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  1. Seychelles: Energy Resources | Open Energy Information

    Open Energy Info (EERE)

    Country Profile Name Seychelles Population 84,000 GDP 2,760,000,000 Energy Consumption 0.01 Quadrillion Btu 2-letter ISO code SC 3-letter ISO code SYC Numeric ISO...

  2. Nicaragua-San Jacinto-Tizate Geothermal Power Project | Open...

    Open Energy Info (EERE)

    Website http:www.iadb.orgprojectsP Program Start 2010 Country Nicaragua UN Region Latin America and the Caribbean References Nicaragua-Geothermal1 Background "The Project...

  3. A New Geothermal Anomaly In Nicaragua | Open Energy Information

    Open Energy Info (EERE)

    Geothermal Anomaly In Nicaragua Jump to: navigation, search OpenEI Reference LibraryAdd to library Journal Article: A New Geothermal Anomaly In Nicaragua Abstract The information...

  4. Nicaragua-IAEA Cooperation | Open Energy Information

    Open Energy Info (EERE)

    IAEA Cooperation Jump to: navigation, search Name Nicaragua-IAEA Cooperation AgencyCompany Organization International Atomic Energy Agency Sector Energy Topics Background...

  5. Nicaragua: Energy Resources | Open Energy Information

    Open Energy Info (EERE)

    imported 63.95 million kWh from its neighbours Panama and Honduras.Nicaragua has no oil production; in 2001, its consumption was of 24,500 bblday. There is one oil refinery...

  6. Integrated: Geospatial Toolkit GIS data for Nicaragua from NREL...

    Open Energy Info (EERE)

    Nicaragua from NREL (Abstract): Geographic Information Systems (GIS) data intended for use in the Geospatial toolkit or with any GIS software. (Purpose): The Solar and Wind Energy...

  7. A New Geothermal Resource Map Of Nicaragua | Open Energy Information

    Open Energy Info (EERE)

    volcanic cordillera. From NW to SE, these areas are Volch Cosiguina, Volcin Casita-San Cristbbal, Volciin Telica-El fiajo, San Jacinto-Tizate, El Hoyo-Monte Galiin,...

  8. The Momotombo Geothermal Field, Nicaragua: Exploration and development case history study

    SciTech Connect (OSTI)

    1982-07-01

    This case history discusses the exploration methods used at the Momotombo Geothermal Field in western Nicaragua, and evaluates their contributions to the development of the geothermal field models. Subsequent reservoir engineering has not been synthesized or evaluated. A geothermal exploration program was started in Nicaragua in 1966 to discover and delineate potential geothermal reservoirs in western Nicaragua. Exploration began at the Momotombo field in 1970 using geological, geochemical, and geophysical methods. A regional study of thermal manifestations was undertaken and the area on the southern flank of Volcan Momotombo was chosen for more detailed investigation. Subsequent exploration by various consultants produced a number of geotechnical reports on the geology, geophysics, and geochemistry of the field as well as describing production well drilling. Geological investigations at Momotombo included photogeology, field mapping, binocular microscope examination of cuttings, and drillhole correlations. Among the geophysical techniques used to investigate the field sub-structure were: Schlumberger and electromagnetic soundings, dipole mapping and audio-magnetotelluric surveys, gravity and magnetic measurements, frequency domain soundings, self-potential surveys, and subsurface temperature determinations. The geochemical program analyzed the thermal fluids of the surface and in the wells. This report presents the description and results of exploration methods used during the investigative stages of the Momotombo Geothermal Field. A conceptual model of the geothermal field was drawn from the information available at each exploration phase. The exploration methods have been evaluated with respect to their contributions to the understanding of the field and their utilization in planning further development. Our principal finding is that data developed at each stage were not sufficiently integrated to guide further work at the field, causing inefficient use of

  9. A reservoir engineering assessment of the San Jacinto-Tizate geothermal field, Nicaragua

    SciTech Connect (OSTI)

    Ostapenko, S.; Spektor, S.; Davila, H.; Porras, E.; Perez, M.

    1996-12-31

    More than twenty years have passed since geothermal research and drilling took place at the geothermal fields in Nicaragua. The well known Momotombo Geothermal Field (70 MWe) has been generating electricity since 1983, and now a new geothermal field is under exploration, the San Jacinto-Tizate. Two reservoirs hydraulic connected were found. The shallow reservoir (270{degrees}C) at the depth of 550 - 1200 meters, and the deep one at > 1600 meters. Both of them are water dominated reservoirs although a two phase condition exist in the upper part of the shallow one. Different transient tests and a multi-well interference test have been carried out, very high transmissivity value were estimated around the well SJ-4 and average values for the others. A preliminary conceptual model of the geothermal system is given in this paper, as the result of the geology, geophysics, hydrology studies, drilling and reservoir evaluation.

  10. A reservoir engineering assessment of the San Jacinto-Tizate Geothermal Field, Nicaragua

    SciTech Connect (OSTI)

    Ostapenko, S.; Spektor, S.; Davila, H.; Porras, E.; Perez, M.

    1996-01-24

    More than twenty yews have passed since geothermal research and drilling took place at the geothermal fields in Nicaragua- Tbe well horn Momotombo Geothermal Field (70 We) has been generating electricity since 1983, and now a new geothermal field is under exploration. the San Jacinto-Tizate. Two reservoirs hydraulic connected were found. The shallow reservoir (270°C) at the depth of 550 - 1200 meters, and the deep one at > 1600 meters. Both of theme are water dominated reservoirs, although a two phase condition exist in the upper part of the shallow one. Different transient tests and a multi-well interference test have been carried out, very high transmissivity value were estimated around the well SJ-4 and average values for the others. A preliminar conceptual model of the geothermal system is given in this paper, as the result of the geology, geophysics, hydrology studies, drilling and reservoir evaluation.

  11. The scaling relationship between self-potential and fluid flow on Masaya volcano, Nicaragua

    SciTech Connect (OSTI)

    Lewicki, J.L.; Hilley, G.E.; Conner, C.

    2003-11-11

    The concurrent measurement of self-potential (SP) and soil CO{sub 2} flux (F{sub s}{sup CO2}) in volcanic systems may be an important tool to monitor intrusive activity and understand interaction between magmatic and groundwater systems. However, quantitative relationships between these parameters must be established to apply them toward understanding processes operating at depth. Power-law scaling exponents calculated for SP and F{sub s}{sup CO2} measured along a fault on the flanks of Masaya volcano, Nicaragua indicate a nonlinear relationship between these parameters. Scaling exponents suggest that there is a declining increase in SP with a given increase in F{sub s}{sup CO2}, until a threshold (log F{sub s}{sup CO2} {approx} 2.5 g m{sup -2}d{sup -1}) above which SP remains constant with increasing F{sub s}{sup CO2}. Implications for subsurface processes that may influence SP at Masaya are discussed.

  12. Self-potential, soil co2 flux, and temperature on masaya volcano, nicaragua

    SciTech Connect (OSTI)

    Lewicki, J.L.; Connor, C.; St-Amand, K.; Stix, J.; Spinner, W.

    2003-07-01

    We investigate the spatial relationship between self-potential (SP), soil CO{sub 2} flux, and temperature and the mechanisms that produce SP anomalies on the flanks of Masaya volcano, Nicaragua. We measured SP, soil CO{sub 2} fluxes (<1 to 5.0 x 10{sup 4} g m{sup -2} d{sup -1}), and temperatures (26 to 80 C) within an area surrounding a normal fault, adjacent to Comalito cinder cone (2002-2003). These variables are well spatially correlated. Wavelengths of SP anomalies are {le}100 m, and high horizontal SP gradients flank the region of elevated flux and temperature. Carbon isotopic compositions of soil CO{sub 2} ({delta}{sup 13}C = -3.3 to -1.1{per_thousand}) indicate a deep gas origin. Given the presence of a deep water table (100 to 150 m), high gas flow rates, and subsurface temperatures above liquid boiling points, we suggest that rapid fluid disruption is primarily responsible for positive SP anomalies here. Concurrent measurement of SP, soil CO{sub 2} flux, and temperature may be a useful tool to monitor intrusive activity.

  13. Comparative soil CO2 flux measurements and geostatisticalestimation methods on masaya volcano, nicaragua

    SciTech Connect (OSTI)

    Lewicki, J.L.; Bergfeld, D.; Cardellini, C.; Chiodini, G.; Granieri, D.; Varley, N.; Werner, C.

    2004-04-27

    We present a comparative study of soil CO{sub 2} flux (F{sub CO2}) measured by five groups (Groups 1-5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1-5 measured F{sub CO2} using the accumulation chamber method at 5-m spacing within a 900 m{sup 2} grid during a morning (AM) period. These measurements were repeated by Groups 1-3 during an afternoon (PM) period. All measured F{sub CO2} ranged from 218 to 14,719 g m{sup -2}d{sup -1}. Arithmetic means and associated CO{sub 2} emission rate estimates for the AM data sets varied between groups by {+-}22%. The variability of the five measurements made at each grid point ranged from {+-}5 to 167% and increased with the arithmetic mean. Based on a comparison of measurements made by Groups 1-3 during AM and PM times, this variability is likely due in large part to natural temporal variability of gas flow, rather than to measurement error. We compared six geostatistical methods (arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods) to estimate the mean and associated CO{sub 2} emission rate of one data set and to map the spatial F{sub CO2} distribution. While the CO{sub 2} emission rates estimated using the different techniques only varied by {+-}1.1%, the F{sub CO2} maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of F{sub CO2} and is most appropriate for volcano monitoring applications.

  14. Solon SE | Open Energy Information

    Open Energy Info (EERE)

    to: navigation, search Name: Solon SE Place: Berlin, Berlin, Germany Zip: D-12489 Sector: Solar Product: Manufacturer of PV modules and tracking systems, and integrator of solar...

  15. About-PHaSe-EFRC

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

    LGRT Conte Buildings The University of Massachusetts Amherst Energy Frontier Research Center (EFRC) - Polymer-Based Materials for Harvesting Solar Energy, PHaSE - was one of 46 ...

  16. Resources-PHaSe-EFRC

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

    Resources This webpage is provided for legacy archive purposes only, as of 30 April 2015. However, the facilities and resources created under PHaSE (thanks to the support of the U.S. Department of Energy) remain available for their original purpose of investigating organic-based electronic materials. Resources As a national and regional center of excellence for energy research, PHaSE has access to many resources linked from the Department of Energy and the greater UMass Amherst campus, as well

  17. News-PHaSe-EFRC

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

    News and Highlights Saxony This page shows highlights and news items about PHaSE activities, research achievements, and people; archived items can be accessed by year at the menu to the left. If you have questions about any items, or want to know more, please contact either Tom Russell or D. Venkataraman. Final archive date: 26 April

  18. Nicaragua Canal Template

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

    ... 30 1500-100,000 -- -- 1.0 30 Source: (FCC 1996) ffrequency in MHz *Plane-wave equivalent power density 2.4.3. Overview of Research for Potential Non-Thermal Effects to Humans ...

  19. Nicaragua Canal Template

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

    - CHAPTER 1 This page intentionally left blank First Responder Network Authority Nationwide Public Safety Broadband Network Draft Programmatic Environmental Impact Statement for the Eastern United States VOLUME 1 - CHAPTER 1 Amanda Goebel Pereira, AICP NEPA Coordinator First Responder Network Authority U.S. Department of Commerce 12201 Sunrise Valley Dr. M/S 243 Reston, VA 20192 Cooperating Agencies Federal Communications Commission General Services Administration U.S. Department of

  20. Nicaragua Canal Template

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

    - CHAPTER 2 This page intentionally left blank First Responder Network Authority Nationwide Public Safety Broadband Network Draft Programmatic Environmental Impact Statement for the Eastern United States VOLUME 1 - CHAPTER 2 Amanda Goebel Pereira, AICP NEPA Coordinator First Responder Network Authority U.S. Department of Commerce 12201 Sunrise Valley Dr. M/S 243 Reston, VA 20192 Cooperating Agencies Federal Communications Commission General Services Administration U.S. Department of

  1. Nicaragua Canal Template

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

    1 This page intentionally left blank Nationwide Public Safety Broadband Network Draft Programmatic Environmental Impact Statement for the Eastern United States VOLUME 15 - CHAPTER 21 April 2016 First Responder Network Authority Amanda Goebel Pereira, AICP NEPA Coordinator First Responder Network Authority U.S. Department of Commerce 12201 Sunrise Valley Dr. M/S 243 Reston, VA 20192 Cooperating Agencies Federal Communications Commission General Services Administration U.S. Department of

  2. Nicaragua Canal Template

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

    ... Canada, Mexico, Japan, and Russia. The MBTA prohibits the take, possession, import, export, transport, selling, ... floodplains and to avoid direct and indirect support of ...

  3. Nicaragua Canal Template

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

    School Amanda Pereira M.S., Urban and Regional Planning, University of ... University Genevieve Walker B.A., Geology, Florida International University BOOZ ...

  4. Barron: Noncompliance Determination (2013-SE-5402) | Department...

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

    Noncompliance Determination (2013-SE-5402) Barron: Noncompliance Determination (2013-SE-5402) December 17, 2015 DOE issued a Notice of Noncompliance Determination to Barron ...

  5. Shandong Hongtai: Noncompliance Determination (2016-SE-42010...

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

    Noncompliance Determination (2016-SE-42010) Shandong Hongtai: Noncompliance Determination (2016-SE-42010) January 6, 2016 DOE issued a Notice of Noncompliance Determination to ...

  6. I2SE | Open Energy Information

    Open Energy Info (EERE)

    I2SE Jump to: navigation, search Name: I2SE Place: Leipzig, Germany Zip: 4103 Sector: Efficiency Product: IT company providing solutions for energy efficiency and data...

  7. SE Project Srl | Open Energy Information

    Open Energy Info (EERE)

    search Name: SE Project Srl Place: San Pietro, Italy Zip: 35010 Sector: Solar Product: Italian manufacturer and supplier of solar modules and solar technology. References: SE...

  8. Li2Se as a Neutron Scintillator

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

    Du, Mao-Hua; Shi, Hongliang; Singh, David J.

    2015-06-23

    We show that Li2Se:Te is a potential neutron scintillator material based on density functional calculations. Li2Se exhibits a number of properties favorable for efficient neutron detection, such as a high Li concentration for neutron absorption, a small effective atomic mass and a low density for reduced sensitivity to background gamma rays, and a small band gap for a high light yield. Our calculations show that Te doping should lead to the formation of deep acceptor complex VLi-TeSe, which can facilitate efficient light emission, similar to the emission activation in Te doped ZnSe.

  9. Oxidation of ultrathin GaSe

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

    Thomas Edwin Beechem; McDonald, Anthony E.; Ohta, Taisuke; Howell, Stephen W.; Kalugin, Nikolai G.; Kowalski, Brian M.; Brumbach, Michael T.; Spataru, Catalin D.; Pask, Jesse A.

    2015-10-26

    Oxidation of exfoliated gallium selenide (GaSe) is investigated through Raman, photoluminescence, Auger, and X-ray photoelectron spectroscopies. Photoluminescence and Raman intensity reductions associated with spectral features of GaSe are shown to coincide with the emergence of signatures emanating from the by-products of the oxidation reaction, namely, Ga2Se3 and amorphous Se. Furthermore, photoinduced oxidation is initiated over a portion of a flake highlighting the potential for laser based patterning of two-dimensional heterostructures via selective oxidation.

  10. Oxidation of ultrathin GaSe

    SciTech Connect (OSTI)

    Thomas Edwin Beechem; McDonald, Anthony E.; Ohta, Taisuke; Howell, Stephen W.; Kalugin, Nikolai G.; Kowalski, Brian M.; Brumbach, Michael T.; Spataru, Catalin D.; Pask, Jesse A.

    2015-10-26

    Oxidation of exfoliated gallium selenide (GaSe) is investigated through Raman, photoluminescence, Auger, and X-ray photoelectron spectroscopies. Photoluminescence and Raman intensity reductions associated with spectral features of GaSe are shown to coincide with the emergence of signatures emanating from the by-products of the oxidation reaction, namely, Ga2Se3 and amorphous Se. Furthermore, photoinduced oxidation is initiated over a portion of a flake highlighting the potential for laser based patterning of two-dimensional heterostructures via selective oxidation.

  11. Q Cells SE | Open Energy Information

    Open Energy Info (EERE)

    Name: Q-Cells SE Place: Thalheim, Brandenburg, Germany Zip: 6766 Product: German PV cell manufacturer; also makes strategic venture capital and corporate investments....

  12. Templates-Resources-PHaSe-EFRC

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

    templates 36 inch high by 48 inch wide, landscape poster template with PHaSE acknowledgements (PPT file download) 36 inch high by 48 inch wide, landscape poster template with PHaSE acknowledgements, 12-panel layout (typical pattern used by UMass PSE) (PPT file download) 42 inch high by 48 inch wide, landscape poster template with PHaSE acknowledgements (PPT file download) 36 inch high by 48 inch wide, portrait poster template with PHaSE acknowledgements (PPT file download) 16:9 Slide Templates

  13. SE Drive Technik | Open Energy Information

    Open Energy Info (EERE)

    Drive Technik Jump to: navigation, search Name: SE Drive Technik Place: Bochum, Germany Zip: 44791 Product: Germany-based R&D subsidiary of Indian turbine maker Suzlon. References:...

  14. Facilities-Resources-PHaSe-EFRC

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

    Various PHaSE EFRC equipment may be accessed by making arrangments for training and acceptance to the list of registered users. Access to the facility rooms requires a password ...

  15. 2013 Archives-News-PHaSe-EFRC

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

    3 Archives Volodimyr Duzhko photo Volodimyr Duzhko promoted to (extension) Assistant Professor of Polymer Science & Engineering. PHaSE is pleased to announce that Facility Director Dr. Volodimyr Duzhko has been promoted to extension Assistant Professor of Polymer Science & Engineering. Volodimyr is a semiconductor physicist with considerable experience in polymer materials. Since joining PHaSE, he has trained over 70 people to use 10 instruments in the Photovoltaic & Optical

  16. A transferable force field for CdS-CdSe-PbS-PbSe solid systems

    SciTech Connect (OSTI)

    Fan, Zhaochuan; Vlugt, Thijs J. H.; Koster, Rik S.; Fang, Changming; Huis, Marijn A. van; Wang, Shuaiwei; Yalcin, Anil O.; Tichelaar, Frans D.; Zandbergen, Henny W.

    2014-12-28

    A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., “Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth,” Nano Lett. 14, 3661–3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and CdS, and provide detailed information on the validation of this force field. The parameterization combines Bader charge analysis, empirical fitting, and ab initio energy surface fitting. When compared with experimental data and density functional theory calculations, it is shown that a wide range of physical properties of bulk PbS, PbSe, CdS, CdSe, and their mixed phases can be accurately reproduced using this force field. The choice of functional forms and parameterization strategy is demonstrated to be rational and effective. This transferable force field can be used in various studies on II-VI and IV-VI semiconductor materials consisting of CdS, CdSe, PbS, and PbSe. Here, we demonstrate the applicability of the force field model by molecular dynamics simulations whereby transformations are initiated by cation exchange.

  17. 2011 Archives-News-PHaSe-EFRC

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

    1 Archives solar cells video clip Solar Cells from Plastics? Mission Possible at the PHaSE energy research center, UMass Amherst!, a YouTube video about work at PHaSE, debuted on 24 March 2011. This video is part of our center's contributions to the Energy Frontier Research Centers Summit & Forum on 25-27 May 2011, which is further described below. Many thanks to Harihara Venkatraman (DV group, ERG 1) and Dr. Emily Pentzer (Emrick group, ERG 1) for starring in the video clip, along with

  18. Anisotropy in CdSe quantum rods

    SciTech Connect (OSTI)

    Li, Liang-shi

    2003-09-01

    The size-dependent optical and electronic properties of semiconductor nanocrystals have drawn much attention in the past decade, and have been very well understood for spherical ones. The advent of the synthetic methods to make rod-like CdSe nanocrystals with wurtzite structure has offered us a new opportunity to study their properties as functions of their shape. This dissertation includes three main parts: synthesis of CdSe nanorods with tightly controlled widths and lengths, their optical and dielectric properties, and their large-scale assembly, all of which are either directly or indirectly caused by the uniaxial crystallographic structure of wurtzite CdSe. The hexagonal wurtzite structure is believed to be the primary reason for the growth of CdSe nanorods. It represents itself in the kinetic stabilization of the rod-like particles over the spherical ones in the presence of phosphonic acids. By varying the composition of the surfactant mixture used for synthesis we have achieved tight control of the widths and lengths of the nanorods. The synthesis of monodisperse CdSe nanorods enables us to systematically study their size-dependent properties. For example, room temperature single particle fluorescence spectroscopy has shown that nanorods emit linearly polarized photoluminescence. Theoretical calculations have shown that it is due to the crossing between the two highest occupied electronic levels with increasing aspect ratio. We also measured the permanent electric dipole moment of the nanorods with transient electric birefringence technique. Experimental results on nanorods with different sizes show that the dipole moment is linear to the particle volume, indicating that it originates from the non-centrosymmetric hexagonal lattice. The elongation of the nanocrystals also results in the anisotropic inter-particle interaction. One of the consequences is the formation of liquid crystalline phases when the nanorods are dispersed in solvent to a high enough

  19. UMass-Resources-PHaSe-EFRC

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

    UMass Resources UMass logo The following links provide information about important local (UMass Amherst) campus and departmental offices and resources, including major interdepartmental research centers that pursue work closely akin to research that was initiated or expanded under PHaSE. The last four links go to sites with energy or research news of potential interest to scientists interested in organic electronic materails. Major UMass User Facilities Vice-Chancellor for Research UMass

  20. Organization-About-PHaSe-EFRC

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

    About Mission Statement (PDF) Organization Contact Us organization This webpage is provided for legacy archive purposes only, as of 30 April 2015. The day to day operations of the University of Massachusetts Amherst PHaSE EFRC are administered by co-directors. Russell is the Samuel Conte Distingushed Professor of Polymer Science and Engineering, with years of previous experience at IBM Research, over 620 publications and 21 patents for polymer chemistry and physics. Lahti has over 29 years at

  1. SE Great Basin Play Fairway Analysis

    SciTech Connect (OSTI)

    Adam Brandt

    2015-11-15

    This submission includes a Na/K geothermometer probability greater than 200 deg C map, as well as two play fairway analysis (PFA) models. The probability map acts as a composite risk segment for the PFA models. The PFA models differ in their application of magnetotelluric conductors as composite risk segments. These PFA models map out the geothermal potential in the region of SE Great Basin, Utah.

  2. 2010 Archives-News-PHaSe-EFRC

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

    0 Archives PHaSE welcomes Dr. Lawrence Friedman as our new Managing Director. Larry comes to us with strong backgrounds in both academic and industrial experience. He is well acquainted with UMass Amherst from his time at Bayer Materials Science, where he was much involved in doctoral level recruiting and in academic/industrial liaison work as Head of University Relations. Before this, he was at Polaroid doing work in flims research as a manager and senior scientist. His academic credentials

  3. 2013 Archives-News-PHaSe-EFRC

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

    4 Archives PHaSE EFRC work was featured in an MRS-TV video production, UMASS Amherst -- Optimal Design: Interdisciplinary Teamwork from Synthesis to Production, that was highlighted on electronic signage throughout the Fall 2014 Boston Materials Research Society meeting. Major vignettes were shown from Maroudas group, DV group, Emrick group. Both faculty and undergraduates/graduates/postdocs described EFRC work and work being carried out by closely allied groups interested in energy-related

  4. AeroSys: Noncompliance Determination (2010-SE-0302) | Department...

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

    Noncompliance Determination (2010-SE-0302) AeroSys: Noncompliance Determination (2010-SE-0302) April 13, 2010 DOE issued a Notice of Noncompliance Determination to AeroSys, Inc. ...

  5. SeQuential Pacific Biodiesel LLC | Open Energy Information

    Open Energy Info (EERE)

    Pacific Biodiesel LLC Jump to: navigation, search Name: SeQuential-Pacific Biodiesel LLC Place: Oregon Sector: Biofuels Product: JV between SeQuential Biofuels, Pacific Biodiesel,...

  6. 2009 Archives-News-PHaSe-EFRC

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

    09 Archives U.S. DOE Announces Energy Frontier Research Centers (08/2009) UMass Amherst EFRC Proposal (08/2009) EFRC Funding Distributed to Successful Centers (08/2009) PHaSE co-director Paul Lahti led off a set of presentations organized by the UMass Amherst Research & Liaison office to meet with a delegation of scientists from various technical research centers of the Gipuzkoa province in the Basque region of northern Spain. The delegation was organized through the Tecnalia Corporation,

  7. 2012 Archives-News-PHaSe-EFRC

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

    2 Archives Tom Russell photo Joint work by Tom Russell, Alex Briseno, and coworkers describes fabrication and a significant degree of device optimization of a low band polymer pDPP/PCBM solar cell, in an article published in Advanced Materials. Photoconversion efficiency up to 5.6% with a fill factor of 60% were obtained. Morphology control based on solvent mixture tuning was critically important for best electrical output. [read more] PHaSE members D. Venkataraman and Tom Russell have edited a

  8. Synthesis and optical study of green light emitting polymer coated CdSe/ZnSe core/shell nanocrystals

    SciTech Connect (OSTI)

    Tripathi, S.K.; Sharma, Mamta

    2013-05-15

    Highlights: ► Synthesis of Polymer coated core CdSe and CdSe/ZnSe core/shell NCs. ► From TEM image, the spherical nature of CdSe and CdSe/ZnSe is obtained. ► Exhibiting green band photoemission peak at 541 nm and 549 nm for CdSe core and CdSe/ZnSe core/shell NCs. ► The shell thickness has been calculated by using superposition of quantum confinement energy model. - Abstract: CdSe/ZnSe Core/Shell NCs dispersed in PVA are synthesized by chemical method at room temperature. This is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectra and photoluminescence spectroscopy (PL). TEM image shows the spherical nature of CdSe/ZnSe core/shell NCs. The red shift of absorption and emission peak of CdSe/ZnSe core/shell NCs as compared to CdSe core confirmed the formation of core/shell. The superposition of quantum confinement energy model is used for calculation of thickness of ZnSe shell.

  9. SE-MA-NO Electric Coop | Open Energy Information

    Open Energy Info (EERE)

    SE-MA-NO Electric Coop Jump to: navigation, search Name: SE-MA-NO Electric Coop Place: Missouri Phone Number: (417) 924-3291 Website: www.semano.com Facebook: https:...

  10. MgSe/ZnSe/CdSe coupled quantum wells grown on InP substrate with intersubband absorption covering 1.55??m

    SciTech Connect (OSTI)

    Chen, Guopeng; Shen, Aidong; De Jesus, Joel; Tamargo, Maria C.

    2014-12-08

    The authors report the observation of intersubband (ISB) transitions in the optical communication wavelength region in MgSe/ZnSe/CdSe coupled quantum wells (QWs). The coupled QWs were grown on InP substrates by molecular beam epitaxy. By inserting ZnSe layers to compensate the strain, samples with high structural quality were obtained, as indicated by well resolved satellite peaks in high-resolution x-ray diffraction. The observed ISB transition energies agree well with the calculated values.

