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1

Success Stories: Quantum Dots  

NLE Websites -- All DOE Office Websites (Extended Search)

Quantum Dots Outshine the Competition for Biomedical Assays Quantum Dots Outshine the Competition for Biomedical Assays Quantum Dots (Qdots), nano-scale semiconductor crystals that emit a range of bright colors when excited by a light source such as a laser, are shining brightly these days. The Berkeley Lab developed technology has been licensed by Quantum Dot Corporation and is being used as fluorescence probes for biomedical assays. The technology just won an R & D 100 Award and Quantum Dot Corporation was named by Fortune magazine as one of 2004's "Cool Companies." Science honored the technology as one of the Top 10 Breakthroughs of the Year in 2003, and Nanotechnology Now named Quantum Dots as the Best Nanotech Product in 2003, among other honors. Quantum Dot Corporation (QDC) is a 1998 start-up biotechnology company

2

Quantum dot cascade laser  

Science Journals Connector (OSTI)

We demonstrated an unambiguous quantum dot cascade laser based on InGaAs/GaAs/InAs/InAlAs heterostructure by making use of self-assembled quantum dots in the Stranski-Krastanow growth mode...??~?6.15 ?m and a bro...

Ning Zhuo; Feng Qi Liu; Jin Chuan Zhang; Li Jun Wang…

2014-03-01T23:59:59.000Z

3

Quantum dot device tunable from single to triple dot system  

SciTech Connect

We present a lateral quantum dot device which has a tunable number of quantum dots. Depending on easily tunable gate voltages, one, two or three quantum dots are found. They are investigated in transport and charge detection.

Rogge, M. C.; Haug, R. J. [Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstrasse 2, 30167 Hannover (Germany); Pierz, K. [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)

2013-12-04T23:59:59.000Z

4

Quantum Dots in Graphene  

Science Journals Connector (OSTI)

We suggest a way of confining quasiparticles by an external potential in a small region of a graphene strip. Transversal electron motion plays a crucial role in this confinement. Properties of thus obtained graphene quantum dots are investigated theoretically for different types of the boundary conditions at the edges of the strip. The (quasi)bound states exist in all systems considered. At the same time, the dependence of the conductance on the gate voltage carries information about the shape of the edges.

P. G. Silvestrov and K. B. Efetov

2007-01-03T23:59:59.000Z

5

Shiny quantum dots brighten future of solar cells  

NLE Websites -- All DOE Office Websites (Extended Search)

Shiny quantum dots brighten future of solar cells Shiny quantum dots brighten future of solar cells The project demonstrates that superior light-emitting properties of quantum dots...

6

Thick-Shell Nanocrystal Quantum Dots  

NLE Websites -- All DOE Office Websites (Extended Search)

Thick-Shell Nanocrystal Quantum Dots Thick-Shell Nanocrystal Quantum Dots Thick-Shell Nanocrystal Quantum Dots Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous excitation conditions for a period of time of at least 10 minutes. Available for thumbnail of Feynman Center (505) 665-9090 Email Thick-Shell Nanocrystal Quantum Dots Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous

7

All inorganic colloidal quantum dot LEDs  

E-Print Network (OSTI)

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 ...

Wood, Vanessa Claire

2007-01-01T23:59:59.000Z

8

CNM Highlight: Quantum Dot-Induced Transparency  

NLE Websites -- All DOE Office Websites (Extended Search)

Quantum Dot-Induced Transparency Quantum Dot-Induced Transparency Using rigorous and realistic numerical simulations, staff in the Nanophotonics and Theory and Modeling groups have recently demonstrated that a single semiconductor nanocrystal, or quantum dot, can cancel the scattering and absorption by a much larger metal nanostructure. Placing a quantum dot near a metal is known to strongly modify the rate at which the dot emits light. If the interaction between the dot and the metal is strong enough, scattering and absorption by the metal can be nearly eliminated at the quantum-dot resonance frequency, according to the simulations. This occurs even though the dot by itself simply absorbs light, and even though this absorption is nearly 100,000 times smaller than absorption by the metal nanostructure.

9

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

SciTech Connect

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

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

2014-02-14T23:59:59.000Z

10

Nanoscale engineering boosts performance of quantum dot light...  

NLE Websites -- All DOE Office Websites (Extended Search)

engineering boosts performance of quantum dot light emitting diodes Quantum dots are nano-sized semiconductor particles whose emission color can be tuned by simply changing...

11

Temperature-Dependent Electron Transport in Quantum Dot Photovoltaics  

E-Print Network (OSTI)

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

Padilla, Derek

2013-01-01T23:59:59.000Z

12

Synthesis and characterization of infrared quantum dots  

E-Print Network (OSTI)

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 ...

Harris, Daniel Kelly

2014-01-01T23:59:59.000Z

13

Fast quantum dot single photon source triggered at telecommunications wavelength  

E-Print Network (OSTI)

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

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

2010-12-01T23:59:59.000Z

14

Double quantum dot as a minimal thermoelectric generator  

Science Journals Connector (OSTI)

Based on numerical renormalization group calculations, we demonstrate that experimentally realized double quantum dots constitute a minimal thermoelectric generator. In the Kondo regime, one quantum dot acts as an n-type and the other one as a p-type thermoelectric device. Properly connected, a capacitively coupled double quantum dot provides a miniature power supply utilizing the thermal energy of the environment.

S. Donsa; S. Andergassen; K. Held

2014-03-05T23:59:59.000Z

15

Scalable quantum computer architecture with coupled donor-quantum dot qubits  

DOE Patents (OSTI)

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.

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

2014-08-26T23:59:59.000Z

16

Bilayer graphene quantum dot defined by topgates  

SciTech Connect

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.

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

2014-06-21T23:59:59.000Z

17

Synthesis of CdSe quantum dots for quantum dot sensitized solar cell  

SciTech Connect

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

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

2014-04-24T23:59:59.000Z

18

Chemically graftedChemically grafted nanoparticlesnanoparticles Quantum dot Nanoparticle  

E-Print Network (OSTI)

Chemically graftedChemically grafted nanoparticlesnanoparticles Quantum dot Nanoparticle (~ 5nm Pb atomic force microscope tip: tether nanoparticle to oxide dot, or H-terminated pit after HF etch Ebeam

Plotkin, Steven S.

19

Electric Field effects on quantum correlations in semiconductor quantum dots  

E-Print Network (OSTI)

We study the effect of external electric bias on the quantum correlations in the array of optically excited coupled semiconductor quantum dots. The correlations are characterized by the quantum discord and concurrence and are observed using excitonic qubits. We employ the lower bound of concurrence for thermal density matrix at different temperatures. The effect of the F\\"orster interaction on correlations will be studied. Our theoretical model detects nonvanishing quantum discord when the electric field is on while concurrence dies, ensuring the existence of nonclassical correlations as measured by the quantum discord.

S. Shojaei; M. Mahdian; R. Yousefjani

2012-05-01T23:59:59.000Z

20

Folded-Light-Path Colloidal Quantum Dot Solar Cells  

E-Print Network (OSTI)

Folded-Light-Path Colloidal Quantum Dot Solar Cells Ghada I. Koleilat*, Illan J. Kramer*, Chris T, Canada. Colloidal quantum dot photovoltaics combine low-cost solution processing with quantum size-effect tuning to match absorption to the solar spectrum. Rapid advances have led to certified solar power

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Photonic Crystal and III-N Quantum Dot Lasers  

Science Journals Connector (OSTI)

Deep UV light emitting devices are important for future medical, environmental and IT applications. Generation of DUV light using quantum dots GaN-related materials and nonlinear...

Aoyagi, Yoshinobu; Inoue, Shinichiro; Takeuchi, Misaichi; Kawasaki, Koji; Hirayama, Hideki

22

Feature issue introduction: quantum dots for photonic applications  

Science Journals Connector (OSTI)

Quantum dots (QDs) are semiconductor nanocrystals with peculiar optoelectronic properties. Their wide application in light-emitting diodes, solar cells, and the medical and defense...

Lee, Kwang-Sup; Prasad, Paras N; Huyet, Guillaume; Tan, Chee Hing

2012-01-01T23:59:59.000Z

23

Solution-Processed Solar Cells using Colloidal Quantum Dots ...  

NLE Websites -- All DOE Office Websites (Extended Search)

of solar cells and light sensors based on solution-processed semiconductors." He is a Fellow of the IEEE "... for contributions to colloidal quantum dot optoelectronic devices."...

24

Microfluidic self-assembly of quantum dot compound micelles.  

E-Print Network (OSTI)

??This thesis is devoted to the development of microfluidic processes for the controlled self-assembly of quantum dot compound micelles (QDCMs). Microfluidic processes are developed to… (more)

Schabas, Greg

2007-01-01T23:59:59.000Z

25

Quantum Dot Tracers for Use in Engineered Geothermal  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

tracers, colloidal quantum dots, that offer great promise for use in characterizing fracture networks in EGS reservoirs. Since the wavelength of fluorescence (color) of these...

26

Quantum Dot Tracers for Use in Engineered Geothermal | Department...  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

tracerspeer2013.pdf More Documents & Publications Tracer Methods for Characterizing Fracture Stimulation in Engineered Geothermal Systems (EGS) Quantum Dot Tracers for Use in...

27

Quantum Dot Tracers for Use in Engineered Geothermal Systems...  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

nanoparticles(quantum dots)that offer great promise for use in characterizing fracture networks in EGS reservoirs. tracersrosequantumdot.pdf More Documents &...

28

Quantum dot nanoparticle conjugation, characterization, and applications in neuroscience  

E-Print Network (OSTI)

Characterization of nanoparticle labeling tools for neuralCALIFORNIA, SAN DIEGO Quantum Dot Nanoparticle Conjugation,resulting in aggregation of nanoparticle-antibody conjugates

Pathak, Smita

2008-01-01T23:59:59.000Z

29

Unraveling the mystery of quantum-dot blinking  

NLE Websites -- All DOE Office Websites (Extended Search)

mystery of quantum-dot blinking Research enhances single particle tracking, allows novel light-emitting diodes, and boosts development of new solar cells. April 3, 2012 Artists...

30

Temperature-Dependent Electron Transport in Quantum Dot Photovoltaics.  

E-Print Network (OSTI)

??Quantum dot photovoltaics have attracted much interest from researchers in recent years. They have the potential to address both costs and efficiencies of solar cells… (more)

Padilla, Derek

2013-01-01T23:59:59.000Z

31

Photovoltaic performance of ultra-small PbSe quantum dots  

E-Print Network (OSTI)

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

Ma, Wanli

2014-01-01T23:59:59.000Z

32

POSSIBLE DEFINTION OF QUANTUM BITS IN COUPLED QUANTUM DOTS  

E-Print Network (OSTI)

by applying transport spectroscopy at ultra low temperatures. We determine the strength of this tunnel coupled quantum dot ­ coupled to leads by tunneling barriers. Due to the ultra small capacitance the Coulomb be operated at temperatures of some 10 mK [1], but by now operation of metallic SETs at temperatures up to 100

Ludwig-Maximilians-Universität, München

33

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

E-Print Network (OSTI)

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

Scully, Marlan O

2010-01-01T23:59:59.000Z

34

NREL: News - NREL and Partners Demonstrate Quantum Dots that Assemble  

NLE Websites -- All DOE Office Websites (Extended Search)

113 113 NREL and Partners Demonstrate Quantum Dots that Assemble Themselves Surprising breakthrough could bolster quantum photonics, solar cell efficiency February 8, 2013 Scientists from the U.S. Department of Energy's National Renewable Energy Laboratory and other labs have demonstrated a process whereby quantum dots can self-assemble at optimal locations in nanowires, a breakthrough that could improve solar cells, quantum computing, and lighting devices. A paper on the new technology, "Self-assembled Quantum Dots in a Nanowire System for Quantum Photonics," appears in the current issue of the scientific journal Nature Materials. Quantum dots are tiny crystals of semiconductor a few billionths of a meter in diameter. At that size they exhibit beneficial behaviors of quantum

35

Numerical simulation of optical feedback on a quantum dot lasers  

SciTech Connect

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.

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)

2012-02-15T23:59:59.000Z

36

Oxygen Reduction Catalyzed by Platinum Nanoparticles Supported on Graphene Quantum Dots  

Science Journals Connector (OSTI)

graphene quantum dot; platinum nanoparticle; oxygen reduction; defect; X-ray diffraction; XPS; Tafel plot ...

Guoqiang He; Yang Song; Ke Liu; Andrew Walter; Sophie Chen; Shaowei Chen

2013-03-19T23:59:59.000Z

37

Optimal tunneling enhances the quantum photovoltaic effect in double quantum dots  

E-Print Network (OSTI)

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, ...

Wang, Chen

38

Radiative Decay Engineering of Direct Bandgap Emission in Silver Ion-Implanted Polarized Silicon Quantum Dots  

Science Journals Connector (OSTI)

Emission from low energy Silver ion implanted crystalline silicon quantum dots can be enhanced due to enhanced radiative recombination induced by polarization of the dots and metal...

Singh, Akhilesh; Gryczynski, Karol; Neogi, Arup; Kim, Moon

39

Lighting Up Individual DNA Binding Proteins with Quantum Dots  

Science Journals Connector (OSTI)

Lighting Up Individual DNA Binding Proteins with Quantum Dots ... Department of Chemistry and Biochemistry, DOE Institute for Genomics and Proteomics, and Department of Physiology, Geffen Medical School, UCLA, Los Angeles, California 90095 ...

Yuval Ebenstein; Natalie Gassman; Soohong Kim; Josh Antelman; Younggyu Kim; Sam Ho; Robin Samuel; Xavier Michalet; Shimon Weiss

2009-03-16T23:59:59.000Z

40

C3Bio.org - Resources: Quantum Dot Lab: Usage  

NLE Websites -- All DOE Office Websites (Extended Search)

.png, .gif) Submit You are here: Home Resources Tools Quantum Dot Lab Usage 0 questions (Ask a question) 0 review(s) (Review this) 15 users, detailed usage 0...

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Optoelectronic and photonic control of single quantum dots  

E-Print Network (OSTI)

Optoelectronic and photonic control of single quantum dots Samuel James Dewhurst Wolfson College University of Cambridge A thesis submitted for the degree of Doctor of Philosophy April 2010 Declaration This thesis describes work carried out...

Dewhurst, Samuel James

2010-10-12T23:59:59.000Z

42

Fluorescence from a quantum dot and metallic nanosphere hybrid system  

SciTech Connect

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.

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

2014-03-31T23:59:59.000Z

43

Effect of carrier dynamics and temperature on two-state lasing in semiconductor quantum dot lasers  

SciTech Connect

It is analytically shown that the both the charge carrier dynamics in quantum dots and their capture into the quantum dots from the matrix material have a significant effect on two-state lasing phenomenon in quantum dot lasers. In particular, the consideration of desynchronization in electron and hole capture into quantum dots allows one to describe the quenching of ground-state lasing observed at high injection currents both qualitatevely and quantitatively. At the same time, an analysis of the charge carrier dynamics in a single quantum dot allowed us to describe the temperature dependences of the emission power via the ground- and excited-state optical transitions of quantum dots.

Korenev, V. V., E-mail: korenev@spbau.ru; Savelyev, A. V.; Zhukov, A. E.; Omelchenko, A. V.; Maximov, M. V. [Saint Petersburg Academic University-Nanotechnology Research and Education Center (Russian Federation)] [Saint Petersburg Academic University-Nanotechnology Research and Education Center (Russian Federation)

2013-10-15T23:59:59.000Z

44

THE FABRICATION AND ANALYSIS OF QUANTUM-DOT THIN FILM LIGHT EMITTING DIODES FOR USE IN DISPLAYS TECHNOLOGIES.  

E-Print Network (OSTI)

??The quantum dot has many applications, one of which is the light emitting diode. Quantum dot light emitting diodes were fabricated for their use in… (more)

Pickering, Shawn

2011-01-01T23:59:59.000Z

45

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

E-Print Network (OSTI)

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 ...

Song, Katherine Wei

2013-01-01T23:59:59.000Z

46

InAs/GaAs Quantum-Dot Intermediate-Band Solar Cells  

Science Journals Connector (OSTI)

Results for quantum-dot intermediate-band solar cells are presented. It is shown that quantum dots in conventional p-i-n structures can extend the photoresponse to 1300 nm, well...

Grenko, Alysha; Kimukin, Ibrahim; Walker, John; Towe, Elias

47

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

DOE Patents (OSTI)

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.

Forrest, Stephen R. (Ann Arbor, MI)

2008-08-19T23:59:59.000Z

48

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

E-Print Network (OSTI)

vacuum technology that is required in crystalline solar cellTechnologies, Inc. “SolarWindow” Quantum Dot Solar Cells

Leow, Shin Woei

2014-01-01T23:59:59.000Z

49

Quantum interference in exciton-Mn spin interactions in a CdTe semiconductor quantum dot  

E-Print Network (OSTI)

We show theoretically and experimentally the existence of a new quantum interference(QI) effect between the electron-hole interactions and the scattering by a single Mn impurity. Theoretical model, including electron-valence hole correlations, the short and long range exchange interaction of Mn ion with the heavy hole and with electron and anisotropy of the quantum dot, is compared with photoluminescence spectroscopy of CdTe dots with single magnetic ions. We show how design of the electronic levels of a quantum dot enable the design of an exciton, control of the quantum interference and hence engineering of light-Mn interaction.

Trojnar, A; Kadantsev, E; Hawrylak, P; Goryca, M; Kazimierczuk, T; Kossacki, P; Wojnar, P; Potemski, M

2011-01-01T23:59:59.000Z

50

Quantum interference in exciton-Mn spin interactions in a CdTe semiconductor quantum dot  

E-Print Network (OSTI)

We show theoretically and experimentally the existence of a new quantum interference(QI) effect between the electron-hole interactions and the scattering by a single Mn impurity. Theoretical model, including electron-valence hole correlations, the short and long range exchange interaction of Mn ion with the heavy hole and with electron and anisotropy of the quantum dot, is compared with photoluminescence spectroscopy of CdTe dots with single magnetic ions. We show how design of the electronic levels of a quantum dot enable the design of an exciton, control of the quantum interference and hence engineering of light-Mn interaction.

A. Trojnar; M. Korkusinski; E. Kadantsev; P. Hawrylak; M. Goryca; T. Kazimierczuk; P. Kossacki; P. Wojnar; M. Potemski

2011-05-04T23:59:59.000Z

51

Tunable few-electron double quantum dots and Klein tunnelling in ultraclean carbon nanotubes  

E-Print Network (OSTI)

Tunable few-electron double quantum dots and Klein tunnelling in ultraclean carbon nanotubes G. A. Steele*, G. Gotz and L. P. Kouwenhoven Quantum dots defined in carbon nanotubes are a platform for both with highly tunable barriers1 , but disorder has prevented tunable nanotube- based quantum-dot devices from

52

Modeling of InAs/GaAs Quantum Dot Solar Cells  

Science Journals Connector (OSTI)

This paper reports electrical characteristics of an intermediate band p-i-n GaAs solar cell with InAs quantum dots embedded in the intrinsic region using Synopsis TCAD simulation tools. Up to five layers of quantum dots have been taken into consideration ... Keywords: Quantum dots, Intermediate band, InAs, GaAs, Solar Cells, TCAD

Ayman Rizk; Kazi Islam; Ammar Nayfeh

2013-11-01T23:59:59.000Z

53

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

E-Print Network (OSTI)

Midwave infrared quantum dot avalanche photodiode David A. Ramirez,a Jiayi Shao, Majeed M. Hayat demonstration of a GaAs based avalanche photodiode APD operating in the midwave infrared region 3­5 m . In the device, called the quantum dot avalanche photodiode, an intersubband quantum dots-in-a-well detector

Hayat, Majeed M.

54

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

DOE Patents (OSTI)

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.

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

2001-01-01T23:59:59.000Z

55

Los Alamos researchers unravel the mystery of quantum dot blinking  

NLE Websites -- All DOE Office Websites (Extended Search)

Researchers unravel the mystery of quantum dot blinking Researchers unravel the mystery of quantum dot blinking Los Alamos researchers unravel the mystery of quantum dot blinking Most exciting is that the Los Alamos researchers have shown that blinking can be controlled and even completely suppressed electrochemically. November 9, 2011 Los Alamos National Laboratory sits on top of a once-remote mesa in northern New Mexico with the Jemez mountains as a backdrop to research and innovation covering multi-disciplines from bioscience, sustainable energy sources, to plasma physics and new materials. Los Alamos National Laboratory sits on top of a once-remote mesa in northern New Mexico with the Jemez mountains as a backdrop to research and innovation covering multi-disciplines from bioscience, sustainable energy

56

Single-Molecule Measurements of Gold-Quenched Quantum Dots  

Science Journals Connector (OSTI)

We report the study of the quenching of quantum dots (CdSe) by gold nanoparticles at the single-molecule level. Double-stranded DNA is used as a rigid spacer to tune the distance between the two nanoparticles. The width of the fluorescent intensity distribution, monitored at different interparticle distances, reflects both the nanoparticle heterogeneity and the fluorescence intermittency of the quantum dot. The fluorescence distribution emitted by single CdSe nanocrystals can easily be distinguished from the fluorescence of partially quenched CdSe. Our results show that the distance-dependence quenching is compatible with a Förster-type process.

Zoher Gueroui and Albert Libchaber

2004-10-15T23:59:59.000Z

57

Electronic structure of quantum dots Stephanie M. Reimann  

E-Print Network (OSTI)

Electronic structure of quantum dots Stephanie M. Reimann Mathematical Physics, Lund Institute are reviewed. Experimental techniques for measuring the electronic shell structure and the effect of magnetic fields are briefly described. The electronic structure is analyzed in terms of simple single

Wu, Zhigang

58

Circuit QED in a double quantum dot system  

SciTech Connect

Strong coupling peculiar feature is demonstrated in a coupled qubit-resonator system consisting of a GaAs double quantum dot and a coplanar waveguide resonator. Qubit-resonator coupling strength (g and the decoherence rate ? are directly derived from the experiment, assuring a strong coupling condition (g/? ? 2)

Toida, Hiraku; Nakajima, Takashi; Komiyama, Susumu [Department of Basic Science, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902 (Japan)

2013-12-04T23:59:59.000Z

59

Quantum dot-based nanomaterials for biological imaging  

E-Print Network (OSTI)

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 ...

Zimmer, John P. (John Philip)

2006-01-01T23:59:59.000Z

60

Depleted-Heterojunction Colloidal Quantum Dot Solar Cells  

E-Print Network (OSTI)

Depleted-Heterojunction Colloidal Quantum Dot Solar Cells Andras G. Pattantyus-Abraham,, Illan J and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada-circuit voltage (Voc) and fill factor (FF). The power conversion efficiency ( ) for an in- put solar intensity

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Colloidal Quantum Dot Photovoltaics: The Effect of Polydispersity David Zhitomirsky,,  

E-Print Network (OSTI)

, Ontario M5S 3G4, Canada Division of Physical Sciences and Engineering, Solar and Photo polydispersity. KEYWORDS: Energy landscaping, colloidal quantum dot, photovoltaics, solar cell, polydispersity diodes,4,5 and solar cells.6,7 At present, the most efficient CQD solar cells8 employ the depleted

62

Switching Individual Quantum Dot Emission through Electrically Controlling Resonant Energy Transfer to Graphene  

Science Journals Connector (OSTI)

Also, as the inhomogeneous broadening of the quantum dot’s bandgap is larger than the QCSE shift, only certain donor–acceptor pairs with highly similar energies are switchable. ... The simulated photoluminescence (solid green) was obtained by calculating the energy transfer rate from quantum dots to graphene. ...

Jiye Lee; Wei Bao; Long Ju; P. James Schuck; Feng Wang; Alexander Weber-Bargioni

2014-11-10T23:59:59.000Z

63

Gallium diffusion into self-assembled InAs quantum dots grown on indium phosphide substrates  

SciTech Connect

The photoluminescence spectrum of small self-assembled In(Ga)As quantum dots grown on InP substrates is composed of distinct spectral lines. These lines correspond to monolayer variations in the dots smallest dimension: their heights. We use this phenomenon in order to study the diffusion of gallium atoms into the self-assembled quantum dots. We demonstrate that substantial amounts of gallium atoms diffuse from a strained GaInP layer underneath the quantum dots into the quantum dots.

Raz, T.; Shuall, N.; Bahir, G.; Ritter, D.; Gershoni, D.; Chu, S.N.G. [Department of Electrical Engineering, Technion - Israel Institute of Technology, Technion City, Haifa 32000 (Israel); Physics Department and The Solid State Institute, Technion - Israel Institute of Technology, Technion City, Haifa 32000 (Israel); Multiplex, Inc., 5000 Hadley Rd., South Plainfield, New Jersey 07080 (United States)

2004-10-18T23:59:59.000Z

64

Double superexchange in quantum dot mesomaterials  

E-Print Network (OSTI)

as the critical obstacles to dramatic enhancements in the energy conversion efficiency of photovoltaic cells based.7­10 A low binding energy allows excitons to thermally dissociate and charge carriers hop from dot exhibits a double superexchange. In addition to enhancing carrier hopping rates, double superexchange plays

Wu, Zhigang

65

Synthesis, Characterization and Application Of PbS Quantum Dots  

SciTech Connect

Lead Chalcogenides (PbS, PbSe, PbTe) quantum dots (QDs) are ideal for fundamental studies of strongly quantum confined systems with possible technological applications. Tunable electronic transitions at near--infrared wavelengths can be obtained with these QDs. Applications of lead chalcogenides encompass quite a good number of important field viz. the fields of telecommunications, medical electronics, optoelectronics etc. Very recently, it has been proposed that 'memristor'(Memory resistor) can be realized in nanoscale systems with coupled ionic and electronic transports. The hystersis characteristics of 'memristor' are observed in many nanoscale electronic devices including semiconductor quantum dot devices. This paper reports synthesis of PbS QDs by chemical route. The fabricated samples are characterized by UV-Vis, XRD, SEM, TEM, EDS, etc. Observed characteristics confirm nano formation. I-V characteristics of the sample are studied for investigating their applications as 'memristor'.

Sarma, Sweety; Datta, Pranayee [Department of Electronics Science, Gauhati University, Gnwahait-781014, Assam (India); Barua, Kishore Kr. [Department of Physics, Central University, Tezpur-784028, Assam (India); Karmakar, Sanjib [Department of Instrumentation and USIC, Gauhati University, Guwahati-781014, Assam (India)

2009-06-29T23:59:59.000Z

66

Time-resolved photoluminescent spectra of CdSe quantum dots with surface treatment  

Science Journals Connector (OSTI)

The surface morphology is one of the important factors to determine the optical properties of colloidal quantum dots. Colloidal CdSe dots were synthesized by the injection of...

Shen, Jian; Zhang, Jiayu; Han, Xudong; Wang, Ziyao; Shen, Li; Cui, Yiping

2005-01-01T23:59:59.000Z

67

Spectrum of electron-hole states of the Si/Ge structure with Ge quantum dots  

SciTech Connect

The lateral photoconductivity spectra of Si/Ge multilayer structures with Ge quantum dots of various sizes are investigated. We observed optical transition lines between the hole levels of quantum dots and electronic states of Si. This enabled us to construct a detailed energy level diagram of the electron-hole spectrum of the Si/Ge structures. It is shown that the hole levels of Ge quantum dots are successfully described by the 'quantum box' model using the actual sizes of Ge islands. It I found that the position of the longwavelength photosensitivity boundary of Si/Ge structures with Ge quantum dots can be controlled by changing the growth parameters.

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

2011-09-15T23:59:59.000Z

68

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

SciTech Connect

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.

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

2011-07-15T23:59:59.000Z

69

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

SciTech Connect

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.

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

2014-03-24T23:59:59.000Z

70

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

SciTech Connect

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

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

2013-07-22T23:59:59.000Z

71

Resonant scattering of surface plasmon polaritons by dressed quantum dots  

SciTech Connect

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.

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

2014-06-23T23:59:59.000Z

72

Quantum interference and control of the optical response in quantum dot molecules  

SciTech Connect

We discuss the optical response of a quantum molecule under the action of two lasers fields. Using a realistic model and parameters, we map the physical conditions to find three different phenomena reported in the literature: the tunneling induced transparency, the formation of Autler-Townes doublets, and the creation of a Mollow-like triplet. We found that the electron tunneling between quantum dots is responsible for the different optical regime. Our results not only explain the experimental results in the literature but also give insights for future experiments and applications in optics using quantum dots molecules.

Borges, H. S.; Sanz, L.; Villas-Boas, J. M.; Alcalde, A. M. [Instituto de Física, Universidade Federal de Uberlândia, 38400-902 Uberlândia-MG (Brazil)] [Instituto de Física, Universidade Federal de Uberlândia, 38400-902 Uberlândia-MG (Brazil)

2013-11-25T23:59:59.000Z

73

Slow Hot-Carrier Relaxation in Colloidal Graphene Quantum Dots  

Science Journals Connector (OSTI)

Here we show that carrier cooling in colloidal graphene quantum dots can be 2 orders of magnitude slower than in bulk materials, which could enable harvesting of hot charge carriers to improve the efficiency of solar energy conversion. ... We speculate that the state(s) should have higher excitation energy because of the shorter lifetime (18 ps), which nevertheless is also significantly longer than those in bulk materials, and greater density of states at higher energies. ...

Mallory L. Mueller; Xin Yan; Bogdan Dragnea; Liang-shi Li

2010-12-02T23:59:59.000Z

74

Photoluminescence upconversion in colloidal CdTe quantum dots  

Science Journals Connector (OSTI)

Efficient photoluminescence (PL) up-conversion has been observed in colloidal CdTe quantum dots with an energy gain of as high as 360 meV. Compared with the normal PL, the peak energy of this up-converted PL (UCPL) shows a redshift of about 80 meV, and the corresponding radiative lifetime becomes nearly twice as long. This UCPL is attributed to the carrier recombination involving surface states mainly through a thermal excitation process.

Xiaoyong Wang; W. William Yu; Jiayu Zhang; Jose Aldana; Xiaogang Peng; Min Xiao

2003-09-22T23:59:59.000Z

75

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

E-Print Network (OSTI)

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.

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

2010-08-28T23:59:59.000Z

76

SciTech Connect: Giant Nanocrystal Quantum Dots as Stable and...  

Office of Scientific and Technical Information (OSTI)

Giant Nanocrystal Quantum Dots as Stable and Efficient Down-Conversion Phosphor for LED based Solid State Lighting Citation Details In-Document Search Title: Giant Nanocrystal...

77

Surface-emitting red, green, and blue colloidal quantum dot distributed feedback lasers  

Science Journals Connector (OSTI)

We demonstrate surface emitting distributed feedback (DFB) lasers across the red, green, and blue from densely packed colloidal quantum dot (CQD) films. The solid CQD films were...

Roh, Kwangdong; Dang, Cuong; Lee, Joonhee; Chen, Songtao; Steckel, Jonathan S; Coe-Sullivan, Seth; Nurmikko, Arto

2014-01-01T23:59:59.000Z

78

Efficient Mn-doped CdS quantum dot sensitized solar cells based on SnO2 microsphere photoelectrodes  

Science Journals Connector (OSTI)

Mn-doped CdS quantum dot sensitized solar cells based on...2...microsphere photoelectrodes are prepared with successive ionic layer adsorption and reaction method. It is found that with Mn-doped CdS quantum dot s...

Lu Liu; Miaoliang Huang; Zhang Lan…

2014-02-01T23:59:59.000Z

79

Two-path transport measurements with bias dependence on a triple quantum dot  

SciTech Connect

We present transport measurements on a lateral triple quantum dot with a star-like geometry and one lead attached to each dot. The system is studied in a regime close to established quadruple points, where all three dots are in resonance. The specific sample structure allows us to apply two different bias voltages to the two source leads and thus to study the influence between the paths with serial double dots.

Kotzian, M.; Rogge, M. C.; Haug, R. J. [Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover (Germany)

2013-12-04T23:59:59.000Z

80

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

E-Print Network (OSTI)

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

Berbezier, Aude

2014-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Universal Non-adiabatic Holonomic Gates in Quantum Dots and Single-Molecule Magnets  

E-Print Network (OSTI)

Geometric manipulation of a quantum system offers a method for fast, universal, and robust quantum information processing. Here, we propose a scheme for universal all-geometric quantum computation using non-adiabatic quantum holonomies. We propose three different realizations of the scheme based on an unconventional use of quantum dot and single-molecule magnet devices, which offer promising scalability and robust efficiency.

Vahid Azimi Mousolou; Carlo M. Canali; Erik Sjöqvist

2012-09-17T23:59:59.000Z

82

Ligand Mediated Surface Reconstruction of Photoluminescent CdTe Quantum Dots.  

E-Print Network (OSTI)

??Enhancement of photoluminescence (PL) is observed for light-shielded dodecylamine-capped colloidal CdTe quantum dots (CdTe/DDA QDs) dispersed in toluene after washing and recapping. The PL quantum… (more)

Onnink, A.J.

2013-01-01T23:59:59.000Z

83

Compact biocompatible quantum dots via RAFT-mediated synthesis of imidazole-based random copolymer ligand  

E-Print Network (OSTI)

We present a new class of polymeric ligands for quantum dot (QD) water solubilization to yield biocompatible and derivatizable QDs with compact size (10?12 nm diameter), high quantum yields (>50%), excellent stability ...

Liu, Wenhao

84

Simulations of magnetic field gradients due to micro-magnets on a triple quantum dot circuit  

SciTech Connect

To quantify the effects of local magnetic fields on triple quantum dots, the Heisenberg Hamiltonian has been diagonalized for three electrons coupled via the exchange interaction. In particular, we have investigated different geometries of micro-magnets located on top of the triple dot in order to optimize the field gradient characteristics. In this paper, we focus on two geometries which are candidates for an addressable EDSR triple quantum dot device.

Poulin-Lamarre, G. [National Research Council of Canada, Ottawa, On., Canada, K1A-0R6 and Département de physique, Université de Sherbrooke, Sherbrooke, Qc. J1K-2R1 (Canada); Bureau-Oxton, C. [Département de physique, Université de Sherbrooke, Sherbrooke, Qc. J1K-2R1 (Canada); Kam, A. [National Research Council of Canada, Ottawa, On. K1A-0R6 (Canada); Zawadzki, P.; Aers, G. [National Research Council of Canada, Ottawa, On. K1A-0R6 (Canada); Studenikin, S. [National Research Council of Canada, Ottawa, On.K1A-0R6 (Canada); Pioro-Ladrière, M. [Département de physique, Université de Sherbrooke, Sherbrooke, Qc. J1K-2R1 (Canada); Sachrajda, A. S. [National Research Council of Canada, Ottawa, On., Canada, K1A-0R6 and Département de physique, Université de Sherbrooke, Sherbrooke, Qc. J1K-2R1 (Canada)

2013-12-04T23:59:59.000Z

85

Quantum Dots Monitor TrkA Receptor Dynamics in the Interior of Neural PC12 Cells  

Science Journals Connector (OSTI)

23 These TrkA vesicles are then loaded onto microtubule motor transport highways within the cell and shuttled to different subcellular sites for interaction with other signaling molecules. ... Limitations and potential future uses of quantum dot probes are also discussed. ... Tracking Individual Kinesin Motors in Living Cells Using Single Quantum-Dot Imaging ...

Sujata Sundara Rajan; Tania Q. Vu

2006-08-22T23:59:59.000Z

86

Photoluminescence beyond 1.5µm from InAs quantum dots  

Science Journals Connector (OSTI)

Photoluminescence measurements were carried out to investigate the origin of long wavelength emissions (~1.6@mm at room temperature) observed from wafers with InAs quantum dots capped with GaAsSb layers. For wafers with high Sb content (22% and 26%) ... Keywords: Photoluminescence, Quantum dots, Type-II

J. S. Ng; H. Y. Liu; M. J. Steer; M. Hopkinson; J. P. R. David

2006-12-01T23:59:59.000Z

87

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

E-Print Network (OSTI)

GaSb/GaAs type II quantum dot solar cells for enhanced infrared spectral response R. B Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106 Received 27 infrared spectral response of GaAs-based solar cells that incorporate type II GaSb quantum dots QDs formed

Jalali. Bahram

88

Self-assembly of silicide quantum dot arrays on stepped silicon surfaces by reactive epitaxy  

E-Print Network (OSTI)

investigated on the epitaxy and self- organization of laterally nanostructured transition metal TM silicideSelf-assembly of silicide quantum dot arrays on stepped silicon surfaces by reactive epitaxy L to be a flexible and a convenient method for the preparation of dense arrays of Co silicide quantum dots

Ortega, Enrique

89

Evidence for formation of multi-quantum dots in hydrogenated graphene  

E-Print Network (OSTI)

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

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

2012-08-16T23:59:59.000Z

90

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

E-Print Network (OSTI)

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

Wu, Shin-Tson

91

Absorption and photoluminescence spectroscopy on a single self-assembled charge-tunable quantum dot  

E-Print Network (OSTI)

Absorption and photoluminescence spectroscopy on a single self-assembled charge-tunable quantum dot PL and absorption spectroscopy on the same single self- assembled quantum dot in a charge the corresponding transition in absorption. We have developed a model of the Coulomb blockade to account

Ludwig-Maximilians-Universität, München

92

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

E-Print Network (OSTI)

Temperature-Tuning of Near-Infrared Monodisperse Quantum Dot Solids at 1.5 µm for Controllable Fo is important in a wide-variety of applications, especially in the near-infrared region where applications transfer in large, monodisperse lead sulfide quantum dots with ground-state transitions near 1.5 µm (0.8 e

Hone, James

93

PHYSICAL REVIEW B 84, 205305 (2011) Spin-phonon coupling in single Mn-doped CdTe quantum dot  

E-Print Network (OSTI)

PHYSICAL REVIEW B 84, 205305 (2011) Spin-phonon coupling in single Mn-doped CdTe quantum dot C. L dynamics of a single Mn atom in a laser driven CdTe quantum dot is addressed theoretically. Recent of single Mn-doped CdTe dots, information about the quantum spin state of a single Mn atom is extracted from

Paris-Sud XI, Université de

94

Photoluminescence Blinking Dynamics of Colloidal Quantum Dots in the Presence of Controlled External Electron Traps  

SciTech Connect

The effect of the external charge trap on the photoluminescence blinking dynamics of individual colloidal quantum dots is investigated with a series of colloidal quantum dot-bridge-fullerene dimers with varying bridge lengths, where the fullerene moiety acts as a well-defined, well-positioned external charge trap. It is found that charge transfer followed by charge recombination is an important mechanism in determining the blinking behavior of quantum dots when the external trap is properly coupled with the excited state of the quantum dot, leading to a quasi-continuous distribution of 'on' states and an early fall-off from a power-law distribution for both 'on' and 'off' times associated with quantum dot photoluminescence blinking.

Cotlet, M.; Xu, Z.

2012-01-23T23:59:59.000Z

95

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

DOE Patents (OSTI)

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.

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

2010-07-06T23:59:59.000Z

96

Towards Quantum Repeaters with Solid-State Qubits: Spin-Photon Entanglement Generation using Self-Assembled Quantum Dots  

E-Print Network (OSTI)

In this chapter we review the use of spins in optically-active InAs quantum dots as the key physical building block for constructing a quantum repeater, with a particular focus on recent results demonstrating entanglement between a quantum memory (electron spin qubit) and a flying qubit (polarization- or frequency-encoded photonic qubit). This is a first step towards demonstrating entanglement between distant quantum memories (realized with quantum dots), which in turn is a milestone in the roadmap for building a functional quantum repeater. We also place this experimental work in context by providing an overview of quantum repeaters, their potential uses, and the challenges in implementing them.

McMahon, Peter L

2015-01-01T23:59:59.000Z

97

Photocurrent extraction efficiency in colloidal quantum dot photovoltaics  

SciTech Connect

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.

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

2013-11-18T23:59:59.000Z

98

High Efficiency Colloidal Quantum Dot Phosphors  

SciTech Connect

The project showed that non-Cd containing, InP-based nanocrystals (semiconductor materials with dimensions of ~6 nm) have high potential for enabling next-generation, nanocrystal-based, on chip phosphors for solid state lighting. Typical nanocrystals fall short of the requirements for on chip phosphors due to their loss of quantum efficiency under the operating conditions of LEDs, such as, high temperature (up to 150 °C) and high optical flux (up to 200 W/cm2). The InP-based nanocrystals invented during this project maintain high quantum efficiency (>80%) in polymer-based films under these operating conditions for emission wavelengths ranging from ~530 to 620 nm. These nanocrystals also show other desirable attributes, such as, lack of blinking (a common problem with nanocrystals which limits their performance) and no increase in the emission spectral width from room to 150 °C (emitters with narrower spectral widths enable higher efficiency LEDs). Prior to these nanocrystals, no nanocrystal system (regardless of nanocrystal type) showed this collection of properties; in fact, other nanocrystal systems are typically limited to showing only one desirable trait (such as high temperature stability) but being deficient in other properties (such as high flux stability). The project showed that one can reproducibly obtain these properties by generating a novel compositional structure inside of the nanomaterials; in addition, the project formulated an initial theoretical framework linking the compositional structure to the list of high performance optical properties. Over the course of the project, the synthetic methodology for producing the novel composition was evolved to enable the synthesis of these nanomaterials at a cost approximately equal to that required for forming typical conventional nanocrystals. Given the above results, the last major remaining step prior to scale up of the nanomaterials is to limit the oxidation of these materials during the tens of thousands of hours of LED operation. Once the LED phosphor lifetime specifications are met, these nanocrystals will enable white LEDs for solid state lighting to simultaneously have increased efficiency and improved light quality, in addition to enabling the creation of custom light spectrums. These improvements to white LEDs will help accelerate the adoption of SSL, leading to large savings in US and worldwide energy costs.

Kahen, Keith

2013-12-31T23:59:59.000Z

99

Optical levitation of microdroplet containing a single quantum dot  

E-Print Network (OSTI)

Semiconductor nanocrystals, also known as quantum dots (QDs), are key ingredients in current quantum optics experiments. They serve as quantum emitters and memories and have tunable energy levels that depend not only on the material but also, through the quantum confinement effect, on the size. The resulting strongly confined electron and hole wave functions lead to large transition dipole moments, which opens a path to ultra strong coupling and even deep strong coupling between light and matter. Such efficient coupling requires the precise positioning of the QD in an optical cavity with a high quality factor and small mode volume, such as micro-Fabry--Perot cavity, whispering-gallery-mode microcavity, or photonic-crystal cavity. However, the absence of a technique for free-space positioning has limited the further research on QD-based cavity quantum electrodynamics. In this paper, we present a technique to overcome this challenge by demonstrating the optical levitation or trapping in helium gas of a single Q...

Minowa, Yosuke; Ashida, Masaaki

2014-01-01T23:59:59.000Z

100

Probing semiconductor quantum dot state and manipulation with superconducting transmission line resonator  

E-Print Network (OSTI)

A coupled system of a superconducting transmission line resonator with a semiconductor double quantum dot is analyzed. We simulate the phase shift of the microwave signal in the resonator, which is sensitive to the quantum dot qubit state and manipulation. The measurement quality is sufficiently high and the results demonstrate a solid-state quantum processor based on this type of circuit can be envisioned.

Zhe Guan

2013-12-08T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

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

SciTech Connect

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

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

2014-05-21T23:59:59.000Z

102

Growth and optical characterization of multilayers of InGaN quantum dots  

E-Print Network (OSTI)

GaN quantum dots Article Type: Research Paper Section/Category: General subjects Keywords: B2. InGaN quantum dots; A1. Photoluminescence; B1. Nitrides; A3. Metal-organic vapour phase epitaxy Corresponding Author: Dr Tongtong Zhu, Ph... , Cambridge, CB2 3QZ, UK Dr Tongtong Zhu Tel: +44 1223 334368 Fax: +44 1223 334437 E-mail: tz234@cam.ac.uk 9 Sep 2011 Dear Editor, Title: Growth and optical characterization of multilayers of InGaN quantum dots Authors: Tongtong Zhu, Haitham A...

