National Library of Energy BETA

Sample records for gray dots transitioning

  1. 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

  2. Effect of geometry and composition on the intraband transitions of holes in quantum dots

    SciTech Connect (OSTI)

    Singh, Satish Kumar Kumar, Jitendra

    2014-12-28

    The effect of shape and size anisotropy on unipolar intraband transitions of holes in quantum dots (QDs) is studied. The optical matrix elements are calculated for transitions of holes in valence band. To get the optical matrix elements, energy eigenvalues and eigenvectors are calculated using 4?×?4 Luttinger Hamiltonian in the effective mass approximation. The formulation is applied to InGaAs/GaAs QD with parabolic confinement potential in xy-plane. The optical matrix elements for intraband hole transitions are calculated for x and y polarised light. The transitions are considered from ground state to other excited states. The effect of In concentration on optical matrix elements is also investigated. It is important to note that the transitions of holes are governed by the character of initial and final states for different light polarisations that give specific transition selection rules. It is found that the polarisation is strongly dependent on the in-plane anisotropy of the QDs.

  3. Quantum-Size Effects on the Pressure-Induced Direct-to-Indirect Band-Gap Transition in InP Quantum Dots

    SciTech Connect (OSTI)

    Fu, H.; Zunger, A.

    1998-06-01

    We predict that the difference in quantum confinement energies of {Gamma} -like and X -like conduction states in a covalent quantum dot will cause the direct-to-indirect transition to occur at substantially lower pressure than in the bulk material. Furthermore, the first-order transition in the bulk is predicted to become, for certain dot sizes, a second-order transition. Measurements of the {open_quotes}anticrossing gap{close_quotes} could thus be used to obtain unique information on the {Gamma}-X- L intervalley coupling, predicted here to be surprisingly large (50{endash}100thinspthinspmeV). {copyright} {ital 1998} {ital The American Physical Society}

  4. Spectroscopy of the D1-transition of cesium by dressed-state resonance fluorescence from a single (In,Ga)As/GaAs quantum dot

    E-Print Network [OSTI]

    Ulrich, S M; Oster, M; Jetter, M; Urvoy, A; Löw, R; Michler, P

    2014-01-01

    We use a laser-driven single (In,Ga)As quantum dot (QD) in the dressed state regime of resonance fluorescence ($T = 4$ K) to observe the four $D_1$-transition lines of alkali atomic cesium ($Cs$) vapor at room temperature. We tune the frequency of the dressing continuous-wave laser in the vicinity of the bare QD resonance $\\sim 335.116$ THz ($\\sim 894.592$ nm) at constant excitation power and thereby controllably tune the center and side channel frequencies of the probe light, i.e. the Mollow triplet. Resonances between individual QD Mollow triplet lines and the atomic hyperfine-split transitions are clearly identified in the $Cs$ absorption spectrum. Our results show that narrow-band (In,Ga)As QD resonance fluorescence (RF) is suitable to optically address individual transitions of the $D_1$ quadruplet without applying magnetic field or electric field tuning.

  5. The Gray Whale, Eschrichtius robustus

    E-Print Network [OSTI]

    and MeadI), but has been extinct there for several cen- turies. Distribution and Migration Eastern North the migration routes. Stippling indicates the winter grounds. In the Atlantic, the gray whale has been extinct). 46(4),1984 7 #12;A new~orn gray whale calf in Laguna Ojo de Liebre, Baja California, Mexico. Each

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

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

    Neda Gray is the Information Systems Security Officer for the Operations and Business Principle Associate Directorate (PAD). Neda Gray is the Information Systems Security Officer...

  7. 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

    2013-09-17

    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.

  8. Grays River Watershed Geomorphic Analysis

    SciTech Connect (OSTI)

    Geist, David R.

    2005-04-30

    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

  9. DEMOGRAPHIC SHEET Biomedical Sciences, Bowman Gray Campus

    E-Print Network [OSTI]

    Anderson, Paul R.

    DEMOGRAPHIC SHEET Biomedical Sciences, Bowman Gray Campus Academic Year 2015-2016 Please complete Graduate School of Arts and Sciences Biomedical Sciences, Bowman Gray Campus Medical Center Blvd. Winston

  10. The showlabels package Norman Gray

    E-Print Network [OSTI]

    Ihn, Thomas

    , the options inner and outer will be ignored, and the label will be placed in the nearer margin. The packageThe showlabels package Norman Gray norman@astro.gla.ac.uk 1996/10/04 This is the showlabels class option. This class option introduces no new commands, it just helps you keep track of all the labels

  11. Placement Testing with Justin Gray

    E-Print Network [OSTI]

    Placement Testing with LON-CAPA Justin Gray Dept. of Mathematics SFU #12;Problem Develop reliable placement tests for students who wish to challenge prerequisites for calculus (Calculus Readiness Test) and other quantitative courses (Q Placement Test). #12;Stages Selecting an assessment system Developing

  12. 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

  13. world cultures J. Patrick Gray, Editor

    E-Print Network [OSTI]

    White, Douglas R.

    1045-0564 world cultures J. Patrick Gray, Editor PROLEGOMENA Contents and How to Use This Issue J: A Reconsideration Andrey Korotayev World Cultures CD Data Disk William Divale Journal of Comparative and Cross-Cultural Research Vol 13 No 1 Spring 2002 #12;WORLD CULTURES PUBLISHER William Divale EDITOR J. Patrick Gray

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

    E-Print Network [OSTI]

    Koski, D.

    2011-01-01

    and Technical Resources for Completing Energy Efficiency Projects ? The DOT/FTA Perspective Don Koski, FTA Region VI CATEE Conference November 9, 2011 ?FTA is part of the US DOT with a mission to support public transit through grant programs and policies...://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...

  15. Healthcare Energy: Massachusetts General Hospital Gray Building...

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

    Floor Space: 332,664 ft2 The Gray Building is an inpatient care facility, and its space types include exam rooms; treatment rooms; procedure rooms; operating rooms; research...

  16. Dynamic Nuclear Spin Polarization in the Resonant Laser Excitation of an InGaAs Quantum Dot

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    Dynamic Nuclear Spin Polarization in the Resonant Laser Excitation of an InGaAs Quantum Dot A. Ho transitions in self-assembled quantum dots leads to nuclear spin polarization that is qualitatively different, we demonstrate that nuclear spin polarization manifests itself in quantum dots subjected to finite

  17. world cultures J. Patrick Gray, Editor

    E-Print Network [OSTI]

    White, Douglas R.

    1045-0564 world cultures J. Patrick Gray, Editor PROLEGOMENA Contents and How to Use This Issue J in Cross-Cultural Perspective: A Reconsideration Andrey Korotayev World Cultures CD Data Disk William Divale Journal of Comparative and Cross-Cultural Research Vol 12 No 2 Fall 2001 #12;WORLD CULTURES

  18. Numerical simulation of optical feedback on a quantum dot lasers

    SciTech Connect (OSTI)

    Al-Khursan, Amin H., E-mail: ameen_2all@yahoo.com [Thi-Qar University, Nassiriya Nanotechnology Research Laboratory (NNRL), Science College (Iraq); Ghalib, Basim Abdullattif [Babylon University, Laser Physics Department, Science College for Women (Iraq); Al-Obaidi, Sabri J. [Al-Mustansiriyah University, Physics Department, Science College (Iraq)

    2012-02-15

    We use multi-population rate equations model to study feedback oscillations in the quantum dot laser. This model takes into account all peculiar characteristics in the quantum dots such as inhomogeneous broadening of the gain spectrum, the presence of the excited states on the quantum dot and the non-confined states due to the presence of wetting layer and the barrier. The contribution of quantum dot groups, which cannot follow by other models, is simulated. The results obtained from this model show the feedback oscillations, the periodic oscillations which evolves to chaos at higher injection current of higher feedback levels. The frequency fluctuation is attributed mainly to wetting layer with a considerable contribution from excited states. The simulation shows that is must be not using simple rate equation models to express quantum dots working at excited state transition.

  19. Quantum Dots: Theory

    SciTech Connect (OSTI)

    Vukmirovic, Nenad; Wang, Lin-Wang

    2009-11-10

    This review covers the description of the methodologies typically used for the calculation of the electronic structure of self-assembled and colloidal quantum dots. These are illustrated by the results of their application to a selected set of physical effects in quantum dots.

  20. Spinal cord gray matter atrophy correlates with multiple sclerosis disability

    E-Print Network [OSTI]

    2014-01-01

    Atrophy Correlates with Multiple Sclerosis Disability Regina1,5,6 Objective: In multiple sclerosis (MS), cerebral grayPMS 5 progressive multiple sclerosis; RMS 5 relapsing

  1. Average End Use Breakdown: Massachusetts General Hospital Gray...

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

    Exhaust Fans Pumps for Hot Water and Heat Recovery Chiller Plant (Allocated): Chillers, Cooling Tower Fans, and Cooling System Pumps Return to Gray Building information page....

  2. 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 and photoluminescence PL spectroscopy of self-assembled Ge dots grown on Si 100 by molecular beam epitaxy. PL spectra show a transition from two- to three-dimensional growth as the Ge thickness exceeds 7 Å. The sum

  3. Gray County Wind Farm | 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 on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIXsource History View New Pages RecentPlantMagma EnergyGooglePrograms JumpGratiot JumpGray

  4. 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)

    2011-07-15

    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.

  5. A quantum dot heterojunction photodetector

    E-Print Network [OSTI]

    Arango, Alexi Cosmos, 1975-

    2005-01-01

    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, ...

  6. DOT specification packages evaluation

    SciTech Connect (OSTI)

    Ratledge, J.E.; Rawl, R.R. )

    1991-01-01

    During the late 1960s and early 1970s, the Department of Transportation (DOT) specification package system was implemented to serve as a useful and equivalent alternative to the Nuclear Regulatory Commission (NRC) and the Bureau of Explosives approval systems for Type B and fissile radioactive material package designs. When a package design was used by a large number of organizations, the package design was added to the DOT regulations as a specification package authorized for use by any shipper. In the mid-1970s, the NRC revised its package design certification system to the one in use today. This paper reports that, while the NRC and DOT transportation regulations have evolved over the years, the DOT specification package designs have remained largely unchanged. Questions have been raised as to whether these designs meet the current and proposed regulations. In order to enable the NRC and DOT to develop a regulatory analysis that will support appropriate action regarding the specification packages, a study is being performed to compile all available design, testing, and analysis information on these packages.

  7. Jane Gray Research Greenhouse And VLSB 6th

    E-Print Network [OSTI]

    Jane Gray Research Greenhouse And VLSB 6th floor Greenhouse Greenhouse User Policies University of California, Berkeley #12;Introduction The Jane Gray Research Greenhouse is 3,600 square foot research of Integrative Biology. The greenhouse uses ARGUS computer automated environmental control technology

  8. 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)

    2006-06-28

    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.

  9. 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

    2015-02-05

    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.

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

    E-Print Network [OSTI]

    Zhou, Zhou

    2009-01-01

    layer for subsequent Cu electroplating, were reported. Gray-for subsequent copper electroplating. Gray-scale technologywas improved by electroplating process optimization to

  11. Efficient all-optical production of large [superscript 6]Li quantum gases using D[subscript 1] gray-molasses cooling

    E-Print Network [OSTI]

    Burchianti, A.

    We use a gray molasses operating on the D[subscript 1] atomic transition to produce degenerate quantum gases of [superscript 6]Li with a large number of atoms. This sub-Doppler cooling phase allows us to lower the initial ...

  12. 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...

  13. Probing the size and environment induced phase transformation in CdSe quantum dots

    SciTech Connect (OSTI)

    Karakoti, Ajay S.; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Yang, Ping; Thevuthasan, Suntharampillai

    2011-11-17

    The structural and electronic properties of CdSe quantum dots in toluene and drop-casted on Si wafer were investigated by in-situ micro X-ray diffraction, X-ray photoelectron spectroscopy and UV-Vis absorption and emission spectroscopy. The in-situ micro diffraction data show that the CdSe quantum dots capped with TOPO or hexadecylamine (HDA) in toluene exhibit predominantly wurtzite crystal structure, which undergoes a phase transformation to zinc blende crystal structure following drop casting on Si and this phase transition increases with decreasing the size of the CdSe quantum dots. Decreasing the size of quantum dots also increases the Se vacancies that facilitate the phase transformation. The X-ray photoelectron spectra show a systematic increase in the core level binding energies of Cd 3d and Se 3d, the band gap and the Cd/Se ratio as the size of the quantum dots decreases from 6.6nm to 2.1nm. This is attributed to the quantum confinement of CdSe crystallites by the capping ligands in toluene which increases with decreasing the size of the quantum dots. However, drop-casting quantum dots on Si alter the density and arrangement of capping ligands and solvent molecules on the quantum dots which causes significant phase transformation.

  14. Prediction of a strain-induced conduction-band minimum in embedded quantum dots

    SciTech Connect (OSTI)

    Williamson, A.J.; Zunger, A.; Canning, A.

    1998-02-01

    Free-standing InP quantum dots have previously been theoretically and experimentally shown to have a direct band gap across a large range of experimentally accessible sizes. We demonstrated that when these dots are embedded coherently within a GaP barrier material, the effects of quantum confinement in conjunction with coherent strain suggest there will be a critical diameter of dot ({approx}60 {Angstrom}), above which the dot is direct, type I, and below which it is indirect, type II. However, the strain in the system acts to produce another conduction state with an even lower energy, in which electrons are localized in small pockets at the interface between the InP dot and the GaP barrier. Since this conduction state is GaP X{sub 1c} derived and the highest occupied valence state is InP, {Gamma} derived, the fundamental transition is predicted to be indirect in both real and reciprocal space ({open_quotes}type II{close_quotes}) for all dot sizes. This effect is peculiar to the strained dot, and is absent in the freestanding dot. {copyright} {ital 1998} {ital The American Physical Society}

  15. DOT WEB PAGES (plain text) 1 DOT WWW Pages --Plain Text Copy June 17, 2015

    E-Print Network [OSTI]

    Rutten, Rob

    DOT WEB PAGES (plain text) 1 DOT WWW Pages -- Plain Text Copy ­ June 17, 2015 http . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 8 pdf copies of these pages 29 Welcome to the DOT web pages! The Dutch Open Telescope on La Palma observing: wiki external usage webcam #12;DOT WEB PAGES (plain text) 2 1 DOT news · January 2012: Utrecht

  16. 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...

  17. Promising future of quantum dots explored in conference

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

    Promising future of quantum dots explored Promising future of quantum dots explored in conference Researchers are gathering to reflect on two decades of quantum dot research at a...

  18. A Mechanism for Detecting Gray Hole Attacks on Synchrophasor Data

    E-Print Network [OSTI]

    Sikdar, Biplab

    in smart grids [1]. Phasor measurement unit (PMU) or synchrophasor data serves to facilitate a number in the maintenance and control of the power generation and distribution system, monitoring and manipulation of PMU. This paper addresses the problem of securing PMU data against packet dropping or gray hole attacks

  19. 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)

    2013-07-15

    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.

  20. All inorganic colloidal quantum dot LEDs

    E-Print Network [OSTI]

    Wood, Vanessa Claire

    2007-01-01

    This thesis presents the first colloidal quantum dot light emitting devices (QD-LEDs) with metal oxide charge transport layers. Colloidally synthesized quantum dots (QDs) have shown promise as the active material in ...

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

    SciTech Connect (OSTI)

    May, Christopher; Geist, David

    2007-04-01

    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

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

    SciTech Connect (OSTI)

    May, Christopher W.; McGrath, Kathleen E.; Geist, David R.; Abbe, Timothy; Barton, Chase

    2008-02-04

    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

  3. Facile synthesis and photoluminescence mechanism of graphene quantum dots

    SciTech Connect (OSTI)

    Yang, Ping; Zhou, Ligang; Zhang, Shenli; Pan, Wei Shen, Wenzhong; Wan, Neng

    2014-12-28

    We report a facile hydrothermal synthesis of intrinsic fluorescent graphene quantum dots (GQDs) with two-dimensional morphology. This synthesis uses glucose, concentrate sulfuric acid, and deionized water as reagents. Concentrated sulfuric acid is found to play a key role in controlling the transformation of as-prepared hydrothermal products from amorphous carbon nanodots to well-crystallized GQDs. These GQDs show typical absorption characteristic for graphene, and have nearly excitation-independent ultraviolet and blue intrinsic emissions. Temperature-dependent PL measurements have demonstrated strong electron-electron scattering and electron-phonon interactions, suggesting a similar temperature behavior of GQDs to inorganic semiconductor quantum dots. According to optical studies, the ultraviolet emission is found to originate from the recombination of electron-hole pairs localized in the C=C bonds, while the blue emission is from the electron transition of sp{sup 2} domains.

  4. 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

    2012-01-01

    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.

  5. 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

    2012-10-03

    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.

  6. The Statistical Theory of Quantum Dots

    E-Print Network [OSTI]

    Y. Alhassid

    2001-02-15

    A quantum dot is a sub-micron-scale conducting device containing up to several thousand electrons. Transport through a quantum dot at low temperatures is a quantum-coherent process. This review focuses on dots in which the electron's dynamics are chaotic or diffusive, giving rise to statistical properties that reflect the interplay between one-body chaos, quantum interference, and electron-electron interactions. The conductance through such dots displays mesoscopic fluctuations as a function of gate voltage, magnetic field, and shape deformation. The techniques used to describe these fluctuations include semiclassical methods, random-matrix theory, and the supersymmetric nonlinear $\\sigma$ model. In open dots, the approximation of noninteracting quasiparticles is justified, and electron-electron interactions contribute indirectly through their effect on the dephasing time at finite temperature. In almost-closed dots, where conductance occurs by tunneling, the charge on the dot is quantized, and electron-electron interactions play an important role. Transport is dominated by Coulomb blockade, leading to peaks in the conductance that at low temperatures provide information on the dot's ground-state properties. Several statistical signatures of electron-electron interactions have been identified, most notably in the dot's addition spectrum. The dot's spin, determined partly by exchange interactions, can also influence the fluctuation properties of the conductance. Other mesoscopic phenomena in quantum dots that are affected by the charging energy include the fluctuations of the cotunneling conductance and mesoscopic Coulomb blockade.

  7. MICHIGAN DOT State Report Answers

    E-Print Network [OSTI]

    MICHIGAN DOT State Report Answers April 26-28, 2011 TTCC/NCC Meeting Theme: QC/QA Requirements for Pavements 1. Summarize your state's current QC/QA requirements for pavements. Current 2003 Standard an acceptable product. Upcoming 2012 Standard Specifications for Construction Contractor Administered Quality

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

    E-Print Network [OSTI]

    Zhou, Zhou

    2009-01-01

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

  9. Optoelectronic devices utilizing materials having enhanced electronic transitions

    DOE Patents [OSTI]

    Black, Marcie R.

    2013-04-09

    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.

  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 on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QAsource History View New PagesSustainableGlynn County, Georgia:Oregon: Energy ResourcesGratingsGrays Harbor County,

  11. Grays Harbor PUD - Net Metering | 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 on Delicious Rank EERE:FinancingPetroleum12,Executive CompensationEnergyGet Current:5LoggingGraphene, HydrogenGrays

  12. George T. "Rusty" Gray named TMS Fellow

    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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home Room NewsInformation Current HABFESOpportunities NuclearlongGeneralGeorge T. "Rusty" Gray

  13. Excited-state spectroscopy of InP quantum dots

    SciTech Connect (OSTI)

    Bertram, D.; Micic, O.I.; Nozik, A.J.

    1998-02-01

    We have measured low-temperature size-selective photoluminescence excitation spectra of high-quality InP quantum dots prepared by collodial chemistry. A set of samples with mean emission energies in the range from 1.9 to 2.2 eV was investigated. All samples have a size distribution of about 10{percent}, resulting in an inhomogeneously broadened photoluminescence lineshape. Due to the finite size distribution, spectra were collected at different detection wavelengths to reveal the energies of the excited excitonic states. The size dependence of the quantization energies of InP nanoparticles was determined by measuring photoluminescence excitation at different detection energies within one sample. Up to eight excited-state transitions in a set of seven samples were observed, as the estimated quantum dot size was scanned from 1.8 to 4.0 nm. A comparison of the observed peaks with a six-band {bold k}{center_dot}{bold p} calculation is given. In contrast to the successful interpretation in the case of CdSe, no agreement between the calculated and the observed excited-state energies is achieved. {copyright} {ital 1998} {ital The American Physical Society}

  14. InP quantum dots: Electronic structure, surface effects, and the redshifted emission

    SciTech Connect (OSTI)

    Fu, H.; Zunger, A.

    1997-07-01

    We present pseudopotential plane-wave electronic-structure calculations on InP quantum dots in an effort to understand quantum confinement and surface effects and to identify the origin of the long-lived and redshifted luminescence. We find that (i) unlike the case in small GaAs dots, the lowest unoccupied state of InP dots is the {Gamma}{sub 1c}-derived direct state rather than the X{sub 1c}-derived indirect state and (ii) unlike the prediction of {bold k}{center_dot}{bold p} models, the highest occupied state in InP dots has a 1sd-type envelope function rather than a (dipole-forbidden) 1pf envelope function. Thus explanations (i) and (ii) to the long-lived redshifted emission in terms of an orbitally forbidden character can be excluded. Furthermore, (iii) fully passivated InP dots have no surface states in the gap. However, (iv) removal of the anion-site passivation leads to a P dangling bond (DB) state just above the valence band, which will act as a trap for photogenerated holes. Similarly, (v) removal of the cation-site passivation leads to an In dangling-bond state below the conduction band. While the energy of the In DB state depends only weakly on quantum size, its radiative lifetime increases with quantum size. The calculated {approximately}300-meV redshift and the {approximately}18 times longer radiative lifetime relative to the dot-interior transition for the 26-{Angstrom} dot with an In DB are in good agreement with the observations of full-luminescence experiments for unetched InP dots. Yet, (vi) this type of redshift due to surface defect is inconsistent with that measured in {ital selective} excitation for HF-etched InP dots. (vii) The latter type of ({open_quotes}resonant{close_quotes}) redshift is compatible with the calculated {ital screened} singlet-triplet splitting in InP dots, suggesting that the slow emitting state seen in selective excitation could be a triplet state. {copyright} {ital 1997} {ital The American Physical Society}

  15. Quantum Dot Light Emitting Diode

    SciTech Connect (OSTI)

    Keith Kahen

    2008-07-31

    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.

  16. Quantum Dot Light Emitting Diode

    SciTech Connect (OSTI)

    Kahen, Keith

    2008-07-31

    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.

  17. & Vesicles |Hot Paper| Unilamellar Vesicles from Amphiphilic Graphene Quantum Dots

    E-Print Network [OSTI]

    Jelinek, Raz

    & Vesicles |Hot Paper| Unilamellar Vesicles from Amphiphilic Graphene Quantum Dots Sukhendu Nandi] Abstract: Graphene quantum dots (GQDs) have attracted considerable interest due to their unique Graphene quantum dots (GQDs) are carbon nanoparticles con- sisting of crystalline graphitic cores

  18. Effect of matrix on InAs self-organized quantum dots on InP substrate

    SciTech Connect (OSTI)

    Ustinov, V.M.; Weber, E.R.; Ruvimov, S.; Liliental-Weber, Z.; Zhukov, A.E.; Egorov, A.Y.; Kovsh, A.R.; Tsatsulnikov, A.F.; Kopev, P.S.

    1998-01-01

    InAs self-organized quantum dots in In{sub 0.53}Ga{sub 0.47}As and In{sub 0.52}Al{sub 0.48}As matrices have been grown on InP substrates by molecular beam epitaxy. The dot size in InGaAs has been found to be 3{endash}4 times larger, but the areal density about an order of magnitude smaller than that in InAlAs. Low-temperature photoluminescence (PL) of the InAs/InGaAs quantum dots is characterized by a narrow (35 meV) PL line as compared to that of InAs/InAlAs quantum dots (170 meV). Quantum dot formation increases the carrier localization energy as compared to quantum well structures with the same InAs thickness in a similar manner for both InAs/InGaAs and InAs/InAlAs structures. The effect of the barrier band gap on the optical transition energy is qualitatively the same for quantum well and quantum dot structures. The results demonstrate a possibility of controlling the quantum dot emission wavelength by varying the matrix composition. {copyright} {ital 1998 American Institute of Physics.}

  19. Sandia Energy - 'Giant' Nanocrystal Quantum Dots

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

    'Giant' Nanocrystal Quantum Dots: A New Class of Optical Nanomaterials for Light Emission Applications (Video Pending) Speaker: Jennifer Hollingsworth, Los Alamos National...

  20. Seasonal Distribution of the Great Gray Owl (Strix nebulosa) in Southwestern Alberta Douglas M. Collister1

    E-Print Network [OSTI]

    Seasonal Distribution of the Great Gray Owl (Strix nebulosa) in Southwestern Alberta Douglas M in the foothills of Alberta from 1986 to 1996. Thirty-six adult owls have been banded: 16 males, 16 females and 4. The Great Gray Owl (Strix nebulosa) breeds in northern and western Alberta south to Waterton Lakes National

  1. Fluorescence modulation in single CdSe quantum dots by moderate applied electric fields

    SciTech Connect (OSTI)

    LeBlanc, Sharonda J. [Department of Physics and Optical Science, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, North Carolina 28223 (United States); Department of Mechanical Engineering and Engineering Science, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, North Carolina 28223 (United States); McClanahan, Mason R.; Moyer, Tully; Moyer, Patrick J. [Department of Physics and Optical Science, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, North Carolina 28223 (United States); Jones, Marcus [Department of Chemistry, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, North Carolina 28223 (United States)

    2014-01-21

    Single molecule time-resolved fluorescence spectroscopy of CdSe/ZnS core-shell quantum dots (QDs) under the influence of moderate applied electric fields reveals distributed emission from states which are neither fully on nor off and pronounced changes in the excited state decay. The data suggest that a 54?kV/cm applied electric field causes small perturbations to the QD surface charge distribution, effectively increasing the surface trapping probability and resulting in the appearance of gray states. We present simultaneous blinking and fluorescence decay results for two sets of QDs, with and without an applied electric field. Further kinetic modeling analysis suggests that a single trapped charged cannot be responsible for a blinking off event.

  2. Temperature-Dependent Electron Transport in Quantum Dot Photovoltaics

    E-Print Network [OSTI]

    Padilla, Derek

    2013-01-01

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

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

    Energy Savers [EERE]

    Connecting the Dots Between the Real Estate Market and Residential Energy Efficiency Mastermind Session: Connecting the Dots Between the Real Estate Market and Residential Energy...

  4. Sandia Energy - InAs Quantum Dot Transitions

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

    Dan Wasserman (EFRC external partner, University of Massachusetts), Stephen Lyon (Princeton University), Paul Davids (EFRC student, Sandia Labs), Weng Chow (EFRC...

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

    SciTech Connect (OSTI)

    Ugur, A.; Hatami, F.; Masselink, W. T.; Vamivakas, A. N.; Lombez, L.; Atatuere, M.

    2008-10-06

    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.

  6. Mn/DOT's Project Peer Review

    E-Print Network [OSTI]

    Minnesota, University of

    issue we share with peers) ·Benchmark Mn/DOT's project management practices ·Initial step in a change decision- making ·Able to manage project change #12;Project Management Opportunities and Challenges ·TheMn/DOT's Project Management Peer Review Creating a Project Management Culture 2010 CTS Research

  7. Advanced Review RNA dot plots: an image

    E-Print Network [OSTI]

    Barash, Danny

    . In addition to similarity, dot plots were extended to possibly repre- sent interactions between building be easily incorporated in the dot plot. We then proceed from their passive use of providing RNA secondary be used to represent interactions between building blocks of biological sequences. This can be done

  8. InAs quantum dot growth on Al{sub x}Ga{sub 1?x}As by metalorganic vapor phase epitaxy for intermediate band solar cells

    SciTech Connect (OSTI)

    Jakomin, R.; Kawabata, R. M. S.; Souza, P. L.; Mourão, R. T.; Pires, M. P.; Micha, D. N.

    2014-09-07

    InAs quantum dot multilayers have been grown using Al{sub x}Ga{sub 1?x}As spacers with dimensions and compositions near the theoretical values for optimized efficiencies in intermediate band photovoltaic cells. Using an aluminium composition of x?=?0.3 and InAs dot vertical dimensions of 5?nm, transitions to an intermediate band with energy close to the ideal theoretical value have been obtained. Optimum size uniformity and density have been achieved by capping the quantum dots with GaAs following the indium-flush method. This approach has also resulted in minimization of crystalline defects in the epilayer structure.

  9. Energy-selective optical excitation and detection in InAs/InP quantum dot ensembles using a one-dimensional optical microcavity

    SciTech Connect (OSTI)

    Gamouras, A.; Britton, M.; Khairy, M. M.; Mathew, R.; Hall, K. C.; Dalacu, D.; Poole, P.; Poitras, D.; Williams, R. L.