  11. Goodman Manufacturing: Order (2011-SE-4301) | Department of Energy

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

    Goodman Manufacturing: Order (2011-SE-4301) Goodman Manufacturing: Order (2011-SE-4301) March 2, 2012 DOE ordered Goodman Manufacturing Company, L.P., to pay a $14,800 civil penalty after finding Goodman had manufactured and distributed in commerce in the U.S. at least 74 units of commercial package air conditioner basic model CPC180*. Goodman Manufacturing: Order (2011-SE-4301) (131.78 KB) More Documents & Publications Goodman Manufacturing: Proposed Penalty (2011-SE-4301) Goodman

  12. Barron: Order (2013-SE-5402) | Department of Energy

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

    Order (2013-SE-5402) Barron: Order (2013-SE-5402) March 22, 2016 DOE ordered Barron Lighting Group, Inc. to pay a $22,849 civil penalty after finding Barron had manufactured and distributed in commerce in the U.S. 429 units of various noncompliant metal halide lamp fixtures. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Barron. Barron: Order (2013-SE-5402) (19.24 KB) More Documents & Publications Barron: Noncompliance Determination (2013-SE-5402)

  13. SE-72/AS-72 generator system based on Se extraction/ As reextraction

    DOE Patents [OSTI]

    Fassbender, Michael Ernst; Ballard, Beau D

    2013-09-10

    The preparation of a .sup.72Se/.sup.72As radioisotope generator involves forming an acidic aqueous solution of an irradiated alkali bromide target such as a NaBr target, oxidizing soluble bromide in the solution to elemental bromine, removing the elemental bromine, evaporating the resulting solution to a residue, removing hydrogen chloride from the residue, forming an acidic aqueous solution of the residue, adding a chelator that selectively forms a chelation complex with selenium, and extracting the chelation complex from the acidic aqueous solution into an organic phase. As the .sup.72Se generates .sup.72As in the organic phase, the .sup.72As may be extracted repeatedly from the organic phase with an aqueous acid solution.

  14. Two-dimensional GaSe/MoSe2 misfit bilayer heterojunctions by van der Waals epitaxy

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

    Li, Xufan; Lin, Ming-Wei; Lin, Junhao; Huang, Bing; Puretzky, Alexander A.; Ma, Cheng; Wang, Kai; Zhou, Wu; Pantelides, Sokrates T.; Chi, Miaofang; et al

    2016-04-01

    Two-dimensional (2D) heterostructures hold the promise for future atomically-thin electronics and optoelectronics due to their diverse functionalities. While heterostructures consisting of different transition metal dichacolgenide monolayers with well-matched lattices and novel physical properties have been successfully fabricated via van der Waals (vdW) or edge epitaxy, constructing heterostructures from monolayers of layered semiconductors with large lattice misfits still remains challenging. Here, we report the growth of monolayer GaSe/MoSe2 heterostructures with large lattice misfit by two-step chemical vapor deposition (CVD). Both vertically stacked and lateral heterostructures are demonstrated. The vertically stacked GaSe/MoSe2 heterostructures exhibit vdW epitaxy with well-aligned lattice orientation between themore » two layers, forming an incommensurate vdW heterostructure. However, the lateral heterostructures exhibit no lateral epitaxial alignment at the interface between GaSe and MoSe2 crystalline domains. Instead of a direct lateral connection at the boundary region where the same lattice orientation is observed between GaSe and MoSe2 monolayer domains in lateral GaSe/MoSe2 heterostructures, GaSe monolayers are found to overgrow MoSe2 during CVD, forming a stripe of vertically stacked vdW heterostructure at the crystal interface. Such vertically-stacked vdW GaSe/MoSe2 heterostructures are shown to form p-n junctions with effective transport and separation of photo-generated charge carriers between layers, resulting in a gate-tunable photovoltaic response. In conclusion, these GaSe/MoSe2 vdW heterostructures should have applications as gate-tunable field-effect transistors, photodetectors, and solar cells.« less

  15. Spectral photoresponse of ZnSe/GaAs(001) heterostructures with CdSe ultra-thin quantum well insertions

    SciTech Connect (OSTI)

    Valverde-Chvez, D. A.; Sutara, F.; Hernndez-Caldern, I.

    2014-05-15

    We present a study of the spectral photoresponse (SPR) of ZnSe/GaAs(001) heterostructures for different ZnSe film thickness with and without CdSe ultra-thin quantum well (UTQW) insertions. We observe a significant increase of the SPR of heterostructures containing 3 monolayer thick CdSe UTQW insertions; these results encourage their use in photodetectors and solar cells.

  16. Twinning effect on photoluminescence spectra of ZnSe nanowires

    SciTech Connect (OSTI)

    Xu, Jing; Wang, Chunrui Wu, Binhe; Xu, Xiaofeng; Chen, Xiaoshuang; Oh, Hongseok; Baek, Hyeonjun; Yi, Gyu-Chul

    2014-11-07

    Bandgap engineering in a single material along the axial length of nanowires may be realized by arranging periodic twinning, whose twin plane is vertical to the axial length of nanowires. In this paper, we report the effect of twin on photoluminescence of ZnSe nanowires, which refers to the bandgap of it. The exciton-related emission peaks of transverse twinning ZnSe nanowires manifest a 10-meV-blue-shift in comparison with those of longitudinal twinning ZnSe nanowires. The blue-shift is attributed to quantum confinement effect, which is influenced severely by the proportion of wurtzite ZnSe layers in ZnSe nanowires.

  17. Thermoelectric transport of Se-rich Ag{sub 2}Se in normal phases and phase transitions

    SciTech Connect (OSTI)

    Mi, Wenlong; Lv, Yanhong; Qiu, Pengfei; Shi, Xun E-mail: cld@mail.sic.ac.cn; Chen, Lidong E-mail: cld@mail.sic.ac.cn; Zhang, Tiansong

    2014-03-31

    Small amount of Se atoms are used to tune the carrier concentrations (n{sub H}) and electrical transport in Ag{sub 2}Se. Significant enhancements in power factor and thermoelectric figure of merit (zT) are observed in the compositions of Ag{sub 2}Se{sub 1.06} and Ag{sub 2}Se{sub 1.08}. The excessive Se atoms do not change the intrinsically electron-conducting character in Ag{sub 2}Se. The detailed analysis reveals the experiment optimum carrier concentration in Ag{sub 2}Se is around 5??10{sup 18}?cm{sup ?3}. We also investigate the temperature of maximum zT and the thermoelectric transport during the first order phase transitions using the recently developed measurement system.

  18. Confined lattice dynamics of single and quadruple SnSe bilayers in [(SnSe) 1.04 ] m [MoSe 2 ] n ferecrystals

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

    Klobes, Benedikt; Hu, Michael Y.; Beekman, Matt; Johnson, David C.; Hermann, Raphaël P.

    2015-11-30

    The Sn specific densities of phonon states in the SnSe subunits of [(SnSe)1.04]m[MoSe2]n ferecrystals with (m,n) = (1,1), (4,1) and in bulk SnSe were derived from nuclear inelastic scattering by the 119Sn M ssbauer resonance. When using different measurement configurations, phonons with polarization parallel and perpendicular to the ferecrystal plane were specifically probed. Vibrational properties and phonon spectral weight are found to strongly depend on the phonon polarization and layer count m. Moreover, a highly peculiar feature of these ferecrystal densities of phonon states is the emergence of rather sharp high energy vibrational modes polarized perpendicular to the ferecrystal plane,more » which contrasts with usual findings in thin layered structures and nanostructured materials in general, and a depletion of modes with a gap appearing between acoustic and high energy modes. The spectral weight of these phonons depends on the overall SnSe content, m, but cannot be unambiguously attributed to SnSe MoSe2 interfaces. Considering the low energy part of lattice dynamics, ferecrystals exhibit rather low average phonon group velocities as compared to the speed of sound in the long wavelength limit. For the (1,1) ferecrystal, this effect is most pronounced for vibrations polarized in the ferecrystal plane. Therefore, an experimental microscopic origin for the vibrational and bonding anisotropy in subunits of ferecrystals is provided.« less

  19. CuInSe/sub 2/-based photoelectrochemical cells: their use in characterization of thin CuInSe/sub 2/ films, and as photovoltaic cells per se

    SciTech Connect (OSTI)

    Cahen, D.; Chen, Y.W.; Ireland, P.J.; Noufi, R.; Turner, J.A.; Rincon, C.; Bachmann, K.J.

    1984-05-01

    Photoelectrochemistry has been employed to characterize the p-CuInSe/sub 2/ component of the CdS/CuInSe/sub 2/ on-metal and a nonaqueous electrolyte containing a redox couple not specifically adsorbed onto the semiconductor, we can test the films for photovoltaic activity and obtain effective electronic properties of them, before CdS deposition, in a nondestructive manner. Electrochemical decomposition of CuInSe/sub 2/ was investigated in acetonitrile solutions to determine the mechanism of decomposition (n and p) in the dark and under illumination. Electrochemical, solution chemical and surface analyses confirmed at the light-assisted decomposition of CuInSe/sub 2/ resulted in metal ions and elemental chalcogen. On the basis of the results from the electrochemical decomposition, and studies on the solid state chemistry of the (Cu/sub 2/Se)/sub x/(In/sub 2/Se/sub 3/)/sub 1-x/ system and surface analyses, the CuInSe/sub 2//polyiodide interface was stabilized and up to 11.7% conversion efficiencies were obtained.

  20. Perlick: Agreement (2010-SE-0109) | Department of Energy

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

    Perlick: Agreement (2010-SE-0109) Perlick: Agreement (2010-SE-0109) February 7, 2011 DOE and Perlick Residential & Hospitality Products entered into a Compromise Agreement in which Perlick agreed to pay a $5,000 civil penalty after DOE found that Perlick had manufactured and distributed in commerce in the U.S. model HP72ROO-S, a noncompliant refrigerator. The Compromise Agreement reflected the settlement terms between DOE and Perlick. Perlick: Agreement (2010-SE-0109) (240.67 KB) More

  1. SeQuential Biofuels LLC | Open Energy Information

    Open Energy Info (EERE)

    Biofuels LLC Jump to: navigation, search Name: SeQuential Biofuels LLC Place: Portland, Oregon Zip: 97231 Sector: Biofuels Product: A biofuels marketing and distribution company...

  2. Research Forum Schedule-Research-PHaSe-EFRC

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

    Research Forum Schedule PHaSE Research Fora and Talks This webpage is provided for legacy archive purposes only, as of 30 April 2015.

  3. SE Idaho Load Service Update - June 10, 2015

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

    SE-Idaho-Load-Service-Update---June-10,-2015 Sign In About | Careers | Contact | Investors | bpa.gov Search Doing Business Expand Doing Business Customer Involvement Expand...

  4. U-105:Oracle Java SE Critical Patch Update Advisory

    Broader source: Energy.gov [DOE]

    Multiple vulnerabilities were reported in Oracle Java SE. A remote user can execute arbitrary code on the target system. A remote user can cause denial of service conditions.

  5. CdSe self-assembled quantum dots with ZnCdMgSe barriers emitting throughout the visible spectrum

    SciTech Connect (OSTI)

    Perez-Paz, M. Noemi; Zhou Xuecong; Munoz, Martin; Lu Hong; Sohel, Mohammad; Tamargo, Maria C.; Jean-Mary, Fleumingue; Akins, Daniel L.

    2004-12-27

    Self-assembled quantum dots of CdSe with ZnCdMgSe barriers have been grown by molecular beam epitaxy on InP substrates. The optical and microstructural properties were investigated using photoluminescence (PL) and atomic force microscopy (AFM) measurements. Control and reproducibility of the quantum dot (QD) size leading to light emission throughout the entire visible spectrum range has been obtained by varying the CdSe deposition time. Longer CdSe deposition times result in a redshift of the PL peaks as a consequence of an increase of QD size. AFM studies demonstrate the presence of QDs in uncapped structures. A comparison of this QD system with CdSe/ZnSe shows that not only the strain but also the chemical properties of the system play an important role in QD formation.

  6. CdSe/ZnSe quantum dot structures grown by molecular beam epitaxy with a CdTe submonolayer stressor

    SciTech Connect (OSTI)

    Sedova, I. V. Lyublinskaya, O. G.; Sorokin, S. V.; Sitnikova, A. A.; Toropov, A. A.; Donatini, F.; Dang, Si Le; Ivanov, S. V.

    2007-11-15

    A procedure for formation of CdSe quantum dots (QDs) in a ZnSe matrix is suggested. The procedure is based on the introduction of a CdTe submonolayer stressor deposited on the matrix surface just before deposition of the material of the QDs. (For CdTe/ZnSe structure, the relative lattice mismatch is {delta}a/a {approx} 14%.) The stressor forms small strained islands at the ZnSe surface, thus producing local fields of high elastic stresses controlling the process of the self-assembling of the QDs. According to the data of transmission electron microscopy, this procedure allows a considerable increase in the surface density of QDs, with a certain decrease in their lateral dimensions (down to 4.5 {+-} 1.5 nm). In the photoluminescence spectra, a noticeable ({approx}150 meV) shift of the peak to longer wavelengths from the position of the reference CdSe/ZnSe QD structure is observed. The shift is due to some transformation of the morphology of the QDs and an increase in the Cd content in the QDs. Comprehensive studies of the nanostructures by recording and analyzing the excitation spectra of photoluminescence, the time-resolved photoluminescence spectra, and the cathodoluminescence spectra show that the emission spectra involve two types of optical transitions, namely, the type-I transitions in the CdSeTe/ZnSe QDs and the type-II transitions caused mainly by the low cadmium content (Zn,Cd)(Se,Te)/ZnSe layer formed between the QDs.

  7. Victory: Order (2015-SE-42033) | Department of Energy

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

    Order (2015-SE-42033) Victory: Order (2015-SE-42033) October 27, 2015 DOE ordered Victory Refrigeration to pay a $1,600 civil penalty after finding Victory had manufactured and distributed in commerce in the U.S. at least 8 units of commercial refrigerator-freezer basic model RFS-1D-S1-EW-PT-HD, a noncompliant product. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Victory. Victory: Order (2015-SE-42033) (21.59 KB) More Documents & Publications

  8. Optical Probing of metamagnetic phases in epitaxial EuSe

    SciTech Connect (OSTI)

    Galgano, G. D.; Henriques, A. B.; Bauer, G.; Springholz, G.

    2011-12-23

    EuSe is a wide gap magnetic semiconductors with a potential for applications in proof-of-concept spintronic devices. When the temperature is lowered, EuSe goes through sharp transitions between a variety of magnetic phases and is thus described as metamagnetic. The purpose of the present investigation is to correlate the magnetic order to the sharp dichroic doublet, discovered recently in high quality thin epitaxial layers of EuSe, grown by molecular beam epitaxy. We report detailed measurements of the doublet positions and intensities as a function of magnetic field in low temperatures, covering several magnetic phases.

  9. Bu Sung: Order (2015-SE-42007) | Department of Energy

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

    Order (2015-SE-42007) Bu Sung: Order (2015-SE-42007) October 13, 2015 DOE ordered Bu Sung America Corporation to pay a $71,480 civil penalty after finding Bu Sung had manufactured and distributed in commerce in the U.S. at least 361 units of basic model ESRF2, a noncompliant commercial refrigerator-freezer. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Bu Sung. Bu Sung: Order (2015-SE-42007) (123.64 KB) More Documents & Publications Bu Sung:

  10. AHT: Order (2015-SE-42031) | Department of Energy

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

    Order (2015-SE-42031) AHT: Order (2015-SE-42031) March 9, 2016 DOE ordered AHT Cooling Systems, Inc. to pay a $179,040 civil penalty after finding AHT had manufactured and distributed in commerce in the U.S. at least 1,032 units of commercial refrigeration equipment model RIO S 68 L F, a noncompliant product. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and AHT. AHT: Order (2015-SE-42031) (66.05 KB) More Documents & Publications AHT: Proposed Penalty

  11. Optical Properties of CdSe Nanoparticle Assemblies

    SciTech Connect (OSTI)

    Huser, T; Gerion, D; Zaitseva, N; Krol, D M; Leon, F R

    2003-11-24

    We report on three-dimensional fluorescence imaging of micron-size faceted crystals precipitated from solutions of CdSe nanocrystals. Such crystals have previously been suggested to be superlattices of CdSe quantum dots [1,2]. Possible applications for these materials include their use in optical and optoelectronic devices. The micron-size crystals were grown by slow evaporation from toluene solutions of CdSe nanocrystals in the range of 3-6 nm, produced by traditional wet-chemistry techniques. By using a confocal microscope with laser illumination, three-dimensional raster-scanning and synchronized hyper-spectral detection, we have generated spatial profiles of the fluorescence emission intensity and spectrum. The fluorescence data of the micro-crystals were compared with spectra of individual nanocrystals obtained from the same solution. The results do not support the assertion that these microcrystals consist of CdSe superlattices.

  12. Synthesis and properties of new CdSe-AgI-As{sub 2}Se{sub 3} chalcogenide glasses

    SciTech Connect (OSTI)

    Kassem, M.; ULCO, LPCA, EAC CNRS 4493 F-59140 Dunkerque ; Le Coq, D.; Fourmentin, M.; Hindle, F.; Bokova, M.; Cuisset, A.; Masselin, P.; Bychkov, E.; ULCO, LPCA, EAC CNRS 4493 F-59140 Dunkerque

    2011-02-15

    Research highlights: {yields} Determination of the glass-forming region in the pseudo-ternary CdSe-AgI-As{sub 2}Se{sub 3} system. {yields} Characterization of macroscopic properties of the new CdSe-AgI-As{sub 2}Se{sub 3} glasses. {yields} Far infrared transmission of chalcogenide glasses. {yields} Characterization of the total conductivity of CdSe-AgI-As{sub 2}Se{sub 3} glasses. -- Abstract: The glass-forming region in the pseudo-ternary CdSe-AgI-As{sub 2}Se{sub 3} system was determined. Measurements including differential scanning calorimetry (DSC), density, and X-ray diffraction were performed. The effect resulting from the addition of CdSe or AgI has been highlighted by examining three series of different base glasses. The characteristic temperatures of the glass samples, including glass transition (T{sub g}), crystallisation (T{sub x}), and melting (T{sub m}) temperatures are reported and used to calculate their {Delta}T = T{sub x} - T{sub g} and their Hruby, H{sub r} = (T{sub x} - T{sub g})/(T{sub m} - T{sub x}), criteria. Evolution of the total electrical conductivity {sigma} and the room temperature conductivity {sigma}{sub 298} was also studied. The terahertz transparency domain in the 50-600 cm{sup -1} region was pointed for different chalcogenide glasses (ChGs) and the potential of the THz spectroscopy was suggested to obtain structural information on ChGs.

  13. Utility: Noncompliance Determination (2016-SE-42003) | Department of Energy

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

    Noncompliance Determination (2016-SE-42003) Utility: Noncompliance Determination (2016-SE-42003) December 30, 2015 DOE issued a Notice of Noncompliance Determination to Utility Refrigerator finding that commercial refrigeration equipment basic model number PT-R-75-SS-3S-3S-N does not comport with the energy conservation standards. DOE determined the product was noncompliant based on DOE testing. Utility must immediately notify each person (or company) to whom Utility distributed the noncompliant

  14. Victory: Noncompliance Determination (2015-SE-42033) | Department of Energy

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

    Noncompliance Determination (2015-SE-42033) Victory: Noncompliance Determination (2015-SE-42033) August 18, 2015 DOE issued a Notice of Noncompliance Determination to Victory Refrigeration finding that commercial refrigeration equipment basic model number RFS-1D-S1-EW-PT-HD (including each individual model within the basic model) does not comport with the energy conservation standards. DOE determined the product was noncompliant based on DOE testing. Victory must immediately notify each person

  15. Victory: Proposed Penalty (2015-SE-42033) | Department of Energy

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

    Proposed Penalty (2015-SE-42033) Victory: Proposed Penalty (2015-SE-42033) September 25, 2015 DOE alleged in a Notice of Proposed Civil Penalty that Victory Refrigeration manufactured and distributed noncompliant commercial refrigerator-freezer model RFS-1D-S1-EW-PT-HD in the U.S. Federal law subjects manufacturers and private labelers to civil penalties if those parties distribute in the U.S. products that do not meet applicable energy conservation standards. This civil penalty notice advises

  16. True: Order (2015-SE-42049) | Department of Energy

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

    True: Order (2015-SE-42049) True: Order (2015-SE-42049) February 4, 2016 DOE ordered True Manufacturing Co., Inc., to pay a $36,400 civil penalty after finding True had manufactured and distributed in commerce in the U.S. 182 units of True commercial refrigerator basic models TCGG-72 and TCGG-72-S, which did not meet the application energy conservation standard. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and True. Federal law subjects manufacturers and

  17. Haier: Compromise Agreement (2011-SE-1428) | Department of Energy

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

    Compromise Agreement (2011-SE-1428) Haier: Compromise Agreement (2011-SE-1428) April 23, 2013 DOE and Haier America Trading, LLC entered into a Compromise Agreement to resolve a case involving the distribution in commerce of residential freezers that did not meet the applicable energy conservation performance standard. Haier agreed to ensure that no additional units of the noncompliant freezers will be distributed in commerce in the U.S. and not to use the same model numbers in the future.

  18. Bu Sung: Proposed Penalty (2015-SE-42007) | Department of Energy

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

    Proposed Penalty (2015-SE-42007) Bu Sung: Proposed Penalty (2015-SE-42007) September 29, 2015 DOE alleged in a Notice of Proposed Civil Penalty that Bu Sung America Corporation d/b/a Everest Refrigeration manufactured and distributed noncompliant commercial refrigerator-freezers in the U.S. Federal law subjects manufacturers and private labelers to civil penalties if those parties distribute in the U.S. products that do not meet applicable energy conservation standards. This civil penalty notice

  19. The influence of interfaces on properties of thin-film inorganic structural isomers containing SnSeNbSe? Subunits

    SciTech Connect (OSTI)

    Alemayehu, Matti B.; Falmbigl, Matthias; Ta, Kim; Johnson, David C.

    2015-08-28

    Inorganic isomers ([SnSe]1+?)m(NbSe?)n([SnSe]1+?)p(NbSe?)q([SnSe]1+?)r(NbSe?)s where m, n, p, q, r, and s are integers and m + p + r = n + q + s = 4 were prepared using the modulated elemental reactant technique. This series of all six possible isomers provides an opportunity to study the influence of interface density on properties while maintaining the same unit cell size and composition. As expected, all six compounds were observed to have the same atomic compositions and an almost c-axis lattice parameter of ?4.90 (5) nm, with a slight trend in the c-axis lattice parameter correlated with the different number of interfaces in the isomers: two, four and six. The structures of the constituents in the ab-plane were independent of one another, confirming the nonepitaxial relationship between them. The temperature dependent electrical resistivities revealed metallic behavior for all the six compounds. Surprisingly, the electrical resistivity at room temperature decreases with increasing number of interfaces. Hall measurements suggest this results from changes in carrier concentration, which increases with increasing thickness of the thickest SnSe block in the isomer. Carrier mobility scales with the thickness of the thickest NbSe? block due to increased interfacial scattering as the NbSe? blocks become thinner. The observed behavior suggests that the two constituents serve different purposes with respect to electrical transport. SnSe acts as a charge donor and NbSe? acts as the charge transport layer. This separation of function suggests that such heterostructures can be designed to optimize performance through choice of constituent, layer thickness, and layer sequence. A simplistic model, which predicts the properties of the complex isomers from a weighted sum of the properties of

  20. Heterojunctions of model CdTe/CdSe mixtures

    SciTech Connect (OSTI)

    van Swol, Frank; Zhou, Xiaowang W.; Challa, Sivakumar R.; Martin, James E.

    2015-03-18

    We report on the strain behavior of compound mixtures of model group IIVI semiconductors. We use the StillingerWeber Hamiltonian that we recently introduced, specifically developed to model binary mixtures of group IIVI compounds such as CdTe and CdSe. We also employ molecular dynamics simulations to examine the behavior of thin sheets of material, bilayers of CdTe and CdSe. The lattice mismatch between the two compounds leads to a strong bending of the entire sheet, with about a 0.5 to 1 deflection between neighboring planes. To further analyze bilayer bending, we introduce a simple one-dimensional model and use energy minimization to find the angle of deflection. The analysis is equivalent to a least-squares straight line fit. We consider the effects of bilayers which are asymmetric with respect to the thickness of the CdTe and CdSe parts. We thus learn that the bending can be subdivided into four kinds depending on the compressive/tensile nature of each outer plane of the sheet. We use this approach to directly compare our findings with experimental results on the bending of CdTe/CdSe rods. To reduce the effects of the lattice mismatch we explore diffuse interfaces, where we mix (i.e. alloy) Te and Se, and estimate the strain response.

  1. Heterojunctions of model CdTe/CdSe mixtures

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

    van Swol, Frank; Zhou, Xiaowang W.; Challa, Sivakumar R.; Martin, James E.

    2015-03-18

    We report on the strain behavior of compound mixtures of model group II-VI semiconductors. We use the Stillinger-Weber Hamiltonian that we recently introduced, specifically developed to model binary mixtures of group II-VI compounds such as CdTe and CdSe. We also employ molecular dynamics simulations to examine the behavior of thin sheets of material, bilayers of CdTe and CdSe. The lattice mismatch between the two compounds leads to a strong bending of the entire sheet, with about a 0.5 to 1° deflection between neighboring planes. To further analyze bilayer bending, we introduce a simple one-dimensional model and use energy minimization tomore » find the angle of deflection. The analysis is equivalent to a least-squares straight line fit. We consider the effects of bilayers which are asymmetric with respect to the thickness of the CdTe and CdSe parts. We thus learn that the bending can be subdivided into four kinds depending on the compressive/tensile nature of each outer plane of the sheet. We use this approach to directly compare our findings with experimental results on the bending of CdTe/CdSe rods. To reduce the effects of the lattice mismatch we explore diffuse interfaces, where we mix (i.e. alloy) Te and Se, and estimate the strain response.« less

  2. Heterojunctions of model CdTe/CdSe mixtures

    SciTech Connect (OSTI)

    van Swol, Frank; Zhou, Xiaowang W.; Challa, Sivakumar R.; Martin, James E.

    2015-03-18

    We report on the strain behavior of compound mixtures of model group II-VI semiconductors. We use the Stillinger-Weber Hamiltonian that we recently introduced, specifically developed to model binary mixtures of group II-VI compounds such as CdTe and CdSe. We also employ molecular dynamics simulations to examine the behavior of thin sheets of material, bilayers of CdTe and CdSe. The lattice mismatch between the two compounds leads to a strong bending of the entire sheet, with about a 0.5 to 1° deflection between neighboring planes. To further analyze bilayer bending, we introduce a simple one-dimensional model and use energy minimization to find the angle of deflection. The analysis is equivalent to a least-squares straight line fit. We consider the effects of bilayers which are asymmetric with respect to the thickness of the CdTe and CdSe parts. We thus learn that the bending can be subdivided into four kinds depending on the compressive/tensile nature of each outer plane of the sheet. We use this approach to directly compare our findings with experimental results on the bending of CdTe/CdSe rods. To reduce the effects of the lattice mismatch we explore diffuse interfaces, where we mix (i.e. alloy) Te and Se, and estimate the strain response.

  3. EMPaSE: an Extensible Multi-Paradigm Simulation Environment

    Energy Science and Technology Software Center (OSTI)

    2010-08-05

    EMPaSE is a hierarchical, extensible, modular modeling environment for developing and running hybrid simulations of sequential-modular, systems dynamics, discrete-event, and agent-based paradigms. It contains two principle components: a multi-paradigm simulation engine and a graphical user interface. EMPaSE models are defined through a hierarchically-defined set of computational modules that define the simulation logic. Inter-module communication occurs through two complimentary systems: pull-based "ports" for general computation patterns and push-based "plugs" for event processing. Entities (i.e. agents) withinmore » the simulation operate within an abstract multi-network environment. The EMPaSE simulation engine is designed around a flexible plug-in architecture, allowing simulations to import computational modules, engine customizations, and interfaces to external applications from independent plug-in libraries. The EMPaSE GUI environment provides an environment for graphically constructing, executing, and debugging EMPaSE models. As with the simulation engine, the GUI is constructed on top of an extensible architecture that supports rapid customization of the user experience through external plug-in libraries.« less

  4. Reverse Monte Carlo simulation of Se{sub 80}Te{sub 20} and Se{sub 80}Te{sub 15}Sb{sub 5} glasses

    SciTech Connect (OSTI)

    Abdel-Baset, A. M.; Rashad, M.; Moharram, A. H.

    2013-12-16

    Two-dimensional Monte Carlo of the total pair distribution functions g(r) is determined for Se{sub 80}Te{sub 20} and Se{sub 80}Te{sub 15}Sb{sub 5} alloys, and then it used to assemble the three-dimensional atomic configurations using the reverse Monte Carlo simulation. The partial pair distribution functions g{sub ij}(r) indicate that the basic structure unit in the Se{sub 80}Te{sub 15}Sb{sub 5} glass is di-antimony tri-selenide units connected together through Se-Se and Se-Te chain. The structure of Se{sub 80}Te{sub 20} alloys is a chain of Se-Te and Se-Se in addition to some rings of Se atoms.