Zhu, Tontong; El-Ella, Haitham; Reid, Benjamin; Holmes, Mark; Taylor, Robert; Kappers, Menno; Oliver, Rachel

2012-01-01T23:59:59.000Z

103

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

SciTech Connect

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.

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)

2013-12-16T23:59:59.000Z

104

Approaches to Future Generation Photovoltaics and Solar Fuels: Multiple Exciton Generation in Quantum Dots, Quantum Dot Arrays, Molecular Singlet Fission, and Quantum Dot Solar Cells  

SciTech Connect

One potential, long-term approach to more efficient future generation solar cells is to utilize the unique properties of quantum dots (QDs) and unique molecular chromophores to control the relaxation pathways of excited states to produce enhanced conversion efficiency through efficient multiple electron-hole pair generation from single photons . We have observed efficient multiple exciton generation (MEG) in PbSe, PbS, PbTe, and Si QDs and efficient singlet fission (SF) in molecules that satisfy specific requirements for their excited state energy level structure to achieve carrier multiplication. We have studied MEG in close-packed QD arrays where the QDs are electronically coupled in the films and thus exhibit good transport while still maintaining quantization and MEG. We have developed simple, all-inorganic QD solar cells that produce large short-circuit photocurrents and power conversion efficiencies in the 3-5% range via both nanocrystalline Schottky junctions and nanocrystalline p-n junctions. These solar cells also show QYs for photocurrent that exceed 100% in the photon energy regions where MEG is possible; the photocurrent MEG QYs as a function of photon energy match those determined via time-resolved spectroscopy. We have also observed very efficient SF in thin films of molecular crystals of 1,3 diphenylisobenzofuran with quantum yields of 200% at the optimum SF threshold of 2Eg (HOMO-LUMO for S{sub 0}-S{sub 1}), reflecting the creation of two excited triplet states from the first excited singlet state. Various possible configurations for novel solar cells based on MEG in QDs and SF in molecules that could produce high conversion efficiencies will be presented, along with progress in developing such new types of solar cells. Recent analyses of the effect of MEG or SF combined with solar concentration on the conversion efficiency of solar cells will be discussed.

Nozik, A. J.; Beard, M. C.; Johnson, J. C.; Hanna, M. C.; Luther, J. M.; Midgett, A.; Semonin, O.; Michel, J.

2012-01-01T23:59:59.000Z

105

Ultra-low density InAs quantum dots  

SciTech Connect

We show that InAs quantum dots (QDs) can be grown by molecular beam epitaxy (MBE) with an ultralow density of sin 10{sup 7} cm{sup -2} without any preliminary or post-growth surface treatment. The strain-induced QD formation proceeds via the standard Stranski-Krastanow mechanism, where the InAs coverage is decreased to 1.3-1.5 monolayers (MLs). By using off-cut GaAs (100) substrates, we facilitate the island nucleation in this subcritical coverage range without any growth interruption. The QD density dependences on the InAs coverage are studied by photoluminescence, atomic force microscopy, transmission electron microscopy, and are well reproduced by the universal double exponential shapes. This method enables the fabrication of InAs QDs with controllable density in the range 10{sup 7}-10{sup 8} cm{sup -2}, exhibiting bright photoluminescence.

Dubrovskii, V. G., E-mail: dubrovskii@mail.ioffe.ru; Cirlin, G. E. [St. Petersburg Academic University Russian Academy of Sciences (Russian Federation)] [St. Petersburg Academic University Russian Academy of Sciences (Russian Federation); Brunkov, P. A. [Ioffe Physical Technical Institute Russian Academy of Sciences (Russian Federation)] [Ioffe Physical Technical Institute Russian Academy of Sciences (Russian Federation); Perimetti, U.; Akopyan, N. [Delft University of Technology, Quantum Transport, Kavli Institute of Nanoscience (Netherlands)] [Delft University of Technology, Quantum Transport, Kavli Institute of Nanoscience (Netherlands)

2013-10-15T23:59:59.000Z

106

Electric-field-induced spin depolarization in graphene quantum dots  

Science Journals Connector (OSTI)

We study the effect of the in-plane electric field on the magnetic properties of charge-neutral triangular zigzag graphene quantum dot (GQD) by using the mean-field Hubbard Hamiltonian. Our calculated results show that spin depolarization begins to occur when the electric field is beyond some critical value. The spin-density distribution is more concentrated in the region of the GQDs with smaller electrostatic potential. This phenomenon is attributed to the competition between the many-body electron-electron interaction and the external electrostatic potential. Numerical results also show that the total spin of larger GQDs are easier to depolarize than the total spin of smaller GQDs. Moreover, the spin of GQDs with weak edge disorder still respond to an electric field but in a more irregular way. Our findings provide a path to electrically tuning the magnetic properties of GQDs.

Wen-Long Ma and Shu-Shen Li

2012-07-30T23:59:59.000Z

107

Valley pair qubits in double quantum dots of gapped graphene  

E-Print Network (OSTI)

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)).

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

2011-07-03T23:59:59.000Z

108

Fluorescence quenching of CdSe quantum dots on graphene  

SciTech Connect

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.

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

2013-11-11T23:59:59.000Z

109

Experimental verification of Förster energy transfer between semiconductor quantum dots  

Science Journals Connector (OSTI)

In recent years, energy transfer (ET) using semiconductor quantum dots (QDs) is getting increased attention. However, it has been postulated that ET between QDs is based on the Förster model, which is a well-established model of ET mechanism in organic dye systems, without verification. In this work, we have investigated ET mechanism in colloidal CdS QDs measuring photoluminescence dynamics of a bilayer structure consisting of differently sized CdS QDs. In the bilayer structure, the distance between the monolayer of donor QDs and that of acceptor QDs was controlled precisely by a spacer layer that is layer-by-layer assembly of polyelectrolytes. The bilayer structure enabled us to systematically measure the spacer-layer dependence of photoluminescence dynamics reflecting the ET process between QDs. It is demonstrated that ET between the donor and acceptor QDs is conclusively dominated by the dipole-dipole interaction, which verifies the appropriateness of the Förster model.

DaeGwi Kim; Shinya Okahara; Masaaki Nakayama; YongGu Shim

2008-10-02T23:59:59.000Z

110

Quantum dots in bio-imaging: Revolution by the small  

SciTech Connect

Visual analysis of biomolecules is an integral avenue of basic and applied biological research. It has been widely carried out by tagging of nucleotides and proteins with traditional fluorophores that are limited in their application by features such as photobleaching, spectral overlaps, and operational difficulties. Quantum dots (QDs) are emerging as a superior alternative and are poised to change the world of bio-imaging and further its applications in basic and applied biology. The interdisciplinary field of nanobiotechnology is experiencing a revolution and QDs as an enabling technology have become a harbinger of this hybrid field. Within a decade, research on QDs has evolved from being a pure science subject to the one with high-end commercial applications.

Arya, Harinder [Gene Function Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan); Kaul, Zeenia [Gene Function Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan); Wadhwa, Renu [Gene Function Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan); Taira, Kazunari [Gene Function Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan); Hirano, Takashi [Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, 7 Ibaraki 305-8562 (Japan); Kaul, Sunil C. [Gene Function Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan)]. E-mail: s-kaul@aist.go.jp

2005-04-22T23:59:59.000Z

111

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

SciTech Connect

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

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

2014-06-15T23:59:59.000Z

112

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)

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.

Ranojoy Bose; Jie Gao; James F. McMillan; Alex D. Williams; Chee Wei Wong

2008-12-01T23:59:59.000Z

113

Argonne CNM Highlight: Coupling of Single Quantum Dots to Smooth Metal  

NLE Websites -- All DOE Office Websites (Extended Search)

Coupling of Single Quantum Dots to Smooth Metal Films Single Quantum Dots Coupledl to Smooth Metal Films Artist¹s rendition of semiconductor nanocrystals near a gold film. The metal increases nanocrystal emission rates depending on their orientation. [selected as cover image for Phys. Chem. Chem. Phys., 11, 5853 (2009)] Staff in the CNM Nanophotonics Group have measured how light emission from individual colloidal semiconductor nanocrystals, or quantum dots, is modified when in proximity to smooth metal films. Metal nanostructures can strongly modify how quantum dots emit light because of their coupling to electron oscillations in the metal, known as surface plasmons. Emission modification is important for the improvement of light-emitting devices,

114

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

E-Print Network (OSTI)

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

Burger, Anat

2006-01-01T23:59:59.000Z

115

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

E-Print Network (OSTI)

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 ...

Coe-Sullivan, Seth (Seth Alexander)

2002-01-01T23:59:59.000Z

116

Two-Photon Oxygen Sensing with Quantum Dot-Porphyrin Conjugates  

E-Print Network (OSTI)

Supramolecular assemblies of a quantum dot (QD) associated to palladium(II) porphyrins have been developed to detect oxygen (pO[subscript 2]) in organic solvents. Palladium porphyrins are sensitive in the 0–160 Torr range, ...

Lemon, Christopher M.

117

Enhance energy transfer between quantum dots by the surface plasmon of Ag island film  

Science Journals Connector (OSTI)

We observed enhanced energy transfer between quantum dots which were spin coated on the surface of Ag island film. By adjusting the thickness of Al2O3 spacer...

Xu, Hui; Liu, Jiaming; Duan, Xiaoyu; Li, Jiahua; Xue, Jiancai; Sun, Xiye; Cai, Yefan; Zhou, Zhang-Kai; Wang, Xuehua

2014-01-01T23:59:59.000Z

118

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

SciTech Connect

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.

Not Available

2013-08-01T23:59:59.000Z

119

Fiber-based cryogenic and time-resolved spectroscopy of PbS quantum dots  

E-Print Network (OSTI)

PbS quantum dots are promising active emitters for use with high-quality Si nanophotonic devices in the telecommunications-band. Measurements of low quantum dot densities are limited both because of low fluorescence levels and the challenges of single photon detection at these wavelengths. Here, we report on methods using a fiber taper waveguide to efficiently extract PbS quantum dot photoluminescence. Temperature dependent ensemble measurements reveal an increase in emitted photons concomitant with an increase in excited-state lifetime from 58.9 ns at 293 K to 657 ns at 40 K. Measurements are also performed on quantum dots on high-$Q$ ($>10^5$) microdisks using cavity-resonant, pulsed excitation.

Matthew T. Rakher; Ranojoy Bose; Chee Wei Wong; Kartik Srinivasan

2010-12-01T23:59:59.000Z

120

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

E-Print Network (OSTI)

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 ...

Bruer, Garrett (Garrett A.)

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Composite system based on CdSe/ZnS quantum dots and GaAs nanowires  

SciTech Connect

The possibility of fabricating a composite system based on colloidal CdSe/ZnS quantum dots and GaAs nanowires is demonstrated and the structural and emission properties of this system are investigated by electron microscopy and photoluminescence spectroscopy techniques. The good wettability and developed surface of the nanowire array lead to an increase in the surface density of quantum dots and, as a consequence, in the luminosity of the system in the 600-nm wavelength region. The photoluminescence spectrum of the quantum dots exhibits good temperature stability in the entire range 10-295 K. The impact of surface states on energy relaxation and the role of exciton states in radiative recombination in the quantum dots are discussed.

Khrebtov, A. I. [St. Petersburg Academic University-Nanotechnology Research and Education Center, Russian Academy of Sciences (Russian Federation)] [St. Petersburg Academic University-Nanotechnology Research and Education Center, Russian Academy of Sciences (Russian Federation); Talalaev, V. G. [St. Petersburg State University, Fock Institute of Physics (Russian Federation)] [St. Petersburg State University, Fock Institute of Physics (Russian Federation); Werner, P. [Max-Planck-Institut fuer Mikrostukturphysik (Germany)] [Max-Planck-Institut fuer Mikrostukturphysik (Germany); Danilov, V. V. [Vavilov State Optical Institute (Russian Federation)] [Vavilov State Optical Institute (Russian Federation); Artemyev, M. V. [Belarussian State University, Institute for Physicochemical Problems (Belarus)] [Belarussian State University, Institute for Physicochemical Problems (Belarus); Novikov, B. V. [St. Petersburg State University, Fock Institute of Physics (Russian Federation)] [St. Petersburg State University, Fock Institute of Physics (Russian Federation); Shtrom, I. V. [St. Petersburg Academic University-Nanotechnology Research and Education Center, Russian Academy of Sciences (Russian Federation)] [St. Petersburg Academic University-Nanotechnology Research and Education Center, Russian Academy of Sciences (Russian Federation); Panfutova, A. S. [Vavilov State Optical Institute (Russian Federation)] [Vavilov State Optical Institute (Russian Federation); Cirlin, G. E. [St. Petersburg Academic University-Nanotechnology Research and Education Center, Russian Academy of Sciences (Russian Federation)] [St. Petersburg Academic University-Nanotechnology Research and Education Center, Russian Academy of Sciences (Russian Federation)

2013-10-15T23:59:59.000Z

122

Colloidal quantum-dot light-emitting diodes with metal-oxide charge  

E-Print Network (OSTI)

across the pixel area, and fabrication required the specialized deposition technique of energy-neutral over previously reported structures8,10 . Previous efforts at building colloidal quantum-dot (QD) LEDs concentrations and energy-band

123

Electrical excitation of colloidally synthesized quantum dots in metal oxide structures  

E-Print Network (OSTI)

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 ...

Wood, Vanessa Claire

2010-01-01T23:59:59.000Z

124

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

Science Journals Connector (OSTI)

We apply a rigorous dipole model to analyze the light outcoupling and angular performance of quantum dot light emitting diode (QLED). To illustrate the design principles, we use a red...

Zhu, Ruidong; Luo, Zhenyue; Wu, Shin-Tson

2014-01-01T23:59:59.000Z

125

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

SciTech Connect

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.

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

2013-12-04T23:59:59.000Z

126

Time Resolved Single Molecule Spectroscopy of Semiconductor Quantum Dot/conjugated Organic Hybrid Nanostructures.  

E-Print Network (OSTI)

??Single molecule studies on CdSe quantum dots functionalized with oligo-phenylene vinylene ligands (CdSe-OPV) provide evidence of strong electronic communication that facilitate charge and energy transport… (more)

Odoi, Michael Yemoh

2010-01-01T23:59:59.000Z

127

Solar Cells Based on Inks of n-Type Colloidal Quantum Dots  

Science Journals Connector (OSTI)

Solar Cells Based on Inks of n-Type Colloidal Quantum Dots ... † Department of Electrical and Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ontario M5S 3G4, Canada ...

Zhijun Ning; Haopeng Dong; Qiong Zhang; Oleksandr Voznyy; Edward H. Sargent

2014-09-16T23:59:59.000Z

128

Formation of graphene quantum dots by “Planting” hydrogen atoms at a graphene nanoribbon  

Science Journals Connector (OSTI)

Different technological approaches for creating graphene quantum dots by the adsorption of hydrogen ... occur both at convex portions of a distorted graphene nanoribbon and in the structure formed by two distorte...

L. A. Chernozatonskii; A. A. Artyukh; D. G. Kvashnin

2012-05-01T23:59:59.000Z

129

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

SciTech Connect

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.

Cotlet, M.; Xu, Z.

2011-06-27T23:59:59.000Z

130

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

SciTech Connect

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

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

2013-08-15T23:59:59.000Z

131

SUNY/Buffalo Developing High-Efficiency Colloidal Quantum Dot Phosphors  

Energy.gov (U.S. Department of Energy (DOE))

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

132

Analytical and numerical calculations of spectral and optical characteristics of spheroidal quantum dots  

SciTech Connect

In the effective mass approximation for electronic (hole) states of a spheroidal quantum dot with and without external fields the perturbation theory schemes are constructed in the framework of the Kantorovich and adiabatic methods. The eigenvalues and eigenfunctions of the problem, obtained in both analytical and numerical forms, were applied for the analysis of spectral and optical characteristics of spheroidal quantum dots in homogeneous electric fields.

Gusev, A. A., E-mail: gooseff@jinr.ru; Hai, L. L.; Vinitsky, S. I.; Chuluunbaatar, O. [Joint Institute for Nuclear Research (Russian Federation)] [Joint Institute for Nuclear Research (Russian Federation); Derbov, V. L.; Klombotskaya, A. S. [Saratov State University (Russian Federation)] [Saratov State University (Russian Federation); Dvoyan, K. G.; Sarkisyan, H. A. [Russian-Armenian (Slavonic) University (Armenia)] [Russian-Armenian (Slavonic) University (Armenia)

2013-08-15T23:59:59.000Z

133

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

E-Print Network (OSTI)

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

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

2011-04-22T23:59:59.000Z

134

Quantum Dot Solar Cells: High Efficiency through Multiple Exciton Generation  

SciTech Connect

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.

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

2005-01-01T23:59:59.000Z

135

Redshifted and blueshifted photoluminescence emission of InAs/InP quantum dots upon amorphization of phase change material  

Science Journals Connector (OSTI)

We present the mechanisms underlying the redshifted and blueshifted photoluminescence (PL) of quantum dots (QDs) upon amorphization of phase change material (PCM). We calculated the...

Humam, Nurrul Syafawati Binti; Sato, Yu; Takahashi, Motoki; Kanazawa, Shohei; Tsumori, Nobuhiro; Regreny, Philippe; Gendry, Michel; Saiki, Toshiharu

2014-01-01T23:59:59.000Z

136

Narrow spectral linewidth of single zinc-blende GaN/AlN self-assembled quantum dots  

SciTech Connect

We study by microphotoluminescence the optical properties of single self-assembled zinc-blende GaN/AlN quantum dots grown by plasma-assisted molecular beam epitaxy. As opposed to previous reports, the high quality of such zinc-blende GaN quantum dots allows us to evidence a weak acoustic phonon sideband as well as a limited spectral diffusion. As a result, we report on resolution-limited quantum dot linewidths as narrow as 500 ± 50 ?eV. We finally confirm the fast radiative lifetime and high-temperature operation of such quantum dots.

Sergent, S. [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)] [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Kako, S. [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)] [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Bürger, M.; As, D. J. [Department Physik, Universität Paderborn, Warburger Str. 100, 33098 Paderborn (Germany)] [Department Physik, Universität Paderborn, Warburger Str. 100, 33098 Paderborn (Germany); Arakawa, Y. [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan) [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)

2013-10-07T23:59:59.000Z

137

Effect of shells on photoluminescence of aqueous CdTe quantum dots  

SciTech Connect

Graphical abstract: Size-tunable CdTe coated with several shells using an aqueous solution synthesis. CdTe/CdS/ZnS quantum dots exhibited high PL efficiency up to 80% which implies the promising applications for biomedical labeling. - Highlights: • CdTe quantum dots were fabricated using an aqueous synthesis. • CdS, ZnS, and CdS/ZnS shells were subsequently deposited on CdTe cores. • Outer ZnS shells provide an efficient confinement of electron and hole inside the QDs. • Inside CdS shells can reduce the strain on the QDs. • Aqueous CdTe/CdS/ZnS QDs exhibited high stability and photoluminescence efficiency of 80%. - Abstract: CdTe cores with various sizes were fabricated in aqueous solutions. Inorganic shells including CdS, ZnS, and CdS/ZnS were subsequently deposited on the cores through a similar aqueous procedure to investigate the effect of shells on the photoluminescence properties of the cores. In the case of CdTe/CdS/ZnS quantum dots, the outer ZnS shell provides an efficient confinement of electron and hole wavefunctions inside the quantum dots, while the middle CdS shell sandwiched between the CdTe core and ZnS shell can be introduced to obviously reduce the strain on the quantum dots because the lattice parameters of CdS is situated at the intermediate-level between those of CdTe and ZnS. In comparison with CdTe/ZnS core–shell quantum dots, the as-prepared water-soluble CdTe/CdS/ZnS quantum dots in our case can exhibit high photochemical stability and photoluminescence efficiency up to 80% in an aqueous solution, which implies the promising applications in the field of biomedical labeling.

Yuan, Zhimin; Yang, Ping, E-mail: mse_yangp@ujn.edu.cn

2013-07-15T23:59:59.000Z

138

Photoluminescence properties of ZnS/CdS/ZnS quantum dot–quantum wells doped with Ag+ ions  

Science Journals Connector (OSTI)

Enhanced photoluminescence and postirradiation luminescence is reported from Ag+-doping ZnS/CdS/ZnS quantum dot–quantum wells (QDQWs)...2O/Heptane system, the size of a QDQW was estimated to be ~6 nm. Compared to...

Hua Qu; Lixin Cao; Wei Liu; Ge Su; Bohua Dong; Hui Zhai

2011-10-01T23:59:59.000Z

139

FEW ELECTRON QUANTUM DOTS IN InAs/InP CORE SHELL NANOWIRES  

E-Print Network (OSTI)

..." Much effort is being directed at harnessing the potential power of quantum com- puting [7]. At the turn electric field (EDSR) is expected to be orders of magnitudes faster. To this effect, InAs nanowires with a thin shell of InP, are explored as a system where a quantum dot can be defined and probed electrically

Nygård, Jesper

140

Frster resonance energy transfer enhanced color-conversion using colloidal semiconductor quantum dots for solid  

E-Print Network (OSTI)

F�rster resonance energy transfer enhanced color-conversion using colloidal semiconductor quantum August 2009; published online 15 October 2009 In this paper, we present F�rster resonance energy transfer FRET -enhanced color-conversion using colloidal semiconductor quantum dot nanocrystals NCs to make

Demir, Hilmi Volkan

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Lead-position dependent regular oscillations and random fluctuations of conductance in graphene quantum dots  

E-Print Network (OSTI)

Lead-position dependent regular oscillations and random fluctuations of conductance in graphene.1088/0953-8984/25/8/085502 Lead-position dependent regular oscillations and random fluctuations of conductance in graphene quantum, for graphene quantum dots, the conductance variations with the lead positions. Since for graphene the types

Lai, Ying-Cheng

142

Selective coherent destruction of tunneling in a quantum-dot array  

Science Journals Connector (OSTI)

The coherent manipulation of quantum states is one of the main tasks required in quantum computation. In this paper we demonstrate that it is possible to control coherently the electronic position of a particle in a quantum-dot array. By tuning an external ac electric field we can selectively suppress the tunneling between dots, trapping the particle in a determined region of the array. The problem is treated nonperturbatively by a time-dependent Hamiltonian in the effective mass approximation and using Floquet theory. We find that the quasienergy spectrum exhibits crossings and anticrossings at certain field intensities that result in the selective suppression of tunneling.

J. M. Villas-Bôas, Sergio E. Ulloa, and Nelson Studart

2004-07-08T23:59:59.000Z

143

Observation of the Kondo effect in a spin-3/2 hole quantum dot  

SciTech Connect

We report the observation of the Kondo effect in a spin-3/2 hole quantum dot formed near pinch-off in a GaAs quantum wire. We clearly observe two distinctive hallmarks of quantum dot Kondo physics. First, the zero-bias peak in the differential conductance splits an in-plane magnetic field and the splitting is independent of gate voltage. Second, the splitting rate is twice as large as that for the lowest one-dimensional subband. We show that the Zeeman splitting of the zero-bias peak is highly anisotropic and attribute this to the strong spin-orbit interaction for holes in GaAs.

Klochan, O.; Micolich, A. P.; Hamilton, A. R. [School of Physics, University of New South Wales, Sydney NSW 2052 (Australia); Trunov, K.; Reuter, D.; Wieck, A. D. [Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)

2013-12-04T23:59:59.000Z

144

Fast Electrical Control of a Quantum Dot Strongly Coupled to a Nano-resonator  

E-Print Network (OSTI)

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.

Andrei Faraon; Arka Majumdar; Hyochul Kim; Pierre Petroff; Jelena Vuckovic

2009-06-03T23:59:59.000Z

145

Negative differential gain in quantum dot systems: Interplay of structural properties and many-body effects  

SciTech Connect

The saturation behaviour of optical gain with increasing excitation density is an important factor for laser device performance. For active materials based on self-organized InGaAs/GaAs quantum dots, we study the interplay between structural properties of the quantum dots and many-body effects of excited carriers in the optical properties via a combination of tight-binding and quantum-kinetic calculations. We identify regimes where either phase-space filling or excitation-induced dephasing dominates the saturation behavior of the optical gain. The latter can lead to the emergence of a negative differential material gain.

Goldmann, E., E-mail: goldmann@itp.uni-bremen.de; Jahnke, F. [Institute for Theoretical Physics, University of Bremen, Bremen 28359 (Germany); Lorke, M.; Frauenheim, T. [Bremen Center for Computational Materials Science BCCMS, University of Bremen, Bremen 28359 (Germany)

2014-06-16T23:59:59.000Z

146

Optical anisotropy in individual CdS quantum dot ensembles  

Science Journals Connector (OSTI)

The polarized microphotoluminescence (PL) spectroscopy of individual spherical and rod-shaped CdS quantum dot (QD) ensembles has been investigated. In a spherical QD ensemble, optical anisotropy was observed despite the spherical shapes of both the ensemble and individual QD components. The directions of the maximum linearly polarized PL were different for different spherical QD ensembles, and independent on the polarization direction of the excitation. However, for a fixed polarization direction of PL, the PL yield significantly varied with the polarization direction of the excitation. In a rod-shaped QD ensemble, the direction of maximum polarized PL was observed to be perpendicular to the length direction of the rod, regardless of the polarization direction of the excitation. The observed PL anisotropies in individual spherical and rod-shaped QD ensembles are explained in terms of the crystallographic orientation of the individual QD components that make up the ensemble and obey the linear polarization selection rules. A statistic model is proposed to qualitatively describe the degree of polarization based on a three-dimensional crystallographic orientation of QDs with respect to the directions of excitation and observation.

Jifa Qi, Chuanbin Mao, John M. White, and Angela M. Belcher

2003-09-24T23:59:59.000Z

147

Theory of coherent dynamic nuclear polarization in quantum dots  

Science Journals Connector (OSTI)

We consider the production of dynamic nuclear spin polarization (DNP) in a two-electron double quantum dot, in which the electronic levels are repeatedly swept through a singlet-triplet avoided crossing. Our analysis helps to elucidate the intriguing interplay between electron-nuclear hyperfine coupling, electronic spin-orbit coupling, and electron and nuclear Larmor precession in an externally applied magnetic field in guiding the production of DNP. In particular, we specifically address the roles of multiple nuclear spin species. By treating the nuclear spin dynamics semiclassically, we identify two contributions to the DNP production rate, a “geometric contribution” and a “dynamic contribution,” which depend in very different ways on control parameters such as the sweep rate and holding time near the level crossing. We find that the dynamical contribution dominates the DNP when the system is held near the singlet-triplet avoided crossing for a time on the order of the nuclear Larmor period. Detailed numerical calculations provide a physical picture for understanding the oscillations observed by Foletti et al. in arXiv:0801.3613.

Izhar Neder; Mark S. Rudner; Bertrand I. Halperin

2014-02-04T23:59:59.000Z

148

Determination of energy scales in few-electron double quantum dots  

SciTech Connect

The capacitive couplings between gate-defined quantum dots and their gates vary considerably as a function of applied gate voltages. The conversion between gate voltages and the relevant energy scales is usually performed in a regime of rather symmetric dot-lead tunnel couplings strong enough to allow direct transport measurements. Unfortunately, this standard procedure fails for weak and possibly asymmetric tunnel couplings, often the case in realistic devices. We have developed methods to determine the gate voltage to energy conversion accurately in the different regimes of dot-lead tunnel couplings and demonstrate strong variations of the conversion factors. Our concepts can easily be extended to triple quantum dots or even larger arrays.

Taubert, D.; Ludwig, S. [Center for NanoScience and Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Geschwister-Scholl-Platz 1, D-80539 Muenchen (Germany); Schuh, D. [Institut fuer Experimentelle Physik, Universitaet Regensburg, D-93040 Regensburg (Germany); Wegscheider, W. [Laboratory for Solid State Physics, ETH Zuerich, CH-8093 Zuerich (Switzerland)

2011-12-15T23:59:59.000Z

149

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

SciTech Connect

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.

Sadeghi, S. M. [Department of Physics, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States); Nano and Micro Device Center, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States); Nejat, A.; West, R. G. [Department of Physics, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States)

2012-11-15T23:59:59.000Z

150

Red light emitting solid state hybrid quantum dot–near-UV GaN LED devices  

Science Journals Connector (OSTI)

We produced core–shell (CdSe)ZnSe quantum dots by direct colloidal chemical synthesis and the surface-passivation method—an overcoating of the core CdSe with a larger-bandgap material ZnSe. The (CdSe)ZnSe quantum dots(QDs) play the role of a colour conversion centre. We call these quantum dots nanophosphors. We fabricated red light emitting hybrid devices of (CdSe)ZnSe QDs and a near-UV GaN LED by combining red light emitting (CdSe)ZnSe quantum dots (as a colour conversion centre) with a near-UV(NUV) GaN LED chip (as an excitation source). A few good red phosphors have been known for UV excitation wavelengths, and red phosphors for UV excitation have been sought for a long time. Here we tested the possibility of using (CdSe)ZnSe QDs as red nanophosphors for UV excitation. The fabricated red light emitting hybrid device of (CdSe)ZnSe and a NUV GaN LED chip showed a good luminance. We demonstrated that the (CdSe)ZnSe quantum dots were promising red nanophosphors for NUV excitation and that a red LED made of QDs and a NUV excitation source was a highly efficient hybrid device.

Hongjoo Song; Seonghoon Lee

2007-01-01T23:59:59.000Z

151

Analysis of the reduced thermal conductivity in InGaAs/GaAs quantum dot lasers from chirp characteristics  

E-Print Network (OSTI)

injection which we term "thermal impact" , the ther- mal conductivity of the active region is estimatedAnalysis of the reduced thermal conductivity in InGaAs/GaAs quantum dot lasers from chirp; published online 21 September 2006 The thermal conductivity of self-organized quantum dot QD active regions

Klotzkin, David

152

Femtosecond gain and index dynamics in an InAs/InGaAsP quantum dot amplifier  

E-Print Network (OSTI)

Femtosecond gain and index dynamics in an InAs/InGaAsP quantum dot amplifier operating at 1.55 µm and refractive index dynamics of an InAs/InGaAsP self-assembled quantum dot semiconductor optical amplifier (SOA-carrier absorption and stimulated transition processes. ©2006 Optical Society of America OCIS codes: (320

Mojahedi, Mohammad

153

Near-infrared peptide-coated quantum dots for small animal imaging Gopal Iyer, Jack J. Li, Fabien Pinaud, James M. Tsay, Laurent A. Bentolila, Xavier  

E-Print Network (OSTI)

Near-infrared peptide-coated quantum dots for small animal imaging Gopal Iyer, Jack J. Li, Fabien ABSTRACT We have synthesized high quality type-II CdTe/CdSe near infrared quantum dots using successive ion used a peptide coating technique on type-II and commercial near infrared quantum dots for delivery

Michalet, Xavier

154

Quantum Dots Promise to Significantly Boost Photovoltaic Efficiencies, The Spectrum of Clean Energy Innovation (Fact Sheet)  

NLE Websites -- All DOE Office Websites (Extended Search)

Semiconductor quantum dots used in so-called "third-generation" solar cells have the potential Semiconductor quantum dots used in so-called "third-generation" solar cells have the potential to dramatically increase-in some cases even double-the efficiency of converting sunlight to electricity. The conversion process works via "multiple exciton generation (MEG)." In this process, when a single photon of light of sufficient energy is absorbed by the quantum dot, it produces more than one bound electron-hole pair, or exciton. NREL scientists were the first to predict this important unusual MEG effect in QDs, which contrasts with conventional photo- voltaic (PV) cells having much larger crystals and many more atoms and in which one photon produces only one electron-hole pair. The electronic process is also very fast, occurring within

155

Mn solid solutions in self-assembled Ge/Si (001) quantum dot heterostructures  

SciTech Connect

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.

Kassim, J.; Nolph, C.; Reinke, P.; Floro, J. [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Jamet, M. [Institut Nanosciences et Cryogenie/SP2M, CEA-UJF, F-38054 Grenoble (France)

2012-12-10T23:59:59.000Z

156

Patterning quantum dot arrays using DNA replication principles.  

SciTech Connect

The convergence of nanoscience and biotechnology has opened the door to the integration of a wide range of biological molecules and processes with synthetic materials and devices. A primary biomolecule of interest has been DNA based upon its role as information storage in living systems, as well as its ability to withstand a wide range of environmental conditions. DNA also offers unique chemistries and interacts with a range of biomolecules, making it an ideal component in biological sensor applications. The primary goal of this project was to develop methods that utilize in vitro DNA synthesis to provide spatial localization of nanocrystal quantum dots (nQDs). To accomplish this goal, three specific technical objectives were addressed: (1) attachment of nQDs to DNA nucleotides, (2) demonstrating the synthesis of nQD-DNA strands in bulk solution, and (3) optimizing the ratio of unlabeled to nQD-labeled nucleotides. DNA nucleotides were successfully attached to nQDs using the biotin-streptavidin linkage. Synthesis of 450-nm long, nQD-coated DNA strands was demonstrated using a DNA template and the polymerase chain reaction (PCR)-based method of DNA amplification. Modifications in the synthesis process and conditions were subsequently used to synthesize 2-{micro}m long linear nQD-DNA assemblies. In the case of the 2-{micro}m structures, both the ratio of streptavidin-coated nQDs to biotinylated dCTP, and streptavidin-coated nQD-dCTPs to unlabeled dCTPs affected the ability to synthesize the nQD-DNA assemblies. Overall, these proof-of-principles experiments demonstrated the successful synthesis of nQD-DNA using DNA templates and in vitro replication technologies. Continued development of this technology may enable rapid, spatial patterning of semiconductor nanoparticles with Angstrom-level resolution, as well as optically active probes for DNA and other biomolecular analyses.

Crown, Kevin K.; Bachand, George David

2004-11-01T23:59:59.000Z

157

Quantum dot coating of baculoviral vectors enables visualization of transduced cells and tissues  

SciTech Connect

Highlights: •The use of quantum dot (QD)-labeled viral vectors for in vivo imaging is not well investigated. •A new method to label enveloped baculovirus with glutathione-capped CdTe QDs is developed. •The labeling enables the identification of transduced, cultured cells based on fluorescence. •The labeling also allows evaluation of viral transduction in a real-time manner in living mice. •The method has the potential to assess viral vector-based gene therapy protocols in future. -- Abstract: Imaging of transduced cells and tissues is valuable in developing gene transfer vectors and evaluating gene therapy efficacy. We report here a simple method to use bright and photostable quantum dots to label baculovirus, an emerging gene therapy vector. The labeling was achieved through the non-covalent interaction of glutathione-capped CdTe quantum dots with the virus envelope, without the use of chemical conjugation. The quantum dot labeling was nondestructive to viral transduction function and enabled the identification of baculoviral vector-transduced, living cells based on red fluorescence. When the labeled baculoviral vectors were injected intravenously or intraventricularly for in vivo delivery of a transgene into mice, quantum dot fluorescence signals allow us monitor whether or not the injected tissues were transduced. More importantly, using a dual-color whole-body imaging technology, we demonstrated that in vivo viral transduction could be evaluated in a real-time manner in living mice. Thus, our method of labeling a read-to-use gene delivery vector with quantum dots could be useful towards the improvement of vector design and will have the potential to assess baculovirus-based gene therapy protocols in future.

Zhao, Ying; Lo, Seong Loong [Institute of Bioengineering and Nanotechnology, Singapore (Singapore)] [Institute of Bioengineering and Nanotechnology, Singapore (Singapore); Zheng, Yuangang [Institute of Materials Research and Engineering, Singapore (Singapore)] [Institute of Materials Research and Engineering, Singapore (Singapore); Lam, Dang Hoang [Institute of Bioengineering and Nanotechnology, Singapore (Singapore) [Institute of Bioengineering and Nanotechnology, Singapore (Singapore); Department of Biological Sciences, National University of Singapore, Singapore (Singapore); Wu, Chunxiao [Institute of Bioengineering and Nanotechnology, Singapore (Singapore)] [Institute of Bioengineering and Nanotechnology, Singapore (Singapore); Han, Ming Yong [Institute of Materials Research and Engineering, Singapore (Singapore)] [Institute of Materials Research and Engineering, Singapore (Singapore); Wang, Shu, E-mail: dbsws@nus.edu.sg [Institute of Bioengineering and Nanotechnology, Singapore (Singapore) [Institute of Bioengineering and Nanotechnology, Singapore (Singapore); Department of Biological Sciences, National University of Singapore, Singapore (Singapore)

2013-04-26T23:59:59.000Z

158

Theory of Coulomb-blockade oscillations in the conductance of a quantum dot  

Science Journals Connector (OSTI)

A linear-response theory is developed for resonant tunneling through a quantum dot of small capacitance, in the regime of thermally broadened resonances. The theory extends the classical theory of Coulomb-blockade oscillations by Kulik and Shekhter to the resonant-tunneling regime. Both the cases of negligible and strong inelastic scattering in the quantum dot are considered. Effects from the non-Fermi-Dirac distribution of electrons among the energy levels (occurring when kT is comparable to the level separation) are fully included. Explicit analytic results are obtained for the periodicity, amplitude, line shape, and activation energy of the conductance oscillations.

C. W. J. Beenakker

1991-07-15T23:59:59.000Z

159

The convergence of quantum-dot-mediated fluorescence resonance energy transfer and  

Science Journals Connector (OSTI)

We present a novel convergence of quantum-dot-mediated fluorescence resonance energy transfer (QD-FRET) and microfluidics, through which molecular interactions were precisely controlled and monitored using highly sensitive quantum-dot-mediated FRET. We demonstrate its potential in studying the kinetics of self-assembly of DNA polyplexes under laminar flow in real time with millisecond resolution. The integration of nanophotonics and microfluidics offers a powerful tool for elucidating the formation of polyelectrolyte polyplexes, which is expected to provide better control and synthesis of uniform and customizable polyplexes for future nucleic acid-based therapeutics.

Yi-Ping Ho; Hunter H Chen; Kam W Leong; Tza-Huei Wang

2009-01-01T23:59:59.000Z

160

Dispersive Coupling Between the Superconducting Transmission Line Resonator and the Double Quantum Dots  

E-Print Network (OSTI)

Realization of controllable interaction between distant qubits is one of the major problems in scalable solid state quantum computing. We study a superconducting transmission line resonator (TLR) as a tunable dispersive coupler for the double-dot molecules. A general interaction Hamiltonian of $n$ two-electron spin-based qubits and the TLR is presented, where the double-dot qubits are biased at the large detuning region and the TLR is always empty and virtually excited. Our analysis o the main decoherence sources indicates that various major quantum operations can be reliably implemented with current technology.

Guo-Ping Guo; Hui Zhang; Yong Hu; Tao Tu; Guang-Can Guo

2008-02-10T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Graphene quantum dots for valley-based quantum computing: A feasibility study  

E-Print Network (OSTI)

At the center of quantum computing1 realization is the physical implementation of qubits - two-state quantum information units. The rise of graphene2 has opened a new door to the implementation. Because graphene electrons simulate two-dimensional relativistic particles with two degenerate and independent energy valleys,3 a novel degree of freedom (d.o.f.), namely, the valley state of an electron, emerges as a new information carrier.4 Here, we expand the Loss-DiVincenzo quantum dot (QD) approach in electron spin qubits,5,6 and investigate the feasibility of double QD (DQD) structures in gapful graphene as "valley qubits", with the logic 0 / 1 states represented by the "valley" singlet / triplet pair. This generalization is characterized by 1) valley relaxation time ~ O(ms), and 2) electric qubit manipulation on the time scale ~ ns, based on the 1st-order "relativistic effect" unique in graphene. A potential for valley-based quantum computing is present.

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

2011-04-04T23:59:59.000Z

162

Suppression of Zeeman gradients by nuclear polarization in double quantum dots  

E-Print Network (OSTI)

We use electric dipole spin resonance to measure dynamic nuclear polarization in InAs nanowire quantum dots. The resonance shifts in frequency when the system transitions between metastable high and low current states, indicating the presence of nuclear polarization. We propose that the low and the high current states correspond to different total Zeeman energy gradients between the two quantum dots. In the low current state, dynamic nuclear polarization efficiently compensates the Zeeman gradient due to the $g$-factor mismatch, resulting in a suppressed total Zeeman gradient. We present a theoretical model of electron-nuclear feedback that demonstrates a fixed point in nuclear polarization for nearly equal Zeeman splittings in the two dots and predicts a narrowed hyperfine gradient distribution.

S. M. Frolov; J. Danon; S. Nadj-Perge; K. Zuo; J. W. W. van Tilburg; V. S. Pribiag; J. W. G. van den Berg; E. P. A. M. Bakkers; L. P. Kouwenhoven

2012-09-07T23:59:59.000Z

163

Excitonic enhancement of nonradiative energy transfer from a quantum well in the optical near field of energy gradient quantum dots  

E-Print Network (OSTI)

. Phys. 111, 113714 (2012) Transport of indirect excitons in a potential energy gradient Appl. Phys. Lett 30 April 2012; published online 13 June 2012) We report strong exciton migration with an efficiency (QWs) to colloidal nanocrystal quantum dots (NQDs) is criti- cal to the energy efficiency in hybrid

Demir, Hilmi Volkan

164

Functionalized Quantum Dots for Biosensing and Bioimaging and Concerns on Toxicity  

Science Journals Connector (OSTI)

In addition, recent concerns on the potential toxic effects of QDs are described as a general guidance for the development on QD formulations in future studies. ... (54) By using this delivery method, individual kinesin motor proteins in HeLa cells were imaged by bioconjugated QDs at single molecule resolution. ... Tracking Individual Kinesin Motors in Living Cells Using Single Quantum-Dot Imaging ...

Yucheng Wang; Rui Hu; Guimiao Lin; Indrajit Roy; Ken-Tye Yong

2013-02-08T23:59:59.000Z

165

Performance study of CdS/Co-Doped-CdSe quantum dot sensitized solar cells  

Science Journals Connector (OSTI)

In order to optimize the charge transfer path in quantum dot sensitized solar cells (QDSCs), we employed successive ionic layer adsorption and reaction method to dope CdSe with Co for fabricating CdS/Co-doped-CdSe QDSCs constructed with CdS/Co-doped-CdSe ...

Xiaoping Zou, Sheng He, Gongqing Teng, Chuan Zhao

2014-01-01T23:59:59.000Z

166

A Study Of Semiconductor Quantum Dots In The Application To Terahertz Sensors  

E-Print Network (OSTI)

A Study Of Semiconductor Quantum Dots In The Application To Terahertz Sensors Raymond Davis M and referenced as part of background information used in this project. Raymond Davis October 1, 2011 ii #12 sensors. For detection of terahertz radia- tion we probe charge excitations of QDs caused

Sheldon, Nathan D.

167

PHYSICAL REVIEW B 85, 085117 (2012) Spin thermopower in interacting quantum dots  

E-Print Network (OSTI)

current without accompanying charge current. For temperatures and fields at or above the Kondo temperature, we relate the spin-Seebeck coefficient to the charge-Seebeck coefficient of a negative-U quantum dot applications, including power generation, refrigeration, and temperature measurement.1 Thermoelectric phenomena

Ramsak, Anton

168

Electrical and Thermal Conductivity of Ge/Si Quantum Dot Superlattices  

E-Print Network (OSTI)

. Good carrier mobility and electric con- ductivity are important for thermoelectric materials where-Riverside, Riverside, California 92521, USA Recently proposed thermoelectric applications of quantum dot superlattices made of different material systems depend crucially on the values of the electrical and thermal

169

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

E-Print Network (OSTI)

on irradiation dose. CdSe/ZnS quantum dots show poor radiation hardness, and severely degrade after less than 20 of light sources to ionizing radiation, it is important to know the levels of irradiation that would de of applica- tions ranging from optoelectronic through photocatalytic to biomedical, including applications

New Mexico, University of

170

Colloidal PbS Quantum Dot Solar Cells with High Fill Factor  

E-Print Network (OSTI)

Colloidal PbS Quantum Dot Solar Cells with High Fill Factor Ni Zhao, Tim P. Osedach,, Liang,§ and Vladimir Bulovic, * Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, School of Engineering and Applied Sciences, Harvard University

171

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

SciTech Connect

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.