    2013-12-16

    We demonstrate the selective optical excitation and detection of subsets of quantum dots (QDs) within an InAs/InP ensemble using a SiO{sub 2}/Ta{sub 2}O{sub 5}-based optical microcavity. The low variance of the exciton transition energy and dipole moment tied to the narrow linewidth of the microcavity mode is expected to facilitate effective qubit encoding and manipulation in a quantum dot ensemble with ease of quantum state readout relative to qubits encoded in single quantum dots.

  10. This year, DOTS employees united to create something B1G out of not much at all. Bus 77, now TERPRIDE, was a transit bus at the end of its life.This spring, it was retrofitted and revived to become

    E-Print Network [OSTI]

    Lathrop, Daniel P.

    . This chart should not be confused with the organization chart which is in the addendum. FUNCTIONS Budget Organizational Charts .....22Parking Statistics #12;The University of Maryland Department management programs on the College Park campus. The chart above illustrates DOTS areas of responsibility

  11. Imaging Electrons in Few-Electron Quantum Dots

    E-Print Network [OSTI]

    Imaging Electrons in Few-Electron Quantum Dots A thesis presented by Parisa Fallahi to The Division Electrons in Few-Electron Quantum Dots Abstract Electrons in a one-electron quantum dot were imaged the tip-induced shift of the electron energy state in the dot. A technique for extracting the amplitude

  12. Quantum dots Orientation-Dependent Optical-Polarization Properties

    E-Print Network [OSTI]

    Quantum dots Orientation-Dependent Optical-Polarization Properties of Single Quantum Dots. Bakkers, Leo P. Kouwenhoven, and Val Zwiller Semiconductor quantum dots (QDs) are sources of single[1 studies, the InP section following dot growth was reduced, while for the samples used in our experiments

  13. Jane Gray Research Greenhouse and IB Sixth Floor Greenhouse Department of Integrative Biology

    E-Print Network [OSTI]

    Jane Gray Research Greenhouse and IB Sixth Floor Greenhouse Department of Integrative Biology UC Berkeley - 200 Centennial Dr. Greenhouse Space Request Form Date of Request____________ Expected time frame_____________________E-mail______________________________________ --------------------------------------------------------------------------------------------------------------------- Greenhouse Environmental Specifications Watering instructions

  14. Western Gray Whale (Eschrichtius robustus) Mother and Calf Ecology Off Sakhalin Island 

    E-Print Network [OSTI]

    Sychenko, Olga Aleksandrovna

    2012-07-16

    The western population of gray whales (Eschrichtius robustus) is endangered with approximately 130 individuals remaining. Many individuals return annually to the same feeding sites off northeastern Sakhalin Island, indicating a site...

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

    E-Print Network [OSTI]

    Gailey, Glenn Andrew

    2013-05-14

    , 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...

  16. Impact of dorsolateral periaqueductal gray lesions on shock-induced hyperalgesia 

    E-Print Network [OSTI]

    McLemore, Sherilyn

    2013-02-22

    the effective impact of subsequent aversive stimuli, a phenomenon known as hyperalgesia. The present study explores whether this hyperalgesia depends on neurons within the dorsolateral periaqueductal gray (d1PAG). Experiment 1 showed that lesioning either...

  17. Phoenix-Based Clone Detection Using Suffix Trees Robert Tairas and Jeff Gray

    E-Print Network [OSTI]

    Gray, Jeffrey G.

    Phoenix-Based Clone Detection Using Suffix Trees Robert Tairas and Jeff Gray Department of Computer into an automatic clone detection technique developed as a plug-in for Microsoft's new Phoenix framework. Our

  18. Wheat Gray Shorts for the Prevention of Slipped Tendons in Battery Brooder Chicks. 

    E-Print Network [OSTI]

    Sherwood, R. M. (Ross Madison); Couch, James Russell

    1936-01-01

    STATION -- - A. B. CONNER, DIRECTOR COLLEGE STATION, BRAZOS COUNTY, TEXAS - BULLETIN 1 -- - JUNE, 1936 DIVISION OF POULTRY HUSBANDRY WHEAT GRAY SHORTS FOR THE PREVENTION OF SLIPPED TENDONS IN BATTERY BROODER CHICKS AGRICULTURAL AND MECHANICAL... COLLEGE OF TEXAS T. 0. WALTON, President Rations containing wheat gray shorts milled from hard wheat produced fewer slipped tendons and'more rapid gains than rations containing shorts milled from soft wheat when fed to chicks ih battery brooders...

  19. Photodetectors based on colloidal quantum dots

    E-Print Network [OSTI]

    Oertel, David C. (David Charles)

    2007-01-01

    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 ...

  20. Synthesis and characterization of infrared quantum dots

    E-Print Network [OSTI]

    Harris, Daniel Kelly

    2014-01-01

    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 ...

  1. Peptide coated quantum dots for biological applications

    E-Print Network [OSTI]

    2006-01-01

    23] W. C. W. Chan and S. M. Nie, “Quantum dot bioconjugatesThe resultant inorganic NIR QDOTs were also peptide-coatedInstitute of Health under Grant NIH 5 R01 EB000312. Asterisk

  2. Cascaded exciton emission of an individual strain-induced quantum dot

    E-Print Network [OSTI]

    Schülein, F J R; Riikonen, J; Mattila, M; Sopanen, M; Lipsanen, H; Finley, J J; Wixforth, A; Krenner, H J; 10.1063/1.3216807

    2010-01-01

    Single strain-induced quantum dots are isolated for optical experiments by selective removal of the inducing InP islands from the sample surface. Unpolarized emission of single, bi- and triexciton transitions are identified by power-dependent photoluminescence spectroscopy. Employing time-resolved experiments performed at different excitation powers we find a pronounced shift of the rise and decay times of these different transitions as expected from cascaded emission. Good agreement is found for a rate equation model for a three step cascade.

  3. Cascaded exciton emission of an individual strain-induced quantum dot

    E-Print Network [OSTI]

    F. J. R. Schülein; A. Laucht; J. Riikonen; M. Mattila; M. Sopanen; H. Lipsanen; J. J. Finley; A. Wixforth; H. J. Krenner

    2009-08-12

    Single strain-induced quantum dots are isolated for optical experiments by selective removal of the inducing InP islands from the sample surface. Unpolarized emission of single, bi- and triexciton transitions are identified by power-dependent photoluminescence spectroscopy. Employing time-resolved experiments performed at different excitation powers we find a pronounced shift of the rise and decay times of these different transitions as expected from cascaded emission. Good agreement is found for a rate equation model for a three step cascade.

  4. Generation of three polarization-correlated photons from a single semiconductor quantum dot

    SciTech Connect (OSTI)

    Arashida, Y.; Ogawa, Y.; Minami, F. [Department of Physics, Tokyo Institute of Technology, Oh-okayama 2-12-1, Tokyo (Japan)

    2013-12-04

    We performed polarization-resolved cross-correlation measurements on a radiative cascade of a charged tri-exciton in a single quantum dot. Photoluminescence spectra showed rich peaks arising from the formation of charged excitonic complexes. The energy structure in the cascade transition of a charged tri-exciton was explained by the exchange interaction. By using one transition pathway of the cascade, whose intermediate states form spin-triplet states, we succeeded in generating three polarization-correlated photons with circular polarization.

  5. First principle thousand atom quantum dot calculations

    SciTech Connect (OSTI)

    Wang, Lin-Wang; Li, Jingbo

    2004-03-30

    A charge patching method and an idealized surface passivation are used to calculate the single electronic states of IV-IV, III-V, II-VI semiconductor quantum dots up to a thousand atoms. This approach scales linearly and has a 1000 fold speed-up compared to direct first principle methods with a cost of eigen energy error of about 20 meV. The calculated quantum dot band gaps are parametrized for future references.

  6. Thermoelectric transport through strongly correlated quantum dots

    E-Print Network [OSTI]

    T. A. Costi; V. Zlatic

    2010-07-08

    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. Numerical study of quasiparticle lifetime in quantum dots

    E-Print Network [OSTI]

    Alejandro M. F. Rivas; Eduardo R. Mucciolo; Alex Kamenev

    2001-09-25

    The decay rate of quasiparticles in quantum dots is studied through the real time calculation of the single-particle Green function in the self-consistent approximation. The method avoids exact diagonalization, transforming the problem into a system of coupled non-linear integral equations which may be solved iteratively. That allows us to study systems larger than previously treated in the literature. Our results for the inverse participation ratio of many-body states show that the threshold energy for the quasiparticle disintegration is $E^\\ast \\sim \\sqrt{g} \\Delta$. The delocalization transition is soft rather than sharp. Three different regimes as function of the effective interaction strength may be clearly identified at high energies.

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

    E-Print Network [OSTI]

    that inserting a transition metal oxide (TMO) between the lead sulfide (PbS) quantum dot (QD) layer and the metalTransition metal oxide improves overall efficiency and maintains performance with inexpensive of performance. n-type TMOs consisting of molybdenum oxide (MoOx) and vanadium oxide (V2Ox) were used

  9. Nanostructured architectures for colloidal quantum dot solar cells

    E-Print Network [OSTI]

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

    2013-01-01

    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 ...

  10. Surface treatment of nanocrystal quantum dots after film deposition

    DOE Patents [OSTI]

    Sykora, Milan; Koposov, Alexey; Fuke, Nobuhiro

    2015-02-03

    Provided are methods of surface treatment of nanocrystal quantum dots after film deposition so as to exchange the native ligands of the quantum dots for exchange ligands that result in improvement in charge extraction from the nanocrystals.

  11. Cornell dots research collaboration leads to $10M cancer center...

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

    Cornell dots research collaboration leads to 10M cancer center September 24th, 2015 ProvidedWiesner Lab A rendering of the molecular structure of a Cornell dot, which is...

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

    E-Print Network [OSTI]

    Amasha, Sami

    2008-01-01

    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 ...

  13. 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

    2015-03-27

    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.

  14. Mechanical nanomanipulation of single strain-induced semiconductor quantum dots

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    Mechanical nanomanipulation of single strain-induced semiconductor quantum dots C. Obermu¨ller, A of single strain-induced Ga0.9In0.1As quantum dots. This was achieved by scanning a metal coated tapered of the dots2 owing to the lattice mismatch between the materials. In this case the InP islands are acting

  15. Quantum Dot-Based Cell Motility Assay

    SciTech Connect (OSTI)

    Gu, Weiwei; Pellegrino, Teresa; Parak Wolfgang J; Boudreau,Rosanne; Le Gros, Mark A.; Gerion, Daniele; Alivisatos, A. Paul; Larabell, Carolyn A.

    2005-06-06

    Because of their favorable physical and photochemical properties, colloidal CdSe/ZnS-semiconductor nanocrystals (commonly known as quantum dots) have enormous potential for use in biological imaging. In this report, we present an assay that uses quantum dots as markers to quantify cell motility. Cells that are seeded onto a homogeneous layer of quantum dots engulf and absorb the nanocrystals and, as a consequence, leave behind a fluorescence-free trail. By subsequently determining the ratio of cell area to fluorescence-free track area, we show that it is possible to differentiate between invasive and noninvasive cancer cells. Because this assay uses simple fluorescence detection, requires no significant data processing, and can be used in live-cell studies, it has the potential to be a powerful new tool for discriminating between invasive and noninvasive cancer cell lines or for studying cell signaling events involved in migration.

  16. 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)

    2014-06-21

    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.

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

    SciTech Connect (OSTI)

    Hansom, Jack; Schulte, Carsten H. H.; Matthiesen, Clemens; Stanley, Megan J.; Atatüre, Mete

    2014-10-27

    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.

  18. Electronic structure of self-assembled InAs quantum dots in InP: An anisotropic quantum-dot system

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    Electronic structure of self-assembled InAs quantum dots in InP: An anisotropic quantum-dot system properties of InAs dots in GaAs for example, Refs. 1­3 and InP dots in GaxIn1 xP.4 An interesting quantum dot; revised manuscript received 9 March 1999 The electronic structure of self-assembled InAs quantum dots

  19. A. Paytan and E.T. Gray Chapter 9 Sulfur Isotope Stratigraphy

    E-Print Network [OSTI]

    Paytan, Adina

    A. Paytan and E.T. Gray Chapter 9 Sulfur Isotope Stratigraphy Abstract: The sulfur isotopic.4. Measurement and Materials for Sulfur Isotope Stratigraphy 171 9.4.1. Isotope Analyses 171 9.4.2. Materials. The features in the record can also be used to correlate between stratigraphic sections and sequences

  20. 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

  1. Time correlations and the second entropy Angus Gray-Weale and Phil Attard

    E-Print Network [OSTI]

    Attard, Phil

    Time correlations and the second entropy Angus Gray-Weale and Phil Attard School of Chemistry F11 entropies. These entropies are calculated from time correlation functions, as are the transport coefficients to the coupling between variables of opposite time parity in the transport matrix, and show that in general

  2. 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 cortices, in lithium-treated patients with bipolar disorder, relative to healthy control subjects (1). Dr patients. Although lithium's effects on body water homeostasis (2) are important to consider, the absence

  3. Using App Inventor in a K-12 Summer Camp Amber Wagner, Jeff Gray, Jonathan Corley

    E-Print Network [OSTI]

    Gray, Jeffrey G.

    Using App Inventor in a K-12 Summer Camp Amber Wagner, Jeff Gray, Jonathan Corley Department students using App Inventor (AI). The paper describes two separate methods (one using a visual block Descriptors D.2.6. [Software Engineering]: Programming Environments Keywords App Inventor, Java Bridge, Summer

  4. Shallow-deep transitions of impurities in semiconductor nanostructures

    SciTech Connect (OSTI)

    Ranjan, V.; Singh, Vijay A.

    2001-06-01

    We study the hydrogenic impurity in a quantum dot (QD). We employ the effective mass theory with realistic barrier and variable effective mass. The model is simple, but it predicts features not previously observed. We observe that the shallow hydrogenic impurity becomes deeper as the dot size (R) is reduced and with further reduction of the dot size it becomes shallow and at times resonant with the conduction band. Such a shallow-deep (SHADE) transition is investigated and a critical size in terms of the impurity Bohr radius (a{sub I}{sup *}) is identified. A relevant aspect of a QD is reduction in the dielectric constant, {epsilon}, as its size decreases. Employing a size dependent {epsilon}(R), we demonstrate that the impurity level gets exceptionally deep in systems for which a{sub I}{sup *} is small. Thus, carrier {open_quotes}freeze out{close_quotes} is a distinct possibility in a wide class of materials such as ZnS, CdS, etc. The behavior of the impurity level with dot size is understood on the basis of simple scaling arguments. Calculations are presented for III{endash}V (AlGaAs) and II{endash}VI (ZnS, CdS) QDs. We speculate that the deepening of the impurity level is related to the high luminescence efficiency of QDs. It is suggested that quantum dots offer an opportunity for defect engineering. {copyright} 2001 American Institute of Physics.

  5. Phase Transitions

    E-Print Network [OSTI]

    Michael Creutz

    1997-08-25

    This is a set of notes on phase transitions and critical phenomena prepared to accompany my lectures for the RHIC '97 summer school, held at Brookhaven from July 6 to 16, 1997.

  6. Geometric spin manipulation in semiconductor quantum dots

    SciTech Connect (OSTI)

    Prabhakar, Sanjay Melnik, Roderick; Inomata, Akira

    2014-04-07

    We propose a method to flip the spin completely by an adiabatic transport of quantum dots. We show that it is possible to flip the spin by inducing a geometric phase on the spin state of a quantum dot. We estimate the geometric spin flip time (approximately 2 ps) which turned out to be much shorter than the experimentally reported decoherence time (approximately 100 ns) that would provide an alternative means of fliping the spin before reaching decoherence. It is important that both the Rashba coupling and the Dresselhaus coupling are present for inducing a phase necessary for spin flip. If one of them is absent, the induced phase is trivial and irrelevant for spin-flip.

  7. Mode Competition in Dual-Mode Quantum Dots Semiconductor Microlaser

    E-Print Network [OSTI]

    Chusseau, Laurent; Viktorovitch, P; Letartre, Xavier

    2013-01-01

    This paper describes the modeling of quantum dots lasers with the aim of assessing the conditions for stable cw dual-mode operation when the mode separation lies in the THz range. Several possible models suited for InAs quantum dots in InP barriers are analytically evaluated, in particular quantum dots electrically coupled through a direct exchange of excitation by the wetting layer or quantum dots optically coupled through the homogeneous broadening of their optical gain. A stable dual-mode regime is shown possible in all cases when quantum dots are used as active layer whereas a gain medium of quantum well or bulk type inevitably leads to bistable behavior. The choice of a quantum dots gain medium perfectly matched the production of dual-mode lasers devoted to THz generation by photomixing.

  8. Mode Competition in Dual-Mode Quantum Dots Semiconductor Microlaser

    E-Print Network [OSTI]

    Laurent Chusseau; Fabrice Philippe; P. Viktorovitch; Xavier Letartre

    2013-03-07

    This paper describes the modeling of quantum dots lasers with the aim of assessing the conditions for stable cw dual-mode operation when the mode separation lies in the THz range. Several possible models suited for InAs quantum dots in InP barriers are analytically evaluated, in particular quantum dots electrically coupled through a direct exchange of excitation by the wetting layer or quantum dots optically coupled through the homogeneous broadening of their optical gain. A stable dual-mode regime is shown possible in all cases when quantum dots are used as active layer whereas a gain medium of quantum well or bulk type inevitably leads to bistable behavior. The choice of a quantum dots gain medium perfectly matched the production of dual-mode lasers devoted to THz generation by photomixing.

  9. Controlling quantum dot energies using submonolayer bandstructure engineering

    SciTech Connect (OSTI)

    Yu, L.; Law, S.; Wasserman, D.; Jung, D.; Lee, M. L.; Shen, J.; Cha, J. J.

    2014-08-25

    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.

  10. Optical investigation of InAs quantum dots inserted in AlGaAs/GaAs modulation doped heterostructure

    SciTech Connect (OSTI)

    Khmissi, H.; Baira, M.; Bouzaieene, L.; Saidi, F.; Maaref, H. [Laboratoire de Micro-optoelectronique et Nanostructures, Universite de Monastir (Tunisia); Sfaxi, L. [Laboratoire de Micro-optoelectronique et Nanostructures, Universite de Monastir (Tunisia); Universite de Sousse Faculte des Sciences de Monastir, Avenue de l'Environnement 5019 Monastir (Tunisia); Bru-Chevallier, C. [Institut des Nanotechnologies de Lyon (INL), CNRS UMR-5270, INSA-LYON, 7, Avenue Jean Capelle, Bat. Blaise Pascal, 69621 Villeurbanne (France)

    2011-03-01

    Optical properties of InAs quantum dots (QDs) inserted in AlGaAs/GaAs modulation doped heterostructure are investigated. To study the effect of carrier transfer behavior on the luminescence of self-assembled quantum dots, a series of sample has been prepared using molecular beam epitaxy (Riber 32 system) in which we have varied the thickness separating the delta dopage and the InAs quantum dots layer. Photoluminescence spectra show the existence of two peaks that can be attributed to transition energies from the ground state (E{sub 1}-HH{sub 1}) and the first excited state (E{sub 2}-HH{sub 2}). Two antagonist effects have been observed, a blue shift of the emission energies result from electron transferred from the AlGaAs/GaAs heterojunction to the InAs quantum dots and a red shift caused by the quantum confined Stark effect due to the internal electric field existing In the AlGaAs/GaAs heterojunction.

  11. Complete All-Optical Quantum Control of Electron Spins in InAs/GaAs Quantum Dot Molecule

    E-Print Network [OSTI]

    Guy Z. Cohen

    2015-01-08

    The spin states of electrons and holes confined in InAs quantum dot molecules have recently come to fore as a promising system for the storage or manipulation of quantum information. We describe here a feasible scheme for complete quantum optical control of two electron spin qubits in two vertically-stacked singly-charged InAs quantum dots coupled by coherent electron tunneling. With an applied magnetic field transverse to the growth direction, we construct a universal set of gates that corresponds to the possible Raman transitions between the spin states. We detail the procedure to decompose a given two-qubit unitary operation, so as to realize it with a successive application of up to 8 of these gates. We give the pulse shapes for the laser pulses used to implement this universal set of gates and demonstrate the realization of the two-qubit quantum Fourier transform with fidelity of 0.881 and duration of 414 ps. Our proposal therefore offers an accessible path to universal computation in quantum dot molecules and points to the advantages of using pulse shaping incoherent manipulation of optically active quantum dots to mitigate the negative effects of unintended dynamics and spontaneous emission.

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

    E-Print Network [OSTI]

    Kim, LeeAnn

    2006-01-01

    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 ...

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

    E-Print Network [OSTI]

    T. Brandes; N. Lambert

    2003-02-13

    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.

  14. Sandia Energy - Research Challenge 2: Quantum Dots and Phosphors

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

    2: Quantum Dots and Phosphors Home Energy Research EFRCs Solid-State Lighting Science EFRC Our SSLS EFRC's Scientific Research Challenges and Publications Research Challenge 2:...

  15. The 21st LH Gray Conference (June 4-6, 2008)

    SciTech Connect (OSTI)

    West, C. M.L.; Martin, C. J.; Sutton, D. G.; Wright, E. G.

    2009-01-12

    The 21st LH Gray Conference, organised by the LH Gray Trust with the Society for Radiological Protection, brought together international experts in radiobiology, epidemiology and risk assessment, and scientists involved in diagnostic and therapeutic radiation exposure. The meeting - held in Edinburgh, Scotland 4?6 June 2008 - aimed to raise awareness, educate and share knowledge of important issues in radiation protection. A distinguished group of speakers discussed topics which included: non-targeted effects of radiation, exposure to high natural background radiation, non-cancer effects in Japanese bomb survivors, lessons learnt from Chernobyl, radiation in the workplace, biokinetic modelling, uncertainties in risk estimation, issues in diagnostic medical exposures, lessons leant from the polonium-210 incidence and how the radiobiology-radiation oncology community is needed to help society prepare for potential future acts of radiation terrorism. The conference highlighted the importance, relevance and topicality of radiobiology today.

  16. Production and Machining of Thin Wall Gray and Ductile Cast Iron

    SciTech Connect (OSTI)

    Fleischman, E.H.; Li, H.; Griffin, R.; Bates, C.E.; Eleftheriou, E.

    2000-11-03

    The University of Alabama at Birmingham, in cooperation with the American Foundry Society, companies across North America, with support from the U.S. Department of Energy, is conducting a project to develop an understanding of the factors that control the machinability of cast gray and ductile iron. Differences of as much as 500% have been found in machinability have been observed at the same strength. The most machinable irons were those with a high cell counts and few carbonitride inclusions. Additions of tin and copper can be added to both gray and ductile iron to stabilize the pearlite, but excessive additions (above those required to produce the desired pearlite content) degrade the machinability.

  17. Quantum Dot Solar Cells: High Efficiency through Multiple Exciton Generation

    SciTech Connect (OSTI)

    Hanna, M. C.; Ellingson, R. J.; Beard, M.; Yu, P.; Micic, O. I.; Nozik, A. J.; c.

    2005-01-01

    Impact ionization is a process in which absorbed photons in semiconductors that are at least twice the bandgap can produce multiple electron-hole pairs. For single-bandgap photovoltaic devices, this effect produces greatly enhanced theoretical thermodynamic conversion efficiencies that range from 45-85%, depending upon solar concentration, the cell temperature, and the number of electron-hole pairs produced per photon. For quantum dots (QDs), electron-hole pairs exist as excitons. We have observed astoundingly efficient multiple exciton generation (MEG) in QDs of PbSe (bulk Eg = 0.28 eV), ranging in diameter from 3.9 to 5.7nm (Eg = 0.73, 0.82, and 0.91 eV, respectively). The effective masses of electron and holes are about equal in PbSe, and the onset for efficient MEG occurs at about three times the QD HOMO-LUMO transition (its ''bandgap''). The quantum yield rises quickly after the onset and reaches 300% at 4 x Eg (3.64 eV) for the smallest QD; this means that every QD in the sample produces three electron-hole pairs/photon.

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

    E-Print Network [OSTI]

    Floyd, Donna Lynne Woodall

    1981-01-01

    FRACTURE TOUGHNESS STUDIES OF GRAY AND DUCTILE CAST IRONS USING A J-INTEGRAL APPROACH A Thesis by DONNA LYNNE WOODALL FLOYD Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree... Toughness Testing. The J-Integral Approach to Fracture Toughness Determination The Effect of Microstructure on Fracture Toughness EXPERIMENTAL PROCEDURES . Specimens and Preparation Single Specimen Approach Data Reduction for the Single...

  19. Gene by Disease Interaction on Orbitofrontal Gray Matter in Cocaine Addiction

    SciTech Connect (OSTI)

    Alia-Klein, N.; Alia-Klein, N.; Parvaz, M.A.; Woicik, P.A.; Konova, A.; Maloney, T.; Shumay, E.; Wang, R.; Telang, F.; Biegon, A.; Wang, G.-J.; Fowler, J.S.; Tomasi, D.; Volkow, N.D.; Goldstein, R.Z.

    2010-12-05

    Chronic cocaine use has been associated with structural deficits in brain regions having dopamine receptive neurons. However, the concomitant use of other drugs and common genetic variability in monoamine regulation present additional structural variability. We therefore examined variations in gray matter volume (GMV) as a function of lifetime drug use and the monoamine oxidase A (MAOA) genotype in cocaine use disorders (CUD) and healthy controls.

  20. Double capping of molecular beam epitaxy grown InAs/InP quantum dots studied by cross-sectional scanning tunneling microscopy

    SciTech Connect (OSTI)

    Ulloa, J. M.; Koenraad, P. M.; Gapihan, E.; Letoublon, A.; Bertru, N.

    2007-08-13

    Cross-sectional scanning tunneling microscopy was used to study at the atomic scale the double capping process of self-assembled InAs/InP quantum dots (QDs) grown by molecular beam epitaxy on a (311)B substrate. The thickness of the first capping layer is found to play a mayor role in determining the final results of the process. For first capping layers up to 3.5 nm, the height of the QDs correspond to the thickness of the first capping layer. Nevertheless, for thicknesses higher than 3.5 nm, a reduction in the dot height compared to the thickness of the first capping layer is observed. These results are interpreted in terms of a transition from a double capping to a classical capping process when the first capping layer is thick enough to completely cover the dots.

  1. R&D Magazine: Windows into Solar Power Sources with Quantum Dots

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

    Dots R&D Magazine: Windows into Solar Power Sources with Quantum Dots A luminescent solar concentrator is an emerging sunlight harvesting technology that has the potential to...

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

    SciTech Connect (OSTI)

    Reilly, J.J.; Fedak, M.A. )

    1990-09-01

    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.

  3. Applicability of the {bold k}{center_dot}{bold p} method to the electronic structure of quantum dots

    SciTech Connect (OSTI)

    Fu, H.; Wang, L.; Zunger, A.

    1998-04-01

    The {bold k}{center_dot}{bold p} method has become the {open_quotes}standard model{close_quotes} for describing the electronic structure of nanometer-size quantum dots. In this paper we perform parallel {bold k}{center_dot}{bold p} (6{times}6 and 8{times}8) and direct-diagonalization pseudopotential studies on spherical quantum dots of an ionic material{emdash}CdSe, and a covalent material{emdash}InP. By using an equivalent input in both approaches, i.e., starting from a given atomic pseudopotential and deriving from it the Luttinger parameters in {bold k}{center_dot}{bold p} calculation, we investigate the effect of the different underlying wave-function representations used in {bold k}{center_dot}{bold p} and in the more exact pseudopotential direct diagonalization. We find that (i) the 6{times}6{bold k}{center_dot}{bold p} envelope function has a distinct (odd or even) parity, while atomistic wave function is parity-mixed. The 6{times}6{bold k}{center_dot}{bold p} approach produces an incorrect order of the highest valence states for both InP and CdSe dots: the p-like level is above the s-like level. (ii) It fails to reveal that the second conduction state in small InP dots is folded from the L point in the Brillouin zone. Instead, all states in {bold k}{center_dot}{bold p} are described as {Gamma}-like. (iii) The {bold k}{center_dot}{bold p} overestimates the confinement energies of both valence states and conduction states. A wave-function projection analysis shows that the principal reasons for these {bold k}{center_dot}{bold p} errors in dots are (a) use of restricted basis set, and (b) incorrect {ital bulk} dispersion relation. Error (a) can be reduced only by increasing the number of basis functions. Error (b) can be reduced by altering the {bold k}{center_dot}{bold p} implementation so as to bend upwards the second lowest bulk band, and to couple the conduction band into the s-like dot valence state. Our direct diagonalization approach provides an accurate and practical replacement to the standard model in that it is rather general, and can be performed simply on a standard workstation. {copyright} {ital 1998} {ital The American Physical Society}

  4. 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)

    2011-07-15

    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.

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

    SciTech Connect (OSTI)

    Lagerquist, Barbara; Winsor, Martha; Mate, Bruce

    2012-12-31

    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.

