Science.gov

Sample records for pn charge-exchange-process yields

  1. The ratio R{sub dp} of the quasielastic nd {yields} p(nn) to the elastic np {yields} pn charge-exchange-process yields at the proton emitting angle {theta}{sub p,lab} = 0 deg. over 0.55-2.0 GeV neutron beam energy region. Experimental results

    SciTech Connect

    Sharov, V. I. Morozov, A. A.; Shindin, R. A.; Antonenko, V. G.; Borzakov, S. B.; Borzunov, Yu. T.; Chernykh, E. V.; Chumakov, V. F.; Dolgii, S. A.; Finger, M.; Finger, M.; Golovanov, L. B.; Guriev, D. K.; Janata, A.; Kirillov, A. D.; Kovalenko, A. D.; Krasnov, V. A.; Kuzmin, N. A.; Kurilkin, A. K.; Kurilkin, P. K.

    2009-06-15

    New experimental results on ratio R{sub dp} of the quasielastic charge-exchange yield at the outgoing proton angle {theta}{sub p,lab} = 0 deg. for the nd {yields} p(nn) reaction to the elastic np {yields} pn charge-exchange yield, are presented. The measurements were carried out at the Nuclotron of the Veksler and Baldin Laboratory of High Energies of the JINR (Dubna) at the neutron-beam kinetic energies of 0.55, 0.8, 1.0, 1.2, 1.4, 1.8, and 2.0 GeV. The intense neutron beam with small momentum spread was produced by breakup of deuterons which were accelerated and extracted to the experimental hall. In both reactions mentioned above the outgoing protons with the momenta p{sub p} approximately equal to the neutron-beam momentum p{sub n,beam} were detected in the directions close to the direction of incident neutrons, i.e., in the vicinity of the scattering angle {theta}{sub p,lab} = 0 deg. Measured in the same data-taking runs, the angular distributions of the charge-exchange-reaction products were corrected for the well-known instrumental effects and averaged in the vicinity of the incident-neutron-beam direction. These corrected angular distributions for every of nd {yields} p(nn) and np {yields} pn charge-exchange processes were proportional to the differential cross sections of the corresponding reactions. The data were accumulated by Delta-Sigma setup magnetic spectrometer with two sets of multiwire proportional chambers located upstream and downstream of the momentum analyzing magnet. Inelastic processes were considerably reduced by the additional detectors surrounding the hydrogen and deuterium targets. The time-of-flight system was applied to identify the detected particles. The accumulated data treatment and analysis, as well as possible sources of the systematic errors are discussed.

  2. The Ratio R{sub dp} of the quasielastic nd {yields} p(nn) to the elastic np {yields} pn charge-exchange-process yields at the proton emitting angle {theta}{sub p,lab} = 0 deg. over 0.55-2.0 GeV neutron-beam energy region. Comparison of the results with the model-dependent calculations

    SciTech Connect

    Sharov, V. I. Morozov, A. A.; Shindin, R. A.; Chernykh, E. V.; Nomofilov, A. A.; Strunov, L. N.

    2009-06-15

    Our new experimental results (see, e.g., Preprint JINR no. E1-2008-61 (Dubna, 2008)) on ratio R{sub dp} of the quasielastic charge-exchange yield at the proton emitting angle {theta}{sub p,lab} = 0 deg. for the nd {yields} p(nn) reaction to the elastic np {yields} pn charge-exchange yield were presented. The measurements were carried out at the Nuclotron of the Veksler and Baldin Laboratory of High Energies of the JINR (Dubna) at the neutron-beam kinetic energies of 0.55, 0.8, 1.0, 1.2, 1.4, 1.8, and 2.0 GeV. In this paper the comparison of the experimental R{sub dp} data with the obtained R{sub dp} calculations within the impulse approximation by using the invariant-amplitude sets from the GW/VPI phase-shift analysis is made. The R{sub dp} values calculated using the set of invariant amplitude data for the elastic np {yields} pn charge exchange at {theta}{sub p,CM} = 0 deg., agree with the experimental data. This confirmed the nd {yields} p(nn) process yield at {theta}{sub p,CM} = 0 deg. is caused by the contribution of the spin-dependent part of the elastic np {yields} pn charge-exchange reaction. Thus, it has been shown that the obtained experimental R{sub dp} results can be used for the Delta-Sigma experimental program to reduce the total ambiguity in the extraction of the amplitude real parts.

  3. Efficient prediction of (p,n) yields

    SciTech Connect

    Swift, D C; McNaney, J M; Higginson, D P; Beg, F

    2009-09-09

    In the continuous deceleration approximation, charged particles decelerate without any spread in energy as they traverse matter. This approximation simplifies the calculation of the yield of nuclear reactions, for which the cross-section depends on the particle energy. We calculated (p,n) yields for a LiF target, using the Bethe-Bloch relation for proton deceleration, and predicted that the maximum yield would be around 0.25% neutrons per incident proton, for an initial proton energy of 70 MeV or higher. Yield-energy relations calculated in this way can readily be used to optimize source and (p,n) converter characteristics.

  4. Solar System X-rays from Charge Exchange Processes

    NASA Astrophysics Data System (ADS)

    Lisse, Carey M.; Christian, D. J.; Bhardwaj, A.; Dennerl, K.; Wolk, S. J.; Bodewits, D.; Combi, M. R.; Zurbuchen, T. H.; Lepri, S. T.

    2013-04-01

    The discovery of high energy x-ray emission in 1996 from comet C/1996 B2 (Hyakutake) uncovered a new class of x-ray emitting objects. Subsequent detections of the morphology, spectra, and time dependence of the x-rays from more than 20 comets have shown that the very soft (E < 1 keV) emission is due to a charge-exchange interaction between highly charged solar wind minor ions and the comet's extended neutral atmosphere. Many solar system objects are now known to shine in the X-ray, including Venus, Mars, the Moon, the Earth, Jupiter, and Saturn, with total power outputs on the MW - GW scale. Like comets, the X-ray emission from the Earth's geo-corona, the Jovian & Saturnian aurorae, and the Martian halo are thought to be driven by charge exchange between highly charged minor (heavy) ions in the solar wind and gaseous neutral species in the bodies' atmosphere. The non-auroral X-ray emissions from Jupiter, Saturn, and Earth, and those from disks of Mars, Venus, and the Moon are produced by scattering of solar X-rays. The first soft X-ray observations of Earth’s aurora by Chandra shows that it is highly variable, and the giant planet aurorae are fascinating puzzles that are just beginning to yield their secrets and may be the only x-ray sources not driven directly by the Sun in the whole system as well as properties of hot exo-solar Jupiters. Observations of local solar system charge exchange processes can also help inform us about x-rays produced at more distant hot ionized gas/cold neutral gas interfaces, like the heliopause, stellar astrospheres, galactic star forming regions, and starburst galaxies.

  5. Charge exchange processes involving highly charged ions and targets of interest in astrophysics and fusion plasmas

    NASA Astrophysics Data System (ADS)

    Otranto, S.

    2012-11-01

    Renewed interest in charge exchange processes involving highly charged ions arises because of their crucial role in the planned ITER reactor as well as to recent X-ray observations in the astrophysical context. In this work, the classical trajectory Monte Carlo method (CTMC) is used to calculate state selective single charge exchange n-level cross sections and line emission cross sections pertinent to both fields. These are contrasted to recent laboratory data from KVI for the Xe18+ + Na(3s) collision system and NIST/BERLIN-EBIT data for the Ar18+ +Ar system.

  6. Dynamics of the fully stripped ion-hydrogen atom charge exchange process in dense quantum plasmas

    SciTech Connect

    Zhang, Ling-yu; Wan, Jiang-feng; Zhao, Xiao-ying; Xiao, Guo-qing; Duan, Wen-shan; Qi, Xin; Yang, Lei

    2014-09-15

    The plasma screening effects of dense quantum plasmas on charge exchange processes of a fully stripped ion colliding with a hydrogen atom are studied by the classical trajectory Monte Carlo method. The inter-particle interactions are described by the exponential cosine-screened Coulomb potentials. It is found that in weak screening conditions, cross sections increase with the increase of the ionic charge Z. However, in strong screening conditions, the dependence of cross sections on the ionic charge is related to the incident particle energy. At high energies, cross sections show a linear increase with the increase of Z, whereas at low energies, cross sections for Z≥4 become approximately the same. The He{sup 2+} and C{sup 6+} impacting charge exchange cross sections in dense quantum plasmas are also compared with those in weakly coupled plasmas. The interactions are described by the static screened Coulomb potential. It is found that for both He{sup 2+} and C{sup 6+}, the oscillatory screening effects of dense quantum plasmas are almost negligible in weak screening conditions. However, in strong screening conditions, the oscillatory screening effects enhance the screening effects of dense quantum plasmas, and the enhancement becomes more and more significant with the increase of the screening parameter and the ionic charge.

  7. Modeling the Hydrogen-Proton Charge-Exchange Process in Global Heliospheric Simulations

    NASA Astrophysics Data System (ADS)

    DeStefano, A.; Heerikhuisen, J.

    2015-12-01

    The environment surrounding our Solar System has a vast and dynamic structure. As the Sun rounds the Milky Way galaxy, interstellar dust and gas interact with the Sun's outflow of solar wind. A bubble of hot plasma forms around the Sun due to this interaction, called the heliosphere. In order to understand the structure of the heliosphere, observations and simulations must work in tandem. Within the past decade or so, 3D models of the heliosphere have been developed exhibiting non- symmmetric as well as predicting structures such as the hydrogen wall and the IBEX ribbon. In this poster we explore new ways to compute charge-exchange source terms. The charge-exchange process is the coupling mechanism between the MHD and kinetic theories. The understanding of this process is crucial in order to make valuable predictions. Energy dependant cross section terms will aid in settling non-linear affects coupling the intestellar and solar particles. Through these new ways of computing source terms, resolving fine structures in the plasma in the heliopause may be possible. In addition, other non-trivial situations, such as charge-exchange mediated shocks, may be addressed.

  8. What can be Learned from X-ray Spectroscopy Concerning Hot Gas in Local Bubble and Charge Exchange Processes?

    NASA Technical Reports Server (NTRS)

    Snowden, Steve

    2007-01-01

    What can be learned from x-ray spectroscopy in observing hot gas in local bubble and charge exchange processes depends on spectral resolution, instrumental grasp, instrumental energy band, signal-to-nose, field of view, angular resolution and observatory location. Early attempts at x-ray spectroscopy include ROSAT; more recently, astronomers have used diffuse x-ray spectrometers, XMM Newton, sounding rocket calorimeters, and Suzaku. Future observations are expected with calorimeters on the Spectrum Roentgen Gamma mission, and the Solar Wind Charge Exchange (SWCX). The Geospheric SWCX may provide remote sensing of the solar wind and magnetosheath and remote observations of solar CMEs moving outward from the sun.

  9. Photocurrent Quantum Yield in Suspended Carbon Nanotube p-n Junctions.

    PubMed

    Aspitarte, Lee; McCulley, Daniel R; Minot, Ethan D

    2016-09-14

    We study photocurrent generation in individual suspended carbon nanotube p-n junctions using spectrally resolved scanning photocurrent microscopy. Spatial maps of the photocurrent allow us to determine the length of the p-n junction intrinsic region, as well as the role of the n-type Schottky barrier. We show that reverse-bias operation eliminates complications caused by the n-type Schottky barrier and increases the length of the intrinsic region. The absorption cross-section of the CNT is calculated using an empirically verified model, and the effect of substrate reflection is determined using FDTD simulations. We find that the room temperature photocurrent quantum yield is approximately 30% when exciting the carbon nanotube at the S44 and S55 excitonic transitions. The quantum yield value is an order of magnitude larger than previous estimates. PMID:27575386

  10. Yield ratio estimates using regional Pn and Pg from North Korea's underground nuclear explosions

    NASA Astrophysics Data System (ADS)

    Kim, Tae Sung; Kang, Ik-Bum; Kim, Geun-Young

    2009-11-01

    On May 25, 2009 North Korea executed a second nuclear test in the vicinity of P'unggyeri where the first nuclear test was performed on October 9, 2006. Seismic signals from the two underground nuclear explosions (UNEs) are recorded at broadband stations in South Korea and China. Seismic signals from fourteen broadband stations operated by the Korea Institute of Geoscience and Mineral Resources (KIGAM), three broadband stations of Korea Meteorological Administration (KMA) in South Korea and the Mudanjiang station (MDJ) of GSN in China are used for this study. Clear Pn, Pg, and Lg phases propagated over 800 km. The nearly co-located two UNEs and seismic recordings at the same stations enable us to estimate the ratio of the Pn and Pg displacement amplitude spectra between two events by eliminating the path effect. The 95% confidence interval of the mean yield ratio is constrained as a function of the depth ratio and all the estimates of Pn and Pg spectral ratios. The mean yield ratio ranges from 3.45 to 6.36 in the 95% confidence interval based on the depth range estimates by Bennett (2008, 2009).

  11. Proposal for studying N* resonances with the pp{yields}pn{pi}{sup +} reaction

    SciTech Connect

    Wu Jiajun; Zou, B. S.; Ouyang Zhen

    2009-10-15

    A theoretical study of the pp{yields}pn{pi}{sup +} reaction for antiproton beam energy from 1 to 4 GeV is made by including contributions from various known N* and {delta}* resonances. It is found that for the beam energy around 1.5 GeV, the contribution of the Roper resonance N{sub (1440)}* produced by the t-channel {sigma} exchange dominates over all other contributions. Since such a reaction can be studied in the forthcoming PANDA experiment at the GSI Facility of Antiproton and Ion Research (FAIR), the reaction will be realistically the cleanest place for studying the properties of the Roper resonance and the best place for looking for other ''missing''N* resonances with large coupling to N{sigma}.

  12. Determination of {sup 16}O and {sup 18}O sensitivity factors and charge-exchange processes in low-energy ion scattering

    SciTech Connect

    Tellez, H.; Chater, R. J.; Fearn, S.; Symianakis, E.; Kilner, J. A.; Brongersma, H. H.

    2012-10-08

    Quantitative analysis in low-energy ion scattering (LEIS) requires an understanding of the charge-exchange processes to estimate the elemental sensitivity factors. In this work, the neutralization of He{sup +} scattered by {sup 18}O-exchanged silica at energies between 0.6 and 7 keV was studied. The process is dominated by Auger neutralization for E{sub i} < 0.8 keV. An additional mechanism starts above the reionization threshold. This collision-induced neutralization becomes the dominant mechanism for E{sub i} > 2 keV. The ion fractions P{sup +} were determined for Si and O using the characteristic velocity method to quantify the surface density. The {sup 18}O/{sup 16}O sensitivity ratio indicates an 18% higher sensitivity for the heavier O isotope.

  13. High-Yield Growth and Characterization of ⟨100⟩ InP p-n Diode Nanowires.

    PubMed

    Cavalli, Alessandro; Wang, Jia; Esmaeil Zadeh, Iman; Reimer, Michael E; Verheijen, Marcel A; Soini, Martin; Plissard, Sebastien R; Zwiller, Val; Haverkort, Jos E M; Bakkers, Erik P A M

    2016-05-11

    Semiconductor nanowires are nanoscale structures holding promise in many fields such as optoelectronics, quantum computing, and thermoelectrics. Nanowires are usually grown vertically on (111)-oriented substrates, while (100) is the standard in semiconductor technology. The ability to grow and to control impurity doping of ⟨100⟩ nanowires is crucial for integration. Here, we discuss doping of single-crystalline ⟨100⟩ nanowires, and the structural and optoelectronic properties of p-n junctions based on ⟨100⟩ InP nanowires. We describe a novel approach to achieve low resistance electrical contacts to nanowires via a gradual interface based on p-doped InAsP. As a first demonstration in optoelectronic devices, we realize a single nanowire light emitting diode in a ⟨100⟩-oriented InP nanowire p-n junction. To obtain high vertical yield, which is necessary for future applications, we investigate the effect of the introduction of dopants on the nanowire growth. PMID:27045232

  14. Predicted neutron yield and radioactivity for laser-induced (p,n) reactions in LiF

    SciTech Connect

    Swift, D C; McNaney, J M

    2009-01-30

    Design calculations are presented for a pulsed neutron source comprising polychromatic protons accelerated from a metal foil by a short-pulse laser, and a LiF converter in which (p,n) reactions occur. Although the proton pulse is directional, neutrons are predicted to be emitted relatively isotropically. The neutron spectrum was predicted to be similar to the proton spectrum, but with more neutrons of low energy in the opposite direction to the incident protons. The angular dependence of spectrum and intensity was predicted. The (p,n) reactions generate unstable nuclei which decay predominantly by positron emission to the original {sup 7}Li and {sup 19}F isotopes. For the initial planned experiments using a converter 1mm thick, we predict that 0.1% of the protons will undergo a (p,n) reaction, producing 10{sup 9} neutrons. Ignoring the unreacted protons, neutrons, and prompt gamma emission as excited nuclear states decay, residual positron radioactivity (and production of pairs of 511 keV annihilation photons) is initially 4.2MBq decaying with a half-life of 17.22 s for 6 mins ({sup 19}Ne decays), then 135Bq decaying with a half-life of 53.22 days ({sup 7}Be decays).

  15. Distinction between coordination and phosphine ligand oxidation: interactions of di- and triphosphines with Pn(3+) (Pn = P, As, Sb, Bi).

    PubMed

    Chitnis, Saurabh S; Vos, Kevin A; Burford, Neil; McDonald, Robert; Ferguson, Michael J

    2016-01-14

    Reactions of polydentate phosphines with sources of Pn(3+) (Pn = P, As, Sb, Bi) yield complexes of Pn(1+) (Pn = P, As) or Pn(3+) (Pn = Sb, Bi) acceptors. The distinction between coordination of a phosphine center to Pn and oxidation of a phosphine ligand is dependent on Pn. The first structurally verified triphosphine complexes of Sb(III) and Bi(III) acceptors are reported.

  16. Spin Correlation Coefficients in {rvec p}{rvec p} {yields} pn{pi}{sup +} from 325 to 400 MeV

    SciTech Connect

    Saha, Swapan K.; Daehnick, W.W.; Flammang, R.W.; Balewski, J.T.; Meyer, H.O.; Pollock, R.E.; Przewoski, B.v.; Rinckel, T.; Thoerngren-Engblom, P.; Lorentz, B.; Rathmann, F.; Schwartz, B.; Wise, T.; Pancella, P.V.

    2000-12-31

    The spin correlation coefficient combinations S {identical_to} A{sub xx} + A{sub yy}, D {identical_to} A{sub xx} {minus} A{sub yy} and the analyzing power A{sub y}({theta}) were measured for {rvec p}{rvec p} {yields} pn{pi}{sup +} at beam energies of 325, 350, 375, and 400 MeV. A polarized internal atomic hydrogen target and a stored, polarized proton beam were used. These polarization observables are sensitive to contributions of higher partial waves. A comparison with recent theoretical calculations is provided.

  17. Investigation of the p+N {yields} [{Sigma}{sup 0}K{sup +}]+N reaction at the proton energy E{sub p} = 70 GeV

    SciTech Connect

    1994-08-01

    The p+N {yields} [{Sigma}{sup 0}K{sup +}]+N reaction was studied in experiments using the SPHINX detector placed in the 70-GeV proton beam of the IHEP accelerator. In the effective mass spectrum of the M({Sigma}{sup 0}K{sup +}) system produced in the coherent diffractive transition, a clear peak with mass M = 1999 {+-} 7 MeV and width {Gamma} = 91 {+-} 17 MeV was observed in addition to the near-threshold structure with mass M {approx_equal} 1800 MeV. 7 refs., 3 figs.

  18. PnMPI

    2008-02-01

    PnMPI is a tool infrastructure for parallel programs implemented using the message passing interface (MPI). It enables users to dynamically assemble multiple tools, both existing and newly developed ones, into a single tool chain and to execute them concurrently. This provides new options for scalable tools designs including (but not concurrently. This provides new options for scalable tool designs including (but not limited to) the transparent virtualization of MPI environments of an application. In addition,more » PnMPI allows tools to export support routines to other tools. This promotes a separation of tasks between tools which leads to enhanced tool modularity. PnMPI has been implemented for a variety of platforms including Linux and AIX clusters, and a static version of PnMPI is available on Blue Gene/L.« less

  19. PN ranging/telemetry transmission

    NASA Technical Reports Server (NTRS)

    Deerkoski, L. F.

    1977-01-01

    System can transmit range-indicating pseudonoise (PN) codes and simultaneously transmit auxiliary information as binary data at a rate at least on order of pseudonoise chipping rate. PN code is modulated by data stream with relatively low bit rate. Data stream with high bit rate can be transmitted in same frequency band as PN ranging code.

  20. Charge-Exchange Processes of Titanium-Doped Aluminate Crystals

    NASA Astrophysics Data System (ADS)

    Wong, Wing Cheong

    1995-01-01

    Titanium exists in more than one charge state in the aluminate crystals: it is stable as Ti^ {3+} and Ti^{4+}. Other than the intense Ti^{4+ } absorption, a ubiquitous absorption/luminescence excitation band in the UV region is identified as a titanium -bound exciton in Al_2rm O_3, Y_3Al_5rm O_{12}, {rm YAlO}_3, MgAl_2O _4, and LaMgAl_{11} {rm O}_{19}. One -step and two-step photoconductivities of Ti^ {3+} are measured and compared. While the selectivity of the two-step process is demonstrated, its use in locating the energy threshold is hampered by the small Franck-Condon factor for the transition between the Ti^{3+} ^2{ rm E} excited state and Ti^ {4+}. The titanium-bound exciton band, together with the one-step photocurrent signal, makes it possible to determine the photoionization energy threshold accurately. The charge-transfer transition energy thresholds of Ti^{4+} are obtained from the emission and the luminescence excitation spectra. Locally and non-locally charge compensated Ti^{4+ } are found in Al_2{rm O}_3. The luminescence kinetics for the two kinds of Ti^{4+} are well explained by a three-level system with a lower triplet excited state and a higher singlet excited state. These charge-exchange threshold energies can be deduced from the Born-Haber thermodynamical cycle. The electrostatic site potentials are calculated and from it, the calculated photoionization and charge-transfer energy thresholds are found to be consistent with the experimental results. The deficiency of this model is pointed out and possible improvement is discussed. Quantitatively, the sum of the two charge-exchange energy thresholds is close to the band-gap energy of the host crystal. This offers a convenient way for material characterization. Provided that any two of the three quantities (band-gap energy, photoionization energy threshold, and charge-transfer transition energy threshold) have been found, the third quantity can be calculated. In addition, the trapping of charge carriers is investigated with thermally-stimulated conductivity and thermally-stimulated luminescence. The identities of the electron traps and hole traps are deduced from the results of several differently doped Al_2{ rm O}_3..

  1. PN lock indicator for dithered PN code tracking loop

    NASA Technical Reports Server (NTRS)

    Carson, L. M. (Inventor)

    1981-01-01

    In a delay-lock one-delta (+or - 1/2 chip) dithered PN code tracking loop, an indication of lock in the PN code tracking loop is provided by delaying the dithered local PN code by a half chip to produce a +0, -1 dithered PN code that is then multiplied with the received PN-spread IF signal to produce a signal proportional to the correlation of this dithered code offset from the received code. The correlation signal is bandpass filtered, amplified with AGC control, and square-law detected to obtain a dc signal proportional to the degree of correlation. The dc signal is multiplied by the dithering control signal to effectivity substract noise voltage from the lock correlation signal which is then compared with a PN lock status signal.

  2. Pion Production in pN Collisions near Threshold

    SciTech Connect

    Zlomanczuk, Jozef; PROMICE /WASA Collaboration

    2000-12-31

    Measurements of the pp{yields}pp{pi}{sup 0} reaction at 310, 320, 340, 360, 400 and 425 MeV, and quasi-free pn{yields}pp{pi}{sup {minus}} production in pd collisions at 320 MeV have been carried out at the PROMICE/WASA facility at CELSIUS. The pp{yields}pp{pi}{sup 0} differential cross sections have been parameterized and used to deduce the poorly known {sigma}{sub 01} total cross section through the relation: {sigma}{sub 01}=2{sigma}(pn{yields}pp{pi}{sup {minus}}){minus}{sigma}(pp{yields}pp{pi}{sup 0}). Preliminary results show the {sigma}{sub 01} to be of the order of 50% of the {sigma}{sub 11} for the pp{pi}{sup {minus}} excess energy between 8 and 40 MeV.

  3. Electrical properties of multi p-n junction devices

    NASA Technical Reports Server (NTRS)

    Katz, J.; Margalit, S.; Yariv, A.

    1982-01-01

    The electrical properties of multi p-n junction devices are analyzed. It is found that this type of device possesses bistable characteristics similar to that of a Shockley diode and thus provides an alternative realization of devices for switching applications. The inherently greater current gains involved in the operations of such a device yield in principle higher breakover voltages and higher holding currents. Furthermore, the incorporation of heterostructures in this device introduces a new degree of freedom in tailoring their switching characteristics. Multi p-n heterojunction devices operating as SCR lasers were fabricated, and the experimental results are presented.

  4. The Magellanic Cloud PN population

    NASA Astrophysics Data System (ADS)

    Reid, Warren Alfred

    2015-08-01

    The Magellanic Clouds (MCs) become an area of focus when comparing how objects behave within low metallicity environments. Over the past few decades this has proven especially true of planetary nebulae (PNe) studies. The Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) allow us to study late stellar evolution in environments that are respectively about a half and a quarter the metallicity of the Milky Way. With a known distance and low reddening, the MCs allow the analysis of PNe across a whole galaxy and have value for multiple studies.Over the past twelve months we have used the UKST H-alpha survey to complete our search for faint PNe in the outer most LMC beyond the 64 deg2 area previously covered. Follow-up spectroscopy using AAOmega on the AAT and the 2.3m telescope at Siding Spring Observatory have yielded a further 132 new LMC PNe while confirming the 102 previously known in the outer LMC. Using the same method, we have confirmed 6 new PNe in the SMC and rejected several objects previously catalogued as PNe.Medium- and high-resolution spectra have been used to measure fluxes and derive central star temperatures for a series of research projects. Recent findings involving chemical abundances, central star properties and kinematics will be presented. The current [OIII]-based PNLF, apart from providing an excellent standard candle, contains information about the parent population. The new PNLF, which extends down 9 magnitudes, permits investigation of the faint end and provides clues to explain the insensitivity of the PNLF cutoff.To better understand the global properties of PNe I will present and compare H-alpha, NIR & MIR PNLFs, discuss PN dust properties and the changes that occur as PNe age. The positions of LMC PNe will then be shown as a function of their radial velocities and compared to the HI disk and other populations. I will also discuss recent radio confirmations of LMC and SMC PNe. Finally I will also take a look at recent multi

  5. Single gate p-n junctions in graphene-ferroelectric devices

    NASA Astrophysics Data System (ADS)

    Hinnefeld, J. Henry; Xu, Ruijuan; Rogers, Steven; Pandya, Shishir; Shim, Moonsub; Martin, Lane W.; Mason, Nadya

    2016-05-01

    Graphene's linear dispersion relation and the attendant implications for bipolar electronics applications have motivated a range of experimental efforts aimed at producing p-n junctions in graphene. Here we report electrical transport measurements of graphene p-n junctions formed via simple modifications to a PbZr0.2Ti0.8O3 substrate, combined with a self-assembled layer of ambient environmental dopants. We show that the substrate configuration controls the local doping region, and that the p-n junction behavior can be controlled with a single gate. Finally, we show that the ferroelectric substrate induces a hysteresis in the environmental doping which can be utilized to activate and deactivate the doping, yielding an "on-demand" p-n junction in graphene controlled by a single, universal backgate.

  6. Combined GMSK Communications and PN Ranging

    NASA Technical Reports Server (NTRS)

    Orr, Richard; Divsalar, Dariush

    2008-01-01

    A document discusses a method by which GMSK (Gaussian minimum shift keying) modulation and a pseudonoise (PN) ranging signal may be combined. By isolating the in-phase and quadrature components after carrier lock, and extracting their low-pass and band-pass filtered components, there is enough information available to both demodulate data and track the PN signal. The proposed combined GMSK communications and PN ranging is one potential approach to address emerging requirements for simultaneous high data rate communications from and tracking of vehicles in deep space or at the Moon.

  7. Photovoltaic device having an extended PN junction

    NASA Technical Reports Server (NTRS)

    D'Aiello, Robert Vincent (Inventor)

    1978-01-01

    A photovoltaic device having essentially only a body of semiconductor material having a first region of one conductivity type in contact with a second region of the opposite conductivity type, forming a portion of the device PN junction therebetween. A plurality of pocket regions of the same conductivity type as the first region extend into the second region thereby further defining a portion of the PN junction in the second region.

  8. Silicon fiber with p-n junction

    SciTech Connect

    Homa, D.; Cito, A.; Pickrell, G.; Hill, C.; Scott, B.

    2014-09-22

    In this study, we fabricated a p-n junction in a fiber with a phosphorous doped silicon core and fused silica cladding. The fibers were fabricated via a hybrid process of the core-suction and melt-draw techniques and maintained overall diameters ranging from 200 to 900 μm and core diameters of 20–800 μm. The p-n junction was formed by doping the fiber with boron and confirmed via the current-voltage characteristic. The demonstration of a p-n junction in a melt-drawn silicon core fiber paves the way for the seamless integration of optical and electronic devices in fibers.

  9. Wave packet methods for charge exchange processes in ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Baloı̈tcha, E.; Desouter-Lecomte, M.; Bacchus-Montabonel, M.-C.; Vaeck, N.

    2001-05-01

    The efficiency of different time-independent and time-dependent wave packet methods to calculate charge-exchange cross sections is discussed. The time-independent spectral projection method is based on the Chebyshev expansion of the resolvent function and represents an interesting alternative to the usual Fourier method which involves a time propagation. On the other hand, the flux operator method still requires propagation in time but uses the properties of absorbing potentials in order to calculate the flux operator matrix elements. We show the necessity of introducing the appropriate Hankel-Riccati functions when the full Hamiltonian contains a centrifugal term in 1/R2 in order to reduce the computational time. The collisional system Si4++He is studied as a test case.

  10. Charge exchange processes in He+/Cu scattering at low energy

    NASA Astrophysics Data System (ADS)

    Khalal-Kouache, K.; Bruckner, B.; Roth, D.; Goebl, D.; Bauer, P.

    2016-09-01

    In this paper we present results on charge exchange of He+ ions at a polycrystalline Cu surface. Monte Carlo simulations were used to calculate the trajectories of projectiles scattered by an angle Θ = 136 ° . By including Auger neutralization and charge exchange in close collisions, energy spectra of the scattered ions as well as ion fraction values were calculated for primary energies in the range 0.5-5 keV and compared to experimental results. In the simulations, the Auger neutralization rate Γ and the probabilities of resonant neutralization (PRN) and reionization (PRI) are treated as free parameters. Using well accepted values from literature for these quantities very good agreement between simulations and experimental data was achieved.

  11. Polynomial driven time base and PN generator

    NASA Technical Reports Server (NTRS)

    Brokl, S. S.

    1983-01-01

    In support of the planetary radar upgrade new hardware was designed to increase resolution and take advantage of new technology. Included is a description of the Polynomial Driven Time Base and PN Generator which is used for range gate coding in the planetary radar system.

  12. DC modeling of PN integrated cross varactors

    NASA Astrophysics Data System (ADS)

    Gonzalez, Benito; Perez, Jose A.; Kemchandani, Sunil L.; Goni-Iturri, Amaya; del Pino, Javier; Garcia, Javier

    2005-06-01

    In this paper models for the capacitance of cross integrated varactors based in the PN junction are presented. Three different approximations are assumed, in order to reproduce the measured results of the capacitance. The relative error with the measured capacitance is under 10% in all cases.

  13. On the auto and cross correlation of PN sequences

    NASA Technical Reports Server (NTRS)

    Morakis, J. C.

    1969-01-01

    The autocorrelation and crosscorrelation properties of pseudorandom (PN) sequences are analyzed by using some important properties of PN sequences. These properties make this discussion understandable without the need of linear algebraic approach. The analysis is followed by some experimental results.

  14. Synthesis of Selected Cationic Pnictanes [LnPnX3-n](n+) (L = Imidazolium-2-yl; Pn = P, As; n = 1-3) and Replacement Reactions with Pseudohalogens.

    PubMed

    Henne, F D; Dickschat, A T; Hennersdorf, F; Feldmann, K-O; Weigand, J J

    2015-07-20

    Herein we report on reactions of "imidazoliumyl-transfer" reagents [L((R/R'))SiMe3][OTf] (4((R/R'))[OTf]); L = imidazolium-2-yl, R/R': Me/Me, (i)Pr/Me, Dipp/H, Dipp/Cl) with pnictogen trichlorides PnCl3 (Pn = P, As, Sb) in various stoichiometries. In the case of the 1:1 reaction of [L((R/R'))SiMe3][OTf] with PCl3 the corresponding cationic imidazoliumyl-substituted dichlorophosphanes [L((R/R'))PCl2](+) (1P((R/R')))(+) are obtained as triflate salts on a multigram scale. We found that the reactions using various stoichiometries of [L((R/R'))SiMe3][OTf] and PnCl3 are less selective in the case of the heavier congeners or by decreasing steric demand of the R-group attached to the N atoms of the heterocycle. An equilibrium between the monocation [L((Me/Me))PCl2](+) (1P((Me/Me)+)), the dication [L((Me/Me))2PCl](2+) (2P((Me/Me)2+)), and the trication [L((Me/Me))3P](3+) (5P((Me/Me)3+)) is observed in solution. Reactions of the monocationic derivatives [L((R/R'))PnCl2][OTf] (Pn = P, As) with Me3SiX (X = CN, N3) resulted in the exchange of the chloro groups for the respective pseudohalogen and yielded the dicyano [L((R/R'))Pn(CN)2][OTf] (6Pn((R/R'))[OTf]) and diazido-substituted pnictanes [L((R/R'))Pn(N3)2][OTf] (7Pn((R/R'))[OTf]), respectively. All new compounds are thoroughly characterized by multinuclear NMR, IR, and Raman spectroscopy. For most cases the molecular structure was confirmed by X-ray crystal structure analysis.

  15. Fabrication and characterization of graphene PN junctions

    NASA Astrophysics Data System (ADS)

    Wang, Dennis; Zhou, Xiaodong; Dadgar, Ali; Agnihotri, Pratik; Lee, Ji Ung; Reuter, Mark; Ross, Frances; Pasupathy, Abhay

    Theoretical predictions of relativistic Klein tunneling and Veselago lensing in graphene have inspired efforts to fabricate graphene p-n junctions where such phenomena could be realized and studied via electronic transport or scanning tunneling microscopy (STM). Here we will discuss the interplay between device geometry and our measurements in a 4-probe STM, which allows for simultaneous back gating, biasing, and scanning of a micromechanically exfoliated graphene sample. A sharp p-n junction is essential to the manifestation of these aforementioned effects, and we examine the benefits and drawbacks of several routes toward this goal from a fabrication standpoint. These methods include lithographically pre-patterned substrates and the stacking of vertical heterostructures. Finally, we will describe our subsequent characterization results for each, including information about topography and spatial mapping of the density of states. This work is supported by NSF IGERT (DGE-1069240).

  16. TDRSS telecommunication system PN code analysis

    NASA Technical Reports Server (NTRS)

    Gold, R.

    1977-01-01

    The pseudonoise (PN) code library for the Tracking and Data Relay Satellite System (TDRSS) Services was defined and described. The code library was chosen to minimize user transponder hardware requirements and optimize system performance. Special precautions were taken to insure sufficient code phase separation to minimize cross-correlation sidelobes, and to avoid the generation of spurious code components which would interfere with system performance.

  17. Pontine Reticular Formation (PnO) Administration of Hypocretin-1 Increases PnO GABA Levels and Wakefulness

    PubMed Central

    Watson, Christopher J.; Soto-Calderon, Haideliza; Lydic, Ralph; Baghdoyan, Helen A.

    2008-01-01

    Study Objectives: GABAergic transmission in the oral part of the pontine reticular formation (PnO) increases wakefulness. The hypothalamic peptide hypocretin-1 (orexin A) promotes wakefulness, and the PnO receives hypocretinergic input. The present study tested the hypothesis that PnO administration of hypocretin-1 increases PnO GABA levels and increases wakefulness. This study also tested the hypothesis that wakefulness is either increased or decreased, respectively, by PnO administration of drugs known to selectively increase or decrease GABA levels. Design: A within-subjects design was used for microdialysis and microinjection experiments. Setting: University of Michigan. Patients or Participants: Experiments were performed using adult male Crl:CD® (SD)IGS BR (Sprague-Dawley) rats (n = 46). Interventions: PnO administration of hypocretin-1, nipecotic acid (a GABA uptake inhibitor that increases extracellular GABA levels), 3-mercaptopropionic acid (a GABA synthesis inhibitor that decreases extracellular GABA levels; 3-MPA), and Ringer solution (vehicle control). Measurements and Results: Dialysis administration of hypocretin-1 to the PnO caused a statistically significant, concentration-dependent increase in PnO GABA levels. PnO microinjection of hypocretin-1 or nipecotic acid caused a significant increase in wakefulness and a significant decrease in non-rapid eye movement (NREM) sleep and REM sleep. Microinjecting 3-MPA into the PnO caused a significant increase in NREM sleep and REM sleep and a significant decrease in wakefulness. Conclusions: An increase or a decrease in PnO GABA levels causes an increase or decrease, respectively, in wakefulness. Hypocretin-1 may promote wakefulness, at least in part, by increasing GABAergic transmission in the PnO. Citation: Watson CJ; Soto-Calderon H; Lydic R; Baghdoyan HA. Pontine reticular formation (PnO) administration of hypocretin-1 increases PnO GABA levels and wakefulness. SLEEP 2008;31(4):453-464. PMID:18457232

  18. TDRSS telecommunications system, PN code analysis

    NASA Technical Reports Server (NTRS)

    Dixon, R.; Gold, R.; Kaiser, F.

    1976-01-01

    The pseudo noise (PN) codes required to support the TDRSS telecommunications services are analyzed and the impact of alternate coding techniques on the user transponder equipment, the TDRSS equipment, and all factors that contribute to the acquisition and performance of these telecommunication services is assessed. Possible alternatives to the currently proposed hybrid FH/direct sequence acquisition procedures are considered and compared relative to acquisition time, implementation complexity, operational reliability, and cost. The hybrid FH/direct sequence technique is analyzed and rejected in favor of a recommended approach which minimizes acquisition time and user transponder complexity while maximizing probability of acquisition and overall link reliability.

  19. Mapping Pn amplitude spreading and attenuation in Asia

    SciTech Connect

    Yang, Xiaoning; Phillips, William S; Stead, Richard J

    2010-12-06

    Pn travels most of its path in the mantle lid. Mapping the lateral variation of Pn amplitude attenuation sheds light on material properties and dynamics of the uppermost region of the mantle. Pn amplitude variation depends on the wavefront geometric spreading as well as material attenuation. We investigated Pn geometric spreading, which is much more complex than a traditionally assumed power-law spreading model, using both synthetic and observed amplitude data collected in Asia. We derived a new Pn spreading model based on the formulation that was proposed previously to account for the spherical shape of the Earth (Yang et. al., BSSA, 2007). New parameters derived for the spreading model provide much better correction for Pn amplitudes in terms of residual behavior. Because we used observed Pn amplitudes to construct the model, the model incorporates not only the effect of the Earth's spherical shape, but also the effect of potential upper-mantle velocity gradients in the region. Using the new spreading model, we corrected Pn amplitudes measured at 1, 2, 4 and 6 Hz and conducted attenuation tomography. The resulting Pn attenuation model correlates well with the regional geology. We see high attenuation in regions such as northern Tibetan Plateau and the western Pacific subduction zone, and low attenuation for stable blocks such as Sichuan and Tarim basins.

  20. Measurement of χcj decaying into pn̄π⁻ and pn̄π⁻π⁰

    DOE PAGESBeta

    Ablikim, M.; Achasov, M. N.; Albayrak, O.; Ambrose, D. J.; An, F. F.; An, Q.; Bai, J. Z.; Ban, Y.; Becker, J.; Bennett, J. V.; et al

    2012-09-26

    Using a data sample of 1.06×10⁸ ψ' events collected with the BESIII detector in 2009, the branching fractions of χcJ→pn̄π⁻ and χcJ→pn̄π⁻π⁰ (J=0, 1, 2) are measured. (Throughout the text, inclusion of charge conjugate modes is implied if not stated otherwise.) The results for χc⁰→pn̄π⁻ and χc²→pn̄π⁻ are consistent with, but much more precise than, those of previous measurements. The decays of χc1→pn̄π⁻ and χcJ→pn̄π⁻π⁰ are observed for the first time.

  1. Novel pneumoviruses (PnVs): Evolution and inflammatory pathology

    SciTech Connect

    Glineur, Stephanie F.; Renshaw, Randall W.; Percopo, Caroline M.; Dyer, Kimberly D.; Dubovi, Edward J.; Domachowske, Joseph B.; Rosenberg, Helene F.

    2013-09-01

    A previous report of a novel pneumovirus (PnV) isolated from the respiratory tract of a dog described its significant homology to the rodent pathogen, pneumonia virus of mice (PVM). The original PnV–Ane4 pathogen replicated in and could be re-isolated in infectious state from mouse lung but elicited minimal mortality compared to PVM strain J3666. Here we assess phylogeny and physiologic responses to 10 new PnV isolates. The G/glycoprotein sequences of all PnVs include elongated amino-termini when compared to the characterized PVMs, and suggest division into groups A and B. While we observed significant differences in cytokine production and neutrophil recruitment to the lungs of BALB/c mice in response to survival doses (50 TCID{sub 50} units) of representative group A (114378-10-29-KY-F) and group B (7968-11-OK) PnVs, we observed no evidence for positive selection (dN>dS) among the PnV/PnV, PVM/PnV or PVM/PVM G/glycoprotein or F/fusion protein sequence pairs. - Highlights: • We consider ten novel isolates of the pneumovirus (PnV) first described by Renshaw and colleagues. • The G/glycoprotein sequences of all PnVs include elongated amino-termini when compared to PVM. • We detect cytokine production and neutrophil recruitment to the lungs of mice in response to PnV. • We observed no evidence for positive selection (dN>dS) among the gene sequence pairs.

  2. (p,n) Charge-Exchange Reactions in Inverse Kinematics

    NASA Astrophysics Data System (ADS)

    Lipschutz, Samuel; NSCL E10003 Collaboration

    2014-09-01

    Charge-exchange experiments at intermediate energy yield important information about collective excitations with spin-isospin degrees of freedom. The properties of isovector giant resonances in neutron-rich rare-isotopes provide stringent tests of theoretical models and are important inputs for modeling of astrophysical phenomena. The (p,n) charge-exchange reaction in inverse kinematics has been developed as a new tool for investigating isovector giant resonances in rare isotopes. The technique, which involves the detection of low-energy neutrons that recoil from a hydrogen target, while detecting fast beam-like ejectiles in a magnetic spectrometer, was successfully employed at NSCL to study the 56Ni(p,n) reaction. Continuing with this technique a 16C(p,n) experiment at 100 MeV/u aimed at extracting isovector multipole strengths up to excitation energies of 30 MeV was preformed. The Low Energy Neutron Detector Array (LENDA) and the Versatile Array of Neutron Detectors at Low Energy (VANDLE) were utilized in combination with the Ursinus Liquid Hydrogen Target and the S800 spectrometer to perform this experiment. Preliminary results will be shown. Charge-exchange experiments at intermediate energy yield important information about collective excitations with spin-isospin degrees of freedom. The properties of isovector giant resonances in neutron-rich rare-isotopes provide stringent tests of theoretical models and are important inputs for modeling of astrophysical phenomena. The (p,n) charge-exchange reaction in inverse kinematics has been developed as a new tool for investigating isovector giant resonances in rare isotopes. The technique, which involves the detection of low-energy neutrons that recoil from a hydrogen target, while detecting fast beam-like ejectiles in a magnetic spectrometer, was successfully employed at NSCL to study the 56Ni(p,n) reaction. Continuing with this technique a 16C(p,n) experiment at 100 MeV/u aimed at extracting isovector multipole

  3. Studies of silicon PN junction solar cells

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.

    1975-01-01

    Silicon pn junction solar cells made with low-resistivity substrates show poorer performance than traditional theory predicts. The purpose of this research was to identify and characterize the physical mechanisms responsible for the discrepancy. Attention was concentrated on the open circuit voltage in shallow junction cells of 0.1 ohm-cm substrate resistivity. A number of possible mechanisms that can occur in silicon devices were considered. Two mechanisms which are likely to be of main importance in explaining the observed low values of open-circuit voltage were found: (1) recombination losses associated with defects introduced during junction formation, and (2) inhomogeneity of defects and impurities across the area of the cell. To explore these theoretical anticipations, various diode test structures were designed and fabricated and measurement configurations for characterizing the defect properties and the areal inhomogeneity were constructed.

  4. Field-effect P-N junction

    DOEpatents

    Regan, William; Zettl, Alexander

    2015-05-05

    This disclosure provides systems, methods, and apparatus related to field-effect p-n junctions. In one aspect, a device includes an ohmic contact, a semiconductor layer disposed on the ohmic contact, at least one rectifying contact disposed on the semiconductor layer, a gate including a layer disposed on the at least one rectifying contact and the semiconductor layer and a gate contact disposed on the layer. A lateral width of the rectifying contact is less than a semiconductor depletion width of the semiconductor layer. The gate contact is electrically connected to the ohmic contact to create a self-gating feedback loop that is configured to maintain a gate electric field of the gate.

  5. Radio frequency interference effect on PN code sequence lock detector

    NASA Technical Reports Server (NTRS)

    Kwon, Hyuck M.; Tu, Kwei; Loh, Y. C.

    1991-01-01

    The authors find the probabilities of detection and false alarm of the pseudonoise (PN) sequence code lock detector when strong radio frequency interference (RFI) hits the communications link. Both a linear model and a soft-limiter nonlinear model for a transponder receiver are considered. In addition, both continuous wave (CW) RFI and pulse RFI are analyzed, and a discussion is included of how strong CW RFI can knock out the PN code lock detector in a linear or a soft-limiter transponder. As an example, the Space Station Freedom forward S-band PN system is evaluated. It is shown that a soft-limiter transponder can protect the PN code lock detector against a typical pulse RFI, but it can degrade the PN code lock detector performance more than a linear transponder if CW RFI hits the link.

  6. Optimum waiting time for acquisition of return link PN signals

    NASA Technical Reports Server (NTRS)

    Kolata, W.

    1982-01-01

    The subject of this paper is a model that takes into account the effect that acquisition of a PN signal on the forward link has on the acquisition of a PN signal on the return link. The model is used to determine how long the start of the PN search on the return link should be delayed in order to minimize the combined acquisition time (delay + acquisition time) as a function of desired acquisition probability. It is assumed that the return link a-priori epoch uncertainty information is available. Software has been developed that models the return link PN receiver and incorporates in it the effect of forward link PN acquisition statistics in assessing performance.

  7. Single P-N junction tandem photovoltaic device

    DOEpatents

    Walukiewicz, Wladyslaw; Ager, III, Joel W.; Yu, Kin Man

    2012-03-06

    A single P-N junction solar cell is provided having two depletion regions for charge separation while allowing the electrons and holes to recombine such that the voltages associated with both depletion regions of the solar cell will add together. The single p-n junction solar cell includes an alloy of either InGaN or InAlN formed on one side of the P-N junction with Si formed on the other side in order to produce characteristics of a two junction (2J) tandem solar cell through only a single P-N junction. A single P-N junction solar cell having tandem solar cell characteristics will achieve power conversion efficiencies exceeding 30%.

  8. Single P-N junction tandem photovoltaic device

    DOEpatents

    Walukiewicz, Wladyslaw; Ager, III, Joel W.; Yu, Kin Man

    2011-10-18

    A single P-N junction solar cell is provided having two depletion regions for charge separation while allowing the electrons and holes to recombine such that the voltages associated with both depletion regions of the solar cell will add together. The single p-n junction solar cell includes an alloy of either InGaN or InAlN formed on one side of the P-N junction with Si formed on the other side in order to produce characteristics of a two junction (2J) tandem solar cell through only a single P-N junction. A single P-N junction solar cell having tandem solar cell characteristics will achieve power conversion efficiencies exceeding 30%.

  9. Pn anisotropic tomography and mantle dynamics beneath China

    NASA Astrophysics Data System (ADS)

    Zhou, Zhigang; Lei, Jianshe

    2016-08-01

    We present a new high-resolution Pn anisotropic tomographic model of the uppermost mantle beneath China inferred from 52,061 Pn arrival-time data manually picked from seismograms recorded at provincial seismic stations in China and temporary stations in Tibet and the Tienshan orogenic belt. Significant features well correlated with surface geology are revealed and provide new insights into the deep dynamics beneath China. Prominent high Pn velocities are visible under the stable cratonic blocks (e.g., the Tarim, Junngar, and Sichuan basins, and the Ordos block), whereas remarkable low Pn velocities are observed in the tectonically active areas (e.g., Pamir, the Tienshan orogenic belt, central Tibet and the Qilian fold belt). A distinct N-S trending low Pn velocity zone around 86°E is revealed under the rift running from the Himalayan block through the Lhasa block to the Qiangtang block, which indicates the hot material upwelling due to the breaking-off of the subducting Indian slab. Two N-S trending low Pn velocity belts with an approximate N-S Pn fast direction along the faults around the Chuan-Dian diamond block suggest that these faults may serve as channels of mantle flow from Tibet. The fast Pn direction changes from N-S in the north across 27°N to E-W in the south, which may reflect different types of mantle deformation. The anisotropy in the south could be caused by the asthenospheric flow resulted from the eastward subduction of the Indian plate down to the mantle transition zone beneath the Burma arc. Across the Talas-Fergana fault in the Tienshan orogenic belt, an obvious difference in velocity and anisotropy is revealed. To the west, high Pn velocities and an arc-shaped fast Pn direction are observed, implying the Indo-Asian collision, whereas to the east low Pn velocities and a range-parallel Pn fast direction are imaged, reflecting the northward underthrusting of the Tarim lithosphere and the southward underthrusting of the Kazakh lithosphere. In

  10. Coinage metal complexes supported by a "PN(3)P" scaffold.

    PubMed

    Rao, Gyandshwar Kumar; Gorelsky, Serge I; Korobkov, Ilia; Richeson, Darrin

    2015-11-28

    A series of monovalent group 11 complexes, [2,6-{Ph2PNMe}2(NC5H3)]CuBr 1, [2,6-{Ph2PNMe}2(NC5H3)]CuOTf 2, [2,6-{Ph2PNMe}2(NC5H3)]AgOTf 3, and [2,6-{Ph2PNMe}2(NC5H3)](AuCl)24, supported by a neutral PN(3)P ligand have been synthesized and characterized by multinuclear NMR and single crystal X-ray diffraction studies. The variation of the coordination properties were analyzed and electronic structure calculations have been carried out to provide insight on the bonding details in these complexes. The Cu(I) complexes displayed an unusual coordination geometry with a tridentate pincer ligand and an overall four coordinate trigonal pyramidal geometry. In contrast the Ag(I) analogue displayed a bidentate κ(2)-P,P' ligation leaving the pyridyl-N atom uncoordinated and yielding a pyramidalized trigonal planar geometry around Ag. The bimetallic Au(I) complex completed the series and displayed a monodentate P-bonded ligand and a linear coordination geometry.

  11. PN velocity beneath Western New Mexico and Eastern Arizona

    NASA Technical Reports Server (NTRS)

    Jaksha, L. H.

    1985-01-01

    The experiment involved observing Pn arrivals on an areal array of 7 seismic stations located in the transition zone and along the Jemez lineament. Explosions in coal and copper mines in New Mexico and Arizona were used as energy sources as well as military detonations at White Sands Missile Range, New Mexico, Yuma, Arizona, and the Nevada Test Site. Very preliminary results suggest a Pn velocity of 7.94 km/s (with a fairly large uncertainty) beneath the study area. The Pn delay times, which can be converted to estimates of crustal thickness given knowledge of the velocity structure of the crust increase both to the north and east of Springerville, Arizona. As a constraint on the velocity of Pn, researchers analyzed the reversed refraction line GNOME-HARDHAT which passes through Springerville oriented NW to SE. This analysis resulted in a Pn velocity of 7.9-8.0 km/s for the transition zone. These preliminary results suggest that a normal Pn velocity might persist even though the crust thins (from north to south) by 15 km along the length of the Arizona-New Mexico border. If the upper mantle is currently hot anywhere in western New Mexico or eastern Arizona then the dimensions of the heat source (or sources) might be small compared to the intra-station distances of the seismic arrays used to estimate the velocity of Pn.

  12. PN velocity beneath Western New Mexico and Eastern Arizona

    NASA Astrophysics Data System (ADS)

    Jaksha, L. H.

    The experiment involved observing Pn arrivals on an areal array of 7 seismic stations located in the transition zone and along the Jemez lineament. Explosions in coal and copper mines in New Mexico and Arizona were used as energy sources as well as military detonations at White Sands Missile Range, New Mexico, Yuma, Arizona, and the Nevada Test Site. Very preliminary results suggest a Pn velocity of 7.94 km/s (with a fairly large uncertainty) beneath the study area. The Pn delay times, which can be converted to estimates of crustal thickness given knowledge of the velocity structure of the crust increase both to the north and east of Springerville, Arizona. As a constraint on the velocity of Pn, researchers analyzed the reversed refraction line GNOME-HARDHAT which passes through Springerville oriented NW to SE. This analysis resulted in a Pn velocity of 7.9-8.0 km/s for the transition zone. These preliminary results suggest that a normal Pn velocity might persist even though the crust thins (from north to south) by 15 km along the length of the Arizona-New Mexico border. If the upper mantle is currently hot anywhere in western New Mexico or eastern Arizona then the dimensions of the heat source (or sources) might be small compared to the intra-station distances of the seismic arrays used to estimate the velocity of Pn.

  13. Photoinduced carrier annihilation in silicon pn junction

    NASA Astrophysics Data System (ADS)

    Sameshima, Toshiyuki; Motoki, Takayuki; Yasuda, Keisuke; Nakamura, Tomohiko; Hasumi, Masahiko; Mizuno, Toshihisa

    2015-08-01

    We report analysis of the photo-induced minority carrier effective lifetime (τeff) in a p+n junction formed on the top surfaces of a n-type silicon substrate by ion implantation of boron and phosphorus atoms at the top and bottom surfaces followed by activation by microwave heating. Bias voltages were applied to the p+ boron-doped surface with n+ phosphorus-doped surface kept at 0 V. The values of τeff were lower than 1 × 10-5 s under the reverse-bias condition. On the other hand, τeff markedly increased to 1.4 × 10-4 s as the forward-bias voltage increased to 0.7 V and then it leveled off when continuous-wave 635 nm light was illuminated at 0.74 mW/cm2 on the p+ surface. The carrier annihilation velocity S\\text{p + } at the p+ surface region was numerically estimated from the experimental τeff. S\\text{p + } ranged from 4000 to 7200 cm/s under the reverse-bias condition when the carrier annihilation velocity S\\text{n + } at the n+ surface region was assumed to be a constant value of 100 cm/s. S\\text{p + } markedly decreased to 265 cm/s as the forward-bias voltage increased to 0.7 V.

  14. Crystal, magnetic, and electronic structures, and properties of new BaMnPnF (Pn = As, Sb, Bi).

    PubMed

    Saparov, Bayrammurad; Singh, David J; Garlea, Vasile O; Sefat, Athena S

    2013-01-01

    New BaMnPnF (Pn = As, Sb, Bi) are synthesized by stoichiometric reaction of elements with BaF₂. They crystallize in the P4/nmm space group, with the ZrCuSiAs-type structure, as indicated by X-ray crystallography. Electrical resistivity results indicate that Pn = As, Sb, and Bi are semiconductors with band gaps of 0.73 eV, 0.48 eV and 0.003 eV (extrinsic value), respectively. Powder neutron diffraction reveals a G-type antiferromagnetic order below T(N) = 338(1) K for Pn = As, and below T(N) = 272(1) K for Pn = Sb. Magnetic susceptibility increases with temperature above 100 K for all the materials. Density functional calculations find semiconducting antiferromagnetic compounds with strong in-plane and weaker out-of-plane exchange coupling that may result in non-Curie Weiss behavior above TN. The ordered magnetic moments are 3.65(5) μ(B)/Mn for Pn = As, and 3.66(3) μ(B)/Mn for Pn = Sb at 4 K, as refined from neutron diffraction experiments.

  15. Analytical theory of the space-charge region of lateral p-n junctions in nanofilms

    SciTech Connect

    Gurugubelli, Vijaya Kumar Karmalkar, Shreepad

    2015-07-21

    There is growing interest in fabricating conventional semiconductor devices in a nanofilm which could be a 3D material with one reduced dimension (e.g., silicon-on-insulator (SOI) film), or single/multiple layers of a 2D material (e.g., MoS{sub 2}), or a two dimensional electron gas/two dimensional hole gas (2DEG/2DHG) layer. Lateral p-n junctions are essential parts of these devices. The space-charge region electrostatics in these nanofilm junctions is strongly affected by the surrounding field, unlike in bulk junctions. Current device physics of nanofilms lacks a simple analytical theory of this 2D electrostatics of lateral p-n junctions. We present such a theory taking into account the film's thickness, permittivity, doping, interface charge, and possibly different ambient permittivities on film's either side. In analogy to the textbook theory of the 1D electrostatics of bulk p-n junctions, our theory yields simple formulas for the depletion width, the extent of space-charge tails beyond this width, and the screening length associated with the space-charge layer in nanofilm junctions; these formulas agree with numerical simulations and measurements. Our theory introduces an electrostatic thickness index to classify nanofilms into sheets, bulk and intermediate sized.

  16. Array analysis of regional Pn and Pg wavefields from the Nevada Test Site

    SciTech Connect

    Leonard, M.A. . Dept. of Geology and Geophysics Lawrence Berkeley Lab., CA )

    1991-06-01

    Small-aperture high-frequency seismic arrays with dimensions of a few kilometers or less, can improve our ability to seismically monitor compliance with a low-yield Threshold Test Ban Treaty. This work studies the characteristics and effectiveness of array processing of the regional Pn and Pg wavefields generated by underground nuclear explosions at the Nevada Test Site. Waveform data from the explosion HARDIN (m{sub b} = 5.5) is recorded at a temporary 12-element, 3-component, 1.5 km-aperture array sited in an area of northern Nevada. The explosions VILLE (m{sub b} = 4.4) and SALUT (m{sub b} = 5.5) are recorded at two arrays sited in the Mojave desert, one a 96-element vertical-component 7 km-aperture array and the other a 155-element vertical-component 4 km-aperture array. Among the mean spectra for the m{sub b} = 5.5 events there are significant differences in low-frequency spectral amplitudes between array sites. The spectra become nearly identical beyond about 6 Hz. Spectral ratios are used to examine seismic source properties and the partitioning of energy between Pn and Pg. Frequency-wavenumber analysis at the 12-element array is used to obtain estimates of signal gain, phase velocity, and source azimuth. This analysis reveals frequency-dependent biases in velocity and azimuth of the coherent Pn and Pg arrivals. Signal correlation, the principal factor governing array performance, is examined in terms of spatial coherence estimates. The coherence is found to vary between the three sites. In all cases the coherence of Pn is greater than that for Pg. 81 refs., 92 figs., 5 tabs.

  17. Search strategy effects on PN acquisition performance. [Pseudonoise

    NASA Technical Reports Server (NTRS)

    Weinberg, A.

    1981-01-01

    The present paper focusses on 'random' and 'expanding window' PN acquisition search strategies and analytically develops the PN acquisition time statistics as functions of salient system parameters such as prediction SNR, detection and false alarm probabilities and a priori information on epoch location. The significance of this analysis is its general applicability to arbitrary postdetection processing schemes. Computed performance results account for the above salient parameters, wherein sequential detection is employed in conjunction with random and selected expanding window search strategies.

  18. Hybrid pn-junction solar cells based on layers of inorganic nanocrystals and organic semiconductors: optimization of layer thickness by considering the width of the depletion region.

    PubMed

    Saha, Sudip K; Guchhait, Asim; Pal, Amlan J

    2014-03-01

    We report the formation and characterization of hybrid pn-junction solar cells based on a layer of copper diffused silver indium disulfide (AgInS2@Cu) nanoparticles and another layer of copper phthalocyanine (CuPc) molecules. With copper diffusion in the nanocrystals, their optical absorption and hence the activity of the hybrid pn-junction solar cells was extended towards the near-IR region. To decrease the particle-to-particle separation for improved carrier transport through the inorganic layer, we replaced the long-chain ligands of copper-diffused nanocrystals in each monolayer with short-ones. Under illumination, the hybrid pn-junctions yielded a higher short-circuit current as compared to the combined contribution of the Schottky junctions based on the components. A wider depletion region at the interface between the two active layers in the pn-junction device as compared to that of the Schottky junctions has been considered to analyze the results. Capacitance-voltage characteristics under a dark condition supported such a hypothesis. We also determined the width of the depletion region in the two layers separately so that a pn-junction could be formed with a tailored thickness of the two materials. Such a "fully-depleted" device resulted in an improved photovoltaic performance, primarily due to lessening of the internal resistance of the hybrid pn-junction solar cells.

  19. Hybrid pn-junction solar cells based on layers of inorganic nanocrystals and organic semiconductors: optimization of layer thickness by considering the width of the depletion region.

    PubMed

    Saha, Sudip K; Guchhait, Asim; Pal, Amlan J

    2014-03-01

    We report the formation and characterization of hybrid pn-junction solar cells based on a layer of copper diffused silver indium disulfide (AgInS2@Cu) nanoparticles and another layer of copper phthalocyanine (CuPc) molecules. With copper diffusion in the nanocrystals, their optical absorption and hence the activity of the hybrid pn-junction solar cells was extended towards the near-IR region. To decrease the particle-to-particle separation for improved carrier transport through the inorganic layer, we replaced the long-chain ligands of copper-diffused nanocrystals in each monolayer with short-ones. Under illumination, the hybrid pn-junctions yielded a higher short-circuit current as compared to the combined contribution of the Schottky junctions based on the components. A wider depletion region at the interface between the two active layers in the pn-junction device as compared to that of the Schottky junctions has been considered to analyze the results. Capacitance-voltage characteristics under a dark condition supported such a hypothesis. We also determined the width of the depletion region in the two layers separately so that a pn-junction could be formed with a tailored thickness of the two materials. Such a "fully-depleted" device resulted in an improved photovoltaic performance, primarily due to lessening of the internal resistance of the hybrid pn-junction solar cells. PMID:24452695

  20. High resolution scanning optical imaging of a frozen polymer p-n junction

    NASA Astrophysics Data System (ADS)

    AlTal, Faleh; Gao, Jun

    2016-09-01

    Semiconductor homojunctions such as p-n or p-i-n junctions are the building blocks of many semiconductor devices such as diodes, photodetectors, transistors, or solar cells. The determination of junction depletion width is crucial for the design and realization of high-performance devices. The polymer analogue of a conventional p-n or p-i-n junction can be created by in situ electrochemical doping in a polymer light-emitting electrochemical cell (LEC). As a result of doping and junction formation, the LECs possess some highly desirable device characteristics. The LEC junction, however, is still poorly understood due to the difficulties of characterizing a dynamic-junction device. Here, we report concerted optical-beam-induced-current (OBIC) and scanning photoluminescence (PL) imaging studies of planar LECs that have been frozen to preserve the doping profile. By optimizing the cell composition, the electrode work function, and the turn-on conditions, we realize a long, straight, and highly emissive p-n junction with an interelectrode spacing of 700 μm. The extremely broad planar cell allows for time-lapse fluorescence imaging of the in situ electrochemical doping process and detailed scanning of the entire cell. A total of eighteen scans at seven locations along the junction have been performed using a versatile, custom cryogenic laser scanning apparatus. The Gaussian OBIC profiles yield an average 1/e2 junction width of only 1.5 μm, which is the smallest ever reported in a planar LEC. The controlled dedoping of the frozen device via warming cycles leads to an unexpectedly narrower OBIC profile, suggesting the presence and disappearance of fine structures at the edges of the frozen p-n junction. The results reported in this work provide new insight into the nature and structure of the LEC p-n junction. Since only about 0.2% of the entire device area is photoactive in response to an incident optical beam, the effective junction width (or volume) must be

  1. What Can Be Learned from X-Ray Spectroscopy Concerning Hot Gas in the Local Bubble and Charge Exchange Processes?

    NASA Technical Reports Server (NTRS)

    Snowden, S. L.

    2008-01-01

    Both solar wind charge exchange emission and diffuse thermal emission from the Local Bubble are strongly dominated in the soft X-ray band by lines from highly ionized elements. While both processes share many of the same lines, the spectra should differ significantly due to the different production mechanisms, abundances, and ionization states. Despite their distinct spectral signatures, current and past observatories have lacked the spectral resolution to adequately distinguish between the two sources. High-resolution X-ray spectroscopy instrumentation proposed for future missions has the potential to answer fundamental questions such as whether there is any hot plasma in the Local Hot Bubble, and if so, what are the abundances of the emitting plasma and whether the plasma is in equilibrium. Such instrumentation will provide dynamic information about the solar wind including data on ion species which are currently difficult to track. It will also make possible remote sensing of the solar wind.

  2. What can be Learned from X-Ray Spectroscopy Concerning Hot Gas in the Local Bubble and Charge Exchange Processes

    NASA Technical Reports Server (NTRS)

    Snowden, Steven L.

    2007-01-01

    Solar wind charge exchange produces diffuse X-ray emission with a variable surface brightness comparable to that of the cosmic background. While the temporal variation of the charge exchange emission allows some separation of the components, there remains a great deal of uncertainty as to the zero level of both. Because the production mechanisms of the two components are considerably different, their spectra would provide critical diagnostics to the understanding of both. However, current X-ray observatories are very limited in both spectral resolution and sensitivity in the critical soft X-ray (less than 1.0 keV) energy range. Non-dispersive high-resolution spectrometers, such as the calorimeter proposed for the Spectrum Roentgen Gamma mission, will be extremely useful in distinguishing the cascade emission of charge exchange from the spectra of thermal bremsstrahlung cosmic plasmas.

  3. Electron optics with p-n junctions in ballistic graphene

    NASA Astrophysics Data System (ADS)

    Chen, Shaowen; Han, Zheng; Elahi, Mirza M.; Habib, K. M. Masum; Wang, Lei; Wen, Bo; Gao, Yuanda; Taniguchi, Takashi; Watanabe, Kenji; Hone, James; Ghosh, Avik W.; Dean, Cory R.

    2016-09-01

    Electrons transmitted across a ballistic semiconductor junction are expected to undergo refraction, analogous to light rays across an optical boundary. In graphene, the linear dispersion and zero-gap band structure admit highly transparent p-n junctions by simple electrostatic gating. Here, we employ transverse magnetic focusing to probe the propagation of carriers across an electrostatically defined graphene junction. We find agreement with the predicted Snell’s law for electrons, including the observation of both positive and negative refraction. Resonant transmission across the p-n junction provides a direct measurement of the angle-dependent transmission coefficient. Comparing experimental data with simulations reveals the crucial role played by the effective junction width, providing guidance for future device design. Our results pave the way for realizing electron optics based on graphene p-n junctions.

  4. Studies of silicon p-n junction solar cells

    NASA Technical Reports Server (NTRS)

    Neugroschel, A.; Lindholm, F. A.

    1979-01-01

    To provide theoretical support for investigating different ways to obtain high open-circuit voltages in p-n junction silicon solar cells, an analytical treatment of heavily doped transparent-emitter devices is presented that includes the effects of bandgap narrowing, Fermi-Dirac statistics, a doping concentration gradient, and a finite surface recombination velocity at the emitter surface. Topics covered include: (1) experimental determination of bandgap narrowing in the emitter of silicon p-n junction devices; (2) heavily doped transparent regions in junction solar cells, diodes, and transistors; (3) high-low-emitter solar cell; (4) determination of lifetimes and recombination currents in p-n junction solar cells; (5) MOS and oxide-charged-induced BSF solar cells; and (6) design of high efficiency solar cells for space and terrestrial applications.

  5. Bounds on the Information Carrying Capacity of Pn Waves

    SciTech Connect

    Harris, D B

    2008-12-01

    Upper and lower bounds on the capacity of the Pn wave to transmit information about source identity are developed using models and measurements of Pn spatial signal structure across the ARCES array. The results show a very significant increase in information carrying capacity when contrasting observed propagation conditions with idealized free-space propagation. In essence, scattering greatly increases Pn channel capacity. As shown in a previous contribution, this increase in information can be captured with matched field calibrations and exploited to resolve sources more closely spaced than the Rayleigh resolution limit. These results mirror practices in cellular telephones that use arrays at the transmitter and receiver to exploit scattering for increased channel capacity.

  6. Optoelectronics with electrically tunable PN diodes in monolayer WSe2

    NASA Astrophysics Data System (ADS)

    Churchill, Hugh; Baugher, Britton; Yang, Yafang; Jarillo-Herrero, Pablo

    2014-03-01

    We describe the transport and optoelectronic behavior of ambipolar monolayer WSe2 devices in which two local gates are used to define a PN junction exclusively within the sheet of WSe2. With these electrically tunable PN junctions, we demonstrate both PN and NP diodes with ideality factors better than 2. Under excitation with light, the diodes show photodetection responsivity of 210 mA/W and photovoltaic power generation with a peak external quantum efficiency of 0.2%, promising numbers for a nearly transparent monolayer sheet in a lateral device geometry. Finally, we demonstrate a light-emitting diode based on monolayer WSe2. These devices provide a fundamental building block for ultra-thin, flexible, and nearly transparent optoelectronic and electronic applications based on ambipolar dichalcogenide materials.

  7. Stability of two-dimensional PN monolayer sheets and their electronic properties.

    PubMed

    Ma, ShuangYing; He, Chaoyu; Sun, L Z; Lin, Haiping; Li, Youyong; Zhang, K W

    2015-12-21

    Three two-dimensional phosphorus nitride (PN) monolayer sheets (named as α-, β-, and γ-PN, respectively) with fantastic structures and properties are predicted based on first-principles calculations. The α-PN and γ-PN have a buckled structure, whereas β-PN shows puckered characteristics. Their unique structures endow these atomic PN sheets with high dynamic stabilities and anisotropic mechanical properties. They are all indirect semiconductors and their band gap sensitively depends on the in-plane strain. Moreover, the nanoribbons patterned from these three PN monolayers demonstrate a remarkable quantum size effect. In particular, the zigzag α-PN nanoribbon shows size-dependent ferromagnetism. Their significant properties show potential in nano-electronics. The synthesis of the three phases of the PN monolayer sheet is proposed theoretically, which is deserving of further study in experiments.

  8. The 'depletion layer' of amorphous p-n junctions

    NASA Technical Reports Server (NTRS)

    Von Roos, O.

