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Sample records for synthesize inp micrometer

  1. Efficient rapid microwave-assisted route to synthesize InP micrometer hollow spheres

    SciTech Connect

    Zheng Xiuwen Hu Qitu; Sun Chuansheng

    2009-01-08

    The efficiencies of two methods of synthesizing InP micro-scale hollow spheres are compared via the analogous solution-liquid-solid (ASLS) growth mechanism, either through a traditional solvothermal procedure, or via a microwave-assisted method. Scanning electronic microscopy (SEM) images show that most of the as-grown samples are micrometer hollow spheres, which indicates the efficiency of both methods. For traditional solvothermal route, long time (10 h) is necessary to obtain the desired samples, however, for the microwave-assisted route, 30 min is enough for hollow spherical products. An optimal choice of microwave irradiating time allows reducing the reaction time from hours to minutes. The proposed ASLS growth mechanism has also been discussed in detail.

  2. Filar Micrometer

    NASA Astrophysics Data System (ADS)

    Argyle, Bob; Argyle, R. W.

    The measurement of double stars is central to the theme of this book and there are many ways of doing this, but this chapter is dedicated to the use of the filar micrometer which has been used seriously since the time of William Herschel. For a thorough discussion of the history and development of the filar micrometer see the paper by Brooks(1991). Much of our knowledge of longer period visual binaries depends on micrometric measures over the last 200 years. The filar micrometer is by far the most well-known device for measuring double stars. Its design remains largely the same as the original instrument which was first applied to an astronomical telescope by the Englishman William Gascoigne (ca. 1620-1644) in the late 1630s. The aim is to use fine threads located in the focal plane of the telescope lens or mirror to measure the relative position of the fainter component of a double star with respect to the brighter, regarding the latter as fixed for this purpose. This is done by the measurement of the angle which the line joining the two stars makes with the N reference in the eyepiece and the angular separation of the fainter star (B) from the brighter (A) in seconds of arc. These quantities are usually known as theta ( θ ) and rho ( ρ ) respectively and are defined in Chap. 1 .

  3. Optical contact micrometer

    DOEpatents

    Jacobson, Steven D.

    2014-08-19

    Certain examples provide optical contact micrometers and methods of use. An example optical contact micrometer includes a pair of opposable lenses to receive an object and immobilize the object in a position. The example optical contact micrometer includes a pair of opposable mirrors positioned with respect to the pair of lenses to facilitate viewing of the object through the lenses. The example optical contact micrometer includes a microscope to facilitate viewing of the object through the lenses via the mirrors; and an interferometer to obtain one or more measurements of the object.

  4. When is an INP not an INP?

    NASA Astrophysics Data System (ADS)

    Simpson, Emma; Connolly, Paul; McFiggans, Gordon

    2016-04-01

    Processes such as precipitation and radiation depend on the concentration and size of different hydrometeors within clouds therefore it is important to accurately predict them in weather and climate models. A large fraction of clouds present in our atmosphere are mixed phase; contain both liquid and ice particles. The number of drops and ice crystals present in mixed phase clouds strongly depends on the size distribution of aerosols. Cloud condensation nuclei (CCN), a subset of atmospheric aerosol particles, are required for liquid drops to form in the atmosphere. These particles are ubiquitous in the atmosphere. To nucleate ice particles in mixed phase clouds ice nucleating particles (INP) are required. These particles are rarer than CCN. Here we investigate the case where CCN and INPs are in direct competition with each other for water vapour within a cloud. Focusing on the immersion and condensation modes of freezing (where an INP must be immersed within a liquid drop before it can freeze) we show that the presence of CCN can suppress the formation of ice. CCN are more hydrophilic than IN and as such are better able to compete for water vapour than, typically insoluble, INPs. Therefore water is more likely to condense onto a CCN than INP, leaving the INP without enough condensed water on it to be able to freeze in the immersion or condensation mode. The magnitude of this suppression effect strongly depends on a currently unconstrained quantity. Here we refer to this quantity as the critical mass of condensed water required for freezing, Mwc. Mwc is the threshold amount of water that must be condensed onto a INP before it can freeze in the immersion or condensation mode. Using the detailed cloud parcel model, Aerosol-Cloud-Precipiation-Interaction Model (ACPIM), developed at the University of Manchester we show that if only a small amount of water is required for freezing there is little suppression effect and if a large amount of water is required there is a

  5. Laser interferometer micrometer system

    NASA Technical Reports Server (NTRS)

    Logue, S. H.

    1969-01-01

    Laser micrometer measures dimensions of precision gyro and gas bearing parts using the principle of measuring light phase changes rather than a direct fringe count. The system uses light beams to eliminate errors due to deformations and surface irregularities, and three interferometers.

  6. Noncontact fiber optic micrometer

    NASA Astrophysics Data System (ADS)

    Betancourt Ibarra, F.; Guajardo-Gonzalez, Candelario; Castillo-Guzman, Arturo; Guzman-Ramos, Valentin; Selvas, Romeo

    2010-10-01

    A sensor instrument able to measuring the thickness of different semitransparent objects with a resolution of one micron is described. This is based on a fiber optic reflectometer and a laser autofocus system and permit to measuring the thickness of thin surfaces such as semiconductor films, plastic materials and semitransparent objects. The response time for the measuring was roughly 2 sec and the thickness results were compared with a digital mechanical micrometer and both are in good agreement.

  7. Automatic readout micrometer

    SciTech Connect

    Lauritzen, T.

    1982-03-23

    A measuring system is disclosed for surveying and very accurately positioning objects with respect to a reference line. A principal use of this surveying system is for accurately aligning the electromagnets which direct a particle beam emitted from a particle accelerator. Prior art surveying systems require highly skilled surveyors. Prior art systems include, for example, optical surveying systems which are susceptible to operator reading errors, and celestial navigation-type surveying systems, with their inherent complexities. The present invention provides an automatic readout micrometer which can very accurately measure distances. The invention has a simplicity of operation which practically eliminates the possibilities of operator optical reading error, owning to the elimination of traditional optical alignments for making measurements. The invention has an extendable arm which carries a laser surveying target. The extendable arm can be continuously positioned over its entire length of travel by either a coarse or fine adjustment without having the fine adjustment outrun the coarse adjustment until a reference laser beam is centered on the target as indicated by a digital readout. The length of the micrometer can then be accurately and automatically read by a computer and compared with a standardized set of alignment measurements. Due to its construction, the micrometer eliminates any errors due to temperature changes when the system is operated within a standard operating temperature range.

  8. Automatic readout micrometer

    DOEpatents

    Lauritzen, T.

    A measuring system is described for surveying and very accurately positioning objects with respect to a reference line. A principle use of this surveying system is for accurately aligning the electromagnets which direct a particle beam emitted from a particle accelerator. Prior art surveying systems require highly skilled surveyors. Prior art systems include, for example, optical surveying systems which are susceptible to operator reading errors, and celestial navigation-type surveying systems, with their inherent complexities. The present invention provides an automatic readout micrometer which can very accurately measure distances. The invention has a simplicity of operation which practically eliminates the possibilities of operator optical reading error, owning to the elimination of traditional optical alignments for making measurements. The invention has an extendable arm which carries a laser surveying target. The extendable arm can be continuously positioned over its entire length of travel by either a coarse of fine adjustment without having the fine adjustment outrun the coarse adjustment until a reference laser beam is centered on the target as indicated by a digital readout. The length of the micrometer can then be accurately and automatically read by a computer and compared with a standardized set of alignment measurements. Due to its construction, the micrometer eliminates any errors due to temperature changes when the system is operated within a standard operating temperature range.

  9. Automatic readout micrometer

    DOEpatents

    Lauritzen, Ted

    1982-01-01

    A measuring system is disclosed for surveying and very accurately positioning objects with respect to a reference line. A principal use of this surveying system is for accurately aligning the electromagnets which direct a particle beam emitted from a particle accelerator. Prior art surveying systems require highly skilled surveyors. Prior art systems include, for example, optical surveying systems which are susceptible to operator reading errors, and celestial navigation-type surveying systems, with their inherent complexities. The present invention provides an automatic readout micrometer which can very accurately measure distances. The invention has a simplicity of operation which practically eliminates the possibilities of operator optical reading error, owning to the elimination of traditional optical alignments for making measurements. The invention has an extendable arm which carries a laser surveying target. The extendable arm can be continuously positioned over its entire length of travel by either a coarse or fine adjustment without having the fine adjustment outrun the coarse adjustment until a reference laser beam is centered on the target as indicated by a digital readout. The length of the micrometer can then be accurately and automatically read by a computer and compared with a standardized set of alignment measurements. Due to its construction, the micrometer eliminates any errors due to temperature changes when the system is operated within a standard operating temperature range.

  10. Micrometer for Measuring Trepanned Grooves

    NASA Technical Reports Server (NTRS)

    Bird, S. K.

    1983-01-01

    Special micrometer measures diameter of circular groove on face of large part, while part is mounted in lathe chuck. Tool has curved frame so it can reach around obstruction on centerline of part. At one end of frame is blade/ micrometer spindle for reaching into groove to be measured; this type of spindle does not rotate when micrometer thimble is turned in taking measurement. Other end of frame has sliding foot with blade.

  11. Identification and characterization of an essential family of inositol polyphosphate 5-phosphatases (INP51, INP52 and INP53 gene products) in the yeast Saccharomyces cerevisiae.

    PubMed Central

    Stolz, L E; Huynh, C V; Thorner, J; York, J D

    1998-01-01

    We recently demonstrated that the S. cerevisiae INP51 locus (YIL002c) encodes an inositol polyphosphate 5-phosphatase. Here we describe two related yeast loci, INP52 (YNL106c) and INP53 (YOR109w). Like Inp51p, the primary structures of Inp52p and Inp53p resemble the mammalian synaptic vesicle-associated protein, synaptojanin, and contain a carboxy-terminal catalytic domain and an amino-terminal SAC1-like segment. Inp51p (108 kD), Inp52p (136 kD) and Inp53p (124 kD) are membrane-associated. Single null mutants (inp51, inp52, or inp53) are viable. Both inp51 inp52 and inp52 inp53 double mutants display compromised cell growth, whereas an inp51 inp53 double mutant does not. An inp51 inp52 inp53 triple mutant is inviable on standard medium, but can grow weakly on media supplemented with an osmotic stabilizer (1 M sorbitol). An inp51 mutation, and to a lesser degree an inp52 mutation, confers cold-resistant growth in a strain background that cannot grow at temperatures below 15 degrees. Analysis of inositol metabolites in vivo showed measurable accumulation of phosphatidylinositol 4,5-bisphosphate in the inp51 mutant. Electron microscopy revealed plasma membrane invaginations and cell wall thickening in double mutants and the triple mutant grown in sorbitol-containing medium. A fluorescent dye that detects endocytic and vacuolar membranes suggests that the vacuole is highly fragmented in inp51 inp52 double mutants. Our observations indicate that Inp51p, Inp52p, and Inp53p have distinct functions and that substrates and/or products of inositol polyphosphate 5-phosphatases may have roles in vesicle trafficking, membrane structure, and/or cell wall formation. PMID:9560389

  12. Airborne astronomy with a 150 micrometer - 500 micrometer heterodyne spectrometer

    NASA Technical Reports Server (NTRS)

    Betz, A. L.

    1991-01-01

    This report summarizes work done under NASA Grant NAG2-254 awarded to the University of California. The project goal was to build a far-infrared heterodyne spectrometer for NASA's Kuiper Airborne Observatory (KAO), and to use this instrument to observe atomic and molecular spectral lines from the interstellar medium. This goal was successfully achieved; the spectrometer is now in routine use aboard the KAO. Detections of particular note have been the 370 micrometers line of neutral atomic carbon, the 158 micrometers transition of ionized carbon, many of the high-J rotational lines of 12CO and 13CO between J=9-8 and J=22-21, the 119 micron ground-state rotational line of OH, and the 219 micron ground-state rotational line of H2D(+). All of these lines were observed at spectral resolutions exceeding 1 part in 10(exp 6), thereby allowing accurate line shapes and Doppler velocities to be measured.

  13. CNPq/INPE-LANDSAT system

    NASA Technical Reports Server (NTRS)

    Debarrosaguirre, J. L.

    1985-01-01

    The current status of the Brazilian LANDSAT facilities operated by Instituto de Pesquisas Espaciais (INPE) and the results achieved during the period from October 1, 1984 to August 31, 1985 are presented. INPE's Receiving Station at Cuiaba, MT, operates normally the two tracking and receiving systems it has installed, the old one (1973) for Band S and the new one (February 1983) for dual S- and X-band. Both MSS and TM recording capabilities are functional. Support to the NASA Backup Plan for MSS data also remains active. Routine recordings are being made for LANDSAT-5 only, for both MSS and TM. Originally, MSS was recorded over the full acquisition range. However, since December, 1984, due to further reduction of operational expenses, both instruments are being recorded over Brazilian territory only.

  14. Toward Unraveling the Nature of the Mysterious 21 and 30 Micrometer Emission Features of Evolved Stars

    NASA Astrophysics Data System (ADS)

    Mishra, Ajay; Li, A.

    2014-01-01

    feature carriers are probably synthesized in the PPN phase while the 30 micrometer feature carrier is being destroyed in the PPN phase through decomposition or shattering.

  15. InP materials/cell fabrication

    NASA Technical Reports Server (NTRS)

    Coutts, T. J.

    1987-01-01

    The main points of discussion, conclusions and recommendations of a workshop on InP materials and cell fabrication are given. The importance of assessing the quality of p-Inp crystals supplied by different vendors, back contacts to solar cells, junction formation, energy conversion efficiency, testing for radiation resistance, and future develpments were among the topics discussed.

  16. Level Indicator On A Tubular Inside Micrometer

    NASA Technical Reports Server (NTRS)

    Malinzak, R. Michael; Booth, Gary N.

    1995-01-01

    Leveling helps to ensure accurate measurements. Attachment helpful because in some situations that involve measurement of large, tight-tolerance inside dimensions, inside micrometers not held level between contact point give inaccurate readings. User adjusts position and orientation of micrometer and verifies level by observing bubble in level indicator. Upon feeling correct drag between micrometer tips and workpiece, user confident that tool used correctly and accurate measurement obtained.

  17. Positioned growth of InP nanowires

    NASA Astrophysics Data System (ADS)

    Poole, P. J.; Dalacu, D.; Lapointe, J.; Kam, A.; Mnaymneh, K.

    2011-02-01

    We describe two different approaches to growing precisely positioned InP nanowires on InP wafers. Both of these approaches utilize the selective area growth capabilities of Chemical Beam Epitaxy, one using the Au catalysed Vapour-Liquid-Solid (VLS) growth mode, the other being catalyst-free. Growth is performed on InP wafers which are first coated with 20 nm of SiO2. These are then patterned using e-beam lithography to create nanometer scale holes in the SiO2 layer to expose the InP surface. For the VLS growth Au is then deposited into the holes in the SiO2 mask layer using a self-aligned lift-off process. For the catalyst-free growth no Au is deposited. In both cases the deposition of InP results in the formation of InP nanowires. In VLS growth the nanowire diameter is controlled by the size of the Au particle, whereas when catalyst-free the diameter is that of the opening in the SiO2 mask. The orientation of the nanowires is also different, <111>B when using Au particles and <111>A when catalyst-free. For the catalysed growth the effect of the Au particle can be turned off by modifying growth conditions allowing the nanowire to be clad, dramatically enhancing the optical emission from InAs quantum dots grown inside the nanowire.

  18. Two-Step Nucleation and Growth of InP Quantum Dots via Magic-Sized Cluster Intermediates

    DOE PAGESBeta

    Gary, Dylan C.; Terban, Maxwell W.; Billinge, Simon J. L.; Cossairt, Brandi M.

    2015-01-30

    We report on the role of magic-sized clusters (MSCs) as key intermediates in the synthesis of indium phosphide quantum dots (InP QDs) from molecular precursors. These observations suggest that previous efforts to control nucleation and growth by tuning precursor reactivity have been undermined by formation of these kinetically persistent MSCs prior to QD formation. The thermal stability of InP MSCs is influenced by the presence of exogenous bases as well as choice of the anionic ligand set. Addition of a primary amine, a common additive in previous InP QD syntheses, to carboxylate terminated MSCs was found to bypass the formationmore » of MSCs, allowing for homogeneous growth of InP QDs through a continuum of isolable sizes. Substitution of the carboxylate ligand set for a phosphonate ligand set increased the thermal stability of one particular InP MSC to 400°C. The structure and optical properties of the MSCs with both carboxylate and phosphonate ligand sets were studied by UV-Vis absorption spectroscopy, powder XRD analysis, and solution ³¹P{¹H} and ¹H NMR spectroscopy. Finally, the carboxylate terminated MSCs were identified as effective single source precursors (SSPs) for the synthesis of high quality InP QDs. Employing InP MSCs as SSPs for QDs effectively decouples the formation of MSCs from the subsequent second nucleation event and growth of InP QDs. The concentration dependence of this SSP reaction, as well as the shape uniformity of particles observed by TEM suggests that the stepwise growth from MSCs directly to QDs proceeds via a second nucleation event rather than an aggregative growth mechanism.« less

  19. Two-Step Nucleation and Growth of InP Quantum Dots via Magic-Sized Cluster Intermediates

    SciTech Connect

    Gary, Dylan C.; Terban, Maxwell W.; Billinge, Simon J. L.; Cossairt, Brandi M.

    2015-01-30

    We report on the role of magic-sized clusters (MSCs) as key intermediates in the synthesis of indium phosphide quantum dots (InP QDs) from molecular precursors. These observations suggest that previous efforts to control nucleation and growth by tuning precursor reactivity have been undermined by formation of these kinetically persistent MSCs prior to QD formation. The thermal stability of InP MSCs is influenced by the presence of exogenous bases as well as choice of the anionic ligand set. Addition of a primary amine, a common additive in previous InP QD syntheses, to carboxylate terminated MSCs was found to bypass the formation of MSCs, allowing for homogeneous growth of InP QDs through a continuum of isolable sizes. Substitution of the carboxylate ligand set for a phosphonate ligand set increased the thermal stability of one particular InP MSC to 400°C. The structure and optical properties of the MSCs with both carboxylate and phosphonate ligand sets were studied by UV-Vis absorption spectroscopy, powder XRD analysis, and solution ³¹P{¹H} and ¹H NMR spectroscopy. Finally, the carboxylate terminated MSCs were identified as effective single source precursors (SSPs) for the synthesis of high quality InP QDs. Employing InP MSCs as SSPs for QDs effectively decouples the formation of MSCs from the subsequent second nucleation event and growth of InP QDs. The concentration dependence of this SSP reaction, as well as the shape uniformity of particles observed by TEM suggests that the stepwise growth from MSCs directly to QDs proceeds via a second nucleation event rather than an aggregative growth mechanism.

  20. Microfabricated High-Moment Micrometer-sized MRI Contrast Agents

    PubMed Central

    Zabow, Gary; Dodd, Stephen J.; Shapiro, Erik; Moreland, John; Koretsky, Alan P.

    2010-01-01

    While chemically synthesized superparamagnetic microparticles have enabled much new research based on MRI-tracking of magnetically labeled cells, signal-to-noise levels still limit the potential range of applications. Here it is shown how, through top-down microfabrication, contrast agent relaxivity can be increased several-fold, which should extend the sensitivity of such cell tracking studies. Microfabricated agents can benefit from both higher magnetic moments and higher uniformity than their chemically synthesized counterparts, implying increased label visibility and more quantitative image analyses. To assess the performance of microfabricated micrometer-sized contrast agent particles, analytic models and numerical simulations are developed and tested against new microfabricated agents described in this paper, as well as against results of previous imaging studies of traditional chemically synthesized microparticle agents. Experimental data showing signal effects of 500-nanometer thick, 2-micrometer diameter, gold-coated iron and gold-coated nickel disks verify the simulations. Additionally, it is suggested that measures of location better than the pixel resolution can be obtained and that these are aided using well-defined contrast agent particles achievable through microfabrication techniques. PMID:20928829

  1. Radiation effects on p+n InP junctions grown by MOCVD

    NASA Technical Reports Server (NTRS)

    Messenger, Scott R.; Walters, Robert J.; Panunto, M. J.; Summers, Geoffrey P.

    1994-01-01

    The superior radiation resistance of InP over other solar cell materials such as Si or GaAs has prompted the development of InP cells for space applications. The early research on radiation effects in InP was performed by Yamaguchi and co-workers who showed that, in diffused p-InP junctions, radiation-induced defects were readily annealed both thermally and by injection, which was accompanied by significant cell recovery. More recent research efforts have been made using p-InP grown by metalorganic chemical vapor deposition (MOCVD). While similar deep level transient spectroscopy (DLTS) results were found for radiation induced defects in these cells and in diffused junctions, significant differences existed in the annealing characteristics. After injection annealing at room temperature, Yamaguchi noticed an almost complete recovery of the photovoltaic parameters, while the MOCVD samples showed only minimal annealing. In searching for an explanation of the different annealing behavior of diffused junctions and those grown by MOCVD, several possibilities have been considered. One possibility is the difference in the emitter structure. The diffused junctions have S-doped graded emitters with widths of approximately 0.3 micrometers, while the MOCVD emitters are often doped with Si and have widths of approximately 300A (0.03 micrometers). The difference in the emitter thickness can have important effects, e.g. a larger fraction of the total photocurrent is generated in the n-type material for thicker emitters. Therefore the properties of the n-InP material may explain the difference in the observed overall annealing behavior of the cells.

  2. InP concentrator solar cells

    NASA Technical Reports Server (NTRS)

    Ward, J. S.; Wanlass, M. W.; Coutts, T. J.; Emery, K. A.; Osterwald, C. R.

    1991-01-01

    The design, fabrication, and characterization of high-performance, n(+)/p InP shallow-homojunction (SHJ) concentrator solar cells are described. The InP device structures were grown by atmospheric-pressure metalorganic vapor phase epitaxy. A preliminary assessment of the effects of grid-collection distance and emitter-sheet resistance on cell performance is presented. At concentration ratios of around 100, cells with efficiencies of 21.4 percent AM0 (24.3 percent direct) at 25 C are fabricated. These are the highest efficiencies yet reported for single-junction InP solar cells. The performance of these cells as a function of temperature is discussed, and areas for future improvement are outlined. Application of these results to other InP-based photovoltaic devices is discussed.

  3. Synthesis and characterization of micrometer Cu/PVP architectures

    SciTech Connect

    Luo, Huajuan; Zhao, Yanbao; Sun, Lei

    2011-08-15

    Graphical abstract: A simple method for the synthesis of novel micrometer flower-like Cu/PVP architectures was introduced. Highlights: {yields} Micrometer flower-like copper/polyvinylpyrrolidone architectures were obtained by a simple chemical route. {yields} The amount of N{sub 2}H{sub 4}{center_dot}H{sub 2}O, the reaction temperature, the molar ratio of CuCl{sub 2} to PVP and different molecular weights of PVP play an important role in the controlling the morphology of the Cu/PVP architectures. {yields} A possible mechanism of the formation of Cu/PVP architectures was discussed. -- Abstract: Micrometer-sized flower-like Cu/polyvinylpyrrolidone (PVP) architectures are synthesized by the reduction of copper (II) salt with hydrazine hydrate in aqueous solution in the presence of PVP capping agent. The resulting Cu/PVP architectures are investigated by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The Cu/PVP flowers have uniform morphologies with an average diameter of 10 {mu}m, made of several intercrossing plates. The formation of Cu/PVP flowers is a new kinetic control process, and the factors such as the amount of N{sub 2}H{sub 4}{center_dot}H{sub 2}O, reaction temperature, molar ratio of CuCl{sub 2} to PVP and molecular weight of PVP have significant effect on the morphology of Cu/PVP architectures. A possible mechanism of the formation of micrometer Cu/PVP architectures was discussed.

  4. The sulfurized InP surface

    SciTech Connect

    Wilmsen, C. W.; Geib, K. M.; Shin, J.; Iyer, R.; Lile, D. L.; Pouch, J. J.

    1989-07-01

    Sulfur treatments have previously been shown to improve the electrical characteristics of InP and GaAs devices. This paper reports the results of an Auger/x-ray photoelectron spectroscopy investigation of the InP surface after sulfur treatment. It is shown that the sulfur remains on the surface bonded to indium. There is no indication of elemental sulfur or sulfur bonded to phosphorus. This suggests that the sulfur has replaced phosphorus on the surface and has filled the phosphorus vacancies.

  5. Electronic and vibrational spectra of InP quantum dots formed by sequential ion implantation

    SciTech Connect

    Mu, R.; Henderson, D.O.; Tung, Y.S.; Ueda, A.; Hall, C.; Collins, W.E.; White, C.W.; Zuhr, R.A.; Zhu, J.G.

    1996-05-01

    Sequential ion implantation of indium and phosphorus into silica combined with controlled thermal annealing has proven to be a novel and effective technique to fabricate InP quantum dots in dielectric hosts. This technique has been applied to synthesize other III{endash}V and II{endash}VI quantum dots. Due to the unique bimodal distribution of the indium in a silica host and a stoichiometric mismatch between the indium and phosphorus concentration profiles, it is believed that two different-sized InP quantum dots were fabricated. More importantly, we have shown that the infrared reflectance technique is a very effective method to identify the species in the dielectric host and is also a powerful tool to investigate surface phonon modes. {copyright} {ital 1996 American Vacuum Society}

  6. Spin Relaxation in InP and Strained InP Nanowires

    NASA Astrophysics Data System (ADS)

    Salimath, Akshaykumar; Ghosh, Bahniman

    2014-08-01

    In this paper, we employ semiclassical Monte Carlo approach to study spin polarized transport in InP and strained InP nanowires on GaAs substrate. Due to higher spin relaxation lengths, InP is being researched as suitable III-V material for spintronics related applications. Spin relaxation in InP channel is as a result of D'yakonov-Perel (DP) relaxation and Elliott-Yafet (EY) relaxation. We have considered injection polarization along z-direction and the magnitude of ensemble averaged spin variation is studied along the x-direction i.e., along transport direction. The effect of strain on various scattering rates and spin relaxation length is studied. We then present the effect of variation of nanowire width on spin relaxation length for the case of both strained and unstrained InP nanowire. The wire cross-section is varied between 4 × 4 nm2 and 10 × 10 nm2.

  7. Grooved surfaces on InP

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Fatemi, Navid S.; Landis, Geoffrey A.; Jenkins, Phillip P.

    1991-01-01

    Formation of a textured or grooved front surface on a solar cell can increase the efficiency in several ways, including enhanced absorption and light trapping. In III-IV materials the (111) plane is chemically different form the (1'1'1') plane, and both etching and epitaxial deposition behave differently on these surfaces. The current state of profile etching in InP is summarized. Data are presented on novel geometries attainable as a function of etchant temperature and composition, substrate orientation and carrier concentration, and the oxide thickness between the substrate and the photoresist. Depending on dopant concentration, the same etchant can produce either anisotropic or isotropic grooves. V-grooved solar cells were manufactured on InP, and the improved optical absorption was demonstrated. Preferred parameters for various applications are listed and discussed.

  8. InP monolithically integrated coherent transmitter.

    PubMed

    Andriolli, N; Fresi, F; Bontempi, F; Malacarne, A; Meloni, G; Klamkin, J; Poti, L; Contestabile, G

    2015-04-20

    A novel InP monolithically integrated coherent transmitter has been designed, fabricated and tested. The photonic integrated circuit consists of a distributed Bragg reflector laser and a modified nested Mach-Zehnder modulator having tunable input power splitters. Back-to-back coherent transmission for PDM-QPSK signals is reported up to 10 Gbaud (40 Gb/s) using the integrated laser and up to 32Gbaud (128 Gb/s) using an external low phase noise laser. PMID:25969111

  9. Electrochemical characterization of InP structures

    NASA Technical Reports Server (NTRS)

    Faur, Maria; Faur, Mircea; Vargas-Aburto, Carlos; Wilt, David M.; Goradia, Manju

    1992-01-01

    Electrochemical (EC) techniques represent a simple and yet accurate method to characterize InP and related materials structures. With EC techniques, uncertainties in the measurements arising from factors such as surface effects, the composition and thickness of a front dead layer, the contacts, etc., can be significantly reduced when both a suitable electrolyte is used and the measuring conditions are carefully selected. In this work, the use of photoelectrochemical techniques with InP structures is reported. The work focuses on both the characterization and the optimization of structures grown by thermal diffusion and by epitaxial methods. Characterization of the structures is done by studying the variation in the density of surface states, number of defects, and net majority carrier concentration as a function of material removed. A step-by-step optimization process of n(sup +)p and p(sup+)n InP structures is also described. This involves the passivation and subsequent removal of damaged layers in order to extract the performance parameters of solar cells fabricated with these structures.

  10. Recent progress in InP solar cell research

    NASA Technical Reports Server (NTRS)

    Weinberg, Irving; Brinker, D. J.; Jain, R. K.; Swartz, C. K.

    1991-01-01

    Significant new developments in InP solar cell research are reviewed. Recent accomplishments include monolithic multibandgap two junction cells (three and two terminal) using InP as the top cell and lattice matched GaInAs and GaInAsP as the bottom, low bandgap component. Concentrator cells include the three terminal multibandgap cell and n + p cell using an InP substrate. The review also includes small scale production of ITO/InP cells and results for n + p InP and ITO/InP cells in space on board the LIPS 3 satellite.

  11. Three-Stage InP Submillimeter-Wave MMIC Amplifier

    NASA Technical Reports Server (NTRS)

    Pukala, David; Samoska, Lorene; Man, King; Gaier, Todd; Deal, William; Lai, Richard; Mei, Gerry; Makishi, Stella

    2008-01-01

    A submillimeter-wave monolithic integrated- circuit (S-MMIC) amplifier has been designed and fabricated using an indium phosphide (InP) 35-nm gate-length high electron mobility transistor (HEMT) device, developed at Northrop Grumman Corporation. The HEMT device employs two fingers each 15 micrometers wide. The HEMT wafers are grown by molecular beam epitaxy (MBE) and make use of a pseudomorphic In0.75Ga0.25As channel, a silicon delta-doping layer as the electron supply, an In0.52Al0.48As buffer layer, and an InP substrate. The three-stage design uses coplanar waveguide topology with a very narrow ground-to-ground spacing of 14 micrometers. Quarter-wave matching transmission lines, on-chip metal-insulator-metal shunt capacitors, series thin-film resistors, and matching stubs were used in the design. Series resistors in the shunt branch arm provide the basic circuit stabilization. The S-MMIC amplifier was measured for S-parameters and found to be centered at 320 GHz with 13-15-dB gain from 300-345 GHz. This chip was developed as part of the DARPA Submillimeter Wave Imaging Focal Plane Technology (SWIFT) program (see figure). Submillimeter-wave amplifiers could enable more sensitive receivers for earth science, planetary remote sensing, and astrophysics telescopes, particularly in radio astronomy, both from the ground and in space. A small atmospheric window at 340 GHz exists and could enable ground-based observations. However, the submillimeter-wave regime (above 300 GHz) is best used for space telescopes as Earth s atmosphere attenuates most of the signal through water and oxygen absorption. Future radio telescopes could make use of S-MMIC amplifiers for wideband, low noise, instantaneous frequency coverage, particularly in the case of heterodyne array receivers.

  12. Wideband 1.064 micrometer detector evaluation

    NASA Technical Reports Server (NTRS)

    Green, S. I.

    1975-01-01

    The performance of several candidate detectors for use as communications detectors in a 400 Mbps 1.064 micrometers laser communication system was evaluated. The results of communication system Bit Error Rate (BER) testing for the best detector of each type are summarized. Complete testing data of each type detector is presented. The 400 Mbps 1.064 micrometers communication system receiver test bed is described. The best communication system results for each detector type are included. Performance comparisons are made at 0.000001 BER, the specification level chosen for satellite laser communication links. The data is presented in two groups. The first indicates the best performance levels that can be expected on normal space laser communication system operation. The second cites the best performance levels which can be achieved by focusing the signal to diffraction limited spots on the photosensitive area.

  13. Unique Three-Dimensional InP Nanopore Arrays for Improved Photoelectrochemical Hydrogen Production.

    PubMed

    Li, Qiang; Zheng, Maojun; Ma, Liguo; Zhong, Miao; Zhu, Changqing; Zhang, Bin; Wang, Faze; Song, Jingnan; Ma, Li; Shen, Wenzhong

    2016-08-31

    Ordered three-dimensional (3D) nanostructure arrays hold promise for high-performance energy harvesting and storage devices. Here, we report the fabrication of InP nanopore arrays (NPs) in unique 3D architectures with excellent light trapping characteristic and large surface areas for use as highly active photoelectrodes in photoelectrochemical (PEC) hydrogen evolution devices. The ordered 3D NPs were scalably synthesized by a facile two-step etching process of (1) anodic etching of InP in neutral 3 M NaCl electrolytes to realize nanoporous structures and (2) wet chemical etching in HCl/H3PO4 (volume ratio of 1:3) solutions for removing the remaining top irregular layer. Importantly, we demonstrated that the use of neutral electrolyte of NaCl instead of other solutions, such as HCl, in anodic etching of InP can significantly passivate the surface states of 3D NPs. As a result, the maximum photoconversion efficiency obtained with ∼15.7 μm thick 3D NPs was 0.95%, which was 7.3 and 1.4 times higher than that of planar and 2D NPs. Electrochemical impedance spectroscopy and photoluminescence analyses further clarified that the improved PEC performance was attributed to the enhanced charge transfer across 3D NPs/electrolyte interfaces, the improved charge separation at 3D NPs/electrolyte junction, and the increased PEC active surface areas with our unique 3D NP arrays. PMID:27501479

  14. Micrometer Instruments, Aviation Quality Control 1: 9225.02.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    Second in a series of five, the course consists of the history and principles of the micrometer. The student must have mastered the skills offered in Introduction to Measurement and the Use of Scaled Instruments--9225.01. Techniques in reading and using the micrometer, checking, adjusting, and calibrating the micrometer are topics covered.…

  15. Facile synthesis of uniform large-sized InP nanocrystal quantum dots using tris(tert-butyldimethylsilyl)phosphine.

    PubMed

    Joung, Somyoung; Yoon, Sungwoo; Han, Chang-Soo; Kim, Youngjo; Jeong, Sohee

    2012-01-01

    Colloidal III-V semiconductor nanocrystal quantum dots [NQDs] have attracted interest because they have reduced toxicity compared with II-VI compounds. However, the study and application of III-V semiconductor nanocrystals are limited by difficulties in their synthesis. In particular, it is difficult to control nucleation because the molecular bonds in III-V semiconductors are highly covalent. A synthetic approach of InP NQDs was presented using newly synthesized organometallic phosphorus [P] precursors with different functional moieties while preserving the P-Si bond. Introducing bulky side chains in our study improved the stability while facilitating InP formation with strong confinement at a readily low temperature regime (210°C to 300°C). Further shell coating with ZnS resulted in highly luminescent core-shell materials. The design and synthesis of P precursors for high-quality InP NQDs were conducted for the first time, and we were able to control the nucleation by varying the reactivity of P precursors, therefore achieving uniform large-sized InP NQDs. This opens the way for the large-scale production of high-quality Cd-free nanocrystal quantum dots. PMID:22289352

  16. Facile synthesis of uniform large-sized InP nanocrystal quantum dots using tris( tert-butyldimethylsilyl)phosphine

    NASA Astrophysics Data System (ADS)

    Joung, Somyoung; Yoon, Sungwoo; Han, Chang-Soo; Kim, Youngjo; Jeong, Sohee

    2012-01-01

    Colloidal III-V semiconductor nanocrystal quantum dots [NQDs] have attracted interest because they have reduced toxicity compared with II-VI compounds. However, the study and application of III-V semiconductor nanocrystals are limited by difficulties in their synthesis. In particular, it is difficult to control nucleation because the molecular bonds in III-V semiconductors are highly covalent. A synthetic approach of InP NQDs was presented using newly synthesized organometallic phosphorus [P] precursors with different functional moieties while preserving the P-Si bond. Introducing bulky side chains in our study improved the stability while facilitating InP formation with strong confinement at a readily low temperature regime (210°C to 300°C). Further shell coating with ZnS resulted in highly luminescent core-shell materials. The design and synthesis of P precursors for high-quality InP NQDs were conducted for the first time, and we were able to control the nucleation by varying the reactivity of P precursors, therefore achieving uniform large-sized InP NQDs. This opens the way for the large-scale production of high-quality Cd-free nanocrystal quantum dots.

  17. Terahertz emission from InP

    SciTech Connect

    Hargreaves, S.; Lewis, R. A.

    2010-01-04

    We investigate the generation of THz radiation by the application of ultra-short near-infrared optical pulses to bulk unbiased InP. The THz radiation is detected in the direction of the specular reflection. While the overall emission characteristics are similar to those displayed by InAs under similar excitation conditions, in contrast to InAs, a single-cycle only variation in THz signal, of about +-20%, is observed as the sample is rotated through 360 deg. around the surface normal.

  18. Improvements in InP solar cells

    NASA Technical Reports Server (NTRS)

    Keavney, Christopher; Vernon, Stanley M.; Haven, Victor E.

    1988-01-01

    Indium phosphide solar cells with very thin n-type emitters have been made by both ion implantation and metal-organic chemical vapor deposition. Air mass zero efficiencies as high as 18.8 percent (NASA measurement) have been achieved. The best cells, which were those made by ion implantation, show an open-circuit voltage of 873 mV, short-circuit current of 35.7 mA/sq cm, and fill factor of 0.829. Improvements are anticipated in all three of these parameters. Internal quantum efficiency peaks at over 90 percent in the red end of the spectrum, but drops to 54 percent in the blue end. Other cells have achieved 74 percent in the blue end. A preliminary investigation of InP solar cells on foreign substrates has been carried out. Although problems have been encountered with doping of the InP by the substrate, cells of 7.1 percent efficiency on silicon and cells of 9.4 percent, efficiency on GaAs have been made.

  19. Nanocavities in He implanted InP

    NASA Astrophysics Data System (ADS)

    Chicoine, M.; Roorda, S.; Masut, R. A.; Desjardins, P.

    2003-11-01

    The formation of nanocavities in InP(001) by room-temperature He implantation and subsequent thermal annealing was studied using a combination of high-resolution x-ray diffraction (HRXRD) and cross-sectional transmission electron microscopy (XTEM) analyses. The nanocavities size and depth distributions were measured as a function of He ion dose φHe (1×1016 to 9×1016cm-2) and ion energy E (25 to 70 keV), as well as annealing temperature Ta (600 to 750 °C) and time ta (5 to 25 min). HRXRD scans from annealed samples indicate an expansion of the InP lattice, contrary to what is usually observed following heavy-ion implantation. The critical φHe and Ta values for the formation of nanocavities were found by XTEM analysis to be between 1 and 2×1016cm-2 and between 600 and 620 °C, respectively. Cavities of diameter 4-50 nm with {110}, {101}, and {001} facets were obtained. Increasing Ta and ta resulted in larger cavities and increasing φHe produced a larger number of cavities. Furthermore we find that nanocavities are metastable as their size first increases with annealing temperature and time but then decreases until they disappear for ta>25 min at Ta=640 °C or ta>10 min at Ta=750 °C. Results are compared with similar work carried out on He-implanted silicon and differences between the two materials are explained in terms of defect diffusivity and surface energy, higher diffusivity enhancing cavity collapse and lower surface energy enhancing cavity growth.

  20. Progress in InP solar cell research

    NASA Technical Reports Server (NTRS)

    Weinberg, Irving; Brinker, David J.

    1988-01-01

    Progress, in the past year, in InP solar cell research is reviewed. Small area cells with AMO, total area efficiencies of 18.8 percent were produced by OMCVD and Ion Implantation. Larger area cells (2 and 4 sq cm) were processed on a production basis. One thousand of the 2 sq cm cells will be used to supply power to a small piggyback lunar orbiter scheduled for launch in February 1990. Laboratory tests of ITO/InP cells, under 10 MeV proton irradiation, indicate radiation resistance comparable to InP n/p homojunction cells. Computer modeling studies indicate that, for identical geometries and dopant concentrations, InP solar cells are significantly more radiation resistant than GaAs under 1 MeV electron irradiation. Additional computer modeling calculations were used to produce rectangular and circular InP concentrator cell designs for both the low concentration SLATS and higher concentration Cassegrainian Concentrators.

  1. Preferentially Etched Epitaxial Liftoff of InP Material

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G. (Inventor); Wilt, David M. (Inventor); DeAngelo, Frank L. (Inventor)

    1997-01-01

    The present invention is directed toward a method of removing epitaxial substrates from host substrates. A sacrificial release layer of ternary material is placed on the substrate. A layer of InP is then placed on the ternary material. Afterward a layer of wax is applied to the InP layer to apply compressive force and an etchant material is used to remove the sacrificial release layer.

  2. InP Heterojunction Bipolar Transistor Amplifiers to 255 GHz

    NASA Technical Reports Server (NTRS)

    Radisic, Vesna; Sawdai, Donald; Scott, Dennis; Deal, William; Dang, Linh; Li, Danny; Cavus, Abdullah; To, Richard; Lai, Richard

    2009-01-01

    Two single-stage InP heterojunction bipolar transistor (HBT) amplifiers operate at 184 and 255 GHz, using Northrop Grumman Corporation s InP HBT MMIC (monolithic microwave integrated circuit) technology. At the time of this reporting, these are reported to be the highest HBT amplifiers ever created. The purpose of the amplifier design is to evaluate the technology capability for high-frequency designs and verify the model for future development work.

  3. InP MMIC Chip Set for Power Sources Covering 80-170 GHz

    NASA Technical Reports Server (NTRS)

    Ngo, Catherine

    2001-01-01

    We will present a Monolithic Millimeter-wave Integrated Circuit (MMIC) chip set which provides high output-power sources for driving diode frequency multipliers into the terahertz range. The chip set was fabricated at HRL Laboratories using a 0.1-micrometer gate-length InAlAs/InGaAs/InP high electron mobility transistor (HEMT) process, and features transistors with an f(sub max) above 600 GHz. The HRL InP HEMT process has already demonstrated amplifiers in the 60-200 GHz range. In this paper, these high frequency HEMTs form the basis for power sources up to 170 GHz. A number of state-of-the-art InP HEMT MMICs will be presented. These include voltage-controlled and fixed-tuned oscillators, power amplifiers, and an active doubler. We will first discuss an 80 GHz voltage-controlled oscillator with 5 GHz of tunability and at least 17 mW of output power, as well as a 120 GHz oscillator providing 7 mW of output power. In addition, we will present results of a power amplifier which covers the full WRIO waveguide band (75-110 GHz), and provides 40-50 mW of output power. Furthermore, we will present an active doubler at 164 GHz providing 8% bandwidth, 3 mW of output power, and an unprecedented 2 dB of conversion loss for an InP HEMT MMIC at this frequency. Finally, we will demonstrate a power amplifier to cover 140-170 GHz with 15-25 mW of output power and 8 dB gain. These components can form a power source in the 155-165 GHz range by cascading the 80 GHz oscillator, W-band power amplifier, 164 GHz active doubler and final 140-170 GHz power amplifier for a stable, compact local oscillator subsystem, which could be used for atmospheric science or astrophysics radiometers.

  4. Characterization of CVD micrometer-size diamond (abstract)

    NASA Astrophysics Data System (ADS)

    Ohsumi, K.; Hagiya, K.; Miyamoto, M.; Matsuda, J.; Ohmasa, M.

    1989-07-01

    formed from carbonaceous materials by impact shock or directly formed from vapor. Recent discovery of vapor-growth diamonds in carbonaceous chondrites has generated a renewed interest in the origin of ureilite diamonds. Two types of micrometer-size diamonds were prepared. One of them was grown under low pressure by chemical vapor deposition (CVD) from gaseous mixtures of H2 and CH4, and another was synthesized by shock effect (kindly offered by Nippon Oil & Fats Co., Ltd.) The micro-Laue method was applied to them in order to get information about their microstructures. Two characteristics are recognized in profiles of reflections themselves and in whole patterns of the Laue photographs. The reflections of CVD diamonds are elongated but symmetric in their profiles and are distributed regularly as they are indexed by the diamond lattice, while those of shock effect are also elongated and asymmetric, and are distributed at random as they cannot be indexed. The characteristics observed by the method may be useful to ascribe the origin to CVD or shock effect.

  5. High-efficiency heteroepitaxial InP solar cells

    NASA Technical Reports Server (NTRS)

    Wanlass, M. W.; Coutts, T. J.; Ward, J. S.; Emery, K. A.

    1991-01-01

    High-efficiency, thin-film InP solar cells grown heteroepitaxially on GaAs and Si single-crystal bulk substrates are being developed as a means of eliminating the problems associated with using single-crystal InP substrates. A novel device structure employing a compositionally graded Ga(x)In(1-x)As layer between the bulk substrate and the InP cell layers is used to reduce the dislocation density and improve the minority carrier properties in the InP. The structures are grown in a continuous sequence of steps using computer-controlled atmospheric pressure metalorganic vapor phase epitaxy (APMOVPE). Dislocation densities as low as 3 x 10(exp 7) sq cm and minority carrier lifetimes as high as 3.3 ns are achieved in the InP layers with this method using both GaAs or Si substrates. Structures prepared in this fashion are also completely free of microcracks. These results represent a substantial improvement in InP layer quality when compared to heteroepitaxial InP prepared using conventional techniques such as thermally cycled growth and post-growth annealing. The present work is is concerned with the fabrication and characterization of high-efficiency, thin-film InP solar cells. Both one-sun and concentrator cells were prepared for device structures grown on GaAs substrates. One-cell cells have efficiencies as high as 13.7 percent at 25 C. However, results for the concentrator cells are emphasized. The concentrator cell performance is characterized as a function of the air mass zero (AM0) solar concentration ratio and operating temperature. From these data, the temperature coefficients of the cell performance parameters are derived as a function of the concentration ratio. Under concentration, the cells exhibit a dramatic increase in efficiency and an improved temperature coefficient of efficiency. At 25 C, a peak conversion efficiency of 18.9 percent is reported. At 80 C, the peak AM0 efficiency is 15.7 percent at 75.6 suns. These are the highest efficiencies yet

  6. Atoms.inp Archive: Crystallographic Data from GSECARS

    DOE Data Explorer

    Newville, Matthew

    The Atoms.inp Archive is a collection of crystallographic data for use in XAFS analysis. The crystallographic data is stored as atoms.inp files, which contain all the information necessary to describe the crystal, and can be used by the program ATOMS to generate feff.inp files. These files can then be used by the FEFF program [See http://leonardo.phys.washington.edu/feff/] to calculate a theoretical XAFS spectrum for the crystal. This archive exists because it can take a considerable amount of time to locate a suitable reference for a model structure to use for making theoretical XAFS standards. Even then, references sometimes give non-standard or incomplete crystallographic notation that ATOMS has difficulty interpreting. All of this means that getting a reliable atoms.inp file can take quite a bit of effort. It is hoped that this collection of well-documented and well-tested atoms.inp files will eliminate much of the work in creating theoretical XAFS standards from FEFF. [Taken from http://cars9.uchicago.edu/~newville/adb/]. The collection currently has more than 200 crystal structures, 2748 data files, and it continues to expand. The collection is related to the UWXAFS Project [http://depts.washington.edu/uwxafs/] and to the work of the Consortium for Advanced Radiation Sources (CARS). After searching the Archive, a user may also choose to run the web version of ATOMS software.

  7. Long-Term INP Measurements within the BACCHUS project

    NASA Astrophysics Data System (ADS)

    Schrod, Jann; Bingemer, Heinz; Curtius, Joachim

    2016-04-01

    The European research project BACCHUS (Impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) studies the interactions between aerosols, clouds and the climate system, and tries to reconstruct pre-industrial aerosol and cloud conditions from data collected in pristine environments. The number concentration of Ice Nucleating Particles (INP) is an important, yet scarcely known parameter. As a partner of Work package 1 of BACCHUS we began in September 2014 to operate a globally spanned network of four INP sampling stations, which is the first of its kind. The stations are located at the ATTO observatory in the Brazilian Rainforest, the Caribbean Sea (Martinique), the Zeppelin Observatory at Svalbard in the Arctic, and in central Europe (Germany). Samples are collected routinely every day or every few days by electrostatic precipitation of aerosol particles onto Si substrates. The samples are stored in petri-slides, and shipped to our laboratory in Frankfurt, Germany. The number of ice nucleating particles on the substrate is analyzed in the isothermal static diffusion chamber FRIDGE by growing ice on the INP and photographing and counting the crystals. The measurements in the temperature range from -20°C to -30°C and relative humidities of 100-135% (with respect to ice) address primarily the deposition/condensation nucleation modes. Here we present INP and supporting aerosol data from this novel INP network for the first time.

  8. Electron guns and collectors developed at INP for electron cooling devices

    SciTech Connect

    Sharapa, A.N.; Shemyakin, A.V.

    1997-09-01

    Institute of Nuclear Physics (INP) has a rich experience in designing electron guns and collectors for electron cooling devices. This paper is a review of the experience of several INP research groups in this field. Some results obtained at INP for systems without a guiding magnetic field are also discussed.

  9. Bridging the Gap between the Nanometer-Scale Bottom-Up and Micrometer-Scale Top-Down Approaches for Site-Defined InP/InAs Nanowires.

    PubMed

    Zhang, Guoqiang; Rainville, Christophe; Salmon, Adrian; Takiguchi, Masato; Tateno, Kouta; Gotoh, Hideki

    2015-11-24

    This work presents a method that bridges the gap between the nanometer-scale bottom-up and micrometer-scale top-down approaches for site-defined nanostructures, which has long been a significant challenge for applications that require low-cost and high-throughput manufacturing processes. We realized the bridging by controlling the seed indium nanoparticle position through a self-assembly process. Site-defined InP nanowires were then grown from the indium-nanoparticle array in the vapor-liquid-solid mode through a "seed and grow" process. The nanometer-scale indium particles do not always occupy the same locations within the micrometer-scale open window of an InP exposed substrate due to the scale difference. We developed a technique for aligning the nanometer-scale indium particles on the same side of the micrometer-scale window by structuring the surface of a misoriented InP (111)B substrate. Finally, we demonstrated that the developed method can be used to grow a uniform InP/InAs axial-heterostructure nanowire array. The ability to form a heterostructure nanowire array with this method makes it possible to tune the emission wavelength over a wide range by employing the quantum confinement effect and thus expand the application of this technology to optoelectronic devices. Successfully pairing a controllable bottom-up growth technique with a top-down substrate preparation technique greatly improves the potential for the mass-production and widespread adoption of this technology. PMID:26348087

  10. High Efficiency InP Solar Cells Through Nanostructuring

    NASA Astrophysics Data System (ADS)

    Goldman, Daniel; Murray, Joseph; Munday, Jeremy

    We describe high efficiency InP solar cells which utilize a periodic array of optically designed TiO2 nanocylinders. Optical and electronic simulations were performed to determine the spectrally resolved reflectivity and I-V characteristics of potential devices under AM1.5G illumination. The reflectivity of InP solar cells with these nanocylinders is found to have an average value of 2% over the visible and near-IR spectral range, which outperforms traditional antireflection coatings. Coupling between Mie scattering resonances and thin film interference effects is found to accurately describe the optical enhancement provided by the nanocylinders. These nanostructured solar cells have power conversion efficiencies greater than 23%, which is comparable to the highest quoted efficiencies for InP solar cells.

  11. Nanophotonic resonators for InP solar cells.

    PubMed

    Goldman, Daniel A; Murray, Joseph; Munday, Jeremy N

    2016-05-16

    We describe high efficiency thin-film InP solar cells that utilize a periodic array of TiO2 nanocylinders. These nanophotonic resonators are found to reduce the solar-weighted average reflectivity of an InP solar cell to ~1.3%, outperforming the best double-layer antireflection coatings. The coupling between Mie scattering resonances and thin-film interference effects accurately describes the optical enhancement provided by the nanocylinders. The spectrally resolved reflectivity and J-V characteristics of the device under AM1.5G illumination are determined via coupled optical and electrical simulations, resulting in a predicted power conversion efficiency > 23%. We conclude that the nanostructured coating reduces reflection without negatively affecting the electronic properties of the InP solar cell by separating the nanostructured optical components from the active layer of the device. PMID:27409965

  12. InP concentrator solar cells for space applications

    NASA Technical Reports Server (NTRS)

    Ward, J. S.; Wanlass, M. W.; Coutts, T. J.; Emery, K. A.

    1991-01-01

    The design, fabrication, and characterization of high-performance, n(+)/p InP shallow-homojunction (SHJ) concentrator solar cells is described. The InP device structures were grown by atmospheric-pressure metalorganic vapor phase epitaxy (APMOVPE). A preliminary assessment of the effects of grid collection distance and emitter sheet resistance on cell performance is presented. At concentration ratios of over 100, cells with AM0 efficiencies in excess of 21 percent at 25 C and 19 percent at 80 C are reported. These results indicate that high-efficiency InP concentrator cells can be fabricated using existing technologies. The performance of these cells as a function of temperature is discussed, and areas for future improvement are outlined.

  13. Lateral spreading of Au contacts on InP

    NASA Technical Reports Server (NTRS)

    Fatemi, Navid S.; Weizer, Victor G.

    1990-01-01

    The contact spreading phenomenon observed when small area Au contacts on InP are annealed at temperatures above about 400 C was investigated. It was found that the rapid lateral expansion of the contact metallization which consumes large quantities of InP during growth is closely related to the third stage in the series of solid state reactions that occur between InP and Au, i.e., to the Au3In-to-Au9In4 transition. Detailed descriptions are presented of both the spreading process and the Au3In-to-Au9In4 transition along with arguments that the two processes are manifestations of the same basic phenomenon.

  14. Radiation effects in heteroepitaxial InP solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Curtis, H. B.; Swartz, C. K.; Brinker, D. J.; Vargas-Aburto, C.

    1993-01-01

    Heteroepitaxial InP solar cells, with GaAs substrates, were irradiated by 0.5 and 3 MeV protons and their performance, temperature dependency, and carrier removal rates determined as a function of fluence. The radiation resistance of the present cells was significantly greater than that of non-heteroepitaxial InP cells at both proton energies. A clear difference in the temperature dependency of V(sub oc), was observed between heteroepitaxial and homoepitaxial InP cells. The analytically predicted dependence of dV(sub oc)/dT on Voc was confirmed by the fluence dependence of these quantities. Carrier removal was observed to increase with decreasing proton energy. The results obtained for performance and temperature dependency were attributed to the high dislocation densities present in the heteroepitaxial cells while the energy dependence of carrier removal was attributed to the energy dependence of proton range.

  15. Palladium nanoparticles on InP for hydrogen detection

    PubMed Central

    2011-01-01

    Layers of palladium (Pd) nanoparticles on indium phosphide (InP) were prepared by electrophoretic deposition from the colloid solution of Pd nanoparticles. Layers prepared by an opposite polarity of deposition showed different physical and morphological properties. Particles in solution are separated and, after deposition onto the InP surface, they form small aggregates. The size of the aggregates is dependent on the time of deposition. If the aggregates are small, the layer has no lateral conductance. Forward and reverse I-V characteristics showed a high rectification ratio with a high Schottky barrier height. The response of the structure on the presence of hydrogen was monitored. PMID:21711487

  16. Comparative modeling of InP solar cell structures

    NASA Technical Reports Server (NTRS)

    Jain, R. K.; Weinberg, I.; Flood, D. J.

    1991-01-01

    The comparative modeling of p(+)n and n(+)p indium phosphide solar cell structures is studied using a numerical program PC-1D. The optimal design study has predicted that the p(+)n structure offers improved cell efficiencies as compared to n(+)p structure, due to higher open-circuit voltage. The various cell material and process parameters to achieve the maximum cell efficiencies are reported. The effect of some of the cell parameters on InP cell I-V characteristics was studied. The available radiation resistance data on n(+)p and p(+)p InP solar cells are also critically discussed.

  17. Workshop on Heteroepitaxial InP Solar Cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Walters, R. W.

    1993-01-01

    In a generic sense, the justification for any sort of InP solar cell research applies, i.e. to take advantage of the inherently high radiation resistance and efficiency of InP solar cells. To be more specific, the approach is justified by its potential for significant cost reduction and the availability of greatly increased cell area afforded by substrates such as Si and Ge. The use of substrates, such as the latter two, would result in increased ruggedness, ease of handling, and improved manufacturability. The use of more rugged substrates would lead to a greatly increased capability for cell thinning leading to the desirable feature of reduced array weight.

  18. Autophagy-regulating TP53INP2 mediates muscle wasting and is repressed in diabetes

    PubMed Central

    Sala, David; Ivanova, Saška; Plana, Natàlia; Ribas, Vicent; Duran, Jordi; Bach, Daniel; Turkseven, Saadet; Laville, Martine; Vidal, Hubert; Karczewska-Kupczewska, Monika; Kowalska, Irina; Straczkowski, Marek; Testar, Xavier; Palacín, Manuel; Sandri, Marco; Serrano, Antonio L.; Zorzano, Antonio

    2014-01-01

    A precise balance between protein degradation and synthesis is essential to preserve skeletal muscle mass. Here, we found that TP53INP2, a homolog of the Drosophila melanogaster DOR protein that regulates autophagy in cellular models, has a direct impact on skeletal muscle mass in vivo. Using different transgenic mouse models, we demonstrated that muscle-specific overexpression of Tp53inp2 reduced muscle mass, while deletion of Tp53inp2 resulted in muscle hypertrophy. TP53INP2 activated basal autophagy in skeletal muscle and sustained p62-independent autophagic degradation of ubiquitinated proteins. Animals with muscle-specific overexpression of Tp53inp2 exhibited enhanced muscle wasting in streptozotocin-induced diabetes that was dependent on autophagy; however, TP53INP2 ablation mitigated experimental diabetes-associated muscle loss. The overexpression or absence of TP53INP2 did not affect muscle wasting in response to denervation, a condition in which autophagy is blocked, further indicating that TP53INP2 alters muscle mass by activating autophagy. Moreover, TP53INP2 expression was markedly repressed in muscle from patients with type 2 diabetes and in murine models of diabetes. Our results indicate that TP53INP2 negatively regulates skeletal muscle mass through activation of autophagy. Furthermore, we propose that TP53INP2 repression is part of an adaptive mechanism aimed at preserving muscle mass under conditions in which insulin action is deficient. PMID:24713655

  19. [Study on pollution for the photoelectronic material InP].

    PubMed

    Xu, Jian-cheng; Ding, Xiao-ping; Chen, Ding-qin

    2002-08-01

    The mass spectrum analysis of crystal face (100) and (111) and the photoluminescence analysis of crystal face (100) in the photoelectronic material InP were given. The Hall coefficient, charge carrier concentration and Hall mobility were determined. Experimental results indicate that the pollution of silicon is predominant. PMID:12938361

  20. InP solar cell with window layer

    NASA Technical Reports Server (NTRS)

    Jain, Raj K. (Inventor); Landis, Geoffrey A. (Inventor)

    1994-01-01

    The invention features a thin light transmissive layer of the ternary semiconductor indium aluminum arsenide (InAlAs) as a front surface passivation or 'window' layer for p-on-n InP solar cells. The window layers of the invention effectively reduce front surface recombination of the object semiconductors thereby increasing the efficiency of the cells.

  1. Experiences with digital processing of images at INPE

    NASA Technical Reports Server (NTRS)

    Mascarenhas, N. D. A. (Principal Investigator)

    1984-01-01

    Four different research experiments with digital image processing at INPE will be described: (1) edge detection by hypothesis testing; (2) image interpolation by finite impulse response filters; (3) spatial feature extraction methods in multispectral classification; and (4) translational image registration by sequential tests of hypotheses.

  2. Growth and properties of InP single crystals

    NASA Astrophysics Data System (ADS)

    Dun-fu, Fang; Xiang-xi, Wang; Yong-quan, Xu; Li-tong, Tan

    1984-04-01

    InP single crystals with various dopants including S, Sn, Zn and Fe have been grown successfully by the Czochralski method under high pressure with liquid encapsulation. It is found that by carefully adjusting the thermal symmetry of the heating field and by further improving the quality of the polycrystals and by dehydrating B 2O 3, twin-free InP crystals can be obtained even with a shoulder angle of up to 54°, and defects caused by thermal decomposition appear on the surface of the crystals during pulling. Furthermore, a comparison of the crystal perfection and uniformity between S-doped and Sn-doped InP crystals shows that the quality of the former is better than that of the latter. Dislocation-free Zn-doped p-InP single crystals without precipitates have also been easily obtained when the carrier concentration is greater than 2×10 18 cm -3 and the diameter less than 30 mm. By controlling the iron content, semi-insulating thermally stable single crystals of InP doped with ⩽0.03 wt% of Fe without precipitates and with a homogeneous resistivity can be produced.

  3. c-Myc inhibits TP53INP1 expression via promoter methylation in esophageal carcinoma

    SciTech Connect

    Weng, Wenhao; Yang, Qinyuan; Huang, Miaolong; Qiao, Yongxia; Xie, Yuan; Yu, Yongchun; Jing, An; Li, Zhi

    2011-02-11

    Research highlights: {yields} TP53INP1 expression is down-regulated in esophageal carcinoma and is associated with CGI-131 methylation. {yields} Inhibition of CGI-131 methylation upregulates TP53INP1 expression in ESCC cell lines. {yields} Ectopic expression of TP53INP1 inhibits growth of ESCC cells by inducing apoptosis and inhibiting cell cycle progression. {yields} c-Myc binds to the promoter of TP53INP1 in vivo and vitro and recruits DNMT3A to TP53INP1 promoter for CGI-131 methylation. -- Abstract: Tumor protein p53-induced nuclear protein 1 (TP53INP1) is a well known stress-induced protein that plays a role in both cell cycle arrest and p53-mediated apoptosis. Loss of TP53INP1 expression has been reported in human melanoma, breast carcinoma, and gastric cancer. However, TP53INP1 expression and its regulatory mechanism in esophageal squamous cell carcinoma (ESCC) remain unclear. Our findings are in agreement with previous reports in that the expression of TP53INP1 was downregulated in 28% (10/36 cases) of ESCC lesions, and this was accompanied by significant promoter methylation. Overexpression of TP53INP1 induced G1 cell cycle arrest and increased apoptosis in ESCC cell lines (EC-1, EC-109, EC-9706). Furthermore, our study showed that the oncoprotein c-Myc bound to the core promoter of TP53INP1 and recruited DNA methyltransferase 3A to methylate the local promoter region, leading to the inhibition of TP53INP1 expression. Our findings revealed that TP53INP1 is a tumor suppressor in ESCC and that c-Myc-mediated DNA methylation-associated silencing of TP53INP1 contributed to the pathogenesis of human ESCC.

  4. High sensitivity infrared 10.6 micrometer heterodyne receiver development

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The results are presented for a study on the design of an infrared 10.6-micrometer quantum-noise-limited optical receiver subsystem. Performance measurements of the HgCdTe photomixer preamplifier combination were carried out for photomixer temperatures up to 152 K and a photomixer frequency response of up to 420 MHz was obtained. Results of temperature and bias cycling of HgCdTe photomixers are reported. Design considerations for an operational 10.6 micrometer heterodyne receiver are presented. These consist of design data on required laser LO illumination, heat load levels for photomixer cooler, photomixer uniformity and the effects of photomixer impedance match on receiver sensitivity. Analysis and measurements of 10.6 micrometer heterodyne detection in an extrinsic photoconductive (p-type) HgCdTe photomixer are also presented.

  5. A single crystalline InP nanowire photodetector

    NASA Astrophysics Data System (ADS)

    Yan, Xin; Li, Bang; Wu, Yao; Zhang, Xia; Ren, Xiaomin

    2016-08-01

    Single crystalline nanowires are critical for achieving high-responsivity, high-speed, and low-noise nanoscale photodetectors. Here, we report a metal-semiconductor-metal photodetector based on a single crystalline InP nanowire. The nanowires are grown by a self-catalyzed method and exhibit stacking-fault-free zinc blende crystal structure. The nanowire exhibits a typical n-type semiconductor property and shows a low room temperature dark current of several hundred pA at moderate biases. A photoresponsivity of 6.8 A/W is obtained at a laser power density of 0.2 mW/cm2. This work demonstrates that single crystalline InP nanowires are good candidates for future optoelectronic device applications.

  6. Azimuthally polarized cathodoluminescence from InP nanowires

    SciTech Connect

    Brenny, B. J. M.; Osorio, C. I.; Polman, A.; Dam, D. van; Gómez Rivas, J.

    2015-11-16

    We determine the angle and polarization dependent emission from 1.75 µm and 2.50 µm long InP nanowires by using cathodoluminescence polarimetry. We excite the vertical wires using a 5 keV electron beam, and find that the 880 nm bandgap emission shows azimuthally polarized rings, with the number of rings depending on the wire height. The data agree well with a model in which spontaneous emission from the wire emitted into the far field interferes with emission reflected off the substrate. From the model, the depth range from which the emission is generated is found to be up to 400 nm below the top surface of the wires, well beyond the extent of the primary electron cloud. This enables a probe of the carrier diffusion length in the InP nanowires.

  7. Effects of mask imperfections on InP etching profiles

    SciTech Connect

    Huo, D.T.C.; Yan, M.F.; Wynn, J.D.; Wilt, D.P. )

    1990-01-01

    The authors have demonstrated that the quality of etch masks has a significant effect on the InP etching profiles. In particular, the authors have shown that mask imperfections can cause defective etching profiles, such as vertical sidewalls and extra mask undercutting in InP. The authors also discovered that the geometry of these defective profiles is determined by the orientation of the substrate relative to the direction of the mask imperfections. Along a {l angle}110{r angle} line mask defect, the downward etching process changes the {l angle}110{r angle} v-grooves to vertical sidewalls without extra undercutting. For v-grooves aligned along the {l angle}110{r angle} direction, defects on the mask give a significant extra undercutting without changing the etching profile.