  6. Semiconductor Few-Electron Quantum Dots as Spin Qubits

    E-Print Network [OSTI]

    the experimental steps we have taken towards using a single electron spin, trapped in a semiconductor quantum dot detector is pushed to a faster regime (100 kHz), to detect single electron tunnel events in real time. WeSemiconductor Few-Electron Quantum Dots as Spin Qubits J.M. Elzerman1,2 , R. Hanson1 , L.H.W. van

  7. State DOT Representative Report Questions National Concrete Consortium

    E-Print Network [OSTI]

    , Texas April 2, 2009 Theme: Ride Quality for Bridges Please provide your state DOT's perspective regarding the following theme questions. Each NCC state DOT representative will be asked to present requirements set forth in the Caltrans Standard Specification 51-1.17 and which are tested for conformance

  8. Hyperfine interactions in silicon quantum dots

    E-Print Network [OSTI]

    Assali, Lucy V C; Capaz, Rodrigo B; Koiller, Belita; Hu, Xuedong; Sarma, S Das

    2010-01-01

    We present an all-electron calculation of the hyperfine parameters for conduction electrons in Si, showing that: (i) all parameters scale linearly with the spin density at a $^{29}$Si site; (ii) the isotropic term is over 30 times larger than the anisotropic part; (iii) conduction electron charge density at a Si nucleus is consistent with experimental estimates; (iv) Overhauser fields in natural Si quantum dots (QDs) are two orders of magnitude smaller than in GaAs QDs. This reinforces the outstanding performance of Si in keeping spin coherence and opens access to reliable quantitative information aiming at spintronic applications.

  9. DOT-7A packaging test procedure

    SciTech Connect (OSTI)

    Kelly, D.L.

    1995-01-23

    This test procedure documents the steps involved with performance testing of Department of Transportation Specification 7A (DOT-7A) Type A packages. It includes description of the performance tests, the personnel involved, appropriate safety considerations, and the procedures to be followed while performing the tests. Westinghouse Hanford Company (WHC) is conducting the evaluation and testing discussed herein for the Department of Energy-Headquarters, Division of Quality Verification and Transportation Safety (EH-321). Please note that this report is not in WHC format. This report is being submitted through the Engineering Documentation System so that it may be used for reference and information purposes.

  10. 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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home Room NewsInformationJessework usesofPublications64NewsroomNontoxic quantum dot research improves

  11. Predicted Ultrafast Single Qubit Operations in Semiconductor Quantum Dots

    E-Print Network [OSTI]

    Pryor, C E

    2002-01-01

    Several recently proposed implementations of scalable quantum computation rely on the ability to manipulate the spin polarization of individual electrons in semiconductors. The most rapid single-spin-manipulation technique to date relies on the generation of an effective magnetic field via a spin-sensitive optical Stark effect. This approach has been used to split spin states in colloidal CdSe quantum dots and to manipulate ensembles of spins in ZnMnSe quantum wells with femtosecond optical pulses. Here we report that the process will produce a coherent rotation of spin in quantum dots containing a single electron. The calculated magnitude of the effective magnetic field depends on the dot bandgap and the strain. We predict that in InAs/InP dots, for reasonable experimental parameters, the magnitude of the rotation is sufficient and the intrinsic error is low enough for them to serve as elements of a quantum dot based quantum computer.

  12. Predicted Ultrafast Single Qubit Operations in Semiconductor Quantum Dots

    E-Print Network [OSTI]

    C. E. Pryor; M. E. Flatté

    2002-11-25

    Several recently proposed implementations of scalable quantum computation rely on the ability to manipulate the spin polarization of individual electrons in semiconductors. The most rapid single-spin-manipulation technique to date relies on the generation of an effective magnetic field via a spin-sensitive optical Stark effect. This approach has been used to split spin states in colloidal CdSe quantum dots and to manipulate ensembles of spins in ZnMnSe quantum wells with femtosecond optical pulses. Here we report that the process will produce a coherent rotation of spin in quantum dots containing a single electron. The calculated magnitude of the effective magnetic field depends on the dot bandgap and the strain. We predict that in InAs/InP dots, for reasonable experimental parameters, the magnitude of the rotation is sufficient and the intrinsic error is low enough for them to serve as elements of a quantum dot based quantum computer.

  13. Competing interactions in semiconductor quantum dots

    SciTech Connect (OSTI)

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

    2014-10-01

    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.

  14. 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.

    2014-10-01

    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

  15. Midwave infrared quantum dot avalanche photodiode David A. Ramirez,a

    E-Print Network [OSTI]

    Hayat, Majeed M.

    Midwave infrared quantum dot avalanche photodiode David A. Ramirez,a Jiayi Shao, Majeed M. Hayat . In the device, called the quantum dot avalanche photodiode, an intersubband quantum dots-in-a-well detector for any quantum dot detector. © 2010 American Institute of Physics. doi:10.1063/1.3520519 Single

  16. WIGNER MOLECULES IN SEMICONDUCTOR QUANTUM DOTS AND TRAPPED ULTRACOLD BOSONIC CLOUDS

    E-Print Network [OSTI]

    Yannouleas, Constantine

    WIGNER MOLECULES IN SEMICONDUCTOR QUANTUM DOTS AND TRAPPED ULTRACOLD BOSONIC CLOUDS Constantine], with a focus on the strongly correlated regime of electrons in two-dimensional semiconductor quantum dots (QDs dot [3]; (3) fractional-quantum-Hall-effect analogies and differences in graphene quantum dots at zero

  17. Serial longitudinal magnetic resonance imaging data indicate non-linear regional gray matter volume recovery in abstinent alcohol-dependent individuals

    E-Print Network [OSTI]

    2015-01-01

    parietal and occipital gray matter (GM) and white matter (WM), total cortical GM and total lobar WM, thalamus andVolume increases in regional GM were significantly greater

  18. 2D phase-sensitive inversion recovery imaging to measure in vivo spinal cord gray and white matter areas in clinically feasible acquisition times

    E-Print Network [OSTI]

    2015-01-01

    TCA) and gray matter (GM) areas based on phase-sensitiveassessment of spinal cord GM and white matter (WM) couldbecause of insufficient GM/WM contrast provided by

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

    SciTech Connect (OSTI)

    Bradley, J.N.; Brislawn, C.M. ); Hopper, T. )

    1993-01-01

    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.

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

    SciTech Connect (OSTI)

    Bradley, J.N.; Brislawn, C.M.; Hopper, T.

    1993-05-01

    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.

  1. MHK Projects/Grays Harbor Ocean Energy and Coastal Protection | Open Energy

    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 on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIXsource HistoryScenarios Towards 2050 JumpCoos Bay OPT WaveFishersInformation Grays

  2. Joe W. Gray, 1986 | U.S. DOE Office of Science (SC)

    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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantityBonneville Power Administration would likeUniverseIMPACT EVALUATIONIntroducingJobs Human Resources andAbout »Joe W. Gray, 1986

  3. L d l l f ti iLandau level formation inLandau level formation inLandau level formation in G h t d tGraphene quantum dotsGraphene quantum dotsGraphene quantum dots

    E-Print Network [OSTI]

    Rotter, Stefan

    Graphene quantum dotsGraphene quantum dotsGraphene quantum dots 1 2 Florian Libisch Stefan Rotter Johannes . 50nm graphene 0 2 0 2010 50nm graphene d k ] 0.2 quantum dot A K K' li Hydrogen-terminated yk V H q measure of K K tt i iCalculate parametric scattering inp evolution of L li d d f / h g experimentevolution

  4. Factorization of Dirac Equation and Graphene Quantum Dot

    E-Print Network [OSTI]

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

    2014-05-14

    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.

  5. Designing Small Silicon Quantum Dots with Low Reorganization Energy

    E-Print Network [OSTI]

    Zang, Xiaoning

    2015-01-01

    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.

  6. Electron states in semiconductor quantum dots

    SciTech Connect (OSTI)

    Dhayal, Suman S.; Ramaniah, Lavanya M.; Ruda, Harry E.; Nair, Selvakumar V.

    2014-11-28

    In this work, the electronic structures of quantum dots (QDs) of nine direct band gap semiconductor materials belonging to the group II-VI and III-V families are investigated, within the empirical tight-binding framework, in the effective bond orbital model. This methodology is shown to accurately describe these systems, yielding, at the same time, qualitative insights into their electronic properties. Various features of the bulk band structure such as band-gaps, band curvature, and band widths around symmetry points affect the quantum confinement of electrons and holes. These effects are identified and quantified. A comparison with experimental data yields good agreement with the calculations. These theoretical results would help quantify the optical response of QDs of these materials and provide useful input for applications.

  7. Magnetic field induced quantum dot brightening in liquid crystal synergized magnetic and semiconducting nanoparticle composite assemblies

    SciTech Connect (OSTI)

    Amaral, Jose Jussi; Wan, Jacky; Rodarte, Andrea L.; Ferri, Christopher; Quint, Makiko T.; Pandolfi, Ronald J.; Scheibner, Michael; Hirst, Linda S.; Ghosh, Sayantani

    2014-10-22

    The design and development of multifunctional composite materials from artificial nano-constituents is one of the most compelling current research areas. This drive to improve over nature and produce ‘meta-materials’ has met with some success, but results have proven limited with regards to both the demonstration of synergistic functionalities and in the ability to manipulate the material properties post-fabrication and in situ. Here, magnetic nanoparticles (MNPs) and semiconducting quantum dots (QDs) are co-assembled in a nematic liquid crystalline (LC) matrix, forming composite structures in which the emission intensity of the quantum dots is systematically and reversibly controlled with a small applied magnetic field (<100 mT). This magnetic field-driven brightening, ranging between a two- to three-fold peak intensity increase, is a truly cooperative effect: the LC phase transition creates the co-assemblies, the clustering of the MNPs produces LC re-orientation at atypical low external field, and this re-arrangement produces compaction of the clusters, resulting in the detection of increased QD emission. These results demonstrate a synergistic, reversible, and an all-optical process to detect magnetic fields and additionally, as the clusters are self-assembled in a fluid medium, they offer the possibility for these sensors to be used in broad ranging fluid-based applications.

  8. 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

    2014-01-01

    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.

  9. Molecular techniques: Extracting DNA from dried dots, PCR and sequencing

    E-Print Network [OSTI]

    Schall, Joseph J.

    blood dot is cut from a disk with a razor blade (single sharp edge). Each blade is used twice, once design new primers for specific parasite genera and species. 5. Sequencing. We use the ABI Big

  10. 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 ...

  11. Design and fabrication of quantum-dot lasers

    E-Print Network [OSTI]

    Nabanja, Sheila

    2008-01-01

    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, ...

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

    DOE Patents [OSTI]

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

    2010-04-13

    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.

  13. Comparison of quantum confinement effects between quantum wires and dots

    SciTech Connect (OSTI)

    Li, Jingbo; Wang, Lin-Wang

    2004-03-30

    Dimensionality is an important factor to govern the electronic structures of semiconductor nanocrystals. The quantum confinement energies in one-dimensional quantum wires and zero-dimensional quantum dots are quite different. Using large-scale first-principles calculations, we systematically study the electronic structures of semiconductor (including group IV, III-V, and II-VI) surface-passivated quantum wires and dots. The band-gap energies of quantum wires and dots have the same scaling with diameter for a given material. The ratio of band-gap-increases between quantum wires and dots is material-dependent, and slightly deviates from 0.586 predicted by effective-mass approximation. Highly linear polarization of photoluminescence in quantum wires is found. The degree of polarization decreases with the increasing temperature and size.

  14. Symmetry causes a huge conductance peak in double quantum dots

    E-Print Network [OSTI]

    Robert S. Whitney; P. Marconcini; M. Macucci

    2009-02-18

    We predict a huge interference effect contributing to the conductance through large ultra-clean quantum dots of chaotic shape. When a double-dot structure is made such that the dots are the mirror-image of each other, constructive interference can make a tunnel barrier located on the symmetry axis effectively transparent. We show (via theoretical analysis and numerical simulation) that this effect can be orders of magnitude larger than the well-known universal conductance fluctuations and weak-localization (both less than a conductance quantum). A small magnetic field destroys the effect, massively reducing the double-dot conductance; thus a magnetic field detector is obtained, with a similar sensitivity to a SQUID, but requiring no superconductors.

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

    E-Print Network [OSTI]

    Coe-Sullivan, Seth (Seth Alexander)

    2005-01-01

    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 ...

  16. 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.

  17. Entanglement generation in a system of two atomic quantum dots coupled to a pool of interacting bosons

    E-Print Network [OSTI]

    Anna Posazhennikova; Reinhard Birmuske; Martin Bruderer; Wolfgang Belzig

    2012-12-12

    We discuss entanglement generation in a closed system of one or two atomic quantum dots (qubits) coupled via Raman transitions to a pool of cold interacting bosons. The system exhibits rich entanglement dynamics, which we analyze in detail in an exact quantum mechanical treatment of the problem. The bipartite setup of only one atomic quantum dot coupled to a pool of bosons turns out to be equivalent to two qubits which easily get entangled being initially in a product state. We show that both the number of bosons in the pool and the boson-boson interaction crucially affect the entanglement characteristics of the system. The tripartite system of two atomic quantum dots and a pool of bosons reduces to a qubit-qutrit-qubit realization. We consider entanglement possibilities of the pure system as well as of reduced ones by tracing out one of the constituents, and show how the entanglement can be controlled by varying system parameters. We demonstrate that the qutrit, as expected, plays a leading role in entangling of the two qubits and the maximum entanglement depends in a nontrivial way on the pool characteristics.

  18. Los Alamos Quantum Dots for Solar, Display Technology

    SciTech Connect (OSTI)

    Klimov, Victor

    2015-04-13

    Quantum dots are ultra-small bits of semiconductor matter that can be synthesized with nearly atomic precision via modern methods of colloidal chemistry. Their emission color can be tuned by simply varying their dimensions. Color tunability is combined with high emission efficiencies approaching 100 percent. These properties have recently become the basis of a new technology – quantum dot displays – employed, for example, in the newest generation of e-readers and video monitors.

  19. Session B--Maintenance of Key Biodiversity Attributes--Gray, Blackwell USDA Forest Service Gen. Tech. Rep. PSW-GTR-189. 2008. 49

    E-Print Network [OSTI]

    Session B--Maintenance of Key Biodiversity Attributes--Gray, Blackwell USDA Forest Service Gen. Tech. Rep. PSW-GTR-189. 2008. 49 The Maintenance of Key Biodiversity Attributes Through Ecosystem Restoration Operations1 Robert W. Gray2 and Bruce A. Blackwell3 Abstract The requirement to manage for key

  20. 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

    2014-08-26

    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.

  1. 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)

    2014-03-31

    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.

  2. Localized surface plasmon and exciton interaction in silver-coated cadmium sulphide quantum dots

    SciTech Connect (OSTI)

    Ghosh, P.; Rustagi, K. C.; Vasa, P.; Singh, B. P.

    2015-05-15

    Localized surface plasmon and exciton coupling has been investigated on colloidal solutions of silver-coated CdS nanoparticles (NPs), synthesized by gamma irradiation. Two broad photoluminescence (PL) bands (blue/red) corresponding to band to band and defect state transitions have been observed for the bare and coated samples. In case of bare CdS NPs, the intensity of the red PL peak is about ten times higher than the blue PL peak intensity. However, on coating the CdS NPs with silver, the peak intensity of the blue PL band gets enhanced and becomes equal to that of the red PL band. High-resolution transmission electron microscopic (HRTEM) images adequately demonstrate size distribution of these metal/semiconductor nanocomposites. UV-Vis absorption studies show quantum confinement effect in these semiconductor quantum dot (SQD) systems. Absorption spectrum of silver-coated SQDs shows signature of surface plasmon-exciton coupling which has been theoretically verified.

  3. Connecticut Transit (CTTRANSIT) Fuel Cell Transit Bus: Preliminary...

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

    Connecticut Transit (CTTRANSIT) Fuel Cell Transit Bus: Preliminary Evaluation Results Connecticut Transit (CTTRANSIT) Fuel Cell Transit Bus: Preliminary Evaluation Results This...

  4. Identification of the Regions of the Bovine Genome Associated with Gray Coat Color in a Nellore-Angus Cross Population 

    E-Print Network [OSTI]

    Holland, Paul W

    2015-05-05

    The genetics of coat color for cattle are important to breeders and breed associations because phenotypes of these animals are used for breed recognition and premiums or discounts can be given due to the phenotypes. The gene for gray coat color has...

  5. A Real Options Framework for Space Mission Design Andrew A. Gray, Payman Arabshahi, Elisabeth Lamassoure, Clayton Okino, Jason Andringa

    E-Print Network [OSTI]

    Arabshahi, Payman

    1 A Real Options Framework for Space Mission Design Andrew A. Gray, Payman Arabshahi, Elisabeth,payman,elama,okino, andringa}@jpl.nasa.gov Abstract--a real options framework for use in space mission design is presented that the flexibility provides; in this application the real options framework becomes a powerful tool. The utility

  6. In spite of the ever increasing prevalence of low-cost, color printing devices, gray-scale

    E-Print Network [OSTI]

    Geist, Robert

    ) standard, and the most common gray-scale conversion algorithm is mapping to luminance, Y, as follows: Y = 0 energy distribution. Three primaries, XX, YY, and ZZ, and three associated matching functions,x,y,z, were identified with the property that, given any spec- tral energy distribution, P(), the nonnegative weights can

  7. Gray QB-sing-faced version 2 (SF2) open environment test report

    SciTech Connect (OSTI)

    Plummer, J.; Immel, D.; Bobbitt, J.; Negron, M.

    2015-02-16

    This report details the design upgrades incorporated into the new version of the GrayQbTM SF2 device and the characterization testing of this upgraded device. Results from controlled characterization testing in the Savannah River National Laboratory (SRNL) R&D Engineering Imaging and Radiation Lab (IRL) and the Savannah River Site (SRS) Health Physics Instrument Calibration Laboratory (HPICL) is presented, as well as results from the open environment field testing performed in the E-Area Low Level Waste Storage Area. Resultant images presented in this report were generated using the SRNL developed Radiation Analyzer (RAzerTM) software program which overlays the radiation contour images onto the visual image of the location being surveyed.

  8. High-temperature low cycle fatigue behavior of a gray cast iron

    SciTech Connect (OSTI)

    Fan, K.L. He, G.Q.; She, M.; Liu, X.S.; Lu, Q.; Yang, Y.; Tian, D.D.; Shen, Y.

    2014-12-15

    The strain controlled low cycle fatigue properties of the studied gray cast iron for engine cylinder blocks were investigated. At the same total strain amplitude, the low cycle fatigue life of the studied material at 523 K was higher than that at 423 K. The fatigue behavior of the studied material was characterized as cyclic softening at any given total strain amplitude (0.12%–0.24%), which was attributed to fatigue crack initiation and propagation. Moreover, this material exhibited asymmetric hysteresis loops due to the presence of the graphite lamellas. Transmission electron microscopy analysis suggested that cyclic softening was also caused by the interactions of dislocations at 423 K, such as cell structure in ferrite, whereas cyclic softening was related to subgrain boundaries and dislocation climbing at 523 K. Micro-analysis of specimen fracture appearance was conducted in order to obtain the fracture characteristics and crack paths for different strain amplitudes. It showed that the higher the temperature, the rougher the crack face of the examined gray cast iron at the same total strain amplitude. Additionally, the microcracks were readily blunted during growth inside the pearlite matrix at 423 K, whereas the microcracks could easily pass through pearlite matrix along with deflection at 523 K. The results of fatigue experiments consistently showed that fatigue damage for the studied material at 423 K was lower than that at 523 K under any given total strain amplitude. - Highlights: • The low cycle fatigue behavior of the HT250 for engine cylinder blocks was investigated. • TEM investigations were conducted to explain the cyclic deformation response. • The low cycle fatigue cracks of HT250 GCI were studied by SEM. • The fatigue life of the examined material at 523 K is higher than that at 423 K.

  9. FUNCTIONAL AND MECHANISTIC STUDY OF DOT1L IN MOUSE EMBRYONIC HEMATOPOIESIS

    E-Print Network [OSTI]

    Feng, Yi

    2012-12-31

    DOT1 is the histone 3 lysine 79 methyltransferase with both unique structure and substrate specificity. It plays critical role in telomere silencing maintenance, transcription regulation, DNA repair, and cell cycle regulation. DOT1L in mammals...

  10. Investigation of the Emission Properties of Quantum Dot-thermoresponsive Polymer Nanocomposite Hydrogels with Temperature 

    E-Print Network [OSTI]

    Juriani, Ameet Rajkumar

    2011-08-08

    This thesis presents a novel method for the preparation of quantum dot-thermoresponsive polymer nanocomposite hydrogels. The quantum dots (QD’s) were synthesized in a microwave reactor using a high temperature organometallic synthesis procedure...

  11. Size-Dependent Optoelectronic Properties and Controlled Doping of Semiconductor Quantum Dots

    E-Print Network [OSTI]

    Engel, Jesse Hart

    2013-01-01

    Quantum Dots by Jesse Hart Engel A dissertation submitted inCopyright 2013 by Jesse Hart Engel Abstract Size-DependentQuantum Dots by Jesse Hart Engel Doctor of Philosophy in

  12. Synthesis and structural characterization of ZnTe/ZnSe core/shell tunable quantum dots

    E-Print Network [OSTI]

    Guan, Juan

    2008-01-01

    Colloidal semiconductor nanocrystals or quantum dots have attracted much attention recently with their unique optical properties. Here we present a novel approach to synthesize ZnTe/ZnSe core/shell tunable quantum dots. ...

  13. Charge transport in nanopatterned PbS colloidal quantum dot arrays

    E-Print Network [OSTI]

    Ray, Nirat

    2015-01-01

    In this thesis, we study charge transport in nanopatterned arrays of PbS colloidal quantum dots using conventional two-probe measurements and an integrated charge sensor. PbS dots are synthesized in solution with an organic ...

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

    E-Print Network [OSTI]

    Song, Katherine Wei

    2013-01-01

    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 ...

  15. Feasibility, pros, and cons of using DOT rights-of-way for stormwater quality treatment

    E-Print Network [OSTI]

    Teal, Michael

    2001-01-01

    DOT RIGHTS-OF-WAY FOR STORMWATER QUALITY TREATMENT MichaelAbstract In the past, DOT stormwater drainage facilitiesBMPs) for controlling stormwater. The idea has been that as

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

    E-Print Network [OSTI]

    Chen, Xiaojia

    2009-05-15

    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...

  17. Surround-gated vertical nanowire quantum dots M. H. M. van Weert,1

    E-Print Network [OSTI]

    arsenide phosphide InAsP quantum dots embedded in vertical surround-gated indium phosphide InP nanowires dots. The InAsP quantum dots, embedded in InP nanowires, are grown in the vapor-liquid-solid mode usingSurround-gated vertical nanowire quantum dots M. H. M. van Weert,1 M. den Heijer,1 M. P. van Kouwen

  18. Superconducting transition temperature in heterogeneous ferromagnet-superconductor systems 

    E-Print Network [OSTI]

    Pokrovsky, Valery L.; Wei, HD.

    2004-01-01

    ,2 , Chernogolovka o o orde e factor S PHYSICAL REVIEW B 69, 104530 ~2004! the magnetization in the FM film and the vorticity of vortices in the SC film alternate together. In this paper we study the SC transition in heterogeneous FM-SC systems including... the FSB, multilayers, and super- conducting film with a periodic array of magnetic dots ~SFMD!. For this purpose we extend the theory of spontane- ous SC-FM structures developed in the work17 to the case of multilayers. We demonstrate that in the FSB...

  19. Surface Induced Magnetism in Quantum Dots

    SciTech Connect (OSTI)

    Meulenberg, R W; Lee, J I

    2009-08-20

    The study of nanometer sized semiconductor crystallites, also known as quantum dots (QDs), has seen rapid advancements in recent years in scientific disciplines ranging from chemistry, physics, biology, materials science, and engineering. QD materials of CdSe, ZnSe, InP, as well as many others, can be prepared in the size range of 1-10 nm producing uniform, nearly monodisperse materials that are typically coated with organic molecules [1-3]. The strength of charge carrier confinement, which dictates the size-dependent properties, in these QDs depends on the nature of the material and can be correlated to the Bohr radius for the system of interest. For instance, the Bohr radius for CdSe is {approx} 5 nm, while in the more covalent structure of InP, the Bohr radius approaches {approx} 10 nm. The study of CdSe QDs has been particularly extensive during the last decade because they exhibit unique and tunable optical properties and are readily synthesized with high-crystallinity and narrow size dispersions. Although the core electronic properties of CdSe are explained in terms of the quantum confinement model, experimental efforts to elucidate the surface structure of these materials have been limited. Typically, colloidal CdSe QDs are coated with an organic surfactant, which typically consists of an organo-phosphine, -thiol, or -amine, that has the function of energetically relaxing defect states via coordination to partially coordinated surface atoms. The organic surfactant also acts to enhance carrier confinement and prevent agglomeration of the particles. Chemically, it has been shown that the bonding of the surfactant to the CdSe QD occurs through Cd atoms resulting cleavage of the Se atoms and formation of a Cd-rich (i.e. non-stoichiometric) particle [5].

  20. Physica E 34 (2006) 488492 Molecular states in a one-electron double quantum dot

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    2006-01-01

    2006 Abstract The transport spectrum of a strongly tunnel-coupled one-electron double quantum dot.20.Jc Keywords: Double quantum dot; Single electron tunneling; Delocalization; Molecular states of electrons trapped in a double quantum dot (DQD) down to N ¼ 1 [4­7]. Here, we study the transport spectrum

  1. Experimental demonstration of a latch in clocked quantum-dot cellular automata

    E-Print Network [OSTI]

    Orlov, Alexei

    by capacitively coupled gates. The middle dot acts as an adjustable barrier to control single-electron tunneling to one of the end dots depending on the input.8 Finally, when the clock is high, the electron is trapped floating micron-size metal dots, connected in series by multiple tunnel junctions and controlled

  2. 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

  3. Version 5; 7 October 1999 Quantum dots induced by strain from buried and surface stressors

    E-Print Network [OSTI]

    Davies, John H.

    induced by strain from buried, self-assembled dot InP stressor InGaAs quantum well GaAs substrate GaVersion 5; 7 October 1999 Quantum dots induced by strain from buried and surface stressors John H 93106­4170 (Dated: 8 November 1999) Abstract Quantum dots can be induced in a quantum well by strain

  4. FEW ELECTRON QUANTUM DOTS IN InAs/InP CORE SHELL NANOWIRES

    E-Print Network [OSTI]

    Nygård, Jesper

    with a thin shell of InP, are explored as a system where a quantum dot can be defined and probed electricallyFEW ELECTRON QUANTUM DOTS IN InAs/InP CORE SHELL NANOWIRES By Shivendra Upadhyay Delft University . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.3 Quantum dots in disordered nanowires . . . . . . . . . . . . . . . . . 14 3 Fabrication 16 3

  5. Pauli-blocking imaging of single strain-induced semiconductor quantum dots

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    19 March 1999 The photoluminescence PL of InP strained-induced quantum dots in a GaInAs/GaAs quantumPauli-blocking imaging of single strain-induced semiconductor quantum dots C. Obermu¨ller, A of the electronic properties of self-assembled semiconductor quantum dots.2 High resolu- tion PL microscopy can

  6. Analysis of the efficiency of intermediate band solar cells based on quantum dot supercrystals

    SciTech Connect (OSTI)

    Heshmati, S; Golmohammadi, S; Abedi, K; Taleb, H

    2014-03-28

    We have studied the influence of the quantum-dot (QD) width and the quantum-dot conduction band (QD-CB) offset on the efficiency of quantum-dot intermediate band solar cells (QD-IBSCs). Simulation results demonstrate that with increasing QD-CB offset and decreasing QD width, the maximum efficiency is achieved. (laser applications and other topics in quantum electronics)

  7. 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)

    2001-01-01

    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.

  8. Operational guidance for using DOT-6M/2R packaging

    SciTech Connect (OSTI)

    Kelly, D.L.; Hummer, J.H.

    1994-03-01

    The purpose of this paper is to describe a new US Department of Energy (DOE), Transportation Management Division task to create a US Department of Transportation (DOT) Specification 6M/2R packaging configuration user`s guide. The need for a user`s guide was identified because the DOT-6M/2R packaging configuration is widely used by DOE site contractors, and DOE receives many questions about the approved packaging configurations. Currently, two DOE organizations have the authority to approve new DOT-6M/2R configurations. For Defense Programs, the Transportation and Packaging Safety Division (EH-332) administers the program. For Environmental Restoration and Waste Management, the Transportation Management Division (EM-261) administers the program.

  9. Quasi-periodic quantum dot arrays produced by electrochemical synthesis

    SciTech Connect (OSTI)

    Bandyopadhyay, S.; Miller, A.E.; Yue, D.F.; Banerjee, G.; Ricker, R.E.; Jones, S.; Eastman, J.A.; Baugher, E.; Chandrasekhar, M.

