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Sample records for selected energy epitaxial

  1. Effects of contamination on selective epitaxial growth

    NASA Astrophysics Data System (ADS)

    MacDonald, Brian J.; Paton, Eric; Adem, Ercan; En, Bill

    2004-06-01

    As MOSFET dimensions scale down in size, it has become increasingly difficult to maintain high drive current while suppressing the off-state leakage current. One method of avoiding short-channel effects is to scale the source/drain (S/D) junction depths proportionally with the gate length. Unfortunately, this increases the S/D resistance, which slows the circuit. To keep the S/D junction shallow without affecting the S/D resistance, a raised S/D (RSD) structure is required. Integrating RSD can be difficult. Selective epitaxial growth (SEG) is the process used to incorporate RSD. This process requires a relatively clean surface to initiate the growth. Insertion of SEG earlier in the process flow facilitates selective epitaxial growth. Insertion of SEG later in the process flow results in higher levels of contamination at the interface of the Si substrate and the RSD structure. In this paper, we identify some mechanisms that determine the quality of the selective epitaxial film. Results indicate that Si defects are not a dominant mechanism in SEG film quality. Instead, results suggest that higher levels of contamination increased the surface roughness of the epitaxial film. PMOS regions were found to have higher levels of contamination and rougher epitaxial films than NMOS regions. Hydrogen bake as high as 900 °C was required to lower the surface contamination and provide excellent epitaxial morphology. Unfortunately, this high temperature causes enhanced dopant diffusion and deactivation of the device. Previous work [H. van Meer, K. De Meyer, Symposium on VLSI Technology Digest of Technical Papers, 2002, p. 170.] identified an alternative integration that provides excellent quality selective epitaxy, without dopant diffusion and deactivation.

  2. Low energy dislocation structures in epitaxy

    NASA Technical Reports Server (NTRS)

    Van Der Merwe, Jan H.; Woltersdorf, J.; Jesser, W. A.

    1986-01-01

    The principle of minimum energy was applied to epitaxial interfaces to show the interrelationship beteen misfit, overgrowth thickness and misfit dislocation spacing. The low energy dislocation configurations were presented for selected interfacial geometries. A review of the interfacial energy calculations was made and a critical assessment of the agreement between theory and experiment was presented. Modes of misfit accommodation were presented with emphasis on the distinction between kinetic effects and equilibrium conditions. Two-dimensional and three-dimensional overgrowths were treated together with interdiffusion-modified interfaces, and several models of interfacial structure were treated including the classical and the current models. The paper is concluded by indicating areas of needed investigation into interfacial structure.

  3. Selective epitaxy using the gild process

    DOEpatents

    Weiner, Kurt H.

    1992-01-01

    The present invention comprises a method of selective epitaxy on a semiconductor substrate. The present invention provides a method of selectively forming high quality, thin GeSi layers in a silicon circuit, and a method for fabricating smaller semiconductor chips with a greater yield (more error free chips) at a lower cost. The method comprises forming an upper layer over a substrate, and depositing a reflectivity mask which is then removed over selected sections. Using a laser to melt the unmasked sections of the upper layer, the semiconductor material in the upper layer is heated and diffused into the substrate semiconductor material. By varying the amount of laser radiation, the epitaxial layer is formed to a controlled depth which may be very thin. When cooled, a single crystal epitaxial layer is formed over the patterned substrate. The present invention provides the ability to selectively grow layers of mixed semiconductors over patterned substrates such as a layer of Ge.sub.x Si.sub.1-x grown over silicon. Such a process may be used to manufacture small transistors that have a narrow base, heavy doping, and high gain. The narrowness allows a faster transistor, and the heavy doping reduces the resistance of the narrow layer. The process does not require high temperature annealing; therefore materials such as aluminum can be used. Furthermore, the process may be used to fabricate diodes that have a high reverse breakdown voltage and a low reverse leakage current.

  4. Chiral habit selection on nanostructured epitaxial quartz films.

    PubMed

    Carretero-Genevrier, Adrián; Gich, Martí; Picas, Laura; Sanchez, Clément; Rodriguez-Carvajal, Juan

    2015-01-01

    Understanding the crystallization of enantiomorphically pure systems can be relevant to diverse fields such as the study of the origins of life or the purification of racemates. Here we report on polycrystalline epitaxial thin films of quartz on Si substrates displaying two distinct types of chiral habits that never coexist in the same film. We combine Atomic Force Microscopy (AFM) analysis and computer-assisted crystallographic calculations to make a detailed study of these habits of quartz. By estimating the surface energies of the observed crystallites we argue that the films are enantiomorphically pure and we briefly outline a possible mechanism to explain the habit and chiral selection in this system.

  5. Computational Approach for Epitaxial Polymorph Stabilization through Substrate Selection

    SciTech Connect

    Ding, Hong; Dwaraknath, Shyam S.; Garten, Lauren; Ndione, Paul; Ginley, David; Persson, Kristin A.

    2016-05-25

    With the ultimate goal of finding new polymorphs through targeted synthesis conditions and techniques, we outline a computational framework to select optimal substrates for epitaxial growth using first principle calculations of formation energies, elastic strain energy, and topological information. To demonstrate the approach, we study the stabilization of metastable VO2 compounds which provides a rich chemical and structural polymorph space. We find that common polymorph statistics, lattice matching, and energy above hull considerations recommends homostructural growth on TiO2 substrates, where the VO2 brookite phase would be preferentially grown on the a-c TiO2 brookite plane while the columbite and anatase structures favor the a-b plane on the respective TiO2 phases. Overall, we find that a model which incorporates a geometric unit cell area matching between the substrate and the target film as well as the resulting strain energy density of the film provide qualitative agreement with experimental observations for the heterostructural growth of known VO2 polymorphs: rutile, A and B phases. The minimal interfacial geometry matching and estimated strain energy criteria provide several suggestions for substrates and substrate-film orientations for the heterostructural growth of the hitherto hypothetical anatase, brookite, and columbite polymorphs. These criteria serve as a preliminary guidance for the experimental efforts stabilizing new materials and/or polymorphs through epitaxy. The current screening algorithm is being integrated within the Materials Project online framework and data and hence publicly available.

  6. Anisotropy of selective epitaxy in nanoscale-patterned growth: GaAs nanowires selectively grown on a SiO2-patterned (001) substrate by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Lee, S. C.; Dawson, L. R.; Brueck, S. R. J.; Jiang, Y.-B.

    2005-12-01

    Anisotropic selective epitaxy in nanoscale-patterned growth (NPG) by molecular-beam epitaxy is investigated on a 355nm period two-dimensional array of circular holes fabricated in a 30-nm-thick SiO2 film on a GaAs(001) substrate. The hole diameter ranged from 70to150nm. The small hole diameter and the very thin masking layer stimulated lateral growth over the SiO2 surface at an early stage of selective epitaxy on this patterned substrate. Lateral overgrowth associated with selective epitaxy, however, did not proceed isotropically along the circular boundary between the open substrate surface and the SiO2 mask. There was preferential growth direction parallel to ⟨111⟩B. This anisotropy in the selective epitaxy resulted in the formation of a nanoscale, nontapered, straight-wire-type epitaxial layer (GaAs nanowires), which had a length of up to 1.8μm for a nominal 200nm deposition. Every GaAs nanowire had a hexagonal prismatic shape directed along ⟨111⟩B and was surrounded by six (110) sidewalls. The anisotropy of selective epitaxy and faceting in NPG were affected by the profile of the SiO2 mask and are interpreted using a minimization of the total surface energy for equilibrium crystal shape.

  7. Selective epitaxial growth of graphene on SiC

    NASA Astrophysics Data System (ADS)

    Camara, N.; Rius, G.; Huntzinger, J.-R.; Tiberj, A.; Mestres, N.; Godignon, P.; Camassel, J.

    2008-09-01

    We present a method of selective epitaxial growth of few layers graphene (FLG) on a "prepatterned" silicon carbide (SiC) substrate. The methods involves, successively, the sputtering of a thin aluminium nitride (AlN) layer on top of a monocrystalline SiC substrate and, then, patterning it with e-beam lithography and wet etching. The sublimation of few atomic layers of Si from the SiC substrate occurs only through the selectively etched AlN layer. The presence of the Raman G-band at ˜1582cm-1 in the AlN-free areas is used to validate the concept. It gives absolute evidence of selective FLG growth.

  8. Selective epitaxial growth of graphene on SiC

    SciTech Connect

    Camara, N.; Rius, G.; Godignon, P.; Huntzinger, J.-R.; Tiberj, A.; Camassel, J.

    2008-09-22

    We present a method of selective epitaxial growth of few layers graphene (FLG) on a ''prepatterned'' silicon carbide (SiC) substrate. The methods involves, successively, the sputtering of a thin aluminium nitride (AlN) layer on top of a monocrystalline SiC substrate and, then, patterning it with e-beam lithography and wet etching. The sublimation of few atomic layers of Si from the SiC substrate occurs only through the selectively etched AlN layer. The presence of the Raman G-band at {approx}1582 cm{sup -1} in the AlN-free areas is used to validate the concept. It gives absolute evidence of selective FLG growth.

  9. Tuning a strain-induced orbital selective Mott transition in epitaxial VO2

    NASA Astrophysics Data System (ADS)

    Mukherjee, Shantanu; Quackenbush, N. F.; Paik, H.; Schlueter, C.; Lee, T.-L.; Schlom, D. G.; Piper, L. F. J.; Lee, Wei-Cheng

    2016-06-01

    We present evidence of strain-induced modulation of electron correlation effects and increased orbital anisotropy in the rutile phase of epitaxial VO2/TiO2 films from hard x-ray photoelectron spectroscopy and soft V L-edge x-ray absorption spectroscopy, respectively. By using the U(1) slave spin formalism, we further argue that the observed anisotropic correlation effects can be understood by a model of orbital selective Mott transition at a filling that is noninteger but close to the half filling. Because the overlaps of wave functions between d orbitals are modified by the strain, orbital-dependent renormalizations of the bandwidths and the onsite energy occur. These renormalizations generally result in different occupation numbers in different orbitals. We find that if the system has a noninteger filling number near the half filling such as for VO2, certain orbitals could reach an occupation number closer to half filling under the strain, resulting in a strong reduction in the quasiparticle weight Zα of that orbital. Our work demonstrates that such an orbital selective Mott transition, defined as the case with Zα=0 in some but not all orbitals, could be accessed by epitaxial-strain engineering of correlated electron systems.

  10. The role of Energy Deposition in the Epitaxial Layer in Triggering SEGR in Power MOSFETs

    NASA Technical Reports Server (NTRS)

    Selva, L.; Swift, G.; Taylor, W.; Edmonds, L.

    1999-01-01

    In these SEGR experiments, three identical-oxide MOSFET types were irradiated with six ions of significantly different ranges. Results show the prime importance of the total energy deposited in the epitaxial layer.

  11. Selective growth of GaAs by organometallic vapor phase epitaxy at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Azoulay, R.; Dugrand, L.

    1991-01-01

    Complete selective epitaxy of GaAs by organometallic vapor phase epitaxy at atmospheric pressure was achieved by using TMG, AsH3, and AsCl3 as starting gases. Selectivity was observed at growth temperatures ranging from 650 to 750 °C. The blocking of polycrystal deposition on the mask, Si3N4, or W, is attributed to the adsorption of HCl on the mask, thus preventing the nucleation of GaAs. On the openings, the growth rate may be adjusted by controlling the TMG/AsCl3 ratio. When TMG/AsCl3<1, no growth occurs, but etching is observed.

  12. The impact of substrate selection for the controlled growth of graphene by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Schumann, T.; Lopes, J. M. J.; Wofford, J. M.; Oliveira, M. H.; Dubslaff, M.; Hanke, M.; Jahn, U.; Geelhaar, L.; Riechert, H.

    2015-09-01

    We examine how substrate selection impacts the resulting film properties in graphene growth by molecular beam epitaxy (MBE). Graphene growth on metallic as well as dielectric templates was investigated. We find that MBE offers control over the number of atomic graphene layers regardless of the substrate used. High structural quality could be achieved for graphene prepared on Ni (111) films which were epitaxially grown on MgO (111). For growth either on Al2O3 (0001) or on (6√3×6√3)R30°-reconstructed SiC (0001) surfaces, graphene with a higher density of defects is obtained. Interestingly, despite their defective nature, the layers possess a well defined epitaxial relation to the underlying substrate. These results demonstrate the feasibility of MBE as a technique for realizing the scalable synthesis of this two-dimensional crystal on a variety of substrates.

  13. Kinetic-energy induced smoothening and delay of epitaxial breakdown in pulsed-laser deposition

    SciTech Connect

    Shin, Byungha; Aziz, Michael J.

    2007-08-15

    We have isolated the effect of kinetic energy of depositing species from the effect of flux pulsing during pulsed-laser deposition (PLD) on surface morphology evolution of Ge(001) homoepitaxy at low temperature (100 deg. C). Using a dual molecular beam epitaxy (MBE) PLD chamber, we compare morphology evolution from three different growth methods under identical experimental conditions except for the differing nature of the depositing flux: (a) PLD with average kinetic energy 300 eV (PLD-KE); (b) PLD with suppressed kinetic energy comparable to thermal evaporation energy (PLD-TH); and (c) MBE. The thicknesses at which epitaxial breakdown occurs are ranked in the order PLD-KE>MBE>PLD-TH; additionally, the surface is smoother in PLD-KE than in MBE. The surface roughness of the films grown by PLD-TH cannot be compared due to the early epitaxial breakdown. These results demonstrate convincingly that kinetic energy is more important than flux pulsing in the enhancement of epitaxial growth, i.e., the reduction in roughness and the delay of epitaxial breakdown.

  14. Selective-area growth of heavily n-doped GaAs nanostubs on Si(001) by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Chang, Yoon Jung; Simmonds, Paul J.; Beekley, Brett; Goorsky, Mark S.; Woo, Jason C. S.

    2016-04-01

    Using an aspect ratio trapping technique, we demonstrate molecular beam epitaxy of GaAs nanostubs on Si(001) substrates. Nanoholes in a SiO2 mask act as a template for GaAs-on-Si selective-area growth (SAG) of nanostubs 120 nm tall and ≤100 nm in diameter. We investigate the influence of growth parameters including substrate temperature and growth rate on SAG. Optimizing these parameters results in complete selectivity with GaAs growth only on the exposed Si(001). Due to the confined-geometry, strain and defects in the GaAs nanostubs are restricted in lateral dimensions, and surface energy is further minimized. We assess the electrical properties of the selectively grown GaAs nanostubs by fabricating heterogeneous p+-Si/n+-GaAs p-n diodes.

  15. Atomic layer epitaxy of hematite on indium tin oxide for application in solar energy conversion

    SciTech Connect

    Martinson, Alex B.; Riha, Shannon; Guo, Peijun; Emery, Jonathan D.

    2016-07-12

    A method to provide an article of manufacture of iron oxide on indium tin oxide for solar energy conversion. An atomic layer epitaxy method is used to deposit an uncommon bixbytite-phase iron (III) oxide (.beta.-Fe.sub.2O.sub.3) which is deposited at low temperatures to provide 99% phase pure .beta.-Fe.sub.2O.sub.3 thin films on indium tin oxide. Subsequent annealing produces pure .alpha.-Fe.sub.2O.sub.3 with well-defined epitaxy via a topotactic transition. These highly crystalline films in the ultra thin film limit enable high efficiency photoelectrochemical chemical water splitting.

  16. Fermi energy tuning with light to control doping profiles during epitaxy

    SciTech Connect

    Sanders, C. E.; Beaton, D. A.; Reedy, R. C.; Alberi, K.

    2015-05-04

    The influence of light stimulation and photogenerated carriers on the process of dopant surface segregation during growth is studied in molecular beam epitaxially grown Si-doped GaAs structures. The magnitude of surface segregation decreases under illumination by above-bandgap photons, wherein splitting of the quasi Fermi levels reduces the band bending at the growth surface and raises the formation energy of compensating defects that can enhance atomic diffusion. We further show that light-stimulated epitaxy can be used as a practical approach to diminish dopant carry-forward in device structures and improve the performance of inverted modulation-doped quantum wells.

  17. Polarity-Induced Selective Area Epitaxy of GaN Nanowires.

    PubMed

    de Souza Schiaber, Ziani; Calabrese, Gabriele; Kong, Xiang; Trampert, Achim; Jenichen, Bernd; Dias da Silva, José Humberto; Geelhaar, Lutz; Brandt, Oliver; Fernández-Garrido, Sergio

    2017-01-11

    We present a conceptually novel approach to achieve selective area epitaxy of GaN nanowires. The approach is based on the fact that these nanostructures do not form in plasma-assisted molecular beam epitaxy on structurally and chemically uniform cation-polar substrates. By in situ depositing and nitridating Si on a Ga-polar GaN film, we locally reverse the polarity to induce the selective area epitaxy of N-polar GaN nanowires. We show that the nanowire number density can be controlled over several orders of magnitude by varying the amount of predeposited Si. Using this growth approach, we demonstrate the synthesis of single-crystalline and uncoalesced nanowires with diameters as small as 20 nm. The achievement of nanowire number densities low enough to prevent the shadowing of the nanowire sidewalls from the impinging fluxes paves the way for the realization of homogeneous core-shell heterostructures without the need of using ex situ prepatterned substrates.

  18. Surface stability and the selection rules of substrate orientation for optimal growth of epitaxial II-VI semiconductors

    SciTech Connect

    Yin, Wan-Jian; Yang, Ji-Hui; Zaunbrecher, Katherine; Gessert, Tim; Barnes, Teresa; Wei, Su-Huai; Yan, Yanfa

    2015-10-05

    The surface structures of ionic zinc-blende CdTe (001), (110), (111), and (211) surfaces are systematically studied by first-principles density functional calculations. Based on the surface structures and surface energies, we identify the detrimental twinning appearing in molecular beam epitaxy (MBE) growth of II-VI compounds as the (111) lamellar twin boundaries. To avoid the appearance of twinning in MBE growth, we propose the following selection rules for choosing optimal substrate orientations: (1) the surface should be nonpolar so that there is no large surface reconstructions that could act as a nucleation center and promote the formation of twins; (2) the surface structure should have low symmetry so that there are no multiple equivalent directions for growth. These straightforward rules, in consistent with experimental observations, provide guidelines for selecting proper substrates for high-quality MBE growth of II-VI compounds.

  19. III-V Nanowire Array Growth by Selective Area Epitaxy

    SciTech Connect

    Chu, Hyung-Joon; Stewart, Lawrence; Yeh, Tingwei; Dapkus, P. Daniel

    2011-12-23

    III-V semiconductor nanowires are unique material phase due to their high aspect ratio, large surface area, and strong quantum confinement. This affords the opportunity to control charge transport and optical properties for electrical and photonic applications. Nanoscale selective area metalorganic chemical vapor deposition growth (NS-SAG) is a promising technique to maximize control of nanowire diameter and position, which are essential for device application. In this work, InP and GaAs nanowire arrays are grown by NS-SAG. We observe enhanced sidewall growth and array uniformity disorder in high growth rate condition. Disorder in surface morphology and array uniformity of InP nanowire array is explained by enhanced growth on the sidewall and stacking faults. We also find that AsH{sub 3} decomposition on the sidewall affects the growth behavior of GaAs nanowire arrays.

  20. Epitaxial Growth of Oriented Metalloporphyrin Network Thin Film for Improved Selectivity of Volatile Organic Compounds.

    PubMed

    Li, De-Jing; Gu, Zhi-Gang; Vohra, Ismail; Kang, Yao; Zhu, Yong-Sheng; Zhang, Jian

    2017-03-03

    This study reports an oriented and homogenous cobalt-metalloporphyrin network (PIZA-1) thin film prepared by liquid phase epitaxial (LPE) method. The thickness of the obtained thin films can be well controlled, and their photocurrent properties can also be tuned by LPE cycles or the introduction of conductive guest molecules (tetracyanoquinodimethane and C60 ) into the PIZA-1 pores. The study of quartz crystal microbalance adsorption confirms that the PIZA-1 thin film with [110]-orientation presents much higher selectivity of benzene over toluene and p-xylene than that of the PIZA-1 powder with mixed orientations. These results reveal that the selective adsorption of volatile organic compounds highly depends on the growth orientations of porphyrin-based metal-organic framework thin films. Furthermore, the work will provide a new perspective for developing important semiconductive sensing materials with improved selectivity of guest compounds.

  1. Process for selectively patterning epitaxial film growth on a semiconductor substrate

    DOEpatents

    Sheldon, P.; Hayes, R.E.

    1984-12-04

    Disclosed is a process for selectively patterning epitaxial film growth on a semiconductor substrate. The process includes forming a masking member on the surface of the substrate, the masking member having at least two layers including a first layer disposed on the substrate and the second layer covering the first layer. A window is then opened in a selected portion of the second layer by removing that portion to expose the first layer thereunder. The first layer is then subjected to an etchant introduced through the window to dissolve the first layer a sufficient amount to expose the substrate surface directly beneath the window, the first layer being adapted to preferentially dissolve at a substantially greater rate than the second layer so as to create an overhanging ledge portion with the second layer by undercutting the edges thereof adjacent the window. The epitaxial film is then deposited on the exposed substrate surface directly beneath the window. Finally, an etchant is introduced through the window to dissolve the remainder of the first layer so as to lift-off the second layer and materials deposited thereon to fully expose the balance of the substrate surface.

  2. Process for selectively patterning epitaxial film growth on a semiconductor substrate

    DOEpatents

    Sheldon, Peter; Hayes, Russell E.

    1986-01-01

    A process is disclosed for selectively patterning epitaxial film growth on a semiconductor substrate. The process includes forming a masking member on the surface of the substrate, the masking member having at least two layers including a first layer disposed on the substrate and the second layer covering the first layer. A window is then opened in a selected portion of the second layer by removing that portion to expose the first layer thereunder. The first layer is then subjected to an etchant introduced through the window to dissolve a sufficient amount of the first layer to expose the substrate surface directly beneath the window, the first layer being adapted to preferentially dissolve at a substantially greater rate than the second layer so as to create an overhanging ledge portion with the second layer by undercutting the edges thereof adjacent to the window. The epitaxial film is then deposited on the exposed substrate surface directly beneath the window. Finally, an etchant is introduced through the window to dissolve the remainder of the first layer so as to lift-off the second layer and materials deposited thereon to fully expose the balance of the substrate surface.

  3. Evolution of GaAs nanowire geometry in selective area epitaxy

    NASA Astrophysics Data System (ADS)

    Bassett, Kevin P.; Mohseni, Parsian K.; Li, Xiuling

    2015-03-01

    Nanowires (NWs) grown via selective area epitaxy (SAE) show great promise for applications in next generation electronic and photonic devices, yet the design of NW-based devices can be complicated due to the complex kinetics involved in the growth process. The presence of the patterned selective area mask, as well as the changing geometry of the NWs themselves during growth, leads to non-linear growth rates which can vary significantly based on location in the mask and the NW size. Here, we present a systematic study of the evolution of GaAs NW geometry during growth as a function of NW size and pitch. We highlight a breakdown of NW uniformity at extended growth times, which is accelerated for NW arrays with larger separations. This work is intended to outline potential fundamental growth challenges in achieving desired III-V NW array patterns and uniformity via SAE.

  4. Selective Epitaxial Growth of SiGe Layers with High Aspect Ratio Mask of Dielectric Films

    NASA Astrophysics Data System (ADS)

    Choi, A.-Ram; Choi, Sang-Sik; Park, Byung-Guan; Suh, Dongwoo; Kim, Gyungock; Kim, Jin-Tae; Choi, Jin-Soo; Cho, Deok-Ho; Han, Tae-Hyun; Shim, Kyu-Hwan

    This paper presents the selective epitaxial growth (SEG) properties of reduced pressure chemical vapor deposition (RPCVD) at low temperatures (LT) of 675-725°C with high aspect ratio mask of dielectric films. The SEG process could be explained in conjunction with the loading effect, the mask pattern shape/size, and the process parameters of RPCVD. The growth rates showed a large non-uniformity up to 40% depending upon the pattern size of the dielectric mask films, but as the SEG film becomes thicker, the growth rate difference converged on -15% between the narrow 2-μm and the wide 100-μm patterns. The evolution of SEG was controlled dominantly by the surface migration control at the initial stage, and converted to the surface topology control. The design of pattern size and distribution with dummy patterns must be useful to accomplish the reliable and uniform LT-SEG.

  5. Evolution of (001) and (111) facets for selective epitaxial growth inside submicron trenches

    SciTech Connect

    Jiang, S. Heyns, M.; Merckling, C.; Guo, W.; Waldron, N.; Caymax, M.; Vandervorst, W.; Seefeldt, M.

    2014-01-14

    The evolution of (001) and (111) facets for the epitaxial growth inside submicron trenches is systematically studied in this report. The analysis with the method of “Lagrange multiplier” indicates the equilibrium crystal shape. In the case of non-equilibrium without external fluxes, we employed the “weighted mean curvature” method to mathematically model the inter-facet migration rate for two extreme kinetic cases: “surface diffusion limited” and “surface attachment/detachment limited.” Coupled with external supply of atoms, the self-limited behavior of facet size is theoretically predicted. Moreover, we find that the self-limited stable facet size in trenches of different widths has a specific relationship determined by the surface energy ratio, kinetic rate ratio, and isolated growth rate difference. The two limited cases could be discriminated according to the mathematical fitting of one exponent in this relationship based on the stable facet size in trenches of different widths.

  6. Selective epitaxial silicon growth in the 650-1100 °C range in a reduced pressure chemical vapor deposition reactor using dichlorosilane

    NASA Astrophysics Data System (ADS)

    Regolini, J. L.; Bensahel, D.; Scheid, E.; Mercier, J.

    1989-02-01

    Selective epitaxial silicon layers have been grown in a reduced pressure (<2 Torr) reactor in the 650-1100 °C temperature range using only dichlorosilane (DCS) gas diluted in hydrogen. The growth rate plotted in Arrhenius coordinates (log G vs 1/T) shows an activation energy of 59 kcal/mol in the 650-800 °C range. A comparison is made between the DCS system and our previous results concerning the SiH4/HCl/H2 system.

  7. Usage of antimony segregation for selective doping of Si in molecular beam epitaxy

    SciTech Connect

    Yurasov, D. V.; Drozdov, M. N.; Murel, A. V.; Shaleev, M. V.; Novikov, A. V.; Zakharov, N. D.

    2011-06-01

    An original approach to selective doping of Si by antimony (Sb) in molecular beam epitaxy (MBE) is proposed and verified experimentally. This approach is based on controllable utilization of the effect of Sb segregation. In particular, the sharp dependence of Sb segregation on growth temperature in the range of 300-550 deg. C is exploited. The growth temperature variations between the kinetically limited and maximum segregation regimes are suggested to be utilized in order to obtain selectively doped structures with abrupt doping profiles. It is demonstrated that the proposed technique allows formation of selectively doped Si:Sb layers, including delta ({delta}-)doped layers in which Sb concentrations can be varied from 5 x 10{sup 15} to 10{sup 20} cm{sup -3}. The obtained doped structures are shown to have a high crystalline quality and the short-term growth interruptions, which are needed to change the substrate temperature, do not lead to any significant accumulation of background impurities in grown samples. Realization of the proposed approach requires neither too low (<300 deg. C), nor too high (>600 deg. C) growth temperatures or any special equipment for the MBE machines.

  8. Energy: An annotated selected bibliography

    NASA Technical Reports Server (NTRS)

    Blow, S. J. (Compiler); Peacock, R. W. (Compiler); Sholy, J. J. (Compiler)

    1979-01-01

    This updated bibliography contains approximately 7,000 selected references on energy and energy related topics from bibliographic and other data sources from June 1977. Under each subject heading the entries are arranged by the date, with the latest works first. Geothermal, solar, wind, and ocean/water power sources are included. Magnetohydrodynamics and electrohydrodynamics, electric power engineering, automotive power plants, and energy storage are also covered.

  9. Big-data reflection high energy electron diffraction analysis for understanding epitaxial film growth processes.

    PubMed

    Vasudevan, Rama K; Tselev, Alexander; Baddorf, Arthur P; Kalinin, Sergei V

    2014-10-28

    Reflection high energy electron diffraction (RHEED) has by now become a standard tool for in situ monitoring of film growth by pulsed laser deposition and molecular beam epitaxy. Yet despite the widespread adoption and wealth of information in RHEED images, most applications are limited to observing intensity oscillations of the specular spot, and much additional information on growth is discarded. With ease of data acquisition and increased computation speeds, statistical methods to rapidly mine the data set are now feasible. Here, we develop such an approach to the analysis of the fundamental growth processes through multivariate statistical analysis of a RHEED image sequence. This approach is illustrated for growth of La(x)Ca(1-x)MnO(3) films grown on etched (001) SrTiO(3) substrates, but is universal. The multivariate methods including principal component analysis and k-means clustering provide insight into the relevant behaviors, the timing and nature of a disordered to ordered growth change, and highlight statistically significant patterns. Fourier analysis yields the harmonic components of the signal and allows separation of the relevant components and baselines, isolating the asymmetric nature of the step density function and the transmission spots from the imperfect layer-by-layer (LBL) growth. These studies show the promise of big data approaches to obtaining more insight into film properties during and after epitaxial film growth. Furthermore, these studies open the pathway to use forward prediction methods to potentially allow significantly more control over growth process and hence final film quality.

  10. Segregation of Sb in Ge epitaxial layers and its usage for the selective doping of Ge-based structures

    SciTech Connect

    Antonov, A. V.; Drozdov, M. N.; Novikov, A. V. Yurasov, D. V.

    2015-11-15

    The segregation of Sb in Ge epitaxial layers grown by the method of molecular beam epitaxy on Ge (001) substrates is investigated. For a growth temperature range of 180–325°C, the temperature dependence is determined for the segregation ratio of Sb in Ge, which shows a sharp increase (by more than three orders of magnitude) with increasing temperature. The strong dependence of the segregation properties of Sb on the growth temperature makes it possible to adapt a method based on the controlled use of segregation developed previously for the doping of Si structures for the selective doping of Ge structures with a donor impurity. Using this method selectively doped Ge:Sb structures, in which the bulk impurity concentration varies by an order of magnitude at distances of 3–5 nm, are obtained.

  11. Facet-selective nucleation and conformal epitaxy of Ge shells on Si nanowires

    DOE PAGES

    Nguyen, Binh -Minh; Swartzentruber, Brian; Ro, Yun Goo; ...

    2015-10-08

    Knowledge of nanoscale heteroepitaxy is continually evolving as advances in material synthesis reveal new mechanisms that have not been theoretically predicted and are different than what is known about planar structures. In addition to a wide range of potential applications, core/shell nanowire structures offer a useful template to investigate heteroepitaxy at the atomistic scale. We show that the growth of a Ge shell on a Si core can be tuned from the theoretically predicted island growth mode to a conformal, crystalline, and smooth shell by careful adjustment of growth parameters in a narrow growth window that has not been exploredmore » before. In the latter growth mode, Ge adatoms preferentially nucleate islands on the {113} facets of the Si core, which outgrow over the {220} facets. Islands on the low-energy {111} facets appear to have a nucleation delay compared to the {113} islands; however, they eventually coalesce to form a crystalline conformal shell. As a result, synthesis of epitaxial and conformal Si/Ge/Si core/multishell structures enables us to fabricate unique cylindrical ring nanowire field-effect transistors, which we demonstrate to have steeper on/off characteristics than conventional core/shell nanowire transistors.« less

  12. Facet-selective nucleation and conformal epitaxy of Ge shells on Si nanowires

    SciTech Connect

    Nguyen, Binh -Minh; Swartzentruber, Brian; Ro, Yun Goo; Dayeh, Shadi A.

    2015-10-08

    Knowledge of nanoscale heteroepitaxy is continually evolving as advances in material synthesis reveal new mechanisms that have not been theoretically predicted and are different than what is known about planar structures. In addition to a wide range of potential applications, core/shell nanowire structures offer a useful template to investigate heteroepitaxy at the atomistic scale. We show that the growth of a Ge shell on a Si core can be tuned from the theoretically predicted island growth mode to a conformal, crystalline, and smooth shell by careful adjustment of growth parameters in a narrow growth window that has not been explored before. In the latter growth mode, Ge adatoms preferentially nucleate islands on the {113} facets of the Si core, which outgrow over the {220} facets. Islands on the low-energy {111} facets appear to have a nucleation delay compared to the {113} islands; however, they eventually coalesce to form a crystalline conformal shell. As a result, synthesis of epitaxial and conformal Si/Ge/Si core/multishell structures enables us to fabricate unique cylindrical ring nanowire field-effect transistors, which we demonstrate to have steeper on/off characteristics than conventional core/shell nanowire transistors.

  13. Application of Silicon Selective Epitaxial Growth and Chemo-Mechanical Polishing to Bipolar and Soi Mosfet Devices.

    NASA Astrophysics Data System (ADS)

    Nguyen, Cuong Tan

    1994-01-01

    Polished Epitaxy, or the combination of silicon Selective Epitaxial Growth and Chemo-Mechanical Polishing, provides new flexibility in process and device design, including optimized isolation, planar active-area definition, low-capacitance contacts, and SOI thin films. In this work, Polished Epitaxy has been developed with particular effort on overcoming junction leakage problems widely reported in devices fabricated in similar processes. It was found that in addition to careful surface preparation and defect control in the selective epitaxy process, issues such as sidewall orientation, junction passivation, crystal annealing, and surface damage removal were equally important and needed to be addressed. Coupled with the proper processing steps, Polished Epitaxy was able to deliver material of comparable quality to bulk silicon, suitable for device applications. By growing epitaxy laterally over an oxide step followed by polishing, a pedestal structure was created in which a thin film of single-crystal silicon was formed over oxide. Serving as the extrinsic base contact to a T-Pedestal bipolar transistor device, this pedestal helped minimize the parasitic extrinsic-base-collector overlap capacitance. The cut-off frequency (f_ {T}) in a device with a 1.0-mu m wide emitter stripe was found to improve from 17GHz to 22GHz when the contact overlap was reduced from a more conventional, larger size of 1.0 mu m to 0.2 mum. It is expected that the high-frequency performance of this structure can still be improved further in an optimized process with reduced emitter and collector resistances. The same pedestal structure was applied to a Pedestal -SOI (Silicon-On-Insulator) MOSFET device concept. At one extreme, a conventional bulk MOSFET structure is obtained when the pedestal is not utilized; quasi-SOI occurs when the drain and part of the channel overlap with the pedestal over buried oxide; at the other extreme, complete-SOI behavior results when source, channel, and drain

  14. Chiral-Selective Growth of Single-Walled Carbon Nanotubes on Lattice-Mismatched Epitaxial Cobalt Nanoparticles

    PubMed Central

    He, Maoshuai; Jiang, Hua; Liu, Bilu; Fedotov, Pavel V.; Chernov, Alexander I.; Obraztsova, Elena D.; Cavalca, Filippo; Wagner, Jakob B.; Hansen, Thomas W.; Anoshkin, Ilya V.; Obraztsova, Ekaterina A.; Belkin, Alexey V.; Sairanen, Emma; Nasibulin, Albert G.; Lehtonen, Juha; Kauppinen, Esko I.

    2013-01-01

    Controlling chirality in growth of single-walled carbon nanotubes (SWNTs) is important for exploiting their practical applications. For long it has been conceptually conceived that the structural control of SWNTs is potentially achievable by fabricating nanoparticle catalysts with proper structures on crystalline substrates via epitaxial growth techniques. Here, we have accomplished epitaxial formation of monometallic Co nanoparticles with well-defined crystal structure, and its use as a catalyst in the selective growth of SWNTs. Dynamics of Co nanoparticles formation and SWNT growth inside an atomic-resolution environmental transmission electron microscope at a low CO pressure was recorded. We achieved highly preferential growth of semiconducting SWNTs (~90%) with an exceptionally large population of (6, 5) tubes (53%) in an ambient CO atmosphere. Particularly, we also demonstrated high enrichment in (7, 6) and (9, 4) at a low growth temperature. These findings open new perspectives both for structural control of SWNTs and for elucidating the growth mechanisms. PMID:23492872

  15. Growth of InGaAs nanowires on Ge(111) by selective-area metal-organic vapor-phase epitaxy

    NASA Astrophysics Data System (ADS)

    Yoshida, Akinobu; Tomioka, Katsuhiro; Ishizaka, Fumiya; Motohisa, Junichi

    2017-04-01

    We report the growth of InGaAs nanowires (NWs) on Ge(111) substrates using selective-area metal-organic vapor-phase epitaxy (SA-MOVPE) for novel InGaAs/Ge hybrid complementary metal-oxide-semiconductor (CMOS) applications. Ge(111) substrates with periodic arrays of mask opening were prepared, and InGaAs was selectively grown on the opening region of Ge(111). A uniform array of InGaAs NWs with a diameter around 100 nm was successfully grown using appropriate preparation of the initial surfaces with an AsH3 thermal treatment and flow-rate modulation epitaxy (FME). We found that optimizing partial pressure of AsH3 and the number of FME cycles improved the yield of vertical InGaAs NWs. Line-scan profile analysis of energy dispersive X-ray (EDX) spectrometry showed that the In composition in the InGaAs NW was almost constant from the bottom to the top. Transmission electron microscope (TEM) analysis revealed that the interface between InGaAs NW and Ge had misfit dislocations, but their distance was longer than that expected from the difference in their lattice constants.

  16. Energy: An annotated selected bibliography

    NASA Technical Reports Server (NTRS)

    Blow, S. J. (Compiler); Peacock, R. W. (Compiler); Sholy, J. J. (Compiler)

    1979-01-01

    This updated bibliography contains approximately 7,000 selected references on energy and energy related topics from bibliographic and other data sources from June 1977. Under each subject heading the entries are arranged by the data, with the latest works first. Subject headings include: resources supply/demand, and forecasting; policy, legislation, and regulation; environment; consumption, conservation, and economics; analysis, systems, and modeling, and information sources and documentation. Fossil fuels, hydrogen and other fuels, liquid/solid wastes and biomass, waste heat utilization, and nuclear power sources are also included.

  17. Numerical approximations for the molecular beam epitaxial growth model based on the invariant energy quadratization method

    NASA Astrophysics Data System (ADS)

    Yang, Xiaofeng; Zhao, Jia; Wang, Qi

    2017-03-01

    The Molecular Beam Epitaxial model is derived from the variation of a free energy, that consists of either a fourth order Ginzburg-Landau double well potential or a nonlinear logarithmic potential in terms of the gradient of a height function. One challenge in solving the MBE model numerically is how to develop proper temporal discretization for the nonlinear terms in order to preserve energy stability at the time-discrete level. In this paper, we resolve this issue by developing a first and second order time-stepping scheme based on the "Invariant Energy Quadratization" (IEQ) method. The novelty is that all nonlinear terms are treated semi-explicitly, and the resulted semi-discrete equations form a linear system at each time step. Moreover, the linear operator is symmetric positive definite and thus can be solved efficiently. We then prove that all proposed schemes are unconditionally energy stable. The semi-discrete schemes are further discretized in space using finite difference methods and implemented on GPUs for high-performance computing. Various 2D and 3D numerical examples are presented to demonstrate stability and accuracy of the proposed schemes.

  18. Low-energy electron diffraction investigation of epitaxial growth: Pt and Pd on Pd(100)

    SciTech Connect

    Flynn-Sanders, D.

    1990-09-21

    We investigate the epitaxial growth of Pt and Pd and Pd(100) via spot profile analysis using conventional low-energy electron diffraction (LEED). We resolve a central-spike and diffuse component in the spot profiles, reflecting the layer-occupations and pair-correlations, respectively. Kinetic limitations inhibit layer-by-layer growth at low temperatures. Our data suggest diffusion switches on at ca. 150 K for Pt and ca. 170 K for Pd indicating activation barriers to surface diffusion of ca. 10 and ca. 13 kcal/mol, respectively. To clarify the role of diffusion in determining the resulting film morphology, we develop a growth model that incorporates the adsorption-site requirement and predicts intensity oscillations. We present a new procedure to experimentally determine out-of-phase scattering conditions. At these energies, ring-structure is evident in the profiles during Pd growth between ca. 200 and 400 K. We report ring intensity oscillations as a function of coverage, which demonstrate the filling of individual layers.

  19. Selective area epitaxy of monolithic white-light InGaN/GaN quantum well microstripes with dual color emission

    SciTech Connect

    Li, Yuejing; Tong, Yuying; Yang, Guofeng Yao, Chujun; Sun, Rui; Cai, Lesheng; Xu, Guiting; Wang, Jin; Zhang, Qing; Ye, Xuanchao; Wu, Mengting; Wen, Zhiqin

    2015-09-15

    Monolithic color synthesis is demonstrated using InGaN/GaN multiple quantum wells (QWs) grown on GaN microstripes formed by selective area epitaxy on SiO{sub 2} mask patterns. The striped microfacet structure is composed of (0001) and (11-22) planes, attributed to favorable surface polarity and surface energy. InGaN/GaN QWs on different microfacets contain spatially inhomogeneous compositions owing to the diffusion of adatoms among the facets. This unique property allows the microfacet QWs to emit blue light from the (11-22) plane and yellow light from the top (0001) plane, the mixing of which leads to the perception of white light emission.

  20. Dislocation reduction via selective-area growth of InN accompanied by lateral growth by rf-plasma-assisted molecular-beam epitaxy

    SciTech Connect

    Kamimura, Jumpei; Kishino, Katsumi; Kikuchi, Akihiko

    2010-10-04

    We investigated the selective-area growth (SAG) of InN by rf-plasma-assisted molecular-beam epitaxy using molybdenum (Mo)-mask-patterned sapphire (0001) substrates, which resulted in the formation of regularly arranged N-polar InN microcrystals. Transmission electron microscopy observation confirmed that the laterally grown side areas were nearly dislocation-free, although many threading dislocations (10{sup 9}-10{sup 10} cm{sup -2}) were generated at the InN/sapphire interface and propagated into the center of the InN microcrystals along the crystal c-axis. The laterally grown InN microcrystals exhibited narrow near-IR emission spectra with a peak photon energy of 0.627 eV and a linewidth of 39 meV at room temperature.

  1. Chemical order and selection of the mechanism for strain relaxation in epitaxial FePd(Pt) thin layers

    SciTech Connect

    Halley, D.; Marty, A.; Bayle-Guillemaud, P.; Attane, J.P.; Samson, Y.

    2004-11-01

    We observed that the relaxation mechanism of the epitaxial strain is dramatically dependent on the chemical ordering within the L1{sub 0} structure in FePd(Pt) thin films. In disordered or weakly ordered layers, the relaxation takes place though perfect (1/2)[101] dislocations, whereas well-ordered films relax through the partial 1/6[112] Shockley dislocations, piled-up within microtwins, with a huge impact on both the morphology and the magnetic properties of the film. We show that the antiphase boundary energy is the key factor preventing the propagation of perfect dislocations in ordered alloys.

  2. Why do dislocations assemble into interfaces in epitaxy as well as in crystal plasticity? To minimize free energy

    NASA Astrophysics Data System (ADS)

    Kuhlmann-Wilsdorf, D.

    2002-08-01

    Dislocations commonly form planar arrays that minimize the free interfacial energy between relatively mismatched crystal volumes. In epitaxy and phase transformations, the causative misfit is that between differences in lattice structure and/or orientations of different phases. In deformed homogeneous crystalline materials, the planar dislocation arrays are grain and mosaic block boundaries that accommodate relative misorientations within the same crystal structure. Thus, overwhelmingly, planar dislocation arrays have a basically common origin, namely minimization of interfacial energies. Consequently, they are all subject to the low-energy dislocation structures (LEDS) hypothesis. While the specific applications of the underlying general theory are well advanced in terms of epitaxy, phase, and grain boundaries, in connection with plastic deformation that very basis is widely overlooked, if not denied. The present article aims to (a) document the fact that, while being formed, dislocation structures due to plastic deformation are in thermodynamical equilibrium, (b) firmly establish the outlined connection between planar dislocation arrays of all types, and, thereby, (c) establish the kinship between epitaxy and plastic deformation of crystalline materials.

  3. Imaging pulsed laser deposition growth of homo-epitaxial SrTiO3 by low-energy electron microscopy

    NASA Astrophysics Data System (ADS)

    van der Torren, A. J. H.; van der Molen, S. J.; Aarts, J.

    2016-12-01

    By combining low-energy electron microscopy with in situ pulsed laser deposition we have developed a new technique for film growth analysis, making use of both diffraction and real-space information. Working at the growth temperature, we can use: the intensity and profile variations of the specular beam to follow the coverage in a layer-by-layer fashion; real-space microscopy to follow e.g. atomic steps at the surface; and electron reflectivity to probe the unoccupied band structure of the grown material. Here, we demonstrate our methodology for homo-epitaxial growth of SrTiO3. Interestingly, the same combination of techniques will also be applicable to hetero-epitaxial oxide growth, largely extending the scope of research possibilities.

  4. Shadowing and mask opening effects during selective-area vapor-liquid-solid growth of InP nanowires by metalorganic molecular beam epitaxy.

    PubMed

    Kelrich, A; Calahorra, Y; Greenberg, Y; Gavrilov, A; Cohen, S; Ritter, D

    2013-11-29

    Indium phosphide nanowires were grown by metalorganic molecular beam epitaxy using the selective-area vapor-liquid-solid method. We show experimentally and theoretically that the size of the annular opening around the nanowire has a major impact on nanowire growth rate. In addition, we observed a considerable reduction of the growth rate in dense two-dimensional arrays, in agreement with a calculation of the shadowing of the scattered precursors. Due to the impact of these effects on growth, they should be considered during selective-area vapor-liquid-solid nanowire epitaxy.

  5. Gradual tilting of crystallographic orientation and configuration of dislocations in GaN selectively grown by vapour phase epitaxy methods

    PubMed

    Kuwan; Tsukamoto; Taki; Horibuchi; Oki; Kawaguchi; Shibata; Sawaki; Hiramatsu

    2000-01-01

    Cross-sectional transmission electron microscope (TEM) observation was performed for selectively grown gallium nitride (GaN) in order to examine the dependence of GaN microstructure on the growth conditions. The GaN films were grown by hydride vapour phase epitaxy (HVPE) or metalorganic vapour phase epitaxy (MOVPE) on GaN covered with a patterned mask. Thin foil specimens for TEM observation were prepared with focused ion beam (FIB) machining apparatus. It was demonstrated that the c-axis of GaN grown over the terrace of the mask tilts towards the centre of the terrace when the GaN is grown in a carrier gas of N2. The wider terrace results in a larger tilting angle if other growth conditions are identical. The tilting is attributed to 'horizontal dislocations' (HDs) generated during the overgrowth of GaN on the mask terrace. The HDs in HVPE-GaN have a semi-loop shape and are tangled with one another, while those in MOVPE-GaN are straight and lined up to form low-angle grain boundaries.

  6. Selective Epitaxy of InP on Si and Rectification in Graphene/InP/Si Hybrid Structure.

    PubMed

    Niu, Gang; Capellini, Giovanni; Hatami, Fariba; Di Bartolomeo, Antonio; Niermann, Tore; Hussein, Emad Hameed; Schubert, Markus Andreas; Krause, Hans-Michael; Zaumseil, Peter; Skibitzki, Oliver; Lupina, Grzegorz; Masselink, William Ted; Lehmann, Michael; Xie, Ya-Hong; Schroeder, Thomas

    2016-10-12

    The epitaxial integration of highly heterogeneous material systems with silicon (Si) is a central topic in (opto-)electronics owing to device applications. InP could open new avenues for the realization of novel devices such as high-mobility transistors in next-generation CMOS or efficient lasers in Si photonics circuitry. However, the InP/Si heteroepitaxy is highly challenging due to the lattice (∼8%), thermal expansion mismatch (∼84%), and the different lattice symmetries. Here, we demonstrate the growth of InP nanocrystals showing high structural quality and excellent optoelectronic properties on Si. Our CMOS-compatible innovative approach exploits the selective epitaxy of InP nanocrystals on Si nanometric seeds obtained by the opening of lattice-arranged Si nanotips embedded in a SiO2 matrix. A graphene/InP/Si-tip heterostructure was realized on obtained materials, revealing rectifying behavior and promising photodetection. This work presents a significant advance toward the monolithic integration of graphene/III-V based hybrid devices onto the mainstream Si technology platform.

  7. Highly manufacturable silicon vertical diode switches for new memories using selective epitaxial growth with batch-type equipment

    NASA Astrophysics Data System (ADS)

    Lee, K. S.; Han, J. J.; Kim, B. H.; Lim, H. J.; Nam, S. W.; Kang, H. K.; Chung, C. H.; Jeong, H. S.; Park, H. H.; Jeong, H. W.; Kim, K. R.; Choi, B. D.

    2011-05-01

    Practical selectivity window of selective epitaxial growth (SEG) using a H2/SiH4/Cl2 cyclic chemical vapor deposition (CVD) system has been investigated with the batch-type vertical furnace equipment, replacing a conventional single-wafer H2/dichlorosilane/HCl CVD system. The process temperature was less than 700 °C, which is suitable for a low thermal budget process applicable to next-generation memories including vertical pn-diode switches. Selectivity loss is quantified by an in-line inspection tool to determine the practical number of selectivity losses. The H2/SiH4/Cl2 cyclic CVD system provides an excellent capacity of 40 wafers per batch. Selectivity loss, which is one of the most crucial features in the SEG process for the diode application, is controlled with both the amount of SiH4 and Cl2 and the period of gas supply, and the practical number of selectivity loss is confirmed to be less than 100 in 200 mm wafers. Without high temperature annealing in hydrogen ambient, low temperature cyclic SEG in the batch reactor ensures the clean interface and improved crystalline quality of SEG-Si, as well as high throughput.

  8. In situ mask designed for selective growth of InAs quantum dots in narrow regions developed for molecular beam epitaxy system

    NASA Astrophysics Data System (ADS)

    Ohkouchi, Shunsuke; Nakamura, Yusui; Ikeda, Naoki; Sugimoto, Yoshimasa; Asakawa, Kiyoshi

    2007-07-01

    We have developed an in situ mask that enables the selective formation of molecular beam epitaxially grown layers in narrow regions. This mask can be fitted to a sample holder and removed in an ultrahigh-vacuum environment; thus, device structures can be fabricated without exposing the sample surfaces to air. Moreover, this mask enables the observation of reflection high-energy electron diffraction during growth with the mask positioned on the sample holder and provides for the formation of marker layers for ensuring alignment in the processes following the selective growth. To explore the effectiveness of the proposed in situ mask, we used it to grow quantum dot (QD) structures in narrow regions and verified the perfect selectivity of the QD growth. The grown QDs exhibited high optical quality with a photoluminescence peak at approximately 1.30μm and a linewidth of 30meV at room temperature. The proposed technique can be applied for the integration of microstructures into optoelectronic functional devices.

  9. All-epitaxial, lithographically defined, current- and mode-confined vertical-cavity surface-emitting laser based on selective interfacial fermi-level pinning

    SciTech Connect

    Ahn, J.; Lu, D.; Deppe, D.G.

    2005-01-10

    An approach is presented to fabricate a current- and mode-confined vertical-cavity surface-emitting laser that is all-epitaxial and lithographically defined. The device uses selective Fermi level pinning to self-align the electrical injection to a mode-confining intracavity phase-shifting mesa.

  10. Phase-field simulations of GaN growth by selective area epitaxy from complex mask geometries

    SciTech Connect

    Aagesen, Larry K.; Thornton, Katsuyo; Coltrin, Michael E.; Han, Jung

    2015-05-21

    Three-dimensional phase-field simulations of GaN growth by selective area epitaxy were performed. The model includes a crystallographic-orientation-dependent deposition rate and arbitrarily complex mask geometries. The orientation-dependent deposition rate can be determined from experimental measurements of the relative growth rates of low-index crystallographic facets. Growth on various complex mask geometries was simulated on both c-plane and a-plane template layers. Agreement was observed between simulations and experiment, including complex phenomena occurring at the intersections between facets. The sources of the discrepancies between simulated and experimental morphologies were also investigated. The model provides a route to optimize masks and processing conditions during materials synthesis for solar cells, light-emitting diodes, and other electronic and opto-electronic applications.

  11. Phase-field simulations of GaN growth by selective area epitaxy on complex mask geometries

    DOE PAGES

    Aagesen, Larry K.; Coltrin, Michael Elliott; Han, Jung; ...

    2015-05-15

    Three-dimensional phase-field simulations of GaN growth by selective area epitaxy were performed. Furthermore, this model includes a crystallographic-orientation-dependent deposition rate and arbitrarily complex mask geometries. The orientation-dependent deposition rate can be determined from experimental measurements of the relative growth rates of low-index crystallographic facets. Growth on various complex mask geometries was simulated on both c-plane and a-plane template layers. Agreement was observed between simulations and experiment, including complex phenomena occurring at the intersections between facets. The sources of the discrepancies between simulated and experimental morphologies were also investigated. We found that the model provides a route to optimize masks andmore » processing conditions during materials synthesis for solar cells, light-emitting diodes, and other electronic and opto-electronic applications.« less

  12. Phase-field simulations of GaN growth by selective area epitaxy on complex mask geometries

    SciTech Connect

    Aagesen, Larry K.; Coltrin, Michael Elliott; Han, Jung; Thornton, Katsuyo

    2015-05-15

    Three-dimensional phase-field simulations of GaN growth by selective area epitaxy were performed. Furthermore, this model includes a crystallographic-orientation-dependent deposition rate and arbitrarily complex mask geometries. The orientation-dependent deposition rate can be determined from experimental measurements of the relative growth rates of low-index crystallographic facets. Growth on various complex mask geometries was simulated on both c-plane and a-plane template layers. Agreement was observed between simulations and experiment, including complex phenomena occurring at the intersections between facets. The sources of the discrepancies between simulated and experimental morphologies were also investigated. We found that the model provides a route to optimize masks and processing conditions during materials synthesis for solar cells, light-emitting diodes, and other electronic and opto-electronic applications.

  13. Highly oriented diamond (111) films synthesized by pulse bias-enhanced nucleation and epitaxial grain selection on a 3C-SiC/Si (111) substrate

    NASA Astrophysics Data System (ADS)

    Suto, Takeru; Yaita, Junya; Iwasaki, Takayuki; Hatano, Mutsuko

    2017-02-01

    We report the synthesis of highly oriented diamond (HOD) (111) films on 3C-SiC/Si (111) substrates. Bias-enhanced nucleation (BEN) is a key process for the heteroepitaxial growth of HOD films. Conventional long nucleation periods have been found to lead to a polycrystalline diamond film on the 3C-SiC (111) surface. Here, we propose a method that combines brief BEN (<30 s), called pulse BEN, and epitaxial grain selection by oxidative etching. Smaller diamond nuclei with a higher spatial density on the substrate were formed by pulse BEN with a pulse duration of <30 s. We found that precisely controlling the pulse duration is important for obtaining a nucleation density that is sufficiently high to obtain the HOD films. By adding oxygen gas to the subsequent growth process, non-epitaxial nuclei were removed and epitaxial diamond grains selectively remained. There was no notable difference in the relative growth rate of [111] to [100] with and without oxygen, and the orientation improvement was observed on both the (100) and (111) substrates. This suggests that the mechanism of oxidative removal was not evolutionary selective growth, but etching of the non-epitaxial interfaces between the nuclei and the (111) substrate. Finally, the HOD (111) films covering the entire 3C-SiC surface were synthesized, and they exhibited distinct diffraction spots, indicating the formation of the oriented diamond.

  14. Low-temperature epitaxial growth of β-SiC by multiple-energy ion implantation

    NASA Astrophysics Data System (ADS)

    Zhang, Z. J.; Naramoto, H.; Miyashita, A.; Stritzker, B.; Lindner, J. K. N.

    1998-11-01

    A cubic silicon carbide (β-SiC) buried layer was synthesized in Si(111) using a combination of multienergy carbon ion implantation at room temperature and post-thermal annealing. The crystal structure and the crystalline quality of the β-SiC layer was identified by x-ray diffraction in the θ-2θ mode and was examined by pole figure measurement of x-ray diffraction. Interestingly, by using the multienergy implantation technique, the β-SiC buried layer showed epitaxial growth at annealing temperatures as low as 400 °C. At an annealing temperature of 800 °C, the x-ray pole figures show that the β-SiC buried layer has a near-perfect epitaxial relationship with the silicon substrate.

  15. Selective area growth of In(Ga)N/GaN nanocolumns by molecular beam epitaxy on GaN-buffered Si(111): from ultraviolet to infrared emission.

    PubMed

    Albert, S; Bengoechea-Encabo, A; Sánchez-García, M A; Kong, X; Trampert, A; Calleja, E

    2013-05-03

    Selective area growth of In(Ga)N/GaN nanocolumns was performed on GaN-buffered Si(111) substrates by plasma-assisted molecular beam epitaxy. Undoped and Si-doped GaN buffer layers were first grown on Si(111) substrates, showing photoluminescence excitonic emission without traces of other low energy contributions, in particular, the yellow band. The GaN buffer surface roughness (between 10 and 14 nm, the rms value in a 10 × 10 μm(2) area) was low enough to allow the fabrication of a thin (7 nm thick) well defined Ti nanohole mask, for the selective area growth. Ordered In(Ga)N/GaN nanocolumns emitting from the ultraviolet (3.2 eV) to the infrared (0.78 eV) were obtained. The morphology and the emission efficiency of the In(Ga)N/GaN nanocolumns emitting at a given wavelength could be substantially improved by tuning the In/Ga and total III/N ratios. An estimated internal quantum efficiency of 36% was derived from photoluminescence data for green emitting nanocolumns.

  16. Magnetism of epitaxial Tb films on W(110) studied by spin-polarized low-energy electron microscopy

    NASA Astrophysics Data System (ADS)

    Prieto, J. E.; Chen, Gong; Schmid, A. K.; de la Figuera, J.

    2016-11-01

    Thin epitaxial films of Tb metal were grown on a clean W(110) substrate in ultrahigh vacuum and studied in situ by low-energy electron microscopy. Annealed films present magnetic contrast in spin-polarized low-energy electron microscopy. The energy dependence of the electron reflectivity was determined and a maximum value of its spin asymmetry of about 1% was measured. The magnetization direction of the Tb films is in-plane. Upon raising the temperature, no change in the domain distribution is observed, while the asymmetry in the electron reflectivity decreases when approaching the critical temperature, following a power law ˜(1-T /TC) β with a critical exponent β of 0.39.

  17. Impact of P/In flux ratio and epilayer thickness on faceting for nanoscale selective area growth of InP by molecular beam epitaxy.

    PubMed

    Fahed, M; Desplanque, L; Coinon, C; Troadec, D; Wallart, X

    2015-07-24

    The impact of the P/In flux ratio and the deposited thickness on the faceting of InP nanostructures selectively grown by molecular beam epitaxy (MBE) is reported. Homoepitaxial growth of InP is performed inside 200 nm wide stripe openings oriented either along a [110] or [1-10] azimuth in a 10 nm thick SiO2 film deposited on an InP(001) substrate. When varying the P/In flux ratio, no major shape differences are observed for [1-10]-oriented apertures. On the other hand, the InP nanostructure cross sections strongly evolve for [110]-oriented apertures for which (111)B facets are more prominent and (001) ones shrink for large P/In flux ratio values. These results show that the growth conditions allow tailoring the nanocrystal shape. They are discussed in the framework of the equilibrium crystal shape model using existing theoretical calculations of the surface energies of different low-index InP surfaces as a function of the phosphorus chemical potential, directly related to the P/In ratio. Experimental observations strongly suggest that the relative (111)A surface energy is probably smaller than the calculated value. We also discuss the evolution of the nanostructure shape with the InP-deposited thickness.

  18. Mushroom-free selective epitaxial growth of Si, SiGe and SiGe:B raised sources and drains

    NASA Astrophysics Data System (ADS)

    Hartmann, J. M.; Benevent, V.; Barnes, J. P.; Veillerot, M.; Lafond, D.; Damlencourt, J. F.; Morvan, S.; Prévitali, B.; Andrieu, F.; Loubet, N.; Dutartre, D.

    2013-05-01

    We have evaluated various Cyclic Selective Epitaxial Growth/Etch (CSEGE) processes in order to grow "mushroom-free" Si and SiGe:B Raised Sources and Drains (RSDs) on each side of ultra-short gate length Extra-Thin Silicon-On-Insulator (ET-SOI) transistors. The 750 °C, 20 Torr Si CSEGE process we have developed (5 chlorinated growth steps with four HCl etch steps in-between) yielded excellent crystalline quality, typically 18 nm thick Si RSDs. Growth was conformal along the Si3N4 sidewall spacers, without any poly-Si mushrooms on top of unprotected gates. We have then evaluated on blanket 300 mm Si(001) wafers the feasibility of a 650 °C, 20 Torr SiGe:B CSEGE process (5 chlorinated growth steps with four HCl etch steps in-between, as for Si). As expected, the deposited thickness decreased as the total HCl etch time increased. This came hands in hands with unforeseen (i) decrease of the mean Ge concentration (from 30% down to 26%) and (ii) increase of the substitutional B concentration (from 2 × 1020 cm-3 up to 3 × 1020 cm-3). They were due to fluctuations of the Ge concentration and of the atomic B concentration [B] in such layers (drop of the Ge% and increase of [B] at etch step locations). Such blanket layers were a bit rougher than layers grown using a single epitaxy step, but nevertheless of excellent crystalline quality. Transposition of our CSEGE process on patterned ET-SOI wafers did not yield the expected results. HCl etch steps indeed helped in partly or totally removing the poly-SiGe:B mushrooms on top of the gates. This was however at the expense of the crystalline quality and 2D nature of the ˜45 nm thick Si0.7Ge0.3:B recessed sources and drains selectively grown on each side of the imperfectly protected poly-Si gates. The only solution we have so far identified that yields a lesser amount of mushrooms while preserving the quality of the S/D is to increase the HCl flow during growth steps.

  19. Surface Reaction Kinetics of InP and InAs Metalorganic Vapor Phase Epitaxy Analyzed by Selective Area Growth Technique

    NASA Astrophysics Data System (ADS)

    Wang, Yunpeng; Song, Haizheng; Sugiyama, Masakazu; Nakano, Yoshiaki; Shimogaki, Yukihiro

    2008-10-01

    The surface kinetic information of metalorganic vapor phase epitaxy (MOVPE) is difficult to obtain, because growth rate is normally limited by diffusional mass-transfer rate. In this study, by using a selective area growth (SAG) technique, the surface kinetics has been successfully clarified for InP and InAs growth. The temperature dependence of surface reaction rate constant (ks) was examined, and it revealed that for both compounds ks continuously increases with activation energies of 20.1 kJ/mol for InP and 15.0 kJ/mol for InAs. The sticking probability of indium species, converted from ks, was in the range of 0.54-0.79. This is two or three times that of gallium species during GaAs MOVPE. For indium-related binary compounds, the ks of InP is always larger than that of InAs. This kinetic information suggests that group V elements have a significant effect on the ks of III-V binary compounds. These preliminary results show that indium species have quite different reactivities in phosphorus and arsenic sites, which could be fundamental for the kinetic analysis of ternary and quaternary compounds, such as InAsP and InGaAsP.

  20. Origin of the low-energy emission band in epitaxially grown para-sexiphenyl nanocrystallites

    SciTech Connect

    Kadashchuk, A.; Schols, S.; Heremans, P.; Skryshevski, Yu.; Piryatinski, Yu.; Beinik, I.; Teichert, C.; Hernandez-Sosa, G.; Sitter, H.; Andreev, A.; Frank, P.; Winkler, A.

    2009-02-28

    A comparative study of steady-state and time-resolved photoluminescence of para-sexiphenyl (PSP) films grown by organic molecular beam epitaxy (OMBE) and hot wall epitaxy (HWE) under comparable conditions is presented. Using different template substrates [mica(001) and KCl(001) surfaces] as well as different OMBE growth conditions has enabled us to vary greatly the morphology of the PSP crystallites while keeping their chemical structure virtually untouched. We prove that the broad redshifted emission band has a structure-related origin rather than being due to monomolecular oxidative defects. We conclude that the growth conditions and type of template substrate impacts substantially on the film morphology (measured by atomic force microscopy) and emission properties of the PSP films. The relative intensity of the defect emission band observed in the delayed spectra was found to correlate with the structural quality of PSP crystallites. In particular, the defect emission has been found to be drastically suppressed when (i) a KCl template substrate was used instead of mica in HWE-grown films, and (ii) in the OMBE-grown films dominated by growth mounds composed of upright standing molecules as opposed to the films consisting of crystallites formed by molecules lying parallel to the substrate.