    1981-01-01

    It is shown that within reasonable approximations for the density of state distribution within the mobility gap of a:Si, a one-to-one correspondence exists between the electric field distribution in the transition region of an amorphous p-n junction and that in the depletion layer of a crystalline p-n junction. Thus it is inferred that the depletion layer approximation which leads to a parabolic potential distribution within the depletion layer of crystalline junctions also constitutes a fair approximation in the case of amorphous junctions. This fact greatly simplifies an analysis of solid-state electronic devices based on amorphous material (i.e., solar cells).

  9. Efficacy of the anti-Candida rAls3p-N or rAls1p-N vaccines against disseminated and mucosal candidiasis.

    PubMed

    Spellberg, Brad J; Ibrahim, Ashraf S; Avanesian, Valentina; Fu, Yue; Myers, Carter; Phan, Quynh T; Filler, Scott G; Yeaman, Michael R; Edwards, John E

    2006-07-15

    We have shown that vaccination with the recombinant N terminus of Als1p (rAls1p-N) protects mice against disseminated and oropharyngeal candidiasis. We now report that vaccination of mice with a related candidate, rAls3p-N, induces a broader antibody response than rAls1p-N and a similar cell-mediated immune response. The rAls3p-N vaccine was equally as effective as rAls1p-N against disseminated candidiasis but was more effective than rAls1p-N against oropharyngeal or vaginal candidiasis. Antibody titers did not correlate with protection against disseminated candidiasis, but delayed-type hypersensitivity did. The rAls3p-N vaccine is a promising new vaccine candidate for further exploration to prevent systemic and mucosal candidal infections.

  10. The emergence of online learning in PN Education.

    PubMed

    Hopkins, David D

    2008-01-01

    For the fifth year in a row the online learning sector outpaced growth rates of the traditional classroom. Online learning continues to garner increasing levels of positive support from administrators, employers, and students who value the option of online education at increasingly greater levels. PN Education has largely remained on the sidelines of this revolution. However, with the nursing crisis growing, students, governments, and institutions demanding more access and convenience to educational options, and the emergence of the Millennial Generation making up the majority of the students, the time has come for PN programs to embrace the potential of online learning. With its diverse mix of didactic, clinical, and lab requirements, PN education is ideally suited for the newest evolution of online delivery-Blended Learning 2.0. This paper will analyze in detail the overall state of affairs of online learning, especially as it pertains to educating the next generation of practical nurses, and finally to provide an overview of the key components of a quality online program in PN Education.

  11. The Oklahoma PN/ADN Articulation Project Report.

    ERIC Educational Resources Information Center

    Oklahoma State Regents for Higher Education, Oklahoma City.

    In response to a critical nursing shortage in the state of Oklahoma, the Oklahoma Practical Nursing (PN)/Associate Degree Nursing (ADN) Articulation Project Coordinating Committee was formed in spring 1990 to develop a proposal for program articulation. A curriculum matrix was designed and adopted for use by five regional subcommittees which…

  12. The Involvement of Protease Nexin-1 (PN1) in the Pathogenesis of Intervertebral Disc (IVD) Degeneration

    PubMed Central

    Wu, Xinghuo; Liu, Wei; Duan, Zhenfeng; Gao, Yong; Li, Shuai; Wang, Kun; Song, Yu; Shao, Zengwu; Yang, Shuhua; Yang, Cao

    2016-01-01

    Protease nexin-1 (PN-1) is a serine protease inhibitor belonging to the serpin superfamily. This study was undertaken to investigate the regulatory role of PN-1 in the pathogenesis of intervertebral disk (IVD) degeneration. Expression of PN-1 was detected in human IVD tissue of varying grades. Expression of both PN-1 mRNA and protein was significantly decreased in degenerated IVD, and the expression levels of PN-1 were correlated with the grade of disc degeneration. Moreover, a decrease in PN-1 expression in primary NP cells was confirmed. On induction by IL-1β, the expression of PN-1 in NP cells was decreased at day 7, 14, and 21, as shown by western blot analysis and immunofluorescence staining. PN-1 administration decreased IL-1β-induced MMPs and ADAMTS production and the loss of Agg and Col II in NP cell cultures through the ERK1/2/NF-kB signaling pathway. The changes in PN-1 expression are involved in the pathogenesis of IVD degeneration. Our findings indicate that PN-1 administration could antagonize IL-1β-induced MMPs and ADAMTS, potentially preventing degeneration of IVD tissue. This study also revealed new insights into the regulation of PN-1 expression via the ERK1/2/NF-kB signaling pathway and the role of PN-1 in the pathogenesis of IVD degeneration. PMID:27460424

  13. Measurement of χcj decaying into pn̄π⁻ and pn̄π⁻π⁰

    SciTech Connect

    Ablikim, M.; Achasov, M. N.; Albayrak, O.; Ambrose, D. J.; An, F. F.; An, Q.; Bai, J. Z.; Ban, Y.; Becker, J.; Bennett, J. V.; Bertani, M.; Bian, J. M.; Boger, E.; Bondarenko, O.; Boyko, I.; Briere, R. A.; Bytev, V.; Cai, X.; Cakir, O.; Calcaterra, A.; Cao, G. F.; Cetin, S. A.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, X.; Chen, Y. B.; Cheng, H. P.; Chu, Y. P.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J. P.; Dedovich, D.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; Ding, W. M.; Ding, Y.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Fang, J.; Fang, S. S.; Fava, L.; Feldbauer, F.; Feng, C. Q.; Ferroli, R. B.; Fu, C. D.; Fu, J. L.; Gao, Y.; Geng, C.; Goetzen, K.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, Y. P.; Han, Y. L.; Harris, F. A.; He, K. L.; He, M.; He, Z. Y.; Held, T.; Heng, Y. K.; Hou, Z. L.; Hu, H. M.; Hu, T.; Huang, G. M.; Huang, G. S.; Huang, J. S.; Huang, X. T.; Huang, Y. P.; Hussain, T.; Ji, C. S.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.; Jiang, L. L.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Jing, F. F.; Kalantar-Nayestanaki, N.; Kavatsyuk, M.; Kuehn, W.; Lai, W.; Lange, J. S.; Li, C. H.; Li, Cheng; Li, Cui; Li, D. M.; Li, F.; Li, G.; Li, H. B.; Li, J. C.; Li, K.; Li, Lei; Li, Q. J.; Li, S. L.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, X. R.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Liao, X. T.; Liu, B. J.; Liu, C. L.; Liu, C. X.; Liu, C. Y.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H.; Liu, H. H.; Liu, H. M.; Liu, H. W.; Liu, J. P.; Liu, K. Y.; Liu, Kai; Liu, P. L.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, Y. B.; Liu, Z. A.; Liu, Zhiqiang; Liu, Zhiqing; Loehner, H.; Lu, G. R.; Lu, H. J.; Lu, J. G.; Lu, Q. W.; Lu, X. R.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lv, M.; Ma, C. L.; Ma, F. C.; Ma, H. L.; Ma, Q. M.; Ma, S.; Ma, T.; Ma, X. Y.; Ma, Y.; Maas, F. E.; Maggiora, M.; Malik, Q. A.; Mao, Y. J.; Mao, Z. P.; Messchendorp, J. G.; Min, J.; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Morales Morales, C.; Motzko, C.; Muchnoi, N. Yu.; Muramatsu, H.; Nefedov, Y.; Nicholson, C.; Nikolaev, I. B.; Ning, Z.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Park, J. W.; Pelizaeus, M.; Peng, H. P.; Peters, K.; Ping, J. L.; Ping, R. G.; Poling, R.; Prencipe, E.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, X. S.; Qin, Y.; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Rong, G.; Ruan, X. D.; Sarantsev, A.; Schaefer, B. D.; Schulze, J.; Shao, M.; Shen, C. P.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, X. Y.; Spataro, S.; Spruck, B.; Sun, D. H.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tapan, I.; Thorndike, E. H.; Toth, D.; Ullrich, M.; Varner, G. S.; Wang, B.; Wang, B. Q.; Wang, D.; Wang, D. Y.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q.; Wang, Q. J.; Wang, S. G.; Wang, X. L.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. Y.; Wei, D. H.; Wei, J. B.; Weidenkaff, P.; Wen, Q. G.; Wen, S. P.; Werner, M.; Wiedner, U.; Wu, L. H.; Wu, N.; Wu, S. X.; Wu, W.; Wu, Z.; Xia, L. G.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, G. M.; Xu, H.; Xu, Q. J.; Xu, X. P.; Xu, Z. R.; Xue, F.; Xue, Z.; Yan, L.; Yan, W. B.; Yan, Y. H.; Yang, H. X.; Yang, Y.; Yang, Y. X.; Ye, H.; Ye, M.; Ye, M. H.; Yu, B. X.; Yu, C. X.; Yu, H. W.; Yu, J. S.; Yu, S. P.; Yuan, C. Z.; Yuan, Y.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, S. H.; Zhang, X. J.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Y. S.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, H. S.; Zhao, J. W.; Zhao, K. X.; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, Q. Z.; Zhao, S. J.; Zhao, T. C.; Zhao, X. H.; Zhao, Y. B.; Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, Y. H.; Zhong, B.; Zhong, J.; Zhong, Z.; Zhou, L.; Zhou, X. K.; Zhou, X. R.; Zhu, C.; Zhu, K.; Zhu, K. J.; Zhu, S. H.; Zhu, X. L.; Zhu, Y. C.; Zhu, Y. M.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zou, B. S.; Zou, J. H.

    2012-09-26

    Using a data sample of 1.06×10⁸ ψ' events collected with the BESIII detector in 2009, the branching fractions of χcJpn̄π⁻ and χcJpn̄π⁻π⁰ (J=0, 1, 2) are measured. (Throughout the text, inclusion of charge conjugate modes is implied if not stated otherwise.) The results for χc⁰pn̄π⁻ and χpn̄π⁻ are consistent with, but much more precise than, those of previous measurements. The decays of χc1pn̄π⁻ and χcJpn̄π⁻π⁰ are observed for the first time.

  14. pN0(i+) Breast Cancer: Treatment Patterns, Locoregional Recurrence, and Survival Outcomes

    SciTech Connect

    Karam, Irene; Lesperance, Maria F.; Berrang, Tanya; Speers, Caroline; Tyldesley, Scott; Truong, Pauline T.

    2013-11-15

    Purpose: To examine treatment patterns, recurrence, and survival outcomes in patients with pN0(i+) breast cancer. Methods and Materials: Subjects were 5999 women with AJCC (6th edition) pT1-3, pN0-N1a, M0 breast cancer diagnosed between 2003 and 2006. Of these, 4342 (72%) had pN0, 96 (2%) had pN0(i+), 349 (6%) had pNmic (micrometastases >0.2 mm to ≤2 mm), and 1212 (20%) had pN1a (1-3 positive macroscopic nodes) disease. Treatment characteristics and 5-year Kaplan-Meier local recurrence, regional recurrence (RR), locoregional recurrence (LRR), and overall survival were compared between nodal subgroups. Multivariable analysis was performed using Cox regression modeling. A 1:3 case-match analysis examined outcomes in pN0(i+) cases compared with pN0 controls matched for similar tumor and treatment characteristics. Results: Median follow-up was 4.8 years. Adjuvant systemic therapy use increased with nodal stage: 81%, 92%, 95%, and 94% in pN0, pN0(i+), pNmic, and pN1a disease, respectively (P<.001). Nodal radiation therapy (RT) use also increased with nodal stage: 1.7% in pN0, 27% in pN0(i+), 33% in pNmic, and 63% in pN1a cohorts (P<.001). Five-year Kaplan-Meier outcomes in pN0 versus pN0(i+) cases were as follows: local recurrence 1.7% versus 3.7% (P=.20), RR 0.5% versus 2.2% (P=.02), and LRR 2.1% versus 5.8% (P=.02). There were no RR events in 26 patients with pN0(i+) disease who received nodal RT and 2 RR events in 70 patients who did not receive nodal RT. On multivariable analysis, pN0(i+) was not associated with worse locoregional control or survival. On case-match analysis, LRR and overall survival were similar between pN0(i+) and matched pN0 counterparts. Conclusions: Nodal involvement with isolated tumor cells is not a significant prognostic factor for LRR or survival in this study's multivariable and case-match analyses. These data do not support the routine use of nodal RT in the setting of pN0(i+) disease. Prospective studies are needed to define optimal

  15. Atomic-scaled characterization of graphene PN junctions

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaodong; Wang, Dennis; Dadgar, Ali; Agnihotri, Pratik; Lee, Ji Ung; Reuter, Mark C.; Ross, Frances M.; Pasupathy, Abhay N.

    Graphene p-n junctions are essential devices for studying relativistic Klein tunneling and the Veselago lensing effect in graphene. We have successfully fabricated graphene p-n junctions using both lithographically pre-patterned substrates and the stacking of vertical heterostructures. We then use our 4-probe STM system to characterize the junctions. The ability to carry out scanning electron microscopy (SEM) in our STM instrument is essential for us to locate and measure the junction interface. We obtain both the topography and dI/dV spectra at the junction area, from which we track the shift of the graphene chemical potential with position across the junction interface. This allows us to directly measure the spatial width and roughness of the junction and its potential barrier height. We will compare the junction properties of devices fabricated by the aforementioned two methods and discuss their effects on the performance as a Veselago lens.

  16. Discovery of a photoresponse amplification mechanism in compensated PN junctions

    SciTech Connect

    Zhou, Yuchun; Rahman, Samia N.; Hall, David; Lo, Yu-Hwa; Liu, Yu-Hsin; Sham, L. J.

    2015-01-19

    We report the experimental evidence of uncovering a photoresponse amplification mechanism in heavily doped, partially compensated silicon p-n junctions under very low bias voltage. We show that the observed photocurrent gain occurs at a bias that is more than an order of magnitude below the threshold voltage for conventional impact ionization. Moreover, contrary to the case of avalanche detectors and p-i-n diodes, the amplified photoresponse is enhanced rather than suppressed with increasing temperature. These distinctive characteristics lead us to hypothesize that the inelastic scattering between energetic electrons (holes) and the ionized impurities in the depletion and charge neutral regions of the p-n junction in a cyclic manner plays a significant role in the amplification process. Such an internal signal amplification mechanism, which occurs at much lower bias than impact ionization and favors room temperature over cryogenic temperature, makes it promising for practical device applications.

  17. Influence of the diffusion geometry on PN integrated varactors

    NASA Astrophysics Data System (ADS)

    García, J.; González, B.; Marrero-Martin, M.; Aldea, I.; del Pino, J.; Hernández, A.

    2007-05-01

    In this work, four different structures based on PN junction are studied. These structures are based on changing the geometry of the p+ diffusion. The designed and fabricated devices will be used like integrated varactors in radiofrequency applications. The measures have been made at frequencies since 500 MHz to 10 GHz, and the influence that diffusion geometry has in the capacitance (C), the quality factor (Q) and the tuning range (TR) have been studied. The pn varactors have been simulated with Taurus Device and have been fabricated in a 0.35um SiGe standard process. In order to obtain better benefits of the varactors, the p + and n + diffusion geometries have been modified. This way, novel structures called crosses, fingers, donuts, and bars have been designed and fabricated. The results of the tuning range have been obtained superior to 40%.

  18. The Discovery of a Bipolar, Rotating, Episodic Jet (BRET) in the Planetary Nebula KjPn 8

    NASA Astrophysics Data System (ADS)

    Lopez, J. A.; Vazquez, R.; Rodriguez, L. F.

    1995-12-01

    A spectacular (~=14' x 4') bipolar nebula, with a symmetric and rotating, high-velocity collimated outflow, with episodic outburst properties, has been discovered in the Cassiopeia-Cepheus region. A compact object classified as the planetary nebula KjPn 8 is located at the center of symmetry of this extraordinary nebula. The angular extent of this bipolar structure is now the largest one known associated with a planetary nebula (PN). A mosaic of H alpha images covering the full extent of the nebula is presented, as well as [N II] lambda 6584, [S II] lambda 6724, [O II] lambda 3729, and [O III] lambda 5007 images of the central (~=5' x 5') region. These images reveal symmetric pairs of bow shocks which are located at different position angles, in a way expected from a rotating, episodic jet. Low-dispersion spectroscopy of regions of the bipolar lobes confirms their shock-excited nature. The core is of low excitation class and seems nitrogen enriched. Our 3.5 cm VLA observations yield a first radio detection of the core of KjPn 8.

  19. PN Initial Data with Waves: Progress in Evolution

    NASA Technical Reports Server (NTRS)

    Kelly, Bernard

    2008-01-01

    In Kelly, Tichy, Campanelli & Whiting Phys. Rev. D vol. 76, 024008 (2007). we presented nonspinning black-hole binary data for numerical relativity, based on solving the constraint equations to 2.5pN order in an ADM-Transverse-Traceless gauge. Here we report on the first steps in evolving this data in full NR. We review the orbital and waveform characteristics, and how these may be improved in future evolutions.

  20. Electrospun Composite Nanofibers of Semiconductive Polymers for Coaxial PN Junctions

    NASA Astrophysics Data System (ADS)

    Serrano, William; Thomas, Sylvia

    The objective of this research is to investigate the conditions under P3HT and Activink, semiconducting polymers, form 1 dimension (1D) coaxial p-n junctions and to characterize their behavior in the presence of UV radiation and organic gases. For the first time, fabrication and characterization of semiconductor polymeric single fiber coaxial arrangements will be studied. Electrospinning, a low cost, fast and reliable method, with a coaxial syringe arrangement will be used to fabricate these fibers. With the formation of fiber coaxial arrangements, there will be investigations of dimensionality crossovers e.g., from one-dimensional (1D) to two-dimensional (2D). Coaxial core/shell fibers have been realized as seen in a recent publication on an electrospun nanofiber p-n heterojunction of oxides (BiFeO3 and TiO2, respectively) using the electrospinning technique with hydrothermal method. In regards to organic semiconducting coaxial p-n junction nanofibers, no reported studies have been conducted, making this study fundamental and essential for organic semiconducting nano devices for flexible electronics and multi-dimensional integrated circuits.

  1. High frequency nanomechanical resonators in ultraclean suspended graphene pn junctions

    NASA Astrophysics Data System (ADS)

    Jung, Minkyung; Rickhaus, Peter; Zihmann, Simon; Makk, Peter; Eichler, Alexander; Weiss, Markus; Schönenberger, Christian; Department of Physics, University of Basel Team; Department of Physics, ETH Zurich Team

    2015-03-01

    Here, we demonstrate high frequency nanomechanical resonators in ultraclean suspended graphene pn junctions. The suspended graphene resonators are fabricated on two bottom gates (left and right) covered with lift-off resist (LOR) by using a mechanical transfer technique. After current annealing, the device exhibits a clear charge neutrality point around zero gate voltage. Depending on the left and right bottom gate voltages, the device shows four different conductance regimes: pp, nn, np and pn corresponding to two different carrier types in the two sides of the sample. At pn and np regimes, the clear Fabry-Perot interference pattern is observed, indicating ballistic transport behavior over 1 μm-long channel. Then, the mechanical resonance is measured in the same device with a frequency modulation (FM) mixing technique at 4.2 K in the vacuum chamber. The resonance frequency is about 405 MHz. By fitting resonance frequency, we deduce both the mass density and the built-in tension in the graphene sheet. In a similar device structure with different strain environment, we observe a resonance frequency as high as 1.17 GHz for the fundamental mode.

  2. Extending the dynamic range of fully depleted pnCCDs

    NASA Astrophysics Data System (ADS)

    Schmidt, J.; Hartmann, R.; Holl, P.; Huth, M.; Lutz, G.; Ryll, H.; Send, S.; Simson, M.; Steigenhöfer, D.; Soltau, J.; Soltau, H.; Strüder, L.

    2014-10-01

    pnCCDs are a special type of charge coupled devices (CCD) which were originally developed for applications in X-ray astronomy. At X-ray Free Electron Lasers (XFEL) pnCCDs are used as imaging X-ray spectrometers due to their outstanding characteristics like high readout speed, high and homogeneous quantum efficiency, low readout noise, radiation hardness and high pixel charge handling capacity. They can be used both as single-photon counting detectors for X-ray spectroscopy and as integrating detectors for X-ray imaging with count rates up to 104 photons of 1 keV per pixel and frame. However, extremely high photon intensities can result in pixel saturation and charge spilling into neighboring pixels. Because of this charge blooming effect, spatial information is reduced. Based on our research concerning the internal potential distribution we can enhance the pixel full well capacity even more and improve the quality of the image. This paper describes the influence of the operation voltages and space charge distribution of the pnCCD on the electric potential profile by using 2D numerical device simulations. Experimental results with signal injection from an optical laser confirm the simulation models.

  3. Prognostic Value of Preoperative Serum Levels of Periostin (PN) in Early Breast Cancer (BCa).

    PubMed

    Nuzzo, Pier Vitale; Rubagotti, Alessandra; Argellati, Francesca; Di Meglio, Antonio; Zanardi, Elisa; Zinoli, Linda; Comite, Paola; Mussap, Michele; Boccardo, Francesco

    2015-01-01

    PN is a secreted cell adhesion protein critical for carcinogenesis. Elevated serum levels of PN have been implicated as playing an important role in different types of cancer, and a few reports suggest a potential role as a prognostic marker. We evaluated the prognostic significance of preoperative serum PN concentration in patients with BCa receiving curative surgery. Enzyme-Linked Immunosorbent Assay (ELISA) was performed to determine the preoperative serum PN level in 182 patients. The correlations between serum PN concentration with clinical pathological features and PN expression in primary tumor samples were analyzed. The prognostic impact of serum PN levels with all-cause and BCa-specific mortality was also investigated. Appropriate statistics were used. Elevated serum PN levels were significantly associated with patient age (p = 0.005), adjuvant systemic therapy (p = 0.04) and progesterone receptor (PgR) status (p = 0.02). No correlation between PN preoperative serum levels and other clinical-pathological parameters, including either the epithelial or the stromal PN expression of primary tumor or the combination of the two, was found. Similarly, no association between serum PN levels and either all-cause or BCa-specific mortality was found. However, subgroup analysis revealed a correlation between higher PN serum levels and all-cause mortality in patients with node-negative disease (p = 0.05) and in those with a low PgR expression (p = 0.03). Higher levels of serum PN were also found to correlate with BCa-specific mortality in the subgroup of patients who did not receive any adjuvant systemic therapy (p = 0.04). Our findings suggest that PN was detectable in the serum of early BCa patients before surgery and increased base-line serum levels predicted worse long-term survival outcomes in specific subgroups of patients.

  4. ZnO PN Junctions for Highly-Efficient, Low-Cost Light Emitting Diodes

    SciTech Connect

    David P. Norton; Stephen Pearton; Fan Ren

    2007-09-30

    By 2015, the US Department of Energy has set as a goal the development of advanced solid state lighting technologies that are more energy efficient, longer lasting, and more cost-effective than current technology. One approach that is most attractive is to utilize light-emitting diode technologies. Although III-V compound semiconductors have been the primary focus in pursuing this objective, ZnO-based materials present some distinct advantages that could yield success in meeting this objective. As with the nitrides, ZnO is a direct bandgap semiconductor whose gap energy (3.2 eV) can be tuned from 3.0 to 4 eV with substitution of Mg for higher bandgap, Cd for lower bandgap. ZnO has an exciton binding energy of 60 meV, which is larger than that for the nitrides, indicating that it should be a superior light emitting semiconductor. Furthermore, ZnO thin films can be deposited at temperatures on the order of 400-600 C, which is significantly lower than that for the nitrides and should lead to lower manufacturing costs. It has also been demonstrated that functional ZnO electronic devices can be fabricated on inexpensive substrates, such as glass. Therefore, for the large-area photonic application of solid state lighting, ZnO holds unique potential. A significant impediment to exploiting ZnO in light-emitting applications has been the absence of effective p-type carrier doping. However, the recent realization of acceptor-doped ZnO material overcomes this impediment, opening the door to ZnO light emitting diode development In this project, the synthesis and properties of ZnO-based pn junctions for light emitting diodes was investigated. The focus was on three issues most pertinent to realizing a ZnO-based solid state lighting technology, namely (1) achieving high p-type carrier concentrations in epitaxial and polycrystalline films, (2) realizing band edge emission from pn homojunctions, and (3) investigating pn heterojunction constructs that should yield efficient light

  5. Gd4Ge(3-x)Pn(x) (Pn = P, Sb, Bi, x = 0.5-3): stabilizing the nonexisting Gd4Ge3 binary through valence electron concentration. Electronic and magnetic properties of Gd4Ge(3-x)Pn(x).

    PubMed

    Cheung, Yan Yin Janice; Svitlyk, Volodymyr; Mozharivskyj, Yurij

    2012-10-01

    Gd(4)Ge(3-x)Pn(x) (Pn = P, Sb, Bi; x = 0.5-3) phases have been prepared and characterized using X-ray diffraction, wavelength-dispersive spectroscopy, and magnetization measurements. All Gd(4)Ge(3-x)Pn(x) phases adopt a cubic anti-Th(3)P(4) structure, and no deficiency on the Gd or p-element site could be detected. Only one P-containing phase with the Gd(4)Ge(2.51(5))P(0.49(5)) composition could be obtained, as larger substitution levels did not yield the phase. Existence of Gd(4)Ge(2.51(5))P(0.49(5)) and Gd(4)Ge(2.49(3))Bi(0.51(3)) suggests that the hypothetical Gd(4)Ge(3) binary can be easily stabilized by a small increase in the valence electron count and that the size of the p element is not a key factor. Electronic structure calculations reveal that large substitution levels with more electron-rich Sb and Bi are possible for charge-balanced (Gd(3+))(4)(Ge(4-))(3) as extra electrons occupy the bonding Gd-Gd and Gd-Ge states. This analysis also supports the stability of Gd(4)Sb(3) and Gd(4)Bi(3). All Gd(4)Ge(3-x)Pn(x) phases order ferromagnetically with relatively high Curie temperatures of 234-356 K. The variation in the Curie temperatures of the Gd(4)Ge(3-x)Sb(x) and Gd(4)Ge(3-x)Bi(x) series can be explained through the changes in the numbers of conduction electrons associated with Ge/Sb(Bi) substitution.

  6. Structural and thermoelectric properties of zintl-phase CaLiPn (Pn=As, Sb, Bi)

    NASA Astrophysics Data System (ADS)

    Chandran, Anoop K.; Gudelli, Vijay Kumar; Sreeparvathy, P. C.; Kanchana, V.

    2016-11-01

    First-principles calculations were carried out to study the structural, mechanical, dynamical and transport properties of zintl phase materials CaLiPn (Pn=As, Sb and Bi). We have used two different approaches to solve the system based on density functional theory. The plane wave pseudopotential approach has been used to study the structural and dynamical properties whereas, full potential linear augment plane wave method is used to examine the electronic structure, mechanical and thermoelectric properties. The calculated ground-state properties agree quite well with experimental values. The computed electronic structure shows the investigated compounds to be direct band gap semiconductors. Further, we have calculated the thermoelectric properties of all the investigated compounds for both the carriers at various temperatures. We found a high thermopower for both the carriers, especially n-type doping to be more favourable, which enabled us to predict that CaLiPn might have promising applications as a good thermoelectric material. Further, the phonon dispersion curves of the investigated compounds showed flat phonon modes and we also find lower optical and acoustic modes to cut each other at the lower frequency range, which further indicate the investigated compounds to possess reasonably low thermal conductivity. We have also analysed the low value of the thermal conductivity through the empirical relations and discussions are presented here.

  7. Results of a real-time irradiation of lithium P/N and conventional N/P silicon solar cells.

    NASA Technical Reports Server (NTRS)

    Reynard, D. L.; Peterson, D. G.

    1972-01-01

    Eight types of lithium-diffused P/N and three types of conventional 10 ohm-cm N/P silicon solar cells were irradiated at four different temperatures with a strontium-90 radioisotope at a rate typical of that expected in earth orbit. The six-month irradiation confirmed earlier accelerator results, showed that certain cell types outperform others at the various temperatures, and, in general, verified the recent improvements and potential usefulness of lithium solar cells. The experimental approach and statistical methods and analyses employed yielded increased confidence in the validity of the results. Injection level effects were observed to be significant.

  8. Experimental study of exclusive $^2$H$(e,e^\\prime p)n$ reaction mechanisms at high $Q^2$

    SciTech Connect

    Kim Egiyan; Gegham Asryan; Nerses Gevorgyan; Keith Griffioen; Jean Laget; Sebastian Kuhn; Gary Adams; Moscov Amaryan; Pawel Ambrozewicz; Marco Anghinolfi; Gerard Audit; Harutyun AVAKIAN; Harutyun Avakian; Hovhannes Baghdasaryan; Nathan Baillie; Jacques Ball; Nathan Baltzell; Steve Barrow; Vitaly Baturin; Marco Battaglieri; Ivan Bedlinski; Ivan Bedlinskiy; Mehmet Bektasoglu; Matthew Bellis; Nawal Benmouna; Barry Berman; Angela Biselli; Lukasz Blaszczyk; Sylvain Bouchigny; Sergey Boyarinov; Robert Bradford; Derek Branford; William Briscoe; William Brooks; Stephen Bueltmann; Volker Burkert; Cornel Butuceanu; John Calarco; Sharon Careccia; Daniel Carman; Antoine Cazes; Shifeng Chen; Philip Cole; Patrick Collins; Philip Coltharp; Dieter Cords; Pietro Corvisiero; Donald Crabb; Volker Crede; John Cummings; Natalya Dashyan; Rita De Masi; Raffaella De Vita; Enzo De Sanctis; Pavel Degtiarenko; Haluk Denizli; Lawrence Dennis; Alexandre Deur; Kahanawita Dharmawardane; Richard Dickson; Chaden Djalali; Gail Dodge; Joseph Donnelly; David Doughty; Michael Dugger; Steven Dytman; Oleksandr Dzyubak; Hovanes Egiyan; Lamiaa Elfassi; Latifa Elouadrhiri; Paul Eugenio; Renee Fatemi; Gleb Fedotov; Gerald Feldman; Robert Feuerbach; Robert Fersch; Michel Garcon; Gagik Gavalian; Gerard Gilfoyle; Kevin Giovanetti; Francois-Xavier Girod; John Goetz; Atilla Gonenc; Christopher Gordon; Ralf Gothe; Michel Guidal; Matthieu Guillo; Hayko Guler; Lei Guo; Vardan Gyurjyan; Cynthia Hadjidakis; Kawtar Hafidi; Hayk Hakobyan; Rafael Hakobyan; Charles Hanretty; John Hardie; F. Hersman; Kenneth Hicks; Ishaq Hleiqawi; Maurik Holtrop; Charles Hyde-Wright; Yordanka Ilieva; David Ireland; Boris Ishkhanov; Eugeny Isupov; Mark Ito; David Jenkins; Hyon-Suk Jo; Kyungseon Joo; Henry Juengst; Narbe Kalantarians; James Kellie; Mahbubul Khandaker; Wooyoung Kim; Andreas Klein; Franz Klein; Alexei Klimenko; Mikhail Kossov; Zebulun Krahn; Laird Kramer; V. Kubarovsky; Joachim Kuhn; Sergey Kuleshov; Jeff Lachniet; Jorn Langheinrich; David Lawrence; Ji Li; Kenneth Livingston; Haiyun Lu; Marion MacCormick; Claude Marchand; Nikolai Markov; Paul Mattione; Simeon McAleer; Bryan McKinnon; John McNabb; Bernhard Mecking; Surik Mehrabyan; Joseph Melone; Mac Mestayer; Curtis Meyer; Tsutomu Mibe; Konstantin Mikhaylov; Ralph Minehart; Marco Mirazita; Rory Miskimen; Viktor Mokeev; Kei Moriya; Steven Morrow; Maryam Moteabbed; James Mueller; Edwin Munevar Espitia; Gordon Mutchler; Pawel Nadel-Turonski; Rakhsha Nasseripour; Silvia Niccolai; Gabriel Niculescu; Maria-Ioana Niculescu; Bogdan Niczyporuk; Megh Niroula; Rustam Niyazov; Mina Nozar; Grant O'Rielly; Mikhail Osipenko; Alexander Ostrovidov; Kijun Park; Evgueni Pasyuk; Craig Paterson; Sergio Pereira; Joshua Pierce; Nikolay Pivnyuk; Dinko Pocanic; Oleg Pogorelko; Sergey Pozdnyakov; Barry Preedom; John Price; Yelena Prok; Dan Protopopescu; Brian Raue; Gregory Riccardi; Giovanni Ricco; Marco Ripani; Barry Ritchie; Federico Ronchetti; Guenther Rosner; Patrizia Rossi; Franck Sabatie; Julian Salamanca; Carlos Salgado; Joseph Santoro; Vladimir Sapunenko; Reinhard Schumacher; Vladimir Serov; Youri Sharabian; Nikolay Shvedunov; Alexander Skabelin; Elton Smith; Lee Smith; Daniel Sober; Daria Sokhan; Aleksey Stavinskiy; Samuel Stepanyan; Stepan Stepanyan; Burnham Stokes; Paul Stoler; Steffen Strauch; Mauro Taiuti; David Tedeschi; Ulrike Thoma; Avtandil Tkabladze; Svyatoslav Tkachenko; Luminita Todor; Clarisse Tur; Maurizio Ungaro; Michael Vineyard; Alexander Vlassov; Daniel Watts; Lawrence Weinstein; Dennis Weygand; M. Williams; Elliott Wolin; Michael Wood; Amrit Yegneswaran; Lorenzo Zana; Jixie Zhang; Bo Zhao; Zhiwen Zhao

    2007-06-01

    The reaction {sup 2}H(e,e{prime} p)n has been studied with full kinematic coverage for photon virtuality 1.75 < 5.5 {approx} GeV{sup 2}. Comparisons of experimental data with theory indicate that for very low values of neutron recoil momentum (p{sub n} < 100 MeV/c) the neutron is primarily a spectator and the reaction can be described by the plane-wave impulse approximation. For 100 < 750 MeV/c proton-neutron rescattering dominates the cross section, while {Delta} production followed by the N{Delta} {yields} NN transition is the primary contribution at higher momenta.

  9. Development of Prevotella nigrescens-specific PCR primers based on the nucleotide sequence of a Pn23 DNA probe.

    PubMed

    Kim, Min Jung; Lee, Young-Seok; Park, Jae-Yoon; Kook, Joong-Ki

    2011-02-01

    A previous study reported the cloning of a putative Prevotella nigrescens-specific DNA probe, Pn23, using random shotgun method. The present study evaluated the species-specificity of Pn23 for P. nigrescens using the clinical strains of Prevotella intermedia and P. nigrescens to develop P. nigrescens-specific polymerase chain reaction (PCR) primers. Southern blot analysis showed that the DNA probe, Pn23, detected only the genomic DNA of P. nigrescens strains. PCR showed that the two sets of PCR primers, Pn23-F1/Pn23-R1 and Pn23-F2/Pn23-R2, had species-specificity for P. nigrescens. Interestingly, the two sets of PCR primers, Pn23-F6/Pn23-R6 and Pn23-F7/Pn23-R7, had strain-specificity for P. nigrescens ATCC 33563. The detection limits of the four primer sets were 40 or 4 pg of the purified genomic DNA of P. nigrescens ATCC 33563. These results suggest that the DNA probe, Pn23, and the two sets of PCR primers, Pn23-F1/Pn23-R1 and Pn23-F2/Pn23-R2, can be useful for the detection of P. nigrescens in the molecular epidemiological studies of oral infectious diseases. PMID:21184839

  10. The 2.5PN gravitational wave polarizations from inspiralling compact binaries in circular orbits

    NASA Astrophysics Data System (ADS)

    Arun, K. G.; Blanchet, Luc; Iyer, Bala R.; Qusailah, Moh'd. S. S.

    2004-08-01

    Using the multipolar post-Minkowskian and matching formalism, we compute the gravitational wave form of inspiralling compact binaries moving in quasi-circular orbits at the second and a half post-Newtonian (2.5PN) approximation to general relativity. The inputs we use include notably the mass-type quadrupole at the 2.5PN order, the mass octupole and current quadrupole at the 2PN order, the mass 25-pole and current 24-pole at 1PN. The nonlinear hereditary terms come from the monopole quadrupole multipole interactions or tails, present at the 1.5PN, 2PN and 2.5PN orders, and the quadrupole quadrupole interaction arising at the 2.5PN level. In particular, the specific effect of nonlinear memory is computed using a simplified model of binary evolution in the past. The 'plus' and 'cross' wave polarizations at the 2.5PN order are obtained in ready-to-use form, extending the 2PN results calculated earlier by Blanchet, Iyer, Will and Wiseman.

  11. Eccentric orbit E/IMRI gravitational wave fluxes to 7PN order

    NASA Astrophysics Data System (ADS)

    Forseth, Erik; Evans, Charles R.; Hopper, Seth

    2016-03-01

    Knowledge of gravitational wave fluxes (energy and angular momentum, at both infinity and the horizon) from eccentric-orbit inspirals is extended from 3PN to 7PN order at lowest order in small mass ratio. Previous post-Newtonian eccentric-orbit results up to 3PN relative order are confirmed by our new black hole perturbation calculations. The calculations are based on Mano, Suzuki, and Takasugi (MST) analytic function expansions, and results are computed to 200 decimal places of accuracy using Mathematica. Over 1,700 distinct orbits were computed, each with as many as 7,000 Fourier-harmonic modes. A large number of PN coefficients between 3.5PN and 7PN orders were determined, either in exact analytic form or with accurate numerical values, in expansions in powers of a PN compactness parameter and its logarithm, and powers of eccentricity. We show a parametrization that removes singularities in the fluxes as the eccentricity approaches unity, thus making the expansions more convergent at high eccentricity. We also found (nearly) arbitrarily accurate expansions for the previously discussed 1.5PN, 2.5PN, and 3PN hereditary terms.

  12. Trees increase their P:N ratio with size

    PubMed Central

    Sardans, J; Peñuelas, J.

    2015-01-01

    Aim Phosphorus (P) tends to become limiting in aging terrestrial ecosystems, and its resorption efficiency is higher than for other elements such as nitrogen (N). We thus hypothesized that trees should store more P than those other elements such as N when tree size increases and that this process should be enhanced in slow-growing late successional trees. Location Catalan forests. Methods We have used data from the Catalan Forest Inventory that contains field data of the P and N contents of total aboveground, foliar and woody biomasses of the diverse Mediterranean, temperate and alpine forests of Catalonia (1018 sites). We used correlation and general lineal models (GLM) to analyze the allometric relationships between nutrient contents of different aboveground biomass fractions (foliar, branches and stems) and total aboveground biomass. Results Aboveground forest P content increases proportionally more than aboveground forest N content with increasing aboveground biomass. Two mechanisms underlie this. First, woody biomass increases proportionally more than foliar biomass having woody biomass higher P:N ratio than foliar biomass. Second, wood P:N ratio increases with tree size. These results are consistent with the generally higher foliar resorption of P than of N. Slow-growing species accumulate more P in total aboveground with size than fast-growing species mainly as a result of their large capacity to store P in wood. Main conclusions Trees may have thus developed long-term adaptive mechanisms to store P in biomass, mainly in wood, thereby slowing the loss of P from the ecosystems, reducing its availability for competitors, and implying an increase in the P:N ratio in forest biomass with aging. This trend to accumulate more P than N with size is more accentuated in slow-growing, large, long-living species of late successional stages. This way they partly counterbalance the gradual decrease of P in the soil. PMID:25983656

  13. Pn anisotropic tomography under the entire Tienshan orogenic belt

    NASA Astrophysics Data System (ADS)

    Zhou, Zhigang; Lei, Jianshe

    2015-11-01

    We present a new anisotropic tomography of the uppermost mantle under the Tienshan orogenic belt and surrounding regions using a number of Pn arrival-time data hand-picked from portable seismic stations and chosen from the Xinjiang provincial observation bulletins and the EHB datasets. Our results exhibit prominent lateral heterogeneities in the study region. Distinct low-velocity anomalies are visible under the tectonically active regions, such as the Tienshan orogenic belt and western Kunlun Mountains, whereas pronounced high-velocity anomalies are imaged beneath the stable blocks, such as the Kazakh shield, the Junggar, Tarim, Qaidam, and Turpan-Hami basins, and the Tajik depression. Most strong earthquakes (Ms > 7.0) are mainly distributed along the transition zone of high to low velocity anomalies, suggesting a possible correlation between the strong earthquakes and the upper mantle structure. The fast directions of Pn anisotropy beneath the Tienshan orogenic belt are generally parallel to its striking orientation, whereas those beneath Pamir show a northward arc-shaped distribution. The Pn fast-velocity directions on the boundaries of the Kazakh shield and the Tarim and Junngar basins are approximately perpendicular to the strike of the Tienshan orogenic belt. By integrating with previous findings, our results suggest that the Tarim and Kazakh lithospheric materials could have underthrusted beneath the Tienshan orogenic belt that leads to the hot mantle material upwelling under the Tienshan orogenic belt, which is attributable to the Indo-Asian collision. These dynamic processes could play important roles in the Tienshan mountain building.

  14. Reflecting boundary conditions for graded p-n junctions

    NASA Technical Reports Server (NTRS)

    Schacham, S. E.

    1990-01-01

    In a graded junction, the formalism for handling reflecting boundary conditions must be modified. Since a significant drift term is present, zero recombination velocity at the surface does not imply a zero excess carrier gradient but rather zero overall flux. A model for analyzing p-n junctions fabricated by implantation or diffusion is presented, assuming the dominant recombination mechanism in the graded region is Auger. The model enables optimization of diode design. By proper selection of parameters, mainly by reducing surface concentration or by increasing the steepness of the dopant profile, it is possible to drastically reduce the saturation current generated by the graded region.

  15. Photocurrent generation efficiency of a carbon nanotube pn junction

    NASA Astrophysics Data System (ADS)

    McCulley, Daniel; Aspitarte, Lee; Minot, Ethan

    Carrier multiplication effects can enhance the quantum efficiency of photovoltaic devices. For example, quantum dot solar cells have demonstrated photon-to-electron conversion efficiencies greater than 100% when photon energies exceed twice the band gap. Carbon nanotube photodiodes exhibit carrier multiplication effects (Gabor et al., Science 2009), but the quantum efficiency of such photodiodes has not previously been characterized. We have reproduced the carrier multiplication phenomena in individual CNT pn junctions and investigated the conditions under which it occurs. We will present early results quantifying the internal quantum efficiency of the process.

  16. A transparent ultraviolet triggered amorphous selenium p-n junction

    SciTech Connect

    Saito, Ichitaro; Soga, Kenichi; Overend, Mauro; Amaratunga, Gehan A. J.; Miyazaki, Wataru; Onishi, Masanori; Masuzawa, Tomoaki; Okano, Ken; Kudo, Yuki; Yamada, Takatoshi; Koh, Angel; Chua, Daniel; Aono, Masami

    2011-04-11

    This paper will introduce a semitransparent amorphous selenium (a-Se) film exhibiting photovoltaic effects under ultraviolet light created through a simple and inexpensive method. We found that chlorine can be doped into a-Se through electrolysis of saturated salt water, and converts the weak p-type material into an n-type material. Furthermore, we found that a p-n diode fabricated through this process has shown an open circuit voltage of 0.35 V toward ultraviolet illumination. Our results suggest the possibility of doping control depending on the electric current during electrolysis and the possibility of developing a simple doping method for amorphous photoconductors.

  17. Time Shifted PN Codes for CW Lidar, Radar, and Sonar

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F. (Inventor); Prasad, Narasimha S. (Inventor); Harrison, Fenton W. (Inventor); Flood, Michael A. (Inventor)

    2013-01-01

    A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere.

  18. Charge transport in pn and npn junctions of silicene

    NASA Astrophysics Data System (ADS)

    Yamakage, Ai; Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

    2013-08-01

    We investigate charge transport of pn and npn junctions made from silicene, a Si analogue of graphene. The conductance shows the distinct gate-voltage dependencies peculiar to the topological and nontopological phases, where the topological phase transition is caused by external electric field. Namely, the conductance is (not) suppressed in the np (nn) regime when both sides are topological, and in the nn (np) regime when one side is topological and the other side is nontopological. Furthermore, we find that the conductance is almost quantized to be 0, 1, and 2. Our findings will open a new way to nanoelectronics based on silicene.

  19. Spin-orbit effects in a graphene bipolar pn junction

    NASA Astrophysics Data System (ADS)

    Yamakage, A.; Imura, K.-I.; Cayssol, J.; Kuramoto, Y.

    2009-08-01

    A graphene pn junction is studied theoretically in the presence of both intrinsic and Rashba spin-orbit couplings. We show that a crossover from perfect reflection to perfect transmission is achieved at normal incidence by tuning the perpendicular electric field. By further studying angular-dependent transmission, we demonstrate that perfect reflection at normal incidence can be clearly distinguished from trivial band gap effects. We also investigate how spin-orbit effects modify the conductance and the Fano factor associated with a potential step in both nn and np cases.

  20. Direct imaging of p-n junction in core-shell GaN wires.

    PubMed

    Tchoulfian, P; Donatini, F; Levy, F; Dussaigne, A; Ferret, P; Pernot, J

    2014-06-11

    While core-shell wire-based devices offer a promising path toward improved optoelectronic applications, their development is hampered by the present uncertainty about essential semiconductor properties along the three-dimensional (3D) buried p-n junction. Thanks to a cross-sectional approach, scanning electron beam probing techniques were employed here to obtain a nanoscale spatially resolved analysis of GaN core-shell wire p-n junctions grown by catalyst-free metal-organic vapor phase epitaxy on GaN and Si substrates. Both electron beam induced current (EBIC) and secondary electron voltage constrast (VC) were demonstrated to delineate the radial and axial junction existing in the 3D structure. The Mg dopant activation process in p-GaN shell was dynamically controlled by the ebeam exposure conditions and visualized thanks to EBIC mapping. EBIC measurements were shown to yield local minority carrier/exciton diffusion lengths on the p-side (∼57 nm) and the n-side (∼15 nm) as well as depletion width in the range 40-50 nm. Under reverse bias conditions, VC imaging provided electrostatic potential maps in the vicinity of the 3D junction from which acceptor Na and donor Nd doping levels were locally determined to be Na = 3 × 10(18) cm(-3) and Nd = 3.5 × 10(18) cm(-3) in both the axial and the radial junction. Results from EBIC and VC are in good agreement. This nanoscale approach provides essential guidance to the further development of core-shell wire devices.

  1. Application of CBZ dimer, C343 and SQ dye as photosensitizers for pn-tandem DSCs

    NASA Astrophysics Data System (ADS)

    Lee, Yong Hyi; Park, Ji Young; Thogiti, Suresh; Cheruku, Rajesh; Kim, Jae Hong

    2016-07-01

    A pn-tandem dye-sensitized solar cell ( pn-DSC) was prepared with three different sensitized dyes CBZ Dimer (CBZD), C343, and SQ in two different compartments of the n-type or p-type cells. The constructed tandem solar cell was exhibited considerable improvement in experimental pn-DSCs parameters, open-circuit voltage, short-circuit current, fill factor, etc. These results were achieved under air mass 1.5 illumination with three different sensitized dyes in the upper and lower compartment of the pn-DSCs. These results demonstrate a complementary absorption among the two photoelectrodes in the pn-DSCs is a good approach to the efficient and low cost pn-DSCs. [Figure not available: see fulltext.

  2. Partial correlation properties of pseudonoise /PN/ codes in noncoherent synchronization/detection schemes

    NASA Technical Reports Server (NTRS)

    Cartier, D. E.

    1976-01-01

    This concise paper considers the effect on the autocorrelation function of a pseudonoise (PN) code when the acquisition scheme only integrates coherently over part of the code and then noncoherently combines these results. The peak-to-null ratio of the effective PN autocorrelation function is shown to degrade to the square root of n, where n is the number of PN symbols over which coherent integration takes place.

  3. High voltage thermally diffused p(+)n solar cells

    NASA Technical Reports Server (NTRS)

    Faur, M.; Faur, M.; Flood, D. J.; Brinker, D. J.; Weinberg, I.; Goradia, C.; Fatemi, N.; Goradia, M.; Thesling, W.

    1991-01-01

    The possibility of fabricating thermally diffused p(+)n InP solar-cells with high open-circuit voltage without sacrificing the short circuit current is discussed. The p(+)n InP junctions were formed by Cd and Zn diffusion through a 3-5-nm-thick anodic or chemical phosphorus-rich oxide cap layer grown on n:InP:S (with ND-NA = 3.5 x 10 exp 16 and 4.5 x 10 exp 17/cu cm) Czochralski LEC-grown substrates. After thinning the emitter from its initial thickness of 1 to 2.5 micron down to 0.06-0.15 micron, the maximum efficiency was found when the emitter was 0.2 to 0.3 micron thick. Typical AM0, 25 C values of 854-860 mV were achieved for Voc, Jsc values were from 25.9 to 29.1 mA/sq cm using only the P-rich passivating layer left after the thinning process as an antireflection coating.

  4. Single pilus motor forces exceed 100 pN.

    PubMed

    Maier, Berenike; Potter, Laura; So, Magdalene; Long, Cynthia D; Seifert, Hank S; Sheetz, Michael P

    2002-12-10

    Force production by type IV pilus retraction is critical for infectivity of Neisseria gonorrhoeae and DNA transfer. We investigated the roles of pilus number and the retraction motor, PilT, in force generation in vivo at the single-molecule level and found that individual retraction events are generated by a single pilus fiber, and only one PilT complex powers retraction. Retraction velocity is constant at low forces but decreases at forces greater than 40 pN, giving a remarkably high average stall force of 110 +/- 30 pN. Further insights into the molecular mechanism of force generation are gained from the effect of ATP-depletion, which reduces the rate of retraction but not the stall force. Energetic considerations suggest that more than one ATP is involved in the removal of a single pilin subunit from a pilus. The results are most consistent with a model in which the ATPase PilT forms an oligomer that disassembles the pilus by a cooperative conformational change. PMID:12446837

  5. Directional quantum transport in graphyne p-n junction

    NASA Astrophysics Data System (ADS)

    Soodchomshom, Bumned; Tang, I.-Ming; Hoonsawat, Rassmidara

    2013-02-01

    Graphyne, a newly proposed allotrope of carbon, has a structure which is topologically equivalent to that of a strongly distorted graphene [B. G. Kim and H. J. Choi, Phys. Rev. B 86, 115435 (2012)]. The energy gap between the valence and conduction bands is due to the symmetry breaking caused by there being three topologically inequivalent hoping elements. The valleyless fermionic transport properties of γ-graphyne are different from those of graphene since the two valleys are merged together in this carbon allotrope. The transmission and conductance of the electrons in γ-graphyne are found to be directionally dependent. Klein tunneling is predicted if the tunneling is in the y-direction. If the tunneling is in the x-direction, perfect back reflection (anti Klein tunneling) is predicted if the tunneling is at normal incidence. The consequences of these directional transport properties on the performances of p-n junctions fabricated with this carbon allotrope are studied. This work reveals the advantages of building p-n junctions based on γ-gaphyne.

  6. Synthesis, crystal and electronic structures of the new Zintl phases Ba3Al3Pn5 (Pn = P, As) and Ba3Ga3P5.

    PubMed

    He, Hua; Tyson, Chauntae; Saito, Maia; Bobev, Svilen

    2013-01-01

    The new Zintl compounds Ba(3)Al(3)P(5), Ba(3)Al(3)As(5,) and Ba(3)Ga(3)P(5) have been synthesized using molten metal fluxes. They are isoelectronic and isotypic, crystallizing with a novel rhombohedral structure type in the space group R3c with unit cell constants a = 14.5886(9) Å, c = 28.990(3) Å for Ba(3)Al(3)P(5), a = 14.613(3) Å, c = 28.884(8) Å for Ba(3)Ga(3)P(5), and a = 14.9727(13) Å, c = 29.689(4) Å for Ba(3)Al(3)As(5), respectively. The structures are based on TrPn(4) (Tr = Al, Ga; Pn = P, As) tetrahedra that share both edges and corners, leading to intricate arrangements embodied in the [Tr(4)Pn(9)](15-) and [Tr(3)Pn(6)](9-) strands, interconnected by dimeric [Tr(2)Pn(6)](12-) units. The Ba(2+) cations reside within cylindrical channels within the polyanionic framework and provide the valence electrons needed for Tr-Pn covalent bonding. In spite of the large and complex structure, there are no homoatomic Tr-Tr or Pn-Pn interactions, hence, the structures can be readily rationalized in the context of the Zintl-Klemm formalism as follows [Ba(2+)](3)[Tr(3+)](3)[Pn(3-)](5); calculations on their electronic band-structures confirm this reasoning and reveal about 1.4-1.9 eV energy band gaps, that is, semiconducting behavior. Structural parallels with other known Zintl compounds are also presented.

  7. High-frequency Pn,Sn phases recorded by ocean bottom seismometers on the Cocos plate

    SciTech Connect

    McCreery, C.S.

    1981-05-01

    Data from ocean bottom seismometers located on the Cocos plate indicate that high-frequency Pn,Sn phases are generated by earthquakes along the subducting margin of that plate and are propagated across the plate. The Sn phase appears to be severely attenuated as it approaches the ridge crest. Estimates of Pn velocity are lower than previous extimates for western Pacific paths, which may indicate a relationship between Pn,Sn velocity and lithospheric age. High frequencies found in these phases suggest that Q for Pn,Sn propagation across the Cocos plate is similar to that for the western Pacific.

  8. Eccentric-orbit extreme-mass-ratio inspiral gravitational wave energy fluxes to 7PN order

    NASA Astrophysics Data System (ADS)

    Forseth, Erik; Evans, Charles R.; Hopper, Seth

    2016-03-01

    We present new results through 7PN order on the energy flux from eccentric extreme-mass-ratio binaries. The black hole perturbation calculations are made at very high accuracy (200 decimal places) using a Mathematica code based on the Mano-Suzuki-Takasugi analytic function expansion formalism. All published coefficients in the expansion through 3PN order at lowest order in the mass ratio are confirmed and new analytic and numeric terms are found to high order in powers of e2 at post-Newtonian orders between 3.5PN and 7PN. We also show original work in finding (nearly) arbitrarily accurate expansions for hereditary terms at 1.5PN, 2.5PN, and 3PN orders. An asymptotic analysis is developed that guides an understanding of eccentricity singular factors, which diverge at unit eccentricity and which appear at each PN order. We fit to a model at each PN order that includes these eccentricity singular factors, which allows the flux to be accurately determined out to e →1 .

  9. Polymorphism in Zintl Phases ACd4Pn3: Modulated Structures of NaCd4Pn3 with Pn = P, As.

    PubMed

    Grotz, Carolin; Baumgartner, Maximilian; Freitag, Katharina M; Baumer, Franziska; Nilges, Tom

    2016-08-01

    NaCd4P3 and NaCd4As3 were synthesized via short-way transport using the corresponding elements and CdI2 as mineralizer. At room temperature, the two β-polymorphs adopt the RbCd4As3 structure type which has been recently reported for alkali metal (A)-d(10) transition metal (T)-pnictides (Pn). The title compounds crystallize rhombohedrally in space group R3̅m at room temperature and show reversible phase transitions to incommensurately modulated α-polymorphs at lower temperatures. The low-temperature phases are monoclinic and can be described in space group Cm(α0γ)s with q vectors of q = (-0.04,0,0.34) for α-NaCd4P3 and q1 = (-0.02,0,0.34) for α-NaCd4As3. Thermal properties, Raman spectroscopy, and electronic structures have been determined. Both compounds are Zintl phases with band gaps of 1.05 eV for β-NaCd4P3 and ∼0.4 eV for β-NaCd4As3.

  10. Velocity structure of uppermost mantle from Pn tomography in Northeast China

    NASA Astrophysics Data System (ADS)

    Sun, L.; Wu, Q.

    2013-12-01

    The Northeast China is an important region of the occurrence of deep earthquakes. It also is the best place where we study the subduction and volcanic activity of the western Pacific plate. In our work we have selected 30648 travel times of Pn arrivals as reported in the Annual Bulletin of Chinese Earthquakes(ABCE) and regional seismic network of Jilin province and Liaoning province. A two-dimensional tomography method is employed to find regional variation of Pn velocity and anisotropy in the uppermost mantle in Northeast China and its adjacent regions. In the most study area 2 degrees are well resolved. The main results show the relations of Pn velocity variation to regional tectonic structure, Moho depth, earth's heatflow and Cenozonic volcanism zones: Pn velocity structure is close to the regional tectonic structure and shows distribution of alternating high and low Pn velocity in the direction of NE~NNE. Low Pn velocities are found beneath Songliao Plain, XiaLiaohe Plain, Hailaer Basin and Bohai Basin. High Pn velocities are beneath Greater Khingan Mountains, Xiao Xingan Mountains and Changbai Mountains. Quantitative analysis result indicates that Pn velocity is positively correlated with crust thickness and negatively correlated with Earth's heatflow. The Pn velocities in the Changbai volcano and Jingpohu volcano activities are obviously low. In addition, the overall performance of Pn anisotropy is weak. Only in Jiamusi massif, Bohai Sea, Changbai volcano and Datong volcano we observe significant anisotropy. In Bohai Basin, the direction of fast Pn velocity is consistent with the direction of present-day crust movement. But not beneath Jiamusi massif, it may be due to the mantle flow caused by the subduction of the Pacific plate. This study was supported by the international cooperation project of the Ministry of Science and Technology of China(NO.2011DFB20120) and NSFC(Grant No.41004034).

  11. PN populations in the Local Group and distant stellar populations

    NASA Astrophysics Data System (ADS)

    Reid, Warren Alfred

    2015-08-01

    Our understanding of galactic structure and evolution is far from complete. Within the past twelve months we have learnt that the Milky Way is about 50% wider than was previously thought. As a consequence, new models are being developed that force us to reassess the kinematic structure of our Galaxy. Similarly, we need to take a fresh look at the halo structure of external galaxies in our Local Group. Studies of stellar populations, star-forming regions, clusters, the interstellar medium, elemental abundances and late stellar evolution are all required in order to understand how galactic assembly has occurred as we see it.PNe play an important role in this investigation by providing a measure of stellar age, mass, abundances, morphology, kinematics and synthesized matter that is returned to the interstellar medium (ISM). PN populations in the halos can be compared to those deeper within each galaxy to reveal any differences in chemical composition that may, through a method of chemical tagging show signs of stellar migration and galactic entwining.In this talk I will outline the advances that have been made in uncovering the full number of PNe in our Local Group galaxies. Current numbers will be presented and compared to total population estimates based on galactic mass and luminosity. A near complete census of PNe is crucial to understanding the initial-to-final mass relation for stars with mass >1 to <8 times the mass of the sun. It also allows us to extract more evolutionary information from luminosity functions and compare dust-to-gas ratios from PNe in different galactic locations. Nucleosynthesised material returned to the ISM during the PN phase can be compared to non-synthesised matter to expose the role PNe play in enriching the galactic environment.With new data provided by the Gaia satellite, space-based telescopes and the rise of giant and extra-large telescopes supplementing future space telescope missions, we are on the verge of observing and

  12. Surface and implantation effects on p-n junctions

    NASA Technical Reports Server (NTRS)

    Schacham, Samuel E.; Finkman, Eliezer

    1990-01-01

    The contribution of the graded region of implanted p-n junctions is analyzed using an exponential profile. Though previously neglected, it was recently shown that this contribution to the saturation current of HgCdTe diodes is significant. Assuming a dominant Auger recombination, an analytical solution to the continuity equation is obtained. An expression for the current generation by the graded region is presented for both ohmic and reflecting boundary conditions. A revised condition for a wide region is derived. When the region is narrow, the current differs drastically from that of the zero-gradient case. The effects of the junction depth and the substrate and surface concentrations on the current are investigated. It is shown that the reverse current does not saturate.

  13. Rectifying behaviour of spin coated pn hetero-junction

    SciTech Connect

    Yogamalar, N. Rajeswari; Bose, A. Chandra

    2015-06-24

    Rectifying pn hetero- junction is fabricated with an acceptor p-type organic semiconductor namely tetra- chloro dihydroxy tetra-iodo fluorescein (Rose Bengal (RB)) followed by an inorganic n-type ZnO semiconductor on indium tin oxide (ITO) substrate. The n-type ZnO films are formed by unintentional doping and doping with aluminium (Al) and yttrium (Y) donors. The surface morphology and the distribution of grains are observed from scanning electron microscopy (SEM) and atomic force microscopy (AFM). The current-voltage (I-V) characteristic of the rectifying diode is measured to characterize the junction properties. The I-V plots obtained from the hetero- junction with electric contact shows a diode characteristic different from that of an ideal behavior. The overall efficiency of the diode exhibits a greater dependency on the film crystallinity, carrier concentration, and reverse saturation current.

  14. Polarimetry of R Aqr and PN M2-9

    NASA Astrophysics Data System (ADS)

    Navarro, Silvana G.; Sabin, Laurence; Ramírez Vélez; , Julio; Hiriart, David

    2014-08-01

    The bipolar or more complex morphology observed in planetary nebulae have been explained by two principal hypothesis: by the existence of a companion and an accreting disk or by the effects of magnetic field, (or a combination of both). Symbiotics are binary systems and some of them show morphologies similar to those observed on planetary nebulae. This fact could support the binary hypothesis for PNe. We have therefore performed polarimetric observations of symbiotic systems and some planetary nebulae in order, first to detect linear polarisation with POLIMA at the San Pedro Mártir observatory, and ultimately to prove the existence and physical properties of those disks. We present here the first results of a project dedicated to the analysis of the polarisation observed in evolved objects starting with the PN M2-9 and R Aqr.

  15. Shallow mantle velocities beneath the southern Appalachians from Pn phases

    NASA Astrophysics Data System (ADS)

    MacDougall, Julia G.; Fischer, Karen M.; Forsyth, Donald W.; Hawman, Robert B.; Wagner, Lara S.

    2015-01-01

    constrain mantle structure that might contribute to the topography of the southern Appalachian Mountains, Pn phases from regional earthquakes recorded in northern Georgia by EarthScope Southeastern Suture of the Appalachian Margin Experiment and Transportable Array stations were used to solve for shallow mantle P wave velocities. Mantle velocities vary laterally, with values of 7.6-7.8 km/s beneath the higher elevations of the Blue Ridge terrane and northwestern flank of the Inner Piedmont terranes and values of 8.3-8.5 km/s farther south where elevation is lower. The zone of low-velocity mantle could represent a source of buoyancy that helps to support the higher elevations, in addition to the root of thickened crust that also exists beneath the mountains.

  16. Investigation of the transport properties and compositions of the Ca2RE7Pn5O5 series (RE=Pr, Sm, Gd, Dy; Pn=Sb, Bi)

    NASA Astrophysics Data System (ADS)

    Forbes, Scott; Yuan, Fang; Kosuda, Kosuke; Kolodiazhnyi, Taras; Mozharivskyj, Yurij

    2016-10-01

    The Ca2RE7Pn5O5 phases (RE=Pr, Sm, Gd, Dy; Pn=Sb, Bi) were successfully prepared from high temperature reactions at 1225-1300 °C. These phases maintain the same structure types as the parent RE9Pn5O5 phases, except for a Ca/RE mixing. The study and preparation of these phases was motivated by the desire to shift the metallic type properties of the parent RE9Pn5O5 phases to a level more suitable for thermoelectric applications. Electrical resistivity measurements performed on pure, bulk samples indicated all phases to be narrow band gap semiconductors or semimetals, supporting the charge balanced electron count of the Ca2RE7Pn5O5 composition. Unfortunately, all samples are too electrically resistive for any potential usage as thermoelectrics. Electronic band structure calculations performed on idealized RE9Pn5O5 structures revealed the presence of a pseudogap at the Fermi level, which is consistent with the observed electrical resistivity and Seebeck coefficient behavior.

  17. An Investigation of NCLEX-PN Performance and Student Perceptions among Practical Nursing Graduates

    ERIC Educational Resources Information Center

    Abston-Coleman, Sharon L.; Levy, Dessie R.

    2010-01-01

    Students in practical nursing programs require 32 weeks of coursework (1 academic year) and completion of a national licensing exam (NCLEX-PN) to secure employment. The purpose of this study was to identify selected academic variables that were related to NCLEX-PN performance for first-time test takers of two types of practical nursing programs at…

  18. The empirical connection between (p,n) cross sections and beta decay transition strengths

    SciTech Connect

    Taddeucci, T.N.

    1988-01-01

    A proportionality is assumed to exist between 0/degree/ (p,n) cross sections and the corresponding beta decay transition strengths. The validity of this assumption is tested by comparison of measured (p,n) cross sections and analogous beta decay strengths. Distorted waves impulse approximation calculations also provide useful estimates of the accuracy of the proportionality relationship. 14 refs., 10 figs.

  19. Naringenin (NAR) and 8-prenylnaringenin (8-PN) reduce the developmental competence of porcine oocytes in vitro.

    PubMed

    Solak, Kamila A; Santos, Regiane R; van den Berg, Martin; Blaauboer, Bas J; Roelen, Bernard A J; van Duursen, Majorie B M

    2014-11-01

    Flavanones such as naringenin (NAR) and 8-prenylnaringenin (8-PN) are increasingly used as dietary supplements despite scientific concern regarding adverse effects on female reproduction upon excessive intake. In the present study, NAR and 8-PN (0.3-1μM) significantly affected porcine oocyte maturation in vitro by decreasing cumulus expansion. In addition, NAR and 8-PN decreased percentages of meiotic spindle formation, oocyte cleavage and blastocyst formation. The effects of NAR and 8-PN were different from estradiol (3.12μM)-induced effects. Still, the flavanone-induced effects were observed at concentrations that can be found in human plasma upon supplement intake and that resemble physiological estrogen equivalence levels in follicular fluids. Considering that abnormal oocyte maturation can cause subfertility, our study warrants that precautions are in place and excessive intake of NAR and 8-PN e.g. via dietary supplements should be avoided by women.

  20. 2PN light propagation in the scalar - tensor theory: an N - point mass case

    NASA Astrophysics Data System (ADS)

    Deng, Xue-Mei; Xie, Yu

    2012-08-01

    Within the framework of the scalar - tensor theory, its second post - Newtonian (2PN) approximation is obtained by Chandrasekhar ’ s approach. By focusing on an N - point mass system as first step, we reduce the metric to its full 2PN form for light propagation. W e find that although there exist s two parameterized post - Newtonian (PPN) parameters gamma and beta in the 2PN metric, only gamma appears in the 2PN equations of light. As a simple example for applications, a gauge - invariant angle between the directions of two incoming photons for a differential measurement is investigated after the light trajectory is solved in a static and spherically symmetric spacetime. It shows the deviation from the general relativity does not depend on beta even at 2PN level in this circumstance.

  1. [Effects of combined application of nitrogen and phosphorus on diurnal variation of photosynthesis at grain-filling stage and grain yield of super high-yielding wheat].

    PubMed

    Zhao, Hai-bo; Lin, Qi; Liu, Yi-guo; Jiang, Wen; Liu, Jian-jun; Zhai, Yan-ju

    2010-10-01

    Taking super high-yielding wheat cultivar Jimai 22 as test material, a field experiment was conducted to study the effects of combined application of nitrogen (N) and phosphorus (P) on the diurnal variation of photosynthesis at grain-filling stage and the grain yield of the cultivar. In treatments CK (without N and P application) and low N/P application (225 kg N x hm(-2) and 75 kg P x hm(-2)), the diurnal variation of net photosynthetic rate (Pn) was presented as double-peak curve, and there existed obvious midday depression of photosynthesis. Under reasonable application of N/P (300 kg N x hm(-2) and 150 kg P x hm(-2), treatment N2P2), the midday depression of photosynthesis weakened or even disappeared. Stomatal and non-stomatal limitations could be the causes of the midday depression. Increasing N and P supply increased the Pn, stomatal conductance (Gs), stomatal limitation value (Ls), and transpiration rate (Tr). Fertilizer P had less effects on the photosynthesis, compared with fertilizer N. When the P supply was over 150 kg x hm(-2), the increment of Pn was alleviated and even decreased. Among the fertilization treatments, treatment N2P2 had the highest Pn, Gs, and water use efficiency, being significantly different from CK. It appeared that fertilizer N had greater regulatory effect on the diurnal variation of photosynthesis, compared with fertilizer P, while the combined application of N and P had significant co-effect on the Pn, Gs, and Tr. A combined application of 300 kg N x hm(-2) and 150 kg P x hm(-2) benefited the enhancement of Pn and grain yield.

  2. Simulation of AZ-PN100 Resist Pattern Fluctuation in X-Ray Lithography, Including Synchrotron Beam Polarization

    NASA Astrophysics Data System (ADS)

    Scheckler, Edward W.; Ogawa, Taro; Tanaka, Toshihiko; Oizumi, Hiroaki; Takeda, Eiji

    1993-12-01

    A new simulation model for nanometer-scale pattern fluctuation in X-ray lithography is presented and applied to a study of AZ-PN100 negative chemical amplification resist. The exposure simulation considers polarized photons from a synchrotron radiation (SR) source. Monte Carlo simulation of Auger and photoelectron generation is followed by electron scattering simulation to determine the deposited energy distribution at the nanometer scale, including beam polarization effects. An acid-catalyst random walk model simulates the post-exposure bake (PEB) step. Fourier transform infrared (FTIR) spectroscopy and developed resist thickness measurements are used to fit PEB and rate models for AZ-PN100. A polymer removal model for development simulation predicts the macroscopic resist shape and pattern roughness. The simulated 3σ linewidth variation is in excess of 24 nm. Simulation also shows a detrimental effect if the beam polarization is perpendicular to the line. Simulation assuming a theoretical ideal exposure yields a 50 nm minimum line for standard process conditions.

  3. Analytical Study of 90Sr Betavoltaic Nuclear Battery Performance Based on p-n Junction Silicon

    NASA Astrophysics Data System (ADS)

    Rahastama, Swastya; Waris, Abdul

    2016-08-01

    Previously, an analytical calculation of 63Ni p-n junction betavoltaic battery has been published. As the basic approach, we reproduced the analytical simulation of 63Ni betavoltaic battery and then compared it to previous results using the same design of the battery. Furthermore, we calculated its maximum power output and radiation- electricity conversion efficiency using semiconductor analysis method.Then, the same method were applied to calculate and analyse the performance of 90Sr betavoltaic battery. The aim of this project is to compare the analytical perfomance results of 90Sr betavoltaic battery to 63Ni betavoltaic battery and the source activity influences to performance. Since it has a higher power density, 90Sr betavoltaic battery yields more power than 63Ni betavoltaic battery but less radiation-electricity conversion efficiency. However, beta particles emitted from 90Sr source could travel further inside the silicon corresponding to stopping range of beta particles, thus the 90Sr betavoltaic battery could be designed thicker than 63Ni betavoltaic battery to achieve higher conversion efficiency.

  4. Recent advances in optimally designed p-n organic semiconductor solar cells

    NASA Astrophysics Data System (ADS)

    Panayotatos, P.; Whitlock, J.; Sauers, R. R.; Husain, S.; Sadrai, M.

