi-layered heterostructure upon a substrate, said method comprising the steps of: a. providing a substrate; b. depositing a buffer layer upon said substrate, said buffer layer being a layer of stable ionic conductor (B); c...... or less; and e. repeating steps b. and c. a total of N times, such that N repeating pairs of layers (A/B) are built up, wherein N is 1 or more. The invention also provides a thin film multi-layered heterostructure as such, and the combination of a thin film multi-layered heterostructure and a substrate...

  12. Evanescent channels and scattering in cylindrical nanowire heterostructures

    Science.gov (United States)

    Racec, P. N.; Racec, E. R.; Neidhardt, H.

    2009-04-01

    We investigate the scattering phenomena produced by a general finite-range nonseparable potential in a multichannel two-probe cylindrical nanowire heterostructure. The multichannel current scattering matrix is efficiently computed using the R -matrix formalism extended for cylindrical coordinates. Considering the contribution of the evanescent channels to the scattering matrix, we are able to put in evidence the specific dips in the tunneling coefficient in the case of an attractive potential. The cylindrical symmetry cancels the “selection rules” known for Cartesian coordinates. If the attractive potential is superposed over a nonuniform potential along the nanowire then resonant transmission peaks appear. We can characterize them quantitatively through the poles of the current scattering matrix. Detailed maps of the localization probability density sustain the physical interpretation of the resonances (dips and peaks). Our formalism is applied to a variety of model systems such as a quantum dot, a core/shell quantum ring, or a double barrier embedded into the nanocylinder.

  13. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays.

    Science.gov (United States)

    Liu, Jian; Wang, Chunrui; Xie, Qingqing; Cai, Junsheng; Zhang, Jing

    2009-10-29

    Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondary nanostructures of SiO2 nanowires are highly dense grown on the primary Cd4SiS6 core-SiO2 sheath nanowires and formed hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.

  14. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Liu Jian

    2009-01-01

    Full Text Available Abstract Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondary nanostructures of SiO2 nanowires are highly dense grown on the primary Cd4SiS6 core-SiO2 sheath nanowires and formed hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.

  15. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

    OpenAIRE

    Liu, Jian; Wang, Chunrui; Xie, Qingqing; Cai, Junsheng; Zhang, Jing

    2009-01-01

    Abstract Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondar...

  16. 5.7  W cw single-frequency laser at 671  nm by single-pass second harmonic generation of a 17.2  W injection-locked 1342  nm Nd : YVO4 ring laser using periodically poled MgO : LiNbO3.

    Science.gov (United States)

    Koch, Peter; Ruebel, Felix; Bartschke, Juergen; L'huillier, Johannes A

    2015-11-20

    We demonstrate a continuous wave single-frequency laser at 671.1 nm based on a high-power 888 nm pumped Nd:YVO4 ring laser at 1342.2 nm. Unidirectional operation of the fundamental ring laser is achieved with the injection-locking technique. A Nd:YVO4 microchip laser serves as the injecting seed source, providing a tunable single-frequency power of up to 40 mW. The ring laser emits a single-frequency power of 17.2 W with a Gaussian beam profile and a beam propagation factor of M2beam profile and a beam propagation factor of M2lasers. This work opens possibilities in cold atoms experiments with lithium, allowing the use of larger ensembles in magneto-optical traps or higher diffraction orders in atomic beam interferometers.

  17. Ring accelerators

    International Nuclear Information System (INIS)

    Gisler, G.; Faehl, R.

    1983-01-01

    We present two-dimensional simulations in (r-z) and r-theta) cylinderical geometries of imploding-liner-driven accelerators of rings of charged particles. We address issues of azimuthal and longitudinal stability of the rings. We discuss self-trapping designs in which beam injection and extraction is aided by means of external cusp fields. Our simulations are done with the 2-1/2-D particle-in-cell plasma simulation code CLINER, which combines collisionless, electromagnetic PIC capabilities with a quasi-MHD finite element package

  18. Topological rings

    CERN Document Server

    Warner, S

    1993-01-01

    This text brings the reader to the frontiers of current research in topological rings. The exercises illustrate many results and theorems while a comprehensive bibliography is also included. The book is aimed at those readers acquainted with some very basic point-set topology and algebra, as normally presented in semester courses at the beginning graduate level or even at the advanced undergraduate level. Familiarity with Hausdorff, metric, compact and locally compact spaces and basic properties of continuous functions, also with groups, rings, fields, vector spaces and modules, and with Zorn''s Lemma, is also expected.

  19. Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures.

    Science.gov (United States)

    Gamucci, A; Spirito, D; Carrega, M; Karmakar, B; Lombardo, A; Bruna, M; Pfeiffer, L N; West, K W; Ferrari, A C; Polini, M; Pellegrini, V

    2014-12-19

    Vertical heterostructures combining different layered materials offer novel opportunities for applications and fundamental studies. Here we report a new class of heterostructures comprising a single-layer (or bilayer) graphene in close proximity to a quantum well created in GaAs and supporting a high-mobility two-dimensional electron gas. In our devices, graphene is naturally hole-doped, thereby allowing for the investigation of electron-hole interactions. We focus on the Coulomb drag transport measurements, which are sensitive to many-body effects, and find that the Coulomb drag resistivity significantly increases for temperatures law, therefore displaying a notable departure from the ordinary quadratic temperature dependence expected in a weakly correlated Fermi-liquid. This anomalous behaviour is consistent with the onset of strong interlayer correlations. Our heterostructures represent a new platform for the creation of coherent circuits and topologically protected quantum bits.

  20. Specific features of the ferroelectric state in two-layer barium strontium titanate-based heterostructures

    Science.gov (United States)

    Stryukov, D. V.; Mukhortov, V. M.; Golovko, Yu. I.; Biryukov, S. V.

    2018-01-01

    The structural properties of one- and two-layer heterostructures based on the barium-strontium titanate of various compositions deposited by the Frank-Van der Merve on a magnesium oxide substrate have been studied. The heterostructures have been prepared by the rf sputtering of the stoichiometric ceramic targets in a Plazma 50 SE deposition system. The principal difference of this method of deposition from known analogs is that the growth of single-crystal films occurs from a disperse oxide phase formed in the plasma of a high-current rf discharge during the ceramic target sputtering at the cluster level. The peculiarities of the manifestation of the ferroelectric state in the two-layer heterostructures when changing the sequence order of the films with various compositions of barium-strontium titanate.

  1. Rare-earth nickelates RNiO3: thin films and heterostructures

    Science.gov (United States)

    Catalano, S.; Gibert, M.; Fowlie, J.; Íñiguez, J.; Triscone, J.-M.; Kreisel, J.

    2018-04-01

    This review stands in the larger framework of functional materials by focussing on heterostructures of rare-earth nickelates, described by the chemical formula RNiO3 where R is a trivalent rare-earth R  =  La, Pr, Nd, Sm, …, Lu. Nickelates are characterized by a rich phase diagram of structural and physical properties and serve as a benchmark for the physics of phase transitions in correlated oxides where electron–lattice coupling plays a key role. Much of the recent interest in nickelates concerns heterostructures, that is single layers of thin film, multilayers or superlattices, with the general objective of modulating their physical properties through strain control, confinement or interface effects. We will discuss the extensive studies on nickelate heterostructures as well as outline different approaches to tuning and controlling their physical properties and, finally, review application concepts for future devices.

  2. A model-based analysis of a simplified beam-specific dose output in proton therapy with a single-ring wobbling system.

    Science.gov (United States)

    Kase, Yuki; Yamashita, Haruo; Numano, Masumi; Sakama, Makoto; Mizota, Manabu; Maeda, Yoshikazu; Tameshige, Yuji; Murayama, Shigeyuki

    2015-01-07

    In radiation therapy, it is necessary to preset a monitor unit in an irradiation control system to deliver a prescribed absolute dose to a reference point in the planning target volume. The purpose of this study was to develop a model-based monitor unit calculation method for proton-beam therapy with a single-ring wobbling system. The absorbed dose at a calibration point per monitor unit had been measured for each beam-specific measurement condition without a patient-specific collimator or range compensator before proton therapeutic irradiation at Shizuoka Cancer Center. In this paper, we propose a simplified dose output model to obtain the output ratio between a beam-specific dose and a reference field dose, from which a monitor unit for the proton treatment could be derived without beam-specific measurements. The model parameters were determined to fit some typical data measured in a proton treatment room, called a Gantry 1 course. Then, the model calculation was compared with 5456 dose output ratios that had been measured for 150-, 190- and 220 MeV therapeutic proton beams in two treatment rooms over the past decade. The mean value and standard deviation of the difference between the measurement and the model calculation were respectively 0.00% and 0.27% for the Gantry 1 course, and -0.25% and 0.35% for the Gantry 2 course. The model calculation was in good agreement with the measured beam-specific doses, within 1%, except for conditions less frequently used for treatment. The small variation for the various beam conditions shows the high long-term reproducibility of the measurement and high degree of compatibility of the two treatment rooms. Therefore, the model was expected to assure the setting value of the dose monitor for treatment, to save the effort required for beam-specific measurement, and to predict the dose output for new beam conditions in the future.

  3. Wave mechanics applied to semiconductor heterostructures

    International Nuclear Information System (INIS)

    Bastard, G.

    1990-01-01

    This book examines the basic electronic and optical properties of two dimensional semiconductor heterostructures based on III-V and II-VI compounds. The book explores various consequences of one-dimensional size-quantization on the most basic physical properties of heterolayers. Beginning with basic quantum mechanical properties of idealized quantum wells and superlattices, the book discusses the occurrence of bound states when the heterostructure is imperfect or when it is shone with near bandgap light

  4. Graphene/Si-nanowire heterostructure molecular sensors.

    Science.gov (United States)

    Kim, Jungkil; Oh, Si Duk; Kim, Ju Hwan; Shin, Dong Hee; Kim, Sung; Choi, Suk-Ho

    2014-06-20

    Wafer-scale graphene/Si-nanowire (Si-NW) array heterostructures for molecular sensing have been fabricated by vertically contacting single-layer graphene with high-density Si NWs. Graphene is grown in large scale by chemical vapour deposition and Si NWs are vertically aligned by metal-assisted chemical etching of Si wafer. Graphene plays a key role in preventing tips of vertical Si NWs from being bundled, thereby making Si NWs stand on Si wafer separately from each other under graphene, a critical structural feature for the uniform Schottky-type junction between Si NWs and graphene. The molecular sensors respond very sensitively to gas molecules by showing 37 and 1280% resistance changes within 3.5/0.15 and 12/0.15 s response/recovery times under O2 and H2 exposures in air, respectively, highest performances ever reported. These results together with the sensor responses in vacuum are discussed based on the surface-transfer doping mechanism.

  5. 600-year reconstruction of the tri-pole Interdecadal Pacific Oscillation (TPI) using tree-ring chronologies and a single coral proxy from Indonesia, Australia and New Zealand.

    Science.gov (United States)

    Palmer, Jonathan; Cook, Edward; Turney, Chris; Cook, Benjamin; Fenwick, Pavla; Allen, Kathy; Baker, Patrick; Henley, Benjamin

    2017-04-01

    The development of the eastern Australia and New Zealand summer drought atlas (i.e. ANZDA; Palmer et al., 2015) highlighted the potential for exploring the reconstruction of the Henley et al. (2015) tripole Interdecadal Pacific Oscillation index (TPI). The approach taken was to use both the 1375 drought atlas scPDSI (self-calibrating Palmer Drought Severity Index) grid-points and the 176 tree-ring and single coral proxies to determine the strength and spatial expression of their relationship to TPI. An important concern was the potential geographic bias of the proxies relative to the TPI. To examine this concern more closely, each of three main TPI regions of sea surface temperatures were extracted and then correlated to the ANZDA scPDSI grid-points. Results showed a robust correlation field to each of the three poles although the closest "Tasman" pole was, as expected, the strongest. Next, the 177 proxies were used in regressions to calibrate/verify to the TPI over the period CE 1871-1975. The positive results provided confidence for the reconstruction "summer" TPI values extending back to CE 1410. The wavelet pattern of the reconstruction shows the ENSO (2-7 year) band frequency has increased during the 20th century while the longer (10-30 year) periodicities are scattered throughout the entire time interval. Finally, the different recognised phases of the IPO are compared to the two reconstructions (grid-points and TPI) and earlier periods discussed. References: Henley BJ, Gergis J, Karoly DJ, Power S, Kennedy J, Folland CK (2015) A Tripole Index for the Inter-decadal Pacific Oscillation. Climate Dynamics 45, 3077-3090. doi:10.1007/s00382-015-2525-1. Palmer J, Cook ER, Turney CSM, Allen K, Fenwick P, Cook BI, O'Donnell A, Lough J, Grierson P, Baker P (2016) Drought variability in the eastern Australia and New Zealand summer drought atlas (ANZDA, CE 1500-2012) modulated by the Interdecadal Pacific Oscillation. Environmental Research Letters 10, 1-12. doi:10.1088/1748-9326/10/12/124002.

  6. Formation and Device Application of Ge Nanowire Heterostructures via Rapid Thermal Annealing

    Directory of Open Access Journals (Sweden)

    Jianshi Tang

    2011-01-01

    Full Text Available We reviewed the formation of Ge nanowire heterostructure and its field-effect characteristics by a controlled reaction between a single-crystalline Ge nanowire and Ni contact pads using a facile rapid thermal annealing process. Scanning electron microscopy and transmission electron microscopy demonstrated a wide temperature range of 400~500°C to convert the Ge nanowire to a single-crystalline Ni2Ge/Ge/Ni2Ge nanowire heterostructure with atomically sharp interfaces. More importantly, we studied the effect of oxide confinement during the formation of nickel germanides in a Ge nanowire. In contrast to the formation of Ni2Ge/Ge/Ni2Ge nanowire heterostructures, a segment of high-quality epitaxial NiGe was formed between Ni2Ge with the confinement of Al2O3 during annealing. A twisted epitaxial growth mode was observed in both two Ge nanowire heterostructures to accommodate the large lattice mismatch in the NixGe/Ge interface. Moreover, we have demonstrated field-effect transistors using the nickel germanide regions as source/drain contacts to the Ge nanowire channel. Our Ge nanowire transistors have shown a high-performance p-type behavior with a high on/off ratio of 105 and a field-effect hole mobility of 210 cm2/Vs, which showed a significant improvement compared with that from unreacted Ge nanowire transistors.

  7. Growth and characterization of epitaxial thin films and multiferroic heterostructures of ferromagnetic and ferroelectric materials

    Science.gov (United States)

    Mukherjee, Devajyoti

    Multiferroic materials exhibit unique properties such as simultaneous existence of two or more of coupled ferroic order parameters (ferromagnetism, ferroelectricity, ferroelasticity or their anti-ferroic counterparts) in a single material. Recent years have seen a huge research interest in multiferroic materials for their potential application as high density non-volatile memory devices. However, the scarcity of these materials in single phase and the weak coupling of their ferroic components have directed the research towards multiferroic heterostructures. These systems operate by coupling the magnetic and electric properties of two materials, generally a ferromagnetic material and a ferroelectric material via strain. In this work, horizontal heterostructures of composite multiferroic materials were grown and characterized using pulsed laser ablation technique. Alternate magnetic and ferroelectric layers of cobalt ferrite and lead zirconium titanate, respectively, were fabricated and the coupling effect was studied by X-ray stress analysis. It was observed that the interfacial stress played an important role in the coupling effect between the phases. Doped zinc oxide (ZnO) heterostructures were also studied where the ferromagnetic phase was a layer of manganese doped ZnO and the ferroelectric phase was a layer of vanadium doped ZnO. For the first time, a clear evidence of possible room temperature magneto-elastic coupling was observed in these heterostructures. This work provides new insight into the stress mediated coupling mechanisms in composite multiferroics.

  8. Vertical-Cavity In-plane Heterostructures: Physics and Applications

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Mørk, Jesper; Chung, Il-Sug

    2015-01-01

    We show that the in-plane heterostructures realized in vertical cavities with high contrast grating(HCG) reflector enables exotic configurations of heterostructure and photonic wells. In photonic crystal heterostructures forming a photonic well, the property of a confined mode is determined by th...

  9. Efficacy of single-agent lenalidomide in patients with JAK2 (V617F) mutated refractory anemia with ring sideroblasts and thrombocytosis

    NARCIS (Netherlands)

    Huls, Gerwin; Mulder, Andre B.; Rosati, Stefano; van de Loosdrecht, Arjan A.; Vellenga, Edo; de Wolf, Joost T. M.

    2010-01-01

    Patients with refractory anemia with ring sideroblasts and thrombocytosis (RARS-T) are difficult to treat because the cytoreductive treatment might be beneficial for the thrombocytosis component but harmful for the RARS component. As lenalidomide has shown to be efficacious in both myelodysplastic

  10. Two-dimensional heterostructures for energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Gogotsi, Yury G. [Drexel Univ., Philadelphia, PA (United States); Pomerantseva, Ekaterina [Drexel Univ., Philadelphia, PA (United States)

    2017-06-12

    Two-dimensional (2D) materials provide slit-shaped ion diffusion channels that enable fast movement of lithium and other ions. However, electronic conductivity, the number of intercalation sites, and stability during extended cycling are also crucial for building high-performance energy storage devices. While individual 2D materials, such as graphene, show some of the required properties, none of them can offer all properties needed to maximize energy density, power density, and cycle life. Here we argue that stacking different 2D materials into heterostructured architectures opens an opportunity to construct electrodes that would combine the advantages of the individual building blocks while eliminating the associated shortcomings. We discuss characteristics of common 2D materials and provide examples of 2D heterostructured electrodes that showed new phenomena leading to superior electrochemical performance. As a result, we also consider electrode fabrication approaches and finally outline future steps to create 2D heterostructured electrodes that could greatly expand current energy storage technologies.

  11. Semiconductor-oxide heterostructured nanowires using postgrowth oxidation.

    Science.gov (United States)

    Wallentin, Jesper; Ek, Martin; Vainorious, Neimantas; Mergenthaler, Kilian; Samuelson, Lars; Pistol, Mats-Erik; Reine Wallenberg, L; Borgström, Magnus T

    2013-01-01

    Semiconductor-oxide heterointerfaces have several electron volts high-charge carrier potential barriers, which may enable devices utilizing quantum confinement at room temperature. While a single heterointerface is easily formed by oxide deposition on a crystalline semiconductor, as in MOS transistors, the amorphous structure of most oxides inhibits epitaxy of a second semiconductor layer. Here, we overcome this limitation by separating epitaxy from oxidation, using postgrowth oxidation of AlP segments to create axial and core-shell semiconductor-oxide heterostructured nanowires. Complete epitaxial AlP-InP nanowire structures were first grown in an oxygen-free environment. Subsequent exposure to air converted the AlP segments into amorphous aluminum oxide segments, leaving isolated InP segments in an oxide matrix. InP quantum dots formed on the nanowire sidewalls exhibit room temperature photoluminescence with small line widths (down to 15 meV) and high intensity. This optical performance, together with the control of heterostructure segment length, diameter, and position, opens up for optoelectrical applications at room temperature.

  12. Cascaded exciton energy transfer in a monolayer semiconductor lateral heterostructure assisted by surface plasmon polariton.

    Science.gov (United States)

    Shi, Jinwei; Lin, Meng-Hsien; Chen, I-Tung; Mohammadi Estakhri, Nasim; Zhang, Xin-Quan; Wang, Yanrong; Chen, Hung-Ying; Chen, Chun-An; Shih, Chih-Kang; Alù, Andrea; Li, Xiaoqin; Lee, Yi-Hsien; Gwo, Shangjr

    2017-06-26

    Atomically thin lateral heterostructures based on transition metal dichalcogenides have recently been demonstrated. In monolayer transition metal dichalcogenides, exciton energy transfer is typically limited to a short range (~1 μm), and additional losses may be incurred at the interfacial regions of a lateral heterostructure. To overcome these challenges, here we experimentally implement a planar metal-oxide-semiconductor structure by placing a WS 2 /MoS 2 monolayer heterostructure on top of an Al 2 O 3 -capped Ag single-crystalline plate. We find that the exciton energy transfer range can be extended to tens of microns in the hybrid structure mediated by an exciton-surface plasmon polariton-exciton conversion mechanism, allowing cascaded exciton energy transfer from one transition metal dichalcogenides region supporting high-energy exciton resonance to a different transition metal dichalcogenides region in the lateral heterostructure with low-energy exciton resonance. The realized planar hybrid structure combines two-dimensional light-emitting materials with planar plasmonic waveguides and offers great potential for developing integrated photonic and plasmonic devices.Exciton energy transfer in monolayer transition metal dichalcogenides is limited to short distances. Here, Shi et al. fabricate a planar metal-oxide-semiconductor structure and show that exciton energy transfer can be extended to tens of microns, mediated by an exciton-surface-plasmon-polariton-exciton conversion mechanism.

  13. Quasi-isochronous storage rings

    International Nuclear Information System (INIS)

    Robin, D.; Forest, E.; Pellegrini, C.; Amiry, A.

    1993-01-01

    A study is made of the single-particle dynamics of an electron-positron storage ring where the phase-slip factor is made small in order to make the ring nearly isochronous and reduce the bunch length. What is found is that a quasi-isochronous ring makes it possible to obtain a bunch length in the millimeter range, about one order of magnitude shorter than present values. In this study we have extended the work of others on isochronous storage rings by quantitatively including higher-order terms in the longitudinal equations of motion. Scaling laws are then derived relating the linear term with the next-highest-order term. These scaling laws, which are derived from a two-dimensional Hamiltonian (one dimension of position and one of momentum), establish criteria for stability. These scaling laws are then checked with full six-dimensional tracking on one particular lattice

  14. Fabrication of vertical GaN/InGaN heterostructure nanowires using Ni-Au bi-metal catalysts.

    Science.gov (United States)

    Ha, Ryong; Kim, Sung-Wook; Choi, Heon-Jin

    2013-06-26

    We have fabricated the vertically aligned coaxial or longitudinal heterostructure GaN/InGaN nanowires. The GaN nanowires are first vertically grown by vapor-liquid-solid mechanism using Au/Ni bi-metal catalysts. The GaN nanowires are single crystal grown in the [0001] direction, with a length and diameter of 1 to 10 μm and 100 nm, respectively. The vertical GaN/InGaN coaxial heterostructure nanowires (COHN) are then fabricated by the subsequent deposition of 2 nm of InxGa1-xN shell on the surface of GaN nanowires. The vertical GaN/InGaN longitudinal heterostructure nanowires (LOHN) are also fabricated by subsequent growth of an InGaN layer on the vertically aligned GaN nanowires using the catalyst. The photoluminescence from the COHN and LOHN indicates that the optical properties of GaN nanowires can be tuned by the formation of a coaxial or longitudinal InGaN layer. Our study demonstrates that the bi-metal catalysts are useful for growing vertical as well as heterostructure GaN nanowires. These vertically aligned GaN/InGaN heterostructure nanowires may be useful for the development of high-performance optoelectronic devices.

  15. Fabrication of vertical GaN/InGaN heterostructure nanowires using Ni-Au bi-metal catalysts

    OpenAIRE

    Ha, Ryong; Kim, Sung-Wook; Choi, Heon-Jin

    2013-01-01

    We have fabricated the vertically aligned coaxial or longitudinal heterostructure GaN/InGaN nanowires. The GaN nanowires are first vertically grown by vapor?liquid-solid mechanism using Au/Ni bi-metal catalysts. The GaN nanowires are single crystal grown in the [0001] direction, with a length and diameter of 1 to 10 ?m and 100 nm, respectively. The vertical GaN/InGaN coaxial heterostructure nanowires (COHN) are then fabricated by the subsequent deposition of 2 nm of InxGa1-xN shell on the sur...

  16. Ringing phenomenon of the fiber ring resonator.

    Science.gov (United States)

    Ying, Diqing; Ma, Huilian; Jin, Zhonghe

    2007-08-01

    A resonator fiber-optic gyro (R-FOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A fiber ring resonator is the core sensing element in the R-FOG. When the frequency of the fiber ring resonator input laser is swept linearly with time, ringing of the output resonance curve is observed. The output field of the fiber ring resonator is derived from the superposition of the light transmitted through the directional coupler directly and the multiple light components circulated in the fiber ring resonator when the frequency of the laser is swept. The amplitude and phase of the output field are analyzed, and it is found that the difference in time for different light components in the fiber ring resonator to reach a point of destructive interference causes the ringing phenomenon. Finally the ringing phenomenon is observed in experiments, and the experimental results agree with the theoretical analysis well.

  17. Thermally excited multiband conduction in LaAlO3/SrTiO3 heterostructures exhibiting scattering

    NARCIS (Netherlands)

    Guduru, V.K.; McCollam, A.; Jost, A.; Wenderich, Sander; Hilgenkamp, H.; Maan, J.C.; Brinkman, Alexander; Zeitler, U.

    2013-01-01

    Magnetotransport measurements of charge carriers at the interface of a LaAlO 3 /SrTiO 3 heterostructure with 26 unit cells of LaAlO 3 show Hall resistance and magnetoresistance which at low and high temperatures is described by a single channel of electronlike charge carriers. At intermediate

  18. FY 1997 report on the study on the formation condition of hetero-structure of single-crystalline semiconductor thin films; 1997 nendo chosa hokokusho (tankessho no handotai usumaku hetero kozo no keisei joken ni kansuru kenkyu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    Since ion implantation causes material degradation by formation of crystalline defects, and hydrogen embrittlement deteriorates material strength, reduction of such defects has been positively studied. Study was made on a new active application of hydrogen separation into ion implantation defects. After H ion implantation of a proper depth into single-crystalline Si and SiC and successive annealing, single-crystalline films of sub-micron to several micron thick were obtained by hydrogen-induced delamination at the implantation depth due to hydrogen embrittlement in crystalline defects. The implantation depth is dependent on implantation energy. H atom forms (111) face defect through connection with dangling bond of crystalline defects. This crystal face defect forms a delamination plane through (100) face cleavage. This hydrogen embrittlement delamination by ion implantation is applicable to production of light-weight high-efficiency single-crystalline Si solar cells, and large single-crystalline SiC wafers as new resource saving process. 33 refs., 19 figs., 2 tabs.

  19. ASSOCIATIVE RINGS SOLVED AS LIE RINGS

    Directory of Open Access Journals (Sweden)

    M. B. Smirnov

    2011-01-01

    Full Text Available The paper has proved that an associative ring which is solvable of a n- class as a Lie ring has a nilpotent ideal of the nilpotent class not more than 3×10n–2  and a corresponding quotient ring satisfies an identity [[x1, x2, [x3, x4

  20. Radical theory of rings

    CERN Document Server

    Gardner, JW

    2003-01-01

    Radical Theory of Rings distills the most noteworthy present-day theoretical topics, gives a unified account of the classical structure theorems for rings, and deepens understanding of key aspects of ring theory via ring and radical constructions. Assimilating radical theory's evolution in the decades since the last major work on rings and radicals was published, the authors deal with some distinctive features of the radical theory of nonassociative rings, associative rings with involution, and near-rings. Written in clear algebraic terms by globally acknowledged authorities, the presentation

  1. One-pot growth of two-dimensional lateral heterostructures via sequential edge-epitaxy.

    Science.gov (United States)

    Sahoo, Prasana K; Memaran, Shahriar; Xin, Yan; Balicas, Luis; Gutiérrez, Humberto R

    2018-01-03

    Two-dimensional heterojunctions of transition-metal dichalcogenides have great potential for application in low-power, high-performance and flexible electro-optical devices, such as tunnelling transistors, light-emitting diodes, photodetectors and photovoltaic cells. Although complex heterostructures have been fabricated via the van der Waals stacking of different two-dimensional materials, the in situ fabrication of high-quality lateral heterostructures with multiple junctions remains a challenge. Transition-metal-dichalcogenide lateral heterostructures have been synthesized via single-step, two-step or multi-step growth processes. However, these methods lack the flexibility to control, in situ, the growth of individual domains. In situ synthesis of multi-junction lateral heterostructures does not require multiple exchanges of sources or reactors, a limitation in previous approaches as it exposes the edges to ambient contamination, compromises the homogeneity of domain size in periodic structures, and results in long processing times. Here we report a one-pot synthetic approach, using a single heterogeneous solid source, for the continuous fabrication of lateral multi-junction heterostructures consisting of monolayers of transition-metal dichalcogenides. The sequential formation of heterojunctions is achieved solely by changing the composition of the reactive gas environment in the presence of water vapour. This enables selective control of the water-induced oxidation and volatilization of each transition-metal precursor, as well as its nucleation on the substrate, leading to sequential edge-epitaxy of distinct transition-metal dichalcogenides. Photoluminescence maps confirm the sequential spatial modulation of the bandgap, and atomic-resolution images reveal defect-free lateral connectivity between the different transition-metal-dichalcogenide domains within a single crystal structure. Electrical transport measurements revealed diode-like responses across the

  2. One-pot growth of two-dimensional lateral heterostructures via sequential edge-epitaxy

    Science.gov (United States)

    Sahoo, Prasana K.; Memaran, Shahriar; Xin, Yan; Balicas, Luis; Gutiérrez, Humberto R.

    2018-01-01

    Two-dimensional heterojunctions of transition-metal dichalcogenides have great potential for application in low-power, high-performance and flexible electro-optical devices, such as tunnelling transistors, light-emitting diodes, photodetectors and photovoltaic cells. Although complex heterostructures have been fabricated via the van der Waals stacking of different two-dimensional materials, the in situ fabrication of high-quality lateral heterostructures with multiple junctions remains a challenge. Transition-metal-dichalcogenide lateral heterostructures have been synthesized via single-step, two-step or multi-step growth processes. However, these methods lack the flexibility to control, in situ, the growth of individual domains. In situ synthesis of multi-junction lateral heterostructures does not require multiple exchanges of sources or reactors, a limitation in previous approaches as it exposes the edges to ambient contamination, compromises the homogeneity of domain size in periodic structures, and results in long processing times. Here we report a one-pot synthetic approach, using a single heterogeneous solid source, for the continuous fabrication of lateral multi-junction heterostructures consisting of monolayers of transition-metal dichalcogenides. The sequential formation of heterojunctions is achieved solely by changing the composition of the reactive gas environment in the presence of water vapour. This enables selective control of the water-induced oxidation and volatilization of each transition-metal precursor, as well as its nucleation on the substrate, leading to sequential edge-epitaxy of distinct transition-metal dichalcogenides. Photoluminescence maps confirm the sequential spatial modulation of the bandgap, and atomic-resolution images reveal defect-free lateral connectivity between the different transition-metal-dichalcogenide domains within a single crystal structure. Electrical transport measurements revealed diode-like responses across the

  3. Construction of CuO/In2S3/ZnO heterostructure arrays for enhanced photocatalytic efficiency.

    Science.gov (United States)

    Chang, Yu-Cheng; Guo, Jin-You; Chen, Chien-Ming; Di, Hsin-Wei; Hsu, Chao-Chun

    2017-09-14

    Novel one-dimensional (1D) heterostructure arrays composed of CuO nanowire cores, intermediate In 2 S 3 nanostructures, and ZnO nanorod sheaths (i.e. CuO/In 2 S 3 /ZnO heterostructure arrays) have been successfully synthesized by a multi-step process. First, single-crystalline CuO nanowires were directly grown on flexible Cu mesh substrates using a one-step annealing process under ambient conditions. Second, In 2 S 3 nanostructures and ZnO nanorods were sequentially grown on the CuO nanowires by a two-step hydrothermal method at low reaction temperature. The morphology, crystal structures, and optical properties of the CuO/In 2 S 3 /ZnO heterostructure arrays were studied by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, energy-dispersive spectroscopy, and photoluminescence spectroscopy. The resultant ternary CuO/In 2 S 3 /ZnO heterostructure arrays exhibit excellent photocatalytic activity in the photodegradation of rhodamine 6G (R6G) under 10 W UV light irradiation, which is much higher than that of single-component (CuO nanowire arrays) or two-component systems (CuO/In 2 S 3 heterostructure arrays). Furthermore, the reusability test demonstrates that the CuO/In 2 S 3 /ZnO heterostructure arrays on the Cu mesh still maintain high photocatalytic activity in the degradation of three kinds of organic pollutants even after five cycles, without any significant decline. These findings provide an insight into the design and synthesis of new CuO-based composites to effectively improve their photocatalytic performance.

  4. Polarization-coupled tunable resistive behavior in oxide ferroelectric heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Gruverman, Alexei [Univ. of Nebraska, Lincoln, NE (United States); Tsymbal, Evgeny Y. [Univ. of Nebraska, Lincoln, NE (United States); Eom, Chang-Beom [Univ. of Wisconsin, Madison, WI (United States)

    2017-05-03

    This research focuses on investigation of the physical mechanism of the electrically and mechanically tunable resistive behavior in oxide ferroelectric heterostructures with engineered interfaces realized via a strong coupling of ferroelectric polarization with tunneling electroresistance and metal-insulator (M-I) transitions. This report describes observation of electrically conductive domain walls in semiconducting ferroelectrics, voltage-free control of resistive switching and demonstration of a new mechanism of electrical control of 2D electron gas (2DEG) at oxide interfaces. The research goals are achieved by creating strong synergy between cutting-edge fabrication of epitaxial single-crystalline complex oxides, nanoscale electrical characterization by scanning probe microscopy and theoretical modeling of the observed phenomena. The concept of the ferroelectric devices with electrically and mechanically tunable nonvolatile resistance represents a new paradigm shift in realization of the next-generation of non-volatile memory devices and low-power logic switches.

  5. The Origin of Tc Enhancement in Heterostructure Cuprate Superconductors

    Directory of Open Access Journals (Sweden)

    Doron L. Bergman

    2011-10-01

    Full Text Available Recent experiments on heterostructures composed of two or more films of cuprate superconductors of different oxygen doping levels have shown a remarkable Tc enhancement (up to 50% relative to single compound films. We provide a simple explanation of the enhancement which arises naturally from a collection of experimental works. We show that the enhancement could be caused by a structural change in the lattice, namely an increase in the distance of the apical oxygen from the copper-oxygen plane. This increase modifies the effective off-site interaction in the plane which in turn enhances the d-wave superconductivity order parameter. To illustrate this point we study the extended Hubbard model using the fluctuation exchange approximation.

  6. Heterostructures based on inorganic and organic van der Waals systems

    Directory of Open Access Journals (Sweden)

    Gwan-Hyoung Lee

    2014-09-01

    Full Text Available The two-dimensional limit of layered materials has recently been realized through the use of van der Waals (vdW heterostructures composed of weakly interacting layers. In this paper, we describe two different classes of vdW heterostructures: inorganic vdW heterostructures prepared by co-lamination and restacking; and organic-inorganic hetero-epitaxy created by physical vapor deposition of organic molecule crystals on an inorganic vdW substrate. Both types of heterostructures exhibit atomically clean vdW interfaces. Employing such vdW heterostructures, we have demonstrated various novel devices, including graphene/hexagonal boron nitride (hBN and MoS2 heterostructures for memory devices; graphene/MoS2/WSe2/graphene vertical p-n junctions for photovoltaic devices, and organic crystals on hBN with graphene electrodes for high-performance transistors.

  7. Growth and properties of low-dimensional III-V semiconductor nanowire heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Heiss, Martin

    2010-08-25

    symmetry from cubic zinc-blende to hexagonal wurtzite structure, while the chemical composition of the material remains constant. The GaAs nanowires synthesized with the Au-free technique can be grown under conditions where a statistical wurtzite/zinc-blende polytypism occurs. A novel method for the direct correlation at the nanoscale of structural and optical properties of single GaAs nanowires is developed in order to characterize the resulting statistically distributed quantum heterostructures. Nanowires consisting of {approx}100% wurtzite and nanowires presenting zinc-blende/wurtzite polytypism are studied by photoluminescence spectroscopy and Transmission Electron Microscopy. The photoluminescence of wurtzite GaAs is found to be consistent with a bulk wurtzite band gap of 1.50 eV, slightly smaller compared to the zinc-blende GaAs band gap. In the polytypic nanowires, it is shown that the regions that are predominantly composed of either zinc-blende or wurtzite phase show photoluminescence emission close to the according bulk band gaps, while regions composed of a non periodic superlattice of wurtzite and zinc-blende phases exhibit a redshift of the photoluminescence spectra as low as 1.455 eV. The dimensions of the quantum heterostructures are correlated with the light emission, allowing us to estimate the band offsets of {delta}E{sub CB}=53{+-}20 meV and {delta}E{sub VB}=76{+-}12 meV between the two crystalline phases. These results are in excellent agreement with recent theoretical band structure calculations. (orig.)

  8. Analysis of Critical Dimensions for Nanowire Core-Multishell Heterostructures

    OpenAIRE

    Yan, Xin; Fan, Shuyu; Zhang, Xia; Ren, Xiaomin

    2015-01-01

    Critical dimensions for nanowire core-multishell heterostructures are analyzed by using finite-element method based on the energy equilibrium criteria. Results show that the nanowire core-shell heterostructure can sufficiently reduce the strain in the shell and increase the critical shell thickness. The critical dimensions for the nanowire core-multishell heterostructure are determined by the stress fields generated at two heterointerfaces. For thin barrier, the critical dimensions decrease a...

  9. Optofluidic ring resonator dye lasers

    Science.gov (United States)

    Sun, Yuze; Suter, Jonathan D.; Fan, Xudong

    2010-02-01

    We overview the recent progress on optofluidic ring resonator (OFRR) dye lasers developed in our research group. The fluidics and laser cavity design can be divided into three categories: capillary optofluidic ring resonator (COFRR), integrated cylindrical optofluidic ring resonator (ICOFRR), and coupled optofluidic ring resonator (CpOFRR). The COFRR dye laser is based on a micro-sized glass capillary with a wall thickness of a few micrometers. The capillary circular cross-section forms the ring resonator and supports the whispering gallery modes (WGMs) that interact evanescently with the gain medium in the core. The laser cavity structure is versatile to adapt to the gain medium of any refractive index. Owing to the high Q-factor (>109), the lasing threshold of 25 nJ/mm2 is achieved. Besides directly pump the dye molecules, lasing through fluorescence resonance energy transfer (FRET) between the donor and acceptor dye molecules is also studied in COFRR laser. The energy transfer process can be further controlled by designed DNA scaffold labeled with donor/acceptor molecules. The ICOFRR dye laser is based on a cylindrical ring resonator fused onto the inner surface of a thick walled glass capillary. The structure has robust mechanical strength to sustain rapid gain medium circulation. The CpOFRR utilizes a cylindrical ring resonator fused on the inner surface of the COFRR capillary. Since the capillary wall is thin, the individual WGMs of the cylindrical ring resonator and the COFRR couples strongly and forms Vernier effect, which provides a way to generate a single mode dye laser.

  10. Stirling engine piston ring

    Science.gov (United States)

    Howarth, Roy B.

    1983-01-01

    A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

  11. Adiabatic compression of ion rings

    International Nuclear Information System (INIS)

    Larrabee, D.A.; Lovelace, R.V.

    1982-01-01

    A study has been made of the compression of collisionless ion rings in an increasing external magnetic field, B/sub e/ = zB/sub e/(t), by numerically implementing a previously developed kinetic theory of ring compression. The theory is general in that there is no limitation on the ring geometry or the compression ratio, lambdaequivalentB/sub e/ (final)/B/sub e/ (initial)> or =1. However, the motion of a single particle in an equilibrium is assumed to be completely characterized by its energy H and canonical angular momentum P/sub theta/ with the absence of a third constant of the motion. The present computational work assumes that plasma currents are negligible, as is appropriate for a low-temperature collisional plasma. For a variety of initial ring geometries and initial distribution functions (having a single value of P/sub theta/), it is found that the parameters for ''fat'', small aspect ratio rings follow general scaling laws over a large range of compression ratios, 1 3 : The ring radius varies as lambda/sup -1/2/; the average single particle energy as lambda/sup 0.72/; the root mean square energy spread as lambda/sup 1.1/; and the total current as lambda/sup 0.79/. The field reversal parameter is found to saturate at values typically between 2 and 3. For large compression ratios the current density is found to ''hollow out''. This hollowing tends to improve the interchange stability of an embedded low β plasma. The implications of these scaling laws for fusion reactor systems are discussed

  12. Alternative loop rings

    CERN Document Server

    Goodaire, EG; Polcino Milies, C

    1996-01-01

    For the past ten years, alternative loop rings have intrigued mathematicians from a wide cross-section of modern algebra. As a consequence, the theory of alternative loop rings has grown tremendously. One of the main developments is the complete characterization of loops which have an alternative but not associative, loop ring. Furthermore, there is a very close relationship between the algebraic structures of loop rings and of group rings over 2-groups. Another major topic of research is the study of the unit loop of the integral loop ring. Here the interaction between loop rings and group ri

  13. Thermal response in van der Waals heterostructures

    KAUST Repository

    Gandi, Appala

    2016-11-21

    We solve numerically the Boltzmann transport equations of the phonons and electrons to understand the thermoelectric response in heterostructures of M2CO2 (M: Ti, Zr, Hf) MXenes with transition metal dichalcogenide monolayers. Low frequency optical phonons are found to occur as a consequence of the van der Waals bonding, contribute significantly to the thermal transport, and compensate for the reduced contributions of the acoustic phonons (increased scattering cross-sections in heterostructures), such that the thermal conductivities turn out to be similar to those of the bare MXenes. Our results indicate that the important superlattice design approach of thermoelectrics (to reduce the thermal conductivity) may be effective for two-dimensional van der Waals materials when used in conjunction with intercalation. © 2016 IOP Publishing Ltd.

  14. A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor

    DEFF Research Database (Denmark)

    Hu, Yongjie; Churchill, Hugh; Reilly, David

    2007-01-01

    Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitation......: the predominance of spin-zero nuclei suppresses the hyperfine interaction and chemical synthesis creates a clean and defect-free system with highly controllable properties. Here we present a top gate-defined double quantum dot based on Ge/Si heterostructure nanowires with fully tunable coupling between the dots...... and to the leads. We also demonstrate a novel approach to charge sensing in a one-dimensional nanostructure by capacitively coupling the double dot to a single dot on an adjacent nanowire. The double quantum dot and integrated charge sensor serve as an essential building block required to form a solid-state spin...

  15. Spin Andreev-like reflection in metal-Mott insulator heterostructures.

    Science.gov (United States)

    Al-Hassanieh, K A; Rincón, Julián; Alvarez, G; Dagotto, E

    2015-02-13

    Using the time-dependent density-matrix renormalization group (tDMRG), we study the time evolution of electron wave packets in one-dimensional (1D) metal-superconductor heterostructures. The results show Andreev reflection at the interface, as expected. By combining these results with the well-known single-spin-species electron-hole transformation in the Hubbard model, we predict an analogous spin Andreev reflection in metal-Mott insulator heterostructures. This effect is numerically confirmed using 1D tDMRG, but it is expected to also be present in higher dimensions, as well as in more general Hamiltonians. We present an intuitive picture of the spin reflection, analogous to that of Andreev reflection at metal-superconductor interfaces. This allows us to discuss a novel antiferromagnetic proximity effect. Possible experimental realizations are discussed.

  16. Growth of high quality InGaAsN heterostructures and their laser application

    Science.gov (United States)

    Egorov, A. Yu.; Bernklau, D.; Borchert, B.; Illek, S.; Livshits, D.; Rucki, A.; Schuster, M.; Kaschner, A.; Hoffmann, A.; Dumitras, Gh.; Amann, M. C.; Riechert, H.

    2001-07-01

    Focus of this work is the optimization of growth to achieve high quality laser material for emission at 1.3 μm and beyond. GaAs/GaAsN/InGaAsN heterostructures were grown by solid source molecular beam epitaxy. To achieve optimum crystal quality of InGaAsN heterostructures, growth was followed by a high temperature treatment at about 700°C. The high optical quality of our annealed material is attested by large exciton recombination lifetimes (more than 2 ns). Consequently, a decrease of single quantum well transparency current density down to 100 A/cm 2 is found and SWQ lasers with threshold current densities as low as 350 A/cm 2 have been made. This represents clearly the lowest laser thresholds reported so far for emission around 1.3 μm from the InGaAsN material system.

  17. Low threshold buried-heterostructure quantum well lasers by excimer laser assisted disordering

    Energy Technology Data Exchange (ETDEWEB)

    Epler, J.E.; Thornton, R.L.; Mosby, W.J.; Paoli, T.L.

    1988-10-17

    Laser assisted disordering based upon a direct-write Ar/sup +/ laser beam has been established as a fabrication technique for high quality optoelectronic devices. In this letter, we report a new form of laser assisted disordering in which an excimer laser beam, photolithographically patterned, is used to define the incorporation of Si impurity into GaAs-AlGaAs heterostructure crystals. During a subsequent thermal anneal the diffusing Si induces layer disordering to a depth of approx.1 ..mu..m. The excimer laser assisted disordering process is characterized as a function of the energy density of the laser beam. Also, this technique is used to fabricate high quality buried-heterostructure lasers. With a reflective rear facet, the typical cw threshold current is 4 mA and the maximum power output is 27 mW. The devices exhibit single fundamental mode operation with subsidiary longitudinal side modes suppressed by 34 dB.