Aly, Abou El-Maaty M., E-mail: drabouelmaaty@hotmail.com, E-mail: ashraf.nasr@gmail.com [Power Electronics and Energy Conversion Department, ERI, NRCB (Egypt); College of Computer, Qassim University, P.O.B. 6688, Buryadah 51453 (Saudi Arabia); Nasr, A., E-mail: drabouelmaaty@hotmail.com, E-mail: ashraf.nasr@gmail.com [Radiation Engineering Department, NCRRT, Atomic Energy Authority (Egypt); College of Computer, Qassim University, P.O.B. 6688, Buryadah 51453 (Saudi Arabia)

2014-03-21T23:59:59.000Z

172

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

E-Print Network (OSTI)

). This hierarchical structure had two advantages in improving the power conversion efficiency (PCE) of the solar cells. INTRODUCTION The establishment of low-cost and high-performance solar cells for sustainable energy sourcesHierarchically Structured ZnO Nanorods-Nanosheets for Improved Quantum-Dot-Sensitized Solar Cells

Cao, Guozhong

173

Self-assembly of triangular quantum dots on (111)A substrates by droplet epitaxy  

SciTech Connect

We report the self-assembly of triangular GaAs quantum dots (QDs) on (111)A substrates using droplet epitaxy. Shape transition from hexagonal to triangular QDs is observed with increasing crystallizing temperature. The mechanism of the morphological change is discussed in terms of different growth rates of step edges on a (111)A substrate.

Jo, M.; Mano, T.; Abbarchi, M.; Kuroda, T. [Advanced Photonics Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Sakoda, K. [Advanced Photonics Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan and Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan)

2014-05-15T23:59:59.000Z

174

Microwave accelerated one-minute synthesis of luminescent ZnO quantum dots  

Science Journals Connector (OSTI)

In this paper we present microwave assisted non-aqueous synthesis of ZnO quantum dots (QDs) by hydrolyzing zinc acetate with lithium hydroxide in ethanol under microwave heating. The processing time for QDs was reduced to few minutes when compared with time consuming sol–gel chemistry. The prepared QDs show good colloidal stability along with stable visible emission.

Adersh Asok; A. R. Kulkarni; Mayuri N. Gandhi

2013-01-01T23:59:59.000Z

175

Synthesis and optical properties of cadmium selenide quantum dots for white light-emitting diode application  

SciTech Connect

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.

Xu, Xianmei; Wang, Yilin; Gule, Teri; Luo, Qiang [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 53000 (China); Zhou, Liya, E-mail: zhouliyatf@163.com [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 53000 (China); Gong, Fuzhong [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 53000 (China)

2013-03-15T23:59:59.000Z

176

Intersubband absorption in boron-doped multiple Ge quantum dots J. L. Liu,a)  

E-Print Network (OSTI)

Intersubband absorption in boron-doped multiple Ge quantum dots J. L. Liu,a) W. G. Wu, A. Balandin; accepted for publication 3 November 1998 The intersubband absorption in self-assembled boron-doped multiple and undoped Si barriers. The infrared absorption as a function of wavelength is measured by Fourier transform

177

Tuning the optical properties of dilute nitride site controlled quantum dots  

SciTech Connect

We show that deterministic control of the properties of pyramidal site-controlled quantum dots (QD) could be achieved by exposing the QD layer to nitrogen precursor unsymmetrical dimethylhydrazine (UDMHy). The properties that could be tuned include an expected emission reduction in dilute nitride materials, excitonic pattern (biexciton binding energy) and improved carrier confinement potential symmetry (reduced fine-structure splitting)

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

2013-12-04T23:59:59.000Z

178

Energy Transfer from an Individual Quantum Dot to a Carbon Nanotube  

E-Print Network (OSTI)

saturation of the energy transfer efficiency at 96%, seemingly independent of CNT chirality. KEYWORDS NanoEnergy Transfer from an Individual Quantum Dot to a Carbon Nanotube Eyal Shafran, Benjamin D. Mangum, and Jordan M. Gerton* Department of Physics and Astronomy, University of Utah, Salt Lake City

Gerton, Jordan M.

179

Study of the self-organization processes in lead sulfide quantum dots  

SciTech Connect

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.

Tarasov, S. A., E-mail: SATarasov@mail.ru; Aleksandrova, O. A.; Maksimov, A. I.; Maraeva, E. V.; Matyushkin, L. B.; Men’kovich, E. A.; Moshnikov, V. A. [St. Petersburg Electrotechnical University LETI (Russian Federation); Musikhin, S. F. [St. Petersburg State Polytechnic University (Russian Federation)

2014-12-15T23:59:59.000Z

180

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

E-Print Network (OSTI)

Ambient-Processed Colloidal Quantum Dot Solar Cells via Individual PreVersity of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada, and Department of Materials Science and Engineering, UniVersity of Toronto, 184 College Street, Toronto, Ontario M5S 3E4, Canada Received February 24

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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181

Prospective Article Materials processing strategies for colloidal quantum dot solar cells  

E-Print Network (OSTI)

Prospective Article Materials processing strategies for colloidal quantum dot solar cells: advances and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada Kang, Toronto, Ontario M5S 3G4, Canada Address all correspondence to Edward H. Sargent at ted

182

Cu2ZnSnS4 nanocrystals and graphene quantum dots for photovoltaics Xukai Xinab  

E-Print Network (OSTI)

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

Lin, Zhiqun

183

Cooling an electron gas using quantum dot based electronic refrigeration  

E-Print Network (OSTI)

comparable to the Fermi wavelength. Con- finement in the other two directions (x and y) is over large enough distances for the quantisation of momentum in the x-y plane to be neglected. The energy of a carrier with effective mass m? can therefore be written... (negative) current from drain to source. The blue lines show non-zero differential conductance. The angles ?S and ?D are used to determine the conversion factor between VG and dot energy. Insets (a)-(c) show the energy levels of the dot at the corresponding...

Prance, Jonathan Robert

2009-10-13T23:59:59.000Z

184

Phonons in quantum dots and their role in exciton dephasing  

E-Print Network (OSTI)

-nitrides. Values are taken from [5]. The values for the nitride compounds are taken from density functional dots (QDs). The state of the art is reported in detail in the present book. A large application- driven the theory of acoustic phonons in QDs is explained in Sec. 3. Special emphasis is given to continuum

Zimmermann, Roland

185

Ultrasmall silicon quantum dots F. A. Zwanenburg,1,a  

E-Print Network (OSTI)

by a model based on the Poisson equation. The smallest dots 12 nm allow identification of the last charge-down planar silicon devices,1­3 produced by etching bulk materials down to nanometer dimensions, often show understanding of the specific system. This has allowed us to realize the first experimental identification

186

Full counting statistics as a probe of quantum coherence in a side-coupled double quantum dot system  

SciTech Connect

We study theoretically the full counting statistics of electron transport through side-coupled double quantum dot (QD) based on an efficient particle-number-resolved master equation. It is demonstrated that the high-order cumulants of transport current are more sensitive to the quantum coherence than the average current, which can be used to probe the quantum coherence of the considered double QD system. Especially, quantum coherence plays a crucial role in determining whether the super-Poissonian noise occurs in the weak inter-dot hopping coupling regime depending on the corresponding QD-lead coupling, and the corresponding values of super-Poissonian noise can be relatively enhanced when considering the spins of conduction electrons. Moreover, this super-Poissonian noise bias range depends on the singly-occupied eigenstates of the system, which thus suggests a tunable super-Poissonian noise device. The occurrence-mechanism of super-Poissonian noise can be understood in terms of the interplay of quantum coherence and effective competition between fast-and-slow transport channels. -- Highlights: •The FCS can be used to probe the quantum coherence of side-coupled double QD system. •Probing quantum coherence using FCS may permit experimental tests in the near future. •The current noise characteristics depend on the quantum coherence of this QD system. •The super-Poissonian noise can be enhanced when considering conduction electron spin. •The side-coupled double QD system suggests a tunable super-Poissonian noise device.

Xue, Hai-Bin, E-mail: xuehaibin@tyut.edu.cn

2013-12-15T23:59:59.000Z

187

Non-adiabatic quantum pumping by a randomly moving quantum dot  

E-Print Network (OSTI)

We look at random 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. Here 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). In the special limit of a delta-correlated continuous Gaussian random walk we obtain closed analytical expressions for the ensemble averaged amplitude in the co-moving frame and demonstrate that the main contribution to the average wavefunction and probability current comes from the Berry-phase component which leads to the saturation of the fluctuations of the electric current and the pumped charge. We also derive the exact expressions for the average propagator (in the co-moving basis representation) for both types of motion.

Stanislav Derevyanko; Daniel Waltner

2015-02-10T23:59:59.000Z

188

Spin Dynamics in Two-Dimensional Arrays of Quantum Dots with Local Ordering of Nanoclusters  

SciTech Connect

Electron paramagnetic resonance (EPR) is used to probe the spin dynamics in two-dimensional (2D) quantum dot (QD) arrays with local ordering of nanoclusters. A careful examination of EPR line shape, width and g-factor values allow us to attribute this signal to the electrons localized in the strain-induced potential wells in Si in the vicinity of the Ge dots. The strong orientation dependence of EPR line width is defined by changing localization degree of electrons at different magnetic field directions. The theoretical approximation of orientation dependence of EPR line width allows estimating the effective radius of electron localization, as {approx}80 nm.

Zinovieva, A. F.; Dvurechenskii, A. V.; Stepina, N. P.; Nikiforov, A. I.; Lyubin, A. S. [Institute of Semiconductor Physics, 630090 Novosibirsk, pr. Lavrentieva 13 (Russian Federation); Sobolev, N.; Carmo, M. C. [Departamento de Fisica e I3N, Universidade de Aveiro, Aveiro (Portugal)

2011-12-23T23:59:59.000Z

189

Generation of quantum-dot cluster states with superconducting transmission line resonator  

E-Print Network (OSTI)

We propose an efficient method to generate cluster states in spatially separated double quantum dots with a superconducting transmission line resonator (TLR). When the detuning between the double-dot qubits transition frequency and the frequency of the full wave mode in the TLR satisfies some conditions, an Ising-like operator between arbitrary two separated qubits can be achieved. Even including the main noise sources, it's shown that the high fidelity cluster states could be generated in this solid system in just one step.

Zhi-Rong Lin; Guo-Ping Guo; Tao Tu; Fei-Yun Zhu; Guang-Can Guo

2008-04-20T23:59:59.000Z

190

Laser Power Meter Large, bright, backlit LCD  

E-Print Network (OSTI)

Laser Power Meter FEATURES · Large, bright, backlit LCD display · Digital accuracy with analog-like movement for laser tuning · Works with thermopile and optical sensors · Intuitive button-driven user COMPATIBILITY · PowerMax® thermal sensors · Optical sensors FieldMaxII-TO Coherent Laser Measurement and Control

Woodall, Jerry M.

191

Enhanced photorefractive performance in CdSe quantum-dot-dispersed poly(styrene-co-acrylonitrile) polymers  

SciTech Connect

This paper reports on the enhanced photorefractive behavior of a CdSe quantum-dot-dispersed less expensive polymer of poly(styrene-co-acrylonitrile). The capability of CdSe quantum dots used as photosensitizers and the associated photorefractive performance are characterized through a photocurrent experiment and a two-beam coupling experiment, respectively. An enhanced two-beam coupling gain coefficient of 12.2 cm{sup -1} at 46 V/mum was observed owning to the reduced potential barrier. The photorefractive performance per CdSe quantum dot is three orders of magnitude higher than that in the sample sensitized by trinitrofluorenone in poly(styrene-co-acrylonitrile), and almost ten times higher than that in the CdSe quantum-dot-sensitized poly(N-vinylcarbazole) polymers.

Li Xiangping; Embden, Joel van; Chon, James W. M.; Gu Min [Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Evans, Richard A. [CSIRO Molecular and Health Technologies, Bag 10, Clayton South, Victoria 3169 (Australia)

2010-06-21T23:59:59.000Z

192

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

E-Print Network (OSTI)

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, ...

Jaffar, Saeeda Mahdi

2005-01-01T23:59:59.000Z

193

Development of a Bioorthogonal and Highly Efficient Conjugation Method for Quantum Dots using Tetrazine-Norbornene Cycloaddition  

E-Print Network (OSTI)

We present a bioorthogonal and modular conjugation method for efficient coupling of organic dyes and biomolecules to quantum dots (QDs) using a norbornene?tetrazine cycloaddition. The use of noncoordinating functional ...

Han, Hee-Sun

194

Physica E 34 (2006) 15 Single-shot readout of electron spins in a semiconductor quantum dot  

E-Print Network (OSTI)

states in a semiconductor quantum dot that is robust against charge noise and can be used even when readout (E-RO), the spin levels are positioned around the electrochemical potential of the reservoir mres

195

Role of surface states and defects in the ultrafast nonlinear optical properties of CuS quantum dots  

SciTech Connect

We report facile preparation of water dispersible CuS quantum dots (2–4 nm) and nanoparticles (5–11 nm) through a nontoxic, green, one-pot synthesis method. Optical and microstructural studies indicate the presence of surface states and defects (dislocations, stacking faults, and twins) in the quantum dots. The smaller crystallite size and quantum dot formation have significant effects on the high energy excitonic and low energy plasmonic absorption bands. Effective two-photon absorption coefficients measured using 100 fs laser pulses employing open-aperture Z-scan in the plasmonic region of 800 nm reveal that CuS quantum dots are better ultrafast optical limiters compared to CuS nanoparticles.

Mary, K. A. Ann; Unnikrishnan, N. V., E-mail: nvu100@yahoo.com [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam 686560 (India); Philip, Reji [Light and Matter Physics Group, Raman Research Institute, C.V. Raman Avenue, Sadashivanagar, Bangalore 560080 (India)

2014-07-01T23:59:59.000Z

196

Creating a Precise Atomic-Scale Map of Quantum Dots | Advanced Photon  

NLE Websites -- All DOE Office Websites (Extended Search)

Getting to the Roots of Lethal Hairs Getting to the Roots of Lethal Hairs Stressing Out the Twins in Magnesium Size-Related Behavior of Anatase Nanocrystals under Extreme Pressure Boron-Based Compounds Trick a Biomedical Protein A Targeted Cancer Treatment using Nanomaterials Science Highlights Archives: 2013 | 2012 | 2011 | 2010 2009 | 2008 | 2007 | 2006 2005 | 2004 | 2003 | 2002 2001 | 2000 | 1998 | Subscribe to APS Science Highlights rss feed Creating a Precise Atomic-Scale Map of Quantum Dots OCTOBER 9, 2009 Bookmark and Share An atomic-scale map of the interface between an atomic dot and its substrate. Each peak represents a single atom. The map, made with high-intensity x-rays at the APS, is a slice through a vertical cross-section of the dot. (Image courtesy of Roy Clarke, University of

197

Stable and unstable dynamics of Overhauser fields in a double quantum dot  

Science Journals Connector (OSTI)

Nonlinear dynamics of nuclear spin ensembles driven by a two-electron system in a double quantum dot in the Pauli spin blockade (SB) regime is studied experimentally in conjunction with numerical simulation. Dynamic nuclear spin polarization (DNP) is systematically studied by evaluating the current level and its fluctuations. We interpret large current noise in the SB regime as stable feedback noise, where identical Overhauser fields of the two dots are preferred. In contrast, stepwise increases of current in the shallow Coulomb blockade region can be understood as unstable dynamics with significant imbalance of the Overhauser fields, which cancels the external magnetic field in one of the two dots. There, an extremely small transverse Overhauser field can easily lift the SB transport, giving the highest current level, when longitudinal components cancel the applied field.

Sonia Sharmin; Koji Muraki; Toshimasa Fujisawa

2014-03-21T23:59:59.000Z

198

Transmission phase of a quantum dot and statistical fluctuations of partial-width amplitudes  

E-Print Network (OSTI)

Experimentally, the phase of the amplitude for electron transmission through a quantum dot (transmission phase) shows the same pattern between consecutive resonances. Such universal behavior, found for long sequences of resonances, is caused by correlations of the signs of the partial-width amplitudes of the resonances. We investigate the stability of these correlations in terms of a statistical model. For a classically chaotic dot, the resonance eigenfunctions are assumed to be Gaussian distributed. Under this hypothesis, statistical fluctuations are found to reduce the tendency towards universal phase evolution. Long sequences of resonances with universal behavior only persist in the semiclassical limit of very large electron numbers in the dot and for specific energy intervals. Numerical calculations qualitatively agree with the statistical model but quantitatively are closer to universality.

Rodolfo A. Jalabert; Guillaume Weick; Hans A. Weidenmüller; Dietmar Weinmann

2013-12-03T23:59:59.000Z

199

Dynamic Acoustic Control of Individual Optically Active Quantum Dot-like Emission Centers in Heterostructure Nanowires  

E-Print Network (OSTI)

We probe and control the optical properties of emission centers forming in radial het- erostructure GaAs-Al0.3Ga0.7As nanowires and show that these emitters, located in Al0.3Ga0.7As layers, can exhibit quantum-dot like characteristics. We employ a radio frequency surface acoustic wave to dynamically control their emission energy and occupancy state on a nanosec- ond timescale. In the spectral oscillations we identify unambiguous signatures arising from both the mechanical and electrical component of the surface acoustic wave. In addition, differ- ent emission lines of a single quantum dot exhibit pronounced anti-correlated intensity oscilla- tions during the acoustic cycle. These arise from a dynamically triggered carrier extraction out of the quantum dot to a continuum in the radial heterostructure. Using finite element modeling and Wentzel-Kramers-Brillouin theory we identify quantum tunneling as the underlying mech- anism. These simulation results quantitatively reproduce the observed switching and show th...

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

2014-01-01T23:59:59.000Z

200

The operation principle of the well in quantum dot stack infrared photodetector  

SciTech Connect

The well in the quantum dot stack infrared photodetector (WD-QDIP) is proposed which can be operated at high temperature ?230?K. The operation principle of this device is investigated, including the carrier transport and the enhancement in the photocurrent. The WD-QDIPs with different well numbers are fabricated to study the mechanisms. It is realized that the carrier transport from the emitter to the collector in traditional quantum dot infrared photodetectors consists of two channels deduced from current-voltage characteristics and dark current activation energy at different temperatures. At temperatures below 77?K, the current transports through the InAs quantum dot channel, whereas at temperatures higher than 77?K, the current is dominated by the GaAs leakage channel. In addition, the non-equilibrium situation at low temperatures is also observed owing to the presence of photovoltaic phenomenon. The carrier distribution inside the QDs is simulated to investigate the reasons for the increase of photocurrent. Based on the simulation and the photocurrent response, the hot carrier (electron) scattering effect by the insertion of a quantum well layer is inferred as the most probable reason that lead to the enhancement of the response and regarded as the key factor to achieve high- temperature operation.

Lee, Jheng-Han; Wu, Zong-Ming [Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Liao, Yu-Min; Wu, Yuh-Renn [Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan (China); Lin, Shih-Yen [Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Research Center for Applied Sciences, Academia Sinica, Taipei 115299, Taiwan (China); Lee, Si-Chen, E-mail: sclee@cc.ee.ntu.edu.tw [Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan (China)

2013-12-28T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
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201

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

SciTech Connect

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.

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

2008-02-01T23:59:59.000Z

202

Positioning effects on quantum dot solar cells grown by molecular beam epitaxy  

SciTech Connect

We report current-voltage and spectral response characteristics of high density InAs/GaAs quantum dot (QD) solar cells with different positions where dots are located. The short circuit current density (J{sub sc}), open circuit voltage (V{sub oc}), and external quantum efficiency of these cells under air mass 1.5 are presented and compared with a GaAs reference cell. An extended photoresponse in contrast to the GaAs reference cell was confirmed for all these cells. The effect of inserting QD layers into emitter and base region on device performance is shown. The J{sub sc} is reduced, while the V{sub oc} is maintained. The cell with QDs located toward the base side shows better performance, confirmed by both current-voltage and spectral response measurements.

Zhou, D.; Sharma, G.; Fimland, B. O. [Department of Electronics and Telecommunications, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway); Vullum, P. E.; Thomassen, S. F.; Holmestad, R.; Reenaas, T. W. [Department of Physics, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway)

2010-02-22T23:59:59.000Z

203

Pulsed laser deposition of Mn doped CdSe quantum dots for improved solar cell performance  

SciTech Connect

In this work, we demonstrate (1) a facile method to prepare Mn doped CdSe quantum dots (QDs) on Zn{sub 2}SnO{sub 4} photoanodes by pulsed laser deposition and (2) improved device performance of quantum dot sensitized solar cells of the Mn doped QDs (CdSe:Mn) compared to the undoped QDs (CdSe). The band diagram of photoanode Zn{sub 2}SnO{sub 4} and sensitizer CdSe:Mn QD is proposed based on the incident-photon-to-electron conversion efficiency (IPCE) data. Mn-modified band structure leads to absorption at longer wavelengths than the undoped CdSe QDs, which is due to the exchange splitting of the CdSe:Mn conduction band by the Mn dopant. Three-fold increase in the IPCE efficiency has also been observed for the Mn doped samples.

Dai, Qilin; Wang, Wenyong, E-mail: wwang5@uwyo.edu, E-mail: jtang2@uwyo.edu; Tang, Jinke, E-mail: wwang5@uwyo.edu, E-mail: jtang2@uwyo.edu [Department of Physics and Astronomy, University of Wyoming, Laramie, Wyoming 82071 (United States); Sabio, Erwin M. [Department of Chemistry, University of Wyoming, Laramie, Wyoming 82071 (United States)

2014-05-05T23:59:59.000Z

204

Matter-wave quantum dots and antidots in ultracold atomic Bose-Fermi mixtures  

Science Journals Connector (OSTI)

The properties of ultracold atomic Bose-Fermi mixtures in external potentials are investigated and the existence of gap solitons of Bose-Fermi mixtures in optical lattices demonstrated. Using a self-consistent approach we compute the energy spectrum and show that gap solitons can be viewed as matter-wave realizations of quantum dots and antidots with the bosonic density playing the role of trapping (expulsive) potential for the fermions. The fermionic states trapped in the condensate are shown to be at the bottom of the Fermi sea and therefore well protected from thermal decoherence. Energy levels, filling factors, and parameters’ dependence of gap soliton quantum dots are also calculated both numerically and analytically.

Mario Salerno

2005-12-02T23:59:59.000Z

205

Strongly confining bare core CdTe quantum dots in polymeric microdisk resonators  

SciTech Connect

We report on a simple route to the efficient coupling of optical emission from strongly confining bare core CdTe quantum dots (QDs) to the eigenmodes of a micro-resonator. The quantum emitters are embedded into QD/polymer sandwich microdisk cavities. This prevents photo-oxidation and yields the high dot concentration necessary to overcome Auger enhanced surface trapping of carriers. In combination with the very high cavity Q-factors, interaction of the QDs with the cavity modes in the weak coupling regime is readily observed. Under nanosecond pulsed excitation the CdTe QDs in the microdisks show lasing with a threshold energy as low as 0.33 ?J.

Flatae, Assegid, E-mail: assegid.flatae@kit.edu; Grossmann, Tobias; Beck, Torsten; Wiegele, Sarah; Kalt, Heinz [Institute of Applied Physics and DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Str.1, 76131 Karlsruhe (Germany)

2014-01-01T23:59:59.000Z

206

High open circuit voltages of solar cells based on quantum dot and dye hybrid-sensitization  

SciTech Connect

A type of solar cell based on quantum dot (QD) and dye hybrid-sensitized mesoporous TiO{sub 2} film electrode was designed and reported. The electrode was consisted of a TiO{sub 2} nanoparticle (NP) thin film layer sensitized with CdS quantum dot (QD) and an amorphous TiO{sub 2} coated TiO{sub 2} NP thin film layer that sensitized with C106 dye. The amorphous TiO{sub 2} layer was obtained by TiCl{sub 4} post-treatment to improve the properties of solar cells. Research showed that the solar cells fabricated with as-prepared hybrid-sensitized electrode exhibited excellent photovoltaic performances and a fairly high open circuit voltage of 796?mV was achieved.

Zhao, Yujie; Zhao, Wanyu; Chen, Jingkuo; Li, Huayang; Fu, Wuyou, E-mail: hari@hpu.edu.cn, E-mail: fuwy56@163.com; Sun, Guang; Cao, Jianliang; Zhang, Zhanying [School of Materials Science and Engineering and Cultivating Base for Key Laboratory of Environment-friendly Inorganic Materials in University of Henan Province, Henan Polytechnic University, Jiaozuo 454000 (China)] [School of Materials Science and Engineering and Cultivating Base for Key Laboratory of Environment-friendly Inorganic Materials in University of Henan Province, Henan Polytechnic University, Jiaozuo 454000 (China); Bala, Hari, E-mail: hari@hpu.edu.cn, E-mail: fuwy56@163.com [School of Materials Science and Engineering and Cultivating Base for Key Laboratory of Environment-friendly Inorganic Materials in University of Henan Province, Henan Polytechnic University, Jiaozuo 454000 (China) [School of Materials Science and Engineering and Cultivating Base for Key Laboratory of Environment-friendly Inorganic Materials in University of Henan Province, Henan Polytechnic University, Jiaozuo 454000 (China); College of Chemistry and Chemical Engineering, Inner Mongolia University for the Nationalities, Tongliao 028043 (China)

2014-01-06T23:59:59.000Z

207

Note: Near infrared spectral and transient measurements of PbS quantum dots luminescence  

SciTech Connect

We describe an experimental setup for the characterization of luminescence from nanostructures. The setup is intended for steady-state and time-resolved luminescence measurements in the near-infrared region. The setup allows us to study spectral luminescence properties in the spectral range of 0.8–2.0 ?m with high spectral resolution and kinetic luminescence properties between 0.8 and 1.7 ?m with a time resolution of 3 ns. The capabilities of the system are illustrated by taking luminescence measurements from PbS quantum dots. We established the size dependencies of the optical properties of the PbS quantum dots over a wide spectral range. Finally, the energy transfer process was studied with a high temporal and spectral resolution.

Parfenov, P. S., E-mail: qrspeter@pochta.ru; Litvin, A. P., E-mail: litvin88@gmail.com; Ushakova, E. V.; Fedorov, A. V.; Baranov, A. V. [National Research University of Informational Technologies, Mechanics and Optics, 197101 49, Kronverkskiy pr., Saint Petersburg (Russian Federation)] [National Research University of Informational Technologies, Mechanics and Optics, 197101 49, Kronverkskiy pr., Saint Petersburg (Russian Federation); Berwick, K. [School of Electronic and Communications Engineering, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland)] [School of Electronic and Communications Engineering, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland)

2013-11-15T23:59:59.000Z

208

Effect of Organic and Inorganic Passivation in Quantum-Dot-Sensitized Solar Cells  

Science Journals Connector (OSTI)

This work was supported by the Institute of Nanotechnologies for Clean Energies (INCE), funded by the Generalitat Valenciana under Project ISIC/2012/008. ... We acknowledge projects CYTED-Nanoenergía, PAPIIT-IN106912 (UNAM-México), and CONACyT-153270 (México) for financial support. ... Quantum dot-sensitized solar cells (QDSSCs) are interesting energy devices because of their (i) impressive ability to harvest sunlight and generate multiple electron/hole pairs, (ii) ease of fabrication, and (iii) low cost. ...

Mauricio Solis de la Fuente; Rafael S. Sánchez; Victoria González-Pedro; Pablo P. Boix; S. G. Mhaisalkar; Marina E. Rincón; Juan Bisquert; Iván Mora-Seró

2013-04-12T23:59:59.000Z

209

Local droplet etching – Nanoholes, quantum dots, and air-gap heterostructures  

SciTech Connect

Local droplet etching (LDE) allows the self-organized generation of nanoholes in semiconductor surfaces and is fully compatible with molecular beam epitaxy (MBE). The influence of the process parameters as well as of droplet and substrate materials on the LDE nanohole morphology is discussed. Furthermore, recent applications of LDE, the fabrication of quantum dots by hole filling and the creation of air-gap heterostructures are addressed.

Heyn, Ch.; Sonnenberg, D.; Graf, A.; Kerbst, J.; Stemmann, A.; Hansen, W. [Institute of Applied Physics, University of Hamburg, Jungiusstr. 11, 20355 Hamburg (Germany)

2014-05-15T23:59:59.000Z

210

Second harmonic generation from direct band gap quantum dots pumped by femtosecond laser pulses  

SciTech Connect

We report on nonlinear optical experiments performed on Cu{sub 2}S quantum dots (QDs) pumped by femtosecond laser pulses. We conduct a theoretical simulation and experiments to determine their second harmonic generation characteristics. Furthermore, we demonstrate that the QDs have a second harmonic generation conversion efficiency of up to 76%. Our studies suggest that these Cu{sub 2}S QDs can be used for solar cells, bioimaging, biosensing, and electric detection.

Liu, Liwei, E-mail: liulw@cust.edu.cn; Wang, Yue; Hu, Siyi; Ren, Yu; Huang, Chen [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022, People's Republic of China and International Joint Research Center for Nanophotonics and Biophotonics, Changchun University of Science and Technology, Changchun, Jilin 130022 (China)

2014-02-21T23:59:59.000Z

211

Electron tunneling characteristics of a cubic quantum dot, (PbS){sub 32}  

SciTech Connect

The electron transport properties of the cubic quantum dot, (PbS){sub 32}, are investigated. The stability of the quantum dot has been established by recent scanning tunneling microscope experiments [B. Kiran, A. K. Kandalam, R. Rallabandi, P. Koirala, X. Li, X. Tang, Y. Wang, H. Fairbrother, G. Gantefoer, and K. Bowen, J. Chem. Phys. 136(2), 024317 (2012)]. In spite of the noticeable energy band gap (?2 eV), a relatively high tunneling current for (PbS){sub 32} is predicted affirming the observed bright images for (PbS){sub 32}. The calculated I-V characteristics of (PbS){sub 32} are predicted to be substrate-dependent; (PbS){sub 32} on the Au (001) exhibits the molecular diode-like behavior and the unusual negative differential resistance effect, though this is not the case with (PbS){sub 32} on the Au (110). Appearance of the conduction channels associated with the hybridized states of quantum dot and substrate together with their asymmetric distribution at the Fermi level seem to determine the tunneling characteristics of the system.

Gupta, Sanjeev K., E-mail: sanjeevg@mtu.edu, E-mail: haiying.he@valpo.edu; Banyai, Douglas; Pandey, Ravindra [Department of Physics, Michigan Technological University, Houghton, Michigan 49931 (United States)] [Department of Physics, Michigan Technological University, Houghton, Michigan 49931 (United States); He, Haiying, E-mail: sanjeevg@mtu.edu, E-mail: haiying.he@valpo.edu [Department of Physics and Astronomy, Valparaiso University, Valparaiso, Indiana 46383 (United States)] [Department of Physics and Astronomy, Valparaiso University, Valparaiso, Indiana 46383 (United States); Kandalam, Anil K. [Department of Physics, West Chester University of Pennsylvania, West Chester, Pennsylvania 19383 (United States)] [Department of Physics, West Chester University of Pennsylvania, West Chester, Pennsylvania 19383 (United States)

2013-12-28T23:59:59.000Z

212

Microchemical systems for the synthesis of nanostructures : quantum dots  

E-Print Network (OSTI)

We have developed a continuous multi-stage high-temperature and high-pressure microfluidic system. High-pressure conditions enabled the use low molecular weight solvents that have previously not been available for quantum ...

Baek, Jinyoung

2012-01-01T23:59:59.000Z

213

Optimization towards high density quantum dots for intermediate band solar cells grown by molecular beam epitaxy  

SciTech Connect

We report high density quantum dots (QDs) formation with optimized growth temperature and V/III ratio. At lower growth temperature, QD density is increased, due to smaller surface migration length of In adatoms. With higher V/III, the QD density is higher but it results in large clusters formation and decreases the QD uniformity. The QD solar cell was fabricated and examined. An extended spectral response in contrast to the GaAs reference cell was presented but the external quantum efficiency at energies higher than GaAs band gap is reduced, resulting from the degradation for the emitter above the strained QD layers.

Zhou, D.; Sharma, G.; Fimland, B. O. [Department of Electronics and Telecommunications, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway); Thomassen, S. F.; Reenaas, T. W. [Department of Physics, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway)

2010-02-08T23:59:59.000Z

214

* bulovic@mit.edu; phone 617 253 7012; fax 617 452 5110; rleweb.mit.edu/organic Method for fabrication of saturated RGB quantum dot light emitting  

E-Print Network (OSTI)

color emission in the red, green and blue regions of the spectrum. Keywords: nanocrystal, quantum dot capping groups, surrounding the QD lumophores, facilitate processing in organic solvents

215

A theoretical analysis of the optical absorption properties in one-dimensional InAs/GaAs quantum dot superlattices  

SciTech Connect

We present theoretical investigations of miniband structures and optical properties of InAs/GaAs one-dimensional quantum dot superlattices (1D-QDSLs). The calculation is based on the multi-band k·p theory, including the conduction and valence band mixing effects, the strain effect, and the piezoelectric effect; all three effects have periodic boundary conditions. We find that both the electronic and optical properties of the 1D-QDSLs show unique states which are different from those of well known single quantum dots (QDs) or quantum wires. We predict that the optical absorption spectra of the 1D-QDSLs strongly depend on the inter-dot spacing because of the inter-dot carrier coupling and changing strain states, which strongly influence the conduction and valence band potentials. The inter-miniband transitions form the absorption bands. Those absorption bands can be tuned from almost continuous (closely stacked QD case) to spike-like shape (almost isolated QD case) by changing the inter-dot spacing. The polarization of the lowest absorption peak for the 1D-QDSLs changes from being parallel to the stacking direction to being perpendicular to the stacking direction as the inter-dot spacing increases. In the case of closely stacked QDs, in-plane anisotropy, especially [110] and [11{sup ¯}0] directions also depend on the inter-dot spacing. Our findings and predictions will provide an additional degree of freedom for the design of QD-based optoelectronic devices.

Kotani, Teruhisa, E-mail: kotani.teruhisa@sharp.co.jp [Advanced Technology Research Laboratories, Sharp Corporation, 2613-1 Ichinomoto-cho, Tenri, Nara 632-8567 (Japan); Institute for Nanoelectronics, Technische Universität München, Arcisstr. 21, 80333 Munich (Germany); Birner, Stefan [Institute for Nanoelectronics, Technische Universität München, Arcisstr. 21, 80333 Munich (Germany); Walter Schottky Institute, Technische Universität München, Am Coulombwall 4, 85748 Garching (Germany); Lugli, Paolo [Institute for Nanoelectronics, Technische Universität München, Arcisstr. 21, 80333 Munich (Germany); Hamaguchi, Chihiro [Advanced Technology Research Laboratories, Sharp Corporation, 2613-1 Ichinomoto-cho, Tenri, Nara 632-8567 (Japan)

2014-04-14T23:59:59.000Z

216

Solution Processed Tungsten Oxide Interfacial Layer for Efficient Hole-Injection in Quantum Dot Light-Emitting Diodes  

E-Print Network (OSTI)

2/2014 Solution Processed Tungsten Oxide Interfacial Layer for Efficient Hole-Injection in Quantum Layer for Efficient Hole-Injection in Quantum Dot Light- Emitting Diodes Xuyong Yang, Evren Mutlugun-based devices, the organic interfacial buffer layers have inferior thermal stability. Efforts to replace PEDOT

Demir, Hilmi Volkan

217

Polarization-entangled photon generation by a semiconductor quantum dot coupled to a cavity interacting with external fields  

E-Print Network (OSTI)

We theoretically investigate polarization-entangled photon generation by using a semiconductor quantum dot embedded in a microcavity. The entangled states can be produced by the application of two cross-circularly polarized laser fields. The quantum dot nanostructure is considered as a four-level system (ground, two excitons and bi-exciton states) and the theoretical study relies on the dressed states scheme. The quantum correlations, reported in terms of the entanglement of formation, are extensively studied for several values of the important parameters of the quantum dot system as the bi-exciton binding energy, {the decoherence times of the characteristic transitions, the quality factor of the cavity} and the intensities of the applied fields.

Kostas Blekos; Nikos Iliopoulos; Maria-Eftaksia Stasinou; Evaggelos Vlachos; Andreas F. Terzis

2014-04-07T23:59:59.000Z

218

Quantum dot based memory devices: Current status and future prospect by simulation perspective  

SciTech Connect

We discuss the simulation of floating gate MOSFET memory performance consists of Si/Ge/Si quantum dots for electronics storage nodes with higk-? material as the tunnel oxide. Heterostructure quantum dot was proposed to maintain the good memory performance without losing the long retention characteristic. As the results, retention time could be increase significantly without deteriorating the writing/erasing speed. By selected the dot size of 9–15nm and the tunnel oxide thickness of 2nm, the retention characteristic can reach up to 10{sup 9}s while the writing and erasing time at the order of 10{sup ?6}s. By replace the SiO{sub 2} tunnel oxide with high-? material such as HfO{sub 2}, ZrO{sub 2}, and Y{sub 2}O{sub 3} the leakage current due to the shrinkage of tunnel oxide thickness can be suppressed by the factor of 10 for the EOT lower than ?1nm. Moreover, the charge-trapping that generated by the defect at Si substrate and higk-? material interface are fully considered. We found that, the charge-trapping affects the retention time and memory operation performance. By increasing the charge-trapping depth and width, the memory operation time decrease significantly while the retention characteristic slightly improved.

Darma, Y., E-mail: yudi@fi.itb.ac.id; Rusydi, A., E-mail: yudi@fi.itb.ac.id [Department of Physics, Institut Teknologi Bandung, Ganesa 10 Bandung 40132, Indonesia and NUSNNI-NanoCore, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 and Singapore Synchrotron Light Source, National U (Singapore)

2014-02-24T23:59:59.000Z

219

Transport properties of a molecular quantum dot coupled to one-dimensional correlated electrons  

Science Journals Connector (OSTI)

We analyze the transport properties of a quantum dot with a harmonic degree of freedom (Holstein phonon) coupled to interacting one-dimensional metallic leads. Using Tomonaga-Luttinger model to describe the interacting leads we construct the generating function of the full counting statistics for a specific constellation of system parameters and give explicit expression for the cumulant generating function. In the resonant case we find the lowest order correction to the current to be negative and divergent when source-drain voltage approaches the phonon frequency. Via a diagram resummation procedure we show, that these divergencies can be repealed. On the contrary, in the off-resonant case the lowest order correction remains finite. This effect can be traced back to the strongly nonmonotonic behavior of the bare transmission coefficient (without phonon) with respect to the dot level energy. We calculate corrections to the noise power as well and discuss possible experimental implications of this phenomenon.

S. Maier and A. Komnik

2010-10-18T23:59:59.000Z

220

Light-mass Bragg cavity polaritons in planar quantum dot lattices  

Science Journals Connector (OSTI)

The exciton-polariton modes of a quantum dot lattice embedded in a planar optical cavity are theoretically investigated. Umklapp terms, in which an exciton interacts with many cavity modes differing by reciprocal lattice vectors, appear in the Hamiltonian due to the periodicity of the dot lattice. We focus on Bragg polariton modes obtained by tuning the exciton and the cavity modes into resonance at high symmetry points of the Brillouin zone. Depending on the microcavity design, these polariton modes at finite in-plane momentum can be guided and can have long lifetimes. Moreover, their effective mass can be extremely small, of the order of 10?8m0 (m0 is the bare electron mass), and they constitute the lightest excitonlike quasiparticles in solids.

E. M. Kessler, M. Grochol, and C. Piermarocchi

2008-02-08T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
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221

Single-photon emission from the natural quantum dots in the InAs/GaAs wetting layer  

Science Journals Connector (OSTI)

A time-resolved microphotoluminescence study is presented for quantum dots that are formed in the InAs/GaAs wetting layer. These dots are due to fluctuations of In composition in the wetting layer. They show spectrally sharp luminescence lines with a low spatial density. We identify lines related to neutral exciton and biexciton as well as trions. Exciton emission antibunching [second-order correlation value of g(2)(0)=0.16] and a biexciton-exciton emission cascade prove nonclassical emission from the dots and confirm their potential as single-photon sources.

T. Kazimierczuk; A. Golnik; P. Kossacki; J. A. Gaj; Z. R. Wasilewski; A. Babi?ski

2011-09-26T23:59:59.000Z

222

Transfer and retrieval of optical coherence to strain-compensated quantum dots using a heterodyne photon-echo technique  

SciTech Connect

We performed the proof-of-principle demonstration of photon-echo quantum memory using strain-compensated InAs quantum dot ensemble in the telecommunication wavelength range. We succeeded in transfer and retrieval of relative phase of a time-bin pulse with a high fidelity. Our demonstration suggests the possibility of realizing ultrabroadband, high time-bandwidth products, multi-mode quantum memory which is operable at telecommunication wavelength.

Suzuki, Kazumasa; Ishi-Hayase, Junko [Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522 (Japan); Akahane, Kouichi; Yamamoto, Naokatsu [National Institute of Information and Communications Technology (NICT), 4-2-1, Nukuikitamchi, Koganei, Tokyo 102-8554 (Japan)

2013-12-04T23:59:59.000Z

223

", Mat. Res. Soc. Symp. Proc., vol. 974E, pp0974-CC06-01 ff. Exciton Lifetime in PbS Quantum Dots in Glass  

E-Print Network (OSTI)

energy conversion efficiency of ~32% for a band gap of ~1.5 eV. The discovery of efficient multiexciton quantum dot state that is optically forbidden [8]. If a dark exciton state lies at lower energy than generation by high energy photons in quantum dots [2, 3] may lead to significant improvements in efficiency

Persans, Peter D.

224

Single Quantum Dot Tracking Reveals that an Individual Multivalent HIV-1 Tat Protein Transduction Domain Can Activate Machinery for Lateral Transport and Endocytosis  

Science Journals Connector (OSTI)

...microtubule-guided motors or diffusion. Two-color...the cortical network. Future studies are needed to...cells utilizing single-quantum dot tracking (SQT...transport of HER2 by motor proteins in living cells...proteins labeled with quantum dots. Exp. Cell Res...

Yasuhiro Suzuki; Chandra Nath Roy; Warunya Promjunyakul; Hiroyasu Hatakeyama; Kohsuke Gonda; Junji Imamura; Biju Vasudevanpillai; Noriaki Ohuchi; Makoto Kanzaki; Hideo Higuchi; Mitsuo Kaku

2013-06-03T23:59:59.000Z

225

Influence of Cationic Precursors on CdS Quantum-Dot-Sensitized Solar Cell Prepared by Successive Ionic Layer Adsorption and  

E-Print Network (OSTI)

solar cells has grown significantly, and the technology has been considered as one of the most costInfluence of Cationic Precursors on CdS Quantum-Dot-Sensitized Solar Cell Prepared by Successive (QDs) onto porous oxide films for quantum-dot-sensitized solar cell (QDSC) applications. In this work

Cao, Guozhong

226

Highly entangled photons from hybrid piezoelectric-semiconductor quantum dot devices  

E-Print Network (OSTI)

Entanglement resources are key ingredients of future quantum technologies. If they could be efficiently integrated into a semiconductor platform a new generation of devices could be envisioned, whose quantum-mechanical functionalities are controlled via the mature semiconductor technology. Epitaxial quantum dots (QDs) embedded in diodes would embody such ideal quantum devices, but QD structural asymmetries lower dramatically the degree of entanglement of the sources and hamper severely their real exploitation in the foreseen applications. In this work, we overcome this hurdle using strain-tunable optoelectronic devices, where any QD can be tuned for the emission of highly polarization-entangled photons. The electrically-controlled sources violate Bell inequalities without the need of spectral or temporal filtering and they feature the highest degree of entanglement ever reported for QDs, with concurrence as high as 0.75(2). These quantum-devices are at present the most promising candidates for the direct implementation of QD-based entanglement-resources in quantum information science and technology.