    Criteria developed for the optimization of organic semiconductor p-n heterojunction solar cells are reviewed, and successful results stemming from the use of these requirements are presented. Over 30 combinations of organic dye pairs have been tested in more than 400 individual cells fabricated by vacuum evaporation of thin dye layers. Well-matched two-dye cells have given full visible solar spectrum coverage with 60-80 percent absorption. Other best AM1 solar values (not on the same cell) are: monochromatic short-circuit current yields of over 19 percent, short-circuit current densities of over 1.4 mA/sq cm fill factor of 43 percent and open-circuit voltage of 500 mV. The best results have been obtained by matching perylenes with phthalocyanines. The author used the above set of requirements and the previous best performing pair of chloroaluminum phthalocyanine (ClAlPc) and the bis-methylimide of perylenetetracarboxylic acid (DMP) to guide the choice of better matched pairs of dyes. These are arrived at by altering the above dyes through chemical substitutions.

  5. Pronounced Photovoltaic Response from Multilayered Transition-Metal Dichalcogenides PN-Junctions.

    PubMed

    Memaran, Shahriar; Pradhan, Nihar R; Lu, Zhengguang; Rhodes, Daniel; Ludwig, Jonathan; Zhou, Qiong; Ogunsolu, Omotola; Ajayan, Pulickel M; Smirnov, Dmitry; Fernández-Domínguez, Antonio I; García-Vidal, Francisco J; Balicas, Luis

    2015-11-11

    Transition metal dichalcogenides (TMDs) are layered semiconductors with indirect band gaps comparable to Si. These compounds can be grown in large area, while their gap(s) can be tuned by changing their chemical composition or by applying a gate voltage. The experimental evidence collected so far points toward a strong interaction with light, which contrasts with the small photovoltaic efficiencies η ≤ 1% extracted from bulk crystals or exfoliated monolayers. Here, we evaluate the potential of these compounds by studying the photovoltaic response of electrostatically generated PN-junctions composed of approximately 10 atomic layers of MoSe2 stacked onto the dielectric h-BN. In addition to ideal diode-like response, we find that these junctions can yield, under AM-1.5 illumination, photovoltaic efficiencies η exceeding 14%, with fill factors of ~70%. Given the available strategies for increasing η such as gap tuning, improving the quality of the electrical contacts, or the fabrication of tandem cells, our study suggests a remarkable potential for photovoltaic applications based on TMDs. PMID:26513598

  6. Photovoltaic Response from Multilayered Transition Metal Dichalcogenides p-n Junctions

    NASA Astrophysics Data System (ADS)

    Memaran, Shahriar; Pradhan, Nihar; Lu, Zhengguang; Rhodes, Daniel; Ludwig, Jonathan; Zhou, Qiong; Ogunsolu, Omotola; Ajayan, Pulickel; Smirnov, Dmitry; Fernandez-Dominguez, Antonio; Garcia-Vidal, Francisco; Balicas, Luis

    Transition metal dichalcogenides (TMDs) are layered semiconductors with indirect band gaps comparable to Si. These compounds can be grown in large area, while their gap(s) can be tuned by changing their chemical composition or by applying a gate voltage. The experimental evidence collected so far points toward a strong interaction with light, which contrasts with the small photovoltaic efficiencies η <= 1 % extracted from bulk crystals or exfoliated monolayers. Here, we evaluate the potential of these compounds by studying the photovoltaic response of electrostatically generated p-n junctions composed of approximately 10 atomic layers of MoSe2 stacked onto the dielectric h-BN. In addition to ideal diode-like response, we find that these junctions can yield, under AM-1.5 illumination, photovoltaic efficiencies η exceeding 14%, with fill factors of ~ 70 % . Given the available strategies for increasing η such as gap tuning, improving the quality of the electrical contacts, or the fabrication of tandem cells, our study suggests a remarkable potential for photovoltaic applications based on TMDs.

  7. Pronounced Photovoltaic Response from Multilayered Transition-Metal Dichalcogenides PN-Junctions.

    PubMed

    Memaran, Shahriar; Pradhan, Nihar R; Lu, Zhengguang; Rhodes, Daniel; Ludwig, Jonathan; Zhou, Qiong; Ogunsolu, Omotola; Ajayan, Pulickel M; Smirnov, Dmitry; Fernández-Domínguez, Antonio I; García-Vidal, Francisco J; Balicas, Luis

    2015-11-11

    Transition metal dichalcogenides (TMDs) are layered semiconductors with indirect band gaps comparable to Si. These compounds can be grown in large area, while their gap(s) can be tuned by changing their chemical composition or by applying a gate voltage. The experimental evidence collected so far points toward a strong interaction with light, which contrasts with the small photovoltaic efficiencies η ≤ 1% extracted from bulk crystals or exfoliated monolayers. Here, we evaluate the potential of these compounds by studying the photovoltaic response of electrostatically generated PN-junctions composed of approximately 10 atomic layers of MoSe2 stacked onto the dielectric h-BN. In addition to ideal diode-like response, we find that these junctions can yield, under AM-1.5 illumination, photovoltaic efficiencies η exceeding 14%, with fill factors of ~70%. Given the available strategies for increasing η such as gap tuning, improving the quality of the electrical contacts, or the fabrication of tandem cells, our study suggests a remarkable potential for photovoltaic applications based on TMDs.

  8. Gas Sensors Based on Ceramic p-n Heterocontacts

    SciTech Connect

    Aygun, Seymen Murat

    2005-01-01

    Ceramic p-n heterocontacts based on CuO/ZnO were successfully synthesized and a systematic study of their hydrogen sensitivity was conducted. The sensitivity and response rates of CuO/ZnO sensors were studied utilizing current-voltage, current-time, and impedance spectroscopy measurements. The heterocontacts showed well-defined rectifying characteristics and were observed to detect hydrogen via both dc and ac measurements. Surface coverage data were derived from current-time measurements which were then fit to a two-site Langmuir adsorption model quite satisfactorily. The fit suggested that there should be two energetically different adsorption sites in the system. The heterocontacts were doped in an attempt to increase the sensitivity and the response rate of the sensor. First, the effects of doping the p-type (CuO) on the sensor characteristics were investigated. Doping the p-type CuO with both acceptor and isovalent dopants greatly improved the hydrogen sensitivity. The sensitivity of pure heterocontact observed via I-V measurements was increased from ~2.3 to ~9.4 with Ni doping. Dopants also enhanced the rectifying characteristics of the heterocontacts. Small amounts of Li addition were shown to decrease the reverse bias (saturation) current to 0.2 mA at a bias level of -5V. No unambiguous trends were observed between the sensitivity, the conductivity, and the density of the samples. Comparing the two phase microstructure to the single phase microstructure there was no dramatic increase in the sensitivity. Kinetic studies also confirmed the improved sensor characteristics with doping. The dopants decreased the response time of the sensor by decreasing the response time of one of the adsorption sites. The n-type ZnO was doped with both acceptor and donor dopants. Li doping resulted in the degradation of the p-n junction and the response time of the sensor. However, the current-voltage behavior of Ga-doped heterocontacts showed the best rectifying characteristics

  9. Pleurotus nebrodensis polysaccharide (PN-S) enhances the immunity of immunosuppressed mice.

    PubMed

    Cui, Hai-Yan; Wang, Chang-Lu; Wang, Yu-Rong; Li, Zhen-Jing; Chen, Mian-Hua; Li, Feng-Juan; Sun, Yan-Ping

    2015-10-01

    In the present study, the effects of Pleurotus nebrodensis polysaccharide (PN-S) on the immune functions of immunosuppressed mice were determined. The immunosuppressed mouse model was established by treating the mice with cyclophosphamide (40 mg/kg/2d, CY) through intraperitoneal injection. The results showed that PN-S administration significantly reversed the CY-induced weight loss, increased the thymic and splenic indices, and promoted proliferation of T lymphocyte, B lymphocyte, and macrophages. PN-S also enhanced the activity of natural killer cells and increased the immunoglobulin M (IgM) and immunoglobulin G (IgG) levels in the serum. In addition, PN-S treatment significantly increased the phagocytic activity of mouse peritoneal macrophages. PN-S also increased the levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interferon-γ (INF-γ), and nitric oxide (NOS) in splenocytes. qRT-PCR results also indicated that PN-S increased the mRNA expression of IL-6, TNF-α, INF-γ, and nitric oxide synthase (iNOS) in the splenocytes. These results suggest that PN-S treatment enhances the immune function of immunosuppressed mice. This study may provide a basis for the application of this fungus in adjacent immunopotentiating therapy against cancer and in the treatment of chemotherapy-induced immunosuppression.

  10. Atomically thin p-n junctions with van der Waals heterointerfaces.

    PubMed

    Lee, Chul-Ho; Lee, Gwan-Hyoung; van der Zande, Arend M; Chen, Wenchao; Li, Yilei; Han, Minyong; Cui, Xu; Arefe, Ghidewon; Nuckolls, Colin; Heinz, Tony F; Guo, Jing; Hone, James; Kim, Philip

    2014-09-01

    Semiconductor p-n junctions are essential building blocks for electronic and optoelectronic devices. In conventional p-n junctions, regions depleted of free charge carriers form on either side of the junction, generating built-in potentials associated with uncompensated dopant atoms. Carrier transport across the junction occurs by diffusion and drift processes influenced by the spatial extent of this depletion region. With the advent of atomically thin van der Waals materials and their heterostructures, it is now possible to realize a p-n junction at the ultimate thickness limit. Van der Waals junctions composed of p- and n-type semiconductors--each just one unit cell thick--are predicted to exhibit completely different charge transport characteristics than bulk heterojunctions. Here, we report the characterization of the electronic and optoelectronic properties of atomically thin p-n heterojunctions fabricated using van der Waals assembly of transition-metal dichalcogenides. We observe gate-tunable diode-like current rectification and a photovoltaic response across the p-n interface. We find that the tunnelling-assisted interlayer recombination of the majority carriers is responsible for the tunability of the electronic and optoelectronic processes. Sandwiching an atomic p-n junction between graphene layers enhances the collection of the photoexcited carriers. The atomically scaled van der Waals p-n heterostructures presented here constitute the ultimate functional unit for nanoscale electronic and optoelectronic devices.

  11. Lateral variation of Pn velocity beneath northeastern marginal region of Qinghai-Xizang plateau

    NASA Astrophysics Data System (ADS)

    Xu, Zhong-Huai; Wang, Su-Yun; Pei, Shun-Ping

    2003-01-01

    Pn arrival time data are collected from the bulletins of both national and regional seismological network in China. These data are tomographically inverted to map the lateral variation and anisotropy of Pn velocity in the northeastern marginal region of Qinghai-Xizang plateau. The average Pn velocity in this region is 8.09 km/s, being a little higher than the average for whole China. Higher velocity is found in tectonically stable Qaidam basin, while lower velocity is seen in and around tectonically active Shanxi graben. The region where the 1920 Haiyuan great earth-quake occurred shows a slightly low Pn velocity. A noticeable result is that, differing from the tectonically compressive Tianshan region, where Pn velocity is low, the Qilianshan region, where the Neotectonic deformation is also primarily compressive, shows high Pn velocity. In the uppermost mantle beneath the Ordos plateau Pn velocity is inhomogeneous, varying from higher velocity in southwestern part to lower one in northeastern part. This may be attributed to possible movement of the Ordos block, as there are strong earthquakes all around the block.

  12. Uptake of Plasmin-PN-1 Complexes in Early Human Atheroma.

    PubMed

    Boukais, Kamel; Bayles, Richard; Borges, Luciano de Figueiredo; Louedec, Liliane; Boulaftali, Yacine; Ho-Tin-Noé, Benoit; Arocas, Véronique; Bouton, Marie-Christine; Michel, Jean-Baptiste

    2016-01-01

    Zymogens are delivered to the arterial wall by radial transmural convection. Plasminogen can be activated within the arterial wall to produce plasmin, which is involved in evolution of the atherosclerotic plaque. Vascular smooth muscle cells (vSMCs) protect the vessels from proteolytic injury due to atherosclerosis development by highly expressing endocytic LDL receptor-related protein-1 (LRP-1), and by producing anti-proteases, such as Protease Nexin-1 (PN-1). PN-1 is able to form covalent complexes with plasmin. We hypothesized that plasmin-PN-1 complexes could be internalized via LRP-1 by vSMCs during the early stages of human atheroma. LRP-1 is also responsible for the capture of aggregated LDL in human atheroma. Plasmin activity and immunohistochemical analyses of early human atheroma showed that the plasminergic system is activated within the arterial wall, where intimal foam cells, including vSMCs and platelets, are the major sites of PN-1 accumulation. Both PN-1 and LRP-1 are overexpressed in early atheroma at both messenger and protein levels. Cell biology studies demonstrated an increased expression of PN-1 and tissue plasminogen activator by vSMCs in response to LDL. Plasmin-PN-1 complexes are internalized via LRP-1 in vSMCs, whereas plasmin alone is not. Tissue PN-1 interacts with plasmin in early human atheroma via two complementary mechanisms: plasmin inhibition and tissue uptake of plasmin-PN-1 complexes via LRP-1 in vSMCs. Despite this potential protective effect, plasminogen activation by vSMCs remains abnormally elevated in the intima in early stages of human atheroma.

  13. Uptake of Plasmin-PN-1 Complexes in Early Human Atheroma

    PubMed Central

    Boukais, Kamel; Bayles, Richard; Borges, Luciano de Figueiredo; Louedec, Liliane; Boulaftali, Yacine; Ho-Tin-Noé, Benoit; Arocas, Véronique; Bouton, Marie-Christine; Michel, Jean-Baptiste

    2016-01-01

    Zymogens are delivered to the arterial wall by radial transmural convection. Plasminogen can be activated within the arterial wall to produce plasmin, which is involved in evolution of the atherosclerotic plaque. Vascular smooth muscle cells (vSMCs) protect the vessels from proteolytic injury due to atherosclerosis development by highly expressing endocytic LDL receptor-related protein-1 (LRP-1), and by producing anti-proteases, such as Protease Nexin-1 (PN-1). PN-1 is able to form covalent complexes with plasmin. We hypothesized that plasmin-PN-1 complexes could be internalized via LRP-1 by vSMCs during the early stages of human atheroma. LRP-1 is also responsible for the capture of aggregated LDL in human atheroma. Plasmin activity and immunohistochemical analyses of early human atheroma showed that the plasminergic system is activated within the arterial wall, where intimal foam cells, including vSMCs and platelets, are the major sites of PN-1 accumulation. Both PN-1 and LRP-1 are overexpressed in early atheroma at both messenger and protein levels. Cell biology studies demonstrated an increased expression of PN-1 and tissue plasminogen activator by vSMCs in response to LDL. Plasmin-PN-1 complexes are internalized via LRP-1 in vSMCs, whereas plasmin alone is not. Tissue PN-1 interacts with plasmin in early human atheroma via two complementary mechanisms: plasmin inhibition and tissue uptake of plasmin-PN-1 complexes via LRP-1 in vSMCs. Despite this potential protective effect, plasminogen activation by vSMCs remains abnormally elevated in the intima in early stages of human atheroma. PMID:27445860

  14. Uptake of Plasmin-PN-1 Complexes in Early Human Atheroma.

    PubMed

    Boukais, Kamel; Bayles, Richard; Borges, Luciano de Figueiredo; Louedec, Liliane; Boulaftali, Yacine; Ho-Tin-Noé, Benoit; Arocas, Véronique; Bouton, Marie-Christine; Michel, Jean-Baptiste

    2016-01-01

    Zymogens are delivered to the arterial wall by radial transmural convection. Plasminogen can be activated within the arterial wall to produce plasmin, which is involved in evolution of the atherosclerotic plaque. Vascular smooth muscle cells (vSMCs) protect the vessels from proteolytic injury due to atherosclerosis development by highly expressing endocytic LDL receptor-related protein-1 (LRP-1), and by producing anti-proteases, such as Protease Nexin-1 (PN-1). PN-1 is able to form covalent complexes with plasmin. We hypothesized that plasmin-PN-1 complexes could be internalized via LRP-1 by vSMCs during the early stages of human atheroma. LRP-1 is also responsible for the capture of aggregated LDL in human atheroma. Plasmin activity and immunohistochemical analyses of early human atheroma showed that the plasminergic system is activated within the arterial wall, where intimal foam cells, including vSMCs and platelets, are the major sites of PN-1 accumulation. Both PN-1 and LRP-1 are overexpressed in early atheroma at both messenger and protein levels. Cell biology studies demonstrated an increased expression of PN-1 and tissue plasminogen activator by vSMCs in response to LDL. Plasmin-PN-1 complexes are internalized via LRP-1 in vSMCs, whereas plasmin alone is not. Tissue PN-1 interacts with plasmin in early human atheroma via two complementary mechanisms: plasmin inhibition and tissue uptake of plasmin-PN-1 complexes via LRP-1 in vSMCs. Despite this potential protective effect, plasminogen activation by vSMCs remains abnormally elevated in the intima in early stages of human atheroma. PMID:27445860

  15. Synthesis, Crystal and Electronic Structures of the Pnictides AE3TrPn3 (AE = Sr, Ba; Tr = Al, Ga; Pn = P, As)

    DOE PAGESBeta

    Stoyko, Stanislav; Voss, Leonard; He, Hua; Bobev, Svilen

    2015-09-24

    New ternary arsenides AE3TrAs3 (AE = Sr, Ba; Tr = Al, Ga) and their phosphide analogs Sr3GaP3 and Ba3AlP3 have been prepared by reactions of the respective elements at high temperatures. Single-crystal X-ray diffraction studies reveal that Sr3AlAs3 and Ba3AlAs3 adopt the Ba3AlSb3-type structure (Pearson symbol oC56, space group Cmce, Z = 8). This structure is also realized for Sr3GaP3 and Ba3AlP3. Likewise, the compounds Sr3GaAs3 and Ba3GaAs3 crystallize with the Ba3GaSb3-type structure (Pearson symbol oP56, space group Pnma, Z = 8). Both structures are made up of isolated pairs of edge-shared AlPn4 and GaPn4 tetrahedra (Pn = pnictogen, i.e.,more » P or As), separated by the alkaline-earth Sr2+ and Ba2+ cations. In both cases, there are no homoatomic bonds, hence, regardless of the slightly different atomic arrangements, both structures can be rationalized as valence-precise [AE2+]3[Tr3+][Pn3-]3, or rather [AE2+]6[Tr2Pn6]12-, i.e., as Zintl phases.« less

  16. p-n Junction Diodes Fabricated on Si-Si/Ge Heteroepitaxial Films

    NASA Technical Reports Server (NTRS)

    Das, K.; Mazumder, M. D. A.; Hall, H.; Alterovitz, Samuel A. (Technical Monitor)

    2000-01-01

    A set of photolithographic masks was designed for the fabrication of diodes in the Si-Si/Ge material system. Fabrication was performed on samples obtained from two different wafers: (1) a complete HBT structure with an n (Si emitter), p (Si/Ge base), and an n/n+ (Si collector/sub-collector) deposited epitaxially (MBE) on a high resistivity p-Si substrate, (2) an HBT structure where epitaxial growth was terminated after the p-type base (Si/Ge) layer deposition. Two different process runs were attempted for the fabrication of Si-Si/Ge (n-p) and Si/Ge-Si (p-n) junction diodes formed between the emitter-base and base-collector layers, respectively, of the Si-Si/Ge-Si HBT structure. One of the processes employed a plasma etching step to expose the p-layer in the structure (1) and to expose the e-layer in structure (2). The Contact metallization used for these diodes was a Cu-based metallization scheme that was developed during the first year of the grant. The plasma-etched base-collector diodes on structure (2) exhibited well-behaved diode-like characteristics. However, the plasma-etched emitter-base diodes demonstrated back-to-back diode characteristics. These back-to back characteristics were probably due to complete etching of the base-layer, yielding a p-n-p diode. The deep implantation process yielded rectifying diodes with asymmetric forward and reverse characteristics. The ideality factor of these diodes were between 1.6 -2.1, indicating that the quality of the MBE grown epitaxial films was not sufficiently high, and also incomplete annealing of the implantation damage. Further study will be conducted on CVD grown films, which are expected to have higher epitaxial quality.

  17. Chaotic Behaviour of a Driven P-N Junction

    NASA Astrophysics Data System (ADS)

    Perez, Jose Maria

    The chaotic behavior of a driven p-n junction is experimentally examined. Bifurcation diagrams for the system are measured, showing period doubling bifurcations up to f/32, onset of chaos, reverse bifurcations of chaotic bands, and periodic windows. Some of the measured bifurcation diagrams are similar to the bifurcation diagram of the logistic map x(,n+1) = (lamda)x(,n)(1 - x(,n)). A return map is also measured showing approximately a one-dimensional map with a single extremum at low driving voltages. The intermittency route to chaos is experimentally observed to occur near a tangent bifurcation as the system approaches a period 5 window at (lamda) = (lamda)(,5). Data are presented for the dependence of the average laminar length on (epsilon) = (lamda)(,5) - (lamda), and for the probability distribution P(l) vs. l. The effects of additive stochastic noise on period doubling, chaos, windows, and intermittency are examined and are found to agree with the logistic model and universal predictions. Three examples of crisis of the attractor are observed. The crises occur when an unstable orbit intersects the chaotic attractor. A period adding sequence is reported in which wide periodic windows of period 2, 3, 4, ... are observed for increasing driving voltage. The initial period doubling cascade and the period adding sequence are compared to two theoretical models, with reasonable success.

  18. Background Studies for the pn-CCD Detector of CAST

    SciTech Connect

    Rodriguez, A.; Beltran, B.; Cebrian, S.; Gomez, H.; Irastorza, I. G.; Luzon, G.; Morales, J.; Ruz, J.; Villar, J. A.; Hartmann, R.; Kotthaus, R.; Klose, C.; Kuster, M.; Strueder, L.

    2007-03-28

    The CERN Axion Solar Telescope (CAST) experiment searches for axions from the Sun converted into photons with energies up to around 10 keV via the inverse Primakoff effect in the high magnetic field of a superconducting Large Hadron Collider (LHC) prototype magnet. A backside illuminated pn-CCD detector in conjunction with an X-ray mirror optics is one of the three detectors used in CAST to register the expected photon signal. Since this signal is very rare a detailed study of the detector background has been undertaken with the aim to understand and further reduce the background level of the detector. The analysis is based on measured data taken during the data taking period of 2003 and 2004 of CAST and on Monte Carlo simulations of background with different origin. The background study performed for this detector show that the level of background (8.00{+-}0.07)x10-5 counts cm-2 s-1 keV-1 between 1 and 7 keV is dominated by the external gamma background due to natural activities at the experimental site, while radioactive impurities in the detector itself and cosmic neutrons contribute with a smaller fraction.

  19. Titanium-dioxide nanotube p-n homojunction diode

    SciTech Connect

    Alivov, Yahya E-mail: pnagpal@colorado.edu; Ding, Yuchen; Singh, Vivek; Nagpal, Prashant E-mail: pnagpal@colorado.edu

    2014-12-29

    Application of semiconductors in functional optoelectronic devices requires precise control over their doping and formation of junction between p- and n-doped semiconductors. While doped thin films have led to several semiconductor devices, need for high-surface area nanostructured devices for photovoltaic, photoelectrochemical, and photocatalytic applications has been hindered by lack of desired doping in nanostructures. Here, we show titanium-dioxide (TiO{sub 2}) nanotubes doped with nitrogen (N) and niobium (Nb) as acceptors and donors, respectively, and formation of TiO{sub 2} nanotubes p-n homojunction. This TiO{sub 2}:N/TiO{sub 2}:Nb homojunction showed distinct diode-like behaviour with rectification ratio of 1115 at ±5 V and exhibited good photoresponse for ultraviolet light (λ = 365 nm) with sensitivity of 0.19 A/W at reverse bias of −5 V. These results can have important implications for development of nanostructured metal-oxide solar-cells, photodiodes, LED's, photocatalysts, and photoelectrochemical devices.

  20. Magnetic electron focusing and tuning of the electron current with a pn-junction

    SciTech Connect

    Milovanović, S. P. Ramezani Masir, M. Peeters, F. M.

    2014-01-28

    Transverse magnetic focusing properties of graphene using a ballistic four terminal structure are investigated. The electric response is obtained using the semiclassical billiard model. The transmission exhibits pronounced peaks as a consequence of skipping orbits at the edge of the structure. When we add a pn-junction between the two probes, snake states along the pn-interface appear. Injected electrons are guided by the pn-interface to one of the leads depending on the value of the applied magnetic field. Oscillations in the resistance are found depending on the amount of particles that end up in each lead.

  1. Copper-catalyzed Suzuki-Miyaura coupling of arylboronate esters: transmetalation with (PN)CuF and identification of intermediates.

    PubMed

    Gurung, Santosh K; Thapa, Surendra; Kafle, Arjun; Dickie, Diane A; Giri, Ramesh

    2014-02-21

    An efficient Cu(I)-catalyzed Suzuki-Miyaura reaction was developed for the coupling of aryl- and heteroarylboronate esters with aryl and heteroaryl iodides at low catalyst loadings (2 mol %). The reaction proceeds under ligand-free conditions for aryl-heteroaryl and heteroaryl-heteroaryl couplings. We also conducted the first detailed mechanistic studies by synthesizing [(PN-2)CuI]2, [(PN-2)CuF]2, and (PN-2)CuPh (PN-2 = o-(di-tert-butylphosphino)-N,N-dimethylaniline) and demonstrated that [(PN-2)CuF]2 is the species that undergoes transmetalation with arylboronate esters.

  2. Many-body effects on optical gain in GaAsPN/GaPN quantum well lasers for silicon integration

    SciTech Connect

    Park, Seoung-Hwan

    2014-02-14

    Many-body effects on the optical gain in GaAsPN/GaP QW structures were investigated by using the multiband effective-mass theory and the non-Markovian gain model with many-body effects. The free-carrier model shows that the optical gain peak slightly increases with increasing N composition. In addition, the QW structure with a larger As composition shows a larger optical gain than that with a smaller As composition. On the other hand, in the case of the many-body model, the optical gain peak decreases with increasing N composition. Also, the QW structure with a smaller As composition is observed to have a larger optical gain than that with a larger As composition. This can be explained by the fact that the QW structure with a smaller As or N composition shows a larger Coulomb enhancement effect than that with a larger As or N composition. This means that it is important to consider the many-body effect in obtaining guidelines for device design issues.

  3. Analysis of sampling and quantization effects on the performance of PN code tracking loops

    NASA Technical Reports Server (NTRS)

    Quirk, K. J.; Srinivasan, M.

    2002-01-01

    Pseudonoise (PN) code tracking loops in direct-sequence spread-spectrum systems are often implemented using digital hardware. Performance degradation due to quantization and sampling effects is not adequately characterized by the traditional analog system feedback loop analysis.

  4. Experimental determination of series resistance of p-n junction diodes and solar cells

    NASA Technical Reports Server (NTRS)

    Chen, P. J.; Pao, S. C.; Neugroschel, A.; Lindholm, F. A.

    1978-01-01

    Various methods for determining the series resistance of p-n junction diodes and solar cells are described and compared. New methods involving the measurement of the ac admittance are shown to have certain advantages over methods proposed earlier.

  5. Investigation of modified p-n junctions in crystalline silicon on glass solar cells

    NASA Astrophysics Data System (ADS)

    Lausch, D.; Werner, M.; Naumann, V.; Schneider, J.; Hagendorf, C.

    2011-04-01

    In this paper various methods for studying p-n junctions in thin film solar cells are applied with the aim to localize and investigate defects on a microscopic scale. Different electron and ion beam characterization methods are introduced to determine the p-n junction position using two different examples from crystalline silicon on glass thin film technology. In a first example, planview and cross section electron beam induced current measurements revealed that oxygen rich columnar growth at textured substrates strongly disturbs the p-n junction. In a second example, diffusion from glass substrate is identified by ToF-SIMS to influence the electrical and structural characteristics of the thin Si layer resulting in a modified p-n junction. A model describing the formation of both defect structures is introduced.

  6. Snake states in graphene quantum dots in the presence of a p-n junction

    NASA Astrophysics Data System (ADS)

    Zarenia, M.; Pereira, J. M., Jr.; Peeters, F. M.; Farias, G. A.

    2013-01-01

    We investigate the magnetic interface states of graphene quantum dots that contain p-n junctions. Within a tight-binding approach, we consider rectangular quantum dots in the presence of a perpendicular magnetic field containing p-n as well as p-n-p and n-p-n junctions. The results show the interplay between the edge states associated with the zigzag terminations of the sample and the snake states that arise at the p-n junction due to the overlap between electron and hole states at the potential interface. Remarkable localized states are found at the crossing of the p-n junction with the zigzag edge having a dumb-bell-shaped electron distribution. The results are presented as a function of the junction parameters and the applied magnetic flux.

  7. Imaging the p-n junction in a gallium nitride nanowire with a scanning microwave microscope

    SciTech Connect

    Imtiaz, Atif; Wallis, Thomas M.; Brubaker, Matt D.; Blanchard, Paul T.; Bertness, Kris A.; Sanford, Norman A.; Kabos, Pavel; Weber, Joel C.; Coakley, Kevin J.

    2014-06-30

    We used a broadband, atomic-force-microscope-based, scanning microwave microscope (SMM) to probe the axial dependence of the charge depletion in a p-n junction within a gallium nitride nanowire (NW). SMM enables the visualization of the p-n junction location without the need to make patterned electrical contacts to the NW. Spatially resolved measurements of S{sub 11}{sup ′}, which is the derivative of the RF reflection coefficient S{sub 11} with respect to voltage, varied strongly when probing axially along the NW and across the p-n junction. The axial variation in S{sub 11}{sup ′}  effectively mapped the asymmetric depletion arising from the doping concentrations on either side of the junction. Furthermore, variation of the probe tip voltage altered the apparent extent of features associated with the p-n junction in S{sub 11}{sup ′} images.

  8. Homo- and hetero- p-n junctions formed on graphene steps.

    PubMed

    Wang, Xiaomu; Xie, Weiguang; Chen, Jian; Xu, Jian-Bin

    2014-01-01

    p-n junction is a fundamental building block in modern electronic circuits. We report graphene p-n junctions formed by a one-step thickness-dependent surface treatment of mono-/bilayer graphene steps. The junction electronic properties are systemically studied by means of Kelvin probe force microscopy (KPFM) and transport measurements. Because of the dissimilar modifications to graphene electronic properties, the junctions behave distinctly, i.e., two-component resistance-like for organic charge transfer doping and Shottky-junction-like for covalent doping. By exploring the spatially potential distribution, we clarify the potential profiles as well as the transport attributes across the graphene p-n junction interface under lateral bias and electrical gating. Our results not only unveil the detailed properties of graphene p-n junction interface, but also gain an insight into its practical applications in nanoelectronics.

  9. Regenerative PN ranging experience with New Horizons during 2012

    NASA Astrophysics Data System (ADS)

    Jensen, J. R.; Haskins, C. B.; DeBoy, C. C.

    The New Horizons mission to Pluto is the first deep space mission to include the capability of supporting regenerative PN ranging. During the current phase of the mission, sequential tone ranging supports the mission navigation requirements but regenerative ranging will expand the conditions (antenna selection, integration time, etc.) over which ranging will be successful during any extended mission following the Pluto fly-by, to objects in the Kuiper belt. Experience with regenerative ranging is being obtained now in preparation for its use in an extended mission. During most of 2012, New Horizons was in a hibernation state. Tracking was conducted between late April and early July. Six regenerative ranging passes were performed to bookend this interval; 2 at the beginning and 4 at the end. During that time, the distance between the spacecraft and Earth was in excess of 22 Astronautical Units (AU) and the Pr/No levels were below 15 dB-Hz. A seventh regenerative ranging pass was performed in May at a higher signal level in order to test the acquisition of the ranging code by the spacecraft during a variety of conditions. The consistency of the regenerative range measurements with the adjacent sequential tone ranging measurements has been demonstrated and serves as a check on the calibration of the regenerative ranging system conditions. The range measurement precision has been shown to follow the predictions that are based on the uplink and downlink signal power. The regenerative ranging system has been shown to acquire the uplink ranging code with and without a commanded reset and regardless of the noise bandwidth setting of the system. This paper will present the data that was obtained during 2012 and will describe the analysis results for the regenerative ranging experience during 2012.

  10. Detection of interstellar PN - The first phosphorus-bearing species observed in molecular clouds

    NASA Technical Reports Server (NTRS)

    Ziurys, L. M.

    1987-01-01

    Phosphorus nitride (PN) has been detected in the interstellar medium. The J = 2-1, 3-2, 5-4, and 6-5 rotational lines of this species have been observed toward Orion-KL, and the J = 2-1 transition in Sgr B2 and W51. The PN line profiles in Orion indicate that the molecule's emission arises from the 'plateau' or 'doughnut' region associated with the outflow from IRc2. The species is thus primarily present in hot, dense gas. Column densities derived for PN toward Orion-KL are (3-4) x 10 to the 13th/sq cm, but may be as high as 10 to the 14th/sq cm, if the species is located in a 10-arcsec region. These column densities imply a fractional abundance for PN in the Orion 'plateau' of (1-4) x 10 to the -10th. Such a large abundance for PN is not predicted by quiescent cloud ion-molecule chemistry and suggests that high-temperature processes are responsible for the synthesis of PN in the KL outflow.

  11. Properties of Edge States at the Graphene P-N Junction Interface

    NASA Astrophysics Data System (ADS)

    Le, Son; Klimov, Nikolai; Newell, David; Yan, Jun; Lee, Ji Ung; Richter, Curt

    The Landau level edge states from the p- and the n-section of a graphene P/N junction (pnJ) interact with each other differently across the junction depending upon the properties of the junction and the graphene. Full equilibration was reported for a two terminal graphene pnJ device in Williams et al.. In our four-terminal device, however, only the lowest Landau level edge state is equilibrated across the pnJ. When the two devices are compared, the LL energy spacings, the length of the edge states along the pnJ interface, and the carrier mobility are similar. Electrostatic simulations for our device geometry and that of contrast the rate of change of the electrostatic potential across the pnJs. Edge states at an electrostatically smooth junction are spatially further apart than those at a relatively abrupt junction, which decreases the probability of edge states mixing. Thus, we attribute the difference in equilibration in our device and that of to the dramatic difference in the shape of the electrostatic junction.

  12. Synthesis, Crystal and Electronic Structures of the Pnictides AE3TrPn3 (AE = Sr, Ba; Tr = Al, Ga; Pn = P, As)

    SciTech Connect

    Stoyko, Stanislav; Voss, Leonard; He, Hua; Bobev, Svilen

    2015-09-24

    New ternary arsenides AE3TrAs3 (AE = Sr, Ba; Tr = Al, Ga) and their phosphide analogs Sr3GaP3 and Ba3AlP3 have been prepared by reactions of the respective elements at high temperatures. Single-crystal X-ray diffraction studies reveal that Sr3AlAs3 and Ba3AlAs3 adopt the Ba3AlSb3-type structure (Pearson symbol oC56, space group Cmce, Z = 8). This structure is also realized for Sr3GaP3 and Ba3AlP3. Likewise, the compounds Sr3GaAs3 and Ba3GaAs3 crystallize with the Ba3GaSb3-type structure (Pearson symbol oP56, space group Pnma, Z = 8). Both structures are made up of isolated pairs of edge-shared AlPn4 and GaPn4 tetrahedra (Pn = pnictogen, i.e., P or As), separated by the alkaline-earth Sr2+ and Ba2+ cations. In both cases, there are no homoatomic bonds, hence, regardless of the slightly different atomic arrangements, both structures can be rationalized as valence-precise [AE2+]3[Tr3+][Pn3-]3, or rather [AE2+]6[Tr2Pn6]12-, i.e., as Zintl phases.

  13. Detection of interstellar PN: the first phosphorus-bearing species observed in molecular clouds.

    PubMed

    Ziurys, L M

    1987-10-01

    Phosphorus nitride (PN) has been detected in the interstellar medium. The J = 2-1, 3-2, 5-4, and 6-5 rotational lines of this species have been observed toward Orion-KL, and the J = 2-1 transition in Sgr B2 and W51. The PN line profiles in Orion indicate that the molecule's emission arises from the "plateau" or "doughnut" region associated with the outflow from IRc2. The species is thus primarily present in hot, dense gas. Column densities derived for PN toward Orion-KL are 3-4 X 10(13) cm-2, but may be as high as 10(14) cm-2, if the species is located in a 10" region. These column densities imply a fractional abundance for PN in the Orion "plateau" of approximately 1-4 X 10(-10). Such a large abundance for phosphorus nitride is not predicted by quiescent cloud ion-molecule chemistry and suggests that high-temperature processes are responsible for the synthesis of PN in the KL outflow.

  14. The photoirradiation induced p-n junction in naphthylamine-based organic photovoltaic cells.

    PubMed

    Bai, Linyi; Gao, Qiang; Xia, Youyi; Ang, Chung Yen; Bose, Purnandhu; Tan, Si Yu; Zhao, Yanli

    2015-09-21

    The bulk heterojunction (BHJ) plays an indispensable role in organic photovoltaics, and thus has been investigated extensively in recent years. While a p-n heterojunction is usually fabricated using two different donor and acceptor materials such as poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM), it is really rare that such a BHJ is constructed by a single entity. Here, we presented a photoirradiation-induced p-n heterojunction in naphthylamine-based organic photovoltaic cells, where naphthylamine as a typical p-type semiconductor could be oxidized under photoirradiation and transformed into a new semiconductor with the n-type character. The p-n heterojunction was realized using both the remaining naphthylamine and its oxidative product, giving rise to the performance improvement in organic photovoltaic devices. The experimental results show that the power conversion efficiency (PCE) of the devices could be achieved up to 1.79% and 0.43% in solution and thin film processes, respectively. Importantly, this technology using naphthylamine does not require classic P3HT and PCBM to realize the p-n heterojunction, thereby simplifying the device fabrication process. The present approach opens up a promising route for the development of novel materials applicable to the p-n heterojunction.

  15. Ternary CaCu{sub 4}P{sub 2}-type pnictides AAg{sub 4}Pn{sub 2} (A=Sr, Eu; Pn=As, Sb)

    SciTech Connect

    Stoyko, Stanislav S.; Khatun, Mansura; Scott Mullen, C.; Mar, Arthur

    2012-08-15

    Four ternary pnictides AAg{sub 4}Pn{sub 2} (A=Sr, Eu; Pn=As, Sb) were prepared by reactions of the elements at 850 Degree-Sign C and their crystal structures were determined from single-crystal X-ray diffraction studies. These silver-containing pnictides AAg{sub 4}Pn{sub 2} adopt the trigonal CaCu{sub 4}P{sub 2}-type structure (Pearson symbol hR21, space group R3-bar m, Z=3; a=4.5555(6) A, c=24.041(3) A for SrAg{sub 4}As{sub 2}; a=4.5352(2) A, c=23.7221(11) A for EuAg{sub 4}As{sub 2}; a=4.7404(4) A, c=25.029(2) A for SrAg{sub 4}Sb{sub 2}; a=4.7239(3) A, c=24.689(2) A for EuAg{sub 4}Sb{sub 2}), which can be derived from the trigonal CaAl{sub 2}Si{sub 2}-type structure of the isoelectronic zinc-containing pnictides AZn{sub 2}Pn{sub 2} by insertion of additional Ag atoms into trigonal planar sites within [M{sub 2}Pn{sub 2}]{sup 2-} slabs built up of edge-sharing tetrahedra. Band structure calculations on SrAg{sub 4}As{sub 2} and SrAg{sub 4}Sb{sub 2} revealed that these charge-balanced Zintl phases actually exhibit no gap at the Fermi level and are predicted to be semimetals. - Graphical abstract: SrAg{sub 4}As{sub 2} and related pnictides adopt a CaCu{sub 4}P{sub 2}-type structure in which additional Ag atoms enter trigonal planar sites within slabs built from edge-sharing tetrahedra. Highlights: Black-Right-Pointing-Pointer AAg{sub 4}Pn{sub 2} are the first Ag-containing members of the CaCu{sub 4}P{sub 2}-type structure. Black-Right-Pointing-Pointer Ag atoms are stuffed in trigonal planar sites within CaAl{sub 2}Si{sub 2}-type slabs. Black-Right-Pointing-Pointer Ag-Ag bonding develops through attractive d{sup 10}-d{sup 10} interactions.

  16. Two-dimensional dopant profiling of gallium nitride p-n junctions by scanning capacitance microscopy

    NASA Astrophysics Data System (ADS)

    Lamhamdi, M.; Cayrel, F.; Frayssinet, E.; Bazin, A. E.; Yvon, A.; Collard, E.; Cordier, Y.; Alquier, D.

    2016-04-01

    Two-dimensional imaging of dopant profiles for n and p-type regions are relevant for the development of new power semiconductors, especially for gallium nitride (GaN) for which classical profiling techniques are not adapted. This is a challenging task since it needs a technique with simultaneously good sensitivity, high spatial resolution and high dopant gradient resolution. To face these challenges, scanning capacitance microscopy combined with Atomic Force Microscopy is a good candidate, presenting reproducible results, as demonstrated in literature. In this work, we attempt to distinguish reliably and qualitatively the various doping concentrations and type at p-n and unipolar junctions. For both p-n and unipolar junctions three kinds of samples were prepared and measured separately. The space-charge region of the p-n metallurgical junction, giving rise to different contrasts under SCM imaging, is clearly observed, enlightening the interest of the SCM technique.

  17. Generation of poikiloderma with neutropenia (PN) induced pluripotent stem cells (iPSCs).

    PubMed

    Mills, Jason A; Hudock, Kristin M; Sullivan, Spencer K; Herrera, Pamela; Sullivan, Lisa M; Gadue, Paul; French, Deborah L

    2015-11-01

    Poikiloderma with neutropenia (PN, Clericuzio-type poikiloderma with neutropenia) is a rare autosomal recessive disorder caused by biallelic mutations in the USB1 gene (Alias C16orf57 and MPN1). To date, there have been only 37 reported cases worldwide of this disorder that presents with neutropenia, early onset poikiloderma, respiratory infections, palmo-plantar hyperkeratosis, and skeletal defects. Here we described the generation of human induced pluripotent stem cell lines (PN1 and PN2) from the peripheral blood of a 1-year-old patient using the dox-inducible STEMCCA vector. This patient presented with bacteremia, pneumonia, and neutropenia. Analysis of bone marrow demonstrated normal cellularity with trilineage hematopoiesis and neutropenia.

  18. The effects of notch filters on the correlation properties of a PN signal

    NASA Technical Reports Server (NTRS)

    Sussman, S. M.; Ferrari, E. J.

    1974-01-01

    With wideband pseudo-noise (PN) communications systems, it is sometimes desirable to supplement the inherent interference rejection capabilities by adding notch filters to attenuate relatively narrowband interference. This correspondence presents an investigation of the effects of notch filters on the performance of PN correlation receivers. A theoretical analysis of the correlation drop due to filter distortion has been conducted and confirmed by experimentation. Additional measurements and analysis have established the trade-off between correlation drop and interference suppression as a function of interference bandwidth. A typical result is that by incurring a penalty of a 1-dB drop in correlation peak, interfering signals having bandwidths of 2 to 3% of the PN chip rate can be attenuated by 25 dB.

  19. Nanoscale imaging of the photoresponse in PN junctions of InGaAs infrared detector.

    PubMed

    Xia, Hui; Li, Tian-Xin; Tang, Heng-Jing; Zhu, Liang; Li, Xue; Gong, Hai-Mei; Lu, Wei

    2016-01-01

    Electronic layout, such as distributions of charge carriers and electric field, in PN junction is determinant for the photovoltaic devices to realize their functionality. Considerable efforts have been dedicated to the carrier profiling of this specific region with Scanning Probe Microscope, yet reliable analysis was impeded by the difficulty in resolving carriers with high mobility and the unclear surface effect, particularly on compound semiconductors. Here we realize nanometer Scanning Capacitance Microscopic study on the cross-section of InGaAs/InP photodetectors with the featured dC/dV layout of PN junction unveiled for the first time. It enables us to probe the photo-excited minority carriers in junction region and diagnose the performance deficiency of the diode devices. This work provides an illuminating insight into the PN junction for assessing its basic capability of harvesting photo-carriers as well as blocking leakage current in nanoscopic scale.

  20. Liquid-state semiconductor p-n junction at 903 K

    NASA Astrophysics Data System (ADS)

    Sasaki, Yasushi; Hirano, Yoshihiko; Iguchi, Manabu; Ishii, Kuniyoshi

    2006-12-01

    A liquid-state semiconductor p-n junction has been fabricated by applying the liquid phase separation of the monotectic Sb-Sb2S3 system at 903K. Electrical conduction types of liquid semiconductor of Sb-S alloy and S2S3-x consisting of the immiscible system are found to be p and n types, respectively, from measured absolute Seebeck coefficients. The p-n junction was formed by the liquid Sb--S alloy and Sb2S3-x; this is confirmed from the asymmetric current-voltage characteristics or its behavior is rectified. The formation of the liquid-state p-n junction in liquid semiconductors has great prospects in the next-generation direct thermal-to-electrical energy conversion materials.

  1. A model of dopant diffusion through a strongly correlated p-n junction

    NASA Astrophysics Data System (ADS)

    Wieteska, Jedrzej; Brierley, Richard; Guzman-Verri, Gian; Moller, Gunnar; Littlewood, Peter; Littlewood group Collaboration

    The diffusion of charged ions in a solid depends on an equation of state that balances diffusive and screened electrostatic forces, and is well understood in the case of conventional semiconductors and metals. In the case of a strongly-correlated material, the physics is different, and expected to be relevant, for example, in Li-ion battery cathodes. We propose a model of dopant ion motion through a strongly correlated p-n junction. Our approach is to consider diffusive (Nernst-Planck) dynamics of dopants under screened electrostatic interactions computed within a mean-field (Thomas-Fermi) approximation. Dopant profiles as function of time are calculated for a p-n junction held at constant voltage. In the case where filling levels are near a correlation-induced gap, Mott insulating regions can form at the p-n interface and their dynamics is studied.

  2. Inhibiting Klein Tunneling in a Graphene p-n Junction without an External Magnetic Field.

    PubMed

    Oh, Hyungju; Coh, Sinisa; Son, Young-Woo; Cohen, Marvin L

    2016-07-01

    We study by first-principles calculations a densely packed island of organic molecules (F_{4}TCNQ) adsorbed on graphene. We find that with electron doping the island naturally forms a p-n junction in the graphene sheet. For example, a doping level of ∼3×10^{13}  electrons per cm^{2} results in a p-n junction with an 800 meV electrostatic potential barrier. Unlike in a conventional p-n junction in graphene, in the case of the junction formed by an adsorbed organic molecular island we expect that the Klein tunneling is inhibited, even without an applied external magnetic field. Here Klein tunneling is inhibited by the ferromagnetic order that spontaneously occurs in the molecular island upon doping. We estimate that the magnetic barrier in the graphene sheet is around 10 mT. PMID:27419583

  3. Veselago lensing in graphene with a p-n junction: Classical versus quantum effects

    SciTech Connect

    Milovanović, S. P. Moldovan, D. Peeters, F. M.

    2015-10-21

    The feasibility of Veselago lensing in graphene with a p-n junction is investigated numerically for realistic injection leads. Two different set-ups with two narrow leads are considered with absorbing or reflecting side edges. This allows us to separately determine the influence of scattering on electron focusing for the edges and the p-n interface. Both semiclassical and tight-binding simulations show a distinctive peak in the transmission probability that is attributed to the Veselago lensing effect. We investigate the robustness of this peak on the width of the injector, the position of the p-n interface, and different gate potential profiles. Furthermore, the influence of scattering by both short- and long-range impurities is considered.

  4. Nanoscale imaging of the photoresponse in PN junctions of InGaAs infrared detector

    PubMed Central

    Xia, Hui; Li, Tian-Xin; Tang, Heng-Jing; Zhu, Liang; Li, Xue; Gong, Hai-Mei; Lu, Wei

    2016-01-01

    Electronic layout, such as distributions of charge carriers and electric field, in PN junction is determinant for the photovoltaic devices to realize their functionality. Considerable efforts have been dedicated to the carrier profiling of this specific region with Scanning Probe Microscope, yet reliable analysis was impeded by the difficulty in resolving carriers with high mobility and the unclear surface effect, particularly on compound semiconductors. Here we realize nanometer Scanning Capacitance Microscopic study on the cross-section of InGaAs/InP photodetctors with the featured dC/dV layout of PN junction unveiled for the first time. It enables us to probe the photo-excited minority carriers in junction region and diagnose the performance deficiency of the diode devices. This work provides an illuminating insight into the PN junction for assessing its basic capability of harvesting photo-carriers as well as blocking leakage current in nanoscopic scale. PMID:26892069

  5. Identification of PN1, a Predominant Voltage-Dependent Sodium Channel Expressed Principally in Peripheral Neurons

    NASA Astrophysics Data System (ADS)

    Toledo-Aral, Juan J.; Moss, Brenda L.; He, Zhi-Jun; Koszowski, Adam G.; Whisenand, Teri; Levinson, Simon R.; Wolf, John J.; Silos-Santiago, Inmaculada; Halegoua, Simon; Mandel, Gail

    1997-02-01

    Membrane excitability in different tissues is due, in large part, to the selective expression of distinct genes encoding the voltage-dependent sodium channel. Although the predominant sodium channels in brain, skeletal muscle, and cardiac muscle have been identified, the major sodium channel types responsible for excitability within the peripheral nervous system have remained elusive. We now describe the deduced primary structure of a sodium channel, peripheral nerve type 1 (PN1), which is expressed at high levels throughout the peripheral nervous system and is targeted to nerve terminals of cultured dorsal root ganglion neurons. Studies using cultured PC12 cells indicate that both expression and targeting of PN1 is induced by treatment of the cells with nerve growth factor. The preferential localization suggests that the PN1 sodium channel plays a specific role in nerve excitability.

  6. Epitaxial Growth of an Organic p-n Heterojunction: C60 on Single-Crystal Pentacene.

    PubMed

    Nakayama, Yasuo; Mizuno, Yuta; Hosokai, Takuya; Koganezawa, Tomoyuki; Tsuruta, Ryohei; Hinderhofer, Alexander; Gerlach, Alexander; Broch, Katharina; Belova, Valentina; Frank, Heiko; Yamamoto, Masayuki; Niederhausen, Jens; Glowatzki, Hendrik; Rabe, Jürgen P; Koch, Norbert; Ishii, Hisao; Schreiber, Frank; Ueno, Nobuo

    2016-06-01

    Designing molecular p-n heterojunction structures, i.e., electron donor-acceptor contacts, is one of the central challenges for further development of organic electronic devices. In the present study, a well-defined p-n heterojunction of two representative molecular semiconductors, pentacene and C60, formed on the single-crystal surface of pentacene is precisely investigated in terms of its growth behavior and crystallographic structure. C60 assembles into a (111)-oriented face-centered-cubic crystal structure with a specific epitaxial orientation on the (001) surface of the pentacene single crystal. The present experimental findings provide molecular scale insights into the formation mechanisms of the organic p-n heterojunction through an accurate structural analysis of the single-crystalline molecular contact.

  7. Fast Risetime Reverse Bias Pulse Failures in SiC PN Junction Diodes

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Fazi, Christian; Parsons, James D.

    1996-01-01

    SiC-based high temperature power devices are being developed for aerospace systems which will require high reliability. One behavior crucial to power device reliability. To date, it has necessarily been assumed to date is that the breakdown behavior of SiC pn junctions will be similar to highly reliable silicon-based pn junctions. Challenging this assumption, we report the observation of anomalous unreliable reverse breakdown behavior in moderately doped (2-3 x 10(exp 17) cm(exp -3)) small-area 4H- and 6H-SiC pn junction diodes at temperatures ranging from 298 K (25 C) to 873 K (600 C). We propose a mechanism in which carrier emission from un-ionized dopants and deep level defects leads to this unstable behavior. The fundamental instability mechanism is applicable to all wide bandgap semiconductors whose dopants are significantly un-ionized at typical device operating temperatures.

  8. Photocurrent generation of a single-gate graphene p-n junction fabricated by interfacial modification.

    PubMed

    Wang, S; Sekine, Y; Suzuki, S; Maeda, F; Hibino, H

    2015-09-25

    A back-gate graphene p-n junction was achieved by selective interfacial modification of a chemical vapor deposition (CVD)-grown graphene field effect transistor (FET). Silane self-assembled monolayer (SAM) patterns were used to fabricate uniform p- and n-doped regions and a sharp p-n junction in the graphene FET channel. A gate-dependent photocurrent response was observed at the graphene p-n junction, and exhibited a maximum signal between two Dirac point voltages of SAM-doped graphene regions. A spatial photocurrent map shows that the photocurrent generated at the junction region was much larger than that from graphene/electrode junctions under the same incident laser power. This single-peak characteristic photocurrent in CVD graphene is dominated by the photothermoelectric contribution, and is highly sensitive to the power of incident laser. The SAM interfacial modification method provides a feasible route for the fabrication of efficient graphene-based photodetectors. PMID:26334952

  9. Creating Reversible p-n Junction on Graphene through Ferritin Adsorption.

    PubMed

    Mulyana, Yana; Uenuma, Mutsunori; Okamoto, Naofumi; Ishikawa, Yasuaki; Yamashita, Ichiro; Uraoka, Yukiharu

    2016-03-01

    An alternative way to construct a stable p-n junction on graphene-based field effect transistor (G-FET) through physical adsorption of ferritin (spherical protein shell) is presented. The produced p-n junction on G-FET could also operate through water-gate. Native ferritins are known to be negatively charged in wet condition; however, we found that native negatively charged ferritins became positively charged after performing electron beam (EB)-irradiation. We utilized this property to construct p-n junction on G-FET. We found also that EB-irradiation could remove the effect of charged impurity adsorbed on graphene layer, thus the Dirac point was adjusted to gate voltage Vg = 0. PMID:26943894

  10. Nanoscale imaging of the photoresponse in PN junctions of InGaAs infrared detector.

    PubMed

    Xia, Hui; Li, Tian-Xin; Tang, Heng-Jing; Zhu, Liang; Li, Xue; Gong, Hai-Mei; Lu, Wei

    2016-01-01

    Electronic layout, such as distributions of charge carriers and electric field, in PN junction is determinant for the photovoltaic devices to realize their functionality. Considerable efforts have been dedicated to the carrier profiling of this specific region with Scanning Probe Microscope, yet reliable analysis was impeded by the difficulty in resolving carriers with high mobility and the unclear surface effect, particularly on compound semiconductors. Here we realize nanometer Scanning Capacitance Microscopic study on the cross-section of InGaAs/InP photodetectors with the featured dC/dV layout of PN junction unveiled for the first time. It enables us to probe the photo-excited minority carriers in junction region and diagnose the performance deficiency of the diode devices. This work provides an illuminating insight into the PN junction for assessing its basic capability of harvesting photo-carriers as well as blocking leakage current in nanoscopic scale. PMID:26892069

  11. New Pn and Sn tomographic images of the uppermost mantle beneath the Mediterranean region

    NASA Astrophysics Data System (ADS)

    Gil, A.; Díaz, J.; Gallart, J.

    2012-04-01

    We present here new images of the seismic velocity and anisotropy variations in the uppermost mantle beneath the Mediterranean region, compiled from inversion of Pn and Sn phases. The method of Hearn (1996) has been applied to Pn and Sn lectures from the catalogs of the International Seismological Center and the Spanish Instituto Geografico Nacional. A total of 1,172,293 Pn arrivals coming from 16,527 earthquakes recorded at 1,657 stations with epicentral distances between 220 km and 1400 km have been retained (331,567 arrivals from 15,487events at 961 stations for Sn). Our results, grossly consistent with available 3D tomography images, show significant features well correlated with surface geology. The Pn velocities are high (>8.2 km/s) beneath major sedimentary basins (western Alboran Sea, Valencia Trough, Adriatic Sea, Aquitaine, Guadalquivir, Rharb, Aquitaine and Po basins), and low (<7.8 km/s) in orogenic areas (Betics, Pyrenees, Alps, Apennines, Dinarides, Helenides and Calabrian Arc), confirming the existence of marked variations in crustal thicknesses already documented in some active seismic experiments. The lowest velocity values are found under the Betics and the eastern and western Alps. Another low velocity anomaly is located below the south of Balearic Islands, probably related to a thermal anomaly associated to the westward displacement of the Alboran block along the Emile Baudot escarpment 16 Ma ago. The Pn anisotropic image shows consistent orientations sub-parallel to major orogenic structures, such as Betics, Apennines, Calabrian Arc and Alps. The station delays beneath Betic and Rif ranges are strongly negative, suggesting the presence of crustal thickening all along the Gibraltar Arc. However, only the Betics have a very strong low-velocity anomaly and a pronounced anisotropy pattern. The Sn tomographic image correlates well with the Pn image, even if some relevant differences can be observed beneath particular regions.

  12. Performance analysis for the expanding search PN acquisition algorithm. [pseudonoise in spread spectrum transmission

    NASA Technical Reports Server (NTRS)

    Braun, W. R.

    1982-01-01

    An approach is described for approximating the cumulative probability distribution of the acquisition time of the serial pseudonoise (PN) search algorithm. The results are applicable to both variable and fixed dwell time systems. The theory is developed for the case where some a priori information is available on the PN code epoch (reacquisition problem or acquisition of very long codes). Also considered is the special case of a search over the whole code. The accuracy of the approximation is demonstrated by comparisons with published exact results for the fixed dwell time algorithm.

  13. Fast and efficient silicon thermo-optic switching based on reverse breakdown of pn junction.

    PubMed

    Li, Xianyao; Xu, Hao; Xiao, Xi; Li, Zhiyong; Yu, Yude; Yu, Jinzhong

    2014-02-15

    We propose and demonstrate a fast and efficient silicon thermo-optic switch based on reverse breakdown of the pn junction. Benefiting from the direct heating of silicon waveguide by embedding the pn junction into the waveguide center, fast switching with on/off time of 330 and 450 ns and efficient thermal tuning of 0.12  nm/mW for a 20 μm radius microring resonator are achieved, indicating a high figure of merit of only 8.8  mW·μs. The results here show great potential for application in the future optical interconnects.

  14. Visualizing the photovoltaic behavior of a type-II p-n heterojunction superstructure

    NASA Astrophysics Data System (ADS)

    Xing, Juanjuan; Takeguchi, Masaki; Hashimoto, Ayako; Cao, Junyu; Ye, Jinhua

    2014-04-01

    Photovoltaic behavior of a CaFe2O4/ZnFe2O4 p-n multi-junction was investigated with electron holography combined with an in situ light irradiation system. Potential profiles of the samples with and without light irradiation were extracted to measure the open circuit photovoltage generated either by the whole heterojunction superstructure or from each p-n junction. Investigation on the variation in the energy band configuration under light irradiation revealed the mechanism involved in the photoelectric effect, with respect to the properties of the heterojunction and its periodic quantum structure.

  15. Porous silicon Bragg reflectors on multi-crystalline silicon wafer with p-n junction

    NASA Astrophysics Data System (ADS)

    Ivanov, I. I.; Skryshevsky, V. A.; Kyslovets, O. S.; Nychyporuk, T.; Lemiti, M.

    2016-04-01

    Bragg reflectors consisting of the sequence of dielectric layers are considered to create p-n junction solar cells (SC) with improved efficiency in the longwave spectral range. Bragg mirrors (BM) based on porous silicon (PS) mutilayers at the backside of single crystalline and multicrystalline silicon wafer were formed by electrochemically etching. Maximal experimental reflectivity for BM on multicrystalline substrate achieves 62% due to the natural crystallites disorientation of multicrystalline substrate, whereas for single crystalline silicon the reflectivity in maximum is 87%. BM was formed also on rear side of multicrystalline silicon wafer with p-n junction.

  16. Transfer to the continuum calculations of quasifree (p,pn) and (p,2p) reactions

    NASA Astrophysics Data System (ADS)

    Gomez-Ramos, M.; Moro, A. M.

    2016-05-01

    Nucleon removal (p, pn) and (p, 2p) reactions at intermediate energies have gained renewed attention in recent years as a tool to extract information from exotic nuclei. The information obtained from these experiments is expected to be sensitive to deeper portions of the wave function of the removed nucleon than knockout reactions with heavier targets. In this contribution, we present calculations for (p, 2p) and (p, pn) reactions performed within the so-called transfer to the continuum method (TR*). Results for stable and unstable nuclei are presented, and compared with experimental data, when available.

  17. Compressional Wave Q in the Uppermost Mantle Beneath the Tibetan Plateau Measured Using Pn Wave Spectra

    NASA Astrophysics Data System (ADS)

    Xie, J.

    2003-12-01

    Pn waves from three near-colocated seismic events in the eastern Tarim Basin are well-recorded by the INDEPTH III and II arrays, which are deployed from northern to southern Tibet with a small east-west spread (between ˜88 and 91° E). The paths run southward and sample the Tibetan mantle with epicentral distances increasing from 870 to 1540 km. These waves have spectral contents that are distinctly different from those collected from the Kyrghistan network (KNET), to which the paths traverse westward through the eastern Tienshan. Pn Q beneath Tibet and Tienshan must therefore be different. Xie and Patton (1999,JGR, 104, 941-954) have simultaneously estimated source spectra of the co-located events, and path-averaged Pn Q to the KNET stations. Under a simplified geometrical spreading of Δ -1.3, they have estimated Q0 and η (Pn Q at 1 Hz and its frequency dependence) to KNET to be about 360 and 0.5, respectively. Using those estimates as a priori knowledge, we estimate that Q0 and η are ~180 and 0.3 along paths to northern Tibet, and ˜260 and 0.0 along paths to southern Tibet. The southward increase of Q0 correlates well with a similar increase in Pn velocity contained in previous tomographic images. Additionally, we measured Pn Q using a two-station method along two profiles (from station SANG to TUNL, and GANZ to MAQI) deployed during the 1991-1992 Sino-US Tibetan Plateau experiment. Both profiles are located to the east of 92° E. Along profile SANG-TUNL, we estimate Q0 and η to be ˜270 and 0.0, respectively. The Q0 value is rather high, but correlates well with the high Pn velocities of > 8.1 km/s re-measured in this study. Our results suggest that the zone of low Pn Q0 and velocity in northern Tibet, which is likely caused by high mantle temperature and partial melting, is confined to the west of 92° E. This is so despite that the zone of high Sn attenuation extends to further east.

  18. Visualizing the photovoltaic behavior of a type-II p-n heterojunction superstructure

    SciTech Connect

    Xing, Juanjuan; Takeguchi, Masaki; Hashimoto, Ayako; Cao, Junyu; Ye, Jinhua

    2014-04-21

    Photovoltaic behavior of a CaFe{sub 2}O{sub 4}/ZnFe{sub 2}O{sub 4} p-n multi-junction was investigated with electron holography combined with an in situ light irradiation system. Potential profiles of the samples with and without light irradiation were extracted to measure the open circuit photovoltage generated either by the whole heterojunction superstructure or from each p-n junction. Investigation on the variation in the energy band configuration under light irradiation revealed the mechanism involved in the photoelectric effect, with respect to the properties of the heterojunction and its periodic quantum structure.

  19. Dopant-induced random telegraph signal in nanoscale lateral silicon pn diodes at low temperatures

    SciTech Connect

    Purwiyanti, Sri; Nowak, Roland; Moraru, Daniel; Mizuno, Takeshi; Tabe, Michiharu; Hartanto, Djoko; Jablonski, Ryszard

    2013-12-09

    We studied current-voltage characteristics of nanoscale pn diodes having the junction formed in a laterally patterned ultrathin silicon-on-insulator layer. At temperatures below 30 K, we observed random telegraph signal (RTS) in a range of forward bias. Since RTS is observed only for pn diodes, but not for pin diodes, one dopant among phosphorus donors or boron acceptors facing across the junction is likely responsible for potential changes affecting the current. Based also on potential measurements by low-temperature Kelvin probe force microscope, RTS is ascribed to trapping/detrapping of carriers by/from a single dopant near the farther edge of the depletion region.

  20. Multilayer ReS2 lateral p-n homojunction for photoemission and photodetection

    NASA Astrophysics Data System (ADS)

    Najmzadeh, Mohammad; Ko, Changhyun; Wu, Kedi; Tongay, Sefaattin; Wu, Junqiao

    2016-05-01

    In this paper, a multilayer ReS2 p-n homojunction is fabricated on an oxidized Si substrate, and its photoemission under a forward bias and its photodetection under a reverse bias are reported for the first time. Au nanoparticles were used to make lateral p-n homojunctions. The device shows room temperature photoemission in the IR range, and in the photodetector mode, it shows a 0.41 A/W responsivity under illumination by a 660 nm red laser.

  1. Semiconductor device PN junction fabrication using optical processing of amorphous semiconductor material

    SciTech Connect

    Sopori, Bhushan; Rangappan, Anikara

    2014-11-25

    Systems and methods for semiconductor device PN junction fabrication are provided. In one embodiment, a method for fabricating an electrical device having a P-N junction comprises: depositing a layer of amorphous semiconductor material onto a crystalline semiconductor base, wherein the crystalline semiconductor base comprises a crystalline phase of a same semiconductor as the amorphous layer; and growing the layer of amorphous semiconductor material into a layer of crystalline semiconductor material that is epitaxially matched to the lattice structure of the crystalline semiconductor base by applying an optical energy that penetrates at least the amorphous semiconductor material.

  2. Synthesis, crystal structure, and magnetic properties of quaternary iron selenides: Ba2FePnSe5 (Pn=Sb, Bi)

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Greenfield, Joshua T.; Kovnir, Kirill

    2016-10-01

    Two new barium iron pnictide-selenides, Ba2FeSbSe5 and Ba2FeBiSe5, were synthesized by a high-temperature solid-state route and their crystal structures were determined using single crystal X-ray diffraction. Both compounds are isomorphic to the high pressure phase Ba3FeS5 and crystallize in the orthorhombic space group Pnma (No. 62) with cell parameters of a=12.603(2)/12.619(2) Å, b=9.106(1)/9.183(1) Å, c=9.145(1)/9.123(1) Å and Z=4 for Ba2FeSbSe5 and Ba2FeBiSe5, respectively. According to differential scanning calorimetry, Ba2FePnSe5 compounds exhibit high thermal stability and melt congruently at 1055(5) K (Pn=Sb) and 1105(5) K (Pn=Bi). Magnetic characterizations reveal strong antiferromagnetic nearest-neighbor interactions in both compounds resulting in an antiferromagnetic ordering at 58(1) K for Ba2FeSbSe5 and 79(2) K for Ba2FeBiSe5. The magnetic interactions between Fe3+ centers, which are at least 6 Å apart from each other, are mediated by superexchange interactions.

  3. The structural classification of the highly disordered crystal phases of [Nn][BF4], [Nn][PF6], [Pn][BF4], and [Pn][PF6] salts (Nn(+) = tetraalkylammonium and Pn(+) = tetraalkylphosphonium).

    PubMed

    Matsumoto, Kazuhiko; Harinaga, Ukyo; Tanaka, Ryo; Koyama, Akira; Hagiwara, Rika; Tsunashima, Katsuhiko

    2014-11-21

    The structures of 16 symmetric tetraalkylammonium (Nn(+)) and tetraalkylphosphonium (Pn(+)) salts ([Nn][BF4], [Nn][PF6], [Pn][BF4], and [Pn][PF6], where n = 1 to 4, and denotes the number of carbon atoms in each alkyl chain) have been investigated by X-ray diffraction in order to elucidate the effect of ion size on the disordered structure of organic salts. All the salts exhibit one or more solid-solid phase transitions in differential scanning calorimetric curves. Powder X-ray diffraction revealed that the highest temperature solid phase of these salts belongs to a crystal system with a high cubic or hexagonal symmetry. The structures are classified into 5 different types: CsCl', NaCl, NaCl', inverse NiAs, and TBPPF6. The CsCl'-type whose octant corresponds to the original CsCl unit cell is observed for [N1][PF6] owing to the orientational difference for the cation or the anion. The NaCl-type structure is observed for the N2(+) and P2(+) salts while the NaCl'-type structure is observed for [N3][PF6], where the configuration of ions is based on the NaCl-type but the four equivalent positions in the original NaCl lattice split into two sets of equivalent positions (three and one). The inverse NiAs structure is observed for [P3][PF6]. Single-crystal X-ray diffraction reveals that the disordering of ions in [P4][PF6] becomes more significant with increasing temperature. The new structure of a cubic phase, the TBPPF6-type structure, is found for the salts with long alkyl chains. The structure is roughly determined at 333 K and the ions therein are highly disordered but not rotating. The validity of the radius ratio rule is confirmed through appropriate assessment of the ion size.

  4. Modeling potential hydrochemical responses to climate change and increasing CO2 at the Hubbard Brook Experimental Forest using a dynamic biogeochemical model (PnET-BGC)

    NASA Astrophysics Data System (ADS)

    Pourmokhtarian, Afshin; Driscoll, Charles T.; Campbell, John L.; Hayhoe, Katharine

    2012-07-01

    Dynamic hydrochemical models are useful tools for understanding and predicting the interactive effects of climate change, atmospheric CO2, and atmospheric deposition on the hydrology and water quality of forested watersheds. We used the biogeochemical model, PnET-BGC, to evaluate the effects of potential future changes in temperature, precipitation, solar radiation, and atmospheric CO2on pools, concentrations, and fluxes of major elements at the Hubbard Brook Experimental Forest in New Hampshire, United States. Future climate projections used to run PnET-BGC were generated specifically for the Hubbard Brook Experimental Forest with a statistical technique that downscales climate output (e.g., air temperature, precipitation, solar radiation) from atmosphere-ocean general circulation models (AOGCMs) to a finer temporal and spatial resolution. These climate projections indicate that over the twenty-first century, average air temperature will increase at the site by 1.7°C to 6.5°C with simultaneous increases in annual average precipitation ranging from 4 to 32 cm above the long-term mean (1970-2000). PnET-BGC simulations under future climate change show a shift in hydrology characterized by later snowpack development, earlier spring discharge (snowmelt), greater evapotranspiration, and a slight increase in annual water yield (associated with CO2 effects on vegetation). Model results indicate that under elevated temperature, net soil nitrogen mineralization and nitrification markedly increase, resulting in acidification of soil and stream water, thereby altering the quality of water draining from forested watersheds. Invoking a CO2 fertilization effect on vegetation under climate change substantially mitigates watershed nitrogen loss, highlighting the need for a more thorough understanding of CO2 effects on forest vegetation.

  5. A critical test of organic P-N photovoltaic cells

    SciTech Connect

    Bird, G.R.

    1996-09-01

    We present an urgent view of the field of organic solid state photovoltaic cells. This is a proper time to select the most promising materials from the Electrophotographic Industry, materials long tried in terms of stability, high quantum yield of charge carriers, but set apart by unusually high quantum yields at low applied fields. Our experience with the candidate dyes has covered new tests for identifiable impurities and removal of these impurities by verifiable methods. A new method of purification, reactive train sublimation, has been developed for DNT, one of the simplest of the outstanding perylene dyes, and the method seems applicable to some of the other promising perylene derivatives. It removes the offending impurity by converting it into the desired pure product. The role of water of hydration in the {open_quotes}wine cellar effect{close_quotes}, the slowly rising performance of newly made phthalocyanine containing cells has been analyzed. Under the concept of feasibility testing before a final refinement for practicality of materials and production methods, the hydration can be controlled for high level testing. At the same time, efforts go forward to eliminate the need. At least one of the best phthalocyanine components, X-H{sub 2}Pc, does not require water for peak performance. Finally, we have attacked BBIP (bis-benzimidazole perylene) one of the best and most enigmatic of the near infrared sensors. It has long been known and used as a mixture of synthetic isomers, and we hypothesize that either of these would be better than the uncontrolled mixture. A partial success in the form of isolating highly enriched crystals for an X-ray structure of the trans-molecule, is first presented here. A simple optical analysis method has been developed to follow enrichment procedures. For all of its difficult history, this material seems closest to a state of readiness for critical feasibility testing.