  18. Structural and optical characteristics of GaN/ZnO coaxial nanotube heterostructure arrays for light-emitting device applications

    International Nuclear Information System (INIS)

    Hong, Young Joon; Jeon, Jong-Myeong; Kim, Miyoung; Jeon, Seong-Ran; Ho Park, Kyung; Yi, Gyu-Chul

    2009-01-01

    We report on the structural and optical characteristics of position-controlled GaN/ZnO coaxial nanotube heterostructure and GaN/In x Ga 1-x N coaxial nanotube quantum structure arrays for light-emitting diode (LED) applications. The GaN/ZnO nanotube heterostructures were fabricated by growing a GaN layer on the entire surface of position-controlled ZnO nanotube arrays using low-pressure metal-organic vapour-phase epitaxy. As determined by transmission-electron microscopy (TEM), an abrupt and coherent interface between the core ZnO and the GaN overlayer was observed. The optical characteristics of heteroepitaxial GaN/ZnO nanotube heterostructures were also investigated using cathodoluminescence (CL) spectroscopy. This position-controlled growth of high-quality single crystalline GaN/ZnO coaxial nanotube heterostructures allowed the fabrication of artificial arrays of high-quality GaN-based coaxial quantum structures by the heteroepitaxial growth of GaN/In x Ga 1-x N multiple quantum wells along the circumference of the GaN/ZnO nanotubes. The optical and structural characteristics of the position-controlled GaN/In x Ga 1-x N coaxial nanotube quantum structures were investigated by using CL spectroscopy and TEM analysis, respectively. The green LED microarrays were successfully fabricated by the controlled heteroepitaxial coaxial coatings of GaN/In x Ga 1-x N coaxial nanotube quantum structures and the outermost Mg-doped p-type GaN layer onto the GaN/ZnO coaxial nanotube heterostructures, presumably implying that the position-controlled growth of high-quality GaN/ZnO coaxial nanotube heterostructure arrays provides a general and rational route of integrating vertical nanodevices for nanoscale electronics and optoelectronics.

  19. Graphene diamond-like carbon films heterostructure

    International Nuclear Information System (INIS)

    Zhao, Fang; Afandi, Abdulkareem; Jackman, Richard B.

    2015-01-01

    A limitation to the potential use of graphene as an electronic material is the lack of control over the 2D materials properties once it is deposited on a supporting substrate. Here, the use of Diamond-like Carbon (DLC) interlayers between the substrate and the graphene is shown to offer the prospect of overcoming this problem. The DLC films used here, more properly known as a-C:H with ∼25% hydrogen content, have been terminated with N or F moieties prior to graphene deposition. It is found that nitrogen terminations lead to an optical band gap shrinkage in the DLC, whilst fluorine groups reduce the DLC's surface energy. CVD monolayer graphene subsequently transferred to DLC, N terminated DLC, and F terminated DLC has then been studied with AFM, Raman and XPS analysis, and correlated with Hall effect measurements that give an insight into the heterostructures electrical properties. The results show that different terminations strongly affect the electronic properties of the graphene heterostructures. G-F-DLC samples were p-type and displayed considerably higher mobility than the other heterostructures, whilst G-N-DLC samples supported higher carrier densities, being almost metallic in character. Since it would be possible to locally pattern the distribution of these differing surface terminations, this work offers the prospect for 2D lateral control of the electronic properties of graphene layers for device applications

  20. Voltage control of magnetism in multiferroic heterostructures.

    Science.gov (United States)

    Liu, Ming; Sun, Nian X

    2014-02-28

    Electrical tuning of magnetism is of great fundamental and technical importance for fast, compact and ultra-low power electronic devices. Multiferroics, simultaneously exhibiting ferroelectricity and ferromagnetism, have attracted much interest owing to the capability of controlling magnetism by an electric field through magnetoelectric (ME) coupling. In particular, strong strain-mediated ME interaction observed in layered multiferroic heterostructures makes it practically possible for realizing electrically reconfigurable microwave devices, ultra-low power electronics and magnetoelectric random access memories (MERAMs). In this review, we demonstrate this remarkable E-field manipulation of magnetism in various multiferroic composite systems, aiming at the creation of novel compact, lightweight, energy-efficient and tunable electronic and microwave devices. First of all, tunable microwave devices are demonstrated based on ferrite/ferroelectric and magnetic-metal/ferroelectric composites, showing giant ferromagnetic resonance (FMR) tunability with narrow FMR linewidth. Then, E-field manipulation of magnetoresistance in multiferroic anisotropic magnetoresistance and giant magnetoresistance devices for achieving low-power electronic devices is discussed. Finally, E-field control of exchange-bias and deterministic magnetization switching is demonstrated in exchange-coupled antiferromagnetic/ferromagnetic/ferroelectric multiferroic hetero-structures at room temperature, indicating an important step towards MERAMs. In addition, recent progress in electrically non-volatile tuning of magnetic states is also presented. These tunable multiferroic heterostructures and devices provide great opportunities for next-generation reconfigurable radio frequency/microwave communication systems and radars, spintronics, sensors and memories.

  1. Real Closed Rings and Real Closed * Rings

    OpenAIRE

    Capco, Jose

    2007-01-01

    Here we try to distinguish and compare different notions of real closedness mainly one developed by N. Schwartz in his Habilitationschrift and the other developed by A. Sankaranand K. Varadarajan which we shall call real closed *. We stick to the definition of real closed rings as defined and characterized N. Schwartz and we try to determine and characterize real closed rings that are real closed *. The main result is that real closed rings have unique real closure * and that real closure of ...

  2. Bias-Controlled Optical Transitions in GaN/AlN Nanowire Heterostructures.

    Science.gov (United States)

    Müßener, Jan; Hille, Pascal; Grieb, Tim; Schörmann, Jörg; Teubert, Jörg; Monroy, Eva; Rosenauer, Andreas; Eickhoff, Martin

    2017-09-26

    We report on the control and modification of optical transitions in 40× GaN/AlN heterostructure superlattices embedded in GaN nanowires by an externally applied bias. The complex band profile of these multi-nanodisc heterostructures gives rise to a manifold of optical transitions, whose emission characteristic is strongly influenced by polarization-induced internal electric fields. We demonstrate that the superposition of an external axial electric field along a single contacted nanowire leads to specific modifications of each photoluminescence emission, which allows to investigate and identify their origin and to control their characteristic properties in terms of transition energy, intensity and decay time. Using this approach, direct transitions within one nanodisc, indirect transitions between adjacent nanodiscs, transitions at the top/bottom edge of the heterostructure, and the GaN near-band-edge emission can be distinguished. While the transition energy of the direct transition can be shifted by external bias over a range of 450 meV and changed in intensity by a factor of 15, the indirect transition exhibits an inverse bias dependence and is only observable and spectrally separated when external bias is applied. In addition, by tuning the band profile close to flat band conditions, the direction and magnitude of the internal electric field can be estimated, which is of high interest for the polar group III-nitrides. The direct control of emission properties over a wide range bears possible application in tunable optoelectronic devices. For more fundamental studies, single-nanowire heterostructures provide a well-defined and isolated system to investigate and control interaction processes in coupled quantum structures.

  3. Electronic structure and STM images simulation of defects on hBN/ black-phosphorene heterostructures: A theoretical study

    Science.gov (United States)

    Ospina, D. A.; Cisternas, E.; Duque, C. A.; Correa, J. D.

    2018-03-01

    By first principles calculations which include van der Waals interactions, we studied the electronic structure of hexagonal boron-nitride/black-phosphorene heterostructures (hBN/BP). In particular the role of several kind of defects on the electronic properties of black-phosphorene monolayer and hBN/BP heterostructure was analyzed. The defects under consideration were single and double vacancies, as well Stone-Wale type defects, all of them present in the phosphorene layer. In this way, we found that the electronic structure of the hBN/BP is modified according the type of defect that is introduced. As a remarkable feature, our results show occupied states at the Fermi Level introduced by a single vacancy in the energy gap of the hBN/BP heterostructure. Additionally, we performed simulations of scanning tunneling microscopy images. These simulations show that is possible to discriminate the kind of defect even when the black-phosphorene monolayer is part of the heterostructure hBN/BP. Our results may help to discriminate among several kind of defects during experimental characterization of these novel materials.

  4. Antiferroelectric Materials, Applications and Recent Progress on Multiferroic Heterostructures

    Science.gov (United States)

    Zhou, Ziyao; Yang, Qu; Liu, Ming; Zhang, Zhiguo; Zhang, Xinyang; Sun, Dazhi; Nan, Tianxiang; Sun, Nianxiang; Chen, Xing

    2015-04-01

    Antiferroelectric (AFE) materials with adjacent dipoles oriented in antiparallel directions have a double polarization hysteresis loops. An electric field (E-field)-induced AFE-ferroelectric (FE) phase transition takes place in such materials, leading to a large lattice strain and energy change. The high dielectric constant and the distinct phase transition in AFE materials provide great opportunities for the realization of energy storage devices like super-capacitors and energy conversion devices such as AFE MEMS applications. Lots of work has been done in this field since 60-70 s. Recently, the strain tuning of the spin, charge and orbital orderings and their interactions in complex oxides and multiferroic heterostructures have received great attention. In these systems, a single control parameter of lattice strain is used to control lattice-spin, lattice-phonon, and lattice-charge interactions and tailor properties or create a transition between distinct magnetic/electronic phases. Due to the large strain/stress arising from the phase transition, AFE materials are great candidates for integrating with ferromagnetic (FM) materials to realize in situ manipulation of magnetism and lattice-ordered parameters by voltage. In this paper, we introduce the AFE material and it's applications shortly and then review the recent progress in AFEs based on multiferroic heterostructures. These new multiferroic materials could pave a new way towards next generation light, compact, fast and energy efficient voltage tunable RF/microwave, spintronic and memory devices promising approaches to in situ manipulation of lattice-coupled order parameters is to grow epitaxial oxide films on FE/ferroelastic substrates.

  5. GaN heterostructures for biosensing and radiation detection

    Energy Technology Data Exchange (ETDEWEB)

    Howgate, John D.

    2012-12-11

    In this thesis I show the results from our investigation of the interface between gallium nitride wide bandgap semiconductor heterostructures and (bio)molecular systems on their surfaces for biosensing, bioelectronics, and photoelectric applications, with a large emphasis on the processes arising from high energy ionizing irradiation, including heterostructure photoelectric gain mechanisms. Wide bandgap semiconductors, such as gallium nitride, have received increasing attention as potential components in advanced organic/inorganic hybrid systems. Working to further this topic, we determine a new semiconductor alignment required for low energy photo-induced charge transfer ionization of alkyl chains well below the energy normally required for molecular cleavage, show original results of the influence of binding methods on enzyme functionality in conjunction with a novel electrochemical and environmental control system and demonstrate new possibilities to significantly improve upon pH measurements through the use of high sensitivity devices. Furthermore, based on the extension of this work to support future studies of radiation effects on cell systems, we present a detailed characterization of new simultaneous chemical sensing and ionizing radiation dosimetry using single devices. We found that their pH sensitivity was retained during X-ray irradiation and that the fundamental characteristics can be used to separate the irradiation signal from the pH response without compromising operational stability. These data provide clear indications of the separate response mechanism tied to the presence of a two-dimensional electron gas channel. Here, we found new results exhibiting exceptionally high gains and independence of the well-known persistent photoconductivity for soft X-rays and high energy particles in the ultralow dose-rate regime. This material system provides the capability for high sensitivity and resolution real time monitoring, which is competitive with and

  6. GaN heterostructures for biosensing and radiation detection

    International Nuclear Information System (INIS)

    Howgate, John D.

    2012-01-01

    In this thesis I show the results from our investigation of the interface between gallium nitride wide bandgap semiconductor heterostructures and (bio)molecular systems on their surfaces for biosensing, bioelectronics, and photoelectric applications, with a large emphasis on the processes arising from high energy ionizing irradiation, including heterostructure photoelectric gain mechanisms. Wide bandgap semiconductors, such as gallium nitride, have received increasing attention as potential components in advanced organic/inorganic hybrid systems. Working to further this topic, we determine a new semiconductor alignment required for low energy photo-induced charge transfer ionization of alkyl chains well below the energy normally required for molecular cleavage, show original results of the influence of binding methods on enzyme functionality in conjunction with a novel electrochemical and environmental control system and demonstrate new possibilities to significantly improve upon pH measurements through the use of high sensitivity devices. Furthermore, based on the extension of this work to support future studies of radiation effects on cell systems, we present a detailed characterization of new simultaneous chemical sensing and ionizing radiation dosimetry using single devices. We found that their pH sensitivity was retained during X-ray irradiation and that the fundamental characteristics can be used to separate the irradiation signal from the pH response without compromising operational stability. These data provide clear indications of the separate response mechanism tied to the presence of a two-dimensional electron gas channel. Here, we found new results exhibiting exceptionally high gains and independence of the well-known persistent photoconductivity for soft X-rays and high energy particles in the ultralow dose-rate regime. This material system provides the capability for high sensitivity and resolution real time monitoring, which is competitive with and

  7. Dynamical black rings with a positive cosmological constant

    International Nuclear Information System (INIS)

    Kimura, Masashi

    2009-01-01

    We construct dynamical black ring solutions in the five-dimensional Einstein-Maxwell system with a positive cosmological constant and investigate the geometrical structure. The solutions describe the physical process such that a thin black ring at early time shrinks and changes into a single black hole as time increases. We also discuss the multiblack rings and the coalescence of them.

  8. Continuous-wave pump-enhanced optical parametric oscillator with ring resonator for wide and continuous tuning of single-frequency radiation.

    Science.gov (United States)

    Stothard, David; Lindsay, Ian; Dunn, Malcolm

    2004-02-09

    We demonstrate a PPLN based pump-enhanced, singly-resonant optical parametric oscillator configured in a traveling wave geometry and pumped by a Ti:sapphire laser. The inclusion of a low finesse etalon within the OPO cavity stabilizes the signal frequency, and rotation of the etalon allows this frequency to be systematically hopped from axial mode to nearest neighbor axial mode over the entire free spectral range of the etalon (83GHz). Tuning of the pump frequency allows the signal frequency to be smoothly tuned over a cavity free spectral range. More than 35mW of single frequency idler power was generated in the spectral range 2800-3000nm for 600mW pump power. The superiority of traveling wave over standing wave geometries in these regards is discussed.

  9. Enhancement of efficiency and stability of phosphorescent OLEDs based on heterostructured light-emitting layers

    Energy Technology Data Exchange (ETDEWEB)

    Chin, Byung Doo, E-mail: bdchin@dankook.ac.kr [Department of Polymer Science and Engineering and Center for Photofunctional Energy Materials, Dankook University, Jukjeon-dong, Suji-gu, Yongin-si, Gyeonggi-do 448-701 (Korea, Republic of)

    2011-03-23

    The light-emitting efficiency and stability of a phosphorescent organic light-emitting device (OLED), whose emission characteristics are strongly dominated not only by the energy transfer but also by the charge carrier trapping influenced by heterostructured emissive layers, are studied. The variation of the material combination of the heterostructured emitter, both for mixed and double layer configuration, affects the charge injection behaviour, luminous efficiency and stability. Both double and mixed emitter configurations yield low-voltage and high-efficiency behaviour (51 lm W{sup -1} at 1000 cd m{sup -2}; 30 lm W{sup -1} at 10 000 cd m{sup -2}). Such an improvement in power efficiency at elevated brightness is sufficiently universal, while the enhancement of device half-lifetime is rather sensitive to the circumstantial layout of heterostructural emitters. With an optimal mixture of hole-transport type and electron-transport type, a half-lifetime of more than 2500 h at 4000 cd m{sup -2} is obtained, which is 8 times the half-lifetime of control devices with a single emitter structure. The origin and criterion for enhancement of efficiency and lifetime are discussed in terms of the carrier transport behaviour with a specific device architecture.

  10. Groups, rings, modules

    CERN Document Server

    Auslander, Maurice

    2014-01-01

    This classic monograph is geared toward advanced undergraduates and graduate students. The treatment presupposes some familiarity with sets, groups, rings, and vector spaces. The four-part approach begins with examinations of sets and maps, monoids and groups, categories, and rings. The second part explores unique factorization domains, general module theory, semisimple rings and modules, and Artinian rings. Part three's topics include localization and tensor products, principal ideal domains, and applications of fundamental theorem. The fourth and final part covers algebraic field extensions

  11. Multiferroicity in oxide thin films and heterostructures

    International Nuclear Information System (INIS)

    Glavic, Artur

    2012-01-01

    In this work a variety of different systems of transition metal oxides ABO 3 (perovskite materials, where B stands for a transition metal and A for a rare earth element) were produced as thin films and heterostructures and analyzed for the structural, magnetic and ferroelectric properties. For the epitaxial film preparation mostly pulse laser deposition (PLD) was applied. For one series high pressure oxide sputter deposition was used as well. The bulk multiferroics TbMnO 3 and DyMnO 3 , which develop their electric polarization due to a cycloidal magnetic order, have been prepared as single layers with thicknesses between 2 and 200 nm on YAlO 3 substrates using PLD and sputter deposition. The structural characterization of the surfaces and crystal structure where performed using X-ray reflectometry and diffraction, respectively. These yielded low surface roughness and good epitaxial growth. The magnetic behavior was macroscopically measured with SQUID magnetometry and microscopically with polarized neutron diffraction and resonant magnetic X-ray scattering. While all investigated samples showed antiferromagnetic order, comparable with the collinear magnetic phase of their bulk materials, only the sputter deposited samples exhibited the multiferroic low temperature cycloidal order. The investigation of the optical second harmonic generation in a TbMnO 3 sample could proof the presence of a ferroelectric order in the low temperature phase. The respective transition temperatures of the thin films have been very similar to those of the bulk materials. In contrast an increase in the rare earth ordering temperature has been observed, which reduces the Mn order slightly, an effect not known from bulk TbMnO 3 crystals. The coupling of the antiferromagnetic order in TbMnO 3 to ferromagnetic layers of LaCoO 3 was investigated in super-lattices containing 20 bilayers produced with PLD on the same substrates. The SQUID magnetometry yielded a strong influence of the

  12. Diffusion in silicon isotope heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Silvestri, Hughes Howland [Univ. of California, Berkeley, CA (United States)

    2004-01-01

    The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and 28Si enriched layers, enables the observation of 30Si self-diffusion from the natural layers into the 28Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale features have created the need for precise physical models of atomic diffusion in Si. The modeling of the experimental profiles of simultaneous diffusion of B and Si under p-type extrinsic conditions revealed that both species are mediated by neutral and singly, positively charged Si self-interstitials. The diffusion of As and Si under extrinsic n-type conditions yielded a model consisting of the interstitialcy and vacancy mechanisms of diffusion via singly negatively charged self-interstitials and neutral vacancies. The simultaneous diffusion of P and Si has been modeled on the basis of neutral and singly negatively charged self-interstitials and neutral and singly

  13. Birth Control Ring

    Science.gov (United States)

    ... Staying Safe Videos for Educators Search English Español Birth Control Ring KidsHealth / For Teens / Birth Control Ring What's in this article? What Is ... español Anillo vaginal anticonceptivo What Is It? The birth control ring is a soft, flexible, doughnut-shaped ...

  14. Single-stage gain-clamped L-band EDFA with C-band ASE self-oscillation in ring cavity

    International Nuclear Information System (INIS)

    Mahdi, M A; Al-Mansoori, M H; Bakar, A A A; Shaari, S; Zamzuri, A K

    2008-01-01

    We demonstrate single-stage gain-clamped L-band Er 3+ -doped fiber amplifier (EDFA) utilizing self-oscillation modes as the control light. The amplifier structure exploits the characteristics of C/L-band coupler to isolate between lasing modes and L-band signal. The self-lasing cavity modes are obtained without any tunable bandpass filter in the loop and generated from the amplified spontaneous emission in the C-band region. The amplifier configuration has lower noise figures as opposed to a dual-stage partially gain-clamped amplifier. The gain and noise figure fluctuations are less than ± 0.4 dB in the gain-clamping region. The transient analysis confirms that the maximum power excursion is less than 0.3 dB for 10-dB add/drop

  15. Fiber Ring Optical Gyroscope (FROG)

    Science.gov (United States)

    1979-01-01

    The design, construction, and testing of a one meter diameter fiber ring optical gyro, using 1.57 kilometers of single mode fiber, are described. The various noise components: electronic, thermal, mechanical, and optical, were evaluated. Both dc and ac methods were used. An attempt was made to measure the Earth rotation rate; however, the results were questionable because of the optical and electronic noise present. It was concluded that fiber ring optical gyroscopes using all discrete components have many serious problems that can only be overcome by discarding the discrete approach and adapting an all integrated optic technique that has the laser source, modulator, detector, beamsplitters, and bias element on a single chip.

  16. Synthesis and photoluminescence properties of comb-like CdS nanobelt/ZnO nanorod heterostructures

    International Nuclear Information System (INIS)

    Lan Changyong; Gong Jiangfeng; Liu Chunming

    2012-01-01

    Highlights: ► Comb-like CdS nanobelt/ZnO nanorod heterostructures were synthesized. ► ZnO nanorods epitaxially grew on the (1 0 0) surface of the CdS nanobelts along [1 0 0]. ► A preliminary growth mechanism was proposed. - Abstract: Comb-like CdS nanobelt/ZnO nanorod heterostructures were synthesized by a two-stage method. X-ray diffractometer, scanning electron microscopy, transmission electron microscopy were used to characterize and analyze the as-synthesized products. The results demonstrate that the CdS nanobelt backbones grow along [2 1 0] and the ZnO nanorod branches epitaxially grow on the (0 0 1) surface of the CdS nanobelt with a growth direction of [0 0 1]. The as-prepared heterostructures exhibit an important feature of single-crystallinity. At room temperature, the comb-like CdS nanobelt/ZnO nanorod heterostructures show strong green emission.

  17. Quantitative analyses of enhanced thermoelectric properties of modulation-doped PEDOT:PSS/undoped Si (001) nanoscale heterostructures.

    Science.gov (United States)

    Lee, Dongwook; Sayed, Sayed Youssef; Lee, Sangyeop; Kuryak, Chris Adam; Zhou, Jiawei; Chen, Gang; Shao-Horn, Yang

    2016-12-01

    Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) has high electrical conductivity (∼10 3 S cm -1 ) but it exhibits a low Seebeck coefficient (PEDOT:PSS with nanostructured semiconductors can enhance the Seebeck coefficient and achieve an improved thermoelectric power factor. However, underlying mechanisms for those composite thermoelectric systems are scarcely understood so far. In this study, quantitative analyses on the electrical conductivity and Seebeck coefficient for the heterostructures of nanometer-thick PEDOT:PSS on single-crystal Si (001) on sapphire (SOS) are reported. The heterostructures have larger Seebeck coefficients up to 7.3 fold and power factors up to 17.5 fold relative to PEDOT:PSS. The electrical conductivity increased with decreasing combined thicknesses of PEDOT:PSS and Si, and the Seebeck coefficient increased with decreasing PEDOT:PSS thickness, which can be attributed to modulation doping caused by diffusion of holes from PEDOT:PSS into undoped Si. This hypothesis is supported by simulation per band alignment. The valence band offset between Si and PEDOT:PSS dominantly controls the electrical conductivity and Seebeck coefficient of the heterostructures. This study not only suggests mechanistic insights to increase the power factors of PEDOT:PSS-based composites but also opens the door for new strategies to enhance the thermoelectric efficiencies of heterostructured nanocomposite materials.

  18. Antimonide Heterostructure Nanowires - Growth, Physics and Devices

    OpenAIRE

    Borg, Mattias

    2012-01-01

    This thesis investigates the growth and application of antimonide heterostructure nanowires for low-power electronics. In the first part of the thesis, GaSb, InSb and InAsSb nanowire growth is presented, and the distinguishing features of the growth are described. It is found that the presence of Sb results in more than 50 at. % group-III concentration in the Au seed particle on top of the nanowires. It is further concluded that the effective V/III ratio inside the seed particle is reduced co...

  19. Monlithic nonplanar ring oscillator and method

    Science.gov (United States)

    Nilsson, Alan C. (Inventor); Byer, Robert L. (Inventor)

    1991-01-01

    A monolithic nonplanar ring oscillator having an optically isotropic solid-state laser body for propagating laser radiation about a nonplanar ring path internal to the laser body is disclosed. The monolithic laser body is configured to produce a 2N reflection nonplanar ring light path, where N is an integer greater than or equal to 2, comprising 2N-1 total internal reflections and one reflection at a coupler in a single round trip. Undirectional traveling wave oscillation of the laser is induced by the geometry of the nonplanar ring path together with the effect of an applied magnetic field and partial polarizer characteristics of the oblique reflection from the coupler. The 6-reflection nonplanar ring oscillator makes possible otpimal unidirectional oscillation (low loss for the oscillating direction of propagation and, simultaneously high loss for the nonoscillating direction of propagation) in monolithic NPROs using materials with index of refraction smaller than the square root of 3, for example, laser glass.

  20. Physics of quantum rings

    CERN Document Server

    Fomin, Vladimir M

    2013-01-01

    This book deals with a new class of materials, quantum rings. Innovative recent advances in experimental and theoretical physics of quantum rings are based on the most advanced state-of-the-art fabrication and characterization techniques as well as theoretical methods. The experimental efforts allow to obtain a new class of semiconductor quantum rings formed by capping self-organized quantum dots grown by molecular beam epitaxy. Novel optical and magnetic properties of quantum rings are associated with non-trivial topologies at the nanoscale. An adequate characterization of quantum rings is po

  1. Nitrile O-ring Cracking: A Case of Vacuum Flange O-ring Failures

    Energy Technology Data Exchange (ETDEWEB)

    Dees, Craig

    2016-07-01

    A review of recent nitrile O-ring failures in ISO-KF vacuum flange connections in glovebox applications is presented. An investigation of a single “isolated” o-ring failure leads to the discovery of cracked nitrile o-rings in a glovebox atmospheric control unit. The initial cause of the o-ring failure is attributed to ozone degradation. However, additional investigation reveals nitrile o-ring cracking on multiple gloveboxes and general purpose piping, roughly 85% of the nitrile o-rings removed for inspection show evidence of visible cracking after being in service for 18 months or less. The results of material testing and ambient air testing is presented, elevated ozone levels are not found. The contributing factors of o-ring failure, including nitrile air sensitivity, inadequate storage practices, and poor installation techniques, are discussed. A discussion of nitrile o-ring material properties, the benefits and limitations, and alternate materials are discussed. Considerations for o-ring material selection, purchasing, storage, and installation are presented in the context of lessons learned from the nitrile o-ring cracking investigation. This paper can be presented in 20 minutes and does not require special accommodations or special audio visual devices.

  2. Highly Confined Electronic and Ionic Conduction in Oxide Heterostructures

    DEFF Research Database (Denmark)

    Pryds, Nini

    2015-01-01

    The conductance confined at the interface of complex oxide heterostructures provides new opportunities to explore nanoelectronic as well as nanoionic devices. In this talk I will present our recent results both on ionic and electronic conductivity at different heterostructures systems. In the first...... unattainable for Bi2O3-based materials, is achieved[1]. These confined heterostructures provide a playground not only for new high ionic conductivity phenomena that are sufficiently stable but also uncover a large variety of possible technological perspectives. At the second part, I will discuss and show our...

  3. Photoresponse of Natural van der Waals Heterostructures.

    Science.gov (United States)

    Ray, Kyle; Yore, Alexander E; Mou, Tong; Jha, Sauraj; Smithe, Kirby K H; Wang, Bin; Pop, Eric; Newaz, A K M

    2017-06-27

    Van der Waals heterostructures consisting of two-dimensional materials offer a platform to obtain materials by design and are very attractive owing to unique electronic states. Research on 2D van der Waals heterostructures (vdWH) has so far been focused on fabricating individually stacked atomically thin unary or binary crystals. Such systems include graphene, hexagonal boron nitride, and members of the transition metal dichalcogenide family. Here we present our experimental study of the optoelectronic properties of a naturally occurring vdWH, known as franckeite, which is a complex layered crystal composed of lead, tin, antimony, iron, and sulfur. We present here that thin film franckeite (60 nm power-resolved and temperature-resolved photocurrent measurements reveal that the photocarrier generation and recombination are dominated by continuously distributed trap states within the band gap. To understand wavelength-resolved photocurrent, we also calculated the optical absorption properties via density functional theory. Finally, we have shown that the device has a fast photoresponse with a rise time as fast as ∼1 ms. Our study provides a fundamental understanding of the optoelectronic behavior in a complex naturally occurring vdWH, and may pave an avenue toward developing nanoscale optoelectronic devices with tailored properties.

  4. Stimulated emission and optical gain in AlGaN heterostructures grown on bulk AlN substrates

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Wei, E-mail: wguo2@ncsu.edu; Bryan, Zachary; Kirste, Ronny; Bryan, Isaac; Hussey, Lindsay; Bobea, Milena; Haidet, Brian; Collazo, Ramón; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States); Xie, Jinqiao; Mita, Seiji [HexaTech, Inc., 991 Aviation Pkwy, Suite 800, Morrisville, North Carolina 27560 (United States); Gerhold, Michael [Engineering Science Directorate, Army Research Office, P.O. BOX 12211, Research Triangle Park, North Carolina 27703 (United States)

    2014-03-14

    Optical gain spectra for ∼250 nm stimulated emission were compared in three different AlGaN-based structures grown on single crystalline AlN substrates: a single AlGaN film, a double heterostructure (DH), and a Multiple Quantum Well (MQW) structure; respective threshold pumping power densities of 700, 250, and 150 kW/cm{sup 2} were observed. Above threshold, the emission was transverse-electric polarized and as narrow as 1.8 nm without a cavity. The DH and MQW structures showed gain values of 50–60 cm{sup −1} when pumped at 1 MW/cm{sup 2}. The results demonstrated the excellent optical quality of the AlGaN-based heterostructures grown on AlN substrates and their potential for realizing electrically pumped sub-280 nm laser diodes.

  5. Variable electronic properties of lateral phosphorene-graphene heterostructures.

    Science.gov (United States)

    Tian, Xiaoqing; Liu, Lin; Du, Yu; Gu, Juan; Xu, Jian-Bin; Yakobson, Boris I

    2015-12-21

    Phosphorene and graphene have a tiny lattice mismatch along the armchair direction, which can result in an atomically sharp in-plane interface. The electronic properties of the lateral heterostructures of phosphorene/graphene are investigated by the first-principles method. Here, we demonstrate that the electronic properties of this type of heterostructure can be highly tunable by the quantum size effects and the externally applied electric field (Eext). At strong Eext, Dirac Fermions can be developed with Fermi velocities around one order smaller than that of graphene. Undoped and hydrogen doped configurations demonstrate three drastically different electronic phases, which reveal the strongly tunable potential of this type of heterostructure. Graphene is a naturally better electrode for phosphorene. The transport properties of two-probe devices of graphene/phosphorene/graphene exhibit tunnelling transport characteristics. Given these results, it is expected that in-plane heterostructures of phosphorene/graphene will present abundant opportunities for applications in optoelectronic and electronic devices.

  6. Quantum dot nanoscale heterostructures for solar energy conversion.

    Science.gov (United States)

    Selinsky, Rachel S; Ding, Qi; Faber, Matthew S; Wright, John C; Jin, Song

    2013-04-07

    Quantum dot nanoscale semiconductor heterostructures (QDHs) are a class of materials potentially useful for integration into solar energy conversion devices. However, realizing the potential of these heterostructured systems requires the ability to identify and synthesize heterostructures with suitably designed materials, controlled size and morphology of each component, and structural control over their shared interface. In this review, we will present the case for the utility and advantages of chemically synthesized QDHs for solar energy conversion, beginning with an overview of various methods of heterostructured material synthesis and a survey of heretofore reported materials systems. The fundamental charge transfer properties of the resulting materials combinations and their basic design principles will be outlined. Finally, we will discuss representative solar photovoltaic and photoelectrochemical devices employing QDHs (including quantum dot sensitized solar cells, or QDSSCs) and examine how QDH synthesis and design impacts their performance.

  7. Organic heterostructures based on arylenevinylene oligomers deposited by MAPLE

    Czech Academy of Sciences Publication Activity Database

    Socol, M.; Preda, N.; Vacareanu, L.; Grigoras, M.; Socol, G.; Mihailescu, I. N.; Stanculescu, F.; Jelínek, Miroslav; Stanculescu, A.; Stoicanescu, M.

    2014-01-01

    Roč. 302, May (2014), s. 216-222 ISSN 0169-4332 Institutional support: RVO:68378271 Keywords : organic heterostructures * MAPLE * oligomer * optoelectronica Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.711, year: 2014

  8. Ge/Si core/multi shell heterostructure FETs

    Energy Technology Data Exchange (ETDEWEB)

    Picraux, Samuel T [Los Alamos National Laboratory; Dayeh, Shadi A [Los Alamos National Laboratory

    2010-01-01

    Concentric heterostructured materials provide numerous design opportunities for engineering strain and interfaces, as well as tailoring energy band-edge combinations for optimal device performance. Key to the realization of such novel device concepts is the complete understanding and full control over their growth, crystal structure, and hetero-epitaxy. We report here on a new route for synthesizing Ge/Si core/multi-shell heterostructure nanowires that eliminate Au seed diffusion on the nanowire sidewalls by engineering the interface energy density difference. We show that such control over core/shell synthesis enable experimental realization of heterostructure FET devices beyond those available in the literature with enhanced transport characteristics. We provide a side-by-side comparison on the transport properties of Ge/Si core/multi-shell nanowires grown with and without Au diffusion and demonstrate heterostructure FETs with drive currents that are {approx} 2X higher than record results for p-type FETs.

  9. Quantum engineering of transistors based on 2D materials heterostructures

    Science.gov (United States)

    Iannaccone, Giuseppe; Bonaccorso, Francesco; Colombo, Luigi; Fiori, Gianluca

    2018-03-01

    Quantum engineering entails atom-by-atom design and fabrication of electronic devices. This innovative technology that unifies materials science and device engineering has been fostered by the recent progress in the fabrication of vertical and lateral heterostructures of two-dimensional materials and by the assessment of the technology potential via computational nanotechnology. But how close are we to the possibility of the practical realization of next-generation atomically thin transistors? In this Perspective, we analyse the outlook and the challenges of quantum-engineered transistors using heterostructures of two-dimensional materials against the benchmark of silicon technology and its foreseeable evolution in terms of potential performance and manufacturability. Transistors based on lateral heterostructures emerge as the most promising option from a performance point of view, even if heterostructure formation and control are in the initial technology development stage.

  10. Token Ring Project

    Directory of Open Access Journals (Sweden)

    Adela Ionescu

    2007-01-01

    Full Text Available Ring topology is a simple configuration used to connect processes that communicate among themselves. A number of network standards such as token ring, token bus, and FDDI are based on the ring connectivity. This article will develop an implementation of a ring of processes that communicate among themselves via pipe links. The processes are nodes in the ring. Each process reads from its standard input and writes in its standard output. N-1 process redirects the its standard output to a standard input of the process through a pipe. When the ring-structure is designed, the project can be extended to simulate networks or to implement algorithms for mutual exclusion

  11. Token ring technology report

    CERN Document Server

    2013-01-01

    Please note this is a Short Discount publication. This report provides an overview of the IBM Token-Ring technology and products built by IBM and compatible vendors. It consists of two sections: 1. A summary of the design trade-offs for the IBM Token-Ring. 2. A summary of the products of the major token-ring compatible vendors broken down by adapters and components, wiring systems, testing, and new chip technology.

  12. Spannungsgesteuerter Ring-Oszillator

    OpenAIRE

    Wang, Z.; Thiede, A.

    1999-01-01

    The oscillator (1) of integrated monolithic design has several analogue amplifier units (2) connected in a ring. The individual amplifiers are frequency selective in regard to a resonance frequency. The phase displacements of the amplifiers are chosen so that the total phase displacement over the ring at the resonance frequencies of the amplifiers amounts to 3600 or a whole number multiple of that. The number of amplifiers selected corresponds to the overall quality factor for the ring oscill...

  13. Radioactive gold ring dermatitis

    Energy Technology Data Exchange (ETDEWEB)

    Miller, R.A.; Aldrich, J.E. (Dalhousie Univ., Halifax, Nova Scotia (Canada))

    1990-08-01

    A superficial squamous cell carcinoma developed in a woman who wore a radioactive gold ring for more than 30 years. Only part of the ring was radioactive. Radiation dose measurements indicated that the dose to basal skin layer was 2.4 Gy (240 rad) per week. If it is assumed that the woman continually wore her wedding ring for 37 years since purchase, she would have received a maximum dose of approximately 4600 Gy.

  14. Vortex and source rings

    DEFF Research Database (Denmark)

    Branlard, Emmanuel Simon Pierre

    2017-01-01

    The velocity field, vector potential and velocity gradient of a vortex ring is derived in this chapter. The Biot-Savart law for the vector potential and velocity is expressed in a first section. Then, the flow is derived at specific locations: on the axis, near the axis and in the far field where...... is dedicated to vortex rings. Source rings are only briefly mentioned....

  15. Radioactive gold ring dermatitis

    International Nuclear Information System (INIS)

    Miller, R.A.; Aldrich, J.E.

    1990-01-01

    A superficial squamous cell carcinoma developed in a woman who wore a radioactive gold ring for more than 30 years. Only part of the ring was radioactive. Radiation dose measurements indicated that the dose to basal skin layer was 2.4 Gy (240 rad) per week. If it is assumed that the woman continually wore her wedding ring for 37 years since purchase, she would have received a maximum dose of approximately 4600 Gy

  16. Picosecond time resolved cathodoluminescence to study semiconductor materials and heterostructures

    OpenAIRE

    Sonderegger, Samuel

    2007-01-01

    A large number of characterization tools for semiconductor based heterostructures are available nowadays. Most of these techniques deliver high temporal resolution (down to hundreds of femtoseconds) or good spatial resolution (down to sub nanometer resolution), but not both simultaneously. However, to get a complete picture of carrier recombination and diffusion processes in heterostructures, one needs a spectroscopic tool which simultaneously yields high temporal and spatial resolutions. The...

  17. Picosecond time resolved cathodoluminescence to study semiconductor materials and heterostructures

    OpenAIRE

    Sonderegger, Samuel; Ganière, Jean-Daniel

    2008-01-01

    A large number of characterization tools for semiconductor based heterostructures are available nowadays. Most of these techniques deliver high temporal resolution (down to hundreds of femtoseconds) or good spatial resolution (down to sub nanometer resolution), but not both simultaneously. However, to get a complete picture of carrier recombination and diffusion processes in heterostructures, one needs a spectroscopic tool which simultaneously yields high temporal and spatial resolutions. The...

  18. The ring laser gyro

    Science.gov (United States)

    Chow, W. W.; Gea-Banacloche, J.; Pedrotti, L. M.; Sanders, V. E.; Schleich, W.; Scully, M. O.

    1985-01-01

    This paper presents a review of both active and passive ring laser devices. The operating principles of the ring laser are developed and discussed, with special emphasis given to the problems associated with the achievement of greater sensitivity and stability. First-principle treatments of the nature of quantum noise in the ring laser gyro and various methods designed to avoid low-rotation-rate lock-in are presented. Descriptions of state-of-the-art devices and current and proposed applications (including a proposed test of metric theories of gravity using a passive cavity ring laser) are given.

  19. Temperature Dependence of the Resonant Magnetoelectric Effect in Layered Heterostructures

    Directory of Open Access Journals (Sweden)

    Dmitrii A. Burdin

    2017-10-01

    Full Text Available The dependence of the resonant direct magnetoelectric effect on temperature is studied experimentally in planar composite structures. Samples of rectangular shapes with dimensions of 5 mm × 20 mm employed ferromagnetic layers of either an amorphous (metallic glass alloy or nickel with a thickness of 20–200 μm and piezoelectric layers of single crystalline langatate material or lead zirconate titanate piezoelectric ceramics with a thickness of 500 μm. The temperature of the samples was varied in a range between 120 and 390 K by blowing a gaseous nitrogen stream around them. It is shown that the effective characteristics of the magnetoelectric effect—such as the mechanical resonance frequency fr, the quality factor Q and the magnitude of the magnetoelectric coefficient αE at the resonance frequency—are contingent on temperature. The interrelations between the temperature changes of the characteristics of the magnetoelectric effect and the temperature variations of the following material parameters—Young’s modulus Y, the acoustic quality factor of individual layers, the dielectric constant ε, the piezoelectric modulus d of the piezoelectric layer as well as the piezomagnetic coefficients λ(n of the ferromagnetic layer—are established. The effect of temperature on the characteristics of the nonlinear magnetoelectric effect is observed for the first time. The results can be useful for designing magnetoelectric heterostructures with specified temperature characteristics, in particular, for the development of thermally stabilized magnetoelectric devices.

  20. Anomalous conductivity noise in gapped bilayer graphene heterostructure

    Science.gov (United States)

    Aamir, Mohammed Ali; Karnatak, Paritosh; Sai, T. Phanindra; Ghosh, Arindam

    Bilayer graphene has unique electronic properties - it has a tunable band gap and also, valley symmetry and pseudospin degree of freedom like its single layer counterpart. In this work, we present a study of conductance fluctuations in dual gated bilayer graphene heterostructures by varying the Fermi energy and the band gap independently. At a fixed band gap, we find that the conductance fluctuations obtained by Fermi energy ensemble sampling increase rapidly as the Fermi energy is tuned to charge neutrality point (CNP) whereas the time-dependent conductance fluctuations diminish rapidly. This discrepancy is completely absent at higher number densities, where the transport is expected to be through the 2D bulk of the bilayer system. This observation indicates that near the CNP, electrical transport is highly sensitive to Fermi energy, but becomes progressively immune to time-varying disorder. A possible explanation may involve transport via edge states which becomes the dominant conduction mechanism when the bilayer graphene is gapped and Fermi energy is situated close to the CNP, thereby causing a dimensional crossover from 2D to 1D transport. Our experiment outlines a possible experimental protocol to probe intrinsic topological states in gapped bilayer graphene.

  1. Development of Novel Two-dimensional Layers, Alloys and Heterostructures

    Science.gov (United States)

    Liu, Zheng

    2015-03-01

    The one-atom-think graphene has fantastic properties and attracted tremendous interests in these years, which opens a window towards various two-dimensional (2D) atomic layers. However, making large-size and high-quality 2D layers is still a great challenge. Using chemical vapor deposition (CVD) method, we have successfully synthesized a wide varieties of highly crystalline and large scale 2D atomic layers, including h-BN, metal dichalcogenides e.g. MoS2, WS2, CdS, GaSe and MoSe2 which belong to the family of binary 2D materials. Ternary 2D alloys including BCN and MoS2xSe2 (1 - x) are also prepared and characterized. In addition, synthesis of 2D heterostructures such as vertical and lateral graphene/h-BN, vertical and lateral TMDs are also demonstrated. Complementary to CVD grown 2D layers, 2D single-crystal (bulk) such as Phosphorene (P), WTe2, SnSe2, PtS2, PtSe2, PdSe2, WSe2xTe2 (1 - x), Ta2NiS5andTa2NiSe5 are also prepared by solid reactions. There work provide a better understanding of the atomic layered materials in terms of the synthesis, atomic structure, alloying and their physical properties. Potential applications of these 2D layers e.g. optoelectronic devices, energy device and smart coating have been explored.

  2. Organic heterostructures deposited by MAPLE on AZO substrate

    Science.gov (United States)

    Socol, M.; Preda, N.; Stanculescu, A.; Breazu, C.; Florica, C.; Stanculescu, F.; Iftimie, S.; Girtan, M.; Popescu-Pelin, G.; Socol, G.

    2017-09-01

    Organic heterostructures based on poly(3-hexylthiophene) (P3HT) and fullerene (C60) as blends or multilayer were deposited on Al:ZnO (AZO) by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. The AZO layers were obtained by Pulsed Laser Deposition (PLD) on glass substrate, the high quality of the films being reflected by the calculated figure of merit. The organic heterostructures were investigated from morphological, optical and electrical point of view by atomic force microscopy (AFM), UV-vis spectroscopy, photoluminescence (PL) and current-voltage (I-V) measurements, respectively. The increase of the C60 content in the blend heterostructure has as result a high roughness. Compared with the multilayer heterostructure, those based on blends present an improvement in the electrical properties. Under illumination, the highest current value was recorded for the heterostructure based on the blend with the higher C60 amount. The obtained results showed that MAPLE is a useful technique for the deposition of the organic heterostructures on AZO as transparent conductor electrode.

  3. Novel phase diagram behavior and materials design in heterostructural semiconductor alloys

    Science.gov (United States)

    Holder, Aaron M.; Siol, Sebastian; Ndione, Paul F.; Peng, Haowei; Deml, Ann M.; Matthews, Bethany E.; Schelhas, Laura T.; Toney, Michael F.; Gordon, Roy G.; Tumas, William; Perkins, John D.; Ginley, David S.; Gorman, Brian P.; Tate, Janet; Zakutayev, Andriy; Lany, Stephan

    2017-01-01

    Structure and composition control the behavior of materials. Isostructural alloying is historically an extremely successful approach for tuning materials properties, but it is often limited by binodal and spinodal decomposition, which correspond to the thermodynamic solubility limit and the stability against composition fluctuations, respectively. We show that heterostructural alloys can exhibit a markedly increased range of metastable alloy compositions between the binodal and spinodal lines, thereby opening up a vast phase space for novel homogeneous single-phase alloys. We distinguish two types of heterostructural alloys, that is, those between commensurate and incommensurate phases. Because of the structural transition around the critical composition, the properties change in a highly nonlinear or even discontinuous fashion, providing a mechanism for materials design that does not exist in conventional isostructural alloys. The novel phase diagram behavior follows from standard alloy models using mixing enthalpies from first-principles calculations. Thin-film deposition demonstrates the viability of the synthesis of these metastable single-phase domains and validates the computationally predicted phase separation mechanism above the upper temperature bound of the nonequilibrium single-phase region. PMID:28630928

  4. Novel phase diagram behavior and materials design in heterostructural semiconductor alloys.

    Science.gov (United States)

    Holder, Aaron M; Siol, Sebastian; Ndione, Paul F; Peng, Haowei; Deml, Ann M; Matthews, Bethany E; Schelhas, Laura T; Toney, Michael F; Gordon, Roy G; Tumas, William; Perkins, John D; Ginley, David S; Gorman, Brian P; Tate, Janet; Zakutayev, Andriy; Lany, Stephan

    2017-06-01

    Structure and composition control the behavior of materials. Isostructural alloying is historically an extremely successful approach for tuning materials properties, but it is often limited by binodal and spinodal decomposition, which correspond to the thermodynamic solubility limit and the stability against composition fluctuations, respectively. We show that heterostructural alloys can exhibit a markedly increased range of metastable alloy compositions between the binodal and spinodal lines, thereby opening up a vast phase space for novel homogeneous single-phase alloys. We distinguish two types of heterostructural alloys, that is, those between commensurate and incommensurate phases. Because of the structural transition around the critical composition, the properties change in a highly nonlinear or even discontinuous fashion, providing a mechanism for materials design that does not exist in conventional isostructural alloys. The novel phase diagram behavior follows from standard alloy models using mixing enthalpies from first-principles calculations. Thin-film deposition demonstrates the viability of the synthesis of these metastable single-phase domains and validates the computationally predicted phase separation mechanism above the upper temperature bound of the nonequilibrium single-phase region.

