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Sample records for zno top contact

  1. ZnO Schottky barriers and Ohmic contacts

    NASA Astrophysics Data System (ADS)

    Brillson, Leonard J.; Lu, Yicheng

    2011-06-01

    ZnO has emerged as a promising candidate for optoelectronic and microelectronic applications, whose development requires greater understanding and control of their electronic contacts. The rapid pace of ZnO research over the past decade has yielded considerable new information on the nature of ZnO interfaces with metals. Work on ZnO contacts over the past decade has now been carried out on high quality material, nearly free from complicating factors such as impurities, morphological and native point defects. Based on the high quality bulk and thin film crystals now available, ZnO exhibits a range of systematic interface electronic structure that can be understood at the atomic scale. Here we provide a comprehensive review of Schottky barrier and ohmic contacts including work extending over the past half century. For Schottky barriers, these results span the nature of ZnO surface charge transfer, the roles of surface cleaning, crystal quality, chemical interactions, and defect formation. For ohmic contacts, these studies encompass the nature of metal-specific interactions, the role of annealing, multilayered contacts, alloyed contacts, metallization schemes for state-of-the-art contacts, and their application to n-type versus p-type ZnO. Both ZnO Schottky barriers and ohmic contacts show a wide range of phenomena and electronic behavior, which can all be directly tied to chemical and structural changes on an atomic scale.

  2. Effect of atomic layer deposition temperature on the performance of top-down ZnO nanowire transistors

    PubMed Central

    2014-01-01

    This paper studies the effect of atomic layer deposition (ALD) temperature on the performance of top-down ZnO nanowire transistors. Electrical characteristics are presented for 10-μm ZnO nanowire field-effect transistors (FETs) and for deposition temperatures in the range 120°C to 210°C. Well-behaved transistor output characteristics are obtained for all deposition temperatures. It is shown that the maximum field-effect mobility occurs for an ALD temperature of 190°C. This maximum field-effect mobility corresponds with a maximum Hall effect bulk mobility and with a ZnO film that is stoichiometric. The optimized transistors have a field-effect mobility of 10 cm2/V.s, which is approximately ten times higher than can typically be achieved in thin-film amorphous silicon transistors. Furthermore, simulations indicate that the drain current and field-effect mobility extraction are limited by the contact resistance. When the effects of contact resistance are de-embedded, a field-effect mobility of 129 cm2/V.s is obtained. This excellent result demonstrates the promise of top-down ZnO nanowire technology for a wide variety of applications such as high-performance thin-film electronics, flexible electronics, and biosensing. PMID:25276107

  3. A graphene barristor using nitrogen profile controlled ZnO Schottky contacts.

    PubMed

    Hwang, Hyeon Jun; Chang, Kyoung Eun; Yoo, Won Beom; Shim, Chang Hoo; Lee, Sang Kyung; Yang, Jin Ho; Kim, So-Young; Lee, Yongsu; Cho, Chunhum; Lee, Byoung Hun

    2017-02-16

    We have successfully demonstrated a graphene-ZnO:N Schottky barristor. The barrier height between graphene and ZnO:N could be modulated by a buried gate electrode in the range of 0.5-0.73 eV, and an on-off ratio of up to 10 7 was achieved. By using a nitrogen-doped ZnO film as a Schottky contact material, the stability problem of previously reported graphene barristors could be greatly alleviated and a facile route to build a top-down processed graphene barristor was realized with a very low heat cycle. This device will be instrumental when implementing logic functions in systems requiring high-performance logic devices fabricated with a low temperature fabrication process such as back-end integrated logic devices or flexible devices on soft substrates.

  4. Selective Dry Etch for Defining Ohmic Contacts for High Performance ZnO TFTs

    DTIC Science & Technology

    2014-03-27

    scale, high-frequency ZnO thin - film transistors (TFTs) could be fabricated. Molybdenum, tantalum, titanium tungsten 10-90, and tungsten metallic contact... thin - film transistor layout utilized in the thesis research . . . . . 42 3.4 Process Flow Diagram for Optical and e-Beam Devices...TFT thin - film transistor TLM transmission line model UV ultra-violet xvii SELECTIVE DRY ETCH FOR DEFINING OHMIC CONTACTS FOR HIGH PERFORMANCE ZnO TFTs

  5. Cd1-xZnxTe photodetectors with transparent conductive ZnO contacts

    NASA Astrophysics Data System (ADS)

    Tang, Ke; Huang, Jian; Lu, Yuanxi; Hu, Yan; Shen, Yibin; Zhang, Jijun; Gu, Qingmiao; Wang, Linjun; Lu, Yicheng

    2018-03-01

    High quality Cd1-xZnxTe (CZT) films were prepared using the close-spaced sublimation (CSS) technique. CZT film UV (ultraviolet) photodetectors were fabricated with B and Ga co-doped ZnO (BGZO) transparent conductive interdigitated contacts. The contact properties of BGZO/CZT were investigated by the transmission line model (TLM). The results indicate that a good ohmic contact is formed between BGZO and CZT with a very low contact resistivity of about 0.26 Ω·cm2. Compared with CZT photodetectors with Au contacts, the detectors with BGZO contacts show a higher value of UV photo response.

  6. Surface plasmon optical sensor with enhanced sensitivity using top ZnO thin film

    NASA Astrophysics Data System (ADS)

    Bao, Ming; Li, Ge; Jiang, Dongmei; Cheng, Wenjuan; Ma, Xueming

    2012-05-01

    Surface plasmon resonance (SPR) is one of the most sensitive label-free detection methods and has been used in a wide range of chemical and biochemical sensing. Upon using a 200 nm top layer of dielectric film with a high value of the real part ɛ' of the dielectric function, on top of an SPR sensor in the Kretschmann configuration, the sensitivity is improved. The refractive index effect of dielectric film on sensitivity is usually ignored. Dielectric films with different refractive indices were prepared by radio frequency magnetron (RF) sputtering and measured with spectroscopic ellipsometry (SE). The imaginary part ɛ'' of the top nanolayer permittivity needs to be small enough in order to reduce the losses and get sharper dips. The stability of the sensor is also improved because the nanolayer is protecting the Ag film from interacting with the environment. The response curves of the Ag/ZnO chips were obtained by using SPR sensor. Theoretical analysis of the sensitivity of the SPR sensors with different ZnO film refractive indices is presented and studied. Both experimental and simulation results show that the Ag/ZnO films exhibit an enhanced SPR over the pure Ag film with a narrower full width at half maximum (FWHM). It shows that the top ZnO layer is effective in enhancing the surface plasmon resonance and thus its sensitivity.

  7. Contact resistance reduction of ZnO thin film transistors (TFTs) with saw-shaped electrode.

    PubMed

    Park, Woojin; Shaikh, Sohail F; Min, Jung-Wook; Lee, Sang Kyung; Lee, Byoung Hun; Hussain, Muhammad M

    2018-08-10

    We report on a saw-shaped electrode architecture ZnO thin film transistor (TFT), which effectively increases the channel width. The contact line of the saw-shaped electrode is almost twice as long at the contact metal/ZnO channel junction. We experimentally observed an enhancement in the output drive current by 50% and a reduction in the contact resistance by over 50%, when compared to a typically shaped electrode ZnO TFT consuming the same chip area. This performance enhancement is attributed to the extension of the channel width. This technique can contribute to device performance enhancement, and in particular reduce the contact resistance, which is a serious challenge.

  8. Enhanced stimulated emission in ZnO thin films using microdisk top-down structuring

    SciTech Connect

    Nomenyo, K.; Kostcheev, S.; Lérondel, G.

    2014-05-05

    Microdisks were fabricated in zinc oxide (ZnO) thin films using a top-down approach combining electron beam lithography and reactive ion etching. These microdisk structured thin films exhibit a stimulated surface emission between 3 and 7 times higher than that from a reference film depending on the excitation power density. Emission peak narrowing, reduction in lasing threshold and blue-shifting of the emission wavelength were observed along with enhancement in the emitted intensity. Results indicate that this enhancement is due to an increase in the internal quantum efficiency combined with an amplification of the stimulated emission. An analysis in terms of waveguidingmore » is presented in order to explain these effects. These results demonstrate that very significant gains in emission can be obtained through conventional microstructuration without the need for more onerous top-down nanostructuration techniques.« less

  9. Influence of the Interaction Between Graphite and Polar Surfaces of ZnO on the Formation of Schottky Contact

    NASA Astrophysics Data System (ADS)

    Yatskiv, R.; Grym, J.

    2018-03-01

    We show that the interaction between graphite and polar surfaces of ZnO affects electrical properties of graphite/ZnO Schottky junctions. A strong interaction of the Zn-face with the graphite contact causes interface imperfections and results in the formation of laterally inhomogeneous Schottky contacts. On the contrary, high quality Schottky junctions form on the O-face, where the interaction is significantly weaker. Charge transport through the O-face ZnO/graphite junctions is well described by the thermionic emission model in both forward and reverse directions. We further demonstrate that the parameters of the graphite/ZnO Schottky diodes can be significantly improved when a thin layer of ZnO2 forms at the interface between graphite and ZnO after hydrogen peroxide surface treatment.

  10. High performance top-gated ferroelectric field effect transistors based on two-dimensional ZnO nanosheets

    NASA Astrophysics Data System (ADS)

    Tian, Hongzheng; Wang, Xudong; Zhu, Yuankun; Liao, Lei; Wang, Xianying; Wang, Jianlu; Hu, Weida

    2017-01-01

    High quality ultrathin two-dimensional zinc oxide (ZnO) nanosheets (NSs) are synthesized, and the ZnO NS ferroelectric field effect transistors (FeFETs) are demonstrated based on the P(VDF-TrFE) polymer film used as the top gate insulating layer. The ZnO NSs exhibit a maximum field effect mobility of 588.9 cm2/Vs and a large transconductance of 2.5 μS due to their high crystalline quality and ultrathin two-dimensional structure. The polarization property of the P(VDF-TrFE) film is studied, and a remnant polarization of >100 μC/cm2 is achieved with a P(VDF-TrFE) thickness of 300 nm. Because of the ultrahigh remnant polarization field generated in the P(VDF-TrFE) film, the FeFETs show a large memory window of 16.9 V and a high source-drain on/off current ratio of more than 107 at zero gate voltage and a source-drain bias of 0.1 V. Furthermore, a retention time of >3000 s of the polarization state is obtained, inspiring a promising candidate for applications in data storage with non-volatile features.

  11. TiN/Al2O3/ZnO gate stack engineering for top-gate thin film transistors by combination of post oxidation and annealing

    NASA Astrophysics Data System (ADS)

    Kato, Kimihiko; Matsui, Hiroaki; Tabata, Hitoshi; Takenaka, Mitsuru; Takagi, Shinichi

    2018-04-01

    Control of fabrication processes for a gate stack structure with a ZnO thin channel layer and an Al2O3 gate insulator has been examined for enhancing the performance of a top-gate ZnO thin film transistor (TFT). The Al2O3/ZnO interface and the ZnO layer are defective just after the Al2O3 layer formation by atomic layer deposition. Post treatments such as plasma oxidation, annealing after the Al2O3 deposition, and gate metal formation (PMA) are promising to improve the interfacial and channel layer qualities drastically. Post-plasma oxidation effectively reduces the interfacial defect density and eliminates Fermi level pinning at the Al2O3/ZnO interface, which is essential for improving the cut-off of the drain current of TFTs. A thermal effect of post-Al2O3 deposition annealing at 350 °C can improve the crystalline quality of the ZnO layer, enhancing the mobility. On the other hand, impacts of post-Al2O3 deposition annealing and PMA need to be optimized because the annealing can also accompany the increase in the shallow-level defect density and the resulting electron concentration, in addition to the reduction in the deep-level defect density. The development of the interfacial control technique has realized the excellent TFT performance with a large ON/OFF ratio, steep subthreshold characteristics, and high field-effect mobility.

  12. Friction and wear behavior of nitrogen-doped ZnO thin films deposited via MOCVD under dry contact

    DOE PAGES

    Mbamara, U. S.; Olofinjana, B.; Ajayi, O. O.; ...

    2016-02-01

    Most researches on doped ZnO thin films are tilted toward their applications in optoelectronics and semiconductor devices. Research on their tribological properties is still unfolding. In this work, nitrogen-doped ZnO thin films were deposited on 304 L stainless steel substrate from a combination of zinc acetate and ammonium acetate precursor by MOCVD technique. Compositional and structural studies of the films were done using Rutherford Backscattering Spectroscopy (RBS) and X-ray Diffraction (XRD). The frictional behavior of the thin film coatings was evaluated using a ball-on-flat configuration in reciprocating sliding under dry contact condition. After friction test, the flat and ball counter-facemore » surfaces were examined to assess the wear dimension and failure mechanism. In conclusion, both friction behavior and wear (in the ball counter-face) were observed to be dependent on the crystallinity and thickness of the thin film coatings.« less

  13. Experimental and numerical investigation of contact-area-limited doping for top-contact pentacene thin-film transistors with Schottky contact.

    PubMed

    Noda, Kei; Wada, Yasuo; Toyabe, Toru

    2015-10-28

    Effects of contact-area-limited doping for pentacene thin-film transistors with a bottom-gate, top-contact configuration were investigated. The increase in the drain current and the effective field-effect mobility was achieved by preparing hole-doped layers underneath the gold contact electrodes by coevaporation of pentacene and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), confirmed by using a thin-film organic transistor advanced simulator (TOTAS) incorporating Schottky contact with a thermionic field emission (TFE) model. Although the simulated electrical characteristics fit the experimental results well only in the linear regime of the transistor operation, the barrier height for hole injection and the gate-voltage-dependent hole mobility in the pentacene transistors were evaluated with the aid of the device simulation. This experimental data analysis with the simulation indicates that the highly-doped semiconducting layers prepared in the contact regions can enhance the charge carrier injection into the active semiconductor layer and concurrent trap filling in the transistor channel, caused by the mitigation of a Schottky energy barrier. This study suggests that both the contact-area-limited doping and the device simulation dealing with Schottky contact are indispensable in designing and developing high-performance organic thin-film transistors.

  14. Search for single top quark production via contact interactions at LEP2

    NASA Astrophysics Data System (ADS)

    Abdallah, J.; Abreu, P.; Adam, W.; Adzic, P.; Albrecht, T.; Alemany-Fernandez, R.; Allmendinger, T.; Allport, P. P.; Amaldi, U.; Amapane, N.; Amato, S.; Anashkin, E.; Andreazza, A.; Andringa, S.; Anjos, N.; Antilogus, P.; Apel, W.-D.; Arnoud, Y.; Ask, S.; Asman, B.; Augustin, J. E.; Augustinus, A.; Baillon, P.; Ballestrero, A.; Bambade, P.; Barbier, R.; Bardin, D.; Barker, G. J.; Baroncelli, A.; Battaglia, M.; Baubillier, M.; Becks, K.-H.; Begalli, M.; Behrmann, A.; Ben-Haim, E.; Benekos, N.; Benvenuti, A.; Berat, C.; Berggren, M.; Bertrand, D.; Besancon, M.; Besson, N.; Bloch, D.; Blom, M.; Bluj, M.; Bonesini, M.; Boonekamp, M.; Booth, P. S. L.; Borisov, G.; Botner, O.; Bouquet, B.; Bowcock, T. J. V.; Boyko, I.; Bracko, M.; Brenner, R.; Brodet, E.; Bruckman, P.; Brunet, J. M.; Buschbeck, B.; Buschmann, P.; Calvi, M.; Camporesi, T.; Canale, V.; Carena, F.; Castro, N.; Cavallo, F.; Chapkin, M.; Charpentier, Ph.; Checchia, P.; Chierici, R.; Chliapnikov, P.; Chudoba, J.; Chung, S. U.; Cieslik, K.; Collins, P.; Contri, R.; Cosme, G.; Cossutti, F.; Costa, M. J.; Crennell, D.; Cuevas, J.; D'Hondt, J.; da Silva, T.; da Silva, W.; Della Ricca, G.; de Angelis, A.; de Boer, W.; de Clercq, C.; de Lotto, B.; de Maria, N.; de Min, A.; de Paula, L.; di Ciaccio, L.; di Simone, A.; Doroba, K.; Drees, J.; Eigen, G.; Ekelof, T.; Ellert, M.; Elsing, M.; Espirito Santo, M. C.; Fanourakis, G.; Fassouliotis, D.; Feindt, M.; Fernandez, J.; Ferrer, A.; Ferro, F.; Flagmeyer, U.; Foeth, H.; Fokitis, E.; Fulda-Quenzer, F.; Fuster, J.; Gandelman, M.; Garcia, C.; Gavillet, Ph.; Gazis, E.; Gokieli, R.; Golob, B.; Gomez-Ceballos, G.; Goncalves, P.; Graziani, E.; Grosdidier, G.; Grzelak, K.; Guy, J.; Haag, C.; Hallgren, A.; Hamacher, K.; Hamilton, K.; Haug, S.; Hauler, F.; Hedberg, V.; Hennecke, M.; Hoffman, J.; Holmgren, S.-O.; Holt, P. J.; Houlden, M. A.; Jackson, J. N.; Jarlskog, G.; Jarry, P.; Jeans, D.; Johansson, E. K.; Jonsson, P.; Joram, C.; Jungermann, L.; Kapusta, F.; Katsanevas, S.; Katsoufis, E.; Kernel, G.; Kersevan, B. P.; Kerzel, U.; King, B. T.; Kjaer, N. J.; Kluit, P.; Kokkinias, P.; Kourkoumelis, C.; Kouznetsov, O.; Krumstein, Z.; Kucharczyk, M.; Lamsa, J.; Leder, G.; Ledroit, F.; Leinonen, L.; Leitner, R.; Lemonne, J.; Lepeltier, V.; Lesiak, T.; Liebig, W.; Liko, D.; Lipniacka, A.; Lopes, J. H.; Lopez, J. M.; Loukas, D.; Lutz, P.; Lyons, L.; MacNaughton, J.; Malek, A.; Maltezos, S.; Mandl, F.; Marco, J.; Marco, R.; Marechal, B.; Margoni, M.; Marin, J.-C.; Mariotti, C.; Markou, A.; Martinez-Rivero, C.; Masik, J.; Mastroyiannopoulos, N.; Matorras, F.; Matteuzzi, C.; Mazzucato, F.; Mazzucato, M.; Mc Nulty, R.; Meroni, C.; Migliore, E.; Mitaroff, W.; Mjoernmark, U.; Moa, T.; Moch, M.; Moenig, K.; Monge, R.; Montenegro, J.; Moraes, D.; Moreno, S.; Morettini, P.; Mueller, U.; Muenich, K.; Mulders, M.; Mundim, L.; Murray, W.; Muryn, B.; Myatt, G.; Myklebust, T.; Nassiakou, M.; Navarria, F.; Nawrocki, K.; Nemecek, S.; Nicolaidou, R.; Nikolenko, M.; Oblakowska-Mucha, A.; Obraztsov, V.; Oliveira, O.; Olshevski, A.; Onofre, A.; Orava, R.; Osterberg, K.; Ouraou, A.; Oyanguren, A.; Paganoni, M.; Paiano, S.; Palacios, J. P.; Palka, H.; Papadopoulou, Th. D.; Pape, L.; Parkes, C.; Parodi, F.; Parzefall, U.; Passeri, A.; Passon, O.; Peralta, L.; Perepelitsa, V.; Perrotta, A.; Petrolini, A.; Piedra, J.; Pieri, L.; Pierre, F.; Pimenta, M.; Piotto, E.; Podobnik, T.; Poireau, V.; Pol, M. E.; Polok, G.; Pozdniakov, V.; Pukhaeva, N.; Pullia, A.; Radojicic, D.; Rebecchi, P.; Rehn, J.; Reid, D.; Reinhardt, R.; Renton, P.; Richard, F.; Ridky, J.; Rivero, M.; Rodriguez, D.; Romero, A.; Ronchese, P.; Roudeau, P.; Rovelli, T.; Ruhlmann-Kleider, V.; Ryabtchikov, D.; Sadovsky, A.; Salmi, L.; Salt, J.; Sander, C.; Savoy-Navarro, A.; Schwickerath, U.; Sekulin, R.; Siebel, M.; Sisakian, A.; Smadja, G.; Smirnova, O.; Sokolov, A.; Sopczak, A.; Sosnowski, R.; Spassov, T.; Stanitzki, M.; Stocchi, A.; Strauss, J.; Stugu, B.; Szczekowski, M.; Szeptycka, M.; Szumlak, T.; Tabarelli, T.; Tegenfeldt, F.; Timmermans, J.; Tkatchev, L.; Tobin, M.; Todorovova, S.; Tome, B.; Tonazzo, A.; Tortosa, P.; Travnicek, P.; Treille, D.; Tristram, G.; Trochimczuk, M.; Troncon, C.; Turluer, M.-L.; Tyapkin, I. A.; Tyapkin, P.; Tzamarias, S.; Uvarov, V.; Valenti, G.; van Dam, P.; van Eldik, J.; van Remortel, N.; van Vulpen, I.; Vegni, G.; Veloso, F.; Venus, W.; Verdier, P.; Verzi, V.; Vilanova, D.; Vitale, L.; Vrba, V.; Wahlen, H.; Washbrook, A. J.; Weiser, C.; Wicke, D.; Wickens, J.; Wilkinson, G.; Winter, M.; Witek, M.; Yushchenko, O.; Zalewska, A.; Zalewski, P.; Zavrtanik, D.; Zhuravlov, V.; Zimin, N. I.; Zintchenko, A.; Zupan, M.

    2011-02-01

    Single top quark production via four-fermion contact interactions associated to flavour-changing neutral currents was searched for in data taken by the DELPHI detector at LEP2. The data were accumulated at centre-of-mass energies ranging from 189 to 209 GeV, with an integrated luminosity of 598.1 pb-1. No evidence for a signal was found. Limits on the energy scale Λ, were set for scalar-, vector- and tensor-like coupling scenarios.

  15. Two-step deposition of Al-doped ZnO on p-GaN to form ohmic contacts.

    PubMed

    Su, Xi; Zhang, Guozhen; Wang, Xiao; Chen, Chao; Wu, Hao; Liu, Chang

    2017-12-01

    Al-doped ZnO (AZO) thin films were deposited directly on p-GaN substrates by using a two-step deposition consisting of polymer assisted deposition (PAD) and atomic layer deposition (ALD) methods. Ohmic contacts of the AZO on p-GaN have been formed. The lowest sheet resistance of the two-step prepared AZO films reached to 145 Ω/sq, and the specific contact resistance reduced to 1.47 × 10 -2 Ω·cm 2 . Transmittance of the AZO films remained above 80% in the visible region. The combination of PAD and ALD technique can be used to prepare p-type ohmic contacts for optoelectronics.

  16. Two-step deposition of Al-doped ZnO on p-GaN to form ohmic contacts

    NASA Astrophysics Data System (ADS)

    Su, Xi; Zhang, Guozhen; Wang, Xiao; Chen, Chao; Wu, Hao; Liu, Chang

    2017-07-01

    Al-doped ZnO (AZO) thin films were deposited directly on p-GaN substrates by using a two-step deposition consisting of polymer assisted deposition (PAD) and atomic layer deposition (ALD) methods. Ohmic contacts of the AZO on p-GaN have been formed. The lowest sheet resistance of the two-step prepared AZO films reached to 145 Ω/sq, and the specific contact resistance reduced to 1.47 × 10-2 Ω·cm2. Transmittance of the AZO films remained above 80% in the visible region. The combination of PAD and ALD technique can be used to prepare p-type ohmic contacts for optoelectronics.

  17. Novel top-contact monolayer pentacene-based thin-film transistor for ammonia gas detection.

    PubMed

    Mirza, Misbah; Wang, Jiawei; Li, Dexing; Arabi, S Atika; Jiang, Chao

    2014-04-23

    We report on the fabrication of an organic field-effect transistor (OFET) of a monolayer pentacene thin film with top-contact electrodes for the aim of ammonia (NH3) gas detection by monitoring changes in its drain current. A top-contact configuration, in which source and drain electrodes on a flexible stamp [poly(dimethylsiloxane)] were directly contacted with the monolayer pentacene film, was applied to maintain pentacene arrangement ordering and enhance the monolayer OFET detection performance. After exposure to NH3 gas, the carrier mobility at the monolayer OFET channel decreased down to one-third of its original value, leading to a several orders of magnitude decrease in the drain current, which tremendously enhanced the gas detection sensitivity. This sensitivity enhancement to a limit of the 10 ppm level was attributed to an increase of charge trapping in the carrier channel, and the amount of trapped states was experimentally evaluated by the threshold voltage shift induced by the absorbed NH3 molecular analyte. In contrast, a conventional device with a 50-nm-thick pentacene layer displayed much higher mobility but lower response to NH3 gas, arising from the impediment of analyte penetrating into the conductive channel, owing to the thick pentacene film.

  18. Top-gate organic depletion and inversion transistors with doped channel and injection contact

    NASA Astrophysics Data System (ADS)

    Liu, Xuhai; Kasemann, Daniel; Leo, Karl

    2015-03-01

    Organic field-effect transistors constitute a vibrant research field and open application perspectives in flexible electronics. For a commercial breakthrough, however, significant performance improvements are still needed, e.g., stable and high charge carrier mobility and on-off ratio, tunable threshold voltage, as well as integrability criteria such as n- and p-channel operation and top-gate architecture. Here, we show pentacene-based top-gate organic transistors operated in depletion and inversion regimes, realized by doping source and drain contacts as well as a thin layer of the transistor channel. By varying the doping concentration and the thickness of the doped channel, we control the position of the threshold voltage without degrading on-off ratio or mobility. Capacitance-voltage measurements show that an inversion channel can indeed be formed, e.g., an n-doped channel can be inverted to a p-type inversion channel with highly p-doped contacts. The Cytop polymer dielectric minimizes hysteresis, and the transistors can be biased for prolonged cycles without a shift of threshold voltage, indicating excellent operation stability.

  19. X-Ray Irradiation Effects in Top Contact, Pentacene Based Field Effect Transistors for Space Related Applications

    DTIC Science & Technology

    2006-01-01

    Journal Article POSTPRINT 3. DATES COVERED (From - To) 2006 4. TITLE AND SUBTITLE X-ray irradiation effects in top contact, pentacene based field 5a...Preliminary studies of the effect of x-ray irradiation, typically used to simulate radiation effects in space, on top contract, pentacene based field effect...irradiation, radiation, radiation effects, pentacene 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF

  20. Growth and interface properties of Au Schottky contact on ZnO grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Asghar, M.; Mahmood, K.; Malik, Faisal; Hasan, M. A.

    2013-06-01

    In this paper, we have discussed the growth of ZnO by molecular beam epitaxy (MBE) and interface properties of Au Schottky contacts on grown sample. After the verification of structure and surface properties by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM), respectively, Au metal contact was fabricated by e-beam evaporation to study contact properties. The high value of ideality factor (2.15) and barrier height (0.61 eV) at room temperature obtained by current-voltage (I-V) characteristics suggested the presence of interface states between metal and semiconductor. To confirm this observation we carried out frequency dependent capacitance-voltage (C-V) and conductance-voltage (G-V) demonstrated that the capacitance of diode decreased with increasing frequency. The reason of this behavior is related with density of interface states, series resistance and image force lowering. The C-2-V plot drawn to calculate the carrier concentration and barrier height with values 1.4×1016 cm-3 and 0.92 eV respectively. Again, high value of barrier height obtained from C-V as compared to the value obtained from I-V measurements revealed the presence of interface states. The density of these interface states (Dit) was calculated by well known Hill-Coleman method. The calculated value of Dit at 1 MHz frequency was 2×1012 eV-1 cm-2. The plot between interface states and frequency was also drawn which demonstrated that density of interface states had inverse proportion with measuring frequency.

  1. Contact effects analyzed by a parameter extraction method based on a single bottom-gate/top-contact organic thin-film transistor

    NASA Astrophysics Data System (ADS)

    Takagaki, Shunsuke; Yamada, Hirofumi; Noda, Kei

    2018-03-01

    Contact effects in organic thin-film transistors (OTFTs) were examined by using our previously proposed parameter extraction method from the electrical characteristics of a single staggered-type device. Gate-voltage-dependent contact resistance and channel mobility in the linear regime were evaluated for bottom-gate/top-contact (BGTC) pentacene TFTs with active layers of different thicknesses, and for pentacene TFTs with contact-doped layers prepared by coevaporation of pentacene and tetrafluorotetracyanoquinodimethane (F4TCNQ). The extracted parameters suggested that the influence of the contact resistance becomes more prominent with the larger active-layer thickness, and that contact-doping experiments give rise to a drastic decrease in the contact resistance and a concurrent considerable improvement in the channel mobility. Additionally, the estimated energy distributions of trap density in the transistor channel probably reflect the trap filling with charge carriers injected into the channel regions. The analysis results in this study confirm the effectiveness of our proposed method, with which we can investigate contact effects and circumvent the influences of characteristic variations in OTFT fabrication.

  2. Down-top nanofabrication of binary (CdO)x (ZnO)1-x nanoparticles and their antibacterial activity.

    PubMed

    Al-Hada, Naif Mohammed; Mohamed Kamari, Halimah; Abdullah, Che Azurahanim Che; Saion, Elias; Shaari, Abdul H; Talib, Zainal Abidin; Matori, Khamirul Amin

    2017-01-01

    In the present study, binary oxide (cadmium oxide [CdO]) x (zinc oxide [ZnO]) 1-x nanoparticles (NPs) at different concentrations of precursor in calcination temperature were prepared using thermal treatment technique. Cadmium and zinc nitrates (source of cadmium and zinc) with polyvinylpyrrolidone (capping agent) have been used to prepare (CdO) x (ZnO) 1-x NPs samples. The sample was characterized by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. XRD patterns analysis revealed that NPs were formed after calcination, which showed a cubic and hexagonal crystalline structure of (CdO) x (ZnO) 1-x NPs. The phase analysis using EDX spectroscopy and FTIR spectroscopy confirmed the presence of Cd and Zn as the original compounds of prepared (CdO) x (ZnO) 1-x NP samples. The average particle size of the samples increased from 14 to 33 nm as the concentration of precursor increased from x=0.20 to x=0.80, as observed by TEM results. The surface composition and valance state of the prepared product NPs were determined by X-ray photoelectron spectroscopy (XPS) analyses. Diffuse UV-visible reflectance spectra were used to determine the optical band gap through the Kubelka-Munk equation; the energy band gap was found to decrease for CdO from 2.92 to 2.82 eV and for ZnO from 3.22 to 3.11 eV with increasing x value. Additionally, photoluminescence (PL) spectra revealed that the intensity in PL increased with an increase in particle size. In addition, the antibacterial activity of binary oxide NP was carried out in vitro against Escherichia coli ATCC 25922 Gram (-ve), Salmonella choleraesuis ATCC 10708, and Bacillus subtilis UPMC 1175 Gram (+ve). This study indicated that the zone of inhibition of 21 mm has good antibacterial activity toward the Gram-positive B. subtilis UPMC 1175.

  3. Solution-processed ultrathin chemically derived graphene films as soft top contacts for solid-state molecular electronic junctions.

    PubMed

    Li, Tao; Hauptmann, Jonas Rahlf; Wei, Zhongming; Petersen, Søren; Bovet, Nicolas; Vosch, Tom; Nygård, Jesper; Hu, Wenping; Liu, Yunqi; Bjørnholm, Thomas; Nørgaard, Kasper; Laursen, Bo W

    2012-03-08

    A novel method using solution-processed ultrathin chemically derived graphene films as soft top contacts for the non-destructive fabrication of molecular junctions is demonstrated. We believe this protocol will greatly enrich the solid-state test beds for molecular electronics due to its low-cost, easy-processing and flexible nature. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Ultrathin reduced graphene oxide films as transparent top-contacts for light switchable solid-state molecular junctions.

    PubMed

    Li, Tao; Jevric, Martyn; Hauptmann, Jonas R; Hviid, Rune; Wei, Zhongming; Wang, Rui; Reeler, Nini E A; Thyrhaug, Erling; Petersen, Søren; Meyer, Jakob A S; Bovet, Nicolas; Vosch, Tom; Nygård, Jesper; Qiu, Xiaohui; Hu, Wenping; Liu, Yunqi; Solomon, Gemma C; Kjaergaard, Henrik G; Bjørnholm, Thomas; Nielsen, Mogens Brøndsted; Laursen, Bo W; Nørgaard, Kasper

    2013-08-14

    A new type of solid-state molecular junction is introduced, which employs reduced graphene oxide as a transparent top contact that permits a self-assembled molecular monolayer to be photoswitched in situ, while simultaneously enabling charge-transport measurements across the molecules. The electrical switching behavior of a less-studied molecular switch, dihydroazulene/vinylheptafulvene, is described, which is used as a test case. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. The Improvement of Electrical Characteristics of Pt/Ti Ohmic Contacts to Ga-Doped ZnO by Homogenized KrF Pulsed Excimer Laser Treatment

    NASA Astrophysics Data System (ADS)

    Oh, Min-Suk

    2018-04-01

    We investigated the effect of KrF excimer laser surface treatment on Pt/Ti ohmic contacts to Ga-doped n-ZnO ( N d = 4.3 × 1017 cm-3). The treatment of the n-ZnO surfaces by laser irradiation greatly improved the electrical characteristics of the metal contacts. The Pt/Ti ohmic layer on the laser-irradiated n-ZnO showed specific contact resistances of 2.5 × 10-4 ˜ 4.8 × 10-4 Ω cm2 depending on the laser energy density and gas ambient, which were about two orders of magnitude lower than that of the as-grown sample, 8.4 × 10-2 Ω cm2. X-ray photoelectron spectroscopy and photoluminescence measurements showed that the KrF excimer laser treatments increased the electron concentration near the surface region of the Ga-doped n-ZnO due to the preferential evaporation of oxygen atoms from the ZnO surface by the laser-induced dissociation of Zn-O bonds.

  6. 3D reconstruction of pentacene structural organization in top-contact OTFTs via resonant soft X-ray reflectivity

    NASA Astrophysics Data System (ADS)

    Capelli, Raffaella; Nardi, Marco Vittorio; Toccoli, Tullio; Verucchi, Roberto; Dinelli, Franco; Gelsomini, Carolina; Koshmak, Konstantin; Giglia, Angelo; Nannarone, Stefano; Pasquali, Luca

    2018-01-01

    Herein, we describe the use of soft X-ray reflectivity at the carbon K-edge to study the molecular organization (orientation, structure, and morphology) of pentacene active films in a top-contact transistor geometry. This technique is not affected by sample charging, and it can be applied in the case of insulating substrates. In addition, the sampling depth is not limited to the near-surface region, giving access to buried device interfaces (metal/organic and dielectric/organic). Spectral lineshape simulations, based on ab-initio calculations using a realistic 3D layer-by-layer model, allow us to unravel the details of the molecular organization in all the specific and crucial areas of the active film, overcoming the limitations of conventional approaches. The tilt angle of the long molecular axis in the whole film is found to progressively decrease with respect to the substrate normal from 25° to 0° with the increasing film thickness. A full vertical alignment, optimal for in-plane charge hopping, is reached only after the complete formation of the first five monolayers. Remarkably, starting from the first one in contact with the dielectric substrate, all the monolayers in the stack show a change in orientation with the increasing thickness. On the other hand, at the buried interface with a gold top-contact, the molecules assume a flat orientation that only propagates for two or three monolayers into the organic film. Top-contact devices with the highest performances can thus be obtained using films of at least ten monolayers. This explains the observed thickness dependence of charge mobility in pentacene transistors.

  7. The investigation of Ga-doped ZnO as an interlayer for ohmic contact to Cd1-xZnxTe films

    NASA Astrophysics Data System (ADS)

    Shen, Yibin; Huang, Jian; Gu, Qingmiao; Meng, Hua; Tang, Ke; Shen, Yue; Zhang, Jijun; Wang, Linjun; Lu, Yicheng

    2017-12-01

    In this work, high quality Cd1-xZnxTe films were prepared on fluorine doped tin oxide (FTO) glass substrates by close-spaced sublimation (CSS) method. A low resistivity sputtered Ga-doped ZnO (GZO) film was used as an interlayer between Au electrodes and Cd1-xZnxTe films try to reduce the contact resistance and contribute to bring about a better Ohmic contact. Circular transmission line model (CTLM) was adopted to investigate the effects of GZO intermediate layer on the contact properties of Au/GZO/Cd1-xZnxTe structure. The results show a low contact resistivity of 0.37 Ω cm2 for Au/GZO contacts on Cd1-xZnxTe films. Cd1-xZnxTe film radiation detectors were also fabricated using Au/GZO contacts and an energy resolution of about 28% was obtained from a 60 KeV 241Am γ-ray source for the first time.

  8. Improved ohmic contact of Ga-Doped ZnO to p-GaN by using copper sulfide intermediate layers

    NASA Astrophysics Data System (ADS)

    Gu, Wen; Xu, Tao; Zhang, Jianhua

    2013-11-01

    Copper sulfide (CuS) was used as the intermediate layer to build ohmic contact of Ga-Doped ZnO (GZO) transparent conduction layer (TCL) to p-GaN. The CuS and GZO layers were prepared by thermal evaporation and RF magnetron sputtering, respectively. Although the GZO-only contacts to p-GaN exhibit nonlinear behavior, ohmic contact with a specific contact resistance of 1.6 × 10-2 Ω cm2 has been realized by inserting 3 nm CuS layer between GZO and p-GaN. The optical transmittance of CuS/GZO film was measured to be higher than 80% in the range of 450-600 nm wavelength. The possible mechanism for the ohmic contact behavior can be attributed to the increased hole concentration of p-GaN surface induced by CuS films after annealing. The forward voltage of LEDs with CuS/GZO TCL has been reduced by 1.7 V at 20 mA and the output power has been increased by 29.6% at 100 mA compared with LEDs without CuS interlayer. These results indicated that using CuS intermediate layer could be a potential ohmic contact method to realize high-efficiency LEDs.

  9. ZnO for solar cell and thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Zhou, Chuanle; Ghods, Amirhossein; Yunghans, Kelcy L.; Saravade, Vishal G.; Patel, Paresh V.; Jiang, Xiaodong; Kucukgok, Bahadir; Lu, Na; Ferguson, Ian

    2017-03-01

    ZnO-based materials show promise in energy harvesting applications, such as piezoelectric, photovoltaic and thermoelectric. In this work, ZnO-based vertical Schottky barrier solar cells were fabricated by MOCVD de- position of ZnO thin films on ITO back ohmic contact, while Ag served as the top Schottky contact. Various rapid thermal annealing conditions were studied to modify the carrier density and crystal quality. Greater than 200 nm thick ZnO films formed polycrystalline crystal structure, and were used to demonstrate Schottky solar cells. I-V characterizations of the devices showed photovoltaic performance, but but need further development. This is the first demonstration of vertical Schottky barrier solar cell based on wide bandgap ZnO film. Thin film and bulk ZnO grown by MOCVD or melt growth were also investigated in regards to their room- temperature thermoelectric properties. The Seebeck coefficient of bulk ZnO was found to be much larger than that of thin film ZnO at room temperature due to the higher crystal quality in bulk materials. The Seebeck coefficients decrease while the carrier concentration increases due to the crystal defects caused by the charge carriers. The co-doped bulk Zn0:96Ga0:02Al0:02O showed enhanced power factors, lower thermal conductivities and promising ZT values in the whole temperature range (300-1300 K).

  10. Theoretical study on the top- and enclosed-contacted single-layer MoS{sub 2} piezotronic transistors

    SciTech Connect

    Liu, Wei, E-mail: wliu@binn.cas.cn, E-mail: zlwang@gatech.edu; Zhou, Yongli; Zhang, Aihua

    Recently, the piezotronic effect has been observed in two-dimensional single-layer MoS{sub 2} materials, which have potential applications in force and pressure triggered or controlled electronic devices, sensors, and human-machine interfaces. However, classical theory faces the difficulty in explaining the mechanism of the piezotronic effect for the top- and enclosed-contacted MoS{sub 2} transistors, since the piezoelectric charges are assumed to exist only at the edge of the MoS{sub 2} flake that is far from the electronic transport pathway. In the present study, we identify the piezoelectric charges at the MoS{sub 2}/metal-MoS{sub 2} interface by employing both the density functional theory andmore » finite element method simulations. This interface is on the transport pathway of both top- and enclosed-contacted MoS{sub 2} transistors, thus it is capable of controlling their transport properties. This study deepens the understanding of piezotronic effect and provides guidance for the design of two-dimensional piezotronic devices.« less

  11. Improvement of GaN light-emitting diodes with surface-treated Al-doped ZnO transparent Ohmic contacts by holographic photonic crystal

    NASA Astrophysics Data System (ADS)

    Yang, W. F.; Liu, Z. G.; Xie, Y. N.; Cai, J. F.; Liu, S.; Gong, H.; Wu, Z. Y.

    2012-06-01

    This letter presents a holographic photonic crystal (H-PhC) Al-doped ZnO (AZO) transparent Ohmic contact layer on p-GaN to increase the light output of GaN-based LEDs without destroying the p-GaN. The operating voltage of the PhC LEDs at 20 mA was almost the same as that of the typical planar AZO LEDs. While the resultant PhC LED devices exhibited significant improvements in light extraction, up to 1.22 times that of planar AZO LEDs without PhC integration. Temperature dependence of the integrated photoluminescence intensity indicates that this improvement can be attributed to the increased extraction efficiency due to the surface modification. These results demonstrate that the surface-treated AZO layer by H-PhCs is suitable for fabricating high-brightness GaN-based LEDs.

  12. Characterization of spatial manipulation on ZnO nanocomposites consisting of Au nanoparticles, a graphene layer, and ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Huang, Shen-Che; Lu, Chien-Cheng; Su, Wei-Ming; Weng, Chen-Yuan; Chen, Yi-Cian; Wang, Shing-Chung; Lu, Tien-Chang; Chen, Ching-Pang; Chen, Hsiang

    2018-01-01

    Three types of ZnO-based nanocomposites were fabricated consisting of 80-nm Au nanoparticles (NPs), a graphene layer, and ZnO nanorods (NRs). To investigate interactions between the ZnO NRs and Au nanoparticle, multiple material analysis techniques including field-emission scanning electron microscopy (FESEM), surface contact angle measurements, secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopic characterizations were performed. Results indicate that incorporating a graphene layer could block the interaction between the ZnO NRs and the Au NPs. Furthermore, the Raman signal of the Au NPs could be enhanced by inserting a graphene layer on top of the ZnO NRs. Investigation of these graphene-incorporated nanocomposites would be helpful to future studies of the physical properties and Raman analysis of the ZnO-based nanostructure design.

  13. Linear facing target sputtering of the epitaxial Ga-doped ZnO transparent contact layer on GaN-based light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Shin, Hyun-Su; Lee, Ju-Hyun; Kwak, Joon-Seop; Lee, Hyun Hwi; Kim, Han-Ki

    2013-10-01

    In this study, we reported on the plasma damage-free sputtering of epitaxial Ga-doped ZnO (GZO) films on the p-GaN layer for use as a transparent contact layer (TCL) for GaN-based light-emitting diodes (LEDs) using linear facing target sputtering (LFTS). Effective confinement of high-density plasma between faced GZO targets and the substrate position located outside of the plasma region led to the deposition of the epitaxial GZO TCL with a low sheet resistance of 25.7 Ω/s and a high transmittance of 84.6% on a p-GaN layer without severe plasma damage, which was found using the conventional dc sputtering process. The low turn-on voltage of the GaN-based LEDs with an LFTS-grown GZO TCL layer that was grown at a longer target-to-substrate distance (TSD) indicates that the plasma damage of the GaN-LED could be effectively reduced by adjusting the TSD during the LFTS process.

  14. Down-top nanofabrication of binary (CdO)x (ZnO)1–x nanoparticles and their antibacterial activity

    PubMed Central

    Al-Hada, Naif Mohammed; Mohamed Kamari, Halimah; Abdullah, Che Azurahanim Che; Saion, Elias; Shaari, Abdul H; Talib, Zainal Abidin; Matori, Khamirul Amin

    2017-01-01

    In the present study, binary oxide (cadmium oxide [CdO])x (zinc oxide [ZnO])1–x nanoparticles (NPs) at different concentrations of precursor in calcination temperature were prepared using thermal treatment technique. Cadmium and zinc nitrates (source of cadmium and zinc) with polyvinylpyrrolidone (capping agent) have been used to prepare (CdO)x (ZnO)1–x NPs samples. The sample was characterized by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. XRD patterns analysis revealed that NPs were formed after calcination, which showed a cubic and hexagonal crystalline structure of (CdO)x (ZnO)1–x NPs. The phase analysis using EDX spectroscopy and FTIR spectroscopy confirmed the presence of Cd and Zn as the original compounds of prepared (CdO)x (ZnO)1–x NP samples. The average particle size of the samples increased from 14 to 33 nm as the concentration of precursor increased from x=0.20 to x=0.80, as observed by TEM results. The surface composition and valance state of the prepared product NPs were determined by X-ray photoelectron spectroscopy (XPS) analyses. Diffuse UV–visible reflectance spectra were used to determine the optical band gap through the Kubelka–Munk equation; the energy band gap was found to decrease for CdO from 2.92 to 2.82 eV and for ZnO from 3.22 to 3.11 eV with increasing x value. Additionally, photoluminescence (PL) spectra revealed that the intensity in PL increased with an increase in particle size. In addition, the antibacterial activity of binary oxide NP was carried out in vitro against Escherichia coli ATCC 25922 Gram (−ve), Salmonella choleraesuis ATCC 10708, and Bacillus subtilis UPMC 1175 Gram (+ve). This study indicated that the zone of inhibition of 21 mm has good antibacterial activity toward the Gram-positive B. subtilis UPMC 1175. PMID:29200844

  15. Effect of an Electrochemically Oxidized ZnO Seed Layer on ZnO Nanorods Grown by using Electrodeposition

    NASA Astrophysics Data System (ADS)

    Jeon, Woosung; Leem, Jae-Young

    2018-05-01

    ZnO nanorods were prepared on a Si substrate with and without a ZnO seed layer formed by electro-oxidation to investigate the effect of the seed layer on their growth. The ZnO nanorods grown on the ZnO seed layer had top surfaces that were flat whereas those grown without it had rough top surfaces, as observed in field-emission scanning electron microscopy images. In the Xray diffraction analysis, all ZnO nanorods showed preferential orientation with the (002) plane. In the case of ZnO nanorods prepared with a ZnO seed layer, the residual stress decreased, and the full width at half maximum of the ZnO (002) plane peak decreased. The photoluminescence spectra show a strong and narrow near-band-edge emission peak and high near-band-edge emission to deep-level emission peak ratio for the ZnO nanorods prepared with the seed layer. With respect to the photoresponse properties, the ZnO nanorods grown with the ZnO seed layer showed higher responsivity and faster rise/decay curves than those grown without it. Thus, the ZnO seed layer formed by electro-oxidation improves the structural, optical, and photoresponse properties of the ZnO nanorods formed on it. This method could serve as a new route for improving the properties of optoelectronic devices.

  16. Contact Stress and Kinematic Analysis of All-Epiphyseal and Over-the-Top Pediatric Reconstruction Techniques for the Anterior Cruciate Ligament

    PubMed Central

    McCarthy, Moira M.; Tucker, Scott; Nguyen, Joseph T.; Green, Daniel W.; Imhauser, Carl W.; Cordasco, Frank A.

    2014-01-01

    Background Anterior cruciate ligament (ACL) injuries are an increasingly recognized problem in the pediatric population. Unfortunately, outcomes with conservative treatment are extremely poor. Furthermore, adult reconstruction techniques may be inappropriate to treat skeletally immature patients due to the risk of physeal complications. “Physeal-sparing” reconstruction techniques exist but their ability to restore knee stability and contact mechanics is not well understood. Purpose (1) To assess the ability of the all-epiphyseal (AE) and over-the-top (OT) reconstructions to restore knee kinematics; (2) to assess whether these reconstructions decrease the high posterior contact stresses seen with ACL deficiency; (3) to determine whether the AE or OT produce abnormal tibiofemoral contact stresses. Hypothesis The AE reconstruction will restore contact mechanics and kinematics similarly to that of the ACL intact knee. Methods Ten fresh-frozen human cadaveric knees were tested using a robotic manipulator. Tibiofemoral motions were recorded with the ACL intact, after sectioning the ACL, and after both reconstructions in each of the 10 specimens. The AE utilized an all-inside technique with tunnels exclusively within the epiphysis and fixed with suspensory cortical fixation devices. The OT had a central and vertical tibial tunnel with an over-the-top femur position and was fixed with staples and posts on both ends. Anterior stability was assessed with 134N anterior force at 0, 15, 30, 60, and 90° of knee flexion. Rotational stability was assessed with combined 8 Nm and 4 Nm of abduction and internal rotation, respectively, at 5, 15, and 30° of knee flexion. Results Both reconstruction techniques offloaded the posterior aspect of the tibial plateau compared to the ACL deficient knee in response to both anterior loads and combined moments as demonstrated by reduced contact stresses in this region at all flexion angles. Compared to the ACL intact condition, both the AE

  17. Low operation voltage of GaN-based LEDs with Al-doped ZnO upper contact directly on p-type GaN without insert layer

    NASA Astrophysics Data System (ADS)

    Chen, P. H.; Chen, Yu An; Chang, L. C.; Lai, W. C.; Kuo, Cheng Huang

    2015-07-01

    Al-doped ZnO (AZO) film was evaporated on double-side polished sapphire, p-GaN layers, n+-InGaN-GaN short-period superlattice (SPS) structures, and GaN-based light-emitting diodes (LEDs) by e-beam. The AZO film on the p-GaN layer after thermal annealing exhibited an extremely high transparency (98% at 450 nm) and a small specific contact resistance of 2.19 × 10-2 Ω cm2, which was almost the same as that of as-deposited AZO on n+-SPS structure. With 20 mA injection current, the forward voltages were 3.30 and 3.27 V, whereas the output powers were 4.32 and 4.07 mW for the LED with AZO on insert n+-SPS upper contact and the LED with AZO on p-GaN upper contact (without insert layer), respectively. The small specific contact resistance and low operation voltage of LED with AZO on p-GaN upper contact was achieved by rapid thermal annealing (RTA) process.

  18. PDMS-based triboelectric and transparent nanogenerators with ZnO nanorod arrays.

    PubMed

    Ko, Yeong Hwan; Nagaraju, Goli; Lee, Soo Hyun; Yu, Jae Su

    2014-05-14

    Vertically-grown ZnO nanorod arrays (NRAs) on indium tin oxide (ITO)-coated polyethylene terephthalate (PET), as a top electrode of nanogenerators, were investigated for the antireflective property as well as an efficient contact surface in bare polydimethysiloxane (PDMS)-based triboelectric nanogenerators. Compared to conventional ITO-coated PET (i.e., ITO/PET), the ZnO NRAs considerably suppressed the reflectance from 20 to 9.7% at wavelengths of 300-1100 nm, creating a highly transparent top electrode, as demonstrated by theoretical analysis. Also, the interval time between the peaks of generated output voltage under external pushing forces was significantly decreased from 1.84 to 0.19 s because the reduced contact area of the PDMS by discrete surfaces of the ZnO NRAs on ITO/PET causes a rapid sequence for triboelectric charge generation process including rubbing and separating. Therefore, the use of this top electrode enabled to operate the transparent PDMS-based triboelectric nanogenerator at high frequency of external pushing force. Under different external forces of 0.3-10 kgf, the output voltage and current were also characterized.

  19. Trioctylphosphine-assisted morphology control of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Hong, Yun-Kun; Cho, GeonHee; Park, YoonSu; Oh, Soong Ju; Ha, Don-Hyung

    2018-06-01

    This study investigates the morphological change in colloidal ZnO nanoparticles (NPs) synthesized with trioctylphosphine (TOP). The addition of TOP to the synthesis causes an evolution in the shape of ZnO NPs to tadpole-like particles from quasi-spherical particles at 300 °C. The total length of the tadpole-like ZnO NPs can be modified by controlling the molar ratio of TOP to oleylamine (OLAM). The tadpole-like particles are elongated as the concentration of TOP increased but decreased when the addition of TOP is excessive. These tadpole-like ZnO NPs transform to quasi-spherical NPs regardless of the amount of TOP at a reaction time of 3 h at 300 °C. At 200 °C, the effect of TOP on the ZnO NP synthesis differs from that at 300 °C. The ZnO NPs synthesized by controlling the molar ratios of surfactant ligands (TOP:OLAM = 2:100 and 70:100) at 200 °C share similar amorphous structures, while a crystalline ZnO phase is formed when the reaction time is 3 h. X-ray photoelectron spectroscopy analysis shows that TOP influences the oxidation of ZnO and suggests that a combination of OLAM and TOP plays a role in controlling the shape of ZnO NPs. These results provide critical insights to the utilization of TOP for a shape controlling ligand in ZnO NPs and suggest a new route to design oxide NPs.

  20. Trioctylphosphine-assisted morphology control of ZnO nanoparticles.

    PubMed

    Hong, Yun-Kun; Cho, GeonHee; Park, YoonSu; Oh, Soong Ju; Ha, Don-Hyung

    2018-06-01

    This study investigates the morphological change in colloidal ZnO nanoparticles (NPs) synthesized with trioctylphosphine (TOP). The addition of TOP to the synthesis causes an evolution in the shape of ZnO NPs to tadpole-like particles from quasi-spherical particles at 300 °C. The total length of the tadpole-like ZnO NPs can be modified by controlling the molar ratio of TOP to oleylamine (OLAM). The tadpole-like particles are elongated as the concentration of TOP increased but decreased when the addition of TOP is excessive. These tadpole-like ZnO NPs transform to quasi-spherical NPs regardless of the amount of TOP at a reaction time of 3 h at 300 °C. At 200 °C, the effect of TOP on the ZnO NP synthesis differs from that at 300 °C. The ZnO NPs synthesized by controlling the molar ratios of surfactant ligands (TOP:OLAM = 2:100 and 70:100) at 200 °C share similar amorphous structures, while a crystalline ZnO phase is formed when the reaction time is 3 h. X-ray photoelectron spectroscopy analysis shows that TOP influences the oxidation of ZnO and suggests that a combination of OLAM and TOP plays a role in controlling the shape of ZnO NPs. These results provide critical insights to the utilization of TOP for a shape controlling ligand in ZnO NPs and suggest a new route to design oxide NPs.

  1. A New Route to Nondestructive Top-Contacts for Molecular Electronics on Si: Pb Evaporated on Organic Monolayers.

    PubMed

    Lovrinčić, Robert; Kraynis, Olga; Har-Lavan, Rotem; Haj-Yahya, Abd-Elrazek; Li, Wenjie; Vilan, Ayelet; Cahen, David

    2013-02-07

    Thermally evaporated Pb preserves the electronic properties of an organic monolayer (ML) on Si and surface passivation of the Si surface itself. The obtained current-voltage characteristics of Pb/ML/Si junctions agree with results obtained with the well-established Hg contact and preserve both the molecule-induced dipole effect on, and length-attenuation of, the current. We rationalize our findings by the lack of interaction between the Pb and the Si substrate. This method is fast, scalable, and compatible with standard semiconductor processing, results in close to 100% yield, and can help the development of large-scale utilization of silicon-organic hybrid electronics. Our experimental data show a dependence of the transport across the molecules on the substrate orientation, expressed in the smaller distance decay parameter with Si(100) than that with Si(111).

  2. Effects of the F4TCNQ-Doped Pentacene Interlayers on Performance Improvement of Top-Contact Pentacene-Based Organic Thin-Film Transistors

    PubMed Central

    Fan, Ching-Lin; Lin, Wei-Chun; Chang, Hsiang-Sheng; Lin, Yu-Zuo; Huang, Bohr-Ran

    2016-01-01

    In this paper, the top-contact (TC) pentacene-based organic thin-film transistor (OTFT) with a tetrafluorotetracyanoquinodimethane (F4TCNQ)-doped pentacene interlayer between the source/drain electrodes and the pentacene channel layer were fabricated using the co-evaporation method. Compared with a pentacene-based OTFT without an interlayer, OTFTs with an F4TCNQ:pentacene ratio of 1:1 showed considerably improved electrical characteristics. In addition, the dependence of the OTFT performance on the thickness of the F4TCNQ-doped pentacene interlayer is weaker than that on a Teflon interlayer. Therefore, a molecular doping-type F4TCNQ-doped pentacene interlayer is a suitable carrier injection layer that can improve the TC-OTFT performance and facilitate obtaining a stable process window. PMID:28787845

  3. Effects of the F₄TCNQ-Doped Pentacene Interlayers on Performance Improvement of Top-Contact Pentacene-Based Organic Thin-Film Transistors.

    PubMed

    Fan, Ching-Lin; Lin, Wei-Chun; Chang, Hsiang-Sheng; Lin, Yu-Zuo; Huang, Bohr-Ran

    2016-01-13

    In this paper, the top-contact (TC) pentacene-based organic thin-film transistor (OTFT) with a tetrafluorotetracyanoquinodimethane (F₄TCNQ)-doped pentacene interlayer between the source/drain electrodes and the pentacene channel layer were fabricated using the co-evaporation method. Compared with a pentacene-based OTFT without an interlayer, OTFTs with an F₄TCNQ:pentacene ratio of 1:1 showed considerably improved electrical characteristics. In addition, the dependence of the OTFT performance on the thickness of the F₄TCNQ-doped pentacene interlayer is weaker than that on a Teflon interlayer. Therefore, a molecular doping-type F₄TCNQ-doped pentacene interlayer is a suitable carrier injection layer that can improve the TC-OTFT performance and facilitate obtaining a stable process window.

  4. Effects of V2O5/Au bi-layer electrodes on the top contact Pentacene-based organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Borthakur, Tribeni; Sarma, Ranjit

    2017-05-01

    Top-contact Pentacene-based organic thin film transistors (OTFTs) with a thin layer of Vanadium Pent-oxide between Pentacene and Au layer are fabricated. Here we have found that the devices with V2O5/Au bi-layer source-drain electrode exhibit better field-effect mobility, high on-off ratio, low threshold voltage and low sub-threshold slope than the devices with Au only. The field-effect mobility, current on-off ratio, threshold voltage and sub-threshold slope of V2O5/Au bi-layer OTFT estimated from the device with 15 nm thick V2O5 layer is .77 cm2 v-1 s-1, 7.5×105, -2.9 V and .36 V/decade respectively.

  5. Application of the top specified boundary layer (TSBL) approximation to initial characterization of an inland aquifer mineralization 1. Direct contact between fresh and saltwater

    USGS Publications Warehouse

    Rubin, H.; Buddemeier, R.W.

    1998-01-01

    This paper presents a basic study in generalized terms that originates from two needs: (1) to understand the major mechanisms involved in the mineralization of groundwater of the Great Bend Prairie aquifer of Kansas by saltwater originating from a deeper Permian bedrock formation, and (2) to develop simple, robust tools that can readily be used for local assessment and management activities in the salt-affected region. A simplified basic conceptual model is adopted, incorporating two horizontal layers of porous medium which come into contact at a specific location within the model domain. The top layer is saturated with freshwater, and the bottom layer is saturated with saltwater. The paper considers various stages of approximation which can be useful for simplified simulation of the build-up of the transition zone (TZ) between the freshwater and the saltwater. The hierarchy of approximate approaches leads to the development of the top specified boundary layer (TSBL) method, which is the major tool used in this study for initial characterization of the development of the TZ. It is shown that the thickness of the TZ is mainly determined by the characteristic dispersivity. The build-up of the TZ is completed after a time period equal to the time needed to advect a fluid particle along the whole extent of the TZ. Potential applications and the effects of natural recharge and pumpage on salinity transport in the domain are discussed and evaluated in the context of demonstrating the practicality of the TSBL approach.

  6. Application of calendering for improving the electrical characteristics of a printed top-gate, bottom-contact organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Lee, Sang Hoon; Lee, Dong Geun; Jung, Hoeryong; Lee, Sangyoon

    2018-05-01

    Interface between the channel and the gate dielectric of organic thin film transistors (OTFTs) needs to be smoothed in order to improve the electrical characteristics. In this study, an optimized calendering process was proposed to improve the surface roughness of the channel. Top-gate, bottom-contact structural p-type OTFT samples were fabricated using roll-to-roll gravure printing (source/drain, channel), spin coating (gate dielectric), and inkjet printing (gate electrode). The calendering process was optimized using the grey-based Taguchi method. The channel surface roughness and electrical characteristics of calendered and non-calendered samples were measured and compared. As a result, the average improvement in the surface roughness of the calendered samples was 26.61%. The average on–off ratio and field-effect mobility of the calendered samples were 3.574 × 104 and 0.1113 cm2 V‑1 s‑1, respectively, which correspond to the improvements of 16.72 and 10.20%, respectively.

  7. Top-Contact Self-Aligned Printing for High-Performance Carbon Nanotube Thin-Film Transistors with Sub-Micron Channel Length.

    PubMed

    Cao, Xuan; Wu, Fanqi; Lau, Christian; Liu, Yihang; Liu, Qingzhou; Zhou, Chongwu

    2017-02-28

    Semiconducting single-wall carbon nanotubes are ideal semiconductors for printed thin-film transistors due to their excellent electrical performance and intrinsic printability with solution-based deposition. However, limited by resolution and registration accuracy of current printing techniques, previously reported fully printed nanotube transistors had rather long channel lengths (>20 μm) and consequently low current-drive capabilities (<0.2 μA/μm). Here we report fully inkjet printed nanotube transistors with dramatically enhanced on-state current density of ∼4.5 μA/μm by downscaling the devices to a sub-micron channel length with top-contact self-aligned printing and employing high-capacitance ion gel as the gate dielectric. Also, the printed transistors exhibited a high on/off ratio of ∼10 5 , low-voltage operation, and good mobility of ∼15.03 cm 2 V -1 s -1 . These advantageous features of our printed transistors are very promising for future high-definition printed displays and sensing systems, low-power consumer electronics, and large-scale integration of printed electronics.

  8. Acceptors in ZnO

    DOE PAGES

    Mccluskey, Matthew D.; Corolewski, Caleb; Lv, Jinpeng; ...

    2015-03-21

    Zinc oxide (ZnO) has potential for a range of applications in the area of optoelectronics. The quest for p-type ZnO has focused much attention on acceptors. In this paper, Cu, N, and Li acceptor impurities are discussed. Experimental evidence shows that these point defects have acceptor levels 3.2, 1.5, and 0.8 eV above the valence-band maximum, respectively. The levels are deep because the ZnO valence band is quite low compared to conventional, non-oxide semiconductors. Using MoO2 contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peakmore » in ZnO nanocrystals has been attributed to an acceptor, which may involve a zinc vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g = 2.0033 and g = 2.0075, along with an isotropic center at g = 2.0053.« less

  9. Electrical characterization of FIB processed metal layers for reliable conductive-AFM on ZnO microstructures

    NASA Astrophysics Data System (ADS)

    Pea, M.; Maiolo, L.; Giovine, E.; Rinaldi, A.; Araneo, R.; Notargiacomo, A.