Rinaldo Trotta; Johannes S. Wildmann; Eugenio Zallo; Oliver G. Schmidt; Armando Rastelli

2014-03-02T23:59:59.000Z

227

Synthesis of indium sulphide quantum dots in perfluoronated ionomer membrane  

SciTech Connect

In this paper, we demonstrate a simple and efficient method for synthesis of ?-indium sulphide (In{sub 2}S{sub 3}) nanoparticles embedded in an ionomer matrix (nafion membrane). The influence of reaction temperature on structural, compositional and optical properties of these films were analysed using X-Ray Diffraction, EDAX, UV-Vis absorption spectroscopy and photoluminescence studies. Average particle diameter was estimated using modified effective mass approximation method. Absorption spectra of In{sub 2}S{sub 3} nanoparticles show blue shift compared to bulk In{sub 2}S{sub 3}, indicating strong quantum size confinement effects. PL emission in the wavelength range 530–600 nm was recorded using a 488 nm line from an Ar{sup +} laser as the excitation source.

Sumi, R. [Centre for Nanotechnology Research, VIT University, Vellore (India); Warrier, Anita R.; Vijayan, C. [Department of Physics, Indian Institute of Technology, Chennai (India)

2014-01-28T23:59:59.000Z

228

Covalent Monofunctionalization of Peptide-Coated Quantum Dots for Single-Molecule Assays  

Science Journals Connector (OSTI)

Since many of the pQD-mSAV1 (? 80%) did not bind to any biotin molecules, a future improvement could be the site-specific conjugation of mSAV, to ensure that its single biotin-binding site is oriented away from the QD surface, with increased accessibility. ... When attached to a substrate surface, these motors are envisioned to shuttle cargo that is bound to reconstituted microtubules-one component of the cell cytoskeleton-from one location to another. ... A combination of quantum dots and fluorescence-interference contrast microscopy can be used to monitor the rotation of microtubules with nanometer accuracy as they glide over motor proteins. ...

Samuel Clarke; Fabien Pinaud; Oliver Beutel; Changjiang You; Jacob Piehler; Maxime Dahan

2010-04-30T23:59:59.000Z

229

Peptide-Conjugated Quantum Dots Activate Neuronal Receptors and Initiate Downstream Signaling of Neurite Growth  

Science Journals Connector (OSTI)

Peptide-Conjugated Quantum Dots Activate Neuronal Receptors and Initiate Downstream Signaling of Neurite Growth ... As a focus of this work, we have chosen to study NGF, a peptide hormone that targets motor, sensory, and autonomic neurons and is critical for neuronal survival, development, and maintenance. ... Future work aimed at modulating cell differentiation by varying parameters such as the concentration, spacer length, and size of the ligand-conjugated QD will be useful for evaluating and optimizing the sensitivity of these nanostructures and their effects on cell function. ...

Tania Q. Vu; Ravikanth Maddipati; Todd A. Blute; Barrett J. Nehilla; Leora Nusblat; Tejal A. Desai

2005-03-24T23:59:59.000Z

230

Effect of internal electric field on InAs/GaAs quantum dot solar cells  

SciTech Connect

We studied time-resolved carrier recombination in InAs/GaAs quantum dot (QD) solar cells. The electric field in a p-i-n diode structure spatially separates photoexcited carriers in QDs, strongly affecting the conversion efficiency of intermediate-band solar cells. The radiative decay lifetime is dramatically reduced in a strong electric field (193?kV/cm) by efficient recombination due to strong carrier localization in each QD and significant tunneling-assisted electron escape. Conversely, an electric field of the order of 10?kV/cm maintains electronic coupling in the stacked QDs and diminishes tunneling-assisted electron escape.

Kasamatsu, Naofumi; Kada, Tomoyuki; Hasegawa, Aiko; Harada, Yukihiro; Kita, Takashi [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)

2014-02-28T23:59:59.000Z

231

Direct Patterning of CdSe Quantum Dots into Sub-100 nm Structures  

SciTech Connect

Ordered, two-dimensional cadmium selenide (CdSe) arrays have been fabricated on indium-doped tin oxide (ITO) electrodes using the pattern replication in nonwetting templates (PRINT) process. CdSe quantum dots (QDs) with an average diameter of 2.7 nm and a pyridine surface ligand were used for patterning. The PRINT technique utilizes a perfluoropolyether (PFPE) elastomeric mold that is tolerant of most organic solvents, thus allowing solutions of CdSe QDs in 4-picoline to be used for patterning without significant deformation of the mold. Nanometer-scale diffraction gratings have been successfully replicated with CdSe QDs.

Hampton, Meredith J.; Templeton, Joseph L.; DeSimone, Joseph M.

2010-01-01T23:59:59.000Z

232

Anomalous decay of photon echo in a quantum dot ensemble in the strong excitation regime  

SciTech Connect

We investigated the coherent dynamics of exciton ground-state transitions in an 150-layer-stacked strain-compensated InAs quantum dot ensemble using photon echo (PE) technique in the strong excitation regime. The time delay dependence of PE signal intensity shows a drastic change depending on the excitation intensity and the aperture position placed in front of a detector. Our results suggest that the excitation-intensity-dependent spatial distribution of PE signal intensity plays an important role in observing PE signal decay in the strong excitation regime.

Suemori, Ryosuke; Ishi-Hayase, Junko [Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522 (Japan); Akahane, Kouichi; Yamamoto, Naokatsu [National Institute of Information and Communications Technology (NICT), 4-2-1, Nukuikitamchi, Koganei, Tokyo 102-8554 (Japan)

2013-12-04T23:59:59.000Z

233

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

SciTech Connect

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.

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

2013-12-04T23:59:59.000Z

234

SiGe quantum dots for fast hole spin Rabi oscillations  

SciTech Connect

We report on hole g-factor measurements in three terminal SiGe self-assembled quantum dot devices with a top gate electrode positioned very close to the nanostructure. Measurements of both the perpendicular as well as the parallel g-factor reveal significant changes for a small modulation of the top gate voltage. From the observed modulations, we estimate that, for realistic experimental conditions, hole spins can be electrically manipulated with Rabi frequencies in the order of 100?MHz. This work emphasises the potential of hole-based nano-devices for efficient spin manipulation by means of the g-tensor modulation technique.

Ares, N.; Prager, A.; De Franceschi, S. [SPSMS/LaTEQS, CEA-INAC/UJF-Grenoble 1, 17 Rue des Martyrs, 38054 Grenoble Cedex 9 (France)] [SPSMS/LaTEQS, CEA-INAC/UJF-Grenoble 1, 17 Rue des Martyrs, 38054 Grenoble Cedex 9 (France); Katsaros, G. [SPSMS/LaTEQS, CEA-INAC/UJF-Grenoble 1, 17 Rue des Martyrs, 38054 Grenoble Cedex 9 (France) [SPSMS/LaTEQS, CEA-INAC/UJF-Grenoble 1, 17 Rue des Martyrs, 38054 Grenoble Cedex 9 (France); Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Johannes Kepler University, Institute of Semiconductor and Solid State Physics, Altenbergerstr. 69, 4040 Linz (Austria); Golovach, V. N. [Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany) [Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU) and Donostia International Physics Center DIPC, E-20018 San Sebastián (Spain); IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao (Spain); Zhang, J. J. [Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany)] [Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Glazman, L. I. [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States)] [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Schmidt, O. G. [Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany) [Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Center for Advancing Electronics Dresden, TU Dresden (Germany)

2013-12-23T23:59:59.000Z

235

GaAs single quantum dot embedded into AlGaAs nanowire  

SciTech Connect

We report on a study of the photoluminescence spectra taken from quasi one-dimensional and quasi zero-dimensional semiconductor heterostructures. The structures were grown by molecular-beam epitaxy in (111) direction and were cylindrical nanowires based on AlGaAs, of 20 - 50 nm in diameter and 0.5 - 1 ?m in length. Inside the nanowires contain one or two GaAs quantum dots, of 2 nm thick and 15 - 45 nm in diameter. We studied a single nanowire. The photoluminescence and photoluminescence excitation spectra were registered as a function of the intensity of optical excitation.

Kochereshko, V. P.; Kats, V. N. [A.F.Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021, St. Petersburg, Russia and Spin Optics Laboratory, Saint Petersburg State University, Ul'yanovskaya 1, Petrodvorets, St. Petersburg, 198904 (Russian Federation); Platonov, A. V. [A.F.Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021, St. Petersburg (Russian Federation); Cirlin, G. E.; Bouravleuv, A. D.; Samsonenko, Yu. B. [A.F.Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021, St. Petersburg, Russia and St. Petersburg Academic University of the RAS Khlopina 8/3, 195220, St. Petersburg (Russian Federation); Besombes, L.; Mariette, H. [CEA-CNRS group Nanophysique et Semiconducteurs, CEA, INAC, SP2M, and Institut Néel, 17 rue des Martyrs, F-38054 Grenoble (France)

2013-12-04T23:59:59.000Z

236

Observation of photo darkening in self assembled InGaAs/GaAs quantum dots  

SciTech Connect

Photo darkening was observed in epitaxial InGaAs/GaAs quantum dots (QDs). The photoluminescence (PL) intensity of the QDs showed a non-reversible decrease under continuous laser irradiation. The time constants varied from tens of minutes to several hours, depending on the applied laser power. Based on the spectral evolution, it was concluded that the observed phenomenon should originate from laser induced structural damage and a sustained increase of non-radiative recombination rate in the wetting layer. Additionally, according to the PL decay dynamics at different laser powers, it is argued that there should exist other processes that hinder PL degradation at a high laser power.

Zhang Hongyi; Chen Yonghai; Zhou Xiaolong; Jia Yanan; Ye Xiaoling; Xu Bo; Wang Zhanguo [Key Laboratory of Semiconductor Materials Science and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

2013-05-07T23:59:59.000Z

237

Mid infrared optical properties of Ge/Si quantum dots with different doping level  

SciTech Connect

Optical characterization of the Ge/Si quantum dots using equilibrium and photo-induced absorption spectroscopy in the mid-infrared spectral range was performed in this work. Equilibrium absorption spectra were measured in structures with various doping levels for different light polarizations. Photo-induced absorption spectra measured in undoped structure under interband optical excitation of non-equilibrium charge carriers demonstrate the same features as doped sample in equilibrium conditions. Hole energy spectrum was determined from the analysis of experimental data.

Sofronov, A. N.; Firsov, D. A.; Vorobjev, L. E.; Shalygin, V. A.; Panevin, V. Yu.; Vinnichenko, M. Ya. [St. Petersburg State Polytechnic University, Polytechnicheskaya str. 29, St. Petersburg (Russian Federation); Tonkikh, A. A. [Max Planck Institute of Microstructure Physics, Weinberg 2 D-06120, Halle (Saale) (Germany); Danilov, S. N. [University of Regensburg, Regensburg (Germany)

2013-12-04T23:59:59.000Z

238

Efficiency, power, and period at two optimum operations of a thermoelectric single-level quantum dot  

Science Journals Connector (OSTI)

We take a single-level quantum dot embedded between two metallic leads at different temperatures and chemical potentials which works as a heat engine. Two optimization criteria were used and their corresponding optimized efficiencies, powers, and periods evaluated. A comparison between similar quantities of the two optimization criteria reveals mixed advantages and disadvantages. We quantify the engine's overall performance by suggesting a figure of merit that takes into account the contribution of each of the three quantities. Based on the proposed figure of merit, one of the optimization criterion presents a clear advantage. This same criterion is found to be invariably advantageous when applied to three other representative models.

Fitsum Borga; Mulugeta Bekele; Yergou B. Tatek; Mesfin Tsige

2012-09-26T23:59:59.000Z

239

Secondary treatment of films of colloidal quantum dots for optoelectronics and devices produced thereby  

DOE Patents (OSTI)

A method of forming an optoelectronic device. The method includes providing a deposition surface and contacting the deposition surface with a ligand exchange chemical and contacting the deposition surface with a quantum dot (QD) colloid. This initial process is repeated over one or more cycles to form an initial QD film on the deposition surface. The method further includes subsequently contacting the QD film with a secondary treatment chemical and optionally contacting the surface with additional QDs to form an enhanced QD layer exhibiting multiple exciton generation (MEG) upon absorption of high energy photons by the QD active layer. Devices having an enhanced QD active layer as described above are also disclosed.

Semonin, Octavi Escala; Luther, Joseph M; Beard, Matthew C; Chen, Hsiang-Yu

2014-04-01T23:59:59.000Z

240

Intersublevel dephasing in InAs/GaAs quantum dots below the Reststrahlen band  

SciTech Connect

Using transient four-wave mixing in the terahertz range, we have measured the s-p inter-sublevel dephasing time in self-assembled InAs/GaAs quantum dots for transition energies below the Reststrahlen band. Dephasing times of up to 600?ps at a photon energy of 18?meV have been determined. By comparing pump-probe and four-wave mixing measurements, we show that there is no significant influence of any pure dephasing process at low temperature. The linear temperature dependence is consistent with acoustic phonon scattering.

Teich, M., E-mail: m.teich@hzdr.de; Stephan, D. R.; Helm, M. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany) [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany); Technische Universität Dresden, 01062 Dresden (Germany); Winnerl, S.; Schneider, H. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany)] [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany); Wilson, L. R. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)] [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)

2013-12-16T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
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241

Quantum Dotting the “i” of Inquiry: A Guided Inquiry Approach to Teaching Nanotechnology  

Science Journals Connector (OSTI)

When illuminating four “mystery” vials of nanoparticle solution with a 405?nm light emitting diode(LED) four distinct colors related to the peak wavelength of fluorescent emission can be observed.1 This phenomenon perplexes high schoolphysics students and leads to the subsequent exploratory question “Why are the four vials emitting a different color light if they all contain the same material and are illuminated with the same light source?” That question gives students the opportunity to collect and analyze data which leads to the development of the inherent scientific concept that the color of the emitted light depends on the size of the material(quantum dot) suspended in solution.

Timothy A. Laubach; Lee A. Elizondo; Patrick J. McCann; Shahryar Gilani

2010-01-01T23:59:59.000Z

242

Size-Controllable and Low-Cost Fabrication of Graphene Quantum Dots Using Thermal Plasma Jet  

Science Journals Connector (OSTI)

graphene quantum dots; thermal plasma jet; mass production; size-controllable fabrication; low-cost fabrication; carbyne-like edges; photoluminescence ... We produced carbon soot by injecting ethylene gas continuously (at a rate of 2.5 L/min) into Ar plasma and attaching a carbon tube (5, 10, or 20 cm in length) to the anode. ... (34) In principle, oxygen is not contained in our fabrication, since only Ar and ethylene gases have been added into a plasma system as the plasma gas and carbon source, respectively. ...

Juhan Kim; Jung Sang Suh

2014-03-30T23:59:59.000Z

243

High excitation power photoluminescence studies of ultra-low density GaAs quantum dots  

SciTech Connect

We fabricate GaAs epitaxial quantum dots (QDs) by filling of self-organized nanoholes in AlGaAs. The QDs are fabricated under optimized process conditions and have ultra-low density in the 10{sup 6} cm{sup ?2} regime. At low excitation power the optical emission of single QDs exhibit sharp excitonic lines, which are attributed to the recombination of excitonic and biexcitonic states. High excitation power measurements reveal surprisingly broad emission lines from at least six QD shell states.

Sonnenberg, D.; Graf, A.; Paulava, V.; Heyn, Ch.; Hansen, W. [Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg, Jungiusstr. 11, 20355 Hamburg (Germany)

2013-12-04T23:59:59.000Z

244

Detection of single quantum dots in model organisms with sheet illumination microscopy  

SciTech Connect

Single-molecule detection and tracking is important for observing biomolecule interactions in the microenvironment. Here we report selective plane illumination microscopy (SPIM) with single-molecule detection in living organisms, which enables fast imaging and single-molecule tracking and optical penetration beyond 300 {mu}m. We detected single nanocrystals in Drosophila larvae and zebrafish embryo. We also report our first tracking of single quantum dots during zebrafish development, which displays a transition from flow to confined motion prior to the blastula stage. The new SPIM setup represents a new technique, which enables fast single-molecule imaging and tracking in living systems.

Friedrich, Mike; Nozadze, Revaz; Gan, Qiang; Zelman-Femiak, Monika; Ermolayev, Vladimir [Molecular Microscopy Group, Rudolf Virchow Center, University of Wuerzburg, Versbacher Str. 9, D-97078 Wuerzburg (Germany)] [Molecular Microscopy Group, Rudolf Virchow Center, University of Wuerzburg, Versbacher Str. 9, D-97078 Wuerzburg (Germany); Wagner, Toni U. [Institute of Physiological Chemistry I, Biocenter, University of Wuerzburg, Am Hubland, D-97074 Wuerzburg (Germany)] [Institute of Physiological Chemistry I, Biocenter, University of Wuerzburg, Am Hubland, D-97074 Wuerzburg (Germany); Harms, Gregory S., E-mail: gregory.harms@virchow.uni-wuerzburg.de [Molecular Microscopy Group, Rudolf Virchow Center, University of Wuerzburg, Versbacher Str. 9, D-97078 Wuerzburg (Germany)

2009-12-18T23:59:59.000Z

245

Four-photon cascade from quadexcitons in a single GaAs quantum dot  

Science Journals Connector (OSTI)

We demonstrate the generation of temporally correlated four photons emitted by the cascade recombination of a quadexciton in a self-assembled GaAs quantum dot (QD) by performing single photon correlation measurements. The cascade decay of the quadexciton involves a triexciton, a biexciton, and an exciton. The emissions of these states are identified in the photoluminescence (PL) spectrum of the QD by cross-correlation measurements. Polarization-resolved cross-correlation measurements show that the polarizations of the four photons are partly correlated. Radiative, nonradiative, and polarization flipping rates in the QD are estimated from the bunching visibilities of the cross-correlation measurements and the PL lifetimes.

Y. Arashida; Y. Ogawa; F. Minami

2011-09-12T23:59:59.000Z

246

Self-frequency summing in quantum dot photonic crystal nanocavity lasers  

SciTech Connect

We demonstrate self-frequency summing in photonic crystal nanocavity lasers with quantum dot gain. Two dipole modes and a hexapole mode, supported in the cavity, simultaneously showed lasing oscillation in the near infrared wavelength region under optical carrier injection. Meanwhile, within the same laser cavity, the internally generated three laser fields are up-converted to exhibit sharp visible emission lines via intra-cavity nonlinear frequency summing (and doubling) processes. This self-frequency summing process in active nanocavities will pave the way for developing nanoscale nonlinear optical light sources.

Ota, Yasutomo; Watanabe, Katsuyuki [Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)] [Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Iwamoto, Satoshi; Arakawa, Yasuhiko [Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan) [Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan)

2013-12-09T23:59:59.000Z

247

Liquid-phase plasma synthesis of silicon quantum dots embedded in carbon matrix for lithium battery anodes  

SciTech Connect

Graphical abstract: - Highlights: • Silicon quantum dots embedded in carbon matrix (SiQDs/C) were fabricated. • SiQDs/C exhibits excellent battery performance as anode materials with high specific capacity. • The good performance was attributed to the marriage of small sized SiQDs and carbon. - Abstract: Silicon quantum dots embedded in carbon matrix (SiQDs/C) nanocomposites were prepared by a novel liquid-phase plasma assisted synthetic process. The SiQDs/C nanocomposites were demonstrated to show high specific capacity, good cycling life and high coulmbic efficiency as anode materials for lithium-ion battery.

Wei, Ying [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou (China); College of Chemistry and Chemical Engineering, Bohai University, Jinzhou 121000 (China); Yu, Hang; Li, Haitao; Ming, Hai; Pan, Keming; Huang, Hui [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou (China); Liu, Yang, E-mail: yangl@suda.edu.cn [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou (China); Kang, Zhenhui, E-mail: zhkang@suda.edu.cn [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou (China)

2013-10-15T23:59:59.000Z

248

InAs/GaAs p-type quantum dot infrared photodetector with higher efficiency  

SciTech Connect

An InAs/GaAs quantum dot infrared photodetector (QDIP) based on p-type valence-band intersublevel hole transitions as opposed to conventional electron transitions is reported. Two response bands observed at 1.5–3 and 3–10??m are due to transitions from the heavy-hole to spin-orbit split-off QD level and from the heavy-hole to heavy-hole level, respectively. Without employing optimized structures (e.g., the dark current blocking layer), the demonstrated QDIP displays promising characteristics, including a specific detectivity of 1.8×10{sup 9} cm·Hz{sup 1/2}/W and a quantum efficiency of 17%, which is about 5% higher than that of present n-type QDIPs. This study shows the promise of utilizing hole transitions for developing QDIPs.

Lao, Yan-Feng; Wolde, Seyoum; Unil Perera, A. G., E-mail: uperera@gsu.edu [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States); Zhang, Y. H.; Wang, T. M.; Liu, H. C. [Key Laboratory of Artificial Structures and Quantum Control, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China)] [Key Laboratory of Artificial Structures and Quantum Control, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Kim, J. O.; Schuler-Sandy, Ted; Tian, Zhao-Bing; Krishna, S. S. [Center for High Technology Materials, Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87106 (United States)] [Center for High Technology Materials, Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87106 (United States)

2013-12-09T23:59:59.000Z

249

Light-assisted recharging of graphene quantum dots in fluorographene matrix  

SciTech Connect

In the present study, the charge transient spectroscopy was used to analyze the transient relaxation of charges in graphene and bilayer-graphene quantum dot (QD) systems formed by chemical functionalization of graphene and few-layer graphene layers. A set of activation energies (one to three different values) for the emission of charges from QDs sized 50 to 70?nm, most likely proceeding via the thermal activation of charge carriers from QD quantum confinement levels, were deduced from measurements performed in the dark. Daylight illumination of samples during measurements was found to result in a strong decrease of the activation energies and in an involvement of an athermal process in the charge relaxation phenomenon. The time of the light-assisted emission of charge carriers from QDs proved to be two to four orders of magnitude shorter than the time of their emission from QDs under no-illumination conditions.

Antonova, I. V. [A.V. Rzhanov Institute of Semiconductor Physics, Russian Academy of Sciences, Siberian Branch, Acad. Lavrentiev Avenue 13, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Pirogov Street 2, Novosibirsk 630090 (Russian Federation); Nebogatikova, N. A.; Prinz, V. Ya. [A.V. Rzhanov Institute of Semiconductor Physics, Russian Academy of Sciences, Siberian Branch, Acad. Lavrentiev Avenue 13, Novosibirsk 630090 (Russian Federation); Popov, V. I.; Smagulova, S. A. [North - East Federal University, Yakutsk (Russian Federation)

2014-10-07T23:59:59.000Z

250

Biphasic quantum dots of cubic and hexagonal Mn doped CdS; necessity of Rietveld analysis  

Science Journals Connector (OSTI)

Abstract Mn2+ doped CdS quantum dots (QDs) were prepared via a simple chemical synthesis method. Incorporation of Mn ions into CdS \\{QDs\\} was monitored by structural, magnetic and optical spectroscopy analysis. Although the diffraction patterns seemed to be single wurtzite hexagonal structure, analysis revealed biphasic composite of CdS \\{QDs\\} hexagonal wurtzite and cubic zinc blende. The band gap, crystal phase and the morphology of CdS \\{QDs\\} were found not to be greatly affected by Mn2+ doping, however there was an optimal Mn2+ doping content of 10% where the magnetism is maximum. The recorded photoluminescence (PL) emission spectra, excited at 370 nm, depict emission lines in the UV and blue-shift regions. The emission band reveals that the band gap of pure CdS \\{QDs\\} is around 3 eV which is greater than that of bulk CdS (2.42 eV). The band gap of Mn:CdS \\{QDs\\} is almost independent of Mn content (x) and the crystallite size remains almost the same for all values of x. The observed structural, magnetic and optical properties have been explained on the basis of formation of two phases of CdS doped with Mn. This work aims to highlight recent advances in the synthesis of Mn:CdS diluted magnetic semiconductor quantum dots and their wonderful performance.

Zein K. Heiba; Mohamed Bakr Mohamed; N.G. Imam

2015-01-01T23:59:59.000Z

251

Photoinduced Surface Oxidation and Its Effect on the Exciton Dynamics of CdSe Quantum Dots  

SciTech Connect

With increased interest in semiconductor nanoparticles for use in quantum dot solar cells there comes a need to understand the long-term photostability of such materials. Colloidal CdSe quantum dots (QDs) were suspended in toluene and stored in combinations of light/dark and N{sub 2}/O{sub 2} to simulate four possible benchtop storage environments. CdSe QDs stored in a dark, oxygen-free environment were observed to better retain their optical properties over the course of 90 days. The excited state lifetimes, determined through femtosecond transient absorption spectroscopy, of air-equilibrated samples exposed to light exhibit a decrease in average lifetime (0.81 ns) when compared to samples stored in a nitrogen/dark environment (8.3 ns). A photoetching technique commonly used for controlled reduction of QD size was found to induce energetic trap states to CdSe QDs and accelerate the rate of electron-hole recombination. X-ray absorption near edge structure (XANES) analysis confirms surface oxidation, the extent of which is shown to be dependent on the thickness of the ligand shell.

Hines, Douglas A.; Becker, Matthew A.; Kamat, Prashant V. (Notre)

2012-11-14T23:59:59.000Z

252

Theory of Linear Optical Absorption in Diamond Shaped Graphene Quantum Dots  

E-Print Network (OSTI)

In this paper, optical and electronic properties of diamond shaped graphene quantum dots (DQDs) have been studied by employing large-scale electron-correlated calculations. The computations have been performed using the $\\pi$-electron Pariser-Parr-Pople model Hamiltonian, which incorporates long-range Coulomb interactions. The influence of electron-correlation effects on the ground and excited states has been included by means of the configuration-interaction approach, used at various levels. Our calculations have revealed that the absorption spectra are red-shifted with the increasing sizes of quantum dots. It has been observed that the first peak of the linear optical absorption, which represents the optical gap, is not the most intense peak. This result is in excellent agreement with the experimental data, but in stark contrast to the predictions of the tight-binding model, according to which the first peak is the most intense peak, pointing to the importance of electron-correlation effects. Furthermore, a...

Basak, Tista; Shukla, Alok

2015-01-01T23:59:59.000Z

253

The engineering of doxorubicin-loaded liposome-quantum dot hybrids for cancer theranostics  

Science Journals Connector (OSTI)

Many studies have recently attempted to develop multifunctional nanoconstructs by integrating the superior fluorescence properties of quantum dots (QD) with therapeutic capabilities into a single vesicle for cancer theranostics. Liposome-quantum dot (L-QD) hybrid vesicles have shown promising potential for the construction of multifunctional nanoconstructs for cancer imaging and therapy. To fulfil such a potential, we report here the further functionalization of L-QD hybrid vesicles with therapeutic capabilities by loading anticancer drug doxorubicin (Dox) into their aqueous core. L-QD hybrid vesicles are first engineered by the incorporation of TOPO-capped, CdSe/ZnS QD into the lipid bilayers of DSPC:Chol:DSPE-PEG2000, followed by Dox loading using the pH-gradient technique. The loading efficiency of Dox into L-QD hybrid vesicles is achieved up to 97%, comparable to liposome control. All these evidences prove that the incorporation of QD into the lipid bilayer does not affect Dox loading through the lipid membrane of liposomes using the pH-gradient technique. Moreover, the release study shows that Dox release profile can be modulated simply by changing lipid composition. In conclusion, the Dox-loaded L-QD hybrid vesicles presented here constitute a promising multifunctional nanoconstruct capable of transporting combinations of therapeutic and diagnostic modalities.

Bowen Tian (???); Wafa' T. Al-Jamal; Kostas Kostarelos

2014-01-01T23:59:59.000Z

254

Quantum Dot Light Enhancement Substrate for OLED Solid-State Lighting  

SciTech Connect

With DOE Award No. DE-EE00000628, QD Vision developed and demonstrated a cost-competitive solution for increasing the light extraction efficiency of OLEDs with efficient and stable color rendering index (CRI) for solid state lighting (SSL). Solution processable quantum dot (QD) films were integrated into OLED ITO-glass substrates to generate tunable white emission from blue emitting OLED) devices as well as outcouple light from the ITO film. This QD light-enhancement substrate (QD-LED) technology demonstrated a 60% increase in OLED forward light out-coupling, a value which increases to 76% when considering total increase in multi-directional light output. The objective for the first year was an 80% increase in light output. This project seeks to develop and demonstrate a cost-competitive solution for realizing increased extraction efficiency organic light emitting devices (OLEDs) with efficient and stable color rendering index (CRI) for SSL. Solution processible quantum dot (QD) films will be utilized to generate tunable white emission from blue emitting phosphorescent OLED (Ph-OLED) devices.

James Perkins; Matthew Stevenson; Gagan Mahan; Seth Coe-Sullivan; Peter Kazlas

2011-01-21T23:59:59.000Z

255

Controllable coupling and quantum correlation dynamics of two double quantum dots coupled via a transmission line resonator  

E-Print Network (OSTI)

We propose a theoretical scheme to generate a controllable and switchable coupling between two double-quantum-dot (DQD) spin qubits by using a transmission line resonator (TLR) as a bus system. We study dynamical behaviors of quantum correlations described by entanglement correlation (EC) and discord correlation (DC) between two DQD spin qubits when the two spin qubits and the TLR are initially prepared in $X$-type quantum states and a coherent state, respectively. We demonstrate that in the EC death regions there exist DC stationary states in which the stable DC amplification or degradation can be generated during the dynamical evolution. It is shown that these DC stationary states can be controlled by initial-state parameters, the coupling, and detuning between qubits and the TLR. We reveal the full synchronization and anti-synchronization phenomena in the EC and DC time evolution, and show that the EC and DC synchronization and anti-synchronization depends on the initial-state parameters of the two DQD spin qubits. These results shed new light on dynamics of quantum correlations.

Qin-Qin Wu; Qing-Shou Tan; Le-Man Kuang

2010-11-25T23:59:59.000Z

256

Magnetotransport theory in quantum dots: 3D-0D and 2D-0D tunneling and angular momentum selection rules  

Science Journals Connector (OSTI)

A study of magnetotransport through quantum dots is presented. The model allows one to analyze tunneling both from bulk-like contacts and from 2D accumulation layers. The fine features in the I-V characteristics due to the quantum dot states are known to be shifted to different voltages depending upon the value of the magnetic field. While this effect is also well reproduced by our calculations, in this work we concentrate on the amplitude of each current resonance as a function of the magnetic field. Such amplitudes show oscillations reflecting the variation of the density of states at the Fermi energy in the emitter. Furthermore the amplitude increases as a function of the magnetic field for certain features while it decreases for others. In particular, we demonstrate that the behavior of the amplitude of the current resonances is linked to the value of the angular momentum of each dot level through which tunneling occurs. We show that a selection rule on the angular momentum must be satisfied. As a consequence, tunneling through specific dot states is strongly suppressed and sometimes prohibited altogether by the presence of the magnetic field. This will allow to extract from the experimental curves detailed information on the nature of the quantum-dot wave functions involved in the electronic transport. Furthermore, when tunneling occurs from a two-dimensional accumulation layer to the quantum dot, the presence of a magnetic field hugely increases the strength of some resonant features. This effect is predicted by our model and, to the best of our knowledge, has never been observed.

B. Jouault; M. Boero; G. Faini; J. C. Inkson

1999-02-15T23:59:59.000Z

257

Phonon-hopping thermal conduction in quantum dot superlattices Manu Shamsa, Weili Liu, and Alexander A. Balandina  

E-Print Network (OSTI)

or polycrystalline materials in terms of thermal transport. © 2005 American Institute of Physics. DOI: 10 strongly depends on interface conditions, is considered as a major thermal resistive mecha- nismPhonon-hopping thermal conduction in quantum dot superlattices Manu Shamsa, Weili Liu

258

Hybrid molecular assemblies composed of hydrogenase enzymes and quantum dots helps to pave the way for the  

E-Print Network (OSTI)

Hybrid molecular assemblies composed of hydrogenase enzymes and quantum dots helps to pave the way- plexes with the hydrogenase and that these hybrid assemblies functioned to catalyze H2 production using Hybrids for Solar Hydrogen Production."Journal of the American Chemical Society, June 28, 2010. Key

259

CdS quantum dot sensitized nanocrystalline Gd-doped TiO2 thin films for photoelectrochemical solar cells  

Science Journals Connector (OSTI)

CdS quantum dot sensitized Gd-doped TiO2 nanocrystalline thin films have been prepared by chemical method. X-ray diffraction analysis reveals that TiO2 and Gd-doped TiO2...nanocrystalline thin films are of anatas...

A. Ranjitha; N. Muthukumarasamy…

2013-08-01T23:59:59.000Z

260

Measuring charge trap occupation and energy level in CdSe/ZnS quantum dots using a scanning tunneling microscope  

E-Print Network (OSTI)

We use a scanning tunneling microscope to probe single-electron charging phenomena in individual CdSe/ZnS (core/shell) quantum dots (QDs) at room temperature. The QDs are deposited on top of a bare Au thin film and form a ...

Bulovic, Vladimir

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
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they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

High efficiency photodetectors fabricated by electrostatic layer-by-layer self-assembly of CdTe quantum dots  

E-Print Network (OSTI)

High efficiency photodetectors fabricated by electrostatic layer-by-layer self-assembly of CdTe 20 October 2008 We demonstrate high-performance photodetectors from multilayers of CdTe quantum dots. The synthesis of CdTe QDs in aqueous solution using cadmium perchlorate hydrate and Al2Te3 was previously re

Lin, Lih Y.

262

InAs(ZnCdS) Quantum Dots Optimized for Biological Imaging in the Near-Infrared  

E-Print Network (OSTI)

We present the synthesis of InAs quantum dots (QDs) with a ZnCdS shell with bright and stable emission in the near-infrared (NIR, 700?900 nm) region for biological imaging applications. We demonstrate how NIR QDs can image ...

Allen, Peter M.

263

Reversible Modification of CdSe-CdS/ZnS Quantum Dot Fluorescence by Surrounding Ca2+  

E-Print Network (OSTI)

Reversible Modification of CdSe-CdS/ZnS Quantum Dot Fluorescence by Surrounding Ca2+ Ions Li Li (3-MPA) coated CdSe-CdS/ZnS core-multishell QDs when free Ca2+ ions were added to and subsequently removed from the QD solution. It was found that QD fluorescence intensity was reduced when Ca2+ ions were

Haviland, David

264

Absorption spectra of CdSe-ZnS core-shell quantum dots at high photon energies : experiment and modeling  

E-Print Network (OSTI)

Absorption spectra of CdSe-ZnS core-shell quantum dots at high photon energies : experiment Tata Institute of Fundamental Research Homi Bhabha Road, Mumbai 400005, India Abstract Absorption. In agreement with previous reports, the absorption coefficient at energies 1 eV above the effective bandgap

Ghosh, Sandip

265

The Architecture of Colloidal Quantum Dot Solar Cells: Materials to Illan J. Kramer and Edward H. Sargent*  

E-Print Network (OSTI)

The Architecture of Colloidal Quantum Dot Solar Cells: Materials to Devices Illan J. Kramer of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada CONTENTS 1. Introduction 863 2. Measuring and Modeling CQD Solar Cells 863 2.1. Solar Cell Characterization Considerations 864 2.2. Drift

266

Adiabatic many-body state preparation and information transfer in quantum dot arrays  

E-Print Network (OSTI)

Quantum simulation of many-body systems are one of the most interesting tasks of quantum technology. Among them is the preparation of a many-body system in its ground state when the vanishing energy gap makes the cooling mechanisms ineffective. Adiabatic theorem, as an alternative to cooling, can be exploited for driving the many-body system to its ground state. In this paper, we study two most common disorders in quantum dot arrays, namely exchange coupling fluctuations and hyperfine interaction, in adiabatically preparation of ground state in such systems. We show that the adiabatic ground state preparation is highly robust against those disorder effects making it good analog simulator. Moreover, we also study the adiabatic classical information transfer, using singlet-triplet states, across a spin chain. In contrast to ground state preparation the transfer mechanism is highly affected by disorder and in particular, the hyperfine interaction is very destructive for the performance. This suggests that for communication tasks across such arrays adiabatic evolution is not as effective and quantum quenches could be preferable.

Umer Farooq; Abolfazl Bayat; Stefano Mancini; Sougato Bose

2014-11-05T23:59:59.000Z

267

Study of valence-band intersublevel transitions in InAs/GaAs quantum dots-in-well infrared photodetectors  

SciTech Connect

The n-type quantum dot (QD) and dots-in-well (DWELL) infrared photodetectors, in general, display bias-dependent multiple-band response as a result of optical transitions between different quantum levels. Here, we present a unique characteristic of the p-type hole response, a well-preserved spectral profile, due to the much reduced tunneling probability of holes compared to electrons. This feature remains in a DWELL detector, with the dominant transition contributing to the response occurring between the QD ground state and the quantum-well states. The bias-independent response will benefit applications where single-color detection is desired and also allows achieving optimum performance by optimizing the bias.

Lao, Yan-Feng; Wolde, Seyoum; Unil Perera, A. G., E-mail: uperera@gsu.edu [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States); Zhang, Y. H.; Wang, T. M. [Key Laboratory of Artificial Structures and Quantum Control, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Kim, J. O.; Schuler-Sandy, Ted; Tian, Zhao-Bing; Krishna, S. S. [Center for High Technology Materials, Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87106 (United States)

2014-04-28T23:59:59.000Z

268

Analyses of smoke management models in TFT-LCD cleanroom  

Science Journals Connector (OSTI)

This study evaluated the effectiveness and performance of smoke management models in a TFT-LCD cleanroom. Several smoke management models are discussed in a distinct 3-level cleanroom compartment. The tools used ...

Chen-Wei Chiu; Chin-Hui Chen; Jia-Ci Chen; Chi-Min Shu

2013-12-01T23:59:59.000Z

269

Carrier capture dynamics of single InGaAs/GaAs quantum-dot layers  

SciTech Connect

Using 800 nm, 25-fs pulses from a mode locked Ti:Al{sub 2}O{sub 3} laser, we have measured the ultrafast optical reflectivity of MBE-grown, single-layer In{sub 0.4}Ga{sub 0.6}As/GaAs quantum-dot (QD) samples. The QDs are formed via two-stage Stranski-Krastanov growth: following initial InGaAs deposition at a relatively low temperature, self assembly of the QDs occurs during a subsequent higher temperature anneal. The capture times for free carriers excited in the surrounding GaAs (barrier layer) are as short as 140 fs, indicating capture efficiencies for the InGaAs quantum layer approaching 1. The capture rates are positively correlated with initial InGaAs thickness and annealing temperature. With increasing excited carrier density, the capture rate decreases; this slowing of the dynamics is attributed to Pauli state blocking within the InGaAs quantum layer.

Chauhan, K. N.; Riffe, D. M.; Everett, E. A.; Kim, D. J.; Yang, H. [Physics Department, Utah State University, Logan, Utah 84322-4415 (United States)] [Physics Department, Utah State University, Logan, Utah 84322-4415 (United States); Shen, F. K. [Center for Surface Analysis and Applications, Utah State University, Logan, Utah 84322-4415 (United States)] [Center for Surface Analysis and Applications, Utah State University, Logan, Utah 84322-4415 (United States)

2013-05-28T23:59:59.000Z

270

A Fluorescence Displacement Assay for Antidepressant Drug Discovery Based on Ligand-Conjugated Quantum Dots  

SciTech Connect

The serotonin (5-hydroxytryptamine, 5-HT) transporter (SERT) protein plays a central role in terminating 5-HT neurotransmission and is the most important therapeutic target for the treatment of major depression and anxiety disorders. We report an innovative, versatile, and target-selective quantum dot (QD) labeling approach for SERT in single Xenopus oocytes that can be adopted as a drug-screening platform. Our labeling approach employs a custom-made, QD-tagged indoleamine derivative ligand, IDT318, that is structurally similar to 5-HT and accesses the primary binding site with enhanced human SERT selectivity. Incubating QD-labeled oocytes with paroxetine (Paxil), a high-affinity SERT-specific inhibitor, showed a concentration- and time-dependent decrease in QD fluorescence, demonstrating the utility of our approach for the identification of SERT modulators. Furthermore, with the development of ligands aimed at other pharmacologically relevant targets, our approach may potentially form the basis for a multitarget drug discovery platform.

Chang, Jerry [Vanderbilt University; Tomlinson, Ian [Oak Ridge National Laboratory (ORNL); Warnement, Michael [Vanderbilt University; Iwamoto, Hideki [Vanderbilt University

2011-01-01T23:59:59.000Z

271

Optimum phase noise reduction and repetition rate tuning in quantum-dot mode-locked lasers  

SciTech Connect

Competing approaches exist, which allow control of phase noise and frequency tuning in mode-locked lasers, but no judgement of pros and cons based on a comparative analysis was presented yet. Here, we compare results of hybrid mode-locking, hybrid mode-locking with optical injection seeding, and sideband optical injection seeding performed on the same quantum dot laser under identical bias conditions. We achieved the lowest integrated jitter of 121 fs and a record large radio-frequency (RF) tuning range of 342?MHz with sideband injection seeding of the passively mode-locked laser. The combination of hybrid mode-locking together with optical injection-locking resulted in 240 fs integrated jitter and a RF tuning range of 167?MHz. Using conventional hybrid mode-locking, the integrated jitter and the RF tuning range were 620 fs and 10?MHz, respectively.

Habruseva, T. [CAPPA, Cork Institute of Technology, Cork (Ireland); Tyndall National Institute, Lee Maltings, Cork (Ireland); Aston University, Aston Triangle, B4 7ET Birmingham (United Kingdom); Arsenijevi?, D.; Kleinert, M.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Berlin (Germany); Huyet, G.; Hegarty, S. P. [CAPPA, Cork Institute of Technology, Cork (Ireland); Tyndall National Institute, Lee Maltings, Cork (Ireland)

2014-01-13T23:59:59.000Z

272

High-performance controllable ambipolar infrared phototransistors based on graphene-quantum dot hybrid  

E-Print Network (OSTI)

The field effect transistors (FETs) exhibited ultrahigh responsivity (107 A/W) to infrared light with great improvement of mobility in graphene / PbS quantum dot (QD) hybrid. These reported transistors are either unipolar or depletion mode devices. In this paper, we presented and fabricated conveniently-controlled grapheme / PbS QD hybrid FETs. Through the investigation on electric and optoelectronic properties, the ambipolar FETs (normally OFF) can be switched ON by raising gate voltage (VG) up to 3.7 V and -0.8 V in the first and third quadrants. Near these thresholds (VT) each carrier species shows comparable mobility (~ 300 cm2V-1s-1). Photo-responsivity reach ~ 107 A/W near each threshold and it will linearly increases with (VG-VT). These hybrid FETs become strongly competitive candidates for devices in flexible integrated circuits with low cost, large area, low-energy consumption and high performances.

Wang, Ran; Wang, Haiyang; Song, Xiaoxian; Jin, Lufan; Dai, Haitao; Wu, Sen; Yao, Jianquan

2014-01-01T23:59:59.000Z

273

Suspending Effect on Low-Frequency Charge Noise in Graphene Quantum Dot  

E-Print Network (OSTI)

Charge noise is critical in the performance of gate-controlled quantum dots (QDs). Here we show the 1/f noise for a microscopic graphene QD is substantially larger than that for a macroscopic graphene field-effect transistor (FET), increasing linearly with temperature. To understand its origin, we suspended the graphene QD above the substrate. In contrast to large area graphene FETs, we find that a suspended graphene QD has an almost-identical noise level as an unsuspended one. Tracking noise levels around the Coulomb blockade peak as a function of gate voltage yields potential fluctuations of order 1 "{\\mu}eV", almost one order larger than in GaAs/GaAlAs QDs. Edge states rather than substrate-induced disorders, appear to dominate the 1/f noise, thus affecting the coherency of graphene nano-devices.

Xiang-Xiang Song; Hai-Ou Li; Jie You; Tian-Yi Han; Gang Cao; Tao Tu; Ming Xiao; Guang-Can Guo; Hong-Wen Jiang; Guo-Ping Guo

2014-06-16T23:59:59.000Z

274

Composite materials with metal oxide attached to lead chalcogenide nanocrystal quantum dots with linkers  

DOE Patents (OSTI)

Composite materials useful for devices such as photoelectrochemical solar cells include a substrate, a metal oxide film on the substrate, nanocrystalline quantum dots (NQDs) of lead sulfide, lead selenide, and lead telluride, and linkers that attach the NQDs to the metal oxide film. Suitable linkers preserve the 1s absorption peak of the NQDs. A suitable linker has a general structure A-B-C where A is a chemical group adapted for binding to a MO.sub.x and C is a chemical group adapted for binding to a NQD and B is a divalent, rigid, or semi-rigid organic spacer moiety. Other linkers that preserve the 1s absorption peak may also be used.