  1. Origin of the low-energy emission band in epitaxially grown para-sexiphenyl nanocrystallites

    NASA Astrophysics Data System (ADS)

    Kadashchuk, A.; Schols, S.; Heremans, P.; Skryshevski, Yu.; Piryatinski, Yu.; Beinik, I.; Teichert, C.; Hernandez-Sosa, G.; Sitter, H.; Andreev, A.; Frank, P.; Winkler, A.

    2009-02-01

    A comparative study of steady-state and time-resolved photoluminescence of para-sexiphenyl (PSP) films grown by organic molecular beam epitaxy (OMBE) and hot wall epitaxy (HWE) under comparable conditions is presented. Using different template substrates [mica(001) and KCl(001) surfaces] as well as different OMBE growth conditions has enabled us to vary greatly the morphology of the PSP crystallites while keeping their chemical structure virtually untouched. We prove that the broad redshifted emission band has a structure-related origin rather than being due to monomolecular oxidative defects. We conclude that the growth conditions and type of template substrate impacts substantially on the film morphology (measured by atomic force microscopy) and emission properties of the PSP films. The relative intensity of the defect emission band observed in the delayed spectra was found to correlate with the structural quality of PSP crystallites. In particular, the defect emission has been found to be drastically suppressed when (i) a KCl template substrate was used instead of mica in HWE-grown films, and (ii) in the OMBE-grown films dominated by growth mounds composed of upright standing molecules as opposed to the films consisting of crystallites formed by molecules lying parallel to the substrate.

  2. Position-controlled III-V compound semiconductor nanowire solar cells by selective-area metal-organic vapor phase epitaxy.

    PubMed

    Fukui, Takashi; Yoshimura, Masatoshi; Nakai, Eiji; Tomioka, Katsuhiro

    2012-01-01

    We demonstrate position-controlled III-V semiconductor nanowires (NWs) by using selective-area metal-organic vapor phase epitaxy and their application to solar cells. Efficiency of 4.23% is achieved for InP core-shell NW solar cells. We form a 'flexible NW array' without a substrate, which has the advantage of saving natural resources over conventional thin film photovoltaic devices. Four junction NW solar cells with over 50% efficiency are proposed and discussed.

  3. Selective-area growth of GaN microrods on strain-induced templates by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lekhal, Kaddour; Bae, Si-Young; Lee, Ho-Jun; Mitsunari, Tadashi; Tamura, Akira; Deki, Manato; Honda, Yoshio; Amano, Hiroshi

    2016-05-01

    In this paper, we discuss the influence of parameters such as type of carrier gas and NH3/HCl flow ratio on the growth of vertical GaN microstructures by selective-area growth (SAG) hydride vapor phase epitaxy (HVPE). On various strain-induced templates such as GaN/sapphire, GaN/Si, and AlN/Si, regular arrays of Ga-polar GaN microrods were properly achieved by adjusting the growth parameters. The photoluminescence and micro-Raman measurements reveal not only the crystal quality of the GaN microrods but also strain distribution. These results will give insight into the control of the morphology of GaN microrods in terms of the strain induced from templates in SAG-HVPE. The precisely controlled arrays of GaN microrods can be used for next-generation light-emitting diodes (LEDs) by realizing InGaN/GaN multi-quantum wells (MQWs) with a radial structure.

  4. Hanle precession in the presence of energy-dependent coupling between localized states and an epitaxial graphene spin channel

    NASA Astrophysics Data System (ADS)

    van den Berg, J. J.; Kaverzin, A.; van Wees, B. J.

    2016-12-01

    Hanle spin precession measurements are a common method to extract the spin transport properties of graphene. In epitaxial graphene on silicon carbide, these measurements show unexpected behavior, due to presumed localized states in the carbon buffer layer that is present between the channel and the substrate. As a consequence, the Hanle curve narrows in its magnetic field dependence and can show an unconventional shape, which has been experimentally observed and modeled in previous studies. Here, we extend the previously developed model by assuming that the localized states are charge traps, that have a power-law distribution of trapping times. Our simulations show that the energy dependence of these trapping times can be extracted from the temperature evolution of the Hanle curve, which was previously observed in experiments. Our extended model gives better insight into what processes play a role when a spin channel is coupled to localized states and their relation to the experimental observations.

  5. On the phase shift of reflection high energy electron diffraction intensity oscillations during Ge(001) homoepitaxy by molecular beam epitaxy

    SciTech Connect

    Shin Byungha; Leonard, John P.; McCamy, James W.; Aziz, Michael J.

    2007-03-15

    The authors have conducted a systematic investigation of the phase shift of the reflection high energy electron diffraction (RHEED) intensity oscillations during homoepitaxy of Ge(001) by molecular beam epitaxy for a wide range of diffraction conditions. Their results show that for small incidence angles with a beam azimuth several degrees away from the <110> crystallographic symmetry direction, the phase is independent of incidence angle; however, it starts to shift once the incidence angle is high enough that the (004) Kikuchi line appears in the RHEED pattern. Moreover, under some conditions they observe the oscillations from only the Kikuchi feature and not from the specular spot, and the oscillatory behavior of the Kikuchi feature is almost out of phase with that of the specular spot. They conclude that the phase shift is caused by the overlap of the specular spot and the Kikuchi features, in contrast to models involving dynamical scattering theory for the phase shift. They discuss necessary conditions for avoiding interference.

  6. Energy Bandgap and Edge States in an Epitaxially Grown Graphene/h-BN Heterostructure

    PubMed Central

    Hwang, Beomyong; Hwang, Jeongwoon; Yoon, Jong Keon; Lim, Sungjun; Kim, Sungmin; Lee, Minjun; Kwon, Jeong Hoon; Baek, Hongwoo; Sung, Dongchul; Kim, Gunn; Hong, Suklyun; Ihm, Jisoon; Stroscio, Joseph A.; Kuk, Young

    2016-01-01

    Securing a semiconducting bandgap is essential for applying graphene layers in switching devices. Theoretical studies have suggested a created bulk bandgap in a graphene layer by introducing an asymmetry between the A and B sub-lattice sites. A recent transport measurement demonstrated the presence of a bandgap in a graphene layer where the asymmetry was introduced by placing a graphene layer on a hexagonal boron nitride (h-BN) substrate. Similar bandgap has been observed in graphene layers on metal substrates by local probe measurements; however, this phenomenon has not been observed in graphene layers on a near-insulating substrate. Here, we present bulk bandgap-like features in a graphene layer epitaxially grown on an h-BN substrate using scanning tunneling spectroscopy. We observed edge states at zigzag edges, edge resonances at armchair edges, and bandgap-like features in the bulk. PMID:27503427

  7. Largely enhanced energy density in epitaxial SmCo5/Fe/SmCo5 exchange spring trilayers

    NASA Astrophysics Data System (ADS)

    Sawatzki, S.; Heller, R.; Mickel, Ch.; Seifert, M.; Schultz, L.; Neu, V.

    2011-06-01

    In order to enhance the energy density (BH)max as a key property for permanent magnet applications, exchanged-coupled trilayers of SmCo5/Fe/SmCo5 with fixed SmCo5 layer thicknesses (25 nm) and varying soft magnetic Fe film thickness have been epitaxially grown by pulsed laser deposition on Cr buffered MgO(110) substrates. The effect of the increasing soft layer thickness on the reversal mechanism and improved remanence due to the higher Fe-volume fraction was investigated by vibrating sample magnetometry in external fields up to 9 T. As the energy density strongly depends on the volume of the samples, emphasis is put on multilayer architecture investigation and reliable thickness determination. Concerning the latter all applied analysis methods as energy dispersive x-ray analysis, Rutherford backscattering spectroscopy and transmission electron microscopy confirm energy densities with maximum values of 312 kJ/m3 (39 MGOe) for a soft layer thickness of 12.6 nm.

  8. Pattern dependency in selective epitaxy of B-doped SiGe layers for advanced metal oxide semiconductor field effect transistors

    NASA Astrophysics Data System (ADS)

    Hâllstedt, J.; Kolahdouz, M.; Ghandi, R.; Radamson, H. H.; Wise, R.

    2008-03-01

    This study presents investigations about the physical mechanisms, origin, and methods to control the pattern dependency in selective epitaxial growth of Si1-xGex (x=0.14-0.32) layers. It is shown with a comprehensive experimental study that the local Si coverage of individual chips on patterned wafers is the main parameter for the layer profile in the epitaxial growth. This was explained by the gas depletion of the growth species in the low velocity boundary layer over the wafer. The gas depletion radius around each oxide opening was in the centimeter range which is related to the boundary layer thickness. The results from these experiments were applied to grow Si0.75Ge0.25 layers with B concentration of 4×1020cm-3 selectively for elevated source and drains in fully depleted ultrathin body silicon on insulator p metal oxide semiconductor field effect transistor (p-MOSFET) devices. The epitaxy control was maintained over a wide range of device sizes by optimized process parameters in combination with a wafer pattern design consisting of dummy features causing a uniform gas depletion over the chips on the wafer.

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

    DOEpatents

    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.

  10. Energy dissipation channels affecting photoluminescence from resonantly excited Er3+ ions doped in epitaxial ZnO host films

    NASA Astrophysics Data System (ADS)

    Akazawa, Housei; Shinojima, Hiroyuki

    2015-04-01

    We identified prerequisite conditions to obtain intense photoluminescence at 1.54 μm from Er3+ ions doped in ZnO host crystals. The epitaxial ZnO:Er films were grown on sapphire C-plane substrates by sputtering, and Er3+ ions were resonantly excited at a wavelength of 532 nm between energy levels of 4I15/2 and 2H11/2. There is a threshold deposition temperature between 500 and 550 °C, above which epitaxial ZnO films become free of miss-oriented domains. In this case, Er3+ ions are outside ZnO crystallites, having the same c-axis lattice parameters as those of undoped ZnO crystals. The improved crystallinity was correlated with enhanced emissions peaking at 1538 nm. Further elevating the deposition temperature up to 650 °C generated cracks in ZnO crystals to relax the lattice mismatch strains, and the emission intensities from cracked regions were three times as large as those from smooth regions. These results can be consistently explained if we assume that emission-active Er3+ ions are those existing at grain boundaries and bonded to single-crystalline ZnO crystallites. In contrast, ZnO:Er films deposited on a ZnO buffer layer exhibited very weak emissions because of their degraded crystallinity when most Er3+ ions were accommodated into ZnO crystals. Optimizing the degree of oxidization of ZnO crystals is another important factor because reduced films suffer from non-radiative decay of excited states. The optimum Er content to obtain intense emissions was between 2 and 4 at. %. When 4 at. % was exceeded, the emission intensity was severely attenuated because of concentration quenching as well as the degradation in crystallinity. Precipitation of Er2O3 crystals was clearly observed at 22 at. % for films deposited above 650 °C. Minimizing the number of defects and impurities in ZnO crystals prevents energy dissipation, thus exclusively utilizing the excitation energy to emissions from Er3+ ions.

  11. Azimuthal reflection high-energy electron diffraction study of MnAs growth on GaAs(001) by molecular beam epitaxy

    SciTech Connect

    Satapathy, Dillip K.; Jenichen, Bernd; Ploog, Klaus H.; Braun, Wolfgang

    2011-07-15

    Azimuthal reflection high-energy electron diffraction (ARHEED) and in situ grazing incidence synchrotron x-ray diffraction techniques are employed to investigate the growth, epitaxial orientation, and interfacial structure of MnAs layers grown on GaAs(001) by molecular beam epitaxy (MBE). We demonstrate the power and reliability of ARHEED scans as a routine tool in characterizing the formation of epitaxial films. The ARHEED scans clearly reveal the formation of the rectangular MnAs unit cell during growth on GaAs(001) for a MnAs layer thickness of 2.1 {+-} 0.2 monolayers with a tensile strain along the MnAs[1120] direction. A periodic coincidence site lattice, which is known to form along the MnAs [0001] direction to release the strain due to the huge lattice mismatch ({approx}30%) also produces periodic satellites of the diffraction spots in the ARHEED scan. The formation of different epitaxial orientations of MnAs during MBE growth can be directly observed using ARHEED scans. ARHEED is demonstrated to have a resolution similar to synchrotron x-ray diffraction with a double crystal monochromator, yielding full width at half maximum values of reflections as small as 0.005 reciprocal lattice units.

  12. Renewable energy recovery through selected industrial wastes

    NASA Astrophysics Data System (ADS)

    Zhang, Pengchong

    Typically, industrial waste treatment costs a large amount of capital, and creates environmental concerns as well. A sound alternative for treating these industrial wastes is anaerobic digestion. This technique reduces environmental pollution, and recovers renewable energy from the organic fraction of those selected industrial wastes, mostly in the form of biogas (methane). By applying anaerobic technique, selected industrial wastes could be converted from cash negative materials into economic energy feed stocks. In this study, three kinds of industrial wastes (paper mill wastes, brown grease, and corn-ethanol thin stillage) were selected, their performance in the anaerobic digestion system was studied and their applicability was investigated as well. A pilot-scale system, including anaerobic section (homogenization, pre-digestion, and anaerobic digestion) and aerobic section (activated sludge) was applied to the selected waste streams. The investigation of selected waste streams was in a gradually progressive order. For paper mill effluents, since those effluents contain a large amount of recalcitrant or toxic compounds, the anaerobic-aerobic system was used to check its treatability, including organic removal efficiency, substrate utilization rate, and methane yield. The results showed the selected effluents were anaerobically treatable. For brown grease, as it is already well known as a treatable substrate, a high rate anaerobic digester were applied to check the economic effect of this substrate, including methane yield and substrate utilization rate. These data from pilot-scale experiment have the potential to be applied to full-scale plant. For thin stillage, anaerobic digestion system has been incorporated to the traditional ethanol making process as a gate-to-gate process. The performance of anaerobic digester was applied to the gate-to-gate life-cycle analysis to estimate the energy saving and industrial cost saving in a typical ethanol plant.

  13. Large-scale self-assembled epitaxial growth of highly-ordered three-dimensional micro/nano single-crystalline PbSe pyramid arrays by selective chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Qiu, Jijun; Weng, Binbin; Li, Lin; Li, Xiaomin; Shi, Zhisheng

    2015-05-01

    Highly ordered three-dimensional micro- and nano- PbSe pyramid arrays were synthesized by using selective epitaxial self-assembled chemical bath deposition method. Each pyramid consists of a very sharp (111) tip with six smooth equivalent {100} facets. Every (100) facet forms an angle of about 54.7° with respect to the (111) facet. The structural features including pyramidal size and period could be precisely tailored by pre-patterned Au mask and etching time. Pyramids are self-assembled on the confined positions by the dual functions of one-dimensional and two-dimensional oriented attachment mechanisms along [110] directions on the (111) surface, following the Gibbs-Curie-Wulff minimum energy principle. This method could effectively create large, bottom-up 3D pyramidal surface patterns in a cost-effective and time-saving manner, which has potential applications in infrared photoconductors, solar cells and light emitting enhancement for display, etc.

  14. Strain in epitaxial Bi2Se3 grown on GaN and graphene substrates: A reflection high-energy electron diffraction study

    NASA Astrophysics Data System (ADS)

    Li, Bin; Guo, Xin; Ho, Wingkin; Xie, Maohai

    2015-08-01

    Topological insulator (TI) has been one of the focus research themes in condensed matter physics in recent years. Due to the relatively large energy bandgap, Bi2Se3 has been identified as one of the most promising three-dimensional TIs with application potentials. Epitaxial Bi2Se3 by molecular-beam epitaxy has been reported by many groups using different substrates. A common feature is that Bi2Se3 grows readily along the c-axis direction irrespective of the type and condition of the substrate. Because of the weak van deer Waals interaction between Bi2Se3 quintuple layers, the grown films are reported to be strain-free, taking the lattice constant of the bulk crystal. At the very initial stage of Bi2Se3 deposition, however, strain may still exist depending on the substrate. Strain may bring some drastic effects to the properties of the TIs and so achieving strained TIs can be of great fundamental interests as well as practical relevance. In this work, we employ reflection high-energy electron diffraction to follow the lattice constant evolution of Bi2Se3 during initial stage depositions on GaN and graphene, two very different substrates. We reveal that epitaxial Bi2Se3 is tensile strained on GaN but strain-free on graphene. Strain relaxation on GaN is gradual.

  15. Characterization of vacancy-type defects in heteroepitaxial GaN grown by low-energy plasma-enhanced vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Calloni, A.; Ferragut, R.; Dupasquier, A.; von Känel, H.; Guiller, A.; Rutz, A.; Ravelli, L.; Egger, W.

    2012-07-01

    The defect concentration in thin GaN layers was estimated by means of positron annihilation spectroscopy. Positron lifetime and Doppler broadening of the annihilation radiation were used. A comparative study of GaN films grown with different techniques was performed. Specific attention has been given to the new low energy plasma enhanced vapor phase epitaxy (LEPEVPE) growth technique. A very high Ga vacancy density (1019 cm-3) was found in a thin GaN layer directly grown by LEPEVPE on a sapphire substrate. However, when a GaN substrate (commercial sample grown by Metal Organic Vapor Phase Epitaxy) is used as a template for LEPEVPE deposition, the vacancy density of the film is low (about 1016 cm-3). This fact provides evidences that the LEPEVPE technique is able to produce high quality GaN layers.

  16. Selective area growth of Bernal bilayer epitaxial graphene on 4H-SiC (0001) substrate by electron-beam irradiation

    NASA Astrophysics Data System (ADS)

    Dharmaraj, P.; Jeganathan, K.; Parthiban, S.; Kwon, J. Y.; Gautam, S.; Chae, K. H.; Asokan, K.

    2014-11-01

    We report selective area growth of large area homogeneous Bernal stacked bilayer epitaxial graphene (BLEG) on 4H-SiC (0001) substrate by electron-beam irradiation. Sublimation of Si occurs by energetic electron irradiations on SiC surface via breaking of Si-C bonds in the localized region, which allows the selective growth of graphene. Raman measurements ensure the formation of homogeneous BLEG with weak compressive strain of -0.08%. The carrier mobility of large area BLEG is ˜5100 cm2 V-1 s-1 with a sheet carrier density of 2.2 × 1013 cm-2. Current-voltage measurements reveal that BLEG on 4H-SiC forms a Schottky junction with an operation at mA level. Our study reveals that the barrier height at the Schottky junction is low (˜0.58 eV) due to the Fermi-level pinning above the Dirac point.

  17. The influence of selective chemical doping on clean, low-carrier density SiC epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Chuang, Chiashain; Yang, Yanfei; Huang, Lung-I.; Liang, Chi-Te; Elmquist, Randolph E.; National Institute of of Standards; Technology Collaboration; National Taiwan University, Department of Physics Collaboration

    2015-03-01

    The charge-transfer effect of ambient air on magneto-transport in polymer-free SiC graphene was investigated. Interestingly, adsorption of atmospheric gas molecules on clean epitaxial graphene can reduce the carrier density to near charge neutrality, allowing observation of highly precise v = 2 quantum Hall plateaus. The atmospheric adsorbates were reproducibly removed and pure gases (N2, O2, CO2, H2O) were used to form new individual adsorbates on SiC graphene. Our experimental results (τt/τq ~ 2) support the theoretical predictions for the ratio of transport relaxation time τt to quantum lifetime τq in clean graphene. The analysis of Shubnikov-de Haas oscillations at intermediate doping levels indicates that the carrier scattering is reduced by water and oxygen so as to increase both the classical and quantum mobility. This study points to the key dopant gases in ambient air and also paves the way towards extremely precise quantized Hall resistance standards in epitaxial graphene systems with carrier density tuned by exposure to highly pure gases and vacuum annealing treatment. National Institute of Standard and Technology.

  18. Financial arrangement selection for energy management projects

    NASA Astrophysics Data System (ADS)

    Woodroof, Eric Aubrey

    Scope and method of study. The purpose of this study was to develop a model (E-FUND) to help facility managers select financial arrangements for energy management projects (EMPs). The model was developed with the help of a panel of expert financiers. The panel also helped develop a list of key objectives critical to the decision process. The E-FUND model was tested by a population of facility managers in four case studies. Findings and conclusions. The results may indicate that having a high economic benefit (from an EMP) is not overwhelmingly important, when compared to other qualitative objectives. The results may also indicate that the true lease and performance contract may be the most applicable financial arrangements for EMPs.

  19. Epitaxial silicon growth for solar cells

    NASA Technical Reports Server (NTRS)

    Daiello, R. V.; Robinson, P. H.; Richman, D.

    1979-01-01

    The epitaxial procedures, solar cell fabrication, and evaluation techniques are described. The development of baseline epitaxial solar cell structures grown on high quality conventional silicon substrates is discussed. Diagnostic layers and solar cells grown on four potentially low cost silicon substrates are considered. The crystallographic properties of such layers and the performance of epitaxially grown solar cells fabricated on these materials are described. An advanced epitaxial reactor, the rotary disc, is described along with the results of growing solar cell structures of the baseline type on low cost substrates. The add on cost for the epitaxial process is assessed and the economic advantages of the epitaxial process as they relate to silicon substrate selection are examined.

  20. Energy use in selected metal casting facilities - 2003

    SciTech Connect

    Eppich, Robert E.

    2004-05-01

    This report represents an energy benchmark for various metal casting processes. It describes process flows and energy use by fuel type and processes for selected casting operations. It also provides recommendations for improving energy efficiency in casting.

  1. Vacancies in epitaxial graphene

    SciTech Connect

    Davydov, S. Yu.

    2015-08-15

    The coherent-potential method is used to consider the problem of the influence of a finite concentration of randomly arranged vacancies on the density of states of epitaxial graphene. To describe the density of states of the substrate, simple models (the Anderson model, Haldane-Anderson model, and parabolic model) are used. The electronic spectrum of free single-sheet graphene is considered in the low-energy approximation. Charge transfer in the graphene-substrate system is discussed. It is shown that, in all cases, the density of states of epitaxial graphene decreases proportionally to the vacancy concentration. At the same time, the average charge transferred from graphene to the substrate increases.

  2. Strain in epitaxial Bi{sub 2}Se{sub 3} grown on GaN and graphene substrates: A reflection high-energy electron diffraction study

    SciTech Connect

    Li, Bin; Guo, Xin; Ho, Wingkin; Xie, Maohai

    2015-08-24

    Topological insulator (TI) has been one of the focus research themes in condensed matter physics in recent years. Due to the relatively large energy bandgap, Bi{sub 2}Se{sub 3} has been identified as one of the most promising three-dimensional TIs with application potentials. Epitaxial Bi{sub 2}Se{sub 3} by molecular-beam epitaxy has been reported by many groups using different substrates. A common feature is that Bi{sub 2}Se{sub 3} grows readily along the c-axis direction irrespective of the type and condition of the substrate. Because of the weak van der Waals interaction between Bi{sub 2}Se{sub 3} quintuple layers, the grown films are reported to be strain-free, taking the lattice constant of the bulk crystal. At the very initial stage of Bi{sub 2}Se{sub 3} deposition, however, strain may still exist depending on the substrate. Strain may bring some drastic effects to the properties of the TIs and so achieving strained TIs can be of great fundamental interests as well as practical relevance. In this work, we employ reflection high-energy electron diffraction to follow the lattice constant evolution of Bi{sub 2}Se{sub 3} during initial stage depositions on GaN and graphene, two very different substrates. We reveal that epitaxial Bi{sub 2}Se{sub 3} is tensile strained on GaN but strain-free on graphene. Strain relaxation on GaN is gradual.

  3. Assessment of Selected Energy Efficiency Policies

    EIA Publications

    2005-01-01

    This report responds to a request from Senator Byron L. Dorgan, asking the Energy Information Administration (EIA) to undertake a quantitative analysis of a variety of energy efficiency policies using assumptions provided by the Alliance to Save Energy (ASE).

  4. Selective epitaxial growth of zinc blende-derivative on wurtzite-derivative: the case of polytypic Cu2CdSn(S(1-x)Se(x))4 nanocrystals.

    PubMed

    Wu, Liang; Fan, Feng-Jia; Gong, Ming; Ge, Jin; Yu, Shu-Hong

    2014-03-21

    Polytypic nanocrystals with zinc blende (ZB) cores and wurtzite (WZ) arms, such as tetrapod and octopod nanocrystals, have been widely reported. However, polytypic nanocrystals with WZ cores and ZB arms or ends have been rarely reported. Here, we report a facile, solution-based approach to the synthesis of polytypic Cu2CdSn(S1-xSex)4 (CCTSSe) nanocrystals with ZB-derivative selectively engineered on (000±2)WZ facets of WZ-derived cores. Accordingly, two typical morphologies, i.e., bullet-like nanocrystals with a WZ-derivative core and one ZB-derivative end, and rugby ball-like nanocrystals with a WZ-derivative core and two ZB-derivative ends, can be selectively prepared. The epitaxial growth mechanism is confirmed by the time-dependent experiments. The ratio of rugby ball-like and bullet-like polytypic CCTSSe nanocrystals can be tuned through changing the amount of Cd precursor to adjust the reactivity difference between (0002)WZ and (000-2)WZ facets. These unique polytypic CCTSSe nanocrystals may find applications in energetic semiconducting materials for energy conversion in the future.

  5. Low-thermal surface preparation, HCl etch and Si/SiGe selective epitaxy on (1 1 0) silicon surfaces

    NASA Astrophysics Data System (ADS)

    Destefanis, V.; Hartmann, J. M.; Hopstaken, M.; Delaye, V.; Bensahel, D.

    2008-10-01

    We have first investigated the influence of the in situ H2 bake temperature (between 750 °C and 850 °C) on (1 0 0) and (1 1 0) fullsheet surface preparations (after 'HF-last' wet cleaning). A strong increase of the (1 1 0) surface roughness occurred when baking between 750 and 775 °C, with high C and O contamination peaks at the Si substrate/Si overlayer interface. A high H2 bake temperature (>=800 °C) is thus mandatory for both (1 0 0) and (1 1 0) Si surfaces. We have also studied the 750 °C-950 °C, high HCl partial pressure etch of blanket Si wafers. HCl etch rates are roughly four times higher on (1 1 0) than on (1 0 0). Etch rate activation energies are however quite close to each other (57 kcal mol-1 on (1 0 0) ⇔ 59 kcal mol-1 on (1 0 0)), suggesting similar etch-limiting mechanisms. We have then investigated the low-temperature growth of high Ge content (10-37%) SiGe layers on blanket Si wafers with dichlorosilane + germane chemistry (selective versus SiO2 on patterned wafers). The SiGe growth rate on (1 1 0) bows downwards from linearity and then saturates when increasing the germane mass flow. In contrast, it almost linearly increases on (1 0 0) surfaces, reaching values more than three times higher than on (1 1 0). A parabolic relationship between experimental Ge concentrations and the F(GeH4)/F(SiH2Cl2) mass-flow ratio has been evidenced on (1 0 0). In contrast, a linear relationship links the (1 1 0) Ge concentration to the F(GeH4)/F(SiH2Cl2) mass-flow ratio. Finally, 63 and 65 kcal mol-1 activation energies are associated with the fullsheet Si growth rate increase with the inverse absolute temperature on (1 0 0) and (1 1 0) (dichlorosilane chemistry). The GR(1 1 0)/GR(1 0 0) Si growth rate ratio, ≈0.74, is close to the dangling bond surface density (DBSD) ratio (DBSD(1 1 0)/DBSD(1 0 0) ≈ 0.71). Such growth rate discrepancies are thus justified by these DBSD differences. Results obtained on fullsheet wafers have been used to selectively grow

  6. Role of strain relaxation in exciton resonance energies of ZnO epitaxial layers grown on SiC substrates

    NASA Astrophysics Data System (ADS)

    Almamun Ashrafi, Abm

    2004-03-01

    The wide bandgap ZnO semiconductor is currently the subject of interest for the study of physics as well as investigations in response to the industrial demand for applications in optoelectronics devices. The most exciting physical properties of ZnO are the largest exciton binding energy of 60 meV and this can be tuned up to 120 meV by controlling the ZnO active layers1. Towards these goals, a great deal of efforts has been made on ZnO layers grown mostly on Al2O3 substrates. It is noted that the lattice mismatch in ZnO/Al2O3 is 18structural defects, and higher residual carrier concentration. To overcome these basic but unavoidable problems for crystalline quality, nearly-matched SiC substrate may play a role including reproducible p-type conductivity in ZnO layers2. Considering the ZnO lattice constant, the estimated lattice mismatch between the ZnO and SiC is to be 5may explore the ZnO epitaxy with the superior crystalline as well as optical properties towards the study of quantum physics in nanoscale level where strain governs the local atomic mechanisms in principle. Recently, we have reported the superior ZnO crystalline quality grown on SiC substrates compared to the ZnO/Al2O3 samples by MOCVD3. In progress to these results, strain relaxation effects in exciton resonance energies of ZnO layers have been addressed in this letter. The surface morphology of ZnO layers grown on SiC exhibited hexagons geometry for the VI/II falux raio of 4 by reflecting the +c ZnO surface. From these layers, therefore, free exciton (FX) emission was appeared with A and B bands to the corresponding energies of 3.377 and 3.390 eV4. With the increase of temperature, however, the FXs emission showed the quenching of excitons energy as well as intensity which may be a subject of overlapping the A and donor-bound (D0X) excitons4. The deduced activation energies of A and D0X exciton emissions suggested a consistency with an inclusion of exciton-defect binding energy in optical bands. The

  7. Antimony segregation in Ge and formation of n-type selectively doped Ge films in molecular beam epitaxy

    SciTech Connect

    Yurasov, D. V. Antonov, A. V.; Drozdov, M. N.; Schmagin, V. B.; Novikov, A. V.; Spirin, K. E.

    2015-10-14

    Antimony segregation in Ge(001) films grown by molecular beam epitaxy was studied. A quantitative dependence of the Sb segregation ratio in Ge on growth temperature was revealed experimentally and modeled theoretically taking into account both the terrace-mediated and step-edge-mediated segregation mechanisms. A nearly 5-orders-of-magnitude increase in the Sb segregation ratio in a relatively small temperature range of 180–350 °C was obtained, which allowed to form Ge:Sb doped layers with abrupt boundaries and high crystalline quality using the temperature switching method that was proposed earlier for Si-based structures. This technique was employed for fabrication of different kinds of n-type Ge structures which can be useful for practical applications like heavily doped n{sup +}-Ge films or δ-doped layers. Estimation of the doping profiles sharpness yielded the values of 2–5 nm per decade for the concentration gradient at the leading edge and 2–3 nm for the full-width-half-maximum of the Ge:Sb δ-layers. Electrical characterization of grown Ge:Sb structures revealed nearly full electrical activation of Sb atoms and the two-dimensional nature of charge carrier transport in δ-layers.

  8. Research and Energy Efficiency: Selected Success Stories

    DOE R&D Accomplishments Database

    Garland, P. W.; Garland, R. W.

    1997-06-26

    Energy use and energy technology play critical roles in the U.S. economy and modern society. The Department of Energy (DOE) conducts civilian energy research and development (R&D) programs for the purpose of identifying promising technologies that promote energy security, energy efficiency, and renewable energy use. DOE-sponsored research ranges from basic investigation of phenomena all the way through development of applied technology in partnership with industry. DOE`s research programs are conducted in support of national strategic energy objectives, however austere financial times have dictated that R&D programs be measured in terms of cost vs. benefit. In some cases it is difficult to measure the return on investment for the basic "curiosity-driven" research, however many applied technology development programs have resulted in measurable commercial successes. The DOE has published summaries of their most successful applied technology energy R&D programs. In this paper, we will discuss five examples from the Building Technologies area of the DOE Energy Efficiency program. Each story will describe the technology, discuss the level of federal funding, and discuss the returns in terms of energy savings, cost savings, or national economic impacts.

  9. Cassava as an energy source: a selected bibliography

    SciTech Connect

    Sherman, C.

    1980-01-01

    This selected bibliography includes 250 articles on cassava as a potential energy source. Factors included are things which influence cassava growth; such as weeding, fertilizer, diseases and genetic selection, as well as the conversion of cassava to ethanol. (DP)

  10. Tailoring the optical property by a three-dimensional epitaxial heterostructure: a case of ZnO/SnO2.

    PubMed

    Kuang, Qin; Jiang, Zhi-Yuan; Xie, Zhao-Xiong; Lin, Shui-Chao; Lin, Zhi-Wei; Xie, Su-Yuan; Huang, Rong-Bin; Zheng, Lan-Sun

    2005-08-24

    Epitaxial growth, as a best strategy to attain a heterostructure with a well-defined and clean interface, usually takes place on a planar substrate. In this paper, using a ZnO/SnO2 core-shell heterostructure as an example, we demonstrate the possibility of establishing a three-dimensional epitaxial interface between two materials with different crystal systems for the first time and show possible tailoring optical properties by building the heteroepitaxial crystal interface. The characterization results of element mapping, high-resolution transmission electron microscopy, and selected area electric diffraction reveal that the as-prepared ZnO/SnO2 heterostructure has a tetrapod-like ZnO core and a SnO2 shell with 15-30 nm, and their special epitaxial relation is (010)SnO2//(010)ZnO and [100]SnO2//[0001]ZnO. Such three-dimensional epitaxy between the ZnO core and SnO2 shell is quite different from the usual planar epitaxy or three-dimensional epitaxy between materials having the same crystal structure. A rational model of such complicated epitaxy has been proposed through investigating the certain structural comparability between the wurtzite ZnO and rutile SnO2 crystals. The as-prepared T-ZnO/SnO2 epitaxial heterostructure exhibits unique luminescence properties in contrast with individual tetrapod ZnO and SnO2 nanostructures, in which the epitaxial interface induces new luminescence properties. This result may inspire great interest in exploring other complicated epitaxy systems and their potential applications in laser, gas sensor, solar energy conversion, photo catalysis, and nanodevices in the future.

  11. Energy-Efficient Electric Motor Selection Handbook

    SciTech Connect

    McCoy, Gilbert A.; Litman, Todd; Douglass, John G.

    1990-10-01

    Substantial reductions in energy and operational costs can be achieved through the use of energy-efficient electric motors. A handbook was compiled to help industry identify opportunities for cost-effective application of these motors. It covers the economic and operational factors to be considered when motor purchase decisions are being made. Its audience includes plant managers, plant engineers, and others interested in energy management or preventative maintenance programs.

  12. Thickness measurement of semiconductor thin films by energy dispersive X-ray fluorescence benchtop instrumentation: Application to GaN epilayers grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Queralt, I.; Ibañez, J.; Marguí, E.; Pujol, J.

    2010-07-01

    The importance of thin films in modern high technology products, such as semiconductors, requires fast and non-destructive analysis. A methodology to determine the thickness of single layers with benchtop energy dispersive X-ray fluorescence (EDXRF) instrumentation is described and tested following analytical validation criteria. The experimental work was carried out on gallium nitride thin films epitaxially grown on sapphire substrate. The results of samples with layers in the range from 400 to 1000 nm exhibit a good correlation with the layer thickness determined by optical reflectance. Spectral data obtained using thin layered samples indicate the possibility to precisely evaluate layer thickness from 5 nm, with a low relative standard deviation (RSD < 2%) of the results. In view of the limits of optical reflectance for very thin layer determination, EDXRF analysis offers the potential for the thickness determination of such kind of samples.

  13. Epitaxial Growth of Mo Single Crystal on Sapphire by H2 Reduction of MoO3 and Characterization by Reflection High-Energy Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Igarashi, Osamu

    1995-05-01

    Mo depositions on sapphire ( Al2O3) were effected by H2 reduction of MoO3, and the crystallinity of the films was characterized by reflection high-energy electron diffraction (RHEED). In the case of growth on the (1\\=102) Al2O3 substrates, single-crystal epitaxial growth of (001) Mo was realized. On (0001) Al2O3, single-crystal Mo was not obtained; Mo deposited on (0001) Al2O3 was composed of three sets of (110)-oriented crystallites. To obtain Debye-Scherrer ring-free Mo films whose RHEED patterns did not include arcs, growth temperatures of 890 and 920° C were required in growths on (1\\=102) and (0001) Al2O3 substrates, respectively.

  14. Morphology and Electrical Characterization of Reduced Epitaxial Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Hu, Yike; Wu, Xiaosong; Sprinkle, Michael; Madiomanana, Nerasoa; Ruan, Ming; Berger, Claire; de Heer, Walter

    2009-03-01

    We present results for on-chip oxidation of epitaxial graphene and sequential reduction of the insulating graphene oxide layers. In our previous work , we have used the Hummer's method to oxidize epitaxial graphene and used electron beam exposure and heat treatment to reduce the epitaxial graphene oxide (EGO) band gap by changing the degree of oxidation. Here we further explore various oxidation and reduction methods on epitaxial graphene. EGO is characterized by atomic force microscopy, low-energy electron diffraction, ellipsometry, and Raman Spectrometry. Mobility measurements of patterned structures are presented where epitaxial graphene layers pads are seamlessly connected to EGO ribbons.

  15. CoSi2 growth on Si(001) by reactive deposition epitaxy: Effects of high-flux, low-energy ion irradiation

    NASA Astrophysics Data System (ADS)

    Lim, C. W.; Greene, J. E.; Petrov, I.

    2006-07-01

    CoSi2 layers, <40nm thick, were grown on Si(001) by reactive deposition epitaxy (RDE) in which Co was deposited at 700°C by magnetically unbalanced ultrahigh vacuum magnetron sputtering. X-ray diffraction pole figures and transmission electron microscopy (TEM) reveal that the layers, which exhibit a cube-on-cube epitaxial relationship with the substrate, (001)CoSi2‖(001)Si and [100]CoSi2‖[100]Si, contain fourfold symmetric {111} twinned domains oriented such that {221}CoSi2‖(001)Si and ⟨110⟩CoSi2‖[110]Si. We demonstrate that high-flux low-energy (EAr+=9.6eV) Ar+ ion irradiation during deposition dramatically increases the area fraction fu of untwinned regions from 0.17 in films grown under standard magnetically balanced conditions in which the ratio JAr+/JCo of the incident Ar+ to Co fluxes is 1.4 to 0.72 with JAr+/JCo=13.3. TEM analyses show that the early stages of RDE CoSi2(001) film growth proceed via the Volmer-Weber mode with independent nucleation of both untwinned and twinned islands. Increasing JAr+/JCo results in larger values of both the number density and area of untwinned with respect to twinned islands. The intense Ar+ ion bombardment creates additional low-energy adsorption sites that favor the nucleation of untwinned islands while collisionally enhancing Co surface mobilities which, in turn, increases the probability of itinerant Co adatoms reaching these sites.

  16. Growth kinetics in position-controlled and catalyst-free InAs nanowire arrays on Si(111) grown by selective area molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Hertenberger, S.; Rudolph, D.; Bichler, M.; Finley, J. J.; Abstreiter, G.; Koblmüller, G.

    2010-12-01

    We investigated the interwire distance dependence on the growth kinetics of vertical, high-yield InAs nanowire arrays on Si(111) grown by catalyst-free selective area molecular beam epitaxy (MBE). Utilizing lithographically defined SiO2 nanomasks on Si(111) with regular hole patterns, catalyst-free and site-selective growth of vertically (111)-oriented InAs nanowires was achieved with very high yields of ˜90 percent. Interestingly, the yield of vertically ordered nanowires was independent of the interwire distance and the initial growth stages. Significant size variation in the nanowires was found to depend critically on the interwire distance and growth time. Two growth regimes were identified—(i) a competitive growth regime with shorter and thinner nanowires for narrow interwire distances and (ii) a diffusion-limited growth regime for wider distances, providing good estimates for the surface diffusion lengths. Surprisingly, despite these size-dependent effects the nanowire geometries remained unaltered with uniform, almost nontapered morphologies even over large variation in nanowire density (˜mid-106-109 cm-2 range). X-ray diffraction further confirmed the vertical (111) directionality with low crystal tilt by rocking curve widths (ω scans) as low as ˜0.6°. These findings demonstrate the capability to precisely tailor the position and size of well-oriented III-V semiconductor nanowires through noncatalytic MBE selective area growth and provide an important step toward fully integrated, uniform vertical III-V nanowire array-on-Si devices.

  17. Wind Energy Developments: Incentives In Selected Countries

    EIA Publications

    1999-01-01

    This paper discusses developments in wind energy for the countries with significant wind capacity. After a brief overview of world capacity, it examines development trends, beginning with the United States - the number one country in wind electric generation capacity until 1997.

  18. Tailoring the morphology and luminescence of GaN/InGaN core-shell nanowires using bottom-up selective-area epitaxy.

    PubMed

    Nami, Mohsen; Eller, Rhett F; Okur, Serdal; Rishinaramangalam, Ashwin K; Liu, Sheng; Brener, Igal; Feezell, Daniel F

    2017-01-13

    Controlled bottom-up selective-area epitaxy (SAE) is used to tailor the morphology and photoluminescence properties of GaN/InGaN core-shell nanowire arrays. The nanowires are grown on c-plane sapphire substrates using pulsed-mode metal organic chemical vapor deposition. By varying the dielectric mask configuration and growth conditions, we achieve GaN nanowire cores with diameters ranging from 80 to 700 nm that exhibit various degrees of polar, semipolar, and nonpolar faceting. A single InGaN quantum well (QW) and GaN barrier shell is also grown on the GaN nanowire cores and micro-photoluminescence is obtained and analyzed for a variety of nanowire dimensions, array pitch spacings, and aperture diameters. By increasing the nanowire pitch spacing on the same growth wafer, the emission wavelength redshifts from 440 to 520 nm, while increasing the aperture diameter results in a ∼35 nm blueshift. The thickness of one QW/barrier period as a function of pitch and aperture diameter is inferred using scanning electron microscopy, with larger pitches showing significantly thicker QWs. Significant increases in indium composition were predicted for larger pitches and smaller aperture diameters. The results are interpreted in terms of local growth conditions and adatom capture radius around the nanowires. This work provides significant insight into the effects of mask configuration and growth conditions on the nanowire properties and is applicable to the engineering of monolithic multi-color nanowire LEDs on a single chip.

  19. Widely tunable alloy composition and crystal structure in catalyst-free InGaAs nanowire arrays grown by selective area molecular beam epitaxy

    SciTech Connect

    Treu, J. E-mail: Gregor.Koblmueller@wsi.tum.de; Speckbacher, M.; Saller, K.; Morkötter, S.; Xu, X.; Riedl, H.; Abstreiter, G.; Finley, J. J.; Koblmüller, G. E-mail: Gregor.Koblmueller@wsi.tum.de; Döblinger, M.

    2016-02-01

    We delineate the optimized growth parameter space for high-uniformity catalyst-free InGaAs nanowire (NW) arrays on Si over nearly the entire alloy compositional range using selective area molecular beam epitaxy. Under the required high group-V fluxes and V/III ratios, the respective growth windows shift to higher growth temperatures as the Ga-content x(Ga) is tuned from In-rich to Ga-rich InGaAs NWs. Using correlated x-ray diffraction, transmission electron microscopy, and micro-photoluminescence spectroscopy, we identify structural defects to govern luminescence linewidths in In-rich (x(Ga) < 0.4) and Ga-rich (x(Ga) > 0.6) NWs, whereas limitations at intermediate Ga-content (0.4 < x(Ga) < 0.6) are mainly due to compositional inhomogeneities. Most remarkably, the catalyst-free InGaAs NWs exhibit a characteristic transition in crystal structure from wurtzite to zincblende (ZB) dominated phase near x(Ga) ∼ 0.4 that is further reflected in a cross-over from blue-shifted to red-shifted photoluminescence emission relative to the band edge emission of the bulk ZB InGaAs phase.

  20. Tailoring the morphology and luminescence of GaN/InGaN core-shell nanowires using bottom-up selective-area epitaxy

    NASA Astrophysics Data System (ADS)

    Nami, Mohsen; Eller, Rhett F.; Okur, Serdal; Rishinaramangalam, Ashwin K.; Liu, Sheng; Brener, Igal; Feezell, Daniel F.

    2017-01-01

    Controlled bottom-up selective-area epitaxy (SAE) is used to tailor the morphology and photoluminescence properties of GaN/InGaN core-shell nanowire arrays. The nanowires are grown on c-plane sapphire substrates using pulsed-mode metal organic chemical vapor deposition. By varying the dielectric mask configuration and growth conditions, we achieve GaN nanowire cores with diameters ranging from 80 to 700 nm that exhibit various degrees of polar, semipolar, and nonpolar faceting. A single InGaN quantum well (QW) and GaN barrier shell is also grown on the GaN nanowire cores and micro-photoluminescence is obtained and analyzed for a variety of nanowire dimensions, array pitch spacings, and aperture diameters. By increasing the nanowire pitch spacing on the same growth wafer, the emission wavelength redshifts from 440 to 520 nm, while increasing the aperture diameter results in a ˜35 nm blueshift. The thickness of one QW/barrier period as a function of pitch and aperture diameter is inferred using scanning electron microscopy, with larger pitches showing significantly thicker QWs. Significant increases in indium composition were predicted for larger pitches and smaller aperture diameters. The results are interpreted in terms of local growth conditions and adatom capture radius around the nanowires. This work provides significant insight into the effects of mask configuration and growth conditions on the nanowire properties and is applicable to the engineering of monolithic multi-color nanowire LEDs on a single chip.

  1. Enhanced energy density with a wide thermal stability in epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 thin films

    NASA Astrophysics Data System (ADS)

    Hu, Guangliang; Ma, Chunrui; Wei, Wei; Sun, Zixiong; Lu, Lu; Mi, Shao-Bo; Liu, Ming; Ma, Beihai; Wu, Judy; Jia, Chun-lin

    2016-11-01

    High-quality epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films of thickness of ˜880 nm were fabricated using pulsed laser deposition on (001) Nb doped SrTiO3 (Nb:STO) substrates. Besides a confirmation of the epitaxial relationship [100]PLZT//[100]Nb:STO and (001)PLZT//(001)Nb:STO using X-ray diffraction, a transmission electron microscopy study has revealed a columnar structure across the film thickness. The recoverable energy density (Wrec) of the epitaxial PLZT thin film capacitors increases linearly with the applied electric field and the best value of ˜31 J/cm3 observed at 2.27 MV/cm is considerably higher by 41% than that of the polycrystalline PLZT film of a comparable thickness. In addition to the high Wrec value, an excellent thermal stability as illustrated in a negligible temperature dependence of the Wrec in the temperature range from room temperature to 180 °C is achieved. The enhanced Wrec and the thermal stability are attributed to the reduced defects and grain boundaries in epitaxial PLZT thin films, making them promising for energy storage applications that require both high energy density, power density, and wide operation temperatures.

  2. Selected Energy Management Options for Small Business and Local Government.

    ERIC Educational Resources Information Center

    Wert, Jonathan M.; Worthington, Barry K.

    This document is a checklist of 257 energy management options for small business and local government. The energy management options are categorized under: (1) Energy management strategies; (2) Buildings; (3) Lighting; (4) Water; (5) Waste operations; (6) Equipment; (7) Transportation; and (8) Food preparation. To select options for…

  3. Theoretical minimum energies to produce steel for selected conditions

    SciTech Connect

    Fruehan, R. J.; Fortini, O.; Paxton, H. W.; Brindle, R.

    2000-03-01

    An ITP study has determined the theoretical minimum energy requirements for producing steel from ore, scrap, and direct reduced iron. Dr. Richard Fruehan's report, Theoretical Minimum Energies to Produce Steel for Selected Conditions, provides insight into the potential energy savings (and associated reductions in carbon dioxide emissions) for ironmaking, steelmaking, and rolling processes (PDF 459 KB).

  4. Correlating low-energy electron microscopy and micro-Raman imaging of epitaxial graphene on SiC

    NASA Astrophysics Data System (ADS)

    Cheng, Guangjun; Calizo, Irene; Meade, Patrick; He, Guowei; Real, M. A.; Elmquist, R. E.; Feenstra, R. M.; Hight Walker, A. R.

    2013-03-01

    Several techniques exist for determining the number of graphene layers grown on SiC such as low-energy electron microscopy (LEEM) and Raman spectroscopy. The method which is arguably the most definitive for SiC-grown graphene isLEEM. Low-energy (0 - 10 eV) electrons interfere with the graphene layers, yielding minima in the electron reflectivity vs. energy curve that can be used to determine the layer number.1 LEEM also provides the means of collecting selected-area diffraction on ?m-size surface regions (micro-LEED), giving access to further useful structural information. While Raman spectroscopy is also commonly used to determine graphene layer number on SiC substrates; such measurements have no definitive calibration for large-area graphene on SiC, unlike the case of exfoliated graphene on SiO2. In this talk, results of correlated LEEM/micro-Raman imaging of large-area, mono and multilayer graphene samples are presented. These initial findings show that LEEM can show the contrast between terrace regions and step edges at particular areas of monolayer-graphene surfaces. Micro-Raman imaging of these same locations show Raman shifts in the G' (2D) band. The influence of heterogeneities on electrical behavior of graphene will be discussed. Comparative studies of multilayer graphene are in progress, and will also be reported. 1. H. Hibino, et al., Phys. Rev. B 77, 075413 (2008). 2. L. I. Johansson, et al., Phys. Rev. B 84, 125405 (2011).

  5. Transactions of the Chinese Solar Energy Society (Selected Articles),

    DTIC Science & Technology

    1983-08-04

    iDAld- 870 TRANSACTIONS OF THE CHINESE SOLAR ENERGY SOCIETY i/i ’A1 (SELECTED ARTICLES)<U) FOREIGN TECHNOLOGY DIV I WRIGHT-PRTTERSON RF8 OH 7 SUN ET...34 . -.-. - - - - , " ’ ’-. . .. .. ...- " . ’ " FTD-ID(RS)T-1067-83 10 00 FOREIGN TECHNOLOGY DIVISION TRANSACTIONS OF THE CHINESE SOLAR ENERGY SOCIETY (Selected Articles...l067-83 4 August 1983 MICROFICHE NR: FTD-83-C-000960 TRANSACTIONS OF THE CHINESE SOLAR ENERGY SOCIETYI(Selected Articles) English pages: 16 Source: Acta

  6. Selection of promising sites for magma energy experiments

    SciTech Connect

    Carson, C.C.

    1985-01-01

    The Long Valley and Coso Hot Springs areas of California have been identified as the most promising sites for conducting a magma energy extraction experiment. These two locations were selected from among the potential sites on the basis of several factors that are critical to the success of the proposed long-term energy extraction experiment. These factors include the likelihood of the existence of shallow magma targets as well as several other drilling, energy extraction and programmatic considerations. As the magma energy extraction program continues, these sites will be analyzed in detail so that one can be selected as the site for the planned magma experiment.

  7. Misfit dislocations in epitaxy

    NASA Astrophysics Data System (ADS)

    van der Merwe, Jan H.

    2002-08-01

    This article on epitaxy highlights the following: the definition and some historical milestones; the introduction by Frenkel and Kontorowa (FK) of a truncated Fourier series to model the periodic interaction at crystalline interfaces; the invention by Frank and van der Merwe (FvdM)—using the FK model—of (interfacial) misfit dislocations as an important mechanism in accommodating misfit at epilayer-substrate interfaces; the generalization of the FvdM theory to multilayers; the application of the parabolic model by Jesser and van der Merwe to describe, for growing multilayers and superlattices, the impact of Fourier coefficients in the realization of epitaxial orientations and the stability of modes of misfit accommodation; the involvement of intralayer interaction in the latter—all features that impact on the attainment of perfection in crystallinity of thin films, a property that is so vital in the fabrication of useful uniformly thick epilayers (uniformity being another technological requirement), which also depends on misfit accommodation through the interfacial energy that function strongly in the criterion for growth modes, proposed by Bauer; and the ingenious application of the Volterra model by Matthews and others to describe misfit accommodation by dislocations in growing epilayers.

  8. Energy dissipation channels affecting photoluminescence from resonantly excited Er{sup 3+} ions doped in epitaxial ZnO host films

    SciTech Connect

    Akazawa, Housei; Shinojima, Hiroyuki

    2015-04-21

    We identified prerequisite conditions to obtain intense photoluminescence at 1.54 μm from Er{sup 3+} ions doped in ZnO host crystals. The epitaxial ZnO:Er films were grown on sapphire C-plane substrates by sputtering, and Er{sup 3+} ions were resonantly excited at a wavelength of 532 nm between energy levels of {sup 4}I{sub 15/2} and {sup 2}H{sub 11/2}. There is a threshold deposition temperature between 500 and 550 °C, above which epitaxial ZnO films become free of miss-oriented domains. In this case, Er{sup 3+} ions are outside ZnO crystallites, having the same c-axis lattice parameters as those of undoped ZnO crystals. The improved crystallinity was correlated with enhanced emissions peaking at 1538 nm. Further elevating the deposition temperature up to 650 °C generated cracks in ZnO crystals to relax the lattice mismatch strains, and the emission intensities from cracked regions were three times as large as those from smooth regions. These results can be consistently explained if we assume that emission-active Er{sup 3+} ions are those existing at grain boundaries and bonded to single-crystalline ZnO crystallites. In contrast, ZnO:Er films deposited on a ZnO buffer layer exhibited very weak emissions because of their degraded crystallinity when most Er{sup 3+} ions were accommodated into ZnO crystals. Optimizing the degree of oxidization of ZnO crystals is another important factor because reduced films suffer from non-radiative decay of excited states. The optimum Er content to obtain intense emissions was between 2 and 4 at. %. When 4 at. % was exceeded, the emission intensity was severely attenuated because of concentration quenching as well as the degradation in crystallinity. Precipitation of Er{sub 2}O{sub 3} crystals was clearly observed at 22 at. % for films deposited above 650 °C. Minimizing the number of defects and impurities in ZnO crystals prevents energy dissipation, thus exclusively utilizing the excitation energy to emissions from

  9. Screening and selection of lignocellulosic crops for energy

    SciTech Connect

    Turhollow, A.F.; Cushman, J.H.; Elmore, J.L.; Johnston, J.W.

    1985-01-01

    The Department of Energy's Herbaceous Energy Crops Program at Oak Ridge National Laboratory is beginning its research on lignocellulosic energy crops with five studies in the Southeast and Midwest/Lakes regions. Early objectives for these studies include selecting species that show promise on marginal croplands typical of the regions, determining productivity rates under various levels of management, defining cost-effective and environmentally sound production systems for each region, and identifying the most promising means of reducing costs. 2 tabs.

  10. Energy and daylight performance of angular selective glazings

    SciTech Connect

    Sullivan, R.; Beltran,; Lee, E.S.; Rubin, M.; Selkowitz, S.E.

    1998-11-01

    This paper presents the results of a study investigating the energy and daylight performance of anisotropic angular selective glazings. The DOE-2.1E energy simulation program was used to determine the annual cooling, lighting and total electricity use, and peak electric demand. RADIANCE, a lighting simulation program, was used to determine daylight illuminance levels and distribution. We simulated a prototypical commercial office building module located in Blythe, California. We chose three hypothetical conventional windows for comparison: a single-pane tinted window, a double-pane low-E window, and a double-pane spectrally selective window. Daylighting controls were used. No interior shades were modeled in order to isolate the energy effects of the angular selective glazing. Our results show that the energy performance of the prototype angular selective windows is about the same as conventional windows for a 9.14 m (30 ft) deep south-facing perimeter zone with a large-area window in the hot, sunny climate of Blythe. It is theoretically possible to tune the angular selectivity of the glazing to achieve annual cooling energy reductions of 18%, total electricity use reductions of 15%, and peak electric demand reductions of 11% when compared to a conventional glazing with the same solar-optical properties at normal incidence. Angular selective glazings can provide more uniformly distributed daylight, particularly in the area next to the window, which will result in a more visually comfortable work environment.

  11. Effects of high-flux low-energy ion bombardment on the low-temperature growth morphology of TiN(001) epitaxial layers

    SciTech Connect

    Karr, Brian W.; Cahill, David G.; Petrov, I.; Greene, J. E.

    2000-06-15

    Ultrahigh vacuum scanning tunneling microscopy (STM) is used to characterize the surface morphology of TiN(001) epitaxial layers grown by dc reactive magnetron sputtering at growth temperatures of T{sub s}=650 and T{sub s}=750 degree sign C. An auxiliary anode is used to bias the N{sub 2} plasma and produce a large flux of low-energy N{sub 2}{sup +} ions that bombard the film surface during growth: the ratio of the N{sub 2}{sup +} flux to the Ti growth flux is {approx_equal}25. At ion energies E{sub i} near the threshold for the production of bulk defects (E{sub i}=43 eV and T{sub s}=650 degree sign C), ion bombardment decreases the amplitude of the roughness, decreases the average distance between growth mounds, and reduces the sharpness of grooves between growth mounds. The critical island radius for second layer nucleation R{sub c} is approximately 12 and 17 nm at growth temperatures of 650 and 750 degree sign C respectively; at 650 degree sign C, R{sub c} is reduced to (approx =)10 nm by ion bombardment. (c) 2000 The American Physical Society.

  12. Measure Guideline: Energy-Efficient Window Performance and Selection

    SciTech Connect

    Carmody, J.; Haglund, K.

    2012-11-01

    This document provides guidelines for the selection of energy-efficient windows in new and existing residential construction in all US climate zones. It includes information on window products, their attributes and performance. It provides cost/benefit information on window energy savings as well as information on non-energy benefits such as thermal comfort and reduced HVAC demands. The document also provides information on energy impacts of design decisions such as window orientation, total glazing area and shading devices and conditions. Information on resources for proper window installation is included as well. This document is for builders, homeowners, designers and anyone making decisions about selecting energy efficient window. It is intended to complement other Building America information and efforts.

  13. Developing a framework for energy technology portfolio selection

    NASA Astrophysics Data System (ADS)

    Davoudpour, Hamid; Ashrafi, Maryam

    2012-11-01

    Today, the increased consumption of energy in world, in addition to the risk of quick exhaustion of fossil resources, has forced industrial firms and organizations to utilize energy technology portfolio management tools viewed both as a process of diversification of energy sources and optimal use of available energy sources. Furthermore, the rapid development of technologies, their increasing complexity and variety, and market dynamics have made the task of technology portfolio selection difficult. Considering high level of competitiveness, organizations need to strategically allocate their limited resources to the best subset of possible candidates. This paper presents the results of developing a mathematical model for energy technology portfolio selection at a R&D center maximizing support of the organization's strategy and values. The model balances the cost and benefit of the entire portfolio.

  14. Measure Guideline. Energy-Efficient Window Performance and Selection

    SciTech Connect

    Carmody, John; Haglund, Kerry

    2012-11-01

    This document provides guidelines for the selection of energy-efficient windows in new and existing residential construction in all U.S. climate zones. It includes information on window products, their attributes and performance. It provides cost/benefit information on window energy savings as well as information on non-energy benefits such as thermal comfort and reduced HVAC demands. The report also provides information on energy impacts of design decisions such as window orientation, total glazing area and shading devices and conditions. Information on resources for proper window installation is included as well.

  15. Improved crystalline properties of laser molecular beam epitaxy grown SrTiO{sub 3} by rutile TiO{sub 2} layer on hexagonal GaN

    SciTech Connect

    Luo, W. B.; Zhu, J.; Chen, H.; Wang, X. P.; Zhang, Y.; Li, Y. R.

    2009-11-15

    Epitaxial SrTiO{sub 3} films were fabricated by laser molecular beam epitaxy on bare and TiO{sub 2} buffered GaN(0002), respectively. The whole deposition processes were in situ monitored by reflection high energy electron diffraction (RHEED). X-ray diffraction (XRD) was carried out to study the growth orientation and crystalline quality of STO films. The interfacial characters and epitaxial relationships were also investigated by high revolution transition electron microscope and selected area electron diffraction (SAED). According to the RHEED observation, the lowest epitaxy temperature of STO on TiO{sub 2} buffered GaN was decreased compared with the direct deposited one. The epitaxial relationship was (111)[110]STO//(0002)[1120]GaN in both cases as confirmed by RHEED, XRD, and SAED. The full width at half maximum of omega-scan and PHI-scan of STO on TiO{sub 2} buffered GaN was reduced compared with that deposited on bare GaN, indicating that epitaxial quality of STO film is improved by inserting TiO{sub 2} layer. In summary, the lattice mismatch was reduced by inserting rutile TiO{sub 2}. As a result, the crystalline temperature was reduced and enhanced epitaxial quality of STO thin film was obtained.

  16. Epitaxial BaTiO3(100) films on Pt(100): a low-energy electron diffraction, scanning tunneling microscopy, and x-ray photoelectron spectroscopy study.

    PubMed

    Förster, Stefan; Huth, Michael; Schindler, Karl-Michael; Widdra, Wolf

    2011-09-14

    The growth of epitaxial ultrathin BaTiO(3) films on a Pt(100) substrate has been studied by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and x-ray photoelectron spectroscopy (XPS). The films have been prepared by radio-frequency-assisted magnetron sputter deposition at room temperature and develop a long-range order upon annealing at 900 K in O(2). By adjusting the Ar and O(2) partial pressures of the sputter gas, the stoichiometry was tuned to match that of a BaTiO(3)(100) single crystal as determined by XPS. STM reveals the growth of continuous BaTiO(3) films with unit cell high islands on top. With LEED already for monolayer thicknesses, the formation of a BaTiO(3)(100)-(1 × 1) structure has been observed. Films of 2-3 unit cell thickness show a brilliant (1 × 1) LEED pattern for which an extended set of LEED I-V data has been acquired. At temperatures above 1050 K the BaTiO(3) thin film starts to decay by formation of vacancy islands. In addition (4 × 4) and (3 × 3) surface reconstructions develop upon prolonged heating.

  17. Probing optical band gaps at the nanoscale in NiFe₂O₄ and CoFe₂O₄ epitaxial films by high resolution electron energy loss spectroscopy

    SciTech Connect

    Dileep, K.; Loukya, B.; Datta, R.; Pachauri, N.; Gupta, A.

    2014-09-14

    Nanoscale optical band gap variations in epitaxial thin films of two different spinel ferrites, i.e., NiFe₂O₄ (NFO) and CoFe₂O₄ (CFO), have been investigated by spatially resolved high resolution electron energy loss spectroscopy. Experimentally, both NFO and CFO show indirect/direct band gaps around 1.52 eV/2.74 and 2.3 eV, and 1.3 eV/2.31 eV, respectively, for the ideal inverse spinel configuration with considerable standard deviation in the band gap values for CFO due to various levels of deviation from the ideal inverse spinel structure. Direct probing of the regions in both the systems with tetrahedral A site cation vacancy, which is distinct from the ideal inverse spinel configuration, shows significantly smaller band gap values. The experimental results are supported by the density functional theory based modified Becke-Johnson exchange correlation potential calculated band gap values for the different cation configurations.

  18. Development of anion-selective membranes. [for energy storage

    NASA Technical Reports Server (NTRS)

    Lacey, R. E.; Cowsar, D. R.

    1975-01-01

    Methods were studied of preparing anion-exchange membranes that would have low resistance, high selectivity, and physical and chemical stability when used in acidic media in a redox energy storage system. Of the twelve systems selected for study, only the system that was based on crosslinked poly-4-vinylpyridinium chloride produced physically strong membranes when equilibrated in l M HCl. The resistivity of the best membrane was 12 ohm-cm, and the transference number for chloride ions was 0.81.

  19. Model selection as a science driver for dark energy surveys

    NASA Astrophysics Data System (ADS)

    Mukherjee, Pia; Parkinson, David; Corasaniti, Pier Stefano; Liddle, Andrew R.; Kunz, Martin

    2006-07-01

    A key science goal of upcoming dark energy surveys is to seek time-evolution of the dark energy. This problem is one of model selection, where the aim is to differentiate between cosmological models with different numbers of parameters. However, the power of these surveys is traditionally assessed by estimating their ability to constrain parameters, which is a different statistical problem. In this paper, we use Bayesian model selection techniques, specifically forecasting of the Bayes factors, to compare the abilities of different proposed surveys in discovering dark energy evolution. We consider six experiments - supernova luminosity measurements by the Supernova Legacy Survey, SNAP, JEDI and ALPACA, and baryon acoustic oscillation measurements by WFMOS and JEDI - and use Bayes factor plots to compare their statistical constraining power. The concept of Bayes factor forecasting has much broader applicability than dark energy surveys.

  20. Supply of and demand for selected energy related mineral commodities

    USGS Publications Warehouse

    Sibley, Scott F.

    2010-01-01

    In this report, subjects discussed include components of mineral supply, production, and consumption data, and information on selected mineral commodities in which the Energy Critical Elements Study Group has an interest, and U.S. Geological Survey (USGS) recycling studies, with some results of these studies.