    2016-05-01

    We report on the conductive-atomic force microscopy (C-AFM) study of metallic layers in order to find the most suitable configuration for electrical characterization of individual ZnO micro-pillars fabricated by focused ion beam (FIB). The electrical resistance between the probe tip and both as deposited and FIB processed metal layers (namely, Cr, Ti, Au and Al) has been investigated. Both chromium and titanium evidenced a non homogenous and non ohmic behaviour, non negligible scanning probe induced anodic oxidation associated to electrical measurements, and after FIB milling they exhibited significantly higher tip-sample resistance. Aluminium had generally a more apparent non conductive behaviour. Conversely, gold films showed very good tip-sample conduction properties being less sensitive to FIB processing than the other investigated metals. We found that a reliable C-AFM electrical characterization of ZnO microstructures obtained by FIB machining is feasible by using a combination of metal films as top contact layer. An Au/Ti bilayer on top of ZnO was capable to sustain the FIB fabrication process and to form a suitable ohmic contact to the semiconductor, allowing for reliable C-AFM measurement. To validate the consistency of this approach, we measured the resistance of ZnO micropillars finding a linear dependence on the pillar height, as expected for an ohmic conductor, and evaluated the resistivity of the material. This procedure has the potential to be downscaled to nanometer size structures by a proper choice of metal films type and thickness.

  10. Preparation, characterization and properties of ZnO nanomaterials

    NASA Astrophysics Data System (ADS)

    Luo, Jiaolian; Zhang, Xiaoming; Chen, Ruxue; Wang, Xiaohui; Zhu, Ji; Wang, Xiaomin

    2017-06-01

    In this paper, using the hydrothermal synthesis method, NaOH, Zn(NO3)2, anhydrous ethanol, deionized water as raw material to prepare ZnO nanomaterial, and by X ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL) on the synthesis of nano materials, surface morphology and phase luminescence characterization. The results show that the nano materials synthesized for single-phase ZnO, belonging to the six wurtzite structure; material surface shaped, arranged evenly distributed, and were the top six party structure; ZnO nano materials synthesized with strong emission spectra, emission peak is located at 394nm.

  11. Micro-patterned ZnO semiconductors for high performance thin film transistors via chemical imprinting with a PDMS stamp.

    PubMed

    Seong, Kieun; Kim, Kyongjun; Park, Si Yun; Kim, Youn Sang

    2013-04-07

    Chemical imprinting was conducted on ZnO semiconductor films via a chemical reaction at the contact regions between a micro-patterned PDMS stamp and ZnO films. In addition, we applied the chemical imprinting on Li doped ZnO thin films for high performance TFTs fabrication. The representative micro-patterned Li doped ZnO TFTs showed a field effect mobility of 4.2 cm(2) V(-1) s(-1) after sintering at 300 °C.

  12. Physical Modeling of Gate-Controlled Schottky Barrier Lowering of Metal-Graphene Contacts in Top-Gated Graphene Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Mao, Ling-Feng; Ning, Huansheng; Huo, Zong-Liang; Wang, Jin-Yan

    2015-12-01

    A new physical model of the gate controlled Schottky barrier height (SBH) lowering in top-gated graphene field-effect transistors (GFETs) under saturation bias condition is proposed based on the energy conservation equation with the balance assumption. The theoretical prediction of the SBH lowering agrees well with the experimental data reported in literatures. The reduction of the SBH increases with the increasing of gate voltage and relative dielectric constant of the gate oxide, while it decreases with the increasing of oxide thickness, channel length and acceptor density. The magnitude of the reduction is slightly enhanced under high drain voltage. Moreover, it is found that the gate oxide materials with large relative dielectric constant (>20) have a significant effect on the gate controlled SBH lowering, implying that the energy relaxation of channel electrons should be taken into account for modeling SBH in GFETs.

  13. Physical Modeling of Gate-Controlled Schottky Barrier Lowering of Metal-Graphene Contacts in Top-Gated Graphene Field-Effect Transistors.

    PubMed

    Mao, Ling-Feng; Ning, Huansheng; Huo, Zong-Liang; Wang, Jin-Yan

    2015-12-17

    A new physical model of the gate controlled Schottky barrier height (SBH) lowering in top-gated graphene field-effect transistors (GFETs) under saturation bias condition is proposed based on the energy conservation equation with the balance assumption. The theoretical prediction of the SBH lowering agrees well with the experimental data reported in literatures. The reduction of the SBH increases with the increasing of gate voltage and relative dielectric constant of the gate oxide, while it decreases with the increasing of oxide thickness, channel length and acceptor density. The magnitude of the reduction is slightly enhanced under high drain voltage. Moreover, it is found that the gate oxide materials with large relative dielectric constant (>20) have a significant effect on the gate controlled SBH lowering, implying that the energy relaxation of channel electrons should be taken into account for modeling SBH in GFETs.

  14. Top-Contact Pentacene-Based Organic Thin Film Transistor (OTFT) with N, N'-Bis(3-Methyl Phenyl)- N, N'-Diphenyl Benzidine (TPD)/Au Bilayer Source-Drain Electrode

    NASA Astrophysics Data System (ADS)

    Borthakur, Tribeni; Sarma, Ranjit

    2018-01-01

    A top-contact Pentacene-based organic thin film transistor (OTFT) with N, N'-Bis (3-methyl phenyl)- N, N'-diphenyl benzidine (TPD)/Au bilayer source-drain electrode is reported. The devices with TPD/Au bilayer source-drain (S-D) electrodes show better performance than the single layer S-D electrode OTFT devices. The field-effect mobility of 4.13 cm2 v-1 s-1, the on-off ratio of 1.86 × 107, the threshold voltage of -4 v and the subthreshold slope of .27 v/decade, respectively, are obtained from the device with a TPD/Au bilayer source-drain electrode.

  15. Enhanced performance of ZnO microballoon arrays for a triboelectric nanogenerator.

    PubMed

    Deng, Weili; Zhang, Binbin; Jin, Long; Chen, Yueqi; Chu, Wenjun; Zhang, Haitao; Zhu, Minhao; Yang, Weiqing

    2017-03-01

    In recent years, triboelectric nanogenerators (TENGs), harvesting energy from the environment as a sustainable power source, have attracted great attention. Currently, many reports focus on the effect of surface modification on the electrical output performance of the TENG. In this work, we have fabricated vertically grown ZnO microballoon (ZnOMB) arrays on top of pyramid-featured PDMS patterned film, contacted with PTFE film to construct the TENG. The electrical output performances of the designed TENG are presented under external forces with different frequencies. The corresponding output open-circuit voltage with ZnOMBs could reach about 57 V the current density about 59 mA m -2 at 100 Hz, which was about 2.3 times higher than without any ZnO. The global maximum of the instantaneous peak power could reach 1.1 W m -2 when the external load resistance was about 2 MΩ. Furthermore, the electrical output of the fabricated device could light 30 commercial LED bulbs without any rectifier circuits or energy-storage elements. This clearly suggests that this kind of surface modification can dramatically enhance the output performance of the TENG. Moreover, the design of TENG demonstrated here can be applied to various energy harvesting applications.

  16. Enhanced performance of ZnO microballoon arrays for a triboelectric nanogenerator

    NASA Astrophysics Data System (ADS)

    Deng, Weili; Zhang, Binbin; Jin, Long; Chen, Yueqi; Chu, Wenjun; Zhang, Haitao; Zhu, Minhao; Yang, Weiqing

    2017-03-01

    In recent years, triboelectric nanogenerators (TENGs), harvesting energy from the environment as a sustainable power source, have attracted great attention. Currently, many reports focus on the effect of surface modification on the electrical output performance of the TENG. In this work, we have fabricated vertically grown ZnO microballoon (ZnOMB) arrays on top of pyramid-featured PDMS patterned film, contacted with PTFE film to construct the TENG. The electrical output performances of the designed TENG are presented under external forces with different frequencies. The corresponding output open-circuit voltage with ZnOMBs could reach about 57 V the current density about 59 mA m-2 at 100 Hz, which was about 2.3 times higher than without any ZnO. The global maximum of the instantaneous peak power could reach 1.1 W m-2 when the external load resistance was about 2 MΩ. Furthermore, the electrical output of the fabricated device could light 30 commercial LED bulbs without any rectifier circuits or energy-storage elements. This clearly suggests that this kind of surface modification can dramatically enhance the output performance of the TENG. Moreover, the design of TENG demonstrated here can be applied to various energy harvesting applications.

  17. Architectural Tops

    ERIC Educational Resources Information Center

    Mahoney, Ellen

    2010-01-01

    The development of the skyscraper is an American story that combines architectural history, economic power, and technological achievement. Each city in the United States can be identified by the profile of its buildings. The design of the tops of skyscrapers was the inspiration for the students in the author's high-school ceramic class to develop…

  18. Fabrication of hierarchical ZnO nanostructures on cotton fabric for wearable device applications

    NASA Astrophysics Data System (ADS)

    Pandiyarasan, V.; Suhasini, S.; Archana, J.; Navaneethan, M.; Majumdar, Abhijit; Hayakawa, Y.; Ikeda, H.

    2017-10-01

    We have investigated ZnO nanostructures on cotton fabric (CF) s a flexible material for an application of wearable thermoelectric (TE) power generator which requires super-hydrophobicity, UV protection, and high TE efficiency. Field emission scanning electron microscopy images revealed that the formed ZnO nanostructures have a mixture of nanorods and nanosheets and are uniformly coated on the CF. XRD pattern and Raman spectra revealed that the ZnO nanostructure has a wurtzite structure. Contact angle measurements showed that the ZnO-nanostructures-coated CF possessed a high super hydrophobic nature with an angle of 132.5°. ZnO nanocomposite/CF sample exhibited an excellent UV protection factor 183.84. Seebeck coefficient, electrical resistivity and thermoelectric power factor of the ZnO nanostructures on cotton fabric were evaluated to be 28 μV/K, 0.04 Ω-cm, and 22 μW/m K2, respectively.

  19. A metal-semiconductor-metal detector based on ZnO nanowires grown on a graphene layer.

    PubMed

    Xu, Qiang; Cheng, Qijin; Zhong, Jinxiang; Cai, Weiwei; Zhang, Zifeng; Wu, Zhengyun; Zhang, Fengyan

    2014-02-07

    High quality ZnO nanowires (NWs) were grown on a graphene layer by a hydrothermal method. The ZnO NWs revealed higher uniform surface morphology and better structural properties than ZnO NWs grown on SiO2/Si substrate. A low dark current metal-semiconductor-metal photodetector based on ZnO NWs with Au Schottky contact has also been fabricated. The photodetector displays a low dark current of 1.53 nA at 1 V bias and a large UV-to-visible rejection ratio (up to four orders), which are significantly improved compared to conventional ZnO NW photodetectors. The improvement in UV detection performance is attributed to the existence of a surface plasmon at the interface of the ZnO and the graphene.

  20. Reversible superhydrophobic-superhydrophilic transition of ZnO nanorod/epoxy composite films.

    PubMed

    Liu, Yan; Lin, Ziyin; Lin, Wei; Moon, Kyoung Sik; Wong, C P

    2012-08-01

    Tuning the surface wettability is of great interest for both scientific research and practical applications. We demonstrated reversible transition between superhydrophobicity and superhydrophilicity on a ZnO nanorod/epoxy composite film. The epoxy resin serves as an adhesion and stress relief layer. The ZnO nanorods were exposed after oxygen reactive ion etching of the epoxy matrix. A subsequent chemcial treatment with fluoroalkyl and alkyl silanes resulted in a superhydrophobic surface with a water contact angle up to 158.4° and a hysteresis as low as 1.3°. Under UV irradiation, the water contact angle decreased gradually, and the surface eventually became superhydrophilic because of UV induced decomposition of alkyl silanes and hydroxyl absorption on ZnO surfaces. A reversible transition of surface wettability was realized by alternation of UV illumination and surface treatment. Such ZnO nanocomposite surface also showed improved mechanical robustness.

  1. Bipolar charge storage characteristics in copper and cobalt co-doped zinc oxide (ZnO) thin film.

    PubMed

    Kumar, Amit; Herng, Tun Seng; Zeng, Kaiyang; Ding, Jun

    2012-10-24

    The bipolar charge phenomenon in Cu and Co co-doped zinc oxide (ZnO) film samples has been studied using scanning probe microscopy (SPM) techniques. Those ZnO samples are made using a pulsed laser deposition (PLD) technique. It is found that the addition of Cu and Co dopants suppresses the electron density in ZnO and causes a significant change in the work function (Fermi level) value of the ZnO film; this results in the ohmic nature of the contact between the electrode (probe tip) and codoped sample, whereas this contact exhibits a Schottky nature in the undoped and single-element-doped samples. These results are verified by Kelvin probe force microscopy (KPFM) and ultraviolet photoelectron spectroscopy (UPS) measurements. It is also found that the co-doping (Cu and Co) can stabilize the bipolar charge, whereas Cu doping only stabilizes the positive charge in ZnO thin films.

  2. Visible electroluminescence from a ZnO nanowires/p-GaN heterojunction light emitting diode.

    PubMed

    Baratto, C; Kumar, R; Comini, E; Faglia, G; Sberveglieri, G

    2015-07-27

    In the current paper we apply catalyst assisted vapour phase growth technique to grow ZnO nanowires (ZnO nws) on p-GaN thin film obtaining EL emission in reverse bias regime. ZnO based LED represents a promising alternative to III-nitride LEDs, as in free devices: the potential is in near-UV emission and visible emission. For ZnO, the use of nanowires ensures good crystallinity of the ZnO, and improved light extraction from the interface when the nanowires are vertically aligned. We prepared ZnO nanowires in a tubular furnace on GaN templates and characterized the p-n ZnO nws/GaN heterojunction for LED applications. SEM microscopy was used to study the growth of nanowires and device preparation. Photoluminescence (PL) and Electroluminescence (EL) spectroscopies were used to characterize the heterojunction, showing that good quality of PL emission is observed from nanowires and visible emission from the junction can be obtained from the region near ZnO contact, starting from onset bias of 6V.

  3. Solvents induced ZnO nanoparticles aggregation associated with their interfacial effect on organic solar cells.

    PubMed

    Li, Pandeng; Jiu, Tonggang; Tang, Gang; Wang, Guojie; Li, Jun; Li, Xiaofang; Fang, Junfeng

    2014-10-22

    ZnO nanofilm as a cathode buffer layer has surface defects due to the aggregations of ZnO nanoparticles, leading to poor device performance of organic solar cells. In this paper, we report the ZnO nanoparticles aggregations in solution can be controlled by adjusting the solvents ratios (chloroform vs methanol). These aggregations could influence the morphology of ZnO film. Therefore, compact and homogeneous ZnO film can be obtained to help achieve a preferable power conversion efficiency of 8.54% in inverted organic solar cells. This improvement is attributed to the decreased leakage current and the increased electron-collecting efficiency as well as the improved interface contact with the active layer. In addition, we find the enhanced maximum exciton generation rate and exciton dissociation probability lead to the improvement of device performance due to the preferable ZnO dispersion. Compared to other methods of ZnO nanofilm fabrication, it is the more convenient, moderate, and effective to get a preferable ZnO buffer layer for high-efficiency organic solar cells.

  4. Resistive switching: An investigation of the bipolar–unipolar transition in Co-doped ZnO thin films

    SciTech Connect

    Santos, Daniel A.A., E-mail: danielandrade.ufs@gmail.com; Department of Physics, University at Buffalo, The State University of New York, Buffalo, NY 14260; Zeng, Hao

    2015-06-15

    Highlights: • A purely bipolar behavior on a Co-doped ZnO thin film has been demonstrated. • We have shown what can happen if a unipolar test is performed in a purely bipolar device. • An explanation for how a sample can show a purely bipolar switching behavior was suggested. • An important open issue about resistive switching effect was put in debate. - Abstract: In order to investigate the resistive switching effect we built devices in a planar structure in which two Al contacts were deposited on the top of the film and separated by a small gap using amore » shadow mask. Therefore, two samples of 10% Co-doped ZnO thin films were sputtered on glass substrate. High resolution X-ray diffraction (HRXRD) revealed a highly c-axis oriented crystalline structure, without secondary phase. The high resolution scanning electron microscopy (HRSEM) showed a flat surface with good coverage and thickness about 300 nm. A Keithley 2425 semiconductor characterization system was used to perform the resistive switching tests in the bipolar and unipolar modes. Considering only the effect of compliance current (CC), the devices showed a purely bipolar behavior since an increase in CC did not induce a transition to unipolar behavior.« less

  5. NOAA Photo Library - Contacts

    Science.gov Websites

    NOAA Photo Library Banner Takes you to the Top Page Takes you to the About this Site page. Takes concerning this site, please contact: NOAA Photo Library NOAA Central Library Email: photolibrary@noaa.gov Library NOAA Privacy Policy | NOAA Disclaimer Last Updated: September 30, 2009

  6. Language Contact.

    ERIC Educational Resources Information Center

    Nelde, Peter Hans

    1995-01-01

    Examines the phenomenon of language contact and recent trends in linguistic contact research, which focuses on language use, language users, and language spheres. Also discusses the role of linguistic and cultural conflicts in language contact situations. (13 references) (MDM)

  7. Growth of bulk ZnO crystals by self-selecting CVT method

    NASA Astrophysics Data System (ADS)

    Fan, Long; Jiang, Tao; Xiao, TingTing; Chen, Jie; Peng, Liping; Wang, Xuemin; Yan, Dawei; Wu, Weidong

    2018-05-01

    Bulk ZnO crystals were grown by self-selecting CVT method using carbon as the transport agent. The crystal growth process took place on the top of the polycrystalline source material, and deep-red colored ZnO crystals of several millimeters were obtained. The as-grown crystals were characterized by X-ray diffraction (XRD), Energy Dispersive Spectrometer (EDS), Raman scattering (RS) spectroscopy, visible-near infrared (VIS-NIR) spectrophotometer and room temperature photoluminescence (PL) spectroscopy. XRD results indicate good crystallinity of the ZnO crystal. The EDS analysis shows that the crystal has a stoichiometry ratio Zn: O = 52: 48. The results suggest the existence of native defects of oxygen vacancies (OV) in the as-grown ZnO samples, which is caused by the stoichiometry shift to Zn-rich.

  8. Nucleant layer effect on nanocolumnar ZnO films grown by electrodeposition

    NASA Astrophysics Data System (ADS)

    Tolosa, Maria D. Reyes; Damonte, Laura C.; Brine, Hicham; Bolink, Henk J.; Hernández-Fenollosa, María A.

    2013-03-01

    Different ZnO nanostructured films were electrochemically grown, using an aqueous solution based on ZnCl2, on three types of transparent conductive oxides grow on commercial ITO (In2O3:Sn)-covered glass substrates: (1) ZnO prepared by spin coating, (2) ZnO prepared by direct current magnetron sputtering, and (3) commercial ITO-covered glass substrates. Although thin, these primary oxide layers play an important role on the properties of the nanostructured films grown on top of them. Additionally, these primary oxide layers prevent direct hole combination when used in optoelectronic devices. Structural and optical characterizations were carried out by scanning electron microscopy, atomic force microscopy, and optical transmission spectroscopy. We show that the properties of the ZnO nanostructured films depend strongly on the type of primary oxide-covered substrate used. Previous studies on different electrodeposition methods for nucleation and growth are considered in the final discussion.

  9. Nucleant layer effect on nanocolumnar ZnO films grown by electrodeposition.

    PubMed

    Tolosa, Maria D Reyes; Damonte, Laura C; Brine, Hicham; Bolink, Henk J; Hernández-Fenollosa, María A

    2013-03-23

    Different ZnO nanostructured films were electrochemically grown, using an aqueous solution based on ZnCl2, on three types of transparent conductive oxides grow on commercial ITO (In2O3:Sn)-covered glass substrates: (1) ZnO prepared by spin coating, (2) ZnO prepared by direct current magnetron sputtering, and (3) commercial ITO-covered glass substrates. Although thin, these primary oxide layers play an important role on the properties of the nanostructured films grown on top of them. Additionally, these primary oxide layers prevent direct hole combination when used in optoelectronic devices. Structural and optical characterizations were carried out by scanning electron microscopy, atomic force microscopy, and optical transmission spectroscopy. We show that the properties of the ZnO nanostructured films depend strongly on the type of primary oxide-covered substrate used. Previous studies on different electrodeposition methods for nucleation and growth are considered in the final discussion.

  10. Nucleant layer effect on nanocolumnar ZnO films grown by electrodeposition

    PubMed Central

    2013-01-01

    Different ZnO nanostructured films were electrochemically grown, using an aqueous solution based on ZnCl2, on three types of transparent conductive oxides grow on commercial ITO (In2O3:Sn)-covered glass substrates: (1) ZnO prepared by spin coating, (2) ZnO prepared by direct current magnetron sputtering, and (3) commercial ITO-covered glass substrates. Although thin, these primary oxide layers play an important role on the properties of the nanostructured films grown on top of them. Additionally, these primary oxide layers prevent direct hole combination when used in optoelectronic devices. Structural and optical characterizations were carried out by scanning electron microscopy, atomic force microscopy, and optical transmission spectroscopy. We show that the properties of the ZnO nanostructured films depend strongly on the type of primary oxide-covered substrate used. Previous studies on different electrodeposition methods for nucleation and growth are considered in the final discussion. PMID:23522332

  11. Growth of high-density ZnO nanorods on wood with enhanced photostability, flame retardancy and water repellency

    NASA Astrophysics Data System (ADS)

    Kong, Lizhuo; Tu, Kunkun; Guan, Hao; Wang, Xiaoqing

    2017-06-01

    Zinc oxide (ZnO) nanorod arrays were successfully assembled on the wood surface in situ via a two-step process consisting of formation of ZnO seeds and subsequent crystal growth under hydrothermal conditions at a low temperature. The morphology and crystalline structure of the formed ZnO nanorods were studied by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Highly dense and uniform arrays of ZnO nanorods with well-defined hexagonal facets were generated on the wood surface by tuning the concentration of the ZnO growth solution during the hydrothermal treatment. Accelerated weathering tests indicated that the assembled ZnO nanorod arrays were highly protective against UV radiation and greatly enhanced the photostability of the coated wood. Meanwhile, the ZnO nanorod-coated wood can withstand continuous exposure to flame with only minor smoldering in contrast with the pristine wood catching fire easily and burning rapidly. Moreover, when further modified with low-surface-energy stearic acid, the ZnO nanorod decorated wood surface can be transformed into a superhydrophobic surface, with a water contact angle (CA) of ∼154°. Such ZnO nanorod-modified woods with enhanced photostability, flame retardancy and water repellency offer an interesting alternative to conventional wood preservation strategies, highlighting their potential applications in some novel wood products.

  12. ZnO Thin Film Electronics for More than Displays

    NASA Astrophysics Data System (ADS)

    Ramirez, Jose Israel

    discharging time constants. Finally, to circumvent fabrication challenges on predetermined complex shapes, like curved mirror optics, a technique to transfer electronics from a rigid substrate to a flexible substrate is used. This technique allows various thin films, regardless of their deposition temperature, to be transferred to flexible substrates. Finally, ultra-low power operation of ZnO TFT gas sensors was demonstrated. The ZnO ozone sensors were optimized to operate with excellent electrical stability in ambient conditions, without using elevated temperatures, while still providing good gas sensitivity. This was achieved by using a post-deposition anneal and by partially passivating the contact regions while leaving the semiconductor sensing area open to the ambient. A novel technique to reset the gas sensor using periodic pulsing of a UV light over the sensor results in less than 25 milliseconds recovery time. A pathway to achieve gas selectivity by using organic thin-film layers as filters deposited over the gas sensors tis demonstrated. The ZnO ozone sensor TFTs and the UV light operate at room temperature with an average power below 1 muW.

  13. ZnO deposition on metal substrates: Relating fabrication, morphology, and wettability

    NASA Astrophysics Data System (ADS)

    Beaini, Sara S.; Kronawitter, Coleman X.; Carey, Van P.; Mao, Samuel S.

    2013-05-01

    It is not common practice to deposit thin films on metal substrates, especially copper, which is a common heat exchanger metal and practical engineering material known for its heat transfer properties. While single crystal substrates offer ideal surfaces with uniform structure for compatibility with oxide deposition, metallic surfaces needed for industrial applications exhibit non-idealities that complicate the fabrication of oxide nanostructure arrays. The following study explored different ZnO fabrication techniques to deposit a (super)hydrophobic thin film of ZnO on a metal substrate, specifically copper, in order to explore its feasibility as an enhanced condensing surface. ZnO was selected for its non-toxicity, ability to be made (super)hydrophobic with hierarchical roughness, and its photoinduced hydrophilicity characteristic, which could be utilized to pattern it to have both hydrophobic-hydrophilic regions. We investigated the variation of ZnO's morphology and wetting state, using SEMs and sessile drop contact angle measurements, as a function of different fabrication techniques: sputtering, pulsed laser deposition (PLD), electrodeposition and annealing Zn. We successfully fabricated (super)hydrophobic ZnO on a mirror finish, commercially available copper substrate using the scalable electrodeposition technique. PLD for ZnO deposition did not prove viable, as the ZnO samples on metal substrates were hydrophilic and the process does not lend itself to scalability. The annealed Zn sheets did not exhibit consistent wetting state results.

  14. Coherently coupled ZnO and VO2 interface studied by photoluminescence and electrical transport across a phase transition

    NASA Astrophysics Data System (ADS)

    Srivastava, Amar; Herng, T. S.; Saha, Surajit; Nina, Bao; Annadi, A.; Naomi, N.; Liu, Z. Q.; Dhar, S.; Ariando; Ding, J.; Venkatesan, T.

    2012-06-01

    We have investigated the photoluminescence and electrical properties of a coherently coupled interface consisting of a ZnO layer grown on top of an oriented VO2 layer on sapphire across the phase transition of VO2. The band edge and defect luminescence of the ZnO overlayer exhibit hysteresis in opposite directions induced by the phase transition of VO2. Concomitantly the phase transition of VO2 was seen to induce defects in the ZnO layer. Such coherently coupled interfaces could be of use in characterizing the stability of a variety of interfaces in situ and also for novel device application.

  15. Superhydrophobic Ag decorated ZnO nanostructured thin film as effective surface enhanced Raman scattering substrates

    NASA Astrophysics Data System (ADS)

    Jayram, Naidu Dhanpal; Sonia, S.; Poongodi, S.; Kumar, P. Suresh; Masuda, Yoshitake; Mangalaraj, D.; Ponpandian, N.; Viswanathan, C.

    2015-11-01

    The present work is an attempt to overcome the challenges in the fabrication of super hydrophobic silver decorated zinc oxide (ZnO) nanostructure thin films via thermal evaporation process. The ZnO nanowire thin films are prepared without any surface modification and show super hydrophobic nature with a contact angle of 163°. Silver is further deposited onto the ZnO nanowire to obtain nanoworm morphology. Silver decorated ZnO (Ag@ZnO) thin films are used as substrates for surface enhanced Raman spectroscopy (SERS) studies. The formation of randomly arranged nanowire and silver decorated nanoworm structure is confirmed using FESEM, HR-TEM and AFM analysis. Crystallinity and existence of Ag on ZnO are confirmed using XRD and XPS studies. A detailed growth mechanism is discussed for the formation of the nanowires from nanobeads based on various deposition times. The prepared SERS substrate reveals a reproducible enhancement of 3.082 × 107 M for Rhodamine 6G dye (R6G) for 10-10 molar concentration per liter. A higher order of SERS spectra is obtained for a contact angle of 155°. Thus the obtained thin films show the superhydrophobic nature with a highly enhanced Raman spectrum and act as SERS substrates. The present nanoworm morphology shows a new pathway for the construction of semiconductor thin films for plasmonic studies and challenges the orderly arranged ZnO nanorods, wires and other nano structure substrates used in SERS studies.

  16. Halloysite Nanotubes Supported Ag and ZnO Nanoparticles with Synergistically Enhanced Antibacterial Activity

    NASA Astrophysics Data System (ADS)

    Shu, Zhan; Zhang, Yi; Yang, Qian; Yang, Huaming

    2017-02-01

    Novel antimicrobial nanocomposite incorporating halloysite nanotubes (HNTs) and silver (Ag) into zinc oxide (ZnO) nanoparticles is prepared by integrating HNTs and decorating Ag nanoparticles. ZnO nanoparticles (ZnO NPs) and Ag nanoparticles (Ag NPs) with a size of about 100 and 8 nm, respectively, are dispersively anchored onto HNTs. The synergistic effects of ZnO NPs, Ag NPs, and HNTs led to the superior antibacterial activity of the Ag-ZnO/HNTs antibacterial nanocomposites. HNTs facilitated the dispersion and stability of ZnO NPs and brought them in close contact with bacteria, while Ag NPs could promote the separation of photogenerated electron-hole pairs and enhanced the antibacterial activity of ZnO NPs. The close contact with cell membrane enabled the nanoparticles to produce the increased concentration of reactive oxygen species and the metal ions to permeate into the cytoplasm, thus induced quick death of bacteria, indicating that Ag-ZnO/HNTs antibacterial nanocomposite is a promising candidate in the antibacterial fields.

  17. Water-repellent coatings prepared by modification of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Chakradhar, R. P. S.; Dinesh Kumar, V.

    Superhydrophobic coatings with a static water contact angle (WCA) > 150° were prepared by modifying ZnO nanoparticles with stearic acid (ZnO@SA). ZnO nanoparticles of size ˜14 nm were prepared by solution combustion method. X-ray diffraction (XRD) studies reveal that as prepared ZnO has hexagonal wurtzite structure whereas the modified coatings convert to zinc stearate. Field emission scanning electron micrographs (FE-SEM) show the dual morphology of the coatings exhibiting both particles and flakes. The flakes are highly fluffy in nature with voids and nanopores. Fourier transformed infrared (FTIR) spectrum shows the stearate ion co-ordinates with Zn2+ in the bidentate form. The surface properties such as surface free energy (γp) and work of adhesion (W) of the unmodified and modified ZnO coatings have been evaluated. The electron paramagnetic resonance (EPR) spectroscopy reveals that surface defects play a major role in the wetting behavior.

  18. Direct Heteroepitaxial Growth of ZnO over GaN Crystal in Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Hamada, Takahiro; Ito, Akihiro; Nagao, Nobuaki; Suzuki, Nobuyasu; Fujii, Eiji; Tsujimura, Ayumu

    2013-04-01

    We report on the structural and electrical properties of ZnO films grown on surface-treated GaN/Al2O3 substrates by chemical bath deposition. X-ray diffraction analysis indicated that the ZnO films had a single-crystalline wurtzite structure with c-axis orientation. The ZnO film exhibited n-type conduction with a carrier concentration of 6.9 ×1018 cm-3, an electron mobility of 41 cm2/(V.s), and a resistivity of 2.2 ×10-2 Ω.cm. A low specific contact resistivity of 4.3 ×10-3 Ω.cm2 was obtained at the ZnO/n-GaN interface. Additionally, the ZnO film exhibited high transparency in the visible and infrared region.

  19. Contact Dermatitis

    MedlinePlus

    ... Us Media contacts Advertising contacts AAD logo Advertising, marketing and sponsorships Legal notice Copyright © 2018 American Academy ... prohibited without prior written permission. AAD logo Advertising, marketing and sponsorships Legal notice Copyright © 2017 American Academy ...

  20. Annealing temperature dependent reversible wettability switching of micro/nano structured ZnO superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Velayi, Elmira; Norouzbeigi, Reza

    2018-05-01

    Superhydrophobic ZnO surfaces with reversibly tunable wettability were fabricated on stainless steel meshes via a facile chemical bath deposition method just by regulating the micro/nano structured ZnO needles without using chemical post modifications. The obtained surfaces can be easily and reversibly switched between superhydrophobic and superhydrophilic/underwater superoleophobic characteristics by altering the annealing temperatures. As-prepared sample exhibited long-term superhydrophobic properties with a water contact angle (WCA) of 163.8° ± 1.8° and contact angle hysteresis (CAH) of 1.1° ± 0.8°. The SEM, XRD, XPS and Raman analyses were employed to characterize the morphological features and surface chemistry of the prepared samples. SEM images showed the formation of ZnO micro/nanoneedles with a diameter of ∼90 nm on the substrate. The superhydrophobic ZnO surface was switched to highly hydrophilic and underwater superoleophobic properties with an oil contact angle (OCA) of about 172.5° after being annealed at 400 °C in air for 30 min and restored to superhydrophobic state again by altering the annealing temperature to 150 °C. Mechanical durability of the ZnO superhydrophobic surface was tested by an abrasion test. Results confirmed that the prepared surface exhibited an excellent robustness after 20 abrasion cycles under the pressure of 4.7 kPa.

  1. Traffic operation strategies : TOPS

    DOT National Transportation Integrated Search

    2000-04-01

    The Legislature required the Department of Transportation to submit a report on Traffic Operations Strategies (TOPS). This report responds to the Legislative requirement by describing the motivation for TOPS, the current status of TOPS, and opportuni...

  2. Top coat or no top coat for immersion lithography?

    NASA Astrophysics Data System (ADS)

    Stepanenko, N.; Kim, Hyun-Woo; Kishimura, S.; Van Den Heuvel, D.; Vandenbroeck, N.; Kocsis, M.; Foubert, P.; Maenhoudt, M.; Ercken, M.; Van Roey, F.; Gronheid, R.; Pollentier, I.; Vangoidsenhoven, D.; Delvaux, C.; Baerts, C.; O'Brien, S.; Fyen, W.; Wells, G.

    2006-03-01

    Since the moment immersion lithography appeared in the roadmaps of IC manufacturers, the question whether to use top coats has become one of the important topics for discussions. The top coats used in immersion lithography have proved to serve as good protectors from leaching of the resist components (PAGs, bases) into the water. However their application complicates the process and may lead to two side effects. First, top coats can affect the process window and resist profile depending on the material's refractive index, thickness, acidity, chemical interaction with the resist and the soaking time. Second, the top coat application may increase the total amount of defects on the wafer. Having an immersion resist which could work without the top coat would be a preferable solution. Still, it is quite challenging to make such a resist as direct water/resist interaction may also result in process window changes, CD variations, generation of additional defects. We have performed a systematic evaluation of a large number of immersion resist and top coat combinations, using the ASML XT:1250Di scanner at IMEC. The samples for the experiments were provided by all the leading resist and top coat suppliers. Particular attention was paid to how the resist and top coat materials from different vendors interacted with each other. Among the factors which could influence the total amount of defects or CD variations on the wafer were: the material's dynamic contact angle and its interaction with the scanner stage speed, top coat thickness and intermixing layer formation, water uptake and leaching. We have examined the importance of all mentioned factors, using such analytical techniques as Resist Development Analyser (RDA), Quartz Crystal Microbalance (QCM), Mass Spectroscopy (MS) and scatterometry. We have also evaluated the influence of the pre- and pos- exposure rinse processes on the defectivity. In this paper we will present the data on imaging and defectivity performance of

  3. Contact us

    Science.gov Websites

    DCIO R&A DCIO CS In the News Library Contact us contact us Contact the Department of Defense Public Queries for DOD General questions or comments concerning the DOD Veteran Affairs Public questions or comments concerning the Department of Veterans Affairs (VA) Army Public questions or comments concerning

  4. A boron and gallium co-doped ZnO intermediate layer for ZnO/Si heterojunction diodes

    NASA Astrophysics Data System (ADS)

    Lu, Yuanxi; Huang, Jian; Li, Bing; Tang, Ke; Ma, Yuncheng; Cao, Meng; Wang, Lin; Wang, Linjun

    2018-01-01

    ZnO (Zinc oxide)/Si (Silicon) heterojunctions were prepared by depositing n-type ZnO films on p-type single crystal Si substrates using magnetron sputtering. A boron and gallium co-doped ZnO (BGZO) high conductivity intermediate layer was deposited between aurum (Au) electrodes and ZnO films. The influence of the BGZO layer on the properties of Au/ZnO contacts and the performance of ZnO/Si heterojunctions was investigated. The results show an improvement in contact resistance by introducing the BGZO layer. Compared with the ZnO/Si heterojunction, the BGZO/ZnO/Si heterojunction exhibits a larger forward current, a smaller turn-on voltage and higher ratio of ultraviolet (UV) photo current/dark current.

  5. Effect of Er3+ doping on structural, morphological and photocatalytical properties of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Bouhouche, S.; Bensouici, F.; Toubane, M.; Azizi, A.; Otmani, A.; Chebout, K.; Kezzoula, F.; Tala-Ighil, R.; Bououdina, M.

    2018-05-01

    In this research work, structure, microstructure, optical and photocatalytic properties of undoped and Erbium doped nanostructured ZnO thin films prepared by sol-gel dip-coating are investigated. X-ray diffraction (XRD) analysis indicates that the deposited films crystallize within the hexagonal wurtzite-type structure with a preferential growth orientation along (002) plane. Morphological observations using scanning electron microscopy (SEM) reveal important influence of Er concentration; displaying homogeneous and dense aspect for undoped to 0.3% then grid-like morphology for 0.4 and 0.5%. UV/vis/NIR transmittance spectroscopy spectra display a transmittance over 70%, and small variation in the energy gap energy 3.263–3.278 eV. Wettability test of ZnO thin films surface ranges from hydrophilic aspect for pure ZnO to hydrophobic one for Er doped ZnO, and the contact angle is found to increase from 58.7° for pure ZnO up to 98.4° for 0.4% Er doped ZnO. The photocatalytic activity measurements evaluated using the degradation of methylene blue (MB) under UV light irradiation demonstrate that undoped ZnO film shows higher photocatalytic activity compared to Er doped ZnO films, which may be attributed to the deterioration of films’crystallinity resulting in lower transmittance.

  6. Role of physical and chemical interactions in the antibacterial behavior of ZnO nanoparticles against E. coli.

    PubMed

    Jiang, Yunhong; Zhang, Lingling; Wen, Dongsheng; Ding, Yulong

    2016-12-01

    Zinc oxide (ZnO) nanoparticles (NPs) exhibit antibacterial activity against both Gram-positive and Gram-negative bacteria. However, the antimicrobial mechanism of ZnO NPs remains unclear. In this study, we investigated the interactions among ZnO NPs, released chemicals (Zn(2+) and Reactive Oxygen Species, ROS) and Escherichia coli (E. coli) cells. ZnO NPs without contacting with bacterial cells showed strong antibacterial effect. The results of the leakage of intracellular K(+) and integrity of carboxyfluoresce in-filled liposomes showed that ZnO NPs have antimicrobial activity against E. coli by non-specifically disrupting E. coli membranes. Traces of zinc ions (1.25mg/L) and hydrogen peroxide (from 1.25 to 4.5μM/L) were detected in ZnO NPs suspensions, but was insufficient to cause the antibacterial effect. However, the addition of radical scavengers suppressed the bactericidal effect of ZnO coated films against E. coli, potentially implicating ROS generation, especially hydroxyl radicals, in the antibacterial ability of ZnO NPs. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Vertical resistivity in nanocrystalline ZnO and amorphous InGaZnO

    NASA Astrophysics Data System (ADS)

    McCandless, Jonathan P.; Leedy, Kevin D.; Schuette, Michael L.

    2018-02-01

    The goal is to gain additional insight into physical mechanisms and the role of microstructure on the formation of ohmic contacts and the reduction of contact resistance. We have measured a decreasing film resistivity in the vertical direction with increasing thickness of pulsed-laser deposited ZnO and IGZO. As the ZnO thickness increases from 122 nm to 441 nm, a reduction in resistivity from 3.29 Ω-cm to 0.364 Ω-cm occurred. The IGZO resistivity changes from 72.4 Ω-cm to 0.642 Ω-cm as the film is increased from 108nm to 219 nm. In the ZnO, the size of nanocolumnar grains increase with thickness resulting in fewer grain boundaries, and in the amorphous IGZO, the thicker region exhibits tunnel-like artifacts which may contribute to the reduced resistivity.

  8. Defect study in ZnO related structures—A multi-spectroscopic approach

    NASA Astrophysics Data System (ADS)

    Ling, C. C.; Cheung, C. K.; Gu, Q. L.; Dai, X. M.; Xu, S. J.; Zhu, C. Y.; Luo, J. M.; Zhu, C. Y.; Tam, K. H.; Djurišić, A. B.; Beling, C. D.; Fung, S.; Lu, L. W.; Brauer, G.; Anwand, W.; Skorupa, W.; Ong, H. C.

    2008-10-01

    ZnO has attracted a great deal of attention in recent years because of its potential applications for fabricating optoelectronic devices. Using a multi-spectroscopic approach including positron annihilation spectroscopy (PAS), deep level transient spectroscopy (DLTS), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS), we have studied the two observed phenomena from ZnO related structures. They namely included the H 2O 2 pre-treatment induced ohmic to rectifying contact conversion on Au/ n-ZnO contact and the p-type doping by nitrogen ion implantation. The aim of the studies was to offering comprehensive views as to how the defects influenced the structures electrical and optical properties of the structures. It was also shown that PAS measurement using the monoenergetic positron beam could offer valuable information of vacancy type defects in the vertical ZnO nanorod array structure.

  9. Large-size porous ZnO flakes with superior gas-sensing performance

    NASA Astrophysics Data System (ADS)

    Wen, Wei; Wu, Jin-Ming; Wang, Yu-De

    2012-06-01

    A simple top-down route is developed to fabricate large size porous ZnO flakes via solution combustion synthesis followed by a subsequent calcination in air, which is template-free and can be easily enlarged to an industrial scale. The achieved porous ZnO flakes, which are tens to hundreds of micrometers in flat and tens of nanometers in thickness, exhibit high response for detecting acetone and ethanol, because the unique two-dimensional architecture shortens effectively the gas diffusion distance and provides highly accessible open channels and active surfaces for the target gas.

  10. Contact Us

    Science.gov Websites

    Speeches Archive Former AF Top 3 Viewpoints and Speeches Air Force Warrior Games 2017 Events 2018 Air Force Strategic Documents Desert Storm 25th Anniversary Observances DoD Warrior Games Portraits in Courage

  11. Analysis of stability improvement in ZnO thin film transistor with dual-gate structure under negative bias stress

    NASA Astrophysics Data System (ADS)

    Yun, Ho-Jin; Kim, Young-Su; Jeong, Kwang-Seok; Kim, Yu-Mi; Yang, Seung-dong; Lee, Hi-Deok; Lee, Ga-Won

    2014-01-01

    In this study, we fabricated dual-gate zinc oxide thin film transistors (ZnO TFTs) without additional processes and analyzed their stability characteristics under a negative gate bias stress (NBS) by comparison with conventional bottom-gate structures. The dual-gate device shows superior electrical parameters, such as subthreshold swing (SS) and on/off current ratio. NBS of VGS = -20 V with VDS = 0 was applied, resulting in a negative threshold voltage (Vth) shift. After applying stress for 1000 s, the Vth shift is 0.60 V in a dual-gate ZnO TFT, while the Vth shift is 2.52 V in a bottom-gate ZnO TFT. The stress immunity of the dual-gate device is caused by the change in field distribution in the ZnO channel by adding another gate as the technology computer aided design (TCAD) simulation shows. Additionally, in flicker noise analysis, a lower noise level with a different mechanism is observed in the dual-gate structure. This can be explained by the top side of the ZnO film having a larger crystal and fewer grain boundaries than the bottom side, which is revealed by the enhanced SS and XRD results. Therefore, the improved stability of the dual-gate ZnO TFT is greatly related to the E-field cancellation effect and crystal quality of the ZnO film.

  12. Mesoporous single-crystal ZnO nanobelts: supported preparation and patterning.

    PubMed

    Nasi, Lucia; Calestani, Davide; Fabbri, Filippo; Ferro, Patrizia; Besagni, Tullo; Fedeli, Paolo; Licci, Francesca; Mosca, Roberto

    2013-02-07

    We demonstrate that highly porous ZnO nanobelts can be prepared by thermally decomposing ZnS(en)(0.5) hybrid nanobelts (NBs) synthesized through a solvothermal route using Zn layers deposited on alumina substrates as both the Zn substrate and source. Hybrid decomposition by thermal annealing at 400 °C gives porous ZnS NBs that are transformed by further annealing at 600 °C into wurtzite single crystal ZnO nanobelts with an axial direction of [0001]. The evolution of the morphological and structural transformation ZnS(en)(0.5)→ ZnS → ZnO is investigated at the nanoscale by transmission and scanning electron microscopy analyses. Control of the ZnO NB distributions by patterning the Zn metallization on alumina is achieved as a consequence of the parent hybrid NB patterned growth. The presence of NBs on alumina in a ∼100 μm wide region between Zn stripes allows us to fabricate two contact devices where contact pads are electrically connected through a porous ZnO NB entanglement. Such devices are suitable for employment in photodetectors as well as in gas and humidity sensors.

  13. Ferroelectric enhancement in heterostructured ZnO /BiFeO3-PbTiO3 film

    NASA Astrophysics Data System (ADS)

    Yu, Shengwen; Chen, Rui; Zhang, Guanjun; Cheng, Jinrong; Meng, Zhongyan

    2006-11-01

    The authors have prepared heterostructured ZnO /BiFeO3-PbTiO3 (BFO-PT) composite film and BFO-PT film on Pt /Ti/SiO2/Si substrates by pulsed-laser deposition. The structure and morphologies of the films were characterized by x-ray diffraction (XRD) and scanning electron microscope. XRD results show that both films are perovskite structured last with different orientations. The leakage current density in the ZnO /BFO-PT film was found to be nearly two orders of magnitude lower. This could be due to the introduced ZnO layer behaving as a Schottky barrier between the BFO-PT film and top electrodes. The dramatic ferroelectric enhancement in ZnO /BFO-PT film is mostly ascribed to the improved insulation.

  14. Contact Us

    Science.gov Websites

    J8 | Force Structure, Resources & Assessment Contact Home : Contact Chairman's Social Media Chairman's Flicker Chairman's Blog SEAC's Social Media SEAC's Facebook SEAC's Flicker SEAC's Twitter Joint Staff's Social Media Joint Staff's Facebook Joint Staff's Flicker Joint Staff 's Twitter Social Media

  15. Mechanical and electrical characterization of semiconducting ZnO nanorings by direct nano-manipulation

    NASA Astrophysics Data System (ADS)

    Mai, Wenjie; Zhang, Long; Gu, Yudong; Huang, Shiqing; Zhang, Zongfu; Lao, Changshi; Yang, Peihua; Qiang, Pengfei; Chen, Zhongwei

    2012-08-01

    With assistance from a nano-manipulator system inside a scanning electron microscope chamber, mechanical and electrical properties of ZnO nanorings were investigated. The change of a fractured nanoring to nearly straight nanobelts was strong evidence to support the previously proposed electrostatic-force-induced self-coiling model, and our computational simulation results indicated the fracture force was 25-30 μN. The contact between a tungsten tip of the manipulator and a ZnO nanoring was confirmed as the Schottky type; therefore, the change of I-V curves of the nanoring under compression was attributed to the Schottky barrier height changes.

  16. Contact dermatitis

    MedlinePlus

    ... BS, Burks AW, et al, eds. Middleton's Allergy: Principles and Practice . 8th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 35. Usatine RP, Riojas M. Diagnosis and management of contact dermatitis. Am Fam Physician . 2010;82( ...

  17. Reducing contact resistance in graphene devices through contact area patterning.

    PubMed

    Smith, Joshua T; Franklin, Aaron D; Farmer, Damon B; Dimitrakopoulos, Christos D

    2013-04-23

    Performance of graphene electronics is limited by contact resistance associated with the metal-graphene (M-G) interface, where unique transport challenges arise as carriers are injected from a 3D metal into a 2D-graphene sheet. In this work, enhanced carrier injection is experimentally achieved in graphene devices by forming cuts in the graphene within the contact regions. These cuts are oriented normal to the channel and facilitate bonding between the contact metal and carbon atoms at the graphene cut edges, reproducibly maximizing "edge-contacted" injection. Despite the reduction in M-G contact area caused by these cuts, we find that a 32% reduction in contact resistance results in Cu-contacted, two-terminal devices, while a 22% reduction is achieved for top-gated graphene transistors with Pd contacts as compared to conventionally fabricated devices. The crucial role of contact annealing to facilitate this improvement is also elucidated. This simple approach provides a reliable and reproducible means of lowering contact resistance in graphene devices to bolster performance. Importantly, this enhancement requires no additional processing steps.

  18. Spherical Tippe Tops

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2013-03-01

    A tippe top (see Fig. 1) is usually constructed as a truncated sphere with a cylindrical peg on top, as indicated in Fig. 2(a). When spun rapidly on a horizontal surface, a tippe top spins about a vertical axis while rotating slowly about a horizontal axis until the peg touches the surface. At that point, weight is transferred to the peg, the truncated sphere rises off the surface, and the top spins on the peg until it is upright. A feature of a tippe top is that its center of mass, labeled G in Fig. 2, is below the geometric center of the sphere, C, when the top is at rest. That is where it will return if the top is tilted sideways and released since that is the stable equilibrium position. The fact that a tippe top turns upside down when it spins is therefore astonishing. The behavior of a tippe top is quite unlike that of a regular top since the spin axis remains closely vertical the whole time. The center of mass of a regular top can also rise, but the spin axis tilts upward as the top rises and enters a "sleeping" position.

  19. Superhydrophobic Surface Based on a Coral-Like Hierarchical Structure of ZnO

    PubMed Central

    Wu, Jun; Xia, Jun; Lei, Wei; Wang, Baoping

    2010-01-01

    Background Fabrication of superhydrophobic surfaces has attracted much interest in the past decade. The fabrication methods that have been studied are chemical vapour deposition, the sol-gel method, etching technique, electrochemical deposition, the layer-by-layer deposition, and so on. Simple and inexpensive methods for manufacturing environmentally stable superhydrophobic surfaces have also been proposed lately. However, work referring to the influence of special structures on the wettability, such as hierarchical ZnO nanostructures, is rare. Methodology This study presents a simple and reproducible method to fabricate a superhydrophobic surface with micro-scale roughness based on zinc oxide (ZnO) hierarchical structure, which is grown by the hydrothermal method with an alkaline aqueous solution. Coral-like structures of ZnO were fabricated on a glass substrate with a micro-scale roughness, while the antennas of the coral formed the nano-scale roughness. The fresh ZnO films exhibited excellent superhydrophilicity (the apparent contact angle for water droplet was about 0°), while the ability to be wet could be changed to superhydrophobicity after spin-coating Teflon (the apparent contact angle greater than 168°). The procedure reported here can be applied to substrates consisting of other materials and having various shapes. Results The new process is convenient and environmentally friendly compared to conventional methods. Furthermore, the hierarchical structure generates the extraordinary solid/gas/liquid three-phase contact interface, which is the essential characteristic for a superhydrophobic surface. PMID:21209931

  20. Optical absorption enhancement by inserting ZnO optical spacer in plasmonic organic solar cells

    NASA Astrophysics Data System (ADS)

    N'Konou, Kekeli; Torchio, Philippe

    2018-01-01

    Optical absorption enhancement (AE) using coupled optical spacer and plasmonic effects in standard and inverted organic solar cells (OSCs) are demonstrated using the finite-difference time-domain numerical method. The influence of an added zinc oxide (ZnO) optical spacer layer inserted below the active layer in standard architecture is first theoretically investigated while the influence of varying the ZnO cathodic buffer layer thickness in inverted design is studied on AE. Then, the embedding of a square periodic array of core-shell silver-silica nanospheres (Ag@SiO2 NSs) at different positions in standard and inverted OSCs is performed while AE and short-circuit current density (Jsc) are calculated. As a result of previous combined effects, the optimized standard plasmonic OSCs present 15% and 79.45% enhancement in J over the reference with and without ZnO optical spacer layer, respectively, and a 16% increase of AE when Ag@SiO2 NSs are placed on top of the PEDOT:PSS layer. Compared to the inverted OSC reference, the plasmonic OSCs present 26% and 27% enhancement in J and AE, respectively, when the Ag@SiO2 NSs are located on top of the ZnO layer. Furthermore, the spatial position of these NSs in such OSCs is a key parameter for increasing light absorption via enhanced electromagnetic field distribution.

  1. CDF Top Physics

    DOE R&D Accomplishments Database

    Tartarelli, G. F.; CDF Collaboration

    1996-05-01

    The authors present the latest results about top physics obtained by the CDF experiment at the Fermilab Tevatron collider. The data sample used for these analysis (about 110 pb{sup{minus}1}) represents almost the entire statistics collected by CDF during four years (1992--95) of data taking. This large data size has allowed detailed studies of top production and decay properties. The results discussed here include the determination of the top quark mass, the measurement of the production cross section, the study of the kinematics of the top events and a look at top decays.

  2. Photocatalytic antibacterial effect of ZnO nanoparticles into coaxial electrospun PCL fibers to prevent infections from skin injuries

    NASA Astrophysics Data System (ADS)

    Prado-Prone, G.; Silva-Bermúdez, P.; García-Macedo, J. A.; Almaguer-Flores, A.; Ibarra, C.; Velasquillo-Martínez, C.

    2017-02-01

    Antibacterial studies of inorganic nanoparticles (nps) have become important due to the increased bacterial resistance against antibiotics. We used Zinc oxide nanoparticles (ZnO nps), which possess excellent photocatalytic properties with a wide band gap (Eg), are listed as "generally recognized as safe" by the Food and Drug Administration (FDA) and have shown antibacterial activity (AA) against many bacterial strains. The AA of ZnO nps is partly attributed to the production of Reactive Oxygen Species (ROS) by photocatalysis. When ZnO nps in aqueous media are illuminated with an energy ZnO nps were dispersed into Polycaprolactone (PCL) fibers obtained by electrospinning technique. To optimize the use of ZnO nps concentration, we developed coreshell coaxial electrospun fibers where the core corresponded to PCL and the shell to a mixture of ZnO nps/PCL. Thus, ZnO nps were only dispersed on the surface of the fibers increasing its superficial contact area. We evaluated the AA against E. coli of different electrospun ZnO nps/PCL fibers under two different conditions: UVA pre-illumination and darkness. Preliminary results suggest that the AA against E. coli is better when electrospun ZnO nps/PCL were preilluminated with UVA than under darkness conditions.

  3. NREL Researcher is Top World Physicist

    Science.gov Websites

    is Top World Physicist For more information contact: Kerry Masson, (303) 275-4083 e:mail physicists in the world by the Institute of Scientific Information (ISI). The standing is based on the number your peers is the ultimate measure of the quality and quantity of world class research being conducted

  4. Physical study on Cobalt-Indium Co-doped ZnO nanofilms as hydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Mimouni, R.; Mahdhi, N.; Boubaker, K.; Madouri, A.; Amlouk, M.

    2016-03-01

    The present work reports some physical investigations on (Co,In) codoped zinc oxide nanofilms deposited on glass substrates at 460 °C by the spray pyrolysis technique. The effect of Co and In concentration on the structural, morphological, optical and surface wettability properties have been investigated using X-ray diffraction (XRD) patterns, Raman spectroscopy, SEM, optical measurement, photoluminescence spectroscopy as well as the measurement of hydrophobicity in terms of water contact angle. It is found that all films crystallized in würtzite ZnO phase, with a preferentially orientation towards (002) direction parallel to c-axis. The Raman spectra of the samples exhibit the presence of E2high characteristic mode of würtzite structure with high crystallinity as well as two dominant bands 1LO and 2LO. Also, no additional modes introduced by codopoing have been found. SEM micrographs show the uniform deposition of fine grains on surface films. Thicknesses of films are less than 100 nm. In addition, optical investigations indicate that the band gap narrowing of (Co,In) codoped ZnO thin films is due to the increase in the band tail width. Indeed, PL study indicates that (Co,In) codoped ZnO nanofilms exhibit a large decrease of the UV luminescence, which is assigned to the trapping of photo-generated electrons by both In3+ and Co2+ ions as well as an improvement of charge separation in the ZnO thin films. Finally, the (Co,In) codoping influences the surface wettability property and transform the ZnO character from hydrophilic (θ < 90°) for pure ZnO nanofilm to hydrophobic (θ > 90°) for (Co,In) codoped ZnO ones.

  5. New insights into the adsorption of 3-(trimethoxysilyl)propylmethacrylate on hydroxylated ZnO nanopowders.

    PubMed

    Bressy, Christine; Ngo, Van Giang; Ziarelli, Fabio; Margaillan, André

    2012-02-14

    Functionalization of zinc oxide (ZnO) nano-objects by silane grafting is an attractive method to provide nanostructured materials with a variety of surface properties. Active hydroxyl groups on the oxide surface are one of the causes governing the interfacial bond strength in nanohybrid particles. Here, "as-prepared" and commercially available zinc oxide nanopowders with a wide range of surface hydroxyl density were functionalized by a well-known polymerizable silane coupling agent, i.e., 3-(trimethoxysilyl)propylmethacrylate (MPS). Fourier transform infrared (FTIR) and solid-state (13)C and (29)Si nuclear magnetic resonance (NMR) spectroscopic investigations demonstrated that the silane coupling agent was fully hydrolyzed and linked to the hydroxyl groups already present on the particle surface through covalent and hydrogen bonds. Due to a basic catalyzed condensation of MPS with water, a siloxane layer was shown to be anchored to the nanoparticles through mono- and tridentate structures. Quantitative investigations were performed by thermogravimetric (TGA) and elemental analyses. The amount of silane linked to ZnO particles was shown to be affected by the amount of isolated hydroxyl groups available to react on the particle surface. For as-prepared ZnO nanoparticles, the number of isolated and available hydroxyl groups per square nanometer was up to 3 times higher than the one found on commercially available ZnO nanoparticles, leading to higher amounts of polymerizable silane agent linked to the surface. The MPS molecules were shown to be mainly oriented perpendicular to the oxide surface for all the as-prepared ZnO nanoparticles, whereas a parallel orientation was found for the preheated commercially ZnO nanopowders. In addition, ZnO nanoparticles were shown to be hydrophobized by the MPS treatment with water contact angles higher than 60°.

  6. Rapid green synthesis of ZnO nanoparticles using a hydroelectric cell without an electrolyte

    NASA Astrophysics Data System (ADS)

    Shah, Jyoti; Kumar Kotnala, Ravinder

    2017-09-01

    In this study, zinc oxide (ZnO) nanoparticles were synthesized using a novel environmentally friendly hydroelectric cell without an electrolyte or external current source. The hydroelectric cell comprised a nanoporous Li substituted magnesium ferrite pellet in contact with two electrodes, with zinc as the anode and silver as an inert cathode. The surface unsaturated cations and oxygen vacancies in the nanoporous ferrite dissociated water molecules into hydronium and hydroxide ions when the hydroelectric cell was dipped into deionized water. Hydroxide ions migrated toward the zinc electrode to form zinc hydroxide and the hydronium ions were evolved as H2 gas at the silver electrode. The zinc hydroxide collected as anode mud was converted into ZnO nanoparticles by heating at 250 °C. Structural analysis using Raman spectroscopy indicated the good crystallinity of the ZnO nanoparticles according to the presence of a high intensity E2-(high) mode. The nanoparticle size distribution was 5-20 nm according to high resolution transmission electron microscopy. An indirect band gap of 2.75 eV was determined based on the Tauc plot, which indicated the existence of an interstitial cation level in ZnO. Near band edge and blue emissions were detected in photoluminescence spectral studies. The blue emissions obtained from the ZnO nanoparticles could potentially have applications in blue lasers and LEDs. The ZnO nanoparticles synthesized using this method had a high dielectric constant value of 5 at a frequency of 1 MHz, which could be useful for fabricating nano-oscillators. This facile, clean, and cost-effective method obtained a significant yield of 0.017 g for ZnO nanoparticles without applying an external current source.

  7. One-dimensional ZnO nanostructures.

    PubMed

    Jayadevan, K P; Tseng, T Y

    2012-06-01

    The wide-gap semiconductor ZnO with nanostructures such as nanoparticle, nanorod, nanowire, nanobelt, nanotube has high potential for a variety of applications. This article reviews the fundamentals of one-dimensional ZnO nanostructures, including processing, structure, property, application and their processing-microstructure-property correlation. Various fabrication methods of the ZnO nanostructures including vapor-liquid-solid process, vapor-solid growth, solution growth, solvothermal growth, template-assisted growth and self-assembly are introduced. The characterization and properties of the ZnO nanostructures are described. The possible applications of these nanostructures are also discussed.

  8. Legislative Affairs Media Contact - Public Affairs - NOAA's National

    Science.gov Websites

    Media Contacts -NWS Media Contacts -NOAA Media Contacts -Legislative Affairs Media Tools -Archived News Media Contact Matthew R. Borgia Congressional Affairs Specialist - All National Weather Service issues (202)482-1939 Back Top Home | Mission | Strategic Plan | NWS Media Contacts | NOAA Media Contacts US

  9. The comprehensive study and the reduction of contact resistivity on the n-InGaAs M-I-S contact system with different inserted insulators

    SciTech Connect

    Liao, M.-H., E-mail: mhliaoa@ntu.edu.tw; Lien, C.

    2015-05-15

    Five different kinds of insulators including BaTiO{sub 3}, TiO{sub 2}, Al{sub 2}O{sub 3}, CdO and ZnO on the n-type InGaAs metal-insulator-semiconductor (M-I-S) ohmic contact structure are studied. The effect for the dielectric constant (ε) of inserted insulator and the conduction band offset (CBO) between an insulator and semiconductor substrate is analyzed by a unified M-I-S contact model. Based on the theoretical model and experimental data, we demonstrates that the inserted ZnO insulator with the high electron affinity and the low CBO (∼0.1 eV) to the InGaAs substrate results in ∼10 times contact resistivity reduction, even the ε of ZnO ismore » not pretty high (∼10)« less

  10. Bi-layer channel structure-based oxide thin-film transistors consisting of ZnO and Al-doped ZnO with different Al compositions and stacking sequences

    NASA Astrophysics Data System (ADS)

    Cho, Sung Woon; Yun, Myeong Gu; Ahn, Cheol Hyoun; Kim, So Hee; Cho, Hyung Koun

    2015-03-01

    Zinc oxide (ZnO)-based bi-layers, consisting of ZnO and Al-doped ZnO (AZO) layers grown by atomic layer deposition, were utilized as the channels of oxide thin-film transistors (TFTs). Thin AZO layers (5 nm) with different Al compositions (5 and 14 at. %) were deposited on top of and beneath the ZnO layers in a bi-layer channel structure. All of the bi-layer channel TFTs that included the AZO layers showed enhanced stability (Δ V Th ≤ 3.2 V) under a positive bias stress compared to the ZnO single-layer channel TFT (Δ V Th = 4.0 V). However, the AZO/ZnO bi-layer channel TFTs with an AZO interlayer between the gate dielectric and the ZnO showed a degraded field effect mobility (0.3 cm2/V·s for 5 at. % and 1.8 cm2/V·s for 14 at. %) compared to the ZnO single-layer channel TFT (5.5 cm2/V·s) due to increased scattering caused by Al-related impurities near the gate dielectric/channel interface. In contrast, the ZnO/AZO bi-layer channel TFTs with an AZO layer on top of the ZnO layer exhibited an improved field effect mobility (7.8 cm2/V·s for 14 at. %) and better stability. [Figure not available: see fulltext.