  5. Electrochemical solar cells using CdSe thin film electrodes

    SciTech Connect (OSTI)

    Xiao, Xu-Rui; Tien, H.Ti.

    1983-01-01

    Electrochemical photocells consisting of a CdSe thin film anode and a Pt cathode immersed in 1M Na/sub 2/S-NaOH-S solution have been studied. CdSe thin films were formed on Ti, Cr, Mo, SnO/sub 2/, glassy carbon, and graphite substrates by coating an aqueous mixture of CdSe, ZnCl/sub 2/, and surfactant, subsequently sintering at 400/sup 0/-500/sup 0/C in air. The current-voltage (I-V) relations, output power efficiency, open-circuit voltage, and short-circuit current were measured. Seven percent power conversion efficiency was obtained at 20 mW/cm/sup 2/ light intensity after photoetching. The monochromatic I-V curves were analyzed.

  6. Utility: Order (2016-SE-42003) | Department of Energy

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

    SE-42003) Utility: Order (2016-SE-42003) March 1, 2016 DOE ordered Utility Refrigerator to pay a $200 civil penalty after finding Utility manufactured and distributed in commerce in the U.S. 1 unit of a Utility brand commercial refrigerator, model PT-R-75-SS-3S-3S-N. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Utility. Federal law subjects manufacturers and private labelers to civil penalties if those parties distribute in the U.S. products that do

  7. Friedrich: Order (2014-SE-15010) | Department of Energy

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

    Order (2014-SE-15010) Friedrich: Order (2014-SE-15010) October 27, 2015 DOE ordered Friedrich Air Conditioning Co. to pay a civil penalty of $1,494,626.25 after finding Friedrich had manufactured and distributed in commerce in the U.S. 8,241 units of Friedrich model SQ10N10, a noncompliant room air conditioner. The Order adopted a Compromise Agreement, which reflected settlement terms between DOE and Friedrich. Federal law subjects manufacturers and private labelers to civil penalties if those

  8. Excited-State Relaxation in PbSe Quantum Dots

    SciTech Connect (OSTI)

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

    2008-01-01

    In solids the phonon-assisted, nonradiative decay from high-energy electronic excited states to low-energy electronic excited states is picosecond fast. It was hoped that electron and hole relaxation could be slowed down in quantum dots, due to the unavailability of phonons energy matched to the large energy-level spacings ('phonon-bottleneck'). However, excited-state relaxation was observed to be rather fast ({le}1 ps) in InP, CdSe, and ZnO dots, and explained by an efficient Auger mechanism, whereby the excess energy of electrons is nonradiatively transferred to holes, which can then rapidly decay by phonon emission, by virtue of the densely spaced valence-band levels. The recent emergence of PbSe as a novel quantum-dot material has rekindled the hope for a slow down of excited-state relaxation because hole relaxation was deemed to be ineffective on account of the widely spaced hole levels. The assumption of sparse hole energy levels in PbSe was based on an effective-mass argument based on the light effective mass of the hole. Surprisingly, fast intraband relaxation times of 1-7 ps were observed in PbSe quantum dots and have been considered contradictory with the Auger cooling mechanism because of the assumed sparsity of the hole energy levels. Our pseudopotential calculations, however, do not support the scenario of sparse hole levels in PbSe: Because of the existence of three valence-band maxima in the bulk PbSe band structure, hole energy levels are densely spaced, in contradiction with simple effective-mass models. The remaining question is whether the Auger decay channel is sufficiently fast to account for the fast intraband relaxation. Using the atomistic pseudopotential wave functions of Pb{sub 2046}Se{sub 2117} and Pb{sub 260}Se{sub 249} quantum dots, we explicitly calculated the electron-hole Coulomb integrals and the P {yields} S electron Auger relaxation rate. We find that the Auger mechanism can explain the experimentally observed P {yields} S

  9. Orbitally-driven giant phonon anharmonicity in SnSe

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

    Li, Chen W.; Hong, Jiawang; May, Andrew F.; Bansal, Dipanshu; Chi, Songxue; Hong, Tao; Ehlers, Georg; Delaire, Olivier A.

    2015-10-19

    We understand that elementary excitations and their couplings in condensed matter systems is critical to develop better energy-conversion devices. In thermoelectric materials, the heat-to-electricity conversion efficiency is directly improved by suppressing the propagation of phonon quasiparticles responsible for macroscopic thermal transport. The material with the current record for thermoelectric conversion efficiency, SnSe, achieves an ultra-low thermal conductivity, but the mechanism enabling this strong phonon scattering remains largely unknown. Using inelastic neutron scattering measurements and first-principles simulations, we mapped the four-dimensional phonon dispersion surfaces of SnSe, and revealed the origin of ionic-potential anharmonicity responsible for the unique properties of SnSe. Wemore » show that the giant phonon scattering arises from an unstable electronic structure, with orbital interactions leading to a ferroelectric-like lattice instability. Our results provide a microscopic picture connecting electronic structure and phonon anharmonicity in SnSe, and offers precious insights on how electron-phonon and phononphonon interactions may lead to the realization of ultra-low thermal conductivity.« less

  10. Orbitally-driven giant phonon anharmonicity in SnSe

    SciTech Connect (OSTI)

    Li, Chen W.; Hong, Jiawang; May, Andrew F.; Bansal, Dipanshu; Chi, Songxue; Hong, Tao; Ehlers, Georg; Delaire, Olivier A.

    2015-10-19

    We understand that elementary excitations and their couplings in condensed matter systems is critical to develop better energy-conversion devices. In thermoelectric materials, the heat-to-electricity conversion efficiency is directly improved by suppressing the propagation of phonon quasiparticles responsible for macroscopic thermal transport. The material with the current record for thermoelectric conversion efficiency, SnSe, achieves an ultra-low thermal conductivity, but the mechanism enabling this strong phonon scattering remains largely unknown. Using inelastic neutron scattering measurements and first-principles simulations, we mapped the four-dimensional phonon dispersion surfaces of SnSe, and revealed the origin of ionic-potential anharmonicity responsible for the unique properties of SnSe. We show that the giant phonon scattering arises from an unstable electronic structure, with orbital interactions leading to a ferroelectric-like lattice instability. Our results provide a microscopic picture connecting electronic structure and phonon anharmonicity in SnSe, and offers precious insights on how electron-phonon and phononphonon interactions may lead to the realization of ultra-low thermal conductivity.

  11. Giant piezoelectricity of monolayer group IV monochalcogenides: SnSe, SnS, GeSe, and GeS

    SciTech Connect (OSTI)

    Fei, Ruixiang; Yang, Li; Li, Wenbin; Li, Ju

    2015-10-26

    We predict enormous, anisotropic piezoelectric effects in intrinsic monolayer group IV monochalcogenides (MX, M=Sn or Ge, X=Se or S), including SnSe, SnS, GeSe, and GeS. Using first-principle simulations based on the modern theory of polarization, we find that their piezoelectric coefficients are about one to two orders of magnitude larger than those of other 2D materials, such as MoS{sub 2} and GaSe, and bulk quartz and AlN which are widely used in industry. This enhancement is a result of the unique “puckered” C{sub 2v} symmetry and electronic structure of monolayer group IV monochalcogenides. Given the achieved experimental advances in the fabrication of monolayers, their flexible character, and ability to withstand enormous strain, these 2D structures with giant piezoelectric effects may be promising for a broad range of applications such as nano-sized sensors, piezotronics, and energy harvesting in portable electronic devices.

  12. Epitaxial growth of CZT(S,Se) on silicon

    DOE Patents [OSTI]

    Bojarczuk, Nestor A.; Gershon, Talia S.; Guha, Supratik; Shin, Byungha; Zhu, Yu

    2016-03-15

    Techniques for epitaxial growth of CZT(S,Se) materials on Si are provided. In one aspect, a method of forming an epitaxial kesterite material is provided which includes the steps of: selecting a Si substrate based on a crystallographic orientation of the Si substrate; forming an epitaxial oxide interlayer on the Si substrate to enhance wettability of the epitaxial kesterite material on the Si substrate, wherein the epitaxial oxide interlayer is formed from a material that is lattice-matched to Si; and forming the epitaxial kesterite material on a side of the epitaxial oxide interlayer opposite the Si substrate, wherein the epitaxial kesterite material includes Cu, Zn, Sn, and at least one of S and Se, and wherein a crystallographic orientation of the epitaxial kesterite material is based on the crystallographic orientation of the Si substrate. A method of forming an epitaxial kesterite-based photovoltaic device and an epitaxial kesterite-based device are also provided.

  13. American Ref-Fuel of SE CT Biomass Facility | Open Energy Information

    Open Energy Info (EERE)

    Ref-Fuel of SE CT Biomass Facility Jump to: navigation, search Name American Ref-Fuel of SE CT Biomass Facility Facility American Ref-Fuel of SE CT Sector Biomass Facility Type...

  14. SpacePak: Proposed Penalty (2014-SE-16012) | Department of Energy

    Office of Environmental Management (EM)

    SpacePak: Proposed Penalty (2014-SE-16012) (19.1 KB) More Documents & Publications SpacePak: Noncompliance Determination (2014-SE-16012) SpacePak: Order (2014-SE-16012) Crane: ...

  15. Deformation potentials of CdSe quantum dots

    SciTech Connect (OSTI)

    Li, Jingbo; Wang, Lin-Wang

    2004-06-02

    The size dependent deformation potentials of CdSe quantum dots are studied by first principle and semi-empirical pseudopotentials calculations. They find that the amplitude of the quantum dot deformation potential is only slightly larger than the bulk value, and this increase is mostly caused by the off {Lambda} point deformation potentials in the bulk, which are larger in amplitude than the {Lambda} point deformation potential.

  16. Major UMass User Facilities-Resources-PHaSe-EFRC

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

    Major UMass User Facilities TRPL photo Researchers can access the capabilities of the various investigator interested in organic electronic materials, in PHaSE's original participating departments, and other centers and facilities, including the following: Materials Research Science & Engineering Center Center for Hierarchal Manufacturing High Field NMR Facility Mass Spectrometry Facility EPR Facility Keck Nanostructures Laboratory X-ray powder and single crystal diffraction Polymer

  17. Islandaire: Noncompliance Determination (2015-SE-43007) | Department of

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

    Energy 7) Islandaire: Noncompliance Determination (2015-SE-43007) February 25, 2016 DOE issued a Notice of Noncompliance Determination to Islandaire, Inc. finding that the Islandaire package terminal air conditioner basic model CPZ-09ANR1-B, which includes models EZ4209B and EZDR09B, does not comport with the applicable energy conservation standards. DOE determined the product was noncompliant based on DOE testing. Islandaire must immediately notify each person (or company) to whom it

  18. Islandaire: Noncompliance Determination (2015-SE-43008) | Department of

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

    Energy 8) Islandaire: Noncompliance Determination (2015-SE-43008) February 25, 2016 DOE issued a Notice of Noncompliance Determination to Islandaire, Inc. finding that the Islandaire package terminal air conditioner basic model CPZ-129ANR1-B, which includes model EZDR12B, does not comport with the applicable energy conservation standards. DOE determined the product was noncompliant based on DOE testing. Islandaire must immediately notify each person (or company) to whom it distributed the

  19. Islandaire: Noncompliance Determination (2015-SE-43009) | Department of

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

    Energy 9) Islandaire: Noncompliance Determination (2015-SE-43009) February 25, 2016 DOE issued a Notice of Noncompliance Determination to Islandaire, Inc. finding that the Islandaire package terminal air conditioner basic model CPZ-07ANR1-B, which includes model EZDR07B, does not comport with the applicable energy conservation standards. DOE determined the product was noncompliant based on DOE testing. Islandaire must immediately notify each person (or company) to whom it distributed the

  20. Quantum confined acceptors and donors in InSe nanosheets

    SciTech Connect (OSTI)

    Mudd, G. W.; Patan, A. Makarovsky, O.; Eaves, L.; Kudrynskyi, Z. R.; Kovalyuk, Z. D.; Fay, M. W.; Zlyomi, V.; Falko, V.

    2014-12-01

    We report on the radiative recombination of photo-excited carriers bound at native donors and acceptors in exfoliated nanoflakes of nominally undoped rhombohedral ?-polytype InSe. The binding energies of these states are found to increase with the decrease in flake thickness, L. We model their dependence on L using a two-dimensional hydrogenic model for impurities and show that they are strongly sensitive to the position of the impurities within the nanolayer.

  1. Pressure-dependent Optical Behaviors of Colloidal CdSe Nanoplatelets...

    Office of Scientific and Technical Information (OSTI)

    dependent Optical Behaviors of Colloidal CdSe Nanoplatelets Citation Details In-Document Search Title: Pressure-dependent Optical Behaviors of Colloidal CdSe Nanoplatelets Authors: ...

  2. Bi-Se doped with Cu, p-type semiconductor

    DOE Patents [OSTI]

    Bhattacharya, Raghu Nath; Phok, Sovannary; Parilla, Philip Anthony

    2013-08-20

    A Bi--Se doped with Cu, p-type semiconductor, preferably used as an absorber material in a photovoltaic device. Preferably the semiconductor has at least 20 molar percent Cu. In a preferred embodiment, the semiconductor comprises at least 28 molar percent of Cu. In one embodiment, the semiconductor comprises a molar percentage of Cu and Bi whereby the molar percentage of Cu divided by the molar percentage of Bi is greater than 1.2. In a preferred embodiment, the semiconductor is manufactured as a thin film having a thickness less than 600 nm.

  3. Phonon anharmonicity and negative thermal expansion in SnSe

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

    Bansal, Dipanshu; Hong, Jiawang; Li, Chen W.; May, Andrew F.; Porter, Wallace; Hu, Michael Y.; Abernathy, Douglas L.; Delaire, Olivier

    2016-08-09

    In this paper, the anharmonic phonon properties of SnSe in the Pnma phase were investigated with a combination of experiments and first-principles simulations. Using inelastic neutron scattering (INS) and nuclear resonant inelastic X-ray scattering (NRIXS), we have measured the phonon dispersions and density of states (DOS) and their temperature dependence, which revealed a strong, inhomogeneous shift and broadening of the spectrum on warming. First-principles simulations were performed to rationalize these measurements, and to explain the previously reported anisotropic thermal expansion, in particular the negative thermal expansion within the Sn-Se bilayers. Including the anisotropic strain dependence of the phonon free energy,more » in addition to the electronic ground state energy, is essential to reproduce the negative thermal expansion. From the phonon DOS obtained with INS and additional calorimetry measurements, we quantify the harmonic, dilational, and anharmonic components of the phonon entropy, heat capacity, and free energy. Finally, the origin of the anharmonic phonon thermodynamics is linked to the electronic structure.« less

  4. Thermodynamic properties of model CdTe/CdSe mixtures

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

    van Swol, Frank; Zhou, Xiaowang W.; Challa, Sivakumar R.; Martin, James E.

    2015-02-20

    We report on the thermodynamic properties of binary compound mixtures of model groups II–VI semiconductors. We use the recently introduced Stillinger–Weber Hamiltonian to model binary mixtures of CdTe and CdSe. We use molecular dynamics simulations to calculate the volume and enthalpy of mixing as a function of mole fraction. The lattice parameter of the mixture closely follows Vegard's law: a linear relation. This implies that the excess volume is a cubic function of mole fraction. A connection is made with hard sphere models of mixed fcc and zincblende structures. We found that the potential energy exhibits a positive deviation frommore » ideal soluton behaviour; the excess enthalpy is nearly independent of temperatures studied (300 and 533 K) and is well described by a simple cubic function of the mole fraction. Using a regular solution approach (combining non-ideal behaviour for the enthalpy with ideal solution behaviour for the entropy of mixing), we arrive at the Gibbs free energy of the mixture. The Gibbs free energy results indicate that the CdTe and CdSe mixtures exhibit phase separation. The upper consolute temperature is found to be 335 K. Finally, we provide the surface energy as a function of composition. Moreover, it roughly follows ideal solution theory, but with a negative deviation (negative excess surface energy). This indicates that alloying increases the stability, even for nano-particles.« less

  5. Photoluminescence study of the substitution of Cd by Zn during the growth by atomic layer epitaxy of alternate CdSe and ZnSe monolayers

    SciTech Connect (OSTI)

    Hernndez-Caldern, I.; Salcedo-Reyes, J. C.

    2014-05-15

    We present a study of the substitution of Cd atoms by Zn atoms during the growth of alternate ZnSe and CdSe compound monolayers (ML) by atomic layer epitaxy (ALE) as a function of substrate temperature. Samples contained two quantum wells (QWs), each one made of alternate CdSe and ZnSe monolayers with total thickness of 12 ML but different growth parameters. The QWs were studied by low temperature photoluminescence (PL) spectroscopy. We show that the Cd content of underlying CdSe layers is affected by the exposure of the quantum well film to the Zn flux during the growth of ZnSe monolayers. The amount of Cd of the quantum well film decreases with higher exposures to the Zn flux. A brief discussion about the difficulties to grow the Zn{sub 0.5}Cd{sub 0.5}Se ordered alloy (CuAu-I type) by ALE is presented.

  6. Magnetooptical study of CdSe/ZnMnSe semimagnetic quantum-dot ensembles with n-type modulation doping

    SciTech Connect (OSTI)

    Reshina, I. I. Ivanov, S. V.

    2014-12-15

    Magnetic and polarization investigations of the photoluminescence and resonant electron spin-flip Raman scattering in ensembles of self-organized CdSe/ZnMnSe semimagnetic quantum dots with n-type modulation doping are carried out. It is demonstrated that exciton transitions contribute to the photoluminescence band intensity, along with the transitions of trions in the singlet state. In the Hanle-effect measurements, negative circular polarization in zero magnetic field is observed, which is related to the optical orientation of a trion heavy hole. The lifetime and spin-relaxation time of a heavy hole are estimated as ?3 and ?1 ps, respectively. Such short times are assumed to be due to Auger recombination with the excitation of an intrinsic transition in a Mn{sup 2+} ion. Investigations of the photoluminescence-maximum intensity and shift in a longitudinal magnetic field at the ?{sup ?}?{sup +} and ?{sup ?}?{sup ?} polarizations reveal the pronounced spin polarization of electrons. Under resonant excitation conditions, a sharp increase in the photoluminescence-band maximum intensity at ?{sup ?} excitation polarization over the ?{sup +} one is observed. The Raman scattering peak at the electron spin-flip transition is observed upon resonant excitation in a transverse magnetic field in crossed linear polarizations. This peak is shown to be a Brillouin function of a magnetic field.

  7. Synthesis, structural, optical and Raman studies of pure and lanthanum doped ZnSe nanoparticles

    SciTech Connect (OSTI)

    Kumar, Pushpendra; Singh, Jai; Pandey, Mukesh Kumar; Jeyanthi, C.E.; Siddheswaran, R.; Paulraj, M.; Hui, K.N.; Hui, K.S.

    2014-01-01

    Graphical abstract: - Highlights: • Template-free synthesis of ZnSe and ZnSe:La nanoparticles was developed at low temperature 100 °C. • Cubic ZnSe and ZnSe:La nanoparticles were obtained by chemical route. • As-synthesized ZnSe:La nanoparticles showed higher emission intensity than ZnSe nanoparticles. • Band gap (E{sub g}) of ZnSe nanoparticles was bigger than ZnSe nanoparticles due to nanosized effect. - Abstract: In this work, a simple, effective and reproducible chemical synthetic route for the production of high-quality, pure ZnSe nanoparticles (NPs), and lanthanum-doped ZnSe (ZnSe:La) NPs is presented. The wide bandgap, luminescent pure ZnSe and ZnSe:La NPs has been synthesized at a low temperature (100 °C) in a single template-free step. The size and optical bandgap of the NPs was analyzed from powder X-ray diffraction (XRD), UV–visible (UV–vis) spectroscopy, transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM). A broad photoluminescence (PL) emission across the visible spectrum has been demonstrated by a systematic blue-shift in emission due to the formation of small nanoparticles. Here, contribution to emission intensity from surface states of NPs increases with La doping. TEM data revealed that the average size of ZnSe and ZnSe:La NPs is 14 and 8 nm, respectively. On the other hand, band gap energy E{sub g} of ZnSe and ZnSe:La NPs were found to be 3.59 eV and 3.65 eV, respectively. Results showed that hydrazine hydrate played multiple roles in the formation of ZnSe and ZnSe:La NPs. A possible reaction mechanism for the growth of NPs is also discussed.

  8. The new misfit compound (BiSe){sub 1.15}(TiSe{sub 2}){sub 2} and the role of dimensionality in the Cu{sub x}(BiSe){sub 1+δ}(TiSe{sub 2}){sub n} series

    SciTech Connect (OSTI)

    Trump, Benjamin A.; Livi, Kenneth J.T.; McQueen, Tyrel M.

    2014-01-15

    The synthesis and physical properties of the new misfit compound (BiSe){sub 1.15}(TiSe{sub 2}){sub 2} are reported. Transmission electron microscopy and powder X-ray diffraction show that the structure consists of alternating rock-salt type BiSe layers and hexagonal (TiSe{sub 2}){sub 2} double layers. Resistivity, specific heat, and magnetization measurements show that it has metallic and diamagnetic behaviors. These results are interpreted and discussed in the context of the transition between single-layer (BiSe){sub 1.13}(TiSe{sub 2}), which shows no charge density wave, and infinite-layered (bulk) 1T-TiSe{sub 2}, which undergoes a charge density wave transition at T=202 K. Intercalation with copper, Cu{sub x}(BiSe){sub 1.15}(TiSe{sub 2}){sub 2}, (0≤x≤0.10) is also reported, but unlike Cu{sub x}TiSe{sub 2}, no superconductivity is observed down to T=0.05 K. Thus, the series Cu{sub x}(BiSe){sub 1+δ}(TiSe{sub 2}){sub n} provides an effective approach to elucidate the impact of dimensionality on charge density wave formation and superconductivity. - Graphical abstract: The newly discovered misfit compound (BiSe){sub 1.15}(TiSe{sub 2}){sub 2} shown in the series (BiSe){sub 1+δ}(TiSe{sub 2}){sub n}. Display Omitted - Highlights: • Reports the structure and properties of the new misfit compound (BiSe){sub 1.15}(TiSe{sub 2}){sub 2}. • The structure consists of a rock salt type BiSe layer and a double (TiSe{sub 2}){sub 2} layer. • The n=1, 2 misfits (BiSe){sub 1+δ}(TiSe{sub 2}){sub n} are found not to exhibit CDW transitions. • Evidence is presented that there is likely a low-lying CDW excited state. • The series Cu{sub x}(BiSe){sub 1+δ}(TiSe{sub 2}){sub 2} does not superconduct, unlike Cu{sub x}TiSe{sub 2}.

  9. Detection of a MoSe{sub 2} secondary phase layer in CZTSe by spectroscopic ellipsometry

    SciTech Connect (OSTI)

    Demircioğlu, Özden; Riedel, Ingo; Gütay, Levent; Mousel, Marina; Redinger, Alex; Rey, Germain; Weiss, Thomas; Siebentritt, Susanne

    2015-11-14

    We demonstrate the application of Spectroscopic Ellipsometry (SE) for identification of secondary phase MoSe{sub 2} in polycrystalline Cu{sub 2}ZnSnSe{sub 4} (CZTSe) samples. A MoSe{sub 2} reference sample was analyzed, and its optical constants (ε{sub 1} and ε{sub 2}) were extracted by SE analysis. This dataset was implemented into an optical model for analyzing SE data from a glass/Mo/CZTSe sample containing MoSe{sub 2} at the back side of the absorber. We present results on the n and k values of CZTSe and show the extraction of the thickness of the secondary phase MoSe{sub 2} layer. Raman spectroscopy and scanning electron microscopy were applied to confirm the SE results.

  10. Intersubband absorption in CdSe/Zn{sub x}Cd{sub y}Mg{sub 1-x-y}Se self-assembled quantum dot multilayers

    SciTech Connect (OSTI)

    Shen, A.; Lu, H.; Charles, W.; Yokomizo, I.; Tamargo, M. C.; Franz, K. J.; Gmachl, C.; Zhang, S. K.; Zhou, X.; Alfano, R. R.; Liu, H. C.

    2007-02-12

    The authors report the observation of intersubband absorption in multilayers of CdSe/Zn{sub x}Cd{sub y}Mg{sub 1-x-y}Se self-assembled quantum dots. The samples were grown by molecular beam epitaxy on InP substrates. For samples with the CdSe dot layers doped with Cl and with the deposited CdSe equivalent layer thickness between 5.2 and 6.9 ML, peak absorption between 2.5 and 3.5 {mu}m was observed. These materials are promising for intersubband devices operating in the mid- and near-infrared ranges.

  11. SE Gobe: Papua New Guinea`s second oil development

    SciTech Connect (OSTI)

    Langston, M.V.; McCaul, T.R.; Fitzmorris, R.E.

    1994-12-31

    A reservoir development plan was developed from a detailed geological model of the SE Gobe Iagifu reservoir. This model incorporated sequence stratigraphy and extensive core and log analysis to provide the detailed layering framework for reservoir simulation. Cross-sectional balancing techniques were applied to field derived dip and strike, dipmeter log, and RFT data to obtain a structural model for the reservoir. Cross-sectional, sector and, finally, full field reservoir simulation models were constructed and used by the team to generate a reservoir development and management plan. The simulation models were used to examine the relative merits of vertical, deviated and horizontal wells, well placement, offtake rates, gas compression requirements and pressure maintenance strategies. Due to the uncertainty in the size and shape of the field, development options were considered at each of three reserve levels: proven, probable and possible. The simulation results showed that well rates should be held to less than 8,000 stb/d and that horizontal wells, with a length of at least 700 m, generally out-performed vertical wells. Oil recovery ranged between 34 and 45% of OOIP. The cases offering the best recoveries included both water injection and horizontal wells.

  12. Pulsed laser deposition of Mn doped CdSe quantum dots for improved...

    Office of Scientific and Technical Information (OSTI)

    Pulsed laser deposition of Mn doped CdSe quantum dots for improved solar cell performance Citation Details In-Document Search Title: Pulsed laser deposition of Mn doped CdSe ...

  13. Thermal stability and photoconductive properties of photosensors with an alternating multilayer structure of amorphous Se and As{sub x}Se{sub 1−x}

    SciTech Connect (OSTI)

    Yu, Tung-Yuan; Pan, Fu-Ming Chang, Cheng-Yi; Lin, Jian-Siang; Huang, Wen-Hsien

    2015-07-28

    In this study, we fabricated a-Se based photosensors with an alternating multilayer structure of a-Se and As{sub x}Se{sub 1−x} by rotational thermal evaporation deposition. During the deposition of the amorphous As{sub x}Se{sub 1−x} layers, As diffuses into the underlying a-Se component layers, thereby improving the thermal stability of the multilayer photosensor and thus increasing the breakdown electric field. Although the As doping introduces carrier traps in the a-Se layers, the multilayer photosensors demonstrate an effective quantum efficiency comparable to the single-layered a-Se sensor under the blue light illumination but are with a lower dark current density by two orders of magnitude. In addition to the top As{sub x}Se{sub 1−x} layer being functioning as an electron blocking layer, carrier traps present in the multilayer structure may decrease the drift mobility of charge carriers and disturb electric field distribution in the photosensors, thereby suppressing the dark current.