  1. Method of forming silicon structures with selectable optical characteristics

    NASA Technical Reports Server (NTRS)

    Fathauer, Robert W. (Inventor); Schowalter, Leo (Inventor)

    1993-01-01

    Silicon and metal are coevaporated onto a silicon substrate in a molecular beam epitaxy system with a larger than stoichiometric amount of silicon so as to epitaxially grow particles of metal silicide embedded in a matrix of single crystal epitaxially grown silicon. The particles interact with incident photons by resonant optical absorption at the surface plasmon resonance frequency. Controlling the substrate temperature and deposition rate and time allows the aspect ratio of the particles to be tailored to desired wavelength photons and polarizations. The plasmon energy may decay as excited charge carriers or phonons, either of which can be monitored to indicate the amount of incident radiation at the selected frequency and polarization.

  2. Interfacing epitaxial oxides to gallium nitride

    NASA Astrophysics Data System (ADS)

    Losego, Mark Daniel

    Molecular beam epitaxy (MBE) is lauded for its ability to control thin film material structures at the atomic level. This precision of control can improve performance of microelectronic devices and cultivate the development of novel device structures. This thesis explores the utility of MBE for designing interfaces between oxide epilayers and the wide band gap semiconductor gallium nitride (GaN). The allure of wide gap semiconductor microelectronics (like GaN, 3.4 eV) is their ability to operate at higher frequencies, higher powers, and higher temperatures than current semiconductor platforms. Heterostructures between ferroelectric oxides and GaN are also of interest for studying the interaction between GaN's fixed polarization and the ferroelectric's switchable polarization. Two major obstacles to successful integration of oxides with GaN are: (1) interfacial trap states; and (2) small electronic band offsets across the oxide/nitride interface due to the semiconductor's large band gap. For this thesis, epitaxial rocksalt oxide interfacial layers (˜8 eV band gap) are investigated as possible solutions to overcoming the challenges facing oxide integration with GaN. The cubic close-packed structure of rocksalt oxides forms a suitable epitaxial interface with the hexagonal close-packed wurtzite lattice of GaN. Three rocksalt oxide compounds are investigated in this thesis: MgO, CaO, and YbO. All are found to have a (111) MO || (0001) GaN; <1 10> MO || <11 20> GaN epitaxial relationship. Development of the epilayer microstructure is dominated by the high-energy polar growth surface (drives 3D nucleation) and the interfacial symmetry, which permits the formation of twin boundaries. Using STEM, strain relief for these ionicly bonded epilayers is observed to occur through disorder within the initial monolayer of growth. All rocksalt oxides demonstrate chemical stability with GaN to >1000°C. Concurrent MBE deposition of MgO and CaO is known to form complete solid

  3. Thermophotovoltaic energy conversion using photonic bandgap selective emitters

    DOEpatents

    Gee, James M.; Lin, Shawn-Yu; Fleming, James G.; Moreno, James B.

    2003-06-24

    A method for thermophotovoltaic generation of electricity comprises heating a metallic photonic crystal to provide selective emission of radiation that is matched to the peak spectral response of a photovoltaic cell that converts the radiation to electricity. The use of a refractory metal, such as tungsten, for the photonic crystal enables high temperature operation for high radiant flux and high dielectric contrast for a full 3D photonic bandgap, preferable for efficient thermophotovoltaic energy conversion.

  4. Temperature-gradient epitaxy under in situ growth mode diagnostics by scanning reflection high-energy electron diffraction

    NASA Astrophysics Data System (ADS)

    Koida, T.; Komiyama, D.; Koinuma, H.; Ohtani, M.; Lippmaa, M.; Kawasaki, M.

    2002-01-01

    We have developed a parallel film growth method on a temperature-gradient substrate to quickly control and optimize the film growth mode. A continuous-wave neodymium-doped yttrium-aluminum-garnet laser heating was used to achieve a stable temperature gradient covering a 300 °C range of temperatures over a distance of 11 mm. The growth mode was determined by time-resolved scanning reflection high-energy electron diffraction. Transition from layer-by-layer to step-flow growth by the deposition temperature was observed during La0.5Sr0.5MnO3 film growth on a single SrTiO3 substrate, proving a powerful tool not only for investigating the growth dynamics but also for seeking the optimized deposition conditions in one run of experiment.

  5. EFFECT OF ENERGY DRINKS ON SELECTED FINE MOTOR TASKS.

    PubMed

    Jacobson, B H; Hughes, P P; Conchola, E C; Hester, G M; Woolsey, C L

    2015-08-01

    This study assessed the effect of energy shots on selected fine motor tasks. The participants were college-age male (n=19; M age=20.5 yr., SD=0.7) and female (n=21; M age=21.1 yr., SD=0.7) volunteers who were assessed on hand steadiness, choice reaction time, rotary pursuit, and simple reaction time. The energy shots group scored significantly poorer on the hand steadiness tests and significantly better on choice reaction time and simple reaction time tests. The enhanced reaction time and disruption in hand steadiness afforded by energy shots would not be apparent in many gross motor activities, but it is possible that reaction time improvement could be beneficial in sports that require quick, reflexive movements. However, the potential adverse psychological and physiological effects warrant discretionary use of such products.

  6. Materials selection guidelines for geothermal energy utilization systems

    SciTech Connect

    Ellis, P.F. II; Conover, M.F.

    1981-01-01

    This manual includes geothermal fluid chemistry, corrosion test data, and materials operating experience. Systems using geothermal energy in El Salvador, Iceland, Italy, Japan, Mexico, New Zealand, and the United States are described. The manual provides materials selection guidelines for surface equipment of future geothermal energy systems. The key chemical species that are significant in determining corrosiveness of geothermal fluids are identified. The utilization modes of geothermal energy are defined as well as the various physical fluid parameters that affect corrosiveness. Both detailed and summarized results of materials performance tests and applicable operating experiences from forty sites throughout the world are presented. The application of various non-metal materials in geothermal environments are discussed. Included in appendices are: corrosion behavior of specific alloy classes in geothermal fluids, corrosion in seawater desalination plants, worldwide geothermal power production, DOE-sponsored utilization projects, plant availability, relative costs of alloys, and composition of alloys. (MHR)

  7. Monitoring non-pseudomorphic epitaxial growth of spinel/perovskite oxide heterostructures by reflection high-energy electron diffraction

    SciTech Connect

    Schütz, P.; Pfaff, F.; Scheiderer, P.; Sing, M.; Claessen, R.

    2015-02-09

    Pulsed laser deposition of spinel γ-Al{sub 2}O{sub 3} thin films on bulk perovskite SrTiO{sub 3} is monitored by high-pressure reflection high-energy electron diffraction (RHEED). The heteroepitaxial combination of two materials with different crystal structures is found to be inherently accompanied by a strong intensity modulation of bulk diffraction patterns from inelastically scattered electrons, which impedes the observation of RHEED intensity oscillations. Avoiding such electron surface-wave resonance enhancement by de-tuning the RHEED geometry allows for the separate observation of the surface-diffracted specular RHEED signal and thus the real-time monitoring of sub-unit cell two-dimensional layer-by-layer growth. Since these challenges are essentially rooted in the difference between film and substrate crystal structure, our findings are of relevance for the growth of any heterostructure combining oxides with different crystal symmetry and may thus facilitate the search for novel oxide heterointerfaces.

  8. Epitaxial Graphene Quantum Electronics

    DTIC Science & Technology

    2014-05-19

    ferromagnetism with spintronics potential. * We have achieved the highest operational frequency in graphene transistors. Epitaxial graphene; quantum transport...important discovery with implications for spintronics . * We have found that ballistic transport most likely involves non-conventional charge carriers

  9. Predictions of Ligand Selectivity from Absolute Binding Free Energy Calculations

    PubMed Central

    2016-01-01

    Binding selectivity is a requirement for the development of a safe drug, and it is a critical property for chemical probes used in preclinical target validation. Engineering selectivity adds considerable complexity to the rational design of new drugs, as it involves the optimization of multiple binding affinities. Computationally, the prediction of binding selectivity is a challenge, and generally applicable methodologies are still not available to the computational and medicinal chemistry communities. Absolute binding free energy calculations based on alchemical pathways provide a rigorous framework for affinity predictions and could thus offer a general approach to the problem. We evaluated the performance of free energy calculations based on molecular dynamics for the prediction of selectivity by estimating the affinity profile of three bromodomain inhibitors across multiple bromodomain families, and by comparing the results to isothermal titration calorimetry data. Two case studies were considered. In the first one, the affinities of two similar ligands for seven bromodomains were calculated and returned excellent agreement with experiment (mean unsigned error of 0.81 kcal/mol and Pearson correlation of 0.75). In this test case, we also show how the preferred binding orientation of a ligand for different proteins can be estimated via free energy calculations. In the second case, the affinities of a broad-spectrum inhibitor for 22 bromodomains were calculated and returned a more modest accuracy (mean unsigned error of 1.76 kcal/mol and Pearson correlation of 0.48); however, the reparametrization of a sulfonamide moiety improved the agreement with experiment. PMID:28009512

  10. Resonance Energy Transfer in Upconversion Nanoplatforms for Selective Biodetection.

    PubMed

    Su, Qianqian; Feng, Wei; Yang, Dongpeng; Li, Fuyou

    2017-01-17

    Resonance energy transfer (RET) describes the process that energy is transferred from an excited donor to an acceptor molecule, leading to a reduction in the fluorescence emission intensity of the donor and an increase in that of the acceptor. By this technique, measurements with the good sensitivity can be made about distance within 1 to 10 nm under physiological conditions. For this reason, the RET technique has been widely used in polymer science, biochemistry, and structural biology. Recently, a number of RET systems incorporated with nanoparticles, such as quantum dots, gold nanoparticles, and upconversion nanoparticles, have been developed. These nanocrystals retain their optical superiority and can act as either a donor or a quencher, thereby enhancing the performance of RET systems and providing more opportunities in excitation wavelength selection. Notably, lanthanide-doped upconversion nanophosphors (UCNPs) have attracted considerable attention due to their inherent advantages of large anti-Stoke shifts, long luminescence lifetimes, and absence of autofluorescence under low energy near-infrared (NIR) light excitation. These nanoparticles are promising for the biodetection of various types of analytes. Undoubtedly, the developments of those applications usually rely on resonance energy transfer, which could be regarded as a flexible technology to mediate energy transfer from upconversion phosphor to acceptor for the design of luminescent functional nanoplatforms. Currently, researchers have developed many RET-based upconversion nanosystems (RET-UCNP) that respond to specific changes in the biological environments. Specifically, small organic molecules, biological molecules, metal-organic complexes, or inorganic nanoparticles were carefully selected and bound to the surface of upconversion nanoparticles for the preparation of RET-UCNP nanosystems. Benefiting from the advantage and versatility offered by this technology, the research of RET

  11. 7 CFR 4280.193 - Selecting energy audit and renewable energy development assistance grant applications for award.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 15 2012-01-01 2012-01-01 false Selecting energy audit and renewable energy development assistance grant applications for award. 4280.193 Section 4280.193 Agriculture Regulations of the... Renewable Energy Development Assistance Grants § 4280.193 Selecting energy audit and renewable...

  12. 7 CFR 4280.193 - Selecting energy audit and renewable energy development assistance grant applications for award.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 15 2014-01-01 2014-01-01 false Selecting energy audit and renewable energy development assistance grant applications for award. 4280.193 Section 4280.193 Agriculture Regulations of the... Renewable Energy Development Assistance Grants § 4280.193 Selecting energy audit and renewable...

  13. 7 CFR 4280.193 - Selecting energy audit and renewable energy development assistance grant applications for award.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 15 2013-01-01 2013-01-01 false Selecting energy audit and renewable energy development assistance grant applications for award. 4280.193 Section 4280.193 Agriculture Regulations of the... Renewable Energy Development Assistance Grants § 4280.193 Selecting energy audit and renewable...

  14. Greater sage-grouse winter habitat selection and energy development

    SciTech Connect

    Doherty, K.E.; Naugle, D.E.; Walker, B.L.; Graham, J.M.

    2008-01-15

    Recent energy development has resulted in rapid and large-scale changes to western shrub-steppe ecosystems without a complete understanding of its potential impacts on wildlife populations. We modeled winter habitat use by female greater sage-grouse (Centrocercus urophasianus) in the Powder River Basin (PRB) of Wyoming and Montana, USA, to 1) identify landscape features that influenced sage-grouse habitat selection, 2) assess the scale at which selection occurred, 3) spatially depict winter habitat quality in a Geographic Information System, and 4) assess the effect of coal-bed natural gas (CBNG) development on winter habitat selection. We developed a model of winter habitat selection based on 435 aerial relocations of 200 radiomarked female sage-grouse obtained during the winters of 2005 and 2006. Percent sagebrush (Artemisia spp.) cover on the landscape was an important predictor of use by sage-grouse in winter. Sage-grouse were 1.3 times more likely to occupy sagebrush habitats that lacked CBNG wells within a 4-km{sup 2} area, compared to those that had the maximum density of 12.3 wells per 4 km{sup 2} allowed on federal lands. We validated the model with 74 locations from 74 radiomarked individuals obtained during the winters of 2004 and 2007. This winter habitat model based on vegetation, topography, and CBNG avoidance was highly predictive (validation R{sup 2} = 0.984). Our spatially explicit model can be used to identify areas that provide the best remaining habitat for wintering sage-grouse in the PRB to mitigate impacts of energy development.

  15. Effects of selective lattice deformation on YbBa2Cu4O8 and YBa2Cu3O7 epitaxial films

    NASA Astrophysics Data System (ADS)

    Mito, M.; Matsui, H.; Imakyurei, T.; Deguchi, H.; Horide, T.; Matsumoto, K.; Ichinose, A.; Yoshida, Y.

    2014-03-01

    Alternating current magnetic measurements of YbBa2Cu4O8 (Yb-124) and YBa2Cu3O7 (Y-123) epitaxial films were performed under hydrostatic pressure (HP). Here, the strain under HP results in uniaxial strain along the c-axis, in addition to the biaxial strain due to mismatching with the substrate. This uniaxial effect on Yb-124 film brings about a prominent increase in the superconducting transition temperature (Tc) against the initial strain. However, a nearly optimal Y-123 film hardly exhibits an initial change in Tc, and even an underdoped one only exhibits an increase in Tc, that is, one-third as much as that in the Yb-124 film. Effective carrier doping by the use of effective out-of-plane contraction prominently appears in the 124-structure rather than in the 123-structure.

  16. InGaAs heterostructure formation in catalyst-free GaAs nanopillars by selective-area metal-organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Shapiro, J. N.; Lin, A.; Wong, P. S.; Scofield, A. C.; Tu, C.; Senanayake, P. N.; Mariani, G.; Liang, B. L.; Huffaker, D. L.

    2010-12-01

    We investigate axial GaAs/InGaAs/GaAs heterostructures embedded in GaAs nanopillars via catalyst-free selective-area metal-organic chemical vapor deposition. Structural characterization by transmission electron microscopy with energy dispersive x-ray spectroscopy (EDS) indicates formation of axial InxGa1-xAs (x˜0.20) inserts with thicknesses from 36 to 220 nm with ±10% variation and graded Ga:In transitions controlled by In segregation. Using the heterointerfaces as markers, the vertical growth rate is determined to increase linearly during growth. Photoluminescence from 77 to 290 K and EDS suggest the presence of strain in the shortest inserts. This capability to control the formation of axial nanopillar heterostructures is crucial for optimized device integration.

  17. Energy band alignment of atomic layer deposited HfO{sub 2} oxide film on epitaxial (100)Ge, (110)Ge, and (111)Ge layers

    SciTech Connect

    Hudait, Mantu K.; Zhu Yan

    2013-03-21

    Crystallographically oriented epitaxial Ge layers were grown on (100), (110), and (111)A GaAs substrates by in situ growth process using two separate molecular beam epitaxy chambers. The band alignment properties of atomic layer hafnium oxide (HfO{sub 2}) film deposited on crystallographically oriented epitaxial Ge were investigated using x-ray photoelectron spectroscopy (XPS). Valence band offset, {Delta}E{sub v} values of HfO{sub 2} relative to (100)Ge, (110)Ge, and (111)Ge orientations were 2.8 eV, 2.28 eV, and 2.5 eV, respectively. Using XPS data, variation in valence band offset, {Delta}E{sub V}(100)Ge>{Delta}E{sub V}(111)Ge>{Delta}E{sub V}(110)Ge, was obtained related to Ge orientation. Also, the conduction band offset, {Delta}E{sub c} relation, {Delta}E{sub c}(110)Ge>{Delta}E{sub c}(111)Ge>{Delta}E{sub c}(100)Ge related to Ge orientations was obtained using the measured bandgap of HfO{sub 2} on each orientation and with the Ge bandgap of 0.67 eV. These band offset parameters for carrier confinement would offer an important guidance to design Ge-based p- and n-channel metal-oxide field-effect transistor for low-power application.

  18. Energy efficiency of substance and energy recovery of selected waste fractions

    SciTech Connect

    Fricke, Klaus; Bahr, Tobias; Bidlingmaier, Werner; Springer, Christian

    2011-04-15

    In order to reduce the ecological impact of resource exploitation, the EU calls for sustainable options to increase the efficiency and productivity of the utilization of natural resources. This target can only be achieved by considering resource recovery from waste comprehensively. However, waste management measures have to be investigated critically and all aspects of substance-related recycling and energy recovery have to be carefully balanced. This article compares recovery methods for selected waste fractions with regard to their energy efficiency. Whether material recycling or energy recovery is the most energy efficient solution, is a question of particular relevance with regard to the following waste fractions: paper and cardboard, plastics and biowaste and also indirectly metals. For the described material categories material recycling has advantages compared to energy recovery. In accordance with the improved energy efficiency of substance opposed to energy recovery, substance-related recycling causes lower emissions of green house gases. For the fractions paper and cardboard, plastics, biowaste and metals it becomes apparent, that intensification of the separate collection systems in combination with a more intensive use of sorting technologies can increase the extent of material recycling. Collection and sorting systems must be coordinated. The objective of the overall system must be to achieve an optimum of the highest possible recovery rates in combination with a high quality of recyclables. The energy efficiency of substance related recycling of biowaste can be increased by intensifying the use of anaerobic technologies. In order to increase the energy efficiency of the overall system, the energy efficiencies of energy recovery plants must be increased so that the waste unsuitable for substance recycling is recycled or treated with the highest possible energy yield.

  19. Energy efficiency of substance and energy recovery of selected waste fractions.

    PubMed

    Fricke, Klaus; Bahr, Tobias; Bidlingmaier, Werner; Springer, Christian

    2011-04-01

    In order to reduce the ecological impact of resource exploitation, the EU calls for sustainable options to increase the efficiency and productivity of the utilization of natural resources. This target can only be achieved by considering resource recovery from waste comprehensively. However, waste management measures have to be investigated critically and all aspects of substance-related recycling and energy recovery have to be carefully balanced. This article compares recovery methods for selected waste fractions with regard to their energy efficiency. Whether material recycling or energy recovery is the most energy efficient solution, is a question of particular relevance with regard to the following waste fractions: paper and cardboard, plastics and biowaste and also indirectly metals. For the described material categories material recycling has advantages compared to energy recovery. In accordance with the improved energy efficiency of substance opposed to energy recovery, substance-related recycling causes lower emissions of green house gases. For the fractions paper and cardboard, plastics, biowaste and metals it becomes apparent, that intensification of the separate collection systems in combination with a more intensive use of sorting technologies can increase the extent of material recycling. Collection and sorting systems must be coordinated. The objective of the overall system must be to achieve an optimum of the highest possible recovery rates in combination with a high quality of recyclables. The energy efficiency of substance related recycling of biowaste can be increased by intensifying the use of anaerobic technologies. In order to increase the energy efficiency of the overall system, the energy efficiencies of energy recovery plants must be increased so that the waste unsuitable for substance recycling is recycled or treated with the highest possible energy yield.

  20. Epitaxial Garnets and Hexagonal Ferrites.

    DTIC Science & Technology

    1983-12-01

    Ferrites Lithium Ferrite Magnetostatic Wave Garnets Epitaxy Yttrium Iron Garnet Liquid Phase Epitaxy Hexagonal Ferrite Microwave Signal Processing...epitaxial ferrit ( materials for use in microwave and millirreter-wave signal processing devices. The major emphasis has been on multiple layer...overall objective of this research is to develop epitaxial single crystal ferrite films suitable for microwave and millimeter-wave signal processing at

  1. Blanket and Patterned Growth of CdTe on (211)Si Substrates by Metal-Organic Vapor Phase Epitaxy

    DTIC Science & Technology

    2012-05-15

    Vapor Deposition, Epitaxial Lateral Overgrowth, Selective Epitaxy, CdTe Ishwara B. Bhat*,1, , Sunil R. Rao1, , Shashidhar Shintri2, , Randolph N...growth of CdTe on (211)Si substrates by metal- organic vapor phase epitaxy Ishwara B. Bhat*,1, Sunil R. Rao1, Shashidhar Shintri2, and Randolph N

  2. Epitaxial stabilization and phase instability of VO2 polymorphs

    PubMed Central

    Lee, Shinbuhm; Ivanov, Ilia N.; Keum, Jong K.; Lee, Ho Nyung

    2016-01-01

    The VO2 polymorphs, i.e., VO2(A), VO2(B), VO2(M1) and VO2(R), have a wide spectrum of functionalities useful for many potential applications in information and energy technologies. However, synthesis of phase pure materials, especially in thin film forms, has been a challenging task due to the fact that the VO2 polymorphs are closely related to each other in a thermodynamic framework. Here, we report epitaxial stabilization of the VO2 polymorphs to synthesize high quality single crystalline thin films and study the phase stability of these metastable materials. We selectively deposit all the phases on various perovskite substrates with different crystallographic orientations. By investigating the phase instability, phonon modes and transport behaviours, not only do we find distinctively contrasting physical properties of the VO2 polymorphs, but that the polymorphs can be on the verge of phase transitions when heated as low as ~400 °C. Our successful epitaxy of both VO2(A) and VO2(B) phases, which are rarely studied due to the lack of phase pure materials, will open the door to the fundamental studies of VO2 polymorphs for potential applications in advanced electronic and energy devices. PMID:26787259

  3. Epitaxial stabilization and phase instability of VO2 polymorphs

    DOE PAGES

    Lee, Shinbuhm; Ivanov, Ilia N.; Keum, Jong K.; ...

    2016-01-20

    The VO2 polymorphs, i.e., VO2(A), VO2(B), VO2(M1) and VO2(R), have a wide spectrum of functionalities useful for many potential applications in information and energy technologies. However, synthesis of phase pure materials, especially in thin film forms, has been a challenging task due to the fact that the VO2 polymorphs are closely related to each other in a thermodynamic framework. Here, we report epitaxial stabilization of the VO2 polymorphs to synthesize high quality single crystalline thin films and study the phase stability of these metastable materials. We selectively deposit all the phases on various perovskite substrates with different crystallographic orientations. Bymore » investigating the phase instability, phonon modes and transport behaviours, not only do we find distinctively contrasting physical properties of the VO2 polymorphs, but that the polymorphs can be on the verge of phase transitions when heated as low as ~400 °C. In conclusion, our successful epitaxy of both VO2(A) and VO2(B) phases, which are rarely studied due to the lack of phase pure materials, will open the door to the fundamental studies of VO2 polymorphs for potential applications in advanced electronic and energy devices.« less

  4. Applications of Optimal Building Energy System Selection and Operation

    SciTech Connect

    Marnay, Chris; Stadler, Michael; Siddiqui, Afzal; DeForest, Nicholas; Donadee, Jon; Bhattacharya, Prajesh; Lai, Judy

    2011-04-01

    Berkeley Lab has been developing the Distributed Energy Resources Customer Adoption Model (DER-CAM) for several years. Given load curves for energy services requirements in a building microgrid (u grid), fuel costs and other economic inputs, and a menu of available technologies, DER-CAM finds the optimum equipment fleet and its optimum operating schedule using a mixed integer linear programming approach. This capability is being applied using a software as a service (SaaS) model. Optimisation problems are set up on a Berkeley Lab server and clients can execute their jobs as needed, typically daily. The evolution of this approach is demonstrated by description of three ongoing projects. The first is a public access web site focused on solar photovoltaic generation and battery viability at large commercial and industrial customer sites. The second is a building CO2 emissions reduction operations problem for a University of California, Davis student dining hall for which potential investments are also considered. And the third, is both a battery selection problem and a rolling operating schedule problem for a large County Jail. Together these examples show that optimization of building u grid design and operation can be effectively achieved using SaaS.

  5. A review of selected energy-related data sets

    SciTech Connect

    Nicholls, A.K.; Elliott, D.B.; Jones, M.L.; Hannifan, J.M.; Degroat, K.J.; Eichner, M.J.; King, J.E.

    1992-09-01

    DOE`s Office of Planning and Assessment (OPA) performs crosscutting technical, policy, and environmental assessments of energy technologies and markets. To support these efforts, OPA is in the process of creating a data base management system (DBMS) that will include relevant data compiled from other sources. One of the first steps is a review of selected data sets that may be considered for inclusion in the DBMS. The review covered data sets in five categories: buildings-specific data, industry-specific data, transportation-specific data, utilities-specific data, and crosscutting/general data. Reviewed data sets covered a broad array of energy efficiency, renewable, and/or benchmark technologies. Most data sets reviewed in this report are sponsored by Federal government entities and major industry organizations. Additional data sets reviewed are sponsored by the states of California and New York and regional entities in the Pacific Northwest. Prior to full review, candidate data sets were screened for their utility to OPA. Screening criteria included requirements that a data set be particularly applicable to OPA`s data needs, documented, current, and obtainable. To fully implement its DBMS, OPA will need to expand the review to other data sources, and must carefully consider the implications of differing assumptions and methodologies when comparing data.

  6. A review of selected energy-related data sets

    SciTech Connect

    Nicholls, A.K.; Elliott, D.B.; Jones, M.L. ); Hannifan, J.M.; Degroat, K.J.; Eichner, M.J.; King, J.E. )

    1992-09-01

    DOE's Office of Planning and Assessment (OPA) performs crosscutting technical, policy, and environmental assessments of energy technologies and markets. To support these efforts, OPA is in the process of creating a data base management system (DBMS) that will include relevant data compiled from other sources. One of the first steps is a review of selected data sets that may be considered for inclusion in the DBMS. The review covered data sets in five categories: buildings-specific data, industry-specific data, transportation-specific data, utilities-specific data, and crosscutting/general data. Reviewed data sets covered a broad array of energy efficiency, renewable, and/or benchmark technologies. Most data sets reviewed in this report are sponsored by Federal government entities and major industry organizations. Additional data sets reviewed are sponsored by the states of California and New York and regional entities in the Pacific Northwest. Prior to full review, candidate data sets were screened for their utility to OPA. Screening criteria included requirements that a data set be particularly applicable to OPA's data needs, documented, current, and obtainable. To fully implement its DBMS, OPA will need to expand the review to other data sources, and must carefully consider the implications of differing assumptions and methodologies when comparing data.

  7. Electronic structure of few-layer epitaxial graphene on Ru(0001).

    PubMed

    Sutter, P; Hybertsen, M S; Sadowski, J T; Sutter, E

    2009-07-01

    The electronic structure of epitaxial monolayer, bilayer, and trilayer graphene on Ru(0001) was determined by selected-area angle-resolved photoelectron spectroscopy (micro-ARPES). Micro-ARPES band maps provide evidence for a strong electronic coupling between monolayer graphene and the adjacent metal, which causes the complete disruption of the graphene pi-bands near the Fermi energy. However, the perturbation by the metal decreases rapidly with the addition of further graphene sheets, and already an epitaxial graphene bilayer on Ru recovers the characteristic Dirac cones of isolated monolayer graphene. A graphene trilayer on Ru behaves like free-standing bilayer graphene. Density-functional theory based calculations show that this decoupling is due to the efficient passivation of metal d-states by the interfacial graphene layer.

  8. White light generation by resonant nonradiative energy transfer from epitaxial InGaN/GaN quantum wells to colloidal CdSe/ZnS core/shell quantum dots

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    We propose and demonstrate white-light-generating nonradiative energy transfer (ET) from epitaxial quantum wells (QWs) to colloidal quantum dots (QDs) in their close proximity. This proof-of-concept hybrid color-converting system consists of chemically synthesized red-emitting CdSe/ZnS core/shell heteronanocrystals intimately integrated on epitaxially grown cyan-emitting InGaN/GaN QWs. The white light is generated by the collective luminescence of QWs and QDs, for which the dot emission is further increased by 63% with nonradiative ET, setting the operating point in the white region of CIE chromaticity diagram. Using cyan emission at 490 nm from the QWs and red emission at 650 nm from the nanocrystal (NC) luminophors, we obtain warm white light generation with a correlated color temperature of Tc = 3135 K and tristimulus coordinates of (x,y) = (0.42, 0.39) in the white region. By analyzing the time-resolved radiative decay of these NC emitters in our hybrid system with a 16 ps time resolution, the luminescence kinetics reveals a fast ET with a rate of (2 ns)-1 using a multiexponential fit with χ 2 = 1.0171.

  9. Epitaxial thin films

    DOEpatents

    Hunt, Andrew Tye; Deshpande, Girish; Lin, Wen-Yi; Jan, Tzyy-Jiuan

    2006-04-25

    Epitatial thin films for use as buffer layers for high temperature superconductors, electrolytes in solid oxide fuel cells (SOFC), gas separation membranes or dielectric material in electronic devices, are disclosed. By using CCVD, CACVD or any other suitable deposition process, epitaxial films having pore-free, ideal grain boundaries, and dense structure can be formed. Several different types of materials are disclosed for use as buffer layers in high temperature superconductors. In addition, the use of epitaxial thin films for electrolytes and electrode formation in SOFCs results in densification for pore-free and ideal gain boundary/interface microstructure. Gas separation membranes for the production of oxygen and hydrogen are also disclosed. These semipermeable membranes are formed by high-quality, dense, gas-tight, pinhole free sub-micro scale layers of mixed-conducting oxides on porous ceramic substrates. Epitaxial thin films as dielectric material in capacitors are also taught herein. Capacitors are utilized according to their capacitance values which are dependent on their physical structure and dielectric permittivity. The epitaxial thin films of the current invention form low-loss dielectric layers with extremely high permittivity. This high permittivity allows for the formation of capacitors that can have their capacitance adjusted by applying a DC bias between their electrodes.

  10. 2D vibrational properties of epitaxial silicene on Ag(111)

    NASA Astrophysics Data System (ADS)

    Solonenko, Dmytro; Gordan, Ovidiu D.; Le Lay, Guy; Sahin, Hasan; Cahangirov, Seymur; Zahn, Dietrich R. T.; Vogt, Patrick

    2017-03-01

    The two-dimensional silicon allotrope, silicene, could spur the development of new and original concepts in Si-based nanotechnology. Up to now silicene can only be epitaxially synthesized on a supporting substrate such as Ag(111). Even though the structural and electronic properties of these epitaxial silicene layers have been intensively studied, very little is known about its vibrational characteristics. Here, we present a detailed study of epitaxial silicene on Ag(111) using in situ Raman spectroscopy, which is one of the most extensively employed experimental techniques to characterize 2D materials, such as graphene, transition metal dichalcogenides, and black phosphorous. The vibrational fingerprint of epitaxial silicene, in contrast to all previous interpretations, is characterized by three distinct phonon modes with A and E symmetries. Both, energies and symmetries of theses modes are confirmed by ab initio theory calculations. The temperature dependent spectral evolution of these modes demonstrates unique thermal properties of epitaxial silicene and a significant electron-phonon coupling. These results unambiguously support the purely two-dimensional character of epitaxial silicene up to about 300 °C, whereupon a 2D-to-3D phase transition takes place. The detailed fingerprint of epitaxial silicene will allow us to identify it in different environments or to study its modifications.

  11. Selection effects on GRB spectral-energy correlations

    SciTech Connect

    Nava, Lara; Ghirlanda, Giancarlo; Ghisellini, Gabriele

    2009-05-25

    Instrumental selection effects can act upon the estimates of the peak energy E{sub peak}{sup obs}, the fluence F and the peak flux P of GRBs. If this were the case, then the correlations involving the corresponding rest frame quantities (i.e. E{sub peak}, E{sub obs} and the peak luminosity L{sub iso}) would be questioned. We estimated, as a function of E{sub peak}{sup obs}, the minimum peak flux necessary to trigger a GRB and the minimum fluence a burst must have to determine the value of E{sub peak}{sup obs} by considering different instruments (BATSE, Swift, BeppoSAX). We find that the latter dominates over the former. We then study the E{sub peak}{sup obs}-fluence (and flux) correlation in the observer plane. GRBs with redshift show well defined E{sub peak}{sup obs}-F and E{sub peak}{sup obs}-P correlations: in this planes the selection effects are present, but do not determine the found correlations. This is not true for Swift GRBs with redshift, for which the spectral analysis threshold does affect their distribution in the observer planes. Extending the sample to GRBs without z, we still find a significant E{sub peak}{sup obs}-F correlation, although with a larger scatter than that defined by GRBs with redshift. We find that 6% are outliers of the Amati correlation. The E{sub peak}{sup obs}-P correlation of GRBs with or without redshift is the same and no outlier is found among bursts without redshift.

  12. Selection of herbaceous energy crops for the western corn belt

    SciTech Connect

    Anderson, I.C.; Buxton, D.R.; Hallam, J.A.

    1994-05-01

    The ultimate economic feasibility of biomass depends on its cost of production and on the cost of competing fuels. The purpose of this research project is to evaluate the production costs of several combinations of species and management systems for producing herbaceous biomass for energy use in Iowa. Herbaceous biomass production systems have costs similar to other crop production systems, such as corn, soybean, and forages. Thus, the factors influencing the costs of producing dedicated biomass energy crops include technological factors such as the cultivation system, species, treatments, soil type, and site and economic factors such as input prices and use of fixed resources. In order to investigate how these production alternatives are influenced by soil resources, and climate conditions, two locations in Iowa, Ames and Chariton, with different soil types and slightly different weather patterns were selected for both the agronomic and economic analyses. Nine crops in thirteen cropping systems were grown at the two sites for five years, from 1988 to 1992. Some of the systems had multiple cropping or interplanting, using combinations of cool-season species and warm-season species, in order to meet multiple objectives of maximum biomass, minimal soil loss, reduced nitrogen fertilization or diminished pesticide inputs. Six of the systems use continuous monocropping of herbaceous crops with an emphasis on production. The seven other systems consist of similar crops, but with crop rotation and soil conservation considerations. While the erosion and other off-site effects of these systems is an important consideration in their overall evaluation, this report will concentrate on direct production costs only.

  13. Near-Infrared Photoluminescence Enhancement in Ge/CdS and Ge/ZnS Core/Shell Nanocrystals: Utilizing IV/II-VI Semiconductor Epitaxy

    SciTech Connect

    Guo, Yijun; Rowland, Clare E; Schaller, Richard D; Vela, Javier

    2014-08-26

    Ge nanocrystals have a large Bohr radius and a small, size-tunable band gap that may engender direct character via strain or doping. Colloidal Ge nanocrystals are particularly interesting in the development of near-infrared materials for applications in bioimaging, telecommunications and energy conversion. Epitaxial growth of a passivating shell is a common strategy employed in the synthesis of highly luminescent II–VI, III–V and IV–VI semiconductor quantum dots. Here, we use relatively unexplored IV/II–VI epitaxy as a way to enhance the photoluminescence and improve the optical stability of colloidal Ge nanocrystals. Selected on the basis of their relatively small lattice mismatch compared with crystalline Ge, we explore the growth of epitaxial CdS and ZnS shells using the successive ion layer adsorption and reaction method. Powder X-ray diffraction and electron microscopy techniques, including energy dispersive X-ray spectroscopy and selected area electron diffraction, clearly show the controllable growth of as many as 20 epitaxial monolayers of CdS atop Ge cores. In contrast, Ge etching and/or replacement by ZnS result in relatively small Ge/ZnS nanocrystals. The presence of an epitaxial II–VI shell greatly enhances the near-infrared photoluminescence and improves the photoluminescence stability of Ge. Ge/II–VI nanocrystals are reproducibly 1–3 orders of magnitude brighter than the brightest Ge cores. Ge/4.9CdS core/shells show the highest photoluminescence quantum yield and longest radiative recombination lifetime. Thiol ligand exchange easily results in near-infrared active, water-soluble Ge/II–VI nanocrystals. We expect this synthetic IV/II–VI epitaxial approach will lead to further studies into the optoelectronic behavior and practical applications of Si and Ge-based nanomaterials.

  14. Germanium epitaxy on silicon

    PubMed Central

    Ye, Hui; Yu, Jinzhong

    2014-01-01

    With the rapid development of on-chip optical interconnects and optical computing in the past decade, silicon-based integrated devices for monolithic and hybrid optoelectronic integration have attracted wide attention. Due to its narrow pseudo-direct gap behavior and compatibility with Si technology, epitaxial Ge-on-Si has become a significant material for optoelectronic device applications. In this paper, we describe recent research progress on heteroepitaxy of Ge flat films and self-assembled Ge quantum dots on Si. For film growth, methods of strain modification and lattice mismatch relief are summarized, while for dot growth, key process parameters and their effects on the dot density, dot morphology and dot position are reviewed. The results indicate that epitaxial Ge-on-Si materials will play a bigger role in silicon photonics. PMID:27877657

  15. Germanium epitaxy on silicon.

    PubMed

    Ye, Hui; Yu, Jinzhong

    2014-04-01

    With the rapid development of on-chip optical interconnects and optical computing in the past decade, silicon-based integrated devices for monolithic and hybrid optoelectronic integration have attracted wide attention. Due to its narrow pseudo-direct gap behavior and compatibility with Si technology, epitaxial Ge-on-Si has become a significant material for optoelectronic device applications. In this paper, we describe recent research progress on heteroepitaxy of Ge flat films and self-assembled Ge quantum dots on Si. For film growth, methods of strain modification and lattice mismatch relief are summarized, while for dot growth, key process parameters and their effects on the dot density, dot morphology and dot position are reviewed. The results indicate that epitaxial Ge-on-Si materials will play a bigger role in silicon photonics.

  16. Germanium epitaxy on silicon

    NASA Astrophysics Data System (ADS)

    Ye, Hui; Yu, Jinzhong

    2014-04-01

    With the rapid development of on-chip optical interconnects and optical computing in the past decade, silicon-based integrated devices for monolithic and hybrid optoelectronic integration have attracted wide attention. Due to its narrow pseudo-direct gap behavior and compatibility with Si technology, epitaxial Ge-on-Si has become a significant material for optoelectronic device applications. In this paper, we describe recent research progress on heteroepitaxy of Ge flat films and self-assembled Ge quantum dots on Si. For film growth, methods of strain modification and lattice mismatch relief are summarized, while for dot growth, key process parameters and their effects on the dot density, dot morphology and dot position are reviewed. The results indicate that epitaxial Ge-on-Si materials will play a bigger role in silicon photonics.

  17. Epitaxial thinning process

    NASA Technical Reports Server (NTRS)

    Siegel, C. M. (Inventor)

    1984-01-01

    A method is described for thinning an epitaxial layer of a wafer that is to be used in producing diodes having a specified breakdown voltage and which also facilitates the thinning process. Current is passed through the epitaxial layer, by connecting a current source between the substrate of the wafer and an electrolyte in which the wafer is immersed. When the wafer is initially immersed, the voltage across the wafer initially drops and then rises at a steep rate. When light is applied to the wafer the voltage drops, and when the light is interrupted the voltage rises again. These changes in voltage, each indicate the breakdown voltage of a Schottky diode that could be prepared from the wafer at that time. The epitaxial layer is thinned by continuing to apply current through the wafer while it is immersed and light is applied, to form an oxide film and when the oxide film is thick the wafer can then be cleaned of oxide and the testing and thinning continued. Uninterrupted thinning can be achieved by first forming an oxide film, and then using an electrolyte that dissolves the oxide about as fast as it is being formed, to limit the thickness of the oxide layer.

  18. Net energy analysis - powerful tool for selecting elective power options

    SciTech Connect

    Baron, S.

    1995-12-01

    A number of net energy analysis studies have been conducted in recent years for electric power production from coal, oil and uranium fuels; synthetic fuels from coal and oil shale; and heat and electric power from solar energy. This technique is an excellent indicator of investment costs, environmental impact and potential economic competitiveness of alternative electric power systems for energy planners from the Eastern European countries considering future options. Energy conservation is also important to energy planners and the net energy analysis technique is an excellent accounting system on the extent of energy resource conservation. The author proposes to discuss the technique and to present the results of his studies and others in the field. The information supplied to the attendees will serve as a powerful tool to the energy planners considering their electric power options in the future.

  19. Transportation Energy Conservation Data Book: A Selected Bibliography. Edition 3,

    DTIC Science & Technology

    1978-11-01

    Administvation WRIWORDS: ENERGY CONSUnPTION; TRA5SPORTATION: (46 CONSTRUTION. HIGHRATS: MRIAS: 111301 Clarkey, A.CO ISRRVAON; ASPHALTS : SULFUR; CRHNTS:. Energy...PETROLEUM INDUSTRY; COAL INDUSTRY; EQUIPMENT DESIGN; DIAGRAMS; BEAT EXCHANGERS; TABLES (DATA); OCTANE PETROLEUM REFINING: CONCRETES; > ASPHALTS ...16 p. SUPPLIES: ENERGY RESOURCES; PIPELINE 1978 TRANSPORTATION: COAL: PETROLEUM: NATURAL GAS: KEYWORDS: TIRES: FRICTION; WEAR ; TESTING; NSEAT; TNUCwS

  20. Time gating for energy selection and scatter rejection: High-energy pulsed neutron imaging at LANSCE

    NASA Astrophysics Data System (ADS)

    Swift, Alicia; Schirato, Richard; McKigney, Edward; Hunter, James; Temple, Brian

    2015-09-01

    The Los Alamos Neutron Science Center (LANSCE) is a linear accelerator in Los Alamos, New Mexico that accelerates a proton beam to 800 MeV, which then produces spallation neutron beams. Flight path FP15R uses a tungsten target to generate neutrons of energy ranging from several hundred keV to ~600 MeV. The beam structure has micropulses of sub-ns width and period of 1.784 ns, and macropulses of 625 μs width and frequency of either 50 Hz or 100 Hz. This corresponds to 347 micropulses per macropulse, or 1.74 x 104 micropulses per second when operating at 50 Hz. Using a very fast, cooled ICCD camera (Princeton Instruments PI-Max 4), gated images of various objects were obtained on FP15R in January 2015. Objects imaged included blocks of lead and borated polyethylene; a tungsten sphere; and a tungsten, polyethylene, and steel cylinder. Images were obtained in 36 min or less, with some in as little as 6 min. This is novel because the gate widths (some as narrow as 10 ns) were selected to reject scatter and other signal not of interest (e.g. the gamma flash that precedes the neutron pulse), which has not been demonstrated at energies above 14 MeV. This proof-of-principle experiment shows that time gating is possible above 14MeV and is useful for selecting neutron energy and reducing scatter, thus forming clearer images. Future work (simulation and experimental) is being undertaken to improve camera shielding and system design and to precisely determine optical properties of the imaging system.

  1. Morphology evolution and emission properties of InGaN/GaN multiple quantum wells grown on GaN microfacets using crossover stripe patterns by selective area epitaxy

    NASA Astrophysics Data System (ADS)

    Wu, Zhenlong; Chen, Peng; Yang, Guofeng; Xu, Zhou; Xu, Feng; Jiang, Fulong; Zhang, Rong; Zheng, Youdou

    2015-03-01

    We investigate the morphological evolution of selective area epitaxy (SAE) GaN microfacets structures on crossover stripe patterns as a function of temperature, and the emission properties of semipolar InGaN/GaN multiple quantum wells (MQWs) grown on these microstructures with semipolar facets are also studied. The shapes of inner rings gradually change from nearly rectangular to hexagonal when the GaN growth temperature elevates, as a result of growth rates and surface stability varies with elevated temperatures. Three types of semipolar facets ({1 1 -2 2}, {2 1 -3 3} and {1 -1 0 1} facets) can be identified on the inner rings of these structures, which are verified by the emission properties of semipolar InGaN/GaN MQWs. The emission wavelengths of MQWs on these semipolar facets are ordered as {1 -1 0 1} > {2 1 -3 3} > {1 1 -2 2}, which is attributed to variations of growth rate and indium incorporation on different planes during InGaN growth. Furthermore, the indium composition of MQWs changes with the morphological evolution.

  2. Theoretical Minimum Energies to Produce Steel for Selected Conditions

    SciTech Connect

    Fruehan, R.J.; Fortini, O.; Paxton, H.W.; Brindle, R.

    2000-05-01

    The energy used to produce liquid steel in today's integrated and electric arc furnace (EAF) facilities is significantly higher than the theoretical minimum energy requirements. This study presents the absolute minimum energy required to produce steel from ore and mixtures of scrap and scrap alternatives. Additional cases in which the assumptions are changed to more closely approximate actual operating conditions are also analyzed. The results, summarized in Table E-1, should give insight into the theoretical and practical potentials for reducing steelmaking energy requirements. The energy values have also been converted to carbon dioxide (CO{sub 2}) emissions in order to indicate the potential for reduction in emissions of this greenhouse gas (Table E-2). The study showed that increasing scrap melting has the largest impact on energy consumption. However, scrap should be viewed as having ''invested'' energy since at one time it was produced by reducing ore. Increasing scrap melting in the BOF mayor may not decrease energy if the ''invested'' energy in scrap is considered.

  3. Island morphologies in epitaxial growth.

    NASA Astrophysics Data System (ADS)

    Hessinger, Uwe; Leskovar, M.; Rumaner, Lee; Ohuchi, Fumio; Olmstead, Marjorie A.; Ueno, Keiji; Koma, Atsushi

    1996-03-01

    Growth of epitaxial films commonly occurs through the coalescence of individual islands. The morphology of islands has therefore a key importance for the film qualities desired. A uniform layer-by-layer growth of the film is achieved when islands in the first layer coalesce to form a uniform layer before a second layer nucleates; a non-uniform multi-layer growth results from multiple layers successively nucleating on top of each other before the first layer coalesces. We developed a kinetic model based on an analytic solution of the diffusion equation between nucleation events to calculate the evolving island morphology during growth. The morphologies depend on deposition rate, substrate temperature, and activation energies for surface diffusion on the substrate and deposited material. By applying this theory to atomic force microscopy data of GaSe multi-layer islands, we extract a value for the activation energy for Ga diffusion across steps of GaSe. Supported by NSF Grant No. ECS-9209652, DOE Grant No. DE-FG06-94ER45516, and the Japanese New Energy Development Organization.

  4. Molecular Beam Epitaxy of

    NASA Astrophysics Data System (ADS)

    Hsieh, Kuan Hsiung

    Ga(,0.48)In(,0.52)As recently emerges as a promising material for high speed applications. It also has a direct bandgap with gap energy suitable for optical applications. It is the purpose of this thesis to grow high quality Ga(,0.47)In(,0.53)As, lattice-matched Al(,0.48)In(,0.52)As and heterojunction structures by molecular beam epitaxy technique for applications in the areas of modulation-doped high mobility devices and internal photoemission Schottky diodes for infrared detection. Single crystal Al metal deposition on GaInAs by MBE is also studied for its electrical properties. Mobility enhancement has been demonstrated in modulation-doped structures at low temperatures. Very high mobilities were obtained: 10,900 cm('2)/Vs at room temperature, 55,500 cm('2)/Vs at 77K and 70,200 cm('2)/Vs at 10K with corresponding two-dimensional electron gas densities greater than 1 x 10('12) l/cm('2). The quality of Ga(,0.47)In(,0.53)As and the parallel conduction in this material are the limiting factors in its mobility. A new ohmic contact phenomenon has been observed in the MBE single crystal Al metal on Ga(,0.47)In(,0.53)AS samples. Its contact resistivity is measured to be as small as 1 x 10('-6) (OMEGA)-cm('2). The Fermi-level pinning near the conduction band edge might be caused by the interface defects. A planar doping technique has been employed to enhance the built-in barrier height to a value of about 0.5 eV in the single crystal Al on n-p('+)-n-Ga(,0.47)In(,0.52)As structures. This novel quasi-Schottky diode also shows a forward ideal factor of 1.03. As for optical detectors, four kinds of diodes were made for internal photoemission studies: Au Schottky on Ga(,0.47)In(,0.53)As in the wavelength range of 1.9 (mu)m to 2.5 (mu)m, Au Schottky on Al(,0.48)In(,0.52)As in 1.1 (mu)m to 2.0 (mu)m range, single crystal Al on (Al(,0.8)Ga(,0.2))(,0.48)In(,0.52)As with improved quantum yields and lastly a Ga(,0.47)In(,0.53)As/Al(,0.48)In(,0.52)As heterojunction with a measured

  5. Selected Energy Education Activities for Pennsylvania Middle School Grades. Draft.

    ERIC Educational Resources Information Center

    Hack, Nancy; And Others

    These activities are intended to help increase awareness and understanding of the energy situation and to encourage students to become energy conservationists. The document is divided into sections according to discipline area. A final section is devoted to interdisciplinary activities involving several discipline areas integrated with the energy…

  6. Summary of selected compressed air energy storage studies

    SciTech Connect

    Allen, R.D.; Doherty, T.J.; Kannberg, L.D.

    1985-01-01

    A descriptive summarily of research and development in compressed air energy storage technology is presented. Research funded primarily by the Department of Energy is described. Results of studies by other groups and experience at the Huntorf plant in West Germany are included. Feasibility studies performed by General Electric are summarized. The feasibility of air storage in dissolved salt cavities is also demonstrated. (BCS)

  7. A Data Envelopment Analysis Model for Renewable Energy Technology Selection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Public and media interest in alternative energy sources, such as renewable fuels, has rapidly increased in recent years due to higher prices for oil and natural gas. However, the current body of research providing comparative decision making models that either rank these alternative energy sources a...

  8. Selected Energy Conservation Options for Homeowners: Options, Expenses and Payoffs.

    ERIC Educational Resources Information Center

    Lengyel, Dorothy L.; And Others

    This publication is a check list for homeowners and renters to help them reduce energy costs. The list consists of 126 energy conservation options. These options range from "change clothes instead of adjusting thermostat" and "air conditioners turned off when not home" to "use sink stopper" and "weatherstripping…

  9. Analysis of interface formation mechanism in GaN double-polarity selective-area growth by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Kuze, Kenta; Osumi, Noriyuki; Fujita, Yohei; Inoue, Yoku; Nakano, Takayuki

    2016-05-01

    The fabrication of quasi-phase-matching (QPM) crystals by selective-area growth on the two asymmetrically polar surfaces of GaN is examined. We attempted the fabrication of GaN-QPM crystals by one-time growth using a carbon mask. For GaN double-polarity selective-area growth (DP-SAG), we investigated the effect of varied nitriding times of the Al2O3 templates patterned with the carbon mask. We optimized the nitriding conditions for the DP-SAG process, and evaluated the substrate fabricated by the optimized DP-SAG process. In addition, we examined the interface formation mechanism of DP-GaN fabricated by GaN DP-SAG process. We determined that it is possible to fabricate DP-GaN with a sharp interface by optimizing the growth conditions.

  10. Energy resources in southern Africa: a select bibliography

    SciTech Connect

    Cavan, A.

    1981-01-01

    The aims, progress, and possibilities involved in Southern Africa's energy development are the subject of this 473-item bibliography. The primary items of information described in this document are relatively recent (1975-81), originate from both indigenous and international sources, and are mostly in English, although a few are in French and Portuguese. The presented information focuses on the African continent, the Southern African region, and the nations of Angola, Botswana, Lesotho, Malawi, Mozambique, Namibia, Swaziland, South Africa, Tanzania, Zambia, and Zimbabwe. The energy source topics include alcohol, coal, gas, oil, solar, uranium, water, wind, and wood; as well as a general energy-development category.

  11. Spectrally Selective Surface Coatings for Energy Efficiency and Solar Applications.

    ERIC Educational Resources Information Center

    Granqvist, C. G.

    1984-01-01

    Outlines how the radiative properties of a surface can be tailored so as to be favorable for efficient utilization of energy. The radiative properties of concern are transmittance, reflectance, absorptance, and emittance. (JN)

  12. Energy Saving Glass Lamination via Selective Radio Frequency Heating

    SciTech Connect

    Shawn M. Allan; Patricia M. Strickland; Holly S. Shulman

    2009-11-11

    Ceralink Inc. developed FastFuse™, a rapid, new, energy saving process for lamination of glass and composites using radio frequency (RF) heating technology. The Inventions and Innovations program supported the technical and commercial research and development needed to elevate the innovation from bench scale to a self-supporting technology with significant potential for growth. The attached report provides an overview of the technical and commerical progress achieved for FastFuse™ during the course of the project. FastFuse™ has the potential to revolutionize the laminate manufacturing industries by replacing energy intensive, multi-step processes with an energy efficient, single-step process that allows higher throughput. FastFuse™ transmits RF energy directly into the interlayer to generate heat, eliminating the need to directly heat glass layers and the surrounding enclosures, such as autoclaves or vacuum systems. FastFuse™ offers lower start-up and energy costs (up to 90% or more reduction in energy costs), and faster cycles times (less than 5 minutes). FastFuse™ is compatible with EVA, TPU, and PVB interlayers, and has been demonstrated for glass, plastics, and multi-material structures such as photovoltaics and transparent armor.

  13. Magnetic Nanostructures by Adaptive Twinning in Strained Epitaxial Films

    NASA Astrophysics Data System (ADS)

    Kauffmann-Weiss, Sandra; Gruner, Markus E.; Backen, Anja; Schultz, Ludwig; Entel, Peter; Fähler, Sebastian

    2011-11-01

    We exploit the intrinsic structural instability of the Fe70Pd30 magnetic shape memory alloy to obtain functional epitaxial films exhibiting a self-organized nanostructure. We demonstrate that coherent epitaxial straining by 54% is possible. The combination of thin film experiments and large-scale first-principles calculations enables us to establish a lattice relaxation mechanism, which is not expected for stable materials. We identify a low twin boundary energy compared to a high elastic energy as key prerequisite for the adaptive nanotwinning. Our approach is versatile as it allows to control both, nanostructure and intrinsic properties for ferromagnetic, ferroelastic, and ferroelectric materials.

  14. Nanocluster dynamics in fast rate epitaxy under mesoplasma condition

    NASA Astrophysics Data System (ADS)

    Chen, L. W.; Shibuta, Y.; Kambara, M.; Yoshida, T.

    2013-03-01

    The dynamics of Si nano-clusters during epitaxial growth has been investigated with molecular dynamics simulation using the Tersoff potential. Several nm sized Si cluster formed during rapid cooling was found to deform instantaneously upon impingement on a Si(1 0 0) substrate at the same time with the spontaneous ordering of the atomic structure to that of the substrate. Due to the increased fraction of high-energy atoms at the surface, smaller clusters (˜1 nm) are favorable for such a deformation even at lower temperatures. This is the advantage of loosely-bound cluster as growth precursor to attain epitaxy with reduced impact energies.

  15. Energy/Environment/Economy. An Annotated Bibliography of Selected U.S. Government Publications Concerning United States Energy Policy, Supplement.

    ERIC Educational Resources Information Center

    ENVIRO/INFO, Green Bay, WI.

    This annotated bibliography supplements ED 077 704. It provides a selective listing of 93 U.S. Federal Government publications germane to the energy crisis and its attendant environmental and economic implications. Primary emphasis is placed upon documents presenting energy policy issues which have emerged, plus statistical reportage which…

  16. Dissociation of energy-selected 1,1-dimethylhydrazine ions.

    PubMed

    Gengeliczki, Zsolt; Borkar, Sampada N; Sztáray, Bálint

    2010-05-27

    The unimolecular dissociation of 1,1-dimethylhydrazine ions was studied by threshold photoelectron photoion coincidence spectroscopy (TPEPICO). Time-of-flight distributions and breakdown curves were recorded in the photon energy range of 9.5-10.4 eV. The 0 K appearance energies of the fragment ions were extracted by modeling the experimental data with rigid activated complex (RAC-) RRKM theory. It was found that the data could be well-reproduced with a single TS for each dissociation channel if two different H-loss channels were assumed, one corresponding to a C-H and the other to a N-H bond dissociation. Once the appearance energies were established, heats of formation of the fragment ions could be derived. The heat of formation of the neutral molecule was computed by applying composite ab initio methods (G3, CBS-APNO, W1U) on a series of isodesmic reactions between methyl hydrazines and methyl amines.

  17. Energy Saving Glass Lamination via Selective Radio-Frequency Heating

    SciTech Connect

    Shulman, Holly S.; Allan, Shawn M.

    2009-11-11

    This Inventions and Innovations program supported the technical and commercial research and development needed to elevate Ceralink's energy saving process for flat glass lamination from bench scale to a self-supporting technology with significant potential for growth. Radio-frequency heating was any un-explored option for laminating glass prior to this program. With significant commercial success through time and energy savings in the wood, paper, and plastics industries, RF heating was found to have significant promise for the energy intensive glass lamination industry. A major technical goal of the program was to demonstrate RF lamination across a wide range of laminate sizes and materials. This was successfully accomplished, dispelling many skeptics' concerns about the abilities of the technology. Ceralink laminated panels up to 2 ft x 3 ft, with four sets processed simultaneously, in a 3 minute cycle. All major categories of interlayer materials were found to work with RF lamination. In addition to laminating glass, other materials including photovoltaic silicon solar cells, light emitting diodes, metallized glass, plastics (acrylic and polycarbonate), and ceramics (alumina) were found compatible with the RF process. This opens up a wide range of commercial opportunities beyond the initially targeted automotive industry. The dramatic energy savings reported for RF lamination at the bench scale were found to be maintained through the scale up of the process. Even at 2 ft x 3 ft panel sizes, energy savings are estimated to be at least 90% compared to autoclaving or vacuum lamination. With targeted promotion through conference presentations, press releases and internet presence, RF lamination has gained significant attention, drawing large audiences at American Ceramic Society meetings. The commercialization success of the project includes the establishment of a revenue-generating business model for providing process development and demonstrations for potential RF

  18. Selecting herbaceous energy crops for the southeast and midwest/lake states

    SciTech Connect

    Cushman, J.H.; Turhollow, A.F.

    1990-01-01

    This paper summarizes an approach to crop selection and development that has evolved through the five years of species screening and selection in the US Department of Energy's Herbaceous Energy Crops Program. The first phase of this program was designed to identify a number of species for development as energy crops for the Southeast and Midwest/Lake States, specifically as feedstocks for the biochemical and thermochemical conversion processes for alcohol fuels now under development. 14 refs., 1 tab.

  19. Energy Savings in School Buildings: A Selected Checklist.

    ERIC Educational Resources Information Center

    Wismer, Don, Comp.

    The 43 references in this booklet emphasize practical, rather than theoretical, information. They were chosen on that basis from two computer-retrievable data bases maintained by the U.S. Department of Energy. The citations, for the most part, are arranged by source and include industry pamphlets, journal articles, and state and consultant…

  20. Determinants of Household Use of Selected Energy Star Appliances

    EIA Publications

    2016-01-01

    The main objective of this paper is to test a series of hypotheses regarding the influences of household characteristics (such as education, age, sex, race, income, and size of household), building characteristics (such as age, ownership, and type), and electricity prices on the use of ENERGY STAR appliances.

  1. Analyses of Selected Provisions of Proposed Energy Legislation: 2003

    EIA Publications

    2003-01-01

    This study responds to a July 31, 2003 request from Senator Byron L. Dorgan. The study is based primarily on analyses the Energy Information Administration has previously done for studies requested by Congress. It includes analysis of the Renewable Portfolio Standard, Renewable Fuels Standard, production in the Alaskan National Wildlife Refuge, the construction of an Alaskan Natural Gas pipeline, and various tax provisions.

  2. Method for making an aluminum or copper substrate panel for selective absorption of solar energy

    NASA Technical Reports Server (NTRS)

    Roberts, M. L.; Sharpe, M. H.; Krupnick, A. C. (Inventor)

    1978-01-01

    A panel is described for selectively absorbing solar energy comprising an aluminum substrate. A zinc layer was covered by a layer of nickel and an outer layer of solar energy absorbing nickel oxide or a copper substrate with a nickel layer. A layer of solar energy absorbing nickel oxide distal from the copper substrate was included. A method for making these panels is disclosed.

  3. The Energy-Wise Homebuyer: A Guide to Selecting an Energy-Efficient Home.

    ERIC Educational Resources Information Center

    Hogarth, Peter T.; And Others

    Presented is a guide for purchasers of new or used homes who wish to make informed comparisons of energy costs. Included are 12 energy features to look for, detailed energy checklists, and charts for calculating energy expenses. Among the considerations discussed are heating systems, insulation, thermostats, caulking and weatherstripping, and…

  4. Selective chemical detection by energy modulation of sensors

    DOEpatents

    Stetter, J.R.; Otagawa, T.

    1985-05-20

    A portable instrument for use in the field in detecting, identifying, and quantifying a component of a sampled fluid includes a sensor which chemically reacts with the component of interest or a derivative thereof, an electrical heating filament for heating the sample before it is applied to the sensor, and modulating means for continuously varying the temperature of the filament (and hence the reaction rate) between two values sufficient to produce the chemical reaction. In response to this thermal modulation, the sensor produces a modulated output signal, the modulation of which is a function of the activation energy of the chemical reaction, which activation energy is specific to the particular component of interest and its concentration. Microprocessor means compares the modulated output signal with standard responses for a plurality of components to identify and quantify the particular component of interest. 4 figs.

  5. Apparatus for generating coherent infrared energy of selected wavelength

    DOEpatents

    Stevens, C.G.

    A tunable source of coherent infrared energy includes a heat pipe having an intermediate region at which cesium is heated to vaporizing temperature and end regions at which the vapor is condensed and returned to the intermediate region for reheating and recirculation. Optical pumping light is directed along the axis of the heat pipe through a first end window to stimulate emission of coherent infrared energy which is transmitted out through an opposite end window. A porous walled tubulation extends along the axis of the heat pipe and defines a region in which cesium vapor is further heated to a temperature sufficient to dissociate cesium dimers which would decrease efficiency by absorbing pump light. Efficient generation of any desired infrared wavelength is realized by varying the wavelength of the pump light.

  6. Apparatus for generating coherent infrared energy of selected wavelength

    DOEpatents

    Stevens, Charles G.

    1985-01-01

    A tunable source (11) of coherent infrared energy includes a heat pipe (12) having an intermediate region (24) at which cesium (22) is heated to vaporizing temperature and end regions (27, 28) at which the vapor is condensed and returned to the intermediate region (24) for reheating and recirculation. Optical pumping light (43) is directed along the axis of the heat pipe (12) through a first end window (17) to stimulate emission of coherent infrared energy which is transmitted out through an opposite end window (18). A porous walled tubulation (44) extends along the axis of the heat pipe (12) and defines a region (46) in which cesium vapor is further heated to a temperature sufficient to dissociate cesium dimers which would decrease efficiency by absorbing pump light (43). Efficient generation of any desired infrared wavelength is realized by varying the wavelength of the pump light (43).

  7. Selected Papers on Low-Energy Antiprotons and Possible Applications

    SciTech Connect

    Noble, Robert

    1998-09-19

    The only realistic means by which to create a facility at Fermilab to produce large amounts of low energy antiprotons is to use resources which already exist. There is simply too little money and manpower at this point in time to generate new accelerators on a time scale before the turn of the century. Therefore, innovation is required to modify existing equipment to provide the services required by experimenters.

  8. Selective chemical detection by energy modulation of sensors

    DOEpatents

    Stetter, J.R.; Otagawa, T.

    1991-09-10

    A portable instrument for use in the field in detecting, identifying, and quantifying a component of a sampled fluid includes a sensor which chemically reacts with the component of interest or a derivative thereof, an electrical heating filament for heating the sample before it is applied to the sensor, and modulator for continuously varying the temperature of the filament (and hence the reaction rate) between two values sufficient to produce the chemical reaction. In response to this thermal modulation, the sensor produces a modulated output signal, the modulation of which is a function of the activation energy of the chemical reaction, which activation energy is specific to the particular component of interest and its concentration. Microprocessor which compares the modulated output signal with standard responses for a plurality of components to identify and quantify the particular component of interest. In particular, the concentration of the component of interest is proportional to the amplitude of the modulated output signal, while the identifying activation output energy of the chemical interaction indicative of that component is proportional to a normalized parameter equal to the peak-to-peak amplitude divided by the height of the upper peaks above a base line signal level. 5 figures.