  5. Quantum and field effects of oxide heterostructures

    DEFF Research Database (Denmark)

    Trier, Felix

    . In these multi-plexed devices, several inputs aretranslated into several outputs through the multiple physical functionalities.A highly prominent example of such an oxide interface is the one between LaAlO3 and SrTiO3. Although both LaAlO3 and SrTiO3 in the bulk are electrically insulating and non...... aspects of sample preparation will initially be covered. Here, the growth of amorphous-LaAlO3 on SrTiO3 will be addressed in a modified pulsed laser deposition setup. This is followed by an investigation of two high-electron mobility interfaces in SrTiO3-based heterostructures. Specifically...

  6. Rashba-Edelstein Magnetoresistance in Metallic Heterostructures.

    Science.gov (United States)

    Nakayama, Hiroyasu; Kanno, Yusuke; An, Hongyu; Tashiro, Takaharu; Haku, Satoshi; Nomura, Akiyo; Ando, Kazuya

    2016-09-09

    We report the observation of magnetoresistance originating from Rashba spin-orbit coupling (SOC) in a metallic heterostructure: the Rashba-Edelstein (RE) magnetoresistance. We show that the simultaneous action of the direct and inverse RE effects in a Bi/Ag/CoFeB trilayer couples current-induced spin accumulation to the electric resistance. The electric resistance changes with the magnetic-field angle, reminiscent of the spin Hall magnetoresistance, despite the fact that bulk SOC is not responsible for the magnetoresistance. We further found that, even when the magnetization is saturated, the resistance increases with increasing the magnetic-field strength, which is attributed to the Hanle magnetoresistance in this system.

  7. Vertical 2D/3D Semiconductor Heterostructures Based on Epitaxial Molybdenum Disulfide and Gallium Nitride.

    Science.gov (United States)

    Ruzmetov, Dmitry; Zhang, Kehao; Stan, Gheorghe; Kalanyan, Berc; Bhimanapati, Ganesh R; Eichfeld, Sarah M; Burke, Robert A; Shah, Pankaj B; O'Regan, Terrance P; Crowne, Frank J; Birdwell, A Glen; Robinson, Joshua A; Davydov, Albert V; Ivanov, Tony G

    2016-03-22

    When designing semiconductor heterostructures, it is expected that epitaxial alignment will facilitate low-defect interfaces and efficient vertical transport. Here, we report lattice-matched epitaxial growth of molybdenum disulfide (MoS2) directly on gallium nitride (GaN), resulting in high-quality, unstrained, single-layer MoS2 with strict registry to the GaN lattice. These results present a promising path toward the implementation of high-performance electronic devices based on 2D/3D vertical heterostructures, where each of the 3D and 2D semiconductors is both a template for subsequent epitaxial growth and an active component of the device. The MoS2 monolayer triangles average 1 μm along each side, with monolayer blankets (merged triangles) exhibiting properties similar to that of single-crystal MoS2 sheets. Photoluminescence, Raman, atomic force microscopy, and X-ray photoelectron spectroscopy analyses identified monolayer MoS2 with a prominent 20-fold enhancement of photoluminescence in the center regions of larger triangles. The MoS2/GaN structures are shown to electrically conduct in the out-of-plane direction, confirming the potential of directly synthesized 2D/3D semiconductor heterostructures for vertical current flow. Finally, we estimate a MoS2/GaN contact resistivity to be less than 4 Ω·cm(2) and current spreading in the MoS2 monolayer of approximately 1 μm in diameter.

  8. Stability of the tungsten diselenide and silicon carbide heterostructure against high energy proton exposure

    Science.gov (United States)

    Walker, Roger C.; Shi, Tan; Jariwala, Bhakti; Jovanovic, Igor; Robinson, Joshua A.

    2017-10-01

    Single layers of tungsten diselenide (WSe2) can be used to construct ultra-thin, high-performance electronics. Additionally, there has been considerable progress in controlled and direct growth of single layers on various substrates. Based on these results, high-quality WSe2-based devices that approach the limit of physical thickness are now possible. Such devices could be useful for space applications, but understanding how high-energy radiation impacts the properties of WSe2 and the WSe2/substrate interface has been lacking. In this work, we compare the stability against high energy proton radiation of WSe2 and silicon carbide (SiC) heterostructures generated by mechanical exfoliation of WSe2 flakes and by direct growth of WSe2 via metal-organic chemical vapor deposition (MOCVD). These two techniques produce WSe2/SiC heterostructures with distinct differences due to interface states generated during the MOCVD growth process. This difference carries over to differences in band alignment from interface states and the ultra-thin nature of the MOCVD-grown material. Both heterostructures are not susceptible to proton-induced charging up to a dose of 1016 protons/cm2, as measured via shifts in the binding energy of core shell electrons and a decrease in the valence band offset. Furthermore, the MOCVD-grown material is less affected by the proton exposure due to its ultra-thin nature and a greater interaction with the substrate. These combined effects show that the directly grown material is suitable for multi-year use in space, provided that high quality devices can be fabricated from it.

  9. EBT ring physics

    International Nuclear Information System (INIS)

    Uckan, N.A.

    1980-04-01

    This workshop attempted to evaluate the status of the current experimental and theoretical understanding of hot electron ring properties. The dominant physical processes that influence ring formation, scaling, and their optimal behavior are also studied. Separate abstracts were prepared for each of the 27 included papers

  10. Children of Sex Rings.

    Science.gov (United States)

    Hunt, Patricia; Baird, Margaret

    1990-01-01

    Outlines three major differentiating categories of children who were sexually abused by sex rings: level of fear, ability to trust, and disclosure confusion. Addresses denial and resistance regarding child sexual exploitation by a ring among practitioners in the child welfare system. (Author/BB)

  11. Illustration of Saturn's Rings

    Science.gov (United States)

    2001-01-01

    This illustration shows a close-up of Saturn's rings. These rings are thought to have formed from material that was unable to form into a Moon because of tidal forces from Saturn, or from a Moon that was broken up by Saturn's tidal forces.

  12. Relativistic ring models

    Energy Technology Data Exchange (ETDEWEB)

    Ujevic, Maximiliano [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil). Centro de Ciencias Naturais e Humanas; Letelier, Patricio S.; Vogt, Daniel [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Inst. de Matematica, Estatistica e Computacao Cientifica. Dept. de Matematica Aplicada

    2011-07-01

    Full text: Relativistic thick ring models are constructed using previously found analytical Newtonian potential-density pairs for flat rings and toroidal structures obtained from Kuzmin-Toomre family of discs. This was achieved by inflating previously constructed Newtonian ring potentials using the transformation |z|{yields}{radical}z{sup 2} + b{sup 2}, and then finding their relativistic analog. The models presented have infinite extension but the physical quantities decays very fast with the distance, and in principle, one could make a cut-off radius to consider it finite. In particular, we present systems with one ring, two rings and a disc with a ring. Also, the circular velocity of a test particle and its stability when performing circular orbits are presented in all these models. Using the Rayleigh criterion of stability of a fluid at rest in a gravitational field, we find that the different systems studied present a region of non-stability that appears in the intersection of the disc and the ring, and between the rings when they become thinner. (author)

  13. Imaging rings in ring imaging Cherenkov counters

    Energy Technology Data Exchange (ETDEWEB)

    Ratcliff, Blair N

    2002-11-25

    The general concepts used to form images in Ring Imaging Cherenkov (RICH) counters are described and their performance properties compared. Particular attention is paid to issues associated with imaging in the time dimension, especially in Detectors of Internally Reflected Cherenkov light (DIRCs).

  14. Rings and their modules

    CERN Document Server

    Bland, Paul E

    2011-01-01

    This book is an introduction to the theory of rings and modules that goes beyond what one normally obtains in a graduate course in abstract algebra. In addition to the presentation of standard topics in ring and module theory, it also covers category theory, homological algebra and even more specialized topics like injective envelopes and projective covers, reflexive modules and quasi-Frobenius rings, and graded rings and modules. The book is a self-contained volume written in a very systematic style: allproofs are clear and easy for the reader to understand and allarguments are based onmaterials contained in the book. A problem sets follow each section. It is suitable for graduate and PhD students who have chosen ring theory for their research subject.

  15. Tuning Light Emission of a Pressure-Sensitive Silicon/ZnO Nanowires Heterostructure Matrix through Piezo-phototronic Effects.

    Science.gov (United States)

    Chen, Mengxiao; Pan, Caofeng; Zhang, Taiping; Li, Xiaoyi; Liang, Renrong; Wang, Zhong Lin

    2016-06-28

    Based on white light emission at silicon (Si)/ZnO hetrerojunction, a pressure-sensitive Si/ZnO nanowires heterostructure matrix light emitting diode (LED) array is developed. The light emission intensity of a single heterostructure LED is tuned by external strain: when the applied stress keeps increasing, the emission intensity first increases and then decreases with a maximum value at a compressive strain of 0.15-0.2%. This result is attributed to the piezo-phototronic effect, which can efficiently modulate the LED emission intensity by utilizing the strain-induced piezo-polarization charges. It could tune the energy band diagrams at the junction area and regulate the optoelectronic processes such as charge carriers generation, separation, recombination, and transport. This study achieves tuning silicon based devices through piezo-phototronic effect.

  16. Measurement of size-dependent single scattering albedo of fresh biomass burning aerosols using the extinction-minus-scattering technique with a combination of cavity ring-down spectroscopy and nephelometry

    Directory of Open Access Journals (Sweden)

    S. Singh

    2016-11-01

    Full Text Available Biomass burning (BB aerosols have a significant effect on regional climate, and represent a significant uncertainty in our understanding of climate change. Using a combination of cavity ring-down spectroscopy and integrating nephelometry, the single scattering albedo (SSA and Ångstrom absorption exponent (AAE were measured for several North American biomass fuels. This was done for several particle diameters for the smoldering and flaming stage of white pine, red oak, and cedar combustion. Measurements were done over a wider wavelength range than any previous direct measurement of BB particles. While the offline sampling system used in this work shows promise, some changes in particle size distribution were observed, and a thorough evaluation of this method is required. The uncertainty of SSA was 6 %, with the truncation angle correction of the nephelometer being the largest contributor to error. While scattering and extinction did show wavelength dependence, SSA did not. SSA values ranged from 0.46 to 0.74, and were not uniformly greater for the smoldering stage than the flaming stage. SSA values changed with particle size, and not systematically so, suggesting the proportion of tar balls to fractal black carbon change with fuel type/state and particle size. SSA differences of 0.15–0.4 or greater can be attributed to fuel type or fuel state for fresh soot. AAE values were quite high (1.59–5.57, despite SSA being lower than is typically observed in wildfires. The SSA and AAE values in this work do not fit well with current schemes that relate these factors to the modified combustion efficiency of a burn. Combustion stage, particle size, fuel type, and fuel condition were found to have the most significant effects on the intrinsic optical properties of fresh soot, though additional factors influence aged soot.

  17. Mechanical seal having a double-tier mating ring

    Science.gov (United States)

    Khonsari, Michael M.; Somanchi, Anoop K.

    2005-09-13

    An apparatus and method to enhance the overall performance of mechanical seals in one of the following ways: by reducing seal face wear, by reducing the contact surface temperature, or by increasing the life span of mechanical seals. The apparatus is a mechanical seal (e.g., single mechanical seals, double mechanical seals, tandem mechanical seals, bellows, pusher mechanical seals, and all types of rotating and reciprocating machines) comprising a rotating ring and a double-tier mating ring. In a preferred embodiment, the double-tier mating ring comprises a first and a second stationary ring that together form an agitation-inducing, guided flow channel to allow for the removal of heat generated at the seal face of the mating ring by channeling a coolant entering the mating ring to a position adjacent to and in close proximity with the interior surface area of the seal face of the mating ring.

  18. Longitudinal dynamics in storage rings

    International Nuclear Information System (INIS)

    Colton, E.P.

    1986-01-01

    The single-particle equations of motion are derived for charged particles in a storage ring. Longitudinal space charge is included in the potential assuming an infinitely conducting circular beam pipe with a distributed inductance. The framework uses Hamilton's equations with the canonical variables phi and W. The Twiss parameters for longitudinal motion are also defined for the small amplitude synchrotron oscillations. The space-charge Hamiltonian is calculated for both parabolic bunches and ''matched'' bunches. A brief analysis including second-harmonic rf contributions is also given. The final sections supply calculations of dynamical quantities and particle simulations with the space-charge effects neglected

  19. Illumination intensity dependent photoresponse of ultra-thin ZnO/graphene/ZnO heterostructure

    Science.gov (United States)

    Dusza, M.; Granek, F.; Strek, W.

    2017-12-01

    A heterostructure of zinc oxide (ZnO) and single layer graphene is fabricated by sandwiching a transferred graphene between two thin ZnO films (∼20 nm each). ZnO thin films were grown using decomposition of Zn(acac)2 and spin-coating technique. Graphene transfer route with PMMA temporary carrier and metal etching process was used to transfer high quality commercial graphene from copper foil on the zinc oxide surface on glass. This novel and ultra-thin heterostructure (∼40 nm) is sensitive for UV illumination and works as a photodetector (PD). In this device, both positive and negative photoconductivity (PC) were observed depends on illumination intensity and spectrum of incident light. Relatively long response and recovery times obtained in ZnO/G/ZnO structure are related to the metastable defect states of ZnO and its interfaces with graphene and/or silver contacts. The obtained results show that the transferred single layer graphene sheet between thin ZnO films could be a novel route for improvement properties this low-cost metal oxide.

  20. Ring chromosome 13

    DEFF Research Database (Denmark)

    Brandt, C A; Hertz, Jens Michael; Petersen, M B

    1992-01-01

    A stillborn male child with anencephaly and multiple malformations was found to have the karyotype 46,XY,r(13) (p11q21.1). The breakpoint at 13q21.1, determined by high resolution banding, is the most proximal breakpoint ever reported in patients with ring chromosome 13. In situ hybridisation...... with the probe L1.26 confirmed the derivation from chromosome 13 and DNA polymorphism analysis showed maternal origin of the ring chromosome. Our results, together with a review of previous reports of cases with ring chromosome 13 with identified breakpoints, could neither support the theory of distinct clinical...

  1. Faithfully quadratic rings

    CERN Document Server

    Dickmann, M

    2015-01-01

    In this monograph the authors extend the classical algebraic theory of quadratic forms over fields to diagonal quadratic forms with invertible entries over broad classes of commutative, unitary rings where -1 is not a sum of squares and 2 is invertible. They accomplish this by: (1) Extending the classical notion of matrix isometry of forms to a suitable notion of T-isometry, where T is a preorder of the given ring, A, or T = A^2. (2) Introducing in this context three axioms expressing simple properties of (value) representation of elements of the ring by quadratic forms, well-known to hold in

  2. Nonlinear dynamics aspects of modern storage rings

    International Nuclear Information System (INIS)

    Helleman, R.H.G.; Kheifets, S.A.

    1986-01-01

    It is argued that the nonlinearity of storage rings becomes an essential problem as the design parameters of each new machine are pushed further and further. Yet the familiar methods of classical mechanics do not allow determination of single particle orbits over reasonable lengths of time. It is also argued that the single particle dynamics of a storage ring is possibly one of the cleanest and simplest nonlinear dynamical systems available with very few degrees of freedom. Hence, reasons are found for accelerator physicists to be interested in nonlinear dynamics and for researchers in nonlinear dynamics to be interested in modern storage rings. The more familiar methods of treating nonlinear systems routinely used in acclerator theory are discussed, pointing out some of their limitations and pitfalls. 39 refs., 1 fig

  3. Topical Workshop on Heterostructure Microelectronics for Information Systems Applications (TWHM-ISA '98) Held in Shonan Village Center, Hayama-machi, Kanagawa, Japan on August 30-September 2, 1998

    National Research Council Canada - National Science Library

    Ishibashi, T

    1998-01-01

    .... The technologies employed are based on heterostructure bipolar transistors, heterostructure field effect transistors and resonant tunneling diodes, and make use of a variety of heterostructure...

  4. The g-2 ring

    CERN Multimedia

    1974-01-01

    The precise measurement of "g-2", the anomalous magnetic moment of the muon, required a special muon storage ring with electrostatic focussing and very accurate knowledge of the magnetic bending field. For more details see under photo 7405430.

  5. Saturn's dynamic D ring

    Science.gov (United States)

    Hedman, M.M.; Burns, J.A.; Showalter, M.R.; Porco, C.C.; Nicholson, P.D.; Bosh, A.S.; Tiscareno, M.S.; Brown, R.H.; Buratti, B.J.; Baines, K.H.; Clark, R.

    2007-01-01

    The Cassini spacecraft has provided the first clear images of the D ring since the Voyager missions. These observations show that the structure of the D ring has undergone significant changes over the last 25 years. The brightest of the three ringlets seen in the Voyager images (named D72), has transformed from a narrow, <40-km wide ringlet to a much broader and more diffuse 250-km wide feature. In addition, its center of light has shifted inwards by over 200 km relative to other features in the D ring. Cassini also finds that the locations of other narrow features in the D ring and the structure of the diffuse material in the D ring differ from those measured by Voyager. Furthermore, Cassini has detected additional ringlets and structures in the D ring that were not observed by Voyager. These include a sheet of material just interior to the inner edge of the C ring that is only observable at phase angles below about 60??. New photometric and spectroscopic data from the ISS (Imaging Science Subsystem) and VIMS (Visual and Infrared Mapping Spectrometer) instruments onboard Cassini show the D ring contains a variety of different particle populations with typical particle sizes ranging from 1 to 100 microns. High-resolution images reveal fine-scale structures in the D ring that appear to be variable in time and/or longitude. Particularly interesting is a remarkably regular, periodic structure with a wavelength of ??? 30 ?? km extending between orbital radii of 73,200 and 74,000 km. A similar structure was previously observed in 1995 during the occultation of the star GSC5249-01240, at which time it had a wavelength of ??? 60 ?? km. We interpret this structure as a periodic vertical corrugation in the D ring produced by differential nodal regression of an initially inclined ring. We speculate that this structure may have formed in response to an impact with a comet or meteoroid in early 1984. ?? 2006 Elsevier Inc. All rights reserved.

  6. High-Performance Single Nanowire Tunnel Diodes

    DEFF Research Database (Denmark)

    Wallentin, Jesper; Persson, Johan Mikael; Wagner, Jakob Birkedal

    2010-01-01

    We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27...

  7. Child sex rings.

    OpenAIRE

    Wild, N J; Wynne, J M

    1986-01-01

    Details of 11 child sex rings identified in one working class community were obtained by interviewing investigating police officers and examining health and social services records. The rings contained 14 adult male perpetrators and 175 children aged 6-15 years. Most perpetrators used child ringleaders to recruit victims; others became a "family friend" or obtained a position of authority over children. Secrecy was encouraged and bribery, threats, and peer pressure used to induce participatio...

  8. Storage ring group summary

    International Nuclear Information System (INIS)

    King, N.M.

    1980-01-01

    The Storage Ring Group set out to identify and pursue salient problems in accelerator physics for heavy ion fusion, divorced from any particular reference design concept. However, it became apparent that some basic parameter framework was required to correlate the different study topics. As the Workshop progressed, ring parameters were modified and updated. Consequently, the accompanying papers on individual topics will be found to refer to slightly varied parameters, according to the stage at which the different problems were tackled

  9. Matrimonial ring structures

    OpenAIRE

    Hamberger, Klaus; Houseman, Michael; Daillant, Isabelle; White, Douglas R.; Barry, Laurent

    2006-01-01

    The paper deals with matrimonial rings, a particular kind of cycles in kinship networks which result when spouses are linked to each other by ties of consanguinity or affinity. By taking a network-analytic perspective, the paper endeavours to put this classical issue of structural kinship theory on a general basis, such as to allow conclusions which go beyond isolated discussions of particular ring types (like "cross-cousin marriage", "sister exchange", and so forth). The paper provides a def...

  10. Proximity coupling in superconductor-graphene heterostructures.

    Science.gov (United States)

    Lee, Gil-Ho; Lee, Hu-Jong

    2018-02-16

    This review discusses the electronic properties and the prospective research directions of superconductor-graphene heterostructures. The basic electronic properties of graphene are introduced to highlight the unique possibility of combining two seemingly unrelated physics, superconductivity and relativity. We then focus on graphene-based Josephson junctions, one of the most versatile superconducting quantum devices. The various theoretical methods that have been developed to describe graphene Josephson junctions are examined, together with their advantages and limitations, followed by a discussion on the advances in device fabrication and the relevant length scales. The phase-sensitive properties and phase-particle dynamics of graphene Josephson junctions are examined to provide an understanding of the underlying mechanisms of Josephson coupling via graphene. Thereafter, microscopic transport of correlated quasiparticles produced by Andreev reflections at superconducting interfaces and their phase-coherent behaviors are discussed. Quantum phase transitions studied with graphene as an electrostatically tunable 2D platform are reviewed. The interplay between proximity-induced superconductivity and the quantum-Hall phase is discussed as a possible route to study topological superconductivity and non-Abelian physics. Finally, a brief summary on the prospective future research directions is given.

  11. Proximity coupling in superconductor-graphene heterostructures

    Science.gov (United States)

    Lee, Gil-Ho; Lee, Hu-Jong

    2018-05-01

    This review discusses the electronic properties and the prospective research directions of superconductor-graphene heterostructures. The basic electronic properties of graphene are introduced to highlight the unique possibility of combining two seemingly unrelated physics, superconductivity and relativity. We then focus on graphene-based Josephson junctions, one of the most versatile superconducting quantum devices. The various theoretical methods that have been developed to describe graphene Josephson junctions are examined, together with their advantages and limitations, followed by a discussion on the advances in device fabrication and the relevant length scales. The phase-sensitive properties and phase-particle dynamics of graphene Josephson junctions are examined to provide an understanding of the underlying mechanisms of Josephson coupling via graphene. Thereafter, microscopic transport of correlated quasiparticles produced by Andreev reflections at superconducting interfaces and their phase-coherent behaviors are discussed. Quantum phase transitions studied with graphene as an electrostatically tunable 2D platform are reviewed. The interplay between proximity-induced superconductivity and the quantum-Hall phase is discussed as a possible route to study topological superconductivity and non-Abelian physics. Finally, a brief summary on the prospective future research directions is given.

  12. Novel engineered compound semiconductor heterostructures for advanced electronics applications

    Science.gov (United States)

    Stillman, Gregory E.; Holonyak, Nick, Jr.; Coleman, James J.

    1992-06-01

    To provide the technology base that will enable SDIO capitalization on the performance advantages offered through novel engineered multiple-lavered compound semiconductor structures, this project has focussed on three specific areas: (1) carbon doping of AlGaAs/GaAs and InP/InGaAs materials for reliable high frequency heterojunction bipolar transistors; (2) impurity induced layer disordering and the environmental degradation of AlxGal-xAs-GaAs quantum-well heterostructures and the native oxide stabilization of AlxGal-xAs-GaAs quantum well heterostructure lasers; and (3) non-planar and strained-layer quantum well heterostructure lasers and laser arrays. The accomplishments in this three year research are reported in fifty-six publications and the abstracts included in this report.

  13. Equivalent circuit analysis of a PbS/ferroelectric heterostructure

    Science.gov (United States)

    Pintilie, L.; Pintilie, I.; Botila, T.; Petre, D.; Licea, I.

    1997-02-01

    The frequency characteristic of the transverse photoelectric signal of a three electroded PbS/ferroelectric heterostructure is analyzed in this paper. The ferroelectric material is a lead titanate-zirconate ceramic obtained by hot pressing. It was found that the frequency characteristic of this signal is similar to a high-pass filter and depends on the properties of the ferroelectric substrates on which the PbS film was deposited. An equivalent circuit was proposed comparing the studied heterostructure with a metal-oxide semiconductor (MOS) structure. The circuit elements were determined fitting the obtained formula for the output signal with the experimental data. Some of the circuit elements were determined experimentally using various measuring techniques. It was found that the experimentally determined values are close to the theoretically determined values. The studied heterostructure can be changed into a band-pass filter adding some external circuit elements such as resistors and capacitors.

  14. Photonic Heterostructures with Properties of Ferroelectrics and Light Polarizers

    Energy Technology Data Exchange (ETDEWEB)

    Palto, S. P., E-mail: palto@online.ru; Draginda, Yu. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2010-11-15

    The optical and electro-optical properties of a new type of photonic heterostructure composed of alternating ferroelectric molecular layers and optically anisotropic layers of another material are considered. A numerical simulation of the real prototype of this heterostructure, which can be prepared by the Langmuir-Blodgett method from layers of a ferroelectric copolymer (polyvinylidene fluoride trifluoroethylene) and an azo dye with photoinduced optical anisotropy, has been performed. It is shown that this heterostructure has pronounced polarization optical properties and yields a significant change in the polarization state of light at the photonic band edges in the ranges of the maximum density of photon states. The latter property can be used to obtain an enhanced electro-optic effect at small spectral shifts of the photonic band (the latter can be provided by the piezoelectric effect in ferroelectric layers).

  15. Multimodal Nonlinear Optical Imaging of MoS₂ and MoS₂-Based van der Waals Heterostructures.

    Science.gov (United States)

    Li, Dawei; Xiong, Wei; Jiang, Lijia; Xiao, Zhiyong; Golgir, Hossein Rabiee; Wang, Mengmeng; Huang, Xi; Zhou, Yunshen; Lin, Zhe; Song, Jingfeng; Ducharme, Stephen; Jiang, Lan; Silvain, Jean-Francois; Lu, Yongfeng

    2016-03-22

    van der Waals layered structures, notably the transitional metal dichalcogenides (TMDs) and TMD-based heterostructures, have recently attracted immense interest due to their unique physical properties and potential applications in electronics, optoelectronics, and energy harvesting. Despite the recent progress, it is still a challenge to perform comprehensive characterizations of critical properties of these layered structures, including crystal structures, chemical dynamics, and interlayer coupling, using a single characterization platform. In this study, we successfully developed a multimodal nonlinear optical imaging method to characterize these critical properties of molybdenum disulfide (MoS2) and MoS2-based heterostructures. Our results demonstrate that MoS2 layers exhibit strong four-wave mixing (FWM), sum-frequency generation (SFG), and second-harmonic generation (SHG) nonlinear optical characteristics. We believe this is the first observation of FWM and SFG from TMD layers. All three kinds of optical nonlinearities are sensitive to layer numbers, crystal orientation, and interlayer coupling. The combined and simultaneous SHG/SFG-FWM imaging not only is capable of rapid evaluation of crystal quality and precise determination of odd-even layers but also provides in situ monitoring of the chemical dynamics of thermal oxidation in MoS2 and interlayer coupling in MoS2-graphene heterostructures. This method has the advantages of versatility, high fidelity, easy operation, and fast imaging, enabling comprehensive characterization of van der Waals layered structures for fundamental research and practical applications.

  16. Pb5Bi24Se41: A new member of the homologous series forming topological insulator heterostructures

    International Nuclear Information System (INIS)

    Segawa, Kouji; Taskin, A.A.; Ando, Yoichi

    2015-01-01

    We have synthesized Pb 5 Bi 24 Se 41 , which is a new member of the (PbSe) 5 (Bi 2 Se 3 ) 3m homologous series with m=4. This series of compounds consist of alternating layers of the topological insulator Bi 2 Se 3 and the ordinary insulator PbSe. Such a naturally-formed heterostructure has recently been elucidated to give rise to peculiar quasi-two-dimensional topological states throughout the bulk, and the discovery of Pb 5 Bi 24 Se 41 expands the tunability of the topological states in this interesting homologous series. The trend in the resistivity anisotropy in this homologous series suggests an important role of hybridization of the topological states in the out-of-plane transport. - Graphical abstract: X-ray diffraction profiles taken on cleaved surfaces of single-crystal samples of the (PbSe) 5 (Bi 2 Se 3 ) 3m homologous series with various m values up to 4, which realizes topological insulator heterostructures. Schematic crystal structure of the new phase, m=4, is also shown. - Highlights: • We have synthesized a new member of the homologous series related to topological insulators. • In this compound, a heterostructure of topological and ordinary insulators naturally forms. • Resistivity anisotropy suggests an important role of hybridization of the topological states. • This compound expands the tunability of the topological states via chemical means

  17. Interface-engineered oxygen octahedral coupling in manganite heterostructures

    Science.gov (United States)

    Huijben, M.; Koster, G.; Liao, Z. L.; Rijnders, G.

    2017-12-01

    Control of the oxygen octahedral coupling (OOC) provides a large degree of freedom to manipulate physical phenomena in complex oxide heterostructures. Recently, local tuning of the tilt angle has been found to control the magnetic anisotropy in ultrathin films of manganites and ruthenates, while symmetry control can manipulate the metal insulator transition in nickelate thin films. The required connectivity of the octahedra across the heterostructure interface enforces a geometric constraint to the 3-dimensional octahedral network in epitaxial films. Such geometric constraint will either change the tilt angle to retain the connectivity of the corner shared oxygen octahedral network or guide the formation of a specific symmetry throughout the epitaxial film. Here, we will discuss the control of OOC in manganite heterostructures by interface-engineering. OOC driven magnetic and transport anisotropies have been realized in LSMO/NGO heterostructures. Competition between the interfacial OOC and the strain further away from the interface leads to a thickness driven sharp transition of the anisotropic properties. Furthermore, octahedral relaxation leading to a change of p-d hybridization driven by interfacial OOC appears to be the strongest factor in thickness related variations of magnetic and transport properties in epitaxial LSMO films on NGO substrates. The results unequivocally link the atomic structure near the interfaces to the macroscopic properties. The strong correlation between a controllable oxygen network and the functionalities will have significant impact on both fundamental research and technological application of correlated perovskite heterostructures. By controlling the interfacial OOC, it is possible to pattern in 3 dimensions the magnetization to achieve non-collinear magnetization in both in-plane and out of plane directions, thus making the heterostructures promising for application in orthogonal spin transfer devices, spin oscillators, and low

  18. Atomic Scale Chemical and Structural Characterization of Ceramic Oxide Heterostructure Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Singh, R. K.

    2003-04-16

    The research plan was divided into three tasks: (a) growth of oxide heterostructures for interface engineering using standard thin film deposition techniques, (b) atomic level characterization of oxide heterostructure using such techniques as STEM-2 combined with AFM/STM and conventional high-resolution microscopy (HRTEM), and (c) property measurements of aspects important to oxide heterostructures using standard characterization methods, including dielectric properties and dynamic cathodoluminescence measurements. Each of these topics were further classified on the basis of type of oxide heterostructure. Type I oxide heterostructures consisted of active dielectric layers, including the materials Ba{sub x}Sr{sub 1-x}TiO{sub 3} (BST), Y{sub 2}O{sub 3} and ZrO{sub 2}. Type II heterostructures consisted of ferroelectric active layers such as lanthanum manganate and Type III heterostructures consist of phosphor oxide active layers such as Eu-doped Y{sub 2}O{sub 3}.

  19. Graphene plasmonic heterostructures for new types of terahertz lasers

    Science.gov (United States)

    Otsuji, Taiichi; Ryzhii, Victor; Boubanga Tombet, Stephane Albon; Watanabe, Takayuki; Satou, Akira; Ryzhii, Maxim; Dubinov, Alexander; Aleshkin, Vladimir Y.; Popov, Vyacheslav; Mitin, Vladimir; Shur, Michael

    2014-09-01

    This paper reviews recent advances in graphene plasmonic heterostructures for new types of terahertz lasers. We theoretically discovered and experimentally manifested that the excitation of surface plasmons in population-inverted graphene by the terahertz photons results in propagating surface plasmon polaritons with a giant gain in a wide terahertz range. Furthermore, double graphene layer heterostructures consisting of a tunnel barrier insulator sandwiched with a pair of gated graphene monolayers are introduced. Photoemission-assisted quantum-mechanical resonant tunneling can be electrically tuned to meet a desired photon energy for lasing, resulting in enormous enhancement of the terahertz gain. Current injection structures are also addressed.

  20. High ionic conductivity in confined bismuth oxide-based heterostructures

    DEFF Research Database (Denmark)

    Sanna, Simone; Esposito, Vincenzo; Christensen, Mogens

    2016-01-01

    Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3) exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure -Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made...... of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ), deposited by pulsed laser deposition. The resulting [δ-Bi2O3=YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C) and exhibits stable high ionic conductivity over a long time comparable to the value...

  1. Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures

    Science.gov (United States)

    2018-02-19

    AFRL-AFOSR-JP-TR-2018-0012 Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures PHILIP Kim HARVARD COLLEGE PRESIDENT... Atomically Controlled van der Waals Quantum Heterostructures 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-15-1-4003 5c.  PROGRAM ELEMENT NUMBER 61102F...Final Report for AOARD Grant FA2386-15-1-4003 “Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures” 2/18/2018 Name of

  2. Experimental study of structural and optical properties of integrated MOCVD GaAs/Si(001) heterostructures

    Science.gov (United States)

    Seredin, P. V.; Lenshin, A. S.; Zolotukhin, D. S.; Arsentyev, I. N.; Nikolaev, D. N.; Zhabotinskiy, A. V.

    2018-02-01

    This is the first report of the control of the structural and optical functional characteristics of integrated GaAs/Si(001) heterostructures due to the use of misoriented Si(001) substrates with protoporous sublayer. The growth of the epitaxial GaAs layer on silicon substrates without formation of the antiphase domains can be performed on substrates deviating less than 4°-6° from the singular (001) plane or without the use of a transition layer of GaAs nano-columns. Preliminary etching of the silicon substrate with protoporous Si sublayer formation facilitated the acquisition of an epitaxial GaAs film in a single-crystalline state with a considerably less residual strain factor using MOCVD, which has a positive effect on the structural quality of the film. These data are in a good agreement with the results of IR reflection spectroscopy as well as PL and UV spectroscopy. The optical properties of the integrated GaAs/Si (001) heterostructures in the IR and UV spectral regions were also determined by the residual strain value.

  3. ZnO-nanowires/PANI inorganic/organic heterostructure light-emitting diode.

    Science.gov (United States)

    He, Ying; Wang, Jun-an; Zhang, Wenfei; Song, Jizhong; Pei, Changlong; Chen, Xiaoban

    2010-11-01

    In this paper, we report a flexible inorganic/organic heterostructure light-emitting diode, in which inorganic ZnO nanowires are the optically active components and organic polyaniline (PANI) is the hole-transporting layer. The fabrication of the hybrid LED is as follows, the ordered single-crystalline ZnO nanowires were uniformly distributed on flexible polyethylene terephthalate (PET)-based indium-tin-oxide-coated substrates by our polymer-assisted growth method, and proper materials were chosen as electrode and carrier. In this construction, an array of ZnO nanowires grown on PET substrate is successfully embedded in a polyaniline thin film. The performance of the hybrid device of organic-inorganic hetero-junction of ITO/(ZnO nanowires-PANI) for LED application in the blue and UV ranges are investigated, and tunable electroluminescence has been demonstrated by contacting the upper tips of ZnO nanowires and the PET substrate. The effect of surface capping with polyvinyl alcohol (PANI) on the photocarrier relaxation of the aqueous chemically grown ZnO nanowires has been investigated. The photoluminescence spectrum shows an enhanced ultraviolet emission and reduced defect-related emission in the capped ZnO NWs compared to bare ZnO. The results of our study may offer a fundamental understanding in the field of inorganic/organic heterostructure light-emitting diode, which may be useful for potential applications of hybrid ZnO nanowires with conductive polymers.

  4. Precise characterization of self-catalyzed III-V nanowire heterostructures via optical second harmonic generation

    Science.gov (United States)

    Yu, Ying; Wang, Jing; Wei, Yu-Ming; Zhou, Zhang-Kai; Ni, Hai-Qiao; Niu, Zhi-Chuan; Wang, Xue-Hua; Yu, Si-Yuan

    2017-09-01

    We demonstrate the utility of optical second harmonic generation (SHG) polarimetry to perform structural characterization of self-assembled zinc-blende/wurtzite III-V nanowire heterostructures. By analyzing four anisotropic SHG polarimetric patterns, we distinguish between wurtzite (WZ), zinc-blende (ZB) and ZB/WZ mixing III-V semiconducting crystal structures in nanowire systems. By neglecting the surface contributions and treating the bulk crystal within the quasi-static approximation, we can well explain the optical SHG polarimetry from the NWs with diameter from 200-600 nm. We show that the optical in-coupling and out-coupling coefficients arising from depolarization field can determine the polarization of the SHG. We also demonstrate micro-photoluminescence of GaAs quantum dots in related ZB and ZB/WZ mixing sections of core-shell NW structure, in agreement with the SHG polarimetry results. The ability to perform in situ SHG-based crystallographic study of semiconducting single and multi-crystalline nanowire heterostructures will be useful in displaying structure-property relationships of nanodevices.

  5. Dynamic acoustic control of individual optically active quantum dot-like emission centers in heterostructure nanowires.

    Science.gov (United States)

    Weiss, Matthias; Kinzel, Jörg B; Schülein, Florian J R; Heigl, Michael; Rudolph, Daniel; Morkötter, Stefanie; Döblinger, Markus; Bichler, Max; Abstreiter, Gerhard; Finley, Jonathan J; Koblmüller, Gregor; Wixforth, Achim; Krenner, Hubert J

    2014-05-14

    We probe and control the optical properties of emission centers forming in radial heterostructure GaAs-Al0.3Ga0.7As nanowires and show that these emitters, located in Al0.3Ga0.7As layers, can exhibit quantum-dot like characteristics. We employ a radio frequency surface acoustic wave to dynamically control their emission energy, and occupancy state on a nanosecond time scale. In the spectral oscillations, we identify unambiguous signatures arising from both the mechanical and electrical component of the surface acoustic wave. In addition, different emission lines of a single emission center exhibit pronounced anticorrelated intensity oscillations during the acoustic cycle. These arise from a dynamically triggered carrier extraction out of the emission center to a continuum in the radial heterostructure. Using finite element modeling and Wentzel-Kramers-Brillouin theory we identify quantum tunneling as the underlying mechanism. These simulation results quantitatively reproduce the observed switching and show that in our systems these emission centers are spatially separated from the continuum by >10.5 nm.

  6. Tunable SnSe2/WSe2Heterostructure Tunneling Field Effect Transistor.

    Science.gov (United States)

    Yan, Xiao; Liu, Chunsen; Li, Chao; Bao, Wenzhong; Ding, Shijin; Zhang, David Wei; Zhou, Peng

    2017-09-01

    The burgeoning 2D semiconductors can maintain excellent device electrostatics with an ultranarrow channel length and can realize tunneling by electrostatic gating to avoid deprivation of band-edge sharpness resulting from chemical doping, which make them perfect candidates for tunneling field effect transistors. Here this study presents SnSe 2 /WSe 2 van der Waals heterostructures with SnSe 2 as the p-layer and WSe 2 as the n-layer. The energy band alignment changes from a staggered gap band offset (type-II) to a broken gap (type-III) when changing the negative back-gate voltage to positive, resulting in the device operating as a rectifier diode (rectification ratio ~10 4 ) or an n-type tunneling field effect transistor, respectively. A steep average subthreshold swing of 80 mV dec -1 for exceeding two decades of drain current with a minimum of 37 mV dec -1 at room temperature is observed, and an evident trend toward negative differential resistance is also accomplished for the tunneling field effect transistor due to the high gate efficiency of 0.36 for single gate devices. The I ON /I OFF ratio of the transfer characteristics is >10 6 , accompanying a high ON current >10 -5 A. This work presents original phenomena of multilayer 2D van der Waals heterostructures which can be applied to low-power consumption devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Resonant tunneling effect in graphene superlattice heterostructures by tuning the electric potential of defect layer

    Science.gov (United States)

    Kumar Mishra, Shakti; Kumar, Amar; Prakash Kaushik, Chetan; Dikshit, Biswaranjan

    2017-05-01

    In this paper, we have demonstrated the electronic resonant tunneling effect in graphene superlattice heterostructures with an electric potential controlled defect layer. This layer is created by a single irregular electrode inserted in between two different superlattices. We have numerically investigated the tunable giant thermoelectric effect in the above-mentioned structure which is caused by complete electronic tunneling using a transfer matrix approach. The magnitude of the maximum Seebeck coefficient generated in the above structures is several times more than that in an individual superlattice as well as in superlattice heterostructures. This structure can be tuned to give a maximum Seebeck coefficient by varying the applied voltage on the defect layer. By this method, the magnitude of the Seebeck coefficient is found to be 384.9 mV/K, which is the largest reported ever. The tunneling state and the maximum value of the Seebeck coefficient are found to be located in the small overlapped forbidden gap of two graphene superlattices. This voltage controlled tuning technique for complete electronic tunneling is practically preferable against the width controlled technique reported in the literature. These types of structures are important for graphene-based devices which can be used for efficient thermoelectric devices in energy harvesting and high-Q narrowband electron wave filters.

  8. MOCVD synthesis of group III-nitride heterostructure nanowires for solid-state lighting.

    Energy Technology Data Exchange (ETDEWEB)

    Wang, George T.; Creighton, James Randall; Talin, Albert Alec

    2006-11-01

    Solid-state lighting (SSL) technologies, based on semiconductor light emitting devices, have the potential to reduce worldwide electricity consumption by more than 10%, which could significantly reduce U.S. dependence on imported energy and improve energy security. The III-nitride (AlGaInN) materials system forms the foundation for white SSL and could cover a wide spectral range from the deep UV to the infrared. For this LDRD program, we have investigated the synthesis of single-crystalline III-nitride nanowires and heterostructure nanowires, which may possess unique optoelectronic properties. These novel structures could ultimately lead to the development of novel and highly efficient SSL nanodevice applications. GaN and III-nitride core-shell heterostructure nanowires were successfully synthesized by metal organic chemical vapor deposition (MOCVD) on two-inch wafer substrates. The effect of process conditions on nanowire growth was investigated, and characterization of the structural, optical, and electrical properties of the nanowires was also performed.

  9. Hidden peculiar magnetic anisotropy at the interface in a ferromagnetic perovskite-oxide heterostructure.

    Science.gov (United States)

    Anh, Le Duc; Okamoto, Noboru; Seki, Munetoshi; Tabata, Hitoshi; Tanaka, Masaaki; Ohya, Shinobu

    2017-08-18

    Understanding and controlling the interfacial magnetic properties of ferromagnetic thin films are crucial for spintronic device applications. However, using conventional magnetometry, it is difficult to detect them separately from the bulk properties. Here, by utilizing tunneling anisotropic magnetoresistance in a single-barrier heterostructure composed of La 0.6 Sr 0.4 MnO 3 (LSMO)/LaAlO 3 (LAO)/Nb-doped SrTiO 3 (001), we reveal the presence of a peculiar strong two-fold magnetic anisotropy (MA) along the [110] c direction at the LSMO/LAO interface, which is not observed in bulk LSMO. This MA shows unknown behavior that the easy magnetization axis rotates by 90° at an energy of 0.2 eV below the Fermi level in LSMO. We attribute this phenomenon to the transition between the e g and t 2g bands at the LSMO interface. Our finding and approach to understanding the energy dependence of the MA demonstrate a new possibility of efficient control of the interfacial magnetic properties by controlling the band structures of oxide heterostructures.

  10. Surface Plasmon Polariton-Assisted Long-Range Exciton Transport in Monolayer Semiconductor Lateral Heterostructure

    Science.gov (United States)

    Shi, Jinwei; Lin, Meng-Hsien; Chen, Yi-Tong; Estakhri, Nasim Mohammadi; Tseng, Guo-Wei; Wang, Yanrong; Chen, Hung-Ying; Chen, Chun-An; Shih, Chih-Kang; Alã¹, Andrea; Li, Xiaoqin; Lee, Yi-Hsien; Gwo, Shangjr

    Recently, two-dimensional (2D) semiconductor heterostructures, i.e., atomically thin lateral heterostructures (LHSs) based on transition metal dichalcogenides (TMDs) have been demonstrated. In an optically excited LHS, exciton transport is typically limited to a rather short spatial range ( 1 micron). Furthermore, additional losses may occur at the lateral interfacial regions. Here, to overcome these challenges, we experimentally implement a planar metal-oxide-semiconductor (MOS) structure by placing a monolayer of WS2/MoS2 LHS on top of an Al2O3 capped Ag single-crystalline plate. We found that the exciton transport range can be extended to tens of microns. The process of long-range exciton transport in the MOS structure is confirmed to be mediated by an exciton-surface plasmon polariton-exciton conversion mechanism, which allows a cascaded energy transfer process. Thus, the planar MOS structure provides a platform seamlessly combining 2D light-emitting materials with plasmonic planar waveguides, offering great potential for developing integrated photonic/plasmonic functionalities.

  11. Ring vortex solitons in nonlocal nonlinear media

    DEFF Research Database (Denmark)

    Briedis, D.; Petersen, D.E.; Edmundson, D.

    2005-01-01

    We study the formation and propagation of two-dimensional vortex solitons, i.e. solitons with a phase singularity, in optical materials with a nonlocal focusing nonlinearity. We show that nonlocality stabilizes the dynamics of an otherwise unstable vortex beam. This occurs for either single...... or higher charge fundamental vortices as well as higher order (multiple ring) vortex solitons. Our results pave the way for experimental observation of stable vortex rings in other nonlocal nonlinear systems including Bose-Einstein condensates with pronounced long-range interparticle interaction....

  12. Pure phase decoherence in a ring geometry

    International Nuclear Information System (INIS)

    Zhu, Z.; Aharony, A.; Entin-Wohlman, O.; Stamp, P. C. E.