    1994-06-01

    We discuss a ``gentle`` electrochemical technique for fabricating quasi-periodic quantum dot arrays. The technique exploits a self-organizing phenomenon to produce quasi-periodic arrangement of dots and provides excellent control over dot size and interdot spacing. Unlike conventional nanolithography, it does not cause radiation damage to the structures during exposure to pattern delineating beams (e-beam, ion-beam or x-ray). Moreover, it does not require harsh processing steps like reactive ion etching, offers a minimum feature size of {approximately}40 {angstrom}, allows the fabrication of structures on nonplanar surfaces (e.g. spherical or cylindrical substrates), is amenable to mass production (millions of wafers can be processed simultaneously) and is potentially orders of magnitude cheaper than conventional nanofabrication. In this paper, we describe our initial results and show the promise of this technique for low-cost and high-yield nanosynthesis.

  10. DOT-7A Type A packaging design guide

    SciTech Connect (OSTI)

    Kelly, D.L.

    1995-01-23

    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.

  11. A prototype silicon double quantum dot with dispersive microwave readout

    SciTech Connect (OSTI)

    Schmidt, A. R. Henry, E.; Namaan, O.; Siddiqi, I.; Lo, C. C.; Wang, Y.-T.; Bokor, J.; Yablonovitch, E.; Li, H.; Greenman, L.; Whaley, K. B.; Schenkel, T.

    2014-07-28

    We present a unique design and fabrication process for a lateral, gate-confined double quantum dot in an accumulation mode metal-oxide-semiconductor (MOS) structure coupled to an integrated microwave resonator. All electrostatic gates for the double quantum dot are contained in a single metal layer, and use of the MOS structure allows for control of the location of the two-dimensional electron gas via the location of the accumulation gates. Numerical simulations of the electrostatic confinement potential are performed along with an estimate of the coupling of the double quantum dot to the microwave resonator. Prototype devices are fabricated and characterized by transport measurements of electron confinement and reflectometry measurements of the microwave resonator.

  12. Optical control of the emission direction of a quantum dot

    SciTech Connect (OSTI)

    Luxmoore, I. J.; Wasley, N. A.; Fox, A. M.; Skolnick, M. S.; Ramsay, A. J.; Thijssen, A. C. T.; Oulton, R.; Hugues, M.; CNRS-CRHEA, rue Bernard Grégory, 06560 Valbonne

    2013-12-09

    Using the helicity of a non-resonant excitation laser, control over the emission direction of an InAs/GaAs quantum dot is demonstrated. The quantum dot is located off-center in a crossed-waveguide structure, such that photons of opposite circular polarization are emitted into opposite waveguide directions. By preferentially exciting spin-polarized excitons, the direction of emission can therefore be controlled. The directional control is quantified by using the ratio of the intensity of the light coupled into the two waveguides, which reaches a maximum of ±35%.

  13. 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)

    2011-11-15

    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.

  14. 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

  15. 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...

  16. "Connecting the Dots" to the Professoriate: Midlife Women's Career Transitions and Strategies 

    E-Print Network [OSTI]

    Cherrstrom, Catherine Ann

    2015-04-13

    Changing faculty characteristics in higher education include increasing numbers of new faculty with prior careers and women faculty. However, traditional adult development and career development theories may not account for the intersection...

  17. Gas turbine combustor transition

    DOE Patents [OSTI]

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

    1999-01-01

    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.

  18. Gas turbine combustor transition

    DOE Patents [OSTI]

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

    1999-05-25

    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.

  19. Structure of droplet-epitaxy-grown InAs/GaAs quantum dots

    SciTech Connect (OSTI)

    Cohen, Eyal; Yochelis, Shira; Westreich, Ohad; Shusterman, Sergey; Kumah, Divine P.; Clarke, Roy; Yacoby, Yizhak; Paltiel, Yossi

    2011-09-06

    We have used a direct x-ray phasing method, coherent Bragg rod analysis, to obtain sub-angstrom resolution electron density maps of the InAs/GaAs dot system. The dots were grown by the droplet heteroepitaxy (DHE) technique and their structural and compositional properties are compared with those of dots grown by the strain-driven Stranski-Krastanov method. Our results show that the Ga diffusion into the DHE-grown dots is somewhat larger; however, other characteristics such as the composition of the dots uppermost layers, the interlayer spacing, and the bowing of the atomic layers are similar.

  20. Increased InAs quantum dot size and density using bismuth as a surfactant

    SciTech Connect (OSTI)

    Dasika, Vaishno D.; Krivoy, E. M.; Nair, H. P.; Maddox, S. J.; Park, K. W.; Yu, E. T.; Bank, S. R.; Jung, D.; Lee, M. L.

    2014-12-22

    We have investigated the growth of self-assembled InAs quantum dots using bismuth as a surfactant to control the dot size and density. We find that the bismuth surfactant increases the quantum dot density, size, and uniformity, enabling the extension of the emission wavelength with increasing InAs deposition without a concomitant reduction in dot density. We show that these effects are due to bismuth acting as a reactive surfactant to kinetically suppress the surface adatom mobility. This mechanism for controlling quantum dot density and size has the potential to extend the operating wavelength and enhance the performance of various optoelectronic devices.

  1. Low frequency gray-body factors and infrared divergences: rigorous results

    E-Print Network [OSTI]

    Anderson, Paul R; Balbinot, Roberto

    2015-01-01

    Formal solutions to the mode equations for both spherically symmetric black holes and Bose-Einstein condensate acoustic black holes are obtained by writing the spatial part of the mode equation as a linear Volterra integral equation of the second kind. The solutions work for a massless minimally coupled scalar field in the s-wave or zero angular momentum sector for a spherically symmetric black hole and in the longitudinal sector of a 1D Bose-Einstein condensate acoustic black hole. These solutions are used to obtain in a rigorous way analytic expressions for the scattering coefficients and gray-body factors in the zero frequency limit. They are also used to study the infrared behaviors of the symmetric two-point function and two functions derived from it: the point-split stress-energy tensor for the massless minimally coupled scalar field in Schwarzschild-de Sitter spacetime and the density-density correlation function for a Bose-Einstein condensate acoustic black hole.

  2. 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.

    1988-10-01

    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.

  3. GrayQbTM Single-Faced Version 2 (SF2) Hanford Plutonium Reclamation Facility (PRF) deployment report

    SciTech Connect (OSTI)

    Plummer, J. R.; Immel, D. M.; Serrato, M. G.; Dalmaso, M. J.; Shull, D. J.

    2015-11-18

    The Savannah River National Laboratory (SRNL) in partnership with CH2M Plateau Remediation Company (CHPRC) deployed the GrayQbTM SF2 radiation imaging device at the Hanford Plutonium Reclamation Facility (PRF) to assist in the radiological characterization of the canyon. The deployment goal was to locate radiological contamination hot spots in the PRF canyon, where pencil tanks were removed and decontamination/debris removal operations are on-going, to support the CHPRC facility decontamination and decommissioning (D&D) effort. The PRF canyon D&D effort supports completion of the CHPRC Plutonium Finishing Plant Decommissioning Project. The GrayQbTM SF2 (Single Faced Version 2) is a non-destructive examination device developed by SRNL to generate radiation contour maps showing source locations and relative radiological levels present in the area under examination. The Hanford PRF GrayQbTM Deployment was sponsored by CH2M Plateau Remediation Company (CHPRC) through the DOE Richland Operations Office, Inter-Entity Work Order (IEWO), DOE-RL IEWO- M0SR900210.

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

    DOE Patents [OSTI]

    Forrest, Stephen R. (Ann Arbor, MI)

    2008-08-19

    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.

  5. Height control of self-assembled quantum dots by strain engineering during capping

    SciTech Connect (OSTI)

    Grossi, D. F., E-mail: d.grossi@tue.nl; Koenraad, P. M. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven (Netherlands); Smereka, P. [Department of Mathematics, University of Michigan, Ann Arbor, Michigan 48109 (United States); Keizer, J. G. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven (Netherlands); Australian Research Council Centre of Excellence for Quantum Computation and Communications, School of Physics, University of New South Wales, Sydney 2052 (Australia); Ulloa, J. M. [Institute for Systems based on Optoelectronics and Microtechnology (ISOM), Universidad Politecnica de Madrid, Avenida Complutense 30, 28040 Madrid (Spain)

    2014-10-06

    Strain engineering during the capping of III-V quantum dots has been explored as a means to control the height of strained self-assembled quantum dots. Results of Kinetic Monte Carlo simulations are confronted with cross-sectional Scanning Tunnel Microscopy (STM) measurements performed on InAs quantum dots grown by molecular beam epitaxy. We studied InAs quantum dots that are capped by In{sub x}Ga{sub (1?x)}As layers of different indium compositions. Both from our realistic 3D kinetic Monte Carlo simulations and the X-STM measurements on real samples, a trend in the height of the capped quantum dot is found as a function of the lattice mismatch between the quantum dot material and the capping layer. Results obtained on additional material combinations show a generic role of the elastic energy in the control of the quantum dot morphology by strain engineering during capping.

  6. 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

  7. Supplementary Document CdSe quantum dot synthesis

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    dots is given as follows. Cadmium oxide, CdO (Acros Org.); oleic acid, OA (JT Baker); 1-octadecene, ODE. The cadmium stock solution has been prepared by mixing CdO, OA and ODE. The mixture is evacuated by raising-type (boron-doped) with a resistivity of 0.1-1 ·cm. The nanopillar diameter is defined by the nanosphere

  8. Hyperbolic metamaterials based on quantum-dot plasmon-resonator

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Hyperbolic metamaterials based on quantum-dot plasmon-resonator nanocomposites S. V. Zhukovsky,1, T function as multilayer hyperbolic metamateri- als. Depending on the thickness of the spacer between (2011)] and confirms that hyperbolic metamaterials are capable of increasing the radiative decay rate

  9. Quantum-Dot Cellular Automata SPICE Macro Model Northeastern University

    E-Print Network [OSTI]

    Ayers, Joseph

    and majority voter. A full-adder is designed with QCA cells using the SPICE model as a test vehicle describes a SPICE model development method- ology for Quantum-Dot Cellular Automata (QCA) cells and presents a SPICE model for QCA cells. The model is val- idated by simulating the basic logic gates such as inverter

  10. Folded-Light-Path Colloidal Quantum Dot Solar Cells

    E-Print Network [OSTI]

    Sargent, Edward H. "Ted"

    Folded-Light-Path Colloidal Quantum Dot Solar Cells Ghada I. Koleilat*, Illan J. Kramer*, Chris T-processed solar cells offer the promise of low cost, large-area processing, and, prospectively, high solar power solar cell performance20,21 . Results In the present work, we sought to increase the interaction

  11. 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

  12. Cavity Enhancement of Single Quantum Dot Emission in the Blue

    E-Print Network [OSTI]

    2009-12-27

    Abstract Cavity-enhanced single-photon emission in the blue spectral region was measured from single InGaN/GaN quantum dots. The low-Q microcavities used were characterized using micro-reflectance spectroscopy where the source was the enhanced blue...

  13. Washington State DOT Report: State Report Questions on MEPDG Implementation

    E-Print Network [OSTI]

    Washington State DOT Report: State Report Questions on MEPDG Implementation 1. Summarize your state to the MEPDG. · We are not confident that the models in MEPDG portray the type of cracking we see in Washington Washington on Interstate 5) but not modeled in the MEPDG. However, longitudinal cracking alone rarely

  14. 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

  15. Quantum dot-based nanomaterials for biological imaging

    E-Print Network [OSTI]

    Zimmer, John P. (John Philip)

    2006-01-01

    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 ...

  16. Polarization entangled photons from quantum dots embedded in nanowires

    E-Print Network [OSTI]

    Tobias Huber; Ana Predojevi?; Milad Khoshnegar; Dan Dalacu; Philip J. Poole; Hamed Majedi; Gregor Weihs

    2014-06-02

    We present a first measurement of photon polarization entanglement from the biexciton to ground state cascade of a single InAsP quantum dot embedded in an InP nanowire. We observe a fidelity of 0.76(2) to a reference maximally entangled state as well as a concurrence of 0.57(6).

  17. Molecular Imaging: Physics and Bioapplications of Quantum Dots

    E-Print Network [OSTI]

    Michalet, Xavier

    the tech- niques used to interface these inorganic materials to the bio- logical world. It concludes 8.3.6 Lasers, LED, and Photovoltaic Cells 117 8.4 Synthesis of Colloidal Nanocrystals 119 8.4.1 Synthesis 119 8.4.2 Solubilization 120 8.4.3 Functionalization 121 8.5 Applications of Quantum Dot

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

    E-Print Network [OSTI]

    are entirely non-destructive. We use maturity meters to approximate strength for opening to traffic, and haveState DOT: UTAH State Report Questions on NDT Testing 1. What NDT testing methods for concrete). Research: NDT methods being investigated include: Visual distress mapping, Pachometer testing, Resistivity

  19. Depleted-Heterojunction Colloidal Quantum Dot Solar Cells

    E-Print Network [OSTI]

    Sargent, Edward H. "Ted"

    -processed single-junction cells and also multijunction architectures. Size-effect tuning also en- ables the useDepleted-Heterojunction Colloidal Quantum Dot Solar Cells Andras G. Pattantyus-Abraham,, Illan J requires thick, high-purity solar cells with correspondingly long carrier transport lengths;3 organic

  20. 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 ...

  1. Transit Users Group Supports Transit Agencies with Natural Gas Buses

    SciTech Connect (OSTI)

    Not Available

    2002-04-01

    Fact sheet describes the benefits of the Transit Users Group, which supports transit groups with compressed natural gas (CNG) buses.

  2. Significance of recurrent fault movement at Grays Point quarry, southeast Missouri

    SciTech Connect (OSTI)

    Diehl, S.F.; Throckmorton, C.K. ); Clendenin, C.W. )

    1993-03-01

    Geologic relationships indicate recurrent movement on a fault exposed at Grays Point, MO. Faulting offsets Middle-Late Ordovician Plattin Group, Decorah Group, Kimmswick Limestone, and Maquoketa Group strata. In plan, the fault is characterized by a relatively narrow zone (30--70 m) of northeast-striking fault slices associated with a northwest-striking zone of right-stepping en echelon fractures. This systematic fracture-fault array identifies right-lateral strike-slip movement. A vertically offset basal Decorah Group contact shows 22 m of down-to-the-southeast dip slip, which indicates a component of oblique slip. Oldest recognizable movement on the fault is evidenced by Maquoketa Group strata that fill a northeast-striking, wedge-shaped synform. Post-Ordovician movement along an adjacent subvertical fault displaces part of this synform 300 m right laterally. In thin section, the northwest-striking fracture set shows a polyphase history of deformation indicated by cataclastic textures and intrusion of carbonate-rich fluids. Three periods of movement occurred: (1) initial fracturing sealed by authigenic mineral cements; (2) renewed fracturing associated with recrystallization of sub-rounded clasts; and (3) subsequent brecciation marked by angular clasts and filling of fractures and vugs. Each successive fluid intrusion is characterized by an increase in grain size of the authigenic cement. The fault is subparallel to the regional, northeast-striking English Hill fault system. Polyphase oblique-slip deformation suggests that the fault, like others in southeastern Missouri, is a reactivated Late Proterozoic-Cambrian zone of weakness. Initial fault reactivation occurred during Middle-Late Ordovician as opposed to Devonian, as commonly interpreted for southeast Missouri. Multiple authigenic mineral cements imply that fluids may have been an important factor influencing the fault's tendency to be reactivated.

  3. Inter-band optoelectronic properties in quantum dot structure of low band gap III-V semiconductors

    SciTech Connect (OSTI)

    Dey, Anup; Maiti, Biswajit; Chanda, Debasree

    2014-04-14

    A generalized theory is developed to study inter-band optical absorption coefficient (IOAC) and material gain (MG) in quantum dot structures of narrow gap III-V compound semiconductor considering the wave-vector (k{sup ?}) dependence of the optical transition matrix element. The band structures of these low band gap semiconducting materials with sufficiently separated split-off valance band are frequently described by the three energy band model of Kane. This has been adopted for analysis of the IOAC and MG taking InAs, InSb, Hg{sub 1?x}Cd{sub x}Te, and In{sub 1?x}Ga{sub x}As{sub y}P{sub 1?y} lattice matched to InP, as example of III–V compound semiconductors, having varied split-off energy band compared to their bulk band gap energy. It has been found that magnitude of the IOAC for quantum dots increases with increasing incident photon energy and the lines of absorption are more closely spaced in the three band model of Kane than those with parabolic energy band approximations reflecting the direct the influence of energy band parameters. The results show a significant deviation to the MG spectrum of narrow-gap materials having band nonparabolicity compared to the parabolic band model approximations. The results reflect the important role of valence band split-off energies in these narrow gap semiconductors.

  4. Enhanced Performance of CdS/CdSe Quantum Dot Cosensitized Solar Cells via Homogeneous Distribution of Quantum Dots in TiO2

    E-Print Network [OSTI]

    Cao, Guozhong

    , simply increasing film thickness did not make significant contribution to improving solar cell efficiencyEnhanced Performance of CdS/CdSe Quantum Dot Cosensitized Solar Cells via Homogeneous Distribution cosensitized solar cells. The CdS and CdSe quantum dots were prepared on TiO2 mesoporous film through

  5. Do you think that DOTS may have your bicycle? DOTS currently has hundreds of bicycles in our bicycle impound that have been lost, abandoned, or

    E-Print Network [OSTI]

    Lathrop, Daniel P.

    Do you think that DOTS may have your bicycle? DOTS currently has hundreds of bicycles in our bicycle impound that have been lost, abandoned, or impounded. Many of these bikes are similar models and colors and therefore we are unable to identify your bicycle without detailed information and time to look

  6. 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. Rahayu, F. Darma, Y.

    2014-03-24

    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.

  7. Optical, electronic, and structural properties of uncoupled and close-packed arrays of InP quantum dots

    SciTech Connect (OSTI)

    Micic, O.I.; Jones, K.M.; Cahill, A.; Nozik, A.J.

    1998-12-03

    Solid films consisting of close-packed arrays of InP quantum dots have been prepared by slowly evaporating colloidal solutions of InP quantum dots. The diameters of the quantum dots were controlled to be between about 30 to 60 {angstrom}; size-selective precipitation yielded a size distribution of about 10% about the mean diameter. The arrays show regions of hexagonal order, as well as disordered regions. Oxide layers can form irreversibly on the quantum dot surface and limit the effectiveness of the size-selective precipitation. Photoluminescence spectra obtained from close-packed films of InP quantum dots formed from quantum dots with a single mean diameter and from a mixture of two quantum dot sizes show that energy transfer occurs from the photoexcited smaller quantum dots to the larger quantum dots. The efficiency of this energy transfer process is high.

  8. Deep level centers and their role in photoconductivity transients of InGaAs/GaAs quantum dot chains

    SciTech Connect (OSTI)

    Kondratenko, S. V. Vakulenko, O. V.; Mazur, Yu. I. Dorogan, V. G.; Marega, E.; Benamara, M.; Ware, M. E.; Salamo, G. J.

    2014-11-21

    The in-plane photoconductivity and photoluminescence are investigated in quantum dot-chain InGaAs/GaAs heterostructures. Different photoconductivity transients resulting from spectrally selecting photoexcitation of InGaAs QDs, GaAs spacers, or EL2 centers were observed. Persistent photoconductivity was observed at 80?K after excitation of electron-hole pairs due to interband transitions in both the InGaAs QDs and the GaAs matrix. Giant optically induced quenching of in-plane conductivity driven by recharging of EL2 centers is observed in the spectral range from 0.83?eV to 1.0?eV. Conductivity loss under photoexcitation is discussed in terms of carrier localization by analogy with carrier distribution in disordered media.

  9. Thermal stability of the deep ultraviolet emission from AlGaN/AlN Stranski-Krastanov quantum dots

    SciTech Connect (OSTI)

    Himwas, C.; Songmuang, R.; Le Si Dang; Bleuse, J.; Monroy, E.; Rapenne, L.; Sarigiannidou, E.

    2012-12-10

    We report on the structural and optical properties of AlGaN/AlN quantum dot (QD) superlattices synthesized by plasma-assisted molecular-beam epitaxy. Modifying the composition and geometry of the QDs, the peak emission wavelength can be shifted from 320 nm to 235 nm while keeping the internal quantum efficiency larger than 30%. The efficient carrier confinement is confirmed by the stability of the photoluminescence (PL) intensity and decay time, from low temperature up to 100 K. Above this threshold, the PL intensity decreases and the radiative lifetime increases due to carrier thermalization. We also identified the intraband electronic transition between the ground level of the conduction band and the first excited state confined along the growth axis (s-p{sub z}).

  10. 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

    2011-10-05

    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.

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

    SciTech Connect (OSTI)

    Huang, Danhong; Cardimona, Dave; Easter, Michelle; Gumbs, Godfrey; Maradudin, A. A.; Lin, Shawn-Yu; Zhang, Xiang

    2014-06-23

    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.

  12. Nanoscale optical positioning of single quantum dots for bright and pure single-photon emission

    E-Print Network [OSTI]

    Luca Sapienza; Marcelo Davanco; Antonio Badolato; Kartik Srinivasan

    2015-08-05

    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 position uncertainty technology for the creation of optimized single quantum dot devices. To that end, we create quantum dot single-photon sources, based on a circular Bragg grating geometry, that simultaneously exhibit high collection efficiency (48 % +/- 5 % into a 0.4 numerical aperture lens, close to the theoretically predicted value of 50 %), low multiphoton probability (g(2)(0) <1 %), and a significant Purcell enhancement factor (~ 3).

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

    E-Print Network [OSTI]

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

    2007-04-13

    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.

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

    SciTech Connect (OSTI)

    Prabhakar, S. Melnik, R. V. N.; Sebetci, A.

    2014-10-06

    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.

  15. Photo-Activated Luminescence of CdSe Quantum Dot Monolayers S. R. Cordero, P. J. Carson, R. A. Estabrook, G. F. Strouse, and S. K. Buratto*

    E-Print Network [OSTI]

    Photo-Activated Luminescence of CdSe Quantum Dot Monolayers S. R. Cordero, P. J. Carson, R. A passivation is even more critical in quantum dot solids where inter-dot coupling reduces the QY of the film

  16. Photoluminescence spectral study of single CdSe/ZnS Colloidal Nanocrystals in Poly(methyl methacrylate) and Quantum Dots molecules

    E-Print Network [OSTI]

    Shen, Yaoming

    2008-01-01

    in self- assembled inp quantum dots in gainp. Phys. Rev. B,in self-assembled inp quantum dots. Phys. Rev. Lett. , 86(also been observed in InP quantum dots in a Ga x In 1?x P

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

    SciTech Connect (OSTI)

    Not Available

    2011-02-01

    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.

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

    SciTech Connect (OSTI)

    Buljan, M.; Bogdanovic-Radovic, I.; Karlusic, M.; Desnica, U. V.; Radic, N.; Dubcek, P.; Drazic, G.; Salamon, K.; Bernstorff, S.; Holy, V.

    2009-08-10

    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.

  19. SEP Program Transition Tables

    Broader source: Energy.gov [DOE]

    The Program Transition Tables provide information concerning the level of effort required to move from a traditional, industrial incentive program to Strategic Energy Management, ISO 50001, or SEP.

  20. Hydrogen Transition Infrastructure Analysis

    SciTech Connect (OSTI)

    Melendez, M.; Milbrandt, A.

    2005-05-01

    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.

  1. King County Metro Transit

    SciTech Connect (OSTI)

    Not Available

    2004-12-01

    Fact sheet describes the National Renewable Energy Laboratory's evaluation of King County Metro's articulated hybrid electric transit buses with Allison electric drives.

  2. 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

    2010-08-28

    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.

  3. Charging dynamics of a floating gate transistor with site-controlled quantum dots

    SciTech Connect (OSTI)

    Maier, P. Hartmann, F.; Emmerling, M.; Schneider, C.; Höfling, S.; Kamp, M.; Worschech, L.

    2014-08-04

    A quantum dot memory based on a GaAs/AlGaAs quantum wire with site-controlled InAs quantum dots was realized by means of molecular beam epitaxy and etching techniques. By sampling of different gate voltage sweeps for the determination of charging and discharging thresholds, it was found that discharging takes place at short time scales of ?s, whereas several seconds of waiting times within a distinct negative gate voltage range were needed to charge the quantum dots. Such quantum dot structures have thus the potential to implement logic functions comprising charge and time dependent ingredients such as counting of signals or learning rules.

  4. Photovoltaic performance of ultra-small PbSe quantum dots

    E-Print Network [OSTI]

    Ma, Wanli

    2014-01-01

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

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

    E-Print Network [OSTI]

    Scully, Marlan O

    2010-01-01

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

  6. Giant Nanocrystal Quantum Dots as Stable and Efficient Down-Conversion

    Office of Scientific and Technical Information (OSTI)

    Dots as Stable and Efficient Down-Conversion Phosphor for LED based Solid State Lighting Kundu, Janardan Los Alamos National Laboratory; Ghosh, Yagnaseni Los Alamos...

  7. Understanding colloidal quantum dot excitation with solution photon correlation fourier spectroscopy

    E-Print Network [OSTI]

    Heathcote, S. Leigh (Stephanie Leigh)

    2015-01-01

    Colloidal quantum dots (CQDs) have useful absorption and emission properties but exist in inhomogenous batches. Solution photon correlation fourier spectroscopy (S-PCFS) combines interferometry with fluorescence correlation ...

  8. Intracellular Tracking of Single Native Molecules with Electroporation-Delivered Quantum Dots

    E-Print Network [OSTI]

    Lu, Chang

    Intracellular Tracking of Single Native Molecules with Electroporation-Delivered Quantum Dots Chen Sun, Zhenning Cao, Min Wu, and Chang Lu*,,§ School of Biomedical Engineering and Sciences, Virginia

  9. Non-adiabatic quantum pumping by a randomly moving quantum dot

    E-Print Network [OSTI]

    Stanislav Derevyanko; Daniel Waltner

    2015-06-22

    We look at the time dependent fluctuations of the electrical charge in an open 1D quantum system represented by a quantum dot experiencing random lateral motion. In essentially non-adiabatic settings we study both diffusive and ballistic (Levy) regimes of the barrier motion where the electric current as well as the net pumped electric charge experience random fluctuations over the static background. We show that in the large-time limit, $t \\to \\infty$, the wavefunction is naturally separated into the Berry-phase component (resulting from the singular part of the wave amplitude in the co-moving frame) and the non-adiabatic correction (arising from fast oscillating, slow decaying tails of the same amplitude). Based on this separation we report two key results: Firstly, the disorder averaged wave function and current are asymptotically mainly determined by the same Berry phase contribution that applies in the case of adiabatic motion. Secondly, after a short transition period the pumped electric charge exhibits fluctuations that grow much faster than predicted by the adiabatic theory. We also derive the exact expressions for the average propagator (in the co-moving basis representation) for the diffusive and ballistic types of motion considered.

  10. Blue and green electroluminescence from CdSe nanocrystal quantum-dot-quantum-wells

    SciTech Connect (OSTI)

    Lu, Y. F.; Cao, X. A.

    2014-11-17

    CdS/CdSe/ZnS quantum dot quantum well (QDQW) nanocrystals were synthesized using the successive ion layer adsorption and reaction technique, and their optical properties were tuned by bandgap and strain engineering. 3-monolayer (ML) CdSe QWs emitted blue photoluminescence at 467?nm with a spectral full-width-at-half-maximum of ?30?nm. With a 3 ML ZnS cladding layer, which also acts as a passivating and strain-compensating layer, the QDQWs acquired a ?35% quantum yield of the QW emission. Blue and green electroluminescence (EL) was obtained from QDQW light-emitting devices with 3–4.5 ML CdSe QWs. It was found that as the peak blueshifted, the overall EL was increasingly dominated by defect state emission due to poor hole injection into the QDQWs. The weak EL was also attributed to strong field-induced charge separation resulting from the unique QDQW geometry, weakening the oscillator strength of optical transitions.

  11. Excited-State Relaxation in PbSe Quantum Dots

    SciTech Connect (OSTI)

    An, J. M.; Califano, M.; Franceschetti, A.; Zunger, A.