  8. Pressure dependence of local vibrational modes in InP

    SciTech Connect

    McCluskey, M. D.; Zhuravlev, K. K.; Davidson, B. R.; Newman, R. C.

    2001-03-15

    Using infrared spectroscopy and a diamond-anvil cell, we have observed carbon and carbon-hydrogen local vibrational modes (LVM's) in InP at hydrostatic pressures as high as 5.5 GPa at liquid-helium temperatures. For pressures beyond 4.5 GPa, the carbon-hydrogen mode was not observed, perhaps as a result of a transformation of the complex into a different configuration. The LVM arising from carbon substitutional impurities varies linearly with pressure, whereas the shift of the carbon-hydrogen mode has a positive curvature. Both of these observations are in qualitative agreement with the pressure dependence of LVM's in GaAs. While the substitutional carbon impurities show very similar pressure shifts in the two materials, the linear pressure coefficient of the carbon-hydrogen stretch mode in InP is nearly three times that in GaAs. For all the measured modes, the Gru''neisen parameters increase with pressure.

  9. Defining capabilities of Si and InP photonics.

    SciTech Connect

    Vawter, Gregory Allen

    2010-05-01

    Monolithic photonic integrated circuits (PICs) have a long history reaching back more than 40 years. During that time, and particularly in the past 15 years, the technology has matured and the application space grown to span sophisticated tunable diode lasers, 40 Gb/s electrical-to-optical signal converters with complex data formats, wavelength multiplexors and routers, as well as chemical/biological sensors. Most of this activity has centered in recent years on optical circuits built on either Silicon or InP substrates. This talk will review the three classes of PIC and highlight the unique strengths, and weaknesses, of PICs based on Silicon and InP substrates. Examples will be provided from recent R&D activity.

  10. Surface accumulation of hydrogen during capless annealing of InP

    SciTech Connect

    Haussler, W.

    1989-06-19

    InP samples, which had received a capless anneal in a phosphine/hydrogenatmosphere, were examined for hydrogen contamination by secondary-ion massspectrometry. It is found that hydrogen accumulates at the InP surface duringannealing. Annealing of Be-implanted InP leads to similar profile shapes for theBe and H atoms. Passivation of the Be acceptors, if effective at all, appears tobe of only minor significance.

  11. High-Energy 2-Micrometers Doppler Lidar for Wind Measurements

    NASA Technical Reports Server (NTRS)

    Koch, Grady J.; Beyon, Jeffrey Y.; Barnes, Bruce W.; Petros, Mulugeta; Yu, Jirong; Amzajerdian, Farzin; Kavaya, Michael J.; Singh, Upendra N.

    2006-01-01

    High-energy 2-micrometer wavelength lasers have been incorporated in a prototype coherent Doppler lidar to test component technologies and explore applications for remote sensing of the atmosphere. Design of the lidar is presented including aspects in the laser transmitter, receiver, photodetector, and signal processing. Calibration tests and sample atmospheric data are presented on wind and aerosol profiling.

  12. 2 Micrometers InAsSb Quantum-dot Lasers

    NASA Technical Reports Server (NTRS)

    Qiu, Yueming; Uhl, David; Keo, Sam

    2004-01-01

    InAsSb quantum-dot lasers near 2 micrometers were demonstrated in cw operation at room temperature with a threshold current density of 733 A,/cm(sup 2), output power of 3 mW/facet and a differential quantum efficiency of 13%.

  13. Quantum confinement of excitons in wurtzite InP nanowires

    SciTech Connect

    Pemasiri, K.; Jackson, H. E.; Smith, L. M.; Wong, B. M.; Paiman, S.; Gao, Q.; Tan, H. H.; Jagadish, C.

    2015-05-21

    Exciton resonances are observed in photocurrent spectra of 80 nm wurtzite InP nanowire devices at low temperatures, which correspond to transitions between the A, B, and C valence bands and the lower conduction band. Photocurrent spectra for 30 nm WZ nanowires exhibit shifts of the exciton resonances to higher energy, which are consistent with finite element calculations of wavefunctions of the confined electrons and holes for the various bands.

  14. Transfer of InP epilayers by wafer bonding

    NASA Astrophysics Data System (ADS)

    Hjort, Klas

    2004-08-01

    Wafer bonding increases the freedom of design in the integration of dissimilar materials. For example, it is interesting to combine III-V compounds that have direct band gap and high mobility with silicon (Si) that is extensively used in microelectronic applications. The interest to integrate III-V-based materials with Si arises primarily from two types of applications: smart pixels for optical intra- and inter-chip interconnects in the so-called optoelectronic integrated circuits, and optoelectronic devices using some material advantages of combining III-V with Si. Also, in the III-V industry larger substrates are crucial for higher efficiency in high-volume production, and especially so for monolithic microwave integrated circuits (MMIC). For indium phosphide (InP) the development of large-area substrates has not been able to keep up with market demands. One way to circumvent this problem is to use silicon substrates that are large-area, low-cost, and mechanically strong with high thermal conductivity. In addition, silicon is transparent at the emission wavelengths most often used in InP-based optoelectronics. Unfortunately, the large lattice-mismatch, 8.1%, between silicon and InP, has limited the success of heteroepitaxial growth. Hence, one alternative to be reviewed is InP-to-Si wafer bonding. When a direct semiconductor interface is not needed there are several other means of wafer bonding, e.g. adhesive, eutectic, and solid-state. These processes can be used for direct integration of small islets of epitaxially thin InP microelectronics onto other substrates, e.g. by transferring of InP-based epilayers to a Si-based microwave circuit by pick-and-place, BCB resist adhesive bonding and sacrificing of the InP substrate.

  15. Texturing of InP surfaces for device applications

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Fatemi, Navid S.; Landis, Geoffrey A.

    1992-01-01

    A unique process for texturing InP (100) wafers by anisotropic etching was developed. The process produces irregular V-grooves on the surface, which reduce the surface reflectivity. The process does not require photolithography or masking. The etching characteristics depend on doping, with etching tending to proceed more rapidly on the more heavily doped samples. Reduced reflectivity surfaces formed using this process can be applied to solar cells, photodetectors, and other optoelectronic devices.

  16. Diameter Dependence of Planar Defects in InP Nanowires.

    PubMed

    Wang, Fengyun; Wang, Chao; Wang, Yiqian; Zhang, Minghuan; Han, Zhenlian; Yip, SenPo; Shen, Lifan; Han, Ning; Pun, Edwin Y B; Ho, Johnny C

    2016-01-01

    In this work, extensive characterization and complementary theoretical analysis have been carried out on Au-catalyzed InP nanowires in order to understand the planar defect formation as a function of nanowire diameter. From the detailed transmission electron microscopic measurements, the density of stacking faults and twin defects are found to monotonically decrease as the nanowire diameter is decreased to 10 nm, and the chemical analysis clearly indicates the drastic impact of In catalytic supersaturation in Au nanoparticles on the minimized planar defect formation in miniaturized nanowires. Specifically, during the chemical vapor deposition of InP nanowires, a significant amount of planar defects is created when the catalyst seed sizes are increased with the lower degree of In supersaturation as dictated by the Gibbs-Thomson effect, and an insufficient In diffusion (or Au-rich enhancement) would lead to a reduced and non-uniform In precipitation at the NW growing interface. The results presented here provide an insight into the fabrication of "bottom-up" InP NWs with minimized defect concentration which are suitable for various device applications. PMID:27616584

  17. Inp1p is a peroxisomal membrane protein required for peroxisome inheritance in Saccharomyces cerevisiae

    PubMed Central

    Fagarasanu, Monica; Fagarasanu, Andrei; Tam, Yuen Yi C.; Aitchison, John D.; Rachubinski, Richard A.

    2005-01-01

    Cells have evolved molecular mechanisms for the efficient transmission of organelles during cell division. Little is known about how peroxisomes are inherited. Inp1p is a peripheral membrane protein of peroxisomes of Saccharomyces cerevisiae that affects both the morphology of peroxisomes and their partitioning during cell division. In vivo 4-dimensional video microscopy showed an inability of mother cells to retain a subset of peroxisomes in dividing cells lacking the INP1 gene, whereas cells overexpressing INP1 exhibited immobilized peroxisomes that failed to be partitioned to the bud. Overproduced Inp1p localized to both peroxisomes and the cell cortex, supporting an interaction of Inp1p with specific structures lining the cell periphery. The levels of Inp1p vary with the cell cycle. Inp1p binds Pex25p, Pex30p, and Vps1p, which have been implicated in controlling peroxisome division. Our findings are consistent with Inp1p acting as a factor that retains peroxisomes in cells and controls peroxisome division. Inp1p is the first peroxisomal protein directly implicated in peroxisome inheritance. PMID:15928207

  18. Comparative endothelial cell response on topographically patterned titanium and silicon substrates with micrometer to sub-micrometer feature sizes.

    PubMed

    Vandrangi, Prashanthi; Gott, Shannon C; Kozaka, Ryan; Rodgers, Victor G J; Rao, Masaru P

    2014-01-01

    In this work, we evaluate the in vitro response of endothelial cells (EC) to variation in precisely-defined, micrometer to sub-micrometer scale topography on two different substrate materials, titanium (Ti) and silicon (Si). Both substrates possess identically-patterned surfaces composed of microfabricated, groove-based gratings with groove widths ranging from 0.5 to 50 µm, grating pitch twice the groove width, and groove depth of 1.3 µm. These specific materials are chosen due to their relevance for implantable microdevice applications, while grating-based patterns are chosen for the potential they afford for inducing elongated and aligned cellular morphologies reminiscent of the native endothelium. Using EA926 cells, a human EC variant, we show significant improvement in cellular adhesion, proliferation, morphology, and function with decreasing feature size on patterned Ti substrates. Moreover, we show similar trending on patterned Si substrates, albeit to a lesser extent than on comparably patterned Ti substrates. Collectively, these results suggest promise for sub-micrometer topographic patterning in general, and sub-micrometer patterning of Ti specifically, as a means for enhancing endothelialization and neovascularisation for novel implantable microdevice applications. PMID:25357245

  19. Comparative Endothelial Cell Response on Topographically Patterned Titanium and Silicon Substrates with Micrometer to Sub-Micrometer Feature Sizes

    PubMed Central

    Kozaka, Ryan; Rodgers, Victor G. J.; Rao, Masaru P.

    2014-01-01

    In this work, we evaluate the in vitro response of endothelial cells (EC) to variation in precisely-defined, micrometer to sub-micrometer scale topography on two different substrate materials, titanium (Ti) and silicon (Si). Both substrates possess identically-patterned surfaces composed of microfabricated, groove-based gratings with groove widths ranging from 0.5 to 50 µm, grating pitch twice the groove width, and groove depth of 1.3 µm. These specific materials are chosen due to their relevance for implantable microdevice applications, while grating-based patterns are chosen for the potential they afford for inducing elongated and aligned cellular morphologies reminiscent of the native endothelium. Using EA926 cells, a human EC variant, we show significant improvement in cellular adhesion, proliferation, morphology, and function with decreasing feature size on patterned Ti substrates. Moreover, we show similar trending on patterned Si substrates, albeit to a lesser extent than on comparably patterned Ti substrates. Collectively, these results suggest promise for sub-micrometer topographic patterning in general, and sub-micrometer patterning of Ti specifically, as a means for enhancing endothelialization and neovascularisation for novel implantable microdevice applications. PMID:25357245

  20. TP53inp1 Gene Is Implicated in Early Radiation Response in Human Fibroblast Cells.

    PubMed

    Sándor, Nikolett; Schilling-Tóth, Boglárka; Kis, Enikő; Fodor, Lili; Mucsányi, Fruzsina; Sáfrány, Géza; Hegyesi, Hargita

    2015-01-01

    Tumor protein 53-induced nuclear protein-1 (TP53inp1) is expressed by activation via p53 and p73. The purpose of our study was to investigate the role of TP53inp1 in response of fibroblasts to ionizing radiation. γ-Ray radiation dose-dependently induces the expression of TP53inp1 in human immortalized fibroblast (F11hT) cells. Stable silencing of TP53inp1 was done via lentiviral transfection of shRNA in F11hT cells. After irradiation the clonogenic survival of TP53inp1 knockdown (F11hT-shTP) cells was compared to cells transfected with non-targeting (NT) shRNA. Radiation-induced senescence was measured by SA-β-Gal staining and autophagy was detected by Acridine Orange dye and microtubule-associated protein-1 light chain 3 (LC3B) immunostaining. The expression of TP53inp1, GDF-15, and CDKN1A and alterations in radiation induced mitochondrial DNA deletions were evaluated by qPCR. TP53inp1 was required for radiation (IR) induced maximal elevation of CDKN1A and GDF-15 expressions. Mitochondrial DNA deletions were increased and autophagy was deregulated following irradiation in the absence of TP53inp1. Finally, we showed that silencing of TP53inp1 enhances the radiation sensitivity of fibroblast cells. These data suggest functional roles for TP53inp1 in radiation-induced autophagy and survival. Taken together, we suppose that silencing of TP53inp1 leads radiation induced autophagy impairment and induces accumulation of damaged mitochondria in primary human fibroblasts. PMID:26512655

  1. A portable spectrometer for use from 5 to 15 micrometers

    NASA Technical Reports Server (NTRS)

    Hoover, G.; Kahle, A. B.

    1986-01-01

    A field portable spectrometer suitable for collecting data relevant to remote sensing applications in the 8 to 12 micrometer atmospheric window has been built at the Jet Propulsion Laboratory. The instrument employs a single cooled HgCdTe detector and a continuously variable filter wheel analyzer. The spectral range covered is 5 to 14.5 micrometers and the resolution is approximately 1.5 percent of the wavelength. A description of the hardware is followed by a discussion of the analysis of the spectral data leading to finished emissivity and radiance spectra. A section is devoted to the evaluation of the instrument performance with respect to spectral resolution, radiometric precision, and accuracy. Several examples of spectra acquired in the field are included.

  2. X-Ray tomography with micrometer spatial resolution

    NASA Astrophysics Data System (ADS)

    Raven, Carsten; Snigirev, Anatoly A.; Koch, Andreas; Snigireva, Irina; Kohn, Victor

    1997-10-01

    3D computed tomographic images with micrometer resolution were made in phase-contrast mode with high energy x-rays at a third generation synchrotron source. The phase-contrast technique enables one to obtain information not only about the amplitude of the wave field behind the object and thus about the absorption, but also about the refractive index distribution inside the sample. Increasing the x-ray energy from the soft x-ray region up to 10-60 keV simplifies the experimental setup and opens the possibility to study organic samples at room-temperature and under normal pressure conditions. The projection data is recorded with a fast, high-resolution x-ray camera consisting of a 5 micrometers thin YAG scintillator crystal, a visible light microscope optics and a slow scan 1k X 1k CCD camera. The spatial resolution of phase-contrast microtomography is currently limited by the resolution of the x-ray detector to about 1-2 micrometers . First applications in biology and geophysics are shown.

  3. InP HEMT Integrated Circuits for Submillimeter Wave Radiometers in Earth Remote Sensing

    NASA Technical Reports Server (NTRS)

    Deal, William R.; Chattopadhyay, Goutam

    2012-01-01

    The operating frequency of InP integrated circuits has pushed well into the Submillimeter Wave frequency band, with amplification reported as high as 670 GHz. This paper provides an overview of current performance and potential application of InP HEMT to Submillimeter Wave radiometers for earth remote sensing.

  4. Crystal facet effect on structural stability and electronic properties of wurtzite InP nanowires

    NASA Astrophysics Data System (ADS)

    Yang, Xiaodong; Shu, Haibo; Jin, Mengting; Liang, Pei; Cao, Dan; Li, Can; Chen, Xiaoshuang

    2014-06-01

    The crystal-facet effect on the structural stability and electronic properties of wurtzite InP nanowires (NWs) with different side-facets are investigated by using first-principles calculation within density-function theory. The surface-energy calculation suggests that side-facet structures of InP NWs are unreconstructed due to the fact that the low-index {11¯00} and {112¯0} facets with paired In-P dimers satisfy the electron counting rule. The calculated formation energies indicate that the structural stability of InP NWs strongly depends on their side-facets. Among considered InP NWs with different side-facets, the {11¯00} faceted NWs present the highest stability due to the relative low surface atom ratio, which is in good agreement with experimental observations where wurtzite InP NWs prefer to be surrounded by {11¯00} facets. The size dependence of NW band gap indicates that the band gap (Eg) of uniform-sized InP NWs with different side-facets follows the trend, Eg -{112¯0} > Eg -{11¯00}-{112¯0} > Eg -{11¯00}, when NW diameter is larger than 3 nm and a reverse trend is found in the smaller sized NWs (d < 3 nm). Our result opens the possibility to engineer the band gap of wurtzite InP NWs by controlling their side-facets.

  5. Gate tunable monolayer MoS{sub 2}/InP heterostructure solar cells

    SciTech Connect

    Lin, Shisheng Wang, Peng; Li, Xiaoqiang; Wu, Zhiqian; Xu, Zhijuan; Zhang, Shengjiao; Xu, Wenli

    2015-10-12

    We demonstrate monolayer molybdenum disulfide (MoS{sub 2})/indium phosphide (InP) van der Waals heterostructure with remarkable photovoltaic response. Furthermore, benefiting from the atomically thin and semiconductor nature of MoS{sub 2}, we have designed the gate tunable MoS{sub 2}/InP heterostructure. Applied with a top gate voltage, the Fermi level of MoS{sub 2} is effectively tuned, and the barrier height at the MoS{sub 2}/InP heterojunction correspondingly changes. The power conversion efficiency of MoS{sub 2}/InP solar cells has reached a value of 7.1% under AM 1.5G illumination with a gate voltage of +6 V. The tunable MoS{sub 2}/InP heterostructure may be promising for highly efficient solar cells.

  6. Electrochemical characterization of p(+)n and n(+)p diffused InP structures

    NASA Technical Reports Server (NTRS)

    Wilt, David M.; Faur, Maria; Faur, Mircea; Goradia, M.; Vargas-Aburto, Carlos

    1993-01-01

    The relatively well documented and widely used electrolytes for characterization and processing of Si and GaAs-related materials and structures by electrochemical methods are of little or no use with InP because the electrolytes presently used either dissolve the surface preferentially at the defect areas or form residual oxides and introduce a large density of surface states. Using an electrolyte which was newly developed for anodic dissolution of InP, and was named the 'FAP' electrolyte, accurate characterization of InP related structures including nature and density of surface states, defect density, and net majority carrier concentration, all as functions of depth was performed. A step-by-step optimization of n(+)p and p(+)n InP structures made by thermal diffusion was done using the electrochemical techniques, and resulted in high performance homojunction InP structures.

  7. Flashlamp Pumped, Room Temperature, Nd:YAG Laser Operating at 0.946 Micrometers

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; Murray, Keith E.; Walsh, Brian M.

    1998-01-01

    Room temperature operation of flashlamp pumped Nd:YAG at 0.946 micrometers was achieved with a laser rod having undoped ends. Performance was characterized and compared with 1.064 micrometer operation and other quasi four level lasers.

  8. Sub-micrometer precision of optical imaging to locate the free surface of a micrometer fluid shape.

    PubMed

    Montanero, J M; Vega, E J; Ferrera, C

    2009-11-01

    In this note, we explore the precision of the optical imaging method for measuring the free surface position of a micrometer fluid shape. For this purpose, images of a liquid film deposited on a rod were acquired and processed. The resulting contour was compared with the corresponding solution to the Young-Laplace equation. The average deviation was about 30nm, 25 times smaller than the pixel size, reflecting the validity of optical imaging for most applications in microfluidics. PMID:19683246

  9. Electron irradiation effects in epitaxial InP solar cells

    NASA Technical Reports Server (NTRS)

    Pearsall, N. M.; Robson, N.; Sambell, A. J.; Anspaugh, B.; Cross, T. A.

    1991-01-01

    Performance data for InP-based solar cells after irradiation with 1-MeV electrons up to a fluence of 1 x 1016 e/cm2 are presented. Three InP cell structures are considered. Two of these have epitaxially grown active regions, these being a homojunction design and in ITO/InP structure. These are compared with ITO/InP cells without the epitaxial base region. The cell parameter variations, the influence of illumination during irradiation, and the effect on cell spectral response and capacitance measurements are discussed. Substantial performance recovery after thermal annealing at 90 C is reported.

  10. Lasers in InP generic photonic integration technology platforms

    NASA Astrophysics Data System (ADS)

    Latkowski, Sylwester; Lenstra, Daan

    2015-04-01

    A review is given of a number of lasers in a form of photonic integrated circuits realized on InP substrate using a generic integration approach. The potential of these photonic circuits lies in their compactness, low power consumption, and significant reduction of fabrication cost by realization in generic foundry runs. Generic integration platforms offer the possibility of realizing functionally advanced photonic circuits using combinations of just a few standardized and parameterized building blocks. This vibrant field opens new doors to innovative product development for SMEs as well as curiosity-driven research.

  11. Photon upconversion in degenerately sulfur doped InP nanowires.

    PubMed

    Mergenthaler, K; Lehmann, S; Wallentin, J; Zhang, W; Borgström, M T; Yartsev, A; Pistol, M-E

    2015-12-28

    Radiative recombination in degenerately n-doped InP nanowires is studied for excitation above and below the Fermi energy of the electron gas, using photoluminescence. Laser-induced electron heating is observed, which allows absorption below the Fermi energy. We observe photon upconversion where photo-excited holes recombine with high |k| electrons. This can be attributed to hole scattering to high |k|-values, and the temperature dependence of this process is measured. We show that hole relaxation via phonon scattering can be observed in continuous wave excitation luminescence measurements. PMID:26585229

  12. Photon upconversion in degenerately sulfur doped InP nanowires

    NASA Astrophysics Data System (ADS)

    Mergenthaler, K.; Lehmann, S.; Wallentin, J.; Zhang, W.; Borgström, M. T.; Yartsev, A.; Pistol, M.-E.

    2015-12-01

    Radiative recombination in degenerately n-doped InP nanowires is studied for excitation above and below the Fermi energy of the electron gas, using photoluminescence. Laser-induced electron heating is observed, which allows absorption below the Fermi energy. We observe photon upconversion where photo-excited holes recombine with high |k| electrons. This can be attributed to hole scattering to high |k|-values, and the temperature dependence of this process is measured. We show that hole relaxation via phonon scattering can be observed in continuous wave excitation luminescence measurements.Radiative recombination in degenerately n-doped InP nanowires is studied for excitation above and below the Fermi energy of the electron gas, using photoluminescence. Laser-induced electron heating is observed, which allows absorption below the Fermi energy. We observe photon upconversion where photo-excited holes recombine with high |k| electrons. This can be attributed to hole scattering to high |k|-values, and the temperature dependence of this process is measured. We show that hole relaxation via phonon scattering can be observed in continuous wave excitation luminescence measurements. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR05472A

  13. Heterogenously-integrated InP on Si microdisk lasers

    NASA Astrophysics Data System (ADS)

    Morthier, G.; Spuesens, T.; Mechet, P.; Olivier, N.; Fedeli, J.-M.; Regreny, P.; Van Thourhout, D.; Roelkens, G.

    2015-03-01

    We review recent theoretical and experimental work on InP membrane microdisk lasers heterogeneously integrated on SOI and coupled to a Si bus waveguide. After a general introduction on the fabrication and the operation principles, we will describe various improvements in the fabrication technology. This includes improvements in the yield of the bonding of the InP die on the SOI die and in the controllability of the bonding layer thickness, as well as an optimization of the alignment of the microdisk with respect to the silicon waveguide and some proposals for better heat sinking and loss reduction. Improvement in the alignment and the bonding has led to interesting results on the uniformity in device characteristics. In a second part, unidirectional behaviour and reflection sensitivity will be briefly discussed. Theoretical, numerical and experimental results will be shown about the unidirectional behavior and it will be explained how unidirectional microdisk lasers can be a lot less sensitive to external reflections than other lasers. We will also show how such lasers can be used as optical signal regenerators that can work with low optical input powers and that have small power consumption. We will end with a description of demonstrations of optical interconnects based on heterogeneously integrated microdisk lasers and heterogeneously integrated photodetectors. Optical interconnects on chip have been demonstrated at 10 Gb/s. An epitaxial layer stack that contains both the laser and the detector structure has been used for this purpose.

  14. Interband polarized absorption in InP polytypic superlattices

    SciTech Connect

    Faria Junior, P. E.; Sipahi, G. M.; Campos, T.

    2014-11-21

    Recent advances in growth techniques have allowed the fabrication of semiconductor nanostructures with mixed wurtzite/zinc-blende crystal phases. Although the optical characterization of these polytypic structures is well reported in the literature, a deeper theoretical understanding of how crystal phase mixing and quantum confinement change the output linear light polarization is still needed. In this paper, we theoretically investigate the mixing effects of wurtzite and zinc-blende phases on the interband absorption and in the degree of light polarization of an InP polytypic superlattice. We use a single 8 × 8 k⋅p Hamiltonian that describes both crystal phases. Quantum confinement is investigated by changing the size of the polytypic unit cell. We also include the optical confinement effect due to the dielectric mismatch between the superlattice and the vaccum and we show it to be necessary to match experimental results. Our calculations for large wurtzite concentrations and small quantum confinement explain the optical trends of recent photoluminescence excitation measurements. Furthermore, we find a high sensitivity to zinc-blende concentrations in the degree of linear polarization. This sensitivity can be reduced by increasing quantum confinement. In conclusion, our theoretical analysis provides an explanation for optical trends in InP polytypic superlattices, and shows that the interplay of crystal phase mixing and quantum confinement is an area worth exploring for light polarization engineering.

  15. Micrometer-size vesicle formation triggered by UV light.

    PubMed

    Shima, Tatsuya; Muraoka, Takahiro; Hamada, Tsutomu; Morita, Masamune; Takagi, Masahiro; Fukuoka, Hajime; Inoue, Yuichi; Sagawa, Takashi; Ishijima, Akihiko; Omata, Yuki; Yamashita, Takashi; Kinbara, Kazushi

    2014-07-01

    Vesicle formation is a fundamental kinetic process related to the vesicle budding and endocytosis in a cell. In the vesicle formation by artificial means, transformation of lamellar lipid aggregates into spherical architectures is a key process and known to be prompted by e.g. heat, infrared irradiation, and alternating electric field induction. Here we report UV-light-driven formation of vesicles from particles consisting of crumpled phospholipid multilayer membranes involving a photoactive amphiphilic compound composed of 1,4-bis(4-phenylethynyl)benzene (BPEB) units. The particles can readily be prepared from a mixture of these components, which is casted on the glass surface followed by addition of water under ultrasonic radiation. Interestingly, upon irradiation with UV light, micrometer-size vesicles were generated from the particles. Neither infrared light irradiation nor heating prompted the vesicle formation. Taking advantage of the benefits of light, we successfully demonstrated micrometer-scale spatiotemporal control of single vesicle formation. It is also revealed that the BPEB units in the amphiphile are essential for this phenomenon. PMID:24898450

  16. Possible identifications of the 3.4 micrometer feature

    NASA Technical Reports Server (NTRS)

    Danks, Anthony C.; Lambert, D. L.

    1988-01-01

    A feature at 3.4 micrometer was first detected in Comet Halley by the IKS spectrometer on board the Vega 1 probe; and subsequently from the ground. The feature has since been reported in Comet Wilson. The presence of the feature is of considerable interest for a number of reasons. First, it may represent the detection of a new parent molecule, and when combined with data from Giotto and Vega yield new information on cometary chemistry and the early solar system composition. Secondly, it may represent a link to the interstellar medium, the feature corresponds in wavelength and shape with an interstellar feature seen in absorption in a luminous star, towards the Galactic center known as GC-IRS7. The feature in turn is thought to be related with a growing family of unidentified infrared emission features seen in stellar objects, planetary nebulae, reflection nebulae, HII regions and extra galactic sources. These features occur at wavelengths 3.3, 3.4, 3.5, 6.2, 7.7, 8.6, and 11.25 micrometers. Further identification theory is given.

  17. Heteroepitaxial InP solar cells on Si and GaAs substrates

    NASA Technical Reports Server (NTRS)

    Weinberg, Irving; Swartz, Clifford K.; Brinker, David J.

    1990-01-01

    The characteristics of InP cells processed from thin layers of InP heteroepitaxially grown on GaAs, on silicon with an intervening GaAs layer, and on GaAs with intervening Ga(x)In(1-x)As layers are described, and the factors affecting cell efficiency are discussed. Under 10 MeV proton irradiations, the radiation resistances of the heteroepitaxial cells were superior to that of homoepitaxial InP cells. The superior radiation resistance is attributed to the high dislocation densities present in the heteroepitaxial cells.

  18. Surface etching for light trapping in encapsulated InP solar cells

    NASA Technical Reports Server (NTRS)

    Jenkins, Phillip; Landis, Geoffrey A.

    1991-01-01

    Reducing the reflection from the surface of InP is important for increasing the efficiency of solar cells and photodetectors. In this paper a new technique for reducing reflectance of glass-encapsulated InP is reported. Low-angle grooves are produced on the surface by a maskless anisotropic etch. Light reflected from the low angle grooves is trapped by total internal reflection at the glass/air interface and directed back to the InP surface. A significant decrease in surface reflection is measured.

  19. Microstructural and Compositional Relations of Granitoid Clasts in Lunar Breccias at the Micrometer to Sub-Micrometer Scale

    NASA Technical Reports Server (NTRS)

    Christoffersen, R.; Simon, J. I.; Mills, R. D.; Ross, D. K.; Tappa, M.

    2015-01-01

    Lunar granitoid lithologies have long been of interest for the information they provide on processes leading to silicic melt compositions on the Moon. The extraction of such melts over time affects the distribution and budget of incompatible materials (i.e., radiogenic heat producing elements and volatiles) of the lunar interior. We have recently shown that in addition to their high concentrations of incompatible lithophile elements, some granitoid clasts in lunar breccias have significant indigenous water contents in their alkali feldspars. This raises the importance of lunar granitoid materials in the expanding search for mineralogic/petrologic hosts of indigenous lunar water-related species. We are undertaking a detailed survey of the petrologic/mineralogical relations of granitoid clasts in lunar breccias to achieve a better understanding of the potential of these diverse assemblages as hosts for volatiles, and as candidates for additional isotope chronology studies. Our preliminary results reported here based on high-resolution field-emission SEM, EPMA and TEM studies uncover immense complexity in these materials at the micrometer to sub-micrometer scale that heretofore have not been fully documented.

  20. Particle detectors based on semiconducting InP epitaxial layers

    NASA Astrophysics Data System (ADS)

    Yatskiv, R.; Grym, J.; Zdansky, K.

    2011-01-01

    A study of electrical properties and detection performance of two types of Indium Phosphide detector structures was performed: (i) with p-n-junction and (ii) with Schottky contact prepared on high purity p-type InP. The p-n junction detectors were based on a high purity InP:Pr layers of both n- and p- type conductivity with carrier concentration on the order of 1014 cm-3 grown on Sn doped n-type substrate. Schottky barrier detectors were prepared by vacuum evaporation of Pd on high purity p-type epitaxial layer grown on Mn doped p-type substrate. The detection performance of particle detectors was measured by pulse-height spectra with alpha particles emitted from 241Am source at room temperature.

  1. Time-resolved photoluminescence of undoped InP

    SciTech Connect

    Keyes, B.M.; Dunlavy, D.J.; Ahrenkiel, R.K. ); Shaw, G.; Summers, G.P. ); Tzafaras, N.; Lentz, C. )

    1994-04-15

    Energy and time-resolved photoluminescence data have been obtained for nominally undoped ([ital n] 4.5[times]10[sup 15] cm[sup [minus]3]) bulk InP grown by the vertical-gradient freeze method. The data were taken as a function of temperature, from 80 to 290 K, and analyzed using a solution to the continuity equation. The resulting lifetime values range from 300 ns to 3.2 [mu]s, and surface recombination velocities were fund to be on the order of 10[sup 3] cm/s. The temperature dependence can be explained by assuming a radiatively limited recombination with a resulting [ital B] coefficient [ge]5.9[times]10[sup [minus]11] cm[sup 3]/s at 300 K.

  2. Anomalous photoluminescence in InP1-xBix.

    PubMed

    Wu, Xiaoyan; Chen, Xiren; Pan, Wenwu; Wang, Peng; Zhang, Liyao; Li, Yaoyao; Wang, Hailong; Wang, Kai; Shao, Jun; Wang, Shumin

    2016-01-01

    Low temperature photoluminescence (PL) from InP1-xBix thin films with Bi concentrations in the 0-2.49% range reveals anomalous spectral features with strong and very broad (linewidth of 700 nm) PL signals compared to other bismide alloys. Multiple transitions are observed and their energy levels are found much smaller than the band-gap measured from absorption measurements. These transitions are related to deep levels confirmed by deep level transient spectroscopy, which effectively trap free holes and enhance radiative recombination. The broad luminescence feature is beneficial for making super-luminescence diodes, which can theoretically enhance spatial resolution beyond 1 μm in optical coherent tomography (OCT). PMID:27291823

  3. Electrical detection of spin hyperpolarization in InP

    SciTech Connect

    Caspers, Christian; Ansermet, Jean-Philippe

    2014-09-29

    The electrical detection of surface spin polarization in Indium Phosphide (InP) is demonstrated. Using a planar four-terminal architecture on top of semi-insulating Fe:InP (001) wafers, optical orientation is separated from electrical detection. Spin filter tunnel contacts consisting of InP/oxide/Co reveal significant asymmetries in the differential resistance upon helicity change of the optical pumping. The iron-rich tunnel oxide provides the main spin selection mechanism. A reproducible helicity-dependent asymmetry as high as 18% could be observed at T = 55 K and an external induction field μ{sub 0}H = 1 T. At room temperature and zero external field, a helicity-dependent asymmetry of 6% suggests the stand-alone applicability of the device either as an electronic spin sensor or as an optical helicity sensor.

  4. InAs nanowire formation on InP(001)

    SciTech Connect

    Parry, H. J.; Ashwin, M. J.; Jones, T. S.

    2006-12-01

    The heteroepitaxial growth of InAs on InP(001) by solid source molecular beam epitaxy has been studied for a range of different growth temperatures and annealing procedures. Atomic force microscopy images show that nanowires are formed for deposition in the temperature range of 400-480 deg. C, and also following high temperature annealing (480 deg. C) after deposition at 400 deg. C. The wires show preferential orientation along <110> and often exhibit pronounced serpentine behavior due to the presence of kinks, an effect that is reduced at increasing growth temperature. The results suggest that the serpentine behavior is related to the degree of initial surface order. Kinks in the wires appear to act as nucleation centers for In adatoms migrating along the wires during annealing, leading to the coexistence of large three-dimensional islands.

  5. A 83 GHz InP DHBT static frequency divider

    NASA Astrophysics Data System (ADS)

    Youtao, Zhang; Xiaopeng, Li; Min, Zhang; Wei, Cheng; Xinyu, Chen

    2014-04-01

    A static frequency divider is presented using 0.7 μm InP DHBTs with 280 GHz ft/fmax. The divider is based on ECL master-slave D-flip-flop topology with 30 HBTs and 20 resistors with a chip size 0.62 × 0.65 mm2. The circuits use peaking inductance as a part of the loads to maximize the highest clock rate. Momentum simulation is used to accurately characterize the effect of the clock feedback lines at the W band. Test results show that the divider can operate from 1 GHz up to 83 GHz. Its phase noise is 139 dBc/Hz with 100 kHz offset. The power dissipation of divider core is 350 mW.

  6. Optical and structural properties of 100 MeV Fe9+ ion irradiated InP

    NASA Astrophysics Data System (ADS)

    Dubey, R. L.; Dubey, S. K.; Bodhane, S. P.; Kanjilal, D.

    2016-05-01

    Single crystal InP samples were irradiated with 100 MeV Fe9+ ions for ion fluences 1x1012 and 1x1013 cm-2. Optical properties of irradiated InP was investigated by Spectroscopic Ellipsometry and UV-VIS-NIR spectroscopy. The optical parameters like, refractive index, extinction coefficient, absorption coefficient is found to be fluence dependent near the surface as well as near the projected range. Small change in the optical parameters near the surface region as investigated by Spectroscopic Ellipsometry indicatesthat the surfaces of irradiated InP are similar to non-irradiated InP. This is also supported by RBS/C measurements. The UV-VIS-NIR study revealed the decrease in the band gap and increase in the defect concentration in the irradiated sample as a result of nuclear energy loss.

  7. High efficiency InP solar cells from low toxicity tertiarybutylphosphine and trimethylindium by OMVPE

    SciTech Connect

    Hoffman, R.W. Jr.; Fatemi, N.S.; Wilt, D.M.; Brinker, D.J.; Jenkins, P.P.; Scheiman, D.A.

    1994-12-31

    Large scale manufacture of phosphide based compound semiconductor devices by organo-metallic vapor phase epitaxy (OMVPE) typically requires the use of highly toxic phosphine. Advancements in phosphine substitutes have identified tertiarybutylphosphine (TBP) as an excellent precursor for OMVPE of InP. High quality undoped and doped InP films were grown using TBP and trimethylindium. Impurity doped InP films were achieved utilizing diethylzinc and silane for p-type and n-type respectively. 16% efficient solar cells under air mass zero, one sun intensity were demonstrated with V{sub oc} of 871 mV and fill factor of 82.6%. It was shown that TBP could replace phosphine, without adversely affecting device quality, in OMVPE deposition of InP thus significantly reducing toxic gas exposure risk.

  8. High efficiency InP solar cells from low toxicity tertiarybutylphosphine

    NASA Astrophysics Data System (ADS)

    Hoffman, Richard W., Jr.; Fatemi, Navid S.; Wilt, David M.; Jenkins, Phillip P.; Brinker, David J.; Scheiman, David A.

    1994-05-01

    Large scale manufacture of phosphide based semiconductor devices by organo-metallic vapor phase epitaxy (OMVPE) typically requires the use of highly toxic phosphine. Advancements in phosphine substitutes have identified tertiarybutylphosphine (TBP) as an excellent precursor for OMVPE of InP. High quality undoped and doped InP films were grown using TBP and trimethylindium. Impurity doped InP films were achieved utilizing diethylzinc and silane for p and n type respectively. 16 percent efficient solar cells under air mass zero, one sun intensity were demonstrated with Voc of 871 mV and fill factor of 82.6 percent. It was shown that TBP could replace phosphine, without adversely affecting device quality, in OMVPE deposition of InP thus significantly reducing toxic gas exposure risk.

  9. INPE LANDSAT-D thematic mapper computer compatible tape format specification

    NASA Technical Reports Server (NTRS)

    Parada, N. D. J. (Principal Investigator); Desouza, R. C. M.

    1982-01-01

    The format of the computer compatible tapes (CCT) which contain Thematic Mapper (TM) imagery data acquired from the LANDSAT D and D Prime satellites by the INSTITUTO DE PERSQUISAS ESPACIALS (CNPq-INPE/BRAZIL) is defined.

  10. Control of persistent photoconductivity in nanostructured InP through morphology design

    NASA Astrophysics Data System (ADS)

    Monaico, Ed; Postolache, V.; Borodin, E.; Ursaki, V. V.; Lupan, O.; Adelung, R.; Nielsch, K.; Tiginyanu, I. M.

    2015-03-01

    In this paper, we show that long-duration-photoconductivity decay (LDPCD) and persistent photoconductivity (PPC) in porous InP structures fabricated by anodic etching of bulk substrates can be controlled through the modification of the sample morphology. Particularly, the PPC inherent at low temperatures to porous InP layers with the thickness of skeleton walls comparable with pore diameters is quenched in structures consisting of ultrathin walls produced at high anodization voltages. The relaxation of photoconductivity in bulk InP substrates, porous layers, and utrathin membranes is investigated as a function of temperature and excitation power density. The obtained results suggest that PPC in porous InP layers is due to porosity induced potential barriers which hinder the recombination of photoexcited carriers, while the photoconductivity relaxation processes in ultrathin membranes are governed by surface states.

  11. High Efficiency InP Solar Cells from Low Toxicity Tertiarybutylphosphine

    NASA Technical Reports Server (NTRS)

    Hoffman, Richard W., Jr.; Fatemi, Navid S.; Wilt, David M.; Jenkins, Phillip P.; Brinker, David J.; Scheiman, David A.

    1994-01-01

    Large scale manufacture of phosphide based semiconductor devices by organo-metallic vapor phase epitaxy (OMVPE) typically requires the use of highly toxic phosphine. Advancements in phosphine substitutes have identified tertiarybutylphosphine (TBP) as an excellent precursor for OMVPE of InP. High quality undoped and doped InP films were grown using TBP and trimethylindium. Impurity doped InP films were achieved utilizing diethylzinc and silane for p and n type respectively. 16 percent efficient solar cells under air mass zero, one sun intensity were demonstrated with Voc of 871 mV and fill factor of 82.6 percent. It was shown that TBP could replace phosphine, without adversely affecting device quality, in OMVPE deposition of InP thus significantly reducing toxic gas exposure risk.

  12. Diffusion of micrometer-sized soft particles in confinement

    NASA Astrophysics Data System (ADS)

    Jordan, Benjamin; Aptowicz, Kevin

    We investigate the diffusion of micrometer sized poly(N-isopropylacrylamide) (PNIPAM) gel particles in confinement. The influence of confinement on the transport of small particles is becoming increasingly important for microfluidics and bio-fluidics. Analytical solutions to this problem are limited to very unique geometries or gross approximations. Computational methods have provided more insight into the problem as well as experimental investigations. However, most research has focused on the hard-sphere problem. In this work, we will explore the diffusion of soft particles in confinement. The dynamics of the particles confined between two parallel walls is captured with video-microscopy. In addition, we use a recently developed technique to measurement confinement of particles in-situ with a precision of 1%. This poster will present some preliminary results of how confinement affects the diffusion of these soft particles. We acknowledge support from Grant DMR-1206231.

  13. Micrometer-scale porosity as a biosignature in carbonate crusts

    NASA Astrophysics Data System (ADS)

    Bosak, Tanja; Souza-Egipsy, Virginia; Corsetti, Frank A.; Newman, Dianne K.

    2004-09-01

    We formed calcite crusts in the presence and absence of the heterotrophic bacterium Desulfovibrio desulfuricans strain G20 to investigate microbial morphological signatures in fast-accreting carbonate precipitates. Submicrometer- to micrometer-sized pores (micropores) were present and ubiquitous in the G20 crusts but absent in abiotically precipitated crusts. Bacterial micropores resemble inclusions under transmitted light, but have distinct size, biological shapes and patterns (swirling or dendritic) and are distributed differently from common fluid inclusions. We observed similar porosity in both modern and ancient carbonate crusts of putative biotic origin. Our experiments support the microbial origin of micropores and help define specific criteria whereby to recognize these features as biosignatures in the rock record.

  14. Enhancing optical absorption in InP and GaAs utilizing profile etching

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Fatemi, Navid S.; Landis, Geoffrey A.

    1991-01-01

    The current state of profile etching in GaAs and InP is summarized, including data on novel geometries attainable as a function of etchant temperature, composition, and rate; substrate orientation; carrier concentration; and oxide thickness between substrate and photoresist. V-grooved solar cells were manufactured with both GaAs and InP, and the improved optical absorption was demonstrated. Preferred parameters for various applications are listed and discussed.

  15. Enhancing optical absorption in InP and GaAs utilizing profile etching

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Fatemi, Navid S.; Landis, Geoffrey A.

    1991-01-01

    The current state of profile etching in GaAs and InP is summarized, including data on novel geometries attainable as a function of etchant temperature, composition, and rate; substrate orientation; carrier concentration; and oxide thickness between substrate and photoresist. V-grooved solar cells have been manufactured with both GaAs and InP, and the improved optical absorption demonstrated. Preferred parameters for various applications are listed and discussed.

  16. Improvement of InP MISFET characteristics using infra-red lamp annealing

    NASA Astrophysics Data System (ADS)

    Hirota, Y.; Okamura, M.; Hisaki, T.; Mikami, O.

    1985-08-01

    An infrared lamp-annealing technique was employed for postannealing Si ion-implanted InP substrates. The effective electron mobility (mu-eff) of SiO2-InP metal-insulator-semiconductor field-effect transistors fabricated using infrared lamp annealing is remarkably temperature-dependent. The maximum mu-eff is about 11000 sq cm/V-s at 75 K and 1500-2500 sq cm/V-s at room temperature.

  17. Operational training for the mission operations at the Brazilian National Institute for Space Research (INPE)

    NASA Technical Reports Server (NTRS)

    Rozenfeld, Pawel

    1993-01-01

    This paper describes the selection and training process of satellite controllers and data network operators performed at INPE's Satellite Tracking and Control Center in order to prepare them for the mission operations of the INPE's first (SCD1) satellite. An overview of the ground control system and SCD1 architecture and mission is given. Different training phases are described, taking into account that the applicants had no previous knowledge of space operations requiring, therefore, a training which started from the basics.

  18. Wafer-scale self-organized InP nanopillars with controlled orientation for photovoltaic devices.

    PubMed

    Sanatinia, Reza; Berrier, Audrey; Dhaka, Veer; Perros, Alexander P; Huhtio, Teppo; Lipsanen, Harri; Anand, Srinivasan

    2015-10-16

    A unique wafer-scale self-organization process for generation of InP nanopillars is demonstrated, which is based on maskless ion-beam etching (IBE) of InP developed to obtain the nanopillars, where the height, shape, and orientation of the nanopillars can be varied by controlling the processing parameters. The fabricated InP nanopillars exhibit broadband suppression of the reflectance, 'black InP,' a property useful for solar cells. The realization of a conformal p-n junction for carrier collection, in the fabricated solar cells, is achieved by a metalorganic vapor phase epitaxy (MOVPE) overgrowth step on the fabricated pillars. The conformal overgrowth retains the broadband anti-reflection property of the InP nanopillars, indicating the feasibility of this technology for solar cells. Surface passivation of the formed InP nanopillars using sulfur-oleylamine solution resulted in improved solar-cell characteristics. An open-circuit voltage of 0.71 V and an increase of 0.13 V compared to the unpassivated device were achieved. PMID:26403979

  19. Wurtzite InP nanowire arrays grown by selective area MOCVD

    SciTech Connect

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

    2010-06-22

    InP nanowires are a unique material phase because this normally zincblende material forms in the wurtzite crystal structure below a critical diameter owing to the contribution of sidewalls to the total formation energy. This may allow control of the carrier transport and optical properties of InP nanowires for applications such as nano scale transistors, lasers and detectors. In this work, we describe the fabrication of InP nanowire arrays by selective area growth using MOCVD in the diameter range where the wurtzite structure is formed. The spatial growth rate in selective area growth is modeled by a diffusion model for the precursors. The proposed model achieves an average error of 9%. Electron microscopy shows that the grown InP nanowires are in the wurtzite crystal phase with many stacking faults. The threshold diameter of the crystal phase transition of InP nanowires is larger than the thermodynamic estimation. In order to explain this tendency, we propose a surface kinetics model based on a 2×2 reconstruction. This model can explain the increased tendency for wurtzite nanowire formation on InP (111)A substrates and the preferred growth direction of binary III-V compound semiconductor nanowires.

  20. Tunable absorption resonances in the ultraviolet for InP nanowire arrays.

    PubMed

    Aghaeipour, Mahtab; Anttu, Nicklas; Nylund, Gustav; Samuelson, Lars; Lehmann, Sebastian; Pistol, Mats-Erik

    2014-11-17

    The ability to tune the photon absorptance spectrum is an attracting way of tailoring the response of devices like photodetectors and solar cells. Here, we measure the reflectance spectra of InP substrates patterned with arrays of vertically standing InP nanowires. Using the reflectance spectra, we calculate and analyze the corresponding absorptance spectra of the nanowires. We show that we can tune absorption resonances for the nanowire arrays into the ultraviolet by decreasing the diameter of the nanowires. When we compare our measurements with electromagnetic modeling, we generally find good agreement. Interestingly, the remaining differences between modeled and measured spectra are attributed to a crystal-phase dependence in the refractive index of InP. Specifically, we find indication of significant differences in the refractive index between the modeled zinc-blende InP nanowires and the measured wurtzite InP nanowires in the ultraviolet. We believe that such crystal-phase dependent differences in the refractive index affect the possibility to excite optical resonances in the large wavelength range of 345 < λ < 390 nm. To support this claim, we investigated how resonances in nanostructures can be shifted in wavelength by geometrical tuning. We find that dispersion in the refractive index can dominate over geometrical tuning and stop the possibility for such shifting. Our results open the door for using crystal-phase engineering to optimize the absorption in InP nanowire-based solar cells and photodetectors. PMID:25402159

  1. Photometry of 433 Eros from 0.65 to 2.2 micrometers

    NASA Technical Reports Server (NTRS)

    Veeder, G. J.; Matson, D. L.; Bergstralh, J. T.; Johnson, T. V.

    1976-01-01

    Lightcurves of 433 Eros are reported for 11 bandpasses ranging from 0.65 to 2.2 micrometer in wavelength. The relative spectral reflectance was not seen to vary during our observations. Eros has a reflectance at 1.6 micrometers of about 1.5 and at 2.2 micrometers of about 1.7, where the spectral reflectance is scaled to unity at 0.56 micrometers. This spectral reflectance is suggestive of a mixture of silicates and material with high infrared reflectance, perhaps a metallic phase such as meteoritic 'iron'.

  2. P/N InP solar cells on Ge wafers

    NASA Technical Reports Server (NTRS)

    Wojtczuk, Steven; Vernon, Stanley; Burke, Edward A.

    1994-01-01

    Indium phosphide (InP) P-on-N one-sun solar cells were epitaxially grown using a metalorganic chemical vapor deposition process on germanium (Ge) wafers. The motivation for this work is to replace expensive InP wafers, which are fragile and must be thick and therefore heavy, with less expensive Ge wafers, which are stronger, allowing use of thinner, lighter weight wafers. An intermediate InxGs1-xP grading layer starting as In(0.49)Ga(0.51) at the GaAs-coated Ge wafer surface and ending as InP at the top of the grading layer (backside of the InP cell) was used to attempt to bend some of the threading dislocations generated by lattice-mismatch between the Ge wafer and InP cell so they would be harmlessly confined in this grading layer. The best InP/Ge cell was independently measured by NASA-Lewis with a one-sun 25 C AMO efficiently measured by NASA-Lewis with a one-circuit photocurrent 22.6 mA/sq cm. We believe this is the first published report of an InP cell grown on a Ge wafer. Why get excited over a 9 percent InP/Ge cell? If we look at the cell weight and efficiency, a 9 percent InP cell on an 8 mil Ge wafer has about the same cell power density, 118 W/kg (BOL), as the best InP cell ever made, a 19 percent InP cell on an 18 mil InP wafer, because of the lighter Ge wafer weight. As cell panel materials become lighter, the cell weight becomes more important, and the advantage of lightweight cells to the panel power density becomes more important. In addition, although InP/Ge cells have a low beginning-of-life (BOL) efficiency due to dislocation defects, the InP/Ge cells are very radiation hard (end-of-life power similar to beginning-of-life). We have irradiated an InP/Ge cell with alpha particles to an equivalent fluence of 1.6 x 10(exp 16) 1 MeV electrons/sq cm and the efficiency is still 83 percent of its BOL value. At this fluence level, the power output of these InP/Ge cells matches the GaAs/Ge cell data tabulated in the JPL handbook. Data are presented

  3. Ultrasonic Nanocoining of Sub-micrometer Surface Features

    NASA Astrophysics Data System (ADS)

    Nowak, William John, Jr.

    The goal of this work is to develop a machining process to rapidly generate large areas of sub-micrometer surface features in industrially-feasible amounts of time. These surface features, inspired by designs found in nature, can be sized to produce desired behavior including anti-reflective (AR), superhydrophobic, or syperhydrophilic properties. Current methods of producing these features produce high-fidelity replications, but often require several steps to complete and are not economically feasible in a mass-production setting. This process uses a diamond die containing thousands of subwavelength features mounted to a high speed actuator on the axis of a diamond turning machine. The die is pressed into the workpiece with an elliptical path that matches the surface speed of the moving workpiece and minimizes distortion caused by mismatches in velocity. These die indents are tiled together to create large areas of uniform features, which can then be easily transferred to pliable coatings. Because the die is small (20x20 im), the indentations must occur rapidly (40 kHz) to make nanocoining an industrially feasible process. To produce the ultrasonic 2-D motion for indenting, an actuator was designed that resonates in two orthogonal directions at the same frequency. Analytical solutions were first used to determine the approximate geometry to achieve the desired resonant behavior. Finite element analysis (FEA) is then employed to fine-tune the geometry of the device to meet amplitude requirements. Prototypes were constructed and measured to demonstrate the utility of the proposed design method. A controller is designed and implemented to automatically track the resonant frequency and maintain the desired actuator behavior to ensure the indents are formed uniformly over large areas despite piezoelectric self-heating effects and other environmental affects that impact device resonance. Other control strategies that are required for maintaining uniform spacing of

  4. Pneumatic System for Concentration of Micrometer-Size Lunar Soil

    NASA Technical Reports Server (NTRS)

    McKay, David; Cooper, Bonnie

    2012-01-01

    A report describes a size-sorting method to separate and concentrate micrometer- size dust from a broad size range of particles without using sieves, fluids, or other processes that may modify the composition or the surface properties of the dust. The system consists of four processing units connected in series by tubing. Samples of dry particulates such as lunar soil are introduced into the first unit, a fluidized bed. The flow of introduced nitrogen fluidizes the particulates and preferentially moves the finer grain sizes on to the next unit, a flat plate impactor, followed by a cyclone separator, followed by a Nuclepore polycarbonate filter to collect the dust. By varying the gas flow rate and the sizes of various orifices in the system, the size of the final and intermediate particles can be varied to provide the desired products. The dust can be collected from the filter. In addition, electron microscope grids can be placed on the Nuclepore filter for direct sampling followed by electron microscope characterization of the dust without further handling.

  5. Adhesion hysteresis and friction at nanometer and micrometer lengths

    SciTech Connect

    Szoszkiewicz, Robert; Bhushan, Bharat; Huey, Bryan D.; Kulik, Andrzej J.; Gremaud, Gerard

    2006-01-01

    Comparisons between adhesion hysteresis and friction at nanometer and micrometer length scales were investigated experimentally and theoretically. Nanoscale adhesion hysteresis was measured using the ultrasonic force microscopy (UFM) on mica, calcite, and a few metallic samples (Pt, Au, Cu, Zn, Ti, and Fe). Obtained adhesion hysteresis ranged between 4x10{sup -19} and 4x10{sup -18} J. At the microscale a similar setup with a nanoindenter was used and the same samples were investigated. Adhesion hysteresis measured at the microscale ranged between 8x10{sup -17} and 14x10{sup -17} J. Friction was investigated via lateral force microscopy, as well as by scratch tests done with the nanoindenter. Numerical simulations based on the UFM model as well as established theories of contact mechanics studied qualitative dependencies of adhesion hysteresis on experimental parameters. Quantitative relations between adhesion hysteresis and friction were obtained through an analytic model relying on elastic and adhesive properties of the contact. The model agreed with measurements and simulations.

  6. 3D active stabilization system with sub-micrometer resolution.

    PubMed

    Kursu, Olli; Tuukkanen, Tuomas; Rahkonen, Timo; Vähäsöyrinki, Mikko

    2012-01-01

    Stable positioning between a measurement probe and its target from sub- to few micrometer scales has become a prerequisite in precision metrology and in cellular level measurements from biological tissues. Here we present a 3D stabilization system based on an optoelectronic displacement sensor and custom piezo-actuators driven by a feedback control loop that constantly aims to zero the relative movement between the sensor and the target. We used simulations and prototyping to characterize the developed system. Our results show that 95% attenuation of movement artifacts is achieved at 1 Hz with stabilization performance declining to ca. 70% attenuation at 10 Hz. Stabilization bandwidth is limited by mechanical resonances within the displacement sensor that occur at relatively low frequencies, and are attributable to the sensor's high force sensitivity. We successfully used brain derived micromotion trajectories as a demonstration of complex movement stabilization. The micromotion was reduced to a level of ∼1 µm with nearly 100 fold attenuation at the lower frequencies that are typically associated with physiological processes. These results, and possible improvements of the system, are discussed with a focus on possible ways to increase the sensor's force sensitivity without compromising overall system bandwidth. PMID:22900045

  7. Recent Developments for Sub-Quarter Micrometer Fabrication

    NASA Astrophysics Data System (ADS)

    Rousseaux, F.; Haghiri-Gosnet, A. M.; Chen, Y.; Ravets, M. F.; Launois, H.

    1992-12-01

    Resolution capability of synchrotron radiation based proximity lithography has been investigated in the sub-quarter micrometer range using an advanced X-ray stepper and high resolution SiC/W X-ray masks. High resolution tungsten gratings and single lines as small as 60 nm are now currently available. Such masks were tested by contact printing in the L2M lithography station implemented at Super-ACO synchrotron facility in Orsay-France. Also, the influence of diffraction on feature sizes was studied with 30-40 μm proximity gap using various positive and negative resists: PMMA, RAY-PF, SAL 601. It was found that 0.10 to 0.12 μm linewidths can be achieved for gratings and 0.15 to 0.20 μm for isolated lines. This resolution limit can be overpassed by a double exposure technique associated with a lateral mask-stage translation. Examples of feature size down to 80 nm were readily achieved at 40 μm gap.

  8. Experimental Study on Electrical Breakdown for Devices with Micrometer Gaps

    NASA Astrophysics Data System (ADS)

    Meng, Guodong; Cheng, Yonghong; Dong, Chengye; Wu, Kai

    2014-12-01

    The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro & nano electronic devices. In this paper, planar aluminum electrodes with gaps ranging from 2 μm to 40 μm were fabricated by microelectromechanical system technology. The influence factors including gap width and surface dielectric states were experimentally investigated using the home-built test and measurement system. Results showed that for SiO2 layers the current sustained at 2-3 nA during most of the pre-breakdown period, and then rose rapidly to 10-30 nA just before breakdown due to field electron emission, followed by the breakdown. The breakdown voltage curves demonstrated three stages: (1) a constantly decreasing region (the gap width d < 5 μm), where the field emission effect played an important role just near breakdown, supplying enough initial electrons for the breakdown process; (2) a plateau region with a near constant breakdown potential (5 μm < d < 10 μm) (3) a region for large gaps that adhered to Paschen's curve (d > 10 μm). And the surface dielectric states including the surface resistivity and secondary electron yield were verified to be related to the propagation of discharge due to the interaction between initial electrons and dielectrics.

  9. Flow and evaporation in single micrometer and nanometer scale pipes

    SciTech Connect

    Velasco, A. E.; Yang, C.; Siwy, Z. S.; Taborek, P.; Toimil-Molares, M. E.

    2014-07-21

    We report measurements of pressure driven flow of fluids entering vacuum through a single pipe of micrometer or nanometer scale diameter. Nanopores were fabricated by etching a single ion track in polymer or mica foils. A calibrated mass spectrometer was used to measure the flow rates of nitrogen and helium through pipes with diameter ranging from 10 μm to 31 nm. The flow of gaseous and liquid nitrogen was studied near 77 K, while the flow of helium was studied from the lambda point (2.18 K) to above the critical point (5.2 K). Flow rates were controlled by changing the pressure drop across the pipe in the range 0–31 atm. When the pressure in the pipe reached the saturated vapor pressure, an abrupt flow transition was observed. A simple viscous flow model is used to determine the position of the liquid/vapor interface in the pipe. The observed mass flow rates are consistent with no slip boundary conditions.

  10. Inhomogeneous Growth of Micrometer Thick Plasma Polymerized Films.

    PubMed

    Akhavan, Behnam; Menges, Bernhard; Förch, Renate

    2016-05-17

    Plasma polymerization is traditionally recognized as a homogeneous film-forming technique. It is nevertheless reasonable to ask whether micrometer thick plasma polymerized structures are really homogeneous across the film thickness. Studying the properties of the interfacial, near-the-substrate (NTS) region in plasma polymer films represents particular experimental challenges due to the inaccessibility of the buried layers. In this investigation, a novel non-destructive approach has been utilized to evaluate the homogeneity of plasma polymerized acrylic acid (PPAc) and 1,7-octadiene (PPOD) films in a single measurement. Studying the variations of refractive index throughout the depth of the films was facilitated by a home-built surface plasmon resonance (SPR)/optical waveguide (OWG) spectroscopy setup. It has been shown that the NTS layer of both PPAc and PPOD films exhibits a significantly lower refractive index than the bulk of the film that is believed to indicate a higher concentration of internal voids. Our results provide new insights into the growth mechanisms of plasma polymer films and challenge the traditional view that considers plasma polymers as homogeneous and continuous structures. PMID:27111265

  11. The Stickiness of Micrometer-sized Water-ice Particles

    NASA Astrophysics Data System (ADS)

    Gundlach, B.; Blum, J.

    2015-01-01

    Water ice is one of the most abundant materials in dense molecular clouds and in the outer reaches of protoplanetary disks. In contrast to other materials (e.g., silicates), water ice is assumed to be stickier due to its higher specific surface energy, leading to faster or more efficient growth in mutual collisions. However, experiments investigating the stickiness of water ice have been scarce, particularly in the astrophysically relevant micrometer-sized region and at low temperatures. In this work, we present an experimental setup to grow aggregates composed of μm-sized water-ice particles, which we used to measure the sticking and erosion thresholds of the ice particles at different temperatures between 114 K and 260 K. We show with our experiments that for low temperatures (below ~210 K), μm-sized water-ice particles stick below a threshold velocity of 9.6 m s-1, which is approximately 10 times higher than the sticking threshold of μm-sized silica particles. Furthermore, erosion of the grown ice aggregates is observed for velocities above 15.3 m s-1. A comparison of the experimentally derived sticking threshold with model predictions is performed to determine important material properties of water ice, i.e., the specific surface energy and the viscous relaxation time. Our experimental results indicate that the presence of water ice in the outer reaches of protoplanetary disks can enhance the growth of planetesimals by direct sticking of particles.

  12. 3D Active Stabilization System with Sub-Micrometer Resolution

    PubMed Central

    Rahkonen, Timo; Vähäsöyrinki, Mikko

    2012-01-01

    Stable positioning between a measurement probe and its target from sub- to few micrometer scales has become a prerequisite in precision metrology and in cellular level measurements from biological tissues. Here we present a 3D stabilization system based on an optoelectronic displacement sensor and custom piezo-actuators driven by a feedback control loop that constantly aims to zero the relative movement between the sensor and the target. We used simulations and prototyping to characterize the developed system. Our results show that 95 % attenuation of movement artifacts is achieved at 1 Hz with stabilization performance declining to ca. 70 % attenuation at 10 Hz. Stabilization bandwidth is limited by mechanical resonances within the displacement sensor that occur at relatively low frequencies, and are attributable to the sensor's high force sensitivity. We successfully used brain derived micromotion trajectories as a demonstration of complex movement stabilization. The micromotion was reduced to a level of ∼1 µm with nearly 100 fold attenuation at the lower frequencies that are typically associated with physiological processes. These results, and possible improvements of the system, are discussed with a focus on possible ways to increase the sensor's force sensitivity without compromising overall system bandwidth. PMID:22900045

  13. High-efficiency, deep-junction, epitaxial InP solar cells on (100) and (111)B InP substrates

    NASA Technical Reports Server (NTRS)

    Venkatasubramanian, R.; Timmons, M. L.; Hutchby, J. A.; Walters, Robert J.; Summers, Geoffrey P.

    1994-01-01

    We report on the development and performance of deep-junction (approximately 0.25 micron), graded-emitter-doped, n(sup +)-p InP solar cells grown by metallorganic chemical vapor deposition (MOCVD). A novel, diffusion-transport process for obtaining lightly-doped p-type base regions of the solar cell is described. The I-V data and external quantum-efficiency response of these cells are presented. The best active-area AMO efficiency for these deep-junction cells on (100)-oriented InP substrates is 16.8 percent, with a J(sub SC) of 31.8 mA/sq cm, a V(sub OC) of 0.843 V, and a fill-factor of 0.85. By comparison, the best cell efficiency on the (111)B-oriented InP substrates was 15.0 percent. These efficiency values for deep-junction cells are encouraging and compare favorably with performance of thin-emitter (0.03 micron) epitaxial cells as well as that of deep-emitter diffused cells. The cell performance and breakdown voltage characteristics of a batch of 20 cells on each of the orientations are presented, indicating the superior breakdown voltage properties and other characteristics of InP cells on the (111)B orientation. Spectral response, dark I-V data, and photoluminescence (PL) measurements on the InP cells are presented with an analysis on the variation in J(sub SC) and V(sub OC) of the cells. It is observed, under open-circuit conditions, that lower-V(sub OC) cells exhibit higher band-edge PL intensity for both the (100) and (111)B orientations. This anomalous behavior suggests that radiative recombination in the heavily-doped n(sup +)-InP emitter may be detrimental to achieving higher V(sub OC) in n(sup +)-p InP solar cells.

  14. Measurements with Reticle Micrometer Performed by a New Double Stars Observing Group from Poland

    NASA Astrophysics Data System (ADS)

    Biskupski, Marcin; Banacka, Natalia; Cupryjak, Justyna; Malinowska, Malgorzata; Bujel, Kamil; Koltek, Zdzislaw; Mazur, Jaroslaw; Muskala, Marcin; Plotkowski, Lukasz; Prowans, Barlomiej; Szkaplewicz, Pawel

    2016-04-01

    Measurements of 19 double stars using a reticle micrometer eyepiece are reported. The observational program was held in spring and summer of 2015 as an extended workshop for a new double stars observing group from Szczecin, Poland. The goal of the program was to learn how to measure position angle and separation using a reticle micrometer eyepiece.

  15. Near-infrared continuum and 3.3 micrometer(s) polycyclic aromatic hydrocarbon imaging of the starburst ring in the type 1 Seyfert galaxy NGC 7469

    NASA Technical Reports Server (NTRS)

    Mazzarella, J. M.; Voit, G. M.; Soifer, B. T.; Matthews, K.; Graham, J. R.; Armus, L.; Shupe, D.