    2010-01-01

    We study the dynamics of pure phase decoherence for a particle hopping around an N-site ring, coupled both to a spin bath and to an Aharonov-Bohm flux which threads the ring. Analytic results are found for the dynamics of the influence functional and of the reduced density matrix of the particle, both for initial single wave-packet states, and for states split initially into two separate wave packets moving at different velocities. We also give results for the dynamics of the current as a function of time.

  13. BERKELEY: ALS ring

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    Everybody at Lawrence Berkeley Laboratory's Center for Beam Physics is pleased with the rapid progress in commissioning LBL's Advanced Light Source (ALS) electron storage ring, the foundation for this third-generation synchrotron radiation facility. Designed for a maximum current of 400 mA, the ALS storage ring reached 407 mA just 24 days after storing the first beam on 16 March. ALS construction as a US Department of Energy (DOE) national user facility to provide high-brightness vacuum ultra-violet and soft x-ray radiation began in October 1987. One technical requirement marking project completion was to accumulate a 50-mA current in the storage ring. The ALS passed this milestone on 24 March, a week ahead of the official deadline. Once injected, the electron beam decays quasi-exponentially primarily because of interactions with residual gas molecules in the storage-ring vacuum chamber. Eventually, when the pressure in the vacuum chamber with beam decreases toward the expected operating level of 1 nano Torr, it will only be necessary to refill the storage ring at intervals of four to eight hours. At present the vacuum is improving rapidly as surfaces are irradiated (scrubbed) by the synchrotron radiation itself. At 100 mA, beam lifetime was about one hour (9 April)

  14. Electronic transport in graphene-based heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Tan, J. Y.; Avsar, A.; Balakrishnan, J.; Taychatanapat, T.; O' Farrell, E. C. T.; Eda, G.; Castro Neto, A. H. [Graphene Research Center, National University of Singapore, Singapore 117542 (Singapore); Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Koon, G. K. W.; Özyilmaz, B., E-mail: barbaros@nus.edu.sg [Graphene Research Center, National University of Singapore, Singapore 117542 (Singapore); Department of Physics, National University of Singapore, Singapore 117542 (Singapore); NanoCore, National University of Singapore, Singapore 117576 (Singapore); Watanabe, K.; Taniguchi, T. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)

    2014-05-05

    While boron nitride (BN) substrates have been utilized to achieve high electronic mobilities in graphene field effect transistors, it is unclear how other layered two dimensional (2D) crystals influence the electronic performance of graphene. In this Letter, we study the surface morphology of 2D BN, gallium selenide (GaSe), and transition metal dichalcogenides (tungsten disulfide (WS{sub 2}) and molybdenum disulfide (MoS{sub 2})) crystals and their influence on graphene's electronic quality. Atomic force microscopy analysis shows that these crystals have improved surface roughness (root mean square value of only ∼0.1 nm) compared to conventional SiO{sub 2} substrate. While our results confirm that graphene devices exhibit very high electronic mobility (μ) on BN substrates, graphene devices on WS{sub 2} substrates (G/WS{sub 2}) are equally promising for high quality electronic transport (μ ∼ 38 000 cm{sup 2}/V s at room temperature), followed by G/MoS{sub 2} (μ ∼ 10 000 cm{sup 2}/V s) and G/GaSe (μ ∼ 2200 cm{sup 2}/V s). However, we observe a significant asymmetry in electron and hole conduction in G/WS{sub 2} and G/MoS{sub 2} heterostructures, most likely due to the presence of sulphur vacancies in the substrate crystals. GaSe crystals are observed to degrade over time even under ambient conditions, leading to a large hysteresis in graphene transport making it a less suitable substrate.

  15. Coupling Magnetism to Electricity in Multiferroic Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ramesh, R [U.S. DOE

    2012-02-15

    Complex perovskite oxides exhibit a rich spectrum of functional responses, including magnetism, ferroelectricity, highly correlated electron behavior, superconductivity, etc. The basic materials physics of such materials provide the ideal playground for interdisciplinary scientific exploration. Over the past decade we have been exploring the science of such materials (for example, colossal magnetoresistance, ferroelectricity, etc) in thin-film form by creating epitaxial heterostructures and nanostructures. Among the large number of materials systems, there exists a small set of materials which exhibit multiple order parameters; these are known as multiferroics. Using our work in the field of ferroelectric and ferromagnetic oxides as the background, we are now exploring such materials as epitaxial thin films, as well as nanostructures. Specifically, we are studying the role of thin-film growth, heteroepitaxy, and processing on the basic properties as well as the magnitude of the coupling between the order parameters. In our work we are exploring the switchability of the antiferromagnetic order using this coupling. What is the importance of this work? Antiferromagnets are pervasive in the recording industry. They are used as exchange biasing layers in magnetic tunnel junctions, etc. However, to date there has been no antiferomagnet that is electrically tunable. We believe that the multiferroic BiFeO3 is one compound where this can be observed at room temperature. The next step is to explore the coupling of a ferromagnet to this antiferromagnet through the exchange biasing concept. Ultimately, this will give us the opportunity to switch the magnetic state in a ferromagnet (and therefore the spin polarization direction) by simply applying an electric field to the underlying antiferromagnetic ferroelectric. In this talk, I will describe our progress to date on this exciting possibility.

  16. Micromagnetic sensors and Dirac fermions in HgTe heterostructures

    International Nuclear Information System (INIS)

    Buettner, Bastian

    2012-01-01

    Within the scope of this thesis two main topics have been investigated: the examination of micromagnetic sensors and transport of massive and massless Dirac fermions in HgTe quantum wells. For the investigation of localized, inhomogeneous magnetic fields, the fabrication and characterization of two different non-invasive and ultra sensitive sensors has been established at the chair ''Experimentelle Physik'' of the University of Wuerzburg. The first sensor is based on the young technique named micro-Hall magnetometry. The necessary semiconductor devices (Hall cross structures) were fabricated by high-resolution electron beam lithography based on two different two dimensional electron gases (2DEGs), namely InAs/(Al,Ga)Sb- and HgTe/(Hg,Cd)Te-heterostructures. The characteristics have been examined in two different ways. Measurements in homogeneous magnetic fields served for characterization of the sensors, whereas the investigation of artificially produced sub-μm magnets substantiates the suitability of the devices for the study of novel nanoscale magnetic materials (e.g. nanowires). Systematic experiments with various magnets are in accordance with the theory of single-domain particles and anisotropic behavior due to shapes with high aspect ratio. The highest sensitivity for strongly localized fields was obtained at T=4.2 K for a (200.200) nm 2 Hall cross - made from shallow, high mobility HgTe 2DEG. Although the field resolution was merely δB∼100 μT, the nanoscale sensor size yields an outstanding flux resolution of δΦ=2.10 -3 Φ 0 , where Φ 0 =h/2e is the flux quantum. Translating this result in terms of magnetic moment, the sensitivity allows for the detection of magnetization changes of a particle centered on top of the sensor as low as δM∼10 2 μ B , with the magnetic moment of a single electron μ B , the Bohr magneton. The further examination of a permalloy nanomagnet with a cross-section of (100.20) nm 2 confirms the expected resolution ability

  17. Micromagnetic sensors and Dirac fermions in HgTe heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Buettner, Bastian

    2012-08-06

    Within the scope of this thesis two main topics have been investigated: the examination of micromagnetic sensors and transport of massive and massless Dirac fermions in HgTe quantum wells. For the investigation of localized, inhomogeneous magnetic fields, the fabrication and characterization of two different non-invasive and ultra sensitive sensors has been established at the chair ''Experimentelle Physik'' of the University of Wuerzburg. The first sensor is based on the young technique named micro-Hall magnetometry. The necessary semiconductor devices (Hall cross structures) were fabricated by high-resolution electron beam lithography based on two different two dimensional electron gases (2DEGs), namely InAs/(Al,Ga)Sb- and HgTe/(Hg,Cd)Te-heterostructures. The characteristics have been examined in two different ways. Measurements in homogeneous magnetic fields served for characterization of the sensors, whereas the investigation of artificially produced sub-{mu}m magnets substantiates the suitability of the devices for the study of novel nanoscale magnetic materials (e.g. nanowires). Systematic experiments with various magnets are in accordance with the theory of single-domain particles and anisotropic behavior due to shapes with high aspect ratio. The highest sensitivity for strongly localized fields was obtained at T=4.2 K for a (200.200) nm{sup 2} Hall cross - made from shallow, high mobility HgTe 2DEG. Although the field resolution was merely {delta}B{approx}100 {mu}T, the nanoscale sensor size yields an outstanding flux resolution of {delta}{Phi}=2.10{sup -3} {Phi}{sub 0}, where {Phi}{sub 0}=h/2e is the flux quantum. Translating this result in terms of magnetic moment, the sensitivity allows for the detection of magnetization changes of a particle centered on top of the sensor as low as {delta}M{approx}10{sup 2} {mu}{sub B}, with the magnetic moment of a single electron {mu}{sub B}, the Bohr magneton. The further examination of a permalloy

  18. Almost ring theory

    CERN Document Server

    2003-01-01

    This book develops thorough and complete foundations for the method of almost etale extensions, which is at the basis of Faltings' approach to p-adic Hodge theory. The central notion is that of an "almost ring". Almost rings are the commutative unitary monoids in a tensor category obtained as a quotient V-Mod/S of the category V-Mod of modules over a fixed ring V; the subcategory S consists of all modules annihilated by a fixed ideal m of V, satisfying certain natural conditions. The reader is assumed to be familiar with general categorical notions, some basic commutative algebra and some advanced homological algebra (derived categories, simplicial methods). Apart from these general prerequisites, the text is as self-contained as possible. One novel feature of the book - compared with Faltings' earlier treatment - is the systematic exploitation of the cotangent complex, especially for the study of deformations of almost algebras.

  19. Decay ring design

    CERN Document Server

    Chancé, A; Bouquerel, E; Hancock, S; Jensen, E

    The study of the neutrino oscillation between its different flavours needs pureand very intense fluxes of high energy, well collimated neutrinos with a welldetermined energy spectrum. A dedicated machine seems to be necessarynowadays to reach the required flux. A new concept based on the β-decayof radioactive ions which were accelerated in an accelerator chain was thenproposed. After ion production, stripping, bunching and acceleration, the unstableions are then stored in a racetrack-shaped superconducting decay ring.Finally, the ions are accumulated in the decay ring until being lost. The incomingbeam is merged to the stored beam by using a specific RF system, whichwill be presented here.We propose here to study some aspects of the decay ring, such as its opticalproperties, its RF system or the management of the losses which occur in thering (mainly by decay or by collimation).

  20. Oxide Thin Films and Nano-heterostructures for Microelectronics (MOS Structures, Ferroelectric Materials and Multiferroic Heterostructures)

    Science.gov (United States)

    Pintilie, I.; Pintilie, L.; Filip, L. D.; Nistor, L. C.; Ghica, C.

    Oxide materials are becoming of increasing interest due to their large variety of physical properties such as dielectric, magnetism, superconductivity, conductivity, ferroelectricity, multiferroism, etc. In addition, interfacing oxides with other materials is conferring new or better device functionalities. The main physical properties of oxides interfaces and their impact on the electrical properties of interest for microelectronic applications are presented. Further on, this subchapter is also devoted to the investigation and understanding of interface effects observed in heterostructures containing linear (SiO2) and non-linear (ferroelectrics) dielectrics in combination with wide-band gap semiconductor materials (e.g. ZnO and SiC) with special emphasis on size effects, interface quality and the opportunity to control the emergent phenomena in Metal-Oxide-Semiconductor (MOS) and Metal-Ferroelectric-Semiconductor (MFS) materials systems.

  1. A rapid protection switching method in carrier ethernet ring networks

    Science.gov (United States)

    Yuan, Liang; Ji, Meng

    2008-11-01

    Abstract: Ethernet is the most important Local Area Network (LAN) technology since more than 90% data traffic in access layer is carried on Ethernet. From 10M to 10G, the improving Ethernet technology can be not only used in LAN, but also a good choice for MAN even WAN. MAN are always constructed in ring topology because the ring network could provide resilient path protection by using less resource (fibre or cable) than other network topologies. In layer 2 data networks, spanning tree protocol (STP) is always used to protect transmit link and preventing the formation of logic loop in networks. However, STP cannot guarantee the efficiency of service convergence when link fault happened. In fact, convergent time of networks with STP is about several minutes. Though Rapid Spanning Tree Protocol (RSTP) and Multi-Spanning Tree Protocol (MSTP) improve the STP technology, they still need a couple of seconds to achieve convergence, and can not provide sub-50ms protection switching. This paper presents a novel rapid ring protection method (RRPM) for carrier Ethernet. Unlike other link-fault detection method, it adopts distributed algorithm to detect link fault rapidly (sub-50ms). When networks restore from link fault, it can revert to the original working state. RRPM can provide single ring protection and interconnected ring protection without the formation of super loop. In normal operation, the master node blocks the secondary port for all non-RRPM Ethernet frames belonging to the given RRPM Ring, thereby avoiding a loop in the ring. When link fault happens, the node on which the failure happens moves from the "ring normal" state to the "ring fault" state. It also sends "link down" frame immediately to other nodes and blocks broken port and flushes its forwarding database. Those who receive "link down" frame will flush forwarding database and master node should unblock its secondary port. When the failure restores, the whole ring will revert to the normal state. That is

  2. Photosensitive heterostructures made of sulfonamide zinc phthalocyanine and organic semiconductor

    Czech Academy of Sciences Publication Activity Database

    Lutsyk, P.; Vertsimakha, Ya.; Nešpůrek, Stanislav; Pomaz, I.

    2011-01-01

    Roč. 535, - (2011), s. 18-29 ISSN 1542-1406 Institutional research plan: CEZ:AV0Z40500505 Keywords : heterostructure * reversal of sign in photovoltage spectra * sulphonamide-substituted phthalocyanine Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.580, year: 2011

  3. Photopatterning of heterostructured polymer Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Li Tiesheng; Mitsuishi, Masaya; Miyashita, Tokuji

    2008-01-01

    Heterostructured polymer Langmuir-Blodgett (LB) film prepared by using poly(N-dodecylacrylamide-co-t-butyl 4-vinylphenyl carbonate) (p(DDA-tBVPC53)) and poly(N-neopentyl methacrylamide-co-9-anthrylmethyl methacrylate) (p(nPMA-AMMA10)) polymer LB films which can act as photogenerator layers were investigated. Patterns with a resolution of 0.75 μm were obtained on heterostructured polymer LB films composed of 4 layers of p(nPMA-AMMA10) LB film (top layers) and 40 layers of p(DDA-tBVPC53) LB film (under layers) on a silicon wafer by deep UV irradiation followed by development with 1% tetramethylammonium hydroxide aqueous solution. The sensitivity of the heterostructured polymer LB films was improved without loss of the resolution compared with p(DDA-tBVPC53) LB film. The etch resistance of the heterostructured polymer LB films was sufficiently good to allow patterning of a copper film suitable for photomask fabrication

  4. Inorganic nanostructure-organic polymer heterostructures useful for thermoelectric devices

    Energy Technology Data Exchange (ETDEWEB)

    See, Kevin C.; Urban, Jeffrey J.; Segalman, Rachel A.; Coates, Nelson E.; Yee, Shannon K.

    2017-11-28

    The present invention provides for an inorganic nanostructure-organic polymer heterostructure, useful as a thermoelectric composite material, comprising (a) an inorganic nanostructure, and (b) an electrically conductive organic polymer disposed on the inorganic nanostructure. Both the inorganic nanostructure and the electrically conductive organic polymer are solution-processable.

  5. Nonlinear properties of a graded-index photonic heterostructure

    Indian Academy of Sciences (India)

    The optical properties of a one-dimensional (1D) photonic heterostructure with gradedindex nonlinear materials are demonstrated theoretically. The influence of the gradation profile of the graded-index nonlinear layers on the linear and nonlinear responses of the structure are analysed. It is shown that the -factor of the ...

  6. Franckeite as a naturally occurring van der Waals heterostructure

    NARCIS (Netherlands)

    Molina-Mendoza, Aday J.; Giovanelli, Emerson; Paz, Wendel S.; Ninõ, Miguel Angel; Island, J.O.; Evangeli, Charalambos; Aballe, Luciá; Foerster, Michael; Van Der Zant, Herre S.J.; Rubio-Bollinger, Gabino; Agraït, Nicolás; Palacios, JJ; Pérez, Emilio M.; Castellanos-Gomez, Andres

    2017-01-01

    The fabrication of van der Waals heterostructures, artificial materials assembled by individual stacking of 2D layers, is among the most promising directions in 2D materials research. Until now, the most widespread approach to stack 2D layers relies on deterministic placement methods, which are

  7. Interface-engineered oxygen octahedral coupling in manganite heterostructures

    NARCIS (Netherlands)

    Huijben, M.; Koster, G.; Liao, Z. L.; Rijnders, G.

    2017-01-01

    Control of the oxygen octahedral coupling (OOC) provides a large degree of freedom to manipulate physical phenomena in complex oxide heterostructures. Recently, local tuning of the tilt angle has been found to control the magnetic anisotropy in ultrathin films of manganites and ruthenates, while

  8. Mesoscopic Elastic Distortions in GaAs Quantum Dot Heterostructures.

    Science.gov (United States)

    Pateras, Anastasios; Park, Joonkyu; Ahn, Youngjun; Tilka, Jack A; Holt, Martin V; Reichl, Christian; Wegscheider, Werner; Baart, Timothy A; Dehollain, Juan Pablo; Mukhopadhyay, Uditendu; Vandersypen, Lieven M K; Evans, Paul G

    2018-04-23

    Quantum devices formed in high-electron-mobility semiconductor heterostructures provide a route through which quantum mechanical effects can be exploited on length scales accessible to lithography and integrated electronics. The electrostatic definition of quantum dots in semiconductor heterostructure devices intrinsically involves the lithographic fabrication of intricate patterns of metallic electrodes. The formation of metal/semiconductor interfaces, growth processes associated with polycrystalline metallic layers, and differential thermal expansion produce elastic distortion in the active areas of quantum devices. Understanding and controlling these distortions present a significant challenge in quantum device development. We report synchrotron X-ray nanodiffraction measurements combined with dynamical X-ray diffraction modeling that reveal lattice tilts with a depth-averaged value up to 0.04° and strain on the order of 10 -4 in the two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. Elastic distortions in GaAs/AlGaAs heterostructures modify the potential energy landscape in the 2DEG due to the generation of a deformation potential and an electric field through the piezoelectric effect. The stress induced by metal electrodes directly impacts the ability to control the positions of the potential minima where quantum dots form and the coupling between neighboring quantum dots.

  9. IZO deposited by PLD on flexible substrate for organic heterostructures

    Science.gov (United States)

    Socol, M.; Preda, N.; Stanculescu, A.; Breazu, C.; Florica, C.; Rasoga, O.; Stanculescu, F.; Socol, G.

    2017-05-01

    In:ZnO (IZO) thin films were deposited on flexible plastic substrates by pulsed laser deposition (PLD) method. The obtained layers present adequate optical and electrical properties competitive with those based on indium tin oxide (ITO). The figure of merit (9 × 10-3 Ω-1) calculated for IZO layers demonstrates that high quality coatings can be prepared by this deposition technique. A thermal annealing (150 °C for 1 h) or an oxygen plasma etching (6 mbar for 10 min.) were applied to the IZO layers to evaluate the influence of these treatments on the properties of the transparent coatings. Using vacuum evaporation, organic heterostructures based on cooper phthalocyanine (CuPc) and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) were deposited on the untreated and treated IZO layers. The optical and electrical properties of the heterostructures were investigated by UV-Vis, FTIR and current-voltage ( I- V) measurements. For the heterostructure fabricated on IZO treated in oxygen plasma, an improvement in the current value with at least one order of magnitude was evidenced in the I- V characteristics recorded in dark conditions. Also, an increase in the current value for the heterostructure deposited on untreated IZO layer can be achieved by adding an organic layer such as tris-8-hydroxyquinoline aluminium (Alq3).

  10. Analysis of Critical Dimensions for Nanowire Core-Multishell Heterostructures.

    Science.gov (United States)

    Yan, Xin; Fan, Shuyu; Zhang, Xia; Ren, Xiaomin

    2015-12-01

    Critical dimensions for nanowire core-multishell heterostructures are analyzed by using finite-element method based on the energy equilibrium criteria. Results show that the nanowire core-shell heterostructure can sufficiently reduce the strain in the shell and increase the critical shell thickness. The critical dimensions for the nanowire core-multishell heterostructure are determined by the stress fields generated at two heterointerfaces. For thin barrier, the critical dimensions decrease as the core radius increases, while when the barrier is thick enough, the critical dimensions show an increase with the increase of core radius conversely. This can be attributed to a competition between the lattice mismatch and strain distribution, which dominate the critical dimensions alternatively. Two critical quantum well thicknesses are obtained in the nanowire core-multishell heterostructure. Below the dislocation-free critical thickness, the structure will be coherent regardless of the barrier thickness. While above the dislocation-unavoidable thickness, dislocations are always energetically favored. In the dislocation-controllable region between the two critical thicknesses, coherent structure can be obtained via controlling the well and barrier thicknesses. The results are in good agreement with the experimental data and may serve as guidance for the design of coherent nanowire core-multishell quantum well structures and devices.

  11. Nonlinear properties of a graded-index photonic heterostructure

    Indian Academy of Sciences (India)

    Abstract. The optical properties of a one-dimensional (1D) photonic heterostructure with graded- index nonlinear materials are demonstrated theoretically. The influence of the gradation profile of the graded-index nonlinear layers on the linear and nonlinear responses of the structure are analysed. It is shown that the ...

  12. Surface- and interface-engineered heterostructures for solar hydrogen generation

    Science.gov (United States)

    Chen, Xiangyan; Li, Yanrui; Shen, Shaohua

    2018-04-01

    Photoelectrochemical (PEC) water splitting based on semiconductor photoelectrodes provides a promising platform for reducing environmental pollution and solving the energy crisis by developing clean, sustainable and environmentally friendly hydrogen energy. In this context, metal oxides with their advantages including low cost, good chemical stability and environmental friendliness, have attracted extensive attention among the investigated candidates. However, the large bandgap, poor charge transfer ability and high charge recombination rate limit the PEC performance of metal oxides as photoelectrodes. To solve this limitation, many approaches toward enhanced PEC water splitting performance, which focus on surface and interface engineering, have been presented. In this topical review, we concentrate on the heterostructure design of some typical metal oxides with narrow bandgaps (e.g. Fe2O3, WO3, BiVO4 and Cu2O) as photoelectrodes. An overview of the surface- and interface-engineered heterostructures, including semiconductor heterojunctions, surface protection, surface passivation and cocatalyst decoration, will be given to introduce the recent advances in metal oxide heterostructures for PEC water splitting. This article aims to provide fundamental references and principles for designing metal oxide heterostructures with high activity and stability as photoelectrodes for PEC solar hydrogen generation.

  13. Storage rings for investigation of ion-atom collisions

    International Nuclear Information System (INIS)

    Schuch, R.

    1987-08-01

    In this survey, we give a brief description of synchrotron storage rings for heavy ions, and examples for their use in ion-atom collision physics. The compression of the phase space distribution of the ions by electron cooling, and the gain factors of in-ring experiments compared to single-pass experiments are explained. Some examples of a new generation of ion-atom collision experiments which may become feasible with storage rings are given. These include the studies of angular differential single- and double-electron capture cross sections, the production of slow highly charged recoil ions, and atomic collision processes using decelerated and crossed beam. 30 refs

  14. Stable CSR in Storage Rings: A Model

    International Nuclear Information System (INIS)

    Sannibale, F.

    2005-01-01

    A comprehensive historical view of the work done on coherent synchrotron radiation (CSR) in storage rings is given in reference [1]. Here we want just to point out that even if the issue of CSR in storage rings was already discussed over 50 years ago, it is only recently that a considerable number of observations have been reported. In fact, intense bursts of coherent synchrotron radiation with a stochastic character were measured in the terahertz frequency range, at several synchrotron light source storage rings [2-8]. It has been shown [8-11], that this bursting emission of CSR is associated with a single bunch instability, usually referred as microbunching instability (MBI), driven by the fields of the synchrotron radiation emitted by the bunch itself. Of remarkably different characteristics was the CSR emission observed at BESSY II in Berlin, when the storage ring was tuned into a special low momentum compaction mode [12, 13]. In fact, the emitted radiation was not the quasi-random bursting observed in the other machines, but a powerful and stable flux of broadband CSR in the terahertz range. This was an important result, because it experimentally demonstrated the concrete possibility of constructing a stable broadband source with extremely high power in the terahertz region. Since the publication of the first successful experiment using the ring as a CSR source [14], BESSY II has regular scheduled user's shifts dedicated to CSR experiments. At the present time, several other laboratories are investigating the possibility of a CSR mode of operation [15-17] and a design for a new ring optimized for CSR is at an advanced stage [18]. In what follows, we describe a model that first accounts for the BESSY II observations and then indicates that the special case of BESSY II is actually quite general and typical when relativistic electron storage rings are tuned for short bunches. The model provides a scheme for predicting and optimizing the performance of ring

  15. Stable CSR in storage rings: A model

    International Nuclear Information System (INIS)

    Sannibale, Fernando; Byrd, John M.; Loftsdottir, Agusta; Venturini, Marco; Abo-Bakr, Michael; Feikes, Jorge; Holldack, Karsten; Kuske, Peter; Wustefeld, Godehart; Hubers, Heinz-Willerm; Warnock, Robert

    2005-01-01

    A comprehensive historical view of the work done on coherent synchrotron radiation (CSR) in storage rings is given in reference [1]. Here we want just to point out that even if the issue of CSR in storage rings was already discussed over 50 years ago, it is only recently that a considerable number of observations have been reported. In fact, intense bursts of coherent synchrotron radiation with a stochastic character were measured in the terahertz frequency range, at several synchrotron light source storage rings [2-8]. It has been shown [8-11], that this bursting emission of CSR is associated with a single bunch instability, usually referred as microbunching instability (MBI), driven by the fields of the synchrotron radiation emitted by the bunch itself. Of remarkably different characteristics was the CSR emission observed at BESSY II in Berlin, when the storage ring was tuned into a special low momentum compaction mode [12, 13]. In fact, the emitted radiation was not the quasi-random bursting observed in the other machines, but a powerful and stable flux of broadband CSR in the terahertz range. This was an important result, because it experimentally demonstrated the concrete possibility of constructing a stable broadband source with extremely high power in the terahertz region. Since the publication of the first successful experiment using the ring as a CSR source [14], BESSY II has regular scheduled user s shifts dedicated to CSR experiments. At the present time, several other laboratories are investigating the possibility of a CSR mode of operation [15-17] and a design for a new ring optimized for CSR is at an advanced stage [18]. In what follows, we describe a model that first accounts for the BESSY II observations and then indicates that the special case of BESSY II is actually quite general and typical when relativistic electron storage rings are tuned for short bunches. The model provides a scheme for predicting and optimizing the performance of ring

  16. Single frequency intracavity SRO

    DEFF Research Database (Denmark)

    Abitan, Haim; Buchhave, Preben

    2000-01-01

    Summary form only given. A single resonance optical parametric oscillator (SRO) is inserted intracavity to a CW high power, single frequency, and ring Nd:YVO4 laser. We obtain a stable single frequency CW SRO with output at 1.7-1.9 μm (idler) and a resonating signal at 2.3-2.6 μm. The behavior...

  17. New diols with imidazoquinazoline ring

    Science.gov (United States)

    Szyszkowska, Agnieszka; Klasek, Antonin; Pawlędzio, Sylwia; Trzybiński, Damian; Woźniak, Krzysztof; Zarzyka, Iwona

    2018-02-01

    The objective of these studies was to synthesize and characterize new diols with an imidazoquinazoline ring. New diols were obtained in reactions of 2,6-bis-(ethoxycarbonylmethyl)-1-phenylimidazo[1,5-c]quinazoline-3,5-dione with excess of ethylene glycol or in reaction of 1-phenyl-2H,6H-imidazo[1,5-c]quinazoline-3,5-dione with 2-M excess of ethylene oxide. The products were isolated at high yield and characterized by instrumental methods (IR, 1H- and 13C-NMR, MS-ESI, UV, TGA). The structure of 2,6-bis(2-hydroxyethyl)-1-phenylimidazo[1,5-c]quinazoline-3,5-dione (BEFIQ) was also investigated by single-crystal X-ray diffraction. BEFIQ crystallizes in the monoclinic P21/n space group with two molecules in the asymmetric unit of the crystal lattice. The nature of the packing of molecules in the crystal lattice of BEFIQ was investigated by Hirshfeld surface analysis. The described methods enable the synthesis of new diols with an imidazoquinazoline ring. The new diols are quite soluble in typical organic solvents. Therefore, they can be used as raw materials for the synthesis of thermally stable polymers, and they can also have biological activity.

  18. Elastic and piezoelectric properties of zincblende and wurtzite crystalline nanowire heterostructures.

    Science.gov (United States)

    Boxberg, Fredrik; Søndergaard, Niels; Xu, H Q

    2012-09-04

    The elastic and piezoelectric properties of zincblende and wurtzite crystalline InAs/InP nanowire heterostructures have been studied using electro-elastically coupled continuum elasticity theory. A comprehensive comparison of strains, piezoelectric potentials and piezoelectric fields in the two crystal types of nanowire heterostructures is presented. For each crystal type, three different forms of heterostructures-core-shell, axial superlattice, and quantum dot nanowire heterostructures-are considered. In the studied nanowire heterostructures, the principal strains are found to be insensitive to the change in the crystal structure. However, the shear strains in the zincblende and wurtzite nanowire heterostructures can be very different. All the studied nanowire heterostructures are found to exhibit a piezoelectric field along the nanowire axis. The piezoelectric field is in general much stronger in a wurtzite nanowire heterostructure than in its corresponding zincblende heterostructure. Our results are expected to be particularly important for analyzing and understanding the properties of epitaxially grown nanowire heterostructures and for applications in nanowire electronics, optoelectronics, and biochemical sensing. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Elastic and piezoelectric properties of zincblende and wurtzite crystalline nanowire heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Boxberg, Fredrik [Division of Solid State Physics, Lund University (Sweden); Soendergaard, Niels [Division of Mathematical Physics, Lund University (Sweden); Xu, H.Q. [Department of Electronics and Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing (China); Division of Solid State Physics, Lund University (Sweden)

    2012-09-04

    The elastic and piezoelectric properties of zincblende and wurtzite crystalline InAs/InP nanowire heterostructures have been studied using electro-elastically coupled continuum elasticity theory. A comprehensive comparison of strains, piezoelectric potentials and piezoelectric fields in the two crystal types of nanowire heterostructures is presented. For each crystal type, three different forms of heterostructures - core-shell, axial superlattice, and quantum dot nanowire heterostructures - are considered. In the studied nanowire heterostructures, the principal strains are found to be insensitive to the change in the crystal structure. However, the shear strains in the zincblende and wurtzite nanowire heterostructures can be very different. All the studied nanowire heterostructures are found to exhibit a piezoelectric field along the nanowire axis. The piezoelectric field is in general much stronger in a wurtzite nanowire heterostructure than in its corresponding zincblende heterostructure. Our results are expected to be particularly important for analyzing and understanding the properties of epitaxially grown nanowire heterostructures and for applications in nanowire electronics, optoelectronics, and biochemical sensing. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Synthesis of WO{sub n}-WX{sub 2} (n=2.7, 2.9; X=S, Se) heterostructures for highly efficient green quantum dot light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Han, Shikui; Tan, Chaoliang; Zhang, Xiao; Chen, Junze; Huang, Ying; Chen, Bo; Luo, Zhimin; Ma, Qinglang; Sindoro, Melinda; Zhang, Hua [Center for Programmable Materials, School of Materials Science and Engineering, Nanyang Technological University, Singapore (Singapore); Yang, Xuyong [Luminous. Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore (Singapore); Zhu, Yihan; Han, Yu [Advanced Membranes and Porous Materials Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal (Saudi Arabia); Zhang, Hao; Li, Hai; Huang, Xiao; Huang, Wei [Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech) (China); Qi, Xiaoying [Singapore Institute of Manufacturing Technology, Singapore (Singapore); Sun, Xiao Wei [Luminous. Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore (Singapore); Dept. of Electrical and Electronic Engineering, College of Engineering, Southern Univ. of Science and Technology, Nanshan, Shenzhen, Guangdong (China)

    2017-08-21

    Preparation of two-dimensional (2D) heterostructures is important not only fundamentally, but also technologically for applications in electronics and optoelectronics. Herein, we report a facile colloidal method for the synthesis of WO{sub n}-WX{sub 2} (n=2.7, 2.9; X=S, Se) heterostructures by sulfurization or selenization of WO{sub n} nanomaterials. The WO{sub n}-WX{sub 2} heterostructures are composed of WO{sub 2.9} nanoparticles (NPs) or WO{sub 2.7} nanowires (NWs) grown together with single- or few-layer WX{sub 2} nanosheets (NSs). As a proof-of-concept application, the WO{sub n}-WX{sub 2} heterostructures are used as the anode interfacial buffer layer for green quantum dot light-emitting diodes (QLEDs). The QLED prepared with WO{sub 2.9} NP-WSe{sub 2} NS heterostructures achieves external quantum efficiency (EQE) of 8.53 %. To our knowledge, this is the highest efficiency in the reported green QLEDs using inorganic materials as the hole injection layer. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Report of the New Rings Study Group

    International Nuclear Information System (INIS)

    Holmes, S.D.; Dugan, G.; Marriner, J.

    1987-01-01

    We have taken the approach here of trying to understand both the feasibility and practicality of varied options for new rings at Fermilab, rather than trying to produce a single detailed design. In other words, this document is not a design report and should not be construed as such. Our perception of the potential needs for new rings (in order of priority) is as follows: Antiproton Storage and/or Recovery: A facility for storing up to 4 x 10 12 antiprotons is needed. Recovery of antiprotons from the collider becomes a viable option if the luminosity is indeed dominated by emittance dilution rather than beam loss. New or Post-Booster: The goal here would be to inject into the existing Main Ring above transition. Improved performance of the Main Ring would be anticipated. New Main Ring: Advantages would include better emittance preservation, a faster cycle time for antiproton production, and the removal of interference/backgrounds at the B0 and D0 detectors. We discuss in this paper various scenarios based on one or more combinations of the above possibilities. 14 figs., 10 tabs

  2. Report of the New Rings Study Group

    Energy Technology Data Exchange (ETDEWEB)

    Holmes, S.D.; Dugan, G.; Marriner, J.

    1987-10-19

    We have taken the approach here of trying to understand both the feasibility and practicality of varied options for new rings at Fermilab, rather than trying to produce a single detailed design. In other words, this document is not a design report and should not be construed as such. Our perception of the potential needs for new rings (in order of priority) is as follows: Antiproton Storage and/or Recovery: A facility for storing up to 4 x 10/sup 12/ antiprotons is needed. Recovery of antiprotons from the collider becomes a viable option if the luminosity is indeed dominated by emittance dilution rather than beam loss. New or Post-Booster: The goal here would be to inject into the existing Main Ring above transition. Improved performance of the Main Ring would be anticipated. New Main Ring: Advantages would include better emittance preservation, a faster cycle time for antiproton production, and the removal of interference/backgrounds at the B0 and D0 detectors. We discuss in this paper various scenarios based on one or more combinations of the above possibilities. 14 figs., 10 tabs.

  3. Fusion rings and fusion ideals

    DEFF Research Database (Denmark)

    Andersen, Troels Bak

    This dissertation investigates fusion rings, which are Grothendieck groups of rigid, monoidal, semisimple, abelian categories. Special interest is in rational fusion rings, i.e., fusion rings which admit a finite basis, for as commutative rings they may be presented as quotients of polynomial rings...... by the so-called fusion ideals. The fusion rings of Wess-Zumino-Witten models have been widely studied and are well understood in terms of precise combinatorial descriptions and explicit generating sets of the fusion ideals. They also appear in another, more general, setting via tilting modules for quantum...

  4. Fusion Rings for Quantum Groups

    DEFF Research Database (Denmark)

    Andersen, Henning Haahr; Stroppel, Catharina

    2012-01-01

    We study the fusion rings of tilting modules for a quantum group at a root of unity modulo the tensor ideal of negligible tilting modules. We identify them in type A with the combinatorial rings from [12] and give a similar description of the sp2n-fusion ring in terms of noncommutative symmetric...... functions. Moreover we give a presentation of all fusion rings in classical types as quotients of polynomial rings. Finally we also compute the fu- sion rings for type G2....

  5. Lattices for antiproton rings

    International Nuclear Information System (INIS)

    Autin, B.

    1984-01-01

    After a description of the constraints imposed by the cooling of Antiprotons on the lattice of the rings, the reasons which motivate the shape and the structure of these machines are surveyed. Linear and non-linear beam optics properties are treated with a special amplification to the Antiproton Accumulator. (orig.)

  6. Flushing Ring for EDM

    Science.gov (United States)

    Earwood, L.

    1985-01-01

    Removing debris more quickly lowers cutting time. Operation, cutting oil and pressurized air supplied to ring placed around workpiece. Air forces oil through small holes and agitates oil as it flows over workpiece. High flow rate and agitation dislodge and remove debris. Electrical discharge removes material from workpiece faster.

  7. SXLS storage ring design

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    X-ray lithography has emerged as a strong candidate to meet the demands of ever finer linewidths on integrated circuits, particularly for linewidths less than .25 microns. Proximity printing X-ray lithography makes use of soft X-rays to shadow print an image of a mask onto a semiconductor wafer to produce integrated circuits. To generate the required X-rays in sufficient quantities to make commercial production viable, electron storage rings have been proposed as the soft X-ray sources. Existing storage rings have been used to do the initial development work and the success of these efforts has led the lithographers to request that new rings be constructed that are dedicated to X-ray lithography. As a result of a series of workshops held at BNL [10.3] which were attended by both semiconductor and accelerator scientists, the following set of zeroth order specifications' on the light and electron beam of a storage ring for X-ray lithography were developed: critical wavelength of light: λ c = 6 to 10 angstroms, white light power: P = 0.25 to 2.5 watts/mrad, horizontal collection angle per port: θ = 10 to 50 mrad, electron beam sizes: σ x ∼ σ y y ' < 1 mrad

  8. Ring Bubbles of Dolphins

    Science.gov (United States)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

  9. FUZZY RINGS AND ITS PROPERTIES

    Directory of Open Access Journals (Sweden)

    Karyati Karyati

    2017-01-01

      One of algebraic structure that involves a binary operation is a group that is defined  an un empty set (classical with an associative binary operation, it has identity elements and each element has an inverse. In the structure of the group known as the term subgroup, normal subgroup, subgroup and factor group homomorphism and its properties. Classical algebraic structure is developed to algebraic structure fuzzy by the researchers as an example semi group fuzzy and fuzzy group after fuzzy sets is introduced by L. A. Zadeh at 1965. It is inspired of writing about semi group fuzzy and group of fuzzy, a research on the algebraic structure of the ring is held with reviewing ring fuzzy, ideal ring fuzzy, homomorphism ring fuzzy and quotient ring fuzzy with its properties. The results of this study are obtained fuzzy properties of the ring, ring ideal properties fuzzy, properties of fuzzy ring homomorphism and properties of fuzzy quotient ring by utilizing a subset of a subset level  and strong level  as well as image and pre-image homomorphism fuzzy ring.   Keywords: fuzzy ring, subset level, homomorphism fuzzy ring, fuzzy quotient ring

  10. Fabricating ZnO single microwire light-emitting diode with transparent conductive ITO film

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yingtian [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Dai, Jun [State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096 (China); Shi, Zhifeng [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Long, Beihong [College of Materials Science and Engineering, Jinlin University, 2699 Qianjin Street, Changchun 130012 (China); Wu, Bin; Cai, Xupu; Chu, Xianwei; Du, Guotong; Zhang, Baolin [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Yin, Jingzhi, E-mail: yjz886666@163.com [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China)

    2014-05-01

    In this paper, n-ZnO single microwire/p{sup +}-Si heterojunction LEDs are fabricated using the transparent conductive ITO film as an electrode. A distinct UV emission resulting from free exciton recombination in a ZnO single microwire is observed in the electroluminescence. Size difference of ZnO single microwire shows significant influence on emission efficiency. The EL spectra of n-ZnO single microwire/p-Si heterostructure exhibited relatively stronger UV emission which was compared with the EL spectra of n-ZnO single nanowire/p-Si heterostructure and n-ZnO film/p-Si heterostructure, respectively. - Highlights: • The ZnO microwires were synthesized with a vapor phase transport method. • ZnO single microwire/Si LEDs were fabricated using the ITO film as an electrode. • The EL spectra had been compared with n-ZnO film/p-Si heterostructure. • The EL spectra had been compared with n-ZnO single nanowire/p-Si heterostructure.

  11. Electrical transport and photovoltaic effects of core-shell CuO/C60 nanowire heterostructure.

    Science.gov (United States)

    Bao, Qiaoliang; Li, Chang Ming; Liao, Lei; Yang, Hongbin; Wang, Wei; Ke, Chang; Song, Qunliang; Bao, Haifeng; Yu, Ting; Loh, Kian Ping; Guo, Jun

    2009-02-11

    An organic/inorganic hybrid heterostructure consisting of p-type CuO nanowire core and n-type C(60) shell was fabricated and its electrical transport properties were studied for the first time. It was found that the devices with contacts on shell-shell show an ohmic behavior but the devices with contacts on core-shell forms a single p-n junction and display a rectifying behavior. Logarithmic current-voltage curves at various temperatures show that the tunneling transport plays a critical role in the electrical transport. Photovoltaic effects were observed in the core-shell contacted CuO/C(60) junctions under illumination. This work demonstrates that an inorganic/organic coaxial nanowire can provide potential in nanoelectronic devices and could further stack high density hybrid nanowires array as a renewable power source.

  12. Electrical transport and photovoltaic effects of core-shell CuO/C60 nanowire heterostructure

    International Nuclear Information System (INIS)

    Bao Qiaoliang; Li Changming; Yang Hongbin; Wang Wei; Song Qunliang; Bao Haifeng; Liao Lei; Yu Ting; Ke Chang; Loh, K P; Guo Jun

    2009-01-01

    An organic/inorganic hybrid heterostructure consisting of p-type CuO nanowire core and n-type C 60 shell was fabricated and its electrical transport properties were studied for the first time. It was found that the devices with contacts on shell-shell show an ohmic behavior but the devices with contacts on core-shell forms a single p-n junction and display a rectifying behavior. Logarithmic current-voltage curves at various temperatures show that the tunneling transport plays a critical role in the electrical transport. Photovoltaic effects were observed in the core-shell contacted CuO/C 60 junctions under illumination. This work demonstrates that an inorganic/organic coaxial nanowire can provide potential in nanoelectronic devices and could further stack high density hybrid nanowires array as a renewable power source.

  13. Spin-polarized ballistic conduction through correlated Au-NiMnSb-Au heterostructures

    KAUST Repository

    Morari, C.

    2017-11-20

    We examine the ballistic conduction through Au-NiMnSb-Au heterostructures consisting of up to four units of the half-metallic NiMnSb in the scattering region, using density functional theory (DFT) methods. For a single NiMnSb unit the transmission function displays a spin polarization of around 50% in a window of 1eV centered around the Fermi level. By increasing the number of layers, an almost complete spin polarization of the transmission is obtained in this energy range. Supplementing the DFT calculations with local electronic interactions, of Hubbard-type on the Mn sites, leads to a hybridization between the interface and many-body states. The significant reduction of the spin polarization seen in the density of states is not apparent in the spin polarization of the conduction electron transmission, which suggests that the hybridized interface and many-body induced states are localized.

  14. Electron transport in InAs nanowires and heterostructure nanowire devices

    Science.gov (United States)

    Thelander, C.; Björk, M. T.; Larsson, M. W.; Hansen, A. E.; Wallenberg, L. R.; Samuelson, L.

    2004-09-01

    Nanowires in the InAs/InP material system are grown with catalyst-assisted chemical beam epitaxy. Ohmic contacts are then fabricated to selected wires, allowing electron transport measurements to be carried out at room-temperature as well as at low T. InAs nanowires show strong quantum confinement effects, where thin wires (Heterostructure barriers of InP are also incorporated into InAs wires to produce resonant tunneling diodes and single-electron transistors (SETs) with different dot lengths. Wires containing dots with a length of 100 nm function as ideal SETs, whereas the transport in wires with 15 nm long dots is strongly governed by quantum confinement and resonant tunneling. For the smaller dots it is possible to observe electron transport through excited states.

  15. Electrical transport and photovoltaic effects of core-shell CuO/C60 nanowire heterostructure

    Science.gov (United States)

    Bao, Qiaoliang; Li, Chang Ming; Liao, Lei; Yang, Hongbin; Wang, Wei; Ke, Chang; Song, Qunliang; Bao, Haifeng; Yu, Ting; Loh, Kian Ping; Guo, Jun

    2009-02-01

    An organic/inorganic hybrid heterostructure consisting of p-type CuO nanowire core and n-type C60 shell was fabricated and its electrical transport properties were studied for the first time. It was found that the devices with contacts on shell-shell show an ohmic behavior but the devices with contacts on core-shell forms a single p-n junction and display a rectifying behavior. Logarithmic current-voltage curves at various temperatures show that the tunneling transport plays a critical role in the electrical transport. Photovoltaic effects were observed in the core-shell contacted CuO/C60 junctions under illumination. This work demonstrates that an inorganic/organic coaxial nanowire can provide potential in nanoelectronic devices and could further stack high density hybrid nanowires array as a renewable power source.

  16. Inorganic glass ceramic slip rings

    Science.gov (United States)

    Glossbrenner, E. W.; Cole, S. R.

