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Sample records for atomically flat single-crystalline

  1. Atomically flat single-crystalline gold nanostructures for plasmonic nanocircuitry.

    PubMed

    Huang, Jer-Shing; Callegari, Victor; Geisler, Peter; Brüning, Christoph; Kern, Johannes; Prangsma, Jord C; Wu, Xiaofei; Feichtner, Thorsten; Ziegler, Johannes; Weinmann, Pia; Kamp, Martin; Forchel, Alfred; Biagioni, Paolo; Sennhauser, Urs; Hecht, Bert

    2010-01-01

    Deep subwavelength integration of high-definition plasmonic nanostructures is of key importance in the development of future optical nanocircuitry for high-speed communication, quantum computation and lab-on-a-chip applications. To date, the experimental realization of proposed extended plasmonic networks consisting of multiple functional elements remains challenging, mainly because of the multi-crystallinity of commonly used thermally evaporated gold layers. This can produce structural imperfections in individual circuit elements that drastically reduce the yield of functional integrated nanocircuits. In this paper we demonstrate the use of large (>100 μm(2)) but thin (<80 nm) chemically grown single-crystalline gold flakes that, after immobilization, serve as an ideal basis for focused ion beam milling and other top-down nanofabrication techniques on any desired substrate. Using this methodology we obtain high-definition ultrasmooth gold nanostructures with superior optical properties and reproducible nano-sized features over micrometre-length scales. Our approach provides a possible solution to overcome the current fabrication bottleneck and realize high-definition plasmonic nanocircuitry. PMID:21267000

  2. Single Crystalline Film of Hexagonal Boron Nitride Atomic Monolayer by Controlling Nucleation Seeds and Domains

    PubMed Central

    Wu, Qinke; Park, Ji-Hoon; Park, Sangwoo; Jung, Seong Jun; Suh, Hwansoo; Park, Noejung; Wongwiriyapan, Winadda; Lee, Sungjoo; Lee, Young Hee; Song, Young Jae

    2015-01-01

    A monolayer hexagonal boron nitride (h-BN) film with controllable domain morphology and domain size (varying from less than 1 μm to more than 100 μm) with uniform crystalline orientation was successfully synthesized by chemical vapor deposition (CVD). The key for this extremely large single crystalline domain size of a h-BN monolayer is a decrease in the density of nucleation seeds by increasing the hydrogen gas flow during the h-BN growth. Moreover, the well-defined shape of h-BN flakes can be selectively grown by controlling Cu-annealing time under argon atmosphere prior to h-BN growth, which provides the h-BN shape varies in triangular, trapezoidal, hexagonal and complex shapes. The uniform crystalline orientation of h-BN from different nucleation seeds can be easily confirmed by polarized optical microscopy (POM) with a liquid crystal coating. Furthermore, seamlessly merged h-BN flakes without structural domain boundaries were evidence by a selective hydrogen etching after a full coverage of a h-BN film was achieved. This seamless large-area and atomic monolayer of single crystalline h-BN film can offer as an ideal and practical template of graphene-based devices or alternative two-dimensional materials for industrial applications with scalability. PMID:26537788

  3. Single Crystalline Film of Hexagonal Boron Nitride Atomic Monolayer by Controlling Nucleation Seeds and Domains.

    PubMed

    Wu, Qinke; Park, Ji-Hoon; Park, Sangwoo; Jung, Seong Jun; Suh, Hwansoo; Park, Noejung; Wongwiriyapan, Winadda; Lee, Sungjoo; Lee, Young Hee; Song, Young Jae

    2015-01-01

    A monolayer hexagonal boron nitride (h-BN) film with controllable domain morphology and domain size (varying from less than 1 μm to more than 100 μm) with uniform crystalline orientation was successfully synthesized by chemical vapor deposition (CVD). The key for this extremely large single crystalline domain size of a h-BN monolayer is a decrease in the density of nucleation seeds by increasing the hydrogen gas flow during the h-BN growth. Moreover, the well-defined shape of h-BN flakes can be selectively grown by controlling Cu-annealing time under argon atmosphere prior to h-BN growth, which provides the h-BN shape varies in triangular, trapezoidal, hexagonal and complex shapes. The uniform crystalline orientation of h-BN from different nucleation seeds can be easily confirmed by polarized optical microscopy (POM) with a liquid crystal coating. Furthermore, seamlessly merged h-BN flakes without structural domain boundaries were evidence by a selective hydrogen etching after a full coverage of a h-BN film was achieved. This seamless large-area and atomic monolayer of single crystalline h-BN film can offer as an ideal and practical template of graphene-based devices or alternative two-dimensional materials for industrial applications with scalability. PMID:26537788

  4. Fully methylated, atomically flat (111) silicon surface

    NASA Astrophysics Data System (ADS)

    Fidélis, A.; Ozanam, F.; Chazalviel, J.-N.

    2000-01-01

    The atomically flat hydrogenated (111) silicon surface has been methylated by anodization in a Grignard reagent and the surface obtained characterized by infrared spectroscopy. 100% substitution of the hydrogen atoms by methyl groups is observed. The resulting surface exhibits preserved ordering and superior chemical stability.