  14. The US/SE Program Offices' FY 2016 Congressional Budget Request |

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

    Department of Energy The US/SE Program Offices' FY 2016 Congressional Budget Request The US/SE Program Offices' FY 2016 Congressional Budget Request Figure 2.1: The US/SE Program Offices' FY 2016 Congressional Budget Request (SEP, page 19) Figure 2.1: The US/SE Program Offices' FY 2016 Congressional Budget Request (SEP, page 19) The Under Secretary for Science and Energy (US/SE) program offices lead the Department's engagement in transformative science, technology innovation, and market

  15. Elastic and surface energies: Two key parameters for CdSe quantum dot formation

    SciTech Connect (OSTI)

    Robin, Ivan-Christophe; Andre, Regis; Bougerol, Catherine; Aichele, Thomas; Tatarenko, Serge

    2006-06-05

    The two-dimensional-three-dimensional transition of a strained CdSe layer on (001) ZnSe induced by the use of amorphous selenium is studied. To precisely control the thickness of the CdSe layer, atomic layer epitaxy growth mode is used. Atomic force microscopy and reflection high-energy electron diffraction measurements reveal the formation of CdSe islands when 3 ML (monolayers) of CdSe, corresponding to the critical thickness, are deposited. When only 2.5 ML of CdSe are deposited another relaxation mechanism is observed, leading to the appearance of strong undulations on the surface. For a 3 ML thick CdSe layer, transmission electron microscopy images indicate that the formation of the islands occurs only after the amorphous selenium desorption.

  16. Method of synthesizing and growing copper-indium-diselenide (CuInSe.sub.2) crystals

    DOE Patents [OSTI]

    Ciszek, Theodore F.

    1987-01-01

    A process for preparing CuInSe.sub.2 crystals includes melting a sufficient quantity of B.sub.2 O.sub.3 along with stoichiometric quantities of Cu, In, and Se in a crucible in a high pressure atmosphere of inert gas to encapsulate the CuInSe.sub.2 melt and confine the Se to the crucible. Additional Se in the range of 1.8 to 2.2 percent over the stoichiometric quantity is preferred to make up for small amounts of Se lost in the process. The crystal is grown by inserting a seed crystal through the B.sub.2 O.sub.3 encapsulate into contact with the CuInSe.sub.2 melt and withdrawing the seed upwardly to grow the crystal thereon from the melt.

  17. Method of synthesizing and growing copper-indium-diselenide (CuInSe/sub 2/) crystals

    DOE Patents [OSTI]

    Ciszek, T.F.

    1984-11-29

    A process for preparing CuInSe/sub 2/ crystals includes melting a sufficient quantity of B/sub 2/O/sub 2/ along with stochiometric quantities of Cu, In, and Se in a crucible in a high-pressure atmosphere of inert gas to encapsulate the CuInSe/sub 2/ melt and confine the Se to the crucible. Additional Se in the range of 1.8 to 2.2% over the stochiometric quantity is preferred to make up for small amounts of Se lost in the process. The melt can then be cooled slowly to form the crystal as direct solidification, or the crystal can be grown by inserting a seed crystal through the B/sub 2/O/sub 3/ encapsulate into contact with the CuInSe/sub 2/ melt and withdrawing the seed upwardly to grow the crystal thereon from the melt.

  18. Electrical properties of In{sub 2}Se{sub 3} single crystals and photosensitivity of Al/In{sub 2}Se{sub 3} Schottky barriers

    SciTech Connect (OSTI)

    Bodnar, I. V.; Ilchuk, G. A.; Petrus', R. Yu.; Rud', V. Yu.; Rud', Yu. V.; Serginov, M.

    2009-09-15

    In{sub 2}Se{sub 3} single crystals {approx}40 mm long and 14 mm in diameter were grown by the Bridgman method. The composition of grown single crystals and their crystal structure were determined. The conductivity ({sigma}) and Hall constant (R) of grown single crystals were measured and the first Schottky barriers Al/n-In{sub 2}Se{sub 3} were fabricated. Rectification and photovoltaic effect were detected in the new structures. Based on the study of the photosensitivity spectra of Al/n-In{sub 2}Se{sub 3} structures, the nature of the interband transitions and band gap of In{sub 2}Se{sub 3} crystals were determined. It was concluded that the new structures can be applied to develop broadband photoconverters of optical radiation.

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

    SciTech Connect (OSTI)

    Dai, Qilin; Wang, Wenyong E-mail: jtang2@uwyo.edu; Tang, Jinke E-mail: jtang2@uwyo.edu; Sabio, Erwin M.

    2014-05-05

    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.

  20. PHaSE | U.S. DOE Office of Science (SC)

    Office of Science (SC) Website

    PHaSE Energy Frontier Research Centers (EFRCs) EFRCs Home Centers EFRC External Websites Research Science Highlights News & Events Publications History Contact BES Home Centers PHaSE Print Text Size: A A A FeedbackShare Page Polymer-Based Materials for Harvesting Solar Energy (PHaSE) Director(s): Thomas P. Russell and Paul M. Lahti Lead Institution: University of Massachusetts, Amherst Years: 2009-2014 Mission: To carry out fundamental photovoltaic-oriented research on the use of

  1. V-181: Oracle Java SE Critical Patch Update Advisory - June 2013 |

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

    Department of Energy 1: Oracle Java SE Critical Patch Update Advisory - June 2013 V-181: Oracle Java SE Critical Patch Update Advisory - June 2013 June 19, 2013 - 1:06am Addthis PROBLEM: Oracle Java SE Critical Patch Update Advisory - June 2013 PLATFORM: Version(s): 5.0 Update 45, 6 Update 45, 7 Update 21; and prior versions ABSTRACT: Multiple vulnerabilities were reported in Oracle Java. REFERENCE LINKS: Oracle Java SE Critical Patch Update June 2013 SecurityTracker Alert ID: 1028679

  2. The PHaSE Photovoltaic & Optical Spectroscopy Facility Facility Director: Dr. Volodimyr Duzhko

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

    ! 32 The PHaSE Photovoltaic & Optical Spectroscopy Facility Facility Director: Dr. Volodimyr Duzhko The central facilities of the DOE-supported Energy Frontier Research Center "Polymer-Based Materials for Harvesting Solar Energy" (PHaSE) are housed in 1305 sq ft of newly renovated space, Rooms B523 and B524 of the Silvio O. Conte National Center for Polymer Research. The renovation was carried out with EFRC PHaSE ARRA funding. These facilities provide the PHaSE members and external

  3. Flow of US/SE Program Funding to National Laboratories (FY 2014 Enacted) |

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

    Department of Energy Flow of US/SE Program Funding to National Laboratories (FY 2014 Enacted) Flow of US/SE Program Funding to National Laboratories (FY 2014 Enacted) Figure 4.2: Flow of US/SE Program Funding to National Laboratories—FY 2014 Enacted (SEP, page 157) Figure 4.2: Flow of US/SE Program Funding to National Laboratories-FY 2014 Enacted (SEP, page 157) This figure illustrates the flow of funding to each of 17 DOE National Laboratories from five of the six Under Secretary for

  4. A Novel and Functional Single Layer Sheet of ZnSe (Journal Article...

    Office of Scientific and Technical Information (OSTI)

    A Novel and Functional Single Layer Sheet of ZnSe Citation ... In this Communication, we report a novel singlelayer sheet ... Type: Accepted Manuscript Journal Name: ACS Applied ...

  5. SE HAN FINALIZADO LOS PREPARATIVOS PARA LA CONFERENCIA NACIONAL DE JUSTICIA MEDIOAMBIENTAL Y PROGRAMA DE FORMACIÓN 2013

    Broader source: Energy.gov [DOE]

    La National Environmental Justice Conference, Inc. (Conferencia de Justicia Medioambiental) se prepara para otro exitoso acontecimiento, ya que se aproxima la Conferencia Nacional de Justicia...

  6. Differences in chemical doping matter: Superconductivity in Ti1-xTaxSe2 but not in Ti1-xNbxSe2

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

    Luo, Huixia; Zhu, Yimei; Xie, Weiwei; Tao, Jing; Pletikosic, Ivo; Valla, Tonica; Sahasrabudhe, Girija S.; Osterhoudt, Gavin; Sutton, Eric; Burch, Kenneth S.; et al

    2016-02-21

    We report that 1T-TiSe2, an archetypical layered transition metal dichalcogenide, becomes superconducting when Ta is substituted for Ti but not when Nb is substituted for Ti. This is unexpected because Nb and Ta should be chemically equivalent electron donors. Superconductivity emerges near x = 0.02 for Ti1–xTaxSe2, while, for Ti1–xNbxSe2, no superconducting transitions are observed above 0.4 K. The equivalent chemical nature of the dopants is confirmed by X-ray photoelectron spectroscopy. ARPES and Raman scattering studies show similarities and differences between the two systems, but the fundamental reasons why the Nb and Ta dopants yield such different behavior are unknown.more » We present a comparison of the electronic phase diagrams of many electron-doped 1T-TiSe2 systems, showing that they behave quite differently, which may have broad implications in the search for new superconductors. Here, we propose that superconducting Ti0.8Ta0.2Se2 will be suitable for devices and other studies based on exfoliated crystal flakes.« less

  7. Development of a Low Cost Insulated Foil Substrate for Cu(InGaSe)2 Photovoltaics

    SciTech Connect (OSTI)

    ERTEN ESER

    2012-01-22

    The project validated the use of stainless steel flexible substrate coated with silicone-based resin dielectric, developed by Dow Corning Corporation, for Cu(InGa)Se2 based photovoltaics. The projects driving force was the high performance of Cu(InGa)Se2 based photovoltaics coupled with potential cost reduction that could be achieved with dielectric coated SS web substrate.

  8. Ligand-Mediated Modification of the Electronic Structure of CdSe Quantum Dots

    SciTech Connect (OSTI)

    Lee, Jonathan R.; Whitley, Heather D.; Meulenberg, Robert W.; Wolcott, Abraham; Zhang, Jin Z.; Prendergast, Peter; Lovingood, Derek D.; Strouse, Geoffrey F.; Ogitsu, Tadashi; Schwegler, Eric; Terminello, Louis J.; Van Buuren, Tony W.

    2012-05-18

    X-ray absorption spectroscopy and ab initio modeling of the experimental spectra have been used to investigate the effects of surface passivation on the unoccupied electronic states of CdSe quantum dots (QDs). Significant differences are observed in the unoccupied electronic structure of the CdSe QDs, which are shown to arise from variations in specific ligand-surface bonding interactions.

  9. Surface Plasmon Excitation via Au Nanoparticles in CdSe Semiconductor

    SciTech Connect (OSTI)

    Pradhan, A. K.; Konda, R. B.; Mundle, R.; Mustafa, H.; Bamiduro, O.; Roy, U. N.; Cui, Y.; Burger, A.

    2008-10-23

    We present experimental evidence for the large Raman and photoluminescence enhancement in CdSe semiconductor films grown on Si and glass substrates due to excitation of surface plasmon resonances in proximate gold metal nanoparticles deposited on the surface of CdSe film. Heterojunction diodes containing n-CdSe on p-Si semiconductor were fabricated and the surface of the diodes was in situ coated with Au nanoparticles using the ultra-high vacuum pulsed-laser deposition technique. A significant enhancement of the photocurrent was obtained in CdSe/p-Si containing Au nanoparticles on the surface compared to CdSe/p-Si due to the enhanced photo-absorption within the semiconductor by the phenomenon of surface plasmon resonance. These observations suggest a variety of approaches for improving the performance of devices such as photodetectors, photovoltaic, and related devices, including biosensors.

  10. Glass formation and the third harmonic generation of Cu{sub 2}Se–GeSe{sub 2}–As{sub 2}Se{sub 3} glasses

    SciTech Connect (OSTI)

    Reshak, A. H.; Klymovych, O. S.; Zmiy, O. F.; Myronchuk, G. L.; Zamuruyeva, O. V.; Alahmed, Z. A.; Chyský, J.; Bila, Jiri; Kamarudin, H.

    2014-10-14

    We have performed the investigation of the nonlinear optical properties namely the third harmonic generation (THG) of the glass-formation region in the Cu{sub 2}Se–GeSe{sub 2}–As{sub 2}Se{sub 3} system. The samples were synthesized by direct single-temperature method from high-purity elementary substances. We have found that the value of disorder parameter Δ depends on the composition of the glassy alloys. The measurements show that increasing the Cu{sub 2}Se concentration leads to increased slope of the absorption edge, which may be explained by the decrease of the height of random potential relief for the electrons in the tails of the state density which border the band edges. A very sharp increase in the THG at low temperature was observed. Significant enhancement in THG was obtained with decreasing the energy gap, which agreed well with the nonlinear optical susceptibilities obtained from other glasses.

  11. Inherent room temperature ferromagnetism and dopant dependent Raman studies of PbSe, Pb{sub 1−x}Cu{sub x}Se, and Pb{sub 1−x}Ni{sub x}Se

    SciTech Connect (OSTI)

    Gayner, Chhatrasal; Kar, Kamal K.

    2015-03-14

    Polycrystalline lead selenide (PbSe) doped with copper (Cu) and nickel (Ni) was prepared to understand its magnetic behaviour and Raman activity. The processing conditions, influence of dopants (magnetically active and non-active) and their respective compositions on the magnetic properties and Raman active mode were studied. A surprising/anomalous room temperature ferromagnetism (hysteresis loop) is noticed in bulk diamagnetic PbSe, which is found to be natural or inherent characteristic of material, and depends on the crystallite size, dopant, and developed strain due to dopant/defects. The magnetic susceptibility (−1.71 × 10{sup −4} emu/mol Oe) and saturated magnetic susceptibility (−2.74 × 10{sup −4} emu/mol Oe) are found to be higher than the earlier reported value (diamagnetic: −1.0 × 10{sup −4} emu/mol Oe) in bulk PbSe. With increase of Cu concentration (2% to 10%) in PbSe, the saturated magnetic susceptibility decreases from −1.22 × 10{sup −4} to −0.85 × 10{sup −4} emu/mol Oe. Whereas for Ni dopant, the saturated magnetic susceptibility increases to −2.96 × 10{sup −4} emu/mol Oe at 2% Ni doped PbSe. But it further decreases with dopant concentration. In these doped PbSe, the shifting of longitudinal (LO) phonon mode was also studied by the Raman spectroscopy. The shifting of LO mode is found to be dopant dependent, and the frequency shift of LO mode is associated with the induced strain that created by the dopants and vacancies. This asymmetry in LO phonon mode (peak shift and shape) may be due to the intraband electronic transition of dopants. The variation in magnetic susceptibility and Raman shifts are sensitive to crystallite size, nature of dopant, concentration of dopants, and induced strain due to dopants.

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

    SciTech Connect (OSTI)

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

    2011-11-17

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

  13. Structural phase transitions in Bi2Se3 under high pressure

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

    Yu, Zhenhai; Gu, Genda; Wang, Lin; Hu, Qingyang; Zhao, Jinggeng; Yan, Shuai; Yang, Ke; Sinogeikin, Stanislav; Mao, Ho -kwang

    2015-11-02

    Raman spectroscopy and angle dispersive X-ray diffraction (XRD) experiments of bismuth selenide (Bi2Se3) have been carried out to pressures of 35.6 and 81.2 GPa, respectively, to explore its pressure-induced phase transformation. The experiments indicate that a progressive structural evolution occurs from an ambient rhombohedra phase (Space group (SG): R-3m) to monoclinic phase (SG: C2/m) and eventually to a high pressure body-centered tetragonal phase (SG: I4/mmm). Evidenced by our XRD data up to 81.2 GPa, the Bi2Se3 crystallizes into body-centered tetragonal structures rather than the recently reported disordered body-centered cubic (BCC) phase. Furthermore, first principles theoretical calculations favor the viewpoint thatmore » the I4/mmm phase Bi2Se3 can be stabilized under high pressure (>30 GPa). Remarkably, the Raman spectra of Bi2Se3 from this work (two independent runs) are still Raman active up to ~35 GPa. Furthermore, it is worthy to note that the disordered BCC phase at 27.8 GPa is not observed here. The remarkable difference in atomic radii of Bi and Se in Bi2Se3 may explain why Bi2Se3 shows different structural behavior than isocompounds Bi2Te3 and Sb2Te3.« less

  14. An oleic acid-capped CdSe quantum-dot sensitized solar cell

    SciTech Connect (OSTI)

    Chen Jing; Song, J. L.; Deng, W. Q.; Sun, X. W.; Jiang, C. Y.; Lei, W.; Huang, J. H.; Liu, R. S.

    2009-04-13

    In this letter, we report an oleic acid (OA)-capped CdSe quantum-dot sensitized solar cell (QDSSC) with an improved performance. The TiO{sub 2}/OA-CdSe photoanode in a two-electrode device exhibited a photon-to-current conversion efficiency of 17.5% at 400 nm. At AM1.5G irradiation with 100 mW/cm{sup 2} light intensity, the QDSSCs based on OA-capped CdSe showed a power conversion efficiency of about 1%. The function of OA was to increase QD loading, extend the absorption range and possibly suppress the surface recombination.

  15. Optimal packing size of non-ligated CdSe nanoclusters for microstructure synthesis

    SciTech Connect (OSTI)

    Tefera, Anteneh G.; Mochena, Mogus D.; Johnson, Elijah; Dickerson, James

    2014-09-14

    Structural and electrostatic properties of nanoclusters of CdSe of diameter 1–2 nm are studied with first principle calculations to determine the optimal size for synthesizing microstructures. Based on robustness of the core structure, i.e., the retention of tetrahedral geometry, hexagonal ring structure, and overall wu{sup ¨}rtzite structure to surface relaxations, we conclude that nanoclusters of ~2 nm diameter are the best candidates to form a dense microstructure with minimal interstitial space. Se-terminated surfaces retain a zigzag structure as Se atoms are pulled out and Cd atoms are pulled in due to relaxation, therefore, are best suited for inter-nanocluster formations.

  16. Low-temperature ferromagnetic properties in Co-doped Ag{sub 2}Se nanoparticles

    SciTech Connect (OSTI)

    Yang, Fengxia E-mail: xia9020@hust.edu.cn; Yu, Gen; Han, Chong; Liu, Tingting; Zhang, Duanming; Xia, Zhengcai E-mail: xia9020@hust.edu.cn

    2014-01-06

    β-Ag{sub 2}Se is a topologically nontrivial insulator. The magnetic properties of Co-doped Ag{sub 2}Se nanoparticles with Co concentrations up to 40% were investigated. The cusp of zero-field-cooling magnetization curves and the low-temperature hysteresis loops were observed. With increasing concentration of Co{sup 2+} ions mainly substituting Ag{sub I} sites in the Ag{sub 2}Se structure, the resistivity, Curie temperature T{sub c}, and magnetization increased. At 10 T, a sharp drop of resistance near T{sub c} was detected due to Co dopants. The ferromagnetic behavior in Co-doped Ag{sub 2}Se might result from the intra-layer ferromagnetic coupling and surface spin. This magnetic semiconductor is a promising candidate in electronics and spintronics.

  17. Flow of US/SE Program Funding to National Laboratories (FY 2014 Enacted)

    Broader source: Energy.gov [DOE]

    This figure illustrates the flow of funding to each of 17 DOE National Laboratories from five of the six US/SE program offices. IE does not directly fund program work at the National Laboratories.

  18. Enhanced spontaneous emission of CdSe quantum dots in monolithic II-VI pillar microcavities

    SciTech Connect (OSTI)

    Lohmeyer, H.; Kruse, C.; Sebald, K.; Gutowski, J.; Hommel, D.

    2006-08-28

    The emission properties of CdSe/ZnSe quantum dots in ZnSe-based pillar microcavities are studied. All-epitaxial cavities made of ZnSSe and MgS/ZnCdSe superlattices with a single quantum-dot sheet embedded have been grown by molecular beam epitaxy. Pillar structures with diameters down to 500 nm have been realized by focused-ion-beam etching. A pronounced enhancement of the spontaneous emission rate of quantum dots coupling to the fundamental mode of the cavities is found as evidence for the Purcell effect. The enhancement by a factor of up to 3.8 depends systematically on the pillar diameter and thus on the Purcell factor of the individual pillars.

  19. Thickness-dependent coherent phonon frequency in ultrathin FeSe...

    Office of Scientific and Technical Information (OSTI)

    After optical excitation, we observe periodic modulations of the photoelectron spectrum as a function of pump-probe delay for 1-unit-cell, 3-unit-cell, and 60-unit-cell thick FeSe ...

  20. Phonon properties of BaFe?X? (X=S, Se) spin ladder compounds

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

    Popovicq, Z. V.; Petrovic, C.; Scepanovic, M.; Lazarevic, N.; Opacic, M.; Radonjic, M. M.; Tanaskovic, D.; Lei, Hechang

    2015-02-27

    We present the Raman scattering spectra of the S=2 spin ladder compounds BaFe?X? (X=S,Se) in a temperature range between 20 and 400 K. Although the crystal structures of these two compounds are both orthorhombic and very similar, they are not isostructural. The unit cell of BaFe?S? (BaFe?Se?) is base-centered Cmcm (primitive Pnma), giving 18 (36) modes to be observed in the Raman scattering experiment. We have detected almost all Raman active modes, predicted by factor group analysis, which can be observed from the cleavage planes of these compounds. Assignment of the observed Raman modes of BaFe?S(Se)? is supported by themorelattice dynamics calculations. The antiferromagnetic long-range spin ordering in BaFe?Se? below TN=255K leaves a fingerprint both in the A1g and B3g phonon mode linewidth and energy.less

  1. Thermoelectric properties of polycrystalline In4Se3 and In4Te3

    SciTech Connect (OSTI)

    Shi, Xun; Cho, Jung Y; Salvador, James R.; Yang, Jihui; Wang, Hsin

    2010-01-01

    High thermoelectric performance of a single crystal layered compound In{sub 4}Se{sub 3} was reported recently. We present here an electrical and thermal transport property study over a wide temperature range for polycrystalline samples of In{sub 4}Se{sub 3} and In{sub 4}Te{sub 3}. Our data demonstrate that these materials are lightly doped semiconductors, leading to large thermopower and resistivity. Very low thermal conductivity, below 1 W/m K, is observed. The power factors for In{sub 4}Se{sub 3} and In{sub 4}Te{sub 3} are much smaller when compared with state-of-the-art thermoelectric materials. This combined with the very low thermal conductivity results in the maximum ZT value of less than 0.6 at 700 K for In{sub 4}Se{sub 3}.

  2. Super-Poissonian Statistics of Photon Emission from Single CdSe...

    Office of Scientific and Technical Information (OSTI)

    Title: Super-Poissonian Statistics of Photon Emission from Single CdSe-CdS Core-Shell Nanocrystals Coupled to Metal Nanostructures Authors: Park, Young-Shin ; Ghosh, Yagnaseni ; ...

  3. Secretary Chu to Lead Delegation to SE4All, CEM Conferences in...

    Office of Environmental Management (EM)

    leading economies in London for the UN Sustainable Energy for All (SE4All) conference and ... Thursday, April 26, 2012 10:00 a.m. Joint Clean Energy Ministerial and Sustainable Energy ...

  4. Spin excitations in a model of FeSe with orbital ordering (Journal...

    Office of Scientific and Technical Information (OSTI)

    Spin excitations in a model of FeSe with orbital ordering Citation Details In-Document Search This content will become publicly available on December 27, 2016 Title: Spin ...

  5. Spin excitations in a model of FeSe with orbital ordering (Journal...

    Office of Scientific and Technical Information (OSTI)

    DOE PAGES Search Results Publisher's Accepted Manuscript: Spin excitations in a model of FeSe with orbital ordering This content will become publicly available on December 27, 2016 ...

  6. Unique Challenges Accompany Thick-Shell CdSe/nCdS (n > 10) Nanocrystal Synthesis

    SciTech Connect (OSTI)

    Guo, Y; Marchuk, K; Abraham, R; Sampat, S; Abraham, R.; Fang, N; Malko, AV; Vela, J

    2011-12-23

    Thick-shell CdSe/nCdS (n {ge} 10) nanocrystals were recently reported that show remarkably suppressed fluorescence intermittency or 'blinking' at the single-particle level as well as slow rates of Auger decay. Unfortunately, whereas CdSe/nCdS nanocrystal synthesis is well-developed up to n {le} 6 CdS monolayers (MLs), reproducible syntheses for n {ge} 10 MLs are less understood. Known procedures sometimes result in homogeneous CdS nucleation instead of heterogeneous, epitaxial CdS nucleation on CdSe, leading to broad and multimodal particle size distributions. Critically, obtained core/shell sizes are often below those desired. This article describes synthetic conditions specific to thick-shell growth (n {ge} 10 and n {ge} 20 MLs) on both small (sub2 nm) and large (>4.5 nm) CdSe cores. We find added secondary amine and low concentration of CdSe cores and molecular precursors give desired core/shell sizes. Amine-induced, partial etching of CdSe cores results in apparent shell-thicknesses slightly beyond those desired, especially for very-thick shells (n {ge} 20 MLs). Thermal ripening and fast precursor injection lead to undesired homogeneous CdS nucleation and incomplete shell growth. Core/shells derived from small CdSe (1.9 nm) have longer PL lifetimes and more pronounced blinking at single-particle level compared with those derived from large CdSe (4.7 nm). We expect our new synthetic approach will lead to a larger throughput of these materials, increasing their availability for fundamental studies and applications.

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

    SciTech Connect (OSTI)

    Singh, Neetu Kapoor, Avinashi; Kumar, Vinod; Mehra, R. M.

    2014-04-24

    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.

  8. Advanced Precursor Reaction Processing for Cu(InGa)(SeS)2 Solar Cells

    SciTech Connect (OSTI)

    Shafarman, William N.

    2015-10-12

    This project “Advanced Precursor Reaction Processing for Cu(InGa)(SeS)2 Solar Cells”, completed by the Institute of Energy Conversion (IEC) at the University of Delaware in collaboration with the Department of Chemical Engineering at the University of Florida, developed the fundamental understanding and technology to increase module efficiency and improve the manufacturability of Cu(InGa)(SeS)2 films using the precursor reaction approach currently being developed by a number of companies. Key results included: (1) development of a three-step H2Se/Ar/H2S reaction process to control Ga distribution through the film and minimizes back contact MoSe2 formation; (2) Ag-alloying to improve precursor homogeneity by avoiding In phase agglomeration, faster reaction and improved adhesion to allow wider reaction process window; (3) addition of Sb, Bi, and Te interlayers at the Mo/precursor junction to produce more uniform precursor morphology and improve adhesion with reduced void formation in reacted films; (4) a precursor structure containing Se and a reaction process to reduce processing time to 5 minutes and eliminate H2Se usage, thereby increasing throughput and reducing costs. All these results were supported by detailed characterization of the film growth, reaction pathways, thermodynamic assessment and device behavior.

  9. Ultrahigh photo-responsivity and detectivity in multilayer InSe nanosheets phototransistors with broadband response

    SciTech Connect (OSTI)

    Feng, Wei; Wu, Jing-Bin; Li, Xiaoli; Zheng, Wei; Zhou, Xin; Xiao, Kai; Cao, Wenwu; Yang, Bin; Idrobo, Juan-Carlos; Basile, Leonardo; Tian, Weiquan; Tan, PingHeng; Hu, PingAn

    2015-05-20

    In this paper, we demonstrate the strategies and principles for the performance improvement of layered semiconductor based photodetectors using multilayer indium selenide (InSe) as the model material. It is discovered that multiple reflection interference at the interfaces in the phototransistor device leads to a thickness-dependent photo-response, which provides a guideline to improve the performance of layered semiconductor based phototransistors. The responsivity and detectivity of InSe nanosheet phototransistor can be adjustable using applied gate voltage. Our InSe nanosheet phototransistor exhibits ultrahigh responsivity and detectivity. An ultrahigh external photo-responsivity of ~104 A W-1 can be achieved from broad spectra ranging from UV to near infrared wavelength using our InSe nanosheet photodetectors. The detectivity of multilayer InSe devices is ~1012 to 1013 Jones, which surpasses that of the currently exploited InGaAs photodetectors (1011 to 1012 Jones). Finally, this research shows that multilayer InSe nanosheets are promising materials for high performance photodetectors.

  10. Doping SrTiO3 supported FeSe by excess atoms and oxygen vacancies

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

    Shanavas, Kavungal Veedu; Singh, David J.