  11. New Insights into Mechanism of Surface Reactions of ZnO Nanorods During Electrons Beam Irradiation.

    PubMed

    Cho, Youngseung; Ji, Hyunjin; Kim, Hyoungsub; Yoon, Jinsuop; Choi, Byoungdeog

    2018-09-01

    This study provides new insight into mechanisms of ionic reactions on the surface of ZnO nanorod networks, which could result in enhanced performance in optical or molecular sensors. The current- voltage characteristics of ZnO nanorod network devices exhibit typical nonlinear behavior in air, which implies the formation of a Schottky barrier when metals are used as contacts. The conductance of the device increased significantly in vacuum, which can be explained by the desorption of hydroxyl groups at very low pressure. While physisorbed water or oxygen-related ions can detach from the ZnO surface during evacuation, exposure to high energy in the electron beam is believed to detach the chemisorbed anions of O- and O-2 from the surface of ZnO nanorods, which releases more electrons into the channel. The increase in available electrons enhances the conductance of the ZnO nanorods. Slow initialization of the conductance under ambient conditions indicates that the ionic re-adsorption is inactive under these conditions. Thus, the electron irradiation process can be used to reset the surface ionic molecules on metal oxide nano-structures by tuning the surface potential prior to the passivation process.

  12. A fast and effective approach for reversible wetting-dewetting transitions on ZnO nanowires

    PubMed Central

    Yadav, Kavita; Mehta, B. R.; Bhattacharya, Saswata; Singh, J. P.

    2016-01-01

    Here, we demonstrate a facile approach for the preparation of ZnO nanowires (NWs) with tunable surface wettability that can be manipulated reversibly in a controlled manner from a superhydrophilic state to a superhydrophobic state. The as-synthesized ZnO NWs obtained by a chemical vapor deposition method are superhydrophilic with a contact angle (CA) value of ~0°. After H2 gas annealing at 300 °C for 90 minutes, ZnO NWs display superhydrophobic behavior with a roll-off angle less than 5°. However, O2 gas annealing converts these superhydrophobic ZnO NWs into a superhydrophilic state. For switching from superhydrophobic to superhydrophilic state and vice versa in cyclic manner, H2 and O2 gas annealing treatment was used, respectively. A model based on density functional theory indicates that the oxygen-related defects are responsible for CA switching. The water resistant properties of the ZnO NWs coating is found to be durable and can be applied to a variety of substrates including glass, metals, semiconductors, paper and even flexible polymers. PMID:27713536

  13. Contact Us

    Science.gov Websites

    Other types of pesticides Disponible en español Contact Us NPIC staff Call us (toll free): 800-858-7378 We have trained pesticide specialists available to help you free of charge from 8:00am to 12:00pm

  14. Contact dermatitis.

    PubMed

    Gurwood, A S; Altenderfer, D S

    2001-01-01

    Anatomically, the eyelid can be divided microscopically into (1) skin, which is made up of epidermis and dermis; (2) submucosa (3) muscular layer; (4) submuscular layer (dense connective tissue); (5) fibrous layer; and (6) palpebral conjunctiva. The thin nature of the eyelid makes it susceptible to inflammation resulting from allergy. Minimum levels of irritants contacting the adnexal area can penetrate the skin to initiate the allergic cascade. Allergic reactions that involve the eye may begin via contact to the skin, but often involve the conjunctiva. Eczema is the general term that describes the superficial inflammatory process involving the epidermis. Contact eczema is characterized by varying elements of epidermal erythema, papules, and vesicles. Allergic dermatoconjunctivitis connotes involvement of both the skin and conjunctiva. A 24-year-old man came to the clinic with a red, swollen left eye. Based on the history, the constellation of signs and symptoms (lack of diffuse or focal pain, presence of periorbital and conjunctival edema, absence of fever), and failed resolution after treatment with injectable antibiotics, the diagnosis of type IV delayed hypersensitivity reaction secondary to toxic/chemical exposure was made. Speedy resolution was accomplished using a sequenced therapy, which included oral antihistamines, topical cycloplegics, topical antibiotics, topical steroids, and palliative therapies. Optometrists should be familiar with the signs and symptoms of contact eczema and allergic dermatoconjunctivitis. Treatment includes management of the skin and adnexae, as well as the ocular manifestations.

  15. NASA Brevard Top Scholars

    NASA Image and Video Library

    2017-11-13

    Retired NASA astronaut Tom Jones is with top scholars from Brevard County public high schools in the Rocket Garden at the NASA Kennedy Space Center Visitor Complex in Florida. Top scholars from the high schools were invited to Kennedy Space Center for a tour of facilities, lunch and a roundtable discussion with engineers and scientists at the center. The 2017-2018 Brevard Top Scholars event was hosted by the center's Education Projects and Youth Engagement office to honor the top three scholars of the 2017-2018 graduating student class from each of Brevard County’s public high schools. They students received a personalized certificate at the end of the day.

  16. NASA Brevard Top Scholars

    NASA Image and Video Library

    2017-11-13

    Top scholars from Brevard County public high schools participate in roundtable discussions with NASA engineers and scientists at the Public Engagement Center at Kennedy Space Center Visitor Complex in Florida. Top scholars from the high schools were invited to Kennedy Space Center for a tour of facilities, lunch and a roundtable discussion. The 2017-2018 Brevard Top Scholars event was hosted by the center's Education Projects and Youth Engagement office to honor the top three scholars of the graduating student class from each of Brevard County’s public high schools. The students received a personalized certificate at the end of the day.

  17. Investigation into the effects of surface stripping ZnO nanosheets.

    PubMed

    Barnett, Chris J; Jackson, Georgina; Jones, Daniel R; Lewis, Aled R; Welsby, Kathryn; Evans, Jon E; McGettrick, James D; Watson, Trystan; Maffeis, Thierry G G; Dunstan, Peter R; Barron, Andrew R; Cobley, Richard J

    2018-04-20

    ZnO nanosheets are polycrystalline nanostructures that are used in devices including solar cells and gas sensors. However, for efficient and reproducible device operation and contact behaviour the conductivity characteristics must be controlled and surface contaminants removed. Here we use low doses of argon bombardment to remove surface contamination and make reproducible lower resistance contacts. Higher doses strip the surface of the nanosheets altering the contact type from near-ohmic to rectifying by removing the donor-type defects, which photoluminescence shows to be concentrated in the near-surface. Controlled doses of argon treatments allow nanosheets to be customised for device formation.

  18. Investigation into the effects of surface stripping ZnO nanosheets

    NASA Astrophysics Data System (ADS)

    Barnett, Chris J.; Jackson, Georgina; Jones, Daniel R.; Lewis, Aled R.; Welsby, Kathryn; Evans, Jon E.; McGettrick, James D.; Watson, Trystan; Maffeis, Thierry G. G.; Dunstan, Peter R.; Barron, Andrew R.; Cobley, Richard J.

    2018-04-01

    ZnO nanosheets are polycrystalline nanostructures that are used in devices including solar cells and gas sensors. However, for efficient and reproducible device operation and contact behaviour the conductivity characteristics must be controlled and surface contaminants removed. Here we use low doses of argon bombardment to remove surface contamination and make reproducible lower resistance contacts. Higher doses strip the surface of the nanosheets altering the contact type from near-ohmic to rectifying by removing the donor-type defects, which photoluminescence shows to be concentrated in the near-surface. Controlled doses of argon treatments allow nanosheets to be customised for device formation.

  19. On the difficulties in characterizing ZnO nanowires.

    PubMed

    Schlenker, E; Bakin, A; Weimann, T; Hinze, P; Weber, D H; Gölzhäuser, A; Wehmann, H-H; Waag, A

    2008-09-10

    The electrical properties of single ZnO nanowires grown by vapor phase transport were investigated. While some samples were contacted by Ti/Au electrodes, another set of samples was investigated using a manipulator tip in a low energy electron point-source microscope. The deduced resistivities range from 1 to 10(3) Ωcm. Additionally, the resistivities of nanowires from multiple publications were brought together and compared to the values obtained from our measurements. The overview of all data shows enormous differences (10(-3)-10(5) Ωcm) in the measured resistivities. In order to reveal the origin of the discrepancies, the influence of growth parameters, measuring methods, contact resistances, crystal structures and ambient conditions are investigated and discussed in detail.

  20. Effects of humidity during formation of zinc oxide electron contact layers from a diethylzinc precursor solution

    DOE PAGES

    Mauger, Scott A.; Steirer, K. Xerxes; Boe, Jonas; ...

    2016-01-19

    Here, this work focuses on the role of humidity in the formation of ZnO thin films from a reactive diethylzinc precursor solution for use as the electron contact layer (ECL) in organic photovoltaic (OPV) devices. This method is well suited for flexible devices because the films are annealed at 120 °C, making the process compatible with polymer substrates. ZnO films were prepared by spin coating and annealing at different relative humidity (RH) levels. It is found that RH during coating and annealing affects the chemical and physical properties of the ZnO films. Using x-ray photoelectron spectroscopy it is found thatmore » increasing RH during the formation steps produces a more stoichiometric oxide and a higher Zn/O ratio. Spectroscopic ellipsometry data shows a small decrease in the optical band gap with increased humidity, consistent with a more stoichiometric oxide. Kelvin probe measurements show that increased RH during formation results in a larger work function (i.e. further from vacuum). Consistent with these data, but counter to what might be expected, when these ZnO films are used as ECLs in OPV devices those with ZnO ECLs processed in low RH (less stoichiometric) had higher power conversion efficiency than those with high-RH processed ZnO due to improved open-circuit voltage. The increase in open-circuit voltage with decreasing humidity was observed with two different donor polymers and fullerene acceptors, which shows the trend is due to changes in ZnO. The observed changes in open-circuit voltage follow the same trend as the ZnO work function indicating that the increase in open-circuit voltage with decreasing humidity is the result of improved energetics at the interface between the bulk-heterojunction and the ZnO layer due to a vacuum level shift.« less

  1. Contact Us

    Science.gov Websites

    Naval History Contact Us Command Addresses (SNDL) FAQ Leadership Secretary of the Navy Under Secretary Chiefs of Staff Defense.gov U.S. Army U.S. Air Force U.S. Marine Corps U.S. Coast Guard Naval History https://awards.navy.mil Naval Heritage And History Command http://www.history.navy.mil/about-us

  2. TVDG Contacts

    Science.gov Websites

    for Sandy Fax By Fax: 1 631 344 4583 Attention Chuck Carlson EMail By E-Mail: Send E-Mail to Chuck Group Leader James Alessi Telephone: 1-631-344-4004 E-Mail: Peter Thieberger Information can be returned 1 631 344 4581. An organizational list of staff members and how to contact them. The BNL E-Mail and

  3. Training Top 125

    ERIC Educational Resources Information Center

    Training, 2011

    2011-01-01

    Top companies realize how vital training is to their success and continue to invest in it, even in trying times. This article presents "Training" magazine's 11th annual ranking of the top companies with employee-sponsored workforce training and development. First-time No. 1 winner Farmers Insurance puts such a premium on learning that its new…

  4. Training Top 50.

    ERIC Educational Resources Information Center

    Training, 2001

    2001-01-01

    Identifies the top 50 companies in terms of the amount spent on training and development, the number of hours of training per employee, and percentage of payroll spent on training. Profiles the top five plus four additional companies selected by the magazine's editors. (SK)

  5. Training Top 125

    ERIC Educational Resources Information Center

    Training, 2012

    2012-01-01

    The best learning and development organizations support business initiatives tactically "and" help drive strategic change. Verizon did just that, earning it the No. 1 spot for the first time on the Training Top 125. Verizon and the other 2012 Top 125 winners continued to invest in training, collectively dedicating a mean of 4.52 percent of their…

  6. Contact planarization of ensemble nanowires

    NASA Astrophysics Data System (ADS)

    Chia, A. C. E.; LaPierre, R. R.

    2011-06-01

    The viability of four organic polymers (S1808, SC200, SU8 and Cyclotene) as filling materials to achieve planarization of ensemble nanowire arrays is reported. Analysis of the porosity, surface roughness and thermal stability of each filling material was performed. Sonication was used as an effective method to remove the tops of the nanowires (NWs) to achieve complete planarization. Ensemble nanowire devices were fully fabricated and I-V measurements confirmed that Cyclotene effectively planarizes the NWs while still serving the role as an insulating layer between the top and bottom contacts. These processes and analysis can be easily implemented into future characterization and fabrication of ensemble NWs for optoelectronic device applications.

  7. Contact planarization of ensemble nanowires.

    PubMed

    Chia, A C E; LaPierre, R R

    2011-06-17

    The viability of four organic polymers (S1808, SC200, SU8 and Cyclotene) as filling materials to achieve planarization of ensemble nanowire arrays is reported. Analysis of the porosity, surface roughness and thermal stability of each filling material was performed. Sonication was used as an effective method to remove the tops of the nanowires (NWs) to achieve complete planarization. Ensemble nanowire devices were fully fabricated and I-V measurements confirmed that Cyclotene effectively planarizes the NWs while still serving the role as an insulating layer between the top and bottom contacts. These processes and analysis can be easily implemented into future characterization and fabrication of ensemble NWs for optoelectronic device applications.

  8. Top physics at CDF

    SciTech Connect

    Hughes, R.E.

    1997-01-01

    We report on top physics results using a 100 pb{sup -1} data sample of p{bar p} collisions at {radical}s = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). We have identified top signals in a variety of decay channels, and used these channels to extract a measurement of the top mass and production cross section. A subset of the data (67 pb{sup -1}) is used to determine M{sub top} = 176 {+-} 8(stat) {+-} 10(syst) and {sigma}(tt) = 7.6 {sub -2.0}{sup +2.4} pb. We present studies of the kinematics of t{bar t} events and extract the first directmore » measurement of V{sub tb}. Finally, we indicate prospects for future study of top physics at the Tevatron.« less

  9. An optimized top contact design for solar cell concentrators

    NASA Technical Reports Server (NTRS)

    Desalvo, Gregory C.; Barnett, Allen M.

    1985-01-01

    A new grid optimization scheme is developed for point focus solar cell concentrators which employs a separated grid and busbar concept. Ideally, grid lines act as the primary current collectors and receive all of the current from the semiconductor region. Busbars are the secondary collectors which pick up current from the grids and carry it out of the active region of the solar cell. This separation of functions leads to a multithickness metallization design, where the busbars are made larger in cross section than the grids. This enables the busbars to carry more current per unit area of shading, which is advantageous under high solar concentration where large current densities are generated. Optimized grid patterns using this multilayer concept can provide a 1.6 to 20 percent increase in output power efficiency over optimized single thickness grids.

  10. Comparative study of textured and epitaxial ZnO films

    NASA Astrophysics Data System (ADS)

    Ryu, Y. R.; Zhu, S.; Wrobel, J. M.; Jeong, H. M.; Miceli, P. F.; White, H. W.

    2000-06-01

    ZnO films were synthesized by pulsed laser deposition (PLD) on GaAs and α-Al 2O 3 substrates. The properties of ZnO films on GaAs and α-Al 2O 3 have been investigated to determine the differences between epitaxial and textured ZnO films. ZnO films on GaAs show very strong emission features associated with exciton transitions as do ZnO films on α-Al 2O 3, while the crystalline structural qualities for ZnO films on α-Al 2O 3 are much better than those for ZnO films on GaAs. The properties of ZnO films are studied by comparing highly oriented, textured ZnO films on GaAs with epitaxial ZnO films on α-Al 2O 3 synthesized along the c-axis.

  11. Contact allergy in cheilitis.

    PubMed

    O'Gorman, Susan M; Torgerson, Rochelle R

    2016-07-01

    Recalcitrant non-actinic cheilitis may indicate contact allergy. This study aimed to determine the prevalence of allergic contact cheilitis (ACC) in patients with non-actinic cheilitis and to identify the most relevant allergens. We used an institutional database to identify patients with non-actinic cheilitis who underwent patch testing between January 1, 2001, and August 31, 2011, and conducted a retrospective review of patch test results in these patients. Additional data were obtained from institutional electronic medical records. Ninety-one patients (70 [77%] female; mean age: 51 years) were included in the study. Almost half (41 [45%]) had a final diagnosis of ACC. Patch testing was performed in line with universally accepted methods, with application on day 1, allergen removal and an initial reading on day 3, and the final reading on day 5. The allergens of most significance were fragrance mix, Myroxylon pereirae resin, dodecyl gallate, octyl gallate, and benzoic acid. Nickel was the most relevant metal allergen. Contact allergy is an important consideration in recalcitrant cheilitis. Fragrances, antioxidants, and preservatives dominated the list of relevant allergens in our patients. Nickel and gold were among the top 10 allergens. Almost half (45%) of these patients had a final diagnosis of ACC. Patch testing beyond the oral complete series should be undertaken in any investigation of non-actinic cheilitis. © 2015 The International Society of Dermatology.

  12. Effect of TiO{sub 2} thickness on nanocomposited aligned ZnO nanorod/TiO{sub 2} for dye-sensitized solar cells

    SciTech Connect

    Saurdi, I., E-mail: saurdy788@gmail.com; Ishak, A.; UiTM Sarawak Kampus Kota Samarahan Jalan Meranek, Sarawak

    2016-07-06

    The TiO{sub 2} films were deposited on glass substrate at different thicknesses with different deposition frequencies (1, 2, 3 and 4 times) using spin coating technique and their structural properties were investigated. Subsequently, the nanocomposited aligned ZnO nanorods and TiO{sub 2} were formed by deposited the TiO{sub 2} on top of aligned ZnO Nanorod on ITO-coated glass at different thicknesses using the same method of TiO{sub 2} deposited on glass substrate. The nanocomposited aligned ZnO nanorod/TiO{sub 2} were coated with different thicknesses of 900µm, 1815µm, 2710µm, 3620µm and ZnO without TiO{sub 2}. The dye-sensitized solar cells were fabricated from themore » nanocomposited aligned ZnO nanorod/TiO{sub 2} with thickness of 900µm, 1815µm, 2710µm and 3620µm and ZnO without TiO{sub 2} and their photovoltaic properties of the DSSCs were investigated. From the solar simulator measurement the solar energy conversion efficiency (η) of 2.543% under AM 1.5 was obtained for the ZnO nanorod/TiO{sub 2} photoanode-2710µm Dye-Sensitized solar cell.« less

  13. Top Quark Properties

    SciTech Connect

    Peters, Yvonne

    2011-12-01

    Since its discovery in 1995 by the CDF and D0 collaborations at the Fermilab Tevatron collider, the top quark has undergone intensive studies. Besides the Tevatron experiments, with the start of the LHC in 2010 a top quark factory started its operation. It is now possible to measure top quark properties simultaneously at four different experiments, namely ATLAS and CMS at LHC and CDF and D0 at Tevatron. Having collected thousands of top quarks each, several top quark properties have been measured precisely, while others are being measured for the first time. In this article, recent measurements of top quarkmore » properties from ATLAS, CDF, CMS and D0 are presented, using up to 5.4 fb{sup -1} of integrated luminosity at the Tevatron and 1.1 fb{sup -1} at the LHC. In particular, measurements of the top quark mass, mass difference, foward backward charge asymmetry, t{bar t} spin correlations, the ratio of branching fractions, W helicity, anomalous couplings, color flow and the search for flavor changing neutral currents are discussed.« less

  14. 75 FR 30007 - Race to the Top Fund Assessment Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-28

    ... DEPARTMENT OF EDUCATION Overview Information Race to the Top Fund Assessment Program Catalog of... Assessment Program. This notice makes two corrections to the April 9 NIA. FOR FURTHER INFORMATION CONTACT..., audiotape, or computer diskette) on request to the contact listed in this section. SUPPLEMENTARY INFORMATION...

  15. NASA Brevard Top Scholars

    NASA Image and Video Library

    2017-11-13

    Retired NASA astronaut Tom Jones talks to high school students during "Lunch with an Astronaut" at the NASA Kennedy Space Center Visitor Complex in Florida. Top scholars from Brevard County public high schools were invited to Kennedy Space Center for a tour of facilities, lunch and a roundtable discussion with engineers and scientists at the center. The 2017-2018 Brevard Top Scholars event was hosted by the center's Education Projects and Youth Engagement office to honor the top three scholars of the 2017-2018 graduating student class from each of Brevard County’s public high schools. The students received a personalized certificate at the end of the day.

  16. NASA Brevard Top Scholars

    NASA Image and Video Library

    2017-11-13

    Students from Brevard County public high schools arrive at the NASA Kennedy Space Center Visitor Complex in Florida. Top scholars from the high schools were invited to Kennedy Space Center for a tour of facilities, lunch and a roundtable discussion with engineers and scientists at the center. The 2017-2018 Brevard Top Scholars event was hosted by the center's Education Projects and Youth Engagement office to honor the top three scholars of the graduating student class from each of Brevard County’s public high schools. The students received a personalized certificate at the end of the day.

  17. Valency configuration of transition metal impurities in ZnO

    SciTech Connect

    Petit, Leon; Schulthess, Thomas C; Svane, Axel

    2006-01-01

    We use the self-interaction corrected local spin-density approximation to investigate the ground state valency configuration of transition metal (TM=Mn, Co) impurities in n- and p-type ZnO. We find that in pure Zn{sub 1-x}TM{sub x}O, the localized TM{sup 2+} configuration is energetically favored over the itinerant d-electron configuration of the local spin density (LSD) picture. Our calculations indicate furthermore that the (+/0) donor level is situated in the ZnO gap. Consequently, for n-type conditions, with the Fermi energy {epsilon}F close to the conduction band minimum, TM remains in the 2+ charge state, while for p-type conditions, with {epsilon}F close to themore » valence band maximum, the 3+ charge state is energetically preferred. In the latter scenario, modeled here by co-doping with N, the additional delocalized d-electron charge transfers into the entire states at the top of the valence band, and hole carriers will only exist, if the N concentration exceeds the TM impurity concentration.« less

  18. Responses of human cells to ZnO nanoparticles: a gene transcription study†

    PubMed Central

    Moos, Philip J.; Olszewski, Kyle; Honeggar, Matthew; Cassidy, Pamela; Leachman, Sancy; Woessner, David; Cutler, N. Shane; Veranth, John M.

    2013-01-01

    The gene transcript profile responses to metal oxide nanoparticles was studied using human cell lines derived from the colon and skin tumors. Much of the research on nanoparticle toxicology has focused on models of inhalation and intact skin exposure, and effects of ingestion exposure and application to diseased skin are relatively unknown. Powders of nominally nanosized SiO2, TiO2, ZnO and Fe2O3 were chosen because these substances are widely used in consumer products. The four oxides were evaluated using colon-derived cell lines, RKO and CaCo-2, and ZnO and TiO2 were evaluated further using skin-derived cell lines HaCaT and SK Mel-28. ZnO induced the most notable gene transcription changes, even though this material was applied at the lowest concentration. Nano-sized and conventional ZnO induced similar responses suggesting common mechanisms of action. The results showed neither a non-specific response pattern common to all substances nor synergy of the particles with TNF-α cotreatment. The response to ZnO was not consistent with a pronounced proinflammatory signature, but involved changes in metal metabolism, chaperonin proteins, and protein folding genes. This response was observed in all cell lines when ZnO was in contact with the human cells. When the cells were exposed to soluble Zn, the genes involved in metal metabolism were induced but the genes involved in protein refoldling were unaffected. This provides some of the first data on the effects of commercial metal oxide nanoparticles on human colon-derived and skin-derived cells. PMID:21769377

  19. Types of Contact Lenses

    MedlinePlus

    ... Consumer Devices Consumer Products Contact Lenses Types of Contact Lenses Share Tweet Linkedin Pin it More sharing ... Orthokeratology (Ortho-K) Decorative (Plano) Contact Lenses Soft Contact Lenses Soft contact lenses are made of soft, ...

  20. Prioritized Contact Transport Stream

    NASA Technical Reports Server (NTRS)

    Hunt, Walter Lee, Jr. (Inventor)

    2015-01-01

    A detection process, contact recognition process, classification process, and identification process are applied to raw sensor data to produce an identified contact record set containing one or more identified contact records. A prioritization process is applied to the identified contact record set to assign a contact priority to each contact record in the identified contact record set. Data are removed from the contact records in the identified contact record set based on the contact priorities assigned to those contact records. A first contact stream is produced from the resulting contact records. The first contact stream is streamed in a contact transport stream. The contact transport stream may include and stream additional contact streams. The contact transport stream may be varied dynamically over time based on parameters such as available bandwidth, contact priority, presence/absence of contacts, system state, and configuration parameters.

  1. Effect of Li doping on the electric and pyroelectric properties of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Trinca, L. M.; Galca, A. C.; Boni, A. G.; Botea, M.; Pintilie, L.

    2018-01-01

    Un-doped ZnO (UDZO) and Li-doped ZnO (LZO) polycrystalline thin films were grown on platinized silicon by pulsed laser deposition (PLD). The electrical properties were investigated on as-grown and annealed UDZO and LZO films with capacitor configuration, using top and bottom platinum electrodes. In the case of the as-grown films it was found that the introduction of Li increases the resistivity of ZnO and induces butterfly shape in the C-V characteristic, suggesting ferroelectric-like behavior in LZO films. The properties of LZO samples does not significantly changes after thermal annealing while the properties of UDZO samples show significant changes upon annealing, manifested in a butterfly shape of the C-V characteristic and resistive-like switching. However, the butterfly shape disappears if long delay time is used in the C-V measurement, the characteristic remaining non-linear. Pyroelectric signal could be measured only on annealed films. Comparing the UDZO results with those obtained in the case of Li:ZnO, it was found that the pyroelectric properties are considerably enhanced by Li doping, leading to pyroelectric signal with about one order of magnitude larger at low modulation frequencies than for un-doped samples. Although the results of this study hint towards a ferroelectric-like behavior of Li doped ZnO, the presence of real ferroelectricity in this material remains controversial.

  2. Power generation from base excitation of a Kevlar composite beam with ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Hwang, Hyun-Sik; Sodano, Henry A.

    2015-04-01

    One-dimensional nanostructures such as nanowires, nanorods, and nanotubes with piezoelectric properties have gained interest in the fabrication of small scale power harvesting systems. However, the practical applications of the nanoscale materials in structures with true mechanical strengths have not yet been demonstrated. In this paper, piezoelectric ZnO nanowires are integrated into the fiber reinforced polymer composites serving as an active phase to convert the induced strain energy from ambient vibration into electrical energy. Arrays of ZnO nanowires are grown vertically aligned on aramid fibers through a low-cost hydrothermal process. The modified fabrics with ZnO nanowires whiskers are then placed between two carbon fabrics as the top and the bottom electrodes. Finally, vacuum resin transfer molding technique is utilized to fabricate these multiscale composites. The fabricated composites are subjected to a base excitation using a shaker to generate charge due to the direct piezoelectric effect of ZnO nanowires. Measuring the generated potential difference between the two electrodes showed the energy harvesting application of these multiscale composites in addition to their superior mechanical properties. These results propose a new generation of power harvesting systems with enhanced mechanical properties.

  3. Nucleation, Growth Mechanism, and Controlled Coating of ZnO ALD onto Vertically Aligned N-Doped CNTs.

    PubMed

    Silva, R M; Ferro, M C; Araujo, J R; Achete, C A; Clavel, G; Silva, R F; Pinna, N

    2016-07-19

    Zinc oxide thin films were deposited on vertically aligned nitrogen-doped carbon nanotubes (N-CNTs) by atomic layer deposition (ALD) from diethylzinc and water. The study demonstrates that doping CNTs with nitrogen is an effective approach for the "activation" of the CNTs surface for the ALD of metal oxides. Conformal ZnO coatings are already obtained after 50 ALD cycles, whereas at lower ALD cycles an island growth mode is observed. Moreover, the process allows for a uniform growth from the top to the bottom of the vertically aligned N-CNT arrays. X-ray photoelectron spectroscopy demonstrates that ZnO nucleation takes place at the N-containing species on the surface of the CNTs by the formation of the Zn-N bonds at the interface between the CNTs and the ZnO film.

  4. Effect of the Molar Ratio of B2O3 to Bi2O3 in Al Paste with Bi2O3-B2O3-ZnO Glass on Screen Printed Contact Formation and Si Solar Cell Performance

    NASA Astrophysics Data System (ADS)

    Kim, Bit-Na; Kim, Hyeong Jun; Chang, Hyo Sik; Hong, Hyun Seon; Ryu, Sung-Soo; Lee, Heon

    2013-10-01

    In this study, eco-friendly Pb-free Bi2O3-B2O3-ZnO glass frits were chosen as an inorganic additive for the Al paste used in Si solar cells. The effects of the molar ratio of Bi2O3 to B2O3 in the glass composition on the electrical resistance of the Al electrode and on the cell performance were investigated. The results showed that as the molar ratio of Bi2O3 to B2O3 increased, the glass transition temperature and softening temperature decreased because of the reduced glass viscosity. In Al screen-printed Si solar cells, as the molar ratio of Bi2O3 to B2O3 increased, the sheet electrical resistance of the Al electrode decreased and the cell efficiency increased. The uniformity and thickness of the back-surface field was significantly influenced by the glass composition.

  5. A Novel Ionic Polymer Metal ZnO Composite (IPMZC)

    PubMed Central

    Kim, Sang-Mun; Tiwari, Rashi; Kim, Kwang J.

    2011-01-01

    The presented research introduces a new Ionic Polymer-Metal-ZnO Composite (IPMZC) demonstrating photoluminescence (PL)-quenching on mechanical bending or application of an electric field. The newly fabricated IPMZC integrates the optical properties of ZnO and the electroactive nature of Ionic Polymer Metal Composites (IPMC) to enable a non-contact read-out of IPMC response. The electro-mechano-optical response of the IPMZC was measured by observing the PL spectra under mechanical bending and electrical regimes. The working range was measured to be 375–475 nm. It was noted that the PL-quenching increased proportionally with the increase in curvature and applied field at 384 and 468 nm. The maximum quenching of 53.4% was achieved with the membrane curvature of 78.74/m and 3.01% when electric field (12.5 × 103 V/m) is applied. Coating IPMC with crystalline ZnO was observed to improve IPMC transduction. PMID:22163869

  6. Multifunctional transparent ZnO nanorod films.

    PubMed

    Kwak, Geunjae; Jung, Sungmook; Yong, Kijung

    2011-03-18

    Transparent ZnO nanorod (NR) films that exhibit extreme wetting states (either superhydrophilicity or superhydrophobicity through surface chemical modification), high transmittance, UV protection and antireflection have been prepared via the facile ammonia hydrothermal method. The periodic 1D ZnO NR arrays showed extreme wetting states as well as antireflection properties due to their unique surface structure and prevented the UVA region from penetrating the substrate due to the unique material property of ZnO. Because of the simple, time-efficient and low temperature preparation process, ZnO NR films with useful functionalities are promising for fabrication of highly light transmissive, antireflective, UV protective, antifogging and self-cleaning optical materials to be used for optical devices and photovoltaic energy devices.

  7. Growth of ZnO nanowires on polypropylene membrane surface-Characterization and reactivity

    NASA Astrophysics Data System (ADS)

    Bojarska, Marta; Nowak, Bartosz; Skowroński, Jarosław; Piątkiewicz, Wojciech; Gradoń, Leon

    2017-01-01

    Need for a new membrane is clearly visible in recent studies, mostly due to the fouling phenomenon. Authors, focused on problem of biofouling caused by microorganisms that are present in water environment. An attempt to form a new membrane with zinc oxide (ZnO) nanowires was made; where plasma treatment was used as a first step of modification followed by chemical bath deposition. Such membrane will exhibit additional reactive properties. ZnO, because of its antibacterial and photocatalytic properties, is more and more often used in commercial applications. The authors used SEM imaging, measurement of the contact angle, XRD and the FT-IR analysis for membrane characterization. Amount of ZnO deposited on membrane surface was also investigated by dithizone method. Photocatalytic properties of such membranes were examined through methylene blue and humic acid degradation in laboratory scale modules with LEDs as either: wide range white or UV light source. Antibacterial and antifouling properties of polypropylene membranes modified with ZnO nanowires were examined through a series of tests involving microorganisms: model gram-positive and -negative bacteria. The obtained results showed that it is possible to modify the membrane surface in such a way, that additional reactive properties will be given. Thus, not only did the membrane become a physical barrier, but also turned out to be a reactive one.

  8. American Contact Dermatitis Society Contact Allergy Management Program: An Epidemiologic Tool to Determine Relative Prevalence of Contact Allergens.

    PubMed

    Scheman, Andrew; Severson, David

    2016-01-01

    Data on the prevalence of contact allergy in North America are currently reported by groups of academic contact allergy specialists at select academic centers. Sampling of data from numerous centers across North America, including practices performing more limited patch testing, would provide a broader perspective of contact allergen prevalence in North America. The American Contact Dermatitis Society Contact Allergy Management Program is an ideal tool for collection of epidemiologic data regarding contact allergy prevalence in North America. The aim of the study was to identify the relative prevalence of contact allergy to common contact allergens in North America. Mapping of Contact Allergy Management Program (CAMP) data was performed to allow analysis of how frequently searches were performed for various contact allergens. The number of searches performed for specific allergens provides a measure of the relative prevalence of contact allergy to these allergens. The top 35 allergens for the period from November 18, 2012 to November 18, 2013 are reported. Although these data are useful, specific recommendations for minor alterations to CAMP are discussed, which will allow future CAMP data to be stratified and more powerful. With minor modifications, CAMP can provide a quantum leap in the reporting of contact allergy epidemiologic data in North America.

  9. Superhydrophobicity of Hierarchical and ZNO Nanowire Coatings

    DTIC Science & Technology

    2014-01-01

    AFRL-RX-WP-TP-2014-0141 SUPERHYDROPHOBICITY OF HIERARCHICAL ZNO NANOWIRE COATINGS (POSTPRINT) Shin Mou AFRL/RXAN JANUARY... SUPERHYDROPHOBICITY OF HIERARCHICAL ZNO NANOWIRE COATINGS (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...or disclose the work. The final publication is available at www.rsc.org/MaterialsA. 14. ABSTRACT Hierarchical superhydrophobic surfaces were

  10. Atomistic Interface Dynamics in Sn-Catalyzed Growth of Wurtzite and Zinc-Blende ZnO Nanowires.

    PubMed

    Jia, Shuangfeng; Hu, Shuaishuai; Zheng, He; Wei, Yanjie; Meng, Shuang; Sheng, Huaping; Liu, Huihui; Zhou, Siyuan; Zhao, Dongshan; Wang, Jianbo

    2018-06-11

    Unraveling the phase selection mechanisms of semiconductor nanowires (NWs) is critical for the applications in future advanced nanodevices. In this study, the atomistic vapor-solid-liquid growth processes of Sn-catalyzed wurtzite (WZ) and zinc blende (ZB) ZnO are directly revealed based on the in situ transmission electron microscopy. The growth kinetics of WZ and ZB crystal phases in ZnO appear markedly different in terms of the NW-droplet interface, whereas the nucleation site as determined by the contact angle ϕ between the seed particle and the NW is found to be crucial for tuning the NW structure through combined experimental and theoretical investigations. These results offer an atomic-scale view into the dynamic growth process of ZnO NW, which has implications for the phase-controllable synthesis of II-VI compounds and heterostructures with tunable band structures.

  11. Veritable electronic characteristics in ZnO nanowire circuits uncovered by the four-terminal method at a low temperature

    NASA Astrophysics Data System (ADS)

    Li, Xin; Zhang, Qi

    2017-04-01

    Understanding the natural electrical properties in semiconductor channels and the carrier transport across the metal-semiconductor contact is essential to improve the performance of nanowire devices. This work presents the true electronic characteristics of ZnO nanowire devices measured by a four-electrode method at a low-temperature environment. The temperature rise leads to the decrease in near-band-gap emission, which is attributed to two non-radiative recombination processes. For ZnO circuits, thermionic emission carrier transport mechanism plays a dominant role at Ti-Au/ZnO interface and the transport mechanism in ZnO nanowires is governed by two competitive thermal activation conduction processes: optical or acoustic phonons assisting hopping.

  12. Effect of growth time to the properties of Al-doped ZnO nanorod arrays

    NASA Astrophysics Data System (ADS)

    Ismail, A. S.; Mamat, M. H.; Malek, M. F.; Saidi, S. A.; Yusoff, M. M.; Mohamed, R.; Sin, N. D. Md; Suriani, A. B.; Rusop, M.

    2018-05-01

    Aluminum (Al)-doped zinc oxide (ZnO) nanorod array films were successfully deposited at different growth time on zinc oxide (ZnO) seed layer coated glass substrate using sol-gel immersion method. The morphology images of the films showed that the thicknesses of the films were increased parallel with the increment of growth period. The surface topology of the films displayed an increment of roughness as the growth period increased. Optical properties of the samples exposed that the percentage of transmittances reduced at higher growth time. Besides, the Urbach energy of the films slightly increased as the immersion time increased. The current-voltage (I-V) measurement indicated that the resistance increased as the immersion time increased owing to the appearance of intrinsic layer on top of the nanorods.

  13. Surface nanostructuring of thin film composite membranes via grafting polymerization and incorporation of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Isawi, Heba; El-Sayed, Magdi H.; Feng, Xianshe; Shawky, Hosam; Abdel Mottaleb, Mohamed S.

    2016-11-01

    A new approach for modification of polyamid thin film composite membrane PA(TFC) using synthesized ZnO nanoparticles (ZnO NPs) was shown to enhance the membrane performances for reverse osmosis water desalination. First, active layer of synthesis PA(TFC) membrane was activated with an aqueous solution of free radical graft polymerization of hydrophilic methacrylic acid (MAA) monomer onto the surface of the PA(TFC) membrane resulting PMAA-g-PA(TFC). Second, the PA(TFC) membrane has been developed by incorporation of ZnO NPs into the MAA grafting solution resulting the ZnO NPs modified PMAA-g-PA(TFC) membrane. The surface properties of the synthesized nanoparticles and prepared membranes were investigated using the FTIR, XRD and SEM. Morphology studies demonstrated that ZnO NPs have been successfully incorporated into the active grafting layer over PA(TFC) composite membranes. The zinc leaching from the ZnO NPs modified PMAA-g-PA(TFC) was minimal, as shown by batch tests that indicated stabilization of the ZnO NPs on the membrane surfaces. Compared with the a pure PA(TFC) and PMAA-g-PA(TFC) membranes, the ZnO NPs modified PMAA-g-PA(TFC) was more hydrophilic, with an improved water contact angle (∼50 ± 3°) over the PMAA-g-PA(TFC) (63 ± 2.5°). The ZnO NPs modified PMAA-g-PA(TFC) membrane showed salt rejection of 97% (of the total groundwater salinity), 99% of dissolved bivalent ions (Ca2+, SO42-and Mg2+), and 98% of mono valent ions constituents (Cl- and Na+). In addition, antifouling performance of the membranes was determined using E. coli as a potential foulant. This demonstrates that the ZnO NPs modified PMAA-g-PA(TFC) membrane can significantly improve the membrane performances and was favorable to enhance the selectivity, permeability, water flux, mechanical properties and the bio-antifouling properties of the membranes for water desalination.

  14. Effect of precursor solutions on ZnO film via solution precursor plasma spray and corresponding gas sensing performances

    NASA Astrophysics Data System (ADS)

    Yu, Z. X.; Ma, Y. Z.; Zhao, Y. L.; Huang, J. B.; Wang, W. Z.; Moliere, M.; Liao, H. L.

    2017-08-01

    Solution precursor plasma spraying (SPPS) as a novel thermal spray method was employed to deposit nano-structured ZnO thin film using different formulations of the precursor solution. This article focuses on the influence of the solution composition on the preferential orientation of crystal growth, on crystal size and surface morphology of the resulting ZnO films. The trend of preferential growth along (002) lattice plane of ZnO film was studied by slow scanning X-ray diffraction using a specific coefficient P(002). It appears that the thermal spray process promotes the buildup of ZnO films preferentially oriented along the c-axis. The shape of single particle tends to change from round shaped beads to hexagonal plates by increasing the volume ratio of ethanol in the solvent. Both cauliflower and honeycomb-like surface morphologies featuring high specific surface area and roughness were obtained through the SPPS process by varying solution composition. These ZnO films are hydrophobic with contact angle as high as 136°, which is seemingly associated with micro reliefs developing high surface specific area. Then the gas sensing performances of ZnO films preferentially oriented along (002) face were tentatively predicted using the "first principle calculation method" and were compared with those of conventional films that are mainly oriented along the (101) face. The (002) face displays better hydrogen adsorption capability than the (101) face with much larger resulting changes in electrical resistance. In conclusion, the c-axis oriented ZnO films obtained through SSPS have favorable performances to be used as sensitive layer in gas sensing applications.

  15. Surface structure, optoelectronic properties and charge transport in ZnO nanocrystal/MDMO-PPV multilayer films.

    PubMed

    Lian, Qing; Chen, Mu; Mokhtar, Muhamad Z; Wu, Shanglin; Zhu, Mingning; Whittaker, Eric; O'Brien, Paul; Saunders, Brian R

    2018-05-07

    Blends of semiconducting nanocrystals and conjugated polymers continue to attract major research interest because of their potential applications in optoelectronic devices, such as solar cells, photodetectors and light-emitting diodes. In this study we investigate the surface structure, morphological and optoelectronic properties of multilayer films constructed from ZnO nanocrystals (NCs) and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV). The effects of layer number and ZnO concentration (C ZnO ) used on the multilayer film properties are investigated. An optimised solvent blend enabled well-controlled layers to be sequentially spin coated and the construction of multilayer films containing six ZnO NC (Z) and MDMO-PPV (M) layers (denoted as (ZM) 6 ). Contact angle data showed a strong dependence on C ZnO and indicated distinct differences in the coverage of MDMO-PPV by the ZnO NCs. UV-visible spectroscopy showed that the MDMO-PPV absorption increased linearly with the number of layers in the films and demonstrates highly tuneable light absorption. Photoluminescence spectra showed reversible quenching as well as a surprising red-shift of the MDMO-PPV emission peak. Solar cells were constructed to probe vertical photo-generated charge transport. The measurements showed that (ZM) 6 devices prepared using C ZnO = 14.0 mg mL -1 had a remarkably high open circuit voltage of ∼800 mV. The device power conversion efficiency was similar to that of a control bilayer device prepared using a much thicker MDMO-PPV layer. The results of this study provide insight into the structure-optoelectronic property relationships of new semiconducting multilayer films which should also apply to other semiconducting NC/polymer combinations.

  16. Enhanced super-hydrophobic and switching behavior of ZnO nanostructured surfaces prepared by simple solution--immersion successive ionic layer adsorption and reaction process.

    PubMed

    Suresh Kumar, P; Sundaramurthy, J; Mangalaraj, D; Nataraj, D; Rajarathnam, D; Srinivasan, M P

    2011-11-01

    A simple and cost-effective successive ionic layer adsorption and reaction (SILAR) method was adopted to fabricate hydrophobic ZnO nanostructured surfaces on transparent indium-tin oxide (ITO), glass and polyethylene terephthalate (PET) substrates. ZnO films deposited on different substrates show hierarchical structures like spindle, flower and spherical shape with diameters ranging from 30 to 300 nm. The photo-induced switching behaviors of ZnO film surfaces between hydrophobic and hydrophilic states were examined by water contact angle and X-ray photoelectron spectroscopy (XPS) analysis. ZnO nanostructured films had contact angles of ~140° and 160°±2 on glass and PET substrates, respectively, exhibiting hydrophobic behavior without any surface modification or treatment. Upon exposure to ultraviolet (UV) illumination, the films showed hydrophilic behavior (contact angle: 15°±2), which upon low thermal stimuli revert back to its original hydrophobic nature. Such reversible and repeatable switching behaviors were observed upon cyclical exposure to ultraviolet radiation. These biomimetic ZnO surfaces exhibit good anti-reflective properties with lower reflectance of 9% for PET substrates. Thus, the present work is significant in terms of its potential application in switching devices, solar coatings and self-cleaning smart windows. Copyright © 2011 Elsevier Inc. All rights reserved.

  17. EDITORIAL: Close contact Close contact

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2010-07-01

    The development of scanning probe techniques, such as scanning tunnelling microscopy [1], has often been touted as the catalyst for the surge in activity and progress in nanoscale science and technology. Images of nanoscale structural detail have served as an invaluable investigative resource and continue to fascinate with the fantastical reality of an intricate nether world existing all around us, but hidden from view of the naked eye by a disparity in scale. As is so often the case, the invention of the scanning tunnelling microscope heralded far more than just a useful new apparatus, it demonstrated the scope for exploiting the subtleties of electronic contact. The shrinking of electronic devices has been a driving force for research into molecular electronics, in which an understanding of the nature of electronic contact at junctions is crucial. In response, the number of experimental techniques in molecular electronics has increased rapidly in recent years. Scanning tunnelling microscopes have been used to study electron transfer through molecular films on a conducting substrate, and the need to monitor the contact force of scanning tunnelling electrodes led to the use of atomic force microscopy probes coated in a conducting layer as studied by Cui and colleagues in Arizona [2]. In this issue a collaboration of researchers at Delft University and Leiden University in the Netherlands report a new device architecture for the independent mechanical and electrostatic tuning of nanoscale charge transport, which will enable thorough studies of molecular transport in the future [3]. Scanning probes can also be used to pattern surfaces, such as through spatially-localized Suzuki and Heck reactions in chemical scanning probe lithography. Mechanistic aspects of spatially confined Suzuki and Heck chemistry are also reported in this issue by researchers in Oxford [4]. All these developments in molecular electronics fabrication and characterization provide alternative

  18. Top Hispanic Degree Producers

    ERIC Educational Resources Information Center

    Diverse: Issues in Higher Education, 2012

    2012-01-01

    This article presents a list of the top 100 producers of associate, bachelor's and graduate degrees awarded to minority students based on research conducted by Dr. Victor M.H. Borden, professor of educational leadership and policy students at the Indiana University Bloomington. For the year 2012, the listings focus on Hispanic students. Data for…

  19. Choosing a Top Ten.

    ERIC Educational Resources Information Center

    IUCN Bulletin, 1984

    1984-01-01

    Presents an annotated list of 34 animals and 32 plants which are candidates for a list of the top 10 endangered species. Also presents the criteria used to formulate these lists. They include the conservation value (urgency prominance, biological value) and operational considerations (such as cost factors) for each species. (JN)

  20. Brevard Top Scholars

    NASA Image and Video Library

    2017-05-05

    About 40 Brevard County high school seniors attended Brevard Top Scholars Day at Kennedy Space Center on May 5. Kennedy's Office of Education coordinated the event that featured a special behind-the-scenes tour of Kennedy, including prototype shops, cryogenic labs and facilities such as the Vehicle Assembly Building and the Launch Control Center firing rooms.

  1. Brevard Top Scholars

    NASA Image and Video Library

    2017-05-05

    About 40 Brevard County high school seniors take in the enormity of the Vehicle Assembly Building during Brevard Top Scholars Day on May 5. Kennedy's Office of Education coordinated the event that featured a special behind-the-scenes tour of Kennedy, including prototype shops, cryogenic labs and the Launch Control Center firing rooms.

  2. Photonics Academy: TOPS project

    NASA Astrophysics Data System (ADS)

    Tyson, Nick; Barwis, Vicky; Maghuk, Faris

    2009-06-01

    Technicians in Opto-Electronics Project (TOP) has five targets: one, to develop and pilot train with at least 10 learners; two, to implement a marketing plan; three, to raise awareness of the sector with young people to increase new entrants into the sector; four, to engage employers in development; and five, to provide information on leadership and management.

  3. Over the Top.

    ERIC Educational Resources Information Center

    American School & University, 1999

    1999-01-01

    Describes how careful preparation and having reliable information can make for a successful roofing project, whether retrofitting an old roof or topping off new construction. Contractor evaluation and warranty analysis are discussed. Also included is a roofing specifications chart for multi-ply and single-ply systems. (GR)

  4. Ten Top Tech Trends

    ERIC Educational Resources Information Center

    McLester, Susan

    2008-01-01

    In this article, the author discusses the major technical issues, products, and practices of the day. The top ten tech trends are listed and discussed. These include: (1) data mining; (2) cyberbullying; (3) 21st century skills; (4) digital content; (5) learning at leisure; (6) personal responders; (7) mobile tools; (8) bandwidth; (9) open-source…

  5. Top Quark Properties at Tevatron

    SciTech Connect

    Lysák, Roman

    2017-11-27

    The latest CDF and D0 experiment measurements of the top quark properties except the top quark mass are presented. The final combination of the CDF and D0 forward-backward asymmetry measurements is shown together with the D0 measurements of the inclusive top quark pair cross-section as well as the top quark polarization.

  6. Morphology engineering of ZnO nanostructures for high performance supercapacitors: enhanced electrochemistry of ZnO nanocones compared to ZnO nanowires

    NASA Astrophysics Data System (ADS)

    He, Xiaoli; Yoo, Joung Eun; Lee, Min Ho; Bae, Joonho

    2017-06-01

    In this work, the morphology of ZnO nanostructures is engineered to demonstrate enhanced supercapacitor characteristics of ZnO nanocones (NCs) compared to ZnO nanowires (NWs). ZnO NCs are obtained by chemically etching ZnO NWs. Electrochemical characteristics of ZnO NCs and NWs are extensively investigated to demonstrate morphology dependent capacitive performance of one dimensional ZnO nanostructures. Cyclic voltammetry measurements on these two kinds of electrodes in a three-electrode cell confirms that ZnO NCs exhibit a high specific capacitance of 378.5 F g-1 at a scan rate of 20 mV s-1, which is almost twice that of ZnO NWs (191.5 F g-1). The charge-discharge and electrochemical impedance spectroscopy measurements also clearly result in enhanced capacitive performance of NCs as evidenced by higher specific capacitances and lower internal resistance. Asymmetric supercapacitors are fabricated using activated carbon (AC) as the negative electrode and ZnO NWs and NCs as positive electrodes. The ZnO NC⫽AC can deliver a maximum specific capacitance of 126 F g-1 at a current density of 1.33 A g-1 with an energy density of 25.2 W h kg-1 at the power density of 896.44 W kg-1. In contrast, ZnO NW⫽AC displays 63% of the capacitance obtained from the ZnO NC⫽AC supercapacitor. The enhanced performance of NCs is attributed to the higher surface area of ZnO nanostructures after the morphology is altered from NWs to NCs.

  7. Morphology engineering of ZnO nanostructures for high performance supercapacitors: enhanced electrochemistry of ZnO nanocones compared to ZnO nanowires.

    PubMed

    He, Xiaoli; Yoo, Joung Eun; Lee, Min Ho; Bae, Joonho

    2017-06-16

    In this work, the morphology of ZnO nanostructures is engineered to demonstrate enhanced supercapacitor characteristics of ZnO nanocones (NCs) compared to ZnO nanowires (NWs). ZnO NCs are obtained by chemically etching ZnO NWs. Electrochemical characteristics of ZnO NCs and NWs are extensively investigated to demonstrate morphology dependent capacitive performance of one dimensional ZnO nanostructures. Cyclic voltammetry measurements on these two kinds of electrodes in a three-electrode cell confirms that ZnO NCs exhibit a high specific capacitance of 378.5 F g -1 at a scan rate of 20 mV s -1 , which is almost twice that of ZnO NWs (191.5 F g -1 ). The charge-discharge and electrochemical impedance spectroscopy measurements also clearly result in enhanced capacitive performance of NCs as evidenced by higher specific capacitances and lower internal resistance. Asymmetric supercapacitors are fabricated using activated carbon (AC) as the negative electrode and ZnO NWs and NCs as positive electrodes. The ZnO NC⫽AC can deliver a maximum specific capacitance of 126 F g -1 at a current density of 1.33 A g -1 with an energy density of 25.2 W h kg -1 at the power density of 896.44 W kg -1 . In contrast, ZnO NW⫽AC displays 63% of the capacitance obtained from the ZnO NC⫽AC supercapacitor. The enhanced performance of NCs is attributed to the higher surface area of ZnO nanostructures after the morphology is altered from NWs to NCs.

  8. Au/n-ZnO rectifying contact fabricated with hydrogen peroxide pretreatment

    NASA Astrophysics Data System (ADS)

    Gu, Q. L.; Cheung, C. K.; Ling, C. C.; Ng, A. M. C.; Djurišić, A. B.; Lu, L. W.; Chen, X. D.; Fung, S.; Beling, C. D.; Ong, H. C.

    2008-05-01

    Au contacts were deposited on n-type ZnO single crystals with and without hydrogen peroxide pretreatment for the ZnO substrate. The Au/ZnO contacts fabricated on substrates without H2O2 pretreatment were Ohmic and those with H2O2 pretreatment were rectifying. With an aim of fabricating a good quality Schottky contact, the rectifying property of the Au/ZnO contact was systemically investigated by varying the treatment temperature and duration. The best performing Schottky contact was found to have an ideality factor of 1.15 and a leakage current of ˜10-7 A cm-2. A multispectroscopic study, including scanning electron microscopy, positron annihilation spectroscopy, deep level transient spectroscopy, x-ray photoelectron spectroscopy, and photoluminescence, showed that the H2O2 treatment removed the OH impurity and created Zn-vacancy related defects hence decreasing the conductivity of the ZnO surface layer, a condition favorable for forming good Schottky contact. However, the H2O2 treatment also resulted in a deterioration of the surface morphology, leading to an increase in the Schottky contact ideality factor and leakage current in the case of nonoptimal treatment time and temperature.

  9. Tailoring the Hydrothermal Synthesis of Stainless Steel Wire Sieve-Supported Ag-Doped ZnO Nanowires to Optimize Their Photo-catalytic Activity

    NASA Astrophysics Data System (ADS)

    Jing, W. X.; Shi, J. F.; Xu, Z. P.; Jiang, Z. D.; Wei, Z. Y.; Zhou, F.; Wu, Q.; Cui, Q. B.

    2018-03-01

    Batches of un-doped and Ag-doped ZnO nanowires (ZnONWs) were prepared hydrothermally on stainless steel wire sieves at varied Zn2+ concentrations of the growth solution and at different Ag+ concentrations of the silver nitrate solution. Methylene blue solution was degraded with these as-prepared ZnONWs in the presences of ultraviolet irradiation. It is found that both the processing parameters greatly affect the surface textures, wettability, and photo-activity of the ZnONWs. The latter synthesizing parameter is optimized only after the former one has been finely regulated. The un-doped and Ag-doped ZnONWs at Zn2+ concentration of 75 mM of the growth solution and at Ag+ concentration of3 mM of the silver nitrate solution both produce Gaussian rough surfaces and in each batch are most hydrophilic. Therefore, in the related batch the contacting surface area of the catalyst is the largest, the hydroxyl radicals attached on the top ends of corresponding ZnONWs the most, and the catalytic activity of these catalysts the optimal. Besides these, the latter synthesizing parameter affects the photo-activity of Ag-doped ZnONWs more significantly than the former one does that of un-doped ZnONWs.

  10. Effect of Pressure on the Stability and Electronic Structure of ZnO0.5S0.5 and ZnO0.5Se0.5

    NASA Astrophysics Data System (ADS)

    Manotum, R.; Klinkla, R.; Phaisangittisakul, N.; Pinsook, U.; Bovornratanaraks, T.

    2017-12-01

    Structures and high-pressure phase transitions in ZnO0.5S0.5 and ZnO0.5Se0.5 have been investigated using density functional theory calculations. The previously proposed structures of ZnO0.5S0.5 and ZnO0.5Se0.5 which are chalcopyrite ( I\\bar{4}2d ), rocksalt ( Fm3m ), wurtzite ( P63 mc ) and CuAu-I ( P\\bar{4}m2 ) have been fully investigated. Stabilities of these materials have been systematically studied up to 40 GPa using various approaches. We have confirmed the stability of the chalcopyrite structure up to 30 GPa for which the CuAu-I structure has been previously proposed. However, our calculation revealed that CuAu-I is not a stable structure under 32 GPa and 33 GPa for both ZnO0.5S0.5 and ZnO0.5Se0.5, respectively, which could explain the failure in several attempts to fabricate these materials under such conditions. We have also examined the pressure-dependence of the bandgap and electronic structure up to 30 GPa. We can conclude from our PDOS analysis that the applied pressure does not change the atomic state characters of electronic states near the top of valence and the bottom of conduction bands, but mainly modifies the dominant Zn-3d atomic state of the deep Bloch state at -1 eV below Fermi level.

  11. Brevard Top Scholars

    NASA Image and Video Library

    2017-05-05

    Kennedy Space Center Associate Director Kelvin Manning addresses about 40 Brevard County high school seniors regarding NASA's and Kennedy’s roles and missions during Brevard Top Scholars Day at Kennedy Space Center on May 5. Kennedy's Office of Education coordinated the event that featured a special behind-the-scenes tour of Kennedy, including prototype shops, cryogenic labs and facilities such as the Vehicle Assembly Building and the Launch Control Center firing rooms.

  12. Complex and oriented ZnO nanostructures.

    PubMed

    Tian, Zhengrong R; Voigt, James A; Liu, Jun; McKenzie, Bonnie; McDermott, Matthew J; Rodriguez, Mark A; Konishi, Hiromi; Xu, Huifang

    2003-12-01

    Extended and oriented nanostructures are desirable for many applications, but direct fabrication of complex nanostructures with controlled crystalline morphology, orientation and surface architectures remains a significant challenge. Here we report a low-temperature, environmentally benign, solution-based approach for the preparation of complex and oriented ZnO nanostructures, and the systematic modification of their crystal morphology. Using controlled seeded growth and citrate anions that selectively adsorb on ZnO basal planes as the structure-directing agent, we prepared large arrays of oriented ZnO nanorods with controlled aspect ratios, complex film morphologies made of oriented nanocolumns and nanoplates (remarkably similar to biomineral structures in red abalone shells) and complex bilayers showing in situ column-to-rod morphological transitions. The advantages of some of these ZnO structures for photocatalytic decompositions of volatile organic compounds were demonstrated. The novel ZnO nanostructures are expected to have great potential for sensing, catalysis, optical emission, piezoelectric transduction, and actuations.

  13. Fluorinated tin oxide back contact for AZTSSe photovoltaic devices

    SciTech Connect

    Gershon, Talia S.; Gunawan, Oki; Haight, Richard A.

    A photovoltaic device includes a substrate, a back contact comprising a stable low-work function material, a photovoltaic absorber material layer comprising Ag.sub.2ZnSn(S,Se).sub.4 (AZTSSe) on a side of the back contact opposite the substrate, wherein the back contact forms an Ohmic contact with the photovoltaic absorber material layer, a buffer layer or Schottky contact layer on a side of the absorber layer opposite the back contact, and a top electrode on a side of the buffer layer opposite the absorber layer.

  14. 11. VIEW SHOWING TOP OF WATER TANK TAKEN FROM TOP ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. VIEW SHOWING TOP OF WATER TANK TAKEN FROM TOP OF ELEVATOR SHAFT. - U.S. Naval Base, Pearl Harbor, Signal Tower, Corner of Seventh Street & Avenue D east of Drydock No. 1, Pearl City, Honolulu County, HI

  15. A ZnO nanowire resistive switch

    NASA Astrophysics Data System (ADS)

    Karthik, K. R. G.; Ramanujam Prabhakar, Rajiv; Hai, L.; Batabyal, Sudip K.; Huang, Y. Z.; Mhaisalkar, S. G.

    2013-09-01

    An individual ZnO nanowire resistive switch is evaluated with Pt/ZnO nanowire/Pt topology. A detailed DC I-V curve analysis is performed to bring both the conduction mechanism and the device characteristics to light. The device is further studied at various vacuum pressures to ascertain the presence of polar charges in ZnO nanowires as the phenomenon leading to the formation of the switch. The disappearance of the resistive switching is also analyzed with two kinds of fabrication approaches Focused Ion/Electron Beam involved in the making the device and a summary of both length and fabrication dependences of resistive switching in the ZnO nanowire is presented.

  16. Magnetic properties of ZnO nanoparticles.

    PubMed

    Garcia, M A; Merino, J M; Fernández Pinel, E; Quesada, A; de la Venta, J; Ruíz González, M L; Castro, G R; Crespo, P; Llopis, J; González-Calbet, J M; Hernando, A

    2007-06-01

    We experimentally show that it is possible to induce room-temperature ferromagnetic-like behavior in ZnO nanoparticles without doping with magnetic impurities but simply inducing an alteration of their electronic configuration. Capping ZnO nanoparticles ( approximately 10 nm size) with different organic molecules produces an alteration of their electronic configuration that depends on the particular molecule, as evidenced by photoluminescence and X-ray absorption spectroscopies and altering their magnetic properties that varies from diamagnetic to ferromagnetic-like behavior.

  17. Jovian Cloud Tops

    NASA Image and Video Library

    2017-05-18

    This enhanced color view of Jupiter's cloud tops was processed by citizen scientist Bjorn Jonsson using data from the JunoCam instrument on NASA's Juno spacecraft. The image highlights a massive counterclockwise rotating storm that appears as a white oval in the gas giant's southern hemisphere. Juno acquired this image on Feb. 2, 2017, at 6:13 a.m. PDT (9:13 a.m. EDT), as the spacecraft performed a close flyby of Jupiter. When the image was taken, the spacecraft was about 9,000 miles (14,500 kilometers) from the planet. https://photojournal.jpl.nasa.gov/catalog/PIA21391

  18. Contact Zone: Missoula

    NASA Image and Video Library

    2015-07-23

    A rock outcrop dubbed "Missoula," near Marias Pass on Mars, is seen in this image mosaic taken by the Mars Hand Lens Imager on NASA's Curiosity rover. Pale mudstone (bottom of outcrop) meets coarser sandstone (top) in this geological contact zone, which has piqued the interest of Mars scientists. White mineral veins that fill fractures in the lower rock unit abruptly end when they meet the upper rock unit. Such clues help scientists understand the possible timing of geological events. First, the fine sediment that now forms the lower unit would have hardened into rock. It then would have fractured, and groundwater would have deposited calcium sulfate minerals into the fractures. Next, the coarser sediment that forms the upper unit would have been deposited. The area pictured is about 16 inches (40 centimeters) across. The image was taken on the 1,031st Martian day, or sol, of the mission (July 1, 2015). MAHLI was built by Malin Space Science Systems, San Diego. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory Project for the NASA Science Mission Directorate, Washington. JPL designed and built the project's Curiosity rover. http://photojournal.jpl.nasa.gov/catalog/PIA19829

  19. Electrochemical modification of properties of ZnO films

    NASA Astrophysics Data System (ADS)

    Abe, Koji; Okubo, Takamasa; Ishikawa, Hirohito

    2017-12-01

    The properties of Al-doped ZnO films and Li- and Al-doped ZnO films were modified by electrochemical treatment. A constant current was applied between a ZnO film and a Pt electrode in an electrolyte solution. The sheet resistance of the ZnO film increased and decreased depending on the direction of current flow during the electrochemical treatment. When the ZnO film was used as a cathode (forward biased condition), the sheet resistance of the ZnO film decreased with increasing treatment time. The optical bandgap of the H2-annealed ZnO film also depended on the direction of current flow and increased under the forward biased condition. The electrochemical treatment caused the Burstein-Moss effect.