    1994-01-01

    High resolution near-infrared images of the type 1 Seyfert galaxy NGC 7469 have been obtained to probe its dusty nuclear environment. Direct J, H, and K images are relatively featureless, but residual images created by subtracting a smooth model based on best-fitting elliptical isophotes reveal a tight inner spiral whose high surface-brightness portions correspond to a previously detected 3 sec (1 kpc) diameter ring of radio continuum emission. The inner infrared spiral arms extended approximately equal to 4 sec NW and SE from the nucleus, and the NW arm joins up with large-scale spiral structure visible in the R band. The residual images also show a bar-like structure aligned with the brightest infrared/radio hotspots at PA approximately equal to 50 deg. Three infrared hotspots are detected which align remarkably well with 6 cm radio continuum sources. The near-infrared ring and the hotspots are visible in the residual images, and in a high-resolution direct K-band image restored to an effective resolution of 0.65 sec (FWHM) using the Richardson-Lucy algorithm. The infrared hotspots have luminosities of nuL(sub nu) (2.2 micrometer(s)) approximately equal to 10(exp 8) solar luminosity (M(sub k) approximately equal to -16 mag), suggesting they are either giant H II regions or individual supernovae. The two brightest regions may be associated with enhanced star formation triggered by orbit crowding of gas where spiral arms emerge from an inner bar. Narrowband (delta lambda/lambda approximately 1.5%) imaging in the 3.28 micrometer(s) dust emission feature and surrounding continuum confirms the 3 sec diameter 3.28 micrometer(s) emission region detected previously using multiaperture photometry. The extended polycyclic aromatic hydrocarbon (PAH) emission is slightly elongated and aligned with published 1O III1 line emission and 12.5 micrometer(s) continuum emission, apparently tracing the starburst. The presence of approximately equal to 25% of the total 3.28 micrometer(s

  16. Modeling of InP metalorganic chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Black, Linda R.; Clark, Ivan O.; Kui, J.; Jesser, William A.

    1991-01-01

    The growth of InP by metalorganic chemical vapor deposition (MOCVD) in a horizontal reactor is being modeled with a commercially available computational fluid dynamics modeling code. The mathematical treatment of the MOCVD process has four primary areas of concern: 1) transport phenomena, 2) chemistry, 3) boundary conditions, and 4) numerical solution methods. The transport processes involved in CVD are described by conservation of total mass, momentum, energy, and atomic species. Momentum conservation is described by a generalized form of the Navier-Stokes equation for a Newtonian fluid and laminar flow. The effect of Soret diffusion on the transport of particular chemical species and on the predicted deposition rate is examined. Both gas-phase and surface chemical reactions are employed in the model. Boundary conditions are specified at the inlet and walls of the reactor for temperature, fluid flow and chemical species. The coupled set of equations described above is solved by a finite difference method over a nonuniform rectilinear grid in both two and three dimensions. The results of the 2-D computational model is presented for gravity levels of zero- and one-g. The predicted growth rates at one-g are compared to measured growth rates on fused silica substrates.

  17. InP shallow-homojunction solar cells

    NASA Technical Reports Server (NTRS)

    Keavney, Christopher; Spitzer, Mark B.; Vernon, Stanley M.; Haven, Victor E.; Augustine, Godfrey

    1989-01-01

    Indium phosphide solar cells with very thin n-type emitters have been made by both ion implantation and metalorganic chemical vapor deposition. Air mass zero efficiencies as high as 18.8 percent (NASA measurement) have been achieved. Although calculations show that, as is the case with GaAs, a heterostructure is expected to be required for the highest efficiencies attainable, the material properties of InP give the shallow-homojunction structure a greater potential than in the case of GaAs. The best cells, which were those made by ion implantation, show open-circuit voltage (V sub oc) of 873 mV, short-circuit current of 357 A/sq m (35.7 mA/sq cm), and fill factor of 0.829. Improvements are anticipated in all three of these parameters. Internal quantum efficiency peaks at over 90 percent in the red end of the spectrum, but drops to 54 percent in the blue end. Other cells have achieved 74 percent in the blue end. Detailed modeling of the data indicates that a high front surface recombination velocity is responsible for the low blue response, that the carrier lifetime is high enough to allow good carrier collection from both the base and the emitter, and that the voltage is base-limited.

  18. Surface processes during purification of InP quantum dots

    PubMed Central

    Emelin, Pavel; Vinokurov, Alexander; Dorofeev, Sergey; Abakumov, Artem; Kuznetsova, Tatiana

    2014-01-01

    Summary Recently, a new simple and fast method for the synthesis of InP quantum dots by using phosphine as phosphorous precursor and myristic acid as surface stabilizer was reported. Purification after synthesis is necessary to obtain samples with good optical properties. Two methods of purification were compared and the surface processes which occur during purification were studied. Traditional precipitation with acetone is accompanied by a small increase in photoluminescence. It occurs that during the purification the hydrolysis of the indium precursor takes place, which leads to a better surface passivation. The electrophoretic purification technique does not increase luminescence efficiency but yields very pure quantum dots in only a few minutes. Additionally, the formation of In(OH)3 during the low temperature synthesis was explained. Purification of quantum dots is a very significant part of postsynthetical treatment that determines the properties of the material. But this subject is not sufficiently discussed in the literature. The paper is devoted to the processes that occur at the surface of quantum dots during purification. A new method of purification, electrophoresis, is investigated and described in particular. PMID:25161857

  19. Modeling and simulation of InP homojunction solar cells

    NASA Technical Reports Server (NTRS)

    Yahia, A. H.; Wanlass, M. W.; Coutts, T. J.

    1988-01-01

    Modeling and simulation of single-crystal InP homojunction solar cells has been performed using the PC-1D code. Cell design and performance have been optimized using the best available estimates of the various materials parameters. A comparison has been made of the predictions of the PC-1D model to those of other models. The optimum performance is predicted to give an efficiency approaching 21 percent at AM0. It is shown that in order to describe the performance of actual cells it is necessary to use larger values of the intrinsic carrier concentration and the surface recombination velocity (SRV) than have been reported in the literature. However, even with a near-maximum value of SRV (e.g., 10 to the 7th cm/s) it is necessary to reduce the minority carrier diffusion length in the emitter to only 0.01 micron in order to account for the relatively low quantum efficiency in the blue part of the spectrum. This indicates that improvement in the emitter bulk properties could be much more important than the SRV. Other loss mechanisms are also discussed; in particular, it is shown that recombination in the base, for good quality material, is relatively insignificant.

  20. Titan's 5 micrometers spectral window: carbon monoxide and the albedo of the surface

    NASA Technical Reports Server (NTRS)

    Noll, K. S.; Geballe, T. R.; Knacke, R. F.; Pendleton, Y. J.

    1996-01-01

    We have measured the spectrum of Titan near 5 micrometers and have found it to be dominated by absorption from the carbon monoxide 1-0 vibration-rotation band. The position of the band edge allows us to constrain the abundance of CO in the atmosphere and/or the location of the reflecting layer in the atmosphere. In the most likely case, 5 micrometers radiation is reflected from the surface and the mole fraction of CO in the atmosphere is qCO=10(+10/-5) ppm, significantly lower than previous estimates for tropospheric CO. The albedo of the reflecting layer is approximately 0.07(+0.02/-0.01) in the 5 micrometers continuum outside the CO band. The 5 micrometers albedo is consistent with a surface of mixed ice and silicates similar to the icy Galilean satellites. Organic solids formed in simulated Titan conditions can also produce similar albedos at 5 micrometers.

  1. Titan's 5 micrometers spectral window: carbon monoxide and the albedo of the surface.

    PubMed

    Noll, K S; Geballe, T R; Knacke, R F; Pendleton, Y J

    1996-12-01

    We have measured the spectrum of Titan near 5 micrometers and have found it to be dominated by absorption from the carbon monoxide 1-0 vibration-rotation band. The position of the band edge allows us to constrain the abundance of CO in the atmosphere and/or the location of the reflecting layer in the atmosphere. In the most likely case, 5 micrometers radiation is reflected from the surface and the mole fraction of CO in the atmosphere is qCO=10(+10/-5) ppm, significantly lower than previous estimates for tropospheric CO. The albedo of the reflecting layer is approximately 0.07(+0.02/-0.01) in the 5 micrometers continuum outside the CO band. The 5 micrometers albedo is consistent with a surface of mixed ice and silicates similar to the icy Galilean satellites. Organic solids formed in simulated Titan conditions can also produce similar albedos at 5 micrometers. PMID:11539388

  2. One-step large-scale synthesis of micrometer-sized silver nanosheets by a template-free electrochemical method

    PubMed Central

    2013-01-01

    We have synthesized micrometer-sized Ag nanosheets via a facile, one-step, template-free electrochemical deposition in an ultra-dilute silver nitrate aqueous electrolyte. The nanosheet growth was revealed to occur in three stages: (1) formation of polygonal Ag nuclei on a substrate, (2) growth of {112}-faceted nanowire from the nuclei, and (3) anisotropic growth of (111)-planar nanosheets, approximately 20 to 50 nm in thickness and 10 μm in width, in the <112>−direction. The vertical growth of the facet nanowire was induced by the strong interface anisotropy between the deposit and electrolyte due to the ultra-dilute concentration of electrolyte and high reduction potential. The thickness of Ag nanosheets was controllable by the adjustment of the reduction/oxidation potential and frequency of the reverse-pulse potentiodynamic mode. PMID:23692676

  3. Tailoring the optical characteristics of microsized InP nanoneedles directly grown on silicon.

    PubMed

    Li, Kun; Sun, Hao; Ren, Fan; Ng, Kar Wei; Tran, Thai-Truong D; Chen, Roger; Chang-Hasnain, Connie J

    2014-01-01

    Nanoscale self-assembly offers a pathway to realize heterogeneous integration of III-V materials on silicon. However, for III-V nanowires directly grown on silicon, dislocation-free single-crystal quality could only be attained below certain critical dimensions. We recently reported a new approach that overcomes this size constraint, demonstrating the growth of single-crystal InGaAs/GaAs and InP nanoneedles with the base diameters exceeding 1 μm. Here, we report distinct optical characteristics of InP nanoneedles which are varied from mostly zincblende, zincblende/wurtzite-mixed, to pure wurtzite crystalline phase. We achieved, for the first time, pure single-crystal wurtzite-phase InP nanoneedles grown on silicon with bandgaps of 80 meV larger than that of zincblende-phase InP. Being able to attain excellent material quality while scaling up in size promises outstanding device performance of these nanoneedles. At room temperature, a high internal quantum efficiency of 25% and optically pumped lasing are demonstrated for single nanoneedle as-grown on silicon substrate. Recombination dynamics proves the excellent surface quality of the InP nanoneedles, which paves the way toward achieving multijunction photovoltaic cells, long-wavelength heterostructure lasers, and advanced photonic integrated circuits. PMID:24299042

  4. Nonepitaxial Thin-Film InP for Scalable and Efficient Photocathodes.

    PubMed

    Hettick, Mark; Zheng, Maxwell; Lin, Yongjing; Sutter-Fella, Carolin M; Ager, Joel W; Javey, Ali

    2015-06-18

    To date, some of the highest performance photocathodes of a photoelectrochemical (PEC) cell have been shown with single-crystalline p-type InP wafers, exhibiting half-cell solar-to-hydrogen conversion efficiencies of over 14%. However, the high cost of single-crystalline InP wafers may present a challenge for future large-scale industrial deployment. Analogous to solar cells, a thin-film approach could address the cost challenges by utilizing the benefits of the InP material while decreasing the use of expensive materials and processes. Here, we demonstrate this approach, using the newly developed thin-film vapor-liquid-solid (TF-VLS) nonepitaxial growth method combined with an atomic-layer deposition protection process to create thin-film InP photocathodes with large grain size and high performance, in the first reported solar device configuration generated by materials grown with this technique. Current-voltage measurements show a photocurrent (29.4 mA/cm(2)) and onset potential (630 mV) approaching single-crystalline wafers and an overall power conversion efficiency of 11.6%, making TF-VLS InP a promising photocathode for scalable and efficient solar hydrogen generation. PMID:26266588

  5. THE STICKINESS OF MICROMETER-SIZED WATER-ICE PARTICLES

    SciTech Connect

    Gundlach, B.; Blum, J.

    2015-01-01

    Water ice is one of the most abundant materials in dense molecular clouds and in the outer reaches of protoplanetary disks. In contrast to other materials (e.g., silicates), water ice is assumed to be stickier due to its higher specific surface energy, leading to faster or more efficient growth in mutual collisions. However, experiments investigating the stickiness of water ice have been scarce, particularly in the astrophysically relevant micrometer-sized region and at low temperatures. In this work, we present an experimental setup to grow aggregates composed of μm-sized water-ice particles, which we used to measure the sticking and erosion thresholds of the ice particles at different temperatures between 114 K and 260 K. We show with our experiments that for low temperatures (below ∼210 K), μm-sized water-ice particles stick below a threshold velocity of 9.6 m s{sup –1}, which is approximately 10 times higher than the sticking threshold of μm-sized silica particles. Furthermore, erosion of the grown ice aggregates is observed for velocities above 15.3 m s{sup –1}. A comparison of the experimentally derived sticking threshold with model predictions is performed to determine important material properties of water ice, i.e., the specific surface energy and the viscous relaxation time. Our experimental results indicate that the presence of water ice in the outer reaches of protoplanetary disks can enhance the growth of planetesimals by direct sticking of particles.

  6. Portable Speech Synthesizer

    NASA Technical Reports Server (NTRS)

    Leibfritz, Gilbert H.; Larson, Howard K.

    1987-01-01

    Compact speech synthesizer useful traveling companion to speech-handicapped. User simply enters statement on board, and synthesizer converts statement into spoken words. Battery-powered and housed in briefcase, easily carried on trips. Unit used on telephones and face-to-face communication. Synthesizer consists of micro-computer with memory-expansion module, speech-synthesizer circuit, batteries, recharger, dc-to-dc converter, and telephone amplifier. Components, commercially available, fit neatly in 17-by 13-by 5-in. briefcase. Weighs about 20 lb (9 kg) and operates and recharges from ac receptable.

  7. Oxidative stress-induced p53 activity is enhanced by a redox-sensitive TP53INP1 SUMOylation

    PubMed Central

    Peuget, S; Bonacci, T; Soubeyran, P; Iovanna, J; Dusetti, N J

    2014-01-01

    Tumor Protein p53-Induced Nuclear Protein 1 (TP53INP1) is a tumor suppressor that modulates the p53 response to stress. TP53INP1 is one of the key mediators of p53 antioxidant function by promoting the p53 transcriptional activity on its target genes. TP53INP1 expression is deregulated in many types of cancers including pancreatic ductal adenocarcinoma in which its decrease occurs early during the preneoplastic development. In this work, we report that redox-dependent induction of p53 transcriptional activity is enhanced by the oxidative stress-induced SUMOylation of TP53INP1 at lysine 113. This SUMOylation is mediated by PIAS3 and CBX4, two SUMO ligases especially related to the p53 activation upon DNA damage. Importantly, this modification is reversed by three SUMO1-specific proteases SENP1, 2 and 6. Moreover, TP53INP1 SUMOylation induces its binding to p53 in the nucleus under oxidative stress conditions. TP53INP1 mutation at lysine 113 prevents the pro-apoptotic, antiproliferative and antioxidant effects of TP53INP1 by impairing the p53 response on its target genes p21, Bax and PUMA. We conclude that TP53INP1 SUMOylation is essential for the regulation of p53 activity induced by oxidative stress. PMID:24608790

  8. Mass spectrometric studies of phosphine pyrolysis and OMVPE growth of InP

    NASA Astrophysics Data System (ADS)

    Larsen, C. A.; Buchan, N. I.; Stringfellow, G. B.

    1987-11-01

    The mechanism of PH3 decomposition was studied by using D2 as a carrier gas and analyzing the reaction products with a mass spectrometer. The effects of InP and silica surfaces were investigated. The only gaseous product below 600 C is H2. Since any gas-phase H atoms would produce HD, the reaction occurs entirely on the surface. The slow step is the unimolecular removal of the first hydrogen atom, with an activation energy of 36.0 kcal/mole on InP surfaces. The reaction on InP is first-order for PH3 concentrations as high as 15 percent, so the surface is not saturated at those conditions. When trimethylindium (TMIn) is added to the gas mixture, the mechanism changes dramatically, probably proceeding via an unstable intermediate adduct of TMIn and PH3 which eliminates CH4 upon formation. This concerted reaction lowers the pyrolysis temperatures of both PH3 and TMIn.

  9. Enhanced monolayer MoS2/InP heterostructure solar cells by graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Lin, Shisheng; Ding, Guqiao; Li, Xiaoqiang; Wu, Zhiqian; Zhang, Shengjiao; Xu, Zhijuan; Xu, Sen; Lu, Yanghua; Xu, Wenli; Zheng, Zheyang

    2016-04-01

    We demonstrate significantly improved photovoltaic response of monolayer molybdenum disulfide (MoS2)/indium phosphide (InP) van der Waals heterostructure induced by graphene quantum dots (GQDs). Raman and photoluminescence measurements indicate that effective charge transfer takes place between GQDs and MoS2, which results in n-type doping of MoS2. The doping effect increases the barrier height at the MoS2/InP heterojunction, thus the averaged power conversion efficiency of MoS2/InP solar cells is improved from 2.1% to 4.1%. The light induced doping by GQD provides a feasible way for developing more efficient MoS2 based heterostructure solar cells.

  10. High performance InP ring resonator for new generation monolithically integrated optical gyroscopes.

    PubMed

    Ciminelli, Caterina; Dell'Olio, Francesco; Armenise, Mario N; Soares, Francisco M; Passenberg, Wolfgang

    2013-01-14

    An InP ring resonator with an experimentally demonstrated quality factor (Q) of the order of 10(6) is reported for the first time. This Q value, typical for low loss technologies such as silica-on-silicon, is a record for the InP technology and improves the state-of-the-art of about one order of magnitude. The cavity has been designed aiming at the Q-factor maximization while keeping the resonance depth of about 8 dB. The device was fabricated using metal-organic vapour-phase-epitaxy, photolithography and reactive ion etching. It has been optically characterized and all its performance parameters have been estimated. InP waveguide loss low as 0.45 dB/cm has been measured, leading to a potential shot noise limited resolution of 10 °/h for a new angular velocity sensor. PMID:23388949

  11. Modified photoresist etch mask process for InP channeled substrate lasers

    SciTech Connect

    Huo, D.T.C.; Yan, M.F.; Wynn, J.D.; Wilt, D.P.

    1989-03-01

    The authors develop a new photoresist etch mask process to etch (001) InP wafers to obtain (111) B-faceted v-grooves for channeled substrate laser applications. They investigate the use of HCl and HF solutions to remove native oxide layers prior to v-groove etching. They also study the relationship between the photoresist mask undercutting and the bath temperature used for native oxide removal. The degree of undercutting in photoresist mask can be reduced about two times by increasing the HF bath temperature from room temperature to 48/sup 0/C during the oxide removal process. They also identify two important factors that control the mask undercutting rates as (i) the thickness of native oxide on InP surface and (ii) the chemical reaction between InP and the oxide removal bath solution.

  12. Excitonic properties of wurtzite InP nanowires grown on silicon substrate.

    PubMed

    Hadj Alouane, M H; Chauvin, N; Khmissi, H; Naji, K; Ilahi, B; Maaref, H; Patriarche, G; Gendry, M; Bru-Chevallier, C

    2013-01-25

    In order to investigate the optical properties of wurtzite (Wz) InP nanowires grown on Si(001) by solid source molecular beam epitaxy with the vapour-liquid-solid method, the growth temperature and V/III pressure ratio have been optimized to remove any zinc-blende insertion. These pure Wz InP nanowires have been investigated by photoluminescence (PL), time-resolved PL and PL excitation. Direct observation of the second and third valence band in Wz InP nanowires using PL spectroscopy at high excitation power have been reported and, from these measurements, a crystal field splitting of 74 meV and a spin-orbit interaction energy of 145 meV were extracted. Based on the study of temperature-dependent optical properties, we have performed an investigation of the thermal escape processes of carriers and the electron-phonon coupling strength. PMID:23262659

  13. InP Double Heterojunction Bipolar Transistor for broadband terahertz detection and imaging systems

    NASA Astrophysics Data System (ADS)

    Coquillat, D.; Nodjiadjim, V.; Konczykowska, A.; Dyakonova, N.; Consejo, C.; Ruffenach, S.; Teppe, F.; Riet, M.; Muraviev, A.; Gutin, A.; Shur, M.; Godin, J.; Knap, W.

    2015-10-01

    This paper presents terahertz detectors based on high performance 0.7-μm InP double heterojunction bipolar transistor (DHBT) technology and reports on the analysis of their voltage responsivity over a wide frequency range of the incoming terahertz radiation. The detectors operated without any spatial antennas to couple terahertz radiation to the device and have been characterized in the 0.25 - 3.1 THz range with the responsivities (normalized to 1 W radiant power) of 5 V/W and 200 μV/W measured at 0.35 THz and 3.11 THz, respectively. The InP DHBTs also performed as the imaging single-pixels at room temperature in the raster scanned transmission mode. A set of the sub-terahertz images of plant leaves suggest potential utility of InP DHBT detectors for terahertz imaging dedicated to non-invasive testing of plants.

  14. Defect reaction network in Si-doped InP : numerical predictions.

    SciTech Connect

    Schultz, Peter Andrew

    2013-10-01

    This Report characterizes the defects in the defect reaction network in silicon-doped, n-type InP deduced from first principles density functional theory. The reaction network is deduced by following exothermic defect reactions starting with the initially mobile interstitial defects reacting with common displacement damage defects in Si-doped InP until culminating in immobile reaction products. The defect reactions and reaction energies are tabulated, along with the properties of all the silicon-related defects in the reaction network. This Report serves to extend the results for intrinsic defects in SAND 2012-3313: %E2%80%9CSimple intrinsic defects in InP: Numerical predictions%E2%80%9D to include Si-containing simple defects likely to be present in a radiation-induced defect reaction sequence.

  15. Effects of rapid quenching on the impurity site location in Zn-diffused InP

    SciTech Connect

    Yu, K.M.; Walukiewicz, W.; Chan, L.Y.; Leon, R.; Haller, E.E.; Jaklevic, J.M. ); Hanson, C.M. )

    1993-07-01

    The lattice locations of Zn atoms in heavily Zn-doped InP single crystal have been investigated by ion channeling techniques. The InP samples were rapidly quenched in diffusion pump oil after high-temperature Zn diffusion. Ion channeling experiments performed along various major crystal axes suggest that a large fraction (20%--30%) of the Zn atoms are in the tetrahedral interstitial position in the InP lattice. It has been found that although the maximum hole concentration is not significantly affected by the cooling rate, there is a substantial increase in the incorporation of Zn on substitutional and tetrahedral interstitial lattice locations in the rapidly cooled samples as compared to the slowly cooled samples. The consequences of these results for understanding the mechanisms leading to the saturation of the free-hole concentration in compound semiconductors are discussed.

  16. Ultrabroadband terahertz field detection by proton-bombarded InP photoconductive antennas.

    PubMed

    Liu, Tze-An; Tani, Masahiko; Nakajima, Makoto; Hangyo, Masanori; Sakai, Kiyomi; Nakashima, Shin-Ichi; Pan, Ci-Ling

    2004-06-28

    Photoconductive (PC) antennas fabricated on InP bombarded with 180 keV protons of different dosages (InP:H+) all exhibit a useful bandwidth of about 30 THz, comparable to that of the LT-GaAs PC antenna. The peak signal current of the best InP: H+ device (dosage of 10;15 ions/cm;2) is slightly higher than that of the LT-GaAs one, while the signal-to-noise ratio (SNR) of the former is about half of that of the latter due to lower resistivity. This suggests that InP: H+ can be a good substrate for THz PC antennas with proper annealing and/or implantation recipe. PMID:19483812

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

    SciTech Connect

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

    2008-10-06

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

  18. Spin reorientation transition in ultrathin Co film on InP(2x4) reconstructed surface

    SciTech Connect

    Park, Yong-Sung; Jeong, Jong-Ryul; Shin, Sung-Chul

    2005-05-15

    We have investigated magnetic properties of monolayer (ML)-thickness Co film deposited on InP(2x4) reconstructed surface using in situ surface magneto-optical Kerr effects (SMOKE) measurement system. InP(2x4) reconstructed surface, obtained by several cycles of sputtering-and-annealing process, was confirmed by reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) measurements. Co film grown on InP(2x4) reconstructed surface shows three distinguishable thickness regions which have different magnetic properties, depending on Co film thickness. In the Co film thickness region smaller than 7 ML, no SMOKE signal was detected. In the thickness region between 8 ML and 15 ML, both longitudinal and polar Kerr hysteresis loops were observed. In the film thickness larger than 16 ML, only longitudinal SMOKE signal without polar signal was detected.

  19. Optical and structural properties of sulfur-doped ELOG InP on Si

    SciTech Connect

    Sun, Yan-Ting Junesand, Carl; Metaferia, Wondwosen; Kataria, Himanshu; Lourdudoss, Sebastian; Julian, Nick; Bowers, John; Pozina, Galia; Hultman, Lars

    2015-06-07

    Optical and structural properties of sulfur-doped epitaxial lateral overgrowth (ELOG) InP grown from nano-sized openings on Si are studied by room-temperature cathodoluminescence and cross-sectional transmission electron microscopy (XTEM). The dependence of luminescence intensity on opening orientation and dimension is reported. Impurity enhanced luminescence can be affected by the facet planes bounding the ELOG layer. Dark line defects formed along the [011] direction are identified as the facet planes intersected by the stacking faults in the ELOG layer. XTEM imaging in different diffraction conditions reveals that stacking faults in the seed InP layer can circumvent the SiO{sub 2} mask during ELOG and extend to the laterally grown layer over the mask. A model for Suzuki effect enhanced stacking fault propagation over the mask in sulfur-doped ELOG InP is constructed and in-situ thermal annealing process is proposed to eliminate the seeding stacking faults.

  20. Growth mechanisms and crystallographic structure of InP nanowires on lattice-mismatched substrates

    NASA Astrophysics Data System (ADS)

    Moewe, Michael; Chuang, Linus C.; Dubrovskii, Vladimir G.; Chang-Hasnain, Connie

    2008-08-01

    We present a growth model that predicts the growth phase and mechanism of InP nanowires (NWs) and the experimental verifications of the model. The NWs were grown on lattice-mismatched GaAs substrates using metal-organic chemical vapor deposition via Au nanodrop-assisted vapor-liquid-solid growth. Nanodrops with larger diameters are shown to grow longer NWs because growth is governed mainly by direct precursor impingement on the nanodrop surface. The theoretical and experimental results also show that growth phase is dependent on NW diameter. We show that InP NWs with a diameter less than a certain value exhibit coherent growth of a single crystalline wurtzite (WZ) phase, whereas larger diameter InP NWs often contain sequences of WZ and zincblende phases and stacking faults. These findings allow one to achieve coherent NW growth and WZ phases free from twinning if the NW diameter is below certain material-dependent critical diameters.

  1. Differential InP HEMT MMIC Amplifiers Embedded in Waveguides

    NASA Technical Reports Server (NTRS)

    Kangaslahti, Pekka; Schlecht, Erich; Samoska, Lorene

    2009-01-01

    Monolithic microwave integrated-circuit (MMIC) amplifiers of a type now being developed for operation at frequencies of hundreds of gigahertz contain InP high-electron-mobility transistors (HEMTs) in a differential configuration. The differential configuration makes it possible to obtain gains greater than those of amplifiers having the single-ended configuration. To reduce losses associated with packaging, the MMIC chips are designed integrally with, and embedded in, waveguide packages, with the additional benefit that the packages are compact enough to fit into phased transmitting and/or receiving antenna arrays. Differential configurations (which are inherently balanced) have been used to extend the upper limits of operating frequencies of complementary metal oxide/semiconductor (CMOS) amplifiers to the microwave range but, until now, have not been applied in millimeter- wave amplifier circuits. Baluns have traditionally been used to transform from single-ended to balanced configurations, but baluns tend to be lossy. Instead of baluns, finlines are used to effect this transformation in the present line of development. Finlines have been used extensively to drive millimeter- wave mixers in balanced configurations. In the present extension of the finline balancing concept, finline transitions are integrated onto the affected MMICs (see figure). The differential configuration creates a virtual ground within each pair of InP HEMT gate fingers, eliminating the need for inductive vias to ground. Elimination of these vias greatly reduces parasitic components of current and the associated losses within an amplifier, thereby enabling more nearly complete utilization of the full performance of each transistor. The differential configuration offers the additional benefit of multiplying (relative to the single-ended configuration) the input and output impedances of each transistor by a factor of four, so that it is possible to use large transistors that would otherwise have

  2. High Beginning-of-Life Efficiency p/n InP Solar Cells

    NASA Technical Reports Server (NTRS)

    Hoffman, Richard W., Jr.; Fatemi, Navid S.; Weizer, Victor G.; Jenkins, Phillip P.; Ringel, Steven A.; Scheiman, David A.; Wilt, David M.; Brinker, David J.

    2004-01-01

    We have achieved a new record efficiency of 17.6%, (AM0) for a p/n InP homo-epitaxy solar cell. In addition, we have eliminated a previously observed photo-degradation of cell performance, which was due to losses in J(sub sc). Cells soaked in AM0 spectrum at one-sun intensity for an hour showed no significant change in cell performance. We have discovered carrier passivation effects when using Zn as the p-type dopant in the OMVPE growth of InP and have found a method to avoid the unexpected effects which result from typical operation of OMVPE cell growth.

  3. An electron cyclotron resonance plasma process for InP passivation

    NASA Astrophysics Data System (ADS)

    Hu, Y. Z.; Li, M.; Wang, Y.; Irene, E. A.

    1993-05-01

    In-situ ellipsometry has been used to monitor electron cyclotron resonance (ECR) plasma oxidation of InP at room temperature in the shadow plasma between a shutter and the sample. This process leaves no detectable excess P at the InP-oxide interface. A capping layer of SiO2 was grown by ECR chemical-vapor deposition at a substrate temperature of 150 deg C. The samples were rapid-thermal annealed at 500 deg C for 1 min in an oxygen ambient. The dielectric layers were evaluated by current-voltage and capacitance-voltage measurements on metal-oxide n-type InP capacitors.

  4. Label swapper device for spectral amplitude coded optical packet networks monolithically integrated on InP.

    PubMed

    Muñoz, P; García-Olcina, R; Habib, C; Chen, L R; Leijtens, X J M; de Vries, T; Robbins, D; Capmany, J

    2011-07-01

    In this paper the design, fabrication and experimental characterization of an spectral amplitude coded (SAC) optical label swapper monolithically integrated on Indium Phosphide (InP) is presented. The device has a footprint of 4.8x1.5 mm2 and is able to perform label swapping operations required in SAC at a speed of 155 Mbps. The device was manufactured in InP using a multiple purpose generic integration scheme. Compared to previous SAC label swapper demonstrations, using discrete component assembly, this label swapper chip operates two order of magnitudes faster. PMID:21747509

  5. Electronic and Vibrational Spectra of InP Quantum Dots Formed by Sequential Ion Implantation

    NASA Technical Reports Server (NTRS)

    Hall, C.; Mu, R.; Tung, Y. S.; Ueda, A.; Henderson, D. O.; White, C. W.

    1997-01-01

    We have performed sequential ion implantation of indium and phosphorus into silica combined with controlled thermal annealing to fabricate InP quantum dots in a dielectric host. Electronic and vibrational spectra were measured for the as-implanted and annealed samples. The annealed samples show a peak in the infrared spectra near 320/cm which is attributed to a surface phonon mode and is in good agreement with the value calculated from Frolich's theory of surface phonon polaritons. The electronic spectra show the development of a band near 390 nm that is attributed to quantum confined InP.

  6. Beyond G-band : a 235 GHz InP MMIC amplifier

    NASA Technical Reports Server (NTRS)

    Dawson, Douglas; Samoska, Lorene; Fung, A. K.; Lee, Karen; Lai, Richard; Grundbacher, Ronald; Liu, Po-Hsin; Raja, Rohit

    2005-01-01

    We present results on an InP monolithic millimeter- wave integrated circuit (MMIC) amplifier having 10-dB gain at 235 GHz. We designed this circuit and fabricated the chip in Northrop Grumman Space Technology's (NGST) 0.07- m InP high electron mobility transistor (HEMT) process. Using a WR3 (220-325 GHz) waveguide vector network analyzer system interfaced to waveguide wafer probes, we measured this chip on-wafer for -parameters. To our knowledge, this is the first time a WR3 waveguide on-wafer measurement system has been used to measure gain in a MMIC amplifier above 230 GHz.

  7. Organometallic vapor phase epitaxial growth of InP using new phosphorus sources

    NASA Astrophysics Data System (ADS)

    Larsen, C. A.; Chen, C. H.; Kitamura, M.; Stringfellow, G. B.; Brown, D. W.; Robertson, A. J.

    1986-06-01

    Two organophosphorus compounds, isobutylphosphine and tertiarybutylphosphine, have been investigated for their possible use as precursors in the organometallic vapor phase epitaxy process. They are the first nonhydride compounds to be used as phosphorus sources. Pyrolysis studies show that the first decomposition products are phosphine and various organic compounds. The phosphine then pyrolyzes to give phosphorus. The materials are less pyrophoric and less toxic than phosphine, and so are safer to use. The compounds have been used to grow epitaxial layers of InP on InP and GaAs substrates. The layers exhibit photoluminescence and electrical properties which are similar to those of layers grown with phosphine.

  8. Surface recombination velocity and lifetime in InP measured by transient microwave reflectance

    NASA Technical Reports Server (NTRS)

    Bothra, S.; Tyagi, S. D.; Ghandhi, S. K.; Borrego, J. M.

    1990-01-01

    Minority carrier lifetime and surface recombination velocity are determined in organometallic vapor-phase epitaxy (OMVPE)-grown InP by a contactless microwave technique. For lightly doped n-type InP, a surface recombination velocity of 5000 cm/s is measured. However, in solar cells with a heavily doped n-type emitter a surface recombination velocity of 1 x 10 to the 6th cm/s is observed. Possible reasons for this due to surface pinning are discussed. The effects of various chemical treatments and SiO on the surface recombination velocity are measured.

  9. Conductivity of nanoporous InP membranes investigated using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Merchant, S. K. E.; Lloyd-Hughes, J.; Sirbu, L.; Tiginyanu, I. M.; Parkinson, P.; Herz, L. M.; Johnston, M. B.

    2008-10-01

    We have investigated the terahertz conductivity of extrinsic and photoexcited electrons in nanoporous indium phosphide (InP) at different pore densities and orientations. The form of electronic transport in the film was found to differ significantly from that for bulk InP. While photo-generated electrons showed Drude-like transport, the behaviour for extrinsic electrons deviated significantly from the Drude model. Time-resolved photoconductivity measurements found that carrier recombination was slow, with lifetimes exceeding 1 ns for all porosities and orientations. When considered together, these findings suggest that the surfaces created by the nanopores strongly alter the dynamics of both extrinsic and photoexcited electrons.

  10. High Temperature Mechanical Behavior of Polycrystalline Alumina from Mixed Nanometer and Micrometer Powders

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.

    2001-01-01

    Sintered aluminum oxide materials were formed using commercial methods from mechanically mixed powders of nano-and micrometer alumina. The powders were consolidated at 1500 and 1600 C with 3.2 and 7.2 ksi applied stress in argon. The conventional micrometer sized powders failed to consolidate. While 100 percent nanometer-sized alumina and its mixture with the micrometer powders achieved less than 99 percent density. Preliminary high temperature creep behavior indicates no super-plastic strains. However high strains (less than 0.65 percent) were generated in the nanometer powder, due to cracks and linked voids initiated by cavitation.

  11. On the Nature of the First Galaxies Selected at 350 Micrometers

    NASA Technical Reports Server (NTRS)

    Khan, Sophia A.; Chanial, Pierre F.; Willner, S. P.; Pearson, Chris P.; Ashby, M. L. N.; Benford, Dominic J.; Clements, David L.; Dye, Simon; Farrah, Duncan; Fazio, G. G.; Huang, J. S.; Lebouteiller, V.; Le Floc'H, Emeric; Mainetti, Gabriele; Harvey Moseley, S.; Negrello, Mattia; Serjeant, Stephen; Shafer, Richard A.; Staguhn, Johannes; Sumner, Timothy J.; Vaccari, Mattia

    2009-01-01

    We present constraints on the nature of the first galaxies selected at 350 micrometers. The sample includes galaxies discovered in the deepest blank-field survey at 350 micrometers (in the Bo6tes Deep Field) and also later serendipitous detections in the Lockman Hole. In determining multiwavelength identifications, the 350 lam position and map resolution of the second generation Submillimeter High Angular Resolution Camera are critical, especially in the cases where multiple radio sources exist and the 24 micrometer counterparts are unresolved. Spectral energy distribution templates are fitted to identified counterparts, and the sample is found to comprise IR-luminous galaxies at 1 < z < 3 predominantly powered by star formation. The first spectrum of a 350 micrometer selected galaxy provides an additional confirmation, showing prominent dust grain features typically associated with star-forming galaxies. Compared to submillimeter galaxies selected at 850 and 1100 micrometers, galaxies selected at 350 micrometers have a similar range of far-infrared color temperatures. However, no 350 micrometer selected sources are reliably detected at 850 or 1100 micrometers. Galaxies in our sample with redshifts 1 < z < 2 show a tight correlation between the far- and mid-infrared flux densities, but galaxies at higher redshifts show a large dispersion in their mid- to far-infrared colors. This implies a limit to which the mid-IR emission traces the far-IR emission in star-forming galaxies. The 350 micrometer flux densities (15 < S(sub 350) < 40 mJy) place these objects near the Herschel/SPIRE 350 micrometer confusion threshold, with the lower limit on the star formation rate density suggesting the bulk of the 350 micrometers contribution will come from less luminous infrared sources and normal galaxies. Therefore, the nature of the dominant source of the 350 micrometers background-star-forming galaxies in the epoch of peak star formation in the universe-could be more effectively

  12. VizieR Online Data Catalog: Micrometer measurements of double stars (Ling+, 2000)

    NASA Astrophysics Data System (ADS)

    Ling, J. F.; Prieto, C.

    2000-10-01

    We report 312 micrometer measurements of 155 visual double stars made with the 50 cm refractor at the Cote D'Azur observatory (Nice, France) and with the 152 cm telescope at Calar Alto observatory (Almeria, Spain). (2 data files).

  13. Some 5-13 micrometer airborne observations of Comet Wilson 1986l: Preliminary results

    NASA Technical Reports Server (NTRS)

    Lynch, David K.; Russell, Ray W.; Witteborn, F. C.; Bregman, Jesse D.; Rank, D. M.; Cohen, M. C; Campins, Humberto C.

    1988-01-01

    Comet Wilson was observed from the Kuiper Airborne Observatory approximately 23.6 and 25.7 Apr. 1987, UT (approx. 3 to 5 days after perihelion) using the NASA-Ames Faint Object Grating Spectrometer. Spectrophotometric data were observed with a 21 inch aperture between 5 and 13 micrometer and with a spectral resolution of 50 to 100. Spectra of the inner coma and nucleus reveal a fairly smooth continuum with little evidence of silicate emission. The 5 to 8 micrometer color temperature of the comet was 300 + or - 15 K, approx. 15 percent higher than the equilibrium blackbody temperature. All three spectra of the nucleus show a new emission feature at approx. 12.25 micrometer approx. two channels (.22 micrometer) wide. Visual and photographic observations made during the time of these observations showed a broad faint, possible two component tail. No outburst activity was observed.

  14. Multiplexed chirp waveform synthesizer

    DOEpatents

    Dudley, Peter A.; Tise, Bert L.

    2003-09-02

    A synthesizer for generating a desired chirp signal has M parallel channels, where M is an integer greater than 1, each channel including a chirp waveform synthesizer generating at an output a portion of a digital representation of the desired chirp signal; and a multiplexer for multiplexing the M outputs to create a digital representation of the desired chirp signal. Preferably, each channel receives input information that is a function of information representing the desired chirp signal.

  15. Infrared images of Jupiter at 5-micrometer wavelength during the Voyager 1 encounter

    NASA Technical Reports Server (NTRS)

    Terrile, R. J.; Capps, R. W.; Backman, D. E.; Becklin, E. E.; Cruikshank, D. P.; Beichman, C. A.; Brown, R. H.; Westphal, J. A.

    1979-01-01

    A coordinated program to observe Jupiter at high spatial resolution in the 5-micrometer wavelength region was undertaken to support Voyager 1 imaging and infrared radiation experiment targeting. Jupiter was observed over a 5-month period from Palomar and Mauna Kea observatories. The frequency of observations allowed the selection of interesting areas for closer Voyager examination and also provided good short-term monitoring of variations in cloud morphology. Significant global changes in the 5-micrometer distribution are seen over this time period.

  16. Acid dissolution experiments - Carbonates and the 6.8-micrometer bands in interplanetary dust particles

    NASA Astrophysics Data System (ADS)

    Sandford, S. A.

    1986-03-01

    A chemical dissolution experiment on an interplanetary dust particle (IDP) showed that carbonates, not acid-insoluble organic compounds, were responsible for virtually all the absorption at 6.8 micrometers seen in the infrared spectra of this particle. The IDP examined had an infrared spectrum characteristic of layer-lattice silicates and belongs to a class of IDP's whose spectra resemble those of protostellar objects like W33 A, which also exhibit a band at 6.8 micrometers.

  17. Focusing of sub-micrometer particles and bacteria enabled by two-dimensional acoustophoresis.

    PubMed

    Antfolk, M; Muller, P B; Augustsson, P; Bruus, H; Laurell, T

    2014-08-01

    Handling of sub-micrometer bioparticles such as bacteria are becoming increasingly important in the biomedical field and in environmental and food analysis. As a result, there is an increased need for less labor-intensive and time-consuming handling methods. Here, an acoustophoresis-based microfluidic chip that uses ultrasound to focus sub-micrometer particles and bacteria, is presented. The ability to focus sub-micrometer bioparticles in a standing one-dimensional acoustic wave is generally limited by the acoustic-streaming-induced drag force, which becomes increasingly significant the smaller the particles are. By using two-dimensional acoustic focusing, i.e. focusing of the sub-micrometer particles both horizontally and vertically in the cross section of a microchannel, the acoustic streaming velocity field can be altered to allow focusing. Here, the focusability of E. coli and polystyrene particles as small as 0.5 μm in diameter in microchannels of square or rectangular cross sections, is demonstrated. Numerical analysis was used to determine generic transverse particle trajectories in the channels, which revealed spiral-shaped trajectories of the sub-micrometer particles towards the center of the microchannel; this was also confirmed by experimental observations. The ability to focus and enrich bacteria and other sub-micrometer bioparticles using acoustophoresis opens the research field to new microbiological applications. PMID:24895052

  18. Effect of Zinc Incorporation on the Performance of Red Light Emitting InP Core Nanocrystals.

    PubMed

    Xi, Lifei; Cho, Deok-Yong; Besmehn, Astrid; Duchamp, Martial; Grützmacher, Detlev; Lam, Yeng Ming; Kardynał, Beata E

    2016-09-01

    This report presents a systematic study on the effect of zinc (Zn) carboxylate precursor on the structural and optical properties of red light emitting InP nanocrystals (NCs). NC cores were assessed using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), energy-dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HRTEM). When moderate Zn:In ratios in the reaction pot were used, the incorporation of Zn in InP was insufficient to change the crystal structure or band gap of the NCs, but photoluminescence quantum yield (PLQY) increased dramatically compared with pure InP NCs. Zn was found to incorporate mostly in the phosphate layer on the NCs. PL, PLQY, and time-resolved PL (TRPL) show that Zn carboxylates added to the precursors during NC cores facilitate the synthesis of high-quality InP NCs by suppressing nonradiative and sub-band-gap recombination, and the effect is visible also after a ZnS shell is grown on the cores. PMID:27551948

  19. A model for rapid synthesis of large volume InP melts

    SciTech Connect

    Iseler, G.; Anselmo, A.P.; Bliss, D.F.; Bryant, G.

    1996-12-31

    The rapid synthesis of InP is routinely carried out in the laboratory by subliming phosphorus into encapsulated liquid In. The authors have constructed the first model of this process by considering the equilibrium vapor pressure over red phosphorus as its temperature increases, and that over In{sub 1{minus}x}P{sub x} as its phosphorus content increases.

  20. X-Ray Photoelectron Spectroscopic Study of Oxidation of InP

    NASA Astrophysics Data System (ADS)

    Shibata, Noboru; Ikoma, Hideaki

    1992-12-01

    InP was oxidized chemically (in boiling deionized water), thermally (dry oxygen, 260°C, 30 min) and chemically under light illumination from a xenon arc lamp. The chemical compositions and their depth distributions from the surface of these oxides as well as the InP native oxide (naturally grown) were studied by angle-resolved X-ray photoelectron spectroscopy (XPS) and XPS combined with in situ Ar+ ion etching. In any oxide, indium is first oxidized to form In2O3 perhaps due to depletion of phosphorus from the InP surface induced by contact annealing, etc. InPO3 and/or InPO4 are then successively grown on an In2O3 or In2O3 rich layer. In and P atoms diffuse through the already grown In2O3 layer and react with oxidant at the surface to form InPO3 and/or InPO4. Light illumination was found to strongly enhance oxidation of InP, and substantially increase InPO3 and InPO4.

  1. Properties of barrier contacts with nanosize TiB{sub x} layers to InP

    SciTech Connect

    Arsentyev, I. N. Bobyl, A. V.; Tarasov, I. S.; Boltovets, N. S. Ivanov, V. N.; Belyaev, A. E.; Kamalov, A. B.; Konakova, R. V. Kudryk, Ya. Ya.; Lytvyn, O. S.; Milenin, V. V.; Russu, E. V.

    2008-07-15

    Structural and electrical properties of Au-TiB{sub x}-nn{sup +}n{sup ++}-InP and TiB{sub x}-nn{sup +}n{sup ++}-InP multilayer barrier structures on standard ('rigid') and soft ('porous')n{sup ++}-InP substrates have been studied, with the semiconductor layers deposited by vapor-phase epitaxy, metallic layers formed by magnetron sputtering, and porous substrates fabricated by electrochemical etching of the standard InP. Samples on porous substrates have the following advantages: leakage currents in their reverse current-voltage characteristics are ten times lower; the range of the exponential rise in current in the forward characteristics is an order of magnitude wider; the changes in the ideality factor and the Schottky barrier height, observed as the contact area varies by a factor of 100, are three and {approx}10 times smaller, respectively; and the structure of the layers is more stable in annealing at up to 800{sup o}C.

  2. Lasing characteristics of InAs quantum dot laers on InP substrate

    NASA Technical Reports Server (NTRS)

    Yang, Y.; Qiu, D.; Uhl, R.; Chacon, R.

    2003-01-01

    Single-stack InAs self-assembled quantum dots (QD) lasers based on InP substrate have been grown by metalorganic vapor phase epitaxy. The narrow ridge waveguide lasers lased up to 260 K in continuous wave operation, and near room temperature in pulsed mode, with wavelengths between 1.59 to 1.74 mu m.

  3. Embossed Bragg Gratings Based on Organically Modified Silane Waveguides in InP.

    PubMed

    Liu, J; Lam, Y L; Chan, Y C; Zhou, Y; Ooi, B S; Tan, G; Yao, J

    2000-09-20

    Considering the large variety of applications for optical glass waveguide gratings, the effective production method of embossing for micropatterning, and the unique advantages of InP-based materials, we expect that hybridization of embossed optical glass waveguide gratings and InP substrates will inevitably lead to new applications in integrated optics. We present our preliminary results of research toward the development of solgel-derived glass waveguide gratings made by embossing on InP. Theoretically, the dependence of the stop-band FWHM and transmission contrast of the grating filter on the grating length, and the relationship between the Bragg grating's reflective wavelength and the dopant concentration in the solgel waveguide, are obtained. Experimentally, using organically modified silane, we solve the problem of mismatching of SiO(2) and InP, and successfully fabricate an embossed glass grating with a second-order Bragg reflection wavelength of 1580 nm and a FWHM of 0.7 nm fabricated upon a solgel waveguide on an InP substrate. PMID:18350088

  4. Status and future directions of InP solar cell research

    NASA Technical Reports Server (NTRS)

    Jain, R. K.; Weinberg, I.

    1992-01-01

    An overview of the current status and future directions of InP space solar cell research is provided. The scope of the paper does not allow us to discuss other recent major developments in InP cell modeling, contacts, and characterization, or developments in other solar cell materials. Solar cells made from InP and related materials are not expected to be used in the near future for terrestrial applications, but significant Air-Mass1.5 (AM1.5) cell efficiencies are given for comparison. This paper deals with the developments in single-junction cells, multijunction tandem cells, and space flight testing, including radiation effects. Concentrator InP solar cells are also discussed, since they offer the possibility of simultaneous thermal and current injection annealing. These cells also promise cost effectiveness and the concentrator elements may provide cells with extra protection from space radiation. The concluding section addresses the steps to be taken in the future and provides guidelines for further research and development.

  5. Amphoteric substitutionality and lattice distortion of Ge in InP

    SciTech Connect

    Yu, K.M.; Moll, A.J.; Walukiewicz, W. ); Derhacobian, N.; Rossington, C. )

    1994-03-21

    We have studied the electrical and structural properties of InP implanted with Ge ions (2[times]10[sup 15]/cm[sup 2]). The implantation was performed at both room temperature (RT) and liquid nitrogen temperature (LNT). After annealing at 850 [degree]C for 5 s, both sets of samples exhibited [ital n]-type conductivity. The [ital n]-type activation efficiency in the RT implanted sample was about a factor of 2 higher than that in the LNT sample (15% and 8%, respectively). Extended x-ray absorption fine structure spectroscopy (EXAFS) shows direct evidence of the amphoteric substitutionality of the Ge atoms in InP for both samples. The ratios of Ge on In sites to Ge on P sites, derived from the EXAFS results, are consistent with the electrical behavior of the samples. The EXAFS results also reveal that the Ge---In and Ge---P bond lengths in the RT sample are very similar to their theoretical values, but are very different from the original In---P bond length. A relaxation in the Ge---In bond is observed in the LNT sample, resulting in a Ge---In bond length very similar to the original In---P bond length.

  6. Submicron gate InP power MISFET's with improved output power density at 18 and 20 GHz

    NASA Technical Reports Server (NTRS)

    Biedenbender, M. D.; Kapoor, Vik J.; Shalkhauser, K. A.; Messick, L. J.; Nguyen, R.; Schmitz, D.; Juergensen, H.

    1991-01-01

    The microwave characteristics are presented at 18 and 20 GHz of submicron gate indium phosphide (InP) metal-insulator-semiconductor field-effect transistors (MISFET's) for high output power density applications. InP power MISFET's were fabricated and the output power density was investigated as a function of drain-source spacing. The best output power density and gain were obtained for drain-source spacing of 3 microns. The output power density is 2.7 times greater than was previously measured for InP MISFET's at 18 and 20 GHz, and the power-added efficiency also increased.

  7. Submicron gate InP power MISFET's with improved output power density at 18 and 20 GHz

    NASA Technical Reports Server (NTRS)

    Biedenbender, Michael D.; Kapoor, Vik J.; Shalkhauser, Kurt A.; Messick, Louis J.; Nguyen, Richard; Schmitz, Dietmar; Jurgensen, Holger

    1991-01-01

    The microwave characteristics are presented at 18 and 20 GHz of submicron gate indium phosphide (InP) metal-insulator-semiconductor field-effect transistors (MISFETs) for high output power density applications. InP power MISFET's were fabricated and the output power density was investigated as a function of drain-source spacing. The best output power density and gain were obtained for drain-source spacing of 3 micron. The output power density is 2.7 times greater than was previously measured for InP MISFET's at 18 and 20 GHz, and the power-added efficiency also increased.

  8. Potential of polarization lidar to provide profiles of CCN- and INP-relevant aerosol parameters

    NASA Astrophysics Data System (ADS)

    Mamouri, R. E.; Ansmann, A.

    2015-12-01

    We investigate the potential of polarization lidar to provide vertical profiles of aerosol parameters from which cloud condensation nucleus (CCN) and ice nucleating particle (INP) number concentrations can be estimated. We show that height profiles of number concentrations of aerosol particles with radius > 50 nm (APC50, reservoir of favorable CCN) and with radius > 250 nm (APC250, reservoir of favorable INP), as well as profiles of the aerosol particle surface area concentration (ASC, used in INP parameterization) can be retrieved from lidar-derived aerosol extinction coefficients (AEC) with relative uncertainties of a factor of around 2 (APC50), and of about 25-50 % (APC250, ASC). Of key importance is the potential of polarization lidar to identify mineral dust particles and to distinguish and separate the aerosol properties of basic aerosol types such as mineral dust and continental pollution (haze, smoke). We investigate the relationship between AEC and APC50, APC250, and ASC for the main lidar wavelengths of 355, 532 and 1064 nm and main aerosol types (dust, pollution, marine). Our study is based on multiyear Aerosol Robotic Network (AERONET) photometer observations of aerosol optical thickness and column-integrated particle size distribution at Leipzig, Germany, and Limassol, Cyprus, which cover all realistic aerosol mixtures of continental pollution, mineral dust, and marine aerosol. We further include AERONET data from field campaigns in Morocco, Cabo Verde, and Barbados, which provide pure dust and pure marine aerosol scenarios. By means of a simple relationship between APC50 and the CCN-reservoir particles (APCCCN) and published INP parameterization schemes (with APC250 and ASC as input) we finally compute APCCCN and INP concentration profiles. We apply the full methodology to a lidar observation of a heavy dust outbreak crossing Cyprus with dust up to 8 km height and to a case during which anthropogenic pollution dominated.

  9. Lattice location of diffused Zn atoms in GaAs and InP single crystals

    SciTech Connect

    Chan, L.Y.; Yu, K.M.; Ben-Tzur, M.; Haller, E.E.; Jaklevic, J.M.; Walukiewicz, W. ); Hanson, C.M. )

    1991-03-01

    We have investigated the saturation phenomenon of the free carrier concentration in {ital p}-type GaAs and InP single crystals doped by zinc diffusion. The free hole saturation occurs at 10{sup 20} cm{sup {minus}3} for GaAs, but the maximum concentration for InP appears at mid 10{sup 18} cm{sup {minus}3}. The difference in the saturation hole concentrations for these materials is investigated by studying the incorporation and the lattice location of the impurity zinc, an acceptor when located on a group III atom site. Zinc is diffused into the III-V wafers in a sealed quartz ampoule. Particle-induced x-ray emission with ion-channeling techniques are employed to determine the exact lattice location of the zinc atoms. We have found that over 90% of all zinc atoms occupy Ga sites in the diffused GaAs samples, while for the InP case, the zinc substitutionality is dependent on the cooling rate of the sample after high-temperature diffusion. For the slowly cooled sample, a large fraction ({similar to}90%) of the zinc atoms form random precipitates of Zn{sub 3}P{sub 2} and elemental Zn. However, when rapidly cooled only 60% of the zinc forms such precipitates while the rest occupies specific sites in the InP. We analyze our results in terms of the amphoteric native defect model. We show that the difference in the electrical activity of the Zn atoms in GaAs and InP is a consequence of the different location of the Fermi level stabilization energy in these two materials.

  10. Fabrication of Sn-3.5Ag Eutectic Alloy Powder by Annealing Sub-Micrometer Sn@Ag Powder Prepared by Citric Acid-Assisted Ag Immersion Plating.

    PubMed

    Chee, Sang-Soo; Choi, Eun Byeol; Lee, Jong-Hyun

    2015-11-01

    A Sn-3.5Ag eutectic alloy powder has been developed by chemically synthesizing sub-micrometer Sn@Ag powder at room temperature. This synthesis was achieved by first obtaining a sub-micrometer Sn powder for the core using a modified variant of the polyol method, and then coating this with a uniformly thin and continuous Ag layer through immersion plating in 5.20 mM citric acid. The citric acid was found to play multiple roles in the Ag coating process, acting as a chelating agent, a reducing agent and a stabilizer to ensure coating uniformity; and as such, the amount used has an immense influence on the coating quality of the Ag shells. It was later verified by transmission electron microscopy and X-ray diffraction analysis that the coated Ag layer transfers to the Sn core via diffusion to form an Ag3Sn phase at room temperature. Differential scanning calorimetry also revealed that the synthesized Sn@Ag powder is nearly transformed into Sn-3.5Ag eutectic alloy powder upon annealing three times at a temperature of up to 250 degrees C, as evidenced by a single melting peak at 220.5 degrees C. It was inferred from this that Sn-3.5Ag eutectic alloy powder can be successfully prepared through the synthesis of core Sn powders by a modified polyol method, immersion plating using citric acid, and annealing, in that order. PMID:26726525

  11. PULSE SYNTHESIZING GENERATOR

    DOEpatents

    Kerns, Q.A.

    1963-08-01

    >An electronlc circuit for synthesizing electrical current pulses having very fast rise times includes several sinewave generators tuned to progressively higher harmonic frequencies with signal amplitudes and phases selectable according to the Fourier series of the waveform that is to be synthesized. Phase control is provided by periodically triggering the generators at precisely controlled times. The outputs of the generators are combined in a coaxial transmission line. Any frequency-dependent delays that occur in the transmission line can be readily compensated for so that the desired signal wave shape is obtained at the output of the line. (AEC)

  12. Wisdom, Intelligence & Creativity Synthesized

    ERIC Educational Resources Information Center

    Sternberg, Robert J.

    2009-01-01

    How is it that smart administrators who want to do a good job often find themselves in situations that degenerate into confrontation and, ultimately, termination? In this article, the author discusses why in terms of a model of leadership--which he refers to it as WICS, an acronym for wisdom, intelligence and creativity synthesized. He describes…

  13. Synthesized night vision goggle

    NASA Astrophysics Data System (ADS)

    Zhou, Haixian

    2000-06-01

    A Synthesized Night Vision Goggle that will be described int his paper is a new type of night vision goggle with multiple functions. It consists of three parts: main observing system, picture--superimposed system (or Cathode Ray Tube system) and Charge-Coupled Device system.

  14. First-principles study of the electronic properties of wurtzite, zinc-blende, and twinned InP nanowires

    SciTech Connect

    Li, Dengfeng; Wang, Zhiguo; Gao, Fei

    2010-12-17

    The electronic properties of zinc blende, wurtzite, and rotationally twinned InP nanowires were studied using first-principles calculations. The results show that all the simulated nanowires exhibit a semiconducting character, and the band gap decreases with increasing the nanowire size. The band gap difference between the zinc blende, wurtzite, and twinned InP nanowires and a bulk InP can be described by several formulas proportional to the diameter of nanowires. The valence band maximum (VBM) and conduction band minimum (CBM) originate mainly from the p-orbitals of the P atoms and s-orbitals of the In atoms at the core regions of the nanowires, respectively. The hexagonal (2H) stacking inside the cubic (3C) stacking has no effect on the electronic properties of thin InP nanowires.

  15. Temperature coefficients and radiation induced DLTS spectra of MOCVD grown n(+)p InP solar cells

    NASA Technical Reports Server (NTRS)

    Walters, Robert J.; Statler, Richard L.; Summers, Geoffrey P.

    1991-01-01

    The effects of temperature and radiation on n(+)p InP solar cells and mesa diodes grown by metallorganic chemical vapor deposition (MOCVD) were studied. It was shown that MOCVD is capable of consistently producing good quality InP solar cells with Eff greater than 19 percent which display excellent radiation resistance due to minority carrier injection and thermal annealing. It was also shown that universal predictions of InP device performance based on measurements of a small group of test samples can be expected to be quite accurate, and that the degradation of an InP device due to any incident particle spectrum should be predictable from a measurement following a single low energy proton irradiation.

  16. Direct observation of the amphoteric behavior of Ge in InP modified by P co-implantation

    SciTech Connect

    Yu, K.M.; Ridgway, M.C.

    1997-08-01

    We have investigated the preferred substitution of Ge in InP by altering the local stoichiometry of the InP substrate. By co-implanting P with Ge to create a group V-rich environment, we directly observed an enhancement of the Ge substituting the In sublattice. A corresponding increase in the n-type conductivity by as much as three times was also observed in the Ge and P co-implanted sample. However, due to the altered local stoichiometry, the Ge solubility in InP was reduced by a factor of 2. The residual crystalline damage in the P co-implanted InP after annealing was also decreased due to the compensation of the nonstoichiometry related damage by the excess P in the middle of the implanted region. {copyright} {ital 1997 American Institute of Physics.}

  17. Observational constraints on the atmospheres of Uranus and Neptune from new measurements near 10 micrometers

    SciTech Connect

    Tokunaga, A.T.; Caldwell, J.

    1983-10-01

    Uranus was detected at 10.3, 11.6 and 12.5 micrometers approximately 1 micrometer spectral bandpasses, with respective brightness temperatures of 74.0 + 0.9 or -1.1, 67.6 + 0.5 or -0.7, and 65.5 + 0.6 or -0.7 K and the first detection of Neptune at 10.3 micrometers with a brightness temperature of 77.5 + 0.7 or -0.9 K. We also detected Neptune at 11.36 micrometers with 2 percent spectral resolution at 81.0 + 0.8 or -0.9 K. The 10 micrometers continuous of both Uranus and Neptune may in part be due to reflected solar radiation as well as thermal emission. If all of the observed flux is reflected light, then the maximum geometric albedo of Uranus is 0.115 + or - 0.020, and that of Neptune is 0.229 + or - 0.043. In the context of previous observations in this region, the maximum stratospheric C2H6 mixing ratio is found to be 3 x 10 to the -8 power for Uranus and 3 x 10 to the -6 power for Neptune. A value for the maximum mixing ratio in the stratosphere of Neptune on the order of 1 - 0.004 appears to be consistent with the available data. Previously announced in STAR as N83-29155.

  18. Performance, defect behavior and carrier enhancement in low energy, proton irradiated p+nn+ InP solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Rybicki, G. C.; Vargas-Aburto, C.; Jain, R. K.; Scheiman, D.

    1994-01-01

    The highest AMO efficiency (19.1 percent) InP solar cell consisted of an n+pp+ structure epitaxially grown on a p+ InP substrate. However, the high cost and relative fragility of InP served as motivation for research efforts directed at heteroepitaxial growth of InP on more viable substrates. The highest AMO efficiency (13.7 percent) for this type of cell was achieved using a GaAs substrate. Considering only cost and fracture toughness, Si would be the preferred substrate. The fact that Si is a donor in InP introduces complexities which are necessary in order to avoid the formation of an efficiency limiting counterdiode. One method used to overcome this problem lies in employing an n+p+ tunnel junction in contact with the cell's p region. A simpler method consists of using an n+ substrate and processing the cell in the p+ nn+ configuration. This eliminates the need for a tunnel junction. Unfortunately, the p/n configuration has received relatively little attention the best cell with this geometry having achieved an efficiency of 17 percent. Irradiation of these homoepitaxial cells, with 1 Mev electrons, showed that they were slightly more radiation resistant than diffused junction n/p cells. Additional p/n InP cells have been processed by some activity aimed at diffusion. Currently, there has been some activity aimed at producing heteroepitaxial p+nn+ InP cells using n+ Ge substrates. Since, like Si, Ge is an n-dopant in InP, use of this configuration obviates the need for a tunnel junction. Obviously, before attempting to process heteroepitaxial cells, one must produce a reasonably good homoepitaxial cell. In the present case we focus our attention on homoepitaxially on an n+ Ge substrate.

  19. Potential of polarization lidar to provide profiles of CCN- and INP-relevant aerosol parameters

    NASA Astrophysics Data System (ADS)

    Mamouri, Rodanthi-Elisavet; Ansmann, Albert

    2016-05-01

    We investigate the potential of polarization lidar to provide vertical profiles of aerosol parameters from which cloud condensation nucleus (CCN) and ice nucleating particle (INP) number concentrations can be estimated. We show that height profiles of particle number concentrations n50, dry considering dry aerosol particles with radius > 50 nm (reservoir of CCN in the case of marine and continental non-desert aerosols), n100, dry (particles with dry radius > 100 nm, reservoir of desert dust CCN), and of n250, dry (particles with dry radius > 250 nm, reservoir of favorable INP), as well as profiles of the particle surface area concentration sdry (used in INP parameterizations) can be retrieved from lidar-derived aerosol extinction coefficients σ with relative uncertainties of a factor of 1.5-2 in the case of n50, dry and n100, dry and of about 25-50 % in the case of n250, dry and sdry. Of key importance is the potential of polarization lidar to distinguish and separate the optical properties of desert aerosols from non-desert aerosol such as continental and marine particles. We investigate the relationship between σ, measured at ambient atmospheric conditions, and n50, dry for marine and continental aerosols, n100, dry for desert dust particles, and n250, dry and sdry for three aerosol types (desert, non-desert continental, marine) and for the main lidar wavelengths of 355, 532, and 1064 nm. Our study is based on multiyear Aerosol Robotic Network (AERONET) photometer observations of aerosol optical thickness and column-integrated particle size distribution at Leipzig, Germany, and Limassol, Cyprus, which cover all realistic aerosol mixtures. We further include AERONET data from field campaigns in Morocco, Cabo Verde, and Barbados, which provide pure dust and pure marine aerosol scenarios. By means of a simple CCN parameterization (with n50, dry or n100, dry as input) and available INP parameterization schemes (with n250, dry and sdry as input) we finally compute

  20. Growth of InP directly on Si by corrugated epitaxial lateral overgrowth

    NASA Astrophysics Data System (ADS)

    Metaferia, Wondwosen; Kataria, Himanshu; Sun, Yan-Ting; Lourdudoss, Sebastian

    2015-02-01

    In an attempt to achieve an InP-Si heterointerface, a new and generic method, the corrugated epitaxial lateral overgrowth (CELOG) technique in a hydride vapor phase epitaxy reactor, was studied. An InP seed layer on Si (0 0 1) was patterned into closely spaced etched mesa stripes, revealing the Si surface in between them. The surface with the mesa stripes resembles a corrugated surface. The top and sidewalls of the mesa stripes were then covered by a SiO2 mask after which the line openings on top of the mesa stripes were patterned. Growth of InP was performed on this corrugated surface. It is shown that growth of InP emerges selectively from the openings and not on the exposed silicon surface, but gradually spreads laterally to create a direct interface with the silicon, hence the name CELOG. We study the growth behavior using growth parameters. The lateral growth is bounded by high index boundary planes of {3 3 1} and {2 1 1}. The atomic arrangement of these planes, crystallographic orientation dependent dopant incorporation and gas phase supersaturation are shown to affect the extent of lateral growth. A lateral to vertical growth rate ratio as large as 3.6 is achieved. X-ray diffraction studies confirm substantial crystalline quality improvement of the CELOG InP compared to the InP seed layer. Transmission electron microscopy studies reveal the formation of a direct InP-Si heterointerface by CELOG without threading dislocations. While CELOG is shown to avoid dislocations that could arise due to the large lattice mismatch (8%) between InP and Si, staking faults could be seen in the layer. These are probably created by the surface roughness of the Si surface or SiO2 mask which in turn would have been a consequence of the initial process treatments. The direct InP-Si heterointerface can find applications in high efficiency and cost-effective Si based III-V semiconductor multijunction solar cells and optoelectronics integration.