Fuke, Nobuhiro; Koposov, Alexey Y; Sykora, Milan; Hoch, Laura

2014-12-16T23:59:59.000Z

275

Volmer-Weber Growth of Nanoscale Self-Assembled Quantum Dots  

SciTech Connect

Our research has focused on the fundamental understanding of the physical mechanisms and experimental methodologies to probe various growth conditions, their effects on density, size uniformity, and spatial organization of self-assembled quantum dots (SAQDs). Theoretical models and numerical simulations have been developed to understand the nonlinear dynamics of surface pattern evolution and self assembly processes. Fabrication processes of semiconductor and metal SAQDs on high-k dielectrics have been developed, which have enabled the technology development of high-speed, low-power nonvolatile memory devices for nanoelectronics applications. Over the four years of the project, six graduate students have been trained in this research project, and four of them have graduated with PhD degrees. Our research has been reported in 11 journal articles. Both PIs and their students have given numerous presentations at national/international conferences as well as invited seminars. A list of publications and presentations is attached to the end of this report.

Huang, Rui

2009-08-15T23:59:59.000Z

276

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

SciTech Connect

We report enhanced sensitization of silicon through nonradiative energy transfer (NRET) of the excitons in an energy-gradient structure composed of a cascaded bilayer of green- and red-emitting CdTe quantum dots (QDs) on bulk silicon. Here NRET dynamics were systematically investigated comparatively for the cascaded energy-gradient and mono-dispersed QD structures at room temperature. We show experimentally that NRET from the QD layer into silicon is enhanced by 40% in the case of an energy-gradient cascaded structure as compared to the mono-dispersed structures, which is in agreement with the theoretical analysis based on the excited state population-depopulation dynamics of the QDs.

Yeltik, Aydan; Guzelturk, Burak; Akhavan, Shahab [Department of Physics and Department of Electrical and Electronics Engineering, UNAM—Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey)] [Department of Physics and Department of Electrical and Electronics Engineering, UNAM—Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey); Ludwig Hernandez-Martinez, Pedro; Volkan Demir, Hilmi, E-mail: volkan@stanfordalumni.org [Department of Physics and Department of Electrical and Electronics Engineering, UNAM—Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey); Luminous Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering and School of Physical and Mathematical Sciences, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)

2013-12-23T23:59:59.000Z

277

Fabrication of fluorescent composite with ultrafast aqueous synthesized high luminescent CdTe quantum dots  

SciTech Connect

Without precursor preparation, inert gas protection and enormous amount of additives and reductants, CdTe quantum dots (QDs) can be rapidly synthesized with high quality. A 600 nm photoluminescence peak wavelength could be obtained within 1 hour's refluxing through minimal addition of 1,2-diaminoethane (DAE). The theoretical design for the experiments are illustrated and further proved by the characterization results with different concentrations and reagents. On the other hand, generation of CdTe QDs was found even under room temperature by applying droplet quantity of DAE. This indicates that QDs can be synthesized with simply a bottle and no enormous additives required. The QDs were mixed into the epoxy matrix through solution casting method with cetyltrimethylammonium (CTA) capping for phase transfer. The acquired epoxy based nanocomposite exhibits good transparency, compatibility and fluorescence.

Zhang, Lei, E-mail: mejswu@ust.hk; Chen, Haibin, E-mail: mejswu@ust.hk, E-mail: mejswu@ust.hk; Wu, Jingshen, E-mail: mejswu@ust.hk, E-mail: mejswu@ust.hk [Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong and Fok Ying Tung Graduate School, The Hong Kong University of Science and Technology (Hong Kong); Bi, Xianghong, E-mail: takubatch@gmail.com [Fok Ying Tung Graduate School, The Hong Kong University of Science and Technology (Hong Kong)

2014-05-15T23:59:59.000Z

278

Growth and optical properties of CdTe quantum dots in ZnTe nanowires  

SciTech Connect

We report on the formation of optically active CdTe quantum dots in ZnTe nanowires. The CdTe/ZnTe nanostructures have been grown by a gold nanocatalyst assisted molecular beam epitaxy in a vapor-liquid solid growth process. The presence of CdTe insertions in ZnTe nanowire results in the appearance of a strong photoluminescence band in the 2.0 eV-2.25 eV energy range. Spatially resolved photoluminescence measurements reveal that this broad emission consists of several sharp lines with the spectral width of about 2 meV. The large degree of linear polarization of these individual emission lines confirms their nanowire origin, whereas the zero-dimensional confinement is proved by photon correlation spectroscopy.

Wojnar, Piotr; Janik, Elzbieta; Baczewski, Lech T.; Kret, Slawomir; Karczewski, G.; Wojtowicz, Tomasz [Institute of Physics, Polish Academy of Sciences, Al Lotnikow 32/46, 02-668 Warsaw (Poland); Goryca, Mateusz; Kazimierczuk, Tomasz; Kossacki, Piotr [Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul Hoza 69, 00-681 Warsaw (Poland)

2011-09-12T23:59:59.000Z

279

Photo-instability of CdSe/ZnS quantum dots in poly(methylmethacrylate) film  

SciTech Connect

The photo-instability of CdSe/ZnS quantum dots (QDs) has been studied under varied conditions. We discussed the main features of the evolution of photoluminescence (PL) intensity and energy at different laser powers, which showed critical dependences on the environment. The PL red shift in a vacuum showed strong temperature dependence, from which we concluded that the thermal activation energy for trapping states of the charge carriers was about 14.7 meV. Furthermore, the PL spectra showed asymmetric evolution during the laser irradiation, for which two possible explanations were discussed. Those results provided a comprehensive picture for the photo-instability of the colloidal QDs under different conditions.

Zhang, Hongyi; Liu, Yu; Ye, Xiaoling; Chen, Yonghai [Key Laboratory of Semiconductor Materials Science and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)] [Key Laboratory of Semiconductor Materials Science and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

2013-12-28T23:59:59.000Z

280

Ge{sub 1-x}Mn{sub x} heteroepitaxial quantum dots: Growth, morphology, and magnetism  

SciTech Connect

Heteroepitaxial Ge{sub 1-x}Mn{sub x} quantum dots (QDs) were grown on Si (001) by molecular beam epitaxial co-deposition, with x = 0 to 0.10, in order to explore the interaction between Mn content, surface morphological evolution, and magnetism. Morphological evolution typical of the Ge/Si (001) system was observed, where the effect of Mn on surface morphology is surprisingly minimal at low Mn content, with no obvious surface morphological indicators of second phase formation. As the Mn content increases, secondary phase formation becomes evident, appearing to heterogeneously nucleate on or within Ge QDs. Still higher Mn concentrations lead to extensive second phase formation interspersed with an array of Ge QDs. Although ferromagnetism up to 220 K is observed, likely arising from intermetallic precipitates, there is no clear evidence for room-temperature ferromagnetism associated with a dilute magnetic solution phase.

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)

2013-02-21T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Quantum dot Ge/TiO{sub 2} heterojunction photoconductor fabrication and performance  

SciTech Connect

Spun cast TiO{sub 2}-Ge quantum dot (QD) heterojunction type photodetectors have been fabricated and characterized, with interest paid to photocurrent enhancements related to device design. Performance as a function of absorber layer thickness, QD size, and back contact is investigated. We have achieved ultra-thin (?200?nm) devices with photocurrents at 0.5?V of 10{sup ?4} A cm{sup ?2} while the thickest devices have photocurrents at 0.5?V of 10{sup ?2} A cm{sup ?2} with on-off ratios >100, which represents 5 orders of magnitude increase in photocurrents over previously fabricated Ge QD devices. At 0.5?V bias, the currents in our devices are competitive with thin-film Ge photovoltaics.

Church, Carena P.; Carter, Sue A., E-mail: sacarter@ucsc.edu [Department of Physics, University of California Santa Cruz, Santa Cruz, California 95064 (United States); Muthuswamy, Elayaraja; Kauzlarich, Susan M. [Department of Chemistry, University of California Davis, Davis, California 95616 (United States)] [Department of Chemistry, University of California Davis, Davis, California 95616 (United States); Zhai, Guangmei [Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education, Taiyuan University of Science and Technology, Taiyuan, Shanxi 030024 (China)] [Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education, Taiyuan University of Science and Technology, Taiyuan, Shanxi 030024 (China)

2013-11-25T23:59:59.000Z

282

Self-assembling of Ge quantum dots in the CaF2/Ge/CaF2/Si heteroepitaxial system and the development of tunnel-resonance diode on its basis  

Science Journals Connector (OSTI)

A CaF2/Ge/CaF2/Si(111) heteroepitaxial structure with Ge quantum dots was grown by molecular-beam ... , is 40–50 meV depending on the Ge dot size.

L. V. Sokolov; A. S. Deryabin; A. I. Yakimov…

2004-01-01T23:59:59.000Z

283

Ferric oxide quantum dots in stable phosphate glass system and their magneto-optical study  

SciTech Connect

Graphical abstract: We report synthesis of ferric oxide embedded low melting phosphate glass nanocomposite and also the effect of ferric oxide nanoparticles (NCs) content on the optical and magneto-optical properties of the glasses. Faraday rotation of the glass nanocomposites was measured and showed variation in Verdet constant with concentration of ferric oxide. Interestingly, the host glass itself showed fairly good Verdet constant (11.5°/T cm) and there is a threefold enhancement in the Verdet constant of ferric oxide quantum dot-glass nanocomposite. Highlights: ? We synthesize ferric oxide embedded low melting stable phosphate glass nanocomposite. ? Glasses doped with 0.25 and 2% ferric oxide show particle size in the range of 4–12 nm. ? The host phosphate glass itself shows fairly good Verdet constant (11.5°/T cm). ? Glasses doped with 0.25% ferric oxide show high Verdet constant (30.525°/T cm). ? The as synthesis glasses may have potential application in magneto optical devices. -- Abstract: Herein, we report the synthesis of ferric oxide embedded low melting phosphate glass nanocomposite and also the effect of ferric oxide nanoparticles content on the optical and magneto-optical properties of the glasses. The optical study clearly showed red shift in optical cut off with increasing ferric oxide concentration. The band gap of the host glass was observed to be 3.48 eV and it shifted to 3.14 eV after doping with ferric oxide. The glasses doped with 0.25 and 2% ferric oxide showed particle size of 4–6 nm and 8–12 nm, respectively. Faraday rotation of the glass nanocomposites was measured and showed variation in the Verdet constant as per increasing concentration of ferric oxide. Interestingly, the host glass itself showed fairly good Verdet constant (11.5°/T cm) and threefold enhancement was observed in the Verdet constant of ferric oxide quantum dot-glass nanocomposite.

Garaje, Sunil N.; Apte, Sanjay K. [Nanocomposite Group, Centre for Materials for Electronics Technology (C-MET), Department of Electronics and Information Technology (DeitY), Government of India, Panchawati, Off Pashan Road, Pune 411008 (India)] [Nanocomposite Group, Centre for Materials for Electronics Technology (C-MET), Department of Electronics and Information Technology (DeitY), Government of India, Panchawati, Off Pashan Road, Pune 411008 (India); Kumar, Ganpathy [Department of Electrical and Computer Engineering, Tennessee Technological University, 1 William L. Jones Drive, Cookeville, TN 38505 (United States)] [Department of Electrical and Computer Engineering, Tennessee Technological University, 1 William L. Jones Drive, Cookeville, TN 38505 (United States); Panmand, Rajendra P.; Naik, Sonali D. [Nanocomposite Group, Centre for Materials for Electronics Technology (C-MET), Department of Electronics and Information Technology (DeitY), Government of India, Panchawati, Off Pashan Road, Pune 411008 (India)] [Nanocomposite Group, Centre for Materials for Electronics Technology (C-MET), Department of Electronics and Information Technology (DeitY), Government of India, Panchawati, Off Pashan Road, Pune 411008 (India); Mahajan, Satish M., E-mail: smahajan@tntech.edu [Department of Electrical and Computer Engineering, Tennessee Technological University, 1 William L. Jones Drive, Cookeville, TN 38505 (United States); Chand, Ramesh [Ministry of Communications and Information Technology, Department of Electronics and Information Technology (DeitY), Electronics Niketan, 6, CGO Complex, New Delhi 110003 (India)] [Ministry of Communications and Information Technology, Department of Electronics and Information Technology (DeitY), Electronics Niketan, 6, CGO Complex, New Delhi 110003 (India); Kale, Bharat B., E-mail: bbkale@cmet.gov.in [Nanocomposite Group, Centre for Materials for Electronics Technology (C-MET), Department of Electronics and Information Technology (DeitY), Government of India, Panchawati, Off Pashan Road, Pune 411008 (India)

2013-02-15T23:59:59.000Z

284

Thin Film Solar Cells Derived from Sintered Semiconductor Quantum Dots: Cooperative Research and Development Final Report, CRADA number CRD-07-00226  

SciTech Connect

The NREL/Evident team will develop techniques to fabricate thin film solar cells where the absorption layers comprising the solar cells are derived from sintered semiconductor quantum dots.

Ginley, D. S.

2010-07-01T23:59:59.000Z

285

The role of transport processes of nonequilibrium charge carriers in radiative properties of arrays of InAs/GaAs quantum dots  

SciTech Connect

The results of time-resolved photoluminescence studies of heterostructures containing monolayer arrays of InAs/GaAs quantum dots are presented. A two-component time dependence of intensity of photoluminescence from the ground state of quantum dots, with characteristic times of the slow component up to hundreds of nanoseconds and those of rapid one several nanoseconds, is studied. It is shown that the slow component is determined by the transport of nonequilibrium charge carriers between the quantum dots. At low temperatures, the time of the slow component is determined by tunneling, and at high temperatures by thermal escape of nonequilibrium charge carriers. The ratio of the contributions of tunneling and thermal escape is determined by the degree of isolation of quantum dots. A theoretical model is constructed that describes the effect of the dynamics of carrier transport on the emergence and decay of the slow component of photoluminescence.

Shkolnik, A. S. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)], E-mail: alix@mbepl.ioffe.ru; Savelyev, A. V. [St. Petersburg State Polytechnical University (Russian Federation); Karachinsky, L. Ya.; Gordeev, N. Yu.; Seisyan, R. P.; Zegrya, G. G. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Pellegrini, S.; Buller, G. S. [Heriot-Watt University, School of Engineering and Physical Science (United Kingdom); Evtikhiev, V. P. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2008-03-15T23:59:59.000Z

286

High-speed Properties of 1.55-micron-wavelength Quantum Dot Semiconductor Amplifiers and Comparison with Higher-Dimensional Structures.  

E-Print Network (OSTI)

??This thesis reports an experimental characterization of the ultrafast gain and refractive index dynamics of a novel InAs/InGaAsP/InP quantum-dot (QD) semiconductor optical amplifier (SOA) operating… (more)

Zilkie, Aaron John

2009-01-01T23:59:59.000Z

287

An electrically driven quantum dot-in-nanowire visible single photon source operating up to 150 K  

SciTech Connect

We demonstrate electrically pumped single photon emission up to 150 K from a single InGaN quantum dot embedded in a GaN nanowire junction diode. The InGaN dot-in-nanowire p-n junctions were grown on silicon by molecular beam epitaxy. The exciton electroluminescence from individual dot-in-nanowires is in the green spectral range (? ? 520 nm) and is detectable up to 150 K. Second order autocorrelation measurements performed at the exciton energy at an ambient temperature of 125 K show a background corrected g{sup (2)}(0) equal to 0.35, indicating dominant single photon emission. The steady state nanowire temperature under these conditions is estimated to be 150 K due to Joule heating induced by the large nanowire series resistance. Time resolved photoluminescence measurements yield an exciton radiative lifetime of 1.1 ns.

Deshpande, Saniya; Bhattacharya, Pallab [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)] [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)

2013-12-09T23:59:59.000Z

288

White Light Generating Nonradiative Energy Transfer Directly from Epitaxial Quantum Wells to Colloidal Nanocrystal Quantum Dots  

Science Journals Connector (OSTI)

We present white light generating nonradiative Förster resonance energy transfer at a rate of (2ns)-1directly from epitaxial InGaN/GaN quantum wells to CdSe/ZnS...

Nizamoglu, Sedat; Sari, Emre; Baek, Jong-Hyeob; Lee, In-Hwan; Demir, Hilmi Volkan

289

Carrier dynamics and activation energy of CdTe quantum dots in a Cd{sub x}Zn{sub 1-x}Te quantum well  

SciTech Connect

We investigate the optical properties of CdTe quantum dots (QDs) in a Cd{sub 0.3}Zn{sub 0.7}Te quantum well (QW) grown on GaAs (100) substrates. Carrier dynamics of CdTe/ZnTe QDs and quantum dots-in-a-well (DWELL) structure is studied using time-resolved photoluminescence (PL) measurements, which show the longer exciton lifetime of the DWELL structure. The activation energy of the electrons confined in the DWELL structure, as obtained from the temperature-dependent PL spectra, was also higher than that of electrons confined in the CdTe/ZnTe QDs. This behavior is attributed to the better capture of carriers into QDs within the surrounding QW.

Han, W. I.; Lee, J. H.; Yu, J. S.; Choi, J. C. [Department of Physics, Yonsei University, Wonju 220-710 (Korea, Republic of); Lee, H. S. [Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)

2011-12-05T23:59:59.000Z

290

Electronic and optical properties of single excitons and biexcitons in type-II quantum dot nanocrystals  

SciTech Connect

In this study, a detailed investigation of the electronic and optical properties (i.e., binding energies, absorption wavelength, overlap of the electron-hole wave functions, recombination oscillator strength, etc.) of an exciton and a biexciton in CdTe/CdSe core/shell type-II quantum dot heterostructures has been carried out in the frame of the single band effective mass approximation. In order to determine the electronic properties, we have self-consistently solved the Poisson-Schrödinger equations in the Hartree approximation. We have considered all probable Coulomb interaction effects on both energy levels and also on the corresponding wave functions for both single exciton and biexciton. In addition, we have taken into account the quantum mechanical exchange-correlation effects in the local density approximation between same kinds of particles for biexciton. Also, we have examined the effect of the ligands and dielectric mismatch on the electronic and optical properties. We have used a different approximation proposed by Sahin and Koc [Appl. Phys. Lett. 102, 183103 (2013)] for the recombination oscillator strength of the biexciton for bound and unbound cases. The results obtained have been presented comparatively as a function of the shell thicknesses and probable physical reasons in behind of the results have been discussed in a detail.

Koc, Fatih, E-mail: fatih.koc@msn.com [Department of Physics, Faculty of Sciences, Selcuk University, 42075 Konya (Turkey); Sahin, Mehmet, E-mail: mehmet.sahin@agu.edu.tr, E-mail: mehsahin@gmail.com [Department of Physics, Faculty of Sciences, Selcuk University, 42075 Konya (Turkey); Department of Material Science and Nanotechnology Engineering, Abdullah Gül University, Kayseri (Turkey)

2014-05-21T23:59:59.000Z

291

Ultrafast single-electron transfer in coupled quantum dots driven by a few-cycle chirped pulse  

SciTech Connect

We theoretically study the ultrafast transfer of a single electron between the ground states of a coupled double quantum dot (QD) structure driven by a nonlinear chirped few-cycle laser pulse. A time-dependent Schrödinger equation without the rotating wave approximation is solved numerically. We demonstrate numerically the possibility to have a complete transfer of a single electron by choosing appropriate values of chirped rate parameters and the intensity of the pulse. Even in the presence of the spontaneous emission and dephasing processes of the QD system, high-efficiency coherent transfer of a single electron can be obtained in a wide range of the pulse parameters. Our results illustrate the potential to utilize few-cycle pulses for the excitation in coupled quantum dot systems through the nonlinear chirp parameter control, as well as a guidance in the design of experimental implementation.

Yang, Wen-Xing, E-mail: wenxingyang2@126.com [Department of Physics, Southeast University, Nanjing 210096 (China); Institute of Photonics Technologies, National Tsing-Hua University, Hsinchu 300, Taiwan (China); Chen, Ai-Xi [Department of Applied Physics, School of Basic Science, East China Jiaotong University, Nanchang 330013 (China); Bai, Yanfeng [Department of Physics, Southeast University, Nanjing 210096 (China); Lee, Ray-Kuang [Institute of Photonics Technologies, National Tsing-Hua University, Hsinchu 300, Taiwan (China)

2014-04-14T23:59:59.000Z

292

Assembly and Transport of Nanocrystal CdSe Quantum Dot Nanocomposites Using Microtubules and Kinesin Motor Proteins  

Science Journals Connector (OSTI)

Assembly and Transport of Nanocrystal CdSe Quantum Dot Nanocomposites Using Microtubules and Kinesin Motor Proteins ... motors in synthetic environments, we use highly oriented poly(tetrafluoroethylene) films functionalized with the motor protein kinesin and find that they are able to direct the motion of microtubules in straight lines along the films' orientation axes. ... The controlling transport direction is considered to be an essential step for future developments of motor protein-based microdevices working in nanometer steps. ...

George D. Bachand; Susan B. Rivera; Andrew K. Boal; Jennifer Gaudioso; Jun Liu; Bruce C. Bunker

2004-03-26T23:59:59.000Z

293

Pulsed-gate measurements of the singlet-triplet relaxation time in a two-electron double quantum dot  

E-Print Network (OSTI)

-gate technique with charge sensing is used to measure the singlet-triplet relaxation time for nearly degenerate spin states in a two-electron double quantum dot. Transitions from the 1,1 charge occupancy state. At dilution refrigerator temperatures, this implies that EZeeman kBT 10 eV, or B 0.5 T. For B 0.5 T, T1 shows

Petta, Jason

294

Improved Performance of CuInS2 Quantum Dot-Sensitized Solar Cells Based on a Multilayered Architecture  

Science Journals Connector (OSTI)

Dye-sensitized solar cells (DSSCs) are a promising renewable solar energy source because of their low cost, high durability, and low environmental impact. ... One of the important factors limiting solar-cell efficiency is that incident photons generate one electron-hole pair, irresp. of the photon energy. ... Among the third-generation photovoltaic devices, much attention is being paid to the so-called Quantum Dot sensitized Solar Cells (QDSCs). ...

Jia-Yaw Chang; Jie-Mo Lin; Li-Fong Su; Chia-Fu Chang

2013-08-12T23:59:59.000Z

295

Coulomb interaction of acceptors in Cd{sub 1?x}Mn{sub x}Te/CdTe quantum dot  

SciTech Connect

The investigation on the effect of confining potential like isotropic harmonic oscillator type potential on the binding and the Coulomb interaction energy of the double acceptors in the presence of magnetic field in a Cd{sub 1?x}Mn{sub x}Te/CdTe Spherical Quantum Dot has been made for the Mn ion composition x=0.3 and compared with the results obtained from the square well type potential using variational procedure in the effective mass approximation.

Kalpana, P.; Nithiananthi, P., E-mail: kjkumar-gri@rediffmail.com; Jayakumar, K., E-mail: kjkumar-gri@rediffmail.com [Department of Physics, Gandhigram Rural University, Gandhigram-624302, TamilNadu (India); Reuben, A. Merwyn Jasper D. [Department of Physics, School of Engineering, Saveetha University, Thandalam, Chennai- 600104, TamilNadu (India)

2014-04-24T23:59:59.000Z

296

Transport through open quantum dots: Making semiclassics quantitative Iva Bezinov,1,* Ludger Wirtz,2 Stefan Rotter,1 Christoph Stampfer,3 and Joachim Burgdrfer1  

E-Print Network (OSTI)

, Vienna University of Technology, Wiedner HauptstraÃ?e 8-10/136, 1040 Vienna, Austria, EU 2Department ISEN, Germany, EU Received 28 October 2009; published 9 March 2010 We investigate electron transport through clean open quantum dots quantum billiards . We present a semi- classical theory that allows

Rotter, Stefan

297

Growth of silicon quantum dots by oxidation of the silicon nanocrystals embedded within silicon carbide matrix  

SciTech Connect

A moderately low temperature (?800 °C) thermal processing technique has been described for the growth of the silicon quantum dots (Si-QD) within microcrystalline silicon carbide (?c-SiC:H) dielectric thin films deposited by plasma enhanced chemical vapour deposition (PECVD) process. The nanocrystalline silicon grains (nc-Si) present in the as deposited films were initially enhanced by aluminium induced crystallization (AIC) method in vacuum at a temperature of T{sub v} = 525 °C. The samples were then stepwise annealed at different temperatures T{sub a} in air ambient. Analysis of the films by FTIR and XPS reveal a rearrangement of the ?c-SiC:H network has taken place with a significant surface oxidation of the nc-Si domains upon annealing in air. The nc-Si grain size (D{sub XRD}) as calculated from the XRD peak widths using Scherrer formula was found to decrease from 7 nm to 4 nm with increase in T{sub a} from 250 °C to 800 °C. A core shell like structure with the nc-Si as the core and the surface oxide layer as the shell can clearly describe the situation. The results indicate that with the increase of the annealing temperature in air the oxide shell layer becomes thicker and the nc-Si cores become smaller until their size reduced to the order of the Si-QDs. Quantum confinement effect due to the SiO covered nc-Si grains of size about 4 nm resulted in a photoluminescence peak due to the Si QDs with peak energy at 1.8 eV.

Kole, Arindam; Chaudhuri, Partha, E-mail: erpc@iacs.res.in [Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata-700032 (India)

2014-10-15T23:59:59.000Z

298

First principles DFT study of dye-sensitized CdS quantum dots  

SciTech Connect

Dye-sensitized quantum dots (QDs) are considered promising candidates for dye-sensitized solar cells. In order to maximize their efficiency, detailed theoretical studies are important. Here, we report a first principles density functional theory (DFT) investigation of experimentally realized dye - sensitized QD / ligand systems, viz., Cd{sub 16}S{sub 16}, capped with acetate molecules and a coumarin dye. The hybrid B3LYP functional and a 6?311+G(d,p)/LANL2dz basis set are used to study the geometric, energetic and electronic properties of these clusters. There is significant structural rearrangement in all the clusters studied - on the surface for the bare QD, and in the positions of the acetate / dye ligands for the ligated QDs. The density of states (DOS) of the bare QD shows states in the band gap, which disappear on surface passivation with the acetate molecules. Interestingly, in the dye-sensitised QD, the HOMO is found to be localized mainly on the dye molecule, while the LUMO is on the QD, as required for photo-induced electron injection from the dye to the QD.

Jain, Kalpna; Singh, Kh. S. [Department of Physics, D. J. College, Baraut -250611, U.P. (India); Kishor, Shyam, E-mail: shyam387@gmail.com [Department of Chemistry, J. V. College, Baraut -250611, U.P. (India); Josefesson, Ida; Odelius, Michael [Fysikum, Albanova University Center, Stockholm University, S-106 91 Stockholm (Sweden); Ramaniah, Lavanya M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

2014-04-24T23:59:59.000Z

299

Nanoindentation and near-field spectroscopy of single semiconductor quantum dots  

Science Journals Connector (OSTI)

Low-temperature near-field scanning optical microscopy was used to study the dependence of the emission spectra of single self-organized InAs on GaAs, InAs on AlAs and InP on GaInP quantum dots (QDs) on contact pressure exerted by a near-field optical fiber tip (nanoindentation). A large energy shift (up to 150 meV), broadening (up to 10 meV), and intensity increase (up to one order of magnitude) of single QD emission lines have been observed at tip compressions up to 70 nm. Ground state energy shift rates from 0.5 to 3.5 meV/nm have been measured for different aperture types (rounded and flat, metal coated and uncoated) and sizes (50–300 nm) in agreement with numerical calculations using Picus–Bir orbital-strain Hamiltonian. A reduction of the hydrostatic pressure coefficient due to a nonuniform In distribution in self-organized QDs has been observed. Anomalously strong lateral inhomogeneity of the local stress field has been observed.

A. M. Mintairov; K. Sun; J. L. Merz; C. Li; A. S. Vlasov; D. A. Vinokurov; O. V. Kovalenkov; V. Tokranov; S. Oktyabrsky

2004-04-05T23:59:59.000Z

300

Layered insulator hexagonal boron nitride for surface passivation in quantum dot solar cell  

SciTech Connect

Single crystalline, two dimensional (2D) layered insulator hexagonal boron nitride (h-BN), is demonstrated as an emerging material candidate for surface passivation on mesoporous TiO{sub 2}. Cadmium selenide (CdSe) quantum dot based bulk heterojunction (BHJ) solar cell employed h-BN passivated TiO{sub 2} as an electron acceptor exhibits photoconversion efficiency ?46% more than BHJ employed unpassivated TiO{sub 2}. Dominant interfacial recombination pathways such as electron capture by TiO{sub 2} surface states and recombination with hole at valence band of CdSe are efficiently controlled by h-BN enabled surface passivation, leading to improved photovoltaic performance. Highly crystalline, confirmed by transmission electron microscopy, dangling bond-free 2D layered h-BN with self-terminated atomic planes, achieved by chemical exfoliation, enables efficient passivation on TiO{sub 2}, allowing electronic transport at TiO{sub 2}/h-BN/CdSe interface with much lower recombination rate compared to an unpassivated TiO{sub 2}/CdSe interface.

Shanmugam, Mariyappan; Jain, Nikhil; Jacobs-Gedrim, Robin; Yu, Bin, E-mail: byu@albany.edu [College of Nanoscale Science and Engineering, State University of New York, Albany, New York 12203 (United States)] [College of Nanoscale Science and Engineering, State University of New York, Albany, New York 12203 (United States); Xu, Yang [Institute of Microelectronics and Optoelectronics, Zhejiang University, Hangzhou 310027 (China)] [Institute of Microelectronics and Optoelectronics, Zhejiang University, Hangzhou 310027 (China)

2013-12-09T23:59:59.000Z

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301

Improvement of the quality of graphene-capped InAs/GaAs quantum dots  

SciTech Connect

In this paper, we study the transfer of graphene onto InAs/GaAs quantum dots (QDs). The graphene is first grown on Cu foils by chemical vapor deposition and then polymer Polymethyl Methacrylate (PMMA) is deposited on the top of graphene/Cu. High quality graphene sheet has been obtained by lowering the dissolving rate of PMMA using vapor processing. Uncapped as well as capped graphene InAs/GaAs QDs have been studied using optical microscopy, scanning electron microscopy, and Raman spectroscopy. We gather from this that the average shifts ?? of QDs Raman peaks are reduced compared to those previously observed in graphene and GaAs capped QDs. The encapsulation by graphene makes the indium atomic concentration intact in the QDs by the reduction of the strain effect of graphene on QDs and the migration of In atoms towards the surface. This gives us a new hetero-structure graphene–InAs/GaAs QDs wherein the graphene plays a key role as a cap layer.

Othmen, Riadh, E-mail: othmenriadh@yahoo.fr; Rezgui, Kamel; Ajlani, Hosni; Oueslati, Meherzi [Faculté des Sciences de Tunis, Université de Tunis El Manar, Campus, 2092 El Manar Tunis (Tunisia); Cavanna, Antonella; Madouri, Ali [CNRS/LPN, Route de Nozay, F-91460 Marcoussis (France); Arezki, Hakim; Gunes, Fethullah [Laboratoire de Génie Electrique de Paris, 11, rue Joliot Curie Plateau de Moulon, 91192 Gif sur Yvette (France)

2014-06-07T23:59:59.000Z

302

Blinking effect and the use of quantum dots in single molecule spectroscopy  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer It is possible to eliminate the blinking effect of a water-soluble QD. Black-Right-Pointing-Pointer We provide a direct method to study protein function and dynamics at the single level. Black-Right-Pointing-Pointer QD, potent tool for single molecule studies of biochemical and biological processes. -- Abstract: Luminescent semiconductor nanocrystals (quantum dots, QD) have unique photo-physical properties: high photostability, brightness and narrow size-tunable fluorescence spectra. Due to their unique properties, QD-based single molecule studies have become increasingly more popular during the last years. However QDs show a strong blinking effect (random and intermittent light emission), which may limit their use in single molecule fluorescence studies. QD blinking has been widely studied and some hypotheses have been done to explain this effect. Here we summarise what is known about the blinking effect in QDs, how this phenomenon may affect single molecule studies and, on the other hand, how the 'on'/'off' states can be exploited in diverse experimental settings. In addition, we present results showing that site-directed binding of QD to cysteine residues of proteins reduces the blinking effect. This option opens a new possibility of using QDs to study protein-protein interactions and dynamics by single molecule fluorescence without modifying the chemical composition of the solution or the QD surface.

Rombach-Riegraf, Verena; Oswald, Peter; Bienert, Roland; Petersen, Jan [Albert-Ludwigs-Universitaet Freiburg, Institut fuer Physikalische Chemie, Albertstrasse 23a, 79104 Freiburg (Germany)] [Albert-Ludwigs-Universitaet Freiburg, Institut fuer Physikalische Chemie, Albertstrasse 23a, 79104 Freiburg (Germany); Domingo, M.P. [Instituto de Carboquimica (CSIC), Miguel Luesma 4, 50018 Zaragoza (Spain)] [Instituto de Carboquimica (CSIC), Miguel Luesma 4, 50018 Zaragoza (Spain); Pardo, Julian [Grupo Apoptosis, Inmunidad y Cancer, Departamento Bioquimica y Biologia Molecular y Celular, Fac. Ciencias, Universidad de Zaragoza, Zaragoza (Spain) [Grupo Apoptosis, Inmunidad y Cancer, Departamento Bioquimica y Biologia Molecular y Celular, Fac. Ciencias, Universidad de Zaragoza, Zaragoza (Spain); Fundacion Aragon I-D (ARAID), Gobierno de Aragon, Zaragoza (Spain); Immune Effector Cells Group, Aragon Health Research Institute (IIS Aragon), Biomedical Research Centre of Aragon (CIBA) Fundacion Aragon I-D - ARAID, Gobierno de Aragon, Zaragoza (Spain); Graeber, P. [Albert-Ludwigs-Universitaet Freiburg, Institut fuer Physikalische Chemie, Albertstrasse 23a, 79104 Freiburg (Germany)] [Albert-Ludwigs-Universitaet Freiburg, Institut fuer Physikalische Chemie, Albertstrasse 23a, 79104 Freiburg (Germany); Galvez, E.M., E-mail: eva@icb.csic.es [Instituto de Carboquimica (CSIC), Miguel Luesma 4, 50018 Zaragoza (Spain); Immune Effector Cells Group, Aragon Health Research Institute (IIS Aragon), Biomedical Research Centre of Aragon (CIBA) Fundacion Aragon I-D - ARAID, Gobierno de Aragon, Zaragoza (Spain)

2013-01-04T23:59:59.000Z

303

Bacteria-mediated in vivo delivery of quantum dots into solid tumor  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer New approach using the probiotic Bifidobacterium bifidum as a vehicle to deliver QDs into the deep tissue of solid tumors in vivo was achieved. Black-Right-Pointing-Pointer Bifidobacterium bifidum delivery system has intrinsic biocompatibility. Black-Right-Pointing-Pointer The targeting efficacy was improved by folic acids. -- Abstract: Semiconductor nanocrystals, so-called quantum dots (QDs), promise potential application in bioimaging and diagnosis in vitro and in vivo owing to their high-quality photoluminescence and excellent photostability as well as size-tunable spectra. Here, we describe a biocompatible, comparatively safe bacteria-based system that can deliver QDs specifically into solid tumor of living animals. In our strategy, anaerobic bacterium Bifidobacterium bifidum (B. bifidum) that colonizes selectively in hypoxic regions of animal body was successfully used as a vehicle to load with QDs and transported into the deep tissue of solid tumors. The internalization of lipid-encapsuled QDs into B. bifidum was conveniently carried by electroporation. To improve the efficacy and specificity of tumor targeting, the QDs-carrying bacterium surface was further conjugated with folic acids (FAs) that can bind to the folic acid receptor overexpressed tumor cells. This new approach opens a pathway for delivering different types of functional cargos such as nanoparticles and drugs into solid tumor of live animals for imaging, diagnosis and therapy.

Liu, Ying [Single-molecule and Nanobiology Lab., Dept. of Biophysics, School of Basic Medical Sciences, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China)] [Single-molecule and Nanobiology Lab., Dept. of Biophysics, School of Basic Medical Sciences, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China); Zhou, Mei [Dept. of Radiation Medicine, School of Basic Medical Sciences, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China)] [Dept. of Radiation Medicine, School of Basic Medical Sciences, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China); Luo, Dan; Wang, Lijun; Hong, Yuankai [Single-molecule and Nanobiology Lab., Dept. of Biophysics, School of Basic Medical Sciences, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China)] [Single-molecule and Nanobiology Lab., Dept. of Biophysics, School of Basic Medical Sciences, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China); Yang, Yepeng, E-mail: yangyepeng@bjmu.edu.cn [Dept. of Radiation Medicine, School of Basic Medical Sciences, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China)] [Dept. of Radiation Medicine, School of Basic Medical Sciences, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China); Sha, Yinlin, E-mail: shyl@hsc.pku.edu.cn [Single-molecule and Nanobiology Lab., Dept. of Biophysics, School of Basic Medical Sciences, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China) [Single-molecule and Nanobiology Lab., Dept. of Biophysics, School of Basic Medical Sciences, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China); Biomed-X Center, Peking University, Peking University, No. 38 Xue Yuan Road, Beijing 100091 (China)

2012-09-07T23:59:59.000Z

304

Spin pumping and spin filtering in double quantum dots with time-dependent spin-orbit interactions  

Science Journals Connector (OSTI)

We propose a scheme of realizing both spin pumping and spin filtering in a double quantum dot with homogeneous Zeeman splittings in the presence of oscillating spin-orbit interactions. We find that a spin-polarized pumping current can be achieved by tuning the relative energies of the Zeeman-split levels of the dots. It is also found that a pure spin current can be generated at zero detuning whose magnitude can be modulated by the external fields. At a certain constellation of system parameters the pumping current can become almost fully spin-polarized. Therefore it is possible to select a particular spin component of the current to be pumped from the left to the right lead. We finally give some discussions on the realization of the spin pumping and spin filtering effects.

Hui Pan; Yinghui Zhao

2012-01-01T23:59:59.000Z

305

Structure of Si-capped Ge/SiC/Si (001) epitaxial nanodots: Implications for quantum dot patterning  

SciTech Connect

Artificially ordered quantum dot (QD) arrays, where confined carriers can interact via direct exchange coupling, may create unique functionalities such as cluster qubits and spintronic bandgap systems. Development of such arrays for quantum computing requires fine control over QD size and spatial arrangement on the sub-35 nm length scale. We employ electron-beam irradiation to locally decompose ambient hydrocarbons onto a bare Si (001) surface. These carbonaceous patterns are annealed in ultra-high vacuum (UHV), forming ordered arrays of nanoscale SiC precipitates that have been suggested to template subsequent epitaxial Ge growth to form ordered QD arrays. We show that 3C-SiC nanodots form, in cube-on-cube epitaxial registry with the Si substrate. The SiC nanodots are fully relaxed by misfit dislocations and exhibit small lattice rotations with respect to the substrate. Ge overgrowth at elevated deposition temperatures, followed by Si capping, results in expulsion of the Ge from SiC template sites due to the large chemical and lattice mismatch between Ge and C. Maintaining an epitaxial, low-defectivity Si matrix around the quantum dots is important for creating reproducible electronic and spintronic coupling of states localized at the QDs.

Petz, C. W.; Floro, J. A. [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Yang, D.; Levy, J. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)

2012-04-02T23:59:59.000Z

306

Excitonic fine-structure splitting in telecom-wavelength InAs/GaAs quantum dots: Statistical distribution and height-dependence  

SciTech Connect

The variation of the excitonic fine-structure splitting is studied for semiconductor quantum dots under the influence of a strain-reducing layer, utilized to shift the emission wavelength of the excitonic transition into the telecom-wavelength regime of 1.3–1.5 ?m. By means of a sp{sup 3}s{sup *}-tight-binding model and configuration interaction, we calculate wavelength shifts and fine-structure splittings for various quantum dot geometries. We find the splittings remaining small and even decreasing with strain-reducing layer composition for quantum dots with large height. Combined with an observed increased emission efficiency, the applicability for generation of entanglement photons is persistent.

Goldmann, Elias, E-mail: goldmann@itp.uni-bremen.de; Barthel, Stefan; Florian, Matthias; Jahnke, Frank [Institute of Theoretical Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen (Germany)] [Institute of Theoretical Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen (Germany); Schuh, Kolja [College of Optical Sciences, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721-0094 (United States)] [College of Optical Sciences, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721-0094 (United States)

2013-12-09T23:59:59.000Z

307

Nuclear Magnetic Resonance Inverse Spectra of InGaAs Quantum Dots: Atomistic Level Structural Information  

E-Print Network (OSTI)

A wealth of atomistic information is buried within a self-assembled quantum dot (QD), carrying the legacy of its chemical composition and the growth history. In the presence of quadrupolar nuclei, as in InGaAs QDs, much of this is inherited to nuclear spins. With this computational study, we identify what sorts of atomistic information can be tapped from a single InGaAs QD, as probed optically by the recently introduced highly sensitive inverse spectra nuclear magnetic resonance technique. To capture the fingerprints of alloying in the spectra, we compare In0.2Ga0.8As QD with the compound InAs QD of the same shape, as well as performing a search over the parameter space of the inverse spectra technique. We display how both the elemental nuclear properties and local bonding take roles. The arsenic nuclei with their small gyromagnetic ratio are the most vulnerable to strain at a given magnetic field. Furthermore, because of their large S44 gradient elastic tensor components, the deviation of the major electric field gradient axis from the static magnetic field is also the largest. Moreover, this axial tilting has a big variance caused by the availability of various arsenic-centric nearest-neighbor configurations under cation alloying. We identify that a signature of alloying as opposed to segregated binaries within the QD is a peak that appears like an additional satellite transition of 75As. The local chemical and strain environment distinctly affect the isotopic line profiles, in particular the central transitions, for which we provide an in-depth analysis. We demonstrate the possibility of restoring to a large extend a monoenergetic distribution of isotopic nuclear spins by simply tilting the sample within a range of angles with respect to static magnetic field.

Ceyhun Bulutay; E. A. Chekhovich; A. I. Tartakovskii

2014-08-02T23:59:59.000Z

308

Entanglement purification and concentration of electron-spin entangled states using quantum-dot spins in optical microcavities  

SciTech Connect

We present an entanglement purification protocol and an entanglement concentration protocol for electron-spin entangled states, resorting to quantum-dot spin and optical-microcavity-coupled systems. The parity-check gates (PCGs) constructed by the cavity-spin-coupling system provide a different method for the entanglement purification of electron-spin entangled states. This protocol can efficiently purify an electron ensemble in a mixed entangled state. The PCGs can also concentrate electron-spin pairs in less-entangled pure states efficiently. The proposed methods are more flexible as only single-photon detection and single-electron detection are needed.

Wang Chuan [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Key Laboratory of Optical Communication and Lightwave Technologies, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Department of Physics, Tsinghua University, Beijing 100084 (China); Zhang Yong; Jin Guangsheng [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Key Laboratory of Optical Communication and Lightwave Technologies, Beijing University of Posts and Telecommunications, Beijing 100876 (China)

2011-09-15T23:59:59.000Z

309

Room temperature spontaneous emission enhancement from quantum dots in photonic crystal slab cavities in the telecommunications C-band  

E-Print Network (OSTI)

We report on the control of the spontaneous emission dynamics from InAsP self-assembled quantum dots emitting in the telecommunications C-band and weakly coupled to the mode of a double heterostructure cavity etched on a suspended InP membrane at room temperature. The quality factor of the cavity mode is 44x10^3 with an ultra-low modal volume of the order of 1.2 lambda/n)^3, inducing an enhancement of the spontaneous emission rate of up a factor of 2.8 at 300 K.