  9. Selective chemical detection by energy modulation of sensors

    DOEpatents

    Stetter, Joseph R.; Otagawa, Takaaki

    1991-01-01

    A portable instrument for use in the field in detecting, identifying, and quantifying a component of a sampled fluid includes a sensor which chemically reacts with the component of interest or a derivative thereof, an electrical heating filament for heating the sample before it is applied to the sensor, and modulator for continuously varying the temperature of the filament (and hence the reaction rate) between two values sufficient to produce the chemical reaction. In response to this thermal modulation, the sensor produces a modulated output signal, the modulation of which is a function of the activation energy of the chemical reaction, which activation energy is specific to the particular component of interest and its concentration. Microprocessor which compares the modulated output signal with standard responses for a plurality of components to identify and quantify the particular component of interest. In particular, the concentration of the component of interest is proportional to the amplitude of the modulated output signal, while the identifying activation output energy of the chemical interaction indicative of that component is proportional to a normalized parameter equal to the peak-to-peak amplitude divided by the height of the upper peaks above a base line signal level.

  10. Increasing the energy yield of mechanochemical transformations: selected case studies.

    PubMed

    Politov, Anatoly; Golyazimova, Olga

    2014-01-01

    The products of mechanical treatment are surface atoms or molecules, substances with a crystal structure different from their initial one (another polymorph, amorphous), point or linear defects, radicals and new chemical substances. It is often assumed, that to increase the yield of the products of a mechanical treatment, it is necessary to increase the treatment time and the mechanical power input. In view of the low energy yield of many mechanochemical transformations, this leads to high power consumption and contamination of the matter under treatment with the wear products of the material of a mill or reactor, in which the mechanical treatment is carried out. As a result, the technological attractiveness of mechanochemical processes is reduced, so that many mechanochemical transformations that have been discovered recently do not reach the stage of commercialization. In the present paper we describe different examples of increasing successfully the energy yield of mechanochemical processes, by a factor of several times to several orders of magnitude, for inorganic and organic substances. An increase in the energy yield of mechanochemical transformations opens new possibilities for their practical usage. In particular, the methods of preliminary treatment and the modes of conducting enzymatic processes that may find application in the production of second-generation biofuels are discussed using lignocellulose materials as examples.

  11. Tandem filters using frequency selective surfaces for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Dziendziel, Randolph J.; DePoy, David Moore; Baldasaro, Paul Francis

    2007-01-23

    This invention relates to the field of thermophotovoltaic (TPV) direct energy conversion. In particular, TPV systems use filters to minimize parasitic absorption of below bandgap energy. This invention constitutes a novel combination of front surface filters to increase TPV conversion efficiency by reflecting useless below bandgap energy while transmitting a very high percentage of the useful above bandgap energy. In particular, a frequency selective surface is used in combination with an interference filter. The frequency selective surface provides high transmission of above bandgap energy and high reflection of long wavelength below bandgap energy. The interference filter maintains high transmission of above bandgap energy and provides high reflection of short wavelength below bandgap energy and a sharp transition from high transmission to high reflection.

  12. Tandem filters using frequency selective surfaces for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Dziendziel, Randolph J.; Baldasaro, Paul F.; DePoy, David M.

    2010-09-07

    This invention relates to the field of thermophotovoltaic (TPV) direct energy conversion. In particular, TPV systems use filters to minimize parasitic absorption of below bandgap energy. This invention constitutes a novel combination of front surface filters to increase TPV conversion efficiency by reflecting useless below bandgap energy while transmitting a very high percentage of the useful above bandgap energy. In particular, a frequency selective surface is used in combination with an interference filter. The frequency selective surface provides high transmission of above bandgap energy and high reflection of long wavelength below bandgap energy. The interference filter maintains high transmission of above bandgap energy and provides high reflection of short wavelength below bandgap energy and a sharp transition from high transmission to high reflection.

  13. Population dynamics in epitaxial Er{sub 2}O{sub 3} thin films grown on Si(111)

    SciTech Connect

    Tawara, T.; Omi, H.; Hozumi, T.; Kaji, R.; Adachi, S.; Gotoh, H.; Sogawa, T.

    2013-06-17

    We grow single crystal erbium-oxide (Er{sub 2}O{sub 3}) epitaxially on a Si (111) substrate by using molecular beam epitaxy and investigate the population dynamics in Er{sup 3+} ions for the coherent manipulation of the population in Er{sub 2}O{sub 3}. Sharp and discrete Stark energy levels of the {sup 4}I{sub 13/2} manifold as small as 200 {mu}eV are observed with inhomogeneous broadening caused by the uniform crystal field of the epitaxial Er{sub 2}O{sub 3}. We also experimentally determine the time constant of the resonant population transfer between spatially distant Er{sup 3+}-ion sites, which is limited to the manipulation time of the population in the Er{sub 2}O{sub 3} crystals. Using selective excitation of the Stark level in the {sup 4}I{sub 13/2} manifold, we obtain the energy transfer times between spatially distant Er{sup 3+} ions, and they are about 2 {mu}s between sites whose crystallographic symmetry is different and 10 {mu}s between sites whose symmetry is the same.

  14. Multicriteria Decision Analysis of Material Selection of High Energy Performance Residential Building

    NASA Astrophysics Data System (ADS)

    Čuláková, Monika; Vilčeková, Silvia; Katunská, Jana; Krídlová Burdová, Eva

    2013-11-01

    In world with limited amount of energy sources and with serious environmental pollution, interest in comparing the environmental embodied impacts of buildings using different structure systems and alternative building materials will be increased. This paper shows the significance of life cycle energy and carbon perspective and the material selection in reducing energy consumption and emissions production in the built environment. The study evaluates embodied environmental impacts of nearly zero energy residential structures. The environmental assessment uses framework of LCA within boundary: cradle to gate. Designed alternative scenarios of material compositions are also assessed in terms of energy effectiveness through selected thermal-physical parameters. This study uses multi-criteria decision analysis for making clearer selection between alternative scenarios. The results of MCDA show that alternative E from materials on nature plant base (wood, straw bales, massive wood panel) present possible way to sustainable perspective of nearly zero energy houses in Slovak republic

  15. Selective excitation, relaxation, and energy channeling in molecular systems

    SciTech Connect

    Rhodes, W.C.

    1993-08-01

    Research involves theoretical studies of response, relaxation, and correlated motion in time-dependent behavior of large molecular systems ranging from polyatomic molecules to protein molecules in their natural environment. Underlying theme is subsystem modulation dynamics. Main idea is that quantum mechanical correlations between components of a system develop with time, playing a major role in determining the balance between coherent and dissipative forces. Central theme is interplay of coherence and dissipation in determining the nature of dynamic structuring and energy flow in molecular transformation mechanisms. Subsystem equations of motion are being developed to show how nonlinear, dissipative dynamics of a particular subsystem arise from correlated interactions with the rest of the system (substituent groups, solvent, lattice modes, etc.); one consequence is resonance structures and networks. Quantum dynamics and thermodynamics are being applied to understand control and energy transfer mechanisms in biological functions of protein molecules; these mechanisms are both global and local. Besides the above theory, the research deals with phenomenological aspects of molecular systems.

  16. DOE (Department of Energy) Epidemiologic Research Program: Selected bibliography

    SciTech Connect

    Not Available

    1991-01-01

    The objective of the Department of Energy (DOE) Epidemiologic Research Program is to determine the human health effects resulting from the generation and use of energy, and from the operation of DOE facilities. The program has been divided into seven general areas of activity: the Radiation Effects Research Foundation (RERF) which supports studies of survivors of the atomic weapons in Hiroshima and Nagasaki, mortality and morbidity studies of DOE workers, studies on internally deposited alpha emitters, medical/histologic studies, studies on the genetic aspects of radiation damage, community health surveillance studies, and the development of computational techniques and of databases to make the results as widely useful as possible. Excluding the extensive literature from the RERF, the program has produced 380 publications in scientific journals, contributing significantly to improving the understanding of the health effects of ionizing radiation exposure. In addition, a large number of public presentations were made and are documented elsewhere in published proceedings or in books. The purpose of this bibliograhpy is to present a guide to the research results obtained by scientists supported by the program. The bibliography, which includes doctoral theses, is classified by national laboratory and by year. Multi-authored studies are indicated only once, according to the main supporting laboratory.

  17. Epitaxial Silicon Doped With Antimony

    NASA Technical Reports Server (NTRS)

    Huffman, James E.; Halleck, Bradley L.

    1996-01-01

    High-purity epitaxial silicon doped with antimony made by chemical vapor deposition, using antimony pentachloride (SbCI5) as source of dopant and SiH4, SiCI2H2, or another conventional source of silicon. High purity achieved in layers of arbitrary thickness. Epitaxial silicon doped with antimony needed to fabricate impurity-band-conduction photodetectors operating at wavelengths from 2.5 to 40 micrometers.

  18. Catalog of selected heavy duty transport energy management models

    NASA Technical Reports Server (NTRS)

    Colello, R. G.; Boghani, A. B.; Gardella, N. C.; Gott, P. G.; Lee, W. D.; Pollak, E. C.; Teagan, W. P.; Thomas, R. G.; Snyder, C. M.; Wilson, R. P., Jr.

    1983-01-01

    A catalog of energy management models for heavy duty transport systems powered by diesel engines is presented. The catalog results from a literature survey, supplemented by telephone interviews and mailed questionnaires to discover the major computer models currently used in the transportation industry in the following categories: heavy duty transport systems, which consist of highway (vehicle simulation), marine (ship simulation), rail (locomotive simulation), and pipeline (pumping station simulation); and heavy duty diesel engines, which involve models that match the intake/exhaust system to the engine, fuel efficiency, emissions, combustion chamber shape, fuel injection system, heat transfer, intake/exhaust system, operating performance, and waste heat utilization devices, i.e., turbocharger, bottoming cycle.

  19. Energy-selective filtration of dental x-ray beams

    SciTech Connect

    Gelskey, D.E.; Baker, C.G.

    1981-11-01

    Samarium is known for its ability to filter simultaneously low- and high-energy x-ray photons from an x-ray beam that are not useful in producing a diagnostic radiograph. This study was undertaken to determine the optimum thickness of samarium required to minimize patient exposure and exposure time. The results indicate that use of a filter thickness of 0.16 mm. minimized patient radiation exposure and permitted the use of an exposure time sufficiently short to minimize motion unsharpness. The incorporation of a 0.16 mm. samarium filter in the x-ray beam reduced exposure by about 40 percent as compared to a 2.5 mm. aluminum filter; the exposure time must be increased approximately twice to obtain optical densities equivalent to those produced with aluminum filtration.

  20. A novel fast-neutron detector concept for energy-selective imaging and imaging spectroscopy

    SciTech Connect

    Cortesi, M.; Prasser, H.-M.; Dangendorf, V.; Zboray, R.

    2014-07-15

    We present and discuss the operational principle of a new fast-neutron detector concept suitable for either energy-selective imaging or for imaging spectroscopy. The detector is comprised of a series of energy-selective stacks of converter foils immersed in a noble-gas based mixture, coupled to a position-sensitive charge readout. Each foil in the various stacks is made of two layers of different thicknesses, fastened together: a hydrogen-rich (plastic) layer for neutron-to-proton conversion, and a hydrogen-free coating to selectively stop/absorb the recoil protons below a certain energy cut-off. The neutron-induced recoil protons, that escape the converter foils, release ionization electrons in the gas gaps between consecutive foils. The electrons are then drifted towards and localized by a position-sensitive charge amplification and readout stage. Comparison of the images detected by stacks with different energy cut-offs allows energy-selective imaging. Neutron energy spectrometry is realized by analyzing the responses of a sufficient large number of stacks of different energy response and unfolding techniques. In this paper, we present the results of computer simulation studies and discuss the expected performance of the new detector concept. Potential applications in various fields are also briefly discussed, in particularly, the application of energy-selective fast-neutron imaging for nuclear safeguards application, with the aim of determining the plutonium content in Mixed Oxide (MOX) fuels.

  1. A novel fast-neutron detector concept for energy-selective imaging and imaging spectroscopy.

    PubMed

    Cortesi, M; Dangendorf, V; Zboray, R; Prasser, H-M

    2014-07-01

    We present and discuss the operational principle of a new fast-neutron detector concept suitable for either energy-selective imaging or for imaging spectroscopy. The detector is comprised of a series of energy-selective stacks of converter foils immersed in a noble-gas based mixture, coupled to a position-sensitive charge readout. Each foil in the various stacks is made of two layers of different thicknesses, fastened together: a hydrogen-rich (plastic) layer for neutron-to-proton conversion, and a hydrogen-free coating to selectively stop/absorb the recoil protons below a certain energy cut-off. The neutron-induced recoil protons, that escape the converter foils, release ionization electrons in the gas gaps between consecutive foils. The electrons are then drifted towards and localized by a position-sensitive charge amplification and readout stage. Comparison of the images detected by stacks with different energy cut-offs allows energy-selective imaging. Neutron energy spectrometry is realized by analyzing the responses of a sufficient large number of stacks of different energy response and unfolding techniques. In this paper, we present the results of computer simulation studies and discuss the expected performance of the new detector concept. Potential applications in various fields are also briefly discussed, in particularly, the application of energy-selective fast-neutron imaging for nuclear safeguards application, with the aim of determining the plutonium content in Mixed Oxide (MOX) fuels.

  2. A novel fast-neutron detector concept for energy-selective imaging and imaging spectroscopy

    NASA Astrophysics Data System (ADS)

    Cortesi, M.; Dangendorf, V.; Zboray, R.; Prasser, H.-M.

    2014-07-01

    We present and discuss the operational principle of a new fast-neutron detector concept suitable for either energy-selective imaging or for imaging spectroscopy. The detector is comprised of a series of energy-selective stacks of converter foils immersed in a noble-gas based mixture, coupled to a position-sensitive charge readout. Each foil in the various stacks is made of two layers of different thicknesses, fastened together: a hydrogen-rich (plastic) layer for neutron-to-proton conversion, and a hydrogen-free coating to selectively stop/absorb the recoil protons below a certain energy cut-off. The neutron-induced recoil protons, that escape the converter foils, release ionization electrons in the gas gaps between consecutive foils. The electrons are then drifted towards and localized by a position-sensitive charge amplification and readout stage. Comparison of the images detected by stacks with different energy cut-offs allows energy-selective imaging. Neutron energy spectrometry is realized by analyzing the responses of a sufficient large number of stacks of different energy response and unfolding techniques. In this paper, we present the results of computer simulation studies and discuss the expected performance of the new detector concept. Potential applications in various fields are also briefly discussed, in particularly, the application of energy-selective fast-neutron imaging for nuclear safeguards application, with the aim of determining the plutonium content in Mixed Oxide (MOX) fuels.

  3. Seed layer technique for high quality epitaxial manganite films

    PubMed Central

    Graziosi, P.; Gambardella, A.; Calbucci, M.; O’Shea, K.; MacLaren, D. A.; Bergenti, I.; Homonnay, N.; Schmidt, G.; Pullini, D.; Busquets-Mataix, D.; Dediu, V.

    2016-01-01

    We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening temperature, strain profile and chemical states are derived. PMID:27648371

  4. Seed layer technique for high quality epitaxial manganite films.

    PubMed

    Graziosi, P; Gambardella, A; Calbucci, M; O'Shea, K; MacLaren, D A; Riminucci, A; Bergenti, I; Fugattini, S; Prezioso, M; Homonnay, N; Schmidt, G; Pullini, D; Busquets-Mataix, D; Dediu, V

    2016-08-01

    We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening temperature, strain profile and chemical states are derived.

  5. Seed layer technique for high quality epitaxial manganite films

    NASA Astrophysics Data System (ADS)

    Graziosi, P.; Gambardella, A.; Calbucci, M.; O'Shea, K.; MacLaren, D. A.; Riminucci, A.; Bergenti, I.; Fugattini, S.; Prezioso, M.; Homonnay, N.; Schmidt, G.; Pullini, D.; Busquets-Mataix, D.; Dediu, V.

    2016-08-01

    We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening temperature, strain profile and chemical states are derived.

  6. Methods of preparing flexible photovoltaic devices using epitaxial liftoff, and preserving the integrity of growth substrates used in epitaxial growth

    DOEpatents

    Forrest, Stephen R; Zimmerman, Jeramy; Lee, Kyusang; Shiu, Kuen-Ting

    2013-02-19

    There is disclosed methods of making photosensitive devices, such as flexible photovoltaic (PV) devices, through the use of epitaxial liftoff. Also described herein are methods of preparing flexible PV devices comprising a structure having a growth substrate, wherein the selective etching of protective layers yields a smooth growth substrate that us suitable for reuse.

  7. Methods of preparing flexible photovoltaic devices using epitaxial liftoff, and preserving the integrity of growth substrates used in epitaxial growth

    DOEpatents

    Forrest, Stephen R; Zimmerman, Jeramy; Lee, Kyusang; Shiu, Kuen-Ting

    2015-01-06

    There is disclosed methods of making photosensitive devices, such as flexible photovoltaic (PV) devices, through the use of epitaxial liftoff. Also described herein are methods of preparing flexible PV devices comprising a structure having a growth substrate, wherein the selective etching of protective layers yields a smooth growth substrate that us suitable for reuse.

  8. Thermodynamic and Kinetic Aspects of III/V Epitaxy

    DTIC Science & Technology

    1992-05-22

    a applications electroniques et optiques University of Utah Dept. of Materials Science & Engineering Salt Lake City, UT 84112 May 22, 1992... microscopic strain energy. The kinetic aspects of epitaxy are by far the most complex and, consequently, the least understood. We are beginning to understand

  9. Carbon-Water-Energy Relations for Selected River Basins

    NASA Technical Reports Server (NTRS)

    Choudhury, B. J.

    1998-01-01

    A biophysical process-based model was run using satellite, assimilated and ancillary data for four years (1987-1990) to calculate components of total evaporation (transpiration, interception, soil and snow evaporation), net radiation, absorbed photosynthetically active radiation and net primary productivity over the global land surface. Satellite observations provided fractional vegetation cover, solar and photosynthetically active radiation incident of the surface, surface albedo, fractional cloud cover, air temperature and vapor pressure. The friction velocity and surface air pressure are obtained from a four dimensional data assimilation results, while precipitation is either only surface observations or a blended product of surface and satellite observations. All surface and satellite data are monthly mean values; precipitation has been disaggregated into daily values. All biophysical parameters of the model are prescribed according to published records. From these global land surface calculations results for river basins are derived using digital templates of basin boundaries. Comparisons with field observations (micrometeorologic, catchment water balance, biomass production) and atmospheric water budget analysis for monthly evaporation from six river basins have been done to assess errors in the calculations. Comparisons are also made with previous estimates of zonal variations of evaporation and net primary productivity. Efficiencies of transpiration, total evaporation and radiation use, and evaporative fraction for selected river basins will be presented.

  10. Guided-wave approaches to spectrally selective energy absorption

    NASA Technical Reports Server (NTRS)

    Stegeman, G. I.; Burke, J. J.

    1987-01-01

    Results of experiments designed to demonstrate spectrally selective absorption in dielectric waveguides on semiconductor substrates are reported. These experiments were conducted with three waveguides formed by sputtering films of PSK2 glass onto silicon-oxide layers grown on silicon substrates. The three waveguide samples were studied at 633 and 532 nm. The samples differed only in the thickness of the silicon-oxide layer, specifically 256 nm, 506 nm, and 740 nm. Agreement between theoretical predictions and measurements of propagation constants (mode angles) of the six or seven modes supported by these samples was excellent. However, the loss measurements were inconclusive because of high scattering losses in the structures fabricated (in excess of 10 dB/cm). Theoretical calculations indicated that the power distribution among all the modes supported by these structures will reach its steady state value after a propagation length of only 1 mm. Accordingly, the measured loss rates were found to be almost independent of which mode was initially excited. The excellent agreement between theory and experiment leads to the conclusion that low loss waveguides confirm the predicted loss rates.

  11. Selective coatings for solar-to-thermal energy converters

    NASA Astrophysics Data System (ADS)

    Gukhman, G. A.; Koltun, M. M.

    1984-02-01

    A selective coating proposed for flat plate solar collectors consists of a thick Al2O3 layer with embedded metal particles and on it an infrared reflecting layer of electrically conducting vitreous ceramic material (PbO or In2O3). Both layers are deposited electromatically on collectors made of aluminum or an aluminum alloy. A double layer of 2 to 3 micron thick chromium on 9 to 10 micron thick nickel is effective in preventing oxidation on copper surfaces. Specimens of such coatings were tested in a laboratory humidity chamber and are now tested under the climatic conditions in the Crimea, 750,000 Wh/sq m of solar radiation at a mean-weekly intensity of 700 W/sq m having been accumulated in nine months. The ratio of heat absorbint to total surface area is or = 0.9 and emissivity is or = 0.2 were not degraded by holding in a furnace at 500 C for 50 h. The feasibility of producing multilayer coatings of this type was established on the basis of computer calculations for various combinations of collector material and protective interlayers.

  12. Selected computer system controls at the Energy Information Administration

    SciTech Connect

    Not Available

    1991-09-01

    The purpose of our review of the Energy Information Administration's (EIA) computer system was to evaluate disk and tape information storage and the adequacy of internal controls in the operating system programs. We used a set of computer-assisted audit techniques called CAATS, developed by the US Department of Transportation, Office of Inspector General, in performing the review at the EIA Forrestal Computer Facility. Improved procedures are needed to assure more efficient use of disk space. By transferring data sets from disk to tape, deleting invalid data, releasing unused reserve space and blocking data efficiently, disk space with an estimated value of $1.1 million a year could be recovered for current use. Also, procedures governing the maximum times for storage of information on tapes should be enforced to help ensure that data is not lost. In addition, improved internal controls are needed over granting users system-wide privileges and over authorized program library names to prevent unauthorized access to the system and possible destruction or manipulation of data. Automated Data Processing (ADP) Services Staff officials indicated that software maintenance was not current, due to contractual difficulties with the operating contractor for the Forrestal Facility. Our review confirmed that improvements were needed to help prevent malfunctions of the operating system, which could cause performance degradations, system failures, or loss of either system or user data. Management generally concurred with the recommendations in the report.

  13. Electric circuit model for strained-layer epitaxy

    NASA Astrophysics Data System (ADS)

    Kujofsa, Tedi; Ayers, John E.

    2016-11-01

    For the design and analysis of a strained-layer semiconductor device structure, the equilibrium strain profile may be determined numerically by energy minimization but this method is computationally intense and non-intuitive. Here we present an electric circuit model approach for the equilibrium analysis of an epitaxial stack, in which each sublayer may be represented by an analogous configuration involving a current source, a resistor, a voltage source, and an ideal diode. The resulting node voltages in the analogous electric circuit correspond to the equilibrium strains in the original epitaxial structure. This new approach enables analysis using widely accessible circuit simulators, and an intuitive understanding of electric circuits may be translated to the relaxation of strained-layer structures. In this paper, we describe the mathematical foundation of the electrical circuit model and demonstrate its application to epitaxial layers of Si1-x Ge x grown on a Si (001) substrate.

  14. High spin spectroscopy near the N=Z line: Channel selection and excitation energy systematics

    SciTech Connect

    Svensson, C.E.; Cameron, J.A.; Flibotte, S.

    1996-12-31

    The total {gamma}-ray and charged-particle energies emitted in fusion-evaporation reactions leading to N=Z compound systems in the A = 50-70 mass region have been measured with the 8{pi} {gamma}-ray spectrometer and the miniball charged-particle detector array. A new method of channel selection has been developed which combines particle identification with these total energy measurements and greatly improves upon the selectivity possible with particle detection alone. In addition, the event by event measurement of total {gamma}-ray energies using the BGO ball of the 8{pi} spectrometer has allowed a determination of excitation energies following particle evaporation for a large number of channels in several different reactions. The new channel selection procedure and excitation energy systematics are illustrated with data from the reaction of {sup 24}Mg on {sup 40}Ca at E{sub lab} = 80MeV.

  15. Observation of core-level binding energy shifts between (100) surface and bulk atoms of epitaxial CuInSe{sub 2}

    SciTech Connect

    Nelson, A.J.; Berry, G.; Rockett, A.

    1997-04-01

    Core-level and valence band photoemission from semiconductors has been shown to exhibit binding energy differences between surface atoms and bulk atoms, thus allowing one to unambiguously distinguish between the two atomic positions. Quite clearly, surface atoms experience a potential different from the bulk due to the lower coordination number - a characteristic feature of any surface is the incomplete atomic coordination. Theoretical accounts of this phenomena are well documented in the literature for III-V and II-VI semiconductors. However, surface state energies corresponding to the equilibrium geometry of (100) and (111) surfaces of Cu-based ternary chalcopyrite semiconductors have not been calculated or experimental determined. These compounds are generating great interest for optoelectronic and photovoltaic applications, and are an isoelectronic analog of the II-VI binary compound semiconductors. Surface core-level binding energy shifts depend on the surface cohesive energies, and surface cohesive energies are related to surface structure. For ternary compound semiconductor surfaces, such as CuInSe{sub 2}, one has the possibility of variations in surface stoichiometry. Applying standard thermodynamical calculations which consider the number of individual surface atoms and their respective chemical potentials should allow one to qualitatively determine the magnitude of surface core-level shifts and, consequently, surface state energies.

  16. Structure and magnetism of epitaxial rare-earth-transition-metal films

    SciTech Connect

    Fullerton, E.E.; Sowers, C.H.; Pearson, J.P.; Bader, S.D.

    1996-10-01

    Growth of epitaxial transition-metal superlattices; has proven essential in elucidating the role of crystal orientation and structure on magnetic properties such as giant magnetoresistance, interlayer coupling, and magnetic surface anisotropies. Extending these studies to the growth of epitaxial rare earth-transition metal (RE-TM) films and superlattices promises to play an equally important role in exploring and optimizing the properties of hard magnets. For instance, Skomski and Coey predict that a giant energy product (120 MG Oe) is possible in multilayer structures consisting of aligned hard-magnet layers exchanged coupled with soft-phase layers with high magnetization. Epitaxy provides one route to synthesizing such exchange-hardened magnets on controlled length scales. Epitaxial growth also allows the magnetic properties to be tailored by controlling the crystal orientation and the anisotropies of the magnetic layers and holds the possibility of stabilizing metastable phases. This paper describes the epitaxy and magnetic properties for several alloys.

  17. Energy Saving Glass Lamination via Selective Radio Frequency Heating

    SciTech Connect

    Allan, Shawn M; Baranova, Inessa; Poley, Joseph; Reis, Henrique

    2012-02-27

    This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates over the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North

  18. Energy Saving Glass Lamination via Selective Radio Frequency Heating

    SciTech Connect

    Allan, Shawn M.

    2012-02-27

    This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates over the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North

  19. Select Results from the Energy Assessor Experiment in the 2012 Commercial Buildings Energy Consumption Survey

    EIA Publications

    2015-01-01

    As part of an effort to make EIA’s energy consumption surveys as accurate and efficient as possible, EIA invited the National Research Council (NRC) to review the Commercial Buildings Energy Consumption Survey (CBECS) data-gathering process and make recommendations for improvements. The NRC suggested sending professional energy assessors to some sites and comparing the data obtained from the survey to the data collected by the assessors. Results from the energy assessment data collection have largely confirmed the quality of data gathered by CBECS interviewers.

  20. Energy Conservation: A Workshop for Selected Eastern U.S. Industrial Arts Teacher Educators.

    ERIC Educational Resources Information Center

    Wenig, Robert E., Ed.

    This set of 25 instructional modules was produced by a group of industrial arts teacher educators, local teachers, and supervisors from eastern United States. Topic areas of these modules include: societal implications of the energy situation; awareness of energy terms, supply, and use; assessment of conventional and selected renewable alternative…

  1. Energy Opinions of Southern, Northern and Academically Prepared Energy Students in Selected Secondary Schools.

    ERIC Educational Resources Information Center

    Karst, Ralph R.

    1985-01-01

    Examines the effects of sex, grade level, region, and academic preparation of secondary school students on energy opinions. Assesses the responses of students on energy items related to the government, cars, and conservation. Results reveal significant regional and sex differences. (ML)

  2. Quantification of correlational selection on thermal physiology, thermoregulatory behavior, and energy metabolism in lizards.

    PubMed

    Artacho, Paulina; Saravia, Julia; Ferrandière, Beatriz Decencière; Perret, Samuel; Le Galliard, Jean-François

    2015-09-01

    Phenotypic selection is widely accepted as the primary cause of adaptive evolution in natural populations, but selection on complex functional properties linking physiology, behavior, and morphology has been rarely quantified. In ectotherms, correlational selection on thermal physiology, thermoregulatory behavior, and energy metabolism is of special interest because of their potential coadaptation. We quantified phenotypic selection on thermal sensitivity of locomotor performance (sprint speed), thermal preferences, and resting metabolic rate in captive populations of an ectothermic vertebrate, the common lizard, Zootoca vivipara. No correlational selection between thermal sensitivity of performance, thermoregulatory behavior, and energy metabolism was found. A combination of high body mass and resting metabolic rate was positively correlated with survival and negatively correlated with fecundity. Thus, different mechanisms underlie selection on metabolism in lizards with small body mass than in lizards with high body mass. In addition, lizards that selected the near average preferred body temperature grew faster that their congeners. This is one of the few studies that quantifies significant correlational selection on a proxy of energy expenditure and stabilizing selection on thermoregulatory behavior.

  3. Quantification of correlational selection on thermal physiology, thermoregulatory behavior, and energy metabolism in lizards

    PubMed Central

    Artacho, Paulina; Saravia, Julia; Ferrandière, Beatriz Decencière; Perret, Samuel; Le Galliard, Jean-François

    2015-01-01

    Phenotypic selection is widely accepted as the primary cause of adaptive evolution in natural populations, but selection on complex functional properties linking physiology, behavior, and morphology has been rarely quantified. In ectotherms, correlational selection on thermal physiology, thermoregulatory behavior, and energy metabolism is of special interest because of their potential coadaptation. We quantified phenotypic selection on thermal sensitivity of locomotor performance (sprint speed), thermal preferences, and resting metabolic rate in captive populations of an ectothermic vertebrate, the common lizard, Zootoca vivipara. No correlational selection between thermal sensitivity of performance, thermoregulatory behavior, and energy metabolism was found. A combination of high body mass and resting metabolic rate was positively correlated with survival and negatively correlated with fecundity. Thus, different mechanisms underlie selection on metabolism in lizards with small body mass than in lizards with high body mass. In addition, lizards that selected the near average preferred body temperature grew faster that their congeners. This is one of the few studies that quantifies significant correlational selection on a proxy of energy expenditure and stabilizing selection on thermoregulatory behavior. PMID:26380689

  4. Selected bibliography: cost and energy savings of conservation and renewable energy technologies

    SciTech Connect

    1980-05-01

    This bibliography is a compilation of reports on the cost and energy savings of conservation and renewable energy applications throughout the United States. It is part of an overall effort to inform utilities of technological developments in conservation and renewable energy technologies and so aid utilities in their planning process to determine the most effective and economic combination of capital investments to meet customer needs. Department of Energy assessments of the applications, current costs and cost goals for the various technologies included in this bibliography are presented. These assessments are based on analyses performed by or for the respective DOE Program Offices. The results are sensitive to a number of variables and assumptions; however, the estimates presented are considered representative. These assessments are presented, followed by some conclusions regarding the potential role of the conservation and renewable energy alternative. The approach used to classify the bibliographic citations and abstracts is outlined.

  5. Submonolayer epitaxy with impurities

    NASA Astrophysics Data System (ADS)

    Kotrla, Miroslav; Krug, Joachim; Smilauer, Pavel

    2000-03-01

    The effect of impurities on epitaxial growth in the submonolayer regime is studied using kinetic Monte Carlo simulations of a two-species solid-on-solid growth model. Both species are mobile, and attractive interactions among adatoms and between adatoms and impurities are incorporated. Impurities can be codeposited with the growing material or predeposited prior to growth. The activated exchange of impurities and adatoms is identified as the key kinetic process in the formation a growth morphology in which the impurities decorate the island edges. The dependence of the island density N on flux F and coverage θ is studied in detail. The impurities strongly increase the island density without appreciably changing the exponent \\chi in the power law relation N ~ F^\\chi, apart from a saturation of the flux dependence at large F and small θ. Within the present model, even completely decorated island edges do not provide efficient barriers to the attachment of adatoms, and therefore the mechanism for the increase of \\chi proposed by D. Kandel [Phys. Rev. Lett. 78, 499 (1997)] is not operative. A simple analytic theory taking into account only the dependence of the adatom diffusion constant on impurity coverage is shown to provide semi-quantitative agreement with many features observed in the simulations.

  6. Aluminium or copper substrate panel for selective absorption of solar energy

    NASA Technical Reports Server (NTRS)

    Roberts, M. L.; Sharpe, M. H.; Krupnick, A. C. (Inventor)

    1979-01-01

    A method for making panels which selectively absorb solar energy is disclosed. The panels are comprised of an aluminum substrate, a layer of zinc thereon, a layer of nickel over the zinc layer and an outer layer of solar energy absorbing nickel oxide or a copper substrate with a layer of nickel thereon and a layer of solar energy absorbing nickel oxide distal from the copper substrate.

  7. Epitaxial integration of nanowires in microsystems by local micrometer-scale vapor-phase epitaxy.

    PubMed

    Mølhave, Kristian; Wacaser, Brent A; Petersen, Dirch Hjorth; Wagner, Jakob B; Samuelson, Lars; Bøggild, Peter

    2008-10-01

    Free-standing epitaxially grown nanowires provide a controlled growth system and an optimal interface to the underlying substrate for advanced optical, electrical, and mechanical nanowire device connections. Nanowires can be grown by vapor-phase epitaxy (VPE) methods such as chemical vapor deposition (CVD) or metal organic VPE (MOVPE). However, VPE of semiconducting nanowires is not compatible with several microfabrication processes due to the high synthesis temperatures and issues such as cross-contamination interfering with the intended microsystem or the VPE process. By selectively heating a small microfabricated heater, growth of nanowires can be achieved locally without heating the entire microsystem, thereby reducing the compatibility problems. The first demonstration of epitaxial growth of silicon nanowires by this method is presented and shows that the microsystem can be used for rapid optimization of VPE conditions. The important issue of the cross-contamination of other parts of the microsystem caused by the local growth of nanowires is also investigated by growth of GaN near previously grown silicon nanowires. The design of the cantilever heaters makes it possible to study the grown nanowires with a transmission electron microscope without sample preparation.

  8. Method of epitaxially depositing cadmium sulfide

    NASA Technical Reports Server (NTRS)

    Hawrylo, Frank Z. (Inventor)

    1980-01-01

    A single crystal layer of either cadmium sulfide or an alloy of cadmium sulfide and indium phosphide is epitaxially deposited on a substrate of cadmium sulfide by liquid phase epitaxy using indium as the solvent.

  9. Dual-energy X-ray photon counting using an LSO-MPPC spectrometer and an energy-selecting device

    NASA Astrophysics Data System (ADS)

    Sato, Eiichi; Oda, Yasuyuki; Yamaguchi, Satoshi; Hagiwara, Osahiko; Matsukiyo, Hiroshi; Watanabe, Manabu; Kusachi, Shinya

    2015-08-01

    Dual-energy photon counting was performed using an energy-selecting device (ESD) and a detector, consisting of a Lu2(SiO4)O [LSO)] crystal and a multipixel photon counter (MPPC). The ESD is used to determine a low-energychannel range for CT and consists of two comparators and a microcomputer (MC). The two threshold channels in proportion to energies are determined using low and high-energy comparators, respectively. The MC in the ESD produces a single logical pulse when only a logical pulse from the low-energy comparator is input to the MC. To determine the high-energy-channel range for CT, logical pulses from the high-energy comparator are input to the MC outside the ESD. Logical pulses from the two MCs are input to frequency-voltage converters (FVCs) to convert count rates into voltages. The output voltages from the two FVCs are sent to a personal computer through an analog-digital converter to reconstruct tomograms. Dual-energy computed tomography was accomplished at a tube voltage of 70 kV and a maximum count rate of 14.3 kilocounts per second, and two-different-energy tomograms were obtained simultaneously.

  10. Epitaxial technology for low cost solar cells

    NASA Technical Reports Server (NTRS)

    Kressel, H.; Raccah, P. M.

    1975-01-01

    Epitaxial solar cell structures on low cost silicon substrates are compared to direct diffusion substrates. Dislocation density in the epitaxial layers is found to be significantly lower than that of the substrate material. The saturation current density of diodes epitaxially formed on the substrate is commonly 2 to 3 orders of magnitude lower than for diodes formed by direct diffusion. Solar cells made epitaxially are substantially better than those made by direct diffusion into similar material.

  11. Fluorination of epitaxial oxides: Creating ferrite and nickelate oxyfluoride films

    NASA Astrophysics Data System (ADS)

    May, Steven; Moon, Eun; Xie, Yujun; Keavney, David; Goebel, Justin; Laird, Eric; Li, Christopher

    2013-03-01

    In ABO3 perovskites, the physical properties are directly coupled to the nominal valence state of the B-site cation. In epitaxial thin films, the dominant strategy to control B-site valence is through the selection of a di- or trivalent cation on the A-site. However, this approach is limited, particularly when electron doping on the B-site is desired. Here we report a simple method for realizing oxyfluoride films, where the substitution of F for O is expected to reduce the B-site valence, providing a new means to tune electronic, optical and magnetic properties in thin films. Fluorination is achieved by spin coating an oxygen deficient film with poly(vinylidene fluoride). The film/polymer bilayer is then annealed, promoting the diffusion of F into the film. We have used this method to synthesize SrFeO3-δFδ and LaNiO3-δFδ (δ ? 0.5) films, as confirmed by x-ray photoemission spectroscopy and x-ray absorption spectroscopy. This work is supported by the U. S. Army Research Office under grant number W911NF-12-1-0132. Work at the Advanced Photon Source is supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences under contract DE-AC02-06CH11357.

  12. Molecular beam epitaxial growth of tin oxide semiconductors

    NASA Astrophysics Data System (ADS)

    Medina, Gabriel A.

    In an effort to develop a method to utilize SnO in transparent electronic and optoelectronic applications, the molecular beam epitaxy method was used to grow a thin film SnO sample. Five samples were grown and studied using various conventional techniques. X-ray diffraction and Raman spectroscopy was used to identify the composition of the samples. The quality and thickness of the samples was studied using Scanning Electron Microscopy. This data was used to determine which samples were successful growths of SnO and how the growth conditions of each may have affected the outcomes. From the compiled data, single phase SnO was identified and selected for further study of it electrical properties. Previous studies have not been able to accurately identify the band gap energy of SnO due to its instability as an oxide. A bandgap energy of 2.56 eV was determined by photoluminescence analysis. This is consistent with reported estimates of between 2.5 to 3 eV for SnO.

  13. Gradient bounds for a thin film epitaxy equation

    NASA Astrophysics Data System (ADS)

    Li, Dong; Qiao, Zhonghua; Tang, Tao

    2017-02-01

    We consider a gradient flow modeling the epitaxial growth of thin films with slope selection. The surface height profile satisfies a nonlinear diffusion equation with biharmonic dissipation. We establish optimal local and global wellposedness for initial data with critical regularity. To understand the mechanism of slope selection and the dependence on the dissipation coefficient, we exhibit several lower and upper bounds for the gradient of the solution in physical dimensions d ≤ 3.

  14. Thermoreversible, epitaxial fcc<-->bcc transitions in block copolymer solutions.

    PubMed

    Bang, Joona; Lodge, Timothy P; Wang, Xiaohui; Brinker, Kristin L; Burghardt, Wesley R

    2002-11-18

    Uncharged block copolymer micelles display thermoreversible transitions between close-packed and bcc lattices for a range of concentration, solvent selectivity, and copolymer composition. Using small-angle x-ray scattering on shear-oriented solutions, highly aligned fcc crystals are seen to transform epitaxially to bcc crystals, with fcc/bcc orientational relationships that are well established in martensitic transformations in metals. The transition is driven by decreasing solvent selectivity with increasing temperature, inducing solvent penetration of the micellar core.

  15. Epitaxial stabilization and phase instability of VO2 polymorphs

    SciTech Connect

    Lee, Shinbuhm; Ivanov, Ilia N.; Keum, Jong K.; Lee, Ho Nyung

    2016-01-20

    The VO2 polymorphs, i.e., VO2(A), VO2(B), VO2(M1) and VO2(R), have a wide spectrum of functionalities useful for many potential applications in information and energy technologies. However, synthesis of phase pure materials, especially in thin film forms, has been a challenging task due to the fact that the VO2 polymorphs are closely related to each other in a thermodynamic framework. Here, we report epitaxial stabilization of the VO2 polymorphs to synthesize high quality single crystalline thin films and study the phase stability of these metastable materials. We selectively deposit all the phases on various perovskite substrates with different crystallographic orientations. By investigating the phase instability, phonon modes and transport behaviours, not only do we find distinctively contrasting physical properties of the VO2 polymorphs, but that the polymorphs can be on the verge of phase transitions when heated as low as ~400 °C. In conclusion, our successful epitaxy of both VO2(A) and VO2(B) phases, which are rarely studied due to the lack of phase pure materials, will open the door to the fundamental studies of VO2 polymorphs for potential applications in advanced electronic and energy devices.

  16. Epitaxial growth of large-gap quantum spin Hall insulator on semiconductor surface

    PubMed Central

    Zhou, Miao; Ming, Wenmei; Liu, Zheng; Wang, Zhengfei; Li, Ping; Liu, Feng

    2014-01-01

    Formation of topological quantum phase on a conventional semiconductor surface is of both scientific and technological interest. Here, we demonstrate epitaxial growth of 2D topological insulator, i.e., quantum spin Hall state, on Si(111) surface with a large energy gap, based on first-principles calculations. We show that the Si(111) surface functionalized with one-third monolayer of halogen atoms [Si(111)-3×3-X (X = Cl, Br, I)] exhibiting a trigonal superstructure provides an ideal template for epitaxial growth of heavy metals, such as Bi, which self-assemble into a hexagonal lattice with high kinetic and thermodynamic stability. Most remarkably, the Bi overlayer is atomically bonded to but electronically decoupled from the underlying Si substrate, exhibiting isolated quantum spin Hall state with an energy gap as large as ∼0.8 eV. This surprising phenomenon originates from an intriguing substrate-orbital-filtering effect, which critically selects the orbital composition around the Fermi level, leading to different topological phases. In particular, the substrate-orbital-filtering effect converts the otherwise topologically trivial freestanding Bi lattice into a nontrivial phase; and the reverse is true for Au lattice. The underlying physical mechanism is generally applicable, opening a new and exciting avenue for exploration of large-gap topological surface/interface states. PMID:25246584

  17. Current and future industrial energy service characterizations. Volume III. Energy data on 15 selected states' manufacturing subsector

    SciTech Connect

    Krawiec, F.; Thomas, T.; Jackson, F.; Limaye, D.R.; Isser, S.; Karnofsky, K.; Davis, T.D.

    1980-11-01

    An examination is made of the current and future energy demands, and uses, and cost to characterize typical applications and resulting services in the US and industrial sectors of 15 selected states. Volume III presents tables containing data on selected states' manufacturing subsector energy consumption, functional uses, and cost in 1974 and 1976. Alabama, California, Illinois, Indiana, Louisiana, Michigan, Missouri, New Jersey, New York, Ohio, Oregon, Pennsylvania, Texas, West Virginia, and Wisconsin were chosen as having the greatest potential for replacing conventional fuel with solar energy. Basic data on the quantities, cost, and types of fuel and electric energy purchased by industr for heat and power were obtained from the 1974 and 1976 Annual Survey of Manufacturers. The specific indutrial energy servic cracteristics developed for each selected state include. 1974 and 1976 manufacturing subsector fuels and electricity consumption by 2-, 3-, and 4-digit SIC and primary fuel (quantity and relative share); 1974 and 1976 manufacturing subsector fuel consumption by 2-, 3-, and 4-digit SIC and primary fuel (quantity and relative share); 1974 and 1976 manufacturing subsector average cost of purchsed fuels and electricity per million Btu by 2-, 3-, and 4-digit SIC and primary fuel (in 1976 dollars); 1974 and 1976 manufacturing subsector fuels and electric energy intensity by 2-, 3-, and 4-digit SIC and primary fuel (in 1976 dollars); manufacturing subsector average annual growth rates of (1) fuels and electricity consumption, (2) fuels and electric energy intensity, and (3) average cost of purchased fuels and electricity (1974 to 1976). Data are compiled on purchased fuels, distillate fuel oil, residual ful oil, coal, coal, and breeze, and natural gas. (MCW)

  18. Growth of EuO/Si and EuO/SrO/Si heteroepitaxial structures by molecular-beam epitaxy

    SciTech Connect

    Teterin, P. E. Averyanov, D. V.; Sadofyev, Yu. G. Parfenov, O. E.; Likhachev, I. A.; Storchak, V. G.

    2015-01-15

    Epitaxial EuO thin films with thickness up to 60 nm have been grown by molecular beam epitaxy both on SrO sublayers and directly on Si (001) substrates. Crystal structure has been controlled in situ by reflection high energy electron diffraction. Ex situ studies by X-ray diffraction and Rutherford backscattering have confirmed high crystalline quality of the films.

  19. Tuning the terahertz low-energy charge dynamics by simultaneous effect of epitaxial and anisotropic strain in PrNi O3 thin films

    NASA Astrophysics Data System (ADS)

    Phanindra, V. Eswara; Das, Sarmistha; Kumar, K. Santhosh; Agarwal, Piyush; Rana, Rakesh; Rana, D. S.

    2017-02-01

    The interplay of charge, spin, and lattice correlations strongly influence the insulator-metal (I-M) transition and magnetic ordering in rare earth nickelates. In this context, we explored the low-energy charge dynamics in structurally modulated PrNi O3 (PNO) thin films to unravel the complexity of ground state across I-M transition using terahertz (THz) spectroscopy. The THz optical constants of compressive film on LaAl O3 (100) substrate and the tensile films on NdGa O3 (100), (001), (110), and (111) substrates with varying orthorhombic distortion exhibit remarkably distinct features as a function of frequency and temperature. The THz conductivity of compressive film sans any I-M transition follows the Drude model. In contrast, the tensile strained films exhibit non-Drude THz conductivity, a giant positive dielectric permittivity, and negative imaginary conductivity, all of which can be explained by the Drude-Smith model. This rich variety of low-energy dynamics manifests as a function of temperature, strain, and crystal orientation. Such distinct THz spectral features, as induced by a subtle variation in strain while crossing over from tensile to compressive strain and with varying degree of orthorhombicity coupled with oxygen vacancies, reveal a novel facet of structure-property relationship of PNO.

  20. Line-on-Line Coincidence: A New Type of Epitaxy Found in Organic-Organic Heterolayers

    NASA Astrophysics Data System (ADS)

    Mannsfeld, Stefan C.; Leo, Karl; Fritz, Torsten

    2005-02-01

    We propose a new type of epitaxy, line-on-line coincidence (LOL), which explains the ordering in the organic-organic heterolayer system PTCDA on HBC on graphite. LOL epitaxy is similar to point-on-line coincidence (POL) in the sense that all overlayer molecules lie on parallel, equally spaced lines. The key difference to POL is that these lines are not restricted to primitive lattice lines of the substrate lattice. Potential energy calculations demonstrate that this new type of epitaxy is indeed characterized by a minimum in the overlayer-substrate interaction potential.

  1. Final report on implementation of energy conservation practices training in selected public housing developments

    SciTech Connect

    Not Available

    1991-10-01

    This report on the implementation of energy conservation practices training in selected public housing developments represents an initiative of the Research and Education Division, Office of Minority Economic Impact, US Department of Energy. The Office of Minority Economic Impact (MI) was created by Congress in 1979, within the US Department of Energy, to afford the Secretary advice on the effect policies, regulations and other actions of DOE respecting minority participation in energy programs. The Director of MI is responsible for the conduct of ongoing research into the effects, including socio-economic and environmental, of national energy programs, policies, and regulations of the Department of minorities. Public housing in the United States is dominated by minorities, public housing is a large consumer of residential energy. Consequently, this project is a logical merging of these two factors and an attempt to somehow influence energy savings through improving public housing residents` energy-consumption practices. This final report attempts to capture the results of this current demonstration, and incorporate the historical basis for today`s results by renewing the efforts that preceded the implementation of energy conservation practices training in selected public housing developments.

  2. Final report on implementation of energy conservation practices training in selected public housing developments

    SciTech Connect

    Not Available

    1991-10-01

    This report on the implementation of energy conservation practices training in selected public housing developments represents an initiative of the Research and Education Division, Office of Minority Economic Impact, US Department of Energy. The Office of Minority Economic Impact (MI) was created by Congress in 1979, within the US Department of Energy, to afford the Secretary advice on the effect policies, regulations and other actions of DOE respecting minority participation in energy programs. The Director of MI is responsible for the conduct of ongoing research into the effects, including socio-economic and environmental, of national energy programs, policies, and regulations of the Department of minorities. Public housing in the United States is dominated by minorities, public housing is a large consumer of residential energy. Consequently, this project is a logical merging of these two factors and an attempt to somehow influence energy savings through improving public housing residents' energy-consumption practices. This final report attempts to capture the results of this current demonstration, and incorporate the historical basis for today's results by renewing the efforts that preceded the implementation of energy conservation practices training in selected public housing developments.

  3. Temperature dependence of the energy gap of zinc-blende CdSe and Cd1 - xZnxSe epitaxial layers

    NASA Astrophysics Data System (ADS)

    Lunz, U.; Kuhn, J.; Goschenhofer, F.; Schüssler, U.; Einfeldt, S.; Becker, C. R.; Landwehr, G.

    1996-12-01

    The temperature dependence of the energy gap of zinc-blende CdSe and Cd1-xZnxSe has been determined over the entire range of composition from optical transmission and reflection measurements at temperatures between 5 and 300 K. The experimental results can be expressed by the following modified empirical Varshni formula, whose parameters are functions of the composition x: Eg(x,T)=Eg(x,0)-β(x)T2/[T+γ(x)]. Eg(x,0) exhibits a nonlinear dependence on composition, according to Eg=Eg(0,0)(1-x)+Eg(1,0)x-ax(1-x). The parameters β(x) and γ(x) can be expressed by β(x)=β(0)(1-x)+β(1)x+bx(1-x) and γ(x)=γ(0)(1-x)+γ(1)x.

  4. Asymmetric shape transitions of epitaxial quantum dots

    NASA Astrophysics Data System (ADS)

    Wei, Chaozhen; Spencer, Brian J.

    2016-06-01

    We construct a two-dimensional continuum model to describe the energetics of shape transitions in fully faceted epitaxial quantum dots (strained islands) via minimization of elastic energy and surface energy at fixed volume. The elastic energy of the island is based on a third-order approximation, enabling us to consider shape transitions between pyramids, domes, multifaceted domes and asymmetric intermediate states. The energetics of the shape transitions are determined by numerically calculating the facet lengths that minimize the energy of a given island type of prescribed island volume. By comparing the energy of different island types with the same volume and analysing the energy surface as a function of the island shape parameters, we determine the bifurcation diagram of equilibrium solutions and their stability, as well as the lowest barrier transition pathway for the island shape as a function of increasing volume. The main result is that the shape transition from pyramid to dome to multifaceted dome occurs through sequential nucleation of facets and involves asymmetric metastable transition shapes. We also explicitly determine the effect of corner energy (facet edge energy) on shape transitions and interpret the results in terms of the relative stability of asymmetric island shapes as observed in experiment.

  5. Expected Satiety: Application to Weight Management and Understanding Energy Selection in Humans.

    PubMed

    Forde, Ciarán G; Almiron-Roig, Eva; Brunstrom, Jeffrey M

    2015-03-01

    Recent advances in the approaches used to quantify expectations of satiation and satiety have led to a better understanding of how humans select and consume food, and the associated links to energy intake regulation. When compared calorie for calorie some foods are expected to deliver several times more satiety than others, and multiple studies have demonstrated that people are able to discriminate between similar foods reliably and with considerable sensitivity. These findings have implications for the control of meal size and the design of foods that can be used to lower the energy density of diets. These methods and findings are discussed in terms of their implications for weight management. The current paper also highlights why expected satiety may also play an important role beyond energy selection, in moderating appetite sensations after a meal has been consumed, through memory for recent eating and the selection of foods across future meals.

  6. Expected Satiety: Application to Weight Management and Understanding Energy Selection in Humans

    PubMed Central

    Forde, Ciarán G.; Almiron-Roig, Eva; Brunstrom, Jeffrey M.

    2016-01-01

    Recent advances in the approaches used to quantify expectations of satiation and satiety have led to a better understanding of how humans select and consume food, and the associated links to energy intake regulation. When compared calorie for calorie some foods are expected to deliver several times more satiety than others, and multiple studies have demonstrated that people are able to discriminate between similar foods reliably and with considerable sensitivity. These findings have implications for the control of meal size and the design of foods that can be used to lower the energy density of diets. These methods and findings are discussed in terms of their implications for weight management. The current paper also highlights why expected satiety may also play an important role beyond energy selection, in moderating appetite sensations after a meal has been consumed, through memory for recent eating and the selection of foods across future meals. PMID:26627096

  7. Epitaxy on Substrates with Hexagonal Lattice Symmetry.

    NASA Astrophysics Data System (ADS)

    Braun, Max Willi Hermann

    A general description of epitaxy between thin films and substrates of general symmetry was developed from a model with rigid substrate and overgrowth and extended to include strain of the overgrowth. The overgrowth-substrate interaction was described by Fourier series, usually truncated, defined on the reciprocal lattice of the interface surfaces of the crystals. Energy considerations lead directly to a criterion that epitaxial configurations occur when a pair of surface reciprocal lattice vectors of the substrate and overgrowth coincide, equivalent to atomic row matching. This is analogous to the von Laue criterion and Bragg equations of diffraction theory, with a geometrical realization related to the Ewald construction. When generalized, misfit strain, the spacing, line sense and Burgers vectors of misfit dislocations and misfit verniers are obtained from the reciprocal lattices of crystals with any symmetry and misfit. The most general structures can be described with convenient unit cells by using structure factors. Homogeneous misfit strain, the interfacial atom positions after local relaxation and misfit and elastic (harmonic approximation) strain energies were obtained by direct minimization of the total interfacial energy of a large (1105 atoms), but finite, system. The local relaxation was calculated with a Finite Element formulation. Systems with fcc {111 } or bcc{ 110} overgrowths on fcc {111} or hcp{0001} substrates were studied with respect to substrate symmetry, overgrowth size and anisotropy of the overgrowth elastic constants. Configurations such as Kurdjumov-Sachs (KS), Nishiyama-Wassermann (NW) and a pseudomorphic phase (2DC) were explained, while several other higher order configurations were predicted. The inherent difference in nature between the KS and NW and their relationship to the 2DC were emphasized. Deviations from the ideal orientation of KS linked to anisotropy for systems undergoing misfit strain were discovered. Deviations were also

  8. Linking habitat selection to fitness-related traits in herbivores: the role of the energy landscape.

    PubMed

    Long, Ryan A; Bowyer, R T; Porter, Warren P; Mathewson, Paul; Monteith, Kevin L; Findholt, Scott L; Dick, Brian L; Kie, John G

    2016-07-01

    Animals may partially overcome environmental constraints on fitness by behaviorally adjusting their exposure to costs and supplies of energy. Few studies, however, have linked spatiotemporal variation in the energy landscape to behaviorally mediated measures of performance that ostensibly influence individual fitness. We hypothesized that strength of selection by North American elk (Cervus elaphus) for areas that reduced costs of thermoregulation and activity, and increased access to high-quality forage, would influence four energetically mediated traits related to fitness: birth mass of young, nutritional condition of adult females at the onset of winter, change in nutritional condition of females between spring and winter, and neonatal survival. We used a biophysical model to map spatiotemporally explicit costs of thermoregulation and activity experienced by elk in a heterogeneous landscape. We then combined model predictions with data on forage characteristics, animal locations, nutritional condition, and mass and survival of young to evaluate behaviorally mediated effects of the energy landscape on fitness-related traits. During spring, when high-quality forage was abundant, female elk that consistently selected low-cost areas before parturition gave birth to larger young than less-selective individuals, and birth mass had a strong, positive influence on probability of survival. As forage quality declined during autumn, however, lactating females that consistently selected the highest quality forage available accrued more fat and entered winter in better condition than less-selective individuals. Results of our study highlight the importance of understanding the dynamic nature of energy landscapes experienced by free-ranging animals.

  9. Transport and energy selection of laser generated protons for postacceleration with a compact linac

    NASA Astrophysics Data System (ADS)

    Sinigardi, Stefano; Turchetti, Giorgio; Londrillo, Pasquale; Rossi, Francesco; Giove, Dario; De Martinis, Carlo; Sumini, Marco

    2013-03-01

    Laser accelerated proton beams have a considerable potential for various applications including oncological therapy. However, the most consolidated target normal sheath acceleration regime based on irradiation of solid targets provides an exponential energy spectrum with a significant divergence. The low count number at the cutoff energy seriously limits at present its possible use. One realistic scenario for the near future is offered by hybrid schemes. The use of transport lines for collimation and energy selection has been considered. We present here a scheme based on a high field pulsed solenoid and collimators which allows one to select a beam suitable for injection at 30 MeV into a compact linac in order to double its energy while preserving a significant intensity. The results are based on a fully 3D simulation starting from laser acceleration.

  10. Free energy calculation provides insight into the action mechanism of selective PARP-1 inhibitor.

    PubMed

    Cao, Ran

    2016-04-01

    Selective poly (ADP-ribose) polymerase (PARP)-1 inhibitor represents promising therapy against cancers with a good balance between efficacy and safety. Owing to the conserved structure between PARP-1 and PARP-2, most of the clinical and experimental drugs show equivalent inhibition against both targets. Most recently, it's disclosed a highly selective PARP-1 inhibitor (NMS-P118) with promising pharmacokinetic properties. Herein, we combined molecular simulation with free energy calculation to gain insights into the selective mechanism of NMS-P118. Our results suggest the reduction of binding affinity for PARP-2 is attributed to the unfavorable conformational change of protein, which is accompanied by a significant energy penalty. Alanine-scanning mutagenesis study further reveals the important role for a tyrosine residue of donor loop (Tyr889(PARP-1) and Tyr455(PARP-2)) in contributing to the ligand selectivity. Retrospective structural analysis indicates the ligand-induced movement of Tyr455(PARP-2) disrupts the intra-molecule hydrogen bonding network, which partially accounts for the "high-energy" protein conformation in the presence of NMS-P118. Interestingly, such effect isn't observed in other non-selective PARP inhibitors including BMN673 and A861695, which validates the computational prediction. Our work provides energetic insight into the subtle variations in the crystal structures and could facilitate rational design of new selective PARP inhibitor.

  11. Merriam's kangaroo rats (Dipodomys merriami) voluntarily select temperatures that conserve energy rather than water.

    PubMed

    Banta, Marilyn R

    2003-01-01

    Desert endotherms such as Merriam's kangaroo rat (Dipodomys merriami) use both behavioral and physiological means to conserve energy and water. The energy and water needs of kangaroo rats are affected by their thermal environment. Animals that choose temperatures within their thermoneutral zone (TNZ) minimize energy expenditure but may impair water balance because the ratio of water loss to water gain is high. At temperatures below the TNZ, water balance may be improved because animals generate more oxidative water and reduce evaporative water loss; however, they must also increase energy expenditure to maintain a normal body temperature. Hence, it is not possible for kangaroo rats to choose thermal environments that simultaneously minimize energy expenditure and increase water conservation. I used a thermal gradient to test whether water stress, energy stress, simultaneous water and energy stress, or no water/energy stress affected the thermal environment selected by D. merriami. During the night (i.e., active phase), animals in all four treatments chose temperatures near the bottom of their TNZ. During the day (i.e., inactive phase), animals in all four treatments settled at temperatures near the top of their TNZ. Thus, kangaroo rats chose thermal environments that minimized energy requirements, not water requirements. Because kangaroo rats have evolved high water use efficiency, energy conservation may be more important than water conservation to the fitness of extant kangaroo rats.

  12. Selective detection of mitochondrial malfunction in situ by energy transfer spectroscopy

    NASA Astrophysics Data System (ADS)

    Schneckenburger, Herbert; Gschwend, Michael H.; Sailer, Reinhard; Strauss, Wolfgang S. L.; Schoch, Lars; Schuh, Alexander; Stock, Karl; Steiner, Rudolf W.; Zipfl, Peter

    1999-01-01

    To establish optical in situ detection of mitochondrial malfunction, non-radiative energy transfer from the coenzyme NADH to the mitochondrial marker rhodamine 123 (R123) was examined. Dual excitation of R123 via energy transfer from excited NADH molecules as well as by direct absorption of light results in two fluorescence signals whose ratio is a measure of mitochondrial NADH. These signals are detected simultaneously using a time-gated (nanosecond) technique for energy transfer measurements and a frequency selective technique for direct excitation and fluorescence monitoring of R123. Optical and electronic components of the experimental setup are described and compared with a previously established microscopic system.

  13. Selected Resource Materials for Developing Energy Conservation Programs in the Small Business/Commercial Sector.

    ERIC Educational Resources Information Center

    Lengyel, Dorothy L.; And Others

    This annotated bibliography is a selected listing of references for use by small business managers in the development of energy conservation programs. The references are listed under the agency through which they are available. The agency listings are alphabetized and include complete mailing addresses. There are 35 agency listings, many of which…

  14. Selective Energy Feasibility Study -- Richmond College, City University of New York

    ERIC Educational Resources Information Center

    Consulting Engineer, 1974

    1974-01-01

    A study of the presently available data on magnitude, duration, and coincidence of electrical demands determined that onsite electrical power generation in the form of a selective energy system should be incorporated within the central utilities plant projected for the Richmond College Campus of the City University of New York (CUNY). (Author/MLF)

  15. Angular selective window systems: Assessment of technical potential for energy savings

    DOE PAGES

    Fernandes, Luis L.; Lee, Eleanor S.; McNeil, Andrew; ...

    2014-10-16

    Static angular selective shading systems block direct sunlight and admit daylight within a specific range of incident solar angles. The objective of this study is to quantify their potential to reduce energy use and peak demand in commercial buildings using state-of-the art whole-building computer simulation software that allows accurate modeling of the behavior of optically-complex fenestration systems such as angular selective systems. Three commercial systems were evaluated: a micro-perforated screen, a tubular shading structure, and an expanded metal mesh. This evaluation was performed through computer simulation for multiple climates (Chicago, Illinois and Houston, Texas), window-to-wall ratios (0.15-0.60), building codes (ASHRAEmore » 90.1-2004 and 2010) and lighting control configurations (with and without). The modeling of the optical complexity of the systems took advantage of the development of state-of-the-art versions of the EnergyPlus, Radiance and Window simulation tools. Results show significant reductions in perimeter zone energy use; the best system reached 28% and 47% savings, respectively without and with daylighting controls (ASHRAE 90.1-2004, south facade, Chicago,WWR=0.45). As a result, angular selectivity and thermal conductance of the angle-selective layer, as well as spectral selectivity of low-emissivity coatings, were identified as factors with significant impact on performance.« less

  16. Angular selective window systems: Assessment of technical potential for energy savings

    SciTech Connect

    Fernandes, Luis L.; Lee, Eleanor S.; McNeil, Andrew; Jonsson, Jacob C.; Nouidui, Thierry; Pang, Xiufeng; Hoffmann, Sabine

    2014-10-16

    Static angular selective shading systems block direct sunlight and admit daylight within a specific range of incident solar angles. The objective of this study is to quantify their potential to reduce energy use and peak demand in commercial buildings using state-of-the art whole-building computer simulation software that allows accurate modeling of the behavior of optically-complex fenestration systems such as angular selective systems. Three commercial systems were evaluated: a micro-perforated screen, a tubular shading structure, and an expanded metal mesh. This evaluation was performed through computer simulation for multiple climates (Chicago, Illinois and Houston, Texas), window-to-wall ratios (0.15-0.60), building codes (ASHRAE 90.1-2004 and 2010) and lighting control configurations (with and without). The modeling of the optical complexity of the systems took advantage of the development of state-of-the-art versions of the EnergyPlus, Radiance and Window simulation tools. Results show significant reductions in perimeter zone energy use; the best system reached 28% and 47% savings, respectively without and with daylighting controls (ASHRAE 90.1-2004, south facade, Chicago,WWR=0.45). As a result, angular selectivity and thermal conductance of the angle-selective layer, as well as spectral selectivity of low-emissivity coatings, were identified as factors with significant impact on performance.