    1972-01-01

    Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

  17. e-læring

    DEFF Research Database (Denmark)

    Helms, Niels Henrik

    e-læring kan defineres på ganske mange måder. Ordet e-læring består jo tydeligt nok af to elementer. E + læring ligesom e-handel eller e-banking, og umiddelbart vil de fleste nok sige, at det så handler om læring vha. internettet. I bidraget advokeres for en læringsmæssig frem for normativ tilgang....

  18. Design of low energy ring(s)

    CERN Document Server

    Lachaize, Antoine

    During the last two years, several upgrades of the initial baseline scenario were studied with the aim of increasing the average intensity of ion beams in the accelerator chain of the Beta Beam complex. This is the reason why the Rapid Cycling Synchrotron (RCS) specifications were reconsidered many times [1], [2], [3].General considerations on the optical design were presented at the Beta Beam Task Meetings held at CERN and at Saclay in 2005 [4]. More detailed beam optics studies were performed during the next months. Lattices, RF system parameters, multi-turn injection scheme, fast extraction, closed orbit correction and chromaticity correction systems were proposed for different versions of the RCS [5], [6], [7].Finally, the RCS specifications have stabilized in November 2006 after the fourth Beta Beam Task Meeting when it was decided to fix the maximum magnetic rigidity of ion beams to 14.47 T.m (3.5 GeV equivalent proton energy) and to adopt a ring physical radius of 40 m in order to facilitate injectio...

  19. Unipolar Vertical Transport in GaN/AlGaN/GaN Heterostructures

    OpenAIRE

    Nath, D. N.; Park, P. S.; Yang, Z. C.; Rajan, S.

    2013-01-01

    In this letter, we report on unipolar vertical transport characteristics in c-plane GaN/AlGaN/GaN heterostructures. Vertical current in heterostructures with random alloy barriers was found to be independent of dislocation density and heterostructure barrier height, and significantly higher than theoretical estimates. Percolation-based transport due to random alloy fluctuations in the ternary AlGaN is suggested as the dominant transport mechanism, and confirmed through experiments showing tha...

  20. Ferroelectric-Driven Performance Enhancement of Graphene Field-Effect Transistors Based on Vertical Tunneling Heterostructures.

    Science.gov (United States)

    Yuan, Shuoguo; Yang, Zhibin; Xie, Chao; Yan, Feng; Dai, Jiyan; Lau, Shu Ping; Chan, Helen L W; Hao, Jianhua

    2016-12-01

    A vertical graphene heterostructure field-effect transistor (VGHFET) using an ultrathin ferroelectric film as a tunnel barrier is developed. The heterostructure is capable of providing new degrees of tunability and functionality via coupling between the ferroelectricity and the tunnel current of the VGHFET, which results in a high-performance device. The results pave the way for developing novel atomic-scale 2D heterostructures and devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Advanced Semiconductor Heterostructures Novel Devices, Potential Device Applications and Basic Properties

    CERN Document Server

    Stroscio, Michael A

    2003-01-01

    This volume provides valuable summaries on many aspects of advanced semiconductor heterostructures and highlights the great variety of semiconductor heterostructures that has emerged since their original conception. As exemplified by the chapters in this book, recent progress on advanced semiconductor heterostructures spans a truly remarkable range of scientific fields with an associated diversity of applications. Some of these applications will undoubtedly revolutionize critically important facets of modern technology. At the heart of these advances is the ability to design and control the pr

  2. Clean elements in abelian rings

    Indian Academy of Sciences (India)

    equivalent to being clean for an abelian ring is 'topologically boolean'. In line with [1] we say that a ring R (not necessarily commutative) is right (resp. left) topologically boolean, or a right (resp. left) tb-ring for short, if for every pair of distinct maximal right (resp. left) ideals of R there is an idempotent in exactly one of them.

  3. Thermoelectric properties of IV–VI-based heterostructures and superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Borges, P.D., E-mail: pabloborges@ufv.br [Instituto de Ciências Exatas e Tec., Universidade Federal de Viçosa, Rio Paranaíba, MG (Brazil); Department of Physics, Texas State University, San Marcos, TX 78666 (United States); Petersen, J.E.; Scolfaro, L. [Department of Physics, Texas State University, San Marcos, TX 78666 (United States); Leite Alves, H.W. [Departamento de Ciências Naturais, Universidade Federal de São João Del Rei, Caixa Postal 110, São João Del Rei 36300-000, MG (Brazil); Myers, T.H. [Department of Physics, Texas State University, San Marcos, TX 78666 (United States)

    2015-07-15

    Doping in a manner that introduces anisotropy in order to reduce thermal conductivity is a significant focus in thermoelectric research today. By solving the semiclassical Boltzmann transport equations in the constant scattering time (τ) approximation, in conjunction with ab initio electronic structure calculations, within Density Functional Theory, we compare the Seebeck coefficient (S) and figure of merit (ZT) of bulk PbTe to PbTe/SnTe/PbTe heterostructures and PbTe doping superlattices (SLs) with periodically doped planes. Bismuth and Thallium were used as the n- and p-type impurities, respectively. The effects of carrier concentration are considered via chemical potential variation in a rigid band approximation. The impurity bands near the Fermi level in the electronic structure of PbTe SLs are of Tl s- and Bi p-character, and this feature is independent of the doping concentration or the distance between impurity planes. We observe the impurity bands to have a metallic nature in the directions perpendicular to the doping planes, yet no improvement on the values of ZT is found when compared to bulk PbTe. For the PbTe/SnTe/PbTe heterostructures, the calculated S presents good agreement with recent experimental data, and an anisotropic behavior is observed for low carrier concentrations (n<10{sup 18} cm{sup −3}). A large value of ZT{sub ||} (parallel to the growth direction) of 3.0 is predicted for n=4.7×10{sup 18} cm{sup −3} and T=700 K, whereas ZT{sub p} (perpendicular to the growth direction) is found to peak at 1.5 for n=1.7×10{sup 17} cm{sup −3}. Both electrical conductivity enhancement and thermal conductivity reduction are analyzed. - Graphical abstract: Figure of merit for PbTe/SnTe/PbTe heterostructure along the [0 0 1] direction, P.D. Borges, J.E. Petersen, L. Scolfaro, H.W. Leite Alves, T.H. Myers, Improved thermoelectric properties of IV–VI-based heterostructures and superlattices. - Highlights: • Thermoelectric properties of IV

  4. Ordering phenomena in transition-metal-oxide heterostructures

    International Nuclear Information System (INIS)

    Frano Pereira, Alex Manuel

    2014-01-01

    This doctoral work presents a study of ordered ground states of transition metal oxide compounds and multilayers using resonant elastic soft x-ray scattering. The technique has developed over the last decades and become especially useful when sample sizes are limited like the case of nanometer-scale films and superlattices. By scattering with photon energies on resonance with the element's electronic transitions, it is an element-specific, sensitive tool providing a combination of spectroscopic and spatial information. The thesis is divided into two central topics. The first part focuses on the investigation of perovskite-type, rare-earth nickelate heterostructures. X-rays tuned to the Ni L 3 -edge were used to unveil unprecedented diffraction evidence of long range magnetic order in LaNiO 3 -RXO 3 (RXO 3 = LaAlO 3 , DyScO 3 ) superlattices. We report on the appearance of magnetic order in such systems with a propagation vector of Q SDW = ((1)/(4),(1)/(4),l) in pseudocubic notation, similar to bulk rare earth nickelates with R ≠ La. With LaNiO 3 being paramagnetic in its bulk form, the magnetic Bragg peak is only present in superlattices where the thickness of the LaNiO 3 layers approaches the 2-dimensional limit. Besides the thickness dependence, the magnetic order was probed on samples grown on varying strain-inducing substrates. Azimuthal scans around Q SDW were done to determine the orientation of the spin spiral under these different conditions. We will explain how the reorientation of the spins can be understood by the magneto-crystalline anisotropy which is determined by the relative occupation of the Ni d-orbitals via spin-orbit coupling. First steps towards control of the spin spiral's orientation will be outlined, and along with the high remanent conductivity found in the magnetic spiral state, an outlook for metallic antiferromagnetic spintronics will be discussed. The second part of this thesis will address the observation of charge density

  5. In-plane heterostructures of Sb/Bi with high carrier mobility

    Science.gov (United States)

    Zhao, Pei; Wei, Wei; Sun, Qilong; Yu, Lin; Huang, Baibiao; Dai, Ying

    2017-06-01

    In-plane two-dimensional (2D) heterostructures have been attracting public attention due to their distinctive properties. However, the pristine materials that can form in-plane heterostructures are reported only for graphene, hexagonal BN, transition-metal dichalcogenides. It will be of great significance to explore more suitable 2D materials for constructing such ingenious heterostructures. Here, we demonstrate two types of novel seamless in-plane heterostructures combined by pristine Sb and Bi monolayers by means of first-principle approach based on density functional theory. Our results indicate that external strain can serve as an effective strategy for bandgap engineering, and the transition from semiconductor to metal occurs when a compressive strain of -8% is applied. In addition, the designed heterostructures possess direct band gaps with high carrier mobility (˜4000 cm2 V-1 s-1). And the mobility of electrons and holes have huge disparity along the direction perpendicular to the interface of Sb/Bi in-plane heterostructures. It is favorable for carriers to separate spatially. Finally, we find that the band edge positions of Sb/Bi in-plane heterostructures can meet the reduction potential of hydrogen generation in photocatalysis. Our results not only offer alternative materials to construct versatile in-plane heterostructures, but also highlight the applications of 2D in-plane heterostructures in diverse nanodevices and photocatalysis.

  6. Electronic properties of phosphorene/graphene heterostructures: Effect of external electric field

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Sumandeep; Srivastava, Sunita; Tankeshwar, K. [Department of Physics, Panjab University, Chandigarh-160014 (India); Kumar, Ashok [Centre for Physical Sciences, School of Basic and Applied Sciences, Central University of Punjab, Bathinda, India 151001 (India)

    2016-05-23

    We report the electronic properties of electrically gated heterostructures of black and blue phosphorene with graphene. The heterostructure of blue phosphorene with graphene is energetically more favorable than black phospherene/graphene. However, both are bonded by weak interlayer interactions. Graphene induces the Dirac cone character in both heterostructure which shows tunabilities with external electric field. It is found that Dirac cone get shifted depending on the polarity of external electric field that results into the so called self induced p-type or n-type doping effect. These features have importance in the fabrication of nano-electronic devices based on the phosphorene/graphene heterostructures.

  7. Ring Confidential Transactions

    Directory of Open Access Journals (Sweden)

    Shen Noether

    2016-12-01

    Full Text Available This article introduces a method of hiding transaction amounts in the strongly decentralized anonymous cryptocurrency Monero. Similar to Bitcoin, Monero is a cryptocurrency which is distributed through a proof-of-work “mining” process having no central party or trusted setup. The original Monero protocol was based on CryptoNote, which uses ring signatures and one-time keys to hide the destination and origin of transactions. Recently the technique of using a commitment scheme to hide the amount of a transaction has been discussed and implemented by Bitcoin Core developer Gregory Maxwell. In this article, a new type of ring signature, A Multilayered Linkable Spontaneous Anonymous Group signature is described which allows one to include a Pedersen Commitment in a ring signature. This construction results in a digital currency with hidden amounts, origins and destinations of transactions with reasonable efficiency and verifiable, trustless coin generation. The author would like to note that early drafts of this were publicized in the Monero Community and on the #bitcoin-wizards IRC channel. Blockchain hashed drafts are available showing that this work was started in Summer 2015, and completed in early October 2015. An eprint is also available at http://eprint.iacr.org/2015/1098.

  8. Cassini discovers a kinematic spiral ring around Saturn.

    Science.gov (United States)

    Charnoz, S; Porco, C C; Déau, E; Brahic, A; Spitale, J N; Bacques, G; Baillie, K

    2005-11-25

    Since the time of the Voyager flybys of Saturn in 1980-1981, Saturn's eccentric F ring has been known to be accompanied on either side by faint strands of material. New Cassini observations show that these strands, initially interpreted as concentric ring segments, are in fact connected and form a single one-arm trailing spiral winding at least three times around Saturn. The spiral rotates around Saturn with the orbital motion of its constituent particles. This structure is likely the result of differential orbital motion stretching an initial cloud of particles scattered from the dense core of the F ring. Different scenarios of formation, implying ringlet-satellite interactions, are explored. A recently discovered moon candidate, S/2004 S6, is on an orbit that crosses the F-ring core at the intersection of the spiral with the ring, which suggests a dynamical connection between S/2004 S6 and the spiral.

  9. Abrupt Schottky Junctions in Al/Ge Nanowire Heterostructures.

    Science.gov (United States)

    Kral, S; Zeiner, C; Stöger-Pollach, M; Bertagnolli, E; den Hertog, M I; Lopez-Haro, M; Robin, E; El Hajraoui, K; Lugstein, A

    2015-07-08

    In this Letter we report on the exploration of axial metal/semiconductor (Al/Ge) nanowire heterostructures with abrupt interfaces. The formation process is enabled by a thermal induced exchange reaction between the vapor-liquid-solid grown Ge nanowire and Al contact pads due to the substantially different diffusion behavior of Ge in Al and vice versa. Temperature-dependent I-V measurements revealed the metallic properties of the crystalline Al nanowire segments with a maximum current carrying capacity of about 0.8 MA/cm(2). Transmission electron microscopy (TEM) characterization has confirmed both the composition and crystalline nature of the pure Al nanowire segments. A very sharp interface between the ⟨111⟩ oriented Ge nanowire and the reacted Al part was observed with a Schottky barrier height of 361 meV. To demonstrate the potential of this approach, a monolithic Al/Ge/Al heterostructure was used to fabricate a novel impact ionization device.

  10. Novel heterostructured Ge nanowires based on polytype transformation.

    Science.gov (United States)

    Vincent, Laetitia; Patriarche, Gilles; Hallais, Géraldine; Renard, Charles; Gardès, Cyrille; Troadec, David; Bouchier, Daniel

    2014-08-13

    We report on a strain-induced phase transformation in Ge nanowires under external shear stresses. The resulted polytype heterostructure may have great potential for photonics and thermoelectric applications. ⟨111⟩-oriented Ge nanowires with standard diamond structure (3C) undergo a phase transformation toward the hexagonal diamond phase referred as the 2H-allotrope. The phase transformation occurs heterogeneously on shear bands along the length of the nanowire. The structure meets the common phenomenological criteria of a martensitic phase transformation. This point is discussed to initiate an on going debate on the transformation mechanisms. The process results in unprecedented quasiperiodic heterostructures 3C/2H along the Ge nanowire. The thermal stability of those 2H domains is also studied under annealing up to 650 °C by in situ TEM.

  11. High ionic conductivity in confined bismuth oxide-based heterostructures

    Directory of Open Access Journals (Sweden)

    Simone Sanna

    2016-12-01

    Full Text Available Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3 exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure δ-Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ, deposited by pulsed laser deposition. The resulting [δ-Bi2O3/YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C and exhibits stable high ionic conductivity over a long time comparable to the value of the pure δ-Bi2O3, which is approximately two orders of magnitude higher than the conductivity of YSZ bulk.

  12. Giant magnetoelectric effect in pure manganite-manganite heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Sanjukta; Pankaj, Ravindra; Yarlagadda, Sudhakar; Majumdar, Pinaki; Littlewood, Peter B.

    2017-11-01

    Obtaining strong magnetoelectric couplings in bulk materials and heterostructures is an ongoing challenge. We demonstrate that manganite heterostructures of the form (Insulator) /(LaMnO3)(n)/Interface/(CaMnO3)(n)/(Insulator) show strong multiferroicity in magnetic manganites where ferroelectric polarization is realized by charges leaking from LaMnO3 to CaMnO3 due to repulsion. Here, an effective nearest-neighbor electron-electron (electron-hole) repulsion (attraction) is generated by cooperative electron-phonon interaction. Double exchange, when a particle virtually hops to its unoccupied neighboring site and back, produces magnetic polarons that polarize antiferromagnetic regions. Thus a striking giant magnetoelectric effect ensues when an external electrical field enhances the electron leakage across the interface.

  13. High ionic conductivity in confined bismuth oxide-based heterostructures

    DEFF Research Database (Denmark)

    Sanna, Simone; Esposito, Vincenzo; Christensen, Mogens

    2016-01-01

    Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3) exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure -Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made...... of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ), deposited by pulsed laser deposition. The resulting [δ-Bi2O3=YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C) and exhibits stable high ionic conductivity over a long time comparable to the value...... of the pure δ-Bi2O3, which is approximately two orders of magnitude higher than the conductivity of YSZ bulk....

  14. Efficient photocarrier injection in a transition metal oxide heterostructure

    CERN Document Server

    Muraoka, Y; Ueda, Y; Hiroi, Z

    2002-01-01

    An efficient method for doping a transition metal oxide (TMO) with hole carriers is presented: photocarrier injection (PCI) in an oxide heterostructure. It is shown that an insulating vanadium dioxide (VO sub 2) film is rendered metallic under light irradiation by PCI from an n-type titanium dioxide (TiO sub 2) substrate doped with Nb. Consequently, a large photoconductivity, which is exceptional for TMOs, is found in the VO sub 2 /TiO sub 2 :Nb heterostructure. We propose an electronic band structure where photoinduced holes created in TiO sub 2 :Nb can be transferred into the filled V 3d band via the low-lying O 2p band of VO sub 2. (letter to the editor)

  15. Multifunctional high-performance van der Waals heterostructures

    Science.gov (United States)

    Huang, Mingqiang; Li, Shengman; Zhang, Zhenfeng; Xiong, Xiong; Li, Xuefei; Wu, Yanqing

    2017-12-01

    A range of novel two-dimensional materials have been actively explored for More Moore and More-than-Moore device applications because of their ability to form van der Waals heterostructures with unique electronic properties. However, most of the reported electronic devices exhibit insufficient control of multifunctional operations. Here, we leverage the band-structure alignment properties of narrow-bandgap black phosphorus and large-bandgap molybdenum disulfide to realize vertical heterostructures with an ultrahigh rectifying ratio approaching 106 and on-off ratio up to 107. Furthermore, we design and fabricate tunable multivalue inverters, in which the output logic state and window of the mid-logic can be controlled by specific pairs of channel length and, most importantly, by the electric field, which shifts the band-structure alignment across the heterojunction. Finally, high gains over 150 are achieved in the inverters with optimized device geometries, showing great potential for future logic applications.

  16. Axial Ge/Si nanowire heterostructure tunnel FETs

    Energy Technology Data Exchange (ETDEWEB)

    Picraux, Sanuel T [Los Alamos National Laboratory; Daych, Shadi A [Los Alamos National Laboratory

    2010-01-01

    The vapor-liquid-solid (VLS) growth of semiconductor nanowires allows doping and composition modulation along their axis and the realization of axial 1 D heterostructures. This provides additional flexibility in energy band-edge engineering along the transport direction which is difficult to attain by planar materials growth and processing techniques. We report here on the design, growth, fabrication, and characterization of asymmetric heterostructure tunnel field-effect transistors (HTFETs) based on 100% compositionally modulated Si/Ge axial NWs for high on-current operation and low ambipolar transport behavior. We discuss the optimization of band-offsets and Schottky barrier heights for high performance HTFETs and issues surrounding their experimental realization. Our HTFET devices with 10 nm PECVD SiN{sub x} gate dielectric resulted in a measured current drive exceeding 100 {mu}A/{mu}m (I/{pi}D) and 10{sup 5} I{sub on}/I{sub off} ratios.

  17. Intrinsic disorder in graphene on transition metal dichalcogenide heterostructures

    Science.gov (United States)

    Yankowitz, Matthew; Larentis, Stefano; Kim, Kyounghwam; Xue, Jiamin; McKenzie, Devin; Huang, Shengqiang; Paggen, Marina; Ali, Mazhar; Cava, Robert; Tutuc, Emanuel; Leroy, Brian J.

    2015-03-01

    Recently, semiconducting materials in the transition metal dichalcogenide (TMD) family have gained great popularity for use in novel graphene-based heterostructure devices such as tunneling transistors, highly efficient flexible photovoltaic devices, and nonvolatile memory cells. TMDs have also been explored as alternatives to hexagonal boron nitride (hBN) as substrates for pristine graphene devices. However, their quality has thus far been significantly worse than comparable hBN devices. We examine graphene on numerous TMD substrates (MoS2, WS2, WSe2, MoTe2) with scanning tunneling microscopy and spectroscopy and find that point and line defects intrinsic to all TMD crystals (both of natural and synthetic origin) result in scattering of electrons in graphene. Our findings suggest that the quality of graphene on TMD heterostructures is limited by the intrinsic crystalline quality of the TMDs.

  18. Extreme Band Engineering of III-Nitride Nanowire Heterostructures for Electronic and Photonic Application

    Science.gov (United States)

    Sarwar, ATM Golam

    Bottom-up nanowires are attractive for realizing semiconductor devices with extreme heterostructures because strain relaxation through the nanowire sidewalls allows the combination of highly lattice mismatched materials without creating dislocations. The resulting nanowires are used to fabricate light-emitting diodes (LEDs), lasers, solar cells, and sensors. The aim of this work is to investigate extreme heterostructures, which are impossible or very hard to realize in conventional planar films, exploiting the strain accommodation property of nanowires and engineer their band structure for novel electronic and photonic applications. To this end, in this thesis, III-Nitride semiconductor nanowires are investigated. In the first part of this work, a complete growth phase diagram of InN nanowires on silicon using plasma assisted molecular beam epitaxy is developed, and structural and optical characteristics are mapped as a function of growth parameters. Next, a novel up-side down pendeoepitaxial growth of InN forming mushroom-like microstructures is demonstrated and detail structural and optical characterizations are performed. Based on this, a method to grow strain-free large area single crystalline InN or thin film is proposed and the growth of InN on patterned GaN is investigated. The optimized growth conditions developed for InN are further used to grow InGaN nanowires graded over the whole composition range. Numerical energy band simulation is performed to better understand the effect of polarization charge on photo-carrier transport in these extremely graded nanowires. A novel photodetector device with negative differential photocurrent is demonstrated using the graded InGaN nanowires. In the second part of this thesis, polarization-induced nanowire light emitting diodes (PINLEDs) are investigated. The electrical and optical properties of the nanowire heterostructure are engineered and optimized for ultraviolet and deep ultraviolet applications. The electrical

  19. One-dimensional hole gas in germanium/silicon nanowire heterostructures

    Science.gov (United States)

    Lu, Wei; Xiang, Jie; Timko, Brian P.; Wu, Yue; Lieber, Charles M.

    2005-07-01

    Two-dimensional electron and hole gas systems, enabled through band structure design and epitaxial growth on planar substrates, have served as key platforms for fundamental condensed matter research and high-performance devices. The analogous development of one-dimensional (1D) electron or hole gas systems through controlled growth on 1D nanostructure substrates, which could open up opportunities beyond existing carbon nanotube and nanowire systems, has not been realized. Here, we report the synthesis and transport studies of a 1D hole gas system based on a free-standing germanium/silicon (Ge/Si) core/shell nanowire heterostructure. Room temperature electrical transport measurements clearly show hole accumulation in undoped Ge/Si nanowire heterostructures, in contrast to control experiments on single-component nanowires. Low-temperature studies show well-controlled Coulomb blockade oscillations when the Si shell serves as a tunnel barrier to the hole gas in the Ge channel. Transparent contacts to the hole gas also have been reproducibly achieved by thermal annealing. In such devices, we observe conductance quantization at low temperatures, corresponding to ballistic transport through 1D subbands, where the measured subband energy spacings agree with calculations for a cylindrical confinement potential. In addition, we observe a “0.7 structure,” which has been attributed to spontaneous spin polarization, suggesting the universality of this phenomenon in interacting 1D systems. Lastly, the conductance exhibits little temperature dependence, consistent with our calculation of reduced backscattering in this 1D system, and suggests that transport is ballistic even at room temperature. Author contributions: W.L., J.X., and C.M.L. designed research; W.L. and J.X. performed research; B.P.T. and Y.W. contributed new reagents/analytic tools; W.L., J.X., and C.M.L. analyzed data; W.L., J.X., and C.M.L. wrote the paper; and B.P.T. and Y.W. developed growth of nanowire

  20. Liquid phase epitaxial growth of heterostructured hierarchical MOF thin films

    KAUST Repository

    Chernikova, Valeriya

    2017-05-10

    Precise control of epitaxial growth of MOF-on-MOF thin films, for ordered hierarchical tbo-type structures is demonstrated. The heterostructured MOF thin film was fabricated by successful sequential deposition of layers from two different MOFs. The 2-periodic layers, edge-transitive 4,4-square lattices regarded as supermolecular building layers, were commendably cross-linked using a combination of inorganic/organic and organic pillars.

  1. 2D Vertical Heterostructures for Novel Tunneling Device Applications

    Science.gov (United States)

    2017-03-01

    tunneling has been explored for the symmetric field - effect transistor (symFET) [1, 2], while opposite-band tunneling has been explored for...the interlayer tunnel field - effect transistor (ITFET) [3, 4] and the Esaki diode [5]. Figure 1. (a) Schematic of the heterostructure, with the... Tunneling Field Effect Transistor ," Journal of Applied Physics, vol. 115, p. 074508, 2014. [4] M. O. Li, D. Esseni, J. J. Nahas, D.

  2. Homogeneous CdTe quantum dots-carbon nanotubes heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, Kayo Oliveira [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil); Bettini, Jefferson [Laboratório Nacional de Nanotecnologia, Centro Nacional de Pesquisa em Energia e Materiais, CEP 13083-970, Campinas, SP (Brazil); Ferrari, Jefferson Luis [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil); Schiavon, Marco Antonio, E-mail: schiavon@ufsj.edu.br [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil)

    2015-01-15

    The development of homogeneous CdTe quantum dots-carbon nanotubes heterostructures based on electrostatic interactions has been investigated. We report a simple and reproducible non-covalent functionalization route that can be accomplished at room temperature, to prepare colloidal composites consisting of CdTe nanocrystals deposited onto multi-walled carbon nanotubes (MWCNTs) functionalized with a thin layer of polyelectrolytes by layer-by-layer technique. Specifically, physical adsorption of polyelectrolytes such as poly (4-styrene sulfonate) and poly (diallyldimethylammonium chloride) was used to deagglomerate and disperse MWCNTs, onto which we deposited CdTe quantum dots coated with mercaptopropionic acid (MPA), as surface ligand, via electrostatic interactions. Confirmation of the CdTe quantum dots/carbon nanotubes heterostructures was done by transmission and scanning electron microscopies (TEM and SEM), dynamic-light scattering (DLS) together with absorption, emission, Raman and infrared spectroscopies (UV–vis, PL, Raman and FT-IR). Almost complete quenching of the PL band of the CdTe quantum dots was observed after adsorption on the MWCNTs, presumably through efficient energy transfer process from photoexcited CdTe to MWCNTs. - Highlights: • Highly homogeneous CdTe-carbon nanotubes heterostructures were prepared. • Simple and reproducible non-covalent functionalization route. • CdTe nanocrystals homogeneously deposited onto multi-walled carbon nanotubes. • Efficient energy transfer process from photoexcited CdTe to MWCNTs.

  3. First-principles design of epitaxial perovskite heterostructures

    Science.gov (United States)

    Neaton, J. B.

    2003-03-01

    Experimental capabilities now allow layer-by-layer epitaxial growth of perovskite-based oxides with atomic-level control. This makes possible a wide range of novel multifunctional oxide heterostructures, composite systems which promise to play an important role in many contemporary applications. The phenomenology of oxides grown in this geometry is rather complex, and expected to be influenced by composition, interfacial structure and chemistry, internal fields arising from non-bulk electrical boundary conditions, and the considerable strains associated with coherent epitaxy. In this talk, the respective roles of each of these features in selected artificial heterostructures is investigated quantitatively using first-principles density-functional theory within the local density approximation. First, the structure, polarization, phonons, and static dielectric response of several standard perovskite materials, such as BaTiO_3, SrTiO_3, and PbTiO_3, are mapped as as a function of epitaxial misfit strains up to 3%. These results are then used to interpret and design properties of paraelectric/ferroelectric superlattices, such as BaTiO_3/SrTiO3 and PbTiO_3/SrTiO_3; inversion-symmetry breaking heterostructures, such as LaAlO_3/SrTiO_3; and multiferroic thin films, such as BiFeO_3. Comparisons with recent experiments, and implications for future work, are discussed in each case.

  4. GaN/NbN epitaxial semiconductor/superconductor heterostructures

    Science.gov (United States)

    Yan, Rusen; Khalsa, Guru; Vishwanath, Suresh; Han, Yimo; Wright, John; Rouvimov, Sergei; Katzer, D. Scott; Nepal, Neeraj; Downey, Brian P.; Muller, David A.; Xing, Huili G.; Meyer, David J.; Jena, Debdeep

    2018-03-01

    Epitaxy is a process by which a thin layer of one crystal is deposited in an ordered fashion onto a substrate crystal. The direct epitaxial growth of semiconductor heterostructures on top of crystalline superconductors has proved challenging. Here, however, we report the successful use of molecular beam epitaxy to grow and integrate niobium nitride (NbN)-based superconductors with the wide-bandgap family of semiconductors—silicon carbide, gallium nitride (GaN) and aluminium gallium nitride (AlGaN). We apply molecular beam epitaxy to grow an AlGaN/GaN quantum-well heterostructure directly on top of an ultrathin crystalline NbN superconductor. The resulting high-mobility, two-dimensional electron gas in the semiconductor exhibits quantum oscillations, and thus enables a semiconductor transistor—an electronic gain element—to be grown and fabricated directly on a crystalline superconductor. Using the epitaxial superconductor as the source load of the transistor, we observe in the transistor output characteristics a negative differential resistance—a feature often used in amplifiers and oscillators. Our demonstration of the direct epitaxial growth of high-quality semiconductor heterostructures and devices on crystalline nitride superconductors opens up the possibility of combining the macroscopic quantum effects of superconductors with the electronic, photonic and piezoelectric properties of the group III/nitride semiconductor family.

  5. Axial Ge/Si nanowire heterostructure tunnel FETs.

    Energy Technology Data Exchange (ETDEWEB)

    Dayeh, Shadi A. (Los Alamos National Laboratory); Gin, Aaron V.; Huang, Jian Yu; Picraux, Samuel Thomas (Los Alamos National Laboratory)

    2010-03-01

    Axial Ge/Si heterostructure nanowires (NWs) allow energy band-edge engineering along the axis of the NW, which is the charge transport direction, and the realization of asymmetric devices for novel device architectures. This work reports on two significant advances in the area of heterostructure NWs and tunnel FETs: (i) the realization of 100% compositionally modulated Si/Ge axial heterostructure NWs with lengths suitable for device fabrication and (ii) the design and implementation of Schottky barrier tunnel FETs on these NWs for high-on currents and suppressed ambipolar behavior. Initial prototype devices with 10 nm PECVD SiN{sub x} gate dielectric resulted in a very high current drive in excess of 100 {micro}A/{micro}m (I/{pi}D) and 10{sup 5} I{sub on}/I{sub off} ratios. Prior work on the synthesis of Ge/Si axial NW heterostructures through the VLS mechanism have resulted in axial Si/Si{sub 1-x}Ge{sub x} NW heterostructures with x{sub max} {approx} 0.3, and more recently 100% composition modulation was achieved with a solid growth catalyst. In this latter case, the thickness of the heterostructure cannot exceed few atomic layers due to the slow axial growth rate and concurrent radial deposition on the NW sidewalls leading to a mixture of axial and radial deposition, which imposes a big challenge for fabricating useful devices form these NWs in the near future. Here, we report the VLS growth of 100% doping and composition modulated axial Ge/Si heterostructure NWs with lengths appropriate for device fabrication by devising a growth procedure that eliminates Au diffusion on the NW sidewalls and minimizes random kinking in the heterostructure NWs as deduced from detailed microscopy analysis. Fig. 1 a shows a cross-sectional SEM image of epitaxial Ge/Si axial NW heterostructures grown on a Ge(111) surface. The interface abruptness in these Ge/Si heterostructure NWs is of the order of the NW diameter. Some of these NWs develop a crystallographic kink that is {approx

  6. M = Mo, W; X = S, Se, Te) heterostructures

    KAUST Repository

    Zhang, Qingyun

    2018-04-16

    Using first-principles calculations, we investigate the electronic properties of the two-dimensional GaX/MX2 (M = Mo, W; X = S, Se, Te) heterostructures. Orbital hybridization between GaX and MX2 is found to result in Rashba splitting at the valence-band edge around the Γ point, which grows for increasing strength of the spin-orbit coupling in the p orbitals of the chalcogenide atoms. The location of the valence-band maximum in the Brillouin zone can be tuned by strain and application of an out-of-plane electric field. The coexistence of Rashba splitting (in-plane spin direction) and band splitting at the K and K′ valleys (out-of-plane spin direction) makes GaX/MX2 heterostructures interesting for spintronics and valleytronics. They are promising candidates for two-dimensional spin-field-effect transistors and spin-valley Hall effect devices. Our findings shed light on the spin-valley coupling in van der Waals heterostructures.

  7. SOR-ring failure

    International Nuclear Information System (INIS)

    Kitamura, Hideo

    1981-01-01

    It was in the autumn of 1976 that the SOR-ring (synchrotron radiation storage ring) has commenced the regular operation. Since then, the period when the operation was interrupted due to the failures of SOR-ring itself is in total about 8 weeks. Failures and accidents have occurred most in the vacuum system. Those failure experiences are described on the vacuum, electromagnet, radio-frequency acceleration and beam transport systems with their interrupted periods. The eleven failures in the vacuum system have been reported, such as bellows breakage in a heating-evacuating period, leakage from the bellows of straight-through valves (made in U.S.A. and Japan), and leakage from the joint flange of the vacuum system. The longest interruption was 5 weeks due to the failure of a domestically manufactured straight-through valve. The failures of the electromagnet system involve the breakage in a cooling water system, short circuit of a winding in the Q magnet power transformer, blow of a fuse protecting the deflection magnet power source by the current less than the rating, and others. The failures of the RF acceleration system include the breakage of an output electronic tube the breakage of a cavity ceramic, RF voltage fluctuation due to the contact deterioration at a cavity electrode, and the failure of grid bias power source. It is necessary to select the highly reliable components for the vacuum system because the vacuum system failures require longer time for recovery, and very likely to induce secondary and tertiary failures. (Wakatsuki, Y.)

  8. Layer-dependent semiconductor-metal transition of SnO/Si(001) heterostructure and device application.

    Science.gov (United States)

    Xiao, Chengcheng; Wang, Fang; Wang, Yao; Yang, Shengyuan A; Jiang, Jianzhong; Yang, Ming; Lu, Yunhao; Wang, Shijie; Feng, Yuanping

    2017-05-31

    As the downscaling of electronic devices continues, the problems of leakage currents and heat dissipation become more and more serious. To address these issues, new materials and new structures are explored. Here, we propose an interesting heterostructure made of ultrathin SnO layers on Si(001) surface. Our first-principle calculations show that a single layer of SnO on Si(001) surface is a semiconductor, but a bilayer SnO on the same surface is metallic. This metal-semiconductor dichotomy allows construction of single-2D-material-based electronic devices with low contact resistance and low leakage currents. In particular, due to the interaction between Sn and the Si substrate, the semiconducting monolayer-SnO/Si(001) has a highly anisotropic band structure with a much lighter hole effective mass along one direction than that of Si and most other 2D materials, indicating a high carrier mobility. Furthermore, by combining density functional theory and nonequilibrium Green's function method, we directly investigate the transport characteristics of a field effect transistor based on the proposed heterostructures, which shows very low contact resistance, negligible leakage current, and easy gate control at a compact channel length.

  9. Femtoslicing in Storage Rings

    CERN Document Server

    Khan, Shaukat

    2005-01-01

    The generation of ultrashort synchrotron radiation pulses by laser-induced energy modulation of electrons and their subsequent transverse displacement, now dubbed "femtoslicing," was demonstrated at the Advanced Light Source in Berkeley. More recently, a femtoslicing user facility was commissioned at the BESSY storage ring in Berlin, and another project is in progress at the Swiss Light Source. The paper reviews the principle of femtoslicing, its merits and shortcomings, as well as the variations of its technical implementation. Various diagnostics techniques to detect successful laser-electron interaction are discussed and experimental results are presented.

  10. Proton storage rings

    International Nuclear Information System (INIS)

    Rau, R.R.

    1978-04-01

    A discussion is given of proton storage ring beam dynamic characteristics. Topics considered include: (1) beam energy; (2) beam luminosity; (3) limits on beam current; (4) beam site; (5) crossing angle; (6) beam--beam interaction; (7) longitudinal instability; (8) effects of scattering processes; (9) beam production; and (10) high magnetic fields. Much of the discussion is related to the design parameters of ISABELLE, a 400 x 400 GeV proton---proton intersecting storage accelerator to be built at Brookhaven National Laboratory

  11. Molybdenum disulphide (MoS2) - gallium arsenide (GaAs) heterostructures for solar cell applications

    International Nuclear Information System (INIS)

    Jamieson, I.M.; Jakovidis, G.

    2004-01-01

    Full text: Heterostructures provide a means of absorbing a greater range of the broad solar spectrum in photovoltaic cells compared with single band gap materials. Several layered transition metal dichalcogenides are potential candidates since they have near ideal top layer band gap energy, high absorption coefficients, long minority carrier lifetimes, and large diffusion lengths. One major problem with heterostructures has been the lattice parameter mismatch leading to misfit dislocations. Such defects act as recombination centres that are detrimental to cell performance. Two dimensional layered materials overcome this difficulty because a weak Van der Waals interaction exists at the interface instead of the usual epitaxial growth, with crystallographic texture an important film structural property. If the layered compounds are to be useful as solar cells then they must be grown in a highly textured manner with the c-axis perpendicular to the substrate. Much effort has been devoted to such growth, to date there is no method which does not rely on metal particles or substrates that promote precursor phases to achieve this aim. In this study, thin films of a model material from this class, molybdenum disulphide, MoS 2 , (band gap E g = 1.8 eV), has been deposited by radio frequency magnetron sputtering and pulsed laser deposition techniques on a gallium arsenide substrate (E g =1.4 eV). Thin film structures are characterised mainly by angle dispersive x-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. These techniques reveal that there exists a region of parameter space where substantial desired bulk texturing of MoS 2 takes place without the need for metal or precursor phases. It was found that higher substrate temperatures, lower power density and higher sputtering gas pressures favoured the desired texture

  12. Fusion Rings for Quantum Groups

    DEFF Research Database (Denmark)

    Andersen, Henning Haahr; Stroppel, Catharina

    2014-01-01

    We study the fusion rings of tilting modules for a quantum group at a root of unity modulo the tensor ideal of negligible tilting modules. We identify them in type A with the combinatorial rings from Korff, C., Stroppel, C.: The sl(ˆn)k-WZNW fusion ring: a combinato-rial construction and a realis......We study the fusion rings of tilting modules for a quantum group at a root of unity modulo the tensor ideal of negligible tilting modules. We identify them in type A with the combinatorial rings from Korff, C., Stroppel, C.: The sl(ˆn)k-WZNW fusion ring: a combinato-rial construction...... and a realisation as quotient of quantum cohomology. Adv. Math. 225(1), 200–268, (2010) and give a similar description of the sp2n-fusion ring in terms of non-commutative symmetric functions. Moreover we give a presentation of all fusion rings in classical types as quotients of polynomial rings. Finally we also...... compute the fusion rings for type G2....

  13. Viscosity of ring polymer melts

    KAUST Repository

    Pasquino, Rossana

    2013-10-15

    We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes, and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the number of entanglements Z. In the unentangled regime η0,linear/η 0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/ η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z 1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z 1.6±0.3) and the simulations (η0,linear/ η0,ring ∼ Z2.0±0.3). Nevertheless, the present collection of state-of-the-art experimental data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-year-old problem. © 2013 American Chemical Society.

  14. Optical magnetism in planar metamaterial heterostructures.

    Science.gov (United States)

    Papadakis, Georgia T; Fleischman, Dagny; Davoyan, Artur; Yeh, Pochi; Atwater, Harry A

    2018-01-18

    Harnessing artificial optical magnetism has previously required complex two- and three-dimensional structures, such as nanoparticle arrays and split-ring metamaterials. By contrast, planar structures, and in particular dielectric/metal multilayer metamaterials, have been generally considered non-magnetic. Although the hyperbolic and plasmonic properties of these systems have been extensively investigated, their assumed non-magnetic response limits their performance to transverse magnetic (TM) polarization. We propose and experimentally validate a mechanism for artificial magnetism in planar multilayer metamaterials. We also demonstrate that the magnetic properties of high-index dielectric/metal hyperbolic metamaterials can be anisotropic, leading to magnetic hyperbolic dispersion in certain frequency regimes. We show that such systems can support transverse electric polarized interface-bound waves, analogous to their TM counterparts, surface plasmon polaritons. Our results open a route for tailoring optical artificial magnetism in lithography-free layered systems and enable us to generalize the plasmonic and hyperbolic properties to encompass both linear polarizations.

  15. Saturn ring temperature variations with approaching ring equinox

    Science.gov (United States)

    Spilker, L.; Leyrat, C.; Flandes, A.; Altobelli, N.; Pilorz, S.; Ferrari, C.; Edgington, S.

    2009-04-01

    Cassini's Composite Infrared Spectrometer (CIRS) has acquired a wide-ranging set of thermal measurements of Saturn's main rings (A, B, C and Cassini Division) at solar elevations ranging from less than one degree to 24 degrees. At Saturn equinox in August the solar elevation angle will reach zero as the sun traverses from the south to north side of the rings. For the data acquired to date, temperatures were retrieved for the lit and unlit rings over a variety of ring geometries that include solar elevation, as well as spacecraft elevation, phase angle and local hour angle. To first order, the largest temperature changes on the lit face of the rings are driven by variations in phase angle while differences in temperature with changing spacecraft elevation and local time are a secondary effect. Decreasing ring temperature with decreasing solar elevation are observed for both the lit and unlit faces of the rings after phase angle and local time effects are taken into account. As the solar elevation continues to decrease, the ring temperatures are decreasing in a non-linear fashion. The difference in temperature between the lit and unlit sides of the rings is decreasing also with decreasing solar elevation. Using ring thermal models developed by Leyrat we extrapolate to the expected minimum ring temperatures at equinox for our planned CIRS ring observations. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA and at CEA Saclay supported by the "Programme National de Planetologie". Copyright 2009 California Institute of Technology. Government sponsorship acknowledged.

  16. Ring Image Analyzer

    Science.gov (United States)

    Strekalov, Dmitry V.

    2012-01-01

    Ring Image Analyzer software analyzes images to recognize elliptical patterns. It determines the ellipse parameters (axes ratio, centroid coordinate, tilt angle). The program attempts to recognize elliptical fringes (e.g., Newton Rings) on a photograph and determine their centroid position, the short-to-long-axis ratio, and the angle of rotation of the long axis relative to the horizontal direction on the photograph. These capabilities are important in interferometric imaging and control of surfaces. In particular, this program has been developed and applied for determining the rim shape of precision-machined optical whispering gallery mode resonators. The program relies on a unique image recognition algorithm aimed at recognizing elliptical shapes, but can be easily adapted to other geometric shapes. It is robust against non-elliptical details of the image and against noise. Interferometric analysis of precision-machined surfaces remains an important technological instrument in hardware development and quality analysis. This software automates and increases the accuracy of this technique. The software has been developed for the needs of an R&TD-funded project and has become an important asset for the future research proposal to NASA as well as other agencies.

  17. Flexible ring seal

    International Nuclear Information System (INIS)

    Abbes, Claude; Gournier, Andre; Rouaud, Christian; Villepoix, Raymond de.

    1976-01-01

    The invention concerns a flexible metal ring seal, able to ensure a perfect seal between two bearings due to the crushing and elastic deformation properties akin to similar properties in elastomers. Various designs of seal of this kind are already known, particularly a seal made of a core formed by a helical wire spring with close-wound turns and with high axial compression ratio, closed on itself and having the shape of an annulus. This wire ring is surrounded by at least one envelope having at rest the shape of a toroidal surface of which the generating circle does not close on itself. In a particular design mode, the seal in question can include, around the internal spring, two envelopes of which one in contact with the spring is composed of a low ductility elastic metal, such as mild steel or stainless steel and the other is, on the contrary, made of a malleable metal, such as copper or nickel. The first envelope evenly distributes the partial crushing of the spring, when the seal is tightened, on the second envelope which closely fits the two surfaces between which the seal operates. The stress-crushing curve characteristic of the seal comprises two separate parts, the first with a relatively sharp slope corresponds to the start of the seal compression phase, enabling at least some of these curves to reach the requisite seal threshold very quickly, then, beyond this, a second part, practically flat, where the stress is appreciably constant for a wide operating bracket [fr

  18. NRL ion ring program

    International Nuclear Information System (INIS)

    Kapetanakos, C.A.; Golden, J.; Drobot, A.; Mahaffey, R.A.; Marsh, S.J.; Pasour, J.A.

    1977-01-01

    An experiment is under way to form a storng proton ring using the 200 ka, 1.2 MeV, 50 nsec hollow proton beam recently generated at NRL. The 5 m long magnetic field configuration consists of a magnetic cusp, a compressing magnetic field, a gate field and a magnetic mirror. The midplane value of the magnetic mirror is such that the major radius of the ring will be about 10 cm. The degree of field reversal that will be achieved with 5 x 10 16 protons per pulse from the existing beam depends upon the field reversal is possible with the 600 kA proton beam that would be generated from the low inductance coaxial triode coupled to the upgraded Gamble II generator. The propagation and trapping of an intense proton beam in the experimental magnetic field configuration is investigated numerically. The results show that the self magnetic has a very pronounced effect on the dynamics of the gyrating protons

  19. PHOTOELECTRIC PROPERTIES OF HETEROSTRUCTURES BASED ON PEPC AND MEH-PPV FILMS DOPED WITH ZINC OCTABUTYLPHTHALOCYANINE

    Directory of Open Access Journals (Sweden)

    Nicolay Davidenko

    2016-06-01

    Full Text Available Planar organic heterostructures were prepared using poly-N- epoxypropylcarbazole films and poly[2-methoxy-5-(2’-ethylhexyloxy-1,4-phenylenevinylene] by the method of successive deposition adding 2,3,9,10,16,17,23,24-zinc octabutylphthalocyanine. Photoelectric, photodielectric and photovoltaic properties of the heterostructures were studied.

