Sample records for gray dots transitioning

  1. Sandia Energy - InAs Quantum Dot Transitions

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of Scienceand RequirementsCoatingsUltra-High-VoltagePower Company'sInAs Quantum Dot Transitions Home

  2. Role of Symmetry Breaking on the Optical Transitions in Lead-Salt Quantum Dots

    E-Print Network [OSTI]

    Van Stryland, Eric

    Role of Symmetry Breaking on the Optical Transitions in Lead-Salt Quantum Dots Gero Nootz to explain optical transitions in lead-salt QDs. Thus, while the band anisotropy of the bulk semiconductor functions. These studies clarify the controversy of the origin of spectral features in lead-salt QDs

  3. Strain-induced fundamental optical transition in (In,Ga)As/GaP quantum dots

    SciTech Connect (OSTI)

    Robert, C., E-mail: cedric.robert@insa-rennes.fr, E-mail: cedric.robert@tyndall.ie; Pedesseau, L.; Cornet, C.; Jancu, J.-M.; Even, J.; Durand, O. [Université Européenne de Bretagne, INSA Rennes, France and CNRS, UMR 6082 Foton, 20 Avenue des Buttes de Coësmes, 35708 Rennes (France)] [Université Européenne de Bretagne, INSA Rennes, France and CNRS, UMR 6082 Foton, 20 Avenue des Buttes de Coësmes, 35708 Rennes (France); Nestoklon, M. O. [Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation)] [Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Pereira da Silva, K. [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain) [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain); Departamento de Física, Universidade Federal do Ceará, P.O. Box 6030, Fortaleza–CE, 60455-970 (Brazil); Alonso, M. I. [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain)] [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain); Goñi, A. R. [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain) [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain); ICREA, Passeig Lluís Companys 23, 08010 Barcelona (Spain); Turban, P. [Equipe de Physique des Surfaces et Interfaces, Institut de Physique de Rennes UMR UR1-CNRS 6251, Université de Rennes 1, F-35042 Rennes Cedex (France)] [Equipe de Physique des Surfaces et Interfaces, Institut de Physique de Rennes UMR UR1-CNRS 6251, Université de Rennes 1, F-35042 Rennes Cedex (France)

    2014-01-06T23:59:59.000Z

    The nature of the ground optical transition in an (In,Ga)As/GaP quantum dot is thoroughly investigated through a million atoms supercell tight-binding simulation. Precise quantum dot morphology is deduced from previously reported scanning-tunneling-microscopy images. The strain field is calculated with the valence force field method and has a strong influence on the confinement potentials, principally, for the conduction band states. Indeed, the wavefunction of the ground electron state is spatially confined in the GaP matrix, close to the dot apex, in a large tensile strain region, having mainly Xz character. Photoluminescence experiments under hydrostatic pressure strongly support the theoretical conclusions.

  4. Spectrum of surface plasmons excited by spontaneous quantum dot transitions

    SciTech Connect (OSTI)

    Andrianov, E. S., E-mail: andrianov.es@mipt.ru; Pukhov, A. A., E-mail: pukhov@mail.ru; Dorofeenko, A. V.; Vinogradov, A. P. [Russian Academy of Sciences, Institute of Theoretical and Applied Electrodynamics (Russian Federation)] [Russian Academy of Sciences, Institute of Theoretical and Applied Electrodynamics (Russian Federation); Lisyansky, A. A. [Queens College of the City University of New York, Department of Physics (United States)] [Queens College of the City University of New York, Department of Physics (United States)

    2013-08-15T23:59:59.000Z

    We consider quantum fluctuations of near fields of a quantum emitter (two-level system (TLS) with population inversion sustained by incoherent pumping) in the near-field zone of a plasmon (metallic) nanoparticle. The spectrum of surface plasmons excited by spontaneous transitions in the quantum emitter is obtained below the lasing threshold of such a system (spaser) in the approximation of a small number of plasmons. It is shown that the relaxation rate is the sum of the quantum emitter's rates of relaxation to its thermal reservoir and the plasmon cavity. The resulting dependence of the average number of plasmons on the pump intensity indicates the nonthreshold nature of the process.

  5. Transition to Landau levels in graphene quantum dots F. Libisch,1,* S. Rotter,1 J. Gttinger,2 C. Stampfer,2,3 and J. Burgdrfer1

    E-Print Network [OSTI]

    Florian, Libisch

    Transition to Landau levels in graphene quantum dots F. Libisch,1,* S. Rotter,1 J. Güttinger,2 C the electronic eigenstates of graphene quantum dots of realistic size up to 80 nm diameter in the presence-level regime at high fields. Details of this transition sensitively depend on the underlying graphene lattice

  6. Transition to Landau levels in graphene quantum dots F. Libisch, 1, * S. Rotter, 1 J. Gttinger, 2 C. Stampfer, 2,3 and J. Burgdrfer 1

    E-Print Network [OSTI]

    Florian, Libisch

    Transition to Landau levels in graphene quantum dots F. Libisch, 1, * S. Rotter, 1 J. Güttinger, 2 investigate the electronic eigenstates of graphene quantum dots of realistic size #up to 80 nm diameter graphene lattice structure, bulk defects, and localization effects at the edges. Key to the understanding

  7. Physica E 32 (2006) 1416 Tuning the cross-gap transition energy of a quantum dot

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    2006-01-01T23:59:59.000Z

    ; Spectroscopy; Energy tuning Self-assembled semiconductor quantum dots (QDs) are of great interest for quantum resistance bridge circuit in combination with a lock in amplifier is used to measure the change in resistance

  8. Theoretical study of intraband optical transitions in conduction band of dot-in-a-well system

    SciTech Connect (OSTI)

    Chaganti, Venkata R.; Apalkov, Vadym [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30302 USA. (Georgia)] [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30302 USA. (Georgia)

    2014-02-15T23:59:59.000Z

    We study numerically absorption optical spectra of n-doped InAs/In{sub 015}Ga{sub 085}As/GaAs quantum dot-in-a-well systems. The absorption spectra are mainly determined by the size of a quantum dot and have weak dependence on the thickness of quantum well and position of the dot in a well. The dot-in-a-well system is sensitive to both in-plane and out-of-plane polarizations of the incident light with much stronger absorption intensities for the in-plane-polarized light. The absorption spectrum of in-plane-polarized light has also a multi-peak structure with two or three peaks of comparable intensities, while the absorption spectrum of out-of-plane polarized light has a single well-pronounced peak.

  9. Indirect and direct optical transitions in In{sub 0.5}Ga{sub 0.5}As/GaP quantum dots

    SciTech Connect (OSTI)

    Stracke, G., E-mail: gernot.stracke@tu-berlin.de; Sala, E. M.; Schliwa, A.; Strittmatter, A.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany); Selve, S. [Zentraleinrichtung Elektronenmikroskopie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany); Niermann, T. [Institut für Optik und Atomare Physik, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany)

    2014-03-24T23:59:59.000Z

    We present a study of self-assembled In{sub 0.5}Ga{sub 0.5}As quantum dots on GaP(001) surfaces linking growth parameters with structural, optical, and electronic properties. Quantum dot densities from 5.0 × 10{sup 7} cm{sup ?2} to 1.5 × 10{sup 11} cm{sup ?2} are achieved. A ripening process during a growth interruption after In{sub 0.5}Ga{sub 0.5}As deposition is used to vary the quantum dot size. The main focus of this work lies on the nature of optical transitions which can be switched from low-efficient indirect to high-efficient direct ones through improved strain relief of the quantum dots by different cap layers.

  10. Creating Direct-write Gray-scale Photomasks with Bimetallic Thin Film Thermal Resists

    E-Print Network [OSTI]

    Chapman, Glenn H.

    that the dots merge to create an exposure intensity that replicates the corresponding gray-scale and 3D energy, resulting alloyed layers appear to become oxides, causing a change of absorption at 365nm from >3 and photoresist strip. Just as in halftone printing, the beam blocking consists of chrome dots whose area varies

  11. Advanced gray rod control assembly

    DOE Patents [OSTI]

    Drudy, Keith J; Carlson, William R; Conner, Michael E; Goldenfield, Mark; Hone, Michael J; Long, Jr., Carroll J; Parkinson, Jerod; Pomirleanu, Radu O

    2013-09-17T23:59:59.000Z

    An advanced gray rod control assembly (GRCA) for a nuclear reactor. The GRCA provides controlled insertion of gray rod assemblies into the reactor, thereby controlling the rate of power produced by the reactor and providing reactivity control at full power. Each gray rod assembly includes an elongated tubular member, a primary neutron-absorber disposed within the tubular member said neutron-absorber comprising an absorber material, preferably tungsten, having a 2200 m/s neutron absorption microscopic capture cross-section of from 10 to 30 barns. An internal support tube can be positioned between the primary absorber and the tubular member as a secondary absorber to enhance neutron absorption, absorber depletion, assembly weight, and assembly heat transfer characteristics.

  12. Grays River Watershed Geomorphic Analysis

    SciTech Connect (OSTI)

    Geist, David R.

    2005-04-30T23:59:59.000Z

    This investigation, completed for the Pacific Northwest National Laboratory (PNNL), is part of the Grays River Watershed and Biological Assessment commissioned by Bonneville Power Administration under project number 2003-013-00 to assess impacts on salmon habitat in the upper Grays River watershed and present recommendations for habitat improvement. This report presents the findings of the geomorphic assessment and is intended to support the overall PNNL project by evaluating the following: 􀂃 The effects of historical and current land use practices on erosion and sedimentation within the channel network 􀂃 The ways in which these effects have influenced the sediment budget of the upper watershed 􀂃 The resulting responses in the main stem Grays River upstream of State Highway 4 􀂃 The past and future implications for salmon habi

  13. QER- Comment of Mike Gray

    Broader source: Energy.gov [DOE]

    The biggest issue with wind energy in ND is the Transmission System. There was a proposal recently by Clean Line Energy This type of forward thinking would allow wind energy to go forward.... The other huge issue is the blockade that the fossil fuel industry has placed on Master Limited Partnerships in 1978!! If the Master Limited Partner Parity Act is passed THAT WOULD BE A GAME CHANGER!! ( this is sponsored bu Senator Coons From DE) Call me directly..... You can also aske Heidi Heitkamp about me.... Mike Gray

  14. Gray molasses cooling of 39 K to a high phase-space density

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    present new techniques in cooling 39 K atoms using laser light close to the D1 transition. First, a newepl draft Gray molasses cooling of 39 K to a high phase-space density G. Salomon1 , L. Fouch´e1 , P, IOGS, CNRS, 351 cours de la Lib´eration, 33405 Talence, France PACS 37.10.De ­ Atom cooling methods

  15. Grays Harbor PUD- Solar Water Heater Loan

    Broader source: Energy.gov [DOE]

    Since October 2001, Grays Harbor PUD has offered a low-interest loan program (currently 4.0%) for the installation of solar water heaters. Loans are available for the installation of solar...

  16. Grays Harbor PUD- Solar Water Heater Rebate

    Broader source: Energy.gov [DOE]

    Since October 2001, Grays Harbor PUD has offered a rebate program for the installation of solar water heaters. Rebates of $600 are available for the installation of solar collectors of 40 square...

  17. Greentree Reservoir Management Matthew J. Gray

    E-Print Network [OSTI]

    Gray, Matthew

    1 Greentree Reservoir Management Matthew J. Gray University of Tennessee Hardwood Bottomlands in Openings Guy Baldassarre Should Manage for Forest Openings >1 acre #12;4 Other Important Functions Bottomline on Bottomlands Hardwood bottomlands are critical ecosystems that play an integral role

  18. Quantum Dots: Theory

    E-Print Network [OSTI]

    Vukmirovic, Nenad

    2010-01-01T23:59:59.000Z

    Petersilka, Density Functional Theory (Springer, New York,Quantum Dots: Theory Nenad Vukmirovi´ and Lin-Wang Wang cdensity functional theory; electronic structure; empirical

  19. A Population Study of the Gray Squirrel in Eastern Texas.

    E-Print Network [OSTI]

    Goodrum, Phil D.

    1940-01-01T23:59:59.000Z

    ................................................ Acknowledgments 32 Summary and Conclusions ......................................... 32 .................................................. Literature Cited 34 POPULA'I'ION STUDY OF THE GRAY SQUIRREL, SCIURUS CAROLINENSIS CAROLINEN- SIS, IN EASTERN TEXAS PHIL...

  20. Grays Harbor PUD- Non-Residential Energy Efficiency Rebate Program

    Broader source: Energy.gov [DOE]

    Grays Harbor PUD's Non-Residential Rebate Program offers financial incentives to its small and large commercial customers, agricultural customers, industrial customers, and institutional customers...

  1. Gray, Maine: Energy Resources | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov You are8COaBulkTransmissionSitingProcess.pdfGetec AG Contracting JumpGoveNebraska: EnergyGratings IncGray, Maine: Energy

  2. Women @ Energy: Neda Gray | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page onYouTube YouTube Note: SinceDevelopment | Department ofPartnershipsAngie CapeceFrancois Women @MelanieMinaNeda Gray Women

  3. Astragalus arrectus Gray Palouse milk-vetch

    E-Print Network [OSTI]

    Fabaceae (pea Family; Astragalus Arrectus; Palouse Milk-vetch; Status Statethreatened; Rank Ggs

    General Description: Erect perennial with a woody taproot and shortly forking caudex; stems numerous, in clumps, 8-16 in. long; herbage green or gray-green; leaves pea-like, glabrous above, 3 to 9 inches long; stipules 3/16 to 5/16 inch long; leaflets mostly 21-31, linear-oblong, lanceolate, 5/16 to inch long; peduncles straight, 4-10 inches long; racemes 15 to 35 flowered; flowers erect, yellowish-white, drying yellowish, about inch long; calyx inch long, the tube c inch long, the teeth about 1/ 16 inch long; petals irregularly graduated, the wings about c inch longer than the abruptly recurved banner, the keel inch long; the pod erect, stipitate, b to 1 inch long, c to inch thick. Identification Tips: Most easily recognized by its irregularly proportioned flowers which ascend from the raceme-axis at an angle of about 45 degrees and are followed by erect, stipitate, dorsally grooved pods of thick texture, pubescent with black or gray-brown, rarely white hairs. The species could be confused with A. leibergii in parts of its range. The flower of A. leibergii is white while the flower of A. arrectus is yellowish white, drying yellow. Also the leaflets of A. arrectus are glabrous above while A. leibergii leaflets are equally pubescent on both sides. Phenology: Flowers from late April to early July. Range: Regional endemic; found along the Lower Snake, Clearwater, and Palouse Rivers in Idaho, and scattered throughout

  4. Evolutionary Ecology Research, 2001, 3: 157177 2001 Gray Stirling

    E-Print Network [OSTI]

    Jensen, Shane T.

    Evolutionary Ecology Research, 2001, 3: 157­177 © 2001 Gray Stirling Does a negative genetic Stirling,1 * Daphne J. Fairbairn,2 Shane Jensen3 and Derek A. Roff1 1 Department of Biology, Mc-off, phenotypic costs. * Address all correspondence to Gray Stirling, Department of Biology, McGill University

  5. Large internal dipole moment in InGaN/GaN quantum dots Irina A. Ostapenko, Gerald Hnig, Christian Kindel, Sven Rodt, Andr Strittmatter et al.

    E-Print Network [OSTI]

    Nabben, Reinhard

    Large internal dipole moment in InGaN/GaN quantum dots Irina A. Ostapenko, Gerald Hönig, Christian transitions in wurtzite InGaN/GaN coupled quantum dot nanowire heterostructures with polarization internal dipole moment in InGaN/GaN quantum dots Irina A. Ostapenko,a Gerald Hönig, Christian Kindel, Sven

  6. Photoconductivity of Si/Ge multilayer structures with Ge quantum dots pseudomorphic to the Si matrix

    SciTech Connect (OSTI)

    Talochkin, A. B., E-mail: tal@thermo.isp.nsc.ru; Chistokhin, I. B. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2011-07-15T23:59:59.000Z

    Longitudinal photoconductivity spectra of Si/Ge multilayer structures with Ge quantum dots grown pseudomorphically to the Si matrix are studied. Lines of optical transitions between hole levels of quantum dots and Si electronic states are observed. This allowed us to construct a detailed energy-level diagram of electron-hole levels of the structure. It is shown that hole levels of pseudomorphic Ge quantum dots are well described by the simplest 'quantum box' model using actual sizes of Ge islands. The possibility of controlling the position of the long-wavelength photosensitivity edge by varying the growth parameters of Si/Ge structures with Ge quantum dots is determined.

  7. Isotopic and internal CX{sub 3} (X=D,H) rotational motion effects in the Ba{center_dot}{center_dot}{center_dot}FCX{sub 3}+h{nu}{yields}BaF+CX{sub 3} intracluster reactions

    SciTech Connect (OSTI)

    Rinaldi, C. A.; Gasmi, K.; Skowronek, S.; Gonzalez Urena, A. [Unidad de Laseres y Haces Moleculares, Instituto Pluridisciplinar, Universidad Complutense de Madrid, Paseo Juan XXIII-1, 28040 Madrid (Spain)

    2006-06-28T23:59:59.000Z

    Photodepletion and action spectra of the laser-induced Ba{center_dot}{center_dot}{center_dot}FCD{sub 3} fragmentation have been measured over the 16 075-16 380 cm{sup -1} range. The observed band and peak structures allowed us to estimate the vibrational and rotational structures of the excited complex at the transition state configuration. The relative reaction probability P{sub R}(E) for the intracluster Ba{center_dot}{center_dot}{center_dot}FCD{sub 3}+h{nu}{yields}BaF+CD{sub 3} reaction has been determined over the cited energy range. P{sub R}(E) shows a peak structure with an energy spacing of 8.9 cm{sup -1} which was attributed to an internal rotation of the CD{sub 3} group in the intermediate state. A comparison with previous Ba{center_dot}{center_dot}{center_dot}FCH{sub 3} photofragmentation spectra reveals the dynamical role of the internal CX{sub 3} (X=H,D) motion which is manifested by the presence of rotational resonances in the laser-induced intracluster reaction.

  8. A Reconfigurable Gate Architecture for Si/SiGe Quantum Dots

    E-Print Network [OSTI]

    D. M. Zajac; T. M. Hazard; X. Mi; K. Wang; J. R. Petta

    2015-02-05T23:59:59.000Z

    We demonstrate a reconfigurable quantum dot gate architecture that incorporates two interchangeable transport channels. One channel is used to form quantum dots and the other is used for charge sensing. The quantum dot transport channel can support either a single or a double quantum dot. We demonstrate few-electron occupation in a single quantum dot and extract charging energies as large as 6.6 meV. Magnetospectroscopy is used to measure valley splittings in the range of 35-70 microeV. By energizing two additional gates we form a few-electron double quantum dot and demonstrate tunable tunnel coupling at the (1,0) to (0,1) interdot charge transition.

  9. A quantum dot heterojunction photodetector

    E-Print Network [OSTI]

    Arango, Alexi Cosmos, 1975-

    2005-01-01T23:59:59.000Z

    This thesis presents a new device architecture for photodetectors utilizing colloidally grown quantum dots as the principle photo-active component. We implement a thin film of cadmium selenide (CdSe) quantum dot sensitizers, ...

  10. Gray Matter Is Targeted in First-Attack Multiple Sclerosis

    SciTech Connect (OSTI)

    Schutzer, Steven E.; Angel, Thomas E.; Liu, Tao; Schepmoes, Athena A.; Xie, Fang; Bergquist, Jonas P.; Vecsei, Lazlo'; Zadori, Denes; Camp, David G.; Holland, Bart K.; Smith, Richard D.; Coyle, Patricia K.

    2013-09-10T23:59:59.000Z

    The cause of multiple sclerosis (MS), its driving pathogenesis at the earliest stages, and what factors allow the first clinical attack to manifest remain unknown. Some imaging studies suggest gray rather than white matter may be involved early, and some postulate this may be predictive of developing MS. Other imaging studies are in conflict. To determine if there was objective molecular evidence of gray matter involvement in early MS we used high-resolution mass spectrometry to identify proteins in the cerebrospinal fluid (CSF) of first-attack MS patients (two independent groups) compared to established relapsing remitting (RR) MS and controls. We found that the CSF proteins in first-attack patients were differentially enriched for gray matter components (axon, neuron, synapse). Myelin components did not distinguish these groups. The results support that gray matter dysfunction is involved early in MS, and also may be integral for the initial clinical presentation.

  11. Essays on Supply Chains Facing Competition from Gray Markets

    E-Print Network [OSTI]

    Iravani, Foad

    2012-01-01T23:59:59.000Z

    University. Bangkok Post. 2010. BMW Thailand to No Longernews-amp-analysis/ bmw-thailand-no-longer-service-gray-2011b). Prior to Mercedes-Benz, BMW Thailand had decided to

  12. Enhanced Two-Photon Processes in Quantum Dots inside Photonic Crystal Nanocavities and Quantum Information Processing Applications

    E-Print Network [OSTI]

    Ziliang Lin; Jelena Vuckovic

    2009-07-02T23:59:59.000Z

    We show that the two-photon transition rates of quantum dots coupled to nanocavities are enhanced by up to 8 orders of magnitude relative to quantum dots in bulk host. We then propose how to take advantage of this enhancement to implement coherent quantum dot excitation by two-photon absorption, entangled photon pair generation by two-photon spontaneous emission, and single-photon generation at telecommunication wavelengths by two-photon stimulated and spontaneous emission.

  13. DOT WEB PAGES (plain text) 1 DOT WWW Pages --Plain Text Copy June 15, 2014

    E-Print Network [OSTI]

    Rutten, Rob

    ://www.staff.science.uu.nl/ rutte101/dot Plain version: no images, photographs or figures Contents 1 DOT news 1 2 DOT at a glance 2. The DOT website is now at http://www.staff.science.uu.nl/~rutte101/dot. The DOT database is now at ftp

  14. On 3-gauge transformations, 3-curvatures, and Gray-categories

    SciTech Connect (OSTI)

    Wang, Wei, E-mail: wwang@zju.edu.cn [Department of Mathematics, Zhejiang University, Zhejiang 310027 (China)] [Department of Mathematics, Zhejiang University, Zhejiang 310027 (China)

    2014-04-15T23:59:59.000Z

    In the 3-gauge theory, a 3-connection is given by a 1-form A valued in the Lie algebra g, a 2-form B valued in the Lie algebra h, and a 3-form C valued in the Lie algebra l, where (g,h,l) constitutes a differential 2-crossed module. We give the 3-gauge transformations from one 3-connection to another, and show the transformation formulae of the 1-curvature 2-form, the 2-curvature 3-form, and the 3-curvature 4-form. The gauge configurations can be interpreted as smooth Gray-functors between two Gray 3-groupoids: the path 3-groupoid P{sub 3}(X) and the 3-gauge group G{sup L} associated to the 2-crossed module L, whose differential is (g,h,l). The derivatives of Gray-functors are 3-connections, and the derivatives of lax-natural transformations between two such Gray-functors are 3-gauge transformations. We give the 3-dimensional holonomy, the lattice version of the 3-curvature, whose derivative gives the 3-curvature 4-form. The covariance of 3-curvatures easily follows from this construction. This Gray-categorical construction explains why 3-gauge transformations and 3-curvatures have the given forms. The interchanging 3-arrows are responsible for the appearance of terms with the Peiffer commutator (, )

  15. Nontoxic quantum dot research improves solar cells

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Nontoxic quantum dot research improves solar cells Nontoxic quantum dot research improves solar cells Solar cells made with low-cost, nontoxic copper-based quantum dots can achieve...

  16. A comparison between semi-spheroid- and dome-shaped quantum dots coupled to wetting layer

    SciTech Connect (OSTI)

    Shahzadeh, Mohammadreza; Sabaeian, Mohammad, E-mail: Sabaeian@scu.ac.ir [Physics Department, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, 61357-43135 (Iran, Islamic Republic of)

    2014-06-15T23:59:59.000Z

    During the epitaxial growth method, self-assembled semi-spheroid-shaped quantum dots (QDs) are formed on the wetting layer (WL). However for sake of simplicity, researchers sometimes assume semi-spheroid-shaped QDs to be dome-shaped (hemisphere). In this work, a detailed and comprehensive study on the difference between electronic and transition properties of dome- and semi-spheroid-shaped quantum dots is presented. We will explain why the P-to-S intersubband transition behaves the way it does. The calculated results for intersubband P-to-S transition properties of quantum dots show two different trends for dome-shaped and semi-spheroid-shaped quantum dots. The results are interpreted using the probability of finding electron inside the dome/spheroid region, with emphasis on the effects of wetting layer. It is shown that dome-shaped and semi-spheroid-shaped quantum dots feature different electronic and transition properties, arising from the difference in lateral dimensions between dome- and semi-spheroid-shaped QDs. Moreover, an analogy is presented between the bound S-states in the quantum dots and a simple 3D quantum mechanical particle in a box, and effective sizes are calculated. The results of this work will benefit researchers to present more realistic models of coupled QD/WL systems and explain their properties more precisely.

  17. The effect of Coulomb interactions on thermoelectric properties of quantum dots

    SciTech Connect (OSTI)

    Zimbovskaya, Natalya A. [Department of Physics and Electronics, University of Puerto Rico-Humacao, CUH Station, Humacao, Puerto Rico 00791, USA and Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Ruco 00931 (United States)] [Department of Physics and Electronics, University of Puerto Rico-Humacao, CUH Station, Humacao, Puerto Rico 00791, USA and Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Ruco 00931 (United States)

    2014-03-14T23:59:59.000Z

    Thermoelectric effects in a quantum dot coupled to the source and drain charge reservoirs are explored using a nonequilibrium Green's functions formalism beyond the Hartree-Fock approximation. Thermal transport is analyzed within a linear response regime. A transition from Coulomb blockade regime to Kondo regime in thermoelectric transport through a single-level quantum dot is traced using unified approximations for the relevant Green's functions.

  18. Global Warming: Connecting the Dots

    E-Print Network [OSTI]

    Hansen, James E.

    Global Warming: Connecting the Dots from Causes to Solutions* Jim Hansen 26 February 2007 National://www.columbia.edu/~jeh1/worldwatch_nov2006.pdf) 5. Communicating dangers and opportunities in global warming, Amer-16, 2006. (http://pubs.giss.nasa.gov/docs/2006/2006_Hansen.pdf) 8. Global warming: Connecting the dots from

  19. Nanoscale engineering boosts performance of quantum dot light...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Quantum dot light emitting diodes Nanoscale engineering boosts performance of quantum dot light emitting diodes Quantum dots are nano-sized semiconductor particles whose emission...

  20. Financial and Technical Resources for Completing Energy Efficiency Projects - The DOT/FTA Perspective

    E-Print Network [OSTI]

    Koski, D.

    2011-01-01T23:59:59.000Z

    ://www.ctod.org/portal/ ? National Transit Institute ? Courses on Land Use/Transportation and Transit Oriented Development ? www.ntionline.com FTA Livability Resource Examples Transportation Planning Capacity Building Program http://planning.dot.gov/ Tools for Regional... Planning for Transit- oriented Development : 1. The Transportation Planning Capacity Building (TPCB) Peer Program is a resource for agencies in need of planning assistance 2. Scenario planning webinars and workshops Additional Resources http://www.sustainablecommunities.gov ...

  1. Discrete Mathematics and Theoretical Computer Science DMTCS vol. 9:2, 2007, 145152 Gray code order for Lyndon words

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Discrete Mathematics and Theoretical Computer Science DMTCS vol. 9:2, 2007, 145­152 Gray code order order yields a Gray code on the Lyndon family. In this paper we give a positive answer. More precisely and Lyndon words in Gray code order. Keywords: Lyndon words, Gray codes, generating algorithms 1 Introduction

  2. Historical bathymetric changes near the entrance to Grays Harbor, Washington

    SciTech Connect (OSTI)

    Burch, T.L.; Sherwood, C.R. (Battelle/Marine Sciences Lab., Sequim, WA (United States))

    1992-12-01T23:59:59.000Z

    Large changes in the distribution of sediment near the entrance to Grays Harbor, Washington, have occurred since the long rock jetties were built to confine flow. Spits to the north and south of the entrance have grown, the entrance channel has deepened, and the outer bar has eroded and moved offshore. The shorelines of North Beach and South Beach have experienced significant amounts of both erosion and accretion since the jetties were constructed around the turn of the century. Recently, the erosion rate at South Beach has increased and, because Half Moon Bay is growing at the expense of the shoreward side of Point Chehalis, the vegetated portion of the spit is now less than 350 ft wide at the narrowest section. The US Army Corps of Engineers, Seattle District, requested that Battelle/Marine Sciences Laboratory evaluate long-term trends in erosion near the entrance to Grays Harbor.

  3. Grays River Watershed and Biological Assessment Final Report 2006.

    SciTech Connect (OSTI)

    May, Christopher W.; McGrath, Kathleen E.; Geist, David R. [Pacific Northwest National Laboratory; Abbe, Timothy; Barton, Chase [Herrera Environmental Consultants, Inc.

    2008-02-04T23:59:59.000Z

    The Grays River Watershed and Biological Assessment was funded to address degradation and loss of spawning habitat for chum salmon (Onchorhynchus keta) and fall Chinook salmon (Onchoryhnchus tshawytscha). In 1999, the National Marine Fisheries Service listed lower Columbia River chum salmon as a threatened Evolutionarily Significant Unit (ESU) under the Endangered Species Act of 1973 (ESA). The Grays River watershed is one of two remaining significant chum salmon spawning locations in this ESU. Runs of Grays River chum and Chinook salmon have declined significantly during the past century, largely because of damage to spawning habitat associated with timber harvest and agriculture in the watershed. In addition, approximately 20-25% of the then-remaining chum salmon spawning habitat was lost during a 1999 channel avulsion that destroyed an important artificial spawning channel operated by the Washington Department of Fish and Wildlife (WDFW). Although the lack of stable, high-quality spawning habitat is considered the primary physical limitation on Grays River chum salmon production today, few data are available to guide watershed management and channel restoration activities. The objectives of the Grays River Watershed and Biological Assessment project were to (1) perform a comprehensive watershed and biological analysis, including hydrologic, geomorphic, and ecological assessments; (2) develop a prioritized list of actions that protect and restore critical chum and Chinook salmon spawning habitat in the Grays River based on comprehensive geomorphic, hydrologic, and stream channel assessments; and (3) gain a better understanding of chum and Chinook salmon habitat requirements and survival within the lower Columbia River and the Grays River. The watershed-based approach to river ecosystem restoration relies on a conceptual framework that describes general relationships between natural landscape characteristics, watershed-scale habitat-forming processes, aquatic habitat conditions, and biological integrity. In addition, human land-use impacts are factored into the conceptual model because they can alter habitat quality and can disrupt natural habitat-forming processes. In this model (Figure S.1), aquatic habitat--both instream and riparian--is viewed as the link between watershed conditions and biologic responses. Based on this conceptual model, assessment of habitat loss and the resultant declines in salmonid populations can be conducted by relating current and historical (e.g., natural) habitat conditions to salmonid utilization, diversity, and abundance. In addition, assessing disrupted ecosystem functions and processes within the watershed can aid in identifying the causes of habitat change and the associated decline in biological integrity. In this same way, restoration, enhancement, and conservation projects can be identified and prioritized. A watershed assessment is primarily a landscape-scale evaluation of current watershed conditions and the associated hydrogeomorphic riverine processes. The watershed assessment conducted for this project focused on watershed processes that form and maintain salmonid habitat. Landscape metrics describing the level of human alteration of natural ecosystem attributes were used as indicators of water quality, hydrology, channel geomorphology, instream habitat, and biotic integrity. Ecological (watershed) processes are related to and can be predicted based on specific aspects of spatial pattern. This study evaluated the hydrologic regime, sediment delivery regime, and riparian condition of the sub-watersheds that comprise the upper Grays River watershed relative to their natural range of conditions. Analyses relied primarily on available geographic information system (GIS) data describing landscape characteristics such as climate, vegetation type and maturity, geology and soils, topography, land use, and road density. In addition to watershed-scale landscape characteristics, the study area was also evaluated on the riparian scale, with appropriate landscape variables analyzed within

  4. Grays River Watershed and Biological Assessment, 2006 Final Report.

    SciTech Connect (OSTI)

    May, Christopher; Geist, David [Pacific Northwest National Laboratory

    2007-04-01T23:59:59.000Z

    The Grays River Watershed and Biological Assessment was funded to address degradation and loss of spawning habitat for chum salmon (Onchorhynchus keta) and fall Chinook salmon (Onchoryhnchus tshawytscha). In 1999, the National Marine Fisheries Service listed lower Columbia River chum salmon as a threatened Evolutionarily Significant Unit (ESU) under the Endangered Species Act of 1973 (ESA). The Grays River watershed is one of two remaining significant chum salmon spawning locations in this ESU. Runs of Grays River chum and Chinook salmon have declined significantly during the past century, largely because of damage to spawning habitat associated with timber harvest and agriculture in the watershed. In addition, approximately 20-25% of the then-remaining chum salmon spawning habitat was lost during a 1999 channel avulsion that destroyed an important artificial spawning channel operated by the Washington Department of Fish and Wildlife (WDFW). Although the lack of stable, high-quality spawning habitat is considered the primary physical limitation on Grays River chum salmon production today, few data are available to guide watershed management and channel restoration activities. The objectives of the Grays River Watershed and Biological Assessment project were to (1) perform a comprehensive watershed and biological analysis, including hydrologic, geomorphic, and ecological assessments; (2) develop a prioritized list of actions that protect and restore critical chum and Chinook salmon spawning habitat in the Grays River based on comprehensive geomorphic, hydrologic, and stream channel assessments; and (3) gain a better understanding of chum and Chinook salmon habitat requirements and survival within the lower Columbia River and the Grays River. The watershed-based approach to river ecosystem restoration relies on a conceptual framework that describes general relationships between natural landscape characteristics, watershed-scale habitat-forming processes, aquatic habitat conditions, and biological integrity. In addition, human land-use impacts are factored into the conceptual model because they can alter habitat quality and can disrupt natural habitat forming processes. In this model (Figure S.1), aquatic habitat--both instream and riparian--is viewed as the link between watershed conditions and biologic responses. Based on this conceptual model, assessment of habitat loss and the resultant declines in salmonid populations can be conducted by relating current and historical (e.g., natural) habitat conditions to salmonid utilization, diversity, and abundance. In addition, assessing disrupted ecosystem functions and processes within the watershed can aid in identifying the causes of habitat change and the associated decline in biological integrity. In this same way, restoration, enhancement, and conservation projects can be identified and prioritized. A watershed assessment is primarily a landscape-scale evaluation of current watershed conditions and the associated hydrogeomorphic riverine processes. The watershed assessment conducted for this project focused on watershed processes that form and maintain salmonid habitat. Landscape metrics describing the level of human alteration of natural ecosystem attributes were used as indicators of water quality, hydrology, channel geomorphology, instream habitat, and biotic integrity. Ecological (watershed) processes are related to and can be predicted based on specific aspects of spatial pattern. This study evaluated the hydrologic regime, sediment delivery regime, and riparian condition of the sub-watersheds that comprise the upper Grays River watershed relative to their natural range of conditions. Analyses relied primarily on available geographic information system (GIS) data describing landscape characteristics such as climate, vegetation type and maturity, geology and soils, topography, land use, and road density. In addition to watershed-scale landscape characteristics, the study area was also evaluated on the riparian scale, with appropriate landscape variables analyzed within

  5. DOT`s perspective on in-line inspection

    SciTech Connect (OSTI)

    Ulrich, L.W. [Dept. of Transportation, Washington, DC (United States). Office of Pipeline Safety

    1996-12-01T23:59:59.000Z

    The US Department of Transportation (DOT) and its Office of Pipeline Safety (OPS) have been involved with in-line inspection (ILI) pigs since the construction of the Alaska crude oil pipeline. Congressionally mandated reports concerning ILI pigs, and a regulation requiring new and replaced pipe and components be designed and constructed to accommodate ILI pigs, were issued by DOT. DOT also may mandate ILI pigs to be run on some pipelines. There is no current federal requirement to run ILI pigs. They are required by OPS in selected compliance cases. DOT supports future ILI pig research. The use of ILI pig surveys, incorporated in pipeline operators` future risk management plans developed as safety alternatives to the established pipeline safety regulations, will be supported.

  6. A fractal set from the binary reflected Gray code

    E-Print Network [OSTI]

    J. A. Oteo; J. Ros

    2005-10-14T23:59:59.000Z

    The permutation associated with the decimal expression of the binary reflected Gray code with $N$ bits is considered. Its cycle structure is studied. Considered as a set of points, its self-similarity is pointed out. As a fractal, it is shown to be the attractor of a IFS. For large values of $N$ the set is examined from the point of view of time series analysis

  7. New framework hydrous silicate K{sub 3}Sc[Si{sub 3}O{sub 9}] {center_dot} H{sub 2}O related to the high-temperature anhydrous silicate K{sub 3}Ho[Si{sub 3}O{sub 9}] and symmetry analysis of a phase transition with prediction of structures

    SciTech Connect (OSTI)

    Belokoneva, E. L., E-mail: elbel@geol.msu.ru; Zorina, A. P.; Dimitrova, O. V. [Moscow State University, Faculty of Geology (Russian Federation)

    2013-07-15T23:59:59.000Z

    Crystals of a new framework silicate K{sub 3}Sc[Si{sub 3}O{sub 9}] {center_dot} H{sub 2}O, space group Pm2{sub 1}n (nonstandard setting of space group Pmn2{sub 1} = C{sub 2v}{sup 7}), are obtained under hydrothermal conditions. The structure is determined without preliminary knowledge of the chemical formula. The absolute configuration is determined. The structure is close to that of the high-temperature K{sub 3}Ho[Si{sub 3}O{sub 9}] phase, which was obtained upon the heating of K{sub 3}HoSi{sub 3}O{sub 8}(OH){sub 2}. This structural similarity is due to the specific conditions of synthesis and an analogous formula, where holmium is replaced by scandium. A symmetry analysis shows that the high local symmetry of a block (rod) is responsible for the first-order phase transition of both the order-disorder (OD) and displacement type. The number of structures in which the simplest and high-symmetry layers are multiplied by different symmetry elements are predicted.

  8. An advanced gray-scale technology and its applications to micro-devices

    E-Print Network [OSTI]

    Zhou, Zhou

    2009-01-01T23:59:59.000Z

    of photosensitive polyimide and its graphitization”, Proc.of photosensitive polyimide and its graphitization [17]. Indeveloping photosensitive polyimide, HD8820. Gray Scale

  9. Fracture toughness studies of gray and ductile cast irons using a J-integral approach 

    E-Print Network [OSTI]

    Floyd, Donna Lynne Woodall

    1981-01-01T23:59:59.000Z

    , and silicon in which more carbon is present than can be retained in solid solution in austenite at the eutectic temperature. In gray cast iron, the iron and carbon solidify as a eutectic structure whose two phases are graphite and iron. Gray iron usually... contains from 1. 7 to 4. 5% carbon and 1 to 3% silicon. 27 The normal microstructure of gray iron is a matrix of pearlite (ferrite and cementite) with the graphite flakes dispersed throughout. Among the properties that the flake graphite 28 in gray...

  10. Grays Harbor County, Washington: Energy Resources | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov You are8COaBulkTransmissionSitingProcess.pdfGetec AG Contracting JumpGoveNebraska: EnergyGratings IncGray, Maine:

  11. Single charge sensing and transport in double quantum dots fabricated from commercially grown Si/SiGe heterostructures

    E-Print Network [OSTI]

    Payette, C; Koppinen, P J; Dovzhenko, Y; Sturm, J C; Petta, J R

    2011-01-01T23:59:59.000Z

    We perform quantum Hall measurements on three types of commercially available modulation doped Si/SiGe heterostructures to determine their suitability for depletion gate defined quantum dot devices. By adjusting the growth parameters, we are able to achieve electron gases with charge densities 1-3 X 10^{11}/cm^2 and mobilities in excess of 100,000 cm^2/Vs. Double quantum dot devices fabricated on these heterostructures show clear evidence of single charge transitions as measured in dc transport and charge sensing and exhibit electron temperatures of 100 mK in the single quantum dot regime.

  12. Single charge sensing and transport in double quantum dots fabricated from commercially grown Si/SiGe heterostructures

    E-Print Network [OSTI]

    C. Payette; K. Wang; P. J. Koppinen; Y. Dovzhenko; J. C. Sturm; J. R. Petta

    2012-03-21T23:59:59.000Z

    We perform quantum Hall measurements on three types of commercially available modulation doped Si/SiGe heterostructures to determine their suitability for depletion gate defined quantum dot devices. By adjusting the growth parameters, we are able to achieve electron gases with charge densities 1-3 X 10^{11}/cm^2 and mobilities in excess of 100,000 cm^2/Vs. Double quantum dot devices fabricated on these heterostructures show clear evidence of single charge transitions as measured in dc transport and charge sensing and exhibit electron temperatures of 100 mK in the single quantum dot regime.

  13. Quasiresonant Excitation of InP/InGaP Quantum Dots Using Second Harmonic Generated in a Photonic Crystal Cavity

    E-Print Network [OSTI]

    Buckley, Sonia; Hatami, Fariba; Vuckovic, Jelena

    2012-01-01T23:59:59.000Z

    Indistinguishable single photons are necessary for quantum information processing applications. Resonant or quasiresonant excitation of single quantum dots provides greater single photon indistinguishability than incoherent pumping, but is also more challenging experimentally. Here, we demonstrate high signal to noise quasiresonant excitation of InP/InGaP quantum dots. The excitation is provided via second harmonic generated from a telecommunications wavelength laser resonant with the fundamental mode of a photonic crystal cavity, fabricated at twice the quantum dot transition wavelength. The second harmonic is generated using the \\chi(2) nonlinearity of the InGaP material matrix.

  14. Quasiresonant Excitation of InP/InGaP Quantum Dots Using Second Harmonic Generated in a Photonic Crystal Cavity

    E-Print Network [OSTI]

    Sonia Buckley; Kelley Rivoire; Fariba Hatami; Jelena Vuckovic

    2012-10-03T23:59:59.000Z

    Indistinguishable single photons are necessary for quantum information processing applications. Resonant or quasiresonant excitation of single quantum dots provides greater single photon indistinguishability than incoherent pumping, but is also more challenging experimentally. Here, we demonstrate high signal to noise quasiresonant excitation of InP/InGaP quantum dots. The excitation is provided via second harmonic generated from a telecommunications wavelength laser resonant with the fundamental mode of a photonic crystal cavity, fabricated at twice the quantum dot transition wavelength. The second harmonic is generated using the \\chi(2) nonlinearity of the InGaP material matrix.

  15. Double superexchange in quantum dot mesomaterials

    E-Print Network [OSTI]

    Wu, Zhigang

    of defects,2 and resist oxidation better.3 In addition, these small dots use their slice of the solar. An idea that has been explored for larger dots is to encapsulate them within an inorganic amorphous matrix yet to be achieved. A second approach is to encapsulate the dots within an organic polymer blend.12

  16. Modeling transport of disposed dredged material from placement sites in Grays Harbor, WA

    E-Print Network [OSTI]

    US Army Corps of Engineers

    Modeling transport of disposed dredged material from placement sites in Grays Harbor, WA E- to mid- term dredge material management strategies for the Federal Navigation Project at Grays Harbor dredging quantities. However, the most heavily used dredged material placement sites lie in proximity

  17. A `Hot Potato' Gray Code for Permutations Xi Sisi Shen 1,3

    E-Print Network [OSTI]

    Williams, Aaron

    A `Hot Potato' Gray Code for Permutations Xi Sisi Shen 1,3 Department of Mathematics and Statistics by the chil- dren's game of Hot Potato. Our order is a transposition Gray code, meaning that consecutive) It must transpose value n (the "hot potato"); (2) It must transpose positions that are circularly adjacent

  18. Modeling of the quantum dot filling and the dark current of quantum dot infrared photodetectors

    SciTech Connect (OSTI)

    Ameen, Tarek A.; El-Batawy, Yasser M.; Abouelsaood, A. A. [Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza (Egypt)

    2014-02-14T23:59:59.000Z

    A generalized drift-diffusion model for the calculation of both the quantum dot filling profile and the dark current of quantum dot infrared photodetectors is proposed. The confined electrons inside the quantum dots produce a space-charge potential barrier between the two contacts, which controls the quantum dot filling and limits the dark current in the device. The results of the model reasonably agree with a published experimental work. It is found that increasing either the doping level or the temperature results in an exponential increase of the dark current. The quantum dot filling turns out to be nonuniform, with a dot near the contacts containing more electrons than one in the middle of the device where the dot occupation approximately equals the number of doping atoms per dot, which means that quantum dots away from contacts will be nearly unoccupied if the active region is undoped.

  19. Optoelectronic devices utilizing materials having enhanced electronic transitions

    DOE Patents [OSTI]

    Black, Marcie R. (Newton, MA)

    2011-02-22T23:59:59.000Z

    An optoelectronic device that includes a material having enhanced electronic transitions. The electronic transitions are enhanced by mixing electronic states at an interface. The interface may be formed by a nano-well, a nano-dot, or a nano-wire.

  20. Optoelectronic devices utilizing materials having enhanced electronic transitions

    DOE Patents [OSTI]

    Black, Marcie R.

    2013-04-09T23:59:59.000Z

    An optoelectronic device that includes a material having enhanced electronic transitions. The electronic transitions are enhanced by mixing electronic states at an interface. The interface may be formed by a nano-well, a nano-dot, or a nano-wire.