  17. Polydomain structures in ferroelectric and ferroelastic epitaxial films

    NASA Astrophysics Data System (ADS)

    Roytburd, Alexander L.; Ouyang, Jun; Artemev, Andrei

    2017-04-01

    A review of theoretical models, phase field modeling and experimental studies of domain structures in epitaxial films is presented. The thermodynamic theory of such domain structures is presented within the macroscopic thermo-mechanical framework. The theory allows for the evaluation of the main parameters of the domain structure using the energy minimization approach applied to the energy of elastic interactions. For homophase (polytwin) films, the thermodynamic theory provides a quantitative tool that can be used to estimate domain fractions in the film and the type of domain structure architecture. For heterophase films, the theory describes (a) the conditions under which two-phase structures can be obtained in epitaxial films, and (b) the phase and domain fractions in these films. The thermodynamic theory can also be used to describe the extrinsic contributions from domain structures to the functional properties of epitaxial ferroelectric films. The review of phase field modeling demonstrates that computational results reproduce the predictions of the thermodynamic theory. It is also shown that the phase field modeling that utilizes the energy minimization procedure for elastic and interfacial energies can be used to predict domain morphology for the films with two-phase structures produced either by phase transformation or through the co-deposition of immiscible phases. The experimental data presented in the review validate predictions of the thermodynamic model and the results of phase field modeling.

  18. Influence of Energy Input on Degradation Behavior of Plastic Components Manufactured by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Drummer, Dietmar; Wudy, Katrin; Drexler, Maximilian

    Additive manufacturing techniques, such as selective laser melting of plastics, generate components directly from a CAD data set without using a specific mold. High building chamber temperatures in combination with long building times lead to physical and chemical degradation of the surrounding powder and the manufactured component in the case of selective laser melting of polyamide 12 (PA12). Thus the following investigations show the influence of energy densities on mechanical properties as well as on the aging behavior of the manufactured components. Therefore several building processes with varying energy densities will be conducted. Aged polymer components were analyzed with physical, thermo analytical and mechanical methods with regards to their process relevant material properties. Considered material properties for example are phase transition temperatures, melting viscosity or molecular weight. The basic understanding of the influence of energy input on material properties will lead to new process strategies with minimized polymer degradation.

  19. Efficient Interlayer Relaxation and Transition of Excitons in Epitaxial and Non-epitaxial MoS2/WS2 Heterostructures

    SciTech Connect

    Yu, Yifei; Hu, Shi; Su, Liqin; Huang, Lujun; Liu, Yi; Jin, Zhenghe; Puretzky, Alexander A.; Geohegan, David B.; Kim, Ki Wook; Zhang, Yong; Cao, Linyou

    2014-12-03

    Semiconductor heterostructurs provide a powerful platform for the engineering of excitons. Here we report on the excitonic properties of two-dimensional (2D) heterostructures that consist of monolayer MoS2 and WS2 stacked epitaxially or non-epitaxially in the vertical direction. We find similarly efficient interlayer relaxation and transition of excitons in both the epitaxial and non-epitaxial heterostructures. This is manifested by a two orders of magnitude decrease in the photoluminescence and an extra absorption peak at low energy region of both heterostructures. The MoS2/WS2 heterostructures show weak interlayer coupling and essentially act as an atomic-scale heterojunction with the intrinsic band structures of the two monolayers largely preserved. They are particularly promising for the applications that request efficient dissociation of excitons and strong light absorption, including photovoltaics, solar fuels, photodetectors, and optical modulators. Our results also indicate that 2D heterostructures promise to provide capabilities to engineer excitons from the atomic level without concerns of interfacial imperfection.

  20. Efficient Interlayer Relaxation and Transition of Excitons in Epitaxial and Non-epitaxial MoS2/WS2 Heterostructures

    DOE PAGES

    Yu, Yifei; Hu, Shi; Su, Liqin; ...

    2014-12-03

    Semiconductor heterostructurs provide a powerful platform for the engineering of excitons. Here we report on the excitonic properties of two-dimensional (2D) heterostructures that consist of monolayer MoS2 and WS2 stacked epitaxially or non-epitaxially in the vertical direction. We find similarly efficient interlayer relaxation and transition of excitons in both the epitaxial and non-epitaxial heterostructures. This is manifested by a two orders of magnitude decrease in the photoluminescence and an extra absorption peak at low energy region of both heterostructures. The MoS2/WS2 heterostructures show weak interlayer coupling and essentially act as an atomic-scale heterojunction with the intrinsic band structures of themore » two monolayers largely preserved. They are particularly promising for the applications that request efficient dissociation of excitons and strong light absorption, including photovoltaics, solar fuels, photodetectors, and optical modulators. Our results also indicate that 2D heterostructures promise to provide capabilities to engineer excitons from the atomic level without concerns of interfacial imperfection.« less

  1. Optimal energy window selection of a CZT-based small-animal SPECT for quantitative accuracy

    NASA Astrophysics Data System (ADS)

    Park, Su-Jin; Yu, A. Ram; Choi, Yun Young; Kim, Kyeong Min; Kim, Hee-Joung

    2015-05-01

    Cadmium zinc telluride (CZT)-based small-animal single-photon emission computed tomography (SPECT) has desirable characteristics such as superior energy resolution, but data acquisition for SPECT imaging has been widely performed with a conventional energy window. The aim of this study was to determine the optimal energy window settings for technetium-99 m (99mTc) and thallium-201 (201Tl), the most commonly used isotopes in SPECT imaging, using CZT-based small-animal SPECT for quantitative accuracy. We experimentally investigated quantitative measurements with respect to primary count rate, contrast-to-noise ratio (CNR), and scatter fraction (SF) within various energy window settings using Triumph X-SPECT. The two ways of energy window settings were considered: an on-peak window and an off-peak window. In the on-peak window setting, energy centers were set on the photopeaks. In the off-peak window setting, the ratios of energy differences between the photopeak from the lower- and higher-threshold varied from 4:6 to 3:7. In addition, the energy-window width for 99mTc varied from 5% to 20%, and that for 201Tl varied from 10% to 30%. The results of this study enabled us to determine the optimal energy windows for each isotope in terms of primary count rate, CNR, and SF. We selected the optimal energy window that increases the primary count rate and CNR while decreasing SF. For 99mTc SPECT imaging, the energy window of 138-145 keV with a 5% width and off-peak ratio of 3:7 was determined to be the optimal energy window. For 201Tl SPECT imaging, the energy window of 64-85 keV with a 30% width and off-peak ratio of 3:7 was selected as the optimal energy window. Our results demonstrated that the proper energy window should be carefully chosen based on quantitative measurements in order to take advantage of desirable characteristics of CZT-based small-animal SPECT. These results provided valuable reference information for the establishment of new protocol for CZT

  2. Infrared Rugates by Molecular Beam Epitaxy

    NASA Technical Reports Server (NTRS)

    Rona, M.

    1993-01-01

    Rugates are optical structures that have a sinusoidal index of refraction (harmonic gradient-index field). As their discrete high/ low index filter counterparts, they can be used as narrow rejection band filters. However, since rugates do not have abrupt interfaces, they tend to have a smaller absorption, hence deliver a higher in band reflectivity. The absence of sharp interfaces makes rugates even more desirable for high-energy narrow band reflectors. In this application, the lack of a sharp interface at the maximum internal standing wave electric field results in higher breakdown strengths. Our method involves fabricating rugates, with molecular beam epitaxy, on GaAs wafers as an Al(x)Ga(1-x)As single-crystal film.

  3. Friction boosted by spontaneous epitaxial rotations

    NASA Astrophysics Data System (ADS)

    Mandelli, Davide; Vanossi, Andrea; Manini, Nicola; Tosatti, Erio

    2015-03-01

    It is well known in surface science that incommensurate adsorbed monolayers undergo a spontaneous, energy-lowering epitaxial rotation from aligned to misaligned relative to a periodic substrate. We show first of all that a model 2D colloidal monolayer in an optical lattice, of recent importance as a frictional model, also develops in full equilibrium a small rotation angle, easy to detect in the Moiré pattern. The colloidal monolayer misalignment is then shown by extensive sliding simulations to increase the dynamic friction by a considerable factor over the aligned case. More generally, this example suggests that spontaneous rotations are rather ubiquitous and should not be ignored in all tribological phenomena between mismatched lattices. This work was mainly supported by the ERC Advanced Grant No. 320796-MODPHYSFRICT, and partly by SINERGIA contract CRSII2 136287, by PRIN/COFIN Contract 2010LLKJBX 004, by COST Action MP1303.

  4. Fuzzy C-Means Clustering and Energy Efficient Cluster Head Selection for Cooperative Sensor Network.

    PubMed

    Bhatti, Dost Muhammad Saqib; Saeed, Nasir; Nam, Haewoon

    2016-09-09

    We propose a novel cluster based cooperative spectrum sensing algorithm to save the wastage of energy, in which clusters are formed using fuzzy c-means (FCM) clustering and a cluster head (CH) is selected based on a sensor's location within each cluster, its location with respect to fusion center (FC), its signal-to-noise ratio (SNR) and its residual energy. The sensing information of a single sensor is not reliable enough due to shadowing and fading. To overcome these issues, cooperative spectrum sensing schemes were proposed to take advantage of spatial diversity. For cooperative spectrum sensing, all sensors sense the spectrum and report the sensed energy to FC for the final decision. However, it increases the energy consumption of the network when a large number of sensors need to cooperate; in addition to that, the efficiency of the network is also reduced. The proposed algorithm makes the cluster and selects the CHs such that very little amount of network energy is consumed and the highest efficiency of the network is achieved. Using the proposed algorithm maximum probability of detection under an imperfect channel is accomplished with minimum energy consumption as compared to conventional clustering schemes.

  5. Fuzzy C-Means Clustering and Energy Efficient Cluster Head Selection for Cooperative Sensor Network

    PubMed Central

    Bhatti, Dost Muhammad Saqib; Saeed, Nasir; Nam, Haewoon

    2016-01-01

    We propose a novel cluster based cooperative spectrum sensing algorithm to save the wastage of energy, in which clusters are formed using fuzzy c-means (FCM) clustering and a cluster head (CH) is selected based on a sensor’s location within each cluster, its location with respect to fusion center (FC), its signal-to-noise ratio (SNR) and its residual energy. The sensing information of a single sensor is not reliable enough due to shadowing and fading. To overcome these issues, cooperative spectrum sensing schemes were proposed to take advantage of spatial diversity. For cooperative spectrum sensing, all sensors sense the spectrum and report the sensed energy to FC for the final decision. However, it increases the energy consumption of the network when a large number of sensors need to cooperate; in addition to that, the efficiency of the network is also reduced. The proposed algorithm makes the cluster and selects the CHs such that very little amount of network energy is consumed and the highest efficiency of the network is achieved. Using the proposed algorithm maximum probability of detection under an imperfect channel is accomplished with minimum energy consumption as compared to conventional clustering schemes. PMID:27618061

  6. Characterizing China's energy consumption with selective economic factors and energy-resource endowment: a spatial econometric approach

    NASA Astrophysics Data System (ADS)

    Jiang, Lei; Ji, Minhe; Bai, Ling

    2014-09-01

    Coupled with intricate regional interactions, the provincial disparity of energy-resource endowment and other economic conditions in China have created spatially complex energy consumption patterns that require analyses beyond the traditional ones. To distill the spatial effect out of the resource and economic factors on China's energy consumption, this study recast the traditional econometric model in a spatial context. Several analytic steps were taken to reveal different aspects of the issue. Per capita energy consumption (AVEC) at the provincial level was first mapped to reveal spatial clusters of high energy consumption being located in either well developed or energy resourceful regions. This visual spatial autocorrelation pattern of AVEC was quantitatively tested to confirm its existence among Chinese provinces. A Moran scatterplot was employed to further display a relatively centralized trend occurring in those provinces that had parallel AVEC, revealing a spatial structure with attraction among high-high or low-low regions and repellency among high-low or low-high regions. By a comparison between the ordinary least square (OLS) model and its spatial econometric counterparts, a spatial error model (SEM) was selected to analyze the impact of major economic determinants on AVEC. While the analytic results revealed a significant positive correlation between AVEC and economic development, other determinants showed some intricate influential patterns. The provinces endowed with rich energy reserves were inclined to consume much more energy than those otherwise, whereas changing the economic structure by increasing the proportion of secondary and tertiary industries also tended to consume more energy. Both situations seem to underpin the fact that these provinces were largely trapped in the economies that were supported by technologies of low energy efficiency during the period, while other parts of the country were rapidly modernized by adopting advanced

  7. Characterizing China's energy consumption with selective economic factors and energy-resource endowment: a spatial econometric approach

    NASA Astrophysics Data System (ADS)

    Jiang, Lei; Ji, Minhe; Bai, Ling

    2015-06-01

    Coupled with intricate regional interactions, the provincial disparity of energy-resource endowment and other economic conditions in China have created spatially complex energy consumption patterns that require analyses beyond the traditional ones. To distill the spatial effect out of the resource and economic factors on China's energy consumption, this study recast the traditional econometric model in a spatial context. Several analytic steps were taken to reveal different aspects of the issue. Per capita energy consumption (AVEC) at the provincial level was first mapped to reveal spatial clusters of high energy consumption being located in either well developed or energy resourceful regions. This visual spatial autocorrelation pattern of AVEC was quantitatively tested to confirm its existence among Chinese provinces. A Moran scatterplot was employed to further display a relatively centralized trend occurring in those provinces that had parallel AVEC, revealing a spatial structure with attraction among high-high or low-low regions and repellency among high-low or low-high regions. By a comparison between the ordinary least square (OLS) model and its spatial econometric counterparts, a spatial error model (SEM) was selected to analyze the impact of major economic determinants on AVEC. While the analytic results revealed a significant positive correlation between AVEC and economic development, other determinants showed some intricate influential patterns. The provinces endowed with rich energy reserves were inclined to consume much more energy than those otherwise, whereas changing the economic structure by increasing the proportion of secondary and tertiary industries also tended to consume more energy. Both situations seem to underpin the fact that these provinces were largely trapped in the economies that were supported by technologies of low energy efficiency during the period, while other parts of the country were rapidly modernized by adopting advanced

  8. Comparative analyisis of energy consumption of selected buildings on morehead state university's main campus

    NASA Astrophysics Data System (ADS)

    Brandt, Ronald E.

    Currently there is a need for energy efficiency on the main campus of Morehead State University main campus. Evidence shows that there is room for improvement in order to lower the usage and cost efficiency at MSU. The purpose of this study is to propose, that Net Zero technology should be implemented towards the main campus of Morehead State University in the near future. The goal is to come up with a study of comparing selected current traditional buildings with the LEED buildings (Wellness Recreational Center and CHER building). To form this analysis will be applied using SPC software on Energy usage for year by year trends from 2012. In conclusion, Net-Zero construction has steadily increased since then, with the number of completed buildings more than doubling since 2008, according to the latest study. Thanks to advances in structural insulation, energy-efficient appliances, this will help the MSU campus in the near future. As for energy efficiency, to make sure we have plenty of energy in the future, it's up to all of us to use energy wisely. We must all conserve energy and use it efficiently. It's also up to those who will create the new energy technologies of the future..

  9. On the density of states of disordered epitaxial graphene

    SciTech Connect

    Davydov, S. Yu.

    2015-05-15

    The study is concerned with two types of disordered epitaxial graphene: (i) graphene with randomly located carbon vacancies and (ii) structurally amorphous graphene. The former type is considered in the coherent potential approximation, and for the latter type, a model of the density of states is proposed. The effects of two types of substrates, specifically, metal and semiconductor substrates are taken into account. The specific features of the density of states of epitaxial graphene at the Dirac point and the edges of the continuous spectrum are analyzed. It is shown that vacancies in epitaxial graphene formed on the metal substrate bring about logarithmic nulling of the density of states of graphene at the Dirac point and the edges of the continuous spectrum. If the Dirac point corresponds to the middle of the band gap of the semiconductor substrate, the linear trend of the density of states to zero in the vicinity of the Dirac point in defect-free graphene transforms into a logarithmic decrease in the presence of vacancies. In both cases, the graphene-substrate interaction is assumed to be weak (quasi-free graphene). In the study of amorphous epitaxial graphene, a simple model of free amorphous graphene is proposed as the initial model, in which account is taken of the nonzero density of states at the Dirac point, and then the interaction of the graphene sheet with the substrate is taken into consideration. It is shown that, near the Dirac point, the quadratic behavior of the density of states of free amorphous graphene transforms into a linear dependence for amorphous epitaxial graphene. In the study, the density of states of free graphene corresponds to the low-energy approximation of the electron spectrum.

  10. Analysis Of Spectrally Selective Liquid Absorption Filters For Hybrid Solar Energy Conversion

    NASA Astrophysics Data System (ADS)

    Chendo, M. A. C.; Osborn, D. E.; Swenson, Rick

    1985-12-01

    Various techniques have been proposed to convert solar energy to both electric power and heat in hybrid systems. Many of these approaches are designed to utilize spectral selectivity to improve the overall conversion efficiency. Examples include spectrally selective beamsplitters and arrangements of long-wave or short-wave-pass glass filters that divide the spectrum so that photon energies are roughly matched to the energies corresponding to the solar-cell bandgaps or to efficient photothermal convertors. This paper describes the analysis of liquid optical filters that have high transmittance in the visible spectrum and high absorptance in the infrared. These qualities make it possible to capture that portion of the spectrum useful to a quantum convertor, such as a photovoltaic cell, while channeling the "excess heat" of the photons with energies below the bandgap to a thermal convertor, thereby enhancing the overall conversion efficiency of the system. The preliminary studies show that spectral responses of the tested solutions (salts in water) are primarily influenced by the cation component of the salt solution. By changing the solutions and concentrations, a variety of spectrally selective filters can be tailored to match system requirements.

  11. Epitaxial Garnets and Hexagonal Ferrites.

    DTIC Science & Technology

    1982-04-20

    Iron Garnet Liquid Phase Epitaxy Hexagonal Ferrite microwave Signal Processing Millimeter-Wave 20. ABSTRACT (Continue ani revee arde if necoeermy and...le.’uIfy by block rns.) e objective of this research is to develop new and improved epitauial ferrite materials for use in microwave and millimeter... ferrite films suitable for microwave and millimeter-wave signal processing at frequencies above 1 GHz. The specific tasks are: a. Analyze and develop

  12. Recent developments in droplet epitaxy

    SciTech Connect

    Mano, Takaaki; Jo, Masafumi; Kuroda, Takashi; Abbarchi, Marco; Noda, Takeshi; Sakoda, Kazuaki

    2014-05-15

    The droplet epitaxy allows for self-assembly of lattice-matched GaAs quantum dots (QDs) with high quality and high uniformity. In this article, we show our efforts to realize the GaAs QDs with excellent optical properties. After the optimization of the several growth processes, we achieved current-injection lasing in the GaAs QDs. In addition, formation of further advanced nanostructure is presented.

  13. The Controller Synthesis of Metastable Oxides Utilizing Epitaxy and Epitaxial Stabilization

    SciTech Connect

    Schlom, Darrell

    2003-12-02

    Molecular beam epitaxy (MBE) has achieved unparalleled control in the integration of semiconductors at the nanometer. These advances were made through the use of epitaxy, epitaxial stabilization, and a combination of composition-control techniques including adsorption-controlled growth and RHEED-based composition control that we have developed, understood, and utilized for the growth of oxides. Also key was extensive characterization (utilizing RHEED, four-circle x-ray diffraction, AFM, TEM, and electrical characterization techniques) in order to study growth modes, optimize growth conditions, and probe the structural, dielectric, and ferroelectric properties of the materials grown. The materials that we have successfully engineered include titanates (PbTiO3, Bi4Ti3O12), tantalates (SrBi2Ta2O9), and niobates (SrBi2Nb2O9); layered combinations of these perovskite-related materials (Bi4Ti3O12-SrTiO3 and Bi4Ti3O12-PbTiO3 Aurivillius phases and metastable PbTiO3/SrTiO3 and BaTiO3/SrTiO3 superlattices), and new metastable phases (Srn+1TinO3n+1 Ruddlesden-Popper phases). The films were grown by reactive MBE and pulsed laser deposition (PLD). Many of these materials are either new or have been synthesized with the highest perfection ever reported. The controlled synthesis of such layered oxide heterostructures offers great potential for tailoring the superconducting, ferroelectric, and dielectric properties of these materials. These properties are important for energy technologies.

  14. Ultrafast laser-driven microlens to focus and energy-select mega-electron volt protons.

    PubMed

    Toncian, Toma; Borghesi, Marco; Fuchs, Julien; d'Humières, Emmanuel; Antici, Patrizio; Audebert, Patrick; Brambrink, Erik; Cecchetti, Carlo Alberto; Pipahl, Ariane; Romagnani, Lorenzo; Willi, Oswald

    2006-04-21

    We present a technique for simultaneous focusing and energy selection of high-current, mega-electron volt proton beams with the use of radial, transient electric fields (10(7) to 10(10) volts per meter) triggered on the inner walls of a hollow microcylinder by an intense subpicosecond laser pulse. Because of the transient nature of the focusing fields, the proposed method allows selection of a desired range out of the spectrum of the polyenergetic proton beam. This technique addresses current drawbacks of laser-accelerated proton beams, such as their broad spectrum and divergence at the source.

  15. The LILIA experiment: Energy selection and post-acceleration of laser generated protons

    NASA Astrophysics Data System (ADS)

    Turchetti, Giorgio; Sinigardi, Stefano; Londrillo, Pasquale; Rossi, Francesco; Sumini, Marco; Giove, Dario; De Martinis, Carlo

    2012-12-01

    The LILIA experiment is planned at the SPARCLAB facility of the Frascati INFN laboratories. We have simulated the laser acceleration of protons, the transport and energy selection with collimators and a pulsed solenoid and the post-acceleration with a compact high field linac. For the highest achievable intensity corresponding to a = 30 over 108 protons at 30 MeV with a 3% spread are selected, and at least107 protons are post-accelerated up to 60 MeV. If a 10 Hz repetition rated can be achieved the delivered dose would be suitable for the treatment of small superficial tumors.

  16. Frequency-sweeping: A new technique for energy-selective transport

    SciTech Connect

    Mynick, H.E.; Pomphrey, N.

    1994-02-01

    A new method is described for inducing energy-selective transport by `sweeping` the frequency of applied low-n magnetic perturbations. The mechanism, formally analogous to the `rising buckets` concept in accelerator physics, can move particles with a selected velocity in a nondiffusive fashion from one specified radius to another. The technique is considered principally as a means for removal of Helium ash. Other likely applications are as a method for burn control, profile control, as a diagnostic, and perhaps as a nonstochastic means of effecting the direct coupling of alpha power recently discussed by Fisch and Rax.

  17. Application configuration selection for energy-efficient execution on multicore systems

    SciTech Connect

    Wang, Shinan; Luo, Bing; Shi, Weisong; Tiwari, Devesh

    2015-09-21

    Balanced performance and energy consumption are incorporated in the design of modern computer systems. Several runtime factors, such as concurrency levels, thread mapping strategies, and dynamic voltage and frequency scaling (DVFS) should be considered in order to achieve optimal energy efficiency fora workload. Selecting appropriate run-time factors, however, is one of the most challenging tasks because the run-time factors are architecture-specific and workload-specific. And while most existing works concentrate on either static analysis of the workload or run-time prediction results, we present a hybrid two-step method that utilizes concurrency levels and DVFS settings to achieve the energy efficiency configuration for a worldoad. The experimental results based on a Xeon E5620 server with NPB and PARSEC benchmark suites show that the model is able to predict the energy efficient configuration accurately. On average, an additional 10% EDP (Energy Delay Product) saving is obtained by using run-time DVFS for the entire system. An off-line optimal solution is used to compare with the proposed scheme. Finally, the experimental results show that the average extra EDP saved by the optimal solution is within 5% on selective parallel benchmarks.

  18. Application configuration selection for energy-efficient execution on multicore systems

    DOE PAGES

    Wang, Shinan; Luo, Bing; Shi, Weisong; ...

    2015-09-21

    Balanced performance and energy consumption are incorporated in the design of modern computer systems. Several runtime factors, such as concurrency levels, thread mapping strategies, and dynamic voltage and frequency scaling (DVFS) should be considered in order to achieve optimal energy efficiency fora workload. Selecting appropriate run-time factors, however, is one of the most challenging tasks because the run-time factors are architecture-specific and workload-specific. And while most existing works concentrate on either static analysis of the workload or run-time prediction results, we present a hybrid two-step method that utilizes concurrency levels and DVFS settings to achieve the energy efficiency configuration formore » a worldoad. The experimental results based on a Xeon E5620 server with NPB and PARSEC benchmark suites show that the model is able to predict the energy efficient configuration accurately. On average, an additional 10% EDP (Energy Delay Product) saving is obtained by using run-time DVFS for the entire system. An off-line optimal solution is used to compare with the proposed scheme. Finally, the experimental results show that the average extra EDP saved by the optimal solution is within 5% on selective parallel benchmarks.« less

  19. Energy and matter-efficient size-selective growth of thin quantum wires in a plasma

    SciTech Connect

    Ostrikov, K.; Mehdipour, H.

    2011-01-17

    It is shown that plasmas can minimize the adverse Gibbs-Thompson effect in thin quantum wire growth. The model of Si nanowire nucleation includes the unprecedented combination of the plasma sheath, ion- and radical-induced species creation and heating effects on the surface and within an Au catalyst nanoparticle. Compared to neutral gas thermal processes, much thinner, size-selective wires can nucleate at the same temperature and pressure while much lower energy and matter budget is needed to grow same-size wires. This explains the experimental observations and may lead to energy- and matter-efficient synthesis of a broader range of one-dimensional quantum structures.

  20. Features of impurity photoconductivity in Si:Er/Si epitaxial diodes

    SciTech Connect

    Antonov, A. V.; Kudryavtsev, K. E. Shengurov, D. V.; Shmagin, V. B.; Krasilnik, Z. F.

    2013-11-15

    The photocurrent spectra of Si:Er/Si epitaxial diode structures are studied. It is shown that the nature of the sub-band-gap photoresponse is determined by the epitaxial growth temperature of the Si:Er layer and is not related to the composition of erbium emission centers. It is found that the absorption of light with photon energies lower than the energy-gap of silicon is determined by impurity-defect complexes that appear during the growth of the epitaxial layer and form a quasi-continuous spectrum of states in the energy gap of silicon. It is assumed that these impurity centers are not related to optically active erbium centers and are not involved in excitation-energy transfer to the rare-earth impurity.

  1. Three-dimensional lattice matching of epitaxially embedded nanoparticles

    NASA Astrophysics Data System (ADS)

    May, Brelon J.; Anderson, Peter M.; Myers, Roberto C.

    2017-02-01

    For a given degree of in-plane lattice mismatch between a two-dimensional (2D) epitaxial layer and a substrate (εIP*), there is a critical thickness above which interfacial defects form to relax the elastic strain energy. Here, we extend the 2D lattice-matching conditions to three-dimensions in order to predict the critical size beyond which epitaxially encased nanoparticles, characterized by both εIP* and out-of-plane lattice mismatch (εOP*), relax by dislocation formation. The critical particle length (Lc) at which defect formation proceeds is determined by balancing the reduction in elastic energy associated with dislocation introduction with the corresponding increase in defect energy. Our results, which use a modified Eshelby inclusion technique for an embedded, arbitrarily-faceted nanoparticle, provide new insight to the nanoepitaxy of low dimensional structures, especially quantum dots and nanoprecipitates. By engineering εIP* and εOP*, the predicted Lc for nanoparticles can be increased to well beyond the case of encapsulation in a homogenous matrix. For the case of truncated pyramidal shaped InAs, Lc 10.8 nm when fully embedded in GaAs (εIP* = εOP* = - 0.072); 16.4 nm when the particle is grown on GaAs, but capped with InSb (εIP* = - 0.072 and εOP* =+0.065); and a maximum of 18.4 nm if capped with an alloy corresponding to εOP* =+0.037. The effect, which we term "3D Poisson-stabilization" provides a means to increase the epitaxial strain tolerance in epitaxial heterostructures by tailoring εOP*.

  2. Considerations of dietary sodium/potassium/energy ratios of selected foods.

    PubMed

    Arbeit, M L; Nicklas, T A; Berenson, G S

    1992-04-01

    Various electrolytes and energy intakes have been shown to contribute to the risk of hypertension and other cardiovascular diseases. Further, dietary sodium (Na) and potassium (K) balance are important in both nonpharmacologic and pharmacologic management of various cardiovascular states. Emphasis is also given to weight reduction and electrolyte balance. As an aid to food selection to enhance K intake and decrease Na intake, we have categorized foods according to their electrolyte density as related to caloric content. More than 100 individual food items were assigned to one of four categories. Ratios of individual Na, K, and energy content were calculated, based on USDA-generated food nutrient values. Category 1 includes foods that are low in Na, high in K and low in energy: fresh or frozen vegetable sources with vitamins A and C. Category 2 contains foods low in Na relative to high K and high energy: most fruit, starchy vegetables, nuts, milk and meat products, and chocolate. Category 3 includes foods high in Na that are also high in K in relation to low energy: vegetables (canned, frozen in butter sauce or au gratin), most cheeses, cured or frozen meats. Category 4 contains foods high in Na and low in K relative to high energy: bread, rice, luncheon meats, commercial cookies and pastries, and fast food entrees. Commercial cereals could be differentiated by the guidelines, with bran cereals in Category 1, shredded wheat products in Category 2, fruit-containing cereals in Category 3, and presweetened or instant cereals in Category 4. Identification of the ratio of Na and K to content of foods, compared with relative energy ratio, is useful in selecting foods that will help meet specific dietary criteria for management of essential hypertension and other cardiovascular-renal states, both in the adult and pediatric populations.

  3. Tunneling Spectroscopy Studies of Epitaxial Graphene on Silicon Carbide(0001) and Its Interfaces

    NASA Astrophysics Data System (ADS)

    Sandin, Andreas Axel Tomas

    graphene. STS, STM along with DFT calculations are used to determine the interface location of Sodium, SiC-bufferlayer or bufferlayer-graphene intercalation. In this thesis, STM, and STS are used to study the interactions of paramagnetic FePc molecules with epitaxial graphene. The molecules, FePc, is found to interact with the graphene substrate where STM images show substrate induced orientation of FePc densely packed square lattice structure. At sub-monolayer coverages, FePc form a molecular gas at room temperature suggesting a low diffusion barrier on the graphene lattice. The substrate interaction is probed by STS and show an abnormally low LUMO energy that suggest strong electronic coupling between graphene and FePc. DFT calculations support the experimental observations and predict a spin-dependent molecule-graphene hybridization close to the Fermi energy in unoccupied states. For majority spins, DFT demonstrates the Dirac cone splits and a delocalized hybrid state is found in the band gap. For minority spin the Dirac cone is intact with energy of Dirac point empty. In addition, a novel method of improving UHV graphene growth on SiC(0001) is presented. During growth the SiC surface is exposed to atomic hydrogen which allows selective etching of Si over Carbon. This result in more uniform non-thermal formation of the buffer layer with many fewer defects and thus leads to nearly pit-free and defect-free thermal graphene layers.

  4. Identity Recognition Algorithm Using Improved Gabor Feature Selection of Gait Energy Image

    NASA Astrophysics Data System (ADS)

    Chao, LIANG; Ling-yao, JIA; Dong-cheng, SHI

    2017-01-01

    This paper describes an effective gait recognition approach based on Gabor features of gait energy image. In this paper, the kernel Fisher analysis combined with kernel matrix is proposed to select dominant features. The nearest neighbor classifier based on whitened cosine distance is used to discriminate different gait patterns. The approach proposed is tested on the CASIA and USF gait databases. The results show that our approach outperforms other state of gait recognition approaches in terms of recognition accuracy and robustness.

  5. High efficiency thermal to electric energy conversion using selective emitters and spectrally tuned solar cells

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L.; Flood, Dennis J.; Lowe, Roland A.

    1992-01-01

    Thermophotovoltaic (TPV) systems are attractive possibilities for direct thermal-to-electric energy conversion, but have typically required the use of black body radiators operating at high temperatures. Recent advances in both the understanding and performance of solid rare-earth oxide selective emitters make possible the use of TPV at temperatures as low as 1500 K. Depending on the nature of parasitic losses, overall thermal-to-electric conversion efficiencies greater than 20 percent are feasible.

  6. STM Properties and Manipulation of Epitaxial Graphene

    NASA Astrophysics Data System (ADS)

    Thibado, Paul

    2014-03-01

    Epitaxial graphene grown on SiC has been identified as one of the most likely avenues to graphene-based electronics. Understanding how morphology affects electronic properties is therefore important. In our work, epitaxial graphene was grown on the polar and non-polar a-, m-, and r-crystallographic oriented surfaces of SiC, and was investigated using scanning tunneling microscopy (STM). Bunched nano-ridges ten times smaller than previously recorded were observed throughout the surface. A new STM technique called electrostatic-manipulation scanning tunneling microscopy (EM-STM) was performed to modify the morphology of the nano-ridges. By modeling the electrostatics involved in the EM-STM measurement, we estimate that a force of 5 nN and energy of 10 eV was required to alter the local interfacial bonding. At the atomic scale, STM images of Moire patterns reveal low-angle, twisted bi-layer graphene, grain boundaries, and an apparent lattice constant dilation. We will show that this dilation is due to the STM tip electrostatically dragging the graphene surface. Collaborators: P. Xu, D. Qi, M.L. Ackerman, S.D. Barber, J.K. Schoelz, and J. Thompson, Department of Physics, University of Arkansas, Fayetteville, AR, 72701, USA; V.D. Wheelr, R.L. Myers-Ward, C.R. Eddy, Jr., and D.K. Gaskill, U.S. Naval Research Laboratory, Washington, DC 20375, USA; and L.O. Nyakiti, Texas A&M University. Department of Physics, University of Arkansas, Fayetteville, AR, 72701, USA.

  7. Spectrally-selective all-inorganic scattering luminophores for solar energy-harvesting clear glass windows.

    PubMed

    Alghamedi, Ramzy; Vasiliev, Mikhail; Nur-E-Alam, Mohammad; Alameh, Kamal

    2014-10-16

    All-inorganic visibly-transparent energy-harvesting clear laminated glass windows are the most practical solution to boosting building-integrated photovoltaics (BIPV) energy outputs significantly while reducing cooling- and heating-related energy consumption in buildings. By incorporating luminophore materials into lamination interlayers and using spectrally-selective thin-film coatings in conjunction with CuInSe2 solar cells, most of the visible solar radiation can be transmitted through the glass window with minimum attenuation while ultraviolet (UV) radiation is down-converted and routed together with a significant part of infrared radiation to the edges for collection by solar cells. Experimental results demonstrate a 10 cm × 10 cm vertically-placed energy-harvesting clear glass panel of transparency exceeding 60%, invisible solar energy attenuation greater than 90% and electrical power output near 30 Wp/m(2) mainly generated by infrared (IR) and UV radiations. These results open the way for the realization of large-area visibly-transparent energy-harvesting clear glass windows for BIPV systems.

  8. Spectrally-selective all-inorganic scattering luminophores for solar energy-harvesting clear glass windows

    NASA Astrophysics Data System (ADS)

    Alghamedi, Ramzy; Vasiliev, Mikhail; Nur-E-Alam, Mohammad; Alameh, Kamal

    2014-10-01

    All-inorganic visibly-transparent energy-harvesting clear laminated glass windows are the most practical solution to boosting building-integrated photovoltaics (BIPV) energy outputs significantly while reducing cooling- and heating-related energy consumption in buildings. By incorporating luminophore materials into lamination interlayers and using spectrally-selective thin-film coatings in conjunction with CuInSe2 solar cells, most of the visible solar radiation can be transmitted through the glass window with minimum attenuation while ultraviolet (UV) radiation is down-converted and routed together with a significant part of infrared radiation to the edges for collection by solar cells. Experimental results demonstrate a 10 cm × 10 cm vertically-placed energy-harvesting clear glass panel of transparency exceeding 60%, invisible solar energy attenuation greater than 90% and electrical power output near 30 Wp/m2 mainly generated by infrared (IR) and UV radiations. These results open the way for the realization of large-area visibly-transparent energy-harvesting clear glass windows for BIPV systems.

  9. Eating frequency and energy regulation in free-living adults consuming self-selected diets.

    PubMed

    McCrory, Megan A; Howarth, Nancy C; Roberts, Susan B; Huang, Terry T-K

    2011-01-01

    The relative importance of eating frequency to weight control is poorly understood. This review examines the evidence to date on the role of eating frequency in weight control in free-living adults. The majority of cross-sectional studies in free-living adults show an inverse relationship between eating frequency and adiposity; however, this is likely an artifact produced by the underreporting of eating frequency concurrent with underreporting of energy intake. When implausible energy intake reporting (which is mostly underreporting) is taken into account, the association between eating frequency and adiposity becomes positive. In studies in which eating frequency is prescribed and food intake is mostly self-selected, there is either no effect or a minor positive effect of eating frequency on energy intake. Most of those studies have been short-term and lack the necessary dietary biomarkers to validate reported energy intakes and eating frequencies. In conclusion, there is some suggestion from cross-sectional studies in which energy intake underreporting is taken into account and from experimental studies to date that greater eating frequency may promote positive energy balance. However, experimental studies of longer-term duration that include objective dietary biomarkers are necessary before firm conclusions about the relative importance of eating frequency in weight control can be made.

  10. Spectrally-selective all-inorganic scattering luminophores for solar energy-harvesting clear glass windows

    PubMed Central

    Alghamedi, Ramzy; Vasiliev, Mikhail; Nur-E-Alam, Mohammad; Alameh, Kamal

    2014-01-01

    All-inorganic visibly-transparent energy-harvesting clear laminated glass windows are the most practical solution to boosting building-integrated photovoltaics (BIPV) energy outputs significantly while reducing cooling- and heating-related energy consumption in buildings. By incorporating luminophore materials into lamination interlayers and using spectrally-selective thin-film coatings in conjunction with CuInSe2 solar cells, most of the visible solar radiation can be transmitted through the glass window with minimum attenuation while ultraviolet (UV) radiation is down-converted and routed together with a significant part of infrared radiation to the edges for collection by solar cells. Experimental results demonstrate a 10 cm × 10 cm vertically-placed energy-harvesting clear glass panel of transparency exceeding 60%, invisible solar energy attenuation greater than 90% and electrical power output near 30 Wp/m2 mainly generated by infrared (IR) and UV radiations. These results open the way for the realization of large-area visibly-transparent energy-harvesting clear glass windows for BIPV systems. PMID:25321890

  11. Report on HVAC option selections for a relocatable classroom energy and indoor environmental quality field study

    SciTech Connect

    Apte, Michael G.; Delp, Woody W.; Diamond, Richard C.; Hodgson, Alfred T.; Kumar, Satish; Rainer, Leo I.; Shendell, Derek G.; Sullivan, Doug P.; Fisk, William J.

    2001-10-11

    It is commonly assumed that efforts to simultaneously develop energy efficient building technologies and to improve indoor environmental quality (IEQ) are unfeasible. The primary reason for this is that IEQ improvements often require additional ventilation that is costly from an energy standpoint. It is currently thought that health and productivity in work and learning environments requires adequate, if not superior, IEQ. Despite common assumptions, opportunities do exist to design building systems that provide improvements in both energy efficiency and IEQ. This report outlines the selection of a heating, ventilation, and air conditioning (HVAC) system to be used in demonstrating such an opportunity in a field study using relocatable school classrooms. Standard classrooms use a common wall mounted heat pump HVAC system. After reviewing alternative systems, a wall-mounting indirect/direct evaporative cooling system with an integral hydronic gas heating is selected. The anticipated advantages of this system include continuous ventilation of 100 percent outside air at or above minimum standards, projected cooling energy reductions of about 70 percent, inexpensive gas heating, improved airborne particle filtration, and reduced peak load electricity use. Potential disadvantages include restricted climate regions and possible increases in indoor relative humidity levels under some conditions.

  12. Selection of energy optimized pump concepts for multi core and multi mode erbium doped fiber amplifiers.

    PubMed

    Krummrich, Peter M; Akhtari, Simon

    2014-12-01

    The selection of an appropriate pump concept has a major impact on amplifier cost and power consumption. The energy efficiency of different pump concepts is compared for multi core and multi mode active fibers. In preamplifier stages, pump power density requirements derived from full C-band low noise WDM operation result in superior energy efficiency of direct pumping of individual cores in a multi core fiber with single mode pump lasers compared to cladding pumping with uncooled multi mode lasers. Even better energy efficiency is achieved by direct pumping of the core in multi mode active fibers. Complexity of pump signal combiners for direct pumping of multi core fibers can be reduced by deploying integrated components.

  13. Parallel cascade selection molecular dynamics for efficient conformational sampling and free energy calculation of proteins

    NASA Astrophysics Data System (ADS)

    Kitao, Akio; Harada, Ryuhei; Nishihara, Yasutaka; Tran, Duy Phuoc

    2016-12-01

    Parallel Cascade Selection Molecular Dynamics (PaCS-MD) was proposed as an efficient conformational sampling method to investigate conformational transition pathway of proteins. In PaCS-MD, cycles of (i) selection of initial structures for multiple independent MD simulations and (ii) conformational sampling by independent MD simulations are repeated until the convergence of the sampling. The selection is conducted so that protein conformation gradually approaches a target. The selection of snapshots is a key to enhance conformational changes by increasing the probability of rare event occurrence. Since the procedure of PaCS-MD is simple, no modification of MD programs is required; the selections of initial structures and the restart of the next cycle in the MD simulations can be handled with relatively simple scripts with straightforward implementation. Trajectories generated by PaCS-MD were further analyzed by the Markov state model (MSM), which enables calculation of free energy landscape. The combination of PaCS-MD and MSM is reported in this work.

  14. Development of a carbonaceous selective absorber for solar thermal energy collection and process for its formation

    NASA Astrophysics Data System (ADS)

    Garrison, John D.

    1989-02-01

    The main goal of the US Department of Energy supported part of this project is to develop information about controlling the complicated chemical processes involved in the formation of a carbonaceous selective absorber and learn what equipment will allow production of this absorber commercially. The work necessary to accomplish this goal is not yet complete. Formation of the carbonaceous selective absorber in the conveyor oven tried so far has been unsatisfactory, because the proper conditions for applying the carbonaceous coating in each conveyor oven fabricated, either have been difficult to obtain, or have been difficult to maintain over an extended period of time. A new conveyor oven is nearing completion which is expected to allow formation of the carbonaceous selective absorber on absorber tubes in a continuous operation over many days without the necessity of cleaning the conveyor oven or changing the thickness of the electroplated nickel catalyst to compensate for changes in the coating environment in the oven. Work under this project concerned with forming and sealing glass panels to test ideas on evacuated glass solar collector designs and production have been generally quite satisfactory. Delays in completion of the selective absorber work, has caused postponement of the fabrication of a small prototype evacuated glass solar collector panel. Preliminary cost estimates of the selective absorber and solar collector panel indicate that this collector system should be lower in cost than evacuated solar collectors now on the market.

  15. Epitaxial growth of europium monoxide on diamond

    SciTech Connect

    Melville, A.; Heeg, T.; Mairoser, T.; Schmehl, A.; Fischer, M.; Gsell, S.; Schreck, M.; Awschalom, D. D.; Holländer, B.; Schubert, J.; Schlom, D. G.

    2013-11-25

    We report the epitaxial integration of phase-pure EuO on both single-crystal diamond and on epitaxial diamond films grown on silicon utilizing reactive molecular-beam epitaxy. The epitaxial orientation relationship is (001) EuO ‖ (001) diamond and [110] EuO ‖[100] diamond. The EuO layer is nominally unstrained and ferromagnetic with a transition temperature of 68 ± 2 K and a saturation magnetization of 5.5 ± 0.1 Bohr magnetons per europium ion on the single-crystal diamond, and a transition temperature of 67 ± 2 K and a saturation magnetization of 2.1 ± 0.1 Bohr magnetons per europium ion on the epitaxial diamond film.

  16. Modeling of a water vapor selective membrane unit to increase the energy efficiency of humidity harvesting

    NASA Astrophysics Data System (ADS)

    Bergmair, D.; Metz, S. J.; de Lange, H. C.; van Steenhoven, A. A.

    2012-11-01

    Air humidity is a promising source of clean and safe drinking water. However, in conventional systems a lot of energy is wasted on the production of cold air, rather than the condensation of water vapor. This study examines the possibility of using a hollow fiber membrane module to make this process more energy efficient, by separating the vapor from other gases, prior to the cooling process with the help of selective membranes. The water vapor concentration within a fiber has been modeled using a random walker approach, and the membrane permeability has been implemented as a re-bounce probability for simulation particles interacting with the membrane. Considering the additional work requirement for driving a feed flow through the membrane section and the computed water vapor permeation it could be shown that the energy demand per unit water is lowest for slow flow speeds and favors short and thin fibers. The total energy requirement was estimated to be less than half of the conventional one. Comparison with other CFD simulations and a real life module has shown a good level of agreement, indicating that a membrane section could improve the energy efficiency of humidity harvesting significantly.

  17. Molecular-Beam-Epitaxy Program

    NASA Technical Reports Server (NTRS)

    Sparks, Patricia D.

    1988-01-01

    Molecular Beam Epitaxy (MBE) computer program developed to aid in design of single- and double-junction cascade cells made of silicon. Cascade cell has efficiency 1 or 2 percent higher than single cell, with twice the open-circuit voltage. Input parameters include doping density, diffusion lengths, thicknesses of regions, solar spectrum, absorption coefficients of silicon (data included for 101 wavelengths), and surface recombination velocities. Results include maximum power, short-circuit current, and open-circuit voltage. Program written in FORTRAN IV.

  18. Characteristics of the Telescope for High Energy Gamma-ray Astronomy Selected for Definition Studies on the Gamma Ray Observatory

    NASA Technical Reports Server (NTRS)

    Hughes, E. B.; Hofstadter, R.; Johansson, A.; Rolfe, J.; Bertsch, D. L.; Cruickshank, W. J.; Ehrmann, C. H.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.

    1979-01-01

    The high energy gamma-ray selected for definition studies on the Gamma Ray Observatory provides a substantial improvement in observational capability over earlier instruments. It will have about 20 times more sensitivity, cover a much broader energy range, have considerably better energy resolution and provide a significantly improved angular resolution. The design and performance are described.

  19. Refrigeration Playbook: Natural Refrigerants; Selecting and Designing Energy-Efficient Commercial Refrigeration Systems That Use Low Global Warming Potential Refrigerants

    SciTech Connect

    Nelson, Caleb; Reis, Chuck; Nelson, Eric; Armer, James; Arthur, Rob; Heath, Richard; Rono, James; Hirsch, Adam; Doebber, Ian

    2015-03-01

    This report provides guidance for selecting and designing energy efficient commercial refrigeration systems using low global warming potential refrigerants. Refrigeration systems are generally the largest energy end use in a supermarket type building, often accounting for more than half of a building's energy consumption.

  20. Performance of solenoids versus quadrupoles in focusing and energy selection of laser accelerated protons

    NASA Astrophysics Data System (ADS)

    Hofmann, Ingo

    2013-04-01

    Using laser accelerated protons or ions for various applications—for example in particle therapy or short-pulse radiographic diagnostics—requires an effective method of focusing and energy selection. We derive an analytical scaling for the performance of a solenoid compared with a doublet/triplet as function of the energy, which is confirmed by TRACEWIN simulations. Generally speaking, the two approaches are equivalent in focusing capability, if parameters are such that the solenoid length approximately equals its diameter. The scaling also shows that this is usually not the case above a few MeV; consequently, a solenoid needs to be pulsed or superconducting, whereas the quadrupoles can remain conventional. It is also important that the transmission of the triplet is found only 25% lower than that of the equivalent solenoid. Both systems are equally suitable for energy selection based on their chromatic effect as is shown using an initial distribution following the RPA simulation model by Yan et al. [Phys. Rev. Lett. 103, 135001 (2009PRLTAO0031-900710.1103/PhysRevLett.103.135001].

  1. Energy and Raw Materials in the Selection of Technologies for Iron and Steel

    NASA Astrophysics Data System (ADS)

    Fortini, Otavio Macedo

    2016-09-01

    This paper discusses the selection of metal extraction technologies according to the regional availability of energy resources. The most important energy sources in iron and steel production are determined from a review of current technologies to inform possible future scenarios of capacity replacement or expansion according to geography. Alternative technologies are not discussed, considering that actual investment in capacity is most often dominated by high degrees of risk aversion. As such, only technologies proven at a reasonable scale are included in the selection matrix. Scenarios of capacity choice are defined in terms of actions from external agents, those which are not directly involved in the industry but have the capacity to regulate actions by metal producing players. Two extreme scenarios corresponding to closed and open economies are used to set bounds for future expectations. Among steelmaking processes under fully open trade conditions, it is found that EAF steelmaking with charge pre-heat should be the technology of choice in all regions of the world except for South America and Europe, where Integrated Steel Mills have a cost advantage. In fully closed exchange scenarios, Integrated Steel Mills would be the prevalent technology in South America, Sub-Saharan Africa, India, and the former USSR, EAF with scrap pre-heating prevailing in all other regions. On the other hand, HYL-ZR would be the iron making technology of choice in all regions under full exchange scenarios. Under fully closed exchange conditions, Mini-Blast Furnaces, COREX, and HYL-ZR would find regional applications. Increases in raw materials and energy costs of 38 pct in steelmaking and 63 pct in ironmaking are found in going from fully open to fully closed exchange regimes. It is also found that Southeast Asia is the most suitable region for deploying new steelmaking capacity, while Australia and Russia are the best selection for new iron making capacity.

  2. The influence of mitigation on sage-grouse habitat selection within an energy development field.

    PubMed

    Fedy, Bradley C; Kirol, Christopher P; Sutphin, Andrew L; Maechtle, Thomas L

    2015-01-01

    Growing global energy demands ensure the continued growth of energy development. Energy development in wildlife areas can significantly impact wildlife populations. Efforts to mitigate development impacts to wildlife are on-going, but the effectiveness of such efforts is seldom monitored or assessed. Greater sage-grouse (Centrocercus urophasianus) are sensitive to energy development and likely serve as an effective umbrella species for other sagebrush-steppe obligate wildlife. We assessed the response of birds within an energy development area before and after the implementation of mitigation action. Additionally, we quantified changes in habitat distribution and abundance in pre- and post-mitigation landscapes. Sage-grouse avoidance of energy development at large spatial scales is well documented. We limited our research to directly within an energy development field in order to assess the influence of mitigation in close proximity to energy infrastructure. We used nest-location data (n = 488) within an energy development field to develop habitat selection models using logistic regression on data from 4 years of research prior to mitigation and for 4 years following the implementation of extensive mitigation efforts (e.g., decreased activity, buried powerlines). The post-mitigation habitat selection models indicated less avoidance of wells (well density β = 0.18 ± 0.08) than the pre-mitigation models (well density β = -0.09 ± 0.11). However, birds still avoided areas of high well density and nests were not found in areas with greater than 4 wells per km2 and the majority of nests (63%) were located in areas with ≤ 1 well per km2. Several other model coefficients differed between the two time periods and indicated stronger selection for sagebrush (pre-mitigation β = 0.30 ± 0.09; post-mitigation β = 0.82 ± 0.08) and less avoidance of rugged terrain (pre-mitigation β = -0.35 ± 0.12; post-mitigation β = -0.05 ± 0.09). Mitigation efforts implemented may

  3. The Influence of Mitigation on Sage-Grouse Habitat Selection within an Energy Development Field

    PubMed Central

    Fedy, Bradley C.; Kirol, Christopher P.; Sutphin, Andrew L.; Maechtle, Thomas L.

    2015-01-01

    Growing global energy demands ensure the continued growth of energy development. Energy development in wildlife areas can significantly impact wildlife populations. Efforts to mitigate development impacts to wildlife are on-going, but the effectiveness of such efforts is seldom monitored or assessed. Greater sage-grouse (Centrocercus urophasianus) are sensitive to energy development and likely serve as an effective umbrella species for other sagebrush-steppe obligate wildlife. We assessed the response of birds within an energy development area before and after the implementation of mitigation action. Additionally, we quantified changes in habitat distribution and abundance in pre- and post-mitigation landscapes. Sage-grouse avoidance of energy development at large spatial scales is well documented. We limited our research to directly within an energy development field in order to assess the influence of mitigation in close proximity to energy infrastructure. We used nest-location data (n = 488) within an energy development field to develop habitat selection models using logistic regression on data from 4 years of research prior to mitigation and for 4 years following the implementation of extensive mitigation efforts (e.g., decreased activity, buried powerlines). The post-mitigation habitat selection models indicated less avoidance of wells (well density β = 0.18 ± 0.08) than the pre-mitigation models (well density β = -0.09 ± 0.11). However, birds still avoided areas of high well density and nests were not found in areas with greater than 4 wells per km2 and the majority of nests (63%) were located in areas with ≤ 1 well per km2. Several other model coefficients differed between the two time periods and indicated stronger selection for sagebrush (pre-mitigation β = 0.30 ± 0.09; post-mitigation β = 0.82 ± 0.08) and less avoidance of rugged terrain (pre-mitigation β = -0.35 ± 0.12; post-mitigation β = -0.05 ± 0.09). Mitigation efforts implemented may

  4. [Selective excitation spectra and energy level structure of Dy3+:ThO2 crystal].

    PubMed

    Yin, M; Krupa, J C

    2001-08-01

    Dy3+:ThO2 crystal was grown by the flux technique for the first time. The emission spectra, excitation spectra and fluorescence decay curves were measured and discussed. By using emission spectra obtained under selective dye laser excitation at 12 K, together with the crystal-field theory, the site symmetry of Dy3+ ions in ThO2 was determined as C3 nu and its energy level structure was tabulated. The lifetime of radiative level 4F9/2 was also determined as 0.40 ms.

  5. The characterization and assessment of selected solar thermal energy systems for residential and process heat applications

    NASA Astrophysics Data System (ADS)

    Hyde, J. C.

    1980-09-01

    Results of studies of seven solar thermal energy applications are presented. Five of these are residential applications: space heating--active liquid, space heating--active air, domestic hot water--active, space heating--passive, and space heating and cooling--active liquid. Denver, Colorado, was selected as a representative location for each of the above applications. The remaining two applications produce industrial process heat: a flat plate collector system producing 50 C - 100 C hot water for a commercial laundry in Indianapolis, Indiana; and a concentrating collector system that could produce 100 C - 300 C process heat adequate to the needs of a pulp mill in Madison, Wisconsin.

  6. The comparison and selection of programming languages for high energy physics applications

    SciTech Connect

    White, B.

    1991-06-01

    This paper discusses the issues surrounding the comparison and selection of a programming language to be used in high energy physics software applications. The evaluation method used was specifically devised to address the issues of particular importance to high energy physics (HEP) applications, not just the technical features of the languages considered. The method assumes a knowledge of the requirements of current HEP applications, the data-processing environments expected to support these applications and relevant non-technical issues. The languages evaluated were Ada, C, FORTRAN 77, FORTRAN 99 (formerly 8X), Pascal and PL/1. Particular emphasis is placed upon the past, present and anticipated future role of FORTRAN in HEP software applications. Upon examination of the technical and practical issues, conclusions are reached and some recommendations are made regarding the role of FORTRAN and other programming languages in the current and future development of HEP software. 54 refs.

  7. Surface energy-mediated construction of anisotropic semiconductor wires with selective crystallographic polarity.

    PubMed

    Sohn, Jung Inn; Hong, Woong-Ki; Lee, Sunghoon; Lee, Sanghyo; Ku, JiYeon; Park, Young Jun; Hong, Jinpyo; Hwang, Sungwoo; Park, Kyung Ho; Warner, Jamie H; Cha, SeungNam; Kim, Jong Min

    2014-07-14

    ZnO is a wide band-gap semiconductor with piezoelectric properties suitable for opto-electronics, sensors, and as an electrode material. Controlling the shape and crystallography of any semiconducting nanomaterial is a key step towards extending their use in applications. Whilst anisotropic ZnO wires have been routinely fabricated, precise control over the specific surface facets and tailoring of polar and non-polar growth directions still requires significant refinement. Manipulating the surface energy of crystal facets is a generic approach for the rational design and growth of one-dimensional (1D) building blocks. Although the surface energy is one basic factor for governing crystal nucleation and growth of anisotropic 1D structures, structural control based on surface energy minimization has not been yet demonstrated. Here, we report an electronic configuration scheme to rationally modulate surface electrostatic energies for crystallographic-selective growth of ZnO wires. The facets and orientations of ZnO wires are transformed between hexagonal and rectangular/diamond cross-sections with polar and non-polar growth directions, exhibiting different optical and piezoelectrical properties. Our novel synthetic route for ZnO wire fabrication provides new opportunities for future opto-electronics, piezoelectronics, and electronics, with new topological properties.

  8. Surface energy-mediated construction of anisotropic semiconductor wires with selective crystallographic polarity

    NASA Astrophysics Data System (ADS)

    Sohn, Jung Inn; Hong, Woong-Ki; Lee, Sunghoon; Lee, Sanghyo; Ku, Jiyeon; Park, Young Jun; Hong, Jinpyo; Hwang, Sungwoo; Park, Kyung Ho; Warner, Jamie H.; Cha, Seungnam; Kim, Jong Min

    2014-07-01

    ZnO is a wide band-gap semiconductor with piezoelectric properties suitable for opto-electronics, sensors, and as an electrode material. Controlling the shape and crystallography of any semiconducting nanomaterial is a key step towards extending their use in applications. Whilst anisotropic ZnO wires have been routinely fabricated, precise control over the specific surface facets and tailoring of polar and non-polar growth directions still requires significant refinement. Manipulating the surface energy of crystal facets is a generic approach for the rational design and growth of one-dimensional (1D) building blocks. Although the surface energy is one basic factor for governing crystal nucleation and growth of anisotropic 1D structures, structural control based on surface energy minimization has not been yet demonstrated. Here, we report an electronic configuration scheme to rationally modulate surface electrostatic energies for crystallographic-selective growth of ZnO wires. The facets and orientations of ZnO wires are transformed between hexagonal and rectangular/diamond cross-sections with polar and non-polar growth directions, exhibiting different optical and piezoelectrical properties. Our novel synthetic route for ZnO wire fabrication provides new opportunities for future opto-electronics, piezoelectronics, and electronics, with new topological properties.

  9. Compliant substrate epitaxy: Au on MoS2

    NASA Astrophysics Data System (ADS)

    Zhou, Yuzhi; Kiriya, Daisuke; Haller, E. E.; Ager, Joel W.; Javey, Ali; Chrzan, D. C.

    2016-02-01

    A theory for the epitaxial growth of Au on MoS2 is developed and analyzed. The theory combines continuum linear elasticity theory with density functional theory to analyze epitaxial growth in this system. It is demonstrated that if one accounts for interfacial energies and strains, the presence of misfit dislocations, and the compliance of the MoS2 substrate, the experimentally observed growth orientation is favored despite the fact that it represents a larger elastic mismatch than two competing structures. The stability of the experimentally preferred orientation is attributed to the formation of a large number of strong Au-S bonds, and it is noted that this strong bond may serve as a means to exfoliate and transfer large single layers sheets of MoS2, as well as to engineer strain within single layers of MoS2. The potential for using a van der Waals-bonded layered material as a compliant substrate for applications in 2D electronic devices and epitaxial thin film growth is discussed.

  10. Hydride vapor phase epitaxy of aluminum nitride

    NASA Astrophysics Data System (ADS)

    Kamber, Derrick Shane

    AlN is a promising substrate material for AlGaN-based UV optoelectronic devices and high-power, high-frequency electronic devices. Since large-area bulk AlN crystals are not readily available, one approach to prepare AlN substrates is to heteroepitaxially deposit thick (e.g., 10-300+ mum) AlN layers by hydride vapor phase epitaxy. Initial efforts focused on growing AlN layers on sapphire substrates with growth rates up to 75 mum/hr. The resulting layers were colorless, smooth, and specular. Subsurface cracking, attributed to the plastic relief of tensile strain from island coalescence, was observed but did not adversely affect the surface morphology of the AlN layers. The surfaces possessed rms roughnesses as low as 0.316 nm over 5 x 5 mum2 sampling areas, but hexagonal hillock formation was observed for thick films grown at high growth rates. TEM revealed that the threading dislocation (TD) density of the films was 2 x 109 cm-2. The high TD densities for direct growth of AlN films on foreign substrates motivated the development of lateral epitaxial overgrowth approaches for defect reduction. Growth of AlN layers on patterned SiC substrates produced coalesced AlN films possessing TD densities below 8.3 x 106 cm -2 in the laterally grown wing regions, as compared to 1.8 x 109 cm-2 in the seed regions. These films, however, cracked on cooldown due to the difference in thermal expansion coefficients for AlN and SiC. To avoid this cracking, AlN layers were grown on patterned sapphire substrates. Although the films were able to be coalesced and contained few or no cracks, the TDs in these films were not confined to the seed regions. This produced a relatively uniform distribution of TDs over the surfaces of the films, with only a modest reduction in the TD density of 1 x 10 8 cm-2. Selective area growth of AlN was also pursued using Si3N4, SiO2, and Ti masks. Growth selectivity and film coalescence was observed for films grown on each masking material, but none of the

  11. Epitaxial Halide Perovskite Lateral Double Heterostructure.

    PubMed

    Wang, Yiping; Chen, Zhizhong; Deschler, Felix; Sun, Xin; Lu, Toh-Ming; Wertz, Esther A; Hu, Jia-Mian; Shi, Jian

    2017-03-28

    Epitaxial III-V semiconductor heterostructures are key components in modern microelectronics, electro-optics, and optoelectronics. With superior semiconducting properties, halide perovskite materials are rising as promising candidates for coherent heterostructure devices. In this report, spinodal decomposition is proposed and experimentally implemented to produce epitaxial double heterostructures in halide perovskite system. Pristine epitaxial mixed halide perovskites rods and films were synthesized via van der Waals epitaxy by chemical vapor deposition method. At room temperature, photon was applied as a knob to regulate the kinetics of spinodal decomposition and classic coarsening. By this approach, halide perovskite double heterostructures were created carrying epitaxial interfaces and outstanding optical properties. Reduced Fröhlich electron-phonon coupling was discovered in coherent halide double heterostructure, which is hypothetically attributed to the classic phonon confinement effect widely existing in III-V double heterostructures. As a proof-of-concept, our results suggest that halide perovskite-based epitaxial heterostructures may be promising for high-performance and low-cost optoelectronics, electro-optics, and microelectronics. Thus, ultimately, for practical device applications, it may be worthy to pursue these heterostructures via conventional vapor phase epitaxy approaches widely practised in III-V field.

  12. Inherent surface roughening as a limiting factor in epitaxial cluster deposition

    NASA Astrophysics Data System (ADS)

    Meinander, K.; Nordlund, K.; Keinonen, J.

    2005-01-01

    Deposition of nanoclusters at thermal energies will result in an onset of roughening of the deposited surface. In order to grow epitaxial films using cluster deposition at soft landing conditions, the effect of this inherent surface roughness on the alignment of deposited clusters must be investigated. Using molecular dynamics computer simulations we have determined the maximum size of Cu clusters that will align epitaxially, upon deposition at thermal energies, on rough (1 0 0) Cu substrates with temperatures ranging from 0 K to 750 K. We have also shown that the likelihood of epitaxial alignment for the resulting structures is dependent on the point of impact of a cluster relative to previously deposited clusters.

  13. Ion implanted epitaxially grown ZnSe

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The epitaxial growth of ZnSe on (100) Ge using the close-spaced transport process is described. Substrate temperature of 575 C and source temperatures of 675 C yield 10 micron, single crystal layers in 10 hours. The Ge substrates provides a nonreplenishable chemical transport agent and the epitaxial layer thickness is limited to approximately 10 microns. Grown epitaxial layers show excellent photoluminescence structure at 77 K. Grown layers exhibit high resistivity, and annealing in Zn vapor at 575 C reduces the resistivity to 10-100 ohms-cm. Zinc vapor annealing quenches the visible photoluminescence.

  14. Electroless epitaxial etching for semiconductor applications

    DOEpatents

    McCarthy, Anthony M.