  5. Epitaxial growth of homogeneous single-crystalline AlN films on single-crystalline Cu (1 1 1) substrates

    NASA Astrophysics Data System (ADS)

    Wang, Wenliang; Yang, Weijia; Liu, Zuolian; Lin, Yunhao; Zhou, Shizhong; Qian, Huirong; Gao, Fangliang; Yang, Hui; Li, Guoqiang

    2014-03-01

    The homogeneous and crack free single-crystalline AlN thin films have been epitaxially grown on single-crystalline Cu (1 1 1) substrates with an in-plane alignment of AlN [11-20]//Cu [1-10] by pulsed laser deposition (PLD) technology with an integrated laser rastering program. The as-grown AlN films are studied by spectroscopic ellipsometry, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), polarized light microscopy, high-resolution X-ray diffraction, and high-resolution transmission electron microscopy (HRTEM). The spectroscopic ellipsometry reveals the excellent thickness uniformity of as-grown AlN films on the Cu (1 1 1) substrates with a root-mean-square (RMS) thickness inhomogeneity less than 2.6%. AFM and FESEM measurements indicate that very smooth and flat surface AlN films are obtained with a surface RMS roughness of 2.3 nm. The X-ray reflectivity image illustrates that there is a maximum of 1.2 nm thick interfacial layer existing between the as-grown AlN and Cu (1 1 1) substrates and is confirmed by HRTEM measurement, and reciprocal space mapping shows that almost fully relaxed AlN films are achieved only with a compressive strain of 0.48% within ˜321 nm thick films. This work demonstrates a possibility to obtain homogeneous and crack free single-crystalline AlN films on metallic substrates by PLD with optimized laser rastering program, and brings up a broad prospect for the application of acoustic filters that require abrupt hetero-interfaces between the AlN films and the metallic electrodes.

  6. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, A.I.; Gargas, Daniel; Jeong Hwang, Yun; Yang, Peidong

    2009-08-04

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. These porous nanowires also retain the crystallographic orientation of the wafer from which they are etched. Electron microscopy and diffraction confirm their single-crystallinity and reveal the silicon surrounding the pores is as thin as several nanometers. Confocal fluorescence microscopy showed that the photoluminescence (PL) of these arrays emanate from the nanowires themselves, and their PL spectrum suggests that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices.

  7. Controlling wave-vector of propagating surface plasmon polaritons on single-crystalline gold nanoplates

    PubMed Central

    Luo, Si; Yang, Hangbo; Yang, Yuanqing; Zhao, Ding; Chen, Xingxing; Qiu, Min; Li, Qiang

    2015-01-01

    Surface plasmon polaritons (SPPs) propagating at metal nanostructures play an important role in breaking the diffraction limit. Chemically synthesized single-crystalline metal nanoplates with atomically flat surfaces provide favorable features compared with traditional polycrystalline metal films. The excitation and propagation of leaky SPPs on micrometer sized (10–20 μm) and thin (30 nm) gold nanoplates are investigated utilizing leakage radiation microscopy. By varying polarization and excitation positions of incident light on apexes of nanoplates, wave-vector (including propagation constant and propagation direction) distributions of leaky SPPs in Fourier planes can be controlled, indicating tunable SPP propagation. These results hold promise for potential development of chemically synthesized single-crystalline metal nanoplates as plasmonic platforms in future applications. PMID:26302955

  8. A Single-Crystalline Mesoporous Quartz Superlattice.

    PubMed

    Matsuno, Takamichi; Kuroda, Yoshiyuki; Kitahara, Masaki; Shimojima, Atsushi; Wada, Hiroaki; Kuroda, Kazuyuki

    2016-05-10

    There has been significant interest in the crystallization of nanostructured silica into α-quartz because of its physicochemical properties. We demonstrate a single-crystalline mesoporous quartz superlattice, a silica polymorph with unprecedentedly ordered hierarchical structures on both the several tens of nanometers scale and the atomic one. The mesoporous quartz superlattice consists of periodically arranged α-quartz nanospheres whose crystalline axes are mostly oriented in an assembly. The superlattice is prepared by thermal crystallization of amorphous silica nanospheres constituting a colloidal crystal. We found that the deposition of a strong flux of Li(+) only on the surface of silica nanospheres is effective for crystallization.

  9. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, Allon; Dargas, Daniel; Hwang, Yun Jeong; Yang, Peidong

    2009-08-18

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. The photoluminescence of these nanowires suggest they are composed of crystalline silicon with small enough dimensions such that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices. A better understanding of this electroless route to mesoporous silicon could lead to facile and general syntheses of different narrow bandgap semiconductor nanostructures for various applications.

  10. Single-crystalline monolayer and multilayer graphene nano switches

    SciTech Connect

    Li, Peng; Cui, Tianhong; Jing, Gaoshan; Zhang, Bo; Sando, Shota

    2014-03-17

    Growth of monolayer, bi-layer, and tri-layer single-crystalline graphene (SCG) using chemical vapor deposition method is reported. SCG's mechanical properties and single-crystalline nature were characterized and verified by atomic force microscope and Raman spectroscopy. Electro-mechanical switches based on mono- and bi-layer SCG were fabricated, and the superb properties of SCG enable the switches to operate at pull-in voltage as low as 1 V, and high switching speed about 100 ns. These devices exhibit lifetime without a breakdown of over 5000 cycles, far more durable than any other graphene nanoelectromechanical system switches reported.