  6. Draft Genome Sequence of Bacillus pseudalcaliphilus PN-137T (DSM 8725), an Alkaliphilic Halotolerant Bacterium Isolated from Garden Soils.

    PubMed

    Wang, Jie-Ping; Liu, Bo; Liu, Guo-Hong; Xiao, Rong-Feng; Zheng, Xue-Fang; Shi, Huai; Ge, Ci-Bin

    2015-01-01

    Bacillus pseudalcaliphilus PN-137(T) (DSM 8725) is a Gram-positive, spore-forming, alkaliphilic, and halotolerant bacterium. Here, we report the 4.49-Mb genome sequence of B. pseudalcaliphilus PN-137(T), which will accelerate the application of this alkaliphile and provide useful information for genomic taxonomy and phylogenomics of Bacillus-like bacteria.

  7. Crystal growth and characterization of the narrow-band-gap semiconductors OsPn₂ (Pn = P, As, Sb).

    PubMed

    Bugaris, Daniel E; Malliakas, Christos D; Shoemaker, Daniel P; Do, Dat T; Chung, Duck Young; Mahanti, Subhendra D; Kanatzidis, Mercouri G

    2014-09-15

    Using metal fluxes, crystals of the binary osmium dipnictides OsPn2 (Pn = P, As, Sb) have been grown for the first time. Single-crystal X-ray diffraction confirms that these compounds crystallize in the marcasite structure type with orthorhombic space group Pnnm. The structure is a three-dimensional framework of corner- and edge-sharing OsPn6 octahedra, as well as [Pn2(4-)] anions. Raman spectroscopy shows the presence of P-P single bonds, consistent with the presence of [Pn2(-4)] anions and formally Os(4+) cations. Optical-band-gap and high-temperature electrical resistivity measurements indicate that these materials are narrow-band-gap semiconductors. The experimentally determined Seebeck coefficients reveal that nominally undoped OsP2 and OsSb2 are n-type semiconductors, whereas OsAs2 is p-type. Electronic band structure using density functional theory calculations shows that these compounds are indirect narrow-band-gap semiconductors. The bonding p orbitals associated with the Pn2 dimer are below the Fermi energy, and the corresponding antibonding states are above, consistent with a Pn-Pn single bond. Thermopower calculations using Boltzmann transport theory and constant relaxation time approximation show that these materials are potentially good thermoelectrics, in agreement with experiment.

  8. A frequency-dependent log-quadratic Pn spreading model in the Northeast China and Korean peninsula

    NASA Astrophysics Data System (ADS)

    Hao, J.; Zhao, L.; Xie, X. B.; Yao, Z.

    2015-12-01

    In 9 October 2006, 25 May 2009, and 12 February 2013, North Korea conducted three successive nuclear tests near the China-Korea border. Based on 297 broadband stations distributed in East China, South Korea, and Japan, the digital seismograms from these nuclear tests are collected to investigate the geometric spreading and attenuation of seismic Pn waves in Northeast China and Korean Peninsula. A highly accurate broadband Pn-wave data set generated by North Korean nuclear tests is used to constrain parameters of a frequency-dependent log-quadratic geometric spreading function and a power-law Pn Q model. The geometric spreading function and apparent Pn wave Q is obtained for the studied area between 2.0 and 10.0 Hz. By taking the two-station amplitude ratios of the Pn spectra, followed by correcting it for the known spreading function, we can strip the effects of source and crust legs from the apparent Pn Q, and retrieve the P-wave attenuation information along the pure upper mantle path. We then use a tomographic approach to obtain the upper mantle P-wave attenuation in Northeast China and Korean Peninsula. The Pn wave spectra observed in China are compared with those recorded in Japan, and the result reveals that the high-frequency Pn signal across the oceanic path attenuated faster than those through the continental path. This work was supported by the National Natural Science Foundation of China (grants 41174048 and 41374065).

  9. Crystal growth and characterization of the narrow-band-gap semiconductors OsPn₂ (Pn = P, As, Sb).

    PubMed

    Bugaris, Daniel E; Malliakas, Christos D; Shoemaker, Daniel P; Do, Dat T; Chung, Duck Young; Mahanti, Subhendra D; Kanatzidis, Mercouri G

    2014-09-15

    Using metal fluxes, crystals of the binary osmium dipnictides OsPn2 (Pn = P, As, Sb) have been grown for the first time. Single-crystal X-ray diffraction confirms that these compounds crystallize in the marcasite structure type with orthorhombic space group Pnnm. The structure is a three-dimensional framework of corner- and edge-sharing OsPn6 octahedra, as well as [Pn2(4-)] anions. Raman spectroscopy shows the presence of P-P single bonds, consistent with the presence of [Pn2(-4)] anions and formally Os(4+) cations. Optical-band-gap and high-temperature electrical resistivity measurements indicate that these materials are narrow-band-gap semiconductors. The experimentally determined Seebeck coefficients reveal that nominally undoped OsP2 and OsSb2 are n-type semiconductors, whereas OsAs2 is p-type. Electronic band structure using density functional theory calculations shows that these compounds are indirect narrow-band-gap semiconductors. The bonding p orbitals associated with the Pn2 dimer are below the Fermi energy, and the corresponding antibonding states are above, consistent with a Pn-Pn single bond. Thermopower calculations using Boltzmann transport theory and constant relaxation time approximation show that these materials are potentially good thermoelectrics, in agreement with experiment. PMID:25162930

  10. Synthesis, physical properties and electronic structure of Sr{sub 1-x}La{sub x}Cu{sub 2}Pn{sub 2} (Pn=P, As, Sb)

    SciTech Connect

    Qin Mingsheng; Yang Chongyin; Wang Yaoming; Yang Zhongtian; Chen Ping; Huang Fuqiang

    2012-03-15

    To explore new series of high-T{sub c} superconductors, Cu-based ternary pnictides of SrCu{sub 2}Pn{sub 2} (Pn=P, As, Sb) with La doping were synthesized at 1073 K from the stoichiometric reaction of the elements. The electrical and magnetic properties as well as the electronic structure were systematically investigated. Absence of superconductive transition was observed over the temperature range from room temperature down to 2 K, and these materials show p-type metal-like conductivity and Pauli paramagnetic behavior. The near E{sub F} bands mainly originate from Cu 3d and Pn np states and the value of total densities of states (DOS) becomes higher as Pn goes from P to Sb. The results provides us with considerable information for a better understanding of the transport properties in pnictides. - Graphical abstract: Sr{sub 1-x}La{sub x}Cu{sub 2}Pn{sub 2} (Pn=P, As, Sb) show metal-like conducting behavior and no superconductive transition was observed from 300 K down to 2 K. Highlights: Black-Right-Pointing-Pointer The superconductivity and electronic structure of Sr{sub 1-x}La{sub x}Cu{sub 2}Pn{sub 2} were investigated. Black-Right-Pointing-Pointer Sr{sub 1-x}La{sub x}Cu{sub 2}Pn{sub 2} show p-type metal-like conducting behavior and paramagnetism. Black-Right-Pointing-Pointer The near E{sub F} electronic structure of SrCu{sub 2}Pn{sub 2} mainly originate from Cu 3d and Pn np states.

  11. Effective Lagrangian of C PN -1 models in the large N limit

    NASA Astrophysics Data System (ADS)

    Rossi, Paolo

    2016-08-01

    The effective low energy Lagrangian of C PN -1 models in d <4 dimensions can be constructed in the large N limit by solving the saddle point equations in the presence of a constant field strength. The two-dimensional case is explicitly worked out, and possible applications are briefly discussed.

  12. Spatioselective Electrochemical and Photoelectrochemical Functionalization of Silicon Microwires with Axial p/n Junctions.

    PubMed

    Milbrat, Alexander; Elbersen, Rick; Kas, Recep; Tiggelaar, Roald M; Gardeniers, Han; Mul, Guido; Huskens, Jurriaan

    2016-02-17

    The spatioselective functionalization of silicon microwires with axial p/n junctions is achieved using the electronic properties of the junction. (Photo)electrochemical deposition of metals is demonstrated at the bottom and top of the wires in the dark and light, respectively. The junction depletion layer remains unmodified, which allows its visualization and comparison with theoretical calculations. PMID:26866621

  13. Diffused P+-N solar cells in bulk GaAs

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Recently melt grown GaAs, made by liquid encapsulation techniques, has become available. This material is of sufficiently good quality to allow the fabrication of solar cells by direct diffusion. Results obtained with p(+)/n junction solar cells made by zinc diffusion are described. The quality of bulk GaAs for this application is evaluated.

  14. Ultimate thin vertical p-n junction composed of two-dimensional layered molybdenum disulfide.

    PubMed

    Li, Hua-Min; Lee, Daeyeong; Qu, Deshun; Liu, Xiaochi; Ryu, Jungjin; Seabaugh, Alan; Yoo, Won Jong

    2015-01-01

    Semiconducting two-dimensional crystals are currently receiving significant attention because of their great potential to be an ultrathin body for efficient electrostatic modulation, which enables to overcome the limitations of silicon technology. Here we report that, as a key building block for two-dimensional semiconductor devices, vertical p-n junctions are fabricated in ultrathin MoS₂ by introducing AuCl₃ and benzyl viologen dopants. Unlike usual unipolar MoS₂, the MoS₂ p-n junctions show ambipolar carrier transport, current rectification via modulation of potential barrier in films thicker than 8 nm and reversed current rectification via tunnelling in films thinner than 8 nm. The ultimate thinness of the vertical p-n homogeneous junctions in MoS₂ is experimentally found to be 3 nm, and the chemical doping depth is found to be 1.5 nm. The ultrathin MoS₂ p-n junctions present a significant potential of the two-dimensional crystals for flexible, transparent, high-efficiency electronic and optoelectronic applications.

  15. P- and PN-Doped Nanotubes for Ultrasensitive and Selective Molecular Detection

    SciTech Connect

    Cruz Silva, Eduardo; Terrones Maldonado, Humberto; Terrones Maldonado, Mauricio; Charlier, Jean Christophe; Meunier, Vincent; Sumpter, Bobby G; Munoz-Sandoval, Emilio; Lopez, Florentino

    2010-01-01

    A first-principles approach is used to establish that substitutional phosphorus atoms strongly modify the chemical properties of the surface of carbon nanotubes, creating highly-localized sites with specific affinity towards acceptor molecules. Phosphorus-nitrogen co-dopants have a similar effect for acceptor molecules, but the P-N bond can also accept charge, resulting in affinity towards donor molecules. This molecular selectivity is illustrated in CO and NH3 adsorbed on PN doped nanotubes, O2 on P-doped nanotubes, and NO2 and SO2 on both P- and PN-doped nanotubes. The adsorption of different chemical species onto the doped nanotubes modifies the dopant-induced localized states, which subsequently alter electronic conductance. Although SO2 and CO adsorption cause minor shifts in electronic conductance; NH3, NO2, and O2 adsorptions induce the suppression of a conductance dip. Conversely, the adsorption of NO2 on PN-doped nanotubes is accompanied with the appearance of an additional dip in conductance, correlated with a shift of the existing ones. Overall these changes in electric conductance provide an efficient way to detect selectively the presence of specific molecules. Additionally, the high oxidation potential of the P-doped nanotubes makes them good candidates for electrode materials in hydrogen fuel cells.

  16. Estimating p-n Diode Bulk Parameters, Bandgap Energy and Absolute Zero by a Simple Experiment

    ERIC Educational Resources Information Center

    Ocaya, R. O.; Dejene, F. B.

    2007-01-01

    This paper presents a straightforward but interesting experimental method for p-n diode characterization. The method differs substantially from many approaches in diode characterization by offering much tighter control over the temperature and current variables. The method allows the determination of important diode constants such as temperature…

  17. Photocurrent generation in lateral graphene p-n junction created by electron-beam irradiation

    PubMed Central

    Yu, Xuechao; Shen, Youde; Liu, Tao; Wu, Tao (Tom); Jie Wang, Qi

    2015-01-01

    Graphene has been considered as an attractive material for optoelectronic applications such as photodetectors owing to its extraordinary properties, e.g. broadband absorption and ultrahigh mobility. However, challenges still remain in fundamental and practical aspects of the conventional graphene photodetectors which normally rely on the photoconductive mode of operation which has the drawback of e.g. high dark current. Here, we demonstrated the photovoltaic mode operation in graphene p-n junctions fabricated by a simple but effective electron irradiation method that induces n-type doping in intrinsic p-type graphene. The physical mechanism of the junction formation is owing to the substrate gating effect caused by electron irradiation. Photoresponse was obtained for this type of photodetector because the photoexcited electron-hole pairs can be separated in the graphene p-n junction by the built-in potential. The fabricated graphene p-n junction photodetectors exhibit a high detectivity up to ~3 × 1010 Jones (cm Hz1/2 W−1) at room temperature, which is on a par with that of the traditional III–V photodetectors. The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices. PMID:26152225

  18. Bismuthoxyiodide Nanoflakes/Titania Nanotubes Arrayed p-n Heterojunction and Its Application for Photoelectrochemical Bioanalysis

    NASA Astrophysics Data System (ADS)

    Zhao, Wei-Wei; Liu, Zhao; Shan, Shu; Zhang, Wen-Wen; Wang, Jing; Ma, Zheng-Yuan; Xu, Jing-Juan; Chen, Hong-Yuan

    2014-03-01

    We have developed sensitive detection of cancer biomarker vascular endothelial growth factor (VEGF) using the p-n heterojunction comprised of p-type BiOI nanoflakes (NFs) array and n-type TiO2 nanotubes (NTs) array. Due to the unique arrayed structure and the synergy effect of photoelectrochemistry in the formed p-n junction, the synthesized configuration has superior excitation efficiency and thus excellent photoresponsibility. Then, the fabricated p-n heterojunction was integrated with an exquisite bioassay protocol for addressing VEGF using a sandwich immunoassay with glucosedehydrogenase (GDH) as the enzyme tags. Due to the excellent performance of BiOI NFs array/TiO2 NTs array and the ingenious signaling mechanism, the proposed system could achieve the sensitive and specific VEGF detection. This work not only presents a simple BiOI NFs array/TiO2 NTs array p-n heterojunction for general applications in the broad photochemistry areas, but also opens a different horizon for current development of advanced PEC biomolecular detection.

  19. The PR in PN for Education Associations. PR Bookshelf, No. 3.

    ERIC Educational Resources Information Center

    National Education Association, Washington, DC.

    This booklet presents suggestions and guidelines for the effective use of public relations (PR) techniques during professional negotiations (PN) among teachers, administrators, and boards of education. Introductory sections present the National Education Association (NEA) position regarding professional negotiation and grievance procedures and…

  20. Photocurrent spectroscopy of exciton and free particle optical transitions in suspended carbon nanotube pn-junctions

    SciTech Connect

    Chang, Shun-Wen; Theiss, Jesse; Hazra, Jubin; Aykol, Mehmet; Kapadia, Rehan; Cronin, Stephen B.

    2015-08-03

    We study photocurrent generation in individual, suspended carbon nanotube pn-junction diodes formed by electrostatic doping using two gate electrodes. Photocurrent spectra collected under various electrostatic doping concentrations reveal distinctive behaviors for free particle optical transitions and excitonic transitions. In particular, the photocurrent generated by excitonic transitions exhibits a strong gate doping dependence, while that of the free particle transitions is gate independent. Here, the built-in potential of the pn-junction is required to separate the strongly bound electron-hole pairs of the excitons, while free particle excitations do not require this field-assisted charge separation. We observe a sharp, well defined E{sub 11} free particle interband transition in contrast with previous photocurrent studies. Several steps are taken to ensure that the active charge separating region of these pn-junctions is suspended off the substrate in a suspended region that is substantially longer than the exciton diffusion length and, therefore, the photocurrent does not originate from a Schottky junction. We present a detailed model of the built-in fields in these pn-junctions, which, together with phonon-assistant exciton dissociation, predicts photocurrents on the same order of those observed experimentally.

  1. Gate-tunable carbon nanotube-MoS2 heterojunction p-n diode.

    PubMed

    Jariwala, Deep; Sangwan, Vinod K; Wu, Chung-Chiang; Prabhumirashi, Pradyumna L; Geier, Michael L; Marks, Tobin J; Lauhon, Lincoln J; Hersam, Mark C

    2013-11-01

    The p-n junction diode and field-effect transistor are the two most ubiquitous building blocks of modern electronics and optoelectronics. In recent years, the emergence of reduced dimensionality materials has suggested that these components can be scaled down to atomic thicknesses. Although high-performance field-effect devices have been achieved from monolayered materials and their heterostructures, a p-n heterojunction diode derived from ultrathin materials is notably absent and constrains the fabrication of complex electronic and optoelectronic circuits. Here we demonstrate a gate-tunable p-n heterojunction diode using semiconducting single-walled carbon nanotubes (SWCNTs) and single-layer molybdenum disulfide as p-type and n-type semiconductors, respectively. The vertical stacking of these two direct band gap semiconductors forms a heterojunction with electrical characteristics that can be tuned with an applied gate bias to achieve a wide range of charge transport behavior ranging from insulating to rectifying with forward-to-reverse bias current ratios exceeding 10(4). This heterojunction diode also responds strongly to optical irradiation with an external quantum efficiency of 25% and fast photoresponse <15 μs. Because SWCNTs have a diverse range of electrical properties as a function of chirality and an increasing number of atomically thin 2D nanomaterials are being isolated, the gate-tunable p-n heterojunction concept presented here should be widely generalizable to realize diverse ultrathin, high-performance electronics and optoelectronics.

  2. Sensitive thermal microsensor with pn junction for heat measurement of a single cell

    NASA Astrophysics Data System (ADS)

    Yamada, Taito; Inomata, Naoki; Ono, Takahito

    2016-02-01

    A sensitive thermal microsensor based on a pn junction diode for heat measurements of biological single cells is developed and evaluated. Using a fabricated device, we demonstrated the heat measurement of a single brown fat cell. The principle of the sensor relies on the temperature dependence of the pn junction diode resistance. This method has a capability of the highly thermal sensitivity by downsizing and the advantage of a simple experimental setup using electrical circuits without any special equipment. To achieve highly sensitive heat measurement of single cells, downsizing of the sensor is necessary to reduce the heat capacity of the sensor itself. The sensor with the pn junction diode can be downsized by microfabrication. A bridge beam structure with the pn junction diode as a thermal sensor is placed in vacuum using a microfludic chip to decrease the heat loss to the surroundings. A temperature coefficient of resistance of 1.4%/K was achieved. The temperature and thermal resolutions of the fabricated device are 1.1 mK and 73.6 nW, respectively. The heat measurements of norepinephrine stimulated and nonstimulated single brown fat cells were demonstrated, and different behaviors in heat generation were observed.

  3. Electrocatalytic Reduction of Carbon Dioxide with a Well-Defined PN 3 -Ru Pincer Complex

    DOE PAGESBeta

    Min, Shixiong; Rasul, Shahid; Li, Huaifeng; Grills, David C.; Takanabe, Kazuhiro; Li, Lain-Jong; Huang, Kuo-Wei

    2015-11-13

    We established a well-defined PN3-Ru pincer complex (5) bearing a redox-active bipyridine ligand with an aminophosphine arm as an effective and stable molecular electrocatalyst for CO2 reduction to CO and HCOOH with negligible formation of H2 in a H2O/MeCN mixture.

  4. First measurements with a frame store PN-CCD X-ray detector

    NASA Astrophysics Data System (ADS)

    Meidinger, Norbert; Bonerz, Stefan; Eckhardt, Rouven; Englhauser, Jakob; Hartmann, Robert; Hasinger, Günther; Holl, Peter; Krause, Norbert; Lutz, Gerhard; Richter, Rainer; Soltau, Heike; Strüder, Lothar; Trümper, Joachim

    2003-10-01

    The PN-CCD camera on the XMM-Newton X-ray astronomy satellite is the most advanced X-ray spectrometer combining high quantum efficiency, high-speed readout and excellent energy resolution. According to the fullframe concept, the whole 6×6cm2 large CCD-chip area is used as image area, i.e. is sensitive and exposed to X-rays. The camera operates since January 2000 successfully in space without performance degradation. Based on the concept and technology development of the XMM-Newton PN-CCD, the `frame store PN-CCD', a further development of the detector has been proposed. For the new detector a frame store area is added, adjacent to the image area, to allow in parallel photon exposure in the image area and signal readout of the previous image in the frame store area. The concept and the new features of the device will be described here. This comprises in particular a reduced probability of out-of-time event occurrence, the optimization of electronic noise and charge transfer losses as well as a method to obtain a cleaner low-energy response. The first measurements with the new frame store PN-CCD are presented with focus on the above addressed detector parameters. It is planned to apply the device as focal plane instrument for the ROSITA mission that has the aim to extend the ROSAT all-sky survey towards higher energies.

  5. Photovoltaic effect in few-layer black phosphorus PN junctions defined by local electrostatic gating.

    PubMed

    Buscema, Michele; Groenendijk, Dirk J; Steele, Gary A; van der Zant, Herre S J; Castellanos-Gomez, Andres

    2014-08-28

    In conventional photovoltaic solar cells, photogenerated carriers are extracted by the built-in electric field of a semiconductor PN junction, defined by ionic dopants. In atomically thin semiconductors, the doping level can be controlled by the field effect, enabling the implementation of electrically tunable PN junctions. However, most two-dimensional (2D) semiconductors do not show ambipolar transport, which is necessary to realize PN junctions. Few-layer black phosphorus (b-P) is a recently isolated 2D semiconductor with direct bandgap, high mobility, large current on/off ratios and ambipolar operation. Here we fabricate few-layer b-P field-effect transistors with split gates and hexagonal boron nitride dielectric. We demonstrate electrostatic control of the local charge carrier type and density in the device. Illuminating a gate-defined PN junction, we observe zero-bias photocurrents and significant open-circuit voltages due to the photovoltaic effect. The small bandgap of the material allows power generation for illumination wavelengths up to 940 nm, attractive for energy harvesting in the near-infrared.

  6. Sodium-dependent inhibition by PN200-110 enantiomers of nicotinic adrenal catecholamine release.

    PubMed Central

    Cárdenas, A. M.; Montiel, C.; Artalejo, A. R.; Sánchez-García, P.; García, A. G.

    1988-01-01

    1. Dimethylphenylpiperazinium (DMPP) or high K concentrations evoke catecholamine release from perfused cat adrenal glands; in both cases the secretory response was significantly enhanced in the absence of Na. Tetrodotoxin did not modify the nicotinic secretory response. 2. The (+)- and (-)-enantiomers of the dihydropyridine Ca channel blocker PN200-110 show a high degree of stereoselectivity in the inhibition of catecholamine secretion evoked by high K or by DMPP in the presence of Na, the (+)-enantiomer being 57 and 80 times more potent, respectively, than the (-)-enantiomer. Both, noradrenaline and adrenaline release were equally depressed by PN200-110. 3. The IC50 values for (+)- and (-)-PN200-110 for blockade of the secretory response induced by K or DMPP in the presence of Na are in the same range. In the absence of Na, (-)-PN200-110 did not affect DMPP-evoked secretion; however, the (+)-enantiomer partially inhibited it. 4. The results suggest that the physiological catecholamine release from chromaffin cells is preceded by Na entry through the nicotinic receptor-associated ionophore; this causes cell depolarization, opening of voltage-dependent, dihydropyridine-sensitive Ca channels and Ca entry into the cell. In the absence of Na, additional Ca influx through an alternative pathway (the nicotinic cholinoceptor ionophore?) might also activate secretion. PMID:2975522

  7. Moment closures based on minimizing the residual of the PN angular expansion in radiation transport

    NASA Astrophysics Data System (ADS)

    Zheng, Weixiong; McClarren, Ryan G.

    2016-06-01

    In this work we present two new closures for the spherical harmonics (PN) method in slab geometry transport problems. Our approach begins with an analysis of the squared-residual of the transport equation where we show that the standard truncation and diffusive closures do not minimize the residual of the PN expansion. Based on this analysis we derive two models, a moment-limited diffusive (ML DN) closure and a transient PN (TPN) closure that attempt to address shortcomings of common closures. The form of these closures is similar to flux-limiters for diffusion with the addition of a time-derivative in the definition of the closure. Numerical results on a pulsed plane source problem, the Gordian knot of slab-geometry transport problems, indicate that our new closure outperforms existing linear closures. Additionally, on a deep penetration problem we demonstrate that the TPN closure does not suffer from the artificial shocks that can arise in the MN entropy-based closure. Finally, results for Reed's problem demonstrate that the TPN solution is as accurate as the PN+3 solution. We further extend the TPN closure to 2D Cartesian geometry. The line source test problem demonstrates the model effectively damps oscillations and negative densities.

  8. Enhanced spin Seebeck effect in a germanene p-n junction

    SciTech Connect

    Zheng, Jun; Chi, Feng; Guo, Yong

    2014-12-28

    Spin Seebeck effect in a germanene p-n junction is studied by using the nonequilibrium Green's function method combined with the tight-binding Hamiltonian. We find that the thermal bias ΔT can generate spin thermopower when a local exchange field is applied on one edge of the germanene nano-ribbon. The magnitude of the spin thermopower can be modulated by the potential drop across the two terminals of the p-n junction. When the value of the potential drop is smaller than the spin-orbit interaction strength, the spin thermopower is enhanced by two orders of magnitude larger as compared to the case of zero p-n voltage. Optimal temperature corresponding to maximum spin thermopower is insensitive to the potential drop. In the p-n region, maximum spin thermopower can be obtained at relatively higher temperatures. When the value of the potential drop is larger than that of the spin-orbit interaction, however, the spin Seebeck effect decays rapidly with increasing potential drop or temperature. By optimizing the structure parameters, the magnitude of the spin thermopower can be remarkably enhanced due to the coexistence of the exchange field and the potential drop.

  9. Parallel p-n junctions across nanowires by one-step ex situ doping.

    PubMed

    Hazut, Ori; Huang, Bo-Chao; Pantzer, Adi; Amit, Iddo; Rosenwaks, Yossi; Kohn, Amit; Chang, Chia-Seng; Chiu, Ya-Ping; Yerushalmi, Roie

    2014-08-26

    The bottom-up synthesis of nanoscale building blocks is a versatile approach for the formation of a vast array of materials with controlled structures and compositions. This approach is one of the main driving forces for the immense progress in materials science and nanotechnology witnessed over the past few decades. Despite the overwhelming advances in the bottom-up synthesis of nanoscale building blocks and the fine control of accessible compositions and structures, certain aspects are still lacking. In particular, the transformation of symmetric nanostructures to asymmetric nanostructures by highly controlled processes while preserving the modified structural orientation still poses a significant challenge. We present a one-step ex situ doping process for the transformation of undoped silicon nanowires (i-Si NWs) to p-type/n-type (p-n) parallel p-n junction configuration across NWs. The vertical p-n junctions were measured by scanning tunneling microscopy (STM) in concert with scanning tunneling spectroscopy (STS), termed STM/S, to obtain the spatial electronic properties of the junction formed across the NWs. Additionally, the parallel p-n junction configuration was characterized by off-axis electron holography in a transmission electron microscope to provide an independent verification of junction formation. The doping process was simulated to elucidate the doping mechanisms involved in the one-step p-i-n junction formation.

  10. Bismuthoxyiodide Nanoflakes/Titania Nanotubes Arrayed p-n Heterojunction and Its Application for Photoelectrochemical Bioanalysis

    PubMed Central

    Zhao, Wei-Wei; Liu, Zhao; Shan, Shu; Zhang, Wen-Wen; Wang, Jing; Ma, Zheng-Yuan; Xu, Jing-Juan; Chen, Hong-Yuan

    2014-01-01

    We have developed sensitive detection of cancer biomarker vascular endothelial growth factor (VEGF) using the p-n heterojunction comprised of p-type BiOI nanoflakes (NFs) array and n-type TiO2 nanotubes (NTs) array. Due to the unique arrayed structure and the synergy effect of photoelectrochemistry in the formed p-n junction, the synthesized configuration has superior excitation efficiency and thus excellent photoresponsibility. Then, the fabricated p-n heterojunction was integrated with an exquisite bioassay protocol for addressing VEGF using a sandwich immunoassay with glucosedehydrogenase (GDH) as the enzyme tags. Due to the excellent performance of BiOI NFs array/TiO2 NTs array and the ingenious signaling mechanism, the proposed system could achieve the sensitive and specific VEGF detection. This work not only presents a simple BiOI NFs array/TiO2 NTs array p-n heterojunction for general applications in the broad photochemistry areas, but also opens a different horizon for current development of advanced PEC biomolecular detection. PMID:24651880

  11. Studies of silicon p-n junction solar cells. [open circuit photovoltage

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.

    1976-01-01

    Single crystal silicon p-n junction solar cells made with low resistivity substrates show poorer solar energy conversion efficiency than traditional theory predicts. The physical mechanisms responsible for this discrepancy are identified and characterized. The open circuit voltage in shallow junction cells of about 0.1 ohm/cm substrate resistivity is investigated under AMO (one sun) conditions.

  12. Electronic transport in graphene: p-n junctions, shot noise, and nanoribbons

    NASA Astrophysics Data System (ADS)

    Williams, James Ryan

    2009-12-01

    Novel, two-dimensional materials have allowed for the inception and elucidation of a plethora of physical phenomena. On such material, a hexagonal lattice of carbon atoms called graphene, is a unique, truly two-dimensional molecular conductor. This thesis describes six experiments that elucidate some interesting physical properties and technological applications of graphene, with an emphasis on graphene-based p-n junctions. A technique for the creation of high-quality p-n junctions of graphene is described. Transport measurements at zero magnetic field demonstrate local control of the carrier type and density bipolar graphene-based junctions. In the quantum Hall regime, new plateaus in the conductance are observed and explained in terms of mode mixing at the p-n interface. Shot noise in unipolar and bipolar graphene devices is measured. A density-independent Fano factor is observed, contrary to theoretical expectations. Further, an independence on device geometry is also observed. The role of disorder on the measured Fano factor is discussed, and comparison to recent theory for disordered graphene is made. The effect of a two-terminal geometry, where the device aspect ratio is different from unity, is measured experimentally and analyzed theoretically. A method for extracting layer number from the conductance extrema is proposed. A method for a conformal mapping of a device with asymmetric contacts to a rectangle is demonstrated. Finally, possible origins of discrepancies between theory and experiment are discussed. Transport along p-n junctions in graphene is reported. Enhanced transport along the junction is observed and attributed to states that exist at the p-n interface. A correspondence between the observed phenomena at low-field and in the quantum Hall regime is observed. An electric field perpendicular to the junction is found to reduce the enhanced conductance at the p-n junction. A corollary between the p-n interface states and "snake states" in an

  13. CH2CHOH2+ + PN: a proton-transfer triple play.

    PubMed

    Petrie, Simon

    2005-07-21

    Quantum chemical calculations are used to explore the proton-transfer reactivity of O-protonated vinyl alcohol, CH2CHOH2+, with phosphorus nitride, PN. This reaction is relevant to the chemical evolution of interstellar clouds, since O-protonated vinyl alcohol has been postulated (and tentatively identified) as a product of the association reaction between interstellar H3O+ and C2H2, while PN is the most widespread and abundant phosphorus-containing molecule seen in astrophysical environments. Furthermore, the reaction exhibits an unusual mechanistic feature, namely, an extended "proton-transport catalysis" mechanism, which we characterize here as a "proton-transfer triple play". The reaction proceeds initially by proton transfer from CH2CHOH2+ to PN, then from PNH+ to CH2CHOH, and finally from CH3CHOH+ to PN, where the emphasized atom indicates the resultant site of protonation/deprotonation. Thus, the ultimate overall bimolecular proton-transfer reaction is expected to occur as CH2CHOH2+ + PN --> CH3CHO + PNH+; that is, the apparent favored product channel exhibits not only proton transfer but also keto/enol tautomerization. The triple-play mechanism can be rationalized in terms of the proton affinities of vinyl alcohol, acetaldehyde, and phosphorus nitride, which here are satisfactorily reproduced by high-level ab initio calculations. Other neutrals with a proton affinity appropriate for the possible triple-play mechanism converting CH2CHOH2+ to CH3CHO are also identified, with a view to encouraging experimental investigation of this mechanism.

  14. Uppermost Mantle Seismic Velocity and Anisotropy in Southwestern Europe and North Africa by Using PN Tomography

    NASA Astrophysics Data System (ADS)

    Gil, A.; Diaz, J.; Gallart, J.

    2011-12-01

    We present here new images of the seismic velocity and anisotropy variations in the uppermost mantle beneath Southwestern Europe and North Africa, compiled from inversion of Pn phases. The method of Hearn (1996) has been applied to Pn lectures from the catalogs of the International Seismological Center and the Spanish Instituto Geografico Nacional, for the time period 1990-2009. A total of 338,691 Pn arrivals coming from 13,027 earthquakes recorded at 802 stations, with epicentral distances between 220 km and 1400 km have been retained after applying quality criteria (maximum depth, minimum number of recordings, maximum residual values...). Our results, grossly consistent with available 3D tomography images, show significant features well correlated with surface geology: (a) The Pn velocities are higher (>8.2 km/s) beneath major sedimentary basins (western edge of the Alboran Sea, Valencia Through, Guadalquivir, Duero, Aquitaine and Po basins), and lower (<7.8 km/s) in orogenic areas (Betics, Pyrenees, Alps, Apennines chains and Calabrian Arc), confirming the existence of marked variations in crustal thicknesses already documented by active seismic experiments. The lowest velocity values are found under the Betics (<7.5 km/s), while a less pronounced low velocity (7.85 km/s) is observed beneath the Iberian Range, an area where the existence of crustal root is still poorly constrained. (b) Pn anisotropy shows consistent orientations sub-parallel to major orogenic structures, such as Betics, Apennines, Calabrian Arc and Alps. (c) The station delays beneath Betic and Rif ranges are strongly negative, suggesting the presence of crustal thickening all along the Gibraltar Arc System. However, only the Betics have a very strong low-velocity anomaly and a pronounced anisotropy pattern, suggesting that high temperature material may be present there at subcrustal levels.

  15. Elevated carbon dioxide influences yield and photosynthetic responses of hydroponically-grown sweetpotato

    NASA Technical Reports Server (NTRS)

    Mortley, D.; Hill, J.; Loretan, P.; Bonsi, C.; Hill, W.; Hileman, D.; Terse, A.

    1996-01-01

    The response of 'TI-155' and 'Georgia Jet' sweetpotato cultivars to elevated CO2 concentrations of 400 (ambient), 750 and 1000 micromoles mol-1 were evaluated under controlled environment conditions using the nutrient film technique (NFT). Growth chamber conditions included photosynthetic photon flux (PPF) of 600 micromoles m-2 s-1, 14/10 light/dark period, and 70% +/- 5% RH. Plants were grown using a modified half-Hoagland nutrient solution with a pH range of 5.5-6.0 and an electrical conductivity of 0.12 S m-1. Gas exchange measurements were made using infrared gas analysis, an open-flow gas exchange system, and a controlled-climate cuvette. Photosynthetic (Pn) measurements were made at CO2 ranges of 50 to 1000 micromoles mol-1. Storage root yield/plant increased with CO2 up to 750 but declined at 1000 micromoles mol-1. Storage root dry matter (DM) and foliage dry weight increased with increasing CO2. Harvest index (HI) for both cultivars was highest at 750 micromoles mol-1. The PPF vs Pn curves were typical for C3 plants with saturation occurring at approximately 600 micromoles m-2 s-1. CO2 concentration did not significantly influence net Pn, transpiration, water-use-efficiency (WUE), and stomatal conductance. As measurement CO2 concentration increased, net Pn and WUE increased while transpiration and stomatal conductance decreased.

  16. Elevated carbon dioxide influences yield and photosynthetic responses of hydroponically-grown [correction of glown] sweetpotato.

    PubMed

    Mortley, D; Hill, J; Loretan, P; Bonsi, C; Hill, W; Hileman, D; Terse, A

    1996-12-01

    The response of 'TI-155' and 'Georgia Jet' sweetpotato cultivars to elevated CO2 concentrations of 400 (ambient), 750 and 1000 micromoles mol-1 were evaluated under controlled environment conditions using the nutrient film technique (NFT). Growth chamber conditions included photosynthetic photon flux (PPF) of 600 micromoles m-2 s-1, 14/10 light/dark period, and 70% +/- 5% RH. Plants were grown using a modified half-Hoagland nutrient solution with a pH range of 5.5-6.0 and an electrical conductivity of 0.12 S m-1. Gas exchange measurements were made using infrared gas analysis, an open-flow gas exchange system, and a controlled-climate cuvette. Photosynthetic (Pn) measurements were made at CO2 ranges of 50 to 1000 micromoles mol-1. Storage root yield/plant increased with CO2 up to 750 but declined at 1000 micromoles mol-1. Storage root dry matter (DM) and foliage dry weight increased with increasing CO2. Harvest index (HI) for both cultivars was highest at 750 micromoles mol-1. The PPF vs Pn curves were typical for C3 plants with saturation occurring at approximately 600 micromoles m-2 s-1. CO2 concentration did not significantly influence net Pn, transpiration, water-use-efficiency (WUE), and stomatal conductance. As measurement CO2 concentration increased, net Pn and WUE increased while transpiration and stomatal conductance decreased.

  17. Gravitational-wave phasing for low-eccentricity inspiralling compact binaries to 3PN order

    NASA Astrophysics Data System (ADS)

    Moore, Blake; Favata, Marc; Arun, K. G.; Mishra, Chandra Kant

    2016-06-01

    Although gravitational radiation causes inspiralling compact binaries to circularize, a variety of astrophysical scenarios suggest that binaries might have small but non-negligible orbital eccentricities when they enter the low-frequency bands of ground- and space-based gravitational-wave detectors. If not accounted for, even a small orbital eccentricity can cause a potentially significant systematic error in the mass parameters of an inspiralling binary [M. Favata, Phys. Rev. Lett. 112, 101101 (2014)]. Gravitational-wave search templates typically rely on the quasicircular approximation, which provides relatively simple expressions for the gravitational-wave phase to 3.5 post-Newtonian (PN) order. Damour, Gopakumar, Iyer, and others have developed an elegant but complex quasi-Keplerian formalism for describing the post-Newtonian corrections to the orbits and waveforms of inspiralling binaries with any eccentricity. Here, we specialize the quasi-Keplerian formalism to binaries with low eccentricity. In this limit, the nonperiodic contribution to the gravitational-wave phasing can be expressed explicitly as simple functions of frequency or time, with little additional complexity beyond the well-known formulas for circular binaries. These eccentric phase corrections are computed to 3PN order and to leading order in the eccentricity for the standard PN approximants. For a variety of systems, these eccentricity corrections cause significant corrections to the number of gravitational-wave cycles that sweep through a detector's frequency band. This is evaluated using several measures, including a modification of the useful cycles. By comparing to numerical solutions valid for any eccentricity, we find that our analytic solutions are valid up to e0≲0.1 for comparable-mass systems, where e0 is the eccentricity when the source enters the detector band. We also evaluate the role of periodic terms that enter the phasing and discuss how they can be incorporated into some of

  18. Yield Improvement in Steel Casting (Yield II)

    SciTech Connect

    Richard A. Hardin; Christoph Beckermann; Tim Hays

    2002-02-18

    This report presents work conducted on the following main projects tasks undertaken in the Yield Improvement in Steel Casting research program: Improvement of Conventional Feeding and Risering Methods, Use of Unconventional Yield Improvement Techniques, and Case Studies in Yield Improvement. Casting trials were conducted and then simulated using the precise casting conditions as recorded by the participating SFSA foundries. These results present a statistically meaningful set of experimental data on soundness versus feeding length. Comparisons between these casting trials and casting trials performed more than forty years ago by Pellini and the SFSA are quite good and appear reasonable. Comparisons between the current SFSA feeding rules and feeding rules based on the minimum Niyama criterion reveal that the Niyama-based rules are generally less conservative. The niyama-based rules also agree better with both the trials presented here, and the casting trails performed by Pellini an d the SFSA years ago. Furthermore, the use of the Niyama criterion to predict centerline shrinkage for horizontally fed plate sections has a theoretical basis according to the casting literature reviewed here. These results strongly support the use of improved feeding rules for horizontal plate sections based on the Niyama criterion, which can be tailored to the casting conditions for a given alloy and to a desired level of soundness. The reliability and repeatability of ASTM shrinkage x-ray ratings was investigated in a statistical study performed on 128 x-rays, each of which were rated seven different times. A manual ''Feeding and Risering Guidelines for Steel Castings' is given in this final report. Results of casting trials performed to test unconventional techniques for improving casting yield are presented. These use a stacked arrangement of castings and riser pressurization to increase the casting yield. Riser pressurization was demonstrated to feed a casting up to four time s the

  19. Atmospheric Nitrogen Fluorescence Yield

    NASA Technical Reports Server (NTRS)

    Adams, J. H., Jr.; Christl, M. J.; Fountain, W. F.; Gregory, J. C.; Martens, K. U.; Sokolsky, Pierre; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Several existing and planned experiments estimate the energies of ultra-high energy cosmic rays from air showers using the atmospheric nitrogen fluorescence. The nitrogen fluorescence yield from air shower electrons depends on the atmospheric composition. We will discuss the uncertainties in the fluorescence yield form electrons in the real atmosphere and describe a concept for a small balloon payload to measure the atmospheric fluorescence yield as a function of attitude.

  20. Electrical/thermal transport and electronic structure of the binary cobalt pnictides CoPn{sub 2} (Pn = As and Sb)

    SciTech Connect

    Goto, Yosuke Miyao, Syuhei; Kamihara, Yoichi; Matoba, Masanori

    2015-06-15

    We demonstrate the electrical and thermal transport properties of polycrystalline CoPn{sub 2} (Pn = As and Sb) between 300 and 900 K. CoAs{sub 2} shows semiconducting electrical transport up to 900 K, while CoSb{sub 2} exhibits degenerate conduction. Sign inversion of the Seebeck coefficient is observed at ∼310 and ∼400 K for CoAs{sub 2} and CoSb{sub 2}, respectively. Thermal conductivity at 300 K is 11.7 Wm{sup −1}K{sup −1} for CoAs{sub 2} and 9.4 Wm{sup −1}K{sup −1} for CoSb{sub 2}. The thermoelectric power factor of CoAs{sub 2} is ∼10 μWcm{sup −1}K{sup −2}, although the dimensionless figure of merit is limited to ∼0.1 due to relatively high thermal conductivity. Using electronic structure calculations, the band gap value is calculated to be 0.55 eV for CoAs{sub 2} and 0.26 eV for CoSb{sub 2}.

  1. A Novel Method to Fabricate Silicon Nanowire p-n Junctions by a Combination of Ion Implantation and in-situ Doping.

    PubMed

    Kanungo, Pratyushdas; Kögler, Reinhard; Werner, Peter; Gösele, Ulrich; Skorupa, Wolfgang

    2009-11-08

    We demonstrate a novel method to fabricate an axial p-n junction inside <111> oriented short vertical silicon nanowires grown by molecular beam epitaxy by combining ion implantation with in-situ doping. The lower halves of the nanowires were doped in-situ with boron (concentration ~1018cm-3), while the upper halves were doubly implanted with phosphorus to yield a uniform concentration of 2 × 1019 cm-3. Electrical measurements of individually contacted nanowires showed excellent diode characteristics and ideality factors close to 2. We think that this value of ideality factors arises out of a high rate of carrier recombination through surface states in the native oxide covering the nanowires.

  2. High-voltage 6H-SiC p-n junction diodes

    NASA Technical Reports Server (NTRS)

    Matus, L. G.; Powell, J. A.; Salupo, C. S.

    1991-01-01

    A chemical vapor deposition (CVD) process has been used to produce device structures of n- and p-type 6H-SiC epitaxial layers on commercially produced single-crystal 6H-SiC wafers. Mesa-style p-n junction diodes were successfully fabricated from these device structures using reactive ion etching, oxide passivation, and electrical contact metallization techniques. When tested in air, the 6H-SiC diodes displayed excellent rectification characteristics up to the highest temperature tested, 600 C. To observe avalanche breakdown of the p-n junction diodes, testing under a high-electrical-strength liquid was necessary. The avalanche breakdown voltage was 1000 V representing the highest reverse breakdown voltage to be reported for any CVD-grown SiC diode.

  3. Hidden quantum mirage by negative refraction in semiconductor P-N junctions

    NASA Astrophysics Data System (ADS)

    Zhang, Shu-Hui; Zhu, Jia-Ji; Yang, Wen; Lin, Hai-Qing; Chang, Kai

    2016-08-01

    We predict a robust quantum interference phenomenon in a semiconductor P-N junction: with a local pump on one side of the junction, the response of a local probe on the other side behaves as if the disturbance emanates not from the pump but instead from its mirror image about the junction. This phenomenon follows from the matching of Fermi surfaces of the constituent materials, thus it is robust against the details of the junction (e.g., width, potential profile, and even disorder), in contrast to the widely studied anomalous focusing caused by negative refraction. The recently fabricated P-N junctions in 2D semiconductors provide ideal platforms to explore this phenomenon and its applications to dramatically enhance charge and spin transport as well as carrier-mediated long-range correlation.

  4. Construction of coaxial ZnSe/ZnO p-n junctions and their photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Zhang, Xiwei; Meng, Dan; Hu, Dan; Tang, Zhenjie; Niu, Xiaoping; Yu, Fengjun; Ju, Lin

    2016-02-01

    Coaxial ZnSe/ZnO nanostructures were fabricated by coating a ZnO thin film on the surface of presynthesized p-type ZnSe 1D nanostructures by a sputtering method. Owing to the n-type behavior of ZnO resulting from intrinsic defects, coaxial ZnSe/ZnO p-n junctions were realized and showed a pronounced rectifying behavior. Photovoltaic devices based on the coaxial ZnSe/ZnO p-n junction showed a power conversion efficiency of 1.24% and a large open-circuit voltage of 0.87 V under UV light. The large bandgaps of ZnSe and ZnO and the high quality of the ZnSe/ZnO interface were considered to be related to the high performance of the devices.

  5. Photoelectrochemical corrosion of GaN-based p-n structures

    NASA Astrophysics Data System (ADS)

    Fomichev, A. D.; Kurin, S. Yu; Ermakovi, I. A.; Puzyk, M. V.; Usikov, A. S.; Helava, H.; Nikiforov, A.; Papchenko, B. P.; Makarov, Yu N.; Chernyakov, A. E.

    2016-08-01

    Direct water photoelectrolysis using III-N materials is a promising way for hydrogen production. GaN/AlGaN based p-n structures were used in a photoelectrochemical process to investigate the material etching (corrosion) in an electrolyte. At the beginning, the corrosion performs through the top p-type layers via channels associated with threading defects and can penetrate deep into the structure. Then, the corrosion process occurs in lateral direction in n- type layers forming voids and cavities in the structure. The lateral etching is due to net positive charges at the AlGaN/GaN interfaces arising because of spontaneous and piezoelectric polarization in the structure and positively charged ionized donors in the space charge region of the p-n junction.

  6. Optoelectronic devices based on MoTe2 p-n junction

    NASA Astrophysics Data System (ADS)

    Bie, Ya-Qing; Heuck, Mikkel; Furchi, Marco; Grosso, Gabriele; Zheng, Jiabao; Cao, Yuan; Navarro-Moratalla, Efren; Englund, Dirk; Jarillo-Herrero, Pablo

    2D transition metal dichalcogenides (2D-TMD), such as MoS2, have been verified with many remarkable physical properties, which include an indirect to direct band transition as a function of thickness and a valley dependent spin polarization. One of the 2D-TMD family members, 2H-MoTe2 has been shown to be a direct bandgap semiconductor as a monolayer and bilayer with a near infrared (NIR) bandgap of about 1.1eV. However, optoelectronic devices based on MoTe2 were so far not experimentally demonstrated. Here, we will present a high on-off ratio MoTe2 p-n junction enabled by a hexagonal boron nitride encapsulation technique. Our study of the MoTe2 p-n junction devices sheds light on designing efficient NIR optoelectronic devices such as photodetectors and energy harvesting cells and light emitters.

  7. Maskless Selective Growth Method for p-n Junction Applications on (001)-Oriented Diamond

    NASA Astrophysics Data System (ADS)

    Kato, Hiromitsu; Makino, Toshiharu; Ogura, Masahiko; Takeuchi, Daisuke; Yamasaki, Satoshi

    2012-09-01

    A maskless selective growth method by chemical vapor deposition (CVD) is a promising technique for fabricating various types of p-n junction devices on diamond semiconductors, instead of the impurity doping by ion-implantation technique. We control diamond growth and impurity doping using patterned surface morphologies of (001)-oriented diamond, which results in a selective growth along the <111> or <110> direction. In the case of phosphorus doping, the diamond with selective <111> growth shows the n-type conducting property, whereas that with selective <110> growth shows the insulating property owing to the coincorporation of hydrogen. Such strong orientational properties are peculiar in CVD phosphorus doping. The detailed procedures of this selective growth method and the electrical properties of fabricated vertical and lateral p-n junction diodes are described in this article.

  8. A compact setup of fast pnCCDs for exotic atom measurements

    SciTech Connect

    Gorke, H.; Erven, W.; Gotta, D.; Hartmann, R.; Strueder, L.; Simons, L.

    2005-10-19

    X-ray measurements at particle accelerators suffer from a high beam-induced background. For low-energy X-rays CCDs can solve this problem due to their pixel structure, which allows to reduce the background by a cluster analysis. To be able to measure at reasonably high count rates, fast read-out capable CCDs, so called pnCCDs, are used, which have been developed at the semiconductor laboratory of the Max Planck Institute (MPI) for the XMM satellite mission. Recently an improved version of pnCCDs was developed. These chips will be available with different geometries, pixel size and allow a frame-store read-out. At the ZEL (Central Laboratory for Electronics) of the research center Juelich a dedicated electronics for fast read-out was developed in collaboration with the MPI.

  9. Thin-layer black phosphorous/GaAs heterojunction p-n diodes

    SciTech Connect

    Gehring, Pascal; Urcuyo, Roberto; Duong, Dinh Loc; Burghard, Marko; Kern, Klaus

    2015-06-08

    Owing to its high carrier mobility and thickness-tunable direct band gap, black phosphorous emerges as a promising component of optoelectronic devices. Here, we evaluate the device characteristics of p-n heterojunction diodes wherein thin black phosphorous layers are interfaced with an underlying, highly n-doped GaAs substrate. The p-n heterojunctions exhibit close-to-ideal diode behavior at low bias, while under illumination they display a photoresponse that is evenly distributed over the entire junction area, with an external quantum efficiency of up to 10% at zero bias. Moreover, the observed maximum open circuit voltage of 0.6 V is consistent with the band gap estimated for a black phosphorous sheet with a thickness on the order of 10 nm. Further analysis reveals that the device performance is limited by the structural quality of the black phosphorous surface.

  10. Effect of reabsorbed recombination radiation on the saturation current of direct gap p-n junctions

    NASA Technical Reports Server (NTRS)

    Von Roos, O.; Mavromatis, H.

    1984-01-01

    The application of the radiative transfer theory for semiconductors to p-n homojunctions subject to low level injection conditions is discussed. By virtue of the interaction of the radiation field with free carriers across the depletion layer, the saturation current density in Shockley's expression for the diode current is reduced at high doping levels. The reduction, due to self-induced photon generation, is noticeable for n-type material owing to the small electron effective mass in direct band-gap III-V compounds. The effect is insignificant in p-type material. At an equilibrium electron concentration of 2 x 10 to the 18th/cu cm in GaAs, a reduction of the saturation current density by 15 percent is predicted. It is concluded that realistic GaAs p-n junctions possess a finite thickness.

  11. Uppermost mantle structure beneath eastern China and its surroundings from Pn and Sn tomography

    NASA Astrophysics Data System (ADS)

    Sun, Weijia; Kennett, B. L. N.

    2016-04-01

    The Pn and Sn residuals from regional events provide strong constraints on the structure and lithological characteristics of the uppermost mantle beneath eastern China and its surroundings. With the dense Chinese Digital Seismic Network in eastern China, separate Pn and Sn tomographic inversions have been exploited to obtain P and S velocities at a resolution of 2° × 2° or better. The patterns of P velocities are quite consistent with the S velocities at depth of 50 and 60 km, but the amplitude of P wave speed anomalies are a little larger than those of S wave speed. The low P wave speed, high S wave speed, and low Vp/Vs ratio beneath the northern part of Ordos Basin are related to upwelling hot material. Abrupt changes in material properties are indicated from the rapid variations in the Vp/Vs ratio.

  12. A modified PN code tracking loop - Its performance analysis and comparative evaluation

    NASA Astrophysics Data System (ADS)

    Yost, R. A.; Boyd, R. W.

    1982-05-01

    A modified PN code tracking loop (MCTL) has been reported by Yost and Boyd (1980). The MCTL makes it possible to reduce the hardware complexity of a noncoherent delay lock loop in multiple data rate applications. The MCTL utilizes the on-time or data channel as the reference. This concept eliminates the need for the traditional loop's sum channel (early signal plus late signal) and, hence, the hardware associated with that channel. This saving may be substantial if the channel were to be optimized for a number of different data rates. With the elimination of an entire IF channel, the MCTL complexity is nearly equivalent to the dithering loop for PN code tracking considered by Hartmann (1974). However, the MCTL does not suffer the loss in tracking performance (with respect to the traditional loop) that the dithering loop experiences.

  13. Ultrafast dynamics. Four-dimensional imaging of carrier interface dynamics in p-n junctions.

    PubMed

    Najafi, Ebrahim; Scarborough, Timothy D; Tang, Jau; Zewail, Ahmed

    2015-01-01

    The dynamics of charge transfer at interfaces are fundamental to the understanding of many processes, including light conversion to chemical energy. Here, we report imaging of charge carrier excitation, transport, and recombination in a silicon p-n junction, where the interface is well defined on the nanoscale. The recorded images elucidate the spatiotemporal behavior of carrier density after optical excitation. We show that carrier separation in the p-n junction extends far beyond the depletion layer, contrary to the expected results from the widely accepted drift-diffusion model, and that localization of carrier density across the junction takes place for up to tens of nanoseconds, depending on the laser fluence. The observations reveal a ballistic-type motion, and we provide a model that accounts for the spatiotemporal density localization across the junction. PMID:25574020

  14. Magmatic Versus Amagmatic Rifting in the East African Rift System from Pn and Sn Tomography

    NASA Astrophysics Data System (ADS)

    O'Donnell, J. P.; Nyblade, A.

    2014-12-01

    Geodynamic models of rifting currently rely on the mechanism of hot mantle upwelling and decompressional melting to weaken lithospheric rock to the degree that rifting can initiate. However, many rift segments worldwide are apparently amagmatic. The East African Rift System is a prime example, with large sections of the system subaerially amagmatic. We seek to address the question of whether these apparently amagmatic rift segments merely lack a surficial expression of magmatism which exists at depth, or whether rifting is genuinely amagmatic. Based on regional earthquakes recorded by the Tanzania Broadband Seismic Experiment, the Kenya Broadband Seismic Experiment, the AfricaArray East African Seismic Experiment and several permanent GSN stations, we probe for uppermost mantle melt signatures along the East African Rift System using P- and S-wave speed ratios derived from Pn and Sn tomography. Pn- and Sn-velocity models, and their ratio which can be diagnostic of the presence of fluids, will be presented.

  15. Photothermoelectric p-n junction photodetector with intrinsic broadband polarimetry based on macroscopic carbon nanotube films.

    PubMed

    He, Xiaowei; Wang, Xuan; Nanot, Sébastien; Cong, Kankan; Jiang, Qijia; Kane, Alexander A; Goldsmith, John E M; Hauge, Robert H; Léonard, François; Kono, Junichiro

    2013-08-27

    Light polarization is used in the animal kingdom for communication, navigation, and enhanced scene interpretation and also plays an important role in astronomy, remote sensing, and military applications. To date, there have been few photodetector materials demonstrated to have direct polarization sensitivity, as is usually the case in nature. Here, we report the realization of a carbon-based broadband photodetector, where the polarimetry is intrinsic to the active photodetector material. The detector is based on p-n junctions formed between two macroscopic films of single-wall carbon nanotubes. A responsivity up to ~1 V/W was observed in these devices, with a broadband spectral response spanning the visible to the mid-infrared. This responsivity is about 35 times larger than previous devices without p-n junctions. A combination of experiment and theory is used to demonstrate the photothermoelectric origin of the responsivity and to discuss the performance attributes of such devices.

  16. High Bias Characteristics of Individual, Suspended Carbon Nanotube p-n Junction Photodiodes

    NASA Astrophysics Data System (ADS)

    Chang, Shun-Wen; Bergemann, Kevin; Dhall, Rohan; Zimmerman, Jeramy; Forrest, Stephen; Cronin, Stephen

    2013-03-01

    We have recently investigated p-n junction diodes formed by electrostatic doping of individual, suspended, single-walled carbon nanotubes (CNTs) using two gate electrodes positioned beneath a free standing nanotube that bridges source and drain electrodes. The electrostatic field imposed by the two gates polarizes the nanotube along its length, thereby allowing independent control of the ``doping'' in the nanotube without introducing impurities or defect states. These pn-devices exhibit rectifying diode behavior and finite photoresponse under illumination. Several interesting phenomena are observed at high bias that arise from Schottky contacts formed between the nanotube and its metal contact electrodes and electron tunneling between the n- and p-doped regions. A model is developed explaining this behavior showing evidence for plasmon-induced band gap shrinkage with electrostatic doping.

  17. Edge-channel interferometer at the graphene quantum Hall pn junction

    SciTech Connect

    Morikawa, Sei; Moriya, Rai; Masubuchi, Satoru Machida, Tomoki; Watanabe, Kenji; Taniguchi, Takashi

    2015-05-04

    We demonstrate a quantum Hall edge-channel interferometer in a high-quality graphene pn junction under a high magnetic field. The co-propagating p and n quantum Hall edge channels traveling along the pn interface functions as a built-in Aharonov-Bohm-type interferometer, the interferences in which are sensitive to both the external magnetic field and the carrier concentration. The trajectories of peak and dip in the observed resistance oscillation are well reproduced by our numerical calculation that assumes magnetic flux quantization in the area enclosed by the co-propagating edge channels. Coherent nature of the co-propagating edge channels is confirmed by the checkerboard-like pattern in the dc-bias and magnetic-field dependences of the resistance oscillations.

  18. Thin-layer black phosphorous/GaAs heterojunction p-n diodes

    NASA Astrophysics Data System (ADS)

    Gehring, Pascal; Urcuyo, Roberto; Duong, Dinh Loc; Burghard, Marko; Kern, Klaus

    2015-06-01

    Owing to its high carrier mobility and thickness-tunable direct band gap, black phosphorus emerges as a promising component of optoelectronic devices. Here, we evaluate the device characteristics of p-n heterojunction diodes wherein thin black phosphorus layers are interfaced with an underlying, highly n-doped GaAs substrate. The p-n heterojunctions exhibit close-to-ideal diode behavior at low bias, while under illumination they display a photoresponse that is evenly distributed over the entire junction area, with an external quantum efficiency of up to 10% at zero bias. Moreover, the observed maximum open circuit voltage of 0.6 V is consistent with the band gap estimated for a black phosphorus sheet with a thickness on the order of 10 nm. Further analysis reveals that the device performance is limited by the structural quality of the black phosphorus surface.

  19. Concatenated shift registers generating maximally spaced phase shifts of PN-sequences

    NASA Technical Reports Server (NTRS)

    Hurd, W. J.; Welch, L. R.

    1977-01-01

    A large class of linearly concatenated shift registers is shown to generate approximately maximally spaced phase shifts of pn-sequences, for use in pseudorandom number generation. A constructive method is presented for finding members of this class, for almost all degrees for which primitive trinomials exist. The sequences which result are not normally characterized by trinomial recursions, which is desirable since trinomial sequences can have some undesirable randomness properties.

  20. Controlled charge extraction—antiblooming capabilities in pnCCD imaging sensors

    NASA Astrophysics Data System (ADS)

    Schmidt, J.; Hartmann, R.; Holl, P.; Huth, M.; Lutz, G.; Pietsch, U.; Ryll, H.; Send, S.; Simson, M.; Soltau, H.; Soltau, J.; Steigenhöfer, D.; Strüder, L.

    2016-01-01

    Blooming in a CCD occurs when the signal charges accumulating in a pixel exceed the pixel saturation level and spill over into adjacent pixels. They start to spill over the weakest threshold in the electric potential of the pixel structure resulting in a degradation of the spatial information. With antiblooming mechanisms, the spatial resolution of the incoming photons can be preserved, but the intensity information is lost in the overflowing pixels. For imaging experiments, relying on a precise image structure, the preservation of the spatial resolution at the expense of precise intensity information is a workable compromise. In contrast to insulated gate CCDs, notably MOSCCDs, the potential wells of the pixel array of a pnCCD are created by p+n junctions, allowing direct electric access to the pixel structure. This allows to directly drain off charges from the pixels and to define a drain level by applying the appropriate operation voltages. Charge packets from 1 000 to more than one billion signal electrons per readout frame were generated without observing a spillover into adjacent pixels. As soon as the saturation level of the pixel is reached, the excess charge carriers are removed through charge drains exclusively created with the modification of the electric potential of the pnCCD by the operation voltages. No additional antiblooming structures were implemented in the device and the pixel full well capacity of approximately 300 000 electrons in standard operation mode was preserved. A physical model of the antiblooming mechanism of pnCCDs with a pixel size of 75 μ m × 75 μ m was established by two-dimensional numerical device simulations and verified by experiments.

  1. Nondestructive determination of the depth of planar p-n junctions by scanning electron microscopy

    NASA Technical Reports Server (NTRS)

    Chi, J.-Y.; Gatos, H. C.

    1977-01-01

    A method was developed for measuring nondestructively the depth of planar p-n junctions in simple devices as well as in integrated-circuit structures with the electron-beam induced current (EBIC) by scanning parallel to the junction in a scanning electron microscope (SEM). The results were found to be in good agreement with those obtained by the commonly used destructive method of lapping at an angle to the junction and staining to reveal the junction.

  2. The Effect of Tides on the Population of PN from Interacting Binaries

    NASA Astrophysics Data System (ADS)

    Madappatt, Niyas; De Marco, Orsola; Villaver, Eva

    2016-08-01

    We have used the tidal equations of Zahn to determine the maximum orbital distance at which companions are brought into Roche lobe contact with their giant primary, when the primary expands during the giant phases. This is a key step when determining the rates of interaction between giants and their companions. Our stellar structure calculations are presented as maximum radii reached during the red and asymptotic giant branch (RGB and AGB, respectively) stages of evolution for masses between 0.8 and 4.0 M⊙ (Z=0.001 - 0.04) and compared with other models to gauge the uncertainty on radii deriving from details of these calculations. We find overall tidal capture distances that are typically 1-4 times the maximum radial extent of the giant star, where companions are in the mass range from 1 MJ to a mass slightly smaller than the mass of the primary. We find that only companions at initial orbital separations between ˜320 and ˜630 R⊙ will be typically captured into a Roche lobe-filling interaction or a common envelope on the AGB. Comparing these limits with the period distribution for binaries that will make PN, we deduce that in the standard scenario where all ˜1-8 M⊙ stars make a PN, at most 2.5 per cent of all PN should have a post-common envelope central star binary, at odds with the observational lower limit of 15-20 per cent. The observed over-abundance of post-interaction central stars of PN cannot be easily explained considering the uncertainties. We examine a range of explanations for this discrepancy.

  3. Photovoltaic characteristics of diffused P/+N bulk GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Borrego, J. M.; Keeney, R. P.; Bhat, I. B.; Bhat, K. N.; Sundaram, L. G.; Ghandhi, S. K.

    1982-01-01

    The photovoltaic characteristics of P(+)N junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are described in this paper.Spectral response measurements were analyzed in detail and compared to a computer simulation in order to determine important material parameters. It is projected that proper optimization of the cell parameters can increase the efficiency of the cells from 12.2 percent to close to 20 percent.

  4. Selectively grown vertical silicon nanowire p-n+ photodiodes via aqueous electroless etching

    NASA Astrophysics Data System (ADS)

    Lee, Hyonik; Hong, Juree; Lee, Seulah; Kim, Sung-Dae; Kim, Young-Woon; Lee, Taeyoon

    2013-06-01

    A facile method to selectively grow vertically-aligned silicon nanowires (SiNWs) which can inherit the doping concentration from its mother wafer, with controllable length, is demonstrated using the combination of photolithography and aqueous electroless etching. The use of SU-8-2002, a chemically and mechanically robust photoresist (PR) material, provided a high selectivity for the etching reaction on the exposed surface of 1-μm-thick n+ doped p-type (1 0 0) Si substrate, resulting in the fabrication of ˜30-μm-long vertically-aligned SiNW photodiode arrays on the desired locations, while the areas covered with SU-8-2002 remained unreacted. Optical and field emission scanning electron microscope analyses confirmed that SiNWs were selectively grown while retaining the shape of the PR patterns. The electrical and optical measurements of the fabricated p-n+ junction SiNW photodiodes were compared to those of reference planar p-n+ junction Si photodiodes: the current density of the p-n+ junction SiNW photodiodes was approximately 3 times greater than that of the planar counterpart at the forward bias of 5 V, which can be attributed to the high density of defect states on the rough surfaces of the synthesized SiNWs, leading to the increased recombination efficiencies for the injected carriers. In addition, the photoresponse of the p-n+ SiNW photodiode arrays was 3.4 times higher than that of the planar device at -3.5 V due to the increase in the light scattering.

  5. The effect of tides on the population of PN from interacting binaries

    NASA Astrophysics Data System (ADS)

    Madappatt, Niyas; De Marco, Orsola; Villaver, Eva

    2016-11-01

    We have used the tidal equations of Zahn to determine the maximum orbital distance at which companions are brought into Roche lobe contact with their giant primary, when the primary expands during the giant phases. This is a key step when determining the rates of interaction between giants and their companions. Our stellar structure calculations are presented as maximum radii reached during the red and asymptotic giant branch (RGB and AGB, respectively) stages of evolution for masses between 0.8 and 4.0 M⊙ (Z = 0.001-0.04) and compared with other models to gauge the uncertainty on radii deriving from details of these calculations. We find overall tidal capture distances that are typically 1-4 times the maximum radial extent of the giant star, where companions are in the mass range from 1 MJ to a mass slightly smaller than the mass of the primary. We find that only companions at initial orbital separations between ˜320 and ˜630 R⊙ will be typically captured into a Roche lobe-filling interaction or a common envelope on the AGB. Comparing these limits with the period distribution for binaries that will make planetary nebula (PN), we deduce that in the standard scenario where all ˜1-8 M⊙ stars make a PN, at most 2.5 per cent of all PN should have a post-common envelope central star binary, at odds with the observational lower limit of 15-20 per cent. The observed overabundance of post-interaction central stars of PN cannot be easily explained considering the uncertainties. We examine a range of explanations for this discrepancy.

  6. VizieR Online Data Catalog: PN towards Galactic bulge. [OIII] fluxes (Kovacevic+, 2011)

    NASA Astrophysics Data System (ADS)

    Kovacevic, A. V.; Parker, Q. A.; Jacoby, G. H.; Sharp, R.; Miszalski, B.; Frew, D. J.

    2016-03-01

    We observed previously known and MASH PN in a 10°x10° region towards the Galactic bulge using the Cerro-Tololo Inter-American Observatory (CTIO) 4-m Blanco Telescope in Chile with the MOSAIC-II CCD Imager. A total of ~95h of photometric imaging was conducted, spread over two observing runs: six nights throughout 2008 June 9-14 and five nights from 2009 June 27 to July 2. (3 data files).

  7. A pnCCD-based, fast direct single electron imaging camera for TEM and STEM

    NASA Astrophysics Data System (ADS)

    Ryll, H.; Simson, M.; Hartmann, R.; Holl, P.; Huth, M.; Ihle, S.; Kondo, Y.; Kotula, P.; Liebel, A.; Müller-Caspary, K.; Rosenauer, A.; Sagawa, R.; Schmidt, J.; Soltau, H.; Strüder, L.

    2016-04-01

    We report on a new camera that is based on a pnCCD sensor for applications in scanning transmission electron microscopy. Emerging new microscopy techniques demand improved detectors with regards to readout rate, sensitivity and radiation hardness, especially in scanning mode. The pnCCD is a 2D imaging sensor that meets these requirements. Its intrinsic radiation hardness permits direct detection of electrons. The pnCCD is read out at a rate of 1,150 frames per second with an image area of 264 x 264 pixel. In binning or windowing modes, the readout rate is increased almost linearly, for example to 4000 frames per second at 4× binning (264 x 66 pixel). Single electrons with energies from 300 keV down to 5 keV can be distinguished due to the high sensitivity of the detector. Three applications in scanning transmission electron microscopy are highlighted to demonstrate that the pnCCD satisfies experimental requirements, especially fast recording of 2D images. In the first application, 65536 2D diffraction patterns were recorded in 70 s. STEM images corresponding to intensities of various diffraction peaks were reconstructed. For the second application, the microscope was operated in a Lorentz-like mode. Magnetic domains were imaged in an area of 256 x 256 sample points in less than 37 seconds for a total of 65536 images each with 264 x 132 pixels. Due to information provided by the two-dimensional images, not only the amplitude but also the direction of the magnetic field could be determined. In the third application, millisecond images of a semiconductor nanostructure were recorded to determine the lattice strain in the sample. A speed-up in measurement time by a factor of 200 could be achieved compared to a previously used camera system.

  8. Abrupt PN junctions: Analytical solutions under equilibrium and non-equilibrium

    NASA Astrophysics Data System (ADS)

    Khorasani, Sina

    2016-08-01

    We present an explicit solution of carrier and field distributions in abrupt PN junctions under equilibrium. An accurate logarithmic numerical method is implemented and results are compared to the analytical solutions. Analysis of results shows reasonable agreement with numerical solution as well as the depletion layer approximation. We discuss extensions to the asymmetric junctions. Approximate relations for differential capacitance C-V and current-voltage I-V characteristics are also found under non-zero external bias.

  9. The origin of teleseismic Pn waves: Multiple crustal scattering of upper mantle whispering gallery phases

    NASA Astrophysics Data System (ADS)

    Nielsen, L.; Thybo, H.