  1. Observations of far-infrared fine structure lines: o III88.35 micrometer and oI 63.2 micrometer

    NASA Technical Reports Server (NTRS)

    Storey, J. W. V.; Watson, D. M.; Townes, C. H.

    1979-01-01

    Observations of the O III 88.35 micrometer line and the O I63.2 micrometer were made with a far infrared spectrometer. The sources M17, NGC 7538, and W51 were mapped in the O III line with 1 arc minute resolution and the emission is found to be quite widespread. In all cases the peak of the emission coincides with the maximum radio continuum. The far infrared continuum was mapped simultaneously and in M17, NGC 7538, and W51 the continuum peak is found to be distinct from the center of ionization. The O III line was also detected in W3, W49, and in a number of positions in the Orion nebula. Upper limits were obtained on NGS 7027, NGC 6572, DR21, G29.9-0.0 and M82. The 63.2 micrometer O I line was detected in M17, M42, and marginally in DR21. A partial map of M42 in this line shows that most of the emission observed arises from the Trapezium and from the bright optical bar to the southeast.

  2. On the usage of classical nucleation theory in quantification of the impact of bacterial INP on weather and climate

    NASA Astrophysics Data System (ADS)

    Sahyoun, Maher; Wex, Heike; Gosewinkel, Ulrich; Šantl-Temkiv, Tina; Nielsen, Niels W.; Finster, Kai; Sørensen, Jens H.; Stratmann, Frank; Korsholm, Ulrik S.

    2016-08-01

    Bacterial ice-nucleating particles (INP) are present in the atmosphere and efficient in heterogeneous ice-nucleation at temperatures up to -2 °C in mixed-phase clouds. However, due to their low emission rates, their climatic impact was considered insignificant in previous modeling studies. In view of uncertainties about the actual atmospheric emission rates and concentrations of bacterial INP, it is important to re-investigate the threshold fraction of cloud droplets containing bacterial INP for a pronounced effect on ice-nucleation, by using a suitable parameterization that describes the ice-nucleation process by bacterial INP properly. Therefore, we compared two heterogeneous ice-nucleation rate parameterizations, denoted CH08 and HOO10 herein, both of which are based on classical-nucleation-theory and measurements, and use similar equations, but different parameters, to an empirical parameterization, denoted HAR13 herein, which considers implicitly the number of bacterial INP. All parameterizations were used to calculate the ice-nucleation probability offline. HAR13 and HOO10 were implemented and tested in a one-dimensional version of a weather-forecast-model in two meteorological cases. Ice-nucleation-probabilities based on HAR13 and CH08 were similar, in spite of their different derivation, and were higher than those based on HOO10. This study shows the importance of the method of parameterization and of the input variable, number of bacterial INP, for accurately assessing their role in meteorological and climatic processes.

  3. A 2.7 Micrometer Feature and Other Spectral Signatures of Asteroid 951 Gaspra

    NASA Astrophysics Data System (ADS)

    Granahan, J. C.

    2011-12-01

    The NASA Galileo spacecraft observed asteroid 951 Gaspra on October 29, 1991 with the Near Infrared Mapping Spectrometer (NIMS) at wavelengths ranging from 0.7 - 5.2 micrometers [Carlson et al., 1992]. Work is being conducted to produce a radiance calibrated spectral image of a 17 channel, 1.3 km per pixel NIMS observation of 951 Gaspra for the NASA Planetary Data System (PDS). Analysis [Granahan, 2011] of this S asteroid data has yielded a detection of a 2.7 micrometer absorption feature in all of the observed surface pixels of this data set. Also measured [Granahan, 2011] were groups of spectra that possessed different band centers near 1.0 micrometers and band depths at 2.0 micrometers due to the minerals olivine and pyroxene. The 2.7 micrometer absorption feature has its strongest absorption within Yeates Regio. Yeates Regio is one of 951 Gaspra's basins [Veverka et al., 1994]. The absorption is weakest in the vicinity of the asteroid's ridges. A material that has an absorption at 2.7 micrometers is structural hydroxyl (OH). The carbonaceous chondrite meteorite Murchison contains structural hydroxyl that creates such a spectral feature [Rivkin et al., 2002]. It has also been observed in the spectra of montmorrilonite [McAdam and Hibbitts, 2011]. Updated measurements of olivine and pyroxene spectral bands were also conducted for this radiance data of 951 Gaspra. Two groups of spectra were observed to be differentiated by spectral band centers measured at 0.99 and 1.05 micrometers with corresponding differences of band depth around 2.0 micrometers. The 0.99 micrometer group of spectra possesses the larger 2.0 micrometer band depth. These families of spectra correspond to those of SI (1.05 micrometer group) and SIII (0.99 micrometer group) classes [Gaffey et al., 1993] of the S asteroids. They are distinct from ordinary chondrite meteorites and imply the occurrence of differentiation on 951 Gaspra. This 17 channel radiance spectral image is being packaged as a

  4. Nanoscale Size-Selective Deposition of Nanowires by Micrometer Scale Hydrophilic Patterns

    PubMed Central

    He, Yong; Nagashima, Kazuki; Kanai, Masaki; Meng, Gang; Zhuge, Fuwei; Rahong, Sakon; Li, Xiaomin; Kawai, Tomoji; Yanagida, Takeshi

    2014-01-01

    Controlling the post-growth assembly of nanowires is an important challenge in the development of functional bottom-up devices. Although various methods have been developed for the controlled assembly of nanowires, it is still a challenging issue to align selectively heterogeneous nanowires at desired spatial positions on the substrate. Here we report a size selective deposition and sequential alignment of nanowires by utilizing micrometer scale hydrophilic/hydrophobic patterned substrate. Nanowires dispersed within oil were preferentially deposited only at a water/oil interface onto the hydrophilic patterns. The diameter size of deposited nanowires was strongly limited by the width of hydrophilic patterns, exhibiting the nanoscale size selectivity of nanowires deposited onto micrometer scale hydrophilic patterns. Such size selectivity was due to the nanoscale height variation of a water layer formed onto the micrometer scale hydrophilic patterns. We successfully demonstrated the sequential alignment of different sized nanowires on the same substrate by applying this size selective phenomenon. PMID:25087699

  5. Total Syntheses of Perenniporides.

    PubMed

    Morita, Masao; Ohmori, Ken; Suzuki, Keisuke

    2015-11-20

    The total syntheses of perenniporide A (1) and related compounds have been achieved. Starting from 1,3,5-trifluorobenzene (9), difluorodienone 6 was obtained by oxidative dearomatization, which served as a platform for the high-pressure cycloaddition and for the introduction of the C3-methoxy group. The synthesis allowed access to the natural congeners 2 and 3, enabling assignment of the absolute structures of these natural products. PMID:26555442

  6. A micrometer-size movable light emitting area in a resonant tunneling light emitting diode

    NASA Astrophysics Data System (ADS)

    Pettinari, G.; Balakrishnan, N.; Makarovsky, O.; Campion, R. P.; Polimeni, A.; Capizzi, M.; Patanè, A.

    2013-12-01

    We report on the fabrication of a micrometer-size movable light emitting area in a GaAs/AlAs quantum well resonant tunneling p-i-n diode. The spatial position of the micrometer-size light emitting area shifts linearly with increasing applied bias, up to 30 μm for a bias increment of 0.2 V. Also, the simultaneous resonant tunneling injection of both electrons and holes into the quantum well states is achieved at specific positions of the diode, thus resulting in a tenfold increase of the electroluminescence intensity.

  7. The Herschel ATLAS: Evolution of the 250 Micrometer Luminosity Function Out to z = 0.5

    NASA Technical Reports Server (NTRS)

    Dye, S.; Dunne, L.; Eales, S.; Smith, D. J. B.; Amblard, A.; Auld, R.; Baes, M.; Baldry, I. K.; Bamford, S.; Blain, A. W.; Bonfield, D. G.; Bremer, M.; Burgarella, D.; Buttiglione, S.; Cameron, E.; Cava, A.; Clements, D. L.; Cooray, A.; Croom, S.; Dariush, A.; de Zotti, G.; Driver, S.; Dunlop, J. S.; Frayer, D.; Leeuw, L.

    2010-01-01

    We have determined the luminosity function of 250 micrometer-selected galaxies detected in the approximately equal to 14 deg(sup 2) science demonstration region of the Herschel-ATLAS project out to a redshift of z = 0.5. Our findings very clearly show that the luminosity function evolves steadily out to this redshift. By selecting a sub-group of sources within a fixed luminosity interval where incompleteness effects are minimal, we have measured a smooth increase in the comoving 250 micrometer luminosity density out to z = 0.2 where it is 3.6(sup +1.4) (sub -0.9) times higher than the local value.

  8. Infrared images of jupiter at 5-micrometer wavelength during the voyager 1 encounter.

    PubMed

    Terrile, R J; Capps, R W; Backman, D E; Becklin, E E; Cruikshank, D P; Beichman, C A; Brown, R H; Westphal, J A

    1979-06-01

    A coordinated program to observe Jupiter at high spatial resolution in the 5-micrometer wavelength region was undertaken to support Voyager 1 imaging and infrared radiation experiment targeting. Jupiter was observed over a 5-month period from Palomar and Mauna Kea observatories. The frequency of observations allowed the selection of interesting areas for closer Voyager examination and also provided good short-term monitoring of variations in cloud morphology. Significant global changes in the 5-micrometer distribution are seen over this time period. PMID:17800441

  9. Wideband 1.064 micrometer detector evaluation. [for application to space laser communication systems

    NASA Technical Reports Server (NTRS)

    Green, S. I.

    1977-01-01

    Several types of communications detectors for use in a 400 Mbps 1.064 micrometer laser communication system were evaluated and characterized. The communication system Bit Error Rate (BER) performance was measured, and test results for the best detector of each type are summarized. The complete BER curves are presented. The 400 Mbps 1.064 micrometer communication system receiver test bed is described. The best performance levels which can be achieved by focusing the signal to diffraction limited spots on the photosensitive area are cited.

  10. Unusual nanostructures of “lattice matched” InP on AlInAs

    SciTech Connect

    Gocalinska, A. Manganaro, M.; Juska, G.; Dimastrodonato, V.; Thomas, K.; Pelucchi, E.; Joyce, B. A.; Zhang, J.; Vvedensky, D. D.

    2014-04-07

    We show that the morphology of the initial monolayers of InP on Al{sub 0.48}In{sub 0.52}As grown by metalorganic vapor-phase epitaxy does not follow the expected layer-by-layer growth mode of lattice-matched systems, but instead develops a number of low-dimensional structures, e.g., quantum dots and wires. We discuss how the macroscopically strain-free heteroepitaxy might be strongly affected by local phase separation/alloying-induced strain and that the preferred aggregation of adatom species on the substrate surface and reduced wettability of InP on AlInAs surfaces might be the cause of the unusual (step) organization and morphology.

  11. Effect of dislocations on properties of heteroepitaxial InP solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Swartz, C. K.; Curtis, H. B.; Brinker, D. J.; Jenkins, P.; Faur, M.

    1991-01-01

    The apparently unrelated phenomena of temperature dependency, carrier removal and photoluminescence are shown to be affected by the high dislocation densities present in heteroepitaxial InP solar cells. Using homoepitaxial InP cells as a baseline, it is found that the relatively high dislocation densities present in heteroepitaxial InP/GaAs cells lead to increased volumes of dVoc/dt and carrier removal rate and substantial decreases in photoluminescence spectral intensities. With respect to dVoc/dt, the observed effect is attributed to the tendency of dislocations to reduce Voc. Although the basic cause for the observed increase in carrier removal rate is unclear, it is speculated that the decreased photoluminescence intensity is attributable to defect levels introduced by dislocations in the heteroepitaxial cells.

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

    SciTech Connect

    Bortoleto, J.R.R.; Gutierrez, H.R.; Cotta, M.A.; Bettini, J.

    2005-07-04

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

  13. The effect of phosphorus and sulfur treatment on the surface properties of InP

    NASA Technical Reports Server (NTRS)

    Iyer, R.; Chang, R. R.; Dubey, A.; Lile, D. L.

    1988-01-01

    Experimental results are presented for InP surfaces treated by using red phosphorus as a source to create an excess overpressure of phosphorus during annealing and prior to silicon dioxide deposition. The surface has been probed by in situ photoluminescence, noncontacting remote gate C-V, and conventional high-frequency and quasi-static C-V methods. A study has also been made of the surface of sulfurized InP following heating in aqueous (NH4)2S(x). MISFETs fabricated using the benefits of these surface treatments show high transconductances and stabilities approaching those of thermal SiO2/Si with less than 5-percent variation in drain current over a 12-hr period.

  14. Temperature dependence and origin of InP(100) reflectance anisotropy down to 20 K

    NASA Astrophysics Data System (ADS)

    Visbeck, S.; Hannappel, T.; Zorn, M.; Zettler, J.-T.; Willig, F.

    2001-06-01

    InP(100) surfaces were investigated by reflectance anisotropy spectroscopy (RAS) in the temperature range between 20 and 840 K. Surfaces were prepared via metal-organic chemical vapor deposition (MOCVD) resulting in P-terminated (2×1)-like and In-terminated (2×4) reconstructions. Additionally, intermediate states of different phosphorus coverage were prepared. RA spectra were recorded both inside the MOCVD reactor and in an ultrahigh vacuum chamber. At low temperatures, features in the RA spectra sharpened significantly due to the reduced lattice vibrations and electron-phonon interactions. The temperature-dependent energy shift of specific RAS features was determined between 20 and 840 K, and fitted with a model containing the Bose-Einstein occupation factor for phonons. The respective fitting parameters were compared to those of the InP bulk critical-point transitions nearby. Careful data analysis provided evidence for surface transitions and surface modified bulk transitions in the RA spectra.

  15. Chemically prepared well-ordered InP(0 0 1) surfaces

    NASA Astrophysics Data System (ADS)

    Tereshchenko, O. E.; Paget, D.; Chiaradia, P.; Placidi, E.; Bonnet, J. E.; Wiame, F.; Taleb-Ibrahimi, A.

    2006-08-01

    In the present work HCl-isopropanol treated and vacuum annealed InP(0 0 1) surfaces were studied by means of low-energy electron diffraction (LEED), soft X-ray photoemission (SXPS), and reflectance anisotropy (RAS) spectroscopies. The treatment removes the natural oxide and leaves on the surface a physisorbed overlayer containing InCl x and phosphorus. Annealing at 230 °C induces desorption of InCl x overlayer and reveals a P-rich (2 × 1) surface. Subsequent annealing at higher temperature induces In-rich (2 × 4) surface. The structural properties of chemically prepared InP(0 0 1) surfaces were found to be similar to those obtained by decapping of As/P-capped epitaxial layers.

  16. Surface passivation of InP solar cells with InAlAs layers

    NASA Technical Reports Server (NTRS)

    Jain, Raj K.; Flood, Dennis J.; Landis, Geoffrey A.

    1993-01-01

    The efficiency of indium phosphide solar cells is limited by high values of surface recombination. The effect of a lattice-matched In(0.52)Al(0.48)As window layer material for InP solar cells, using the numerical code PC-1D is investigated. It was found that the use of InAlAs layer significantly enhances the p(+)n cell efficiency, while no appreciable improvement is seen for n(+)p cells. The conduction band energy discontinuity at the heterojunction helps in improving the surface recombination. An optimally designed InP cell efficiency improves from 15.4 percent to 23 percent AMO for a 10 nm thick InAlAs layer. The efficiency improvement reduces with increase in InAlAs layer thickness, due to light absorption in the window layer.

  17. Ohmic contacts to p-type InP using Be-Au metallization

    NASA Astrophysics Data System (ADS)

    Temkin, H.; McCoy, R. J.; Keramidas, V. G.; Bonner, W. A.

    1980-03-01

    A new contact to p-InP is reported with beryllium as the acceptor. The contact consists of a thin layer of 3 wt.% Be in Au alloy and a Au overlay sequentially deposited by e-gun evaporation. Alloying at 420 °C yields Ohmic contacts with low specific contact resistance rc⩽8×10-5 Ω cm2 for InP with NA-ND ≲1×1018 cm-3. To minimize the tendency of InP for thermal dissociation, the alloying temperature can be reduced to 375 °C by adding a thin Pd layer at the semiconductor metallization interface. This is achieved at the expense of a slight increase in resistance.

  18. Far field emission profile of pure wurtzite InP nanowires

    SciTech Connect

    Bulgarini, Gabriele Reimer, Michael E.; Zwiller, Val; Dalacu, Dan; Poole, Philip J.; Lapointe, Jean

    2014-11-10

    We report on the far field emission profile of pure wurtzite InP nanowires in comparison to InP nanowires with predominantly zincblende crystal structure. The emission profile is measured on individual nanowires using Fourier microscopy. The most intense photoluminescence of wurtzite nanowires is collected at small angles with respect to the nanowire growth axis. In contrast, zincblende nanowires present a minimum of the collected light intensity in the direction of the nanowire growth. Results are explained by the orientation of electric dipoles responsible for the photoluminescence, which is different from wurtzite to zincblende. Wurtzite nanowires have dipoles oriented perpendicular to the nanowire growth direction, whereas zincblende nanowires have dipoles oriented along the nanowire axis. This interpretation is confirmed by both numerical simulations and polarization dependent photoluminescence spectroscopy. Knowledge of the dipole orientation in nanostructures is crucial for developing a wide range of photonic devices such as light-emitting diodes, photodetectors, and solar cells.

  19. Minority-carrier lifetime in InP as a function of light bias

    NASA Technical Reports Server (NTRS)

    Yater, Jane A.; Weinberg, I.; Jenkins, Phillip P.; Landis, Geoffrey A.

    1995-01-01

    Minority-carrier lifetime in InP is studied as a function of doping level and laser intensity using time-resolved photoluminescence. A continuous wave diode laser illuminates bulk InP and acts as a light bias, injecting a steady-state concentration of carriers. A 200 ps laser pulse produces a small transient signal on top of the steady-state luminescence, allowing lifetime to be measured directly as a function of incident intensity. For p-InP, lifetime increases with light bias up to a maximum value. Bulk recombination centers are presumably filled to saturation, allowing minority carriers to live longer. The saturation bias scales with dopant concentration for a particular dopant species. As light bias is increased for n-InP, minority-carrier lifetime increases slightly but then decreases, suggesting radiative recombination as a dominant decay mechanism.

  20. InP photonic wire waveguide using InAlAs oxide cladding layer.

    PubMed

    Takenaka, Mitsuru; Nakano, Yoshiaki

    2007-06-25

    We proposed a novel InP based photonic wire waveguide with an InAlAs oxide cladding. The InGaAsP/InAlAs-oxide structure in the vertical direction provides an ultrahigh index contrast waveguide, and it allows a bend radius of a few mum with no vertical leakage loss. The InP photonic wire waveguide with a 500x300-nm rectangular channel core (refractive index n ~ 3.36) and an InAlAs oxide cladding (n ~ 2.4) was numerically analyzed using the three-dimensional time-domain beam propagation method (3D TD-BPM). We predicted that the U-bend waveguide with a 3-mum bend radius can be realized with the propagation loss of < 0.5 dB. PMID:19547173

  1. Effects of Be doping on InP nanowire growth mechanisms

    NASA Astrophysics Data System (ADS)

    Yee, R. J.; Gibson, S. J.; Dubrovskii, V. G.; LaPierre, R. R.

    2012-12-01

    Be-doped InP nanowires were grown by the gold-assisted vapour-liquid-solid mechanism in a gas source molecular beam epitaxy system. The InP nanowire length versus diameter [L(D)] dependence revealed an unexpected transition with increasing Be dopant concentration. At Be dopant concentration below ˜1018 cm-3, nanowires exhibited the usual inverse L(D) relationship, indicating a diffusion-limited growth regime. However, as dopant concentration increased, the nanowire growth rate was suppressed for small diameters, resulting in an unusual L(D) dependence that increased before saturating in height at about 400 nm. The cause of this may be a change in the droplet chemical potential, introducing a barrier to island nucleation. We propose a model accounting for the limitations of diffusion length and monolayer nucleation to explain this behaviour.

  2. Observation of edge-facets in <100> InP crystals grown by LEC method

    NASA Astrophysics Data System (ADS)

    Shibata, Masatomo; Sasaki, Yukio; Inada, Tomoki; Kuma, Shoji

    1990-05-01

    The growth of edge-facets on <100> InP crystals has been investigated using microscopy. The solid/liquid interface in the region of edge-facets was found to have a knife-edged shape, while that of a region without facets had a smooth shape. The irregular patterns of edge-facets point to instability in the growth at the periphery of a crystal, and this instability is found to be related to the generation of twins.

  3. InP and GaAs characterization with variable stoichiometry obtained by molecular spray

    NASA Technical Reports Server (NTRS)

    Massies, J.; Linh, N. T.; Olivier, J.; Faulconnier, P.; Poirier, R.

    1979-01-01

    Both InP and GaAs surfaces were studied in parallel. A molecular spray technique was used to obtain two semiconductor surfaces with different superficial compositions. The structures of these surfaces were examined by electron diffraction. Electron energy loss was measured spectroscopically in order to determine surface electrical characteristics. The results are used to support conclusions relative to the role of surface composition in establishing a Schottky barrier effect in semiconductor devices.

  4. Surface characterization of InP trenches embedded in oxide using scanning probe microscopy

    SciTech Connect

    Mannarino, Manuel E-mail: manuelmannarino@gmail.com; Chintala, Ravi; Vandervorst, Wilfried; Moussa, Alain; Merckling, Clement; Eyben, Pierre; Paredis, Kristof

    2015-12-14

    Metrology for structural and electrical analyses at device level has been identified as one of the major challenges to be resolved for the sub-14 nm technology nodes. In these advanced nodes, new high mobility semiconductors, such as III–V compounds, are grown in narrow trenches on a Si substrate. Probing the nature of the defects, the defect density, and the role of processing steps on the surface of such structures are prime metrology requirements. In order to enable defect analysis on a (III–V) surface, a proper sample preparation for oxide removal is of primary importance. In this work, the effectiveness of different chemical cleanings and thermal annealing procedures is investigated on both blanket InP and oxide embedded InP trenches by means of scanning probe microscopy techniques. It is found that the most effective approach is a combination of an HCl-based chemical cleaning combined with a low-temperature thermal annealing leading to an oxide free surface with atomically flat areas. Scanning tunneling microscopy (STM) has been the preferred method for such investigations on blanket films due to its intrinsic sub-nm spatial resolution. However, its application on oxide embedded structures is non-trivial. To perform STM on the trenches of interest (generally <20 nm wide), we propose a combination of non-contact atomic force microscopy and STM using the same conductive atomic force microscopy tip Our results prove that with these procedures, it is possible to perform STM in narrow InP trenches showing stacking faults and surface reconstruction. Significant differences in terms of roughness and terrace formation are also observed between the blanket and the oxide embedded InP.

  5. W-Band InP Wideband MMIC LNA with 30K Noise Temperature

    NASA Technical Reports Server (NTRS)

    Weinreb, S.; Lai, R.; Erickson, N.; Gaier, T.; Wielgus, J.

    2000-01-01

    This paper describe a millimeter wave low noise amplifier with extraordinary low noise, low consumption, and wide frequency range. These results are achieved utilizing state-of-the-art InP HEMT transistors coupled with CPW circuit design. The paper describes the transistor models, modeled and measured on-wafer and in-module results at both 300K am 24K operating temperatures for many samples of the device.

  6. Schottky Barriers Based on Nanoporous InP with Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Barlas, Tetyana; Dmitruk, Mykola; Kotova, Nataliya; Mamykin, Sergii

    2016-04-01

    Schottky barrier structures based on nanoporous InP with inclusion of Au nanoparticles and evaporated semitransparent Au film have been made. The spectra of short-circuit photocurrent in the visible range and current-voltage characteristics have been measured. Prepared structures are characterized by increased photocurrent due to the microrelief interface and surface plasmon excitation in gold nanoparticles as well as increased surface recombination especially in the short wavelength region.

  7. High-efficiency ultrasmall polarization converter in InP membrane.

    PubMed

    Pello, Josselin; van der Tol, Jos; Keyvaninia, Shahram; van Veldhoven, René; Ambrosius, Huub; Roelkens, Gunther; Smit, Meint

    2012-09-01

    An ultrasmall (<10  μm length) polarization converter in InP membrane is fabricated and characterized. The device relies on the beating between the two eigenmodes of chemically etched triangular waveguides. Measurements show a very high polarization conversion efficiency of >99% with insertion losses of <-1.2  dB at a wavelength of 1.53 μm. Furthermore, our design is found to be broadband and tolerant to dimension variations. PMID:22940999

  8. Surface characterization of InP trenches embedded in oxide using scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Mannarino, Manuel; Chintala, Ravi; Moussa, Alain; Merckling, Clement; Eyben, Pierre; Paredis, Kristof; Vandervorst, Wilfried

    2015-12-01

    Metrology for structural and electrical analyses at device level has been identified as one of the major challenges to be resolved for the sub-14 nm technology nodes. In these advanced nodes, new high mobility semiconductors, such as III-V compounds, are grown in narrow trenches on a Si substrate. Probing the nature of the defects, the defect density, and the role of processing steps on the surface of such structures are prime metrology requirements. In order to enable defect analysis on a (III-V) surface, a proper sample preparation for oxide removal is of primary importance. In this work, the effectiveness of different chemical cleanings and thermal annealing procedures is investigated on both blanket InP and oxide embedded InP trenches by means of scanning probe microscopy techniques. It is found that the most effective approach is a combination of an HCl-based chemical cleaning combined with a low-temperature thermal annealing leading to an oxide free surface with atomically flat areas. Scanning tunneling microscopy (STM) has been the preferred method for such investigations on blanket films due to its intrinsic sub-nm spatial resolution. However, its application on oxide embedded structures is non-trivial. To perform STM on the trenches of interest (generally <20 nm wide), we propose a combination of non-contact atomic force microscopy and STM using the same conductive atomic force microscopy tip Our results prove that with these procedures, it is possible to perform STM in narrow InP trenches showing stacking faults and surface reconstruction. Significant differences in terms of roughness and terrace formation are also observed between the blanket and the oxide embedded InP.

  9. Schottky Barriers Based on Nanoporous InP with Gold Nanoparticles.

    PubMed

    Barlas, Tetyana; Dmitruk, Mykola; Kotova, Nataliya; Mamykin, Sergii

    2016-12-01

    Schottky barrier structures based on nanoporous InP with inclusion of Au nanoparticles and evaporated semitransparent Au film have been made. The spectra of short-circuit photocurrent in the visible range and current-voltage characteristics have been measured. Prepared structures are characterized by increased photocurrent due to the microrelief interface and surface plasmon excitation in gold nanoparticles as well as increased surface recombination especially in the short wavelength region. PMID:27075341

  10. Minority carrier diffusion length and edge surface-recombination velocity in InP

    NASA Technical Reports Server (NTRS)

    Hakimzadeh, Roshanak; Bailey, Sheila G.

    1993-01-01

    A scanning electron microscope was used to obtain the electron-beam-induced current (EBIC) profiles in InP specimens containing a Schottky barrier perpendicular to the scanned (edge) surface. An independent technique was used to measure the edge surface-recombination velocity. These values were used in a fit of the experimental EBIC data with a theoretical expression for normalized EBIC (Donolato, 1982) to obtain the electron (minority carrier) diffusion length.

  11. Amphoteric behavior and precipitation of Ge dopants in InP

    SciTech Connect

    Yu, K.M.; Moll, A.J.; Walukiewicz, W.

    1996-11-01

    We have directly correlated the electrical behavior, the impurity lattice site location, ion damage, and the local bonding environments of Ge-dopant ions implanted into InP. We have found that after rapid thermal annealing the free electron concentration in the samples implanted at room temperature (RT) are always higher than those implanted at liquid nitrogen temperature (LNT). Although the macroscopic structure seems to be insensitive to the implantation temperature, significantly more local disorder is created in the LNT implanted amorphous layers. Moreover, the amphoteric bonding structure of the Ge atoms is found to be well established already in the as-implanted amorphous InP. After high temperature annealing ({approx_gt}800{degree}C), the Ge atoms rearrange locally with more of the Ge substituting the In site than the P site resulting in {ital n}-type conductivity. The solid solubility of Ge in the InP is measured to be {approximately}1.4{endash}1.6{times}10{sup 20}/cm{sup 3} while the free electron concentration is estimated to saturate at {approximately}3.4{times}10{sup 19}/cm{sup 3}. The relatively low electron concentration can be explained by Ge precipitation and the compensation of Ge{sub In} donors by Ge{sub P} acceptors in the RT implanted case. The further reduction in electron concentration in the LNT implanted samples is believed to be related to the high residual damage found in these samples. The high solubility of Ge in InP can be attributed to the availability of two possible sublattice sites for the dopant and the compensation of the local strains due to the amphoteric substitution of the Ge. The concentration ratio of the Ge{sub In} to Ge{sub P} determined in the heavily implanted material has been used to estimate the difference in the formation energy of Ge substituting those two different sites.

  12. Thin films of InP for photovoltaic energy conversion. Final report, July 5, 1979-July 4, 1980

    SciTech Connect

    Manasevit, H. M.; Ruth, R. P.; Moudy, L. A.; Yang, J. J.J.; Johnson, R. E.

    1980-08-01

    Research to develop a low-cost high-efficiency thin-film InP heterojunction solar cell, using the metalorganic chemical vapor deposition (MO-CVD) technique for InP film growth on suitable substrates is reported. Heterostructure devices of CdS/InP, using InP films prepared by CO-CVD, were prepared and characterized. The research effort involved three major technical tasks: (1) materials growth; (2) materials characterization; and (3) device fabrication and characterization. The principal results achieved in the investigations are as follows: (1) temperature-activated orientation-dependent background donor doping was observed in undoped epitaxial InP films; (2) p-type epitaxial InP films were prepared by Zn and by Cd doping during growth; (3) the efficacy of Cd doping was found to vary exponentially with the reciprocal of the deposition temperature in the range 650 to 730/sup 0/C; (4) Cd doping appeared to offer no clear advantages over Zn doping for preparation of p-type InP by the MO-CVD process; (5) GaP grown by MO-CVD was investigated as a possible intermediate-layer material for growth of InP films on low-cost substrates; (6) p/sup +/GaAs polycrystalline layers (p > /sup 19/ cm/sup -3/) were successfully prepared by Zn doping during MO-CVD growth on various low-cost substrates and used as surfaces for growth of p-type polycrystalline InP:Zn layers; (7) nCdS/pInP heterojunction solar cells were prepared by vacuum deposition of CdS onto p-type InP films grown by MO-CVD as well as on InP single-crystal wafers; (8) the best polycrystalline CdS/InP cells were obtained in structures on P/sup +/GaAs:Zn layers on both Mo sheet and Corning Code 0317 Glass; and (9) structure analyses of the Cds films used in the heterojunction cells indicated the presence of polycrystalline hexagonal CdS even in films grown on single-crystal InP films or bulk-wafer substrates. (WHK)

  13. Improved nucleosome-positioning algorithm iNPS for accurate nucleosome positioning from sequencing data.

    PubMed

    Chen, Weizhong; Liu, Yi; Zhu, Shanshan; Green, Christopher D; Wei, Gang; Han, Jing-Dong Jackie

    2014-01-01

    Accurate determination of genome-wide nucleosome positioning can provide important insights into global gene regulation. Here, we describe the development of an improved nucleosome-positioning algorithm-iNPS-which achieves significantly better performance than the widely used NPS package. By determining nucleosome boundaries more precisely and merging or separating shoulder peaks based on local MNase-seq signals, iNPS can unambiguously detect 60% more nucleosomes. The detected nucleosomes display better nucleosome 'widths' and neighbouring centre-centre distance distributions, giving rise to sharper patterns and better phasing of average nucleosome profiles and higher consistency between independent data subsets. In addition to its unique advantage in classifying nucleosomes by shape to reveal their different biological properties, iNPS also achieves higher significance and lower false positive rates than previously published methods. The application of iNPS to T-cell activation data demonstrates a greater ability to facilitate detection of nucleosome repositioning, uncovering additional biological features underlying the activation process. PMID:25233085

  14. The electrochemical capacitance-voltage characterization of InP based p-i-n structures

    NASA Astrophysics Data System (ADS)

    Wang, Li-wei; Lu, Yi-dan; Xu, Jin-tong; Li, Xiang-yang

    2013-09-01

    Electrochemical Capacitance-Voltage (EC-V) profiling is currently one of the most often used methods for majority carrier concentration depth profiling of semiconductors. The experiments of EC-V profiling on InP based structures were conducted by Wafer Profiler CVP21, and there are two problems in the experiments of InP based p-i-n structures : a)the experimental results of EC-V profiling of i layer were not in line with the theoretically data after the EC-V profiling of p layer, which can be measured within the error range; b) The measurements of etching depth were not very accurate. In this paper, we made comparative experiments on InP based n-i-n structures, and find out a method to deal with the first problem: firstly etch p layer before EC-V profiling, so we can gain a relatively accurate result of EC-V profiling of i layer. Besides, use back contacts instead of front contacts to do the EC-V profiling according to the instruction book of the Wafer Profiler CVP21. Then the author tried to infer the reason that results in the first problem theoretically. Meanwhile we can calibrate the etching depth through Profile-system and Scanning Probe Microscope (SPM). And there are two possible reasons which result in the second problem: the defects of the semiconductors and the electrolyte we used to etch the semiconductors.

  15. MOVPE growth of InP using isobutylphosphine and tert-butylphosphine

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Larsen, C. A.; Stringfellow, G. B.; Brown, D. W.; Robertson, A. J.

    1986-09-01

    Two organophosphorus compounds, isobutylphosphine and tertiarybutylphosphine, have been investigated for their possible use as precursors in the metalorganic vapor phase epitaxy (MOVPE) process. They are the first organometallic compounds to be used as phosphorus sources. Pyrolysis studies show that the first decomposition products are phosphine and various organic compounds. The phosphine then pyrolyzes to give phosphorus. The materials are less pyrophoric and less toxic than phosphine. Since they are used as liquids in atmospheric pressure bubblers, they are much safer to use. The compounds have been used to grow epitaxial layers of InP on InP and GaAs substrates using trimethylindium in a flowing hydrogen ambient. No evidence of deleterious gas phase reaction is observed. The optimum temperature for growth using IBP is approximately 630°C. This yields excellent morphology layers with the strongest photoluminescence intensity and narrowest half-width, both of which are comparable to InP grown using PH 3. Carbon incorporation is nearly identical using IBP and PH 3. The IBP and TBP are not quite as pure as the best PH 3. The lowest carrier concentration measured was in the low 10 16 cm -3 range with room temperature mobilities as high as 2800 cm 2/V·s for TBP. Using TBP slightly higher mobilities of 3100 cm 2/V· were obtained.

  16. Preparation of clean InP(100) surfaces studied by synchrotron radiation photoemission

    NASA Astrophysics Data System (ADS)

    Sun, Yun; Liu, Zhi; Machuca, Francisco; Pianetta, Piero; Spicer, William E.

    2003-01-01

    The chemical cleaning of indium phosphide (InP),(100) surfaces is studied systematically by using photoemission electron spectroscopy. In order to achieve the necessary surface sensitivity and spectral resolution, synchrotron radiation with photon energies ranging from 60 to 600 eV are used to study the indium 4d, phosphorus 2p, carbon 1s, and oxygen 1s core levels, and the valence band. Typical H2SO4:H2O2:H2O solutions used to etch GaAs(100) surfaces are applied to InP(100) surfaces. It is found that the resulting surface species are significantly different from those found on GaAs(100) surfaces and that a second chemical cleaning step using a strong acid is required to remove residual surface oxide. This two-step cleaning process leaves the surface oxide free and with approximately 0.4 ML of elemental phosphorus, which is removed by vacuum annealing. The carbon coverage is also reduced dramatically from approximately 1 to about 0.05 ML. The chemical reactions are investigated, the resulting InP surface species at different cleaning stages are determined, and the optimum cleaning procedure is presented.

  17. Room-temperature annealing of Si implantation damage in InP

    SciTech Connect

    Akano, U.G.; Mitchell, I.V. . Dept. of Physics); Shepherd, F.R. )

    1991-11-11

    Spontaneous recovery at 295 K of Si implant damage in InP is reported. InP(Zn) and InP(S) wafers of (100) orientation have been implanted at room temperature with 600 keV Si{sup +} ions to doses ranging from 3.6{times}10{sup 11} to 2{times}10{sup 14} cm{sup {minus}2}. Room-temperature annealing of the resultant damage has been monitored by the Rutherford backscattering/channeling technique. For Si doses {le}4{times}10{sup 13} cm{sup {minus}2}, up to 70% of the initial damage (displaced atoms) annealed out over a period of {approx}85 days. The degree of recovery was found to depend on the initial level of damage. Recovery is characterized by at least two time constants {ital t}{sub 1}{lt}5 days and a longer {ital t}{sub 2}{approx}100 days. Anneal rates observed between 295 and 375 K are consistent with an activation energy of 1.2 eV, suggesting that the migration of implant-induced vacancies is associated with the reordering of the InP lattice.

  18. Optical reflectance studies of highly specular anisotropic nanoporous (111) InP membrane

    NASA Astrophysics Data System (ADS)

    Steele, J. A.; Lewis, R. A.; Sirbu, L.; Enachi, M.; Tiginyanu, I. M.; Skuratov, V. A.

    2015-04-01

    High-precision optical angular reflectance measurements are reported for a specular anisotropic nanoporous (111) InP membrane prepared by doping-assisted wet-electrochemical etching. The membrane surface morphology was investigated using scanning electron microscope imaging and revealed a quasi-uniform and self-organized nanoporous network consisting of semiconductor ‘islands’ in the sub-wavelength regime. The optical response of the nanoporous InP surface was studied at 405 nm (740 THz; UV), 633 nm (474 THz; VIS) and 1064 nm (282 THz; NIR), and exhibited a retention of basic macro-dielectric properties. Refractive index determinations demonstrate an optical anisotropy for the membrane which is strongly dependent on the wavelength of incident light, and exhibits an interesting inversion (positive anisotropy to negative) between 405 and 633 nm. The inversion of optical anisotropy is attributed to a strongly reduced ‘metallic’ behaviour in the membrane when subject to above-bandgap illumination. For the simplest case of sub-bandgap incident irradiation, the optical properties of the nanoporous InP sample are analysed in terms of an effective refractive index neff and compared to effective media approximations.

  19. Bandgap Engineering of InP QDs Through Shell Thickness and Composition

    SciTech Connect

    Dennis, Allison M.; Mangum, Benjamin D.; Piryatinski, Andrei; Park, Young-Shin; Htoon, Han; Hollingsworth, Jennifer A.

    2012-06-21

    Fields as diverse as biological imaging and telecommunications utilize the unique photophysical and electronic properties of nanocrystal quantum dots (NQDs). The development of new NQD compositions promises material properties optimized for specific applications, while addressing material toxicity. Indium phosphide (InP) offers a 'green' alternative to the traditional cadmium-based NQDs, but suffers from extreme susceptibility to oxidation. Coating InP cores with more stable shell materials significantly improves nanocrystal resistance to oxidation and photostability. We have investigated several new InP-based core-shell compositions, correlating our results with theoretical predictions of their optical and electronic properties. Specifically, we can tailor the InP core-shell QDs to a type-I, quasi-type-II, or type-II bandgap structure with emission wavelengths ranging from 500-1300 nm depending on the shell material used (ZnS, ZnSe, CdS, or CdSe) and the thickness of the shell. Single molecule microscopy assessments of photobleaching and blinking are used to correlate NQD properties with shell thickness.

  20. Ab-Initio Calculations of Electronic Properties of InP and GaP

    NASA Astrophysics Data System (ADS)

    Malozovsky, Y.; Franklin, L.; Ekuma, E. C.; Zhao, G. L.; Bagayoko, D.

    2013-06-01

    We present results from ab-initio, self-consistent local density approximation (LDA) calculations of electronic and related properties of zinc blende indium phosphide (InP) and gallium phosphide (GaP). We employed a LDA potential and implemented the linear combination of atomic orbitals (LCAO) formalism. This implementation followed the Bagayoko, Zhao and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). This method searches for the optimal basis set that yields the minima of the occupied energies. This search entails increases of the size of the basis set and the related modifications of angular symmetry and of radial orbitals. Our calculated, direct band gap of 1.398 eV (1.40 eV), at the Γ point, is in excellent agreement with experimental values, for InP, and our preliminary result for the indirect gap of GaP is 2.135 eV, from the Γ to X high symmetry points. We have also calculated electron and hole effective masses for both InP and GaP. These calculated properties also agree with experimental findings. We conclude that the BZW-EF method could be employed in calculations of electronic properties of high-Tc superconducting materials to explain their complex properties.

  1. Ab-initio Calculations of Electronic Properties of InP and GaP

    NASA Astrophysics Data System (ADS)

    Malozovsky, Yuriy; Franklin, Lashounda; Ekuma, Chinedu; Zhao, Guang-Lin; Bagayoko, Diola

    2013-03-01

    We present results from ab-initio, self consistent local density approximation (LDA) calculations of electronic and related properties of zinc blende indium and gallium phosphides (InP & GaP) We employed a local density approximation (LDA) potential and implemented the linear combination of atomic orbitals (LCAO) formalism. This implementation followed the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). This method searches for the optimal basis set that yields the minima of the occupied energies. This search entails methodically increasing the size of the basis set, up to the optimal one, and the accompanying enrichment of angular symmetry and of radial orbitals. Our calculated, direct band gap of 1.398 eV (1.40 eV) for InP, at the Γ point, is in excellent agreement with experimental values. We discuss our preliminary results for the indirect band gap, from Γ to X, of GaP. We also report calculated electron and hole effective masses for both InP and GaP and the total (DOS) and partial (pDOS) densities of states. This work was funded in part by the National Science Foundation and the Louisiana Board of Regents, through LASiGMA and LS-LAMP, [EPS-1003897, No. NSF (2010-15)-RII-SUBR, and HRD-1002541] and by the Louisiana Optical Network Initiative (LONI) at SUBR.

  2. Synthesizing folded band chaos.

    PubMed

    Corron, Ned J; Hayes, Scott T; Pethel, Shawn D; Blakely, Jonathan N

    2007-04-01

    A randomly driven linear filter that synthesizes Lorenz-like, reverse-time chaos is shown also to produce Rössler-like folded band wave forms when driven using a different encoding of the random source. The relationship between the topological entropy of the random source, dissipation in the linear filter, and the positive Lyapunov exponent for the reverse-time wave form is exposed. The two drive encodings are viewed as grammar restrictions on a more general encoding that produces a chaotic superset encompassing both the Lorenz butterfly and Rössler folded band paradigms of nonlinear dynamics. PMID:17500950

  3. Micrometer scale spacings between fibronectin nanodots regulate cell morphology and focal adhesions

    NASA Astrophysics Data System (ADS)

    Horzum, Utku; Ozdil, Berrin; Pesen-Okvur, Devrim

    2014-04-01

    Cell adhesion to extracellular matrix is an important process for both health and disease states. Surface protein patterns that are topographically flat, and do not introduce other chemical, topographical or rigidity related functionality and, more importantly, that mimic the organization of the in vivo extracellular matrix are desired. Previous work showed that vinculin and cytoskeletal organization are modulated by size and shape of surface nanopatterns. However, quantitative analysis on cell morphology and focal adhesions as a function of micrometer scale spacings of FN nanopatterns was absent. Here, electron beam lithography was used to pattern fibronectin nanodots with micrometer scale spacings on a K-casein background on indium tin oxide coated glass which, unlike silicon, is transparent and thus suitable for many light microscopy techniques. Exposure times were significantly reduced using the line exposure mode with micrometer scale step sizes. Micrometer scale spacings of 2, 4 and 8 μm between fibronectin nanodots proved to modulate cell adhesion through modification of cell area, focal adhesion number, size and circularity. Overall, cell behavior was shown to shift at the apparent threshold of 4 μm spacing. The findings presented here offer exciting new opportunities for cell biology research.

  4. FIB-TEM Anatomy of a Sub-Micrometer Impact Crater on a Hayabusa Grain

    NASA Astrophysics Data System (ADS)

    Harries, D.; Yakame, S.; Uesugi, M.; Langenhorst, F.

    2015-07-01

    We investigated Hayabusa grain RA-QD02-0265, which was found to contain a cluster of sub-micrometer-sized crater-like features. The cluster of craters is most likely due to secondary impacts of particles generated by an nearby (micro-)impact event.

  5. Nuclear Technology. Course 27: Metrology. Module 27-2, Fixed Gages, Dividers, Calipers, and Micrometers.

    ERIC Educational Resources Information Center

    Selleck, Ben; Espy, John

    This second in a series of eight modules for a course titled Metrology dscribes fixed gages, dividers, calipers, vernier and dial calipers, and micrometers. The module follows a typical format that includes the following sections: (l) introduction, (2) module prerequisites, (3) objectives, (4) notes to instructor/student, (5) subject matter, (6)…

  6. Efficient Single-Frequency Thulium Doped Fiber Laser Near 2-micrometers

    NASA Technical Reports Server (NTRS)

    Geng, Jihong; Wu, Jianfeng; Jiang, Shibin; Yu, Jirong

    2007-01-01

    We demonstrate highly efficient diode-pumped single-frequency fiber laser with 35% slope efficiency and 50mW output power operating near 2 micrometers, which generated from a 2-cm long piece of highly Tm(3+)-doped germanate glass fiber pumped at 800nm.

  7. The Brazilian INPE-UFSM NANOSATC-BR CubeSat Development Capacity Building Program

    NASA Astrophysics Data System (ADS)

    Schuch, Nelson Jorge; Cupertino Durao, Otavio S.

    The Brazilian INPE-UFSM NANOSATC-BR CubeSat Development Capacity Building Program (CBP) and the results of the NANOSATC-BR1, the first Brazilian CubeSat launching, expected for 2014's first semester, are presented. The CBP consists of two CubeSats, NANOSATC-BR 1 (1U) & 2 (2U) and is expected operate in orbit for at least 12 months each, with capacity building in space science, engineering and computer sciences for the development of space technologies using CubeSats satellites. The INPE-UFSM’s CBP Cooperation is basically among: (i) the Southern Regional Space Research Center (CRS), from the Brazilian INPE/MCTI, where acts the Program's General Coordinator and Projects NANOSATC-BR 1 & 2 Manager, having technical collaboration and management of the Mission’s General Coordinator for Engineering and Space Technology at INPE’s Headquarter (HQ), in São José dos Campos, São Paulo; (ii) the Santa Maria Space Science Laboratory (LACESM/CT) from the Federal University of Santa Maria - (UFSM); (iii) the Santa Maria Design House (SMDH); (iv) the Graduate Program in Microelectronics from the Federal University of Rio Grande do Sul (MG/II/UFRGS); and (v) the Aeronautic Institute of Technology (ITA/DCTA/CA-MD). The INPE-UFSM’s CBP has the involvement of UFSM' undergraduate students and graduate students from: INPE/MCTI, MG/II/UFRGS and ITA/DCTA/CA-MD. The NANOSATC-BR 1 & 2 Projects Ground Stations (GS) capacity building operation with VHF/UHF band and S-band antennas, are described in two specific papers at this COSPAR-2014. This paper focuses on the development of NANOSATC-BR 1 & 2 and on the launching of NANOSATC-BR1. The Projects' concepts were developed to: i) monitor, in real time, the Geospace, the Ionosphere, the energetic particle precipitation and the disturbances at the Earth's Magnetosphere over the Brazilian Territory, and ii) the determination of their effects on regions such as the South American Magnetic Anomaly (SAMA) and the Brazilian sector of the

  8. InP tunnel junction for InGaAs/InP tandem solar cells

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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 (450-530 C). We have previously shown that CBE is perfectly suited toward the fabrication of complex photovoltaic devices such as InP/InGaAs monolithically integrated tandem solar cells, because its low process temperature preserves the electrical characteristics of the InGaAs tunnel junction commonly used as an ohmic interconnect. In this work using CBE for the fabrication of optically transparent (with respect to the bottom cell) InP tunnel diodes is demonstrated. Epitaxial growth were performed in a Riber CBE 32 system using PH3 and TMIn as III and V precursors. Solid Be (p-type) and Si (n-type) have been used as doping sources, allowing doping levels up to 2 x 10(exp -19)/cu cm and 1 x 10(exp -19)/cu cm for n and p type respectively. The InP tunnel junction characteristics and the influence of the growth's conditions (temperature, growth rate) over its performance have been carefully investigated. InP p(++)/n(++) tunnel junction with peak current densities up to 1600 A/sq cm and maximum specific resistivities (V(sub p)/I(sub p) - peak voltage to peak current ratio) in the range of 10(exp -4) Omega-sq cm were obtained. The obtained peak current densities exceed the highest results previously reported for their lattice matched counterparts, In(0.53)Ga( 0.47)As and should allow the realization of improved minimal absorption losses in the interconnect InP/InGaAs tandem devices for Space applications. Owing to the low process temperature required for the top cell, these devices exhibit almost no degradation of its characteristics after the growth of subsequent thick InP layer suggesting

  9. SYNTH: A spectrum synthesizer

    NASA Astrophysics Data System (ADS)

    Hensley, W. K.; McKinnon, A. D.; Miley, H. S.; Panisko, M. E.; Savard, R. M.

    1993-10-01

    A computer code has been written at the Pacific Northwest Laboratory (PNL) to synthesize the results of typical gamma ray spectroscopy experiments. The code, dubbed SYNTH, allows a user to specify physical characteristics of a gamma ray source, the quantity of the nuclides producing the radiation, the source-to-detector distance and the presence of absorbers, the type and size of the detector, and the electronic set up used to gather the data. In the process of specifying the parameters needed to synthesize a spectrum, several interesting intermediate results are produced, including a photopeak transmission function versus energy, a detector efficiency curve, and a weighted list of gamma and x rays produced from a set of nuclides. All of these intermediate results are available for graphical inspection and for printing. SYNTH runs on personal computers. It is menu driven and can be customized to user specifications. SYNTH contains robust support for coaxial germanium detectors and some support for sodium iodide detectors. SYNTH is not a finished product. A number of additional developments are planned. However, the existing code has been compared carefully to spectra obtained from National Institute for Standards and Technology (NIST) certified standards with very favorable results. Examples of the use of SYNTH and several spectral results are presented.

  10. Programmable electronic synthesized capacitance

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard L. (Inventor)

    1987-01-01

    A predetermined and variable synthesized capacitance which may be incorporated into the resonant portion of an electronic oscillator for the purpose of tuning the oscillator comprises a programmable operational amplifier circuit. The operational amplifier circuit has its output connected to its inverting input, in a follower configuration, by a network which is low impedance at the operational frequency of the circuit. The output of the operational amplifier is also connected to the noninverting input by a capacitor. The noninverting input appears as a synthesized capacitance which may be varied with a variation in gain-bandwidth product of the operational amplifier circuit. The gain-bandwidth product may, in turn, be varied with a variation in input set current with a digital to analog converter whose output is varied with a command word. The output impedance of the circuit may also be varied by the output set current. This circuit may provide very small ranges in oscillator frequency with relatively large control voltages unaffected by noise.

  11. A Meteorological Distribution System for High Resolution Terrestrial Modeling (MicroMet)

    NASA Astrophysics Data System (ADS)

    Liston, G. E.; Elder, K.

    2004-12-01

    Spatially distributed terrestrial models generally require atmospheric forcing data on horizontal grids that are of higher resolution than available meteorological data. Furthermore, the meteorological data collected may not necessarily represent the area of interest's meteorological variability. To address these deficiencies, computationally efficient and physically realistic methods must be developed to take available meteorological data sets (e.g., meteorological tower observations) and generate high-resolution atmospheric-forcing distributions. This poster describes MicroMet, a quasi-physically-based, but simple meteorological distribution model designed to produce high-resolution (e.g., 5-m to 1-km horizontal grid increments) meteorological data distributions required to run spatially distributed terrestrial models over a wide variety of landscapes. The model produces distributions of the seven fundamental atmospheric forcing variables required to run most terrestrial models: air temperature, relative humidity, wind speed, wind direction, incoming solar radiation, incoming longwave radiation, and precipitation. MicroMet includes a preprocessor that analyzes meteorological station data and identifies and repairs potential data deficiencies. The model uses known relationships between meteorological variables and the surrounding area (primarily topography) to distribute those variables over any given landscape. MicroMet performs two kinds of adjustments to available meteorological data: 1) when there are data at more than one location, at a given time, the data are spatially interpolated over the domain using a Barnes objective analysis scheme, and 2) physical sub-models are applied to each MicroMet variable to improve its realism at a given point in space and time with respect to the terrain. The three, 25-km by 25-km, Cold Land Processes Experiment (CLPX) mesoscale study areas (MSAs: Fraser, North Park, and Rabbit Ears) will be used as example MicroMet

  12. M&A For Lithography Of Sparse Arrays Of Sub-Micrometer Features

    DOEpatents

    Brueck, Steven R.J.; Chen, Xiaolan; Zaidi, Saleem; Devine, Daniel J.

    1998-06-02

    Methods and apparatuses are disclosed for the exposure of sparse hole and/or mesa arrays with line:space ratios of 1:3 or greater and sub-micrometer hole and/or mesa diameters in a layer of photosensitive material atop a layered material. Methods disclosed include: double exposure interferometric lithography pairs in which only those areas near the overlapping maxima of each single-period exposure pair receive a clearing exposure dose; double interferometric lithography exposure pairs with additional processing steps to transfer the array from a first single-period interferometric lithography exposure pair into an intermediate mask layer and a second single-period interferometric lithography exposure to further select a subset of the first array of holes; a double exposure of a single period interferometric lithography exposure pair to define a dense array of sub-micrometer holes and an optical lithography exposure in which only those holes near maxima of both exposures receive a clearing exposure dose; combination of a single-period interferometric exposure pair, processing to transfer resulting dense array of sub-micrometer holes into an intermediate etch mask, and an optical lithography exposure to select a subset of initial array to form a sparse array; combination of an optical exposure, transfer of exposure pattern into an intermediate mask layer, and a single-period interferometric lithography exposure pair; three-beam interferometric exposure pairs to form sparse arrays of sub-micrometer holes; five- and four-beam interferometric exposures to form a sparse array of sub-micrometer holes in a single exposure. Apparatuses disclosed include arrangements for the three-beam, five-beam and four-beam interferometric exposures.

  13. Flattening and Cooling of Millimeter- and Micrometer-Sized Alumina Drops

    NASA Astrophysics Data System (ADS)

    Goutier, S.; Vardelle, M.; Labbe, J. C.; Fauchais, P.

    2011-01-01

    An experimental setup was developed to produce fully melted, millimeter-sized, ceramic or metallic drops with impact velocities up to 10 m/s. Such impact velocities allow achievement of impact Weber numbers, close to those of the plasma spray process ( We = 2300) with droplets in the tens of micrometer size range. A fast camera (4000 image/s) combined with a fast pyrometer (4000 Hz), allowed the flattening of the drop to be followed. To study the flattening of micrometer-sized droplets, a direct-current (dc) plasma torch was used to melt alumina particles (around 45 μm in diameter). The experimental setup was composed of a fast (50 ns) two-color pyrometer and two fast (at best an exposure time of 2 μs) charge-coupled device cameras (one orthogonal and other tangential to the substrate). The flattening behaviors of millimeter- and micrometer-sized particles were compared. First, impacts of alumina drops (millimeter-sized) with velocities up to 10 m/s were studied. Results were then compared with micrometer-sized alumina particles (about 45 μm in diameter) sprayed with the dc plasma torch. A correlation was found between both flattening scales, and, in spite of the lower impact velocity at the millimeter scale, droplet ejections were also found as obtained at the micrometer scale. This work shows that for a sound comparison of phenomena at the two different scales it is mandatory to have Weber numbers as close as possible in both cases.

  14. Solvent resistant microfluidic DNA synthesizer.

    PubMed

    Huang, Yanyi; Castrataro, Piero; Lee, Cheng-Chung; Quake, Stephen R

    2007-01-01

    We fabricated a microfluidic DNA synthesizer out of perfluoropolyether (PFPE), an elastomer with excellent chemical compatibility which makes it possible to perform organic chemical reactions, and synthesized 20-mer oligonucleotides on chip. PMID:17180201

  15. Method for synthesizing HMX

    SciTech Connect

    McGuire, R.R.; Coon, C.L.; Harrar, J.E.; Pearson, R.K.

    1984-02-21

    A method and apparatus for electrochemically synthesizing N/sub 2/O/sub 5/ includes oxidizing a solution of N/sub 2/O/sub 4//HNO/sub 3/ at an anode, while maintaining a controlled potential between the N/sub 2/O/sub 4//HNO/sub 3/ solution and the anode. A potential of about 1.35 to 2.0 V vs. SCE is preferred, while a potential of about 1.80 V vs. SCE is most preferred. Thereafter, the N/sub 2/O/sub 5/ is reacted with either 1.5-diacetyl-3,7-dinitro-1,3,5,7-tetraazacyclooctane (DADN) or 1,3,5,7-tetraacetyl-1,3,5,7-tetraazacyclooctane (TAT) to form cyclotetramethylenetetraamine (HMX).

  16. Method for synthesizing HMX

    DOEpatents

    McGuire, Raymond R.; Coon, Clifford L.; Harrar, Jackson E.; Pearson, Richard K.

    1984-01-01

    A method and apparatus for electrochemically synthesizing N.sub.2 O.sub.5 cludes oxidizing a solution of N.sub.2 O.sub.4 /HNO.sub.3 at an anode, while maintaining a controlled potential between the N.sub.2 O.sub.4 /HNO.sub.3 solution and the anode. A potential of about 1.35 to 2.0 V vs. SCE is preferred, while a potential of about 1.80 V vs. SCE is most preferred. Thereafter, the N.sub.2 O.sub.5 is reacted with either 1.5-diacetyl-3,7-dinitro-1,3,5,7-tetraazacyclooctane (DADN) or 1,3,5,7-tetraacetyl-1,3,5,7-tetraazacyclooctane (TAT) to form cyclotetramethylenetetraamine (HMX).

  17. K promoted oxidation and nitridation on InP(100) surface: A soft-X-ray photoemission study

    NASA Astrophysics Data System (ADS)

    Xu, P. S.; Xu, S. H.; Lu, E. D.; Yu, X. J.; Ji, H.; Liang, Q.; Zhao, T. X.

    1995-05-01

    The effects of exposure of molecular nitrogen and oxygen on p-type InP(100) surfaces modified by potassium overlayers were studied by core level and valence band (VB) photoemission using synchrotron radiation. On the K pre-covered surface, the potassium coverage enhanced the nitrogen and oxygen sticking coefficients dramatically. As far as the process of nitrogen adsorption is concerned, nitrogen atoms react mainly with P atoms rather than not react directly with indium atoms. Two kinds of nitride complexes, InPXx and InPNx + y were formed at the K-precovered InP(100) surface. In case of oxygen adsorption, O may bond with K and produce the peroxides O22- and superoxides O2-. Following this a few kinds of phosphate phases, In(PO4)x, were formed on the surface. In comparison with InP(110) surface, we found that the oxidation and nitridation promotion for the InP(100) surface was much stronger. The reasons may be the number of surface defects as well as the polarity of the InP(100) surface.

  18. Defects in mitophagy promote redox-driven metabolic syndrome in the absence of TP53INP1

    PubMed Central

    Seillier, Marion; Pouyet, Laurent; N'Guessan, Prudence; Nollet, Marie; Capo, Florence; Guillaumond, Fabienne; Peyta, Laure; Dumas, Jean-François; Varrault, Annie; Bertrand, Gyslaine; Bonnafous, Stéphanie; Tran, Albert; Meur, Gargi; Marchetti, Piero; Ravier, Magalie A; Dalle, Stéphane; Gual, Philippe; Muller, Dany; Rutter, Guy A; Servais, Stéphane; Iovanna, Juan L; Carrier, Alice

    2015-01-01

    The metabolic syndrome covers metabolic abnormalities including obesity and type 2 diabetes (T2D). T2D is characterized by insulin resistance resulting from both environmental and genetic factors. A genome-wide association study (GWAS) published in 2010 identified TP53INP1 as a new T2D susceptibility locus, but a pathological mechanism was not identified. In this work, we show that mice lacking TP53INP1 are prone to redox-driven obesity and insulin resistance. Furthermore, we demonstrate that the reactive oxygen species increase in TP53INP1-deficient cells results from accumulation of defective mitochondria associated with impaired PINK/PARKIN mitophagy. This chronic oxidative stress also favors accumulation of lipid droplets. Taken together, our data provide evidence that the GWAS-identified TP53INP1 gene prevents metabolic syndrome, through a mechanism involving prevention of oxidative stress by mitochondrial homeostasis regulation. In conclusion, this study highlights TP53INP1 as a molecular regulator of redox-driven metabolic syndrome and provides a new preclinical mouse model for metabolic syndrome clinical research. PMID:25828351

  19. Defects in mitophagy promote redox-driven metabolic syndrome in the absence of TP53INP1.

    PubMed

    Seillier, Marion; Pouyet, Laurent; N'Guessan, Prudence; Nollet, Marie; Capo, Florence; Guillaumond, Fabienne; Peyta, Laure; Dumas, Jean-François; Varrault, Annie; Bertrand, Gyslaine; Bonnafous, Stéphanie; Tran, Albert; Meur, Gargi; Marchetti, Piero; Ravier, Magalie A; Dalle, Stéphane; Gual, Philippe; Muller, Dany; Rutter, Guy A; Servais, Stéphane; Iovanna, Juan L; Carrier, Alice

    2015-06-01

    The metabolic syndrome covers metabolic abnormalities including obesity and type 2 diabetes (T2D). T2D is characterized by insulin resistance resulting from both environmental and genetic factors. A genome-wide association study (GWAS) published in 2010 identified TP53INP1 as a new T2D susceptibility locus, but a pathological mechanism was not identified. In this work, we show that mice lacking TP53INP1 are prone to redox-driven obesity and insulin resistance. Furthermore, we demonstrate that the reactive oxygen species increase in TP53INP1-deficient cells results from accumulation of defective mitochondria associated with impaired PINK/PARKIN mitophagy. This chronic oxidative stress also favors accumulation of lipid droplets. Taken together, our data provide evidence that the GWAS-identified TP53INP1 gene prevents metabolic syndrome, through a mechanism involving prevention of oxidative stress by mitochondrial homeostasis regulation. In conclusion, this study highlights TP53INP1 as a molecular regulator of redox-driven metabolic syndrome and provides a new preclinical mouse model for metabolic syndrome clinical research. PMID:25828351

  20. Growth of high quality InP layers in STI trenches on miscut Si (0 0 1) substrates

    NASA Astrophysics Data System (ADS)

    Wang, G.; Leys, M. R.; Nguyen, N. D.; Loo, R.; Brammertz, G.; Richard, O.; Bender, H.; Dekoster, J.; Meuris, M.; Heyns, M. M.; Caymax, M.

    2011-01-01

    In this work, we report the selective area epitaxial growth of high quality InP in shallow trench isolation (STI) structures on Si (0 0 1) substrates 6° miscut toward (1 1 1) using a thin Ge buffer layer. We studied the impact of growth rates and steric hindrance effects on the nano-twin formation at the STI side walls. It was found that a too high growth rate induces more nano-twins in the layer and results in InP crystal distortion. The STI side wall tapering angle and the substrate miscut angle induced streric hindrance between the InP facets and the STI side walls also contribute to defect formation. In the [1¯ 1 0] orientated trenches, when the STI side wall tapering angle is larger than 10°, crystal distortion was observed while the substrate miscut angle has no significant impact on the InP defect formation. In the [1¯ 1 0] trenches, both the increased STI tapering angle and the substrate miscut angle induce high density of defects. With a small STI tapering angle and a thin Ge layer, we obtained extended defect free InP in the top region of the [1 1 0] trenches with aspect ratio larger than 2.

  1. Colloidal Synthesis of Quantum Confined Single Crystal CsPbBr3 Nanosheets with Lateral Size Control up to the Micrometer Range

    PubMed Central

    2016-01-01

    We report the nontemplated colloidal synthesis of single crystal CsPbBr3 perovskite nanosheets with lateral sizes up to a few micrometers and with thickness of just a few unit cells (i.e., below 5 nm), hence in the strong quantum confinement regime, by introducing short ligands (octanoic acid and octylamine) in the synthesis together with longer ones (oleic acid and oleylamine). The lateral size is tunable by varying the ratio of shorter ligands over longer ligands, while the thickness is mainly unaffected by this parameter and stays practically constant at 3 nm in all the syntheses conducted at short-to-long ligands volumetric ratio below 0.67. Beyond this ratio, control over the thickness is lost and a multimodal thickness distribution is observed. PMID:27228475

  2. Colloidal Synthesis of Quantum Confined Single Crystal CsPbBr3 Nanosheets with Lateral Size Control up to the Micrometer Range.