  11. Single-crystalline aluminum film for ultraviolet plasmonic nanolasers

    PubMed Central

    Chou, Bo-Tsun; Chou, Yu-Hsun; Wu, Yen-Mo; Chung, Yi-Cheng; Hsueh, Wei-Jen; Lin, Shih-Wei; Lu, Tien-Chang; Lin, Tzy-Rong; Lin, Sheng-Di

    2016-01-01

    Significant advances have been made in the development of plasmonic devices in the past decade. Plasmonic nanolasers, which display interesting properties, have come to play an important role in biomedicine, chemical sensors, information technology, and optical integrated circuits. However, nanoscale plasmonic devices, particularly those operating in the ultraviolet regime, are extremely sensitive to the metal and interface quality. Thus, these factors have a significant bearing on the development of ultraviolet plasmonic devices. Here, by addressing these material-related issues, we demonstrate a low-threshold, high-characteristic-temperature metal-oxide-semiconductor ZnO nanolaser that operates at room temperature. The template for the ZnO nanowires consists of a flat single-crystalline Al film grown by molecular beam epitaxy and an ultrasmooth Al2O3 spacer layer synthesized by atomic layer deposition. By effectively reducing the surface plasmon scattering and metal intrinsic absorption losses, the high-quality metal film and the sharp interfaces formed between the layers boost the device performance. This work should pave the way for the use of ultraviolet plasmonic nanolasers and related devices in a wider range of applications. PMID:26814581

  12. Single-crystalline aluminum film for ultraviolet plasmonic nanolasers.

    PubMed

    Chou, Bo-Tsun; Chou, Yu-Hsun; Wu, Yen-Mo; Chung, Yi-Cheng; Hsueh, Wei-Jen; Lin, Shih-Wei; Lu, Tien-Chang; Lin, Tzy-Rong; Lin, Sheng-Di

    2016-01-01

    Significant advances have been made in the development of plasmonic devices in the past decade. Plasmonic nanolasers, which display interesting properties, have come to play an important role in biomedicine, chemical sensors, information technology, and optical integrated circuits. However, nanoscale plasmonic devices, particularly those operating in the ultraviolet regime, are extremely sensitive to the metal and interface quality. Thus, these factors have a significant bearing on the development of ultraviolet plasmonic devices. Here, by addressing these material-related issues, we demonstrate a low-threshold, high-characteristic-temperature metal-oxide-semiconductor ZnO nanolaser that operates at room temperature. The template for the ZnO nanowires consists of a flat single-crystalline Al film grown by molecular beam epitaxy and an ultrasmooth Al2O3 spacer layer synthesized by atomic layer deposition. By effectively reducing the surface plasmon scattering and metal intrinsic absorption losses, the high-quality metal film and the sharp interfaces formed between the layers boost the device performance. This work should pave the way for the use of ultraviolet plasmonic nanolasers and related devices in a wider range of applications. PMID:26814581

  13. A pseudo-single-crystalline germanium film for flexible electronics

    SciTech Connect

    Higashi, H.; Yamada, S.; Kanashima, T.; Hamaya, K.; Kasahara, K.; Park, J.-H.; Miyao, M.; Kudo, K.; Okamoto, H.; Moto, K.; Tsunoda, I.

    2015-01-26

    We demonstrate large-area (∼600 μm), (111)-oriented, and high-crystallinity, i.e., pseudo-single-crystalline, germanium (Ge) films at 275 °C, where the temperature is lower than the softening temperature of a flexible substrate. A modulated gold-induced layer exchange crystallization method with an atomic-layer deposited Al{sub 2}O{sub 3} barrier and amorphous-Ge/Au multilayers is established. From the Raman measurements, we can judge that the crystallinity of the obtained Ge films is higher than those grown by aluminum-induced-crystallization methods. Even on a flexible substrate, the pseudo-single-crystalline Ge films for the circuit with thin-film transistor arrays can be achieved, leading to high-performance flexible electronics based on an inorganic-semiconductor channel.

  14. Atomically flat superconducting nanofilms: multiband properties and mean-field theory

    NASA Astrophysics Data System (ADS)

    Shanenko, A. A.; Aguiar, J. Albino; Vagov, A.; Croitoru, M. D.; Milošević, M. V.

    2015-05-01

    Recent progress in materials synthesis enabled fabrication of superconducting atomically flat single-crystalline metallic nanofilms with thicknesses down to a few monolayers. Interest in such nano-thin systems is attracted by the dimensional 3D-2D crossover in their coherent properties which occurs with decreasing the film thickness. The first fundamental aspect of this crossover is dictated by the Mermin-Wagner-Hohenberg theorem and concerns frustration of the long-range order due to superconductive fluctuations and the possibility to track its impact with an unprecedented level of control. The second important aspect is related to the Fabri-Pérot modes of the electronic motion strongly bound in the direction perpendicular to the nanofilm. The formation of such modes results in a pronounced multiband structure that changes with the nanofilm thickness and affects both the mean-field behavior and superconductive fluctuations. Though the subject is very rich in physics, it is scarcely investigated to date. The main obstacle is that there are no manageable models to study a complex magnetic response in this case. Full microscopic consideration is rather time consuming, if practicable at all, while the standard Ginzburg-Landau theory is not applicable. In the present work we review the main achievements in the subject to date, and construct and justify an efficient multiband mean-field formalism which allows for numerical and even analytical treatment of nano-thin superconductors in applied magnetic fields.

  15. Atomically flat nickel film grown on synthetic mica

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiroyuki; Taniguchi, Masateru

    2016-07-01

    We have grown nickel heteroepitaxially on muscovite and synthetic mica in vacuo for use as substrates for scanning probe microscopy (SPM) and graphene formation. We have determined annealing conditions that could generate atomically flat surfaces (with rms surface roughness of less than 1 nm). Owing to accelerated degradation at temperatures above 600 °C, muscovite mica was unsuitable as a substrate at high growth temperatures. Thermally stable synthetic fluorophlogopite mica [KMg3(AlSi3O10)F2], on the other hand, was found to be stable at 800 °C and successfully employed for the formation of atomically flat films.