    2008-01-01

    In solids the phonon-assisted, nonradiative decay from high-energy electronic excited states to low-energy electronic excited states is picosecond fast. It was hoped that electron and hole relaxation could be slowed down in quantum dots, due to the unavailability of phonons energy matched to the large energy-level spacings ('phonon-bottleneck'). However, excited-state relaxation was observed to be rather fast ({le}1 ps) in InP, CdSe, and ZnO dots, and explained by an efficient Auger mechanism, whereby the excess energy of electrons is nonradiatively transferred to holes, which can then rapidly decay by phonon emission, by virtue of the densely spaced valence-band levels. The recent emergence of PbSe as a novel quantum-dot material has rekindled the hope for a slow down of excited-state relaxation because hole relaxation was deemed to be ineffective on account of the widely spaced hole levels. The assumption of sparse hole energy levels in PbSe was based on an effective-mass argument based on the light effective mass of the hole. Surprisingly, fast intraband relaxation times of 1-7 ps were observed in PbSe quantum dots and have been considered contradictory with the Auger cooling mechanism because of the assumed sparsity of the hole energy levels. Our pseudopotential calculations, however, do not support the scenario of sparse hole levels in PbSe: Because of the existence of three valence-band maxima in the bulk PbSe band structure, hole energy levels are densely spaced, in contradiction with simple effective-mass models. The remaining question is whether the Auger decay channel is sufficiently fast to account for the fast intraband relaxation. Using the atomistic pseudopotential wave functions of Pb{sub 2046}Se{sub 2117} and Pb{sub 260}Se{sub 249} quantum dots, we explicitly calculated the electron-hole Coulomb integrals and the P {yields} S electron Auger relaxation rate. We find that the Auger mechanism can explain the experimentally observed P {yields} S intraband decay time scale without the need to invoke any exotic relaxation mechanisms.

  12. 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

    2003-11-01

    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.

  13. Noise-induced transitions vs. noise-induced phase transitions

    E-Print Network [OSTI]

    Toral, Raúl

    Noise-induced transitions vs. noise-induced phase transitions Raul Toral IFISC (Instituto de Física the field of noise-induced phase transitions, emphasizing the main differences with the phase-induced transitions and showing that they appear in different systems. I will show that a noise-induced transition can

  14. Grazing-incidence small-angle X-ray scattering: application to the study of quantum dot lattices

    SciTech Connect (OSTI)

    Buljan, Maja Radi?, Nikola; Bernstorff, Sigrid; Draži?, Goran; Bogdanovi?-Radovi?, Iva; Holý, Václav

    2012-01-01

    The modelling of grazing-incidence small-angle X-ray scattering (GISAXS) from three-dimensional quantum dot lattices is described. The ordering of quantum dots in three-dimensional quantum dot lattices is investigated by grazing-incidence small-angle X-ray scattering (GISAXS). Theoretical models describing GISAXS intensity distributions for three general classes of lattices of quantum dots are proposed. The classes differ in the type of disorder of the positions of the quantum dots. The models enable full structure determination, including lattice type, lattice parameters, the type and degree of disorder in the quantum dot positions and the distributions of the quantum dot sizes. Applications of the developed models are demonstrated using experimentally measured data from several types of quantum dot lattices formed by a self-assembly process.

  15. 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]

    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 years. · Mauna Loa, in Hawaii, is the world's largest active volcano. · The Cascade Range--home to more

  16. Energy stories, equations and transition

    E-Print Network [OSTI]

    Ernst, Damien

    Energy stories, equations and transition Une histoire d'énergie: équations et transition% - Transition #12;ERoEI · ERoEI for « Energy Sustainable Energy April 28th, 2015 Raphael Fonteneau, University of Liège, Belgium @R_Fonteneau #12;Energy

  17. 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

  18. Shot-Noise Detection in a Carbon Nanotube Quantum Dot E. Onac,1,* F. Balestro,1,

    E-Print Network [OSTI]

    Shot-Noise Detection in a Carbon Nanotube Quantum Dot E. Onac,1,* F. Balestro,1, B. Trauzettel,1-chip detection scheme for high frequency signals is used to detect noise generated by a quantum dot formed in a single wall carbon nanotube. The noise detection is based on photon assisted tunneling

  19. Fate of Spin Doublets in Quantum Dot with Many Interacting Electrons. M. Brodsky1

    E-Print Network [OSTI]

    Finkelstein, Gleb

    Fate of Spin Doublets in Quantum Dot with Many Interacting Electrons. M. Brodsky1 , G. Finkelstein1 Abstract: Using the Single Electron Capacitance Spectroscopy, we study the energies required to add electrons to a quantum dot in a broad range of electron occupancy N. Following evolution of these energies

  20. Energy Development Impacts on State Roadways: A Review of DOT Policies, Programs

    E-Print Network [OSTI]

    Energy Development Impacts on State Roadways: A Review of DOT Policies, Programs and Practices across Eight States Final Report PRC 14-29 F #12;2 Energy Development Impacts on State Roadways: A Review of DOT Policies, Programs and Practices across Eight States Texas A&M Transportation Institute PRC 14

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

    E-Print Network [OSTI]

    Illinois at Chicago, University of

    of cumulative energy supply (Michaels, 2008). The demand for solar energy has enabled the funding of research: Life cycle assessment Quantum dots Nanophotovoltaics Quantum dot photovoltaic modules Solar energy to overcome two current barriers of solar technology: low efficiencies and high manufacturing costs. If higher

  2. Experimental demonstration of clocked single-electron switching in quantum-dot cellular automata

    E-Print Network [OSTI]

    Orlov, Alexei

    tunnel junctions where the location of an excess electron is defined by electrostatic potentials on gates, the electrons remain trapped on the dots regardless of the state of the input signal. Although semiconductorExperimental demonstration of clocked single-electron switching in quantum-dot cellular automata

  3. 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

  4. Statistical theory of Coulomb blockade oscillations: Quantum chaos in quantum dots

    SciTech Connect (OSTI)

    Jalabert, R.A.; Stone, A.D.; Alhassid, Y. (Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06511 (United States))

    1992-06-08

    We develop a statistical theory of the amplitude of Coulomb blockade oscillations in semiconductor quantum dots based on the hypothesis that chaotic dynamics in the dot potential leads to behavior described by random-matrix theory. Breaking time-reversal symmetry is predicted to cause an experimentally observable change in the distribution of amplitudes. The theory is tested numerically and good agreement is found.

  5. Uptake, Translocation, and Transformation of Quantum Dots with Cationic versus Anionic Coatings by Populus deltoides nigra

    E-Print Network [OSTI]

    Alvarez, Pedro J.

    Uptake, Translocation, and Transformation of Quantum Dots with Cationic versus Anionic Coatings Supporting Information ABSTRACT: Manipulation of the organic coatings of nano- particles such as quantum dotsSe/CdZnS QDs coated with cationic polyethylenimine (PEI) (35.3 ± 6.6 nm) or poly(ethylene glycol) of anionic

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

    E-Print Network [OSTI]

    Cao, Guozhong

    , suffer from high cost of manufacturing and installation. Now the focus is on next generation solar cellsA 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

  7. Hierarchically Structured ZnO Nanorods-Nanosheets for Improved Quantum-Dot-Sensitized Solar Cells

    E-Print Network [OSTI]

    Cao, Guozhong

    Hierarchically Structured ZnO Nanorods-Nanosheets for Improved Quantum-Dot-Sensitized Solar Cells NR-NS photoelectrode for constructing CdS/ CdSe quantum-dot-sensitized solar cells (QDSCs). This hierarchical structure had two advantages in improving the power conversion efficiency (PCE) of the solar cells

  8. 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

  9. Hybrid mode-locking in a 40 GHz monolithic quantum dot laser G. Fiol,1,a

    E-Print Network [OSTI]

    Vladimirov, Andrei G.

    Hybrid mode-locking in a 40 GHz monolithic quantum dot laser G. Fiol,1,a D. Arsenijevi,1 D. Bimberg; accepted 30 November 2009; published online 5 January 2010 Hybrid mode-locking in monolithic quantum dot QD of hybrid mode-locking ML , a commonly used technique for improving quality of mode- locked pulses

  10. 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

  11. Coulomb Oscillations and Hall Effect in Quasi-2D Graphite Quantum Dots

    E-Print Network [OSTI]

    McEuen, Paul L.

    Coulomb Oscillations and Hall Effect in Quasi-2D Graphite Quantum Dots J. Scott Bunch, Yuval Yaish-temperature electrical transport measurements on gated, quasi-2D graphite quantum dots. In devices with low contact of graphene, a zero band gap semiconductor with two linearly dispersing bands that touch at the corners

  12. Perovskite Quantum Dots Modeled Using ab Initio and Replica Exchange Molecular Dynamics

    E-Print Network [OSTI]

    Sargent, Edward H. "Ted"

    Perovskite Quantum Dots Modeled Using ab Initio and Replica Exchange Molecular Dynamics Andrei Buin halide perovskites have recently attracted tremen- dous attention at both the experimental. Here we investigate perovskite quantum dots from theory, predicting an upper bound of the Bohr radius

  13. Growth of a single freestanding multiwall carbon nanotube on each nanonickel dot

    E-Print Network [OSTI]

    Reed, Mark

    nanotube s on submicron nickel dot s on silicon has been achieved by plasma that the structures are indeed hollow nanotubes. The diameter and height depend on the nickel dot size and growth time aligned carbon nanotubes has been dem- onstrated on glass,10 on nickel,11 and on silicon.12,13 Here we

  14. Atomic force microscopy of nickel dot arrays with tuning fork and nanotube probe

    E-Print Network [OSTI]

    Chandrasekhar, Venkat

    Atomic force microscopy of nickel dot arrays with tuning fork and nanotube probe S. Rozhok,a) S microscopy are combined with the unique properties of carbon nanotubes to improve the spatial resolution of atomic force microscopy AFM images of nickel dot arrays. These arrays have high relief features

  15. Nuclear spin relaxation probed by a single quantum dot A. K. Huttel,1

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    Nuclear spin relaxation probed by a single quantum dot A. K. Hu¨ttel,1 J. Weber,1 A. W. Holleitner February 2004 We present measurements on nuclear spin relaxation probed by a single quantum dot formed the electronic to the nuclear spin system. Applying electron spin resonance, the transfer mechanism is suppressed

  16. Depleted-heterojunction colloidal quantum dot photovoltaics employing low-cost electrical contacts

    E-Print Network [OSTI]

    Sargent, Edward H. "Ted"

    solution-processed single-junction cells and also multijunction architectures.1 Size-effect tuning also of depleted-heterojunction colloidal quantum dot solar cells, we describe herein a strategy that replaces energy conver- sion. Recently, colloidal quantum dot CQD solar cells were reported that reached above 5

  17. GaSb/GaAs type II quantum dot solar cells for enhanced infrared spectral response

    E-Print Network [OSTI]

    Jalali. Bahram

    into existing multijunction cells either as a means to increase the current or efficiency by using low band gapGaSb/GaAs type II quantum dot solar cells for enhanced infrared spectral response R. B infrared spectral response of GaAs-based solar cells that incorporate type II GaSb quantum dots QDs formed

  18. Control of Nanostructures and Interfaces of Metal Oxide Semiconductors for Quantum-Dots-Sensitized Solar Cells

    E-Print Network [OSTI]

    Cao, Guozhong

    for the solar cells, solar fuel, photo catalyst, and energy storage devices due to their excellent photoelectric-Dots-Sensitized Solar Cells Jianjun Tian, and Guozhong Cao*,,§ Beijing Institute of Nanoenergy and Nanosystems, Chinese for the quantum dots sensitized solar cells (QDSCs), owing to their large specific surface area for loading

  19. 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

  20. Physica E 35 (2006) 278284 Spectroscopy of molecular states in a few-electron double quantum dot

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    2006-01-01

    . In particular, the tunnel splitting of the double well potential for up to one trapped electron is unambiguously the trapping potential of a single quantum dot, a strongly tunnel-coupled double quantum dot can be defined reserved. PACS: 73.21.La; 73.23.Hk; 73.20.Jc Keywords: Double quantum dot; Single electron tunneling

  1. Counting statistics of coherent population trapping in quantum dots C. W. Groth, B. Michaelis, and C. W. J. Beenakker

    E-Print Network [OSTI]

    tunneling between three quantum dots can trap an electron in a coherent superposition of charge on two, is based on destructive interference of single-electron tunnel- ing between three quantum dots see Fig. 1 . The trapped state is a coherent superposition of the electronic charge in two of these quantum dots, so

  2. 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

    2007-03-20

    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.

  3. 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 applications. Resonant or quasiresonant excitation of single quantum dots provides greater single photon

  4. 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)

    2002-01-01

    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.

  5. Nonequilibrium stabilization of charge states in double quantum dots

    E-Print Network [OSTI]

    Udo Hartmann; Frank K. Wilhelm

    2004-04-29

    We analyze the decoherence of charge states in double quantum dots due to cotunneling. The system is treated using the Bloch-Redfield generalized master equation for the Schrieffer-Wolff transformed Hamiltonian. We show that the decoherence, characterized through a relaxation $\\tau_{r}$ and a dephasing time $\\tau_{\\phi}$, can be controlled through the external voltage and that the optimum point, where these times are maximum, is not necessarily in equilibrium. We outline the mechanism of this nonequilibrium-induced enhancement of lifetime and coherence. We discuss the relevance of our results for recent charge qubit experiments.

  6. 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)

    2011-10-04

    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.

  7. Thermal transport through non-ideal Andreev quantum dots

    E-Print Network [OSTI]

    Pedro Vidal

    2015-01-07

    We consider the scenario of thermal transport through two types of Andreev quantum dots which are coupled to two leads, belonging to the Class D and Class C symmetry classes. Using the random matrix description we derive the joint probability density function (j.p.d.f.) in term of Hypergeometric Function of Matrix Arguments when we consider one lead to be attached ideally and one lead non ideally. For the class C ensemble we derive a more explicit representation of the j.p.d.f. which results in a new type of random matrix model.

  8. The dosimetric consequences of the new DOT LSA definition

    SciTech Connect (OSTI)

    Mis, F.J.

    1996-10-01

    As a result of the new regulations for the transportation of radioactive materials, the DOT and the NRC have implemented a rule designed to limit the activity in an LSA container. This is a new regulation designed to insure that the spirit of the law as well as the letter of the law are followed for LSA shipments. Specifically, it limits the dose rate at any location on an unshielded LSA container to less than 1 rem/hr at 3 meters. Other possible alternatives had been discussed prior to the implementation of this regulation including multiples of A{sub 2} values, as implemented by the French.

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

    SciTech Connect (OSTI)

    Vlahovic, Branislav Filikhin, Igor

    2014-10-06

    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.

  10. Photoluminescence-enhanced biocompatible quantum dots by phospholipid functionalization

    SciTech Connect (OSTI)

    Shi Yunfeng; He Peng Zhu Xinyuan

    2008-10-02

    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.

  11. Photocurrent extraction efficiency in colloidal quantum dot photovoltaics

    SciTech Connect (OSTI)

    Kemp, K. W.; Wong, C. T. O.; Hoogland, S. H.; Sargent, E. H.

    2013-11-18

    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.

  12. Solid-state photonic interfaces using semiconductor quantum dots

    E-Print Network [OSTI]

    Boyer de la Giroday, Antoine

    2012-02-07

    . Rev. Lett. 106, 216802 (2011) 5. Coherent entangled light generated by quantum dots in the presence of nuclear magnetic fields R.M. Stevenson, C.L. Salter, A. Boyer de la Giroday, I. Farrer, C.A. Nicoll, D.A. Ritchie, and A.J. Shields arXiv:1103.2969v1... Bragg reflectors (DBRs) surround- ing the cavity region made of a GaAs spacer layer containing the QDs. Each DBR consists of alternating layers of high- and low-refractive index materi- als (respectively GaAs with n = 3.54 and AlAs n = 2.97 in our case...

  13. Charge-transfer dynamics in multilayered PbS and PbSe quantum dot architectures

    SciTech Connect (OSTI)

    Xu, F.; Ma, X.; Haughn, C. R.; Doty, M. F.; Cloutier, S. G.

    2014-02-03

    We demonstrate control of the charge transfer process in PbS and PbSe quantum dot assemblies. We first demonstrate efficient charge transfer from donor quantum dots to acceptor quantum dots in a multi-layer PbSe cascade structure. Then, we assemble type-I and type-II heterostructures using both PbS and PbSe quantum dots via careful control of the band alignment. In type-I structures, photo-generated carriers are transferred and localized in the smaller bandgap (acceptor) quantum dots, resulting in a significant luminescence enhancement. In contrast, a significant luminescence quenching and shorter emission lifetime confirms an efficient separation of photo-generated carriers in the type-II architecture.

  14. 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)

    2010-07-06

    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.

  15. Certificate in Transit Management and

    E-Print Network [OSTI]

    Massachusetts at Amherst, University of

    , and perform minor maintenance and staff responsibilities. UMass Transit has been a fare free public transit Intro to Transportation Systems FINOPMGT 341 Logistics & Transportation Functions FINOPMGT 347 Intro

  16. Energy Transition Initiative

    Office of Energy Efficiency and Renewable Energy (EERE)

    Through the Energy Transition Initiative (ETI), the U.S. Department of Energy and its partners work with government entities and other stakeholders to establish a long-term energy vision and successfully implement energy efficiency and renewable energy solutions.

  17. site_transition.cdr

    Office of Environmental Management (EM)

    OF This fact sheet explains the process for transferring a site to the U.S. Department of Energy Office of Legacy Management. Site Transition Process Upon Cleanup Completion...

  18. Induced spin-accumulation and spin-polarization in a quantum-dot ring by using magnetic quantum dots and Rashba spin-orbit effect

    SciTech Connect (OSTI)

    Eslami, L., E-mail: Leslami@iust.ac.ir; Faizabadi, E. [School of Physics, Iran University of Science and Technology, Tehran 16846 (Iran, Islamic Republic of)

    2014-05-28

    The effect of magnetic contacts on spin-dependent electron transport and spin-accumulation in a quantum ring, which is threaded by a magnetic flux, is studied. The quantum ring is made up of four quantum dots, where two of them possess magnetic structure and other ones are subjected to the Rashba spin-orbit coupling. The magnetic quantum dots, referred to as magnetic quantum contacts, are connected to two external leads. Two different configurations of magnetic moments of the quantum contacts are considered; the parallel and the anti-parallel ones. When the magnetic moments are parallel, the degeneracy between the transmission coefficients of spin-up and spin-down electrons is lifted and the system can be adjusted to operate as a spin-filter. In addition, the accumulation of spin-up and spin-down electrons in non-magnetic quantum dots are different in the case of parallel magnetic moments. When the intra-dot Coulomb interaction is taken into account, we find that the electron interactions participate in separation between the accumulations of electrons with different spin directions in non-magnetic quantum dots. Furthermore, the spin-accumulation in non-magnetic quantum dots can be tuned in the both parallel and anti-parallel magnetic moments by adjusting the Rashba spin-orbit strength and the magnetic flux. Thus, the quantum ring with magnetic quantum contacts could be utilized to create tunable local magnetic moments which can be used in designing optimized nanodevices.

  19. 8 Lighten the LoadTM Carbon Neutral Laundry Rooms Mac-Gray Campus Solutions recognizes that carbon offsetting is not without controversy, but also

    E-Print Network [OSTI]

    Alexandrova, Ivana

    and to invest in emerging technologies and proven ways of negating a carbon footprint. Of course, reducing48 8 Lighten the LoadTM Carbon Neutral Laundry Rooms Mac-Gray Campus Solutions recognizes that carbon offsetting is not without controversy, but also understands that offsetting is a viable short

  20. 1850 Am J Psychiatry 164:12, December 2007ajp.psychiatryonline.org Gray Matter Decrease of the Anterior Cingulate Cortex

    E-Print Network [OSTI]

    Gaser, Christian

    of the Anterior Cingulate Cortex in Anorexia Nervosa Mark Mühlau, M.D. Christian Gaser, Ph.D. Rüdiger Ilg, M in the pathophysiology of anorexia nervosa have not been clearly elucidated. Moreover, decrease in cere- bral tissue-specific gray matter changes and glo- bal cerebral volumes in recovered pa- tients with anorexia nervosa. Method

  1. Gray-box model for energy-efficient selection of set point hysteresis in heating, ventilation, air conditioning, and refrigeration controllers

    E-Print Network [OSTI]

    Bahrami, Majid

    Energy efficiency Gray-box model a b s t r a c t Many heating, ventilation, air conditioning by Heating, Ventilation, Air Conditioning, and Refrigeration (HVAC­R) systems [1]. HVAC­R energy consumption, for instance, may use up to 80% of the total energy consumed in the supermarket [3]. Moreover, Air Conditioning

  2. SEA-STARS OF NORTH CAROLINA . By I. E. GRAY,' MAUREEN E. DOWNEY,2 AND M. J. CERAME-VIVAS3

    E-Print Network [OSTI]

    SEA-STARS OF NORTH CAROLINA . By I. E. GRAY,' MAUREEN E. DOWNEY,2 AND M. J. CERAME-VIVAS3 ABSTRACT North Carolina southward, nine range from North Carolina northward, and six occur both north and south of North Carolina. The affinities of the various Although isolated records exist., no previous at- t

  3. "Granular jets and hydraulic jumps on an inclined plane", C. G. Johnson, J. M. N. T. Gray ( ), J. Fluid Mech., (Submitted)

    E-Print Network [OSTI]

    Sidorov, Nikita

    · "Granular jets and hydraulic jumps on an inclined plane", C. G. Johnson, J. M. N. T. Gray ( ), J material impinging on an inclined plane pro- duces a diverse range of ows, from steady hydraulic jumps-moving radial ow, surrounded by either a teardrop-shaped, or a `blunted' hydraulic jump. A depth

  4. Effect of band alignment on photoluminescence and carrier escape from InP surface quantum dots grown by metalorganic chemical vapor deposition on Si

    SciTech Connect (OSTI)

    Halder, Nripendra N.; Biswas, Pranab; Banerji, P.; Dhabal Das, Tushar; Das, Sanat Kr.; Chattopadhyay, S.; Biswas, D.

    2014-01-28

    A detailed analysis of photoluminescence (PL) from InP quantum dots (QDs) grown on Si has been carried out to understand the effect of substrate/host material in the luminescence and carrier escape process from the surface quantum dots. Such studies are required for the development of monolithically integrated next generation III-V QD based optoelectronics with fully developed Si microelectronics. The samples were grown by atmospheric pressure metalorganic chemical vapor deposition technique, and the PL measurements were made in the temperature range 10–80?K. The distribution of the dot diameter as well as the dot height has been investigated from atomic force microscopy. The origin of the photoluminescence has been explained theoretically. The band alignment of InP/Si heterostructure has been determined, and it is found be type II in nature. The positions of the conduction band minimum of Si and the 1st excited state in the conduction band of InP QDs have been estimated to understand the carrier escape phenomenon. A blue shift with a temperature co-efficient of 0.19?meV/K of the PL emission peak has been found as a result of competitive effect of different physical processes like quantum confinement, strain, and surface states. The corresponding effect of blue shift by quantum confinement and strain as well as the red shift by the surface states in the PL peaks has been studied. The origin of the luminescence in this heterojunction is found to be due to the recombination of free excitons, bound excitons, and a transition from the 1st electron excited state in the conduction band (e{sub 1}) to the heavy hole band (hh{sub 1}). Monotonic decrease in the PL intensity due to increase of thermally escaped carriers with temperature has been observed. The change in barrier height by the photogenerated electric-field enhanced the capture of the carriers by the surface states rather than their accumulation in the QD excited state. From an analysis of the dependence of the PL intensity, peak position, and line width with temperature and excitation source, the existence of free and bound excitonic recombination together with e{sub 1} ? hh{sub 1} transitions in the QDs is established.

  5. Understanding electric field control of electronic and optical properties of strongly-coupled multi-layer quantum dot molecules

    E-Print Network [OSTI]

    Usman, Muhammad

    2015-01-01

    Strongly-coupled quantum dot molecules (QDMs) are widely deployed in the design of a variety of optoelectronic, photovoltaic, and quantum information devices. An efficient and optimized performance of these devices demands engineering of the electronic and optical properties of the underlying QDMs. The application of electric fields offers a knob to realise such control over the QDM characteristics for a desired device operation. We perform multi-million-atom atomistic tight-binding calculations to study the influence of electric fields on the electron and hole wave function confinements and symmetries, the ground-state transition energies, the band-gap wavelengths, and the optical transition modes. The electrical fields both parallel ($\\vec{E_p}$) and anti-parallel ($\\vec{E_a}$) to the growth direction are investigated to provide a comprehensive guide on the understanding of the electric field effects. The strain-induced asymmetry of the hybridized electron states is found to be weak and can be balanced by a...

  6. Colloidal quantum dot solar cells on curved and flexible substrates

    SciTech Connect (OSTI)

    Kramer, Illan J.; Moreno-Bautista, Gabriel; Minor, James C.; Kopilovic, Damir; Sargent, Edward H.

    2014-10-20

    Colloidal quantum dots (CQDs) are semiconductor nanocrystals synthesized with, processed in, and deposited from the solution phase, potentially enabling low-cost, facile manufacture of solar cells. Unfortunately, CQD solar cell reports, until now, have only explored batch-processing methods—such as spin-coating—that offer limited capacity for scaling. Spray-coating could offer a means of producing uniform colloidal quantum dot films that yield high-quality devices. Here, we explore the versatility of the spray-coating method by producing CQD solar cells in a variety of previously unexplored substrate arrangements. The potential transferability of the spray-coating method to a roll-to-roll manufacturing process was tested by spray-coating the CQD active layer onto six substrates mounted on a rapidly rotating drum, yielding devices with an average power conversion efficiency of 6.7%. We further tested the manufacturability of the process by endeavoring to spray onto flexible substrates, only to find that spraying while the substrate was flexed was crucial to achieving champion performance of 7.2% without compromise to open-circuit voltage. Having deposited onto a substrate with one axis of curvature, we then built our CQD solar cells onto a spherical lens substrate having two axes of curvature resulting in a 5% efficient device. These results show that CQDs deposited using our spraying method can be integrated to large-area manufacturing processes and can be used to make solar cells on unconventional shapes.

  7. Effect of swift heavy ion irradiation on bare and coated ZnS quantum dots

    SciTech Connect (OSTI)

    Chowdhury, S. Hussain, A.M.P.; Ahmed, G.A.; Singh, F.; Avasthi, D.K.; Choudhury, A.

    2008-12-01

    The present study compares structural and optical modifications of bare and silica (SiO{sub 2}) coated ZnS quantum dots under swift heavy ion (SHI) irradiation. Bare and silica coated ZnS quantum dots were prepared following an inexpensive chemical route using polyvinyl alcohol (PVA) as the dielectric host matrix. X-ray diffraction (XRD) and transmission electron microscopy (TEM) study of the samples show the formation of almost spherical ZnS quantum dots. The UV-Vis absorption spectra reveal blue shift relative to bulk material in absorption energy while photoluminescence (PL) spectra suggests that surface state and near band edge emissions are dominating in case of bare and coated samples, respectively. Swift heavy ion irradiation of the samples was carried out with 160 MeV Ni{sup 12+} ion beam with fluences 10{sup 12} to 10{sup 13} ions/cm{sup 2}. Size enhancement of bare quantum dots after irradiation has been indicated in XRD and TEM analysis of the samples which has also been supported by optical absorption spectra. However similar investigations on irradiated coated quantum dots revealed little change in quantum dot size and emission. The present study thus shows that the coated ZnS quantum dots are stable upon SHI irradiation compared to the bare one.

  8. 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.; Buljan, M.; Chahboun, A.; Roldan, M. A.; Molina, S. I.; Bernstorff, S.; Varela, M.; Pennycook, S. J.; Barradas, N. P.; Alves, E.

    2012-04-01

    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.

  9. 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)

    2006-01-15

    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.

  10. Electroweak phase transitions

    SciTech Connect (OSTI)

    Anderson, G.W.

    1991-09-16

    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.

  11. Electroweak phase transitions

    SciTech Connect (OSTI)

    Anderson, G.W.

    1991-09-16

    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.

  12. Observations of Rabi oscillations in a non-polar InGaN quantum dot

    E-Print Network [OSTI]

    Reid, Benjamin P. L.; Kocher, Claudius; Zhu, Tongtong; Oehler, Fabrice; Emery, Robert; Chan, Christopher C. S.; Oliver, Rachel A.; Taylor, Robert A.

    2014-07-03

    . A pattern of such apertures was sufficient to enable optical isolation of single quantum dots. The samples were mounted in a continuous helium flow cryostat (Janis ST-500) with a feedback loop temperature controller (Lakeshore 331) enabling cooling... to sustain excitonic emission at high temperatures, evidenced by single photon emission at 200K from InGaN [8] and at 300K from GaN quantum dots [9]. Demonstration of coherent control of quantum dot qubit states in the III-nitride system has been hampered...

  13. Far off-resonant coupling between photonic crystal microcavity and single quantum dot with resonant excitation

    SciTech Connect (OSTI)

    Banihashemi, Mehdi; Ahmadi, Vahid, E-mail: v-ahmadi@modares.ac.ir [Department of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, P.O. Box 14115-194 (Iran, Islamic Republic of)] [Department of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, P.O. Box 14115-194 (Iran, Islamic Republic of); Nakamura, Tatsuya; Kojima, Takanori; Kojima, Kazunobu; Noda, Susumu [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan)] [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan)

    2013-12-16

    In this paper, we experimentally demonstrate that with sub-nanowatt coherent s-shell excitation of a single InAs quantum dot, off-resonant coupling of 4.1?nm is possible between L3 photonic crystal microcavity and the quantum dot at 50?K. This resonant excitation reduces strongly the effect of surrounding charges to quantum dot, multiexciton complexes and pure dephasing. It seems that this far off-resonant coupling is the result of increased number of acoustical phonons due to high operating temperature of 50?K. The 4.1?nm detuning is the largest amount for this kind of coupling.