    2015-07-24

    Photoemission studies of FeSe monolayer films on SrTiO3 substrate have shown electronic structures that deviate from pristine FeSe, consistent with heavy electron doping. With the help of first-principles calculations we studied the effect of excess Fe and Se atoms on the monolayer and oxygen vacancies in the substrate in order to understand the reported Fermi surface in this system. We find that both excess Fe and Se atoms prefer the same adsorption site above the bottom Se atoms on the monolayer. The adsorbed Fe is strongly magnetic and contributes electrons to the monolayer, while excess Se hybridizes with the monolayermore » Fe-d states and partially opens a gap just above the Fermi energy. We also find that the two-dimensional electron gas generated by the oxygen vacancies is partly transferred to the monolayer and can potentially suppress the hole pockets around the Γ point. Furthermore, both O vacancies in the SrTiO3 substrate and excess Fe over the monolayer can provide high levels of electron doping.« less

  11. Recrystallization method to selenization of thin-film Cu(In,Ga)Se.sub.2 for semiconductor device applications

    DOE Patents [OSTI]

    Albin, David S.; Carapella, Jeffrey J.; Tuttle, John R.; Contreras, Miguel A.; Gabor, Andrew M.; Noufi, Rommel; Tennant, Andrew L.

    1995-07-25

    A process for fabricating slightly Cu-poor thin-films of Cu(In,Ga)Se.sub.2 on a substrate for semiconductor device applications includes the steps of forming initially a slightly Cu-rich, phase separated, mixture of Cu(In,Ga)Se.sub.2 :Cu.sub.x Se on the substrate in solid form followed by exposure of the Cu(In,Ga)Se.sub.2 :Cu.sub.x Se solid mixture to an overpressure of Se vapor and (In,Ga) vapor for deposition on the Cu(In,Ga)Se.sub.2 :Cu.sub.x Se solid mixture while simultaneously increasing the temperature of the solid mixture toward a recrystallization temperature (about 550.degree. C.) at which Cu(In,Ga)Se.sub.2 is solid and Cu.sub.x Se is liquid. The (In,Ga) flux is terminated while the Se overpressure flux and the recrystallization temperature are maintained to recrystallize the Cu.sub.x Se with the (In, Ga) that was deposited during the temperature transition and with the Se vapor to form the thin-film of slightly Cu-poor Cu.sub.x (In,Ga).sub.y Se.sub.z. The initial Cu-rich, phase separated large grain mixture of Cu(In,Ga)Se.sub.2 :Cu.sub.x Se can be made by sequentially depositing or co-depositing the metal precursors, Cu and (In, Ga), on the substrate at room temperature, ramping up the thin-film temperature in the presence of Se overpressure to a moderate anneal temperature (about 450.degree. C.) and holding that temperature and the Se overpressure for an annealing period. A nonselenizing, low temperature anneal at about 100.degree. C. can also be used to homogenize the precursors on the substrates before the selenizing, moderate temperature anneal.

  12. CdSe/ZnSe quantum dot with a single Mn{sup 2+} ionA new system for a single spin manipulation

    SciTech Connect (OSTI)

    Smole?ski, T.

    2015-03-21

    We present a magneto-optical study of individual self-assembled CdSe/ZnSe quantum dots doped with single Mn{sup 2+} ions. Properties of the studied dots are analyzed analogously to more explored system of Mn-doped CdTe/ZnTe dots. Characteristic sixfold splitting of the neutral exciton emission line as well as its evolution in the magnetic field are described using a spin Hamiltonian model. Dynamics of both exciton recombination and Mn{sup 2+} spin relaxation are extracted from a series of time-resolved experiments. Presence of a single dopant is shown not to affect the average excitonic lifetime measured for a number of nonmagnetic and Mn-doped dots. On the other hand, non-resonant pumping is demonstrated to depolarize the Mn{sup 2+} spin in a quantum dot placed in external magnetic field. This effect is utilized to determine the ion spin relaxation time in the dark.

  13. A comparative transport study of Bi{sub 2}Se{sub 3} and Bi{sub 2}Se{sub 3}/yttrium iron garnet

    SciTech Connect (OSTI)

    Jiang, Zilong; Tang, Chi; Shi, Jing; Katmis, Ferhat; Wei, Peng; Moodera, Jagadeesh S.

    2014-06-02

    Bilayers of 20 quintuple layer Bi{sub 2}Se{sub 3} on 30 nm thick yttrium iron garnet (YIG) have been grown with molecular beam epitaxy in conjunction with pulsed laser deposition. The presence of the ferri-magnetic insulator YIG causes additional scattering to the surface states of the Bi{sub 2}Se{sub 3} topological insulator layer, as indicated by the temperature dependence of the resistivity. From the two-channel analysis of the Hall data, we find that the surface contribution in the bilayer samples is greatly reduced. Furthermore, the weak antilocalization effect from the surface states is clearly suppressed due to the presence of the YIG layer.

  14. Non-H{sub 2}Se, ultra-thin CuInSe{sub 2} devices. Annual subcontract report, November 10, 1992--November 9, 1993

    SciTech Connect (OSTI)

    Delahoy, A.E.; Britt, J.; Faras, F.; Kiss, Z.

    1994-09-01

    This report describes advances made during Phase II (November 10, 1992-November 9, 1993) of a three-phase, cost-shared subcontract whose ultimate goal is the demonstration of thin film CuInSe{sub 2} photovoltaic modules prepared by methods adaptable to safe, high yield, high volume manufacturing. At the end of Phase I, EPV became one of the first groups to clear the 10% efficiency barrier for CIS cells prepared by non-H{sub 2}Se selenization. During Phase II a total area efficiency of 12.5% was achieved for a 1 cm{sup 2} cell. The key achievement of Phase II was the production of square foot CIS modules without the use of H{sub 2}Se. This is seen as a crucial step towards the commercialization of CIS. Using a novel interconnect technology, EPV delivered an 8.0% aperture area efficiency mini-module and a 6.2% aperture area efficiency 720 cm{sub 2} module to NREL. On the processing side, advances were made in precursor formation and the selenization profile, both of which contributed to higher quality CIS. The higher band gap quaternary chalcopyrite material CuIn(S{sub x}, Se{sub 1{minus}X}){sub 2} was prepared and 8% cells were fabricated using this material. Device analysis revealed a correlation between long wavelength quantum efficiency and the CIS Cu/In ratio. Temperature dependent studies highlighted the need for high V{sub OC} devices to minimize the impact of the voltage drop at operating temperature. Numerical modeling of module performance was performed in order to identify the correct ZnO sheet resistance for modules. Efforts in Phase III will focus on increase of module efficiency to 9-10%, initiation of an outdoor testing program, preparation of completely uniform CIS plates using second generation selenization equipment, and exploration of alternative precursors for CIS formation.

  15. Hidden Superlattice in Tl2(SC6H4S) and Tl2(SeC6H4Se) Solved from Powder X-ray Diffraction

    SciTech Connect (OSTI)

    K Stone; D Turner; M Singh; T Vaid; P Stephens

    2011-12-31

    The crystal structures of the isostructural title compounds poly[({mu}-benzene-1,4-dithiolato)dithallium], Tl{sub 2}(SC{sub 6}H{sub 4}S), and poly[({mu}-benzene-1,4-diselenolato)dithallium], Tl{sub 2}(SeC{sub 6}H{sub 4}Se), were solved by simulated annealing from high-resolution synchrotron X-ray powder diffraction. Rietveld refinements of an initial structure with one formula unit per triclinic cell gave satisfactory agreement with the data, but led to a structure with impossibly close non-bonded contacts. A disordered model was proposed to alleviate this problem, but an alternative supercell structure leads to slightly improved agreement with the data. The isostructural superlattice structures were confirmed for both compounds through additional data collection, with substantially better counting statistics, which revealed the presence of very weak superlattice peaks not previously seen. Overall, each structure contains Tl-S or Tl-Se two-dimensional networks, connected by phenylene bridges. The sulfur (or selenium) coordination sphere around each thallium is a highly distorted square pyramid or a 'see-saw' shape, depending upon how many Tl-S or Tl-Se interactions are considered to be bonds. In addition, the two compounds contain pairs of Tl{sup I} ions that interact through a closed-shell 'thallophilic' interaction: in the sulfur compound there are two inequivalent pairs of Tl atoms with Tl-Tl distances of 3.49 and 3.58 {angstrom}, while in the selenium compound those Tl-Tl interactions are at 3.54 and 3.63 {angstrom}.

  16. Persistent photoconductivity in two-dimensional Mo1-xW xSe2–MoSe2 van der Waals heterojunctions

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

    Puretzky, Alexander A.; Basile, Leonardo; Idrobo, Juan Carlos; Rouleau, Christopher M.; Geohegan, David B.; Xiao, Kai; Li, Xufan; Lin, Ming -Wei; Wang, Kei

    2016-02-16

    Van der Waals (vdW) heterojunctions consisting of vertically-stacked individual or multiple layers of two-dimensional (2D) layered semiconductors, especially the transition metal dichalcogenides (TMDs), are fascinating new artificial solids just nanometers-thin that promise novel optoelectronic functionalities due to the sensitivity of their electronic and optical properties to strong quantum confinement and interfacial interactions. Here, monolayers of n-type MoSe2 and p-type Mo1-xW xSe2–MoSe2 are grown by vapor transport methods, then transferred and stamped to form artificial vdW heterostructures with different interlayer orientations. Atomic-resolution Z-contrast electron microscopy and electron diffraction are used to characterize both the individual monolayers and the atomic registry betweenmore » layers in the bilayer vdW heterostructures. These measurements are compared with photoluminescence and low-frequency Raman spectroscopy, which indicates strong interlayer coupling in heterostructures. Remarkably, the heterojunctions exhibit an unprecedented photoconductivity effect that persists at room temperature for several days. This persistent photoconductivity is shown to be tunable by applying a gate bias that equilibrates the charge distribution. Furthermore, these measurements indicate that such ultrathin vdW heterojunctions can function as rewritable optoelectronic switches or memory elements under time-dependent photo-illumination, an effect which appears promising for new monolayer TMDs-based optoelectronic devices applications.« less

  17. Method of fabricating high-efficiency Cu(In,Ga)(Se,S){sub 2} thin films for solar cells

    DOE Patents [OSTI]

    Noufi, R.; Gabor, A.M.; Tuttle, J.R.; Tennant, A.L.; Contreras, M.A.; Albin, D.S.; Carapella, J.J.

    1995-08-15

    A process for producing a slightly Cu-poor thin film of Cu(In,Ga)(Se,S){sub 2} comprises depositing a first layer of (In,Ga){sub x} (Se,S){sub y} followed by depositing just enough Cu+(Se,S) or Cu{sub x} (Se,S) to produce the desired slightly Cu-poor material. In a variation, most, but not all, (about 90 to 99%) of the (In,Ga){sub x} (Se,S){sub y} is deposited first, followed by deposition of all the Cu+(Se,S) or Cu{sub x} (Se,S) to go near stoichiometric, possibly or even preferably slightly Cu-rich, and then in turn followed by deposition of the remainder (about 1 to 10%) of the (In,Ga){sub x} (Se,S){sub y} to end with a slightly Cu-poor composition. In yet another variation, a small portion (about 1 to 10%) of the (In,Ga){sub x} (Se,S){sub y} is first deposited as a seed layer, followed by deposition of all of the Cu+(Se,S) or Cu{sub x} (Se,S) to make a very Cu-rich mixture, and then followed deposition of the remainder of the (In,Ga){sub x} (Se,S){sub y} to go slightly Cu-poor in the final Cu(In,Ga)(Se,S){sub 2} thin film. 5 figs.

  18. Method of fabricating high-efficiency Cu(In,Ga)(SeS).sub.2 thin films for solar cells

    DOE Patents [OSTI]

    Noufi, Rommel; Gabor, Andrew M.; Tuttle, John R.; Tennant, Andrew L.; Contreras, Miguel A.; Albin, David S.; Carapella, Jeffrey J.

    1995-01-01

    A process for producing a slightly Cu-poor thin film of Cu(In,Ga)(Se,S).sub.2 comprises depositing a first layer of (In,Ga).sub.x (Se,S).sub.y followed by depositing just enough Cu+(Se,S) or Cu.sub.x (Se,S) to produce the desired slightly Cu-poor material. In a variation, most, but not all, (about 90 to 99%) of the (In,Ga).sub.x (Se,S).sub.y is deposited first, followed by deposition of all the Cu+(Se,S) or Cu.sub.x (Se,S) to go near stoichiometric, possibly or even preferably slightly Cu-rich, and then in turn followed by deposition of the remainder (about 1 to 10%) of the (In,Ga).sub.x (Se,S).sub.y to end with a slightly Cu-poor composition. In yet another variation, a small portion (about 1 to 10%) of the (In,Ga).sub.x (Se,S).sub.y is first deposited as a seed layer, followed by deposition of all of the Cu+(Se,S) or Cu.sub.x (Se,S) to make a very Cu-rich mixture, and then followed deposition of the remainder of the (In,Ga).sub.x (Se,S).sub.y to go slightly Cu-poor in the final Cu(In,Ga)(Se,S).sub.2 thin film.

  19. Novel Approaches to Wide Bandgap CuInSe2 Based Absorbers

    SciTech Connect (OSTI)

    William N. Shafarman

    2011-04-28

    This project targeted the development of high performance wide bandgap solar cells based on thin film alloys of CuInSe2 to relax constraints on module design and enable tandem solar cell structures. This addressed goals of the Solar Energy Technologies Program for Next Generation PV to develop technology needed for higher thin film module efficiency as a means to reduce costs. Specific objectives of the research project were: 1) to develop the processes and materials required to improve the performance of wide bandgap thin film solar cells based on alloys of CuInSe2, and 2) to provide the fundamental science and engineering basis for the material, electronic, and device properties required to effectively apply these processes and materials to commercial manufacture. CuInSe2-based photovoltaics have established the highest efficiencies of the thin film materials at both the cell and module scales and are actively being scaled up to commercialization. In the highest efficiency cells and modules, the optical bandgap, a function of the CuInSe2-based alloy composition, is relatively low compared to the optimum match to the solar spectrum. Wider bandgap alloys of CuInSe2 produce higher cell voltages which can improve module performance and enable the development of tandem solar cells to boost the overall efficiency. A focus for the project was alloying with silver to form (AgCu)(InGa)Se2 pentenary thin films deposited by elemental co-evaporation which gives the broadest range of control of composition and material properties. This alloy has a lower melting temperature than Ag-free, Cu-based chalcopyrite compounds, which may enable films to be formed with lower defect densities and the (AgCu)(InGa)Se2 films give improved material properties and better device performance with increasing bandgap. A comprehensive characterization of optical, structural, and electronic properties of (AgCu)(InGa)Se2 was completed over the complete compositional range 0 ≤ Ga/(In+Ga) ≤ 1 and

  20. Superconductivity in strong spin orbital coupling compound Sb2Se3

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

    Kong, P. P.; Sun, F.; Xing, L. Y.; Zhu, J.; Zhang, S. J.; Li, W. M.; Liu, Q. Q.; Wang, X. C.; Feng, S. M.; Yu, X. H.; et al

    2014-10-20

    Recently, A2B3 type strong spin orbital coupling compounds such as Bi2Te3, Bi2Se3 and Sb2Te3 were theoretically predicated to be topological insulators and demonstrated through experimental efforts. The counterpart compound Sb2Se3 on the other hand was found to be topological trivial, but theoretical studies indicated that the pressure might induce Sb2Se3 into a topological nontrivial state. We report on the discovery of superconductivity in Sb2Se3 single crystal induced via pressure. Our experiments indicated that Sb2Se3 became superconductive at high pressures above 10 GPa proceeded by a pressure induced insulator to metal like transition at ~3 GPa which should be related tomore » the topological quantum transition. The superconducting transition temperature (TC) increased to around 8.0 K with pressure up to 40 GPa while it keeps ambient structure. As a result, high pressure Raman revealed that new modes appeared around 10 GPa and 20 GPa, respectively, which correspond to occurrence of superconductivity and to the change of TC slop as the function of high pressure in conjunction with the evolutions of structural parameters at high pressures.« less

  1. Electronic structure, irreversibility line and magnetoresistance of Cu0.3Bi2Se3 superconductor

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

    Hemian, Yi; Gu, Genda; Chen, Chao -Yu; Sun, Xuan; Xie, Zhuo -Jin; Feng, Ya; Liang, Ai -Ji; Peng, Ying -Ying; He, Shao -Long; Zhao, Lin; et al

    2015-06-01

    CuxBi2Se3 is a superconductor that is a potential candidate for topological superconductors. We report our laser-based angle-resolved photoemission measurement on the electronic structure of the CuxBi2Se3 superconductor, and a detailed magneto-resistance measurement in both normal and superconducting states. We find that the topological surface state of the pristine Bi2Se3 topological insulator remains robust after the Cu-intercalation, while the Dirac cone location moves downward due to electron doping. Detailed measurements on the magnetic field-dependence of the resistance in the superconducting state establishes an irreversibility line and gives a value of the upper critical field at zero temperature of ~4000 Oe formore » the Cu0.3Bi2Se3 superconductor with a middle point Tc of 1.9K. The relation between the upper critical field Hc2 and temperature T is different from the usual scaling relation found in cuprates and in other kinds of superconductors. Small positive magneto-resistance is observed in Cu0.3Bi2Se3 superconductors up to room temperature. As a result, these observations provide useful information for further study of this possible candidate for topological superconductors.« less

  2. In-situ surface composition measurements of CuGaSe{sub 2} thin films

    SciTech Connect (OSTI)

    Fons, P.; Yamada, A.; Niki, S.; Oyanagi, H.

    1998-12-31

    Two CuGaSe{sub 2} films were grown by molecular beam epitaxy onto GaAs (001) substrates with varying Cu/Ga flux ratios under Se overpressure conditions. Growth was interrupted at predetermined times and the surface composition was measured using Auger electron spectroscopy after which growth was continued. After growth, the film composition was analyzed using voltage dependent electron microprobe spectroscopy. Film structure and morphology were also analyzed using x-ray diffraction and atomic force microscopy. The film with a Cu/Ga ratio larger than unity showed evidence of surface segregation of a second Cu-rich phase with a Cu/Se composition ratio slightly greater than unity. A second CuGaSe{sub 2} film with a Cu/Ga ratio of less than unity showed no change in surface composition with time and was also consistent with bulk composition measurements. Diffraction measurements indicated a high concentration of twins as well as the presence of domains with mixed c and a axes in the Ga-rich film. The Cu-rich films by contrast were single domain and had a narrower mosaics. High sensitivity scans along the [001] reciprocal axis did not exhibit any new peaks not attributable to either the substrate or the CuGaSe{sub 2} thin film.

  3. Hydrothermal model of the Momotombo geothermal system, Nicaragua

    SciTech Connect (OSTI)

    Verma, M.P.; Martinez, E.; Sanchez, M.; Miranda, K.; Gerardo, J.Y.; Araguas, L.

    1996-01-24

    The Momotombo geotherinal field is situated on the northern shore of Lake Managua at the foot of the active Momotombo volcano. The field has been producing electricity since 1983 and has an installed capacity of 70 MWe. The results of geological, geochemical and geophysical studies have been reported in various internal reports. The isotopic studies were funded by the International Atomic Energy Agency (IAEA), Vienna to develop a hydrothermal model of the geothermal system. The chemical and stable isotopic data (δ18O and δD) of the geothermal fluid suggest that the seasonal variation in the production characteristics of the wells is related to the rapid infiltration of local precipitation into the reservoir. The annual average composition of Na+, K+ and Mg2+ plotted on the Na- K-Mg triangular diagram presented by Giggenbach (1988) to identify the state of rock-water interaction in geothermal reservoirs, shows that the fluids of almost every well are shifting towards chemically immature water due to resenroir exploitation. This effect is prominent in wells Mt-2. Mt-12, Mt-22 and Mt-27. The local groundwaters including surface water from Lake Managua have much lower tritium concentrations than sonic of the geothermal well fluids, which have about 6 T.U. The high-tritium wells are located along a fault inferred froin a thermal anomaly. The tritium concentration is also higher in fluids from wells close to the lake. This could indicate that older local precipitation waters are stored in a deep layer within the lake and that they are infiltrating into the geothermal reservoir.

  4. Assessment of the SE2-ANL code using EBR-II temperature measurements

    SciTech Connect (OSTI)

    Yang, W.S.; Yacout, A.M.

    1995-01-01

    The SE2-ANL code is a modified version of the SUPERENERGY-2 code [1]. This code is used at Argonne National Laboratory (ANL) to compute the core-wide temperature profiles in Liquid Metal Reactor (LMR) cores. The accuracy of this code has recently been tested by comparing the predicted temperatures with measured values in the Experimental Breeder Reactor R (EBR-II). The detailed temperature distributions in two experimental subassemblies and the mixed mean subassembly outlet temperatures were used in this validation study. The SE2-ANL predictions were found to agree well with measured values. It was also found that SE2-ANL yields results with accuracy comparable to the more detailed COBRA-WC [2] calculations at much lower computational cost.

  5. Role of polycrystallinity in CdTe and CuInSe sub 2 photovoltaic cells

    SciTech Connect (OSTI)

    Sites, J.R. )

    1991-01-01

    The polycrystalline nature of thin-film CdTe and CuInSe{sub 2} solar cells continues to be a major factor in several individual losses that limit overall cell efficiency. This report describes progress in the quantitative separation of these losses, including both measurement and analysis procedures. It also applies these techniques to several individual cells to help document the overall progress with CdTe and CuInSe{sub 2} cells. Notably, CdTe cells from Photon Energy have reduced window photocurrent losses to 1 mA/Cm{sup 2}; those from the University of South Florida have achieved a maximum power voltage of 693 mV; and CuInSe{sub 2} cells from International Solar Electric Technology have shown a hole density as high as 7 {times} 10{sup 16} cm{sup {minus}3}, implying a significant reduction in compensation. 9 refs.

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

    SciTech Connect (OSTI)

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

    2009-02-15

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

  7. A Novel and Functional Single-Layer Sheet of ZnSe

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

    Zhou, Jia; Sumpter, Bobby G.; Kent, Paul R. C.; Huang, Jingsong

    2014-12-23

    In this Communication, we report a novel singlelayer sheet of ZnSe, with a three-atomic thickness, which demonstrates a strong quantum confinement effect by exhibiting a large blue shift of 2.0 eV in its absorption edge relative to the zinc blende (ZB) bulk phase. Theoretical optical absorbance shows that the largest absorption of this ultrathin single-layer sheet of ZnSe occurs at a wavelength similar to its four-atom-thick doublelayer counterpart but with higher photoabsorption efficiency, suggesting a superior behavior on incident photon-to-current conversion efficiency for solar water splitting, among other potential applications. The results presented herein for ZnSe may be generalized tomore » other group II-VI analogues.« less

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

    SciTech Connect (OSTI)

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

    2014-02-03

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

  9. Two-step growth of two-dimensional WSe2/MoSe2 heterostructures

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

    Gong, Yongji; Lei, Sidong; Lou, Jun; Liu, Zheng; Vajtai, Robert; Zhou, Wu; Ajayan, Pullikel M.; Ye, Gonglan; Li, Bo; He, Yongmin; et al

    2015-08-03

    Two dimensional (2D) materials have attracted great attention due to their unique properties and atomic thickness. Although various 2D materials have been successfully synthesized with different optical and electrical properties, a strategy for fabricating 2D heterostructures must be developed in order to construct more complicated devices for practical applications. Here we demonstrate for the first time a two-step chemical vapor deposition (CVD) method for growing transition-metal dichalcogenide (TMD) heterostructures, where MoSe2 was synthesized first and followed by an epitaxial growth of WSe2 on the edge and on the top surface of MoSe2. Compared to previously reported one-step growth methods, thismore » two-step growth has the capability of spatial and size control of each 2D component, leading to much larger (up to 169 μm) heterostructure size, and cross-contamination can be effectively minimized. Furthermore, this two-step growth produces well-defined 2H and 3R stacking in the WSe2/MoSe2 bilayer regions and much sharper in-plane interfaces than the previously reported MoSe2/WSe2 heterojunctions obtained from one-step growth methods. The resultant heterostructures with WSe2/MoSe2 bilayer and the exposed MoSe2 monolayer display rectification characteristics of a p-n junction, as revealed by optoelectronic tests, and an internal quantum efficiency of 91% when functioning as a photodetector. As a result, a photovoltaic effect without any external gates was observed, showing incident photon to converted electron (IPCE) efficiencies of approximately 0.12%, providing application potential in electronics and energy harvesting.« less

  10. Orbital alignment at the internal interface of arylthiol functionalized CdSe molecular hybrids

    SciTech Connect (OSTI)

    Li, Zhi; Schlaf, Rudy; Mazzio, Katherine A.; Okamoto, Ken; Luscombe, Christine K.

    2015-04-21

    Organic-inorganic nanoparticle molecular hybrid materials are interesting candidates for improving exciton separation in organic solar cells. The orbital alignment at the internal interface of cadmium selenide (ArS-CdSe) hybrid materials functionalized with covalently attached arylthiolate moieties was investigated through X-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). A physisorbed interface between arylthiol (ArSH) ligands and CdSe nanoparticles was also investigated for comparison. This interface was created via a multi-step thin film deposition procedure in-vacuo, where the surface was characterized after each experimental step. This enabled the direct comparison of ArSH/CdSe interfaces produced via physisorption and ArS-CdSe covalently attached hybrid materials, which rely on a chemical reaction for their synthesis. All material depositions were performed using an electrospray deposition, which enabled the direct injection of solution-originating molecular species into the vacuum system. This method allows XPS and UPS measurements to be performed immediately after deposition without exposure to the atmosphere. Transmission electron microscopy was used to determine the morphology and particle size of the deposited materials. Ultraviolet-visible spectroscopy was used to estimate the optical band gap of the CdSe nanoparticles and the HOMO-LUMO gap of the ArSH ligands. These experiments showed that hybridization via covalent bonds results in an orbital realignment at the ArSH/CdSe interface in comparison to the physisorbed interface. The orbital alignment within the hybrid caused a favorable electron injection barrier, which likely facilitates exciton-dissociation while preventing charge-recombination.

  11. Direct Observation of Energy-Gap Scaling Law in CdSe Quantum Dots with Positrons

    SciTech Connect (OSTI)

    Denison, Arthur Blanchard; Weber, M. H.; Lynn, K. G.; Barbiellini, B.; Sterne, P. A.

    2002-07-01

    CdSe quantum dot samples with sizes in the range of 1.8~6 nm in diameter were examined by positron annihilation spectroscopy. The results were compared to data obtained for single-crystal bulk CdSe. Evidence is provided that the positrons annihilate within the nanospheres. The annihilation line shape shows a smearing at the boundary of the Jones zone proportional to the widening of the band gap due to a reduction in the size of the quantum dots. The data confirm that the change in the band gap is inversely proportional to the square of the quantum dot diameter.

  12. Tuning thermoelectricity in a Bi2Se3 topological insulator via varied film thickness

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

    Guo, Minghua; Wang, Zhenyu; Xu, Yong; Huang, Huaqing; Zang, Yunyi; Liu, Chang; Duan, Wenhui; Gan, Zhongxue; Zhang, Shou-Cheng; He, Ke; et al

    2016-01-12

    We report thermoelectric transport studies on Bi2Se3 topological insulator thin films with varied thickness grown by molecular beam epitaxy. We find that the Seebeck coefficient and thermoelectric power factor decrease systematically with the reduction of film thickness. These experimental observations can be explained quantitatively by theoretical calculations based on realistic electronic band structure of the Bi2Se3 thin films. Lastly, this work illustrates the crucial role played by the topological surface states on the thermoelectric transport of topological insulators, and sheds new light on further improvement of their thermoelectric performance.

  13. Potential thermoelectric performance from optimization of hole-doped Bi2Se3

    SciTech Connect (OSTI)

    Parker, David S; Singh, David J

    2011-01-01

    We present an analysis of the potential thermoelectric performance of hole-doped Bi2Se3, which is commonly considered to show inferior room temperature performance when compared to Bi2Te3. We find that if the lattice thermal conductivity can be reduced by nanostructuring techniques (as have been applied to Bi2Te3) the material may show optimized ZT values of unity or more in the 300 - 500 K temperature range and thus be suitable for cooling and moderate temperature waste heat recovery and thermoelectric solar cell applications. Central to this conclusion are the larger band gap and the relatively heavier valence bands of Bi2Se3.