  16. Controlled synthesis of single-crystalline graphene

    SciTech Connect

    Xueshen, Wang Jinjin, Li Qing, Zhong; Yuan, Zhong; Mengke, Zhao; Yonggang, Liu

    2014-03-15

    This paper reports the controlled synthesis of single-crystalline graphene on the back side of copper foil using CH{sub 4} as the precursor. The influence of growth time and the pressure ratio of CH{sub 4}/H{sub 2} on the structure of graphene are examined. An optimized polymer-assisted method is used to transfer the synthesized graphene onto a SiO{sub 2}/Si substrate. Scanning electron microscopy and Raman spectroscopy are used to characterize the graphene.

  17. Atomically Flat Surfaces Developed for Improved Semiconductor Devices

    NASA Technical Reports Server (NTRS)

    Powell, J. Anthony

    2001-01-01

    New wide bandgap semiconductor materials are being developed to meet the diverse high temperature, -power, and -frequency demands of the aerospace industry. Two of the most promising emerging materials are silicon carbide (SiC) for high-temperature and high power applications and gallium nitride (GaN) for high-frequency and optical (blue-light-emitting diodes and lasers) applications. This past year Glenn scientists implemented a NASA-patented crystal growth process for producing arrays of device-size mesas whose tops are atomically flat (i.e., step-free). It is expected that these mesas can be used for fabricating SiC and GaN devices with major improvements in performance and lifetime. The promising new SiC and GaN devices are fabricated in thin-crystal films (known as epi films) that are grown on commercial single-crystal SiC wafers. At this time, no commercial GaN wafers exist. Crystal defects, known as screw defects and micropipes, that are present in the commercial SiC wafers propagate into the epi films and degrade the performance and lifetime of subsequently fabricated devices. The new technology isolates the screw defects in a small percentage of small device-size mesas on the surface of commercial SiC wafers. This enables atomically flat surfaces to be grown on the remaining defect-free mesas. We believe that the atomically flat mesas can also be used to grow GaN epi films with a much lower defect density than in the GaN epi films currently being grown. Much improved devices are expected from these improved low-defect epi films. Surface-sensitive SiC devices such as Schottky diodes and field effect transistors should benefit from atomically flat substrates. Also, we believe that the atomically flat SiC surface will be an ideal surface on which to fabricate nanoscale sensors and devices. The process for achieving atomically flat surfaces is illustrated. The surface steps present on the "as-received" commercial SiC wafer is also illustrated. because of the

  18. Improved Silicon Carbide Crystals Grown From Atomically Flat Surfaces

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.

    2003-01-01

    The NASA Glenn Research Center is demonstrating that atomically flat (i.e., step-free) silicon carbide (SiC) surfaces are ideal for realizing greatly improved wide bandgap semiconductor films with lower crystal defect densities. Further development of these improved films could eventually enable harsh-environment electronics beneficial to jet engine and other aerospace and automotive applications, as well as much more efficient and compact power distribution and control. The technique demonstrated could also improve blue-light lasers and light-emitting-diode displays.

  19. Single-crystalline octahedral Au-Ag nanoframes.

    PubMed

    Hong, Xun; Wang, Dingsheng; Cai, Shuangfei; Rong, Hongpan; Li, Yadong

    2012-11-01

    We report the formation of single-crystalline octahedral Au-Ag nanoframes by a modified galvanic replacement reaction. Upon sequential addition of AgNO(3), CuCl, and HAuCl(4) to octadecylamine solution, truncated polyhedral silver nanoparticles formed first and then changed into octahedral Au-Ag nanoframes, without requiring a conventional Ag removal step with additional oxidation etchant. The nanoframes have 12 sides, and all of the eight {111} faces are empty. The side grows along the [110] direction, and the diameter is less than 10 nm. The selective gold deposition on the high-energy (110) surface, the diffusion, and the selective redeposition of Au and Ag atoms are the key reasons for the formation of octahedral nanoframes.

  20. Plasma-assisted self-sharpening of platelet-structured single-crystalline carbon nanocones

    SciTech Connect

    Levchenko, I.; Ostrikov, K.; Long, J. D.; Xu, S.

    2007-09-10

    A mechanism and model for the vertical growth of platelet-structured vertically aligned single-crystalline carbon nanostructures by the formation of graphene layers on a flat top surface are proposed and verified experimentally. It is demonstrated that plasma-related effects lead to self-sharpening of tapered nanocones to form needlelike nanostructures, in a good agreement with the predicted dependence of the radius of a nanocone's flat top on the incoming ion flux and surface temperature. The growth mechanism is relevant to a broad class of nanostructures including nanotips, nanoneedles, and nanowires and can be used to improve the predictability of nanofabrication processes.

  1. Growth Of Single Crystalline Copper Nanowhiskers

    SciTech Connect

    Kolb, Matthias; Richter, Gunther

    2010-11-24

    Nanowhiskers are defect free single crystals with high aspect ratios and as result exhibit superior physical, e.g. mechanical properties. This paper sheds light on the kinetics of copper nanowhisker growth and thickening. Whisker growth was provoked by covering silicon wafers with a thin carbon film and subsequently coating them with copper by molecular beam epitaxy. The whiskers grown were examined by scanning electron microscopy and the length and diameter were measured as a function of the amount of copper deposited. The experiments show that nanowhisker growth follows Ruth and Hirth's growth model. A fit of the model parameters to the acquired data shows that adsorption of atoms on the substrate and on the whisker surface, with subsequent surface diffusion to the whisker tip, delivers by far the greatest portion of material for whisker growth. Additionally, the experiments demonstrate that the crystallographic orientation of the substrate surface greatly influences the growth rate in the early stage of whisker growth.