    2003-10-01

    Teleseismic Pn arrivals with an extensive coda are observed to offsets beyond 3000 km along the peaceful nuclear explosion seismic profiles Quartz and Ruby, which were recorded in the western part of the former Soviet Union. We interpret these arrivals as multiply reflected sub-Moho refractions that travel over large distances due to a positive vertical upper mantle velocity gradient, which is characteristic for the study area. Analysis of the observed data shows that the teleseismic Pn and its coda contain significant amounts of energy at all frequencies between 0 and 10 Hz. Our modeling results show that crustal scattering may fully explain the teleseismic Pn coda contrary to another published model with upper mantle heterogeneity in the ˜35-130 km depth range. These conclusions are based on two-dimensional viscoelastic finite-difference seismic wave field simulations in 2000-km-long and 250-km-deep models of the crust and upper mantle. The computationally demanding calculations are facilitated by the use of supercomputer systems. Our preferred model of crustal scattering is consistent with the results of other high-resolution wide-angle and normal-incidence seismic investigations of the crust and upper mantle. They show pronounced reflectivity of the lower crust above an almost transparent uppermost mantle down to ˜80-100 km depth. Our model includes a high vertical velocity gradient in the upper mantle based on the results from seismic refraction studies. We suggest that the teleseismic Pn wave travels as an upper mantle whispering gallery phase and that the origin of its long coda is crustal scattering.

  10. Ballistic conductivity of graphene channel with p-n junction at ferroelectric domain wall

    NASA Astrophysics Data System (ADS)

    Morozovska, Anna N.; Eliseev, Eugene A.; Strikha, Maksym V.

    2016-06-01

    The influence of a ferroelectric domain wall on the ballistic conductance of a single-layer graphene channel in the graphene/physical gap/ferroelectric film heterostructure has been studied in the Wentzel-Kramers-Brillouin approximation. The self-consistent numerical simulation of the electric field and the space charge dynamics in the heterostructure, as well as the approximate analytical theory, show that the contact between the domain wall and the surface creates a p-n junction in the graphene channel. We calculated that the carrier concentration induced in graphene by uncompensated ferroelectric dipoles originated from the abrupt spontaneous polarization change near the surface can reach values of about 1019 m-2, which are two orders of magnitude higher than those obtained for the graphene on non-ferroelectric substrates. Therefore, we predict that the graphene channel with the p-n junction caused by the ferroelectric domain wall would be characterized by rather a high ballistic conductivity. Moreover, the graphene p-n junction at the ferroelectric domain wall can be an excellent rectifier with a conductivity ratio of about 10 between the direct and reverse polarities of the applied voltage.

  11. Lateral MoS2 p-n junctions formed by chemical doping method

    NASA Astrophysics Data System (ADS)

    Yoo, Won Jong; Choi, Min Sup; Qu, Deshun; Lee, Daeyeong; Liu, Xiaochi; Jang, Youngdae; Kim, Changsik; Ryu, Jungjin

    2015-03-01

    Interests on transition metal dichalcogenides, especially MoS2, are growing immensely due to its semiconducting nature with visible light range bandgap and strong light absorption property, which can pave the way to replace Si-based electronics and realize flexible and transparent electronics. For more versatile applications and industrialization, however, a proper doping process is required because various devices such as photonics and tunneling devices are composed of p-n junctions. Here, we demonstrated the formation of lateral MoS2 p-n junction by using partially stacked of hBN and p-doping with Au Cl3 solution. The fabricated devices showed an ideal rectifying behavior with ideality factor about 1. Under the exposure of monochromatic light, it revealed the properties of conventional p-n diode and also highly efficient photonic properties, showing feasibility to be applied for photovoltaic cells and photodetectors. Furthermore, we fabricated novel tunneling devices with similar device structure where local gates are located under MoS2. Its Fermi level can be effectively controlled by local gate modulation, so that the tunneling current can flow by band-to-band tunneling. This study provides an effective way to realize the practical devices such as photonics and tun

  12. Fully porous GaN p-n junction diodes fabricated by chemical vapor deposition.

    PubMed

    Bilousov, Oleksandr V; Carvajal, Joan J; Geaney, Hugh; Zubialevich, Vitaly Z; Parbrook, Peter J; Martínez, Oscar; Jiménez, Juan; Díaz, Francesc; Aguiló, Magdalena; O'Dwyer, Colm

    2014-10-22

    Porous GaN based LEDs produced by corrosion etching techniques demonstrated enhanced light extraction efficiency in the past. However, these fabrication techniques require further postgrown processing steps, which increases the price of the final system. Also, the penetration depth of these etching techniques is limited, and affects not only the semiconductor but also the other elements constituting the LED when applied to the final device. In this paper, we present the fabrication of fully porous GaN p-n junctions directly during growth, using a sequential chemical vapor deposition (CVD) process to produce the different layers that form the p-n junction. We characterized their diode behavior from room temperature to 673 K and demonstrated their ability as current rectifiers, thus proving the potential of these fully porous p-n junctions for diode and LEDs applications. The electrical and luminescence characterization confirm that high electronic quality porous structures can be obtained by this method, and we believe this investigation can be extended to other III-N materials for the development of white light LEDs, or to reduce reflection losses and narrowing the output light cone for improved LED external quantum efficiencies.

  13. Temperature-Dependent Asymmetry of Anisotropic Magnetoresistance in Silicon p-n Junctions

    PubMed Central

    Yang, D. Z.; Wang, T.; Sui, W. B.; Si, M. S.; Guo, D. W.; Shi, Z.; Wang, F. C.; Xue, D. S.

    2015-01-01

    We report a large but asymmetric magnetoresistance in silicon p-n junctions, which contrasts with the fact of magnetoresistance being symmetric in magnetic metals and semiconductors. With temperature decreasing from 293 K to 100 K, the magnetoresistance sharply increases from 50% to 150% under a magnetic field of 2 T. At the same time, an asymmetric magnetoresistance, which manifests itself as a magnetoresistance voltage offset with respect to the sign of magnetic field, occurs and linearly increases with magnetoresistance. More interestingly, in contrast with other materials, the lineshape of anisotropic magnetoresistance in silicon p-n junctions significantly depends on temperature. As temperature decreases from 293 K to 100 K, the width of peak shrinks from 90° to 70°. We ascribe these novel magnetoresistance to the asymmetric geometry of the space charge region in p-n junction induced by the magnetic field. In the vicinity of the space charge region the current paths are deflected, contributing the Hall field to the asymmetric magnetoresistance. Therefore, the observed temperature-dependent asymmetry of magnetoresistance is proved to be a direct consequence of the spatial configuration evolution of space charge region with temperature. PMID:26323495

  14. Uncooled IR sensor based on lateral polysilicon pn junction diode: initial results

    NASA Astrophysics Data System (ADS)

    Xu, De-hui; Xiong, Bin; Wang, Yue-lin

    2011-08-01

    These days, uncooled IR image sensors utilizing MEMS technologies have been widely studied for night vision and temperature sensing. Compared with other uncooled IR image sensor, uncooled IR image sensor utilizing p-n junction diode detector has merits of good CMOS compatibility, better mass-production, and better detecting uniformity. In this paper, we proposed a novel uncooled IR sensor based on lateral polysilicon p-n junction diode. In the CMOS process, p-type polysilicon is used for PMOS gate electrode material, while n-type polysilicon is used for NMOS gate electrode material. Due to that polysilicon diode is adopted for sensing, the silicon substrate under the microstructure can be completely removed, and a better thermal isolation and a small thermal mass can be achieved. By using the FEM software Ansys, 3D models of the silicon diode and polysilicon diode have been built for thermal simulation. Simulation results verify that a better thermal isolation can be achieved for polysilicon diode. The device was fabricated by standard CMOS process and a XeF2 post-CMOS maskless dry etching step. Measurement results of the fabricated lateral polysilicon p-n junction diode is also reported.

  15. Giant magnetoresistance modulated by magnetic field in graphene p-n junction

    SciTech Connect

    Li, Yuan; Jalil, Mansoor B. A.; Zhou, Guanghui

    2014-11-10

    We investigate the tunneling transport across a graphene p-n junction under the influence of a perpendicular magnetic field (B field). We observe a sideway deflection of the transmission profile, which can be quantitatively explained by invoking the classical Lorentz force. By considering the trajectory of the Dirac fermions along their cyclotron orbits, we analytically derive the incident angles for transmission across the graphene junction under a B field, as well as the critical magnetic field for full suppression of tunneling across the junction. These analytical predictions are consistent with the numerical results obtained via the non-equilibrium Green's function method. A stronger B-field conductance modulation is obtained for a p-n as opposed to an n-n or p-p type graphene junction. The magnetic field also induces a forbidden region of almost zero transmission for electron energy close to the Dirac point, which can be utilized to achieve a giant magnetoresistance effect. Based on our analysis, we devise an optimal magneto-electrical transport modulation, which can potentially realize a giant magnetoresistance effect in graphene p-n junction systems.

  16. Al00.3Ga0.7N PN diode with breakdown voltage >1600 V

    DOE PAGESBeta

    Allerman, A. A.; Armstrong, A. M.; Fischer, A. J.; Dickerson, J. R.; Crawford, M. H.; King, M. P.; Moseley, M. W.; Wierer, J. J.; Kaplar, R. J.

    2016-07-21

    Demonstration of Al00.3Ga0.7N PN diodes grown with breakdown voltages in excess of 1600 V is reported. The total epilayer thickness is 9.1 μm and was grown by metal-organic vapour-phase epitaxy on 1.3-mm-thick sapphire in order to achieve crack-free structures. A junction termination edge structure was employed to control the lateral electric fields. A current density of 3.5 kA/cm2 was achieved under DC forward bias and a reverse leakage current <3 nA was measured for voltages <1200 V. The differential on-resistance of 16 mΩ cm2 is limited by the lateral conductivity of the n-type contact layer required by the front-surface contactmore » geometry of the device. An effective critical electric field of 5.9 MV/cm was determined from the epilayer properties and the reverse current–voltage characteristics. To our knowledge, this is the first aluminium gallium nitride (AlGaN)-based PN diode exhibiting a breakdown voltage in excess of 1 kV. Finally, we note that a Baliga figure of merit (Vbr2/Rspec,on) of 150 MW/cm2 found is the highest reported for an AlGaN PN diode and illustrates the potential of larger-bandgap AlGaN alloys for high-voltage devices.« less

  17. Measurement results from an avalanche amplifying pnCCD for single photon imaging

    NASA Astrophysics Data System (ADS)

    Ordavo, I.; Hartmann, R.; Holl, P.; Irlbeck, A.; Lutz, G.; Richter, R. H.; Schaller, G.; Soltau, H.; Strüder, L.

    2010-12-01

    The company PNSensor and the MPI Semiconductor Laboratory are developing and have produced first prototypes of pnCCDs with an avalanche readout which aim at single photon sensitivity in the visible wavelength range. This resolution is provided by an avalanche diode integrated in the readout chain of every CCD column. The diode features a new topology and can collect signal electrons from the CCDs' depleted buried channel. The pixel-structure has been derived from pnCCDs and was optimized for lowest leakage current and for compatibility with the avalanche structures. All advantages of the pnCCDs are maintained, including high quantum efficiency (between 80% and 100%), high frame rate (up to 1000 frames/s) and low leakage current. Possible applications are in the field of High Time Resolution Astrophysics (HTRA). There, fast imaging of faint objects in the visible, such as, e.g. close binary stars or fast rotating neutron stars, requires single photon sensitivity and high frame rates. We present results from proof-of-principle tests carried out on first laboratory prototypes of such devices.

  18. Gravitational waveforms in scalar-tensor gravity at 2PN relative order

    NASA Astrophysics Data System (ADS)

    Sennett, Noah; Marsat, Sylvain; Buonanno, Alessandra

    2016-10-01

    We compute the gravitational waveform from a binary system in scalar-tensor gravity at 2PN relative order. We restrict our calculation to nonspinning binary systems on quasicircular orbits and compute the spin-weighted spherical modes of the radiation. The evolution of the phase of the waveform is computed in the time and frequency domains. The emission of dipolar radiation is the lowest-order dissipative process in scalar-tensor gravity. However, stringent constraints set by current astrophysical observations indicate that this effect is subdominant to quadrupolar radiation for most prospective gravitational-wave sources. We compute the waveform for systems whose inspiral is driven by: (a) dipolar radiation (e.g., binary pulsars or spontaneously scalarized systems) and (b) quadrupolar radiation (e.g., typical sources for space-based and ground-based detectors). For case (a), we provide complete results at 2PN, whereas for case (b), we must introduce unknown terms in the 2PN flux; these unknown terms are suppressed by constraints on scalar-tensor gravity.

  19. Growth and electrical rectification in axial in-situ doped p-n junction germanium nanowires

    SciTech Connect

    Picraux, Samuel T; Dayeh, Shadi; Zaslavsky, Alexander; Le, Son T

    2009-01-01

    In this work, we demonstrate the vapor-liquid-solid (VLS) growth and electrical properties of axial in-situ doped p-n junction Ge nanowires (NWs). In-situ doping of the NWs was accomplished by introducing dopant gases (diborane and phosphine) together with GeH{sub 4} in the growth process. By changing dopant sources during growth, a p-n junction can be realized along the axis of the NWs. Metal contacts to the wires were defined using e-beam lithography patterning, followed by 100 nm Ni sputter deposition and lift-off. Four-point measurements of the fabricated devices at room temperature and at 77 K clearly show rectification with on/off current ratio up to two orders of magnitude when the bias is applied across the p-n junction. The ideality factor of the junction current points to a significant generation-recombination contribution. The Ohmic characteristics in the p and n regions outside the junction make it possible to estimate the doping levels. We also observed backgate control of the NW junction current.

  20. The ZnO p-n homojunctions modulated by ZnMgO barriers

    SciTech Connect

    Yang, Jing-Jing; Fang, Qing-Qing Wang, Dan-Dan; Du, Wen-Han

    2015-04-15

    In this paper, we fabricated the ultrathin ZnO p-n homojunctions, which modulated by ZnMgO asymmetrical double barriers (ADB). The ADB p-n homojunctions displays step-like curve in the absorption spectrums, this is the first time that quantum confinement effect has been observed in the absorption spectrums at room temperature (RT). The Hall-effect data confirm there is 2-dimensional electron gas in the interface of the ZnMgO ADB p-n junctions. The quantum confinement effect enhances the hall-mobility μ to 10{sup 3} cm{sup 2}V {sup −1}s{sup −1} based on the polarity of the films. There was no rectification property in the ZnO homojunctions with thickness of 250nm, however, when the ADB was added in the n-type layer of the homojunctions, it displays a typical Zener diode rectification property in the I-V curve.

  1. Uppermost mantle Pn Velocity of the Arabian Plate, a Preliminary study

    NASA Astrophysics Data System (ADS)

    Al-Lazki, A. I.; Al-Damegh, K. S.; Al-Enizi, A.; Elhusain, I.; Al-Mahrooqi, I.

    2005-12-01

    The Arabian plate represents a unique tectonic setup. The uniqueness of this plate is its boundaries that constitute the three known types of plate boundaries. The Red Sea and the Gulf of Aden represent the south and southwest plate boundary with Africa plate. Farther north the Dead Sea Fault system represents the remainder of the northwestern boundary with Africa plate. Continent-continent collision along the Bitlis-Zagros Suture zones represents the northern and northeastern boundary with Eurasia plate. Farther south the convergent plate boundary is manifested by the Makran Subduction Zone. Finally, the Owen and Murray Transform Faults represent the southeast boundary of Arabia with India plate. The broad objective of this study is to map uppermost mantle Pn velocity and anisotropy within the Arabian plate and around its boundaries. Zones that are along the north and the northeast boundaries of Arabia plate historically and in recent years has been effected by devastating earthquakes, a recent example is the Bam earthquake on December, 2003. In this region, accurate earthquake location is essential to delineate seismically active zones, where, without proper velocity models for the region, located earthquake may have large location error. In this preliminary study we present uppermost mantle Pn velocity tomography results of the north and northeastern regions of Arabia plate. We used in this study Pn phase data from the bulletins of Oman Seismic Network, Saudi Seismic Network, Kuwait Seismic Network, International Seismological Center and the National Earthquake Information Center,USA.

  2. Characterization of a pnCCD for applications with synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Send, S.; Abboud, A.; Hartmann, R.; Huth, M.; Leitenberger, W.; Pashniak, N.; Schmidt, J.; Strüder, L.; Pietsch, U.

    2013-05-01

    In this work we study the response of a pnCCD by means of X-ray spectroscopy in the energy range between 6 keV and 20 keV and by Laue diffraction techniques. The analyses include measurements of characteristic detector parameters like energy resolution, count rate capability and effects of different gain settings. The limit of a single photon counting operation in white beam X-ray diffraction experiments is discussed with regard to the occurrence of pile-up events, for which the energy information about individual photons is lost. In case of monochromatic illumination the pnCCD can be used as a fast conventional CCD with a charge handling capacity (CHC) of about 300,000 electrons per pixel. If the CHC is exceeded, any surplus charge will spill to neighboring pixels perpendicular to the transfer direction due to electrostatic repulsion. The possibilities of increasing the number of storable electrons are investigated for different voltage settings by exposing a single pixel with X-rays generated by a microfocus X-ray source. The pixel binning mode is tested as an alternative approach that enables a pnCCD operation with significantly shorter readout times.

  3. Comparison between variable and fixed dwell-time PN acquisition algorithms. [for synchronization in pseudonoise spread spectrum systems

    NASA Technical Reports Server (NTRS)

    Braun, W. R.

    1981-01-01

    Pseudo noise (PN) spread spectrum systems require a very accurate alignment between the PN code epochs at the transmitter and receiver. This synchronism is typically established through a two-step algorithm, including a coarse synchronization procedure and a fine synchronization procedure. A standard approach for the coarse synchronization is a sequential search over all code phases. The measurement of the power in the filtered signal is used to either accept or reject the code phase under test as the phase of the received PN code. This acquisition strategy, called a single dwell-time system, has been analyzed by Holmes and Chen (1977). A synopsis of the field of sequential analysis as it applies to the PN acquisition problem is provided. From this, the implementation of the variable dwell time algorithm as a sequential probability ratio test is developed. The performance of this algorithm is compared to the optimum detection algorithm and to the fixed dwell-time system.

  4. Bipolar resistive switching in YMnO3/Nb:SrTiO3 pn-heterojunctions

    NASA Astrophysics Data System (ADS)

    Bogusz, Agnieszka; Bürger, Danilo; Skorupa, Ilona; Schmidt, Oliver G.; Schmidt, Heidemarie

    2016-11-01

    Resistively switching oxides are promising materials for use in electronic applications such as nonvolatile memories, logic gates, and artificial synapses. This work presents the bipolar resistive switching (BRS) in YMnO3/Nb:SrTiO3 pn-heterojunctions. A thermally driven electroforming process is required prior to the observed BRS. Results indicate that the BRS in YMnO3/Nb:SrTiO3 originates from the combined effects of charge trapping and detrapping processes along with the electro-migration of charged point defects in the depletion layer of the pn-heterojunction. It is shown that the built-in voltage of the pn-heterojunctions can be tuned by the oxygen partial pressure during growth of the YMnO3 thin film and impacts the working parameters of the resistively switching cell. This study provides a guideline for material engineering of bipolar resistive switches based on pn-heterojunctions.

  5. Acceptance Data Package: SXI Stepper Motor/Encoder. Aeroflex P/N 16187. A; Engineering Drawings and Associated Lists

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Acceptance data package - engineering drawings and associated lists for fabrication, assembly and maintenance (cleaning, fluidized bed coating, bounding and staking) motor/encoded solar x-ray imager (SXI) (Aeroflex p/n 16187) were given.

  6. Snake states and Majorana's in graphene quantum dots in the presence of a p-n junction

    NASA Astrophysics Data System (ADS)

    Peeters, Francois; Zarenia, M.; Pereira, J. M., Jr.; Farias, G. A.

    2013-03-01

    We investigate the magnetic interface states of graphene quantum dots that contain p-n junctions. Within a tight-binding approach, we consider rectangular quantum dots in the presence of a perpendicular magnetic field containing p-n, as well as p-n-p and n-p-n junctions. The results show the interplay between the edge states associated with the zigzag terminations of the sample and the snake states that arise at the p-n junction, due to the overlap between electron and hole states at the potential interface. Remarkable localized states are found at the crossing of the p-n junction with the zigzag edge having a dumb-bell shaped electron distribution. These states are localized Majorana states. The results are presented as function of the junction parameters and the applied magnetic flux.

  7. High-quality graphene p-n junctions via resist-free fabrication and solution-based noncovalent functionalization.

    PubMed

    Cheng, Hung-Chieh; Shiue, Ren-Jye; Tsai, Chia-Chang; Wang, Wei-Hua; Chen, Yit-Tsong

    2011-03-22

    An essential issue in graphene nanoelectronics is to engineer the carrier type and density and still preserve the unique band structure of graphene. We report the realization of high-quality graphene p-n junctions by noncovalent chemical functionalization. A generic scheme for the graphene p-n junction fabrication is established by combining the resist-free approach and spatially selective chemical modification process. The effectiveness of the chemical functionalization is systematically confirmed by surface topography and potential measurements, spatially resolved Raman spectroscopic imaging, and transport/magnetotransport measurements. The transport characteristics of graphene p-n junctions are presented with observations of high carrier mobilities, Fermi energy difference, and distinct quantum Hall plateaus. The chemical functionalization of graphene p-n junctions demonstrated in this study is believed to be a feasible scheme for modulating the doping level in graphene for future graphene-based nanoelectronics.

  8. The iron-age of superconductivity: structural correlations and commonalities among the various families having -Fe-Pn- slabs (Pn = P, As and Sb).

    PubMed

    Ganguli, Ashok K; Prakash, Jai; Thakur, Gohil S

    2013-01-21

    The fascination of mankind towards a sudden change of a property, like colour, shape, elasticity, viscosity, electrical conductivity and magnetism, is well known. If the change in property is such that it leads to disapperance of an existing property or development of a new property then the effect is magical. It is for this reason that superconductivity remains an enigma for scientists for over a century after Kammerlingh Onnes discovered that the electrical resistance of mercury falls to zero below a temperature of 4.2 K. Since then scientists have been enchanted by superconductivity. Over these hundred years attempts have been made to discover materials which show this effect at higher temperatures. After a very exciting period of Cu oxide superconductors (1986-1993) there has been a lull in the search for high T(c) materials. The discovery of superconductivity in 2008 at 26 K in LaOFeAs (F-doped) has renewed the excitement in the field of superconductivity. This breakthrough in an Fe-containing compound led to the discovery of several new families of Fe-based superconductors having either pnictogens (P, As) or chalcogen (Se, Te) of the type AFFeAs (A = alkaline-earth metal), AFe(2)As(2), AFeAs (A = alkali metals), A(3)M(2)O(5)Fe(2)As(2) (M = transition metals) and A(4)M(2)O(6)Fe(2)As(2). This review article discusses in detail the structural aspects of these new Fe-based superconductors which primarily consist of edge-shared distorted FeX(4) (X = pnictogen and chalcogen) tetrahedra and these tetrahedral layers are reponsible for enabling superconductivity. Extremely large upper critical field (>200 Tesla) of these superconductors make them promising for high field application. Structural commonalities and differences among different families of these superconductors have been outlined. We also discuss the common features and differences with the copper-oxide based superconductors. Here we have discussed all the Fe-based oxypnictide families (like LnOFePn, AFe(2

  9. What can be learned from binding energy differences about nuclear structure: The example of {delta}V{sub pn}

    SciTech Connect

    Bender, M.

    2011-06-15

    We perform an analysis of a binding energy difference called {delta}V{sub pn}(N,Z){identical_to}-(1/4)[E(Z,N)-E(Z,N-2)-E(Z-2,N)+E(Z-2,N-2)] in the framework of a realistic nuclear model. It has been suggested that {delta}V{sub pn} values provide a sensitive probe of nuclear structure, and it has been put forward as a primary motivation for the measurement of specific nuclear masses. Using the angular momentum and particle-number projected generator coordinate method and the Skyrme interaction SLy4, we analyze the contribution brought to {delta}V{sub pn} by static deformation and dynamic fluctuations around the mean-field ground state. Our method gives a good overall description of {delta}V{sub pn} throughout the chart of nuclei with the exception of the anomaly related to the Wigner energy along the N=Z line. The main conclusions of our analysis of {delta}V{sub pn}, which are at variance with its standard interpretation, are that (i) the structures seen in the systematics of {delta}V{sub pn} throughout the chart of nuclei can be easily explained combining a smooth background related to the symmetry energy and correlation energies due to deformation and collective fluctuations, (ii) the characteristic pattern of {delta}V{sub pn} having a much larger size for nuclei that add only particles or only holes to a doubly magic nucleus than for nuclei that add particles for one nucleon species and holes for the other is a trivial consequence of the asymmetric definition of {delta}V{sub pn} and not due to a the different structure of these nuclei, (iii) {delta}V{sub pn} does not provide a very reliable indicator for structural changes, (iv){delta}V{sub pn} does not provide a reliable measure of the proton-neutron interaction in the nuclear energy density functional (EDF) or of that between the last filled orbits or of the one summed over all orbits, and (v) {delta}V{sub pn} does not provide a conclusive benchmark for nuclear EDF methods that is superior or complementary to

  10. Uppermost mantle velocity from Pn tomography in the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Corbeau, Jordane; Rolandone, Frédérique; Leroy, Sylvie; Al-Lazki, Ali; Keir, Derek; Stuart, Graham; Stork, Anna

    2013-04-01

    We present an analysis of Pn traveltimes to determine lateral variations of velocity in the uppermost mantle and crustal thickness beneath the Gulf of Aden and its margins. No detailed tomographic image of the entire Gulf of Aden was available. Previous tomographic studies covered the eastern Gulf of Aden and were thus incomplete or at a large scale with a too low resolution to see the lithospheric structures. From 1990 to 2010, 49206 Pn arrivals were selected from the International Seismological Center catalogue. We also used temporary networks : YOCMAL (Young Conjugate Margins Laboratory) networks with broadband stations located in Oman, Yemen and Socotra from 2003 to 2011, and Djibouti network from 2009 to 2011. From these networks we picked Pn arrivals and selected 4110 rays. Using a least-squares tomographic code (Hearn, 1996), these data were analyzed to solve for velocity variations in the mantle lithosphere. We perform different inversions for shorter and longer ray path data sets in order to separate the shallow and deep structure within the mantle lid. In the upper lid, zones of low velocity (7.7 km/s) around Sanaa, Aden, Afar, and along the Gulf of Aden are related to active volcanism. Off-axis volcanism and a regional melting anomaly in the Gulf of Aden area may be connected to the Afar plume, and explained by the model of channeling material away from the Afar plume along ridge-axis. Our study validates the channeling model and shows that the influence of the Afar hotspot may extend much farther eastwards along the Aden and Sheba ridges into the Gulf of Aden than previously believed. Still in the upper lid, high Pn velocities (>8,2 km/s) are observed in Yemen and may be related to the presence of a magmatic underplating under the volcanic margin of Aden and under the Red Sea margins. In the lower lid, zones of low velocities are spatially located differently than in the upper lid. On the Oman margin, a low velocity zone (7.6 km/s) suggests deep partial

  11. Spin-polarized transport in inhomogeneous magnetic semiconductors: theory of magnetic/nonmagnetic p-n junctions.

    PubMed

    Zutić, Igor; Fabian, Jaroslav; Das Sarma, S

    2002-02-11

    A theory of spin-polarized transport in inhomogeneous magnetic semiconductors is developed and applied to magnetic/nonmagnetic p-n junctions. Several phenomena with possible spintronic applications are predicted, including spin-voltaic effect, spin valve effect, exponential and giant magnetoresistance. It is demonstrated that only nonequilibrium spin can be injected across the space-charge region of a p-n junction, so that there is no spin injection (or extraction) at low bias. PMID:11863835

  12. The polysaccharide isolated from Pleurotus nebrodensis (PN-S) shows immune-stimulating activity in RAW264.7 macrophages.

    PubMed

    Cui, Hai-Yan; Wang, Chang-Lu; Wang, Yu-Rong; Li, Zhen-Jing; Zhang, Ya-Nan

    2015-05-01

    A novel Pleurotus nebrodensis polysaccharide (PN-S) was purified and characterized, and its immune-stimulating activity was evaluated in RAW264.7 macrophages. PN-S induced the proliferation of RAW264.7 cells in a dose-dependent manner, as determined by the MTT assay. After exposure to PN-S, the phagocytosis of the macrophages was significantly improved, with remarkable changes in morphology being observed. Flow cytometric analysis demonstrated that PN-S promoted RAW264.7 cells to progress through S and G2/M phases. PN-S treatment enhanced the productions of interleukin-6 (IL-6), nitric oxide (NO), interferon gamma (INF-γ), and tumor necrosis factor-α (TNF-α) in the macrophages, with up-regulation of mRNA expressions of interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS), interferon gamma(INF-γ) and tumor necrosis factor-α (TNF-α) being observed in a dose-dependent manner, as measured by qRT-PCR. In conclusion, these results suggest that the purified PN-S can improve immunity by activating macrophages.

  13. Peanut witches' broom (PnWB) phytoplasma-mediated leafy flower symptoms and abnormal vascular bundles development.

    PubMed

    Liu, Chi-Te; Huang, Hsin-Mei; Hong, Syuan-Fei; Kuo-Huang, Ling-Long; Yang, Chiao-Yin; Lin, Yen-Yu; Lin, Chan-Pin; Lin, Shih-Shun

    2015-01-01

    The peanut witches' broom (PnWB) phytoplasma causes virescence symptoms such as phyllody (leafy flower) in infected peanuts. However, the obligate nature of phytoplasma limits the study of host-pathogen interactions, and the detailed anatomy of PnWB-infected plants has yet to be reported. Here, we demonstrate that 4',6'-diamidino-2-phenylindole (DAPI) staining can be used to track PnWB infection. The DAPI-stained phytoplasma cells were observed in phloem/internal phloem tissues, and changes in vascular bundle morphology, including increasing pith rays and thinner cell walls in the xylem, were found. We also discerned the cell types comprising PnWB in infected sieve tube members. These results suggest that the presence of PnWB in phloem tissue facilitates the transmission of phytoplasma via sap-feeding insect vectors. In addition, PnWB in sieve tube members and changes in vascular bundle morphology might strongly promote the ability of phytoplasmas to assimilate nutrients. These data will help further an understanding of the obligate life cycle and host-pathogen interactions of phytoplasma.

  14. Peanut witches' broom (PnWB) phytoplasma-mediated leafy flower symptoms and abnormal vascular bundles development

    PubMed Central

    Liu, Chi-Te; Huang, Hsin-Mei; Hong, Syuan-Fei; Kuo-Huang, Ling-Long; Yang, Chiao-Yin; Lin, Yen-Yu; Lin, Chan-Pin; Lin, Shih-Shun

    2015-01-01

    The peanut witches' broom (PnWB) phytoplasma causes virescence symptoms such as phyllody (leafy flower) in infected peanuts. However, the obligate nature of phytoplasma limits the study of host-pathogen interactions, and the detailed anatomy of PnWB-infected plants has yet to be reported. Here, we demonstrate that 4′,6′-diamidino-2-phenylindole (DAPI) staining can be used to track PnWB infection. The DAPI-stained phytoplasma cells were observed in phloem/internal phloem tissues, and changes in vascular bundle morphology, including increasing pith rays and thinner cell walls in the xylem, were found. We also discerned the cell types comprising PnWB in infected sieve tube members. These results suggest that the presence of PnWB in phloem tissue facilitates the transmission of phytoplasma via sap-feeding insect vectors. In addition, PnWB in sieve tube members and changes in vascular bundle morphology might strongly promote the ability of phytoplasmas to assimilate nutrients. These data will help further an understanding of the obligate life cycle and host-pathogen interactions of phytoplasma. PMID:26492318

  15. Low-Yield Cigarettes

    MedlinePlus

    ... Secondhand Smoke Smokeless Products Youth Tobacco Prevention Tobacco Industry and Products Federal Tax Increase Tobacco Ingredient Reporting ... be used. 3 In the past, the tobacco industry categorized low-yield cigarettes using measurements of tar ...

  16. Argentina soybean yield model

    NASA Technical Reports Server (NTRS)

    Callis, S. L.; Sakamoto, C.

    1984-01-01

    A model based on multiple regression was developed to estimate soybean yields for the country of Argentina. A meteorological data set was obtained for the country by averaging data for stations within the soybean growing area. Predictor variables for the model were derived from monthly total precipitation and monthly average temperature. A trend variable was included for the years 1969 to 1978 since an increasing trend in yields due to technology was observed between these years.

  17. Argentina corn yield model

    NASA Technical Reports Server (NTRS)

    Callis, S. L.; Sakamoto, C.

    1984-01-01

    A model based on multiple regression was developed to estimate corn yields for the country of Argentina. A meteorological data set was obtained for the country by averaging data for stations within the corn-growing area. Predictor variables for the model were derived from monthly total precipitation, average monthly mean temperature, and average monthly maximum temperature. A trend variable was included for the years 1965 to 1980 since an increasing trend in yields due to technology was observed between these years.

  18. δ-Ctenitoxin-Pn1a, a Peptide from Phoneutria nigriventer Spider Venom, Shows Antinociceptive Effect Involving Opioid and Cannabinoid Systems, in Rats

    PubMed Central

    Emerich, Bruna Luiza; Ferreira, Renata C. M.; Cordeiro, Marta N.; Borges, Márcia Helena; Pimenta, Adriano M. C.; Figueiredo, Suely G.; Duarte, Igor Dimitri G.; de Lima, Maria Elena

    2016-01-01

    PnTx4(6-1), henceforth renamed δ-Ctenitoxin-Pn1a (δ-CNTX-Pn1a), a peptide from Phoneutria nigriventer spider venom, initially described as an insect toxin, binds to site 3 of sodium channels in nerve cord synaptosomes and slows down sodium current inactivation in isolated axons in cockroaches (Periplaneta americana). δ-CNTX-Pn1a does not cause any apparent toxicity to mice, when intracerebroventricularly injected (30 μg). In this study, we evaluated the antinociceptive effect of δ-CNTX-Pn1a in three animal pain models and investigated its mechanism of action in acute pain. In the inflammatory pain model, induced by carrageenan, δ-CNTX-Pn1a restored the nociceptive threshold of rats, when intraplantarly injected, 2 h and 30 min after carrageenan administration. Concerning the neuropathic pain model, δ-CNTX-Pn1a, when intrathecally administered, reversed the hyperalgesia evoked by sciatic nerve constriction. In the acute pain model, induced by prostaglandin E2, intrathecal administration of δ-CNTX-Pn1a caused a dose-dependent antinociceptive effect. Using antagonists of the receptors, we showed that the antinociceptive effect of δ-CNTX-Pn1a involves both the cannabinoid system, through CB1 receptors, and the opioid system, through μ and δ receptors. Our data show, for the first time, that δ-Ctenitoxin-Pn1a is able to induce antinociception in inflammatory, neuropathic and acute pain models. PMID:27077886

  19. δ-Ctenitoxin-Pn1a, a Peptide from Phoneutria nigriventer Spider Venom, Shows Antinociceptive Effect Involving Opioid and Cannabinoid Systems, in Rats.

    PubMed

    Emerich, Bruna Luiza; Ferreira, Renata C M; Cordeiro, Marta N; Borges, Márcia Helena; Pimenta, Adriano M C; Figueiredo, Suely G; Duarte, Igor Dimitri G; de Lima, Maria Elena

    2016-04-01

    PnTx4(6-1), henceforth renamed δ-Ctenitoxin-Pn1a (δ-CNTX-Pn1a), a peptide from Phoneutria nigriventer spider venom, initially described as an insect toxin, binds to site 3 of sodium channels in nerve cord synaptosomes and slows down sodium current inactivation in isolated axons in cockroaches (Periplaneta americana). δ-CNTX-Pn1a does not cause any apparent toxicity to mice, when intracerebroventricularly injected (30 μg). In this study, we evaluated the antinociceptive effect of δ-CNTX-Pn1a in three animal pain models and investigated its mechanism of action in acute pain. In the inflammatory pain model, induced by carrageenan, δ-CNTX-Pn1a restored the nociceptive threshold of rats, when intraplantarly injected, 2 h and 30 min after carrageenan administration. Concerning the neuropathic pain model, δ-CNTX-Pn1a, when intrathecally administered, reversed the hyperalgesia evoked by sciatic nerve constriction. In the acute pain model, induced by prostaglandin E₂, intrathecal administration of δ-CNTX-Pn1a caused a dose-dependent antinociceptive effect. Using antagonists of the receptors, we showed that the antinociceptive effect of δ-CNTX-Pn1a involves both the cannabinoid system, through CB₁ receptors, and the opioid system, through μ and δ receptors. Our data show, for the first time, that δ-Ctenitoxin-Pn1a is able to induce antinociception in inflammatory, neuropathic and acute pain models. PMID:27077886

  20. δ-Ctenitoxin-Pn1a, a Peptide from Phoneutria nigriventer Spider Venom, Shows Antinociceptive Effect Involving Opioid and Cannabinoid Systems, in Rats.

    PubMed

    Emerich, Bruna Luiza; Ferreira, Renata C M; Cordeiro, Marta N; Borges, Márcia Helena; Pimenta, Adriano M C; Figueiredo, Suely G; Duarte, Igor Dimitri G; de Lima, Maria Elena

    2016-04-12

    PnTx4(6-1), henceforth renamed δ-Ctenitoxin-Pn1a (δ-CNTX-Pn1a), a peptide from Phoneutria nigriventer spider venom, initially described as an insect toxin, binds to site 3 of sodium channels in nerve cord synaptosomes and slows down sodium current inactivation in isolated axons in cockroaches (Periplaneta americana). δ-CNTX-Pn1a does not cause any apparent toxicity to mice, when intracerebroventricularly injected (30 μg). In this study, we evaluated the antinociceptive effect of δ-CNTX-Pn1a in three animal pain models and investigated its mechanism of action in acute pain. In the inflammatory pain model, induced by carrageenan, δ-CNTX-Pn1a restored the nociceptive threshold of rats, when intraplantarly injected, 2 h and 30 min after carrageenan administration. Concerning the neuropathic pain model, δ-CNTX-Pn1a, when intrathecally administered, reversed the hyperalgesia evoked by sciatic nerve constriction. In the acute pain model, induced by prostaglandin E₂, intrathecal administration of δ-CNTX-Pn1a caused a dose-dependent antinociceptive effect. Using antagonists of the receptors, we showed that the antinociceptive effect of δ-CNTX-Pn1a involves both the cannabinoid system, through CB₁ receptors, and the opioid system, through μ and δ receptors. Our data show, for the first time, that δ-Ctenitoxin-Pn1a is able to induce antinociception in inflammatory, neuropathic and acute pain models.

  1. 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.

  2. Electrical and photovoltaic characteristics of MoS{sub 2}/Si p-n junctions

    SciTech Connect

    Hao, Lanzhong Liu, Yunjie Gao, Wei; Han, Zhide; Xue, Qingzhong; Zeng, Huizhong; Wu, Zhipeng; Zhu, Jun; Zhang, Wanli

    2015-03-21

    Bulk-like molybdenum disulfide (MoS{sub 2}) thin films were deposited on the surface of p-type Si substrates using dc magnetron sputtering technique and MoS{sub 2}/Si p-n junctions were formed. The vibrating modes of E{sup 1}{sub 2g} and A{sub 1g} were observed from the Raman spectrum of the MoS{sub 2} films. The current density versus voltage (J-V) characteristics of the junction were investigated. A typical J-V rectifying effect with a turn-on voltage of 0.2 V was shown. In different voltage range, the electrical transporting of the junction was dominated by diffusion current and recombination current, respectively. Under the light illumination of 15 mW cm{sup −2}, the p-n junction exhibited obvious photovoltaic characteristics with a short-circuit current density of 3.2 mA cm{sup −2} and open-circuit voltage of 0.14 V. The fill factor and energy conversion efficiency were 42.4% and 1.3%, respectively. According to the determination of the Fermi-energy level (∼4.65 eV) and energy-band gap (∼1.45 eV) of the MoS{sub 2} films by capacitance-voltage curve and ultraviolet-visible transmission spectra, the mechanisms of the electrical and photovoltaic characteristics were discussed in terms of the energy-band structure of the MoS{sub 2}/Si p-n junctions. The results hold the promise for the integration of MoS{sub 2} thin films with commercially available Si-based electronics in high-efficient photovoltaic devices.

  3. Uncooled CMOS terahertz imager using a metamaterial absorber and pn diode.

    PubMed

    Escorcia, Ivonne; Grant, James; Gough, John; Cumming, David R S

    2016-07-15

    We demonstrate a low-cost uncooled terahertz (THz) imager fabricated in a standard 180 nm CMOS process. The imager is composed of a broadband THz metamaterial absorber coupled with a diode microbolometer sensor where the pn junction is used as a temperature sensitive device. The metamaterial absorber array is integrated in the top metallic layers of a six metal layer process allowing for complete monolithic integration of the metamaterial absorber and sensor. We demonstrate the capability of the detector for stand-off imaging applications by using it to form transmission and reflection images of a metallic object hidden in a manila envelope.

  4. The radiation damage of crystalline silicon PN diode in tritium beta-voltaic battery.

    PubMed

    Lei, Yisong; Yang, Yuqing; Liu, Yebing; Li, Hao; Wang, Guanquan; Hu, Rui; Xiong, Xiaoling; Luo, Shunzhong

    2014-08-01

    A tritium beta-voltaic battery using a crystalline silicon convertor composed of (100)Si/SiO2/Si3N4 film degrades remarkably with radiation from a high intensity titanium tritide film. Simulation and experiments were carried out to investigate the main factor causing the degradation. The radiation damages mainly comes from the x-ray emitted from the titanium tritide film and beta particle can relieve the damages. The x-ray radiation induced positive charges in the SiO2 film destroying the output property of the PN diode with the induction of an electric field.

  5. Model of human breathing reflected signal received by PN-UWB radar.

    PubMed

    Mabrouk, Mohamed; Rajan, Sreeraman; Bolic, Miodrag; Batkin, Izmail; Dajani, Hilmi R; Groza, Voicu Z

    2014-01-01

    Human detection is an integral component of civilian and military rescue operations, military surveillance and combat operations. Human detection can be achieved through monitoring of vital signs. In this article, a mathematical model of human breathing reflected signal received in PN-UWB radar is proposed. Unlike earlier published works, both chest and abdomen movements are considered for modeling the radar return signal along with the contributions of fundamental breathing frequency and its harmonics. Analyses of recorded reflected signals from three subjects in different postures and at different ranges from the radar indicate that ratios of the amplitudes of the harmonics contain information about posture and posture change.

  6. Chemical Visualization of a GaN p-n junction by XPS.

    PubMed

    Caliskan, Deniz; Sezen, Hikmet; Ozbay, Ekmel; Suzer, Sefik

    2015-01-01

    We report on an operando XPS investigation of a GaN diode, by recording the Ga2p3/2 peak position under both forward and reverse bias. Areal maps of the peak positions under reverse bias are completely decoupled with respect to doped regions and allow a novel chemical visualization of the p-n junction in a 2-D fashion. Other electrical properties of the device, such as leakage current, resistivity of the domains are also tapped via recording line-scan spectra. Application of a triangular voltage excitation enables probing photoresponse of the device. PMID:26359762

  7. Charge collection at large angles of incidence. [exibited by p-n junctions

    NASA Technical Reports Server (NTRS)

    Mcnulty, P. J.; Beauvais, W. J.; Reed, R. A.; Roth, D. R.; Stassinopoulos, E. G.; Brucker, G. J.

    1992-01-01

    Charge collection exhibited by p-n junctions, which have at least one small dimension, deviates from the geometric assumptions commonly used in SEU (single event upset) testing. The amount of charge collected did not increase with the secant of the angle of incidence. The number of events under the peak in the charge collection spectrum did not decrease as the cosine of the angle of incidence. Both the position of the peak and the number of events under the peak measured at a given angle of incidence depended upon which symmetry axis of the device was chosen to be the axis of rotation.

  8. Laser processing for bevel termination of high voltage pn junction in SiC

    NASA Astrophysics Data System (ADS)

    Kubiak, A.; Ruta, Ł.; Rosowski, A.; French, P.

    2016-04-01

    Proper edge termination of the p-n junction in silicon carbide is a key requirement in the fabrication of discrete devices able to withstand high voltages in reverse polarization. Due to the hardness of SiC the creation of the bevel termination remains difficult using mechanical machining. The use of laser beam sources with medium wavelength (532 nm) gives new possibilities in the machining of the silicon carbide. The paper presents the fabrication of the bevel termination structure in SiC using a green DPSS laser equipped with scanner and dedicated rotating sample holder. Characterization of the resulting structures proves the high potential of the proposed approach.

  9. On the determination of diffusion lengths by means of angle-lapped p-n junctions

    NASA Technical Reports Server (NTRS)

    Von Roos, O.

    1979-01-01

    A standard procedure for determining the minority carrier diffusion length by means of SEM consists of scanning an angle-lapped surface of a p-n junction and measuring the resulting short circuit current as a function of beam position. The present paper points out that the usual expression linking the short circuit current induced by the electron beam to the angle between the semiconductor surface and the junction plane is incorrect. The correct expression is discussed and it is noted that, for angles less than 10 deg, the new and the old expression are practically indistinguishable.

  10. The radiation damage of crystalline silicon PN diode in tritium beta-voltaic battery.

    PubMed

    Lei, Yisong; Yang, Yuqing; Liu, Yebing; Li, Hao; Wang, Guanquan; Hu, Rui; Xiong, Xiaoling; Luo, Shunzhong

    2014-08-01

    A tritium beta-voltaic battery using a crystalline silicon convertor composed of (100)Si/SiO2/Si3N4 film degrades remarkably with radiation from a high intensity titanium tritide film. Simulation and experiments were carried out to investigate the main factor causing the degradation. The radiation damages mainly comes from the x-ray emitted from the titanium tritide film and beta particle can relieve the damages. The x-ray radiation induced positive charges in the SiO2 film destroying the output property of the PN diode with the induction of an electric field. PMID:24751350

  11. Using Colored Stochastic Petri Net (CS-PN) software for protocol specification, validation, and evaluation

    NASA Technical Reports Server (NTRS)

    Zenie, Alexandre; Luguern, Jean-Pierre

    1987-01-01

    The specification, verification, validation, and evaluation, which make up the different steps of the CS-PN software are outlined. The colored stochastic Petri net software is applied to a Wound/Wait protocol decomposable into two principal modules: request or couple (transaction, granule) treatment module and wound treatment module. Each module is specified, verified, validated, and then evaluated separately, to deduce a verification, validation and evaluation of the complete protocol. The colored stochastic Petri nets tool is shown to be a natural extension of the stochastic tool, adapted to distributed systems and protocols, because the color conveniently takes into account the numerous sites, transactions, granules and messages.

  12. Electronic and structural properties of femtosecond laser sulfur hyperdoped silicon pn-junctions

    NASA Astrophysics Data System (ADS)

    Saring, Philipp; Lena Baumann, Anna; Schlieper-Ludewig, Bettina; Kontermann, Stefan; Schade, Wolfgang; Seibt, Michael

    2013-08-01

    The structural properties of femtosecond laser sulfur hyperdoped silicon pn-junctions are correlated to electronic transport characteristics at the interface. The depth of the planar space charge region obtained from cross-sectional electron beam induced current analysis is in good agreement with the sulfur concentration depth profile, derived from secondary ion mass spectroscopy. EBIC signals from the crest regions of the laser structured surface reveal increased recombination activity. Using transmission electron microscopy, we show that such recombination is related to dislocations, which are most probably highly decorated with sulfur.

  13. Upgrades to the Inmarsat PN transmission test bed and initial results

    NASA Astrophysics Data System (ADS)

    Kinal, George; Razumovsky, Oleg

    The various improvements incorporated in several stages to enhance the stability of the signal and the accuracy of the measurement techniques of the Inmarsat PN test bed are presented. It is indicated how relatively inexpensive equipment can form the basis for timing compensation and satellite ranging systems needed to make a signal relayed through a 'bent pipe' repeater function as an augmentation to the GPS for civil applications. The navigation repeater channels proposed for Inmarsat-3 will have a parallel downlink path at C-bank, providing a dual frequency path so that ionospheric delay variations may be accounted for.

  14. The northern Walker Lane refraction experiment: Pn arrivals and the northern Sierra Nevada root

    NASA Astrophysics Data System (ADS)

    Louie, John N.; Thelen, Weston; Smith, Shane B.; Scott, James B.; Clark, Matthew; Pullammanappallil, Satish

    2004-09-01

    In May 2002, we collected a new crustal refraction profile from Battle Mountain, Nevada across western Nevada, the Reno area, Lake Tahoe, and the northern Sierra Nevada Mountains to Auburn, CA. Mine blasts and earthquakes were recorded by 199 Texan instruments extending across this more than 450-km-long transect. The use of large mine blasts and the ultra-portable Texan recorders kept the field costs of this profile to less than US$10,000. The seismic sources at the eastern end were mining blasts at Barrick's GoldStrike mine. The GoldStrike mine produced several ripple-fired blasts using 8000-44,000 kg of ANFO each, a daily occurrence. First arrivals from the larger GoldStrike blasts are obvious to distances of 300 km in the raw records. First arrivals from a quarry blast west of the survey near Watsonville, CA, located by the Northern California Seismic Network with a magnitude of 2.2, can be picked across the recording array to distances of 600 km. The Watsonville blast provides a western source, nearly reversing the GoldStrike blasts. A small earthquake near Bridgeport, CA. also produced pickable P-wave arrivals across the transect, providing fan-shot data. Arrivals from M5 events in the Mariana and Kuril Islands also appear in the records. This refraction survey observes an unexpectedly deep crustal root under the northern Sierra Nevada range, over 50 km in thickness and possibly centered west of the topographic crest. Pn delays of 4-6 s support this interpretation. At Battle Mountain, Nevada, we observe anomalously thin crust over a limited region perhaps only 150 km wide, with a Moho depth of 19-23 km. Pn crossover distances of less than 80 km support this anomaly, which is surrounded by observations of more normal, 30-km-thick crust. A 10-km-thick and high-velocity lower-crustal "pillow" is an alternative hypothesis, but unlikely due to the lack of volcanics west of Battle Mountain. Large mine and quarry blasts prove very effective crustal refraction sources

  15. Fabrication of p(+)-n junction GaAs solar cells by a novel method

    NASA Technical Reports Server (NTRS)

    Ghandhi, S. K.; Mathur, G.; Rode, H.; Borrego, J. M.

    1984-01-01

    A novel method for making p(+)-n diffused junction GaAs solar cells, with the formation of a diffusion source, an anti-reflective coating, and a protective cover glass in a single chemical-vapor deposition operation is discussed. Consideration is given to device fabrication and to solar-cell characteristics. The advantages of the technique are that the number of process steps is kept to an absolute minimum, the fabrication procedure is low-cost, and the GaAs surface is protected during the entire operation.

  16. Investigation of the exclusive 3He(e,e' pn)1H reaction.

    PubMed

    Middleton, D G; Annand, J R M; Antelo, M Ases; Ayerbe, C; Barneo, P; Baumann, D; Bermuth, J; Bernauer, J; Blok, H P; Böhm, R; Bosnar, D; Ding, M; Distler, M O; Friedrich, J; Llongo, J García; Glazier, D I; Golak, J; Glöckle, W; Grabmayr, P; Hehl, T; Heim, J; Hesselink, W H A; Jans, E; Kamada, H; Mañas, G Jover; Kohl, M; Lapikás, L; MacGregor, I J D; Martin, I; McGeorge, J C; Merkel, H; Merle, P; Monstad, K; Moschini, F; Müller, U; Nogga, A; Pérez-Benito, R; Pospischil, Th; Potokar, M; Rosner, G; Seimetz, M; Skibiński, R; de Vries, H; Walcher, Th; Watts, D P; Weinriefer, M; Weiss, M; Witała, H; Zihlmann, B

    2009-10-01

    Cross sections for the 3He(e,e' pn)1H reaction were measured for the first time at energy transfers of 220 and 270 MeV for several momentum transfers ranging from 300 to 450 MeV/c. Cross sections are presented as a function of the momentum of the recoil proton and the momentum transfer. Continuum Faddeev calculations using the Argonne V18 and Bonn-B nucleon-nucleon potentials overestimate the measured cross sections by a factor 5 at low recoil proton momentum with the discrepancy becoming smaller at higher recoil proton momentum. PMID:19905628

  17. Disorder effects in the quantum Hall effect of graphene p-n junctions

    NASA Astrophysics Data System (ADS)

    Li, Jian; Shen, Shun-Qing

    2008-11-01

    The quantum Hall effect in graphene p-n junctions is studied numerically with emphasis on the effect of disorder at the interface of two adjacent regions. Conductance plateaus are found to be attached to the intensity of the disorder and are accompanied by universal conductance fluctuations in the bipolar regime, which is in good agreement with theoretical predictions of the random matrix theory on quantum chaotic cavities. The calculated Fano factors can be used in an experimental identification of the underlying transport character.

  18. Femtosecond optical excitation of coherent acoustic phonons in a piezoelectric p-n junction

    NASA Astrophysics Data System (ADS)

    Wen, Yu-Chieh; Chern, Gia-Wei; Lin, Kung-Hsuan; Yeh, Jeffrey Jarren; Sun, Chi-Kuang

    2011-11-01

    We present a theoretical model for the photogeneration of coherent acoustic phonons in a piezoelectric p-n junction. In our model, the transport of photoexcited carriers is governed by the drift-diffusion equation, whereas the dynamics of acoustic phonons obeys a loaded string equation. Among various mechanisms, the piezoelectric coupling is found to dominate the acoustic-phonon generation process. The waveform of the photogenerated acoustic pulse is strongly influenced by the various dynamics of the photoexcited carriers, especially the picosecond hole drifting. Our calculation also confirms the crucial role of the built-in electric field in the formation of coherent acoustic phonons under optical excitations.

  19. Temporal characteristics of surface-acoustic-wave-driven luminescence from a lateral p-n junction

    NASA Astrophysics Data System (ADS)

    Gell, J. R.; Ward, M. B.; Shields, A. J.; Atkinson, P.; Bremner, S. P.; Anderson, D.; Kataoka, M.; Barnes, C. H. W.; Jones, G. A. C.; Ritchie, D. A.

    2007-07-01

    Short radio frequency pulses were used to study the surface-acoustic-wave-driven light emission from a molecular beam epitaxy regrown GaAs /AlGaAs lateral p-n junction. The luminescence provides a fast probe of the signals arriving at the junction allowing the authors to temporally separate the effect of the surface-acoustic-wave from pickup of the free space electromagnetic wave. Oscillations in the light intensity are resolved at the resonant frequency of the transducer, suggesting that the surface-acoustic-wave is transporting electrons across the junction in packets.

  20. Surface-acoustic-wave-driven luminescence from a lateral p-n junction

    NASA Astrophysics Data System (ADS)

    Gell, J. R.; Atkinson, P.; Bremner, S. P.; Sfigakis, F.; Kataoka, M.; Anderson, D.; Jones, G. A. C.; Barnes, C. H. W.; Ritchie, D. A.; Ward, M. B.; Norman, C. E.; Shields, A. J.

    2006-12-01

    The authors report surface-acoustic-wave-driven luminescence from a lateral p-n junction formed by molecular beam epitaxy regrowth of a modulation doped GaAs /AlGaAs quantum well on a patterned GaAs substrate. Surface-acoustic-wave-driven transport is demonstrated by peaks in the electrical current and light emission from the GaAs quantum well at the resonant frequency of the transducer. This type of junction offers high carrier mobility and scalability. The demonstration of surface-acoustic-wave luminescence is a significant step towards single-photon applications in quantum computation and quantum cryptography.

  1. 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.

  2. Chemical Visualization of a GaN p-n junction by XPS

    PubMed Central

    Caliskan, Deniz; Sezen, Hikmet; Ozbay, Ekmel; Suzer, Sefik

    2015-01-01

    We report on an operando XPS investigation of a GaN diode, by recording the Ga2p3/2 peak position under both forward and reverse bias. Areal maps of the peak positions under reverse bias are completely decoupled with respect to doped regions and allow a novel chemical visualization of the p-n junction in a 2-D fashion. Other electrical properties of the device, such as leakage current, resistivity of the domains are also tapped via recording line-scan spectra. Application of a triangular voltage excitation enables probing photoresponse of the device. PMID:26359762

  3. Lateral graphene p-n junctions formed by the graphene/MoS2 hybrid interface

    NASA Astrophysics Data System (ADS)

    Meng, Jie; Song, Hua-Ding; Li, Cai-Zhen; Jin, Yibo; Tang, Lei; Liu, Dameng; Liao, Zhi-Min; Xiu, Faxian; Yu, Da-Peng

    2015-07-01

    Graphene/two-dimensional (2D) semiconductor heterostructures have been demonstrated to possess many advantages for electronic and optoelectronic devices. However, there are few reports about the utilization of a 2D semiconductor monolayer to tune the properties of graphene. Here, we report the fabrication and characterization of graphene p-n junctions based on graphene/MoS2 hybrid interfaces. Monolayered graphene across the monolayered MoS2 boundary is divided into n-type regions on the MoS2 and p-type regions on the SiO2 substrate. Such van der Waals heterostructure based graphene p-n junctions show good photoelectric properties. The photocurrent modulation of such devices by a single back gate is also demonstrated for the first time, which shows that the graphene on and off MoS2 regions have different responses to the gate voltage. Our results suggest that the atomic thin hybrid structure can remarkably extend the device applications.Graphene/two-dimensional (2D) semiconductor heterostructures have been demonstrated to possess many advantages for electronic and optoelectronic devices. However, there are few reports about the utilization of a 2D semiconductor monolayer to tune the properties of graphene. Here, we report the fabrication and characterization of graphene p-n junctions based on graphene/MoS2 hybrid interfaces. Monolayered graphene across the monolayered MoS2 boundary is divided into n-type regions on the MoS2 and p-type regions on the SiO2 substrate. Such van der Waals heterostructure based graphene p-n junctions show good photoelectric properties. The photocurrent modulation of such devices by a single back gate is also demonstrated for the first time, which shows that the graphene on and off MoS2 regions have different responses to the gate voltage. Our results suggest that the atomic thin hybrid structure can remarkably extend the device applications. Electronic supplementary information (ESI) available: More details on device fabrication, control

  4. THREE-DIMENSIONAL FIELD MODELS FOR REVERSE BIASED P-N JUNCTIONS.

    SciTech Connect

    UBALDI,F.; POZZI, G.; FAZZINI, P.F.; BELEGGIA, M.

    2007-04-02

    In order to obtain reliable quantitative information on the electrostatic field associated with reverse-biased p-n junctions and on the distribution of dopants, the physics of the so-called ''dead layer'' and the influence of charged oxide layers are of paramount importance. To this purpose, experimental observations near the edge of a TEM sample can be useful. In these conditions, however, phase computations required to interpret the experimental results are very challenging as the problem is intrinsically three-dimensional. In order to cope with this problem, a mixed analytical-numerical approach is presented and discussed.

  5. Groups of symmetries in the two-body problem associated to Einstein's PN field

    NASA Astrophysics Data System (ADS)

    Mioc, V.

    The two-body problem associated to a spherical post-Newtonian (PN) field with Einsteinian parameterization is revisited from the single standpoint of symmetries. The corresponding vector fields, in Hamiltonian and standard polar coordinates, or in collision-blow-up and infinity-blow-up McGehee-type coordinates, present symmetries that form diffeomorphic commutative groups endowed with a Boolean structure. The existence of such symmetries is of much help in understanding characteristics of the global flow, or in finding symmetric periodic orbits in more complex problems depending on a small parameter.

  6. Flexible infrared detectors based on p-n junctions of multi-walled carbon nanotubes.

    PubMed

    Huang, Zhenlong; Gao, Min; Yan, Zhuocheng; Pan, Taisong; Liao, Feiyi; Lin, Yuan

    2016-05-14

    Different types of multi-walled carbon nanotubes (CNTs), synthesized by chemical vapor deposition, are used to fabricate infrared (IR) detectors on flexible substrates based on CNT p-n junctions. It is found that this kind of detector is sensitive to infrared signals with a power density as low as 90 μW mm(-2) even at room temperature. Besides, unlike other devices, the detector with this unique structure can be bent for 100 cycles without any damage and its functionality does not degenerate once it recovers to the initial state. The results give a good reference for developing efficient, low-cost, and flexible IR detectors. PMID:27101973

  7. [Effects of alternate partial root-zone subsurface drip irrigation on potato yield and water use efficiency].

    PubMed

    Huang, Zhong-Dong; Qi, Xue-Bin; Fan, Xiang-Yang; Hu, Chao; Zhu, Dong-Hai; Li, Ping; Qiao, Dong-Mei

    2010-01-01

    Field experiment was conducted to investigate the effects of alternate partial root-zone subsurface drip irrigation (APRSDI) on the physiological responses, yield, and water use efficiency of potato. Compared with conventional drip irrigation (CDI), APRSDI had less negative effects on the potato leaf photosynthesis rate (P(n)), but decreased the transpiration rate and stomatal conductance significantly. The slightly higher P(n) under CDI was at the expense of consuming more water. No significant difference was observed in the potato yield under APRSDI and CDI, but APRSDI saved the irrigation amount by 25.8% and increased the irrigation water use efficiency and total water use efficiency by 27.5% and 15.3%, respectively, suggesting that APRSDI would be a feasible water-saving irrigation technique for the planting of potato.

  8. Yield gaps and yield relationships in US soybean production systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The magnitude of yield gaps (YG) (potential yield – farmer yield) provides some indication of the prospects for increasing crop yield to meet the food demands of future populations. Quantile regression analysis was applied to county soybean [Glycine max (L.) Merrill] yields (1971 – 2011) from Kentuc...

  9. Heterosubtypic protection conferred by the human monoclonal antibody PN-SIA28 against influenza A virus lethal infections in mice.

    PubMed

    Retamal, Miguel; Abed, Yacine; Rhéaume, Chantal; Cappelletti, Francesca; Clementi, Nicola; Mancini, Nicasio; Clementi, Massimo; Burioni, Roberto; Boivin, Guy

    2015-05-01

    PN-SIA28 is a human monoclonal antibody (Hu-MAb) targeting highly conserved epitopes within the stem portion of the influenza virus hemagglutinin (HA) (N. Clementi, et al, PLoS One 6:e28001, 2011, http://dx.doi.org/10.1371/journal.pone.0028001). Previous in vitro studies demonstrated PN-SIA28 neutralizing activities against phylogenetically divergent influenza A subtypes. In this study, the protective activity of PN-SIA28 was evaluated in mice inoculated with lethal influenza A/WSN/33 (H1N1), A/Quebec/144147/09 (H1N1)pdm09, and A/Victoria/3/75 (H3N2) viruses. At 24 h postinoculation (p.i.), animals received PN-SIA28 intraperitoneally (1 or 10 mg/kg of body weight) or 10 mg/kg of unrelated Hu-MAb (mock). Body weight loss and mortality rate (MR) were recorded for 14 days postinfection (p.i.). Lung viral titers (LVT) were determined at day 5 p.i. In A/WSN/33 (H1N1)-infected groups, all untreated and mock-receiving mice died, whereas MRs of 87.5% and 25% were observed in mice that received PN-SIA28 1 and 10 mg/kg, respectively. In influenza A(H1N1) pdm09-infected groups, an MR of 75% was recorded for untreated and mock-treated groups, whereas the PN-SIA28 1-mg/kg and 10-mg/kg groups had rates of 62.5% and 0%, respectively. In A/Victoria/3/75 (H3N2)-infected animals, untreated and mock-treated animals had MRs of 37.5% and 25%, respectively, and no mortalities were recorded after PN-SIA28 treatments. Accordingly, PN-SIA28 treatments significantly reduced weight losses and resulted in a ≥ 1-log reduction in LVT compared to the control in all infection groups. This study confirms that antibodies targeting highly conserved epitopes in the influenza HA stem region, like PN-SIA28, not only neutralize influenza A viruses of clinically relevant subtypes in vitro but also, more importantly, protect from a lethal influenza virus challenge in vivo.

  10. Tuning Chemical Potential Difference across Alternately Doped Graphene p-n Junctions for High-Efficiency Photodetection.

    PubMed

    Lin, Li; Xu, Xiang; Yin, Jianbo; Sun, Jingyu; Tan, Zhenjun; Koh, Ai Leen; Wang, Huan; Peng, Hailin; Chen, Yulin; Liu, Zhongfan

    2016-07-13

    Being atomically thin, graphene-based p-n junctions hold great promise for applications in ultrasmall high-efficiency photodetectors. It is well-known that the efficiency of such photodetectors can be improved by optimizing the chemical potential difference of the graphene p-n junction. However, to date, such tuning has been limited to a few hundred millielectronvolts. To improve this critical parameter, here we report that using a temperature-controlled chemical vapor deposition process, we successfully achieved modulation-doped growth of an alternately nitrogen- and boron-doped graphene p-n junction with a tunable chemical potential difference up to 1 eV. Furthermore, such p-n junction structure can be prepared on a large scale with stable, uniform, and substitutional doping and exhibits a single-crystalline nature. This work provides a feasible method for synthesizing low-cost, large-scale, high efficiency graphene p-n junctions, thus facilitating their applications in optoelectronic and energy conversion devices.

  11. Design and fabrication of a 20 MHz pn-diode silicon ring resonator with in-plane vibration mode

    NASA Astrophysics Data System (ADS)

    Asahi, Yoichi; Tanigawa, Hiroshi; Nishino, Tomoki; Furutsuka, Takashi; Suzuki, Kenichiro

    2016-06-01

    In this paper, we report a new microelectromechanical system (MEMS) resonator based on the pn-diode principle. The pn-diode-based resonator can eliminate the narrow gap that conventional electrostatic MEMS resonators need between driving electrodes. This is expected to solve several serious problems related to fabrication, packaging, and lifetime. However, the resonators previously reported had pn-diodes formed in the vertical direction. Because the resonant frequency is determined by the thickness of the resonator plate, the resonant frequency in formed resonators cannot be changed in the same chip. To solve this problem, we newly design a pn-diode resonator with a lateral vibration. Because the resonant frequency is determined by plate width, this new resonator can provide various resonators with different frequencies in a chip, which is most suitable for the integration of MEMS resonators with electronic circuits. Our research objective at present is related to design and fabrication. By using a simulator, we design a ring resonator of 20 MHz. In the fabrication, we develop a technique of using ion implantation to form a 3-µm-thick pn-diode. The results shown here are very useful for improving the MEMS resonators.

  12. Investigation of pn Correlations in {sup 4}Hep Interactions at a Momentum of 5 GeV/c

    SciTech Connect

    Blinov, A.V.; Turov, V.F.; Chadeyeva, M.V.

    2005-08-01

    Proton-neutron correlations in {sup 4}Hep interactions are studied in an exclusive experiment by using a 2-m bubble chamber exposed to a 5-GeV/c beam of {alpha} particles (the kinetic energy of the protons in the nucleus rest frame is T{sub p} = 620 MeV). Data on the production of pn pairs in 4{pi} geometry for three channels, where it is possible to reconstruct the neutron momentum unambiguously, are used to determine the pn correlation function in {sup 4}Hep interactions. The experimental results are compared with the predictions of a modified Lednicky-Lyuboshitz model. The value obtained for the root-mean-square radius of the pn-emission region is R{sub pn} = 2.1 {+-} 0.3 fm. The dependence of the correlation function on the modulus of the total momentum of the emitted nucleon pair and on the direction of the momentum transfer is studied. An indication that the emission of a pn pair proceeds predominantly through the production of a virtual deuteron is obtained.

  13. Tuning Chemical Potential Difference across Alternately Doped Graphene p-n Junctions for High-Efficiency Photodetection.

    PubMed

    Lin, Li; Xu, Xiang; Yin, Jianbo; Sun, Jingyu; Tan, Zhenjun; Koh, Ai Leen; Wang, Huan; Peng, Hailin; Chen, Yulin; Liu, Zhongfan

    2016-07-13

    Being atomically thin, graphene-based p-n junctions hold great promise for applications in ultrasmall high-efficiency photodetectors. It is well-known that the efficiency of such photodetectors can be improved by optimizing the chemical potential difference of the graphene p-n junction. However, to date, such tuning has been limited to a few hundred millielectronvolts. To improve this critical parameter, here we report that using a temperature-controlled chemical vapor deposition process, we successfully achieved modulation-doped growth of an alternately nitrogen- and boron-doped graphene p-n junction with a tunable chemical potential difference up to 1 eV. Furthermore, such p-n junction structure can be prepared on a large scale with stable, uniform, and substitutional doping and exhibits a single-crystalline nature. This work provides a feasible method for synthesizing low-cost, large-scale, high efficiency graphene p-n junctions, thus facilitating their applications in optoelectronic and energy conversion devices. PMID:27351273

  14. Anisotropic surface melting in lyotropic cubic crystals. Part 1: Pn3m/L1 interface, poor faceting

    NASA Astrophysics Data System (ADS)

    Grenier, J.; Plötzing, T.; Rohe, D.; Pieranski, P.

    2006-02-01

    From experiments with ice or metal crystals, in the vicinity of their crystal/liquid/vapor triple points, it is known that melting of crystals starts on their surfaces and is anisotropic. It is shown here by direct observations under an optical microscope that this anisotropic surface melting phenomenon occurs also in lyotropic systems. In the case of C12EO2/water mixture, it takes place in the vicinity of the peritectic Pn3m/L3/L1 triple point. Above the peritectic triple point, where the Pn3m and L1 phases coexist in the bulk, the surface of a Pn3m-in-L1 crystal is composed of (111)-type facets surrounded by rough surfaces. The angular junction suggests that rough surfaces are wet by a L3-like layer while facets stay “dry”. This is analogous to the pre-melting at rough surfaces in solid crystals. Upon cooling below the peritectic triple point, where L3 and L1 phases coexist in the bulk, a thick layer of the L3 phase grows from the pre-melted, rough Pn3m/L1 interface. Simultaneously, facets stay dry and their radius decreases. In this tri-phasic configuration, stable in a narrow temperature range, the L3/L1 and L3/Pn3m interfaces have shapes of constant mean curvature surfaces having common borders: edges of facets.

  15. Functional expression of a recombinant toxin - rPnTx2-6 - active in erectile function in rat.

    PubMed

    Torres, F S; Silva, C N; Lanza, L F; Santos, Agenor V; Pimenta, A M C; De Lima, M E; Diniz, M R V

    2010-12-15

    In the current study, the putative cDNA for PnTx2-6 toxin of the Phoneutria nigriventer spider venom was cloned and expressed as tioredoxin fusion protein in the cytoplasm of Escherichia coli. The fusion protein was purified from the bacterial extracts by combination of immobilized Ni-ion affinity and gel filtration chromatographies. Then, it was cleaved by enterokinase and the generated recombinant PnTx2-6 (rPnTx2-6) was further purified by reverse-phase HPLC. Likewise the native toxin purified from the spider venom, rPnTx2-6 potentiates the erectile function when injected in rats. This result indicates that the production of functional recombinant PnTx2-6 might be an alternative to provide this basic and valuable tool for study, as well as for further understanding such complex physiological system, including its correlation with the central nervous system and local tissue factors. PMID:20417652

  16. Continuous p-n junction with extremely low leakage current for micro-structured solid-state neutron detector applications

    NASA Astrophysics Data System (ADS)

    Huang, Kuan-Chih; Dahal, Rajendra; Lu, James J.-Q.; Danon, Yaron; Bhat, Ishwara B.