    PubMed

    Shamsi, Javad; Dang, Zhiya; Bianchini, Paolo; Canale, Claudio; Stasio, Francesco Di; Brescia, Rosaria; Prato, Mirko; Manna, Liberato

    2016-06-15

    We report the nontemplated colloidal synthesis of single crystal CsPbBr3 perovskite nanosheets with lateral sizes up to a few micrometers and with thickness of just a few unit cells (i.e., below 5 nm), hence in the strong quantum confinement regime, by introducing short ligands (octanoic acid and octylamine) in the synthesis together with longer ones (oleic acid and oleylamine). The lateral size is tunable by varying the ratio of shorter ligands over longer ligands, while the thickness is mainly unaffected by this parameter and stays practically constant at 3 nm in all the syntheses conducted at short-to-long ligands volumetric ratio below 0.67. Beyond this ratio, control over the thickness is lost and a multimodal thickness distribution is observed. PMID:27228475

  3. Micrometer-sized ice particles for planetary-science experiments - I. Preparation, critical rolling friction force, and specific surface energy

    NASA Astrophysics Data System (ADS)

    Gundlach, B.; Kilias, S.; Beitz, E.; Blum, J.

    2011-08-01

    Coagulation models assume a higher sticking threshold for micrometer-sized ice particles than for micrometer-sized silicate particles. However, in contrast to silicates, laboratory investigations of the collision properties of micrometer-sized ice particles (in particular, of the most abundant H 2O-ice) have not been conducted yet. Thus, we used two different experimental methods to produce micrometer-sized H 2O-ice particles, i.e. by spraying H 2O droplets into liquid nitrogen and by spraying H 2O droplets into a cold nitrogen atmosphere. The mean particle radii of the ice particles produced with these experimental methods are (1.49 ± 0.79) μm and (1.45 ± 0.65) μm. Ice aggregates composed of the micrometer-sized ice particles are highly porous (volume filling factor: ϕ = 0.11 ± 0.01) or rather compact (volume filling factor: ϕ = 0.72 ± 0.04), depending on the method of production. Furthermore, the critical rolling friction force of FRoll, ice = (114.8 ± 23.8) × 10 -10 N was measured for micrometer-sized ice particles, which exceeds the critical rolling friction force of micrometer-sized SiO 2 particles (F=(12.1±3.6)×10-10N). This result implies that the adhesive bonding between micrometer-sized ice particles is stronger than the bonding strength between SiO 2 particles. An estimation of the specific surface energy of micrometer-sized ice particles, derived from the measured critical rolling friction forces and the surface energy of micrometer-sized SiO 2 particles, results in γice = 0.190 J m -2.

  4. Doclet To Synthesize UML

    NASA Technical Reports Server (NTRS)

    Barry, Matthew R.; Osborne, Richard N.

    2005-01-01

    The RoseDoclet computer program extends the capability of Java doclet software to automatically synthesize Unified Modeling Language (UML) content from Java language source code. [Doclets are Java-language programs that use the doclet application programming interface (API) to specify the content and format of the output of Javadoc. Javadoc is a program, originally designed to generate API documentation from Java source code, now also useful as an extensible engine for processing Java source code.] RoseDoclet takes advantage of Javadoc comments and tags already in the source code to produce a UML model of that code. RoseDoclet applies the doclet API to create a doclet passed to Javadoc. The Javadoc engine applies the doclet to the source code, emitting the output format specified by the doclet. RoseDoclet emits a Rose model file and populates it with fully documented packages, classes, methods, variables, and class diagrams identified in the source code. The way in which UML models are generated can be controlled by use of new Javadoc comment tags that RoseDoclet provides. The advantage of using RoseDoclet is that Javadoc documentation becomes leveraged for two purposes: documenting the as-built API and keeping the design documentation up to date.

  5. Synthesizing Exoplanet Demographics

    NASA Astrophysics Data System (ADS)

    Clanton, Christian

    2016-01-01

    The discovery of thousands of exoplanets has revealed a large diversity of systems, the majority of which look nothing like our own. On the theoretical side, we are able to make ab initio calculations that make predictions about the properties of exoplanets. However, in order to link these predictions with observations, we must construct a statistical census of exoplanet demographics over as broad a range of parameters as possible. Current constraints on exoplanet demographics are typically constructed using the results of individual surveys using a single detection technique, and thus are incomplete. The only way to derive a statistically-complete census that samples a wide region of exoplanet parameter space is to synthesize the results from surveys employing all of the different discovery methods at our disposal. I present the first studies to demonstrate that this is actually possible, and describe a (mostly) de-biased exoplanet census that is constructed from the synthesis of results from microlensing, radial velocity, and direct imaging surveys. I will also discuss future work that will include the results of transit surveys (in particular, Kepler discoveries) to complete the census of exoplanets in our Galaxy, and describe the application of this census to develop the most comprehensive, observationally-constrained models of planet formation and evolution that have been derived to date.

  6. Mass spectrometric studies of phosphine pyrolysis and OMVPE growth of InP. [organometallic vapor phase epitaxy

    NASA Technical Reports Server (NTRS)

    Larsen, C. A.; Buchan, N. I.; Stringfellow, G. B.

    1987-01-01

    The mechanism of PH3 decomposition was studied by using D2 as a carrier gas and analyzing the reaction products with a mass spectrometer. The effects of InP and silica surfaces were investigated. The only gaseous product below 600 C is H2. Since any gas-phase H atoms would produce HD, the reaction occurs entirely on the surface. The slow step is the unimolecular removal of the first hydrogen atom, with an activation energy of 36.0 kcal/mole on InP surfaces. The reaction on InP is first-order for PH3 concentrations as high as 15 percent, so the surface is not saturated at those conditions. When trimethylindium (TMIn) is added to the gas mixture, the mechanism changes dramatically, probably proceeding via an unstable intermediate adduct of TMIn and PH3 which eliminates CH4 upon formation. This concerted reaction lowers the pyrolysis temperatures of both PH3 and TMIn.

  7. Formation of cesium peroxide and cesium superoxide on InP photocathode activated by cesium and oxygen

    SciTech Connect

    Sun Yun; Liu Zhi; Pianetta, Piero; Lee, Dong-Ick

    2007-10-01

    Activation of p-type III-V semiconductors with cesium and oxygen has been widely used to prepare negative electron affinity (NEA) photocathodes. However, the nature of the chemical species on the surface after the activation is not well understood. In this study, InP NEA photocathodes activated with cesium and oxygen are studied using synchrotron radiation photoelectron spectroscopy, also called photoemission. Based on the O 1s core level as well as the valence band spectra, Cs peroxide and Cs superoxide are identified on the InP surface. Transformation from Cs peroxide to Cs superoxide is observed after the activation, and is probably the major reason for the decay of the quantum yield of the photocathode. The oxidation of the InP substrate is also observed with elapse of time, adding to the decay of the quantum yield.

  8. Studies of zinc-blende type MnAs thin films grown on InP(001) substrates by XRD

    NASA Astrophysics Data System (ADS)

    Oomae, H.; Irizawa, S.; Jinbo, Y.; Toyota, H.; Kambayashi, T.; Uchitomi, N.

    2013-09-01

    The detailed crystalline structure of molecular beam epitaxially grown MnAs thin films on InP(001) substrate has been investigated using high resolution X-ray diffraction techniques. Reciprocal space mapping of the MnAs/InP(001) samples indicates that the MnAs has a cubic zinc-blende (zb) structure with the epitaxial relationship zb-MnAs[110]|InP[110]. The lattice constant of zb-MnAs is ˜6.06 Å. The MnAs lattice is relaxed and is mosaic-like likely due to large lattice mismatch between the film and InP substrate. The isotropic nature of the magnetic properties supported our conjecture that the MnAs epitaxial film under study has indeed a cubic structure.

  9. The Dependence of the Oxidation Enhancement of InP(100) Surface on the Coverage of the Adsorbed Cs

    SciTech Connect

    Sun, Yun

    2010-06-07

    We report the oxidation of the InP(100) surface promoted by adsorbed Cs by synchrotron radiation photoemission. Oxygen exposure causes reduction of the charge transferred to the InP substrate from Cs and the growth of indium oxide and phosphorous oxide. The oxide growth displays a clear dependence on the Cs coverage. The oxidation of phosphorous is negligible up to 1000 L of O{sub 2} exposure when the Cs coverage is less than half a monolayer (ML), but the formation of the second half monolayer of Cs greatly accelerates the oxidation. This different enhancement of the InP oxidation by the first and the second half monolayer of Cs is due to the double layer structure of the adsorbed Cs atoms, and consequently the higher 6s electron density in the Cs atoms when Cs coverage is larger than 0.5 ML.

  10. 19.2% Efficient InP Heterojunction Solar Cell with Electron-Selective TiO2 Contact

    PubMed Central

    2015-01-01

    We demonstrate an InP heterojunction solar cell employing an ultrathin layer (∼10 nm) of amorphous TiO2 deposited at 120 °C by atomic layer deposition as the transparent electron-selective contact. The TiO2 film selectively extracts minority electrons from the conduction band of p-type InP while blocking the majority holes due to the large valence band offset, enabling a high maximum open-circuit voltage of 785 mV. A hydrogen plasma treatment of the InP surface drastically improves the long-wavelength response of the device, resulting in a high short-circuit current density of 30.5 mA/cm2 and a high power conversion efficiency of 19.2%. PMID:25679010

  11. 19.2% Efficient InP Heterojunction Solar Cell with Electron-Selective TiO2 Contact

    DOE PAGESBeta

    Yin, Xingtian; Battaglia, Corsin; Lin, Yongjing; Chen, Kevin; Hettick, Mark; Zheng, Maxwell; Chen, Cheng-Ying; Kiriya, Daisuke; Javey, Ali

    2014-09-25

    We demonstrate an InP heterojunction solar cell employing an ultrathin layer (~10 nm) of amorphous TiO2 deposited at 120°C by atomic layer deposition as the transparent electron-selective contact. The TiO2 film selectively extracts minority electrons from the conduction band of p-type InP while blocking the majority holes due to the large valence band offset, enabling a high maximum open-circuit voltage of 785 mV. Lastly, a hydrogen plasma treatment of the InP surface drastically improves the long-wavelength response of the device, resulting in a high short-circuit current density of 30.5 mA/cm2 and a high power conversion efficiency of 19.2%.

  12. Electronic properties of InP (001)/HfO{sub 2} (001) interface: Band offsets and oxygen dependence

    SciTech Connect

    KC, Santosh; Dong, Hong; Longo, Roberto C.; Xiong, Ka; Wang, Weichao; Wallace, Robert M.; Cho, Kyeongjae

    2014-01-14

    Using ab-initio methods, atomic structures and electronic properties of InP (001)/HfO{sub 2} (001) interface are studied within the framework of density functional theory. We examine the InP/HfO{sub 2} model interface electronic structures under varying oxidation conditions. The effects of indium and phosphorous concentrations on interfacial bonding, defect states, band offsets, and the thermodynamic stability at the interface are also investigated. The origin of interfacial gap states in InP (001)/HfO{sub 2} (001) interface are proposed, mainly from the P-rich oxides, which is validated by our experimental work. This highlights the importance of surface passivation prior to high-κ deposition based on the in situ spectroscopic results of atomic layer deposition of HfO{sub 2} on InP.

  13. Computation and use of the reflectivity at 3.75 micrometers from AVHRR thermal channels

    NASA Technical Reports Server (NTRS)

    Roger, J. C.; Vermote, E. F.

    1994-01-01

    Global study of land surface properties uses AVHRR channels 1 and 2, but channel 3 may be of interest, although its use requires preprocessing. It consists of both a reflective part and an emissive part, the former can be derived from T3, T4 and T5. Since the water vapor affects channel 3, its content is retrieved from the channel 4 and 5 using the split window technique. A formula of reflective part retrieval at 3.75 micrometers is tested in the case of sunglint observations where the emissivities of channels 4 and 5 can be set to the unity. The formula is adapted and validated to land surface using the FIFE-87 data set. Preliminary applications of the reflectance at 3.75 micrometers to the studies of surface properties retrieval, aerosol retrieval over land, and desertic aerosol retrieval, are addressed.

  14. Cryogenic Fourier transform spectrometer for infrared spectral calibrations from 4 to 20 micrometers

    NASA Astrophysics Data System (ADS)

    Woods, Solomon I.; Kaplan, Simon G.; Jung, Timothy M.; Carter, Adriaan C.; Datla, Raju U.

    2010-04-01

    We present initial performance data from a cryogenic Fourier transform spectrometer (Cryo-FTS) designed for lowbackground spectral infrared calibrations. The Cryo-FTS operates at a temperature of approximately 15 K and has been integrated into an infrared transfer radiometer containing a calibrated Si:As blocked impurity band (BIB) detector. Because of its low operating temperature, the spectrometer exhibits negligible thermal background signal and low drift. Data from tests of basic spectrometer function, such as modulation efficiency, scan jitter, spectral range, spectral resolution and sweep speed will be presented. We will also discuss calibration techniques and results pertinent to operation of the Cryo-FTS as part of a calibration instrument, including background, signal offset and gain, and spectral noise equivalent power. The spectrometer is presently limited to wavelengths below 25 micrometers but can be in principle extended to longer wavelengths by replacing its KBr beamsplitter with another beamsplitter engineered for use beyond 25 micrometers.

  15. A diagnostic for micrometer sensitive positioning of solid targets in intense laser-matter interaction

    NASA Astrophysics Data System (ADS)

    Singh, Prashant Kumar; Kakolee, K. F.; Jeong, T. W.; Ter-Avetisyan, Sargis

    2016-09-01

    A target position monitoring diagnostic, relevant to intense laser-solid interaction, is presented. The alignment system, having a sensitivity of few micrometers, consist of an infinity corrected long working distance objective, a broadband illuminating source and a CCD camera. The imaging system, placed along the axis of incident laser pulse, serves the dual purpose of laser focus diagnosis and precise positioning of the target in three dimension axis. By employing this technique, solid targets with thickness varying from opaque micrometer thick foils to few nanometer thin transparent foils can be aligned precisely. The effectiveness of the entire alignment system is demonstrated in enhanced acceleration of ions in intense laser-matter interaction, with very high reproducibility.

  16. Sub-micrometer salt aerosol production intended for marine cloud brightening

    NASA Astrophysics Data System (ADS)

    Neukermans, Armand; Cooper, Gary; Foster, Jack; Gadian, Alan; Galbraith, Lee; Jain, Sudhanshu; Latham, John; Ormond, Bob

    2014-06-01

    This paper is largely concerned with research focused on, but not restricted to, aspects of Marine Cloud Brightening (MCB), one of several geo-engineering ideas for reducing the amount of sunlight arriving at the Earth's surface, thereby compensating for global warming resulting from fossil-fuel burning. Predominant attention is given to the development of techniques for generating sprays of sub-micrometer salt particles that can enter marine stratocumulus clouds and increase their albedo, thus producing a cooling. Generation of sub-micrometer salt particles by spraying salt solutions at supercritical conditions is described, along with a description of the apparatus used. Log-normal particle size distributions having median diameters of 32 to 286 nm, with GSDs (Geometric Standard Deviations) around 2, were generated by two variations on the technique.

  17. The spectral appearance of comets from 5 to 20 micrometers: A survey of the data

    NASA Technical Reports Server (NTRS)

    Bregman, Jesse D.

    1988-01-01

    Based on the concept of comets as being conglomerates of rocks and ices, it is expected that they reflect these components in their emission spectra. Silicate materials (rocks) are common in many astronomical environments and show prominent features at about 10 and 18 micrometers. Carbon should be abundant, but is much more difficult to detect spectroscopically since it has no strong features (except for the hydrogenated form). Ices are present in comets, but they are difficult to detect since they are volatile enough to dissipate when the comet is bright enough to be easily observed in the IR, with present equipment. There are other materials present in comets, but the ones listed above should be the most common and thus dominate the thermal IR spectrum. Most of the IR observations made on comets between 5 and 20 micrometers are summarized. They fall into three broad categories: (1) filter photometry; (2) circular variable filter wheel spectroscopy; and (3) spectra obtained with multidetector grating spectrometers.

  18. Jupiter's Cloud Distribution Between the Voyager 1 and 2 Encounters: Results from 5-Micrometer Imaging.

    PubMed

    Terrile, R J; Capps, R W; Becklin, E E; Cruikshank, D P

    1979-11-23

    As part of a continuing effort of ground-based support for Voyager target selection, infrared images in the 5-micrometer wavelength region were acquired in preparation for the Voyager 2 flyby of Jupiter. Observations were made during May 1979 from the Palomar 5-meter telescope and the new 3-meter NASA Infrared Telescope Facility at Mauna Kea and are compared to previous observations. Variations seen in the 5-micrometer flux distribution suggest global patterns of clouding over of some Jovian belts and clearing ofothers. These data were used to predict the Jovian cloud distribution at the time of the Voyager 2 encounter in order to target the imaging and infrared experiments to areas free of high obscuring clouds. PMID:17733922

  19. Impressive electromagnetic shielding effects exhibited by highly ordered, micrometer thick polyaniline films

    NASA Astrophysics Data System (ADS)

    Mohan, Ranjini R.; Varma, Sreekanth J.; Sankaran, Jayalekshmi

    2016-04-01

    The present work highlights the remarkably high shielding effectiveness of about 68 dB, exhibited by highly ordered and doped polyaniline films, in the microwave frequency range 4-12 GHz, obtained by self-stabilized dispersion polymerization as the synthesis route. The observed shielding effectiveness is found to depend quite sensitively on the electrical conducting properties, which are predominantly controlled by the nature and concentration of the dopants. The structural and morphological characterization of the films using XRD and TEM techniques reveals surprisingly high extent of crystallinity, which contributes significantly towards enhancing the electrical conductivity of the films. Most of the available reports on the microwave response of conducting polymer film samples deal with much thicker films, compared to the micrometer thick films of the present studies. The shielding effectiveness of acid doped, micrometer thick polyaniline films reported in the present work far exceeds most of the previously reported values and meets the commercial requirements.

  20. Derivation of midinfrared (5-25 micrometers) optical constants of some silicates and palagonite.

    PubMed

    Roush, T; Pollack, J; Orenberg, J

    1991-01-01

    The midinfrared 2000-400 cm-1 (5-25 micrometers) optical constants (real (n) and imaginary (k) indices of refraction) are presented for: (1) pyrophyllite; (2) kaolinite; (3) serpentine; (4) montmorillonite; (5) saponite; (6) palagonite; and (7) orthopyroxene. Comparison of the values derived here with those previously presented for serpentine, montmorillonite, and palagonite is generally quite good and discrepancies between values are probably due to either chemical differences between the actual samples or different techniques used to derive the values. For montmorillonite, saponite, and palagonite we were able to derive optical constants in the region of the H2O-bending fundamental near 6 micrometers. We find that if a pellet of pure material can be produced with a mirror-like surface then the optical constants of clays and other noncohesive materials can be readily derived. PMID:11538089

  1. High T(sub c) Superconducting Bolometer on Chemically Etched 7 Micrometer Thick Sapphire

    NASA Technical Reports Server (NTRS)

    Lakew, B.; Brasunas, J. C.; Pique, A.; Fettig, R.; Mott, B.; Babu, S.; Cushman, G. M.

    1997-01-01

    A transition-edge IR detector, using a YBa2Cu3O(7-x) (YBCO) thin film deposited on a chemically etched, 7 micrometer thick sapphire substrate has been built. To our knowledge it is the first such high T(sub c) superconducting (HTS) bolometer on chemically thinned sapphire. The peak optical detectivity obtained is l.2 x 10(exp 10) cmHz(sup 1/2)/W near 4Hz. Result shows that it is possible to obtain high detectivity with thin films on etched sapphire with no processing after the deposition of the YBCO film. We discuss the etching process and its potential for micro-machining sapphire and fabricating 2-dimensional detector arrays with suspended sapphire membranes. A 30 micrometer thick layer of gold black provided IR absorption. Comparison is made with the current state of the art on silicon substrates.

  2. Temperature dependence of the electron spin g factor in CdTe and InP

    NASA Astrophysics Data System (ADS)

    Pfeffer, Pawel; Zawadzki, Wlodek

    2012-04-01

    Temperature dependence of the electron spin g factors in bulk CdTe and InP is calculated and compared with experiment. It is assumed that the only modification of the band structure related to temperature is a dilatation change in the fundamental energy gap. The dilatation changes of fundamental gaps are calculated for both materials using available experimental data. Computations of the band structures in the presence of a magnetic field are carried out employing five-level P.p model appropriate for medium-gap semiconductors. In particular, the model takes into account spin splitting due to bulk inversion asymmetry (BIA) of the materials. The resulting theoretical effective masses and g factors increase with electron energy due to band nonparabolicity. Average g values are calculated by summing over populated Landau and spin levels properly accounting for the thermal distribution of electrons in the band. It is shown that the spin splitting due to BIA in the presence of a magnetic field gives observable contributions to g values. Our calculations are in good agreement with experiments in the temperature range of 0 K to 300 K for CdTe and 0 K to 180 K for InP. The temperature dependence of g is stronger in CdTe than in InP due to different signs of band-edge g values in the two materials. Good agreement between the theory and experiments strongly indicates that the temperature dependence of spin g factors is correctly explained. In addition, we discuss formulas for the energy dependence of spin g factor due to band nonparabolicity, which are liable to misinterpretation.

  3. Improving INPE'S balloon ground facilities for operation of the protoMIRAX experiment

    NASA Astrophysics Data System (ADS)

    Mattiello-Francisco, F.; Rinke, E.; Fernandes, J. O.; Cardoso, L.; Cardoso, P.; Braga, J.

    2014-10-01

    The system requirements for reusing the scientific balloon ground facilities available at INPE were a challenge to the ground system engineers involved in the protoMIRAX X-ray astronomy experiment. A significant effort on software updating was required for the balloon ground station. Considering that protoMIRAX is a pathfinder for the MIRAX satellite mission, a ground infrastructure compatible with INPE's satellite operation approach would be useful and highly recommended to control and monitor the experiment during the balloon flights. This approach will make use of the SATellite Control System (SATCS), a software-based architecture developed at INPE for satellite commanding and monitoring. SATCS complies with particular operational requirements of different satellites by using several customized object-oriented software elements and frameworks. We present the ground solution designed for protoMIRAX operation, the Control and Reception System (CRS). A new server computer, properly configured with Ethernet, has extended the existing ground station facilities with switch, converters and new software (OPS/SERVER) in order to support the available uplink and downlink channels being mapped to TCP/IP gateways required by SATCS. Currently, the CRS development is customizing the SATCS for the kernel functions of protoMIRAX command and telemetry processing. Design-patterns, component-based libraries and metadata are widely used in the SATCS in order to extend the frameworks to address the Packet Utilization Standard (PUS) for ground-balloon communication, in compliance with the services provided by the data handling computer onboard the protoMIRAX balloon.

  4. Status of diffused junction p+n InP solar cells for space applications

    SciTech Connect

    Faur, M.; Goradia, C.; Faur, M.; Fatemi, N.S.; Jenkins, P.P.; Flood, D.J.; Brinker, D.J.; Wilt, D.M.; Bailey, S.; Goradia, M.

    1994-09-01

    Recently, the authors have succeeded in fabricating diffused junction p{sup +}n(Cd,S) InP solar cells with measured AMO, 25 C open circuit voltage (V{sub OC}) of 887.6 mV, which, to the best of their knowledge, is higher than previously reported V{sub OC} values for any InP homojunction solar cells. The experiment-based projected achievable efficiency of these cells using LEC grown substrates is 21.3 percent. The maximum AMO, 25 C internal losses due to date on bare cells is, however, only 13.2 percent. This is because of large external and internal losses due to non-optimized front grid design, antireflection (AR) coating and emitter thickness. This paper summarizes recent advances in the technology of fabrication of p{sup +}n InP diffused structures and solar cells, resulted from a study undertaken in an effort to increase the cell efficiency. The topics discussed in this paper include advances in: (1) the formation on thin p{sup +} InP:Cd emitter layers, (2) electroplated front contacts, (3) surface passivation and (4) the design of a new native oxide/Al2O3/MgF2 tree layer AR coating using a chemically-grown P-rich passivating oxide as a first layer. Based on the high radiation resistance and the excellent post-irradiation annealing and recovery demonstrated in the early tests done to date, as well as the projected high efficiency and low-cost high-volume fabricability, these cells show a very good potential for space photovoltaic applications.

  5. Correlation of electron and proton irradiation-induced damage in InP solar cells

    SciTech Connect

    Walters, R.J.; Summers, G.P.; Messenger, S.R.; Burke, E.A.

    1995-10-01

    When determining the best solar cell technology for a particular space flight mission, accurate prediction of solar cell performance in a space radiation environment is essential. The current methodology used to make such predictions requires extensive experimental data measured under both electron and proton irradiation. Due to the rising cost of accelerators and irradiation facilities, such extensive data sets are expensive to obtain. Moreover, with the rapid development of novel cell designs, the necessary data are often not available. Therefore, a method for predicting cell degradation based on limited data is needed. Such a method has been developed at the Naval Research Laboratory based on damage correlation using `displacement damage dose` which is the product of the non-ionizing energy loss (NIEL) and the particle fluence. Displacement damage dose is a direct analog of the ionization dose used to correlate the effects of ionizing radiations. In this method, the performance of a solar cell in a complex radiation environment can be predicted from data on a single proton energy and two electron energies, or one proton energy, one electron energy, and Co(exp 60) gammas. This method has been used to accurately predict the extensive data set measured by Anspaugh on GaAs/Ge solar cells under a wide range of electron and proton energies. In this paper, the method is applied to InP solar cells using data measured under 1 MeV electron and 3 MeV proton irradiations, and the calculations are shown to agree well with the measured data. In addition to providing accurate damage predictions, this method also provides a basis for quantitative comparisons of the performance of different cell technologies. The performance of the present InP cells is compared to that published for GaAs/Ge cells. The results show InP to be inherently more resistant to displacement energy deposition than GaAs/Ge.

  6. Correlation of electron and proton irradiation-induced damage in InP solar cells

    NASA Astrophysics Data System (ADS)

    Walters, Robert J.; Summers, Geoffrey P.; Messenger, Scott R.; Burke, Edward A.

    1995-10-01

    When determining the best solar cell technology for a particular space flight mission, accurate prediction of solar cell performance in a space radiation environment is essential. The current methodology used to make such predictions requires extensive experimental data measured under both electron and proton irradiation. Due to the rising cost of accelerators and irradiation facilities, such extensive data sets are expensive to obtain. Moreover, with the rapid development of novel cell designs, the necessary data are often not available. Therefore, a method for predicting cell degradation based on limited data is needed. Such a method has been developed at the Naval Research Laboratory based on damage correlation using 'displacement damage dose' which is the product of the non-ionizing energy loss (NIEL) and the particle fluence. Displacement damage dose is a direct analog of the ionization dose used to correlate the effects of ionizing radiations. In this method, the performance of a solar cell in a complex radiation environment can be predicted from data on a single proton energy and two electron energies, or one proton energy, one electron energy, and Co(exp 60) gammas. This method has been used to accurately predict the extensive data set measured by Anspaugh on GaAs/Ge solar cells under a wide range of electron and proton energies. In this paper, the method is applied to InP solar cells using data measured under 1 MeV electron and 3 MeV proton irradiations, and the calculations are shown to agree well with the measured data. In addition to providing accurate damage predictions, this method also provides a basis for quantitative comparisons of the performance of different cell technologies. The performance of the present InP cells is compared to that published for GaAs/Ge cells. The results show InP to be inherently more resistant to displacement energy deposition than GaAs/Ge.

  7. Correlation of electron and proton irradiation-induced damage in InP solar cells

    NASA Technical Reports Server (NTRS)

    Walters, Robert J.; Summers, Geoffrey P.; Messenger, Scott R.; Burke, Edward A.

    1995-01-01

    When determining the best solar cell technology for a particular space flight mission, accurate prediction of solar cell performance in a space radiation environment is essential. The current methodology used to make such predictions requires extensive experimental data measured under both electron and proton irradiation. Due to the rising cost of accelerators and irradiation facilities, such extensive data sets are expensive to obtain. Moreover, with the rapid development of novel cell designs, the necessary data are often not available. Therefore, a method for predicting cell degradation based on limited data is needed. Such a method has been developed at the Naval Research Laboratory based on damage correlation using 'displacement damage dose' which is the product of the non-ionizing energy loss (NIEL) and the particle fluence. Displacement damage dose is a direct analog of the ionization dose used to correlate the effects of ionizing radiations. In this method, the performance of a solar cell in a complex radiation environment can be predicted from data on a single proton energy and two electron energies, or one proton energy, one electron energy, and Co(exp 60) gammas. This method has been used to accurately predict the extensive data set measured by Anspaugh on GaAs/Ge solar cells under a wide range of electron and proton energies. In this paper, the method is applied to InP solar cells using data measured under 1 MeV electron and 3 MeV proton irradiations, and the calculations are shown to agree well with the measured data. In addition to providing accurate damage predictions, this method also provides a basis for quantitative comparisons of the performance of different cell technologies. The performance of the present InP cells is compared to that published for GaAs/Ge cells. The results show InP to be inherently more resistant to displacement energy deposition than GaAs/Ge.

  8. Progress in p(+)n InP solar cells fabricated by thermal diffusion

    NASA Technical Reports Server (NTRS)

    Flood, D. J.; Brinker, D. J.; Weinberg, I.; Vargas, C.; Faur, Mircea; Faur, Maria; Goradia, C.; Goradia, M.; Fatemi, N. S.

    1993-01-01

    The performance results of our most recently thermally diffused InP solar cells using the p(+)n (Cd,S) structures are presented. We have succeeded in fabricating cells with measured AMO, 25 C V(sub oc) exceeding 880 mV (bare cells) which to the best of our knowledge is higher than previously reported V(sub oc) values for any InP homojunction solar cells. The cells were fabricated by thinning the emitter, after Au-Zn front contacting, from its initial thickness of about 4.5 microns to about 0.6 microns. After thinning, the exposed surface of the emitter was passivated by a thin (approximately 50A) P-rich oxide. Based on the measured EQY and J(sub sc)-V(sub oc) characteristics of our experimental high V(sub oc) p(+)n InP solar cells, we project that reducing the emitter thickness to 0.3 microns, using an optimized AR coating, maintaining the surface hole concentration of 3 x 10(exp 18)cm(sup -3), reducing the grid shadowing from actual 10.55 percent to 6 percent and reducing the contact resistance will increase the actual measured 12.57 percent AMO 25 C efficiency to about 20.1 percent. By using our state-of-the-art p(+)n structures which have a surface hole concentration of 4 x 10(exp 18)cm(sup -3) and slightly improving the front surface passivation, an even higher practically achievable AMO, 25 C efficiency of 21.3 percent is projected.

  9. Status of diffused junction p+n InP solar cells for space applications

    NASA Technical Reports Server (NTRS)

    Faur, Mircea; Goradia, C.; Faur, Maria; Fatemi, N. S.; Jenkins, P. P.; Flood, D. J.; Brinker, D. J.; Wilt, D. M.; Bailey, S.; Goradia, M.

    1994-01-01

    Recently, we have succeeded in fabricating diffused junction p(sup +)n(Cd,S) InP solar cells with measured AMO, 25 C open circuit voltage (V(sub OC)) of 887.6 mV, which, to the best of our knowledge, is higher than previously reported V(sub OC) values for any InP homojunction solar cells. The experiment-based projected achievable efficiency of these cells using LEC grown substrates is 21.3 percent. The maximum AMO, 25 C internal losses due to date on bare cells is, however, only 13.2 percent. This is because of large external and internal losses due to non-optimized front grid design, antireflection (AR) coating and emitter thickness. This paper summarizes recent advances in the technology of fabrication of p(sup +)n InP diffused structures and solar cells, resulted from a study undertaken in an effort to increase the cell efficiency. The topics discussed in this paper include advances in: (1) the formation on thin p(sup +) InP:Cd emitter layers, (2) electroplated front contacts, (3) surface passivation and (4) the design of a new native oxide/Al2O3/MgF2 tree layer AR coating using a chemically-grown P-rich passivating oxide as a first layer. Based on the high radiation resistance and the excellent post-irradiation annealing and recovery demonstrated in the early tests done to date, as well as the projected high efficiency and low-cost high-volume fabricability, these cells show a very good potential for space photovoltaic applications.

  10. Status of Diffused Junction p(+)n InP Solar Cells for Space Applications

    NASA Technical Reports Server (NTRS)

    Faur, Mircea; Faur, Maria; Flood, D. J.; Brinker, D. J.; Goradia, C.; Fatemi, N. S.; Jenkins, P. P.; Wilt, D. M.; Bailey, S.

    1994-01-01

    Recently, we have succeeded in fabricating diffused junction p(+)n(Cd,S) InP solar cells with measured AMO, 25 C open circuit voltage (V(sub OC)) of 887.6 mV, which, to the best of our knowledge, is higher than previously reported V(sub OC) values for any InP homojunction solar cells. The experiment-based projected achievable efficiency of these cells using LEC grown substrates is 21.3%. The maximum AMO, 25 C efficiency recorded to date on bare cells is, however, only 13.2%. This is because of large external and internal losses due to non-optimized front grid design, antireflection (AR) coating and emitter thickness. This paper summarizes recent advances in the technology of fabrication of p(+)n InP diffused structures and solar cells, resulted from a study undertaken in an effort to increase the cell efficiency. The topics discussed in this paper include advances in: 1) the formation of thin p(+) InP:Cd emitter layers, 2) electroplated front contacts, 3) surface passivation and 4) the design of a new native oxide/AI203/MgF2 three layer AR coating using a chemically-grown P-rich passivating oxide as a first layer. Based on the high radiation resistance and the excellent post-irradiation annealing and recovery demonstrated in the early tests done to date, as well as the projected high efficiency and low-cost high-volume fabricability, these cells show a very good potential for space photovoltaic applications.

  11. InP tunnel junction for InGaAs/InP tandem solar cells

    SciTech Connect

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

    1995-10-01

    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 (450-530 C). The authors have previously shown that CBE is perfectly suited toward the fabrication of complex photovoltaic devices such as InP/InGaAs monolithically integrated tandem solar cells, because its low process temperature preserves the electrical characteristics of the InGaAs tunnel junction commonly used as an ohmic interconnect. In this work using CBE for the fabrication of optically transparent (with respect to the bottom cell) InP tunnel diodes is demonstrated. Epitaxial growth were performed in a Riber CBE 32 system using PH3 and TMIn as III and V precursors. Solid Be (p-type) and Si (n-type) have been used as doping sources, allowing doping levels up to 2 x 10(exp {minus}19)/cu cm and 1 x 10(exp {minus}19)/cu cm for n and p type respectively. The InP tunnel junction characteristics and the influence of the growth`s conditions (temperature, growth rate) over its performance have been carefully investigated. InP p(++)/n(++) tunnel junction with peak current densities up to 1600 A/sq cm and maximum specific resistivities (V(sub p)/I(sub p) - peak voltage to peak current ratio) in the range of 10(exp {minus}4) Omega-sq cm were obtained. The obtained peak current densities exceed the highest results previously reported for their lattice matched counterparts, In(0.53)Ga(0.47)As, and should allow the realization of improved minimal absorption losses in the interconnect InP/InGaAs tandem devices for Space applications.

  12. Chemical sensing with pulsed QC-DFB lasers operating at 15.6 micrometers

    NASA Technical Reports Server (NTRS)

    Kosterev, A. A.; Curl, R. F.; Tittel, F. K.; Rochat, M.; Beck, M.; Hofstetter, D.; Faist, J.

    2002-01-01

    Pulsed thermoelectrically cooled QC-DFB lasers operating at 15.6 micrometers were characterized for spectroscopic gas sensing applications. A new method for wavelength scanning based on repetition rate modulation was developed. A non-wavelength-selective pyroelectric detector was incorporated in the sensor configuration giving the advantage of room-temperature operation and low cost. Absorption lines of CO2 and H2O were observed in ambient air, providing information about the concentration of these species.

  13. Brightness Temperatures of Saturn's Disk and Rings at 400 and 700 Micrometers.

    PubMed

    Whitcomb, S E; Hildebrand, R H; Keene, J

    1980-11-14

    Saturn was observed in two broad submillimeter photometric bands with the rings nearly edge-on. The observed brightness temperatures fall below the predictions of atmospheric models constructed from data at shorter wavelenths, indicating the presence of an opacity source besides pressure-broadened hydrogen lines in the submillimeter region. In combination with earlier measurements at larger inclination angles, these results yield a 400-micrometer brightness temperature for the rings of approximately 75 K. PMID:17739549

  14. 2.4 Micrometer Cutoff Wavelength AlGaAsSb/InGaAsSb Phototransistors

    NASA Technical Reports Server (NTRS)

    Sulima, O. V.; Swaminathan, K.; Refaat, T. F.; Faleev, N. N.; Semenov, A. N.; Solov'ev, V. A.; Ivanov, S. V.; Abedin, M. N.; Singh, U. N.; Prather, D.

    2006-01-01

    We report the first AlGaAsSb/InGaAsSb phototransistors with a cutoff wavelength (50% of peak responsivity) of 2.4 micrometers operating in a broad range of temperatures. These devices are also the first AlGaAsSb/InGaAsSb heterojunction phototransistors (HPT) grown by molecular beam epitaxy (MBE). This work is a continuation of a preceding study, which was carried out using LPE (liquid phase epitaxy)-grown AlGaAsSb/InGaAsSb/GaSb heterostructures. Although the LPE-related work resulted in the fabrication of an HPT with excellent parameters [1-4], the room temperature cutoff wavelength of these devices (approximately 2.15 micrometers) was determined by fundamental limitations implied by the close-to-equilibrium growth from Al-In-Ga-As-Sb melts. As the MBE technique is free from the above limitations, AlGaAsSb/InGaAsSb/GaSb heterostructures for HPT with a narrower bandgap of the InGaAsSb base and collector - and hence sensitivity at longer wavelengths (lambda) - were grown in this work. Moreover, MBE - compared to LPE - provides better control over doping levels, composition and width of the AlGaAsSb and InGaAsSb layers, compositional and doping profiles, especially with regard to abrupt heterojunctions. The new MBE-grown HPT exhibited both high responsivity R (up to 2334 A/W for lambda=2.05 micrometers at -20 deg C.) and specific detectivity D* (up to 2.1 x 10(exp 11) cmHz(exp 1/2)/W for lambda=2.05 micrometers at -20 deg C).

  15. Hydrogen Passivation of N(+)P and P(+)N Heteroepitaxial InP Solar Cell Structures

    NASA Technical Reports Server (NTRS)

    Chatterjee, B.; Davis, W. C.; Ringel, S. A.; Hoffman, R., Jr.

    1995-01-01

    Dislocations and related point defect complexes caused by lattice mismatch currently limit the performance of heteroepitaxial InP cells by introducing shunting paths across the active junction and by the formation of deep traps within the base region. We have previously demonstrated that plasma hydrogenation is an effective and stable means to passivate the electrical activity of such defects in specially designed heteroepitaxial InP test structures to probe hydrogen passivation at typical base depths within a cell structure. In this work, we present our results on the hydrogen passivation of actual heteroepitaxial n(+)p and p(+)n InP cell structures grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD). We have found that a 2 hour exposure to a 13.56 MHz hydrogen plasma at 275 C reduces the deep level concentration in the base regions of both n(+)p and p(+)n heteroepitaxial InP cell structures from as-grown values of 5 - 7 x 10(exp 14)/cc, down to 3 - 5 x 10(exp 12)/cc. All dopants were successfully reactivated by a 400 C, 5 minute anneal With no detectable activation of deep levels. I-V analysis indicated a subsequent approx. 100 fold decrease In reverse leakage current at -1 volt reverse bias, and an improved built in voltage for the p(+)n structures. ln addition to being passivated,dislocations are also shown to participate in secondary interactions during hydrogenation. We find that the presence of dislocations enhances hydrogen diffusion into the cell structure, and lowers the apparent dissociation energy of Zn-H complexes from 1.19 eV for homoepitaxial Zn-doped InP to 1.12 eV for heteroepitaxial Zn-doped InP. This is explained by additional hydrogen trapping at dislocations subsequent to the reactivation of Zn dopants after hydrogenation.

  16. Hydrogen passivation of N(+)-P and P(+)-N heteroepitaxial InP solar cell structures

    NASA Technical Reports Server (NTRS)

    Chatterjee, Basab; Davis, William C.; Ringel, Steve A.; Hoffman, Richard, Jr.

    1996-01-01

    Dislocations and related point defect complexes caused by lattice mismatch currently limit the performance of heteroepitaxial InP cells by introducing shunting paths across the active junction and by the formation of deep traps within the base region. We have previously demonstrated that plasma hydrogenation is an effective and stable means to passivate the electrical activity of such defects in specially designed heteroepitaxial InP test structures to probe hydrogen passivation at typical base depths within a cell structure. In this work, we present our results on the hydrogen passivation of actual heteroepitaxial n-p and p-n InP cell structures grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD). We have found that a 2 hour exposure to a 13.56 MHz hydrogen plasma at 275 C reduces the deep level concentration in the base regions of both n(+)-p and p(+)-n heteroepitaxial InP cell structures from as-grown values of 5-7 x 10(exp 14) cm(exp -3), down to 3-5 x 10(exp 12) cm(exp -3). All dopants were successfully reactivated by a 400 C, 5 minute anneal with no detectable activation of deep levels. One to five analysis indicated a subsequent approximately 100 fold decrease in reverse leakage current at -1 volt reverse bias, and an improved built in voltage for the p(+)-n structures. In addition to being passivated, dislocations are also shown to participate in secondary interactions during hydrogenation. We find that the presence of dislocations enhances hydrogen diffusion into the cell structure, and lowers the apparent dissociation energy of Zn-H complexes from 1.19 eV for homoepitaxial Zn-doped InP to 1.12 eV for heteroepitaxial Zn-doped InP. This is explained by additional hydrogen trapping at dislocations subsequent to the reactivation of Zn dopants after hydrogenation.

  17. Frequency stability of InP HBT over 0.2 to 220 GHz

    NASA Astrophysics Data System (ADS)

    Zhijiang, Zhou; Kun, Ren; Jun, Liu; Wei, Cheng; Haiyan, Lu; Lingling, Sun

    2015-02-01

    The frequency stabilities of InP DHBTs in a broadband over 1 to 220 GHz are investigated. A hybrid π-topology small-signal model is used to accurately capture the parasitics of devices. The model parameters are extracted from measurements analytically. The investigation results show that the excellent agreement between the measured and simulated data is obtained in the frequency range 200 MHz to 220 GHz. The dominant parameters of the π-topology model, bias conditions and emitter area have significant effects on the stability factor K. The HBT model can be unconditionally stable by reasonable selection of the proper bias condition and the physical layout of the device.

  18. InP tunnel junctions for InP/InGaAs tandem solar cells

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    We report, for the first time, an epitaxially grown InP p(+)/n(++) tunnel junction. A diode with peak current densities up to 1600 A/cm and maximum specific resistivities (Vp/Ip - peak voltage to peak current ratio) in the range of 10(exp -4)Omega cm(exp 2) is obtained. This peak current density is comparable to the highest results previously reported for lattice matched In(0.53)Ga(0.47)As tunnel junctions. Both results were obtained using chemical beam epitaxy (CBE). In this paper we discuss the electrical characteristics of these tunnel diodes and how the growth conditions influence them.

  19. InP Tunnel Junctions for InP/InGaAs Tandem Solar Cells

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    We report, for the first time, an epitaxially grown InP p(+)/n(++) tunnel junction. A diode with peak current densities up to 1600 Al/sq cm and maximum specific resistivities (Vp/lp - peak voltage to peak current ratio) in the range of 10(exp -4)Om sq cm is obtained. This peak current density is comparable to the highest results previously reported for lattice matched In(0.53)Ga(0.47)As tunnel junctions. Both results were obtained using chemical beam epitaxy (CBE). In this paper we discuss the electrical characteristics of these tunnel diodes and how the growth conditions influence them.

  20. Femtosecond Transfer Dynamics of Photogenerated Electrons at a Surface Resonance of Reconstructed InP(100)

    NASA Astrophysics Data System (ADS)

    Töben, L.; Gundlach, L.; Ernstorfer, R.; Eichberger, R.; Hannappel, T.; Willig, F.; Zeiser, A.; Förstner, J.; Knorr, A.; Hahn, P. H.; Schmidt, W. G.

    2005-02-01

    Time-dependent two-photon photoemission spectra are used to resolve the femtosecond dynamics of hot electrons at the energetically lowest surface resonance of reconstructed InP(100). Two different cases are studied, where electrons either are lifted into the surface resonance via a direct optical transition or are captured from bulk states. These data are the first of this kind recorded with a time resolution below 70 fs. The microscopic analysis shows that electron-phonon scattering is a major mechanism for electron transfer between surface and bulk states.

  1. InP solar cell improvement by inverse delta-doping

    SciTech Connect

    Piprek, J.; Boeer, K.W.

    1994-12-31

    Recombination loss mechanisms in InP homojunction solar cells are analyzed using numerical modeling. To reduce the junction leakage current, it is proposed to introduce a thin undoped layer with low recombination center density near the pn-junction. This inverse delta-doping is found to be most beneficial in low efficiency p{sup +}n-InP cells, improving the open circuit voltage by 50 mV, the fill factor by 0.09, and the efficiency by 2 percentage points.

  2. Schottky barriers based on metal nanoparticles deposited on InP epitaxial layers

    NASA Astrophysics Data System (ADS)

    Grym, Jan; Yatskiv, Roman

    2013-04-01

    Fabrication of high-quality Schottky barriers on InP epitaxial layers prepared by liquid-phase epitaxy from rare-earth treated melts is reported. The Schottky structures are based on metal nanoparticles and a graphite layer deposited from colloidal solutions onto epitaxial layers with varying carrier concentration. The structures have notably high values of the barrier height and of the rectification ratio giving evidence of a small degree of the Fermi-level pinning. Electrical characteristics of these diodes are shown to be extremely sensitive to the exposure of gas mixtures with small hydrogen content.

  3. Hydrogen sensors based on electrophoretically deposited Pd nanoparticles onto InP

    PubMed Central

    2011-01-01

    Electrophoretic deposition of palladium nanoparticles prepared by the reverse micelle technique onto InP substrates is addressed. We demonstrate that the substrate pre-deposition treatment and the deposition conditions can extensively influence the morphology of the deposited palladium nanoparticle films. Schottky diodes based on these films show notably high values of the barrier height and of the rectification ratio giving evidence of a small degree of the Fermi level pinning. Moreover, electrical characteristics of these diodes are exceptionally sensitive to the exposure to gas mixtures with small hydrogen content. PMID:21711912

  4. Hydrogen sensors based on electrophoretically deposited Pd nanoparticles onto InP

    NASA Astrophysics Data System (ADS)

    Grym, Jan; Procházková, Olga; Yatskiv, Roman; Piksová, Kateřina

    2011-05-01

    Electrophoretic deposition of palladium nanoparticles prepared by the reverse micelle technique onto InP substrates is addressed. We demonstrate that the substrate pre-deposition treatment and the deposition conditions can extensively influence the morphology of the deposited palladium nanoparticle films. Schottky diodes based on these films show notably high values of the barrier height and of the rectification ratio giving evidence of a small degree of the Fermi level pinning. Moreover, electrical characteristics of these diodes are exceptionally sensitive to the exposure to gas mixtures with small hydrogen content.

  5. Hydrogen sensors based on electrophoretically deposited Pd nanoparticles onto InP.

    PubMed

    Grym, Jan; Procházková, Olga; Yatskiv, Roman; Piksová, Kateřina

    2011-01-01

    Electrophoretic deposition of palladium nanoparticles prepared by the reverse micelle technique onto InP substrates is addressed. We demonstrate that the substrate pre-deposition treatment and the deposition conditions can extensively influence the morphology of the deposited palladium nanoparticle films. Schottky diodes based on these films show notably high values of the barrier height and of the rectification ratio giving evidence of a small degree of the Fermi level pinning. Moreover, electrical characteristics of these diodes are exceptionally sensitive to the exposure to gas mixtures with small hydrogen content. PMID:21711912

  6. Nuclear geophysics in space and atmospheric research at INPE/BRAZIl

    NASA Astrophysics Data System (ADS)

    Nordemann, D. J. R.; Pereira, E. B.; Marinho, E. V. A.; Sircillineto, F.

    1986-05-01

    In recent years, INPE's research in Nuclear Geophysics has developed in fields of interest to the Institute, the scientific community and the society in general. In the space research field a contribution has been made to the history of meteorite falls on our planet and its possible collision with large meteorites, which may have been the cause of important effects such as biological extinction and extraterrestrial matter gathering. In atmospheric research, spatial and temporal variations of radon measurements in the lower atmosphere permit correlations from micrometeorology to mesoscale phenomena, related to the dynamics of air masses.

  7. Solar cells in bulk InP using an open tube diffusion process

    NASA Technical Reports Server (NTRS)

    Parat, K. K.; Bothra, S.; Borrego, J. M.; Ghandhi, S. K.

    1987-01-01

    A simple open tube diffusion technique for the fabrication of n+p junction solar cells is described. Large area (greater than 0.25 square cm) solar cells have been made by this process with a photovoltaic conversion efficiency of 15.2 percent under simulated AMO illumination. An ideality factor is 1.04 and a saturation current density of 9.6 times 10 to the minus 16th power A/square cm have been observed for these cells. These are the lowest (best) values reported to date for diffused structures in bulk InP.

  8. In-P based optoelectronic components for measurements, communications, and computers

    SciTech Connect

    Ishak, W.S.

    1996-12-31

    Optoelectronic and electronic devices will play a key role in the emerging information age. In particular, devices based on InP materials and operating in the 1--2 {micro}m wavelength regime are becoming a necessity for applications in long-haul fiber-optic communications, local area networks and lightwave test and measurement instrumentation. Some of these applications require very high-performance devices and, hence, are not very sensitive to cost. On the other hand, many other applications (for example, computer interconnects), cost is the most important parameter and large-scale manufacturing techniques must be implemented. Examples for both applications will be addressed.

  9. The penetration of acoustic cavitation bubbles into micrometer-scale cavities.

    PubMed

    Vaidya, Haresh Anant; Ertunç, Özgür; Lichtenegger, Thomas; Delgado, Antonio; Skupin, Andreas

    2016-04-01

    The penetration of acoustically induced cavitation bubbles in micrometer-scale cavities is investigated experimentally by means of high-speed photography and acoustic measurements. Micrometer-scale cavities of different dimensions (width=40 μm, 80 μm, 10 mm and depth=50 μm) are designed to replicate the cross section of microvias in a PCB. The aim here is to present a method for enhancing mass transfer due to the penetration of bubbles in such narrow geometries under the action of ultrasound. The micrometer-scale cavities are placed in a test-cell filled with water and subjected to an ultrasound excitation at 75 kHz. A cavitation bubble cluster is generated at the mouth of the cavity which acts as a continuous source of bubbles that penetrate into the cavity. The radial oscillation characteristics and translation of these bubbles are investigated in detail here. It is observed that the bubbles arrange themselves into streamer-like structures inside the cavity. Parameters such as bubble population and size distribution and their correlation with the phase of the incident ultrasound radiation are investigated in detail here. This provides a valuable insight into the dynamics of bubbles in narrow confined spaces. Mass transfer investigations show that fresh liquid can be continuously introduced in the cavities under the action of ultrasound. Our findings may have important consequences in optimizing the filling processes for microvias with high aspect ratios. PMID:26763751

  10. Dry Sliding Behavior of Sub-Micrometer-Sized Suspension Plasma Sprayed Ceramic Oxide Coatings

    NASA Astrophysics Data System (ADS)

    Darut, Geoffrey; Ben-Ettouil, Fadhel; Denoirjean, Alain; Montavon, Ghislain; Ageorges, Hélène; Fauchais, Pierre

    2010-01-01

    Almost half of the energy produced by an automotive engine is dissipated by friction in the cylinders, the clutch, etc. In the context of reduction of the emissions of greenhouse gases (GHGs) to mitigate climate global warming (CGW), reduction of energy losses due to friction is a critical issue. Surface treatments appear in such a context, as never than before, to be able to provide pertinent solutions to improve sliding behavior of mechanical parts. Numerous studies have clearly shown that decreasing the scale of coating structure below the micrometer scale was leading to an improvement of its tribological behavior in terms of friction coefficient and wear rate thanks to improved mechanical properties, the toughness in particular. Suspension Plasma Spraying (SPS) appears as a thermal spray process to be able to manufacture thick (i.e., a few tens of micrometers) coatings exhibiting a sub-micrometer-sized or even a nanometer-sized architecture, while keeping the versatility and flexibility of the thermal spray routes: i.e., the ability to process a wide range of material natures onto a wide range of substrate materials of various geometries. This article aims at studying the tribological behavior of several ceramic oxide composite coatings under dry conditions. The structural scale and the effect of composition are considered in particular.

  11. Modeling thermal infrared (2-14 micrometer) reflectance spectra of frost and snow

    NASA Technical Reports Server (NTRS)

    Wald, Andrew E.

    1994-01-01

    Existing theories of radiative transfer in close-packed media assume that each particle scatters independently of its neighbors. For opaque particles, such as are common in the thermal infrared, this assumption is not valid, and these radiative transfer theories will not be accurate. A new method is proposed, called 'diffraction subtraction', which modifies the scattering cross section of close-packed large, opaque spheres to account for the effect of close packing on the diffraction cross section of a scattering particle. This method predicts the thermal infrared reflectance of coarse (greater than 50 micrometers radius), disaggregated granular snow. However, such coarse snow is typically old and metamorphosed, with adjacent grains welded together. The reflectance of such a welded block can be described as partly Fresnel in nature and cannot be predicted using Mie inputs to radiative transfer theory. Owing to the high absorption coefficient of ice in the thermal infrared, a rough surface reflectance model can be used to calculate reflectance from such a block. For very small (less than 50 micrometers), disaggregated particles, it is incorrect in principle to treat diffraction independently of reflection and refraction, and the theory fails. However, for particles larger than 50 micrometers, independent scattering is a valid assumption, and standard radiative transfer theory works.

  12. Redox-sensitive TP53INP1 SUMOylation as an oxidative stress sensor to activate TP53

    PubMed Central

    Bonacci, Thomas; Peuget, Sylvain; Soubeyran, Philippe; Iovanna, Juan; Dusetti, Nelson J

    2014-01-01

    Oxidative stress-induced sumoylation of TP53INP1 (tumor protein p53-induced nuclear protein 1) is essential to enhance the TP53 response. Sumoylation of TP53INP1 on the K113 residue, which is mediated by protein inhibitor of activated STAT 3 (PIAS3) and chromobox homolog 4 (CBX4) and removed by SUMO1/sentrin specific peptidase (SENP1, 2 and 6), favors its interaction with TP53 in the nucleus and enhances TP53-induced gene expression. PMID:27308354

  13. Electrical activation of the Fe{sup 2+/3+} trap in Fe-implanted InP

    SciTech Connect

    Fraboni, B.; Gasparotto, A.; Cesca, T.; Verna, A.; Impellizzeri, G.; Priolo, F.

    2005-12-19

    We have studied the electrical activation of the Fe{sup 2+/3+} trap in Fe-implanted InP by means of capacitance-voltage and deep level transient spectroscopy analyses. Five deep traps have been identified and we have characterized the concentration and depth distribution of the Fe{sup 2+/3+} deep trap, located at E{sub C}-0.66 eV. The InP substrate background doping, i.e., the Fermi-level position, plays a crucial role in the Fe activation process by setting an upper limit to the amount of Fe centers electrically activated as deep acceptor traps.

  14. SiC nanowires synthesized from graphene and silicon vapors

    NASA Astrophysics Data System (ADS)

    Weichenpei, Luo; Gong-yi, Li; Zengyong, Chu; Tianjiao, Hu; Xiaodong, Li; Xuefei, Zhang

    2016-04-01

    The preparation of silicon carbide (SiC) nanowires is basically important for its potential applications in nanodevices, nanocomposites, etc. In the present work, a simple route was reported to synthesize SiC nanowires by heating commercial graphene with silicon vapors and no catalyst. Characterization by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, electron energy scattering, X-ray diffraction, and Raman dispersive spectrum demonstrates the products are composed of β-SiC crystal. The SiC nanowires have the average diameter of about 50 nm and length of tens of micrometers. The vapor-solid mechanism was employed to interpret the SiC nanowires growth. Gaseous SiO which was produced by the reaction of Si powders with its surface oxidation reacted with the solid graphene to form SiC crystal nuclei. And SiC crystal nuclei would act as active sites for further growing into nanowires.

  15. The effect of process conditions on the performance of epitaxial InP solar cells

    NASA Technical Reports Server (NTRS)

    Borrego, J. M.; Ghandi, S. K.

    1991-01-01

    Indium phosphide solar cells have a higher resistance to electron irradiation than Si or GaAs cells of comparable junction depth. As a result, there is much interest in the use of this material for space applications. Cells of this material were made in bulk InP by a number of techniques, including ion implantation, direct diffusion in sealed ampoules, and by open tube diffusion. However, it is generally considered that the epitaxial approach will be superior to all of these techniques. The epitaxy of InP is considerably more difficult than that of gallium arsenide, for a number of reasons. Perhaps the most important is the fact that the native oxides of Indium are extremely difficult to remove, as compared to that of Gallium. In addition, thermal treatments for the desorption of these oxides often result in the formation of phosphorus vacancies and free indium on the surface. Thus, inadequate sample preparation before epitaxy, poor reactor cleaning procedures, or poor transition procedures between the growth of successive layers, all give rise to trap phenomena and to high interface recombination velocities. Moreover, the lifetime of the grown material is dominated by the occurrence of native defects, so that it is a strong function of growth parameters. These problems are of special interest to the fabrication of solar cells, where long life-time, combined with the absence of traps, is highly desirable. A study of this problem is described using a non-invasive diagnostic technique which was developed.

  16. Triple and Quadruple Junctions Thermophotovoltaic Devices Lattice Matched to InP

    NASA Technical Reports Server (NTRS)

    Bhusal, L.; Freundlich, A.

    2007-01-01

    Thermophotovoltaic (TPV) conversion of IR radiation emanating from a radioisotope heat source is under consideration for deep space exploration. Ideally, for radiator temperatures of interest, the TPV cell must convert efficiently photons in the 0.4-0.7 eV spectral range. Best experimental data for single junction cells are obtained for lattice-mismatched 0.55 eV InGaAs based devices. It was suggested, that a tandem InGaAs based TPV cell made by monolithically combining two or more lattice mismatched InGaAs subcells on InP would result in a sizeable efficiency improvement. However, from a practical standpoint the implementation of more than two subcells with lattice mismatch systems will require extremely thick graded layers (defect filtering systems) to accommodate the lattice mismatch between the sub-cells and could detrimentally affect the recycling of the unused IR energy to the emitter. A buffer structure, consisting of various InPAs layers, is incorporated to accommodate the lattice mismatch between the high and low bandgap subcells. There are evidences that the presence of the buffer structure may generate defects, which could extend down to the underlying InGaAs layer. The unusual large band gap lowering observed in GaAs(1-x)N(x) with low nitrogen fraction [1] has sparked a new interest in the development of dilute nitrogen containing III-V semiconductors for long-wavelength optoelectronic devices (e.g. IR lasers, detector, solar cells) [2-7]. Lattice matched Ga1-yInyNxAs1-x on InP has recently been investigated for the potential use in the mid-infrared device applications [8], and it could be a strong candidate for the applications in TPV devices. This novel quaternary alloy allows the tuning of the band gap from 1.42 eV to below 1 eV on GaAs and band gap as low as 0.6eV when strained to InP, but it has its own limitations. To achieve such a low band gap using the quaternary Ga1-yInyNxAs1-x, either it needs to be strained on InP, which creates further

  17. Structural, electronic, and magnetic properties of Mn-Doped InP nanowire

    NASA Astrophysics Data System (ADS)

    Srivastava, Pankaj; Kumar, Avaneesh; Jaiswal, Neeraj K.

    2016-04-01

    In the present work, we investigate structural stability, electronic and magnetic properties of InP nanowire (NW) oriented along (111) direction and doped with Mn using first-principles calculations. Structural analysis revealed that incorporation of Mn atom in NW geometry results in strong reconstructions of surface atoms relative to core atoms. For single Mn-doped NW, partially filled d orbital of Mn atom results in magnetic semiconducting behavior due to non-degenerate electronic band-gap (∼0.1 eV). We have further considered the effect of Mn-Mn coupling on the electronic/magnetic properties of InP NW. Anti-ferromagnetic coupling state is observed as most favorable state based on total energy calculations. A half-metallic ferromagnetic coupling is also observed in case of Mn-pair doped at sub-surface of NW. The present results predict that the system doped with Mn pair between surface and core region are energetically more favorable than others.

  18. Elucidation of the organometallic vapor phase epitaxial growth mechanism for InP

    NASA Technical Reports Server (NTRS)

    Buchan, N. I.; Larsen, C. A.; Stringfellow, G. B.

    1987-01-01

    A new technique for tracing the organometallic vapor epitaxial growth is reported. The pyrolysis of PH3, alone and in the presence of trimethylindium (TMIn), and of TMIn alone was studied by conducting the epitaxial growth of InP in D2 as the carrier gas, tracing growth reactions by mass spectrometric analysis of the product molecules. The TMIn alone pyrolyzes mostly homogeneously in the gas phase, while the PH3 pyrolysis is completely heterogeneous at the InP surface. Adding TMIn to PH3 results in a dramatic decrease in the pyrolysis temperature. PH3 molecules which interact with TMIn in the gas phase pyrolyze at temperatures as low as 250, and those decomposing without TMIn interaction pyrolyze at temperatures approximately 200 C higher. Similarly, the presence of PH3 lowers the TMIn pyrolysis temperature by at least 50 C. TMIn alone in D2 produces mainly CH3D molecules. For high PH3:TMIn ratios, CH4 is the only carbon-containing reaction product.

  19. Pressure-Dependent Photoluminescence Study of Wurtzite InP Nanowires.

    PubMed

    Chauvin, Nicolas; Mavel, Amaury; Patriarche, Gilles; Masenelli, Bruno; Gendry, Michel; Machon, Denis

    2016-05-11

    The elastic properties of InP nanowires are investigated by photoluminescence measurements under hydrostatic pressure at room temperature and experimentally deduced values of the linear pressure coefficients are obtained. The pressure-induced energy shift of the A and B transitions yields a linear pressure coefficient of αA = 88.2 ± 0.5 meV/GPa and αB = 89.3 ± 0.5 meV/GPa with a small sublinear term of βA = βB = -2.7 ± 0.2 meV/GPa(2). Effective hydrostatic deformation potentials of -6.12 ± 0.04 and -6.2 ± 0.04 eV are derived from the results for the A and B transitions, respectively. A decrease of the integrated intensity is observed above 0.5 GPa and is interpreted as a carrier transfer from the first to the second conduction band of the wurtzite InP. PMID:27046672

  20. Simple intrinsic defects in GaP and InP

    NASA Astrophysics Data System (ADS)

    Schultz, Peter A.

    2012-02-01

    To faithfully simulate evolution of defect chemistry and electrical response in irradiated semiconductor devices requires accurate defect reaction energies and energy levels. In III-Vs, good data is scarce, theory hampered by band gap and supercell problems. I apply density functional theory (DFT) to intrinsic defects in GaP and InP, predicting stable charge states, ground state configurations, defect energy levels, and identifying mobile species. The SeqQuest calculations incorporate rigorous charge boundary conditions removing supercell artifacts, demonstrated converged to the infinite limit. Computed defect levels are not limited by a band gap problem, despite Kohn-Sham gaps much smaller than the experimental gap. As in GaAs, [P.A. Schultz and O.A. von Lilienfeld, Modeling Simul. Mater. Sci. Eng. 17, 084007 (2009)], defects in GaP and InP exhibit great complexity---multitudes of charge states, bistabilities, and negative U systems---but show similarities to each other (and to GaAs). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  1. Growth of ternary and quaternary compounds on non-planar InP substrates

    SciTech Connect

    Mullan, C.A.; Robinson, B.J.; Thompson, D.A.; Weatherly, G.C.

    1996-12-31

    InP based ternary and quaternary materials are in wide use for optoelectronic systems. It has been well documented that phase separation occurs when these are deposited onto planar substrates. The use of non-planar substrates is becoming increasingly popular for the fabrication of novel devices. Obviously, epitaxial growth of these materials onto a non-planar surface will differ from growth on a planar surface. The effect of simultaneously growing on two or more crystal planes which have different atom migration lengths and sticking coefficients must now be considered. Since phase segregation occurs in InP-based materials the question arises, what effect will growth on a patterned substrate have? The authors have previously shown how InP, InGaAs and InGaAsP deposited onto etched DFB gratings under the same conditions act differently and here they will show both how the atomic concentrations change in deposited InGaAs and InGaAsP layers with position above the grating and how the total incorporation rate changes when compared to growth on a planar substrate.