  2. Epitaxial layers of 2122 BCSCO superconductor thin films having single crystalline structure

    NASA Technical Reports Server (NTRS)

    Pandey, Raghvendra K. (Inventor); Raina, Kanwal K. (Inventor); Solayappan, Narayanan (Inventor)

    1995-01-01

    A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

  3. Method for forming single phase, single crystalline 2122 BCSCO superconductor thin films by liquid phase epitaxy

    NASA Technical Reports Server (NTRS)

    Pandey, Raghvendra K. (Inventor); Raina, Kanwal (Inventor); Solayappan, Narayanan (Inventor)

    1994-01-01

    A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83 K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

  4. A single crystalline InP nanowire photodetector

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  5. Magnetism in single-crystalline CePtSn.

    SciTech Connect

    Bordallo, H. N.; Chang, S.; Lacerda, A. H.; Nakotte, H.; Takabatake, T.; Torikachvili, M. S.

    1999-08-04

    CePtSn exhibits two antiferromagnetic transitions at low temperatures. We report on magnetoresistance and in magnetization studies of single-crystalline CePtSn in magnetic fields up to 18 T. The data were taken to establish the magnetic phase diagrams for CePtSn in fields applied along the principal directions.

  6. Cavity polaritons in an organic single-crystalline rubrene microcavity

    NASA Astrophysics Data System (ADS)

    Tsuchimoto, Yuta; Nagai, Hikaru; Amano, Masamitsu; Bando, Kazuki; Kondo, Hisao

    2014-06-01

    We fabricated a single-crystalline rubrene microcavity using a simple solution technique and observed cavity polaritons in the microcavity at room temperature (RT). Large Rabi splitting energies were obtained from dispersion of the cavity polaritons. Furthermore, photoluminescence from the cavity polaritons was observed at RT. The findings will be of importance for the application of cavity polaritons.

  7. Patterned Aqueous Growth of Single Crystalline Zinc Oxide for Photonic Applications

    NASA Astrophysics Data System (ADS)

    Pooley, Kathryn Jessica

    Typically a top-down approach is used in the fabrication of functional nanodevices beginning with the bulk material and imposing a two or three-dimensional structure on the material through a combination of lithography and etching. Pre-patterning of a substrate, resulting in the selective growth of a material, has potential for forming three-dimensional device structures in ways that can be more efficient and which can avoid process complexity and process induced damage. In this thesis, the low temperature (90°C) aqueous growth of complex, single crystalline zinc oxide (ZnO) three-dimensional devices through pre-patterned micron and nanometer sized molds is presented. This work focuses on the quality of the single crystalline ZnO material, the constrained growth of ZnO through various sizes and shapes of molds, and the fabrication of several device structures including pillars, rings, and photonic crystals. Due to their single crystalline nature and crystallographically smooth sidewalls, photonic devices created using this growth method have the potential to outperform traditionally fabricated structures in a range of optoelectronic applications. In addition, metal-oxide interfaces are the critical components of many electrical and optical devices, and it is rare to find epitaxial metal-oxide structures. In this work, the first demonstration of low temperature, epitaxial growth of ZnO on single crystalline gold plates is presented. The quality and structure of the ZnO on the gold plates is investigated using scanning electron microscopy, atomic force microscopy, and photoluminescence spectroscopy. The epitaxial growth is confirmed using electron backscatter diffraction and transmission electron microscopy. The metal-oxide interfaces fabricated have the potential to be used in a number of technologically important applications. Possible examples include creating high quality electrical contacts on high bandgap materials and improving light extraction from planar

  8. Epitaxial growth of 2 inch diameter homogeneous AlN single-crystalline films by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Wang, Wenliang; Liu, Zuolian; Li, Guoqiang

    2013-03-01

    2 inch diameter homogeneous AlN films are epitaxially grown on sapphire substrates by pulsed laser deposition (PLD). By optimizing laser rastering and PLD growth conditions, the 2 inch diameter single-crystalline AlN films exhibit excellent thickness uniformity with root-mean-square (RMS) inhomogeneity less than 4.5% and very smooth surface with RMS roughness less than 1.53 nm. There is a maximum of 1.5 nm thick interfacial layer, if there is any, existing between the as-grown AlN and the pre-nitrided sapphire substrate, and the as-grown AlN films are almost fully relaxed only with a 0.26% in-plane compressive strain. The achievement of high-quality large-scale AlN films with uniform thickness and atomically abrupt interface is of great interest for the commercial development of AlN-based devices, particularly acoustic filters where abrupt heterointerfaces with substrates and flat surfaces for AlN films are highly desired.

  9. Proton irradiation effects on the thermoelectric properties in single-crystalline Bi nanowires

    SciTech Connect

    Chang, Taehoo; Kim, Jeongmin; Song, Min-Jung; Lee, Wooyoung

    2015-05-15

    The effects of proton irradiation on the thermoelectric properties of Bi nanowires (Bi-NWs) were investigated. Single crystalline Bi-NWs were grown by the on-film formation of nanowires method. The devices based on individual Bi-NWs were irradiated with protons at different energies. The total number of displaced atoms was estimated using the Kinchin-Pease displacement model. The electric conductivity and Seebeck coefficient in the Bi-NW devices were investigated before and after proton irradiation at different temperatures. Although the Seebeck coefficient remained stable at various irradiation energies, the electrical conductivity significantly declined with increasing proton energy up to 40 MeV.