    2013-05-01

    Considerable progress has been achieved recently to enhance the thermal neutron detection efficiency of solid-state neutron detectors that incorporate neutron sensitive materials such as 10B and 6LiF in Si micro-structured p-n junction diode. Here, we describe the design, fabrication process optimization and characterization of an enriched boron filled honeycomb structured neutron detector with a continuous p+-n junction. Boron deposition and diffusion processes were carried out using a low pressure chemical vapor deposition to study the effect of diffusion temperature on current density-voltage characteristics of p+-n diodes. TSUPREM-4 was used to simulate the thickness and surface doping concentration of p+-Si layers. MEDICI was used to simulate the depletion width and the capacitance of the microstructured devices with continuous p+-n junction. Finally, current density-voltage and pulse height distribution of fabricated devices with 2.5×2.5 mm2 size were studied. A very low leakage current density of ~2×10-8 A/cm2 at -1 V (for both planar and honeycomb structured devices) and a bias-independent thermal neutron detection efficiency of ~26% under zero bias voltage were achieved for an enriched boron filled honeycomb structured neutron detector with a continuous p+-n junction.

  17. [Effects of different sowing dates and low-light stress at heading stage on the physiological characteristics and grain yield of hybrid rice].

    PubMed

    Sun, Yuan-Yuan; Sun, Yong-Jian; Chen, Lin; Xu, Hui; Ma, Jun

    2012-10-01

    Hybrid rice Chuanxiang 9838 with medium shade-endurance was taken as the test material to investigate the effects of different sowing dates and low-light stress at heading stage on the flag leaf photosynthetic rate (P(n)), osmotic regulators, antioxidant enzyme activities and the grain yield of hybrid rice. Sowing date and low-light stress at heading stage had significant effects on the flag leaf P(n) and antioxidant enzyme activities and plant dry matter accumulation at heading stage and the grain yield. With the delay of sowing date, the whole period of rice growth and development shortened notably, and the grain yield decreased to different degrees. Compared with the control, shortterm slight low-light stress (20% shading) at heading stage could relieve the harms from high temperature and strong light, and further, relieve the decrease of flag leaf P(n) and plant dry matter accumulation at heading stage, adjust the flag leaf antioxidant enzyme activities, and moderately improve the seed setting rate. However, short-term medium low-light stress (40% shading) and serious low-light stress (60% shading) were not beneficial to the rice growth. Correlation analysis indicated that the flag leaf P(n), malondialdehyde (MDA) content, and superoxide dismutase (SOD) were more sensitive to the sowing date and low-light stress at heading stage, and there existed a highly significant positive correlation between the flag leaf P(n) at initial heading stage (1-5 d) and the plant dry matter accumulation at late heading stage and grain yield.

  18. Flexible infrared detectors based on p-n junctions of multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Huang, Zhenlong; Gao, Min; Yan, Zhuocheng; Pan, Taisong; Liao, Feiyi; Lin, Yuan

    2016-05-01

    Different types of multi-walled carbon nanotubes (CNTs), synthesized by chemical vapor deposition, are used to fabricate infrared (IR) detectors on flexible substrates based on CNT p-n junctions. It is found that this kind of detector is sensitive to infrared signals with a power density as low as 90 μW mm-2 even at room temperature. Besides, unlike other devices, the detector with this unique structure can be bent for 100 cycles without any damage and its functionality does not degenerate once it recovers to the initial state. The results give a good reference for developing efficient, low-cost, and flexible IR detectors.Different types of multi-walled carbon nanotubes (CNTs), synthesized by chemical vapor deposition, are used to fabricate infrared (IR) detectors on flexible substrates based on CNT p-n junctions. It is found that this kind of detector is sensitive to infrared signals with a power density as low as 90 μW mm-2 even at room temperature. Besides, unlike other devices, the detector with this unique structure can be bent for 100 cycles without any damage and its functionality does not degenerate once it recovers to the initial state. The results give a good reference for developing efficient, low-cost, and flexible IR detectors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08791k

  19. Total internal reflection optical switch using the reverse breakdown of a pn junction in silicon.

    PubMed

    Kim, Jong-Hun; Park, Hyo-Hoon

    2015-11-01

    We demonstrate a new type of silicon total-internal-reflection optical switch with a simple pn junction functioning both as a reflector and a heater. The reflector is placed between asymmetrically y-branched multimode waveguides with an inclination angle corresponding to half of the branch angle. When the reflector is at rest, incident light is reflected in accordance to the refractive index difference due to the plasma dispersion effect of the pre-doped carriers. Switching to the transmission state is attained under a reverse breakdown of the pn junction by the thermo-optic effect which smears the refractive index difference. From this switching scheme, we confirmed the switching operation with a shallow total-internal-reflection region of 1 μm width. At a 6° branch angle, an extinction ratio of 12 dB and an insertion loss of -4.2  dB are achieved along with a thermal heating power of 151.5 mW.

  20. PN-type carrier-induced filter with modulatable extinction ratio.

    PubMed

    Fang, Qing; Tu, Xiaoguang; Song, Junfeng; Jia, Lianxi; Luo, Xianshu; Yang, Yan; Yu, Mingbin; Lo, Guoqiang

    2014-12-01

    We demonstrate the first PN-type carrier-induced silicon waveguide Bragg grating filter on a SOI wafer. The optical extinction ratio of this kind of filter can be efficiently modulated under both reverse and forward biases. The carrier-induced Bragg grating based on a PN junction is fabricated on the silicon waveguide using litho compensation technology. The measured optical bandwidth and the extinction ratio of the filter are 0.45 nm and 19 dB, respectively. The optical extinction ratio modulation under the reverse bias is more than 11.5 dB and it is more than 10 dB under the forward bias. Only 1-dB optical transmission loss is realized in this Bragg grating under a reverse bias. The shifting rates of the central wavelength under forward and reverse biases are ~-1.25 nm/V and 0.01 nm/V, respectively. The 3-dB modulation bandwidth of this filter is 5.1 GHz at a bias of -10 V.

  1. Anisotropic photocurrent response at black phosphorus-MoS2 p-n heterojunctions.

    PubMed

    Hong, Tu; Chamlagain, Bhim; Wang, Tianjiao; Chuang, Hsun-Jen; Zhou, Zhixian; Xu, Ya-Qiong

    2015-11-28

    We investigate the photocurrent generation mechanisms at a vertical p-n heterojunction between black phosphorus (BP) and molybdenum disulfide (MoS2) flakes through polarization-, wavelength-, and gate-dependent scanning photocurrent measurements. When incident photon energy is above the direct band gap of MoS2, the photocurrent response demonstrates a competitive effect between MoS2 and BP in the junction region. In contrast, if the incident photon energy is below the band gap of MoS2 but above the band gap of BP, the photocurrent response at the p-n junction exhibits the same polarization dependence as that at the BP-metal junction, which is nearly parallel to the MoS2 channel. This result indicates that the photocurrent signals at the MoS2-BP junction primarily result from the direct band gap transition in BP. These fundamental studies shed light on the knowledge of photocurrent generation mechanisms in vertical 2D semiconductor heterojunctions, offering a new way of engineering future two-dimensional materials based optoelectronic devices. PMID:26489362

  2. High-breakdown-voltage pn-junction diodes on GaN substrates

    NASA Astrophysics Data System (ADS)

    Yoshizumi, Yusuke; Hashimoto, Shin; Tanabe, Tatsuya; Kiyama, Makoto

    2007-01-01

    GaN pn-junction diodes have been grown on GaN and sapphire substrates by metalorganic vapor phase epitaxy and their electrical characteristics have been studied. For the diode on the GaN substrate, the reverse leakage current is lower and the breakdown voltage VB is higher than those on the sapphire substrate owing to the lower dislocation density. The breakdown voltage is further improved with decreasing Mg concentration in p-GaN layers. Analysis of the depletion-layer capacitance of pn diodes has revealed that the Mg acceptors are fully ionized in the depletion layer. By optimizing the growth conditions, the diodes on GaN substrates show extremely low leakage current and the ideal hard breakdown at -925 V. The breakdown field is estimated to be 3.27 MV/cm. The specific on-resistance RON of 6.3 mΩ cm 2 is obtained, leading to the figure of merit, VB2/R, of 136 MW/cm 2.

  3. Solar-energy conversion and light emission in an atomic monolayer p-n diode.

    PubMed

    Pospischil, Andreas; Furchi, Marco M; Mueller, Thomas

    2014-04-01

    The limitations of the bulk semiconductors currently used in electronic devices-rigidity, heavy weight and high costs--have recently shifted the research efforts to two-dimensional atomic crystals such as graphene and atomically thin transition-metal dichalcogenides. These materials have the potential to be produced at low cost and in large areas, while maintaining high material quality. These properties, as well as their flexibility, make two-dimensional atomic crystals attractive for applications such as solar cells or display panels. The basic building blocks of optoelectronic devices are p-n junction diodes, but they have not yet been demonstrated in a two-dimensional material. Here, we report a p-n junction diode based on an electrostatically doped tungsten diselenide (WSe2) monolayer. We present applications as a photovoltaic solar cell, a photodiode and a light-emitting diode, and obtain light-power conversion and electroluminescence efficiencies of ∼ 0.5% and ∼ 0.1%, respectively. Given recent advances in the large-scale production of two-dimensional crystals, we expect them to profoundly impact future developments in solar, lighting and display technologies.

  4. Solar-energy conversion and light emission in an atomic monolayer p-n diode

    NASA Astrophysics Data System (ADS)

    Pospischil, Andreas; Furchi, Marco M.; Mueller, Thomas

    2014-04-01

    The limitations of the bulk semiconductors currently used in electronic devices--rigidity, heavy weight and high costs--have recently shifted the research efforts to two-dimensional atomic crystals such as graphene and atomically thin transition-metal dichalcogenides. These materials have the potential to be produced at low cost and in large areas, while maintaining high material quality. These properties, as well as their flexibility, make two-dimensional atomic crystals attractive for applications such as solar cells or display panels. The basic building blocks of optoelectronic devices are p-n junction diodes, but they have not yet been demonstrated in a two-dimensional material. Here, we report a p-n junction diode based on an electrostatically doped tungsten diselenide (WSe2) monolayer. We present applications as a photovoltaic solar cell, a photodiode and a light-emitting diode, and obtain light-power conversion and electroluminescence efficiencies of ~0.5% and ~0.1%, respectively. Given recent advances in the large-scale production of two-dimensional crystals, we expect them to profoundly impact future developments in solar, lighting and display technologies.

  5. Record high efficiency single-walled carbon nanotube/silicon p-n junction solar cells.

    PubMed

    Jung, Yeonwoong; Li, Xiaokai; Rajan, Nitin K; Taylor, André D; Reed, Mark A

    2013-01-01

    Carrier transport characteristics in high-efficiency single-walled carbon nanotubes (SWNTs)/silicon (Si) hybrid solar cells are presented. The solar cells were fabricated by depositing intrinsic p-type SWNT thin-films on n-type Si wafers without involving any high-temperature process for p-n junction formation. The optimized cells showed a device ideality factor close to unity and a record-high power-conversion-efficiency of >11%. By investigating the dark forward current density characteristics with varying temperature, we have identified that the temperature-dependent current rectification originates from the thermally activated band-to-band transition of carriers in Si, and the role of the SWNT thin films is to establish a built-in potential for carrier separation/collection. We have also established that the dominant carrier transport mechanism is diffusion, with minimal interface recombination. This is further supported by the observation of a long minority carrier lifetime of ~34 μs, determined by the transient recovery method. This study suggests that these hybrid solar cells operate in the same manner as single crystalline p-n homojunction Si solar cells.

  6. Horizontal Silicon Nanowires with Radial p-n Junctions: A Platform for Unconventional Solar Cells.

    PubMed

    Zhang, Xing; Pinion, Christopher W; Christesen, Joseph D; Flynn, Cory J; Celano, Thomas A; Cahoon, James F

    2013-06-20

    The silicon p-n junction is the most successful solar energy technology to date, yet it accounts for a marginal percentage of worldwide energy production. To change the status quo, a disruptive technological breakthrough is needed. In this Perspective, we discuss the potential for complex silicon nanowires to serve as a platform for next-generation photovoltaic devices. We review the synthesis, electrical characteristics, and optical properties of core/shell silicon nanowires that are subwavelength in diameter and contain radial p-n junctions. We highlight the unique features of these nanowires, such as optical antenna effects that concentrate light and intense built-in electric fields that enable ultrafast charge-carrier separation. We advocate a paradigm in which nanowires are arranged in periodic horizontal arrays to form ultrathin devices. Unlike conventional planar silicon, nanowire structures provide the flexibility to incorporate multiple semiconductor, dielectric, and metallic materials in a single system, providing the foundation for a disruptive, unconventional solar energy technology.

  7. Horizontal Silicon Nanowires with Radial p-n Junctions: A Platform for Unconventional Solar Cells.

    PubMed

    Zhang, Xing; Pinion, Christopher W; Christesen, Joseph D; Flynn, Cory J; Celano, Thomas A; Cahoon, James F

    2013-06-20

    The silicon p-n junction is the most successful solar energy technology to date, yet it accounts for a marginal percentage of worldwide energy production. To change the status quo, a disruptive technological breakthrough is needed. In this Perspective, we discuss the potential for complex silicon nanowires to serve as a platform for next-generation photovoltaic devices. We review the synthesis, electrical characteristics, and optical properties of core/shell silicon nanowires that are subwavelength in diameter and contain radial p-n junctions. We highlight the unique features of these nanowires, such as optical antenna effects that concentrate light and intense built-in electric fields that enable ultrafast charge-carrier separation. We advocate a paradigm in which nanowires are arranged in periodic horizontal arrays to form ultrathin devices. Unlike conventional planar silicon, nanowire structures provide the flexibility to incorporate multiple semiconductor, dielectric, and metallic materials in a single system, providing the foundation for a disruptive, unconventional solar energy technology. PMID:26283243

  8. Effect of uniaxial strain on the electronic transport through disordered graphene p-n junctions

    NASA Astrophysics Data System (ADS)

    Deng, Min; Wang, Yong-Jian; Gang, Yu; Chen, Jian-Fei

    2016-09-01

    Using the non-equilibrium Green’s function method, we investigated theoretically the electron transport through a disordered graphene p-n junction under a perpendicular magnetic field. A uniaxial strain is applied to the graphene sheet. It is found that the conductance versus the on-site energy of the right electrode exhibits the successive step-like structure in the n-n region, however, a zero value plateau followed by the successive oscillation peaks in the p-n region. When the longitudinal or transverse strain is applied, the zero value plateau almost remains intact, while the oscillation peaks are greatly enhanced with increasing the strain strength, and depending on the orientation of the applied strain, the oscillation peaks shift towards the positive or negative energy upon increasing the strain. In the presence of the disorder, the characteristic conductance plateaus emerge at e2/h, (3/2)e2/h, etc. for the appropriate disorder strength. With the rise of the strain, the original plateau structure is destroyed, instead, the conductance exhibits new plateaus whose amplitude and position strongly depend on the strain strength and direction.

  9. Light emitting diode fault detection using p-n junction photovoltaic effect.

    PubMed

    Li, Ping; Wen, Yumei; Cai, Youhai; Li, Lian

    2009-05-01

    This paper proposes an online noncontact fault detection method during light emitting diode (LED) chip packaging, which is based on the photovoltaic effect in p-n junctions. Once a LED chip bonded on a lead frame is illuminated, the photocurrent will flow through the loop circuits formed by the lead frame. Through characterization of the weak photovoltaic response in the lead frame with the 20 LED chips, five LED faults, including chip defects (chip quality and chip contamination) and bonding deficiencies (disconnection, debonding, and rebonding), can be detected before packaging. A high-sensitivity photocurrent detection instrument has been developed to detect different color (red, yellow, green, and blue) and different size LED chips (9-15 mil) on LED assembly line. A key feature of the new instrument is the capability to tune and implement the maximum output power (photocurrent) in the loop lead frame by designing the high-efficiency magnetic core, the magnetic coil and the detecting system. Experiments demonstrate that the photovoltaic behaviors for LED p-n junctions are directly related to the LED electroluminescent characteristics, and the internal optoelectronic characteristics and the external Ohmic contact performances can be derived by detecting the photocurrent of LED chips. The LED online noncontact fault detection instrument based on the photovoltaic effect can be used to substitute for the ordinary electroluminescence online contact fault detection instrument.

  10. Solar-energy conversion and light emission in an atomic monolayer p-n diode.

    PubMed

    Pospischil, Andreas; Furchi, Marco M; Mueller, Thomas

    2014-04-01

    The limitations of the bulk semiconductors currently used in electronic devices-rigidity, heavy weight and high costs--have recently shifted the research efforts to two-dimensional atomic crystals such as graphene and atomically thin transition-metal dichalcogenides. These materials have the potential to be produced at low cost and in large areas, while maintaining high material quality. These properties, as well as their flexibility, make two-dimensional atomic crystals attractive for applications such as solar cells or display panels. The basic building blocks of optoelectronic devices are p-n junction diodes, but they have not yet been demonstrated in a two-dimensional material. Here, we report a p-n junction diode based on an electrostatically doped tungsten diselenide (WSe2) monolayer. We present applications as a photovoltaic solar cell, a photodiode and a light-emitting diode, and obtain light-power conversion and electroluminescence efficiencies of ∼ 0.5% and ∼ 0.1%, respectively. Given recent advances in the large-scale production of two-dimensional crystals, we expect them to profoundly impact future developments in solar, lighting and display technologies. PMID:24608229

  11. Atomistic nature in band-to-band tunneling in two-dimensional silicon pn tunnel diodes

    NASA Astrophysics Data System (ADS)

    Tabe, Michiharu; Tan, Hoang Nhat; Mizuno, Takeshi; Muruganathan, Manoharan; Anh, Le The; Mizuta, Hiroshi; Nuryadi, Ratno; Moraru, Daniel

    2016-02-01

    We study low-temperature transport properties of two-dimensional (2D) Si tunnel diodes, or Si Esaki diodes, with a lateral layout. In ordinary Si Esaki diodes, interband tunneling current is severely limited because of the law of momentum conservation, while nanoscale Esaki diodes may behave differently due to the dopants in the narrow depletion region, by atomistic effects which release such current limitation. In thin-Si lateral highly doped pn diodes, we find clear signatures of interband tunneling between 2D-subbands involving phonon assistance. More importantly, the tunneling current is sharply enhanced in a narrow voltage range by resonance via a pair of a donor- and an acceptor-atom in the pn junction region. Such atomistic behavior is recognized as a general feature showing up only in nanoscale tunnel diodes. In particular, a donor-acceptor pair with deeper ground-state energies is likely to be responsible for such a sharply enhanced current peak, tunable by external biases.

  12. High photoresponsivity in an all-graphene p-n vertical junction photodetector.

    PubMed

    Kim, Chang Oh; Kim, Sung; Shin, Dong Hee; Kang, Soo Seok; Kim, Jong Min; Jang, Chan Wook; Joo, Soong Sin; Lee, Jae Sung; Kim, Ju Hwan; Choi, Suk-Ho; Hwang, Euyheon

    2014-01-01

    Intensive studies have recently been performed on graphene-based photodetectors, but most of them are based on field effect transistor structures containing mechanically exfoliated graphene, not suitable for practical large-scale device applications. Here we report high-efficient photodetector behaviours of chemical vapor deposition grown all-graphene p-n vertical-type tunnelling diodes. The observed photodetector characteristics well follow what are expected from its band structure and the tunnelling of current through the interlayer between the metallic p- and n-graphene layers. High detectivity (~10(12) cm Hz(1/2) W(-1)) and responsivity (0.4~1.0 A W(-1)) are achieved in the broad spectral range from ultraviolet to near-infrared and the photoresponse is almost consistent under 6-month operations. The high photodetector performance of the graphene p-n vertical diodes can be understood by the high photocurrent gain and the carrier multiplication arising from impact ionization in graphene.

  13. Opto-electronic modeling of light emission from avalanche-mode silicon p+n junctions

    NASA Astrophysics Data System (ADS)

    Dutta, Satadal; Hueting, Raymond J. E.; Annema, Anne-Johan; Qi, Lin; Nanver, Lis K.; Schmitz, Jurriaan

    2015-09-01

    This work presents the modeling of light emission from silicon based p+n junctions operating in avalanche breakdown. We revisit the photon emission process under the influence of relatively high electric fields in a reverse biased junction ( > 10 5 V/cm). The photon emission rate is described as a function of the electron temperature T e , which is computed from the spatial distribution of the electric field. The light emission spectra lie around the visible spectral range ( λ ˜ 300-850 nm), where the peak wavelength and the optical intensity are both doping level dependent. It is theoretically derived that a specific minimum geometrical width ( ˜ 170 nm) of the active region of avalanche is required, corresponding to a breakdown voltage of ˜5 V, below which the rate of photon emission in the desired spectrum drops. The derived model is validated using experimental data obtained from ultra-shallow p+n junctions with low absorption through a nm-thin p+ region and surface coverage of solely 3 nm of pure boron. We observe a peak in the emission spectra near 580 nm and 650 nm for diodes with breakdown voltages 7 V and 14 V, respectively, consistent with our model.

  14. Atmospheric Fluorescence Yield

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.; Christl, M. J.; Fountain, W. F.; Gregory, J. C.; Martens, K.; Sokolsky, P.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Several existing and planned experiments estimate the energies of ultra-high energy cosmic rays from air showers using the atmospheric fluorescence from these showers. Accurate knowledge of the conversion from atmospheric fluorescence to energy loss by ionizing particles in the atmosphere is key to this technique. In this paper we discuss a small balloon-borne instrument to make the first in situ measurements versus altitude of the atmospheric fluorescence yield. The instrument can also be used in the lab to investigate the dependence of the fluorescence yield in air on temperature, pressure and the concentrations of other gases that present in the atmosphere. The results can be used to explore environmental effects on and improve the accuracy of cosmic ray energy measurements for existing ground-based experiments and future space-based experiments.

  15. Efficient photocatalytic degradation of acid orange 7 on metal oxide p-n junction composites under visible light

    NASA Astrophysics Data System (ADS)

    Suk Jang, Jum; Gyu Kim, Hyun; Lee, Se-Hee

    2012-11-01

    MO(=CuO, Co3O4, NiO)/BiVO4 p-n junction composites were synthesized by urea-precipitation and wet impregnation method. The physicochemical and optical properties of the as-prepared materials were investigated by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-visible diffuse reflectance spectra. The photocatalytic performance of the as-prepared materials was investigated for decomposition of azo dye, acid orange 7. The CuO/BiVO4 and Co3O4/BiVO4 p-n junction composite photocatalysts exhibited the higher photocatalytic degradation of acid orange 7 than those of BiVO4 and NiO/BiVO4 as-prepared samples under visible light irradiation. We also discussed the mechanism of enhanced photocatalytic activity of p-n junctioned composites based on their energy band structures.

  16. An organic p-n junction for electrode-independent electron injection layer in organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Lee, Jeong-Hwan; Kim, Ji Whan; Kim, Sei-Yong; Yoo, Seung-Jun; Lee, Jae-Hyun; Kim, Jang-Joo

    2012-09-01

    We demonstrated that an organic p-n junction was successfully adapted to inverted organic light emitting diodes (IOLEDs) as an electron injection layer (EIL). The organic p-n junction composed of a ReO3 doped copper phthalocyanine (CuPc)/Rb2CO3 doped 4,7-diphenyl-1,10-phenanthroline (Bphen) layer showed very efficient charge generation under a reverse bias reaching to 100 mA/cm2 at 0.3 V and efficient electron injection from indium tin oxide (ITO) when adopted in IOLEDs. Moreover, the organic p-n junction resulted in the same current density-voltage-luminance characteristics independent of the work function of the cathode, which is a valuable advantage for flexible displays.

  17. Classical and quantum magneto-oscillations of current flow near a p-n junction in graphene

    NASA Astrophysics Data System (ADS)

    Patel, Aavishkar A.; Davies, Nathan; Cheianov, Vadim; Fal'ko, Vladimir I.

    2012-08-01

    The proposed semiclassical theory predicts two types of oscillations in the flow of current injected from a point source near a ballistic p-n junction in graphene in a strong magnetic field. One originates from the classical effect of bunching of cyclotron orbits of electrons passing back and forth across the p-n interface, which displays a pronounced dependence on the commensurability between the cyclotron radii in the n and p regions. The other effect is caused by the interference of monochromatic electron waves in p-n junctions with equal carrier densities on the two sides and it consists of magneto-oscillations in the current transmission through the interface with periodicity similar to Shubnikov-de Haas oscillations.

  18. Improved photocatalytic activity of single crystal ZnO nanorod derived from highly effective P/N heterojunction

    SciTech Connect

    Yan, Xiaoyan; Gong, Changwei; Wang, Jian; Liang, Liping; Zhao, Li; Zhang, Mingang; Chai, Yuesheng

    2013-10-15

    Graphical abstract: Schematic showing on photocatalytic degradation 2,4-DCP of ZnO NRs/BDD heterojunction. - Highlights: • Single-crystal ZnO nanorods based P/N heterojunction has been synthesized. • Vertical growth ZnO NRs on BDD can effectively photocatalytic decompose 2,4-DCP. • The rate constant of photocatalysis can be enhanced due to P/N heterojunction. - Abstract: Highly effective single-crystal ZnO nanorods based P/N heterojunction has been synthesized by a controllable crystal seed-induced hydrothermal vertical growth method, which facilitates the separation of the photogenerated electrons and holes due to its endogenous space charge region and suitable band structure. Therefore, photocatalytic activity for degradation of the toxic pollutants is markedly enhanced.

  19. Microdisk resonator assisted all-optical switching with improved speed using a reverse-biased p-n diode

    NASA Astrophysics Data System (ADS)

    Xie, Jingya; Zhou, Linjie; Li, Xinwan; Chen, Jianping

    2015-05-01

    We present a compact and power efficient all-optical switching using a silicon microdisk resonator integrated with a p-n junction. We study the dependence of free-carrier lifetime, one of the most critical parameters to determine the switching speed, on reverse bias, optical intensity, and p-n junction position and dimension. Our experiments reveal that the carrier lifetime decreases with the increasing reverse bias, consistent with the theoretical results. The all-optical switching of a 211-1 non-return-to-zero pseudo-random binary sequence (PRBS) signal at a data rate of 10 Gbits/s is demonstrated with p-n junction reversely biased at -15 V and the pump power being 5.96 dBm.

  20. Electrostatically tunable lateral MoTe2 p-n junction for use in high-performance optoelectronics

    NASA Astrophysics Data System (ADS)

    Wang, Zhenxing; Wang, Feng; Yin, Lei; Huang, Yun; Xu, Kai; Wang, Fengmei; Zhan, Xueying; He, Jun

    2016-07-01

    Because of their ultimate thickness, layered structure and high flexibility, pn junctions based on layered two-dimensional semiconductors have been attracting increasing attention recently. In this study, for the first time, we fabricated lateral pn junctions (LPNJs) based on ultrathin MoTe2 by introducing two separated electrostatic back gates, and investigated their electronic and photovoltaic performance. Pn, np, nn, and pp junctions can be easily realized by modulating the conductive channel type using gate voltages with different polarities. Strong rectification effects were observed in the pn and np junctions and the rectification ratio reached ~5 × 104. Importantly, we find a unique phenomenon that the parameters for MoTe2 LPNJs experience abrupt changes during the transition from p to n or n to p. Furthermore, a high performance photovoltaic device with a filling factor of above 51% and electrical conversion efficiency (η) of around 0.5% is achieved. Our findings are of importance to comprehensively understand the electronic and optoelectronic properties of MoTe2 and may further open up novel electronic and optoelectronic device applications.Because of their ultimate thickness, layered structure and high flexibility, pn junctions based on layered two-dimensional semiconductors have been attracting increasing attention recently. In this study, for the first time, we fabricated lateral pn junctions (LPNJs) based on ultrathin MoTe2 by introducing two separated electrostatic back gates, and investigated their electronic and photovoltaic performance. Pn, np, nn, and pp junctions can be easily realized by modulating the conductive channel type using gate voltages with different polarities. Strong rectification effects were observed in the pn and np junctions and the rectification ratio reached ~5 × 104. Importantly, we find a unique phenomenon that the parameters for MoTe2 LPNJs experience abrupt changes during the transition from p to n or n to p. Furthermore

  1. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction

    NASA Astrophysics Data System (ADS)

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A.; Casanova, Fèlix; van der Zant, Herre S. J.; Castellanos-Gomez, Andres; Hueso, Luis E.

    2015-09-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 104, while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ~11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications.The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 104, while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ~11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials

  2. Optimization of Silicon parameters as a betavoltaic battery: Comparison of Si p-n and Ni/Si Schottky barrier

    NASA Astrophysics Data System (ADS)

    Rahmani, Faezeh; Khosravinia, Hossein

    2016-08-01

    Theoretical studies on the optimization of Silicon (Si) parameters as the base of betavoltaic battery have been presented using Monte Carlo simulations and the state equations in semiconductor to obtain maximum power. Si with active area of 1 cm2 has been considered in p-n junction and Schottky barrier structure to collect the radiation induced-charge from 10 mCi cm-2 of Nickle-63 (63Ni) Source. The results show that the betavoltaic conversion efficiency in the Si p-n structure is about 2.7 times higher than that in the Ni/Si Schottky barrier structure.

  3. The PN.S Elliptical Galaxy Survey: a standard ΛCDM halo around NGC 4374?

    NASA Astrophysics Data System (ADS)

    Napolitano, N. R.; Romanowsky, A. J.; Capaccioli, M.; Douglas, N. G.; Arnaboldi, M.; Coccato, L.; Gerhard, O.; Kuijken, K.; Merrifield, M. R.; Bamford, S. P.; Cortesi, A.; Das, P.; Freeman, K. C.

    2011-03-01

    As part of our current programme to test ΛCDM predictions for dark matter (DM) haloes using extended kinematical observations of early-type galaxies, we present a dynamical analysis of the bright elliptical galaxy NGC 4374 (M84) based on ˜450 planetary nebulae (PNe) velocities from the PN.Spectrograph, along with extended long-slit stellar kinematics. This is the first such analysis of a galaxy from our survey with a radially constant velocity dispersion profile. We find that the spatial and kinematical distributions of the PNe agree with the field stars in the region of overlap. The velocity kurtosis is consistent with zero at almost all radii. We construct a series of Jeans models, fitting both velocity dispersion and kurtosis to help break the mass-anisotropy degeneracy. Our mass models include DM haloes either with shallow cores or with central cusps as predicted by cosmological simulations - along with the novel introduction in this context of adiabatic halo contraction from baryon infall. Both classes of models confirm a very massive dark halo around NGC 4374, demonstrating that PN kinematics data are well able to detect such haloes when present. Considering the default cosmological mass model, we confirm earlier suggestions that bright galaxies tend to have halo concentrations higher than ΛCDM predictions, but this is found to be solved if either a Salpeter initial mass function (IMF) or an adiabatic contraction with a Kroupa IMF is assumed. Thus for the first time a case is found where the PN dynamics may well be consistent with a standard dark matter halo. A cored halo can also fit the data, and prefers a stellar mass consistent with a Salpeter IMF. The less dramatic dark matter content found in lower-luminosity 'ordinary' ellipticals suggests a bimodality in the halo properties which may be produced by divergent baryonic effects during their assembly histories. Based on observations made with the William Herschel Telescope operated on the island of La

  4. A V-grooved AlGaAs/GaAs passivated pn junction

    NASA Technical Reports Server (NTRS)

    Bailey, S. G.; Leon, R. P.; Arrison, A.

    1987-01-01

    A passivated, V-grooved GaAs solar cell offers important advantages in terms of improved optical coupling, higher short-circuit current, and increased tolerance to particle radiation when compared to the planar cell configuration. An AlGaAs epilayer has been deposited on a p-type GaAs epilayer grown on an n-type V-grooved GaAs surface using MOCVD. A wet chemical etching process was used to produce a V-pattern with a 7.0-micron periodicity. Reflectivity measurements substantiate the expected decrease in solar reflectance. Scanning electron microscopy techniques were used to confirm the presence of the AlGaAs layer and verify the existence of a pn junction.

  5. Hybrid MOS-PN photodiode with positive feedback for pulse-modulation imaging.

    PubMed

    Sallin, Denis; Koukab, Adil; Kayal, Maher

    2014-06-16

    A new type of CMOS compatible photodetector, exhibiting intrinsic light-to-time conversion, is proposed. Its main objective is to start the time-to-digital conversion directly at its output, thereby avoiding the cumbersome analog processing. The operation starts with an internal charge integration, followed by a positive feedback, and a sharp switching-current. The device, consisting of a deeply depleted MOS structure controlling the conduction of a forward-based PN diode, is presented and its operation explained. TCAD simulations are used to show the effects of semiconductor parameters and bias conditions. The photodetector and its detection circuit are designed and fabricated in a 0.18µm CMOS process. Measurements of this new device under different biasing and illumination conditions show highly promising properties in terms of linearity, internal gain, and noise performances.

  6. A V-grooved AlGaAs/GaAs passivated PN junction

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Leon, Rosa P.; Arrison, Anne

    1987-01-01

    A passivated, V-grooved GaAs solar cell offers important advantages in terms of improved optical coupling, higher short circuit current, and increased tolerance to particle radiation when compared to the planar cell configuration. An AlGaAs epilayer has been deposited on a p-type GaAs epilayer grown on an n-type V-grooved GaAs surface using MOCVD. A wet chemical etching process was used to produce a V-pattern with a 7.0 micron periodicity. Reflectivity measurements substantiate the expected decrease in solar reflectance. Scanning electron microscopy techniques were used to confirm the presence of the AlGaAs layer and verify the existence of a pn junction.

  7. Measurement of the Induced Proton Polarization Pn in the 12C(e, e', p) reaction

    SciTech Connect

    Woo, R J; Barkhuff, David; Bertozzi, William; Chen, Jian-ping; Dale, Dan; Dodson, G; Dow, K A; Epstein, Marty; Farkhondeh, Manouchehr; Finn, Mike; Gilad, Shalev; Jones, Mark K; Joo, Kyungseon; Kelly, James; Kowalski, Stanley; Lourie, Bob; Madey, Richard; Margaziotis, Dimitri; Markowitz, Pete; McIntyre, Justin; Mertz, Christoph; Milbrath, Brian; Mitchell, Joseph; Perdrisat, Charles F; Punjabi, Vina; Rutt, Paul; Sarty, Adam; Tieger, D; Tschalaer, C; Turchinetz, William; Ulmer, Paul E; Van Verst, S P; Vellidis, C; Warren, Glen; Weinstein, Lawrence

    1998-01-19

    The first measurements of the induced proton polarization Pn for the 12C(e,e',p) reaction are reported. The experiment was performed at quasifree kinematics for energy and momentum transfer (w,q) = (294 MeV, 765 MeV/c) and sampled a missing momentum range of 0-250 MeV/c. The induced polarization arises from final-state interactions and for these kinematics is dominated by the real part of the spin-orbit optical potential. The distorted-wave impulse approximation provides good agreement with data for the 1 p3/2 shell. The data for the continuum suggest that both the 1s1/2 shell and underlying l > 1 configurations contribute.

  8. Gate-tunable electron focusing across graphene p-n junction

    NASA Astrophysics Data System (ADS)

    Chen, Shaowen; Han, Zheng; Wang, Lei; Dean, Cory; Hone, James

    Electrons moving across a ballistic semiconductor junction experience a change in trajectory described by an electronic version of Snell's law. In the case of a barrier separating regions of n and ptype carriers, negative refraction is expected, which theoretically leads to a Veselago type of electron focusing. Being a ballistic bipolar 2D system, hexagonal Boron Nitride-encapsulated graphene is expected to be a model a system to realize this effect, however, robust demonstration of veselago lensing has remained limited. We describe novel methods to fabricate high quality graphene p-n junctions with atomically sharp boundaries. Using a magnetic focusing measurement scheme, we demonstrate unambiguous signatures of negative refraction in these devices. Our observations are in good agreement with simulations and shed light on future application for electronic optics in ballistic graphene.

  9. Fabrication of transparent p-n heterojunction thin film diodes based entirely on oxide semiconductors

    NASA Astrophysics Data System (ADS)

    Kudo, Atsushi; Yanagi, Hiroshi; Ueda, Kazushige; Hosono, Hideo; Kawazoe, Hiroshi; Yano, Yoshihiko

    1999-11-01

    All oxide-based, transparent polycrystalline p-n heterojunctions on a glass substrate were fabricated. The structure of the diode was n+-ZnO electrode/n-ZnO/p-SrCu2O2/In2-xSnxO3 electrode on the substrate. The contact between the n- and p-type semiconducting oxides was found to be rectifying. The ratio of forward current to the reverse current exceeded 80 within the range of applied voltages of -1.5 to +1.5 V and the estimated diode factor (n value) was 1.62. The diode structure was fabricated on a glass plate with the total thickness of 1.3 μm and possessed an optical transmission of 70%-80% in the visible region.

  10. 25 Gbit/s silicon microring modulator based on misalignment-tolerant interleaved PN junctions.

    PubMed

    Xiao, Xi; Xu, Hao; Li, Xianyao; Hu, Yingtao; Xiong, Kang; Li, Zhiyong; Chu, Tao; Yu, Yude; Yu, Jinzhong

    2012-01-30

    A high-speed depletion-mode silicon-based microring modulator with interleaved PN junctions optimized for high modulation efficiency and large alignment tolerance is demonstrated. It is fabricated using standard 0.18 μm complementary metal-oxide-semiconductor processes and provides low V(π)L(π)s of 0.68 V·cm to 1.64 V·cm with a moderate doping concentration of 2 × 10(17) cm(-3). The measured modulation efficiency decreases by only 12.4% under ± 150 nm alignment errors. 25 Gbit/s non-return-zero modulation with a 4.5 dB extinction ratio is experimentally realized at a peak-to-peak driving voltage of 2 V, demonstrating the excellent performance of the novel doping profile. PMID:22330488

  11. Shot noise suppression in p-n junctions due to carrier generation-recombination

    NASA Astrophysics Data System (ADS)

    Maione, I. A.; Pellegrini, B.; Fiori, G.; Macucci, M.; Guidi, L.; Basso, G.

    2011-04-01

    We present a theoretical and experimental investigation of shot noise suppression in gallium arsenide and silicon p-n junctions due the to effect of generation-recombination phenomena. In particular, the availability of the cross-correlation technique and of ultra-low-noise amplifiers has allowed us to significantly extend, down to 10 pA, the range of bias current values for which results were available in the literature. To provide a quantitative understanding of the observed V-shape noise behavior, we have extended the Shockley-Read-Hall model for the trap-assisted generation-recombination mechanism. Such a model has represented the theoretical background for the performed Monte Carlo noise simulations, which have provided good agreement with the experimental results.

  12. Solution-route low-temperature fabrication of thin-film p-n junctions

    NASA Astrophysics Data System (ADS)

    Panamá, Gustavo; Ayag, Kevin; Kim, Hongdoo

    2016-11-01

    In this work, p-n junctions were fabricated at low temperature by means of UV-assisted thermal annealing. At 200 °C, remarkable rectifying and optical properties were observed due to the conversion of the sol–gel precursors to oxide films, which was aided by UV exposure. The resulting p-NiO/n-ZnO structures are featured as the thinnest ever reported (≈55 nm) based on a solution process with a large forward electrical current 10 ‑2 –10 ‑1 A cm‑2 and the lowest leakage current (1 μA cm‑2). UV light and precursor solution engineering contributed to form metal-oxide bonding at relatively low temperature in ambient conditions. The heterojunctions fabricated by the proper combination of these alternatives and simple processes were evaluated using UV-vis and FT-IR spectroscopy, FE-SEM, AFM, XRD, XPS, and I–V curves.

  13. Spin-Based Mach-Zehnder Interferometry in Topological Insulator p-n Junctions.

    PubMed

    Ilan, Roni; de Juan, Fernando; Moore, Joel E

    2015-08-28

    Transport in three-dimensional topological insulators relies on the existence of a spin-momentum locked surface state that encloses the insulating bulk. In this work we show how, in a topological insulator p-n junction, a magnetic field turns this surface state into an electronic Mach-Zehnder interferometer. Transmission of the junction can be tuned from zero to unity, resulting in virtually perfect visibility of the interference pattern, and the reflected and transmitted currents carry opposite spin polarization so that the junction also acts as a spin filter. Our setup therefore realizes a novel and highly tunable spintronic device where the effects of spin-momentum locking in topological insulator surface states can be probed directly in a transport experiment. PMID:26371673

  14. Direct Measurement of the Electrical Abruptness of a Nanowire p-n Junction.

    PubMed

    Darbandi, Ali; McNeil, James C; Akhtari-Zavareh, Azadeh; Watkins, Simon P; Kavanagh, Karen L

    2016-07-13

    Electrostatic potential maps of GaAs nanowire, p-n junctions have been measured via off-axis electron holography and compared to results from in situ electrical probing, and secondary electron emission microscopy using scanning electron microscopy. The built-in potential and depletion length of an axial junction was found to be 1.5 ± 0.1 V and 74 ± 9 nm, respectively, to be compared with 1.53 V and 64 nm of an abrupt junction of the same end point carrier concentrations. Associated with the switch from Te to Zn dopant precursor was a reduction in GaAs nanowire diameter 3 ± 1 nm that occurred prior to the junction center (n = p) and was followed by a rapid increase in Zn doping. The delay in Zn incorporation is attributed to the time required for Zn to equilibrate within the Au catalyst. PMID:27254390

  15. MIS and PN junction solar cells on thin-film polycrystalline silicon

    SciTech Connect

    Ariotedjo, A.; Emery, K.; Cheek, G.; Pierce, P.; Surek, T.

    1981-05-01

    The Photovoltaic Advanced Silicon (PVAS) Branch at the Solar Energy Research Institute (SERI) has initiated a comparative study to assess the potential of MIS-type solar cells for low-cost terrestrial photovoltaic systems in terms of performance, stability, and cost-effectiveness. Several types of MIS and SIS solar cells are included in the matrix study currently underway. This approach compares the results of MIS and p/n junction solar cells on essentially identical thin-film polycrystalline silicon materials. All cell measurements and characterizations are performed using uniform testing procedures developed in the Photovoltaic Measurements and Evaluation (PV M and E) Laboratory at SERI. Some preliminary data on the different cell structures on thin-film epitaxial silicon on metallurgical-grade substrates are presented here.

  16. Assessing thermal damage in silicon PN-junctions using Raman thermometry

    SciTech Connect

    Beechem, Thomas E.; Serrano, Justin R.; McDonald, Anthony; Mani, Seethambal

    2013-03-28

    Laser machining is frequently utilized in the manufacture of photovoltaics. A natural by-product of these fabrication processes, heat, not only serves as a means of material removal but also modifies the material in an extended region beyond that ideally intended for alteration. This modified region, termed the heat affected zone, is detrimental to performance and should therefore be minimized. While undoubtedly thermal in origin, it is unclear exactly how the thermal environment during laser machining correlates to changes in the PN-junction that reduce performance. In response, we combine in-situ Raman based thermometry measurements with post-event failure analysis to identify the physical mechanisms damaging the junction during laser machining. From this approach, damage is shown to initiate prior to melting and be driven primarily by the diffusion of dopants for fluences that do not induce ablation. Additionally, comparatively small regions of damage are shown to have a large impact on operation.

  17. High breakdown single-crystal GaN p-n diodes by molecular beam epitaxy

    SciTech Connect

    Qi, Meng; Zhao, Yuning; Yan, Xiaodong; Li, Guowang; Verma, Jai; Fay, Patrick; Nomoto, Kazuki; Zhu, Mingda; Hu, Zongyang; Protasenko, Vladimir; Song, Bo; Xing, Huili Grace; Jena, Debdeep; Bader, Samuel

    2015-12-07

    Molecular beam epitaxy grown GaN p-n vertical diodes are demonstrated on single-crystal GaN substrates. A low leakage current <3 nA/cm{sup 2} is obtained with reverse bias voltage up to −20 V. With a 400 nm thick n-drift region, an on-resistance of 0.23 mΩ cm{sup 2} is achieved, with a breakdown voltage corresponding to a peak electric field of ∼3.1 MV/cm in GaN. Single-crystal GaN substrates with very low dislocation densities enable the low leakage current and the high breakdown field in the diodes, showing significant potential for MBE growth to attain near-intrinsic performance when the density of dislocations is low.

  18. Template method for fabricating interdigitate p-n heterojunction for organic solar cell

    PubMed Central

    2012-01-01

    Anodic aluminum oxide (AAO) templates are used to fabricate arrays of poly(3-hexylthiophene) (P3HT) pillars. This technique makes it possible to control the dimensions of the pillars, namely their diameters, intervals, and heights, on a tens-of-nanometer scale. These features are essential for enhancing carrier processes such as carrier generation, exciton diffusion, and carrier dissociation and transport. An interdigitated p-n junction between P3HT pillars and fullerene (C60) exhibits a photovoltaic effect. Although the device properties are still preliminary, the experimental results indicate that an AAO template is an effective tool with which to develop organic solar cells because highly regulated nanostructures can be produced on large areas exceeding 100 mm2. PMID:22908897

  19. High breakdown single-crystal GaN p-n diodes by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Qi, Meng; Nomoto, Kazuki; Zhu, Mingda; Hu, Zongyang; Zhao, Yuning; Protasenko, Vladimir; Song, Bo; Yan, Xiaodong; Li, Guowang; Verma, Jai; Bader, Samuel; Fay, Patrick; Xing, Huili Grace; Jena, Debdeep

    2015-12-01

    Molecular beam epitaxy grown GaN p-n vertical diodes are demonstrated on single-crystal GaN substrates. A low leakage current <3 nA/cm2 is obtained with reverse bias voltage up to -20 V. With a 400 nm thick n-drift region, an on-resistance of 0.23 mΩ cm2 is achieved, with a breakdown voltage corresponding to a peak electric field of ˜3.1 MV/cm in GaN. Single-crystal GaN substrates with very low dislocation densities enable the low leakage current and the high breakdown field in the diodes, showing significant potential for MBE growth to attain near-intrinsic performance when the density of dislocations is low.

  20. Quantum Hall effect in a gate-controlled p-n junction of graphene.

    PubMed

    Williams, J R; Dicarlo, L; Marcus, C M

    2007-08-01

    The unique band structure of graphene allows reconfigurable electric-field control of carrier type and density, making graphene an ideal candidate for bipolar nanoelectronics. We report the realization of a single-layer graphene p-n junction in which carrier type and density in two adjacent regions are locally controlled by electrostatic gating. Transport measurements in the quantum Hall regime reveal new plateaus of two-terminal conductance across the junction at 1 and 32 times the quantum of conductance, e(2)/h, consistent with recent theory. Beyond enabling investigations in condensed-matter physics, the demonstrated local-gating technique sets the foundation for a future graphene-based bipolar technology.

  1. Dephasing effect on transport of a graphene p-n junction in a quantum Hall regime.

    PubMed

    Chen, Jiang-chai; Zhang, Hui; Shen, Shun-Qing; Sun, Qing-feng

    2011-12-14

    The influence of the dephasing effect on the conductance distribution of disordered graphene p-n junctions is studied. Without the dephasing, the conductance distribution has a very wide range and the conductance fluctuation is large. In this case, the conductance plateaus cannot be obtained in a single sample with the fixed disorder configuration. However, by introducing the dephasing, we find that the distribution becomes narrow dramatically and the fluctuation is suppressed strongly, so that the conductance plateaus are obtained clearly for one single sample, which is consistent with experimental measurements. Furthermore, we also investigate the scaling feature of the conductance distribution and find that it has good scaling behavior in the strong dephasing case.

  2. Application of PN and avalanche silicon photodiodes to low-level optical

    NASA Technical Reports Server (NTRS)

    Eppeldauer, G.; Schaefer, A. R.

    1988-01-01

    New approaches to the discovery of other planetary systems require very sensitive and stable detection techniques in order to succeed. Two methods in particular, the astrometric and the photometric methods, require this. To begin understanding the problems and limitations of solid state detectors regarding this application, preliminary experiments were performed at the National Bureau of Standards and a low light level detector characterization facility was built. This facility is briefly described, and the results of tests conducted in it are outlined. A breadboard photometer that was used to obtain stellar brightness ratio precision data is described. The design principles of PN and avalanche silicon photodiodes based on low light level measuring circuits are discussed.

  3. TETRAQUARK X(udbar sbar s) PRODUCTION IN pn → ΛΛX

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Hai; Zhao, Qiang

    We propose to search for a tetraquark candidate X(udbar sbar s) in pn -> Λ Λ X(udbar sbar s) -> Λ Λ K^ + K0 or ΛΛKK*. The existence of tetraquark state X(udbar sbar s) was predicted in the literature due to specific diquark effective degrees of freedom inside hadrons. In order to understand the underlying dynamics for exotic hadrons, a search for the tetraquark X(udbar sbar s) is strongly recommended. We make an estimate of the production rate of X(udbar sbar s) in an effective lagrangian theory. The proposed reaction involves two Λ production, of which the narrow widths make it a great advantage in the analysis of the final state missing mass spectrum.

  4. Study of novel chemical surface passivation techniques on GaAs pn junction solar cells

    SciTech Connect

    Mauk, M.G.; Xu, S.; Arent, D.J.; Mertens, R.P.; Borghs, G.

    1989-01-16

    Novel methods of GaAs surface passivation are investigated. Passivation is acheived by simple chemical treatments using aqueous solutions of Na/sub 2/S, KOH, RuCl/sub 3/, and K/sub 2/Se. GaAs pn homojunction solar cells are used to evaluate the effectiveness of these passivation techniques. A significant reduction in minority-carrier surface recombination velocity is demonstrated. In the best case, the surface recombination velocity decreased from 5 x 10/sup 6/ cm/s (untreated surface) to 10/sup 3/ cm/s. In addition, we observe improvements in solar cell photogenerated current, short wavelength spectral response, open-circuit voltage, and junction ''dark'' current.

  5. V-grooved AlGaAs/GaAs passivated PN junction

    SciTech Connect

    Bailey, S.G.; Leon, R.P.; Arrison, A.

    1987-05-01

    A passivated, V-grooved GaAs solar cell offers important advantages in terms of improved optical coupling, higher short circuit current, and increased tolerance to particle radiation when compared to the planar cell configuration. An AlGaAs epilayer has been deposited on a p-type GaAs epilayer grown on an n-type V-grooved GaAs surface using MOCVD. A wet chemical etching process was used to produce a V-pattern with a 7.0 micron periodicity. Reflectivity measurements substantiate the expected decrease in solar reflectance. Scanning electron microscopy techniques were used to confirm the presence of the AlGaAs layer and verify the existence of a pn junction.

  6. Atomically thin lateral p-n junction photodetector with large effective detection area

    NASA Astrophysics Data System (ADS)

    Xu, Zai-Quan; Zhang, Yupeng; Wang, Ziyu; Shen, Yuting; Huang, Wenchao; Xia, Xue; Yu, Wenzhi; Xue, Yunzhou; Sun, Litao; Zheng, Changxi; Lu, Yuerui; Liao, Lei; Bao, Qiaoliang

    2016-12-01

    The widely used photodetector design based on atomically thin transition metal dichalcogenides (TMDs) has a lateral metal-TMD-metal junction with a fairly small, line shape photoresponsive active area at the TMD-electrode interface. Here, we report a highly efficient photodetector with extremely large photoresponsive active area based on a lateral junction of monolayer-bilayer WSe2. Impressively, the separation of the electron-hole pairs (excitons) extends onto the whole 1L-2L WSe2 junction surface. The responsivity of the WSe2 junction photodetector is over 3200 times higher than that of a monolayer WSe2 device and leads to a highest external quantum efficiency of 256% due to the efficient carrier extraction. Unlike the TMD p-n junctions modulated by dual gates or localized doping, which require complex fabrication procedures, our study establishes a simple, controllable, and scalable method to improve the photodetection performance by maximizing the active area for current generation.

  7. Method utilizing laser-processing for the growth of epitaxial p-n junctions

    DOEpatents

    Young, R.T.; Narayan, J.; Wood, R.F.

    1979-11-23

    This invention is a new method for the formation of epitaxial p-n junctions in silicon. The method is relatively simple, rapid, and reliable. It produces doped epitaxial layers which are of well-controlled thickness and whose electrical properties are satisfactory. An illustrative form of the method comprises co-depositing a selected dopant and amorphous silicon on a crystalline silicon substrate to form a doped layer of amorphous silicon thereon. This layer then is irradiated with at least one laser pulse to generate a melt front which moves through the layer, into the silicon body to a depth effecting melting of virginal silicon, and back to the surface of the layer. The method may be conducted with dopants (e.g., boron and phosphorus) whose distribution coefficients approximate unity.

  8. 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.

  9. Design of a Miniaturized Langmuir Plasma Probe for the QuadSat/PnP

    NASA Astrophysics Data System (ADS)

    Landavazo, M.; Jorgensen, A. M.; Del Barga, C.; Ferguson, D.; Guillette, D.; Huynh, A.; Klepper, J.; Kuker, J.; Lyke, J. C.; Marohn, B.; Mason, J.; Quiroga, J.; Ravindran, V.; Yelton, C.; Zagrai, A. N.; Zufelt, B.

    2011-12-01

    We have developed a miniaturized Langmuir plasma probe for measuring plasma density in low-earth orbit. Measuring plasma density in the upper ionosphere is important as a diagnostic for the rest of the ionosphere and as an input to space weather forecasting models. Developing miniaturized instrumentation allows easier deployment of a large number of small satellites for monitoring space weather. Our instrument was designed for the Swedish QuadSat/PnP, with the following constraints: A volume constraint of 5x5x1.25cm for the electronics enclosure, a mass budget 100 g, and a power budget of 0.5 W. We met the volume and mass constraints and where able to use less power than budgeted, only 0.25 W. We designed the probe for a bias range of +/-15V and current measurements in the 1 nA to 1 mA range (6 orders of magnitude). Necessary voltage of +/- 15 V and 3.3 V were generated on-board from a single 5 V supply. The electronics suite is based off carefully selected yet affordable commercial components that exhibit low noise, low leakage currents and low power consumption. Size constraints, low noise and low leakage requirements called for a carefully designed four layer PCB with a properly guarded current path using surface mount components on both sides. An ultra-low power microcontroller handles instrument functionality and is fully controllable over i2c using SPA-1 space plug and play. We elected for a probe launched deployed, which required careful design to survive launch vibrations while staying within the mass budget. The QuadSat/PnP has not been launched at the time of writing. We will present details of the instrument design and initial calibration data.

  10. A crust and upper mantle model of Eurasia and North Africa for Pn travel time calculation

    SciTech Connect

    Myers, S; Begnaud, M; Ballard, S; Pasyanos, M; Phillips, W S; Ramirez, A; Antolik, M; Hutchenson, K; Dwyer, J; Rowe, C; Wagner, G

    2009-03-19

    We develop a Regional Seismic Travel Time (RSTT) model and methods to account for the first-order effect of the three-dimensional crust and upper mantle on travel times. The model parameterization is a global tessellation of nodes with a velocity profile at each node. Interpolation of the velocity profiles generates a 3-dimensional crust and laterally variable upper mantle velocity. The upper mantle velocity profile at each node is represented as a linear velocity gradient, which enables travel time computation in approximately 1 millisecond. This computational speed allows the model to be used in routine analyses in operational monitoring systems. We refine the model using a tomographic formulation that adjusts the average crustal velocity, mantle velocity at the Moho, and the mantle velocity gradient at each node. While the RSTT model is inherently global and our ultimate goal is to produce a model that provides accurate travel time predictions over the globe, our first RSTT tomography effort covers Eurasia and North Africa, where we have compiled a data set of approximately 600,000 Pn arrivals that provide path coverage over this vast area. Ten percent of the tomography data are randomly selected and set aside for testing purposes. Travel time residual variance for the validation data is reduced by 32%. Based on a geographically distributed set of validation events with epicenter accuracy of 5 km or better, epicenter error using 16 Pn arrivals is reduced by 46% from 17.3 km (ak135 model) to 9.3 km after tomography. Relative to the ak135 model, the median uncertainty ellipse area is reduced by 68% from 3070 km{sup 2} to 994 km{sup 2}, and the number of ellipses with area less than 1000 km{sup 2}, which is the area allowed for onsite inspection under the Comprehensive Nuclear Test Ban Treaty, is increased from 0% to 51%.

  11. The effect of PN-1, a Traditional Chinese Prescription, on the Learning and Memory in a Transgenic Mouse Model of Alzheimer's Disease.

    PubMed

    Yao, Zhi-Gang; Zhang, Ling; Liang, Liang; Liu, Yu; Yang, Ya-Jun; Huang, Lan; Zhu, Hua; Ma, Chun-Mei; Qin, Chuan

    2013-01-01

    Traditional Chinese Medicine (TCM) is a complete medical system that has been practiced for more than 3000 years. Prescription number 1 (PN-1) consists of several Chinese medicines and is designed according to TCM theories to treat patients with neuropsychiatric disorders. The evidence of clinical practice suggests the benefit effects of PN-1 on cognitive deficits of dementia patients. We try to prove and explain this by using contemporary methodology and transgenic animal models of Alzheimer's disease (AD). The behavioral studies were developed to evaluate the memory of transgenic animals after intragastric administration of PN-1 for 3 months. Amyloid beta-protein (A β ) neuropathology was quantified using immunohistochemistry and ELISA. The western blotting was used to detect the levels of plasticity associated proteins. The safety of PN-1 on mice was also assessed through multiple parameters. Results showed that PN-1 could effectively relieve learning and memory impairment of transgenic animals. Possible mechanisms showed that PN-1 could significantly reduce plaque burden and A β levels and boost synaptic plasticity. Our observations showed that PN-1 could improve learning and memory ability through multiple mechanisms without detectable side effects on mice. We propose that PN-1 is a promising alternative treatment for AD in the future.

  12. A tetrodotoxin-resistant voltage-gated sodium channel from human dorsal root ganglia, hPN3/SCN10A.

    PubMed

    Rabert, D K; Koch, B D; Ilnicka, M; Obernolte, R A; Naylor, S L; Herman, R C; Eglen, R M; Hunter, J C; Sangameswaran, L

    1998-11-01

    Neuropathic pain may be produced, at least in part, by the increased activity of primary afferent neurons. Studies have suggested that an accumulation of voltage-gated sodium channels at the site of peripheral nerve injury is a primary precursory event for subsequent afferent hyperexcitability. In this study, a human sodium channel (hPN3, SCN10A) has been cloned from the lumbar 4/5 dorsal root ganglia (DRG). Expression of hPN3 in Xenopus oocytes showed that this clone is a functional voltage-gated sodium channel. The amino acid sequence of hPN3 is most closely related to the rat PN3/SNS sodium channels which are expressed primarily in the small neurons of rat DRGs. The homologous relationship between rPN3 and hPN3 is defined by (i) a high level of sequence identity (ii) sodium currents that are highly resistant to tetrodotoxin (TTX) (iii) similar tissue distribution profiles and (iv) orthologous chromosomal map positions. Since rPN3/SNS has been implicated in nociceptive transmission, hPN3 may prove to be a valuable target for therapeutic agents against neuropathic pain. PMID:9839820

  13. Development of Critical Thinking: Career Ladder P.N. and A.D. Nursing Students, Pre-Health Science Freshmen, Generic Baccalaureate Sophomore Nursing Students.

    ERIC Educational Resources Information Center

    Kintgen-Andrews, Jean

    A study compared career ladder practical nursing (PN) and associate degree (AD) nursing students with their university counterparts with regard to the development of critical thinking over an academic year. The sample included 55 PN students, 55 AD students, 38 pre-health science freshmen, and 29 generic baccalaureate sophomore nursing students.…

  14. Six-coordinate high-spin iron(ii) complexes with bidentate PN ligands based on 2-aminopyridine - new Fe(ii) spin crossover systems.

    PubMed

    Holzhacker, Christian; Calhorda, Maria José; Gil, Adrià; Carvalho, Maria Deus; Ferreira, Liliana P; Stöger, Berthold; Mereiter, Kurt; Weil, Matthias; Müller, Danny; Weinberger, Peter; Pittenauer, Ernst; Allmaier, Günter; Kirchner, Karl

    2014-08-01

    Several new octahedral iron(ii) complexes of the type [Fe(PN(R)-Ph)2X2] (X = Cl, Br; R = H, Me) containing bidentate PN(R)-Ph (R = H, Me) (1a,b) ligands based on 2-aminopyridine were prepared. (57)Fe Mössbauer spectroscopy and magnetization studies confirmed in all cases their high spin nature at room temperature with magnetic moments very close to 4.9μB reflecting the expected four unpaired d-electrons in all these compounds. While in the case of the PN(H)-Ph ligand an S = 2 to S = 0 spin crossover was observed at low temperatures, complexes with the N-methylated analog PN(Me)-Ph retain an S = 2 spin state also at low temperatures. Thus, [Fe(PN(H)-Ph)2X2] (2a,3a) and [Fe(PN(Me)-Ph)2X2] (2b,3b) adopt different geometries. In the first case a cis-Cl,P,N-arrangement seems to be most likely, as supported by various experimental data derived from (57)Fe Mössbauer spectroscopy, SQUID magnetometry, UV/Vis, Raman, and ESI-MS as well as DFT and TDDFT calculations, while in the case of the PN(Me)-Ph ligand a trans-Cl,P,N-configuration is adopted. The latter is also confirmed by X-ray crystallography. In contrast to [Fe(PN(Me)-Ph)2X2] (2b,3b), [Fe(PN(H)-Ph)2X2] (2a,3a) is labile and undergoes rearrangement reactions. In CH3OH, the diamagnetic dicationic complex [Fe(PN(H)-Ph)3](2+) (5) is formed via the intermediacy of cis-P,N-[Fe(κ(2)-P,N-PN(H)-Ph)2(κ(1)-P-PN(H)-Ph)(X)](+) (4a,b) where one PN ligand is coordinated in a κ(1)-P-fashion. In CH3CN the diamagnetic dicationic complex cis-N,P,N-[Fe(PN(H)-Ph)2(CH3CN)2](2+) (6) is formed as a major isomer where the two halide ligands are replaced by CH3CN.

  15. Resonant plasmonic terahertz detection in graphene split-gate field-effect transistors with lateral p-n junctions

    NASA Astrophysics Data System (ADS)

    Ryzhii, V.; Ryzhii, M.; Shur, M. S.; Mitin, V.; Satou, A.; Otsuji, T.

    2016-08-01

    We evaluate the proposed resonant terahertz (THz) detectors on the basis of field-effect transistors (FETs) with split gates, electrically induced lateral p-n junctions, uniform graphene layer (GL) or perforated (in the p-n junction depletion region) graphene layer (PGL) channel. The perforated depletion region forms an array of the nanoconstions or nanoribbons creating the barriers for the holes and electrons. The operation of the GL-FET- and PGL-FET-detectors is associated with the rectification of the ac current across the lateral p-n junction enhanced by the excitation of bound plasmonic oscillations in the p- and n-sections of the channel. Using the developed device model, we find the GL-FET- and PGL-FET-detector characteristics. These detectors can exhibit very high voltage responsivity at the THz radiation frequencies close to the frequencies of the plasmonic resonances. These frequencies can be effectively voltage tuned. We show that in PL-FET-detectors the dominant mechanism of the current rectification is due to the tunneling nonlinearity, whereas in the PGL-FET-detector the current rectification is primarily associated with the thermionic processes. Due to much lower p-n junction conductance in the PGL-FET-detectors, their resonant response can be substantially more pronounced than in the GL-FET-detectors corresponding to fairly high detector responsivity.

  16. Semiconducting ZnSnN2 thin films for Si/ZnSnN2 p-n junctions

    NASA Astrophysics Data System (ADS)

    Qin, Ruifeng; Cao, Hongtao; Liang, Lingyan; Xie, Yufang; Zhuge, Fei; Zhang, Hongliang; Gao, Junhua; Javaid, Kashif; Liu, Caichi; Sun, Weizhong

    2016-04-01

    ZnSnN2 is regarded as a promising photovoltaic absorber candidate due to earth-abundance, non-toxicity, and high absorption coefficient. However, it is still a great challenge to synthesize ZnSnN2 films with a low electron concentration, in order to promote the applications of ZnSnN2 as the core active layer in optoelectronic devices. In this work, polycrystalline and high resistance ZnSnN2 films were fabricated by magnetron sputtering technique, then semiconducting films were achieved after post-annealing, and finally Si/ZnSnN2 p-n junctions were constructed. The electron concentration and Hall mobility were enhanced from 2.77 × 1017 to 6.78 × 1017 cm-3 and from 0.37 to 2.07 cm2 V-1 s-1, corresponding to the annealing temperature from 200 to 350 °C. After annealing at 300 °C, the p-n junction exhibited the optimum rectifying characteristics, with a forward-to-reverse ratio over 103. The achievement of this ZnSnN2-based p-n junction makes an opening step forward to realize the practical application of the ZnSnN2 material. In addition, the nonideal behaviors of the p-n junctions under both positive and negative voltages are discussed, in hope of suggesting some ideas to further improve the rectifying characteristics.

  17. Electrostatically tunable lateral MoTe2 p-n junction for use in high-performance optoelectronics.

    PubMed

    Wang, Zhenxing; Wang, Feng; Yin, Lei; Huang, Yun; Xu, Kai; Wang, Fengmei; Zhan, Xueying; He, Jun

    2016-07-21

    Because of their ultimate thickness, layered structure and high flexibility, pn junctions based on layered two-dimensional semiconductors have been attracting increasing attention recently. In this study, for the first time, we fabricated lateral pn junctions (LPNJs) based on ultrathin MoTe2 by introducing two separated electrostatic back gates, and investigated their electronic and photovoltaic performance. Pn, np, nn, and pp junctions can be easily realized by modulating the conductive channel type using gate voltages with different polarities. Strong rectification effects were observed in the pn and np junctions and the rectification ratio reached ∼5 × 10(4). Importantly, we find a unique phenomenon that the parameters for MoTe2 LPNJs experience abrupt changes during the transition from p to n or n to p. Furthermore, a high performance photovoltaic device with a filling factor of above 51% and electrical conversion efficiency (η) of around 0.5% is achieved. Our findings are of importance to comprehensively understand the electronic and optoelectronic properties of MoTe2 and may further open up novel electronic and optoelectronic device applications. PMID:27335271

  18. Fluorescent Organic Planar pn Heterojunction Light-Emitting Diodes with Simplified Structure, Extremely Low Driving Voltage, and High Efficiency.

    PubMed

    Chen, Dongcheng; Xie, Gaozhan; Cai, Xinyi; Liu, Ming; Cao, Yong; Su, Shi-Jian

    2016-01-13

    Fluorescent organic light-emitting diodes capable of radiative utilization of both singlet and triplet excitons are achieved via a simple double-layer planar pn hetero-junction configuration without a conventional emission layer, leading to high external quantum efficiency above 10% and extremely low driving voltages close to the theoretical minima.

  19. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction.

    PubMed

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A; Casanova, Fèlix; van der Zant, Herre S J; Castellanos-Gomez, Andres; Hueso, Luis E

    2015-10-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 10(4), while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ∼11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications.

  20. Realization of radial p-n junction silicon nanowire solar cell based on low-temperature and shallow phosphorus doping.

    PubMed

    Dong, Gangqiang; Liu, Fengzhen; Liu, Jing; Zhang, Hailong; Zhu, Meifang

    2013-01-01

    A radial p-n junction solar cell based on vertically free-standing silicon nanowire (SiNW) array is realized using a novel low-temperature and shallow phosphorus doping technique. The SiNW arrays with excellent light trapping property were fabricated by metal-assisted chemical etching technique. The shallow phosphorus doping process was carried out in a hot wire chemical vapor disposition chamber with a low substrate temperature of 250°C and H2-diluted PH3 as the doping gas. Auger electron spectroscopy and Hall effect measurements prove the formation of a shallow p-n junction with P atom surface concentration of above 1020 cm-3 and a junction depth of less than 10 nm. A short circuit current density of 37.13 mA/cm2 is achieved for the radial p-n junction SiNW solar cell, which is enhanced by 7.75% compared with the axial p-n junction SiNW solar cell. The quantum efficiency spectra show that radial transport based on the shallow phosphorus doping of SiNW array improves the carrier collection property and then enhances the blue wavelength region response. The novel shallow doping technique provides great potential in the fabrication of high-efficiency SiNW solar cells.

  1. Organic/inorganic hybrid pn-junction between copper phthalocyanine and CdSe quantum dot layers as solar cells

    NASA Astrophysics Data System (ADS)

    Saha, Sudip K.; Guchhait, Asim; Pal, Amlan J.

    2012-08-01

    We have introduced an organic/inorganic hybrid pn-junction for solar cell applications. Layers of II-VI quantum dots and a metal-phthalocyanine in sequence have been used as n- and p-type materials, respectively, to form a junction. The film of quantum dots has been formed through a layer-by-layer process by replacing the long-chain ligands of the nanoparticles in each ultrathin layer or a monolayer with short-chain ones so that interparticle distance becomes small leading to a decrease in resistance of the quantum dot layer. With indium tin oxide and Au as electrodes, we have formed an inverted sandwiched structure. These electrodes formed ohmic contacts with the neighboring materials. From the current-voltage characteristics of the hybrid heterostructure, we have inferred formation of a depletion region at the pn-junction that played a key role in charge separation and correspondingly a photocurrent in the external circuit. For comparison, we have also formed and characterized Schottky devices based on components of the pn-junction keeping the electrode combination same. From capacitance-voltage characteristics, we have observed that the depletion region of the hybrid pn-junction was much wider as compared to that in Schottky devices based on components of the junction.

  2. Solution-processed anthradithiophene-PCBM p-n junction photovoltaic cells fabricated by using the photoprecursor method.

    PubMed

    Yamada, Hiroko; Yamaguchi, Yuji; Katoh, Ryuta; Motoyama, Takao; Aotake, Tatsuya; Kuzuhara, Daiki; Suzuki, Mitsuharu; Okujima, Tetsuo; Uno, Hidemitsu; Aratani, Naoki; Nakayama, Ken-ichi

    2013-12-25

    P-n junction solar cells based on anthradithiophene (ADT) as a p-type semiconductor were fabricated by using the photoprecursor method in which an α-diketone-type precursor was spin-coated and then transformed to ADT in situ by photoirradiation. Combination with PC71BM as an n-layer material led to 1.54% photoconversion efficiency.

  3. The behavior of series resistance of a p-n junction: the diode and the solar cell cases

    NASA Astrophysics Data System (ADS)

    Bueno, Poliana H.; Costa, Diogo F.; Eick, Alexander; Carvalho, André; Monteiro, Davies W. L.