  14. Red light-emitting diodes based on InP/GaP quantum dots

    SciTech Connect (OSTI)

    Hatami, F.; Lordi, V.; Harris, J.S.; Kostial, H.; Masselink, W.T.

    2005-05-01

    The growth, fabrication, and device characterization of InP quantum-dot light-emitting diodes based on GaP are described and discussed. The diode structures are grown on gallium phosphide substrates using gas-source molecular-beam epitaxy and the active region of the diode consists of self-assembled InP quantum dots embedded in a GaP matrix. Red electroluminescence originating from direct band-gap emission from the InP quantum dots is observed at low temperatures.With increasing temperature, however, the emission line shifts to the longer wavelength. The emission light is measured to above room temperature.

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

    E-Print Network [OSTI]

    Pang, Shuo

    2008-10-10

    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... stream_source_info Shuo.pdf.txt stream_content_type text/plain stream_size 66833 Content-Encoding UTF-8 stream_name Shuo.pdf.txt Content-Type text/plain; charset=UTF-8 WHISPERING GALLERY MODES IN QUANTUM DOT...

  16. The use of bulk states to accelerate the band edge statecalculation of a semiconductor quantum dot

    SciTech Connect (OSTI)

    Vomel, Christof; Tomov, Stanimire Z.; Wang, Lin-Wang; Marques,Osni A.; Dongarra, Jack J.

    2006-05-10

    We present a new technique to accelerate the convergence of the folded spectrum method in empirical pseudopotential band edge state calculations for colloidal quantum dots. We use bulk band states of the materials constituent of the quantum dot to construct initial vectors and a preconditioner. We apply these to accelerate the convergence of the folded spectrum method for the interior states at the top of the valence and the bottom of the conduction band. For large CdSe quantum dots, the number of iteration steps until convergence decreases by about a factor of 4 compared to previous calculations.

  17. Heralded entanglement of two distant quantum dot spins via optical interference

    E-Print Network [OSTI]

    Li-Bo Chen; Wen Yang; Zhang-Qi Yin

    2015-05-19

    We present a proposal for heralded entanglement between two quantum dots via Hong--Ou--Mandel effect. Each of the quantum dots, drived off-resonance by two lasers, can be entangled with the coherent cavity mode. The output photons from the two coherent cavity modes interfering by a beamsplitter, we could entangle the two QDs with nearly unit success probability. Our scheme requires neither direct coupling between qubits nor the detection of single photons. Moreover the quantum dots do not need to have the same frequencies and coupling constants.

  18. On-chip generation and guiding of quantum light from a site-controlled quantum dot

    SciTech Connect (OSTI)

    Jamil, Ayesha; Farrer, Ian; Griffiths, Jonathan P.; Jones, Geb A. C.; Ritchie, David A.; Skiba-Szymanska, Joanna; Kalliakos, Sokratis; Ward, Martin B.; Ellis, David J. P.; Shields, Andrew J.; Schwagmann, Andre; Brody, Yarden; Cambridge Research Laboratory, Toshiba Research Europe Limited, 208 Science Park, Milton Road, Cambridge, CB4 0GZ

    2014-03-10

    We demonstrate the emission and routing of single photons along a semiconductor chip originating from carrier recombination in an actively positioned InAs quantum dot. Device–scale arrays of quantum dots are formed by a two–step regrowth process. We precisely locate the propagating region of a unidirectional photonic crystal waveguide with respect to the quantum dot nucleation site. Under pulsed optical excitation, the multiphoton emission probability from the waveguide's exit is 12%?±?5% before any background correction. Our results are a major step towards the deterministic integration of a quantum emitter with the waveguiding components of photonic quantum circuits.

  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.

    1993-10-20

    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. Gate-Tunable Graphene Quantum Dot and Dirac Oscillator

    E-Print Network [OSTI]

    Abdelhadi Belouad; Ahmed Jellal; Youness Zahidi

    2015-05-29

    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.

  1. Gate-Tunable Graphene Quantum Dot and Dirac Oscillator

    E-Print Network [OSTI]

    Belouad, Abdelhadi; Zahidi, Youness

    2015-01-01

    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.

  2. Cooling a nanomechanical resonator by a triple quantum dot

    E-Print Network [OSTI]

    Li, Zeng-Zhao; Lam, Chi-Hang; You, J Q

    2012-01-01

    We propose an approach for achieving ground-state cooling of a nanomechanical resonator (NAMR) capacitively coupled to a triple quantum dot (TQD). This TQD is an electronic analog of a three-level atom in $\\Lambda$ configuration which allows an electron to enter it via lower-energy states and to exit only from a higher-energy state. By tuning the degeneracy of the two lower-energy states in the TQD, an electron can be trapped in a dark state caused by destructive quantum interference between the two tunneling pathways to the higher-energy state. Therefore, ground-state cooling of an NAMR can be achieved when electrons absorb readily and repeatedly energy quanta from the NAMR for excitations.

  3. Cooling a nanomechanical resonator by a triple quantum dot

    E-Print Network [OSTI]

    Zeng-Zhao Li; Shi-Hua Ouyang; Chi-Hang Lam; J. Q. You

    2012-05-26

    We propose an approach for achieving ground-state cooling of a nanomechanical resonator (NAMR) capacitively coupled to a triple quantum dot (TQD). This TQD is an electronic analog of a three-level atom in $\\Lambda$ configuration which allows an electron to enter it via lower-energy states and to exit only from a higher-energy state. By tuning the degeneracy of the two lower-energy states in the TQD, an electron can be trapped in a dark state caused by destructive quantum interference between the two tunneling pathways to the higher-energy state. Therefore, ground-state cooling of an NAMR can be achieved when electrons absorb readily and repeatedly energy quanta from the NAMR for excitations.

  4. Interaction of graphene quantum dots with bulk semiconductor surfaces

    SciTech Connect (OSTI)

    Mohapatra, P. K.; Singh, B. P.; Kushavah, Dushyant; Mohapatra, J.

    2015-05-15

    Highly luminescent graphene quantum dots (GQDs) are synthesized through thermolysis of glucose. The average lateral size of the synthesized GQDs is found to be ?5 nm. The occurrence of D and G band at 1345 and 1580 cm{sup ?1} in Raman spectrum confirms the presence of graphene layers. GQDs are mostly consisting of 3 to 4 graphene layers as confirmed from the AFM measurements. Photoluminescence (PL) measurement shows a distinct broadening of the spectrum when GQDs are on the semiconducting bulk surface compared to GQDs in water. The time resolved PL measurement shows a significant shortening in PL lifetime due to the substrate interaction on GQDs compared to the GQDs in solution phase.

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

    E-Print Network [OSTI]

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

    2011-07-03

    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)).

  6. Soliton nanoantennas in two-dimensional arrays of quantum dots

    E-Print Network [OSTI]

    Gligori?, G; Hadžievski, Lj; Slepyan, G Ya; Malomed, B A

    2015-01-01

    We consider two-dimensional (2D) arrays of self-organized semiconductor quantum dots (QDs) strongly interacting with electromagnetic field in the regime of Rabi oscillations. The QD array built of two-level states is modelled by two coupled systems of discrete nonlinear Schr\\"{o}dinger equations. Localized modes in the form of single-peaked fundamental and vortical stationary Rabi solitons and self-trapped breathers have been found. The results for the stability, mobility and radiative properties of the Rabi modes suggest a concept of a self-assembled 2D \\textit{% soliton-based nano-antenna}, which should be stable against imperfections In particular, we discuss the implementation of such a nano-antenna in the form of surface plasmon solitons in graphene, and illustrate possibilities to control their operation by means of optical tools.

  7. Quantum Dot Solar Cells with Multiple Exciton Generation

    SciTech Connect (OSTI)

    Hanna, M. C.; Beard, M. C.; Johnson, J. C.; Murphy, J.; Ellingson, R. J.; Nozik, A. J.

    2005-11-01

    We have measured the quantum yield of the multiple exciton generation (MEG) process in quantum dots (QDs) of the lead-salt semiconductor family (PbSe, PbTe, and PbS) using fs pump-probe transient absorption measurements. Very high quantum yields (up to 300%) for charge carrier generation from MEG have been measured in all of the Pb-VI QDs. We have calculated the potential maximum performance of various MEG QD solar cells in the detailed balance limit. We examined a two-cell tandem PV device with singlet fission (SF), QD, and normal dye (N) absorbers in the nine possible series-connected combinations to compare the tandem combinations and identify the combinations with the highest theoretical efficiency. We also calculated the maximum efficiency of an idealized single-gap MEG QD solar cell with M multiplications and its performance under solar concentration.

  8. 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)

    2014-08-25

    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.

  9. Quantum Dot Spin Cellular Automata for Realizing a Quantum Processor

    E-Print Network [OSTI]

    Abolfazl Bayat; Charles E. Creffield; John H. Jefferson; Michael Pepper; Sougato Bose

    2015-09-09

    We show how "single" quantum dots, each hosting a singlet-triplet qubit, can be placed in arrays to build a spin quantum cellular automaton. A fast ($\\sim 10$ ns) deterministic coherent singlet-triplet filtering, as opposed to current incoherent tunneling/slow-adiabatic based quantum gates (operation time $\\sim 300$ ns), can be employed to produce a two-qubit gate through capacitive (electrostatic) coupling that can operate over significant distances. This is the coherent version of the widely discussed charge and nano-magnet cellular automata and would offer speed, reduce dissipation, perform quantum computation, while interfacing smoothly with its classical counterpart. This combines the best of two worlds -- the coherence of spin pairs known from quantum technologies, and the strength and range of electrostatic couplings from the charge based classical cellular automata.

  10. 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)

    2013-11-11

    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.

  11. Variational transition state theory

    SciTech Connect (OSTI)

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

    1993-12-01

    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.

  12. Transition Implementation Guide

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

    2001-04-24

    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.

  13. 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)

    2006-09-01

    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.

  14. Quantum chaos in quantum dots coupled to bosons

    E-Print Network [OSTI]

    S. Ahadpour; N. Hematpour

    2012-07-24

    Chaos transition, as an important topic, has become an active research subject in non-linear science. By considering a Dicke Hamiltonian coupled to a bath of harmonic oscillator, we have been able to introduce a logistic map with quantum corrections. Some basic dynamical properties, such as Lyapunov exponents and bifurcation diagram of the model are studied. we show that in this model, the transition from integrable motion to periodic, chaotic and hyperchaotic as the control parameter $r$ is increased.

  15. Electronic structure, morphology and emission polarization of enhanced symmetry InAs quantum-dot-like structures grown on InP substrates by molecular beam epitaxy

    SciTech Connect (OSTI)

    Mary?ski, A.; S?k, G.; Musia?, A.; Andrzejewski, J.; Misiewicz, J.; Gilfert, C.; Reithmaier, J. P.; Capua, A.; Karni, O.; Gready, D.; Eisenstein, G.; Atiya, G.; Kaplan, W. D.; Kölling, S.

    2013-09-07

    The optical and structural properties of a new kind of InAs/InGaAlAs/InP quantum dot (QD)-like objects grown by molecular beam epitaxy have been investigated. These nanostructures were found to have significantly more symmetrical shapes compared to the commonly obtained dash-like geometries typical of this material system. The enhanced symmetry has been achieved due to the use of an As{sub 2} source and the consequent shorter migration length of the indium atoms. Structural studies based on a combination of scanning transmission electron microscopy (STEM) and atom probe tomography (APT) provided detailed information on both the structure and composition distribution within an individual nanostructure. However, it was not possible to determine the lateral aspect ratio from STEM or APT. To verify the in-plane geometry, electronic structure calculations, including the energy levels and transition oscillator strength for the QDs have been performed using an eight-band k·p model and realistic system parameters. The results of calculations were compared to measured polarization-resolved photoluminescence data. On the basis of measured degree of linear polarization of the surface emission, the in-plane shape of the QDs has been assessed proving a substantial increase in lateral symmetry. This results in quantum-dot rather than quantum-dash like properties, consistent with expectations based on the growth conditions and the structural data.

  16. Alameda-Contra Costa Transit District (AC Transit) Fuel Cell...

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

    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...

  17. 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

    2013-01-01

    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 ...

  18. QUANTUM DOTS Elliott H. Lieb \\Lambda and Jan Philip Solovej \\Lambda\\Lambda

    E-Print Network [OSTI]

    QUANTUM DOTS Elliott H. Lieb \\Lambda and Jan Philip Solovej \\Lambda\\Lambda Department shown that a Thomas­Fermi type theory for the ground state is asymptotically correct when N and B tend

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

    E-Print Network [OSTI]

    Shirasaki, Yasuhiro

    2013-01-01

    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 ...

  20. Lead Telluride Quantum Dot Solar Cells Displaying External Quantum Efficiencies Exceeding 120%

    E-Print Network [OSTI]

    Böhm, Marcus L.; Jellicoe, Tom C.; Tabachnyk, Maxim; Davis, Nathaniel J. L. K.; Wisnivesky-Rocca-Rivarola, Florencia; Ducati, Caterina; Ehrler, Bruno; Bakulin, Artem A.; Greenham, Neil C.

    2015-10-21

    Multiple exciton generation (MEG) in semiconducting quantum dots is a process which produces multiple charge-carrier pairs from a single excitation. MEG is a possible route to bypass the Shockley-Queisser limit in single-junction solar cells...

  1. North Carolina DOT's Experience with Fiber Reinforced Polymers Authors: Rodger D. Rochelle

    E-Print Network [OSTI]

    North Carolina DOT's Experience with Fiber Reinforced Polymers Authors: Rodger D. Rochelle Gichuru Muchane Sami H. Rizkalla Janos Gergely #12;ABSTRACT This paper discusses North Carolina Department Research Engineer, Research and Development Unit, North Carolina Department of Transportation, 1549 Mail

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

    SciTech Connect (OSTI)

    Not Available

    2013-08-01

    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.

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

    E-Print Network [OSTI]

    Bruer, Garrett (Garrett A.)

    2010-01-01

    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. 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, ...

  5. IEEE TRANSACTIONS ON NANOBIOSCIENCE, VOL. 5, NO. 4, DECEMBER 2006 231 Peptide Coated Quantum Dots for

    E-Print Network [OSTI]

    Michalet, Xavier

    IEEE TRANSACTIONS ON NANOBIOSCIENCE, VOL. 5, NO. 4, DECEMBER 2006 231 Peptide Coated Quantum Dots and 5­8 are available online at http://ieeexplore. ieee.org. Digital Object Identifier 10.1109/TNB.2006

  6. 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.

    2005-07-04

    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.

  7. Mechanistic Insights into the Formation of InP Quantum Dots

    E-Print Network [OSTI]

    Allen, Peter M.

    The molecular mechanism of InP colloidal quantum dot (QD) syntheses was investigated by NMR spectroscopy. Unlike methods for monodisperse PbSe and CdSe, existing InP syntheses result in total depletion of molecular phosphorous ...

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

    E-Print Network [OSTI]

    Balasubramanian, Haribhaskar

    2009-05-15

    semiconductor nanocrystals or quantum dots (QD’s) both theoretically and experimentally. Compared to standard organic dyes, QD’s possess a relatively broad, uniform spectral response that enables better use of the full bandwidth from the broadband laser...

  9. 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

    2015-04-13

    Carbon quantum dots (CQDs) are established as excellent photosensitizers in combination with a molecular catalyst for solar light driven hydrogen production in aqueous solution. The inexpensive CQDs can be prepared by straightforward thermolysis...

  10. Developing an array of site-controlled pyramidal quantum dots emitting polarization-entangled photons

    SciTech Connect (OSTI)

    Juska, G.; Dimastrodonato, V.; Mereni, L. O.; Gocalinska, A.; Pelucchi, E. [Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland)

    2013-12-04

    We present a site-controlled, highly symmetric quantum dot system with a density of at least 15 % of polarization-entangled photon emitters. Fidelity values of the entangled state as high as 0.721±0.043 were found.

  11. Zeeman energy and spin relaxation in a one-electron quantum dot

    E-Print Network [OSTI]

    R. Hanson; B. Witkamp; L. M. K. Vandersypen; L. H. Willems van Beveren; J. M. Elzerman; L. P. Kouwenhoven

    2003-11-10

    We have measured the relaxation time, T1, of the spin of a single electron confined in a semiconductor quantum dot (a proposed quantum bit). In a magnetic field, applied parallel to the two-dimensional electron gas in which the quantum dot is defined, Zeeman splitting of the orbital states is directly observed by measurements of electron transport through the dot. By applying short voltage pulses, we can populate the excited spin state with one electron and monitor relaxation of the spin. We find a lower bound on T1 of 50 microseconds at 7.5 T, only limited by our signal-to-noise ratio. A continuous measurement of the charge on the dot has no observable effect on the spin relaxation.

  12. 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) ...

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

    E-Print Network [OSTI]

    Jarosz, Mirna, 1981-

    2004-01-01

    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 ...

  14. Efficient light emitting devices utilizing CdSe(ZnS) quantum dots in organic host matrices

    E-Print Network [OSTI]

    Coe-Sullivan, Seth (Seth Alexander)

    2002-01-01

    We demonstrate efficient electroluminescence from thin film structures containing core-shell CdSe(ZnS) quantum dots dispersed in molecular organic host materials. In the most efficient devices, excitons are created on the ...

  15. Caltrans Experience with Ternary Mix for Long-performing Concrete Mehdi Parvini, CA DOT

    E-Print Network [OSTI]

    Caltrans Experience with Ternary Mix for Long-performing Concrete Mehdi Parvini, CA DOT Introduction and Background The Project The Result Ternary Mix is a concrete mixture containing three strength, low permeability, corrosion resistance, sulfate resistance, ASR resistance, and elimination

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

    E-Print Network [OSTI]

    Wood, Vanessa Claire

    2010-01-01

    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 ...

  17. R&D Magazine: Windows into Solar Power Sources with Quantum Dots

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

    30, 2015 R&D Magazine: Windows into Solar Power Sources with Quantum Dots A luminescent solar concentrator is an emerging sunlight harvesting technology that has the potential to...

  18. Enhanced ripening behavior of Mg-doped CdSe quantum dots

    E-Print Network [OSTI]

    Kim, Tae-Geun

    In this study, CdO and Mg acetate were added into a mixture of paraffin oil and oleic acid (45:5) by 5 and 1 mEnhanced ripening behavior of Mg-doped CdSe quantum dots Yun-Mo Sung,a) Woo-Chul Kwak, and Woong November 2007; accepted 24 March 2008) Pure CdSe and Mg-doped CdSe nanocrystal quantum dots were

  19. Reach of Environmental Influences on the Indistinguishability of Single Photons from Quantum Dots

    E-Print Network [OSTI]

    Huber, Tobias; Föger, Daniel; Solomon, Glenn; Weihs, Gregor

    2015-01-01

    In this letter, we present a detailed, all optical study of the influence of different excitation schemes on the indistinguishability of single photons from a single InAs quantum dot. For this study, we measure the Hong-Ou-Mandel interference of consecutive photons from the spontaneous emission of an InAs quantum dot state under various excitation schemes and different excitation conditions and give a comparison.

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

    E-Print Network [OSTI]

    Björn Sothmann

    2014-10-27

    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.

  1. Quantum Dot–Bridge–Fullerene Heterodimers with Controlled Photoinduced Electron Transfer

    SciTech Connect (OSTI)

    Cotlet, M.; Xu, Z.

    2011-06-27

    A series of donor-bridge-acceptor systems in the form of core/shell CdSe/ZnS quantum dot-bridge-fullerene heterodimers (see picture) with varying bridge length and varying quantum dot size were self-assembled by a surface-based stepwise method to demonstrate control of the rate and of the magnitude of fluctuations of photoinduced electron transfer at the single-molecule level.

  2. Final Progress Report for Project Entitled: Quantum Dot Tracers for Use in Engineered Geothermal Systems

    SciTech Connect (OSTI)

    Rose, Peter; Bartl, Michael; Reimus, Paul; Williams, Mark; Mella, Mike

    2015-09-12

    The objective of this project was to develop and demonstrate a new class of tracers that offer great promise for use in characterizing fracture networks in EGS reservoirs. From laboratory synthesis and testing through numerical modeling and field demonstrations, we have demonstrated the amazing versatility and applicability of quantum dot tracers. This report summarizes the results of four years of research into the design, synthesis, and characterization of semiconductor nanocrystals (quantum dots) for use as geothermal tracers.

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

    SciTech Connect (OSTI)

    Kelly, D.L.

    1996-06-04

    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`).

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

    E-Print Network [OSTI]

    Rinaldo Trotta; Armando Rastelli

    2015-03-01

    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.

  5. Certificate in Transit Management and

    E-Print Network [OSTI]

    Massachusetts at Amherst, University of

    , and perform minor maintenance and staff responsibilities. UMass Transit has been a fare free public transit operation, and management. CTTransit CEE 310 Intro to Transportation Systems FINOPMGT 341 Logistics

  6. 220 NAW 5/13 nr. 3 september 2012 New books about Henri Poincare Jean-Marc Ginoux, Ferdinand Verhulst, Jeremy Gray Jean-Marc Ginoux

    E-Print Network [OSTI]

    Verhulst, Ferdinand

    1 1 220 NAW 5/13 nr. 3 september 2012 New books about Henri Poincar´e Jean-Marc Ginoux, Ferdinand Verhulst, Jeremy Gray Jean-Marc Ginoux Laboratoire PROTEE, EA 3819 I.U.T. de Toulon Universit´e du Sud on life and work of Henri Poincar´e. Each of the respective authors Jean-Marc Ginoux, Ferdinand Verhulst

  7. Precision photometry for planetary transits

    E-Print Network [OSTI]

    Frederic Pont; Claire Moutou

    2007-02-06

    We review the state of the art in follow-up photometry for planetary transit searches. Three topics are discussed: (1) Photometric monitoring of planets discovered by radial velocity to detect possible transits (2) Follow-up photometry of candidates from photometric transit searches to weed out eclipsing binaries and false positives (3) High-precision lightcurves of known transiting planets to increase the accuracy on the planet parameters.

  8. 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

    2015-01-01

    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 < 30 nm (< 10 nm), which represents an enabling technology for the creation of optimized single quantum dot devices. To that end, we create quantum dot single-photon sources, based on a circular Bragg grating geometry, that simultaneously exhibit high collection efficiency (48 % +/- 5 % into a 0.4 numerical aperture lens, close to the theoretically predicted value of 50 %), low multiphoton prob...

  9. Refrigerants in Transition 

    E-Print Network [OSTI]

    Stouppe, D. E.

    1991-01-01

    . 27-30. 7. Hayes, Floyd C., "Centrifugal\\~ater Chillers," CFCs: Today's Options Tomorrow's Solutions, ASHRAE Publication, Atlanta, GA, 1990, pp. 71-73. 8. Lorenz, Michael R., "CFCs: The Designer's Dilemma," Heating/Piping/Air Conditioning, April 1990... IN TRANSITION DAVID E. STOUPPE, P.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...

  10. TRANSITIONAL DISKS AND THEIR ORIGINS: AN INFRARED SPECTROSCOPIC SURVEY OF ORION A

    SciTech Connect (OSTI)

    Kim, K. H.; Watson, Dan M.; Manoj, P.; Forrest, W. J.; Arnold, Laura; Najita, Joan; Furlan, Elise; Sargent, Benjamin; Espaillat, Catherine; Muzerolle, James; Megeath, S. T.; Calvet, Nuria; Green, Joel D.

    2013-06-01

    Transitional disks are protoplanetary disks around young stars, with inner holes or gaps which are surrounded by optically thick outer, and often inner, disks. Here we present observations of 62 new transitional disks in the Orion A star-forming region. These were identified using the Spitzer Space Telescope's Infrared Spectrograph and followed up with determinations of stellar and accretion parameters using the Infrared Telescope Facility's SpeX. We combine these new observations with our previous results on transitional disks in Taurus, Chamaeleon I, Ophiuchus, and Perseus, and with archival X-ray observations. This produces a sample of 105 transitional disks of ''cluster'' age 3 Myr or less, by far the largest hitherto assembled. We use this sample to search for trends between the radial structure in the disks and many other system properties, in order to place constraints on the possible origins of transitional disks. We see a clear progression of host-star accretion rate and the different disk morphologies. We confirm that transitional disks with complete central clearings have median accretion rates an order of magnitude smaller than radially continuous disks of the same population. Pre-transitional disks-those objects with gaps that separate inner and outer disks-have median accretion rates intermediate between the two. Our results from the search for statistically significant trends, especially related to M-dot , strongly support that in both cases the gaps are far more likely to be due to the gravitational influence of Jovian planets or brown dwarfs orbiting within the gaps, than to any of the photoevaporative, turbulent, or grain-growth processes that can lead to disk dissipation. We also find that the fraction of Class II YSOs which are transitional disks is large, 0.1-0.2, especially in the youngest associations.

  11. Analytic equivalence of geometric transitions

    E-Print Network [OSTI]

    Michele Rossi

    2014-08-28

    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.

  12. 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)

    2014-03-10

    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.

  13. High color rendering index white light emitting diodes fabricated from a combination of carbon dots and zinc copper indium sulfide quantum dots

    SciTech Connect (OSTI)

    Sun, Chun; Liu, Wenyan; Zhang, Xiaoyu; Zhang, Yu E-mail: wyu6000@gmail.com; Wang, Yu; Kalytchuk, Sergii; Kershaw, Stephen V.; Rogach, Andrey L.; Zhang, Tieqiang; Zhao, Jun; Yu, William W. E-mail: wyu6000@gmail.com

    2014-06-30

    In a line with most recent trends in developing non-toxic fluorescent nanomaterials, we combined blue emissive carbon dots with green and red emissive zinc copper indium sulfide (ZCIS) core/shell quantum dots (QDs) to achieve white light-emitting diodes (WLEDs) with a high color rendering index of 93. This indicates that ZCIS QDs, with their broad emission bands, can be employed to effectively make up the emission of carbon dots in the yellow and red regions to produce WLEDs in the wide region of color temperature by tuning the volume ratio of these constituting luminophores. Their electroluminescence characteristics including color rendering index, Commission Internationale de l'Eclairage (CIE) color coordinates, and color temperatures were evaluated as a function of forward current. The CIE-1931 chromaticity coordinates of the as-prepared WLEDs, exhibiting good stability, were slightly shifted from (0.321, 0.312) at 10?mA to (0.351, 0.322) at 30?mA, which was mainly caused by the different thermal quenching coefficients of carbon dots and ZCIS QDs.

  14. Investigation of Umbral Dots with the New Vacuum Solar Telescope

    E-Print Network [OSTI]

    Kaifan, Ji; Song, Feng; Yunfei, Yang; Hui, Deng; Feng, Wang

    2015-01-01

    Umbral dots (UDs) are small isolated brightening observed in sunspot umbrae. They are convective phenomena existing inside umbrae. UDs are usually divided into central UDs (CUDs) and peripheral UDs (PUDs) with respect to their positions inside an umbra. Our purpose is to investigate UD properties and analyze their relationships, and further to find whether or not the properties depend on the umbral magnetic field variation. For the purpose, we selected the high-resolution TiO images of four active regions (ARs) obtained under the best seeing conditions with the \\emph{New Vacuum Solar Telescope} (NVST) in Fuxian Solar Observatory of Yunnan Astronomical Observatory, China. The four ARs (NOAA 11598, 11801, 12158, and 12178) include six sunspots. A total of 1220 CUDs were extracted from six sunspots, and 603 PUDs from three sunspots. Meanwhile, the radial component of the magnetic field of the sunspots obtained with the \\emph{Helioseismic and Magnetic Imager} onboard the \\emph{Solar Dynamics Observatory} was used...

  15. Quantum-Dots Based Electrochemical Immunoassay of Interleukin-1?

    SciTech Connect (OSTI)

    Wu, Hong; Liu, Guodong; Wang, Jun; Lin, Yuehe

    2007-07-01

    We describe a quantum-dot (QD, CdSe@ZnS)-based electrochemical immunoassay to detect a protein biomarker, interleukin-1? (IL-1?). QD conjugated with anti-IL-1? antibody was used as a label in an immunorecognition event. After a complete sandwich immunoreaction among the primary IL-1? antibody (immobilized on the avidin-modified magnetic beads), IL-1?, and the QD-labeled secondary antibody, QD labels were attached to the magnetic-bead surface through the antibody-antigen immunocomplex. Electrochemical stripping analysis of the captured QDs was used to quantify the concentration of IL-1? after an acid-dissolution step. The streptavidin-modified magnetic beads and the magnetic separation platform were used to integrate a facile antibody immobilization (through a biotin/streptavidin interaction) with immunoreactions and the isolation of immunocomplexes from reaction solutions in the assay. The voltammetric response is highly linear over the range of 0.5 to 50 ng mL-1 IL 1?, and the limit of detection is estimated to be 0.3 ng mL-1 (18 pM). This QD-based electrochemical immunoassay shows great promise for rapid, simple, and cost-effective analysis of protein biomarkers.