  1. Superconducting transition temperature in heterogeneous ferromagnet-superconductor systems

    E-Print Network [OSTI]

    Pokrovsky, Valery L.; Wei, HD.

    2004-01-01T23:59:59.000Z

    We study the superconducting phase transition in two systems: ferromagnet-superconductor bilayer (FSB) and a thin superconducting film with a periodic array of magnetic dots (SFMD) upon it. We show that this transition is of the first order in FSB...

  2. Efficient all-optical production of large $^6$Li quantum gases using D$_1$ gray-molasses cooling

    E-Print Network [OSTI]

    A. Burchianti; G. Valtolina; J. A. Seman; E. Pace; M. De Pas; M. Inguscio; M. Zaccanti; G. Roati

    2014-06-18T23:59:59.000Z

    We use a gray molasses operating on the D$_1$ atomic transition to produce degenerate quantum gases of $^{6}$Li with a large number of atoms. This sub-Doppler cooling phase allows us to lower the initial temperature of 10$^9$ atoms from 500 to 40 $\\mu$K in 2 ms. We observe that D$_1$ cooling remains effective into a high-intensity infrared dipole trap where two-state mixtures are evaporated to reach the degenerate regime. We produce molecular Bose-Einstein condensates of up to 5$\\times$10$^{5}$ molecules and weakly-interacting degenerate Fermi gases of $7\\times$10$^{5}$ atoms at $T/T_{F}<0.1$ with a typical experimental duty cycle of 11 seconds.

  3. Heat induced nanoforms of zinc oxide quantum dots and their characterization

    SciTech Connect (OSTI)

    Dey, Anindita [Jadavpur University, Physics Department (India); Basu, Ruma [Jogamaya Devi College, Physics department (India); Das, Sukhen, E-mail: sukhendasju@gmail.com; Nandy, Papiya [Jadavpur University, Physics Department (India)

    2012-02-15T23:59:59.000Z

    In our studies we observed heat induced phase transitions of Zinc oxide quantum dots at 60, 200, 360 and 400 Degree-Sign C, where all the transitions were irreversible except the transition at 60 Degree-Sign C which wasa reversible one. The phase transition at 60 Degree-Sign C indicated a heat induced conformational change which was supported here by studying polarizing micrographs of ZnO quantum dots thin film. The X-ray diffraction studies of the sample fired at different temperatures as indicated by the thermal analysis were performed in order to understand the changes occurred due to transitions. The study also indicated a new and simple approach to develop ZnO nanorods by just thermal decomposition of the ZnO quantum dots firing in furnace at 200 Degree-Sign C with 2h soaking. In order to have a proper insight of the structural changes we performed scanning electron microscopy. Optical characterization was done by UV-Vis and fluorescence spectrophotometer.

  4. Transition metal oxide improves overall efficiency and maintains performance with inexpensive metals.

    E-Print Network [OSTI]

    Transition metal oxide improves overall efficiency and maintains performance with inexpensive that inserting a transition metal oxide (TMO) between the lead sulfide (PbS) quantum dot (QD) layer and the metal-Yu Chen; Octavi E. Semonin; Arthur J. Nozik; Randy J. Ellingson; Matthew C. Beard."n-Type Transition Metal

  5. Pervious Pavement A Strategic Plan For NYC DOT

    E-Print Network [OSTI]

    Qian, Ning

    Pervious Pavement A Strategic Plan For NYC DOT Presented By: Rene Brana Spring 2012 Capstone: Pervious Pavement - A Strategic Plan for NYC DOT 2 Capstone: Pervious Pavement - A Strategic Plan for NYC DOT 3 Image courtesy of

  6. Dynamics of Quantum Dot Photonic Crystal Lasers

    E-Print Network [OSTI]

    Bryan Ellis; Ilya Fushman; Dirk Englund; Bingyang Zhang; Yoshihisa Yamamoto; Jelena Vuckovic

    2007-03-07T23:59:59.000Z

    Quantum dot photonic crystal membrane lasers were fabricated and the large signal modulation characteristics were studied. We find that the modulation characteristics of quantum dot lasers can be significantly improved using cavities with large spontaneous emission coupling factor. Our experiments show, and simulations confirm, that the modulation rate is limited by the rate of carrier capture into the dots to around 30GHz in our present system.

  7. Quantum Dot Light Emitting Diode

    SciTech Connect (OSTI)

    Kahen, Keith

    2008-07-31T23:59:59.000Z

    The project objective is to create low cost coatable inorganic light emitting diodes, composed of quantum dot emitters and inorganic nanoparticles, which have the potential for efficiencies equivalent to that of LEDs and OLEDs and lifetime, brightness, and environmental stability between that of LEDs and OLEDs. At the end of the project the Recipient shall gain an understanding of the device physics and properties of Quantum-Dot LEDs (QD-LEDs), have reliable and accurate nanocrystal synthesis routines, and have formed green-yellow emitting QD-LEDs with a device efficiency greater than 3 lumens/W, a brightness greater than 400 cd/m{sup 2}, and a device operational lifetime of more than 1000 hours. Thus the aim of the project is to break the current cost-efficiency paradigm by creating novel low cost inorganic LEDs composed of inorganic nanoparticles.

  8. Quantum Dot Light Emitting Diode

    SciTech Connect (OSTI)

    Keith Kahen

    2008-07-31T23:59:59.000Z

    The project objective is to create low cost coatable inorganic light emitting diodes, composed of quantum dot emitters and inorganic nanoparticles, which have the potential for efficiencies equivalent to that of LEDs and OLEDs and lifetime, brightness, and environmental stability between that of LEDs and OLEDs. At the end of the project the Recipient shall gain an understanding of the device physics and properties of Quantum-Dot LEDs (QD-LEDs), have reliable and accurate nanocrystal synthesis routines, and have formed green-yellow emitting QD-LEDs with a device efficiency greater than 3 lumens/W, a brightness greater than 400 cd/m2, and a device operational lifetime of more than 1000 hours. Thus the aim of the project is to break the current cost-efficiency paradigm by creating novel low cost inorganic LEDs composed of inorganic nanoparticles.

  9. Electron counting in quantum dots

    E-Print Network [OSTI]

    Fominov, Yakov

    source drain pg M. Sigrist Ciorga et al., PRB 61, R16315 (2000) Elzerman et al. PRB 67, 161308 (2003) #12 extreme near field optics #12;Photons or phonons? GaAs InAs Gustavsson et al., PRB 78, 035324 (2008) #12S. Schnez et al. PRB 78 (2008) 140 nm circular dot 1000-100-200 Energy (meV) 0 2 4 6 8 B(T) 0 100 200

  10. Temperature-Dependent Electron Transport in Quantum Dot Photovoltaics

    E-Print Network [OSTI]

    Padilla, Derek

    2013-01-01T23:59:59.000Z

    4.4 Photovoltaics in Practice . . . . . . . . . . . . . .milestones. Quantum dot photovoltaics is in the bottom-rightIN QUANTUM DOT PHOTOVOLTAICS A dissertation submitted in

  11. Temperature-Dependent Electron Transport in Quantum Dot Photovoltaics

    E-Print Network [OSTI]

    Padilla, Derek

    2013-01-01T23:59:59.000Z

    cell efficiency milestones. Quantum dot photovoltaics is inphotovoltaics provide the potential to create high-efficiencycell efficiency milestones. Quantum dot photovoltaics is in

  12. Sclerosing cellular blue nevus simulating melanoma

    E-Print Network [OSTI]

    Aydingoz, Ikbal Esen; Dikicioglu-Cetin, Emel

    2012-01-01T23:59:59.000Z

    in close association with slate gray pigmented dots inin close association with slate gray pigmented dots incollagenized fibrosis. The slate blue dots were regarded as

  13. Anthropogenic Disturbance of Western Gray Whale Behavior Off Sakhalin Island, Russia 

    E-Print Network [OSTI]

    Gailey, Glenn Andrew

    2013-05-14T23:59:59.000Z

    , the western gray whale population face several threats to their future survival. On their only known feeding grounds off the northeastern coast of Sakhalin Island, Russia, anthropogenic activity has increased in the past decade due to oil and gas exploration...

  14. DRAFT Lower Columbia Salmon and Steelhead Recovery Plan GRAYS II, 3-1 May 2004

    E-Print Network [OSTI]

    . Approximately 95% of the Grays Subbasin is forested and commercial timber companies own 73% of the land. State ownership comprises the bulk of the remaining lands. Much of the basin has been impacted by timber harvest

  15. Petrographic, stratigraphic, and structural study of the Smackover gray sand (Jurassic) in north Louisiana

    SciTech Connect (OSTI)

    Miciotto, S.A.

    1980-01-01T23:59:59.000Z

    The gas-producing gray sand, a dark gray to black, very fine-grained sand, occurs as 3 sand tongues in the lower member of the Smackover Formation in the subsurface of Bossier, Webster, Claiborne, and Lincoln parishes, Louisiana. A Flaser-bedded silty shale facies indicates deposition on a mid-tidal flat environment. Smackover deposition during the Jurassic in the study area was located on the gently dipping slope between a broad coastal shelf to the north and a basin to the south. The gray sand was deposited over the Norphlet formation and Louann salt before flowage and swelling of the Louann salt began. Uplift and swelling of the Louann salt later in the Jurassic created growing anticlines; sediment slumped off the structural highs of the growing salt anticlines into basinal muds and silts. The Smackover gray sand continues to challenge exploration geologists because of the lateral pinch out of its sand tongues. 11 references.

  16. Gray Level Co-Occurrence Matrices: Generalisation and Some New Features

    E-Print Network [OSTI]

    Sebastian, Bino; Balakrishnan, Kannan

    2012-01-01T23:59:59.000Z

    Gray Level Co-occurrence Matrices (GLCM) are one of the earliest techniques used for image texture analysis. In this paper we defined a new feature called trace extracted from the GLCM and its implications in texture analysis are discussed in the context of Content Based Image Retrieval (CBIR). The theoretical extension of GLCM to n-dimensional gray scale images are also discussed. The results indicate that trace features outperform Haralick features when applied to CBIR.

  17. Single-dot optical emission from ultralow density well-isolated InP quantum dots

    SciTech Connect (OSTI)

    Ugur, A.; Hatami, F.; Masselink, W. T. [Department of Physics, Humboldt-Universitaet zu Berlin, Newtonstrasse 15, D-12489 Berlin (Germany); Vamivakas, A. N.; Lombez, L.; Atatuere, M. [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2008-10-06T23:59:59.000Z

    We demonstrate a straightforward way to obtain single well-isolated quantum dots emitting in the visible part of the spectrum and characterize the optical emission from single quantum dots using this method. Self-assembled InP quantum dots are grown using gas-source molecular-beam epitaxy over a wide range of InP deposition rates, using an ultralow growth rate of about 0.01 atomic monolayers/s, a quantum-dot density of 1 dot/{mu}m{sup 2} is realized. The resulting isolated InP quantum dots embedded in an InGaP matrix are individually characterized without the need for lithographical patterning and masks on the substrate. Such low-density quantum dots show excitonic emission at around 670 nm with a linewidth limited by instrument resolution. This system is applicable as a single-photon source for applications such as quantum cryptography.

  18. Toolbox Safety Talk DOT Materials of Trade

    E-Print Network [OSTI]

    Pawlowski, Wojtek

    Toolbox Safety Talk DOT ­ Materials of Trade Environmental Health & Safety Facilities Safety by Trades personnel that meet the definition of hazardous materials even though they may be sold as consumer commodities. The DOT regulations have exceptions for Materials of Trade (MOT). The MOT exception provides

  19. Thick-shell nanocrystal quantum dots

    DOE Patents [OSTI]

    Hollingsworth, Jennifer A. (Los Alamos, NM); Chen, Yongfen (Eugene, OR); Klimov, Victor I. (Los Alamos, NM); Htoon, Han (Los Alamos, NM); Vela, Javier (Los Alamos, NM)

    2011-05-03T23:59:59.000Z

    Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous excitation conditions for a period of time of at least 10 minutes.

  20. Phonon Mediated Off-Resonant Quantum Dot-Cavity Coupling

    E-Print Network [OSTI]

    Arka Majumdar; Yiyang Gong; Erik D. Kim; Jelena Vuckovic

    2010-12-14T23:59:59.000Z

    A theoretical model for the phonon-mediated off-resonant coupling between a quantum dot and a cavity, under resonant excitation of the quantum dot, is presented. We show that the coupling is caused by electron-phonon interaction in the quantum dot and is enhanced by the cavity. We analyze recently observed resonant quantum dot spectroscopic data by our theoretical model.

  1. The enzymatic synthesis of rubber polymer in Parthenium argentatum Gray

    SciTech Connect (OSTI)

    Benedict, C.R.; Madhavan, S.; Greenblatt, G.A.; Venkatachalam, K.V.; Foster, M.A. (Texas A M Univ., College Station (USA))

    1990-03-01T23:59:59.000Z

    Washed rubber particles isolated from stem homogenates of Parthenium argentatum Gray by ultracentrifugation and gel filtration on columns of LKB Ultrogel AcA34 contain rubber transferase which catalyzes the polymerization of isopentenyl pyrophosphate into rubber polymer. The polymerization reaction requires Mg{sup 2+} isopentenyl pyrophosphate, and an allylic pyrophosphate. The K{sub m} values for Mg{sup 2+}, isopentenyl pyrophosphate, and dimethylallyl pyrophosphate were 5.2 {times} 10{sup {minus}4} molar, 8.3 {times} 10{sup {minus}5} molar, and 9.6 {times} 10{sup {minus}5} molar, respectively. The molecular characteristics of the rubber polymer synthesized from ({sup 14}C)isopentenyl pyrophosphate were examined by gel permeation chromatography. The peak molecular weight of the radioactive polymer increased from 70,000 in 15 minutes to 750,000 in 3 hours. The weight average molecular weight of the polymer synthesized over a 3 hour period was 1.17 {times} 10{sup 6} compared to 1.49 {times} 10{sup 6} for the natural rubber polymer extracted from the rubber particles. Over 90% of the in vitro formation of the rubber polymer was de novo from dimethylallyl pyrophosphate and isopentenyl pyrophosphate. Treatment of the washed rubber particles with 3-((3-cholamidopropyl) dimethylammonio) -1-propanesulfonate solubilized the rubber transferase. The solubilized enzyme(s) catalyzed the polymerization of isopentenyl pyrophosphate into rubber polymer with a peak molecular weight of 1 {times} 10{sup 5} after 3 hours of incubation with Mg{sup 2+} and dimethylallyl pyrophosphate. The data support the conclusion that the soluble preparation of rubber transferase is capable of catalyzing the formation of a high molecular weight rubber polymer from an allylic pyrophosphate initiator and isopentenyl pyrophosphate monomer.

  2. Semiconductor Quantum Dots and Quantum Dot Arrays and Applications of Multiple Exciton Generation to Third-Generation Photovoltaic Solar Cells

    E-Print Network [OSTI]

    George, Steven C.

    to Third-Generation Photovoltaic Solar Cells A. J. Nozik,*,, M. C. Beard, J. M. Luther, M. Law,§ R. J. Applications: Quantum Dot Solar Cells 6884 6.1. Quantum Dot Solar Cell Configurations 6885 6.1.1. Photoelectrodes Composed of Quantum Dot Arrays 6885 6.1.2. Quantum Dot-Sensitized Nanocrystalline TiO2 Solar Cells

  3. Room temperature infrared photoresponse of self assembled Ge/Si (001) quantum dots grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Singha, R. K.; Manna, S.; Das, S.; Dhar, A.; Ray, S. K. [Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

    2010-06-07T23:59:59.000Z

    We report on the observation of intraband near infrared (approx3.1 mum) and mid infrared (approx6.2 mum) photocurrent response at room temperature using Ge/Si self-assembled quantum dots grown by molecular beam epitaxy. Due to the bimodal size distribution and SiGe intermixing, distinguishable photoluminescence transitions are observed at 10 K, below and above the optical band gap of bulk Ge. The observed redshift in photocurrent with increasing temperature has been explained by the excitonic electric field originated due to infrared excitation at low temperatures. A good correlation between the spectral photocurrent response and photoluminescence of the quantum dots has been established.

  4. Photodetectors based on colloidal quantum dots

    E-Print Network [OSTI]

    Oertel, David C. (David Charles)

    2007-01-01T23:59:59.000Z

    Inspired by recent work demonstrating photocurrent enhancement in quantum-dot (QD) solids via post-deposition chemical annealing and by recent successes incorporating single monolayers of QDs in light-emitting devices ...

  5. Synthesis and characterization of infrared quantum dots

    E-Print Network [OSTI]

    Harris, Daniel Kelly

    2014-01-01T23:59:59.000Z

    This thesis focuses on the development of synthetic methods to create application ready quantum dots (QDs) in the infrared for biological imaging and optoelectronic devices. I concentrated primarily on controlling the size ...

  6. Thermoelectric transport through strongly correlated quantum dots

    E-Print Network [OSTI]

    T. A. Costi; V. Zlatic

    2010-07-08T23:59:59.000Z

    The thermoelectric properties of strongly correlated quantum dots, described by a single level Anderson model coupled to conduction electron leads, is investigated using Wilson's numerical renormalization group method. We calculate the electronic contribution, $K_{\\rm e}$, to the thermal conductance, the thermopower, $S$, and the electrical conductance, $G$, of a quantum dot as a function of both temperature, $T$, and gate voltage, ${\\rm v}_g$, for strong, intermediate and weak Coulomb correlations, $U$, on the dot. For strong correlations and in the Kondo regime, we find that the thermopower exhibits two sign changes, at temperatures $T_{1}({\\rm v}_g)$ and $T_{2}({\\rm v}_g)$ with $T_{1}< T_{2}$. Such sign changes in $S(T)$ are particularly sensitive signatures of strong correlations and Kondo physics. The relevance of this to recent thermopower measurements of Kondo correlated quantum dots is discussed. We discuss the figure of merit, power factor and the degree of violation of the Wiedemann-Franz law in quantum dots. The extent of temperature scaling in the thermopower and thermal conductance of quantum dots in the Kondo regime is also assessed.

  7. The Interactive Routine as Key Construct in Theories of Interactive Behavior Wayne D. Gray (grayw@rpi.edu)

    E-Print Network [OSTI]

    Gray, Wayne

    The Interactive Routine as Key Construct in Theories of Interactive Behavior Wayne D. Gray (grayw together in dependency networks of constraints to form interactive routines (Gray, Sims, Fu, & Schoelles, 2006). Interactive behavior proceeds by selecting one interactive routine after another or by selecting

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

    SciTech Connect (OSTI)

    Kaur, Gurvir; Kaur, Harmandeep [Centre of Advanced Study in Physics, Department of Physics, Panjab University, Chandigarh-160014 (India); Tripathi, S. K., E-mail: surya@pu.ac.in [Centre of Advanced Study in Physics, Panjab University, Chandigarh- 160014 (India)

    2014-04-24T23:59:59.000Z

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

  9. Adsorption of Charge-Bidisperse Mixtures of Colloidal Jeffrey J. Gray and Roger T. Bonnecaze*

    E-Print Network [OSTI]

    Gray, Jeffrey J.

    Adsorption of Charge-Bidisperse Mixtures of Colloidal Particles Jeffrey J. Gray and Roger T with the number of components in the system. Here, we perform simulations of the adsorption of binary mixtures%. In sequential adsorption, small amounts of the second component adsorb only for parameter combinations

  10. Fast scanning probe for tokamak plasmas J. Boedo, D. Gray, L. Chousal, and R. Conn

    E-Print Network [OSTI]

    Krstic, Miroslav

    Fast scanning probe for tokamak plasmas J. Boedo, D. Gray, L. Chousal, and R. Conn Department of tokamaks. The probe described here has five tips which obtain a full spectrum of plasma parameters such as turbulence and anomalous radial particle transport.3 Understanding the tokamak boundary has pro- found

  11. PRESIDENTIAL LEADERSHIP ACADEMY LEADERSHIP, THINKING, AND ACTION IN A GRAY WORLD

    E-Print Network [OSTI]

    Yener, Aylin

    PRESIDENTIAL LEADERSHIP ACADEMY LEADERSHIP, THINKING, AND ACTION IN A GRAY WORLD The world rarely leadership program for a select number of our most promising students. The Presidential Leadership Academy Leadership Academy will maximize the impact and value of the Penn State experience for a distinct group

  12. Reply: Lithium and Increased Cortical Gray Matter--More Tissue or More Water?

    E-Print Network [OSTI]

    Thompson, Paul

    Reply: Lithium and Increased Cortical Gray Matter--More Tissue or More Water? To the Editor: W e. Regenold voices some disappointment that we did not determine whether an increase in brain tissue water patients. Although lithium's effects on body water homeostasis (2) are important to consider, the absence

  13. Stable spheromak formation by merging in an oblate flux conserver T. Gray,1,a

    E-Print Network [OSTI]

    Brown, Michael R.

    Stable spheromak formation by merging in an oblate flux conserver T. Gray,1,a M. R. Brown,1 C. D; accepted 4 February 2010; published online 29 March 2010 An axisymmetric spheromak formed by the dynamic merging of two smaller spheromaks of the same magnetic helicity in the Swarthmore Spheromak Experiment SSX

  14. Nanostructured architectures for colloidal quantum dot solar cells

    E-Print Network [OSTI]

    Jean, Joel, S.M. Massachusetts Institute of Technology

    2013-01-01T23:59:59.000Z

    This thesis introduces a novel ordered bulk heterojunction architecture for colloidal quantum dot (QD) solar cells. Quantum dots are solution-processed nanocrystals whose tunable bandgap energies make them a promising ...

  15. Electron tunneling and spin relaxation in a lateral quantum dot

    E-Print Network [OSTI]

    Amasha, Sami

    2008-01-01T23:59:59.000Z

    We report measurements that use real-time charge sensing to probe a single-electron lateral quantum dot. The charge sensor is a quantum point contact (QPC) adjacent to the dot and the sensitivity is comparable to other ...

  16. Fast quantum dot single photon source triggered at telecommunications wavelength

    E-Print Network [OSTI]

    Kelley Rivoire; Sonia Buckley; Arka Majumdar; Hyochul Kim; Pierre Petroff; Jelena Vuckovic

    2010-12-20T23:59:59.000Z

    We demonstrate a quantum dot single photon source at 900 nm triggered at 300 MHz by a continuous wave telecommunications wavelength laser followed by an electro-optic modulator. The quantum dot is excited by on-chip-generated second harmonic radiation, resonantly enhanced by a GaAs photonic crystal cavity surrounding the InAs quantum dot. Our result suggests a path toward the realization of telecommunications-wavelength-compatible quantum dot single photon sources with speeds exceeding 1 GHz.

  17. Mini Review Water-soluble quantum dots for biomedical applications

    E-Print Network [OSTI]

    ­emission matrix (EEM) reveals that quantum dots always emit the same lights no matter what excita- tion wavelength

  18. Coherent Optical Spectroscopy of a Single Quantum Dot Via an Off-Resonant Cavity

    E-Print Network [OSTI]

    Arka Majumda; Alexander Papageorge; Erik D. Kim; Michal Bajscy; Hyochul Kim; Pierre Petroff; Jelena Vuckovic

    2011-03-14T23:59:59.000Z

    In recent experiments on coupled quantum dot (QD) optical cavity systems a pronounced interaction between the dot and the cavity has been observed even for detunings of many cavity linewidths. This interaction has been attributed to an incoherent phonon-mediated scattering process and is absent in atomic systems. Here, we demonstrate that despite its incoherent nature, this process preserves the signatures of coherent interaction between a QD and a strong driving laser, which may be observed via the optical emission from the off-resonant cavity. Under bichromatic driving of the QD, the cavity emission exhibits spectral features consistent with optical dressing of the QD transition. In addition to revealing new aspects of the off-resonant QD-cavity interaction, this result provides a new, simpler means of coherently probing QDs than traditional approaches and opens the possibility of employing off-resonant cavities to optically interface QD-nodes in quantum networks.

  19. Quantum dot nonlinearity through cavity-enhanced feedback with a charge memory

    E-Print Network [OSTI]

    Morten P. Bakker; Thomas Ruytenberg; Wolfgang Loffler; Ajit V. Barve; Larry Coldren; Martin P. van Exter; Dirk Bouwmeester

    2015-03-27T23:59:59.000Z

    In an oxide apertured quantum dot (QD) micropillar cavity-QED system, we found strong QD hysteresis effects and lineshape modifications even at very low intensities corresponding to less than 0.001 intracavity photons. We attribute this to the excitation of charges by the intracavity field; charges that get trapped at the oxide aperture, where they screen the internal electric field and blueshift the QD transition. This in turn strongly modulates light absorption by cavity QED effects, eventually leading to the observed hysteresis and lineshape modifications. The cavity also enables us to observe the QD dynamics in real time, and all experimental data agrees well with a power-law charging model. This effect can serve as a novel tuning mechanism for quantum dots.

  20. Thermoelectric transport through strongly correlated quantum dots

    E-Print Network [OSTI]

    Costi, T A; 10.1103/PhysRevB.81.235127

    2010-01-01T23:59:59.000Z

    The thermoelectric properties of strongly correlated quantum dots, described by a single level Anderson model coupled to conduction electron leads, is investigated using Wilson's numerical renormalization group method. We calculate the electronic contribution, $K_{\\rm e}$, to the thermal conductance, the thermopower, $S$, and the electrical conductance, $G$, of a quantum dot as a function of both temperature, $T$, and gate voltage, ${\\rm v}_g$, for strong, intermediate and weak Coulomb correlations, $U$, on the dot. For strong correlations and in the Kondo regime, we find that the thermopower exhibits two sign changes, at temperatures $T_{1}({\\rm v}_g)$ and $T_{2}({\\rm v}_g)$ with $T_{1}law in ...

  1. Engineered Quantum Dot Single Photon Sources

    E-Print Network [OSTI]

    Sonia Buckley; Kelley Rivoire; Jelena Vuckovic

    2012-10-03T23:59:59.000Z

    Fast, high efficiency, and low error single photon sources are required for implementation of a number of quantum information processing applications. The fastest triggered single photon sources to date have been demonstrated using epitaxially grown semiconductor quantum dots (QDs), which can be conveniently integrated with optical microcavities. Recent advances in QD technology, including demonstrations of high temperature and telecommunications wavelength single photon emission, have made QD single photon sources more practical. Here we discuss the applications of single photon sources and their various requirements, before reviewing the progress made on a quantum dot platform in meeting these requirements.

  2. Bilayer graphene quantum dot defined by topgates

    SciTech Connect (OSTI)

    Müller, André; Kaestner, Bernd; Hohls, Frank; Weimann, Thomas; Pierz, Klaus; Schumacher, Hans W., E-mail: hans.w.schumacher@ptb.de [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)

    2014-06-21T23:59:59.000Z

    We investigate the application of nanoscale topgates on exfoliated bilayer graphene to define quantum dot devices. At temperatures below 500 mK, the conductance underneath the grounded gates is suppressed, which we attribute to nearest neighbour hopping and strain-induced piezoelectric fields. The gate-layout can thus be used to define resistive regions by tuning into the corresponding temperature range. We use this method to define a quantum dot structure in bilayer graphene showing Coulomb blockade oscillations consistent with the gate layout.

  3. Frequency stabilization of the zero-phonon line of a quantum dot via phonon-assisted active feedback

    E-Print Network [OSTI]

    Jack Hansom; Carsten H. H. Schulte; Clemens Matthiesen; Megan Stanley; Mete Atature

    2014-10-17T23:59:59.000Z

    We report on the feedback stabilization of the zero-phonon emission frequency of a single InAs quantum dot. The spectral separation of the phonon-assisted component of the resonance fluorescence provides a probe of the detuning between the zero-phonon transition and the resonant driving laser. Using this probe in combination with active feedback, we stabilize the zero-phonon transition frequency against environmental fluctuations. This protocol reduces the zero-phonon fluorescence intensity noise by a factor of 22 by correcting for environmental noise with a bandwidth of 191 Hz, limited by the experimental collection efficiency. The associated sub-Hz fluctuations in the zero-phonon central frequency are reduced by a factor of 7. This technique provides a means of stabilizing the quantum dot emission frequency without requiring access to the zero-phonon emission.

  4. Synthesis of CdSe quantum dots for quantum dot sensitized solar cell

    SciTech Connect (OSTI)

    Singh, Neetu, E-mail: singh.neetu1985@gmail.com; Kapoor, Avinashi [Department of Electronic Science, University of Delhi South Campus, New Delhi-110 021 (India); Kumar, Vinod [Department of Physics, University of the Free State, Bloemfontein, ZA9300 (South Africa); Mehra, R. M. [School of Engineering and Technology, Sharda University, Greater Noida-201 306, U.P. (India)

    2014-04-24T23:59:59.000Z

    CdSe Quantum Dots (QDs) of size 0.85 nm were synthesized using chemical route. ZnO based Quantum Dot Sensitized Solar Cell (QDSSC) was fabricated using CdSe QDs as sensitizer. The Pre-synthesized QDs were found to be successfully adsorbed on front ZnO electrode and had potential to replace organic dyes in Dye Sensitized Solar Cells (DSSCs). The efficiency of QDSSC was obtained to be 2.06 % at AM 1.5.

  5. Mn/DOT's Project Peer Review

    E-Print Network [OSTI]

    Minnesota, University of

    and sustain this culture #12;Project Management #12;Recent National Work in Transportation Project ManagementMn/DOT's Project Management Peer Review Creating a Project Management Culture 2010 CTS Research a Peer Review? Why Project Management? ·Improve project delivery performance ­ on time, on budget (an

  6. Spin dynamics characterization in magnetic dots

    E-Print Network [OSTI]

    Mozaffari, Mohammad Reza; Esfarjani, Keivan

    2007-01-01T23:59:59.000Z

    J= 0.1 meV Frequency (JS) SDF J=0.6 meV Fig. 2. (Colorfrom diagonalization (SDF: J=1 eV) Frequency spectrum fromMagnon DOS for a circular dot SDF: J=0.6 meV N=1600 N=400 N=

  7. Watch for the red dot indicating

    E-Print Network [OSTI]

    > http:// > Watch for the red dot indicating expanded stories online sdm.mit.edu/pulse continued its facilities by constructing the European Extremely Large Telescope (E-ELT) on a mountain in Chile isolated from the grid. The planned construction of the E-ELT and the challenges faced by the current

  8. Enhanced Joule Heating in Umbral Dots

    E-Print Network [OSTI]

    Chandan Joshi; Lokesh Bharti; S. N. A. Jaaffrey

    2007-05-10T23:59:59.000Z

    We present a study of magnetic profiles of umbral dots (UDs) and its consequences on the Joule heating mechanisms. Hamedivafa (2003) studied Joule heating using vertical component of magnetic field. In this paper UDs magnetic profile has been investigated including the new azimuthal component of magnetic field which might explain the relatively larger enhancement of Joule heating causing more brightness near circumference of UD.

  9. Chemical contaminants in gray whales (eschichtius robustus) stranded in Alaska, Washington, and California, USA. Technical memo

    SciTech Connect (OSTI)

    Varanasi, U.; Stein, J.E.; Tilbury, K.L.; Meador, J.P.; Sloan, C.A.

    1993-08-01T23:59:59.000Z

    The concentrations of chlorinated hydrocarbons (CHs) such as polychlorinated biphenyls (PCBs), 1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethanes (DDTs), 1,1-dichloro-2,2-bis(p- chlorophenyl) ethenes (DDEs), and chlordanes, and essential (e.g., zinc, selenium, copper) and toxic (e.g., mercury, lead) elements were measured in tissues and stomach contents from 22 gray whales (Eschrichtius robustus) stranded between 1988 and 1991. The stranding sites ranged from the relatively pristine areas of Kodiak Island, Alaska, to more urbanized areas in Puget Sound, Washington, and San Francisco Bay, California, with the majority of the sites on the Washington outer coast and in Puget Sound. Similar to concentrations in tissues, no significant differences were observed in concentrations of elements in stomach contents between whales stranded in Puget Sound and whales stranded at the more pristine sites. The lack of data from apparently healthy gray whales limits the assessment of whether the levels of anthropogenic contaminants found in tissues may have deleterious effects on the health of gray whales.

  10. Measurement of the body composition of living gray seals by hydrogen isotope dilution

    SciTech Connect (OSTI)

    Reilly, J.J.; Fedak, M.A. (Natural Environment Research Council, High Cross, Cambridge (England))

    1990-09-01T23:59:59.000Z

    The body composition of living gray seals (Halichoerus grypus) can be accurately predicted from a two-step model that involves measurement of total body water (TBW) by {sup 2}H or {sup 3}H dilution and application of predictive relationships between body components and TBW that were derived empirically by slaughter chemical analysis. TBW was overestimated by both {sup 2}HHO and {sup 3}HHO dilution; mean overestimates were 2.8 +/- 0.9% (SE) with 2H and 4.0 +/- 0.6% with {sup 3}H. The relationships for prediction of total body fat (TBF), protein (TBP), gross energy (TBGE), and ash (TBA) were as follows: %TBF = 105.1 - 1.47 (%TBW); %TBP = 0.42 (%TBW) - 4.75; TBGE (MJ) = 40.8 (mass in kg) - 48.5 (TBW in kg) - 0.4; and TBA (kg) = 0.1 - 0.008 (mass in kg) + 0.05 (TBW in kg). These relationships are applicable to gray seals of both sexes over a wide range of age and body conditions, and they predict the body composition of gray seals more accurately than the predictive equations derived from ringed seals (Pusa hispida) and from the equation of Pace and Rathbun, which has been reported to be generally applicable to mammals.

  11. Gender, Truth & Transition

    E-Print Network [OSTI]

    Ní Aoláin, Pionnuala; Turner, Catherine

    2007-01-01T23:59:59.000Z

    50. Id. GENDER, TRUTH & TRANSITION contested, as evidencedG. Teitel, Human Rights in Transition: Transitional JusticeU.N. GENDER, TRUTH & TRANSITION Organization of American

  12. Spectral dependence of the linewidth enhancement factor in quantum dot lasers

    SciTech Connect (OSTI)

    Zubov, F. I., E-mail: fedyazu@mail.ru [Russian Academy of Sciences, St. Petersburg Academic University-Nanotechnology Research and Education Center (Russian Federation); Shernyakov, Yu. M.; Maximov, M. V. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Zhukov, A. E. [Russian Academy of Sciences, St. Petersburg Academic University-Nanotechnology Research and Education Center (Russian Federation); Livshits, D. A. [Innolume GmbH (Germany); Payusov, A. S.; Nadtochiy, A. M. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Savelyev, A. V.; Kryzhanovskaya, N. V. [Russian Academy of Sciences, St. Petersburg Academic University-Nanotechnology Research and Education Center (Russian Federation); Gordeev, N. Yu. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2013-12-15T23:59:59.000Z

    The spectral analysis of amplified spontaneous emission is used to determine the linewidth enhancement factor (?-factor) in lasers based on InAs/InGaAs quantum dots (QDs) in a wide spectral range near the ground-state optical transition energy. The effect of the pump current and number of QDs on the spectral dependences of the ?-factor is examined. The temperature dependence of the spectra of the ?-factor is experimentally determined for the first time for lasers with InAs/InGaAs QDs. An explanation is suggested for the observed anomalous decrease in the ?-factor with increasing temperature.

  13. Fabrication and characterization of p-channel Si double quantum dots

    SciTech Connect (OSTI)

    Yamada, Ko; Kambara, Tomohiro; Oda, Shunri [Quantum Nanoelectronics Research Center, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552 (Japan); Kodera, Tetsuo, E-mail: kodera.t.ac@m.titech.ac.jp [Department of Physical Electronics, Quantum Nanoelectronics Research Center, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552 (Japan); PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan)

    2014-09-15T23:59:59.000Z

    Lithographically defined p-channel Si single hole transistors (SHTs) and double quantum dot (DQD) devices are fabricated and characterized. Coulomb oscillations are clearly evident at a temperature of 4.2?K. The charging energy and the diameter of the SHT are estimated from the Coulomb diamonds. Honeycomb-like charge stability diagrams are observed from measurements of the DQD devices. Single hole transitions through the DQD are detected using an integrated SHT as a charge sensor, and a few-hole regime of the DQD is observed.

  14. Strain-induced vertical self-organization of semiconductor quantum dots: A computational study

    SciTech Connect (OSTI)

    Shtinkov, N., E-mail: nshtinkov@uottawa.ca [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa (Ontario) K1N 6N5 (Canada)

    2013-12-28T23:59:59.000Z

    Atomistic strain simulations based on the valence force field method are employed to study the vertical arrangements of semiconductor quantum dot (QD) multilayers. The effects of the QD shape, dimensions, and materials parameters are systematically investigated, varying independently the following parameters: spacer width H, QD lateral spacing D, base b, and height h, slope of the side facets, elastic properties of the dot and the substrate materials, and lattice mismatch between the dot and the substrate. The transition between vertically aligned and anti-aligned structures is found to be determined mainly by the ratios H/D and b/D, as well as by the strain anisotropy of the substrate and to a lesser extent of the QD. The dependence on the QD height h is significant only for steep side facets and large aspect ratios h/b, and the effects of the lattice mismatch strain and the bulk elastic moduli are found to be negligible. The comparison with experimental data shows an excellent agreement with the results from the simulations, demonstrating that the presented analysis results in precise theoretical predictions for the vertical self-organization regime in a wide range of QD materials systems.

  15. Testing the effectiveness of an acoustic deterrent for gray whales along the Oregon coast

    SciTech Connect (OSTI)

    Lagerquist, Barbara [Oregon State University Marine Mammal Institute; Winsor, Martha [Oregon State University Marine Mammal Institute; Mate, Bruce [Oregon State University Marine Mammal Institute

    2012-12-31T23:59:59.000Z

    This study was conducted to determine whether a low-powered sound source could be effective at deterring gray whales from areas that may prove harmful to them. With increased interest in the development of marine renewal energy along the Oregon coast the concern that such development may pose a collision or entanglement risk for gray whales. A successful acoustic deterrent could act as a mitigation tool to prevent harm to whales from such risks. In this study, an acoustic device was moored on the seafloor in the pathway of migrating gray whales off Yaquina Head on the central Oregon coast. Shore-based observers tracked whales with a theodolite (surveyor’s tool) to accurately locate whales as they passed the headland. Individual locations of different whales/whale groups as well as tracklines of the same whale/whale groups were obtained and compared between times with the acoustic device was transmitting and when it was off. Observations were conducted on 51 d between January 1 and April 15, 2012. A total of 143 individual whale locations were collected for a total of 243 whales, as well as 57 tracklines for a total of 142 whales. Inclement weather and equipment problems resulted in very small sample sizes, especially during experimental periods, when the device was transmitting. Because of this, the results of this study were inconclusive. We feel that another season of field testing is warranted to successfully test the effectiveness of the deterrent, but recommend increasing the zone of influence to 3 km to ensure the collection of adequate sample sizes. Steps have been taken to acquire the necessary federal research permit modification to authorize the increased zone of influence and to modify the acoustic device for the increased power. With these changes we are confident we will be able to determine whether the deterrent is effective at deflecting gray whales. A successful deterrent device may serve as a valuable mitigation tool to protect gray whales, and other baleen whales, in the event that marine energy development poses a collision or entanglement risk.

  16. Establishment of correlated states in a quantum dot interacting with an acoustic phonon reservoir

    E-Print Network [OSTI]

    Hui Huang; Gao-xiang Li; Wen-ju Gu; Zbigniew Ficek

    2014-08-20T23:59:59.000Z

    We investigate the effects of a low frequency (acoustic) phonon bath on the dynamics of a quantum dot modelled as a cascade three-level system. We show that the phonon bath appears to the upper transition of the cascade system as a broadband reservoir of inverted rather than conventional harmonic oscillators. The action of the annihilation and creation operators of the inverted oscillator are interchanges relative to those of the usual harmonic oscillator that it serves as a linear amplifier to the system, and thereby gives rise to unusual features in the dynamics of the quantum dot. We find that the phonon bath, although being in a thermal state, affects the quantum dot as a correlated-type reservoir which results in the decay of the system to a correlated two-photon state with the population distribution no longer obeying a Boltzmann distribution. It is particularly interesting that even for a zero temperature phonon reservoir the steady state is a correlated state which under appropriate conditions on the Rabi frequencies and the damping rates can reduce to a strongly correlated pure state. It is shown that the two-photon correlations result in a significant squeezing and strong two-photon correlations in the radiation field emitted by the quantum dot. The presence of the correlations in the system is manifest in the presence of quantum beats in the time evolution of the populations and the radiation intensity. The effect of the ordinary spontaneous emission on the features induced by the phonon bath is also discussed.

  17. TRANSITION DE MOTT METAL-INSULATOR TRANSITIONS

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    TRANSITION DE MOTT METAL-INSULATOR TRANSITIONS IN TRANSITION METAL OXIDES by D. B. McWHAN, A. MENTH oxydes de metaux de transition on observe une transition d'isolant a metal puis de metal a isolant de type Mott lorsque l'on augmentelenombre d'electrons d. Danslesysthe(V1-~Cr~)203une transition de Mott

  18. Deposition of colloidal quantum dots by microcontact printing for LED display technology

    E-Print Network [OSTI]

    Kim, LeeAnn

    2006-01-01T23:59:59.000Z

    This thesis demonstrates a new deposition method of colloidal quantum dots within a quantum dot organic light-emitting diode (QD-LED). A monolayer of quantum dots is microcontact printed as small as 20 ,Lm lines as well ...

  19. An environmental impact assessment of quantum dot photovoltaics (QDPV) from raw material acquisition through use

    E-Print Network [OSTI]

    Illinois at Chicago, University of

    An environmental impact assessment of quantum dot photovoltaics (QDPV) from raw material of Environmental Engineering, Beytepe, Ankara, Turkey b Institute for Environmental Science and Policy, University: Life cycle assessment Quantum dots Nanophotovoltaics Quantum dot photovoltaic modules Solar energy

  20. Elastic fields of quantum dots in subsurface layers A. E. Romanov

    E-Print Network [OSTI]

    Beltz, Glenn E.

    to vertical stacking of dots provided that the thickness of the intervening layer ``spacer layer'' is in the order or thinner than the lateral dimensions of the dot.4 It is now clear that dot ordering is driven

  1. Controlling quantum dot energies using submonolayer bandstructure engineering

    SciTech Connect (OSTI)

    Yu, L.; Law, S.; Wasserman, D. [Department of Electrical and Computer Engineering, University of Illinois Urbana Champaign, Urbana, Illinois 61801 (United States); Jung, D.; Lee, M. L. [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520 (United States); Shen, J.; Cha, J. J. [Department of Mechanical Engineering and Materials Science and Energy Science Institute, Yale University, New Haven, Connecticut 06520 (United States)

    2014-08-25T23:59:59.000Z

    We demonstrate control of energy states in epitaxially-grown quantum dot structures formed by stacked submonolayer InAs depositions via engineering of the internal bandstructure of the dots. Transmission electron microscopy of the stacked sub-monolayer regions shows compositional inhomogeneity, indicative of the presence of quantum dots. The quantum dot ground state is manipulated not only by the number of deposited InAs layers, but also by control of the thickness and material composition of the spacing layers between submonolayer InAs depositions. In this manner, we demonstrate the ability to shift the quantum dot ground state energy at 77?K from 1.38?eV to 1.88?eV. The results presented offer a potential avenue towards enhanced control of dot energies for a variety of optoelectronic applications.

  2. Local Quantum Dot Tuning on Photonic Crystal Chips

    E-Print Network [OSTI]

    Andrei Faraon; Dirk Englund; Ilya Fushman; Nick Stoltz; Pierre Petroff; Jelena Vuckovic

    2007-03-28T23:59:59.000Z

    Quantum networks based on InGaAs quantum dots embedded in photonic crystal devices rely on QDs being in resonance with each other and with the cavities they are embedded in. We developed a new technique based on temperature tuning to spectrally align different quantum dots located on the same chip. The technique allows for up to 1.8nm reversible on-chip quantum dot tuning.

  3. Steering of a Bosonic Mode with a Double Quantum Dot

    E-Print Network [OSTI]

    T. Brandes; N. Lambert

    2003-02-13T23:59:59.000Z

    We investigate the transport and coherence properties of a double quantum dot coupled to a single damped boson mode. Our numerically results reveal how the properties of the boson distribution can be steered by altering parameters of the electronic system such as the energy difference between the dots. Quadrature amplitude variances and the Wigner function are employed to illustrate how the state of the boson mode can be controlled by a stationary electron current through the dots.

  4. Separability and dynamical symmetry of Quantum Dots

    SciTech Connect (OSTI)

    Zhang, P.-M., E-mail: zhpm@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Zou, L.-P., E-mail: zoulp@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Horvathy, P.A., E-mail: horvathy@lmpt.univ-tours.fr [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Laboratoire de Mathématiques et de Physique Théorique, Tours University (France); Gibbons, G.W., E-mail: G.W.Gibbons@damtp.cam.ac.uk [Department of Applied Mathematics and Theoretical Physics, Cambridge University, Cambridge (United Kingdom)

    2014-02-15T23:59:59.000Z

    The separability and Runge–Lenz-type dynamical symmetry of the internal dynamics of certain two-electron Quantum Dots, found by Simonovi? et al. (2003), are traced back to that of the perturbed Kepler problem. A large class of axially symmetric perturbing potentials which allow for separation in parabolic coordinates can easily be found. Apart from the 2:1 anisotropic harmonic trapping potential considered in Simonovi? and Nazmitdinov (2013), they include a constant electric field parallel to the magnetic field (Stark effect), the ring-shaped Hartmann potential, etc. The harmonic case is studied in detail. -- Highlights: • The separability of Quantum Dots is derived from that of the perturbed Kepler problem. • Harmonic perturbation with 2:1 anisotropy is separable in parabolic coordinates. • The system has a conserved Runge–Lenz type quantity.