  10. Electric dipolar interaction assisted growth of single crystalline organic thin films

    SciTech Connect

    Jin-ming, Cai; Yu-Yang, Zhang; Hao, Hu; Li-Hong, Bao; Li-Da, Pan; Wei, Tang; Guo, Li; Shi-Xuan, Du; Jian, Shen; Hong-Jun, Gao

    2010-01-01

    We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the growth process and are able to reproduce the experimental patterns. The energy of electric dipole interaction is calculated and determined to be the driving force for the pattern formation and evolution. Based on these results, single crystalline films are obtained by enhancing the electric dipole interaction while limiting effects of other growth parameters.

  11. Freestanding single-crystalline magnetic structures fabricated by ion bombardment

    SciTech Connect

    Schoenherr, P.; Bischof, A.; Boehm, B.; Eib, P.; Grimm, S.; Gross, L.; Allenspach, R.; Alvarado, S. F.

    2015-01-19

    Starting from an ultrathin Fe film grown epitaxially on top of a GaAs(001) substrate, we show that freestanding structures can be created by ion-beam treatment. These structures are single-crystalline blisters and only a few nanometers thick. Anisotropic stress in the rim of a blister induces magnetic domain states magnetized in the direction normal to the blister edge. Experimental evidence is provided that the lateral size can be confined by starting from a nanostructured template.

  12. Oxygen recoil implant from SiO{sub 2} layers into single-crystalline silicon

    SciTech Connect

    Wang, G.; Chen, Y.; Li, D.; Oak, S.; Srivastav, G.; Banerjee, S.; Tasch, A.; Merrill, P.; Bleiler, R.

    2001-06-01

    It is important to understand the distribution of recoil-implanted atoms and the impact on device performance when ion implantation is performed at a high dose through surface materials into single crystalline silicon. For example, in ultralarge scale integration impurity ions are often implanted through a thin layer of screen oxide and some of the oxygen atoms are inevitably recoil implanted into single-crystalline silicon. Theoretical and experimental studies have been performed to investigate this phenomenon. We have modified the Monte Carlo ion implant simulator, UT-Marlowe (B. Obradovic, G. Wang, Y. Chen, D. Li, C. Snell, and A. F. Tasch, UT-MARLOWE Manual, 1999), which is based on the binary collision approximation, to follow the full cascade and to dynamically modify the stoichiometry of the Si layer as oxygen atoms are knocked into it. CPU reduction techniques are used to relieve the demand on computational power when such a full cascade simulation is involved. Secondary ion mass spectrometry (SIMS) profiles of oxygen have been carefully obtained for high dose As and BF{sub 2} implants at different energies through oxide layers of various thicknesses, and the simulated oxygen profiles are found to agree very well with the SIMS data. {copyright} 2001 American Institute of Physics.

  13. Geometric effects on quantum transport of ultracold atoms in optical lattices: Quantum acceleration and flat band

    NASA Astrophysics Data System (ADS)

    Chien, Chih-Chun; Metcalf, Mekena; di Ventra, Massimiliano; Chern, Gia-Wei

    2015-05-01

    The realizations of interesting optical lattices for ultracold atoms provide opportunities for investigating geometric effects on many-body physics. Thesquare, triangular, honeycomb, kagome lattices, and other geometries have been experimentally demonstrated. When the atoms are driven out of equilibrium by manipulations of the density or trapping potential, their quantum transport can be monitored and fundamental questions regarding transport in isolated systems can be addressed unambiguously. We found that the propagation velocity of the matter wave representing the flowing atoms can be accelerated by tuning the lattice geometry. This acceleration is a pure quantum effect because no shorter path is created as the geometry changes. For lattice geometries supporting a dispersionless flat band, the localized atoms in the flat band do not participate in transport but interfere with the mobile atoms. We found a generic insulating phase exhibiting a density jump in the profile that can be dynamically generated. Interesting spatial patterns may emerge if those flat-band lattices are manipulated, and an analogue of geometric frustration in quantum transport will be presented.

  14. Epitaxial single crystalline ferrite films for high frequency applications

    SciTech Connect

    Suzuki, Y.; Dover, R.B. van; Korenivski, V.; Werder, D.; Chen, C.H.; Felder, R.J.; Phillips, J.M.

    1996-11-01

    The successful growth of single crystal ferrites in thin film form is an important step towards their future incorporation into integrated circuits operating at microwave frequencies. The authors have successfully grown high quality single crystalline spinel ferrite thin films of (Mn,Zn)Fe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} on (100) and (110) SrTiO{sub 3} and MgAl{sub 2}O{sub 4} at low temperature. These ferrite films are buffered with spinel structure layers that are paramagnetic at room temperature. In contrast to ferrite films grown directly on the substrates, ferrite films grown on buffered substrates exhibit excellent crystallinity and bulk saturation magnetization values, thus indicating the importance of lattice match and structural similarity between the film and the immediately underlying layer. X-ray, RBS, AFM and TEM analysis provide a consistent picture of the structural properties of these ferrite films. The authors then use this technique to grow exchange-coupled bilayers of single crystalline CoFe{sub 2}O{sub 4} and (Mn,Zn)Fe{sub 2}O{sub 4}. In these bilayers, they observe strong exchange coupling across the interface that is similar in strength to the exchange coupling in the individual layers.