  16. PROPERTIES OF UMBRAL DOTS FROM STRAY LIGHT CORRECTED HINODE FILTERGRAMS

    SciTech Connect (OSTI)

    Louis, Rohan E.; Mathew, Shibu K.; Bayanna, A. Raja; Rubio, Luis R. Bellot; Ichimoto, Kiyoshi; Ravindra, B.

    2012-06-20

    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.

  17. Superradiance Transition in Graphene

    E-Print Network [OSTI]

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

    2015-06-12

    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.

  18. Transition Metal Switchable Mirror

    ScienceCinema (OSTI)

    None

    2010-01-08

    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.

  19. Transition Metal Switchable Mirror

    ScienceCinema (OSTI)

    None

    2013-05-29

    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

  20. Transition Metal Switchable Mirror

    SciTech Connect (OSTI)

    2009-08-21

    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.

  1. Transition Metal Switchable Mirror

    SciTech Connect (OSTI)

    None

    2009-01-01

    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

  2. 309 Building transition plan

    SciTech Connect (OSTI)

    Graves, C.E.

    1994-08-31

    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.

  3. Connecticut Transit (CTTRANSIT) Fuel Cell Transit Bus: Second...

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

    Connecticut Transit (CTTRANSIT) in Hartford for one prototype fuel cell bus and three new diesel buses operating from the same location. 45670-2.pdf More Documents & Publications...

  4. Alameda-Contra Costa Transit District (AC Transit) Fuel Cell...

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

    Alameda-Contra Costa Transit district for three protoype fuel cell buses and six diesel buses operating from the same location. 43545-2.pdf More Documents & Publications...

  5. Connecticut Transit (CTTRANSIT) Fuel Cell Transit Bus: Third...

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

    describes operations at Connecticut Transit (CTTRANSIT) in Hartford for one prototype fuel cell bus and three new diesel buses operating from the same location. The prototype...

  6. Tuning the Optical Properties of Nanoscale Materials on Surfaces Through Controlled Exchange Reactions on Cadmium Selenide Quantum Dots and Patterning of Gold and QD Nanoparticle Arrays 

    E-Print Network [OSTI]

    Pravitasari, Arika

    2013-11-11

    This work focused on the integration of CdSe quantum dots (QDs) and Au nanoparticles (NPs) as building blocks for the development of quantum dot and plasmonic based optical and sensing devices. The manipulation of nanomaterials ...

  7. The impact of disorder on charge transport in three dimensional quantum dot resonant tunneling structures

    SciTech Connect (OSTI)

    Puthen-Veettil, B. Patterson, R.; König, D.; Conibeer, G.; Green, M. A.

    2014-10-28

    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/.

  8. Test and evaluation document for DOT Specification 7A type A packaging. Volume 1

    SciTech Connect (OSTI)

    Kelly, D L

    1997-08-04

    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). This document summarizes the evaluation and testing performed for all of the packagings successfully qualified in this program. This document supersedes DOE Evaluation Document for DOT-7A Type A Packaging (Edling 1987), originally issued in 1987 by Monsanto Research Corporation Mound Laboratory (MLM), Miamisburg, Ohio, for the Department of Energy, Security Evaluation Program (I)P-4. Mound Laboratory issued four revisions to the document between November 1988 and December 1989. In September 1989, the program was transferred to Westinghouse Hanford Company (Westinghouse Hanford) in Richland, Washington. One additional revision was issued in March 1990 by Westinghouse Hanford. This revision reflects the earlier material and incorporates a number of changes. Evaluation and testing activities on 1208 three DOT-7A Program Dockets resulted in the qualification of three new packaging configurations, which are incorporated herein and summarized. This document presents approximately 300 different packagings that have been determined to meet the requirements for a DOT-7A, type A packaging per 49 CFR 178.350.

  9. Inhibition of plasmonically enhanced interdot energy transfer in quantum dot solids via photo-oxidation

    SciTech Connect (OSTI)

    Sadeghi, S. M.; Nejat, A.; West, R. G.

    2012-11-15

    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.

  10. 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

    2013-01-28

    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.

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

    SciTech Connect (OSTI)

    Nozik, Arthur J.; Beard, Matthew C.; Luther, Joseph M.; Law, Matt; Ellingson, Randy J.; Johnson, Justin C.

    2010-10-14

    Here, we will first briefly summarize the general principles of QD synthesis using our previous work on InP as an example. Then we will focus on QDs of the IV-VI Pb chalcogenides (PbSe, PbS, and PbTe) and Si QDs because these were among the first QDs that were reported to produce multiple excitons upon absorbing single photons of appropriate energy (a process we call multiple exciton generation (MEG)). We note that in addition to Si and the Pb-VI QDs, two other semiconductor systems (III-V InP QDs(56) and II-VI core-shell CdTe/CdSe QDs(57)) were very recently reported to also produce MEG. Then we will discuss photogenerated carrier dynamics in QDs, including the issues and controversies related to the cooling of hot carriers and the magnitude and significance of MEG in QDs. Finally, we will discuss applications of QDs and QD arrays in novel quantum dot PV cells, where multiple exciton generation from single photons could yield significantly higher PV conversion efficiencies.

  12. Smarter Parking at Transit Stations

    E-Print Network [OSTI]

    Shaheen, Susan; Kemmerer, Charlene

    2007-01-01

    The High Cost of Free Parking (Chicago, Illinois: Americanand Amanda Eaken. Smart Parking Management Field Test: A BayTransit (BART) District Parking Demonstration—Phase One

  13. Planetary Transits of TRES-1

    E-Print Network [OSTI]

    A. Price; R. Bissinger; G. Laughlin; B. Gary; T. Vanmunster; A. Henden; D. Starkey; D. Kaiser; J. Holtzman; L. Marschall; T. Michalik; T. Wellington; P. Paakonen; Z. S. Kereszty; R. Durkee; K. Richardson; R. Leadbeater; T. Castellano

    2004-12-17

    Observations of TRES-1b transits made during the late summer and fall 2004 observing season reveal a statistically significant but low amplitude brightening event during egress.

  14. Non-Hermitian scattering theory: Resonant tunneling probability amplitude in a quantum dot Hadas Barkay, Edvardas Narevicius, and Nimrod Moiseyev*

    E-Print Network [OSTI]

    Narevicius, Edvardas

    properties of quantum dots, phenomena such as tunneling of electrons must be characterized. Phase, in a manner that enabled them to control the potential of the electrons trapped in it by varying the plungerNon-Hermitian scattering theory: Resonant tunneling probability amplitude in a quantum dot Hadas

  15. Statistics of Coulomb-blockade peak spacings for a partially open quantum dot A. Kaminski and L. I. Glazman

    E-Print Network [OSTI]

    Glazman, Leonid

    Statistics of Coulomb-blockade peak spacings for a partially open quantum dot A. Kaminski and L. I by a sum of two terms. The first one is the electrostatic charging energy, which does not fluctuate all interactions except the charging energy are ignored . For a disordered or chaotic quantum dot

  16. Graphene quantum dots: Beyond a Dirac billiard Florian Libisch,1 Christoph Stampfer,2 and Joachim Burgdrfer1

    E-Print Network [OSTI]

    Florian, Libisch

    Graphene quantum dots: Beyond a Dirac billiard Florian Libisch,1 Christoph Stampfer,2 and Joachim confinement effects in phase-coherent graphene quantum dots with linear dimensions of 10­40 nm. We determine.45.Mt, 73.23. b, 81.05.Uw I. INTRODUCTION Graphene,1,2 the first true two-dimensional 2D solid

  17. Improved device performance of InAs/GaAs quantum dot solar cells with GaP strain compensation layers

    E-Print Network [OSTI]

    Jalali. Bahram

    Improved device performance of InAs/GaAs quantum dot solar cells with GaP strain compensation Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico optical, electrical, and spectral response characteristics of three-stack InAs/GaAs quantum dot solar

  18. 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 online 25 September 2012 a b s t r a c t We quantify the influence of coupled electromechanical effects

  19. Edge states in graphene quantum dots: Fractional quantum Hall effect analogies and differences at zero magnetic field

    E-Print Network [OSTI]

    Yannouleas, Constantine

    quantum Hall effect FQHE in two-dimensional 2D semiconductor heterostruc- tures in the presence of a high in finite 2D electronic systems, such as semiconductor quantum dots QDs under high B, ledEdge states in graphene quantum dots: Fractional quantum Hall effect analogies and differences

  20. Atomic and Molecular Quantum Theory Course Number: C561 10 Quantum Confinement in "Quantum dots", Thomas Fermi

    E-Print Network [OSTI]

    Iyengar, Srinivasan S.

    "niche" area called quantum dots. 1. A quantum dot is a very small chunk of semiconductor material with quantum-like properties. These are any effects that the bulk form of the same material does not possess quantum mechanical proper- ties and discrete energy levels. 3. As a first approximation these materials

  1. Large-Area (over 50 cm 50 cm) Freestanding Films of Colloidal InP/ ZnS Quantum Dots

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Large-Area (over 50 cm × 50 cm) Freestanding Films of Colloidal InP/ ZnS Quantum Dots Evren of flexible, freestanding films of InP/ZnS quantum dots (QDs) using fatty acid ligands across very large areas avoiding the need for ligand exchange. When pumped by a blue LED, these Cd-free QD films allow for high

  2. High-Efficiency Photoelectrocatalytic Hydrogen Generation Enabled by Palladium Quantum Dots-Sensitized TiO2 Nanotube Arrays

    E-Print Network [OSTI]

    Lin, Zhiqun

    High-Efficiency Photoelectrocatalytic Hydrogen Generation Enabled by Palladium Quantum Dots of hydrogen as a potential fuel for renewable energy.1 Among the various catalysts, the noble metal palladium ABSTRACT: TiO2 nanotube arrays (TNTAs) sensitized by palladium quantum dots (Pd QDs) exhibit highly

  3. Energy levels of double triangular graphene quantum dots

    SciTech Connect (OSTI)

    Liang, F. X.; Jiang, Z. T. Zhang, H. Y.; Li, S.; Lv, Z. T.

    2014-09-28

    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.

  4. Colloidal quantum dot solar cells on curved and flexible substrates Illan J. Kramer, Gabriel Moreno-Bautista, James C. Minor, Damir Kopilovic, and Edward H. Sargent

    E-Print Network [OSTI]

    Sargent, Edward H. "Ted"

    .1063/1.4810176 Impact of CdSe/ZnS quantum dot spectrum converters on InGaP/GaAs/Ge multi-junction solar cells J. VacColloidal quantum dot solar cells on curved and flexible substrates Illan J. Kramer, Gabriel Moreno Articles you may be interested in Efficient, air-stable colloidal quantum dot solar cells encapsulated

  5. Quantitative strain mapping of InAs/InP quantum dots with 1 nm spatial resolution using dark field electron holography

    E-Print Network [OSTI]

    Dunin-Borkowski, Rafal E.

    used to measure the strain in InAs quantum dots grown in InP with a spatial resolution of 1 nmQuantitative strain mapping of InAs/InP quantum dots with 1 nm spatial resolution using dark field of semiconductor quantum dots are greatly influenced by their strain state. Dark field electron holography has been

  6. Atomic and Molecular Quantum Theory Course Number: C561 C A Measurement is a Projection or a "dot" product (or inner

    E-Print Network [OSTI]

    Iyengar, Srinivasan S.

    of obtaining these measurements is basically a dot product. The dot product can also be interpreted as a proAtomic and Molecular Quantum Theory Course Number: C561 C A Measurement is a Projection or a "dot" product (or inner product)!! 1. Lets go back and consider the Stern Gerlach experiment that we studied

  7. Engineering quantum dots for electrical control of the fine structure splitting

    E-Print Network [OSTI]

    Pooley, M A; Farrer, I; Ritchie, D A; Shields, A J

    2015-01-01

    We have studied the variation in fine-structure splitting (FSS) under application of vertical electric field in a range of quantum dots grown by different methods. In each sample we confirm that this energy splitting changes linearly over the field range we can access. We conclude that this linear tuning is a general feature of self-assembled quantum dots, observed under different growth conditions, emission wavelengths and in different material systems. Statistical measurements of characteristic parameters such as emission energy, Stark shift and FSS tuning are presented which may provide a guide for future attempts to increase the yield of quantum dots that can be tuned to a minimal value of FSS with vertical electric field.

  8. Engineering quantum dots for electrical control of the fine structure splitting

    E-Print Network [OSTI]

    M. A. Pooley; A. J. Bennett; I. Farrer; D. A. Ritchie; A. J. Shields

    2015-07-22

    We have studied the variation in fine-structure splitting (FSS) under application of vertical electric field in a range of quantum dots grown by different methods. In each sample we confirm that this energy splitting changes linearly over the field range we can access. We conclude that this linear tuning is a general feature of self-assembled quantum dots, observed under different growth conditions, emission wavelengths and in different material systems. Statistical measurements of characteristic parameters such as emission energy, Stark shift and FSS tuning are presented which may provide a guide for future attempts to increase the yield of quantum dots that can be tuned to a minimal value of FSS with vertical electric field.

  9. 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)

    2012-12-10

    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.

  10. Microscopic model for intersubband gain from electrically pumped quantum-dot structures

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

    Michael, Stephan; Chow, Weng Wah; Schneider, Han Christian

    2014-10-03

    We study theoretically the performance of electrically pumped self-organized quantum dots as a gain material in the mid-IR range at room temperature. We analyze an AlGaAs/InGaAs based structure composed of dots-in-a-well sandwiched between two quantum wells. We numerically analyze a comprehensive model by combining a many-particle approach for electronic dynamics with a realistic modeling of the electronic states in the whole structure. We investigate the gain both for quasi-equilibrium conditions and current injection. Comparing different structures, we find that steady-state gain can only be realized by an efficient extraction process, which prevents an accumulation of electrons in continuum states, thatmore »make the available scattering pathways through the quantum dot active region too fast to sustain inversion.« less

  11. Manipulation of electron orbitals in hard-wall InAs/InP nanowire quantum dots

    E-Print Network [OSTI]

    Roddaro, Stefano; Ercolani, Daniele; Sorba, Lucia; Beltram, Fabio

    2010-01-01

    We present a novel technique for the manipulation of the energy spectrum of hard-wall InAs/InP nanowire quantum dots. By using two local gate electrodes, we induce a strong electric dipole moment on the dot and demonstrate the controlled modification of its electronic orbitals. Our approach allows us to dramatically enhance the single-particle energy spacing between the first two quantum levels in the dot and thus to increment the working temperature of our InAs/InP single-electron transistors. Our devices display a very robust modulation of the conductance even at liquid nitrogen temperature, while allowing an ultimate control of the electron filling down to the last free carrier. Potential further applications of the technique to time-resolved spin manipulation are also discussed.

  12. Manipulation of electron orbitals in hard-wall InAs/InP nanowire quantum dots

    E-Print Network [OSTI]

    Stefano Roddaro; Andrea Pescaglini; Daniele Ercolani; Lucia Sorba; Fabio Beltram

    2010-12-22

    We present a novel technique for the manipulation of the energy spectrum of hard-wall InAs/InP nanowire quantum dots. By using two local gate electrodes, we induce a strong electric dipole moment on the dot and demonstrate the controlled modification of its electronic orbitals. Our approach allows us to dramatically enhance the single-particle energy spacing between the first two quantum levels in the dot and thus to increment the working temperature of our InAs/InP single-electron transistors. Our devices display a very robust modulation of the conductance even at liquid nitrogen temperature, while allowing an ultimate control of the electron filling down to the last free carrier. Potential further applications of the technique to time-resolved spin manipulation are also discussed.

  13. Carrier multiplication detected through transient photocurrent in device-grade films of lead selenide quantum dots

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

    Gao, Jianbo; Fidler, Andrew F.; Klimov, Victor I.

    2015-09-08

    In carrier multiplication, the absorption of a single photon results in two or more electron–hole pairs. Quantum dots are promising materials for implementing carrier multiplication principles in real-life technologies. So far, however, most of research in this area has focused on optical studies of solution samples with yet to be proven relevance to practical devices. We report ultra-fast electro-optical studies of device-grade films of electronically coupled quantum dots that allow us to observe multiplication directly in the photocurrent. Our studies help rationalize previous results from both optical spectroscopy and steady-state photocurrent measurements and also provide new insights into effects ofmore »electric field and ligand treatments on multiexciton yields. Importantly, we demonstrate that using appropriate chemical treatments of the films, extra charges produced by carrier multiplication can be extracted from the quantum dots before they are lost to Auger recombination and hence can contribute to photocurrent of practical devices.« less

  14. High fidelity ac gate operations of the quantum dot hybrid qubit

    E-Print Network [OSTI]

    Clement H. Wong

    2015-10-20

    Semiconductor quantum dots in silicon are promising qubits because of long spin coherence times and their potential for scalability. However, such qubits with complete electrical control and fidelities above the threshold for quantum error correction have not yet been achieved. We show theoretically that the threshold fidelity can be achieved with ac gate operation of the quantum dot hybrid qubit. Formed by three electrons in a double dot, this qubit is electrically controlled, does not require magnetic fields, and runs at GHz gate speeds. We analyze the decoherence caused by 1/f charge noise in this qubit, find parameters that minimize the charge noise dependence in the qubit frequency, and determine the optimal working points for ac gate operations that drive the detuning and tunnel coupling.

  15. Luminescence of CdSe/ZnS quantum dots infiltrated into an opal matrix

    SciTech Connect (OSTI)

    Gruzintsev, A. N. Emelchenko, G. A.; Masalov, V. M.; Yakimov, E. E.; Barthou, C.; Maitre, A.

    2009-02-15

    The effect of the photonic band gap in the photonic crystal, the synthesized SiO{sub 2} opal with embedded CdSe/ZnS quantum dots, on its luminescence in the visible spectral region is studied. It is shown that the position of the photonic band gap in the luminescence and reflectance spectra for the infiltrated opal depends on the diameter of the constituent nanospheres and on the angle of recording the signal. The optimal conditions for embedding the CdSe/ZnS quantum dots from the solution into the opal matrix are determined. It is found that, for the opal-CdSe/ZnS nanocomposites, the emission intensity decreases and the luminescence decay time increases in the spatial directions, in which the spectral positions of the photonic band gap and the luminescence peak of the quantum dots coincide.

  16. 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.

    2011-10-15

    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.

  17. SIX HIGH-PRECISION TRANSITS OF OGLE-TR-113b

    SciTech Connect (OSTI)

    Adams, E. R.; Elliot, J. L.; Seager, S.; Lopez-Morales, M.; Osip, D. J.

    2010-10-01

    We present six new transits of the hot Jupiter OGLE-TR-113b observed with MagIC on the Magellan Telescopes between 2007 January and 2009 May. We update the system parameters and revise the planetary radius to R{sub p} = 1.084 {+-} 0.029R{sub J} , where the error is dominated by stellar radius uncertainties. The new transit midtimes reveal no transit timing variations from a constant ephemeris of greater than 13 {+-} 28 s over two years, placing an upper limit of 1-2 M{sub +} on the mass of any perturber in a 1:2 or 2:1 mean-motion resonance with OGLE-TR-113b. Combining the new transit epochs with five epochs published between 2002 and 2006, we find hints that the orbital period of the planet may not be constant, with the best fit indicating a decrease of P-dot =-60{+-}15 ms yr{sup -1}. If real, this change in period could result from either a long-period (more than eight years) timing variation due to a massive external perturber or more intriguingly from the orbital decay of the planet. The detection of a changing period is still tentative and requires additional observations, but if confirmed it would enable direct tests of tidal stability and dynamical models of close-in planets.

  18. AUTHORIZING THE DOT SPECIFICATION 6M PACKAGING FOR CONTINUED USE AT THE SAVANNAH RIVER SITE

    SciTech Connect (OSTI)

    Watkins, R.; Loftin, B.; Hoang, D.

    2010-03-04

    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.

  19. Washington Metropolitan Area Transit Authority: Compressed Natural Gas Transit Bus Evaluation

    SciTech Connect (OSTI)

    Chandler, K.; Eberts, E.; Melendez, M.

    2006-04-01

    Evaluates compressed natural gas (CNG) powered transit buses at Washington Metropolitan Area Transit Authority (WMATA), providing a comparison between them and standard diesel transit buses.

  20. 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.; Igusa, R.; Iwamoto, S.; Arakawa, Y.

    2014-09-15

    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.

  1. g-factor anisotropy in nanowire-based InAs quantum dots

    SciTech Connect (OSTI)

    D'Hollosy, Samuel; Fábián, Gábor; Baumgartner, Andreas; Schönenberger, Christian; Nygård, Jesper

    2013-12-04

    The determination and control of the electron g-factor in semiconductor quantum dots (QDs) are fundamental prerequisites in modern concepts of spintronics and spin-based quantum computation. We study the dependence of the g-factor on the orientation of an external magnetic field in quantum dots (QDs) formed between two metallic contacts on stacking fault free InAs nanowires. We extract the g-factor from the splitting of Kondo resonances and find that it varies continuously in the range between |g*| = 5 and 15.

  2. Photo-induced conductance fluctuations in mesoscopic Ge/Si systems with quantum dots

    SciTech Connect (OSTI)

    Stepina, N. P.; Dvurechenskii, A. V.; Nikiforov, A. I.; Moers, J.; Gruetzmacher, D.

    2014-08-20

    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.

  3. Magnetic field induced quantum dot brightening in liquid crystal synergized magnetic and semiconducting nanoparticle composite assemblies

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

    Amaral, Jose Jussi; Wan, Jacky; Rodarte, Andrea L.; Ferri, Christopher; Quint, Makiko T.; Pandolfi, Ronald J.; Scheibner, Michael; Hirst, Linda S.; Ghosh, Sayantani

    2014-10-22

    The design and development of multifunctional composite materials from artificial nano-constituents is one of the most compelling current research areas. This drive to improve over nature and produce ‘meta-materials’ has met with some success, but results have proven limited with regards to both the demonstration of synergistic functionalities and in the ability to manipulate the material properties post-fabrication and in situ. Here, magnetic nanoparticles (MNPs) and semiconducting quantum dots (QDs) are co-assembled in a nematic liquid crystalline (LC) matrix, forming composite structures in which the emission intensity of the quantum dots is systematically and reversibly controlled with a small appliedmore »magnetic field (« less

  4. 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)

    2014-10-15

    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.

  5. 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

    2009-06-03

    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.

  6. Test and evaluation document for DOT Specification 7A Type A Packaging. Revision 3

    SciTech Connect (OSTI)

    1996-01-30

    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. Spontaneous emission control of single quantum dots by electromechanical tuning of a photonic crystal cavity

    E-Print Network [OSTI]

    Midolo, L; Hoang, T B; Xia, T; van Otten, F W M; Li, L H; Linfield, E; Lermer, M; Höfling, S; Fiore, A

    2012-01-01

    We demonstrate the control of the spontaneous emission rate of single InAs quantum dots embedded in a double-membrane photonic crystal cavity by the electromechanical tuning of the cavity resonance. Controlling the separation between the two membranes with an electrostatic field we obtain the real-time spectral alignment of the cavity mode to the excitonic line and we observe an enhancement of the spontaneous emission rate at resonance. The cavity has been tuned over 13 nm without shifting the exciton energies. A spontaneous emission enhancement of 4.5 has been achieved with a coupling efficiency of the dot to the mode 92%.

  8. 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

    2006-04-06

    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.

  9. Safety analysis report for packaging: the ORNL DOT specification 6M - special form package

    SciTech Connect (OSTI)

    Schaich, R.W.

    1982-07-01

    The ORNL DOT Specification 6M - Special Form Package was fabricated at the Oak Ridge Nation al Laboratory (ORNL) for the transport of Type B solid non-fissile radioactive materials in special form. The package was evaluated on the basis of tests performed by the Dow Chemical Company, Rocky Flats Division, on the DOT-6M container and special form tests performed on a variety of stainless steel capsules at ORNL by Operations Division personnel. The results of these evaluations demonstrate that the package is in compliance with the applicable regulations for the transport of Type B quantities in special form of non-fissile radioactive materials.

  10. 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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantityBonneville Power AdministrationRobust,Field-effectWorkingLosThe 26th Annual ConferenceFall 2001, $$" .Find Report

  11. Improving PbS Quantum Dot Solar Cell Power Conversion Efficiency to an NREL-Certified 4.4% (Fact Sheet)

    SciTech Connect (OSTI)

    Not Available

    2012-01-01

    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.

  12. Multiobjective Optimization and Phase Transitions

    E-Print Network [OSTI]

    Seoane, Luís F

    2015-01-01

    Many complex systems obey to optimality conditions that are usually not simple. Conflicting traits often interact making a Multi Objective Optimization (MOO) approach necessary. Recent MOO research on complex systems report about the Pareto front (optimal designs implementing the best trade-off) in a qualitative manner. Meanwhile, research on traditional Simple Objective Optimization (SOO) often finds phase transitions and critical points. We summarize a robust framework that accounts for phase transitions located through SOO techniques and indicates what MOO features resolutely lead to phase transitions. These appear determined by the shape of the Pareto front, which at the same time is deeply related to the thermodynamic Gibbs surface. Indeed, thermodynamics can be written as an MOO from where its phase transitions can be parsimoniously derived; suggesting that the similarities between transitions in MOO-SOO and Statistical Mechanics go beyond mere coincidence.

  13. 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

    2009-11-09

    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.

  14. TiO2 Nanotubes with a ZnO Thin Energy Barrier for Improved Current Efficiency of CdSe Quantum-Dot-Sensitized Solar Cells

    SciTech Connect (OSTI)

    Lee, W.; Kang, S. H.; Kim, J. Y.; Kolekar, G. B.; Sung, Y. E.; Han, S. H.

    2009-01-01

    This paper reports the formation of a thin ZnO energy barrier between a CdSe quantum dot (Q dots) sensitizer and TiO{sub 2} nanotubes (TONTs) for improved current efficiency of Q dot-sensitized solar cells. The formation of a ZnO barrier between TONTs and the Q dot sensitizer increased the short-circuit current under illumination and also reduced the dark current in a dark environment. The power conversion efficiency of Q dot-sensitized TONT solar cells increased by 25.9% in the presence of the ZnO thin layer due to improved charge-collecting efficiency and reduced recombination.

  15. Spinfluid Phase Transitions

    E-Print Network [OSTI]

    Marcus S. Cohen

    2009-07-10

    We start with the spinfluid: a nearly-homogeneous, 8-spinor medium, with small local eddies and twists. As it expends, these seed a raft of intersecting codimension-J singularities: a spinfoam. As this expands, the energy trapped in each (4-J) brane varies as the Jth power of the scale factor. Summing on J=(0,1,2,3,4) creates a quartic dilation potential with either 1 or 2 minima: preferred length and mass scales. The spinfoam expands forever with 1 minimum, but recontracts with 2. To quantize it, we take a canonical ensemble of spinfoams, immersed in a heat bath of vacuum spinors, whose microstates vastly outnumber the matter states. It's evolution is governed by a free energy which admits phase transitions at two critical scale, separated by a triple point.Their critical droplets correspond to the varieties of leptons and hadrons.We identify the first as inflation, the second as baryogenesis; and the heat bath of vacuum spinors as dark energy.

  16. SunLine Transit Agency Fuel Cell Transit Bus: Fourth Evaluation...

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

    44646-2.pdf More Documents & Publications SunLine Transit Agency, Hydrogen-Powered Transit Buses: Preliminary Evaluation Results SunLine Transit Agency Fuel Cell Transit Bus:...

  17. Spectral multiplexing using quantum dot tagged microspheres with diffusing colloidal probe microscopy 

    E-Print Network [OSTI]

    Muthukumar, Shankarapandian

    2009-05-15

    Se/ZnS quantum dots is shown in Figure 11. A stirrer was connected to a stir bar made of aluminium to stir the reaction sample. A heating mantle filled with a bismuth alloy served as the heat bath. A temperature probe and controller were used to monitor...

  18. Photophysics of dopamine-modified quantum dots and effects on biological

    E-Print Network [OSTI]

    Minarik, William

    between a small molecule (the neurotransmitter dopamine) and CdSe/ZnS QDs. QD­dopamine conjugates label that has been studied extensively for the creation of solar cells and optoelectronic devices (see ref. 1 established with CdSe and CdSe/ZnS quantum dots (QDs)3­5 , its application to living systems has not yet been

  19. 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)

    2014-12-15

    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.

  20. Controlled placement of colloidal quantum dots in sub-15 nm clusters

    E-Print Network [OSTI]

    Han, Hee-Sun

    We demonstrated a technique to control the placement of 6 nm-diameter CdSe and 5 nm-diameter CdSe/CdZnS colloidal quantum dots (QDs) through electron-beam lithography. This QD-placement technique resulted in an average of ...