  5. Mastermind Session: Connecting the Dots Between the Real Estate...

    Energy Savers [EERE]

    and Residential Energy Efficiency Better Buildings Residential Network Program Sustainability Series Mastermind Call: Connecting the Dots Between the Real Estate Market and...

  6. alloy quantum dots: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Quantum Dot Arrays and Applications of Multiple Exciton Generation to Third-Generation Photovoltaic Solar Cells Biology and Medicine Websites Summary: to Third-Generation...

  7. assembled quantum dots: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Quantum Dot Arrays and Applications of Multiple Exciton Generation to Third-Generation Photovoltaic Solar Cells Biology and Medicine Websites Summary: to Third-Generation...

  8. anisn format dot: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Quantum Dot Arrays and Applications of Multiple Exciton Generation to Third-Generation Photovoltaic Solar Cells Biology and Medicine Websites Summary: to Third-Generation...

  9. asymmetry quantum dots: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Quantum Dot Arrays and Applications of Multiple Exciton Generation to Third-Generation Photovoltaic Solar Cells Biology and Medicine Websites Summary: to Third-Generation...

  10. How Analysts Cognitively “Connect the Dots

    SciTech Connect (OSTI)

    Bradel, Lauren; Self, Jessica S.; Endert, Alexander; Hossain, Shahriar M.; North, Chris; Ramakrishnan, Naren

    2013-06-04T23:59:59.000Z

    As analysts attempt to make sense of a collection of documents, such as intelligence analysis reports, they may wish to “connect the dots” between pieces of information that may initially seem unrelated. This process of synthesizing information between information requires users to make connections between pairs of documents, creating a conceptual story. We conducted a user study to analyze the process by which users connect pairs of documents and how they spatially arrange information. Users created conceptual stories that connected the dots using organizational strategies that ranged in complexity. We propose taxonomies for cognitive connections and physical structures used when trying to “connect the dots” between two documents. We compared the user-created stories with a data-mining algorithm that constructs chains of documents using co-occurrence metrics. Using the insight gained into the storytelling process, we offer design considerations for the existing data mining algorithm and corresponding tools to combine the power of data mining and the complex cognitive processing of analysts.

  11. Photovoltaic performance of ultra-small PbSe quantum dots

    E-Print Network [OSTI]

    Ma, Wanli

    2014-01-01T23:59:59.000Z

    Colloidal Quantum Dots for Photovoltaics: Fundamentals andSchottky-Quantum Dot Photovoltaics for Efficient InfraredDJ; Klimov, VI, Hybrid Photovoltaics Based on Semiconductor

  12. Quantum-dot all-optical logic in a structured vacuum

    SciTech Connect (OSTI)

    Ma Xun; John, Sajeev [Department of Physics, University of Toronto, Toronto, M5S 1A7 (Canada)

    2011-07-15T23:59:59.000Z

    We demonstrate multiwavelength channel optical logic operations on the Bloch vector of a quantum two-level system in the structured electromagnetic vacuum of a bimodal photonic crystal waveguide. This arises through a bichromatic strong-coupling effect that enables unprecedented control over single quantum-dot (QD) excitation through two beams of ultrashort femtojoule pulses. The second driving pulse (signal) with slightly different frequency and weaker strength than the first (holding) pulse leads to controllable strong modulation of the QD Bloch vector evolution path. This occurs through resonant coupling of the signal pulse with the Mollow sideband transitions created by the holding pulse. The movement of the Mollow sidebands during the passage of the holding pulse leads to an effective chirping in transition frequency seen by the signal. Bloch vector dynamics in the rotating frame of the signal pulse and within the dressed-state basis created by the holding pulse reveals that this chirped coupling between the signal pulse and the Mollow sidebands leads to either augmentation or negation of the final quantum-dot population (after pulse passage) compared to the outcome of the holding pulse alone and depending on the relative frequencies of the pulses. By making use of this extra degree of freedom for ultrafast control of QD excitations, applications in ultrafast all-optical logic and, or, and not gates are proposed in the presence of significant (0.1) THz nonradiative dephasing and (about 1%) inhomogeneous broadening.

  13. Application of Gray codes to the study of the theory of symbolic dynamics of unimodal maps

    E-Print Network [OSTI]

    David Arroyo; Gonzalo Alvarez

    2012-04-29T23:59:59.000Z

    In this paper we provide a closed mathematical formulation of our previous results in the field of symbolic dynamics of unimodal maps. This being the case, we discuss the classical theory of applied symbolic dynamics for unimodal maps and its reinterpretation using Gray codes. This connection was previously emphasized but no explicit mathematical proof was provided. The work described in this paper not only contributes to the integration of the different interpretations of symbolic dynamics of unimodal maps, it also points out some inaccuracies that exist in previous works.

  14. The FBI wavelet/scalar quantization standard for gray-scale fingerprint image compression

    SciTech Connect (OSTI)

    Bradley, J.N.; Brislawn, C.M. (Los Alamos National Lab., NM (United States)); Hopper, T. (Federal Bureau of Investigation, Washington, DC (United States))

    1993-01-01T23:59:59.000Z

    The FBI has recently adopted a standard for the compression of digitized 8-bit gray-scale fingerprint images. The standard is based on scalar quantization of a 64-subband discrete wavelet transform decomposition of the images, followed by Huffman coding. Novel features of the algorithm include the use of symmetric boundary conditions for transforming finite-length signals and a subband decomposition tailored for fingerprint images scanned at 500 dpi. The standard is intended for use in conjunction with ANSI/NBS-CLS 1-1993, American National Standard Data Format for the Interchange of Fingerprint Information, and the FBI's Integrated Automated Fingerprint Identification System.

  15. The FBI wavelet/scalar quantization standard for gray-scale fingerprint image compression

    SciTech Connect (OSTI)

    Bradley, J.N.; Brislawn, C.M. [Los Alamos National Lab., NM (United States); Hopper, T. [Federal Bureau of Investigation, Washington, DC (United States)

    1993-05-01T23:59:59.000Z

    The FBI has recently adopted a standard for the compression of digitized 8-bit gray-scale fingerprint images. The standard is based on scalar quantization of a 64-subband discrete wavelet transform decomposition of the images, followed by Huffman coding. Novel features of the algorithm include the use of symmetric boundary conditions for transforming finite-length signals and a subband decomposition tailored for fingerprint images scanned at 500 dpi. The standard is intended for use in conjunction with ANSI/NBS-CLS 1-1993, American National Standard Data Format for the Interchange of Fingerprint Information, and the FBI`s Integrated Automated Fingerprint Identification System.

  16. Quasi-bound states and continuum absorption background of polar Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots

    SciTech Connect (OSTI)

    Elmaghraoui, D., E-mail: elmaghraouidonia@yahoo.fr; Triki, M. [Laboratoire de physique de la matière condensé, Faculté des sciences de Tunis, Campus universitaire 2092 El Manar (Tunisia); Jaziri, S. [Laboratoire de physique de la matière condensé, Faculté des sciences de Tunis, Campus universitaire 2092 El Manar (Tunisia); Laboratoire de Physique des Matériaux, Faculté des Sciences de Bizerte 7021 Jarzouna (Tunisia); Leroux, M.; Brault, J. [Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, Rue B. Gregory, 06560 Valbonne (France)

    2014-07-07T23:59:59.000Z

    A theoretical interpretation of the photoluminescence excitation spectra of self-organized polar GaN/(Al,Ga)N quantum dots is presented. A numerical method assuming a realistic shape of the dots and including the built-in electric field effects is developed to calculate their energy structure and hence their optical absorption. The electron and hole spectra show the existence of a set of quasi-bound states that does not originate from the wetting layer and plays a crucial role in the observed absorption spectrum of the GaN/(Al,Ga)N dots. Transitions involving these quasi-bound states and wetting layer states give a sufficient explanation for the observed continuum absorption background. The properties of this absorption band, especially its extension, depend strongly on the dot's size. Our simulation provides a natural explanation of the experimental luminescence excitation spectra of ensembles of dots of different heights. Our theoretical model can be convenient for future optical studies including systems with more complicated potentials.

  17. State DOT: PENNSYLVANIA State Report Questions on NDT Testing

    E-Print Network [OSTI]

    capacity surveys, management of load restrictions, fatigue tests and compaction control. On concreteState DOT: PENNSYLVANIA State Report Questions on NDT Testing 1. What NDT testing methods for concrete materials, concrete pavements, and overlays are you trying? PennDOT performs Falling Weight

  18. State DOT: Missouri State Report Questions on NDT Testing

    E-Print Network [OSTI]

    State DOT: Missouri State Report Questions on NDT Testing 1. What NDT testing methods for concrete maturity meter MoDOT has utilized the rebound hammer to evaluate in-place concrete when cylinder testing materials, concrete pavements, and overlays are you trying? a) Maturity Method b) Rebound Hammer c) Cover

  19. Manipulating Quantum Dots to Nanometer Precision by Control of Flow

    E-Print Network [OSTI]

    Waks, Edo

    Manipulating Quantum Dots to Nanometer Precision by Control of Flow Chad Ropp, Roland Probst on the dynamically manipulated QD. KEYWORDS Quantum dots, control, electroosmotic flow, subpixel averaging, photon of Standards and Technology, Gaithersburg, Maryland 20899 ABSTRACT We present a method for manipulating

  20. Minnesota Guidestar www.dot.state.mn.us/guidestar

    E-Print Network [OSTI]

    Minnesota, University of

    .dot.state.mn.us/guidestar What is ITS? · Application of technology to improve the safety and efficiency of the transportation system. #12;Minnesota Guidestar www.dot.state.mn.us/guidestar What is ITS? · Traffic Management ­ Signal Systems ­ Ramp Meters · Emergency Response ­ Mobile Data Terminals ­ 911 Dispatch ­ RF Data Networks

  1. State DOT: Michigan State Report Questions on MEPDG Implementation

    E-Print Network [OSTI]

    State DOT: Michigan State Report Questions on MEPDG Implementation 1. Summarize your state's status as far as MEPDG Implementation. Michigan DOT has purchased a single copy of DARWin-ME for the statewide, a research project will begin with Michigan State University involving local calibration and validation

  2. How to make dried blood dots for genetic studies

    E-Print Network [OSTI]

    Schall, Joseph J.

    How to make dried blood dots for genetic studies If a vertebrate is in-hand, and blood being taken, it is easy to make both a blood smear and dried blood dots. Modern research on malaria parasites demands that BOTH a blood smear and blood samples be taken. Blood can be stored in lysis buffers of various kinds

  3. Consequentialism in Transition

    E-Print Network [OSTI]

    Coons, Christian

    2008-01-01T23:59:59.000Z

    the value of state transitions will allow us to sayConsequentialism in Transition Christian Coons Bowling Greenvalue of the state transitions, and not the states of

  4. Sampling diffusive transition paths

    E-Print Network [OSTI]

    F. Miller III, Thomas

    2009-01-01T23:59:59.000Z

    Sampling di?usive transition paths Thomas F. Miller III ?the algorithm to sample the transition path ensemble for thedynamics I. INTRODUCTION Transition path sampling (TPS) is a

  5. Nontoxic quantum dot research improves solar cells

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of Science (SC)Integrated CodesTransparencyDOE Project Taps HPCNew4OrganicNontoxic quantum dot

  6. Women @ Energy: Dot Harris | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels DataDepartment of Energy Your DensityEnergy U.S.-China Electric VehicleCenters | Department ofoftoMayWisingJoanne Bard Women @DebraDot

  7. Three-dimensional reconnection and relaxation of merging spheromak plasmas T. Gray, V. S. Lukin, M. R. Brown, and C. D. Cothran

    E-Print Network [OSTI]

    Brown, Michael R.

    Three-dimensional reconnection and relaxation of merging spheromak plasmas T. Gray, V. S. Lukin, M-dimensional reconnection and relaxation of merging spheromak plasmas" [Phys. Plasmas17, 102106 (2010)] Phys. Plasmas 17 and relaxation of merging spheromak plasmas T. Gray,1,a V. S. Lukin,2 M. R. Brown,1 and C. D. Cothran1,b 1

  8. Temperature Dependence of Single CdSe/ZnS Quantum Dots Luminescence Lifetime

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    , such as quantum dots (QDs), has grown dramatically. These semiconductor QDs bridge the gap between single

  9. Competing interactions in semiconductor quantum dots

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    van den Berg, R.; Brandino, G. P.; El Araby, O.; Konik, R. M.; Gritsev, V.; Caux, J. -S.

    2014-10-01T23:59:59.000Z

    We introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free induction decay and spin echo simulations we characterize the combined effect of both types of interactions on the decoherence of the electron spin, for external fields ranging from low to high values. We show that for spin echo simulations the hyperfine interaction is the dominant source of decoherence at short times for low fields, and competes with the dipole-dipole interactions at longer times. Onmore »the contrary, at high fields the main source of decay is due to the dipole-dipole interactions. In the latter regime an asymmetry in the echo is observed. Furthermore, the non-decaying fraction previously observed for zero field free induction decay simulations in quantum dots with only hyperfine interactions, is destroyed for longer times by the mean-field treatment of the dipolar interactions.« less

  10. Competing interactions in semiconductor quantum dots

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    van den Berg, R. [Univ. of Amsterdam (Netherlands). Inst. for Theoretical Physics; Brandino, G. P. [Univ. of Amsterdam (Netherlands). Inst. for Theoretical Physics; El Araby, O. [Univ. of Amsterdam (Netherlands). Inst. for Theoretical Physics; Konik, R. M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Gritsev, V. [Univ. of Amsterdam (Netherlands). Inst. for Theoretical Physics; Caux, J. -S. [Univ. of Amsterdam (Netherlands). Inst. for Theoretical Physics

    2014-10-01T23:59:59.000Z

    We introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free induction decay and spin echo simulations we characterize the combined effect of both types of interactions on the decoherence of the electron spin, for external fields ranging from low to high values. We show that for spin echo simulations the hyperfine interaction is the dominant source of decoherence at short times for low fields, and competes with the dipole-dipole interactions at longer times. On the contrary, at high fields the main source of decay is due to the dipole-dipole interactions. In the latter regime an asymmetry in the echo is observed. Furthermore, the non-decaying fraction previously observed for zero field free induction decay simulations in quantum dots with only hyperfine interactions, is destroyed for longer times by the mean-field treatment of the dipolar interactions.

  11. Linewidth broadening of a quantum dot coupled to an off-resonant cavity

    E-Print Network [OSTI]

    Arka Majumdar; Andrei Faraon; Erik Kim; Dirk Englund; Hyochul Kim; Pierre Petroff; Jelena Vuckovic

    2010-03-11T23:59:59.000Z

    We study the coupling between a photonic crystal cavity and an off-resonant quantum dot under resonant excitation of the cavity or the quantum dot. Linewidths of the quantum dot and the cavity as a function of the excitation laser power are measured. We show that the linewidth of the quantum dot, measured by observing the cavity emission, is significantly broadened compared to the theoretical estimate. This indicates additional incoherent coupling between the quantum dot and the cavity.

  12. Perturbation Growth at the Convective Scale G. Leoncini, R. S. Plant, S. L. Gray and P. A. Clark

    E-Print Network [OSTI]

    Plant, Robert

    Perturbation Growth at the Convective Scale G. Leoncini, R. S. Plant, S. L. Gray and P. A. Clark. Improvements in computational power mean that operational weather prediction models can now be run (during the entire simulation) of the perturbations. Diagnostics included root mean square precipitation

  13. Water column structure during deposition of Middle DevonianLower Mississippian black and green/gray shales of the

    E-Print Network [OSTI]

    Kenig, Fabien

    26 August 2004 Abstract The extractable organic matter of organic-rich black shales and associated is analyzed to constrain the water column structure during their deposition. All black shale samples contain water euxinic conditions during black shale deposition. Analysis of green/gray shales also reveals

  14. ADVANCED WETLAND ECOLOGY Instructors: Dr. Matthew Gray (mgray11@utk.edu); Dr. Heath Hagy (hhagy@utk.edu)

    E-Print Network [OSTI]

    Gray, Matthew

    (all day workshop) Biebighauser (USFS) 17 Treatment Wetlands Ludwig (UT) 22 Optional Field TripWFS 536 ADVANCED WETLAND ECOLOGY Fall 2011 Instructors: Dr. Matthew Gray (mgray11@utk.edu); Dr Text: Wetlands, 2000, 3rd edition, Wiley (www.wiley.com, ISBN 047129232X) or Wetlands, 2007, 4th

  15. Coherent excitation of a strongly coupled quantum dot - cavity system

    E-Print Network [OSTI]

    Dirk Englund; Arka Majumdar; Andrei Faraon; Mitsuru Toishi; Nick Stoltz; Pierre Petroff; Jelena Vuckovic

    2009-02-19T23:59:59.000Z

    We have studied the coherent excitation of a strongly coupled QD/photonic crystal cavity system. Time-resolved reflectivity measurements show the vacuum Rabi oscillation of the dot in the cavity. Next, we considered the resonant driving of a cavity-detuned dot, which efficiently populates the cavity mode. This cavity-controlled read-out channel allows high-resolution single quantum dot spectroscopy. Autocorrelation measurements on the cavity mode show antibunching and suggest the use of the resonantly driven QD/cavity system as an on-demand source of single photons with potentially near-unity indistinguishability.

  16. Designing Small Silicon Quantum Dots with Low Reorganization Energy

    E-Print Network [OSTI]

    Zang, Xiaoning

    2015-01-01T23:59:59.000Z

    A first principles, excited state analysis is carried out to identify ways of producing silicon quantum dots with low excitonic reorganization energy. These focus on the general strategy of either reducing or constraining exciton-phonon coupling, and four approaches are explored. The results can be implemented in quantum dot solids to mitigate polaronic effects and increase the lifetime of coherent excitonic superpositions. It is demonstrated that such designs can also be used to alter the shape of the spectral density for reorganization so as to reduce the rates of both decoherence and dissipation. The results suggest that it may be possible to design quantum dot solids that support partially coherent exciton transport.

  17. Factorization of Dirac Equation and Graphene Quantum Dot

    E-Print Network [OSTI]

    Youness Zahidi; Ahmed Jellal; Hocine Bahlouli; Mohammed El Bouziani

    2014-05-14T23:59:59.000Z

    We consider a quantum dot described by a cylindrically symmetric 2D Dirac equation. The potentials representing the quantum dot are taken to be of different types of potential configuration, scalar, vector and pseudo-scalar to enable us to enrich our study. Using various potential configurations, we found that in the presence of a mass term an electrostatically confined quantum dot can accommodate true bound states, which is in agreement with previous work. The differential cross section associated with one specific potential configuration has been computed and discussed as function of the various potential parameters.

  18. Effect of Ligands on Characteristics of (CdSe)13 Quantum Dot

    SciTech Connect (OSTI)

    Gao, Yang; Zhou, Bo; Kang, Seung-gu; Xin, Minsi; Yang, Ping; Dai, Xing; Wang, Zhigang; Zhou, Ruhong

    2014-01-01T23:59:59.000Z

    The widespread applications of quantum dots (QDs) have spurred an increasing interest in the study of their coating ligands, which can not only protect the electronic structures of the central QDs, but also control their permeability through biological membranes with both size and shape. In this work, we have used density functional theory (DFT) to investigate the electronic structures of (CdSe)13 passivated by OPMe2(CH2)nMe ligands with different lengths and various numbers of branches (Me=methyl group, n = 0, 1-3). Our results show that the absorption peak in the ultraviolet-visible (UV-vis) spectra displays a clear blue-shift, on the scale of ~100 nm, upon the binding of ligands. Once the total number of ligands bound with (CdSe)13 reached a saturated number (9 or 10), no more blue-shift occurred in the absorption peak in the UV-vis spectra. On the other hand, the aliphatic chain length of ligands has a negligible effect on the optical properties of the QD core. Analyses of the bonding characteristics confirm that optical transitions are dominantly governed by the central QD core rather than the organic passivation. Interestingly, the density of states (DOS) share similar characteristics as vibrational spectra, even though there is no coordination vibration mode between the ligands and the central QD. These findings might provide insights on the material design for the passivation of quantum dots for biomedical applications.

  19. Application of Mn/DOT Utility Coordination Process to Local Agencies Based on national best practices, the Minnesota Department of Transportation (Mn/DOT) Utility

    E-Print Network [OSTI]

    Minnesota, University of

    Application of Mn/DOT Utility Coordination Process to Local Agencies Based on national best practices, the Minnesota Department of Transportation (Mn/DOT) Utility Coordination Process incorporates Processes There are projects where the full process is not necessary. The Mn/DOT Utilities Manual provides

  20. Temperature-Dependent Electron Transport in Quantum Dot Photovoltaics

    E-Print Network [OSTI]

    Padilla, Derek

    2013-01-01T23:59:59.000Z

    to enhanced photovoltaic device efficiency. ACS nano, 2(11):Photovoltaic Devices Introduction Thin-film quantum dot (QD) photovoltaics provide the potential to create high-efficiencyefficiency under such illumina- tion. A non-ideal model of a photovoltaic

  1. Cumulative Effects Guidance 2007 MnDOT Environmental

    E-Print Network [OSTI]

    Minnesota, University of

    relevant for actions requiring an environmental impact statement § Analysis for projects processed as EACumulative Effects Guidance 2007 MnDOT Environmental Stewardship & Streamlining Workshop Presented by Dave Gamble Federal Highway Administration Resource Center Environmental Technical Service Team #12

  2. Engineering a Robust Photovoltaic Device with Quantum Dots and Bacteriorhodopsin

    E-Print Network [OSTI]

    Renugopalakrishnan, Venkatesan

    We present a route toward a radical improvement in solar cell efficiency using resonant energy transfer and sensitization of semiconductor metal oxides with a light-harvesting quantum dot (QD)/bacteriorhodopsin (bR) layer ...

  3. Quantum Dot Tracers for Use in Engineered Geothermal Systems

    Broader source: Energy.gov [DOE]

    DOE Geothermal Peer Review 2010 - Presentation. Project objective: To develop and demonstrate a new class of tracers?semiconductor nanoparticles(quantum dots)?that offer great promise for use in characterizing fracture networks in EGS reservoirs.

  4. Quantum dot conjugates in a sub-micrometer fluidic channel

    DOE Patents [OSTI]

    Stavis, Samuel M.; Edel, Joshua B.; Samiee, Kevan T.; Craighead, Harold G.

    2010-04-13T23:59:59.000Z

    A nanofluidic channel fabricated in fused silica with an approximately 500 nm square cross section was used to isolate, detect and identify individual quantum dot conjugates. The channel enables the rapid detection of every fluorescent entity in solution. A laser of selected wavelength was used to excite multiple species of quantum dots and organic molecules, and the emission spectra were resolved without significant signal rejection. Quantum dots were then conjugated with organic molecules and detected to demonstrate efficient multicolor detection. PCH was used to analyze coincident detection and to characterize the degree of binding. The use of a small fluidic channel to detect quantum dots as fluorescent labels was shown to be an efficient technique for multiplexed single molecule studies. Detection of single molecule binding events has a variety of applications including high throughput immunoassays.

  5. Self-Sustaining Dynamical Nuclear Polarization Oscillations in Quantum Dots

    E-Print Network [OSTI]

    Rudner, M. S.

    Early experiments on spin-blockaded double quantum dots revealed robust, large-amplitude current oscillations in the presence of a static (dc) source-drain bias. Despite experimental evidence implicating dynamical nuclear ...

  6. Study of field driven electroluminescence in colloidal quantum dot solids

    E-Print Network [OSTI]

    Bozyigit, Deniz

    Semiconductor nanocrystals, or quantum dots(QDs), promise to drive advances in electronic light generation. It was recently shown that long range transport of charge, which is typically required for electric excitation and ...

  7. Hybrid organic/quantum dot thin film structures and devices

    E-Print Network [OSTI]

    Coe-Sullivan, Seth (Seth Alexander)

    2005-01-01T23:59:59.000Z

    Organic light emitting diodes have undergone rapid advancement over the course of the past decade. Similarly, quantum dot synthesis has progressed to the point that room temperature highly efficient photoluminescence can ...

  8. Design and fabrication of quantum-dot lasers

    E-Print Network [OSTI]

    Nabanja, Sheila

    2008-01-01T23:59:59.000Z

    Semiconductor lasers using quantum-dots in their active regions have been reported to exhibit significant performance advantages over their bulk semiconductor and quantum-well counterparts namely: low threshold current, ...

  9. Scalable quantum computer architecture with coupled donor-quantum dot qubits

    DOE Patents [OSTI]

    Schenkel, Thomas; Lo, Cheuk Chi; Weis, Christoph; Lyon, Stephen; Tyryshkin, Alexei; Bokor, Jeffrey

    2014-08-26T23:59:59.000Z

    A quantum bit computing architecture includes a plurality of single spin memory donor atoms embedded in a semiconductor layer, a plurality of quantum dots arranged with the semiconductor layer and aligned with the donor atoms, wherein a first voltage applied across at least one pair of the aligned quantum dot and donor atom controls a donor-quantum dot coupling. A method of performing quantum computing in a scalable architecture quantum computing apparatus includes arranging a pattern of single spin memory donor atoms in a semiconductor layer, forming a plurality of quantum dots arranged with the semiconductor layer and aligned with the donor atoms, applying a first voltage across at least one aligned pair of a quantum dot and donor atom to control a donor-quantum dot coupling, and applying a second voltage between one or more quantum dots to control a Heisenberg exchange J coupling between quantum dots and to cause transport of a single spin polarized electron between quantum dots.

  10. Charge tuning in [111] grown GaAs droplet quantum dots

    SciTech Connect (OSTI)

    Bouet, L.; Vidal, M.; Marie, X.; Amand, T.; Wang, G.; Urbaszek, B. [INSA-CNRS-UPS, LPCNO, Université de Toulouse, 135 Ave. Rangueil, 31077 Toulouse (France); Mano, T.; Ha, N.; Kuroda, T.; Sakoda, K. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Durnev, M. V.; Glazov, M. M.; Ivchenko, E. L. [Ioffe Physical-Technical Institute RAS, 194021 St.-Petersburg (Russian Federation)

    2014-08-25T23:59:59.000Z

    We demonstrate charge tuning in strain free GaAs/AlGaAs quantum dots (QDs) grown by droplet epitaxy on a GaAs(111)A substrate. Application of a bias voltage allows the controlled charging of the QDs from ?3|e| to +2|e|. The resulting changes in QD emission energy and exciton fine-structure are recorded in micro-photoluminescence experiments at T?=?4?K. We uncover the existence of excited valence and conduction states, in addition to the s-shell-like ground state. We record a second series of emission lines about 25?meV above the charged exciton emission coming from excited charged excitons. For these excited interband transitions, a negative diamagnetic shift of large amplitude is uncovered in longitudinal magnetic fields.

  11. Fluorescence from a quantum dot and metallic nanosphere hybrid system

    SciTech Connect (OSTI)

    Schindel, Daniel G. [Department of Mathematics and Statistics, University of Winnipeg, 515 Portage Avenue, Winnipeg, MB, R3B 2E9 (Canada); Singh, Mahi R. [Department of Physics and Astronomy, University of Western Ontario, 1151 Richmond Street, London, ON, N6A 3K7 (Canada)

    2014-03-31T23:59:59.000Z

    We present energy absorption and interference in a quantum dot-metallic nanosphere system embedded on a dielectric substrate. A control field is applied to induce dipole moments in the nanosphere and the quantum dot, and a probe field is applied to monitor absorption. Dipole moments in the quantum dot or the metal nanosphere are induced, both by the external fields and by each other's dipole fields. Thus, in addition to direct polarization, the metal nanosphere and the quantum dot will sense one another via the dipole-dipole interaction. The density matrix method was used to show that the absorption spectrum can be split from one peak to two peaks by the control field, and this can also be done by placing the metal sphere close to the quantum dot. When the two are extremely close together, a self-interaction in the quantum dot produces an asymmetry in the absorption peaks. In addition, the fluorescence efficiency can be quenched by the addition of a metal nanosphere. This hybrid system could be used to create ultra-fast switching and sensing nanodevices.

  12. Asynchronous-Transition HMM 

    E-Print Network [OSTI]

    Matsuda, Shigeki; Nakai, Mitsuru; Shimodaira, Hiroshi; Sagayama, Shigeki

    We propose a new class of hidden Markov model (HMM) called asynchronous-transition HMM (AT-HMM). Opposed to conventional HMMs where hidden state transition occurs simultaneously to all features, the new class of HMM allows state transitions...

  13. A Review of "Women Writers and Public Debate in 17th-Century Britain" by Catharine Gray

    E-Print Network [OSTI]

    Farina, Maurizio

    2009-01-01T23:59:59.000Z

    Gray. Women Writers and Public Debate in 17th-Century Britain. New York: Houndmills, Basingstoke: Palgrave Macmillan, 2007. x + 262 pp. $69.95. Review by maurizio farina, university of palermo. Apparently remote from the open-minded salon debates... testimonies ?of an active and engaged citizenry who create[d] widespread debate? (19). Kate Chedgzoy. Women?s Writing in the British Atlantic World: Memory, Place and History, 1550-1700. Cambridge: Cambridge University Press, 2007. viii + 267 pp. $95...

  14. Health-hazard evaluation report HETA-86-053-1933, Gray Pprinting Company, Fostoria, Ohio

    SciTech Connect (OSTI)

    Crandall, M.S.; Boiano, J.M.; Fidler, A.T.; Cantor, F.

    1988-10-01T23:59:59.000Z

    The Gray Printing Company, located in Fostoria, Ohio was studied for potential employee exposures to solvents used in the offset-printing process at that site. The company produced 30 monthly magazines plus various commercial catalogs and brochures. The employment at the site was 185 persons. Equipment used in the production of printed material included photographic-typesetting and sheet-fed and roll fed offset lithographic printing processes. Over two workdays the sheet fed press operator's isopropanol exposures ranged from 247 to 501 mg/m/sup 3/ with personal breathing zone naphtha concentrations of 0.03 to 8.9 mg/m/sup 3/. The web press operator's naphtha exposures ranged from 0.03 to 7.7 mg/m/sup 3/. These workers were also exposed to low concentrations of isopropanol. The highest short term isopropanol exposure was 726 mg/m/sup 3/. Short term exposures to blanket and roller cleaning solvent were low, less than 10 mg/m/sup 3/. A higher than expected reporting of symptoms related to central nervous system depression, difficulty in concentrating, dizziness, cough, chest pain, and dry skin were noted among workers. The authors conclude that there was an increased prevalence of neurotoxic, respiratory, and skin problems among workers using organic solvents. Due to the prevalence of these symptoms, the authors recommend measures for reducing employee exposure to solvents.

  15. Fabrication and optimization of light emitting devices with core-shell quantum dots

    E-Print Network [OSTI]

    Song, Katherine Wei

    2013-01-01T23:59:59.000Z

    Quantum dot light emitting devices (QD-LEDs) are promising options for the next generation of solid state lighting, color displays, and other optoelectronic applications. Overcoating quantum dots (QDs) -- semiconducting ...

  16. Low-Cost Photovoltaics: Luminescent Solar Concentrators And Colloidal Quantum Dot Solar Cells

    E-Print Network [OSTI]

    Leow, Shin Woei

    2014-01-01T23:59:59.000Z

    enhancing the efficiency of solar cells and extending theirA. J. Nozik, “Quantum dot solar cells,” Phys. E Low-Dimens.oxide PbS quantum dot solar cells at low temperature,” Appl.

  17. An Investigation on Gel Electrophoresis with Quantum Dots End-labeled DNA

    E-Print Network [OSTI]

    Chen, Xiaojia

    2009-05-15T23:59:59.000Z

    explored manipulating DNA fragments by end labeling DNA molecules with quantum dot nanocrystals. The quantum dot-DNA conjugates can be further modified through binding interactions with biotinylated single-stranded DNA primers. Single molecule visualization...

  18. Fluorescent of C-dot composite thin films and its properties

    SciTech Connect (OSTI)

    Mahen, Ea Cahya Septia, E-mail: ferry@fi.itb.ac.id; Nuryadin, Bebeh W., E-mail: ferry@fi.itb.ac.id; Iskandar, Ferry, E-mail: ferry@fi.itb.ac.id; Abdullah, Mikrajuddin, E-mail: ferry@fi.itb.ac.id; Khairurrijal, E-mail: ferry@fi.itb.ac.id [Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung, 40132 (Indonesia)

    2014-02-24T23:59:59.000Z

    In the present work, we report the preparation of a fluorescent carbon nanodots (C-dots) epoxy composite thin films on a glass substrate. C-dots were prepared directly by a simple hydrothermal method using citric acid as a carbon source. The C-dots solutions were mixed with a transparent epoxy resin to form C-dot epoxy composite. Furthermore, the composite precursor was deposited on the glass substrate using a spin coating method in order to fabricate C-dot epoxy composite thin film. The transmittance intensity of C-dot composite film reached up to 90% in the visible light spectra. Using Swanopoel method, the film thickness of fabricated C-dot composite film was determined at about 1.45 ?m, a value lies in a typical range needed for a wide range application. Thus, the C-dot composite film is promising in broadening applications in various fields such as energy conversion, optoelectronics, and display technology.

  19. Postdoctoral Positions: Si/SiGe Quantum Dots and Quantum Computing Eriksson Group

    E-Print Network [OSTI]

    Saffman, Mark

    Postdoctoral Positions: Si/SiGe Quantum Dots and Quantum Computing Eriksson Group Department in the area of Si/SiGe quantum dots and quantum computing. Recent advances in our group include single

  20. Manipulating surface diffusion and elastic interactions to obtain quantum dot multilayer arrangements over different length scales

    SciTech Connect (OSTI)

    Placidi, E., E-mail: ernesto.placidi@ism.cnr.it; Arciprete, F. [Istituto di Struttura della Materia, CNR, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Università di Roma “Tor Vergata”, Dipartimento di Fisica, via della Ricerca Scientifica 1, 00133 Rome (Italy); Latini, V.; Latini, S.; Patella, F. [Università di Roma “Tor Vergata”, Dipartimento di Fisica, via della Ricerca Scientifica 1, 00133 Rome (Italy); Magri, R. [Dipartimento di Scienze Fisiche, Informatiche e Matematiche (FIM), Università di Modena e Reggio Emilia, and Centro S3 CNR-Istituto Nanoscienze, Via Campi 213/A, 4100 Modena (Italy); Scuderi, M.; Nicotra, G. [CNR-IMM, Strada VIII, 5, 95121 Catania (Italy)

    2014-09-15T23:59:59.000Z

    An innovative multilayer growth of InAs quantum dots on GaAs(100) is demonstrated to lead to self-aggregation of correlated quantum dot chains over mesoscopic distances. The fundamental idea is that at critical growth conditions is possible to drive the dot nucleation only at precise locations corresponding to the local minima of the Indium chemical potential. Differently from the known dot multilayers, where nucleation of new dots on top of the buried ones is driven by the surface strain originating from the dots below, here the spatial correlations and nucleation of additional dots are mostly dictated by a self-engineering of the surface occurring during the growth, close to the critical conditions for dot formation under the fixed oblique direction of the incoming As flux, that drives the In surface diffusion.

  1. FISH and Chips: Automation of Fluorescent Dot Counting in Interphase Cell Nuclei

    E-Print Network [OSTI]

    van Vliet, Lucas J.

    ) in each cell nucleus. This system works with two fluorescent dyes, one for the DNA hybridization dotsFISH and Chips: Automation of Fluorescent Dot Counting in Interphase Cell Nuclei Hans Netten,1 Ian abnormalities in inter- phase cell nuclei. This process is called dot counting. To estimate the distribution

  2. Self-organized formation of quantum dots of a material on a substrate

    DOE Patents [OSTI]

    Zhang, Zhenyu (232 Long Bow Rd., Knoxville, TN 37922); Wendelken, John F. (925 Suwanee Rd., Knoxville, TN 37923); Chang, Ming-Che (F4-2, No. 178 Sec 5 Minsheng East Rd., Taipei, TW); Pai, Woei Wu (1F, No. 17, Alley 11, Lane 202, Ming Chyuan Rd., Pan Chou City, Taipei County, TW)

    2001-01-01T23:59:59.000Z

    Systems and methods are described for fabricating arrays of quantum dots. A method for making a quantum dot device, includes: forming clusters of atoms on a substrate; and charging the clusters of atoms such that the clusters of atoms repel one another. The systems and methods provide advantages because the quantum dots can be ordered with regard to spacing and/or size.

  3. A highly efficient (>6%) Cd1xMnxSe quantum dot sensitized solar cell

    E-Print Network [OSTI]

    Cao, Guozhong

    A highly efficient (>6%) Cd1ÀxMnxSe quantum dot sensitized solar cell Jianjun Tian,*a Lili Lv,a Chengbin Fei,b Yajie Wang,b Xiaoguang Liua and Guozhong Cao*bc Quantum dot sensitized solar cells (QDSCs-effective solar cell. The design and synthesis of quantum dots (QDs) for achieving high photoelectric performance

  4. Properties of GaN and ZnO Quantum Dots

    E-Print Network [OSTI]

    CHAPTER 3 Properties of GaN and ZnO Quantum Dots Vladimir A. Fonoberov, Alexander A. Balandin Nano. GaN Quantum Dots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 2.1. Electron and Hole States in Strained Wurtzite and Zincblende GaN Quantum Dots

  5. Temperature-Tuning of Near-Infrared Monodisperse Quantum Dot Solids at

    E-Print Network [OSTI]

    Hone, James

    include solar energy conversion as well as quantum communication. In quantum dot systems, the dot sizes photovoltaics, capturing the infrared spectrum, and also exhibiting possible multi- exciton generation.4. Incoherent Fo¨rster resonance energy transfer (FRET) 8­11 can occur between different-sized quantum dots

  6. Quantum dots and etch-induced depletion of a silicon two-dimensional electron gas

    E-Print Network [OSTI]

    Coppersmith, Susan N.

    Quantum dots and etch-induced depletion of a silicon two-dimensional electron gas L. J. Klein, K. L coupled quantum dots containing individual electrons whose spins act as qubits.4 We have made recent in a silicon quantum dot can be held constant for up to 11 hours. This fulfills an important milestone towards

  7. DOT-7A Type A packaging design guide

    SciTech Connect (OSTI)

    Kelly, D.L.

    1995-01-23T23:59:59.000Z

    The purpose of this Design Guide is to provide instruction for designing a U.S. Department of Transportation Specification 7A (DOT-7A) Type A packaging. Another purpose for this Design Guide is to support the evaluation and testing activities that are performed on new designs by a U.S. Department of Energy (DOE) test facility. This evaluation and testing program is called the DOT-7A Program. When an applicant has determined that a DOT-7A packaging is needed and not commercially available, a design may be created according to this document. The design should include a packaging drawing, specifications, analysis report, operating instructions, and a Packaging Qualification Checklist; all of which should be forwarded to a DOE/HQ approved test facility for evaluation and testing. This report is being submitted through the Engineering Documentation System so that it may be used for reference and information purposes.

  8. A GENERAL CIRCULATION MODEL FOR GASEOUS EXOPLANETS WITH DOUBLE-GRAY RADIATIVE TRANSFER

    SciTech Connect (OSTI)

    Rauscher, Emily [Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721-0092 (United States); Menou, Kristen [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States)

    2012-05-10T23:59:59.000Z

    We present a new version of our code for modeling the atmospheric circulation on gaseous exoplanets, now employing a 'double-gray' radiative transfer scheme, which self-consistently solves for fluxes and heating throughout the atmosphere, including the emerging (observable) infrared flux. We separate the radiation into infrared and optical components, each with its own absorption coefficient, and solve standard two-stream radiative transfer equations. We use a constant optical absorption coefficient, while the infrared coefficient can scale as a power law with pressure; however, for simplicity, the results shown in this paper use a constant infrared coefficient. Here we describe our new code in detail and demonstrate its utility by presenting a generic hot Jupiter model. We discuss issues related to modeling the deepest pressures of the atmosphere and describe our use of the diffusion approximation for radiative fluxes at high optical depths. In addition, we present new models using a simple form for magnetic drag on the atmosphere. We calculate emitted thermal phase curves and find that our drag-free model has the brightest region of the atmosphere offset by {approx}12 Degree-Sign from the substellar point and a minimum flux that is 17% of the maximum, while the model with the strongest magnetic drag has an offset of only {approx}2 Degree-Sign and a ratio of 13%. Finally, we calculate rates of numerical loss of kinetic energy at {approx}15% for every model except for our strong-drag model, where there is no measurable loss; we speculate that this is due to the much decreased wind speeds in that model.

  9. Electrically-protected resonant exchange qubits in triple quantum dots

    E-Print Network [OSTI]

    J. M. Taylor; V. Srinivasa; J. Medford

    2013-04-12T23:59:59.000Z

    We present a modulated microwave approach for quantum computing with qubits comprising three spins in a triple quantum dot. This approach includes single- and two-qubit gates that are protected against low-frequency electrical noise, due to an operating point with a narrowband response to high frequency electric fields. Furthermore, existing double quantum dot advances, including robust preparation and measurement via spin-to-charge conversion, are immediately applicable to the new qubit. Finally, the electric dipole terms implicit in the high frequency coupling enable strong coupling with superconducting microwave resonators, leading to more robust two-qubit gates.

  10. DOT-7A Type A packaging test and evaluation procedure

    SciTech Connect (OSTI)

    Kelly, D.L., Westinghouse Hanford

    1996-06-13T23:59:59.000Z

    The purpose of this document is to provide guidance for qualifying a DOT-7A Type A packaging for use. WHC qualifies DOT-7A packaging for two purposes. The first is to provide packages for use by WHC (manufacturer-qualified). The second is to provide a contracted service in support of DOE/EM-76 (DOE-qualified). This document includes descriptions of the performance tests, the personnel involved and their qualifications, appropriate safety and quality assurance considerations, and the procedures to be followed when WHC performs the tests (either as the manufacturer, or on behalf of the DOE`s certification program).

  11. Cooling an electron gas using quantum dot based electronic refrigeration

    E-Print Network [OSTI]

    Prance, Jonathan Robert

    2009-10-13T23:59:59.000Z

    Cooling an electron gas using quantum dot based electronic refrigeration Jonathan Robert Prance August 28, 2009 Downing College, University of Cambridge A thesis submitted for the degree of Doctor of Philosophy Preface The work presented... dots. Conventionally, low temperature measurements of 2DEGs are made by cooling the sample to 1.5 K with liquid Helium-4, to 300 mK with liquid Helium-3, or even down to a few mK using a dilution refrigerator. However, at lower temperatures the electron...

  12. Optical pulse dynamics for quantum-dot logic operations in a photonic-crystal waveguide

    SciTech Connect (OSTI)

    Ma, Xun; John, Sajeev [Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7 Canada (Canada)

    2011-11-15T23:59:59.000Z

    We numerically demonstrate all-optical logic operations with quantum dots (QDs) embedded in a bimodal photonic-crystal waveguide using Maxwell-Bloch equations in a slowly varying envelope approximation (SVEA). The two-level QD excitation level is controlled by one or more femtojoule optical driving pulses passing through the waveguide. Specific logic operations depend on the relative pulse strengths and their detunings from an inhomogeneouslly broadened (about 1% for QD transitions centered at 1.5 {mu}m) QD transition. This excitation controlled two-level medium then determines passage of subsequent probe optical pulses. Envelope equations for electromagnetic waves in the linear dispersion and cutoff waveguide modes are derived to simplify solution of the coupled Maxwell-Bloch equations in the waveguide. These determine the quantum mechanical evolution of the QD excitation and its polarization, driven by classical electromagnetic (EM) pulses near a sharp discontinuity in the EM density of states of the bimodal waveguide. Different configurations of the driving pulses lead to distinctive relations between driving pulse strength and probe pulse passage, representing all-optical logic and, or, and not operations. Simulation results demonstrate that such operations can be done on picosecond time scales and within a waveguide length of about 10 {mu}m in a photonic-band-gap (PBG) optical microchip.

  13. Simulations of the spontaneous emission of a quantum dot near a gap plasmon waveguide

    SciTech Connect (OSTI)

    Perera, Chamanei S., E-mail: cp.hettiarachchige@qut.edu.au; Vernon, Kristy C.; Mcleod, Angus [Plasmonic Device Group, Queensland University of Technology, GPO box 2434, Brisbane, Queensland (Australia)

    2014-02-07T23:59:59.000Z

    In this paper, we modeled a quantum dot at near proximity to a gap plasmon waveguide to study the quantum dot-plasmon interactions. Assuming that the waveguide is single mode, this paper is concerned about the dependence of spontaneous emission rate of the quantum dot on waveguide dimensions such as width and height. We compare coupling efficiency of a gap waveguide with symmetric configuration and asymmetric configuration illustrating that symmetric waveguide has a better coupling efficiency to the quantum dot. We also demonstrate that optimally placed quantum dot near a symmetric waveguide with 50?nm?×?50?nm cross section can capture 80% of the spontaneous emission into a guided plasmon mode.

  14. Gas turbine combustor transition

    DOE Patents [OSTI]

    Coslow, Billy Joe (Winter Park, FL); Whidden, Graydon Lane (Great Blue, CT)

    1999-01-01T23:59:59.000Z

    A method of converting a steam cooled transition to an air cooled transition in a gas turbine having a compressor in fluid communication with a combustor, a turbine section in fluid communication with the combustor, the transition disposed in a combustor shell and having a cooling circuit connecting a steam outlet and a steam inlet and wherein hot gas flows from the combustor through the transition and to the turbine section, includes forming an air outlet in the transition in fluid communication with the cooling circuit and providing for an air inlet in the transition in fluid communication with the cooling circuit.