    2002-01-01

    A method for fabricating thin-film single-crystal silicon on insulator substrates using electroless etching for achieving efficient etch stopping on epitaxial silicon substrates. Microelectric circuits and devices are prepared on epitaxial silicon wafers in a standard fabrication facility. The wafers are bonded to a holding substrate. The silicon bulk is removed using electroless etching leaving the circuit contained within the epitaxial layer remaining on the holding substrate. A photolithographic operation is then performed to define streets and wire bond pad areas for electrical access to the circuit.

  15. Large-Area Dry Transfer of Single-Crystalline Epitaxial Bismuth Thin Films.

    PubMed

    Walker, Emily S; Na, Seung Ryul; Jung, Daehwan; March, Stephen D; Kim, Joon-Seok; Trivedi, Tanuj; Li, Wei; Tao, Li; Lee, Minjoo L; Liechti, Kenneth M; Akinwande, Deji; Bank, Seth R

    2016-11-09

    We report the first direct dry transfer of a single-crystalline thin film grown by molecular beam epitaxy. A double cantilever beam fracture technique was used to transfer epitaxial bismuth thin films grown on silicon (111) to silicon strips coated with epoxy. The transferred bismuth films retained electrical, optical, and structural properties comparable to the as-grown epitaxial films. Additionally, we isolated the bismuth thin films on freestanding flexible cured-epoxy post-transfer. The adhesion energy at the bismuth/silicon interface was measured to be ∼1 J/m(2), comparable to that of exfoliated and wet transferred graphene. This low adhesion energy and ease of transfer is unexpected for an epitaxially grown film and may enable the study of bismuth's unique electronic and spintronic properties on arbitrary substrates. Moreover, this method suggests a route to integrate other group-V epitaxial films (i.e., phosphorus) with arbitrary substrates, as well as potentially to isolate bismuthene, the atomic thin-film limit of bismuth.

  16. Selected configuration interaction with truncation energy error and application to the Ne atom.

    PubMed

    Bunge, Carlos F

    2006-07-07

    Selected configuration interaction (SCI) for atomic and molecular electronic structure calculations is reformulated in a general framework encompassing all CI methods. The linked cluster expansion is used as an intermediate device to approximate CI coefficients B(K) of disconnected configurations (those that can be expressed as products of combinations of singly and doubly excited ones) in terms of CI coefficients of lower-excited configurations where each K is a linear combination of configuration-state-functions (CSFs) over all degenerate elements of K. Disconnected configurations up to sextuply excited ones are selected by Brown's energy formula, Delta E(K) = (E-H(KK))B(K)2/(1-B(K)2), with B(K) determined from coefficients of singly and doubly excited configurations. The truncation energy error from disconnected configurations, Delta E(dis), is approximated by the sum of Delta E(K)s of all discarded Ks. The remaining (connected) configurations are selected by thresholds based on natural orbital concepts. Given a model CI space M, a usual upper bound E(S) is computed by CI in a selected space S, and E(M) = E(S) + Delta E(dis) + delta E, where delta E is a residual error which can be calculated by well-defined sensitivity analyses. An SCI calculation on Ne ground state featuring 1077 orbitals is presented. Convergence to within near spectroscopic accuracy (0.5 cm(-1)) is achieved in a model space M of 1.4 x 10(9) CSFs (1.1 x 10(12) determinants) containing up to quadruply excited CSFs. Accurate energy contributions of quintuples and sextuples in a model space of 6.5 x 10(12) CSFs are obtained. The impact of SCI on various orbital methods is discussed. Since Delta E(dis) can readily be calculated for very large basis sets without the need of a CI calculation, it can be used to estimate the orbital basis incompleteness error. A method for precise and efficient evaluation of E(S) is taken up in a companion paper.

  17. A Study of Quasar Selection in the Supernova Fields of the Dark Energy Survey

    NASA Astrophysics Data System (ADS)

    Tie, S. S.; Martini, P.; Mudd, D.; Ostrovski, F.; Reed, S. L.; Lidman, C.; Kochanek, C.; Davis, T. M.; Sharp, R.; Uddin, S.; King, A.; Wester, W.; Tucker, B. E.; Tucker, D. L.; Buckley-Geer, E.; Carollo, D.; Childress, M.; Glazebrook, K.; Hinton, S. R.; Lewis, G.; Macaulay, E.; O'Neill, C. R.; Abbott, T. M. C.; Abdalla, F. B.; Annis, J.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Finley, D. A.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Menanteau, F.; Miller, C. J.; Miquel, R.; Nichol, R. C.; Nord, B.; Ogando, R.; Plazas, A. A.; Romer, A. K.; Sanchez, E.; Santiago, B.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Walker, A. R.; DES Collaboration

    2017-03-01

    We present a study of quasar selection using the supernova fields of the Dark Energy Survey (DES). We used a quasar catalog from an overlapping portion of the SDSS Stripe 82 region to quantify the completeness and efficiency of selection methods involving color, probabilistic modeling, variability, and combinations of color/probabilistic modeling with variability. In all cases, we considered only objects that appear as point sources in the DES images. We examine color selection methods based on the Wide-field Infrared Survey Explorer (WISE) mid-IR W1-W2 color, a mixture of WISE and DES colors (g ‑ i and i-W1), and a mixture of Vista Hemisphere Survey and DES colors (g ‑ i and i ‑ K). For probabilistic quasar selection, we used XDQSO, an algorithm that employs an empirical multi-wavelength flux model of quasars to assign quasar probabilities. Our variability selection uses the multi-band χ 2-probability that sources are constant in the DES Year 1 griz-band light curves. The completeness and efficiency are calculated relative to an underlying sample of point sources that are detected in the required selection bands and pass our data quality and photometric error cuts. We conduct our analyses at two magnitude limits, i < 19.8 mag and i < 22 mag. For the subset of sources with W1 and W2 detections, the W1-W2 color or XDQSOz method combined with variability gives the highest completenesses of >85% for both i-band magnitude limits and efficiencies of >80% to the bright limit and >60% to the faint limit; however, the giW1 and giW1+variability methods give the highest quasar surface densities. The XDQSOz method and combinations of W1W2/giW1/XDQSOz with variability are among the better selection methods when both high completeness and high efficiency are desired. We also present the OzDES Quasar Catalog of 1263 spectroscopically confirmed quasars from three years of OzDES observation in the 30 deg2 of the DES supernova fields. The catalog includes quasars with

  18. A Study of Quasar Selection in the Supernova Fields of the Dark Energy Survey

    DOE PAGES

    Tie, S. S.; Martini, P.; Mudd, D.; ...

    2017-02-15

    In this paper, we present a study of quasar selection using the supernova fields of the Dark Energy Survey (DES). We used a quasar catalog from an overlapping portion of the SDSS Stripe 82 region to quantify the completeness and efficiency of selection methods involving color, probabilistic modeling, variability, and combinations of color/probabilistic modeling with variability. In all cases, we considered only objects that appear as point sources in the DES images. We examine color selection methods based on the Wide-field Infrared Survey Explorer (WISE) mid-IR W1-W2 color, a mixture of WISE and DES colors (g - i and i-W1),more » and a mixture of Vista Hemisphere Survey and DES colors (g - i and i - K). For probabilistic quasar selection, we used XDQSO, an algorithm that employs an empirical multi-wavelength flux model of quasars to assign quasar probabilities. Our variability selection uses the multi-band χ2-probability that sources are constant in the DES Year 1 griz-band light curves. The completeness and efficiency are calculated relative to an underlying sample of point sources that are detected in the required selection bands and pass our data quality and photometric error cuts. We conduct our analyses at two magnitude limits, i < 19.8 mag and i < 22 mag. For the subset of sources with W1 and W2 detections, the W1-W2 color or XDQSOz method combined with variability gives the highest completenesses of >85% for both i-band magnitude limits and efficiencies of >80% to the bright limit and >60% to the faint limit; however, the giW1 and giW1+variability methods give the highest quasar surface densities. The XDQSOz method and combinations of W1W2/giW1/XDQSOz with variability are among the better selection methods when both high completeness and high efficiency are desired. We also present the OzDES Quasar Catalog of 1263 spectroscopically confirmed quasars from three years of OzDES observation in the 30 deg2 of the DES supernova fields. Finally, the catalog

  19. Assessing risk to birds from industrial wind energy development via paired resource selection models.

    PubMed

    Miller, Tricia A; Brooks, Robert P; Lanzone, Michael; Brandes, David; Cooper, Jeff; O'Malley, Kieran; Maisonneuve, Charles; Tremblay, Junior; Duerr, Adam; Katzner, Todd

    2014-06-01

    When wildlife habitat overlaps with industrial development animals may be harmed. Because wildlife and people select resources to maximize biological fitness and economic return, respectively, we estimated risk, the probability of eagles encountering and being affected by turbines, by overlaying models of resource selection for each entity. This conceptual framework can be applied across multiple spatial scales to understand and mitigate impacts of industry on wildlife. We estimated risk to Golden Eagles (Aquila chrysaetos) from wind energy development in 3 topographically distinct regions of the central Appalachian Mountains of Pennsylvania (United States) based on models of resource selection of wind facilities (n = 43) and of northbound migrating eagles (n = 30). Risk to eagles from wind energy was greatest in the Ridge and Valley region; all 24 eagles that passed through that region used the highest risk landscapes at least once during low altitude flight. In contrast, only half of the birds that entered the Allegheny Plateau region used highest risk landscapes and none did in the Allegheny Mountains. Likewise, in the Allegheny Mountains, the majority of wind turbines (56%) were situated in poor eagle habitat; thus, risk to eagles is lower there than in the Ridge and Valley, where only 1% of turbines are in poor eagle habitat. Risk within individual facilities was extremely variable; on average, facilities had 11% (SD 23; range = 0-100%) of turbines in highest risk landscapes and 26% (SD 30; range = 0-85%) of turbines in the lowest risk landscapes. Our results provide a mechanism for relocating high-risk turbines, and they show the feasibility of this novel and highly adaptable framework for managing risk of harm to wildlife from industrial development.

  20. Energy-aware Gateway Selection for increasing the lifetime of Wireless Body Area Sensor Networks.

    PubMed

    Bayilmis, Cuneyt; Younis, Mohamed

    2012-06-01

    A Wireless Body Area Sensor Network (WBASN) is composed of a set of sensor nodes, placed on, near or within a human body. WBASNs opt to continuously monitor the health conditions of individuals under medical risk, e.g., elders and chronically ill people, without keeping them in a hospital or restraining their motion. A WBASN needs to stay connected to local or wide area networks using wireless technologies in order to send sensor readings to a medical center. The WBASN nodes are implanted within the human body and would thus have limited energy supply. Since the mission of the WBASN is very critical, increasing the lifetime of nodes is essential in order to maintain both practicality and effectiveness. This paper presents a new Gateway Selection Algorithm (GSA) that factors in the use of energy harvesting technologies and dynamically picks the most suitable WBASN node that serves as a gateway to other wireless networks. The goal of GSA is to balance the load among the nodes by adaptively changing the gateway node in WBASN depending on the energy reserve of nodes. Computer modeling and simulations of the proposed GSA are carried out using OPNET. The simulation results demonstrate the effectiveness of the proposed GSA approach.

  1. Predicting and mapping potential Whooping Crane stopover habitat to guide site selection for wind energy projects.

    PubMed

    Belaire, J Amy; Kreakie, Betty J; Keitt, Timothy; Minor, Emily

    2014-04-01

    Migratory stopover habitats are often not part of planning for conservation or new development projects. We identified potential stopover habitats within an avian migratory flyway and demonstrated how this information can guide the site-selection process for new development. We used the random forests modeling approach to map the distribution of predicted stopover habitat for the Whooping Crane (Grus americana), an endangered species whose migratory flyway overlaps with an area where wind energy development is expected to become increasingly important. We then used this information to identify areas for potential wind power development in a U.S. state within the flyway (Nebraska) that minimize conflicts between Whooping Crane stopover habitat and the development of clean, renewable energy sources. Up to 54% of our study area was predicted to be unsuitable as Whooping Crane stopover habitat and could be considered relatively low risk for conflicts between Whooping Cranes and wind energy development. We suggest that this type of analysis be incorporated into the habitat conservation planning process in areas where incidental take permits are being considered for Whooping Cranes or other species of concern. Field surveys should always be conducted prior to construction to verify model predictions and understand baseline conditions.

  2. Optical and electrical properties of high-quality Ti2O3 epitaxial film grown on sapphire substrate

    NASA Astrophysics Data System (ADS)

    Fan, Haibo; Wang, Mingzi; Yang, Zhou; Ren, Xianpei; Yin, Mingli; Liu, Shengzhong

    2016-11-01

    Epitaxial film of Ti2O3 with high crystalline quality was grown on Al2O3 substrate by pulsed laser deposition process using a powder-pressed TiO2 target in active O2 flow. X-ray diffraction clearly reveals the (0006) crystalline Ti2O3 orientation and its (10overline{1} 0)_{{{{Ti}}_{ 2} {{O}}_{ 3} }} ||(10overline{1} 0)_{{sapphire}} in-plane epitaxial relationship with the substrate. Scanning electron microscopy images show that the film grew uniformly on the substrate with a Volmer-Weber mode. High-resolution transmission electron microscopy and selected area electron diffraction further confirm the high crystalline quality of the film. Transmittance spectrum shows that the Ti2O3 film is highly transparent in 400-800 nm with the optical band gap estimated to be 3.53 eV by Tauc plot. The temperature-dependent Hall effect measurement indicates that the Ti2O3 film appears to be n-type semiconductor with carrier concentration, mobility, and resistivity showing typical temperature-dependent behavior. The donor ionization energy was estimated to be 83.6 meV by linear relationship of conductivity versus temperature.

  3. Epitaxial growth of silicon for layer transfer

    DOEpatents

    Teplin, Charles; Branz, Howard M

    2015-03-24

    Methods of preparing a thin crystalline silicon film for transfer and devices utilizing a transferred crystalline silicon film are disclosed. The methods include preparing a silicon growth substrate which has an interface defining substance associated with an exterior surface. The methods further include depositing an epitaxial layer of silicon on the silicon growth substrate at the surface and separating the epitaxial layer from the substrate substantially along the plane or other surface defined by the interface defining substance. The epitaxial layer may be utilized as a thin film of crystalline silicon in any type of semiconductor device which requires a crystalline silicon layer. In use, the epitaxial transfer layer may be associated with a secondary substrate.

  4. Amorphous/epitaxial superlattice for thermoelectric application

    NASA Astrophysics Data System (ADS)

    Ishida, Akihiro; Thao, Hoang Thi Xuan; Shibata, Mamoru; Nakashima, Seisuke; Tatsuoka, Hirokazu; Yamamoto, Hidenari; Kinoshita, Yohei; Ishikiriyama, Mamoru; Nakamura, Yoshiaki

    2016-08-01

    An amorphous/epitaxial superlattice system is proposed for application to thermoelectric devices, and the superlattice based on a PbGeTeS system was prepared by the alternate deposition of PbS and GeTe using a hot wall epitaxy technique. The structure was analyzed by high-resolution transmission electron microscopy (HRTEM) and X-ray analysis, and it was found that the superlattice consists of an epitaxial PbTe-based layer and a GeS-based amorphous layer by the reconstruction of the constituents. A reduction in thermal conductivity due to the amorphous/epitaxial system was confirmed by a 2ω method. Electrical and thermoelectric properties were measured for the samples.

  5. Overall Energy Considerations for Algae Species Comparison and Selection in Algae-to-Fuels Processes

    SciTech Connect

    Link, D.; Kail, B.; Curtis, W.; Tuerk,A.

    2011-01-01

    The controlled growth of microalgae as a feedstock for alternative transportation fuel continues to receive much attention. Microalgae have the characteristics of rapid growth rate, high oil (lipid) content, and ability to be grown in unconventional scenarios. Algae have also been touted as beneficial for CO{sub 2} reuse, as algae can be grown using CO{sub 2} emissions from fossil-based energy generation. Moreover, algae does not compete in the food chain, lessening the 'food versus fuel' debate. Most often, it is assumed that either rapid production rate or high oii content should be the primary factor in algae selection for algae-to-fuels production systems. However, many important characteristics of algae growth and lipid production must be considered for species selection, growth condition, and scale-up. Under light limited, high density, photoautotrophic conditions, the inherent growth rate of an organism does not affect biomass productivity, carbon fixation rate, and energy fixation rate. However, the oil productivity is organism dependent, due to physiological differences in how the organisms allocate captured photons for growth and oil production and due to the differing conditions under which organisms accumulate oils. Therefore, many different factors must be considered when assessing the overall energy efficiency of fuel production for a given algae species. Two species, Chlorella vulgaris and Botryococcus braunii, are popular choices when discussing algae-to-fuels systems. Chlorella is a very robust species, often outcompeting other species in mixed-culture systems, and produces a lipid that is composed primarily of free fatty acids and glycerides. Botryococcus is regarded as a slower growing species, and the lipid that it produces is characterized by high hydrocarbon content, primarily C28-C34 botryococcenes. The difference in growth rates is often considered to be an advantage oiChlorella. However, the total energy captured by each algal species in

  6. Microbial catabolic activities are naturally selected by metabolic energy harvest rate

    PubMed Central

    González-Cabaleiro, Rebeca; Ofiţeru, Irina D; Lema, Juan M; Rodríguez, Jorge

    2015-01-01

    The fundamental trade-off between yield and rate of energy harvest per unit of substrate has been largely discussed as a main characteristic for microbial established cooperation or competition. In this study, this point is addressed by developing a generalized model that simulates competition between existing and not experimentally reported microbial catabolic activities defined only based on well-known biochemical pathways. No specific microbial physiological adaptations are considered, growth yield is calculated coupled to catabolism energetics and a common maximum biomass-specific catabolism rate (expressed as electron transfer rate) is assumed for all microbial groups. Under this approach, successful microbial metabolisms are predicted in line with experimental observations under the hypothesis of maximum energy harvest rate. Two microbial ecosystems, typically found in wastewater treatment plants, are simulated, namely: (i) the anaerobic fermentation of glucose and (ii) the oxidation and reduction of nitrogen under aerobic autotrophic (nitrification) and anoxic heterotrophic and autotrophic (denitrification) conditions. The experimentally observed cross feeding in glucose fermentation, through multiple intermediate fermentation pathways, towards ultimately methane and carbon dioxide is predicted. Analogously, two-stage nitrification (by ammonium and nitrite oxidizers) is predicted as prevailing over nitrification in one stage. Conversely, denitrification is predicted in one stage (by denitrifiers) as well as anammox (anaerobic ammonium oxidation). The model results suggest that these observations are a direct consequence of the different energy yields per electron transferred at the different steps of the pathways. Overall, our results theoretically support the hypothesis that successful microbial catabolic activities are selected by an overall maximum energy harvest rate. PMID:26161636

  7. Chemical beam epitaxy for high efficiency photovoltaic devices

    NASA Technical Reports Server (NTRS)

    Bensaoula, A.; Freundlich, A.; Vilela, M. F.; Medelci, N.; Renaud, P.

    1994-01-01

    InP-based multijunction tandem solar cells show great promise for the conversion efficiency (eta) and high radiation resistance. InP and its related ternary and quanternary compound semiconductors such as InGaAs and InGaAsP offer desirable combinations for energy bandgap values which are very suitable for multijunction tandem solar cell applications. The monolithically integrated InP/In(0.53)Ga(0.47)As tandem solar cells are expected to reach efficiencies above 30 percent. Wanlass, et.al., have reported AMO efficiencies as high as 20.1% for two terminal cells fabricated using atmospheric-pressure metalorganic vapor phase epitaxy (APMOVPE). The main limitations in their technique are first related to the degradation of the intercell ohmic contact (IOC), in this case the In(0.53)Ga(0.47)As tunnel junction during the growth of the top InP subcell structure, and second to the current matching, often limited by the In(0.53)Ga(0.47)As bottom subcell. Chemical beam epitaxy (CBE) has been shown to allow the growth of high quality materials with reproducible complex compositional and doping profiles. The main advantage of CBE compared to metalorganic chemical vapor deposition (MOCVD), the most popular technique for InP-based photovoltaic device fabrication, is the ability to grow high purity epilayers at much lower temperatures (450 C - 530 C). In a recent report it was shown that cost-wise CBE is a breakthrough technology for photovoltaic (PV) solar energy progress in the energy conversion efficiency of InP-based solar cells fabricated using chemical beam epitaxy. This communication summarizes our recent results on PV devices and demonstrates the strength of this new technology.

  8. Silicon Holder For Molecular-Beam Epitaxy

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael E.; Grunthaner, Paula J.; Grunthaner, Frank J.

    1993-01-01

    Simple assembly of silicon wafers holds silicon-based charge-coupled device (CCD) during postprocessing in which silicon deposited by molecular-beam epitaxy. Attains temperatures similar to CCD, so hotspots suppressed. Coefficients of thermal expansion of holder and CCD equal, so thermal stresses caused by differential thermal expansion and contraction do not develop. Holder readily fabricated, by standard silicon processing techniques, to accommodate various CCD geometries. Silicon does not contaminate CCD or molecular-beam-epitaxy vacuum chamber.

  9. Epitaxial Deposition Of Germanium Doped With Gallium

    NASA Technical Reports Server (NTRS)

    Huffman, James E.

    1994-01-01

    Epitaxial layers of germanium doped with gallium made by chemical vapor deposition. Method involves combination of techniques and materials used in chemical vapor deposition with GeH4 or GeCl4 as source of germanium and GaCl3 as source of gallium. Resulting epitaxial layers of germanium doped with gallium expected to be highly pure, with high crystalline quality. High-quality material useful in infrared sensors.

  10. Experimental measurement of binding energy, selectivity, and allostery using fluctuation theorems.

    PubMed

    Camunas-Soler, Joan; Alemany, Anna; Ritort, Felix

    2017-01-27

    Thermodynamic bulk measurements of binding reactions rely on the validity of the law of mass action and the assumption of a dilute solution. Yet, important biological systems such as allosteric ligand-receptor binding, macromolecular crowding, or misfolded molecules may not follow these assumptions and may require a particular reaction model. Here we introduce a fluctuation theorem for ligand binding and an experimental approach using single-molecule force spectroscopy to determine binding energies, selectivity, and allostery of nucleic acids and peptides in a model-independent fashion. A similar approach could be used for proteins. This work extends the use of fluctuation theorems beyond unimolecular folding reactions, bridging the thermodynamics of small systems and the basic laws of chemical equilibrium.

  11. Delayed Shutters For Dual-Beam Molecular Epitaxy

    NASA Technical Reports Server (NTRS)

    Grunthaner, Frank J.; Liu, John L.; Hancock, Bruce

    1989-01-01

    System of shutters for dual-molecular-beam epitaxy apparatus delays start of one beam with respect to another. Used in pulsed-beam equipment for deposition of low-dislocation layers of InAs on GaAs substrates, system delays application of arsenic beam with respect to indium beam to assure proper stoichiometric proportions on newly forming InAs surface. Reflectance high-energy electron diffraction (RHEED) instrument used to monitor condition of evolving surface of deposit. RHEED signal used to time pulsing of molecular beams in way that minimizes density of defects and holds lattice constant of InAs to that of GaAs substrate.

  12. Modeling of Gallium Nitride Hydride Vapor Phase Epitaxy

    NASA Technical Reports Server (NTRS)

    Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

    1997-01-01

    A reactor model for the hydride vapor phase epitaxy of GaN is presented. The governing flow, energy, and species conservation equations are solved in two dimensions to examine the growth characteristics as a function of process variables and reactor geometry. The growth rate varies with GaCl composition but independent of NH3 and H2 flow rates. A change in carrier gas for Ga source from H2 to N2 affects the growth rate and uniformity for a fixed reactor configuration. The model predictions are in general agreement with observed experimental behavior.

  13. The Demand for Scientific and Technical Manpower in Selected Energy-Related Industries, 1970-85: A Methodology Applied to a Selected Scenario of Energy Output. A Summary.

    ERIC Educational Resources Information Center

    Gutmanis, Ivars; And Others

    The primary purpose of the study was to develop and apply a methodology for estimating the need for scientists and engineers by specialty in energy and energy-related industries. The projections methodology was based on the Case 1 estimates by the National Petroleum Council of the results of "maximum efforts" to develop domestic fuel sources by…

  14. Sharp chemical interface in epitaxial Fe{sub 3}O{sub 4} thin films

    SciTech Connect

    Gálvez, S.; Rubio-Zuazo, J. Salas-Colera, E.; Muñoz-Noval, A.; Castro, G. R.

    2014-12-15

    Chemically sharp interface was obtained on single phase single oriented Fe{sub 3}O{sub 4} (001) thin film (7 nm) grown on NiO (001) substrate using oxygen assisted molecular beam epitaxy. Refinement of the atomic structure, stoichiometry, and oxygen vacancies were determined by soft and hard x-ray photoelectron spectroscopy, low energy electron diffraction and synchrotron based X-ray reflectivity, and X-ray diffraction. Our results demonstrate an epitaxial growth of the magnetite layer, perfect iron stoichiometry, absence of oxygen vacancies, and the existence of an intermixing free interface. Consistent magnetic and electrical characterizations are also shown.

  15. Perpendicularly magnetized τ-MnAl (001) thin films epitaxied on GaAs

    NASA Astrophysics Data System (ADS)

    Nie, S. H.; Zhu, L. J.; Lu, J.; Pan, D.; Wang, H. L.; Yu, X. Z.; Xiao, J. X.; Zhao, J. H.

    2013-04-01

    Perpendicularly magnetized τ-MnAl films have been epitaxied on GaAs (001) by molecular-beam epitaxy. Crystalline quality and magnetic properties of the samples were strongly dependent on growth temperature. The highest coercivity of 10.7 kOe, saturation magnetization of 361.4 emu/cm3, perpendicular magnetic anisotropy constant of 13.65 Merg/cm3, and magnetic energy product of 4.44 MGOe were achieved. These tunable magnetic properties make MnAl films valuable as excellent and cost-effective alternative for not only high density perpendicular magnetic recording storage and spintronics devices but also permanent magnets.

  16. Mn-assisted molecular-beam epitaxy growth (Ga,Mn)As nanowires

    NASA Astrophysics Data System (ADS)

    Reznik, R. R.; Samsonenko, Yu B.; Khrebtov, A. I.; Bouravleuv, A. D.; Werner, P.; Cirlin, G. E.

    2016-11-01

    Arrays of (Ga,Mn)As crystal nanowires on a GaAs (100) substrate were obtained using molecular-beam epitaxy at the substrate temperature 485°C. From the high energy electron diffraction patterns, the crystallographic phase of the nanowires is detected to be cubic which is supporting by ex situ microscopy study.

  17. Conceptual framework for describing selected urban and community impacts of federal energy policies

    SciTech Connect

    Morris, F.A,; Marcus, A.A.; Keller, D.

    1980-06-01

    A conceptual framework is presented for describing selected urban and community impacts of Federal energy policies. The framework depends on a simple causal model. The outputs of the model are impacts, changes in the state of the world of particular interest to policymakers. At any given time, a set of determinants account for the state of the world with respect to an impact category. Application of the model to a particular impact category requires: establishing a definition and measure for the impact category and identifying the determinants of these impacts. Analysis of the impact of a particular policy requires the following: identifying the policy and its effects (as estimated by others), isolating any effects that themselves constitute an urban and community impact, identifying any effects that change the value of determinants, and describing the impact with reference to the new values of determinants. This report provides a framework for these steps. Three impacts addressed are: neighborhood stability, housing availability, and quality and availability of public services. In each chapter, a definition and measure for the impact are specified; its principal determinants are identified; how the causal model can be used to estimate impacts by applying it to three illustrative Federal policies (domestic oil price decontrol, building energy performance standards, and increased Federal aid for mass transit) is demonstrated. (MCW)

  18. Cyclotron resonance in epitaxial Bi1-xSbx films grown by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Heremans, J.; Partin, D. L.; Thrush, C. M.; Karczewski, G.; Richardson, M. S.; Furdyna, J. K.

    1993-10-01

    The far-infrared magnetotransmission of thin films of semiconducting and semimetallic Bi1-xSbx alloys grown by molecular-beam epitaxy has been measured at fixed photon energies between 2.5 and 21.4 meV in magnetic fields up to 6 T, at T=1.8 K. The samples, grown on BaF2 substrates with composition 0<=x<=22.5%, were monocrystalline, with the trigonal axis perpendicular to the surface plane. The measurements were carried out in Faraday and Voigt geometries, with the magnetic field oriented parallel to binary, bisectrix, and trigonal axes of the films. Cyclotron-resonance lines of both electrons and holes were observed. From them, we establish the composition dependence of the effective-mass tensor, of the direct L-point band gap, and of the energy overlap in the semimetallic samples. We conclude that all band-structure parameters are the same in the films as in bulk Bi1-xSbx alloys, except for the energy overlap, which is increased by 16 meV independently of composition, possibly because of the strain induced by the substrate.

  19. Design of a large acceptance, high efficiency energy selection system for the ELIMAIA beam-line

    NASA Astrophysics Data System (ADS)

    Schillaci, F.; Maggiore, M.; Andó, L.; Cirrone, G. A. P.; Cuttone, G.; Romano, F.; Scuderi, V.; Allegra, L.; Amato, A.; Gallo, G.; Korn, G.; Leanza, R.; Margarone, D.; Milluzzo, G.; Petringa, G.

    2016-08-01

    A magnetic chicane based on four electromagnetic dipoles is going to be realized by INFN-LNS to be used as an Energy Selection System (ESS) for laser driven proton beams up to 300 MeV and C6+ up to 70 MeV/u. The system will provide, as output, ion beams with a contrallable energy spread varying from 5% up to 20% according to the aperture slit size. Moreover, it has a very wide acceptance in order to ensure a very high transmission efficiency and, in principle, it has been designed to be used also as an active energy modulator. This system is the core element of the ELIMED (ELI-Beamlines MEDical and Multidisciplinary applications) beam transport, dosimetry and irradiation line that will be developed by INFN-LNS (It) and installed at the ELI-Beamlines facility in Prague (Cz). ELIMED will be the first user's open transport beam-line where a controlled laser-driven ion beam will be used for multidisciplinary research. The definition of well specified characteristics, both in terms of performance and field quality, of the magnetic chicane is crucial for the system realization, for the accurate study of the beam dynamics and for the proper matching with the Permanent Magnet Quadrupoles (PMQs) used as a collection system already designed. Here, the design of the magnetic chicane is described in details together with the adopted solutions in order to realize a robust system form the magnetic point of view. Moreover, the first preliminary transport simulations are also described showing the good performance of the whole beam line (PMQs+ESS).

  20. Advances in modeling semiconductor epitaxy: Contributions of growth orientation and surface reconstruction to InN metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Kusaba, Akira; Kangawa, Yoshihiro; Kempisty, Pawel; Shiraishi, Kenji; Kakimoto, Koichi; Koukitu, Akinori

    2016-12-01

    We propose a newly improved thermodynamic analysis method that incorporates surface energies. The new theoretical approach enables us to investigate the effects of the growth orientation and surface reconstruction. The obtained knowledge would be indispensable for examining the preferred growth conditions in terms of the contribution of the surface state. We applied the theoretical approach to study the growth processes of InN(0001) and (000\\bar{1}) by metalorganic vapor phase epitaxy. Calculation results reproduced the difference in optimum growth temperature. That is, we successfully developed a new theoretical approach that can predict growth processes on various growth surfaces.

  1. Epitaxial strain-engineered self-assembly of magnetic nanostructures in FeRh thin films

    NASA Astrophysics Data System (ADS)

    Witte, Ralf; Kruk, Robert; Molinari, Alan; Wang, Di; Schlabach, Sabine; Brand, Richard A.; Provenzano, Virgil; Hahn, Horst

    2017-01-01

    In this paper we introduce an innovative bottom-up approach for engineering self-assembled magnetic nanostructures using epitaxial strain-induced twinning and phase separation. X-ray diffraction, 57Fe Mössbauer spectroscopy, scanning tunneling microscopy, and transmission electron microscopy show that epitaxial films of a near-equiatomic FeRh alloy respond to the applied epitaxial strain by laterally splitting into two structural phases on the nanometer length scale. Most importantly, these two structural phases differ with respect to their magnetic properties, one being paramagnetic and the other ferromagnetic, thus leading to the formation of a patterned magnetic nanostructure. It is argued that the phase separation directly results from the different strain-dependence of the total energy of the two competing phases. This straightforward relation directly enables further tailoring and optimization of the nanostructures’ properties.

  2. Low temperature growth of crystalline magnesium oxide on hexagonal silicon carbide (0001) by molecular beam epitaxy

    SciTech Connect

    Goodrich, T. L.; Parisi, J.; Cai, Z.; Ziemer, K. S.

    2007-01-22

    Magnesium oxide (111) was grown epitaxially on hexagonal silicon carbide (6H-SiC) (0001) substrates at low temperatures by molecular beam epitaxy and a remote oxygen plasma source. The films were characterized by reflection high-energy electron diffraction, Auger electron spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscopy. Crystal structure, morphology, and growth rate of the magnesium oxide (MgO) films were found to be dependent on the magnesium flux, indicating a magnesium adsorption controlled growth mechanism. The single crystalline MgO thin films had an epitaxial relationship where MgO (111) parallel 6H-SiC (0001) and were stable in both air and 10{sup -9} Torr up to 1023 K.

  3. Growth of epitaxial iron nitride ultrathin film on zinc-blende gallium nitride

    SciTech Connect

    Pak, J.; Lin, W.; Wang, K.; Chinchore, A.; Shi, M.; Ingram, D. C.; Smith, A. R.; Sun, K.; Lucy, J. M.; Hauser, A. J.; Yang, F. Y.

    2010-07-15

    The authors report the growth of iron nitride on zinc-blende gallium nitride using molecular beam epitaxy. First, zinc-blende GaN is grown on a magnesium oxide substrate having (001) orientation; second, an ultrathin layer of FeN is grown on top of the GaN layer. In situ reflection high-energy electron diffraction is used to monitor the surface during growth, and a well-defined epitaxial relationship is observed. Cross-sectional transmission electron microscopy is used to reveal the epitaxial continuity at the gallium nitride-iron nitride interface. Surface morphology of the iron nitride, similar to yet different from that of the GaN substrate, can be described as plateau valley. The FeN chemical stoichiometry is probed using both bulk and surface sensitive methods, and the magnetic properties of the sample are revealed.

  4. Decoupling of epitaxial graphene via gold intercalation probed by dispersive Raman spectroscopy

    SciTech Connect

    Pillai, P. B. E-mail: m.desouza@sheffield.ac.uk; DeSouza, M. E-mail: m.desouza@sheffield.ac.uk; Narula, R.; Reich, S.; Wong, L. Y.; Batten, T.; Pokorny, J.

    2015-05-14

    Signatures of a superlattice structure composed of a quasi periodic arrangement of atomic gold clusters below an epitaxied graphene (EG) layer are examined using dispersive Raman spectroscopy. The gold-graphene system exhibits a laser excitation energy dependant red shift of the 2D mode as compared to pristine epitaxial graphene. The phonon dispersions in both the systems are mapped using the experimentally observed Raman signatures and a third-nearest neighbour tight binding electronic band structure model. Our results reveal that the observed excitation dependent Raman red shift in gold EG primarily arise from the modifications of the phonon dispersion in gold-graphene and shows that the extent of decoupling of graphene from the underlying SiC substrate can be monitored from the dispersive nature of the Raman 2D modes. The intercalated gold atoms restore the phonon band structure of epitaxial graphene towards free standing graphene.

  5. Energy from biological processes. Volume III. Appendixes, Part B: Agriculture, unconventional crops, and select biomass wastes

    SciTech Connect

    Not Available

    1980-09-01

    This volume contains the following working papers written for OTA to assist in preparation of the report, Energy from Biological Processes: The Potential of Producing Energy From Agriculture; Cropland Availability for Biomass Production; Energy From Agriculture: Unconventional Crops; Energy From Aquaculture Biomass Systems: Fresh and Brackish Water Aquatic Plants; Energy From Agriculture: Animal Wastes; and Energy From Agriculture: Agricultural Processing Wastes.

  6. Microstructure of Co/X (X=Cu,Ag,Au) epitaxial thin films grown on Al{sub 2}O{sub 3}(0001) substrates

    SciTech Connect

    Ohtake, Mitsuru; Akita, Yuta; Futamoto, Masaaki; Kirino, Fumiyoshi

    2007-05-01

    Epitaxial thin films of Co/X (X=Cu,Ag,Au) were prepared on Al{sub 2}O{sub 3}(0001) substrates at substrate temperatures of 100 and 300 degree sign C by UHV molecular beam epitaxy. A complicated microstructure was realized for the epitaxial thin films. In-situ reflection high-energy electron diffraction observation has shown that X atoms of the buffer layer segregated to the surface during Co layer deposition, and it yielded a unique epitaxial granular structure. The structure consists of small Co grains buried in the X buffer layer, where both the magnetic small Co grains and the nonmagnetic X layer are epitaxially grown on the single crystal substrate. The structure varied depending on the X element and the substrate temperature. The crystal structure of Co grains is influenced by the buffer layer material and determined to be hcp and fcc structures for the buffer layer materials of Au and Cu, respectively.

  7. Thermodynamic theory of epitaxial alloys: first-principles mixed-basis cluster expansion of (In, Ga)N alloy film.

    PubMed

    Liu, Jefferson Zhe; Zunger, Alex

    2009-07-22

    Epitaxial growth of semiconductor alloys onto a fixed substrate has become the method of choice to make high quality crystals. In the coherent epitaxial growth, the lattice mismatch between the alloy film and the substrate induces a particular form of strain, adding a strain energy term into the free energy of the alloy system. Such epitaxial strain energy can alter the thermodynamics of the alloy, leading to a different phase diagram and different atomic microstructures. In this paper, we present a general-purpose mixed-basis cluster expansion method to describe the thermodynamics of an epitaxial alloy, where the formation energy of a structure is expressed in terms of pair and many-body interactions. With a finite number of first-principles calculation inputs, our method can predict the energies of various atomic structures with an accuracy comparable to that of first-principles calculations themselves. Epitaxial (In, Ga)N zinc-blende alloy grown on GaN(001) substrate is taken as an example to demonstrate the details of the method. Two (210) superlattice structures, (InN)(2)/(GaN)(2) (at x = 0.50) and (InN)(4)/(GaN)(1) (at x = 0.80), are identified as the ground state structures, in contrast to the phase-separation behavior of the bulk alloy.

  8. Job satisfaction in relation to energy resource consciousness and perceptions of energy utilization in selected Illinois manufacturing firms

    SciTech Connect

    Haynes, T.S.

    1986-01-01

    This study was developed through a synthesis and review of literature and research related to the current status of job satisfaction, energy resources, and perceptions of how energy is utilized in the manufacturing work environment. This synthesis and review revolved around several proven contributing factors of job satisfaction, such as age, education, and challenge from work itself. Quality of work life programs and their components are discussed in relation to their impact on job satisfaction. The nature of energy resource utilization is traced back through history with an emphasis on the limitations of current resources and options for the future. The review highlights the current debate over what should be the future path of energy resource development. The concept of satisfaction of human needs is reviewed and related to job satisfaction and energy resources. The purpose of this research study was to contribute to the understanding of how perceptions of energy resources relate to job satisfaction. Results of the study indicated that there were no significant differences between an individual's energy resource consciousness and perceptions of energy utilization in the work place, energy resource consciousness and job satisfaction, and job satisfaction and perceptions of energy utilization in the workplace.

  9. Children in school cafeterias select foods containing more saturated fat and energy than the Institute of Medicine recommendations.

    PubMed

    Martin, Corby K; Thomson, Jessica L; LeBlanc, Monique M; Stewart, Tiffany M; Newton, Robert L; Han, Hongmei; Sample, Alicia; Champagne, Catherine M; Williamson, Donald A

    2010-09-01

    In this study, we examined if children's food selection met the School Meals Initiative (SMI) standards and the recently released Institute of Medicine (IOM) recommendations. Mean food selection, plate waste, and food intake were also examined. Food intake of 2049 4th-6th grade students was measured objectively at lunch over 3 d with digital photography in 33 schools. The percent of children whose food selection met the SMI standards and IOM recommendations for energy (kJ), fat and saturated fat, calcium, iron, and vitamin A and C were calculated. The SMI standards provide lower limits for most nutrients; the IOM provides a range of values, including an upper limit for energy. Seventy-seven percent of children's energy selection met the SMI lower limit, but only 16% of children met the IOM's recommended range and 74% of children exceeded the upper limit. More than 70% of children exceeded the SMI and IOM's saturated fat recommendations. Children selected (mean +/- SD) 3168 +/- 621 kJ, discarded 882 +/- 581 kJ, and consumed 2286 +/- 716 kJ. Children were less likely to discard fat than carbohydrate, resulting in proportionally more fat being consumed. Most children met SMI and IOM recommendations for protein, calcium, iron, and vitamin A. With few exceptions, energy selection was similar among groups of children, but plate waste differed (P < 0.001), resulting in greater energy intake among boys compared with girls, Caucasians compared with African Americans, and heavier compared with lighter children. Children's selection was high in saturated fat and, based on IOM criteria, included excess energy.

  10. Selectively-grown InGaP/GaAs on silicon heterostructures for application to photovoltaic photoelectrolysis cells

    NASA Astrophysics Data System (ADS)

    Mauk, Michael G.; Tata, Anthony N.; Feyock, Bryan W.

    2001-05-01

    Photovoltaic-photoelectrochemical (PV-PEC) cells based on InGaP/GaAs show excellent prospects for efficient production of hydrogen by electrolysis of water using solar energy. We describe a combined close-spaced vapor transport (CSVT)/liquid-phase epitaxy (LPE) process to produce arrays of selectively-grown mesas of InGaP/GaAs on silicon substrates. Unlike other semiconductor devices, the PV-PEC cell is well suited for such selectively-grown, discontinuous heteroepitaxial films. Thus, this device application affords exploiting the potential advantages of selective epitaxy, namely, the substantial reduction of stress and defects caused by thermal expansion and lattice mismatch between the silicon substrate and III-V epilayers.

  11. Outage Performance Analysis of Relay Selection Schemes in Wireless Energy Harvesting Cooperative Networks over Non-Identical Rayleigh Fading Channels.

    PubMed

    Do, Nhu Tri; Bao, Vo Nguyen Quoc; An, Beongku

    2016-02-26

    In this paper, we study relay selection in decode-and-forward wireless energy harvesting cooperative networks. In contrast to conventional cooperative networks, the relays harvest energy from the source's radio-frequency radiation and then use that energy to forward the source information. Considering power splitting receiver architecture used at relays to harvest energy, we are concerned with the performance of two popular relay selection schemes, namely, partial relay selection (PRS) scheme and optimal relay selection (ORS) scheme. In particular, we analyze the system performance in terms of outage probability (OP) over independent and non-identical (i.n.i.d.) Rayleigh fading channels. We derive the closed-form approximations for the system outage probabilities of both schemes and validate the analysis by the Monte-Carlo simulation. The numerical results provide comprehensive performance comparison between the PRS and ORS schemes and reveal the effect of wireless energy harvesting on the outage performances of both schemes. Additionally, we also show the advantages and drawbacks of the wireless energy harvesting cooperative networks and compare to the conventional cooperative networks.

  12. Engineering epitaxial graphene with oxygen

    NASA Astrophysics Data System (ADS)

    Kimouche, Amina; Martin, Sylvain; Winkelmann, Clemens; Fruchart, Olivier; Courtois, Hervé; Coraux, Johann; Hybrid system at low dimension Team

    2013-03-01

    Almost free-standing graphene can be obtained on metals by decoupling graphene from its substrate, for instance by intercalation of atoms beneath graphene, as it was shown with oxygen atoms. We show that the interaction of oxygen with epitaxial graphene on iridium leads to the formation of an ultrathin crystalline oxide extending between graphene and the metallic substrate via the graphene wrinkles. Graphene studied in this work was prepared under ultra-high vacuum by CVD. The samples were studied by combining scanning probe microscopy (STM, AFM) and spatially resolved spectroscopy (Raman, STS). The ultrathin oxide forms a decoupling barrier layer between graphene and Ir, yielding truly free-standing graphene whose hybridization and charge transfers with the substrate have been quenched. Our work presents novel types of graphene-based nanostructures, and opens the route to the transfer-free preparation of graphene directly onto an insulating support contacted to the metallic substrate which could serve as a gate electrode. Work supported by the EU-NMP GRENADA project

  13. Effects of Steering and Shadowing in Epitaxial Growth

    NASA Astrophysics Data System (ADS)

    Amar, Jacques

    2005-03-01

    While shadowing has been known to play a role in some thin-film deposition processes, until recently it has been assumed that in epitaxial growth the effects of steering and shadowing are negligible. Here we present analytical and molecular dynamics results describing the effects of steering due to the short-range and long-range van der Waals (vdW) attraction in metal (100), (111) and (110) epitaxial growth. Our results lead to a general picture of the process of deposition near step-edges^1,2 which is quite different from the standard downward funneling picture. In particular, we find that short-range attraction plays an important role not only before but also after collision with the step. As a result, it can significantly enhance the uphill current, selected mound angle, and surface roughness in epitaxial growth. In the case of deposition on metal (111) and (110) surfaces we also find a significant asymmetry between the interaction at A and B steps which may be explained by differences in the step geometry. General expressions for the surface current and selected mound angle valid for arbitrary crystal geometry are also presented. We have also calculated the vdW constant describing the long-range interaction between a Cu atom and a Cu(100) surface.^3 Our result is large enough to explain recent observations^4 of a significant increase in mound angle in Cu/Cu(100) growth for large angles of incidence (θ> 50^o) and also indicates that for smaller angles of incidence the dominant effects are due to the short-range rather than to the long-range interaction. Finally, we discuss the effects of shadowing in oblique incidence epitaxial growth and its implications for the control of nanoscale patterning.1. J. Yu and J.G. Amar, Phys. Rev. Lett. 89, 286103 (2002).2. J. Yu and J.G. Amar, Phys. Rev. B 69, 045426 (2004).3. J.G. Amar, Phys. Rev. B 67, 165425 (2003).4. S. van Dijken et al, Phys. Rev. B 61, 14047 (2000).

  14. Manufacture of energy storage and return prosthetic feet using selective laser sintering.

    PubMed

    South, Brian J; Fey, Nicholas P; Bosker, Gordon; Neptune, Richard R

    2010-01-01

    Proper selection of prosthetic foot-ankle components with appropriate design characteristics is critical for successful amputee rehabilitation. Elastic energy storage and return (ESAR) feet have been developed in an effort to improve amputee gait. However, the clinical efficacy of ESAR feet has been inconsistent, which could be due to inappropriate stiffness levels prescribed for a given amputee. Although a number of studies have analyzed the effect of ESAR feet on gait performance, the relationships between the stiffness characteristics and gait performance are not well understood. A challenge to understanding these relationships is the inability of current manufacturing techniques to easily generate feet with varying stiffness levels. The objective of this study was to develop a rapid prototyping framework using selective laser sintering (SLS) for the creation of prosthetic feet that can be used as a means to quantify the influence of varying foot stiffness on transtibial amputee walking. The framework successfully duplicated the stiffness characteristics of a commercial carbon fiber ESAR foot. The feet were mechanically tested and an experimental case study was performed to verify that the locomotor characteristics of the amputee's gait were the same when walking with the carbon fiber ESAR and SLS designs. Three-dimensional ground reaction force, kinematic, and kinetic quantities were measured while the subject walked at 1.2 m/s. The SLS foot was able to replicate the mechanical loading response and locomotor patterns of the ESAR foot within +/-2 standard deviations. This validated the current framework as a means to fabricate SLS-based ESAR prosthetic feet. Future work will be directed at creating feet with a range of stiffness levels to investigate appropriate prescription criteria.

  15. Building-Integrated Solar Energy Devices based on Wavelength Selective Films

    NASA Astrophysics Data System (ADS)

    Ulavi, Tejas

    A potentially attractive option for building integrated solar is to employ hybrid solar collectors which serve dual purposes, combining solar thermal technology with either thin film photovoltaics or daylighting. In this study, two hybrid concepts, a hybrid photovoltaic/thermal (PV/T) collector and a hybrid 'solar window', are presented and analyzed to evaluate technical performance. In both concepts, a wavelength selective film is coupled with a compound parabolic concentrator (CPC) to reflect and concentrate the infrared portion of the solar spectrum onto a tubular absorber. The visible portion of the spectrum is transmitted through the concentrator to either a thin film Cadmium Telluride (CdTe) solar panel for electricity generation or into the interior space for daylighting. Special attention is given to the design of the hybrid devices for aesthetic building integration. An adaptive concentrator design based on asymmetrical truncation of CPCs is presented for the hybrid solar window concept. The energetic and spectral split between the solar thermal module and the PV or daylighting module are functions of the optical properties of the wavelength selective film and the concentrator geometry, and are determined using a Monte Carlo Ray-Tracing (MCRT) model. Results obtained from the MCRT can be used in conjugation with meteorological data for specific applications to study the impact of CPC design parameters including the half-acceptance angle thetac, absorber diameter D and truncation on the annual thermal and PV/daylighting efficiencies. The hybrid PV/T system is analyzed for a rooftop application in Phoenix, AZ. Compared to a system of the same area with independent solar thermal and PV modules, the hybrid PV/T provides 20% more energy, annually. However, the increase in total delivered energy is due solely to the addition of the thermal module and is achieved at an expense of a decrease in the annual electrical efficiency from 8.8% to 5.8% due to shading by

  16. Epitaxy and Microstructure Evolution in Metal Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Basak, Amrita; Das, Suman

    2016-07-01

    Metal additive manufacturing (AM) works on the principle of incremental layer-by-layer material consolidation, facilitating the fabrication of objects of arbitrary complexity through the controlled melting and resolidification of feedstock materials by using high-power energy sources. The focus of metal AM is to produce complex-shaped components made of metals and alloys to meet demands from various industrial sectors such as defense, aerospace, automotive, and biomedicine. Metal AM involves a complex interplay between multiple modes of energy and mass transfer, fluid flow, phase change, and microstructural evolution. Understanding the fundamental physics of these phenomena is a key requirement for metal AM process development and optimization. The effects of material characteristics and processing conditions on the resulting epitaxy and microstructure are of critical interest in metal AM. This article reviews various metal AM processes in the context of fabricating metal and alloy parts through epitaxial solidification, with material systems ranging from pure-metal and prealloyed to multicomponent materials. The aim is to cover the relationships between various AM processes and the resulting microstructures in these material systems.

  17. Multiple growths of epitaxial lift-off solar cells from a single InP substrate

    SciTech Connect

    Lee, Kyusang; Shiu, Kuen-Ting; Zimmerman, Jeramy D.; Forrest, Stephen R.; Renshaw, Christopher K.

    2010-09-06

    We demonstrate multiple growths of flexible, thin-film indium tin oxide-InP Schottky-barrier solar cells on a single InP wafer via epitaxial lift-off (ELO). Layers that protect the InP parent wafer surface during the ELO process are subsequently removed by selective wet-chemical etching, with the active solar cell layers transferred to a thin, flexible plastic host substrate by cold welding at room temperature. The first- and second-growth solar cells exhibit no performance degradation under simulated Atmospheric Mass 1.5 Global (AM 1.5G) illumination, and have a power conversion efficiency of {eta}{sub p}=14.4{+-}0.4% and {eta}{sub p}=14.8{+-}0.2%, respectively. The current-voltage characteristics for the solar cells and atomic force microscope images of the substrate indicate that the parent wafer is undamaged, and is suitable for reuse after ELO and the protection-layer removal processes. X-ray photoelectron spectroscopy, reflection high-energy electron diffraction observation, and three-dimensional surface profiling show a surface that is comparable or improved to the original epiready wafer following ELO. Wafer reuse over multiple cycles suggests that high-efficiency; single-crystal thin-film solar cells may provide a practical path to low-cost solar-to-electrical energy conversion.

  18. Accurate determination of optical bandgap and lattice parameters of Zn{sub 1-x}Mg{sub x}O epitaxial films (0{<=}x{<=}0.3) grown by plasma-assisted molecular beam epitaxy on a-plane sapphire

    SciTech Connect

    Laumer, Bernhard; Schuster, Fabian; Stutzmann, Martin; Bergmaier, Andreas; Dollinger, Guenther; Eickhoff, Martin

    2013-06-21

    Zn{sub 1-x}Mg{sub x}O epitaxial films with Mg concentrations 0{<=}x{<=}0.3 were grown by plasma-assisted molecular beam epitaxy on a-plane sapphire substrates. Precise determination of the Mg concentration x was performed by elastic recoil detection analysis. The bandgap energy was extracted from absorption measurements with high accuracy taking electron-hole interaction and exciton-phonon complexes into account. From these results a linear relationship between bandgap energy and Mg concentration is established for x{<=}0.3. Due to alloy disorder, the increase of the photoluminescence emission energy with Mg concentration is less pronounced. An analysis of the lattice parameters reveals that the epitaxial films grow biaxially strained on a-plane sapphire.

  19. High efficiency direct thermal to electric energy conversion from radioisotope decay using selective emitters and spectrally tuned solar cells

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L.; Flood, Dennis J.; Lowe, Roland A.

    1993-01-01

    Thermophotovoltaic (TPV) systems are attractive possibilities for direct thermal-to-electric energy conversion, but have typically required the use of black body radiators operating at high temperatures. Recent advances in both the understanding and performance of solid rare-earth oxide selective emitters make possible the use of TPV at temperatures as low as 1200K. Both selective emitter and filter system TPV systems are feasible. However, requirements on the filter system are severe in order to attain high efficiency. A thin-film of a rare-earth oxide is one method for producing an efficient, rugged selective emitter. An efficiency of 0.14 and power density of 9.2 W/KG at 1200K is calculated for a hypothetical thin-film neodymia (Nd2O3) selective emitter TPV system that uses radioisotope decay as the thermal energy source.

  20. World Best Practice Energy Intensity Values for SelectedIndustrial Sectors

    SciTech Connect

    Worrell, Ernst; Price, Lynn; Neelis, Maarten; Galitsky,Christina; Zhou, Nan

    2007-06-05

    "World best practice" energy intensity values, representingthe most energy-efficient processes that are in commercial use in atleast one location worldwide, are provided for the production of iron andsteel, aluminium, cement, pulp and paper, ammonia, and ethylene. Energyintensity is expressed in energy use per physical unit of output for eachof these commodities; most commonly these are expressed in metric tonnes(t). The energy intensity values are provided by major energy-consumingprocesses for each industrial sector to allow comparisons at the processlevel. Energy values are provided for final energy, defined as the energyused at the production facility as well as for primary energy, defined asthe energy used at the production facility as well as the energy used toproduce the electricity consumed at the facility. The "best practice"figures for energy consumption provided in this report should beconsidered as indicative, as these may depend strongly on the materialinputs.

  1. What types of nutrition menu labelling lead consumers to select less energy-dense fast food? An experimental study.

    PubMed

    Morley, Belinda; Scully, Maree; Martin, Jane; Niven, Philippa; Dixon, Helen; Wakefield, Melanie

    2013-08-01

    This study assessed whether the inclusion of kilojoule labelling alone or accompanied by further nutrition information on menus led adults to select less energy-dense fast food meals. A between-subjects experimental design was used with online menu boards systematically varied to test the following labelling conditions: none (control); kilojoule; kilojoule+percent daily intake; kilojoule+traffic light; and kilojoule+traffic light+percent daily intake. Respondents were 1294 adults aged 18-49 in Victoria, Australia who had purchased fast food in the last month and were randomly assigned to conditions. Respondents in the no labelling condition selected meals with the highest mean energy content and those viewing the kilojoule and kilojoule+traffic light information selected meals with a significantly lower mean energy content, that constituted a reduction of around 500kJ (120kcal). Respondents most commonly reported using the traffic light labels in making their selections. These findings provide support for the policy of disclosure of energy content on menus at restaurant chains. Given the magnitude of the reduction in energy density reported, and the prevalence of fast food consumption, this policy initiative has the potential to yield health benefits at the population level.

  2. Potential social, institutional, and environmental impacts of selected energy-conservation measures in two Washington communities. [Seattle and Yakima

    SciTech Connect

    Edelson, E.; Olsen, M.

    1980-03-01

    The likely environmental, social, and institutional impacts of selected energy-conservation measures in two communities in Washington state are reported. The five conservation measures investigated in this study were: (1) retrofitting existing buildings; (2) district heating and Integrated Community Energy Systems (ICES); (3) small automobiles and vehicle redesign; (4) land-use and housing modifications; and (5) electric-utility rate reform. Twenty potential impact areas were selected for analysis. These areas were divided into five categories of environmental impacts, economic impacts, community impacts, personal impacts, and overall quality of life in the community. The research was conducted in Seattle and Yakima, Washington. In each location, about two dozen public officials and business, labor, and community leaders were interviewed. Their diverse views are summarized. The Seattle respondents saw energy conservation as a highly desirable policy with a number of temporary, transitional problems arising as energy-conservation measures were implemented. Yakima respondents, in contrast, did not expect to encounter many serious energy problems in the foreseeable future and consequently viewed energy conservation as a relatively minor community concern. Moreover, they anticipated that many conservation measures, if implemented by the government, would encounter either apathy or resistance in their community. Two broad generalizations can bedrawn from these interviews: (1) energy conservation will basically be beneficial for the natural environment and our society; and (2) if energy conservation does become a dominant thrust in our society, it could stimulate and reinforce a much broader process of fundamental social change. (LCL)

  3. Tunable bands in biased multilayer epitaxial graphene.

    PubMed

    Williams, Michael D; Samarakoon, Duminda K; Hess, Dennis W; Wang, Xiao-Qian

    2012-04-28

    We have studied the electronic characteristics of multilayer epitaxial graphene under a perpendicularly applied electric bias. Ultraviolet photoemission spectroscopy measurements reveal that there is notable variation of the electronic density-of-states in valence bands near the Fermi level. Evolution of the electronic structure of graphite and rotational-stacked multilayer epitaxial graphene as a function of the applied electric bias is investigated using first-principles density-functional theory including interlayer van der Waals interactions. The experimental and theoretical results demonstrate that the tailoring of electronic band structure correlates with the interlayer coupling tuned by the applied bias. The implications of controllable electronic structure of rotationally fault-stacked epitaxial graphene grown on the C-face of SiC for future device applications are discussed.

  4. Parameter Selection for Department of Energy Spent Nuclear Fuel to be Used in the Yucca Mountain License Application

    SciTech Connect

    D. L. Fillmore

    2003-10-01

    This report contains the chemical, physical, and radiological parameters that were chosen to represent the U.S. Department of Energy spent nuclear fuel in the Yucca Mountain license application. It also contains the selected packaging requirements for the various fuel types and the criticality controls that were used. The data are reported for representative fuels and bounding fuels in groups of fuels that were selected for the analysis. The justification for the selection of each parameter is given. The data reported were not generated under any quality assurance program.

  5. Crystal growth of calcium phosphates - epitaxial considerations

    NASA Astrophysics Data System (ADS)

    Koutsoukos, P. G.; Nancollas, G. H.

    1981-05-01

    The growth of one crystalline phase on the surface of another that offers a good crystal lattice match, may be important in environmental, physiological and pathological mineralization processes. The epitaxial relationships and kinetics of growth of hydroxyapatite on crystals of dicalcium phosphate dihydrate, calcium fluoride and calcite have been studied at sustained low supersaturation with respect to hydroxyapatite. At the very low supersaturations, the crystallization of hydroxyapatite takes place without the formation of precursor phases. The experimental results are in agreement with theoretical predictions for epitaxial growth, while the kinetics of hydroxyapatite crystallization on the foreign substrates is the same as that for the growth of hydroxyapatite on synthetic hydroxyapatite crystals.

  6. Chemical vapor deposition of epitaxial silicon

    DOEpatents

    Berkman, Samuel

    1984-01-01

    A single chamber continuous chemical vapor deposition (CVD) reactor is described for depositing continuously on flat substrates, for example, epitaxial layers of semiconductor materials. The single chamber reactor is formed into three separate zones by baffles or tubes carrying chemical source material and a carrier gas in one gas stream and hydrogen gas in the other stream without interaction while the wafers are heated to deposition temperature. Diffusion of the two gas streams on heated wafers effects the epitaxial deposition in the intermediate zone and the wafers are cooled in the final zone by coolant gases. A CVD reactor for batch processing is also described embodying the deposition principles of the continuous reactor.

  7. Investigation of dual-energy X-ray photon counting using a cadmium telluride detector with dual-energy selection electronics

    NASA Astrophysics Data System (ADS)

    Sato, Eiichi; Kosuge, Yoshiyuki; Yamanome, Hayato; Mikata, Akiko; Miura, Tatsuya; Oda, Yasuyuki; Ishii, Tomotaka; Hagiwara, Osahiko; Matsukiyo, Hiroshi; Watanabe, Manabu; Kusachi, Shinya

    2017-01-01

    To obtain two kinds of tomograms at two different X-ray energy ranges simultaneously, we have developed a dual-energy X-ray photon counter with a cadmium telluride (CdTe) detector and two energy-selecting devices (ESDs). The ESD consists of two comparators and a microcomputer (MC). X-ray photons are detected using the CdTe detector, and the event pulses from a shaping amplifier are sent to two ESDs simultaneously to determine two energy ranges. X-ray photons in the two ranges are counted using the MCs, and the logical pulses from the MCs are input to frequency-to-voltage converters (FVCs). The outputs from the two FVCs are input to a personal computer through an analog-to-digital converter to carry out dual-energy computed tomography. The tube voltage and current were 80 kV and 8.5 μA, respectively. Two tomograms were obtained simultaneously with two energy ranges. K-edge CT using iodine and gadolinium media was carried out utilizing two energy ranges of 33-45 and 50-65 keV, respectively. The maximum count rate was 6.8 kilocounts per second with energies ranging from 10 to 80 keV, and the exposure time for tomography was 9.8 min.

  8. Förster resonance energy transfer and trapping in selected systems: analysis by Monte-Carlo simulation.

    PubMed

    Bojarski, P; Synak, A; Kułak, L; Rangelowa-Jankowska, S; Kubicki, A; Grobelna, B

    2012-01-01

    Monte-Carlo simulation method is described and applied as an efficient tool to analyze experimental data in the presence of energy transfer in selected systems, where the use of analytical approaches is limited or even impossible. Several numerical and physical problems accompanying Monte-Carlo simulation are addressed. It is shown that the Monte-Carlo simulation enables to obtain orientation factor in partly ordered systems and other important energy transfer parameters unavailable directly from experiments. It is shown how Monte-Carlo simulation can predict some important features of energy transport like its directional character in ordered media.

  9. Energy efficient residential new construction: market transformation. Spectral selective glass. Final project report

    SciTech Connect

    Hammon, Robert

    2000-12-18

    This final report describes the following tasks associated with this project: cost and availability of spectrally selective glass (SSG); window labeling problem and field verification of glass; availability of SSG replacement glass and tempered glass; HVAC load reduction due to spectrally selective glass; and comsumer appreciation of spectrally selective glass. Also included in the report are four attachments: builder and HVAC subcontractor presentation, sample advertisements, spectrally selective glass demonstration model, and invitation to SCE Glass mini trade-show.

  10. Infrared Spectral Energy Distribution Decomposition of WISE-selected, Hyperluminous Hot Dust-obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Fan, Lulu; Han, Yunkun; Nikutta, Robert; Drouart, Guillaume; Knudsen, Kirsten K.