  2. High-efficiency red electroluminescent device based on multishelled InP quantum dots.

    PubMed

    Jo, Jung-Ho; Kim, Jong-Hoon; Lee, Ki-Heon; Han, Chang-Yeol; Jang, Eun-Pyo; Do, Young Rag; Yang, Heesun

    2016-09-01

    We report on the synthesis of highly fluorescent red-emitting InP quantum dots (QDs) and their application to the fabrication of a high-efficiency QD-light-emitting diode (QLED). The core/shell heterostructure of the QDs is elaborately tailored toward a multishelled structure with a composition-gradient ZnSeS intermediate shell and an outer ZnS shell. Using the resulting InP/ZnSeS/ZnS QDs as an emitting layer, all-solution-processible red InP QLEDs are fabricated with a hybrid multilayered device structure having an organic hole transport layer (HTL) and an inorganic ZnO nanoparticle electron transport layer. Two HTLs of poly(9-vinlycarbazole) or poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenyl-amine), whose hole mobilities are different by at least three orders of magnitude, are individually applied for QLED fabrication and such HTL-dependent device performances are compared. Our best red device displays exceptional figures of merit such as a maximum luminance of 2849  cd/m2, a current efficiency of 4.2  cd/A, and an external quantum efficiency of 2.5%. PMID:27607953

  3. Scalar and anisotropic J interactions in undoped InP: A triple-resonance NMR study

    NASA Astrophysics Data System (ADS)

    Tomaselli, Marco; Degraw, David; Yarger, Jeffery L.; Augustine, Matthew P.; Pines, Alexander

    1998-10-01

    The heteronuclear J-coupling tensor between nearest neighbor 31P and 113In spins in undoped InP is investigated by means of 113In-->31P polarization transfer under rapid magic angle spinning (MAS). The scalar contribution can be measured directly and is found to have the value \\|Jiso(31P-113,115In)\\|=(225+/-10) Hz. The principal value of the traceless anisotropic J-coupling tensor (pseudodipolar coupling) is determined to be Janiso(31P-113,115In)=2/3[J||(31P-113,115In)-J⊥(31P-113,115In)]=(813+/-50) or (1733+/-50) Hz, assuming axial symmetry with the principal axis parallel to the In-P bond. Our values deviate from those reported previously [M. Engelsberg and R. E. Norberg, Phys. Rev. B 5, 3395 (1972)] [based on a moment analysis of the 31P resonance \\|Jiso(31P-113,115In)\\|=350 Hz and Janiso(31P-113,115In)=1273 Hz], but confirm the postulate that the nearest neighbor 31P-113,115In magnetic dipolar and pseudodipolar interactions are of the same order of magnitude and partially cancel each other.

  4. 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.

  5. Multiple growths of epitaxial lift-off solar cells from a single InP substrate

    SciTech Connect

    Lee, K.; Shiu, K. T.; Zimmerman, J.; Forrest, Stephen R.

    2010-01-01

    We demonstrate multiple growths of flexible, thin-film indium tin oxide-InP Schottky-barriersolar 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 η{sub p}=14.4±0.4% and η{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-filmsolar cells may provide a practical path to low-cost solar-to-electrical energy conversion.

  6. Annealing of irradiated n+p InP buried homojunctions

    NASA Technical Reports Server (NTRS)

    Walters, Robert J.; Summers, Geoffrey P.; Timmons, M. L.; Venkatasubramanian, R.; Hancock, J. A.; Hills, J. S.

    1994-01-01

    At the last SPRAT conference, the Naval Research Laboratory (NRL) presented results from two experiments. One studied n+p diffused junction (DJ) InP solar cells, and the other studied n+p shallow homojunction (SHJ) InP mesa diodes grown by metalorganic chemical vapor deposition (MOCVD). The former work showed that a DJ solar cell in which the maximum power P(sub max) had been degraded by nearly 80 percent under irradiation recovered completely under short circuit illumination at 450K. The recovery was accompanied by the removal of all but one of the radiation-induced defect levels. The latter work, on the other hand, showed that the radiation-induced defects in the SHJ diodes did not anneal until the temperature reached 650K. These results suggest that an irradiated DJ solar cell, under illumination, will anneal at a temperature 200K lower than an irradiated SHJ cell. This is an unexpected result considering the similarity of the devices. The goal of the present research is to explain this different behavior. This paper investigates two points which arose from the previous studies. The first point is that the DJ cells were annealed under illumination while the SHJ diodes were annealed without bias. The second point investigated here is that the emitters of the DJ and SHJ devices were significantly different.

  7. (In,Ga)As sidewall quantum wires on shallow-patterned InP (311)A

    SciTech Connect

    Zhou, D.; Noetzel, R.; Gong, Q.; Offermans, P.; Koenraad, P.M.; Veldhoven, P.J. van; Otten, F.W.M. van; Eijkemans, T.J.; Wolter, J.H.

    2005-03-15

    (In,Ga)As sidewall quantum wires (QWires) are realized by chemical beam epitaxy along [01-1] mesa stripes on shallow-patterned InP (311)A substrates. The QWires exhibit strong lateral carrier confinement due to larger thickness and In composition compared to the adjacent quantum wells, as determined by cross-sectional scanning-tunneling microscopy and microphotoluminescence (micro-PL) spectroscopy. The PL of the (In,Ga)As QWires with InP and quaternary (Ga,In)(As,P) barriers reveals narrow linewidth, high efficiency, and large lateral carrier confinement energies of 60-70 meV. The QWires are stacked in growth direction with identical PL peak emission energy. The PL emission energy is not only controlled by the (In,Ga)As layer thickness but also by the patterned mesa height. Stacked (In,Ga)As QWires with quaternary barriers exhibit room temperature PL emission at 1.55 {mu}m in the technologically important wavelength region for telecommunication applications.

  8. TP53INP1, a tumor suppressor, interacts with LC3 and ATG8-family proteins through the LC3-interacting region (LIR) and promotes autophagy-dependent cell death

    PubMed Central

    Seillier, M; Peuget, S; Gayet, O; Gauthier, C; N'Guessan, P; Monte, M; Carrier, A; Iovanna, J L; Dusetti, N J

    2012-01-01

    TP53INP1 (tumor protein 53-induced nuclear protein 1) is a tumor suppressor, whose expression is downregulated in cancers from different organs. It was described as a p53 target gene involved in cell death, cell-cycle arrest and cellular migration. In this work, we show that TP53INP1 is also able to interact with ATG8-family proteins and to induce autophagy-dependent cell death. In agreement with this finding, we observe that TP53INP1, which is mainly nuclear, relocalizes in autophagosomes during autophagy where it is eventually degraded. TP53INP1-LC3 interaction occurs via a functional LC3-interacting region (LIR). Inactivating mutations of this sequence abolish TP53INP1-LC3 interaction, relocalize TP53INP1 in autophagosomes and decrease TP53INP1 ability to trigger cell death. Interestingly, TP53INP1 binds to ATG8-family proteins with higher affinity than p62, suggesting that it could partially displace p62 from autophagosomes, modifying thereby their composition. Moreover, silencing the expression of autophagy related genes (ATG5 or Beclin-1) or inhibiting caspase activity significantly decreases cell death induced by TP53INP1. These data indicate that cell death observed after TP53INP1-LC3 interaction depends on both autophagy and caspase activity. We conclude that TP53INP1 could act as a tumor suppressor by inducing cell death by caspase-dependent autophagy. PMID:22421968

  9. [C II] 158-micrometer Observations of a Sample of Late-type Galaxies from the Virgo Cluster

    NASA Technical Reports Server (NTRS)

    Leech, K. J.; Volk, H. J.; Heinrichsen, I.; Hippelein, H.; Metcalfe, L.; Pierini, D.; Popescu, C. C.; Tuffs, R. J.; Xu, C.

    1998-01-01

    We have observed 19 Virgo cluster spiral galaxies with the Long Wavelength Spectrometer (LWS) onboard ESAs Infrared Space Observatory (ISO) obtaining spectral around the (C II) 157.741-micrometer fine structure line.

  10. Controllable growth and optical properties of InP and InP/InAs nanostructures on the sidewalls of GaAs nanowires

    SciTech Connect

    Yan, Xin; Zhang, Xia Li, Junshuai; Cui, Jiangong; Ren, Xiaomin

    2014-12-07

    The growth and optical properties of InP and InP/InAs nanostructures on GaAs nanowires are investigated. InP quantum well and quantum dots (QDs) are formed on the sidewalls of GaAs nanowires successively with increasing the deposition time of InP. The GaAs/InP nanowire heterostructure exhibits a type-II band alignment. The wavelength of the InP quantum well is in the range of 857–892 nm at 77 K, which means that the quantum well is nearly fully strained. The InP quantum dot, which has a bow-shaped cross section, exhibits dislocation-free pure zinc blende structure. Stranski-Krastanow InAs quantum dots are subsequently formed on the GaAs/InP nanowire core-shell structure. The InAs quantum dots are distributed over the middle part of the nanowire, indicating that the In atoms contributing to the quantum dots mainly come from the vapor rather than the substrate. The longest emission wavelength obtained from the InAs QDs is 1039 nm at 77 K. The linewidth is as narrow as 46.3 meV, which is much narrower than those on planar InP substrates and wurtzite InP nanowires, suggesting high-crystal-quality, phase-purity, and size-uniformity of quantum dots.

  11. Common base amplifier with 7 - dB gain at 176 GHz in InP mesa DHBT technology

    NASA Technical Reports Server (NTRS)

    Samoska, Lorene; Paidi, V.; Griffith, Z.; Dahlstrom, M.; Wei, Y.; Urteaga, M.; Rodell, M. J. W.; Fung, A.

    2004-01-01

    We report a single stage tunded amplifier that exhibits 7 dB small signal gain at 176 GHz. Common Base topology is chosen as it has the best maximum stable gain (MSG) in this frequency band when compared to common emitter and common collector topologies. The amplifiers are designed and fabricated in InP mesa double heterojunction bipolar transistor (DHBT) technology.

  12. Reproducible group-V partial pressure rapid thermal annealing of InP and GaAs

    NASA Astrophysics Data System (ADS)

    Pearton, S. J.; Katz, A.; Geva, M.

    1990-09-01

    We compare the effectiveness of two types of SiC-coated graphite susceptors in providing degradation-free rapid thermal annealing of InP and GaAs. The first type of susceptor must be charged with the group-V species prior to any annealing cycles. Under the optimum charging conditions, effective surface protection is provided for up to five sequential high-temperature (900 °C, 10 s) anneals of GaAs, or only one anneal (750 °C, 10 s) of InP before recharging is necessary. The incorporation of small reservoirs into the susceptor allows for the provision of a constant group-V partial pressure over the wafer, and it appears that for this type of susceptor many dozens of InP or GaAs wafers can be annealed without any apparent surface degradation. The relative merits of using InAs, GaAs, or InP as the group-V source in the reservoirs have been compared, and it is found that the best protection is achieved when one uses the same semiconductor in the reservoirs as is being annealed.

  13. Radiation resistance and comparative performance of ITO/InP and n/p InP homojunction solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Swartz, C. K.; Hart, R. E., Jr.; Coutts, T. J.

    1988-01-01

    The radiation resistance of ITO/InP cells processed by DC magnetron sputtering is compared to that of standard n/p InP and GaAs homojunction cells. After 20 MeV proton irradiations, it is found that the radiation resistance of the present ITO/InP cell is comparable to that of the n/p homojunction InP cell and that both InP cell types have radiation resistance significantly greater than GaAs. The relatively lower radiation resistance, observed at higher fluence, for the InP cell with the deepest junction depth, is attributed to losses in the cells emitter region. Diode parameters obtained from I sub sc - V sub oc plots, data from surface Raman spectroscopy, and determinations of surface conductivity types are used to investigate the configuration of the ITO/InP cells. It is concluded that thesee latter cells are n/p homojunctions, the n-region consisting of a disordered layer at the oxide semiconductor.

  14. Crystallinity, Surface Morphology, and Photoelectrochemical Effects in Conical InP and InN Nanowires Grown on Silicon.

    PubMed

    Parameshwaran, Vijay; Xu, Xiaoqing; Clemens, Bruce

    2016-08-24

    The growth conditions of two types of indium-based III-V nanowires, InP and InN, are tailored such that instead of yielding conventional wire-type morphologies, single-crystal conical structures are formed with an enlarged diameter either near the base or near the tip. By using indium droplets as a growth catalyst, combined with an excess indium supply during growth, "ice cream cone" type structures are formed with a nanowire "cone" and an indium-based "ice cream" droplet on top for both InP and InN. Surface polycrystallinity and annihilation of the catalyst tip of the conical InP nanowires are observed when the indium supply is turned off during the growth process. This growth design technique is extended to create single-crystal InN nanowires with the same morphology. Conical InN nanowires with an enlarged base are obtained through the use of an excess combined Au-In growth catalyst. Electrochemical studies of the InP nanowires on silicon demonstrate a reduction photocurrent as a proof of photovolatic behavior and provide insight as to how the observed surface polycrystallinity and the resulting interface affect these device-level properties. Additionally, a photovoltage is induced in both types of conical InN nanowires on silicon, which is not replicated in epitaxial InN thin films. PMID:27455379

  15. Study of surface passivation as a function of InP closed-ampoule solar cell fabrication processing variables

    NASA Technical Reports Server (NTRS)

    Faur, Mircea; Faur, Maria; Jenkins, Phillip; Goradia, Manju; Goradia, Chandra; Bailey, Sheila; Weinberg, Irving; Jayne, Douglas

    1990-01-01

    The effects of various surface preparation procedures, including chemical treatment and anodic or chemical oxidation, closed-ampoule diffusion conditions, and post-diffusion surface preparation and annealing conditions, on the passivating properties of InP have been investigated in order to optimize the fabrication procedures of n(+)p InP solar cells made by closed-ampoule diffusion of sulfur into p-type InP. The InP substrates used were p-type Cd-doped to a level of 1.7 x 10 to the 16th/cu cm, Zn-doped to levels of 2.2 x 10 to the 16th and 1.2 x 10 to the 18th/cu cm, and n-type S-doped to 4.4 x 10 to the 18th/cu cm. The passivating properties have been evaluated from photoluminescence (PL) and conductance-voltage (G-V) data. Good agreement was found between the level of surface passivation and the composition of different surface layers as revealed by X-ray photoelectron spectroscopy (XPS) analysis.

  16. Use of tertiarybutylphosphine for the growth of InP and GaAs1-xPx

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Cao, D. S.; Stringfellow, G. B.

    1988-01-01

    A newly-developed phosphorus source, tertiarybutylphosphine (TBP), which is much less toxic than PH3, has been used to grow InP and GaAs1-xPx by atmospheric pressure organometallic vapor phase epitaxy (OMVPE). Excellent morphologies are obtained for the growth of InP between 560 and 630° C for TBP partial pressures larger than 0.5 x 10-3. For the first time, V/III ratios as low as 3 have been used to grow InP epilayers with featureless morphologies at 600° C. To obtain good morphologies at both lower and higher temperatures, higher TBP partial pressures are necessary. The electron mobility increases and the electron density decreases as the temperature is increased. The highest room temperature mobilities and lowest electron densities, obtained at 630° C, are 3800 cm2/V-sec and 3 x 1015 cm-3, respectively. The 10 K photoluminescence spectra of the InP epilayers at higher growth temperatures show no carbon contamination. Bound excition half widths as low as 3.0 meV have been measured. The use of TBP to replace PH3 in the growth of GaAs1-xPx results in a nearly linear relationship between vapor and solid composition at 610° C, i.e., the P distribution coefficient is nearly unity. This contrasts sharply with the very low P distribution coefficient obtained using PH3 at such low growth temperatures.

  17. High-quality InP epitaxial layers grown by metal-organic chemical vapor deposition using tertiarybutylphosphine (TBP) source

    NASA Astrophysics Data System (ADS)

    Kuan, H.; Su, Yan-Kuin; Tzou, W. J.

    1994-10-01

    One organophosphrous compound, tertiarybutylphosphine has been investigated for their possible use as precursors in the metalorganic chemical vapor deposition (MOCVD). This material is less pyrophoric and less toxic than phosphine, the compound has used to grow epitaxial layers of InP on semi-insulating InP substrate using trimethylindium (TMIn) in a flowing hydrogen ambient. High quality InP epilayer have been successfully grown and specular surface was obtained at growth temperature 600 degree(s)C and x-ray was used to measure the lattice mismatch (Delta) a/a. The highest quality InP epilayer, which was grown at a V/III ratio of 60 and a growth pressure of 250 Torr, the highest n-type electron Hall mobility were 4500 cm2/Vs with the electron concentration of 3.4 X 1015 cm-3 at 300 K and 18260 cm2/Vs with the electron concentration of 2.8 X 1015 cm-3 at 77 K. The low temperature (10 K) photoluminescence optical properties measurements show intense near bandgap emission with a full width half maximum (FWHM) is about 8 meV.

  18. Wet chemical cleaning of InP surfaces investigated by in situ and ex situ infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Pluchery, O.; Chabal, Y. J.; Opila, R. L.

    2003-08-01

    Wet chemical cleaning is central to semiconductor device processing. For InP-based optoelectronic devices, controlling wet processing is challenging because of the high reactivity of InP surfaces in ambient air. In situ techniques are therefore critical to monitor and understand wet chemical etching and oxidation. We have combined in situ and ex situ Fourier transform infrared absorption spectroscopy, in direct transmission and multiple internal reflection configurations, with ex situ x-ray photoelectron spectroscopy to investigate the wet-chemical removal of "epi-ready" oxides on InP(100). Even dilute solutions of HCl, HF, or H2SO4 are found to completely remove the epi-ready oxides. For both HCl and HF, the InP surface is left unpassivated, exhibiting rapid recontamination and reoxidation upon air exposure. In contrast, H2SO4 aggressively etches the surface, and forms a thick and fragile oxide cap that can be washed away during a subsequent water rinse. This systematic in situ vibrational study of InP oxide chemistry provides a basis for a mechanistic understanding of wet chemical etching and oxidation.

  19. Correlation between overgrowth morphology and optical properties of single self-assembled InP quantum dots

    NASA Astrophysics Data System (ADS)

    Johansson, M. K.-J.; Håkanson, U.; Holm, M.; Persson, J.; Sass, T.; Johansson, J.; Pryor, C.; Montelius, L.; Seifert, W.; Samuelson, L.; Pistol, M.-E.

    2003-09-01

    We have studied the early stages of GaInP overgrowth on InP quantum dots (QD’s) experimentally and theoretically. A direct correlation between the surface morphology and the optical properties of individual InP QD’s is made using scanning tunneling microscopy (STM) and scanning tunneling luminescence. The geometric structure of the islands is further investigated using cross-sectional transmission electron microscopy (TEM). The overgrowth occurs in three stages; initially the InP QD’s act as seeding points for the overgrowth, where the GaInP grows laterally from the side facets of the QD. The growth occurs preferentially in the [110] direction and elongated GaInP/InP islands are formed. As the overgrowth continues the islands increase laterally in size and GaInP also starts to grow between the islands, but not covering the top of the InP QD’s. The growth of GaInP on top of the QD’s commences once the islands have begun to coalesce. Using a model based on the STM and TEM results the electronic structures of the QD’s have been calculated by eight-band kṡp theory. The calculations are in good agreement with the experimental results. Our findings unravel the details of the strain induced energy shift of the QD luminescence previously reported [Pistol et al., Appl. Phys. Lett. 67, 1438 (1995)].

  20. 1.12 Tb/s superchannel coherent PM-QPSK InP transmitter photonic integrated circuit (PIC).

    PubMed

    Evans, P; Fisher, M; Malendevich, R; James, A; Goldfarb, G; Vallaitis, T; Kato, M; Samra, P; Corzine, S; Strzelecka, E; Studenkov, P; Salvatore, R; Sedgwick, F; Kuntz, M; Lal, V; Lambert, D; Dentai, A; Pavinski, D; Zhang, J; Cornelius, J; Tsai, T; Behnia, B; Bostak, J; Dominic, V; Nilsson, A; Taylor, B; Rahn, J; Sanders, S; Sun, H; Wu, K-T; Pleumeekers, J; Muthiah, R; Missey, M; Schneider, R; Stewart, J; Reffle, M; Butrie, T; Nagarajan, R; Ziari, M; Kish, F; Welch, D

    2011-12-12

    In this work, a 10-wavelength, polarization-multiplexed, monolithically integrated InP coherent QPSK transmitter PIC is demonstrated to operate at 112 Gb/sec per wavelength and total chip superchannel bandwidth of 1.12 Tb/s. This demonstration suggests that increasing data capacity to multi-Tb/s per chip is possible and likely in the future. PMID:22274012

  1. Radiation resistance and comparative performance of ITO/InP and n/p InP homojunction solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Swartz, C. K.; Hart, R. E., Jr.; Coutts, T. J.

    1988-01-01

    The radiation resistance of ITO/InP cells processed by dc magnetron sputtering is compared to that of standard n/p InP and GaAs homojunction cells. After 20 MeV proton irradiations, it is found that the radiation resistance of the present ITO/InP cell is comparable to that of the n/p homojunction InP cell and that both InP cell types have radiation resistances significantly greater than GaAs. The relatively lower radiation resistance, observed at higher fluence, for the InP cell with the deepest junction depth, is attributed to losses in the cells emitter region. Diode parameters obtained from I sub sc - V sub oc plots, data from surface Raman spectrosocpy, and determinations of surface conductivity type are used to investigate the configuration of the ITO/InP cells. It is concluded that these latter cells are n/p homojunctions, the n-region consisting of a disordered layer at the oxide semiconductor.

  2. Modeling, design, fabrication, and testing of InP Gunn devices in the D-band (110 GHz - 170 GHz)

    NASA Technical Reports Server (NTRS)

    Kamoua, R.; Eisele, H.; East, J. R.; Haddad, G. I.; Munns, G.; Sherwin, M.

    1992-01-01

    The development of fundamental Gunn sources for D-band frequencies requires improvements of doping profiles, processing technology, and circuit design. We have developed a technology for fabricating InP Gunn diodes using an InGaAs etch-stop layer between the InP substrate and the device layers. The epitaxial layers were grown by CBE. During device processing, the substrate is completely removed. Substrateless devices with an n(+) InGaAs cap layer are expected to have reduced contact and series resistances, and skin effect losses. This technology gives better uniformity and control of the device geometry across the processed chip. InP Gunn devices with a 1.7 micron long active region (doping : 9 x 10(exp 15) cm(exp -3)) have been mounted on copper heat sinks. Two tapered leads were then bonded to the diode and to four quartz standoffs. As a preliminary result, an output power of 13 mW at 82 GHz was obtained. Based on these RF measurements, we determine appropriate material parameters to be used in the Ensemble Monte Carlo model. Subsequently, we use this model to design and evaluate the performance of InP Gunn Devices for D-band frequencies. Using the same technology, we are currently processing Gunn devices with a 1 micron long active region for operation at higher frequencies.

  3. Electrical deactivation of interstitial Zn in heteroepitaxial InP by hydrogen and its effect on electronic properties

    NASA Astrophysics Data System (ADS)

    Ringel, S. A.; Chatterjee, B.

    1998-06-01

    Hydrogen passivation of InP layers grown on lattice-mismatched substrates can achieve thermally stable deactivation of dislocation-related deep levels, making this a promising process for improving the performance of heteroepitaxial InP space solar cells. However, in addition to dislocation-related defects, interstitial Zn (Zni) defects that are characteristic of Zn-doped InP and which form deep donor states within the InP band gap, are important considerations for optimizing the electronic quality of these layers. Here, we show that hydrogen forms complexes with and deactivates Zni donor states within Zn-doped InP grown by metalorganic chemical vapor deposition. A combination of photoluminescence (PL), electrochemical capacitance-voltage dopant profiling, secondary ion mass spectroscopy and current-voltage (I-V) measurements are applied to a set of samples receiving systematic hydrogenation and annealing treatments. We find that the deactivation of Zni deep donors, as detected by monitoring the evolution of the donor-acceptor transition using PL measurements, causes an increase of ˜50% in the net acceptor concentration of heavily Zn-doped heteroepitaxial InP by elimination of the acceptor compensation effect due to active Zni donors. Analysis of I-V characteristics indicates that Zni passivation sharply reduces depletion region recombination and shunt currents within heteroepitaxial diodes, causing an increase in the diode turn-on voltage from 680 to 960 mV. Subsequent annealing above 500 °C reactivates the Zni defects, resulting in a systematic increase in doping compensation as well as a decrease in VTO toward the original, as-grown value. A study of the reactivation kinetics for the H-Zni complex reveals a greater thermal stability than that of H-Zn acceptor complexes but less than that of H-dislocation complexes in InP, with an estimated dissociation energy for the H-Zni complex of 2.3 eV. While these effects are observed for both homoepitaxial and

  4. Hydrogen passivation of n+p and p+n heteroepitaxial InP solar cell structures

    NASA Technical Reports Server (NTRS)

    Chatterjee, B.; Ringel, S. A.; Hoffman, R., Jr.

    1995-01-01

    High-efficiency, heteroepitaxial (HE) InP solar cells, grown on GaAs, Si or Ge substrates, are desirable for their mechanically strong, light-weight and radiation-hard properties. However, dislocations, caused by lattice mismatch, currently limit the performance of the HE cells. This occurs through shunting paths across the active photovoltaic junction and by the formation of deep levels. In previous work we have demonstrated that plasma hydrogenation is an effective and stable means to passivate the electrical activity of dislocations in specially designed HE InP test structures. In this work, we present the first report of successful hydrogen passivation in actual InP cell structures grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD). We have found that a 2 hour exposure to a 13.56 MHz hydrogen plasma at 275 C reduces the deep level concentration in HE n+n InP cell structures from as-grown values of approximately 10(exp 15)/cm(exp -3), down to 1-2 x 10(exp 13)/cm(exp -3). The deep levels in the p-type base region of the cell structure match those of our earlier p-type test structures, which were attributed to dislocations or related point defect complexes. All dopants were successfully reactivated by a 400 C, 5 minute anneal with no detectable activation of deep levels. I-V analysis indicated a subsequent approximately 10 fold decrease in reverse leakage current at -1 volt reverse bias, and no change in the forward biased series resistance of the cell structure which indicates complete reactivation of the n+ emitter. Furthermore, electrochemical C-V profiling indicates greatly enhanced passivation depth, and hence hydrogen diffusion, for heteroepitaxial structures when compared with identically processed homoepitaxial n+p InP structures. An analysis of hydrogen diffusion in dislocated InP will be discussed, along with comparisons of passivation effectiveness for n+p versus p+n heteroepitaxial cell configurations. Preliminary hydrogen

  5. Spanning From Atoms to Micrometers in Simulations of Contact, Adhesion and Friction

    NASA Astrophysics Data System (ADS)

    Robbins, Mark

    Improved understanding of the forces between realistic solid surfaces is needed to optimize adhesion and friction. Modeling these forces is challenging because they arise from interactions between atoms separated by less than a nanometer, but the number and spatial distribution of these contacting atoms depends on surface roughness and deformation on micrometer and larger scales. There are also strong scale effects in the role of elastic deformations along the surface. The talk will first describe a seamless Greens function (GF) method that allows a full treatment of elastic deformations and atomic contact for micrometer scale surfaces and multibody potentials. Next applications of the method to calculations of the contact area, contact stiffness, adhesion and friction for a range of geometries and interactions will be described. The results can be captured with simple analytic expressions and explain why most contacting surfaces do not adhere. Theoretical and experimental studies of single nanometer-scale asperities show that the frictional shear stress depends strongly on whether surfaces are commensurate. A large constant stress is obtained for identical, aligned crystalline surfaces, but the stress averages to zero in the more common case of incommensurate surfaces. The resulting ultralow friction is called superlubricity and is found in experiments and simulations of small contacts. Our simulations reveal dramatic changes in this behavior because different parts of the surface are able to advance independently as the contact radius increases towards micrometer scales. The friction between identical surfaces drops with increasing radius and then saturates at a low value. The force between incommensurate surfaces saturates at a similar value that can be related to the Peierls stress for dislocation motion at the interface. Studies of multiasperity contacts also show that incoherent motion along the interface can lead to pronounced changes in the macroscopic

  6. Cell visco-elasticity measured with AFM and optical trapping at sub-micrometer deformations.

    PubMed

    Nawaz, Schanila; Sánchez, Paula; Bodensiek, Kai; Li, Sai; Simons, Mikael; Schaap, Iwan A T

    2012-01-01

    The measurement of the elastic properties of cells is widely used as an indicator for cellular changes during differentiation, upon drug treatment, or resulting from the interaction with the supporting matrix. Elasticity is routinely quantified by indenting the cell with a probe of an AFM while applying nano-Newton forces. Because the resulting deformations are in the micrometer range, the measurements will be affected by the finite thickness of the cell, viscous effects and even cell damage induced by the experiment itself. Here, we have analyzed the response of single 3T3 fibroblasts that were indented with a micrometer-sized bead attached to an AFM cantilever at forces from 30-600 pN, resulting in indentations ranging from 0.2 to 1.2 micrometer. To investigate the cellular response at lower forces up to 10 pN, we developed an optical trap to indent the cell in vertical direction, normal to the plane of the coverslip. Deformations of up to two hundred nanometers achieved at forces of up to 30 pN showed a reversible, thus truly elastic response that was independent on the rate of deformation. We found that at such small deformations, the elastic modulus of 100 Pa is largely determined by the presence of the actin cortex. At higher indentations, viscous effects led to an increase of the apparent elastic modulus. This viscous contribution that followed a weak power law, increased at larger cell indentations. Both AFM and optical trapping indentation experiments give consistent results for the cell elasticity. Optical trapping has the benefit of a lower force noise, which allows a more accurate determination of the absolute indentation. The combination of both techniques allows the investigation of single cells at small and large indentations and enables the separation of their viscous and elastic components. PMID:23028915

  7. THE PHYSICS OF PROTOPLANETESIMAL DUST AGGLOMERATES. VI. EROSION OF LARGE AGGREGATES AS A SOURCE OF MICROMETER-SIZED PARTICLES

    SciTech Connect

    Schraepler, Rainer; Blum, Juergen

    2011-06-20

    Observed protoplanetary disks consist of a large amount of micrometer-sized particles. Dullemond and Dominik pointed out for the first time the difficulty in explaining the strong mid-infrared excess of classical T Tauri stars without any dust-retention mechanisms. Because high relative velocities in between micrometer-sized and macroscopic particles exist in protoplanetary disks, we present experimental results on the erosion of macroscopic agglomerates consisting of micrometer-sized spherical particles via the impact of micrometer-sized particles. We find that after an initial phase, in which an impacting particle erodes up to 10 particles of an agglomerate, the impacting particles compress the agglomerate's surface, which partly passivates the agglomerates against erosion. Due to this effect, the erosion halts for impact velocities up to {approx}30 m s{sup -1} within our error bars. For higher velocities, the erosion is reduced by an order of magnitude. This outcome is explained and confirmed by a numerical model. In a next step, we build an analytical disk model and implement the experimentally found erosive effect. The model shows that erosion is a strong source of micrometer-sized particles in a protoplanetary disk. Finally, we use the stationary solution of this model to explain the amount of micrometer-sized particles in the observational infrared data of Furlan et al.

  8. Radiation cooler for 10 micrometer wavelength engineering model receiver model no. 7172, serial no. 201

    NASA Technical Reports Server (NTRS)

    1975-01-01

    The design, fabrication, and testing of a radiative cooler are described. This cooler is an engineering model suitable for bench testing in the laboratory as a part of the 10-micrometer wavelength engineering model receiver, and conforms to the standard radiative cooler configuration, except that the inner stage and its support system were redesigned to accommodate the larger, heavier SAT detector. This radiative cooler will cool the detector to cryogenic temperature levels when the receiver is in a space environment or in a suitable thermal vacuum chamber. Equipment specifications are given along with the results of thermal tests, vibration tests, and electrical integrity tests.

  9. Development of a 0.5 micrometer incoherent Doppler lidar for space application

    NASA Technical Reports Server (NTRS)

    Rosenberg, A.; Sroga, J.

    1985-01-01

    This paper describes the current status of a prototype 0.53 micrometer Doppler lidar system under development at RCA. This system consists of a frequency doubled Nd:YAG laser constrained to yield a narrow bandwidth, single frequency pulse, a Fabry-Perot Inteferometer (FPI) using an Image Plane Detector (IPD) to measure the backscatter spectrum for each pulse and a Data Acquisition System (DAS) to sample, store, and analyze the backscattered signal. These individual subsystem components have been assembled and preliminary atmospheric testing has recently begun. Atmospheric backscatter spectra are presented which demonstrate the capabilities of this system to distinguish between return signals from aerosols, molecules, and clouds.

  10. Large-scale proton radiography with micrometer spatial resolution using femtosecond petawatt laser system

    NASA Astrophysics Data System (ADS)

    Wang, W. P.; Shen, B. F.; Zhang, H.; Lu, X. M.; Wang, C.; Liu, Y. Q.; Yu, L. H.; Chu, Y. X.; Li, Y. Y.; Xu, T. J.; Zhang, H.; Zhai, S. H.; Leng, Y. X.; Liang, X. Y.; Li, R. X.; Xu, Z. Z.

    2015-10-01

    An image of dragonfly with many details is obtained by the fundamental property of the high-energy proton source on a femtosecond petawatt laser system. Equal imaging of the dragonfly and high spatial resolution on the micrometer scale are simultaneously obtained. The head, wing, leg, tail, and even the internal tissue structures are clearly mapped in detail by the proton beam. Experiments show that image blurring caused by multiple Coulomb scattering can be reduced to a certain extent and the spatial resolution can be increased by attaching the dragonfly to the RCFs, which is consistent with theoretical assumptions.

  11. Integrated GHz silicon photonic interconnect with micrometer-scale modulators and detectors

    NASA Astrophysics Data System (ADS)

    Chen, Long; Preston, Kyle; Manipatruni, Sasikanth; Lipson, Michal

    2009-08-01

    We report an optical link on silicon using micrometer-scale ring-resonator enhanced silicon modulators and waveguide-integrated germanium photodetectors. We show 3 Gbps operation of the link with 0.5 V modulator voltage swing and 1.0 V detector bias. The total energy consumption for such a link is estimated to be ~120 fJ/bit. Such compact and low power monolithic link is an essential step towards large-scale on-chip optical interconnects for future microprocessors.

  12. Liquid scanning transmission electron microscopy: Nanoscale imaging in micrometers-thick liquids

    NASA Astrophysics Data System (ADS)

    Schuh, Tobias; de Jonge, Niels

    2014-02-01

    Scanning transmission electron microscopy (STEM) of specimens in liquid is possible using a microfluidic chamber with thin silicon nitride windows. This paper includes an analytic equation of the resolution as a function of the sample thickness and the vertical position of an object in the liquid. The equipment for STEM of liquid specimen is briefly described. STEM provides nanometer resolution in micrometer-thick liquid layers with relevance for both biological research and materials science. Using this technique, we investigated tagged proteins in whole eukaryotic cells, and gold nanoparticles in liquid with time-lapse image series. Possibly future applications are discussed.

  13. Sub-micrometer transverse beam size diagnostics using optical transition radiation

    NASA Astrophysics Data System (ADS)

    Kruchinin, K.; Aryshev, A.; Karataev, P.; Bolzon, B.; Lefevre, T.; Mazzoni, S.; Shevelev, M.; Boogert, S. T.; Nevay, L. J.; Terunuma, N.; Urakawa, J.

    2014-05-01

    Optical transition radiation (OTR) arising when a relativistic charged particle crosses a boundary between two media with different optical properties is widely used as a tool for diagnostics of particle beams in modern accelerator facilities. The resolution of the beam profile monitors based on OTR depends on different effects of the optical system such as spherical and chromatic aberrations and diffraction. In this paper we present a systematic study of the different optical effects influencing the OTR beam profile monitor resolution. Obtained results have shown that such monitors can be used for sub-micrometer beam profile diagnostics. Further improvements and studies of the monitor are discussed.

  14. Large-scale proton radiography with micrometer spatial resolution using femtosecond petawatt laser system

    SciTech Connect

    Wang, W. P.; Shen, B. F. Zhang, H.; Lu, X. M.; Wang, C.; Liu, Y. Q.; Yu, L. H.; Chu, Y. X.; Li, Y. Y.; Xu, T. J.; Zhang, H.; Zhai, S. H.; Leng, Y. X.; Liang, X. Y.; Li, R. X.; Xu, Z. Z.

    2015-10-15

    An image of dragonfly with many details is obtained by the fundamental property of the high-energy proton source on a femtosecond petawatt laser system. Equal imaging of the dragonfly and high spatial resolution on the micrometer scale are simultaneously obtained. The head, wing, leg, tail, and even the internal tissue structures are clearly mapped in detail by the proton beam. Experiments show that image blurring caused by multiple Coulomb scattering can be reduced to a certain extent and the spatial resolution can be increased by attaching the dragonfly to the RCFs, which is consistent with theoretical assumptions.

  15. High brightness InP micropillars grown on silicon with Fermi level splitting larger than 1 eV.

    PubMed

    Tran, Thai-Truong D; Sun, Hao; Ng, Kar Wei; Ren, Fan; Li, Kun; Lu, Fanglu; Yablonovitch, Eli; Chang-Hasnain, Constance J

    2014-06-11

    The growth of III-V nanowires on silicon is a promising approach for low-cost, large-scale III-V photovoltaics. However, performances of III-V nanowire solar cells have not yet been as good as their bulk counterparts, as nanostructured light absorbers are fundamentally challenged by enhanced minority carriers surface recombination rates. The resulting nonradiative losses lead to significant reductions in the external spontaneous emission quantum yield, which, in turn, manifest as penalties in the open-circuit voltage. In this work, calibrated photoluminescence measurements are utilized to construct equivalent voltage-current characteristics relating illumination intensities to Fermi level splitting ΔF inside InP microillars. Under 1 sun, we show that splitting can exceed ΔF ∼ 0.90 eV in undoped pillars. This value can be increased to values of ΔF ∼ 0.95 eV by cleaning pillar surfaces in acidic etchants. Pillars with nanotextured surfaces can yield splitting of ΔF ∼ 0.90 eV, even though they exhibit high densities of stacking faults. Finally, by introducing n-dopants, ΔF of 1.07 eV can be achieved due to a wider bandgap energy in n-doped wurzite InP, the higher brightness of doped materials, and the extraordinarily low surface recombination velocity of InP. This is the highest reported value for InP materials grown on a silicon substrate. These results provide further evidence that InP micropillars on silicon could be a promising material for low-cost, large-scale solar cells with high efficiency. PMID:24841253

  16. Formulation of the Microbicide INP0341 for In Vivo Protection against a Vaginal Challenge by Chlamydia trachomatis

    PubMed Central

    Pedersen, Christian; Slepenkin, Anatoly; Andersson, Sara B. E.; Fagerberg, Jonas H.; Bergström, Christel A. S.; Peterson, Ellena M.

    2014-01-01

    The salicylidene acylhydrazide (SA) compounds have exhibited promising microbicidal properties. Previous reports have shown the SA compounds, using cell cultures, to exhibit activity against Chlamydia trachomatis, herpes simplex virus and HIV-1. In addition, using an animal model of a vaginal infection the SA compound INP0341, when dissolved in a liquid, was able to significantly protect mice from a vaginal infection with C. trachomatis. To expand upon this finding, in this report INP0341 was formulated as a vaginal gel, suitable for use in humans. Gelling agents (polymers) with inherent antimicrobial properties were chosen to maximize the total antimicrobial effect of the gel. In vitro formulation work generated a gel with suitable rheology and sustained drug release. A formulation containing 1 mM INP0341, 1.6 wt% Cremophor ELP (solubility enhancer) and 1.5 wt% poly(acrylic acid) (gelling and antimicrobial agent), was chosen for studies of efficacy and toxicity using a mouse model of a vaginal infection. The gel formulation was able to attenuate a vaginal challenge with C. trachomatis, serovar D. Formulations with and without INP0341 afforded protection, but the inclusion of INP0341 increased the protection. Mouse vaginal tissue treated with the formulation showed no indication of gel toxicity. The lack of toxicity was confirmed by in vitro assays using EpiVaginal tissues, which showed that a 24 h exposure to the gel formulation did not decrease the cell viability or the barrier function of the tissue. Therefore, the gel formulation described here appears to be a promising vaginal microbicide to prevent a C. trachomatis infection with the potential to be expanded to other sexually transmitted diseases. PMID:25356686

  17. AES, EELS and TRIM simulation method study of InP(100) subjected to Ar+, He+ and H+ ions bombardment.

    NASA Astrophysics Data System (ADS)

    Ghaffour, M.; Abdellaoui, A.; Bouslama, M.; Ouerdane, A.; Abidri, B.

    2012-06-01

    Auger Electron Spectroscopy (AES) and Electron Energy Loss Spectroscopy (EELS) have been performed in order to investigate the InP(100) surface subjected to ions bombardment. The InP(100) surface is always contaminated by carbon and oxygen revealed by C-KLL and O-KLL AES spectra recorded just after introduction of the sample in the UHV spectrometer chamber. The usually cleaning process of the surface is the bombardment by argon ions. However, even at low energy of ions beam (300 eV) indium clusters and phosphorus vacancies are usually formed on the surface. The aim of our study is to compare the behaviour of the surface when submitted to He+ or H+ ions bombardment. The helium ions accelerated at 500V voltage and for 45 mn allow removing contaminants but induces damaged and no stoichiometric surface. The proton ions were accelerated at low energy of 500 eV to bombard the InP surface at room temperature. The proton ions broke the In-P chemical bonds to induce the formation of In metal islands. Such a chemical reactivity between hydrogen and phosphorus led to form chemical species such as PH and PH3, which desorbed from the surface. The chemical susceptibly and the small size of H+ advantaged their diffusion into bulk. Since the experimental methods alone were not able to give us with accuracy the disturbed depth of the target by these ions. We associate to the AES and EELS spectroscopies, the TRIM (Transport and Range of Ions in Matter) simulation method in order to show the mechanism of interaction between Ar+, He+ or H+ ions and InP and determine the disturbed depth of the target by argon, helium or proton ions.

  18. X-ray photoelectron spectroscopy/Ar sup + ion profile study of thin oxide layers on InP

    SciTech Connect

    Thurgate, S.M.; Erickson, N.E. )

    1990-09-01

    The effect of incremental ion bombardment on the surface layers of an aqua regia etched InP sample was studied by monitoring the components of the In 3{ital d}{sub 5/2} and O 1{ital s} x-ray photoelectron spectroscopy (XPS) lines as the sample was bombarded with low energy (1 keV) Ar{sup +} ions. The changes in the stoichiometry of the surface produced large shifts in the position of the In 3{ital d} and O 1{ital s} lines that were not paralleled by shifts in the P 2{ital p} line. Analysis of these shifts indicated that the surface was covered with a mixture of indium hydroxide and indium phosphate, with the phosphate closer to the InP substrate. It is proposed that this layer structure is due to differences in the dissolution rates of the oxidation products in the acid etch and the effect of the distilled water rinse. It may be possible to alter the composition of such oxides by carefully tailoring the etch conditions to optimize the kinetics for the particular oxide phase required. The analysis of the XPS lines also showed that the InP substrate was damaged at very low ion doses, and finally decomposed by the ion beam. When the ion cleaned'' sample was exposed to oxygen, a different oxide system was produced which consisted largely of In{sub 2}O{sub 3} and InPO{sub 4} (or In(PO{sub 3} ){sub {ital x}}). This model of the oxidized surface of InP is consistent with other measurements and we conclude that ion milling together with XPS and careful curve fitting can be used to find the nature of the thin oxides on InP.

  19. In vivo penetration mechanics and mechanical properties of mouse brain tissue at micrometer scales.

    PubMed

    Sharp, Andrew A; Ortega, Alicia M; Restrepo, Diego; Curran-Everett, Douglas; Gall, Ken

    2009-01-01

    Substantial advancement in the understanding of the neuronal basis of behavior and the treatment of neurological disorders has been achieved via the implantation of various devices into the brain. To design and optimize the next generation of neuronal implants while striving to minimize tissue damage, it is necessary to understand the mechanics of probe insertion at relevant length scales. Unfortunately, a broad-based understanding of brain-implant interactions at the necessary micrometer scales is largely missing. This paper presents a generalizable description of the micrometer-scale penetration mechanics and material properties of mouse brain tissue in vivo. Cylindrical stainless steel probes were inserted into the cerebral cortex and olfactory bulb of mice. The effects of probe size, probe geometry, insertion rate, insertion location, animal age, and the presence of the dura and pia on the resulting forces were measured continuously throughout probe insertion and removal. Material properties (modulus, cutting force, and frictional force) were extracted using mechanical analysis. The use of rigid, incompressible, cylindrical probes allows for a general understanding of how probe design and insertion methods influence the penetration mechanics of brain tissue in vivo that can be applied to the quantitative design of most future implantable devices. PMID:19224718

  20. Filtration of bioaerosols using a granular metallic filter with micrometer-sized collectors

    SciTech Connect

    Damit, Brian E; Bischoff, Brian L; Phelps, Tommy Joe; Wu, Dr. Chang-Yu; Cheng, Mengdawn

    2014-01-01

    Several experimental studies with granular bed filters composed of micrometer-sized spherical or sintered metallic granules have demonstrated their use in aerosol filtration. However, the effectiveness of these metallic membrane filters against bioaerosols has not been established. In this work, the filtration efficiency and filter quality of these filters against airborne B. subtilis endospore and MS2 virus were determined as a function of face velocity and loading time. In experiments, a physical removal efficiency greater than 99.9% and a viable removal efficiency of greater than 5-log were observed for both bacterial spore and viral aerosols. A lower face velocity produced both higher collection efficiency and filter quality for virus but was not statistically significant for spore filtration. Although the filter had high filtration efficiency of the test bioaerosols, the filter's high pressure drop resulted in a low filter quality (0.25-0.75 kPa- 1). Overall, filters with micrometer-sized collectors capture bioaerosols effectively but their applications in aerosol filtration may be limited by their high pressure drop.

  1. Design and analysis of a laser micrometer for undulator gap measurement applications

    NASA Astrophysics Data System (ADS)

    Khullar, Roma; Tiwari, Shradha; Bhanage, Viraj P.; Mishra, G.

    2015-05-01

    In this paper we report the design of a laser micrometer for undulator gap measurement studies. In this scheme, the parallel light emerging from the rotating polygon mirror passes through an F-theta lens makes a vertical line on the image plane. When an object intercepts the line, the interrupted and the uninterrupted light is detected in a DSO through a detector. The beam spot size and the linear velocity of the beam spot on the scan line are the two important parameters of the laser micrometer. The beam spot size measurements show that it is constant along the scan line for a number of RPMs. It measures a constant value at ±3 mm to the effective focal length of the F-theta lens. The measurements are verified for two types of objects i.e. solid object and a circular hole and also for an electromagnet undulator. The electromagnet undulator is measured with an accuracy of 3-5 μm.

  2. Portable 4.6 Micrometers Laser Absorption Spectrometer for Carbon Monoxide Monitoring and Fire Detection

    NASA Technical Reports Server (NTRS)

    Briggs, Ryan M.; Frez, Clifford; Forouhar, Siamak; May, Randy D.; Ruff, Gary A.

    2013-01-01

    The air quality aboard manned spacecraft must be continuously monitored to ensure crew safety and identify equipment malfunctions. In particular, accurate real-time monitoring of carbon monoxide (CO) levels helps to prevent chronic exposure and can also provide early detection of combustion-related hazards. For long-duration missions, environmental monitoring grows in importance, but the mass and volume of monitoring instruments must be minimized. Furthermore, environmental analysis beyond low-Earth orbit must be performed in-situ, as sample return becomes impractical. Due to their small size, low power draw, and performance reliability, semiconductor-laser-based absorption spectrometers are viable candidates for this purpose. To reduce instrument form factor and complexity, the emission wavelength of the laser source should coincide with strong fundamental absorption lines of the target gases, which occur in the 3 to 5 micrometers wavelength range for most combustion products of interest, thereby reducing the absorption path length required for low-level concentration measurements. To address the needs of current and future NASA missions, we have developed a prototype absorption spectrometer using a semiconductor quantum cascade laser source operating near 4.6 micrometers that can be used to detect low concentrations of CO with a compact single-pass absorption cell. In this study, we present the design of the prototype instrument and report on measurements of CO emissions from the combustion of a variety of aerospace plastics.

  3. Frequency synthesizers for telemetry receivers

    NASA Astrophysics Data System (ADS)

    Stirling, Ronald C.

    1990-07-01

    The design of a frequency synthesizer is presented for telemetry receivers. The synthesizer contains two phase-locked loops, each with a programmable frequency counter, and incorporates fractional frequency synthesis but does not use a phase accumulator. The selected receiver design has a variable reference loop operating as a part of the output loop. Within the synthesizer, a single VTO generates the output frequency that is voltage-tunable from 375-656 MHz. The single-sideband phase noise is measured with an HP 8566B spectrum analyzer, and the receiver's bit error rate (BER) is measured with a carrier frequency of 250 MHz, synthesized LO at 410 MHz, and the conditions of BPSK, NRZ-L, and 2.3 kHz bit rate. The phase noise measurement limits and the BER performance data are presented in tabular form.

  4. Retroreflection of light from nanoporous InP: correlation with high absorption

    NASA Astrophysics Data System (ADS)

    Prislopski, S. Ya.; Tiginyanu, I. M.; Ghimpu, L.; Monaico, E.; Sirbu, L.; Gaponenko, S. V.

    2014-09-01

    Pronounced retroreflection behavior is reported for a fishnet nanoporous strongly absorbing semiconductor material. Retroreflection appears along with diffusive specular reflection for all angles of incidence for light wavelength corresponding to interband optical transitions, where absorption coefficient is of the order of 105 cm-1 (green and red light). Retroreflection is apparent by the naked eye with daylight illumination and exhibits no selectivity with respect to wavelength and polarization of incident light featuring minor depolarization of retroreflected light. Retroreflection vanishes for wavelength corresponding to optical transparency range where photon energy is lower than the InP bandgap (1.064 μm). The phenomenon can be classified neither as coherent backscattering nor as Anderson localization of light. The primary model includes light scattering from strongly absorptive and refractive super-wavelength clusters existing within the porous fishnet structure. We found that retroreflection vanishes for wavelength where absorption becomes negligible.

  5. Anomalous photoluminescence in InP1‑xBix

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoyan; Chen, Xiren; Pan, Wenwu; Wang, Peng; Zhang, Liyao; Li, Yaoyao; Wang, Hailong; Wang, Kai; Shao, Jun; Wang, Shumin

    2016-06-01

    Low temperature photoluminescence (PL) from InP1‑xBix thin films with Bi concentrations in the 0–2.49% range reveals anomalous spectral features with strong and very broad (linewidth of 700 nm) PL signals compared to other bismide alloys. Multiple transitions are observed and their energy levels are found much smaller than the band-gap measured from absorption measurements. These transitions are related to deep levels confirmed by deep level transient spectroscopy, which effectively trap free holes and enhance radiative recombination. The broad luminescence feature is beneficial for making super-luminescence diodes, which can theoretically enhance spatial resolution beyond 1 μm in optical coherent tomography (OCT).

  6. Photovoltaic characteristics of n(+)pp(+) InP solar cells grown by OMVPE

    NASA Technical Reports Server (NTRS)

    Tyagi, S.; Singh, K.; Bhimnathwala, H.; Ghandhi, S. K.; Borrego, J. M.

    1990-01-01

    The photovoltaic characteristics of n(+)/p/p(+) homojunction InP solar cells fabricated by organometallic vapor-phase epitaxy (OMVPE) are described. The cells are characterized by I-V, C-V and quantum efficiency measurements, and simulations are used to obtain various device and material parameters. The I-V characteristics show a high recombination rate in the depletion region; this is shown to be independent of the impurity used. It is shown that cadmium is easier to use as an acceptor for the p base and p(+) buffer and is therefore beneficial. The high quantum efficiency of 98 percent at long wavelengths measured in these cells indicates a very good collection efficiency in the base. The short-wavelength quantum efficiency is poor, indicating a high surface recombination.

  7. Incorporation and desorption of sulphur In InP grown by MBE

    NASA Astrophysics Data System (ADS)

    Airaksinen, V. M.; Cheng, T. S.; Stanley, C. R.

    1987-02-01

    Sulphur doped InP has been grown by molecular beam epitaxy (MBE) using an electrochemical cell as a source of sulphur dimer S 2. At growth temperatures of over 500°C sulphur is lost from the layers as a volatile indium sulphide which desorbs with an activation energy of 4.5 eV. The concentration of incorporated sulphur ( C S) is linearly proportional to the incident sulphur flux both at low ( T s < 500°C) and high ( T s > 500°C) growth temperatures, indicating first order kinetics of incorporation and desorption f sulphur. The desorption cannot be suppressed by increasing the P 2: In flux ratio. The desorption rate is also independent of the incident indium flux. A thermodynamic analysis shows that the most likely desorbing species is In 2S.

  8. Wide bandgap, strain-balanced quantum well tunnel junctions on InP substrates

    NASA Astrophysics Data System (ADS)

    Lumb, M. P.; Yakes, M. K.; González, M.; Bennett, M. F.; Schmieder, K. J.; Affouda, C. A.; Herrera, M.; Delgado, F. J.; Molina, S. I.; Walters, R. J.

    2016-05-01

    In this work, the electrical performance of strain-balanced quantum well tunnel junctions with varying designs is presented. Strain-balanced quantum well tunnel junctions comprising compressively strained InAlAs wells and tensile-strained InAlAs barriers were grown on InP substrates using solid-source molecular beam epitaxy. The use of InAlAs enables InP-based tunnel junction devices to be produced using wide bandgap layers, enabling high electrical performance with low absorption. The impact of well and barrier thickness on the electrical performance was investigated, in addition to the impact of Si and Be doping concentration. Finally, the impact of an InGaAs quantum well at the junction interface is presented, enabling a peak tunnel current density of 47.6 A/cm2 to be realized.

  9. InAs nanostructures grown by droplet epitaxy directly on InP(001) substrates

    NASA Astrophysics Data System (ADS)

    Fuster, David; Abderrafi, Kamal; Alén, Benito; González, Yolanda; Wewior, Lukasz; González, Luisa

    2016-01-01

    This work deals with the development of growth processes by droplet epitaxy to obtain InAs quantum dots directly on InP (001) surfaces (without any InGaAs or InAlAs intermediate layer). The indium atoms for droplet formation were deposited at different substrate temperatures, TS, below 300 °C in a solid source molecular beam epitaxy system. From the evolution of the size and shape of the nanostructures with TS, values of magnitudes related with indium atoms diffusivity have been extracted. The photoluminescence signal is investigated for ensemble and single InAs nanostructures emitting around 1.3-1.5 μm. The emission properties drastically change with thermal annealing processes that improve the crystalline quality.

  10. Ab initio calculations on the compensation mechanisms in InP

    NASA Astrophysics Data System (ADS)

    Schmidt, T. M.; Miwa, R. H.; Fazzio, A.; Mota, R.

    2001-01-01

    Compensation mechanisms which become semi-insulating InP from intrinsic n-type materials are investigated by first principles total energy calculations. Associated to the possible mechanisms two intrinsic defects are shown to play an important role in the transition, induced by annealing, from the n-type to the semi-insulating character. The single defect V In3- results from the In-vacancy-H-complex, which, before the annealing, was identified by infra-red spectra as responsible for the n-type conductivity, and the P In+V P complex defect comes from the diffusion of the neutral In vacancy. Both defects are shown to present localized levels inside the band gap which compensate for the free electron.

  11. Simultaneous Selective-Area and Vapor-Liquid-Solid Growth of InP Nanowire Arrays.

    PubMed

    Gao, Qian; Dubrovskii, Vladimir G; Caroff, Philippe; Wong-Leung, Jennifer; Li, Li; Guo, Yanan; Fu, Lan; Tan, Hark Hoe; Jagadish, Chennupati

    2016-07-13

    Selective-area epitaxy is highly successful in producing application-ready size-homogeneous arrays of III-V nanowires without the need to use metal catalysts. Previous works have demonstrated excellent control of nanowire properties but the growth mechanisms remain rather unclear. Herein, we report a detailed growth study revealing that fundamental growth mechanisms of pure wurtzite InP ⟨111⟩A nanowires can indeed differ significantly from the simple picture of a facet-limited selective-area growth process. A dual growth regime with and without metallic droplet is found to coexist under the same growth conditions for different diameter nanowires. Incubation times and highly nonmonotonous growth rate behaviors are revealed and explained within a dedicated kinetic model. PMID:27253040

  12. Anomalous photoluminescence in InP1−xBix

    PubMed Central

    Wu, Xiaoyan; Chen, Xiren; Pan, Wenwu; Wang, Peng; Zhang, Liyao; Li, Yaoyao; Wang, Hailong; Wang, Kai; Shao, Jun; Wang, Shumin

    2016-01-01

    Low temperature photoluminescence (PL) from InP1−xBix thin films with Bi concentrations in the 0–2.49% range reveals anomalous spectral features with strong and very broad (linewidth of 700 nm) PL signals compared to other bismide alloys. Multiple transitions are observed and their energy levels are found much smaller than the band-gap measured from absorption measurements. These transitions are related to deep levels confirmed by deep level transient spectroscopy, which effectively trap free holes and enhance radiative recombination. The broad luminescence feature is beneficial for making super-luminescence diodes, which can theoretically enhance spatial resolution beyond 1 μm in optical coherent tomography (OCT). PMID:27291823

  13. Channeling investigations of MeV Zn implanted InP

    NASA Astrophysics Data System (ADS)

    Kling, A.; Krause, H.; Flagmeyer, R.-H.; Vogt, J.; Butz, T.

    1995-03-01

    The high-energy Zn + ion implantation of InP is a promising method for the formation of buried p-type conducting layers. Defect properties and inclusion mechanism of zinc implanted samples with energies of 1.2 and 2.5 MeV to doses of 5 × 10 14-5 × 10 15 cm -2 at a temperature of 200°C were investigated with ion beam methods, XTEM and SNMS to some extent. Also the influence of rapid thermal annealing on the structural properties was studied. After implantation we found no evidence for amorphization or extended defects but point-like defects. During annealing the surface region recovered nearly completely while in depth the point-like defects agglomerated in dislocation loops. Further we observed a remarkable redistribution of the Zn atoms due to annealing.

  14. Determining the base resistance of InP HBTs: An evaluation of methods and structures

    NASA Astrophysics Data System (ADS)

    Nardmann, Tobias; Krause, Julia; Pawlak, Andreas; Schroter, Michael

    2016-09-01

    Many different methods can be found in the literature for determining both the internal and external base series resistance based on single transistor terminal characteristics. Those methods are not equally reliable or applicable for all technologies, device sizes and speeds. In this review, the most common methods are evaluated regarding their suitability for InP heterojunction bipolar transistors (HBTs) based on both measured and simulated data. Using data generated by a sophisticated physics-based compact model allows an evaluation of the extraction method precision by comparing the extracted parameter value to its known value. Based on these simulations, this study provides insight into the limitations of the applied methods, causes for errors and possible error mitigation. In addition to extraction methods based on just transistor terminal characteristics, test structures for separately determining the components of the base resistance from sheet and specific contact resistances are discussed and applied to serve as reference for the experimental evaluation.

  15. Locally measuring the adhesion of InP directly bonded on sub-100 nm patterned Si

    NASA Astrophysics Data System (ADS)

    Pantzas, K.; Le Bourhis, E.; Patriarche, G.; Troadec, D.; Beaudoin, G.; Itawi, A.; Sagnes, I.; Talneau, A.

    2016-03-01

    A nano-scale analogue to the double cantilever experiment that combines instrumented nano-indentation and atomic force microscopy is used to precisely and locally measure the adhesion of InP bonded on sub-100 nm patterned Si using oxide-free or oxide-mediated bonding. Surface-bonding energies of 0.548 and 0.628 J m-2, respectively, are reported. These energies correspond in turn to 51% and 57% of the surface bonding energy measured in unpatterned regions on the same samples, i.e. the proportion of unetched Si surface in the patterned areas. The results show that bonding on patterned surfaces can be as robust as on unpatterned surfaces, provided care is taken with the post-patterning surface preparation process and, therefore, open the path towards innovative designs that include patterns embedded in the Si guiding layer of hybrid III-V/Si photonic integrated circuits.

  16. Locally measuring the adhesion of InP directly bonded on sub-100 nm patterned Si.

    PubMed

    Pantzas, K; Bourhis, E Le; Patriarche, G; Troadec, D; Beaudoin, G; Itawi, A; Sagnes, I; Talneau, A

    2016-03-18

    A nano-scale analogue to the double cantilever experiment that combines instrumented nano-indentation and atomic force microscopy is used to precisely and locally measure the adhesion of InP bonded on sub-100 nm patterned Si using oxide-free or oxide-mediated bonding. Surface-bonding energies of 0.548 and 0.628 J m(-2), respectively, are reported. These energies correspond in turn to 51% and 57% of the surface bonding energy measured in unpatterned regions on the same samples, i.e. the proportion of unetched Si surface in the patterned areas. The results show that bonding on patterned surfaces can be as robust as on unpatterned surfaces, provided care is taken with the post-patterning surface preparation process and, therefore, open the path towards innovative designs that include patterns embedded in the Si guiding layer of hybrid III-V/Si photonic integrated circuits. PMID:26878333

  17. Plasma deposited hydrogenated carbon on GaAs and InP

    NASA Technical Reports Server (NTRS)

    Warner, J. D.; Pouch, J. J.; Alterovitz, S. A.; Liu, D. C.; Lanford, W. A.

    1985-01-01

    The properties of diamond like carbon films grown by RF flow discharge 30 kHz plasma using methane are reported. The Cis XPS line shape of films showed localized hybrid carbon bonds as low as 40 to as high as 95 percent. Infrared spectroscopy and N(15) nuclear reaction profiling data indicated 35 to 42 percent hydrogen, depending inversely on deposition temperature. The deposition rate of films on Si falls off exponentially with substrate temperature, and nucleation does not occur above 200 C on GaAs and InP. Optical data of the films showed bandgap values of 2.0 to 2.4 eV increasing monotonically with CH4 flow rate.

  18. Plasma deposited diamondlike carbon on GaAs and InP

    NASA Technical Reports Server (NTRS)

    Warner, J. D.; Pouch, J. J.; Alterovitz, S. A.; Liu, D. C.; Lanford, W. A.

    1984-01-01

    The properties of diamond like carbon films grown by RF flow discharge 30 kHz plasma using methane are reported. The Cls XPS line shape of films showed localized hybrid carbon bonds as low as 40 to as high as 95 percent. Infrared spectroscopy and N(15) nuclear reaction profiling data indicated 35 to 42 percent hydrogen, depending inversely on deposition temperature. The deposition rate of films on Si falls off exponentially with substrate temperature, and nucleation does not occur above 200 C on GaAs and InP. Optical data of the films showed bandgap values of 2.0 to 2.4 eV increasing monotonically with CH4 flow rate.

  19. Dose and doping dependence of damage annealing in Fe MeV implanted InP

    SciTech Connect

    Carnera, A.; Fraboni, B.; Gasparotto, A. |; Priolo, F. |; Camporese, A.; Rossetto, G.; Frigeri, C.; Cassa, A.

    1996-12-31

    High energy (2 MeV) ion implantation of Fe in InP has been investigated by means of Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM) and secondary ions mass spectrometry (SIMS). The implanted doses ranged between 5 {times} 10{sup 13} and 5 {times} 10{sup 14} at/cm{sup 2}. Annealing in the 650--800 C range was performed and the primary as well as secondary damage evolution has been studied. The correlations between defect structure and Fe redistribution properties have been carefully analyzed. The results show the role of the primary defect structure in determining the annealing properties, both for damage recovery and Fe redistribution. The latter is also influenced by the doping of the substrate.

  20. Carrier Recombination Dynamics in Sulfur-Doped InP Nanowires.

    PubMed

    Zhang, Wei; Lehmann, Sebastian; Mergenthaler, Kilian; Wallentin, Jesper; Borgström, Magnus T; Pistol, Mats-Erik; Yartsev, Arkady

    2015-11-11

    Measuring lifetime of photogenerated charges in semiconductor nanowires (NW) is important for understanding light-induced processes in these materials and is relevant for their photovoltaic and photodetector applications. In this paper, we investigate the dynamics of photogenerated charge carriers in a series of as-grown InP NW with different levels of sulfur (S) doping. We observe that photoluminescence (PL) decay time as well as integrated PL intensity decreases with increasing S doping. We attribute these observations to hole trapping with the trap density increased due to S-doping level followed by nonradiative recombination of trapped charges. This assignment is proven by observation of the trap saturation in three independent experiments: via excitation power and repetition rate PL lifetime dependencies and by PL pump-probe experiment. PMID:26421505

  1. An empirical investigation of the InP shallow-homojunction solar cell

    NASA Technical Reports Server (NTRS)

    Wanlass, M. W.; Gessert, T. A.; Emery, K. A.; Coutts, T. J.

    1988-01-01

    An experimental study of the performance of epitaxially grown InP shallow-homojunction solar cells as a function of the thickness and carrier concentration in the base and emitter layers is presented. Identification of improvements to cell design leading to higher performance is emphasized. As a result, using a near-optimum set of design parameters, cells with conversion efficiencies of 20.3 percent (global) and 17.6 percent (AM0) have been achieved. For such cells, it is shown that the internal response of the base layer is essentially perfect, whereas the emitter-layer properties can be improved substantially and warrant further investigation. Discrepancies between the results of the present study and those of earlier modeling efforts are discussed.

  2. The role of vapour etching in the growth of epitaxial InP

    NASA Astrophysics Data System (ADS)

    Ashen, D. J.; Anderson, D. A.; Apsley, N.; Emeny, M. T.

    1982-12-01

    Undoped single epitaxial layers of InP have been grown by the In-PCI 3-H 2 technique. Hall data, carrier concentration profile and layer surface quality have been studied as a function of pre-growth vapour etching and source saturation conditions. Incomplete vapour etching is shown to lead to layers with low room temperature mobility, large carrier freeze-out between 290 and 77 K, and a large density of defects on the epitaxial layer surface. Carrier concentration profiles through such layers show evidence of a high conductivity region at the interface with the substrate which we suggest is formed by material grown during source saturation. We demonstrate that the growth of high carrier concentration material can take place from an unsaturated source, and we show that a two-layer model accounts quantitatively for the Hall data. These results can be used to specify the appropriate etching conditions to grow epitaxial layers with abrupt interfaces and high mobility.