  15. Gas turbine combustor transition

    DOE Patents [OSTI]

    Coslow, B.J.; Whidden, G.L.

    1999-05-25T23:59:59.000Z

    A method is described for converting a steam cooled transition to an air cooled transition in a gas turbine having a compressor in fluid communication with a combustor, a turbine section in fluid communication with the combustor, the transition disposed in a combustor shell and having a cooling circuit connecting a steam outlet and a steam inlet and wherein hot gas flows from the combustor through the transition and to the turbine section, includes forming an air outlet in the transition in fluid communication with the cooling circuit and providing for an air inlet in the transition in fluid communication with the cooling circuit. 7 figs.

  16. Intermediate-band photosensitive device with quantum dots having tunneling barrier embedded in organic matrix

    DOE Patents [OSTI]

    Forrest, Stephen R. (Ann Arbor, MI)

    2008-08-19T23:59:59.000Z

    A plurality of quantum dots each have a shell. The quantum dots are embedded in an organic matrix. At least the quantum dots and the organic matrix are photoconductive semiconductors. The shell of each quantum dot is arranged as a tunneling barrier to require a charge carrier (an electron or a hole) at a base of the tunneling barrier in the organic matrix to perform quantum mechanical tunneling to reach the respective quantum dot. A first quantum state in each quantum dot is between a lowest unoccupied molecular orbital (LUMO) and a highest occupied molecular orbital (HOMO) of the organic matrix. Wave functions of the first quantum state of the plurality of quantum dots may overlap to form an intermediate band.

  17. Components for quantum computing based on optical transitions in single quantum dots

    E-Print Network [OSTI]

    Pooley, Matthew Anthony

    , the valence band is normally full and the conduction band is normally empty. Carriers can be introduced into the QDs using a variety of methods ranging from electrical injection[8, 9], such as in a light emitting diode, to more exotic methods involving surface...

  18. Systematic study of different transitions in high operating temperature quantum dots in a well photodetectors

    E-Print Network [OSTI]

    Krishna, Sanjay

    . For example, the readout integrated circuit poses significant limitations on the maximum applied bias, maximum 1 Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87106, USA to large volume low cost infrared imaging systems. High operating temperature allows system design- ers

  19. Plane and oblique shocks in shallow granular flows J.M.N.T. Gray1

    E-Print Network [OSTI]

    Gray, Nico

    force is the difference between the gravitational acceleration and the Coulomb rate-independent dry angle of friction in the Mohr- Coulomb constitutive relation. The transition be- tween the two states of an incompress- ible Mohr-Coulomb granular material sliding down a rigid surface. Using a slope fitted

  20. Tips for Transition

    E-Print Network [OSTI]

    Kellems, Ryan Owen; Morningstar, Mary E.

    2010-01-01T23:59:59.000Z

    The article focuses on the best practices solicited by the Division on Career Development & Transition (DCDT) for the student to adult life transition planning for youth with disabilities. The DCDT launched an effort to identify field...

  1. Photon-Assisted Tunneling in a Carbon Nanotube Quantum Dot

    E-Print Network [OSTI]

    not use highly doped Si to avoid leakage of the high- frequency signal to the back gate. The quantum dot is formed between aluminum source/drain contacts, and the potential can be tuned using an aluminum side to source and drain contacts. To transport the microwave signal to the device, we use semirigid coaxial

  2. Portland Cement Concrete Pavement Shannon Golden, Alabama DOT

    E-Print Network [OSTI]

    Portland Cement Concrete Pavement Shannon Golden, Alabama DOT PORTLAND CEMENT CONCRETE PAVEMENT may be substituted for part of the required Portland cement. Substitution of mineral admixtures shall Cement shall not exceed the percentages shown in the following table: MAXIMUM ALLOWABLE SUBSTITUTION

  3. TRICOLOR LIGHT EMITTING DIODE DOT MATRIX DISPLAY SYSTEM WITHAUDIO OUTPUT

    E-Print Network [OSTI]

    Pang, Grantham

    1 TRICOLOR LIGHT EMITTING DIODE DOT MATRIX DISPLAY SYSTEM WITHAUDIO OUTPUT Grantham Pang, Chi emitting diodes; tricolor display; audio communication. I. Introduction This paper relates to a tricolor broadcasting through the visible light rays transmitted by the display panel or assembly. Keywords: light

  4. Alabama DOT: Alabama Report Questions on NDT Testing

    E-Print Network [OSTI]

    Alabama DOT: Alabama Report Questions on NDT Testing 1. What NDT testing methods for concrete materials, concrete pavements, and overlays are you trying? · We perform pavement smoothness testing, pavement friction testing and FWD testing · We are currently using GPR on the I-59 project to locate voids

  5. State DOT: California State Report Questions on NDT Testing

    E-Print Network [OSTI]

    test for this purpose. For concrete pavement, California has used falling weight deflectometer (FWD locations within concrete pavement. 2. In your experience, how does the reliability of NDT testing methodsState DOT: California State Report Questions on NDT Testing 1. What NDT testing methods

  6. State DOT: Louisiana State Report Questions on NDT Testing

    E-Print Network [OSTI]

    State DOT: Louisiana State Report Questions on NDT Testing 1. What NDT testing methods for concrete materials, concrete pavements, and overlays are you trying? LADOTD does not test concrete pavements or overlays non-destructively. We do use the surface resistivity meter for non-destructive testing

  7. Nonclassical Radiation from a Single Quantum Dot P. Michler1

    E-Print Network [OSTI]

    Buratto, Steve

    Nonclassical Radiation from a Single Quantum Dot P. Michler1 ) (a, b), A. Imamoglu (a), A. Kiraz (a nature of radiation and provides direct evi- dence that the emission source is a single two-level quantum of a single atom in an atomic beam [1] and from a single ion which has been stored in a radiofrequency trap [2

  8. Quantum Dot-Aptamer Conjugates for Synchronous Cancer Imaging, Therapy,

    E-Print Network [OSTI]

    Zhang, Liangfang

    a novel quantum dot (QD)-aptamer(Apt)-doxorubicin (Dox) conjugate [QD-Apt(Dox)] as a targeted cancer of prostate cancer cells that express the PSMA protein. The intercalation of Dox, a widely used antineoplastic in a targeted QD-Apt(Dox) conjugate with reversible self- quenching properties based on a Bi-FRET mechanism

  9. Wisconsin DOT 1. Briefly summarize your current pavement smoothness requirements.

    E-Print Network [OSTI]

    Wisconsin DOT 1. Briefly summarize your current pavement smoothness requirements. We currently-contact profiling equipment. Most PCC pavements are profiled using lightweight profilers when the project is still closed to traffic. Most HMA pavements are profiled using high speed profilers (with the same measuring

  10. California DOT 1. Briefly summarize your current pavement smoothness requirements.

    E-Print Network [OSTI]

    California DOT 1. Briefly summarize your current pavement smoothness requirements. For HMA pavement to OGFC placed on existing pavement not constructed under the same project. If concrete pavement is placed ordered. 39-1.12B Straightedge The top layer of HMA pavement must not vary from the lower edge of a12-foot

  11. Quantum dot-based nanomaterials for biological imaging

    E-Print Network [OSTI]

    Zimmer, John P. (John Philip)

    2006-01-01T23:59:59.000Z

    Quantum dot-based fluorescent probes were synthesized and applied to biological imaging in two distinct size regimes: (1) 100-1000 nm and (2) < 10 nm in diameter. The larger diameter range was accessed by doping CdSe/ZnS ...

  12. Supplementary Document CdSe quantum dot synthesis

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    , TOP (Sigma Aldrich) have been used as pure as supplied from the companies without further purification solar cell The reflection measurements have been carried out for the nanopillar solar cells before that the reflection of Si nanopillar solar cells drops off with the integration of quantum dots by 9-14%, which shows

  13. Mn/DOT's Ombudsman Program Collaboration and Process

    E-Print Network [OSTI]

    Minnesota, University of

    Mn/DOT's Ombudsman Program Collaboration and Process #12;Overview Ombudsman exists to rebuild trust on the environmental and municipal consent processes can be critical #12;A Large Organization #12;Tragedy;Ombudsman Does Not... ·! Advocate for one party or point of view ·! Own any formal process or policy

  14. One-particle transition.

    E-Print Network [OSTI]

    Adler, Joan

    One-particle di#11;usional model to mimic some properties of glass transition. Sorkin A.V., Ivanov #15; Computer studies of glass transition #15; Model and simulations #15; Results #15; Conclusions 2 #12; Introduction In recent time many properties of glass transitions have been investigated

  15. Light Rail Transit Strengthening

    E-Print Network [OSTI]

    Minnesota, University of

    Light Rail Transit Improving mobility Easing congestion Strengthening our communities Central Corridor Communicating to the Public During Major Construction May 25, 2011 #12;2 Light Rail Transit;Light Rail Transit Central Corridor Route and Stations 3 · 18 new stations · 9.8 miles of new double

  16. Photocurrent spectrum study of a quantum dot single-photon detector based on resonant tunneling effect with near-infrared response

    SciTech Connect (OSTI)

    Weng, Q. C. [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200241 (China); An, Z. H., E-mail: anzhenghua@fudan.edu.cn, E-mail: luwei@mail.sitp.ac.cn [State Key Laboratory of Surface Physics and Institute of Advanced Materials, Fudan University, Shanghai 200433 (China); Xiong, D. Y.; Zhu, Z. Q. [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200241 (China); Zhang, B.; Chen, P. P.; Li, T. X.; Lu, W., E-mail: anzhenghua@fudan.edu.cn, E-mail: luwei@mail.sitp.ac.cn [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China)

    2014-07-21T23:59:59.000Z

    We present the photocurrent spectrum study of a quantum dot (QD) single-photon detector using a reset technique which eliminates the QD's “memory effect.” By applying a proper reset frequency and keeping the detector in linear-response region, the detector's responses to different monochromatic light are resolved which reflects different detection efficiencies. We find the reset photocurrent tails up to 1.3??m wavelength and near-infrared (?1100?nm) single-photon sensitivity is demonstrated due to interband transition of electrons in QDs, indicating the device a promising candidate both in quantum information applications and highly sensitive imaging applications operating in relative high temperatures (>80?K).

  17. The chiral transition as an Anderson transition

    E-Print Network [OSTI]

    Matteo Giordano; Sandor D. Katz; Tamas G. Kovacs; Ferenc Pittler

    2014-10-31T23:59:59.000Z

    At low temperature the low-lying QCD Dirac spectrum obeys random matrix statistics. Recently we found that above $T_{c}$ the lowest part of the spectrum consists of localized modes that obey Poisson statistics. An interesting implication of this is that as the system crosses $T_{c}$ from above, the spectral statistics at $\\lambda=0$ changes from Poisson to random matrix. Here we study this transition and its possible implications for the finite temperature transition of QCD-like theories.

  18. A carrier relaxation bottleneck probed in single InGaAs quantum dots using integrated superconducting single photon detectors

    SciTech Connect (OSTI)

    Reithmaier, G., E-mail: guenther.reithmaier@wsi.tum.de; Flassig, F.; Hasch, P.; Lichtmannecker, S.; Kaniber, M. [Walter Schottky Institut, Technische Universität München (Germany); Müller, K. [Walter Schottky Institut, Technische Universität München (Germany); E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States); Vu?kovi?, J. [E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States); TUM Institute of Advanced Study, Lichtenbergstraße 2a, 85748 Garching (Germany); Gross, R. [Walther Meißner Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Nanosystems Initiative Munich (NIM), Schellingstraße 4, 80799 München (Germany); Finley, J. J., E-mail: finley@wsi.tum.de [Walter Schottky Institut, Technische Universität München (Germany); Nanosystems Initiative Munich (NIM), Schellingstraße 4, 80799 München (Germany)

    2014-08-25T23:59:59.000Z

    Using integrated superconducting single photon detectors, we probe ultra-slow exciton capture and relaxation dynamics in single self-assembled InGaAs quantum dots embedded in a GaAs ridge waveguide. Time-resolved luminescence measurements performed with on- and off-chip detection reveal a continuous decrease in the carrier relaxation time from 1.22?±?0.07?ns to 0.10?±?0.07?ns upon increasing the number of non-resonantly injected carriers. By comparing off-chip time-resolved spectroscopy with spectrally integrated on-chip measurements, we identify the observed dynamics in the rise time (?{sub r}) as arising from a relaxation bottleneck at low excitation levels. From the comparison with the temporal dynamics of the single exciton transition with the on-chip emission signal, we conclude that the relaxation bottleneck is circumvented by the presence of charge carriers occupying states in the bulk material and the two-dimensional wetting layer continuum. A characteristic ?{sub r} ? P{sup ?2?3} power law dependence is observed suggesting Auger-type scattering between carriers trapped in the quantum dot and the two-dimensional wetting layer continuum which circumvents the phonon relaxation bottleneck.

  19. Simulation of quantum dots size and spacing effect for intermediate band solar cell application based on InAs quantum dots arrangement in GaAs

    SciTech Connect (OSTI)

    Hendra, P. I. B., E-mail: ib.hendra@gmail.com; Rahayu, F., E-mail: ib.hendra@gmail.com; Darma, Y., E-mail: ib.hendra@gmail.com [Physical Vapor Deposition Laboratory, Physics of Material Electronics Research, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia)

    2014-03-24T23:59:59.000Z

    Intermediate band solar cell (IBSC) has become a promising technology in increasing solar cell efficiency. In this work we compare absorption coefficient profile between InAs quantum dots with GaAs bulk. We calculate the efficiency of GaAs bulk and GaAs doped with 2, 5, and 10 nm InAs quantum dot. Effective distances in quantum dot arrangement based on electron tunneling consideration were also calculated. We presented a simple calculation method with low computing power demand. Results showed that arrangement of quantum dot InAs in GaAs can increase solar cell efficiency from 23.9 % initially up to 60.4%. The effective distance between two quantum dots was found 2 nm in order to give adequate distance to prevent electron tunneling and wave functions overlap.

  20. Ordered quantum dot molecules and single quantum dots formed by self-organized anisotropic strain engineering

    SciTech Connect (OSTI)

    Lippen, T. van; Noetzel, R.; Hamhuis, G.J.; Wolter, J.H. [European Institute of Telecommunication Technologies/Communication Technology, Basic Research and Applications (eiTT/COBRA) Inter-University Research Institute, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands)

    2005-02-15T23:59:59.000Z

    An ordered lattice of lateral InAs quantum dot (QD) molecules is created by self-organized anisotropic strain engineering of an (In,Ga)As/GaAs superlattice (SL) template on GaAs(311)B by molecular-beam epitaxy, constituting a Turing pattern in solid state. The SL template and InAs QD growth conditions, such as the number of SL periods, growth temperatures, amount and composition of deposited (In,Ga)As, and insertion of Al-containing layers, are studied in detail for an optimized QD ordering within and among the InAs QD molecules on the SL template nodes, which is evaluated by atomic force microscopy. The average number of InAs QDs within the molecules is controlled by the thickness of the upper GaAs separation layer on the SL template and the (In,Ga)As growth temperature in the SL. The strain-correlated growth in SL template formation and QD ordering is directly confirmed by high-resolution x-ray diffraction. Ordered arrays of single InAs QDs on the SL template nodes are realized for elevated SL template and InAs QD growth temperatures together with the insertion of a second InAs QD layer. The InAs QD molecules exhibit strong photoluminescence (PL) emission up to room temperature. Temperature-dependent PL measurements exhibit an unusual behavior of the full width at half maximum, indicating carrier redistribution solely within the QD molecules.

  1. The red triangles are volcano locations. Dark-orange areas have a higher volcanic hazard; light-orange areas have a lower volcanic hazard. Dark-gray areas have a higher ash fall hazard;

    E-Print Network [OSTI]

    Torgersen, Christian

    The red triangles are volcano locations. Dark-orange areas have a higher volcanic hazard; light-orange areas have a lower volcanic hazard. Dark-gray areas have a higher ash fall hazard; light-gray areas have a lower ash fall hazard. Information is based on data during the past 10,000 years. Bottom, from left

  2. Emerging factors associated with the decline of a gray fox population and multi-scale land cover associations of mesopredators in the Chicago metropolitan area.

    SciTech Connect (OSTI)

    Willingham, Alison N.; /Ohio State U.; ,

    2008-01-01T23:59:59.000Z

    Statewide surveys of furbearers in Illinois indicate gray (Urocyon cinereoargenteus) and red (Vulpes vulpes) foxes have experienced substantial declines in relative abundance, whereas other species such as raccoons (Procyon lotor) and coyotes (Canis latrans) have exhibited dramatic increases during the same time period. The cause of the declines of gray and red foxes has not been identified, and the current status of gray foxes remains uncertain. Therefore, I conducted a large-scale predator survey and tracked radiocollared gray foxes from 2004 to 2007 in order to determine the distribution, survival, cause-specific mortality sources and land cover associations of gray foxes in an urbanized region of northeastern Illinois, and examined the relationships between the occurrence of gray fox and the presence other species of mesopredators, specifically coyotes and raccoons. Although generalist mesopredators are common and can reach high densities in many urban areas their urban ecology is poorly understood due to their secretive nature and wariness of humans. Understanding how mesopredators utilize urbanized landscapes can be useful in the management and control of disease outbreaks, mitigation of nuisance wildlife issues, and gaining insight into how mesopredators shape wildlife communities in highly fragmented areas. I examined habitat associations of raccoons, opossums (Didelphis virginiana), domestic cats (Felis catus), coyotes, foxes (gray and red), and striped skunks (Mephitis mephitis) at multiple spatial scales in an urban environment. Gray fox occurrence was rare and widely dispersed, and survival estimates were similar to other studies. Gray fox occurrence was negatively associated with natural and semi-natural land cover types. Fox home range size increased with increasing urban development suggesting that foxes may be negatively influenced by urbanization. Gray fox occurrence was not associated with coyote or raccoon presence. However, spatial avoidance and mortality due to coyote predation was documented and disease was a major mortality source for foxes. The declining relative abundance of gray fox in Illinois is likely a result of a combination of factors. Assessment of habitat associations indicated that urban mesopredators, particularly coyotes and foxes, perceived the landscape as relatively homogeneous and that urban mesopredators interacted with the environment at scales larger than that accommodated by remnant habitat patches. Coyote and fox presence was found to be associated with a high degree of urban development at large and intermediate spatial scales. However, at a small spatial scale fox presence was associated with high density urban land cover whereas coyote presence was associated with urban development with increased forest cover. Urban habitats can offer a diversity of prey items and anthropogenic resources and natural land cover could offer coyotes daytime resting opportunities in urban areas where they may not be as tolerated as smaller foxes. Raccoons and opossums were found to utilize moderately developed landscapes with interspersed natural and semi-natural land covers at a large spatial scale, which may facilitate dispersal movements. At intermediate and small spatial scales, both species were found to utilize areas that were moderately developed and included forested land cover. These results indicated that raccoons and opossums used natural areas in proximity to anthropogenic resources. At a large spatial scale, skunk presence was associated with highly developed landscapes with interspersed natural and semi-natural land covers. This may indicate that skunks perceived the urban matrix as more homogeneous than raccoons or opossums. At an intermediate spatial scale skunks were associated with moderate levels of development and increased forest cover, which indicated that they might utilize natural land cover in proximity to human-dominated land cover. At the smallest spatial scale skunk presence was associated with forested land cover surrounded by a suburban matrix. Compared to raccoon

  3. Impact of nanostructure configuration on the photovoltaic performance of quantum dot arrays

    E-Print Network [OSTI]

    Berbezier, Aude

    2014-01-01T23:59:59.000Z

    In this work, an effective quantum model based on the non-equilibrium Green's function formalism is used to investigate a selectively contacted high density quantum dot array in an wide band gap host matrix for operation as a quantum dot-enhanced single junction solar cell. By establishing a direct relation between nanostructure configuration and optoelectronic properties, the investigation reveals the influence of inter-dot and dot-contact coupling strength on the radiative rates and consequently on the ultimate performance of photovoltaic devices with finite quantum dot arrays as the active medium. The dominant effects originate in the dependence of the Joint Density of States on the inter-dot coupling in terms of band width and effective band gap.

  4. Antimony mediated growth of high-density InAs quantum dots for photovoltaic cells

    SciTech Connect (OSTI)

    Tutu, F. K.; Wu, J.; Lam, P.; Tang, M.; Liu, H. [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)] [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Miyashita, N.; Okada, Y. [Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-Ku, Tokyo 153-8904 (Japan)] [Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-Ku, Tokyo 153-8904 (Japan); Wilson, J.; Allison, R. [Defence Science and Technology Laboratory, Portsdown West, Portsdown Hill Road, Fareham Hants PO17 6AD (United Kingdom)] [Defence Science and Technology Laboratory, Portsdown West, Portsdown Hill Road, Fareham Hants PO17 6AD (United Kingdom)

    2013-07-22T23:59:59.000Z

    We report enhanced solar cell performance using high-density InAs quantum dots. The high-density quantum dot was grown by antimony mediated molecular beam epitaxy. In-plane quantum dot density over 1 × 10{sup 11} cm{sup ?2} was achieved by applying a few monolayers of antimony on the GaAs surface prior to quantum dot growth. The formation of defective large clusters was reduced by optimization of the growth temperature and InAs coverage. Comparing with a standard quantum dot solar cell without the incorporation of antimony, the high-density quantum dot solar cell demonstrates a distinct improvement in short-circuit current from 7.4 mA/cm{sup 2} to 8.3 mA/cm{sup 2}.

  5. Entanglement distribution for a practical quantum-dot-based quantum processor architecture

    E-Print Network [OSTI]

    Timothy P. Spiller; Irene D'Amico; Brendon W. Lovett

    2007-04-13T23:59:59.000Z

    We propose a quantum dot architecture for enabling universal quantum information processing. Quantum registers, consisting of arrays of vertically stacked self-assembled semiconductor quantum dots, are connected by chains of in-plane self-assembled dots. We propose an entanglement distributor, a device for producing and distributing maximally entangled qubits on demand, communicated through in-plane dot chains. This enables the transmission of entanglement to spatially separated register stacks, providing a resource for the realisation of a sizeable quantum processor built from coupled register stacks of practical size. Our entanglement distributor could be integrated into many of the present proposals for self-assembled quantum dot-based quantum computation. Our device exploits the properties of simple, relatively short, spin-chains and does not require microcavities. Utilizing the properties of self-assembled quantum dots, after distribution the entanglement can be mapped into relatively long lived spin qubits and purified, providing a flexible, distributed, off-line resource.

  6. Formation of long-range ordered quantum dots arrays in amorphous matrix by ion beam irradiation

    SciTech Connect (OSTI)

    Buljan, M. [Charles University in Prague, Prague 12116 (Czech Republic); Ruder Boskovic Institute, Zagreb 10000 (Croatia); Bogdanovic-Radovic, I.; Karlusic, M.; Desnica, U. V.; Radic, N.; Dubcek, P. [Ruder Boskovic Institute, Zagreb 10000 (Croatia); Drazic, G. [Jozef Stefan Institute, Ljubljana 1000 (Slovenia); Salamon, K. [Institute of Physics, Zagreb 10000 (Croatia); Bernstorff, S. [Sincrotrone Trieste, Basovizza 34012 (Italy); Holy, V. [Charles University in Prague, Prague 12116 (Czech Republic)

    2009-08-10T23:59:59.000Z

    We demonstrate the production of a well ordered three-dimensional array of Ge quantum dots in amorphous silica matrix. The ordering is achieved by ion beam irradiation and annealing of a multilayer film. Structural analysis shows that quantum dots nucleate along the direction of the ion beam used for irradiation, while the mutual distance of the quantum dots is determined by the diffusion properties of the multilayer material rather than the distances between traces of ions that are used for irradiation.

  7. Phonon-mediated coupling between quantum dots through an off-resonant microcavity

    E-Print Network [OSTI]

    Arka Majumdar; Michal Bajcsy; Armand Rundquist; Erik Kim; Jelena Vuckovic

    2011-11-30T23:59:59.000Z

    We present experimental results showing phonon-mediated coupling between two quantum dots embedded inside a photonic crystal microcavity. With only one of the dots being spectrally close to the cavity, we observe both frequency up-conversion and down-conversion of the pump light via a $\\sim1.2$ THz phonon. We demonstrate this process for both weak and strong regimes of dot-cavity coupling, and provide a simple theoretical model explaining our observations.

  8. Quantum optics and cavity QED with quantum dots in photonic crystals

    E-Print Network [OSTI]

    Jelena Vuckovic

    2014-02-11T23:59:59.000Z

    This chapter will primarily focus on the studies of quantum optics with semiconductor, epitaxially grown quantum dots embedded in photonic crystal cavities. We will start by giving brief introductions into photonic crystals and quantum dots, then proceed with the introduction to cavity quantum electrodynamics (QED) effects, with a particular emphasis on the demonstration of these effects on the quantum dot-photonic crystal platform. Finally, we will focus on the applications of such cavity QED effects.

  9. Features of the electronic spectrum in a type-I core - shell quantum dot

    SciTech Connect (OSTI)

    Igoshina, S E; Karmanov, A A [Penza State University, Penza (Russian Federation)

    2013-01-31T23:59:59.000Z

    The model is proposed, which allows one to solve the problem of finding the energy spectrum and the wave function of an electron in a type-I core - shell quantum dot. It is shown that the size of the core and shell can serve as control parameters for the optimisation of the energy structure of the quantum dot in order to obtain the real structures with desired electrophysical and optical properties. (quantum dots)

  10. Whispering gallery modes in quantum dot-embedded dielectric microspheres for tagless remote refractometric sensing

    E-Print Network [OSTI]

    Pang, Shuo

    2008-10-10T23:59:59.000Z

    S coating. The CdSe/Zns core/shell quantum dots are prepared colloidally via organometallic synthesis. In these experiments, green quantum dots with an emission peak at 530nm are used. The absorption and emission spectra are shown in Figure 9. 23... WHISPERING GALLERY MODES IN QUANTUM DOT-EMBEDDED DIELECTRIC MICROSPHERES FOR TAGLESS REMOTE REFRACTOMETRIC SENSING A Thesis by SHUO PANG Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment...

  11. NREL Certifies First All-Quantum-Dot Photovoltaic Cell; Demonstrates Stability, Performance (Fact Sheet)

    SciTech Connect (OSTI)

    Not Available

    2011-02-01T23:59:59.000Z

    Researchers at the National Renewable Energy Laboratory (NREL) have certified the first all-quantum-dot photovoltaic cell, which was based on lead sulfide and demonstrated reasonable quantum dot solar cell performance for an initial efficiency measurement along with good stability. The certified open-circuit voltage of the quantum dot cell is greater than that possible from bulk lead sulfide because of quantum confinement.

  12. Single-electron shuttle based on a silicon quantum dot

    E-Print Network [OSTI]

    K. W. Chan; M. Mottonen; A. Kemppinen; N. S. Lai; K. Y. Tan; W. H. Lim; A. S. Dzurak

    2011-10-05T23:59:59.000Z

    We report on single-electron shuttling experiments with a silicon metal-oxide-semiconductor quantum dot at 300 mK. Our system consists of an accumulated electron layer at the Si/SiO_2 interface below an aluminum top gate with two additional barrier gates used to deplete the electron gas locally and to define a quantum dot. Directional single-electron shuttling from the source and to the drain lead is achieved by applying a dc source-drain bias while driving the barrier gates with an ac voltage of frequency f_p. Current plateaus at integer levels of ef_p are observed up to f_p = 240 MHz operation frequencies. The observed results are explained by a sequential tunneling model which suggests that the electron gas may be heated substantially by the ac driving voltage.

  13. Resonant scattering of surface plasmon polaritons by dressed quantum dots

    SciTech Connect (OSTI)

    Huang, Danhong; Cardimona, Dave [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117 (United States); Easter, Michelle [Department of Mechanical Engineering, Stevens Institute of Technology, 1 Castle Point Terrace, Hoboken, New Jersey 07030 (United States); Gumbs, Godfrey [Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065 (United States); Maradudin, A. A. [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Lin, Shawn-Yu [Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180 (United States); Zhang, Xiang [Department of Mechanical Engineering, 3112 Etcheverry Hall, University of California at Berkeley, Berkeley, California 94720 (United States)

    2014-06-23T23:59:59.000Z

    The resonant scattering of surface plasmon-polariton waves (SPP) by embedded semiconductor quantum dots above the dielectric/metal interface is explored in the strong-coupling regime. In contrast to non-resonant scattering by a localized dielectric surface defect, a strong resonant peak in the spectrum of the scattered field is predicted that is accompanied by two side valleys. The peak height depends nonlinearly on the amplitude of SPP waves, reflecting the feedback dynamics from a photon-dressed electron-hole plasma inside the quantum dots. This unique behavior in the scattered field peak strength is correlated with the occurrence of a resonant dip in the absorption spectrum of SPP waves due to the interband photon-dressing effect. Our result on the scattering of SPP waves may be experimentally observable and applied to spatially selective illumination and imaging of individual molecules.

  14. Hydrogen Transition Infrastructure Analysis

    SciTech Connect (OSTI)

    Melendez, M.; Milbrandt, A.

    2005-05-01T23:59:59.000Z

    Presentation for the 2005 U.S. Department of Energy Hydrogen Program review analyzes the hydrogen infrastructure needed to accommodate a transitional hydrogen fuel cell vehicle demand.

  15. Manipulating shear-induced non-equilibrium transitions by feedback control

    E-Print Network [OSTI]

    Tarlan A. Vezirov; Sascha Gerloff; Sabine H. L. Klapp

    2014-11-04T23:59:59.000Z

    Using Brownian Dynamics (BD) simulations we investigate non-equilibrium transitions of sheared colloidal films under controlled shear stress $\\sigma_{\\mathrm{xz}}$. In our approach the shear rate $\\dot\\gamma$ is a dynamical variable, which relaxes on a timescale $\\tau_c$ such that the instantaneous, configuration-dependent stress $\\sigma_{\\mathrm{xz}}(t)$ approaches a pre-imposed value. Investigating the dynamics under this "feedback-control" scheme we find unique behavior in regions where the flow curve $\\sigma_{\\mathrm{xz}}(\\dot\\gamma)$ of the uncontrolled system is monotonic. However, in non-monotonic regions our method allows to {\\em select} between dynamical states characterized by different in-plane structure and viscosities. Indeed, the final state strongly depends on $\\tau_c$ relative to an {\\em intrinsic} relaxation time of the uncontrolled system. The critical values of $\\tau_c$ are estimated on the basis of a simple model.

  16. Computational models for the berry phase in semiconductor quantum dots

    SciTech Connect (OSTI)

    Prabhakar, S., E-mail: rmelnik@wlu.ca; Melnik, R. V. N., E-mail: rmelnik@wlu.ca [M2NeT Lab, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON N2L 3C5 (Canada); Sebetci, A. [Department of Mechanical Engineering, Mevlana University, 42003, Konya (Turkey)

    2014-10-06T23:59:59.000Z

    By developing a new model and its finite element implementation, we analyze the Berry phase low-dimensional semiconductor nanostructures, focusing on quantum dots (QDs). In particular, we solve the Schrödinger equation and investigate the evolution of the spin dynamics during the adiabatic transport of the QDs in the 2D plane along circular trajectory. Based on this study, we reveal that the Berry phase is highly sensitive to the Rashba and Dresselhaus spin-orbit lengths.

  17. Overview of DOE ? DOT December 2009 CNG and Hydrogen Fuels Workshop

    Broader source: Energy.gov (indexed) [DOE]

    (Ambrish Mishra, Oil Industry Safety Directorate, Ministry of Petroleum and Natural Gas) China (Jinyang Zheng, Zhejiang University) United States (Barbara Hennessey, DOT...

  18. artificial quantum-dot helium: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Quantum Dot Arrays and Applications of Multiple Exciton Generation to Third-Generation Photovoltaic Solar Cells Biology and Medicine Websites Summary: to Third-Generation...

  19. acid-capped cdse quantum-dot: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Quantum Dot Arrays and Applications of Multiple Exciton Generation to Third-Generation Photovoltaic Solar Cells Biology and Medicine Websites Summary: to Third-Generation...

  20. Comment on "Analysis of quantum coherent semiconductor quantum dot p-i-n junction photovoltaic cells"

    E-Print Network [OSTI]

    Scully, Marlan O

    2010-01-01T23:59:59.000Z

    This is a comment on PRL paper by A.P. Kirk "Analysis of quantum coherent semiconductor quantum dot p-i-n junction photovoltaic cells"

  1. A Graphene Quantum Dot with a Single Electron Transistor as Integrated Charge Sensor

    E-Print Network [OSTI]

    Ling-Jun Wang; Gang Cao; Tao Tu; Hai-Ou Li; Cheng Zhou; Xiao-Jie Hao; Zhan Su; Guang-Can Guo; Guo-Ping Guo; Hong-Wen Jiang

    2010-08-28T23:59:59.000Z

    We have developed an etching process to fabricate a quantum dot and a nearby single electron transistor as a charge detector in a single layer graphene. The high charge sensitivity of the detector is used to probe Coulomb diamonds as well as excited spectrum in the dot, even in the regime where the current through the quantum dot is too small to be measured by conventional transport means. The graphene based quantum dot and integrated charge sensor serve as an essential building block to form a solid-state qubit in a nuclear-spin-free quantum world.

  2. Photovoltaic performance of ultra-small PbSe quantum dots

    E-Print Network [OSTI]

    Ma, Wanli

    2014-01-01T23:59:59.000Z

    Y; Alivisatos, AP, Photovoltaic Devices Employing TernaryPhotovoltaic performance of ultra-small PbSe quantum dotsquantum dot, solar cell, photovoltaic, quantum size effect

  3. Size and spatial homogeneity of SiGe quantum dots in amorphous silica matrix

    SciTech Connect (OSTI)

    Buljan, Maja [Faculty of Mathematics and Physics, Charles University in Prague, Prague 12116 (Czech Republic); Ruder Boskovic Institute, P.O. Box 180, 10002 Zagreb (Croatia); Pinto, Sara R. C.; Rolo, Anabela G.; Levichev, Sergey; Gomes, Maria J. M. [Physics Department, University of Minho, 4710-057 Braga (Portugal); Kashtiban, Reza J.; Bangert, Ursel [Nanostructured Materials Research Group, School of Materials, University of Manchester, P.O. Box 88, Manchester, M1 7HS (United Kingdom); Chahboun, Adil [Physics Department, University of Minho, 4710-057 Braga (Portugal); Department of Physics, Dhar Mehraz Sciences Faculty, BP 1796, Fes (Morocco); Holy, Vaclav [Faculty of Mathematics and Physics, Charles University in Prague, Prague 12116 (Czech Republic)

    2009-10-15T23:59:59.000Z

    In this paper, we present a study of structural properties of SiGe quantum dots formed in amorphous silica matrix by magnetron sputtering technique. We investigate deposition conditions leading to the formation of dense and uniformly sized quantum dots, distributed homogeneously in the matrix. X-ray and Raman spectroscopy were used to estimate the Si content. A detailed analysis based on grazing incidence small angle x-ray scattering revealed the influence of the deposition conditions on quantum dot sizes, size distributions, spatial arrangement, and concentration of quantum dots in the matrix, as well as the Si:Ge content.

  4. Biexciton recombination rates in self-assembled quantum dots Michael Wimmer,1, 2,

    E-Print Network [OSTI]

    Shumway, John

    GaAs/GaAs, CdSe/ZnSe, and InP/InGaP dots are evaluated, including anisotropic effective masses. Depending

  5. Optical Nonlinearities and Ultrafast Carrier Dynamics in Semiconductor Quantum Dots

    SciTech Connect (OSTI)

    Klimov, V.; McBranch, D.; Schwarz, C.

    1998-08-10T23:59:59.000Z

    Low-dimensional semiconductors have attracted great interest due to the potential for tailoring their linear and nonlinear optical properties over a wide-range. Semiconductor nanocrystals (NC's) represent a class of quasi-zero-dimensional objects or quantum dots. Due to quantum cordhement and a large surface-to-volume ratio, the linear and nonlinear optical properties, and the carrier dynamics in NC's are significantly different horn those in bulk materials. napping at surface states can lead to a fast depopulation of quantized states, accompanied by charge separation and generation of local fields which significantly modifies the nonlinear optical response in NC's. 3D carrier confinement also has a drastic effect on the energy relaxation dynamics. In strongly confined NC's, the energy-level spacing can greatly exceed typical phonon energies. This has been expected to significantly inhibit phonon-related mechanisms for energy losses, an effect referred to as a phonon bottleneck. It has been suggested recently that the phonon bottleneck in 3D-confined systems can be removed due to enhanced role of Auger-type interactions. In this paper we report femtosecond (fs) studies of ultrafast optical nonlinearities, and energy relaxation and trap ping dynamics in three types of quantum-dot systems: semiconductor NC/glass composites made by high temperature precipitation, ion-implanted NC's, and colloidal NC'S. Comparison of ultrafast data for different samples allows us to separate effects being intrinsic to quantum dots from those related to lattice imperfections and interface properties.

  6. Evaluation of postpartum udder characteristics of F1 cows sired by Angus, Gray Brahman, Gir, Indu-Brazil, Nellore and Red Brahman bulls

    E-Print Network [OSTI]

    Riley, David Greg

    1997-01-01T23:59:59.000Z

    Semen from Angus (A), Gray Brahman (GB), Gir (G), Indu-Brazil (IB), Nellore (N) and Red Brahman (RB) bulls was used to artificially inseminate Hereford cows for four years. The F, heifer offspring of these matings were bred to calve annually from...

  7. The impact of Greenland on the predictability of European weather systems Supervisors: Sue Gray (U. Reading), Ian Renfrew (U. East Anglia) and Richard Swinbank (Met

    E-Print Network [OSTI]

    Renfrew, Ian

    The impact of Greenland on the predictability of European weather systems Supervisors: Sue Gray (U-to-high latitude of Greenland means it has a major influence on the atmospheric circulation of the North Atlantic by the presence of Greenland as is the atmosphere well downstream, for example over the British Isles

  8. Synthesis, structure, and optical properties of colloidal GaN quantum dots

    SciTech Connect (OSTI)

    Micic, O.I.; Ahrenkiel, S.P.; Bertram, D.; Nozik, A.J. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)] [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

    1999-07-01T23:59:59.000Z

    Colloidal chemistry was used to synthesize GaN quantum dots. A GaN precursor, polymeric gallium imide, {l_brace}Ga(NH){sub 3/2}{r_brace}{sub n}, which was prepared by the reaction of dimeric amidogallium with ammonia at room temperature, was heated in trioctylamine at 360&hthinsp;{degree}C for one day to produce GaN nanocrystals. The GaN particles were separated, purified, and partially dispersed in a nonpolar solvent to yield transparent colloidal solutions that consisted of individual GaN particles. The GaN nanocrystals have a spherical shape and mean diameter of about 30{plus_minus}12&hthinsp;{Angstrom}. The spectroscopic behavior of colloidal transparent dispersion has been investigated and shows that the band gap of the GaN nanocrystals shifts to slightly higher energy due to quantum confinement. The photoluminescence spectrum at 10 K (excited at 310 nm) shows band edge emission with several emission peaks in the range between 3.2 and 3.8 eV, while the photoluminescence excitation spectrum shows two excited-state transitions at higher energies. {copyright} {ital 1999 American Institute of Physics.}

  9. The solubility of selenate-AFt (3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}3CaSeO{sub 4}{center_dot}37.5H{sub 2}O) and selenate-AFm (3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaSeO{sub 4}{center_dot}xH{sub 2}O)

    SciTech Connect (OSTI)

    Baur, Isabel; Johnson, C. Annette

    2003-11-01T23:59:59.000Z

    The Se(VI)-analogues of ettringite and monosulfate, selenate-AFt (3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}3CaSeO{sub 4}{center_dot}37.5H{sub 2}O), and selenate-AFm (3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaSeO{sub 4}{center_dot}xH{sub 2}O) were synthesised and characterised by bulk chemical analysis and X-ray diffraction. Their solubility products were determined from a series of batch and resuspension experiments conducted at 25 deg. C. For selenate-AFt suspensions, the pH varied between 11.37 and 11.61, and a solubility product, log K{sub so}=61.29{+-}0.60 (I=0 M), was determined for the reaction 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}3CaSeO{sub 4}{center_dot}37.5H{sub 2}O+12 H{sup +} implies 6Ca{sup 2+}+2Al{sup 3+}+3SeO{sub 4}{sup 2-}+43.5H{sub 2}O. Selenate-AFm synthesis resulted in the uptake of Na, which was leached during equilibration and resuspension. For the pH range of 11.75 to 11.90, a solubility product, log K{sub so}=73.40{+-}0.22 (I=0 M), was determined for the reaction 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaSeO{sub 4}{center_dot}xH{sub 2}O+12 H{sup +} implies 4Ca{sup 2+}+2Al{sup 3+}+SeO{sub 4}{sup 2-}+(x+6)H{sub 2}O. Thermodynamic modelling suggested that both selenate-AFt and selenate-AFm are stable in the cementitious matrix; and that in a cement limited in sulfate, selenate concentration may be limited by selenate-AFm to below the millimolar range above pH 12.

  10. Accessibility-based transit planning

    E-Print Network [OSTI]

    Busby, Jeffrey R

    2004-01-01T23:59:59.000Z

    A method for evaluating transit planning proposals using accessibility metrics is advanced in this research. A transit-accessibility model is developed intended for use by in-house transit agency planning staff as a ...

  11. Coupled electromechanical effects in wurtzite quantum dots with wetting layers in gate controlled electric fields: The multiband case

    E-Print Network [OSTI]

    Melnik, Roderick

    Coupled electromechanical effects in wurtzite quantum dots with wetting layers in gate controlled quantifies the electromechanical effects on the band structure of wurtzite quantum dots. c Systematic study on the band structure calculations of wurtzite AlN/GaN quantum dots with wetting layers (WLs). Based

  12. Water-soluble luminescent quantum dots and biomolecular conjugates thereof and related compositions and method of use

    DOE Patents [OSTI]

    Nie, Shuming (Bloomington, IN); Chan, Warren C. W. (Bloomington, IN); Emory, Steven R. (Los Alamos, NM)

    2002-01-01T23:59:59.000Z

    The present invention provides a water-soluble luminescent quantum dot, a biomolecular conjugate thereof and a composition comprising such a quantum dot or conjugate. Additionally, the present invention provides a method of obtaining a luminescent quantum dot, a method of making a biomolecular conjugate thereof, and methods of using a biomolecular conjugate for ultrasensitive nonisotopic detection in vitro and in vivo.

  13. Water-soluble luminescent quantum dots and biomolecular conjugates thereof and related compositions and methods of use

    DOE Patents [OSTI]

    Nie, Shuming; Chan, Warren C. W.; Emory, Stephen

    2007-03-20T23:59:59.000Z

    The present invention provides a water-soluble luminescent quantum dot, a biomolecular conjugate thereof and a composition comprising such a quantum dot or conjugate. Additionally, the present invention provides a method of obtaining a luminescent quantum dot, a method of making a biomolecular conjugate thereof, and methods of using a biomolecular conjugate for ultrasensitive nonisotopic detection in vitro and in vivo.

  14. Holographic Magnetic Phase Transition

    E-Print Network [OSTI]

    Gilad Lifschytz; Matthew Lippert

    2009-06-21T23:59:59.000Z

    We study four-dimensional interacting fermions in a strong magnetic field, using the holographic Sakai-Sugimoto model of intersecting D4 and D8 branes in the deconfined, chiral-symmetric parallel phase. We find that as the magnetic field is varied, while staying in the parallel phase, the fermions exhibit a first-order phase transition in which their magnetization jumps discontinuously. Properties of this transition are consistent with a picture in which some of the fermions jump to the lowest Landau level. Similarities to known magnetic phase transitions are discussed.

  15. Title: Development of Plasmon Assisted Quantum DOT Sensors Multispectral and Polarization Selective Imaging

    E-Print Network [OSTI]

    Johnson, Eric E.

    Title: Development of Plasmon Assisted Quantum DOT Sensors for Multispectral and Polarization in plasmonic nanostructures. Spectral and polarization sensitive EO sensors provide unique remote sensing of subwavelength plasmon-polariton assisted quantum dot (QD) photodetectors (PDs) for pixel-level spectral

  16. Mid Infrared Focal Plane Arrays With Nanoscale Quantum Dots and Superlattices

    E-Print Network [OSTI]

    Krishna, Sanjay

    Mid Infrared Focal Plane Arrays With Nanoscale Quantum Dots and Superlattices S. Krishna Center- Molecular beam epitaxy, Nanoscale, Quantum Dots Superlattices, Antimonides, Mid-infrared photodetector. I. INTRODUCTION Presently, the state of the art photon detectors for the mid wave infrared (MWIR, 3-5 µm) and long

  17. Enlarged symmetry and coherence in arrays of quantum dots A. V. Onufriev and J. B. Marston

    E-Print Network [OSTI]

    Onufriev, Alexey

    . A Hubbard model then describes a pillar array of coupled dots, and at half-filling the system can be mapped materials. Recent advances in nanofabrication tech- niques offer the possibility of constructing artificial- teractions that lift the degeneracy. However, as Stafford and Das Sarma noticed,3 semiconducting quantum dots

  18. Photovoltaic quantum dot quantum cascade infrared photodetector A. V. Barve and S. Krishna

    E-Print Network [OSTI]

    Krishna, Sanjay

    Photovoltaic quantum dot quantum cascade infrared photodetector A. V. Barve and S. Krishna Citation subject to AIP license or copyright; see http://apl.aip.org/about/rights_and_permissions #12;Photovoltaic) Design and characterization of a quantum dot quantum cascade detector for photovoltaic midwave infrared

  19. Bioimaging 4 (1996) 93106. Printed in the UK Fluorescent dot counting in

    E-Print Network [OSTI]

    van Vliet, Lucas J.