  1. Deep-level transient spectroscopy of InAs/GaAs quantum dot superlattices

    SciTech Connect (OSTI)

    Sobolev, M. M.; Nevedomskii, V. N.; Zolotareva, R. V.; Vasil'ev, A. P.; Ustinov, V. M.

    2014-02-21

    Deep level transient spectroscopy (DLTS) has been applied to study the carrier emission from states of a 10-layer system of tunnel-coupled vertically correlated quantum dots (VCQDs) in p-n InAs/GaAs heterostructures with different widths of GaAs spacers under varied reverse bias (U{sub r}) and filling voltage pulse U{sub f}.

  2. High-harmonic generation by quantum-dot nanorings Ioan Bldea,1,

    E-Print Network [OSTI]

    Moiseyev, Nimrod

    High-harmonic generation by quantum-dot nanorings Ioan Bâldea,1, * Ashish K. Gupta,2, Lorenz S with a circularly polarized light. The results show that the high-harmonic generation (HHG) spectra obtained from of the high-order harmonics is studied, and it is shown that it can increase the intensity of the high

  3. Shot noise in tunneling through a quantum dot array G. Kiesslich*; 1

    E-Print Network [OSTI]

    Hohls, Frank

    Shot noise in tunneling through a quantum dot array G. Kiesslich*; 1 , A. Wacker1 , E. Schæll1 , A 2003 PACS 72.70.+m, 73.40.Gk, 73.63.Kv The shot noise suppression in a sample containing a layer be qualitatively reproduced by an analy- tical expression. 1 Introduction Shot noise measurements provide

  4. Shot noise in tunneling through a single InAs quantum dot Frank Hohls

    E-Print Network [OSTI]

    Hohls, Frank

    Shot noise in tunneling through a single InAs quantum dot Frank Hohls , André Nauen , Niels Maire by measuring the shot noise of the current. We observe an approximately linear voltage dependence of both the shot noise, characterized by the Fano factor, and the tunneling current itself. We ascribe

  5. Shot noise in self-assembled InAs quantum dots A. Nauen,1,

    E-Print Network [OSTI]

    Hohls, Frank

    Shot noise in self-assembled InAs quantum dots A. Nauen,1, * I. Hapke-Wurst,1 F. Hohls,1 U. Zeitler Braunschweig, Germany Received 10 July 2002; published 4 October 2002 We investigate the noise properties-electron tunneling regime. We analyze the dependence of the relative noise amplitude of the shot noise on bias

  6. Quantum computation with moving quantum dots generated by surface acoustic waves

    E-Print Network [OSTI]

    X. Shi; M. Zhang; L. F. Wei

    2011-02-15

    Motivated by the recent experimental observations [M. Kataoka et al., Phys. Rev. Lett. {\\bf102}, 156801 (2009)], we propose here an theoretical approach to implement quantum computation with bound states of electrons in moving quantum dots generated by the driving of surface acoustic waves. Differing from static quantum dots defined by a series of static electrodes above the two-dimensional electron gas (2DEG), here a single electron is captured from a 2DEG-reservoir by a surface acoustic wave (SAW) and then trapped in a moving quantum dot (MQD) transporting across a quasi-one dimensional channel (Q1DC), wherein all the electrons have been excluded out by the actions of the surface gates. The flying qubit introduced here is encoded by the two lowest adiabatic levels of the electron in the MQD, and the Rabi oscillation between these two levels could be implemented by applying finely-selected microwave pulses to the surface gates. By using the Coulomb interaction between the electrons in different moving quantum dots, we show that a desirable two-qubit operation, i.e., i-SWAP gate, could be realized. Readouts of the present flying qubits are also feasible with the current single-electron detected technique.

  7. Micromagnetics Simulation of Asymmetric Pseudo-Spin Valve Dots C. A. Ross,2

    E-Print Network [OSTI]

    Donahue, Michael J.

    Micromagnetics Simulation of Asymmetric Pseudo-Spin Valve Dots N. Dao,1 C. A. Ross,2 F. J. Castaño)/Co (4nm) pseudo-spin valves. These simulations have been conducted on several different aspect ratios and pseudo-spin valves [2-4]. There have been recent reports of fabrication of pseudo-spin valves with sub

  8. 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

    2015-03-17

    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.

  9. Longitudinal wave function control in single quantum dots with an applied magnetic field

    E-Print Network [OSTI]

    Shuo Cao; Jing Tang; Yunan Gao; Yue Sun; Kangsheng Qiu; Yanhui Zhao; Min He; Jin-An Shi; Lin Gu; David A. Williams; Weidong Sheng; Kuijuan Jin; Xiulai Xu

    2015-01-29

    Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots.

  10. Spins in few-electron quantum dots Center for Spintronics and Quantum Computation, University of California,

    E-Print Network [OSTI]

    Zumbühl, Dominik

    Spins in few-electron quantum dots R. Hanson* Center for Spintronics and Quantum Computation these subjects are directly relevant for the fields of quantum information processing and spintronics with single spins i.e., single spintronics . DOI: 10.1103/RevModPhys.79.1217 PACS number s : 73.63.Kv, 03.67.Lx, 85

  11. 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

  12. Ultrafast Population Switching of Quantum Dots in a Structured Vacuum Xun Ma and Sajeev John

    E-Print Network [OSTI]

    John, Sajeev

    optical pulses in a 3D photonic band gap waveguide. This is the result of giant Mollow splitting caused. In a 3D PBG material with suitable waveguide architectures, the coherent coupling of Q dots to an external field can be made several orders of magnitudes stronger [11,12]. Strong light localization in 3D

  13. Lateral redistribution of excitons in CdSeZnSe quantum dots M. Strassburg,a)

    E-Print Network [OSTI]

    Nabben, Reinhard

    of quantum dot QD structures strongly depends on the growth conditions and the material system. Pronounced- neously QD ensemble we chose a system with well-known optical and structural properties.13­15 A single formed in a Stranski­Krastanow-like mode pro- vide for 3D confinement, i.e., QD states. Despite

  14. 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

  15. Tandem colloidal quantum dot solar cells employing a graded recombination layer

    E-Print Network [OSTI]

    Sargent, Edward H. "Ted"

    -based photodetectors1­5 and photovoltaic6­12 devices to be tailored. Multi-junction solar cells made from a combi- bandgap single-junction solar cells. In principle it also allows tandem and multi-junction cellsTandem colloidal quantum dot solar cells employing a graded recombination layer Xihua Wang1 , Ghada

  16. Quantum Interference Induced Photon Blockade in a Coupled Single Quantum Dot-Cavity System

    E-Print Network [OSTI]

    Jing Tang; Weidong Geng; Xiulai Xu

    2015-03-18

    We propose an experimental scheme to implement a strong photon blockade with a single quantum dot coupled to a nanocavity. The photon blockade effect can be tremendously enhanced by driving the cavity and the quantum dot simultaneously with two classical laser fields. This enhancement of photon blockade is ascribed to the quantum interference effect to avoid two-photon excitation of the cavity field. Comparing with Jaynes-Cummings model, the second-order correlation function at zero time delay $g^{(2)}(0)$ in our scheme can be reduced by two orders of magnitude and the system sustains a large intracavity photon number. A red (blue) cavity-light detuning asymmetry for photon quantum statistics with bunching or antibunching characteristics is also observed. The photon blockade effect has a controllable flexibility by tuning the relative phase between the two pumping laser fields and the Rabi coupling strength between the quantum dot and the pumping field. Moreover, the photon blockade scheme based on quantum interference mechanism does not require a strong coupling strength between the cavity and the quantum dot, even with the pure dephasing of the system. This simple proposal provides an effective way for potential applications in solid state quantum computation and quantum information processing.

  17. Excitonic enhancement of nonradiative energy transfer to bulk silicon with the hybridization of cascaded quantum dots

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Excitonic enhancement of nonradiative energy transfer to bulk silicon with the hybridization energy transfer to bulk silicon with the hybridization of cascaded quantum dots Aydan Yeltik,1 Burak sensitization of silicon through nonradiative energy transfer (NRET) of the excitons in an energy

  18. Color-tunable light emitting diodes based on quantum dot suspension

    E-Print Network [OSTI]

    Wu, Shin-Tson

    Color-tunable light emitting diodes based on quantum dot suspension Zhenyue Luo, Haiwei Chen, Yifan March 2015 We propose a color-tunable light emitting diode (LED) consisting of a blue LED as the light, rendering and metamerism; (230.3670) Light-emitting diodes. http://dx.doi.org/10.1364/AO.54.002845 1

  19. 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)

    2013-03-15

    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.

  20. Transport spectroscopy of disordered graphene quantum dots etched into a single graphene flake

    E-Print Network [OSTI]

    Zumbühl, Dominik

    Transport spectroscopy of disordered graphene quantum dots etched into a single graphene flake of sizes 45, 60 and 80 nm etched with an Ar/O2-plasma into a single graphene sheet, allowing a size comparison avoiding effects from different graphene flakes. The transport gaps and addition energies increase

  1. Whispering-Gallery Modes in Quantum Dot Embedded Microspheres for Sensing Applications 

    E-Print Network [OSTI]

    Beier, Hope T.

    2011-02-22

    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...

  2. 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

  3. Theoretical performance of solar cell based on mini-bands quantum dots

    SciTech Connect (OSTI)

    Aly, Abou El-Maaty M. E-mail: ashraf.nasr@gmail.com; Nasr, A. E-mail: ashraf.nasr@gmail.com

    2014-03-21

    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.

  4. Electric-field-controlled spin reversal in a quantum dot with ferromagnetic contacts

    E-Print Network [OSTI]

    Loss, Daniel

    realization of this tunnelling-induced spin splitting in a carbon-nanotube quantum dot coupled to ferromagnetic nickel electrodes with a strong tunnel coupling ensuring a sizeable exchange field. As charge and reversed merely by tuning the gate voltage. Since their discovery, carbon nanotubes (CNTs) have been

  5. Colloidal Quantum Dot Solar Cells Exploiting Hierarchical Structuring Andre J. Labelle,

    E-Print Network [OSTI]

    Sargent, Edward H. "Ted"

    -tuned CQDs offer the prospect of readily fabricated tandem and multijunction cells to provide improvedColloidal Quantum Dot Solar Cells Exploiting Hierarchical Structuring Andre J. Labelle, Susanna M: Extremely thin-absorber solar cells offer low materials utilization and simplified manufacture but require

  6. Solution-processed colloidal quantum dot photovoltaics: A perspective Ratan Debnath,a

    E-Print Network [OSTI]

    Sargent, Edward H. "Ted"

    ) photovol- taic devices offer considerable promise as a third-generation photovoltaic candidateInGaSe2, offer dramatically improved costs per square meter, but at the price of lower efficiencies. Third-generationSolution-processed colloidal quantum dot photovoltaics: A perspective Ratan Debnath,a Osman Bakrbc

  7. Optimal Deployment Plan of Emission Reduction Technologies for TxDOT's Construction Equipment 

    E-Print Network [OSTI]

    Bari, Muhammad Ehsanul

    2010-10-12

    -road equipment of TxDOT to reduce emissions in a cost effective and optimal manner. Three technologies were considered for deployment in this research, (1) hydrogen enrichment (HE), (2) selective catalytic reduction (SCR) and (3) fuel additive (FA... Gas ....................................................................... 24 Biodiesel ............................................................................ 24 Hydrogen...

  8. Spin waves in circular soft magnetic dots at the crossover between vortex and single domain state

    E-Print Network [OSTI]

    Metlushko, Vitali

    Facility, Cornell University, Ithaca, New York, 14853 USA 6Departamento de Fisica de Materiales We report on linear spin dynamics in the vortex state of Permalloy cylindrical dots subjected In many physical systems such as liquids, plasma, super- conductors, ferromagnets, etc., the topological

  9. Photometry and transit-timing analysis for eleven transiting exoplanets

    E-Print Network [OSTI]

    De Kleer, Katherine Rebecca

    2009-01-01

    This thesis presents time-series photometry of transits of 11 different extrasolar planets. Observations were conducted with the Fred L. Whipple Observatory 1.2m telescope and the Wise Observatory im telescope, in standard ...

  10. Power Marketing Administrations Leading the Nation's Transition...

    Energy Savers [EERE]

    Leading the Nation's Transition to a 21st Century Electric Grid Power Marketing Administrations Leading the Nation's Transition to a 21st Century Electric Grid November 19, 2012 -...

  11. Detecting quantum-coherent nanomechanical oscillations using the current-noise spectrum of a double quantum dot

    E-Print Network [OSTI]

    Neill Lambert; Franco Nori

    2008-12-17

    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.

  12. Feeding the Transition Dairy Cow 

    E-Print Network [OSTI]

    Stokes, Sandra R.

    1999-09-20

    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...

  13. Toxicological studies of semiconductor quantum dots on immune cells.

    SciTech Connect (OSTI)

    Ricken, James Bryce; Rios, Lynette; Poschet, Jens Fredrich; Bachand, Marlene; Bachand, George David; Greene, Adrienne Celeste; Carroll-Portillo, Amanda

    2008-11-01

    Nanoengineered materials hold a vast promise of enabling revolutionary technologies, but also pose an emerging and potentially serious threat to human and environmental health. While there is increasing knowledge concerning the risks posed by engineered nanomaterials, significant inconsistencies exist within the current data based on the high degree of variability in the materials (e.g., synthesis method, coatings, etc) and biological test systems (e.g., cell lines, whole organism, etc). In this project, we evaluated the uptake and response of two immune cell lines (RAW macrophage and RBL mast cells) to nanocrystal quantum dots (Qdots) with different sizes and surface chemistries, and at different concentrations. The basic experimental design followed a 2 x 2 x 3 factorial model: two Qdot sizes (Qdot 520 and 620), two surface chemistries (amine 'NH{sub 2}' and carboxylic acid 'COOH'), and three concentrations (0, 1 nM, and 1 {micro}M). Based on this design, the following Qdots from Evident Technologies were used for all experiments: Qdot 520-COOH, Qdot 520-NH{sub 2}, Qdot 620-COOH, and Qdot 620-NH{sub 2}. Fluorescence and confocal imaging demonstrated that Qdot 620-COOH and Qdot 620-NH{sub 2} nanoparticles had a greater level of internalization and cell membrane association in RAW and RBL cells, respectively. From these data, a two-way interaction between Qdot size and concentration was observed in relation to the level of cellular uptake in RAW cells, and association with RBL cell membranes. Toxicity of both RBL and RAW cells was also significantly dependent on the interaction of Qdot size and concentration; the 1 {micro}M concentrations of the larger, Qdot 620 nanoparticles induced a greater toxic effect on both cell lines. The RBL data also demonstrate that Qdot exposure can induce significant toxicity independent of cellular uptake. A significant increase in TNF-{alpha} and decrease in IL-10 release was observed in RAW cells, and suggested that Qdot exposure induced a pro-inflammatory response. In contrast, significant decreases in both TNF-{alpha} and IL-4 releases were observed in RBL cells, which is indicative of a suppressed inflammatory response. The changes in cytokine release observed in RAW and RBL cells were primarily dependent on Qdot concentration and independent of size and surface chemistry. Changes in the activity of superoxide dismutase were observed in RAW, but not RBL cells, suggesting that RAW cells were experiencing oxidative stress induced by Qdot exposure. Overall, our results demonstrate that the uptake/association and biomolecular response of macrophage and mast cells is primarily driven by an interaction between Qdot size and concentration. Based on these findings, a more detailed understanding of how size directly impacts cellular interactions and response will be critical to developing predictive models of Qdot toxicity.

  14. Quantum Dot Targeting with Lipoic Acid Ligase and HaloTag for Single-Molecule Imaging on Living Cells

    E-Print Network [OSTI]

    Liu, Daniel S.

    We present a methodology for targeting quantum dots to specific proteins on living cells in two steps. In the first step, Escherichia coli lipoic acid ligase (LplA) site-specifically attaches 10-bromodecanoic acid onto a ...

  15. Selective turn-on fluorescence detection of cyanide in water using hydrophobic CdSe quantum dots 

    E-Print Network [OSTI]

    Dryden D.T.F.; Mareque-Rivas J.C.; Galve-Gasion J.A.; Stevenson E.I.; Touceda-Varela A.

    2008-05-01

    The ability of 2,2'-bipyridine-bound copper(II) ions to quench the photoluminescence of hydrophobic CdSe quantum dots is used to create a novel, selective turn-on fluorescence cyanide sensor.

  16. Self-interaction-free density-functional theoretical study of the electronic structure of spherical and vertical quantum dots

    E-Print Network [OSTI]

    Jiang, T. F.; Tong, Xiao-Min; Chu, Shih-I

    2001-01-09

    We study the electronic structure and shell-filling effects of both spherical and vertical quantum dots by means of the density functional theory (DFT) with optimized effective potential (OEP) and self-interaction-correction (SIC) recently developed...

  17. Optical studies of colloidal quantum dots : optical trapping with plasmonic nanoapertures and thermal recovery from photoinduced dimming

    E-Print Network [OSTI]

    Jensen, Russell Andrew

    2015-01-01

    This doctoral research has been defined by two main goals. The first has been to develop single colloidal quantum dot (QD) absorption as a new spectroscopic tool for investigating single QD electronic properties, dynamics, ...

  18. Layer-by-layer surface manipulation and biointegration of quantum dots : assembly of nanostructured DNA delivery vehicles

    E-Print Network [OSTI]

    Jaffar, Saeeda Mahdi

    2005-01-01

    Objectives: The aims of this investigation are to (i) prepare hybrid quantum dot (QD)-polymer compleses, (ii) maniplulate structural and chemical properties of the hybrids and characterize their effects on biocompatibility, ...

  19. 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

  20. Gray, W. D. (2008). Cognitive modeling for cognitive engineering. In R. Sun (Ed.), The Cambridge handbook of computational psychology (pp. 565-588). New York: Cambridge University Press. Page 1

    E-Print Network [OSTI]

    Gray, Wayne

    2008-01-01

    Gray, W. D. (2008). Cognitive modeling for cognitive engineering. In R. Sun (Ed.), The Cambridge is the degree to which we have developed robust and powerful theories. The degree to which we fail at this task. (2008). Cognitive modeling for cognitive engineering. In R. Sun (Ed.), The Cambridge handbook

  1. Microsphere Light-Scattering Layer Assembled by ZnO Nanosheets for the Construction of High Efficiency (>5%) Quantum Dots

    E-Print Network [OSTI]

    Cao, Guozhong

    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. As a result, the solar cell displayed Jsc of 17.13 mA/cm2 , Voc of 0.56 V, FF of 0.53, and PCE of 5.08%, one

  2. Hubble's View of Transiting Planets

    E-Print Network [OSTI]

    David Charbonneau

    2004-10-27

    The Hubble Space Telescope is uniquely able to study planets that are observed to transit their parent stars. The extremely stable platform afforded by an orbiting spacecraft, free from the contaminating effects of the Earth's atmosphere, enables HST to conduct ultra-high precision photometry and spectroscopy of known transiting extrasolar planet systems. Among HST's list of successful observations of the first such system, HD 209458, are (1) the first detection of the atmosphere of an extrasolar planet, (2) the determination that gas is escaping from the planet, and (3) a search for Earth-sized satellites and circumplanetary rings. Numerous wide-field, ground-based transit surveys are poised to uncover a gaggle of new worlds for which HST may undertake similar studies, such as the newly-discovered planet TrES-1. With regard to the future of Hubble, it must be noted that it is the only observatory in existence capable of confirming transits of Earth-like planets that may be detected by NASA's Kepler mission. Kepler could reveal Earth-like transits by the year 2010, but without a servicing mission it is very unlikely that HST would still be in operation.

  3. 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)

    2014-10-13

    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.

  4. 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.; Sadeghi, Seyed M.; Mao, Chuanbin

    2014-09-21

    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.

  5. Vanishing fine structure splittings in telecom wavelength quantum dots grown on (111)A surfaces by droplet epitaxy

    E-Print Network [OSTI]

    X. Liu; N. Ha; H. Nakajima; T. Mano; T. Kuroda; B. Urbaszek; H. Kumano; I. Suemune; Y. Sakuma; K. Sakoda

    2014-06-18

    The emission cascade of a single quantum dot is a promising source of entangled photons. A prerequisite for this source is the use of a symmetric dot analogous to an atom in a vacuum, but the simultaneous achievement of structural symmetry and emission in a telecom band poses a challenge. Here we report the growth and characterization of highly symmetric InAs/InAlAs quantum dots self-assembled on C3v symmetric InP(111)A. The broad emission spectra cover the O (1.3 micron-m), C (1.55 micron-m), and L (1.6 micron-m) telecom bands. The distribution of the fine-structure splittings is considerably smaller than those reported in previous works on dots at similar wavelengths. The presence of dots with degenerate exciton lines is further confirmed by the optical orientation technique. Thus, our dot systems are expected to serve as efficient entangled photon emitters for long-distance fiber-based quantum key distribution.

  6. 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.; Shuvayev, Vladimir; Deligiannakis, Vasilios; Tamargo, Maria C.; Ludwig, Jonathan; Smirnov, Dmitry; Wang, Alice

    2014-10-28

    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.

  7. Adhesion Transition of Flexible Sheets

    E-Print Network [OSTI]

    Arthur A. Evans; Eric Lauga

    2009-05-31

    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.

  8. Comparative Habitability of Transiting Exoplanets

    E-Print Network [OSTI]

    Barnes, Rory; Evans, Nicole

    2015-01-01

    Exoplanet habitability is traditionally assessed by comparing a planet's semi-major axis to the location of its host star's "habitable zone," the shell around a star for which Earth-like planets can possess liquid surface water. The Kepler space telescope has discovered numerous planet candidates near the habitable zone, and many more are expected from missions such as K2, TESS and PLATO. These candidates often require significant follow-up observations for validation, so prioritizing planets for habitability from transit data has become an important aspect of the search for life in the universe. We propose a method to compare transiting planets for their potential to support life based on transit data, stellar properties and previously reported limits on planetary emitted flux. For a planet in radiative equilibrium, the emitted flux increases with eccentricity, but decreases with albedo. As these parameters are often unconstrained, there is an "eccentricity-albedo degeneracy" for the habitability of transiti...

  9. Intrinsic phonon decoherence and quantum gates in coupled lateral quantum dot charge qubits

    E-Print Network [OSTI]

    Markus J. Storcz; Udo Hartmann; Sigmund Kohler; Frank K. Wilhelm

    2005-07-28

    Recent experiments by Hayashi et al. [Phys. Rev. Lett. 91, 226804 (2003)] demonstrate coherent oscillations of a charge quantum bit (qubit) in laterally defined quantum dots. We study the intrinsic electron-phonon decoherence and gate performance for the next step: a system of two coupled charge qubits. The effective decoherence model contains properties of local as well as collective decoherence. Decoherence channels can be classified by their multipole moments, which leads to different low-energy spectra. It is shown that due to the super-Ohmic spectrum, the gate quality is limited by the single-qubit Hadamard gates. It can be significantly improved, by using double-dots with weak tunnel coupling.

  10. Surface acoustic wave controlled carrier injection into self-assembled quantum dots and quantum posts

    E-Print Network [OSTI]

    Hubert J. Krenner; Stefan Völk; Florian J. R. Schülein; Florian Knall; Achim Wixforth; Dirk Reuter; Andreas D. Wieck; Hyochul Kim; Tuan A. Truong; Pierre M. Petroff

    2011-10-20

    We report on recent progress in the acousto-electrical control of self-assembled quantum dot and quantum post using radio frequency surface acoustic waves (SAWs). We show that the occupancy state of these optically active nanostructures can be controlled via the SAW-induced dissociation of photogenerated excitons and the resulting sequential bipolar carrier injection which strongly favors the formation of neutral excitons for quantum posts in contrast to conventional quantum dots. We demonstrate high fidelity preparation of the neutral biexciton which makes this approach suitable for deterministic entangled photon pair generation. The SAW driven acoustic charge conveyance is found to be highly efficient within the wide quantum well surrounding the quantum posts. Finally we present the direct observation of acoustically triggered carrier injection into remotely positioned, individual quantum posts which is required for a low-jitter SAW-triggered single photon source.

  11. 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

    2011-01-01

    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.

  12. 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)

    2014-03-17

    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.

  13. Exciton fine-structure splitting of telecom wavelength single quantum dots: statistics and external strain tuning

    E-Print Network [OSTI]

    Luca Sapienza; Ralph N. E. Malein; Christopher E. Kuklewicz; Peter E. Kremer; Kartik Srinivasan; Andrew Griffiths; Edmund Clarke; Ming Gong; Richard J. Warburton; Brian D. Gerardot

    2013-09-18

    In a charge tunable device, we investigate the fine structure splitting of neutral excitons in single long-wavelength (1.1\\mu m eV are measured and manipulated. We observe varied response of the splitting to the external strain, including positive and negative tuning slopes, different tuning ranges, and linear and parabolic dependencies, indicating that these physical parameters depend strongly on the unique microscopic structure of the individual quantum dot. To better understand the experimental results, we apply a phenomenological model describing the exciton polarization and fine-structure splitting under uniaxial strain. The model predicts that, with an increased experimental strain tuning range, the fine-structure can be effectively canceled for select telecom wavelength dots using uniaxial strain. These results are promising for the generation of on-demand entangled photon pairs at telecom wavelengths.

  14. Final LDRD report : infrared detection and power generation using self-assembled quantum dots.

    SciTech Connect (OSTI)

    Cederberg, Jeffrey George; Ellis, Robert; Shaner, Eric Arthur

    2008-02-01

    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.

  15. 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)

    2014-10-21

    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.

  16. Controlling circular polarization of light emitted by quantum dots using chiral photonic crystal slab

    E-Print Network [OSTI]

    Lobanov, S V; Gippius, N A; Maksimov, A A; Filatov, E V; Tartakovskii, I I; Kulakovskii, V D; Weiss, T; Schneider, C; Geßler, J; Kamp, M; Höfling, S

    2015-01-01

    Polarization properties of the emission have been investigated for quantum dots embedded in chiral photonic crystal structures made of achiral planar GaAs waveguides. A modification of the electromagnetic mode structure due to the chiral grating fabricated by partial etching of the waveguide layer has been shown to result in a high circular polarization degree $\\rho_c$ of the quantum dot emission in the absence of external magnetic field. The physical nature of the phenomenon can be understood in terms of the reciprocity principle taking into account the structural symmetry. At the resonance wavelength, the magnitude of $|\\rho_c|$ is predicted to exceed 98%. The experimentally achieved value of $|\\rho_c|=81$% is smaller, which is due to the contribution of unpolarized light scattered by grating defects, thus breaking its periodicity. The achieved polarization degree estimated removing the unpolarized nonresonant background from the emission spectra can be estimated to be as high as 96%, close to the theoretic...

  17. 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

    2015-04-14

    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.

  18. Coherent control and interplay of three-electron spin states in a triple quantum dot

    E-Print Network [OSTI]

    Gaudreau, L; Kam, A; Aers, G C; Studenikin, S A; Zawadzki, P; Pioro-Ladrière, M; Wasilewski, Z R; Sachrajda, A S

    2011-01-01

    Spin qubits involving one or two spins have emerged as potential building blocks for quantum information processing applications, resulting in many double quantum dot (DQD) studies. Coherent control of a two-electron spin qubit close to the singlet/triplet (S/T+) anticrossing through Landau-Zener-St\\"uckelberg (LZS) oscillations has been studied theoretically and demonstrated experimentally in DQDs. Recent advances with triple quantum dot (TQD) technology have suggested additional advantages, such as their potential for encoding quantum information, that may soon be possible. Towards these goals we demonstrate, for for first time, the coherent manipulation of three-particle spin states in a TQD where all three spins play a role.

  19. Inverted Singlet-Triplet Qubit Coded on a Two-Electron Double Quantum Dot

    E-Print Network [OSTI]

    Sebastian Mehl; David P. DiVincenzo

    2014-11-26

    The $s_z=0$ spin configuration of two electrons confined at a double quantum dot (DQD) encodes the singlet-triplet qubit (STQ). We introduce the inverted STQ (ISTQ) that emerges from the setup of two quantum dots (QDs) differing significantly in size and out-of-plane magnetic fields. The strongly confined QD has a two-electron singlet ground state, but the weakly confined QD has a two-electron triplet ground state in the $s_z=0$ subspace. Spin-orbit interactions act nontrivially on the $s_z=0$ subspace and provide universal control of the ISTQ together with electrostatic manipulations of the charge configuration. GaAs and InAs DQDs can be operated as ISTQs under realistic noise conditions.

  20. Tuning photoluminescence of reduced graphene oxide quantum dots from blue to purple

    SciTech Connect (OSTI)

    Liu, Fuchi; Tang, Tao; Feng, Qian; Li, Ming; Liu, Yuan; Tang, Nujiang Zhong, Wei; Du, Youwei

    2014-04-28

    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.