  15. Electrochemical immobilization of Cs in single-crystalline SYNROC

    NASA Astrophysics Data System (ADS)

    Abe, Hideki; Satoh, Akira; Nishida, Kenji; Abe, Eiji; Naka, Takashi; Imai, Motoharu; Kitazawa, Hideaki

    2006-05-01

    The development of a disposal technique for the radiotoxic 137Cs in nuclear wastes is one of the most urgent issues in nuclear fuel technology. An effective disposal method of 137Cs is to immobilize it in a synthetic rock (SYNROC) material: cesium titanate hollandite, 137Cs xTi 8O 16 ( I4/ m, a=10.2866(3) Å, c=2.9669(1) Å). Practical applications of 137Cs xTi 8O 16 have been restricted so far because the conventional synthetic method requires strong chemical reducers and reaction temperatures higher than 1250 °C. In this report, we present a milder preparation method of Cs xTi 8O 16 by electrolysis of a mixture of Cs 2MoO 4 and TiO 2 in ambient atmosphere at 900 °C. The Cs content in the resultant single-crystalline Cs 1.35Ti 8O 16 is competitive with the highest value in polycrystalline Cs 1.36±0.03Ti 8O 16 prepared by the conventional synthetic method. The electrochemical preparation of Cs 1.35Ti 8O 16 is a promising way to immobilize a high quantity of 137Cs ions in a stable form of single-crystalline SYNROC.

  16. Frictional Properties of Single Crystalline and Quasicrystalline Surfaces

    NASA Astrophysics Data System (ADS)

    Gellman, Andrew

    2000-03-01

    The use of ultra-high vacuum surface science methods has been aplied to the problem of studying friction between single srystalline and quasicrystalline metal surfaces. A experimental apparatus has been developed that combines the ability to perform surface preparation and analysis with the ability to make measurements of macroscopic friction forces between surfaces in sliding contact. This UHV chamber allows simultaneous preparation and characterization of two sample surfaces. These are usually single crystalline samples of the same metal and can be either perfectly clean or modified by adsorbed species such as atoms or molecules. Once prepared these two surfaces can be brought into contact under an applied normal load (Fn = 0.001 0.1 N) and sheared relative to one another at constant velocity (vs = 1 100 mm/s). Both normal and shear forces are measured simultaneously enabling one to determine a coefficient of friction. This unique apparatus has been used to study a number of problems in tribology. Adsorbed species on metal surfaces serve as a lubricants and prevent direct metal-metal contact. We have addressed the issue of surface coverage effects on interfacial friction. Surfaces have been prepared with adsorbed species ranging continuously in coverage from zero monolayers to many ( 100) monolayers. These experiments have been performed with pairs of both Ni(100) and Cu(111) surfaces. The interesting observation has been that adsorbed layers of atoms have little or no influence on friction coefficients between the two surfaces at coverages below one monolayer. Adsorbed molecules such as ethanol or trifluoroethanol are more interesting in this regard. They also have little influence on friction when adsorbed at coverages of < 1 monolayer, however, once the coverage exceeds 1 monolayer the coefficient of friction drops substantially. Friction reaches its limit at coverages of 5 10 monolayer. It is quite interesting to note that these metal single crystal surface

  17. Single crystalline nature of para-sexiphenyl crystallites grown on KCl(100).

    PubMed

    Haber, T; Oehzelt, M; Resel, R; Andreev, A; Thierry, A; Sitter, H; Smilgies, D M; Schaffer, B; Grogger, W; Resel, R

    2006-03-01

    This work focuses on studies of the single crystal nature of para-sexiphenyl structures grown on freshly cleaved KCl(100) surfaces. Two different kinds of morphologies, namely terrace like structures and needle like structures, are found by atomic force microscopy as well as by electron microscopy. Regardless of the morphology the individual crystallites show highly regular shapes. The crystalline alignment and the degree of order of the crystallites on the surface are determined by X-ray diffraction. Several epitaxial alignments of para-sexiphenyl on KCl(100) are observed and all of them are perfectly aligned on the surface. The rocking curve widths of the organic crystallites do not exceed 800" which is approximately only the four fold of the substrates' ones. The single crystalline nature of para-sexiphenyl crystallites is proven by transmission electron microscopy, diffraction patterns, dark field imaging and high resolution techniques. Single crystalline terraced mounds reach diameters of several microns and heights of 50 nm. Single crystal needles show heights and breadths of more than 100 nm and lengths of several microns. PMID:16573123

  18. Preparation of atomically flat rutile TiO2(001) surfaces for oxide film growth

    DOE PAGESBeta

    Wang, Yang; Lee, Shinbuhm; Vilmercati, P.; Lee, Ho Nyung; Weitering, Hanno; Snijders, Paul C.

    2016-01-01

    The availability of low-index rutile TiO2 single crystal substrates with atomically flat surfaces is essential for enabling epitaxialgrowth of rutile transition metal oxide films. The high surface energy of the rutile (001) surface often leads to surface faceting, which precludes the sputter and annealing treatment commonly used for the preparation of clean and atomically flat TiO2(110) substrate surfaces. In this work, we reveal that stable and atomically flat rutile TiO2(001) surfaces can be prepared with an atomically ordered reconstructedsurface already during a furnace annealing treatment in air. We tentatively ascribe this result to the decrease in surface energy associated withmore » the surface reconstruction, which removes the driving force for faceting. Despite the narrow temperature window where this morphology can initially be formed, we demonstrate that it persists in homoepitaxialgrowth of TiO2(001) thin films. The stabilization of surface reconstructions that prevent faceting of high-surface-energy crystal faces may offer a promising avenue towards the realization of a wider range of high quality epitaxial transition metal oxide heterostructures.« less

  19. Atomically flat reconstructed rutile TiO2(001) surfaces for oxide film growth

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Lee, S.; Vilmercati, P.; Lee, H. N.; Weitering, H. H.; Snijders, P. C.