  20. On thickness of Saturn rings

    International Nuclear Information System (INIS)

    Brahic, Andre; Laques, Pierre; Lecacheux, Jean; Servan, Bernard; Despiau, Raymond; Michet, Daniel; Renard, Leopold

    1980-01-01

    Electronographic plates of Saturn were taken during the transit of the Earth through the ring plane. Observing conditions were more favorable than those prevailing in 1966. Thanks to the quality of the detectors and the telescopes, it has been possible to make a more precise photometric determination of the brightness of the ring seen edge on and to measure the brightness variation with respect to the distance to the center of the planet. Extrapolating to the case where the elevation of the Earth above the ring plane is strictly zero, we deduce an apparent photometric ring thickness equal to 1.5+-0.3 km. For an homogeneous layer of small particles colliding inelastically, theory predicts a thickness of the order of a few particles radii, i.e. a few tens of meters. The observed brightness could be explained by the E ring, the brightness of large chunks, condensations and warping of the ring [fr

  1. Stability of Moonlets Embedded in Rings

    Science.gov (United States)

    Lewis, Mark C.; Burdon, C.

    2011-04-01

    Previous work on moonlets assumed that they were just a single indestructible spherical particle and focused primarily on the effects such a body would have on the surrounding ring material (Lewis and Stewart 2009, Icarus 199:387-412; Sremcevic et al. 2007, Nature 449:1019-1021). Both observations and numerical simulations of Saturn's small inner moons show them as very low density rubble piles (Porco et al. 2007, Science 318:1602). Unlike the small moons, moonlets embedded in the ring material will experience regular collisions with self gravity wakes tens of meters across. Even with a single spherical core, these collisions can lead to the shedding of significant amounts of accreted material. We describe numerical simulations in which we explore the parameters required for stability of moonlets embedded in the ring material. Because of their location well inside the Roche limit, these bodies require either higher densities or some internal strength in order to stay together. We explore how much strength is required for these moonlets to be stable against the regular impacts they sustain in that environment. This work was funded by NSF AAG award number 0907972.

  2. Saturn's Rings and Associated Ring Plasma Cavity: Evidence for Slow Ring Erosion

    Science.gov (United States)

    Farrell, W. M.; Kurth, W. S.; Gurnett, D. A.; Persoon, A. M.; MacDowall, R. J.

    2017-01-01

    We re-examine the radio and plasma wave observations obtained during the Cassini Saturn orbit insertion period, as the spacecraft flew over the northern ring surface into a radial distance of 1.3 Rs (over the C-ring). Voyager era studies suggest the rings are a source of micro-meteoroid generated plasma and dust, with theorized peak impact-created plasma outflows over the densest portion of the rings (central B-ring). In sharp contrast, the Cassini Radio and Plasma Wave System (RPWS) observations identify the presence of a ring-plasma cavity located in the central portion of the B-ring, with little evidence of impact-related plasma. While previous Voyager era studies have predicted unstable ion orbits over the C- ring, leading to field-aligned plasma transport to Saturns ionosphere, the Cassini RPWS observations do not reveal evidence for such instability-created plasma fountains. Given the passive ring loss processes observed by Cassini, we find that the ring lifetimes should extend >10(exp 9) years, and that there is limited evidence for prompt destruction (loss in <100 Myrs).

  3. ELASR – An electrostatic storage ring for atomic and molecular physics at KACST

    Directory of Open Access Journals (Sweden)

    Mohamed O.A. El Ghazaly

    2015-01-01

    Full Text Available A new ELectrostAtic Storage Ring (ELASR has been designed and built at the King Abdulaziz City for Science and Technology (KACST, in Riyadh, Saudi Arabia. It was developed to be the core of a new storage ring laboratory for atomic and molecular physics at KACST. ELASR follows the standard design of the pioneering storage ring ELISA and it thereby features a racetrack single-bend shaped ring. Complementary simulation code packages were used to work out the design under the requirements of the projected experiments. This paper reports a short description of the ELASR storage ring through an overview of its design and construction.

  4. Caustic rings of dark matter

    International Nuclear Information System (INIS)

    Sikivie, P.

    1997-01-01

    It is shown that the infall of collisionless dark matter onto isolated galaxies produce a series of caustic rings in the halo dark matter distribution. The properties of these caustics are investigated. It is found in particular that the density profile of the caustic behaves as the inverse distance to the ring. Bumps in the rotation curve of NGC 3198 are interpreted as due to caustic rings of dark matter

  5. Spin transport properties of partially edge-hydrogenated MoS2 nanoribbon heterostructure

    International Nuclear Information System (INIS)

    Peng, Li; Yao, Kailun; Zhu, Sicong; Ni, Yun; Zu, Fengxia; Wang, Shuling; Guo, Bin; Tian, Yong

    2014-01-01

    We report ab initio calculations of electronic transport properties of heterostructure based on MoS 2 nanoribbons. The heterostructure consists of edge hydrogen-passivated and non-passivated zigzag MoS 2 nanoribbons (ZMoS 2 NR-H/ZMoS 2 NR). Our calculations show that the heterostructure has half-metallic behavior which is independent of the nanoribbon width. The opening of spin channels of the heterostructure depends on the matching of particular electronic orbitals in the Mo-dominated edges of ZMoS 2 NR-H and ZMoS 2 NR. Perfect spin filter effect appears at small bias voltages, and large negative differential resistance and rectifying effects are also observed in the heterostructure.

  6. Investigation of band alignment in Co doped ZnO/ZnO heterostructure

    Science.gov (United States)

    Girish, Rajput, Parasmani; Nand, Mangla; Kumar, Manvendra; Gupta, Mukul; Jha, S. N.; Bhattacharyya, D.; Sahoo, N. K.

    2017-05-01

    The band alignment of Zn0.9Co0.1O/ZnO thin film heterostructure was investigated using photoelectron spectroscopy. The ZnO, Zn0.9Co0.1O and Zn0.9Co0.1O/ZnO thin film heterostructure has been prepared using RF ion beam sputtering, The band offset of prepared heterostructure were calculated form valance band maximum and core level peaks. The valance band and conduction band offset for Zn0.9Co0.1O/ZnO heterostructure thin film were found to be 0.36 eV and 0.51 eV, respectively, which indicates type-II band alignment in the Zn0.9Co0.1O/ZnO heterostructure.

  7. Vacuum-evaporated ferroelectric films and heterostructures of vinylidene fluoride/trifluoroethylene copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Draginda, Yu. A., E-mail: lbf@ns.crys.ras.ru; Yudin, S. G.; Lazarev, V. V.; Yablonskii, S. V.; Palto, S. P. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2012-05-15

    The potential of the vacuum method for preparing ferroelectric films and photonic heterostructures from organic materials is studied. Vacuum-evaporated films of fluoropolymers and heterostructures on their basis are obtained and their ferroelectric and spectral properties are studied. In particular, homogeneous films of the well-known piezoelectric polymer polyvinylidene fluoride and ferroelectric material vinylidene fluoride/trifluoroethylene copolymer (P(VDF/TFE)) are produced. Experimental studies of vacuum-evaporated P(VDF/TFE) films confirmed their ferroelectric properties. The heterostructures composed of alternating layers of P(VDF/TFE) copolymer molecules and azodye molecules are fabricated by vacuum evaporation. Owing to the controlled layer thickness and a significant difference in the refractive indices of the P(VDF/TFE) copolymer and azodyes, these heterostructures exhibit properties of photonic crystals. This finding is confirmed by the occurrence of a photonic band in the absorption spectra of the heterostructures.

  8. Acceleration of magnetized plasma rings

    International Nuclear Information System (INIS)

    Hartman, D.; Eddleman, J.; Hammer, J.H.

    1982-01-01

    One scheme is considered, acceleration of a ring between coaxial electrodes by a B/sub theta/ field as in a coaxial rail-gun. If the electrodes are conical, a ring accelerated towards the apex of the cone undergoes self-similar compression (focussing) during acceleration. Because the allowable acceleration force F/sub a/ = kappa U/sub m//R (kappa - 2 , the accelerating distance for conical electrodes is considerably shortened over that required for coaxial electrodes. In either case however, since the accelerating flux can expand as the ring moves, most of the accelerating field energy can be converted into kinetic energy of the ring leading to high efficiency

  9. Saturn's Rings Edge-on

    Science.gov (United States)

    1995-01-01

    In one of nature's most dramatic examples of 'now-you see-them, now-you-don't', NASA's Hubble Space Telescope captured Saturn on May 22, 1995 as the planet's magnificent ring system turned edge-on. This ring-plane crossing occurs approximately every 15 years when the Earth passes through Saturn's ring plane.For comparison, the top picture was taken by Hubble on December 1, 1994 and shows the rings in a more familiar configuration for Earth observers.The bottom picture was taken shortly before the ring plane crossing. The rings do not disappear completely because the edge of the rings reflects sunlight. The dark band across the middle of Saturn is the shadow of the rings cast on the planet (the Sun is almost 3 degrees above the ring plane.) The bright stripe directly above the ring shadow is caused by sunlight reflected off the rings onto Saturn's atmosphere. Two of Saturn's icy moons are visible as tiny starlike objects in or near the ring plane. They are, from left to right, Tethys (slightly above the ring plane) and Dione.This observation will be used to determine the time of ring-plane crossing and the thickness of the main rings and to search for as yet undiscovered satellites. Knowledge of the exact time of ring-plane crossing will lead to an improved determination of the rate at which Saturn 'wobbles' about its axis (polar precession).Both pictures were taken with Hubble's Wide Field Planetary Camera 2. The top image was taken in visible light. Saturn's disk appears different in the bottom image because a narrowband filter (which only lets through light that is not absorbed by methane gas in Saturn's atmosphere) was used to reduce the bright glare of the planet. Though Saturn is approximately 900 million miles away, Hubble can see details as small as 450 miles across.The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.This image and other images and

  10. Integrated Ring Resonators The Compendium

    CERN Document Server

    Rabus, Dominik G

    2007-01-01

    The optical filter, which has emerged in the last few years in integrated optics, is resonator based. Ring-resonator filters do not require facets or gratings for optical feedback and are thus particularly suited for monolithic integration with other components. Ring resonators find applications not only in optical networks, but also as sensors. The required passband shape of ring resonator-filters can be custom designed by the use of configurations of various ring coupled resonators. This book describes the current state-of-the-art on these devices with respect to design, fabrication and application.

  11. ring og refleksion

    DEFF Research Database (Denmark)

    Wahlgren, B.; Rattleff, Pernille; Høyrup, S.

    State of the art inden for forskning om læring på arbejdspladsen samt gennemgang af læringsteori og refleksionsbegrebet hos Dewey, Dreyfus, Schön, Argyris, Kolb, Jarvis, Mezirow og Brookfield. Afsluttes med diskussion af syntetiseret model for læring på arbejdspladsen.......State of the art inden for forskning om læring på arbejdspladsen samt gennemgang af læringsteori og refleksionsbegrebet hos Dewey, Dreyfus, Schön, Argyris, Kolb, Jarvis, Mezirow og Brookfield. Afsluttes med diskussion af syntetiseret model for læring på arbejdspladsen....

  12. High-performance single nanowire tunnel diodes.

    Science.gov (United States)

    Wallentin, Jesper; Persson, Johan M; Wagner, Jakob B; Samuelson, Lars; Deppert, Knut; Borgström, Magnus T

    2010-03-10

    We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27.6 at liquid helium temperature. These sub-100-nm-diameter structures are promising components for solar cells as well as electronic applications.

  13. Coiffured black rings

    Science.gov (United States)

    Bena, Iosif; Ross, Simon F.; Warner, Nicholas P.

    2014-08-01

    We describe a new type of hair on supersymmetric black string and black ring solutions, which produces the largest known violation of black hole uniqueness, parameterized by an arbitrary function and hence an infinite number of continuous parameters. The new solutions can have non-trivial density profiles for the electric fields along the horizon, and yet have a geometry that is regular, although generically not infinitely differentiable, at the horizon. Both neutral and charged probes can cross the horizon without experiencing divergent forces. We also find restricted examples, parameterized by a few arbitrary continuous parameters, where the charge densities fluctuate but the metric does not and hence is completely differentiable. Our new class of solutions owes its existence to a mechanism reminiscent of the Q-ball: in the simplest examples the metric has more symmetry than the matter that supports it.

  14. Ring-constrained Join

    DEFF Research Database (Denmark)

    Yiu, Man Lung; Karras, Panagiotis; Mamoulis, Nikos

    2008-01-01

    We introduce a novel spatial join operator, the ring-constrained join (RCJ). Given two sets P and Q of spatial points, the result of RCJ consists of pairs (p, q) (where p ε P, q ε Q) satisfying an intuitive geometric constraint: the smallest circle enclosing p and q contains no other points in P, Q....... This new operation has important applications in decision support, e.g., placing recycling stations at fair locations between restaurants and residential complexes. Clearly, RCJ is defined based on a geometric constraint but not on distances between points. Thus, our operation is fundamentally different...... from the conventional distance joins and closest pairs problems. We are not aware of efficient processing algorithms for RCJ in the literature. A brute-force solution requires computational cost quadratic to input size and it does not scale well for large datasets. In view of this, we develop efficient...

  15. On separable extensions of group rings and quaternion rings

    Directory of Open Access Journals (Sweden)

    George Szeto

    1978-01-01

    Full Text Available The purposes of the present paper are (1 to give a necessary and sufficient condition for the uniqueness of the separable idempotent for a separable group ring extension RG(R may be a non-commutative ring, and (2 to give a full description of the set of separable idempotents for a quaternion ring extension RQ over a ring R, where Q are the usual quaternions i,j,k and multiplication and addition are defined as quaternion algebras over a field. We shall show that RG has a unique separable idempotent if and only if G is abelian, that there are more than one separable idempotents for a separable quaternion ring RQ, and that RQ is separable if and only if 2 is invertible in R.

  16. Wedding ring shaped excitation coil

    Science.gov (United States)

    MacLennan, Donald A.; Tsai, Peter

    2001-01-01

    A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and/or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency.

  17. Rational construction of multiple interfaces in ternary heterostructure for efficient spatial separation and transfer of photogenerated carriers in the application of photocatalytic hydrogen evolution

    Science.gov (United States)

    Shi, Jian-Wen; Ma, Dandan; Zou, Yajun; Fan, Zhaoyang; Shi, Jinwen; Cheng, Linhao; Ji, Xin; Niu, Chunming

    2018-03-01

    The design of efficient and stable photocatalyst plays a critical role in the photocatalytic hydrogen evolution from water splitting. Herein, we develop a novel ZnS/CdS/ZnO ternary heterostructure by the in-situ sulfuration of CdS/ZnO, which includes four contact interfaces: CdS-ZnS interface, ZnS-ZnO interface, CdS-ZnO interface and ZnS-CdS-ZnO ternary interface, forming three charge carrier-transfer modes (type-I, type-II and direct Z-scheme) through five carrier-transfer pathways. As a result, the separation and transfer of photoexcited electron-hole pairs are promoted significantly, resulting in a high hydrogen evolution rate of 44.70 mmol h-1 g-1, which is 2, 3.7 and 8 times higher than those of binary heterostructures, CdS/ZnO, CdS/ZnS and ZnS/ZnO, respectively, and 26.5, 280 and 298 times higher than those of single CdS, ZnO and ZnS, respectively. As a counterpart ternary heterostructure, CdS/ZnS/ZnO contains only two interfaces: CdS-ZnS interface and ZnS-ZnO interface, which form two charge carrier-transfer modes (type-I and type-II) through two carrier-transfer pathways, leading to its much lower hydrogen evolution rate (27.25 mmol h-1 g-1) than ZnS/CdS/ZnO ternary heterostructure. This work is relevant for understanding the charge-transfer pathways between multi-interfaces in multicomponent heterojunctions.

  18. Mixed multilayered vertical heterostructures utilizing strained monolayer WS2

    Science.gov (United States)

    Sheng, Yuewen; Xu, Wenshuo; Wang, Xiaochen; He, Zhengyu; Rong, Youmin; Warner, Jamie H.

    2016-01-01

    Creating alternating layers of 2D materials forms vertical heterostructures with diverse electronic and opto-electronic properties. Monolayer WS2 grown by chemical vapour deposition can have inherent strain due to interactions with the substrate. The strain modifies the band structure and properties of monolayer WS2 and can be exploited in a wide range of applications. We demonstrate a non-aqueous transfer method for creating vertical stacks of mixed 2D layers containing a strained monolayer of WS2, with Boron Nitride and Graphene. The 2D materials are all grown by CVD, enabling large area vertical heterostructures to be formed. WS2 monolayers grown by CVD directly on Si substrates with SiO2 surface are easily washed off by water and this makes aqueous based transfer methods challenging for creating vertical stacks on the growth substrate. 2D hexagonal Boron Nitride films are used to provide an insulating layer that limits interactions with a top graphene layer and preserve the strong photoluminescence from the WS2. This transfer method is suitable for layer by layer control of 2D material vertical stacks and is shown to be possible for all CVD grown samples, which opens up pathways for the rapid large scale fabrication of vertical heterostructure systems with atomic thickness depth control and large area coverage.Creating alternating layers of 2D materials forms vertical heterostructures with diverse electronic and opto-electronic properties. Monolayer WS2 grown by chemical vapour deposition can have inherent strain due to interactions with the substrate. The strain modifies the band structure and properties of monolayer WS2 and can be exploited in a wide range of applications. We demonstrate a non-aqueous transfer method for creating vertical stacks of mixed 2D layers containing a strained monolayer of WS2, with Boron Nitride and Graphene. The 2D materials are all grown by CVD, enabling large area vertical heterostructures to be formed. WS2 monolayers grown by

  19. DELPHI's Ring Imaging Cherenkov Chamber

    CERN Multimedia

    1989-01-01

    The hundreds of mirrors around this Ring Imaging Cherenkov Chamber reflect cones of light created by fast moving particles to a detector. The velocity of a particle can be measured by the size of the ring produced on the detector. DELPHI, which ran from 1989 to 2000 on the LEP accelerator, was primarily concerned with particle identification.

  20. Caustic rings of dark matter

    OpenAIRE

    Sikivie, Pierre

    1997-01-01

    It is shown that the infall of collisionless dark matter onto isolated galaxies produces a series of caustic rings in the halo dark matter distribution. The properties of these caustics are investigated. The density profile of the caustic is derived for a specific case. Bumps in the rotation curve of NGC 3198 are interpreted as due to caustic rings of dark matter.

  1. Pyrimidine-pyridine ring interconversion

    NARCIS (Netherlands)

    Plas, van der H.C.

    2003-01-01

    This chapter discusses the pyrimidine-to-pyridine ring transformation and pyridine-to-pyrimidine ring transformation. In nucleophile-induced pyrimidine-to-pyridine rearrangements, two types of reactions can be distinguished depending on the structure of the nucleophile: (1) reactions in which the

  2. Schottky barrier tuning of the graphene/SnS2 van der Waals heterostructures through electric field

    Science.gov (United States)

    Zhang, Fang; Li, Wei; Ma, Yaqiang; Dai, Xianqi

    2018-03-01

    Combining the electronic structures of two-dimensional monolayers in ultrathin hybrid nanocomposites is expected to display new properties beyond their single components. The effects of external electric field (Eext) on the electronic structures of monolayer SnS2 with graphene hybrid heterobilayers are studied by using the first-principle calculations. It is demonstrated that the intrinsic electronic properties of SnS2 and graphene are quite well preserved due to the weak van der Waals (vdW) interactions. We find that the n-type Schottky contacts with the significantly small Schottky barrier are formed at the graphene/SnS2 interface. In the graphene/SnS2 heterostructure, the vertical Eext can control not only the Schottky barriers (n-type and p-type) but also contact types (Schottky contact or Ohmic contact) at the interface. The present study would open a new avenue for application of ultrathin graphene/SnS2 heterostructures in future nano- and optoelectronics.

  3. Voltage-controlled ferromagnetism and magnetoresistance in LaCoO3/SrTiO3 heterostructures

    International Nuclear Information System (INIS)

    Hu, Chengqing; Park, Keun Woo; Yu, Edward T.; Posadas, Agham; Demkov, Alexander A.; Jordan-Sweet, Jean L.

    2013-01-01

    A LaCoO 3 /SrTiO 3 heterostructure grown on Si (001) is shown to provide electrically switchable ferromagnetism, a large, electrically tunable magnetoresistance, and a vehicle for achieving and probing electrical control over ferromagnetic behavior at submicron dimensions. Fabrication of devices in a field-effect transistor geometry enables application of a gate bias voltage that modulates strain in the heterostructure via the converse piezoelectric effect in SrTiO 3 , leading to an artificial inverse magnetoelectric effect arising from the dependence of ferromagnetism in the LaCoO 3 layer on strain. Below the Curie temperature of the LaCoO 3 layer, this effect leads to modulation of resistance in LaCoO 3 as large as 100%, and magnetoresistance as high as 80%, both of which arise from carrier scattering at ferromagnetic-nonmagnetic interfaces in LaCoO 3 . Finite-element numerical modeling of electric field distributions is used to explain the dependence of carrier transport behavior on gate contact geometry, and a Valet-Fert transport model enables determination of spin polarization in the LaCoO 3 layer. Piezoresponse force microscopy is used to confirm the existence of piezoelectric response in SrTiO 3 grown on Si (001). It is also shown that this structure offers the possibility of achieving exclusive-NOR logic functionality within a single device

  4. Voltage-controlled ferromagnetism and magnetoresistance in LaCoO{sub 3}/SrTiO{sub 3} heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Chengqing; Park, Keun Woo; Yu, Edward T. [Microelectronics Research Center, The University of Texas at Austin, 10100 Burnet Rd., Austin, Texas 78758 (United States); Posadas, Agham; Demkov, Alexander A. [Department of Physics, The University of Texas at Austin, 1 University Station C1600, Austin, Texas 78712 (United States); Jordan-Sweet, Jean L. [IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (United States)

    2013-11-14

    A LaCoO{sub 3}/SrTiO{sub 3} heterostructure grown on Si (001) is shown to provide electrically switchable ferromagnetism, a large, electrically tunable magnetoresistance, and a vehicle for achieving and probing electrical control over ferromagnetic behavior at submicron dimensions. Fabrication of devices in a field-effect transistor geometry enables application of a gate bias voltage that modulates strain in the heterostructure via the converse piezoelectric effect in SrTiO{sub 3}, leading to an artificial inverse magnetoelectric effect arising from the dependence of ferromagnetism in the LaCoO{sub 3} layer on strain. Below the Curie temperature of the LaCoO{sub 3} layer, this effect leads to modulation of resistance in LaCoO{sub 3} as large as 100%, and magnetoresistance as high as 80%, both of which arise from carrier scattering at ferromagnetic-nonmagnetic interfaces in LaCoO{sub 3}. Finite-element numerical modeling of electric field distributions is used to explain the dependence of carrier transport behavior on gate contact geometry, and a Valet-Fert transport model enables determination of spin polarization in the LaCoO{sub 3} layer. Piezoresponse force microscopy is used to confirm the existence of piezoelectric response in SrTiO{sub 3} grown on Si (001). It is also shown that this structure offers the possibility of achieving exclusive-NOR logic functionality within a single device.

  5. Binomial Rings: Axiomatisation, Transfer and Classification

    OpenAIRE

    Xantcha, Qimh Richey

    2011-01-01

    Hall's binomial rings, rings with binomial coefficients, are given an axiomatisation and proved identical to the numerical rings studied by Ekedahl. The Binomial Transfer Principle is established, enabling combinatorial proofs of algebraical identities. The finitely generated binomial rings are completely classified. An application to modules over binomial rings is given.

  6. Burnside Rings of Fusion Systems

    DEFF Research Database (Denmark)

    Reeh, Sune Precht

    In this thesis we study the interactions between saturated fusion systems and group actions of the underlying p-groups. For a saturated fusion system F on a finite p-group S we construct the Burnside ring of F in terms of the finite S-sets whose actions respect the structure of the fusion system...... of Burnside rings given by multiplication with the characteristic idempotent, and we show that this map is the transfer map previously constructed. Applying these results, we show that for every saturated fusion system the ring generated by all (non-idempotent) characteristic elements in the p-local double...... Burnside ring is isomorphic to the p-local Burnside ring of the fusion system, and we disprove a conjecture by Park-Ragnarsson-Stancu on the composition product of fusion systems....

  7. Ionization cooling ring for muons

    Directory of Open Access Journals (Sweden)

    R. Palmer

    2005-06-01

    Full Text Available Practical ionization cooling rings could lead to lower cost or improved performance in neutrino factory or muon collider designs. The ring modeled here uses realistic three-dimensional fields. The performance of the ring compares favorably with the linear cooling channel used in the second U.S. Neutrino Factory Study. The normalized 6D emittance of an ideal ring is decreased by a factor of approximately 240, compared with a factor of only 15 for the linear channel. We also examine such real-world effects as windows on the absorbers and rf cavities and leaving empty lattice cells for injection and extraction. For realistic conditions the ring decreases the normalized 6D emittance by a factor of 49.

  8. Spin-polarized photoemission from SiGe heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, A.; Bottegoni, F.; Isella, G.; Cecchi, S.; Chrastina, D.; Finazzi, M.; Ciccacci, F. [LNESS-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2013-12-04

    We apply the principles of Optical Orientation to measure by Mott polarimetry the spin polarization of electrons photoemitted from different group-IV heterostructures. The maximum measured spin polarization, obtained from a Ge/Si{sub 0.31}Ge{sub 0.69} strained film, undoubtedly exceeds the maximum value of 50% attainable in bulk structures. The explanation we give for this result lies in the enhanced band orbital mixing between light hole and split-off valence bands as a consequence of the compressive strain experienced by the thin Ge layer.

  9. Npn double heterostructure bipolar transistor with ingaasn base region

    Science.gov (United States)

    Chang, Ping-Chih; Baca, Albert G.; Li, Nein-Yi; Hou, Hong Q.; Ashby, Carol I. H.

    2004-07-20

    An NPN double heterostructure bipolar transistor (DHBT) is disclosed with a base region comprising a layer of p-type-doped indium gallium arsenide nitride (InGaAsN) sandwiched between n-type-doped collector and emitter regions. The use of InGaAsN for the base region lowers the transistor turn-on voltage, V.sub.on, thereby reducing power dissipation within the device. The NPN transistor, which has applications for forming low-power electronic circuitry, is formed on a gallium arsenide (GaAs) substrate and can be fabricated at commercial GaAs foundries. Methods for fabricating the NPN transistor are also disclosed.

  10. Upper critical field of Mo-Ni heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Uher, C.; Watson, W.J.; Cohn, J.L.; Schuller, I.K.

    1985-12-01

    Upper critical field and its anisotropy have been measured on two very short wavelength Mo-Ni heterostructures of different degrees of perfection, lambda = 13.8A (disordered structure) and lambda = 16.6A (layered structure). In both cases the parallel critical field has an unexpected temperature dependence, a large and temperature dependent anisotropy, and over 60% enhancement over the Clogston-Chandrasekhar limit. Data are fit to the Werthamer-Helfand-Hohenberg theory and the spin-orbit scattering times are found to be 1.79 x 10 T s and 2 x 10 T s, respectively.

  11. Upper critical field of Mo-Ni heterostructures

    International Nuclear Information System (INIS)

    Uher, C.; Watson, W.J.; Cohn, J.L.; Schuller, I.K.

    1985-12-01

    Upper critical field and its anisotropy have been measured on two very short wavelength Mo-Ni heterostructures of different degrees of perfection, lambda = 13.8A (disordered structure) and lambda = 16.6A (layered structure). In both cases the parallel critical field has an unexpected temperature dependence, a large and temperature dependent anisotropy, and over 60% enhancement over the Clogston-Chandrasekhar limit. Data are fit to the Werthamer-Helfand-Hohenberg theory and the spin-orbit scattering times are found to be 1.79 x 10 -13 s and 2 x 10 -13 s, respectively

  12. Magnetized jet creation using a hollow ring of laser beams

    Science.gov (United States)

    Lu, Yingchao; Liang, Edison; Han, Lily; Gao, Lan; Ji, Hantao; Li, Chi Kiang; Petrasso, Richard; Froula, Dustin; Follett, Russ; Tzeferacos, Petros; Lamb, Don

    2016-10-01

    We report results of magnetized jet creation experiment using the Omega laser. Using 20 Omega beams to irradiate a flat plastic target in a hollow ring pattern, we demonstrated that the on-axis electron and ion density, temperature and velocity are higher than when all beams are focused onto a single spot. The jet created by the hollow ring laser is also more collimated. Proton radiography was used to probe the magnetic field in the jet. Proton images show ordered quasi-linear filaments whose divergence decreases with increasing ring radius. Proton density contrasts are consistent with filamentary field bundles with peak values in the tens of Teslas. These results demonstrate that magnetized jets created by a hollow ring of laser beams can become a versatile new platform for laboratory astrophysics.

  13. Silicon Self-Diffusion in Isotope Heterostructures

    International Nuclear Information System (INIS)

    Bracht, H.; Haller, E.E.; Clark-Phelps, R.

    1998-01-01

    Self-diffusion of silicon is measured between 855 and 1388thinsp degree C in highly isotopically enriched 28 Si layers. The profiles of 29 Si and 30 Si are determined by secondary ion mass spectrometry. Temperature dependence of the self-diffusion coefficients is accurately described over seven orders of magnitude with one diffusion enthalpy of 4.75thinspthinspeV. This single enthalpy indicates that self-interstitials dominate self-diffusion. The high accuracy of our data enables us to estimate an upper bound for the vacancy-assisted diffusion enthalpy of 4.14thinspthinspeV, which agrees with recent theoretical calculations. copyright 1998 The American Physical Society

  14. Physical and Thermal Comfort Properties of Viscose Fabrics made from Vortex and Ring Spun Yarns

    Science.gov (United States)

    Thilagavathi, G.; Muthukumar, N.; Kumar, V. Kiran; Sadasivam, Sanjay; Sidharth, P. Mithun; Nikhil Jain, G.

    2017-06-01

    Viscose fiber is frequently preferred for various types of inner and outer knitwear products for its comfort and visual characteristics. In this study, the physical and thermal comfort properties of viscose fabrics made from ring and vortex yarns have been studied to explore the impact of spinning process on fabric properties. 100% viscose fibers were spun into yarns by ring and vortex spinning and the developed yarns were converted to single jersey fabrics. The results indicated that fabrics made from vortex spun yarns had better pilling resistance over that of those from ring spun yarns. There was no significant difference between bursting strength values of vortex and ring spun yarn fabrics. Fabrics made from ring yarn had better dimensional stability compared to fabrics made from vortex yarn. The air permeability and water vapour permeability of vortex yarn fabrics were higher than ring spun yarn fabrics. The vortex yarn fabrics had better thermal comfort properties compared to ring yarn fabrics.

  15. Overcurvature describes the buckling and folding of rings from curved origami to foldable tents

    Science.gov (United States)

    Mouthuy, Pierre-Olivier; Coulombier, Michael; Pardoen, Thomas; Raskin, Jean-Pierre; Jonas, Alain M.

    2012-12-01

    Daily-life foldable items, such as popup tents, the curved origami sculptures exhibited in the Museum of Modern Art of New York, overstrained bicycle wheels, released bilayered microrings and strained cyclic macromolecules, are made of rings buckled or folded in tridimensional saddle shapes. Surprisingly, despite their popularity and their technological and artistic importance, the design of such rings remains essentially empirical. Here we study experimentally the tridimensional buckling of rings on folded paper rings, lithographically processed foldable microrings, human-size wood sculptures or closed arcs of Slinky springs. The general shape adopted by these rings can be described by a single continuous parameter, the overcurvature. An analytical model based on the minimization of the energy of overcurved rings reproduces quantitatively their shape and buckling behaviour. The model also provides guidelines on how to efficiently fold rings for the design of space-saving objects.

  16. Magnetotransport Properties of Epitaxial Ge/AlAs Heterostructures Integrated on GaAs and Silicon.

    Science.gov (United States)

    Hudait, Mantu K; Clavel, Michael; Goley, Patrick S; Xie, Yuantao; Heremans, Jean J

    2015-10-14

    The magnetotransport properties of epitaxial Ge/AlAs heterostructures with different growth conditions and substrate architectures have been studied under ±9 T magnetic field and at 390 mK temperature. Systematic mobility measurements of germanium (Ge) epilayers grown on GaAs substrates at growth temperatures from 350 to 450 °C allow us to extract a precise growth window for device-quality Ge, corroborated by structural and morphological properties. Our results on Si substrate using a composite metamorphic AlAs/GaAs buffer at 400 °C Ge growth temperature, show that the Ge/AlAs system can be tailored to have a single carrier transport while keeping the charge solely in the Ge layer. Single carrier transport confined to the Ge layer is demonstrated by the weak-localization quantum correction to the conductivity observed at low magnetic fields and 390 mK temperature. The weak localization effect points to a near-absence of spin-orbit interaction for carriers in the electronically active layer and is used here for the first time to pinpoint Ge as this active layer. Thus, the epitaxial Ge grown on Si using AlAs/GaAs buffer architecture is a promising candidate for next-generation energy-efficient fin field-effect transistor applications.

  17. Evaluation of ring impedance of the Photon Factory storage ring

    International Nuclear Information System (INIS)

    Kiuchi, T.; Izawa, M.; Tokumoto, S.; Hori, Y.; Sakanaka, S.; Kobayashi, M.; Kobayakawa, H.

    1992-05-01

    The loss parameters of the ducts in the Photon Factory (PF) storage ring were evaluated using the wire method and the code TBCI. Both the measurement and the calculation were done for a different bunch length (σ) ranging from 23 to 80 ps. The PF ring impedance was estimated to be |Z/n|=3.2 Ω using the broadband impedance model. The major contribution to the impedance comes from the bellows and the gate valve sections. Improvements of these components will lower the ring impedance by half. (author)

  18. Design studies for the electron storage ring EUTERPE

    International Nuclear Information System (INIS)

    Xi Boling.

    1995-01-01

    The 400 MeV electron storage ring EUTERPE is under construction at Eindhoven University of Technology. The ring is to be used as an experimental tool for accelerator physics studies and synchroton radiation applications. The main task of the current research work is the electron optical design of the ring. Lattice design is a basis for machine design as a whole. Design aspects regarding the basic lattice, based on single particle dynamics, include determination of the equilibrium beam size and bunch length, design of achromatic bending sections, selection of tune values, correction of chromaticity, and minimization of the natural emittance in the ring. The basic lattice designed for the EUTERPE ring has a high flexibility so that different electron optical modes can be realized easily. In low energy storage rings with a high beam current, collective effects can cause a significant change in the bunch length, the transverse emittance and the beam lifetime. In order to ensure a good optical performance for the ring, the choice of suitable parameters concerning the vacuum and RF system are essential as far as collective effects are concerned. An estimation of the collective effects in the ring is given. The injector for EUTERPE is a 75 MeV racetrack microtron which is injected from a 10 MeV linac. In order to get sufficient beam current in the ring, a special procedure of continuous injection with an adjustable locally shifted closed orbit has been presented. Details of the injection procedure and numerical simulations are given. (orig./HSI)

  19. Design studies for the electron storage ring EUTERPE

    Energy Technology Data Exchange (ETDEWEB)

    Xi Boling

    1995-05-18

    The 400 MeV electron storage ring EUTERPE is under construction at Eindhoven University of Technology. The ring is to be used as an experimental tool for accelerator physics studies and synchroton radiation applications. The main task of the current research work is the electron optical design of the ring. Lattice design is a basis for machine design as a whole. Design aspects regarding the basic lattice, based on single particle dynamics, include determination of the equilibrium beam size and bunch length, design of achromatic bending sections, selection of tune values, correction of chromaticity, and minimization of the natural emittance in the ring. The basic lattice designed for the EUTERPE ring has a high flexibility so that different electron optical modes can be realized easily. In low energy storage rings with a high beam current, collective effects can cause a significant change in the bunch length, the transverse emittance and the beam lifetime. In order to ensure a good optical performance for the ring, the choice of suitable parameters concerning the vacuum and RF system are essential as far as collective effects are concerned. An estimation of the collective effects in the ring is given. The injector for EUTERPE is a 75 MeV racetrack microtron which is injected from a 10 MeV linac. In order to get sufficient beam current in the ring, a special procedure of continuous injection with an adjustable locally shifted closed orbit has been presented. Details of the injection procedure and numerical simulations are given. (orig./HSI).

  20. Silicon dual-ring modulator driven by differential signal.

    Science.gov (United States)

    Yu, Hui; Pantouvaki, Marianna; Verheyen, Peter; Lepage, Guy; Absil, Philippe; Bogaerts, Wim; Van Campenhout, Joris

    2014-11-15

    A silicon dual-ring modulator consisting of two serially cascaded rings with embedded PN junctions is driven by a differential signal pair. We show by simulation and experiment that the device has advantages over the single-ring modulator in terms of optical bandwidth, 3-dB modulation bandwidth and bit rate, at the expense of a 1.7-dB increase in the transmission penalty and a twofold increase of the RF power consumption. Driven by differential pseudo random binary sequence (PRBS) signals of 0.5-V peak-to-peak voltage (Vpp), the dual-ring modulator exhibits optical bandwidths of 66 pm and 40 pm at 12.5  Gb/s and 20  Gb/s, respectively. In contrast, the single-ring modulator has an optical bandwidth of 26 pm under a single-end PRBS signal of 0.5  Vpp at 12.5  Gb/s, and its eye diagram closes if the bit rate rises to 20  Gb/s.

  1. Decay ring status / studies

    CERN Document Server

    Chance, A

    2008-01-01

    The aim of "beta-beams" is to produce highly energetic pure electron neutrino and anti-neutrino beams coming from β-decay of radioactive ions. In CERN baseline, after accelerating, the ions 6He2+ and 18Ne10+ are stored in a racetrack-shaped-decay ring until they are lost [1]. Consequently, the injection compensates the losses which occurred between two cycles. Two main loss sources were identified: the β decay and the injection scheme. After giving the optics, we will see how to protect the magnetic elements from the decay products. The injections scheme will be then detailed with its implications. We will see that the injection process makes a collimation section in energy necessary. Since the magnetic elements are not perfect, we will take into account the magnet misalignment and the multipole defects in the dipoles. We will talk then about the closed orbit distortion due to misalignment defects and about the long-term transverse stability with the dynamic aperture.

  2. JAERI storage ring JSR

    International Nuclear Information System (INIS)

    Yokomizo, H.; Harada, S.; Yanagida, K.; Yokoyama, M.; Nagai, T.; Suzuki, Y.; Mashiko, K.; Ishizaki, N.; Tayama, H.

    1990-01-01

    A design study for a next generation 8 GeV synchrotron radiation facility is in progress in Japan, and the Japan Atomic Energy Research Institute (JAERI) and Institute of Physical and Chemical Research (RIKEN) have join forces in this project. A compact electron storage ring JSR has been under construction in the linac building in the Tokai Research Establishment of JAERI to serve for studies of various kind of accelerator technologies, examination of insertion devices and beam monitors, and training of young researchers. This paper describes the lattice design, injection system, magnets, vacuum system, RF system, control system and beam monitors and presents some operation results regarding the electron beam injection and storage. The JSR is presently in good condition concerning it's fundamental functions such as injection, storage at around 150 MeV and 300 MeV, and acceleration from 150 MeV and 300 MeV. Photon induced gas desorption is still large because the vacuum chamber has not been aged heavily by synchrotron radiation. (N.K.)

  3. Is the bell ringing?

    CERN Multimedia

    Francesco Poppi

    2010-01-01

    During the Nobel prize-winning UA1 experiment, scientists in the control room used to ring a bell if a particularly interesting event had occurred. Today, the “CMS Exotica hotline” routine produces a daily report that lists the exotic events that were recorded the day before.   Display of an event selected by the Exotica routine. Take just a very small fraction of the available data (max. 5%); define the events that you want to keep and set the parameters accordingly; run the Exotica routine and only look at the very few images that the system has selected for you. This is the recipe that a small team of CMS researchers has developed to identify the signals coming from possible new physics processes. “This approach does not replace the accurate data analysis on the whole set of data. However, it is a very fast and effective way to focus on just a few events that are potentially very interesting”, explains Maurizio Pierini (CERN), who developed the...

  4. Particle properties and processes in Uranus' rings

    Science.gov (United States)

    Esposito, L. W.; Brahic, A.; Burns, J. A.; Marouf, Essam A.

    1991-01-01

    The particle properties and processes in the Uranian rings are analyzed from Voyager observations and ground-based data. Occultation observations of the epsilon ring are interpreted to yield an effective size of the ring particles that exceeds 70 cm, a surface mass density that exceeds 80 g/sq cm, and a ring vertical thickness greater than tens of meters for solid ice particles. The particles forming the classic rings are dark and gray, with albedo of 0.014 +/-0.004. It is argued that the small amount of dust that exists in the classical rings and between the rings in bands is created by erosion of ring particles and unseen satellites resulting from collisions and micrometeoroid bombardment. As proposed for regions of the other known ring systems, new ring material can be continually created by the destruction of small moons near the rings, which may explain the youthful appearance of the Uranian rings.

  5. Ion Rings for Magnetic Fusion

    Energy Technology Data Exchange (ETDEWEB)

    Greenly, John, B.

    2005-07-31

    This Final Technical Report presents the results of the program, Ion Rings for Magnetic Fusion, which was carried out under Department of Energy funding during the period August, 1993 to January, 2005. The central objective of the program was to study the properties of field-reversed configurations formed by ion rings. In order to reach this objective, our experimental program, called the Field-reversed Ion Ring Experiment, FIREX, undertook to develop an efficient, economical technology for the production of field-reversed ion rings. A field-reversed configuration (FRC) in which the azimuthal (field-reversing) current is carried by ions with gyro-radius comparable to the magnetic separatrix radius is called a field-reversed ion ring. A background plasma is required for charge neutralization of the ring, and this plasma will be confined within the ring's closed magnetic flux. Ion rings have long been of interest as the basis of compact magnetic fusion reactors, as the basis for a high-power accelerator for an inertial fusion driver, and for other applications of high power ion beams or plasmas of high energy density. Specifically, the FIREX program was intended to address the longstanding question of the contribution of large-orbit ions to the observed stability of experimental FRCs to the MHD tilt mode. Typical experimental FRCs with s {approx} 2-4, where s is the ratio of separatrix radius to ion gyro-radius, have been stable to tilting, but desired values for a fusion reactor, s > 20, should be unstable. The FIREX ring would consist of a plasma with large s for the background ions, but with s {approx} 1 for the ring ions. By varying the proportions of these two populations, the minimum proportion of large-orbit ions necessary for stability could be determined. The incorporation of large-orbit ions, perhaps by neutral-beam injection, into an FRC has been advanced for the purpose of stabilizing, heating, controlling angular momentum, and aiding the formation

  6. Optical resonant tunneling in photonic heterostructures containing a tunable dielectric layer

    Science.gov (United States)

    Cui, Liyong; Lu, Guang; Zhang, Shan; Liu, Fen; Xin, Yanqing; Wang, Kunlun; Yang, Tianlin; Wang, Li; Du, Guiqiang

    2017-10-01

    We demonstrate theoretically and experimentally that complete light transmission can be realized using a photonic heterostructure containing a tunable dielectric layer inserted between two different truncated photonic crystals (PCs). A perfect tunneling state is produced within enlarged photonic band gap (PBG) of the heterostructure by varying the thickness of inserted dielectric layer and the transmittance of the tunneling state depends on the dielectric layer thickness. Additionally, the tunneling state frequency varies with inserted layer thickness but is always located within the small overlapped PBG of two PCs. Therefore, both a perfect tunneling state and an ultrawide PBG can be realized in these heterostructures. The experimental results showed good agreement with theoretical values.

  7. Resistance switching of the interfacial conductance in amorphous SrTiO3 heterostructures

    DEFF Research Database (Denmark)

    Christensen, Dennis; Trier, Felix; Chen, Yunzhong

    Complex oxides have attracted a lot of interest recently as this class of material exhibits a plethora of remarkable properties. In particular, a great variety of properties is observed in the heterostructure composed of lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3). For instance...... by an electric field. It has previously been demonstrated that SrTiO3 heterostructures with amorphous LaAlO3 top layers can display interfacial conductivity with similar critical thickness dependence. Here, we report resistance switching of the interfacial conductance for SrTiO3 heterostructures with amorphous...

  8. Interlayer coupling effects on Schottky barrier in the arsenene-graphene van der Waals heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Congxin, E-mail: xiacongxin@htu.edu.cn; Xue, Bin; Wang, Tianxing; Peng, Yuting [Department of Physic, Henan Normal University, Xinxiang 453007 (China); Jia, Yu [School of Physics and Engineering, Zhengzhou University, Zhengzhou 450052 (China)

    2015-11-09

    The electronic characteristics of arsenene-graphene van der Waals (vdW) heterostructures are studied by using first-principles methods. The results show that a linear Dirac-like dispersion relation around the Fermi level can be quite well preserved in the vdW heterostructures. Moreover, the p-type Schottky barrier (0.18 eV) to n-type Schottky barrier (0.31 eV) transition occurs when the interlayer distance increases from 2.8 to 4.5 Å, which indicates that the Schottky barrier can be tuned effectively by the interlayer distance in the vdW heterostructures.

  9. Heterostructures manufactured by annealing of InSe monocrystals in sulfur vapor

    Directory of Open Access Journals (Sweden)

    Kovalyuk Z. D.