  20. Miniaturized accelerometer made with ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Song, Sangho; Kim, Jeong Woong; Kim, Hyun Chan; Yun, Youngmin; Kim, Jaehwan

    2017-04-01

    Miniaturized accelerometer is required in many applications, such as, robotics, haptic devices, gyroscopes, simulators and mobile devices. ZnO is an essential semiconductor material with wide direct band gap, thermal stability and piezoelectricity. Especially, well aligned ZnO nanowire is appropriate for piezoelectric applications since it can produce high electrical signal under mechanical load. To miniaturize accelerometer, an aligned ZnO nanowire is adopted to implement active piezoelectric layer of the accelerometer and copper is chosen for the head mass. To grow ZnO nanowire on the copper head mass, hydrothermal synthesis is conducted and the effect of ZnO nanowire length on the accelerometer performance is investigated. Refresh hydrothermal synthesis can increase the length of ZnO nanowire. The performance of the fabricated ZnO accelerometers is compared with a commercial accelerometer. Sensitivity and linearity of the fabricated accelerometers are investigated.

  1. Lattice diffusion and vapor solid growths forming nanoarchitectures on ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Sombrio, Guilherme; Rivaldo-Gómez, C. M.; Pomar, Cesar A. D.; Souza, Jose A.

    2017-12-01

    We report hierarchical nanoarchitectures formed on the tips and sidewalls of ZnO nanowires which is formed on the top of microtubes. The whole growth process of these micro/nanostructures during thermal oxidation combines lattice/grain/surface ionic diffusion along with vapor solid mechanism. All the process takes place along with the presence of an electric current, which plays an important role forming the ZnO molecules due to Zn metal evaporation and attracting them to condense into nanostructures of several morphologies. The observation of a very long needle-like nanowire reveals the stack nature of the growth. These nanoarchitectures are rarely observed experimentally. Raman scattering confirms phonon confinement in the nanostructures. Photoluminescence measurements indicate a route for engineering defects on the surface of ZnO microtubes after the complete coalescence of the nanostructures through heat treatment. This experiment would be useful for improving nanostructure organization which could provide an impact in the manufacturability of nanostructure-based systems.

  2. Contact Lens Care

    MedlinePlus

    ... your prescription expires Lens measurements The contact lens brand name and material Your doctor’s name and contact ... mail-order sellers may send you a different brand. Contact lenses may look the same, but materials ...

  3. Contact Lens Risks

    MedlinePlus

    ... Health and Consumer Devices Consumer Products Contact Lenses Contact Lens Risks Share Tweet Linkedin Pin it More ... redness blurred vision swelling pain Serious Hazards of Contact Lenses Symptoms of eye irritation can indicate a ...

  4. Intrinsic and extrinsic doping of ZnO and ZnO alloys

    NASA Astrophysics Data System (ADS)

    Ellmer, Klaus; Bikowski, André

    2016-10-01

    In this article the doping of the oxidic compound semiconductor ZnO is reviewed with special emphasis on n-type doping. ZnO naturally exhibits n-type conductivity, which is used in the application of highly doped n-type ZnO as a transparent electrode, for instance in thin film solar cells. For prospective application of ZnO in other electronic devices (LEDs, UV photodetectors or power devices) p-type doping is required, which has been reported only minimally. Highly n-type doped ZnO can be prepared by doping with the group IIIB elements B, Al, Ga, and In, which act as shallow donors according to the simple hydrogen-like substitutional donor model of Bethe (1942 Theory of the Boundary Layer of Crystal Rectifiers (Boston, MA: MIT Rad Lab.)). Group IIIA elements (Sc, Y, La etc) are also known to act as shallow donors in ZnO, similarly explainable by the shallow donor model of Bethe. Some reports showed that even group IVA (Ti, Zr, Hf) and IVB (Si, Ge) elements can be used to prepare highly doped ZnO films—which, however, can no longer be explained by the simple hydrogen-like substitutional donor model. More probably, these elements form defect complexes that act as shallow donors in ZnO. On the other hand, group V elements on oxygen lattice sites (N, P, As, and Sb), which were viewed for a long time as typical shallow acceptors, behave instead as deep acceptors, preventing high hole concentrations in ZnO at room temperature. Also, ‘self’-compensation, i.e. the formation of a large number of intrinsic donors at high acceptor concentrations seems to counteract the p-type doping of ZnO. At donor concentrations above about 1020 cm-3, the electrical activation of the dopant elements is often less than 100%, especially in polycrystalline thin films. Reasons for the electrical deactivation of the dopant atoms are (i) the formation of dopant-defect complexes, (ii) the compensation of the electrons by acceptors (Oi, VZn) or (iii) the formation of secondary phases, for

  5. Electrical contact tool set station

    DOEpatents

    Byers, M.E.

    1988-02-22

    An apparatus is provided for the precise setting to zero of electrically conductive cutting tools used in the machining of work pieces. An electrically conductive cylindrical pin, tapered at one end to a small flat, rests in a vee-shaped channel in a base so that its longitudinal axis is parallel to the longitudinal axis of the machine's spindle. Electronic apparatus is connected between the cylindrical pin and the electrically conductive cutting tool to produce a detectable signal when contact between tool and pin is made. The axes of the machine are set to zero by contact between the cutting tool and the sides, end or top of the cylindrical pin. Upon contact, an electrical circuit is completed, and the detectable signal is produced. The tool can then be set to zero for that axis. Should the tool contact the cylindrical pin with too much force, the cylindrical pin would be harmlessly dislodged from the vee-shaped channel, preventing damage either to the cutting tool or the cylindrical pin. 5 figs.

  6. Curly Top Disease of Tomato

    USDA-ARS?s Scientific Manuscript database

    Curly top disease, caused by viruses in the genus, Curtovirus, has impacted western US agriculture for over a century; and is a significant threat to tomato production. The two most abundant curtovirus species today are Beet severe curly top virus (BSCTV) and Beet mild curly top virus (BMCTV) but ot...

  7. Effect of Rapid Thermal Annealing on the Electrical Characteristics of ZnO Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Remashan, Kariyadan; Hwang, Dae-Kue; Park, Seong-Ju; Jang, Jae-Hyung

    2008-04-01

    Thin-film transistors (TFTs) with a bottom-gate configuration were fabricated with an RF magnetron sputtered undoped zinc oxide (ZnO) channel layer and plasma-enhanced chemical vapor deposition (PECVD) grown silicon nitride as a gate dielectric. Postfabrication rapid thermal annealing (RTA) and subsequent nitrous oxide (N2O) plasma treatment were employed to improve the performance of ZnO TFTs in terms of on-current and on/off current ratio. The RTA treatment increases the on-current of the TFT significantly, but it also increases its off-current. The off-current of 2×10-8 A and on/off current ratio of 3×103 obtained after the RTA treatment were improved to 10-10 A and 105, respectively, by the subsequent N2O plasma treatment. The better device performance can be attributed to the reduction of oxygen vacancies at the top region of the channel due to oxygen incorporation from the N2O plasma. X-ray photoelectron spectroscopy (XPS) analysis of the TFT samples showed that the RTA-treated ZnO surface has more oxygen vacancies than as-deposited samples, which results in the increased drain current. The XPS study also showed that the subsequent N2O plasma treatment reduces oxygen vacancies only at the surface of ZnO so that the better off-current and on/off current ratio can be obtained.

  8. Coherently Coupled ZnO and VO2 Interface studied by Photoluminescence and electrical transport across a phase transition

    NASA Astrophysics Data System (ADS)

    Srivastava, Amar; Saha, S.; Annadi, A.; Zhao, Y. L.; Gopinadhan, K.; Wang, X.; Naomi, N.; Liu, Z. Q.; Dhar, S.; Herng, T. S.; Nina, Bao; Ariando, -; Ding, Jun; Venkatesan, T.

    2012-02-01

    In this work we report a study of a coherently coupled interface consisting of a ZnO layer grown on top of an oriented VO2 layer on sapphire by photoluminescence and electrical transport measurements across the VO2 metal insulator phase transition (MIT). The photoluminescence of the ZnO layer showed a broad hysteresis induced by the phase transition of VO2 while the width of the electrical hysteresis was narrow and unaffected by the over layer. The enhanced width of the PL hysteresis was due to the formation of defects during the MIT as evidenced by a broad hysteresis in the opposite direction to that of the band edge PL in the defect luminescense. Unlike VO2 the defects in ZnO did not fully recover across the phase transition. From the defect luminescence data, oxygen interstitials were found to be the predominant defects in ZnO mediated by the strain from the VO2 phase transition. Such coherently coupled interfaces could be of use in characterizing the stability of a variety of interfaces and also for novel device application.

  9. Contact resistance improvement by the modulation of peripheral length to area ratio of graphene contact pattern

    SciTech Connect

    Cho, Chunhum; Lee, Sangchul; Lee, Sang Kyung

    2015-05-25

    High contact resistance between graphene and metal is a major huddle for high performance electronic device applications of graphene. In this work, a method to improve the contact resistance of graphene is investigated by varying the ratio of peripheral length and area of graphene pattern under a metal contact. The contact resistance decreased to 0.8 kΩ·μm from 2.1 kΩ·μm as the peripheral length increased from 312 to 792 μm. This improvement is attributed to the low resistivity of edge-contacted graphene, which is 8.1 × 10{sup 5} times lower than that of top-contacted graphene.

  10. Under Jupiter's Cloud Tops

    NASA Image and Video Library

    2017-05-25

    NASA's Juno spacecraft carries an instrument called the Microwave Radiometer, which examines Jupiter's atmosphere beneath the planet's cloud tops. This image shows the instrument's view of the outer part of Jupiter's atmosphere. Before Juno began using this instrument, scientists expected the atmosphere to be uniform at depths greater than 60 miles (100 kilometers). But with the Microwave Radiometer, scientists have discovered that the atmosphere has variations down to at least 220 miles (350 kilometers), as deep as the instrument can see. In the cut-out image to the right, orange signifies high ammonia abundance and blue signifies low ammonia abundance. Jupiter appears to have a band around its equator high in ammonia abundance, with a column shown in orange. This is contrary to scientists' expectations that ammonia would be uniformly mixed. https://photojournal.jpl.nasa.gov/catalog/PIA21642

  11. Top quark pair production and top quark properties at CDF

    SciTech Connect

    Moon, Chang-Seong

    2016-06-02

    We present the most recent measurements of top quark pairs production and top quark properties in proton-antiproton collisions with center-of-mass energy of 1.96 TeV using CDF II detector at the Tevatron. The combination of top pair production cross section measurements and the direct measurement of top quark width are reported. The test of Standard Model predictions for top quark decaying intomore » $b$-quarks, performed by measuring the ratio $R$ between the top quark branching fraction to $b$-quark and the branching fraction to any type of down quark is shown. The extraction of the CKM matrix element $$|V_{tb}|$$ from the ratio $R$ is discussed. We also present the latest measurements on the forward-backward asymmetry ($$A_{FB}$$) in top anti-top quark production. With the full CDF Run II data set, the measurements are performed in top anti-top decaying to final states that contain one or two charged leptons (electrons or muons). In addition, we combine the results of the leptonic forward-backward asymmetry in $$t\\bar t$$ system between the two final states. All the results show deviations from the next-to-leading order (NLO) standard model (SM) calculation.« less

  12. Contact Us | NREL

    Science.gov Websites

    Contact Us Contact Us Find a contact to help answer your question, resolve a website issue, or job or internship, or want to report an issue with the application process, contact us about careers

  13. All-inkjet-printed flexible ZnO micro photodetector for a wearable UV monitoring device.

    PubMed

    Tran, Van-Thai; Wei, Yuefan; Yang, Hongyi; Zhan, Zhaoyao; Du, Hejun

    2017-03-03

    Fabrication of small-sized patterns of inorganic semiconductor onto flexible substrates is a major concern when manufacturing wearable devices for measuring either biometric or environmental parameters. In this study, micro-sized flexible ZnO UV photodetectors have been thoroughly prepared by a facile inkjet printing technology and followed with heat treatments. A simple ink recipe of zinc acetate precursor solution was investigated. It is found that the substrate temperature during zinc precursor ink depositing has significant effects on ZnO pattern shape, film morphology, and crystallization. The device fabricated from the additive manufacturing approach has good bendability, Ohmic contact, short response time as low as 0.3 s, and high on/off ratio of 3525. We observed the sensor's dependence of response/decay time by the illuminating UV light intensity. The whole process is based on additive manufacturing which has many benefits such as rapid prototyping, saving material, being environmentally friendly, and being capable of creating high-resolution patterns. In addition, this method can be applied to flexible substrates, which makes the device more applicable for applications requiring flexibility such as wearable devices. The proposed all-inkjet-printing approach for a micro-sized ZnO UV photodetector would significantly simplify the fabrication process of micro-sized inorganic semiconductor-based devices. A potential application is real-time monitoring of UV light exposure to warn users about unsafe direct sunlight to implement suitable avoidance solutions.

  14. In situ reduced graphene oxide interlayer for improving electrode performance in ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Venkatesan, A.; Ramesha, C. K.; Kannan, E. S.

    2016-06-01

    The effect of reduced graphene oxide (RGO) thin film on the transport characteristics of vertically aligned zinc oxide nanorods (ZnO NRs) grown on ITO substrate was studied. GO was uniformly drop casted on ZnO NRs as a passivation layer and then converted into RGO by heating it at 60 °C prior to metal electrode deposition. This low temperature reduction is facilitated by the thermally excited electrons from ZnI interstitial sites (~30 meV). Successful reduction of GO was ascertained from the increased disorder band (D) intensity in the Raman spectra. Temperature (298 K-10 K) dependent transport measurements of RGO-ZnO NRs indicate that the RGO layer not only acts as a short circuiting inhibitor but also reduces the height of the potential barrier for electron tunneling. This is confirmed from the temperature dependent electrical characteristics which revealed a transition of carrier transport from thermionic emission at high temperature (T  >  100 K) to tunneling at low temperature (T  <  100 K) across the interface. Our technique is the most promising approach for making reliable electrical contacts on vertically aligned ZnO NRs and improving the reproducibility of device characteristics.

  15. All-inkjet-printed flexible ZnO micro photodetector for a wearable UV monitoring device

    NASA Astrophysics Data System (ADS)

    Tran, Van-Thai; Wei, Yuefan; Yang, Hongyi; Zhan, Zhaoyao; Du, Hejun

    2017-03-01

    Fabrication of small-sized patterns of inorganic semiconductor onto flexible substrates is a major concern when manufacturing wearable devices for measuring either biometric or environmental parameters. In this study, micro-sized flexible ZnO UV photodetectors have been thoroughly prepared by a facile inkjet printing technology and followed with heat treatments. A simple ink recipe of zinc acetate precursor solution was investigated. It is found that the substrate temperature during zinc precursor ink depositing has significant effects on ZnO pattern shape, film morphology, and crystallization. The device fabricated from the additive manufacturing approach has good bendability, Ohmic contact, short response time as low as 0.3 s, and high on/off ratio of 3525. We observed the sensor’s dependence of response/decay time by the illuminating UV light intensity. The whole process is based on additive manufacturing which has many benefits such as rapid prototyping, saving material, being environmentally friendly, and being capable of creating high-resolution patterns. In addition, this method can be applied to flexible substrates, which makes the device more applicable for applications requiring flexibility such as wearable devices. The proposed all-inkjet-printing approach for a micro-sized ZnO UV photodetector would significantly simplify the fabrication process of micro-sized inorganic semiconductor-based devices. A potential application is real-time monitoring of UV light exposure to warn users about unsafe direct sunlight to implement suitable avoidance solutions.

  16. Transparent ZnO-based ohmic contact to p-GaN

    SciTech Connect

    Kaminska, E.; Piotrowska, A.; Golaszewska, K.

    2002-04-09

    Highly conductive ZnO films were fabricated on p-GaN in a two-step process. First, zinc was thermally evaporated on p-GaN. Next, zinc film was oxidized in oxygen flow. To increase the conductivity of ZnO, nitrogen was introduced into zinc during its deposition. The above procedure proved successful in fabricating ZnO of the resistivity of {approx}1 x 10{sup -3} {Omega}cm and resulted in ohmic contacts of resistivity {approx}1 x 10{sup -2} {Omega}cm{sup 2} to low-doped p-GaN, and light transmittance of {approx}75% in the wavelength range of 400-700 nm.

  17. Contact Dermatitis in Pediatrics.

    PubMed

    Pelletier, Janice L; Perez, Caroline; Jacob, Sharon E

    2016-08-01

    Contact dermatitis is an umbrella term that describes the skin's reaction to contacted noxious or allergenic substances. The two main categories of contact dermatitis are irritant type and allergic type. This review discusses the signs, symptoms, causes, and complications of contact dermatitis. It addresses the testing, treatment, and prevention of contact dermatitis. Proper management of contact dermatitis includes avoidance measures for susceptible children. Implementation of a nickel directive (regulating the use of nickel in jewelry and other products that come into contact with the skin) could further reduce exposure to the most common allergens in the pediatric population. [Pediatr Ann. 2016;45(8):e287-e292.]. Copyright 2016, SLACK Incorporated.

  18. Top squark with mass close to the top quark

    NASA Astrophysics Data System (ADS)

    Buckley, Matthew R.; Plehn, Tilman; Ramsey-Musolf, Michael J.

    2014-07-01

    The most natural supersymmetric solution to the hierarchy problem prefers the scalar top partner to be close in mass to the top quark. Experimental searches exclude top squarks across a wide range of masses, but a gap remains when the difference between the masses of the stop and the lightest supersymmetric particle is close to the top mass. We propose to search for stops in this regime by exploiting the azimuthal angular correlation of forward tagging jets in (s)top pair production. As shown in earlier work, this correlation is sensitive to the spin of the heavy states, allowing one to distinguish between top and stop pair production. Here, we demonstrate that this angular information can give a statistically significant stop pair production signal in the upcoming LHC run. While the appropriate simulation including parton showering and detector simulation requires some care, we find stable predictions for the angular correlation using multijet merging.

  19. Highly stable precursor solution containing ZnO nanoparticles for the preparation of ZnO thin film transistors.

    PubMed

    Huang, Heh-Chang; Hsieh, Tsung-Eong

    2010-07-23

    ZnO particles with an average size of about 5 nm were prepared via a sol-gel chemical route and the silane coupling agent, (3-glycidyloxypropyl)-trimethoxysilane (GPTS), was adopted to enhance the dispersion of the ZnO nanoparticles in ethyl glycol (EG) solution. A ZnO surface potential as high as 66 mV was observed and a sedimentation test showed that the ZnO precursor solution remains transparent for six months of storage, elucidating the success of surface modification on ZnO nanoparticles. The ZnO thin films were then prepared by spin coating the precursor solution on a Si wafer and annealing treatments at temperatures up to 500 degrees C were performed for subsequent preparation of ZnO thin film transistors (TFTs). Microstructure characterization revealed that the coalescence of ZnO nanoparticles occurs at temperatures as low as 200 degrees C to result in a highly uniform, nearly pore-free layer. However, annealing at higher temperatures was required to remove organic residues in the ZnO layer for satisfactory device performance. The 500 degrees C-annealed ZnO TFT sample exhibited the best electrical properties with on/off ratio = 10(5), threshold voltage = 17.1 V and mobility (micro) = 0.104 cm(2) V(-1) s(-1).

  20. Physically separating printed circuit boards with a resilient, conductive contact

    NASA Technical Reports Server (NTRS)

    Baker, John D. (Inventor); Montalvo, Alberto (Inventor)

    1999-01-01

    A multi-board module provides high density electronic packaging in which multiple printed circuit boards are stacked. Electrical power, or signals, are conducted between the boards through a resilient contact. One end of the contact is located at a via in the lower circuit board and soldered to a pad near the via. The top surface of the contact rests against a via of the facing printed circuit board.

  1. Fabrication of thin ZnO films with wide-range tuned optical properties by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Davydova, A.; Tselikov, G.; Dilone, D.; Rao, K. V.; Kabashin, A. V.; Belova, L.

    2018-02-01

    We report the manufacturing of thin zinc oxide films by reactive magnetron sputtering at room temperature, and examine their structural and optical properties. We show that the partial oxygen pressure in DC mode can have dramatic effect on absorption and refractive index (RI) of the films in a broad spectral range. In particular, the change of the oxygen pressure from 7% to 5% can lead to either conventional crystalline ZnO films having low absorption and characteristic descending dependence of RI from 2.4-2.7 RIU in the visible to 1.8-2 RIU in the near-infrared (1600 nm) range, or to untypical films, composed of ZnO nano-crystals embedded into amorphous matrix, exhibiting unexpectedly high absorption in the visible-infrared region and ascending dependence of RI with values varying from 1.5 RIU in the visible to 4 RIU in the IR (1600 nm), respectively. Untypical optical characteristics in the second case are explained by defects in ZnO structure arising due to under-oxidation of ZnO crystals. We also show that the observed defect-related film structure remains stable even after annealing of films under relatively high temperatures (30 min under 450 °C). We assume that both types of films can be of importance for photovoltaic (as contact or active layers, respectively), as well as for chemical or biological sensing, optoelectronics etc.

  2. ZnO nanosheet arrays constructed on weaved titanium wire for CdS-sensitized solar cells

    PubMed Central

    2014-01-01

    Ordered ZnO nanosheet arrays were grown on weaved titanium wires by a low-temperature hydrothermal method. CdS nanoparticles were deposited onto the ZnO nanosheet arrays using the successive ionic layer adsorption and reaction method to make a photoanode. Nanoparticle-sensitized solar cells were assembled using these CdS/ZnO nanostructured photoanodes, and their photovoltaic performance was studied systematically. The best light-to-electricity conversion efficiency was obtained to be 2.17% under 100 mW/cm2 illumination, and a remarkable short-circuit photocurrent density of approximately 20.1 mA/cm2 was recorded, which could attribute to the relatively direct pathways for transportation of electrons provided by ZnO nanosheet arrays as well as the direct contact between ZnO and weaved titanium wires. These results indicate that CdS/ZnO nanostructures on weaved titanium wires would open a novel possibility for applications of low-cost solar cells. PMID:24618047

  3. Synthesis of ZnO and Zn nanoparticles in microwave plasma and their deposition on glass slides.

    PubMed

    Irzh, Alexander; Genish, Isaschar; Klein, Lior; Solovyov, Leonid A; Gedanken, Aharon

    2010-04-20

    This work represents a new method to synthesis of ZnO and/or Zn nanoparticles by means of microwave plasma whose electrons are the reducing agents. Glass quadratic slides sized 2.5 x 2.5 cm were coated by ZnO and/or Zn particles whose sizes ranged from a few micrometers to approximately 20 nm. The size of the particles can be controlled by the type of the precursor and its concentration. In the current paper, the mechanism of the reactions of ZnO and/or Zn formation was proposed. Longer plasma irradiation and lower precursor concentration favor the fabrication of metallic Zn nanoparticles. The nature of the precursor's ion (acetate, nitrate, or chloride) is also of importance in determining the composition of the product. The glass slides coated by ZnO and/or Zn nanoparticles were characterized by HR-SEM, HR-TEM, AFM, XRD, ESR, contact angle and diffuse reflectance spectroscopy (DRS).

  4. The Fate of Polyol-Made ZnO and CdS Nanoparticles in Seine River Water (Paris, France).

    PubMed

    da Rocha, Alice; Sivry, Yann; Gelabert, Alexandre; Beji, Zyed; Benedetti, Marc F; Menguy, Nicolas; Brayner, Roberta

    2015-05-01

    This study aims to characterize nanoparticles with different compositions and structures as well as seeing their evolutions over time in a natural environment such as Seine river water (Paris, France). Face centered cubic (fcc) and hexagonal (hcp) CdS as well as hexagonal (hcp) ZnO nanoparticles were synthesized by the Polyol method. CdS nanoparticles (i) cfc structure: are agglomerated, present 100 nm length with heterogeneous diameter and 10 m2 g(-1) specific surface area (S(g)) from Brunauer Emett and Teller (BET) measurements; (ii) hcp structure: 20 nm and S(g) = 67 m2 g(-1). ZnO hcp nanoparticles presents 50 nm length and 15 nm diameter and S(g) = 54 m2 g(-1). These results are in agreement with X-ray diffraction (XRD), and small angle X-ray scattering (SAXs). After 48 h interaction with Seine river water, cryo-TEM analysis showed that ZnO nanoparticles form spherical agglomerates with 300 nm diameter; CdS nanoparticles (fcc) are agglomerated presenting large diameters (> 500 nm); and CdS nanoparticles (hcp) are not agglomerated and present the same characteristics of the starting material. After 168h of contact with Seine river water, CdS (fcc) presents only 14% of dissolution, CdS (hcp) presents both 60% dissolution and 30% reprecipitation in a cadmium carbonate form and finally almost 90% of ZnO nanoparticles are dissolved.

  5. Identification of Zn-vacancy-hydrogen complexes in ZnO single crystals: A challenge to positron annihilation spectroscopy

    NASA Astrophysics Data System (ADS)

    Brauer, G.; Anwand, W.; Grambole, D.; Grenzer, J.; Skorupa, W.; Čížek, J.; Kuriplach, J.; Procházka, I.; Ling, C. C.; So, C. K.; Schulz, D.; Klimm, D.

    2009-03-01

    A systematic study of various, nominally undoped ZnO single crystals, either hydrothermally grown (HTG) or melt grown (MG), has been performed. The crystal quality has been assessed by x-ray diffraction, and a comprehensive estimation of the detailed impurity and hydrogen contents by inductively coupled plasma mass spectrometry and nuclear reaction analysis, respectively, has been made also. High precision positron lifetime experiments show that a single positron lifetime is observed in all crystals investigated, which clusters at 180-182 ps and 165-167 ps for HTG and MG crystals, respectively. Furthermore, hydrogen is detected in all crystals in a bound state with a high concentration (at least 0.3at.% ), whereas the concentrations of other impurities are very small. From ab initio calculations it is suggested that the existence of Zn-vacancy-hydrogen complexes is the most natural explanation for the given experimental facts at present. Furthermore, the distribution of H at a metal/ZnO interface of a MG crystal, and the H content of a HTG crystal upon annealing and time afterward has been monitored, as this is most probably related to the properties of electrical contacts made at ZnO and the instability in p -type conductivity observed at ZnO nanorods in literature. All experimental findings and presented theoretical considerations support the conclusion that various types of Zn-vacancy-hydrogen complexes exist in ZnO and need to be taken into account in future studies, especially for HTG materials.

  6. Superior environment resistance of quartz crystal microbalance with anatase TiO2/ZnO nanorod composite films

    NASA Astrophysics Data System (ADS)

    Qiang, Wei; Wei, Li; Shaodan, Wang; Yu, Bai

    2015-08-01

    The precise measurement of quartz crystal microbalance (QCM) in the detection and weighing of organic gas molecules is achieved due to excellent superhydrophobicity of a deposited film composite. Photocatalysis is utilized as a method for the self-cleaning of organic molecules on the QCM for extended long-term stability in the precision of the instrument. In this paper, ZnO nanorod array is prepared via in situ methods on the QCM coated with Au film via hydrothermal process. Subsequently, a TiO2/ZnO composite film is synthesized by surface modification with TiO2 via sol-gel methods. Results show the anatase TiO2/ZnO nanorod composite film with a sharp, pencil-like structure exhibiting excellent superhydrophobicity (water contact angle of 155°), non-sticking water properties, and an autonomous cleaning property under UV irradiation. The anatase TiO2/ZnO nanorod composite film facilitates the precise measurement and extended lifetime of the QCM for the detection of organic gas molecules.

  7. Synthesis and characterization of ZnO thin films

    SciTech Connect

    Anilkumar, T. S., E-mail: anil24march@gmail.com; Girija, M. L., E-mail: girija.ml.grt1@gmail.com; Venkatesh, J., E-mail: phph9502@yahoo.com

    2016-05-06

    Zinc oxide (ZnO) Thin films were deposited on glass substrate using Spin coating method. Zinc acetate dehydrate, Carbinol and Mono-ethanolamine were used as the precursor, solvent and stabilizer respectively to prepare ZnO Thin-films. The molar ratio of Monoethanolamine to Zinc acetate was maintained as approximately 1. The thickness of the films was determined by Interference technique. The optical properties of the films were studied by UV Vis-Spectrophotometer. From transmittance and absorbance curve, the energy band gap of ZnO is found out. Electrical Conductivity measurements of ZnO are carried out by two probe method and Activation energy for the electrical conductivitymore » of ZnO are found out. The crystal structure and orientation of the films were analyzed by XRD. The XRD patterns show that the ZnO films are polycrystalline with wurtzite hexagonal structure.« less

  8. Enhanced photoluminescence properties of Al doped ZnO films

    NASA Astrophysics Data System (ADS)

    Chen, H. X.; Ding, J. J.

    2018-01-01

    Al doped ZnO films are fabricated by radio frequency magnetron sputtering. In general, visible emission is related to various defects in ZnO films. However, too much defects will cause light emission quench. So it is still a controversial issue to control appropriate defect concentrations. In this paper, based on our previous results, appropriate Al doping concentration is chosen to introduce more both interstitial Zn and O vacancy defects, which is responsible for main visible emission of ZnO films. A strong emission band located at 405 nm and a long tail peak is observed in the samples. As Al is doped in ZnO films, the intensity of emission peaks increases. Zn interstitial might increase with the increasing Al3+ substitute because ZnO was a self-assembled oxide compound. So Zn interstitial defect concentration in Al doped ZnO films will increase greatly, which results in the intensity of emission peaks increases.

  9. Top of the World

    NASA Image and Video Library

    2017-08-28

    These turbulent clouds are on top of the world at Saturn. NASA's Cassini spacecraft captured this view of Saturn's north pole on April 26, 2017 - the day it began its Grand Finale -- as it approached the planet for its first daring dive through the gap between the planet and its rings. Although the pole is still bathed in sunlight at present, northern summer solstice on Saturn occurred on May 24, 2017, bringing the maximum solar illumination to the north polar region. Now the Sun begins its slow descent in the northern sky, which eventually will plunge the north pole into Earth-years of darkness. Cassini's long mission at Saturn enabled the spacecraft to see the Sun rise over the north, revealing that region in great detail for the first time. This view looks toward the sunlit side of the rings from about 44 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 166,000 miles (267,000 kilometers) from Saturn. Image scale is about 10 miles (16 kilometers) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21343

  10. A flexible nonvolatile resistive switching memory device based on ZnO film fabricated on a foldable PET substrate.

    PubMed

    Sun, Bai; Zhang, Xuejiao; Zhou, Guangdong; Yu, Tian; Mao, Shuangsuo; Zhu, Shouhui; Zhao, Yong; Xia, Yudong

    2018-06-15

    In this work, a flexible resistive switching memory device based on ZnO film was fabricated using a foldable Polyethylene terephthalate (PET) film as substrate while Ag and Ti acts top and bottom electrode. Our as-prepared device represents an outstanding nonvolatile memory behavior with good "write-read-erase-read" stability at room temperature. Finally, a physical model of Ag conductive filament is constructed to understanding the observed memory characteristics. The work provides a new way for the preparation of flexible memory devices based on ZnO films, and especially provides an experimental basis for the exploration of high-performance and portable nonvolatile resistance random memory (RRAM). Copyright © 2018 Elsevier Inc. All rights reserved.

  11. Non-classical logic inverter coupling a ZnO nanowire-based Schottky barrier transistor and adjacent Schottky diode.

    PubMed

    Hosseini Shokouh, Seyed Hossein; Raza, Syed Raza Ali; Lee, Hee Sung; Im, Seongil

    2014-08-21

    On a single ZnO nanowire (NW), we fabricated an inverter-type device comprising a Schottky diode (SD) and field-effect transistor (FET), aiming at 1-dimensional (1D) electronic circuits with low power consumption. The SD and adjacent FET worked respectively as the load and driver, so that voltage signals could be easily extracted as the output. In addition, NW FET with a transparent conducting oxide as top gate turned out to be very photosensitive, although ZnO NW SD was blind to visible light. Based on this, we could achieve an array of photo-inverter cells on one NW. Our non-classical inverter is regarded as quite practical for both logic and photo-sensing due to its performance as well as simple device configuration.

  12. Room temperature ferromagnetism in Cu doped ZnO

    NASA Astrophysics Data System (ADS)

    Ali, Nasir; Singh, Budhi; Khan, Zaheer Ahmed; Ghosh, Subhasis

    2018-05-01

    We report the room temperature ferromagnetism in 2% Cu doped ZnO films grown by RF magnetron sputtering in different argon and oxygen partial pressure. X-ray photoelectron spectroscopy was used to ascertain the oxidation states of Cu in ZnO. The presence of defects within Cu-doped ZnO films can be revealed by electron paramagnetic resonance. It has been observed that saturated magnetic moment increase as we increase the zinc vacancies during deposition.

  13. Effect of aging on ZnO and nitrogen doped P-Type ZnO

    NASA Astrophysics Data System (ADS)

    Majumdar, Sayanee; Bhunia, S.

    2012-06-01

    The withholding of p-type conductivity in as-prepared and 3% nitrogen (N) doped zinc oxide (ZnO) even after 2 months of preparation was systematically studied. The films were grown on glass substrates by pulsed laser deposition (PLD) at 350 °C under different conditions, viz. under vacuum and at oxygen (O) ambience using 2000 laser pulses. In O ambience for as-prepared ZnO the carrier concentration reduces and mobility increases with increasing number of laser shots. The resistivity of as-prepared and 3% N-doped ZnO is found to increase with reduction in hole concentration after 60 days of aging while maintaining its p-type conductivity irrespective of growth condition. AFM and electrical properties showed aging effect on the doped and undoped samples. For as-prepared ZnO, with time, O migration makes the film high resistive by reducing free electron concentrations. But for N-doped p-type ZnO, O-migration, metastable N and hydrogen atom present in the source induced instability in structure makes it less conducting p-type.

  14. High performance non-volatile ferroelectric copolymer memory based on a ZnO nanowire transistor fabricated on a transparent substrate

    NASA Astrophysics Data System (ADS)

    Nedic, Stanko; Tea Chun, Young; Hong, Woong-Ki; Chu, Daping; Welland, Mark

    2014-01-01

    A high performance ferroelectric non-volatile memory device based on a top-gate ZnO nanowire (NW) transistor fabricated on a glass substrate is demonstrated. The ZnO NW channel was spin-coated with a poly (vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) layer acting as a top-gate dielectric without buffer layer. Electrical conductance modulation and memory hysteresis are achieved by a gate electric field induced reversible electrical polarization switching of the P(VDF-TrFE) thin film. Furthermore, the fabricated device exhibits a memory window of ˜16.5 V, a high drain current on/off ratio of ˜105, a gate leakage current below ˜300 pA, and excellent retention characteristics for over 104 s.

  15. Sodium doping in ZnO crystals

    NASA Astrophysics Data System (ADS)

    Parmar, N. S.; Lynn, K. G.

    2015-01-01

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1-3.5) × 1017 cm-3. Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a NaZn level at ˜(220-270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4-5) orders of magnitude at room temperature.

  16. Improving ultraviolet photodetection of ZnO nanorods by Cr doped ZnO encapsulation process

    NASA Astrophysics Data System (ADS)

    Safa, S.; Mokhtari, S.; Khayatian, A.; Azimirad, R.

    2018-04-01

    Encapsulated ZnO nanorods (NRs) with different Cr concentration (0-4.5 at.%) were prepared in two different steps. First, ZnO NRs were grown by hydrothermal method. Then, they were encapsulated by dip coating method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, and ultraviolet (UV)-visible spectrophotometer analyses. XRD analysis proved that Cr incorporated into the ZnO structure successfully. Based on optical analysis, band gap changes in the range of 2.74-3.84 eV. Finally, UV responses of all samples were deeply investigated. It revealed 0.5 at.% Cr doped sample had the most photocurrent (0.75 mA) and photoresponsivity (0.8 A/W) of all which were about three times greater than photocurrent and photoresponsivity of the undoped sample.

  17. Dermatitis, contact (image)

    MedlinePlus

    This picture shows a skin inflammation (dermatitis) caused by contact with a material that causes an allergic reaction in this person. Contact dermatitis is a relatively common condition, and can be caused ...

  18. Avoiding Cross-Contact

    MedlinePlus

    ... View more examples of cross-contact > Talking to Restaurant Personnel about Cross-Contact It is important to ... meals. Do not be nervous about calling a restaurant you would like to dine at. The chef ...

  19. Contact Us about Asbestos

    EPA Pesticide Factsheets

    How to contact EPA for more information on asbestos, including state and regional contacts, EPA’s Asbestos Abatement/Management Ombudsman and the Toxic Substances Control Act (TSCA) Assistance Information Service (TSCA Hotline).

  20. Spin noise spectroscopy of ZnO

    NASA Astrophysics Data System (ADS)

    Horn, H.; Berski, F.; Balocchi, A.; Marie, X.; Mansur-Al-Suleiman, M.; Bakin, A.; Waag, A.; Hübner, J.; Oestreich, M.

    2013-12-01

    We investigate the thermal equilibrium dynamics of electron spins bound to donors in nanoporous ZnO by optical spin noise spectroscopy. The spin noise spectra reveal two noise contributions: A weak spin noise signal from undisturbed localized donor electrons with a dephasing time of 24 ns due to hyperfine interaction and a strong spin noise signal with a spin dephasing time of 5 ns which we attribute to localized donor electrons which interact with lattice defects.

  1. The Phase Relations in the In 2O 3-Al 2ZnO 4-ZnO System at 1350°C

    NASA Astrophysics Data System (ADS)

    Nakamura, Masaki; Kimizuka, Noboru; Mohri, Takahiko; Isobe, Mitsumasa

    1993-08-01

    Phase relations in the In 2O 3-Al 2ZnO 4-ZnO system at 1350°C are determined by a classical quenching method. This system consists of In 2O 3, Al 2ZnO 4, ZnO, and homologous phases InAlO 3(ZnO) m ( m = 2, 3, …) having solid solutions with LuFeO 3(ZnO) m-type crystal structures. These solid solution ranges are as follows: In 1+ x1Al 1- x1O 3(ZnO) 2 ( x1 = 0.70)-In 1+ x2Al 1- x2O 3(ZnO) 2 ( x2 = 0.316-0.320), In 2O 3(ZnO) 3-In 1+ xAl 1- xO 3(ZnO) 3 ( x = 0.230), In 2O 3(ZnO) 4-In 1+ xAl 1- xO 3(ZnO) 4 ( x = 0.15-0.16), In 2O 3(ZnO) 5-In 1+ xAl 1- xO 3(ZnO) 5 ( x = 0.116-0.130), In 2O 3(ZnO) 6-In 1+ xAl 1- xO 3(ZnO) 6 ( x = 0.000-0.111), In 2O 3(ZnO) 7-In 1+ xAl 1- xO 3(ZnO) 7 ( x = 0.08), In 2O 3(ZnO) 8-In 1+ xAl 1- xO 3(ZnO) 8 ( x: undetermined), and In 2O 3(ZnO) m-InAlO 3(ZnO) m ( m = 9, 10, 11, 13, 15, 17, and 19). The space groups of these homologous phases belong to R3¯ m for m = odd or P6 3/ mmc for m = even. Their crystal structures, In 1+ xAl 1- xO 3(ZnO) m (0 < x < 1), consist of three kinds of layers: an InO 1.5 layer, an (In xAl 1- xZn)O 2.5 layer, and ZnO layers. A comparison of the phase relations in the In 2O 3- M2ZnO 4-ZnO systems ( M = Fe, Ga, or Al) is made and their characteristic features are discussed in terms of the ionic radii and site preferences of the M cations.

  2. Hydrogenation of passivated contacts

    DOEpatents

    Nemeth, William; Yuan, Hao-Chih; LaSalvia, Vincenzo; Stradins, Pauls; Page, Matthew R.

    2018-03-06

    Methods of hydrogenation of passivated contacts using materials having hydrogen impurities are provided. An example method includes applying, to a passivated contact, a layer of a material, the material containing hydrogen impurities. The method further includes subsequently annealing the material and subsequently removing the material from the passivated contact.

  3. Contact solution algorithms

    NASA Technical Reports Server (NTRS)

    Tielking, John T.

    1989-01-01

    Two algorithms for obtaining static contact solutions are described in this presentation. Although they were derived for contact problems involving specific structures (a tire and a solid rubber cylinder), they are sufficiently general to be applied to other shell-of-revolution and solid-body contact problems. The shell-of-revolution contact algorithm is a method of obtaining a point load influence coefficient matrix for the portion of shell surface that is expected to carry a contact load. If the shell is sufficiently linear with respect to contact loading, a single influence coefficient matrix can be used to obtain a good approximation of the contact pressure distribution. Otherwise, the matrix will be updated to reflect nonlinear load-deflection behavior. The solid-body contact algorithm utilizes a Lagrange multiplier to include the contact constraint in a potential energy functional. The solution is found by applying the principle of minimum potential energy. The Lagrange multiplier is identified as the contact load resultant for a specific deflection. At present, only frictionless contact solutions have been obtained with these algorithms. A sliding tread element has been developed to calculate friction shear force in the contact region of the rolling shell-of-revolution tire model.

  4. Naturalness from a composite top?

    DOE PAGES

    Pierce, Aaron; Zhao, Yue

    2017-01-12

    Here, we consider a theory with composite top quarks but an elementary Higgs boson. The hierarchy problem can be solved by supplementing TeV scale top compositeness with either supersymmetry or Higgs compositeness appearing at the multi-TeV scale. Furthermore, the Higgs boson couples to uncolored partons within the top quark. We also study how this approach can give rise to a novel screening effect that suppresses production of the colored top partners at the LHC. Strong constraints arise from Z tomore » $$\\bar{b}$$b, as well potentially from avor physics. Independent of flavor considerations, current constraints imply a compositeness scale &TeV; this implies that the model is likely tuned at the percent level. Four top quark production at the LHC is a smoking-gun probe of this scenario. New CP violation in D meson mixing is also possible.« less

  5. Top mass from asymptotic safety

    NASA Astrophysics Data System (ADS)

    Eichhorn, Astrid; Held, Aaron

    2018-02-01

    We discover that asymptotically safe quantum gravity could predict the top-quark mass. For a broad range of microscopic gravitational couplings, quantum gravity could provide an ultraviolet completion for the Standard Model by triggering asymptotic freedom in the gauge couplings and bottom Yukawa and asymptotic safety in the top-Yukawa and Higgs-quartic coupling. We find that in a part of this range, a difference of the top and bottom mass of approximately 170GeV is generated and the Higgs mass is determined in terms of the top mass. Assuming no new physics below the Planck scale, we construct explicit Renormalization Group trajectories for Standard Model and gravitational couplings which link the transplanckian regime to the electroweak scale and yield a top pole mass of Mt,pole ≈ 171GeV.

  6. Robust superhydrophobic needle-like nanostructured ZnO surfaces prepared without post chemical-treatment

    NASA Astrophysics Data System (ADS)

    Velayi, Elmira; Norouzbeigi, Reza

    2017-12-01

    Robust superhydrophobic ZnO surfaces with micro/nano hybrid hierarchical structures were synthesized on the stainless steel mesh by a facile single-step chemical bath deposition (CBD) method without using further low surface energy materials. The Taguchi L16 experimental design was applied to evaluate the effects of reaction time, type and concentration of the additive, type of the chelating agent, and the molar ratio of the chelating agent to the initial zinc (II) ions. The prepared sample at the optimal conditions exhibited a sustainable and time-independent superhydrophobic behavior with the water contact angle (WCA) of 162.8° ± 2.5° and contact angle hysteresis (CAH) of 1.8° ± 0.5°. The XRD, SEM, TEM and FTIR analyses were used to characterize the prepared samples. Surface characterization using scanning electron microscopy (SEM) indicated accumulation of micro/nano branched ZnO needles on the substrate with the average diameters of ∼85 nm. After 20 abrasion cycles the optimum sample indicated an excellent mechanical robustness via exposure to the pressure of 4.7 kPa. A suitable chemical resistance to the acidic and basic droplets with the pH range of 4 and 9 was observed.

  7. Wave Engine Topping Cycle Assessment

    NASA Technical Reports Server (NTRS)

    Welch, Gerard E.

    1996-01-01

    The performance benefits derived by topping a gas turbine engine with a wave engine are assessed. The wave engine is a wave rotor that produces shaft power by exploiting gas dynamic energy exchange and flow turning. The wave engine is added to the baseline turboshaft engine while keeping high-pressure-turbine inlet conditions, compressor pressure ratio, engine mass flow rate, and cooling flow fractions fixed. Related work has focused on topping with pressure-exchangers (i.e., wave rotors that provide pressure gain with zero net shaft power output); however, more energy can be added to a wave-engine-topped cycle leading to greater engine specific-power-enhancement The energy addition occurs at a lower pressure in the wave-engine-topped cycle; thus the specific-fuel-consumption-enhancement effected by ideal wave engine topping is slightly lower than that effected by ideal pressure-exchanger topping. At a component level, however, flow turning affords the wave engine a degree-of-freedom relative to the pressure-exchanger that enables a more efficient match with the baseline engine. In some cases, therefore, the SFC-enhancement by wave engine topping is greater than that by pressure-exchanger topping. An ideal wave-rotor-characteristic is used to identify key wave engine design parameters and to contrast the wave engine and pressure-exchanger topping approaches. An aerodynamic design procedure is described in which wave engine design-point performance levels are computed using a one-dimensional wave rotor model. Wave engines using various wave cycles are considered including two-port cycles with on-rotor combustion (valved-combustors) and reverse-flow and through-flow four-port cycles with heat addition in conventional burners. A through-flow wave cycle design with symmetric blading is used to assess engine performance benefits. The wave-engine-topped turboshaft engine produces 16% more power than does a pressure-exchanger-topped engine under the specified topping

  8. ZnO nanorods/graphene/Ni/Au hybrid structures as transparent conductive layer in GaN LED for low work voltage and high light extraction

    NASA Astrophysics Data System (ADS)

    Xu, Kun; Xie, Yiyang; Ma, Huali; Du, Yinxiao; Zeng, Fanguang; Ding, Pei; Gao, Zhiyuan; Xu, Chen; Sun, Jie

    2016-12-01

    In this paper, by virtue of one-dimensional ZnO nanorods and two-dimensional graphene film hybrid structures, both the enhanced current spreading and enhanced light extraction were realized at the same time. A 1 nm/1 nm Ni/Au layer was used as an interlayer between graphene and pGaN to form ohmic contact, which makes the device have a good forward conduction properties. Through the comparison of the two groups of making ZnO nanorods or not, it was found that the 30% light extraction efficiency of the device was improved by using the ZnO nanorods. By analysis key parameters of two groups such as the turn-on voltage, work voltage and reverse leakage current, it was proved that the method for preparing surface nano structure by hydrothermal method self-organization growth ZnO nanorods applied in GaN LEDs has no influence to device's electrical properties. The hybrid structure application in GaN LED, make an achievement of a good ohmic contact, no use of ITO and enhancement of light extraction at the same time, meanwhile it does not change the device structure, introduce additional process, worsen the electrical properties.

  9. Retraction policies of top scientific journals ranked by impact factor.

    PubMed

    Resnik, David B; Wager, Elizabeth; Kissling, Grace E

    2015-07-01

    This study gathered information about the retraction policies of the top 200 scientific journals, ranked by impact factor. Editors of the top 200 science journals for the year 2012 were contacted by email. One hundred forty-seven journals (74%) responded to a request for information. Of these, 95 (65%) had a retraction policy. Of journals with a retraction policy, 94% had a policy that allows the editors to retract articles without authors' consent. The majority of journals in this sample had a retraction policy, and almost all of them would retract an article without the authors' permission.

  10. Three-dimensional finite analysis of acetabular contact pressure and contact area during normal walking.

    PubMed

    Wang, Guangye; Huang, Wenjun; Song, Qi; Liang, Jinfeng

    2017-11-01

    This study aims to analyze the contact areas and pressure distributions between the femoral head and mortar during normal walking using a three-dimensional finite element model (3D-FEM). Computed tomography (CT) scanning technology and a computer image processing system were used to establish the 3D-FEM. The acetabular mortar model was used to simulate the pressures during 32 consecutive normal walking phases and the contact areas at different phases were calculated. The distribution of the pressure peak values during the 32 consecutive normal walking phases was bimodal, which reached the peak (4.2 Mpa) at the initial phase where the contact area was significantly higher than that at the stepping phase. The sites that always kept contact were concentrated on the acetabular top and leaned inwards, while the anterior and posterior acetabular horns had no pressure concentration. The pressure distributions of acetabular cartilage at different phases were significantly different, the zone of increased pressure at the support phase distributed at the acetabular top area, while that at the stepping phase distributed in the inside of acetabular cartilage. The zones of increased contact pressure and the distributions of acetabular contact areas had important significance towards clinical researches, and could indicate the inductive factors of acetabular osteoarthritis. Copyright © 2016. Published by Elsevier Taiwan.

  11. Modeling Thermal Contact Resistance

    NASA Technical Reports Server (NTRS)

    Kittel, Peter; Sperans, Joel (Technical Monitor)

    1994-01-01

    One difficulty in using cryocoolers is making good thermal contact between the cooler and the instrument being cooled. The connection is often made through a bolted joint. The temperature drop associated with this joint has been the subject of many experimental and theoretical studies. The low temperature behavior of dry joints have shown some anomalous dependence on the surface condition of the mating parts. There is also some doubts on how well one can extrapolate from the test samples to predicting the performance of a real system. Both finite element and analytic models of a simple contact system have been developed. The model assumes (a) the contact is dry (contact limited to a small portion of the total available area and the spaces in-between the actual contact patches are perfect insulators), (b) contacts are clean (conductivity of the actual contact is the same as the bulk), (c) small temperature gradients (the bulk conductance may be assumed to be temperature independent), (d) the absolute temperature is low (thermal radiation effects are ignored), and (e) the dimensions of the nominal contact area are small compared to the thickness of the bulk material (the contact effects are localized near the contact). The models show that in the limit of actual contact area much less than the nominal area (a much less than A), that the excess temperature drop due to a single point of contact scales as a(exp -1/2). This disturbance only extends a distance approx. A(exp 1/2) into the bulk material. A group of identical contacts will result in an excess temperature drop that scales as n(exp -1/2), where n is the number of contacts and n dot a is constant. This implies that flat rough surfaces will have a lower excess temperature drop than flat polished surfaces.

  12. Contact reactions to fragrances.

    PubMed

    Katsarou, A; Armenaka, M; Kalogeromitros, D; Koufou, V; Georgala, S

    1999-05-01

    The most common reaction to fragrances is contact dermatitis, a delayed hypersensitivity reaction; however, other reactions include immediate contact reactions (contact urticaria) and photo-allergic reactions. Fragrance mix (FM) and balsam of Peru (BP) are used to screen for fragrance allergy. To study the different types of allergic skin reactions to fragrance compounds. Delayed hypersensitivity reactions to FM and BP were studied in 4,975 patients with suspected contact dermatitis by routine patch testing interpreted at 48 and 96 hours. In 664 of the patients, patch tests were read at 30 minutes to evaluate for immediate (wheal-and-flare) contact reactions and again at 48 and 96 hours. Photopatch tests to FM were performed in 111 patients with suspected photo-allergic dermatitis. Delayed contact reactions to FM occurred in 6.6% of females and 5.4% of males and to BP in 3.9% of females and 4.1% of males. Analysis of data over time (12 study years) showed an increased trend for reactions to fragrances, particularly in males. Sensitivity to other contact allergens (polysensitivity) was found in 62% of patients and polysensitivity presented more often with generalized contact dermatitis. The most sensitizing components of the fragrance mix that were tested in 38 patients were cinnamic alcohol, oak moss, and cinnamic aldehyde. There were 112 immediate patch test reactions to FM and 113 to BP in 664 patients. Immediate contact reactions were followed by delayed contact reactions in 13.4% of patients for FM and 8.8% for BP, representing a significant increase in the frequency of delayed contact reactions. Patients with immediate contact reactions to fragrances did not have a higher incidence of atopy (25.9%). No cases of positive photopatch test reactions to FM were seen. Fragrances commonly cause both delayed and immediate patch test reactions and patients with immediate contact reactions have an increase in delayed contact reactions to the same allergen.

  13. Fast synthesize ZnO quantum dots via ultrasonic method.

    PubMed

    Yang, Weimin; Zhang, Bing; Ding, Nan; Ding, Wenhao; Wang, Lixi; Yu, Mingxun; Zhang, Qitu

    2016-05-01

    Green emission ZnO quantum dots were synthesized by an ultrasonic sol-gel method. The ZnO quantum dots were synthesized in various ultrasonic temperature and time. Photoluminescence properties of these ZnO quantum dots were measured. Time-resolved photoluminescence decay spectra were also taken to discover the change of defects amount during the reaction. Both ultrasonic temperature and time could affect the type and amount of defects in ZnO quantum dots. Total defects of ZnO quantum dots decreased with the increasing of ultrasonic temperature and time. The dangling bonds defects disappeared faster than the optical defects. Types of optical defects first changed from oxygen interstitial defects to oxygen vacancy and zinc interstitial defects. Then transformed back to oxygen interstitial defects again. The sizes of ZnO quantum dots would be controlled by both ultrasonic temperature and time as well. That is, with the increasing of ultrasonic temperature and time, the sizes of ZnO quantum dots first decreased then increased. Moreover, concentrated raw materials solution brought larger sizes and more optical defects of ZnO quantum dots. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Optical properties of P ion implanted ZnO

    NASA Astrophysics Data System (ADS)

    Pong, Bao-Jen; Chou, Bo-Wei; Pan, Ching-Jen; Tsao, Fu-Chun; Chi, Gou-Chung

    2006-02-01

    Red and green emissions are observed from P ion implanted ZnO. Red emission at ~680 nm (1.82 eV) is associated with the donor-acceptor pair (DAP) transition, where the corresponding donor and acceptor are interstitial zinc (Zn i) and interstitial oxygen (O i), respectively. Green emission at ~ 516 nm (2.40 eV) is associated with the transition between the conduction band and antisite oxygen (O Zn). Green emission at ~516nm (2.403 eV) was observed for ZnO annealed at 800 oC under ambient oxygen, whereas, it was not visible when it was annealed in ambient nitrogen. Hence, the green emission is most likely not related to oxygen vacancies on ZnO sample, which might be related to the cleanliness of ZnO surface, a detailed study is in progress. The observed micro-strain is larger for N ion implanted ZnO than that for P ion implanted ZnO. It is attributed to the larger straggle of N ion implanted ZnO than that of P ion implanted ZnO. Similar phenomenon is also observed in Be and Mg ion implanted GaN.

  15. Photoluminescent ZnO Nanoparticles and Their Biological Applications

    PubMed Central

    Zhang, Zheng-Yong; Xiong, Huan-Ming

    2015-01-01

    During the past decades, numerous achievements concerning luminescent zinc oxide nanoparticles (ZnO NPs) have been reported due to their improved luminescence and good biocompatibility. The photoluminescence of ZnO NPs usually contains two parts, the exciton-related ultraviolet (UV) emission and the defect-related visible emission. With respect to the visible emission, many routes have been developed to synthesize and functionalize ZnO NPs for the applications in detecting metal ions and biomolecules, biological fluorescence imaging, nonlinear multiphoton imaging, and fluorescence lifetime imaging. As the biological applications of ZnO NPs develop rapidly, the toxicity of ZnO NPs has attracted more and more attention because ZnO can produce the reactive oxygen species (ROS) and release Zn2+ ions. Just as a coin has two sides, both the drug delivery and the antibacterial effects of ZnO NPs become attractive at the same time. Hence, in this review, we will focus on the progress in the synthetic methods, luminescent properties, and biological applications of ZnO NPs.

  16. Influence of Dopants in ZnO Films on Defects

    NASA Astrophysics Data System (ADS)

    Peng, Cheng-Xiao; Weng, Hui-Min; Zhang, Yang; Ma, Xing-Ping; Ye, Bang-Jiao

    2008-12-01

    The influence of dopants in ZnO films on defects is investigated by slow positron annihilation technique. The results show S that parameters meet SAl > Sun > SAg for Al-doped ZnO films, undoped and Ag-doped ZnO films. Zinc vacancies are found in all ZnO films with different dopants. According to S parameter and the same defect type, it can be induced that the zinc vacancy concentration is the highest in the Al-doped ZnO film, and it is the least in the Ag-doped ZnO film. When Al atoms are doped in the ZnO films grown on silicon substrates, Zn vacancies increase as compared to the undoped and Ag-doped ZnO films. The dopant concentration could determine the position of Fermi level in materials, while defect formation energy of zinc vacancy strongly depends on the position of Fermi level, so its concentration varies with dopant element and dopant concentration.

  17. Variable range hopping in ZnO films

    NASA Astrophysics Data System (ADS)

    Ali, Nasir; Ghosh, Subhasis

    2018-04-01

    We report the variable range hopping in ZnO films grown by RF magnetron sputtering in different argon and oxygen partial pressure. It has been found that Mott variable range hopping dominant over Efros variable range hopping in all ZnO films. It also has been found that hopping distance and energy increases with increasing oxygen partial pressure.

  18. Epitaxial ZnO/LiNbO{sub 3}/ZnO stacked layer waveguide for application to thin-film Pockels sensors

    SciTech Connect

    Akazawa, Housei, E-mail: akazawa.housei@lab.ntt.co.jp; Fukuda, Hiroshi

    We produced slab waveguides consisting of a LiNbO{sub 3} (LN) core layer that was sandwiched with Al-doped ZnO cladding layers. The ZnO/LN/ZnO stacked layers were grown on sapphire C-planes by electron cyclotron resonance (ECR) plasma sputtering and were subjected to structural, electrical, and optical characterizations. X-ray diffraction confirmed that the ZnO and LN layers were epitaxial without containing misoriented crystallites. The presence of 60°-rotational variants of ZnO and LN crystalline domains were identified from X-ray pole figures. Cross-sectional transmission electron microscopy images revealed a c-axis orientated columnar texture for LN crystals, which ensured operation as electro-optic sensors based on opticalmore » anisotropy along longitudinal and transversal directions. The interfacial roughness between the LN core and ZnO bottom layers as well as that between the ZnO top and the LN core layers was less than 20 nm, which agreed with surface images observed with atomic force microscopy. Outgrowth of triangular LN crystalline domains produced large roughness at the LN film surface. The RMS roughness of the LN film surface was twice that of the same structure grown on sapphire A-planes. Vertical optical transmittance of the stacked films was higher than 85% within the visible and infrared wavelength range. Following the approach adopted by Teng and Man [Appl. Phys. Lett. 56, 1734 (1990)], ac Pockels coefficients of r{sub 33} = 24-28 pm/V were derived for c-axis oriented LN films grown on low-resistive Si substrates. Light propagation within a ZnO/LN/ZnO slab waveguide as well as within a ZnO single layer waveguide was confirmed. The birefringence of these waveguides was 0.11 for the former and 0.05 for the latter.« less

  19. Toward blue emission in ZnO based LED

    NASA Astrophysics Data System (ADS)

    Viana, Bruno; Pauporté, Thierry; Lupan, Oleg; Le Bahers, Tangui; Ciofini, Ilaria

    2012-03-01

    The bandgap engineering of ZnO nanowires by doping is of great importance for tunable light emitting diode (LED) applications. We present a combined experimental and computational study of ZnO doping with Cd or Cu atoms in the nanomaterial. Zn1-xTMxO (TM=Cu, Cd) nanowires have been epitaxially grown on magnesium-doped p-GaN by electrochemical deposition. The Zn1-xTMxO/p-GaN heterojunction was integrated in a LED structure. Nanowires act as the light emitters and waveguides. At room temperature, TM-doped ZnO based LEDs exhibit low-threshold emission voltage and electroluminescence emission shifted from ultraviolet to violet-blue spectral region compared to pure ZnO LEDs. The emission wavelength can be tuned by changing the transition metal (TM) content in the ZnO nanomaterial and the shift is discussed, including insights from DFT computational investigations.

  20. Contrasting emission behaviour of phenanthroimidazole with ZnO nanoparticles.

    PubMed

    Karunakaran, C; Jayabharathi, J; Sathishkumar, R; Jayamoorthy, K; Vimal, K

    2013-11-01

    A new fluorophore 2-(4-fluorophenyl)-1-phenyl-1H-phenanthro [9,10-d]imidazole has been synthesized and characterized by spectroscopic techniques. Nanoparticulate ZnO enhances the fluorescence of the synthesised fluorophore. The absorption, fluorescence, lifetime, cyclic voltammetry and infrared studies reveal that fluorophore is attached to the surface of ZnO semiconductor. Photo-induced electron transfer (PET) explains the enhancement of fluorescence by nanoparticulate ZnO and the apparent binding constant has been obtained. Adsorption of the fluorophore on ZnO nanoparticle lowers the HOMO and LUMO energy levels of the fluorophore. The strong adsorption of the phenanthrimidazole derivative on the surface of ZnO nanocrystals is likely due to the chemical affinity of the nitrogen atom of the organic molecule to the zinc ion on the surface of nanocrystal. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Fabrication and Performance Study on Individual Zno Nanowires Based Bioelectrode

    NASA Astrophysics Data System (ADS)

    Zhao, Yanguang; Yan, Xiaoqin; Kang, Zhuo; Lin, Pei

    2012-08-01

    One-dimensional zinc oxide nanowires (ZnO NWs) have unique advantages for use in biosensors as follows: oxide stable surface, excellent biosafety, high specific surface area, high isoelectric point (IEP = 9.5). In this work, we have prepared a kind of electrochemical bioelectrode based on individual ZnO NWs. Here, ZnO NWs with high quality were successfully synthesized by CVD method, which were characterized by scanning electron microscopy, X-ray diffraction and photoluminescence. Then the Raman spectra and electrical characterization demonstrated the adsorption of uricase on ZnO wires. At last, a series of electrochemical measurements were carried out by using an electrochemical workstation with a conventional three-electrode system to obtain the cyclic voltammetry characteristics of the bioelectrodes. The excellent performance of the fabricated bioelectrode implies the potential application for single ZnO nanowire to construct electrochemical biosensor for the detection of uric acid.

  2. [Smart drug delivery systems based on nanoscale ZnO].