    Bioimaging 4 (1996) 93­106. Printed in the UK Fluorescent dot counting in interphase cell nuclei allows the enumeration of chromosomal abnormalities in interphase cell nuclei. This process is called dot counting. To estimate the distribution of chromosomes per cell, a large number of cells have to be analysed

  20. Double-dot charge transport in Si single-electronhole transistors L. P. Rokhinson,a)

    E-Print Network [OSTI]

    Rokhinson, Leonid

    ­oxide­ semiconductor field-effect transistors MOSFETs brought to light several issues related to the electrical beneath the dot transforming it into a free-standing bridge. Subsequently, 40 or 50 nm of oxide are thermally grown which further reduce the size of the dot. Polysilicon gate is deposited over the bridge

  1. Light extraction analysis and enhancement in a quantum dot light emitting diode

    E-Print Network [OSTI]

    Wu, Shin-Tson

    Light extraction analysis and enhancement in a quantum dot light emitting diode Ruidong Zhu outcoupling and angular performance of quantum dot light emitting diode (QLED). To illustrate the design principles, we use a red QLED as an example and compare its performance with an organic light emitting diode

  2. How common are dot-like distributions? Taxonomical oversplitting in western European Agrodiaetus

    E-Print Network [OSTI]

    Pierce, Naomi E.

    How common are dot-like distributions? Taxonomical oversplitting in western European Agrodiaetusbij_1481 130..154 Approximately 50 taxa of butterflies in Western Europe have been described as new, the Balkan Peninsula and Crimea, or to small Mediterranean islands (Kudrna, 2002). Usually, these dot

  3. Are you shipping a DOT Hazardous Material? Is your material listed

    E-Print Network [OSTI]

    Pawlowski, Wojtek

    Are you shipping a DOT Hazardous Material? Is your material listed on the DOT Hazmat Table? http://www.myregs.com/dotrspa/ (select Hazmat Table upper left) Your material is a Hazardous Material and must be shipped following the full regulations. Follow the instructions on the linked page, select the hazard of the material

  4. Minimal Self-Contained Quantum Refrigeration Machine Based on Four Quantum Dots

    E-Print Network [OSTI]

    Davide Venturelli; Rosario Fazio; Vittorio Giovannetti

    2013-06-22T23:59:59.000Z

    We present a theoretical study of an electronic quantum refrigerator based on four quantum dots arranged in a square configuration, in contact with as many thermal reservoirs. We show that the system implements the basic minimal mechanism for acting as a self-contained quantum refrigerator, by demonstrating heat extraction from the coldest reservoir and the cooling of the nearby quantum-dot.

  5. GeSi intermixing in Ge quantum dots on Si,,001... and Si,,111... F. Boscherinia)

    E-Print Network [OSTI]

    Ge­Si intermixing in Ge quantum dots on Si,,001... and Si,,111... F. Boscherinia) Laboratori December 1999 Exploiting Ge K-edge x-ray absorption spectroscopy we provide direct evidence of Si­Ge intermixing in self-organized strained and unstrained Ge quantum dots on Si, and provide a quantitative

  6. Rapid degradation of CdSe/ZnS colloidal quantum dots exposed to gamma irradiation

    E-Print Network [OSTI]

    New Mexico, University of

    Rapid degradation of CdSe/ZnS colloidal quantum dots exposed to gamma irradiation Nathan J. Withers are reported. Optical degradation is evaluated by tracking the dependence of photoluminescence intensity on irradiation dose. CdSe/ZnS quantum dots show poor radiation hardness, and severely degrade after less than 20

  7. Commensurability effects induced by a periodic array of nanoscale anti-dots in Nb superconductor

    E-Print Network [OSTI]

    Metlushko, Vitali

    Commensurability effects induced by a periodic array of nanoscale anti-dots in Nb superconductor A. PACS: 74.25.Ha; 74.76.)w Keywords: Nanostructures; Anti-dots; Commensurability 1. Introduction atomic layers on periodical substrate [5], magnetic bubble arrays [6] and the magnetically induced Wigner

  8. Large open telescope: size-upscaling from DOT to LOT Robert H. Hammerschlaga

    E-Print Network [OSTI]

    Rutten, Rob

    Large open telescope: size-upscaling from DOT to LOT Robert H. Hammerschlaga , Aswin P. L. Jägersb, telescope drives 1. INTRODUCTION The Dutch Open Telescope (DOT) on the Canary island La Palma consists temperature homogeneous. No warm air bubbles are forced upwards against the closed wall of a tower and no heat

  9. Mechanism for thermoelectric figure-of-merit enhancement in regimented quantum dot superlattices

    E-Print Network [OSTI]

    Mechanism for thermoelectric figure-of-merit enhancement in regimented quantum dot superlattices propose a mechanism for enhancement of the thermoelectric figure-of-merit in regimented quantum dot, as a result, to the thermoelectric figure-of-merit enhancement. To maximize the improvement, one has to tune

  10. Evidence for formation of multi-quantum dots in hydrogenated graphene

    E-Print Network [OSTI]

    Chuang, Chiashain; Puddy, Reuben K; Connolly, Malcolm R; Lo, Shun-Tsung; Lin, Huang-De; Chen, Tse-Ming; Smith, Charles G; Liang, Chi-Te

    2012-08-16T23:59:59.000Z

    Abstract We report the experimental evidence for the formation of multi-quantum dots in a hydrogenated single-layer graphene flake. The existence of multi-quantum dots is supported by the low-temperature measurements on a field effect transistor...

  11. Review paper: Toward highly efficient quantum-dot-and dye-sensitized solar cells

    E-Print Network [OSTI]

    Park, Byungwoo

    Review paper: Toward highly efficient quantum-dot- and dye-sensitized solar cells Hongsik Choi Interface control Light harvesting Tandem solar cell a b s t r a c t Dye- and quantum-dot-sensitized solar technologies of silicon-based solar cells should be resolved [7]. Dye-sensitized solar cells (DSSCs) have been

  12. Arrays of nanoscale magnetic dots: Fabrication by x-ray interference lithography and characterization

    SciTech Connect (OSTI)

    Heyderman, L.J.; Solak, H.H.; David, C.; Atkinson, D.; Cowburn, R.P.; Nolting, F. [Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Nanomagnetism Group, Department of Physics, University of Durham, Rochester Building, Science Laboratories, South Road, Durham DH1 3LE (United Kingdom); Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)

    2004-11-22T23:59:59.000Z

    X-ray interference lithography (XIL) was employed in combination with electrodeposition to fabricate arrays of nanoscale nickel dots which are uniform over 40 {mu}m and have periods down to 71 nm. Using extreme-ultraviolet light, XIL has the potential to produce magnetic dot arrays over large areas with periods well below 50 nm, and down to a theoretical limit of 6.5 nm for a 13 nm x-ray wavelength. In the nickel dot arrays, we observed the effect of interdot magnetic stray field interactions. Measuring the hysteresis loops using the magneto-optical Kerr effect, a double switching via the vortex state was observed in the nickel dots with diameters down to 44 nm and large dot separations. As the dot separations are reduced to below around 50 nm a single switching, occurring by collective rotation of the magnetic spins, is favored due to interdot magnetic stray field interactions. This results in magnetic flux closure through several dots which could be visualized with micromagnetic simulations. Further evidence of the stray field interactions was seen in photoemission electron microscopy images, where bands of contrast corresponding to chains of coupled dots were observed.

  13. Characterization of a microwave frequency resonator via a nearby quantum dot

    E-Print Network [OSTI]

    Wallraff, Andreas

    and superconducting qubits. The study of the inter- action between the electromagnetic field of such a resonator of a hybrid system consisting of a microwave transmission-line resonator and a lateral quantum dot defined is studied by monitoring the electrical conductance through the quantum dot. The presence of a strong

  14. Ambient-Processed Colloidal Quantum Dot Solar Cells via Individual Pre-Encapsulation of Nanoparticles

    E-Print Network [OSTI]

    Ambient-Processed Colloidal Quantum Dot Solar Cells via Individual Pre-Encapsulation, 2010; E-mail: ted.sargent@utoronto.ca Solution-processed solar cells employing colloidal quantum dots-junction and tandem solar cells both rely on IR-band-gap semiconductors, there has been much recent emphasis

  15. Wildfire Policy in Transition Yellowstone

    E-Print Network [OSTI]

    Wildfire Policy in Transition 1910 #12;Yellowstone 1988 #12;Colorado South Canyon Fire 1994 #12;#12;Wildfire Policy in Transition 1910 #12;

  16. Coupling of PbS Quantum Dots to Photonic Crystal Cavities at Room Temperature

    E-Print Network [OSTI]

    Ilya Fushman; Dirk Englund; Jelena Vuckovic

    2005-05-14T23:59:59.000Z

    We demonstrate the coupling of PbS quantum dot emission to photonic crystal cavities at room temperature. The cavities are defined in 33% Al, AlGaAs membranes on top of oxidized AlAs. Quantum dots were dissolved in Poly-methyl-methacrylate (PMMA) and spun on top of the cavities. Quantum dot emission is shown to map out the structure resonances, and may prove to be viable sources for room temperature cavity coupled single photon generation for quantum information processing applications. These results also indicate that such commercially available quantum dots can be used for passive structure characterization. The deposition technique is versatile and allows layers with different dot densities and emission wavelengths to be re-deposited on the same chip.

  17. Intermediate-band photosensitive device with quantum dots embedded in energy fence barrier

    DOE Patents [OSTI]

    Forrest, Stephen R. (Ann Arbor, MI); Wei, Guodan (Ann Arbor, MI)

    2010-07-06T23:59:59.000Z

    A plurality of layers of a first semiconductor material and a plurality of dots-in-a-fence barriers disposed in a stack between a first electrode and a second electrode. Each dots-in-a-fence barrier consists essentially of a plurality of quantum dots of a second semiconductor material embedded between and in direct contact with two layers of a third semiconductor material. Wave functions of the quantum dots overlap as at least one intermediate band. The layers of the third semiconductor material are arranged as tunneling barriers to require a first electron and/or a first hole in a layer of the first material to perform quantum mechanical tunneling to reach the second material within a respective quantum dot, and to require a second electron and/or a second hole in a layer of the first semiconductor material to perform quantum mechanical tunneling to reach another layer of the first semiconductor material.

  18. Single photon emission from site-controlled InGaN/GaN quantum dots

    SciTech Connect (OSTI)

    Zhang, Lei; Hill, Tyler A.; Deng, Hui, E-mail: dengh@umich.edu [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109 (United States)] [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109 (United States); Teng, Chu-Hsiang; Lee, Leung-Kway; Ku, Pei-Cheng, E-mail: peicheng@umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109 (United States)] [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109 (United States)

    2013-11-04T23:59:59.000Z

    Single photon emission was observed from site-controlled InGaN/GaN quantum dots. The single-photon nature of the emission was verified by the second-order correlation function up to 90?K, the highest temperature to date for site-controlled quantum dots. Micro-photoluminescence study on individual quantum dots showed linearly polarized single exciton emission with a lifetime of a few nanoseconds. The dimensions of these quantum dots were well controlled to the precision of state-of-the-art fabrication technologies, as reflected in the uniformity of their optical properties. The yield of optically active quantum dots was greater than 90%, among which 13%–25% exhibited single photon emission at 10?K.

  19. Single photon absorption and dynamic control of a coupled quantum dot-cavity system

    E-Print Network [OSTI]

    Robert Johne; Andrea Fiore

    2011-10-11T23:59:59.000Z

    We theoretically investigate the dynamic interaction of a quantum dot in a nanocavity with timesymmetric single photon pulses. The simulations, based on a wavefunction approach, reveal that almost perfect single photon absorption occurs for quantum dot-cavity systems operating on the edge between strong and weak coupling regime. The computed maximum absorptions probability is close to unity for pulses with a typical length comparable to the half of the Rabi period. Furthermore, the dynamic control of the quantum dot energy via electric fields allows the freezing of the light-matter interaction leaving the quantum dot in its excited state. Shaping of single photon wavepackets by the electric field control is limited by the occurrence of chirping of the single photon pulse. This understanding of the interaction of single photon pulses with the quantum dot-cavity system provides the basis for the development of advanced protocols for quantum information processing in the solid state.

  20. Bus Centric Rapid Transit

    E-Print Network [OSTI]

    Banasiak, J.

    2011-01-01T23:59:59.000Z

    Transfer Center TOD ? SmartCode/CNU Goals ? Public/private development partnership ? Emphasis on the pedestrian ? Bicycle and transit oriented development ? Dover Kohl TOD report, Dec. 2010 ? WTC will be anchor and terminus for BRT 11 18 Westside... Transfer Center 18 18 Five Points TOD #2 15 Five Points TOD 16 ? SmartCode/CNU Goals ? Public/private development partnership ? Emphasis on the pedestrian ? Bicycle and transit oriented development ? Dover Kohl TOD report, Dec. 2010 ? Five...

  1. Cancrinite: Crystal Structure, Phase Transitions, and Dehydration Behavior with Temperature

    SciTech Connect (OSTI)

    Hassan,I.; Antao, S.; Parise, J.

    2006-01-01T23:59:59.000Z

    The structural behavior of a cancrinite, Na{sub 5.96}Ca{sub 1.52}[Al{sub 6}Si{sub 6}O{sub 24}](CO{sub 3}){sub 1.57}{center_dot}1.75H{sub 2}O, was determined by using in situ synchrotron X-ray powder diffraction data [{lambda} = 0.91806(5) {angstrom}] at room pressure and from 25 to 982 {sup o}C. The sample was heated at a rate of about 9.5 {sup o}C/min, and X-ray traces were collected at about 15 {sup o}C intervals. The satellite reflections in cancrinite were lost at about 504 {sup o}C, where a phase transition occurs. All the unit-cell parameters for cancrinite also show a discontinuity at 504 {sup o}C. Initially, the [Ca{center_dot}CO{sub 3}] clusters and their vacancies are ordered in the channels, and this ordering is destroyed on heating to give rise to the phase transition. Cancrinite loses water continuously until about 625 {sup o}C; thereafter an anhydrous cancrinite phase exists. From 25 to 952 {sup o}C, a minimal amount of CO{sub 2} is lost from the structure. Over this temperature range, the average bridging angle, which is an indication of the degree of rotation of the tetrahedra, increases from 143.7(4) to 147.7(5){sup o}. Rotations of the tetrahedra are caused by expansion of the Na1-O2 bond lengths.

  2. A quantum dot implementation of the quantum NAND algorithm

    E-Print Network [OSTI]

    J. M. Taylor

    2007-08-10T23:59:59.000Z

    We propose a physical implementation of the quantum NAND tree evaluation algorithm. Our approach, based on continuous time quantum walks, uses the wave interference of a single electron in a heirarchical set of tunnel coupled quantum dots. We find that the query complexity of the NAND tree evaluation does not suffer strongly from disorder and dephasing, nor is it directly limited by temperature or restricted dimensionality for 2-d structures. Finally, we suggest a potential application of this algorithm to the efficient determination of high-order correlation functions of complex quantum systems.

  3. Computational modeling of electrophotonics nanomaterials: Tunneling in double quantum dots

    SciTech Connect (OSTI)

    Vlahovic, Branislav, E-mail: vlahovic@nccu.edu; Filikhin, Igor, E-mail: vlahovic@nccu.edu [Department of Physics, North Carolina Central University, 1801 Fayetteville Street, Durham, North Carolina 27707 (United States)

    2014-10-06T23:59:59.000Z

    Single electron localization and tunneling in double quantum dots (DQD) and rings (DQR) and in particular the localized-delocalized states and their spectral distributions are considered in dependence on the geometry of the DQDs (DQRs). The effect of violation of symmetry of DQDs geometry on the tunneling is studied in details. The cases of regular and chaotic geometries are considered. It will be shown that a small violation of symmetry drastically affects localization of electron and that anti-crossing of the levels is the mechanism of tunneling between the localized and delocalized states in DQRs.

  4. Photocurrent extraction efficiency in colloidal quantum dot photovoltaics

    SciTech Connect (OSTI)

    Kemp, K. W.; Wong, C. T. O.; Hoogland, S. H.; Sargent, E. H. [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada)] [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada)

    2013-11-18T23:59:59.000Z

    The efficiency of photocurrent extraction was studied directly inside operating Colloidal Quantum Dot (CQD) photovoltaic devices. A model was derived from first principles for a thin film p-n junction with a linearly spatially dependent electric field. Using this model, we were able to clarify the origins of recent improvement in CQD solar cell performance. From current-voltage diode characteristics under 1 sun conditions, we extracted transport lengths ranging from 39 nm to 86 nm for these materials. Characterization of the intensity dependence of photocurrent extraction revealed that the dominant loss mechanism limiting the transport length is trap-mediated recombination.

  5. Photoluminescence-enhanced biocompatible quantum dots by phospholipid functionalization

    SciTech Connect (OSTI)

    Shi Yunfeng [School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); He Peng [Department of Chemistry, North Carolina State University, Raleigh, NC 27695 (United States)], E-mail: phe@ncsu.edu; Zhu Xinyuan [School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Instrumental Analysis Center, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai 200030 (China)], E-mail: xyzhu@sjtu.edu.cn

    2008-10-02T23:59:59.000Z

    A simple two-step strategy using phospholipid (PPL) to functionalize core/shell CdSe/ZnS quantum dots (QDs) has been described. The experimental data show that the use of S-H terminated PPL results not only in the high colloidal stability of core/shell CdSe/ZnS QDs in the aqueous phase, but also in the significant enhancement of photoluminescence. The degree of the enhancement is a function of the PPL-CdSe/ZnS QDs sample concentration. These results might be promising for future biological platform in new devices ranging from photovoltaic cells to biosensors and other devices.

  6. Resonant excitation and photon entanglement from semiconductor quantum dots

    E-Print Network [OSTI]

    Ana Predojevi?

    2015-03-01T23:59:59.000Z

    In this chapter we review the use of semiconductor quantum dots as sources of quantum light. Principally, we focus on resonant two-photon excitation, which is a method that allows for on-demand generation of photon pairs. We explore the advantages of resonant excitation and present a number of measurements that were made in this excitation regime. In particular, we cover the following topics: photon statistics, coherent manipulation of the ground-excited state superposition, and generation of time-bin entangled photon pairs.

  7. Nanoscale engineering boosts performance of quantum dot light emitting

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of Science (SC)Integrated CodesTransparency VisitSilver Toyota PriusNSRdiodes Quantum dot light

  8. Activation of molecular catalysts using semiconductor quantum dots

    DOE Patents [OSTI]

    Meyer, Thomas J. (Chapel Hill, NC); Sykora, Milan (Los Alamos, NM); Klimov, Victor I. (Los Alamos, NM)

    2011-10-04T23:59:59.000Z

    Photocatalytic materials based on coupling of semiconductor nanocrystalline quantum dots (NQD) and molecular catalysts. These materials have capability to drive or catalyze non-spontaneous chemical reactions in the presence of visible radiation, ultraviolet radiation, or both. The NQD functions in these materials as a light absorber and charge generator. Following light absorption, the NQD activates a molecular catalyst adsorbed on the surface of the NQD via transfer of one or more charges (either electrons or electron-holes) from the NQD to the molecular catalyst. The activated molecular catalyst can then drive a chemical reaction. A photoelectrolytic device that includes such photocatalytic materials is also described.

  9. Shiny quantum dots brighten future of solar cells

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del Sol HomeFacebookScholarship Fund scholarshipsShedding LightShiny quantum dots

  10. TxDOT - Certification for Utility Accommodation | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov YouKizildere IRaghuraji Agro IndustriesTown of Ladoga, IndianaTurtle Airships Jump to:TwiggsJemezwells. (SINDA-3GTxDOT -

  11. Theory of dynamic nuclear polarization and feedback in quantum dots

    E-Print Network [OSTI]

    Sophia E. Economou; Edwin Barnes

    2014-04-06T23:59:59.000Z

    An electron confined in a quantum dot interacts with its local nuclear spin environment through the hyperfine contact interaction. This interaction combined with external control and relaxation or measurement of the electron spin allows for the generation of dynamic nuclear polarization. The quantum nature of the nuclear bath, along with the interplay of coherent external fields and incoherent dynamics in these systems renders a wealth of intriguing phenomena seen in recent experiments such as electron Zeeman frequency focusing, hysteresis, and line dragging. We develop in detail a fully quantum, self-consistent theory that can be applied to such experiments and that moreover has predictive power. Our theory uses the operator sum representation formalism in order to incorporate the incoherent dynamics caused by the additional, Markovian bath, which in self-assembled dots is the vacuum field responsible for electron-hole optical recombination. The beauty of this formalism is that it reduces the complexity of the problem by encoding the joint dynamics of the external coherent and incoherent driving in an effective dynamical map that only acts on the electron spin subspace. This together with the separation of timescales in the problem allows for a tractable and analytically solvable formalism. The key role of entanglement between the electron spin and the nuclear spins in the formation of dynamic nuclear polarization naturally follows from our solution. We demonstrate the theory in detail for an optical pulsed experiment and present an in-depth discussion and physical explanation of our results.

  12. Quantum Dots-based Reverse Phase Protein Microarray

    SciTech Connect (OSTI)

    Shingyoji, Masato; Gerion, Daniele; Pinkel, Dan; Gray, Joe W.; Chen, Fanqing

    2005-07-15T23:59:59.000Z

    CdSe nanocrystals, also called quantum dots (Qdots) are a novel class of fluorophores, which have a diameter of a few nanometers and possess high quantum yield, tunable emission wavelength and photostability. They are an attractive alternative to conventional fluorescent dyes. Quantum dots can be silanized to be soluble in aqueous solution under biological conditions, and thus be used in bio-detection. In this study, we established a novel Qdot-based technology platform that can perform accurate and reproducible quantification of protein concentration in a crude cell lysate background. Protein lysates have been spiked with a target protein, and a dilution series of the cell lysate with a dynamic range of three orders of magnitude has been used for this proof-of-concept study. The dilution series has been spotted in microarray format, and protein detection has been achieved with a sensitivity that is at least comparable to standard commercial assays, which are based on horseradish peroxidase (HRP) catalyzed diaminobenzidine (DAB) chromogenesis. The data obtained through the Qdot method has shown a close linear correlation between relative fluorescence unit and relative protein concentration. The Qdot results are in almost complete agreement with data we obtained with the well-established HRP-DAB colorimetric array (R{sup 2} = 0.986). This suggests that Qdots can be used for protein quantification in microarray format, using the platform presented here.

  13. In vitro adrenal bioactivation and effects on steroid metabolism of DDT, PCBs and their metabolites in the gray seal (Halichoerus grypus)

    SciTech Connect (OSTI)

    Lund, B.O. (Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept. of Pharmacology and Toxicology)

    1994-06-01T23:59:59.000Z

    The irreversible binding of the DDT metabolites o,p[prime]-DDD [2-(2-chlorophenyl)-2(4-chlorophenyl)-1,1-dichloroethane] and MeSO[sub 2]-DDE [3-methylsulfonyl-2,2-bis(4-chlorophenyl)-1,1-dichloroethene], as well as their potential to inhibit mitochondrial steroid 11[beta]-hydroxylation in the gray seal adrenal gland, was studied. The adrenal bioactivated both o,p[prime]-DDD and MeSO[sub 2[minus

  14. Effects of boat traffic on the behavior of gray whales, Eschrichtius robustus, in Bahia Magdalena, Baja California Sur, Mexico: a bioacoustic assessment

    E-Print Network [OSTI]

    Ollervides, Francisco

    1997-01-01T23:59:59.000Z

    functions, whales are dependent on acoustic signaling for spacing (positioning), attracting conspecifics (advertising reproductive status), and alerting against danger (predators) (Reeves 1977). Whales must be able to accommodate to the ambient noise... that prevails at their specific location, so that their sounds and signals are receivable, Dahlheim (1987) suggested that gray whales occupy specific acoustic niches related to specific ambient noise of these lagoons. Survival probabilities of any species...

  15. Functionalized Silicone Nanospheres: Synthesis, Transition Metal...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Functionalized Silicone Nanospheres: Synthesis, Transition Metal Immobilization, and Catalytic Applications. Functionalized Silicone Nanospheres: Synthesis, Transition Metal...

  16. Examining hydrogen transitions.

    SciTech Connect (OSTI)

    Plotkin, S. E.; Energy Systems

    2007-03-01T23:59:59.000Z

    This report describes the results of an effort to identify key analytic issues associated with modeling a transition to hydrogen as a fuel for light duty vehicles, and using insights gained from this effort to suggest ways to improve ongoing modeling efforts. The study reported on here examined multiple hydrogen scenarios reported in the literature, identified modeling issues associated with those scenario analyses, and examined three DOE-sponsored hydrogen transition models in the context of those modeling issues. The three hydrogen transition models are HyTrans (contractor: Oak Ridge National Laboratory), MARKAL/DOE* (Brookhaven National Laboratory), and NEMS-H2 (OnLocation, Inc). The goals of these models are (1) to help DOE improve its R&D effort by identifying key technology and other roadblocks to a transition and testing its technical program goals to determine whether they are likely to lead to the market success of hydrogen technologies, (2) to evaluate alternative policies to promote a transition, and (3) to estimate the costs and benefits of alternative pathways to hydrogen development.

  17. Tuning the properties of Ge-quantum dots superlattices in amorphous silica matrix through deposition conditions

    SciTech Connect (OSTI)

    Pinto, S. R. C.; Ramos, M. M. D.; Gomes, M. J. M. [University of Minho, Centre of Physics and Physics Department, Braga 4710-057 (Portugal); Buljan, M. [Ruder Boskovic Institute, Bijenicka cesta 54, Zagreb 10000 (Croatia); Chahboun, A. [University of Minho, Centre of Physics and Physics Department, Braga 4710-057 (Portugal); Physics Department, FST Tanger, Tanger BP 416 (Morocco); Roldan, M. A.; Molina, S. I. [Departamento de Ciencia de los Materiales e Ing. Metalurgica y Q. I., Universidad de Cadiz, Cadiz (Spain); Bernstorff, S. [Sincrotrone Trieste, SS 14 km163, 5, Basovizza 34012 (Italy); Varela, M.; Pennycook, S. J. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Barradas, N. P.; Alves, E. [Instituto Superior Tecnico e Instituto Tecnologico e Nuclear-, EN10, Sacavem 2686-953 (Portugal)

    2012-04-01T23:59:59.000Z

    In this work, we investigate the structural properties of Ge quantum dot lattices in amorphous silica matrix, prepared by low-temperature magnetron sputtering deposition of (Ge+SiO{sub 2})/SiO{sub 2} multilayers. The dependence of quantum dot shape, size, separation, and arrangement type on the Ge-rich (Ge + SiO{sub 2}) layer thickness is studied. We show that the quantum dots are elongated along the growth direction, perpendicular to the multilayer surface. The size of the quantum dots and their separation along the growth direction can be tuned by changing the Ge-rich layer thickness. The average value of the quantum dots size along the lateral (in-plane) direction along with their lateral separation is not affected by the thickness of the Ge-rich layer. However, the thickness of the Ge-rich layer significantly affects the quantum dot ordering. In addition, we investigate the dependence of the multilayer average atomic composition and also the quantum dot crystalline quality on the deposition parameters.

  18. Tuning the properties of Ge-quantum dots superlattices in amorphous silica matrix through deposition conditions

    SciTech Connect (OSTI)

    Pinto, S. [University of Minho, Portugal; Roldan Gutierrez, Manuel A [ORNL; Ramos, M. M.D. [University of Minho, Portugal; Gomes, M.J.M. [University of Minho, Portugal; Molina, S. I. [Universidad de Cadiz, Spain; Pennycook, Stephen J [ORNL; Varela del Arco, Maria [ORNL; Buljan, M. [R. Boskovic Institute, Zagreb, Croatia; Barradas, N. [Instituto Tecnologico e Nuclear (ITN), Lisbon, Portugal; Alves, E. [Instituto Tecnologico e Nuclear (ITN), Lisbon, Portugal; Chahboun, A. [FST Tanger, Morocco; Bernstorff, S. [Sincrotrone Trieste, Basovizza, Italy

    2012-01-01T23:59:59.000Z

    In this work, we investigate the structural properties of Ge quantum dot lattices in amorphous silica matrix, prepared by low-temperature magnetron sputtering deposition of (Ge+SiO{sub 2})/SiO{sub 2} multilayers. The dependence of quantum dot shape, size, separation, and arrangement type on the Ge-rich (Ge + SiO{sub 2}) layer thickness is studied. We show that the quantum dots are elongated along the growth direction, perpendicular to the multilayer surface. The size of the quantum dots and their separation along the growth direction can be tuned by changing the Ge-rich layer thickness. The average value of the quantum dots size along the lateral (in-plane) direction along with their lateral separation is not affected by the thickness of the Ge-rich layer. However, the thickness of the Ge-rich layer significantly affects the quantum dot ordering. In addition, we investigate the dependence of the multilayer average atomic composition and also the quantum dot crystalline quality on the deposition parameters.

  19. Comparison of LNG, CNG, and diesel transit bus economics. Topical report, July 1992-September 1993

    SciTech Connect (OSTI)

    Powars, C.A.; Moyer, C.B.; Luscher, D.R.; Lowell, D.D.; Pera, C.J.

    1993-10-20T23:59:59.000Z

    The purpose of the report is to compare the expected costs of operating a transit bus fleet on liquefied natural gas (LNG), compressed natural gas (CNG), and diesel fuel. The special report is being published prior to the overall project final report in response to the current high level of interest in LNG transit buses. It focuses exclusively on the economics of LNG buses as compared with CNG and diesel buses. The reader is referred to the anticipated final report, or to a previously published 'White Paper' report (Reference 1), for information regarding LNG vehicle and refueling system technology and/or the economics of other LNG vehicles. The LNG/CNG/diesel transit bus economics comparison is based on total life-cycle costs considering all applicable capital and operating costs. The costs considered are those normally borne by the transit property, i.e., the entity facing the bus purchase decision. These costs account for the portion normally paid by the U.S. Department of Transportation (DOT) Federal Transit Administration (FTA). Transit property net costs also recognize the sale of emissions reduction credits generated by using natural gas (NG) engines which are certified to levels below standards (particularly for NOX).

  20. Sudden gravitational transition

    SciTech Connect (OSTI)

    Caldwell, Robert R. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, New Hampshire 03755 (United States); Komp, William [Physics Department, University of Louisville, 102 Natural Sciences, Louisville, Kentucky 40292 (United States); Parker, Leonard [Physics Department, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201 (United States); Vanzella, Daniel A. T. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo (IFSC-USP), Av. Trabalhador Sao-carlense, 400 Cx. Postal 369 - CEP 13560-970, Sao Carlos, Sao Paulo (Brazil)

    2006-01-15T23:59:59.000Z

    We investigate the properties of a cosmological scenario which undergoes a gravitational phase transition at late times. In this scenario, the Universe evolves according to general relativity in the standard, hot big bang picture until a redshift z < or approx. 1. Nonperturbative phenomena associated with a minimally-coupled scalar field catalyzes a transition, whereby an order parameter consisting of curvature quantities such as R{sup 2}, R{sub ab}R{sup ab}, R{sub abcd}R{sup abcd} acquires a constant expectation value. The ensuing cosmic acceleration appears driven by a dark-energy component with an equation-of-state w<-1. We evaluate the constraints from type 1a supernovae, the cosmic microwave background, and other cosmological observations. We find that a range of models making a sharp transition to cosmic acceleration are consistent with observations.

  1. Green synthesis of highly efficient CdSe quantum dots for quantum-dots-sensitized solar cells

    SciTech Connect (OSTI)

    Gao, Bing; Shen, Chao; Zhang, Mengya; Yuan, Shuanglong; Yang, Yunxia, E-mail: yangyunxia@ecust.edu.cn, E-mail: grchen@ecust.edu.cn; Chen, Guorong, E-mail: yangyunxia@ecust.edu.cn, E-mail: grchen@ecust.edu.cn [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zhang, Bo [Department of Physics, East China University of Science and Technology, Shanghai 200237 (China)

    2014-05-21T23:59:59.000Z

    Green synthesis of CdSe quantum dots for application in the quantum-dots-sensitized solar cells (QDSCs) is investigated in this work. The CdSe QDs were prepared with glycerol as the solvent, with sharp emission peak, full width at half maximum around 30?nm, and absorption peak from 475?nm to 510?nm. The reaction is environmental friendly and energy saving. What's more, the green synthesized CdSe QDs are coherence to the maximum remittance region of the solar spectrum and suitable as sensitizers to assemble onto TiO{sub 2} electrodes for cell devices application. What's more, the dynamic procedure of the carriers' excitation, transportation, and recombination in the QDSCs are discussed. Because the recombination of the electrons from the conduction band of TiO{sub 2}'s to the electrolyte affects the efficiency of the solar cells greatly, 3-Mercaptopropionic acid capped water-dispersible QDs were used to cover the surface of TiO{sub 2}. The resulting green synthesized CdSe QDSCs with Cu{sub 2}S as the electrode show a photovoltaic performance with a conversion efficiency of 3.39%.

  2. Electroweak phase transitions

    SciTech Connect (OSTI)

    Anderson, G.W.

    1991-09-16T23:59:59.000Z

    An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, {l_angle}{phi}{r_angle}{sub T} is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of {l_angle}{phi}{r_angle}{sub T}. In very minimal extensions of the standard model it is quite easy to increase {l_angle}{phi}{r_angle}{sub T} so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value {l_angle}{phi}{r_angle} = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state {l_angle}{phi}{r_angle} = 246 GeV unstable. The requirement that the state {l_angle}{phi}{r_angle} = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.

  3. Electroweak phase transitions

    SciTech Connect (OSTI)

    Anderson, G.W.

    1991-09-16T23:59:59.000Z

    An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, {l angle}{phi}{r angle}{sub T} is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of {l angle}{phi}{r angle}{sub T}. In very minimal extensions of the standard model it is quite easy to increase {l angle}{phi}{r angle}{sub T} so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value {l angle}{phi}{r angle} = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state {l angle}{phi}{r angle} = 246 GeV unstable. The requirement that the state {l angle}{phi}{r angle} = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.

  4. Viscosity near phase transitions

    E-Print Network [OSTI]

    Antonio Dobado; Felipe J. Llanes-Estrada; Juan M. Torres-Rincon

    2010-09-30T23:59:59.000Z

    Probably the most enticing observation in theoretical physics during the last decade was the discovery of the great amount of consequences obtained from the AdS/CFT conjecture put forward by Maldacena. In this work we review how this correspondence can be used to address hydrodynamic properties such as the viscosity of some strongly interacting systems. We also employ the Boltzmann equation for those systems closer to low-energy QCD, and argue that this kind of transport coefficients can be related to phase transitions, in particular the QGP/hadronic phase transition studied in heavy ion collisions.

  5. Theory of Electro-optic Modulation via a Quantum Dot Coupled to a Nano-resonator

    E-Print Network [OSTI]

    Arka Majumdar; Nicolas Manquest; Andrei Faraon; Jelena Vuckovic

    2009-11-27T23:59:59.000Z

    In this paper, we analyze the performance of an electro-optic modulator based on a single quantum dot strongly coupled to a nano-resonator, where electrical control of the quantum dot frequency is achieved via quantum confined Stark effect. Using realistic system parameters, we show that modulation speeds of a few tens of GHz are achievable with this system, while the energy per switching operation can be as small as 0.5 fJ. In addition, we study the non-linear distortion, and the effect of pure quantum dot dephasing on the performance of the modulator.

  6. Real-time effective-action approach to the Anderson quantum dot

    E-Print Network [OSTI]

    Sexty, Denes; Pawlowski, Jan

    2010-01-01T23:59:59.000Z

    The non-equilibrium time evolution of an Anderson quantum dot is investigated. The quantum dot is coupled between two leads forming a chemical-potential gradient. We use Kadanoff-Baym dynamic equations within a non-perturbative resummation of the s-channel bubble chains. The effect of the resummation leads to the introduction of a frequency-dependent 4-point vertex. The tunneling to the leads is taken into account exactly. The method allows the determination of the transient as well as stationary transport through the quantum dot, and results are compared with different schemes discussed in the literature (fRG, ISPI, tDMRG and QMC).

  7. Real-time effective-action approach to the Anderson quantum dot

    E-Print Network [OSTI]

    Denes Sexty; Thomas Gasenzer; Jan Pawlowski

    2010-12-20T23:59:59.000Z

    The non-equilibrium time evolution of an Anderson quantum dot is investigated. The quantum dot is coupled between two leads forming a chemical-potential gradient. We use Kadanoff-Baym dynamic equations within a non-perturbative resummation of the s-channel bubble chains. The effect of the resummation leads to the introduction of a frequency-dependent 4-point vertex. The tunneling to the leads is taken into account exactly. The method allows the determination of the transient as well as stationary transport through the quantum dot, and results are compared with different schemes discussed in the literature (fRG, ISPI, tDMRG and QMC).

  8. Gates controlled parallel-coupled double quantum dot on both single layer and bilayer graphene

    E-Print Network [OSTI]

    Lin-Jun Wang; Guo-Ping Guo; Da Wei; Gang Cao; Tao Tu; Ming Xiao; Guang-Can Guo; A. M. Chang

    2011-04-22T23:59:59.000Z

    Here we report the fabrication and quantum transport measurements of gates controlled parallel-coupled double quantum dot on both bilayer and single layer graphene. It is shown that the interdot coupling strength of the parallel double dots can be effectively tuned from weak to strong regime by both the in-plane plunger gates and back gate. All the relevant energy scales and parameters of the graphene parallel-coupled double dot can be extracted from the honeycomb charge stability diagrams revealed through the transport measurements.

  9. Optical spectra and intensities of graphene magnetic dot bound to a negatively charged Coulomb impurity

    SciTech Connect (OSTI)

    Lee, C. M., E-mail: mesimon-hk@yahoo.com.hk, E-mail: apkschan@cityu.edu.hk; Chan, K. S., E-mail: mesimon-hk@yahoo.com.hk, E-mail: apkschan@cityu.edu.hk [Department of Physics and Materials Science and Center for Functional Photonics, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Shenzhen Research Institute, City University of Hong Kong, Shenzhen (China)

    2014-07-28T23:59:59.000Z

    Employing numerical diagonalization, we study the optical properties of an electron in a monolayer-graphene magnetic dot bound to an off-center negatively charged Coulomb impurity based on the massless Dirac-Weyl model. Numerical results show that, since the electron-hole symmetry is broken by the Coulomb potential, the optical absorption spectra of the magnetic dot in the presence of a Coulomb impurity are different between the electron states and the hole states. Effects of both the magnetic field and the dot size on the absorption coefficient are presented as functions of the incident photon energies.

  10. Transition temperature in QCD

    SciTech Connect (OSTI)

    Cheng, M.; Christ, N. H.; Mawhinney, R. D. [Physics Department, Columbia University, New York, New York 10027 (United States); Datta, S.; Jung, C.; Schmidt, C.; Umeda, T. [Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Heide, J. van der; Kaczmarek, O.; Laermann, E.; Miao, C. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Karsch, F. [Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Petreczky, P. [Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); RIKEN-BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973 (United States); Petrov, K. [Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100 Copenhagen (Denmark)

    2006-09-01T23:59:59.000Z

    We present a detailed calculation of the transition temperature in QCD with two light and one heavier (strange) quark mass on lattices with temporal extent N{sub {tau}}=4 and 6. Calculations with improved staggered fermions have been performed for various light to strange quark mass ratios in the range, 0.05{<=}m-circumflex{sub l}/m-circumflex{sub s}{<=}0.5, and with a strange quark mass fixed close to its physical value. From a combined extrapolation to the chiral (m-circumflex{sub l}{yields}0) and continuum (aT{identical_to}1/N{sub {tau}}{yields}0) limits we find for the transition temperature at the physical point T{sub c}r{sub 0}=0.457(7) where the scale is set by the Sommer-scale parameter r{sub 0} defined as the distance in the static quark potential at which the slope takes on the value (dV{sub qq}(r)/dr){sub r=r{sub 0}}=1.65/r{sub 0}{sup 2}. Using the currently best known value for r{sub 0} this translates to a transition temperature T{sub c}=192(7)(4) MeV. The transition temperature in the chiral limit is about 3% smaller. We discuss current ambiguities in the determination of T{sub c} in physical units and also comment on the universal scaling behavior of thermodynamic quantities in the chiral limit.

  11. Transition Implementation Guide

    Broader source: Directives, Delegations, and Requirements [Office of Management (MA)]

    2001-04-24T23:59:59.000Z

    This Guide was prepared to aid in the development, planning, and implementation of requirements and activities during the transition phase at Department of Energy (DOE) facilities that have been declared or are forecast to become excess to any future mission requirements.

  12. TRANSITION STRATEGIES Sig Gronich

    E-Print Network [OSTI]

    Options. ·Natural Gas Hydrogen · Biomass Hydrogen ·Distributed Coal / IGCC Hydrogen · Compressed Gas special attention to the transition to a nascent hydrogen economy · Analyze cost goals and Liquid Storage · Electrolysis · Compressed Gas Delivery · Cold Gas Delivery and Liquid Delivery · Co

  13. Variational transition state theory

    SciTech Connect (OSTI)

    Truhlar, D.G. [Univ. of Minnesota, Minneapolis (United States)

    1993-12-01T23:59:59.000Z

    This research program involves the development of variational transition state theory (VTST) and semiclassical tunneling methods for the calculation of gas-phase reaction rates and selected applications. The applications are selected for their fundamental interest and/or their relevance to combustion.

  14. Transitions for the People: Theory and Practice of `Transition' and

    E-Print Network [OSTI]

    Watson, Andrew

    respond to the challenges, and opportunities, of Peak Oil and Climate Change?" [Transition Network 2008 change and peak-oil. There is much of interest here, for academics of sustainability transitions

  15. High performance tunnel injection quantum dot comb laser

    SciTech Connect (OSTI)

    Lee, C.-S.; Guo Wei; Basu, Debashish; Bhattacharya, Pallab [Department of Electrical Engineering and Computer Science, Solid State Electronics Laboratory, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)

    2010-03-08T23:59:59.000Z

    A high-speed multiwavelength quantum dot comb laser, grown by molecular beam epitaxy, is demonstrated. The device is characterized with a 75.9 nm (full width at half maximum) and a 91.4 nm (DELTA{sub -15dB}) wide lasing spectrum. There are 105 and 185 simultaneously emitted longitudinal modes with a maximum channel intensity nonuniformity of less than 3 dB in the spectral range of 1231-1252 nm and 1274-1311 nm, respectively, for a laser with 1040 mum cavity length. The channel spacing can be tuned with cavity length and remains invariant in the temperature range of 300-323 K. The small signal modulation bandwidth is 7.5 GHz.

  16. Valley pair qubits in double quantum dots of gapped graphene

    E-Print Network [OSTI]

    G. Y. Wu; N. -Y. Lue; L. Chang

    2011-07-03T23:59:59.000Z

    The rise of graphene opens a new door to qubit implementation, as discussed in the recent proposal of valley pair qubits in double quantum dots of gapped graphene (Wu et al., arXiv: 1104.0443 [cond-mat.mes-hall]). The work here presents the comprehensive theory underlying the proposal. It discusses the interaction of electrons with external magnetic and electric fields in such structures. Specifically, it examines a strong, unique mechanism, i.e., the analogue of the 1st-order relativistic effect in gapped graphene. This mechanism is state mixing free and allows, together with the electrically tunable exchange coupling, a fast, all-electric manipulation of qubits via electric gates, in the time scale of ns. The work also looks into the issue of fault tolerance in a typical case, yielding at 10oK a long qubit coherence time (~O(ms)).

  17. Fluorescence quenching of CdSe quantum dots on graphene

    SciTech Connect (OSTI)

    Guo, Xi Tao; Hua Ni, Zhen, E-mail: zhni@seu.edu.cn; Yan Nan, Hai; Hui Wang, Wen [Department of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189 (China)] [Department of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189 (China); Yan Liao, Chun [Physics Department, National Photoelectric Technology and Functional Materials and Application of Science and Technology International Cooperation Base, Northwest University, Xi'an 710069 (China)] [Physics Department, National Photoelectric Technology and Functional Materials and Application of Science and Technology International Cooperation Base, Northwest University, Xi'an 710069 (China); Zhang, Yan; Wei Zhao, Wei [Jiangsu Key Laboratory for Design and Fabrication of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189 (China)] [Jiangsu Key Laboratory for Design and Fabrication of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189 (China)

    2013-11-11T23:59:59.000Z

    We studied systematically the fluorescence quenching of CdSe quantum dots (QDs) on graphene and its multilayers, as well as graphene oxide (GO) and reduced graphene oxide (rGO). Raman intensity of QDs was used as a quantitatively measurement of its concentration in order to achieve a reliable quenching factor (QF). It was found that the QF of graphene (?13.1) and its multilayers is much larger than rGO (?4.4), while GO (?1.5) has the lowest quenching efficiency, which suggests that the graphitic structure is an important factor for quenching the fluorescence of QDs. It was also revealed that the QF of graphene is not strongly dependent on its thicknesses.