  14. Optical studies of carriers’ vertical transport in the alternately-strained ZnS{sub 0.4}Se{sub 0.6}/CdSe superlattice

    SciTech Connect (OSTI)

    Evropeytsev, E. A. Sorokin, S. V.; Gronin, S. V.; Sedova, I. V.; Klimko, G. V.; Ivanov, S. V.; Toropov, A. A.

    2015-03-15

    We present the results of theoretical modelling and experimental optical studies of the alternatively-strained CdSe/ZnS{sub y}Se{sub 1−y} (y = 0.4) superlattice (SL) with effective band-gap E{sub g}{sup eff} ∼ 2.580 eV and a thickness of ∼300 nm, which was grown by molecular-beam epitaxy on a GaAs substrate. The thicknesses and composition of the layers of the superlattice are determined on the basis of the SL minibands parameters calculated implying both full lattice matching of the SL as a whole to a GaAs substrate and high efficiency of photoexcited carriers transport along the growth axis. Photoluminescence studies of the transport properties of the structure (including a superlattice with one enlarged quantum well) show that the characteristic time of the diffusion of charge carriers at 300 K is shorter than the times defined by recombination processes. Such superlattices seem to be promising for the formation of a wide-gap photoactive region in a multijunction solar cell, which includes both III–V and II–VI compounds.

  15. Ordering mechanism of stacked CdSe/ZnS{sub x}Se{sub 1-x} quantum dots: A combined reciprocal-space and real-space approach

    SciTech Connect (OSTI)

    Schmidt, Th.; Roventa, E.; Clausen, T.; Flege, J. I.; Alexe, G.; Rosenauer, A.; Hommel, D.; Falta, J.; Bernstorff, S.; Kuebel, C.

    2005-11-15

    The vertical and lateral ordering of stacked CdSe quantum dot layers embedded in ZnS{sub x}Se{sub 1-x} has been investigated by means of grazing incidence small angle x-ray scattering and transmission electron microscopy. Different growth parameters have been varied in order to elucidate the mechanisms leading to quantum dot correlation. From the results obtained for different numbers of quantum dot layers, we conclude on a self-organized process which leads to increasing ordering for progressive stacking. The dependence on the spacer layer thickness indicates that strain induced by lattice mismatch drives the ordering process, which starts to break down for too thick spacer layers in a thickness range from 45 to 80 A. Typical quantum dot distances in a range from about 110 to 160 A have been found. A pronounced anisotropy of the quantum dot correlation has been observed, with the strongest ordering along the [110] direction. Since an increased ordering is found with increasing growth temperature, the formation of stacking faults as an additional mechanism for quantum dot alignment can be ruled out.

  16. Enhanced quality thin film Cu(In,Ga)Se.sub.2 for semiconductor device applications by vapor-phase recrystallization

    DOE Patents [OSTI]

    Tuttle, John R.; Contreras, Miguel A.; Noufi, Rommel; Albin, David S.

    1994-01-01

    Enhanced quality thin films of Cu.sub.w (In,Ga.sub.y)Se.sub.z for semiconductor device applications are fabricated by initially forming a Cu-rich, phase-separated compound mixture comprising Cu(In,Ga):Cu.sub.x Se on a substrate to form a large-grain precursor and then converting the excess Cu.sub.x Se to Cu(In,Ga)Se.sub.2 by exposing it to an activity of In and/or Ga, either in vapor In and/or Ga form or in solid (In,Ga).sub.y Se.sub.z. Alternatively, the conversion can be made by sequential deposition of In and/or Ga and Se onto the phase-separated precursor. The conversion process is preferably performed in the temperature range of about 300.degree.-600.degree. C., where the Cu(In,Ga)Se.sub.2 remains solid, while the excess Cu.sub.x Se is in a liquid flux. The characteristic of the resulting Cu.sub.w (In,Ga).sub.y Se.sub.z can be controlled by the temperature. Higher temperatures, such as 500.degree.-600.degree. C., result in a nearly stoichiometric Cu(In,Ga)Se.sub.2, whereas lower temperatures, such as 300.degree.-400.degree. C., result in a more Cu-poor compound, such as the Cu.sub.z (In,Ga).sub.4 Se.sub.7 phase.

  17. Enhanced quality thin film Cu(In,Ga)Se[sub 2] for semiconductor device applications by vapor-phase recrystallization

    DOE Patents [OSTI]

    Tuttle, J.R.; Contreras, M.A.; Noufi, R.; Albin, D.S.

    1994-10-18

    Enhanced quality thin films of Cu[sub w](In,Ga[sub y])Se[sub z] for semiconductor device applications are fabricated by initially forming a Cu-rich, phase-separated compound mixture comprising Cu(In,Ga):Cu[sub x]Se on a substrate to form a large-grain precursor and then converting the excess Cu[sub x]Se to Cu(In,Ga)Se[sub 2] by exposing it to an activity of In and/or Ga, either in vapor In and/or Ga form or in solid (In,Ga)[sub y]Se[sub z]. Alternatively, the conversion can be made by sequential deposition of In and/or Ga and Se onto the phase-separated precursor. The conversion process is preferably performed in the temperature range of about 300--600 C, where the Cu(In,Ga)Se[sub 2] remains solid, while the excess Cu[sub x]Se is in a liquid flux. The characteristic of the resulting Cu[sub w](In,Ga)[sub y]Se[sub z] can be controlled by the temperature. Higher temperatures, such as 500--600 C, result in a nearly stoichiometric Cu(In,Ga)Se[sub 2], whereas lower temperatures, such as 300--400 C, result in a more Cu-poor compound, such as the Cu[sub z](In,Ga)[sub 4]Se[sub 7] phase. 7 figs.

  18. Low-temperature photoluminescence analysis of CdTeSe crystals for radiation-detector applications

    SciTech Connect (OSTI)

    YANG G.; Roy, U. N.; Bolotnikov, A. E.; Cui, Y.; Camarda, G.S.; Hossain, A.; and James, R. B.

    2015-10-05

    Goal: Understanding the changes of material defects in CdTeSe following annealing. Experimental results and discussions: Infrared (IR) transmission microscopy; current-voltage measurements (Highlight: Improvement of resistivity of un-doped crystals after annealing); low-temperature photoluminescence (PL) spectrum of as-grown and annealed samples.

  19. Molecular beam epitaxial growth of Bi{sub 2}Se{sub 3} nanowires and nanoflakes

    SciTech Connect (OSTI)

    Knebl, G. M. Gessler, J. R.; Kamp, M.; Höfling, S.

    2014-09-29

    Topological Insulators are in focus of immense research efforts and rapid scientific progress is obtained in that field. Bi{sub 2}Se{sub 3} has proven to be a topological insulator material that provides a large band gap and a band structure with a single Dirac cone at the Γ-point. This makes Bi{sub 2}Se{sub 3} one of the most promising three dimensional topological insulator materials. While Bi{sub 2}Se{sub 3} nanowires and nanoflakes so far were fabricated with different methods and for different purposes, we here present the first Bi{sub 2}Se{sub 3} nanowires as well as nanoflakes grown by molecular beam epitaxy. The nanostructures were nucleated on pretreated, silicon (100) wafers. Altering the growth conditions nanoflakes could be fabricated instead of nanowires; both with high crystalline quality, confirmed by scanning electron microscopy as well as transmission electron microscopy. These nanostructures have promise for spintronic devices and Majorana fermion observation in contact to superconductor materials.

  20. Stability of S and Se induced reconstructions on GaP(001)(21) surface

    SciTech Connect (OSTI)

    Li , D. F.; Guo, Zhi C.; Xiao, Hai Yan; Zu, Xiaotao T.; Gao, Fei

    2010-10-15

    The structural and electronic properties of S- and Se- passivated GaP(001)(21) surfaces were studied using first-principles simulations. Our calculations showed that the most stable structure consists of a single chalcogen atom (S or Se) in the first crystal layer, which is bonded to two Ga atoms of the second layer, and the third P layer replaced by chalcogen atoms, similar to the passivation of GaAs(001)(21) surface by chalcogen atoms. The structural parameters were determined and the surface band characters and the local density of states were also analyzed. The results showed that the preferable structure has no surface states in the bulk band gap, but the energy band gaps of the S- and Se-adsorbed GaP(001) surfaces are 1.83eV and 1.63eV, respectively. The passivation effects for the S- and Se-adsorbed surfaces are similar to each other.

  1. T-558: Oracle Java SE and Java for Business Critical Patch Update Advisory- February 2011

    Broader source: Energy.gov [DOE]

    This Critical Patch Update contains 21 new security fixes for Oracle Java SE and Java for Business. 19 of these vulnerabilities may be remotely exploitable without authentication, i.e., may be exploited over a network without the need for a username and password.

  2. T-641: Oracle Java SE Critical Patch Update Advisory- June 2011

    Office of Energy Efficiency and Renewable Energy (EERE)

    This Critical Patch Update contains 17 new security fixes for Oracle Java SE - 5 apply to client and server deployments of Java SE, 11 apply to client deployments of Java SE only, and 1 applies to server deployments of Java SE only. All of these vulnerabilities may be remotely exploitable without authentication, i.e., may be exploited over a network without the need for a username and password. Oracle CVSS scores assume that a user running a Java applet or Java Web Start application has administrator privileges (typical on Windows). Where the user does not run with administrator privileges (typical on Solaris and Linux), the corresponding CVSS impact scores for Confidentiality, Integrity, and Availability are "Partial" instead of "Complete", and the corresponding CVSS Base score is 7.5 instead of 10 respectively. For issues in Deployment, fixes are only made available for JDK and JRE 6. Users should use the Java Web Start in JRE 6 and the new Java Plug-in introduced in 6 Update 10. CVE-2011-0862, CVE-2011-0873, CVE-2011-0815, CVE-2011-0817, CVE-2011-0863, CVE-2011-0864, CVE-2011-0802, CVE-2011-0814, CVE-2011-0871, CVE-2011-0786, CVE-2011-0788, CVE-2011-0866, CVE-2011-0868, CVE-2011-0872, CVE-2011-0867, CVE-2011-0869, and CVE-2011-0865

  3. Manufacturable CuIn(Ga)Se{sub 2}-based solar cells via development of co-sputtered CuInSe{sub 2} absorber layers

    SciTech Connect (OSTI)

    Dr. Ingrid Eisgruber

    1999-03-20

    Yield and reproducibility remain issues in CuIn(Ga)Se{sub 2} (CIGS) photovoltaic module fabrication. While small-area cells (<1 cm{sup 2}) over 18% efficient have been reported, the best large-area manufactured devices (>1 ft{sup 2}) are 11% efficient with about 60% yield. If improvements in large-area manufacturing can accomplish 15% efficiency and 90% yield, the result is a doubling in throughput leading to a reduction in cost per watt of over 50%. The challenge now facing the photovoltaics industry is to bring the efficiencies of small-area cells and large-area industrial modules closer together and to raise manufacturing yields.

  4. Photoluminescence studies of type-II CdSe/CdTe superlattices

    SciTech Connect (OSTI)

    Li Jingjing; Johnson, Shane R.; Wang Shumin; Ding Ding; Ning Cunzheng; Zhang Yonghang; Yin Leijun; Skromme, B. J.; Liu Xinyu; Furdyna, Jacek K.

    2012-08-06

    CdSe/CdTe type-II superlattices grown on GaSb substrates by molecular beam epitaxy are studied using time-resolved and steady-state photoluminescence (PL) spectroscopy at 10 K. The relatively long carrier lifetime of 188 ns observed in time-resolved PL measurements shows good material quality. The steady-state PL peak position exhibits a blue shift with increasing excess carrier concentration. Self-consistent solutions of the Schroedinger and Poisson equations show that this effect can be explained by band bending as a result of the spatial separation of electrons and holes, which is critical confirmation of a strong type-II band edge alignment between CdSe and CdTe.

  5. CdS/PbSe heterojunction for high temperature mid-infrared photovoltaic detector applications

    SciTech Connect (OSTI)

    Weng, Binbin E-mail: shi@ou.edu; Qiu, Jijun; Zhao, Lihua; Chang, Caleb; Shi, Zhisheng E-mail: shi@ou.edu

    2014-03-24

    n-CdS/p-PbSe heterojunction is investigated. A thin CdS film is deposited by chemical bath deposition on top of epitaxial PbSe film by molecular beam epitaxy on Silicon. Current-voltage measurements demonstrate very good junction characteristics with rectifying ratio of ∼178 and ideality factor of 1.79 at 300 K. Detectors made with such structure exhibit mid-infrared spectral photoresponse at room temperature. The peak responsivity R{sub λ} and specific detectivity D{sup *} are 0.055 A/W and 5.482 × 10{sup 8} cm·Hz{sup 1/2}/W at λ = 4.7 μm under zero-bias photovoltaic mode. Temperature-dependent photoresponse measurements show abnormal intensity variation below ∼200 K. Possible reasons for this phenomenon are also discussed.

  6. Record Seebeck coefficient and extremely low thermal conductivity in nanostructured SnSe

    SciTech Connect (OSTI)

    Serrano-Sánchez, F.; Gharsallah, M.; Nemes, N. M.; Mompean, F. J.; Martínez, J. L.; Alonso, J. A.

    2015-02-23

    SnSe has been prepared by arc-melting, as mechanically robust pellets, consisting of highly oriented polycrystals. This material has been characterized by neutron powder diffraction (NPD), scanning electron microscopy, and transport measurements. A microscopic analysis from NPD data demonstrates a quite perfect stoichiometry SnSe{sub 0.98(2)} and a fair amount of anharmonicity of the chemical bonds. The Seebeck coefficient reaches a record maximum value of 668 μV K{sup −1} at 380 K; simultaneously, this highly oriented sample exhibits an extremely low thermal conductivity lower than 0.1 W m{sup −1} K{sup −1} around room temperature, which are two of the main ingredients of good thermoelectric materials. These excellent features exceed the reported values for this semiconducting compound in single crystalline form in the moderate-temperatures region and highlight its possibilities as a potential thermoelectric material.

  7. Algorithmically scalable block preconditioner for fully implicit shallow-water equations in CAM-SE

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

    Lott, P. Aaron; Woodward, Carol S.; Evans, Katherine J.

    2014-10-19

    Performing accurate and efficient numerical simulation of global atmospheric climate models is challenging due to the disparate length and time scales over which physical processes interact. Implicit solvers enable the physical system to be integrated with a time step commensurate with processes being studied. The dominant cost of an implicit time step is the ancillary linear system solves, so we have developed a preconditioner aimed at improving the efficiency of these linear system solves. Our preconditioner is based on an approximate block factorization of the linearized shallow-water equations and has been implemented within the spectral element dynamical core within themore » Community Atmospheric Model (CAM-SE). Furthermore, in this paper we discuss the development and scalability of the preconditioner for a suite of test cases with the implicit shallow-water solver within CAM-SE.« less

  8. Low-cost CuInSe[sub 2] submodule development

    SciTech Connect (OSTI)

    Basol, B.M.; Kapur, V.K.; Halani, A.; Leidholm, C. )

    1992-10-01

    Aim of this project is development and demonstration of processing steps necessary for fabrication of high efficiency CuInSe[sub 2] solar cells and sub-modules by the two-stage technique (also called the selenization method.) During this period, we have optimized the processing parameters of this method and demonstrated CuInSe[sub 2]/CdS/ZnO devices with a 1[endash]4 cm[sup 2] area and up to 12.4% active area efficiency. We have also developed a novel approach for the preparation of Cu/In precursors that improved the stoichiometric and morphological uniformity in these films. We have developed processing steps and tooling for handling up to 1 ft[sup 2] size substrates and as a result of these efforts demonstrated our first monolithically integrated sub-module of 1 ft[sup 2] area. 16 figs, 1 tab, 15 refs.

  9. Algorithmically scalable block preconditioner for fully implicit shallow-water equations in CAM-SE

    SciTech Connect (OSTI)

    Lott, P. Aaron; Woodward, Carol S.; Evans, Katherine J.

    2014-10-19

    Performing accurate and efficient numerical simulation of global atmospheric climate models is challenging due to the disparate length and time scales over which physical processes interact. Implicit solvers enable the physical system to be integrated with a time step commensurate with processes being studied. The dominant cost of an implicit time step is the ancillary linear system solves, so we have developed a preconditioner aimed at improving the efficiency of these linear system solves. Our preconditioner is based on an approximate block factorization of the linearized shallow-water equations and has been implemented within the spectral element dynamical core within the Community Atmospheric Model (CAM-SE). Furthermore, in this paper we discuss the development and scalability of the preconditioner for a suite of test cases with the implicit shallow-water solver within CAM-SE.

  10. A WSe{sub 2}/MoSe{sub 2} heterostructure photovoltaic device

    SciTech Connect (OSTI)

    Flöry, Nikolaus; Jain, Achint; Bharadwaj, Palash; Parzefall, Markus; Novotny, Lukas; Taniguchi, Takashi; Watanabe, Kenji

    2015-09-21

    We report on the photovoltaic effect in a WSe{sub 2}/MoSe{sub 2} heterojunction, demonstrating gate tunable current rectification with on/off ratios of over 10{sup 4}. Spatially resolved photocurrent maps show the photovoltaic effect to originate from the entire overlap region. Compared to WSe{sub 2}/MoS{sub 2} heterostructures, our devices perform better at long wavelengths and yield higher quantum efficiencies, in agreement with Shockley-Queisser theory.

  11. Barrier to Trap Filling CuIn1-xGaxSe2: Preprint

    SciTech Connect (OSTI)

    Young, D. L.; Ramanathan, K.; Contreras, M.; Abushama, J.; Crandall, R. S.

    2003-04-01

    Voltage pulses of variable length were applied to CuIn1-xGaxSe2/CdS (0< x< 1) junction solar cells. The resulting transient capacitance emission signal was recorded for several minutes. The amplitude of the capacitance emission signal increased linearly with the log of pulse time. These data do not follow the standard model for trap capture and emission of carriers. Instead they follow a simple electrostatic model based on electrostatic charging of traps.

  12. Radiative lifetimes of zincblende CdSe/CdS quantum dots

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

    Gong, Ke; Martin, James E.; Shea-Rohwer, Lauren E.; Lu, Ping; Kelley, David F.

    2015-01-02

    Recent synthetic advances have made available very monodisperse zincblende CdSe/CdS quantum dots having near-unity photoluminescence quantum yields. Because of the absence of nonradiative decay pathways, accurate values of the radiative lifetimes can be obtained from time-resolved PL measurements. Radiative lifetimes can also be obtained from the Einstein relations, using the static absorption spectra and the relative thermal populations in the angular momentum sublevels. We found that one of the inputs into these calculations is the shell thickness, and it is useful to be able to determine shell thickness from spectroscopic measurements. We use an empirically corrected effective mass model tomore » produce a “map” of exciton wavelength as a function of core size and shell thickness. These calculations use an elastic continuum model and the known lattice and elastic constants to include the effect of lattice strain on the band gap energy. The map is in agreement with the known CdSe sizing curve and with the shell thicknesses of zincblende core/shell particles obtained from TEM images. Furthermore, if selenium–sulfur diffusion is included and lattice strain is omitted from the calculation then the resulting map is appropriate for wurtzite CdSe/CdS quantum dots synthesized at high temperatures, and this map is very similar to one previously reported (J. Am. Chem. Soc. 2009, 131, 14299). Radiative lifetimes determined from time-resolved measurements are compared to values obtained from the Einstein relations, and found to be in excellent agreement. For a specific core size (2.64 nm diameter, in the present case), radiative lifetimes are found to decrease with increasing shell thickness. Thus, this is similar to the size dependence of one-component CdSe quantum dots and in contrast to the size dependence in type-II quantum dots.« less

  13. Radiative lifetimes of zincblende CdSe/CdS quantum dots

    SciTech Connect (OSTI)

    Gong, Ke; Martin, James E.; Shea-Rohwer, Lauren E.; Lu, Ping; Kelley, David F.

    2015-01-02

    Recent synthetic advances have made available very monodisperse zincblende CdSe/CdS quantum dots having near-unity photoluminescence quantum yields. Because of the absence of nonradiative decay pathways, accurate values of the radiative lifetimes can be obtained from time-resolved PL measurements. Radiative lifetimes can also be obtained from the Einstein relations, using the static absorption spectra and the relative thermal populations in the angular momentum sublevels. We found that one of the inputs into these calculations is the shell thickness, and it is useful to be able to determine shell thickness from spectroscopic measurements. We use an empirically corrected effective mass model to produce a “map” of exciton wavelength as a function of core size and shell thickness. These calculations use an elastic continuum model and the known lattice and elastic constants to include the effect of lattice strain on the band gap energy. The map is in agreement with the known CdSe sizing curve and with the shell thicknesses of zincblende core/shell particles obtained from TEM images. Furthermore, if selenium–sulfur diffusion is included and lattice strain is omitted from the calculation then the resulting map is appropriate for wurtzite CdSe/CdS quantum dots synthesized at high temperatures, and this map is very similar to one previously reported (J. Am. Chem. Soc. 2009, 131, 14299). Radiative lifetimes determined from time-resolved measurements are compared to values obtained from the Einstein relations, and found to be in excellent agreement. For a specific core size (2.64 nm diameter, in the present case), radiative lifetimes are found to decrease with increasing shell thickness. Thus, this is similar to the size dependence of one-component CdSe quantum dots and in contrast to the size dependence in type-II quantum dots.

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

    SciTech Connect (OSTI)

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

    2014-11-17

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

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

    SciTech Connect (OSTI)

    Hines, Douglas A.; Becker, Matthew A.; Kamat, Prashant V.

    2012-11-14

    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.

  16. Cr-doped TiSe2 - A layered dichalcogenide spin glass

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

    Luo, Huixia; Tao, Jing; Krizan, Jason W.; Seibel, Elizabeth M.; Xie, Weiwei; Sahasrabudhe, Girija S.; Bergman, Susanna L.; Phelan, Brendan F.; Wang, Zhen; Zhang, Jiandi; et al

    2015-09-17

    We report the magnetic characterization of the Cr-doped layered dichalcogenide TiSe2. The temperature dependent magnetic susceptibilities are typical of those seen in geometrically frustrated insulating antiferromagnets. The Cr moment is close to the spin-only value, and the Curie–Weiss temperatures (θcw) are between –90 and –230 K. Freezing of the spin system, which is glassy, characterized by peaks in the ac and dc susceptibility and specific heat, does not occur until below T/θcw = 0.05. The CDW transition seen in the resistivity for pure TiSe2 is still present for 3% Cr substitution but is absent by 10% substitution, above which themore » materials are metallic and p-type. Structural refinements, magnetic characterization, and chemical considerations indicate that the materials are of the type Ti1–xCrxSe2-x/2 for 0 ≤ x ≤ 0.6.« less

  17. Novel thin-film CuInSe sub 2 fabrication

    SciTech Connect (OSTI)

    Mooney, G.D.; Hermann, A.M. )

    1992-03-01

    This report describes research in Rapid Thermal Processing (RTP), a process that allows the formation of CuInSe{sub 2} without the use of H{sub 2}Se. RTP is a well-established method of rapidly achieving temperatures necessary to melt and recrystallize materials such as Si and and silicides. RTP processes can rapidly and uniformly heat large surface areas to hundreds of degrees Celsius. RTP is the most promising method of rapid recrystallization studied to date, being readily scalable from the research to the production level. The approach to the experiment was divided into two sections: (1) fabricating the precursor film and (2) processing the precursor film. The objective of the first phase of the work was to fabricate the thin films by RTP, then fully characterize them, to demonstrate the viability of the process as a method by which to make device-quality CuInSe{sub 2}. The second phase was to demonstrate that material made by this method could be used to make an active photovoltaic device. 24 refs.

  18. Cr-doped TiSe2 - A layered dichalcogenide spin glass

    SciTech Connect (OSTI)

    Luo, Huixia; Tao, Jing; Krizan, Jason W.; Seibel, Elizabeth M.; Xie, Weiwei; Sahasrabudhe, Girija S.; Bergman, Susanna L.; Phelan, Brendan F.; Wang, Zhen; Zhang, Jiandi; Cava, R. J.

    2015-09-17

    We report the magnetic characterization of the Cr-doped layered dichalcogenide TiSe2. The temperature dependent magnetic susceptibilities are typical of those seen in geometrically frustrated insulating antiferromagnets. The Cr moment is close to the spin-only value, and the Curie–Weiss temperatures (θcw) are between –90 and –230 K. Freezing of the spin system, which is glassy, characterized by peaks in the ac and dc susceptibility and specific heat, does not occur until below T/θcw = 0.05. The CDW transition seen in the resistivity for pure TiSe2 is still present for 3% Cr substitution but is absent by 10% substitution, above which the materials are metallic and p-type. Structural refinements, magnetic characterization, and chemical considerations indicate that the materials are of the type Ti1–xCrxSe2-x/2 for 0 ≤ x ≤ 0.6.

  19. High Compositional Homogeneity of CdTexSe1-x Crystals Grown by the Bridgman Method

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

    Roy, U. N.; Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; Hossain, A.; Lee, K.; Lee, W.; Tappero, R.; Yang, G.; Gul, R.; et al

    2015-02-03

    We obtained high-quality CdTexSe1-x (CdTeSe) crystals from ingots grown by the vertical Bridgman technique. The compositional uniformity of the ingots was evaluated by X-ray fluorescence at BNL’s National Synchrotron Light Source X27A beam line. The resulting compositional homogeneity was highly uniform throughout the ingot, and the effective segregation coefficient of Se was ~1.0. This uniformity offers potential opportunity to enhance the yield of the materials for both infrared substrate and radiation-detector applications, so greatly lowering the cost of production and also offering us the prospect to grow large-diameter ingots for use as large-area substrates and for producing higher efficiency gamma-raymore » detectors. The concentration of secondary phases was found to be much lower, by eight- to ten fold compared to that of conventional CdxZn1-xTe (CdZnTe or CZT).« less

  20. Investigation of Fe:ZnSe laser in pulsed and repetitively pulsed regimes

    SciTech Connect (OSTI)

    Velikanov, S D; Zaretskiy, N A; Zotov, E A; Maneshkin, A A; Chuvatkin, R S; Yutkin, I M; Kozlovsky, V I; Korostelin, Yu V; Krokhin, O N; Podmar'kov, Yu P; Savinova, S A; Skasyrsky, Ya K; Frolov, M P

    2015-01-31

    The characteristics of a Fe:ZnSe laser pumped by a single-pulse free-running Er : YAG laser and a repetitively pulsed HF laser are presented. An output energy of 4.9 J is achieved in the case of liquid-nitrogen cooling of the Fe{sup 2+}:ZnSe active laser element longitudinally pumped by an Er:YAG laser with a pulse duration of 1 ms and an energy up to 15 J. The laser efficiency with respect to the absorbed energy is 47%. The output pulse energy at room temperature is 53 mJ. The decrease in the output energy is explained by a strong temperature dependence of the upper laser level lifetime and by pulsed heating of the active element. The temperature dependence of the upper laser level lifetime is used to determine the pump parameters needed to achieve high pulse energies at room temperature. Stable repetitively-pulsed operation of the Fe{sup 2+}:ZnSe laser at room temperature with an average power of 2.4 W and a maximum pulse energy of 14 mJ is achieved upon pumping by a 1-s train of 100-ns HF laser pulses with a repetition rate of 200 Hz. (lasers)

  1. Local-moment magnetism in superconducting FeTe0.35Se0.65 as seen...

    Office of Scientific and Technical Information (OSTI)

    Local-moment magnetism in superconducting FeTe0.35Se0.65 as seen via inelastic neutron scattering Prev Next Title: Local-moment magnetism in superconducting FeTe0.35Se0.65 as ...