    PubMed

    Huang, Xiao; Chen, Chun; Yi, Caixia; Zheng, Xi

    2018-04-01

    In view of the excellent biocompatibility as well as the low cost, nanoscale ZnO shows great potential for drug delivery application. Moreover, The charming character enable nanoscale ZnO some excellent features (e.g. dissolution in acid, ultrasonic permeability, microwave absorbing, hydrophobic/hydrophilic transition). All of that make nanoscale ZnO reasonable choices for smart drug delivery. In the recent decade, more and more studies have focused on controlling the drug release behavior via smart drug delivery systems based on nanoscale ZnO responsive to some certain stimuli. Herein, we review the recent exciting progress on the pH-responsive, ultrasound-responsive, microwave-responsive and UV-responsive nanoscale ZnO-based drug delivery systems. A brief introduction of the drug controlled release behavior and its effect of the drug delivery systems is presented. The biocompatibility of nanoscale ZnO is also discussed. Moreover, its development prospect is looked forward.

  3. Influence of Atomic Hydrogen, Band Bending, and Defects in the Top Few Nanometers of Hydrothermally Prepared Zinc Oxide Nanorods

    NASA Astrophysics Data System (ADS)

    Al-Saadi, Mubarak J.; Al-Harthi, Salim H.; Kyaw, Htet H.; Myint, Myo T. Z.; Bora, Tanujjal; Laxman, Karthik; Al-Hinai, Ashraf; Dutta, Joydeep

    2017-01-01

    We report on the surface, sub-surface (top few nanometers) and bulk properties of hydrothermally grown zinc oxide (ZnO) nanorods (NRs) prior to and after hydrogen treatment. Upon treating with atomic hydrogen (H*), upward and downward band bending is observed depending on the availability of molecular H2O within the structure of the NRs. In the absence of H2O, the H* treatment demonstrated a cleaning effect of the nanorods, leading to a 0.51 eV upward band bending. In addition, enhancement in the intensity of room temperature photoluminescence (PL) signals due to the creation of new surface defects could be observed. The defects enhanced the visible light activity of the ZnO NRs which were subsequently used to photocatalytically degrade aqueous phenol under simulated sunlight. On the contrary, in the presence of H2O, H* treatment created an electronic accumulation layer inducing downward band bending of 0.45 eV ( 1/7th of the bulk ZnO band gap) along with the weakening of the defect signals as observed from room temperature photoluminescence spectra. The results suggest a plausible way of tailoring the band bending and defects of the ZnO NRs through control of H2O/H* species.

  4. Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles.

    PubMed

    Ibupoto, Zafar Hussain; Khun, Kimleang; Eriksson, Martin; AlSalhi, Mohammad; Atif, Muhammad; Ansari, Anees; Willander, Magnus

    2013-08-19

    Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c -axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002) peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL) spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

  5. Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles

    PubMed Central

    Ibupoto, Zafar Hussain; Khun, Kimleang; Eriksson, Martin; AlSalhi, Mohammad; Atif, Muhammad; Ansari, Anees; Willander, Magnus

    2013-01-01

    Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002) peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL) spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role. PMID:28811454

  6. Forum outlines top emerging technologies

    NASA Astrophysics Data System (ADS)

    Extance, Andy

    2015-04-01

    Additive manufacturing, next-generation robotics, "sense and avoid" drones that fly themselves, artificial intelligence and "neuromorphic" computing have all made it into the World Economic Forum's top 10 emerging technologies for 2015.

  7. Trajectory correction propulsion for TOPS

    NASA Technical Reports Server (NTRS)

    Long, H. R.; Bjorklund, R. A.

    1972-01-01

    A blowdown-pressurized hydrazine propulsion system was selected to provide trajectory correction impulse for outer planet flyby spacecraft as the result of cost/mass/reliability tradeoff analyses. Present hydrazine component and system technology and component designs were evaluated for application to the Thermoelectric Outer Planet Spacecraft (TOPS); while general hydrazine technology was adequate, component design changes were deemed necessary for TOPS-type missions. A prototype hydrazine propulsion system was fabricated and fired nine times for a total of 1600 s to demonstrate the operation and performance of the TOPS propulsion configuration. A flight-weight trajectory correction propulsion subsystem (TCPS) was designed for the TOPS based on actual and estimated advanced components.

  8. Calculate the Top Quark Mass

    Science.gov Websites

    Searching for Top How do today's scientists use conservation of momentum? Particle physicists mass into energy and then energy into mass! You can use the principle of conservation of momentum which

  9. Australia's Next Top Fraction Model

    ERIC Educational Resources Information Center

    Gould, Peter

    2013-01-01

    Peter Gould suggests Australia's next top fraction model should be a linear model rather than an area model. He provides a convincing argument and gives examples of ways to introduce a linear model in primary classrooms.

  10. Properties of the Top Quark

    DOE PAGES

    Déliot, Frédéric; Hadley, Nicholas; Parke, Stephen; ...

    2014-10-19

    We report that the top quark is the heaviest known elementary particle, and it is often seen as a window to search for new physics processes in particle physics. A large program to study the top-quark properties has been performed both at the Tevatron and LHC colliders by the D0, CDF, ATLAS and CMS experiments. The most recent results are discussed here in this article.

  11. Top 10 Products of 2011

    ERIC Educational Resources Information Center

    American School & University, 2011

    2011-01-01

    In 2011, American School & University (AS&U) showcased some of the hottest products in the industry. This article presents the top ten most requested products as determined by readers. The top one on the list is the Bulb crusher which can cut recycling costs by 50%, can hold 1,350 4-foot lamps in a single 55-gallon drum, can crush a 4-foot lamp in…

  12. Control of GaAs Microwave Schottky Diode Electrical Characteristics by Contact Geometry: The Gap Diode.

    DTIC Science & Technology

    1982-05-01

    semiconductor Schottky-barrier contacts are used in many semiconductor devices, including switches, rectifiers, varactors , IMPATTs, mixer and detector...ionic materials such as most of the II-VI compound semiconductors (e.g. ZnS and ZnO) and the transition-metal oxides , the barrier height is strongly...the alloying process described above is nonuniformity, due to the incomplete removal of residual surface oxides prior to the evaporation of the metal

  13. FreeContact: fast and free software for protein contact prediction from residue co-evolution.

    PubMed

    Kaján, László; Hopf, Thomas A; Kalaš, Matúš; Marks, Debora S; Rost, Burkhard

    2014-03-26

    20 years of improved technology and growing sequences now renders residue-residue contact constraints in large protein families through correlated mutations accurate enough to drive de novo predictions of protein three-dimensional structure. The method EVfold broke new ground using mean-field Direct Coupling Analysis (EVfold-mfDCA); the method PSICOV applied a related concept by estimating a sparse inverse covariance matrix. Both methods (EVfold-mfDCA and PSICOV) are publicly available, but both require too much CPU time for interactive applications. On top, EVfold-mfDCA depends on proprietary software. Here, we present FreeContact, a fast, open source implementation of EVfold-mfDCA and PSICOV. On a test set of 140 proteins, FreeContact was almost eight times faster than PSICOV without decreasing prediction performance. The EVfold-mfDCA implementation of FreeContact was over 220 times faster than PSICOV with negligible performance decrease. EVfold-mfDCA was unavailable for testing due to its dependency on proprietary software. FreeContact is implemented as the free C++ library "libfreecontact", complete with command line tool "freecontact", as well as Perl and Python modules. All components are available as Debian packages. FreeContact supports the BioXSD format for interoperability. FreeContact provides the opportunity to compute reliable contact predictions in any environment (desktop or cloud).

  14. Uncovering the single top: observation of electroweak top quark production

    SciTech Connect

    Benitez, Jorge Armando

    2009-01-01

    The top quark is generally produced in quark and anti-quark pairs. However, the Standard Model also predicts the production of only one top quark which is mediated by the electroweak interaction, known as 'Single Top'. Single Top quark production is important because it provides a unique and direct way to measure the CKM matrix element V tb, and can be used to explore physics possibilities beyond the Standard Model predictions. This dissertation presents the results of the observation of Single Top using 2.3 fb -1 of Data collected with the D0 detector at the Fermilab Tevatron collider. The analysis includes the Single Top muon+jets and electron+jets final states and employs Boosted Decision Tress as a method to separate the signal from the background. The resulting Single Top cross section measurement is: (1) σ(pmore » $$\\bar{p}$$→ tb + X, tqb + X) = 3.74 -0.74 +0.95 pb, where the errors include both statistical and systematic uncertainties. The probability to measure a cross section at this value or higher in the absence of signal is p = 1.9 x 10 -6. This corresponds to a standard deviation Gaussian equivalence of 4.6. When combining this result with two other analysis methods, the resulting cross section measurement is: (2) σ(p$$\\bar{p}$$ → tb + X, tqb + X) = 3.94 ± 0.88 pb, and the corresponding measurement significance is 5.0 standard deviations.« less

  15. Contacts to Semiconductor Nanowires

    DTIC Science & Technology

    2009-10-03

    SiNW diameters and the amount of metal deposited, or alternatively, the atomic ratio between Pt and Si. The uniformity of the silicided NWs was...program. The Schottky contact is a metal silicide formed by rapid thermal annealing of the deposited contact metal . The θ- Ni2Si/n-Si NW Schottky...decision. unless so designated by other documentation. 14. ABSTRACT Metal contacts to semiconductor nanowires share similarities with their thin-film

  16. Contact-metal dependent current injection in pentacene thin-film transistors

    NASA Astrophysics Data System (ADS)

    Wang, S. D.; Minari, T.; Miyadera, T.; Tsukagoshi, K.; Aoyagi, Y.

    2007-11-01

    Contact-metal dependent current injection in top-contact pentacene thin-film transistors is analyzed, and the local mobility in the contact region was found to follow the Meyer-Neldel rule. An exponential trap distribution, rather than the metal/organic hole injection barrier, is proposed to be the dominant factor of the contact resistance in pentacene thin-film transistors. The variable temperature measurements revealed a much narrower trap distribution in the copper contact compared with the corresponding gold contact, and this is the origin of the smaller contact resistance for copper despite a lower work function.

  17. Contact lens complications.

    PubMed

    Suchecki, Jeanine K; Donshik, Peter; Ehlers, William H

    2003-09-01

    Complications associated with contact lenses range from mild to severe and occur with all lens modalities. Contact lens wear can cause a change in corneal physiology, which can lead to epithelial, stromal, and endothelial compromise. Other complications include lens deposition, allergic conjunctivitis, giant papillary conjunctivitis, peripheral infiltrates, microbial keratitis, and neovascularization. Pre-existing conditions can contribute to these complications, or they can occur in association with contact lens wear and care regimens. Patient-related factors, such as alteration of the recommended wearing or replacement schedules and noncompliance with recommended contact lens care regimens for economic reasons, convenience, or in error, contribute to contact lens-related complications and have led to difficulty in accurate determination of complication rates among the various lens wear modalities. Complications may require discontinuation of contact lenses, topical therapy, and changes in contact lens wearing schedules, materials, and care solutions. On initial lens fitting and follow-up evaluations, practitioners should review contact lens replacement and cleaning regimens with patients and discuss complications. To avoid serious complications, patients should be reminded to remove their contact lenses as soon as ocular irritation occurs, and to call their eye care practitioner immediately if symptoms persist.

  18. Colors and contact dermatitis.

    PubMed

    Bonamonte, Domenico; Foti, Caterina; Romita, Paolo; Vestita, Michelangelo; Angelini, Gianni

    2014-01-01

    The diagnosis of skin diseases relies on several clinical signs, among which color is of paramount importance. In this review, we consider certain clinical presentations of both eczematous and noneczematous contact dermatitis in which color plays a peculiar role orientating toward the right diagnosis. The conditions that will be discussed include specific clinical-morphologic subtypes of eczematous contact dermatitis, primary melanocytic, and nonmelanocytic contact hyperchromia, black dermographism, contact chemical leukoderma, and others. Based on the physical, chemical, and biologic factors underlying a healthy skin color, the various skin shades drawing a disease picture are thoroughly debated, stressing their etiopathogenic origins and histopathologic aspects.

  19. Optical contact micrometer

    DOEpatents

    Jacobson, Steven D.

    2014-08-19

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

  20. Harvesting Mechanical and Thermal Energy by Combining ZnO Nanowires and NiTi Shape Memory Alloy

    DOE PAGES

    Radousky, Harry; Qian, Fang; An, Yonghao; ...

    2017-02-19

    In the expanding world of small scale energy harvesting, the ability to combine thermal and mechanical harvesting is growing ever more important. Here, we demonstrate the feasibility of using ZnO nanowires to harvest both mechanical and low-quality thermal energy in simple, scalable devices. These devices were fabricated on kapton films and used ZnO nanowires with the same growth direction to assure alignment of the piezoelectric potentials of all of the wires. Mechanical harvesting from these devices was demonstrated using a periodic application of force, modeling the motion of the human body. Tapping the device from the top of the devicemore » with a wood stick, for example yielded an Open Circuit Voltage (OCV) of 0.2 - 4 V, which is in an ideal range for device applications. In order to demonstrate thermal harvesting from low quality heat sources, a commercially available Nitinol (Ni-Ti alloy) foil was attached to the nanowire piezoelectric device to create a compound thermoelectric. When bent at room temperature and then heated to 50°C, the Nitinol foil was restored to its original flat shape, which yielded an output voltage of nearly 1 V from the ZnO nanowire device.« less

  1. Harvesting Mechanical and Thermal Energy by Combining ZnO Nanowires and NiTi Shape Memory Alloy

    SciTech Connect

    Radousky, Harry; Qian, Fang; An, Yonghao

    In the expanding world of small scale energy harvesting, the ability to combine thermal and mechanical harvesting is growing ever more important. Here, we demonstrate the feasibility of using ZnO nanowires to harvest both mechanical and low-quality thermal energy in simple, scalable devices. These devices were fabricated on kapton films and used ZnO nanowires with the same growth direction to assure alignment of the piezoelectric potentials of all of the wires. Mechanical harvesting from these devices was demonstrated using a periodic application of force, modeling the motion of the human body. Tapping the device from the top of the devicemore » with a wood stick, for example yielded an Open Circuit Voltage (OCV) of 0.2 - 4 V, which is in an ideal range for device applications. In order to demonstrate thermal harvesting from low quality heat sources, a commercially available Nitinol (Ni-Ti alloy) foil was attached to the nanowire piezoelectric device to create a compound thermoelectric. When bent at room temperature and then heated to 50°C, the Nitinol foil was restored to its original flat shape, which yielded an output voltage of nearly 1 V from the ZnO nanowire device.« less

  2. NREL Honored with Three Top R&D Awards

    Science.gov Websites

    Honored with Three Top R&D Awards For more information contact: Sarah Holmes Barba, 303-275 Renewable Energy Laboratory will receive three R&D 100 awards this week for technologies judged by R& fuels. This is Ginley's second R&D 100 award. Real-time biomass analysis can help analyze wood chips

  3. Evaluation of ZnO:Al as a contact material to CdZnTe for radiation detector applications (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Roy, Utpal N.; Camarda, Giuseppe S.; Cui, Yonggang; Gul, Rubi; Hossain, Anwar; Yang, Ge; James, Ralph B.; Pradhan, Aswini K.; Mundle, Rajeh

    2016-09-01

    Aluminum (Al) doped ZnO with very high Al concentration acts as metal regarding its electrical conductivity. ZnO offers many advantages over the commonly-known metals being used today as electrode materials for nuclear detector fabrication. Often, the common metals show poor adhesion to CdZnTe or CdTe surfaces and have a tendency to peel off. In addition, there is a large mismatch of the coefficients of thermal expansion (CTE) between the metals and underlying CdZnTe, which is one of the reasons for mechanical degradation of the contact. In contrast ZnO has a close match of the CTE with CdZnTe and possesses 8-20 times higher hardness than the commonly-used metals. In this presentation, we will explore and discuss the properties of CdZnTe detectors with ZnO:Al contacts.

  4. The roles of buffer layer thickness on the properties of the ZnO epitaxial films

    NASA Astrophysics Data System (ADS)

    Tang, Kun; Huang, Shimin; Gu, Shulin; Zhu, Shunming; Ye, Jiandong; Xu, Zhonghua; Zheng, Youdou

    2016-12-01

    In this article, the authors have investigated the optimization of the buffer thickness for obtaining high-quality ZnO epi-films on sapphire substrates. The growth mechanism of the buffers with different thickness has been clearly revealed, including the initial nucleation and vertical growth, the subsequent lateral growth with small grain coalescence, and the final vertical growth along the existing larger grains. Overall, the quality of the buffer improves with increasing thickness except the deformed surface morphology. However, by a full-scale evaluation of the properties for the epi-layers, the quality of the epi-film is briefly determined by the surface morphology of the buffer, rather than the structural, optical, or electrical properties of it. The best quality epi-layer has been grown on the buffer with a smooth surface and well-coalescent grains. Meanwhile, due to the huge lattice mismatch between sapphire and ZnO, dislocations are inevitably formed during the growth of buffers. More importantly, as the film grows thicker, the dislocations may attracting other smaller dislocations and defects to reduce the total line energy and thus result in the formation of V-shape defects, which are connected with the bottom of the threading dislocations in the buffers. The V-defects appear as deep and large hexagonal pits from top view and they may act as electron traps which would affect the free carrier concentration of the epi-layers.

  5. Performance of ZnO based piezo-generators under controlled compression

    NASA Astrophysics Data System (ADS)

    Tao, Ran; Parmar, Mitesh; Ardila, Gustavo; Oliveira, Paulo; Marques, Daniel; Montès, Laurent; Mouis, Mireille

    2017-06-01

    This paper reports on the fabrication and characterization of ZnO based vertically integrated nanogenerator (VING) devices under controlled compression. The basic NG structure is a composite material integrating hydrothermally grown vertical piezoelectric zinc oxide (ZnO) nanowires (NWs) into a dielectric matrix (PMMA). A specific characterization set-up has been developed to control the applied compression and the perpendicularity of the applied force on the devices. The role of different fabrication parameters has been evaluated experimentally and compared with previously reported theoretical models, including the thickness of the top PMMA layer and the density of the NWs array in the matrix. Finally, the performance of the VING structure has been evaluated experimentally for different resistive loads obtaining a power density of 85 μW cm-3 considering only the active layer of the device. This has been compared to the performance of a commercial bulk layer of PZT (25 μW cm-3) under the same applied force of 5 N.

  6. Morphology Transition Engineering of ZnO Nanorods to Nanoplatelets Grafted Mo8O23-MoO2 by Polyoxometalates: Mechanism and Possible Applicability to other Oxides.

    PubMed

    Abdelmohsen, Ahmed H; Rouby, Waleed M A El; Ismail, Nahla; Farghali, Ahmed A

    2017-07-19

    A new fundamental mechanism for reliable engineering of zinc oxide (ZnO) nanorods to nanoplatelets grafted Mo 8 O 23 -MoO 2 mixed oxide with controlled morphology, composition and precise understanding of the nanoscale reaction mechanism was developed. These hybrid nanomaterials are gaining interest due to their potential use for energy, catalysis, biomedical and other applications. As an introductory section, we demonstrate a new expansion for the concept 'materials engineering' by discussing the fabrication of metal oxides nanostructures by bottom-up approach and carbon nanoparticles by top-down approach. Moreover, we propose a detailed mechanism for the novel phenomenon that was experienced by ZnO nanorods when treated with phosphomolybdic acid (PMA) under ultra-sonication stimulus. This approach is expected to be the basis of a competitive fabrication approach to 2D hybrid nanostructures. We will also discuss a proposed mechanism for the catalytic deposition of Mo 8 O 23 -MoO 2 mixed oxide over ZnO nanoplatelets. A series of selection rules (SRs) which applied to ZnO to experience morphology transition and constitute Abdelmohsen theory for morphology transition engineering (ATMTE) will be demonstrated through the article, besides a brief discussion about possibility of other oxides to obey this theory.

  7. Backside contacted field effect transistor array for extracellular signal recording.

    PubMed

    Ingebrandt, S; Yeung, C K; Staab, W; Zetterer, T; Offenhäusser, A

    2003-04-01

    A new approach to the design of field-effect transistor (FET) sensors and the use of these FETs in detecting extracellular electrophysiological recordings is reported. Backside contacts were engineered by deep reactive ion etching and a gas phase boron doping process of the holes using planar diffusion sources. The metal contacts were designed to fit on top of the bonding pads of a standard industrial 22-pin DIL (dual inline) chip carrier. To minimise contact resistance, the metal backside contacts of the chips were electroless plated with gold. The chips were mounted on top of the bonding pads using a standard flip-chip process and a fineplacer unit previously described. Rat embryonic myocytes were cultured on these new devices (effective growth area 6 x 6 mm(2)) in order to confirm their validity in electrophysiological recording. Copyright 2003 Elsevier Science B.V.

  8. SW New Mexico Oil Well Formation Tops

    DOE Data Explorer

    Shari Kelley

    2015-10-21

    Rock formation top picks from oil wells from southwestern New Mexico from scout cards and other sources. There are differing formation tops interpretations for some wells, so for those wells duplicate formation top data are presented in this file.

  9. Enhancing Intergenerational Contact.

    ERIC Educational Resources Information Center

    Ralston, Penny A.; And Others

    This document is a curriculum module designed to assist secondary school home economic teachers in teaching students about aging. The three major purposes of this module are to provide data-based information on aging related to needs of students to enhance intergenerational contact; to facilitate the expansion of intergenerational contacts by…

  10. Miniature intermittent contact switch

    NASA Technical Reports Server (NTRS)

    Sword, A.

    1972-01-01

    Design of electric switch for providing intermittent contact is presented. Switch consists of flexible conductor surrounding, but separated from, fixed conductor. Flexing of outside conductor to contact fixed conductor completes circuit. Advantage is small size of switch compared to standard switches.

  11. Glasses and Contact Lenses

    MedlinePlus

    ... vision problems; this includes prescribing eyeglasses and contact lenses, but also doing eye surgery for other eye-related problems. An optometrist ... them clean. The most important thing about contact lenses is good hygiene to prevent infections in your eye. But the really fun part of new glasses ...

  12. Contacts | Galaxy of Images

    Science.gov Websites

    This site has moved! Please go to our new Image Gallery site! dot header Contact Us About the Image Galaxy For licensing and other usage questions, please contact: Image use and licensing ! Enter a search term and hit the search button to quickly find an image Go The above "Quick Search

  13. Noneczematous Contact Dermatitis

    PubMed Central

    Foti, Caterina; Vestita, Michelangelo; Angelini, Gianni

    2013-01-01

    Irritant or allergic contact dermatitis usually presents as an eczematous process, clinically characterized by erythematoedematovesicous lesions with intense itching in the acute phase. Such manifestations become erythematous-scaly as the condition progresses to the subacute phase and papular-hyperkeratotic in the chronic phase. Not infrequently, however, contact dermatitis presents with noneczematous features. The reasons underlying this clinical polymorphism lie in the different noxae and contact modalities, as well as in the individual susceptibility and the various targeted cutaneous structures. The most represented forms of non-eczematous contact dermatitis include the erythema multiforme-like, the purpuric, the lichenoid, and the pigmented kinds. These clinical entities must obviously be discerned from the corresponding “pure” dermatitis, which are not associated with contact with exogenous agents. PMID:24109520

  14. Effect of indium on photovoltaic property of n-ZnO/p-Si heterojunction device prepared using solution-synthesized ZnO nanowire film

    NASA Astrophysics Data System (ADS)

    Kathalingam, Adaikalam; Kim, Hyun-Seok; Park, Hyung-Moo; Valanarasu, Santiyagu; Mahalingam, Thaiyan

    2015-01-01

    Preparation of n-ZnO/p-Si heterostructures using solution-synthesized ZnO nanowire films and their photovoltaic characterization is reported. The solution-grown ZnO nanowire film is characterized using scanning electron microscope, electron dispersive x-ray, and optical absorption studies. Electrical and photovoltaic properties of the fabricated heterostructures are studied using e-beam-evaporated aluminum as metal contacts. In order to use transparent contact and to simultaneously collect the photogenerated carriers, sandwich-type solar cells were fabricated using ZnO nanorod films grown on p-silicon and indium tin oxide (ITO) coated glass as ITO/n-ZnO NR/p-Si. The electrical properties of these structures are analyzed from current-voltage (I-V) characteristics. ZnO nanowire film thickness-dependent photovoltaic properties are also studied. Indium metal was also deposited over the ZnO nanowires and its effects on the photovoltaic response of the devices were studied. The results demonstrated that all the samples exhibit a strong rectifying behavior indicating the diode nature of the devices. The sandwich-type ITO/n-ZnO NR/p-Si solar cells exhibit improved photovoltaic performance over the Al-metal-coated n-ZnO/p-Si structures. The indium deposition is found to show enhancement in photovoltaic behavior with a maximum open-circuit voltage (Voc) of 0.3 V and short-circuit current (Isc) of 70×10-6 A under ultraviolet light excitation.

  15. Contact mechanics for layered materials with randomly rough surfaces.

    PubMed

    Persson, B N J

    2012-03-07

    The contact mechanics model of Persson is applied to layered materials. We calculate the M function, which relates the surface stress to the surface displacement, for a layered material, where the top layer (thickness d) has different elastic properties than the semi-infinite solid below. Numerical results for the contact area as a function of the magnification are presented for several cases. As an application, we calculate the fluid leak rate for laminated rubber seals.

  16. The Effect of Thickness of ZnO Thin Films on Hydrophobic Self-Cleaning Properties

    NASA Astrophysics Data System (ADS)

    Mufti, N.; Arista, D.; Diantoro, M.; Fuad, A.; Taufiq, A.; Sunaryono

    2017-05-01

    Glass coating can be conducted by using ZnO-photocatalyst based semiconductor material since it is preeminent in decomposing organics compound and dangerous bacteria which often contaminates the environment. If there are dirt containing organics compound on the glass, the ZnO photocatalyst coat can be applied as self-cleaning, usually called self-cleaning glass. It depends on the coating thickness which can be controlled by setting the speed of spin coating. In this research, the various rotating speeds of spin coating were conducted at 2000 rpm, 3000 rpm, and 4000 rpm to control the thickness. The raw materials used in this research were Zn(CH3COOH)2.2H2O (PA 99,5%), Ethylene glycol, Diethanolamine (PA 99%), Isopropanol Alkohol, Glycerol, and Ashton. Synthesis methods used were sol-gel prior to spin coating technic were applied. The results of the film were characterized by using SEM, XRD, and UV-Spectrophotometer. The crystal structure was analyzed by using Highscore plus and GSAS software, the size crystal was calculated by using Scherrer equation, a contact angle with ImageJ software. It was shown that ZnO thin film had been successfully synthesized with the crystal size around 21 nm up to 26 nm. The absorption value is higher due to the increasing of coat thickness with bandgap ± 3.2 eV. The test result of hydrophobic and hydrophilic characteristics show that all samples of ZnO thin film with the thickness ± 1.050 μm, ± 0.450 μm, ± 0.250 μm can be applied as self-cleaning glass. The best result was gained with the thickness of thin film ± 1.050 μm.

  17. Electrical contacts for a thin-film semiconductor device

    DOEpatents

    Carlson, David E.; Dickson, Charles R.; D'Aiello, Robert V.

    1989-08-08

    A method of fabricating spaced-apart back contacts on a thin film of semiconductor material by forming strips of buffer material on top of the semiconductor material in locations corresponding to the desired dividing lines between back contacts, forming a film of metal substantially covering the semiconductor material and buffer strips, and scribing portions of the metal film overlying the buffer strips with a laser without contacting the underlying semiconductor material to separate the metal layer into a plurality of back contacts. The buffer material serves to protect the underlying semiconductor material from being damaged during the laser scribing. Back contacts and multi-cell photovoltaic modules incorporating such back contacts also are disclosed.

  18. Contacting graphene in a 200 mm wafer silicon technology environment

    NASA Astrophysics Data System (ADS)

    Lisker, Marco; Lukosius, Mindaugas; Kitzmann, Julia; Fraschke, Mirko; Wolansky, Dirk; Schulze, Sebastian; Lupina, Grzegorz; Mai, Andreas

    2018-06-01

    Two different approaches for contacting graphene in a 200 mm wafer silicon technology environment were tested. The key is the opportunity to create a thin SiN passivation layer on top of the graphene protecting it from the damage by plasma processes. The first approach uses pure Ni contacts with a thickness of 200 nm. For the second attempt, Ni is used as the contact metal which substitutes the Ti compared to a standard contact hole filling process. Accordingly, the contact hole filling of this "stacked via" approach is Ni/TiN/W. We demonstrate that the second "stacked Via" is beneficial and shows contact resistances of a wafer scale process with values below 200 Ohm μm.

  19. Hierarchical structures of ZnO spherical particles synthesized solvothermally

    NASA Astrophysics Data System (ADS)

    Saito, Noriko; Haneda, Hajime

    2011-12-01

    We review the solvothermal synthesis, using a mixture of ethylene glycol (EG) and water as the solvent, of zinc oxide (ZnO) particles having spherical and flower-like shapes and hierarchical nanostructures. The preparation conditions of the ZnO particles and the microscopic characterization of the morphology are summarized. We found the following three effects of the ratio of EG to water on the formation of hierarchical structures: (i) EG restricts the growth of ZnO microcrystals, (ii) EG promotes the self-assembly of small crystallites into spheroidal particles and (iii) the high water content of EG results in hollow spheres.

  20. The growth of ZnO nanostructures using Arginine

    NASA Astrophysics Data System (ADS)

    Singh, Baljinder; Moudgil, Lovika; Singh, Gurinder; Kaura, Aman

    2018-05-01

    The growth mechanism of Zinc oxide (ZnO) nanomaterial with amino acid (Arginine) is explained at different shapes. The present study of ZnO nanostructures (NSs) in the presence of Arginine has enabled us to not only determine the growth mechanism of ZnO NSs but also to determine the effect of Arginine at different temperature of reactants. The synthesized samples are characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Results reveal that Arginine is responsible for formation of NSs. Based on these results, a plausible mechanism is explained.

  1. Ultrathin strain-gated field effect transistor based on In-doped ZnO nanobelts

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng; Du, Junli; Li, Bing; Zhang, Shuhao; Hong, Mengyu; Zhang, Xiaomei; Liao, Qingliang; Zhang, Yue

    2017-08-01

    In this work, we fabricated a strain-gated piezoelectric transistor based on single In-doped ZnO nanobelt with ±(0001) top/bottom polar surfaces. In the vertical structured transistor, the Pt tip of the AFM and Au film are used as source and drain electrode. The electrical transport performance of the transistor is gated by compressive strains. The working mechanism is attributed to the Schottky barrier height changed under the coupling effect of piezoresistive and piezoelectric. Uniquely, the transistor turns off under the compressive stress of 806 nN. The strain-gated transistor is likely to have important applications in high resolution mapping device and MEMS devices.

  2. Temperature- and frequency-dependent dielectric behaviors of insulator/semiconductor (Al2O3/ZnO) nanolaminates with various ZnO thicknesses

    NASA Astrophysics Data System (ADS)

    Li, Jin; Bi, Xiaofang

    2016-07-01

    Al2O3/ZnO nanolaminates (NLs) with various ZnO sublayer thicknesses were prepared by atomic layer deposition. The Al2O3 sublayers are characterized as amorphous and the ZnO sublayers have an oriented polycrystalline structure. As the ZnO thickness decreases to a certain value, each NL exhibits a critical temperature at which its dielectric constant starts to rise quickly. Moreover, this temperature increases as the ZnO thickness is decreased further. On the other hand, the permittivity demonstrates a large value of several hundred at a frequency  ⩽1000 Hz, followed by a steplike decrease at a higher frequency. The change in the cut-off frequency with ZnO thickness is characterized by a hook function. It is revealed that the Coulomb confinement effect becomes predominant in the dielectric behaviors of the NLs with very thin ZnO. As the ZnO thickness decreases to about the same as or even smaller than the Bohr radius of ZnO, a great change in the carrier concentration and effective mass of ZnO is induced, which is shown to be responsible for the peculiar dielectric behaviors of Al2O3/ZnO with very thin ZnO. These findings provide insight into the prevailing mechanisms to optimize the dielectric properties of semiconductor/insulator laminates with nanoscale sublayer thickness.

  3. Influence of ZnO nanostructures in liquid crystal interfaces for bistable switching applications

    NASA Astrophysics Data System (ADS)

    Pal, Kaushik; Zhan, Bihong; Madhu Mohan, M. L. N.; Schirhagl, Romana; Wang, Guoping

    2015-12-01

    The controlled fabrication of nanometer-scale objects is without doubt one of the central issues in current science and technology. In this article, we exhibit a simple, one-step bench top synthesis of zinc oxide nano-tetrapods and nano-spheres which were tailored by the facial growth of nano-wires (diameter ≈ 24 nm; length ≈ 118 nm) and nano-cubes (≈395 nm edge) to nano-sphere (diameter ≈ 585 nm) appeaded. The possibilities of inexpensive, simple solvo-chemical synthesis of nanostructures were considered. In this article, a successful attempt has been made that ZnO nano-structures dispersed on well aligned hydrogen bonded liquid crystals (HBLC) comprising azelaic acid (AC) with p-n-alkyloxy benzoic acid (nBAO) by varying the respective alkyloxy carbon number (n = 5). The dispersion of nanomaterials with HBLC is an effective route to enhance the existing functionalities. A series of these composite materials were analyzed by polarizing optical microscope's electro-optical switching. An interesting feature of AC + nBAO is the inducement of tilted smectic G phase with increasing carbon chain length. Phase diagrams of the above hybrid ZnO nanomaterial influenced LC complex and pure LC were constructed and compared. The switching times, the contrast ratio and spontaneous polarization of the nanostructures-HBLC composite film were carried out by systematic investigation. The sample preparation parameters, such as the curing time and curing intensity were optimized. The critical applied voltage to achieve the switching bi-stability of our device is only 4.5 V, which is approximately twice its threshold voltage for Freedericksz transition. This performance puts the hybrid structure at the top level in the state of the art in application oriented research in optics of liquid crystalline composite materials.

  4. Durable antimicrobial cotton textiles coated sonochemically with ZnO nanoparticles embedded in an in-situ enzymatically generated bioadhesive.

    PubMed

    Salat, Marc; Petkova, Petya; Hoyo, Javier; Perelshtein, Ilana; Gedanken, Aharon; Tzanov, Tzanko

    2018-06-01

    An important preventive measure for providing a bacteria-free environment for the patients is the introduction of highly efficient and durable antibacterial textiles in hospitals. This work describes a single step sono-enzymatic process for coating of cotton medical textiles with antibacterial ZnO nanoparticles (NPs) and gallic acid (GA) to produce biocompatible fabrics with durable antibacterial properties. Cellulose substrates, however, need pre-activation to achieve sufficient stability of the NPs on their surface. Herein, this drawback is overcome by the simultaneous sonochemical deposition of ZnO NPs and the synthesis of a bio-based adhesive generated by the enzymatic cross-linking of GA in which the NPs were embedded. GA possesses the multiple functions of an antibacterial agent, a building block of the cross-linked phenolic network, and as a compound providing the safe contact of the coated materials with human skin. The ZnO NPs-GA coated fabrics maintained above 60% antibacterial efficacy even after 60 washing cycles at 75 °C hospital laundry regime. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. A high speed PE-ALD ZnO Schottky diode rectifier with low interface-state density

    NASA Astrophysics Data System (ADS)

    Jin, Jidong; Zhang, Jiawei; Shaw, Andrew; Kudina, Valeriya N.; Mitrovic, Ivona Z.; Wrench, Jacqueline S.; Chalker, Paul R.; Balocco, Claudio; Song, Aimin; Hall, Steve

    2018-02-01

    Zinc oxide (ZnO) has recently attracted attention for its potential application to high speed electronics. In this work, a high speed Schottky diode rectifier was fabricated based on a ZnO thin film deposited by plasma-enhanced atomic layer deposition and a PtOx Schottky contact deposited by reactive radio-frequency sputtering. The rectifier shows an ideality factor of 1.31, an effective barrier height of 0.79 eV, a rectification ratio of 1.17  ×  107, and cut-off frequency as high as 550 MHz. Low frequency noise measurements reveal that the rectifier has a low interface-state density of 5.13  ×  1012 cm-2 eV-1, and the noise is dominated by the mechanism of a random walk of electrons at the PtO x /ZnO interface. The work shows that the rectifier can be used for both noise sensitive and high frequency electronics applications.

  6. Electrodeposition of ZnO window layer for an all-atmospheric fabrication process of chalcogenide solar cell

    PubMed Central

    Tsin, Fabien; Venerosy, Amélie; Vidal, Julien; Collin, Stéphane; Clatot, Johnny; Lombez, Laurent; Paire, Myriam; Borensztajn, Stephan; Broussillou, Cédric; Grand, Pierre Philippe; Jaime, Salvador; Lincot, Daniel; Rousset, Jean

    2015-01-01

    This paper presents the low cost electrodeposition of a transparent and conductive chlorine doped ZnO layer with performances comparable to that produced by standard vacuum processes. First, an in-depth study of the defect physics by ab-initio calculation shows that chlorine is one of the best candidates to dope the ZnO. This result is experimentally confirmed by a complete optical analysis of the ZnO layer deposited in a chloride rich solution. We demonstrate that high doping levels (>1020 cm−3) and mobilities (up to 20 cm2 V−1 s−1) can be reached by insertion of chlorine in the lattice. The process developed in this study has been applied on a CdS/Cu(In,Ga)(Se,S)2 p-n junction produced in a pilot line by a non vacuum process, to be tested as solar cell front contact deposition method. As a result efficiency of 14.3% has been reached opening the way of atmospheric production of Cu(In,Ga)(Se,S)2 solar cell. PMID:25753657

  7. Electrodeposition of ZnO window layer for an all-atmospheric fabrication process of chalcogenide solar cell.

    PubMed

    Tsin, Fabien; Venerosy, Amélie; Vidal, Julien; Collin, Stéphane; Clatot, Johnny; Lombez, Laurent; Paire, Myriam; Borensztajn, Stephan; Broussillou, Cédric; Grand, Pierre Philippe; Jaime, Salvador; Lincot, Daniel; Rousset, Jean

    2015-03-10

    This paper presents the low cost electrodeposition of a transparent and conductive chlorine doped ZnO layer with performances comparable to that produced by standard vacuum processes. First, an in-depth study of the defect physics by ab-initio calculation shows that chlorine is one of the best candidates to dope the ZnO. This result is experimentally confirmed by a complete optical analysis of the ZnO layer deposited in a chloride rich solution. We demonstrate that high doping levels (>10(20) cm(-3)) and mobilities (up to 20 cm(2) V(-1) s(-1)) can be reached by insertion of chlorine in the lattice. The process developed in this study has been applied on a CdS/Cu(In,Ga)(Se,S)2 p-n junction produced in a pilot line by a non vacuum process, to be tested as solar cell front contact deposition method. As a result efficiency of 14.3% has been reached opening the way of atmospheric production of Cu(In,Ga)(Se,S)2 solar cell.

  8. Contact allergy: an update.

    PubMed

    Ljubojević Hadžavdić, Suzana; Pustišek, Nives; Žužul, Kristina; Švigir, Alen

    2018-06-01

    Contact allergies are common cause of eczema in all age groups and are one of the most common causes of occupational disability. Contact dermatitis (CD) can be divided into irritant and allergic contact dermatitis. Distinguishing between irritant and allergic triggers of CD by clinical and histologic examinations can be challenging. The approach to patients with CD should consist of a detailed (work and leisure) history, skin examination, patch tests with allergens based on history, physical examination, education on materials that contain the allergen and adequate therapy and prevention.

  9. Optical contacting of quartz

    NASA Technical Reports Server (NTRS)

    Payne, L. L.

    1982-01-01

    The strength of the bond between optically contacted quartz surfaces was investigated. The Gravity Probe-B (GP-B) experiment to test the theories of general relativity requires extremely precise measurements. The quartz components of the instruments to make these measurements must be held together in a very stable unit. Optical contacting is suggested as a possible method of joining these components. The fundamental forces involved in optical contacting are reviewed and relates calculations of these forces to the results obtained in experiments.

  10. Bottom-up meets top-down: tailored raspberry-like Fe 3 O 4 –Pt nanocrystal superlattices

    DOE PAGES

    Qiu, Fen; Vervuurt, René H. J.; Verheijen, Marcel A.; ...

    2018-01-01

    Bottom up colloidal synthesis is combined with top down atomic layer deposition to achieve raspberry-like Pt-decorated Fe 3 O 4 nanoparticle superlattices with good metal–oxide–metal contact for photoelectrocatalysis.

  11. Bottom-up meets top-down: tailored raspberry-like Fe 3 O 4 –Pt nanocrystal superlattices

    SciTech Connect

    Qiu, Fen; Vervuurt, René H. J.; Verheijen, Marcel A.

    Bottom up colloidal synthesis is combined with top down atomic layer deposition to achieve raspberry-like Pt-decorated Fe 3 O 4 nanoparticle superlattices with good metal–oxide–metal contact for photoelectrocatalysis.

  12. Electrical properties of lightly Ga-doped ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Alagha, S.; Heedt, S.; Vakulov, D.; Mohammadbeigi, F.; Senthil Kumar, E.; Schäpers, Th; Isheim, D.; Watkins, S. P.; Kavanagh, K. L.

    2017-12-01

    We investigated the growth, crystal structure, elemental composition and electrical transport characteristics of ZnO nanowires, a promising candidate for optoelectronic applications in the UV-range. Nominally-undoped and Ga-doped ZnO nanowires were grown by metal-organic chemical vapor deposition. Photoluminescence measurements confirmed the incorporation of Ga via donor-bound exciton emission. With atom-probe tomography we estimated an upper limit of the Ga impurity concentration ({10}18 {{cm}}-3). We studied the electrical transport characteristics of these nanowires with a W-nanoprobe technique inside a scanning electron microscope and with lithographically-defined contacts allowing back-gated measurements. An increase in apparent resistivity by two orders of magnitude with decreasing radius was measured with both techniques with a much larger distribution width for the nanoprobe method. A drop in the effective carrier concentration and mobility was found with decreasing radius which can be attributed to carrier depletion and enhanced scattering due to surface states. Little evidence of a change in resistivity was observed with Ga doping, which indicates that the concentration of native or background dopants is higher than the Ga doping concentration.

  13. ZnO and ZnTiO3 nanopowders for antimicrobial stone coating

    NASA Astrophysics Data System (ADS)

    Ruffolo, S. A.; La Russa, M. F.; Malagodi, M.; Oliviero Rossi, C.; Palermo, A. M.; Crisci, G. M.

    2010-09-01

    In the past a great variety of biocidal compounds and persistent organic pesticides were applied on a large scale for preventive measures aimed at the long-term preservation of our cultural heritage. Only recently, public and expert attention has started to focus increasingly on the risks resulting from these treatments on human health, works of art and environment in general. The work done in this field demonstrated that the most effective way for inactivation can be achieved by using highly efficient photocatalysts with the illumination of UV radiation. Following this direction our group focused its attention on well-known photocatalysts, ZnO and ZnTiO3, in the degradation and complete mineralisation of environmental pollutants. This explorative work deals with an experimental investigation on biocidal efficient of ZnO and ZnTiO3. In particular micro-quantities of the two nanopowdered photocatalysts were spread on plated dishes. They were filled by the MEA (Malt Extract Agar) medium containing given quantities of Aspergillus Niger (a chromogen filamentous fungus involved in biodeterioration). At the same time the two oxides were dispersed in different polymeric matrices, acrylic and fluorinated, in order to obtain a new coating technology, with hydrophobic, consolidant and biocidal properties for the restoration of building stone material. The mixtures obtained were applied on marble samples and capillary water absorption, simulated solar ageing, colourimetric measurements and contact angle measurements have been performed to evaluate its properties.

  14. High-performance optical projection controllable ZnO nanorod arrays for microweighing sensors.

    PubMed

    Wang, Hongbo; Jiang, Shulan; Zhang, Lei; Yu, Bingjun; Chen, Duoli; Yang, Weiqing; Qian, Linmao

    2018-03-08

    Optical microweighing sensors are an essential component of micro-force measurements in physical, chemical, and biological detection fields, although, their limited detection range (less than 15°) severely hinders their wide application. Such a limitation is mainly attributed to the essential restrictions of traditional light reflection and optical waveguide modes. Here, we report a high-performance optical microweighing sensor based on the synergistic effects of both a new optical projection mode and a ZnO nanorod array sensor. Ascribed to the unique configuration design of this sensing method, this optical microweighing sensor has a wide detection range (more than 80°) and a high sensitivity of 90 nA deg -1 , which is much larger than that of conventional microcantilever-based optical microweighing sensors. Furthermore, the location of the UV light source can be adjusted within a few millimeters, meaning that the microweighing sensor does not need repetitive optical calibration. More importantly, for low height and small incident angles of the UV light source, we can obtain highly sensitive microweighing properties on account of the highly sensitive ZnO nanorod array-based UV sensor. Therefore, this kind of large detection range, non-contact, and non-destructive microweighing sensor has potential applications in air quality monitoring and chemical and biological detection.

  15. ZnO transparent conductive oxide for thin film silicon solar cells

    NASA Astrophysics Data System (ADS)

    Söderström, T.; Dominé, D.; Feltrin, A.; Despeisse, M.; Meillaud, F.; Bugnon, G.; Boccard, M.; Cuony, P.; Haug, F.-J.; Faÿ, S.; Nicolay, S.; Ballif, C.

    2010-03-01

    There is general agreement that the future production of electric energy has to be renewable and sustainable in the long term. Photovoltaic (PV) is booming with more than 7GW produced in 2008 and will therefore play an important role in the future electricity supply mix. Currently, crystalline silicon (c-Si) dominates the market with a share of about 90%. Reducing the cost per watt peak and energy pay back time of PV was the major concern of the last decade and remains the main challenge today. For that, thin film silicon solar cells has a strong potential because it allies the strength of c-Si (i.e. durability, abundancy, non toxicity) together with reduced material usage, lower temperature processes and monolithic interconnection. One of the technological key points is the transparent conductive oxide (TCO) used for front contact, barrier layer or intermediate reflector. In this paper, we report on the versatility of ZnO grown by low pressure chemical vapor deposition (ZnO LP-CVD) and its application in thin film silicon solar cells. In particular, we focus on the transparency, the morphology of the textured surface and its effects on the light in-coupling for micromorph tandem cells in both the substrate (n-i-p) and superstrate (p-i-n) configurations. The stabilized efficiencies achieved in Neuchâtel are 11.2% and 9.8% for p-i-n (without ARC) and n-i-p (plastic substrate), respectively.

  16. The Top STEM Degree Producers

    ERIC Educational Resources Information Center

    Diverse: Issues in Higher Education, 2012

    2012-01-01

    This article presents a list of the top Science, Technology, Engineering, and Mathematics (STEM) degree producers in the U.S. This list is broken down into seven categories: (1) Total Minority Research/Scholarship and Other Doctoral: Mathematics and Statistics; (2) Total Minority Bachelors: Biological and Biomedical Sciences; (3) Total Minority…

  17. The 2003 Training Top 100.

    ERIC Educational Resources Information Center

    Galvin, Tammy

    2003-01-01

    Identifies the top 100 U.S. companies in terms of the amount spent on training and development, the number of hours of training per employee, percentage of payroll spent on training, and tuition allotment per employee. Describes best practices in succession planning and leadership development, mentoring, and job shadowing and provides a detailed…

  18. The 2002 Training Top 100.

    ERIC Educational Resources Information Center

    Training, 2002

    2002-01-01

    Identifies the top 100 companies in terms of the amount spent on training and development, the number of hours of training per employee, percentage of payroll spent on training, and tuition allotment per employee. Describes best practices in succession planning and leadership development, mentoring, and job shadowing and provides a detailed…

  19. The Top Theological Degree Producers

    ERIC Educational Resources Information Center

    Diverse: Issues in Higher Education, 2012

    2012-01-01

    Each year, "Diverse: Issues in Higher Education" publishes a list of the Top 100 producers of associate, bachelor's and graduate degrees awarded to minority students based on research conducted by Dr. Victor M. H. Borden, professor of educational leadership and policy studies at Indiana University Bloomington. This year, for the first…

  20. The Top 100: Associate Rankings

    ERIC Educational Resources Information Center

    Blackmon, Olivia

    2009-01-01

    This year, Diverse has added a new addition to its annual Top 100 degree producers series--recognizing, with this edition, the institutions that award the most associate degrees to students of color. More than half of minority undergraduate students start their degree quest at a community college with 55 percent of all Hispanic and Native American…

  1. "Top School Problems" Are Myths.

    ERIC Educational Resources Information Center

    Males, Mike

    1992-01-01

    A well-known "study" comparing the top school problems of 1940 (talking and gum chewing) with those of 1987 (drug abuse, pregnancy, and violence) is nonexistent. In 1940, 49 percent of all youth did not finish high school, 37,000 teenagers died from violence or disease, and 335,000 teens gave birth. Educators should discount pastoral…

  2. Tether Optical Phenomena (TOP) experiment

    NASA Image and Video Library

    1996-03-14

    STS075-310-002 (22 Feb.-9 March 1996) --- Astronaut Maurizio Cheli, STS-75 mission specialist, works with the Tether Optical Phenomenon System (TOPS) on the flight deck of the Earth-orbiting Space Shuttle Columbia. Cheli, representing the European Space Agency (ESA), joined four other astronauts and an international payload specialists for 16 days of scientific research in Earth-orbit.

  3. Intersection of All Top Quantile

    EPA Pesticide Factsheets

    This layer combines the Top quantiles of the CES, CEVA, and EJSM layers so that viewers can see the overlap of 00e2??hot spots00e2?? for each method. This layer was created by James Sadd of Occidental College of Los Angeles

  4. Observation of the Top Quark

    DOE R&D Accomplishments Database

    Kim, S. B.

    1995-08-01

    Top quark production is observed in{bar p}p collisions at{radical}s= 1.8 TeV at the Fermilab Tevatron. The Collider Detector at Fermilab (CDF) and D{O} observe signals consistent with t{bar t} to WWb{bar b}, but inconsistent with the background prediction by 4.8{sigma} (CDF), 4.6a (D{O}). Additional evidence for the top quark Is provided by a peak in the reconstructed mass distribution. The kinematic properties of the excess events are consistent with the top quark decay. They measure the top quark mass to be 176{plus_minus}8(stat.){plus_minus}10(sys.) GeV/c{sup 2} (CDF), 199{sub -21}{sup+19}(stat.){plus_minus}22(sys.) GeV/c{sup 2} (D{O}), and the t{bar t} production cross section to be 6.8{sub -2.4}{sup+3.6}pb (CDF), 6.4{plus_minus}2.2 pb (D{O}).

  5. Hydrodynamic fabrication of structurally gradient ZnO nanorods.

    PubMed

    Kim, Hyung Min; Youn, Jae Ryoun; Song, Young Seok

    2016-02-26

    We studied a new approach where structurally gradient nanostructures were fabricated by means of hydrodynamics. Zinc oxide (ZnO) nanorods were synthesized in a drag-driven rotational flow in a controlled manner. The structural characteristics of nanorods such as orientation and diameter were determined by momentum and mass transfer at the substrate surface. The nucleation of ZnO was induced by shear stress which plays a key role in determining the orientation of ZnO nanorods. The nucleation and growth of such nanostructures were modeled theoretically and analyzed numerically to understand the underlying physics of the fabrication of nanostructures controlled by hydrodynamics. The findings demonstrated that the precise control of momentum and mass transfer enabled the formation of ZnO nanorods with a structural gradient in diameter and orientation.

  6. Inverter Circuits using Pentacene and ZnO Transistors

    NASA Astrophysics Data System (ADS)

    Iechi, Hiroyuki; Watanabe, Yasuyuki; Kudo, Kazuhiro

    2007-04-01

    We report two types of integrated circuits based on a pentacene static-induction transistor (SIT), a pentacene thin-film transistor (TFT) and a zinc oxide (ZnO) TFT. The operating characteristics of a p-p inverter using pentacene SITs and a complementary inverter using a p-channel pentacene TFT and an n-channel ZnO TFT are described. The basic operation of logic circuits at a low voltage was achieved for the first time using the pentacene SIT inverter and complementary circuits with hybrid inorganic and organic materials. Furthermore, we describe the electrical properties of the ZnO films depending on sputtering conditions, and the complementary circuits using ZnO and pentacene TFTs.

  7. Hexagonal and prismatic nanowalled ZnO microboxes.

    PubMed

    Zhao, Fenghua; Lin, Wenjiao; Wu, Mingmei; Xu, Ningsheng; Yang, Xianfeng; Tian, Z Ryan; Su, Qiang

    2006-04-17

    We hereby report hydrothermal syntheses of new microstructures of semiconducting ZnO. Single-crystalline prismatic ZnO microboxes formed by nanowalls and hexagonal hollow microdisks closed by plates with micron-sized inorganic fullerene-like structures have been made in a base-free medium through a one-step hydrothermal synthesis with the help of n-butanol (NB). Structures and morphologies of the products were confirmed by results from powder X-ray diffraction and scanning electron microscopy. NB has been found to play a crucial role in the growth of these hollow structures. It is indicated that these hollow ZnO crystals were grown from redissolution of interiors. These ZnO microboxes exhibit a band emission in the visible range, implying the possession of a high content of defects.

  8. Nanostructured ZnO Films for Room Temperature Ammonia Sensing

    NASA Astrophysics Data System (ADS)

    Dhivya Ponnusamy; Sridharan Madanagurusamy

    2014-09-01

    Zinc oxide (ZnO) thin films have been deposited by a reactive dc magnetron sputtering technique onto a thoroughly cleaned glass substrate at room temperature. X-ray diffraction revealed that the deposited film was polycrystalline in nature. The field emission scanning electron micrograph (FE-SEM) showed the uniform formation of a rugby ball-shaped ZnO nanostructure. Energy dispersive x-ray analysis (EDX) confirmed that the film was stoichiometric and the direct band gap of the film, determined using UV-Vis spectroscopy, was 3.29 eV. The ZnO nanostructured film exhibited better sensing towards ammonia (NH3) at room temperature (˜30°C). The fabricated ZnO film based sensor was capable of detecting NH3 at as low as 5 ppm, and its parameters, such as response, selectivity, stability, and response/recovery time, were also investigated.

  9. Enhanced antimicrobial activity in biosynthesized ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumari, Niraj; Kumari, Priti; Jha, Anal K.; Prasad, K.

    2018-05-01

    Biological synthesis of different metallic and/or oxide nanoparticles and their applications especially in agriculture and biomedical sciences are gaining prominence nowadays due to their handy and reproducible synthetic protocols which are cost-effective and eco-friendly. In this work, green synthesis of zinc oxide nanoparticles (ZnO NPs) using the alcoholic extract of Azadirachta indica as a reducing and stabilizing agent has been presented. Formation of ZnO NPs was confirmed by X-ray diffraction, scanning and transmission electron microscopy techniques. The phytochemicals responsible for nano-transformation were principally alkaloids, flavanoids, terpenoids, tannins and organic acids present in the Azadirachta indica leaves. The synthesized ZnO NPs were used for antimicrobial assays by disc diffusion method against Staphylococcus aureus and Candida albicans. Results showed that ZnO NPs may act as antimicrobial agent especially against skin infections.

  10. SAM Technical Contacts

    EPA Pesticide Factsheets

    These technical contacts are available to help with questions regarding method deviations, modifications, sample problems or interferences, quality control requirements, the use of alternative methods, or the need to address analytes or sample types.

  11. Fragrance allergic contact dermatitis.

    PubMed

    Cheng, Judy; Zug, Kathryn A

    2014-01-01

    Fragrances are a common cause of allergic contact dermatitis in Europe and in North America. They can affect individuals at any age and elicit a spectrum of reactions from contact urticaria to systemic contact dermatitis. Growing recognition of the widespread use of fragrances in modern society has fueled attempts to prevent sensitization through improved allergen identification, labeling, and consumer education. This review provides an overview and update on fragrance allergy. Part 1 discusses the epidemiology and evaluation of suspected fragrance allergy. Part 2 reviews screening methods, emerging fragrance allergens, and management of patients with fragrance contact allergy. This review concludes by examining recent legislation on fragrances and suggesting potential additions to screening series to help prevent and detect fragrance allergy.

  12. Contact | FNLCR Staging

    Cancer.gov

    The ATOM Consortium is actively seeking additional partnerships with qualified pharma, biotech, technology, academic, government, and other organizations. If you are interested in getting involved,please contact: info@atomscience.org F

  13. Occupational contact dermatitis.

    PubMed

    Lushniak, Boris D

    2004-01-01

    The dermatologist should be aware of the many facets of occupational skin diseases, which can be caused by physical, chemical, and biological insults. The most common manifestation of occupational skin diseases is contact dermatitis (both irritant and allergic). Three factors point out the importance of occupational skin diseases as diseases that have a public health impact: 1) occupational skin diseases are common; 2) they often have a poor prognosis; and 3) they result in a noteworthy economic impact for society and for an individual. They are also diseases amenable to public health interventions. Specific industries and exposures may put a worker at risk of occupational contact dermatitis. The accuracy of the diagnosis of occupational contact dermatitis is related to the skill level, experience, and knowledge of the medical professional who makes the diagnosis and confirms the relationship with a workplace exposure. Prevention of occupational contact dermatitis is important, and a variety of prevention strategies are available.

  14. Contact Line Dynamics

    NASA Astrophysics Data System (ADS)

    Kreiss, Gunilla; Holmgren, Hanna; Kronbichler, Martin; Ge, Anthony; Brant, Luca

    2017-11-01

    The conventional no-slip boundary condition leads to a non-integrable stress singularity at a moving contact line. This makes numerical simulations of two-phase flow challenging, especially when capillarity of the contact point is essential for the dynamics of the flow. We will describe a modeling methodology, which is suitable for numerical simulations, and present results from numerical computations. The methodology is based on combining a relation between the apparent contact angle and the contact line velocity, with the similarity solution for Stokes flow at a planar interface. The relation between angle and velocity can be determined by theoretical arguments, or from simulations using a more detailed model. In our approach we have used results from phase field simulations in a small domain, but using a molecular dynamics model should also be possible. In both cases more physics is included and the stress singularity is removed.

  15. NCI Contact Center

    Cancer.gov

    The NCI Contact Center (formerly the Cancer Information Service) provides accurate, up-to-date, and reliable information on cancer that is easy to understand. Trained information specialists provide personalized responses to a range of cancer questions.

  16. Improved efficiency of ZnO hierarchical particle based dye sensitized solar cell by incorporating thin passivation layer in photo-anode

    NASA Astrophysics Data System (ADS)

    Das, Priyanka; Mondal, Biswanath; Mukherjee, Kalisadhan

    2018-01-01

    Present article describes the DSSC performances of photo-anodes prepared using hydrothermal route derived ZnO particles having dissimilar morphologies i.e. simple micro-rod and nano-tips decorated micro-rod. The surface of nano-tips decorated micro-rod is uneven and patterned which facilitate more dye adsorption and better scattering of the incident light resulting superior photo-conversion efficiency (PCE) ( η 1.09%) than micro-rod ZnO ( η 0.86%). To further improve the efficiency of nano-tips decorated micro-rod ZnO based DSSC, thin passivation layer of ZnO is introduced in the corresponding photo-anode and a higher PCE ( η 1.29%) is achieved. The compact thin passivation layer here expedites the transportation of photo-excited electrons, restricts the undesired recombination reactions and prevents the direct contact of electrolyte with conducting substrates. Attempt is made to understand the effect of passivation layer on the transportation kinetics of photo-excited electrons by analyzing the electrochemical impedance spectra of the developed cells.

  17. Self-assembled hierarchical direct Z-scheme g-C3N4/ZnO microspheres with enhanced photocatalytic CO2 reduction performance

    NASA Astrophysics Data System (ADS)

    Nie, Ning; Zhang, Liuyang; Fu, Junwei; Cheng, Bei; Yu, Jiaguo

    2018-05-01

    Photocatalytic reduction of CO2 into hydrocarbon fuels has been regarded as a promising approach to ease the greenhouse effect and the energy shortage. Herein, an electrostatic self-assembly method was exploited to prepare g-C3N4/ZnO composite microsphere. This method simply utilized the opposite surface charge of each component, achieving a hierarchical structure with intimate contact between them. A much improved photocatalytic CO2 reduction activity was attained. The CH3OH production rate was 1.32 μmol h-1 g-1, which was 2.1 and 4.1 times more than that of the pristine ZnO and g-C3N4, respectively. This facile design bestowed the g-C3N4/ZnO composite an extended light adsorption caused by multi-light scattering effect. It also guaranteed the uniform distribution of g-C3N4 nanosheets on the surface of ZnO microspheres, maximizing their advantage and synergistic effect. Most importantly, the preeminent performance was proposed and validated based on the direct Z-scheme. The recombination rate was considerably suppressed. This work features the meliority of constructing hierarchical direct Z-scheme structures in photocatalytic CO2 reduction reactions.

  18. ELECTRIC CONTACT MEANS

    DOEpatents

    Grear, J.W. Jr.

    1959-03-10

    A switch adapted to maintain electrical connections under conditions of vibration or acceleration is described. According to the invention, thc switch includes a rotatable arm carrying a conductive bar arranged to close against two contacts spaced in the same plane. The firm and continuous engagement of the conductive bar with the contacts is acheived by utilizeing a spring located betwenn the vbar and athe a rem frzme and slidable mounting the bar in channel between two arms suspendef from the arm frame.

  19. Focal Contacts as Mechanosensors

    PubMed Central

    Riveline, Daniel; Zamir, Eli; Balaban, Nathalie Q.; Schwarz, Ulrich S.; Ishizaki, Toshimasa; Narumiya, Shuh; Kam, Zvi; Geiger, Benjamin; Bershadsky, Alexander D.

    2001-01-01

    The transition of cell–matrix adhesions from the initial punctate focal complexes into the mature elongated form, known as focal contacts, requires GTPase Rho activity. In particular, activation of myosin II–driven contractility by a Rho target known as Rho-associated kinase (ROCK) was shown to be essential for focal contact formation. To dissect the mechanism of Rho-dependent induction of focal contacts and to elucidate the role of cell contractility, we applied mechanical force to vinculin-containing dot-like adhesions at the cell edge using a micropipette. Local centripetal pulling led to local assembly and elongation of these structures and to their development into streak-like focal contacts, as revealed by the dynamics of green fluorescent protein–tagged vinculin or paxillin and interference reflection microscopy. Inhibition of Rho activity by C3 transferase suppressed this force-induced focal contact formation. However, constitutively active mutants of another Rho target, the formin homology protein mDia1 (Watanabe, N., T. Kato, A. Fujita, T. Ishizaki, and S. Narumiya. 1999. Nat. Cell Biol. 1:136–143), were sufficient to restore force-induced focal contact formation in C3 transferase-treated cells. Force-induced formation of the focal contacts still occurred in cells subjected to myosin II and ROCK inhibition. Thus, as long as mDia1 is active, external tension force bypasses the requirement for ROCK-mediated myosin II contractility in the induction of focal contacts. Our experiments show that integrin-containing focal complexes behave as individual mechanosensors exhibiting directional assembly in response to local force. PMID:11402062

  20. The impact of contact

    NASA Astrophysics Data System (ADS)

    Finney, B.