  3. Deep level domain spectroscopy of low frequency oscillations in semi-insulating InP

    NASA Astrophysics Data System (ADS)

    Backhouse, C.; Young, L.

    1992-11-01

    It is known that low frequency current oscillations occur in semi-insulating GaAs due to the formation and transit of high field domains caused by enhanced trapping of hot electrons by deep levels and that power density spectra of the current show peaks whose temperature dependence gives information on deep levels. In the present work Fe-compensated InP was investigated. The peaks rose from an approximately {1}/{f}{3}/{2} background and by estimating and removing this and by averaging many spectra, no less than 14 frequency peaks were resolved which gave straight lines on an Arrhenius plot of log( {T 2}/{2f}) vs{1}/{T}. Although the amplitude of the current oscillations is not so large as to preclude multiple domain propagation, it seems more likely that the domains are caused by hot electron trapping by one level only, rather than that several traps should have the necessary characteristics to launch domains. The multiplicity of peaks could be partly due to harmonics of the basic high field domain oscillation and partly due to conductivity modulation by other levels whose occupancies are changed by the passage of the domains: the task, if so, is to determine which peaks are which. The activation energies from the Arrhenius plots fell into groups close to 0.30, 0.39, 0.41, 0.44 and 0.49 eV. The 14 peaks thus are believed to arise from 5 deep levels. Evidence was found that the 0.49 eV level is iron-related and is responsible for producing the high field domains and for drain current drift in InP metal-insulator-semiconductor field-effect transistors.

  4. Diffusion length damage coefficient and annealing studies in proton-irradiated InP

    NASA Technical Reports Server (NTRS)

    Hakimzadeh, Roshanak; Vargas-Aburto, Carlos; Bailey, Sheila G.; Williams, Wendell

    1993-01-01

    We report on the measurement of the diffusion length damage coefficient (K(sub L)) and the annealing characteristics of the minority carrier diffusion length (L(sub n)) in Czochralski-grown zinc-doped indium phosphide (InP), with a carrier concentration of 1 x 10(exp l8) cm(exp -3). In measuring K(sub L) irradiations were made with 0.5 MeV protons with fluences ranging from 1 x 10(exp 11) to 3 x 10(exp 13) cm(exp -2). Pre- and post-irradiation electron-beam induced current (EBIC) measurements allowed for the extraction of L(sub n) from which K(sub L) was determined. In studying the annealing characteristics of L(sub n) irradiations were made with 2 MeV protons with fluence of 5 x 10(exp 13) cm(exp -2). Post-irradiation studies of L(sub n) with time at room temperature, and with minority carrier photoinjection and forward-bias injection were carried out. The results showed that recovery under Air Mass Zero (AMO) photoinjection was complete. L(sub n) was also found to recover under forward-bias injection, where recovery was found to depend on the value of the injection current. However, no recovery of L(sub n) after proton irradiation was observed with time at room temperature, in contrast to the behavior of 1 MeV electron-irradiated InP solar cells reported previously.

  5. A simple route to synthesize manganese germanate nanorods

    SciTech Connect

    Pei, L.Z. Yang, Y.; Yuan, C.Z.; Duan Taike; Zhang Qianfeng

    2011-06-15

    Manganese germanate nanorods have been synthesized by a simple route using germanium dioxide and manganese acetate as the source materials. X-ray diffraction observation shows that the nanorods are composed of orthorhombic and monoclinic manganese germanate phases. Scanning electron microscopy and transmission electron microscopy observations display that the manganese germanate nanorods have flat tips with the length of longer than 10 micrometers and diameter of 60-350 nm, respectively. The role of the growth conditions on the formation of the manganese germanate nanorods shows that the proper selection and combination of the growth conditions are the key factor for controlling the formation of the manganese germanate nanorods. The photoluminescence spectrum of the manganese germanate nanorods exhibits four fluorescence emission peaks centered at 422 nm, 472 nm, 487 nm and 530 nm showing the application potential for the optical devices. - Research Highlights: {yields} Manganese germanate nanorods have been synthesized by simple hydrothermal process. {yields} The formation of manganese germanate nanorods can be controlled by growth conditions. {yields} Manganese germanate nanorods exhibit good PL emission ability for optical device.

  6. Enhancement of intensity-dependent absorption in InP and GaAs at 1.9 microns by doping

    NASA Technical Reports Server (NTRS)

    Li, N.-L.; Bass, M.; Swimm, R.

    1985-01-01

    It is pointed out that the study of intensity-dependent absorption (IDA) in general, and two-photon absorption (TPA), in particular, has suffered from experimental difficulties and inadequate theoretical models. Bass et al. (1979) could improve the experimental situation by making use of laser calorimetry to obtain directly the TPA coefficient of a medium with a high degree of sensitivity. In the present investigation, the employed technique has been used to study the effect of deep level dopants on IDA in InP and GaAs. It is found that the coefficient for IDA is strongly dependent on the presence of Fe in InP and Cr in GaAs. The conducted investigation had the objective to examine the effect of deep level impurities on IDA processes in InP and GaAs. Fe-doped InP and Cr-doped GaAs were compared with undoped crystals.

  7. RAMESES publication standards: realist syntheses

    PubMed Central

    2013-01-01

    Background There is growing interest in realist synthesis as an alternative systematic review method. This approach offers the potential to expand the knowledge base in policy-relevant areas - for example, by explaining the success, failure or mixed fortunes of complex interventions. No previous publication standards exist for reporting realist syntheses. This standard was developed as part of the RAMESES (Realist And MEta-narrative Evidence Syntheses: Evolving Standards) project. The project's aim is to produce preliminary publication standards for realist systematic reviews. Methods We (a) collated and summarized existing literature on the principles of good practice in realist syntheses; (b) considered the extent to which these principles had been followed by published syntheses, thereby identifying how rigor may be lost and how existing methods could be improved; (c) used a three-round online Delphi method with an interdisciplinary panel of national and international experts in evidence synthesis, realist research, policy and/or publishing to produce and iteratively refine a draft set of methodological steps and publication standards; (d) provided real-time support to ongoing realist syntheses and the open-access RAMESES online discussion list so as to capture problems and questions as they arose; and (e) synthesized expert input, evidence syntheses and real-time problem analysis into a definitive set of standards. Results We identified 35 published realist syntheses, provided real-time support to 9 on-going syntheses and captured questions raised in the RAMESES discussion list. Through analysis and discussion within the project team, we summarized the published literature and common questions and challenges into briefing materials for the Delphi panel, comprising 37 members. Within three rounds this panel had reached consensus on 19 key publication standards, with an overall response rate of 91%. Conclusion This project used multiple sources to develop and

  8. On-machine measurement of turned parts with a laser micrometer

    NASA Astrophysics Data System (ADS)

    Valiño, G.; Suárez, C. M.; Rico, J. C.; Álvarez, B. J.

    2012-04-01

    The need for an efficient dimensional inspection of manufactured parts has lead to the development of different in process and on-machine measurement (OMM) techniques. Among these, the most utilized on a lathe consist on a touch trigger probe (TTP) similar to those used on coordinate measuring machines, but which accuracy on the machine is not sufficient for precision machining. Therefore, a different OMM technique is proposed in this work, which consists on a laser micrometer (LM) commonly used in-process for measurement of continues products. The behaviour of TTP and LM is analysed and discussed in terms of repeatability and reproducibility. A comparison is made between the two probes by measuring a cylindrical workpiece and checking the results with those obtained on a CMM.

  9. Large increase in fracture resistance of stishovite with crack extension less than one micrometer

    NASA Astrophysics Data System (ADS)

    Yoshida, Kimiko; Wakai, Fumihiro; Nishiyama, Norimasa; Sekine, Risako; Shinoda, Yutaka; Akatsu, Takashi; Nagoshi, Takashi; Sone, Masato

    2015-06-01

    The development of strong, tough, and damage-tolerant ceramics requires nano/microstructure design to utilize toughening mechanisms operating at different length scales. The toughening mechanisms so far known are effective in micro-scale, then, they require the crack extension of more than a few micrometers to increase the fracture resistance. Here, we developed a micro-mechanical test method using micro-cantilever beam specimens to determine the very early part of resistance-curve of nanocrystalline SiO2 stishovite, which exhibited fracture-induced amorphization. We revealed that this novel toughening mechanism was effective even at length scale of nanometer due to narrow transformation zone width of a few tens of nanometers and large dilatational strain (from 60 to 95%) associated with the transition of crystal to amorphous state. This testing method will be a powerful tool to search for toughening mechanisms that may operate at nanoscale for attaining both reliability and strength of structural materials.

  10. Pluto-Charon: Infrared Reflectance from 3.6 to 8.0 Micrometers

    NASA Technical Reports Server (NTRS)

    Cruikshank, Dale P.; Emery, Joshua P.; Stansberry, John A.; VanCleve, Jeffrey E.

    2004-01-01

    We have measured the spectral reflectance of the Pluto-Charon pair at 3.6, 4.5, 5.8, and 8.0 micrometers with the Infrared Array Camera (IRAC) (G. G. Fazzio et al. Ap.J.Supp. 154, 10-17, 2004) on the Spitzer Space Telescope (STS), at eight different longitudes that cover a full rotation of the planet. STS does not have sufficient resolution to separate the light from the planet and the satellite. The image of the Pluto-Charon pair is clearly visible at each of the four wavelengths. We will discuss the spectral reflectance in terms of models that include the known components of Pluto and Charon s surfaces, and evidence for diurnal variations.

  11. Sub-micrometer Geometrically Encoded Fluorescent Barcodes Self-Assembled from DNA

    PubMed Central

    Lin, Chenxiang; Jungmann, Ralf; Leifer, Andrew M.; Li, Chao; Levner, Daniel; Church, George M.; Shih, William M.; Yin, Peng

    2012-01-01

    The identification and differentiation of a large number of distinct molecular species with high temporal and spatial resolution is a major challenge in biomedical science. Fluorescence microscopy is a powerful tool, but its multiplexing ability is limited by the number of spectrally distinguishable fluorophores. Here we use DNA-origami technology to construct sub-micrometer nanorods that act as fluorescent barcodes. We demonstrate that spatial control over the positioning of fluorophores on the surface of a stiff DNA nanorod can produce 216 distinct barcodes that can be unambiguously decoded using epifluorescence or total internal reflection fluorescence (TIRF) microscopy. Barcodes with higher spatial information density were demonstrated via the construction of super-resolution barcodes with features spaced by ~40 nm. One species of the barcodes was used to tag yeast surface receptors, suggesting their potential applications as in situ imaging probes for diverse biomolecular and cellular entities in their native environments. PMID:23000997

  12. Micrometer-Thick Graphene Oxide-Layered Double Hydroxide Nacre-Inspired Coatings and Their Properties.

    PubMed

    Yan, You-Xian; Yao, Hong-Bin; Mao, Li-Bo; Asiri, Abdullah M; Alamry, Khalid A; Marwani, Hadi M; Yu, Shu-Hong

    2016-02-10

    Robust, functional, and flame retardant coatings are attractive in various fields such as building construction, food packaging, electronics encapsulation, and so on. Here, strong, colorful, and fire-retardant micrometer-thick hybrid coatings are reported, which can be constructed via an enhanced layer-by-layer assembly of graphene oxide (GO) nanosheets and layered double hydroxide (LDH) nanoplatelets. The fabricated GO-LDH hybrid coatings show uniform nacre-like layered structures that endow them good mechanic properties with Young's modulus of ≈ 18 GPa and hardness of ≈ 0.68 GPa. In addition, the GO-LDH hybrid coatings exhibit nacre-like iridescence and attractive flame retardancy as well due to their well-defined 2D microstructures. This kind of nacre-inspired GO-LDH hybrid thick coatings will be applied in various fields in future due to their high strength and multifunctionalities. PMID:26682698

  13. 158 micrometers (CII) mapping of NGC 6946: Probing the atomic medium

    NASA Technical Reports Server (NTRS)

    Madden, S. C.; Geis, N.; Genzel, R.; Herrmann, F.; Jackson, J. M.; Poglitsch, A.; Stacey, G. J.; Townes, C. H.

    1992-01-01

    The strong 158 micrometers (C2) cooling line of the NGC 6946 galaxy is investigated. The data was acquired with a far infrared imaging Fabry-Perot interferometer with 55 minutes resolution. About 1 percent of the total far infrared luminosity of the galaxy is analyzed. The (C2) emission comes from a mizture of components of interstellar gas. The brightest emission is associated with the nucleus, a second component traces the spiral arms and the largest star forming/H2 regions contained within them, and a third extended component of low brightness can be detected at least 12 kpc from the nucleus. The nuclear and spiral arm components are most likely associated with dense photon dominated regions at molecular cloud surfaces that are exposed to ultraviolet radiation produced by young massive stars. The (C2) emission is analyzed and the cooling rate in the atomic medium is consistent with photoelectric heating by diffuse ultraviolet radiation.

  14. Performance of a 2-micrometer coherent Doppler lidar for wind measurements

    NASA Technical Reports Server (NTRS)

    Frehlich, Rod; Hannon, Stephen M.; Henderson, Sammy W.

    1994-01-01

    Measurements of boundary layer winds are presented using a 2-micrometer coherent Doppler lidar and the optimal performance of the maximum likelihood estimator. The systematic error for single-shot estimates was estimated as 3.6 cm/s using measurements from a stationary hard target. The estimation error for measurements of the radial component of the wind field was determined, as well as the fraction of the estimates that are randomly distributed over the velocity search space, when the signal power is low and speckle fading is important. The results from actual data are compared with the results from ideal simulations. The first direct estimation of the spatial structure function of the radial wind field and of the energy dissipation rate is presented for both horizontal and vertical directions of propagation. The rms estimation error of the velocity estimates is found to be within 30% of ideal performance based on simulation.

  15. Imaging Nano- and Micrometer-sized Magnetic Insulator Devices in the Presence of Spin-Torque

    NASA Astrophysics Data System (ADS)

    Rosenberg, Aaron; Jermain, Colin; Nowack, Katja; Kirtley, John; Paik, Hanjong; Aradhya, Sriharsha; Wang, Hailong; Heron, John; Schlom, Darrell; Yang, Fengyuan; Ralph, Dan; Moler, Kathryn

    2015-03-01

    Recent results demonstrate that a giant spin-hall effect in Tantalum can produce large spin torques. We intend to employ this large spin torque to manipulate the magnetic moment in electrically insulating ferrimagnetic Lu3Fe5O12(LuIG)andY3Fe5O12 (YIG) devices. Using a scanning SQUID microscope, we can study the possibility of performing reversible switching between magnetic states of nano- and micrometer-sized iron garnet devices induced by current pulses applied to a Tantalum layer in contact with the devices by directly imaging the magnetic state of the device before and after a current pulse. Successful manipulation of magnetic insulators by electrical pulses can be a platform for magnetic memory devices and spintronics.

  16. Micrometer-scale cavities in fibrous and cloudy diamonds — A glance into diamond dissolution events

    NASA Astrophysics Data System (ADS)

    Klein-BenDavid, Ofra; Wirth, Richard; Navon, Oded

    2007-12-01

    Micrometer sized internal cavities in diamonds preserve evidence of diamond dissolution events. Combining the methods of focused ion beam (FIB) sample preparation and transmission electron microscopy (TEM) enables these features to be studied in detail. Micrometer-scale cavities are found in the inner parts of fibrous and cloudy kimberlitic diamonds. Their filling consists of amorphous matrix, secondary nano-crystals, volatiles and in some cases larger resorbed crystals. Trapped minerals include corundum, Kappa-alumina, quartz, olivine, moissanite-6H and Ca-Mg carbonates. This is the first observation of Kappa-alumina in nature. Secondary nano-minerals are observed within the amorphous matrix and include carbonates, Al-oxide, fluorite, ilmenite and secondary diamond crystals. The amorphous matrix is spongy and its composition is dominated by amorphous carbon, nitrogen, chlorine and also contains water. When no crystalline phases are observed, the matrix is also enriched in alumina, silica and in some cases calcium. We propose that micrometer scale cavities in diamonds form during dissolution events induced by the introduction of oxidizing hydrous fluids into the diamond growth area. Hydrous fluids are the main dissolving agents for most kimberlitic diamonds [Fedortchouk, Y., Canil, D., Semenets, E., 2007. Mechanisms of diamond oxidation and their bearing on the fluid composition in kimberlite magmas. Am. Mineral. 92, 1200-1212]. At diamond forming conditions silica and alumina are enriched in hydrous fluids that are in equilibrium with eclogites [Kessel, R., Ulmer, P., Pettke, T., Schmidt, M.W., Thompson, A.B., 2005. The water-basalt system at 4 to 6 GPa: Phase relations and second critical endpoint in a K-free eclogite at 700 to 1400 °C. Earth Planet. Sci. Lett. 237, 873-892]; this is consistent with the increased solubility of alumina with increased pressure and temperature in the Na-Cl bearing fluids [Manning, C.E., 2006. Mobilizing aluminum in crustal and

  17. Observation of fluctuation-induced tunneling conduction in micrometer-sized tunnel junctions

    NASA Astrophysics Data System (ADS)

    Lai, Yu-Ren; Yu, Kai-Fu; Lin, Yong-Han; Wu, Jong-Ching; Lin, Juhn-Jong

    2012-09-01

    Micrometer-sized Al/AlOx/Y tunnel junctions were fabricated by the electron-beam lithography technique. The thin (≈ 1.5-2 nm thickness) insulating AlOx layer was grown on top of the Al base electrode by O2 glow discharge. The zero-bias conductances G(T) and the current-voltage characteristics of the junctions were measured in a wide temperature range 1.5-300 K. In addition to the direct tunneling conduction mechanism observed in low-G junctions, high-G junctions reveal a distinct charge transport process which manifests the thermally fluctuation-induced tunneling conduction (FITC) through short nanoconstrictions. We ascribe the experimental realization of the FITC mechanism to originating from the formations of "hot spots" (incomplete pinholes) in the AlOx layer owing to large junction-barrier interfacial roughness.

  18. Efficient second-harmonic generation in micrometer-thick slabs with indefinite permittivity

    NASA Astrophysics Data System (ADS)

    Ciattoni, A.; Spinozzi, E.

    2012-04-01

    We theoretically predict efficient optical second-harmonic generation (SHG) from a micrometer-thick slab consisting of a quadratic nonlinear anisotropic medium whose linear principal permittivities have, at the fundamental wavelength, real parts of different signs (indefinite permittivity) and magnitude smaller than 1. We show that, by illuminating the slab with a p-polarized fundamental wave (with intensity of a few MW/cm2), highly efficient scattering of the second-harmonic field occurs in conditions at which the slab is linearly fully transparent for the fundamental wave. The high efficiency of the SHG process stems from the enhancement of the longitudinal field, perpendicular to the slab surface, produced by the very small value of the slab dielectric permittivities. We investigate the role played by medium losses, showing that, even in the strong-absorption regime, the described process yields a second-harmonic field which is much stronger than that produced by a standard (not indefinite) nonlinear slab.

  19. Non-destructive, ultra-low resistance, thermally stable contacts for use on shallow junction InP solar cells

    NASA Technical Reports Server (NTRS)

    Weizer, V. G.; Fatemi, N. S.; Korenyi-Both, A. L.

    1993-01-01

    Contact formation to InP is plagued by violent metal-semiconductor intermixing that takes place during the contact sintering process. Because of this the InP solar cell cannot be sintered after contact deposition. This results in cell contact resistances that are orders of magnitude higher than those that could be achieved if sintering could be performed in a non-destructive manner. We report here on a truly unique contact system involving Au and Ge, which is easily fabricated, which exhibits extremely low values of contact resistivity, and in which there is virtually no metal-semiconductor interdiffusion, even after extended sintering. We present a description of this contact system and suggest possible mechanisms to explain the observed behavior.

  20. Self-catalyzed growth of pure zinc blende 〈110〉 InP nanowires

    SciTech Connect

    Yan, Xin; Zhang, Xia Li, Junshuai; Wu, Yao; Ren, Xiaomin

    2015-07-13

    We demonstrate the self-catalyzed vapor-liquid-solid growth of 〈110〉 InP nanowires (NWs) by metal organic chemical vapor deposition. The 〈110〉 InP nanowire is formed via a spontaneous kinking from the original 〈111〉 growth direction, which is attributed to instabilities at the liquid/solid interface caused by a fast In incorporation into the droplet. The NW length before kinking has a nearly linear relationship with the diameter, offering a way to control the NW morphology for different applications. The 〈110〉 nanowire exhibits pure zinc blende crystal structure and a narrower emission linewidth in comparison with a typical 〈111〉 nanowire, demonstrating its potential applications in high-performance electronic and photonic devices.

  1. Chemical nature of silicon nitride-indium phosphide interface and rapid thermal annealing for InP MISFETs

    NASA Technical Reports Server (NTRS)

    Biedenbender, M. D.; Kapoor, V. J.

    1990-01-01

    A rapid thermal annealing (RTA) process in pure N2 or pure H2 was developed for ion-implanted and encapsulated indium phosphide compound semiconductors, and the chemical nature at the silicon nitride-InP interface before and after RTA was examined using XPS. Results obtained from SIMS on the atomic concentration profiles of the implanted silicon in InP before and after RTA are presented, together with electrical characteristics of the annealed implants. Using the RTA process developed, InP metal-insulator semiconductor FETs (MISFETS) were fabricated. The MISFETS prepared had threshold voltages of +1 V, transconductance of 27 mS/mm, peak channel mobility of 1200 sq cm/V per sec, and drain current drift of only 7 percent.

  2. The LANDSAT system operated in Brazil by CNPq/INPE - results obtained in the area of mapping and future perspectives

    NASA Technical Reports Server (NTRS)

    Dejesusparada, N. (Principal Investigator); Barbosa, M. N.

    1981-01-01

    The LANDSAT system, operated in the country by CNPg/INPE since 1973, systematically acquires, produces, and distributes both multispectral and panchromatic images obtained through remote sensing satellites to thousands of researchers and technicians involved in the natural resources survey. To cooperate in the solution of national problems, CNPq/INPE is developing efforts in the area of manipulation of those images with the objective of making them useful as planimetric bases for the simple revision of already published maps or for its utilization as basic material in regions not yet reliability mapped. The results obtained from performed tests are presented and the existing limitations are discussed. The new system purchased to handle data from the next series of LANDSAT as well as from MAPSAT and SPOT which will be in operation within the 80's decade, and are designed not only for natural resources survey but also for the solution of cartographic problems.

  3. Insight into the photoelectron angular dependent energy distribution of negative-electron-affinity InP photocathodes

    SciTech Connect

    Chen, Zhanghui; Jiang, Xiangwei; Dong, Shan; Li, Jingbo Li, Shushen; Wang, Linwang

    2014-01-13

    Energy distribution and angular distribution of the photoelectrons from InP photocathodes are investigated using a precise Monte Carlo model. It is found that Γ-valley electrons contribute to the first peak of the energy distribution curve, but the second peak is contributed by both Γ-valley and L-valley electrons rather than only L-valley electrons. L valley electrons are shown to have a smaller angular spread than Γ-valley electrons, which is attributed to the much higher potential energy of L-valley minimum. The further simulation indicates that the performance of InP photocathodes can be improved by increasing the hole concentration or decreasing the temperature, but the activation layer thickness variation only has very slight influence on either energy or angular distribution.

  4. Characterization of ion-irradiation-induced nanodot structures on InP surfaces by atom probe tomography.

    PubMed

    Gnaser, Hubert; Radny, Tobias

    2015-12-01

    Surfaces of InP were bombarded by 1.9 keV Ar(+) ions under normal incidence. The total accumulated ion fluence the samples were exposed to was varied from 1 × 10(17) cm(-2) to 3 × 10(18)cm(-2) and ion flux densities f of (0.4-2) × 10(14) cm(-2) s(-1) were used. Nanodot structures were found to evolve on the surface from these ion irradiations, their dimensions however, depend on the specific bombardment conditions. The resulting surface morphology was examined by atomic force microscopy (AFM). As a function of ion fluence, the mean radius, height, and spacing of the dots can be fitted by power-law dependences. In order to determine possible local compositional changes in these nanostructures induced by ion impact, selected samples were prepared for atom probe tomography (APT). The results indicate that by APT the composition of individual InP nanodots evolving under ion bombardment could be examined with atomic spatial resolution. At the InP surface, the values of the In/P concentration ratio are distinctly higher over a distance of ~1 nm and amount to 1.3-1.8. However, several aspects critical for the analyses were identified: (i) because of the small dimensions of these nanostructures a successful tip preparation proved very challenging. (ii) The elemental compositions obtained from APT were found to be influenced pronouncedly by the laser pulse energy; typically, low energies result in the correct stoichiometry whereas high ones lead to an inhomogeneous evaporation from the tips and deviations from the nominal composition. (iii) Depending again on the laser energy, a prolific emission of Pn cluster ions was observed, with n ≤ 11. PMID:25980895

  5. Growth of InP single crystals by liquid encapsulated Czochralski (LEC) using glassy-carbon crucibles

    SciTech Connect

    Oliveira, C.E.M. de; Miskys, C.R.; Carvalho, M.M.G. de

    1996-12-31

    Using a high pressure puller and Glassy-Carbon crucibles, undoped InP single crystals weighing 100g and with 25 mm diameter were grown in the <100> direction. The residual carrier concentration of samples, measure by the Van der Pauw method at 300K, was about 5 {times} 10{sup 15}cm{sup {minus}3}, result as good as those obtained with Quartz crucibles with the advantage that Glassy-Carbon crucibles are fully reusable.

  6. Improved dot size uniformity and luminescense of InAs quantum dots on InP substrate

    NASA Technical Reports Server (NTRS)

    Qiu, Y.; Uhl, D.

    2002-01-01

    InAs self-organized quantum dots have been grown in InGaAs quantum well on InP substrates by metalorganic vapor phase epitaxy. Atomic Force Microscopy confirmed of quantum dot formation with dot density of 3X10(sup 10) cm(sup -2). Improved dot size uniformity and strong room temperature photoluminescence up to 2 micron were observed after modifying the InGaAs well.

  7. Surface dipole formation and lowering of the work function by Cs adsorption on InP(100) surface

    SciTech Connect

    Sun Yun; Liu Zhi; Pianetta, Piero

    2007-09-15

    The Cs adsorption on InP(100) surface is studied with synchrotron radiation photoelectron spectroscopy. The charge transfer from Cs to the InP substrate is observed from the Cs induced In 4d and P 2p components, and this charge transfer results in surface dipole formation and lowering of the work function. The Cs 4d intensity saturates at coverage of 1 ML. However, a break point is observed at 0.5 ML, which coincides with the achievement of the minimum work function. This break point is due to the different vertical placements of the first and the second half monolayer of Cs atoms. Based on this information, a simple bilayer structure for the Cs layer is presented. This bilayer structure is consistent with the behavior of the charge transfer from the Cs to the InP substrate at different Cs coverages. This, in turn, explains why the work function decreases to a minimum at 0.5 ML of Cs and remains almost constant beyond this coverage. The depolarization of the surface dipoles is attributed to the saturation of charge transfer to the surface In atoms and the polarization of the Cs atoms in the second half monolayer induced by the positively charged Cs atoms in the first half monolayer.

  8. Surface Dipole Formation and Lowering of the Work Function by Cs Adsorption on InP(100) Surface

    SciTech Connect

    Sun, Y.; Liu, Z.; Pianetta, P.

    2007-06-08

    The Cs adsorption on InP(100) surface is studied with Synchrotron Radiation Photoelectron Spectroscopy. The charge transfer from Cs to the InP substrate is observed from the Cs induced In4d and P2p components, and this charge transfer results in surface dipole formation and lowering of the work function. The Cs4d intensity saturates at coverage of one monolayer (ML). However, a break point is observed at 0.5 ML, which coincides with the achievement of the minimum work function. This break point is due to the different vertical placement of the first and the second half monolayer of Cs atoms. Based on this information, a simple bi-layer structure for the Cs layer is presented. This bi-layer structure is consistent with the behavior of the charge transfer from the Cs to the InP substrate at different Cs coverages. This, in turn, explains why the work function decreases to a minimum at 0.5 ML of Cs and remains almost constant beyond this coverage. The depolarization of the surface dipoles is attributed to the saturation of charge transfer to the surface In atoms and the polarization of the Cs atoms in the second half monolayer induced by the positively charged Cs atoms in the first half monolayer.

  9. Rapid thermal anneal in InP, GaAs and GaAs/GaAlAs

    NASA Astrophysics Data System (ADS)

    Descouts, B.; Duhamel, N.; Godefroy, S.; Krauz, P.

    Ion implantation in semiconductors provides a doping technique with several advantages over more conventional doping methods and is now extensively used for device applications, e.g. field effect transistors (MESFET GaAs, MIS (InP), GaAs/GaAlAs heterojunction bipolar transistors (HBT). Because of the lattice disorder produced by the implantation, the dopant must be made electrically active by a postimplant anneal. As the device performances are very dependent on its electrical characteristics, the anneal is a very important stage of the process. Rapid anneal is known to provide less exodiffusion and less induffusion of impurities compared to conventional furnace anneal, so this technique has been used in this work to activate an n-type dopant (Si) in InP and a p-type dopant (Mg) in GaAs and GaAs/GaAIAs. These two ions have been chosen to realize implanted MIS InP and the base contacts for GaAs/GaAlAs HBTs. The experimental conditions to obtain the maximum electrical activity in these two cases will be detailed. For example, although we have not been able to obtain a flat profile in Mg + implanted GaAs/GaAlAs heterostructure by conventional thermal anneal, rapid thermal anneal gives a flat hole profile over a depth of 0.5 μm with a concentration of 1 x 10 19 cm -3.

  10. Molecular beam epitaxial growth of high-quality InSb on InP and GaAs substrates

    NASA Technical Reports Server (NTRS)

    Oh, J. E.; Bhattacharya, P. K.; Chen, Y. C.; Tsukamoto, S.

    1989-01-01

    Epitaxial layers of InSb were grown on InP and GaAs substrates by molecular beam epitaxy. The dependence of the epilayer quality on flux ratio, J sub Sb4/J sub In, was studied. Deviation from an optimum value of J sub Sb4/J sub In (approx. 2) during growth led to deterioration in the surface morphology and the electrical and crystalline qualities of the films. Room temperature electron mobilities as high as 70,000 and 53,000 sq cm /V-s were measured in InSb layers grown on InP and GaAs substrates, respectively. Unlike the previous results, the conductivity in these films is n-type even at T = 13 K, and no degradation of the electron mobility due to the high density of dislocations was observed. The measured electron mobilities (and carrier concentrations) at 77 K in InSb layers grown on InP and GaAs substrates are 110,000 sq cm/V-s (3 x 10(15) cm(-3)) and 55,000 sq cm/V-s (4.95 x 10(15) cm(-3)), respectively, suggesting their application to electronic devices at cryogenic temperatures.

  11. Electron beam induced damage in PECVD Si3N4 and SiO2 films on InP

    NASA Technical Reports Server (NTRS)

    Pantic, Dragan M.; Kapoor, Vik J.; Young, Paul G.; Williams, Wallace D.; Dickman, John E.

    1990-01-01

    Phosphorus rich plasma enhanced chemical vapor deposition (PECVD) of silicon nitride and silicon dioxide films on n-type indium phosphide (InP) substrates were exposed to electron beam irradiation in the 5 to 40 keV range for the purpose of characterizing the damage induced in the dielectic. The electron beam exposure was on the range of 10(exp -7) to 10(exp -3) C/sq cm. The damage to the devices was characterized by capacitance-voltage (C-V) measurements of the metal insulator semiconductor (MIS) capacitors. These results were compared to results obtained for radiation damage of thermal silicon dioxide on silicon (Si) MOS capacitors with similar exposures. The radiation induced damage in the PECVD silicon nitride films on InP was successfully annealed out in an hydrogen/nitrogen (H2/N2) ambient at 400 C for 15 min. The PECVD silicon dioxide films on InP had the least radiation damage, while the thermal silicon dioxide films on Si had the most radiation damage.

  12. Effect of InP Doping on the Phase Transition of Thin GeSbTe Films

    NASA Astrophysics Data System (ADS)

    Bang, Ki Su; Oh, Yong Jun; Lee, Seung-Yun

    2015-08-01

    We report the crystallization and phase-transition behavior of GeSbTe thin films doped with indium phosphorus (InP). Pure GeSbTe thin films and InP-doped GeSbTe thin films were prepared by use of an rf magnetron sputtering method. After thermal annealing, electrical and optical changes in the thin films were observed. Sheet resistance and reflectance measurements revealed that InP doping suppresses crystallization of GeSbTe. X-ray diffraction analysis confirmed that addition of In and P atoms inhibits the phase transition from face-centered cubic to hexagonal closed-packed. Nucleation of the doped GeSbTe thin films was delayed at an annealing temperature of 100°C; after thermal annealing, neither segregation nor formation of a secondary phase occurred. These results indicate that InP doping improves the amorphous stability of GeSbTe thin films. It is believed this enhanced amorphous stability is a result of the formation of multiple, strong crosslinks by the In and P atoms.

  13. Electronic properties of GaAs, InAs and InP nanowires studied by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Joyce, Hannah J.; Docherty, Callum J.; Gao, Qiang; Tan, H. Hoe; Jagadish, Chennupati; Lloyd-Hughes, James; Herz, Laura M.; Johnston, Michael B.

    2013-05-01

    We have performed a comparative study of ultrafast charge carrier dynamics in a range of III-V nanowires using optical pump-terahertz probe spectroscopy. This versatile technique allows measurement of important parameters for device applications, including carrier lifetimes, surface recombination velocities, carrier mobilities and donor doping levels. GaAs, InAs and InP nanowires of varying diameters were measured. For all samples, the electronic response was dominated by a pronounced surface plasmon mode. Of the three nanowire materials, InAs nanowires exhibited the highest electron mobilities of 6000 cm2 V-1 s-1, which highlights their potential for high mobility applications, such as field effect transistors. InP nanowires exhibited the longest carrier lifetimes and the lowest surface recombination velocity of 170 cm s-1. This very low surface recombination velocity makes InP nanowires suitable for applications where carrier lifetime is crucial, such as in photovoltaics. In contrast, the carrier lifetimes in GaAs nanowires were extremely short, of the order of picoseconds, due to the high surface recombination velocity, which was measured as 5.4 × 105  cm s-1. These findings will assist in the choice of nanowires for different applications, and identify the challenges in producing nanowires suitable for future electronic and optoelectronic devices.

  14. Ab-initio Calculations of Electronic Properties of AlP, GaP and InP

    NASA Astrophysics Data System (ADS)

    Malozovsky, Yuriy; Saliev, Azizjon; Franklin, Lashaunda; Ekuma, Chinedu; Zhao, Guang-Lin; Bagayoko, Diola

    2014-03-01

    We present results from ab-initio, self consistent local density approximation (LDA) calculations of electronic and related properties of zinc blende aluminum, gallium and indium phosphides (AlP, GaP & InP). We employed a local density approximation (LDA) potential and implemented the linear combination of atomic orbitals (LCAO) formalism. This implementation followed the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). Our calculated, indirect band gap of 2.56 eV for AlP, and of 2.14 eV for GaP, from Γ to X, are in excellent agreement with experimental values. Our calculated direct band gap of 1.40 eV, at Γ -point for InP is also in excellent agreement with experimental value. We also report calculated electron and hole effective masses for AlP, GaP and InP and total (DOS) and partial (pDOS) densities of states. This research is funded in part by the National Science Foundation (NSF) and the Louisiana Board of Regents, through LASiGMA [Award Nos. EPS- 1003897, NSF (2010-15)-RII-SUBR] and NSF HRD-1002541, the US Department of Energy - National, Nuclear Security Administration (NNSA) (Award No. DE-NA0001861), LaSPACE, and LONI-SUBR.

  15. Laboratory Syntheses of Insect Pheromones.

    ERIC Educational Resources Information Center

    Cormier, Russell A.; Hoban, James N.

    1984-01-01

    Provides background information and procedures for the multi-step synthesis of tiger moth and boll weevil pheromones (sex attractants). These syntheses require several laboratory periods. The tiger moth pheromone synthesis is suitable for introductory organic chemistry while the boll weevil pheromone is recommended for an advanced laboratory…

  16. Method of synthesizing pyrite nanocrystals

    DOEpatents

    Wadia, Cyrus; Wu, Yue

    2013-04-23

    A method of synthesizing pyrite nanocrystals is disclosed which in one embodiment includes forming a solution of iron (III) diethyl dithiophosphate and tetra-alkyl-ammonium halide in water. The solution is heated under pressure. Pyrite nanocrystal particles are then recovered from the solution.

  17. TP53INP2/DOR, a mediator of cell autophagy, promotes rDNA transcription via facilitating the assembly of the POLR1/RNA polymerase I preinitiation complex at rDNA promoters.

    PubMed

    Xu, Yinfeng; Wan, Wei; Shou, Xin; Huang, Rui; You, Zhiyuan; Shou, Yanhong; Wang, Lingling; Zhou, Tianhua; Liu, Wei

    2016-07-01

    Cells control their metabolism through modulating the anabolic and catabolic pathways. TP53INP2/DOR (tumor protein p53 inducible nuclear protein 2), participates in cell catabolism by serving as a promoter of autophagy. Here we uncover a novel function of TP53INP2 in protein synthesis, a major biosynthetic and energy-consuming anabolic process. TP53INP2 localizes to the nucleolus through its nucleolar localization signal (NoLS) located at the C-terminal domain. Chromatin immunoprecipitation (ChIP) assays detected an association of TP53INP2 with the ribosomal DNA (rDNA), when exclusion of TP53INP2 from the nucleolus repressed rDNA promoter activity and the production of ribosomal RNA (rRNA) and proteins. The removal of TP53INP2 also impaired the association of the POLR1/RNA polymerase I preinitiation complex (PIC) with rDNA. Further, TP53INP2 interacts directly with POLR1 PIC, and is required for the assembly of the complex. These data indicate that TP53INP2 promotes ribosome biogenesis through facilitating rRNA synthesis at the nucleolus, suggesting a dual role of TP53INP2 in cell metabolism, assisting anabolism on the nucleolus, and stimulating catabolism off the nucleolus. PMID:27172002

  18. Realistic multiband k .p approach from ab initio and spin-orbit coupling effects of InAs and InP in wurtzite phase

    NASA Astrophysics Data System (ADS)

    Faria Junior, Paulo E.; Campos, Tiago; Bastos, Carlos M. O.; Gmitra, Martin; Fabian, Jaroslav; Sipahi, Guilherme M.

    2016-06-01

    Semiconductor nanowires based on non-nitride III-V compounds can be synthesized under certain growth conditions to favor the appearance of the wurtzite crystal phase. Despite reports in the literature of ab initio band structures for these wurtzite compounds, we still lack effective multiband models and parameter sets that can be simply used to investigate physical properties of such systems, for instance, under quantum confinement effects. In order to address this deficiency, in this study we calculate the ab initio band structure of bulk InAs and InP in the wurtzite phase and develop an 8 ×8 k .p Hamiltonian to describe the energy bands around the Γ point. We show that our k .p model is robust and can be fitted to describe the important features of the ab initio band structure. The correct description of the spin-splitting effects that arise due to the lack of inversion symmetry in wurtzite crystals is obtained with the k -dependent spin-orbit term in the Hamiltonian, often neglected in the literature. All the energy bands display a Rashba-like spin texture for the in-plane spin expectation value. We also provide the density of states and the carrier density as functions of the Fermi energy. Alternatively, we show an analytical description of the conduction band, valid close to the Γ point. The same fitting procedure is applied to the 6 ×6 valence band Hamiltonian. However, we find that the most reliable approach is the 8 ×8 k .p Hamiltonian for both compounds. The k .p Hamiltonians and parameter sets that we develop in this paper provide a reliable theoretical framework that can be easily applied to investigate electronic, transport, optical, and spin properties of InAs- and InP-based nanostructures.

  19. Effect of the Surface Morphology of Seed and Mask Layers on InP Grown on Si by Epitaxial Lateral Overgrowth

    NASA Astrophysics Data System (ADS)

    Junesand, Carl; Hu, Chen; Wang, Zhechao; Metaferia, Wondwosen; Dagur, Pritesh; Pozina, Galia; Hultman, Lars; Lourdudoss, Sebastian

    2012-09-01

    Heteroepitaxy of InP on Si by epitaxial lateral overgrowth (ELOG) using a thin seed layer of InP as starting material is investigated, with special attention given to the effect of the surface morphology of the seed and the mask layers on the quality of the ELOG layers. Chemical mechanical polishing (CMP) has been used to improve the morphological and optical quality of InP grown by hydride vapor-phase epitaxy (HVPE) using ELOG. Two approaches have been investigated: polishing the InP seed layer on Si before depositing the SiO2 mask and polishing the SiO2 mask after its deposition on the unprocessed seed layer. For polishing the InP (seed)/Si, a two-step process with an aluminum oxide- and sodium hypochlorite-containing slurry as well as a slurry based on sodium hypochlorite mixed with citric acid was used. For SiO2 mask polishing, a slurry with colloidal silica as an abrasive was employed. In both cases, the SiO2 mask was patterned with double line openings and ELOG carried out in an HVPE reactor. Morphology and crystal quality of the resulting ELOG layers were studied with atomic force microscopy (AFM) and room-temperature panchromatic cathodoluminescence (PC-CL) in situ in a scanning electron microscope (SEM), respectively. The results show that, whereas both polishing approaches result in an ELOG InP layer with good morphology, its surface roughness is lower when the InP (seed)/Si is subjected to CMP prior to deposition of the SiO2 mask, than when only the SiO2 mask is polished. This approach also leads to a decrease in the number of defects generated during coalescence of the ELOG layers.

  20. Characterization of the S. cerevisiae inp51 mutant links phosphatidylinositol 4,5-bisphosphate levels with lipid content, membrane fluidity and cold growth.

    PubMed

    Córcoles-Sáez, Isaac; Hernández, Maria Luisa; Martínez-Rivas, Jose Manuel; Prieto, Jose A; Randez-Gil, Francisca

    2016-03-01

    Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and its derivatives diphosphoinositol phosphates (DPIPs) play key signaling and regulatory roles. However, a direct function of these molecules in lipid and membrane homeostasis remains obscure. Here, we have studied the cold tolerance phenotype of yeast cells lacking the Inp51-mediated phosphoinositide-5-phosphatase. Genetic and biochemical approaches showed that increased metabolism of PI(4,5)P2 reduces the activity of the Pho85 kinase by increasing the levels of the DPIP isomer 1-IP7. This effect was key in the cold tolerance phenotype. Indeed, pho85 mutant cells grew better than the wild-type at 15 °C, and lack of this kinase abolished the inp51-mediated cold phenotype. Remarkably, reduced Pho85 function by loss of Inp51 affected the activity of the Pho85-regulated target Pah1, the yeast phosphatidate phosphatase. Cells lacking Inp51 showed reduced Pah1 abundance, derepression of an INO1-lacZ reporter, decreased content of triacylglycerides and elevated levels of phosphatidate, hallmarks of the pah1 mutant. However, the inp51 phenotype was not associated to low Pah1 activity since deletion of PAH1 caused cold sensitivity. In addition, the inp51 mutant exhibited features not shared by pah1, including a 40%-reduction in total lipid content and decreased membrane fluidity. These changes may influence the activity of membrane-anchored and/or associated proteins since deletion of INP51 slows down the transit to the vacuole of the fluorescent dye FM4-64. In conclusion, our work supports a model in which changes in the PI(4,5)P2 pool affect the 1-IP7 levels modulating the activity of Pho85, Pah1 and likely additional Pho85-controlled targets, and regulate lipid composition and membrane properties. PMID:26724696

  1. Thin films of InP for photovoltaic energy conversion. Second quarterly technical progress report, September 29, 1979-December 28, 1979

    SciTech Connect

    Manasevit, H M; Ruth, R P; Moudy, L A; Yang, J J.J.; Johnson, R E

    1980-01-01

    A research study is being conducted for the purpose of developing a low-cost high-efficiency thin-film InP heterojunction solar cell based on InP films grown by the metalorganic chemical vapor deposition (MO-CVD) process on suitable substrates. Heterostructure devices of CdS/InP (and possibly indium-tin oxide/InP) are to be prepared at Stanford University using the MO-CVD InP films grown at Rockwell. The work of the second quarter of the program is summarized. Growth parameters have been established using new triethylindium, diethylzinc (DEZn), and PH/sub 3/ sources for the formation of Zn-doped p-type InP films in the modified MO-CVD reactor system. Appropriately doped films have been prepared and sent to Stanford for use in deposition of CdS layers. An investigation of the properties of grains and grain boundaries in polycrystalline InP films was begun using several polycrystalline film/substrate combinations, including tungsten (W) layers produced by roller coating and screen-printing on polycrystalline alumina, and mechanically abraded surfaces of single-crystal bulk InP:Fe wafers. An investigation was also undertaken into the use of GaP as an alternative intermediate-layer material to GaAs on low-cost substrates for subsequent growth of InP films. Auger electron spectroscopy analysis done on a group of specially prepared Zn-treated films of polycrystalline InP indicated the presence of Zn at surfaces of InP:Zn films grown on Al and/or heat-treated in high concentrations of DEZn at approx. 600/sup 0/C. However, no Zn was detected in polycrystalline films grown under deposition conditions that would be expected to produce highly doped p-type epitaxial films if single-crystal substrates were used.

  2. DNA damage on nano- and micrometer scales impacts dicentric induction: computer modelling of ion microbeam experiments

    NASA Astrophysics Data System (ADS)

    Friedland, Werner; Kundrat, Pavel; Schmitt, Elke

    2016-07-01

    Detailed understanding of the enhanced relative biological effectiveness (RBE) of ions, in particular at high linear energy transfer (LET) values, is needed to fully explore the radiation risk of manned space missions. It is generally accepted that the enhanced RBE of high-LET particles results from the DNA lesion patterns, in particular DNA double-strand breaks (DSB), due to the spatial clustering of energy deposits around their trajectories. In conventional experiments on biological effects of radiation types of diverse quality, however, clustering of energy deposition events on nanometer scale that is relevant for the induction and local complexity of DSB is inherently interlinked with regional (sub-)micrometer-scale DSB clustering along the particle tracks. Due to this limitation, the role of both (nano- and micrometer) scales on the induction of diverse biological endpoints cannot be frankly separated. To address this issue in a unique way, experiments at the ion microbeam SNAKE [1] and corresponding track-structure based model calculations of DSB induction and subsequent repair with the biophysical code PARTRAC [2] have been performed. In the experiments, hybrid human-hamster A_{L} cells were irradiated with 20 MeV (2.6 keV/μm) protons, 45 MeV (60 keV/μm) lithium ions or 55 MeV (310 keV/μm) carbon ions. The ions were either quasi-homogeneously distributed or focused to 0.5 x 1 μm^{2} spots on regular matrix patterns of 5.4 μm, 7.6 μm and 10.6 μm grid size, with pre-defined particle numbers per spot so as to deposit a mean dose of 1.7 Gy for all irradiation patterns. As expected, the induction of dicentrics by homogeneous irradiation increased with LET: lithium and carbon ions induced about two- and four-fold higher yields of dicentrics than protons. The induction of dicentrics is, however, affected by µm-scale, too: focusing 20 lithium ions or 451 protons per spot on a 10.6 μm grid induced two or three times more dicentrics, respectively, than a

  3. A high frequency GaAlAs travelling wave electro-optic modulator at 0.82 micrometers

    NASA Technical Reports Server (NTRS)

    Chorey, Christopher M.; Ferendeci, Altan; Bhasin, Kul B.

    1988-01-01

    Experimental GaAlAs modulators operating at 0.82 micrometers using a Mach-Zehnder interferometer configuration were designed and fabricated. Coplanar 50 ohm travelling wave microwave electrodes were used to obtain a bandwidth length product of 11.95 GHz-cm. The design, fabrication and dc performance of the GaAlAs travelling wave modulator is presented.

  4. Opto-mechanical subsystem of a 10 micrometer wavelength receiver terminal. Waveguide laser local oscillator. Servo system

    NASA Technical Reports Server (NTRS)

    1975-01-01

    An engineering model opto-mechanical subsystem for a 10.6-micrometer laser heterodyne receiver is developed, and a CO2 waveguide local oscillator and servo electronics are provided for the receiver. Design goals are presented for the subsystems and overall package design is described. Thermal and mechanical distortion loading tests were performed and the results are included.

  5. Infrared receivers for low background astronomy: Incoherent detectors and coherent devices from one micrometer to one millimeter

    NASA Technical Reports Server (NTRS)

    Boggess, N. W.; Greenberg, L. T.; Hauser, M. G.; Houck, J. R.; Low, F. J.; Mccreight, C. R.; Rank, D. M.; Richards, P. L.; Weiss, R.

    1979-01-01

    The status of incoherent detectors and coherent receivers over the infrared wavelength range from one micrometer to one millimeter is described. General principles of infrared receivers are included, and photon detectors, bolometers, coherent receivers, and important supporting technologies are discussed, with emphasis on their suitability for low background astronomical applications. Broad recommendations are presented and specific opportunities are identified for development of improved devices.

  6. Frequency Synthesizer For Tracking Filter

    NASA Technical Reports Server (NTRS)

    Randall, Richard L.

    1990-01-01

    Digital frequency-synthesizing subsystem generates trains of pulses, free of jitter, for use as frequency-control signals in tracking filters. Part of assembly of electronic equipment used to measure vibrations in bearings in rotating machinery. Designed to meet requirements for tracking narrow-band cage-rotation and ball-pass components of vibrations, as discussed in "Frequency-Tracking Error Detector" (MFS-29538) and "Ball-Pass Cage-Modulation Detector" (MFS-29539). Synthesizer includes preset counter, output of which controls signal for ball-pass filter. Input to this preset counter updated every 2 microseconds: responds almost immediately, effectively eliminating relatively long response time (lock-in time) and phase jitter.

  7. Catalytic method for synthesizing hydrocarbons

    DOEpatents

    Sapienza, Richard S.; Sansone, Michael J.; Slegeir, William A. R.

    1984-01-01

    A method for synthesizing hydrocarbons from carbon monoxide and hydrogen by contacting said gases with a slurry of a catalyst composed of palladium or platinum and cobalt supported on a solid phase is disclosed. The catalyst is prepared by heating a heterogeneous component of the palladium or platinum deposited on the solid support in a solution of cobalt carbonyl or precursors thereof. The catalyst exhibits excellent activity, stability in air, and produces highly desirable product fractions even with dilute gaseous reactants.

  8. Catalytic method for synthesizing hydrocarbons

    DOEpatents

    Sapienza, R.S.; Sansone, M.J.; Slegeir, W.A.R.

    A method for synthesizing hydrocarbons from carbon monoxide and hydrogen by contacting said gases with a slurry of a catalyst composed of palladium or platinum and cobalt supported on a solid phase is disclosed. The catalyst is prepared by heating a heterogeneous component of the palladium or platinum deposited on the solid support in a solution of cobalt carbonyl or precursors thereof. The catalyst exhibits excellent activity, stability in air, and produces highly desirable product fractions even with dilute gaseous reactants.

  9. Determinism in synthesized chaotic waveforms.

    PubMed

    Corron, Ned J; Blakely, Jonathan N; Hayes, Scott T; Pethel, Shawn D

    2008-03-01

    The output of a linear filter driven by a randomly polarized square wave, when viewed backward in time, is shown to exhibit determinism at all times when embedded in a three-dimensional state space. Combined with previous results establishing exponential divergence equivalent to a positive Lyapunov exponent, this result rigorously shows that such reverse-time synthesized waveforms appear equally to have been produced by a deterministic chaotic system. PMID:18517561

  10. SYNTH - Gamma Ray Spectrum Synthesizer

    Energy Science and Technology Software Center (ESTSC)

    2009-05-18

    SYNTH was designed to synthesize the results of typical gamma-ray spectroscopy experiments. The code allows a user to specify the physical characteristics of a gamma-ray source, the quantity of radionuclides emitting gamma radiation, the source-to-detector distance and the presence and type of any intervening absorbers, the size and type of the gamma-ray detector, and the electronic set-up used to gather the data.

  11. TSS-Thermal Synthesizer System

    NASA Technical Reports Server (NTRS)

    Chimenti, Edward; Rickman, Steven; Vogt, Robert; Longo, Carlos R. Ortiz; Bauman, Noel; Lepore, Joseph; Mackey, Phil; Pavlovsky, James, II; Welch, Mark; Fogerson, Peter; Dawber, Mark; Fong, Cynthia Jone; Hecke, Peter; Morrison, Susan; Castillo, Ernie; Chou, ZU; Fried, Lawrence; Howard, Jerry; Lombardi, Mike; Middleton, Jack

    1996-01-01

    Thermal Synthesizer System (TSS) is integrated set of thermal-analysis application programs designed to solve problems encountered by thermal engineers. Combines functionality of Systems Improved Numerical Differencing Analyzer/Fluid Integrator (SINDA/FLUINT) and radiation analysis with friendly and easily understood user-interface environment coupled with powerful interactive color graphics and geometric modeling capability. Enables thermal engineers to spend more time solving engineering problems instead of laboriously constructing and verifying math models. Written in FORTRAN and C language.

  12. Method for synthesizing powder materials

    DOEpatents

    Buss, R.J.; Ho, P.

    1988-01-21

    A method for synthesizing ultrafine powder materials, for example, ceramic and metal powders, comprises admitting gaseous reactants from which the powder material is to be formed into a vacuum reaction chamber maintained at a pressure less than atmospheric and at a temperature less than about 400/degree/K (127/degree/C). The gaseous reactants are directed through a glow discharge provided in the vacuum reaction chamber to form the ultrafine powder material. 1 fig.

  13. A novel optical fibre doped with the nano-material as InP

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Lee, Ly Guat; Zhang, Ru

    2007-11-01

    As the key of these optical devices which are widely used in the communication system, high nonlinear optical fibre will play an important role in the future optical fibre communication. With recent growth of nano-technology, researchers are hoping to obtain some kinds of optical fibre by combining the optical fibre with the nanotechnology. According to this current situation, the optical fibre doped with nano-material as InP (indium phosphide) is manufactured by using the MCVD (modified chemical vapor deposition) technology after our comprehensive consideration of many relative factors. Proved by experiments, this novel optical fibre has an excellent waveguide characteristic. After a consideration of the model of this novel optical fibre, its propagation constant β has been simulated by using the FEM (finite element method), and the graphs of presentation of magnetic field of the core are also obtained. In accordance with the results, the effective refractive index n eff = 1.401 has be calculated. Both the calculated result and the simulated graphs are matching well with the test, and this result is a step-stone bridge for future research of nonlinear parameter on this novel optical fiber.

  14. Doping evaluation of InP nanowires for tandem junction solar cells

    NASA Astrophysics Data System (ADS)

    Lindelöw, F.; Heurlin, M.; Otnes, G.; Dagytė, V.; Lindgren, D.; Hultin, O.; Storm, K.; Samuelson, L.; Borgström, M.

    2016-02-01

    In order to push the development of nanowire-based solar cells further using optimized nanowire diameter and pitch, a doping evaluation of the nanowire geometry is necessary. We report on a doping evaluation of n-type InP nanowires with diameters optimized for light absorption, grown by the use of metal-organic vapor phase epitaxy in particle-assisted growth mode using tetraethyltin (TESn) as the dopant precursor. The charge carrier concentration was evaluated using four-probe resistivity measurements and spatially resolved Hall measurements. In order to reach the highest possible nanowire doping level, we set the TESn molar fraction at a high constant value throughout growth and varied the trimethylindium (TMIn) molar fraction for different runs. Analysis shows that the charge carrier concentration in nanowires grown with the highest TMIn molar fraction (not leading to kinking nanowires) results in a low carrier concentration of approximately 1016 cm-3. By decreasing the molar fraction of TMIn, effectively increasing the IV/III ratio, the carrier concentration increases up to a level of about 1019 cm-3, where it seems to saturate. Axial carrier concentration gradients along the nanowires are found, which can be correlated to a combination of changes in the nanowire growth rate, measured in situ by optical reflectometry, and polytypism of the nanowires observed in transmission electron microscopy.

  15. Broadband Phase-Sensitive Single InP Nanowire Photoconductive Terahertz Detectors.

    PubMed

    Peng, Kun; Parkinson, Patrick; Boland, Jessica L; Gao, Qian; Wenas, Yesaya C; Davies, Christopher L; Li, Ziyuan; Fu, Lan; Johnston, Michael B; Tan, Hark H; Jagadish, Chennupati

    2016-08-10

    Terahertz time-domain spectroscopy (THz-TDS) has emerged as a powerful tool for materials characterization and imaging. A trend toward size reduction, higher component integration, and performance improvement for advanced THz-TDS systems is of increasing interest. The use of single semiconducting nanowires for terahertz (THz) detection is a nascent field that has great potential to realize future highly integrated THz systems. In order to develop such components, optimized material optoelectronic properties and careful device design are necessary. Here, we present antenna-optimized photoconductive detectors based on single InP nanowires with superior properties of high carrier mobility (∼1260 cm(2) V(-1) s(-1)) and low dark current (∼10 pA), which exhibit excellent sensitivity and broadband performance. We demonstrate that these nanowire THz detectors can provide high quality time-domain spectra for materials characterization in a THz-TDS system, a critical step toward future application in advanced THz-TDS system with high spectral and spatial resolution. PMID:27413813

  16. Micromanipulation of InP lasers with optoelectronic tweezers for integration on a photonic platform.

    PubMed

    Juvert, Joan; Zhang, Shuailong; Eddie, Iain; Mitchell, Colin J; Reed, Graham T; Wilkinson, James S; Kelly, Anthony; Neale, Steven L

    2016-08-01

    The integration of light sources on a photonic platform is a key aspect of the fabrication of self-contained photonic circuits with a small footprint that does not have a definitive solution yet. Several approaches are being actively researched for this purpose. In this work we propose optoelectronic tweezers for the manipulation and integration of light sources on a photonic platform and report the positional and angular accuracy of the micromanipulation of standard Fabry-Pérot InP semiconductor laser die. These lasers are over three orders of magnitude bigger in volume than any previously assembled with optofluidic techniques and the fact that they are industry standard lasers makes them significantly more useful than previously assembled microdisk lasers. We measure the accuracy to be 2.5 ± 1.4 µm and 1.4 ± 0.4° and conclude that optoelectronic tweezers are a promising technique for the micromanipulation and integration of optoelectronic components in general and semiconductor lasers in particular. PMID:27505781

  17. Activation energy and capture cross section of majority carrier traps in Zn doped InP

    NASA Technical Reports Server (NTRS)

    Rybicki, George; Williams, Wendell

    1993-01-01

    Schottky barrier diodes were fabricated on Zn doped InP Wafers. The diodes were radiation damaged with 2 MeV protons to a dose of 2 x 10(exp 12)cm(sup -2). The damage was analyzed by DLTS (deep level transient spectroscopy) using the double correlation technique. Capture cross sections were measured directly. Two major defects were observed in the DLTS spectra. The first defect, was H4 at Ev + 0.29 eV, with capture cross section 1.1 x 10(exp -17)cm(sup 2). The second defect, was H5 at Ev + 0.53 eV. Its capture cross section varied with temperature as described by the relationship sigma = sigma(sub 0) exp(delta(E)/kT) where sigma(sub 0) = 1.3 x 10(exp -19)cm(sup 2) and delta(E) = .08 eV. This relationship yields a sigma of 5.9 x 10(exp -21)cm(sup 2) at room temperature. The surprisingly small capture cross section of H5 and its temperature dependence are discussed in terms of the multiphonon emission process for carrier capture at the defect. The advantages of the improved experimental techniques used are also discussed.

  18. InP Nanoflag Growth from a Nanowire Template by in Situ Catalyst Manipulation.

    PubMed

    Kelrich, Alexander; Sorias, Ofir; Calahorra, Yonatan; Kauffmann, Yaron; Gladstone, Ran; Cohen, Shimon; Orenstein, Meir; Ritter, Dan

    2016-04-13

    Quasi-two-dimensional semiconductor materials are desirable for electronic, photonic, and energy conversion applications as well as fundamental science. We report on the synthesis of indium phosphide flag-like nanostructures by epitaxial growth on a nanowire template at 95% yield. The technique is based on in situ catalyst unpinning from the top of the nanowire and its induced migration along the nanowire sidewall. Investigation of the mechanism responsible for catalyst movement shows that its final position is determined by the structural defect density along the nanowire. The crystal structure of the "flagpole" nanowire is epitaxially transferred to the nanoflag. Pure wurtzite InP nanomembranes with just a single stacking fault originating from the defect in the flagpole that pinned the catalyst were obtained. Optical characterization shows efficient highly polarized photoluminescence at room temperature from a single nanoflag with up to 90% degree of linear polarization. Electric field intensity enhancement of the incident light was calculated to be 57, concentrated at the nanoflag tip. The presented growth method is general and thus can be employed for achieving similar nanostructures in other III-V semiconductor material systems with potential applications in active nanophotonics. PMID:26999355

  19. Passive and electro-optic polymer photonics and InP electronics integration

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Katopodis, V.; Groumas, P.; Konczykowska, A.; Dupuy, J.-.; Beretta, A.; Dede, A.; Miller, E.; Choi, J. H.; Harati, P.; Jorge, F.; Nodjiadjim, V.; Dinu, R.; Cangini, G.; Vannucci, A.; Felipe, D.; Maese-Novo, A.; Keil, N.; Bach, H.-.; Schell, Martin; Avramopoulos, H.; Kouloumentas, Ch.

    2015-05-01

    Hybrid photonic integration allows individual components to be developed at their best-suited material platforms without sacrificing the overall performance. In the past few years a polymer-enabled hybrid integration platform has been established, comprising 1) EO polymers for constructing low-complexity and low-cost Mach-Zehnder modulators (MZMs) with extremely high modulation bandwidth; 2) InP components for light sources, detectors, and high-speed electronics including MUX drivers and DEMUX circuits; 3) Ceramic (AIN) RF board that links the electronic signals within the package. On this platform, advanced optoelectronic modules have been demonstrated, including serial 100 Gb/s [1] and 2x100 Gb/s [2] optical transmitters, but also 400 Gb/s optoelectronic interfaces for intra-data center networks [3]. To expand the device functionalities to an unprecedented level and at the same time improve the integration compatibility with diversified active / passive photonic components, we have added a passive polymer-based photonic board (polyboard) as the 4th material system. This passive polyboard allows for low-cost fabrication of single-mode waveguide networks, enables fast and convenient integration of various thin-film elements (TFEs) to control the light polarization, and provides efficient thermo-optic elements (TOEs) for wavelength tuning, light amplitude regulation and light-path switching.

  20. Heteroepitaxial InP, and ultrathin, directly glassed, GaAs 3-5 solar cells

    NASA Technical Reports Server (NTRS)

    Hardingham, C. M.; Cross, T. A.

    1993-01-01

    The commercial application of Indium Phosphide solar cells in practical space missions is crucially dependent upon achieving a major cost reduction which could be offered by heteroepitaxy on cheaper, more rugged substrates. Furthermore, significant mass reduction, compatibility with mechanically stacked multijunction cells, and elimination of the current loss through glue discoloration, is possible in III-V solar cells by the development of ultrathin, directly glassed cells. The progress of a UK collaborative program to develop high efficiency, homojunction InP solar cells, grown by MOCVD on Si substrates, is described. Results of homoepitaxial cells (is greater than 17 percent 1 Sun AM0) are presented, together with progress in achieving low dislocation density heteroepitaxy. Also, progress in a UK program to develop ultrathin directly-glassed GaAs cells is described. Ultrathin (5 micron) GaAs cells, with 1 Sun AM0 efficiencies up to 19.1 percent, are presented, together with progress in achieving a direct (adhesive-less) bond between the cell and coverglass. Consequential development to, for example, cell grids, are also discussed.

  1. Surface photovoltage studies of n-type and p-type InP

    NASA Astrophysics Data System (ADS)

    Thurgate, S. M.; Blight, K.; Laceusta, T. D.

    1994-05-01

    Surface photovoltage spectroscopy (SPV) was used to study the initial stages of oxidation of single crystal InP(110) in an attempt to understand the nature and origin of the surface states that develop. Distinct surface states were seen to develop on n-type as the surface was exposed to oxygen. A surface state, associated with cleavage damage, was also observed on p-type. A detailed fit to the experimental data was made by using a model of the dependence of surface charge on photon energy. This was used to unfold the position and intensity of the states. States trailing into the band gap from the bulk bands were seen on both n- and p-types. The analysis also indicated that pairs of isolated states, a donor and an acceptor state, were produced. On p-type, these were present on the clean, cleaved surface while they developed with oxygen exposure on n-type. These states are consistent with the point defect states proposed by the unified defect model. The time response of the SPV signal was also recorded for these surfaces. They were analysed by careful fitting to a model describing the charging and discharging characteristics. This revealed that the midgap state on n-type had a fast and a slow component.

  2. Multi-junction Thermophotovoltaic Converters Based on Dilute Nitride Superlattices Lattice Matched to InP

    NASA Astrophysics Data System (ADS)

    Bhusal, L.; Freundlich, A.

    2007-02-01

    Recently we have shown that by adjusting the thickness of individual sublayers and the nitrogen composition, strain balanced GaAs1-xNx/InAs1-yNy superlattices can be designed to be both lattice matched to InP and have effective bangaps in the desirable 0.4-0.65 eV range. The effect of insertion of such superlattice-like alloy within the intrinsic region of a 0.74 eV InGaAs p-i-n diode was also evaluated and it was shown that such a single junction device exhibits a photovoltaic response comparable to its lattice-mismatched 0.55 eV-InGaAs counterpart. In this work we have extended the approach to multi-junctions devices. Here two or more subcells with different effective bandgaps for the superlattice region are monolithically series connected. Maximum power output and performance of double, triple and quadruple junction TPV cells are evaluated as a function of the superlattice/cell design for a relatively low temperature black body emitters (1350K). The study stresses the potential of the proposed approach for a significant enhancement of TPV converter performance.