Richard Hostein; Rémy Braive; Matthieu Larqué; Ko-Hsin Lee; Anne Talneau; Luc Le Gratiet; Isabelle Robert-Philip; Isabelle Sagnes; Alexios Beveratos

2009-03-25T23:59:59.000Z

310

Dynamic nuclear polarization and Hanle effect in (In,Ga)As/GaAs quantum dots. Role of nuclear spin fluctuations  

SciTech Connect

The degree of circular polarization of photoluminescence of (In,Ga)As quantum dots as a function of magnetic field applied perpendicular to the optical axis (Hanle effect) is experimentally studied. The measurements have been performed at various regimes of the optical excitation modulation. The analysis of experimental data has been performed in the framework of a vector model of regular nuclear spin polarization and its fluctuations. The analysis allowed us to evaluate the magnitude of nuclear polarization and its dynamics at the experimental conditions used.

Gerlovin, I. Ya. [Spin Optics Laboratory, Saint Petersburg State University, Petrodvorets, 198504 St. Petersburg (Russian Federation); Cherbunin, R. V.; Ignatiev, I. V.; Kuznetsova, M. S.; Verbin, S. Yu. [Spin Optics Laboratory, Saint Petersburg State University, Petrodvorets, 198504 St. Petersburg, Russia and Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund (Germany); Flisinski, K.; Bayer, M. [Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund (Germany); Reuter, D.; Wieck, A. D. [Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Yakovlev, D. R. [Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany and A. F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation)

2013-12-04T23:59:59.000Z

311

Bound state energies and wave functions of spherical quantum dots in presence of a confining potential model  

E-Print Network (OSTI)

We obtain the exact energy spectra and corresponding wave functions of the radial Schr\\"odinger equation (RSE) for any (n,l) state in the presence of a combination of psudoharmonic, Coulomb and linear confining potential terms using an exact analytical iteration method. The interaction potential model under consideration is Cornell-modified plus harmonic (CMpH) type which is a correction form to the harmonic, Coulomb and linear confining potential terms. It is used to investigates the energy of electron in spherical quantum dot and the heavy quarkonia (QQ-onia).

Sameer M. Ikhdair

2011-10-03T23:59:59.000Z

312

Dramatically enhanced self-assembly of GeSi quantum dots with superior photoluminescence induced by the substrate misorientation  

SciTech Connect

A dramatically enhanced self-assembly of GeSi quantum dots (QDs) is disclosed on slightly miscut Si (001) substrates, leading to extremely dense QDs and even a growth mode transition. The inherent mechanism is addressed in combination of the thermodynamics and the growth kinetics both affected by steps on the vicinal surface. Moreover, temperature-dependent photoluminescence spectra from dense GeSi QDs on the miscut substrate demonstrate a rather strong peak persistent up to 300 K, which is attributed to the well confinement of excitons in the dense GeSi QDs due to the absence of the wetting layer on the miscut substrate.

Zhou, Tong; Zhong, Zhenyang, E-mail: zhenyangz@fudan.edu.cn [State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433 (China)

2014-02-01T23:59:59.000Z

313

Self-organized arrays of graphene and few-layer graphene quantum dots in fluorographene matrix: Charge transient spectroscopy  

SciTech Connect

Arrays of graphene or few-layer graphene quantum dots (QDs) embedded in a partially fluorinated graphene matrix were created by chemical functionalization of layers. Charge transient spectroscopy employed for investigation of obtained QD systems (size 20–70 nm) has allowed us to examine the QD energy spectra and the time of carrier emission (or charge relaxation) from QDs as a function of film thickness. It was found that the characteristic time of carrier emission from QDs decreased markedly (by about four orders of magnitude) on increasing the QD thickness from one graphene monolayer to 3 nm. Daylight-assisted measurements also demonstrate a strong decrease of the carrier emission time.

Antonova, Irina V., E-mail: antonova@isp.nsc.ru [Rzhanov Institute of Semiconductor Physics, SB RAS, Lavrentiev Avenue 13, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Pirogov st. 2, Novosibirsk 630090 (Russian Federation); Nebogatikova, Nadezhda A.; Prinz, Victor Ya. [Rzhanov Institute of Semiconductor Physics, SB RAS, Lavrentiev Avenue 13, Novosibirsk 630090 (Russian Federation)

2014-05-12T23:59:59.000Z

314

Efficient, air-stable colloidal quantum dot solar cells encapsulated using atomic layer deposition of a nanolaminate barrier  

SciTech Connect

Atomic layer deposition was used to encapsulate colloidal quantum dot solar cells. A nanolaminate layer consisting of alternating alumina and zirconia films provided a robust gas permeation barrier which prevented device performance degradation over a period of multiple weeks. Unencapsulated cells stored in ambient and nitrogen environments demonstrated significant performance losses over the same period. The encapsulated cell also exhibited stable performance under constant simulated solar illumination without filtration of harsh ultraviolet photons. This monolithically integrated thin film encapsulation method is promising for roll-to-roll processed high efficiency nanocrystal solar cells.

Ip, Alexander H.; Labelle, André J.; Sargent, Edward H., E-mail: ted.sargent@utoronto.ca [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada)

2013-12-23T23:59:59.000Z

315

Structural properties and spatial ordering in multilayered ZnMgTe/ZnSe type-II quantum dot structures  

SciTech Connect

We report the structural properties and spatial ordering of multilayer ZnMgTe quantum dots (QDs) embedded in ZnSe, where sub-monolayer quantities of Mg were introduced periodically during growth in order to reduce the valence band offset of ZnTe QDs. The periodicity, period dispersion, individual layer thickness, and the composition of the multilayer structures were determined by comparing the experimental high resolution x-ray diffraction (HRXRD) spectra to simulated ones for the allowed (004) and quasi-forbidden (002) reflections in combination with transmission electron microscopy (TEM) results. Secondary ion mass spectroscopy (SIMS) profiles confirmed the incorporation of Mg inside the QD layers, and the HRXRD analysis revealed that there is approximately 32% Mg in the ZnMgTe QDs. The presence of Mg contributes to higher scattering intensity of the HRXRD, leading to the observation of higher order superlattice peaks in both the (004) and (002) reflections. The distribution of scattered intensity in the reciprocal space map (RSM) shows that the diffuse scattered intensity is elongated along the q{sub x} axis, indicating a vertical correlation of the dots, which is found to be less defined for the sample with larger periodicity. The diffuse scattered intensity is also found to be weakly correlated along the q{sub z} direction indicating a weak lateral correlation of the dots.

Manna, U.; Noyan, I. C.; Neumark, G. F. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Zhang, Q.; Moug, R. [Department of Chemistry, City College of CUNY, New York, New York 10031 (United States); Salakhutdinov, I. F. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Department of Physics, Queens College of CUNY, Flushing, New York 11367 (United States); Dunn, K. A.; Novak, S. W. [College of Nanoscale Science and Engineering, University at Albany-SUNY, Albany, New York 12203 (United States); Tamargo, M. C. [Department of Chemistry, City College of CUNY, New York, New York 10031 (United States); Graduate Center of CUNY, New York, New York 10016 (United States); Kuskovsky, I. L. [Department of Physics, Queens College of CUNY, Flushing, New York 11367 (United States); Graduate Center of CUNY, New York, New York 10016 (United States)

2012-02-01T23:59:59.000Z

316

Nonlinear optical spectra having characteristics of Fano interferences in coherently coupled lowest exciton biexciton states in semiconductor quantum dots  

SciTech Connect

Optical nonlinear effects are examined using a two-color micro-photoluminescence (micro-PL) method in a coherently coupled exciton-biexciton system in a single quantum dot (QD). PL and photoluminescence excitation spectroscopy (PLE) are employed to measure the absorption spectra of the exciton and biexciton states. PLE for Stokes and anti-Stokes PL enables us to clarify the nonlinear optical absorption properties in the lowest exciton and biexciton states. The nonlinear absorption spectra for excitons exhibit asymmetric shapes with peak and dip structures, and provide a distinct contrast to the symmetric dip structures of conventional nonlinear spectra. Theoretical analyses with a density matrix method indicate that the nonlinear spectra are caused not by a simple coherent interaction between the exciton and biexciton states but by coupling effects among exciton, biexciton and continuum states. These results indicate that Fano quantum interference effects appear in exciton-biexciton systems at QDs and offer important insights into their physics.

Gotoh, Hideki, E-mail: gotoh.hideki@lab.ntt.co.jp; Sanada, Haruki; Yamaguchi, Hiroshi; Sogawa, Tetsuomi [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan)

2014-10-15T23:59:59.000Z

317

Exploring size and state dynamics in CdSe quantum dots using two-dimensional electronic spectroscopy  

SciTech Connect

Development of optoelectronic technologies based on quantum dots depends on measuring, optimizing, and ultimately predicting charge carrier dynamics in the nanocrystal. In such systems, size inhomogeneity and the photoexcited population distribution among various excitonic states have distinct effects on electron and hole relaxation, which are difficult to distinguish spectroscopically. Two-dimensional electronic spectroscopy can help to untangle these effects by resolving excitation energy and subsequent nonlinear response in a single experiment. Using a filament-generated continuum as a pump and probe source, we collect two-dimensional spectra with sufficient spectral bandwidth to follow dynamics upon excitation of the lowest three optical transitions in a polydisperse ensemble of colloidal CdSe quantum dots. We first compare to prior transient absorption studies to confirm excitation-state-dependent dynamics such as increased surface-trapping upon excitation of hot electrons. Second, we demonstrate fast band-edge electron-hole pair solvation by ligand and phonon modes, as the ensemble relaxes to the photoluminescent state on a sub-picosecond time-scale. Third, we find that static disorder due to size polydispersity dominates the nonlinear response upon excitation into the hot electron manifold; this broadening mechanism stands in contrast to that of the band-edge exciton. Finally, we demonstrate excitation-energy dependent hot-carrier relaxation rates, and we describe how two-dimensional electronic spectroscopy can complement other transient nonlinear techniques.

Caram, Justin R.; Zheng, Haibin; Rolczynski, Brian S.; Griffin, Graham B.; Engel, Gregory S., E-mail: gsengel@uchicago.edu [Department of Chemistry, The Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Dahlberg, Peter D. [Graduate Program in the Biophysical Sciences, The Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States)] [Graduate Program in the Biophysical Sciences, The Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Dolzhnikov, Dmitriy S.; Talapin, Dmitri V. [Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States)

2014-02-28T23:59:59.000Z

318

Cathodoluminescence imaging and spectroscopy of excited states in InAs self-assembled quantum dots  

SciTech Connect

We have examined state filling and thermal activation of carriers in buried InAs self-assembled quantum dots (SAQDs) with excitation-dependent cathodoluminescence (CL) imaging and spectroscopy. The InAs SAQDs were formed during molecular-beam epitaxial growth of InAs on undoped planar GaAs (001). The intensities of the ground- and excited-state transitions were analyzed as a function of temperature and excitation density to study the thermal activation and reemission of carriers. The thermal activation energies associated with the thermal quenching of the luminescence were measured for ground- and excited-state transitions of the SAQDs, as a function of excitation density. By comparing these activation energies with the ground- and excited-state transition energies, we have considered various processes that describe the reemission of carriers. Thermal quenching of the intensity of the QD ground- and first excited-state transitions at low excitations in the {approx}230-300-K temperature range is attributed to dissociation of excitons from the QD states into the InAs wetting layer. At high excitations, much lower activation energies of the ground and excited states are obtained, suggesting that thermal reemission of single holes from QD states into the GaAs matrix is responsible for the observed temperature dependence of the QD luminescence in the {approx}230-300-K temperature range. The dependence of the CL intensity of the ground-and first excited-state transition on excitation density was shown to be linear at all temperatures at low-excitation density. This result can be understood by considering that carriers escape and are recaptured as excitons or correlated electron-hole pairs. At sufficiently high excitations, state-filling and spatial smearing effects are observed together with a sublinear dependence of the CL intensity on excitation. Successive filling of the ground and excited states in adjacent groups of QDs that possess different size distributions is assumed to be the cause of the spatial smearing.

Khatsevich, S.; Rich, D.H.; Kim, Eui-Tae; Madhukar, A. [Department of Physics, Ilse Katz Center for Meso and Nanoscale Science and Technology, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105 (Israel); Department of Materials Science and Engineering, Nanostructure Materials and Devices Laboratory, University of Southern California, Los Angeles, California 90089-0241 (United States)

2005-06-15T23:59:59.000Z

319

Exciton relaxation and coupling dynamics in a GaAs/AlxGa1-xAs quantum well and quantum dot ensemble  

Science Journals Connector (OSTI)

Exciton inter- and intra-actions in a GaAs/AlGaAs quantum well (QW) and quantum dot (QD) ensemble are studied using optical two-dimensional Fourier transform spectroscopy. We measure population dynamics for times up to 300 ps and temperatures up to 50 K and observe biexponential decay for both QW and QD excitons, strong QW ? QD relaxation, and weak QD ? QW activation. The population dynamics are modeled using a system of rate equations that incorporate radiative and nonradiative decay, coupling between bright and dark exciton states, and QW ? QD coupling. The fast decay rates are attributed to exciton-bound hole spin flips between optically active and inactive states and are similar for the QW and QDs, indicating excitons are weakly localized in the QDs. The QW ? QD relaxation rate increases with temperature, and QD ? QW excitation is observed at temperatures ?35 K.

G. Moody; M. E. Siemens; A. D. Bristow; X. Dai; A. S. Bracker; D. Gammon; S. T. Cundiff

2011-06-27T23:59:59.000Z

320

Spin-Cast Deposition of CdSe-CdS Core-Shell Colloidal Quantum Dots on Doped GaAs Substrates: Structural and Optical Characterization  

Science Journals Connector (OSTI)

The detailed study of the effects of spin recipe and GaAs substrate doping (i.e., semi-insulating, n-type, or p-type) on the structural and optical properties of spin-cast CdSe-CdS core-shell CQDs provides insight into the surface adsorption and charge ... Keywords: Charge transfer, colloidal quantum dots, hybrid junctions, photoluminescence

A. D. Stiff-Roberts; Wanming Zhang; Jian Xu; Hongying Peng; H. O. Everitt

2007-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
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321

Measurement of Temporal Correlations of the Overhauser Field in a Double Quantum Dot D. J. Reilly,1,* J. M. Taylor,2  

E-Print Network (OSTI)

of high-bandwidth proximal charge sensing [30]. Fluctuations are found to be broadband over in a dilution refrigerator with base electron temperature of $120 mK. The conductance GQPC of a proximal radio frequency quantum point contact (rf QPC) is sensitive to the charge configuration of the double dot. GQPC

Petta, Jason

322

Ab Initio Time-Domain Study of Phonon-Assisted Relaxation of Charge Carriers in a PbSe Quantum Dot  

E-Print Network (OSTI)

Ab Initio Time-Domain Study of Phonon-Assisted Relaxation of Charge Carriers in a PbSe Quantum Dot optical modes. Holes decay only slightly faster than electrons, rendering the hole-assisted Auger that was reported recently in relation to improved solar power conversion. 1. Introduction Nanometer-size crystals

323

Nanocrystalline-Si-dot multi-layers fabrication by chemical vapor deposition with H-plasma surface treatment and evaluation of structure and quantum confinement effects  

SciTech Connect

100-nm-thick nanocrystalline silicon (nano-Si)-dot multi-layers on a Si substrate were fabricated by the sequential repetition of H-plasma surface treatment, chemical vapor deposition, and surface oxidation, for over 120 times. The diameter of the nano-Si dots was 5–6 nm, as confirmed by both the transmission electron microscopy and X-ray diffraction analysis. The annealing process was important to improve the crystallinity of the nano-Si dot. We investigated quantum confinement effects by Raman spectroscopy and photoluminescence (PL) measurements. Based on the experimental results, we simulated the Raman spectrum using a phenomenological model. Consequently, the strain induced in the nano-Si dots was estimated by comparing the experimental and simulated results. Taking the estimated strain value into consideration, the band gap modulation was measured, and the diameter of the nano-Si dots was calculated to be 5.6 nm by using PL. The relaxation of the q ? 0 selection rule model for the nano-Si dots is believed to be important to explain both the phenomena of peak broadening on the low-wavenumber side observed in Raman spectra and the blue shift observed in PL measurements.

Kosemura, Daisuke, E-mail: d-kose@isc.meiji.ac.jp; Mizukami, Yuki; Takei, Munehisa; Numasawa, Yohichiroh; Ogura, Atsushi [School of Science and Technology, Meiji University, Kawasaki 214-8571 (Japan)] [School of Science and Technology, Meiji University, Kawasaki 214-8571 (Japan); Ohshita, Yoshio [Toyota Technological Institute, Nagoya 468-8511 (Japan)] [Toyota Technological Institute, Nagoya 468-8511 (Japan)

2014-01-15T23:59:59.000Z

324

Accurate determination of energy scales in few-electron double quantum dots D. Taubert,1  

E-Print Network (OSTI)

methods to determine the gate voltage to energy conversion accurately in the different regimes of dot-lead tunnel couplings and demonstrate strong variations of the conversion factors. Our concepts can easily involves a conversion of the applied gate voltages to energy differences between the electronic states

Ludwig-Maximilians-Universität, München

325

Laser irradiation effects on the CdTe/ZnTe quantum dot structure studied by Raman and AFM spectroscopy  

SciTech Connect

Micro-Raman spectroscopy has been applied to investigate the impact of laser irradiation on semiconducting CdTe/ZnTe quantum dots (QDs) structures. A reference sample (without dots) was also studied for comparison. Both samples were grown by molecular beam epitaxy technique on the p-type GaAs substrate. The Raman spectra have been recorded for different time of a laser exposure and for various laser powers. The spectra for both samples exhibit peak related to the localized longitudinal (LO) ZnTe phonon of a wavenumber equal to 210 cm{sup -1}. For the QD sample, a broad band corresponding to the LO CdTe phonon related to the QD-layer appears at a wavenumber of 160 cm{sup -1}. With increasing time of a laser beam exposure and laser power, the spectra get dominated by tellurium-related peaks appearing at wavenumbers around 120 cm{sup -1} and 140 cm{sup -1}. Simultaneously, the ZnTe surface undergoes rising damage, with the formation of Te aggregates at the pinhole edge as reveal atomic force microscopy observations. Local temperature of irradiated region has been estimated from the anti-Stokes/Stokes ratio of the Te modes intensity and it was found to be close or exceeding ZnTe melting point. Thus, the laser damage can be explained by the ablation process.

Zielony, E.; Placzek-Popko, E.; Henrykowski, A.; Gumienny, Z.; Kamyczek, P.; Jacak, J. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Nowakowski, P.; Karczewski, G. [Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warsaw (Poland)

2012-09-15T23:59:59.000Z

326

Evidence of significant down-conversion in a Si-based solar cell using CuInS{sub 2}/ZnS core shell quantum dots  

SciTech Connect

We report on the increase of up to 37.5% in conversion efficiency of a Si-based solar cell after deposition of light-emitting Cd-free, CuInS{sub 2}/ZnS core shell quantum dots on the active area of the cell due to the combined effect of down-conversion and the anti- reflecting property of the dots. We clearly distinguished the effect of down-conversion from anti-reflection and estimated an enhancement of up to 10.5% in the conversion efficiency due to down-conversion.

Gardelis, Spiros, E-mail: S.Gardelis@imel.demokritos.gr; Nassiopoulou, Androula G. [NCSR Demokritos INN, Terma Patriarchou Grigoriou, Aghia Paraskevi, 15310 Athens (Greece)

2014-05-05T23:59:59.000Z

327

Suppression of nuclear spin diffusion at a GaAs/AlGaAs interface measured with a single quantum dot nano-probe  

E-Print Network (OSTI)

Nuclear spin polarization dynamics are measured in optically pumped individual GaAs/AlGaAs interface quantum dots by detecting the time-dependence of the Overhauser shift in photoluminescence (PL) spectra. Long nuclear polarization decay times of ~ 1 minute have been found indicating inefficient nuclear spin diffusion from the GaAs dot into the surrounding AlGaAs matrix in externally applied magnetic field. A spin diffusion coefficient two orders lower than that previously found in bulk GaAs is deduced.

A. E. Nikolaenko; E. A. Chekhovich; M. N. Makhonin; I. W. Drouzas; A. B. Vankov; J. Skiba-Szymanska; M. S. Skolnick; P. Senellart; A. Lemaitre; A. I. Tartakovskii

2009-01-15T23:59:59.000Z

328

A quantum dot single-photon source with on-the-fly all-optical polarization control and timed emission  

E-Print Network (OSTI)

Sources of single photons are key elements in the study of basic quantum optical concepts and applications in quantum information science. Among the different sources available, semiconductor quantum dots excel with their straight forward integrability in semiconductor based on-chip solutions and the potential that photon emission can be triggered on demand. Usually, the photon emission event is part of a cascaded biexciton-exciton emission scheme. Important properties of the emitted photon such as polarization and time of emission are either probabilistic in nature or pre-determined by electronic properties of the system. In this work, we study the direct two-photon emission from the biexciton. We show that emission through this higher-order transition provides a much more versatile approach to generate a single photon. In the scheme we propose, the two-photon emission from the biexciton is enabled by a laser field (or laser pulse) driving the system into a virtual state inside the band gap. From this interm...

Heinze, Dirk; Schumacher, Stefan

2014-01-01T23:59:59.000Z

329

New Pathway Developed to Silicon Quantum Dot Devices (Fact Sheet), Highlights in Science, NREL (National Renewable Energy Laboratory)  

NLE Websites -- All DOE Office Websites (Extended Search)

Researchers create a way to prepare doped nanocrystal Researchers create a way to prepare doped nanocrystal solutions for solar thin films that are nontoxic and less expensive than heavy metal-based thin films. Scientists at the National Renewable Energy Laboratory (NREL) and the University of Minnesota have developed a method for preparing doped colloids (solutions) of silicon nanocrystals (NCs) as potential nontoxic infrared-absorbing and -emitting alternatives to metal chalcogenide quantum dots. Significant progress in the methods for preparing thin films of semiconductor NCs has recently led to very promising results in which metal chalcogenide (cadmium selenide, lead sulfide, etc.) NC thin films are used as the photoactive layer in solar cells, photodetectors, light-emitting diodes (LEDs), and related technologies.

330

The feasibility of high-efficiency InAs/GaAs quantum dot intermediate band solar cells  

Science Journals Connector (OSTI)

Abstract In recent years, all the operating principles of intermediate band behaviour have been demonstrated in InAs/GaAs quantum dot (QD) solar cells. Having passed this hurdle, a new stage of research is underway, whose goal is to deliver QD solar cells with efficiencies above those of state-of-the-art single-gap devices. In this work, we demonstrate that this is possible, using the present InAs/GaAs QD system, if the \\{QDs\\} are made to be radiatively dominated, and if absorption enhancements are achieved by a combination of increasing the number of \\{QDs\\} and light trapping. A quantitative prediction is also made of the absorption enhancements required, suggesting that a 30 fold increase in the number of \\{QDs\\} and a light trapping enhancement of 10 are sufficient. Finally, insight is given into the relative merits of absorption enhancement via increasing QD numbers and via light trapping.

A. Mellor; A. Luque; I. Tobías; A. Martí

2014-01-01T23:59:59.000Z

331

Analyzing carrier escape mechanisms in InAs/GaAs quantum dot p-i-n junction photovoltaic cells  

Science Journals Connector (OSTI)

Intermediate band solar cells (IBSCs) are third-generation photovoltaic (PV) devices that can harvest sub-bandgap photons normally not absorbed in a single-junction solar cell. Despite the large increase in total solar energy conversion efficiency predicted for IBSC devices substantial challenges remain to realizing these efficiency gains in practical devices. We evaluate carrier escape mechanisms in an InAs/GaAs quantum dot intermediate band p-i-n junction PV device using photocurrent measurements under sub-bandgap illumination. We show that sub-bandgap photons generate photocurrent through a two-photon absorption process but that carrier trapping and retrapping limit the overall photocurrent. The results identify a key obstacle that must be overcome in order to realize intermediate band devices that outperform single junction photovoltaic cells.

S. Polly; S. M. Hubbard; M. F. Doty

2014-01-01T23:59:59.000Z

332

Near-infrared InN quantum dots on high-In composition InGaN  

SciTech Connect

We report the growth of InN quantum dots (QDs) on thick InGaN layers with high In composition (>50%) by molecular beam epitaxy. Optimized growth conditions are identified for the InGaN layers at reduced growth temperature and increased active N flux resulting in minimized phase separation and defect generation. The InN QDs grown on top of the optimized InGaN layer exhibit small size, high density, and photoluminescence up to room temperature. The InN/InGaN QDs reveal excellent potential for intermediate band solar cells with the InGaN and InN QD bandgap energies tuned to the best match of absorption to the solar spectrum.

Soto Rodriguez, Paul E. D.; Gomez, Victor J.; Kumar, Praveen; Calleja, Enrique; Noetzel, Richard [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)] [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

2013-04-01T23:59:59.000Z

333

Strong enhancement of terahertz emission from GaAs in InAs/GaAs quantum dot structures  

SciTech Connect

We report on the intense terahertz emission from InAs/GaAs quantum dot (QD) structures grown by molecular beam epitaxy. Results reveal that the QD sample emission was as high as 70% of that of a p-type InAs wafer, the most intense semiconductor emitter to date. Excitation wavelength studies showed that the emission was due to absorption in strained undoped GaAs, and corresponds to a two order-of-magnitude enhancement. Moreover, it was found that multilayer QDs emit more strongly compared with a single layer QD sample. At present, we ascribe the intense radiation to huge strain fields at the InAs/GaAs interface.

Estacio, Elmer; Pham, Minh Hong; Takatori, Satoru; Cadatal-Raduban, Marilou; Nakazato, Tomoharu; Shimizu, Toshihiko; Sarukura, Nobuhiko [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Somintac, Armando; Defensor, Michael; Awitan, Fritz Christian B.; Jaculbia, Rafael B.; Salvador, Arnel [National Institute of Physics, University of the Philippines, Diliman, Quezon City 1101 (Philippines); Garcia, Alipio [Department of Physical Sciences, University of the Philippines, Baguio City 2600 (Philippines)

2009-06-08T23:59:59.000Z

334

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

SciTech Connect

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

Reshina, I. I.; Ivanov, S. V.; Toropov, A. A. [Ioffe Physical Technical Institute of RAS, Polytechnicheskaya 26, 194021 St. Petersburg (Russian Federation)

2013-12-04T23:59:59.000Z

335

Comparative electron paramagnetic resonance investigation of reduced graphene oxide and carbon nanotubes with different chemical functionalities for quantum dot attachment  

SciTech Connect

Electron paramagnetic resonance (EPR) spectroscopy has been applied to different chemically treated reduced graphene oxide (rGO) and multiwalled carbon nanotubes (CNTs). A narrow EPR signal is visible at g?=?2.0029 in both GO and CNT-Oxide from carbon-related dangling bonds. EPR signals became broader and of lower intensity after oxygen-containing functionalities were reduced and partially transformed into thiol groups to obtain thiol-functionalized reduced GO (TrGO) and thiol-functionalized CNT (CNT-SH), respectively. Additionally, EPR investigation of CdSe quantum dot-TrGO hybrid material reveals complete quenching of the TrGO EPR signal due to direct chemical attachment and electronic coupling. Our work confirms that EPR is a suitable tool to detect spin density changes in different functionalized nanocarbon materials and can contribute to improved understanding of electronic coupling effects in nanocarbon-nanoparticle hybrid nano-composites promising for various electronic and optoelectronic applications.

Pham, Chuyen V.; Krueger, Michael, E-mail: michael.krueger@fmf.uni-freiburg.de, E-mail: emre.erdem@physchem.uni-freiburg.de; Eck, Michael [Freiburg Materials Research Center (FMF), University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg (Germany); Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg (Germany); Weber, Stefan; Erdem, Emre, E-mail: michael.krueger@fmf.uni-freiburg.de, E-mail: emre.erdem@physchem.uni-freiburg.de [Institute of Physical Chemistry, University of Freiburg, Albertstr. 21, 79104 Freiburg (Germany)

2014-03-31T23:59:59.000Z

336

Controllable Organization of Quantum Dots into Mesoscale Wires and Cables via Interfacial Block Copolymer Self-Assembly  

Science Journals Connector (OSTI)

Controllable Organization of Quantum Dots into Mesoscale Wires and Cables via Interfacial Block Copolymer Self-Assembly ... Figure 2b,c shows higher magnification AFM images of interesting features within the branched cable network, including a typical branch point (b) and a QD/polymer ring incorporated into the cable (c). ... It was noted that several of the LB films containing ring/cable structures also contained small planar aggregates along the length of the cables where an elevated rim was present at the edge of a relatively flat surface, similar to a continent as described by Devereaux et al.26 It appears that these flat surfaces tend to rupture by formation of a single central hole in a secondary dewetting process, followed by the radial growth of the hole. ...

Robert B. Cheyne; Matthew G. Moffitt

2007-02-23T23:59:59.000Z

337

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

E-Print Network (OSTI)

ca qu T nte pu ef pt pro si sc st em l n an d ith r ity along the vertical direction. Due to such strong confine- PHYSICAL REVIEW B, VOLUME 63, 045317atoms. The number of electrons in a quantum dot N can be controlled experimentally, allowing..., the total energy of a 3D spherical har- monic oscillator is Enrlm5S 2nr1l1 3 2 Dv’5S N1 3 2 Dv’ , ~40! where nr50,1,2,3, . . . , and N52nr1l . We use the desig- nation (nr ,l) to denote the energy level with the radial quan- tum numbers nr and the orbital...

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

2001-01-09T23:59:59.000Z

338

Object-based local dimming for LCD systems with LED BLUs  

Science Journals Connector (OSTI)

An LED-based BLU architecture has enabled local dimming, which can produce higher power saving than global dimming in LCD-based devices. However, existing local dimming techniques have not considered human visual system-awareness much. In this paper, ... Keywords: backlight dimming, fidelity, led blu-based lcd., object-based dimming, power

Aldhino Anggorosesar; Young-Jin Kim

2011-08-01T23:59:59.000Z

339

Exciton-exciton and exciton-phonon interactions in an interfacial GaAs quantum dot ensemble  

Science Journals Connector (OSTI)

Using optical two-dimensional Fourier transform spectroscopy, we report temperature- and excitation-density-dependent measurements of the homogeneous linewidth of the exciton ground-state transition in a single layer of interfacial GaAs quantum dots (QDs). We show that the homogeneous linewidth increases nonlinearly with temperature from 6 to 50 K and that the thermal broadening is well described by an activation term and offset. The absence of a phonon-activation peak in the two-dimensional spectra reveals that elastic scattering of excitons with acoustic phonons via virtual transitions between the ground and excited states significantly contributes to the thermal broadening. We find that the combination of increasing virtual activation energy and exciton-phonon coupling strength with decreasing QD size results in greater thermal broadening for excitons localized in smaller QDs. The homogeneous linewidth also exhibits a strong excitation-density dependence and is shown to increase linearly as the photon density increases from 2×1011 to 1×1012 photons pulse-1 cm-2 at 6 K. This trend is attributed to strong coupling of excitons within the same QD and is independent of the quantum-well exciton population density.

G. Moody; M. E. Siemens; A. D. Bristow; X. Dai; D. Karaiskaj; A. S. Bracker; D. Gammon; S. T. Cundiff

2011-03-23T23:59:59.000Z

340

Regular and irregular dynamics of spin polarized wavepackets in a mesoscopic quantum dot at the edge of topological insulator  

E-Print Network (OSTI)

The dynamics of spin-polarized wavepackets driven by periodic electric field is considered for the electrons is in a mesoscopic quantum dot formed at the edge of two-dimensional HgTe/CdTe topological insulator representing a new class of materials with Weyl massless energy spectra, where the motion of carriers is less sensitive to disorder and impurity potentials. It is found that the interplay of strongly coupled spin and charge degrees of freedom creates the regimes of both regular and irregular dynamics with certain universal properties manifested for both free and driven evolution, in the clean limit and in the presence of the moderate disorder. The weak disorder influence is predicted to be overcome by periodic driving while the moderate disorder induces the in-plane spin relaxation, leading to possibility of establishing novel types of driven evolution in nanostructures formed in the topological insulators. The dynamical properties of regular and chaotic behavior of charge and spin in these structures may be of interest for future progress in both quantum nonlinear dynamics on the nanoscale and in the applied nanoscience such as spintronics and nanoelectronics.

D. V. Khomitsky; A. A. Chubanov; A. A. Konakov

2014-08-07T23:59:59.000Z

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341

Fluorescence enhancement of CdTe MPA-capped quantum dots by glutathione for hydrogen peroxide determination  

Science Journals Connector (OSTI)

Abstract The manipulation of the surface chemistry of semiconductor nanocrystals has been exploited to implement distinct sensing strategies in many analytical applications. In this work, reduced glutathione (GSH) was added at reaction time, as an electron-donor ligand, to markedly increase the quantum yield and the emission efficiency of MPA-capped CdTe quantum dots. The developed approach was employed in the implementation of an automated flow methodology for hydrogen peroxide determination, as this can oxidize GSH preventing its surface passivating effect and producing a manifest fluorescence quenching. After optimization, linear working calibration curve for hydrogen peroxide concentrations between 0.0025% and 0.040% were obtained (n=6), with a correlation coef?cient of 0.9975. The detection limit was approximately 0.0012%. The developed approach was employed in the determination of H2O2 in contact lens preservation solutions and the obtained results complied with those furnished by the reference method, with relative deviations comprised between ?1.18 and 4.81%.

S. Sofia M. Rodrigues; David S.M. Ribeiro; L. Molina-Garcia; A. Ruiz Medina; João A.V. Prior; João L.M. Santos

2014-01-01T23:59:59.000Z

342

Infrared spectroscopy of lattice vibrations in ZnTe/CdTe superlattices with quantum dots on the GaAs substrate with the ZnTe buffer layer  

SciTech Connect

The results of the analysis of the infrared lattice reflectance spectra of multiperiod ZnTe/CdTe superlattices with CdTe quantum dots are reported. The samples are grown by molecular beam epitaxy on the GaAs substrate with the ZnTe buffer layer. Due to the large number of periods of the superlattices, it is possible to observe CdTe-like vibration modes in the quantum dots, i.e., the dislocation-free stressed islands formed during the growth due to relaxation of elastic stresses between the ZnTe and CdTe layers are markedly different in their lattice parameters. From the frequency shifts of the CdTe- and ZnTe-like vibration modes with respect to the corresponding modes in the unstressed materials, it is possible to estimate the level of elastic stresses.

Kozyrev, S. P. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)], E-mail: skozyrev@sci.lebedev.ru

2009-03-15T23:59:59.000Z

343

Green and Orange CdTe Quantum Dots as Effective pH-Sensitive Fluorescent Probes for Dual Simultaneous and Independent Detection of Viruses  

Science Journals Connector (OSTI)

Green and Orange CdTe Quantum Dots as Effective pH-Sensitive Fluorescent Probes for Dual Simultaneous and Independent Detection of Viruses ... 26 The F0F1-ATP synthase is a nanoscale rotary biological motor. ... On the basis of this primary model, more than three different kinds of QDs could be mixed together to construct multicolor QD biosensors, which may be a feasible method to optical encoding detection of various viruses in the future. ...

Zhengtao Deng; Yun Zhang; Jiachang Yue; Fangqiong Tang; Qun Wei

2007-09-21T23:59:59.000Z

344

Direct and indirect capture of carriers into the lasing ground state and the light-current characteristic of quantum dot lasers  

SciTech Connect

We calculate the light-current characteristic (LCC) of a quantum dot (QD) laser under the conditions of both direct and indirect capture of carriers from the optical confinement layer into the lasing ground state in QDs. We show that direct capture is a dominant process determining the ground-state LCC. Only when direct capture is slow, the role of indirect capture (capture into the QD excited state and subsequent intradot relaxation to the ground state) becomes important.

Wu, Yuchang, E-mail: yuchangw@vt.edu; Asryan, Levon V., E-mail: asryan@vt.edu [Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (United States)

2014-03-14T23:59:59.000Z

345

Optical Stark Effect and Dressed Exciton States in a Mn-Doped CdTe Quantum Dot C. Le Gall,1  

E-Print Network (OSTI)

Optical Stark Effect and Dressed Exciton States in a Mn-Doped CdTe Quantum Dot C. Le Gall,1 A spin in a CdTe QD, like the strain- induced magnetic anisotropy or hyperfine coupling to the nuclei in this study is grown on a ZnTe substrate and contains CdTe QDs. A 6.5 monolayer thick CdTe layer is deposited

Boyer, Edmond

346

Theory of optical properties of II-VI semiconductor quantum dots containing a single magnetic ion in a strong magnetic field  

Science Journals Connector (OSTI)

We present a microscopic theory of the magnetic field dependence of the optical properties of II–VI semiconductor quantum dots containing a single magnetic (Mn) impurity. The single-particle electron and heavy-hole states are described exactly by two-dimensional harmonic oscillators in a magnetic field, the Mn ion is treated as a spin of an isoelectronic impurity, and the quantum dot anisotropy is included perturbatively. The electron-hole direct, short-, and long-range exchange electron-hole Coulomb interactions, as well as the short-range spin-spin contact exchange interaction of the electron and the hole with the magnetic impurity is included. The electron-hole-Mn states are expanded in a finite number of configurations controlled by the number of confined electronic quantum dot shells and the full interacting Hamiltonian is diagonalized numerically in this basis. The absorption and emission spectrum is predicted as a function of photon energy, magnetic field, number of confined shells, and anisotropy. It is shown that the magnetic-field-induced enhancement of the exchange interaction of the Mn spin with the exciton is largely canceled by increased electron-hole Coulomb interactions. The predicted weak magnetic field dependence of the spacing of emission lines agrees well with the results of the spin model at low magnetic fields but differs at higher magnetic fields. Correlations in the exciton-Mn complex are predicted to determine absorption spectra.

Anna H. Trojnar; Marek Korkusi?ski; Marek Potemski; Pawel Hawrylak

2012-04-06T23:59:59.000Z

347

Raman E{sub 1} and E{sub 1} + {delta}{sub 1} resonances in a system of unstrained germanium quantum dots  

SciTech Connect

The positions and shapes of the Raman E{sub 1} and E{sub 1} + {delta}{sub 1} resonances of optical phonons are studied as functions of the size of unstrained germanium quantum dots. The quantum dots are grown by molecular-beam epitaxy in GaAs/ZnSe/Ge/ZnSe structures on GaAs(111) wafers. The positions of the E{sub 1} and E{sub 1} + {delta}{sub 1} resonances are found to shift by at most 0.3 eV. This shift is shown to be well described in terms of a cylindrical model using the quantization of the spectrum of bulk electron-hole states in germanium that form an exciton in a two-dimensional critical point. The fact that the peaks of the E{sub 1} and E{sub 1} + {delta}{sub 1} resonances appear separately has been detected for the first time, and it is related to the transformation of the interband density of states into a delta function because of spectrum quantization. An increase in the resonance amplitudes in quantum dots as compared to the bulk case is related to the degeneracy multiplicity of the exciton state in the (111) direction.

Talochkin, A. B., E-mail: tal@thermo.isp.nsc.ru; Teys, S. A.; Suprun, S. P. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Division (Russian Federation)

2006-05-15T23:59:59.000Z

348

A urea electrochemical sensor based on molecularly imprinted chitosan film doping with CdS quantum dots  

Science Journals Connector (OSTI)

An improved imprinted film-based electrochemical sensor for urea recognition was developed using CdS quantum dots (QDs) doped chitosan as the functional matrix. The microstructure and composition of the imprinted films depicted by scanning electron microscopy (SEM), attenuated total reflection infrared (ATR–IR), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS) indicated the fabricated feasibility of the nanoparticle doped films via in situ electrodeposition. Differential pulse voltammetric responses under the optimal fabrication conditions showed that the sensitivity of CdS QDs–MIP (molecularly imprinted polymer) electrochemical sensor was enhanced from the favorable electron transfer and magnified surface area of CdS \\{QDs\\} with a short adsorption equilibrium time (7 min), wide linear range (5.0 × 10?12 to 4.0 × 10?10 M and 5.0 × 10?10 to 7.0 × 10?8 M), and low detection limit (1.0 × 10?12 M). Meanwhile, the fabricated sensor showed excellent specific recognition to template molecule among the structural similarities and coexistence substances. Furthermore, the proposed sensor was applied to determine the urea in human blood serum samples based on its good reproducibility and stability, and the acceptable recovery implied its feasibility for practical application.

Hui-Ting Lian; Bin Liu; Yan-Ping Chen; Xiang-Ying Sun

2012-01-01T23:59:59.000Z

349

Distinct expression profiles of stress defense and DNA repair genes in Daphnia pulex exposed to cadmium, zinc, and quantum dots  

Science Journals Connector (OSTI)

Abstract The ever-increasing production and use of nanocrystaline semiconductors (Quantum dots; QDs) will inevitably result in increased appearance of these nanomaterials in the aquatic environment. However, the behavior and potential toxicity of heavy metal constituted nanoparticulates in aquatic invertebrates is largely unknown, especially with regard to molecular responses. The freshwater crustacean Daphnia pulex is a well-suited toxicological and ecological model to study molecular responses to environmental stressors. In this study, D. pulex were exposed for 48 h to sublethal doses of \\{QDs\\} (25% and 50% of LC50) with differing spectral properties (CdTe and CdSe/ZnS QDs) and Cd and Zn salts. Our data suggest that acute exposure to both CdSO4 and Cd-based \\{QDs\\} leads to Cd uptake in vivo, which was biologically supported by the observation of increased expression of metallothionein (MT-1). Furthermore, Cd, Zn, and CdSe/ZnS \\{QDs\\} induced different patterns of gene expression regarding stress defense and DNA repair, which furthers our knowledge regarding which response pathways are affected by nanoparticulate forms of metals versus ionic forms in aquatic crustaceans.

Song Tang; Yonggan Wu; Caitlin N. Ryan; Shuangying Yu; Guangqiu Qin; Donn S. Edwards; Gregory D. Mayer

2015-01-01T23:59:59.000Z

350

Cadmium sulfate and CdTe-quantum dots alter DNA repair in zebrafish (Danio rerio) liver cells  

SciTech Connect

Increasing use of quantum dots (QDs) makes it necessary to evaluate their toxicological impacts on aquatic organisms, since their contamination of surface water is inevitable. This study compares the genotoxic effects of ionic Cd versus CdTe nanocrystals in zebrafish hepatocytes. After 24 h of CdSO{sub 4} or CdTe QD exposure, zebrafish liver (ZFL) cells showed a decreased number of viable cells, an accumulation of Cd, an increased formation of reactive oxygen species (ROS), and an induction of DNA strand breaks. Measured levels of stress defense and DNA repair genes were elevated in both cases. However, removal of bulky DNA adducts by nucleotide excision repair (NER) was inhibited with CdSO{sub 4} but not with CdTe QDs. The adverse effects caused by acute exposure of CdTe QDs might be mediated through differing mechanisms than those resulting from ionic cadmium toxicity, and studying the effects of metallic components may be not enough to explain QD toxicities in aquatic organisms. - Highlights: • Both CdSO{sub 4} and CdTe QDs lead to cell death and Cd accumulation. • Both CdSO{sub 4} and CdTe QDs induce cellular ROS generation and DNA strand breaks. • Both CdSO{sub 4} and CdTe QDs induce the expressions of stress defense and DNA repair genes. • NER repair capacity was inhibited with CdSO{sub 4} but not with CdTe QDs.

Tang, Song; Cai, Qingsong [The Institute of Environmental and Human Health, Texas Tech University, Lubbock, TX 79416 (United States); Chibli, Hicham [Department of Biomedical Engineering, McGill University, Montréal, QC H3A 2B4 (Canada); Allagadda, Vinay [The Institute of Environmental and Human Health, Texas Tech University, Lubbock, TX 79416 (United States); Nadeau, Jay L. [Department of Biomedical Engineering, McGill University, Montréal, QC H3A 2B4 (Canada); Mayer, Gregory D., E-mail: greg.mayer@ttu.edu [The Institute of Environmental and Human Health, Texas Tech University, Lubbock, TX 79416 (United States)

2013-10-15T23:59:59.000Z

351

Room-temperature optical absorption in the InAs/GaAs quantum-dot superlattice under an electric field  

SciTech Connect

Electroluminescence and absorption spectra of a ten-layer InAs/GaAs quantum dot (QD) superlattice built in a two-section laser with sections of equal length is experimentally studied at room temperature. The thickness of the GaAs spacer layer between InAs QD layers, determined by transmission electron microscopy, is {approx}6 nm. In contrast to tunnel-coupled QDs, QD superlattices amplify the optical polarization intensity and waveguide absorption of the TM mode in comparison with the TE mode. It is found that variations in the multimodal periodic spectrum of differential absorption of the QD superlattice structure are strongly linearly dependent on the applied electric field. Differential absorption spectra exhibit the Wannier-Stark effect in the InAs/GaAs QD superlattice, in which, in the presence of an external electric field, coupling of wave functions of miniband electron states is suppressed and a series of discrete levels called the Wannier-Stark ladder states are formed.