  2. Study of optical and structural properties of CdSe quantum dot embedded in PVA polymer matrix

    SciTech Connect (OSTI)

    Tyagi, Chetna Sharma, Ambika

    2015-08-28

    To enhance the properties and applicability of devices it is essential to incorporate semiconductor nanoparticles into polymer matrix. This introduces a new branch of science which includes device fabrications such as gas sensors, nonlinear optics, catalysis etc. Herein, we have synthesized CdSe/PVA nanocomposite (NC) material using wet chemical synthesis technique. The XRD studies revealed the formation of crystalline structure of CdSe nanoparticles (NP’s) and PVA NC’s with an average size of 100 nm and 5 nm respectively. Energy band gap is determined using UV-VIS Spectroscopy. A red shift in the absorption edge of CdSe/PVA NC is observed with respect to CdSe Np’s, The photoluminescence spectra also show red shift for CdSe/PVA NC as compared to CdSe NP’s Thus the use of CdSe/PVA for solar cell application would be more preferable than CdSe NP’s.

  3. Synthesis of monodispersed CdSe nanocrystals in poly(styrene-alt-maleic anhydride) at room temperature

    SciTech Connect (OSTI)

    Liu, S.H.; Qian, X.F.; Yuan, J.Y.; Yin, J.; He, R.; Zhu, Z.K

    2003-07-14

    Nanocomposite of CdSe/poly(styrene-alt-maleic anhydride) (PSM) was successfully prepared via an in situ reaction process at room temperature and ambient pressure. Transmission electron microscopy (TEM) analysis revealed that CdSe nanoparticles with a small size and narrow size distribution were obtained. The obtained nanocomposite was also characterized by FT-IR, XRD, ultraviolet-visible, and fluorescence spectroscopy.

  4. X-ray irradiation induced changes in electron transport in stabilized a-Se photoconductors

    SciTech Connect (OSTI)

    Walornyj, M.; Kasap, S. O.

    2013-12-07

    We have examined the effect of high-dose x-ray irradiation on electron transport in stabilized amorphous selenium (a-Se) x-ray photoconductive films (of the type used in x-ray image detectors) by measuring the electron lifetime ?{sub e} through interrupted-field time-of-flight experiments. X-ray induced effects have been examined through two types of experiments. In recovery experiments, the a-Se was preirradiated with and without an applied field (5 V/?m) during irradiation with sufficient dose (typically ?20 Gy at 21 C) to significantly reduce the electron lifetime by ?50%, and then the recovery of the lifetime was monitored as a function of time at three different temperatures, 10 C, 21 C, and 35 C. The lifetime recovery kinetics was exponential with a relaxation time ?{sub r} that is thermally activated with an activation energy of 1.66 eV. ?{sub r} is a few hours at 21 C and only a few minutes at 35 C. In experiments examining the irradiation induced effects, the a-Se film was repeatedly exposed to x-ray radiation and the changes in the drift mobility and lifetime were monitored as a function of accumulated dose D. There was no observable change in the drift mobility. At 21 C, the concentration of x-ray induced deep traps (or capture centers), N{sub d}, increases linearly with D (N{sub d} ? D) whereas at 35 C, the recovery process prevents a linear increase in N{sub d} with D, and N{sub d} saturates. In all cases, even under high dose irradiation (?50 Gy), the lifetime was recoverable to its original equilibrium (pre-exposure) value within a few relaxation times.

  5. ZnO/Cu(InGa)Se.sub.2 solar cells prepared by vapor phase Zn doping

    DOE Patents [OSTI]

    Ramanathan, Kannan; Hasoon, Falah S.; Asher, Sarah E.; Dolan, James; Keane, James C.

    2007-02-20

    A process for making a thin film ZnO/Cu(InGa)Se.sub.2 solar cell without depositing a buffer layer and by Zn doping from a vapor phase, comprising: depositing Cu(InGa)Se.sub.2 layer on a metal back contact deposited on a glass substrate; heating the Cu(InGa)Se.sub.2 layer on the metal back contact on the glass substrate to a temperature range between about 100.degree. C. to about 250.degree. C.; subjecting the heated layer of Cu(InGa)Se.sub.2 to an evaporant species from a Zn compound; and sputter depositing ZnO on the Zn compound evaporant species treated layer of Cu(InGa)Se.sub.2.

  6. Migrating data from TcSE to DOORS : an evaluation of the T-Plan Integrator software application.

    SciTech Connect (OSTI)

    Post, Debra S.; Manzanares, David A.; Taylor, Jeffrey L.

    2011-02-01

    This report describes our evaluation of the T-Plan Integrator software application as it was used to transfer a real data set from the Teamcenter for Systems Engineering (TcSE) software application to the DOORS software application. The T-Plan Integrator was evaluated to determine if it would meet the needs of Sandia National Laboratories to migrate our existing data sets from TcSE to DOORS. This report presents the struggles of migrating data and focuses on how the Integrator can be used to map a data set and its data architecture from TcSE to DOORS. Finally, this report describes how the bulk of the migration can take place using the Integrator; however, about 20-30% of the data would need to be transferred from TcSE to DOORS manually. This report does not evaluate the transfer of data from DOORS to TcSE.

  7. Phase equilibria in the quasi-ternary system Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} and physical properties of (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er{sub 0.01}){sub 2}Se{sub 3} single crystals

    SciTech Connect (OSTI)

    Ivashchenko, I.A.; Danyliuk, I.V.; Olekseyuk, I.D.; Halyan, V.V.

    2014-02-15

    The quasi-ternary system Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} was investigated by differential thermal, X-ray phase, X-ray structure, microstructure analysis and microhardness measurements. Five quasi-binary phase diagrams, six polythermal sections, isothermal section at 820 K and the liquidus surface projection were constructed. The character and temperature of the invariant processes were determined. The specific resistance of the single crystals (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er{sub 0.01}){sub 2}Se{sub 3} was measured, 7.5×10{sup 5} and 3.15×10{sup 5} Ω m, respectively, optical absorption spectra in the 600–1050 nm range were recorded at room temperature, and the band gap energy was estimated which is 1.95±0. 01 eV for both samples. - Graphical abstract: The article reports for the first time the investigated liquidus surface projection of the Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} system and isothermal section at 820 K of the system. Five phase diagrams, six polythermal sections, isothermal section at 820 K and the liquidus surface projection were built at the first time. The existence of the large region of the solid solutions based on AgIn{sub 5}Se{sub 8}, Ga{sub 2}Se{sub 3} and AgGa{sub 1−x}In{sub x}Se{sub 2} was investigated. The existence of two ternary phases was established in the Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} system. Two single crystals (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er{sub 0.01}){sub 2}Se{sub 3} were grown and some of optical properties of them were studied at first time. Display Omitted - Highlights: • Liquidus surface projection was built for Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} system. • Solid solution ranges of AgIn{sub 5}Se{sub 8}, Ga{sub 2}Se{sub 3} and AgGa{sub 1−x}In{sub x}Se{sub 2} were investigated. • Two single crystals (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er

  8. Determination of the Exciton Binding Energy in CdSe Quantum Dots

    SciTech Connect (OSTI)

    Meulenberg, R; Lee, J; Wolcott, A; Zhang, J; Terminello, L; van Buuren, T

    2009-10-27

    The exciton binding energy (EBE) in CdSe quantum dots (QDs) has been determined using x-ray spectroscopy. Using x-ray absorption and photoemission spectroscopy, the conduction band (CB) and valence band (VB) edge shifts as a function of particle size have been determined and combined to obtain the true band gap of the QDs (i.e. without and exciton). These values can be compared to the excitonic gap obtained using optical spectroscopy to determine the EBE. The experimental EBE results are compared with theoretical calculations on the EBE and show excellent agreement.

  9. Nanosecond switching in GeSe phase change memory films by atomic force microscopy

    SciTech Connect (OSTI)

    Bosse, James L.; Huey, Bryan D.; Grishin, Ilya; Kolosov, Oleg V.; Gyu Choi, Yong; Cheong, Byung-ki; Lee, Suyoun

    2014-02-03

    Nanosecond scale threshold switching is investigated with conducting atomic force microscopy (AFM) for an amorphous GeSe film. Switched bits exhibit 2–3 orders of magnitude variations in conductivity, as demonstrated in phase change based memory devices. Through the nm-scale AFM probe, this crystallization was achieved with pulse durations of as low as 15 ns, the fastest reported with scanning probe based methods. Conductance AFM imaging of the switched bits further reveals correlations between the switched volume, pulse amplitude, and pulse duration. The influence of film heterogeneities on switching is also directly detected, which is of tremendous importance for optimal device performance.

  10. Microsized structures assisted nanostructure formation on ZnSe wafer by femtosecond laser irradiation

    SciTech Connect (OSTI)

    Wang, Shutong; Feng, Guoying E-mail: zhoush@scu.edu.cn

    2014-12-22

    Micro/nano patterning of ZnSe wafer is demonstrated by femtosecond laser irradiation through a diffracting pinhole. The irradiation results obtained at fluences above the ablation threshold are characterized by scanning electron microscopy. The microsized structure with low spatial frequency has a good agreement with Fresnel diffraction theory. Laser induced periodic surface structures and laser-induced periodic curvelet surface structures with high spatial frequency have been found on the surfaces of microsized structures, such as spikes and valleys. We interpret its formation in terms of the interference between the reflected laser field on the surface of the valley and the incident laser pulse.

  11. Experimental study of the valence band of Bi2Se3

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

    Gao, Yi-Bin; He, Bin; Parker, David; Androulakis, Ioannis; Heremans, Joseph P.

    2014-09-26

    The valence band of Bi2Se3 is investigated with Shubnikov - de Haas measurements, galvanomagnetic and thermoelectric transport. At low hole concentration, the hole Fermi surface is closed and box-like, but at higher concentrations it develops tube-like extensions that are open. The experimentally determined density-of-states effective mass is lighter than density-functional theory calculations predict; while we cannot give a definitive explanation for this, we suspect that the theory may lack sufficient precision to compute room-temperature transport properties, such as the Seebeck coefficient, in solids in which there are Van der Waals interlayer bonds.

  12. Multiband semimetallic electronic structure of superconducting Ta2PdSe5

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

    Singh, David Joseph

    2015-04-24

    We report the electronic structure and related properties of the superconductor Ta2PdSe5 as determined from density functional calculations. The Fermi surface has two disconnected sheets, both derived from bands of primarily chalcogenide p states. These are a corrugated hole cylinder and a heavier complex shaped electron sheet. The sheets contain 0.048 holes and a compensating number of electrons per formula unit, making the material a semimetallic superconductor. The results support the presence of two band superconductivity, although a discrepancy in the specific heat is noted. This discrepancy is discussed as a possible consequence of Pd deficiency in samples.

  13. ScanningTunneling Luminescence of Grain Boundaries in Cu(In,Ga)Se2

    SciTech Connect (OSTI)

    Romero, M. J.; Jiang, C.-S.; Al-Jassim, M. M.; Noufi, R.

    2005-01-01

    At the Laboratory, photon emission in semiconductors has been mapped in the nanoscale using scanning tunneling microscopy (STM). In this Solar Program Review Meeting, we report on the latest results obtained in Cu(In,Ga)Se2 (CIGS) thin films by this adapted STM. Scanning tunneling luminescence (STL) spectroscopy suggests that photons are emitted near the surface of CIGS. STL is excited either by (1) diffusion of tunneling electrons and subsequent recombination with available holes in CIGS or (2) impact ionization by hot electrons. Which process becomes predominant depends on the voltage applied to the STM tip. Photon mapping shows electronically active, extended defects near the surface of CIGS thin films.

  14. Tensile Strain Switched Ferromagnetism in Layered NbS2 and NbSe2

    SciTech Connect (OSTI)

    Zhou, Yungang; Wang, Zhiguo; Yang, Ping; Zu, Xiaotao; Yang, Li; Sun, Xin; Gao, Fei

    2012-11-01

    Developing approaches to effectively induce and control the magnetic states is critical to the use of magnetic nanostructures in quantum information devices but is still challenging. Here we have demonstrated, by employing the density functional theory calculations, an existence of infinite magnetic sheets with structural integrity and magnetic homogeneity. Examination from a series of transition metal dichalcogenides shows that the biaxial tensile strained NbS2 and NbSe2 structures can be magnetized with a ferromagnetic character due to the competitive effects of through-bond interaction and through-space interaction. The estimated Curie temperatures (387 and 542 K under the 10% strain for NbS2 and NbSe2 structures, respectively) suggest that the unique ferromagnetic character can be achieved above room temperature. The self-exchange of population between 4d orbitals of Nb atom that leads to the exchange splitting is the mechanism behind the transition of the spin moment. The induced magnetic moments can be significantly enhanced by the tensile strain, even giving rise to half-metallic character with the strong spin polarization around the Fermi level. Given the recent progress that the desired strain can be achieved on two-dimensional nanostructures, such as graphene and BN layer in a controlled way, we believe that our calculated results are suitable for experimental verification and implementation opening a new path to explore the spintronics in pristine two-dimensional nanostructures.

  15. Biexciton formation and exciton coherent coupling in layered GaSe

    SciTech Connect (OSTI)

    Dey, P.; Paul, J.; Stevens, C. E.; Glikin, N.; Karaiskaj, D.; Moody, G.; Kovalyuk, Z. D.; Kudrynskyi, Z. R.; Romero, A. H.; Cantarero, A.; Hilton, D. J.

    2015-06-07

    Nonlinear two-dimensional Fourier transform (2DFT) and linear absorption spectroscopy are used to study the electronic structure and optical properties of excitons in the layered semiconductor GaSe. At the 1s exciton resonance, two peaks are identified in the absorption spectra, which are assigned to splitting of the exciton ground state into the triplet and singlet states. 2DFT spectra acquired for co-linear polarization of the excitation pulses feature an additional peak originating from coherent energy transfer between the singlet and triplet. At cross-linear polarization of the excitation pulses, the 2DFT spectra expose a new peak likely originating from bound biexcitons. The polarization dependent 2DFT spectra are well reproduced by simulations using the optical Bloch equations for a four level system, where many-body effects are included phenomenologically. Although biexciton effects are thought to be strong in this material, only moderate contributions from bound biexciton creation can be observed. The biexciton binding energy of ?2 meV was estimated from the separation of the peaks in the 2DFT spectra. Temperature dependent absorption and 2DFT measurements, combined with ab initio theoretical calculations of the phonon spectra, indicate strong interaction with the A{sub 1}{sup ?} phonon mode. Excitation density dependent 2DFT measurements reveal excitation induced dephasing and provide a lower limit for the homogeneous linewidth of the excitons in the present GaSe crystal.

  16. Transient and steady state photoelectronic analysis in TlInSe{sub 2} crystals

    SciTech Connect (OSTI)

    Qasrawi, A.F.; Gasanly, N.M.

    2011-08-15

    Highlights: {yields} The steady state and time dependent photoconductivity kinetics of the TlInSe{sub 2} crystals are investigated in the temperature region of 100-350 K. {yields} The photocurrent of the sample exhibited linear, sublinear, and supralinear recombination mechanisms, at, above and below 160 K, respectively. {yields} Steady state photoconductivity revealed two recombination centres located at 234 and 94 meV. {yields} The transient photoconductivity is limited by a trapping center located at 173 meV. {yields} The capture coefficient of the trap for holes was determined as 3.11 x 10{sup -22} cm{sup -2}. -- Abstract: The temperature and illumination effects on the transient and steady state photoconductivities of TlInSe{sub 2} crystals have been studied. Namely, two recombination centres located at 234 and at 94 meV and one trap center located at 173 meV were determined from the temperature-dependent steady state and transient photoconductivities, respectively. The illumination dependence of photoconductivity indicated the domination of sublinear and supralinear recombination mechanisms above and below 160 K, respectively. The change in the recombination mechanism is attributed to the exchange of roles between the linear recombination at the surface and trapping centres in the crystal, which become dominant as temperature decreases. The transient photoconductivity measurement allowed the determination of the capture coefficient of traps for holes as 3.11 x 10{sup -22} cm{sup -2}.

  17. Nonmonotonic pressure evolution of the upper critical field in superconducting FeSe

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

    Kaluarachchi, Udhara S.; Taufour, Valentin; Böhmer, Anna E.; Tanatar, Makariy A.; Bud'ko, Sergey L.; Kogan, Vladimir G.; Prozorov, Ruslan; Canfield, Paul C.

    2016-02-01

    The pressure dependence of the upper critical field, Hc2,c, of single crystalline FeSe was studied using measurements of the interplane resistivity, ρc, in magnetic fields parallel to tetragonal c axis. Hc2,c(T) curves obtained under hydrostatic pressures up to 1.56 GPa, the range over which the superconducting transition temperature, Tc, of FeSe exhibits a nonmonotonic dependence with local maximum at p1 ≈ 0.8 GPa and local minimum at p2 ≈ 1.2 GPa. The slope of the upper critical field at Tc,(dHc2,c/dT)Tc, also exhibits a nonmonotonic pressure dependence with distinct changes at p1 and p2. For p < p1 the slope canmore » be described within a multiband orbital model. For both p1 < p < p2 and p > p2 the slope is in good semiquantitative agreement with a single band, orbital Helfand-Werthamer theory with Fermi velocities determined from Shubnikov–de Haas measurements. Lastly, this finding indicates that Fermi surface changes are responsible for the local minimum of Tc(p) at p2 ≈ 1.2 GPa.« less

  18. The role of ligands in the optical and electronic spectra of CdSe nanoclusters

    SciTech Connect (OSTI)

    Kilina, Svletana; Sergei, Ivanov A; Victor, Klimov I; Sergei, Tretiak

    2008-01-01

    We investigate the impact of ligands on morphology, electronic structure, and optical response of the Cd33Se33 cluster, which already overlapps in size with the smallest synthesized CdSe quantum dots (QDs). Our Density Functional Theory (DFT) calculations demonstrate significant surface reorganization both for the bare cluster and for the cluster capped by amine and phosphine oxide ligand models. We observe strong surface-ligand interactions leading to substantial charge redistribution and polarization effects on the surface. This effect results in the appearance of hybridized states, where the electronic density is spread over the cluster and the ligands. Neither the ligand's nor hybridized molecular orbitals appear as trap states inside or near the band gap of the QD. Instead, being optically dark, dense hybridized states from the edges of the valence and the conduction bands could open new relaxation channels for high energy photoexcitations. Comparing quantum dots passivated by different ligands, we found that hybridized states are denser in at the edge of the conduction band of the cluster ligated with phosphine oxide molecules than that with primary amines. Such a different manifestation of ligand binding may potentially lead to the faster electron relaxation in dots passivated by phosphine oxide than by amine ligands, which is in agreement with experimental data.

  19. Electronic Structure of Ligated CdSe Clusters: Dependence on DFT Methodology

    SciTech Connect (OSTI)

    Albert, VV; Ivanov, SA; Tretiak, S; Kilina, SV

    2011-07-07

    Simulations of ligated semiconductor quantum dots (QDs) and their physical properties, such as morphologies, QD-ligand interactions, electronic structures, and optical transitions, are expected to be very sensitive to computational methodology. We utilize Density Functional Theory (DFT) and systematically study how the choice of density functional, atom-localized basis set, and a solvent affects the physical properties of the Cd{sub 33}Se{sub 33} cluster ligated with a trimethyl phosphine oxide ligand. We have found that qualitative performance of all exchange-correlation (XC) functionals is relatively similar in predicting strong QD-ligand binding energy ({approx}1 eV). Additionally, all functionals predict shorter Cd-Se bond lengths on the QD surface than in its core, revealing the nature and degree of QD surface reconstruction. For proper modeling of geometries and QD-ligand interactions, however, augmentation of even a moderately sized basis set with polarization functions (e.g., LANL2DZ* and 6-31G*) is very important. A polar solvent has very significant implications for the ligand binding energy, decreasing it to 0.2-0.5 eV. However, the solvent model has a minor effect on the optoelectronic properties, resulting in persistent blue shifts up to {approx}0.3 eV of the low-energy optical transitions. For obtaining reasonable energy gaps and optical transition energies, hybrid XC functionals augmented by a long-range Hartree-Fock orbital exchange have to be applied.

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

    SciTech Connect (OSTI)

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

    2014-01-01

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

  1. Lattice dynamics of BaFe2X3(X=S,Se) compounds

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

    Popović, Z. V.; Šćepanović, M.; Lazarević, N.; Opačić, M.; Radonjić, M. M.; Tanasković, D.; Lei, Hechang; Petrovic, C.

    2015-02-27

    We present the Raman scattering spectra of the S=2 spin ladder compounds BaFe₂X₃ (X=S,Se) in a temperature range between 20 and 400 K. Although the crystal structures of these two compounds are both orthorhombic and very similar, they are not isostructural. The unit cell of BaFe₂S₃ (BaFe₂Se₃) is base-centered Cmcm (primitive Pnma), giving 18 (36) modes to be observed in the Raman scattering experiment. We have detected almost all Raman active modes, predicted by factor group analysis, which can be observed from the cleavage planes of these compounds. Assignment of the observed Raman modes of BaFe₂S(Se)₃ is supported by themore » lattice dynamics calculations. The antiferromagnetic long-range spin ordering in BaFe₂Se₃ below TN=255K leaves a fingerprint both in the A1g and B3g phonon mode linewidth and energy.« less

  2. Manufacturing technology development for CuInGaSe sub 2 solar cell modules

    SciTech Connect (OSTI)

    Stanbery, B.J. )

    1991-11-01

    The report describes research performed by Boeing Aerospace and Electronics under the Photovoltaic Manufacturing Technology project. We anticipate that implementing advanced semiconductor device fabrication techniques to the production of large-area CuIn{sub 1-x}Ga{sub x}Se{sub 2} (CIGS)/Cd{sub 1-y}Zn{sub y}S/ZnO monolithically integrated thin-film solar cell modules will enable 15% median efficiencies to be achieved in high-volume manufacturing. We do not believe that CuInSe{sub 2} (CIS) can achieve this efficiency in production without sufficient gallium to significantly increase the band gap, thereby matching it better to the solar spectrum (i.e., x{ge}0.2). Competing techniques for CIS film formation have not been successfully extended to CIGS devices with such high band gaps. The SERI-confirmed intrinsic stability of CIS-based photovoltaics renders them far superior to a-Si:H-based devices, making a 30-year module lifetime feasible. The minimal amounts of cadmium used in the structure we propose, compared to CdTe-based devices, makes them environmentally safer and more acceptable to both consumers and relevant regulatory agencies. Large-area integrated thin-film CIGS modules are the product most likely to supplant silicon modules by the end of this decade and enable the cost improvements which will lead to rapid market expansion.

  3. Probing Interfacial Electronic States in CdSe Quantum Dots using Second Harmonic Generation Spectroscopy

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

    Doughty, Benjamin L.; Ma, Yingzhong; Shaw, Robert W

    2015-01-07

    Understanding and rationally controlling the properties of nanomaterial surfaces is a rapidly expanding field of research due to the dramatic role they play on the optical and electronic properties vital to light harvesting, emitting and detection technologies. This information is essential to the continued development of synthetic approaches designed to tailor interfaces for optimal nanomaterial based device performance. In this work, closely spaced electronic excited states in model CdSe quantum dots (QDs) are resolved using second harmonic generation (SHG) spectroscopy, and the corresponding contributions from surface species to these states are assessed. Two distinct spectral features are observed in themore » SHG spectra, which are not readily identified in linear absorption and photoluminescence excitation spectra. These features include a weak band at 395 6 nm, which coincides with transitions to the 2S1/2 1Se state, and a much more pronounced band at 423 4 nm arising from electronic transitions to the 1P3/2 1Pe state. Chemical modification of the QD surfaces through oxidation resulted in disappearance of the SHG band corresponding to the 1P3/2 1Pe state, indicating prominent surface contributions. Signatures of deep trap states localized on the surfaces of the QDs are also observed. We further find that the SHG signal intensities depend strongly on the electronic states being probed and their relative surface contributions, thereby offering additional insight into the surface specificity of SHG signals from QDs.« less

  4. Resonance photoelectron spectroscopy of TiX{sub 2} (X = S, Se, Te) titanium dichalcogenides

    SciTech Connect (OSTI)

    Shkvarin, A. S. Yarmoshenko, Yu. M.; Skorikov, N. A.; Yablonskikh, M. V.; Merentsov, A. I.; Shkvarina, E. G.; Titov, A. N.

    2012-11-15

    The photoelectron valence band spectra of TiS{sub 2}, TiSe{sub 2}, and TiTe{sub 2} dichalcogenides are investigated in the Ti 2p-3d resonance regime. Resonance bands in the vicinity of the Fermi energy are found for TiS{sub 2} and TiTe{sub 2}. The nature of these bands is analyzed based on model calculations of the density of electronic states in TiS{sub 2}, TiSe{sub 2}, and TiTe{sub 2} compounds intercalated by titanium atoms. Analysis of experimental data and their comparison with model calculations showed that these bands have different origins. It is found that the resonance enhancement of an additional band observed in TiS{sub 2} is explained by self-intercalation by titanium during the synthesis of this compound. The resonance enhancement in TiTe{sub 2} is caused by occupation of the 3d band in Ti.

  5. Electronic structure of titanium dichalcogenides TiX{sub 2} (X = S, Se, Te)

    SciTech Connect (OSTI)

    Shkvarin, A. S. Yarmoshenko, Yu. M.; Skorikov, N. A.; Yablonskikh, M. V.; Merentsov, A. I.; Shkvarina, E. G.; Titov, A. N.

    2012-01-15

    The electronic structure and the chemical bond in titanium dichalcogenides TiX{sub 2} (X = S, Se, Te), which are promising electrode materials for lithium batteries, are studied experimentally and theoretically. It is found that the X-ray photoelectron spectra of the valence bands and the core levels of titanium and its X-ray L{sub 2,3} absorption spectra demonstrate a change in the ionic and covalent components of the chemical bond in these compounds. The densities of states in these compounds are calculated by the full-potential augmented-plane-wave method, and multiplet calculations of the X-ray L{sub 2,3} absorption spectra of titanium are performed. It is shown that, in the row TiS{sub 2}-TiSe{sub 2}-TiTe{sub 2}, the covalence increases, the ionicity of the chemical bond decreases, and the effect of the crystal field of a ligand is weakened.

  6. Dependence of superconductivity in CuxBi?Se? on quenching conditions

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

    Schneeloch, J. A.; Zhong, R. D.; Xu, Z. J.; Gu, G. D.; Tranquada, J. M.

    2015-04-20

    Topological superconductivity, implying gapless protected surface states, has recently been proposed to exist in the compound CuxBi?Se?. Unfortunately, low diamagnetic shielding fractions and considerable inhomogeneity have been reported in this compound. In an attempt to understand and improve on the finite superconducting volume fractions, we have investigated the effects of various growth and post-annealing conditions. With a melt-growth (MG) method, diamagnetic shielding fractions of up to 56% in Cu???Bi?Se? have been obtained, the highest value reported for this method. We investigate the efficacy of various quenching and annealing conditions, finding that quenching from temperatures above 560C is essential for superconductivity,morewhereas quenching from lower temperatures or not quenching at all is detrimental. A modified floating zone (FZ) method yielded large single crystals but little superconductivity. Even after annealing and quenching, FZ-grown samples had much less chance of being superconducting than MG-grown samples. From the low shielding fractions in FZ-grown samples and the quenching dependence, we suggest that a metastable secondary phase having a small volume fraction in most of the samples may be responsible for the superconductivity.less

  7. Polytypism, polymorphism, and superconductivity in TaSe2-xTex

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

    Luo, Huixia; Tao, Jing; Xie, Weiwei; Inoue, Hiroyuki; Gyenis, Andras; Krizan, Jason W.; Yazdani, Ali; Zhu, Yimei; Cava, R. J.

    2015-03-17

    Polymorphism in materials often leads to significantly different physical properties - the rutile and anatase polymorphs of TiO? are a prime example. Polytypism is a special type of polymorphism, occurring in layered materials when the geometry of a repeating structural layer is maintained but the layer stacking sequence of the overall crystal structure can be varied; SiC is an example of a material with many polytypes. Although polymorphs can have radically different physical properties, it is much rarer for polytypism to impact physical properties in a dramatic fashion. Here we study the effects of polytypism and polymorphism on the superconductivitymoreof TaSe?, one of the archetypal members of the large family of layered dichalcogenides. We show that it is possible to access 2 stable polytypes and 2 stable polymorphs in the TaSe2-xTex solid solution, and find that the 3R polytype shows a superconducting transition temperature that is between 6 and 17 times higher than that of the much more commonly found 2H polytype. The reason for this dramatic change is not apparent, but we propose that it arises either from a remarkable dependence of Tc on subtle differences in the characteristics of the single layers present, or from a surprising effect of the layer stacking sequence on electronic properties that instead are expected to be dominated by the properties of a single layer in materials of this kind.less

  8. Characterization and device performance of (AgCu)(InGa)Se2 absorber layers

    SciTech Connect (OSTI)

    Hanket, Gregory; Boyle, Jonathan H.; Shafarman, William N.