    2016-06-01

    We utilize a Bayesian approach to fit the observed mid-IR-to-submillimeter/millimeter spectral energy distributions (SEDs) of 22 WISE-selected and submillimeter-detected, hyperluminous hot dust-obscured galaxies (Hot DOGs), with spectroscopic redshift ranging from 1.7 to 4.6. We compare the Bayesian evidence of a torus plusgraybody (Torus+GB) model with that of a torus-only (Torus) model and find that the Torus+GB model has higher Bayesian evidence for all 22 Hot DOGs than the torus-only model, which presents strong evidence in favor of the Torus+GB model. By adopting the Torus+GB model, we decompose the observed IR SEDs of Hot DOGs into torus and cold dust components. The main results are as follows. (1) Hot DOGs in our submillimeter-detected sample are hyperluminous ({L}{IR}≥slant {10}13{L}⊙ ), with torus emission dominating the IR energy output. However, cold dust emission is non-negligible, contributing on average ˜ 24% of total IR luminosity. (2) Compared to QSO and starburst SED templates, the median SED of Hot DOGs shows the highest luminosity ratio between mid-IR and submillimeter at rest frame, while it is very similar to that of QSOs at ˜ 10{--}50 μ {{m}}, suggesting that the heating sources of Hot DOGs should be buried AGNs. (3) Hot DOGs have high dust temperatures ({T}{dust}˜ 72 K) and high IR luminosity of cold dust. The {T}{dust}{--}{L}{IR} relation of Hot DOGs suggests that the increase in IR luminosity for Hot DOGs is mostly due to the increase of the dust temperature, rather than dust mass. Hot DOGs have lower dust masses than submillimeter galaxies (SMGs) and QSOs within a similar redshift range. Both high IR luminosity of cold dust and relatively low dust mass in Hot DOGs can be expected by their relatively high dust temperatures. (4) Hot DOGs have high dust-covering factors (CFs), which deviate from the previously proposed trend of the dust CF decreasing with increasing bolometric luminosity. Finally, we can reproduce the observed

  11. Optimized Energy Harvesting, Cluster-Head Selection and Channel Allocation for IoTs in Smart Cities

    PubMed Central

    Aslam, Saleem; Hasan, Najam Ul; Jang, Ju Wook; Lee, Kyung-Geun

    2016-01-01

    This paper highlights three critical aspects of the internet of things (IoTs), namely (1) energy efficiency, (2) energy balancing and (3) quality of service (QoS) and presents three novel schemes for addressing these aspects. For energy efficiency, a novel radio frequency (RF) energy-harvesting scheme is presented in which each IoT device is associated with the best possible RF source in order to maximize the overall energy that the IoT devices harvest. For energy balancing, the IoT devices in close proximity are clustered together and then an IoT device with the highest residual energy is selected as a cluster head (CH) on a rotational basis. Once the CH is selected, it assigns channels to the IoT devices to report their data using a novel integer linear program (ILP)-based channel allocation scheme by satisfying their desired QoS. To evaluate the presented schemes, exhaustive simulations are carried out by varying different parameters, including the number of IoT devices, the number of harvesting sources, the distance between RF sources and IoT devices and the primary user (PU) activity of different channels. The simulation results demonstrate that our proposed schemes perform better than the existing ones. PMID:27918424

  12. Optimized Energy Harvesting, Cluster-Head Selection and Channel Allocation for IoTs in Smart Cities.

    PubMed

    Aslam, Saleem; Hasan, Najam Ul; Jang, Ju Wook; Lee, Kyung-Geun

    2016-12-02

    This paper highlights three critical aspects of the internet of things (IoTs), namely (1) energy efficiency, (2) energy balancing and (3) quality of service (QoS) and presents three novel schemes for addressing these aspects. For energy efficiency, a novel radio frequency (RF) energy-harvesting scheme is presented in which each IoT device is associated with the best possible RF source in order to maximize the overall energy that the IoT devices harvest. For energy balancing, the IoT devices in close proximity are clustered together and then an IoT device with the highest residual energy is selected as a cluster head (CH) on a rotational basis. Once the CH is selected, it assigns channels to the IoT devices to report their data using a novel integer linear program (ILP)-based channel allocation scheme by satisfying their desired QoS. To evaluate the presented schemes, exhaustive simulations are carried out by varying different parameters, including the number of IoT devices, the number of harvesting sources, the distance between RF sources and IoT devices and the primary user (PU) activity of different channels. The simulation results demonstrate that our proposed schemes perform better than the existing ones.

  13. Influence of epitaxial strain on the magnetic properties of (110) SmFe{sub 2} thin film

    SciTech Connect

    Fuente, C. de la; Arnaudas, J. I.; Ciria, M.; Moral, A. del; Dufour, C.; Dumesnil, K.

    2009-03-30

    A novel nonlinear influence of the magnetoelastic energy because of the epitaxial strain allows us to explain the spontaneous magnetization and the cubic magnetostriction of a molecular-beam-epitaxy-grown SmFe{sub 2} thin film. Under this scope, new crystal-field parameters A{sub 4} and A{sub 6} and exchange coupling parameter {lambda}{sub ex} have been found. These new parameters could account for the change of the energy balance in the spin reorientation transition and explain the softening it has with respect to the bulk case.

  14. Selected Intakes of Energy from Empty Calories, U.S. Population, 2001-04

    Cancer.gov

    This section provides information on population distributions of energy intakes from solid fats, alcoholic beverages and added sugars. These sources of energy comprise a major portion of the discretionary calories consumed by the US population.

  15. Characterization of selected application of biomass energy technologies and a solar district heating and cooling system

    SciTech Connect

    D'Alessio, Dr., Gregory J.; Blaunstein, Robert P.

    1980-09-01

    The following systems are discussed: energy self-sufficient farms, wood gasification, energy from high-yield silviculture farms, and solar district heating and cooling. System descriptions and environmental data are included for each one. (MHR)

  16. Assessing the ligand selectivity of sphingosine kinases using molecular dynamics and MM-PBSA binding free energy calculations.

    PubMed

    Fang, Liang; Wang, Xiaojian; Xi, Meiyang; Liu, Tianqi; Yin, Dali

    2016-04-01

    The dynamic balance of sphingolipids plays a crucial role in diverse biological processes such as mitogenesis, cell migration and angiogenesis. Sphingosine kinases (SKs) including SK1 and SK2 phosphorylate sphingosine to sphingosine 1-phosphate (S1P), and control the critical balance. SK1 overexpression was reported to increase cell survival and proliferation. Although several SK1 selective inhibitors have been reported, detailed analysis toward their selectivity to understand the molecular mechanism has not been performed to our knowledge. Herein, the crystal structure of SK1 and a homology model of SK2 were used to dock five inhibitors (1, 2, 3, 4 and 5). Protein-ligand complexes were then subjected to a molecular dynamics study and MM-PBSA binding free energy calculations. By analyzing the binding model of these inhibitors, we found that residues ILE170, PHE188 and THR192 in SK1 significantly contribute a favorable binding energy to the selectivity.

  17. Growth and characterization of epitaxial silver indium diselenide

    NASA Astrophysics Data System (ADS)

    Pena Martin, Pamela

    Photovoltaics (solar cells) are a key player in the renewable energy frontier, and will become increasingly important as their cost per watt continues to drop, especially if fossil fuel costs increase. One particularly promising photovoltaic technology is based on chalcopyrite-structure semiconductors. Within the chalcopyrite compounds the highest efficiency thin film solar cell absorber material to date is Cu(In,Ga)Se2 (CIGS). While current efficiency records are over 21% for single-junction cells, there is still room for improvement. Replacing some of the Cu with Ag has been shown to be beneficial in CIGS devices. However, the Ag- containing chalcopyrites are still relatively unknown in terms of their growth mechanism, energetics, and surface atomic and electronic properties. These are best inferred through study of epitaxial films, yet they have little mention in literature and have not been the subject of a detailed study. This work describes the growth of epitaxial AgInSe2 (AIS) on GaAs substrates, studying the morphology, structure, and surface properties to understand how growth takes place. It also seeks to experimentally determine the surface electronic and atomic structure at the atomic scale to gain insight into the part of the material that forms the heterojunction that collects photon energy in the device. Finally, this work seeks to compare and contrast these findings with what is known about CIGS to determine where similarities and, more importantly, the differences may lie. This study has found that single phase tetragonal AIS can be epitaxially grown on GaAs, as illustrated by x-ray diffraction (XRD), transmission electron microscope (TEM), and surface morphology data. Like CIGS, the close packed polar (112) planes have the lowest energy. The morphology points to a difference in step dynamics, leading to less faceted, straight edged island shapes compared to CIGS. Epitaxial temperature as a function of growth direction shows a different trend in

  18. Substrate Preparations in Epitaxial ZnO Film Growth

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, C.-H.; Lehoczky, S. L.; Harris, M. T.; Callahan, M. J.; George, M. A.

    2000-01-01

    Epitaxial ZnO films were grown on the two polar surfaces (O-face and Zn-face) of (0001) ZnO single crystal substrates using off-axis magnetron sputtering deposition. Annealing-temperature dependence of ZnO substrates was studied. ZnO films grown on sapphire substrates have also been investigated for comparison purposes and the annealing temperature of A1203 substrates is 1000 C. Substrates and films were characterized using photoluminescence (PL) spectrum, x-ray diffraction, atomic force microscope, energy dispersive spectrum, and electric transport measurements. It has been found that the ZnO film properties were different when films were grown on the two polarity surfaces of ZnO substrates and the A1203 substrates. An interesting result shows that high temperature annealing of ZnO single crystals will improve the surface structure on the O-face surface rather than the opposite surface. The measurements of homoepitaxial ZnO films indicate that the O-terminated surface is better for ZnO epitaxial film growth.

  19. Structure and transport of topological insulators on epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Kally, James; Reifsnyder Hickey, Danielle; Lin, Yu-Chuan; Richardella, Anthony; Lee, Joon Sue; Robinson, Joshua; Mkhoyan, K. Andre; Samarth, Nitin

    Recent advancements in spintronics have shown that a class of materials, topological insulators (TI), can be used as a spin-current generator or detector. Topological insulators have protected surface states with the electron's spin locked to its momentum. To access these surface states, (Bi, Sb)2Te3 can be grown by molecular beam epitaxy to have the Fermi energy near the Dirac point so that transport occurs only through the spin-dependent surface states. Graphene is another 2D material of great interest for spintronics because of its very long spin diffusion length. This is an ideal material to act as a spin channel in devices. The van der Waals nature of the growth exhibited by 2D materials such as (Bi, Sb)2Te3 and graphene allows heterostructures to be formed despite the large lattice mismatch. We explore the structure and transport of (Bi, Sb)2Te3 grown on epitaxial graphene on 6H-SiC substrates for spintronic applications. This work was supported in part by C-SPIN and LEAST, two of the six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

  20. Point defects in epitaxial silicene on Ag(111) surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Hongsheng; Feng, Haifeng; Du, Yi; Chen, Jian; Wu, Kehui; Zhao, Jijun

    2016-06-01

    Silicene, a counterpart of graphene, has achieved rapid development due to its exotic electronic properties and excellent compatibility with the mature silicon-based semiconductor technology. Its low room-temperature mobility of ˜100 cm2 V-1 s-1, however, inhibits device applications such as in field-effect transistors. Generally, defects and grain boundaries would act as scattering centers and thus reduce the carrier mobility. In this paper, the morphologies of various point defects in epitaxial silicene on Ag(111) surfaces have been systematically investigated using first-principles calculations combined with experimental scanning tunneling microscope (STM) observations. The STM signatures for various defects in epitaxial silicene on Ag(111) surface are identified. In particular, the formation energies of point defects in Ag(111)-supported silicene sheets show an interesting dependence on the superstructures, which, in turn, may have implications for controlling the defect density during the synthesis of silicene. Through estimating the concentrations of various point defects in different silicene superstructures, the mystery of the defective appearance of \\sqrt{13}× \\sqrt{13} and 2\\sqrt{3}× 2\\sqrt{3} silicene in experiments is revealed, and 4 × 4 silicene sheet is thought to be the most suitable structure for future device applications.

  1. Dewetting of Epitaxial Silver Film on Silicon by Thermal Annealing

    NASA Astrophysics Data System (ADS)

    Sanders, Charlotte E.; Kellogg, Gary L.; Shih, C.-K.

    2013-03-01

    It has been shown that noble metals can grow epitaxially on semiconducting and insulating substrates, despite being a non-wetting system: low temperature deposition followed by room temperature annealing leads to atomically flat film morphology. However, the resulting metastable films are vulnerable to dewetting, which has limited their utility for applications under ambient conditions. The physics of this dewetting is of great interest but little explored. We report on an investigation of the dewetting of epitaxial Ag(111) films on Si(111) and (100). Low energy electron microscopy (LEEM) shows intriguing evolution in film morphology and crystallinity, even at temperatures below 100oC. On the basis of these findings, we can begin to draw compelling inferences about film-substrate interaction and the kinetics of dewetting. Financial support is from NSF, DGE-0549417 and DMR-0906025. This work was performed, in part, at the Center for Integrated Nanotechnologies, User Facility operated for the U.S. DOE Office of Science. Sandia National Lab is managed and operated by Sandia Corp., a subsidiary of Lockheed Martin Corp., for the U.S. DOE's National Nuclear Security Administration under DE-AC04-94AL85000.

  2. Energy use efficiency is characterized by an epigenetic component that can be directed through artificial selection to increase yield.

    PubMed

    Hauben, Miriam; Haesendonckx, Boris; Standaert, Evi; Van Der Kelen, Katrien; Azmi, Abdelkrim; Akpo, Hervé; Van Breusegem, Frank; Guisez, Yves; Bots, Marc; Lambert, Bart; Laga, Benjamin; De Block, Marc

    2009-11-24

    Quantitative traits, such as size and weight in animals and seed yield in plants, are distributed normally, even within a population of genetically identical individuals. For example, in plants, various factors, such as local soil quality, microclimate, and sowing depth, affect growth differences among individual plants of isogenic populations. Besides these physical factors, also epigenetic components contribute to differences in growth and yield. The network that regulates crop yield is still not well understood. Although this network is expected to have epigenetic elements, it is completely unclear whether it would be possible to shape the epigenome to increase crop yield. Here we show that energy use efficiency is an important factor in determining seed yield in canola (Brassica napus) and that it can be selected artificially through an epigenetic feature. From an isogenic canola population of which the individual plants and their self-fertilized progenies were recursively selected for respiration intensity, populations with distinct physiological and agronomical characteristics could be generated. These populations were found to be genetically identical, but epigenetically different. Furthermore, both the DNA methylation patterns as well as the agronomical and physiological characteristics of the selected lines were heritable. Hybrids derived from parent lines selected for high energy use efficiencies had a 5% yield increase on top of heterosis. Our results demonstrate that artificial selection allows the increase of the yield potential by selecting populations with particular epigenomic states.

  3. Surface roughness in sulfur ion-implanted InP with molecular beam epitaxy regrown double-heterojunction bipolar transistor layers

    SciTech Connect

    Hu, T.-C.; Chang, M.F.; Weimann, Nils; Chen Jianxin; Chen, Y.-K.

    2005-04-04

    We report on deep ion-implantation of sulfur into InP substrates to replace the epitaxial subcollector layer of double-heterojunction bipolar transistors. Using optimized implantation conditions of 350 keV energy and 1x10{sup 15} cm{sup -2} dose, we achieved a subcollector sheet resistance of 15 {omega}/square. Under well-controlled regrowth conditions a root-mean-square roughness of 12 A is measured from DHBT epitaxial layers grown on implanted InP substrates, comparable to DHBT epitaxial layers grown on n{sup +} epiready unimplanted substrates. We observe a pronounced increase in surface roughness of epitaxial layer beyond a threshold ion dose, depending on implantation energy. Large-area DHBT devices result with sulfur-ion implanted subcollector shows similar characteristics compared to devices fabricated on n{sup +}-doped InP substrates.

  4. Epitaxial growth of three dimensionally structured III-V photonic crystal via hydride vapor phase epitaxy

    SciTech Connect

    Zheng, Qiye; Kim, Honggyu; Zhang, Runyu; Zuo, Jianmin; Braun, Paul V.; Sardela, Mauro; Balaji, Manavaimaran; Lourdudoss, Sebastian; Sun, Yan-Ting

    2015-12-14

    Three-dimensional (3D) photonic crystals are one class of materials where epitaxy, and the resultant attractive electronic properties, would enable new functionalities for optoelectronic devices. Here we utilize self-assembled colloidal templates to fabricate epitaxially grown single crystal 3D mesostructured Ga{sub x}In{sub 1−x}P (GaInP) semiconductor photonic crystals using hydride vapor phase epitaxy (HVPE). The epitaxial relationship between the 3D GaInP and the substrate is preserved during the growth through the complex geometry of the template as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy. XRD reciprocal space mapping of the 3D epitaxial layer further demonstrates the film to be nearly fully relaxed with a negligible strain gradient. Fourier transform infrared spectroscopy reflection measurement indicates the optical properties of the photonic crystal which agree with finite difference time domain simulations. This work extends the scope of the very few known methods for the fabrication of epitaxial III-V 3D mesostructured materials to the well-developed HVPE technique.

  5. Epitaxial Overgrowth of Gallium Nitride Nano-Rods on Silicon (111) Substrates by RF-Plasma-Assisted Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Ku, Jui-Tai; Yang, Tsung-Hsi; Chang, Jet-Rung; Wong, Yuen-Yee; Chou, Wu-Ching; Chang, Chun-Yen; Chen, Chiang-Yao

    2010-04-01

    Strain-free gallium nitride (GaN) overgrowth on GaN nano-rods is realized by RF-plasma assisted molecular beam epitaxy (RF-MBE) on silicon (Si) substrate. The strain-free condition was identified by the strong free A exciton (FXA) photoluminescence (PL) peak at 3.478 eV and the E2 high phonon Raman shift of 567 cm-1. It is clearly demonstrated that the critical diameter of GaN nano-rods is around 80 nm for the overgrowth of strain-free GaN. The blue-shift of PL peak energy and phonon Raman energy with decreasing the diameter of nano-rod result from the strain relaxation of overgrowth GaN.

  6. Balancing Energy Budget in a Central-Place Forager: Which Habitat to Select in a Heterogeneous Environment?

    PubMed Central

    Patenaude-Monette, Martin; Bélisle, Marc; Giroux, Jean-François

    2014-01-01

    Foraging animals are influenced by the distribution of food resources and predation risk that both vary in space and time. These constraints likely shape trade-offs involving time, energy, nutrition, and predator avoidance leading to a sequence of locations visited by individuals. According to the marginal-value theorem (MVT), a central-place forager must either increase load size or energy content when foraging farther from their central place. Although such a decision rule has the potential to shape movement and habitat selection patterns, few studies have addressed the mechanisms underlying habitat use at the landscape scale. Our objective was therefore to determine how Ring-billed gulls (Larus delawarensis) select their foraging habitats while nesting in a colony located in a heterogeneous landscape. Based on locations obtained by fine-scale GPS tracking, we used resource selection functions (RSFs) and residence time analyses to identify habitats selected by gulls for foraging during the incubation and brood rearing periods. We then combined this information to gull survey data, feeding rates, stomach contents, and calorimetric analyses to assess potential trade-offs. Throughout the breeding season, gulls selected landfills and transhipment sites that provided higher mean energy intake than agricultural lands or riparian habitats. They used landfills located farther from the colony where no deterrence program had been implemented but avoided those located closer where deterrence measures took place. On the other hand, gulls selected intensively cultured lands located relatively close to the colony during incubation. The number of gulls was then greater in fields covered by bare soil and peaked during soil preparation and seed sowing, which greatly increase food availability. Breeding Ring-billed gulls thus select habitats according to both their foraging profitability and distance from their nest while accounting for predation risk. This supports the

  7. Epitaxial solar-cell fabrication, phase 2

    NASA Technical Reports Server (NTRS)

    Daiello, R. V.; Robinson, P. H.; Kressel, H.

    1977-01-01

    Dichlorosilane (SiH2Cl2) was used as the silicon source material in all of the epitaxial growths. Both n/p/p(+) and p/n/n(+) structures were studied. Correlations were made between the measured profiles and the solar cell parameters, especially cell open-circuit voltage. It was found that in order to obtain consistently high open-circuit voltage, the epitaxial techniques used to grow the surface layer must be altered to obtain very abrupt doping profiles in the vicinity of the junction. With these techniques, it was possible to grow reproducibly both p/n/n(+) and n/p/p(+) solar cell structures having open-circuit voltages in the 610- to 630-mV range, with fill-factors in excess of 0.80 and AM-1 efficiencies of about 13%. Combinations and comparisons of epitaxial and diffused surface layers were also made. Using such surface layers, we found that the blue response of epitaxial cells could be improved, resulting in AM-1 short-circuit current densities of about 30 mA/cm sq. The best cells fabricated in this manner had AM-1 efficiency of 14.1%.

  8. New Sources for Chemical Beam Epitaxy.

    DTIC Science & Technology

    2007-11-02

    TBP, BPE , TDMAP, and TBBDMAP. This work has resulted in: (1) further development of safe and improved sources specifically for chemical beam epitaxy... BPE , TDMAP, and TBBDMAP was performed. The first reported growth of GaInP without precracking the phosphorous source, TDMAP, and the first reported

  9. Improved Boat For Liquid-Phase Epitaxy

    NASA Technical Reports Server (NTRS)

    Connolly, John C.

    1991-01-01

    Liquid-phase epitaxial (LPE) growth boat redesigned. Still fabricated from ultra-high-purity graphite, but modified to permit easy disassembly and cleaning, along with improved wiping action for more complete removal of melt to reduce carry-over of gallium. Larger substrates and more uniform composition obtained.

  10. Electrostatic transfer of epitaxial graphene to glass.

    SciTech Connect

    Ohta, Taisuke; Pan, Wei; Howell, Stephen Wayne; Biedermann, Laura Butler; Beechem Iii, Thomas Edwin; Ross, Anthony Joseph, III

    2010-12-01

    We report on a scalable electrostatic process to transfer epitaxial graphene to arbitrary glass substrates, including Pyrex and Zerodur. This transfer process could enable wafer-level integration of graphene with structured and electronically-active substrates such as MEMS and CMOS. We will describe the electrostatic transfer method and will compare the properties of the transferred graphene with nominally-equivalent 'as-grown' epitaxial graphene on SiC. The electronic properties of the graphene will be measured using magnetoresistive, four-probe, and graphene field effect transistor geometries [1]. To begin, high-quality epitaxial graphene (mobility 14,000 cm2/Vs and domains >100 {micro}m2) is grown on SiC in an argon-mediated environment [2,3]. The electrostatic transfer then takes place through the application of a large electric field between the donor graphene sample (anode) and the heated acceptor glass substrate (cathode). Using this electrostatic technique, both patterned few-layer graphene from SiC(000-1) and chip-scale monolayer graphene from SiC(0001) are transferred to Pyrex and Zerodur substrates. Subsequent examination of the transferred graphene by Raman spectroscopy confirms that the graphene can be transferred without inducing defects. Furthermore, the strain inherent in epitaxial graphene on SiC(0001) is found to be partially relaxed after the transfer to the glass substrates.

  11. Directed surfaces structures and interfaces for enhanced electrocatalyst activity, selectivity, and stability for energy conversion reactions

    SciTech Connect

    Jaramillo, Thomas F.

    2016-04-20

    In this project, we have employed a systematic approach to develop active, selective, and stable catalyst materials for important electrochemical reactions involving energy conversion. In particular, we have focused our attention on developing active catalyst materials for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). HER: We have synthesized and investigated several highly active and acid stable non-precious metal HER catalysts, including: [Mo3S13]2- nanoclusters (Nature Chemistry, 2014) and molybdenum phosphosulfide (MoP|S) (Angewandte Chemie, 2014). We have also aimed to engineer these catalyst formulations in a membrane electrode assembly (MEA) for fundamental studies of water electrolysis at high current densities, approximately 1 A/cm2 (ChemSusChem, 2015). We furthermore investigated transition metal phosphide (TMP) catalysts for HER by a combined experimental–theoretical approach (Energy & Environmental Science, 2015). By synthesizing different TMPs and comparing experimentally determined HER activities with the hydrogen adsorption free energies, ΔGH, calculated by density functional theory, we showed that the TMPs follow a volcano relationship for the HER. Using our combined experimental–theoretical model, we predicted that the mixed metal TMP, Fe0.5Co0.5P, should have a near-optimal ΔGH. We synthesized several mixtures of Co and Fe phosphides alloys and confirmed that Fe0.5Co0.5P exhibits the highest HER activity of the investigated TMPs (Energy & Environmental Science, 2015). The understanding gained as to how to improve catalytic activity for the HER, particularly for non-precious metal materials, is important to DOE targets for sustainable H2 production. OER: We have developed a SrIrO3/IrOx catalyst for acidic conditions (submitted, 2016). The Sr

  12. The New Methodology and Chemical Contrast Observation by Use of the Energy-Selective Back-Scattered Electron Detector.

    PubMed

    Drab, Marek; Krajniak, Janusz; Grzelakowski, Krzysztof P

    2016-12-01

    We report on a robust method for chemical element-sensitive imaging by scanning electron microscopy (SEM). The commercial Auriga FE-SEM microscope (Carl Zeiss, Oberkochen, Germany), equipped with an energy-selective grid detector (EsB) as a part of the experimental setup, was applied for generation of chemical contrast at low accelerating voltages, which is gentle for sensitive samples. The EsB-grid detector, conceptually adapted by us as an energy retarding field analyzer (RFA), was used to detect the two-dimensional (2D) energy spectrum for the first time. The electron energy spectrum measured by sweeping the retarding grid potential revealed thresholds corresponding to electronic transitions in the specimen, followed by 2D-derivation treatment applied just at the observed thresholds. This allowed chemical mapping by SEM. In this report the 273 eV Auger transition in carbon deposited onto the Si(100) sample was chosen as a source for chemical contrast in the SEM image. In addition to Auger electrons, we expect analogous energy-selective contrast enhancement for inelastically scattered electrons, for example, in plasmonic contrast and elastically scattered electrons, for example in phase contrast, our method, proved for carbon, is expected to apply to a broader list of elements as a general capability of chemical mapping, at several-fold better lateral resolution when compared with energy dispersive spectroscopy (EDS).

  13. The National Fuel End-Use Efficiency Field Test: Energy Savings and Performance of an Improved Energy Conservation Measure Selection Technique

    SciTech Connect

    Ternes, M.P.

    1991-01-01

    The performance of an advanced residential energy conservation measure (ECM) selection technique was tested in Buffalo, New York, to verify the energy savings and program improvements achieved from use of the technique in conservation programs and provide input into determining whether utility investments in residential gas end-use conservation are cost effective. The technique analyzes a house to identify all ECMs that are cost effective in the building envelope, space-heating system, and water-heating system. The benefit-to-cost ratio (BCR) for each ECM is determined and cost-effective ECMs (BCR > 1.0) are selected once interactions between ECMs are taken into account. Eighty-nine houses with the following characteristics were monitored for the duration of the field test: occupants were low-income, houses were single-family detached houses but not mobile homes, and primary space- and water-heating systems were gas-fired. Forty-five houses received a mix of ECMs as selected by the measure selection technique (audit houses) and 44 served as a control group. Pre-weatherization data were collected from January to April 1988 and post-weatherization data were collected from December 1988 to April 1989. Space- and waterheating gas consumption and indoor temperature were monitored weekly during the two winters. A house energy consumption model and regression analysis were employed to normalize the space-heating energy savings to average outdoor temperature conditions and a 68 F indoor temperature. Space and water-heating energy savings for the audit houses were adjusted by the savings for the control houses. The average savings of 257 therms/year for the audit houses was 17% of the average pre-weatherization house gas consumption and 78% of that predicted. Average space-heating energy savings was 252 therms/year (25% of pre-weatherization space-heating energy consumption and 85% of the predicted value) and average water-heating savings was 5 therms/year (2% of pre

  14. Consequences of scale of flow field observation on apparent energy expenditure and habitat selection by juvenile coho

    NASA Astrophysics Data System (ADS)

    Tullos, D. D.; Walter, C.; Dunham, J.

    2015-12-01

    We conducted a 1:1 scale model of a full-channel log jam in an outdoor experimental channel with the objectives of 1) evaluating how the magnitude and variability of velocity changes with increasing discretization of the flow field; 2) demonstrating how velocities at different resolutions impact perceived selection of fish habitat; 3) documenting how energy expenditure estimated from velocity measured at different scales (indirect method) corresponds to estimates based on tailbeat frequencies (direct method); and 4) investigating the temporal and spatial variability of the flow field that might explain differences between direct and indirect estimates of energy expenditure. Velocities were measured in a 10cm grid spacing using Acoustic Doppler Velocimetry and fish locations were observed using underwater videogrammetry. Results indicate that scale of observation matters. As predicted, the mean and variance of velocity decreases with coarsening resolution of the flow field observations, illustrating how observed velocities are compressed into a narrower and lower range at coarser scales relative to finer scales. This trend of compressed variability also occurs for the locations where fish were observed, indicating that coarser-resolution observations underestimate the magnitude and range of velocities that fish select. Regarding energy expenditure, in comparing estimates direct and indirect estimates, we find that energy expenditure from the indirect estimates is always lower than the direct estimates, though the degree depend on the scale of velocity measurements. These results are consistent with our hypothesis that coarser resolution observations underestimate the amount of energy that fish expend in resting and foraging, but also indicate that velocity-based measurements generally underestimate energy expenditure by fish. Spatial and temporal variability of velocities do not fully explain the discrepancies between direct and indirect estimates in energy

  15. Air-bridged lateral epitaxial overgrowth of GaN thin films

    NASA Astrophysics Data System (ADS)

    Kidoguchi, Isao; Ishibashi, Akihiko; Sugahara, Gaku; Ban, Yuzaburoh

    2000-06-01

    A promising technique of selective lateral epitaxy, namely air-bridged lateral epitaxial overgrowth, is demonstrated in order to reduce the wing tilt as well as the threading dislocation density in GaN thin films. A seed GaN layer was etched to make ridge-stripe along <11¯00>GaN direction and a GaN material was regrown from the exposed (0001) top facet of the ridged GaN seed structures, whose sidewalls and etched bottoms were covered with silicon nitride mask, using low-pressure metalorganic vapor phase epitaxy. The density of dislocations in the wing region was reduced to be <107cm-2, which was at least two orders of magnitude lower than that of underlying GaN. The magnitude of the wing tilt was determined to be 0.08° by x-ray diffraction (XRD) measurements, which was smaller than other lateral epitaxial overgrown GaN thin films. The full width at half maximum of XRD for the wing region was 138 arc sec, indicating high uniformity of c-axis orientation.

  16. Monochromatic X-ray photon counting using an energy-selecting device and its application to iodine imaging

    NASA Astrophysics Data System (ADS)

    Oda, Yasuyuki; Sato, Eiichi; Yamaguchi, Satoshi; Hagiwara, Osahiko; Matsukiyo, Hiroshi; Watanabe, Manabu; Kusachi, Shinya

    2015-08-01

    Quasi-monochromatic photon counting was performed using a cadmium telluride detector and an energy-selecting device, consisting of two comparators and a microcomputer (MC). The two threshold energies are determined using low and high-energy comparators, respectively. The MC produces a single logical pulse when only a logical pulse from a low-energy comparator is input to the MC. Next, the MC never produces the pulse when two pulses from low and high-energy comparators are input to the MC, simultaneously. The logical pulses from the MC are input to a frequency-voltage converter (FVC) to convert count rates into voltages; the rate is proportional to the voltage. The output voltage from the FVC is sent to a personal computer through an analog-digital converter to reconstruct tomograms. The X-ray projection curves for tomography are obtained by repeated linear scans and rotations of the object at a tube voltage of 70 kV and a current of 12 μA. Iodine (I) K-edge CT was performed using contrast media and X-ray photons with a count rate of 2.2 kilocounts per second and energies ranging from 34 to 50 keV, since these photons with energies beyond I-K-edge energy 33.2 keV are absorbed effectively by I atoms.

  17. CHARACTERIZING COSTS, SAVINGS AND BENEFITS OF A SELECTION OF ENERGY EFFICIENT EMERGING TECHNOLOGIES IN THE UNITED STATES

    SciTech Connect

    Xu, T.; Slaa, J.W.; Sathaye, J.

    2010-12-15

    Implementation and adoption of efficient end-use technologies have proven to be one of the key measures for reducing greenhouse gas (GHG) emissions throughout the industries. In many cases, implementing energy efficiency measures is among one of the most cost effective investments that the industry could make in improving efficiency and productivity while reducing CO2 emissions. Over the years, there have been incentives to use resources and energy in a cleaner and more efficient way to create industries that are sustainable and more productive. With the working of energy programs and policies on GHG inventory and regulation, understanding and managing the costs associated with mitigation measures for GHG reductions is very important for the industry and policy makers around the world. Successful implementation of emerging technologies not only can help advance productivities and competitiveness but also can play a significant role in mitigation efforts by saving energy. Providing evaluation and estimation of the costs and energy savings potential of emerging technologies is the focus of our work in this project. The overall goal of the project is to identify and select emerging and under-utilized energy-efficient technologies and practices as they are important to reduce energy consumption in industry while maintaining economic growth. This report contains the results from performing Task 2"Technology evaluation" for the project titled"Research Opportunities in Emerging and Under-Utilized Energy-Efficient Industrial Technologies," which was sponsored by California Energy Commission and managed by CIEE. The project purpose is to analyze market status, market potential, and economic viability of selected technologies applicable to the U.S. In this report, LBNL first performed re-assessments of all of the 33 emerging energy-efficient industrial technologies, including re-evaluation of the 26 technologies that were previously identified by Martin et al. (2000) and

  18. Room-temperature Domain-epitaxy of Copper Iodide Thin Films for Transparent CuI/ZnO Heterojunctions with High Rectification Ratios Larger than 10(9).

    PubMed

    Yang, Chang; Kneiß, Max; Schein, Friedrich-Leonhard; Lorenz, Michael; Grundmann, Marius

    2016-02-26

    CuI is a p-type transparent conductive semiconductor with unique optoelectronic properties, including wide band gap (3.1 eV), high hole mobility (>40 cm(2)V(-1)s(-1) in bulk), and large room-temperature exciton binding energy (62 meV). The difficulty in epitaxy of CuI is the main obstacle for its application in advanced solid-state electronic devices. Herein, room-temperature heteroepitaxial growth of CuI on various substrates with well-defined in-plane epitaxial relations is realized by reactive sputtering technique. In such heteroepitaxial growth the formation of rotation domains is observed and hereby systematically investigated in accordance with existing theoretical study of domain-epitaxy. The controllable epitaxy of CuI thin films allows for the combination of p-type CuI with suitable n-type semiconductors with the purpose to fabricate epitaxial thin film heterojunctions. Such heterostructures have superior properties to structures without or with weakly ordered in-plane orientation. The obtained epitaxial thin film heterojunction of p-CuI(111)/n-ZnO(00.1) exhibits a high rectification up to 2 × 10(9) (± 2 V), a 100-fold improvement compared to diodes with disordered interfaces. Also a low saturation current density down to 5 × 10(-9)Acm(-2) is formed. These results prove the great potential of epitaxial CuI as a promising p-type optoelectronic material.

  19. Selection for Improved Energy Use Efficiency and Drought Tolerance in Canola Results in Distinct Transcriptome and Epigenome Changes.

    PubMed

    Verkest, Aurine; Byzova, Marina; Martens, Cindy; Willems, Patrick; Verwulgen, Tom; Slabbinck, Bram; Rombaut, Debbie; Van de Velde, Jan; Vandepoele, Klaas; Standaert, Evi; Peeters, Marrit; Van Lijsebettens, Mieke; Van Breusegem, Frank; De Block, Marc

    2015-08-01

    To increase both the yield potential and stability of crops, integrated breeding strategies are used that have mostly a direct genetic basis, but the utility of epigenetics to improve complex traits is unclear. A better understanding of the status of the epigenome and its contribution to agronomic performance would help in developing approaches to incorporate the epigenetic component of complex traits into breeding programs. Starting from isogenic canola (Brassica napus) lines, epilines were generated by selecting, repeatedly for three generations, for increased energy use efficiency and drought tolerance. These epilines had an enhanced energy use efficiency, drought tolerance, and nitrogen use efficiency. Transcriptome analysis of the epilines and a line selected for its energy use efficiency solely revealed common differentially expressed genes related to the onset of stress tolerance-regulating signaling events. Genes related to responses to salt, osmotic, abscisic acid, and drought treatments were specifically differentially expressed in the drought-tolerant epilines. The status of the epigenome, scored as differential trimethylation of lysine-4 of histone 3, further supported the phenotype by targeting drought-responsive genes and facilitating the transcription of the differentially expressed genes. From these results, we conclude that the canola epigenome can be shaped by selection to increase energy use efficiency and stress tolerance. Hence, these findings warrant the further development of strategies to incorporate epigenetics into breeding.

  20. Molecular dynamics and quasidynamics simulations of the annealing of bulk and near-surface interstitials formed in molecular-beam epitaxial Si due to low-energy particle bombardment during deposition

    NASA Technical Reports Server (NTRS)

    Kitabatake, M.; Fons, P.; Greene, J. E.

    1991-01-01

    The relaxation, diffusion, and annihilation of split and hexagonal interstitials resulting from 10 eV Si irradiation of (2x1)-terminated Si(100) are investigated. Molecular dynamics and quasidynamics simulations, utilizing the Tersoff many-body potential are used in the investigation. The interstitials are created in layers two through six, and stable atomic configurations and total potential energies are derived as a function of site symmetry and layer depth. The interstitial Si atoms are allowed to diffuse, and the total potential energy changes are calculated. Lattice configurations along each path, as well as the starting configurations, are relaxed, and minimum energy diffusion paths are derived. The results show that the minimum energy paths are toward the surface and generally involved tetrahedral sites. The calculated interstitial migration activation energies are always less than 1.4 eV and are much lower in the near-surface region than in the bulk.

  1. H+CH4 → H2 + CH3 initial state-selected reaction probabilities on different potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Ellerbrock, Roman; Manthe, Uwe

    2017-01-01

    Initial state-selected reaction probabilities for the H +CH4 →H2 +CH3 reaction on a recently developed potential energy surface which employs neutral network fitting based on permutational invariant polynomials are reported. The quantum dynamics calculations use the quantum transition state concept and the multi-layer multi-configurational time-dependent Hartree approach and study the reaction process in full-dimensionality for vanishing total angular momentum. A detailed comparison with previous results obtained on other high-level potential energy surfaces is given. The connection between the level of quantum state resolution and the sensitivity of the results on differences in the potential energy surfaces is highlighted. Employing a decomposition of the total reactivity into contributions of the different vibrational states of the activated complex, it is found that differences between the potential energy surfaces are mainly related to the umbrella motion of the methyl group.

  2. Comparative study of microstructural characteristics of electrospark and Nd:YAG laser epitaxially growing coatings

    NASA Astrophysics Data System (ADS)

    Xie, Yu-jiang; Wang, Mao-cai; Huang, Da-wei

    2007-05-01

    As low-heat input welding processes, electrospark deposition and pulsed Nd:YAG laser cladding can be commonly used to prepare epitaxially growing coatings. However, these two processes have quite different characteristics in the energy input, the amount of materials involved, and the temperature gradient, and hence might result in dissimilar microstructural characteristics. In this paper, a comparative study has been made between microstructural characteristics in epitaxial growth coatings prepared by electrospark deposition and pulsed Nd:YAG laser cladding. Some interesting results have been achieved. Firstly, epitaxial growth coatings can be commonly achieved by these two techniques. Secondly, microstructural morphologies of these two epitaxial growth coatings are obviously different, cellular columnar structure prevails in the electrospark coating while columnar dendritic structure occupies most of the laser coating thickness, more importantly, electrospark coating remains fully columnar in the whole layer whereas laser coating tends to change from columnar to equiaxed at the top of the layer. Thirdly, electrospark coating possesses finer and more homogeneous microstructure than laser coating.

  3. Criterion for material selection in design of bulk piezoelectric energy harvesters.

    PubMed

    Priya, Shashank

    2010-12-01

    Vibration energy harvesting has gained tremendous attention in the past decade and continues to grow rapidly. There are various transduction mechanisms for converting the vibration energy into electrical energy, out of which the piezoelectric mechanism has been shown to provide advantages at the micro-to-meso scale. In the past few years, several studies have tried to address the question of which piezoelectric composition is better for energy harvesting; however, discussion on this subject continues. The intent of this letter is to provide an answer for this question through a simple criterion which can be used in routine material evaluation.

  4. Epitaxial growth of Ruddlesden-Popper Lan+1NinO3n+1 series using reactive molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Lee, June Hyuk; Tung, I.-Cheng; Moyer, Jarrett; Luo, Guangfu; Chang, Seo Hyoung; Morgan, Dane; Hong, Hawoong; Schiffer, Peter; Fong, Dillon; Freeland, John

    2014-03-01

    We report the growth of single crystalline Lan+1NinO3n+1 epitaxial thin films using reactive molecular-beam epitaxy. Ruddlesden-Popper Lan+1NinO3n+1 compounds, consisting of LaO+ and NiO2- layers, have been considered a potential candidate for solid-oxide fuel cell cathodes and thermoelectrics. However, the growth of higher order Lan+1NinO3n+1 single crystals has not been possible so far. We utilize synchrotron x-ray diffraction at the Advanced Photon Source during layer?by?layer deposition together with density functional theory calculations to understand how LaO+ and NiO2- oxide layers re-arrange dynamically during growth. Using this layer re-arrangement, epitaxial La2NiO4, La3Ni2O7,andLaSUB>4Ni3O10 films on (001)-oriented SrTiO3 have been synthesized with the proper nickel valance state and structure. Here we will discuss the connection between structure and electrical transport properties. Work at the APS, Argonne is supported by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

  5. Incorporation of La in epitaxial SrTiO3 thin films grown by atomic layer deposition on SrTiO3-buffered Si (001) substrates

    NASA Astrophysics Data System (ADS)

    McDaniel, Martin D.; Posadas, Agham; Ngo, Thong Q.; Karako, Christine M.; Bruley, John; Frank, Martin M.; Narayanan, Vijay; Demkov, Alexander A.; Ekerdt, John G.

    2014-06-01

    Strontium titanate, SrTiO3 (STO), thin films incorporated with lanthanum are grown on Si (001) substrates at a thickness range of 5-25 nm. Atomic layer deposition (ALD) is used to grow the LaxSr1-xTiO3 (La:STO) films after buffering the Si (001) substrate with four-unit-cells of STO deposited by molecular beam epitaxy. The crystalline structure and orientation of the La:STO films are confirmed via reflection high-energy electron diffraction, X-ray diffraction, and cross-sectional transmission electron microscopy. The low temperature ALD growth (˜225 °C) and post-deposition annealing at 550 °C for 5 min maintains an abrupt interface between Si (001) and the crystalline oxide. Higher annealing temperatures (650 °C) show more complete La activation with film resistivities of ˜2.0 × 10-2 Ω cm for 20-nm-thick La:STO (x ˜ 0.15); however, the STO-Si interface is slightly degraded due to the increased annealing temperature. To demonstrate the selective incorporation of lanthanum by ALD, a layered heterostructure is grown with an undoped STO layer sandwiched between two conductive La:STO layers. Based on this work, an epitaxial oxide stack centered on La:STO and BaTiO3 integrated with Si is envisioned as a material candidate for a ferroelectric field-effect transistor.

  6. A look inside epitaxial cobalt-on-fluorite nanoparticles with three-dimensional reciprocal space mapping using GIXD, RHEED and GISAXS.

    PubMed

    Suturin, S M; Fedorov, V V; Korovin, A M; Valkovskiy, G A; Konnikov, S G; Tabuchi, M; Sokolov, N S

    2013-08-01

    In this work epitaxial growth of cobalt on CaF2(111), (110) and (001) surfaces has been extensively studied. It has been shown by atomic force microscopy that at selected growth conditions stand-alone faceted Co nanoparticles are formed on a fluorite surface. Grazing-incidence X-ray diffraction (GIXD) and reflection high-energy electron diffraction (RHEED) studies have revealed that the particles crystallize in the face-centered cubic lattice structure otherwise non-achievable in bulk cobalt under normal conditions. The particles were found to inherit lattice orientation from the underlying CaF2 layer. Three-dimensional reciprocal space mapping carried out using X-ray and electron diffraction has revealed that there exist long bright 〈111〉 streaks passing through the cobalt Bragg reflections. These streaks are attributed to stacking faults formed in the crystal lattice of larger islands upon coalescence of independently nucleated smaller islands. Distinguished from the stacking fault streaks, crystal truncation rods perpendicular to the {111} and {001} particle facets have been observed. Finally, grazing-incidence small-angle X-ray scattering (GISAXS) has been applied to decouple the shape-related scattering from that induced by the crystal lattice defects. Particle faceting has been verified by modeling the GISAXS patterns. The work demonstrates the importance of three-dimensional reciprocal space mapping in the study of epitaxial nanoparticles.

  7. A look inside epitaxial cobalt-on-fluorite nanoparticles with three-dimensional reciprocal space mapping using GIXD, RHEED and GISAXS

    PubMed Central

    Suturin, S. M.; Fedorov, V. V.; Korovin, A. M.; Valkovskiy, G. A.; Konnikov, S. G.; Tabuchi, M.; Sokolov, N. S.

    2013-01-01

    In this work epitaxial growth of cobalt on CaF2(111), (110) and (001) surfaces has been extensively studied. It has been shown by atomic force microscopy that at selected growth conditions stand-alone faceted Co nanoparticles are formed on a fluorite surface. Grazing-incidence X-ray diffraction (GIXD) and reflection high-energy electron diffraction (RHEED) studies have revealed that the particles crystallize in the face-centered cubic lattice structure otherwise non-achievable in bulk cobalt under normal conditions. The particles were found to inherit lattice orientation from the underlying CaF2 layer. Three-dimensional reciprocal space mapping carried out using X-ray and electron diffraction has revealed that there exist long bright 〈111〉 streaks passing through the cobalt Bragg reflections. These streaks are attributed to stacking faults formed in the crystal lattice of larger islands upon coalescence of independently nucleated smaller islands. Distinguished from the stacking fault streaks, crystal truncation rods perpendicular to the {111} and {001} particle facets have been observed. Finally, grazing-incidence small-angle X-ray scattering (GISAXS) has been applied to decouple the shape-related scattering from that induced by the crystal lattice defects. Particle faceting has been verified by modeling the GISAXS patterns. The work demonstrates the importance of three-dimensional reciprocal space mapping in the study of epitaxial nanoparticles. PMID:24046491

  8. Analysis of Selected Provisions of the Domestic Manufacturing and Energy Jobs Act of 2010

    EIA Publications

    2010-01-01

    This report responds to a letter dated August 16, 2010, from Janice Mays, Staff Director of the U.S. House of Representatives' Committee on Ways and Means, requesting that the U.S. Energy Information Administration (EIA) analyze several provisions included in the July 26, 2010, discussion draft of the Domestic Manufacturing and Energy Jobs Act of 2010.

  9. Energy Literacy: A Challenging Role for the Educator in the Coal and Nuclear Resource Selection Process.

    ERIC Educational Resources Information Center

    Journey, Drexel D.

    There is a pressing need for the involvement of the educational community in electrical energy matters. The case for that involvement is persuasive as evidenced by examples of energy illiteracy in the mass communication media. Intellectual wastelands breed governmental indecision and foster conditions in which the entrepreneurial sector cannot…

  10. Developmental Growth in Students' Concept of Energy: Analysis of Selected Items from the TIMSS Database

    ERIC Educational Resources Information Center

    Liu, Xiufeng; McKeough, Anne

    2005-01-01

    The aim of this study was to develop a model of students' energy concept development. Applying Case's (1985, 1992) structural theory of cognitive development, we hypothesized that students' concept of energy undergoes a series of transitions, corresponding to systematic increases in working memory capacity. The US national sample from the Third…

  11. Selected Sources of Energy-Related Material for School Children and Educators.

    ERIC Educational Resources Information Center

    Altman, Paula, Comp.

    This document is the result of a study to determine the general availability of free or low-cost energy-related educational materials for primary and secondary school students and educators. Some of the organizations represented in this list take policy positions on energy issues and express them in the school level materials. Contained in this…

  12. Mechanism of the swift heavy ion induced epitaxial recrystallization in predamaged silicon carbide

    SciTech Connect

    Benyagoub, A.; Audren, A.

    2009-10-15

    Although silicon carbide has attracted extensive investigations of ion irradiation effects at low energy owing to its potential use in harsh environments, very few works were carried out in the field of ion irradiation at high energy. A recent preliminary study exploring the combination of low and high energy ion irradiation effects in silicon carbide revealed that the damaged layer formed by low energy ion irradiation can undergo an epitaxial recrystallization under subsequent swift heavy ion irradiation. The present paper is devoted to the investigation of the mechanisms at the origin of this phenomenon by performing additional experiments. A detailed analysis of the kinetics of this recrystallization effect demonstrates that the latter cannot be explained by the models proposed for the well-known ion-beam-induced epitaxial crystallization process. Furthermore, it is found that this effect can be accounted for by a mechanism combining the melting within the ion tracks of the amorphous zones through a thermal spike process and their subsequent epitaxial recrystallization initiated from the neighboring crystalline regions wherever the size of the latter surpasses a certain critical value.

  13. Technical applications of solar energy. Project photovoltaic systems and project selective coatings

    NASA Astrophysics Data System (ADS)

    Gindele, K.; Honstetter, K.; Karl, H.; Koehl, M.; Lehner, G.; Mast, M.; Spohn, C.; Wagner, A.

    1983-12-01

    Long time stability of photovoltaic generators, hybrid collectors, and measuring devices for solar cells and solar cell generators were investigated. No aging of electrical features is stated after 6 yr working, while thermal and electrical efficiencies of collectors amount to 70% and 8% respectively. Radiative properties of selective coatings were measured, composition and structure of selective surfaces, vapor deposition methods (e.g., cermet-coatings), and chemical methods (e.g., cooper-oxide) were investigated.

  14. Siting-selection study for the Soyland Power Cooperative, Inc. , compressed-air energy-storage system (CAES)

    SciTech Connect

    Not Available

    1982-01-01

    A method used for siting a compressed air energy storage (CAES) system using geotechnical and environmental criteria is explained using the siting of a proposed 220 MW water-compensated CAES plant in Illinois as an example. Information is included on the identification and comparative ranking of 28 geotechnically and environmental sites in Illinois, the examination of fatal flaws, e.g., mitigation, intensive studies, costly studies, permit denials, at 7 sites; and the selection of 3 sites for further geological surveying. (LCL)

  15. 1/f Noise in Gated Epitaxial Graphene Nanoribbons

    NASA Astrophysics Data System (ADS)

    Vail, Owen; Yang, Jeremy; Miettinen, Anna; Hankinson, John; Berger, Claire; de Heer, Walter; Jiang, Zhigang

    Epitaxial Graphene Nanoribbons (EGNR) grown on sidewall SiC have gained interest as a high-quality interconnect enabling room temperature ballistic transport over micron lengths. To be useful as an interconnect a proper characterization of the noise level in the EGNR needs to be determined. Toward this end, we fabricated EGNR devices with an Aluminum-Oxide top gate and use field effect to tune the fermi energy in the graphene channel. Our studies of the electronic noise and its dependence on the charge density in the ribbon reveal information about the subband structure of the density of states in addition to the ribbon's spectral density at low frequencies. Comparisons to the widely reported 1/f noise in silicon and other forms of graphene provide strong references for analyzing our results.

  16. Compensation in epitaxial cubic SiC films

    NASA Technical Reports Server (NTRS)

    Segall, B.; Alterovitz, S. A.; Haugland, E. J.; Matus, L. G.

    1986-01-01

    Hall measurements on four n-type cubic SiC films epitaxially grown by chemical vapor deposition on SiC substrates are reported. The temperature dependent carrier concentrations indicate that the samples are highly compensated. Donor ionization energies, E sub D, are less than one half the values previously reported. The values for E sub D and the donor concentration N sub D, combined with results for small bulk platelets with nitrogen donors, suggest the relation E sub D (N sub D) = E sub D(O) - alpha N sub N sup 1/3 for cubic SiC. A curve fit gives alpha is approx 2.6x10/5 meV cm and E sub D (O) approx 48 meV, which is the generally accepted value of E sub D(O) for nitrogen donors in cubic SiC.

  17. Atomic scale structure investigations of epitaxial Fe/Cr multilayers

    NASA Astrophysics Data System (ADS)

    Kąc, M.; Morgiel, J.; Polit, A.; Zabila, Y.; Marszałek, M.

    2014-06-01

    Fe/Cr multilayers were deposited by molecular beam epitaxy on the MgO(1 0 0) substrate. Structural properties of the samples were analyzed by low energy electron diffraction, high resolution transmission electron microscopy (HRTEM), as well as by X-ray reflectivity, conversion electron Mössbauer spectroscopy (CEMS) and Auger electron spectroscopy. Investigations revealed multilayered system built of well-ordered Fe and Cr thin films with (1 0 0) orientation. A high geometrical perfection of the system, i.e. planar form of interfaces and reproducible thickness of layers, was also proven. Fe/Cr interface roughness was determined to be 2-3 atomic layers. CEMS studies allowed to analyze at atomic scale the structure of buried Fe/Cr interfaces, as well as to distinguish origin of interface roughness. Roughnesses resulting from interface corrugations and from the Fe-Cr interdiffusion at interfaces were observed. Fe/Cr multilayers showed strong antiferromagnetic coupling of Fe layers.

  18. Urbach absorption edge in epitaxial erbium-doped silicon

    SciTech Connect

    Shmagin, V. B. Kudryavtsev, K. E.; Shengurov, D. V.; Krasilnik, Z. F.

    2015-02-07

    We investigate the dependencies of the photocurrent in Si:Er p-n junctions on the energy of the incident photons. The exponential absorption edge (Urbach edge) just below fundamental edge of silicon was observed in the absorption spectra of epitaxial Si:Er layers grown at 400–600 C. It is shown that the introduction of erbium significantly enhances the structural disorder in the silicon crystal which was estimated from the slope of the Urbach edge. We discuss the possible nature of the structural disorder in Si:Er and a new mechanism of erbium excitation, which does not require the presence of deep levels in the band gap of silicon.

  19. Reversible metal-hydride phase transformation in epitaxial films.

    PubMed

    Roytburd, Alexander L; Boyerinas, Brad M; Bruck, Hugh A

    2015-03-11

    Metal-hydride phase transformations in solids commonly proceed with hysteresis. The extrinsic component of hysteresis is the result of the dissipation of energy of internal stress due to plastic deformation and fracture. It can be mitigated on the nanoscale, where plastic deformation and fracture are suppressed and the transformation proceeds through formation and evolution of coherent phases. However, the phase coherency introduces intrinsic thermodynamic hysteresis, preventing reversible transformation. In this paper, it is shown that thermodynamic hysteresis of coherent metal-hydride transformation can be eliminated in epitaxial film due to substrate constraint. Film-substrate interaction leads to formation of heterophase polydomain nanostructure with variable phase fraction which can change reversibly by varying temperature in a closed system or chemical potential in an open system.

  20. Reversible metal-hydride phase transformation in epitaxial films

    NASA Astrophysics Data System (ADS)

    Roytburd, Alexander L.; Boyerinas, Brad M.; Bruck, Hugh A.

    2015-03-01

    Metal-hydride phase transformations in solids commonly proceed with hysteresis. The extrinsic component of hysteresis is the result of the dissipation of energy of internal stress due to plastic deformation and fracture. It can be mitigated on the nanoscale, where plastic deformation and fracture are suppressed and the transformation proceeds through formation and evolution of coherent phases. However, the phase coherency introduces intrinsic thermodynamic hysteresis, preventing reversible transformation. In this paper, it is shown that thermodynamic hysteresis of coherent metal-hydride transformation can be eliminated in epitaxial film due to substrate constraint. Film-substrate interaction leads to formation of heterophase polydomain nanostructure with variable phase fraction which can change reversibly by varying temperature in a closed system or chemical potential in an open system.

  1. Diffraction studies for stoichiometry effects in BaTiO3 grown by molecular beam epitaxy on Ge(001)

    NASA Astrophysics Data System (ADS)

    Hsu, Min-Hsiang Mark; Merckling, Clement; El Kazzi, Salim; Pantouvaki, Marianna; Richard, Oliver; Bender, Hugo; Meersschaut, Johan; Van Campenhout, Joris; Absil, Philippe; Van Thourhout, Dries

    2016-12-01

    In this work, we present a systematic study of the effect of the stoichiometry of BaTiO3 (BTO) films grown on the Ge(001) substrate by molecular-beam-epitaxy using different characterization methods relying on beam diffraction, including reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and selected-area electron diffraction in transmission electron microscopy. Surprisingly, over a wide range of [Ba]/[Ti] ratios, as measured by the Rutherford backscattering spectrometry, all the BTO layers exhibit the same epitaxial relationship <100>BTO(001)//<110>Ge(001) with the substrate, describing a 45° lattice rotation of the BTO lattice with respect to the Ge lattice. However, varying the [Ba]/[Ti] ratio does change the diffraction behavior. From RHEED patterns, we can derive that excessive [Ba] and [Ti] generate twinning planes and a rougher surface in the non-stoichiometric BTO layers. XRD allows us to follow the evolution of the lattice constants as a function of the [Ba]/[Ti] ratio, providing an option for tuning the tetragonality of the BTO layer. In addition, we found that the intensity ratio of the 3 lowest-order Bragg peaks I(001)/I(002), I(101)/I(002), and I(111)/I(002) derived from ω - 2θ scans characteristically depend on the BTO stoichiometry. To explain the relation between observed diffraction patterns and the stoichiometry of the BTO films, we propose a model based on diffraction theory explaining how excess [Ba] or [Ti] in the layer influences the diffraction response.

  2. Silicon Carbide Epitaxial Films Studied by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Silicon carbide (SiC) holds great potential as an electronic material because of its wide band gap energy, high breakdown electric field, thermal stability, and resistance to radiation damage. Possible aerospace applications of high-temperature, high-power, or high-radiation SiC electronic devices include sensors, control electronics, and power electronics that can operate at temperatures up to 600 C and beyond. Commercially available SiC devices now include blue light-emitting diodes (LED's) and high-voltage diodes for operation up to 350 C, with other devices under development. At present, morphological defects in epitaxially grown SiC films limit their use in device applications. Research geared toward reducing the number of structural inhomogeneities can benefit from an understanding of the type and nature of problems that cause defects. The Atomic Force Microscope (AFM) has proven to be a useful tool in characterizing defects present on the surface of SiC epitaxial films. The in-house High-Temperature Integrated Electronics and Sensors (HTIES) Program at the NASA Lewis Research Center not only extended the dopant concentration range achievable in epitaxial SiC films, but it reduced the concentration of some types of defects. Advanced structural characterization using the AFM was warranted to identify the type and structure of the remaining film defects and morphological inhomogeneities. The AFM can give quantitative information on surface topography down to molecular scales. Acquired, in part, in support of the Advanced High Temperature Engine Materials Technology Program (HITEMP), the AFM had been used previously to detect partial fiber debonding in composite material cross sections. Atomic force microscopy examination of epitaxial SiC film surfaces revealed molecular-scale details of some unwanted surface features. Growth pits propagating from defects in the substrate, and hillocks due, presumably, to existing screw dislocations in the substrates, were

  3. Bioenergetic modeling reveals that Chinese green tree vipers select postprandial temperatures in laboratory thermal gradients that maximize net energy intake.

    PubMed

    Tsai, Tein-Shun; Lee, How-Jing; Tu, Ming-Chung

    2009-11-01

    With bioenergetic modeling, we tested the hypothesis that reptiles maximize net energy gain by postprandial thermal selection. Previous studies have shown that Chinese green tree vipers (Trimeresurus s. stejnegeri) have postprandial thermophily (mean preferred temperature T(p) for males =27.8 degrees C) in a linear thigmothermal gradient when seclusion sites and water existed. With some published empirical models of digestion associated factors for this snake, we calculated the average rate (E(net)) and efficiency (K(net)) of net energy gain from possible combinations of meal size, activity level, and feeding frequency at each temperature. The simulations consistently revealed that E(net) maximizes at the T(p) of these snakes. Although the K(net) peaks at a lower temperature than E(net), the value of K(net) remains high (>=0.85 in ratio to maximum) at the peak temperature of E(net). This suggested that the demands of both E(net) and K(net) can be attained by postprandial thermal selection in this snake. In conclusion, the data support our prediction that postprandial thermal selection may maximize net energy gain.

  4. Energy profiles of selected Latin American and Caribbean countries. Report series No. 2

    SciTech Connect

    Wu, K.

    1994-07-01

    Countries in this report include Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Mexico, Peru, Trinidad and Tobago, and Venezuela. These ten countries are the most important oil and gas producers in the Latin American and the Caribbean region. In the following sections, the primary energy supply (oil, gas, coal, hydroelectricity, and nuclear power whenever they are applicable), primary energy consumption, downstream oil sector development, gas utilization are discussed for each of the ten countries. The report also presents our latest forecasts of petroleum product consumption in each country toward 2000, which form the basis of the outlook for regional energy production and consumption outlined in Report No 1. Since the bulk of primary energy supply and demand is hydrocarbons for many countries, brief descriptions of the important hydrocarbons policy issues are provided at the end of the each country sections.

  5. Barriers and opportunities: A review of selected successful energy-efficiency programs

    SciTech Connect

    Worrell, Ernst; Price, Lynn

    2001-03-20

    In industry, barriers may exist at various points in the decision making process, and in the implementation and management of measures to improve energy efficiency. Barriers may take many forms, and are determined by the business environment and include decision-making processes, energy prices, lack of information, a lack of confidence in the information, or high transaction costs for obtaining reliable information, as well as limited capital availability. Other barriers are the ''invisibility'' of energy efficiency measures and the difficulty of quantifying the impacts, and slow diffusion of innovative technology into markets while firms typically under-invest in R and D, despite the high pay-backs. Various programs try to reduce the barriers to improve the uptake of innovative technologies. A wide array of policies has been used and tested in the industrial sector in industrialized countries, with varying success rates. We review some new approaches to industrial energy efficiency improvement in industrialized countries, focusing on voluntary agreements.

  6. Energy Efficiency Potential in Existing Commercial Buildings: Review of Selected Recent Studies

    SciTech Connect

    Belzer, David B.

    2009-04-03

    This report reviews six recent studies (from 2002 through 2006) by states and utilities to assess the energy saving potential in existing commercial buildings. The studies cover all or portions of California, Connecticut, Vermont, Colorado, Illinois, and the Pacific Northwest. The studies clearly reveal that lighting remains the single largest and most cost effective end use that can be reduced to save energy. Overall the study indicated that with existing technologies and costs, a reasonable range of economic savings potential in existing commercial buildings is between 10 and 20 percent of current energy use. While not a focus of the study, an additional conclusion is that implementation of commercial building monitoring and controls would also play an important role in the nation’s efforts to improve energy efficiency of existing buildings.

  7. Selecting and Effectively Using Sports Drinks, Carbohydrate Gels and Energy Bars

    MedlinePlus

    ... stream, giving the muscles a quick injection of fuel. Bars with low glycemic index, best before exercise, result in a slower release of sugar into the circulation, creating sustained energy. Carbohydrates are digested and appear in the circulation ...

  8. Material and Energy Flows Associated with Select Metals in GREET 2. Molybdenum, Platinum, Zinc, Nickel, Silicon

    SciTech Connect

    Benavides, Pahola T.; Dai, Qiang; Sullivan, John L.; Kelly, Jarod C.; Dunn, Jennifer B.

    2015-09-01

    In this work, we analyzed the material and energy consumption from mining to production of molybdenum, platinum, zinc, and nickel. We also analyzed the production of solar- and semiconductor-grade silicon. We described new additions to and expansions of the data in GREET 2. In some cases, we used operating permits and sustainability reports to estimate the material and energy flows for molybdenum, platinum, and nickel, while for zinc and silicon we relied on information provided in the literature.

  9. Environmentally-acceptable fossil energy site evaluation and selection: methodology and user's guide. Volume 1

    SciTech Connect

    Northrop, G.M.

    1980-02-01

    This report is designed to facilitate assessments of environmental and socioeconomic impacts of fossil energy conversion facilities which might be implemented at potential sites. The discussion of methodology and the User's Guide contained herein are presented in a format that assumes the reader is not an energy technologist. Indeed, this methodology is meant for application by almost anyone with an interest in a potential fossil energy development - planners, citizen groups, government officials, and members of industry. It may also be of instructional value. The methodology is called: Site Evaluation for Energy Conversion Systems (SELECS) and is organized in three levels of increasing sophistication. Only the least complicated version - the Level 1 SELECS - is presented in this document. As stated above, it has been expressly designed to enable just about anyone to participate in evaluating the potential impacts of a proposed energy conversion facility. To accomplish this objective, the Level 1 calculations have been restricted to ones which can be performed by hand in about one working day. Data collection and report preparation may bring the total effort required for a first or one-time application to two to three weeks. If repeated applications are made in the same general region, the assembling of data for a different site or energy conversion technology will probably take much less time.

  10. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S.; Techert, Simone; Strocov, Vladimir N.; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.

  11. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering.

    PubMed

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S; Techert, Simone; Strocov, Vladimir N; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-29

    Thermally driven chemistry as well as materials' functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.