    2016-03-01

    This paper presents a comparison of the impact of the internal parasitic series resistance of a p-n junction, as seen from the microelectronics and photovoltaic communities. The elusive thermal behavior of the aforementioned resistance gave this work its origin. Each community uses a different approach to interpret the operational current-voltage behavior of a p-n junction, which might lead to confusion, since scientists and engineers of these two realms seldom interact. An improvement in the understanding of the different approaches will help one to better model the performance of devices based on p-n junctions and therefore it will favor the performance predictions of photovoltaic cells. For diodes, series resistance is usually determined from a specific forward-bias region of the I-V curve on a semi-logarithmic scale. However, in Photovoltaics this region is not commonly reported and therefore other methods to determine Rs are employed. We mathematically modeled an experimentally obtained I-V curve with various pairs of the ideality factor and Rs and found that more than one pair accurately synthesizes the measured curve. We can conclude that the reported series resistance not only depends on physical parameters, e.g. temperature or irradiance, but also on fitting parameters, i.e. the ideality factor. Generally the behavior of a p-n junction depends on its operating conditions and electrical modeling.

  4. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction.

    PubMed

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A; Casanova, Fèlix; van der Zant, Herre S J; Castellanos-Gomez, Andres; Hueso, Luis E

    2015-10-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 10(4), while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ∼11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications. PMID:26335856

  5. Realization of radial p-n junction silicon nanowire solar cell based on low-temperature and shallow phosphorus doping

    PubMed Central

    2013-01-01

    A radial p-n junction solar cell based on vertically free-standing silicon nanowire (SiNW) array is realized using a novel low-temperature and shallow phosphorus doping technique. The SiNW arrays with excellent light trapping property were fabricated by metal-assisted chemical etching technique. The shallow phosphorus doping process was carried out in a hot wire chemical vapor disposition chamber with a low substrate temperature of 250°C and H2-diluted PH3 as the doping gas. Auger electron spectroscopy and Hall effect measurements prove the formation of a shallow p-n junction with P atom surface concentration of above 1020 cm−3 and a junction depth of less than 10 nm. A short circuit current density of 37.13 mA/cm2 is achieved for the radial p-n junction SiNW solar cell, which is enhanced by 7.75% compared with the axial p-n junction SiNW solar cell. The quantum efficiency spectra show that radial transport based on the shallow phosphorus doping of SiNW array improves the carrier collection property and then enhances the blue wavelength region response. The novel shallow doping technique provides great potential in the fabrication of high-efficiency SiNW solar cells. PMID:24369781

  6. Electrostatically tunable lateral MoTe2 p-n junction for use in high-performance optoelectronics.

    PubMed

    Wang, Zhenxing; Wang, Feng; Yin, Lei; Huang, Yun; Xu, Kai; Wang, Fengmei; Zhan, Xueying; He, Jun

    2016-07-21

    Because of their ultimate thickness, layered structure and high flexibility, pn junctions based on layered two-dimensional semiconductors have been attracting increasing attention recently. In this study, for the first time, we fabricated lateral pn junctions (LPNJs) based on ultrathin MoTe2 by introducing two separated electrostatic back gates, and investigated their electronic and photovoltaic performance. Pn, np, nn, and pp junctions can be easily realized by modulating the conductive channel type using gate voltages with different polarities. Strong rectification effects were observed in the pn and np junctions and the rectification ratio reached ∼5 × 10(4). Importantly, we find a unique phenomenon that the parameters for MoTe2 LPNJs experience abrupt changes during the transition from p to n or n to p. Furthermore, a high performance photovoltaic device with a filling factor of above 51% and electrical conversion efficiency (η) of around 0.5% is achieved. Our findings are of importance to comprehensively understand the electronic and optoelectronic properties of MoTe2 and may further open up novel electronic and optoelectronic device applications.

  7. Development of high-order PN models for radiative heat transfer in special geometries and boundary conditions

    NASA Astrophysics Data System (ADS)

    Ge, Wenjun; Modest, Michael F.; Roy, Somesh P.

    2016-03-01

    The high-order spherical harmonics (PN) method for 2-D Cartesian domains is extracted from the 3-D formulation. The number of equations and intensity coefficients reduces to (N + 1)2 / 4 in the 2-D Cartesian formulation compared with N(N + 1) / 2 for the general 3-D PN formulation. The Marshak boundary conditions are extended to solve problems with nonblack and mixed diffuse-specular surfaces. Additional boundary conditions for specified radiative wall flux, for symmetry/specular reflection boundaries have also been developed. The mathematical details of the formulations and their implementation in the OpenFOAM finite volume based CFD software platform are presented. The accuracy and computational cost of the 2-D Cartesian PN are compared with that of the 3-D PN solver and a Photon Monte Carlo solver for a square enclosure, as well as a 45° wedge geometry with variable radiative properties. The new boundary conditions have been applied for both test cases, and the boundary condition for mixed diffuse-specular surfaces is further illustrated by numerical examples of a rectangular geometry enclosed by walls with different surface characteristics.

  8. Drilling ban yields verdict

    SciTech Connect

    Nation, L.M.

    1992-01-01

    This paper briefly reviews a lawsuit which is under appeal by the State of Michigan regarding a takings claim filed over a petroleum exploration site. The dispute arose as a result of a 1987 decision by the Michigan Department of Natural Resources forbidding the property owners from developing the mineral rights leased to Miller Brothers in the Huron/Manistee National Forest. This area is bisected by a trend of Silurian Niagaran reef complexes which has a known production history throughout the State. The dunes area of the national forest has been deemed a wilderness area. As a result of the State's decision, the courts have awarded a sum of 71 million dollars to the developer to cover damages and lost resources. The reserve estimates were taken from adjacent areas which showed that the Niagaran reefs are relatively consistent in their yield.

  9. Serpine2/PN-1 Is Required for Proliferative Expansion of Pre-Neoplastic Lesions and Malignant Progression to Medulloblastoma

    PubMed Central

    Vaillant, Catherine; Kool, Marcel; Schwarzentruber-Schauerte, Alexandra; Méreau, Hélène; Cabuy, Erik; Lobrinus, Johannes A.; Pfister, Stefan; Zuniga, Aimée; Frank, Stephan; Zeller, Rolf

    2015-01-01

    Background Medulloblastomas are malignant childhood brain tumors that arise due to the aberrant activity of developmental pathways during postnatal cerebellar development and in adult humans. Transcriptome analysis has identified four major medulloblastoma subgroups. One of them, the Sonic hedgehog (SHH) subgroup, is caused by aberrant Hedgehog signal transduction due to mutations in the Patched1 (PTCH1) receptor or downstream effectors. Mice carrying a Patched-1 null allele (Ptch1∆/+) are a good model to study the alterations underlying medulloblastoma development as a consequence of aberrant Hedgehog pathway activity. Results Transcriptome analysis of human medulloblastomas shows that SERPINE2, also called Protease Nexin-1 (PN-1) is overexpressed in most medulloblastomas, in particular in the SHH and WNT subgroups. As siRNA-mediated lowering of SERPINE2/PN-1 in human medulloblastoma DAOY cells reduces cell proliferation, we analyzed its potential involvement in medulloblastoma development using the Ptch1∆/+ mouse model. In Ptch1∆/+ mice, medulloblastomas arise as a consequence of aberrant Hedgehog pathway activity. Genetic reduction of Serpine2/Pn-1 interferes with medulloblastoma development in Ptch1∆/+ mice, as ~60% of the pre-neoplastic lesions (PNLs) fail to develop into medulloblastomas and remain as small cerebellar nodules. In particular the transcription factor Atoh1, whose expression is essential for development of SHH subgroup medulloblastomas is lost. Comparative molecular analysis reveals the distinct nature of the PNLs in young Ptch1∆/+Pn-1Δ/+ mice. The remaining wild-type Ptch1 allele escapes transcriptional silencing in most cases and the aberrant Hedgehog pathway activity is normalized. Furthermore, cell proliferation and the expression of the cell-cycle regulators Mycn and Cdk6 are significantly reduced in PNLs of Ptch1∆/+Pn-1Δ/+ mice. Conclusions Our analysis provides genetic evidence that aberrant Serpine2/Pn-1 is required for

  10. Preparation, characterization and activity evaluation of p-n junction photocatalyst p-ZnO/n-TiO 2

    NASA Astrophysics Data System (ADS)

    Chen, Shifu; Zhao, Wei; Liu, Wei; Zhang, Sujuan

    2008-12-01

    In this paper, p-type ZnO powder was prepared by decomposition of zinc nitrate at 350 °C for 1 h. p-n junction photocatalyst p-ZnO/TiO 2 was prepared by ball milling of TiO 2 in H 2O solution doped with p-ZnO. The p-n junction photocatalyst p-ZnO/TiO 2 was characterized by UV-vis diffuse reflection spectrum, scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and the fluorescence emission spectra. The photocatalytic activity of the photocatalyst was evaluated by photocatalytic reduction of Cr 2O 72- and photocatalytic oxidation of methyl orange (MO). The results showed that the photocatalytic activity of the p-n junction p-ZnO/TiO 2 is much higher than that of TiO 2 on the photocatalytic reduction of Cr 2O 72-. However, the photocatalytic activity of the photocatalyst is much lower than that of TiO 2 on the photocatalytic oxidation of methyl orange. Namely, the p-n junction photocatalyst p-ZnO/TiO 2 has higher photocatalytic reduction activity, but lower photocatalytic oxidation activity. When the amounts of doped p-ZnO are 0.0 and 2.0 wt.%, illumination for 20 min, the photoreduction efficiencies are 15.7 and 42.8%, and the photooxidation efficiencies are 68.1 and 26.1%, respectively. Effect of ball milling time on the photocatalytic activity of the photocatalyst was also investigated. The mechanisms of influence on the photocatalytic activity were also discussed by the p-n junction principle.

  11. Uppermost mantle seismic velocity and anisotropy in the Euro-Mediterranean region from Pn and Sn tomography

    NASA Astrophysics Data System (ADS)

    Díaz, J.; Gil, A.; Gallart, J.

    2013-01-01

    In the last 10-15 years, the number of high quality seismic stations monitoring the Euro-Mediterranean region has increased significantly, allowing a corresponding improvement in structural constraints. We present here new images of the seismic velocity and anisotropy variations in the uppermost mantle beneath this complex area, compiled from inversion of Pn and Sn phases sampling the whole region. The method of Hearn has been applied to the traveltime arrivals of the International Seismological Center catalogue for the time period 1990-2010. A total of 579 753 Pn arrivals coming from 12 377 events recorded at 1 408 stations with epicentral distances between 220 km and 1 400 km have been retained after applying standard quality criteria (maximum depth, minimum number of recordings, maximum residual values …). Our results show significant features well correlated with surface geology and evidence the heterogeneous character of the Euro-Mediterranean lithosphere. The station terms reflect the existence of marked variations in crustal thickness, consistent with available Moho depths inferred from active seismic experiments. The highest Pn velocities are observed along a continuous band from the Po Basin to the northern Ionian Sea. Other high velocity zones include the Ligurian Basin, the Valencia Trough, the southern Alboran Sea and central part of the Algerian margin. Most significant low-velocity values are associated to orogenic belts (Betics, Pyrenees, Alps, Apennines and Calabrian Arc, Dinarides-Hellenides), and low-velocity zones are also identified beneath Sardinia and the Balearic Islands. The introduction of an anisotropic term enhances significantly the lateral continuity of the anomalies, in particular in the most active tectonic areas. Pn anisotropy shows consistent orientations subparallel to major orogenic structures, such as Betics, Apennines, Calabrian Arc and Alps. The Sn tomographic image has lower resolution but confirms independently most of the

  12. Yield enhancement with DFM

    NASA Astrophysics Data System (ADS)

    Paek, Seung Weon; Kang, Jae Hyun; Ha, Naya; Kim, Byung-Moo; Jang, Dae-Hyun; Jeon, Junsu; Kim, DaeWook; Chung, Kun Young; Yu, Sung-eun; Park, Joo Hyun; Bae, SangMin; Song, DongSup; Noh, WooYoung; Kim, YoungDuck; Song, HyunSeok; Choi, HungBok; Kim, Kee Sup; Choi, Kyu-Myung; Choi, Woonhyuk; Jeon, JoongWon; Lee, JinWoo; Kim, Ki-Su; Park, SeongHo; Chung, No-Young; Lee, KangDuck; Hong, YoungKi; Kim, BongSeok

    2012-03-01

    A set of design for manufacturing (DFM) techniques have been developed and applied to 45nm, 32nm and 28nm logic process technologies. A noble technology combined a number of potential confliction of DFM techniques into a comprehensive solution. These techniques work in three phases for design optimization and one phase for silicon diagnostics. In the DFM prevention phase, foundation IP such as standard cells, IO, and memory and P&R tech file are optimized. In the DFM solution phase, which happens during ECO step, auto fixing of process weak patterns and advanced RC extraction are performed. In the DFM polishing phase, post-layout tuning is done to improve manufacturability. DFM analysis enables prioritization of random and systematic failures. The DFM technique presented in this paper has been silicon-proven with three successful tape-outs in Samsung 32nm processes; about 5% improvement in yield was achieved without any notable side effects. Visual inspection of silicon also confirmed the positive effect of the DFM techniques.

  13. Secondary Electron Emission Yields

    NASA Technical Reports Server (NTRS)

    Krainsky, I.; Lundin, W.; Gordon, W. L.; Hoffman, R. W.

    1981-01-01

    The secondary electron emission (SEE) characteristics for a variety of spacecraft materials were determined under UHV conditions using a commercial double pass CMA which permits sequential Auger electron electron spectroscopic analysis of the surface. The transparent conductive coating indium tin oxide (ITO) was examined on Kapton and borosilicate glass and indium oxide on FED Teflon. The total SEE coefficient ranges from 2.5 to 2.6 on as-received surfaces and from 1.5 to 1.6 on Ar(+) sputtered surfaces with 5 nm removed. A cylindrical sample carousel provides normal incidence of the primary beam as well as a multiple Faraday cup measurement of the approximately nA beam currents. Total and true secondary yields are obtained from target current measurements with biasing of the carousel. A primary beam pulsed mode to reduce electron beam dosage and minimize charging of insulating coatings was applied to Mg/F2 coated solar cell covers. Electron beam effects on ITO were found quite important at the current densities necessary to do Auger studies.

  14. Crop yield gaps in Cameroon.

    PubMed

    Yengoh, Genesis T; Ardö, Jonas

    2014-03-01

    Although food crop yields per hectare have generally been increasing in Cameroon since 1961, the food price crisis of 2008 and the ensuing social unrest and fatalities raised concerns about the country's ability to meet the food needs of its population. This study examines the country's potential for increasing crop yields and food production to meet this food security challenge. Fuzzy set theory is used to develop a biophysical spatial suitability model for different crops, which in turn is employed to ascertain whether crop production is carried out in biophysically suited areas. We use linear regression to examine the trend of yield development over the last half century. On the basis of yield data from experimental stations and farmers' fields we assess the yield gap for major food crops. We find that yields have generally been increasing over the last half century and that agricultural policies can have significant effects on them. To a large extent, food crops are cultivated in areas that are biophysically suited for their cultivation, meaning that the yield gap is not a problem of biophysical suitability. Notwithstanding, there are significantly large yield gaps between actual yields on farmers' farms and maximum attainable yields from research stations. We conclude that agronomy and policies are likely to be the reasons for these large yield gaps. A key challenge to be addressed in closing the yield gaps is that of replenishing and properly managing soil nutrients.

  15. Nanostructured p-type CZTS thin films prepared by a facile solution process for 3D p-n junction solar cells.

    PubMed

    Park, Si-Nae; Sung, Shi-Joon; Sim, Jun-Hyoung; Yang, Kee-Jeong; Hwang, Dae-Kue; Kim, JunHo; Kim, Gee Yeong; Jo, William; Kim, Dae-Hwan; Kang, Jin-Kyu

    2015-07-01

    Nanoporous p-type semiconductor thin films prepared by a simple solution-based process with appropriate thermal treatment and three-dimensional (3D) p-n junction solar cells fabricated by depositing n-type semiconductor layers onto the nanoporous p-type thin films show considerable photovoltaic performance compared with conventional thin film p-n junction solar cells. Spin-coated p-type Cu2ZnSnS4 (CZTS) thin films prepared using metal chlorides and thiourea show unique nanoporous thin film morphology, which is composed of a cluster of CZTS nanograins of 50-500 nm, and the obvious 3D p-n junction structure is fabricated by the deposition of n-type CdS on the nanoporous CZTS thin films by chemical bath deposition. The photovoltaic properties of 3D p-n junction CZTS solar cells are predominantly affected by the scale of CZTS nanograins, which is easily controlled by the sulfurization temperature of CZTS precursor films. The scale of CZTS nanograins determines the minority carrier transportation within the 3D p-n junction between CZTS and CdS, which are closely related with the photocurrent of series resistance of 3D p-n junction solar cells. 3D p-n junction CZTS solar cells with nanograins below 100 nm show power conversion efficiency of 5.02%, which is comparable with conventional CZTS thin film solar cells. PMID:26061271

  16. The physics and kinematics of the evolved, interacting planetary nebula PN G342.0-01.7

    NASA Astrophysics Data System (ADS)

    Ali, A.; Amer, M. A.; Dopita, M. A.; Vogt, F. P. A.; Basurah, H. M.

    2015-11-01

    Integral field spectroscopy has been obtained for very few evolved planetary nebulae (PNe). Here we aim to study the physical and kinematical characteristics of the unstudied old planetary nebula PN G342.0-01.7, which shows evidence of interaction with its surrounding interstellar medium. We used integral field spectra from the Wide Field Spectrograph on the ANU 2.3 m telescope to provide spectroscopy across the whole object covering the spectral range 3400-7000 Å. We formed narrow-band images to investigate the excitation structure. The spectral analysis shows that the object is a distant Peimbert Type I planetary nebula (PN) of low excitation, formally of excitation class of 0.5. The low electron density, high dynamical age, and low surface brightness of the object confirm that it is observed fairly late in its evolution. It shows clear evidence for dredge-up of CN-processed material characteristic of its class. In addition, the low peculiar velocity of 7 km s-1 shows it to be a member of the young disk component of our Galaxy. We further determined an average expansion velocity of Vexp = 20.2 ± 1.3 km s-1, a local standard of rest radial velocity RVLSR = -27.7 ± 1.7 km s-1, and a distance of 2.06 ± 0.6 kpc for the object. We built a self-consistent photoionisation model for the PN matching the observed spectrum, the Hβ luminosity, and the diameter. On the basis of this we derive an effective temperature log Teff ~ 5.05 and luminosity 1.85 < log L< 2.25. The temperature is much higher than might have been expected using the excitation class, proving that this can be misleading in classifying evolved PNe. PN G342.0-01.7 is in interaction with its surrounding interstellar medium through which the object is moving in the south-west direction. This interaction drives a slow shock into the outer PN ejecta. A shock model suggests that it only accounts for about 10% of the total luminosity, but has an important effect on the global spectrum of the PN.

  17. Synthesis and structural characterization of the ternary Zintl phases AE{sub 3}Al{sub 2}Pn{sub 4} and AE{sub 3}Ga{sub 2}Pn{sub 4} (AE=Ca, Sr, Ba, Eu; Pn=P, As)

    SciTech Connect

    He, Hua; Tyson, Chauntae; Saito, Maia; Bobev, Svilen

    2012-04-15

    Ten new ternary phosphides and arsenides with empirical formulae AE{sub 3}Al{sub 2}Pn{sub 4} and AE{sub 3}Ga{sub 2}Pn{sub 4} (AE=Ca, Sr, Ba, Eu; Pn=P, As) have been synthesized using molten Ga, Al, and Pb fluxes. They have been structurally characterized by single-crystal and powder X-ray diffraction to form with two different structures-Ca{sub 3}Al{sub 2}P{sub 4}, Sr{sub 3}Al{sub 2}As{sub 4}, Eu{sub 3}Al{sub 2}P{sub 4}, Eu{sub 3}Al{sub 2}As{sub 4}, Ca{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}As{sub 4}, and Eu{sub 3}Ga{sub 2}As{sub 4} crystallize with the Ca{sub 3}Al{sub 2}As{sub 4} structure type (space group C2/c, Z=4); Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4} adopt the Na{sub 3}Fe{sub 2}S{sub 4} structure type (space group Pnma, Z=4). The polyanions in both structures are made up of TrPn{sub 4} tetrahedra, which share common corners and edges to form {sup 2}{sub {infinity}}[TrPn{sub 2}]{sub 3-} layers in the phases with the Ca{sub 3}Al{sub 2}As{sub 4} structure, and {sup 1}{sub {infinity}}[TrPn{sub 2}]{sub 3-} chains in Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4} with the Na{sub 3}Fe{sub 2}S{sub 4} structure type. The valence electron count for all of these compounds follows the Zintl-Klemm rules. Electronic band structure calculations confirm them to be semiconductors. - Graphical abstract: AE{sub 3}Al{sub 2}Pn{sub 4} and AE{sub 3}Ga{sub 2}Pn{sub 4} (AE=Ca, Sr, Ba, Eu; Pn=P, As) crystallize in two different structures-Ca{sub 3}Al{sub 2}P{sub 4}, Sr{sub 3}Al{sub 2}As{sub 4}, Eu{sub 3}Al{sub 2}P{sub 4}, Eu{sub 3}Al{sub 2}As{sub 4}, Ca{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}As{sub 4}, and Eu{sub 3}Ga{sub 2}As{sub 4}, are isotypic with the previously reported Ca{sub 3}Al{sub 2}As{sub 4} (space group C2/c (No. 15)), while Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4} adopt a different structure known for Na{sub 3}Fe{sub 2}S{sub 4} (space group Pnma (No. 62

  18. Experimental Investigation of (p,n) reactions relevant to the astrophysical νp process

    NASA Astrophysics Data System (ADS)

    Perdikakis, G.; Almus, R. M.; Avetisyan, R.; Bataglia, A. A.; Bucher, B. M.; Casarella, C. R.; Fröhlich, C.; Lipschutz, S.; Long, A. M.; Lyons, S.; Marley, S. T.; Ostdiek, K. M.; Redpath, T. H.; Smith, K. I.; Smith, M. K.; Spyrou, A.; Stech, E. J.; Tan, W.; Talwar, R.; Wiescher, M.; Zegers, R. G. T.

    2013-10-01

    A recently discovered nucleosynthesis process, the νp process is thought to take place in core-collapse supernovae and could explain some of the observed abundance trends. The underlying nuclear physics and its role is not yet known due to a lack of experimental information. Aiming to study relevant reaction rates, the (n,p) reactions on 61Cu and 59Ni have been studied through their time-inverse reactions 61Ni(p,n) and 59Co(p,n). Protons with energies between 2.2 and 4 MeV from the FN Tandem of the University of Notre Dame were used to extract excitation functions in 100 keV steps covering the energy range of relevance. Neutrons from the (p,n) reactions with energies between 130 keV and 1 MeV where detected using a subset of the LENDA neutron array. Preliminary results from this investigation will be presented and the impact to nucleosynthesis will be discussed.

  19. A van der Waals pn heterojunction with organic/inorganic semiconductors

    SciTech Connect

    He, Daowei; Yang, Ziyi; Wu, Bing; Xu, Bingchen; Zhang, Yuhan; Li, Yun; Shi, Yi E-mail: xrwang@nju.edu.cn; Wang, Xinran E-mail: xrwang@nju.edu.cn; Pan, Yiming; Wang, Baigeng; Nan, Haiyan; Luo, Xiaoguang; Ni, Zhenhua; Gu, Shuai; Zhu, Jia; Chai, Yang

    2015-11-02

    van der Waals (vdW) heterojunctions formed by two-dimensional (2D) materials have attracted tremendous attention due to their excellent electrical/optical properties and device applications. However, current 2D heterojunctions are largely limited to atomic crystals, and hybrid organic/inorganic structures are rarely explored. Here, we fabricate the hybrid 2D heterostructures with p-type dioctylbenzothienobenzothiophene (C{sub 8}-BTBT) and n-type MoS{sub 2}. We find that few-layer C{sub 8}-BTBT molecular crystals can be grown on monolayer MoS{sub 2} by vdW epitaxy, with pristine interface and controllable thickness down to monolayer. The operation of the C{sub 8}-BTBT/MoS{sub 2} vertical heterojunction devices is highly tunable by bias and gate voltages between three different regimes: interfacial recombination, tunneling, and blocking. The pn junction shows diode-like behavior with rectifying ratio up to 10{sup 5} at the room temperature. Our devices also exhibit photovoltaic responses with a power conversion efficiency of 0.31% and a photoresponsivity of 22 mA/W. With wide material combinations, such hybrid 2D structures will offer possibilities for opto-electronic devices that are not possible from individual constituents.

  20. Polaron absorption for photovoltaic energy conversion in a manganite-titanate pn heterojunction

    NASA Astrophysics Data System (ADS)

    Saucke, Gesine; Norpoth, Jonas; Jooss, Christian; Su, Dong; Zhu, Yimei

    2012-04-01

    The relation among structure, electric transport, and photovoltaic effect is investigated for a pn heterojunction with strong correlation interactions. A perovskite interface is chosen as a model system consisting of the p-doped strongly correlated manganite Pr0.64Ca0.36MnO3 (PCMO) and the n-doped titanate SrTi1-yNbyO3 (y=0.002 and 0.01). High-resolution electron microscopy and spectroscopy reveal a nearly dislocation-free, epitaxial interface and give insight into the local atomic and electronic structure. The presence of a photovoltaic effect under visible light at room temperature suggests the existence of mobile excited polarons within the band-gap-free PCMO absorber. The temperature-dependent rectifying current-voltage characteristics prove to be mainly determined by the presence of an interfacial energy spike in the conduction band and are affected by the colossal electroresistance effect. From the comparison of photocurrents and spatiotemporal distributions of photogenerated carriers (deduced from optical absorption spectroscopy), we discuss the range of the excited polaron diffusion length.

  1. UNUSUAL CARBONACEOUS DUST DISTRIBUTION IN PN G095.2+00.7

    SciTech Connect

    Ohsawa, Ryou; Onaka, Takashi; Sakon, Itsuki; Mori, Tamami I.; Miyata, Takashi; Asano, Kentaro; Matsuura, Mikako; Kaneda, Hidehiro

    2012-12-01

    We investigate the polycyclic aromatic hydrocarbon (PAH) features in the young Galactic planetary nebula PN G095.2+00.7 based on mid-infrared observations. The near- to mid-infrared spectra obtained with the AKARI/IRC and the Spitzer/IRS show the PAH features as well as the broad emission feature at 12 {mu}m usually seen in proto-planetary nebulae (pPNe). The spatially resolved spectra obtained with Subaru/COMICS suggest that the broad emission around 12 {mu}m is distributed in a shell-like structure, but the unidentified infrared band at 11.3 {mu}m is selectively enhanced at the southern part of the nebula. The variation can be explained by a difference in the amount of the UV radiation to excite PAHs, and does not necessarily require the chemical processing of dust grains and PAHs. It suggests that the UV self-extinction is important to understand the mid-infrared spectral features. We propose a mechanism which accounts for the evolutionary sequence of the mid-infrared dust features seen in a transition from pPNe to PNe.

  2. Contacts between Two- and Three-Dimensional Materials: Ohmic, Schottky, and p-n Heterojunctions.

    PubMed

    Xu, Yang; Cheng, Cheng; Du, Sichao; Yang, Jianyi; Yu, Bin; Luo, Jack; Yin, Wenyan; Li, Erping; Dong, Shurong; Ye, Peide; Duan, Xiangfeng

    2016-05-24

    After a decade of intensive research on two-dimensional (2D) materials inspired by the discovery of graphene, the field of 2D electronics has reached a stage with booming materials and device architectures. However, the efficient integration of 2D functional layers with three-dimensional (3D) systems remains a significant challenge, limiting device performance and circuit design. In this review, we investigate the experimental efforts in interfacing 2D layers with 3D materials and analyze the properties of the heterojunctions formed between them. The contact resistivity of metal on graphene and related 2D materials deserves special attention, while the Schottky junctions formed between metal/2D semiconductor or graphene/3D semiconductor call for careful reconsideration of the physical models describing the junction behavior. The combination of 2D and 3D semiconductors presents a form of p-n junctions that have just marked their debut. For each type of the heterojunctions, the potential applications are reviewed briefly. PMID:27132492

  3. RKKY interaction in P-N junction based on surface states of 3D topological insulator

    NASA Astrophysics Data System (ADS)

    Zhang, Shuhui; Yang, Wen; Chang, Kai

    The RKKY interaction mediated by conduction electrons supplies a mechanism to realize the long-range coupling of localized spins which is desired for the spin devices. Here, we examine the controllability of RKKY interaction in P-N junction (PNJ) based on surface states of 3D topological insulator (3DTI). In this study, through quantum way but not usual classical analogy to light propagation, the intuitive picture for electron waves across the interface of PNJ is obtained, e.g., Klein tunneling, negative refraction and focusing. Moreover, we perform the numerical calculations for all kinds of RKKY interaction including the Heisenberg, Ising, and Dzyaloshinskii-Moriya terms. We find the focusing of surface states leads to the local augmentation of RKKY interaction. Most importantly, a dimension transition occurs, i.e., the decay rate of RKKY interaction from the deserved 1/R 2 to 1/ R . In addition, the quadratic gate-dependence of RKKY interaction is also beneficial to the application of 3DTI PNJ in the fields of spintronics and quantum computation. This work was supported by the MOST (Grant No. 2015CB921503, and No. 2014CB848700) and NSFC (Grant No. 11434010, No. 11274036, No. 11322542, and No. 11504018).

  4. Growth and investigation of p-n structures based on Fe3O4thin films

    NASA Astrophysics Data System (ADS)

    Šliužienė, K.; Lisauskas, V.; Butkutė, R.; Vengalis, B.; Tamulevicius, S.; Andrulevicius, M.

    2008-03-01

    We report preparation and investigation of p-n heterostructures based on Fe3O4 thin films grown on n-Si(111) substrates as well as indium oxide (IO) and tin doped indium oxide (ITO) layers deposited on lattice-matched monocrystalline ZrO2:Y2O3(100). Thin Fe3O4 films with thickness ranging from 100 to 300 nm were grown in situ at 400 K using dc magnetron sputtering technique. The measurement of microstructure revealed polycrystalline quality of Fe3O4 films on silicon substrate and epitaxial growth on (IO)ITO/YSZ. Investigation of surface composition by X-ray Photoelectron Spectroscopy (XPS) showed that Fe 2p peak consists of three main peaks, namely, metallic iron Fe(0), Fe(II) and Fe(III). Transport measurements of Fe3O4/n-Si heterostructures demonstrated rectifying behaviour in a wide temperature range (T = 78÷300 K) while those prepared by growing Fe3O4 layers on indium oxide (IO) demonstrated nonlinear current-voltage (I-V) dependencies at low temperatures (T<120K).

  5. Carbon doping induced peculiar transport properties of boron nitride nanoribbons p-n junctions

    SciTech Connect

    Liu, N.; Gao, G. Y.; Zhu, S. C.; Ni, Y.; Wang, S. L.; Yao, K. L.; Liu, J. B.

    2014-07-14

    By applying nonequilibrium Green's function combined with density functional theory, we investigate the electronic transport properties of carbon-doped p-n nanojunction based on hexagonal boron nitride armchair nanoribbons. The calculated I-V curves show that both the center and edge doping systems present obvious negative differential resistance (NDR) behavior and excellent rectifying effect. At low positive bias, the edge doping systems possess better NDR performance with larger peak-to-valley ratio (∼10{sup 5}), while at negative bias, the obtained peak-to-valley ratio for both of the edge and center doping systems can reach the order of 10{sup 7}. Meanwhile, center doping systems present better rectifying performance than the edge doping ones, and giant rectification ratio up to 10{sup 6} can be obtained in a wide bias range. These outstanding transport properties are explained by the evolution of the transmission spectra and band structures with applied bias, together with molecular projected self-consistent Hamiltonian eigenvalues and eigenstates.

  6. Method for forming p-n junctions and solar-cells by laser-beam processing

    DOEpatents

    Narayan, Jagdish; Young, Rosa T.

    1979-01-01

    This invention is an improved method for preparing p-n junction devices, such as diodes and solar cells. High-quality junctions are prepared by effecting laser-diffusion of a selected dopant into silicon by means of laser pulses having a wavelength of from about 0.3 to 1.1 .mu.m, an energy area density of from about 1.0 to 2.0 J/cm.sup.2, and a duration of from about 20 to 60 nanoseconds. Initially, the dopant is deposited on the silicon as a superficial layer, preferably one having a thickness in the range of from about 50 to 100 A. Depending on the application, the values for the above-mentioned pulse parameters are selected to produce melting of the silicon to depths in the range from about 1000 A to 1 .mu.m. The invention has been used to produce solar cells having a one-sun conversion efficiency of 10.6%, these cells having no antireflective coating or back-surface fields.

  7. Thermal influence on charge carrier transport in solar cells based on GaAs PN junctions

    SciTech Connect

    Osses-Márquez, Juan; Calderón-Muñoz, Williams R.

    2014-10-21

    The electron and hole one-dimensional transport in a solar cell based on a Gallium Arsenide (GaAs) PN junction and its dependency with electron and lattice temperatures are studied here. Electrons and heat transport are treated on an equal footing, and a cell operating at high temperatures using concentrators is considered. The equations of a two-temperature hydrodynamic model are written in terms of asymptotic expansions for the dependent variables with the electron Reynolds number as a perturbation parameter. The dependency of the electron and hole densities through the junction with the temperature is analyzed solving the steady-state model at low Reynolds numbers. Lattice temperature distribution throughout the device is obtained considering the change of kinetic energy of electrons due to interactions with the lattice and heat absorbed from sunlight. In terms of performance, higher values of power output are obtained with low lattice temperature and hot energy carriers. This modeling contributes to improve the design of heat exchange devices and thermal management strategies in photovoltaic technologies.

  8. Coherent control of single spins in a silicon carbide pn junction device at room temperature

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Yun; Widmann, Matthias; Booker, Ian; Niethammer, Matthias; Ohshima, Takeshi; Gali, Adam; Son, Nguyen T.; Janzén, Erik; Wrachtrup, Joerg

    Spins in single defects have been studied for quantum information science and quantum metrology. It has been proven that spins of the single nitrogen-vacancy (NV) centers in diamond can be used as a quantum bit, and a single spin sensor operating at ambient conditions. Recently, there has been a growing interest in a new material in which color centers similar to NV centers can be created and whose electrical properties can also be well controlled, thus existing electronic devices can easily be adapted as a platform for quantum applications. We recently reported that single spins of negatively charged silicon vacancies in SiC can be coherently controlled and long-lived at room temperature. As a next step, we isolated single silicon vacancies in a SiC pn junction device and investigated how the change in Fermi level, induced by applying bias, alters the charge state of silicon vacancies, thus affects the spin state control. This study will allow us to envision quantum applications based on single defects incorporated in modern electronic devices.

  9. Nonpolar a-plane p-type GaN and p-n Junction Diodes

    SciTech Connect

    Chakraborty, Arpan; Xing, H.; Craven, M.D.; Keller, S.; Mates, T.; Speck, J.S.; Baars, S.P. den; Mishra, U.K.

    2004-10-15

    Growth and electrical characteristics of Mg-doped p-type nonpolar (1120) a-plane GaN films, grown on (1102) r-plane sapphire substrates via metalorganic chemical vapor deposition, were investigated as a function of growth rate, the ammonia to trimethylgallium flow ratio (V/III ratio), and the growth temperature. The electrical conductivity of the films exhibited a strong dependence on the growth parameters. Secondary-ion-mass-spectroscopy measurements indicated that more Mg was incorporated at higher growth rate and at lower growth temperatures. The Mg concentration in the films increased linearly with the Mg flow. A maximum hole concentration of 6.8x10{sup 17}cm{sup -3} was achieved at room temperature for a Mg concentration of 7.6x10{sup 19}cm{sup -3}, corresponding to 0.9% ionization. Further increase in the Mg concentration resulted in increased surface roughness as well as a significant decrease in the hole concentration. p-n junction diodes were fabricated using nonpolar a-plane GaN, and the current-voltage characteristics of these diodes showed a sharp turn-on at {approx}3 V.

  10. Unusual Carbonaceous Dust Distribution in PN G095.2+00.7

    NASA Astrophysics Data System (ADS)

    Ohsawa, Ryou; Onaka, Takashi; Sakon, Itsuki; Mori, Tamami I.; Miyata, Takashi; Asano, Kentaro; Matsuura, Mikako; Kaneda, Hidehiro

    2012-12-01

    We investigate the polycyclic aromatic hydrocarbon (PAH) features in the young Galactic planetary nebula PN G095.2+00.7 based on mid-infrared observations. The near- to mid-infrared spectra obtained with the AKARI/IRC and the Spitzer/IRS show the PAH features as well as the broad emission feature at 12 μm usually seen in proto-planetary nebulae (pPNe). The spatially resolved spectra obtained with Subaru/COMICS suggest that the broad emission around 12 μm is distributed in a shell-like structure, but the unidentified infrared band at 11.3 μm is selectively enhanced at the southern part of the nebula. The variation can be explained by a difference in the amount of the UV radiation to excite PAHs, and does not necessarily require the chemical processing of dust grains and PAHs. It suggests that the UV self-extinction is important to understand the mid-infrared spectral features. We propose a mechanism which accounts for the evolutionary sequence of the mid-infrared dust features seen in a transition from pPNe to PNe. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  11. Carrier phase recovery performance for PN-spread TDRSS link with radio-frequency interference

    NASA Technical Reports Server (NTRS)

    Mckenzie, T. M.; Braun, W. R.

    1979-01-01

    The carrier-phase recovery performance of a Costas loop for a nonlinear satellite channel with uplink and downlink noise is analyzed, and the extension of these results to the case where uplink radio-frequency interference (RFI) is present is considered. The signal format here is binary phase-shift-keyed (BPSK) or unbalanced quaternary phase-shift-keyed (UQPSK), the signals being either the non-return-to-zero (NRZ) or biphase (Manchester) type. With UQPSK, at least one data stream must be PN-spread. The channel comprises additive white Gaussian noise (WGN), a wideband filter, a bandpass nonlinearity and more additive WGN. The RFI being considered is pulsed continuous-wave, pulsed WGN, or a combination of the two. It is noted that the Tracking and Data Relay Satellite System (TDRSS) will be subjected to RFI from certain locations, especially in the S-band of frequencies. The characteristics of this link are generalized to form the assumptions underlying this analysis. The analytical results given include the S-curve of the equivalent loop and the phase-error variance of the linearized loop.

  12. Comparison of Ge, InGaAs p-n junction solar cell

    NASA Astrophysics Data System (ADS)

    Korun, M.; Navruz, T. S.

    2016-04-01

    In this paper, the effect of material parameters on the efficiency of Ge and InGaAs p-n junction solar cells which are most commonly used as the sub-cell of multi-junction solar cells are investigated and the results due to these two cells are compared. The efficiency of Ge (EG =0.67 eV) solar cell which is easy to manufacture and inexpensive in cost, is compared with the efficiency of InGaAs (EG =0.74 eV) solar cell which is coming with drawback of high production difficulties and cost. The theoretical efficiency limit of Ge and InGaAs solar cells with optimum thickness were determined by using detailed balance model under one sun AM1.5 illumination. Since the band gap values of two cells are close to each other, approximate detailed balance efficiency limits of 16% for InGaAs and 14% for Ge are obtained. When drift-diffusion model is used and the thicknesses and doping concentrations are optimized, the maximum efficiency values are calculated as 13% for InGaAs and 9% for Ge solar cell. For each solar cell external quantum efficiency curves due to wavelength are also sketched and compared.

  13. Contacts between Two- and Three-Dimensional Materials: Ohmic, Schottky, and p-n Heterojunctions.

    PubMed

    Xu, Yang; Cheng, Cheng; Du, Sichao; Yang, Jianyi; Yu, Bin; Luo, Jack; Yin, Wenyan; Li, Erping; Dong, Shurong; Ye, Peide; Duan, Xiangfeng

    2016-05-24

    After a decade of intensive research on two-dimensional (2D) materials inspired by the discovery of graphene, the field of 2D electronics has reached a stage with booming materials and device architectures. However, the efficient integration of 2D functional layers with three-dimensional (3D) systems remains a significant challenge, limiting device performance and circuit design. In this review, we investigate the experimental efforts in interfacing 2D layers with 3D materials and analyze the properties of the heterojunctions formed between them. The contact resistivity of metal on graphene and related 2D materials deserves special attention, while the Schottky junctions formed between metal/2D semiconductor or graphene/3D semiconductor call for careful reconsideration of the physical models describing the junction behavior. The combination of 2D and 3D semiconductors presents a form of p-n junctions that have just marked their debut. For each type of the heterojunctions, the potential applications are reviewed briefly.

  14. New Aspects of Photocurrent Generation at Graphene pn Junctions Revealed by Ultrafast Optical Measurements

    NASA Astrophysics Data System (ADS)

    Aivazian, Grant; Sun, Dong; Jones, Aaron; Ross, Jason; Yao, Wang; Cobden, David; Xu, Xiaodong

    2012-02-01

    The remarkable electrical and optical properties of graphene make it a promising material for new optoelectronic applications. However, one important, but so far unexplored, property is the role of hot carriers in charge and energy transport at graphene interfaces. Here we investigate the photocurrent (PC) dynamics at a tunable graphene pn junction using ultrafast scanning PC microscopy. Pump-probe measurements show a temperature dependent relaxation time of photogenerated carriers that increases from 1.5ps at 290K to 4ps at 20K; while the amplitude of the PC is independent of the lattice temperature. These observations imply that it is hot carriers, not phonons, which dominate ultrafast energy transport. Gate dependent measurements show many interesting features such as pump induced saturation, enhancement, and sign reversal of probe generated PC. These observations reveal that the underlying PC mechanism is a combination of the thermoelectric and built-in electric field effects. Our results enhance the understanding of non-equilibrium electron dynamics, electron-electron interactions, and electron-phonon interactions in graphene. They also determine fundamental limits on ultrafast device operation speeds (˜500 GHz) for graphene-based photodetectors.

  15. Organic nanowire/crystalline silicon p-n heterojunctions for high-sensitivity, broadband photodetectors.

    PubMed

    Deng, Wei; Jie, Jiansheng; Shang, Qixun; Wang, Jincheng; Zhang, Xiujuan; Yao, Shenwen; Zhang, Qing; Zhang, Xiaohong

    2015-01-28

    Organic/inorganic hybrid devices are promising candidates for high-performance, low-cost optoelectronic devices, by virtue of their unique properties. Polycrystalline/amorphous organic films are widely used in hybrid devices, because defects in the films hamper the improvement of device performance. Here, we report the construction of 2,4-bis[4-(N,N-dimethylamino)phenyl]squaraine (SQ) nanowire (NW)/crystalline Si (c-Si) p-n heterojunctions. Thanks to the high crystal quality of the SQ NWs, the heterojunctions exhibit excellent diode characteristics in darkness. It is significant that the heterojunctions have been found to be capable of detecting broadband light with wavelengths spanning from ultraviolet (UV) light, to visible (Vis) light, to near-infrared (NIR) light, because of the complementary spectrum absorption of SQ NWs with Si. The junction is demonstrated to play a core role in enhancing the device performance, in terms of ultrahigh sensitivity, excellent stability, and fast response. The photovoltaic characteristics of the heterojunctions are further investigated, revealing a power conversion efficiency (PCE) of up to 1.17%. This result also proves the potential of the device as self-powered photodetectors operating at zero external bias voltage. This work presents an important advance in constructing single-crystal organic nanostructure/inorganic heterojunctions and will enable future exploration of their applications in broadband photodetectors and solar cells.

  16. A pn heterojunction diode constructed with a n-type ZnO nanowire and a p-type HgTe nanoparticle thin film

    NASA Astrophysics Data System (ADS)

    Seong, Hojun; Cho, Kyoungah; Kim, Sangsig

    2009-01-01

    We demonstrate a pn heterojunction diode constructed with a n-type ZnO nanowire (NW) and a p-type HgTe nanoparticle (NP) thin film on a SiO2/p-Si substrate. For the pn heterojunction diode, the rectifying characteristics of both the dark current and the photocurrent excited by 633 nm wavelength light were observed, but the photocurrent excited by 325 nm wavelength light possesses Ohmic characteristics. The optoelectronic characteristics of the pn heterojunction diode were compared with those of the ZnO NW and HgTe NP thin film composing it.

  17. Greatly improved 3C-SiC p-n junction diodes grown by chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Larkin, David J.; Starr, Jonathan E.; Powell, J. A.; Salupo, Carl S.; Matus, Lawrence G.

    1993-01-01

    This paper reports the fabrication and initial electrical characterization of greatly improved 3C-SiC (beta-SiC) p-n junction diodes. These diodes, which were grown on commercially available 6H-SiC substrates by chemical vapor deposition, demonstrate rectification to -200 V at room temperature, representing a fourfold improvement in reported 3C-SiC diode blocking voltage. The reverse leakage currents and saturation current densities measured on these diodes also show significant improvement compared to previously reported 3C-SiC p-n junction diodes. When placed under sufficient forward bias, the diodes emit significantly bright green-yellow light. These results should lead to substantial advancements in 3C-SiC transistor performance.

  18. Long-term performance and microbial ecology of a two-stage PN-ANAMMOX process treating mature landfill leachate.

    PubMed

    Li, Huosheng; Zhou, Shaoqi; Ma, Weihao; Huang, Pengfei; Huang, Guotao; Qin, Yujie; Xu, Bin; Ouyang, Hai

    2014-05-01

    Long-term performance of a two-stage partial nitritation (PN)-anaerobic ammonium oxidation (ANAMMOX) process treating mature landfill leachate was investigated. Stable partial nitritation performance was achieved in a sequencing batch reactor (SBR) using endpoint pH control, providing an effluent with a ratio of NO2(-)-N/NH4(+)-N at 1.23 ± 0.23. High rate nitrogen removal over 4 kg N/m(3)/d was observed in the ANAMMOX reactor in the first three months. However, during long-term operation, the ANAMMOX reactor can only stably operate under nitrogen load of 1 kg N/m(3)/d, with 85 ± 1% of nitrogen removal. The ammonium oxidizing bacteria (AOB) in the PN-SBR were mainly affiliated to Nitrosomonas sp. IWT514, Nitrosomonas eutropha and Nitrosomonas eutropha, the anaerobic ammonium oxidizing bacteria (AnAOB) in the ANAMMOX reactor were mainly affiliated to Kuenenia stuttgartiensis.

  19. Sub-bandgap linear-absorption-based photodetectors in avalanche mode in PN-diode-integrated silicon microring resonators.

    PubMed

    Li, Yu; Feng, Shaoqi; Zhang, Yu; Poon, Andrew W

    2013-12-01

    We report a sub-bandgap linear-absorption-based photodetector in avalanche mode at 1550 nm in a PN-diode-integrated silicon microring resonator. The photocurrent is primarily generated by the defect-state absorption introduced by the boron and phosphorous ion implantation during the PN diode formation. The responsivity is enhanced by both the cavity effect and the avalanche multiplication. We measure a responsivity of ~72.8 mA/W upon 8 V at cavity resonances in avalanche mode, corresponding to a gain of ~72 relative to the responsivity of ~1.0 mA/W upon 3 V at cavity resonances in normal mode. Our device exhibits a 3 dB bandwidth of ~7 GHz and an open eye diagram at 15 Gbit/s upon 8 V.

  20. Fabrication of stable pn junction single-walled carbon nanotube thin films by position selective Cs plasma irradiation method

    NASA Astrophysics Data System (ADS)

    Abiko, Y.; Kato, T.; Hatakeyama, R.; Kaneko, T.

    2014-06-01

    Stable n-type thin film transistors (TFTs) are fabricated with Cs encapsulated single-walled carbon nanotubes (Cs@SWNTs). The transport property of SWNTs-TFTs clearly changes from p- to n-type characteristic after the Cs plasma irradiation. Based on the systematic investigations, it is revealed that there is an optimum ion energy for the effective Cs encapsulation, which is around 50 eV. Furthermore, it is also found that the n-type feature is stable even in water and high temperature (< 400 °C) conditions. The pn junction structure is also realized by position selective doping of Cs. This very stable pn junction TFT is important for the practical application of SWNTs-based thin film electronics.

  1. Measurement of Beta Particles Induced Electron-Hole Pairs Recombination in Depletion Region of GaAs PN Junction

    NASA Astrophysics Data System (ADS)

    Chen, Hai-Yang; Jiang, Lan; Li, Da-Rang

    2011-05-01

    PN junctions and schottky diodes are widely employed as electron-hole pair collectors in electron beam induced current (EBIC) techniques and betavoltaic batteries, in which the recombination in depletion regions is ignored. We measured the beta particles induced electron-hole pairs recombination in the depletion region of a GaAs P+PN+ junction, based on comparisons between measured short currents and ideal values. The results show that only 20% electron-hole pairs in the depletion can be collected, causing the short current. This indicates an electron-hole pair diffusion length of 0.2μm in the depletion region. Hence, it is necessary to evaluate the recombination in the EBIC techniques and betavoltaic design.

  2. High Fill Factors of Si Solar Cells Achieved by Using an Inverse Connection Between MOS and PN Junctions

    NASA Astrophysics Data System (ADS)

    Wang, Liang-Xing; Zhou, Zhi-Quan; Zhang, Tian-Ning; Chen, Xin; Lu, Ming

    2016-10-01

    Fill factors (FFs) of ~0.87 have been obtained for crystalline Si (c-Si) solar cells based on Ag front contacts after rapid thermal annealing. The usual single PN junction model fails to explain the high FF result. A metal/oxide/semiconductor (MOS) junction at the emitter is found to be inversely connected to the PN one, and when its barrier height/ e is close to the open-circuit voltage of the solar cell, very high FF is obtainable. In this work, although the open-circuit voltage (<580 mV) is not high here, the efficiency of c-Si solar cell still reaches the state-of-the-art value (>20 %) due to the high FF achieved.

  3. Determination of some basic physical parameters of SnO based on SnO/Si pn heterojunctions

    SciTech Connect

    Li, Xiuxia; Liang, Lingyan E-mail: h-cao@nimte.ac.cn; Cao, Hongtao E-mail: h-cao@nimte.ac.cn; Qin, Ruifeng; Zhang, Hongliang; Gao, Junhua; Zhuge, Fei

    2015-03-30

    P-SnO/n-Si heterojunctions were constructed by using e-beam evaporation in combination with ultra-violet lithography technique. The current-voltage and capacitance-voltage characteristics of the pn heterojunctions were systematically investigated, through which the diode parameters, such as the turn-on voltage, forward-to-reverse current ratio, series resistance, ideality factor, and build-in voltage, were also determined. In particular, the pn heterojunctions presented a relatively good electrical rectifying behavior, with a forward-to-reverse current ratio up to 58 ± 5 at ±2.0 V. The relative permittivity and work function of the SnO films were measured to be 18.8 ± 1.7 and 4.3 eV, respectively. The energy band diagram of the heterojunctions was depicted in detail, which can interpret the rectifying behavior very well.

  4. Four-terminal magneto-transport in graphene p-n junctions created by spatially selective doping.

    PubMed

    Lohmann, Timm; von Klitzing, Klaus; Smet, Jurgen H

    2009-05-01

    In this paper, we describe a graphene p-n junction created by chemical doping. We find that chemical doping does not reduce mobility in contrast to top-gating. The preparation technique has been developed from systematic studies about influences on the initial doping of freshly prepared graphene. We investigated the removal of adsorbates by vacuum treatment, annealing, and compensation doping using NH(3). Hysteretic behavior is observed in the electric field effect due to dipolar adsorbates like water and NH(3). Finally we demonstrate spatially selective doping of graphene using patterned PMMA. Four-terminal transport measurements of the p-n devices reveal edge channel mixing in the quantum hall regime. Quantized resistances of h/e(2), h/3e(2) and h/15e(2) can be observed as expected from theory.

  5. Estimation of defect activation energy around pn interfaces of Cu(In,Ga)Se2 solar cells using impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Sakakura, Hidenori; Itagaki, Masayuki; Sugiyama, Mutsumi

    2016-01-01

    We investigate the defect activation energy around the pn interface of Cu(In,Ga)Se2 (CIGS)-based solar cells using a simple electrochemical impedance spectroscopy. By applying AC and DC voltages to the solar cells, we observed an “inductive” element around the pn interface, which is ignored in conventional deep-level transient spectroscopy or admittance spectroscopy. A defect model is evaluated by proposing an equivalent circuit that includes a positive/negative constant phase element (CPE) to represent the area around the CdS/CIGS interface. By fitting the impedance data, the CPE index and CPE constant show a relationship with the defect activation energy or defect concentration. This result is significant because it may help reveal the defect properties of CIGS solar cells or any other semiconductor devices.

  6. Imaging of built-in electric field at a p-n junction by scanning transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Shibata, Naoya; Findlay, Scott D.; Sasaki, Hirokazu; Matsumoto, Takao; Sawada, Hidetaka; Kohno, Yuji; Otomo, Shinya; Minato, Ryuichiro; Ikuhara, Yuichi

    2015-06-01

    Precise measurement and characterization of electrostatic potential structures and the concomitant electric fields at nanodimensions are essential to understand and control the properties of modern materials and devices. However, directly observing and measuring such local electric field information is still a major challenge in microscopy. Here, differential phase contrast imaging in scanning transmission electron microscopy with segmented type detector is used to image a p-n junction in a GaAs compound semiconductor. Differential phase contrast imaging is able to both clearly visualize and quantify the projected, built-in electric field in the p-n junction. The technique is further shown capable of sensitively detecting the electric field variations due to dopant concentration steps within both p-type and n-type regions. Through live differential phase contrast imaging, this technique can potentially be used to image the electromagnetic field structure of new materials and devices even under working conditions.

  7. Optical properties of InGaPN epilayer with low nitrogen content grown by molecular beam epitaxy

    SciTech Connect

    Kim, Kang Min; Nonoguchi, Shogo; Krishnamurthy, Daivasigamani; Emura, Shuichi; Hasegawa, Shigehiko; Asahi, Hajime

    2012-09-15

    The effect of nitrogen concentration on the optical properties of InGaP(N) epilayer was investigated. The temperature dependence of the photoluminescence (PL) peak energy of InGaPN (N = 1%) epilayer around room temperature was found to be almost one-half of that of InGaP epilayer. The incorporation of N causes the reduction of the coupling constant for the electron-phonon interaction, leading to the reduced temperature dependence of the PL peak shift. Thermal activation energy, which is deduced from the Arrhenius plot of PL intensity, was decreased by N incorporation. The reduced PL quenching is discussed in terms of the changes in the band alignment at the InGaPN/GaAs heterointerface by the increase in the N concentration.

  8. Polarization induced pn-junction without dopant in graded AlGaN coherently strained on GaN

    NASA Astrophysics Data System (ADS)

    Li, Shibin; Ware, Morgan; Wu, Jiang; Minor, Paul; Wang, Zhiming; Wu, Zhiming; Jiang, Yadong; Salamo, Gregory J.

    2012-09-01

    We propose a type of pn-junction not formed by impurity-doping, but rather by grading the Al composition in an AlxGa1-xN thin film, resulting in alternating p and n conducting regions due to polarization charge. By linearly grading AlxGa1-xN from 0% to x (x ≤ 30%) and back to 0% Al, a polarization induced pn-junction is formed, even in the absence of any impurity doping. X-ray diffraction reciprocal space maps are used to determine the strain state of the different graded composition samples. Polarization induced doping also provides a solution to the problem of p-type doping efficiency for III-nitrides.

  9. Imaging of built-in electric field at a p-n junction by scanning transmission electron microscopy.

    PubMed

    Shibata, Naoya; Findlay, Scott D; Sasaki, Hirokazu; Matsumoto, Takao; Sawada, Hidetaka; Kohno, Yuji; Otomo, Shinya; Minato, Ryuichiro; Ikuhara, Yuichi

    2015-06-12

    Precise measurement and characterization of electrostatic potential structures and the concomitant electric fields at nanodimensions are essential to understand and control the properties of modern materials and devices. However, directly observing and measuring such local electric field information is still a major challenge in microscopy. Here, differential phase contrast imaging in scanning transmission electron microscopy with segmented type detector is used to image a p-n junction in a GaAs compound semiconductor. Differential phase contrast imaging is able to both clearly visualize and quantify the projected, built-in electric field in the p-n junction. The technique is further shown capable of sensitively detecting the electric field variations due to dopant concentration steps within both p-type and n-type regions. Through live differential phase contrast imaging, this technique can potentially be used to image the electromagnetic field structure of new materials and devices even under working conditions.

  10. Yield: it's now an entitlement

    NASA Astrophysics Data System (ADS)

    George, Bill

    1994-09-01

    Only a few years ago, the primary method of cost reduction and productivity improvement in the semiconductor industry was increasing manufacturing yields throughout the process. Many of the remarkable reliability improvements realized over the past decade have come about as a result of actions that were originally taken primarily to improve device yields. Obviously, the practice of productivity improvement through yield enhancement is limited to the attainment of 100% yield, at which point some other mechanism must be employed. Traditionally, new products have been introduced to manufacturing at a point of relative immaturity, and semiconductor producers have relied on the traditional `learning curve' method of yield improvement to attain profitable levels of manufacturing yield. Recently, results of a survey of several fabs by a group of University of California at Berkeley researchers in the Competitive Semiconductor Manufacturing Program indicate that most factories learn at about the same rate after startup, in terms of both line yield and defectivity. If this is indeed generally true, then the most competitive factor is the one that starts with the highest yield, and it is difficult to displace a leader once his lead has been established. The two observations made above carry enormous implications for the semiconductor development or manufacturing professional. First, one must achieve very high yields in order to even play the game. Second, the achievement of competitive yields over time in the life of a factory is determined even before the factory is opened, in the planning and development phase. Third, and perhaps most uncomfortable for those of us who have relied on yield improvement as a cost driver, the winners of the nineties will find new levers to drive costs down, having already gotten the benefit of very high yield. This paper looks at the question of how the winners will achieve the critical measures of success, high initial yield and utilization

  11. A Multi-institutional Investigation of the Prognostic Value of Lymph Nodal Yield in Advanced Stage Oral Cavity Squamous Cell Carcinoma (OCSCC)

    PubMed Central

    Jaber, James J.; Zender, Chad A.; Mehta, Vikas; Davis, Kara; Ferris, Robert L.; Lavertu, Pierre; Rezaee, Rod; Feustel, Paul J.

    2014-01-01

    Background Although existing literature provides surgical recommendations for treating occult disease (cN0) in early stage oral cavity squamous cell carcinoma, a focus on late stage OCSCC is less pervasive. Methods The records of 162 late stage OCSCC pN0 individuals that underwent primary neck dissections were reviewed. Lymph node yield (LNY) as a prognosticator was examined. Results Despite being staged pN0, patients that had a higher LNY had an improved regional/distant control rates, DFS, DSS, and OS. LNY consistently outperformed all other standard variables as being the single best prognostic factor with a tight risk ratio range (RR = 0.95–0.98) even when correcting for the number of lymph nodes examined. Conclusion The results of this study showed that lower regional recurrence rates and improved survival outcomes were seen as lymph node yield increased for advanced T-stage OCSCC pN0. This suggests that increasing lymph node yield with an extended cervical lymphadenectomy may result in lower recurrence rates and improved survival outcomes for this advanced stage group. PMID:24038739

  12. Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Performance Verification Report: METSAT (S/N) AMSU-A1 Receiver Assemblies P/N 1356429-1 S/N F06 and P/N 1356409-1 S/N F06

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This is the Performance Verification Report, METSAT (S/N 109) AMSU-A1 Receiver Assemblies, P/N 1356429-1 S/N F06 and P/N 1356409 S/N F06, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

  13. A possible cooperative structural transition of DNA in the 0.25-2.0 pN range.

    PubMed

    Schurr, J Michael

    2015-05-28

    The measured effective torsional rigidities of single twisted DNAs under various tensions conflict with theoretical predictions of Moroz and Nelson (MN) at low forces in the 0.25-2.0 pN range. However, MN theory was recently shown to agree well with effective torsional rigidities obtained from simulations, indicating that MN theory is valid down to 0.25 pN for a filament with a constant intrinsic torsional rigidity. Here MN theory is used with an assumed persistence length, 50 nm, to obtain the force-dependent intrinsic torsional rigidity of the filament at each force from its measured effective torsional rigidity. The resulting values rise ∼1.8-fold with increasing force from 0.25 to 2.0 pN. Unexpected behavior of the relative extensions of the untwisted DNAs of Mosconi et al. is noted, and ascribed to a small increase in contour length with force over the 0.18-2.0 pN range. The variations of both the intrinsic torsional rigidity and rise per base pair (bp) with force are suggested to arise from a force-induced shift of a cooperative equilibrium between two conformations with different rises per bp. A two-state nearest-neighbor model is formulated, and ranges of optimal parameters are determined by fitting the model to the experimental differences in rise per bp as a function of force. Optimal adjustment of the torsion elastic constants of the two states enables the same optimal model(s) with fixed parameters to provide reasonably good fits of the experimental torsion elastic constant data. The results reconcile single-molecule measurements on DNAs under tension with numerous results from fluorescence polarization anisotropy, topoisomer distributions, X-ray scattering of DNAs with attached gold colloids, and other kinds of measurements.

  14. Diffused junction p(+)-n solar cells in bulk GaAs. II - Device characterization and modelling

    NASA Technical Reports Server (NTRS)

    Keeney, R.; Sundaram, L. M. G.; Rode, H.; Bhat, I.; Ghandhi, S. K.; Borrego, J. M.

    1984-01-01

    The photovoltaic characteristics of p(+)-n junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are presented in detail. Quantum efficiency measurements were analyzed and compared to computer simulations of the cell structure in order to determine material parameters such as diffusion length, surface recombination velocity and junction depth. From the results obtained it is projected that proper optimization of the cell parameters can increase the efficiency of the cells to close to 20 percent.

  15. Electrocatalytic Reduction of Carbon Dioxide with a Well-Defined PN 3 -Ru Pincer Complex

    SciTech Connect

    Min, Shixiong; Rasul, Shahid; Li, Huaifeng; Grills, David C.; Takanabe, Kazuhiro; Li, Lain-Jong; Huang, Kuo-Wei

    2015-11-13

    We established a well-defined PN3-Ru pincer complex (5) bearing a redox-active bipyridine ligand with an aminophosphine arm as an effective and stable molecular electrocatalyst for CO2 reduction to CO and HCOOH with negligible formation of H2 in a H2O/MeCN mixture.

  16. Direct assessment of p-n junctions in single GaN nanowires by Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Minj, Albert; Cros, Ana; Auzelle, Thomas; Pernot, Julien; Daudin, Bruno

    2016-09-01

    Making use of Kelvin probe force microscopy, in dark and under ultraviolet illumination, we study the characteristics of p-n junctions formed along the axis of self-organized GaN nanowires (NWs). We map the contact potential difference of the single NW p-n junctions to locate the space charge region and directly measure the depletion width and the junction voltage. Simulations indicate a shrinkage of the built-in potential for NWs with small diameter due to surface band bending, in qualitative agreement with the measurements. The photovoltage of the NW/substrate contact is studied by analyzing the response of NW segments with p- and n-type doping under illumination. Our results show that the shifts of the Fermi levels, and not the changes in surface band bending, are the most important effects under above band-gap illumination. The quantitative electrical information obtained here is important for the use of NW p-n junctions as photovoltaic or rectifying devices at the nanoscale, and is especially relevant since the technique does not require the formation of ohmic contacts to the NW junction.

  17. Chemically fixed p-n heterojunctions for polymer electronics by means of covalent B-F bond formation

    NASA Astrophysics Data System (ADS)

    Hoven, Corey V.; Wang, Huiping; Elbing, Mark; Garner, Logan; Winkelhaus, Daniel; Bazan, Guillermo C.

    2010-03-01

    Widely used solid-state devices fabricated with inorganic semiconductors, including light-emitting diodes and solar cells, derive much of their function from the p-n junction. Such junctions lead to diode characteristics and are attained when p-doped and n-doped materials come into contact with each other. Achieving bilayer p-n junctions with semiconducting polymers has been hindered by difficulties in the deposition of thin films with independent p-doped and n-doped layers. Here we report on how to achieve permanently fixed organic p-n heterojunctions by using a cationic conjugated polyelectrolyte with fluoride counteranions and an underlayer composed of a neutral conjugated polymer bearing anion-trapping functional groups. Application of a bias leads to charge injection and fluoride migration into the neutral layer, where irreversible covalent bond formation takes place. After the initial charging and doping, one obtains devices with no delay in the turn on of light-emitting electrochemical behaviour and excellent current rectification. Such devices highlight how mobile ions in organic media can open opportunities to realize device structures in ways that do not have analogies in the world of silicon and promise new opportunities for integrating organic materials within technologies now dominated by inorganic semiconductors.

  18. Polymer Light-Emitting Electrochemical Cells:  In Situ Formation of a Light-Emitting p-n Junction.

    PubMed

    Pei, Q; Yang, Y; Yu, G; Zhang, C; Heeger, A J

    1996-04-24

    Solid-state polymer light-emitting electrochemical cells have been fabricated using thin films of blends of poly(1,4-phenylenevinylene) and poly(ethylene oxide) complexed with lithium trifluoromethanesulfonate. The cells contain three layers:  the polymer film (as the emissive layer) and indium-tin oxide and aluminum films as the two contact electrodes. When externally biased, the conjugated polymers are p-doped and n-doped on opposite sides of the polymer layer, and a light-emitting p-n junction is formed in between. The admixed polymer electrolyte provides the counterions and the ionic conductivity necessary for doping. The p-n junction is dynamic and reversible, with an internal built-in potential close to the band gap of the redox-active conjugated polymer (2.4 eV for PPV). Green light emitted from the p-n junction was observed with a turn-on voltage of about 2.4 V. The devices reached 8 cd/m(2) at 3 V and 100 cd/m(2) at 4 V, with an external quantum efficiency of 0.3-0.4% photons/electron. The response speed of these cells was around 1 s, depending on the diffusion of ions. Once the light-emitting junction had been formed, the subsequent operation had fast response (microsecond scale or faster) and was no longer diffusion-controlled. PMID:27579778

  19. Direct assessment of p-n junctions in single GaN nanowires by Kelvin probe force microscopy.

    PubMed

    Minj, Albert; Cros, Ana; Auzelle, Thomas; Pernot, Julien; Daudin, Bruno

    2016-09-23

    Making use of Kelvin probe force microscopy, in dark and under ultraviolet illumination, we study the characteristics of p-n junctions formed along the axis of self-organized GaN nanowires (NWs). We map the contact potential difference of the single NW p-n junctions to locate the space charge region and directly measure the depletion width and the junction voltage. Simulations indicate a shrinkage of the built-in potential for NWs with small diameter due to surface band bending, in qualitative agreement with the measurements. The photovoltage of the NW/substrate contact is studied by analyzing the response of NW segments with p- and n-type doping under illumination. Our results show that the shifts of the Fermi levels, and not the changes in surface band bending, are the most important effects under above band-gap illumination. The quantitative electrical information obtained here is important for the use of NW p-n junctions as photovoltaic or rectifying devices at the nanoscale, and is especially relevant since the technique does not require the formation of ohmic contacts to the NW junction.

  20. Identification of PSEN2 mutation p.N141I in Argentine pedigrees with early-onset familial Alzheimer's disease.

    PubMed

    Muchnik, Carolina; Olivar, Natividad; Dalmasso, María Carolina; Azurmendi, Pablo Javier; Liberczuk, Cynthia; Morelli, Laura; Brusco, Luis Ignacio

    2015-10-01

    Presenilin 2 gene (PSEN2) mutations account for <5% of all early-onset familial Alzheimer's disease (EOFAD) cases and only 13 have strong evidence for pathogenicity. We aimed to investigate the presence of PSEN2 mutation p.N141I and characterize the clinical phenotypes in 2 Argentine pedigrees (AR2 and AR3) with clinical symptoms of EOFAD. Detailed clinical assessments and genetic screening for PSEN2 and APOE genes were carried out in 19 individuals of AR2 and AR3 families. The p.N141I mutation was identified in all affected subjects and was associated with prominent early onset, rapidly progressive dementia, neurologic, and behavioral symptoms. AR2 and AR3 families share the same Volga German ancestry as all the families reported presenting this mutation. To our knowledge, this is the first report of PSEN2 mutation p.N141I in Argentina and even more, in South America. Our contribution increases the total number of described families carrying this mutation and help to improve the characterization of clinical phenotype in EOFAD associated to PSEN2 mutations.

  1. Direct assessment of p-n junctions in single GaN nanowires by Kelvin probe force microscopy.

    PubMed

    Minj, Albert; Cros, Ana; Auzelle, Thomas; Pernot, Julien; Daudin, Bruno

    2016-09-23

    Making use of Kelvin probe force microscopy, in dark and under ultraviolet illumination, we study the characteristics of p-n junctions formed along the axis of self-organized GaN nanowires (NWs). We map the contact potential difference of the single NW p-n junctions to locate the space charge region and directly measure the depletion width and the junction voltage. Simulations indicate a shrinkage of the built-in potential for NWs with small diameter due to surface band bending, in qualitative agreement with the measurements. The photovoltage of the NW/substrate contact is studied by analyzing the response of NW segments with p- and n-type doping under illumination. Our results show that the shifts of the Fermi levels, and not the changes in surface band bending, are the most important effects under above band-gap illumination. The quantitative electrical information obtained here is important for the use of NW p-n junctions as photovoltaic or rectifying devices at the nanoscale, and is especially relevant since the technique does not require the formation of ohmic contacts to the NW junction. PMID:27518150

  2. AlGaAs/InGaAsN/GaAs PnP double heterojunction bipolar transistor

    SciTech Connect

    Chang, P.C.; Baca, A.G.; Li, N.Y.; Sharps, P.R.; Hou, H.Q.; Laroche, J.R.; Ren, F.

    2000-01-04

    The authors demonstrated a functional PnP double heterojunction bipolar transistor (DHBT) using AlGaAs, InGaAsN, and GaAs. The band alignment between InGaAsN and GaAs has a large {triangle}E{sub c} and negligible {triangle}E{sub v}, this unique characteristic is very suitable for PnP DHBT applications. The metalorganic vapor phase epitaxy (MOCVD) grown Al{sub 0.3}Ga{sub 0.7}As/In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01}/GaAs PnP DHBT is lattice matched to GaAs and has a peak current gain of 25. Because of the smaller bandgap (E{sub g}=1.20eV) of In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} used for the base layer, this device has a low V{sub ON} of 0.79 V, which is 0.25 V lower than in a comparable Pnp AlGaAs/GaAs HBT. And because GaAs is used for the collector, its BV{sub CEO} is 12 V, consistent with BV{sub CEO} of AlGaAs/GaAs HBTs.