  18. Gate-Tunable Graphene Quantum Dot and Dirac Oscillator

    E-Print Network [OSTI]

    Abdelhadi Belouad; Ahmed Jellal; Youness Zahidi

    2015-05-29T23:59:59.000Z

    We obtain the solution of the Dirac equation in (2+1) dimensions in the presence of a constant magnetic field normal to the plane together with a two-dimensional Dirac-oscillator potential coupling. We study the energy spectrum of graphene quantum dot (QD) defined by electrostatic gates. We give discussions of our results based on different physical settings, whether the cyclotron frequency is similar or larger/smaller compared to the oscillator frequency. This defines an effective magnetic field that produces the effective quantized Landau levels. We study analytically such field in gate-tunable graphene QD and show that our structure allow us to control the valley degeneracy. Finally, we compare our results with already published work and also discuss the possible applications of such QD.

  19. Gate-Tunable Graphene Quantum Dot and Dirac Oscillator

    E-Print Network [OSTI]

    Belouad, Abdelhadi; Zahidi, Youness

    2015-01-01T23:59:59.000Z

    We obtain the solution of the Dirac equation in (2+1) dimensions in the presence of a constant magnetic field normal to the plane together with a two-dimensional Dirac-oscillator potential coupling. We study the energy spectrum of graphene quantum dot (QD) defined by electrostatic gates. We give discussions of our results based on different physical settings, whether the cyclotron frequency is similar or larger/smaller compared to the oscillator frequency. This defines an effective magnetic field that produces the effective quantized Landau levels. We study analytically such field in gate-tunable graphene QD and show that our structure allow us to control the valley degeneracy. Finally, we compare our results with already published work and also discuss the possible applications of such QD.

  20. Energy spectra of two electrons in a circular quantum dot

    E-Print Network [OSTI]

    Anjana Sinha; Y. P. Varshni

    2002-08-27T23:59:59.000Z

    The electron interaction energy of two interacting electrons in a circular quantum dot (with hard wall confinement) is investigated in the framework of the semi-classical Wentzel-Kramers-Brillouin (WKB) approximation. The two electrons are assumed to be in an infinitely deep well of radius $r_0$, in a simple configuration with one electron fixed at the origin. The corresponding Schrodinger equation, with hard wall boundary conditions, is also solved exactly by numerical integration. It is observed that the agreement between the two energy values is quite good, suggesting that the WKB approximation works well for such a confined quantum system as well. This may provide motivation to extend this to more realistic confined potentials.

  1. Location deterministic biosensing from quantum-dot-nanowire assemblies

    SciTech Connect (OSTI)

    Liu, Chao [Materials Science and Engineering Program, Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712 (United States); Kim, Kwanoh [Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States); Fan, D. L., E-mail: dfan@austin.utexas.edu [Materials Science and Engineering Program, Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712 (United States); Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States)

    2014-08-25T23:59:59.000Z

    Semiconductor quantum dots (QDs) with high fluorescent brightness, stability, and tunable sizes, have received considerable interest for imaging, sensing, and delivery of biomolecules. In this research, we demonstrate location deterministic biochemical detection from arrays of QD-nanowire hybrid assemblies. QDs with diameters less than 10?nm are manipulated and precisely positioned on the tips of the assembled Gold (Au) nanowires. The manipulation mechanisms are quantitatively understood as the synergetic effects of dielectrophoretic (DEP) and alternating current electroosmosis (ACEO) due to AC electric fields. The QD-nanowire hybrid sensors operate uniquely by concentrating bioanalytes to QDs on the tips of nanowires before detection, offering much enhanced efficiency and sensitivity, in addition to the position-predictable rationality. This research could result in advances in QD-based biomedical detection and inspires an innovative approach for fabricating various QD-based nanodevices.

  2. Optimal tunneling enhances the quantum photovoltaic effect in double quantum dots

    E-Print Network [OSTI]

    Wang, Chen

    We investigate the quantum photovoltaic effect in double quantum dots by applying the nonequilibrium quantum master equation. A drastic suppression of the photovoltaic current is observed near the open circuit voltage, ...

  3. Luminescent, quantum dot-based anti-reflective coatings for crystalline silicon photovoltaics

    E-Print Network [OSTI]

    Bruer, Garrett (Garrett A.)

    2010-01-01T23:59:59.000Z

    This thesis demonstrates and evaluates the potential application of luminescent quantum dot/polymer solutions on crystalline silicon photovoltaics. After spin coating the QD/polymer onto silicon photodiodes, an increase ...

  4. Optimization of a microwave resonator cavity to perform electron spin resonance measurements on quantum dots

    E-Print Network [OSTI]

    Burger, Anat

    2006-01-01T23:59:59.000Z

    This thesis attempts to improve on an ongoing experiment of detecting electron spin resonance (ESR) on AlGaAs/GaAs lateral quantum dots. The experiment is performed in a 2.5 Tesla magnetic field at temperatures around ...

  5. Quantum Dots Promise to Significantly Boost Solar Cell Efficiencies (Fact Sheet)

    SciTech Connect (OSTI)

    Not Available

    2013-08-01T23:59:59.000Z

    In the search for a third generation of solar-cell technologies, a leading candidate is the use of 'quantum dots' -- tiny spheres of semiconductor material measuring only about 2-10 billionths of a meter in diameter. Quantum dots have the potential to dramatically increase the efficiency of converting sunlight into energy -- perhaps even doubling it in some devices -- because of their ability to generate more than one bound electron-hole pair, or exciton, per incoming photon. NREL has produced quantum dots using colloidal suspensions; then, using molecular self-assembly, they have been fabricated into the first-ever quantum-dot solar cells. While these devices operate with only 4.4% efficiency, they demonstrate the capability for low-cost manufacturing.

  6. Efficiency loss mechanisms in colloidal quantum-dot light-emitting diodes

    E-Print Network [OSTI]

    Shirasaki, Yasuhiro

    2013-01-01T23:59:59.000Z

    Saturated and tunable emission colors make colloidal quantum-dot light-emitting diodes (QD-LEDs) interesting for the next generation of display and lighting technologies. However, there still remain various hurdles to the ...

  7. Multispectral imaging via luminescent down-shifting with colloidal quantum dots

    E-Print Network [OSTI]

    Jaworski, Frank B.

    The high infrared quantum yield, continuous absorption spectrum, and band edge tunability of colloidal quantum dots (QD) has opened up new opportunities to use luminescent down shifting for multispectral imaging in the ...

  8. Development of low-temperature solution-processed colloidal quantum dot-based solar cells

    E-Print Network [OSTI]

    Chang, Liang-Yi, Ph. D. Massachusetts Institute of Technology

    2013-01-01T23:59:59.000Z

    Solution-processed solar cells incorporating organic semiconductors and inorganic colloidal quantum dots (QDs) are potential alternatives to conventional solar cells fabricated via vacuum or high-temperature sintering ...

  9. The physics and chemistry of transport in CdSe quantum dot solids

    E-Print Network [OSTI]

    Jarosz, Mirna, 1981-

    2004-01-01T23:59:59.000Z

    Semiconductor quantum dots (QDs) have tunable opto-electronic properties and can be chemically synthesized and manipulated with ease, making them a promising novel material for many diverse applications. An understanding ...

  10. Exchange Control of Nuclear Spin Diffusion in a Double Quantum Dot

    E-Print Network [OSTI]

    Reilly, D. J.

    The influence of gate-controlled two-electron exchange on the relaxation of nuclear polarization in small ensembles (N?10[superscript 6]) of nuclear spins is examined in a GaAs double quantum dot system. Waiting in the ...

  11. Electrical excitation of colloidally synthesized quantum dots in metal oxide structures

    E-Print Network [OSTI]

    Wood, Vanessa Claire

    2010-01-01T23:59:59.000Z

    This thesis develops methods for integrating colloidally synthesized quantum dots (QDs) and metal oxides in optoelectronic devices, presents three distinct light emitting devices (LEDs) with metal oxides surrounding a QD ...

  12. Nuclear spin dynamics in double quantum dots: Fixed points, transients, and intermittency

    E-Print Network [OSTI]

    Rudner, M. S.

    Transport through spin-blockaded quantum dots provides a means for electrical control and detection of nuclear spin dynamics in the host material. Although such experiments have become increasingly popular in recent years, ...

  13. Lateral heterojunction photodetector consisting of molecular organic and colloidal quantum dot thin films

    E-Print Network [OSTI]

    exception being the dye- sensitized solar cell.3 Owing to its unique geometry, the present device also and that is sensitized across visible wavelengths by a thin film of colloidal CdSe nanocrystal quantum dots QDs . High

  14. Gain dynamics of quantum dot devices for dual-state operation

    SciTech Connect (OSTI)

    Kaptan, Y., E-mail: yuecel.kaptan@physik.tu-berlin.de; Herzog, B.; Kolarczik, M.; Owschimikow, N.; Woggon, U. [Institut für Optik und Atomare Physik, Technische Universität Berlin, Berlin (Germany); Schmeckebier, H.; Arsenijevi?, D.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Berlin (Germany); Mikhelashvili, V.; Eisenstein, G. [Technion Institute of Technology, Faculty of Electrical Engineering, Haifa (Israel)

    2014-06-30T23:59:59.000Z

    Ground state gain dynamics of In(Ga)As-quantum dot excited state lasers are investigated via single-color ultrafast pump-probe spectroscopy below and above lasing threshold. Two-color pump-probe experiments are used to localize lasing and non-lasing quantum dots within the inhomogeneously broadened ground state. Single-color results yield similar gain recovery rates of the ground state for lasing and non-lasing quantum dots decreasing from 6 ps to 2 ps with increasing injection current. We find that ground state gain dynamics are influenced solely by the injection current and unaffected by laser operation of the excited state. This independence is promising for dual-state operation schemes in quantum dot based optoelectronic devices.

  15. InGaAs Quantum Dots Coupled to a Reservoir of Nonequilibrium Free Carriers

    E-Print Network [OSTI]

    Laemmlin, Matthias

    We discuss the impact of a 2D-charged carrier reservoir for high-speed optical amplification and modulated lasing in quantum dot (QD)-based devices by testing the amplification of short trains of high power, femtosecond ...

  16. Solar Hydrogen Production Using Carbon Quantum Dots and a Molecular Nickel Catalyst

    E-Print Network [OSTI]

    Martindale, Benjamin C. M.; Hutton, Georgina A. M.; Caputo, Christine A.; Reisner, Erwin

    2015-04-13T23:59:59.000Z

    Solar Hydrogen Production Using Carbon Quantum Dots and a Molecular Nickel Catalyst Benjamin C. M. Martindale,† Georgina A. M. Hutton,† Christine A. Caputo, and Erwin Reisner* Christian Doppler Laboratory for Sustainable SynGas Chemistry, Department...

  17. Mechanism of lateral ordering of InP dots grown on InGaP layers

    SciTech Connect (OSTI)

    Bortoleto, J.R.R.; Gutierrez, H.R.; Cotta, M.A.; Bettini, J. [Instituto de Fisica Gleb Wataghin, DFA, UNICAMP, CP 6165, 13081-970 Campinas-SP (Brazil); Laboratorio Nacional de Luz Sincrotron, CP 6192, 13084-971, Campinas-SP (Brazil)

    2005-07-04T23:59:59.000Z

    The mechanisms leading to the spontaneous formation of a two-dimensional array of InP/InGaP dots grown by chemical-beam epitaxy are discussed. Samples where the InGaP buffer layer was grown at different conditions were characterized by transmission electron microscopy. Our results indicate that a periodic strain field related to lateral two-dimensional compositional modulation in the InGaP buffer layer determines the dot nucleation positions during InP growth. Although the periodic strain field in the InGaP is large enough to align the InP dots, both their shape and optical properties are effectively unaltered. This result shows that compositional modulation can be used as a tool for in situ dot positioning.

  18. Narrow-Band Absorption-Enhanced Quantum Dot/J-Aggregate Conjugates

    E-Print Network [OSTI]

    Walker, Brian J.

    We report narrow-band absorption enhancement of semiconductor nanocrystals via Förster resonance energy transfer from cyanine J-aggregates. These J-aggregated dyes associate electrostatically with short quantum-dot (QD) ...

  19. A compact ultranarrow high-power laser system for experiments with 578nm Ytterbium clock transition

    E-Print Network [OSTI]

    Cappellini, Giacomo; Mancini, Marco; Pagano, Guido; Pizzocaro, Marco; Fallani, Leonardo; Catani, Jacopo

    2015-01-01T23:59:59.000Z

    In this paper we present the realization of a compact, high-power laser system able to excite the Ytterbium clock transition at 578 nm. Starting from an external-cavity laser based on a quantum dot chip at 1156 nm with an intra-cavity electro-optic modulator, we were able to obtain up to 60 mW of visible light at 578 nm via frequency doubling. The laser is locked with a 500 kHz bandwidth to a ultra-low-expansion glass cavity stabilized at its zero coefficient of thermal expansion temperature through an original thermal insulation and correction system. This laser allowed the observation of the clock transition in fermionic $^{173}$Yb with a < 50 Hz linewidth over 5 minutes, limited only by a residual frequency drift of some 0.1 Hz/s.

  20. Two photon luminescence from quantum dots using broad and narrowband ultrafast laser pulses

    E-Print Network [OSTI]

    Balasubramanian, Haribhaskar

    2008-10-10T23:59:59.000Z

    TWO PHOTON LUMINESCENCE FROM QUANTUM DOTS USING BROAD AND NARROWBAND ULTRAFAST LASER PULSES A Thesis by HARIBHASKAR BALASUBRAMANIAN Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE December 2007 Major Subject: Biomedical Engineering TWO PHOTON LUMINESCENCE FROM QUANTUM DOTS USING BROAD AND NARROWBAND ULTRAFAST LASER PULSES A Thesis by HARIBHASKAR...

  1. Off-resonant coupling between a single quantum dot and a nanobeam photonic crystal cavity

    E-Print Network [OSTI]

    Armand Rundquist; Arka Majumdar; Jelena Vuckovic

    2011-10-05T23:59:59.000Z

    We demonstrate off-resonant coupling between a single quantum dot and a nanobeam photonic crystal cavity, under resonant excitation of the quantum dot or the cavity. These results are consistent with previous descriptions of off-resonant coupling as an incoherent phonon-mediated process. The extension of this phenomenon to a nanobeam photonic crystal cavity presents interesting possibilities for coherent control of this interaction by tailoring the phonon density of states.

  2. Ultrafast photon-photon interaction in a strongly coupled quantum dot-cavity system

    E-Print Network [OSTI]

    Dirk Englund; Arka Majumdar; Michal Bajcsy; Andrei Faraon; Pierre Petroff; Jelena vuckovic

    2011-07-14T23:59:59.000Z

    We study dynamics of the interaction between two weak light beams mediated by a strongly coupled quantum dot-photonic crystal cavity system. First, we perform all optical switching of a weak continuous-wave signal with a pulsed control beam, and then perform switching between two pulsed beams (40ps pulses) at the single photon level. Our results show that the quantum dot-nanocavity system creates strong, controllable interactions at the single photon level.

  3. Control of excitation transfer in coupled quantum dots by a nonresonant laser pulse

    E-Print Network [OSTI]

    P. A. Golovinski; V. A. Astapenko; A. V. Yakovets

    2014-08-06T23:59:59.000Z

    We study theoretically fast transfer of excitons between pairs of coupled quantum dots driven by the optical Stark effect that is produced by a short nonresonant laser pulse. The Schr\\"odinger equation, in which the relative position of energy levels of quantum dot subsystems is time-dependent, is solved numerically. Computer simulation shows a way to achieve efficient excitation transfer by the action of a picosecond laser pulse with a rectangular envelope function.

  4. Regulatory compliance guide for DOT-7A type A packaging design

    SciTech Connect (OSTI)

    Kelly, D.L.

    1996-06-04T23:59:59.000Z

    The purpose of this guide is to provide instruction for assuring that the regulatory design requirements for a DOT-7A Type A packaging are met. This guide also supports the testing and evaluation activities that are performed on new packaging designs by a DOE-approved test facility through the DOE`s DOT-7A Test Program. This Guide was updated to incorporate regulatory changes implemented by HM-169A (49 CFR, `Transportation`).

  5. SU(4) Kondo Effect in Carbon Nanotube Quantum Dots: Kondo Effect without Charge Quantization

    E-Print Network [OSTI]

    Finkelstein, Gleb

    for 1 electron: Double dots, dots with symmetries: D. Boese et al., PRB (2002) L. Borda et al., PRL (2003) K. Le Hur and P. Simon, PRB (2003) G. Zarand et al., SSC (2003) W. Izumida et al., J.R. Krishnamurthy, PRL (2005) C.A. Busser and G.B. Martins, PRB (2007) 2-e Kondo in nanotubes ­ triplet or SU(4) W

  6. SUNY/Buffalo Developing High-Efficiency Colloidal Quantum Dot Phosphors

    Broader source: Energy.gov [DOE]

    The State University of New York at Buffalo is working to reduce the cost and increase the performance of LEDs for general illumination by developing high-efficiency colloidal quantum dot phosphors to replace conventional phosphors (i.e., those placed directly on the chip). Colloidal quantum dot phosphors are nanocrystal emitters and contain no rare-earth elements. What's more, it's possible to tune the emission wavelength merely by changing their size.

  7. Electronic waiting-time distribution of a quantum-dot spin valve

    E-Print Network [OSTI]

    Björn Sothmann

    2014-10-27T23:59:59.000Z

    We discuss the electronic waiting-time distribution of a quantum-dot spin valve, i.e. a single-level quantum dot coupled to two ferromagnetic electrodes with magnetizations that can point in arbitrary directions. We demonstrate that the rich transport physics of this setup such as dynamical channel blockade and spin precession in an interaction-driven exchange field shows up in the waiting-time distribution and analyze the conditions necessary to observe the various effects.

  8. (In,Mn)As quantum dots: Molecular-beam epitaxy and optical properties

    SciTech Connect (OSTI)

    Bouravleuv, A. D., E-mail: bour@mail.ioffe.ru; Nevedomskii, V. N. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Ubyivovk, E. V. [St. Petersburg State University (Russian Federation)] [St. Petersburg State University (Russian Federation); Sapega, V. F. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Khrebtov, A. I. [St. Petersburg Academic University, Nanotechnology Research and Education Centre (Russian Federation)] [St. Petersburg Academic University, Nanotechnology Research and Education Centre (Russian Federation); Samsonenko, Yu. B.; Cirlin, G. E.; Ustinov, V. M. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2013-08-15T23:59:59.000Z

    Self-assembled (In,Mn)As quantum dots are synthesized by molecular-beam epitaxy on GaAs (001) substrates. The experimental results obtained by transmission electron microscopy show that doping of the central part of the quantum dots with Mn does not bring about the formation of structural defects. The optical properties of the samples, including those in external magnetic fields, are studied.

  9. GaN/AlN Quantum Dots for Single Qubit Emitters M. Winkelnkemper

    E-Print Network [OSTI]

    Nabben, Reinhard

    GaN/AlN Quantum Dots for Single Qubit Emitters M. Winkelnkemper , R. Seguin, S. Rodt, A. Hoffmann-plane GaN/AlN quantum dots (QDs) with focus on their potential as sources of single polarized photons emission lines from single InGaN/GaN [4­11] and GaN/AlN QDs grown on the c-plane [12­16] and a-plane [17

  10. Transition-fault test generation

    E-Print Network [OSTI]

    Cobb, Bradley Douglas

    2013-02-22T23:59:59.000Z

    . One way to detect these timing defects is to apply test patterns to the integrated circuit that are generated using the transition-fault model. Unfortunately, industry's current transition-fault test generation schemes produce test sets that are too...

  11. Calixarene supported transition metal clusters 

    E-Print Network [OSTI]

    Taylor, Stephanie Merac

    2013-06-29T23:59:59.000Z

    This thesis describes a series of calix[n]arene polynuclear transition metal and lanthanide complexes. Calix[4]arenes possess lower-rim polyphenolic pockets that are ideal for the complexation of various transition metal ...

  12. Size dependent optical properties of Si quantum dots in Si-rich nitride/Si{sub 3}N{sub 4} superlattice synthesized by magnetron sputtering

    SciTech Connect (OSTI)

    So, Yong-Heng; Huang, Shujuan; Conibeer, Gavin; Green, Martin A. [ARC Photovoltaics Centre of Excellence, University of New South Wales, Sydney, New South Wales 2052 (Australia); Gentle, Angus [Physics and Advanced Materials, University of Technology Sydney, P. O. Box 123, Broadway, New South Wales 2007 (Australia)

    2011-03-15T23:59:59.000Z

    A spectroscopic ellipsometry compatible approach is reported for the optical study of Si quantum dots (QDs) in Si-rich nitride/silicon nitride (SRN/Si{sub 3}N{sub 4}) superlattice, which based on Tauc-Lorentz model and Bruggeman effective medium approximation. It is shown that the optical constants and dielectric functions of Si QDs are strongly size dependent. The suppressed imaginary dielectric function of Si QDs exhibits a single broad peak analogous to amorphous Si, which centered between the transition energies E{sub 1} and E{sub 2} of bulk crystalline Si and blue shifted toward E{sub 2} as the QD size reduced. A bandgap expansion observed by the TL model when the size of Si QD reduced is in good agreement with the PL measurement. The bandgap expansion with the reduction of Si QD size is well supported by the first-principles calculations based on quantum confinement.

  13. Effects of capping on GaN quantum dots deposited on Al{sub 0.5}Ga{sub 0.5}N by molecular beam epitaxy

    SciTech Connect (OSTI)

    Korytov, M. [CRHEA-CNRS, rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France) and University of Nice Sophia-Antipolis, Parc Valrose, 06103 Nice (France); Benaissa, M. [CNRST, angle Allal-Fassi/FAR, Madinat al-irfane, 10000 Rabat (Morocco); Brault, J.; Vennegues, P. [CRHEA-CNRS, rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Huault, T. [CRHEA-CNRS, rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne, France and RIBER S.A., 31 rue Casimir Perier, BP 70083, 95873 Bezons Cedex (France); Neisius, T. [CP2M, Faculte Saint Jerome, 13397 Marseille Cedex 20 (France)

    2009-04-06T23:59:59.000Z

    The impact of the capping process on the structural and morphological properties of GaN quantum dots (QDs) grown on fully relaxed Al{sub 0.5}Ga{sub 0.5}N templates was studied by transmission electron microscopy. A morphological transition between the surface QDs, which have a pyramidal shape, and the buried ones, which have a truncated pyramid shape, is evidenced. This shape evolution is accompanied by a volume change: buried QDs are bigger than surface ones. Furthermore a phase separation into Al{sub 0.5}Ga{sub 0.5}N barriers was observed in the close vicinity of buried QDs. As a result, the buried QDs were found to be connected with the nearest neighbors by thin Ga-rich zones, whereas Al-rich zones are situated above the QDs.

  14. Chemical bonding and defect states of LPCVD grown silicon-rich Si{sub 3}N{sub 4} for quantum dot applications

    SciTech Connect (OSTI)

    Mohammed, Shakil, E-mail: smohammed@utdallas.edu; Hinkle, Christopher L., E-mail: chris.hinkle@utdallas.edu [Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080 (United States); Nimmo, Michael T.; Malko, Anton V. [Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080 (United States)

    2014-03-15T23:59:59.000Z

    Si-rich Si{sub 3}N{sub 4} (SRN) thin films were investigated to understand the various defect states present within the SRN that can lead to reduced performance in quantum dot based devices made of these materials. The SRN films, deposited by low pressure chemical vapor deposition followed by furnace anneals over a range of temperatures, were determined to be comprised of two distinct phase separated SRN regions with different compositions (precipitates within a host matrix). Photoluminescence (PL) spectra showed multiple peaks convoluted together within the visible and near-visible range. Depending on deposition and annealing conditions, the films displayed changes in PL peak intensities which were correlated with chemical bonding utilizing x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, spectroscopic ellipsometry, and capacitance–voltage measurements. It is found that the PL originates from defect-state to defect-state and band edge to defect-state electronic transitions.

  15. Engineering of quantum dot photon sources via electro-elastic fields

    E-Print Network [OSTI]

    Rinaldo Trotta; Armando Rastelli

    2015-03-01T23:59:59.000Z

    The possibility to generate and manipulate non-classical light using the tools of mature semiconductor technology carries great promise for the implementation of quantum communication science. This is indeed one of the main driving forces behind ongoing research on the study of semiconductor quantum dots. Often referred to as artificial atoms, quantum dots can generate single and entangled photons on demand and, unlike their natural counterpart, can be easily integrated into well-established optoelectronic devices. However, the inherent random nature of the quantum dot growth processes results in a lack of control of their emission properties. This represents a major roadblock towards the exploitation of these quantum emitters in the foreseen applications. This chapter describes a novel class of quantum dot devices that uses the combined action of strain and electric fields to reshape the emission properties of single quantum dots. The resulting electro-elastic fields allow for control of emission and binding energies, charge states, and energy level splittings and are suitable to correct for the quantum dot structural asymmetries that usually prevent these semiconductor nanostructures from emitting polarization-entangled photons. Key experiments in this field are presented and future directions are discussed.

  16. Effect of quantum dot position and background doping on the performance of quantum dot enhanced GaAs solar cells

    SciTech Connect (OSTI)

    Driscoll, Kristina, E-mail: kmdsps@rit.edu; Bennett, Mitchell F.; Polly, Stephen J.; Forbes, David V.; Hubbard, Seth M., E-mail: smhsps@rit.edu [NanoPower Research Laboratories, Rochester Institute of Technology, Rochester, New York (United States)

    2014-01-13T23:59:59.000Z

    The effect of the position of InAs quantum dots (QD) within the intrinsic region of pin-GaAs solar cells is reported. Simulations suggest placing the QDs in regions of reduced recombination enables a recovery of open-circuit voltage (V{sub OC}). Devices with the QDs placed in the center and near the doped regions of a pin-GaAs solar cell were experimentally investigated. While the V{sub OC} of the emitter-shifted device was degraded, the center and base-shifted devices exhibited V{sub OC} comparable to the baseline structure. This asymmetry is attributed to background doping which modifies the recombination profile and must be considered when optimizing QD placement.

  17. The energy transition Gerald Leach

    E-Print Network [OSTI]

    Kammen, Daniel M.

    The energy transition Gerald Leach The paper considers the substitution of tradition. The In the context of energy policy and planning, the paper concludes with a review of the reasons why transition. In the IS THE TRANSITION HAPPENING? poorest developing countries biomass fuels account for 60-95% of total energy use

  18. IDEA Reauthorized Statute SECONDARY TRANSITION

    E-Print Network [OSTI]

    IDEA ­ Reauthorized Statute SECONDARY TRANSITION (See also Individualized Education Program (IEP This document addresses only the changes to the IDEA provisions regarding secondary transition that took effect from the term "transition services" now refers to a "child" instead of a "student," The definition

  19. Radiative Transitions in Charmonium

    SciTech Connect (OSTI)

    Jozef Dudek; Robert Edwards; David Richards

    2005-10-01T23:59:59.000Z

    The form factors for the radiative transitions between charmonium mesons are investigated. We employ an anisotropic lattice using a Wilson gauge action, and domain-wall fermion action. We extrapolate the form factors to Q{sup 2} = 0, corresponding to a real photon, using quark-model-inspired functions. Finally, comparison is made with photocouplings extracted from the measured radiative widths, where known. Our preliminary results find photocouplings commensurate with these experimentally extracted values.

  20. Refrigerants in Transition

    E-Print Network [OSTI]

    Stouppe, D. E.

    .E. Senior Engineer The Hartford Steam Boiler Inspection and Insurance Company Hartford,. Connecticut ABSTRACT The massive growth of air conditioning and refrigeration has been a direct result of the development of a class of chemicals called fluorocarbons..., Gordon, "Forty Years Research on Atmospheric Ozone at Oxford: A !Iistory," Applied Optics, March t968, pp. 387-405. 4. Downing, R., "Development of Chloro fluorocarbon Refrigerants," CFCs: Time of Transition, ASHRAE Publication, Atlanta, GA, 1989...

  1. Quasiresonant excitation of InP/InGaP quantum dots using second harmonic generated in a photonic crystal cavity

    E-Print Network [OSTI]

    Vuckovic, Jelena

    Quasiresonant excitation of InP/InGaP quantum dots using second harmonic generated in a photonic://apl.aip.org/about/rights_and_permissions #12;Quasiresonant excitation of InP/InGaP quantum dots using second harmonic generated in a photonic signal to noise quasiresonant excitation of InP/InGaP quantum dots. The excitation is provided via second

  2. Optical Properties of Wurtzite GaN and ZnO Quantum Dots Vladimir A. Fonoberov and Alexander A. Balandin

    E-Print Network [OSTI]

    Fonoberov, Vladimir

    Optical Properties of Wurtzite GaN and ZnO Quantum Dots Vladimir A. Fonoberov and Alexander A-Riverside, Riverside, California 92521, U.S.A. ABSTRACT We have investigated exciton states in wurtzite GaN/AlN and ZnO quantum dots. A strong piezoelectric field in GaN/AlN quantum dots is found to tilt conduction and valence

  3. Alameda-Contra Costa Transit District (AC Transit) Fuel Cell Transit Buses: Preliminary Evaluation Results

    SciTech Connect (OSTI)

    Chandler, K.; Eudy, L.

    2007-03-01T23:59:59.000Z

    This report provides an evaluation of three prototype fuel cell-powered transit buses operating at AC Transit in Oakland, California, and six baseline diesel buses similar in design to the fuel cell buses.

  4. Investigations of segregation phenomena in highly strained Mn-doped Ge wetting layers and Ge quantum dots embedded in silicon

    SciTech Connect (OSTI)

    Prestat, E., E-mail: eric.prestat@gmail.com; Porret, C.; Favre-Nicolin, V.; Tainoff, D.; Boukhari, M.; Bayle-Guillemaud, P.; Jamet, M.; Barski, A., E-mail: andre.barski@cea.com [INAC, SP2M, CEA and Université Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France)

    2014-03-10T23:59:59.000Z

    In this Letter, we investigate manganese diffusion and the formation of Mn precipitates in highly strained, few monolayer thick, Mn-doped Ge wetting layers and nanometric size Ge quantum dot heterostructures embedded in silicon. We show that in this Ge(Mn)/Si system manganese always precipitates and that the size and the position of Mn clusters (precipitates) depend on the growth temperature. At high growth temperature, manganese strongly diffuses from germanium to silicon, whereas decreasing the growth temperature reduces the manganese diffusion. In the germanium quantum dots layers, Mn precipitates are detected, not only in partially relaxed quantum dots but also in fully strained germanium wetting layers between the dots.

  5. Impact of heavy hole-light hole coupling on optical selection rules in GaAs quantum dots

    SciTech Connect (OSTI)

    Belhadj, T.; Amand, T.; Kunz, S.; Marie, X.; Urbaszek, B. [INSA-CNRS-UPS, LPCNO, Universite de Toulouse, 135 Av. Rangueil, 31077 Toulouse (France); Kunold, A. [INSA-CNRS-UPS, LPCNO, Universite de Toulouse, 135 Av. Rangueil, 31077 Toulouse (France); Departamento de Ciencias Basicas, UAM-A, Col. Reynosa Tamaulipas, 02200 Mexico D.F. (Mexico); Simon, C.-M. [INSA-CNRS-UPS, LPCNO, Universite de Toulouse, 135 Av. Rangueil, 31077 Toulouse (France); CNRS-UPS, LCAR, IRSAMC, Universite de Toulouse, 31062 Toulouse (France); Kuroda, T.; Abbarchi, M.; Mano, T.; Sakoda, K. [National Institute for Material Science, Namiki 1-1, Tsukuba 305-0044 (Japan)

    2010-08-02T23:59:59.000Z

    We report strong heavy hole-light hole mixing in GaAs quantum dots grown by droplet epitaxy. Using the neutral and charged exciton emission as a monitor we observe the direct consequence of quantum dot symmetry reduction in this strain free system. By fitting the polar diagram of the emission with simple analytical expressions obtained from k{center_dot}p theory we are able to extract the mixing that arises from the heavy-light hole coupling due to the geometrical asymmetry of the quantum dot.

  6. Electrically driven single photon emission from a CdSe/ZnSSe single quantum dot at 200?K

    SciTech Connect (OSTI)

    Quitsch, Wolf; Kümmell, Tilmar; Bacher, Gerd [Werkstoffe der Elektrotechnik and CENIDE, Universität Duisburg-Essen, Bismarckstraße 81, 47057 Duisburg (Germany); Gust, Arne; Kruse, Carsten; Hommel, Detlef [Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28334 Bremen (Germany)

    2014-09-01T23:59:59.000Z

    High temperature operation of an electrically driven single photon emitter based on a single epitaxial quantum dot is reported. CdSe/ZnSSe/MgS quantum dots are embedded into a p-i-n diode architecture providing almost background free excitonic and biexcitonic electroluminescence from individual quantum dots through apertures in the top contacts. Clear antibunching with g{sup 2}(??=?0)?=?0.28?±?0.20 can be tracked up to T?=?200?K, representing the highest temperature for electrically triggered single photon emission from a single quantum dot device.

  7. Analytic equivalence of geometric transitions

    E-Print Network [OSTI]

    Michele Rossi

    2014-08-28T23:59:59.000Z

    In this paper \\emph{analytic equivalence} of geometric transition is defined in such a way that equivalence classes of geometric transitions turn out to be the \\emph{arrows} of the \\cy web. Then it seems natural and useful, both from the mathematical and physical point of view, look for privileged arrows' representatives, called \\emph{canonical models}, laying the foundations of an \\emph{analytic} classification of geometric transitions. At this purpose a numerical invariant, called \\emph{bi--degree}, summarizing the topological, geometric and physical changing properties of a geometric transition, is defined for a large class of geometric transitions.

  8. gray-98.pdf

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:Energy: Grid Integration Redefining What'sis Taking Over OurThe Iron4 Self-Scrubbing:,, , ., Decembergangh AmesAFind Report . The

  9. Transition Strategies: Government Options and Market Penetration...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Strategies: Government Options and Market Penetration Scenarios Transition Strategies: Government Options and Market Penetration Scenarios Presentation on Transition Strategies:...

  10. Using quantum dots to tag subsurface damage in lapped and polished glass samples

    SciTech Connect (OSTI)

    Williams, Wesley B.; Mullany, Brigid A.; Parker, Wesley C.; Moyer, Patrick J.; Randles, Mark H.

    2009-09-20T23:59:59.000Z

    Grinding, lapping, and polishing are finishing processes used to achieve critical surface parameters in a variety of precision optical and electronic components. As these processes remove material from the surface through mechanical and chemical interactions, they may induce a damaged layer of cracks, voids, and stressed material below the surface. This subsurface damage (SSD) can degrade the performance of a final product by creating optical aberrations due to diffraction, premature failure in oscillating components, and a reduction in the laser induced damage threshold of high energy optics. As these defects lie beneath the surface, they are difficult to detect, and while many methods are available to detect SSD, they can have notable limitations regarding sample size and type, preparation time, or can be destructive in nature. The authors tested a nondestructive method for assessing SSD that consisted of tagging the abrasive slurries used in lapping and polishing with quantum dots (nano-sized fluorescent particles). Subsequent detection of fluorescence on the processed surface is hypothesized to indicate SSD. Quantum dots that were introduced to glass surfaces during the lapping process were retained through subsequent polishing and cleaning processes. The quantum dots were successfully imaged by both wide field and confocal fluorescence microscopy techniques. The detected fluorescence highlighted features that were not observable with optical or interferometric microscopy. Atomic force microscopy and additional confocal microscope analysis indicate that the dots are firmly embedded in the surface but do not appear to travel deep into fractures beneath the surface. Etching of the samples exhibiting fluorescence confirmed that SSD existed. SSD-free samples exposed to quantum dots did not retain the dots in their surfaces, even when polished in the presence of quantum dots.

  11. Transition Metal Switchable Mirror

    ScienceCinema (OSTI)

    None

    2010-01-08T23:59:59.000Z

    The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft.

  12. Transition Metal Switchable Mirror

    ScienceCinema (OSTI)

    None

    2013-05-29T23:59:59.000Z

    The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft. More information at: http://windows.lbl.gov/materials/chromogenics/default.htm

  13. Superradiance Transition in Graphene

    E-Print Network [OSTI]

    Alexander I. Nesterov; Fermín Aceves de la Cruz; Valeriy A. Luchnikov; Gennady P. Berman

    2015-06-04T23:59:59.000Z

    We study theoretically and numerically the conditions required for the appearance of a superradiance transition in graphene. The electron properties of graphene are described in the single $p_z$-orbital tight-binding approximation, in which the model is reduced to the effective two-level pseudo-spin $1/2$ system. For each level we introduce the electron transfer rate of escape into a continuum. We demonstrate that, under some conditions, the superradiance experiences the maximal quantum coherent escape to the continuum.

  14. Transition Metal Switchable Mirror

    SciTech Connect (OSTI)

    None

    2009-01-01T23:59:59.000Z

    The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft. More information at: http://windows.lbl.gov/materials/chromogenics/default.htm

  15. Transition Metal Switchable Mirror

    SciTech Connect (OSTI)

    2009-08-21T23:59:59.000Z

    The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft.

  16. Superradiance Transition in Graphene

    E-Print Network [OSTI]

    Alexander I. Nesterov; Fermín Aceves de la Cruz; Valeriy A. Luchnikov; Gennady P. Berman

    2015-06-12T23:59:59.000Z

    We study theoretically and numerically the conditions required for the appearance of a superradiance transition in graphene. The electron properties of graphene are described in the single $p_z$-orbital tight-binding approximation, in which the model is reduced to the effective two-level pseudo-spin $1/2$ system. For each level we introduce the electron transfer rate of escape into a continuum. We demonstrate that, under some conditions, the superradiance experiences the maximal quantum coherent escape to the continuum.

  17. arXiv:cond-mat/0005262v116May2000 Spin transitions in a small Si quantum dot

    E-Print Network [OSTI]

    during every tunneling event. PACS numbers: 73.23.Hk, 85.30.Wx, 85.30.Vw, 85.30.Tv, 71.70.Ej The spin, the Coulomb blockade is lifted in the corresponding conduction val- ley at low temperatures. Indeed, valleys

  18. Ultrafast dynamics of strongly coupled quantum dot-nanocavity systems

    E-Print Network [OSTI]

    Kai Müller; Kevin A. Fischer; Armand Rundquist; Constantin Dory; Konstantinos G. Lagoudakis; Tomas Sarmiento; Victoria Borish; Yousif A. Kelaita; Jelena Vu?kovi?

    2015-03-18T23:59:59.000Z

    We investigate the influence of exciton-phonon coupling on the dynamics of a strongly coupled quantum dot-photonic crystal cavity system and explore the effects of this interaction on different schemes for non-classical light generation. By performing time-resolved measurements, we map out the detuning-dependent polariton lifetime and extract the spectrum of the polariton-to-phonon coupling. Photon-blockade experiments are presented for different pulse-length and detuning conditions that are in very good agreement with quantum-optical simulations; we demonstrate that achieving high-fidelity photon blockade requires an intricate understanding of this parameter space. Furthermore, we show that detuned photon blockade, which is more efficient than resonant photon blockade, is also more dramatically affected by phonons. Finally, we achieve coherent control of the polariton states of a strongly coupled system and demonstrate that their efficient coupling to phonons can be exploited for novel concepts in high-fidelity single photon generation.

  19. PROPERTIES OF UMBRAL DOTS FROM STRAY LIGHT CORRECTED HINODE FILTERGRAMS

    SciTech Connect (OSTI)

    Louis, Rohan E.; Mathew, Shibu K.; Bayanna, A. Raja [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Badi Road, Udaipur, Rajasthan 313004 (India); Rubio, Luis R. Bellot [Instituto de Astrofisica de Andalucia (CSIC), Apartado de Correos 3004, 18080 Granada (Spain); Ichimoto, Kiyoshi [Kwasan and Hida Observatories, Kyoto University, Yamashina-ku, Kyoto 607-8417 (Japan); Ravindra, B., E-mail: eugene@prl.res.in [Indian Institute of Astrophysics, II Block, Koramangla, Bangalore 560034 (India)

    2012-06-20T23:59:59.000Z

    High-resolution blue continuum filtergrams from Hinode are employed to study the umbral fine structure of a regular unipolar sunspot. The removal of scattered light from the images increases the rms contrast by a factor of 1.45 on average. Improvement in image contrast renders identification of short filamentary structures resembling penumbrae that are well separated from the umbra-penumbra boundary and comprise bright filaments/grains flanking dark filaments. Such fine structures were recently detected from ground-based telescopes and have now been observed with Hinode. A multi-level tracking algorithm was used to identify umbral dots (UDs) in both the uncorrected and corrected images and to track them in time. The distribution of the values describing the photometric and geometric properties of UDs is more easily affected by the presence of stray light while it is less severe in the case of kinematic properties. Statistically, UDs exhibit a peak intensity, effective diameter, lifetime, horizontal speed, and a trajectory length of 0.29I{sub QS}, 272 km, 8.4 minutes, 0.45 km s{sup -1}, and 221 km, respectively. The 2 hr 20 minute time sequence depicts several locations where UDs tend to appear and disappear repeatedly with various time intervals. The correction for scattered light in the Hinode filtergrams facilitates photometry of umbral fine structure, which can be related to results obtained from larger telescopes and numerical simulations.

  20. 309 Building transition plan

    SciTech Connect (OSTI)

    Graves, C.E.

    1994-08-31T23:59:59.000Z

    The preparation for decontamination and decommissioning (transition) of the 309 Building is projected to be completed by the end of the fiscal year (FY) 1998. The major stabilization and decontamination efforts include the Plutonium Recycle Test Reactor (PRTR), fuel storage and transfer pits, Transfer Waste (TW) tanks and the Ion Exchange Vaults. In addition to stabilizing contaminated areas, equipment, components, records, waste products, etc., will be dispositioned. All nonessential systems, i.e., heating, ventilation, and air conditioning (HVAC), electrical, monitoring, fluids, etc., will be shut down and drained/de-energized. This will allow securing of the process, laboratory, and office areas of the facility. After that, the facility will be operated at a level commensurate with its surveillance needs while awaiting D&D. The implementation costs for FY 1995 through FY 1998 for the transition activities are estimated to be $1,070K, $2,115K, $2,939K, and $4,762K, respectively. Costs include an assumed company overhead of 20% and a 30% out year contingency.

  1. Tunnel-injection GaN quantum dot ultraviolet light-emitting diodes

    SciTech Connect (OSTI)

    Verma, Jai; Kandaswamy, Prem Kumar; Protasenko, Vladimir; Verma, Amit; Grace Xing, Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)] [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

    2013-01-28T23:59:59.000Z

    We demonstrate a GaN quantum dot ultraviolet light-emitting diode that uses tunnel injection of carriers through AlN barriers into the active region. The quantum dot heterostructure is grown by molecular beam epitaxy on AlN templates. The large lattice mismatch between GaN and AlN favors the formation of GaN quantum dots in the Stranski-Krastanov growth mode. Carrier injection by tunneling can mitigate losses incurred in hot-carrier injection in light emitting heterostructures. To achieve tunnel injection, relatively low composition AlGaN is used for n- and p-type layers to simultaneously take advantage of effective band alignment and efficient doping. The small height of the quantum dots results in short-wavelength emission and are simultaneously an effective tool to fight the reduction of oscillator strength from quantum-confined Stark effect due to polarization fields. The strong quantum confinement results in room-temperature electroluminescence peaks at 261 and 340 nm, well above the 365 nm bandgap of bulk GaN. The demonstration opens the doorway to exploit many varied features of quantum dot physics to realize high-efficiency short-wavelength light sources.

  2. Inhibition of plasmonically enhanced interdot energy transfer in quantum dot solids via photo-oxidation

    SciTech Connect (OSTI)

    Sadeghi, S. M. [Department of Physics, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States); Nano and Micro Device Center, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States); Nejat, A.; West, R. G. [Department of Physics, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States)

    2012-11-15T23:59:59.000Z

    We studied the impact of photophysical and photochemical processes on the interdot Forster energy transfer in monodisperse CdSe/ZnS quantum dot solids. For this, we investigated emission spectra of CdSe/ZnS quantum dot solids in the vicinity of gold metallic nanoparticles coated with chromium oxide. The metallic nanoparticles were used to enhance the rate of the energy transfer between the quantum dots, while the chromium oxide coating led to significant increase of their photo-oxidation rates. Our results showed that irradiation of such solids with a laser beam can lead to unique spectral changes, including narrowing and blue shift. We investigate these effects in terms of inhibition of the plasmonically enhanced interdot energy transfer between quantum dots via the chromium-oxide accelerated photo-oxidation process. We demonstrate this considering energy-dependent rate of the interdot energy transfer process, plasmonic effects, and the way photo-oxidation enhances non-radiative decay rates of quantum dots with different sizes.

  3. Preparation of Non-equilibrium Nuclear Spin States in Double Quantum Dots

    E-Print Network [OSTI]

    M. Gullans; J. J. Krich; J. M. Taylor; B. I. Halperin; M. D. Lukin

    2014-07-25T23:59:59.000Z

    We theoretically study the dynamic polarization of lattice nuclear spins in GaAs double quantum dots containing two electrons. In our prior work [Phys. Rev. Lett. 104, 226807 (2010)] we identified three regimes of long-term dynamics, including the build up of a large difference in the Overhauser fields across the dots, the saturation of the nuclear polarization process associated with formation of so-called "dark states," and the elimination of the difference field. In particular, when the dots are different sizes we found that the Overhauser field becomes larger in the smaller dot. Here we present a detailed theoretical analysis of these problems including a model of the polarization dynamics and the development of a new numerical method to efficiently simulate semiclassical central-spin problems. When nuclear spin noise is included, the results agree with our prior work indicating that large difference fields and dark states are stable configurations, while the elimination of the difference field is unstable; however, in the absence of noise we find all three steady states are achieved depending on parameters. These results are in good agreement with dynamic nuclear polarization experiments in double quantum dots.