    1986-10-01

    Scenarios of the impact on human society of radio contact with an extraterrestrial civilization are presented. Some believe that contact with advanced extraterrestrials would quickly devastate the human spirit, while others believe that these super-intelligent beings would show the inhabitants of the earth how to live in peace. It is proposed that the possible existence of extraterrestrial civilizations and the development of means of studying and communicating with them need to be considered.

  1. Lettuce contact allergy.

    PubMed

    Paulsen, Evy; Andersen, Klaus E

    2016-02-01

    Lettuce (Lactuca sativa L.) and its varieties are important vegetable crops worldwide. They are also well-known, rarely reported, causes of contact allergy. As lettuce allergens and extracts are not commercially available, the allergy may be underdiagnosed. The aims of this article are to present new data on lettuce contact allergy and review the literature. Lettuce is weakly allergenic, and occupational cases are mainly reported. Using aimed patch testing in Compositae-allergic patients, two recent Danish studies showed prevalence rates of positive lettuce reactions of 11% and 22%. The majority of cases are non-occupational, and may partly be caused by cross-reactivity. The sesquiterpene lactone mix seems to be a poor screening agent for lettuce contact allergy, as the prevalence of positive reactions is significantly higher in non-occupationally sensitized patients. Because of the easy degradability of lettuce allergens, it is recommended to patch test with freshly cut lettuce stem and supplement this with Compositae mix. As contact urticaria and protein contact dermatitis may present as dermatitis, it is important to perform prick-to-prick tests, and possibly scratch patch tests as well. Any person who is occupationally exposed to lettuce for longer periods, especially atopics, amateur gardeners, and persons keeping lettuce-eating pets, is potentially at risk of developing lettuce contact allergy. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  2. Training Top 10 Hall of Fame

    ERIC Educational Resources Information Center

    Training, 2012

    2012-01-01

    Microsoft Corporation and SCC Soft Computer are the newest inductees into the Training Top 10 Hall of Fame, joining the ranks of the 11 companies named to the hall since its inception in 2008 (Wyeth Pharmaceuticals subsequently was acquired by Pfizer Inc. in 2009). These 11 companies held Top 10 spots in the Training Top 50, Top 100, and now Top…

  3. Synthesis of p-type ZnO films

    NASA Astrophysics Data System (ADS)

    Ryu, Y. R.; Zhu, S.; Look, D. C.; Wrobel, J. M.; Jeong, H. M.; White, H. W.

    2000-06-01

    p-Type ZnO obtained by arsenic (As) doping is reported for the first time. Arsenic-doped ZnO (ZnO : As) films have been deposited on (0 0 1)-GaAs substrates by pulsed laser ablation. The process of synthesizing p-type ZnO : As films was performed in an ambient gas of ultra-pure (99.999%) oxygen. The ambient gas pressure was 35 mTorr with the substrate temperature in the range 300-450°C. ZnO films grown at 400°C and 450°C are p-type and As is a good acceptor. The acceptor peak is located at 3.32 eV and its binding energy is about 100 meV. Acceptor concentrations of As atoms in ZnO films were in the range from high 10 17 to high 10 21 atoms/cm 3 as determined by secondary ion mass spectroscopy (SIMS) and Hall effect measurements.

  4. ZnO nanorods for electronic and photonic device applications

    NASA Astrophysics Data System (ADS)

    Yi, Gyu-Chul; Yoo, Jinkyoung; Park, Won Il; Jung, Sug Woo; An, Sung Jin; Kim, H. J.; Kim, D. W.

    2005-11-01

    We report on catalyst-free growth of ZnO nanorods and their nano-scale electrical and optical device applications. Catalyst-free metalorganic vapor-phase epitaxy (MOVPE) enables fabrication of size-controlled high purity ZnO single crystal nanorods. Various high quality nanorod heterostructures and quantum structures based on ZnO nanorods were also prepared using the MOVPE method and characterized using scanning electron microscopy, transmission electron microscopy, and optical spectroscopy. From the photoluminescence spectra of ZnO/Zn 0.8Mg 0.2O nanorod multi-quantum-well structures, in particular, we observed a systematic blue-shift in their PL peak position due to quantum confinement effect of carriers in nanorod quantum structures. For ZnO/ZnMgO coaxial nanorod heterostructures, photoluminescence intensity was significantly increased presumably due to surface passivation and carrier confinement. In addition to the growth and characterizations of ZnO nanorods and their quantum structures, we fabricated nanoscale electronic devices based on ZnO nanorods. We report on fabrication and device characteristics of metal-oxidesemiconductor field effect transistors (MOSFETs), Schottky diodes, and metal-semiconductor field effect transistors (MESFETs) as examples of the nanodevices. In addition, electroluminescent devices were fabricated using vertically aligned ZnO nanorods grown p-type GaN substrates, exhibiting strong visible electroluminescence.

  5. Synthesis of ZnO Photocatalysts Using Various Surfactants

    NASA Astrophysics Data System (ADS)

    Yao, Chengli; Zhu, Jinmiao; Li, Hongying; Zheng, Bin; Wei, Yanxin

    2017-12-01

    Zinc oxide (ZnO) nanostructured materials have received significant attention because of their unique physicochemical and electronic properties. In particular, the functional properties of ZnO are owed to its morphology and defect structure. ZnO particles were successfully synthesized by chemical precipitation. CTAB (cetyltrimethylammonium bromide), BS-12 (dodecyl dimethyl betaine) and graphene oxide (GO) were selected as templates to induce the formation of ZnO, respectively. By varying the amount of surfactant added during the synthesis process, the structural properties and the crystalline phase of the synthesized nanospheres were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet and visible spectrophotometry (UV‒Vis). Simultaneously, photo catalytic degradation of Rhodamine B (RhB) was carried out under natural sunlight irradiation while ZnO or ZnO/GO particles were used as catalyst. GO is prone to induce formation of wurtzite hexagonal phase of ZnO. Compared with CTAB and BS-12, ZnO/GO composites had a remarkably photocatalytic degradation.

  6. Photoluminescent properties of electrochemically synthetized ZnO nanotubes

    SciTech Connect

    Gracia Jiménez, J.M.

    ZnO nanotubes were prepared by a sequential combination of electrochemical deposition, chemical attack and regeneration. ZnO nanocolumns were initially electrodeposited on conductive substrates and then converted into nanotubes by a process involving chemical etching and subsequent regrowth. The morphology of these ZnO nanocolumns and derived nanotubes was monitored by Scanning Electron Microscopy and their optical properties was studied by photoluminescence spectroscopy. Photoluminescence were measured as a function of temperature, from 6 to 300 K, for both nanocolumns and nanotubes. In order to study the behaviour of induced intrinsic defect all ZnO films were annealed in air at 400 °C andmore » their photoluminescent properties were also registered before and after annealing. The behaviour of photoluminescence is explained taking into account the contribution of different point defects. A band energy diagram related to intrinsic defects was proposed to describe the behaviour of photoluminescence spectra. - Highlights: •ZnO nanotubes were obtained after etching and regrowth of electrodeposited ZnO films. •Photoluminescence spectra contain two parts involving excitonic and defects transitions. •Annealing produces a blue shift in the PL peaks in both ZnO nanocolumns and nanotubes. •Etching causes a blue shift in PL peaks due to confinement effect in nanotubes walls.« less

  7. ZnO based potentiometric and amperometric nanosensors.

    PubMed

    Willander, Magnus; Khun, Kimleang; Ibupoto, Zafar Hussain

    2014-09-01

    The existence of nanomaterials provides the solid platform for sensing applications due to owing of high sensitivity and a low concentration limit of detection. More likely used nanomaterials for sensing applications includes gold nanoparticles, carbon nanotubes, magnetic nanoparticles such as Fe3O4, quantum dots and metal oxides etc. Recently nanomaterial and biological detection becomes an interdisciplinary field and is very much focussed by the researchers. Among metal oxides ZnO is largely considered due to its less toxic nature, biocompatible, cheap and easy to synthesis. ZnO nanomaterial is highly used for the chemical sensing, especially electrochemical sensing due to its fascinating properties such as high surface to volume ratio, atoxic, biosafe and biocompatible. Moreover, ZnO nanostructures exhibit unique features which could expose a suitable nanoenviroment for the immobilization of proteineous material such as enzymes, DNA, antibodies, etc. and in doing so it retains the biological efficiency of the immobilized bio sensitive material. The following review describes the two different coatings (i.e., ionophore and enzyme) on the surface of ZnO nanorods for the chemical sensing of zinc ion detection, thallium (I) ion detection, and L-lactic acid and the measurement of galactose molecules. ZnO nanorods provide the excellent transducing properties in the generation of strong electrical signals. Moreover, this review is very much focused on the applications of ZnO nanostructures in the sensing field.

  8. ZnO Nanostructures for Tissue Engineering Applications

    PubMed Central

    Laurenti, Marco; Cauda, Valentina

    2017-01-01

    This review focuses on the most recent applications of zinc oxide (ZnO) nanostructures for tissue engineering. ZnO is one of the most investigated metal oxides, thanks to its multifunctional properties coupled with the ease of preparing various morphologies, such as nanowires, nanorods, and nanoparticles. Most ZnO applications are based on its semiconducting, catalytic and piezoelectric properties. However, several works have highlighted that ZnO nanostructures may successfully promote the growth, proliferation and differentiation of several cell lines, in combination with the rise of promising antibacterial activities. In particular, osteogenesis and angiogenesis have been effectively demonstrated in numerous cases. Such peculiarities have been observed both for pure nanostructured ZnO scaffolds as well as for three-dimensional ZnO-based hybrid composite scaffolds, fabricated by additive manufacturing technologies. Therefore, all these findings suggest that ZnO nanostructures represent a powerful tool in promoting the acceleration of diverse biological processes, finally leading to the formation of new living tissue useful for organ repair. PMID:29113133

  9. Theory of copper impurities in ZnO

    NASA Astrophysics Data System (ADS)

    Lyons, John; Alkauskas, Audrius; Janotti, Anderson; van de Walle, Chris G.

    Due to its connection to deep luminescence signals and its potential use as an acceptor dopant, copper has been one the most studied impurities in ZnO. From experiment, copper incorporating on the Zn site (CuZn) is known to lead to an acceptor level residing near the conduction band of ZnO, making CuZn an exceedingly deep acceptor. CuZn in ZnO has also long been linked with broad 2.4 eV green luminescence (GL) signals. In this work we explore the electrical and optical properties of Cu in ZnO using density functional theory (DFT). Due to the limitations of traditional forms of DFT, an accurate theoretical description of the electrical and optical properties of such deep centers has been difficult to achieve. Here we employ a screened hybrid density functional (HSE) to calculate the properties of Cu in ZnO. We determine the thermodynamic transition levels associated with CuZn in ZnO as well as the associated luminescence lineshapes of characteristic optical transitions. We find that HSE-calculated optical transitions are in close agreement with experimental studies. This work was supported in part by NSF and by ARO.

  10. Synthesis, characteristics and antimicrobial activity of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Janaki, A. Chinnammal; Sailatha, E.; Gunasekaran, S.

    2015-06-01

    The utilization of various plant resources for the bio synthesis of metallic nano particles is called green technology and it does not utilize any harmful protocols. Present study focuses on the green synthesis of ZnO nano particles by Zinc Carbonate and utilizing the bio-components of powder extract of dry ginger rhizome (Zingiber officinale). The ZnO nano crystallites of average size range of 23-26 nm have been synthesized by rapid, simple and eco friendly method. Zinc oxide nano particles were characterized by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX). FTIR spectra confirmed the adsorption of surfactant molecules at the surface of ZnO nanoparticles and the presence of ZnO bonding. Antimicrobial activity of ZnO nano particles was done by well diffusion method against pathogenic organisms like Klebsiella pneumonia, Staphylococcus aureus and Candida albicans and Penicillium notatum. It is observed that the ZnO synthesized in the process has the efficient antimicrobial activity.

  11. N doped ZnO and ZnO nanorods based p-n homojunction fabricated by ion implantation

    NASA Astrophysics Data System (ADS)

    Chakraborty, Mohua; Thangavel, R.; Asokan, K.

    2018-05-01

    Nitrogen (N) doped and undoped Zinc Oxide (ZnO) nanorod p-n homojunctions were fabricated by ion implantation method. The structural and optical characterizations showed that the N atoms doped into the ZnO crystal lattice. The UV-Vis absorption spectra revealed shift in optical absorption edge towards higher wavelength with ion implantation on ZnO, which attributed N acceptor levels above the valence band. The current-voltage (I-V) measurements exhibit a typical semiconductor rectification characteristic indicating the electrical conductivity of the N-doped ZnO nanorod have p-type conductivity. Moreover, a high photocurrent response has been observed with these p-n homojunctions.

  12. Contact Us about NREL | NREL

    Science.gov Websites

    Contact Us about NREL Contact Us about NREL Find mailing addresses, phone numbers, and contact -2157 202-488-2200 Phone Phone Numbers View a list of important phone numbers. Address book Contact a Staff Member at NREL Our searchable staff directory has contact information for staff. Questions

  13. Acanthamoeba keratitis in patients wearing scleral contact lenses.

    PubMed

    Sticca, Matheus Porto; Carrijo-Carvalho, Linda C; Silva, Isa M B; Vieira, Luiz A; Souza, Luciene B; Junior, Rubens Belfort; Carvalho, Fábio Ramos S; Freitas, Denise

    2018-06-01

    To report a series of cases of Acanthamoeba keratitis (AK) in scleral lens wearers with keratoconus to determine whether this type of contact lens presents a greater risk for development of infection. This study reports three patients who wore scleral contact lenses to correct keratoconus and developed AK. The diagnoses of AK were established based on cultures of the cornea, scleral contact lenses, and contact lens paraphernalia. This study investigated the risk factors for infections. The possible risks for AK in scleral contact lens wearers are hypoxic changes in the corneal epithelium because of the large diameter and minimal tear exchange, use of large amounts of saline solution necessary for scleral lens fitting, storing the scleral lens overnight in saline solution rather than contact lens multipurpose solutions, not rubbing the contact lens during cleaning, and the space between the cornea and the back surface of the scleral lens that might serve as a fluid reservoir and environment for Acanthamoeba multiplication. Two patients responded well to medical treatment of AK; one is still being treated. The recommendations for use and care of scleral contact lenses should be emphasized, especially regarding use of sterile saline (preferably single use), attention to rubbing the lens during cleaning, cleaning of the plunger, and overnight storage in fresh contact lens multipurpose solutions without topping off the lens solution in the case. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  14. Joint Contact Stress

    PubMed Central

    Brand, Richard A

    2005-01-01

    A joint's normal mechanical history contributes to the maintenance of articular cartilage and underlying bone. Loading facilitates the flow of nutrients into cartilage and waste products away, and additionally provides the mechanical signals essential for normal cell and tissue maintenance. Deleteriously low or high contact stresses have been presumed to result in joint deterioration, and particular aspects of the mechanical environment may facilitate repair of damaged cartilage. For decades, investigators have explored static joint contact stresses (under some more or less arbitrary condition) as a surrogate of the relevant mechanical history. Contact stresses have been estimated in vitro in many joints and in a number of species, although only rarely in vivo. Despite a number of widely varying techniques (and spatial resolutions) to measure these contact stresses, reported ranges of static peak normal stresses are relatively similar from joint to joint across species, and in the range of 0.5 to 5.0 MPa. This suggests vertebrate diarthrodial joints have evolved to achieve similar mechanical design criteria. Available evidence also suggests some disorders of cartilage deterioration are associated with somewhat higher peak pressures ranging from 1-20 MPa, but overlapping the range of normal pressures. Some evidence and considerable logic suggests static contact stresses per se do not predict cartilage responses, but rather temporal aspects of the contact stress history. Static contact stresses may therefore not be a reasonable surrogate for biomechanical studies. Rather, temporal and spatial aspects of the loading history undoubtedly induce beneficial and deleterious biological responses. Finally, since all articular cartilage experiences similar stresses, the concept of a "weight-bearing" versus a "non-weight-bearing" joint seems flawed, and should be abandoned. PMID:16089079

  15. Effect of Mg doping in ZnO buffer layer on ZnO thin film devices for electronic applications

    NASA Astrophysics Data System (ADS)

    Giri, Pushpa; Chakrabarti, P.

    2016-05-01

    Zinc Oxide (ZnO) thin films have been grown on p-silicon (Si) substrate using magnesium doped ZnO (Mg: ZnO) buffer layer by radio-frequency (RF) sputtering method. In this paper, we have optimized the concentration of Mg (0-5 atomic percent (at. %)) ZnO buffer layer to examine its effect on ZnO thin film based devices for electronic and optoelectronic applications. The crystalline nature, morphology and topography of the surface of the thin film have been characterized. The optical as well as electrical properties of the active ZnO film can be tailored by varying the concentration of Mg in the buffer layer. The crystallite size in the active ZnO thin film was found to increase with the Mg concentration in the buffer layer in the range of 0-3 at. % and subsequently decrease with increasing Mg atom concentration in the ZnO. The same was verified by the surface morphology and topography studies carried out with scanning electron microscope (SEM) and atomic electron microscopy (AFM) respectively. The reflectance in the visible region was measured to be less than 80% and found to decrease with increase in Mg concentration from 0 to 3 at. % in the buffer region. The optical bandgap was initially found to increase from 3.02 eV to 3.74 eV by increasing the Mg content from 0 to 3 at. % but subsequently decreases and drops down to 3.43 eV for a concentration of 5 at. %. The study of an Au:Pd/ZnO Schottky diode reveals that for optimum doping of the buffer layer the device exhibits superior rectifying behavior. The barrier height, ideality factor, rectification ratio, reverse saturation current and series resistance of the Schottky diode were extracted from the measured current voltage (I-V) characteristics.

  16. Flower-like ZnO nanorod arrays grown on HF-etched Si (111): constraining relation between ZnO seed layer and Si (111)

    NASA Astrophysics Data System (ADS)

    Brahma, Sanjaya; Liu, C.-W.; Huang, R.-J.; Chang, S.-J.; Lo, K.-Y.

    2015-11-01

    We demonstrate the formation of self-assembled homogenous flower-like ZnO nanorods over a ZnO seed layer deposited on a HF-etched Si (111) substrate. The typical flower-like morphology of ZnO nanorod arrays is ascribed to the formation of the island-like seed layer which is deposited by the drop method followed by annealing at 300 °C. The island-like ZnO seed layer consists of larger ZnO grains, and is built by constraining of the Si (111) surface due to pattern matching. Pattern matching of Si with ZnO determines the shape and size of the seed layer and this controls the final morphology of ZnO nanorods to be either flower like or vertically aligned. The high quality of the island-like ZnO seed layer enhances the diameter and length of ZnO nanorods. Besides, while the amorphous layer formed during the annealing process would influence the strained ZnO grain, that subsequent amorphous layer will not block the constraining between the ZnO grain and the substrate.

  17. Microwave synthesis and photocatalytic activities of ZnO bipods with different aspect ratios

    SciTech Connect

    Sun, Fazhe; Zhao, Zengdian; Qiao, Xueliang, E-mail: xuelqiao@163.com

    2016-02-15

    Highlights: • We synthesized linked ZnO nanorods by a facile microwave method. • The effect of reaction parameters on ZnO was investigated. • ZnO bipods with different aspect ratios were prepared. • The photocatalytic performance of ZnO bipods was evaluated. - Abstract: Linked ZnO nanorods have been successfully prepared via a facile microwave method without any post-synthesis treatment. The X-ray diffraction (XRD) patterns indicated the precursor had completely transformed into the pure ZnO crystal. The images of field emitting scanning electron microscope (FESEM) and transmission electron microscope (TEM) showed that linked ZnO nanorods consisted predominantly of ZnO bipods. The formationmore » process of the ZnO bipods was clearly discussed. ZnO bipods with different aspect ratios have been obtained by tuning the concentrations of reagents and microwave power. Moreover, the photocatalytic performance of ZnO bipods with different aspect ratios for degradation of methylene blue was systematically evaluated. The results of photocatalytic experiments showed that the photocatalytic activity increased with the aspect ratios of ZnO bipods increased. The reason is that ZnO bipods with larger aspect ratio have higher surface area, which can absorb more MB molecules to react with ·OH radicals.« less

  18. Chemical manipulation of oxygen vacancy and antibacterial activity in ZnO.

    PubMed

    V, Lakshmi Prasanna; Vijayaraghavan, Rajagopalan

    2017-08-01

    Pure and doped ZnO (cation and anion doping) compositions have been designed in order to manipulate oxygen vacancy and antibacterial activity of ZnO. In this connection, we have synthesized and characterized micron sized ZnO, N doped micron sized ZnO, nano ZnO, nano Na and La doped ZnO. The intrinsic vacancies in pure ZnO and the vacancies created by N and Na doping in ZnO have been confirmed by X-ray Photoelectron Spectroscopy(XPS) and Photoluminiscence Spectroscopy(PL). Reactive oxygen species (ROS) such as hydroxyl radicals, superoxide radicals and H 2 O 2 responsible for antibacterial activity have been estimated by PL, UV-Vis spectroscopy and KMnO 4 titrations respectively. It was found that nano Na doped ZnO releases highest amount of ROS followed by nano ZnO, micron N doped ZnO while micron ZnO releases the least amount of ROS. The concentration of vacancies follows the same sequence. This illustrates directly the correlation between ROS and oxygen vacancy in well designed pure and doped ZnO. For the first time, material design in terms of cation doping and anion doping to tune oxygen vacancies has been carried out. Interaction energy (E g ), between the bacteria and nanoparticles has been calculated based on Extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory and is correlated with antibacterial activity. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Synthesis of ZnO nanowires for thin film network transistors

    NASA Astrophysics Data System (ADS)

    Dalal, S. H.; Unalan, H. E.; Zhang, Y.; Hiralal, Pritesh; Gangloff, L.; Flewitt, Andrew J.; Amaratunga, Gehan A. J.; Milne, William I.

    2008-08-01

    Zinc oxide nanowire networks are attractive as alternatives to organic and amorphous semiconductors due to their wide bandgap, flexibility and transparency. We demonstrate the fabrication of thin film transistors (TFT)s which utilize ZnO nanowires as the semiconducting channel. These thin film transistors can be transparent and flexible and processed at low temperatures on to a variety of substrates. The nanowire networks are created using a simple contact transfer method that is easily scalable. Apparent nanowire network mobility values can be as high as 3.8 cm2/Vs (effective thin film mobility: 0.03 cm2/Vs) in devices with 20μm channel lengths and ON/OFF ratios of up to 104.

  20. Structural, optical, and LED characteristics of ZnO and Al doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Sandeep, K. M.; Bhat, Shreesha; Dharmaprakash, S. M.

    2017-05-01

    ZnO (pristine) and Al doped ZnO (AZO) films were prepared using sol-gel spin coating method. The XRD analysis showed the enhanced compressive stress in AZO film. The presence of extended states below the conduction band edge in AZO accounts for the redshift in optical bandgap. The PL spectra of AZO showed significant blue emission due to the carrier recombination from defect states. The TRPL curves showed the dominant DAP recombination in ZnO film, whereas defect related recombination in Al doped ZnO film. Color parameters viz: the dominant wavelength, color coordinates (x,y), color purity, luminous efficiency and correlated color temperature (CCT) of ZnO and AZO films are calculated using 1931 (CIE) diagram. Further, a strong blue emission with color purity more than 96% is observed in both the films. The enhanced blue emission in AZO significantly increased the luminous efficiency (22.8%) compared to ZnO film (10.8%). The prepared films may be used as blue phosphors in white light generation.

  1. Synthesis of ZnO nanorods and observation of resistive switching memory in ZnO based polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Nair, Manjula G.; Malakar, Meenakshi; Mohapatra, Saumya R.; Chowdhury, Avijit

    2018-05-01

    This research reports the observation of bipolar resistive switching memory in ZnO nanorod based polymer nanocomposites. We synthesized ZnO nanorods by wet-chemical method and characterized them using XRD, UV-VIS spectroscopy and SEM. The synthesized materials have hexagonal ZnO phase with grain size of 24 nm and having strong orientation along (101) direction as observed from XRD. The SEM micrograph confirms the formation of ZnO nanorods with diameter in the range of 10 to 20 nm and length of the order of 1 µm. From optical absorption spectra the band gap is estimated to be 2.42 eV. ZnO nanorods were dispersed in PVDF-HFP polymer matrix to prepare the nanocomposite. This nanocomposite was used as active layer in the devices having sandwich structure of ITO/PVDF-HFP+ZnO nanorods/Al. Bipolar non-volatile memory was observed with ON-OFF resistance ratio of the order of 103 and with a wide voltage window of 2.3V. The switching mechanism could be due to the trapping and de-trapping of electrons by the ZnO nanorods in the nanocomposite during ON and OFF states respectively.

  2. Thermoelectric Outer Planets Spacecraft (TOPS)

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The research and advanced development work is reported on a ballistic-mode, outer planet spacecraft using radioisotope thermoelectric generator (RTG) power. The Thermoelectric Outer Planet Spacecraft (TOPS) project was established to provide the advanced systems technology that would allow the realistic estimates of performance, cost, reliability, and scheduling that are required for an actual flight mission. A system design of the complete RTG-powered outer planet spacecraft was made; major technical innovations of certain hardware elements were designed, developed, and tested; and reliability and quality assurance concepts were developed for long-life requirements. At the conclusion of its active phase, the TOPS Project reached its principal objectives: a development and experience base was established for project definition, and for estimating cost, performance, and reliability; an understanding of system and subsystem capabilities for successful outer planets missions was achieved. The system design answered long-life requirements with massive redundancy, controlled by on-board analysis of spacecraft performance data.

  3. Attitude propulsion technology for TOPS

    NASA Technical Reports Server (NTRS)

    Moynihan, P. I.

    1972-01-01

    The thermoelectric outer planet spacecraft (TOPS) attitude propulsion subsystem (APS) effort is discussed. It includes the tradeoff rationale that went into the selection of an anhydrous hydrazine baseline system, followed by a discussion of the 0.22 N thruster and its integration into a portable, self-contained propulsion module that was designed, developed, and man rated to support the TOPS single-axis attitude control tests. The results of a cold-start feasibility demonstration with a modified thruster are presented. A description of three types of 0.44 thrusters that were procured for in-house evaluation is included along with the results of the test program. This is followed by a description of the APS feed system components, their evaluations, and a discussion of an evaluation of elastomeric material for valve seat seals. A list of new technology items which will be of value for application to future systems of this type is included.

  4. Solar cell contacts

    NASA Technical Reports Server (NTRS)

    Meier, D. L.; Campbell, R. B.; Davis, J. R., Jr.; Rai-Choudhury, P.; Sienkiewicz, L. J.

    1982-01-01

    Two experimental contact systems were examined and compared to a baseline contact system consisting of evaporated layers of titanium, palladium, and silver and an electroplated layer of copper. The first experimental contact system consisted of evaporated layers of titanium, nickel, and copper and an electroplated layer of copper. This system performed as well as the baseline system in all respects, including its response to temperature stress tests, to a humidity test, and to an accelerated aging test. In addition, the cost of this system is estimated to be only 43 percent of the cost of the baseline system at a production level of 25 MW/year. The second experimental contact system consisted of evaporated layers of nickel and copper and an electroplated layer of copper. Cells with this system show serious degradation in a temperature stress test at 350 C for 30 minutes. Auger electron spectroscopy was used to show that the evaporated nickel layer is not an adequate barrier to copper diffusion even at temperatures as low as 250 C. This fact brings into question the long-term reliability of this contact system.

  5. Cloud Top Scanning radiometer (CTS)

    NASA Technical Reports Server (NTRS)

    1978-01-01

    A scanning radiometer to be used for measuring cloud radiances in each of three spectral regions is described. Significant features incorporated in the Cloud Top Scanner design are: (1) flexibility and growth potential through use of easily replaceable modular detectors and filters; (2) full aperture, multilevel inflight calibration; (3) inherent channel registration through employment of a single shared field stop; and (4) radiometric sensitivity margin in a compact optical design through use of Honeywell developed (Hg,Cd)Te detectors and preamplifiers.

  6. Alternative Fuels Data Center: Contacts

    Science.gov Websites

    this section... Project Assistance News & Features Spanish Resources Contacts Contacts Use these APIs About Project Assistance News & Features Spanish Resources Contacts The AFDC is a resource of

  7. Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer.

    PubMed

    Khun, Kimleang; Ibupoto, Zafar Hussain; AlSalhi, Mohamad S; Atif, Muhammad; Ansari, Anees A; Willander, Magnus

    2013-09-30

    In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices.

  8. Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer

    PubMed Central

    Khun, Kimleang; Ibupoto, Zafar Hussain; AlSalhi, Mohamad S.; Atif, Muhammad; Ansari, Anees A.; Willander, Magnus

    2013-01-01

    In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices. PMID:28788336

  9. Resonant tunneling diodes based on ZnO for quantum cascade structures (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hinkov, Borislav; Schwarz, Benedikt; Harrer, Andreas; Ristanic, Daniela; Schrenk, Werner; Hugues, Maxime; Chauveau, Jean-Michel; Strasser, Gottfried

    2017-02-01

    The terahertz (THz) spectral range (lambda 30µm - 300µm) is also known as the "THz-gap" because of the lack of compact semiconductor devices. Various real-world applications would strongly benefit from such sources like trace-gas spectroscopy or security-screening. A crucial step is the operation of THz-emitting lasers at room temperature. But this seems out of reach with current devices, of which GaAs-based quantum cascade lasers (QCLs) seem to be the most promising ones. They are limited by the parasitic, non-optical LO-phonon transitions (36meV in GaAs), being on the same order as the thermal energy at room temperature (kT = 26meV). This can be solved by using larger LO-phonon materials like ZnO (E_LO = 72meV). But to master the fabrication of ZnO-based QC structures, a high quality epitaxial growth is crucial followed by a well-controlled fabrication process including ZnO/ZnMgO etching. We use devices grown on m-plane ZnO-substrate by molecular beam epitaxy. They are patterned by reactive ion etching in a CH4-based chemistry (CH4:H2:Ar/30:3:3 sccm) into 50μm to 150μm square mesas. Resonant tunneling diode structures are investigated in this geometry and are presented including different barrier- and well-configurations. We extract contact resistances of 8e-5 Omega cm^2 for un-annealed Ti/Au contacts and an electron mobility of above 130cm^2/Vs, both in good agreement with literature. Proving that resonant electron tunneling can be achieved in ZnO is one of the crucial building blocks of a QCL. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 665107.

  10. Mutant p53 perturbs DNA replication checkpoint control through TopBP1 and Treslin.

    PubMed

    Liu, Kang; Lin, Fang-Tsyr; Graves, Joshua D; Lee, Yu-Ju; Lin, Weei-Chin

    2017-05-09

    Accumulating evidence supports the gain-of-function of mutant forms of p53 (mutp53s). However, whether mutp53 directly perturbs the DNA replication checkpoint remains unclear. Previously, we have demonstrated that TopBP1 forms a complex with mutp53s and mediates their gain-of-function through NF-Y and p63/p73. Akt phosphorylates TopBP1 and induces its oligomerization, which inhibits its ATR-activating function. Here we show that various contact and conformational mutp53s bypass Akt to induce TopBP1 oligomerization and attenuate ATR checkpoint response during replication stress. The effect on ATR response caused by mutp53 can be exploited in a synthetic lethality strategy, as depletion of another ATR activator, DNA2, in mutp53-R273H-expressing cancer cells renders cells hypersensitive to cisplatin. Expression of mutp53-R273H also makes cancer cells more sensitive to DNA2 depletion or DNA2 inhibitors. In addition to ATR-activating function during replication stress, TopBP1 interacts with Treslin in a Cdk-dependent manner to initiate DNA replication during normal growth. We find that mutp53 also interferes with TopBP1 replication function. Several contact, but not conformational, mutp53s enhance the interaction between TopBP1 and Treslin and promote DNA replication despite the presence of a Cdk2 inhibitor. Together, these data uncover two distinct mechanisms by which mutp53 enhances DNA replication: ( i ) Both contact and conformational mutp53s can bind TopBP1 and attenuate the checkpoint response to replication stress, and ( ii ) during normal growth, contact (but not conformational) mutp53s can override the Cdk2 requirement to promote replication by facilitating the TopBP1/Treslin interaction.

  11. Cross-contact chain

    NASA Technical Reports Server (NTRS)

    Lieneweg, Udo (Inventor)

    1988-01-01

    A system is provided for use with wafers that include multiple integrated circuits that include two conductive layers in contact at multiple interfaces. Contact chains are formed beside the integrated circuits, each contact chain formed of the same two layers as the circuits, in the form of conductive segments alternating between the upper and lower layers and with the ends of the segments connected in series through interfaces. A current source passes a current through the series-connected segments, by way of a pair of current tabs connected to opposite ends of the series of segments. While the current flows, voltage measurements are taken between each of a plurality of pairs of voltage tabs, the two tabs of each pair connected to opposite ends of an interface that lies along the series-connected segments. A plot of interface conductances on a normal probability chart, enables prediction of the yield of good integrated circuits from the wafer.

  12. Cross-contact chain

    NASA Technical Reports Server (NTRS)

    Lieneweg, U. (Inventor)

    1986-01-01

    A system is provided for use with wafers that include multiple integrated circuits that include two conductive layers in contact at multiple interfaces. Contact chains are formed beside the integrated circuits, each contact chain formed of the same two layers as the circuits, in the form of conductive segments alternating between the upper and lower layers and with the ends of the segments connected in series through interfaces. A current source passes a current through the series-connected segments, by way of a pair of current tabs connected to opposite ends of the series of segments. While the current flows, voltage measurements are taken between each of a plurality of pairs of voltage tabs, the two tabs of each pair connected to opposite ends of an interface that lies along the series-connected segments. A plot of interface conductances on normal probability chart enables prediction of the yield of good integrated circuits from the wafer.

  13. Shoe allergic contact dermatitis.

    PubMed

    Matthys, Erin; Zahir, Amir; Ehrlich, Alison

    2014-01-01

    Foot dermatitis is a widespread condition, affecting men and women of all ages. Because of the location, this condition may present as a debilitating problem to those who have it. Allergic contact dermatitis involving the feet is frequently due to shoes or socks. The allergens that cause shoe dermatitis can be found in any constituent of footwear, including rubber, adhesives, leather, dyes, metals, and medicaments. The goal of treatment is to identify and minimize contact with the offending allergen(s). The lack of product information released from shoe manufacturers and the continually changing trends in footwear present a challenge in treating this condition. The aim of this study is to review the current literature on allergic contact shoe dermatitis; clinical presentation, allergens, patch testing, and management will be discussed. PubMed and MEDLINE databases were used for the search, with a focus on literature updates from the last 15 years.

  14. Acrylate Systemic Contact Dermatitis.

    PubMed

    Sauder, Maxwell B; Pratt, Melanie D

    2015-01-01

    Acrylates, the 2012 American Contact Dermatitis Society allergen of the year, are found in a range of products including the absorbent materials within feminine hygiene pads. When fully polymerized, acrylates are nonimmunogenic; however, if not completely cured, the monomers can be potent allergens.A 28-year-old woman is presented, who had her teeth varnished with Isodan (Septodont, Saint-Maur-des-Fossés, France) containing HEMA (2-hydroxyethyl methacrylate) with no initial reaction. Approximately 1 month later, the patient developed a genital dermatitis secondary to her feminine hygiene pads. The initial reaction resolved, but 5 months later, the patient developed a systemic contact dermatitis after receiving a second varnishing.The patient was dramatically patch test positive to many acrylates. This case demonstrates a reaction to likely unpolymerized acrylates within a feminine hygiene pad, as well as broad cross-reactivity or cosensitivity to acrylates, and possibly a systemic contact dermatitis with systemic re-exposure to unpolymerized acrylates.

  15. Fabrication and photovoltaic properties of ZnO nanorods/perovskite solar cells

    SciTech Connect

    Shirahata, Yasuhiro; Tanaike, Kohei; Akiyama, Tsuyoshi

    2016-02-01

    ZnO nanorods/perovskite solar cells with different lengths of ZnO nanorods were fabricated. The ZnO nanorods were prepared by chemical bath deposition and directly confirmed to be hexagon-shaped nanorods. The lengths of the ZnO nanorads were controlled by deposition condition of ZnO seed layer. Photovoltaic properties of the ZnO nanorods/CH{sub 3}NH{sub 3}PbI{sub 3} solar cells were investigated by measuring current density-voltage characteristics and incident photon to current conversion efficiency. The highest conversion efficiency was obtained in ZnO nanorods/CH{sub 3}NH{sub 3}PbI{sub 3} with the longest ZnO nanorods.

  16. Electrochemical Sensing, Photocatalytic and Biological Activities of ZnO Nanoparticles: Synthesis via Green Chemistry Route

    NASA Astrophysics Data System (ADS)

    Yadav, L. S. Reddy; Archana, B.; Lingaraju, K.; Kavitha, C.; Suresh, D.; Nagabhushana, H.; Nagaraju, G.

    2016-05-01

    In this paper, we have successfully synthesized ZnO nanoparticles (Nps) via solution combustion method using sugarcane juice as the novel fuel. The structure and morphology of the synthesized ZnO Nps have been analyzed using various analytical tools. The synthesized ZnO Nps exhibit excellent photocatalytic activity for the degradation of methylene blue dye, indicating that the ZnO Nps are potential photocatalytic semiconductor materials. The synthesized ZnO Nps also show good electrochemical sensing of dopamine. ZnO Nps exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Eschesichia coli and Staphylococcus aureus using agar well diffusion method. Furthermore, the ZnO Nps show good antioxidant activity by potentially scavenging 1-diphenyl-2-picrylhydrazyl (DPPH) radicals. The above studies clearly demonstrate versatile applications of ZnO synthesized by simple eco-friendly route.

  17. Defect evolution in ZnO and its effect on radiation tolerance.

    PubMed

    Lv, Jinpeng; Li, Xingji

    2018-05-03

    The origin of ZnO radiation resistance is fascinating but still unclear. Herein, we found that radiation tolerance of ZnO can be tuned by engineering intrinsic defects into the ZnO. The role played by native defects in the radiation tolerance of ZnO was systematically explored by carrying out N+ implantation on a set of home-grown ZnO nanocrystals with various lattice defect types and concentrations. Interestingly, decreasing the VO and Zni concentration significantly aggravated N+ radiation damage, indicating the presence of O-deficient defects to be the potential cause of the radiation hardness of ZnO. A similar phenomenon was also observed for H+-implanted ZnO. This work offers a new way to manipulate ZnO and endow it with desired physicochemical properties, and is expected to pave the way for its application in radiative environments.

  18. Arginine-assisted immobilization of silver nanoparticles on ZnO nanorods: an enhanced and reusable antibacterial substrate without human cell cytotoxicity

    NASA Astrophysics Data System (ADS)

    Agnihotri, Shekhar; Bajaj, Geetika; Mukherji, Suparna; Mukherji, Soumyo

    2015-04-01

    Silver-based hybrid nanomaterials are gaining interest as potential alternatives for conventional antimicrobial agents. Herein, we present a simple, facile and eco-friendly approach for the deposition of silver nanoparticles (AgNPs) on ZnO nanorods, which act as a nanoreactor for in situ synthesis and as an immobilizing template in the presence of arginine. The presence of arginine enhanced the stability of ZnO deposition on the glass substrate by hindering the dissolution of zinc under alkaline conditions. Various Ag/ZnO hybrid nanorod (HNR) samples were screened to obtain a high amount of silver immobilization on the ZnO substrate. Ag/ZnO HNRs displayed potent antibacterial ability and could achieve 100% kill for both Escherichia coli and Bacillus subtilis strains under various test conditions. The hybrid material mediated its dual mode of antibacterial action through direct contact-killing and release of silver ions/nanoparticles and showed superior bactericidal performance compared to pure ZnO nanorods and colloidal AgNPs. No significant decline in antibacterial efficacy was observed even after the same substrate was repeatedly reused multiple times. Interestingly, the amount of Ag and Zn release was much below their maximal limit in drinking water, thus preventing potential health hazards. Immobilized AgNPs showed no cytotoxic effects on the human hepatocarcinoma cell line (HepG2). Moreover, treating cells with the antibacterial substrate for 24 hours did not lead to significant generation of reactive oxygen species (ROS). The good biocompatibility and bactericidal efficacy would thus make it feasible to utilize this immobilization strategy for preparing new-generation antibacterial coatings.Silver-based hybrid nanomaterials are gaining interest as potential alternatives for conventional antimicrobial agents. Herein, we present a simple, facile and eco-friendly approach for the deposition of silver nanoparticles (AgNPs) on ZnO nanorods, which act as a

  19. Microstructure of ZnO Thin Films Deposited by High Power Impulse Magnetron Sputtering (Postprint)

    DTIC Science & Technology

    2015-03-01

    AFRL-RX-WP-JA-2015-0185 MICROSTRUCTURE OF ZNO THIN FILMS DEPOSITED BY HIGH POWER IMPULSE MAGNETRON SPUTTERING (POSTPRINT) A. N. Reed...COVERED (From – To) 29 January 2013 – 16 February 2015 4. TITLE AND SUBTITLE MICROSTRUCTURE OF ZNO THIN FILMS DEPOSITED BY HIGH POWER IMPULSE MAGNETRON...ABSTRACT High power impulse magnetron sputtering was used to deposit thin (~100 nm) zinc oxide (ZnO) films from a ceramic ZnO target onto substrates

  20. Effects of Chromium Dopant on Ultraviolet Photoresponsivity of ZnO Nanorods

    NASA Astrophysics Data System (ADS)

    Mokhtari, S.; Safa, S.; Khayatian, A.; Azimirad, R.

    2017-07-01

    Structural and optical properties of bare ZnO nanorods, ZnO-encapsulated ZnO nanorods, and Cr-doped ZnO-encapsulated ZnO nanorods have been investigated. Encapsulated ZnO nanorods were grown using a simple two-stage method in which ZnO nanorods were first grown on a glass substrate directly from a hydrothermal bath, then encapsulated with a thin layer of Cr-doped ZnO by dip coating. Comparative study of x-ray diffraction patterns showed that Cr was successfully incorporated into the shell layer of ZnO nanorods. Moreover, energy-dispersive x-ray spectroscopy confirmed presence of Cr in this sample. It was observed that the thickness of the shell layer around the core of the ZnO nanorods was at least about 20 nm. Transmission electron microscopy of bare ZnO nanorods revealed single-crystalline structure. Based on optical results, both the encapsulation process and addition of Cr dopant decreased the optical bandgap of the samples. Indeed, the optical bandgap values of Cr-doped ZnO-encapsulated ZnO nanorods, ZnO-encapsulated ZnO nanorods, and bare ZnO nanorods were 2.89 eV, 3.15 eV, and 3.34 eV, respectively. The ultraviolet (UV) parameters demonstrated that incorporation of Cr dopant into the shell layer of ZnO nanorods considerably facilitated formation and transportation of photogenerated carriers, optimizing their performance as a practical UV detector. As a result, the photocurrent of the Cr-doped ZnO-encapsulated ZnO nanorods was the highest (0.6 mA), compared with ZnO-encapsulated ZnO nanorods and bare ZnO nanorods (0.21 mA and 0.06 mA, respectively).

  1. Hierarchical Carbon Fibers with ZnO Nanowires for Volatile Sensing in Composite Curing (Postprint)

    DTIC Science & Technology

    2014-07-01

    needed to demonstrate the use of Zinc Oxide (ZnO) nanowire coated carbon fibers as a volatile sensor. ZnO nanowires are demonstrated to function as...processing. For this work, we report on the foundational study needed to demonstrate the use of Zinc Oxide (ZnO) nanowire coated carbon fibers as a...array of ZnO nanowires. Zinc oxide nanowires become more conductive in the presence of ethanol – as analyte sorbs to the surface, electron density

  2. Investigation of ZnO Nanowire Interfaces for Multi-Scale Composites

    DTIC Science & Technology

    2012-03-06

    growth of zinc oxide ( ZnO ) nanowires on the surface of the...through the growth of zinc oxide ( ZnO ) nanowires on the surface of the reinforcing fibers. The nanowires functionally grade the interface, improve bonding...bulk composite. This has been accomplished through the growth of zinc oxide ( ZnO ) nanowires on the surface of the reinforcing fibers. ZnO

  3. Sulfur-Doped Zinc Oxide (ZnO) Nanostars: Synthesis and Simulation of Growth Mechanism

    DTIC Science & Technology

    2011-10-01

    Zinc Oxide ( ZnO ) Nanostars: Synthesis and Simulation of Growth Mechanism Jinhyun Cho1, Qiubao Lin2,3, Sungwoo...characterization, and ab initio simulations of star-shaped hexagonal zinc oxide ( ZnO ) nanowires. The ZnO nanostructures were synthesized by a low...Introduction Zinc oxide ( ZnO ) is a wide bandgap (3.37 eV), Ⅱ–Ⅵ semiconductor of great interest for optoelectronic applications [1–3]. Its

  4. Top quark studies at hadron colliders

    SciTech Connect

    Sinervo, P.K.

    1997-01-01

    The techniques used to study top quarks at hadron colliders are presented. The analyses that discovered the top quark are described, with emphasis on the techniques used to tag b quark jets in candidate events. The most recent measurements of top quark properties by the CDF and DO Collaborations are reviewed, including the top quark cross section, mass, branching fractions, and production properties. Future top quark studies at hadron colliders are discussed, and predictions for event yields and uncertainties in the measurements of top quark properties are presented.

  5. Contact Us | DOepatents

    Science.gov Websites

    ORCID Search Authors Patent Number: Patent Application Number: Contract Number: Subject: Lab/Technology us by phone Phone Phone (865) 241-5275 Contact us in writing Mail U.S. Department of Energy Office of

  6. Compact contacting device

    NASA Technical Reports Server (NTRS)

    Acharya, Arun (Inventor); Gottzmann, Christian F. (Inventor); Lockett, Michael J. (Inventor); Schneider, James S. (Inventor); Victor, Richard A. (Inventor); Zawierucha, Robert (Inventor)

    1994-01-01

    An apparatus comprising a rotatable mass of structured packing for mass or heat transfer between two contacting fluids of different densities wherein the packing mass is made up of corrugated sheets of involute shape relative to the axis of the packing mass and form a logarithmic spiral curved counter to the direction of rotation.

  7. Pizza makers' contact dermatitis.

    PubMed

    Lembo, Serena; Lembo, Claudio; Patruno, Cataldo; Balato, Anna; Balato, Nicola; Ayala, Fabio

    2014-01-01

    Contact eczema to foods, spices, and food additives can occur in occupational and nonoccupational settings in those who grow, handle, prepare, or cook food. Pizza is one of the most eaten foods in every continent, and pizza making is a common work in many countries. We aimed to evaluate the occurrence and the causes of contact dermatitis in pizza makers in Naples. We performed an observational study in 45 pizza makers: all the enrolled subjects had to answer a questionnaire designed to detect personal history of respiratory or cutaneous allergy, atopy; work characteristics and timing were also investigated. Every subject attended the dermatology clinic for a complete skin examination, and when needed, patients were patch tested using the Italian baseline series of haptens integrated with an arbitrary pizza makers series. Our results reported that 13.3% of the enrolled pizza makers (6/45) presented hand eczema, and that 8.9% (4/45) were affected by occupational allergic contact dermatitis. Diallyl disulfide and ammonium persulfate were the responsible substances. Performing patch tests in pizza makers and food handlers affected by hand contact dermatitis is useful. We propose a specific series of haptens for this wide working category.

  8. NWS Marine Contacts

    Science.gov Websites

    ! Boating Safety Beach Hazards Rip Currents Hypothermia Hurricanes Thunderstorms Lightning Coastal Flooding , Verification Richard May 301-427-9378 301-713-1520 FAX richard.may@noaa.gov Coastal Weather, Great Lakes, Ice operational nature relating to near shore and coastal forecasts, contact your local National Weather Service

  9. Multigrid contact detection method

    NASA Astrophysics Data System (ADS)

    He, Kejing; Dong, Shoubin; Zhou, Zhaoyao

    2007-03-01

    Contact detection is a general problem of many physical simulations. This work presents a O(N) multigrid method for general contact detection problems (MGCD). The multigrid idea is integrated with contact detection problems. Both the time complexity and memory consumption of the MGCD are O(N) . Unlike other methods, whose efficiencies are influenced strongly by the object size distribution, the performance of MGCD is insensitive to the object size distribution. We compare the MGCD with the no binary search (NBS) method and the multilevel boxing method in three dimensions for both time complexity and memory consumption. For objects with similar size, the MGCD is as good as the NBS method, both of which outperform the multilevel boxing method regarding memory consumption. For objects with diverse size, the MGCD outperform both the NBS method and the multilevel boxing method. We use the MGCD to solve the contact detection problem for a granular simulation system based on the discrete element method. From this granular simulation, we get the density property of monosize packing and binary packing with size ratio equal to 10. The packing density for monosize particles is 0.636. For binary packing with size ratio equal to 10, when the number of small particles is 300 times as the number of big particles, the maximal packing density 0.824 is achieved.

  10. Have Confidence in Contact

    ERIC Educational Resources Information Center

    Crisp, Richard J.; Turner, Rhiannon N.

    2010-01-01

    In an article in the May-June 2009 "American Psychologist," we discussed a new approach to reducing prejudice and encouraging more positive intergroup relations (Crisp & Turner, 2009). We named the approach imagined intergroup contact and defined it as "the mental simulation of a social interaction with a member or members of an outgroup category"…

  11. [Contact allergies in musicians].

    PubMed

    Gasenzer, E R; Neugebauer, E A M

    2012-12-01

    During the last years, the problem of allergic diseases has increased. Allergies are errant immune responses to a normally harmless substance. In musicians the allergic contact dermatitis to exotic woods is a special problem. Exotic rosewood contains new flavonoids, which trigger an allergic reaction after permanent contact with the instrument. High quality woodwind instruments such as baroque flute or clarinets are made in ebony or palisander because of its great sound. Today instruments for non-professional players are also made in these exotic materials and non-professionals may have the risk to develop contact dermatitis, too. Brass-player has the risk of an allergic reaction to the different metals contained in the metal sheets of modern flutes and brass instruments. Specially nickel and brass alloys are used to product flute tubes or brass instruments. Special problem arises in children: patients who are allergic to plants or foods have a high risk to develop contact dermatitis. Parents don't know the materials of low-priced instruments for beginners. Often unknown cheap woods from exotic areas are used. Low-priced brass instruments contain high amount of brass and other cheap metals. Physicians should advice musician-patients or parents about the risks of the different materials and look for the reason of eczema on mouth, face, or hands. © Georg Thieme Verlag KG Stuttgart · New York.

  12. Contact laser microsurgery.

    PubMed

    Jallo, George I; Kothbauer, Karl F; Epstein, Fred J

    2002-07-01

    Lasers are commonly understood as instruments that produce a freestanding light beam that can cut or vaporize tissue. In contrast, a contact laser is an instrument where the laser beam resides entirely within a coated sapphire crystal probe tip. The authors describe the use of the contact laser for a variety of intraspinal procedures. The probe is mounted on a curved handpiece and can be used in the same way as any microsurgical instrument. The laser energy is delivered only at the probe tip and only on contact of the tip with tissue. Different probe sizes and shapes allow for sharp cutting or tissue vaporization with minimal tissue penetration. We have used this laser in 95 operations for dysraphic conditions, and intradural (both intra- and extramedullary) spinal tumors. It was easy to use for the microsurgically trained neurosurgeon. It is safer than a freestanding, noncontact, laser beam. To lyse scar tissue, evaporate lipomatous tissue, perform a precise myelotomy, and dissect, cut and debulk firm and fibrous intradural spinal lesions this instrument is superior to microscissors, suction, or the ultrasonic aspirator. The contact laser is a useful microsurgical instrument for use in neurosurgery. It combines the advantages of lasers with those of microinstruments and avoids most shortcomings of both.

  13. Contact: Releasing the news

    NASA Astrophysics Data System (ADS)

    Pinotti, Roberto

    The problem of mass behavior after man's future contacts with other intelligences in the universe is not only a challenge for social scientists and political leaders all over the world, but also a cultural time bomb as well. In fact, since the impact of CETI (Contact with Extraterrestrial Intelligence) on human civilization, with its different cultures, might cause a serious socio-anthropological shock, a common and predetermined worldwide strategy is necessary in releasing the news after the contact, in order to keep possible manifestations of fear, panic and hysteria under control. An analysis of past studies in this field and of parallel historical situations as analogs suggests a definite "authority crisis" in the public as a direct consequence of an unexpected release of the news, involving a devastating "chain reaction" process (from both the psychological and sociological viewpoints) of anomie and maybe the collapse of today's society. The only way to prevent all this is to prepare the world's public opinion concerning contact before releasing the news, and to develop a long-term strategy through the combined efforts of scientists, political leaders, intelligence agencies and the mass media, in order to create the cultural conditions in which a confrontation with ETI won't affect mankind in a traumatic way. Definite roles and tasks in this multi-level model are suggested.

  14. Lubrication Of Nonconformal Contacts

    NASA Technical Reports Server (NTRS)

    Jeng, Yeau-Ren

    1991-01-01

    Report discusses advances in knowledge of lubrication of nonconformal contacts in bearings and other machine elements. Reviews previous developments in theory of lubrication, presents advances in theory of lubrication to determine minimum film thickness, and describes experiments designed to investigate one of regimes of lubrication for ball bearings.

  15. Contact Lenses on Submarines

    DTIC Science & Technology

    1985-04-29

    speculate why no medical eye problems occurred. There are two possible reasons. One is the degree of patient education and adherence to instructions...Management of this situation can only be accomplished through continuing patient education . Contact lens wearers should also be aware of the problem

  16. Disproportionate Minority Contact.

    PubMed

    Fix, Rebecca L; Cyperski, Melissa A; Burkhart, Barry R

    2017-04-01

    The overrepresentation of racial/ethnic minorities within the criminal justice system relative to their population percentage, a phenomenon termed disproportionate minority contact, has been examined within general adult and adolescent offender populations; yet few studies have tested whether this phenomenon extends to juvenile sexual offenders (JSOs). In addition, few studies have examined whether offender race/ethnicity influences registration and notification requirements, which JSOs are subject to in some U.S. states. The present study assessed for disproportionate minority contact among general delinquent offenders and JSOs, meaning it aimed to test whether the criminal justice system treats those accused of sexual and non-sexual offenses differently by racial/ethnic group. Furthermore, racial/ethnic group differences in risk, legal classification, and sexual offending were examined for JSOs. Results indicated disproportionate minority contact was present among juveniles with non-sexual offenses and JSOs in Alabama. In addition, offense category and risk scores differed between African American and European American JSOs. Finally, registration classifications were predicted by offending characteristics, but not race/ethnicity. Implications and future directions regarding disproportionate minority contact among JSOs and social and legal policy affecting JSOs are discussed.

  17. Fermilab | Contact Fermilab

    Science.gov Websites

    Book Newsroom Newsroom News and features Press releases Photo gallery Fact sheets and brochures Media Tevatron experiments Tevatron operation Shutdown process For the media Video of shutdown event Guest book Cookies Quick Links Home Contact Phone Book Fermilab at Work For Industry Jobs Interact Facebook Twitter

  18. [Current contact allergens].

    PubMed

    Geier, J; Uter, W; Lessmann, H; Schnuch, A

    2011-10-01

    Ever-changing exposure to contact allergens, partly due to statutory directives (e.g. nickel, chromate, methyldibromo glutaronitrile) or recommendations from industrial associations (e.g. hydroxyisohexyl 3-cyclohexene carboxaldehyde), requires on-going epidemiologic surveillance of contact allergy. In this paper, the current state with special focus in fragrances and preservatives is described on the basis of data of the Information Network of Departments of Dermatology (IVDK) of the year 2010. In 2010, 12,574 patients were patch tested in the dermatology departments belonging to the IVDK. Nickel is still the most frequent contact allergen. However the continuously improved EU nickel directive already has some beneficial effect; sensitization frequency in young women is dropping. In Germany, chromate-reduced cement has been in use now for several years, leading to a decline in chromate sensitization in brick-layers. Two fragrance mixes are part of the German baseline series; they are still relevant. The most important fragrances in these mixes still are oak moss absolute and hydroxyisohexyl 3-cyclohexene carboxaldehyde. However, in relation to these leading allergens, sensitization frequency to other fragrances contained in the mixes seems to be increasing. Among the preservatives, MCI/MI has not lost its importance as contact allergen, in contrast to MDBGN. Sources of MCI/MI sensitization obviously are increasingly found in occupational context. Methylisothiazolinone is a significant allergen in occupational settings, and less frequently in body care products.

  19. Contact activation: a revision.

    PubMed

    Schmaier, A H

    1997-07-01

    In conclusion, a revised view of the contact system has been presented. This system has little to do with the initiation of hemostasis. Like lupus anticoagulants, deficiencies of contact proteins give prolonged APTTs but may be risk factors for thrombosis. BK from kininogens is a potent modulator of vascular biology inducing vasodilation, tissue plasminogen activator release, and prostacyclin liberation. Kininogens, themselves, are selective inhibitors of alpha-thrombin-induced platelet activation preventing alpha-thrombin from cleaving the cloned thrombin receptor after arginine41. Kininogens' alpha-thrombin inhibitory activity exists in intact kininogens, BK, and all of BK's breakdown products. HK also is the pivotal protein for contact protein assembly on endothelium. It is the receptor for prekallikrein which when bound to HK becomes activated to kallikrein by an endothelial cell enzyme system independent of activated forms of plasma factor XII. Prekallikrein activation on endothelial cells results in kinetically favorable single chain urokinase and plasminogen activation. Thus the "physiologic, negatively charged surface" for contact system activation is really the assembly of these proteins on cell membranes and activation by membrane-associated enzymes.

  20. Enhanced ultraviolet photo-response in Dy doped ZnO thin film

    NASA Astrophysics Data System (ADS)

    Kumar, Pawan; Singh, Ranveer; Pandey, Praveen C.

    2018-02-01

    In the present work, a Dy doped ZnO thin film deposited by the spin coating method has been studied for its potential application in a ZnO based UV detector. The investigations on the structural property and surface morphology of the thin film ensure that the prepared samples are crystalline and exhibit a hexagonal crystal structure of ZnO. A small change in crystallite size has been observed due to Dy doping in ZnO. AFM analysis ascertains the grain growth and smooth surface of the thin films. The Dy doped ZnO thin film exhibits a significant enhancement in UV region absorption as compared to the pure ZnO thin film, which suggests that Dy doped ZnO can be used as a UV detector. Under UV irradiation of wavelength 325 nm, the photocurrent value of Dy doped ZnO is 105.54 μA at 4.5 V, which is 31 times greater than that of the un-doped ZnO thin film (3.39 μA). The calculated value of responsivity is found to increase significantly due to the incorporation of Dy in the ZnO lattice. The observed higher value of photocurrent and responsivity could be attributed to the substitution of Dy in the ZnO lattice, which enhances the conductivity, electron mobility, and defects in ZnO and benefits the UV sensing property.

  1. Gd{sup 3+} incorporated ZnO nanoparticles: A versatile material

    SciTech Connect

    Kumar, Surender, E-mail: surender40@gmail.com; Sahare, P.D.

    Graphical abstract: - Highlights: • Chemically synthesized Gd{sup 3+} doped ZnO nanoparticles. • The broad visible emission of the ZnO is dependent on the surface defects and can be tailored by Gd{sup 3+} doing. • PL and magnetic properties are modified by Gd{sup 3+} doping. • Photocatalysis experiment reveals that the ZnO: Gd{sup 3+} degrades the Rh B dye faster than the undoped ZnO. - Abstract: Gd{sup 3+} doped ZnO nanoparticles are synthesized by wet chemical route method and investigated through structural, optical, magnetic and photocatalytic properties. Transmission Electron Microscopy technique has been performed on undoped and Gd{sup 3+} dopedmore » ZnO nanoparticles. X-ray diffraction, X-ray photoelectron spectroscopy and Raman analyses are carried out in order to examine the desired phase formation and substitution of Gd{sup 3+} in the ZnO matrix. Gd{sup 3+} doped ZnO nanoparticles show enhanced photoluminescent and ferromagnetic properties as compared to undoped ZnO. The broad visible emission of ZnO is found to be largely dependent on the surface defects and these surface defects can be tailored by Gd{sup 3+} doping concentration. Furthermore, Gd{sup 3+} doped ZnO nanoparticles also show improved photocatalytic properties as compared with undoped ZnO nanoparticles under ultraviolet irradiation.« less

  2. Al-doped ZnO seed layer-dependent crystallographic control of ZnO nanorods by using electrochemical deposition

    SciTech Connect

    Son, Hyo-Soo; Choi, Nak-Jung; Kim, Kyoung-Bo

    Highlights: • Polar and semipolar ZnO NRs were successfully achieved by hydrothermal synthesis. • Semipolar and polar ZnO NRs were grown on ZnO and AZO/m-sapphire, respectively. • Al % of AZO/m-sapphire enhanced the lateral growth rate of polar ZnO NRs. - Abstract: We investigated the effect of an Al-doped ZnO film on the crystallographic direction of ZnO nanorods (NRs) using electrochemical deposition. From high-solution X-ray diffraction measurements, the crystallographic plane of ZnO NRs grown on (1 0 0) ZnO/m-plane sapphire was (1 0 1). The surface grain size of the (100) Al-doped ZnO (AZO) film decreased with increasing Al contentmore » in the ZnO seed layer, implying that the Al dopant accelerated the three-dimensional (3D) growth of the AZO film. In addition, it was found that with increasing Al doping concentration of the AZO seed layer, the crystal orientation of the ZnO NRs grown on the AZO seed layer changed from [1 0 1] to [0 0 1]. With increasing Al content of the nonpolar (1 0 0) AZO seed layer, the small surface grains with a few crystallographic planes of the AZO film changed from semipolar (1 0 1) ZnO NRs to polar (0 0 1) ZnO NRs due to the increase of the vertical [0 0 1] growth rate of the ZnO NRs owing to excellent electrical properties.« less

  3. HUBBLE'S TOP TEN GRAVITATIONAL LENSES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The NASA Hubble Space Telescope serendipitous survey of the sky has uncovered exotic patterns, rings, arcs and crosses that are all optical mirages produced by a gravitational lens, nature's equivalent of having giant magnifying glass in space. Shown are the top 10 lens candidates uncovered in the deepest 100 Hubble fields. Hubble's sensitivity and high resolution allow it to see faint and distant lenses that cannot be detected with ground-based telescopes whose images are blurred by Earth's atmosphere. [Top Left] - HST 01248+0351 is a lensed pair on either side of the edge-on disk lensing galaxy. [Top Center] - HST 01247+0352 is another pair of bluer lensed source images around the red spherical elliptical lensing galaxy. Two much fainter images can be seen near the detection limit which might make this a quadruple system. [Top Right] - HST 15433+5352 is a very good lens candidate with a bluer lensed source in the form of an extended arc about the redder elliptical lensing galaxy. [Middle Far Left] - HST 16302+8230 could be an 'Einstein ring' and the most intriguing lens candidate. It has been nicknamed the 'the London Underground' since it resembles that logo. [Middle Near Left] - HST 14176+5226 is the first, and brightest lens system discovered in 1995 with the Hubble telescope. This lens candidate has now been confirmed spectroscopically using large ground-based telescopes. The elliptical lensing galaxy is located 7 billion light-years away, and the lensed quasar is about 11 billion light-years distant. [Middle Near Right] - HST 12531-2914 is the second quadruple lens candidate discovered with Hubble. It is similar to the first, but appears smaller and fainter. [Middle Far Right] - HST 14164+5215 is a pair of bluish lensed images symmetrically placed around a brighter, redder galaxy. [Bottom Left] - HST 16309+8230 is an edge-on disk-like galaxy (blue arc) which has been significantly distorted by the redder lensing elliptical galaxy. [Bottom Center] - HST 12368

  4. Surface modification of oxygen-deficient ZnO nanotubes by interstitially incorporated carbon: a superior photocatalytic platform for sustainable water and surface treatments

    NASA Astrophysics Data System (ADS)

    Ninnora Meethal, Bhabhina; Ramanarayanan, Rajita; Swaminathan, Sindhu

    2018-05-01

    An interesting architecture of robust, highly reproducible, template-free synthesis of phase pure carbon-incorporated short ZnO nanotubes through polymer assisted sol-gel method is presented here. These nanotubes exhibit enormous surface oxygen vacancies and mid bandgap levels confirmed by X-ray photoelectron spectroscopy. These carbon-modified nanotubes exhibit encouraging results in photocatalytic studies, as there is a 16% greater degradation of contaminant dye than in the pristine ZnO nanotube. The reactive oxygen species generated from the photocatalysts were experimentally confirmed and quantified. Super hydrophilic nature renders these nanotubes suitable for antifogging application as observed from contact angle measurements. Characterisation and mechanism of a competent material with improved photoresponse, promising greater energy efficiency and anti-fog have been described in this investigation.