  3. Significant Prognostic Factors for Completely Resected pN2 Non-small Cell Lung Cancer without Neoadjuvant Therapy

    PubMed Central

    Nakao, Masayuki; Mun, Mingyon; Nakagawa, Ken; Nishio, Makoto; Ishikawa, Yuichi; Okumura, Sakae

    2015-01-01

    Purpose: To identify prognostic factors for pathologic N2 (pN2) non-small cell lung cancer (NSCLC) treated by surgical resection. Methods: Between 1990 and 2009, 287 patients with pN2 NSCLC underwent curative resection at the Cancer Institute Hospital without preoperative treatment. Results: The 5-year overall survival (OS), cancer-specific survival (CSS), and recurrence-free survival (RFS) rates were 46%, 55% and 24%, respectively. The median follow-up time was 80 months. Multivariate analysis identified four independent predictors for poor OS: multiple-zone mediastinal lymph node metastasis (hazard ratio [HR], 1.616; p = 0.003); ipsilateral intrapulmonary metastasis (HR, 1.042; p = 0.002); tumor size >30 mm (HR, 1.013; p = 0.002); and clinical stage N1 or N2 (HR, 1.051; p = 0.030). Multivariate analysis identified three independent predictors for poor RFS: multiple-zone mediastinal lymph node metastasis (HR, 1.457; p = 0.011); ipsilateral intrapulmonary metastasis (HR, 1.040; p = 0.002); and tumor size >30 mm (HR, 1.008; p = 0.032). Conclusion: Multiple-zone mediastinal lymph node metastasis, ipsilateral intrapulmonary metastasis, and tumor size >30 mm were common independent prognostic factors of OS, CSS, and RFS in pN2 NSCLC. PMID:25740454

  4. [Effects of endophytic Paenibacillus polymyxa S-7 on photosynthesis, yield, and quality of sugar beet].

    PubMed

    Shi, Ying-wu; Lou, Kai; Li, Chun; Yang, Liang; Wang, Xing-qin; Liu, Wen-yu

    2009-03-01

    This study showed that inoculation of endophytic Paenibacillus polymyxa S-7 could significantly (P < 0.05) promote the photosynthesis of sugar beet. After the inoculation, the leaf net photosynthetic rate (Pn), stomatal limitation (Ls), stomatal conductance (Gs), and transpiration rate (Tr) increased by 16.11%, 23.82%, 41.91%, and 34.80%, respectively, while the stomatal intercellular CO2 concentration (Ci) decreased by 21.09%. Inoculation of endophytic P. polymyxa S-7 could also increase sugar beet yield and its quality significantly (P < 0.05), with the tuberous root biomass and its sugar content increased by 25.63% and 17.46%, respectively. It was concluded that endophytic P. polymyxa S-7 not only affected the photosynthetic parameters, but also promoted the yield and quality of sugar beet.

  5. Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Performance Verification Report: Antenna Drive Subsystem METSAT AMSU-A2 (PN:1331200-2, SN:108)

    NASA Technical Reports Server (NTRS)

    Haapala, C.

    1999-01-01

    This is the Performance Verification Report, Antenna Drive Subassembly, Antenna Drive Subsystem, METSAT AMSU-A2 (P/N 1331200-2, SN: 108), for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

  6. Chemical abundances of planetary nebulae from optical recombination lines - III. The Galactic bulge PN M 1-42 and M 2-36

    NASA Astrophysics Data System (ADS)

    Liu, X.-W.; Luo, S.-G.; Barlow, M. J.; Danziger, I. J.; Storey, P. J.

    2001-10-01

    We present deep, high-resolution optical spectra of two Galactic bulge planetary nebulae (PN), M 1-42 and M 2-36. The spectra show very prominent and rich optical recombination lines (ORLs) from C, N, O and Ne ions. Infrared spectra from [formmu10]2.4-197μm were also obtained using the Short and Long Wavelength Spectrometer (SWS and LWS) on board ISO. The optical and infrared spectra, together with archival IUE spectra, are used to study their density and thermal characteristics and to determine elemental abundances. We determine the optical and UV extinction curve towards these two bulge PN using observed Hi and Heii recombination line fluxes and the radio free-free continuum flux density. In the optical, the reddening curve is found to be consistent with the standard Galactic extinction law, with a total to selective extinction ratio [formmu11]R≡A(V)/E(B-V)=3.1. However, the extinction in the UV is found to be much steeper, consistent with the earlier finding of Walton, Barlow & Clegg. The rich ORL spectra from C, N, O and Ne ions detected from the two nebulae have been used to determine the abundances of these elements relative to hydrogen. In all cases, the resultant ORL abundances are found to be significantly higher than the corresponding values deduced from collisionally excited lines (CELs). In M 2-36, the discrepancies are about a factor of 5 for all four elements studied. In M 1-42, the discrepancies reach a factor of about 20, the largest ever observed in a PN. M 1-42 also has the lowest Balmer jump temperature ever determined for a PN, [formmu12]Te(BJ)=3560K, 5660K lower than its [Oiii] forbidden line temperature. We compare the observed intensities of the strongest Oii ORLs from different electronic configurations, including λ4649 from [formmu13]3s-3p, λ4072 from [formmu14]3p-3d, λ4089 from [formmu15]3d-4f, and λ4590 and λ4190 from the doubly excited [formmu16]3s'-3p' and [formmu17]3p'-3d' configurations, respectively. In all cases, in spite of

  7. Quantum yield spectra and I-V properties of a GaAs solar cell grown on a Ge substrate

    NASA Astrophysics Data System (ADS)

    Partain, L. D.; Virshup, G. F.; Kaminar, N. R.

    A measured quantum yield spectrum showed a weak Ge junction in tandem with a strong GaAs junction for a heteroface p/n GaAs junction grown by MOCVD (metal-organic chemical vapor deposition) on an n-Ge substrate. In natural sunlight, this device had a notched-shaped I-V that limited its fill factor (FF) to 0.612 and its efficiency to 18 percent AM2.6D, which are values below those typical of similar heteroface p/n GaAs junctions grown on n-GaAs substrates. The notch disappeared and the FF increased to 0.806 under infrared-rich incandescent light. The notch deepened and the FF decreased to 0.606 under infrared-poor xenon light. This is modeled as a Ge junction with a soft I-V in tandem with a standard GaAs p/n junction. Calculations of the relative infrared content of sunlight predicts that this cell's FF should progressively decrease as the air mass spectrum progressively loses infrared content in going from AM2.6 through AM1.5 to AM0. The best model found for the Ge junction transport properties is an n-GaAs/n-Ge isotype heterojunction possibly controlled by space-charge-limited-current mechanisms.

  8. A Comparison of Photocurrent Mechanisms in Quasi-Metallic and Semiconducting Carbon Nanotube pn-Junctions.

    PubMed

    Chang, Shun-Wen; Hazra, Jubin; Amer, Moh; Kapadia, Rehan; Cronin, Stephen B

    2015-12-22

    We present a comparative study of quasi-metallic (Eg ∼ 100 meV) and semiconducting (Eg ∼ 1 eV) suspended carbon nanotube pn-junctions introduced by electrostatic gating. While the built-in fields of the quasi-metallic carbon nanotubes (CNTs) are 1-2 orders of magnitude smaller than those of the semiconducting CNTs, their photocurrent is 2 orders of magnitude higher than the corresponding semiconducting CNT devices under the same experimental conditions. Here, the large exciton binding energy in semiconducting nanotubes (∼400 meV) makes it difficult for excitons to dissociate into free carriers that can contribute to an externally measured photocurent. As such, semiconducting nanotubes require a phonon to assist in the exciton dissociation process, in order to produce a finite photocurrent, while quasi-metallic nanotubes do not. The quasi-metallic nanotubes have much lower exciton binding energies (∼50 meV) as well as a continuum of electronic states to decay into and, therefore, do not require the absorption of a phonon in order to dissociate, making it much easier for these excitons to produce a photocurrent. We performed detailed simulations of the band energies in quasi-metallic and semiconducting nanotube devices in order to obtain the electric field profiles along the lengths of the nanotubes. These simulations predict maximum built-in electric field strengths of 2.3 V/μm for semiconducting and 0.032-0.22 V/μm for quasi-metallic nanotubes under the applied gate voltages used in this study.

  9. Electrical and Optical Performance Characteristics of p/n InGaAs Monolithic Interconnected Modules

    NASA Technical Reports Server (NTRS)

    Wilt, David M.; Fatemi, Navid S.; Jenkins, Phillip P.; Weizer, Victor G.; Hoffman, Richard W., Jr.; Murray, Christopher S.; Riley, David R.

    1997-01-01

    There has been a traditional trade-off in ThermoPhotoVoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A Monolithic Interconnected Module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual Indium Gallium Arsenide (InGaAs) devices series-connected on a single semi-insulating Indium Phosphide (InP) substrate. The MIMs are exposed to the entire emitter output, thereby maximizing output power density. An InfraRed (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74eV InGaAs, have demonstrated V(sub infinity) = 3.2 volts, J(sub sc) = 70 mA/sq cm and a fill factor of 66% under flashlamp testing. IR reflectance measurements (greater than 2 microns) of these devices indicate a reflectivity of greater than 82%. MIM devices produced from 0.55 eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

  10. The 2H(e, e' p)n reaction at large energy transfers

    NASA Astrophysics Data System (ADS)

    Willering, Hendrik Willem

    2003-04-01

    At the ELSA accelerator facillity in Bonn, Germany, we have measured the deutron breakup reaction 2H(e, e' p)n at four-momentum transfers around Q2 = -0 .20(GeV/c)2 with an electron beam energy of E0 = 1.6 GeV. The cross section has been determined for energy transfers extending from the quasielastic region to just below the Delta(1232)-resonance, and for proton polar angles up to Thetanp = 145 o in the center-of-momentum system. This angular range represents missing momenta up to pm = 1000 MeV/c. By detecting the scattered protons in two segmented 3 3 m2 scintillator time-of-flight detectors, we have covered a considerable part of the out-of-plane region. The clearly visible variation of the cross section with the proton azimuthal angle fnp has enabled us to extract values for the longitudinal-transverse interference form factor fLT and for a combination of the non-interference form factors fL and fT for proton angles up to Thetanp = 40o in the center-of-momentum system. The experimental results have been compared to the full model calculations by Arenhövel et al. For the major part of our kinematical range the shape of the cross section and of the form factors is reproduced by the model, but some differences remain in the normalization, especially at higher energy transfers. Our results corroborate the conclusions from other recent experiments concerning the importance of subnuclear degrees-of-freedom beyond the quasielastic region, but the discrepancy indicates that the model can still be improved

  11. 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.

  12. GaAsPN-based PIN solar cells MBE-grown on GaP substrates: toward the III-V/Si tandem solar cell

    NASA Astrophysics Data System (ADS)

    Da Silva, M.; Almosni, S.; Cornet, C.; Létoublon, A.; Levallois, C.; Rale, P.; Lombez, L.; Guillemoles, J.-F.; Durand, O.

    2015-03-01

    GaAsPN semiconductors are promising material for the elaboration of high efficiencies tandem solar cells on silicon substrates. GaAsPN diluted nitride alloy is studied as the top junction material due to its perfect lattice matching with the Si substrate and its ideal bandgap energy allowing a perfect current matching with the Si bottom cell. We review our recent progress in materials development of the GaAsPN alloy and our recent studies of some of the different building blocks toward the elaboration of a PIN solar cell. A lattice matched (with a GaP(001) substrate, as a first step toward the elaboration on a Si substrate) 1μm-thick GaAsPN alloy has been grown by MBE. After a post-growth annealing step, this alloy displays a strong absorption around 1.8-1.9 eV, and efficient photoluminescence at room temperature suitable for the elaboration of the targeted solar cell top junction. Early stage GaAsPN PIN solar cells prototypes have been grown on GaP (001) substrates, with 2 different absorber thicknesses (1μm and 0.3μm). The external quantum efficiencies and the I-V curves show that carriers have been extracted from the GaAsPN alloy absorbers, with an open-circuit voltage of 1.18 V, while displaying low short circuit currents meaning that the GaAsPN structural properties needs a further optimization. A better carrier extraction has been observed with the absorber displaying the smallest thickness, which is coherent with a low carriers diffusion length in our GaAsPN compound. Considering all the pathways for improvement, the efficiency obtained under AM1.5G is however promising.

  13. Genotypic variability in physiological, biomass and yield response to drought stress in pigeonpea.

    PubMed

    Vanaja, M; Maheswari, M; Sathish, P; Vagheera, P; Jyothi Lakshmi, N; Vijay Kumar, G; Yadav, S K; Razzaq, Abdul; Singh, Jainender; Sarkar, B

    2015-10-01

    Three pigeonpea (Cajanus cajan L. Millsp.) genotypes- GT-1, AKP-1 and PRG-158 with varying crop duration, growth habit and flowering pattern were evaluated for variability in their response for drought stress. Drought stress was imposed at initiation of flowering and the observations on biomass and seed yield parameters were recorded at harvest. The magnitude of response of individual component to drought stress was found to be genotype specific. Drought stress significantly decreased photosynthetic rate (PN), transpiration rate (Tr) and relative water content (RWC) in all the genotypes, however the magnitude of reduction differed with genotype. With drought stress, the reduction of PN was highest in GT-1 while reduction in Tr was highest in PRG-158. The genotype AKP-1, accumulated significantly higher concentrations of osmotic solutes especially proline under water deficit stress, this facilitated it to maintain higher relative water content (RWC) and lower malondialdehyde (MDA) content as compared to other genotypes. Drought stress also impacted biomass production and their partitioning to vegetative and reproductive components at harvest. There was significant variability between the genotypes for seed yield under drought stress while it was non-significant under well-watered condition. Drought stress enhanced flower drop and decreased flower to pod conversion resulting in reduced pod number and seed number in PRG-158 and GT-1. The genotype AKP-1 recorded superior performance for seed yield under stress environment due to its ability in maintaining pod and seed number as well as improved test weight (100 seed weight). Under drought stress, significant positive association of seed yield with proline, seed number, pod number and test weight clearly indicating their role in drought tolerance. PMID:26600680

  14. [Effects of potato/soybean intercropping on photosynthetic characteristics and yield of three soybean varieties].

    PubMed

    Chen, Guang-rong; Yang, Wen-yu; Zhang, Guo-hong; Wang, Li-ming; Yang, Ru-ping; Yong, Tai-wen; Liu, Wei-guo

    2015-11-01

    The potato/soybean intercropping trials using three soybean varieties including Zhonghuang 30 (early-maturing variety) , Jidou 17 (mid maturing variety) and Qihuang 34 (late maturing variety) with the sole cropping potato as control were carried out to determine the dynamic changes of leaf area index (LAI) of soybean, accumulation of dry matter, photosynthetic characteristics, yield and yield components. The results showed that the LAI, dry matter accumulation, net photosynthesis (Pn), transpiration rate (Tr) and stomatal conduction (g(s)) of soybean in all intercropping systems were lower than in monoculture because of the influence of intensified lower light during earlier growing stage, and the duration from planting to flowering was extended. When the potato was harvested, the LAI, dry matter accumulation, Pn, Tr and g(s) of soybean in all intercropping systems increased, especially for mid-maturing and late-maturing varieties, which became much closer to those in the monoculture. Compared with sole cropping, the pods per plant, seeds per plant and seeds per pod in intercropping system significantly decreased by 22.0%, 36.0% and 17.6% for early-maturing soybean, 5.1%, 13.1% and 8.9% for mid-maturing soybean, 5.7%, 7.6% and 2.1% for late-maturing soybean, respectively. The yields of mid-maturing and late-maturing varieties in intercropping systems were higher than that of the early-maturing, which increased by 92.4% and 163.4%, with the land equivalent ratio (LER) of 1.81 and 1.84, respectively. This suggested that mid-maturing and late-maturing soybean varieties were suitable for intercropping with the potato to improve photosynthetic efficiency, dry matter accumulation and yield of intercropping soybean. PMID:26915189

  15. [Effects of potato/soybean intercropping on photosynthetic characteristics and yield of three soybean varieties].

    PubMed

    Chen, Guang-rong; Yang, Wen-yu; Zhang, Guo-hong; Wang, Li-ming; Yang, Ru-ping; Yong, Tai-wen; Liu, Wei-guo

    2015-11-01

    The potato/soybean intercropping trials using three soybean varieties including Zhonghuang 30 (early-maturing variety) , Jidou 17 (mid maturing variety) and Qihuang 34 (late maturing variety) with the sole cropping potato as control were carried out to determine the dynamic changes of leaf area index (LAI) of soybean, accumulation of dry matter, photosynthetic characteristics, yield and yield components. The results showed that the LAI, dry matter accumulation, net photosynthesis (Pn), transpiration rate (Tr) and stomatal conduction (g(s)) of soybean in all intercropping systems were lower than in monoculture because of the influence of intensified lower light during earlier growing stage, and the duration from planting to flowering was extended. When the potato was harvested, the LAI, dry matter accumulation, Pn, Tr and g(s) of soybean in all intercropping systems increased, especially for mid-maturing and late-maturing varieties, which became much closer to those in the monoculture. Compared with sole cropping, the pods per plant, seeds per plant and seeds per pod in intercropping system significantly decreased by 22.0%, 36.0% and 17.6% for early-maturing soybean, 5.1%, 13.1% and 8.9% for mid-maturing soybean, 5.7%, 7.6% and 2.1% for late-maturing soybean, respectively. The yields of mid-maturing and late-maturing varieties in intercropping systems were higher than that of the early-maturing, which increased by 92.4% and 163.4%, with the land equivalent ratio (LER) of 1.81 and 1.84, respectively. This suggested that mid-maturing and late-maturing soybean varieties were suitable for intercropping with the potato to improve photosynthetic efficiency, dry matter accumulation and yield of intercropping soybean.

  16. Brazil soybean yield covariance model

    NASA Technical Reports Server (NTRS)

    Callis, S. L.; Sakamoto, C.

    1984-01-01

    A model based on multiple regression was developed to estimate soybean yields for the seven soybean-growing states of Brazil. The meteorological data of these seven states were pooled and the years 1975 to 1980 were used to model since there was no technological trend in the yields during these years. Predictor variables were derived from monthly total precipitation and monthly average temperature.

  17. Incorporating phenology into yield models

    NASA Astrophysics Data System (ADS)

    Gray, J. M.; Friedl, M. A.

    2015-12-01

    Because the yields of many crops are sensitive to meteorological forcing during specific growth stages, phenological information has potential utility in yield mapping and forecasting exercises. However, most attempts to explain the spatiotemporal variability in crop yields with weather data have relied on growth stage definitions that do not change from year-to-year, even though planting, maturity, and harvesting dates show significant interannual variability. We tested the hypothesis that quantifying temperature exposures over dynamically determined growth stages would better explain observed spatiotemporal variability in crop yields than statically defined time periods. Specifically, we used National Agricultural and Statistics Service (NASS) crop progress data to identify the timing of the start of the maize reproductive growth stage ("silking"), and examined the correlation between county-scale yield anomalies and temperature exposures during either the annual or long-term average silking period. Consistent with our hypothesis and physical understanding, yield anomalies were more correlated with temperature exposures during the actual, rather than the long-term average, silking period. Nevertheless, temperature exposures alone explained a relatively low proportion of the yield variability, indicating that other factors and/or time periods are also important. We next investigated the potential of using remotely sensed land surface phenology instead of NASS progress data to retrieve crop growth stages, but encountered challenges related to crop type mapping and subpixel crop heterogeneity. Here, we discuss the potential of overcoming these challenges and the general utility of remotely sensed land surface phenology in crop yield mapping.

  18. Fabrication of BiOBr nanosheets@TiO2 nanobelts p-n junction photocatalysts for enhanced visible-light activity

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Huang, Xiang; Tan, Xin; Yu, Tao; Li, Xiangli; Yang, Libin; Wang, Shucong

    2016-03-01

    The construction of p-n junction structure is a smart strategy for improving the photocatalytic activity, since p-n junctions can inhibit the recombination of photo-induced charges. Herein, BiOBr nanosheets@TiO2 nanobelts p-n junction photocatalysts were prepared by assembling BiOBr nanosheets on the surface of TiO2 nanobelts via a hydrothermal route followed by a co-precipitation process. BiOBr@TiO2 p-n junction photocatalysts exhibited enhanced photocatalytic activity in photocatalytic H2 production over water splitting and photodegradation of Rhodamine B (RhB) under visible light irradiation. Mott-Schottky plots confirmed the formation of p-n junctions in the interface of BiOBr and TiO2. The enhanced photocatalytic performance can be ascribed to the 1D nanostructure and the formation of p-n junctions. This work shows a potential application of low cost BiOBr as a substitute for noble metals in photocatalytic H2 production under visible light irradiation.

  19. The coating of conducting copolymer on coordination polymer nanorod: A visible light active p-n heterojunction photocatalyst for H2 production

    NASA Astrophysics Data System (ADS)

    Jia, Yuan; Mei, Ming-liang; Xu, Xin-xin; Wang, Lin-shan

    2016-06-01

    A visible light active p-n heterojunction photocatalyst was synthesized successfully through in-situ chemical oxidation copolymerization of aniline (ANI) and diphenylamine-4-sulfonate (DPAS) with the existence of coordination polymer nanorod (CPNR) under initiation of ammonium persulfate (APS). Compared with neat coordination polymer nanorod, the resulted p-n heterojunction photocatalyst exhibits higher H2 generationrate under visible light irradiation. In this heterojunction photocatalyst, as a p-type semiconductor possessing suitable energy levels with coordination polymer nanorod, poly-(aniline-co-N-(4-sulfophenyl)-aniline) (PAPSA) forms p-n heterojunction with n-type coordination polymer nanorod, the inner electric field of p-n heterojunction accelerates the separation of electrons and holes, which enhances H2 production performance. Furthermore, the influence of concentration ratio between DPAS and ANI on photocatalytic property of the p-n heterojunction photocatalyst was discussed and a reasonable condition to fabricate photocatalyst with high H2 generationrate had been obtained. During photocatalytic water splitting H2 generation, the p-n heterojunction photocatalyst exhibited outstanding stability.

  20. Decomposing global crop yield variability

    NASA Astrophysics Data System (ADS)

    Ben-Ari, Tamara; Makowski, David

    2014-11-01

    Recent food crises have highlighted the need to better understand the between-year variability of agricultural production. Although increasing future production seems necessary, the globalization of commodity markets suggests that the food system would also benefit from enhanced supplies stability through a reduction in the year-to-year variability. Here, we develop an analytical expression decomposing global crop yield interannual variability into three informative components that quantify how evenly are croplands distributed in the world, the proportion of cultivated areas allocated to regions of above or below average variability and the covariation between yields in distinct world regions. This decomposition is used to identify drivers of interannual yield variations for four major crops (i.e., maize, rice, soybean and wheat) over the period 1961-2012. We show that maize production is fairly spread but marked by one prominent region with high levels of crop yield interannual variability (which encompasses the North American corn belt in the USA, and Canada). In contrast, global rice yields have a small variability because, although spatially concentrated, much of the production is located in regions of below-average variability (i.e., South, Eastern and South Eastern Asia). Because of these contrasted land use allocations, an even cultivated land distribution across regions would reduce global maize yield variance, but increase the variance of global yield rice. Intermediate results are obtained for soybean and wheat for which croplands are mainly located in regions with close-to-average variability. At the scale of large world regions, we find that covariances of regional yields have a negligible contribution to global yield variance. The proposed decomposition could be applied at any spatial and time scales, including the yearly time step. By addressing global crop production stability (or lack thereof) our results contribute to the understanding of a key

  1. Grapevine canopy reflectance and yield

    NASA Technical Reports Server (NTRS)

    Minden, K. A.; Philipson, W. R.

    1982-01-01

    Field spectroradiometric and airborne multispectral scanner data were applied in a study of Concord grapevines. Spectroradiometric measurements of 18 experimental vines were collected on three dates during one growing season. Spectral reflectance, determined at 30 intervals from 0.4 to 1.1 microns, was correlated with vine yield, pruning weight, clusters/vine, and nitrogen input. One date of airborne multispectral scanner data (11 channels) was collected over commercial vineyards, and the average radiance values for eight vineyard sections were correlated with the corresponding average yields. Although some correlations were significant, they were inadequate for developing a reliable yield prediction model.

  2. P/N In(Al) GaAs multijunction laser power converters

    NASA Astrophysics Data System (ADS)

    Wojtczuk, Steven; Parados, Themis; Walker, Gilbert

    1994-09-01

    Eight In(AI)GaAs PN junctions grown epitaxially on the semi-insulating wafer were monolithically integrated in series to boost the approximately 0.4V photovoltage per typical In(Al)GaAs junction to over 3 volts for the 1 sq cm laser power converted (LPC) chip. Advantages of multijunction LCP designs include the need for less circuitry for power reconditioning and the potential for lower I(sup 2)R power loss. As an example, these LPC's have a responsivity of approximately 1 amp/watt. With a single junction LPC, 100 watts/sq cm incident power would lead to about 100 A/sq cm short-circuit current at approximately 0.4V open-cicuit voltage. One disadvantage is the large current would lead to a large I(sup 2)R loss which would lower the fill factor so that 40 watts/sq cm output would not be obtained. Another is that few circuits are designed to work at 0.4 volts, so DC-DC power conversion circuitry would be necessary to raise the voltage to a reasonable level. The multijunction LPC being developed in this program is a step toward solving these problems. In the above example, an eight-junction LPC would have eight times the voltage, approximately 3V, so that DC-DC power conversion may not be needed in many instances. In addition, the multijunction LPC would have 1/8 the current of a single-junction LPC, for only 1/64 the I(sup 2)R loss if the series resistance is the same. Working monolithic multijunction laser power converters (LPC's) were made in two different compositions of the In(x)Al(y)Ga(1-x-y)As semiconductor alloy, In(0.53)Ga(0.47)As (0.74 eV) and In(0.5)Al(0.1)Ga(0.4)As (0.87 eV). The final 0.8 sq cm LPC's had output voltages of about 3 volts and output currents up to about one-half amp. Maximum 1.3 micron power conversion efficiencies were approximately 22 percent. One key advantage of multijunction LPC's is that they have higher output voltages, so that less DC-DC power conversion circuitry is needed in applications.

  3. Geochronology of Danube Delta sediments The PN-II-RU-TE-2012-3-0351 project

    NASA Astrophysics Data System (ADS)

    Robert-Csaba, Begy; Andra-Rada, Iurian; (Rusu) Oana Alexandra, Dumitru; Luminita, Preoteasa; Hedvig, Simon; Alida, Timar-Gabor; Szabolcs, Kelemen

    2014-05-01

    fluxes within the Danube Delta and over the associated Danubian continental shelf, using the radiometric method of 210Pb (210Po) and 137Cs. The detailed stratigraphical survey of the deltaic sediments will provide an accurate view of the sedimentation characteristics in the last ~100 years, including the impact of the hydrotechnical works built within the Danube basin on the sedimentation rates and on the deltaic continental shelf evolution. Another important aspect of the present project is featured by the combined application of three complex radiometric and nuclear tools: alpha spectrometry (210Po), gamma-spectrometry (210Pb, 137Cs, and 226Ra) and luminescence absolute method. Acknoledgement: The financial support from the grant of the Romanian National Authority for Scientific Research CNCS-UEFISCDI, PN-II-RU-TE-2012-3-0351 (2013-2015) is acknoledged.

  4. P/N In(Al) GaAs multijunction laser power converters

    NASA Technical Reports Server (NTRS)

    Wojtczuk, Steven; Parados, Themis; Walker, Gilbert

    1994-01-01

    Eight In(AI)GaAs PN junctions grown epitaxially on the semi-insulating wafer were monolithically integrated in series to boost the approximately 0.4V photovoltage per typical In(Al)GaAs junction to over 3 volts for the 1 sq cm laser power converted (LPC) chip. Advantages of multijunction LCP designs include the need for less circuitry for power reconditioning and the potential for lower I(sup 2)R power loss. As an example, these LPC's have a responsivity of approximately 1 amp/watt. With a single junction LPC, 100 watts/sq cm incident power would lead to about 100 A/sq cm short-circuit current at approximately 0.4V open-cicuit voltage. One disadvantage is the large current would lead to a large I(sup 2)R loss which would lower the fill factor so that 40 watts/sq cm output would not be obtained. Another is that few circuits are designed to work at 0.4 volts, so DC-DC power conversion circuitry would be necessary to raise the voltage to a reasonable level. The multijunction LPC being developed in this program is a step toward solving these problems. In the above example, an eight-junction LPC would have eight times the voltage, approximately 3V, so that DC-DC power conversion may not be needed in many instances. In addition, the multijunction LPC would have 1/8 the current of a single-junction LPC, for only 1/64 the I(sup 2)R loss if the series resistance is the same. Working monolithic multijunction laser power converters (LPC's) were made in two different compositions of the In(x)Al(y)Ga(1-x-y)As semiconductor alloy, In(0.53)Ga(0.47)As (0.74 eV) and In(0.5)Al(0.1)Ga(0.4)As (0.87 eV). The final 0.8 sq cm LPC's had output voltages of about 3 volts and output currents up to about one-half amp. Maximum 1.3 micron power conversion efficiencies were approximately 22 percent. One key advantage of multijunction LPC's is that they have higher output voltages, so that less DC-DC power conversion circuitry is needed in applications.

  5. In-Situ Grown P-N Junctions in MERCURY(1-X) Cadmium(x) Telluride for IR Detectors.

    NASA Astrophysics Data System (ADS)

    Rao, Vithal Rajaram

    In-situ grown p-n junctions in mercury cadmium telluride (Hg_{1-x}Cd _{x}Te with x between 0.2-0.3) were fabricated and characterized in this study. Fabrication of these junctions involved the growth of p-n structures at 370^circC on CdTe substrates by Organometallic Vapor Phase Epitaxy. P-type doping with arsenic was achieved by using tertiarybutylarsine as the precursor. N-type doping was obtained either with indium, using trimethylindium as the precursor or by leaving the layer undoped. These p-n structures were processed to fabricate photodiodes. Their electrical performance was evaluated and conclusions regarding current mechanisms which determine their behavior were drawn. By varying the Hg pressure between 0.07-0.13 atm, p-type doping level in the 10^{16 }/cm^3-rm2times10 ^{17}/cm^3 range was achieved. At higher values of Hg pressure, the arsenic doping level in the layer increased significantly. This is possibly due to an increase in Te vacancies, allowing arsenic to occupy more group VI sites where they behave as acceptors. The activation efficiency of arsenic in the layers was measured to be equal to 50%. A high temperature anneal at 415 ^circC for 15 minutes did not result in any increase in the activation efficiency, possibly indicating the presence of stable As-complexes in the layer. Growth of p^+n structures was carried out in a single run. The acceptor concentration in the p-type cap layer was 5-rm10times10 ^{16}/cm^3. Indium doped n-type base layers had a carrier concentration of 1- rm2times10^{16}/cm^3 , while undoped layers had a n-type background carrier concentration of 4-rm6times10^ {14}/cm^3. The cap layer was 3 μm thick with x = 0.30, while the base layer was 8mum thick with x = 0.26. Under the growth conditions, arsenic showed a diffusion coefficient of rm2times10 ^{13}cm^2/s, which was higher than the interdiffusion coefficient of the alloy junction. This resulted in placement of the p-n junction in the lower bandgap base layer, which is

  6. Brazil wheat yield covariance model

    NASA Technical Reports Server (NTRS)

    Callis, S. L.; Sakamoto, C.

    1984-01-01

    A model based on multiple regression was developed to estimate wheat yields for the wheat growing states of Rio Grande do Sul, Parana, and Santa Catarina in Brazil. The meteorological data of these three states were pooled and the years 1972 to 1979 were used to develop the model since there was no technological trend in the yields during these years. Predictor variables were derived from monthly total precipitation, average monthly mean temperature, and average monthly maximum temperature.

  7. Fission yield measurements at IGISOL

    NASA Astrophysics Data System (ADS)

    Lantz, M.; Al-Adili, A.; Gorelov, D.; Jokinen, A.; Kolhinen, V. S.; Mattera, A.; Moore, I.; Penttilä, H.; Pomp, S.; Prokofiev, A. V.; Rakopoulos, V.; Rinta-Antila, S.; Simutkin, V.; Solders, A.

    2016-06-01

    The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL) technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyväskylä, fission products can be isobarically separated, making it possible to measure relative independent fission yields. In some cases it is even possible to resolve isomeric states from the ground state, permitting measurements of isomeric yield ratios. So far the reactions U(p,f) and Th(p,f) have been studied using the IGISOL-JYFLTRAP facility. Recently, a neutron converter target has been developed utilizing the Be(p,xn) reaction. We here present the IGISOL-technique for fission yield measurements and some of the results from the measurements on proton induced fission. We also present the development of the neutron converter target, the characterization of the neutron field and the first tests with neutron-induced fission.

  8. 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.

  9. 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.

  10. Identification and characterization of another 4-nitrophenol degradation gene cluster, nps, in Rhodococcus sp. strain PN1.

    PubMed

    Yamamoto, Kenta; Nishimura, Munehiro; Kato, Dai-ichiro; Takeo, Masahiro; Negoro, Seiji

    2011-06-01

    4-Nitrophenol (4-NP) is a toxic compound formed in soil by the hydrolysis of organophosphorous pesticides, such as parathion. We previously reported the presence of the 4-NP degradation gene cluster (nphRA1A2) in Rhodococcus sp. strain PN1, which encodes a two-component 4-NP hydroxylase system that oxidizes 4-NP into 4-nitrocatechol. In the current study, another gene cluster (npsC and npsRA2A1B) encoding a similar 4-NP hydroxylase system was cloned from strain PN1. The enzymes from this 4-NP hydroxylase system (NpsA1 and NpsA2) were purified as histidine-tagged (His-) proteins and then characterized. His-NpsA2 showed NADH/FAD oxidoreductase activity, and His-NpsA1 showed 4-NP oxidizing activity in the presence of His-NpsA2. In the 4-NP oxidation using the reconstituted enzyme system (His-NpsA1 and His-NpsA2), hydroquinone (35% of 4-NP disappeared) and hydroxyquinol (59% of 4-NP disappeared) were detected in the presence of ascorbic acid as a reducing reagent, suggesting that, without the reducing reagent, 4-NP was converted into their oxidized forms, 1,4-benzoquinone and 2-hydroxy-1,4-benzoquinone. In addition, in the cell extract of recombinant Escherichia coli expressing npsB, a typical spectral change showing conversion of hydroxyquinol into maleylacetate was observed. These results indicate that this nps gene cluster, in addition to the nph gene cluster, is also involved in 4-NP degradation in strain PN1.

  11. The PN.S Elliptical Galaxy Survey: Data Reduction, Planetary Nebula Catalog, and Basic Dynamics for NGC 3379

    NASA Astrophysics Data System (ADS)

    Douglas, N. G.; Napolitano, N. R.; Romanowsky, A. J.; Coccato, L.; Kuijken, K.; Merrifield, M. R.; Arnaboldi, M.; Gerhard, O.; Freeman, K. C.; Merrett, H. R.; Noordermeer, E.; Capaccioli, M.

    2007-07-01

    We present results from Planetary Nebula Spectrograph (PN.S) observations of the elliptical galaxy NGC 3379 and a description of the data reduction pipeline. We detected 214 planetary nebulae, of which 191 are ascribed to NGC 3379 and 23 to the companion galaxy NGC 3384. Comparison with data from the literature shows that the PN.S velocities have an internal error of <~20 km s-1 and a possible offset of similar magnitude. We present the results of kinematic modeling and show that the PN kinematics is consistent with absorption-line data in the region where they overlap. The resulting combined kinematic data set, running from the center of NGC 3379 out to more than 7 effective radii (Reff), reveals a mean rotation velocity that is small compared to the random velocities and a dispersion profile that declines rapidly with radius. From a series of Jeans dynamical models we find the B-band mass-to-light ratio inside 5Reff to be 8-12 in solar units, and the dark matter fraction inside this radius to be less than 40%. We compare these and other results of dynamical analysis with those of dark matter-dominated merger simulations, finding that significant discrepancies remain, reiterating the question of whether NGC 3379 has the kind of dark matter halo that the current ΛCDM paradigm requires. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  12. The micronucleus test and erythropoiesis. Effects of erythropoietin and a mutagen on the ratio of polychromatic to normochromatic erythrocytes (P/N ratio).

    PubMed

    Suzuki, Y; Nagae, Y; Li, J; Sakaba, H; Mozawa, K; Takahashi, A; Shimizu, H

    1989-11-01

    It is considered that a decrease of the ratio of polychromatic erythrocytes (PCE) to normochromatic erythrocytes (NCE) (P/N) in the micronucleus test is an indicator of bone marrow toxicity induced by mutagens. However, the exact meaning of fluctuation in the P/N ratio is not yet known. We have studied this point by counting the total number of erythrocytes and nucleated cells in the bone marrow following various treatments. The P/N ratio decreased gradually with time after administration of mitomycin C. Our data suggest that the decrease of P/N ratio was attributable to an increase in the numbers of the denominator, i.e. NCE, caused by rapid differentiation and multiplication or denucleation of erythroblasts which remained in the bone marrow instead of entering the peripheral blood stream. A decrease of P/N ratio was also observed in the early phase after administration of erythropoietin, an agent which induces differentiation and multiplication of erythroblasts. This phenomenon might result from an increase of PCE delivery into the blood circulation. However, following the initial decrease, the P/N ratio increased gradually 48 h after administration of erythropoietin. It is supposed that this increase probably resulted from an increase in PCE in the bone marrow due to the direct effects of erythropoietin on erythropoiesis. The drastic change in erythropoiesis in the bone marrow induced by either mutagen or erythropoietin treatment will affect the fluctuations of the P/N ratio or the number of micronucleated erythrocytes per non-micronucleated erythocytes in the micronucleus test. This contrasts with the original explanation for such fluctuations which attributed them to replenishment of the marrow by peripheral blood. PMID:2516221

  13. Increased cavernosal relaxation by Phoneutria nigriventer toxin, PnTx2-6, via activation at NO/cGMP signaling

    PubMed Central

    Nunes, K.P.; Wynne, B.M.; Cordeiro, M.N.; Borges, M.H.; Richardson, M; Leite, R.; DeLima, M.E.; Webb, R. C

    2011-01-01

    Erectile dysfunction mechanisms in diabetic patients are multifactorial and often lead to resistance to current therapy. Animal toxins have been used as pharmacological tools to study penile erection. Human accidents involving the venom of Phoneutria nigriventer spider are characterized by priapism. We hypothesize that PnTx2-6 potentiates cavernosal relaxation in diabetic mice by increasing cGMP. This effect is nNOS dependent. Cavernosal strips were contracted with phenylephrine (10−5 M) and relaxed by electrical field stimulation (EFS, 20V, 1–32 Hz) in the presence or absence of PnTx2-6 (10−8 M).Cavernosal strips from nNOS and eNOS knocaut (KO) mice, besides nNOS inhibitor (10−5M), were used to evaluate the role of this enzyme in the potentiation effect evoked by PnTx2-6. Tissue cGMP levels were determined after stimulation with PnTx2-6 in presence or absence of L-NAME (10−4M) and ω-conotoxin GVIA (10−6M), an N-type calcium channel inhibitor. Results showed PnTx2-6 enhanced cavernosal relaxation in diabetic mice (65%) and eNOS KO mice, but not in nNOS KO mice. The toxin effect in the cavernosal relaxation was abolished by nNOS inhibitor. cGMP levels are increased by PnTx2-6, however L-NAME abolished this enhancement as well as ω-conotoxin GVIA. We conclude PnTx2-6 facilitates penile relaxation in diabetic mice through a mechanism dependent on nNOS, probably via increasing NO/cGMP production. PMID:21975567

  14. Acid soil infertility effects on peanut yields and yield components

    SciTech Connect

    Blamey, F.P.C.

    1983-01-01

    The interpretation of soil amelioration experiments with peanuts is made difficult by the unpredictibility of the crop and by the many factors altered when ameliorating acid soils. The present study was conducted to investigate the effects of lime and gypsum applications on peanut kernel yield via the three first order yield components, pods per ha, kernels per pod, and kernel mass. On an acid medium sandy loam soil (typic Plinthustult), liming resulted in a highly significant kernel yield increase of 117% whereas gypsum applications were of no significant benefit. As indicated by path coefficient analysis, an increase in the number of pods per ha was markedly more important in increasing yield than an increase in either the number of kernels per pod or kernel mass. Furthermore, exch. Al was found to be particularly detrimental to pod number. It was postulated that poor peanut yields resulting from acid soil infertility were mainly due to the depressive effect of exch. Al on pod number. Exch. Ca appeared to play a secondary role by ameliorating the adverse effects of exch. Al.

  15. [Flag leaf photosynthetic characteristics, change in chlorophyll fluorescence parameters, and their relationships with yield of winter wheat sowed in spring].

    PubMed

    Xu, Lan; Gao, Zhi-qang; An, Wei; Li, Yan-liang; Jiao, Xiong-fei; Wang, Chuang-yun

    2016-01-01

    With five good winter wheat cultivars selected from the middle and lower reaches of Yangtze River and Southwest China as test materials, a field experiment in Xinding basin area of Shanxi Province was conducted to study the photosynthetic characteristics, chlorophyll content, and chlorophyll fluorescence parameters of flag leaf at different sowing dates, as well as the correlations between these indices and yield for two years (2013-2014). The results showed that the difference in most fluorescence parameters except chlorophyll content among cultivars was significant. The correlations between these fluorescence parameters and yield were significant. The variation coefficient of chlorophyll (Chl) content was low (0.12-0.17), and that of performance index based on absorption (PIabs) was high (0.32-0.39), with the partial correlation coefficients of them with grain yield from 2013 to 2014 ranged in 0.70-0.81. Under the early sowing condition, the grain yield positively correlated with PIabs at flowering and filling stages and chlorophyll content at grain filling stage, but negatively correlated with the relative variable fluorescence at I point (Vi) at grain filling stage. About 81.1%-82.8% of grain yield were determined by the variations of PIabs, Chl, and Vi. Wheat cultivars had various performances in the treatments with different sowing dates and a consistent trend was observed in the two experimental years. Among these 5 cultivars, Yangmai 13 was suitable for early sowing, with the flag leaf photosynthetic rate (Pn), Chl, most fluorescence parame-ters, and grain yield showed obviously high levels. In conclusion, under early sowing condition chlorophyll content at grain filling stages, PIabs at flowering and filling stages, and Pn were important indices for selecting wheat cultivars with high photosynthetic efficiency.

  16. [Flag leaf photosynthetic characteristics, change in chlorophyll fluorescence parameters, and their relationships with yield of winter wheat sowed in spring].

    PubMed

    Xu, Lan; Gao, Zhi-qang; An, Wei; Li, Yan-liang; Jiao, Xiong-fei; Wang, Chuang-yun

    2016-01-01

    With five good winter wheat cultivars selected from the middle and lower reaches of Yangtze River and Southwest China as test materials, a field experiment in Xinding basin area of Shanxi Province was conducted to study the photosynthetic characteristics, chlorophyll content, and chlorophyll fluorescence parameters of flag leaf at different sowing dates, as well as the correlations between these indices and yield for two years (2013-2014). The results showed that the difference in most fluorescence parameters except chlorophyll content among cultivars was significant. The correlations between these fluorescence parameters and yield were significant. The variation coefficient of chlorophyll (Chl) content was low (0.12-0.17), and that of performance index based on absorption (PIabs) was high (0.32-0.39), with the partial correlation coefficients of them with grain yield from 2013 to 2014 ranged in 0.70-0.81. Under the early sowing condition, the grain yield positively correlated with PIabs at flowering and filling stages and chlorophyll content at grain filling stage, but negatively correlated with the relative variable fluorescence at I point (Vi) at grain filling stage. About 81.1%-82.8% of grain yield were determined by the variations of PIabs, Chl, and Vi. Wheat cultivars had various performances in the treatments with different sowing dates and a consistent trend was observed in the two experimental years. Among these 5 cultivars, Yangmai 13 was suitable for early sowing, with the flag leaf photosynthetic rate (Pn), Chl, most fluorescence parame-ters, and grain yield showed obviously high levels. In conclusion, under early sowing condition chlorophyll content at grain filling stages, PIabs at flowering and filling stages, and Pn were important indices for selecting wheat cultivars with high photosynthetic efficiency. PMID:27228602

  17. Formation of a pn junction on an anisotropically etched GaAs surface using metalorganic chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Leon, R. P.; Bailey, S. G.; Mazaris, G. A.; Williams, W. D.

    1986-01-01

    A continuous p-type GaAs epilayer has been deposited on an n-type sawtooth GaAs surface using MOCVD. A wet chemical etching process was used to expose the intersecting (111)Ga and (-1 -1 1)Ga planes with 6-micron periodicity. Charge-collection microscopy was used to verify the presence of the pn junction thus formed and to measure its depth. The ultimate goal of this work is to fabricate a V-groove GaAs cell with improved absorptivity, high short-circuit current, and tolerance to particle radiation.

  18. Optical bistability in a one-dimensional photonic crystal resonator using a reverse-biased pn-junction.

    PubMed

    Sodagar, Majid; Miri, Mehdi; Eftekhar, Ali A; Adibi, Ali

    2015-02-01

    Optical bistability provides a simple way to control light with light. We demonstrate low-power thermo-optical bistability caused by the Joule heating mechanism in a one-dimensional photonic crystal (PC) nanobeam resonator with a moderate quality factor (Q ~8900) with an embedded reverse-biased pn-junction. We show that the photocurrent induced by the linear absorption in this compact resonator considerably reduces the threshold optical power. The proposed approach substantially relaxes the requirements on the input optical power for achieving optical bistability and provides a reliable way to stabilize the bistable features of the device.

  19. A study of the electrical properties of p-n junctions formed by ion-implantation into gallium arsenide

    NASA Technical Reports Server (NTRS)

    Lin, A. H.

    1972-01-01

    In the process of ion implantation, ion beams bombard the surface and create undesirable surface effects. The surface effects were investigated, and surface leakage currents were shown to be reduced by surface treatment. I-V characteristics and C-V measurements were obtained for the Zn-GaAs and Zn-(In,Ga)As junction is considered as a p-i-n heterojunction, without generation-recombination current. The Zn-GaAs junction is considered as a p-n homojunction with appreciable generation-recombination currents.

  20. N.G. Basov and early works on semiconductor lasers at P.N. Lebedev Physics Institute

    SciTech Connect

    Eliseev, P G

    2012-12-31

    A survey is presented of works on creation and investigation of semiconductor lasers during 1957 - 1977 at the P.N. Lebedev Physics Institute. Many of these works were initiated by N.G. Basov, starting from pre-laser time, when N.G. Basov and his coworkers formulated principal conditions of creation of lasers on interband transitions in semiconductors. Main directions of further works were diode lasers based on various materials and structures, their characteristics of output power, high-speed operation and reliability. (special issue devoted to the 90th anniversary of n.g. basov)

  1. Investigation of the Exclusive {sup 3}He(e,e{sup '}pn){sup 1}H Reaction

    SciTech Connect

    Middleton, D. G.; Grabmayr, P.; Hehl, T.; Heim, J.; Martin, I.; Moschini, F.; Annand, J. R. M.; Glazier, D. I.; MacGregor, I. J. D.; McGeorge, J. C.; Monstad, K.; Rosner, G.; Watts, D. P.; Antelo, M. Ases; Ayerbe, C.; Baumann, D.; Bermuth, J.; Bernauer, J.; Boehm, R.; Ding, M.

    2009-10-09

    Cross sections for the {sup 3}He(e,e{sup '}pn){sup 1}H reaction were measured for the first time at energy transfers of 220 and 270 MeV for several momentum transfers ranging from 300 to 450 MeV/c. Cross sections are presented as a function of the momentum of the recoil proton and the momentum transfer. Continuum Faddeev calculations using the Argonne V18 and Bonn-B nucleon-nucleon potentials overestimate the measured cross sections by a factor 5 at low recoil proton momentum with the discrepancy becoming smaller at higher recoil proton momentum.

  2. Studies of Valence Band Alignment Between Nitrided GaPN/GaP (111) Interface Using X-ray Photoelectron Spectroscopy

    SciTech Connect

    Khamari, Shailesh K.; Sinha, A. K.; Oak, S. M.; Banik, S.; Barman, S. R.; Dixit, V. K.

    2011-07-15

    The analysis of core levels positions of Ga{sub 3}d, N{sub 1s} and P{sub 2}p at different etching depth from the plasma nitrided GaP (111) surface shows that the nitrogen ions interact with both Gallium and Phosphorous ions with nearly equal probability. The analysis of valence band spectra shows the type-II band alignment between GaPN{sub 0.22}/GaP and the valence band offset is {approx}2.2{+-}0.1 eV.

  3. The Expression of TaRca2-α Gene Associated with Net Photosynthesis Rate, Biomass and Grain Yield in Bread Wheat (Triticum aestivum L.) under Field Conditions.

    PubMed

    Saeed, Iqbal; Bachir, Daoura Goudia; Chen, Liang; Hu, Yin-Gang

    2016-01-01

    Improvement in activation of Rubisco by Rubisco activase can potentially enhance CO2 assimilation and photosynthetic efficiency in plants. The three homoeologous copies of TaRca2-α were identified on chromosomes 4AL, 4BS and 4DS (TaRca2-α-4AL, TaRca2-α-4BS, and TaRca2-α-4DS) in bread wheat. Expression patterns of the three copies at heading (Z55), anthesis (Z67) and grain-filling (Z73) stages were investigated through qRT-PCR analyses in a panel of 59 bread wheat genotypes and their effects on net photosynthesis rate (Pn), biomass plant-1 (BMPP) and grain yield plant-1 (GYPP) were further explored. Different but similar expression patterns were observed for the three copies of TaRca2-α at the three growth stages with highest expression at grain-filling stage. TaRca2-α-4BS expressed higher at the three stages than TaRca2-α-4AL and TaRca2-α-4DS. The 59 genotypes could be clustered into three groups as high (7 genotypes), intermediate (41 genotypes) and low (11 genotypes) expression based on the expression of the three copies of TaRca2-α at three growth stages. Significant variations (P<0.01) were observed among the three groups of bread wheat genotypes for Pn, BMPP and GYPP. Generally, the genotypes with higher TaRca2-α expression also showed higher values for Pn, BMPP and GYPP. The expressions of the three copies of TaRca2-α at heading, anthesis and grain-filling stages were positively correlated with Pn, BMPP and GYPP (P<0.01) with stronger association for TaRca2-α-4BS at grain-filling stage. These results revealed that the expression of TaRca2-α contribute substantially to Pn, BMPP and GYPP, and suggested that manipulating TaRca-α expression may efficiently improve Pn, BMPP and GYPP in bread wheat and detecting TaRca-α expression levels with emphasis on TaRca2-α-4BS may be a positive strategy for selection in improving photosynthetic efficiency and grain yield of bread wheat. PMID:27548477

  4. The Expression of TaRca2-α Gene Associated with Net Photosynthesis Rate, Biomass and Grain Yield in Bread Wheat (Triticum aestivum L.) under Field Conditions

    PubMed Central

    Saeed, Iqbal; Bachir, Daoura Goudia; Chen, Liang; Hu, Yin-Gang

    2016-01-01

    Improvement in activation of Rubisco by Rubisco activase can potentially enhance CO2 assimilation and photosynthetic efficiency in plants. The three homoeologous copies of TaRca2-α were identified on chromosomes 4AL, 4BS and 4DS (TaRca2-α-4AL, TaRca2-α-4BS, and TaRca2-α-4DS) in bread wheat. Expression patterns of the three copies at heading (Z55), anthesis (Z67) and grain-filling (Z73) stages were investigated through qRT-PCR analyses in a panel of 59 bread wheat genotypes and their effects on net photosynthesis rate (Pn), biomass plant-1 (BMPP) and grain yield plant-1 (GYPP) were further explored. Different but similar expression patterns were observed for the three copies of TaRca2-α at the three growth stages with highest expression at grain-filling stage. TaRca2-α-4BS expressed higher at the three stages than TaRca2-α-4AL and TaRca2-α-4DS. The 59 genotypes could be clustered into three groups as high (7 genotypes), intermediate (41 genotypes) and low (11 genotypes) expression based on the expression of the three copies of TaRca2-α at three growth stages. Significant variations (P<0.01) were observed among the three groups of bread wheat genotypes for Pn, BMPP and GYPP. Generally, the genotypes with higher TaRca2-α expression also showed higher values for Pn, BMPP and GYPP. The expressions of the three copies of TaRca2-α at heading, anthesis and grain-filling stages were positively correlated with Pn, BMPP and GYPP (P<0.01) with stronger association for TaRca2-α-4BS at grain-filling stage. These results revealed that the expression of TaRca2-α contribute substantially to Pn, BMPP and GYPP, and suggested that manipulating TaRca-α expression may efficiently improve Pn, BMPP and GYPP in bread wheat and detecting TaRca-α expression levels with emphasis on TaRca2-α-4BS may be a positive strategy for selection in improving photosynthetic efficiency and grain yield of bread wheat. PMID:27548477

  5. The transport properties of the Phosphorus and Chlorine doped single layer MoS2 p-n junctions: A first-principles study

    NASA Astrophysics Data System (ADS)

    Zeng, Qingyi; Pan, Jiangling; Yang, Zhixiong; Peng, Shenglin; Zou, Hui; Ouyang, Fangping

    2016-11-01

    We investigate the electronic transport properties of the Phosphorus (P) and Chlorine (Cl) doped single-layer MoS2 p-n junctions with different doping concentration and position by first-principles calculations. The n- and p-type doping of single-layer MoS2 p-n junctions are achieved by substituting doping of sulfur (S) atoms with P atoms and Cl atoms, respectively. The calculation results show that the current increases obviously when the bias is greater than 1.7 V for all models and these p-n junctions exhibit diode-like behavior under positive bias. When the bias ranges from 0.2 V to 1.3 V, the p-n junctions have excellent rectification performance. Only one p-n junction will display negative differential resistance (NDR) effect under the negative bias ranging of -0.5 V to -1.2 V and -1.5 V to -1.7 V. It is expected that our findings may promote the experiment on MoS2 layered material for further exploration of optoelectronic devices.

  6. Changes in screen-printed ZnO/CuInSe2 p-n junction before and after laser ablation

    NASA Astrophysics Data System (ADS)

    Ogurcovs, A.; Gerbreders, Vj; Tamanis, E.; Gerbreders, A.

    2015-06-01

    In the experiments, ZnO and CuInSe2 semiconductor powders were used (the latter produced by the high-temperature synthesis method). Microstructural properties of the powders were analyzed using X-Ray diffraction and SEM. The experimental ZnO/CuInSe2 samples were prepared by the screen printing technique. The V-I measurements of the samples indicated the presence of a p-n junction in the ZnO/CuInSe2 contact zone. The samples were exposed to artificial solar radiation, during which an exponential decay of photo-emf was observed. It was shown that the starting conductive properties of the p-n junction restores in ˜ 15 min after the exposition. Laser ablation technique was applied to ZnO/CuInSe2 p-n junction with purpose to improve its performance and quality. After several attempts, significant changes in electrical properties of samples was observed. Improvenent of p-n junction can be achieved only at single attempt at certain amount of delivered energy. Futherablation attempt leads to degradation of p-n junction of samples.

  7. P/N In(Al) GaAs Multijunction Laser Power Converters

    NASA Technical Reports Server (NTRS)

    Wojtczuk, Steven; Parodos, Themis; Walker, Gilbert

    1994-01-01

    Eight In(Al)GaAs P/N junctions grown epitaxially on a semi-insulating wafer were monolithically integrated in series to boost the approx. 0.4 V photovoltage per typical In(Al)GaAs junction to over 3 volts for the 1 sq cm laser power converter (LPC) chip. This is the first report of a multijunction LPC for the 1.3 to 1.5 microns wavelength range. This wavelength range is optimum for laser power transmission over low- loss single-mode silica optical fiber, and is also useful with high efficiency 1.315 microns iodine lasers in free-space power transmission. Advantages of multijunction LPC designs include the need for less circuitry for power reconditioning and the potential for lower I(exp 2)R power loss. As an example, these LPCs have a responsivity of approx.1 amp/watt. With a single junction LPC, 100 watts/sq cm incident power would lead to about 100 A/sq cM short-circuit current at approx. 0.4 V open-circuit voltage. One disadvantage is the large current would lead to a large 1(exp 2)R loss which would lower the fill factor so that 40 wattS/sq cm output would not be obtained. Another is that few circuits are designed to work at 0.4 volts, so DC-DC power conversion circuitry would be necessary to raise the voltage to a reasonable level. The multijunction LPC being developed in this program is a step toward solving these problems. In the above example, an eight-junction LPC would have eight times the voltage, approx. 3 V, so that DC-DC power conversion may not be needed in many instances. In addition, the multijunction LPC would have 1/8 the current of a single-junction LPC, for only 1/64 the 1(exp 2)R loss if the series resistance is the same. Working monolithic multijunction laser power converters (LPCs) were made in two different compositions of the ln(x)Al(y)Ga(l-x-y)As semiconductor alloy, In(0.53)Ga(0.47)As (0.74 eV) and In(0.5)Al(0.1)Ga(0.4)As (0.87 eV). The final 0.8 sq cm LPCs had output voltages of about 3 volts and output currents up to about one-half amp

  8. Collective coordinate quantization and spin statistics of the solitons in the C PN Skyrme-Faddeev model

    NASA Astrophysics Data System (ADS)

    Amari, Yuki; Klimas, Paweł; Sawado, Nobuyuki

    2016-07-01

    The C PN extended Skyrme-Faddeev model possesses planar soliton solutions. We consider quantum aspects of the solutions applying collective coordinate quantization in regime of rigid body approximation. In order to discuss statistical properties of the solutions we include an Abelian Chern-Simons term (the Hopf term) in the Lagrangian. Since Π3(C P1)=Z then for N =1 the term becomes an integer. On the other hand for N >1 it became perturbative because Π3(C PN) is trivial. The prefactor of the Hopf term (anyon angle) Θ is not quantized and its value depends on the physical system. The corresponding fermionic models can fix value of the angle Θ for all N in a way that the soliton with N =1 is not an anyon type whereas for N >1 it is always an anyon even for Θ =n π , n ∈Z . We quantize the solutions and calculate several mass spectra for N =2 . Finally we discuss generalization for N ≧3 .

  9. Astrocyte-like glial cells physiologically regulate olfactory processing through the modification of ORN-PN synaptic strength in Drosophila.

    PubMed

    Liu, He; Zhou, Bangyu; Yan, Wenjun; Lei, Zhengchang; Zhao, Xiaoliang; Zhang, Ke; Guo, Aike

    2014-09-01

    Astrocyte-like glial cells are abundant in the central nervous system of adult Drosophila and exhibit morphology similar to astrocytes of mammals. Previous evidence has shown that astrocyte-like glial cells are strongly associated with synapses in the antennal lobe (AL), the first relay of the olfactory system, where olfactory receptor neurons (ORNs) transmit information into projection neurons (PNs). However, the function of astrocyte-like glia in the AL remains obscure. In this study, using in vivo calcium imaging, we found that astrocyte-like glial cells exhibited spontaneous microdomain calcium elevations. Using simultaneous manipulation of glial activity and monitoring of neuronal function, we found that the astrocyte-like glial activation, but not ensheathing glial activation, could inhibit odor-evoked responses of PNs. Ensheathing glial cells are another subtype of glia, and are of functional importance in the AL. Electrophysiological experiments indicated that astrocyte-like glial activation decreased the amplitude and slope of excitatory postsynaptic potentials evoked through electrical stimulation of the antennal nerve. These results suggest that astrocyte-like glial cells may regulate olfactory processing through negative regulation of ORN-PN synaptic strength. Beyond the antennal lobe we observed astrocyte-like glial spontaneous calcium activities in the ventromedial protocerebrum, indicating that astrocyte-like glial spontaneous calcium elevations might be general in the adult fly brain. Overall, our study demonstrates a new function for astrocyte-like glial cells in the physiological modulation of olfactory information transmission, possibly through regulating ORN-PN synapse strength.

  10. Properties of the fullerene C60-containing PN Lin49 in the SMC; Explanations of strong near-IR excess

    NASA Astrophysics Data System (ADS)

    Otsuka, Masaaki; Kemper, Francisca; Leal-Ferreira, Marcelo L.; Aleman, Isabel; Bernard-Salas, Jeronimo; Cami, Jan; Ochsendorf, Bram; Peeters, Els

    2016-07-01

    We performed a detailed spectroscopic analysis of the fullerene C6o-containing planetary nebula (PN) Lin49 in the Small Magellanic Cloud (SMC). Lin49 is a C-rich and metal- deficient PN (Z∼⃒0.0006) and its nebular abundances are in agreement with the AGB model for the initially 1.25Mʘ stars with the metallicity Z = 0.001 of Fishlock et al. (2014, [1]). By stellar absorption fitting with TLUSTY, we derived stellar abundances, effective temperature, and surface gravity. We constructed the photo-ionization model with CLOUDY in order to investigate physical conditions of Lin49. The model with the 0.005-0.1 μm radius graphite and a constant hydrogen density shell could not fit the ∼⃒1-5 μm SED owing to the strong near-IR excess. We propose that the near-IR excess indicates (1) the presence of extremely small carbon molecules or (2) the presence of high-density structure surrounding the central star.

  11. Black Phosphorus-Zinc Oxide Nanomaterial Heterojunction for p-n Diode and Junction Field-Effect Transistor.

    PubMed

    Jeon, Pyo Jin; Lee, Young Tack; Lim, June Yeong; Kim, Jin Sung; Hwang, Do Kyung; Im, Seongil

    2016-02-10

    Black phosphorus (BP) nanosheet is two-dimensional (2D) semiconductor with distinct band gap and attracting recent attention from researches because it has some similarity to gapless 2D semiconductor graphene in the following two aspects: single element (P) for its composition and quite high mobilities depending on its fabrication conditions. Apart from several electronic applications reported with BP nanosheet, here we report for the first time BP nanosheet-ZnO nanowire 2D-1D heterojunction applications for p-n diodes and BP-gated junction field effect transistors (JFETs) with n-ZnO channel on glass. For these nanodevices, we take advantages of the mechanical flexibility of p-type conducting of BP and van der Waals junction interface between BP and ZnO. As a result, our BP-ZnO nanodimension p-n diode displays a high ON/OFF ratio of ∼10(4) in static rectification and shows kilohertz dynamic rectification as well while ZnO nanowire channel JFET operations are nicely demonstrated by BP gate switching in both electrostatics and kilohertz dynamics. PMID:26771206

  12. Forward-bias capacitance and current measurements for determining lifetimes and band narrowing in p-n junction solar cells

    NASA Technical Reports Server (NTRS)

    Neugroschel, A.; Chen, P. J.; Pao, S. C.; Lindholm, F. A.

    1978-01-01

    A new method is described and illustrated for determining the minority-carrier diffusion length and lifetime in the base region of p-n junction solar cells. The method requires only capacitance measurements at the device terminals and its accuracy is estimated to be + or - 5%. It is applied to a set of silicon p-n junction devices and the values of the diffusion lengths agree with those obtained using the current response to X-ray excitation but disagree with those obtained by the OCVD method. The reasons for the relative inaccuracy of OCVD applied to silicon devices are discussed. The capacitance method includes corrections for a two-dimensional fringing effects which occur in small area devices. For a device having highly-doped base region and surface (emitter) layer, the method can be extended to enable the determination of material properties of the degenerately doped surface layer. These material properties include the phenomenological emitter lifetime and a measure of the energy band-gap narrowing in the emitter. An alternate method for determining the energy band-gap narrowing from temperature dependence of emitter current is discussed and demonstrated.

  13. Binary Oxide p-n Heterojunction Piezoelectric Nanogenerators with an Electrochemically Deposited High p-Type Cu2O Layer.

    PubMed

    Baek, Seung Ki; Kwak, Sung Soo; Kim, Joo Sung; Kim, Sang Woo; Cho, Hyung Koun

    2016-08-31

    The high performance of ZnO-based piezoelectric nanogenerators (NGs) has been limited due to the potential screening from intrinsic electron carriers in ZnO. We have demonstrated a novel approach to greatly improve piezoelectric power generation by electrodepositing a high-quality p-type Cu2O layer between the piezoelectric semiconducting film and the metal electrode. The p-n heterojunction using only oxides suppresses the screening effect by forming an intrinsic depletion region, and thus sufficiently enhances the piezoelectric potential, compared to the pristine ZnO piezoelectric NG. Interestingly, a Sb-doped Cu2O layer has high mobility and low surface trap states. Thus, this doped layer is an attractive p-type material to significantly improve piezoelectric performance. Our results revealed that p-n junction NGs consisting of Au/ZnO/Cu2O/indium tin oxide with a Cu2O:Sb (cuprous oxide with a small amount of antimony) layer of sufficient thickness (3 μm) exhibit an extraordinarily high piezoelectric potential of 0.9 V and a maximum output current density of 3.1 μA/cm(2).

  14. Applications of nanosecond laser annealing to fabricating p-n homo junction on ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Shimogaki, T.; Ofuji, T.; Tetsuyama, N.; Okazaki, K.; Higashihata, M.; Nakamura, D.; Ikenoue, H.; Asano, T.; Okada, T.

    2013-03-01

    Zinc oxide (ZnO) has attracted considerable attension due to its wide applications in particular ultra violet light emitting diode (UV-LED). In addition, the one-dimensional ZnO crystals are quite attractive as building blocks for light emitting devices like laser and LED, because of their high crystallinity and light confinement properties. However, a method for the realization of the stable p-type ZnO has not been well established. In our study, we have investigated the effect of the nanosecond laser irradiation to the ZnO nanorods as an ultrafast melting and recrystallizing process for realization of the p-type ZnO. Fabrication of the p-n homo junction along ZnO nanorods has been demonstrated using phosphorus ion implantation and ns-laser annealing by a KrF excimer laser. Rectifying I-V characteristics attributed to p-n junction were observed from the measurement of electrical properties. In addition, the penetration depth of laser annealed layer was measured by observing cathode luminescence images. Then, it was turned out that high repetition rate laser annealing can anneal ZnO nanorods over the optical-absorption length. In this report, optical, structural, and electrical characteristics of the phosphorus ion-implanted ZnO nanorods annealed by the KrF excimer laser are discussed.

  15. Process For Direct Integration Of A Thin-Film Silicon P-N Junction Diode With A Magnetic Tunnel Junction

    DOEpatents

    Toet, Daniel; Sigmon, Thomas W.

    2005-08-23

    A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition. The film is then irradiated with short pulse laser energy that is efficiently absorbed in the silicon, which results in the crystallization of the film and simultaneously in the activation of the dopants via ultrafast melting and solidification. The silicon film can be patterned either before or after crystallization.

  16. Process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction

    DOEpatents

    Toet, Daniel; Sigmon, Thomas W.

    2004-12-07

    A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition. The film is then irradiated with short pulse laser energy that is efficiently absorbed in the silicon, which results in the crystallization of the film and simultaneously in the activation of the dopants via ultrafast melting and solidification. The silicon film can be patterned either before or after crystallization.

  17. Process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction

    DOEpatents

    Toet, Daniel; Sigmon, Thomas W.

    2003-01-01

    A process for direct integration of a thin-film silicon p-n junction diode with a magnetic tunnel junction for use in advanced magnetic random access memory (MRAM) cells for high performance, non-volatile memory arrays. The process is based on pulsed laser processing for the fabrication of vertical polycrystalline silicon electronic device structures, in particular p-n junction diodes, on films of metals deposited onto low temperature-substrates such as ceramics, dielectrics, glass, or polymers. The process preserves underlayers and structures onto which the devices are typically deposited, such as silicon integrated circuits. The process involves the low temperature deposition of at least one layer of silicon, either in an amorphous or a polycrystalline phase on a metal layer. Dopants may be introduced in the silicon film during or after deposition. The film is then irradiated with short pulse laser energy that is efficiently absorbed in the silicon, which results in the crystallization of the film and simultaneously in the activation of the dopants via ultrafast melting and solidification. The silicon film can be patterned either before or after crystallization.

  18. Optically and thermally detected deep levels in n-type Schottky and p+-n GaN diodes

    NASA Astrophysics Data System (ADS)

    Hierro, A.; Kwon, D.; Ringel, S. A.; Hansen, M.; Speck, J. S.; Mishra, U. K.; DenBaars, S. P.

    2000-05-01

    N-Schottky and p+-n GaN junctions are currently used for different technologies. A comparison of the deep levels found throughout the entire band gap of n-GaN grown by metal-organic chemical vapor deposition under both configurations is presented. Both deep level optical spectroscopy and deep level transient spectroscopy measurements are used allowing the observation of both majority and minority carrier traps. Deep levels at Ec-Et=0.58-0.62, 1.35, 2.57-2.64, and 3.22 eV are observed for both diode configurations, with concentrations in the ˜1014-1016cm-3 range. The 0.58-0.62 eV level appears correlated with residual Mg impurities in the n side of the p+-n diode measured by secondary-ion-mass spectroscopy, while the 1.35 eV level concentration increases by a factor of ˜4 for the Schottky junction possibly correlating with the carbon profile. The 2.57-2.64 eV level is a minority carrier hole trap in n-GaN, likely related to the yellow photoluminescence band, and is detected both optically from the conduction band (2.64 eV) and thermally from the valence band (0.87 eV).

  19. Black Phosphorus-Zinc Oxide Nanomaterial Heterojunction for p-n Diode and Junction Field-Effect Transistor.

    PubMed

    Jeon, Pyo Jin; Lee, Young Tack; Lim, June Yeong; Kim, Jin Sung; Hwang, Do Kyung; Im, Seongil

    2016-02-10

    Black phosphorus (BP) nanosheet is two-dimensional (2D) semiconductor with distinct band gap and attracting recent attention from researches because it has some similarity to gapless 2D semiconductor graphene in the following two aspects: single element (P) for its composition and quite high mobilities depending on its fabrication conditions. Apart from several electronic applications reported with BP nanosheet, here we report for the first time BP nanosheet-ZnO nanowire 2D-1D heterojunction applications for p-n diodes and BP-gated junction field effect transistors (JFETs) with n-ZnO channel on glass. For these nanodevices, we take advantages of the mechanical flexibility of p-type conducting of BP and van der Waals junction interface between BP and ZnO. As a result, our BP-ZnO nanodimension p-n diode displays a high ON/OFF ratio of ∼10(4) in static rectification and shows kilohertz dynamic rectification as well while ZnO nanowire channel JFET operations are nicely demonstrated by BP gate switching in both electrostatics and kilohertz dynamics.

  20. Binary Oxide p-n Heterojunction Piezoelectric Nanogenerators with an Electrochemically Deposited High p-Type Cu2O Layer.

    PubMed

    Baek, Seung Ki; Kwak, Sung Soo; Kim, Joo Sung; Kim, Sang Woo; Cho, Hyung Koun

    2016-08-31

    The high performance of ZnO-based piezoelectric nanogenerators (NGs) has been limited due to the potential screening from intrinsic electron carriers in ZnO. We have demonstrated a novel approach to greatly improve piezoelectric power generation by electrodepositing a high-quality p-type Cu2O layer between the piezoelectric semiconducting film and the metal electrode. The p-n heterojunction using only oxides suppresses the screening effect by forming an intrinsic depletion region, and thus sufficiently enhances the piezoelectric potential, compared to the pristine ZnO piezoelectric NG. Interestingly, a Sb-doped Cu2O layer has high mobility and low surface trap states. Thus, this doped layer is an attractive p-type material to significantly improve piezoelectric performance. Our results revealed that p-n junction NGs consisting of Au/ZnO/Cu2O/indium tin oxide with a Cu2O:Sb (cuprous oxide with a small amount of antimony) layer of sufficient thickness (3 μm) exhibit an extraordinarily high piezoelectric potential of 0.9 V and a maximum output current density of 3.1 μA/cm(2). PMID:27547841