Sobolev, M. M., E-mail: m.sobolev@mail.ioffe.ru; Gadzhiev, I. M.; Bakshaev, I. O.; Nevedomskii, V. N.; Buyalo, M. S.; Zadiranov, Yu. M.; Portnoi, E. L. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2011-08-15T23:59:59.000Z

352

Colloidal Quantum Dot Light-Emitting Diodes Employing Phosphorescent Small Organic Molecules as Efficient Exciton  

E-Print Network (OSTI)

engineer, the potential energy transfer pumping scheme. Only Zhang et al. reported an enhancement enhancement factor in the external quantum efficiency over the conventional QLED structure, in which energy as Efficient Exciton Harvesters Evren Mutlugun,,,§, Burak Guzelturk,,§, Agus Putu Abiyasa,§, Yuan Gao,§ Xiao

Demir, Hilmi Volkan

353

Impact of stress relaxation in GaAsSb cladding layers on quantum dot creation in InAs/GaAsSb structures grown on GaAs (001)  

SciTech Connect

We describe InAs quantum dot creation in InAs/GaAsSb barrier structures grown on GaAs (001) wafers by molecular beam epitaxy. The structures consist of 20-nm-thick GaAsSb barrier layers with Sb content of 8%, 13%, 15%, 16%, and 37% enclosing 2 monolayers of self-assembled InAs quantum dots. Transmission electron microscopy and X-ray diffraction results indicate the onset of relaxation of the GaAsSb layers at around 15% Sb content with intersected 60° dislocation semi-loops, and edge segments created within the volume of the epitaxial structures. 38% relaxation of initial elastic stress is seen for 37% Sb content, accompanied by the creation of a dense net of dislocations. The degradation of In surface migration by these dislocation trenches is so severe that quantum dot formation is completely suppressed. The results highlight the importance of understanding defect formation during stress relaxation for quantum dot structures particularly those with larger numbers of InAs quantum-dot layers, such as those proposed for realizing an intermediate band material.

Bremner, S. P. [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052 (Australia)] [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052 (Australia); Ban, K.-Y.; Faleev, N. N.; Honsberg, C. B. [School of Electrical, Computer and Energy Engineering, Ira A. Fulton Schools of Engineering, Solar Power Lab, Arizona State University, Tempe, Arizona 85287 (United States)] [School of Electrical, Computer and Energy Engineering, Ira A. Fulton Schools of Engineering, Solar Power Lab, Arizona State University, Tempe, Arizona 85287 (United States); Smith, D. J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)] [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)

2013-09-14T23:59:59.000Z

354

Theoretical and Experimental Examination of the Intermediate-Band Concept for Strain-Balanced (In,Ga)As/Ga(As,P) Quantum Dot Solar Cells  

SciTech Connect

The intermediate-band solar cell (IBSC) concept has been recently proposed to enhance the current gain from the solar spectrum while maintaining a large open-circuit voltage. Its main idea is to introduce a partially occupied intermediate band (IB) between the valence band (VB) and conduction band (CB) of the semiconductor absorber, thereby increasing the photocurrent by the additional VB {yields} IB and IB {yields} CB absorptions. The confined electron levels of self-assembled quantum dots (QDs) were proposed as potential candidates for the implementation of such an IB. Here we report experimental and theoretical investigations on In{sub y}Ga{sub 1-y}As dots in a GaAs{sub 1-x}P{sub x} matrix, examining its suitability for acting as IBSCs. The system has the advantage of allowing strain symmetrization within the structure, thus enabling the growth of a large number of defect-free QD layers, despite the significant size mismatch between the dot material and the surrounding matrix. We examine the various conditions related to the optimum functionality of the IBSC, in particular those connected to the optical and electronic properties of the system. We find that the intensity of absorption between QD-confined electron states and host CB is weak because of their localized-to-delocalized character. Regarding the position of the IB within the matrix band gap, we find that, whereas strain symmetrization can indeed permit growth of multiple dot layers, the current repertoire of GaAs{sub 1-x}P{sub x} barrier materials, as well as In{sub y}Ga{sub 1-y} As dot materials, does not satisfy the ideal energetic locations for the IB. We conclude that other QD systems must be considered for QD-IBSC implementations.

Popescu, V.; Bester, G.; Hanna, M. C.; Norman, A. G.; Zunger, A.

2008-11-01T23:59:59.000Z

355

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

SciTech Connect

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.

Mary?ski, A.; S?k, G.; Musia?, A.; Andrzejewski, J.; Misiewicz, J. [Institute of Physics, Wroc?aw University of Technology, Wybrze?e Wyspia?skiego 27, 50-370 Wroc?aw (Poland)] [Institute of Physics, Wroc?aw University of Technology, Wybrze?e Wyspia?skiego 27, 50-370 Wroc?aw (Poland); Gilfert, C.; Reithmaier, J. P. [Technische Physik, Institute of Nanostructure Technology and Analytics, CINSaT, University of Kassel, Heinrich Plett-Str. 40, D-34132 Kassel (Germany)] [Technische Physik, Institute of Nanostructure Technology and Analytics, CINSaT, University of Kassel, Heinrich Plett-Str. 40, D-34132 Kassel (Germany); Capua, A.; Karni, O.; Gready, D.; Eisenstein, G. [Department of Electrical Engineering, Technion, Haifa 32000 (Israel)] [Department of Electrical Engineering, Technion, Haifa 32000 (Israel); Atiya, G.; Kaplan, W. D. [Department of Materials Science and Engineering, Technion, Haifa 32000 (Israel)] [Department of Materials Science and Engineering, Technion, Haifa 32000 (Israel); Kölling, S. [Fraunhofer Institute for Photonic Microsystems, Center for Nanoelectronic Technologies, Königsbrücker Straße 180, D-01099 Dresden (Germany)] [Fraunhofer Institute for Photonic Microsystems, Center for Nanoelectronic Technologies, Königsbrücker Straße 180, D-01099 Dresden (Germany)

2013-09-07T23:59:59.000Z

356

Photoluminescence properties and crystallization of silicon quantum dots in hydrogenated amorphous Si-rich silicon carbide films  

SciTech Connect

Silicon quantum dots (QDs) embedded in hydrogenated amorphous Si-rich silicon carbide (?-SiC:H) thin films were realized by plasma-enhanced chemical vapor deposition process and post-annealing. Fluorescence spectroscopy was used to characterize the room-temperature photoluminescence properties. X-ray photoelectron spectroscopy was used to analyze the element compositions and bonding configurations. Ultraviolet visible spectroscopy, Raman scattering, and high-resolution transmission electron microscopy were used to display the microstructural properties. Photoluminescence measurements reveal that there are six emission sub-bands, which behave in different ways. The peak wavelengths of sub-bands P1, P2, P3, and P6 are pinned at about 425.0, 437.3, 465.0, and 591.0?nm, respectively. Other two sub-bands, P4 is red-shifted from 494.6 to 512.4?nm and P5 from 570.2 to 587.8?nm with temperature increasing from 600 to 900?°C. But then are both blue-shifted, P4 to 500.2?nm and P5 to 573.8?nm from 900 to 1200?°C. The X-ray photoelectron spectroscopy analysis shows that the samples are in Si-rich nature, Si-O and Si-N bonds consumed some silicon atoms. The structure characterization displays that a separation between silicon phase and SiC phase happened; amorphous and crystalline silicon QDs synthesized with increasing the annealing temperature. P1, P2, P3, and P6 sub-bands are explained in terms of defect-related emission, while P4 and P5 sub-bands are explained in terms of quantum confinement effect. A correlation between the peak wavelength shift, as well as the integral intensity of the spectrum and crystallization of silicon QDs is supposed. These results help clarify the probable luminescence mechanisms and provide the possibility to optimize the optical properties of silicon QDs in Si-rich ?-SiC: H materials.

Wen, Guozhi [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); School of Electronic and Electrical Engineering, Wuhan Polytechnic University, Wuhan, Hubei 430023 (China); Zeng, Xiangbin, E-mail: eexbzeng@mail.hust.edu.cn; Wen, Xixin; Liao, Wugang [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

2014-04-28T23:59:59.000Z

357

Power spectra and auto correlation analysis of hyperfine-induced long period oscillations in the tunneling current of coupled quantum dots  

SciTech Connect

We outline power spectra and auto correlation analysis performed on temporal oscillations in the tunneling current of coupled vertical quantum dots. The current is monitored for ?2325 s blocks as the magnetic field is stepped through a high bias feature displaying hysteresis and switching: hallmarks of the hyperfine interaction. Quasi-periodic oscillations of ?2 pA amplitude and of ?100 s period are observed in the current inside the hysteretic feature. Compared to the baseline current outside the hysteretic feature the power spectral density is enhanced by up to three orders of magnitude and the auto correlation displays clear long lived oscillations about zero.

Harack, B.; Leary, A.; Coish, W. A.; Hilke, M. [Department of Physics, McGill University, Ernest Rutherford Building, 3600 rue University, Montreal, Quebec H3A 2T8 (Canada); Yu, G.; Gupta, J. A. [National Research Council of Canada, M50, Montreal Road, Ottawa, Ontario K1A 0R6 (Canada); Payette, C.; Austing, D. G. [Department of Physics, McGill University, Ernest Rutherford Building, 3600 rue University, Montreal, Quebec H3A 2T8, Canada and National Research Council of Canada, M50, Montreal Road, Ottawa, Ontario K1A 0R6 (Canada)

2013-12-04T23:59:59.000Z

358

Synthesis of Cysteine-Capped ZnxCd1-xSe Alloyed Quantum Dots Emitting in the Blue?Green Spectral Range  

Science Journals Connector (OSTI)

Department of Chemistry, National Sun Yat-sen University, Taiwan, Faculty of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan, and National Sun Yat-sen University?Kaohsiung Medical University Joint Research Center, Kaohsiung, Taiwan ... Colloidal semiconductor nanocrystals (quantum dots, QDs) are of great interest to fundamental studies and technical applications, such as light-emitting devices,1 fluorescent biosensor,2 and biolabeling,3 as well as solar cells. ... This new class of alloyed QDs has the potential to be applied to solid-state lighting technologies and molecular imaging. ...

Fang-Chen Liu; Tian-Lu Cheng; Chien-Chih Shen; Wei-Lung Tseng; Michael Y. Chiang

2008-01-19T23:59:59.000Z

359

Control of the direction and rate of nuclear spin flips in InAs quantum dots using detuned optical pulse trains  

E-Print Network (OSTI)

We find that detuning an optical pulse train from electronic transitions in quantum dots controls the direction of nuclear spin flips. The optical pulse train generates electron spins that precess about an applied magnetic field, with a spin component parallel to the field only for detuned pulses. This component leads to asymmetry in the nuclear spin flips, providing a way to produce a stable and precise value of the nuclear spin polarization. This effect is observed using two-color, time-resolved Faraday rotation and ellipticity.

S. G. Carter; A. Shabaev; Sophia E. Economou; T. A. Kennedy; A. S. Bracker; T. L. Reinecke

2009-01-16T23:59:59.000Z

360

Quantum-dot light-emitting diodes utilizing CdSe/ZnS nanocrystals embedded in TiO{sub 2} thin film  

SciTech Connect

Quantum-dot (QD) light-emitting diodes (LEDs) are demonstrated on Si wafers by embedding core-shell CdSe/ZnS nanocrystals in TiO{sub 2} thin films via plasma-enhanced metallorganic chemical vapor deposition. The n-TiO{sub 2}/QDs/p-Si LED devices show typical p-n diode current-voltage and efficient electroluminescence characteristics, which are critically affected by the removal of QD surface ligands. The TiO{sub 2}/QDs/Si system we presented can offer promising Si-based optoelectronic and electronic device applications utilizing numerous nanocrystals synthesized by colloidal solution chemistry.

Kang, Seung-Hee; Kumar, Ch. Kiran; Kim, Eui-Tae [Department of Materials Science and Engineering, Chungnam National University, Daeduk Science Town, Daejeon 305-764 (Korea, Republic of); Lee, Zonghoon [National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 72-150, Berkeley, California 94720 (United States); Kim, Kyung-Hyun; Huh, Chul [Electronics and Telecommunications Research Institute, Daeduk Science Town, Daejeon 305-350 (Korea, Republic of)

2008-11-10T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

IR spectroscopy of lattice vibrations and comparative analysis of the ZnTe/CdTe quantum-dot superlattices on the GaAs substrate and with the ZnTe and CdTe buffer layers  

SciTech Connect

A comparative analysis of multiperiod ZnTe/CdTe superlattices with the CdTe quantum dots grown by molecular beam epitaxy on the GaAs substrate with the ZnTe and CdTe buffer layers is carried out. The elastic-stress-induced shifts of eigenfrequencies of the modes of the CdTe- and ZnTe-like vibrations of materials forming similar superlattices but grown on different buffer ZnTe and CdTe layers are compared. The conditions of formation of quantum dots in the ZnTe/CdTe superlattices on the ZnTe and CdTe buffer layers differ radically.

Kozyrev, S. P. [Russian Academy of Sciences, Lebedev Institute of Physics (Russian Federation)], E-mail: skozyrev@sci.lebedev.ru

2009-07-15T23:59:59.000Z

362

The effect of photo-generated carriers on the spectral diffusion of a quantum dot coupled to a photonic crystal cavity  

E-Print Network (OSTI)

We experimentally observe the effect of photo-generated carriers on the spectral diffusion of a quantum dot (QD) coupled to a photonic crystal (PC) cavity. In this system, spectral diffusion arises in part from charge fluctuations on the etched surfaces of the PC. We find that these fluctuations may be suppressed by photo-generated carriers, leading to a reduction of the measured QD linewidth by a factor of ~2 compared to the case where the photo-generated carriers are not present. This result demonstrates a possible means of countering the effects of spectral diffusion in QD-PC cavity systems and thus may be useful for quantum information applications where narrow QD linewidths are desired.

Arka Majumdar; Erik D. Kim; Jelena Vuckovic

2011-07-24T23:59:59.000Z

363

Effects of air annealing on CdS quantum dots thin film grown at room temperature by CBD technique intended for photosensor applications  

SciTech Connect

Graphical abstract: The effect of different intensities (40, 60 100 and 200 W) of light on CdS quantum dots thin film annealed at 350 °C indicating enhancement in (a) photo-current and (b) photosensitivity. Highlights: ? The preparation of CdS nanodot thin film at room temperature by M-CBD technique. ? Study of air annealing on prepared CdS nanodots thin film. ? The optimized annealing temperature for CdS nanodot thin film is 350 °C. ? Modified CdS thin films can be used in photosensor application. -- Abstract: CdS quantum dots thin-films have been deposited onto the glass substrate at room temperature using modified chemical bath deposition technique. The prepared thin films were further annealed in air atmosphere at 150, 250 and 350 °C for 1 h and subsequently characterized by scanning electron microscopy, ultraviolet–visible spectroscopy, electrical resistivity and I–V system. The modifications observed in morphology and opto-electrical properties of the thin films are presented.

Shaikh, Shaheed U.; Desale, Dipalee J.; Siddiqui, Farha Y.; Ghosh, Arindam; Birajadar, Ravikiran B. [Thin film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, M.S. (India)] [Thin film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, M.S. (India); Ghule, Anil V. [Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, M.S. (India)] [Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, M.S. (India); Sharma, Ramphal, E-mail: ramphalsharma@yahoo.com [Thin film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, M.S. (India)] [Thin film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, M.S. (India)

2012-11-15T23:59:59.000Z

364

Tunnel-injection quantum dot deep-ultraviolet light-emitting diodes with polarization-induced doping in III-nitride heterostructures  

SciTech Connect

Efficient semiconductor optical emitters in the deep-ultraviolet spectral window are encountering some of the most deep rooted problems of semiconductor physics. In III-Nitride heterostructures, obtaining short-wavelength photon emission requires the use of wide bandgap high Al composition AlGaN active regions. High conductivity electron (n-) and hole (p-) injection layers of even higher bandgaps are necessary for electrical carrier injection. This approach requires the activation of very deep dopants in very wide bandgap semiconductors, which is a difficult task. In this work, an approach is proposed and experimentally demonstrated to counter the challenges. The active region of the heterostructure light emitting diode uses ultrasmall epitaxially grown GaN quantum dots. Remarkably, the optical emission energy from GaN is pushed from 365?nm (3.4?eV, the bulk bandgap) to below 240?nm (>5.2?eV) because of extreme quantum confinement in the dots. This is possible because of the peculiar bandstructure and band alignments in the GaN/AlN system. This active region design crucially enables two further innovations for efficient carrier injection: Tunnel injection of carriers and polarization-induced p-type doping. The combination of these three advances results in major boosts in electroluminescence in deep-ultraviolet light emitting diodes and lays the groundwork for electrically pumped short-wavelength lasers.

Verma, Jai, E-mail: jverma@nd.edu; Islam, S. M.; Protasenko, Vladimir; Kumar Kandaswamy, Prem; Xing, Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

2014-01-13T23:59:59.000Z

365

The effects of wetting layer on electronic and optical properties of intersubband P-to-S transitions in strained dome-shaped InAs/GaAs quantum dots  

SciTech Connect

The authors report on the impact of wetting layer thickness and quantum dot size on the electronic and optical properties of dome-shaped InAs/GaAs quantum dots (QDs) with strained potential. Two wetting layer thicknesses of 0.5 and 2.0 nm were compared. A strong size dependence of P-to-S transition energy, transition dipole moment, oscillator strength, and linear and third-order nonlinear susceptibilities were concluded. The P-to-S transition dipole moment was shown to be purely in-plane polarization. The linear and nonlinear absorption and dispersion showed a red shift when the wetting layer thickness was increased. Our results revealed that the nonlinear susceptibility is much more sensitive to QD size compared to the linear susceptibility. An interpretation of the results was presented based on the probability density of finding the electron inside the dot and wetting layer. The results are in good agreement with previously reported experimental data.

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

2014-06-15T23:59:59.000Z

366

Classical versus quantum coherence  

Science Journals Connector (OSTI)

...M. Stoneham Classical versus quantum coherence P. T. Greenland Department of Physics...nanostructures| Classical versus quantum coherence. | Quantum dots are structures engineered...2002.1134 Classical versus quantum coherence By P. T. Greenland Department of Physics...

2003-01-01T23:59:59.000Z

367

Statistics of the Coulomb-blockade peak spacings of a silicon quantum dot Center for NanoScience and Sektion Physik, LMU Munchen, Geschwister-Scholl-Platz 1, D-80539 Munchen, Germany  

E-Print Network (OSTI)

Statistics of the Coulomb-blockade peak spacings of a silicon quantum dot F. Simmel Center for NanoScience-Magder* Center for NanoScience and Sektion Physik, LMU Mu¨nchen, Geschwister-Scholl-Platz 1, D-80539 Mu, Cambridge, Massachusetts 02139 J. P. Kotthaus Center for NanoScience and Sektion Physik, LMU Mu

Ludwig-Maximilians-Universität, München

368

Determination of energy scales in few-electron double quantum dots D. Taubert, D. Schuh, W. Wegscheider, and S. Ludwig  

E-Print Network (OSTI)

gate volt- ages to energy differences between the electronic states. The conversion factors devices. We have developed methods to determine the gate voltage to energy conversion accurately in the different regimes of dot-lead tunnel couplings and demonstrate strong variations of the conversion factors

Ludwig-Maximilians-Universität, München

369

Fuzzy multiple goal programming applied to TFT-LCD supplier selection by downstream manufacturers  

Science Journals Connector (OSTI)

In today's highly competitive environment, a good supply chain relationship is essential for a company to survive and to acquire reasonable profit. While a few large companies may be able to vertically integrate from the design stage to the final distribution ... Keywords: Fuzzy analytic hierarchy process, Fuzzy multiple goal programming, Performance, Supplier selection, TFT-LCD

Amy H. I. Lee; He-Yau Kang; Ching-Ter Chang

2009-04-01T23:59:59.000Z

370

Power Minimization in a Backlit TFT-LCD Display by Concurrent Brightness and Contrast Scaling  

E-Print Network (OSTI)

Brightness and Contrast Scaling (CBCS) technique for a cold cathode fluorescent lamp (CCFL) backlit TFT out that the cold cathode fluorescent lamp (CCFL) backlight of an LCD display dominates the energy be used to characterize the optical power emitted from a spot light source, such as a light bulb

Pedram, Massoud

371

Power Minimization in a Backlit TFT-LCD Display by Concurrent Brightness and Contrast Scaling  

E-Print Network (OSTI)

Brightness and Contrast Scaling (CBCS) technique for a cold cathode fluorescent lamp (CCFL) backlit TFT fluorescent lamp (CCFL) backlight of an LCD display dominates the energy consumption of the whole system [1 be used to characterize the optical power emitted from a spot light source, such as a light bulb

Pedram, Massoud

372

Modeling and Optimization of the Turbo-Compression Chiller Systems in the LCD Process  

Science Journals Connector (OSTI)

Modeling and Optimization of the Turbo-Compression Chiller Systems in the LCD Process ... The refrigerator can be divided into two parts, as shown in Figure 2: the mechanical part, consisting of a compressor, an expander or a valve, and two heat exchangers (e.g., an evaporator and a condenser); and the chemical-material part of the refrigerant cycle. ...

Changhyun Jeong; Kiwook Song; Jiyeon Nam; Chonghun Han

2012-01-16T23:59:59.000Z

373

Investigation of pure green-colour emission from inorganic-organic hybrid LEDs based on colloidal CdSe/ZnS quantum dots  

Science Journals Connector (OSTI)

We studied the operation characteristics of inorganic-organic hybrid light emitting devices (HLEDs) that have a green CdSe/ZnS quantum dot (QD) emitting layer (EML) and a 1,3,5-tris(N-phenylbenzimidazol-2-yl)-benzene (TPBi) hole blocking layer (HBL). A series of devices with a different thickness TPBi HBL all showed pure electroluminescence that is consistent with green photoluminescence of colloidal QDs without any colour contamination from organic layers. The best performance, which we attributed to more balanced charge carrier supply to a QD EML and efficient energy transfer from excitions in a TPBi layer to QDs, was observed from the device with a TPBi HBL of 20 nm thickness: the deep green emission with the luminous efficiency of 1.55 cd/A at standard video brightness (200 cd/m²) and the luminance as large as ~1800 cd/m².

Nguyen Huu Tuan; Soonil Lee; Nguyen Nang Dinh

2013-01-01T23:59:59.000Z

374

Assessment of penetration of quantum dots through in vitro and in vivo human skin using the human skin equivalent model and the tape stripping method  

SciTech Connect

Quantum dots (QDs) are rapidly emerging as an important class of nanoparticles (NPs) with potential applications in medicine. However, little is known about penetration of QDs through human skin. This study investigated skin penetration of QDs in both in vivo and in vitro human skin. Using the tape stripping method, this study demonstrates for the first time that QDs can actually penetrate through the stratum corneum (SC) of human skin. Transmission electron microscope (TEM) and energy diverse X-ray (EDX) analysis showed accumulation of QDs in the SC of a human skin equivalent model (HSEM) after dermal exposure to QDs. These findings suggest possible transdermal absorption of QDs after dermal exposure over a relatively long period of time.

Jeong, Sang Hoon; Kim, Jae Hwan; Yi, Sang Min [Laboratory of Cell Signaling and Nanomedicine, Department of Dermatology and Division of Brain Korea 21 Project for Biomedical Science, Korea University College of Medicine, Seoul (Korea, Republic of)] [Laboratory of Cell Signaling and Nanomedicine, Department of Dermatology and Division of Brain Korea 21 Project for Biomedical Science, Korea University College of Medicine, Seoul (Korea, Republic of); Lee, Jung Pyo; Kim, Jin Ho; Sohn, Kyung Hee; Park, Kui Lea [National Institute of Toxicological Research, Seoul (Korea, Republic of)] [National Institute of Toxicological Research, Seoul (Korea, Republic of); Kim, Meyoung-Kon [Department of Biochemistry and Molecular Biology, Korea University College of Medicine, Seoul (Korea, Republic of)] [Department of Biochemistry and Molecular Biology, Korea University College of Medicine, Seoul (Korea, Republic of); Son, Sang Wook, E-mail: skin4u@korea.ac.kr [Laboratory of Cell Signaling and Nanomedicine, Department of Dermatology and Division of Brain Korea 21 Project for Biomedical Science, Korea University College of Medicine, Seoul (Korea, Republic of)

2010-04-09T23:59:59.000Z

375

Electrically Confined Quantum Dot Intersubband Optoelectronic Devices Wei Wu, Dibyendu Dey, Omer G. Memis, Alex Katnelson, and *Hooman Mohseni  

E-Print Network (OSTI)

and optoelectronic devices, lasers and their applications. The Systems area focuses on wireless communication systems 361 Quantum Mechanics For Engineers ELEC 462 Optoelectronic Devices PHYS 302 Intermediate

Mohseni, Hooman

376

Influence of As{sub 4} flux on the growth kinetics, structure, and optical properties of InAs/GaAs quantum dots  

SciTech Connect

We report the effects of variations in As{sub 4} growth flux on the evolution of molecular beam epitaxy grown InAs quantum dots (QDs) and their structures and optical properties. For InAs QDs grown under As-stable conditions, evaluated through photoluminescence and atomic force microscopy (AFM) measurements, it is evident that QD size increases with As{sub 4} pressure along with improvement in size uniformity. Furthermore, transmission electron microscopy measurements for InAs layers of critical thicknesses ({approx}1.7 ML) showed decreasing QD density with increasing As{sub 4} pressure accompanied by a strong reduction in photoluminescence (PL) integral intensity. These show that high As{sub 4} fluxes suppress InAs QD formation while the decreasing PL intensity seems to indicate cluster formation that features nonradiative recombination. AFM measurements show larger and denser QDs for samples grown at higher As{sub 4} pressures. These are explained on the basis of adatom condensation during surface cooling and the influence of As{sub 4} pressure on indium incorporation.

Garcia, A.; Mateo, C. M.; Defensor, M.; Salvador, A.; Hui, H. K.; Boothroyd, C. B.; Philpott, E. [Condensed Matter Physics Laboratory, National Institute of Physics, University of the Philippines, Diliman, 1101 Quezon City (Philippines); Institute of Materials Research and Engineering, 3 Research Link (Singapore)

2007-10-01T23:59:59.000Z

377

Enhancement of current collection in epitaxial lift-off InAs/GaAs quantum dot thin film solar cell and concentrated photovoltaic study  

SciTech Connect

We report the fabrication of a thin film InAs/GaAs quantum dot solar cell (QD cell) by applying epitaxial lift-off (ELO) approach to the GaAs substrate. We confirmed significant current collection enhancement (?0.91?mA/cm{sup 2}) in the ELO-InAs QD cell within the wavelength range of 700?nm–900?nm when compared to the ELO-GaAs control cell. This is almost six times of the sub-GaAs bandgap current collection (?0.16?mA/cm{sup 2}) from the wavelength range of 900?nm and beyond, we also confirmed the ELO induced resonance cavity effect was able to increase the solar cell efficiency by increasing both the short circuit current and open voltage. The electric field intensity of the resonance cavity formed in the ELO film between the Au back reflector and the GaAs front contact layer was analyzed in detail by finite-differential time-domain (FDTD) simulation. We found that the calculated current collection enhancement within the wavelength range of 700?nm–900?nm was strongly influenced by the size and shape of InAs QD. In addition, we performed concentrated light photovoltaic study and analyzed the effect of intermediate states on the open voltage under varied concentrated light intensity for the ELO-InAs QD cell.

Sogabe, Tomah, E-mail: sogabe@mbe.rcast.u-tokyo.ac.jp; Shoji, Yasushi; Tamayo, Efrain; Okada, Yoshitaka [Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8504 (Japan); Mulder, Peter; Schermer, John [Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands)

2014-09-15T23:59:59.000Z

378

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

SciTech Connect

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.

Not Available

2012-01-01T23:59:59.000Z

379

Impact of the non-planar morphology of pre-patterned substrates on the structural and electronic properties of embedded site-controlled InAs quantum dots  

SciTech Connect

We present an experimental and theoretical analysis of the influence of a surface nanopattern on the properties of embedded InAs/GaAs quantum dots (QD). In particular, we analyze QDs grown on nanoimprint lithography (NIL) patterned grooves and investigate the influence of the non-planar surface morphology on the size, shape, strain distribution, and electronic structure of the embedded QDs. We show that the height reduction of InAs QDs during GaAs capping is significantly less pronounced for the QDs grown on the pattern than for the self-assembled QDs. Furthermore, the pattern has a strong impact on the strain and composition profile within the QD. The experimentally observed strain distribution was successfully reproduced with a three-dimensional model assuming an inverse-cone type composition gradient. Moreover, we show that the specific morphology of the QDs grown in the grooves gives rise to an increase of the vertically polarized photoluminescence emission which was explained by employing 8-band k.p calculations. Our findings emphasize that the surface curvature of the pattern not only determines the nucleation sites of the QDs but also has a strong impact on their morphological properties including shape, size, composition profile, and strain distribution. These properties are strongly cross-correlated and determine the electronic and optical characteristics of the QDs.

Hakkarainen, T. V.; Tommila, J.; Schramm, A.; Guina, M. [Optoelectronics Research Centre, Tampere University of Technology, P.O. Box 692, FIN-33101 Tampere (Finland); Luna, E. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

2013-11-07T23:59:59.000Z

380

Self assembly of CdSe/ZnS quantum dots for organic/inorganic light emitting devices for the next generation display technology  

Science Journals Connector (OSTI)

We have investigated the effect of quantum dot (QD) concentrations, spin speed and temperature on the self assembly of CdSe/ZnS QDs on substrate for the optimisation of QDs used in organic light-emitting devices (OLEDs) applications. The atomic force microscopy (AFM) results showed that surface morphology and coverage are varied with different process parameters. There is also a tendency for the formation of aggregates/islands on a smooth substrate that could be caused by spinodal phase separation. The uniform distribution of QDs with controllable density was achieved using the conventional spin-coating method. We fabricated and investigated the effect of CdSe/ZnS QD concentrations on the self-assembly hybrid organic/inorganic light emitting diodes (QD-OLEDs) for the tuning of performance. There was a QD threshold concentration below which there was no emission from the QDs. The estimated QD concentration was around 9 × 1011 cm?2 for the best performance of QD-OLED. The annealing of QD-OLED increased the QD emission about three times. No wavelength shift was observed in the electroluminescence spectra from the QD before and after the annealing of QD-OLEDs. The mechanism of this emission improvement is discussed.

A. Uddin; C.C. Teo

2009-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Use of Quantum Dot Luminescent Probes To Achieve Single-Cell Resolution of Human Oral Bacteria in Biofilms  

Science Journals Connector (OSTI)

...Mattoussi, P. T. Charles, and J. M. Mauro. 2002. Conjugation of luminescent quantum...H. Mattoussi, M. K. Kuno, J. M. Mauro, P. T. Tran, and G. P. Anderson...P. Anderson, H. T. Uyeda, J. M. Mauro, I. L. Medintz, and H. Mattoussi...

Natalia I. Chalmers; Robert J. Palmer Jr.; Laurence Du-Thumm; Richard Sullivan; Wenyuan Shi; Paul E. Kolenbrander

2006-11-17T23:59:59.000Z

382

Proposed Rabi-Kondo Correlated State in a Laser-Driven Semiconductor Quantum Dot B. Sbierski,1,2  

E-Print Network (OSTI)

. Imamoglu1 1 Institute for Quantum Electronics, ETH Zu¨rich, CH-8093 Zu¨rich, Switzerland 2 Dahlem Center Department of Physics, Yale University, 217 Prospect Street, New Haven, Connecticut 06520, USA (Received 28 by weak laser light, the resulting emission spectrum allows for a direct probe of these correlations

von Delft, Jan

383

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

E-Print Network (OSTI)

of Quantum Electronics, ETH Zu¨rich, CH-8093, Zu¨rich, Switzerland 3 Physics Department, Harvard University, 17 Oxford Street, Cambridge, Massachusetts 02138, USA 4 Department of Applied Physics, Stanford- sive picture of unidirectional optical orientation of QD nuclear spins effected by light

Ludwig-Maximilians-Universität, München

384

Thermally oxidized formation of new Ge dots over as-grown Ge dots in the Si capping layer  

SciTech Connect

A Si-capped Ge quantum dot sample was self-assembly grown via Stranski-Krastanov mode in a molecular beam epitaxy system with the Si capping layer deposited at 300 deg. C. After annealing the sample in an oxygen atmosphere at 1000 deg. C, a structure, namely two layers of quantum dots, was formed with the newly formed Ge-rich quantum dots embedded in the oxidized matrix with the position accurately located upon the as-grown quantum dots. It has been found that the formation of such nanostructures strongly depends upon the growth temperature and oxygen atmosphere. A growth mechanism was proposed to explain the formation of the nanostructure based on the Ge diffusion from the as-grown quantum dots, Ge segregation from the growing oxide, and subsequent migration/agglomeration.

Nie Tianxiao [State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433 (China); Materials Engineering, University of Queensland, Brisbane, Queensland QLD 4072 (Australia); Lin Jinhui; Shao Yuanmin; Wu Yueqin; Yang Xinju; Fan Yongliang; Jiang Zuimin [State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433 (China); Chen Zhigang [Materials Engineering, University of Queensland, Brisbane, Queensland QLD 4072 (Australia); Zou Jin [Materials Engineering, University of Queensland, Brisbane, Queensland QLD 4072 (Australia); Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, Queensland QLD 4072 (Australia)

2011-12-01T23:59:59.000Z

385

Microstructural and nonlinear optical properties of silica–titania sol-gel film doped with PbS quantum dots  

Science Journals Connector (OSTI)

Thin silica–titania filmsdoped with different concentration of PbSquantum dots (PbS/oxide molar ratios ranging from 5% to 25%) were fabricated via a sol-gel route. The structuralproperties were studied by x-ray diffraction high-resolution transmission electron microscopy and Rutherford backscattering spectrometry. The PbS crystals were found to have a mean diameter in the range 2.3–3.5 nm with narrow size distribution. The resonant nonlinear optical properties were studied by the nonlinear m-line technique and degenerate four-wave mixing. High negative nonlinear refractive indices (n 2 ) were measured at 1.064 ?m. Different n 2 values were obtained for nanosecond excitation (n 2 =10 ?7 –10 ?8 ? cm 2 /kW ) and for picosecond excitation (n 2 =10 ?9 –10 ?10 ? cm 2 /kW ). The differences can be explained by saturation effects. Measurements at 532 nm showed n 2 values ten times higher than at 1.064 ?m. The response time of the nonlinearity for both wavelengths was below 35 ps.

A. Martucci; J. Fick; J. Schell; G. Battaglin; M. Guglielmi

1999-01-01T23:59:59.000Z

386

Effects of built-in internal fields and Al alloy content on donor binding energy of a hydrogenic impurity in a wurtzite GaN/AlGaN quantum dot  

Science Journals Connector (OSTI)

Built-in internal field induced donor hydrogenic binding energy of an impurity in a wurtzite GaN/AlGaN quantum dot is investigated. The built-in internal electric field has the contribution from spontaneous and piezo-electric polarisation. The computations are carried out with the inclusion of conduction band non-parabolicity through the energy dependent effective mass. It is calculated with a variational approach within the framework of single band effective-mass approximation. A two-parametric trial wave function is employed in order to improve the results. The effects of quantum confinement and the strength of internal electric fields on the donor binding energy are discussed. The results show that the strength of the internal field is of the order MV/cm and it has more influence on the geometrical confinement and the composition of Al alloy content in the GaN/AlxGa1-xN quantum dot. These results are in good agreement with the other investigators.

M. Pattammal; A. John Peter

2014-01-01T23:59:59.000Z

387

High power-saving and fidelity-conserving object-based local dimming for LCD systems with LED-based backlight units  

Science Journals Connector (OSTI)

A local dimming technique which is enabled on LED-based LCD systems is expected to give more power saving than a global one. However, prior local dimming techniques have not considered human visual system-awareness much as done in an advanced global ... Keywords: Backlight dimming, Complexity, Fidelity, Human visual system, LED BLU-based LCD, Object-based local dimming, Power

Aldhino Anggorosesar, Young-Jin Kim

2014-09-01T23:59:59.000Z

388

Comparing Multiple Exciton Generation in Quantum Dots To Impact Ionization in Bulk Semiconductors: Implications for Enhancement of Solar Energy Conversion  

Science Journals Connector (OSTI)

Interband optical excitation of PbSe NCs at low pump intensities, for which less than one exciton is initially generated per NC on average, results in the formation of two or more excitons (carrier multiplication) when pump photon energies are more than 3 times the NC band gap energy. ... on film doping, NC carrier dynamics, and inter-NC interactions is necessary to build solar energy conversion devices that can harvest the multiple carriers produced by MEG. ... A single-threshold quantum-using device in which the excited carriers thermally equilibrate among themselves, but not with the environment, converts solar energy with an efficiency approaching that of an infinite-threshold device. ...

Matthew C. Beard; Aaron G. Midgett; Mark C. Hanna; Joseph M. Luther; Barbara K. Hughes; Arthur J. Nozik

2010-07-26T23:59:59.000Z

389

Strategies to Boost Efficiencies of Quantum Pralay K. Santra  

E-Print Network (OSTI)

for achieving low cost, high efficiency conversion of solar energy to electricity. quantum dot solar cells Efficiencies of Quantum Dot Solar Cells Pralay K. Santra of Chemical Engineering, Stanford University The most is that of the quantum dot which has the potential for achieving low cost, high efficiency conversion of solar energy

Shyamasundar, R.K.

390

Quantum top inside a Bose-Einstein-condensate Josephson junction  

SciTech Connect

We consider an atomic quantum dot confined between two weakly coupled Bose-Einstein condensates, where the dot serves as an additional tunneling channel. It is shown that the thus-embedded atomic quantum dot is a pseudospin subject to an external torque, and therefore equivalent to a quantum top. We demonstrate by numerical analysis of the time-dependent coupled evolution equations that this microscopic quantum top is very sensitive to any deviation from linear oscillatory behavior of the condensates. For sufficiently strong dot-condensate coupling, the atomic quantum dot can induce or modify the tunneling between the macroscopic condensates in the two wells.

Bausmerth, Ingrid; Posazhennikova, Anna [Institut fuer Theoretische Festkoerperphysik, Universitaet Karlsruhe, D-76128 Karlsruhe (Germany); Fischer, Uwe R. [Institut fuer Theoretische Physik, Eberhard-Karls-Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2007-05-15T23:59:59.000Z

391

Effect of spacer layer thickness on multi-stacked InGaAs quantum dots grown on GaAs (311)B substrate for application to intermediate band solar cells  

Science Journals Connector (OSTI)

We have investigated the properties of multi-stacked layers of self-organized In0.4Ga0.6As quantum dots(QDs) on GaAs (311)B grown by molecular beam epitaxy. We found that a high degree of in-plane ordering of QDs structure with a six-fold symmetry was maintained though the growth has been performed at a higher growth rate than the conventional conditions. The dependence of photoluminescence characteristics on spacer layer thickness showed an increasing degree of electronic coupling between the stacked QDs for thinner spacer layers. The external quantum efficiency for an InGaAs/GaAs quantum dotsolar cell (QDSC) with a thin spacer layer thickness increased in the longer wavelength range due to additive contribution from QD layers inserted in the intrinsic region. Furthermore a photocurrent production by 2-step photon absorption has been observed at room temperature for the InGaAs/GaAs QDSC with a spacer layer thickness of 15?nm.

Yasushi Shoji; Kohei Narahara; Hideharu Tanaka; Takashi Kita; Katsuhiro Akimoto; Yoshitaka Okada

2012-01-01T23:59:59.000Z

392

Developing Mixed Films of Immobilized Oligonucleotides and Quantum Dots for the Multiplexed Detection of Nucleic Acid Hybridization Using a Combination of Fluorescence Resonance Energy Transfer and Direct Excitation of Fluorescence  

Science Journals Connector (OSTI)

The probes were selected on the basis of having practical application: seq. 1 is complementary to a portion of the E. coli hemolysin coding gene (hly A);(38) seq. 2 is complementary to a portion of the L. monocytogenes listeriolysin O coding gene (hly A);(39) seq. 3 is complementary to a portion of the S. enterica invasion protein A coding gene (inv A);(40) seq. 4 is complementary to a portion of the E. coli beta-glucuronidase enzyme coding gene (uid A);(41) and seq. 5 is complementary to a portion of the H. sapiens survival of motor neuron protein coding gene (SMN 1). ... We also explore toxicity issues surrounding these materials and speculate about the future uses of quantum dots in a clin. ...

W. Russ Algar; Ulrich J. Krull

2009-12-09T23:59:59.000Z

393

Lateral Quantum Dots for Quantum Information Processing  

E-Print Network (OSTI)

a superconducting Josephson junction device to a microwavequbits constructed from Josephson junction devices, coupled

House, Matthew Gregory

2012-01-01T23:59:59.000Z

394

Lateral Quantum Dots for Quantum Information Processing  

E-Print Network (OSTI)

V T by ?tting. The equivalent resistance R r and capacitanceare the RLC model equivalent resistance R r and capacitanceV T by ?tting. The equivalent resistance R r and capacitance

House, Matthew Gregory

2012-01-01T23:59:59.000Z

395

National Clean Energy Business Plan Competition | Department...  

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

crystal displays (LCD), quantum dots improve energy efficiency by up to 35 percent and in solar panels can increase efficiency up to 45 percent. Learn More NuMat Technologies, Inc....

396

National Clean Energy Business Plan Competition | Department...  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

crystal displays (LCD), quantum dots improve energy efficiency by up to 35 percent and in solar panels can increase efficiency up to 45 percent. Learn More SolidEnergy Systems...

397

Radiator Labs | Department of Energy  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

crystal displays (LCD), quantum dots improve energy efficiency by up to 35 percent and in solar panels can increase efficiency up to 45 percent. Learn More NuMat Technologies, Inc....

398

Decay of electronic excitations in CdS and CdS/ZnS colloidal quantum dots: spectral and kinetic investigations  

Science Journals Connector (OSTI)

Using the spectral methods of induced absorption, luminescence, and photostimulated luminescence flash, we have experimentally investigated processes of decay of electronic excitations in CdS colloidal quantum...

M. S. Smirnov; D. I. Stasel’ko; O. V. Ovchinnikov…

2013-11-01T23:59:59.000Z

399

Dot Density Maps Dot density maps, or dot maps, portray the geographic distribution of discrete phenomena  

E-Print Network (OSTI)

Dot Density Maps Dot density maps, or dot maps, portray the geographic distribution of discrete for representing geographic patterns. Dot density maps are particularly useful for understanding global distribution of the mapped phenomenon and comparing relative densities of different regions on the map. Dot

Klippel, Alexander

400

Work demonstrates that smaller can be better: quantum confinement can lead to increased PV efficiency and could  

E-Print Network (OSTI)

the first all-quantum-dot photovoltaic cell, which was based on lead sulfide and demonstrated reasonable% post consumer waste. NREL Certifies First All-Quantum-Dot Photovoltaic Cell; Demonstrates Stability efficiency and could lead to a doubling of third-generation solar cell efficiencies. Tiny quantum dots

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While these samples are representative of the content of NLEBeta,
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to obtain the most current and comprehensive results.