  3. Improvements in contact resistivity and thermal stability of Au-contacted InP solar cells

    NASA Technical Reports Server (NTRS)

    Fatemi, Navid S.; Weizer, Victor G.

    1991-01-01

    Specific contact resistivities for as-fabricated Au contacts on n-p InP solar cells are typically in the 10(exp -3) ohm/sq cm range, but contact resistivities in the 10(exp -6) ohm/sq cm range can be obtained if the cells are heat treated at 400 C for a few minutes. This heat treatment, however, results in a dramatic drop in the open circuit voltage of the cell due to excessive dissolution of the emitter into the metallization. It was found that low values of contact resistivity can be secured without the accompanying drop in the open circuit voltage by adding Ga and In in the Au metallization. It is shown that Au contacts containing as little as 1 percent atomic Ga can suppress the reaction that takes place at the metal-InP interface during heat treatment, while exhibiting contact resistivity values in the low 10(exp -5) ohm/sq cm. Detailed explanations for the observed superior thermal stability of these contacts are presented.

  4. Laue-DIC: a new method for improved stress field measurements at the micrometer scale.

    PubMed

    Petit, J; Castelnau, O; Bornert, M; Zhang, F G; Hofmann, F; Korsunsky, A M; Faurie, D; Le Bourlot, C; Micha, J S; Robach, O; Ulrich, O

    2015-07-01

    A better understanding of the effective mechanical behavior of polycrystalline materials requires an accurate knowledge of the behavior at a scale smaller than the grain size. The X-ray Laue microdiffraction technique available at beamline BM32 at the European Synchrotron Radiation Facility is ideally suited for probing elastic strains (and associated stresses) in deformed polycrystalline materials with a spatial resolution smaller than a micrometer. However, the standard technique used to evaluate local stresses from the distortion of Laue patterns lacks accuracy for many micromechanical applications, mostly due to (i) the fitting of Laue spots by analytical functions, and (ii) the necessary comparison of the measured pattern with the theoretical one from an unstrained reference specimen. In the present paper, a new method for the analysis of Laue images is presented. A Digital Image Correlation (DIC) technique, which is essentially insensitive to the shape of Laue spots, is applied to measure the relative distortion of Laue patterns acquired at two different positions on the specimen. The new method is tested on an in situ deformed Si single-crystal, for which the prescribed stress distribution has been calculated by finite-element analysis. It is shown that the new Laue-DIC method allows determination of local stresses with a strain resolution of the order of 10(-5). PMID:26134802

  5. IR and green femtosecond laser machining of heat sensitive materials for medical devices at micrometer scale

    NASA Astrophysics Data System (ADS)

    Stolberg, Klaus; Friedel, Susanna; Kremser, Bert; Roehner, Markus

    2014-03-01

    In medical device manufacturing there is an increasing interest to enhance machining of biocompatible materials on a micrometer scale. Obviously there is a trend to generate smaller device structures like cavities, slits or total size of the device to address new applications. Another trend points to surface modification, which allows controlling selective growth of defined biological cell types on medical implants. In both cases it is interesting to establish machining methods with minimized thermal impact, because biocompatible materials often show degradation of mechanical properties under thermal treatment. Typical examples for this effect is embrittlement of stainless steel at the edge of a cutting slit, which is caused by oxidation and phase change. Also for Nitinol (NiTi alloy) which is used as another stent material reduction of shape-memory behavior is known if cutting temperature is too high. For newest biodegradable materials like Polylactic acid (PLA) based polymers, lowest thermal impact is required due to PLA softening point (65°C) and melting temperature (~170 °C ). Laser machining with ultra-short pulse lasers is a solution for this problem. In our work we demonstrate a clean laser cut of NiTi and PLA based polymers with a high repetition-rate 1030 nm, 400-800 fs laser source at a pulse energy of up to 50 μJ and laser repetition rate of up to 500 kHz.

  6. Constraints on Exotic Dipole-Dipole Couplings between Electrons at the Micrometer Scale.

    PubMed

    Kotler, Shlomi; Ozeri, Roee; Kimball, Derek F Jackson

    2015-08-21

    New constraints on exotic dipole-dipole interactions between electrons at the micrometer scale are established, based on a recent measurement of the magnetic interaction between two trapped 88Sr(+) ions. For light bosons (mass≤0.1  eV) we obtain a 90% confidence interval for an axial-vector-mediated interaction strength of |g(A)(e)g(A)(e)/4πℏc|≤1.2×10(-17). Assuming CPT invariance, this constraint is compared to that on anomalous electron-positron interactions, derived from positronium hyperfine spectroscopy. We find that the electron-electron constraint is 6 orders of magnitude more stringent than the electron-positron counterpart. Bounds on pseudoscalar-mediated interaction as well as on torsion gravity are also derived and compared with previous work performed at different length scales. Our constraints benefit from the high controllability of the experimental system which contained only two trapped particles. It therefore suggests a useful new platform for exotic particle searches, complementing other experimental efforts. PMID:26340180

  7. Correlation between micrometer-scale ripple alignment and atomic-scale crystallographic orientation of monolayer graphene

    PubMed Central

    Choi, Jin Sik; Chang, Young Jun; Woo, Sungjong; Son, Young-Woo; Park, Yeonggu; Lee, Mi Jung; Byun, Ik-Su; Kim, Jin-Soo; Choi, Choon-Gi; Bostwick, Aaron; Rotenberg, Eli; Park, Bae Ho

    2014-01-01

    Deformation normal to the surface is intrinsic in two-dimensional materials due to phononic thermal fluctuations at finite temperatures. Graphene's negative thermal expansion coefficient is generally explained by such an intrinsic property. Recently, friction measurements on graphene exfoliated on a silicon oxide surface revealed an anomalous anisotropy whose origin was believed to be the formation of ripple domains. Here, we uncover the atomistic origin of the observed friction domains using a cantilever torsion microscopy in conjunction with angle-resolved photoemission spectroscopy. We experimentally demonstrate that ripples on graphene are formed along the zigzag direction of the hexagonal lattice. The formation of zigzag directional ripple is consistent with our theoretical model that takes account of the atomic-scale bending stiffness of carbon-carbon bonds and the interaction of graphene with the substrate. The correlation between micrometer-scale ripple alignment and atomic-scale arrangement of exfoliated monolayer graphene is first discovered and suggests a practical tool for measuring lattice orientation of graphene. PMID:25434431

  8. Synthesis of novel tantalum oxide sub-micrometer hollow spheres with tailored shell thickness.

    PubMed

    Agrawal, Mukesh; Pich, Andrij; Gupta, Smrati; Zafeiropoulos, Nikolaos E; Simon, Paul; Stamm, Manfred

    2008-02-01

    Sub-micrometer-sized hollow tantalum oxide (Ta2O5) spheres with tunable shell thickness and void size have been fabricated exploiting beta-diketone-functionalized polystyrene (PS) beads as sacrificial templates in a sol-gel process. First, a controlled precipitation of Ta2O5 nanoparticles was carried out on the template surface by hydrolyzing tantalum ethoxide (Ta(OEt)5) at room temperature, and subsequently, the polymer core was removed either via chemical treatment with toluene or calcination at 650 degrees C. The thickness of the tantala shell precipitated on the PS core during the coating process was tuned between 100 and 142 nm by varying the concentration of tantala precursor in the reaction media. The obtained Ta2O5-coated PS particles and hollow microspheres were characterized by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Due to the unique optical and dielectric properties, these nanostructured materials are envisaged to be used in applications such as novel building blocks for the fabrication of advanced materials, surface coatings, catalysts, and drug delivery systems. PMID:18171090

  9. Correlation between micrometer-scale ripple alignment and atomic-scale crystallographic orientation of monolayer graphene

    SciTech Connect

    Choi, Jin Sik; Chang, Young Jun; Woo, Sungjong; Son, Young-Woo; Park, Yeonggu; Lee, Mi Jung; Byun, Ik-Su; Kim, Jin-Soo; Choi, Choon-Gi; Bostwick, Aaron; Rotenberg, Eli; Park, Bae Ho

    2014-12-01

    Deformation normal to the surface is intrinsic in two-dimensional materials due to phononic thermal fluctuations at finite temperatures. Graphene's negative thermal expansion coefficient is generally explained by such an intrinsic property. Recently, friction measurements on graphene exfoliated on a silicon oxide surface revealed an anomalous anisotropy whose origin was believed to be the formation of ripple domains. Here, we uncover the atomistic origin of the observed friction domains using a cantilever torsion microscopy in conjunction with angle-resolved photoemission spectroscopy. We experimentally demonstrate that ripples on graphene are formed along the zigzag direction of the hexagonal lattice. The formation of zigzag directional ripple is consistent with our theoretical model that takes account of the atomic-scale bending stiffness of carbon-carbon bonds and the interaction of graphene with the substrate. Lastly, the correlation between micrometer-scale ripple alignment and atomic-scale arrangement of exfoliated monolayer graphene is first discovered and suggests a practical tool for measuring lattice orientation of graphene.

  10. Correlation between micrometer-scale ripple alignment and atomic-scale crystallographic orientation of monolayer graphene

    DOE PAGESBeta

    Choi, Jin Sik; Chang, Young Jun; Woo, Sungjong; Son, Young-Woo; Park, Yeonggu; Lee, Mi Jung; Byun, Ik-Su; Kim, Jin-Soo; Choi, Choon-Gi; Bostwick, Aaron; et al

    2014-12-01

    Deformation normal to the surface is intrinsic in two-dimensional materials due to phononic thermal fluctuations at finite temperatures. Graphene's negative thermal expansion coefficient is generally explained by such an intrinsic property. Recently, friction measurements on graphene exfoliated on a silicon oxide surface revealed an anomalous anisotropy whose origin was believed to be the formation of ripple domains. Here, we uncover the atomistic origin of the observed friction domains using a cantilever torsion microscopy in conjunction with angle-resolved photoemission spectroscopy. We experimentally demonstrate that ripples on graphene are formed along the zigzag direction of the hexagonal lattice. The formation of zigzagmore » directional ripple is consistent with our theoretical model that takes account of the atomic-scale bending stiffness of carbon-carbon bonds and the interaction of graphene with the substrate. Lastly, the correlation between micrometer-scale ripple alignment and atomic-scale arrangement of exfoliated monolayer graphene is first discovered and suggests a practical tool for measuring lattice orientation of graphene.« less

  11. Large increase in fracture resistance of stishovite with crack extension less than one micrometer.

    PubMed

    Yoshida, Kimiko; Wakai, Fumihiro; Nishiyama, Norimasa; Sekine, Risako; Shinoda, Yutaka; Akatsu, Takashi; Nagoshi, Takashi; Sone, Masato

    2015-01-01

    The development of strong, tough, and damage-tolerant ceramics requires nano/microstructure design to utilize toughening mechanisms operating at different length scales. The toughening mechanisms so far known are effective in micro-scale, then, they require the crack extension of more than a few micrometers to increase the fracture resistance. Here, we developed a micro-mechanical test method using micro-cantilever beam specimens to determine the very early part of resistance-curve of nanocrystalline SiO2 stishovite, which exhibited fracture-induced amorphization. We revealed that this novel toughening mechanism was effective even at length scale of nanometer due to narrow transformation zone width of a few tens of nanometers and large dilatational strain (from 60 to 95%) associated with the transition of crystal to amorphous state. This testing method will be a powerful tool to search for toughening mechanisms that may operate at nanoscale for attaining both reliability and strength of structural materials. PMID:26051871

  12. A Rotating Coil Apparatus with Sub-Micrometer Magnetic Center Measurement Stability

    SciTech Connect

    Spencer, Cherrill M.; Anderson, Scott, D.; Jensen, David R.; Wolf, Zachary R.; /SLAC

    2005-12-02

    A rotating double coil apparatus has been designed and built so that the relative magnetic center change of a quadrupole is measured to an uncertainty smaller than 0.02 micrometers (=micron, {micro}m) for a single measurement. Furthermore, repeated measurements over about an hour vary by less than 0.1 {micro}m and by less than 1 {micro}m for periods of 24 hrs or longer. Correlation analyses of long data runs show that the magnet center measurement is sensitive to mechanical effects, such as vibration and rotating part wear, as well as to environmental effects, such as temperature and relative humidity. Evolving apparatus design has minimized mechanical noise and environmental isolation has reduced the effects of the surrounding environment so that sub-micron level measurement uncertainties and micron level stability have been achieved for multi-day measurement periods. Apparatus design evolution will be described in detail and correlation data taken on water-cooled electromagnet and adjustable permanent quadrupoles, which are about 350 mm in overall length, will be shown. These quads were prototypes for the linac quads of the Next Linear Collider (NLC) that had to meet the requirement that their magnetic centers change less than 1 micron during a 20% change in field strength. Thus it was necessary to develop an apparatus that could track the magnetic center with a fraction of a micron uncertainty.

  13. Laue-DIC: a new method for improved stress field measurements at the micrometer scale

    PubMed Central

    Petit, J.; Castelnau, O.; Bornert, M.; Zhang, F. G.; Hofmann, F.; Korsunsky, A. M.; Faurie, D.; Le Bourlot, C.; Micha, J. S.; Robach, O.; Ulrich, O.

    2015-01-01

    A better understanding of the effective mechanical behavior of polycrystalline materials requires an accurate knowledge of the behavior at a scale smaller than the grain size. The X-ray Laue microdiffraction technique available at beamline BM32 at the European Synchrotron Radiation Facility is ideally suited for probing elastic strains (and associated stresses) in deformed polycrystalline materials with a spatial resolution smaller than a micrometer. However, the standard technique used to evaluate local stresses from the distortion of Laue patterns lacks accuracy for many micromechanical applications, mostly due to (i) the fitting of Laue spots by analytical functions, and (ii) the necessary comparison of the measured pattern with the theoretical one from an unstrained reference specimen. In the present paper, a new method for the analysis of Laue images is presented. A Digital Image Correlation (DIC) technique, which is essentially insensitive to the shape of Laue spots, is applied to measure the relative distortion of Laue patterns acquired at two different positions on the specimen. The new method is tested on an in situ deformed Si single-crystal, for which the prescribed stress distribution has been calculated by finite-element analysis. It is shown that the new Laue-DIC method allows determination of local stresses with a strain resolution of the order of 10−5. PMID:26134802

  14. Development of doped-germanium photoconductors for astronomical observations at wavelengths from 30 to 120 micrometers

    NASA Technical Reports Server (NTRS)

    Bratt, P. R.; Lewis, N. N.

    1976-01-01

    Technology was developed for production of doped-germanium detectors which have optimized performance in the 30- to 120-micrometer wavelength range and are capable of achieving the objectives of the Infrared Astronomy Satellite space mission. The work of this phase was divided into the following major tasks: (1) growth of Ge:Ga crystals from high-purity starting material with Ga concentrations different from that previously produced, and development of a zone leveling method to produce a uniform Ga doping concentration; (2) growth of uncompensated Ge:Be crystals from high-purity starting material with a range of Be concentrations between 10 to the 14th power and 10 to the 16th power atoms/cubic cm; (3) evaluation of crystals by means of Hall effect and resistance measurements as a function of temperature; (4) fabrication and test of detectors made from both Ge:Be and Ge:Ga crystals to determine the relative performance between different crystals. Correlation of detector test data with material evaluation data and analysis of how to further optimize detector performance.

  15. The 1.06 micrometer wideband laser modulator: Fabrication and life testing

    NASA Technical Reports Server (NTRS)

    Teague, J. R.

    1975-01-01

    The design, fabrication, testing and delivery of an optical modulator which will operate with a mode-locked Nd:YAG laser at 1.06 micrometers were performed. The system transfers data at a nominal rate of 400 Mbps. This wideband laser modulator can transmit either Pulse Gated Binary Modulation (PGBM) or Pulse Polarization Binary Modulation (PPBM) formats. The laser beam enters the modulator and passes through both crystals; approximately 1% of the transmitted beam is split from the main beam and analyzed for the AEC signal; the remaining part of the beam exits the modulator. The delivered modulator when initially aligned and integrated with laser and electronics performed very well. The optical transmission was 69.5%. The static extinction ratio was 69:1. A 1000 hour life test was conducted with the delivered modulator. A 63 bit pseudorandom code signal was used as a driver input. At the conclusion of the life test the modulator optical transmission was 71.5% and the static extinction ratio 65:1.

  16. New versatile x-ray analyzer using capillary focusing in the micrometer scale

    NASA Astrophysics Data System (ADS)

    Burggraf, Charles; Fougeres, Paul; Burggraf, Chris; Hage-Ali, Makram; Koebel, Jean M.; Krauth, A.; Regal, R.; Baltzinger, J. L.; Siffert, Paul

    1999-10-01

    In this paper, we will give first the description of a versatile material analyzer for x-ray crystallographic and compositional analyses. We will describe how we calculate and elaborate glass capillaries; we will describe some important parameters of the total reflection of x-rays: focusing, transparency, gain and divergence. Our first results concern a compositional study of CdZnTe crystals with a n x-ray beam diameter of 10 micrometers and we will show the variation of Zn on the surface of such a crystal. Another possibility of this device is x-ray microtopography of a film or of a wafer. We show, on one hand the way to find in classical centers by Laue micropatterns on the other hand we could establish a Bragg reflection pattern like those obtained in classical x-ray surface topography. In some heat treatments we can see so-called texture effects. We have also on our device the possibility to see microtexture effects in a way which can be compared to the Seeman-Bohlin experiment. The compositional experiments were also tested by SEM in order to see how these two devices complete each other. We can notice in some studies the advantages of x-rays because photons are less destructive than electrons.

  17. Vacuolization in Cytoplasm and Cell Membrane Permeability Enhancement Triggered by Micrometer-Sized Graphene Oxide.

    PubMed

    Wu, Congyu; Wang, Chong; Zheng, Jing; Luo, Chao; Li, Yanfang; Guo, Shouwu; Zhang, Jingyan

    2015-08-25

    A deep understanding of the interaction of a graphene oxide (GO) sheet with cells at the molecular level may expedite its biomedical application and predict its new functions and adverse effects. Herein we inspect the interaction between micrometer-sized GO (mGO), commonly used in biomedical research, and cells at the molecular level through a variety of techniques. A major finding is that, instead of direct cellular penetration, the mGO sheets can stimulate the cellular response by interacting with the membrane protein and the membrane. Specifically, it is illustrated that even within a short exposure time the mGO sheets can induce the formation of vacuoles in the cytosolic compartment and enhance the cell permeability. The vacuolization is only observed in the cells that strongly express aquaporin (AQP1), indicating the specific interaction of the mGO with AQP1. Moreover, inhibition of the AQP1 activity prevents the formation of vacuoles, revealing that the interaction of the mGO with AQP1 occurs most probably at the vestibule of AQP1 at the extracellular side. Additionally, though the cell permeability was enhanced, it only improves the penetration of small molecules, not for macromolecules such as proteins. These findings are potentially valuable in cancer therapy because AQPs are strongly expressed in tumor cells of different origins, particularly aggressive tumors, and it will also be beneficial for drug transport across barrier membranes. PMID:26207693

  18. Constraints on Exotic Dipole-Dipole Couplings between Electrons at the Micrometer Scale

    NASA Astrophysics Data System (ADS)

    Kotler, Shlomi; Ozeri, Roee; Kimball, Derek F. Jackson

    2015-08-01

    New constraints on exotic dipole-dipole interactions between electrons at the micrometer scale are established, based on a recent measurement of the magnetic interaction between two trapped 88Sr+ ions. For light bosons (mass≤0.1 eV ) we obtain a 90% confidence interval for an axial-vector-mediated interaction strength of |gAegAe/4 π ℏc | ≤1.2 ×10-17 . Assuming C P T invariance, this constraint is compared to that on anomalous electron-positron interactions, derived from positronium hyperfine spectroscopy. We find that the electron-electron constraint is 6 orders of magnitude more stringent than the electron-positron counterpart. Bounds on pseudoscalar-mediated interaction as well as on torsion gravity are also derived and compared with previous work performed at different length scales. Our constraints benefit from the high controllability of the experimental system which contained only two trapped particles. It therefore suggests a useful new platform for exotic particle searches, complementing other experimental efforts.

  19. Application of sub-micrometer patterned permalloy thin film in tunable radio frequency inductors

    SciTech Connect

    Rahman, B.M. Farid; Divan, Ralu; Rosenmann, Daniel; Wang, Tengxing; Peng, Yujia; Wang, Guoan

    2015-01-01

    Electrical tunable meander line inductor using coplanar waveguide structures with patterned permalloy (Py) thin film has been designed and implemented in this paper. High resistivity Si substrate is used to reduce the dielectric loss from the substrate. Inductor is implemented with a 60 nm thick Py deposited and patterned on top of the gold meander line, and Py film is patterned with dimension of 440 nm 10 lm to create the shape anisotropy field, which in turn increases the FMR frequency. Compared to a regular meanderline inductor without the application of sub-micrometer patterned Py thin film, the inductance density has been increased to 20% for the implemented inductor with patterned Py. Measured FMR frequency of the patterned Py is 4.51 GHz without the application of any external magnetic field. This has enabled the inductor application in the practical circuit boards, where the large external magnet is unavailable. Inductance tunability of the implemented inductor is demonstrated by applying a DC current. Applied DC current creates a magnetic field along the hard axis of the patterned Py thin film, which changes the magnetic moment of the thin film and thus, decreases the inductance of the line. Measured results show that the inductance density of the inductor can be varied 5% by applying 300 mA DC current, larger inductance tunability is achievable by increasing the thickness of Py film. VC 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4918766

  20. Microfluidic production of single micrometer-sized hydrogel beads utilizing droplet dissolution in a polar solvent

    PubMed Central

    Sugaya, Sari; Yamada, Masumi; Hori, Ayaka; Seki, Minoru

    2013-01-01

    In this study, a microfluidic process is proposed for preparing monodisperse micrometer-sized hydrogel beads. This process utilizes non-equilibrium aqueous droplets formed in a polar organic solvent. The water-in-oil droplets of the hydrogel precursor rapidly shrunk owing to the dissolution of water molecules into the continuous phase. The shrunken and condensed droplets were then gelled, resulting in the formation of hydrogel microbeads with sizes significantly smaller than the initial droplet size. This study employed methyl acetate as the polar organic solvent, which can dissolve water at 8%. Two types of monodisperse hydrogel beads—Ca-alginate and chitosan—with sizes of 6–10 μm (coefficient of variation < 6%) were successfully produced. In addition, we obtained hydrogel beads with non-spherical morphologies by controlling the degree of droplet shrinkage at the time of gelation and by adjusting the concentration of the gelation agent. Furthermore, the encapsulation and concentration of DNA molecules within the hydrogel beads were demonstrated. The process presented in this study has great potential to produce small and highly concentrated hydrogel beads that are difficult to obtain by using conventional microfluidic processes. PMID:24396529

  1. Large increase in fracture resistance of stishovite with crack extension less than one micrometer

    PubMed Central

    Yoshida, Kimiko; Wakai, Fumihiro; Nishiyama, Norimasa; Sekine, Risako; Shinoda, Yutaka; Akatsu, Takashi; Nagoshi, Takashi; Sone, Masato

    2015-01-01

    The development of strong, tough, and damage-tolerant ceramics requires nano/microstructure design to utilize toughening mechanisms operating at different length scales. The toughening mechanisms so far known are effective in micro-scale, then, they require the crack extension of more than a few micrometers to increase the fracture resistance. Here, we developed a micro-mechanical test method using micro-cantilever beam specimens to determine the very early part of resistance-curve of nanocrystalline SiO2 stishovite, which exhibited fracture-induced amorphization. We revealed that this novel toughening mechanism was effective even at length scale of nanometer due to narrow transformation zone width of a few tens of nanometers and large dilatational strain (from 60 to 95%) associated with the transition of crystal to amorphous state. This testing method will be a powerful tool to search for toughening mechanisms that may operate at nanoscale for attaining both reliability and strength of structural materials. PMID:26051871

  2. Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber

    NASA Astrophysics Data System (ADS)

    Stranks, Samuel; Eperon, Giles; Grancini, Giulia; Menelaou, Christopher; Alcocer, Marcelo; Leijtens, Tomas; Herz, Laura; Petrozza, Annamaria; Snaith, Henry

    2014-03-01

    Organic-inorganic perovskites have shown promise as high-performance absorbers in solar cells, first as a coating on a mesoporous metal oxide scaffold and more recently as a solid layer in planar heterojunction architectures. Here, we report transient absorption and photoluminescence-quenching measurements to determine the electron-hole diffusion lengths, diffusion constants, and lifetimes in mixed halide (CH3NH3PbI3-xClx) and triiodide (CH3NH3PbI3) perovskite absorbers. We found that the diffusion lengths are greater than 1 micrometer in the mixed halide perovskite, which is an order of magnitude greater than the absorption depth. In contrast, the triiodide absorber has electron-hole diffusion lengths of order 100 nanometers. Finally, we fabricated solution-processed thin-film planar heterojunction devices, achieving power conversion efficiencies of over 12% using the mixed halide absorber but only 4% with the triiodide perovskite. Our results show that the long diffusion lengths justify the high efficiency of planar heterojunction perovskite solar cells, and identify a critical parameter to optimize for future perovskite absorber development.

  3. A simple indentation device for measuring micrometer-scale tissue stiffness

    NASA Astrophysics Data System (ADS)

    Levental, I.; Levental, K. R.; Klein, E. A.; Assoian, R.; Miller, R. T.; Wells, R. G.; Janmey, P. A.

    2010-05-01

    Mechanical properties of cells and extracellular matrices are critical determinants of function in contexts including oncogenic transformation, neuronal synapse formation, hepatic fibrosis and stem cell differentiation. The size and heterogeneity of biological specimens and the importance of measuring their mechanical properties under conditions that resemble their environments in vivo present a challenge for quantitative measurement. Centimeter-scale tissue samples can be measured by commercial instruments, whereas properties at the subcellular (nm) scale are accessible by atomic force microscopy, optical trapping, or magnetic bead microrheometry; however many tissues are heterogeneous on a length scale between micrometers and millimeters which is not accessible to most current instrumentation. The device described here combines two commercially available technologies, a micronewton resolution force probe and a micromanipulator for probing soft biological samples at sub-millimeter spatial resolution. Several applications of the device are described. These include the first measurement of the stiffness of an intact, isolated mouse glomerulus, quantification of the inner wall stiffness of healthy and diseased mouse aortas, and evaluation of the lateral heterogeneity in the stiffness of mouse mammary glands and rat livers with correlation of this heterogeneity with malignant or fibrotic pathology as evaluated by histology.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  5. Self-Catalyzed Growth and Characterization of In(As)P Nanowires on InP(111)B Using Metal-Organic Chemical Vapor Deposition.

    PubMed

    Park, Jeung Hun; Pozuelo, Marta; Setiawan, Bunga P D; Chung, Choong-Heui

    2016-12-01

    We report the growth of vertical <111>-oriented InAs x P1-x (0.11 ≤ x ≤ 0.27) nanowires via metal-organic chemical vapor deposition in the presence of indium droplets as catalysts on InP(111)B substrates at 375 °C. Trimethylindium, tertiarybutylphosphine, and tertiarybutylarsine are used as the precursors, corresponding to P/In and As/In molar ratios of 29 and 0.01, respectively. The as-grown nanowire growth morphologies, crystallinity, composition, and optical characteristics are determined using a combination of scanning and transmission electron microscopies, electron diffraction, and X-ray photoelectron, energy dispersive X-ray, and Raman spectroscopies. We find that the InAs x P1-x nanowires are tapered with narrow tops, wider bases, and In-rich In-As alloy tips, characteristic of vapor-liquid-solid process. The wires exhibit a mixture of zinc blende and wurtzite crystal structures and a high density of structural defects such as stacking faults and twins. Our results suggest that the incorporation of As into InP wires decreases with increasing substrate temperature. The Raman spectra obtained from the In(As)P nanowires reveal a red-shift and lower intensity of longitudinal optical mode relative to both InP nanowires and InP(111)B bulk, due to the incorporation of As into the InP matrix. PMID:27094822

  6. Self-Catalyzed Growth and Characterization of In(As)P Nanowires on InP(111)B Using Metal-Organic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Park, Jeung Hun; Pozuelo, Marta; Setiawan, Bunga P. D.; Chung, Choong-Heui

    2016-04-01

    We report the growth of vertical <111>-oriented InAs x P1- x (0.11 ≤ x ≤ 0.27) nanowires via metal-organic chemical vapor deposition in the presence of indium droplets as catalysts on InP(111)B substrates at 375 °C. Trimethylindium, tertiarybutylphosphine, and tertiarybutylarsine are used as the precursors, corresponding to P/In and As/In molar ratios of 29 and 0.01, respectively. The as-grown nanowire growth morphologies, crystallinity, composition, and optical characteristics are determined using a combination of scanning and transmission electron microscopies, electron diffraction, and X-ray photoelectron, energy dispersive X-ray, and Raman spectroscopies. We find that the InAs x P1- x nanowires are tapered with narrow tops, wider bases, and In-rich In-As alloy tips, characteristic of vapor-liquid-solid process. The wires exhibit a mixture of zinc blende and wurtzite crystal structures and a high density of structural defects such as stacking faults and twins. Our results suggest that the incorporation of As into InP wires decreases with increasing substrate temperature. The Raman spectra obtained from the In(As)P nanowires reveal a red-shift and lower intensity of longitudinal optical mode relative to both InP nanowires and InP(111)B bulk, due to the incorporation of As into the InP matrix.

  7. SEM and XPS studies of nanohole arrays on InP(1 0 0) surfaces created by coupling AAO templates and low energy Ar + ion sputtering

    NASA Astrophysics Data System (ADS)

    Robert-Goumet, C.; Monier, G.; Zefack, B.; Chelda, S.; Bideux, L.; Gruzza, B.; Awitor, O. K.

    2009-10-01

    The aim of the present study is to demonstrate the feasibility to form well-ordered nanoholes on InP(1 0 0) surfaces by low Ar + ion sputtering process in UHV conditions from anodized aluminum oxide (AAO) templates. This process is a promising approach in creating ordered arrays of surface nanostructures with controllable size and morphology. To follow the Ar + ion sputtering effects on the AAO/InP surfaces, X-ray photoelectron spectroscopy (XPS) was used to determine the different surface species. In 4d and P 2p core level spectra were recorded on different InP(1 0 0) surfaces after ions bombardment. XPS results showed the presence of metallic indium on both smooth InP(1 0 0) and AAO/InP(1 0 0) surfaces. Finally, we showed that this experiment led to the formation of metallic In dropplets about 10 nm in diameter on nanoholes patterned InP surface while the as-received InP(1 0 0) surface generated metallic In about 60 nm in diameter.

  8. 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. PMID:26134951

  9. Vertically Well-Aligned ZnO Nanowire Arrays Directly Synthesized from Zn Vapor Deposition Without Catalyst

    NASA Astrophysics Data System (ADS)

    Van Khai, Tran; Van Thu, Le; Huu, Nguyen The; Lam, Tran Dai

    2016-05-01

    Vertically well-aligned ZnO nanowire (NW) arrays with high density have been successfully synthesized on sapphire substrate by thermal evaporation of the zinc powders without catalysts or additives. The ZnO NWs were characterized by scanning electron microscopy, transmission electronic microscopy (TEM), x-ray diffraction, ultraviolet-visible, photoluminescence, Raman, and x-ray photoelectron spectroscopy. The results showed that the obtained ZnO NWs had diameters in the range of 100-130 nm, lengths over several micrometers and well aligned in the direction perpendicular to the substrate surface. The as-synthesized ZnO NWs, which were single crystalline in a hexagonal structure, showed uniform morphology, faceted planes at the tips of the NWs, and grown along the [001] direction. The as-synthesized NW arrays had a good crystal quality with excellent optical properties, showing a sharp and strong ultraviolet emission at 380 nm and a weak visible emission at around 500 nm.

  10. Physiologically driven avian vocal synthesizer

    NASA Astrophysics Data System (ADS)

    Sitt, Jacobo D.; Arneodo, Ezequiel M.; Goller, Franz; Mindlin, Gabriel B.

    2010-03-01

    In this work, we build an electronic syrinx, i.e., a programmable electronic device capable of integrating biomechanical model equations for the avian vocal organ in order to synthesize song. This vocal prosthesis is controlled by the bird’s neural instructions to respiratory and the syringeal motor systems, thus opening great potential for studying motor control and its modification by sensory feedback mechanisms. Furthermore, a well-functioning subject-controlled vocal prosthesis can lay the foundation for similar devices in humans and thus provide directly health-related data and procedures.

  11. Method of synthesizing tungsten nanoparticles

    DOEpatents

    Thoma, Steven G; Anderson, Travis M

    2013-02-12

    A method to synthesize tungsten nanoparticles has been developed that enables synthesis of nanometer-scale, monodisperse particles that can be stabilized only by tetrahydrofuran. The method can be used at room temperature, is scalable, and the product concentrated by standard means. Since no additives or stabilizing surfactants are required, this method is particularly well suited for producing tungsten nanoparticles for dispersion in polymers. If complete dispersion is achieved due to the size of the nanoparticles, then the optical properties of the polymer can be largely maintained.

  12. Microstructural improvements of InP on GaAs (001) grown by molecular beam epitaxy by in situ hydrogenation and postgrowth annealing

    SciTech Connect

    Morales, F. M.; Garcia, R.; Molina, S. I.; Aouni, A.; Postigo, P. A.; Fonstad, C. G.

    2009-01-26

    The characterization of high quality InP on GaAs (001) fabricated by molecular beam epitaxy using a two-step growth method involving hydrogenation during growth is reported. Electron diffraction and high-resolution transmission electron microscopy confirm that {approx}2 {mu}m thick InP epilayers on GaAs are heteroepitaxial and strain relaxed. Stacking faults and threading dislocations are mostly confined near the InP/GaAs interface and their densities decrease monotonically toward the InP surface. Additionally, rapid-thermal annealing following growth is found to result in a marked reduction in the number of dislocations and the disappearance of planar defects.

  13. 19.2% Efficient InP Heterojunction Solar Cell with Electron-Selective TiO2 Contact

    SciTech Connect

    Yin, Xingtian; Battaglia, Corsin; Lin, Yongjing; Chen, Kevin; Hettick, Mark; Zheng, Maxwell; Chen, Cheng-Ying; Kiriya, Daisuke; Javey, Ali

    2014-09-25

    We demonstrate an InP heterojunction solar cell employing an ultrathin layer (~10 nm) of amorphous TiO2 deposited at 120°C by atomic layer deposition as the transparent electron-selective contact. The TiO2 film selectively extracts minority electrons from the conduction band of p-type InP while blocking the majority holes due to the large valence band offset, enabling a high maximum open-circuit voltage of 785 mV. Lastly, a hydrogen plasma treatment of the InP surface drastically improves the long-wavelength response of the device, resulting in a high short-circuit current density of 30.5 mA/cm2 and a high power conversion efficiency of 19.2%.

  14. Catalyst-free growth of InP nanowires on patterned Si (001) substrate by using GaAs buffer layer

    NASA Astrophysics Data System (ADS)

    Li, Shiyan; Zhou, Xuliang; Kong, Xiangting; Li, Mengke; Mi, Junping; Pan, Jiaoqing

    2016-04-01

    The catalyst-free metal organic vapor phase epitaxial growth of InP nanowires on silicon (001) substrate is investigated using selectively grown GaAs buffer layers in V-shaped trenches. A yield up to 70% of nanowires is self-aligned in uncommon <112> directions under the optimized growth conditions. The evolution mechanism of self-aligned <112> directions for nanowires is discussed and demonstrated. Using this growth method, we can achieve branched and direction switched InP nanowires by varying the V/III ratio in situ. The structure of the nanowires is characterized by scanning electron microscope and transmission electron microscopy measurements. The crystal structure of the InP nanowires is stacking-faults-free wurtzite with its c axis perpendicular to the nanowire axis.

  15. Self-assembled InAs quantum wire lasers on (001)InP at 1.6 {mu}m

    SciTech Connect

    Suarez, F.; Fuster, D.; Gonzalez, L.; Gonzalez, Y.; Garcia, J. M.; Dotor, M. L.

    2006-08-28

    In this work, the authors present results on the growth by atomic layer molecular beam epitaxy and characterization of lasers with one and three stacked layers of InAs quantum wires (QWRs) as active zone and aluminum-free waveguides on (001) InP substrates. The separated confinement heterostructure consists of n-p InP claddings and a waveguide formed by short period superlattices of (InP){sub 5}/(GaInAs){sub 4} lattice matched to the InP substrate. The optimum growth conditions (substrate temperature and As and P pressures) have been determined to obtain waveguides with a flat surface in order to get a uniform QWR distribution. Lasing emission is observed at a wavelength of {approx}1.66 {mu}m up to 270 K from 15x3000 {mu}m{sup 2} devices, with a threshold current density at that temperature of 2 kA/cm{sup 2}.

  16. Investigation of anodic and chemical oxides grown on p-type InP with applications to surface passivation for n(+)-p solar cell fabrication

    NASA Technical Reports Server (NTRS)

    Faur, Maria; Faur, Mircea; Goradia, Manju; Goradia, Chandra; Jenkins, Phillip; Jayne, Douglas; Weinberg, Irving

    1991-01-01

    Most of the previously reported InP anodic oxides were grown on a n-type InP with applications to fabrication of MISFET structures and were described as a mixture of In2O3 and P2O5 stoichiometric compounds or nonstoichiometric phases which have properties similar to crystalline compounds In(OH)3, InPO4, and In(PO3)3. Details of the compositional change of the anodic oxides grown under different anodization conditions were previously reported. The use of P-rich oxides grown either by anodic or chemical oxidation are investigated for surface passivation of p-type InP and as a protective cap during junction formation by closed-ampoule sulfur diffusion. The investigation is based on but not limited to correlations between PL intensity and X-ray photoelectron spectroscopy (XPS) chemical composition data.

  17. Study of Potential Sub-Micrometer-Thick Frost Events and Soil Water Content at Gale Crater

    NASA Astrophysics Data System (ADS)

    Martinez, G.; Fischer, E.; Renno, N. O.; De La Torre Juarez, M.; Meslin, P. Y.; Kemppinen, O.; Genzer, M.; Harri, A. M.; Ramos, M.; Borlina, C.; Schröder, S.; Gómez-Elvira, J.

    2014-12-01

    We analyze the highest confidence measurements of relative humidity [1] and ground temperature [2] to identify potential frost events at the surface of Gale Crater during the first 600 sols of the MSL mission. We find that between 4 and 6 am on sols 533, 535, 555, 557, 559 and 560 the ground temperature falls below the calculated frost point. Order-of-magnitude estimate for the thickness of the frost layer indicates that it is of the order of micrometers or less. Additionally, we analyze the relation between water vapor pressure and ground temperature to provide additional constraints on potential frost events and to quantify the exchange of adsorbed water between the surface and the atmosphere. Adsorbed water could be forced into liquid-like state at the of Gale because van der Waals forces between water ice molecules and mineral surfaces reduces the freezing point [3]. This form of liquid water is relevant to habitability because microorganisms could survive in liquid-like adsorbed water [4].References: [1] Harri, Ari-Matti et al., Mars Science Laboratory Relative Humidity Observations - Initial Results (2014), JGR (in press). [2] Martínez, G. M. et al., Surface Energy Budget and Thermal Inertia at Gale Crater: Calculations from Ground-Based Measurements (2014), JGR (in press). [3] Möhlmann, D., The influence of van der Waals forces on the state of water in the shallow subsurface of Mars (2008), Icarus 195 (1), 131-139. [4] Rivkina, E. M. et al., Metabolic activity of permafrost bacteria below the freezing point (2000), Appl. Environ. Microbiol., 66(8), 3230-3233.

  18. HD 172555: Detection of 63 micrometers [OI] Emission in a Debris Disc

    NASA Technical Reports Server (NTRS)

    Riviere-Marichalar, P.; Barrado, D.; Augereau, J. -C.; Thi, W. F.; Roberge, A.; Eiroa, C.; Montesinos, B.; Meeus, G.; Howard, C.; Sandell, G.; Duchene, G.; Dent, W. R. F.; Lebreton, J.; Mendigutia, I.; Huelamo, N.; Menard, F.; Pinte, C.

    2012-01-01

    Context. HD 172555 is a young A7 star belonging to the Beta Pictoris Moving Group that harbours a debris disc. The Spitzer IRS spectrum of the source showed mid-IR features such as silicates and glassy silica species, indicating the presence of a warm dust component with small grains, which places HD 172555 among the small group of debris discs with such properties. The IRS spectrum also shows a possible emission of SiO gas. Aims. We aim to study the dust distribution in the circumstellar disc of HD 172555 and to asses the presence of gas in the debris disc. Methods. As part of the GASPS Open Time Key Programme, we obtained Herschel-PACS photometric and spectroscopic observations of the source. We analysed PACS observations of HD 172555 and modelled the Spectral Energy Distribution (SED) with a modified blackbody and the gas emission with a two-level population model with no collisional de-excitation. Results. We report for the first time the detection of [OI] atomic gas emission at 63.18 micrometers in the HD 172555 circumstellar disc.We detect excesses due to circumstellar dust toward HD 172555 in the three photometric bands of PACS (70, 100, and 160 m). We derive a large dust particle mass of (4.8 plus-minus 0.6)x10(exp -4) Mass compared to Earth and an atomic oxygen mass of 2.5x10(exp -2)R(exp 2) Mass compared to Earth, where R in AU is the separation between the star and the inner disc. Thus, most of the detected mass of the disc is in the gaseous phase.

  19. Six degrees of freedom, sub-micrometer positioning system for secondary mirrors

    NASA Astrophysics Data System (ADS)

    Sneed, Ryan C.; Cash, Michael F.; Chambers, Trevor S.; Janzen, Paul C.

    2010-07-01

    Secondary mirrors for large ground-based telescopes often require positioning systems with payload capacities around 1000 kg, relative accuracies within a few micrometers, and resonant frequencies above 15 Hz. A suitable six-legged parallel manipulator, or hexapod, has been developed for sub-micron level positioning of large optical payloads in six degrees of freedom. This 1000 kg class hexapod has tip/tilt rotational ranges of +/-1800 arcsec, relative accuracies within 1%, and resolutions of better than +/-0.2 arcsec, along with a piston translational range of +/-30 mm, relative accuracy within 1%, and resolution of better than +/-1 μm. The center of rotation of the system may be placed at an arbitrary location within the overall range limitations. The axial stiffness of each of the six actuators tested greater than 100 N/μm. The actuators use high precision roller screws and employ two degree of freedom universal end-joints. The preload on the joints eliminates backlash due to transitions from tension to compression and maintains friction moment of <10 Nm. An additional rotational degree of freedom is allowed in the body of the actuator to achieve the proper kinematic constraints for the motion platform. The actuators have power-off hold capability to protect against power loss and reduce heat dissipation. Overall heat dissipation has been measured and techniques have been studied to reduce its impact. The paper describes the actuator design and hexapod performance in support of planned use in ground test and validation of the James Webb Space Telescope.

  20. Dense molecular cloud cores as a source of micrometer-sized grains in galaxies

    NASA Astrophysics Data System (ADS)

    Hirashita, Hiroyuki; Asano, Ryosuke S.; Nozawa, Takaya; Li, Zhi-Yun; Liu, Ming-Chang

    2014-10-01

    Coreshine in dense molecular cloud cores (dense cores) is interpreted as evidence for micrometer-sized grains (referred to as very large grains, VLGs). VLGs may have a significant influence on the total dust amount and the extinction curve. We estimate the total abundance of VLGs in the Galaxy, assuming that dense cores are the site of VLG formation. We find that the VLG abundance relative to the total dust mass is roughly ϕVLG~0.01(1-ε)/ε((fVLG/0.5)(tshat/108 year), where ε is the star formation efficiency in dense cores, τSF is the timescale of gas consumption by star formation, fVLG is the fraction of dust mass eventually coagulated into VLGs in dense cores, and tshat is the lifetime of VLGs (determined by shattering). Adopting their typical values for the Galaxy, we obtain ϕVLG~0.02-0.09. This abundance is well below the value detected in the heliosphere by Ulysses and Galileo, which means that local enhancement of VLG abundance in the solar neighborhood is required if the VLGs originate from dense cores. We also show that the effects of VLGs on the extinction curve are negligible even with the upper value of the above range, ϕVLG~0.09. If we adopt an extreme value, ϕVLG~0.5, close to that inferred from the above spacecraft data, the extinction curve is still in the range of the variation in Galactic extinction curves, but is not typical of the diffuse ISM.

  1. Sub-micrometer particles produced by a low-powered AC electric arc in liquids.

    PubMed

    Jaworski, Jacek A; Fleury, Eric

    2012-01-01

    The article presents the report of the production of composites of sub-micrometer metal particles in matrix consisted of the metal compounds by means of an AC electric arc in water and paraffin solutions using electrodes carbon-metal and metal-metal (metal: Ni, Fe, Co, Cu). The advantage of this method is the low electric power (from 5 to 10 W) needed in comparison to standard DC arc-discharge methods (0.8 to 3 kW). This method enables the production of particles from conductive material also in wide range of temperature and in solvent which could be either transparent to light or opaque. Moreover the solvent can be electrolyte or insulating liquid. The microstructure of the composite layer was investigated by scanning electron microscopy (SEM), Electron Probe Microanalysis (EPMA) and X-ray. During particles production in water metal oxides were created. Additionally using cobalt-copper, nickel-copper as couple electrodes, insoluble in water copper (II) hydroxide crystal grains were created additionally which crystals shape was depended on transition metal. For iron-copper couple electrodes system the copper (II) hydroxide was not formed. Experiments with sequence production of Ni and Fe particles with C electrode assisting in molten paraffin let to obtain both Ni and Fe particles surrounded by paraffin. After solidification the material was insulator but if locally magnetic field influenced on the liquid solution in that place after solidification a new composite was created which was electric current conductor with resistivity around 0.1 omega x m, was attracted by magnetic field and presented magneto resistance around 0.4% in changing magnetic field in a range 150 mT. After mixing the concentrated paraffin with normal paraffin resistivity of the mixture increased and it became photosensitive and created small voltage under light influence. PMID:22524027

  2. Online Aerosol Mass Spectrometry of Single Micrometer-Sized Particles Containing Poly(ethylene glycol)

    SciTech Connect

    Bogan, M J; Patton, E; Srivastava, A; Martin, S; Fergenson, D; Steele, P; Tobias, H; Gard, E; Frank, M

    2006-10-25

    Analysis of poly(ethylene glycol)(PEG)-containing particles by online single particle aerosol mass spectrometers equipped with laser desorption ionization (LDI) is reported. We demonstrate that PEG-containing particles are useful in the development of aerosol mass spectrometers because of their ease of preparation, low cost, and inherently recognizable mass spectra. Solutions containing millimolar quantities of PEGs were nebulized and, after drying, the resultant micrometer-sized PEG containing particles were sampled. LDI (266 nm) of particles containing NaCl and PEG molecules of average molecular weight <500 generated mass spectra reminiscent of mass spectra of PEG collected by other MS schemes including the characteristic distribution of positive ions (Na{sup +} adducts) separated by the 44 Da of the ethylene oxide units separating each degree of polymerization. PEGs of average molecular weight >500 were detected from particles that also contained t the tripeptide tyrosine-tyrosine-tyrosine or 2,5-dihydroxybenzoic acid, which were added to nebulized solutions to act as matrices to assist LDI using pulsed 266 nm and 355 nm lasers, respectively. Experiments were performed on two aerosol mass spectrometers, one reflectron and one linear, that each utilize two time-of-flight mass analyzers to detect positive and negative ions created from a single particle. PEG-containing particles are currently being employed in the optimization of our bioaerosol mass spectrometers for the application of measurements of complex biological samples, including human effluents, and we recommend that the same strategies will be of great utility to the development of any online aerosol LDI mass spectrometer platform.

  3. Science Rationale for a Micro-Met Mission to Augment InterMarsNet

    NASA Technical Reports Server (NTRS)

    Haberle, Robert M.; Cuzzi, Jeffrey N. (Technical Monitor)

    1995-01-01

    The 2003 opportunity has the potential to carry out for the first time in Mars exploration history, coordinated measurements from the surface and from orbit that can address fundamental issues associated with the Martian global circulation and climate system. Coordinated measurements are defined here to mean collecting meteorological data from a network of 12-16 globally distributed surface stations simultaneously with an orbiter carrying an atmospheric sounder. With such measurements it is possible to define the horizontally varying (barotropic) and vertically varying (baroclinic) components of the global circulation from which the full 3-dimensional horizontal wind field can be reconstructed. It is also possible to precisely define the CO2 cycle, the main component of the current climate system. InterMarsNet, as currently envisioned, consists of 3-4 landers with a supporting communications orbiter that may carry some instrumentation. The landers are likely to touch down in low latitudes and will probably be configured to optimize seismological objectives. We propose to augment the InterMarsNet meteorological objectives by flying an additional 10-15 "MicroMet" landers equipped to measure surface pressure and nothing else. Surface pressure is the most fundamental meteorological parameter and it is the easiest to measure. The sensors are light, operate with minimal power, and do not require orientation or deployment. Consequently the landers can be very small (< 10 kg) and 10-15 of them can be delivered by a Med-lite launcher. This would enable global network science for meteorology and, when combined wAh the more sophisticated measurements from the InterMarsNet landers and the simultaneous temperature and dust profiling measurements from an atmospheric sounder aboard the orbiter, it would enable us to reconstruct global scale circulation patterns.

  4. Ultraviolet illuminated molecular cloud boundaries: Extended (C II) 158 micrometer emission toward L1630

    NASA Technical Reports Server (NTRS)

    Jaffe, D. T.; Zhou, S.; Howe, J. E.; Herrmann, F.; Madden, S. C.; Poglitsch, A.; Vanderwerf, P. P.; Stacey, G. J.

    1994-01-01

    The construction of a large scale map of the 158 micrometer C+ line toward the L1630/Orion B molecular cloud, covering an approximately 35' by 45' area which includes the NGC 2024 H II region, zeta-Ori, the reflection nebula NGC 2023, and the Horsehead nebula, is reported. Emission in the C II line is very widespread. The line was detected at levels in excess of a few 0.0001 erg/sq cm/s/sr over almost the entire mapped region. Extended emission associated with the NGC 2024 H II region and its envelope accounts for more than half of the C II flux. Over this approximately 1.5 by 2.5 pc region, the amount of gas phase carbon in the form of C+ is comparable to the amount of carbon in CO. This result, together with the C II distribution implies that C II emission arises on the surface of clumps throughout the cloud rather than in a single layer at the H II region boundary. Away from the H II region, most of the C II emission comes from the western edge of the L1630 cloud and probably results from excitation by external OB stars. The overall extent of the C II emission is comparable to that of millimeter molecular lines but the distributions are different in detail. The difference in C II and molecular line distributions, in particular, the larger extent of the C II emission west of NGC 2024 implies large variations in the ratio of the C II and J = 1 towards 0 intensities. Models of photon dominated regions can explain the relation between C II and CO intensities only if the cloud edges and cloud interior are considered separately. A method for using C II and radio continuum emission to characterize the relationship between OB stars and photon dominated regions is proposed.

  5. Performance, Defect Behavior and Carrier Enhancement in Low Energy, Proton Irradiated p(+)nn(+) InP Solar Cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Rybicki, G. C.; Vargas-Aburto, C.; Jain, R. K.; Scheiman, D.

    1994-01-01

    InP p(+)nn(+) cells, processed by MOCVD, were irradiated by 0.2 MeV protons and their performance and defect behavior observed to a maximum fluence of 10(exp 13)/sq cm. Their radiation induced degradation, over this fluence range, was considerably+less than observed for similarly irradiated, diffused junction n p InP cells. Significant degradation occurred in both the cell's emitter and base regions the least degradation occurring in the depletion region. A significant increase in series resistance occurs at the highest fluenc.e. Two majority carrier defect levels, E7 and E10, are observed by DLTS with activation energies at (E(sub C) - 0.39)eV and (E(sub C) - 0.74)eV respectively. The relative concentration of these defects differs considerably from that observed after 1 MeV electron irradiation. An increased carrier concentration in the cell's n-region was observed at the highest proton fluence, the change in carrier concentration being insignificant at the lower fluences. In agreement with previous results, for 1 and 1.5 MeV electron irradiated InP p(+)n junctions, the defect level E10 is attributed to a complex between zinc, diffused into the n-region from the zinc doped emitter, and a radiation induced defect. The latter is assumed to be either a phosphorus vacancy or interstitial. The increased, or enhanced carrier concentration is attributed to this complex acting as a donor.

  6. Progress in p(+)n InP solar cells fabricated by thermal diffusion

    NASA Technical Reports Server (NTRS)

    Faur, Mircea; Faur, Maria; Flood, D. J.; Brinker, D. J.; Weinberg, I.; Fatemi, N. S.; Vargas-Aburto, Carlos; Goradia, C.; Goradia, Manju

    1992-01-01

    In SPRAT XI, we proposed that p(sup +)n diffused junction InP solar cells should exhibit a higher conversion efficiency than their n(sup +)p counterparts. This was mainly due to the fact that our p(sup +)n (Cd,S) cell structures consistently showed higher V (sub OC) values than our n(sup +)p (S,Cd) structures. The highest V(sub OC) obtained with the p(sup +)n (Cd,S) cell configuration was 860 mV, as compared to the highest V(sub OC) 840 mV obtained with the n(sup +)p (S,Cd) configuration (AMO, 25 C). In this work, we present the performance results of our most recent thermally diffused cells using the p(sup +)n (Cd,S) structure. We have been able to fabricate cells with V(sub OC) values approaching 880 mV. Our best cell with an unoptimized front contact grid design (GS greater than or equal to 10%) showed a conversion efficiency of 13.4% (AMO, 25 C) without an AR coating layer. The emitter surface was passivated by a -50A P rich oxide. Achievement of such high V(sub OC) values was primarily due to the fabrication of emitter surfaces, having EPD densities as low as 2E2 cm(sup -2) and N(sub a)N(sub d) of about 3E18 cm (sup -3). In addition, our preliminary investigation of p(sup +)n structures seem to suggest that Cd-doped emitter cells are more radiation resistant than Zn-doped emitter cells against both high energy electron and proton irradiation.

  7. Thin films of InP for photovoltaic energy conversion. Third quarterly technical progress report, December 29, 1979-March 28, 1980

    SciTech Connect

    Manasevit, H M; Ruth, R P; Moudy, L A; Yang, J J.J.; Johnson, R E

    1980-04-01

    A research study is being conducted for the purpose of developing a low-cost high-efficiency thin-film InP heterojunction solar cell based on InP films grown by the metalorganic chemical vapor deposition (MO-CVD) process on suitable substrates. Heterostructure devices of CdS/InP (and possibly indium tin oxide/InP) are to be prepared at Stanford University under subcontract, using the MO-CVD InP films grown at Rockwell. The work of the third quarter of the program is summarized. Experiments continued on evaluation of GaP as an intermediate layer material for subsequent growth of InP films on various substrate materials, and Cd (obtained from dimethylcadmium) was evaluated as a p-type dopant (an alternative to Zn obtained from diethylzinc) for InP films made by the MO-CVD process. A preliminary x-ray diffraction analysis was conducted of the crystallographic structure of the vacuum-deposited CdS films prepared at Stanford as part of the process of fabricating CdS/InP heterojunction solar cells. A group of CdS/InP heterostructure cells involving vacuum-deposited CdS and p-type epitaxial InP films grown by MO-CVD was prepared and evaluated. High J/sub 0/ values and low fill factors were observed in all of the cells, resulting in AM1.5 efficiencies in the 2 to 5 percent range. (WHK)

  8. Defect behavior, carrier removal and predicted in-space injection annealing of InP solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Swartz, C. K.; Drevinsky, P. J.

    1992-01-01

    Defect behavior, observed by deep level transient spectroscopy (DLTS), is used to predict carrier removal and the effects of simultaneous electron irradiation and injection annealing of the performance of InP solar cells. For carrier removal, the number of holes trapped per defect is obtained from measurements of both carrier concentrations and defect concentrations during an isochronal anneal. In addition, from kinetic considerations, the behavior of the dominant defect during injection annealing is used to estimate the degradation expected from exposure to the ambient electron environment in geostationary orbit.

  9. Low-loss passive waveguides in a generic InP foundry process via local diffusion of zinc.

    PubMed

    D'Agostino, Domenico; Carnicella, Giuseppe; Ciminelli, Caterina; Thijs, Peter; Veldhoven, Petrus J; Ambrosius, Huub; Smit, Meint

    2015-09-21

    Generic InP foundry processes allow monolithic integration of active and passive elements into a common p-n doped layerstack. The passive loss can be greatly reduced by restricting the p-dopant to active regions. We report on a localized Zn-diffusion process based on MOVPE, which allows to reduce waveguide loss from 2 dB/cm to below 0.4 dB/cm. We confirm this value by fabrication of a 73 mm long spiral ring resonator, with a record quality factor of 1.2 million and an extinction ratio of 9.7 dB. PMID:26406713

  10. Measurement of the minority carrier diffusion length and edge surface-recombination velocity in InP

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Hakimzadeh, Roshanak

    1993-01-01

    A scanning electron microscope (SEM) was used to measure the electron (minority carrier) diffusion length (L(sub n)) and the edge surface-recombination velocity (V(sub s)) in zinc-doped Czochralski-grown InP wafers. Electron-beam-induced current (EBIC) profiles were obtained in specimens containing a Schottky barrier perpendicular to the scanned (edge) surface. An independent technique was used to measure V(sub s), and these values were used in a theoretical expression for normalized EBIC. A fit of the experimental data with this expression enabled us to determine L(sub n).

  11. Two-photon photoemission as a probe of unoccupied and occupied surface states of InP(1 0 0)

    NASA Astrophysics Data System (ADS)

    Töben, L.; Hannappel, T.; Eichberger, R.; Möller, K.; Gundlach, L.; Ernstorfer, R.; Willig, F.

    2003-02-01

    Two-photon photoemission was employed to study the electronic structure of the ordered (2×4)-reconstructed In-rich surface of InP(1 0 0). Dangling bond surface states, two unoccupied and one occupied, were identified near the Γ-point of the surface Brillouin zone in good agreement with the theoretical predictions of Schmidt et al. (Phys. Rev. B 61 (2000) R16335). In addition, one photon photoemission from occupied electronic states in the band gap was observed that is tentatively ascribed to small In-droplets or clusters.

  12. A theoretical and experimental study of λ>2 μm luminescence of quantum dots on InP substrate

    NASA Astrophysics Data System (ADS)

    Doré, F.; Even, J.; Cornet, C.; Schliwa, A.; Bertru, N.; Dehaese, O.; Alghoraibi, I.; Folliot, H.; Piron, R.; Le Corre, A.; Loualiche, S.

    2007-04-01

    Theoretical and experimental studies of the electronic properties of InAs(Sb) quantum dots (QDs) grown by molecular beam epitaxy (MBE) on InP(100) substrate are presented. Eight-band kṡp calculations including strain and piezoelectric effects are performed on InAs/InP(100) quantum dot (QD) structure to study the influence of the quantum dot height. Photoluminescence (PL) spectroscopy experiments show promising results. High arsine flow rate during the growth of InAs QDs makes possible long emission wavelength beyond 2 μm. Emission wavelength as long as 2.35 μm is observed with InAsSb QDs.

  13. Electrochemical characterization of InP and GaAs based structures for space solar cell applications

    SciTech Connect

    Faur, M.; Flood, D.J.; Jenkins, P.P.; Wilt, D.M.; Faur, M.; Goradia, M.

    1994-12-31

    In this paper the emphasis is on accurate majority carrier concentration EC-V profiling of structures based on InP and GaAs, using a newly developed electrolyte based on HF, CH{sub 3}COOH, o-H{sub 3}PO{sub 4}, C{sub 9}H{sub 14}ClN and NH{sub 3}F{sub 2}. Some preliminary data on the use of this electrolyte for determining the energy distribution of surface and deep states of these structures, applicable to fabrication process optimization and radiation induced defects studies of solar cells, are also provided.

  14. Kinetics of low pressure CVD growth of SiO2 on InP and Si

    NASA Technical Reports Server (NTRS)

    Iyer, R.; Lile, D. L.

    1988-01-01

    The kinetics of low pressure CVD growth of SiO2 from SiH4 and O2 has been investigated for the case of an indirect (remote) plasma process. Homogeneous (gas phase) and heterogeneous operating ranges have been experimentally identified. The process was shown to be consistent within the heterogeneous surface-reaction dominated range of operation. A kinetic rate equation is given for growth at 14 W RF power input and 400 mtorr total pressure on both InP and Si substrates. The process exhibits an activation energy of 8.4 + or - 0.6 kcal/mol.

  15. The effect of nanoscratching direction on the plastic deformation and surface morphology of InP crystals

    SciTech Connect

    Huang, J. Y.; Ponce, F. A.; Caldas, P. G.; Prioli, R.; Almeida, C. M.

    2013-11-28

    The microstructure of (001) InP crystals scratched with a sharp diamond tip depends strongly on the scratching direction. The scratch surface is found to conform to the radius of curvature of the tip (∼60 nm) by the formation of atomic crystal steps produced by dislocation glide along (111) planes. 〈110〉 scratches lead to coherent local crystal lattice movement and rotation causing deep dislocation propagation into the crystal and irregular pileups at the sides of the scratch surface. 〈100〉 scratches lead to incoherent lattice movement causing dislocation locking that inhibits their propagation and results in regular pileups.

  16. Effect of heavy noble gas ion irradiation on terahertz emission efficiency of InP (100) and (111) crystal planes

    NASA Astrophysics Data System (ADS)

    Radhanpura, K.; Lewis, R. A.; Sirbu, L.; Enachi, M.; Tiginyanu, I. M.; Skuratov, V. A.

    2014-09-01

    Emission of terahertz (THz) electromagnetic radiation from heavily-doped (5 × 1018 cm-3) (100) and (111) InP bulk materials and nanoporous honeycomb membranes, irradiated with heavy noble gas (Kr and Xe) ions, is presented. Irradiating samples with Kr or Xe improves THz emission efficiency. For (111) samples, as for unirradiated samples, the irradiated porous structures generate more THz radiation than their bulk counterparts. On the other hand, in contrast to unirradiated (100) samples, the irradiated (100) samples show a decrease in THz emission with porosity. We attribute this behaviour to changes in the local electric field due to the combined effect of the irradiation and nanoporosity.

  17. Development of III-Sb metamorphic DBR membranes on InP for vertical cavity laser applications

    NASA Astrophysics Data System (ADS)

    Addamane, S. J.; Mansoori, A.; Renteria, E. J.; Dawson, N.; Shima, D. M.; Rotter, T. J.; Hains, C. P.; Dawson, L. R.; Balakrishnan, G.

    2016-04-01

    Sb-based metamorphic DBR membranes are developed for InP-based vertical cavity laser applications. The reflectivity of the metamorphic DBR membrane is compared to the reflectivity of a lattice-matched DBR to characterize the optical quality of the DBR membrane. The metamorphic interface between InP and the III-antimonides is found to degrade the reflectivity of the DBR. Therefore, the growth temperature for the metamorphic DBR is optimized in order to obtain highly reflective (>99.8%) III-Sb thin-film membranes.

  18. Fabrication of InAs quantum dot stacked structure on InP(311)B substrate by digital embedding method

    NASA Astrophysics Data System (ADS)

    Akahane, Kouichi; Yamamoto, Naokatsu; Kawanishi, Tetsuya

    2015-12-01

    Self-assembled InAs quantum dots (QDs) grown on an InP(311)B substrate were embedded using lattice-matched InAlAs/InGaAs superlattice with the digital embedding method. The thickness of quantum wells and barriers of the superlattice varied from 2 to 16 monolayers. The six layer stacking structures were successfully grown without any degradation of the QD and superlattice structure. The cross-sections of QDs embedded within the superlattice were visualized by scanning transmission microscope. The emission wavelength of the QDs was measured by photoluminescence and could be changed by changing the thickness of the superlattice.

  19. Application of free-standing InP nanowire arrays and their optical properties for resource-saving solar cells

    NASA Astrophysics Data System (ADS)

    Chen, Muyi; Nakai, Eiji; Tomioka, Katsuhiro; Fukui, Takashi

    2015-01-01

    III-V compound semiconductor nanowire (NW) arrays have exhibited remarkable behavior in photovoltaic applications. We embedded an orderly vertical InP NW array in poly(dimethylsiloxane) (PDMS) and peeled it off from the substrate to form a AuZn contact. The sample with the substrate exhibited a very high average absorptance of 92%. However, when the array was peeled off, the optical absorptance degraded, particularly in the longer-wavelength region. After the AuZn was deposited on the back side of the NW array, the absorptance increased. This technology could enable a new approach for NW-based photovoltaics with a lower fabrication cost.

  20. Control of vascular network location in millimeter-sized 3D-tissues by micrometer-sized collagen coated cells.

    PubMed

    Liu, Chun-Yen; Matsusaki, Michiya; Akashi, Mitsuru

    2016-03-25

    Engineering three-dimensional (3D) vascularized constructs remains a central challenge because capillary network structures are important for sufficient oxygen and nutrient exchange to sustain the viability of engineered constructs. However, construction of 3D-tissues at single cell level has yet to be reported. Previously, we established a collagen coating method for fabricating a micrometer-sized collagen matrix on cell surfaces to control cell distance or cell densities inside tissues. In this study, a simple fabrication method is presented for constructing vascular networks in 3D-tissues over micrometer-sized or even millimeter-sized with controlled cell densities. From the results, well vascularized 3D network structures can be observed with a fluorescence label method mixing collagen coated cells and endothelia cells, indicating that constructed ECM rich tissues have the potential for vascularization, which opens up the possibility for various applications in pharmaceutical or tissue engineering fields. PMID:26920051