  5. Nanoporous structures on ZnO thin films

    NASA Astrophysics Data System (ADS)

    Gür, Emre; Kılıç, Bayram; Coşkun, C.; Tüzemen, S.; Bayrakçeken, Fatma

    2010-01-01

    Porous structures were formed on ZnO thin films which were grown by an electrochemical deposition (ECD) method. The growth processes were carried out in a solution of dimethylsulfoxide (DMSO) zinc perchlorate, Zn(ClO 4) 2, at 120 ∘C on indium tin oxide (ITO) substrates. Optical and structural characterizations of electrochemically grown ZnO thin films have shown that the films possess high (0002) c-axis orientation, high nucleation, high intensity and low FWHM of UV emission at the band edge region and a sharp UV absorption edge. Nanoporous structures were formed via self-assembled monolayers (SAMs) of hexanethiol (C 6SH) and dodecanethiol (C 12SH). Scanning electron microscope (SEM) measurements showed that while a nanoporous structure (pore radius 20 nm) is formed on the ZnO thin films by hexanathiol solution, a macroporous structure (pore radius 360 nm) is formed by dodecanethiol solution. No significant variation is observed in X-ray diffraction (XRD) measurements on the ZnO thin films after pore formation. However, photoluminescence (PL) measurements showed that green emission is observed as the dominant emission for the macroporous structures, while no variation is observed for the thin film nanoporous ZnO sample.

  6. Chemical Sensing Applications of ZnO Nanomaterials

    PubMed Central

    Chaudhary, Savita; Umar, Ahmad; Bhasin, K. K.

    2018-01-01

    Recent advancement in nanoscience and nanotechnology has witnessed numerous triumphs of zinc oxide (ZnO) nanomaterials due to their various exotic and multifunctional properties and wide applications. As a remarkable and functional material, ZnO has attracted extensive scientific and technological attention, as it combines different properties such as high specific surface area, biocompatibility, electrochemical activities, chemical and photochemical stability, high-electron communicating features, non-toxicity, ease of syntheses, and so on. Because of its various interesting properties, ZnO nanomaterials have been used for various applications ranging from electronics to optoelectronics, sensing to biomedical and environmental applications. Further, due to the high electrochemical activities and electron communication features, ZnO nanomaterials are considered as excellent candidates for electrochemical sensors. The present review meticulously introduces the current advancements of ZnO nanomaterial-based chemical sensors. Various operational factors such as the effect of size, morphologies, compositions and their respective working mechanisms along with the selectivity, sensitivity, detection limit, stability, etc., are discussed in this article. PMID:29439528

  7. Hydrogen-Induced Plastic Deformation in ZnO

    NASA Astrophysics Data System (ADS)

    Lukáč, F.; Čížek, J.; Vlček, M.; Procházka, I.; Anwand, W.; Brauer, G.; Traeger, F.; Rogalla, D.; Becker, H.-W.

    In the present work hydrothermally grown ZnO single crystals covered with Pd over-layer were electrochemically loaded with hydrogen and the influence of hydrogen on ZnO micro structure was investigated by positron annihilation spectroscopy (PAS). Nuclear reaction analysis (NRA) was employed for determination of depth profile of hydrogen concentration in the sample. NRA measurements confirmed that a substantial amount of hydrogen was introduced into ZnO by electrochemical charging. The bulk hydrogen concentration in ZnO determined by NRA agrees well with the concentration estimated from the transported charge using the Faraday's law. Moreover, a subsurface region with enhanced hydrogen concentration was found in the loaded crystals. Slow positron implantation spectroscopy (SPIS) investigations of hydrogen-loaded crystal revealed enhanced concentration of defects in the subsurface region. This testifies hydrogen-induced plastic deformation of the loaded crystal. Absorbed hydrogen causes a significant lattice expansion. At low hydrogen concentrations this expansion is accommodated by elastic straining, but at higher concentrations hydrogen-induced stress exceeds the yield stress in ZnO and plastic deformation of the loaded crystal takes place. Enhanced hydrogen concentration detected in the subsurface region by NRA is, therefore, due to excess hydrogen trapped at open volume defects introduced by plastic deformation. Moreover, it was found that hydrogen-induced plastic deformation in the subsurface layer leads to typical surface modification: formation of hexagonal shape pyramids on the surface due to hydrogen-induced slip in the [0001] direction.

  8. The thermodynamic activity of ZnO in silicate melts

    NASA Astrophysics Data System (ADS)

    Reyes, R. A.; Gaskell, D. R.

    1983-12-01

    The activity of ZnO in ZnO-SiO2 and CaO-ZnO-SiO2 melts has been measured at 1560 °C using a transpiration technique with CO-CO2 mixtures as the carrier gas. The activities of ZnO in dilute solution in 42 wt pct SiO2-38 wt pct CaO-20 wt pct A12O3 in the range 1400° to 1550 °C and in 62 wt pct SiO2-23.3 wt pct CaO-14.7 wt pct A12O3 at 1550 °C have also been measured. The measured free energies of formation of ZnO-SiO2 melts are significantly more negative than published estimated values and this, together with the behavior observed in the system CaO-Al2O3-SiO2, indicate that ZnO is a relatively basic oxide. The results are discussed in terms of the polymerization model of binary silicate melts and ideal silicate mixing in ternary silicate melts. The behavior of ZnO in dilute solution in CaO-Al2O3-SiO2 melts is discussed in terms of the possibility of the fluxing of ZnO by iron blast furnace slags.

  9. Confocal Raman microscopy of one dimensional ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Singamaneni, Srikanth; Gupta, Maneesh; Yang, Rusen; Wang, Zhong; Tsukruk, Vladimir

    2009-03-01

    ZnO nanostructures with various shapes (vertically aligned nanorods, nanobelts, nanohelixes, nanorings) have been synthesized using both vapor phase and solution growth methods. In the simplest example of a nanobelt, the fast growth direction can be either (21 1 0) or (011 0) or (0001). Here, we show that confocal Raman microscopy can be employed as a fast and nondestructive analytical technique to identify the crystal planes and reveal the relative orientation of the ZnO nanostructure. Various features of the Raman spectrum of ZnO nanostructures (presence of the A1(TO) mode, width of the E2 mode) were found to be sensitive to relative orientation of the incident source laser and the crystal plane. Furthermore, owing to the optical anisotropy of ZnO, Raman scattering from the substrate is modulated (either enhanced or suppressed with respect to the background) depending on the polarization of the incident light with respect to orientation of the nanobelt. The results presented here describe a novel method to nondestructively identify the growth, relative orientation, and the waveguiding properties of the ZnO nanostructures.

  10. Results on top-quark physics and top-quark-like signatures by CMS

    NASA Astrophysics Data System (ADS)

    Chabert, Eric; CMS Collaboration

    2017-07-01

    This report reviews the results obtained by the CMS Collaboration on top quark physics, focusing on the latest ones based on p-p collisions provided by the LHC at \\sqrt{s}=13{{TeV}} during Run II. It covers measurements of single-top, top quark pairs and associated productions as well as measurements of top quark properties. Finally several beyond the standard model searches involving top quark in the final states are presented, such as searches for supersymmetry in the third generation, heavy resonances decaying into a top quark pair, or dark matter produced in association to a single-top or a top quark pair.

  11. Computational Fluid Dynamic Modeling of Zinc Slag Fuming Process in Top-Submerged Lance Smelting Furnace

    NASA Astrophysics Data System (ADS)

    Huda, Nazmul; Naser, Jamal; Brooks, Geoffrey; Reuter, Markus A.; Matusewicz, Robert W.

    2012-02-01

    Slag fuming is a reductive treatment process for molten zinciferous slags for extracting zinc in the form of metal vapor by injecting or adding a reductant source such as pulverized coal or lump coal and natural gas. A computational fluid dynamic (CFD) model was developed to study the zinc slag fuming process from imperial smelting furnace (ISF) slag in a top-submerged lance furnace and to investigate the details of fluid flow, reaction kinetics, and heat transfer in the furnace. The model integrates combustion phenomena and chemical reactions with the heat, mass, and momentum interfacial interaction between the phases present in the system. A commercial CFD package AVL Fire 2009.2 (AVL, Graz, Austria) coupled with a number of user-defined subroutines in FORTRAN programming language were used to develop the model. The model is based on three-dimensional (3-D) Eulerian multiphase flow approach, and it predicts the velocity and temperature field of the molten slag bath, generated turbulence, and vortex and plume shape at the lance tip. The model also predicts the mass fractions of slag and gaseous components inside the furnace. The model predicted that the percent of ZnO in the slag bath decreases linearly with time and is consistent broadly with the experimental data. The zinc fuming rate from the slag bath predicted by the model was validated through macrostep validation process against the experimental study of Waladan et al. The model results predicted that the rate of ZnO reduction is controlled by the mass transfer of ZnO from the bulk slag to slag-gas interface and rate of gas-carbon reaction for the specified simulation time studied. Although the model is based on zinc slag fuming, the basic approach could be expanded or applied for the CFD analysis of analogous systems.

  12. [News on occupational contact dermatitis].

    PubMed

    Crépy, Marie-Noëlle; Bensefa-Colas, Lynda

    2014-03-01

    Contact dermatitis--irritant contact dermatitis, allergic contact dermatitis and protein contact dermatitis--are the most common occupational skin diseases, most often localized to the hands. Contact urticaria is rarer The main occupational irritants are wet work, detergents and disinfectants, cutting oils, and solvents. The main occupational allergens are rubber additives, metals (chromium, nickel, cobalt), plastics (epoxy resins, acrylic), biocides and plants. Diagnosis is based on clinical examination, medical history and allergy testing. For a number of irritating or sensitizing agents, irritant or allergic dermatitis can be notified as occupational diseases. The two main prevention measures are reducing skin contact with irritants and complete avoidance of skin contact with offending allergens.

  13. Contact Graph Routing

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.

    2011-01-01

    Contact Graph Routing (CGR) is a dynamic routing system that computes routes through a time-varying topology of scheduled communication contacts in a network based on the DTN (Delay-Tolerant Networking) architecture. It is designed to enable dynamic selection of data transmission routes in a space network based on DTN. This dynamic responsiveness in route computation should be significantly more effective and less expensive than static routing, increasing total data return while at the same time reducing mission operations cost and risk. The basic strategy of CGR is to take advantage of the fact that, since flight mission communication operations are planned in detail, the communication routes between any pair of bundle agents in a population of nodes that have all been informed of one another's plans can be inferred from those plans rather than discovered via dialogue (which is impractical over long one-way-light-time space links). Messages that convey this planning information are used to construct contact graphs (time-varying models of network connectivity) from which CGR automatically computes efficient routes for bundles. Automatic route selection increases the flexibility and resilience of the space network, simplifying cross-support and reducing mission management costs. Note that there are no routing tables in Contact Graph Routing. The best route for a bundle destined for a given node may routinely be different from the best route for a different bundle destined for the same node, depending on bundle priority, bundle expiration time, and changes in the current lengths of transmission queues for neighboring nodes; routes must be computed individually for each bundle, from the Bundle Protocol agent's current network connectivity model for the bundle s destination node (the contact graph). Clearly this places a premium on optimizing the implementation of the route computation algorithm. The scalability of CGR to very large networks remains a research topic

  14. Assembly and installation of the Belle II TOP detector

    NASA Astrophysics Data System (ADS)

    Suzuki, Kazuhito; Belle II TOP Group

    2017-12-01

    The Time-of-Propagation (TOP) detector is a new type of ring-imaging Cherenkov detector developed for particle identification in the barrel region of the Belle II spectrometer. In the assembly and installation, it is crucial for the detector performance to achieve precision alignment and secure gluing of the optical components as well as to mechanically support them managing the stress, attitude, optical and electrical contacts, and limited installation space. Various efforts were made to develop the procedures and jigs along with the development of the mechanical structure. Such efforts accomplished the assembly and installation in April and May 2016, respectively, without a significant incident.

  15. Fabrication of ZnO and doped ZnO waveguides deposited by Spin Coating

    NASA Astrophysics Data System (ADS)

    Mohan, Rosmin Elsa; R, Neha P.; T, Shalu; C, Darshana K.; Sreelatha, K. S.

    2015-02-01

    In this paper, the synthesis of ZnO and doped Zn1-xAgxO (where x=0.03) nanoparticles by co- precipitation is reported. The precursors used were Zinc Nitrate and Potassium hydroxide pellets. For doping, 3% AgNO3 in ZnNO3 was considered as a separate buffer solution. The prepared nanoparticles were subsequently spin coated onto silica glass substrates at a constant chuck rate of 3000 rpm. The substrate acts as the lower cladding of a waveguide structure. The upper cladding is assumed to be air in the present investigation. The nanostructures of the ZnO powders in the doped and undoped cases were studied using X-ray Diffraction patterns. There was a decrease in the grain size with doping which increase the tunability of the powders to be used as photoluminescent devices. The optical characteristics of the sample were also investigated using UV-Visible spectrophotometer at 200-900 nm wavelengths. The photoluminescence peaks also report a dramatic increase in intensity at the same wavelength for the doped case compared to the undoped one.

  16. In Praise of Top-Down Leadership

    ERIC Educational Resources Information Center

    Dufour, Richard

    2007-01-01

    In the ongoing debate of the efficacy of top-down versus bottom-up strategies to improve school districts, top-down is clearly losing. Many district leaders are reluctant to champion improvement for fear of being labeled with the epithet "top-down leader," the unkindest cut of all. In this article, the author presents the change…

  17. Contact dynamics math model

    NASA Technical Reports Server (NTRS)

    Glaese, John R.; Tobbe, Patrick A.

    1986-01-01

    The Space Station Mechanism Test Bed consists of a hydraulically driven, computer controlled six degree of freedom (DOF) motion system with which docking, berthing, and other mechanisms can be evaluated. Measured contact forces and moments are provided to the simulation host computer to enable representation of orbital contact dynamics. This report describes the development of a generalized math model which represents the relative motion between two rigid orbiting vehicles. The model allows motion in six DOF for each body, with no vehicle size limitation. The rotational and translational equations of motion are derived. The method used to transform the forces and moments from the sensor location to the vehicles' centers of mass is also explained. Two math models of docking mechanisms, a simple translational spring and the Remote Manipulator System end effector, are presented along with simulation results. The translational spring model is used in an attempt to verify the simulation with compensated hardware in the loop results.

  18. Contact stress sensor

    DOEpatents

    Kotovsky, Jack

    2014-02-11

    A method for producing a contact stress sensor that includes one or more MEMS fabricated sensor elements, where each sensor element of includes a thin non-recessed portion, a recessed portion and a pressure sensitive element adjacent to the recessed portion. An electric circuit is connected to the pressure sensitive element. The circuit includes a pressure signal circuit element configured to provide a signal upon movement of the pressure sensitive element.

  19. Contact stress sensor

    DOEpatents

    Kotovsky, Jack [Oakland, CA

    2012-02-07

    A contact stress sensor includes one or more MEMS fabricated sensor elements, where each sensor element of includes a thin non-recessed portion, a recessed portion and a pressure sensitive element adjacent to the recessed portion. An electric circuit is connected to the pressure sensitive element. The circuit includes a thermal compensator and a pressure signal circuit element configured to provide a signal upon movement of the pressure sensitive element.

  20. Occupational protein contact dermatitis.

    PubMed

    Barbaud, Annick; Poreaux, Claire; Penven, Emmanuelle; Waton, Julie

    2015-01-01

    Occupational contact dermatitis is generally caused by haptens but can also be induced by proteins causing mainly immunological contact urticaria (ICU); chronic hand eczema in the context of protein contact dermatitis (PCD). In a monocentric retrospective study, from our database, only 31 (0.41%) of patients with contact dermatitis had positive skin tests with proteins: 22 had occupational PCD, 3 had non-occupational PCD, 5 occupational ICU and 1 cook had a neutrophilic fixed food eruption (NFFE) due to fish. From these results and analysis of literature, the characteristics of PCD can be summarized as follows. It is a chronic eczematous dermatitis, possibly exacerbated by work, suggestive if associated with inflammatory perionyxix and immediate erythema with pruritis, to be investigated when the patient resumes work after a period of interruption. Prick tests with the suspected protein-containing material are essential, as patch tests have negative results. In case of multisensitisation revealed by prick tests, it is advisable to analyse IgE against recombinant allergens. A history of atopy, found in 56 to 68% of the patients, has to be checked for. Most of the cases are observed among food-handlers but PCD can also be due to non-edible plants, latex, hydrolysed proteins or animal proteins. Occupational exposure to proteins can thus lead to the development of ICU. Reflecting hypersensitivity to very low concentrations of allergens, investigating ICU therefore requires caution and prick tests should be performed with a diluted form of the causative protein-containing product. Causes are food, especially fruit peel, non-edible plants, cosmetic products, latex, animals.

  1. [Contact allergy to dexpanthenol].

    PubMed

    Keilig, W

    1987-01-01

    A case report is given of a 56-year-old female patient with a postthrombotic leg ulcer and stasis dermatitis, in whom contact dermatitis to a dexpanthenol-containing ointment was first described in 1965. Recent allergy testing confirmed this finding and revealed positive reactions to the pure substance dexpanthenol as well as to two additives. Based on this case history the importance of dexpanthenol as an allergen is discussed.

  2. Contact dermatitis in children.

    PubMed

    Rademaker, M; Forsyth, A

    1989-02-01

    125 children under the age of 12 years were patch tested over a period of 7 years. 60 (48%) of the children had 1 or more positive (+ve) reactions, of which 92% (55/60) were considered relevant. The most common allergens were metals (35 + ves), fragrances (24 + ves) and rubber compounds (11 + ves). 40 of the children were also tested for contact urticaria against food additives and fragrances, of whom 20 were positive (benzoic acid 14, cinnamaldehyde 12).

  3. Effect of Water on Ethanol Conversion over ZnO

    SciTech Connect

    Rahman, Muhammad Mahfuzur; Davidson, Stephen D.; Sun, Junming

    2015-10-01

    This work focuses on understanding the role of water on ethanol conversion over zinc oxide (ZnO). It was found that a competitive adsorption between ethanol and water occurs on ZnO, which leads to the blockage of the strong Lewis acid site by water on ZnO. As a result, both dehydration and dehydrogenation reactions are inhibited. However, the extent of inhibition for dehydration is orders of magnitude higher than that for dehydrogenation, leading to the shift of reaction pathway from ethanol dehydration to dehydrogenation. In the secondary reactions for acetaldehyde conversion, water inhibits the acetaldehyde aldol-condensation to crotonaldehyde, favoring the oxidationmore » of acetaldehyde to acetic acid, and then to acetone via ketonization at high temperature (i.e., 400 °C).« less

  4. Mobility of indium on the ZnO(0001) surface

    SciTech Connect

    Heinhold, R.; Reeves, R. J.; Allen, M. W.

    2015-02-02

    The mobility of indium on the Zn-polar (0001) surface of single crystal ZnO wafers was investigated using real-time x-ray photoelectron spectroscopy. A sudden transition in the wettability of the ZnO(0001) surface was observed at ∼520 °C, with indium migrating from the (0001{sup ¯}) underside of the wafer, around the non-polar (11{sup ¯}00) and (112{sup ¯}0) sidewalls, to form a uniform self-organized (∼20 Å) adlayer. The In adlayer was oxidized, in agreement with the first principles calculations of Northrup and Neugebauer that In{sub 2}O{sub 3} precipitation can only be avoided under a combination of In-rich and Zn-rich conditions. These findings suggest that unintentionalmore » In adlayers may form during the epitaxial growth of ZnO on indium-bonded substrates.« less

  5. Synthesis and characterization of Ni doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Tamgadge, Y. S.; Gedam, P. P.; Ganorkar, R. P.; Mahure, M. A.; Pahurkar, V. G.; Muley, G. G.

    2018-05-01

    In this paper, we present synthesis of L-valine assisted surface modification of Ni doped ZnO nanoparticles (NPs) using chemical precipitation method. Samples were calcined at 500oC for 2h. Uncalcined and calcined samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet-visible (UV-vis) spectroscopy. Ni doped ZnO NPs with average particle size of 8 nm have been successfully obtained using L-valine as surface modifying agent. Increase in the particle size was observed after the calcination. XRD and TEM studies confirmed the purity, surface morphology and hexagonal wurtzite crystal structure of ZnO NPs. UV-vis spectroscopy indicated the blue shift of excitons absorption wavelength and surface modification by L-valine.

  6. ZnO nanodisk based UV detectors with printed electrodes.

    PubMed

    Alenezi, Mohammad R; Alshammari, Abdullah S; Alzanki, Talal H; Jarowski, Peter; Henley, Simon John; Silva, S Ravi P

    2014-04-08

    The fabrication of highly functional materials for practical devices requires a deep understanding of the association between morphological and structural properties and applications. A controlled hydrothermal method to produce single crystal ZnO hexagonal nanodisks, nanorings, and nanoroses using a mixed solution of zinc sulfate (ZnSO4) and hexamethylenetetramine (HMTA) without the need of catalysts, substrates, or templates at low temperature (75 °C) is introduced. Metal-semiconductor-metal (MSM) ultraviolet (UV) detectors were fabricated based on individual and multiple single-crystal zinc oxide (ZnO) hexagonal nanodisks. High quality single crystal individual nanodisk devices were fabricated with inkjet-printed silver electrodes. The detectors fabricated show record photoresponsivity (3300 A/W) and external quantum efficiency (1.2 × 10(4)), which we attribute to the absence of grain boundaries in the single crystal ZnO nanodisk and the polarity of its exposed surface.

  7. Curcumin: A Contact Allergen.

    PubMed

    Chaudhari, Soham P; Tam, Alison Y; Barr, Jason A

    2015-11-01

    Herbal medicines are used by thousands of patients all over the world. However, they can often cause adverse effects. Turmeric, made from the root of Curcuma, longa, is a yellow spice used throughout South Asia for its flavor as well as for its medicinal properties. Curcumin is the main ingredient in turmeric. It is known for downregulating the expression of various proinflammatory cytokines and has been studied for its antiinflammatory mechanism. However, it has also been reported to cause contact dermatitis. Kumkum, a turmeric-based powder applied by Hindu women on their foreheads, has also been found as an allergen. The authors have reviewed the anti-inflammatory properties of curcumin and reports of contact dermatitis to understand the possible harmful effects of this commonly used spice, while also examining its beneficial role in dermatologic conditions. They aim to increase awareness regarding this common herb and its prevalent use not only in South Asia, but also in North America. A thorough literature search of the PubMed database was conducted to identify studies that examined the antiinflammatory role of curcumin and its role in contact dermatitis. Eleven studies demonstrate that although curcumin does have antiinflammatory properties, it is an allergen. Curcumin has many valuable properties that can be exploited to treat dermatologic conditions. However, patients and dermatologists must be keen of possible allergic reactions. Further studies are needed to completely understand this widely used herb and its efficacy in dermatology.

  8. Systemic Contact Dermatitis.

    PubMed

    Aquino, Marcella; Rosner, Greg

    2018-05-15

    Systemic contact dermatitis (SCD) traditionally refers to a skin condition where an individual who is cutaneously sensitized to an allergen will subsequently react to that same allergen or a cross reacting allergen via a different route. It occurs to allergens including metals, medications, and foods. The exact pathophysiology underlying this disease remains unknown, although it appears to be mediated by type 4 hypersensitivity reactions and possibly type 3 hypersensitivity reactions. The p-I concept (pharmacologic interaction with immunoreceptors) hypothesized that drugs are able to bind directly to a T cell receptor without first being presented by MHC (major histocompatibility complex) molecules and without prior metabolism, which would help explain why SCD can be seen on first exposure to medications. Nomenclature remains a challenge as SCD can be subcategorized using terms such as ACDS (allergic contact dermatitis syndrome) and its four clinical stages, Baboon syndrome, and SDRIFE (symmetrical drug-related intertriginous and flexural exanthema), which share many overlapping features. Food allergens may be responsible for uncontrolled or persistent symptoms in patients with contact dermatitis who do not respond to topical avoidance. With medications, symptoms may be induced by topical application versus systemic administration. Patch testing (PT) may be beneficial in diagnosing SCD caused by metals and many topical medications including corticosteroids, antimicrobials (ampicillin, bacitracin, erythromycin, neomycin, nystatin), NSAIDs (diclofenac, ibuprofen), anesthetics, and antihistamines (chlorphenamine, piperazine). Current treatment options include topical steroids and oral antihistamines for symptom relief and dietary avoidance to causative foods or metals.

  9. Low temperature synthesis of hexagonal ZnO nanorods and their hydrogen sensing properties

    NASA Astrophysics Data System (ADS)

    Qurashi, Ahsanulhaq; Faiz, M.; Tabet, N.; Alam, Mir Waqas

    2011-08-01

    The growth of hexagonal ZnO nanorods was demonstrated by low temperature chemical synthesis approach. X-ray diffraction (XRD) analysis revealed a wurtzite hexagonal structure of the ZnO nanorods. The optical properties were measured by UV-vis spectrophotometer at room temperature. X-ray photoelectron spectroscopy (XPS) confirmed high purity of the ZnO nanorods. The hydrogen sensor made of the ZnO nanorods showed reversible response. The hydrogen gas tests were carried out in presence of ambient air and the influence of operation temperature on the hydrogen gas sensing property of ZnO nanorods was also investigated.

  10. Effect of bath temperature on surface morphology and photocatalytic activity of ZnO nanorods

    SciTech Connect

    Sriharan, N.; Senthil, T. S., E-mail: tssenthi@gmail.com; Muthukumarasamy, N.

    2016-05-06

    ZnO nanorods were prepared by using simple hydrothermal method using four different bath temperatures. All the prepared ZnO nanorods are annealed at 450°C and are characterized by using various techniques such as X-ray diffraction, UV spectra and scanning electron microscopy. Photocatalytic activity of the prepared ZnO nanorods is analyzed. A novel photocatalytic reactor designed with ZnO nanorods prepared at 90°C shows enhanced catalytic efficiency. The role of light irradiation time, bath temperature and surface morphology of the ZnO nanorods on the performance of photocatalytic reaction is analyzed.

  11. Growth of ZnO nanorods on glass substrate deposited using dip coating method

    NASA Astrophysics Data System (ADS)

    Rani, Rozina Abdul; Ghafar, Safiah Ab; Zoolfakar, Ahmad Sabirin; Rusop, M.

    2018-05-01

    ZnO unique properties make it attractive for electronics and optoelectronics application. There are varieties synthesis of ZnO nanostructure but one of the best ways is by using dip coating method due to its simplicity, low cost and reliability. This research investigated the effect of precursor concentration on the morphology of ZnO nanorods using dip coating technique. ZnO nanorods is synthesized by using zinc nitrate as precursor and glass slide as substrate. The morphology of ZnO is characterized using Field Emission Scanning Electron Microscope (FESEM). By using different concentration of precursor, each outcome demonstrated diverse morphologies.

  12. Surface potential driven dissolution phenomena of [0 0 0 1]-oriented ZnO nanorods grown from ZnO and Pt seed layers

    NASA Astrophysics Data System (ADS)

    Seo, Youngmi; Kim, Jung Hyeun

    2011-06-01

    Highly oriented ZnO nanorods are synthesized hydrothermally on ZnO and Pt seed layers, and they are dissolved in KOH solution. The rods grown on ZnO seed layer show uniform dissolution, but those grown on Pt seed layer are rod-selectively dissolved. The ZnO nanorods from both seed layers show the same crystalline structure through XRD and Raman spectrometer data. However, the surface potential analysis reveals big difference for ZnO and Pt seed cases. The surface potential distribution is very uniform for the ZnO seed case, but it is much fluctuated on the Pt seed case. It suggests that the rod-selective dissolution phenomena on Pt seed case are likely due to the surface energy difference.

  13. Investigation and characterization of ZnO single crystal microtubes

    SciTech Connect

    Al-Naser, Qusay A.H.; Zhou, Jian, E-mail: jianzhou@whut.edu.cn; Liu, Guizhen

    2016-04-15

    Morphological, structural, and optical characterization of microwave synthesized ZnO single crystal microtubes were investigated in this work. The structure and morphology of the ZnO microtubes are characterized using X-ray diffraction (XRD), single crystal diffraction (SCD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The results reveal that the as-synthesized ZnO microtube has a highly regular hexagonal cross section and smooth surfaces with an average length of 650–700 μm, an average outer diameter of 50 μm and wall thickness of 1–3 μm, possessing a single crystal wurtzite hexagonal structure. Optical properties of ZnOmore » single crystal microtubes were investigated by photoluminescence (PL) and ultraviolet-visible (UV-vis) absorption techniques. Room-temperature PL spectrum of the microtube reveal a strong UV emission peak at around 375.89 nm and broad and a weak visible emission with a main peak identified at 577 nm, which was assigned to the nearest band-edge emission and the deep-level emission, respectively. The band gap energy of ZnO microtube was found to be 3.27 eV. - Highlights: • ZnO microtube length of 650–700 μm, diameter of 50 μm, wall thickness of 1–3 μm • ZnO microtube possesses a single crystal wurtzite hexagonal structure. • The crystal system is hexahedral oriented along a-axis with indices of (100). • A strong and sharp UV emission at 375.89 nm (3.29 eV) • One prominent absorption band around 378.88 nm (3.27 eV)« less

  14. Photoluminescence of Sequential Infiltration Synthesized ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Ocola, Leonidas; Gosztola, David; Yanguas-Gil, Angel; Connolly, Aine

    We have investigated a variation of atomic layer deposition (ALD), called sequential infiltration synthesis (SiS), as an alternate method to incorporate ZnO and other oxides inside polymethylmethacrylate (PMMA) and other polymers. Energy dispersive spectroscopy (EDS) results show that we synthesize ZnO up to 300 nm inside a PMMA film. Photoluminescence data on a PMMA film shows that we achieve a factor of 400X increase in photoluminescence (PL) intensity when comparing a blank Si sample and a 270 nm thick PMMA film, where both were treated with the same 12 alternating cycles of H2O and diethyl zinc (DEZ). PMMA is a well-known ebeam resist. We can expose and develop patterns useful for photonics or sensing applications first, and then convert them afterwards into a hybrid polymer-oxide material. We show that patterning does indeed affect the photoluminescence signature of native ZnO. We demonstrate we can track the growth of the ZnO inside the PMMA polymer using both photoluminescence and Raman spectroscopy and determine the point in the process where ZnO is first photoluminescent and also at which point ZnO first exhibits long range order in the polymer. This work was supported by the Department of Energy under Contract No. DE-AC02-06CH11357. Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

  15. Measurements of top quark properties at CDF

    SciTech Connect

    Kraan, Aafke C.; /Pennsylvania U.

    The top quark with its mass of about 172 GeV/c{sup 2} is the most massive fundamental particle observed by experiment. In this talk they highlight the most recent measurements of several top quark properties performed with the CDF detector based on data samples corresponding to integrated luminosities up to 1 fb{sup -1}. These results include a search for top quark pair production via new massive resonances, measurements of the helicity of the W boson from top-quark decay, and a direct limit on the lifetime of the top quark.

  16. Top Quark Studies at D0

    SciTech Connect

    Peters, Reinhild Yvonne

    2014-11-26

    Years after its discovery in 1995 by CDF and D0, the top quark still undergoes intense investigations at the Tevatron. Using up to the full Run II data sample, new measurements of top quark production and properties by the D0 Collaboration are presented. In particular, the first observation of single top quark s-channel production, the measurement of differential tbar t distributions, forward-backward tbar t asymmetry, a new measurement of the top quark mass, and a measurement of the top quark charge are discussed.

  17. Comparative study of ZnO nanorods and thin films for chemical and biosensing applications and the development of ZnO nanorods based potentiometric strontium ion sensor

    NASA Astrophysics Data System (ADS)

    Khun, K.; Ibupoto, Z. H.; Chey, C. O.; Lu, Jun.; Nur, O.; Willander, M.

    2013-03-01

    In this study, the comparative study of ZnO nanorods and ZnO thin films were performed regarding the chemical and biosensing properties and also ZnO nanorods based strontium ion sensor is proposed. ZnO nanorods were grown on gold coated glass substrates by the hydrothermal growth method and the ZnO thin films were deposited by electro deposition technique. ZnO nanorods and thin films were characterised by field emission electron microscopy [FESEM] and X-ray diffraction [XRD] techniques and this study has shown that the grown nanostructures are highly dense, uniform and exhibited good crystal quality. Moreover, transmission electron microscopy [TEM] was used to investigate the quality of ZnO thin film and we observed that ZnO thin film was comprised of nano clusters. ZnO nanorods and thin films were functionalised with selective strontium ionophore salicylaldehyde thiosemicarbazone [ST] membrane, galactose oxidase, and lactate oxidase for the detection of strontium ion, galactose and L-lactic acid, respectively. The electrochemical response of both ZnO nanorods and thin films sensor devices was measured by using the potentiometric method. The strontium ion sensor has exhibited good characteristics with a sensitivity of 28.65 ± 0.52 mV/decade, for a wide range of concentrations from 1.00 × 10-6 to 5.00 × 10-2 M, selectivity, reproducibility, stability and fast response time of 10.00 s. The proposed strontium ion sensor was used as indicator electrode in the potentiometric titration of strontium ion versus ethylenediamine tetra acetic acid [EDTA]. This comparative study has shown that ZnO nanorods possessed better performance with high sensitivity and low limit of detection due to high surface area to volume ratio as compared to the flat surface of ZnO thin films.

  18. Nanostructured ZnO films on stainless steel are highly safe and effective for antimicrobial applications.

    PubMed

    Shim, Kyudae; Abdellatif, Mohamed; Choi, Eunsoo; Kim, Dongkyun

    2017-04-01

    The safety and effectiveness of antimicrobial ZnO films must be established for general applications. In this study, the antimicrobial activity, skin irritation, elution behavior, and mechanical properties of nanostructured ZnO films on stainless steel were evaluated. ZnO nanoparticle (NP) and ZnO nanowall (NW) structures were prepared with different surface roughnesses, wettability, and concentrations using an RF magnetron sputtering system. The thicknesses of ZnO NP and ZnO NW were approximately 300 and 620 nm, respectively, and ZnO NW had two diffraction directions of [0002] and [01-10] based on high-resolution transmission electron microscopy. The ZnO NW structure demonstrated 99.9% antimicrobial inhibition against Escherichia coli, Staphylococcus aureus, and Penicillium funiculosum, and no skin irritation was detected using experimental rabbits. Approximately 27.2 ± 3.0 μg L -1 Zn ions were eluted from the ZnO NW film at 100 °C for 24 h, which satisfies the WHO guidelines for drinking water quality. Furthermore, the Vickers hardness and fracture toughness of ZnO NW films on stainless steel were enhanced by 11 and 14% compared to those of the parent stainless steel. Based on these results, ZnO NW films on STS316L sheets are useful for household supplies, such as water pipes, faucets, and stainless steel containers.

  19. [Sport injuries in full contact and semi-contact karate].

    PubMed

    Greier, K; Riechelmann, H; Ziemska, J

    2014-03-01

    Karate enjoys great popularity both in professional and recreational sports and can be classified into full, half and low contact styles. The aim of this study was the analysis of sports injuries in Kyokushinkai (full contact) and traditional Karate (semi-contact). In a retrospective study design, 215 active amateur karateka (114 full contact, 101 semi-contact) were interviewed by means of a standardised questionnaire regarding typical sport injuries during the last 36 months. Injuries were categorised into severity grade I (not requiring medical treatment), grade II (single medical treatment), grade III (several outpatient medical treatments) and grade IV (requiring hospitalisation). In total, 217 injuries were reported in detail. 125 injuries (58%) occurred in full contact and 92 (42%) in semi-contact karate. The time related injury rate of full contact karateka was 1.9/1000 h compared to 1.3/1000 h of semi-contact karateka (p < 0.05). The most common types of injuries were musculoskeletal contusions (33% full contact, 20% semi-contact), followed by articular sprains with 19% and 16%. The lower extremity was affected twice as often in full contact (40%) as in semi-contact (20%) karate. Training injuries were reported by 80% of the full contact and 77% of the semi-contact karateka. Most injuries, both in training and competition, occurred in kumite. 75% of the reported injuries of full contact and 70% of semi-contact karateka were classified as low grade (I or II). The high rate of injuries during training and kumite (sparring) points to specific prevention goals. The emphasis should be put on proprioceptive training and consistent warm-up. In the actual competition the referees play a vital role regarding prevention. © Georg Thieme Verlag KG Stuttgart · New York.

  20. Investigation of Excitonic Polaritons in ZnO Microcavities

    DTIC Science & Technology

    2006-07-28

    defects on the nonradiative processes in L-MBE ZnO were studied using time-resolved PL making a connection with the results of positron annihilation...IMPLANTATION DEPTH (nm) S PA R A M E T E R POSITRON ENERGY (keV) 150010005003001000 0 5 10 15 20 25 30 0.42 0.44 0.46 0.48 0.50 ZnO single crystal 0.42...photoluminescence (TRPL) and monoenergetic positron annihilation methods, and elimination of point defects as a fundamental pathway in improving

  1. Nature of native defects in ZnO.

    PubMed

    Selim, F A; Weber, M H; Solodovnikov, D; Lynn, K G

    2007-08-24

    This study revealed the nature of native defects and their roles in ZnO through positron annihilation and optical transmission measurements. It showed oxygen vacancies are the origin for the shift in the optical absorption band that causes the red or orange coloration. It also revealed experimental evidence that the donor nature of oxygen vacancy is approximately 0.7 eV. In addition, this work showed the Zn interstitial was not the donor in the as-grown ZnO and supported recent calculations that predicted hydrogen in an oxygen vacancy forms multicenter bonds and acts as a shallow donor.

  2. Fabrication of highly efficient ZnO nanoscintillators

    NASA Astrophysics Data System (ADS)

    Procházková, Lenka; Gbur, Tomáš; Čuba, Václav; Jarý, Vítězslav; Nikl, Martin

    2015-09-01

    Photo-induced synthesis of high-efficiency ultrafast nanoparticle scintillators of ZnO was demonstrated. Controlled doping with Ga(III) and La(III) ions together with the optimized method of ZnO synthesis and subsequent two-step annealing in air and under reducing atmosphere allow to achieve very high intensity of UV exciton luminescence, up to 750% of BGO intensity magnitude. Fabricated nanoparticles feature extremely short sub-nanosecond photoluminescence decay times. Temperature dependence of the photoluminescence spectrum within 8-340 K range was investigated and shows the absence of visible defect-related emission within all temperature intervals.

  3. Permanent bending and alignment of ZnO nanowires.

    PubMed

    Borschel, Christian; Spindler, Susann; Lerose, Damiana; Bochmann, Arne; Christiansen, Silke H; Nietzsche, Sandor; Oertel, Michael; Ronning, Carsten

    2011-05-06

    Ion beams can be used to permanently bend and re-align nanowires after growth. We have irradiated ZnO nanowires with energetic ions, achieving bending and alignment in different directions. Not only the bending of single nanowires is studied in detail, but also the simultaneous alignment of large ensembles of ZnO nanowires. Computer simulations reveal how the bending is initiated by ion beam induced damage. Detailed structural characterization identifies dislocations to relax stresses and make the bending and alignment permanent, even surviving annealing procedures.

  4. Dual contact pogo pin assembly

    DOEpatents

    Hatch, Stephen McGarry

    2015-01-20

    A contact assembly includes a base and a pair of electrical contacts supported by the base. A first end of the first electrical contact corresponds to a first end of the base and is configured to engage a first external conductive circuit element. A first end of the second electrical contact also corresponds to the first end of the base and is configured to engage a second external conductive circuit element. The first contact and the second contact are electrically isolated from one another and configured to compress when engaging an external connector element. The base includes an aperture positioned on a second end of the base outboard of a second end of the first and second electrical contacts. The aperture presents a narrowing shape with a wide mouth distal the electrical contacts and a narrow internal through-hole proximate the electrical contacts.

  5. Dual contact pogo pin assembly

    DOEpatents

    Hatch, Stephen McGarry

    2016-06-21

    A contact assembly includes a base and a pair of electrical contacts supported by the base. A first end of the first electrical contact corresponds to a first end of the base and is configured to engage a first external conductive circuit element. A first end of the second electrical contact also corresponds to the first end of the base and is configured to engage a second external conductive circuit element. The first contact and the second contact are electrically isolated from one another and configured to compress when engaging an external connector element. The base includes an aperture positioned on a second end of the base outboard of a second end of the first and second electrical contacts. The aperture presents a narrowing shape with a wide mouth distal the electrical contacts and a narrow internal through-hole proximate the electrical contacts.

  6. Table-top job analysis

    SciTech Connect

    Not Available

    1994-12-01

    The purpose of this Handbook is to establish general training program guidelines for training personnel in developing training for operation, maintenance, and technical support personnel at Department of Energy (DOE) nuclear facilities. TTJA is not the only method of job analysis; however, when conducted properly TTJA can be cost effective, efficient, and self-validating, and represents an effective method of defining job requirements. The table-top job analysis is suggested in the DOE Training Accreditation Program manuals as an acceptable alternative to traditional methods of analyzing job requirements. DOE 5480-20A strongly endorses and recommends it as the preferred method for analyzing jobsmore » for positions addressed by the Order.« less

  7. Top down electroweak dipole operators

    NASA Astrophysics Data System (ADS)

    Fuyuto, Kaori; Ramsey-Musolf, Michael

    2018-06-01

    We derive present constraints on, and prospective sensitivity to, the electric dipole moment (EDM) of the top quark (dt) implied by searches for the EDMs of the electron and nucleons. Above the electroweak scale v, the dt arises from two gauge invariant operators generated at a scale Λ ≫ v that also mix with the light fermion EDMs under renormalization group evolution at two-loop order. Bounds on the EDMs of first generation fermion systems thus imply bounds on |dt |. Working in the leading log-squared approximation, we find that the present upper bound on |dt | is 10-19 e cm for Λ = 1 TeV, except in regions of finely tuned cancellations that allow for |dt | to be up to fifty times larger. Future de and dn probes may yield an order of magnitude increase in dt sensitivity, while inclusion of a prospective proton EDM search may lead to an additional increase in reach.

  8. Electronic Transport Properties of One Dimensional Zno Nanowires Studied Using Maximally-Localized Wannier Functions

    NASA Astrophysics Data System (ADS)

    Sun, Xu; Gu, Yousong; Wang, Xueqiang

    2012-08-01

    One dimensional ZnO NWs with different diameters and lengths have been investigated using density functional theory (DFT) and Maximally Localized Wannier Functions (MLWFs). It is found that ZnO NWs are direct band gap semiconductors and there exist a turn on voltage for observable current. ZnO nanowires with different diameters and lengths show distinctive turn-on voltage thresholds in I-V characteristics curves. The diameters of ZnO NWs are greatly influent the transport properties of ZnO NWs. For the ZnO NW with large diameter that has more states and higher transmission coefficients leads to narrow band gap and low turn on voltage. In the case of thinner diameters, the length of ZnO NW can effects the electron tunneling and longer supercell lead to higher turn on voltage.

  9. Elemental, morphological, structural, optical, and magnetic properties of erbium doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Poornaprakash, B.; Chalapathi, U.; Purusottam Reddy, B.; Prabhakar Vattikuti, S. V.; Siva Pratap Reddy, M.; Park, Si-Hyun

    2018-03-01

    The sensible tuning of the structural, optical, and magnetic properties of ZnO nanoparticles (NPs) with suitable doping can enhance their applicability in diverse fields. In this study, we synthesized ZnO NPs with Er (0-4 at%) doping and their elemental, structural, optical, and magnetic properties were studied. Both field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) studies of the suspensions consist of hexagonal shaped NPs. All the prepared NPs exhibited hexagonal phase as demonstrated by powder x-ray diffraction studies. A blue shift was observed in the Er doped ZnO NPs compared to pure ZnO, indicating the increased optical bandgap. Vibrating sample magnetometer studies exhibited the pure ZnO NPs was typical diamagnetic feature whereas all the Er doped ZnO NPs were paramagnetic feature at 300 K. This is the first paramagnetic report on Er doped ZnO NPs.

  10. Nanostructured ZnO - its challenging properties and potential for device applications

    NASA Astrophysics Data System (ADS)

    Dimova-Malinovska, D.

    2017-01-01

    Nanostructured ZnO possessing interesting structural and optical properties offers challenging opportunities for innovative applications. In this lecture the review of the optical and structural properties of ZnO nanostructured layers is presented. It is shown that they have a direct impact on the parameters of devices involving ZnO. An analysis of current trends in the photovoltaic (PV) field shows that improved light harvesting and efficiency of solar cells can be obtained by implementing nanostructured ZnO layers to process advanced solar cell structures. Because of amenability to doping, high chemical stability, sensitivity to different adsorbed gases, nontoxicity and low cost ZnO attracted much attention for application as gas sensors. The sensitivity of nano-grain ZnO gas elements is comparatively high because of the grain-size effect. Application of nanostructured ZnO for gas sensors and for increasing of light harvesting in solar cells is demonstrated.

  11. Stability of Contact Lines in Fluids: 2D Stokes Flow

    NASA Astrophysics Data System (ADS)

    Guo, Yan; Tice, Ian

    2018-02-01

    In an effort to study the stability of contact lines in fluids, we consider the dynamics of an incompressible viscous Stokes fluid evolving in a two-dimensional open-top vessel under the influence of gravity. This is a free boundary problem: the interface between the fluid in the vessel and the air above (modeled by a trivial fluid) is free to move and experiences capillary forces. The three-phase interface where the fluid, air, and solid vessel wall meet is known as a contact point, and the angle formed between the free interface and the vessel is called the contact angle. We consider a model of this problem that allows for fully dynamic contact points and angles. We develop a scheme of a priori estimates for the model, which then allow us to show that for initial data sufficiently close to equilibrium, the model admits global solutions that decay to equilibrium exponentially quickly.

  12. Vertical growth of ZnO nanorods on ZnO seeded FTO substrate for dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Marimuthu, T.; Anandhan, N.

    2018-04-01

    Zinc oxide (ZnO) nanorods (NRs) were electrochemically grown on fluorine doped tin oxide (FTO) and ZnO seeded FTO substrates. X-ray diffraction (XRD) patterns, Raman spectra and photoluminescence (PL) spectra reveal that the hexagonal wurtzite structured ZnO grown on a seeded FTO substrate has a high crystallinity, crystal quality and less atomic defects. Felid emission scanning electron microscope (FE-SEM) images display a high growth density of NRs grown on seeded FTO substrate compared to NRs grown on FTO substrate. The efficiency of the DSSCs based on NRs grown on FTO and seeded FTO substrates is 0.85 and 1.52 %, respectively. UV-Vis absorption spectra and electrochemical impedance spectra depict that the NRs grown on seeded FTO photoanode have higher dye absorption and charge recombination resistance than that of the NRs grown on FTO substrate.

  13. Study of ZnO and Mg doped ZnO nanoparticles by sol-gel process

    SciTech Connect

    Ansari, Mohd Meenhaz, E-mail: meenhazphysics@gmail.com; Arshad, Mohd; Tripathi, Pushpendra

    Nano-crystalline undoped and Mg doped ZnO (Mg-ZnO) nanoparticles with compositional formula Mg{sub x}Zn{sub 1-x}O (x=0,1,3,5,7,10 and 12 %) were synthesized using sol-gel process. The XRD diffraction peaks match with the pattern of the standard hexagonal structure of ZnO that reveals the formation of hexagonal wurtzite structure in all samples. SEM images demonstrates clearly the formation of spherical ZnO nanoparticles, and change of the morphology of the nanoparticles with the concentration of the magnesium, which is in close agreement with that estimated by Scherer formula based on the XRD pattern. To investigate the doping effect on optical properties, the UV–VIS absorptionmore » spectra was obtained and the band gap of the samples calculated.« less

  14. In vitro antibacterial activity of ZnO and Nd doped ZnO nanoparticles against ESBL producing Escherichia coli and Klebsiella pneumoniae

    NASA Astrophysics Data System (ADS)

    Hameed, Abdulrahman Syedahamed Haja; Karthikeyan, Chandrasekaran; Ahamed, Abdulazees Parveez; Thajuddin, Nooruddin; Alharbi, Naiyf S.; Alharbi, Sulaiman Ali; Ravi, Ganasan

    2016-04-01

    Pure ZnO and Neodymium (Nd) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure. From FESEM studies, ZnO and Nd doped ZnO NPs showed nanorod and nanoflower like morphology respectively. The FT-IR spectra confirmed the Zn-O stretching bands at 422 and 451 cm-1 for ZnO and Nd doped ZnO NPs respectively. From the UV-VIS spectroscopic measurement, the excitonic peaks were found around 373 nm and 380 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of ten different bands due to zinc vacancies, oxygen vacancies and surface defects. The antibacterial studies performed against extended spectrum β-lactamases (ESBLs) producing strains of Escherichia coli and Klebsiella pneumoniae showed that the Nd doped ZnO NPs possessed a greater antibacterial effect than the pure ZnO NPs. From confocal laser scanning microscopic (CLSM) analysis, the apoptotic nature of the cells was confirmed by the cell shrinkage, disorganization of cell wall and cell membrane and dead cell of the bacteria. SEM analysis revealed the existence of bacterial loss of viability due to an impairment of cell membrane integrity, which was highly consistent with the damage of cell walls.

  15. In vitro antibacterial activity of ZnO and Nd doped ZnO nanoparticles against ESBL producing Escherichia coli and Klebsiella pneumoniae

    PubMed Central

    Hameed, Abdulrahman Syedahamed Haja; Karthikeyan, Chandrasekaran; Ahamed, Abdulazees Parveez; Thajuddin, Nooruddin; Alharbi, Naiyf S.; Alharbi, Sulaiman Ali; Ravi, Ganasan

    2016-01-01

    Pure ZnO and Neodymium (Nd) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure. From FESEM studies, ZnO and Nd doped ZnO NPs showed nanorod and nanoflower like morphology respectively. The FT-IR spectra confirmed the Zn-O stretching bands at 422 and 451 cm−1 for ZnO and Nd doped ZnO NPs respectively. From the UV-VIS spectroscopic measurement, the excitonic peaks were found around 373 nm and 380 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of ten different bands due to zinc vacancies, oxygen vacancies and surface defects. The antibacterial studies performed against extended spectrum β-lactamases (ESBLs) producing strains of Escherichia coli and Klebsiella pneumoniae showed that the Nd doped ZnO NPs possessed a greater antibacterial effect than the pure ZnO NPs. From confocal laser scanning microscopic (CLSM) analysis, the apoptotic nature of the cells was confirmed by the cell shrinkage, disorganization of cell wall and cell membrane and dead cell of the bacteria. SEM analysis revealed the existence of bacterial loss of viability due to an impairment of cell membrane integrity, which was highly consistent with the damage of cell walls. PMID:27071382

  16. An elastic-plastic contact model for line contact structures

    NASA Astrophysics Data System (ADS)

    Zhu, Haibin; Zhao, Yingtao; He, Zhifeng; Zhang, Ruinan; Ma, Shaopeng

    2018-06-01

    Although numerical simulation tools are now very powerful, the development of analytical models is very important for the prediction of the mechanical behaviour of line contact structures for deeply understanding contact problems and engineering applications. For the line contact structures widely used in the engineering field, few analytical models are available for predicting the mechanical behaviour when the structures deform plastically, as the classic Hertz's theory would be invalid. Thus, the present study proposed an elastic-plastic model for line contact structures based on the understanding of the yield mechanism. A mathematical expression describing the global relationship between load history and contact width evolution of line contact structures was obtained. The proposed model was verified through an actual line contact test and a corresponding numerical simulation. The results confirmed that this model can be used to accurately predict the elastic-plastic mechanical behaviour of a line contact structure.

  17. Structural studies of ZnO nanostructures by varying the deposition parameters

    NASA Astrophysics Data System (ADS)

    Yunus, S. H. A.; Sahdan, M. Z.; Ichimura, M.; Supee, A.; Rahim, S.

    2017-01-01

    The effect of Zinc Oxide (ZnO) thin film on the growth of ZnO nanorods (NRs) was investigated. The structures of ZnO NRs were synthesized by chemical bath deposition (CBD) method in aqueous solution of N2O6Zn.6H2O and C6H12N4 at 90°C of deposition temperature. One of the ZnO NRs samples was deposited on a ZnO seed layer coated on a glass substrate to investigate the properties of ZnO NRs without receiving effect of other materials. Next, for diode application, the ZnO NRs was deposited on tin monosulfide (SnS) coated on indium-tin-oxide (ITO) coated glass substrate (SnS/ITO). The next, the ZnO structural properties were studied from surface morphology, X-ray diffractometer (XRD) spectra, and chemical composition by using field emission scanning electron microscope (FESEM), XRD and energy dispersive X-ray Spectroscopy (EDX). The growth of ZnO NRs on ZnO seed layer was investigated by ZnO seed layer condition while the growth of ZnO NRs on SnS/ITO was investigated by deposition time and deposition temperature parameters. From FESEM images, aligned ZnO NRs were obtained, and the diameters of ZnO NRs were 0.024-3.94 µm. The SnS thin film was affected by the diameter of ZnO NRs which are the ZnO NRs grow on SnS thin films has a larger diameter compared to ZnO NRs grow on ZnO seed layer. Besides that, all of ZnO peaks observed from XRD corresponding to the wurzite structure and preferentially oriented along the c-axis. In addition, EDX shows a high composition of zinc (Zn) and oxygen (O) signals, which indicated that the NRs are indeed made up of Zn and O.

  18. CONFOLD2: improved contact-driven ab initio protein structure modeling.

    PubMed

    Adhikari, Badri; Cheng, Jianlin

    2018-01-25

    Contact-guided protein structure prediction methods are becoming more and more successful because of the latest advances in residue-residue contact prediction. To support contact-driven structure prediction, effective tools that can quickly build tertiary structural models of good quality from predicted contacts need to be developed. We develop an improved contact-driven protein modelling method, CONFOLD2, and study how it may be effectively used for ab initio protein structure prediction with predicted contacts as input. It builds models using various subsets of input contacts to explore the fold space under the guidance of a soft square energy function, and then clusters the models to obtain the top five models. CONFOLD2 obtains an average reconstruction accuracy of 0.57 TM-score for the 150 proteins in the PSICOV contact prediction dataset. When benchmarked on the CASP11 contacts predicted using CONSIP2 and CASP12 contacts predicted using Raptor-X, CONFOLD2 achieves a mean TM-score of 0.41 on both datasets. CONFOLD2 allows to quickly generate top five structural models for a protein sequence when its secondary structures and contacts predictions at hand. The source code of CONFOLD2 is publicly available at https://github.com/multicom-toolbox/CONFOLD2/ .

  19. In vitro degradation of ZnO flowered coated Zn-Mg alloys in simulated physiological conditions.

    PubMed

    Alves, Marta M; Prosek, Tomas; Santos, Catarina F; Montemor, Maria F

    2017-01-01

    Flowered coatings composed by ZnO crystals were successfully electrodeposited on Zn-Mg alloys. The distinct coatings morphologies were found to be dependent upon the solid interfaces distribution, with the smaller number of bigger flowers (ø 46μm) obtained on Zn-Mg alloy containing 1wt.% Mg (Zn-1Mg) contrasting with the higher number of smaller flowers (ø 38μm) achieved on Zn-Mg alloy with 2wt.% Mg (Zn-2Mg). To assess the in vitro behaviour of these novel resorbable materials, a detailed evaluation of the degradation behaviour, in simulated physiological conditions, was performed by electrochemical impedance spectroscopy (EIS). The opposite behaviours observed in the corrosion resistances resulted in the build-up of distinct corrosion layers. The products forming these layers, preferentially detected at the flowers, were identified and their spatial distribution disclosed by EDS and Raman spectroscopy techniques. The presence of smithsonite, simonkolleite, hydrozincite, skorpionite and hydroxyapatite were assigned to both corrosion layers. However the distinct spatial distributions depicted may impact the biocompatibility of these resorbable materials, with the bone analogue compounds (hydroxyapatite and skorpionite) depicted in-between the ZnO crystals and on the top corrosion layer of Zn-1Mg flowers clearly contrasting with the hindered layer formed at the interface of the substrate with the flowers on Zn-2Mg. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Electrochemical synthesis of one-dimensional ZnO nanostructures on ZnO seed layer for DSSC applications

    NASA Astrophysics Data System (ADS)

    Marimuthu, T.; Anandhan, N.; Thangamuthu, R.

    2018-01-01

    Electrochemical deposition of vertically aligned zinc oxide (ZnO) nanorods were prepared on ZnO seeded fluorine doped tin oxide (FTO) substrate in the solutions consisting of different concentrations of hexamethylenetetramine (HMTA). The electrochemical, structural, morphological, vibrational and optical properties were characterized by cyclic voltammetry (CV), X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy and photoluminescence (PL) spectroscopy, respectively. CV curves confirm that metallic zinc phase is not deposited as the HMTA concentration is about 9 mM in a deposition solution. XRD patterns of the as-prepared films show that the increasing HMTA concentrations from 0 mM to 9 mM not only increase the formation of zinc hydrate chloride (Zn5(OH)8Cl2·H2O) but also decrease and finally disappear the metallic Zn deposition. After the as-prepared films annealed at 450 ° C, the crystalline phases of Zn and Zn5(OH)8Cl2·H2O are completely converted to ZnO hexagonal wurtzite phase with high intense growth (002) plane orientation. SEM images support that the vertical growth of ZnO nanostructures (nanorods and petals) with a few flowers is found to be in the cordillera structure as the films are deposited in the solutions consisting of 3 mM, 6 mM and 9 mM HMTA respectively. Raman and PL spectra confirm that the ZnO film deposited in the solution consisting of 9 mM HMTA has a higher crystalline nature with lesser atomic defects and is also higher c-axis growth than that of other films deposited in the solutions consisting of 0 mM, 3 mM and 6 mM, respectively. UV-vis absorbance spectra corroborate that the ZnO film deposited in the solution consisting of 9 mM HMTA shows a high dye absorbance as compared with other films. The efficiency of DSSCs based on ZnO photoanodes deposited in the solutions consisting of 0 mM and 9 mM HMTA was 1.79 and 3.75%, respectively. Electrochemical impedance spectra revealed that DSSC based on ZnO photoanode

  1. [Contact allergy to dexpanthenol].

    PubMed

    Schulze-Dirks, A; Frosch, P J

    1988-06-01

    Eleven cases of contact allergy to dexpanthenol are reported (5 females, 6 males; mean age 62.4 years). Five patients suffered from a leg ulcer and/or stasis dermatitis. In five patients the sensitization occurred after the application of dexpanthenol-containing ointments to the face. Only one patient did not show sensitization to other common allergens. Three patients were sensitive to wool wax alcohols, which are present in a commonly used product. Dexpanthenol seems to be a rare sensitizer, yet clinically most relevant for patients with stasis dermatitis and multiple allergies.

  2. Contact Control, Version 1

    SciTech Connect

    von Sternberg, Alex

    The contact control code is a generalized force control scheme meant to interface with a robotic arm being controlled using the Robot Operating System (ROS). The code allows the user to specify a control scheme for each control dimension in a way that many different control task controllers could be built from the same generalized controller. The input to the code includes maximum velocity, maximum force, maximum displacement, and a control law assigned to each direction and the output is a 6 degree of freedom velocity command that is sent to the robot controller.

  3. Adhesive Contact Sweeper

    NASA Technical Reports Server (NTRS)

    Patterson, Jonathan D.

    1993-01-01

    Adhesive contact sweeper removes hair and particles vacuum cleaner leaves behind, without stirring up dust. Also cleans loose rugs. Sweeper holds commercially available spools of inverted adhesive tape. Suitable for use in environments in which air kept free of dust; optics laboratories, computer rooms, and areas inhabited by people allergic to dust. For carpets, best used in tandem with vacuum cleaner; first pass with vacuum cleaner removes coarse particles, and second pass with sweeper extracts fine particles. This practice extends useful life of adhesive spools.