    2009-02-01

    Full Text Available InS/InSe heterostructures were created by a long-term (during 120 h thermal processing of InSe monocrystals in sulfur vapor. Investigations of electrical and photoelectric properties of structures manufactured by this method showed essential advantage of the anysotype heterostructure n-InS/p-InSe in comparison with its isotype analog. A comparison of the spectral properties of n-InS/p-InSe heterostructures obtained at different times of annealing were performed. The quantities of interband transitions and parameters of the unit lattice cell were determined defined for the InS film.

  10. Heterostructured electrode with concentration gradient shell for highly efficient oxygen reduction at low temperature

    OpenAIRE

    Zhou, Wei; Liang, Fengli; Shao, Zongping; Chen, Jiuling; Zhu, Zhonghua

    2011-01-01

    Heterostructures of oxides have been widely investigated in optical, catalytic and electrochemical applications, because the heterostructured interfaces exhibit pronouncedly different transport, charge, and reactivity characteristics compared to the bulk of the oxides. Here we fabricated a three-dimensional (3D) heterostructured electrode with a concentration gradient shell. The concentration gradient shell with the composition of Ba0.5-xSr0.5-yCo0.8Fe0.2O3-? (BSCF-D) was prepared by simply t...

  11. Fabrication and transport studies of graphene-superconductor heterostructures

    Science.gov (United States)

    Hu, Jiuning; Wu, Tailung; Tian, Jifa; Chen, Yong

    2014-03-01

    Recently, graphene based stacked heterostructures, e.g., graphene and boron nitride (BN) multi-layers, have attracted much attention as a system to study novel interaction-driven physics (e.g., excitonic condensation) and perform interesting measurements (eg. Coulomb drag and tunneling). The realm of graphene-superconductor heterostructures remains less unexplored, while such a system offers various interesting prospects (effects of superconductor vortices lattices on over-layering graphene and quantum Hall states, where novel phenomena such as anionic excitations have been predicted). We have used polyvinyl alcohol (PVA) based carrier films and a micro-manipulator to transfer mechanically exfoliated flakes and fabricated graphene/BN/NbSe2 structures to study the transport properties of graphene in close proximity to electrically isolated superconducting NbSe2 films. The NbSe2 film shows the superconducting transition temperature of ~7 K and upper critical field of ~3.5 T after device fabrication. We will present results from magneto-transport in graphene and graphene-NbSe2 Coulomb drag and tunneling measurements.

  12. Polarized neutron reflectivity and scattering studies of magnetic heterostructures

    Science.gov (United States)

    Zabel, H.; Theis-Bröhl, K.

    2003-02-01

    The current interest in the magnetism of ultrathin films and multilayers is driven by their manifold applications in the magneto-and spin-electronic areas, for instance as magnetic field sensors or as information storage devices. In this regard, there is a large interest in exploring spin structures and spin disorder at the interface of magnetic heterostructures, to investigate magnetic domains in thin films and superlattices, and to understand remagnetization processes of various laterally shaped magnetic nanostructures. Traditionally neutron scattering has played a dominant role in the determination of spin structures, phase transitions and magnetic excitations in bulk materials. Today, its potential for the investigation of thin magnetic films has to be redefined. Polarized neutron reflectivity (PNR) at small wavevectors can provide precise information on the magnetic field distribution parallel to the film plane and on layer resolved magnetization vectors. In addition, PNR is not only sensitive to structural interface roughness but also to the magnetic roughness. Furthermore, magnetic hysteresis measurements from polarized small angle Bragg reflections allows us to filter out correlation effects during magnetization reversals of magnetic stripes and islands. An overview is provided on most recent PNR investigations of magnetic heterostructures.

  13. Epitaxial Heterostructures of Lead Selenide Quantum Dots on Hematite Nanowires.

    Science.gov (United States)

    Selinsky, Rachel S; Shin, Sanghun; Lukowski, Mark A; Jin, Song

    2012-06-21

    We present a novel method for synthesizing epitaxial quantum dot-nanowire (QD-NW) heterostructures using the example of colloidal PbSe QDs decorated on furnace-grown hematite (α-Fe2O3) NWs. The direct heterogeneous nucleation of QDs on Fe2O3 NWs relies upon an aggressive surface dehydration of the as-synthesized Fe2O3 NWs at 350 °C under vacuum and subsequent introduction of colloidal reactants resulting in direct growth of PbSe QDs on Fe2O3. The synthesis is tunable: the QD diameter distribution and density of QDs on the NWs increase with increased dehydration time, and QD diameters and size distributions decrease with decreased injection temperature of the colloidal synthesis. Transmission electron microscopy (TEM) structural analysis reveals direct heteroepitaxial heterojunctions where the matching faces can be PbSe (002) and Fe2O3 (003) with their respective [11̅0] crystallographic directions aligned. This can be a general approach for integrating colloidal and furnace synthetic techniques, thus broadening possible material combinations for future high-quality, epitaxial nanoscale heterostructures for solar applications.

  14. Thermionic Energy Conversion Based on Graphene van der Waals Heterostructures

    Science.gov (United States)

    Liang, Shi-Jun; Liu, Bo; Hu, Wei; Zhou, Kun; Ang, L. K.

    2017-04-01

    Seeking for thermoelectric (TE) materials with high figure of merit (or ZT), which can directly converts low-grade wasted heat (400 to 500 K) into electricity, has been a big challenge. Inspired by the concept of multilayer thermionic devices, we propose and design a solid-state thermionic devices (as a power generator or a refrigerator) in using van der Waals (vdW) heterostructure sandwiched between two graphene electrodes, to achieve high energy conversion efficiency in the temperature range of 400 to 500 K. The vdW heterostructure is composed of suitable multiple layers of transition metal dichalcogenides (TMDs), such as MoS2, MoSe2, WS2 and WSe2. From our calculations, WSe2 and MoSe2 are identified as two ideal TMDs (using the reported experimental material’s properties), which can harvest waste heat at 400 K with efficiencies about 7% to 8%. To our best knowledge, this design is the first in combining the advantages of graphene electrodes and TMDs to function as a thermionic-based device.

  15. Supported plasma-made 1D heterostructures: perspectives and applications

    Energy Technology Data Exchange (ETDEWEB)

    Borras, Ana; Macias-Montero, Manuel; Romero-Gomez, Pablo; Gonzalez-Elipe, Agustin R, E-mail: anaisabel.borras@icmse.csic.es [Materials Science Institute of Seville (CSIC-Universidad Sevilla), C/Americo Vespucio 49 41092, Sevilla (Spain)

    2011-05-04

    Plasma-related methods have been widely used in the fabrication of carbon nanotubes and nanofibres (NFs) and semiconducting inorganic nanowires (NWs). A natural progression of the research in the field of 1D nanostructures is the synthesis of multicomponent NWs and NFs. In this paper we review the state of the art of the fabrication by plasma methods of 1D heterostructures including applications and perspectives. Furthermore, recent developments on the use of metal seeds (Ag, Au, Pt) to obtain metal-oxide nanostructures are also extensively described. Results are shown for various metal substrates, either metal foils or supported nanoparticles/thin films of the metal where the effects of the size, surface coverage, percolation degree and thickness of the metal seeds have been systematically evaluated. The possibilities of the process are illustrated by the preparation of nanostructured films and supported NFs of different metal-oxides (Ag, Au and SiO{sub 2}, TiO{sub 2}, ZnO). Particularly, in the case of silver, the application of an oxygen plasma treatment prior to the deposition of the oxide was critical for efficiently controlling the growth of the 1D heterostructures. A phenomenological model is proposed to account for the thin-film nanostructuring and fibre formation by considering basic phenomena such as stress relaxation, inhomogeneities in the plasma sheath electrical field and the local disturbance of the oxide growth.

  16. Polarized neutron reflectivity and scattering studies of magnetic heterostructures

    International Nuclear Information System (INIS)

    Zabel, H; Theis-Broehl, K

    2003-01-01

    The current interest in the magnetism of ultrathin films and multilayers is driven by their manifold applications in the magneto-and spin-electronic areas, for instance as magnetic field sensors or as information storage devices. In this regard, there is a large interest in exploring spin structures and spin disorder at the interface of magnetic heterostructures, to investigate magnetic domains in thin films and superlattices, and to understand remagnetization processes of various laterally shaped magnetic nanostructures. Traditionally neutron scattering has played a dominant role in the determination of spin structures, phase transitions and magnetic excitations in bulk materials. Today, its potential for the investigation of thin magnetic films has to be redefined. Polarized neutron reflectivity (PNR) at small wavevectors can provide precise information on the magnetic field distribution parallel to the film plane and on layer resolved magnetization vectors. In addition, PNR is not only sensitive to structural interface roughness but also to the magnetic roughness. Furthermore, magnetic hysteresis measurements from polarized small angle Bragg reflections allows us to filter out correlation effects during magnetization reversals of magnetic stripes and islands. An overview is provided on most recent PNR investigations of magnetic heterostructures

  17. Magnetotransport in heterostructures of transition metal dichalcogenides and graphene

    Science.gov (United States)

    Völkl, Tobias; Rockinger, Tobias; Drienovsky, Martin; Watanabe, Kenji; Taniguchi, Takashi; Weiss, Dieter; Eroms, Jonathan

    2017-09-01

    We use a van der Waals pickup technique to fabricate different heterostructures containing WSe2(WS2) and graphene. The heterostructures were structured by plasma etching, contacted by one-dimensional edge contacts, and a top gate was deposited. For graphene /WSe2/SiO2 samples we observe mobilities of ˜12 000 cm2V-1s-1 . Magnetic-field-dependent resistance measurements on these samples show a peak in the conductivity at low magnetic fields. This dip is attributed to the weak antilocalization (WAL) effect, stemming from spin-orbit coupling. Samples where graphene is encapsulated between WSe2(WS2) and hexagonal boron nitride show a much higher mobility of up to ˜120 000 cm2V-1s-1 . However, in these samples no WAL peak can be observed. We attribute this to a transition from the diffusive to the quasiballistic regime. At low magnetic fields a resistance peak appears, which we ascribe to a size effect due to boundary scattering. Shubnikov-de Haas oscillations in fully encapsulated samples show all integer filling factors due to complete lifting of the spin and valley degeneracies.

  18. Multiferroic properties of artificially designed Perovskite-Spinel Heterostructures

    Science.gov (United States)

    Dussan, Sandra; Singh, Manoj K.; Katiyar, Ram S.

    2009-03-01

    Multiferroics materials are a class of functional material that combines two or more ordered parameters i.e. ferromagnetic, ferroelectric and ferroelastic. The recent finding of multiferroic composite material with the coexistence of these properties has attracted the attention of various researchers due to its potential applications in highly sensitive sensors and actuators as well as multistate memory devices. We synthesized and characterizatied CoFe2O4-BiFeO3 (CFO-BFO) heterostructure thin films grown on SrTiO3 (111), (100) substrates using Pulsed laser deposition. The XRD patterns of CFO-BFO multilayered films evidenced that all picks correspond to CFO and BFO structure also confirmed by their respective Raman spectra. We observed three peaks at 136, 168, and 215 cm-1 that can be assigned to A1(TO) modes of the BFO pure phase and at 468 and 695 cm-1 correspond to CFO. Room temperature M-H exhibited well-shaped magnetization hysteresis loops, good saturation and high coercivity. Preliminary results evidenced the existence of ferroelectricity and magnetic properties in heterostructure.

  19. Treatment of Unstable Pelvic Ring Injuries.

    Science.gov (United States)

    Kim, Weon-Yoo

    2014-06-01

    Pelvic fractures are classified according to the stability of the pelvic ring. Unlike stable pelvic fractures, which heal without complications, unstable fractures may lead to pelvic ring deformities, which cause severe complications. An orthopedic surgeon must determine the stability of the pelvic ring by radiography and physical examination of the patient in order to ensure early, prompt treatment. This article includes anatomy of the pelvic ring, classification of pelvic ring injuries, its treatment algorithm, and corresponding cases involving unstable pelvic ring injury.

  20. Distributively generated matrix near rings

    International Nuclear Information System (INIS)

    Abbasi, S.J.

    1993-04-01

    It is known that if R is a near ring with identity then (I,+) is abelian if (I + ,+) is abelian and (I,+) is abelian if (I*,+) is abelian [S.J. Abbasi, J.D.P. Meldrum, 1991]. This paper extends these results. We show that if R is a distributively generated near ring with identity then (I,+) is included in Z(R), the center of R, if (I + ,+) is included in Z(M n (R)), the center of matrix near ring M n (R). Furthermore (I,+) is included in Z(R) if (I*,+) is included in Z(M n (R)). (author). 5 refs

  1. Researches on the Piston Ring

    Science.gov (United States)

    Ehihara, Keikiti

    1944-01-01

    In internal combustion engines, steam engines, air compressors, and so forth, the piston ring plays an important role. Especially, the recent development of Diesel engines which require a high compression pressure for their working, makes, nowadays, the packing action of the piston ring far more important than ever. Though a number of papers have been published in regard to researches on the problem of the piston ring, none has yet dealt with an exact measurement of pressure exerted on the cylinder wall at any given point of the ring. The only paper that can be traced on this subject so far is Mr. Nakagawa's report on the determination of the relative distribution of pressure on the cylinder wall, but the measuring method adopted therein appears to need further consideration. No exact idea has yet been obtained as to how the obturation of gas between the piston and cylinder, the frictional resistance of the piston, and the wear of the cylinder wall are affected by the intensity and the distribution of the radial pressure of the piston ring. Consequently, the author has endeavored, by employing an apparatus of his own invention, to get an exact determination of the pressure distribution of the piston ring. By means of a newly devised ring tester, to which piezoelectricity of quartz was applied, the distribution of the radial pressure of many sample rings on the market was accurately determined. Since many famous piston rings show very irregular pressure distribution, the author investigated and achieved a manufacturing process of the piston ring which will exert uniform pressure on the cylinder wall. Temperature effects on the configuration and on the mean spring power have also been studied. Further, the tests were performed to ascertain how the gas tightness of the piston ring may be affected by the number or spring power. The researches as to the frictional resistance between the piston ring and the cylinder wall were carried out, too. The procedure of study, and

  2. SMARANDACHE NON-ASSOCIATIVE RINGS

    OpenAIRE

    Vasantha, Kandasamy

    2002-01-01

    An associative ring is just realized or built using reals or complex; finite or infinite by defining two binary operations on it. But on the contrary when we want to define or study or even introduce a non-associative ring we need two separate algebraic structures say a commutative ring with 1 (or a field) together with a loop or a groupoid or a vector space or a linear algebra. The two non-associative well-known algebras viz. Lie algebras and Jordan algebras are mainly built using a vecto...

  3. Data Mining for New Two- and One-Dimensional Weakly Bonded Solids and Lattice-Commensurate Heterostructures.

    Science.gov (United States)

    Cheon, Gowoon; Duerloo, Karel-Alexander N; Sendek, Austin D; Porter, Chase; Chen, Yuan; Reed, Evan J

    2017-03-08

    Layered materials held together by weak interactions including van der Waals forces, such as graphite, have attracted interest for both technological applications and fundamental physics in their layered form and as an isolated single-layer. Only a few dozen single-layer van der Waals solids have been subject to considerable research focus, although there are likely to be many more that could have superior properties. To identify a broad spectrum of layered materials, we present a novel data mining algorithm that determines the dimensionality of weakly bonded subcomponents based on the atomic positions of bulk, three-dimensional crystal structures. By applying this algorithm to the Materials Project database of over 50,000 inorganic crystals, we identify 1173 two-dimensional layered materials and 487 materials that consist of weakly bonded one-dimensional molecular chains. This is an order of magnitude increase in the number of identified materials with most materials not known as two- or one-dimensional materials. Moreover, we discover 98 weakly bonded heterostructures of two-dimensional and one-dimensional subcomponents that are found within bulk materials, opening new possibilities for much-studied assembly of van der Waals heterostructures. Chemical families of materials, band gaps, and point groups for the materials identified in this work are presented. Point group and piezoelectricity in layered materials are also evaluated in single-layer forms. Three hundred and twenty-five of these materials are expected to have piezoelectric monolayers with a variety of forms of the piezoelectric tensor. This work significantly extends the scope of potential low-dimensional weakly bonded solids to be investigated.

  4. Deceleration of electron rings by ions

    International Nuclear Information System (INIS)

    Schumacher, U.; Hofmann, I.; Merkel, P.; Reiser, M.

    1976-02-01

    The deceleration of intense relativistic electron rings by ions created by impact ionization in the electron rings is calculated analytically and numerically. It turns out that the stopping of rings with initial axial velocities of about β 0 = 0.1 is possible under conditions that easily can be realized experimentally in the Maryland ERA. The stopping length of the electron rings, however, depends sensitively on the initial axial ring velocities β 0 (as β 0 3 ). If the method of ring deceleration by ions is used, the reproducibility of the initial ring parameters (especially that of β 0 ) should be very good to get reliable electron ring loading and acceleration. (orig.) [de

  5. A close look at Saturn's rings with Cassini VIMS

    Science.gov (United States)

    Nicholson, P.D.; Hedman, M.M.; Clark, R.N.; Showalter, M.R.; Cruikshank, D.P.; Cuzzi, J.N.; Filacchione, G.; Capaccioni, F.; Cerroni, P.; Hansen, G.B.; Sicardy, B.; Drossart, P.; Brown, R.H.; Buratti, B.J.; Baines, K.H.; Coradini, A.

    2008-01-01

    Soon after the Cassini-Huygens spacecraft entered orbit about Saturn on 1 July 2004, its Visual and Infrared Mapping Spectrometer obtained two continuous spectral scans across the rings, covering the wavelength range 0.35-5.1 ??m, at a spatial resolution of 15-25 km. The first scan covers the outer C and inner B rings, while the second covers the Cassini Division and the entire A ring. Comparisons of the VIMS radial reflectance profile at 1.08 ??m with similar profiles at a wavelength of 0.45 ??m assembled from Voyager images show very little change in ring structure over the intervening 24 years, with the exception of a few features already known to be noncircular. A model for single-scattering by a classical, many-particle-thick slab of material with normal optical depths derived from the Voyager photopolarimeter stellar occultation is found to provide an excellent fit to the observed VIMS reflectance profiles for the C ring and Cassini Division, and an acceptable fit for the inner B ring. The A ring deviates significantly from such a model, consistent with previous suggestions that this region may be closer to a monolayer. An additional complication here is the azimuthally-variable average optical depth associated with "self-gravity wakes" in this region and the fact that much of the A ring may be a mixture of almost opaque wakes and relatively transparent interwake zones. Consistently with previous studies, we find that the near-infrared spectra of all main ring regions are dominated by water ice, with a typical regolith grain radius of 5-20 ??m, while the steep decrease in visual reflectance shortward of 0.6 ??m is suggestive of an organic contaminant, perhaps tholin-like. Although no materials other than H2O ice have been identified with any certainty in the VIMS spectra of the rings, significant radial variations are seen in the strength of the water-ice absorption bands. Across the boundary between the C and B rings, over a radial range of ???7000 km, the

  6. Interaction of multiple co-axial co-rotating vortex rings

    Science.gov (United States)

    Qin, Suyang; Liu, Hong; Liu, Xiaoyu; Xiang, Yang

    2015-11-01

    Fish and birds gain hydrodynamic force from a wake of discrete or linked vortex chain, which is the existence form of vortex rings in nature. Vortex rings with the same formation time are generated successively with different time interval by a piston-cylinder arrangement, and the velocity fields are measured using DPIV. The motion of multiple interacting vortex rings is first reported in laboratorial experiments. Besides the most attracting leapfrogging phenomenon, two other phenomena, suction and weak influence, are also clearly presented using the method of Lagrangian coherent structures. Due to the induced effect of wake vortex rings, the formation process of the forming vortex rings is different from that of a single isolated vortex ring, indicating that another distinct timescale exists, together with formation number proposed by Gharib (1998 JFM), determining the mechanisms of vortex rings. When the rear vortex ring leapfrogs, the limiting case is that the rear contracting ring is axis-touching. If an axis-touching ring is further squeezed by the wake vortex, the vortex structure will collapse, which can be explained by Kelvin-Benjamin variational principle. According to this principle, it is impossible for two optimal formed vortex rings to leapfrog. Financial support from the State Key Development Program of Basic Research of China (2014CB744802) is gratefully acknowledged.

  7. Minimal Gromov-Witten rings

    International Nuclear Information System (INIS)

    Przyjalkowski, V V

    2008-01-01

    We construct an abstract theory of Gromov-Witten invariants of genus 0 for quantum minimal Fano varieties (a minimal class of varieties which is natural from the quantum cohomological viewpoint). Namely, we consider the minimal Gromov-Witten ring: a commutative algebra whose generators and relations are of the form used in the Gromov-Witten theory of Fano varieties (of unspecified dimension). The Gromov-Witten theory of any quantum minimal variety is a homomorphism from this ring to C. We prove an abstract reconstruction theorem which says that this ring is isomorphic to the free commutative ring generated by 'prime two-pointed invariants'. We also find solutions of the differential equation of type DN for a Fano variety of dimension N in terms of the generating series of one-pointed Gromov-Witten invariants

  8. Autumn study on storage rings

    CERN Multimedia

    1974-01-01

    The first two weeks of October have seen storage ring people from accelerator Laboratories throughout the world at CERN to study the fundamental problems of very high energy protonproton colliding beam machines.

  9. ring i familien

    DEFF Research Database (Denmark)

    Kryger, Niels

    2015-01-01

    Artiklen diskutere de senere års eksplosionsagtig interesse for børns læring i familien, og sætter et kritisk lys på den snævre investeringslogik (læring skal give afkast i form af økonomisk produktivitet), der har ledsaget mange af de programmer, der er sat i gang for at fremme denne ”familielær......Artiklen diskutere de senere års eksplosionsagtig interesse for børns læring i familien, og sætter et kritisk lys på den snævre investeringslogik (læring skal give afkast i form af økonomisk produktivitet), der har ledsaget mange af de programmer, der er sat i gang for at fremme denne...

  10. Ring lasers - a brief history

    Science.gov (United States)

    Klein, Tony

    2017-10-01

    Used these days in inertial navigation, ring lasers are also used in recording the tiniest variations in the Earth's spin, as well in detecting earthquakes and even the drift of continents. How did it all begin?

  11. Prototype moving-ring reactor

    International Nuclear Information System (INIS)

    Smith, A.C. Jr.; Ashworth, C.P.; Abreu, K.E.

    1982-01-01

    We have completed a design of the Prototype Moving-Ring Reactor. The fusion fuel is confined in current-carrying rings of magnetically-field-reversed plasma (Compact Toroids). The plasma rings, formed by a coaxial plasma gun, undergo adiabatic magnetic compression to ignition temperature while they are being injected into the reactor's burner section. The cylindrical burner chamber is divided into three burn stations. Separator coils and a slight axial guide field gradient are used to shuttle the ignited toroids rapidly from one burn station to the next, pausing for 1/3 of the total burn time at each station. D-T- 3 He ice pellets refuel the rings at a rate which maintains constant radiated power

  12. The Composition of Saturn's Rings

    Science.gov (United States)

    Clark, R. N.; Cuzzi, J.; Filacchione, G.; Cruikshank, D. P.; Curchin, J. M.; Hoefen, T. M.; Nicholson, P. D.; Hedman, M.; Brown, R. H.; Buratti, B. J.; Baines, K. H.; Nelson, R. M.

    2008-12-01

    The Cassini spacecraft has obtained a unique collection of data about Saturn's rings, as it has observed the rings from 0 to 180 degrees in phase angle, and on both lit and unlit sides. Identification of trace contaminants, especially organic compounds, requires that spectra of the rings be uncontaminated by light from Saturn. The Cassini Visual and Infrared Mapping Spectrometer (VIMS) has acquired 0.35 to 5.1 micron, high spatial resolution spectroscopic data near the shadow of Saturn on the rings where scattered light is at a minimum. At low phase angles, the ring spectra show classic crystalline-ice spectral features except for a contaminant causing a UV absorption. VIMS spectra at 180-degree phase angle are generally flat, with only a weak positive feature at 2.86 microns in spectra of the F-ring. The general transmission decrease is due to large ring particles completely blocking light. The 2.86-micron feature indicates the presence of fine ice dust, where the ice's index of refraction is near 1.0, and light is not refracted or diffracted. There are no indications of interparticle scattering in the VIMS data at any phase angle. The lack of interparticle scattering indicates that the dense A and B rings must be very thin, approaching a monolayer, but rigorous constraints have yet to be modeled. Previous studies used tholins and amorphous carbon for the contaminant causing the UV absorption, but these models display additional absorptions and spectral structure in the near infrared not seen in VIMS data. Clark et al. (Icarus, v193, p372, 2008) modeled the changing blue peak and UV absorber observed on Phoebe, Iapetus, Hyperion, and Dione with amorphous carbon and nano-sized hematite. Nanohematite has muted spectral features compared to larger grained hematite, due to crystal field effects at the surfaces of small grains. Nanohematite has a strong UV absorber that matches the steep UV slope observed in spectra of Saturn's rings and has no strong IR absorptions

  13. Collector ring project at FAIR

    International Nuclear Information System (INIS)

    Dolinskii, A; Blell, U; Dimopoulou, C; Gorda, O; Leibrock, H; Litvinov, S; Laier, U; Schurig, I; Weinrich, U; Berkaev, D; Koop, I; Starostenko, A; Shatunov, P

    2015-01-01

    The collector ring is a dedicated ring for fast cooling of ions coming from separators at the FAIR project. To accommodate optimal technical solutions, a structure of a magnet lattice was recently reviewed and modified. Consequently, more appropriate technical solutions for the main magnets could be adopted. A general layout and design of the present machine is shown. The demanding extraction schemes have been detailed and open design issues were completed. (paper)

  14. Synlig læring

    DEFF Research Database (Denmark)

    Brandsen, Mads

    2017-01-01

    Introduktionen af John Hatties synlig læring i den danske skoleverden møder stadig meget kritik. Mange lærere og pædagoger oplever synlig læring som en tornado, der vil opsuge og ødelægge deres særlige danske udgave af den kontinentale dannelsestænkning, didaktik og pædagogik. Spørgsmålet er om...

  15. MUON STORAGE RINGS - NEUTRINO FACTORIES

    International Nuclear Information System (INIS)

    PARSA, Z.

    2000-01-01

    The concept of a muon storage ring based Neutrino Source (Neutrino Factory) has sparked considerable interest in the High Energy Physics community. Besides providing a first phase of a muon collider facility, it would generate more intense and well collimated neutrino beams than currently available. The BNL-AGS or some other proton driver would provide an intense proton beam that hits a target, produces pions that decay into muons. The muons must be cooled, accelerated and injected into a storage ring with a long straight section where they decay. The decays occurring in the straight sections of the ring would generate neutrino beams that could be directed to detectors located thousands of kilometers away, allowing studies of neutrino oscillations with precisions not currently accessible. For example, with the neutrino source at BNL, detectors at Soudan, Minnesota (1,715 km), and Gran Sasso, Italy (6,527 km) become very interesting possibilities. The feasibility of constructing and operating such a muon-storage-ring based Neutrino-Factory, including geotechnical questions related to building non-planar storage rings (e.g. at 8degree angle for BNL-Soudan, and 3degree angle for BNL-Gran Sasso) along with the design of the muon capture, cooling, acceleration, and storage ring for such a facility is being explored by the growing Neutrino Factory and Muon Collider Collaboration (NFMCC). The authors present overview of Neutrino Factory concept based on a muon storage ring, its components, physics opportunities, possible upgrade to a full muon collider, latest simulations of front-end, and a new bowtie-muon storage ring design

  16. Resonance capture and Saturn's rings

    International Nuclear Information System (INIS)

    Patterson, C.W.

    1986-05-01

    We have assigned the resonances apparently responsible for the stabilization of the Saturn's shepherd satellites and for the substructure seen in the F-ring and the ringlets in the C-ring. We show that Saturn's narrow ringlets have a substructure determined by three-body resonances with Saturn's ringmoons and the sun. We believe such resonances have important implications to satellite formation. 17 refs., 1 fig., 1 tab

  17. Ring insertions as light sources

    International Nuclear Information System (INIS)

    Green, G.K.

    1975-01-01

    Bending magnets can be inserted in the long straight sections of electron storage rings to produce synchrotron radiation. If the design is carefully proportioned, the bending magnets create only a small perturbation of the properties of the ring. The resulting spectra have favorable optical properties as sources for spectroscopy and diffraction studies. The characteristics of the source are discussed, and the geometrical requirements of the magnets are presented

  18. Commuting Π-regular rings

    Directory of Open Access Journals (Sweden)

    Shervin Sahebi

    2014-05-01

    Full Text Available ‎$R$ is called commuting regular ring (resp‎. ‎semigroupif‎ for each $x,y\\in R$ there exists $a\\in R$‎ such that$xy=yxayx$‎. ‎In this paper‎, ‎we introduce the concept of‎‎commuting $\\pi$-regular rings (resp‎. ‎semigroups and‎‎study various properties of them.

  19. The Circular RFQ Storage Ring

    International Nuclear Information System (INIS)

    Ruggiero, A. G.

    1999-01-01

    This paper presents a novel idea of storage ring for the accumulation of intense beams of light and heavy ions at low energy. The new concept is a natural development of the combined features of conventional storage rings and ion traps, and is basically a linear RFQ bent on itself. The advantages are: smaller beam dimensions, higher beam intensity, and a more compact storage device

  20. Standard Fibre Optic Ring LANs

    Science.gov (United States)

    Beale, N. C. L.

    1985-08-01

    The paper begins with a reminder of the particular need for standards in LANs. We then describe the requirements of High Integrity LANs. Current developments in LAN standards are then outlined. It is argued that the requirements of industrial LANs lead ideally to reconfiguring fibre optic rings, for which there are two major emerging standards. These two (IEEE 802.5 and ANSI FDDI) and the Cambridge Ring are discussed and compared. One implementation - the HILAN is discussed.

  1. Graphene-based tunable terahertz filter with rectangular ring ...

    Indian Academy of Sciences (India)

    In addition, by introducing narrow gaps in the rectangular ring resonators, it shows the single frequency filtering effect. Moreover, the structure also shows high sensitivity fordifferent surrounding mediums. This work provides a novel method for designing all-optical integrated components in optical communication.

  2. Of Rings and Volcanoes

    Science.gov (United States)

    2002-01-01

    Office National d'Etudes et de Recherches Aérospatiales (ONERA) , Laboratoire d'Astrophysique de Grenoble (LAOG) and the DESPA and DASGAL laboratories of the Observatoire de Paris in France, in collaboration with ESO. The CONICA infra-red camera was built, under an ESO contract, by the Max-Planck-Institut für Astronomie (MPIA) (Heidelberg) and the Max-Planck Institut für Extraterrestrische Physik (MPE) (Garching) in Germany, in collaboration with ESO. Saturn - Lord of the rings ESO PR Photo 04a/02 ESO PR Photo 04a/02 [Preview - JPEG: 460 x 400 pix - 54k] [Normal - JPEG: 1034 x 800 pix - 200k] Caption : PR Photo 04a/02 shows the giant planet Saturn, as observed with the VLT NAOS-CONICA Adaptive Optics instrument on December 8, 2001; the distance was 1209 million km. It is a composite of exposures in two near-infrared wavebands (H and K) and displays well the intricate, banded structure of the planetary atmosphere and the rings. Note also the dark spot at the south pole at the bottom of the image. One of the moons, Tethys, is visible as a small point of light below the planet. It was used to guide the telescope and to perform the adaptive optics "refocussing" for this observation. More details in the text. Technical information about this photo is available below. This NAOS/CONICA image of Saturn ( PR Photo 04a/02 ), the second-largest planet in the solar system, was obtained at a time when Saturn was close to summer solstice in the southern hemisphere. At this moment, the tilt of the rings was about as large as it can be, allowing the best possible view of the planet's South Pole. That area was on Saturn's night side in 1982 and could therefore not be photographed during the Voyager encounter. The dark spot close to the South Pole is a remarkable structure that measures approximately 300 km across. It was only recently observed in visible light from the ground with a telescope at the Pic du Midi Observatory in the Pyrenees (France) - this is the first infrared image to

  3. Quantum ring states in magnetic field and delayed half-cycle pulses

    Indian Academy of Sciences (India)

    The present work is dedicated to the time evolution of excitation of a quantum ring in external electric and magnetic fields. Such a ring of mesoscopic dimensions in an external magnetic field is known to exhibit a wide variety of interesting physical phenomena. We have studied the dynamics of the single electron quantum ...

  4. Enhanced UV photoresponse with Au nanoparticles incorporated rGO/Si heterostructure

    Science.gov (United States)

    Chandrakalavathi, T.; Rao Peta, Koteswara; Jeyalakshmi, R.

    2018-02-01

    In this work, we demonstrated Au nanoparticles incorporated reduced graphene oxide (rGO)/Si heterostructure based UV photodetector. The pristine and Au nanoparticles incorporated heterostructure was analyzed and characterized by x-ray photo electron spectroscopy (XPS), Current- Voltage (I-V) characteristics and UV photo detective properties were examined by using UV light emitting diode (LED) with 382 nm wavelengths. The UV photoresponse properties revealed that the Au-rGO/Si heterostructure showed much better photoresponse activity toward UV light than pristine rGO/Si. The experimental results clearly revealed that the photoresponse of Au-rGO/Si heterostructure can be effectively enhanced by 30 times at 382 nm wavelength over pristine rGO/Si. The effect of rGO thickness on performance of UV photodetector was also examined. The improved photoresponse was attributed to localized surface plasmon resonance, in addition high electron transport capability of rGO number of photoexcited electrons collected at interface.

  5. Heterostructures based on two-dimensional layered materials and their potential applications

    KAUST Repository

    Li, Ming-yang

    2015-12-04

    The development of two-dimensional (2D) layered materials is driven by fundamental interest and their potential applications. Atomically thin 2D materials provide a wide range of basic building blocks with unique electrical, optical, and thermal properties which do not exist in their bulk counterparts. The van der Waals interlayer interaction enables the possibility to exfoliate and reassemble different 2D materials into arbitrarily and vertically stacked heterostructures. Recently developed vapor phase growth of 2D materials further paves the way of directly synthesizing vertical and lateral heterojunctions. This review provides insights into the layered 2D heterostructures, with a concise introduction to preparative approaches for 2D materials and heterostructures. These unique 2D heterostructures have abundant implications for many potential applications.

  6. Capacitance-voltage characteristics of ZnO/GaN heterostructures

    International Nuclear Information System (INIS)

    Oh, D.C.; Suzuki, T.; Kim, J.J.; Makino, H.; Hanada, T.; Yao, T.; Ko, H.J.

    2005-01-01

    We have investigated the electrical properties of ZnO/GaN heterostructures by capacitance-voltage (C-V) measurements. ZnO/GaN heterostructures are fabricated on Ga-polar GaN templates by plasma-assisted molecular-beam epitaxy. The ZnO/GaN heterostructures exhibit a plateau region of 6.5 V in the C-V curves measured at 10 kHz and room temperature. Moreover, it is found that a large electron density is accumulated at the interface of ZnO/GaN, where the concentration approaches ∼10 18 cm -3 . The distinct C-V characteristics are ascribed to large conduction-band discontinuity at the ZnO/GaN heterointerface. It is suggested that the ZnO/GaN heterostructure is a very promising material for the application to heterojunction transistors

  7. Graphene encapsulated gold nanoparticle-quantum dot heterostructures and their electrochemical characterization

    Science.gov (United States)

    Li, Yuan; Chopra, Nitin

    2015-07-01

    A simple technique for patterning multilayer graphene shell encapsulated gold nanoparticles (GNPs) on the silicon substrate and their further surface decoration with semiconducting quantum dots (QDs) is reported. This leads to the fabrication of a novel silicon electrode decorated with GNP-QD hybrids or heterostructures. The morphology, structure, and composition of the GNPs and GNP-QD heterostructures were evaluated using microscopic and spectroscopic techniques. The heterostructures decorated silicon electrode was also evaluated for the electronic and electrochemical properties. The results showed that the electrical characteristics of the silicon substrate were significantly improved by decorating with GNPs and quantum dots. Furthermore, GNP-QD heterostructure electrode was observed to show significantly increased electrochemical charge transfer activity.

  8. Optical and electrical properties of colloidal (spherical Au)-(spinel ferrite nanorod) heterostructures.

    Science.gov (United States)

    George, Chandramohan; Genovese, Alessandro; Qiao, Fen; Korobchevskaya, Kseniya; Comin, Alberto; Falqui, Andrea; Marras, Sergio; Roig, Anna; Zhang, Yang; Krahne, Roman; Manna, Liberato

    2011-11-01

    We report here a simple synthetic route to Au-Fe(x)O(y) heterostructures in which spinel ferrite (Fe(x)O(y)) grows as a nanorod on a spherical gold (Au) seed. The large red shift in the plasmon resonance in the heterostructures could be explained by a dielectric effect (although we could not entirely exclude a contribution due to electron transfer from Au to defect states at the Au-Fe(x)O(y) interface), while the magnetic properties of the Au-Fe(x)O(y) heterostructures were basically the same as those of the corresponding nanocrystals after Au leaching. In films of Au-Fe(x)O(y) heterostructures the electrical conductivity appeared to be mediated by the Au domains.

  9. Arsenene-Based Heterostructures: Highly Efficient Bifunctional Materials for Photovoltaics and Photocatalytics.

    Science.gov (United States)

    Niu, Xianghong; Li, Yunhai; Zhou, Qionghua; Shu, Huabing; Wang, Jinlan

    2017-12-13

    Constructing suitable type II heterostructures is a reliable solution for high-efficient photovoltaic and photocatalytic materials. Arsenene, as a rising member of monoelemental two-dimensional materials, shows great potential as a building block of heterostructures because of its suitable band gap, high carrier mobility, and good optical properties. On the basis of accurate band structure calculations by combining the many-body perturbation GW method with an extrapolation technique, we demonstrate that arsenene-based heterostructures paired with molybdenum disulfide, tetracyano-quinodimethane, or tetracyanonaphtho-quinodimethane can form type II band alignments. These arsenene-based heterostructures cannot only satisfy all the requirements as photocatalysts for photocatalytic water splitting but can also show an excellent power conversion efficiency of ∼20% as potential photovoltaics.

  10. Two-Dimensional Semiconductor Optoelectronics Based on van der Waals Heterostructures

    Directory of Open Access Journals (Sweden)

    Jae Yoon Lee

    2016-10-01

    Full Text Available Two-dimensional (2D semiconductors such as transition metal dichalcogenides (TMDCs and black phosphorous have drawn tremendous attention as an emerging optical material due to their unique and remarkable optical properties. In addition, the ability to create the atomically-controlled van der Waals (vdW heterostructures enables realizing novel optoelectronic devices that are distinct from conventional bulk counterparts. In this short review, we first present the atomic and electronic structures of 2D semiconducting TMDCs and their exceptional optical properties, and further discuss the fabrication and distinctive features of vdW heterostructures assembled from different kinds of 2D materials with various physical properties. We then focus on reviewing the recent progress on the fabrication of 2D semiconductor optoelectronic devices based on vdW heterostructures including photodetectors, solar cells, and light-emitting devices. Finally, we highlight the perspectives and challenges of optoelectronics based on 2D semiconductor heterostructures.

  11. Synthesis, fabrication and characterization of Ge/Si axial nanowire heterostructure tunnel FETs

    Energy Technology Data Exchange (ETDEWEB)

    Picraux, Samuel T [Los Alamos National Laboratory; Dayeh, Shadi A [Los Alamos National Laboratory

    2010-01-01

    Axial Ge/Si heterostructure nanowires allow energy band-edge engineering along the axis of the nanowire, which is the charge transport direction, and the realization of asymmetric devices for novel device architectures. This work reports on two advances in the area of heterostructure nanowires and tunnel FETs: (i) the realization of 100% compositionally modulated Si/Ge axial heterostructure nanowires with lengths suitable for device fabrication and (ii) the design and implementation of Schottky barrier tunnel FETs on these nanowires for high-on currents and suppressed ambipolar behavior. Initial prototype devices resulted in a current drive in excess of 100 {micro}A/{micro}m (I/{pi}D) and 10{sup 5} I{sub on}/I{sub off} ratios. These results demonstrate the potential of such asymmetric heterostructures (both in the semiconductor channel and metal-semiconductor barrier heights) for low-power and high performance electronics.

  12. Connecting ring and process to fix heaters in a pressure vessel by means of these rings

    International Nuclear Information System (INIS)

    Bailleul, G.; Caloine, P.; Coville, P.

    1984-01-01

    The invention can applies to the installation of heaters for nuclear reactor pressurizer or to the installation of any kind of reheaters by means of electric resistances when these reheaters have to work under important pressures. The connecting ring is made of a single metallic piece, two coaxial tubes joined each other by a skirt nearly radial; the skirt joins an end of the outer cylindrical tube and an intermediate zone of the inner cylindrical tube. The invention concerns also a heater provided with such a connecting ring, substituted for a part of its metallic envelope, and a process of fastening of these heaters on a pressure vessel. The description given in the frame of a pressurizer applies to the case of a gas reheater or to a reheater for liquid under pressure such as liquid sodium in a tank [fr

  13. Electron density enhancement in a quasi isochronous storage ring

    International Nuclear Information System (INIS)

    Pellegrini, C.; Robin, D.

    1991-01-01

    The six dimensional phase-space density of an electron beam in a storage ring is determined by the emission of synchrotron radiation, and by the transverse and longitudinal focusing forces determining the particle trajectories. In the simplest case of uncoupled horizontal, vertical and longitudinal motion, the phase space volume occupied by the beam can be characterized by the product of its three projections on the single degree of freedom planes, the horizontal, vertical, and longitudinal emittances. To minimize the beam phase space volume the authors can minimize the transverse and longitudinal emittances. In the case of transverse emittances this problem is very important for synchrotron radiation sources, and has been studied by several authors. A method to minimize the longitudinal emittance, and produce electron bunches with a short pulse length, small energy spread and large peak current has been proposed and discussed recently by C. Pellegrini and D. Robin. This method uses a ring in which the revolution period is weakly dependent on the particle energy, Quasi Isochronous Ring (QIR), in other words a ring with a momentum compaction nearly zero. In this paper they will extend the previous analysis of the conditions for stable single particle motion in such a ring, and give simple criteria for the estimate of the energy spread and phase acceptance of a QIR

  14. Large area double p-i-n heterostructure for signal multiplexing and demultiplexing in the visible range

    International Nuclear Information System (INIS)

    Vieira, M.; Louro, P.; Fernandes, M.; Vieira, M.A.; Fantoni, A.; Barata, M.

    2009-01-01

    Results on the use of a double a-SiC:H p-i-n heterostructure for signal multiplexing and demultiplexing applications in the visible range, are presented. Modulated monochromatic beams together (multiplexing mode), or a single polychromatic beam (demultiplexing mode) impinge in the device and are absorbed, accordingly to their wavelength, giving rise to a time and wavelength dependent electrical field modulation. Red, green and blue pulsed input channels are transmitted together, each one with a specific transmission rate. The combined optical signal is analyzed by reading out, under different applied voltages, the generated photocurrent. Results show that in the multiplexing mode the output signal is balanced by the wavelength and transmission rate of each input channel, keeping the memory of the incoming optical carriers. In the demultiplexing mode the photocurrent is controlled by the applied voltage allowing regaining the transmitted information. An electrical model gives insight into the device operation.

  15. High efficiency phototransducers based on a novel vertical epitaxial heterostructure architecture (VEHSA) with thin p/n junctions

    Science.gov (United States)

    York, Mark C. A.; Fafard, Simon

    2017-05-01

    This review outlines a series of developments in the design, modelling and growth of multi-junction laser power converters, including several observations of multi-junction GaAs monolithic vertical epitaxial heterostructure architecture devices with astonishing mono-chromatic optical to electrical conversion efficiencies in the 65-70% range. Experimental data is presented for devices ranging from single up to 20 p/n junctions, generally exhibiting weak dependence on source detuning which serves as evidence for strong photon recycling effects in these devices. Considerations for further design optimizations are discussed in detail, as well as the future direction of this research including the growth of devices with up to 100 subcells.

  16. Interlayer coupling enhancement in graphene/hexagonal boron nitride heterostructures by intercalated defects and vacancies

    OpenAIRE

    Park, Sohee; Park, Changwon; Kim, Gunn

    2014-01-01

    Among two-dimensional atomic crystals, hexagonal boron nitride (hBN) is one of the most remarkable materials to fabricate heterostructures revealing unusual properties. We perform first-principles calculations to determine whether intercalated metal atoms and vacancies can mediate interfacial coupling and influence the structural and electronic properties of the graphene/hBN heterostructure. Metal impurity atoms (Li, K, Cr, Mn, Co, and Cu) as extrinsic defects between the graphene and hBN she...

  17. Quantum Engineering of States in Heterostructure-based Detectors for Enhance Performance

    Science.gov (United States)

    2017-05-26

    each year. This is UIC’s highest teaching award. Elected to the College of Fellows, American Institute of Medical and Biomedical Engineers ...AFRL-AFOSR-VA-TR-2017-0109 Quantum engineering of heterostructure detectors for enhanced performance Michael Stroscio UNIVERSITY OF ILLINOIS Final...SUBTITLE Quantum Engineering of States in Heterostructure-based Detectors for Enhance Performance 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-15-1

  18. Organoclay hybrid materials as precursors of porous ZnO/silica-clay heterostructures for photocatalytic applications

    OpenAIRE

    Akkari, Marwa; Aranda, Pilar; Ben Haj Amara, Abdessalem; Ruiz-Hitzky, Eduardo

    2016-01-01

    In this study, ZnO/SiO2-clay heterostructures were successfully synthesized by a facile two-step process applied to two types of clays: montmorillonite layered silicate and sepiolite microfibrous clay mineral. In the first step, intermediate silica–organoclay hybrid heterostructures were prepared following a colloidal route based on the controlled hydrolysis of tetramethoxysilane in the presence of the starting organoclay. Later on, pre-formed ZnO nanoparticles (NP) dispersed in 2-propanol we...

  19. Coupled-bunch instabilities in the APS ring

    International Nuclear Information System (INIS)

    Emery, L.