401

Improving conversion efficiency of CdS quantum dots-sensitized TiO2 nanotube arrays by doping with Zn2+ and decorating with ZnO nanoparticles  

Science Journals Connector (OSTI)

Abstract The Zn-doped TiO2 nanotube arrays (TNTs) decorated with ZnO nanoparticles have been prepared via electrochemical anodization and immersing method. Furthermore, the CdS quantum dots (QDs) were deposited on the prepared Zn-doped TNTs-ZnO thin films by chemical bath deposition (CBD) method to fabricate the CdS QDs-sensitized Zn-doped TNTs-ZnO photoelectrodes. The nanostructure, morphology, optical properties and electrochemical properties of the CdS/Zn-doped TNTs-ZnO photoelectrode with comparison to those of the CdS/TNTs photoelectrodes were investigated. It has been found that the Zn-doped TNTs-ZnO photoelectrodes significantly increased the UV–vis light absorption of the CdS/Zn-doped TNTs-ZnO photoelectrodes and reduced the charge recombination at the surfaces of the CdS/Zn-doped TNTs-ZnO photoelectrodes. As a consequence, when the Zn-doped TNTs-ZnO film was adopted instead of the plain \\{TNTs\\} film, the light-chemical energy conversion efficiency of the CdS/Zn-doped TNTs-ZnO photoelectrode was much improved compared with the CdS/TNTs photoelectrode. A maximum energy conversion efficiency achieved for the CdS/Zn-doped TNTs-ZnO photoelectrode is 3.86%, which is a 17% improvement compared with the maximum energy conversion efficiency of 3.29% achieved for the CdS/TNTs photoelectrodes.

Chong Chen; Lei Wang; Fumin Li; Lanyu Ling

2014-01-01T23:59:59.000Z

402

Excitation resolved color conversion of CdSe/ZnS core/shell quantum dot solids for hybrid white light emitting diodes  

E-Print Network (OSTI)

-volume spectrum-specific applications in- cluding scotopic street lighting, greenhouse lighting, and high-CRI warm light emitting diodes Sedat Nizamoglu and Hilmi Volkan Demira Department of Electrical and Electronics light emitting diodes LEDs , we present spectrally resolved relative quantum efficiency and relative

Demir, Hilmi Volkan

403

Defects and Faults in Quantum Cellular Automata at Nano Scale  

E-Print Network (OSTI)

Defects and Faults in Quantum Cellular Automata at Nano Scale Mehdi Baradaran Tahoori, Mariam considerable research on quantum dot cellular automata (QCA) as a new computing scheme in the nano, quantum dot cellular automata (QCA) not only gives a solution at nano scale, but also it offers a new

404

White light generation by resonant nonradiative energy transfer from epitaxial InGaN/GaN quantum wells to colloidal CdSe/ZnS core/shell quantum dots  

E-Print Network (OSTI)

White light generation by resonant nonradiative energy transfer from epitaxial InGaN/GaN quantum n a l f o r p h y s i c s New Journal of Physics White light generation by resonant nonradiative white-light-generating nonradiative energy transfer (ET) from epitaxial quantum wells (QWs) to colloidal

Demir, Hilmi Volkan

405

Layered architecture for quantum computing  

E-Print Network (OSTI)

We develop a layered quantum computer architecture, which is a systematic framework for tackling the individual challenges of developing a quantum computer while constructing a cohesive device design. We discuss many of the prominent techniques for implementing circuit-model quantum computing and introduce several new methods, with an emphasis on employing surface code quantum error correction. In doing so, we propose a new quantum computer architecture based on optical control of quantum dots. The timescales of physical hardware operations and logical, error-corrected quantum gates differ by several orders of magnitude. By dividing functionality into layers, we can design and analyze subsystems independently, demonstrating the value of our layered architectural approach. Using this concrete hardware platform, we provide resource analysis for executing fault-tolerant quantum algorithms for integer factoring and quantum simulation, finding that the quantum dot architecture we study could solve such problems on the timescale of days.

N. Cody Jones; Rodney Van Meter; Austin G. Fowler; Peter L. McMahon; Jungsang Kim; Thaddeus D. Ladd; Yoshihisa Yamamoto

2012-09-27T23:59:59.000Z

406

DOT | OpenEI  

Open Energy Info (EERE)

50 50 Varnish cache server Browse Upload data GDR 429 Throttled (bot load) Error 429 Throttled (bot load) Throttled (bot load) Guru Meditation: XID: 2142257150 Varnish cache server DOT Dataset Summary Description The data included in this submission is United States Department of Transportation (DOT) data on rates and revenue statistics up to 1995. The data includes state motor-fuel tax receipts, 1919-1995, state motor fuel taxes and related receipts, 1950-1995, and state and federal motor fuel tax rates, 1919-1995 The data is presented in .xlsx format. Source DOT Date Released Unknown Date Updated Unknown Keywords DOT highway motor vehicles rates revenues Data application/vnd.openxmlformats-officedocument.spreadsheetml.sheet icon State motor-fuel tax receipts, 1919-1995 (xlsx, 13.8 KiB)

407

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

SciTech Connect

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

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

2014-02-15T23:59:59.000Z

408

dot5301.PDF  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Transportation Transportation Office of the Secretary of Transportation SUBJECT: Department of Transportation Programs, Policies, and Procedures Affecting American Indians, Alaska Natives, and Tribes ORDER DOT 5301.1 1. PURPOSE. To ensure that programs, policies, and procedures administered by the Department of Transportation (DOT) are responsive to the needs and concerns of American Indians, Alaska Natives, and tribes. 2. REFERENCES. This list is not all-inclusive but is intended to help in the understanding of this DOT Order. a. Executive Orders and Memoranda: (1) Executive Order 12866, Regulatory Planning and Review (58 Federal Register 51739, October 4, 1993), dated September 30, 1993. (2) Executive Order 12875, Enhancing the Intergovernmental Partnership (58 Federal Register 58093, October 28, 1993), dated October 26, 1993.

409

E-Print Network 3.0 - asymmetric inas quantum Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

at Stony Brook, Department of Electrical Engineering and Computer Engineering, Optoelectronics Research Group Collection: Engineering 6 InAs quantum dot infrared photodetectors...

410

Magnetism in strained graphene dots  

Science Journals Connector (OSTI)

We study the magnetization of square and hexagonal graphene dots. It is shown that two classes of hexagonal dots have a second-order phase transition at a critical Hubbard energy U, whose value is similar to the one in bulk graphene, albeit the dots do not have a density of states proportional to the absolute value of the energy, relatively to the Dirac point. Furthermore, we show that a particular class of hexagonal dots, having zigzag edges, does not exhibit zero-energy edge states. We also study the effect of uniaxial strain on the evolution of the magnetization of square dots and find that the overall effect is an enhancement of magnetization with strain. The enhancement can be as large as 100% for strain on the order of 20%. Additionally, stress induces a spatial displacement of the magnetization over the dot, moving it from the zigzag to the armchair edges.

J. Viana-Gomes; Vitor M. Pereira; N. M. R. Peres

2009-12-29T23:59:59.000Z

411

Blinking Statistics of Silicon Quantum Dots  

Science Journals Connector (OSTI)

These results are in contrast to many other publications, which present statistical aging in QD ensembles in accordance with power-law blinking statistics. ... Specifically, with improved time resoln., trajectory durations, and photon statistics, we report a near-exponential falloff of on-time probability distributions at long times. ... Investigation of this falloff behavior as a function of laser wavelength and power demonstrate that these deviations originate from multiexciton dynamics, whose formation probabilities can be very low on a "per laser pulse" basis, but become nearly unity on the time scales of the longest on-times. ...

Benjamin Bruhn; Jan Valenta; Fatemeh Sangghaleh; Jan Linnros

2011-11-22T23:59:59.000Z

412

Ultrafast carrier dynamics in semiconductor quantum dots  

Science Journals Connector (OSTI)

The dynamics of band-edge photoluminescence (PL) in CdS nanocrystals (NC’s) dispersed in a glass matrix are studied with the femtosecond up-conversion technique. The time-resolved PL spectra exhibit several discrete features (three of them are in the NC energy band gap) which are not pronounced in a cw PL spectrum. The initial stage of a PL decay is governed by a depopulation of the lowest extended states due to carrier trapping (localization) on the time scale of 1 ps. The low-energy bands originating from the extended-to-localized state transitions exhibit extremely fast buildup dynamics (rise time is 400–700 fs) which is explained by the preexisting occupation of the localized states. © 1996 The American Physical Society.

V. Klimov; P. Haring Bolivar; H. Kurz

1996-01-15T23:59:59.000Z

413

Quantum Dot Photovoltaics in the Extreme Quantum Confinement Regime  

E-Print Network (OSTI)

, 184 College Street, Toronto, Ontario M5S 3E4, Canada, and Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada P hotovoltaics reaching the earth. One oppor- tunity for further improvement in solution- cast solar cells' efficiency

414

Quantum Dot Light-Emitting Diode with Quantum Dots Inside the Hole Transporting Layers  

E-Print Network (OSTI)

architecture using a noninverted structure with the QDs sandwiched between hole transporting layers (HTLs

Demir, Hilmi Volkan

415

Enhanced EP halftones with hexagonal dot packing  

E-Print Network (OSTI)

Enhanced EP halftones with hexagonal dot packing Tomasz J. Cholewo, Steve Weed, Brian Cooper advantages for electropho- tographic (EP) printing over conventional dot placement on a square grid [1] reported that hexagonal dot packing could have some unique benefits for EP printing. These were

Cholewo, Tomasz

416

Coherence-Preserving Quantum Bits  

Science Journals Connector (OSTI)

Real quantum systems couple to their environment and lose their intrinsic quantum nature through the process known as decoherence. Here we present a method for minimizing decoherence by making it energetically unfavorable. We present a Hamiltonian made up solely of two-body interactions between four two-level systems (qubits) which has a 2-fold degenerate ground state. This degenerate ground state has the property that any decoherence process acting on an individual physical qubit must supply energy from the bath to the system. Quantum information can be encoded into the degeneracy of the ground state and such coherence-preserving qubits will then be robust to local decoherence at low bath temperatures. We show how this quantum information can be universally manipulated and indicate how this approach may be applied to a quantum dot quantum computer.

Dave Bacon; Kenneth R. Brown; K. Birgitta Whaley

2001-11-26T23:59:59.000Z

417

Quantum key distribution system in standard telecommunications fiber using a short wavelength single-photon source  

E-Print Network (OSTI)

A demonstration of the principles of quantum key distribution is performed using a single-photon source in a proof of concept test-bed over a distance of 2 km in standard telecommunications optical fiber. The single-photon source was an optically-pumped quantum dot in a microcavity emitting at a wavelength of 895 nm. Characterization of the quantum key distribution parameters was performed at a range of different optical excitation powers. An investigation of the effect of varying the optical excitation power of the quantum dot microcavity on the quantum bit error rate and cryptographic key exchange rate of the system are presented.

R. J. Collins; P. J. Clarke; V. Fernandez; K. J. Gordon; M. N. Makhonin; J. A. Timpson; A. Tahraoui; M. Hopkinson; A. M. Fox; M. S. Skolnick; G. S. Buller

2010-04-27T23:59:59.000Z

418

Women @ Energy: Dot Harris | Department of Energy  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Dot Harris Dot Harris Women @ Energy: Dot Harris March 15, 2013 - 1:06pm Addthis LaDoris (Dot) Harris is the Director of the Office of Economic Impact and Diversity. LaDoris (Dot) Harris is the Director of the Office of Economic Impact and Diversity. LaDoris (Dot) Harris is the Director of the Office of Economic Impact and Diversity. She was nominated by President Obama and confirmed by the U.S. Senate on March 29, 2012. She has served at some of the world's largest firms including General Electric, ABB Service, and Westinghouse Electric Company. Ms. Harris leads the Department's efforts to ensure minorities and historically underrepresented communities participate fully in Departmental programs. Ms. Harris oversees funding for minority institutions, advocates for small business contracting opportunities, and

419

Radiation effects in Si-Ge quantum size structure (Review)  

SciTech Connect

The article is dedicated to the review and analysis of the effects and processes occurring in Si-Ge quantum size semiconductor structures upon particle irradiation including ion implantation. Comparisons to bulk materials are drawn. The reasons of the enhanced radiation hardness of superlattices and quantum dots are elucidated. Some technological applications of the radiation treatment are reviewed.

Sobolev, N. A., E-mail: sobolev@ua.pt [Universidade de Aveiro, Departamento de Fisica and I3N (Portugal)

2013-02-15T23:59:59.000Z

420

E-Print Network 3.0 - assisted transport quantum Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

Photodetectors With a High Detectivity Zhengmao Ye, Joe C. Campbell, Zhonghui Chen... , Eui-Tae Kim, and Anupam Madhukar Abstract--An InAsAlGaAs quantum-dot infrared photode-...

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Fabrication and characterization of quantum-confined optoelectronic devices based on CdSe nanocrystals  

E-Print Network (OSTI)

Colloidal semiconductor quantum dots (QDs), or nanocrystals (NCs), are the subject of intense research for their novel size dependent optical and electronic properties. Since the development of synthetic methods to produce ...

Woo, Wing-Keung, 1972-

2002-01-01T23:59:59.000Z

422

Investigation of lateral gated quantum devices in Si/SiGe heterostructures  

E-Print Network (OSTI)

Quantum dots in Si/SiGe have long spin decoherence times, due to the low density of nuclear spins and weak coupling between nuclear and electronic spins. Because of this, they are excellent candidates for use as solid state ...

Lai, Andrew P. (Andrew Pan)

2013-01-01T23:59:59.000Z

423

Decoherence control by quantum decoherence itself  

E-Print Network (OSTI)

We propose a general approach of protecting a two-level system against decoherence via quantum engineering of non-classical multiple superpositions of coherent states in a non-Markovian reservoir. The scheme surprisingly only uses the system-environment interaction responsible for the decoherence and projective measurements of the two-level system. We demonstrate the method on the example of an excitonic qubit in self-assembled semiconductor quantum dots coupled to super-Ohmic reservoir of acoustic phonons.

Katarzyna Roszak; Radim Filip; TomᚠNovotný

2014-01-20T23:59:59.000Z

424

High photo-excited carrier multiplication by charged InAs dots in AlAs/GaAs/AlAs resonant tunneling diode  

E-Print Network (OSTI)

We present an approach for the highly sensitive photon detection based on the quantum dots (QDs) operating at temperature of 77K. The detection structure is based on an AlAs/GaAs/AlAs double barrier resonant tunneling diode combined with a layer of self-assembled InAs QDs (QD-RTD). A photon rate of 115 photons per second had induced 10nA photocurrent in this structure, corresponding to the photo-excited carrier multiplication factor of 10^7. This high multiplication factor is achieved by the quantum dot induced memory effect and the resonant tunneling tuning effect of QD-RTD structure.

Wangping Wang; Ying Hou; Dayuan Xiong; Ning Li; Wei Lu

2007-10-15T23:59:59.000Z

425

Graphene-based qubits in quantum communications  

E-Print Network (OSTI)

We explore the potential application of graphene-based qubits in photonic quantum communications. In particular, the valley pair qubit in double quantum dots of gapped graphene is investigated as a quantum memory in the implementation of quantum repeaters. For the application envisioned here, our work extends the recent study of the qubit (Wu et al., arXiv: 1104.0443; Phys. Rev. B 84, 195463 (2011)) to the case where the qubit is placed in a normal magnetic field-free configuration. It develops, for the configuration, a method of qubit manipulation, based on a unique AC electric field-induced, valley-orbit interaction-derived mechanism in gapped graphene. It also studies the optical response of graphene quantum dots in the configuration, in terms of valley excitation with respect to photonic polarization, and illustrates faithful photon \\leftrightarrow valley quantum state transfers. This work suggests the interesting prospect of an all-graphene approach for the solid state components of a quantum network, e.g., quantum computers and quantum memories in communications.

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

2012-04-28T23:59:59.000Z

426

Modulating quantum transport by transient chaos Rui Yang, Liang Huang, Ying-Cheng Lai, and Louis M. Pecora  

E-Print Network (OSTI)

by a symmetric dipolar spin battery J. Appl. Phys. 111, 053708 (2012) Forming delocalized intermediate states-dimensional electron gas (2DEG) and relativistic (graphene3 ) quantum-dot (QD)

Lai, Ying-Cheng

427

UltraDots Inc formely UltraPhotonics | Open Energy Information  

Open Energy Info (EERE)

UltraDots Inc formely UltraPhotonics UltraDots Inc formely UltraPhotonics Jump to: navigation, search Name UltraDots Inc (formely UltraPhotonics ) Place Fremont, California Zip CA 94539 Product Nanotechnology company developing "quantum dot" technology for a range of energy, communications and medical applications. Originally included photovoltaics, but this application seems to no longer be the focus. Coordinates 44.2605°, -88.880509° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":44.2605,"lon":-88.880509,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

428

Persistent spectral-hole-burning spectroscopy of CuCl quantum cubes  

Science Journals Connector (OSTI)

A persistent spectral-hole-burning (PSHB) phenomenon was successfully applied to the precise site-selective spectroscopy of CuCl quantum dots embedded in NaCl crystals. In the PSHB spectra of CuCl quantum dots, a resonantly burned hole and lower-energy satellite holes were observed. These satellite holes are supposed to originate from hole burning of the ground states, which results from site-selective excitation of the corresponding excited states of excitons confined in CuCl quantum dots. Energy relation between the resonantly burned hole and each satellite hole is well explained by the simple concept of a particle in a quantum cube with an infinitely high potential barrier. However, actual quantum dots are considered to be a little deviated from cubes, resulting in the violation of the optical selection rule in quantum cubes. A cubic-shaped quantum-dot model is almost consistent with oscillatory fine structures observed in the Z3 exciton absorption band. Its spectral decomposition into the ground state and the first excited state of excitons was made, and showed that the first excited state is in majority at the higher-energy region of the Z3 exciton absorption band. This result was supported by the photoluminescence spectrum of the Z3 exciton.

Naru Sakakura and Yasuaki Masumoto

1997-08-15T23:59:59.000Z

429

Vibration-enhanced quantum transport  

E-Print Network (OSTI)

In this paper, we study the role of collective vibrational motion in the phenomenon of electronic energy transfer (EET) along a chain of coupled electronic dipoles with varying excitation frequencies. Previous experimental work on EET in conjugated polymer samples has suggested that the common structural framework of the macromolecule introduces correlations in the energy gap fluctuations which cause coherent EET. Inspired by these results, we present a simple model in which a driven nanomechanical resonator mode modulates the excitation energy of coupled quantum dots and find that this can indeed lead to an enhancement in the transport of excitations across the quantum network. Disorder of the on-site energies is a key requirement for this to occur. We also show that in this solid state system phase information is partially retained in the transfer process, as experimentally demonstrated in conjugated polymer samples. Consequently, this mechanism of vibration enhanced quantum transport might find applications in quantum information transfer of qubit states or entanglement.

F. L. Semião; K. Furuya; G. J. Milburn

2009-09-09T23:59:59.000Z

430

Mn/DOT County Road Safety Plans  

E-Print Network (OSTI)

Roads Program !! Minnesota Central Safety Funds !! Foster safety culture among county stakeholders 41 Mn/DOT County Road Safety Plans CTS Annual Research Conference April 27 & 28, 2010 Howard Preston & Objectives !! Project Overview !! Schedule, Participating Counties, Approach !! Safety Emphasis Areas

Minnesota, University of

431

PHYSICAL REVIEW B 83, 075104 (2011) Spatiotemporal evolution of polaronic states in finite quantum systems  

E-Print Network (OSTI)

Laboratory, Los Alamos, New Mexico 87545, USA (Received 11 August 2010; revised manuscript received 17 and polaron transport through finite quantum structures in the framework of the one-dimensional Holstein model a quantum wall or dot is generally accompanied by strong phonon number fluctuations due to phonon emission

Fehske, Holger

432

Multiple Energy Exciton Shelves in Quantum-Dot–DNA Nanobioelectronics  

Science Journals Connector (OSTI)

The DNA molecules joining the QDs form an energetic bridge that provides an efficient conduction pathway for the different energy carriers, capturing the hot electron before it can cool to the bandedge via nonradiative relaxation. ... Interband optical excitation of PbSe NCs at low pump intensities, for which less than one exciton is initially generated per NC on average, results in the formation of two or more excitons (carrier multiplication) when pump photon energies are more than 3 times the NC band gap energy. ...

Samuel M. Goodman; Vivek Singh; Josep Casamada Ribot; Anushree Chatterjee; Prashant Nagpal

2014-10-24T23:59:59.000Z

433

Molecular Imaging: Physics and Bioapplications of Quantum Dots  

E-Print Network (OSTI)

, the Fermi-Dirac statistics defines the occupancy of each state and, in particular, which energy levels the tech- niques used to interface these inorganic materials to the bio- logical world. It concludes numbers of extremely closely spaced electronic energy levels, E, that, in effect, blend together to form

Michalet, Xavier

434

3D Printed Quantum Dot Light-Emitting Diodes  

Science Journals Connector (OSTI)

Developing the ability to 3D print various classes of materials possessing distinct properties could enable the freeform generation of active electronics in unique functional, interwoven architectures. ... Finally, we show that novel architectures that are not easily accessed using standard microfabrication techniques can be constructed, by 3D printing a 2 × 2 × 2 cube of encapsulated LEDs, in which every component of the cube and electronics are 3D printed. ... These include (1) increasing the resolution of the 3D printer such that smaller devices can be printed, (2) improving the performance and yield of the printed devices, and (3) incorporating other classes of nanoscale functional building blocks and devices, including semiconductor, plasmonic, and ferroelectric materials. ...

Yong Lin Kong; Ian A. Tamargo; Hyoungsoo Kim; Blake N. Johnson; Maneesh K. Gupta; Tae-Wook Koh; Huai-An Chin; Daniel A. Steingart; Barry P. Rand; Michael C. McAlpine

2014-10-31T23:59:59.000Z

435

Quantum dot nanoparticle conjugation, characterization, and applications in neuroscience  

E-Print Network (OSTI)

and the Journal of Nanoscience and Nanotechnology and areastrocytes in the Journal of Nanoscience and Nanotechnology,astrocytes. Journal of Nanoscience and Nanotechnology.

Pathak, Smita

2008-01-01T23:59:59.000Z

436

Temperature-Dependent Electron Transport in Quantum Dot Photovoltaics  

E-Print Network (OSTI)

product is what matters for PCE, therefore their values atdevices with more than 1% PCE were Schottky cells [36–38],cell with greater than 15% PCE is reached [42]. The Schottky

Padilla, Derek

2013-01-01T23:59:59.000Z

437

Supramolecular quantum dot-porphyrin assemblies for biological oxygen sensing  

E-Print Network (OSTI)

Generating metabolic profiles of tumors provides a spatiotemporal map of the concentration of key species to assess and quantify tumor growth, metabolism, and response to therapy. Because the tumor microenvironment is ...

Lemon, Christopher M. (Christopher Michael)

2013-01-01T23:59:59.000Z

438

Assembly and characterization of quantum-dot solar cells.  

E-Print Network (OSTI)

??Environmentally clean renewable energy resources such as solar energy have gained significant attention due to a continual increase in worldwide energy demand. A variety of… (more)

Leschkies, Kurtis Siegfried

2009-01-01T23:59:59.000Z

439

Comment on “Level Statistics of Quantum Dots Coupled to Reservoirs”  

Science Journals Connector (OSTI)

A Comment on the Letter by Jürgen König, Yuval Gefen, and Gerd Schön, Phys. Rev. Lett. 81, 4468 (1998).

M. Pascaud and G. Montambaux

1999-08-02T23:59:59.000Z

440

Graphene Quantum Dot-Based Organic Solar Cells  

Science Journals Connector (OSTI)

Current research in organic photovoltaic (OPV) is largely focused on ... they are promising for efficient light harvesting in solar cells. Keeping this in view, we present ... so far for the application of GQDs i...

Vinay Gupta; Tanvi Upreti; Suresh Chand

2014-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

Exploring Competing Kinetic Processes in Quantum Dots Linked...  

NLE Websites -- All DOE Office Websites (Extended Search)

semiconductors, semiconductor surfaces and interfaces, cuprates, porous silicon, optoelectronic device physics). He supervised the Device and Materials Physics Group in the...

442

Study of exciton transfer in dense quantum dot nanocomposites  

E-Print Network (OSTI)

, optoelectronic devices, topological insulators, electrocatalysts, and so on.4­16 In the rich family of 2D structures not only boosts the development of 2D TMD electronic and optoelectronic devices, a Department

Demir, Hilmi Volkan

443

Modeling and fabrication of electrically tunable quantum dot intersubband devices  

E-Print Network (OSTI)

to their excel- lent electrical, optical, and mechanical properties.1 The progress on CNT optoelectronic devices and simulators have been developed to un- derstand the operation of CNT optoelectronic devices.8 It has been

Mohseni, Hooman

444

Thermal Imaging of Single Living Cells Using Semiconductor Quantum Dots  

E-Print Network (OSTI)

Berkeley. Thermoelectric Peltier temperature control unitsPetri dish. Eight small Peltier units (No. 81162, Ferrotec)Petri dish and two large Peltier units (No. 83335, Ferrotec)

Yang, Jui-Ming

2009-01-01T23:59:59.000Z

445

Quantum Dot Tracers for Use in Engineered Geothermal Systems  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

define the subsurface system of fractures and mapping of fluid flow. * limited fracture detection capability * lack of high-temperature monitoring tools and sensors *...

446

Effects of Quantum Dots Adsorption on Algal Photosynthesis  

Science Journals Connector (OSTI)

Department of Physics and Astronomy, Department of Horticulture, Department of Agriculture and Biological Engineering, and Center of Optical Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634 ... Previous spectroscopic and electron microscopic results suggest that small QDs of less than 5 nm in diameter, when aided by light, can enter bacteria possibly by means of oxidative damage to the cell wall and the cell membrane. ... All measurements were made at room temperature, under identical lighting conditions. ...

Sijie Lin; Priyanka Bhattacharya; Nihal C. Rajapakse; David E. Brune; Pu Chun Ke

2009-06-02T23:59:59.000Z

447

Carrier Multiplication in Nanocrystal Quantum Dots and Solar Energy Conversion  

Science Journals Connector (OSTI)

This paper discusses aspects of carrier multiplication (multiexciton generation by single photons) in semiconductor nanocrystals such as its mechanism, competing relaxation channels,...

Klimov, Victor I

448

Towards bulk based preconditioning for quantum dot computations  

E-Print Network (OSTI)

Pseudopotential Electronic Structure Calculations forproblems in electronic structure calculations. BIT, 36(3):1–rst-principles electronic structure calculations which are

2006-01-01T23:59:59.000Z

449

A Quantum Dot Single-Photon Turnstile Device  

Science Journals Connector (OSTI)

...repetition rate of 10 MHz at 50 mK were reported. This device...device can only be operated at ultra-low temperatures (T ? 1...rate of 10-MHz at 50-mK were reported. This device...device can only be operated at ultra-low temperatures (T...

P. Michler; A. Kiraz; C. Becher; W. V. Schoenfeld; P. M. Petroff; Lidong Zhang; E. Hu; A. Imamoglu

2000-12-22T23:59:59.000Z

450

C3Bio.org - Resources: Quantum Dot Lab  

NLE Websites -- All DOE Office Websites (Extended Search)

Mickey Mouse is a... - Select an answer - Mouse Suitcase Chicken Teapot Penguin Please leave this field blank. required Problem: required Attach a screenshot: optional (.jpg,...

451

Ge quantum dots structural peculiarities depending on the preparation conditions  

Science Journals Connector (OSTI)

EXAFS and XANES spectroscopy methods have been applied in a study of the influence of the preparation conditions on the spatial and electronic structure of Ge/Si heterostructures.

Erenburg, S.

2003-08-28T23:59:59.000Z

452

Enhanced normal incidence photocurrent in quantum dot infrared photodetectors  

E-Print Network (OSTI)

, New Mexico 87106 Thomas E. Vandervelde Department of Electrical and Computer Engineering, Tufts for High Technology Materials, ECE Department, University of New Mexico, 1313 Goddard St. SE, Albuquerque, and Sanjay Krishna Center for High Technology Materials, ECE Department, University of New Mexico, 1313

Krishna, Sanjay

453

Spectrally adaptive infrared photodetectors with bias-tunable quantum dots  

E-Print Network (OSTI)

Tyo, and Majeed M. Hayat Department of Electrical and Computer Engineering, University of New Mexico and Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131, Albuquerque, New Mexico 87131 Sunil Raghavan and Sanjay Krishna Center for High Technology Materials

Hayat, Majeed M.

454

Thermal Imaging of Single Living Cells Using Semiconductor Quantum Dots  

E-Print Network (OSTI)

wrapped nanoscaled thermometer for temperature control inA fluorescent molecular thermometer based on the nickel(II)Fluorescent Nanogel Thermometer for Intracellular

Yang, Jui-Ming

2009-01-01T23:59:59.000Z

455

16 - Microcavities and quantum cascade laser structures based on silicon–germanium (SiGe) nanostructures  

Science Journals Connector (OSTI)

Abstract: This chapter discusses two types of Si-based light-emitting devices based on Ge quantum dots in optical microcavities and SiGe quantum cascade (QC) structures. After reviewing various solutions for Si-based light-emitting devices, the chapter describes the method to enhance light emission from Ge dots through embedding them into optical microcavities. It then reviews SiGe quantum cascade laser (QCL) structures on issues of material growth, electroluminescence from SiGe QC structures, n-type SiGe QC structures, and waveguides for SiGe QCLs.

J. Xia; Y. Shiraki; J. Yu

2011-01-01T23:59:59.000Z

456

Quantum Privacy and Quantum Coherence  

Science Journals Connector (OSTI)

We derive a simple relation between a quantum channel's capacity to convey coherent (quantum) information and its usefulness for quantum cryptography.

Benjamin Schumacher and Michael D. Westmoreland

1998-06-22T23:59:59.000Z

457

A hybrid double-dot in silicon  

SciTech Connect

We report electrical measurements of a single arsenic dopant atom in the tunnel barrier of a silicon single-electron transistor (SET). In addition to performing the electrical characterisation of the individual dopants, we study the series electrical transport through the dopant and SET. We measure the bias triangles of this hybrid double-dot and show that we can tune the electrostatic coupling between the two sub-systems. Additionally, we measured SET in which an additional plunger gate allows the reduction of the electron number in the SET down to the few-electron regime where the dot presents well-defined spin configurations. Finally, we discuss the challenges of operating a dopant-dot hybrid system in the few-electron regime.

Gonzalez-Zalba, M. F.; Heiss, D.; Ferguson, A. J. [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge (United Kingdom)

2013-12-04T23:59:59.000Z

458

U.S. DOT Federal Railroad Administration  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

DOT DOT Federal Railroad Administration U.S. Department of Energy Transportation External Coordination Working Group (TEC) July 24-25, 2007 Kansas City, Missouri Evaluation of Shortline Railroads Tasked for the Transportation of Spent Nuclear Fuel Evaluation of Shortline Railroads  Task:  Identify Shortline Railroads Serving Nuclear Power Plants or Involved in the Transportation Link  Establish Contact Information with Railroads Officials  Field Review of each Railroad's Physical and Operational Infrastructure  Qualify each Railroads Present Operational Status Against a Safe Acceptable Standard  Facilitate Upgrades to Meet Safe Acceptable Standards Evaluation of Shortline Railroads

459

Optical phonon modes in InGaN/GaN dot-in-a-wire heterostructures grown by molecular beam epitaxy  

SciTech Connect

We report on the studies of optical phonon modes in nearly defect-free GaN nanowires embedded with intrinsic InGaN quantum dots by using oblique angle transmission infrared spectroscopy. These phonon modes are dependent on the nanowire fill-factor, doping densities of the nanowires, and the presence of InGaN dots. These factors can be applied for potential phonon based photodetectors whose spectral responses can be tailored by varying a combination of these three parameters. The optical anisotropy along the growth (c-) axis of the GaN nanowire contributes to the polarization agility of such potential photodetectors.

Titus, J.; Perera, A. G. U. [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States)] [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States); Nguyen, H. P. T.; Mi, Z. [Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec H3A 2A7 (Canada)] [Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec H3A 2A7 (Canada)

2013-03-25T23:59:59.000Z

460

Navillum Nanotechnologies | Department of Energy  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Navillum Nanotechnologies Navillum Nanotechnologies National Clean Energy Business Plan Competition Navillum Nanotechnologies University of Utah Navillum Nanotechnologies' innovative method for fabricating quantum dots and other types of semiconducting nanocrystals at commercial scale that can both save energy and produce renewable energy. Quantum dots emit light at specific colors when stimulated by light or applied electrical source. Semiconducting nanocrystals can make solar panels up to 45 percent more efficient, which is more than a two-fold increase over existing commercial solar technologies. When used in LCD displays, quantum dots can increase energy efficiency by up to 35 percent over existing display technologies and improve color quality by 50 percent. Adoption of quantum dot-based

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Navillum Nanotechnologies | Department of Energy  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Navillum Nanotechnologies Navillum Nanotechnologies National Clean Energy Business Plan Competition Navillum Nanotechnologies University of Utah Navillum Nanotechnologies' innovative method for fabricating quantum dots and other types of semiconducting nanocrystals at commercial scale that can both save energy and produce renewable energy. Quantum dots emit light at specific colors when stimulated by light or applied electrical source. Semiconducting nanocrystals can make solar panels up to 45 percent more efficient, which is more than a two-fold increase over existing commercial solar technologies. When used in LCD displays, quantum dots can increase energy efficiency by up to 35 percent over existing display technologies and improve color quality by 50 percent. Adoption of quantum dot-based

462

A Powerful Dot Of Solar Energy  

Science Journals Connector (OSTI)

A Powerful Dot Of Solar Energy ... The ongoing supermassive thermo­nuclear explosion that powers the sun emits energy at a mind-boggling rate exceeding 100 trillion trillion watts. ... To meet that challenge, scientists have been searching for ways to make low-cost solar cells—photovoltaic devices that convert light ... ...

MITCH JACOBY

2013-09-23T23:59:59.000Z

463

Enhanced Joule Heating in Umbral Dots  

E-Print Network (OSTI)

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

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

2007-05-08T23:59:59.000Z

464

Mn/DOT's Project Peer Review  

E-Print Network (OSTI)

Mn/DOT's Project Management Peer Review Creating a Project Management Culture 2010 CTS Research and perspectives ·Peer Review Process and Results ·Construction Industry Perspective ·Next Steps ·Q & A #12;Why a Peer Review? Why Project Management? ·Improve project delivery performance ­ on time, on budget (an

Minnesota, University of

465

Quantum Tetrahedra  

E-Print Network (OSTI)

We discuss in details the role of Wigner 6j symbol as the basic building block unifying such different fields as state sum models for quantum geometry, topological quantum field theory, statistical lattice models and quantum computing. The apparent twofold nature of the 6j symbol displayed in quantum field theory and quantum computing -a quantum tetrahedron and a computational gate- is shown to merge together in a unified quantum-computational SU(2)-state sum framework.

Mauro Carfora; Annalisa Marzuoli; Mario Rasetti

2010-01-25T23:59:59.000Z

466

Quantum correlation via quantum coherence  

E-Print Network (OSTI)

Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition--------quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes of quantum coherence. We propose a revised measure for total coherence and find that this measure can lead to a symmetric version of geometric quantum correlation which is analytic for two qubits. In particular, this measure can also arrive at a monogamy equality on the distribution of quantum coherence. Finally, we also quantify a remaining type of quantum coherence and find that for two qubits it is directly connected with quantum nonlocality.

Chang-shui Yu; Yang Zhang; Haiqing Zhao

2014-02-19T23:59:59.000Z

467

Parity meter for charge qubits: An efficient quantum entangler B. Trauzettel,1,2 A. N. Jordan,3,4 C. W. J. Beenakker,1 and M. Bttiker3  

E-Print Network (OSTI)

Parity meter for charge qubits: An efficient quantum entangler B. Trauzettel,1,2 A. N. Jordan,3,4 C parity meter based on two double quantum dots alongside a quantum point contact. Such a device off the parity meter. Two applications of the parity meter are discussed: the measurement of Bell

468

Parity meter for charge qubits: an efficient quantum entangler  

E-Print Network (OSTI)

We propose a realization of a charge parity meter based on two double quantum dots alongside a quantum point contact. Such a device is a specific example of the general class of mesoscopic quadratic quantum measurement detectors previously investigated by Mao et al. [Phys. Rev. Lett. 93, 056803 (2004)]. Our setup accomplishes entangled state preparation by a current measurement alone, and allows the qubits to be effectively decoupled by pinching off the parity meter. Two applications of the parity meter are discussed: the measurement of Bell's inequality in charge qubits and the realization of a controlled NOT gate.

B. Trauzettel; A. N. Jordan; C. W. J. Beenakker; M. Buttiker

2006-04-26T23:59:59.000Z

469

Potential value extraction from TxDOT’s right of way and other property assets.  

E-Print Network (OSTI)

??Many Departments of Transportation (DOTs), including Texas Department of Transportation (TxDOT), have been challenged by inadequate funding from traditional federal and state fuel taxes, increasing… (more)

Paes, Thiago Mesquita

2012-01-01T23:59:59.000Z

470

Quantum Institute  

NLE Websites -- All DOE Office Websites (Extended Search)

Quantum Institute Quantum Institute Quantum Institute A new research frontier awaits! Our door is open and we thrive on mutually beneficial partnerships, collaborations that drive innovations and new technologies. Contact Leader Malcolm Boshier (505) 665-8892 Email Two of LANL's most successful quantum technology initiatives: quantum cryptography and the race for quantum computer The area of quantum information, science, and technology is rapidly evolving, with important applications in the areas of quantum cryptography, quantum computing, quantum metrology, and advanced quantum-based sensors, some of which are directly relevant to the Laboratory's national security mission. Mission Foster a vigorous intellectual environment at LANL Define and develop strategic thrusts Target and pursue funding opportunities

471

Quantum discord  

NLE Websites -- All DOE Office Websites (Extended Search)

Quantum discord Quantum discord 1663 Los Alamos science and technology magazine Latest Issue:November 2013 All Issues » submit Quantum discord A distinguishing aspect of quantum mechanics discovered at Los Alamos that may be critical to building a quantum computer March 25, 2013 Spinning coins turning into binary numbers Quantum computing Quantum computing can be carried out without the delicate entanglement of qubits previously believed to be necessary Quantum computing, in which quantum bits of information (or qubits) juggle a "superposition" of multiple values simultaneously, offers to unleash tremendous computational power if the qubits can be effectively isolated to prevent decoherence: information describing quantum states dispersing into the environment. But recent research has shown that quantum computing can be carried out

472

Quantum Simulation  

E-Print Network (OSTI)

Simulating quantum mechanics is known to be a difficult computational problem, especially when dealing with large systems. However, this difficulty may be overcome by using some controllable quantum system to study another less controllable or accessible quantum system, i.e., quantum simulation. Quantum simulation promises to have applications in the study of many problems in, e.g., condensed-matter physics, high-energy physics, atomic physics, quantum chemistry and cosmology. Quantum simulation could be implemented using quantum computers, but also with simpler, analog devices that would require less control, and therefore, would be easier to construct. A number of quantum systems such as neutral atoms, ions, polar molecules, electrons in semiconductors, superconducting circuits, nuclear spins and photons have been proposed as quantum simulators. This review outlines the main theoretical and experimental aspects of quantum simulation and emphasizes some of the challenges and promises of this fast-growing field.

I. M. Georgescu; S. Ashhab; Franco Nori

2014-03-13T23:59:59.000Z

473

Quantum Machines  

E-Print Network (OSTI)

We discuss quantum information processing machines. We start with single purpose machines that either redistribute quantum information or identify quantum states. We then move on to machines that can perform a number of functions, with the function they perform being determined by a program, which is itself a quantum state. Examples of both deterministic and probabilistic programmable machines are given, and we conclude with a discussion of the utility of quantum programs.

Mark Hillery; Vladimir Buzek

2009-03-24T23:59:59.000Z

474

Peak External Photocurrent Quantum Efficiency Exceeding 100% via MEG in a Quantum Dot Solar Cell  

Science Journals Connector (OSTI)

...conversion efficiency of photovoltaic and photoelectrolysis...collection in a sensitized photovoltaic system . Science 330...nl803600v 19170560 18 Law M. ., Determining...characterization, and modeling; and details of the...18597536 27 Ma W. ., Photovoltaic performance of ultrasmall...

Octavi E. Semonin; Joseph M. Luther; Sukgeun Choi; Hsiang-Yu Chen; Jianbo Gao; Arthur J. Nozik; Matthew C. Beard

2011-12-16T23:59:59.000Z

475

the dynamics of quantum systems for many years. In these systems the  

E-Print Network (OSTI)

-mechanical oscillations of charge in a small superconducting circuit under the influence of electric pulses. However), single- electron charge or spin states in semiconductor quantum dots (Phys.Rev. 1998 A57 120) and charge their superconducting circuit in a microwave- tight copper box inside a dilution refrigerator at 30 millikelvin

van der Wal, Caspar H.

476

Optoelectronic Properties of Self-Assembled InAs/InGaAs Quantum SANJAY KRISHNA  

E-Print Network (OSTI)

CHAPTER 10 Optoelectronic Properties of Self-Assembled InAs/InGaAs Quantum Dots SANJAY KRISHNA that exists in zero-dimensional systems but also for their application in electronic and optoelectronic-speed- and opto-electronics". In particular, with the advent of optical fibers and the ever increasing need

Krishna, Sanjay

477

I, Quantum Robot: Quantum Mind control on a Quantum Computer  

E-Print Network (OSTI)

The logic which describes quantum robots is not orthodox quantum logic, but a deductive calculus which reproduces the quantum tasks (computational processes, and actions) taking into account quantum superposition and quantum entanglement. A way toward the realization of intelligent quantum robots is to adopt a quantum metalanguage to control quantum robots. A physical implementation of a quantum metalanguage might be the use of coherent states in brain signals.

Paola Zizzi

2008-12-25T23:59:59.000Z

478

Navillum Nanotechnologies | Department of Energy  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Science & Innovation » Innovation » Commercialization » National Science & Innovation » Innovation » Commercialization » National Clean Energy Business Plan Competition » Navillum Nanotechnologies National Clean Energy Business Plan Competition Navillum Nanotechnologies University of Utah Navillum Nanotechnologies' innovative method for fabricating quantum dots and other types of semiconducting nanocrystals at commercial scale that can both save energy and produce renewable energy. Quantum dots emit light at specific colors when stimulated by light or applied electrical source. Semiconducting nanocrystals can make solar panels up to 45 percent more efficient, which is more than a two-fold increase over existing commercial solar technologies. When used in LCD displays, quantum dots can increase energy efficiency by up to 35 percent over existing display technologies

479

A multiplexed quantum memory  

Science Journals Connector (OSTI)

A quantum repeater is a system for long-distance quantum communication that employs quantum memory elements to mitigate optical fiber transmission losses. The multiplexed quantum...

Lan, S -Y; Radnaev, A G; Collins, O A; Matsukevich, D N; Kennedy, T A; Kuzmich, A

2009-01-01T23:59:59.000Z

480

Blue Dots Team Transits Working Group Review  

E-Print Network (OSTI)

Transiting planet systems offer an unique opportunity to observationally constrain proposed models of the interiors (radius, composition) and atmospheres (chemistry, dynamics) of extrasolar planets. The spectacular successes of ground-based transit surveys (more than 60 transiting systems known to-date) and the host of multi-wavelength, spectro-photometric follow-up studies, carried out in particular by HST and Spitzer, have paved the way to the next generation of transit search projects, which are currently ongoing (CoRoT, Kepler), or planned. The possibility of detecting and characterizing transiting Earth-sized planets in the habitable zone of their parent stars appears tantalizingly close. In this contribution we briefly review the power of the transit technique for characterization of extrasolar planets, summarize the state of the art of both ground-based and space-borne transit search programs, and illustrate how the science of planetary transits fits within the Blue Dots perspective.

Sozzetti, A; Alonso, R; Blank, D L; Catala, C; Deeg, H; Grenfell, J L; Hellier, C; Latham, D W; Minniti, D; Pont, F; Rauer, H

2009-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "lcd quantum dots" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.