  4. The impact of disorder on charge transport in three dimensional quantum dot resonant tunneling structures

    SciTech Connect (OSTI)

    Puthen-Veettil, B., E-mail: b.puthen-veettil@unsw.edu.au; Patterson, R.; König, D.; Conibeer, G.; Green, M. A. [Australian Centre for Advanced Photovoltaics, UNSW, Sydney 2052 (Australia)

    2014-10-28T23:59:59.000Z

    Efficient iso-entropic energy filtering of electronic waves can be realized through nanostructures with three dimensional confinement, such as quantum dot resonant tunneling structures. Large-area deployment of such structures is useful for energy selective contacts but such configuration is susceptible to structural disorders. In this work, the transport properties of quantum-dot-based wide-area resonant tunneling structures, subject to realistic disorder mechanisms, are studied. Positional variations of the quantum dots are shown to reduce the resonant transmission peaks while size variations in the device are shown to reduce as well as broaden the peaks. Increased quantum dot size distribution also results in a peak shift to lower energy which is attributed to large dots dominating transmission. A decrease in barrier thickness reduces the relative peak height while the overall transmission increases dramatically due to lower “series resistance.” While any shift away from ideality can be intuitively expected to reduce the resonance peak, quantification allows better understanding of the tolerances required for fabricating structures based on resonant tunneling phenomena/.

  5. Showcasing the research of quantum dot sensitized solar cells from Prof. J.J.Tian's and Prof. G.Z.Cao's lab,

    E-Print Network [OSTI]

    Cao, Guozhong

    . Introduction Quantum dot sensitized solar cells (QDSCs) can be regarded as a derivative of dye-sensitized solarShowcasing the research of quantum dot sensitized solar cells from Prof. J.J.Tian's and Prof. G cells A hierarchical structure of ZnO/TiO2 nanocable photoanode for quantum dot sensitized solar cells

  6. Absorption spectra of CdSe-ZnS core-shell quantum dots at high photon energies : experiment and modeling

    E-Print Network [OSTI]

    Ghosh, Sandip

    Absorption spectra of CdSe-ZnS core-shell quantum dots at high photon energies : experiment spectra of CdSe-ZnS core-shell quantum dot (QD) ensembles, with average core diameters ranging from 2.6 nm. In agreement with previous reports, the absorption coefficient at energies 1 eV above the effective bandgap

  7. Excitonic properties of strained wurtzite and zinc-blende GaNAlxGa1xN quantum dots

    E-Print Network [OSTI]

    Fonoberov, Vladimir

    Excitonic properties of strained wurtzite and zinc-blende GaNÕAlxGa1ÀxN quantum dots Vladimir A 2003 We investigate exciton states theoretically in strained GaN/AlN quantum dots with wurtzite WZ of GaN QDs.1­8 Molecu- lar beam epitaxial growth in the Stranski­Krastanov mode of wurtzite WZ Ga

  8. Optical properties of wurtzite and zinc-blende GaNAlN quantum dots Vladimir A. Fonoberova)

    E-Print Network [OSTI]

    Fonoberov, Vladimir

    Optical properties of wurtzite and zinc-blende GaNÕAlN quantum dots Vladimir A. Fonoberova; published 20 August 2004 We investigate theoretically and compare optical properties of wurtzite and zincN/AlN interface governs optical properties of wurtzite quantum dots while having a small effect on zinc

  9. Getting Informations of Wavefunctions in Quantum Dots from the Fano Effect Shingo KATSUMOTO, Hisashi AIKAWA, Kensuke KOBAYASHI and Yasuhiro IYE

    E-Print Network [OSTI]

    Iye, Yasuhiro

    by around Coulomb (resonant) peaks obeying the Breit-Wigner law. On the other hand, there appeared-phase Coulomb peaks" in quantum dots. KEYWORDS: quantum dot, Fano effect, phase shift, AB effect 1. Introduction of the phase shift just at the Coulomb peaks. This was soon turned out to be a kind of artifact due to the two

  10. Double-Dot Quantum Ratchet Driven by an Independently Biased Quantum Point Contact V. S. Khrapai,1,2

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    Double-Dot Quantum Ratchet Driven by an Independently Biased Quantum Point Contact V. S. Khrapai,1 of the two quantum dots. The results are interpreted in terms of a quantum ratchet phenomenon in a DQD possessing current be- cause of broken spatial symmetry, so-called ratchets, ap- pear in a variety

  11. Microsphere Light-Scattering Layer Assembled by ZnO Nanosheets for the Construction of High Efficiency (>5%) Quantum Dots

    E-Print Network [OSTI]

    Cao, Guozhong

    performance solar cells for sustainable energy sources to replace fossil fuels has become an urgent subject for CdS/CdSe quantum dot cosensitized solar cells (QDSCs) with a power conversion efficiency (PCE Efficiency (>5%) Quantum Dots Sensitized Solar Cells Jianjun Tian,*, Lili Lv, Xuyang Wang, Chengbin Fei

  12. SiGe quantum dot single-hole transistor fabricated by atomic force microscope nanolithography and silicon epitaxial-regrowth

    E-Print Network [OSTI]

    Rokhinson, Leonid

    SiGe quantum dot single-hole transistor fabricated by atomic force microscope nanolithography; published online 10 November 2006 A SiGe quantum dot single-hole transistor passivated by silicon epitaxial are reproducible, in sharp contrast with the noisy and irreproducible I-V characteristics of unpassivated SiGe

  13. Single-electron quantum dot in Si/SiGe with integrated charge sensing C. B. Simmons,a

    E-Print Network [OSTI]

    Coppersmith, Susan N.

    Single-electron quantum dot in Si/SiGe with integrated charge sensing C. B. Simmons,a Madhu that are important for quantum information processing. Si/SiGe is of interest for semiconductor spin qubits and measurement of a top-gated quantum dot occupied by a single electron in a Si/SiGe heterostructure. Transport

  14. Connecticut Transit (CTTRANSIT) Fuel Cell Transit Bus: Preliminary Evaluation Results

    SciTech Connect (OSTI)

    Chandler, K.; Eudy, L.

    2008-10-01T23:59:59.000Z

    This report provides preliminary results from a National Renewable Energy Laboratory evaluation of a protoptye fuel cell transit bus operating at Connecticut Transit in Hartford. Included are descriptions of the planned fuel cell bus demonstration and equipment; early results and agency experience are also provided.

  15. Monolithic phosphor-free InGaN/GaN quantum dot wavelength converter white light emitting diodes

    SciTech Connect (OSTI)

    Jahangir, Shafat; Bhattacharya, Pallab, E-mail: pkb@eecs.umich.edu [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States); Pietzonka, Ines; Strassburg, Martin [OSRAM Opto Semiconductors GmbH, Leibnizstrasse 4, Regensburg (Germany)

    2014-09-15T23:59:59.000Z

    We report the characteristics of phosphor-free self-organized InGaN/GaN quantum dot wavelength converter white light emitting diodes grown by plasma assisted molecular beam epitaxy. The exciting quantum dots, in which electrically injected carriers recombine, are blue-emitting and the converter dots are red-emitting. We have studied the effect of tuning the number of dot layers and the peak emission wavelength of the exciting and converter dots on the nature of the emitted white light, in terms of the chromaticity coordinates and correlated color temperature. Depending on the values of these wavelengths, color temperatures in the range of 4420–6700?K have been derived at a current density of 45?A/cm{sup 2} across multiple devices. The variation of the color temperature with change in injection current is found to be very small.

  16. Investigation of steady-state and time-dependent luminescence properties of colloidal InGaP quantum dots

    E-Print Network [OSTI]

    Chatterjee, Subhasish; Menon, Vinod M

    2012-01-01T23:59:59.000Z

    Quantum dots play a promising role in the development of novel optical and biosensing devices. In this study, we investigated steady-state and time-dependent luminescence properties of InGaP/ZnS core/shell colloidal quantum dots in a solution phase at room temperature. The steady state experiments exhibited an emission maximum at 650 nm with full width at half maximum of ~ 85 nm, and strong first-excitonic absorption peak at 600 nm. The time-resolved luminescence measurements depicted a bi-exponential decay profile with lifetimes of {\\tau}1\\sim 47 ns and {\\tau} 2\\sim 142 ns at the emission maximum. Additionally, luminescence quenching and lifetime reduction due to resonance energy transfer between the quantum dot and an absorber are demonstrated. Our results support the plausibility of using these InGaP quantum dots as an effective alternative to highly toxic conventional Cd or Pb based colloidal quantum dots for biological applications.

  17. Mn solid solutions in self-assembled Ge/Si (001) quantum dot heterostructures

    SciTech Connect (OSTI)

    Kassim, J.; Nolph, C.; Reinke, P.; Floro, J. [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Jamet, M. [Institut Nanosciences et Cryogenie/SP2M, CEA-UJF, F-38054 Grenoble (France)

    2012-12-10T23:59:59.000Z

    Heteroepitaxial Ge{sub 0.98}Mn{sub 0.02} quantum dots (QDs) on Si (001) were grown by molecular beam epitaxy. The standard Ge wetting layer-hut-dome-superdome sequence was observed, with no indicators of second phase formation in the surface morphology. We show that Mn forms a dilute solid solution in the Ge quantum dot layer, and a significant fraction of the Mn partitions into a sparse array of buried, Mn-enriched silicide precipitates directly underneath a fraction of the Ge superdomes. The magnetic response from the ultra-thin film indicates the absence of robust room temperature ferromagnetism, perhaps due to anomalous intermixing of Si into the Ge quantum dots.

  18. Design of quantum dot lattices in amorphous matrices by ion beam irradiation

    SciTech Connect (OSTI)

    Buljan, M.; Bogdanovic-Radovic, I.; Karlusic, M.; Desnica, U. V.; Radic, N.; Jaksic, M.; Salamon, K.; Drazic, G.; Bernstorff, S.; Holy, V. [Rudjer Boskovic Institute, Bijenicka cesta 54, HR-10000 Zagreb (Croatia); Institute of Physics, Bijenicka cesta 46, HR-10000 Zagreb (Croatia); Jozef Stefan Institute, Jamova 39, SLO-1000 Ljubljana (Slovenia); Sincrotrone Trieste, I-34149 Basovizza (Italy); Charles University in Prague, CZ-12116 Prague (Czech Republic)

    2011-10-15T23:59:59.000Z

    We report on the highly controllable self-assembly of semiconductor quantum dots and metallic nanoparticles in a solid amorphous matrix, induced by ion beam irradiation of an amorphous multilayer. We demonstrate experimentally and theoretically a possibility to tune the basic structural properties of the quantum dots in a wide range. Furthermore, the sizes, distances, and arrangement type of the quantum dots follow simple equations dependent on the irradiation and the multilayer properties. We present a Monte Carlo model for the simulation and prediction of the structural properties of the materials formed by this method. The presented results enable engineering and simple production of functional materials or simple devices interesting for applications in nanotechnology.

  19. High-brightness single photon source from a quantum dot in a directional-emission nanocavity

    E-Print Network [OSTI]

    Mitsuru Toishi; Dirk Englund; Andrei Faraon; Jelena Vuckovic

    2009-04-08T23:59:59.000Z

    We analyze a single photon source consisting of an InAs quantum dot coupled to a directional-emission photonic crystal (PC) cavity implemented in GaAs. On resonance, the dot's lifetime is reduced by more than 10 times, to 45ps. Compared to the standard three-hole defect cavity, the perturbed PC cavity design improves the collection efficiency into an objective lens (NA=0.75) by factor 6, and improves the coupling efficiency of the collected light into a single mode fiber by factor 1.9. The emission frequency is determined by the cavity mode, which is antibunched to g(2)=0.05. The cavity design also enables efficient coupling to a higher-order cavity mode for local optical excitation of cavity-coupled quantum dots.

  20. Nuclear Spin Dynamics in Double Quantum Dots: Multi-Stability, Dynamical Polarization, Criticality and Entanglement

    E-Print Network [OSTI]

    Martin J. A. Schuetz; Eric M. Kessler; Lieven M. K. Vandersypen; J. Ignacio Cirac; Geza Giedke

    2014-05-30T23:59:59.000Z

    We theoretically study the nuclear spin dynamics driven by electron transport and hyperfine interaction in an electrically-defined double quantum dot (DQD) in the Pauli-blockade regime. We derive a master-equation-based framework and show that the coupled electron-nuclear system displays an instability towards the buildup of large nuclear spin polarization gradients in the two quantum dots. In the presence of such inhomogeneous magnetic fields, a quantum interference effect in the collective hyperfine coupling results in sizable nuclear spin entanglement between the two quantum dots in the steady state of the evolution. We investigate this effect using analytical and numerical techniques, and demonstrate its robustness under various types of imperfections.

  1. Photoinduced band filling in strongly confined colloidal PbS quantum dots

    SciTech Connect (OSTI)

    Ullrich, B., E-mail: bruno@fis.unam.mx [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210 (Mexico); Ullrich Photonics LLC, Wayne, Ohio 43466 (United States); Xi, H. [Department of Physics and Astronomy, Bowling Green State University, Bowling Green, Ohio 43403-0209 (United States); Wang, J. S. [Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright Patterson AFB, Ohio 45433-7707 (United States)

    2014-06-21T23:59:59.000Z

    Increase in continuous wave laser excitation (6?W/cm{sup 2} to 120?W/cm{sup 2}) of colloidal PbS quantum dots in the strongly quantized regime (diameters 2.0?nm and 4.7?nm) deposited on semi-insulating GaAs and glass causes a clear blue shift (0.019?eV and 0.080?eV) of the emission spectra. Proof of the applicability of a dynamic three-dimensional band filling model is the significance of the presented results and demonstrates the effective electronic coupling in quantum dot arrays similar to superlattices. The work also reveals the influence of quantum dot sizes on photo-doping effects.

  2. Distinctive Signature of Indium Gallium Nitride Quantum Dot Lasing in Microdisks Cavities

    E-Print Network [OSTI]

    Woolf, Alexander; Aharanovich, Igor; Zhu, Tongtong; Niu, Nan; Wang, Danqing; Oliver, Rachel A; Hu, Evelyn L

    2014-01-01T23:59:59.000Z

    Low threshold lasers realized within compact, high quality optical cavities enable a variety of nanophotonics applications. Gallium nitride (GaN) materials containing indium gallium nitride (InGaN) quantum dots and quantum wells offer an outstanding platform to study light matter interactions and realize practical devices such as efficient light emitting diodes and nanolasers. Despite progress in the growth and characterization of InGaN quantum dots, their advantages as the gain medium in low threshold lasers have not been clearly demonstrated. This work seeks to better understand the reasons for these limitations by focusing on the simpler, limited-mode microdisk cavities, and by carrying out comparisons of lasing dynamics in those cavities using varying gain media including InGaN quantum wells, fragmented quantum wells, and a combination of fragmented quantum wells with quantum dots. For each gain medium, we utilize the distinctive, high quality (Q~5500) modes of the cavities, and the change in the highest ...

  3. AUTHORIZING THE DOT SPECIFICATION 6M PACKAGING FOR CONTINUED USE AT THE SAVANNAH RIVER SITE

    SciTech Connect (OSTI)

    Watkins, R.; Loftin, B.; Hoang, D.

    2010-03-04T23:59:59.000Z

    The U.S. Department of Transportation (DOT) Specification 6M packaging was in extensive use for more than 40 years for in-commerce shipments of Type B quantities of fissile and radioactive material (RAM) across the USA, among the Department of Energy (DOE) laboratories, and between facilities in the DOE production complex. In January 2004, the DOT Research and Special Programs Administration (RSPA) Agency issued a final rule in the Federal Register to ammend requirements in the Hazardous Materials Regulations (HMR) pertaining to the transportation of radioactive materials. The final rule became effective on October 1, 2004. One of those changes discontinued the use of the DOT specification 6M, along with other DOT specification packagings, on October 1, 2008. A main driver for the change was due to the fact that 6M specification packagings were not supported by a Safety Analysis Report for Packagings (SARP) that was compliant with Title 10 of the Code of Federal Regulations (CFR) Part 71 (10 CFR 71). The regulatory rules for the discontinued use have been edited in Title 49 of the CFR Parts 100-185, 2004 edition and thereafter. Prior to October 1, 2008, the use of the 6M within the boundaries of the Savannah River Site (SRS), called an onsite transfer, was governed by an onsite transportation document that referenced 49 CFR Parts 100-185. SRS had to develop an Onsite Safety Assessment (OSA) which was independent of 49 CFR in order to justify the continued use of the DOT Specification 6M for the transfer of radioactive material (RAM) at the SRS after October 1, 2008. This paper will discuss the methodology for and difficulties associated with authorizing the DOT Specification 6M Packaging for continued use at the Savannah River Site.

  4. Section 9: Laminar flows and transition 1 Section 9: Laminar flows and transition

    E-Print Network [OSTI]

    Kohlenbach, Ulrich

    :20 ­ 16:40: Andreas Nold, Martin Oberlack (TU Darmstadt): Connecting the dots: Symme- try Analysis bubble bursting Abstract 17:40 ­ 18:00: Mario Aigner, Stefan Braun (TU Wien): Cauchy Problems

  5. Energy levels of double triangular graphene quantum dots

    SciTech Connect (OSTI)

    Liang, F. X.; Jiang, Z. T., E-mail: ztjiang616@hotmail.com; Zhang, H. Y.; Li, S. [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Lv, Z. T. [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); School of Physical Science and Information Engineering, Liaocheng University, Liaocheng 252059 (China)

    2014-09-28T23:59:59.000Z

    We investigate theoretically the energy levels of the coupled double triangular graphene quantum dots (GQDs) based on the tight-binding Hamiltonian model. The double GQDs including the ZZ-type, ZA-type, and AA-type GQDs with the two GQDs having the zigzag or armchair boundaries can be coupled together via different interdot connections, such as the direct coupling, the chains of benzene rings, and those of carbon atoms. It is shown that the energy spectrum of the coupled double GQDs is the amalgamation of those spectra of the corresponding two isolated GQDs with the modification triggered by the interdot connections. The interdot connection is inclined to lift up the degeneracies of the energy levels in different degree, and as the connection changes from the direct coupling to the long chains, the removal of energy degeneracies is suppressed in ZZ-type and AA-type double GQDs, which indicates that the two coupled GQDs are inclined to become decoupled. Then we consider the influences on the spectra of the coupled double GQDs induced by the electric fields applied on the GQDs or the connection, which manifests as the global spectrum redistribution or the local energy level shift. Finally, we study the symmetrical and asymmetrical energy spectra of the double GQDs caused by the substrates supporting the two GQDs, clearly demonstrating how the substrates affect the double GQDs' spectrum. This research elucidates the energy spectra of the coupled double GQDs, as well as the mechanics of manipulating them by the electric field and the substrates, which would be a significant reference for designing GQD-based devices.

  6. Test and evaluation document for DOT Specification 7A Type A Packaging. Revision 3

    SciTech Connect (OSTI)

    NONE

    1996-01-30T23:59:59.000Z

    The US Department of Energy (DOE) has been conducting, through several of its operating contractors, an evaluation and testing program to qualify Type A radioactive material packagings per US Department of Transportation (DOT) Specification 7A (DOT-7A) of the Code of Federal Regulations (CFR), Title 49, Part 178 (49 CFR 178). The program is currently administered by the DOE, Office of Facility Safety Analysis, DOE/EH-32, at DOE-Headquarters (DOE-HQ) in Germantown, Maryland. This document summarizes the evaluation and testing performed for all of the packagings successfully qualified in this program.

  7. Growth and optical characterization of multilayers of InGaN quantum dots

    E-Print Network [OSTI]

    Zhu, Tontong; El-Ella, Haitham; Reid, Benjamin; Holmes, Mark; Taylor, Robert; Kappers, Menno; Oliver, Rachel

    2012-01-01T23:59:59.000Z

    carried out using a two photon excitation technique employing a picosecond mode-locked Ti-sapphire laser emitting at 790 nm. Samples were mounted in a cold -finger cryostat that could be cooled down to 4.2 K and the laser was focused through a microscope... GaN quantum dots Article Type: Research Paper Section/Category: General subjects Keywords: B2. InGaN quantum dots; A1. Photoluminescence; B1. Nitrides; A3. Metal-organic vapour phase epitaxy Corresponding Author: Dr Tongtong Zhu, Ph...

  8. Sub-microsecond correlations in photoluminescence from InAs quantum dots

    E-Print Network [OSTI]

    Charles Santori; David Fattal; Jelena Vuckovic; Glenn S. Solomon; Edo Waks; Yoshihisa Yamamoto

    2003-08-16T23:59:59.000Z

    Photon correlation measurements reveal memory effects in the optical emission of single InAs quantum dots with timescales from 10 to 800 ns. With above-band optical excitation, a long-timescale negative correlation (antibunching) is observed, while with quasi-resonant excitation, a positive correlation (blinking) is observed. A simple model based on long-lived charged states is presented that approximately explains the observed behavior, providing insight into the excitation process. Such memory effects can limit the internal efficiency of light emitters based on single quantum dots, and could also be problematic for proposed quantum-computation schemes.

  9. An Efficient Source of Single Photons: A Single Quantum Dot in a Micropost Microcavity

    E-Print Network [OSTI]

    Matthew Pelton; Charles Santori; Jelena Vuckovic; Bingyang Zhang; Glenn S. Solomon; Jocelyn Plant; Yoshihisa Yamamoto

    2002-08-08T23:59:59.000Z

    We have demonstrated efficient production of triggered single photons by coupling a single semiconductor quantum dot to a three-dimensionally confined optical mode in a micropost microcavity. The efficiency of emitting single photons into a single-mode travelling wave is approximately 38%, which is nearly two orders of magnitude higher than for a quantum dot in bulk semiconductor material. At the same time, the probability of having more than one photon in a given pulse is reduced by a factor of seven as compared to light with Poissonian photon statistics.

  10. Cavity Quantum Electrodynamics with a Single Quantum Dot Coupled to a Photonic Molecule

    E-Print Network [OSTI]

    Arka Majumdar; Armand Rundquist; Michal Bajcsy; Jelena Vu?kovi?

    2012-01-30T23:59:59.000Z

    We demonstrate the effects of cavity quantum electrodynamics for a quantum dot coupled to a photonic molecule, consisting of a pair of coupled photonic crystal cavities. We show anti-crossing between the quantum dot and the two super-modes of the photonic molecule, signifying achievement of the strong coupling regime. From the anti-crossing data, we estimate the contributions of both mode-coupling and intrinsic detuning to the total detuning between the super-modes. Finally, we also show signatures of off-resonant cavity-cavity interaction in the photonic molecule.

  11. Fast Electrical Control of a Quantum Dot Strongly Coupled to a Nano-resonator

    E-Print Network [OSTI]

    Andrei Faraon; Arka Majumdar; Hyochul Kim; Pierre Petroff; Jelena Vuckovic

    2009-06-03T23:59:59.000Z

    The resonance frequency of an InAs quantum dot strongly coupled to a GaAs photonic crystal cavity was electrically controlled via quantum confined Stark effect. Stark shifts up to 0.3meV were achieved using a lateral Schottky electrode that created a local depletion region at the location of the quantum dot. We report switching of a probe laser coherently coupled to the cavity up to speeds as high as 150MHz, limited by the RC constant of the transmission line. The coupling rate and the magnitude of the Stark shift with electric field were investigated while coherently probing the system.

  12. Temperature dependency of the emission properties from positioned In(Ga)As/GaAs quantum dots

    SciTech Connect (OSTI)

    Braun, T.; Schneider, C.; Maier, S.; Forchel, A.; Höfling, S.; Kamp, M. [Technische Physik, Physikalisches Institut and Wilhelm Conrad Röntgen-Research Center for Complex Material Systems, Universität Würzburg, Am Hubland, D-97074, Würzburg (Germany); Igusa, R.; Iwamoto, S.; Arakawa, Y. [University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2014-09-15T23:59:59.000Z

    In this letter we study the influence of temperature and excitation power on the emission linewidth from site-controlled InGaAs/GaAs quantum dots grown on nanoholes defined by electron beam lithography and wet chemical etching. We identify thermal electron activation as well as direct exciton loss as the dominant intensity quenching channels. Additionally, we carefully analyze the effects of optical and acoustic phonons as well as close-by defects on the emission linewidth by means of temperature and power dependent micro-photoluminescence on single quantum dots with large pitches.

  13. Noise-Protected Gate for Six-Electron Double-Dot Qubits

    E-Print Network [OSTI]

    Sebastian Mehl; David P. DiVincenzo

    2014-08-05T23:59:59.000Z

    Singlet-triplet spin qubits in six-electron double quantum dots, in moderate magnetic fields, can show superior immunity to charge noise. This immunity results from the symmetry of orbitals in the second energy shell of circular quantum dots: singlet and triplet states in this shell have identical charge distributions. Our phase-gate simulations, which include $1/f$ charge noise from fluctuating traps, show that this symmetry is most effectively exploited if the gate operation switches rapidly between sweet spots deep in the (3,3) and (4,2) charge stability regions; fidelities very close to one are predicted if subnanosecond switching can be performed.

  14. Controlling the nuclear polarization in quantum dots using optical pulses with a modest bandwidth

    E-Print Network [OSTI]

    S. G. Carter; Sophia E. Economou; A. Shabaev; A. S. Bracker

    2011-02-02T23:59:59.000Z

    We show that detuned optical pulse trains with a modest spectral width can polarize nuclear spins in InAs quantum dots. The pulse bandwidth is large enough to excite a coherent superposition of both electron spin eigenstates in these negatively charged dots but narrow enough to give partial spectral selectivity between the eigenstates. The coherent precession of electron spin states and periodic excitation focuses the nuclear spin distribution, producing a discrete set of precession modes. The spectral selectivity generates a net nuclear polarization, through a mechanism that relies on optical spin rotations rather than electron spin relaxation.

  15. Investigation of quantum confinement behavior of zinc sulphide quantum dots synthesized via various chemical methods

    SciTech Connect (OSTI)

    Jose, Meera, E-mail: gunasekaran@karunya.edu; Sakthivel, T., E-mail: gunasekaran@karunya.edu; Chandran, Hrisheekesh T., E-mail: gunasekaran@karunya.edu; Nivea, R., E-mail: gunasekaran@karunya.edu; Gunasekaran, V., E-mail: gunasekaran@karunya.edu [Nanomaterials Research Lab, Department of Nanoscience and Technology, Karunya University, Coimbatore - 641 114, Tamil Nadu (India)

    2014-10-15T23:59:59.000Z

    In this work, undoped and Ag-doped ZnS quantum dots were synthesized using various chemical methods. The products were characterized using X-ray diffraction (XRD), UV-visible spectroscopy and Photoluminescence spectroscopy. Our results revealed that the size of the as-prepared samples range from 1–6 nm in diameter and have a cubic zinc-blende structure. Also, we observed the emission of different wavelength of light from different sized quantum dots of the same material due to quantum confinement effect. The results will be presented in detail and ZnS can be a potential candidate for optical device development and applications.

  16. Photo-induced conductance fluctuations in mesoscopic Ge/Si systems with quantum dots

    SciTech Connect (OSTI)

    Stepina, N. P.; Dvurechenskii, A. V.; Nikiforov, A. I. [Institute of Semiconductor Physics, 630090 Novosibirsk (Russian Federation); Moers, J.; Gruetzmacher, D. [Institute of Bio- and Nanosystems, Forschungszentrum Julich GmbH 52425 Julich (Germany)

    2014-08-20T23:59:59.000Z

    We study the evolution of electron transport in strongly localized mesoscopic system with quantum dots under small photon flux. Exploring devices with narrow transport channels lead to the observation of giant fluctuations of the photoconductance, which is attributed to the strong dependence of hopping current on the filling of dots by holes. In our experiments, single-photon mode operation is indicated by the linear dependence of the frequency of photo-induced fluctuations on the light intensity and the step-like response of conductance on the pulse excitation. The effect of the light wavelength, measurement temperature, size of the conductive channel on the device efficiency are considered.

  17. A finite element analysis of a silicon based double quantum dot structure

    E-Print Network [OSTI]

    S. Rahman; J. Gorman; C. H. W. Barnes; D. A. Williams; H. P. Langtangen

    2006-04-06T23:59:59.000Z

    We present the results of a finite-element solution of the Laplace equation for the silicon-based trench-isolated double quantum-dot and the capacitively-coupled single-electron transistor device architecture. This system is a candidate for charge and spin-based quantum computation in the solid state, as demonstrated by recent coherent-charge oscillation experiments. Our key findings demonstrate control of the electric potential and electric field in the vicinity of the double quantum-dot by the electric potential applied to the in-plane gates. This constitutes a useful theoretical analysis of the silicon-based architecture for quantum information processing applications.

  18. Improving PbS Quantum Dot Solar Cell Power Conversion Efficiency to an NREL-Certified 4.4% (Fact Sheet)

    SciTech Connect (OSTI)

    Not Available

    2012-01-01T23:59:59.000Z

    Transition metal oxide improves overall efficiency and maintains performance with inexpensive metals. A research team at the National Renewable Energy Laboratory (NREL) has demonstrated that inserting a transition metal oxide (TMO) between the lead sulfide (PbS) quantum dot (QD) layer and the metal electrode eliminates the Schottky barrier that impedes efficient hole extraction and thereby improves the overall conversion efficiency. This allows for inexpensive metals such as Al to be employed without loss of performance. n-type TMOs consisting of molybdenum oxide (MoO{sub x}) and vanadium oxide (V{sub 2}O{sub x}) were used as an efficient hole extraction layer (HEL) in heterojunction ZnO/PbS QD solar cells. A 4.4% NREL-certified device was reported based on the MoO{sub x} HEL with Al as the back contact material, representing a more than 65% efficiency improvement compared with the case of Au contacting the PbS QD layer directly. The team finds the acting mechanism of the HEL to be a dipole formed at the MoO{sub x} and PbS interface, which enhances band bending to allow efficient hole extraction from the valence band of the PbS layer by MoO{sub x}. The carrier transport to the metal anode is likely enhanced through shallow gap states in the MoO{sub x} layer.

  19. Photoluminescence from In0.5Ga0.5As/GaP quantum dots coupled to photonic crystal cavities

    E-Print Network [OSTI]

    Kelley Rivoire; Sonia Buckley; Yuncheng Song; Minjoo Larry Lee; Jelena Vuckovic

    2012-01-05T23:59:59.000Z

    We demonstrate room temperature visible wavelength photoluminescence from In0.5Ga0.5As quantum dots embedded in a GaP membrane. Time-resolved above band photoluminescence measurements of quantum dot emission show a biexpontential decay with lifetimes of ~200 ps. We fabricate photonic crystal cavities which provide enhanced outcoupling of quantum dot emission, allowing the observation of narrow lines indicative of single quantum dot emission. This materials system is compatible with monolithic integration on Si, and is promising for high efficiency detection of single quantum dot emission as well as optoelectronic devices emitting at visible wavelengths.

  20. Cryogenic spectroscopy of ultra-low density colloidal lead chalcogenide quantum dots on chip-scale optical cavities towards single quantum dot near-infrared cavity QED

    E-Print Network [OSTI]

    Ranojoy Bose; Jie Gao; James F. McMillan; Alex D. Williams; Chee Wei Wong

    2009-11-09T23:59:59.000Z

    We present evidence of cavity quantum electrodynamics from a sparse density of strongly quantum-confined Pb-chalcogenide nanocrystals (between 1 and 10) approaching single-dot levels on moderately high-Q mesoscopic silicon optical cavities. Operating at important near-infrared (1500-nm) wavelengths, large enhancements are observed from devices and strong modifications of the QD emission are achieved. Saturation spectroscopy of coupled QDs is observed at 77K, highlighting the modified nanocrystal dynamics for quantum information processing.

  1. Problem Set 1 Solutions GFD1 Winter 2011 P. Rhines, A.Gray out: Friday 7 Jan 2011 back: Friday 1. Suppose we heat a small sample of dry air confined in a

    E-Print Network [OSTI]

    Problem Set 1 Solutions GFD1 Winter 2011 P. Rhines, A.Gray out: Friday 7 Jan 2011 back: Friday 14, and calculate the change in PE and E due to this change. Here we take the basic isothermal atmosphere (the final

  2. Zajac, R.N. 1999. Understanding the seafloor landscape in relation to assessing and managing impacts on coastal environments. Pp 211-227 in: J.S. Gray, W. Ambrose Jr., A. Szaniawska (eds) Biogeochemical Cycling and Sediment

    E-Print Network [OSTI]

    Zajac, Roman N.

    of organisms, and have borne much of man's long history of development and associated environmental impacts IN RELATION TO IMPACT ASSESSMENT AND ENVIRONMENTAL MANAGEMENT IN COASTAL MARINE SEDIMENTS ROMAN N. ZAJAC impacts on coastal environments. Pp 211-227 in: J.S. Gray, W. Ambrose Jr., A. Szaniawska (eds

  3. Crossover transition in bag-like models

    E-Print Network [OSTI]

    Ferroni, Lorenzo

    2009-01-01T23:59:59.000Z

    DE-AC02-05CH11231 Crossover transition in bag-like models L.We show that a crossover transition qualitatively similar toI. INTRODUCTION The phase transition of strongly interacting

  4. Ising model: secondary phase transition

    E-Print Network [OSTI]

    You-gang Feng

    2012-04-09T23:59:59.000Z

    Lttice-spin phonons are considered, which make the heat capacity at the critical temperature satisfy experimental observations better. There is a BEC phase transition in an Ising model attributable to the lattice-spin phonons. We proved that the spin-wave theory only is available after BEC transition, and the magnons have the same characteristics as the lattice-spin phonons', resulting from quantum effect. Energy-level overlap effect at ultralow temperature is found. A prediction of BEC phase transition in a crystal is put forward as our theory generalization.

  5. Intermediate-band solar cells based on quantum dot supracrystals Q. Shao and A. A. Balandina

    E-Print Network [OSTI]

    parameter in the photovoltaic PV solar cell technology. It is defined as = FFVocJsc Pin , 1 where FFIntermediate-band solar cells based on quantum dot supracrystals Q. Shao and A. A. Balandina Nano to implement the intermediate-band solar cell with the efficiency exceeding the Shockley-Queisser limit

  6. A Surface Plasmon Enhanced Infrared Photodetector Based on InAs Quantum Dots

    E-Print Network [OSTI]

    Krishna, Sanjay

    A Surface Plasmon Enhanced Infrared Photodetector Based on InAs Quantum Dots Chun-Chieh Chang-QD photodetector can facilitate a strong plasmonic-QD interaction, leading to a 130% absolute enhancement of infrared photoresponse at the plasmonic resonance. Our study indicates two key mechanisms

  7. Distance-Engineered Plasmon-Enhanced Light Harvesting in CdSe Quantum Dots

    E-Print Network [OSTI]

    Distance-Engineered Plasmon-Enhanced Light Harvesting in CdSe Quantum Dots Shengye Jin,,§, Erica De) is essential for the development of efficient QD-based solar energy conversion systems. In this study, plasmon as a function of interparticle (QD to Ag NP) distance. Up to 24-fold plasmonic enhancement of fluorescence from

  8. Infrared and photoluminescence spectroscopy of p-doped self-assembled Ge dots on Si

    E-Print Network [OSTI]

    Rokhinson, Leonid

    Infrared and photoluminescence spectroscopy of p-doped self-assembled Ge dots on Si L. P Received 14 June 1999; accepted for publication 17 August 1999 We report infrared photocurrent PC-8 Quantum well infrared photodetector QWIP technol- ogy has matured rapidly in the last several years.1

  9. Growth of a single freestanding multiwall carbon nanotube on each nanonickel dot

    E-Print Network [OSTI]

    Reed, Mark

    that the structures are indeed hollow nanotubes. The diameter and height depend on the nickel dot size and growth time displays FEDs . Attempts to manipulate nano- tubes for these applications have been made by postgrowth deposition CVD on mesopo- rous silica with imbedded iron particles.9 The growth of large arrays of well

  10. Spin States in Graphene Quantum Dots J. Guttinger,* T. Frey, C. Stampfer,

    E-Print Network [OSTI]

    Ihn, Thomas

    is connected via tunneling constrictions to source (s) and drain (d) contacts. It is tunable by the back gate with a base tempera- ture of 90 mK. The source-drain conductance of the device measured over a large back gate) Quantum dot source-drain con- ductance for varying back gate voltage (Vb ¼ 100 V). (b) Coulomb diamond

  11. Fine Structure of Highly Charged Excitons in Semiconductor Quantum Dots B. Urbaszek,1

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    quantum dots (QDs) are artificial atoms whose properties can be individually measured in their solid, the degeneracy of the excitonic ground state is lifted by the electron-hole (EH) exchange interaction, resultingV, they can be much larger in semiconductor nanocrystals [3] or polymers [4]. In all these systems

  12. Targeting quantum dots to surface proteins in living cells with biotin ligase

    E-Print Network [OSTI]

    coli biotin ligase site-specifically biotinylates a lysine side chain within a 15-amino acid acceptor molecule Quantum dots (QDs) are semiconductor nanoparticles that greatly expand the possibilities target the functional groups of one protein amidst all of the other expressed proteins containing

  13. Theoretical performance of solar cell based on mini-bands quantum dots

    SciTech Connect (OSTI)

    Aly, Abou El-Maaty M., E-mail: drabouelmaaty@hotmail.com, E-mail: ashraf.nasr@gmail.com [Power Electronics and Energy Conversion Department, ERI, NRCB (Egypt); College of Computer, Qassim University, P.O.B. 6688, Buryadah 51453 (Saudi Arabia); Nasr, A., E-mail: drabouelmaaty@hotmail.com, E-mail: ashraf.nasr@gmail.com [Radiation Engineering Department, NCRRT, Atomic Energy Authority (Egypt); College of Computer, Qassim University, P.O.B. 6688, Buryadah 51453 (Saudi Arabia)

    2014-03-21T23:59:59.000Z

    The tremendous amount of research in solar energy is directed toward intermediate band solar cell for its advantages compared with the conventional solar cell. The latter has lower efficiency because the photons have lower energy than the bandgap energy and cannot excite mobile carriers from the valence band to the conduction band. On the other hand, if mini intermediate band is introduced between the valence and conduction bands, then the smaller energy photons can be used to promote charge carriers transfer to the conduction band and thereby the total current increases while maintaining a large open circuit voltage. In this article, the influence of the new band on the power conversion efficiency for structure of quantum dots intermediate band solar cell is theoretically investigated and studied. The time-independent Schrödinger equation is used to determine the optimum width and location of the intermediate band. Accordingly, achievement of a maximum efficiency by changing the width of quantum dots and barrier distances is studied. Theoretical determination of the power conversion efficiency under the two different ranges of QD width is presented. From the obtained results, the maximum power conversion efficiency is about 70.42%. It is carried out for simple cubic quantum dot crystal under fully concentrated light. It is strongly dependent on the width of quantum dots and barrier distances.

  14. Photovoltaic nanopillar radial junction diode architecture enhanced by integrating semiconductor quantum dot nanocrystals as light harvesters

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Photovoltaic nanopillar radial junction diode architecture enhanced by integrating semiconductor hybridized, radial p-n junction based, nanopillar solar cells with photovoltaic performance enhanced. By furnishing Si based nanopillar photovoltaic diodes with CdSe quantum dots, we experimentally showed up

  15. Cu2ZnSnS4 nanocrystals and graphene quantum dots for photovoltaics Xukai Xinab

    E-Print Network [OSTI]

    Lin, Zhiqun

    Cu2ZnSnS4 nanocrystals and graphene quantum dots for photovoltaics Jun Wang,a Xukai Xinab advances in the synthesis and utilization of CZTS nanocrystals and colloidal GQDs for photovoltaics emerged to achieve low cost, high perfor- mance photovoltaics, including organic solar cells,2­6 dye

  16. Single pulse ultrafast laser imprinting of axial dot arrays in bulk glasses C. Mauclair,1,

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Single pulse ultrafast laser imprinting of axial dot arrays in bulk glasses C. Mauclair,1, A sam- ples were irradiated with 160 fs pulses from an 800 nm Ti:Sapphire amplified ultrafast laser.mauclair@univ-st-etienne.fr Compiled December 20, 2010 Ultrafast laser processing of bulk transparent materials can significantly gain

  17. Synthesis and optical properties of cadmium selenide quantum dots for white light-emitting diode application

    SciTech Connect (OSTI)

    Xu, Xianmei; Wang, Yilin; Gule, Teri; Luo, Qiang [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 53000 (China); Zhou, Liya, E-mail: zhouliyatf@163.com [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 53000 (China); Gong, Fuzhong [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 53000 (China)

    2013-03-15T23:59:59.000Z

    Highlights: ? Stable CdSe QDs were synthesized by the one-step and two-level process respectively. ? The fabricated white LEDs show good white balance. ? CdSe QDs present well green to yellow band luminescence. ? CdSe QDs displayed a broad excitation band. - Abstract: Yellow light-emitting cadmium selenide quantum dots were synthesized using one-step and two-step methods in an aqueous medium. The structural luminescent properties of these quantum dots were investigated. The obtained cadmium selenide quantum dots displayed a broad excitation band suitable for blue or near-ultraviolet light-emitting diode applications. White light-emitting diodes were fabricated by coating the cadmium selenide samples onto a 460 nm-emitting indium gallium nitrite chip. Both samples exhibited good white balance. Under a 20 mA working current, the white light-emitting diode fabricated via the one-step and two-step methods showed Commission Internationale de l’Éclairage coordinates at (0.27, 0.23) and (0.27, 0.33), respectively, and a color rendering index equal to 41 and 37, respectively. The one-step approach was simpler, greener, and more effective than the two-step approach. The one-step approach can be enhanced by combining cadmium selenide quantum dots with proper phosphors.

  18. Coupling an electron spin in a semiconductor quantum dot to an optical nano-cavity

    E-Print Network [OSTI]

    Arka Majumdar; Per Kaer; Michal Bajcsy; Erik D. Kim; Konstantinos G. Lagoudakis; Armand Rundquist; Jelena Vuckovic

    2013-04-07T23:59:59.000Z

    We propose a scheme to efficiently couple a single quantum dot electron spin to an optical nano-cavity, which enables us to simultaneously benefit from a cavity as an efficient photonic interface, as well as to perform high fidelity (nearly 100%) spin initialization and manipulation achievable in bulk semiconductors. Moreover, the presence of the cavity speeds up the spin initialization process beyond GHz.

  19. Influence of pair coherence on charge tunneling through a quantum dot connected to a superconducting lead

    E-Print Network [OSTI]

    Domanski, Tadeusz

    Influence of pair coherence on charge tunneling through a quantum dot connected the temperature below T* larger than Tc the single particle states become gradually depleted over a certain energy to a close neighborhood to the Mott insulating state, or because of competition with some other types

  20. Magnetic domain structure and magnetization reversal in submicron-scale Co dots

    SciTech Connect (OSTI)

    Fernandez, A., LLNL

    1998-02-17T23:59:59.000Z

    We present a magnetic force microscopy (MFM) analysis of arrays of submicron-scale Co dots fabricated by interference lithography. The dots are thin (180-300 A) and are elliptical in shape. MFM of these structures reveals that they relax into highly ordered remanent states whose symmetry and configuration are governed by their shape anisotropy. In particular, when the dots are saturated along the easy-axis, a uniformly magnetized state persists at remanence. However, when the dots are saturated in hard-axis, they relax into a single-vortex state in which the circulation can have either sign. Both remanent states are characterized by smoothly varying magnetization patterns and a high degree of uniformity across the array. We attribute the ordered behavior of these structures to the film microstructure, which allows the shape anisotropy to dominate over magnetocrystalline anisotropy. By imaging a series of minor-loop remanent states, we show that magnetization reversal in these structures occurs via the nucleation and annihilation of a single vortex. Magnetic hysteresis loop measurements are consistent with these observations and provide additional details. Furthermore, we present the results of micromagnetic simulations, which are in excellent agreement with both the MFM images and the hysteresis loop measurements.