  4. Experimental study on electromagnetic-assisted ZnO nanofluid flooding for enhanced oil recovery (EOR)

    PubMed Central

    Ahmad Latiff, Noor Rasyada; Alnarabiji, Mohamad Sahban

    2018-01-01

    Recently, nano-EOR has emerged as a new frontier for improved and enhanced oil recovery (IOR & EOR). Despite their benefits, the nanoparticles tend to agglomerate at reservoir conditions which cause their detachment from the oil/water interface, and are consequently retained rather than transported through a porous medium. Dielectric nanoparticles including ZnO have been proposed to be a good replacement for EOR due to their high melting point and thermal properties. But more importantly, these particles can be polarized under electromagnetic (EM) irradiation, which provides an innovative smart Nano-EOR process denoted as EM-Assisted Nano-EOR. In this study, parameters involved in the oil recovery mechanism under EM waves, such as reducing mobility ratio, lowering interfacial tensions (IFT) and altering wettability were investigated. Two-phase displacement experiments were performed in sandpacks under the water-wet condition at 95°C, with permeability in the range of 265–300 mD. A crude oil from Tapis oil field was employed; while ZnO nanofluids of two different particle sizes (55.7 and 117.1 nm) were prepared using 0.1 wt. % nanoparticles that dispersed into brine (3 wt. % NaCl) along with SDBS as a dispersant. In each flooding scheme, three injection sequential scenarios have been conducted: (i) brine flooding as a secondary process, (ii) surfactant/nano/EM-assisted nano flooding, and (iii) second brine flooding to flush nanoparticles. Compare with surfactant flooding (2% original oil in place/OOIP) as tertiary recovery, nano flooding almost reaches 8.5–10.2% of OOIP. On the other hand, EM-assisted nano flooding provides an incremental oil recovery of approximately 9–10.4% of OOIP. By evaluating the contact angle and interfacial tension, it was established that the degree of IFT reduction plays a governing role in the oil displacement mechanism via nano-EOR, compare to mobility ratio. These results reveal a promising way to employ water-based ZnO nanofluid

  5. Experimental study on electromagnetic-assisted ZnO nanofluid flooding for enhanced oil recovery (EOR).

    PubMed

    Adil, Muhammad; Lee, Keanchuan; Mohd Zaid, Hasnah; Ahmad Latiff, Noor Rasyada; Alnarabiji, Mohamad Sahban

    2018-01-01

    Recently, nano-EOR has emerged as a new frontier for improved and enhanced oil recovery (IOR & EOR). Despite their benefits, the nanoparticles tend to agglomerate at reservoir conditions which cause their detachment from the oil/water interface, and are consequently retained rather than transported through a porous medium. Dielectric nanoparticles including ZnO have been proposed to be a good replacement for EOR due to their high melting point and thermal properties. But more importantly, these particles can be polarized under electromagnetic (EM) irradiation, which provides an innovative smart Nano-EOR process denoted as EM-Assisted Nano-EOR. In this study, parameters involved in the oil recovery mechanism under EM waves, such as reducing mobility ratio, lowering interfacial tensions (IFT) and altering wettability were investigated. Two-phase displacement experiments were performed in sandpacks under the water-wet condition at 95°C, with permeability in the range of 265-300 mD. A crude oil from Tapis oil field was employed; while ZnO nanofluids of two different particle sizes (55.7 and 117.1 nm) were prepared using 0.1 wt. % nanoparticles that dispersed into brine (3 wt. % NaCl) along with SDBS as a dispersant. In each flooding scheme, three injection sequential scenarios have been conducted: (i) brine flooding as a secondary process, (ii) surfactant/nano/EM-assisted nano flooding, and (iii) second brine flooding to flush nanoparticles. Compare with surfactant flooding (2% original oil in place/OOIP) as tertiary recovery, nano flooding almost reaches 8.5-10.2% of OOIP. On the other hand, EM-assisted nano flooding provides an incremental oil recovery of approximately 9-10.4% of OOIP. By evaluating the contact angle and interfacial tension, it was established that the degree of IFT reduction plays a governing role in the oil displacement mechanism via nano-EOR, compare to mobility ratio. These results reveal a promising way to employ water-based ZnO nanofluid for

  6. Enhanced light extraction in tunnel junction-enabled top emitting UV LEDs

    DOE PAGES

    Zhang, Yuewei; Allerman, Andrew A.; Krishnamoorthy, Sriram; ...

    2016-04-11

    The efficiency of ultra violet LEDs has been critically limited by the absorption losses in p-type and metal layers. In this work, surface roughening based light extraction structures are combined with tunneling based p-contacts to realize highly efficient top-side light extraction efficiency in UV LEDs. Surface roughening of the top n-type AlGaN contact layer is demonstrated using self-assembled Ni nano-clusters as etch mask. The top surface roughened LEDs were found to enhance external quantum efficiency by over 40% for UV LEDs with a peak emission wavelength of 326 nm. The method described here can enable highly efficient UV LEDs withoutmore » the need for complex manufacturing methods such as flip chip bonding.« less

  7. Configuration of the top of the Floridan aquifer, Southwest Florida Water Management District and adjacent areas

    USGS Publications Warehouse

    Buono, A.; Rutledge, A.T.

    1978-01-01

    This map depicts the approximate top of the rock that composes the Floridan aquifer. The contours represent the elevation of the top of the Floridan aquifer to mean sea level. Rock units recognized to be part of the Floridan aquifer are limestone and dolomite ranging from middle Eocene to early Miocene. They are Lake City Limestone, Avon Park Limestone, Ocala Limestone, Suwannee Limestone, and Tampa Limestone. In this report, the top of the Floridan aquifer is a limestone defined as the first consistent rock of early Miocene age or older below which occur no clay confining beds. Although the Hawthorn formation of middle Miocene is considered part of the Floridan aquifer when it is in direct hydrologic contact with lower lying rock units, it is not considered here because of a lack of detailed delineation of areas where contact exists. (Woodard-USGS)

  8. Inverted Silicon Nanopencil Array Solar Cells with Enhanced Contact Structures.

    PubMed

    Liang, Xiaoguang; Shu, Lei; Lin, Hao; Fang, Ming; Zhang, Heng; Dong, Guofa; Yip, SenPo; Xiu, Fei; Ho, Johnny C

    2016-09-27

    Although three-dimensional nanostructured solar cells have attracted extensive research attention due to their superior broadband and omnidirectional light-harvesting properties, majority of them are still suffered from complicated fabrication processes as well as disappointed photovoltaic performances. Here, we employed our newly-developed, low-cost and simple wet anisotropic etching to fabricate hierarchical silicon nanostructured arrays with different solar cell contact design, followed by systematic investigations of their photovoltaic characteristics. Specifically, nano-arrays with the tapered tips (e.g. inverted nanopencils) are found to enable the more conformal top electrode deposition directly onto the nanostructures for better series and shunt conductance, but its insufficient film coverage at the basal plane would still restrict the charge carrier collection. In contrast, the low-platform contact design facilitates a substantial photovoltaic device performance enhancement of ~24%, as compared to the one of conventional top electrode design, due to the shortened current path and improved lateral conductance for the minimized carrier recombination and series resistance. This enhanced contact structure can not only maintain excellent photon-trapping behaviors of nanostructures, but also help to eliminate adverse impacts of these tapered nano-morphological features on the contact resistance, providing further insight into design consideration in optimizing the contact geometry for high-performance nanostructured photovoltaic devices.

  9. Inverted Silicon Nanopencil Array Solar Cells with Enhanced Contact Structures

    PubMed Central

    Liang, Xiaoguang; Shu, Lei; Lin, Hao; Fang, Ming; Zhang, Heng; Dong, Guofa; Yip, SenPo; Xiu, Fei; Ho, Johnny C.

    2016-01-01

    Although three-dimensional nanostructured solar cells have attracted extensive research attention due to their superior broadband and omnidirectional light-harvesting properties, majority of them are still suffered from complicated fabrication processes as well as disappointed photovoltaic performances. Here, we employed our newly-developed, low-cost and simple wet anisotropic etching to fabricate hierarchical silicon nanostructured arrays with different solar cell contact design, followed by systematic investigations of their photovoltaic characteristics. Specifically, nano-arrays with the tapered tips (e.g. inverted nanopencils) are found to enable the more conformal top electrode deposition directly onto the nanostructures for better series and shunt conductance, but its insufficient film coverage at the basal plane would still restrict the charge carrier collection. In contrast, the low-platform contact design facilitates a substantial photovoltaic device performance enhancement of ~24%, as compared to the one of conventional top electrode design, due to the shortened current path and improved lateral conductance for the minimized carrier recombination and series resistance. This enhanced contact structure can not only maintain excellent photon-trapping behaviors of nanostructures, but also help to eliminate adverse impacts of these tapered nano-morphological features on the contact resistance, providing further insight into design consideration in optimizing the contact geometry for high-performance nanostructured photovoltaic devices. PMID:27671709

  10. Numerical simulation and growth of Li2Zn2(MoO4)3 single crystals by the top seeded solution growth technique

    NASA Astrophysics Data System (ADS)

    Sukharev, V.; Sukhanova, E.; Mozhevitina, E.; Sadovsky, A.; Avetissov, I.

    2017-06-01

    Li2O - ZnO - MoO3 pseudo ternary system was used for the growth of Li2Zn2(MoO4)3 crystals by the top seeded solution growth technique in which MoO3 was used as a solvent. Properties of the melts (density, viscosity) have been experimentally measured at different temperatures and compositions of Li2O - ZnO - MoO3 pseudo ternary system. Heat mass transfer in the crystal growth setup was numerically simulated. Using the simulation results a real growth setup was made, Li2Zn2(MoO4)3 crystals were grown and their properties were studied.

  11. In situ biasing and off-axis electron holography of a ZnO nanowire

    NASA Astrophysics Data System (ADS)

    den Hertog, Martien; Donatini, Fabrice; McLeod, Robert; Monroy, Eva; Sartel, Corinne; Sallet, Vincent; Pernot, Julien

    2018-01-01

    Quantitative characterization of electrically active dopants and surface charges in nano-objects is challenging, since most characterization techniques using electrons [1-3], ions [4] or field ionization effects [5-7] study the chemical presence of dopants, which are not necessarily electrically active. We perform cathodoluminescence and voltage contrast experiments on a contacted and biased ZnO nanowire with a Schottky contact and measure the depletion length as a function of reverse bias. We compare these results with state-of-the-art off-axis electron holography in combination with electrical in situ biasing on the same nanowire. The extension of the depletion length under bias observed in scanning electron microscopy based techniques is unusual as it follows a linear rather than square root dependence, and is therefore difficult to model by bulk equations or finite element simulations. In contrast, the analysis of the axial depletion length observed by holography may be compared with three-dimensional simulations, which allows estimating an n-doping level of 1 × 1018 cm-3 and negative sidewall surface charge of 2.5 × 1012 cm-2 of the nanowire, resulting in a radial surface depletion to a depth of 36 nm. We found excellent agreement between the simulated diameter of the undepleted core and the active thickness observed in the experimental data. By combining TEM holography experiments and finite element simulation of the NW electrostatics, the bulk-like character of the nanowire core is revealed.

  12. Optimal contact definition for reconstruction of contact maps.

    PubMed

    Duarte, Jose M; Sathyapriya, Rajagopal; Stehr, Henning; Filippis, Ioannis; Lappe, Michael

    2010-05-27

    Contact maps have been extensively used as a simplified representation of protein structures. They capture most important features of a protein's fold, being preferred by a number of researchers for the description and study of protein structures. Inspired by the model's simplicity many groups have dedicated a considerable amount of effort towards contact prediction as a proxy for protein structure prediction. However a contact map's biological interest is subject to the availability of reliable methods for the 3-dimensional reconstruction of the structure. We use an implementation of the well-known distance geometry protocol to build realistic protein 3-dimensional models from contact maps, performing an extensive exploration of many of the parameters involved in the reconstruction process. We try to address the questions: a) to what accuracy does a contact map represent its corresponding 3D structure, b) what is the best contact map representation with regard to reconstructability and c) what is the effect of partial or inaccurate contact information on the 3D structure recovery. Our results suggest that contact maps derived from the application of a distance cutoff of 9 to 11A around the Cbeta atoms constitute the most accurate representation of the 3D structure. The reconstruction process does not provide a single solution to the problem but rather an ensemble of conformations that are within 2A RMSD of the crystal structure and with lower values for the pairwise average ensemble RMSD. Interestingly it is still possible to recover a structure with partial contact information, although wrong contacts can lead to dramatic loss in reconstruction fidelity. Thus contact maps represent a valid approximation to the structures with an accuracy comparable to that of experimental methods. The optimal contact definitions constitute key guidelines for methods based on contact maps such as structure prediction through contacts and structural alignments based on maximum

  13. Optimal contact definition for reconstruction of Contact Maps

    PubMed Central

    2010-01-01

    Background Contact maps have been extensively used as a simplified representation of protein structures. They capture most important features of a protein's fold, being preferred by a number of researchers for the description and study of protein structures. Inspired by the model's simplicity many groups have dedicated a considerable amount of effort towards contact prediction as a proxy for protein structure prediction. However a contact map's biological interest is subject to the availability of reliable methods for the 3-dimensional reconstruction of the structure. Results We use an implementation of the well-known distance geometry protocol to build realistic protein 3-dimensional models from contact maps, performing an extensive exploration of many of the parameters involved in the reconstruction process. We try to address the questions: a) to what accuracy does a contact map represent its corresponding 3D structure, b) what is the best contact map representation with regard to reconstructability and c) what is the effect of partial or inaccurate contact information on the 3D structure recovery. Our results suggest that contact maps derived from the application of a distance cutoff of 9 to 11Å around the Cβ atoms constitute the most accurate representation of the 3D structure. The reconstruction process does not provide a single solution to the problem but rather an ensemble of conformations that are within 2Å RMSD of the crystal structure and with lower values for the pairwise average ensemble RMSD. Interestingly it is still possible to recover a structure with partial contact information, although wrong contacts can lead to dramatic loss in reconstruction fidelity. Conclusions Thus contact maps represent a valid approximation to the structures with an accuracy comparable to that of experimental methods. The optimal contact definitions constitute key guidelines for methods based on contact maps such as structure prediction through contacts and structural

  14. Contact Lenses in the Laboratory.

    ERIC Educational Resources Information Center

    Kingston, David W.

    1981-01-01

    Summarizes results of a three-item questionnaire returned by 43 Michigan institutions expressing views on wearing contact lenses in chemical laboratories. Questions focused on eye protection, type of protection, and use of contact lenses. (SK)

  15. Contact Sport Concussion Incidence

    PubMed Central

    Tommasone, Beth A; Valovich McLeod, Tamara C

    2006-01-01

    Reference/Citation: Koh JO, Cassidy JD, Watkinson EJ. Incidence of concussion in contact sports: a systematic review of the evidence. Brain Inj.20031790191712963556. Clinical Question: What is the incidence of concussion in various contact sports? Data Sources: Studies for the review were found through a MEDLINE search (1985–2000) and by gathering and reviewing older articles referenced in the searched articles. The main terms that were included in the search were brain injuries, brain concussion, and incidence. Text words that were also included were mild traumatic brain injury, concussion, incidence, injury, and head injury, along with the names of 8 contact sports ( American football, boxing, ice hockey, judo, karate, tae kwon do, rugby, and soccer). Study Selection: For this review, concussion was defined as “a mild brain injury resulting from a direct blow to the head resulting in physiological changes in brain function.” Cohort studies with documented incidence of concussion in athletes from 8 identified contact sports were the target of the search. All studies of male and female athletes in any of the 8 contact sports, including practices and games and regardless of level of competition, were included in the study search. Possible articles for review were identified through a 3-step screening process. Article titles were initially screened by one of the authors. If the title seemed to be relevant to the purpose of the review, the abstract of the article was then screened for inclusion/exclusion criteria as the second step. To be included, studies had to relate to the incidence of injury to the head and brain, report results relevant to concussion, involve 1 of the 8 identified contact sports, and be published between 1985 and 2000. All systematic reviews about mild traumatic brain injury (TBI) or concussion were also included. Studies were excluded if they discussed concussion due to whiplash injury or concussion associated with spinal cord injury

  16. TopHat: discovering splice junctions with RNA-Seq

    PubMed Central

    Trapnell, Cole; Pachter, Lior; Salzberg, Steven L.

    2009-01-01

    Motivation: A new protocol for sequencing the messenger RNA in a cell, known as RNA-Seq, generates millions of short sequence fragments in a single run. These fragments, or ‘reads’, can be used to measure levels of gene expression and to identify novel splice variants of genes. However, current software for aligning RNA-Seq data to a genome relies on known splice junctions and cannot identify novel ones. TopHat is an efficient read-mapping algorithm designed to align reads from an RNA-Seq experiment to a reference genome without relying on known splice sites. Results: We mapped the RNA-Seq reads from a recent mammalian RNA-Seq experiment and recovered more than 72% of the splice junctions reported by the annotation-based software from that study, along with nearly 20 000 previously unreported junctions. The TopHat pipeline is much faster than previous systems, mapping nearly 2.2 million reads per CPU hour, which is sufficient to process an entire RNA-Seq experiment in less than a day on a standard desktop computer. We describe several challenges unique to ab initio splice site discovery from RNA-Seq reads that will require further algorithm development. Availability: TopHat is free, open-source software available from http://tophat.cbcb.umd.edu Contact: cole@cs.umd.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:19289445

  17. Self-focused ZnO transducers for ultrasonic biomicroscopy

    NASA Astrophysics Data System (ADS)

    Cannata, J. M.; Williams, J. A.; Zhou, Q. F.; Sun, L.; Shung, K. K.; Yu, H.; Kim, E. S.

    2008-04-01

    A simple fabrication technique was developed to produce high frequency (100MHz) self-focused single element transducers with sputtered zinc oxide (ZnO) crystal films. This technique requires the sputtering of a ZnO film directly onto a curved backing substrate. Transducers were fabricated by sputtering an 18μm thick ZnO layer on 2mm diameter aluminum rods with ends shaped and polished to produce a 2mm focus or f-number equal to one. The aluminum rod served a dual purpose as the backing layer and positive electrode for the resultant transducers. A 4μm Parylene matching layer was deposited on the transducers after housing and interconnect. This matching layer was used to protect the substrate and condition the transfer of acoustic energy between the ZnO film and the load medium. The pulse-echo response for a representative transducer was centered at 101MHz with a -6dB bandwidth of 49%. The measured two way insertion loss was 44dB. A tungsten wire phantom and an adult zebrafish eye were imaged to show the capability of these transducers.

  18. Ligand induced ferromagnetism in ZnO nanostructures.

    PubMed

    Wang, Qian; Sun, Qiang; Jena, P

    2008-10-28

    Complementary to the experimental finding that ZnO nanoparticles become ferromagnetic when coated with N and S containing ligands such as dodecylamine and dodecanethiol [Garcia et al., Nano Lett. 7, 1489 (2007)], we provide the first theoretical understanding of the origin of magnetism in ligated ZnO nanoparticles as well as the structural properties of the ligated systems by using density functional theory and generalized gradient approximation for exchange and correlation, and a cluster model for the nanoparticles. We show that N or S atoms of the ligand bind to the Zn sites. The accompanying changes in the Zn-O bond length, hybridization between Zn 4s orbitals with N 2p or S 3p orbitals, and consequently the redistribution of charges between Zn and O atoms result in a magnetic system where the 2p electrons in O and N, and 3p electrons in S sites are spin polarized. Furthermore, the sites nearest to the Zn atom attached to the ligand carry bulk of the magnetic moment. Studies, as a function of cluster size, also illustrate that magnetism resides only on the surface. Our results confirm that the use of ligands can pave a new way for introducing magnetism in ZnO nanostructures, which can be used to develop magnetic sensors to detect N and S containing molecules.

  19. Co-Doped ZnO nanoparticles: minireview.

    PubMed

    Djerdj, Igor; Jaglicić, Zvonko; Arcon, Denis; Niederberger, Markus

    2010-07-01

    Diluted magnetic semiconductors with a Curie temperature exceeding 300 K are promising candidates for spintronic devices and spin-based electronic technologies. We review recent achievements in the field of one of them: Co-doped ZnO at the nanoparticulate scale.

  20. Growth Kinetics and Modeling of ZnO Nanoparticles

    ERIC Educational Resources Information Center

    Hale, Penny S.; Maddox, Leone M.; Shapter, Joe G.; Voelcker, Nico H.; Ford, Michael J.; Waclawik, Eric R.

    2005-01-01

    The technique for producing quantum-sized zinc oxide (ZnO) particles is much safer than a technique that used hydrogen sulfide gas to produce cadmium sulfide and zinc sulfide nanoparticles. A further advantage of this method is the ability to sample the solution over time and hence determine the growth kinetics.

  1. Field emission and photoluminescence of ZnO nanocombs

    NASA Astrophysics Data System (ADS)

    Wang, B.; Wu, H. Y.; Zheng, Z. Q.; Yang, Y. H.

    2013-11-01

    Three kinds of new comb-shape nanostructures of ZnO have been grown on single silicon substrates without catalyst-assisted thermal evaporation of Zn and active carbon powders. The morphology and structure of the prepared nanorods are determined on the basis of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). The growth mechanism of the ZnO nanocombs can be explained on the basis of the vapor-solid (VS) processes. In nanocombs 1 and nanocombs 2, the comb teeth grow along [0001] and the comb stem grows along [], while in nanocombs 3, nanoteeth grow along [] and stem grows along [0001]. The photoluminescence and field-emission properties of ZnO nanocombs 1-3 have been investigated. The turn-on electric field of ZnO nanocombs 1-3, which is defined as the field required to producing a current density of 10 μA/cm2, is 9, 7.7 and 7.1 V/μm, respectively. The field-emission performance relies not only on the tip’s radius of curvature and field enhancement factor, but also on the factor evaluating the degree of the screening effect.

  2. Ecotoxicity of Manufactured ZnO Nanoparticles - A Review

    EPA Science Inventory

    This report presents an exhaustive literature review on the toxicity of manufactured ZnO nanoparticles (NPs) to ecological receptors across different phylum: bacteria, algae and plants, aquatic and terrestrial invertebrates and freshwater fish. Results show that the majority of s...

  3. Transparent photostable ZnO nonvolatile memory transistor with ferroelectric polymer and sputter-deposited oxide gate

    NASA Astrophysics Data System (ADS)

    Park, C. H.; Im, Seongil; Yun, Jungheum; Lee, Gun Hwan; Lee, Byoung H.; Sung, Myung M.

    2009-11-01

    We report on the fabrication of transparent top-gate ZnO nonvolatile memory thin-film transistors (NVM-TFTs) with 200 nm thick poly(vinylidene fluoride/trifluoroethylene) ferroelectric layer; semitransparent 10 nm thin AgOx and transparent 130 nm thick indium-zinc oxide (IZO) were deposited on the ferroelectric polymer as gate electrode by rf sputtering. Our semitransparent NVM-TFT with AgOx gate operates under low voltage write-erase (WR-ER) pulse of ±20 V, but shows some degradation in retention property. In contrast, our transparent IZO-gated device displays very good retention properties but requires anomalously higher pulse of ±70 V for WR and ER states. Both devices stably operated under visible illuminations.

  4. Ohmic contacts for laser diodes

    NASA Technical Reports Server (NTRS)

    Ladany, I.; Marinelli, D. P.

    1983-01-01

    Requirements for ohmic contacts to laser diodes are discussed, and properties of Schottky barrier tunneling contacts are reviewed. A procedure is described for measuring contact resistance on fabricated laser material without the need for specially constructed samples and contact configurations. Measurements of contact resistance and estimates of specific contact resistance are given for Ti/Pt/Au contacts to surfaces with three different doping levels. It was found that below a p-type carrier concentration of 1 x 10 to the 19th per cu cm the contact resistance is likely to be too high for good device performance. At higher doping levels, a specific contact resistance as low as 2 x 10 to the -6th ohm sq cm was obtained. Oxide stripe lasers provided with the type of contact discussed in this paper have been operated without failures for periods up to 7 years at a current density at the contact of 6-8 kA/sq cm. It appears therefore that these contacts satisfy the need for low resistance and durability and that, at the same time, they do not cause any obvious material degradation.

  5. Contact position sensor using constant contact force control system

    NASA Technical Reports Server (NTRS)

    Sturdevant, Jay (Inventor)

    1995-01-01

    A force control system (50) and method are provided for controlling a position contact sensor (10) so as to produce a constant controlled contact force therewith. The system (50) includes a contact position sensor (10) which has a contact probe (12) for contacting the surface of a target to be measured and an output signal (V.sub.o) for providing a position indication thereof. An actuator (30) is provided for controllably driving the contact position sensor (10) in response to an actuation control signal (I). A controller (52) receives the position indication signal (V.sub.o) and generates in response thereto the actuation control signal (I) so as to provide a substantially constant selective force (F) exerted by the contact probe (12). The actuation drive signal (I) is generated further in response to substantially linear approximation curves based on predetermined force and position data attained from the sensor (10) and the actuator (30).

  6. Disproportionate minority contact.

    PubMed

    Piquero, Alex R

    2008-01-01

    For many years, notes Alex Piquero, youth of color have been overrepresented at every stage of the U.S. juvenile justice system. As with racial disparities in a wide variety of social indicators, the causes of these disparities are not immediately apparent. Some analysts attribute the disparities to "differential involvement"--that is, to differences in offending by minorities and whites. Others attribute them to "differential selection"--that is, to the fact that the justice system treats minority and white offenders in different ways. Still others believe the explanation lies in a combination of the two. Differential involvement may be important earlier in the judicial process, especially in youths' contacts with police, and may influence differential selection later as individuals make their way through the juvenile justice system. Adjudicating between these options, says Piquero, is difficult and may even be impossible. Asking how much minority overrepresentation is due to differences in offending and how much to differences in processing no longer seems a helpful way to frame the discussion. Piquero urges future research to move beyond the debate over "which one matters more" and seek to understand how each of the two hypotheses can explain both the fact of minority overrepresentation in the juvenile justice system and how best to address it. Piquero cites many sizable gaps in the research and policy-relevant literature. Work is needed especially, he says, in analyzing the first stage of the justice system that juveniles confront: police contacts. The police are a critical part of the juvenile justice decision-making system and are afforded far more discretion than any other formal agent of social control, but researchers have paid surprisingly little attention to contacts between police and citizens, especially juveniles. Piquero notes that some states and localities are undertaking initiatives to reduce racial and ethnic disparities. He urges researchers and

  7. TOP500 Supercomputers for June 2004

    SciTech Connect

    Strohmaier, Erich; Meuer, Hans W.; Dongarra, Jack

    2004-06-23

    23rd Edition of TOP500 List of World's Fastest Supercomputers Released: Japan's Earth Simulator Enters Third Year in Top Position MANNHEIM, Germany; KNOXVILLE, Tenn.;&BERKELEY, Calif. In what has become a closely watched event in the world of high-performance computing, the 23rd edition of the TOP500 list of the world's fastest supercomputers was released today (June 23, 2004) at the International Supercomputer Conference in Heidelberg, Germany.

  8. Development of nanostructured ZnO thin film via electrohydrodynamic atomization technique and its photoconductivity characteristics.

    PubMed

    Duraisamy, Navaneethan; Kwon, Ki Rin; Jo, Jeongdai; Choi, Kyung-Hyun

    2014-08-01

    This article presents the non-vacuum technique for the preparation of nanostructured zinc oxide (ZnO) thin film on glass substrate through electrohydrodynamic atomization (EHDA) technique. The detailed process parameters for achieving homogeneous ZnO thin films are clearly discussed. The crystallinity and surface morphology of ZnO thin film are investigated by X-ray diffraction and field emission scanning electron microscopy. The result shows that the deposited ZnO thin film is oriented in the wurtzite phase with void free surface morphology. The surface roughness of deposited ZnO thin film is found to be ~17.8 nm. The optical properties of nanostructured ZnO thin films show the average transmittance is about 90% in the visible region and the energy band gap is found to be 3.17 eV. The surface chemistry and purity of deposited ZnO thin films are analyzed by fourier transform infrared and X-ray photoelectron spectroscopy, conforming the presence of Zn-O in the deposited thin films without any organic moiety. The photocurrent measurement of nanostructured ZnO thin film is examined in the presence of UV light illumination with wavelength of 365 nm. These results suggest that the deposited nanostructured ZnO thin film through EHDA technique possess promising applications in the near future.

  9. Long-term effect of ZnO nanoparticles on waste activated sludge anaerobic digestion.

    PubMed

    Mu, Hui; Chen, Yinguang

    2011-11-01

    The increasing use of zinc oxide nanoparticles (ZnO NPs) raises concerns about their environmental impacts, but the potential effect of ZnO NPs on sludge anaerobic digestion remains unknown. In this paper, long-term exposure experiments were carried out to investigate the influence of ZnO NPs on methane production during waste activated sludge (WAS) anaerobic digestion. The presence of 1 mg/g-TSS of ZnO NPs did not affect methane production, but 30 and 150 mg/g-TSS of ZnO NPs induced 18.3% and 75.1% of inhibition respectively, which showed that the impact of ZnO NPs on methane production was dosage dependant. Then, the mechanisms of ZnO NPs affecting sludge anaerobic digestion were investigated. It was found that the toxic effect of ZnO NPs on methane production was mainly due to the release of Zn(2+) from ZnO NPs, which may cause the inhibitory effects on the hydrolysis and methanation steps of sludge anaerobic digestion. Further investigations with enzyme and fluorescence in situ hybridization (FISH) assays indicated that higher concentration of ZnO NPs decreased the activities of protease and coenzyme F(420), and the abundance of methanogenesis Archaea. Copyright © 2011 Elsevier Ltd. All rights reserved.

  10. Effect of nanocomposite packaging containing ZnO on growth of Bacillus subtilis and Enterobacter aerogenes.

    PubMed

    Esmailzadeh, Hakimeh; Sangpour, Parvaneh; Shahraz, Farzaneh; Hejazi, Jalal; Khaksar, Ramin

    2016-01-01

    Recent advances in nanotechnology have opened new windows in active food packaging. Nano-sized ZnO is an inexpensive material with potential antimicrobial properties. The aim of the present study is to evaluate the antibacterial effect of low density Polyethylene (LDPE) containing ZnO nanoparticles on Bacillus subtilis and Enterobacter aerogenes. ZnO nanoparticles have been synthesized by facil molten salt method and have been characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM). Nanocomposite films containing 2 and 4 wt.% ZnO nanoparticles were prepared by melt mixing in a twin-screw extruder. The growth of both microorganisms has decreased in the presence of ZnO containing nanocomposites compared with controls. Nanocomposites with 4 wt.% ZnO nanoparticles had stronger antibacterial effect against both bacteria in comparison with the 2 wt.% ZnO containing nanocomposites. B. subtilis as Gram-positive bacteria were more sensitive to ZnO containing nanocomposite films compared with E. aerogenes as Gram-negative bacteria. There were no significant differences between the migration of Zn ions from 2 and 4 wt.% ZnO containing nanocomposites and the released Zn ions were not significantly increased in both groups after 14 days compared with the first. Regarding the considerable antibacterial effects of ZnO nanoparticles, their application in active food packaging can be a suitable solution for extending the shelf life of food. Copyright © 2015. Published by Elsevier B.V.

  11. Room temperature photoluminescence properties of ZnO nanorods grown by hydrothermal reaction

    SciTech Connect

    Iwan, S., E-mail: iwan-sugihartono@unj.ac.id; Prodi Ilmu Material, Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok; Fauzia, Vivi

    Zinc oxide (ZnO) nanorods were fabricated by a hydrothermal reaction on silicon (Si) substrate at 95 °C for 6 hours. The ZnO seed layer was fabricated by depositing ZnO thin films on Si substrates by ultrasonic spray pyrolisis (USP). The annealing effects on crystal structure and optical properties of ZnO nanorods were investigated. The post-annealing treatment was performed at 800 °C with different environments. The annealed of ZnO nanorods were characterized by X-ray diffraction (XRD) and photoluminescence (PL) in order to analyze crystal structure and optical properties, respectively. The results show the orientations of [002], [101], [102], and [103] diffractionmore » peaks were observed and hexagonal wurtzite structure of ZnO nanorods were vertically grown on Si substrates. The room temperature PL spectra show ultra-violet (UV) and visible emissions. The annealed of ZnO nanorods in vacuum condition (3.8 × 10{sup −3} Torr) has dominant UV emission. Meanwhile, non-annealed of ZnO nanorods has dominant visible emission. It was expected that the annealed of ZnO in vacuum condition suppresses the existence of native defects in ZnO nanorods.« less

  12. Study of ZnO nanoparticles: Antibacterial property and light depolarization property using light scattering tool

    NASA Astrophysics Data System (ADS)

    Roy, Sanchita; Barua, Nilakshi; Buragohain, Alak K.; Ahmed, Gazi A.

    2013-03-01

    Investigations on treatment of ZnO nanoparticles on Staphylococcus aureus MTCC 737 strain was essentially made by using standard biochemical method. The anti-microbial assay against S. aureus, and time kill assay revealed the anti-bacterial activity of ZnO nanoparticles. We have substantiated this property of ZnO nanoparticles and light depolarization property by using light scattering tool. Light scattering measurements were carried out for ZnO, S. aureus, and ZnO treated S. aureus as a function of scattering angle at 543.5 and 632.8 nm wavelengths. This was done in order to find the scattering profile of the consequent product after the action of ZnO nanoparticles on bacteria by means of light scattering tool. S. aureus treated with ZnO nanoparticles showed closer agreement of the scattering profiles at both the wavelengths, however, the scattering profiles of ZnO nanoparticles and untreated S. aureus significantly varied for the two different laser wavelengths. It was also observed that there was higher intensity of scattering from all S. aureus treated with ZnO particles compared to the untreated ones. In our work, we have studied ZnO nanoparticles and the possibility of observing its anti-bacterial activity by using light scattering tool.

  13. Synthesis, characterization and photocatalysis enhancement of Eu2O3-ZnO mixed oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Mohamed, W. S.; Abu-Dief, Ahmed M.

    2018-05-01

    Pure ZnO nanoparticles (NPs) and mixed Eu2O3 and ZnO NPs with different Eu2O3 ratios (5%, 10%, and 15%) were synthesized by a precipitation method under optimum conditions. The synthesized samples were characterized by means of X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and UV-vis diffuse reflectance spectroscopy. The as-synthesized ZnO NPs exhibit high phase purity and a highly crystalline wurtzite ZnO structure. The mixed Eu2O3 and ZnO NPs exhibit a Eu2O3 zinc blend phase in addition to the wurtzite phase of pure ZnO, confirming the high purity and good crystallinity of the as-synthesized samples. The high-purity formation of ZnO and Eu2O3 phases was confirmed by FTIR and Raman spectra. Microstructural analysis by SEM and TEM confirmed the sphere-like morphology with different particle sizes (29-40 nm) of the as-synthesized samples. The photocatalytic activities of pure ZnO NPs and mixed Eu2O3 and ZnO NPs for the degradation of methylene blue were evaluated under ultraviolet (UV) irradiation. The results show that Eu2O3 plays an important role in the enhancement of the photocatalytic properties of ZnO NPs. We found that mixed 5% Eu2O3 and ZnO NPs exhibit the highest photocatalytic activity (degradation efficiency of 96.5% after 180 min of UV irradiation) as compared with pure ZnO NPs (degradation efficiency of 80.3% after 180 min of UV irradiation). The increased photocatalytic activity of the optimum mixed Eu2O3 and ZnO NPs is due to the high crystallinity, high surface area with small particle size, and narrow energy gap.

  14. Single Top Quark Production at the Tevatron

    SciTech Connect

    Peters, Yvonne

    2013-01-01

    While the heaviest known elementary particle, the top quark, has been discovered in 1995 by the CDF and D0 collaborations in ttbar events, it took 14 more years until the observation of single top quark production. In this article, we discuss recent studies of single top quark production by the CDF and D0 collaborations at the Tevatron. In particular, we present the measurement of single top quark s- and t-channel production combined, the first observation of t-channel production, the simultaneous measurement of s- and t-channel production cross sections as well as the extraction of the CMK matrix element |Vtb}|.

  15. Top Quark Mass Measurements at the Tevatron

    SciTech Connect

    Peters, Reinhild Yvonne

    2014-01-01

    Since the discovery of the top quark in 1995 by the CDF and D0 collaborations at the Fermilab Tevatron proton antiproton collider, precise measurements of its mass are ongoing. Using data recorded by the D0 and CDF experiment, corresponding to up to the full Tevatron data sample, top quark mass measurements performed in different final states using various extraction techniques are presented in this article. The recent Tevatron top quark mass combination yields m_t=173.20 +-0.87 GeV. Furthermore, measurements of the top antitop quark mass difference from the Tevatron are discussed.

  16. Piezoelectric and semiconducting coupled power generating process of a single ZnO belt/wire. A technology for harvesting electricity from the environment.

    PubMed

    Song, Jinhui; Zhou, Jun; Wang, Zhong Lin

    2006-08-01

    This paper presents the experimental observation of piezoelectric generation from a single ZnO wire/belt for illustrating a fundamental process of converting mechanical energy into electricity at nanoscale. By deflecting a wire/belt using a conductive atomic force microscope tip in contact mode, the energy is first created by the deflection force and stored by piezoelectric potential, and later converts into piezoelectric energy. The mechanism of the generator is a result of coupled semiconducting and piezoelectric properties of ZnO. A piezoelectric effect is required to create electric potential of ionic charges from elastic deformation; semiconducting property is necessary to separate and maintain the charges and then release the potential via the rectifying behavior of the Schottky barrier at the metal-ZnO interface, which serves as a switch in the entire process. The good conductivity of ZnO is rather unique because it makes the current flow possible. This paper demonstrates a principle for harvesting energy from the environment. The technology has the potential of converting mechanical movement energy (such as body movement, muscle stretching, blood pressure), vibration energy (such as acoustic/ultrasonic wave), and hydraulic energy (such as flow of body fluid, blood flow, contraction of blood vessels) into electric energy that may be sufficient for self-powering nanodevices and nanosystems in applications such as in situ, real-time, and implantable biosensing, biomedical monitoring, and biodetection.

  17. Contact sensing from force measurements

    NASA Technical Reports Server (NTRS)

    Bicchi, Antonio; Salisbury, J. K.; Brock, David L.

    1993-01-01

    This article addresses contact sensing (i.e., the problem of resolving the location of a contact, the force at the interface, and the moment about the contact normals). Called 'intrinsic' contact sensing for the use of internal force and torque measurements, this method allows for practical devices that provide simple, relevant contact information in practical robotic applications. Such sensors have been used in conjunction with robot hands to identify objects, determine surface friction, detect slip, augment grasp stability, measure object mass, probe surfaces, and control collision and for a variety of other useful tasks. This article describes the theoretical basis for their operation and provides a framework for future device design.

  18. Clinical contact preceding suicide.

    PubMed

    Obafunwa, J O; Busuttil, A

    1994-06-01

    Of the 400 consecutive completed suicides investigated over a 5-year period, 114 (28.5%) who had consulted a doctor in the week preceding death were specifically reviewed and compared with those who did not. The study comprised an analysis of the medical history, the scene of death and a complete autopsy with histological and toxicological examination and the identification of features which occurred more frequently in this group when compared with other suicides not contacting their doctors. Suicide-associated factors include psychiatric illness (58.8%), deteriorating health (16.7%), and a loss of spouse (7.0%); all these features were manifested by this group of suicides more frequently than by those who made no clinical contact (P < 0.001). A pre-indication of suicidal intention was made by 45% of these patients. This feature, as with previous attempts, occurred more commonly in patients who consulted a doctor (P < 0.001). Drug overdose was the most common suicidal method chosen (50.9%) and anti-depressants predominated (35%); 78% of those who overdosed ingested prescribed drugs. Poisoning was more common in this group (P < 0.001). Half of the victims committed suicide within 24 hours following consultation; of these, 51% overdosed on drugs with 61% of them ingesting their prescribed drugs. Of these 114 cases, the final consultation in 43% was to collect more drugs. All suicidal threats should be taken seriously, and particular care should be taken in prescribing and dispensing medication which may be fatal in overdose.

  19. Contact angle and local wetting at contact line.

    PubMed

    Li, Ri; Shan, Yanguang

    2012-11-06

    This theoretical study was motivated by recent experiments and theoretical work that had suggested the dependence of the static contact angle on the local wetting at the triple-phase contact line. We revisit this topic because the static contact angle as a local wetting parameter is still not widely understood and clearly known. To further clarify the relationship of the static contact angle with wetting, two approaches are applied to derive a general equation for the static contact angle of a droplet on a composite surface composed of heterogeneous components. A global approach based on the free surface energy of a thermodynamic system containing the droplet and solid surface shows the static contact angle as a function of local surface chemistry and local wetting state at the contact line. A local approach, in which only local forces acting on the contact line are considered, results in the same equation. The fact that the local approach agrees with the global approach further demonstrates the static contact angle as a local wetting parameter. Additionally, the study also suggests that the wetting described by the Wenzel and Cassie equations is also the local wetting of the contact line rather than the global wetting of the droplet.

  20. Equilibrium contact angle or the most-stable contact angle?

    PubMed

    Montes Ruiz-Cabello, F J; Rodríguez-Valverde, M A; Cabrerizo-Vílchez, M A

    2014-04-01

    It is well-established that the equilibrium contact angle in a thermodynamic framework is an "unattainable" contact angle. Instead, the most-stable contact angle obtained from mechanical stimuli of the system is indeed experimentally accessible. Monitoring the susceptibility of a sessile drop to a mechanical stimulus enables to identify the most stable drop configuration within the practical range of contact angle hysteresis. Two different stimuli may be used with sessile drops: mechanical vibration and tilting. The most stable drop against vibration should reveal the changeless contact angle but against the gravity force, it should reveal the highest resistance to slide down. After the corresponding mechanical stimulus, once the excited drop configuration is examined, the focus will be on the contact angle of the initial drop configuration. This methodology needs to map significantly the static drop configurations with different stable contact angles. The most-stable contact angle, together with the advancing and receding contact angles, completes the description of physically realizable configurations of a solid-liquid system. Since the most-stable contact angle is energetically significant, it may be used in the Wenzel, Cassie or Cassie-Baxter equations accordingly or for the surface energy evaluation. © 2013 Elsevier B.V. All rights reserved.

  1. A Prototype Antifungal Contact Lens

    PubMed Central

    Ciolino, Joseph B.; Hudson, Sarah P.; Mobbs, Ashley N.; Hoare, Todd R.; Iwata, Naomi G.; Fink, Gerald R.

    2011-01-01

    Purpose. To design a contact lens to treat and prevent fungal ocular infections. Methods. Curved contact lenses were created by encapsulating econazole-impregnated poly(lactic-co-glycolic) acid (PLGA) films in poly(hydroxyethyl methacrylate) (pHEMA) by ultraviolet photopolymerization. Release studies were conducted in phosphate-buffered saline at 37°C with continuous shaking. The contact lenses and their release media were tested in an antifungal assay against Candida albicans. Cross sections of the pre- and postrelease contact lenses were characterized by scanning electron microscopy and by Raman spectroscopy. Results. Econazole-eluting contact lenses provided extended antifungal activity against Candida albicans fungi. Fungicidal activity varied in duration and effectiveness depending on the mass of the econazole-PLGA film encapsulated in the contact lens. Conclusions. An econazole-eluting contact lens could be used as a treatment for fungal ocular infections. PMID:21527380

  2. Effect of ZnO seed layer on the morphology and optical properties of ZnO nanorods grown on GaN buffer layers

    SciTech Connect

    Nandi, R., E-mail: rajunandi@iitb.ac.in; Mohan, S., E-mail: rajunandi@iitb.ac.in; Major, S. S.

    2014-04-24

    ZnO nanorods were grown by chemical bath deposition on sputtered, polycrystalline GaN buffer layers with and without ZnO seed layer. Scanning electron microscopy and X-ray diffraction show that the ZnO nanorods on GaN buffer layers are not vertically well aligned. Photoluminescence spectrum of ZnO nanorods grown on GaN buffer layer, however exhibits a much stronger near-band-edge emission and negligible defect emission, compared to the nanorods grown on ZnO buffer layer. These features are attributed to gallium incorporation at the ZnO-GaN interface. The introduction of a thin (25 nm) ZnO seed layer on GaN buffer layer significantly improves the morphology andmore » vertical alignment of ZnO-NRs without sacrificing the high optical quality of ZnO nanorods on GaN buffer layer. The presence of a thick (200 nm) ZnO seed layer completely masks the effect of the underlying GaN buffer layer on the morphology and optical properties of nanorods.« less

  3. Effects of surface morphology of ZnO seed layers on growth of ZnO nanostructures prepared by hydrothermal method and annealing.

    PubMed

    Yim, Kwang Gug; Kim, Min Su; Leem, Jae-Young

    2013-05-01

    ZnO nanostructures were grown on Si (111) substrates by a hydrothermal method. Prior to growing the ZnO nanostructures, ZnO seed layers with different post-heat temperatures were prepared by a spin-coating process. Then, the ZnO nanostructures were annealed at 500 degrees C for 20 min under an Ar atmosphere. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out at room temperature (RT) to investigate the structural and optical properties of the as-grown and annealed ZnO nanostructures. The surface morphologies of the seed layers changed from a smooth surface to a mountain chain-like structure as the post-heating temperatures increased. The as-grown and annealed ZnO nanostructures exhibited a strong (002) diffraction peak. Compared to the as-grown ZnO nanostructures, the annealed ZnO nanostructures exhibited significantly strong enhancement in the PL intensity ratio by almost a factor of 2.

  4. Comparative in vitro genotoxicity study of ZnO nanoparticles, ZnO macroparticles and ZnCl2 to MDCK kidney cells: Size matters.

    PubMed

    Kononenko, Veno; Repar, Neža; Marušič, Nika; Drašler, Barbara; Romih, Tea; Hočevar, Samo; Drobne, Damjana

    2017-04-01

    In the present study, we evaluated the roles that ZnO particle size and Zn ion release have on cyto- and genotoxicity in vitro. The Madin-Darby canine kidney (MDCK) cells were treated with ZnO nanoparticles (NPs), ZnO macroparticles (MPs), and ZnCl 2 as a source of free Zn ions. We first tested cytotoxicity to define sub-cytotoxic exposure concentrations and afterwards we performed alkaline comet and cytokinesis-block micronucleus assays. Additionally, the activities of both catalase (CAT) and glutathione S-transferase (GST) were evaluated in order to examine the potential impairment of cellular stress-defence capacity. The amount of dissolved Zn ions from ZnO NPs in the cell culture medium was evaluated by an optimized voltammetric method. The results showed that all the tested zinc compounds induced similar concentration-dependent cytotoxicity, but only ZnO NPs significantly elevated DNA and chromosomal damage, which was accompanied by a reduction of GST and CAT activity. Although Zn ion release from ZnO NPs in cell culture medium was significant, our results show that this reason alone cannot explain the ZnO genotoxicity seen in this experiment. We discuss that genotoxicity of ZnO NPs depends on the particle size, which determines the physical principles of their dissolution and cellular internalisation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. ZnO nanofiber (NFs) growth from ZnO nanowires (NWs) by controlling growth temperature on flexible Teflon substrate by CBD technique for UV photodetector

    NASA Astrophysics Data System (ADS)

    Farhat, O. F.; Halim, M. M.; Ahmed, Naser M.; Qaeed, M. A.

    2016-12-01

    In this study, ZnO nanofibers (ZnO NFs) were successfully grown for the first time on Teflon substrates using CBD technique. The well-aligned ZnO nanorods (ZnO NRs) were transformed to ZnO nanofibers (NFs) by varying growth temperature and growth time. The high intensity and distinct growth orientation of peaks observed in the XRD spectra of the NFs indicate high crystal quality. The field emission scanning electron microscopy (FESEM) revealed high density of small diameter sized and long ZnO nanofibers (NFs) that are distributed in random directions. Raman analyses revealed a high E2 (high) peak at 436 nm, which indicates the wurtzite structure of ZnO. A flexible ZnO nanofiber (NFs)-based metal-semiconductor-metal UV detector was fabricated and analyzed for photo response and sensitivity under low power illumination (375 nm, 1.5 mW/cm2). The results showed a sensitivity of 4045% which can be considered a relatively high response and baseline recovery for UV detection.

  6. Photocurrent enhancement mechanisms in bilayer nanofilm-based ultraviolet photodetectors made from ZnO and ZnS spherical nanoshells

    PubMed Central

    2014-01-01

    Hollow-sphere bilayer nanofilm-based ultraviolet light photodetectors made from ZnO and ZnS spherical nanoshells show enhanced photocurrent, which are comparable to or even better than those of other semiconductor nanostructures with different shapes. In this work, the photocurrent enhancement mechanisms of these bilayer nanofilm-based ultraviolet light photodetectors are explained, which could be attributed to the strong light absorption based on the whispering gallery mode resonances, the separation of the photogenerated carriers through the internal electric field within the bilayer nanofilms, the hopping-like electrical transport, and the effective charge injection from Cr/Au contacts to the nanofilms. PMID:25136287

  7. Ultrafast photodynamics of the indoline dye D149 adsorbed to porous ZnO in dye-sensitized solar cells.

    PubMed

    Rohwer, Egmont; Richter, Christoph; Heming, Nadine; Strauch, Kerstin; Litwinski, Christian; Nyokong, Tebello; Schlettwein, Derck; Schwoerer, Heinrich

    2013-01-14

    We investigate the ultrafast dynamics of the photoinduced electron transfer between surface-adsorbed indoline D149 dye and porous ZnO as used in the working electrodes of dye-sensitized solar cells. Transient absorption spectroscopy was conducted on the dye in solution, on solid state samples and for the latter in contact to a I(-)/I(3)(-) redox electrolyte typical for dye-sensitized solar cells to elucidate the effect of each component in the observed dynamics. D149 in a solution of 1:1 acetonitrile and tert-butyl alcohol shows excited-state lifetimes of 300±50 ps. This signature is severely quenched when D149 is adsorbed to ZnO, with the fastest component of the decay trace measured at 150±20 fs due to the charge-transfer mechanism. Absorption bands of the oxidized dye molecule were investigated to determine regeneration times which are in excess of 1 ns. The addition of the redox electrolyte to the system results in faster regeneration times, of the order of 1 ns. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Size-dependent Young’s modulus in ZnO nanowires with strong surface atomic bonds

    NASA Astrophysics Data System (ADS)

    Fan, Shiwen; Bi, Sheng; Li, Qikun; Guo, Qinglei; Liu, Junshan; Ouyang, Zhongliang; Jiang, Chengming; Song, Jinhui

    2018-03-01

    The mechanical properties of size-dependent nanowires are important in nano-electro-mechanical systems (NEMSs), and have attracted much research interest. Characterization of the size effect of nanowires in atmosphere directly to broaden their practical application instead of just in high vacuum situations, as reported previously, is desperately needed. In this study, we systematically studied the Young’s modulus of vertical ZnO nanowires in atmosphere. The diameters ranged from 48 nm to 239 nm with a resonance method using non-contact atomic force microscopy. The values of Young’s modulus in atmosphere present extremely strong increasing tendency with decreasing diameter of nanowire due to stronger surface atomic bonds compared with that in vacuum. A core-shell model for nanowires is proposed to explore the Young’s modulus enhancement in atmosphere, which is correlated with atoms of oxygen occurring near the nanowire surface. The modified model is more accurate for analyzing the mechanical behavior of nanowires in atmosphere compared with the model in vacuum. Furthermore, it is possible to use this characterization method to measure the size-related elastic properties of similar wire-sharp nanomaterials in atmosphere and estimate the corresponding mechanical behavior. The study of the size-dependent Young’s modulus in ZnO nanowires in atmosphere will improve the understanding of the mechanical properties of nanomaterials as well as providing guidance for applications in NEMSs, nanogenerators, biosensors and other related areas.

  9. ZnO nanoneedle/H2O solid-liquid heterojunction-based self-powered ultraviolet detector

    PubMed Central

    2013-01-01

    ZnO nanoneedle arrays were grown vertically on a fluorine-doped tin oxide-coated glass by hydrothermal method at a relatively low temperature. A self-powered photoelectrochemical cell-type UV detector was fabricated using the ZnO nanoneedles as the active photoanode and H2O as the electrolyte. This solid-liquid heterojunction offers an enlarged ZnO/water contact area and a direct pathway for electron transport simultaneously. By connecting this UV photodetector to an ammeter, the intensity of UV light can be quantified using the output short-circuit photocurrent without a power source. High photosensitivity, excellent spectral selectivity, and fast photoresponse at zero bias are observed in this UV detector. The self-powered behavior can be well explained by the formation of a space charge layer near the interface of the solid-liquid heterojunction, which results in a built-in potential and makes the solid-liquid heterojunction work in photovoltaic mode. PMID:24103153

  10. Piezoelectric potential gated field-effect transistor based on a free-standing ZnO wire.

    PubMed

    Fei, Peng; Yeh, Ping-Hung; Zhou, Jun; Xu, Sheng; Gao, Yifan; Song, Jinhui; Gu, Yudong; Huang, Yanyi; Wang, Zhong Lin

    2009-10-01

    We report an external force triggered field-effect transistor based on a free-standing piezoelectric fine wire (PFW). The device consists of an Ag source electrode and an Au drain electrode at two ends of a ZnO PFW, which were separated by an insulating polydimethylsiloxane (PDMS) thin layer. The working principle of the sensor is proposed based on the piezoelectric potential gating effect. Once subjected to a mechanical impact, the bent ZnO PFW cantilever creates a piezoelectric potential distribution across it width at its root and simultaneously produces a local reverse depletion layer with much higher donor concentration than normal, which can dramatically change the current flowing from the source electrode to drain electrode when the device is under a fixed voltage bias. Due to the free-standing structure of the sensor device, it has a prompt response time less than 20 ms and quite high and stable sensitivity of 2%/microN. The effect from contact resistance has been ruled out.

  11. Investigations into the impact of various substrates and ZnO ultra thin seed layers prepared by atomic layer deposition on growth of ZnO nanowire array

    PubMed Central

    2012-01-01

    The impact of various substrates and zinc oxide (ZnO) ultra thin seed layers prepared by atomic layer deposition on the geometric morphology of subsequent ZnO nanowire arrays (NWs) fabricated by the hydrothermal method was investigated. The investigated substrates included B-doped ZnO films, indium tin oxide films, single crystal silicon (111), and glass sheets. Scanning electron microscopy and X-ray diffraction measurements revealed that the geometry and aligment of the NWs were controlled by surface topography of the substrates and thickness of the ZnO seed layers, respectively. According to atomic force microscopy data, we suggest that the substrate, fluctuate amplitude and fluctuate frequency of roughness on ZnO seed layers have a great impact on the alignment of the resulting NWs, whereas the influence of the seed layers' texture was negligible. PMID:22759838

  12. Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application

    PubMed Central

    Chao, Chung-Hua; Wei, Da-Hua

    2015-01-01

    In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto silicon (Si) substrates via different synthesized temperatures by using plasma enhanced chemical vapor deposition (PECVD) system. The effects of different synthesized temperatures on the crystal structure, surface morphologies and optical properties have been investigated. The X-ray diffraction (XRD) patterns indicated that the intensity of (0002) diffraction peak became stronger with increasing synthesized temperature until 400 oC. The diffraction intensity of (0002) peak gradually became weaker accompanying with appearance of (10-10) diffraction peak as the synthesized temperature up to excess of 400 oC. The RT photoluminescence (PL) spectra exhibited a strong near-band-edge (NBE) emission observed at around 375 nm and a negligible deep-level (DL) emission located at around 575 nm under high c-axis ZnO thin films. Field emission scanning electron microscopy (FE-SEM) images revealed the homogeneous surface and with small grain size distribution. The ZnO thin films have also been synthesized onto glass substrates under the same parameters for measuring the transmittance. For the purpose of ultraviolet (UV) photodetector application, the interdigitated platinum (Pt) thin film (thickness ~100 nm) fabricated via conventional optical lithography process and radio frequency (RF) magnetron sputtering. In order to reach Ohmic contact, the device was annealed in argon circumstances at 450 oC by rapid thermal annealing (RTA) system for 10 min. After the systematic measurements, the current-voltage (I-V) curve of photo and dark current and time-dependent photocurrent response results exhibited a good responsivity and reliability, indicating that the high c-axis ZnO thin film is a suitable sensing layer for UV photodetector application. PMID:26484561

  13. Enhanced removal of Cr(VI) from aqueous solution by supported ZnO nanoparticles on biochar derived from waste water hyacinth.

    PubMed

    Yu, Jiangdong; Jiang, Chunyan; Guan, Qingqing; Ning, Ping; Gu, Junjie; Chen, Qiuling; Zhang, Junmin; Miao, Rongrong

    2018-03-01

    Biochar derived from waste water hyacinth was prepared and modified by ZnO nanoparticles for Cr(VI) removal from aqueous solution with the aim of Cr(VI) removal and management of waste biomass. The effect of carbonization temperature (500-800 °C), ZnO content (10-50 wt%) loaded on biochar and contact time (0.17-14 h) on the Cr(VI) removal were investigated. It was found that higher than 95% removal efficiency of Cr(VI) can be achieved with the biochar loaded 30 wt% ZnO. The adsorption kinetics of the sorbent is consistent with the pseudo-second-order kinetic model and adsorption isotherm follows the Langmuir model with maximum adsorption capacity of 43.48 mg g -1 for Cr(VI). Multiple techniques such as XRD, XPS, SEM, EDX and FT-IR were performed to investigate the possible mechanisms involved in the Cr (VI) adsorption. The results show that there is precipitation between chromium ions and Zn oxide. Furthermore, the ZnO nanoparticles acts as photo-catalyst to generate photo-generated electrons to enhance the reduction of Cr(VI) to Cr(III). The as-prepared ZnO/BC possess good recyclability and the removal ratio remained at about 70% in the fifth cycle, which suggests that both contaminants removal and effective management of water hyacinth can be achieved by the approach. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

    PubMed Central

    2014-01-01

    Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol–gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol–gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices. PMID:24521308

  15. Hydrothermal temperature effect on crystal structures, optical properties and electrical conductivity of ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Dhafina, Wan Almaz; Salleh, Hasiah; Daud, Mohd Zalani; Ghazali, Mohd Sabri Mohd; Ghazali, Salmah Mohd

    2017-09-01

    ZnO is an wide direct band gap semiconductor and possess rich family of nanostructures which turned to be a key role in the nanotechnology field of applications. Hydrothermal method was proven to be simple, robust and low cost among the reported methods to synthesize ZnO nanostructures. In this work, the properties of ZnO nanostructures were altered by varying temperatures of hydrothermal process. The changes in term of morphological, crystal structures, optical properties and electrical conductivity were investigated. A drastic change of ZnO nanostructures morphology and decreases of 002 diffraction peak were observed as the hydrothermal temperature increased. The band gap of samples decreased as the size of ZnO nanostructure increased, whereas the electrical conductivity had no influence on the band gap value but more on the morphology of ZnO nanostructures instead.

  16. Single-walled carbon nanotubes coated with ZnO by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Pal, Partha P.; Gilshteyn, Evgenia; Jiang, Hua; Timmermans, Marina; Kaskela, Antti; Tolochko, Oleg V.; Kurochkin, Alexey V.; Karppinen, Maarit; Nisula, Mikko; Kauppinen, Esko I.; Nasibulin, Albert G.

    2016-12-01

    The possibility of ZnO deposition on the surface of single-walled carbon nanotubes (SWCNTs) with the help of an atomic layer deposition (ALD) technique was successfully demonstrated. The utilization of pristine SWCNTs as a support resulted in a non-uniform deposition of ZnO in the form of nanoparticles. To achieve uniform ZnO coating, the SWCNTs first needed to be functionalized by treating the samples in a controlled ozone atmosphere. The uniformly ZnO coated SWCNTs were used to fabricate UV sensing devices. An UV irradiation of the ZnO coated samples turned them from hydrophobic to hydrophilic behaviour. Furthermore, thin films of the ZnO coated SWCNTs allowed us switch p-type field effect transistors made of pristine SWCNTs to have ambipolar characteristics.

  17. Single-walled carbon nanotubes coated with ZnO by atomic layer deposition.

    PubMed

    Pal, Partha P; Gilshteyn, Evgenia; Jiang, Hua; Timmermans, Marina; Kaskela, Antti; Tolochko, Oleg V; Karppinen, Maarit; Nisula, Mikko; Kauppinen, Esko I; Nasibulin, Albert G

    2016-12-02

    The possibility of ZnO deposition on the surface of single-walled carbon nanotubes (SWCNTs) with the help of an atomic layer deposition (ALD) technique was successfully demonstrated. The utilization of pristine SWCNTs as a support resulted in a non-uniform deposition of ZnO in the form of nanoparticles. To achieve uniform ZnO coating, the SWCNTs first needed to be functionalized by treating the samples in a controlled ozone atmosphere. The uniformly ZnO coated SWCNTs were used to fabricate UV sensing devices. An UV irradiation of the ZnO coated samples turned them from hydrophobic to hydrophilic behaviour. Furthermore, thin films of the ZnO coated SWCNTs allowed us switch p-type field effect transistors made of pristine SWCNTs to have ambipolar characteristics.

  18. Defect-induced ferromagnetism in ZnO nanoparticles prepared by mechanical milling

    NASA Astrophysics Data System (ADS)

    Phan, The-Long; Zhang, Y. D.; Yang, D. S.; Nghia, N. X.; Thanh, T. D.; Yu, S. C.

    2013-02-01

    Though ZnO is known as a diamagnetic material, recent studies have revealed that its nanostructures can be ferromagnetic (FM). The FM origin has been ascribed to intrinsic defects. This work shines light on an alternate method based on mechanical milling to induce defect-related ferromagnetism in ZnO nanoparticles (NPs) from initial diamagnetic ZnO powders. Our idea is motivated by the fact that mechanical milling introduces more defects to a ground material. We point out that the FM order increases with increasing the density of defects in ZnO NPs. The experimental results obtained from analyzing X-ray absorption, electron spin resonance, and Raman scattering spectra demonstrate that the ferromagnetism in ZnO NPs is due to intrinsic defects mainly related to oxygen and zinc vacancies. Among these, zinc vacancies play a decisive role in introducing a high FM order in ZnO NPs.

  19. UV-Enhanced Ethanol Sensing Properties of RF Magnetron-Sputtered ZnO Film.

    PubMed

    Huang, Jinyu; Du, Yu; Wang, Quan; Zhang, Hao; Geng, Youfu; Li, Xuejin; Tian, Xiaoqing

    2017-12-26

    ZnO film was deposited by the magnetron sputtering method. The thickness of ZnO film is approximately 2 μm. The influence of UV light illumination on C₂H₅OH sensing properties of ZnO film was investigated. Gas sensing results revealed that the UV-illuminated ZnO film displays excellent C₂H₅OH characteristics in terms of high sensitivity, excellent selectivity, rapid response/recovery, and low detection limit down to 0.1 ppm. The excellent sensing performance of the sensor with UV activation could be attributed to the photocatalytic oxidation of ethanol on the surface of the ZnO film, the planar film structure with high utilizing efficiency of UV light, high electron mobility, and a good surface/volume ratio of of ZnO film with a relatively rough and porous surface.

  20. Room temperature synthesis and optical properties of small diameter (5 nm) ZnO nanorod arrays.

    PubMed

    Cho, Seungho; Jang, Ji-Wook; Lee, Jae Sung; Lee, Kun-Hong

    2010-10-01

    We report a simple wet-chemical synthesis of ∼5 nm diameter ZnO nanorod arrays at room temperature (20 °C) and normal atmospheric pressure (1 atm) and their optical properties. They were single crystalline in nature, and grew in the [001] direction. These small diameter ZnO nanorod arrays can also be synthesized at 0 °C. Control experiments were also conducted. On the basis of the results, we propose a mechanism for the spontaneous growth of the small diameter ZnO structures. The optical properties of the 5 nm diameter ZnO nanorod arrays synthesized using this method were probed by UV-Visible diffuse reflectance spectroscopy. A clear blue-shift, relative to the absorption band from 50 nm diameter ZnO nanorod arrays, was attributed to the quantum confinement effects caused by the small nanocrystal size in the 5 nm diameter ZnO nanorods.