  12. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering

    PubMed Central

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S.; Techert, Simone; Strocov, Vladimir N.; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future. PMID:26821751

  13. Suppression of vacancy defects in epitaxial La-doped SrTiO{sub 3} films

    SciTech Connect

    Keeble, D. J.; Kanda, G.; Jalan, B.; Stemmer, S.; Ravelli, L.; Egger, W.

    2011-12-05

    Variable energy positron annihilation lifetime spectroscopy of high-mobility La-doped SrTiO{sub 3} grown by molecular beam epitaxy found that the films contained sufficiently low concentrations of Sr vacancies and vacancy cluster defects to allow the observation of positron annihilation events from the perfect lattice. This enabled the concentrations of charged cation vacancies to be estimated, and these were found to be at least an order of magnitude below the La-dopant concentrations.

  14. Antimony-assisted carbonization of Si(111) with solid source molecular beam epitaxy

    SciTech Connect

    Hackley, Justin; Richardson, Christopher J. K.; Sarney, Wendy L.

    2013-11-15

    The carbonization of an antimony-terminated Si (111) surface in a solid source molecular beam epitaxy system is presented. Reflection high-energy electron diffraction, atomic force microscopy, x-ray photoelectron spectroscopy, and cross-sectional transmission electron microscopy are used to characterize samples grown with and without antimony termination. It is shown that the antimony-terminated surface promotes the formation of thin, smooth and continuous SiC films at a relatively low temperature of 800 °C.

  15. Molecular beam epitaxial growth and structural characterization of ZnS on (001) GaAs

    NASA Technical Reports Server (NTRS)

    Benz, R. G., II; Huang, P. C.; Stock, S. R.; Summers, C. J.

    1988-01-01

    The effect of surface nucleation processes on the quality of ZnS layers grown on (001) GaAs substrates by molecular beam epitaxy is reported. Reflection high energy electron diffraction indicated that nucleation at high temperatures produced more planar surfaces than nucleation at low temperatures, but the crystalline quality as assessed by X-ray double crystal diffractometry is relatively independent of nucleation temperature. A critical factor in layer quality was the initial roughness of the GaAs surfaces.

  16. Fabrication of precision high quality facets on molecular beam epitaxy material

    DOEpatents

    Petersen, Holly E.; Goward, William D.; Dijaili, Sol P.

    2001-01-01

    Fabricating mirrored vertical surfaces on semiconductor layered material grown by molecular beam epitaxy (MBE). Low energy chemically assisted ion beam etching (CAIBE) is employed to prepare mirrored vertical surfaces on MBE-grown III-V materials under unusually low concentrations of oxygen in evacuated etching atmospheres of chlorine and xenon ion beams. UV-stabilized smooth-surfaced photoresist materials contribute to highly vertical, high quality mirrored surfaces during the etching.

  17. Growth and micromagnetism of self-assembled epitaxial fcc(111) cobalt dots.

    PubMed

    Fruchart, O; Masseboeuf, A; Toussaint, J C; Bayle-Guillemaud, P

    2013-12-11

    We develop the self-assembly of epitaxial submicrometer-sized face-centered-cubic (fcc) Co(111) dots using pulsed laser deposition. The dots display atomically flat facets, from which the ratios of surface and interface energies for fcc Co are deduced. Zero-field magnetic structures are investigated with magnetic force and Lorentz microscopies, revealing vortex-based flux-closure patterns. A good agreement is found with micromagnetic simulations.

  18. Epitaxial Cu{sub 2}ZnSnS{sub 4} thin film on Si (111) 4° substrate

    SciTech Connect

    Song, Ning; Liu, Fangyang; Huang, Yidan; Hao, Xiaojing E-mail: xj.hao@unsw.edu.au; Green, Martin A.; Young, Matthew; Erslev, Pete; Harvey, Steven P.; Teeter, Glenn E-mail: xj.hao@unsw.edu.au; Wilson, Samual

    2015-06-22

    To explore the possibility of Cu{sub 2}ZnSnS{sub 4} (CZTS)/Si based tandem solar cells, the heteroepitaxy of tetragonal Cu{sub 2}ZnSnS{sub 4} thin films on single crystalline cubic Si (111) wafers with 4° miscut is obtained by molecular beam epitaxy. The X-ray θ-2θ scan and selected area diffraction patterns of the CZTS thin films and Si substrates, and the high resolution transmission electron microscopy image of the CZTS/Si interface region demonstrate that the CZTS thin films are epitaxially grown on the Si substrates. A CZTS/Si P-N junction is formed and shows photovoltaic responses, indicating the promising application of epitaxial CZTS thin films on Si.

  19. van der Waals epitaxy of CdTe thin film on graphene

    NASA Astrophysics Data System (ADS)

    Mohanty, Dibyajyoti; Xie, Weiyu; Wang, Yiping; Lu, Zonghuan; Shi, Jian; Zhang, Shengbai; Wang, Gwo-Ching; Lu, Toh-Ming; Bhat, Ishwara B.

    2016-10-01

    van der Waals epitaxy (vdWE) facilitates the epitaxial growth of materials having a large lattice mismatch with the substrate. Although vdWE of two-dimensional (2D) materials on 2D materials have been extensively studied, the vdWE for three-dimensional (3D) materials on 2D substrates remains a challenge. It is perceived that a 2D substrate passes little information to dictate the 3D growth. In this article, we demonstrated the vdWE growth of the CdTe(111) thin film on a graphene buffered SiO2/Si substrate using metalorganic chemical vapor deposition technique, despite a 46% large lattice mismatch between CdTe and graphene and a symmetry change from cubic to hexagonal. Our CdTe films produce a very narrow X-ray rocking curve, and the X-ray pole figure analysis showed 12 CdTe (111) peaks at a chi angle of 70°. This was attributed to two sets of parallel epitaxy of CdTe on graphene with a 30° relative orientation giving rise to a 12-fold symmetry in the pole figure. First-principles calculations reveal that, despite the relatively small energy differences, the graphene buffer layer does pass epitaxial information to CdTe as the parallel epitaxy, obtained in the experiment, is energetically favored. The work paves a way for the growth of high quality CdTe film on a large area as well as on the amorphous substrates.

  20. Highly Selective Oxidation of Carbohydrates in an Efficient Electrochemical Energy Converter: Cogenerating Organic Electrosynthesis.

    PubMed

    Holade, Yaovi; Servat, Karine; Napporn, Teko W; Morais, Cláudia; Berjeaud, Jean-Marc; Kokoh, Kouakou B

    2016-02-08

    The selective electrochemical conversion of highly functionalized organic molecules into electricity, heat, and added-value chemicals for fine chemistry requires the development of highly selective, durable, and low-cost catalysts. Here, we propose an approach to make catalysts that can convert carbohydrates into chemicals selectively and produce electrical power and recoverable heat. A 100% Faradaic yield was achieved for the selective oxidation of the anomeric carbon of glucose and its related carbohydrates (C1-position) without any function protection. Furthermore, the direct glucose fuel cell (DGFC) enables an open-circuit voltage of 1.1 V in 0.5 m NaOH to be reached, a record. The optimized DGFC delivers an outstanding output power Pmax =2 mW cm(-2) with the selective conversion of 0.3 m glucose, which is of great interest for cogeneration. The purified reaction product will serve as a raw material in various industries, which thereby reduces the cost of the whole sustainable process.

  1. Synaptic Plasticity Selectively Activated by Polarization-Dependent Energy-Efficient Ion Migration in an Ultrathin Ferroelectric Tunnel Junction.

    PubMed

    Yoon, Chansoo; Lee, Ji Hye; Lee, Sangik; Jeon, Ji Hoon; Jang, Jun Tae; Kim, Dae Hwan; Kim, Young Heon; Park, Bae Ho

    2017-03-08

    Selectively activated inorganic synaptic devices, showing a high on/off ratio, ultrasmall dimensions, low power consumption, and short programming time, are required to emulate the functions of high-capacity and energy-efficient reconfigurable human neural systems combining information storage and processing ( Li et al. Sci. Rep. 2014 , 4 , 4096 ). Here, we demonstrate that such a synaptic device is realized using a Ag/PbZr0.52Ti0.48O3 (PZT)/La0.8Sr0.2MnO3 (LSMO) ferroelectric tunnel junction (FTJ) with ultrathin PZT (thickness of ∼4 nm). Ag ion migration through the very thin FTJ enables a large on/off ratio (10(7)) and low energy consumption (potentiation energy consumption = ∼22 aJ and depression energy consumption = ∼2.5 pJ). In addition, the simple alignment of the downward polarization in PZT selectively activates the synaptic plasticity of the FTJ and the transition from short-term plasticity to long-term potentiation.

  2. Photoluminescence studies in epitaxial CZTSe thin films

    NASA Astrophysics Data System (ADS)

    Sendler, Jan; Thevenin, Maxime; Werner, Florian; Redinger, Alex; Li, Shuyi; Hägglund, Carl; Platzer-Björkman, Charlotte; Siebentritt, Susanne

    2016-09-01

    Epitaxial Cu 2 ZnSnSe 4 (CZTSe) thin films were grown by molecular beam epitaxy on GaAs(001) using two different growth processes, one containing an in-situ annealing stage as used for solar cell absorbers and one for which this step was omitted. Photoluminescences (PL) measurements carried out on these samples show no dependence of the emission shape on the excitation intensity at different temperatures ranging from 4 K to 300 K . To describe the PL measurements, we employ a model with fluctuating band edges in which the density of states of the resulting tail states does not seem to depend on the excited charge carrier density. In this interpretation, the PL measurements show that the annealing stage removes a defect level, which is present in the samples without this annealing.

  3. Wafer bonded epitaxial templates for silicon heterostructures

    NASA Technical Reports Server (NTRS)

    Atwater, Harry A., Jr. (Inventor); Zahler, James M. (Inventor); Morral, Anna Fontcubera I (Inventor)

    2008-01-01

    A heterostructure device layer is epitaxially grown on a virtual substrate, such as an InP/InGaAs/InP double heterostructure. A device substrate and a handle substrate form the virtual substrate. The device substrate is bonded to the handle substrate and is composed of a material suitable for fabrication of optoelectronic devices. The handle substrate is composed of a material suitable for providing mechanical support. The mechanical strength of the device and handle substrates is improved and the device substrate is thinned to leave a single-crystal film on the virtual substrate such as by exfoliation of a device film from the device substrate. An upper portion of the device film exfoliated from the device substrate is removed to provide a smoother and less defect prone surface for an optoelectronic device. A heterostructure is epitaxially grown on the smoothed surface in which an optoelectronic device may be fabricated.

  4. Domain epitaxy for thin film growth

    DOEpatents

    Narayan, Jagdish

    2005-10-18

    A method of forming an epitaxial film on a substrate includes growing an initial layer of a film on a substrate at a temperature T.sub.growth, said initial layer having a thickness h and annealing the initial layer of the film at a temperature T.sub.anneal, thereby relaxing the initial layer, wherein said thickness h of the initial layer of the film is greater than a critical thickness h.sub.c. The method further includes growing additional layers of the epitaxial film on the initial layer subsequent to annealing. In some embodiments, the method further includes growing a layer of the film that includes at least one amorphous island.

  5. Wafer bonded epitaxial templates for silicon heterostructures

    DOEpatents

    Atwater, Jr., Harry A.; Zahler, James M.; Morral, Anna Fontcubera I

    2008-03-11

    A heterostructure device layer is epitaxially grown on a virtual substrate, such as an InP/InGaAs/InP double heterostructure. A device substrate and a handle substrate form the virtual substrate. The device substrate is bonded to the handle substrate and is composed of a material suitable for fabrication of optoelectronic devices. The handle substrate is composed of a material suitable for providing mechanical support. The mechanical strength of the device and handle substrates is improved and the device substrate is thinned to leave a single-crystal film on the virtual substrate such as by exfoliation of a device film from the device substrate. An upper portion of the device film exfoliated from the device substrate is removed to provide a smoother and less defect prone surface for an optoelectronic device. A heterostructure is epitaxially grown on the smoothed surface in which an optoelectronic device may be fabricated.

  6. In situ transmission electron microscopy study on the epitaxial growth of CoSi2 on Si(111) at temperatures below 150 C

    NASA Technical Reports Server (NTRS)

    Nieh, C. W.; Lin, T. L.

    1989-01-01

    This paper reports an in situ transmission electron microscopy study on the epitaxial growth of CoSi2 on Si(111) from a 10-nm-thick amorphous mixture of Co and Si in the ratio 1:2, which was formed by codeposition of Co and Si near room temperature. Nuclei of CoSi2 are observed in the as-deposited film. These nuclei are epitaxial and extend through the whole film thickness. Upon annealing, these columnar epitaxial CoSi2 grains grow laterally at temperatures as low as 50 C. The kinetics of this lateral epitaxial growth was studied at temperatures between 50 and 150 C. The activation energy of the growth process is 0.8 + or - 0.1 eV.

  7. State-selective electron capture in {sup 3}He{sup 2+} + He collisions at intermediate impact energies

    SciTech Connect

    Alessi, M.; Otranto, S.; Focke, P.

    2011-01-15

    In this work we have measured single-electron capture in collisions of {sup 3}He{sup 2+} projectiles incident on a helium target for energies of 13.3-100 keV/amu with the cold-target recoil-ion momentum spectroscopy setup implemented at the Centro Atomico Bariloche. State-selective single-capture cross sections were measured as a function of the impact energy. They were found to agree with previous existing data from the Frankfurt group, starting at the impact energy of 60 keV/amu; as well as with recent data, at 7.5 keV/amu, from the Lanzhou group. The present experimental results are also contrasted to the classical trajectory Monte Carlo method with dynamical screening.

  8. Effect of a boron implantation on the electrical properties of epitaxial HgCdTe with different material composition

    NASA Astrophysics Data System (ADS)

    Lyapunov, D. V.; Pishchagin, A. A.; Grigoryev, D. V.; Korotaev, A. G.; Voitsekhovskii, A. V.; Kokhanenko, A. P.; Iznin, I. I.; Savytskyy, H. V.; Bonchik, A. U.; Dvoretskii, S. A.; Mikhailov, N. N.

    2016-08-01

    In this work the experimental results of investigations of the dynamics of accumulation and spatial distribution of electrically active radiation defects when irradiating epitaxial films of Hg1-xCdxTe (MCT) with different material composition (x). The films, grown by molecular beam epitaxy (MBE) were irradiated by B ions at room temperature in the radiation dose range 1012 -1015 ions/cm2 and with ion energy 100 keV. The results give the differences in implantation profiles, damage accumulation and electrical properties as a function of the material composition of the films.

  9. Influence of substrate orientation on the structural quality of GaAs nanowires in molecular beam epitaxy.

    PubMed

    Zhang, Zhi; Shi, Sui-Xing; Chen, Ping-Ping; Lu, Wei; Zou, Jin

    2015-01-26

    In this study, the effect of substrate orientation on the structural quality of Au-catalyzed epitaxial GaAs nanowires grown by a molecular beam epitaxy reactor has been investigated. It was found that the substrate orientations can be used to manipulate the nanowire catalyst composition and the catalyst surface energy and, therefore, to alter the structural quality of GaAs nanowires grown on different substrates. Defect-free wurtzite-structured GaAs nanowires grown on the GaAs (110) substrate have been achieved under our growth conditions.

  10. Structural characterization of metastable hcp-Ni thin films epitaxially grown on Au(100) single-crystal underlayers

    SciTech Connect

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-05-15

    Ni(1120) epitaxial thin films with hcp structure were prepared on Au(100) single-crystal underlayers at 100 deg. C by ultra high vacuum molecular beam epitaxy. The detailed film structure is studied by in situ reflection high energy electron diffraction, x-ray diffraction, and transmission electron microscopy. The hcp-Ni film consists of two types of variants whose c-axes are rotated around the film normal by 90 deg. each other. An atomically sharp boundary is recognized between the film and the underlayer, where misfit dislocations are introduced. Presence of such dislocations seems to relieve the strain caused by the lattice mismatch between the film and the underlayer.

  11. Control of the stacking fault areas in pseudomorphic ZnSe layers by photo-molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Ohno, Y.; Taishi, T.; Yonenaga, I.; Ichikawa, S.; Hirai, R.; Takeda, S.

    2007-12-01

    Pseudomorphic ZnSe layers on GaAs(0 0 1) were grown by molecular beam epitaxy under the light illumination with photon energy of about 1.8 eV. In the layers, isolated Shockley-type stacking faults on (1 1 1), bordering not on the ZnSe/GaAs interface but on the ZnSe surface, as well as the well-known stacking fault pairs, were formed. The sum of the stacking fault areas was small in comparison with the layers grown by molecular beam epitaxy without light illumination.

  12. Energy and chemicals from the selective electrooxidation of renewable diols by organometallic fuel cells.

    PubMed

    Bellini, Marco; Bevilacqua, Manuela; Filippi, Jonathan; Lavacchi, Alessandro; Marchionni, Andrea; Miller, Hamish A; Oberhauser, Werner; Vizza, Francesco; Annen, Samuel P; Grützmacher, H

    2014-09-01

    Organometallic fuel cells catalyze the selective electrooxidation of renewable diols, simultaneously providing high power densities and chemicals of industrial importance. It is shown that the unique organometallic complex [Rh(OTf)(trop2NH)(PPh3)] employed as molecular active site in an anode of an OMFC selectively oxidizes a number of renewable diols, such as ethylene glycol , 1,2-propanediol (1,2-P), 1,3-propanediol (1,3-P), and 1,4-butanediol (1,4-B) to their corresponding mono-carboxylates. The electrochemical performance of this molecular catalyst is discussed, with the aim to achieve cogeneration of electricity and valuable chemicals in a highly selective electrooxidation from diol precursors.

  13. Junction Transport in Epitaxial Film Silicon Heterojunction Solar Cells: Preprint

    SciTech Connect

    Young, D. L.; Li, J. V.; Teplin, C. W.; Stradins, P.; Branz, H. M.

    2011-07-01

    We report our progress toward low-temperature HWCVD epitaxial film silicon solar cells on inexpensive seed layers, with a focus on the junction transport physics exhibited by our devices. Heterojunctions of i/p hydrogenated amorphous Si (a-Si) on our n-type epitaxial crystal Si on n++ Si wafers show space-charge-region recombination, tunneling or diffusive transport depending on both epitaxial Si quality and the applied forward voltage.

  14. Method of deposition by molecular beam epitaxy

    DOEpatents

    Chalmers, Scott A.; Killeen, Kevin P.; Lear, Kevin L.

    1995-01-01

    A method is described for reproducibly controlling layer thickness and varying layer composition in an MBE deposition process. In particular, the present invention includes epitaxially depositing a plurality of layers of material on a substrate with a plurality of growth cycles whereby the average of the instantaneous growth rates for each growth cycle and from one growth cycle to the next remains substantially constant as a function of time.

  15. Method of deposition by molecular beam epitaxy

    DOEpatents

    Chalmers, S.A.; Killeen, K.P.; Lear, K.L.

    1995-01-10

    A method is described for reproducibly controlling layer thickness and varying layer composition in an MBE deposition process. In particular, the present invention includes epitaxially depositing a plurality of layers of material on a substrate with a plurality of growth cycles whereby the average of the instantaneous growth rates for each growth cycle and from one growth cycle to the next remains substantially constant as a function of time. 9 figures.

  16. Chemical Beam Epitaxy of ZnSe

    DTIC Science & Technology

    1990-10-17

    is curren:ly underway in Japan and Europe with major investment in funds and manpower. However, the problems which remain are largely still an issue...of availability of suitable materials, specifically availability of p-type ZnSe with sufficient useable hole carrier concentrations. The problem ...contract provided essential seed funding necessary to accumulate sufficient funds to build and equip a state-or-the-art chemical beam epitaxy facility at

  17. Low-temperature atomic layer epitaxy of AlN ultrathin films by layer-by-layer, in-situ atomic layer annealing

    PubMed Central

    Shih, Huan-Yu; Lee, Wei-Hao; Kao, Wei-Chung; Chuang, Yung-Chuan; Lin, Ray-Ming; Lin, Hsin-Chih; Shiojiri, Makoto; Chen, Miin-Jang

    2017-01-01

    Low-temperature epitaxial growth of AlN ultrathin films was realized by atomic layer deposition (ALD) together with the layer-by-layer, in-situ atomic layer annealing (ALA), instead of a high growth temperature which is needed in conventional epitaxial growth techniques. By applying the ALA with the Ar plasma treatment in each ALD cycle, the AlN thin film was converted dramatically from the amorphous phase to a single-crystalline epitaxial layer, at a low deposition temperature of 300 °C. The energy transferred from plasma not only provides the crystallization energy but also enhances the migration of adatoms and the removal of ligands, which significantly improve the crystallinity of the epitaxial layer. The X-ray diffraction reveals that the full width at half-maximum of the AlN (0002) rocking curve is only 144 arcsec in the AlN ultrathin epilayer with a thickness of only a few tens of nm. The high-resolution transmission electron microscopy also indicates the high-quality single-crystal hexagonal phase of the AlN epitaxial layer on the sapphire substrate. The result opens a window for further extension of the ALD applications from amorphous thin films to the high-quality low-temperature atomic layer epitaxy, which can be exploited in a variety of fields and applications in the near future. PMID:28045075

  18. Low-temperature atomic layer epitaxy of AlN ultrathin films by layer-by-layer, in-situ atomic layer annealing

    NASA Astrophysics Data System (ADS)

    Shih, Huan-Yu; Lee, Wei-Hao; Kao, Wei-Chung; Chuang, Yung-Chuan; Lin, Ray-Ming; Lin, Hsin-Chih; Shiojiri, Makoto; Chen, Miin-Jang

    2017-01-01

    Low-temperature epitaxial growth of AlN ultrathin films was realized by atomic layer deposition (ALD) together with the layer-by-layer, in-situ atomic layer annealing (ALA), instead of a high growth temperature which is needed in conventional epitaxial growth techniques. By applying the ALA with the Ar plasma treatment in each ALD cycle, the AlN thin film was converted dramatically from the amorphous phase to a single-crystalline epitaxial layer, at a low deposition temperature of 300 °C. The energy transferred from plasma not only provides the crystallization energy but also enhances the migration of adatoms and the removal of ligands, which significantly improve the crystallinity of the epitaxial layer. The X-ray diffraction reveals that the full width at half-maximum of the AlN (0002) rocking curve is only 144 arcsec in the AlN ultrathin epilayer with a thickness of only a few tens of nm. The high-resolution transmission electron microscopy also indicates the high-quality single-crystal hexagonal phase of the AlN epitaxial layer on the sapphire substrate. The result opens a window for further extension of the ALD applications from amorphous thin films to the high-quality low-temperature atomic layer epitaxy, which can be exploited in a variety of fields and applications in the near future.

  19. The investigation of cobalt intercalation underneath epitaxial graphene on 6H-SiC(0 0 0 1)

    NASA Astrophysics Data System (ADS)

    Zhang, Yuxi; Zhang, Hanjie; Cai, Yiliang; Song, Junjie; He, Pimo

    2017-02-01

    The intercalation behaviour of cobalt underneath both epitaxial graphene monolayer and bilayer on 6H-SiC(0001) have been investigated by scanning tunneling microscopy (STM) and density functional theory (DFT). Upon deposition, cobalt atoms prefer to agglomerate into clusters on the epitaxial graphene. After annealing the sample to 850 °C, the intercalation of the adsorbed cobalt atoms into both monolayer and bilayer epitaxial graphene on SiC takes place, as observed by the atomically resolved STM images. Further studies based on DFT modeling and simulated STM images show that, resulting from the interplay between the intercalated cobalt atoms and the carbon layers sandwiching it, the most energetically favourable intercalation sites of cobalt atoms underneath monolayer and bilayer graphene differ. Furthermore, the results show energy barriers of 0.60 eV and 0.41 eV for cobalt penetration through mono-vacancy defects at monolayer and bilayer graphene.

  20. Epitaxial growth and electrochemical transfer of graphene on Ir(111)/α-Al2O3(0001) substrates

    NASA Astrophysics Data System (ADS)

    Koh, Shinji; Saito, Yuta; Kodama, Hideyuki; Sawabe, Atsuhito

    2016-07-01

    Low-pressure chemical vapor deposition growth of graphene on Iridium (Ir) layers epitaxially deposited on α-Al2O3 (0001) substrates was investigated. The X-ray diffraction, Raman and reflection high energy electron diffraction characterizations revealed that graphene films were epitaxially grown on Ir(111) layers, and the in-plane epitaxial relationship between graphene, Ir(111), and α-Al2O3(0001) was graphene ⟨ 1 1 ¯ 00 ⟩//Ir⟨ 11 2 ¯ ⟩//α-Al2O3⟨ 11 2 ¯ 0 ⟩. The graphene on Ir(111) was electrochemically transferred onto SiO2/Si substrates. We also demonstrated the reuse of the Ir(111)/α-Al2O3(0001) substrates in multiple growth and transfer cycles.

  1. Epitaxy: Programmable Atom Equivalents Versus Atoms.

    PubMed

    Wang, Mary X; Seo, Soyoung E; Gabrys, Paul A; Fleischman, Dagny; Lee, Byeongdu; Kim, Youngeun; Atwater, Harry A; Macfarlane, Robert J; Mirkin, Chad A

    2017-01-24

    The programmability of DNA makes it an attractive structure-directing ligand for the assembly of nanoparticle (NP) superlattices in a manner that mimics many aspects of atomic crystallization. However, the synthesis of multilayer single crystals of defined size remains a challenge. Though previous studies considered lattice mismatch as the major limiting factor for multilayer assembly, thin film growth depends on many interlinked variables. Here, a more comprehensive approach is taken to study fundamental elements, such as the growth temperature and the thermodynamics of interfacial energetics, to achieve epitaxial growth of NP thin films. Both surface morphology and internal thin film structure are examined to provide an understanding of particle attachment and reorganization during growth. Under equilibrium conditions, single crystalline, multilayer thin films can be synthesized over 500 × 500 μm(2) areas on lithographically patterned templates, whereas deposition under kinetic conditions leads to the rapid growth of glassy films. Importantly, these superlattices follow the same patterns of crystal growth demonstrated in atomic thin film deposition, allowing these processes to be understood in the context of well-studied atomic epitaxy and enabling a nanoscale model to study fundamental crystallization processes. Through understanding the role of epitaxy as a driving force for NP assembly, we are able to realize 3D architectures of arbitrary domain geometry and size.

  2. Epitaxial Crystal Growth: Methods and Materials

    NASA Astrophysics Data System (ADS)

    Capper, Peter; Irvine, Stuart; Joyce, Tim

    The epitaxial growth of thin films of material for a wide range of applications in electronics and optoelectronics is a critical activity in many industries. The original growth technique used, in most instances, was liquid-phase epitaxy (LPE), as this was the simplest and often the cheapest route to producing device-quality layers. These days, while some production processes are still based on LPE, most research into and (increasingly) much of the production of electronic and optoelectronic devices now centers on metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). These techniques are more versatile than LPE (although the equipment is more expensive), and they can readily produce multilayer structures with atomic-layer control, which has become more and more important in the type of nanoscale engineering used to produce device structures in as-grown multilayers. This chapter covers these three basic techniques, including some of their more common variants, and outlines the relative advantages and disadvantages of each. Some examples of growth in various important systems are also outlined for each of the three techniques.

  3. Wafer Bonding and Epitaxial Transfer of GaSb-based Epitaxy to GaAs for Monolithic Interconnection of Thermophotovoltaic Devices

    SciTech Connect

    C.A. Wang; D.A. Shiau; P.G. Murphy; P.W. O'brien; R.K. Huang; M.K. Connors; A.C. Anderson; D. Donetsky; S. Anikeev; G. Belenky; D.M. Depoy; G. Nichols

    2003-06-16

    GaInAsSb/AlGaAsSb/InAsSb/GaSb epitaxial layers were bonded to semi-insulating GaAs handle wafers with SiO{sub x}/Ti/Au as the adhesion layer for monolithic interconnection of thermophotovoltaic (TPV) devices. Epitaxial transfer was completed by removal of the GaSb substrate, GaSb buffer, and InAsSb etch-stop layer by selective chemical etching. The SiO{sub x}/TiAu provides not only electrical isolation, but also high reflectivity and is used as an internal back-surface reflector. Characterization of wafer-bonded epitaxy by high-resolution x-ray diffraction and time-decay photoluminescence indicates minimal residual stress and enhancement in optical quality. 0.54-eV GaInAsSb cells were fabricated and monolithically interconnected in series. A 10-junction device exhibited linear voltage building with an open-circuit voltage of 1.8 V.

  4. Controlled energy-selected electron capture and release in double quantum dots

    NASA Astrophysics Data System (ADS)

    Pont, Federico M.; Bande, Annika; Cederbaum, Lorenz S.

    2013-12-01

    Highly accurate quantum electron dynamics calculations demonstrate that energy can be efficiently transferred between quantum dots. Specifically, in a double quantum dot an incoming electron is captured by one dot and the excess energy is transferred to the neighboring dot and used to remove an electron from this dot. This process is due to long-range electron correlation and shown to be operative at rather large distances between the dots. The efficiency of the process is greatly enhanced by preparing the double quantum dot such that the incoming electron is initially captured by a two-electron resonance state of the system. In contrast to atoms and molecules in nature, double quantum dots can be manipulated to achieve this enhancement. This mechanism leads to a surprisingly narrow distribution of the energy of the electron removed in the process which is explained by resonance theory. We argue that the process could be exploited in practice.

  5. 2WHSP: A multi-frequency selected catalogue of high energy and very high energy γ-ray blazars and blazar candidates

    NASA Astrophysics Data System (ADS)

    Chang, Y.-L.; Arsioli, B.; Giommi, P.; Padovani, P.

    2017-01-01

    Aims: High synchrotron peaked blazars (HSPs) dominate the γ-ray sky at energies higher than a few GeV; however, only a few hundred blazars of this type have been cataloged so far. In this paper we present the 2WHSP sample, the largest and most complete list of HSP blazars available to date, which is an expansion of the 1WHSP catalogue of γ-ray source candidates off the Galactic plane. Methods: We cross-matched a number of multi-wavelength surveys (in the radio, infrared and X-ray bands) and applied selection criteria based on the radio to IR and IR to X-ray spectral slopes. To ensure the selection of genuine HSPs, we examined the SED of each candidate and estimated the peak frequency of its synchrotron emission (νpeak) using the ASDC SED tool, including only sources with νpeak > 1015 Hz (equivalent to νpeak > 4 eV). Results: We have assembled the largest and most complete catalogue of HSP blazars to date, which includes 1691 sources. A number of population properties, such as infrared colours, synchrotron peak, redshift distributions, and γ-ray spectral properties have been used to characterise the sample and maximize completeness. We also derived the radio log N-log S distribution. This catalogue has already been used to provide seeds to discover new very high energy objects within Fermi-LAT data and to look for the counterparts of neutrino and ultra high energy cosmic ray sources, showing its potential for the identification of promising high-energy γ-ray sources and multi-messenger targets. Table 4 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/598/A17

  6. High-speed energy efficient selective removal of large area copper layer by laser induced delamination

    NASA Astrophysics Data System (ADS)

    Kmetec, Blaž; Kovačič, Drago; Možina, Janez; Podobnik, Boštjan

    2009-07-01

    An indirect laser-induced method for selective removal of large copper areas from a printed circuit board is theoretically and experimentally investigated. The results show that the threshold condition for the process involves phase transition of the epoxy-based substrate resin. Optimal parameters for maximizing process speed are found and discussed.

  7. Materials Down Select Decisions Made Within the Department of Energy Hydrogen Sorption Center of Excellence

    SciTech Connect

    Simpson, Lin

    2009-11-30

    Technical report describing DOE's Hydrogen Sorption Center of Excellence investigation into various adsorbent and chemisorption materials and progress towards meeting DOE's hydrogen storage targets. The report presents a review of the material status as related to DOE hydrogen storage targets and explains the basis for the down select decisions.

  8. A Study of Quasar Selection in the Dark Energy Survey Supernova fields

    SciTech Connect

    Tie, S.S.; et al.

    2016-11-16

    We present a study of quasar selection using the DES supernova fields. We used a quasar catalog from an overlapping portion of the SDSS Stripe 82 region to quantify the completeness and efficiency of selection methods involving color, probabilistic modeling, variability, and combinations of color/probabilistic modeling with variability. We only considered objects that appear as point sources in the DES images. We examine color selection methods based on the WISE mid-IR W1-W2 color, a mixture of WISE and DES colors (g-i and i-W1) and a mixture of VHS and DES colors (g-i and i-K). For probabilistic quasar selection, we used XDQSOz, an algorithm that employs an empirical multi-wavelength flux model of quasars to assign quasar probabilities. Our variability selection uses the multi-band chi2-probability that sources are constant in the DES Year 1 griz-band light curves. The completeness and efficiency are calculated relative to an underlying sample of point sources that are detected in the required selection bands and pass our data quality and photometric error cuts. We conduct our analyses at two magnitude limits, i<19.8 mag and i<22 mag. For sources with W1 and W2 detections, the W1-W2 color or XDQSOz method combined with variability gives the highest completenesses of >85% for both i-band magnitude limits and efficiencies of >80% to the bright limit and >60% to the faint limit; however, the giW1 and giW1+variability methods give the highest quasar surface densities. The XDQSOz method and combinations of W1W2/giW1/XDQSOz with variability are among the better selection methods when both high completeness and high efficiency are desired. We also present the OzDES Quasar Catalog of 1,263 spectroscopically-confirmed quasars taken by the OzDES survey. The catalog includes quasars with redshifts up to z~4 and brighter than i=22 mag, although the catalog is not complete up this magnitude limit.

  9. Site selection feasibility for a solar energy system on the Fairbanks Federal Building

    NASA Technical Reports Server (NTRS)

    1978-01-01

    A feasibility study was performed for the installation of a solar energy system on the Federal Building in Fairbanks, Alaska, a multifloor office building with an enclosed parking garge. The study consisted of determining the collectable solar energy at the Fairbanks site on a monthly basis and comparing this to the monthly building heating load. Potential conventional fuel savings were calculated on a monthly basis and the overall economics of the solar system applications were considered. Possible solar system design considerations, collector and other system installation details, interface of the solar system with the conventional HVAC systems, and possible control modes were all addressed. Conclusions, recommendations and study details are presented.

  10. Laser Induced Surface Chemical Epitaxy

    DTIC Science & Technology

    1990-03-01

    eV was observed in this study for DMTe adlay ,,;s annealed at 423 K, a condition which is likely to produce a metallic Te adlayer , the Cd 3d5 /2...processes were studied by irradiating the adlayer with ultraviolet photons produced by a Questek excimer laser. These were introduced into the deposition...binding energy observed for similarly annealed DMCd adlayers was 405.1 eV. Based on room temperature measurements and ligand shift and electronegativity

  11. Analyzing the components of the free-energy landscape in a calcium selective ion channel by Widom's particle insertion method.

    PubMed

    Boda, Dezso; Giri, Janhavi; Henderson, Douglas; Eisenberg, Bob; Gillespie, Dirk

    2011-02-07

    The selectivity filter of the L-type calcium channel works as a Ca(2+) binding site with a very large affinity for Ca(2+) versus Na(+). Ca(2+) replaces half of the Na(+) ions in the filter even when these ions are present in 1 μM and 30 mM concentrations in the bath, respectively. The energetics of this strong selectivity is analyzed in this paper. We use Widom's particle insertion method to compute the space-dependent profiles of excess chemical potential in our grand canonical Monte Carlo simulations. These profiles define the free-energy landscape for the various ions. Following Gillespie [Biophys. J. 94, 1169 (2008)], the difference of the excess chemical potentials for the two competing ions defines the advantage that one of the ions has over the other in the competition for space in the crowded selectivity filter. These advantages depend on ionic bath concentrations: the ion that is present in the bath in larger quantity (Na(+)) has the "number" advantage which is balanced by the free-energy advantage of the other ion (Ca(2+)). The excess chemical potentials are decomposed into hard sphere exclusion and electrostatic components. The electrostatic terms correspond to interactions with the mean electric field produced by ions and induced charges as well to ionic correlations beyond the mean field description. Dielectrics are needed to produce micromolar Ca(2+) versus Na(+) selectivity in the L-type channel. We study the behavior of these terms with changes in bath concentrations of ions, charges, and diameters of ions, as well as geometrical parameters such as radius of the pore and the dielectric constant of the protein. Ion selectivity in calcium binding proteins probably has a similar mechanism.

  12. Selected translated abstracts of Russian-language climate-change publications: I, Surface energy budget

    SciTech Connect

    Burtis, M.D.

    1992-09-01

    This report presents abstracts (translated into English) of important Russian-language literature concerning the surface energy budget as it relates to climate change. In addition to the bibliographic citations and abstracts translated into English, this report presents the original citations and abstracts in Russian. Author and title indexes are included, to assist the reader in locating abstracts of particular interest.

  13. Selected Translated Abstracts of Russian-Language Climate-Change Publications, I. Surface Energy Budget

    SciTech Connect

    Ravina, C.B.

    1992-01-01

    This report presents abstracts (translated into English) of important Russian-language literature concerning the surface energy budget as it relates to climate change. In addition to the bibliographic citations and abstracts translated into English, this report presents the original citations and abstracts in Russian. Author and title indexes are included, to assist the reader in locating abstracts of particular interest.

  14. Building America Top Innovations 2014 Profile: California Energy Standards Recognize the Importance of Filter Selection

    SciTech Connect

    none,

    2014-11-01

    This 2014 Top Innovation profile describes Building America research on HVAC air filter sizing that prompted a change in the California “Title 24” Energy Code requiring filter manufacturers, HVAC designers, and HERS raters to make changes that will encourage the use of higher MERV filters without degrading HVAC performance.

  15. PIP-II Injector Test’s Low Energy Beam Transport: Commissioning and Selected Measurements

    SciTech Connect

    Shemyakin, A.; Alvarez, M.; Andrews, R.; Carneiro, J.-P.; Chen, A.; Hanna, B.; Prost, L.; Scarpine, V.; D'Arcy, R.; Wiesner, C.

    2016-09-16

    The PIP2IT test accelerator is under construction at Fermilab. Its ion source and Low Energy Beam Transport (LEBT) in its initial (straight) configuration have been commissioned to full specification parameters. This paper introduces the LEBT design and summarizes the outcome of the commissioning activities.

  16. Selected List of Low Energy Beam Transport Facilities for Light-Ion, High-Intensity Accelerators

    SciTech Connect

    Prost, L. R.

    2016-02-17

    This paper presents a list of Low Energy Beam Transport (LEBT) facilities for light-ion, high-intensity accelerators. It was put together to facilitate comparisons with the PXIE LEBT design choices. A short discussion regarding the importance of the beam perveance in the choice of the transport scheme follows.

  17. Enzyme Selectivity of HIV Reverse Transcriptase: Conformations, Ligands, and Free Energy Partition

    PubMed Central

    Kirmizialtin, Serdal; Johnson, Kenneth A; Elber, Ron

    2015-01-01

    Atomically detailed simulations of HIV RT are performed to investigate the contributions of the conformational transition to the overall rate and specificity of enzyme catalysis. A number of different scenarios are considered within Milestoning theory to provide a more complete picture of the process of opening and closing the enzyme. We consider the open to closed transition in the absence of and with the correct and incorrect substrates. We also consider the free energy profile and the kinetics of the conformational change after the chemistry step in which a new base was added to the DNA, but the DNA was not yet displaced. We partition the free energy along the reaction coordinate and analyze the importance of different protein domains. Strikingly, significant influence on the free energy profile is detected for amino acids far from the active site. The overall long-range impact is about fifty percent of the total. We also illustrate that the overall rate is not necessarily determined by the highest free energy barrier along the reaction path (with respect to the free enzyme and substrate) and that the specificity is not necessarily determined by the same reaction step that determines the rate. PMID:26225641

  18. Policies to Promote Non-Hydro Renewable Energy in the United States and Selected Countries

    EIA Publications

    2005-01-01

    This article examines policies designed to encourage the development of non-hydro renewable energy in four countries - Germany, Denmark, the Netherlands, and Japan - and compares the policies enacted in each of these countries to policies that were used in the United States between 1970 and 2003.

  19. Epitaxial Approaches to Carbon Nanotube Organization

    NASA Astrophysics Data System (ADS)

    Ismach, Ariel

    Carbon nanotubes have unique electronic, mechanical, optical and thermal properties, which make them ideal candidates as building blocks in nano-electronic and electromechanical systems. However, their organization into well-defined geometries and arrays on surfaces remains a critical challenge for their integration into functional nanosystems. In my PhD, we developed a new approach for the organization of carbon nanotubes directed by crystal surfaces. The principle relies on the guided growth of single-wall carbon nanotubes (SWNTs) by atomic features presented on anisotropic substrates. We identified three different modes of surface-directed growth (or 'nanotube epitaxy'), in which the growth of carbon nanotubes is directed by crystal substrates: We first observed the nanotube unidirectional growth along atomic steps ('ledge-directed epitaxy') and nanofacets ('graphoepitaxy') on the surface of miscut C-plane sapphire and quartz. The orientation along crystallographic directions ('lattice-directed epitaxy') was subsequently observed by other groups on different crystals. We have proposed a "wake growth" mechanism for the nanotube alignment along atomic steps and nanofacets. In this mechanism, the catalyst nanoparticle slides along the step or facet, leaving the nanotube behind as a wake. In addition, we showed that the combination of surface-directed growth with external forces, such as electric-field and gas flow, can lead to the simultaneous formation of complex nanotube structures, such as grids and serpentines. The "wake growth" model, which explained the growth of aligned nanotubes, could not explain the formation of nanotube serpentines. For the latter, we proposed a "falling spaghetti" mechanism, in which the nanotube first grows by a free-standing process, aligned in the direction of the gas flow, then followed by absorption on the stepped surface in an oscillatory manner, due to the competition between the drag force caused by the gas flow on the suspended

  20. The Intake of Energy and Selected Nutrients by Thai Urban Sedentary Workers: An Evaluation of Adherence to Dietary Recommendations

    PubMed Central

    Chongsuwat, Rewadee; Viwatwongkasem, Chukiat; Kitvorapat, Wanicha

    2014-01-01

    Rapid changes in Thailand's nutrition and lifestyles have led to increasing diet-related pathologies among people with sedentary occupations. This study examines the extent to which the dietary intake of nutrients and energy by a sample of Thai sedentary workers conforms to the Thai Dietary Reference Intakes (Thai DRIs). The nutrients and energy intake estimates were based on self-reported information collected with a single 24-hour dietary recall and nonweighed 2-day food record. The study participants were Thai adults aged 20–50 years employed in sedentary occupations. A convenience sample of 215 healthy individuals (75 males and 140 females) was based on four randomly selected worksites in the Bangkok metropolitan area. For male participants, the study found a median energy intake of 1,485 kcal/day, with 54.4% of energy coming from carbohydrate, 15.9% from protein, and 29.6% from fat. Females' median energy intake was 1,428 kcal/day, 56% of which came from carbohydrate, 16.2% from protein, and 28.6% from fat. Both genders showed insufficient intake of fiber and most micronutrients. This study provides the material for preventive public health interventions focusing on nutrition-related diseases affecting Thailand's rapidly growing sedentary workforce. PMID:25525512

  1. Bulk NaI(Tl) scintillation low energy events selection with the ANAIS-0 module

    NASA Astrophysics Data System (ADS)

    Cuesta, C.; Amaré, J.; Cebrián, S.; García, E.; Ginestra, C.; Martínez, M.; Oliván, M. A.; Ortigoza, Y.; de Solórzano, A. Ortiz; Pobes, C.; Puimedón, J.; Sarsa, M. L.; Villar, J. A.; Villar, P.

    2014-11-01

    Dark matter particles scattering off target nuclei are expected to deposit very small energies in form of nuclear recoils (below 100 keV). Because of the low scintillation efficiency for nuclear recoils as compared to electron recoils, in most of the scintillating targets considered in the search for dark matter, the region below 10 keVee (electron equivalent energy) concentrates most of the expected dark matter signal. For this reason, very low energy threshold (at or below 2 keVee) and very low background are required to be competitive in the search for dark matter with such detection technique. This is the case of Annual modulation with NaI Scintillators (ANAIS), which is an experiment to be carried out at the Canfranc Underground Laboratory. A good knowledge of the detector response function for real scintillation events in the active volume, a good characterization of other anomalous or noise event populations contributing in that energy range, and the development of convenient filtering procedures for the latter are mandatory in order to achieve the required low background at such a low energy. In this work we present the characteristics of different types of events observed in large size NaI(Tl) detectors, and the event-type identification techniques developed. Such techniques allow distinguishing among events associated with bulk NaI scintillation, and events related to muon interactions in the detectors or shielding, photomultiplier origin events, and analysis event fakes. We describe the specific protocols developed to build bulk scintillation events spectra from the raw data and we apply them to data obtained with one of the ANAIS prototypes, ANAIS-0. Nuclear recoil type events were also explored using data from a neutron calibration; however pulse shape cuts were found not to be effective to discriminate them from electron recoil events. The effect of the filtering procedures developed in this nuclear recoils population has been analyzed in order to

  2. Dissociative Ionization Mechanism and Appearance Energies in Adipic Acid Revealed by Imaging Photoelectron Photoion Coincidence, Selective Deuteration, and Calculations.

    PubMed

    Heringa, Maarten F; Slowik, Jay G; Prévôt, André S H; Baltensperger, Urs; Hemberger, Patrick; Bodi, Andras

    2016-05-26

    Adipic acid, a model compound for oxygenated organic aerosol, has been studied at the VUV beamline of the Swiss Light Source. Internal energy selected cations were prepared by threshold photoionization using vacuum ultraviolet synchrotron radiation and imaging photoelectron photoion coincidence spectroscopy (iPEPICO). The threshold photoelectron spectrum yields a vertical ionization energy (IE) of 10.5 eV, significantly above the calculated adiabatic IE of 8.6 eV. The cationic minimum is accessible after vertical ionization by H-transfer from one of the γ-carbons to a carbonyl oxygen and is sufficiently energetic to decay by water loss at the ionization onset. The slope of the breakdown curves, quantum chemical calculations, and selective deuteration of the carboxylic hydrogens establish the dissociative photoionization mechanism. After ionization, one γ-methylene hydrogen and the two carboxylic hydrogens are randomized prior to H2O loss. On the basis of the deuteration degree in the H2O + CO-loss product at higher energies, a direct water-loss channel without complete randomization also exists. The breakdown diagram and center of gravity of the H2O + CO-loss peak were modeled to obtain 0 K appearance energies of 10.77, 10.32, and 11.53 eV for H2O + CO loss, CH2COOH loss, and H2O + CH2COOH loss from adipic acid. These agree well with the CBS-QB3 calculated values of 10.68, 10.45, and 11.57 eV, respectively, which shows that threshold photoionization can yield energetics data as long as the dissociation is statistical, even when the parent ion cannot be observed. The results can be used as a starting point for a deeper understanding of the ionization and low-energy fragmentation of organic aerosol components.

  3. 18 CFR Appendix A 1 to Part 281 - Comparison of Selected Fuel Price Data, FPC Form No. 423 Versus Monthly Energy Review, 1976...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Fuel Price Data, FPC Form No. 423 Versus Monthly Energy Review, 1976-January 1980 A Appendix A 1 to... Selected Fuel Price Data, FPC Form No. 423 Versus Monthly Energy Review, 1976—January 1980 1 As reported in DOE/EIA Energy Data Report entitled Cost and Quality of Fuels for Electric Utility Plants...

  4. Energy.

    ERIC Educational Resources Information Center

    Online-Offline, 1998

    1998-01-01

    This issue focuses on the theme of "Energy," and describes several educational resources (Web sites, CD-ROMs and software, videos, books, activities, and other resources). Sidebars offer features on alternative energy, animal energy, internal combustion engines, and energy from food. Subthemes include harnessing energy, human energy, and…

  5. Preparation of a selected high vibrational energy level of isolated molecules

    NASA Astrophysics Data System (ADS)

    Perreault, William E.; Mukherjee, Nandini; Zare, Richard N.

    2016-10-01

    Stark induced adiabatic Raman passage (SARP) allows us to prepare an appreciable concentration of isolated molecules in a specific, high-lying vibrational level. The process has general applicability, and, as a demonstration, we transfer nearly 100 percent of the HD (v = 0, J = 0) in a supersonically expanded molecular beam of HD molecules to HD (v = 4, J = 0). This is achieved with a sequence of partially overlapping nanosecond pump (355 nm) and Stokes (680 nm) single-mode laser pulses of unequal intensities. By comparing our experimental data with our theoretical calculations, we are able to draw two important conclusions: (1) using SARP a large population (>1010 molecules per laser pulse) is prepared in the (v = 4, J = 0) level of HD and (2) the polarizability α00,40 (≅0.6 × 10-41 C m2 V-1) for the (v = 0, J = 0) to (v = 4, J = 0) Raman overtone transition is only about five times smaller than α00,10 for the (v = 0, J = 0) to (v = 1, J = 0) fundamental Raman transition. Moreover, the SARP process selects a specific rotational level in the vibrational manifold and can prepare one or a phased linear combination of magnetic sublevels (M states) within the selected vibrational-rotational level. This capability of preparing selected, highly excited vibrational levels of molecules under collision-free conditions opens new opportunities for fundamental scattering experiments.

  6. Low energy impact of size selected FeCo nanoparticles with a W(1 1 0) surface

    NASA Astrophysics Data System (ADS)

    Rosellen, W.; Bettermann, H.; Veltum, T.; Getzlaff, M.

    2012-04-01

    Deposited mass-filtered FeCo nanoparticles were investigated in situ by means of scanning tunneling microscopy (STM). The particles are generated in the gas-phase by a continuously working, UHV compatible Arc Cluster Ion Source (ACIS) and subsequently mass-, i.e. size-selected by an electrostatic quadrupole. After size-selection these particles were deposited on a clean W(1 1 0)-crystal surface. The size of the deposited FeCo particles is tuned between 5 and 15 nm. Because of the preparation, deposition and characterization is carried out under UHV conditions neither oxidation nor contamination takes place. The kinetic energy of the nanoparticles can be varied by applying an external field at the substrate because they are charged thus allowing an acceleration or deceleration. We focus on the landing behavior of these nanoparticles and their possible structural change after the collision with the target surface. It is shown that for different deposition energies slightly above and below the one for softlanding condition a significant change of the crystallographic structure occurs. We found an unexpected thermal induced phase transition of the nanoparticles after the impact on the surface at kinetic energies being ≈0.2 eV/atom.

  7. Process for depositing epitaxial alkaline earth oxide onto a substrate and structures prepared with the process

    DOEpatents

    McKee, Rodney A.; Walker, Frederick J.

    1996-01-01

    A process and structure involving a silicon substrate utilize molecular beam epitaxy (MBE) and/or electron beam evaporation methods and an ultra-high vacuum facility to grow a layup of epitaxial alkaline earth oxide films upon the substrate surface. By selecting metal constituents for the oxides and in the appropriate proportions so that the lattice parameter of each oxide grown closely approximates that of the substrate or base layer upon which oxide is grown, lattice strain at the film/film or film/substrate interface of adjacent films is appreciably reduced or relieved. Moreover, by selecting constituents for the oxides so that the lattice parameters of the materials of adjacent oxide films either increase or decrease in size from one parameter to another parameter, a graded layup of films can be grown (with reduced strain levels therebetween) so that the outer film has a lattice parameter which closely approximates that of, and thus accomodates the epitaxial growth of, a pervoskite chosen to be grown upon the outer film.

  8. Stereo-epitaxial growth of single-crystal Ni nanowires and nanoplates from aligned seed crystals

    NASA Astrophysics Data System (ADS)

    Lee, Hyoban; Yoo, Youngdong; Kang, Taejoon; Lee, Jiyoung; Kim, Eungwang; Fang, Xiaosheng; Lee, Sungyul; Kim, Bongsoo

    2016-05-01

    Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni seeds are determined by the interfacial energy between the bottom plane of the seeds and the substrates. The as-synthesized Ni NWs and nanoplates have blocking temperature values greater than 300 K at 500 Oe, verifying that these Ni nanostructures can form large magnetic DWs with high magnetic anisotropy properties. We anticipate that epitaxially grown Ni NWs and nanoplates will be used in various types of 3-dimensional magnetic devices.Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni

  9. The Dark Energy Spectroscopic Instrument (DESI): The NOAO DECam Legacy Imaging Survey and DESI Target Selection

    NASA Astrophysics Data System (ADS)

    Schlegel, David J.; Blum, Robert D.; Castander, Francisco Javier; Dey, Arjun; Finkbeiner, Douglas P.; Foucaud, Sebastien; Honscheid, Klaus; James, David; Lang, Dustin; Levi, Michael; Moustakas, John; Myers, Adam D.; Newman, Jeffrey; Nord, Brian; Nugent, Peter E.; Patej, Anna; Reil, Kevin; Rudnick, Gregory; Rykoff, Eli S.; Ford Schlafly, Eddie; Stark, Casey; Valdes, Francisco; Walker, Alistair R.; Weaver, Benjamin; DECam Legacy Survey Collaboration

    2015-01-01

    The DECam Legacy Survey will conduct a 3-band imaging survey of the Sloan Digital Sky Survey (SDSS) extragalactic footprint. The Dark Energy Camera (DECam) will be used to image the 6700 square degree footprint overlapping SDSS in the region -20 < Dec < +30 deg, to depths of g=24.7, r=23.9, z=23.0. The survey will be conducted from Fall 2014 through Spring 2017, with periodic data releases beginning in March 2015. These releases will include catalogs constructed with the Tractor-based multi-wavelength forced photometry applied to the DECam and WISE satellite data.The Dark Energy Spectroscopic Instrument (DESI) will observe 24 million galaxies and quasars in a 14,000 square degree extragalactic footprint. The targeting in that footprint will be provided by a combination of these DECam data, the MOSAIC camera on the Mayall 4-meter, and the 90Prime camera on the Bok Telescope.

  10. [Frequency of intake and energy value of breakfast for students from selected primary schools in Warsaw].

    PubMed

    Hamułka, J; Gronowska-Senger, A; Witkowska, K

    2000-01-01

    Energy value and frequency breakfast intake in Warsaw primary schools were estimated in a group of 330 children aged 7-15 years. The research was carried out in autumn 1998 year. The nutrition mode was assessed by questionnaire interviews and of 24-hour recall [4] and computer programme "Zywienie". The size of the consumed portion was determined with an album containing colour photographs of products and dishes of different size [14]. Food consumption quality was estimated using test of Bielińska modified by Kulesza et al. [8]. Frequency breakfast intake decreased at older schoolchildren. Breakfast milk and products, vegetables and fruits intake was too low; intake of fat sweets and beverages like "coca-cola" was too high. Breakfast energy value was too low compared with recommended dietary allowances.

  11. Performance comparisons of selected personnel-dosimetry systems in use at Department of Energy facilities

    SciTech Connect

    Roberson, P.L; Holbrook, K.L.; Yoder, R.C.; Fox, R.A.; Hadley, R.T.; Hogan, B.T.; Hooker, C.D.

    1983-10-01

    Dosimeter performance data were collected to help develop a uniform approach to the calibration and use of personnel dosimetry systems for Department of Energy (DOE) laboratories. Eleven DOE laboratories participated in six months of testing using the American National Draft Standard, Criteria for Testing Personnel Dosimetry Performance, ANSI N13.11, and additional testing categories. The tests described in ANSI N13.11 used a pass/fail system to determine compliance with the draft standard. Recalculation to PNL irradiations showed that the /sup 137/Cs, /sup 90/Sr//sup 90/Y, and /sup 252/Cf categories can be recalibrated to have acceptable performance for nearly all participant systems. Deficient dosimeter design or handling techniques caused poor performance in the x-ray category for nearly half of the participants. Too little filtration for the deep-dose element caused poor performance in the beta/photon mixture category for one participant. Two participants had excessively high standard deviations in the neutron category due to dosimeter design or handling deficiencies. The participating dosimetry systems were separated into three categories on their dose evaluation procedure for low-energy photons. These were film dosimeters, fixed-calibration thermoluminescent (TL) dosimeters, and variable-calibration TL dosimeters. The performance of the variable-calibration design was best while the film dosimeters performed considerably worse than either TL dosimeter design. Beta energy dependence studies confirmed a strong correlation between sensitive element thickness, shallow element filtration and low-energy beta response. Studies of neutron calibration conditions for each participant suggested a relationship between response and calibration facility design.

  12. Studies of Energy Transfer and Selective Chemical Reaction Using Tunable IR Radiation.

    DTIC Science & Technology

    1982-09-01

    OPO over its tuning range, compared with the energy level diagram of HCN. More details of the performance can be found in the papers by Arnold et a17...Nitrogen Dioxide. OH + NO2 + M (= He, CO2 ) in the Temperature Range 213 - 300 K. Ber. Bunsen. Gesell . Phys. Chem., 81, 22 (1977). U I.W.,I. Smith...The Dynamics of Collisions between Vibrationally 4 Excited Diatomic Molecules and Potentially Reactive Atoms Ber. Bunsen. Gesell . Phys. Chem., 1, 126

  13. Method utilizing laser-processing for the growth of epitaxial p-n junctions

    DOEpatents

    Young, R.T.; Narayan, J.; Wood, R.F.

    1979-11-23

    This invention is a new method for the formation of epitaxial p-n junctions in silicon. The method is relatively simple, rapid, and reliable. It produces doped epitaxial layers which are of well-controlled thickness and whose electrical properties are satisfactory. An illustrative form of the method comprises co-depositing a selected dopant and amorphous silicon on a crystalline silicon substrate to form a doped layer of amorphous silicon thereon. This layer then is irradiated with at least one laser pulse to generate a melt front which moves through the layer, into the silicon body to a depth effecting melting of virginal silicon, and back to the surface of the layer. The method may be conducted with dopants (e.g., boron and phosphorus) whose distribution coefficients approximate unity.

  14. InAs nanowire growth modes on Si (111) by gas source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Robson, M. T.; LaPierre, R. R.

    2016-02-01

    InAs nanowires (NWs) were grown on silicon substrates by gas source molecular beam epitaxy using five different growth modes: (1) Au-assisted growth, (2) positioned (patterned) Au-assisted growth, (3) Au-free growth, (4) positioned Au-assisted growth using a patterned oxide mask, and (5) Au-free selective-area epitaxy (SAE) using a patterned oxide mask. Optimal growth conditions (temperature, V/III flux ratio) were identified for each growth mode for control of NW morphology and vertical NW yield. The highest yield (72%) was achieved with the SAE method at a growth temperature of 440 °C and a V/III flux ratio of 4. Growth mechanisms are discussed for each of the growth modes.

  15. Epitaxial aluminum on hybridized InAs/GaSb quantum wells

    NASA Astrophysics Data System (ADS)

    Tong, Bing-Bing; Li, Ting-Xin; Mu, Xiao-Yang; Zhang, Chi; Du, Rui-Rui

    Hybridized InAs/GaSb quantum wells (QW) are approved the existence of helical edge channels. According to the theoretical prediction, the combination with superconductor will lead to superconducting topological phase and realization of Majorana bound state (MBS). Besides, InAs/GaSb material shows a low Schottky barrier to superconductor, and high quality of superconductor-topological insulator interface will result in hard induced gap. In recent report, under low temperature of substrate, there is a good lattice match between InAs naowire and Al in the same direction. In our lab, we perform aluminum epitaxy on the in-situ cleaved InAs/GaSb QW with similar methods in our ultra-high vacuum STM system. After metal epitaxy, the Al layer can be selectively etched for fabricating the superconductor-topological insulator junction devices.

  16. Sidewall GaAs tunnel junctions fabricated using molecular layer epitaxy.

    PubMed

    Ohno, Takeo; Oyama, Yutaka

    2012-02-01

    In this article we review the fundamental properties and applications of sidewall GaAs tunnel junctions. Heavily impurity-doped GaAs epitaxial layers were prepared using molecular layer epitaxy (MLE), in which intermittent injections of precursors in ultrahigh vacuum were applied, and sidewall tunnel junctions were fabricated using a combination of device mesa wet etching of the GaAs MLE layer and low-temperature area-selective regrowth. The fabricated tunnel junctions on the GaAs sidewall with normal mesa orientation showed a record peak current density of 35 000 A cm(-2). They can potentially be used as terahertz devices such as a tunnel injection transit time effect diode or an ideal static induction transistor.

  17. Molecular-beam epitaxial regrowth on oxygen-implanted GaAs substrates for device integration

    NASA Astrophysics Data System (ADS)

    Chen, C. L.; Mahoney, L. J.; Calawa, S. D.; Molvar, K. M.; Maki, P. A.; Mathews, R. H.; Sage, J. P.; Sollner, T. C. L. G.

    1999-06-01

    Device-quality layers were regrown on GaAs wafers by molecular-beam epitaxy over conductive pregrown areas and on selectively patterned high-resistivity areas formed by oxygen implantation. The regrowth over both areas resulted in comparable device-quality GaAs. The high resistivity of the oxygen-implanted area was maintained after the regrowth and no oxygen incorporation was observed in the regrown layer. The cutoff frequency of a 1.5-μm-gate metal-semiconductor field-effect transistor fabricated on the regrown layer over the high-resistivity areas is 7 GHz. This demonstration shows that planar technology can be used in epitaxial regrowth, simplifying the integration of vastly different devices into monolithic circuits.

  18. Ge nanopillar solar cells epitaxially grown by metalorganic chemical vapor deposition

    PubMed Central

    Kim, Youngjo; Lam, Nguyen Dinh; Kim, Kangho; Park, Won-Kyu; Lee, Jaejin

    2017-01-01

    Radial junction solar cells with vertically aligned wire arrays have been widely studied to improve the power conversion efficiency. In this work, we report the first Ge nanopillar solar cell. Nanopillar arrays are selectively patterned on p-type Ge (100) substrates using nanosphere lithography and deep reactive ion etching processes. Nanoscale radial and planar junctions are realized by an n-type Ge emitter layer which is epitaxially grown by MOCVD using isobutylgermane. In situ epitaxial surface passivation is employed using an InGaP layer to avoid high surface recombination rates and Fermi level pinning. High quality n-ohmic contact is realized by protecting the top contact area during the nanopillar patterning. The short circuit current density and the power conversion efficiency of the Ge nanopillar solar cell are demonstrated to be improved up to 18 and 30%, respectively, compared to those of the Ge solar cell with a planar surface. PMID:28209964

  19. Layer matching epitaxy of NiO thin films on atomically stepped sapphire (0001) substrates

    PubMed Central

    Yamauchi, Ryosuke; Hamasaki, Yosuke; Shibuya, Takuto; Saito, Akira; Tsuchimine, Nobuo; Koyama, Koji; Matsuda, Akifumi; Yoshimoto, Mamoru

    2015-01-01

    Thin-film epitaxy is critical for investigating the original properties of materials. To obtain epitaxial films, careful consideration of the external conditions, i.e. single-crystal substrate, temperature, deposition pressure and fabrication method, is significantly important. In particular, selection of the single-crystal substrate is the first step towards fabrication of a high-quality film. Sapphire (single-crystalline α-Al2O3) is commonly used in industry as a thin-film crystal-growth substrate, and functional thin-film materials deposited on sapphire substrates have found industrial applications. However, while sapphire is a single crystal, two types of atomic planes exist in accordance with step height. Here we discuss the need to consider the lattice mismatch for each of the sapphire atomic layers. Furthermore, through cross-sectional transmission electron microscopy analysis, we demonstrate the uniepitaxial growth of cubic crystalline thin films on bistepped sapphire (0001) substrates. PMID:26402241

  20. Epitaxial self-assembly of binary molecular components into branched nanowire heterostructures for photonic applications.

    PubMed

    Kong, Qinghua; Liao, Qing; Xu, Zhenzhen; Wang, Xuedong; Yao, Jiannian; Fu, Hongbing

    2014-02-12

    We report a sequential epitaxial growth to prepare organic branched nanowire heterostructures (BNwHs) consisting of a microribbon trunk of 1,4-dimethoxy-2,5-di[4'-(cyano)styryl]benzene (COPV) with multiple nanowire branches of 2,4,5-triphenylimidazole (TPI) in a one-pot solution synthesis. The synthesis involves a seeded-growth process, where COPV microribbons are grown first as a trunk followed by a seeded-growth of TPI nanowire branches at the pregrown trunk surfaces. Selected area electron diffraction characterizations reveal that multiple hydrogen-bonding interactions between TPI and COPV components play an essential role in the epitaxial growth as a result of the structural matching between COPV and TPI crystals. A multichannel optical router was successfully realized on the basis of the passive waveguides of COPV green photoluminescence (PL) along TPI nanowire branches in a single organic BNwH.