  1. Effect of the (OH) Surface Capping on ZnO Quantum Dots

    E-Print Network [OSTI]

    Nabben, Reinhard

    in air at different temperatures from 150­500 C for 30 min. In comparison, highly purified bulk Zn is related to oxygen deficiency [1]; the other is a much narrower ultraviolet (UV) emission band at around, compared with good quality ZnO single crystals or ZnO powders, the UV bandgap luminescence in quantum dots

  2. Enhanced quantum dot optical down-conversion using asymmetric 2D photonic crystals

    E-Print Network [OSTI]

    Cunningham, Brian

    -performance crosslinked colloidal quantum-dot light-emitting diodes," Nat. Photonics 3(6), 341­345 (2009). 10. D. Englund. Medvedev, M. Kazes, S. H. Kan, and U. Banin, "Efficient near-infrared polymer nanocrystal light- emitting diodes," Science 295(5559), 1506­1508 (2002). 8. V. Wood, M. J. Panzer, J. L. Chen, M. S. Bradley, J. E

  3. Electronic structure of wurtzite quantum dots with cylindrical symmetry L. C. Lew Yan Voona

    E-Print Network [OSTI]

    Melnik, Roderick

    Electronic structure of wurtzite quantum dots with cylindrical symmetry L. C. Lew Yan Voona July 2005 This paper presents a six-band k·p theory for wurtzite semiconductor nanostructures to the Rashba-Sheka-Pikus Hamiltonian for wurtzite semiconductors, without the need for the axial approximation

  4. Single hole quantum dot transistors in silicon Effendi Leobandung, Lingjie Guo, and Stephen Y. Choua)

    E-Print Network [OSTI]

    of the gate voltage have been observed at temperatures over 81 K and drain biases over 66 mV. The oscillations to the drain. As the gate voltage was scanned, the drain current i.e., the hole current oscil- lated Fig. 3-dot transistors were fabricated in silicon-on-insulator. Strong oscillations in the drain current as a function

  5. Wave-Function Mapping of Graphene Quantum Dots with Soft Confinement D. Subramaniam,1

    E-Print Network [OSTI]

    Florian, Libisch

    Wave-Function Mapping of Graphene Quantum Dots with Soft Confinement D. Subramaniam,1 F. Libisch,2) Using low-temperature scanning tunneling spectroscopy, we map the local density of states of graphene the graphene K point, the electronic properties of the QDs are dominantly graphenelike. Indeed, we compare

  6. Whispering-Gallery Modes in Quantum Dot Embedded Microspheres for Sensing Applications

    E-Print Network [OSTI]

    Beier, Hope T.

    2011-02-22T23:59:59.000Z

    that shift position with variations in the local index of refraction sampled by the evanescent tail of the WGMs. To excite these WGMs, we embed quantum dots (QDs) in the periphery of polystyrene microspheres to serve as local light sources. By coupling...

  7. Towards a feasible implementation of quantum neural networks using quantum dots

    E-Print Network [OSTI]

    M. V. Altaisky; N. N. Zolnikova; N. E. Kaputkina; V. A. Krylov; Yu. E. Lozovik; N. S. Dattani

    2015-03-17T23:59:59.000Z

    We propose an implementation of quantum neural networks using an array of single-electron quantum dots with dipole-dipole interactions. We demonstrate that this implementation is both feasible and versatile by studying it within the framework of GaAs based quantum dot qubits coupled to a reservoir of acoustic phonons; a system whose decoherence properties have been experimentally and theoretically characterized with meticulous detail, and is considered one of the most accurately understood open quantum systems. Using numerically exact Feynman integral calculations, we have found that the quantum coherence in our neural networks survive for several ns even at liquid nitrogen temperatures (77 K), which is three orders of magnitude higher than current implementations which are based on SQUIDs operating at temperatures in the mK range. Furthermore, the previous quantum dot based proposals required control via manipulating the phonon bath, which is extremely difficult in real experiments. An advantage of our implementation is that it can be easily controlled, since dipole-dipole interaction strengths can be changed via the spacing between the dots and applying external fields.

  8. Warm-white light-emitting diodes integrated with colloidal quantum dots for high luminous

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Warm-white light-emitting diodes integrated with colloidal quantum dots for high luminous efficacy NQD-LED design with both high luminous efficacy of optical radiation and CRI is presented to have luminous efficacy of optical ra- diation (LER), which is challenging using conventional phosphors

  9. Accurate determination of energy scales in few-electron double quantum dots D. Taubert,1

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    methods to determine the gate voltage to energy conversion accurately in the different regimes of dot-lead tunnel couplings and demonstrate strong variations of the conversion factors. Our concepts can easily involves a conversion of the applied gate voltages to energy differences between the electronic states

  10. Depleted-heterojunction colloidal quantum dot photovoltaics employing low-cost electrical contacts

    E-Print Network [OSTI]

    Department of Materials Science and Engineering, 184 College Street, Toronto, Ontario M5S 3E4, Canada 3 of depleted-heterojunction colloidal quantum dot solar cells, we describe herein a strategy that replaces. © 2010 American Institute of Physics. doi:10.1063/1.3463037 Solar energy harvesting requires

  11. Prospective Article Materials processing strategies for colloidal quantum dot solar cells

    E-Print Network [OSTI]

    energy sources, particularly with cheap and plentiful natural gas, solar photovoltaic systems must cost of the solar panels themselves. Third-generation photovoltaic systems, including organic, dye-sensitized, and colloidal quantum dot (CQD) solar cells, offer a path to low-weight, low-cost, and prospectively high

  12. PHYSICAL REVIEW B 85, 085117 (2012) Spin thermopower in interacting quantum dots

    E-Print Network [OSTI]

    Ramsak, Anton

    2012-01-01T23:59:59.000Z

    renormalization group method, we investigate the spin thermopower of a quantum dot in a magnetic field, the dependence of the spin-Seebeck coefficient on the temperature and the magnetic field is explained in terms applications, including power generation, refrigeration, and temperature measurement.1 Thermoelectric phenomena

  13. GaN/AlN Quantum Wells and Quantum Dots for Unipolar Devices at Telecommunication Wavelengths

    SciTech Connect (OSTI)

    Julien, Francois H.; Tchernycheva, Maria; Doyennette, Laetitia; Nevou, Laurent; Lupu, Anatole; Warde, Elias [Institut d'Electronique Fondamentale, Universite Paris Sud, UMR 8622 CNRS, 91405 Orsay (France); Guillot, Fabien; Monroy, Eva; Bellet-Amalric, Edith [Equipe mixte CEACNRS-UJF, DRFMC/SP2M/PSC, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble (France); Vardi, Alon; Bahir, Gad [Departement of Electrical Engineering, Technion-Israel Institute of Technology, Haifa 3200 (Israel)

    2007-04-10T23:59:59.000Z

    We report on the latest achievements in terms of growth and optical investigation of ultrathin GaN/AlN isolated and coupled quantum wells grown by plasma-assisted molecular-beam epitaxy. We also present the observation of intraband absorption in self-organized GaN quantum dots and on the application to infrared photodetection at telecommunication wavelengths.

  14. Study of the self-organization processes in lead sulfide quantum dots

    SciTech Connect (OSTI)

    Tarasov, S. A., E-mail: SATarasov@mail.ru; Aleksandrova, O. A.; Maksimov, A. I.; Maraeva, E. V.; Matyushkin, L. B.; Men’kovich, E. A.; Moshnikov, V. A. [St. Petersburg Electrotechnical University LETI (Russian Federation); Musikhin, S. F. [St. Petersburg State Polytechnic University (Russian Federation)

    2014-12-15T23:59:59.000Z

    A procedure is described for the synthesis of nanoparticles based on lead chalcogenides. The procedure combines the synthesis of colloidal quantum dots (QDs) in aqueous solutions with simultaneous organization of the QDs into ordered arrays. The processes of the self-organization of QDs are analyzed at the nano- and microscopic levels by the photoluminescence method, atomic-force microscopy, and optical microscopy.

  15. Vehicle Technologies Office: Transitioning the Transportation...

    Energy Savers [EERE]

    Transitioning the Transportation Sector - Exploring the Intersection of H2 Fuel Cell and Natural Gas Vehicles Vehicle Technologies Office: Transitioning the Transportation Sector -...

  16. Transition Strategies for 2006 and 2007

    Broader source: Energy.gov [DOE]

    Presentation on Transition Strategies given by Sigmund Gronich of the U.S. Department of Energy during the DOE Hydrogen Transition Analysis Workshop on January 26, 2006.

  17. Detecting quantum-coherent nanomechanical oscillations using the current-noise spectrum of a double quantum dot

    E-Print Network [OSTI]

    Neill Lambert; Franco Nori

    2008-12-17T23:59:59.000Z

    We consider a nanomechanical resonator coupled to a double quantum dot. We demonstrate how the finite-frequency current noise spectrum through the double quantum dot can be used to distinguish classical and quantum behaviour in the nearby nano-electromechanical resonator. We also show how the full frequency current noise spectrum gives important information on the combined double quantum dot-resonator energy spectrum. Finally, we point out regimes where the quantum state of the resonator becomes squeezed, and also examine the cross-correlated electron-phonon current noise.

  18. Phase transition towards strange matter

    E-Print Network [OSTI]

    F. Gulminelli; Ad. R. Raduta; M. Oertel

    2012-08-31T23:59:59.000Z

    The phase diagram of a system constituted of neutrons and $\\Lambda$-hyperons in thermal equilibrium is evaluated in the mean-field approximation. It is shown that this simple system exhibits a complex phase diagram with first and second order phase transitions. Due to the generic presence of attractive and repulsive couplings, the existence of phase transitions involving strangeness appears independent of the specific interaction model. In addition we will show under which conditions a phase transition towards strange matter at high density exists, which is expected to persist even within a complete treatment including all the different strange and non- strange baryon states. The impact of this transition on the composition of matter in the inner core of neutron stars is discussed.

  19. Feeding the Transition Dairy Cow 

    E-Print Network [OSTI]

    Stokes, Sandra R.

    1999-09-20T23:59:59.000Z

    Proper nutrition management during a cow's transition period (from the last 3 weeks of gestation through the first 2 weeks of lactation), is critical to successful lactation. This publication gives details for nutrition management. Two charts list...

  20. Transition between Two Oscillation Modes

    E-Print Network [OSTI]

    Ricardo Lopez-Ruiz; Yves Pomeau

    2002-05-17T23:59:59.000Z

    A model for the symmetric coupling of two self-oscillators is presented. The nonlinearities cause the system to vibrate in two modes of different symmetries. The transition between these two regimes of oscillation can occur by two different scenarios. This might model the release of vortices behind circular cylinders with a possible transition from a symmetric to an antisymmetric Benard-von Karman vortex street.

  1. Role of surface states and defects in the ultrafast nonlinear optical properties of CuS quantum dots

    SciTech Connect (OSTI)

    Mary, K. A. Ann; Unnikrishnan, N. V., E-mail: nvu100@yahoo.com [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam 686560 (India); Philip, Reji [Light and Matter Physics Group, Raman Research Institute, C.V. Raman Avenue, Sadashivanagar, Bangalore 560080 (India)

    2014-07-01T23:59:59.000Z

    We report facile preparation of water dispersible CuS quantum dots (2–4 nm) and nanoparticles (5–11 nm) through a nontoxic, green, one-pot synthesis method. Optical and microstructural studies indicate the presence of surface states and defects (dislocations, stacking faults, and twins) in the quantum dots. The smaller crystallite size and quantum dot formation have significant effects on the high energy excitonic and low energy plasmonic absorption bands. Effective two-photon absorption coefficients measured using 100 fs laser pulses employing open-aperture Z-scan in the plasmonic region of 800 nm reveal that CuS quantum dots are better ultrafast optical limiters compared to CuS nanoparticles.

  2. Spin and Conductance-Peak-Spacing Distributions in Large Quantum Dots: A Density-Functional Theory Study

    E-Print Network [OSTI]

    Baranger, Harold U.

    of solid-state physics. A semiconductor quantum dot (QD) [1,2]--a nanodevice in which electron motion was regu- lar in shape [24]. Our aim here is to bridge the gap between the two theoretical approaches

  3. High Throughput Synthesis of Uniform Biocompatible Polymer Beads with High Quantum Dot Loading Using Microfluidic Jet-Mode Breakup

    E-Print Network [OSTI]

    Lee, Seung-Kon

    Uniform polymer microbeads with highly loaded quantum dots (QDs) are produced using high-throughput coherent jet breakup of a biocompatible poly(ethylene glycol) diacrylate (PEGDA) prepolymer resin, followed by in-line ...

  4. Nanoscale optical positioning of single quantum dots for bright, pure, and on-demand single-photon emission

    E-Print Network [OSTI]

    Sapienza, Luca; Badolato, Antonio; Srinivasan, Kartik

    2015-01-01T23:59:59.000Z

    Self-assembled, epitaxially-grown InAs/GaAs quantum dots are promising semiconductor quantum emitters that can be integrated on a chip for a variety of photonic quantum information science applications. However, self-assembled growth results in an essentially random in-plane spatial distribution of quantum dots, presenting a challenge in creating devices that exploit the strong interaction of single quantum dots with highly confined optical modes. Here, we present a photoluminescence imaging approach for locating single quantum dots with respect to alignment features with an average (minimum) position uncertainty efficiency (48 % +/- 5 % into a 0.4 numerical aperture lens, close to the theoretically predicted value of 50 %), low multiphoton prob...

  5. Transition Path Theory E. Vanden-Eijnden

    E-Print Network [OSTI]

    Van Den Eijnden, Eric

    Transition Path Theory E. Vanden-Eijnden Courant Institute of Mathematical Sciences, New York University New York, NY 10012 eve2cims.nyu.edu Eric Vanden-Eijnden E. Vanden-Eijnden: Transition Path Theory of the Current and Transition Tubes . . . . . . . . . . . . . . . . . . . . . . 451 5 Comparison with Transition

  6. 12 August 2005 Observing Optical Transition

    E-Print Network [OSTI]

    Anlage, Steven

    12 August 2005 Observing Optical Transition Radiation from 10keV Electrons 1 #12;12 August 2005 Observing Optical Transition Radiation from 10keV Electrons 2 #12;12 August 2005 Observing Optical Transition Radiation from 10keV Electrons 3 #12;12 August 2005 Observing Optical Transition Radiation from 10

  7. Regional Transit System: Return on Investment Assessment

    E-Print Network [OSTI]

    Minnesota, University of

    Regional Transit System: Return on Investment Assessment May 2014 #12;1 Today's agenda Itasca transit options Enables strategic, efficient investment in long-term infrastructure, e.g., energy grid are seeking cities with good transit Transit can be a cost-efficient way to add capacity in corridors

  8. Hole Spin Pumping and Re-pumping in a p-type ?-doped InAs Quantum Dot

    E-Print Network [OSTI]

    Konstantinos G. Lagoudakis; Kevin A. Fischer; Tomas Sarmiento; Kai Mueller; Jelena Vu?kovi?

    2014-08-29T23:59:59.000Z

    We have grown high quality p-type {\\delta}-doped InAs quantum dots and have demonstrated coherent spin pumping and repumping of a hole spin in a positively charged quantum dot by means of a single-laser driving scheme under a high magnetic field in the Voigt configuration. Modeling of our system shows excellent qualitative agreement with the experimental findings and further explores the performance of the single-laser scheme for spin pumping and re-pumping.

  9. Measuring Cost Variability in Provision of Transit Service

    E-Print Network [OSTI]

    Taylor, Brian D.; Garrett, Mark; Iseki, Hiroyuki

    2010-01-01T23:59:59.000Z

    Comprehensive Transit Performance Indicators. UCTC WorkingModal Transit Performance Indicators. Ph.D. dissertation.

  10. An Information And Institutional Inventory Of California Transit Agencies

    E-Print Network [OSTI]

    Hickman, Mark; Day, Theodore

    1996-01-01T23:59:59.000Z

    Salinas Transit 1 Ryan Ranch Road Monterey CA 93940 Jim Andrew, Interim Transit Manager Morongo Basin

  11. Determination of lateral size distribution of type-II ZnTe/ZnSe stacked submonolayer quantum dots via spectral analysis of optical signature of the Aharanov-Bohm excitons

    SciTech Connect (OSTI)

    Ji, Haojie; Dhomkar, Siddharth; Roy, Bidisha; Kuskovsky, Igor L. [Department of Physics, Queens College of CUNY, Queens, New York 11367 (United States); The Graduate Center of CUNY, New York, New York 10016 (United States); Shuvayev, Vladimir [Department of Physics, Queens College of CUNY, Queens, New York 11367 (United States); Deligiannakis, Vasilios; Tamargo, Maria C. [The Graduate Center of CUNY, New York, New York 10016 (United States); Department of Chemistry, City College of CUNY, New York, New York 10031 (United States); Ludwig, Jonathan [National High Magnetic Field Laboratory, Tallahassee, Florida 32310 (United States); Department of Physics, Florida State University, Tallahassee, Florida 32306 (United States); Smirnov, Dmitry [National High Magnetic Field Laboratory, Tallahassee, Florida 32310 (United States); Wang, Alice [Evans Analytical Group, Sunnyvale, California 94086 (United States)

    2014-10-28T23:59:59.000Z

    For submonolayer quantum dot (QD) based photonic devices, size and density of QDs are critical parameters, the probing of which requires indirect methods. We report the determination of lateral size distribution of type-II ZnTe/ZnSe stacked submonolayer QDs, based on spectral analysis of the optical signature of Aharanov-Bohm (AB) excitons, complemented by photoluminescence studies, secondary-ion mass spectroscopy, and numerical calculations. Numerical calculations are employed to determine the AB transition magnetic field as a function of the type-II QD radius. The study of four samples grown with different tellurium fluxes shows that the lateral size of QDs increases by just 50%, even though tellurium concentration increases 25-fold. Detailed spectral analysis of the emission of the AB exciton shows that the QD radii take on only certain values due to vertical correlation and the stacked nature of the QDs.

  12. Chains of quantum dot molecules grown on Si surface pre-patterned by ion-assisted nanoimprint lithography

    SciTech Connect (OSTI)

    Smagina, Zh. V.; Stepina, N. P., E-mail: stepina@isp.nsc.ru; Zinovyev, V. A.; Kuchinskaya, P. A. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Lavrenteva 13, 630090 Novosibirsk (Russian Federation); Novikov, P. L.; Dvurechenskii, A. V. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Lavrenteva 13, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova, 2, 630090 Novosibirsk (Russian Federation)

    2014-10-13T23:59:59.000Z

    An original approach based on the combination of nanoimprint lithography and ion irradiation through mask has been developed for fabrication of large-area periodical pattern on Si(100). Using the selective etching of regions amorphized by ion irradiation ordered structures with grooves and ridges were obtained. The shape and depth of the relief were governed by ion energy and by the number of etching stages as well. Laterally ordered chains of Ge quantum dots were fabricated by molecular beam epitaxy of Ge on the pre-patterned Si substrates. For small amount of Ge deposited chains contain separate quantum dot molecules. The increase of deposition amount leads to overlapping of quantum dot molecules with formation of dense homogeneous chains of quantum dots. It was shown that the residual irradiation-induced bulk defects underneath the grooves suppress nucleation of Ge islands at the bottom of grooves. On pre-patterned substrates with whole defect regions, etched quantum dots grow at the bottom of grooves. The observed location of Ge quantum dots is interpreted in terms of local strain-mediated surface chemical potential which controls the sites of islands nucleation. The local chemical potential is affected by additional strain formed by the residual defects. It was shown by molecular dynamics calculations that these defects form the compressive strain at the bottom of grooves.

  13. Probing the structural dependency of photoinduced properties of colloidal quantum dots using metal-oxide photo-active substrates

    SciTech Connect (OSTI)

    Patty, Kira; Campbell, Quinn; Hamilton, Nathan; West, Robert G. [Department of Physics, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States); Sadeghi, Seyed M., E-mail: seyed.sadeghi@uah.edu [Department of Physics, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States); Nano and Micro Device Center, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States); Mao, Chuanbin [Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, Oklahoma 73019 (United States)

    2014-09-21T23:59:59.000Z

    We used photoactive substrates consisting of about 1 nm coating of a metal oxide on glass substrates to investigate the impact of the structures of colloidal quantum dots on their photophysical and photochemical properties. We showed during irradiation these substrates can interact uniquely with such quantum dots, inducing distinct forms of photo-induced processes when they have different cores, shells, or ligands. In particular, our results showed that for certain types of core-shell quantum dot structures an ultrathin layer of a metal oxide can reduce suppression of quantum efficiency of the quantum dots happening when they undergo extensive photo-oxidation. This suggests the possibility of shrinking the sizes of quantum dots without significant enhancement of their non-radiative decay rates. We show that such quantum dots are not influenced significantly by Coulomb blockade or photoionization, while those without a shell can undergo a large amount of photo-induced fluorescence enhancement via such blockade when they are in touch with the metal oxide.

  14. Quark condensates and the deconfinement transition

    E-Print Network [OSTI]

    Christian S. Fischer; Jens A. Mueller

    2009-08-18T23:59:59.000Z

    In this talk we present results on the chiral and the deconfinement transition of quenched QCD from Dyson-Schwinger equations. We determine the ordinary quark condensate signaling the chiral transition and the dual quark condensate signaling the deconfinement transition from the Landau gauge quark propagator evaluated at generalized boundary conditions. We find only slightly different transition temperatures at finite quark masses, whereas the transition temperatures coincide in the chiral limit.

  15. Adhesion Transition of Flexible Sheets

    E-Print Network [OSTI]

    Arthur A. Evans; Eric Lauga

    2009-05-31T23:59:59.000Z

    Intermolecular forces are known to precipitate adhesion events between solid bodies. Inspired by a macro-scale experiment showing the hysteretic adhesion of a piece of flexible tape over a plastic substrate, we develop here a model of far-field dry adhesion between two flexible sheets interacting via a power-law potential. We show that phase transitions from unadhered to adhered states occur as dictated by a dimensionless bending parameter representing the ratio of interaction strength to bending stiffness. The order of the adhesion transitions, as well as their hysteretic nature, is shown to depend on the form of the interaction potential between the flexible sheets. When three or more sheets interact, additional geometrical considerations determine the hierarchical or sequential nature of the adhesion transitions.

  16. Finding Transition Pathways on Manifolds

    E-Print Network [OSTI]

    Tiejun Li; Xiaoguang Li; Xiang Zhou

    2014-08-13T23:59:59.000Z

    We consider noise-induced transition paths in randomly perturbed dynami- cal systems on a smooth manifold. The classical Freidlin-Wentzell large devia- tion theory in Euclidean spaces is generalized and new forms of action functionals are derived in the spaces of functions and the space of curves to accommodate the intrinsic constraints associated with the manifold. Numerical meth- ods are proposed to compute the minimum action paths for the systems with constraints. The examples of conformational transition paths for a single and double rod molecules arising in polymer science are numerically investigated.

  17. Carrier transfer from InAs quantum dots to ErAs metal nanoparticles

    SciTech Connect (OSTI)

    Haughn, C. R.; Chen, E. Y.; Zide, J. M. O.; Doty, M. F., E-mail: doty@udel.edu [Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716 (United States); Steenbergen, E. H.; Bissell, L. J.; Eyink, K. G. [AFRL/RXAN, Wright Patterson AFB, Ohio 45433 (United States)

    2014-09-08T23:59:59.000Z

    Erbium arsenide (ErAs) is a semi-metallic material that self-assembles into nanoparticles when grown in GaAs via molecular beam epitaxy. We use steady-state and time-resolved photoluminescence to examine the mechanism of carrier transfer between indium arsenide (InAs) quantum dots and ErAs nanoparticles in a GaAs host. We probe the electronic structure of the ErAs metal nanoparticles (MNPs) and the optoelectronic properties of the nanocomposite and show that the carrier transfer rates are independent of pump intensity. This result suggests that the ErAs MNPs have a continuous density of states and effectively act as traps. The absence of a temperature dependence tells us that carrier transfer from the InAs quantum dots to ErAs MNPs is not phonon assisted. We show that the measured photoluminescence decay rates are consistent with a carrier tunneling model.

  18. Enhanced single-photon emission from a quantum dot in a micropost microcavity

    E-Print Network [OSTI]

    Jelena Vuckovic; David Fattal; Charles Santori; Glenn Solomon; Yoshihisa Yamamoto

    2003-07-03T23:59:59.000Z

    We demonstrate a single-photon source based on a quantum dot in a micropost microcavity that exhibits a large Purcell factor together with a small multi-photon probability. For a quantum dot on resonance with the cavity, the spontaneous emission rate is increased by a factor of five, while the probability to emit two or more photons in the same pulse is reduced to 2% compared to a Poisson-distributed source of the same intensity. In addition to the small multi-photon probability, such a strong Purcell effect is important in a single-photon source for improving the photon outcoupling efficiency and the single-photon generation rate, and for bringing the emitted photon pulses closer to the Fourier transform limit.

  19. Reducing charge trapping in PbS colloidal quantum dot solids

    SciTech Connect (OSTI)

    Balazs, D. M.; Nugraha, M. I.; Bisri, S. Z.; Loi, M. A., E-mail: m.a.loi@rug.nl [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747AG (Netherlands); Sytnyk, M.; Heiss, W. [Institute for Semiconductor and Solid State Physics, University of Linz, Altenbergerstr. 69, Linz 4040 (Austria)

    2014-03-17T23:59:59.000Z

    Understanding and improving charge transport in colloidal quantum dot solids is crucial for the development of efficient solar cells based on these materials. In this paper, we report high performance field-effect transistors based on lead-sulfide colloidal quantum dots (PbS CQDs) crosslinked with 3-mercaptopropionic acid (MPA). Electron mobility up to 0.03 cm{sup 2}/Vs and on/off ratio above 10{sup 5} was measured; the later value is the highest in the literature for CQD Field effect transistors with silicon-oxide gating. This was achieved by using high quality material and preventing trap generation during fabrication and measurement. We show that air exposure has a reversible p-type doping effect on the devices, and that intrinsically MPA is an n-type dopant for PbS CQDs.

  20. All-electrical single-electron shuttle in a silicon quantum dot

    E-Print Network [OSTI]

    Chan, K W; Kemppinen, A; Lai, N S; Tan, K Y; Lim, W H; Dzurak, A S

    2011-01-01T23:59:59.000Z

    We report on single-electron shuttling experiments with a silicon metal-oxide-semiconductor quantum dot at 300 mK. Our system consists of an accumulated electron layer at the Si/SiO2 interface below an aluminum top gate with two additional barrier gates used to deplete the electron gas locally and to define a quantum dot. Directional single-electron shuttling from the source and to the drain lead is achieved by applying a dc source-drain bias while driving the barrier gates with an ac voltage of frequency fp. Current plateaus at integer levels of efp are observed up to fp = 240 MHz operation frequencies. The observed results are explained by a sequential tunneling model which suggests that the electron gas may be heated substantially by the ac driving voltage.

  1. Synthesis of Non-blinking Semiconductor Quantum Dots Emitting in the Near-Infrared

    SciTech Connect (OSTI)

    Dennis, Allison M. [Los Alamos National Laboratory; Mangum, Benjamin D. [Los Alamos National Laboratory; Piryatinski, Andrei [Los Alamos National Laboratory; Park, Young-Shin [Los Alamos National Laboratory; Htoon, Han [Los Alamos National Laboratory; Hollingsworth, Jennifer A. [Los Alamos National Laboratory

    2012-06-21T23:59:59.000Z

    Our previous work demonstrates that Quasi-Type II CdSe/CdS core-shell quantum dots with thick shells (3-5 nm) exhibit unique photophysical characteristics, including improved chemical robustness over typical thin-shelled core/shell systems and the elimination of blinking through suppression of nonradiative Auger recombination. Here we describe a new thick-shelled heterostructure, InP/CdS, which exhibits a Type II bandgap alignment producing near-infrared (NIR) emission. Samples with a range of shell thicknesses were synthesized, enabling shell-thickness-dependent study of the absorbance and emission spectra, fluorescence lifetimes, and quantum yields. InP/CdS/ZnS core/shell/shell structures were also synthesized to reduce cadmium exposure for applications in the biological environment. Single particle spectroscopy indicates reduced blinking and improved photostability with increasing shell thickness, resulting in thick-shelled dots that are appropriate for single-particle tracking measurements with NIR emission.

  2. Single photoelectron spin detection and angular momentum transfer in a gate defined quantum dot

    E-Print Network [OSTI]

    Takafumi Fujita; Kazuhiro Morimoto; Haruki Kiyama; Giles Allison; Marcus Larsson; Arne Ludwig; Sascha R. Valentin; Andreas D. Wieck; Akira Oiwa; Seigo Tarucha

    2015-04-14T23:59:59.000Z

    Recent innovations in fabricating nanoscale confined spin systems have enabled investigation of fundamental quantum correlations between single quanta of photons and matter states. Realization of quantum state transfer from photon polarization to electron spin using gate defined quantum dots (QDs) may give evidence of preserved coherence of angular momentum basis states at the photon-spin interface. The interface would enlarge the concept of quantum information technology, in which single photogenerated electron spins are manipulated with the dots, but this remains a serious challenge. Here, we report the detection of single electron spins generated by polarized single photons via a double QD (DQD) to verify the angular momentum transfer from single photons to single electrons. Pauli spin blockade (PSB) is used to project the photoelectron spin state onto the up or down spin state. Our result promises the realization of coherent quantum state transfer and development of hybrid photon and spin quantum technology.

  3. Green's functions technique for calculating the emission spectrum in a quantum dot-cavity system

    E-Print Network [OSTI]

    Edgar A. Gomez; J. D. Hernandez-Rivero; Herbert Vinck-Posada

    2015-02-01T23:59:59.000Z

    We introduce the Green's functions technique as an alternative theory to the quantum regression theorem formalism for calculating the two-time correlation functions in open quantum systems. In particular, we investigate the potential of this theoretical approach by its application to compute the emission spectrum of a dissipative system composed by a single quantum dot inside of a semiconductor cavity. We also describe a simple algorithm based on the Green's functions technique for calculating the emission spectrum of the quantum dot as well as of the cavity which can easily be implemented in any numerical linear algebra package. We find that the Green's functions technique demonstrates a better accuracy and efficiency in the calculation of the emission spectrum and it allows to overcome the inherent theoretical difficulties associated to the direct application of the quantum regression theorem approach.

  4. Phonon-assisted robust and deterministic two-photon biexciton preparation in a quantum dot

    E-Print Network [OSTI]

    S. Bounouar; M. Müller; A. M. Barth; M. Glässl; V. M. Axt; P. Michler

    2014-08-29T23:59:59.000Z

    We investigate both experimentally and theoretically a simple yet more robust and flexible alternative to Rabi oscillation-type biexciton preparation protocols traditionally used for semiconductor quantum dots. The quantum dot is excited by a strong laser pulse positively detuned from the two-photon resonance yielding an on demand initialization of the biexciton state by making use of the phonon-induced thermalization of the photon dressed states. It is shown that for excitation pulses in the picosecond range, a stable and high fidelity of up to $f_{XX}=0.98\\pm 0.01$ is reached. Notably, the generated photons show similar coherence properties as measured in the resonant two-photon scheme. This protocol is a powerful tool for the control of complex solid state systems combining radiative cascades, entanglement and resonant cavity modes.

  5. Height stabilization of GaSb/GaAs quantum dots by Al-rich capping

    SciTech Connect (OSTI)

    Smakman, E. P., E-mail: e.p.smakman@tue.nl; Koenraad, P. M. [Department of Applied Physics, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven (Netherlands); DeJarld, M.; Martin, A. J.; Millunchick, J. [Department of Material Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Luengo-Kovac, M.; Sih, V. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

    2014-09-01T23:59:59.000Z

    GaSb quantum dots (QDs) in a GaAs matrix are investigated with cross-sectional scanning tunneling microscopy (X-STM) and photoluminescence (PL). We observe that Al-rich capping materials prevent destabilization of the nanostructures during the capping stage of the molecular beam epitaxy (MBE) growth process and thus preserves the QD height. However, the strain induced by the absence of destabilization causes many structural defects to appear around the preserved QDs. These defects originate from misfit dislocations near the GaSb/GaAs interface and extend into the capping layer as stacking faults. The lack of a red shift in the QD PL suggests that the preserved dots do not contribute to the emission spectra. We suggest that a better control over the emission wavelength and an increase of the PL intensity is attainable by growing smaller QDs with an Al-rich overgrowth.

  6. SiGe/sSi quantum dot electron spin decoherence dependence on $^{73}$Ge

    E-Print Network [OSTI]

    Witzel, Wayne M; Carroll, Malcolm S

    2011-01-01T23:59:59.000Z

    We theoretically study the nuclear spin induced decoherence of a quantum dot in Si that is confined at a SiGe interface. We calculate decoherence time dependence on $^{73}$Ge in the barrier layer to evaluate the importance of Ge as well as Si enrichment for long decoherence times. We use atomistic tight-binding modeling for an accurate account of the electron wavefunction which is particularly important for determining the contact hyperfine interactions with the Ge nuclear spins. We find decoherence times due to Ge spins at natural concentrations to be milliseconds. This suggests SiGe/sSi quantum dot devices employing enriched Si will require enriched Ge as well in order to benefit from long coherence times. We provide a comparison of $T_2$ times for various fractions of nonzero spin isotopes of Si and Ge.

  7. SiGe/Si quantum dot electron spin decoherence dependence on $^{73}$Ge

    E-Print Network [OSTI]

    Wayne M. Witzel; Rajib Rahman; Malcolm S. Carroll

    2012-05-14T23:59:59.000Z

    We theoretically study the nuclear spin induced decoherence of a quantum dot in Si that is confined at a SiGe interface. We calculate decoherence time dependence on $^{73}$Ge in the barrier layer to evaluate the importance of Ge as well as Si enrichment for long decoherence times. We use atomistic tight-binding modeling for an accurate account of the electron wavefunction which is particularly important for determining the contact hyperfine interactions with the Ge nuclear spins. We find decoherence times due to Ge spins at natural concentrations to be milliseconds. This suggests SiGe/Si quantum dot devices employing enriched Si will require enriched Ge as well in order to benefit from long coherence times. We provide a comparison of $T_2$ times for various fractions of nonzero spin isotopes of Si and Ge.

  8. Final LDRD report : infrared detection and power generation using self-assembled quantum dots.

    SciTech Connect (OSTI)

    Cederberg, Jeffrey George; Ellis, Robert; Shaner, Eric Arthur

    2008-02-01T23:59:59.000Z

    Alternative solutions are desired for mid-wavelength and long-wavelength infrared radiation detection and imaging arrays. We have investigated quantum dot infrared photodetectors (QDIPs) as a possible solution for long-wavelength infrared (8 to 12 {mu}m) radiation sensing. This document provides a summary for work done under the LDRD 'Infrared Detection and Power Generation Using Self-Assembled Quantum Dots'. Under this LDRD, we have developed QDIP sensors and made efforts to improve these devices. While the sensors fabricated show good responsivity at 80 K, their detectivity is limited by high noise current. Following efforts concentrated on how to reduce or eliminate this problem, but with no clear path was identified to the desired performance improvements.

  9. Decision making based on optical excitation transfer via near-field interactions between quantum dots

    SciTech Connect (OSTI)

    Naruse, Makoto, E-mail: naruse@nict.go.jp [Photonic Network Research Institute, National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795 (Japan); Nomura, Wataru; Ohtsu, Motoichi [Department of Electrical Engineering and Information Systems, Graduate School of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Aono, Masashi [Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguru-ku, Tokyo 152-8550 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi-shi, Saitama 332-0012 (Japan); Sonnefraud, Yannick; Drezet, Aurélien; Huant, Serge [Université Grenoble Alpes, Inst. NEEL, F-38000 Grenoble (France); CNRS, Inst. NEEL, F-38042 Grenoble (France); Kim, Song-Ju [WPI Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

    2014-10-21T23:59:59.000Z

    Optical near-field interactions between nanostructured matters, such as quantum dots, result in unidirectional optical excitation transfer when energy dissipation is induced. This results in versatile spatiotemporal dynamics of the optical excitation, which can be controlled by engineering the dissipation processes and exploited to realize intelligent capabilities such as solution searching and decision making. Here, we experimentally demonstrate the ability to solve a decision making problem on the basis of optical excitation transfer via near-field interactions by using colloidal quantum dots of different sizes, formed on a geometry-controlled substrate. We characterize the energy transfer behavior due to multiple control light patterns and experimentally demonstrate the ability to solve the multi-armed bandit problem. Our work makes a decisive step towards the practical design of nanophotonic systems capable of efficient decision making, one of the most important intellectual attributes of the human brain.

  10. FUNCTIONAL AND MECHANISTIC STUDY OF DOT1L IN MOUSE EMBRYONIC HEMATOPOIESIS

    E-Print Network [OSTI]

    Feng, Yi

    2012-12-31T23:59:59.000Z

    both starved and restimulated MEF ………..………… 51 2.8 Whole-mount immunolabeling for fluorescence …………..……………………... 51 2.9 Analysis of primitive and definitive hematopoiesis by colony forming unit assay ………………………………………………………… 52 2... and KO primitive and definitive erythroid colonies ………….……………………………………………….. 79 Figure 3.8 C-kit/CD41 staining of E10.5 yolk sacs from WT and Dot1L KO embryos ……….……………………………………………………….. 80 Figure 3.9 c-kit+/CD45...

  11. Tuning photoluminescence of reduced graphene oxide quantum dots from blue to purple

    SciTech Connect (OSTI)

    Liu, Fuchi [Physics Department and Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 (China); College of Physics and Technology, Guangxi Normal University, Guilin 541004 (China); Tang, Tao; Feng, Qian; Li, Ming; Liu, Yuan; Tang, Nujiang, E-mail: tangnujiang@nju.edu.cn; Zhong, Wei; Du, Youwei [Physics Department and Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 (China)

    2014-04-28T23:59:59.000Z

    Reduced graphene oxide quantum dots (rGOQDs) were synthesized by annealing GOQDs in H{sub 2} atmosphere. The photoluminescence (PL) properties of GOQDs and the rGOQDs samples were investigated. The results showed that compared to GOQDs, a blue to purple tunable PL of rGOQDs can be obtained by regulating the annealing temperature. The increase fraction of the newly formed isolated sp{sup 2} clusters may be responsible for the observed tunable PL.

  12. Probing the ladder of dressed states and nonclassical light generation in quantum dot-cavity QED

    E-Print Network [OSTI]

    Arka Majumdar; Michal Bajcsy; Jelena Vuckovic

    2011-10-21T23:59:59.000Z

    We investigate the photon induced tunneling phenomena in a photonic crystal cavity containing a strongly coupled quantum dot and describe how this tunneling can be used to generate photon states consisting mainly of a particular Fock state. Additionally, we study experimentally the photon-induced tunneling as a function of excitation laser power and frequency and show the signature of second rung of the Jaynes-Cummings Hamiltonian in the observed photon-statistics.

  13. Local droplet etching – Nanoholes, quantum dots, and air-gap heterostructures

    SciTech Connect (OSTI)

    Heyn, Ch.; Sonnenberg, D.; Graf, A.; Kerbst, J.; Stemmann, A.; Hansen, W. [Institute of Applied Physics, University of Hamburg, Jungiusstr. 11, 20355 Hamburg (Germany)

    2014-05-15T23:59:59.000Z

    Local droplet etching (LDE) allows the self-organized generation of nanoholes in semiconductor surfaces and is fully compatible with molecular beam epitaxy (MBE). The influence of the process parameters as well as of droplet and substrate materials on the LDE nanohole morphology is discussed. Furthermore, recent applications of LDE, the fabrication of quantum dots by hole filling and the creation of air-gap heterostructures are addressed.

  14. Observations of Rabi oscillations in a non-polar InGaN quantum dot

    SciTech Connect (OSTI)

    Reid, Benjamin P. L., E-mail: benjamin.reid@physics.ox.ac.uk; Chan, Christopher C. S.; Taylor, Robert A. [Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Kocher, Claudius [Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Konstanz University, Konstanz (Germany); Zhu, Tongtong; Oehler, Fabrice; Emery, Robert; Oliver, Rachel A. [Department of Materials Science and Metallurgy, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom)

    2014-06-30T23:59:59.000Z

    Experimental observation of Rabi rotations between an exciton excited state and the crystal ground state in a single non-polar InGaN quantum dot is presented. The exciton excited state energy is determined by photoluminescence excitation spectroscopy using two-photon excitation from a pulsed laser. The population of the exciton excited state is seen to undergo power dependent damped Rabi oscillations.

  15. Brightly photoluminescent phosphor materials based on silicon quantum dots with oxide shell

    E-Print Network [OSTI]

    Cao, Guozhong

    .-J. Cheng, Y. Tian, M. S. Liu, J. Zhao, J. A. Bardecker, I. J.-L. Plante, D. S. Ginger, and A. K.-Y. Jen for display backlights," Adv. Mater. (Deerfield Beach Fla.) 22(28), 3076­3080 (2010). 9. Z. Ding, B. M. Quinn quantum dot-organic light-emitting diodes," Appl. Phys. Lett. 98(21), 213102 (2011). 11. K.-Y. Cheng, R

  16. Second harmonic generation from direct band gap quantum dots pumped by femtosecond laser pulses

    SciTech Connect (OSTI)

    Liu, Liwei, E-mail: liulw@cust.edu.cn; Wang, Yue; Hu, Siyi; Ren, Yu; Huang, Chen [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022, People's Republic of China and International Joint Research Center for Nanophotonics and Biophotonics, Changchun University of Science and Technology, Changchun, Jilin 130022 (China)

    2014-02-21T23:59:59.000Z

    We report on nonlinear optical experiments performed on Cu{sub 2}S quantum dots (QDs) pumped by femtosecond laser pulses. We conduct a theoretical simulation and experiments to determine their second harmonic generation characteristics. Furthermore, we demonstrate that the QDs have a second harmonic generation conversion efficiency of up to 76%. Our studies suggest that these Cu{sub 2}S QDs can be used for solar cells, bioimaging, biosensing, and electric detection.

  17. Valley splitting in Si quantum dots embedded in SiGe S. Srinivasan,1,2

    E-Print Network [OSTI]

    Rokhinson, Leonid

    Valley splitting in Si quantum dots embedded in SiGe S. Srinivasan,1,2 G. Klimeck,1,2 and L. P subband.4 Recently, calculations predicted that valley splitting in nar- row few nanometers SiGe/Si/SiGe that prediction, which has been explained12 by the disorders of the Si/SiGe interface and in the SiGe buffer

  18. Photoconductivity of structures based on the SnO{sub 2} porous matrix coupled with core-shell CdSe/CdS quantum dots

    SciTech Connect (OSTI)

    Drozdov, K. A.; Kochnev, V. I.; Dobrovolsky, A. A.; Khokhlov, D. R. [Department of Physics, Moscow State University, 119991 Moscow (Russian Federation)] [Department of Physics, Moscow State University, 119991 Moscow (Russian Federation); Popelo, A. V. [Department of Materials Science, Moscow State University, 119991 Moscow (Russian Federation)] [Department of Materials Science, Moscow State University, 119991 Moscow (Russian Federation); Rumyantseva, M. N.; Gaskov, A. M.; Ryabova, L. I. [Department of Chemistry, Moscow State University, 119991 Moscow (Russian Federation)] [Department of Chemistry, Moscow State University, 119991 Moscow (Russian Federation); Vasiliev, R. B. [Department of Materials Science, Moscow State University, 119991 Moscow (Russian Federation) [Department of Materials Science, Moscow State University, 119991 Moscow (Russian Federation); Department of Chemistry, Moscow State University, 119991 Moscow (Russian Federation)

    2013-09-23T23:59:59.000Z

    Embedding of quantum dots into porous oxide matrixes is a perspective technique for photosensitization of a structure. We show that the sensitization efficiency may be increased by the use of core-shell quantum dots. It is demonstrated that the photoresponse amplitude in a SnO{sub 2} porous matrix with CdSe/CdS quantum dots depends non-monotonously on the number of atomic layers in a shell. The best results are obtained for SnO{sub 2} matrixes coupled with the quantum dots with three atomic layers of a shell. Mechanisms responsible for the structure sensitization are discussed.

  19. Spectral properties of a hybrid-qubit model based on a two-dimensional quantum dot

    E-Print Network [OSTI]

    Alba Y. Ramos; Omar Osenda

    2015-03-27T23:59:59.000Z

    The design and study of hybrid qubits is driven by their ability to get along the best of charge qubits and of spin qubits, {\\em i.e.} the speed of operation of the former and the very slow decoherence rates of the latter ones. There are several proposals to implement hybrid qubits, this works focuses on the spectral properties of an one-electron hybrid qubit. By design, the information would be stored in the electronic spin and the switching between the qubit basis states would be achieved using an external ac electric field. The electron is confined in a two-dimensional quantum dot, whose confining potential is given by a quartic potential, features that are typical of GaAS quantum dots. Besides the confining potential that characterizes the quantum dot there are two static magnetic fields applied to the system, one is a large constant Zeeman field and the other one has a constant gradient. We study the spectral properties of the model Hamiltonian, a Scr\\"odinger-Pauli Hamiltonian with realistic parameters, using the Ritz method. In particular, we look for regions of the parameter space where the lowest eigenenergies and their eigenfunctions allow to define a qubit which is stable under perturbations to the design parameters. We put special attention to the constraints that the design imposes over the magnetic fields, the tuning of the energy gap between the qubit states and the expectation value of the spin operator where the information would be stored.

  20. Evaluating charge noise acting on semiconductor quantum dots in the circuit quantum electrodynamics architecture

    SciTech Connect (OSTI)

    Basset, J.; Stockklauser, A.; Jarausch, D.-D.; Frey, T.; Reichl, C.; Wegscheider, W.; Wallraff, A.; Ensslin, K.; Ihn, T. [Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich (Switzerland)

    2014-08-11T23:59:59.000Z

    We evaluate the charge noise acting on a GaAs/GaAlAs based semiconductor double quantum dot dipole-coupled to the voltage oscillations of a superconducting transmission line resonator. The in-phase (I) and the quadrature (Q) components of the microwave tone transmitted through the resonator are sensitive to charging events in the surrounding environment of the double dot with an optimum sensitivity of 8.5×10{sup ?5}?e/?(Hz). A low frequency 1/f type noise spectrum combined with a white noise level of 6.6×10{sup ?6} e{sup 2}/Hz above 1?Hz is extracted, consistent with previous results obtained with quantum point contact charge detectors on similar heterostructures. The slope of the 1/f noise allows to extract a lower bound for the double-dot charge qubit dephasing rate which we compare to the one extracted from a Jaynes-Cummings Hamiltonian approach. The two rates are found to be similar emphasizing that charge noise is the main source of dephasing in our system.