    1991-01-01

    A study of coupled bunch instabilities for the APS storage ring is presented. The instabilities are driven by the higher-order modes of the fifteen 352-MHz single-cell RF cavities. These modes are modeled using the 2-D cavity program URMEL. The program ZAP is then used to estimate the growth time of the instabilities for an equally-spaced bunch pattern. The cavity modes most responsible for the instabilities will be singles out for damping. 7 refs., 5 tabs

  20. Heterostructure of Au nanocluster tipping on a ZnS quantum rod: controlled synthesis and novel luminescence.

    Science.gov (United States)

    Tian, Yang; Wang, Ligang; Yu, Shanshan; Zhou, Weiwei

    2015-08-14

    Heterostructures of metal nanoparticles and semiconductors are widely studied for their unique properties. However, few reports are available on the heterostructure of metal nanoclusters and semiconductors. In the present study, a heterostructure, in which gold nanoclusters selectively locate at ZnS quantum rod (QR) tips, was fabricated using a two-step solvothermal route. The composition, intrinsic crystallography, and junction of the prepared heterostructure were thoroughly investigated, and it was observed to exhibit novel luminescent behaviours. By comparison with the individual components of ZnS QRs and gold clusters, the resultant heterostructure shows an enhanced exciton emission and complete depression of defect emission for the ZnS component, and a pronounced red emission for the gold nanocluster component. The mechanism of these properties and the charge transfer between gold nanoclusters and ZnS QRs were also explored. The size and location of gold in the heterostructure were also controlled during synthesis to study their effects on the luminescence.

  1. Rhythmic ring-ring stacking drives the circadian oscillator clockwise.

    Science.gov (United States)

    Chang, Yong-Gang; Tseng, Roger; Kuo, Nai-Wei; LiWang, Andy

    2012-10-16

    The oscillator of the circadian clock of cyanobacteria is composed of three proteins, KaiA, KaiB, and KaiC, which together generate a self-sustained ∼24-h rhythm of phosphorylation of KaiC. The mechanism propelling this oscillator has remained elusive, however. We show that stacking interactions between the CI and CII rings of KaiC drive the transition from the phosphorylation-specific KaiC-KaiA interaction to the dephosphorylation-specific KaiC-KaiB interaction. We have identified the KaiB-binding site, which is on the CI domain. This site is hidden when CI domains are associated as a hexameric ring. However, stacking of the CI and CII rings exposes the KaiB-binding site. Because the clock output protein SasA also binds to CI and competes with KaiB for binding, ring stacking likely regulates clock output. We demonstrate that ADP can expose the KaiB-binding site in the absence of ring stacking, providing an explanation for how it can reset the clock.

  2. Numerical solution of multiband k.p model for tunnelling in type-II heterostructures

    Directory of Open Access Journals (Sweden)

    A.E. Botha

    2010-01-01

    Full Text Available A new and very general method was developed for calculating the charge and spin-resolved electron tunnelling in type-II heterojunctions. Starting from a multiband k.p description of the bulk energy-band structure, a multiband k.p Riccati equation was derived. The reflection and transmission coefficients were obtained for each channel by integrating the Riccati equation over the entire heterostructure. Numerical instability was reduced through this method, in which the multichannel log-derivative of the envelope function matrix, rather than the envelope function itself, was propagated. As an example, a six-band k.p Hamiltonian was used to calculate the current-voltage characteristics of a 10-nm wide InAs/ GaSb/InAs single quantum well device which exhibited negative differential resistance at room temperature. The calculated current as a function of applied (bias voltage was found to be in semiquantitative agreement with the experiment, a result which indicated that inelastic transport mechanisms do not contribute significantly to the valley currents measured in this particular device.

  3. Tunable quasiparticle band gap in few-layer GaSe/graphene van der Waals heterostructures

    Science.gov (United States)

    Ben Aziza, Zeineb; Pierucci, Debora; Henck, Hugo; Silly, Mathieu G.; David, Christophe; Yoon, Mina; Sirotti, Fausto; Xiao, Kai; Eddrief, Mahmoud; Girard, Jean-Christophe; Ouerghi, Abdelkarim

    2017-07-01

    Two-dimensional (2D) materials have recently been the focus of extensive research. By following a similar trend as graphene, other 2D materials, including transition metal dichalcogenides (M X2 ) and metal mono-chalcogenides (MX), show great potential for ultrathin nanoelectronic and optoelectronic devices. Despite the weak nature of interlayer forces in semiconducting MX materials, their electronic properties are highly dependent on the number of layers. Using scanning tunneling microscopy and spectroscopy, we demonstrate the tunability of the quasiparticle energy gap of few-layered gallium selenide (GaSe) directly grown on a bilayer graphene substrate by molecular beam epitaxy. Our results show that the band gap is about 3.50 ± 0.05 eV for single-tetralayer, 3.00 ±0.05 eV for bi-tetralayer, and 2.30 ±0.05 eV for tri-tetralayer GaSe. This band-gap evolution of GaSe, particularly the shift of the valence band with respect to the Fermi level, was confirmed by angle-resolved photoemission spectroscopy (ARPES) measurements and our theoretical calculations. Moreover, we observed a charge transfer in the GaSe/graphene van der Waals (vdW) heterostructure using ARPES. These findings demonstrate the high impact on the GaSe electronic band structure and electronic properties that can be obtained by the control of 2D materials layer thickness and the graphene induced doping.

  4. Skyrmions and Novel Spin Textures in FeGe Thin Films and Artificial B20 Heterostructures

    Science.gov (United States)

    Ahmed, Adam Saied

    Skyrmions are magnetic spin textures that have a non-zero topological winding number associated with them. They have attracted much interest recently since they can be as small as 1 nm and could be the next generation of magnetic memory and logic. First, we grow epitaxial films of FeGe by molecular beam epitaxy and characterized the skyrmion properties. This had led us to image skyrmions in real-space with Lorentz transmission electron microscopy for the first time in the United States. Next, from an extensive series of thin and thick films, we have experimentally shown the existence of a magnetic surface state in FeGe and, consequently, any skyrmion material for the first time. Complementary theoretical calculations supported the existence of chiral bobbers--a surface state only predicted in 2015. Next, we fabricated for the first time a new class of skyrmion materials: B20 superlattices. These novel heterostructures of [FeGe/MnGe/CrGe] have now opened the door for tunable skyrmion systems with both Dresselhaus and Rashba Dzyaloshinskii-Moriya interactions. Additionally, we perform resonant soft x-ray scattering to image magnetic spin textures in reciprocal space for FeGe thin films in transmission. We have accomplished the removal of substrate and left an isolated single-crystal FeGe film. Lastly, SrO is grown on graphene as a crystalline, atomically smooth, and pinhole free tunnel barrier for spin injection.

  5. Tunable M-channel filter based on Thue-Morse heterostructures containing meta materials

    Directory of Open Access Journals (Sweden)

    H Pashaei Adl

    2015-01-01

    Full Text Available In this paper the tunable M-channel filters based on Thue-Morse heterostructures consisting of single -negative materials has been studied. The results showed that the number of resonance modes inside the zero- gap increases as the number of heterogenous interface, M, increases. The number of resonance modes inside the zero- gap is equal to that of heterogenous interface M, and it can be used as M channels filter. This result provides a feasible method to adjust the channel number of multiple-channel filters. When losses are involved, the results showed that the electric fields of the resonance modes decay largely with the increase of the number of heterogenous interface and damping factors. Besides, the relationship between the quality factor of multiple-channel filters and the number of heterogenous interface M is linear, and the quality factor of multiple-channel filters decreases with the increase of the damping factor. These results provide feasible methods to adjust the quality factor of multiple-channel filters

  6. Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Kai Ding

    2017-10-01

    Full Text Available We overview recent progress in growth aspects of group III-nitride heterostructures for deep ultraviolet (DUV light-emitting diodes (LEDs, with particular emphasis on the growth approaches for attaining high-quality AlN and high Al-molar fraction AlGaN. The discussion commences with the introduction of the current status of group III-nitride DUV LEDs and the remaining challenges. This segues into discussion of LED designs enabling high device performance followed by the review of advances in the methods for the growth of bulk single crystal AlN intended as a native substrate together with a discussion of its UV transparency. It should be stated, however, that due to the high-cost of bulk AlN substrates at the time of writing, the growth of DUV LEDs on foreign substrates such as sapphire still dominates the field. On the deposition front, the heteroepitaxial growth approaches incorporate high-temperature metal organic chemical vapor deposition (MOCVD and pulsed-flow growth, a variant of MOCVD, with the overarching goal of enhancing adatom surface mobility, and thus epitaxial lateral overgrowth which culminates in minimization the effect of lattice- and thermal-mismatches. This is followed by addressing the benefits of pseudomorphic growth of strained high Al-molar fraction AlGaN on AlN. Finally, methods utilized to enhance both p- and n-type conductivity of high Al-molar fraction AlGaN are reviewed.

  7. A two-layer diagnostic model of the long-term physical evolution of warm-core ring 82B

    Science.gov (United States)

    Olson, D. B.; Schmitt, R. W.; Kennelly, M.; Joyce, T. M.

    1985-01-01

    The present shipboard data in the 1982 time series on a single Gulf Stream warm core ring are composited on a cylindrical coordinate system following ring motion; 10 C-isotherm depth measurements are used in a two-layer model of the ring's structure to compute gradient current, kinetic energy, available potential energy (APE), and potential vorticity. The ring's evolution can be divided into two periods: April-late June, while the ring is isolated from strong Gulf Stream interaction, during which the ring loses APE at a low rate, and from July onward, following ring interactions with the Gulf Stream and topography with much higher energy loss. Within measurement errors, the potential vorticity at the center of the ring is conserved from April through August, implying nearly inviscid dynamics.

  8. Accretion in Saturn's F Ring

    Science.gov (United States)

    Meinke, B. K.; Esposito, L. W.; Stewart, G.

    2012-12-01

    Saturn's F ring is the solar system's principal natural laboratory for direct observation of accretion and disruption processes. The ring resides in the Roche zone, where tidal disruption competes with self-gravity, which allows us to observe the lifecycle of moonlets. Just as nearby moons create structure at the B ring edge (Esposito et al. 2012) and the Keeler gap (Murray 2007), the F ring "shepherding" moons Prometheus and Pandora stir up ring material and create observably changing structures on timescales of days to decades. In fact, Beurle et al (2010) show that Prometheus makes it possible for "distended, yet gravitationally coherent clumps" to form in the F ring, and Barbara and Esposito (2002) predicted a population of ~1 km bodies in the ring. In addition to the observations over the last three decades, the Cassini Ultraviolet Imaging Spectrograph (UVIS) has detected 27 statistically significant features in 101 occultations by Saturn's F ring since July 2004. Seventeen of those 27 features are associated with clumps of ring material. Two features are opaque in occultation, which makes them candidates for solid objects, which we refer to as Moonlets. The 15 other features partially block stellar signal for 22 m to just over 3.7 km along the radial expanse of the occultation. Upon visual inspection of the occultation profile, these features resemble Icicles, thus we will refer to them as such here. The density enhancements responsible for such signal attenuations are likely due to transient clumping of material, evidence that aggregations of material are ubiquitous in the F ring. Our lengthy observing campaign reveals that Icicles are likely transient clumps, while Moonlets are possible solid objects. Optical depth is an indicator of clumping because more-densely aggregated material blocks more light; therefore, it is natural to imagine moonlets as later evolutionary stage of icicle, when looser clumps of material compact to form a feature that appears

  9. Synthesis, Characterization, and Properties of the Two-Dimensional Chalcogenides: Monolayers, Alloys, and Heterostructures

    Science.gov (United States)

    Cain, Jeffrey D.

    Inspired by the triumphs of graphene, and motivated by its limitations, the science and engineering community is rapidly exploring the landscape of other layered materials in their atomically-thin forms. Dominating this landscape are the layered chalcogenides; diverse in chemistry, crystal structure, and properties, there are well over 100 primary members of this material family. Driven by quantum confinement, single layers (or few, in some cases) of these materials exhibit electronic, optical, and mechanical properties that diverge dramatically from their bulk counterparts. While initially isolated in monolayer form via mechanical exfoliation, the field of two-dimensional (2D) materials is being forced evolve to more scalable and reliable methods. Focusing on the chalcogenides (e.g. MoS2, Bi 2Se3, etc.), this dissertation introduces and mechanistically examines multiple novel synthetic approaches for the direct growth of monolayers, heterostructures, and alloys with the desired quality, reproducibility and generality. The first methods described in this thesis are physical vapor transport (PVT) and evaporative thinning (ET): a facile, top-down synthesis approach for creating ultrathin specimens of layered materials down to the two-dimensional limit. Evaporative thinning, applied in this study to the fabrication of A2X3 (Bi2Se3 and Sb2Te3) monolayers, is based on the controlled evaporation of material from initially thick specimens until the 2D limit is reached. The resultant flakes are characterized with a suite of imaging and spectroscopic techniques and the mechanism of ET is investigated via in-situ heating within a transmission electron microscope. Additionally, the basic transport properties of the resultant flakes are probed. The growth of ultrathin GeSe flakes is explored using PVT and the material's basic structure, properties, and stability are addressed. Second, oxide precursor based chemical vapor deposition (CVD) is presented for the direct growth of

  10. Graphene/blue-phosphorus heterostructure as potential anode materials for sodium-ion batteries

    Science.gov (United States)

    Fan, Kaimin; Tang, Ting; Wu, Shiyun; Zhang, Zhiyuan

    2018-01-01

    The first-principles calculations based on density functional theory (DFT) have been implemented to investigate the graphene/blue-phosphorus (G/BP) heterostructure as potential anode material for SIBs. The adsorption and diffusion behaviors of sodium (Na) in G/BP heterostructure and the effect of external electric field on Na adsorption have been investigated. The results indicate that G/BP heterostructure with Na adsorption is metallic due to Na incorporation, which is of benefit for electronic conductivity as anode material. The results show that the design of G/BP heterostructure is an efficient scheme to enhance the Na adsorption in G/BP without affecting the high mobility of Na in the G/BP heterostructure surface. The present work demonstrates that the external electric field can effectively modulate the adsorption of Na, and the adsorption behavior of Na is more sensitive to the external electric field when E > 0.10 V Å-1 in G/BP heterostructure. The Mulliken population analysis and DOS calculations have been performed to explore the charge transfer and the interaction between Na and G/BP.

  11. High-efficiency super capacitors based on hetero-structured α-MnO2 nanorods

    International Nuclear Information System (INIS)

    Ghouri, Zafar Khan; Shaheer Akhtar, M.; Zahoor, Awan; Barakat, Nasser A.M.; Han, Weidong; Park, Mira; Pant, Bishweshwar; Saud, Prem Singh; Lee, Cho Hye; Kim, Hak Yong

    2015-01-01

    Highlights: • Hetero-structured α-MnO 2 nanorods are prepared by a facile hydrothermal route. • It is applied as active electrode materials for supercapacitor. • A high specific capacitance of 298 Fg −1 with a superior long term cyclic stability is achieved. • Supercapacitor shows high specific capacitance retention 94% after 1000 cycles. - Abstract: Hetero-structured manganese dioxide nanorods with α phase (α-MnO 2 ) were prepared by a facile hydrothermal route at low temperature. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption measurements were used to characterize the prepared hetero-structured α-MnO 2 nanorods. Supercapacitive performance of the hetero-structured α-MnO 2 nanomaterials as active electrode material was evaluated by cyclic voltammetry (CV) in alkaline medium. The MnO 2 hetero-structure with 2 × 2 tunnels constructed from double chains of octahedral [MnO 6 ] structure yield a significantly high specific capacitance of 298 Fg −1 at 5 mV s −1 and demonstrated a superior long term cyclic stability, with specific capacitance retention about 94% after 1000 cycles. The superior supercapacitive performance of the hetero-structured α-MnO 2 electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport

  12. Size-tunable band alignment and optoelectronic properties of transition metal dichalcogenide van der Waals heterostructures

    Science.gov (United States)

    Zhao, Yipeng; Yu, Wangbing; Ouyang, Gang

    2018-01-01

    2D transition metal dichalcogenide (TMDC)-based heterostructures exhibit several fascinating properties that can address the emerging market of energy conversion and storage devices. Current achievements show that the vertical stacked TMDC heterostructures can form type II band alignment and possess significant optoelectronic properties. However, a detailed analytical understanding of how to quantify the band alignment and band offset as well as the optimized power conversion efficiency (PCE) is still lacking. Herein, we propose an analytical model to exhibit the PCEs of TMDC van der Waals (vdW) heterostructures and explore the intrinsic mechanism of photovoltaic conversion based on the detailed balance principle and atomic-bond-relaxation correlation mechanism. We find that the PCE of monolayer MoS2/WSe2 can be up to 1.70%, and that of the MoS2/WSe2 vdW heterostructures increases with thickness, owing to increasing optical absorption. Moreover, the results are validated by comparing them with the available evidence, providing realistic efficiency targets and design principles. Highlights • Both electronic and optoelectronic models are developed for vertical stacked MoS2/WSe2 heterostructures. • The underlying mechanism on size effect of electronic and optoelectronic properties for vertical stacked MoS2/WSe2 heterostructures is clarified. • The macroscopically measurable quantities and the microscopical bond identities are connected.

  13. Organoclay hybrid materials as precursors of porous ZnO/silica-clay heterostructures for photocatalytic applications

    Directory of Open Access Journals (Sweden)

    Marwa Akkari

    2016-12-01

    Full Text Available In this study, ZnO/SiO2-clay heterostructures were successfully synthesized by a facile two-step process applied to two types of clays: montmorillonite layered silicate and sepiolite microfibrous clay mineral. In the first step, intermediate silica–organoclay hybrid heterostructures were prepared following a colloidal route based on the controlled hydrolysis of tetramethoxysilane in the presence of the starting organoclay. Later on, pre-formed ZnO nanoparticles (NP dispersed in 2-propanol were incorporated under ultrasound irradiation to the silica–organoclay hybrid heterostructures dispersed in 2-propanol, and finally, the resulting solids were calcinated to eliminate the organic matter and to produce ZnO nanoparticles (NP homogeneously assembled to the clay–SiO2 framework. In the case of montmorillonite the resulting materials were identified as delaminated clays of ZnO/SiO2-clay composition, whereas for sepiolite, the resulting heterostructure is constituted by the assembling of ZnO NP to the sepiolite–silica substrate only affecting the external surface of the clay. The structural and morphological features of the prepared heterostructures were characterized by diverse physico-chemical techniques (such as XRD, FTIR, TEM, FE-SEM. The efficiency of these new porous ZnO/SiO2-clay heterostructures as potential photocatalysts in the degradation of organic dyes and the removal of pharmaceutical drugs in water solution was tested using methylene blue and ibuprofen compounds, respectively, as model of pollutants.

  14. The dynamics of particles in the bending waves of the planetary rings

    International Nuclear Information System (INIS)

    Chakrabarti, S.K.

    1988-10-01

    We study the motion of a single particle in the bending wave of finite thickness in the planetary ring. We include the forcing due to the planet, the moon, the coriolis force and the self gravity of the ring. In particular, we study the variation of the velocity arising due to the variation of the amplitude and the phase of the epicyclic motion across the height of the ring. We suggest that the dissipation of energy of this shear layer through collisions of ring particles from different heights may contribute significantly to the damping of the bending waves observed in the Voyger data. (author). 16 refs, 7 figs

  15. Double acting stirling engine piston ring

    Science.gov (United States)

    Howarth, Roy B.

    1986-01-01

    A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

  16. Enhancement-mode two-channel triple quantum dot from an undoped Si/Si0.8Ge0.2 quantum well hetero-structure.

    Energy Technology Data Exchange (ETDEWEB)

    Studenikin, S. A.; Gaudreau, L.; Kataoka, K.; Austing, D. G.; Lu, Tzu-Ming; Luhman, Dwight; Bethke, Donald Thomas; Wanke, Michael; Lilly, Michael; Carroll, Malcolm S.; Sachrajda, A. S.

    2017-12-01

    We demonstrate coupled triple dot operation and charge sensing capability for the recently introduced quantum dot technology employing undoped Si/Si0.8Ge0.2 hetero-structures which also incorporate a single metal-gate layer to simplify fabrication [T. M. Lu et al., Appl. Phys. Lett. 109, 093102 (2016)]. Si/SiGe hetero-structures with a Ge concentration of 20% rather than the more usual 30% typically encountered offer higher electron mobility. The devices consist of two in-plane parallel electron channels that host a double dot in one channel and a single dot in the other channel. In a device where the channels are sufficiently close a triple dot in a triangular configuration is induced leading to regions in the charge stability diagram where three addition lines of different slope approach each other and anti-cross. In a device where the channels are further apart the single dot charge-senses the double dot with relative change of ~2% in the sensor current. We also highlight temporal drifting and metastability of the Coulomb oscillations. These effects are induced if the temperature environment of the device is not kept constant and arise from non-equilibrium charge redistribution and subsequent slow recovery.

  17. Magnetization Reversal by Out-of-plane Voltage in BiFeO3-based Multiferroic Heterostructures

    OpenAIRE

    Wang, J. J.; Hu, J.M.; Peng, Ren-Ci; Gao, Y.; Shen, Y.; Chen, L. Q.; Nan, C. W.

    2015-01-01

    Voltage controlled 180? magnetization reversal has been achieved in BiFeO3-based multiferroic heterostructures, which is promising for the future development of low-power spintronic devices. However, all existing reports involve the use of an in-plane voltage that is unfavorable for practical device applications. Here, we investigate, using phase-field simulations, the out-of-plane (i.e., perpendicular to heterostructures) voltage controlled magnetism in heterostructures consisting of CoFe na...

  18. Interfacial thermal conductance in multilayer graphene/phosphorene heterostructure

    International Nuclear Information System (INIS)

    Zhang, Ying-Yan; Pei, Qing-Xiang; Mai, Yiu-Wing; Lai, Siu-Kai

    2016-01-01

    Vertical integration of 2D materials has recently appeared as an effective method for the design of novel nano-scale devices. Using non-equilibrium molecular dynamics simulations, we study the interfacial thermal transport property of graphene/phosphorene heterostructures where phosphorene is sandwiched in between graphene. Various modulation techniques are thoroughly explored. We found that the interfacial thermal conductance at the interface of graphene and phosphorene can be enhanced significantly by using vacancy defects, hydrogenation and cross-plane compressive strain. By contrast, the reduction in the interfacial thermal conductance can be achieved by using cross-plane tensile strain. Our results provide important guidelines for manipulating the thermal transport in graphene/phosphorene based-nano-devices. (paper)

  19. Giant thermopower in superconducting heterostructures with spin-active interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kalenkov, Mikhail S. [I.E. Tamm Department of Theoretical Physics, P.N. Lebedev Physical Institute, 119991 Moscow (Russian Federation); Laboratory of Cryogenic Nanoelectronics, Nizhny Novgorod State Technical University, 603950 Nizhny Novgorod (Russian Federation); Zaikin, Andrei D. [Institut für Nanotechnologie, Karlsruher Institut für Technologie (KIT), 76021 Karlsruhe (Germany); I.E. Tamm Department of Theoretical Physics, P.N. Lebedev Physical Institute, 119991 Moscow (Russian Federation)

    2015-06-01

    We predict parametrically strong enhancement of the thermoelectric effect in metallic bilayers consisting of two superconductors separated by a spin-active interface. The physical mechanism for such an enhancement is directly related to electron–hole imbalance generated by spin-sensitive quasiparticle scattering at the interface between superconducting layers. We explicitly evaluate the thermoelectric currents flowing in the system and demonstrate that they can reach maximum values comparable to the critical ones for superconductors under consideration. - Highlights: • Strong enhancement of the thermoelectric effect in superconducting heterostructures. • Generation of the electron-hole imbalance by spin-sensitive quasiparticle scattering. • Thermoelectric currents can reach maximum values comparable to the critical ones.

  20. Numerical methods for semiconductor heterostructures with band nonparabolicity

    International Nuclear Information System (INIS)

    Wang Weichung; Hwang Tsungmin; Lin Wenwei; Liu Jinnliang

    2003-01-01

    This article presents numerical methods for computing bound state energies and associated wave functions of three-dimensional semiconductor heterostructures with special interest in the numerical treatment of the effect of band nonparabolicity. A nonuniform finite difference method is presented to approximate a model of a cylindrical-shaped semiconductor quantum dot embedded in another semiconductor matrix. A matrix reduction method is then proposed to dramatically reduce huge eigenvalue systems to relatively very small subsystems. Moreover, the nonparabolic band structure results in a cubic type of nonlinear eigenvalue problems for which a cubic Jacobi-Davidson method with an explicit nonequivalence deflation method are proposed to compute all the desired eigenpairs. Numerical results are given to illustrate the spectrum of energy levels and the corresponding wave functions in rather detail

  1. Biaxial Compressive Strain Engineering in Graphene/Boron Nitride Heterostructures

    Science.gov (United States)

    Pan, Wei; Xiao, Jianliang; Zhu, Junwei; Yu, Chenxi; Zhang, Gang; Ni, Zhenhua; Watanabe, K.; Taniguchi, T.; Shi, Yi; Wang, Xinran

    2012-11-01

    Strain engineered graphene has been predicted to show many interesting physics and device applications. Here we study biaxial compressive strain in graphene/hexagonal boron nitride heterostructures after thermal cycling to high temperatures likely due to their thermal expansion coefficient mismatch. The appearance of sub-micron self-supporting bubbles indicates that the strain is spatially inhomogeneous. Finite element modeling suggests that the strain is concentrated on the edges with regular nano-scale wrinkles, which could be a playground for strain engineering in graphene. Raman spectroscopy and mapping is employed to quantitatively probe the magnitude and distribution of strain. From the temperature-dependent shifts of Raman G and 2D peaks, we estimate the TEC of graphene from room temperature to above 1000K for the first time.

  2. Epitaxial growth of Fe/BaTiO3 heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Brivio, S., E-mail: m.gooley@elsevier.com [LNESS, Dipartimento di Fisica, Politecnico di Milano, via Anzani 42, 22100, Como (Italy); Rinaldi, C.; Petti, D.; Bertacco, R. [LNESS, Dipartimento di Fisica, Politecnico di Milano, via Anzani 42, 22100, Como (Italy); Sanchez, F. [Institut de Ciencia de Materials de Barcelona, Consejo Superior de Investigaciones Cientificas, Campus Universitat Autonoma de Barcelona, Bellaterra 08193, Catalunya (Spain)

    2011-06-30

    The realization of epitaxial heterostructures involving ferroelectric (FE) and ferromagnetic (FM) materials is one of the possible routes towards the realization of devices exploiting sizable magnetoelectric effects. In this paper we demonstrate the epitaxial growth of Fe on BaTiO{sub 3}(001) as this system represents a prototypical example of interface between well known FE and FM materials with bcc and perovskite structure respectively, both with Curie temperature well above 300 K. Fe grows on BaTiO{sub 3} with 45 deg. rotation of its cubic lattice with respect to that of the substrate in order to reduce the lattice mismatch. Negligible interdiffusion of Ba and Ti cations or Fe atoms is found by X-ray photoemission spectroscopy, while a sizable Fe oxidation occurs within an interfacial layer with thicknesses thinner than 3 nm.

  3. Multi-color imaging of magnetic Co/Pt heterostructures

    Directory of Open Access Journals (Sweden)

    Felix Willems

    2017-01-01

    Full Text Available We present an element specific and spatially resolved view of magnetic domains in Co/Pt heterostructures in the extreme ultraviolet spectral range. Resonant small-angle scattering and coherent imaging with Fourier-transform holography reveal nanoscale magnetic domain networks via magnetic dichroism of Co at the M2,3 edges as well as via strong dichroic signals at the O2,3 and N6,7 edges of Pt. We demonstrate for the first time simultaneous, two-color coherent imaging at a free-electron laser facility paving the way for a direct real space access to ultrafast magnetization dynamics in complex multicomponent material systems.

  4. Manipulation of vortex rings for flow control

    International Nuclear Information System (INIS)

    Toyoda, Kuniaki; Hiramoto, Riho

    2009-01-01

    This paper reviews the dynamics of vortex rings and the control of flow by the manipulation of vortex rings. Vortex rings play key roles in many flows; hence, the understanding of the dynamics of vortex rings is crucial for scientists and engineers dealing with flow phenomena. We describe the structures and motions of vortex rings in circular and noncircular jets, which are typical examples of flows evolving into vortex rings. For circular jets the mechanism of evolving, merging and breakdown of vortex rings is described, and for noncircular jets the dynamics of three-dimensional deformation and interaction of noncircular vortex rings under the effect of self- and mutual induction is discussed. The application of vortex-ring manipulation to the control of various flows is reviewed with successful examples, based on the relationship between the vortex ring dynamics and the flow properties. (invited paper)

  5. Novel Heterostructure Devices for Ultra-Scaled Logic

    Science.gov (United States)

    Fay, Patrick

    Continuing increases in circuit complexity and capability for logic and computational applications as well as for emerging low-power distributed systems require fundamental advances in device technology and scaling. Dimensional scaling of conventional devices are approaching fundamental limitations. In addition, due to power constraints, devices capable of achieving switching slopes (SS) steeper than 60 mV/decade are essential if conventional computational architectures are to continue scaling. Similarly, low power systems such as distributed sensing applications also benefit from devices capable of delivering high performance in low-voltage operation. Tunneling field effect transistors (TFETs) are one promising alternative to achieve these objectives. A great deal of work has been devoted to realizing TFETs in Si, Ge, and narrow-gap III-V materials, but the use of two-dimensional materials and III-N heterostructures offer unique opportunities. From physics-based simulations, GaN/InGaN/GaN heterostructure TFETs offer the potential for achieving switching slopes approaching 20 mV/decade with on-current densities approaching 1 mA/ μm in nanowire configurations, while recent results in two-dimensional materials have also shown potential for sub-thermionic switching slopes. In this talk, the operational principles of candidate devices for steep switching will be described, and device design and performance considerations will be discussed. In addition, experimental efforts demonstrating these devices will be reviewed, and the future prospects for these and related devices to enable future generations of scaled technologies will be discussed. This work is sponsored in part by LEAST, a funded center of STARnet, a Semiconductor Research Corporation (SRC) program sponsored by MARCO and DARPA.

  6. Multilayer Graphene–WSe2 Heterostructures for WSe2 Transistors

    KAUST Repository

    Tang, Hao-Ling

    2017-11-29

    Two-dimensional (2D) materials are drawing growing attention for next-generation electronics and optoelectronics owing to its atomic thickness and unique physical properties. One of the challenges posed by 2D materials is the large source/drain (S/D) series resistance due to their thinness, which may be resolved by thickening the source and drain regions. Recently explored lateral graphene–MoS21−3 and graphene–WS21,4 heterostructures shed light on resolving the mentioned issues owing to their superior ohmic contact behaviors. However, recently reported field-effect transistors (FETs) based on graphene–TMD heterostructures have only shown n-type characteristics. The lack of p-type transistor limits their applications in complementary metal-oxide semiconductor electronics. In this work, we demonstrate p-type FETs based on graphene–WSe2 lateral heterojunctions grown with the scalable CVD technique. Few-layer WSe2 is overlapped with the multilayer graphene (MLG) at MLG–WSe2 junctions such that the contact resistance is reduced. Importantly, the few-layer WSe2 only forms at the junction region while the channel is still maintained as a WSe2 monolayer for transistor operation. Furthermore, by imposing doping to graphene S/D, 2 orders of magnitude enhancement in Ion/Ioff ratio to ∼108 and the unipolar p-type characteristics are obtained regardless of the work function of the metal in ambient air condition. The MLG is proposed to serve as a 2D version of emerging raised source/drain approach in electronics.

  7. Design and realization of one-dimensional double hetero-structure photonic crystals for infrared-radar stealth-compatible materials applications

    International Nuclear Information System (INIS)

    Wang, Zhixun; Cheng, Yongzhi; Nie, Yan; Wang, Xian; Gong, Rongzhou

    2014-01-01

    In this paper, a new type one-dimensional (1D) double hetero-structure composite photonic crystal (CPC) for infrared-radar stealth-compatible materials applications was proposed and studied numerically and experimentally. First, based on transfer matrix method of thin-film optical theory, the propagation characteristics of the proposed structure comprising a stack of different alternating micrometer-thick layers of germanium and zinc sulfide were investigated numerically. Calculation results exhibit that this 1D single hetero-structure PC could achieve a flat high reflectivity gradually with increasing the number of the alternating media layers in a single broadband range. Then, based on principles of distributed Bragg reflector micro-cavity, a 1D double hetero-structure CPC comprising four PCs with thickness of 0.797 μm, 0.592 μm, 1.480 μm, and 2.114 μm, respectively, was proposed. Calculation results exhibit that this CPC could achieve a high reflectance of greater than 0.99 in the wavelength ranges of 3–5 μm and 8–14 μm and agreed well with experiment. Further experiments exhibit that the infrared emissivity of the proposed CPC is as low as 0.073 and 0.042 in the wavelength ranges of 3–5 μm and 8–12 μm, respectively. In addition, the proposed CPC can be used to construct infrared-radar stealth-compatible materials due to its high transmittance in radar wave band

  8. Design and realization of one-dimensional double hetero-structure photonic crystals for infrared-radar stealth-compatible materials applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhixun; Cheng, Yongzhi, E-mail: cyz0715@126.com; Nie, Yan; Wang, Xian; Gong, Rongzhou, E-mail: rzhgong@mail.hust.edu.cn [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-08-07

    In this paper, a new type one-dimensional (1D) double hetero-structure composite photonic crystal (CPC) for infrared-radar stealth-compatible materials applications was proposed and studied numerically and experimentally. First, based on transfer matrix method of thin-film optical theory, the propagation characteristics of the proposed structure comprising a stack of different alternating micrometer-thick layers of germanium and zinc sulfide were investigated numerically. Calculation results exhibit that this 1D single hetero-structure PC could achieve a flat high reflectivity gradually with increasing the number of the alternating media layers in a single broadband range. Then, based on principles of distributed Bragg reflector micro-cavity, a 1D double hetero-structure CPC comprising four PCs with thickness of 0.797 μm, 0.592 μm, 1.480 μm, and 2.114 μm, respectively, was proposed. Calculation results exhibit that this CPC could achieve a high reflectance of greater than 0.99 in the wavelength ranges of 3–5 μm and 8–14 μm and agreed well with experiment. Further experiments exhibit that the infrared emissivity of the proposed CPC is as low as 0.073 and 0.042 in the wavelength ranges of 3–5 μm and 8–12 μm, respectively. In addition, the proposed CPC can be used to construct infrared-radar stealth-compatible materials due to its high transmittance in radar wave band.

  9. Synthetic gauge fields in Jaynes-Cummings-Hubbard ring lattices

    Science.gov (United States)

    Nunnenkamp, Andreas; Koch, Jens; Girvin, Steven

    2011-03-01

    Recently there has been much interest in many-body physics with photons in circuit-QED arrays. Here we explore the physics of a Jaynes-Cummings-Hubbard ring lattice subject to a synthetic gauge field, i.e.~where the hopping terms carry a complex phase factor due to Josephson couplers between the resonators. There are critical phase twists at which the single-particle spectrum is degenerate so that even weak interactions can give rise to strong correlations. We compare to ultracold bosons in rotating ring lattices and study the out-of-equilibrium physics as relevant for current experiments.

  10. Treatment of Unstable Pelvic Ring Injuries

    OpenAIRE

    Kim, Weon-Yoo

    2014-01-01

    Pelvic fractures are classified according to the stability of the pelvic ring. Unlike stable pelvic fractures, which heal without complications, unstable fractures may lead to pelvic ring deformities, which cause severe complications. An orthopedic surgeon must determine the stability of the pelvic ring by radiography and physical examination of the patient in order to ensure early, prompt treatment. This article includes anatomy of the pelvic ring, classification of pelvic ring injuries, its...

  11. Optimizing ring-based CSR sources

    International Nuclear Information System (INIS)

    Byrd, J.M.; De Santis, S.; Hao, Z.; Martin, M.C.; Munson, D.V.; Li, D.; Nishimura, H.; Robin, D.S.; Sannibale, F.; Schlueter, R.D.; Schoenlein, R.; Jung, J.Y.; Venturini, M.; Wan, W.; Zholents, A.A.; Zolotorev, M.

    2004-01-01

    Coherent synchrotron radiation (CSR) is a fascinating phenomenon recently observed in electron storage rings and shows tremendous promise as a high power source of radiation at terahertz frequencies. However, because of the properties of the radiation and the electron beams needed to produce it, there are a number of interesting features of the storage ring that can be optimized for CSR. Furthermore, CSR has been observed in three distinct forms: as steady pulses from short bunches, bursts from growth of spontaneous modulations in high current bunches, and from micro modulations imposed on a bunch from laser slicing. These processes have their relative merits as sources and can be improved via the ring design. The terahertz (THz) and sub-THz region of the electromagnetic spectrum lies between the infrared and the microwave . This boundary region is beyond the normal reach of optical and electronic measurement techniques and sources associated with these better-known neighbors. Recent research has demonstrated a relatively high power source of THz radiation from electron storage rings: coherent synchrotron radiation (CSR). Besides offering high power, CSR enables broadband optical techniques to be extended to nearly the microwave region, and has inherently sub-picosecond pulses. As a result, new opportunities for scientific research and applications are enabled across a diverse array of disciplines: condensed matter physics, medicine, manufacturing, and space and defense industries. CSR will have a strong impact on THz imaging, spectroscopy, femtosecond dynamics, and driving novel non-linear processes. CSR is emitted by bunches of accelerated charged particles when the bunch length is shorter than the wavelength being emitted. When this criterion is met, all the particles emit in phase, and a single-cycle electromagnetic pulse results with an intensity proportional to the square of the number of particles in the bunch. It is this quadratic dependence that can

  12. Ring wormholes via duality rotations

    Directory of Open Access Journals (Sweden)

    Gary W. Gibbons

    2016-09-01

    Full Text Available We apply duality rotations and complex transformations to the Schwarzschild metric to obtain wormhole geometries with two asymptotically flat regions connected by a throat. In the simplest case these are the well-known wormholes supported by phantom scalar field. Further duality rotations remove the scalar field to yield less well known vacuum metrics of the oblate Zipoy–Voorhees–Weyl class, which describe ring wormholes. The ring encircles the wormhole throat and can have any radius, whereas its tension is always negative and should be less than −c4/4G. If the tension reaches the maximal value, the geometry becomes exactly flat, but the topology remains non-trivial and corresponds to two copies of Minkowski space glued together along the disk encircled by the ring. The geodesics are straight lines, and those which traverse the ring get to the other universe. The ring therefore literally produces a hole in space. Such wormholes could perhaps be created by negative energies concentrated in toroidal volumes, for example by vacuum fluctuations.

  13. Dream of Isochronous Ring Again

    CERN Document Server

    Hama, H

    2005-01-01

    More than 20 years ago, D.A.G. Deacon proposed an isochronous storage ring for FEL to avoid bunch heating and decreasing instantaneous gain [1]. Some of low momentum compaction (alpha) operations have been carried out, and recently coherent infrared radiation are observed on a 3rd generation light source. Because the 3rd generation rings are optimized to obtain very low emittance beam, the dispersion function in the arc sections are much reduced by introducing large bending radius, so that those are very big machines. Meanwhile N.A. Vinokurov et al. recently proposed a ring type SASE FEL based on a complete isochronous bending transport [2]. At least, experimental and theoretical study of the isochronous ring so far suggests nonlinear effects resulted from higher order dispersion and chromaticity declines the "complete" isochronous system. On the other hand, in a wavelength region of THz, tolerance of the path length along a turn of the ring seems to be within our reach. A concept to preserve of a form factor...

  14. Primitivity and weak distributivity in near rings and matrix near rings

    International Nuclear Information System (INIS)

    Abbasi, S.J.

    1993-08-01

    This paper shows the structure of matrix near ring constructed over a weakly distributive and primative near ring. It is proved that a weakly distributive primitive near ring is a ring and the matrix near rings constructed over it is also a bag. (author). 14 refs

  15. Process for producing curved surface of membrane rings for large containers, particulary for prestressed concrete pressure vessels of nuclear reactors

    International Nuclear Information System (INIS)

    Kumpf, H.

    1977-01-01

    Membrane rings for large pressure vessels, particularly for prestressed-concrete pressure vessels, often have curved surfaces. The invention describes a process of producing these at site, which is particularly advantageous as the forming and installation of the vessel component coincide. According to the invention, the originally flat membrane ring is set in a predetermined position, is then pressed in sections by a forming tool (with a preformed support ring as opposite tool), and shaped. After this, the shaped parts are welded to the ring-shaped wall parts of the large vessel. The manufacture of single and double membrane rings arrangements is described. (HP) [de

  16. Proton storage ring summer workshop

    International Nuclear Information System (INIS)

    Lawrence, G.P.; Cooper, R.K.

    1977-10-01

    During the week of August 16, 1976 a Workshop was held at the Los Alamos Scientific Laboratory (LASL) on the Proton Storage Ring (PSR) for the Weapons Neutron Research Facility (WNRF). Written contributions were solicited from each of the participants in the Workshop, and the contributions that were received are presented. The papers do not represent polished or necessarily complete work, but rather represent ''first cuts'' at their respective areas. Topics covered include: (1) background information on the storage ring; (2) WNRF design; (3) rf transient during filling; (4) rf capture; (5) beam bunch compression; (6) transverse space charge limits; (7) transverse resistive instability in the PSR; (8) longitudinal resistive instability; (9) synchrotron frequency splitting; (10) E Quintus Unum--off resonance; (11) first harmonic bunching in the storage ring; (12) kicker considerations; (13) beam extraction; (14) ferrite kicker magnets; and (15) E Quintus Unum: a possible ejection scheme

  17. Tree rings and radiocarbon calibration

    International Nuclear Information System (INIS)

    Barbetti, M.

    1999-01-01

    Only a few kinds of trees in Australia and Southeast Asia are known to have growth rings that are both distinct and annual. Those that do are therefore extremely important to climatic and isotope studies. In western Tasmania, extensive work with Huon pine (Lagarostrobos franklinii) has shown that many living trees are more than 1,000 years old, and that their ring widths are sensitive to temperature, rainfall and cloud cover (Buckley et al. 1997). At the Stanley River there is a forest of living (and recently felled) trees which we have sampled and measured. There are also thousands of subfossil Huon pine logs, buried at depths less than 5 metres in an area of floodplain extending over a distance of more than a kilometre with a width of tens of metres. Some of these logs have been buried for 50,000 years or more, but most of them belong to the period between 15,000 years and the present. In previous expeditions in the 1980s and 1990s, we excavated and sampled about 350 logs (Barbetti et al. 1995; Nanson et al. 1995). By measuring the ring-width patterns, and matching them between logs and living trees, we have constructed a tree-ring dated chronology from 571 BC to AD 1992. We have also built a 4254-ring floating chronology (placed by radiocarbon at ca. 3580 to 7830 years ago), and an earlier 1268-ring chronology (ca. 7,580 to 8,850 years ago). There are many individuals, or pairs of logs which match and together span several centuries, at 9,000 years ago and beyond

  18. Superconducting proton ring for PETRA

    International Nuclear Information System (INIS)

    Baynham, E.

    1979-01-01

    A powerful new facility for colliding beam physics could be provided by adding a proton storage ring in the range of several hundred GeV to the electron-positron storage ring PETRA at DESY. This can be achieved in an economic way utilizing the PETRA tunnel and taking advantage of the higher magnetic fields of superconducting magnets which would be placed above or below the PETRA magnets. A central field of 4 Tesla in the bending magnets corresponds to a proton energy of 225 GeV. (orig.)

  19. InAlN/InGaN/GaN double heterostructure with improved carrier confinement and high-temperature transport performance grown by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Zhao, Yi; Xue, Jun Shuai; Zhang, Jin Cheng; Zhou, Xiao Wei; Zhang, Ya Chao; Hao, Yue

    2015-01-01

    A nearly lattice-matched InAlN/InGaN/GaN double heterostructure (DH) and traditional InAlN/GaN single heterostructure (SH) were grown by metal–organic chemical vapor deposition. The InN mole fraction of InGaN channel was deduced by XRD and photoluminescence. The electrical properties were characterized by capacitance-voltage and temperature-dependent Hall measurements. Both results revealed that the InAlN/InGaN/GaN DH possessed superior carrier confinement over traditional InAlN/GaN SH owing to the back barrier formed at the InGaN/GaN interface, which prevents the spilling over of carriers and thus remarkably improves the transport performance at high temperature. Furthermore, a thin InGaN layer was preferable for carrier channel applications to a thick one. (paper)

  20. The effect of annealing atmosphere on magnetoelectric coupling of the La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/BaTiO{sub 3} layered heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tingxian, E-mail: wxlltx@126.com [College of Physics and Electrical Engineering, Anyang Normal University, Anyang 455002 (China); Wang, Hongwei [School of Mathematics and Statistics, Anyang Normal University, Anyang 455002 (China); Ju, Lin; Tang, Zhenjie; Ma, Dongwei [College of Physics and Electrical Engineering, Anyang Normal University, Anyang 455002 (China); Li, Kuoshe [National Engineering Research Central for Rare earth Materials, Beijing 100088 (China)

    2015-10-15

    The epitaxial La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/BaTiO{sub 3} (LSMO/BTO) layered heterostructure was grown on (001) oriented LaAlO{sub 3} single-crystal substrate by pulsed laser deposition. Our results showed that the in-situ annealing process in oxygen made the LSMO/BTO interface possess higher oxygen content than that of the one annealing in vacuum, which leaded to the LSMO film presented higher magnetic permeability and higher saturated magnetization. The P–E hystersis loop only could be detected in the sample annealing in oxygen. The ME voltage coefficient of the LSMO/BTO heterostructure annealing in oxygen was higher than that of the one annealing in vacuum, which suggested a more effective ME coupling. It was a combined effect of the two main ME coupling mechanisms, including strain mediation, and polarized carrier mediation.