    2009-06-08

    The study of (AgCu)(InGa)Se2 absorber layers is of interest in that Ag-chalcopyrites exhibit both wider bandgaps and lower melting points than their Cu counterparts. (AgCu)(InGa)Se2 absorber layers were deposited over the composition range 0 < Ag/(Ag+Cu) < 1 and 0.3 < Ga/(In+Ga) < 1.0 using a variety of elemental co-evaporation processes. Films were found to be singlephase over the entire composition range, in contrast to prior studies. Devices with Ga content 0.3 < Ga/(In+Ga) <0.5 tolerated Ag incorporation up to Ag/(Ag+Cu) = 0.5 without appreciable performance loss. Ag-containing films with Ga/(In+Ga) = 0.8 showed improved device characteristics over Cu-only control samples, in particular a 30-40% increase in short-circuit current. An absorber layer with composition Ag/(Ag+Cu) = 0.75 and Ga/(In+Ga) = 0.8 yielded a device with VOC = 890 mV, JSC = 20.5mA/cm2, fill factor = 71.3%, and ? = 13.0%.

  9. Properties of Cu(In,Ga,Al)Se{sub 2} thin films fabricated by magnetron sputtering

    SciTech Connect (OSTI)

    Hameed, Talaat A.; Cao, Wei; Mansour, Bahiga A.; Elzawaway, Inas K.; Abdelrazek, El-Metwally M.; Elsayed-Ali, Hani E.

    2015-05-15

    Cu(In,Ga,Al)Se{sub 2} (CIGAS) thin films were studied as an alternative absorber layer material to Cu(In{sub x}Ga{sub 1?x})Se{sub 2}. CIGAS thin films with varying Al content were prepared by magnetron sputtering on Si(100) and soda-lime glass substrates at 350?C, followed by postdeposition annealing at 520?C for 5 h in vacuum. The film composition was measured by an electron probe microanalyzer while the elemental depth profiles were determined by secondary ion mass spectrometry. X-ray diffraction studies indicated that CIGAS films are single phase with chalcopyrite structure and that the (112) peak clearly shifts to higher 2? values with increasing Al content. Scanning electron microscopy images revealed dense and well-defined grains, as well as sharp CIGAS/Si(100) interfaces for all films. Atomic force microscopy analysis indicated that the roughness of CIGAS films decreases with increasing Al content. The bandgap of CIGAS films was determined from the optical transmittance and reflectance spectra and was found to increase as Al content increased.

  10. Crystal and electronic structures of two new iron selenides: Ba{sub 4}Fe{sub 3}Se{sub 10} and BaFe{sub 2}Se{sub 4}

    SciTech Connect (OSTI)

    Berthebaud, David; Perez, Olivier; Tobola, Janusz; Pelloquin, Denis; Maignan, Antoine

    2015-10-15

    The new ternary selenides, Ba{sub 4}Fe{sub 3}Se{sub 10} and BaFe{sub 2}Se{sub 4,} were synthesized from a reaction of appropriate amounts of elements at high temperature in a silica sealed tube, and their structures were resolved using X-ray single crystal diffraction. BaFe{sub 2}Se{sub 4} crystallizes in the tetragonal space group I4/m with a=8.008(9) Å and c=5.483(3) Å as cell parameters. It is a new compound with a structure isotypical to the sulfide BaFe{sub 2}S{sub 4} which belongs to the infinitely adaptive structures series Ba{sub 1+x}Fe{sub 2}S{sub 4}. The second compound, Ba{sub 4}Fe{sub 3}Se{sub 10}, crystallizes in the monoclinic space group P2{sub 1}/n with a=8.8593(1) Å, b=8.8073(1) Å, c=12.2724(1) Å and β=109.037(6)° as cell parameters. It exhibits an original structure with a new type of iron selenide polyhedra. These data were consistent with the powder X-ray diffraction and TEM analyses. Their electronic structures point towards metallicity and electronic correlations for both selenides. - Graphical abstract: Experimental [010] oriented ED pattern and corresponding HREM image of Ba{sub 4}Fe{sub 3}Se{sub 10}. Image calculated with a focus and thickness to 15nm and 8 nm respectively is inserted. Bright contrasts are correlated to Se rows belonging to FeSe{sub 3}(Se{sub 2}){sup 2−}–FeSe{sub 6}–FeSe{sub 3}(Se{sub 2}){sup 2−} trimers. The corresponding structure projection is also shown. - Highlights: • Two new barium iron selenide compounds. • An original structure type Ba4Fe3Se10. • Electronic structure calculations.

  11. Investigation of size dependent structural and optical properties of thin films of CdSe quantum dots

    SciTech Connect (OSTI)

    Sharma, Madhulika; Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay, Powai, Mumbai 400076 ; Sharma, A.B.; Mishra, N.; Pandey, R.K.

    2011-03-15

    Research highlights: {yields} CdSe q-dots have been synthesized using simple chemical synthesis route. {yields} Thin film of CdSe quantum dots exhibited self-organized growth. {yields} Size dependent blue shift observed in the absorption edge of CdSe nanocrystallites. {yields} PL emission band corresponds to band edge luminescence and defect luminescence. {yields} Organized growth led to enhancement in luminescence yield of smaller size Q-dots. -- Abstract: Cadmium selenide (CdSe) quantum dots were grown on indium tin oxide substrate using wet chemical technique for possible application as light emitting devices. The structural, morphological and luminescence properties of the as deposited thin films of CdSe Q-dot have been investigated, using X-ray diffraction, transmission electron microscopy, atomic force microscopy and optical and luminescence spectroscopy. The quantum dots have been shown to deposit in an organized array on ITO/glass substrate. The as grown Q-dots exhibited size dependent blue shift in the absorption edge. The effect of quantum confinement also manifested as a blue shift of photoluminescence emission. It is shown that the nanocrystalline CdSe exhibits intense photoluminescence as compared to the large grained polycrystalline CdSe films.

  12. Single-step in-situ synthesis and optical properties of ZnSe nanostructured dielectric nanocomposites

    SciTech Connect (OSTI)

    Dey, Chirantan; Rahaman Molla, Atiar; Tarafder, Anal; Karmakar, Basudeb; Kr Mishra, Manish; De, Goutam; Goswami, Madhumita; Kothiyal, G. P.

    2014-04-07

    This work provides the evidence of visible red photoluminescent light emission from ZnSe nanocrystals (NCs) grown within a dielectric (borosilicate glass) matrix synthesized by a single step in-situ technique for the first time and the NC sizes were controlled by varying only the concentration of ZnSe in glass matrix. The ZnSe NCs were investigated by UV-Vis optical absorption spectroscopy, Raman spectroscopy, and transmission electron microscopy (TEM). The sizes of the ZnSe NCs estimated from the TEM images are found to alter in the range of 2–53 nm. Their smaller sizes of the NCs were also calculated by using the optical absorption spectra and the effective mass approximation model. The band gap enlargements both for carrier and exciton confinements were evaluated and found to be changed in the range of 0–1.0 eV. The Raman spectroscopic studies showed blue shifted Raman peaks of ZnSe at 295 and 315 cm{sup −1} indicating phonon confinement effect as well as compressive stress effect on the surface atoms of the NCs. Red photoluminescence in ZnSe-glass nanocomposite reveals a broad multiple-peak structure due to overlapping of emission from NC size related electron-hole recombination (∼707 nm) and emissions from defects to traps, which were formed due to Se and Zn vacancies signifying potential application in photonics.

  13. Green route synthesis of high quality CdSe quantum dots for applications in light emitting devices

    SciTech Connect (OSTI)

    Bera, Susnata, E-mail: susnata.bera@gmail.com [Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Singh, Shashi B. [Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Ray, S.K., E-mail: physkr@phy.iitkgp.ernet.in [Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

    2012-05-15

    Investigation was made on light emitting diodes fabricated using CdSe quantum dots. CdSe quantum dots were synthesized chemically using olive oil as the capping agent, instead of toxic phosphine. Room temperature photoluminescence investigation showed sharp 1st excitonic emission peak at 568 nm. Bi-layer organic/inorganic (P3HT/CdSe) hybrid light emitting devices were fabricated by solution process. The electroluminescence study showed low turn on voltage ({approx}2.2 V) .The EL peak intensity was found to increase by increasing the operating current. - Graphical abstract: Light emitting diode was fabricated using CdSe quantum dots using olive oil as the capping agent, instead of toxic phosphine. Bi-layer organic/inorganic (P3HT/CdSe) hybrid light emitting device shows strong electroluminescence in the range 630-661 nm. Highlights: Black-Right-Pointing-Pointer CdSe Quantum dots were synthesized using olive oil as the capping agent. Black-Right-Pointing-Pointer Light emitting device was fabricated using CdSe QDs/P3HT polymer heterojunction. Black-Right-Pointing-Pointer The I-V characteristics study showed low turn on voltage at {approx}2.2 V. Black-Right-Pointing-Pointer The EL peak intensity increases with increasing the operating current.

  14. Effects of competing magnetic interactions on the electronic transport properties of CuCrSe{sub 2}

    SciTech Connect (OSTI)

    Tewari, Girish C.; Jawaharlal Nehru University, New Delhi 110067 ; Karppinen, Maarit; Rastogi, Ashok K.

    2013-02-15

    We have synthesized single-phase samples of the CuCrSe{sub 2} phase that exhibits hexagonal-rhombohedral layered crystal structure with space group R3m. Here we present a detailed study of electronic transport and magnetic properties of CuCrSe{sub 2}. We moreover investigate the heat capacity of CuCrSe{sub 2} in comparison to that of CuCrS{sub 2}. The electrical resistivity of CuCrSe{sub 2} shows metallic-like behavior down to 2 K, while the thermoelectric power is large around 100 {mu}V K{sup -1} at 300 K. A weak anomaly in resistivity and a rounded maximum in magnetic susceptibility are observed around 55 K. No sharp transition at 55 K is observed in the heat capacity of CuCrSe{sub 2}, rather a visible maximum is seen. At low temperatures from 2 to 14 K, the magnetic heat capacity follows T{sup 2}-dependence. We tentatively believe this behavior of CuCrSe{sub 2} to be due to competing magnetic interactions between intralayer Cr atoms. The ferromagnetic Cr-Se-Cr indirect exchange among intralayer Cr atoms is enhanced in the selenide compound (that is more metallic than the sulfide compound), and competes with the antiferromagnetic Cr-Cr direct interactions. The interlayer antiferromagnetic exchange through Cu atoms leads to magnetic ordering at low temperature at T{sub N}=55 K. - Graphical abstract: Comparison of magnetic properties of CuCrSe{sub 2} and CuCrS{sub 2} indicates a sharp cusp-like anomaly in magnetic susceptibility at the antiferromagnetic transition of CuCrS{sub 2} while the maximum of CuCrSe{sub 2} is well rounded. Magnetization is reversible after field-cooling (FC) and zero-field-cooling (ZFC) for both compounds. Highlights: Black-Right-Pointing-Pointer Layered CuCrSe{sub 2} can be synthesized in both fully and partially cation-ordered forms. Black-Right-Pointing-Pointer Contrary to previously believed insulating nature the cation-ordered phase is metallic. Black-Right-Pointing-Pointer Magnetic property of CuCrSe{sub 2} is somewhat different from

  15. Flowing versus Static Conditions for Measuring Multiple Exciton Generation in PbSe Quantum Dots

    SciTech Connect (OSTI)

    Midgett, Aaron G. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States); Hillhouse, Hugh W. [Univ. of Washington, Seattle, WA (United States); Hughes, Barbara K. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States); Nozik, Arthur J. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States); Beard, Matthew C. [Univ. of Colorado, Boulder, CO (United States)

    2010-09-22

    Recent reports question the validity of pulsed fs-laser experiments for measuring the photon-to-exciton quantum yields (QYs) that result from multiple exciton generation (MEG). The repetitive nature of these experiments opens up an alternative relaxation pathway that may produce artificially high results. We present transient-absorption (TA) data for 4.6 and 6.6 nm diameter PbSe quantum dots (QDs) at a variety of pump photon energies. The data are collected under laminar flow conditions with volumetric flow rates ranging from 0 to 150 mL/min (resulting in Reynolds numbers up to 460). The results are modeled with a spatially resolved population balance of generation, recombination, convective replacement, and accumulation of long-lived excited QDs. By comparing the simulations and experiments, the steady-state population of the long-lived QD-excited states and their kinetics are determined for different experimental conditions. We also improve upon reported photon-to-exciton QYs for PbSe QDs. We find differences in the observed TA dynamics between flowing and static conditions that depend upon photon fluence, pump photon energy, and quality of the QD surfaces. For excitation energies below 2 Eg, independent of QD size or photon fluence, we observe no flow rate dependence in the TA dynamics. At excitation energies of h? > 3 Eg, we observe differences between static and flowing conditions that are most pronounced for high photon fluences. At 3.7 Eg and for 4.6 nm PbSe QDs we find a QY of 1.2 0.1 and at 4.5 Eg the QY is 1.55 0.05. With 6.6 nm QDs excited at 4.7 Eg we observe no difference between static and flowing conditions and find a QY of 1.61 0.05. We also find that by treating the surface of QDs, we can decrease the charging probability (Pg ? 5 10-5) by a factor of 3-4. The observed variations suggest that different QD samples vary regarding their susceptibility to the creation

  16. Superconductivity in a Misfit Phase That Combines the Topological Crystalline Insulator Pb1-xSnxSe with the CDW-Bearing Transition Metal Dichalcogenide TiSe2

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

    Luo, H.; Yan, K.; Pletikosic, I.; Xie, W.; Phelan, B. F.; Valla, T.; Cava, R. J.

    2016-05-13

    We report the characterization of the misfit compound (Pb1-xSnxSe2)1.16(TiSe2)2 for 0 ≤ x ≤ 0.6, in which a [100] rocksalt-structure bilayer of Pb1-xSnxSe, which is a topological crystalline insulator in bulk form, alternates with a double layer of the normally nonsuperconducting transition metal dichalcogenide TiSe2. The x dependence of Tc displays a weak dome-like shape with a maximum Tc of 4.5 K at x = 0.2; there is only a subtle change in Tc at the composition where the trivial to topological transition occurs in bulk Pb1-xSnxSe. We present the characterization of the superconductor at x = 0.4, for whichmore » the bulk Pb1-xSnxSe phase is in the topological crystalline insulator regime. For this material, the Sommerfeld parameter γ = 11.06 mJ mol-1 K-2, the Debye temperature ΘD = 161 K, the normalized specific heat jump value ΔC/γTc = 1.38 and the electron-phonon constant value γep = 0.72, suggesting that (Pb0.6Sn0.4Se)1.16(TiSe2)2 is a BCS-type weak coupling superconductor. This material may be of interest for probing the interaction of superconductivity with the surface states of a topological crystalline insulator.« less

  17. Co-Evaporated Cu2ZnSnSe4 Films and Devices

    SciTech Connect (OSTI)

    Repins, I.; Beall, C.; Vora, N.; DeHart, C.; Kuciauskas, D.; Dippo, P.; To, B.; Mann, J.; Hsu, W. C.; Goodrich, A.; Noufi, R.

    2012-06-01

    The use of vacuum co-evaporation to produce Cu2ZnSnSe4 photovoltaic devices with 9.15% total-area efficiency is described. These new results suggest that the early success of the atmospheric techniques for kesterite photovoltaics may be related to the ease with which one can control film composition and volatile phases, rather than a fundamental benefit of atmospheric conditions for film properties. The co-evaporation growth recipe is documented, as is the motivation for various features of the recipe. Characteristics of the resulting kesterite films and devices are shown in scanning electron micrographs, including photoluminescence, current-voltage, and quantum efficiency. Current-voltage curves demonstrate low series resistance without the light-dark cross-over seen in many devices in the literature. Band gap indicated by quantum efficiency and photoluminescence is roughly consistent with that expected from first principles calculation.

  18. Stable n-CuInSe/sub 2/iodide-iodine photoelectrochemical cell

    DOE Patents [OSTI]

    Cahen, D.; Chen, Y.W.

    1984-09-20

    In a photoelectrochemical solar cell, stable output and solar efficiency in excess of 10% are achieved with a photoanode of n-CuInSe/sub 2/ electrode material and an iodine/iodide redox couple used in a liquid electrolyte. The photoanode is prepared by treating the electrode material by chemical etching, for example in Br/sub 2//MeOH; heating the etched electrode material in air or oxygen; depositing a surface film coating of indium on the electrode material after the initial heating; and thereafter again heating the electrode material in air or oxygen to oxidize the indium. The electrolyte is treated by the addition of Cu/sup +/ or Cu/sup 2 +/ salts and in In/sup 3 +/ salts.

  19. Stable N-CuInSe.sub.2 /iodide-iodine photoelectrochemical cell

    DOE Patents [OSTI]

    Cahen, David; Chen, Yih W.

    1985-01-01

    In a photoelectrochemical solar cell, stable output and solar efficiency in excess of 10% are achieved with a photoanode of n-CuInSe.sub.2 electrode material and an iodine/iodide redox couple used in a liquid electrolyte. The photoanode is prepared by treating the electrode material by chemical etching, for example in Br.sub.2 /MeOH; heating the etched electrode material in air or oxygen; depositing a surface film coating of indium on the electrode material after the initial heating; and thereafter again heating the electrode material in air or oxygen to oxidize the indium. The electrolyte is treated by the addition of Cu.sup.+ or Cu.sup.2+ salts and In.sup.3+ salts.

  20. Fano q-reversal in topological insulator Bi2Se3

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

    S. V. Dordevic; Petrovic, C.; Foster, G. M.; Wolf, M. S.; Stojilovic, N.; Lei, Hechang; Chen, Z.; Li, Z. Q.; Tung, L. C.

    2016-03-22

    Here, we studied the magneto-optical response of a canonical topological insulator Bi2Se3 with the goal of addressing a controversial issue of electron–phonon coupling. Magnetic-field induced modifications of reflectance are very pronounced in the infrared part of the spectrum, indicating strong electron–phonon coupling. This coupling causes an asymmetric line-shape of the 60 cm–1 phonon mode, and is analyzed within the Fano formalism. The analysis reveals that the Fano asymmetry parameter (q) changes sign when the cyclotron resonance is degenerate with the phonon mode. To the best of our knowledge this is the first example of magnetic field driven q-reversal.

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

    SciTech Connect (OSTI)

    Zhang, Hongyi; Liu, Yu; Ye, Xiaoling; Chen, Yonghai

    2013-12-28

    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.

  2. Inelastic x-ray scattering studies on dynamic structure factor of polymeric liquid Se under pressure

    SciTech Connect (OSTI)

    Inui, Masanori; Kajihara, Yukio; Kimura, Koji; Matsuda, Kazuhiro; Ohara, Koji; Tsutsui, Satoshi; Ishikawa, Daisuke

    2015-08-17

    Inelastic X-ray scattering measurements at 25 MPa using synchrotron radiation were carried out for semiconducting liquid Se at high temperatures up to 1673 K. The excitation energy of the acoustic mode disperses approximately 10-50 % faster than the ultrasonic sound velocity in the observed temperature range while the ultrasonic sound rapidly slows down with increasing temperature. We carried out X-ray scattering measurements and found that the average coordination number at 1673 K is 1.3, indicating that the high temperature liquid consists of short chain molecules. These results suggest that weakening of the interatomic interaction is correlated with breaking of polymeric chain molecules.

  3. Development and characterization of PCDTBT:CdSe QDs hybrid solar cell

    SciTech Connect (OSTI)

    Dixit, Shiv Kumar Bhatnagar, Chhavi Kumari, Anita Madhwal, Devinder Bhatnagar, P. K. Mathur, P. C.

    2014-10-15

    Solar cell consisting of low band gap polymer poly[N-900-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10, 30-benzothiadiazole)] (PCDTBT) as donor and cadmium selenide/zinc sulphide (CdSe/ZnS) core shell quantum dots (QDs) as an acceptor has been developed. The absorption measurements show that the absorption coefficient increases in bulk heterojunction (BHJ) structure covering broad absorption spectrum (200nm–700nm). Also, the photoluminescence (PL) of the PCDTBT:QDs film is found to decrease by an order of magnitude showing a significant transfer of electrons to the QDs. With this approach and under broadband white light with an irradiance of 8.19 mW/cm{sup 2}, we have been able to achieve a power conversion efficiency (PCE) of 3.1 % with fill factor 0.42 for our typical solar cell.

  4. Enhanced Thermoelectric Properties of Cu2ZnSnSe4 with Ga-doping

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

    Wei, Kaya; Beauchemin, Laura; Wang, Hsin; Porter, Wallace D.; Martin, Joshua; Nolas, George S.

    2015-08-10

    Gallium doped Cu2ZnSnSe4 quaternary chalcogenides with and without excess Cu were synthesized by elemental reaction and densified using hot pressing in order to investigate their high temperature thermoelectric properties. The resistivity, , and Seebeck coefficient, S, for these materials decrease with increased Ga-doping while both mobility and effective mass increase with Ga doping. The power factor (S2/ρ) therefore increases with Ga-doping. The highest thermoelectric figure of merit (ZT = 0.39 at 700 K) was obtained for the composition that had the lowest thermal conductivity. Our results suggest an approach to achieving optimized thermoelectric properties and are part of the continuingmore » effort to explore different quaternary chalcogenide compositions and structure types, as this class of materials continues to be of interest for thermoelectrics applications.« less

  5. Visualization of atomic-scale phenomena in superconductors: application to FeSe

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

    Choubey, Peayush; Berlijn, Tom; Kreisel, Andreas; Cao, Chao; Hirschfeld, Peter J.

    2014-10-31

    Here we propose a simple method of calculating inhomogeneous, atomic-scale phenomena in superconductors which makes use of the wave function information traditionally discarded in the construction of tight-binding models used in the Bogoliubov-de Gennes equations. The method uses symmetry- based first principles Wannier functions to visualize the effects of superconducting pairing on the distribution of electronic states over atoms within a crystal unit cell. Local symmetries lower than the global lattice symmetry can thus be exhibited as well, rendering theoretical comparisons with scanning tunneling spectroscopy data much more useful. As a simple example, we discuss the geometric dimer states observedmore » near defects in superconducting FeSe.« less

  6. Time-resolved terahertz dynamics in thin films of the topological insulator Bi2Se3

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

    Valdés Aguilar, R.; Qi, J.; Brahlek, M.; Bansal, N.; Azad, A.; Bowlan, J.; Oh, S.; Taylor, A. J.; Prasankumar, R. P.; Yarotski, D. A.

    2015-01-07

    We use optical pump–THz probe spectroscopy at low temperatures to study the hot carrier response in thin Bi2Se3 films of several thicknesses, allowing us to separate the bulk from the surface transient response. We find that for thinner films the photoexcitation changes the transport scattering rate and reduces the THz conductivity, which relaxes within 10 picoseconds (ps). For thicker films, the conductivity increases upon photoexcitation and scales with increasing both the film thickness and the optical fluence, with a decay time of approximately 5 ps as well as a much higher scattering rate. Furthermore, these different dynamics are attributed tomore » the surface and bulk electrons, respectively, and demonstrate that long-lived mobile surface photo-carriers can be accessed independently below certain film thicknesses for possible optoelectronic applications.« less

  7. Strain-dependent photoluminescence behavior in three geometries of CdSe/CdS nanocrystals

    SciTech Connect (OSTI)

    Choi, Charina L; Koski, Kristie J; Sivasankar, Sanjeevi; Alivisatos, A Paul

    2009-05-26

    In recent years, a new generation of quantum confined colloidal semiconductor structures has emerged, with more complex shapes than simple quantum dots1, 2. These include nanorods3 and tetrapods4. Beyond shape, it is also now possible to spatially vary the electron and hole potentials within these nanoparticles by varying the composition. Examples of these new structures include seeded dots, rods, and tetrapods, which contain a CdSe core embedded within a CdS shell5, 6. These structures may have many uses beyond those envisioned for simple quantum dots, which are frequently employed in luminescent applications7. This paper is concerned with changes in the optoelectronic properties of tetrapods when the arms are bent. We demonstrate that seeded tetrapods can serve as an optical strain gauge, capable of measuring forces on the order of nanonewtons. We anticipate that a nanocrystal strain gauge with optical readout will be useful for applications ranging from sensitive optomechanical devices to biological force investigations.

  8. Apparent critical phenomena in the superionic phase transition of Cu2-xSe

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

    Kang, Stephen Dongmin; Danilkin, Sergey A.; Aydemir, Umut; Avdeev, Maxim; Studer, Andrew; Snyder, G. Jeffrey

    2016-01-11

    The superionic phase transition ofmore » $${\\mathrm{Cu}}_{2-x}\\mathrm{Se}$$ accompanies drastic changes in transport properties. The Seebeck coefficient increases sharply while the electrical conductivity and thermal diffusivity drops. Such behavior has previously been attributed to critical phenomena under the assumption of a continuous phase transition. However, applying Landau's criteria suggests that the transition should be first order. Using the phase diagram that is consistent with a first order transition, we show that the observed transport properties and heat capacity curves can be accounted for and modeled with good agreement. The apparent critical phenomena is shown to be a result of compositional degree-of-freedom. In conclusion, understanding of the phase transition allows to explain the enhancement in the thermoelectric figure-of-merit that is accompanied with the transition.« less

  9. Doping Effects on the Thermoelectric Properties of Cu3SbSe4

    SciTech Connect (OSTI)

    Skoug, Eric; Cain, Jeffrey D.; Morelli, Donald; Majsztrik, Paul W; Kirkham, Melanie J; Lara-Curzio, Edgar

    2011-01-01

    We present the first systematic doping study on the ternary semiconductor Cu3SbSe 4 . We have developed a novel synthesis procedure that produces high-quality polycrystalline samples with hole concentrations an order of magnitude lower than have been reported for the undoped compound. The hole concentration can be increased by adding small amounts of either Ge or Sn on the Sb site. The power factor increases with increasing doping, reaching a maximum value of 16 W/cmK^2 . The thermoelectric properties are optimized for the 2% Sn doped compound which has ZT=0.72 at 630K, rivaling that of state-of-the-art thermoelectric materials in this temperature range.

  10. Nuclear Structure Relevant to Neutrinoless Double {beta} Decay: {sup 76}Ge and {sup 76}Se

    SciTech Connect (OSTI)

    Schiffer, J. P.; Gros, S.; Jiang, C. L.; Rehm, K. E. [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Freeman, S. J.; Fitzpatrick, C. R.; Kay, B. P. [University of Manchester, Manchester M13 9PL (United Kingdom); Clark, J. A.; Deibel, C.; Heinz, A.; Parikh, A.; Parker, P. D.; Werner, V.; Wrede, C. [Yale University, New Haven, Connecticut 06520 (United States); Hirata, D. [GANIL (IN2P3/CNRS -DSM/CEA), B.P. 55027 14076 Caen Cedex 5 (France); Dept. of Physics and Astronomy, Open University, Milton Keynes, MK7 6AA (United Kingdom); Villari, A. C. C. [GANIL (IN2P3/CNRS -DSM/CEA), B.P. 55027 14076 Caen Cedex 5 (France)

    2008-03-21

    The possibility of observing neutrinoless double {beta} decay offers the opportunity of determining the effective neutrino mass if the nuclear matrix element were known. Theoretical calculations are uncertain, and measurements of the occupations of valence orbits by nucleons active in the decay can be important. The occupation of valence neutron orbits in the ground states of {sup 76}Ge (a candidate for such decay) and {sup 76}Se (the daughter nucleus) were determined by precisely measuring cross sections for both neutron-adding and removing transfer reactions. Our results indicate that the Fermi surface is much more diffuse than in theoretical calculations. We find that the populations of at least three orbits change significantly between these two ground states while in the calculations, the changes are confined primarily to one orbit.