    2016-02-01

    The availability of low-index rutile TiO2 single crystal substrates with atomically flat surfaces is essential for enabling epitaxial growth of rutile transition metal oxide films. The high surface energy of the rutile (001) surface often leads to surface faceting, which precludes the sputter and annealing treatment commonly used for the preparation of clean and atomically flat TiO2(110) substrate surfaces. In this work, we reveal that stable and atomically flat rutile TiO2(001) surfaces can be prepared with an atomically ordered reconstructed surface already during a furnace annealing treatment in air. We tentatively ascribe this result to the decrease in surface energy associated with the surface reconstruction, which removes the driving force for faceting. Despite the narrow temperature window where this morphology can initially be formed, we demonstrate that it persists in homoepitaxial growth of TiO2(001) thin films. The stabilization of surface reconstructions that prevent faceting of high-surface-energy crystal faces may offer a promising avenue towards the realization of a wider range of high quality epitaxial transition metal oxide heterostructures.

  20. Physical properties of single crystalline BaSn{sub 5}

    SciTech Connect

    Lin, Xiao; Budko, Sergey; Canfield, Paul

    2012-01-30

    We present a comprehensive study of the binary intermetallic superconductor, BaSn{sub 5}. High-quality single crystalline BaSn{sub 5} was grown out of a Sn flux. Detailed thermodynamic and transport measurements were performed to study BaSn{sub 5}'s normal and superconducting state properties. This material appears to be a strongly coupled, multiband superconductor. H{sub c2}(T) is almost isotropic. De Haas–van Alphen oscillations were observed and two effective masses were estimated from the FFT spectra. Hydrostatic pressure causes a decrease in the superconducting transition temperature at the rate of ≈−0.053 ± 0.001 K/kbar.

  1. Single crystalline Si substrate growth by lateral diffusion epitaxy

    NASA Astrophysics Data System (ADS)

    Li, Bo; Yu, Hao Ling; Shen, Huaxiang; Kitai, Adrian

    2013-03-01

    A novel crystal growth method named lateral diffusion epitaxy (LDE) as well as the necessary growth apparatus are described in detail. Single crystalline Si strips are grown on (1 1 1) Si substrates by LDE. The thickness of the LDE Si strips is around 100 μm, and the aspect ratio of width to thickness is around 2 which is an improvement compared with Si strips grown by conventional liquid phase epitaxy (LPE). The LDE Si strip can be peeled off from the substrate for further device processing since the 100 μm thickness provides reasonable mechanical strength. Due to the low cost of LDE technology it is potentially a good candidate for PV application if the LDE can achieve continuous growth and therefore grow Si strips in sizes for practical application.

  2. Periodic magnetic domains in single-crystalline cobalt filament arrays

    NASA Astrophysics Data System (ADS)

    Chen, Fei; Wang, Fan; Jia, Fei; Li, Jingning; Liu, Kai; Huang, Sunxiang; Luan, Zhongzhi; Wu, Di; Chen, Yanbin; Zhu, Jianmin; Peng, Ru-Wen; Wang, Mu

    2016-02-01

    Magnetic structures with controlled domain wall pattern may be applied as potential building blocks for three-dimensional magnetic memory and logic devices. Using a unique electrochemical self-assembly method, we achieve regular single-crystalline cobalt filament arrays with specific geometric profile and crystallographic orientation, and the magnetic domain configuration can be conveniently tailored. We report the transition of periodic antiparallel magnetic domains to compressed vortex magnetic domains depending on the ratio of height to width of the wires. A "phase diagram" is obtained to describe the dependence of the type of magnetic domain and the geometrical profiles of the wires. Magnetoresistance of the filaments demonstrates that the contribution of a series of 180∘ domain walls is over 0.15 % of the zero-field resistance ρ (H =0 ) . These self-assembled magnetic nanofilaments, with controlled periodic domain patterns, offer an interesting platform to explore domain-wall-based memory and logic devices.

  3. Fatigue crack propagation behavior of a single crystalline superalloy

    NASA Technical Reports Server (NTRS)

    Lerch, B. A.; Antolovich, Stephen D.

    1990-01-01

    Crack propagation mechanisms occurring at various temperatures in a single crystalline Ni-base alloy, Rene N4, were investigated. The rates of crack growth at 21, 704, 927, 1038, and 1093 C were measured in specimens with 001-line and 110-line directions parallel to the load axis and the machined notch, respectively, using a pulsed dc potential drop apparatus, and the fracture surfaces at each temperature were examined using SEM. Crack growth rates (CGRs) for specimens tested at or below 927 C were similar, while at two higher temperatures, the CGRs were about an order of magnitude higher than at the lower temperatures. Results of SEM observations showed that surface morphologies depended on temperature.

  4. Flat-response spin-exchange relaxation free atomic magnetometer under negative feedback.

    PubMed

    Lee, Hyun Joon; Shim, Jeong Hyun; Moon, Han Seb; Kim, Kiwoong

    2014-08-25

    We demonstrate that the use of negative feedback extends the detection bandwidth of an atomic magnetometer in a spin-exchange relaxation free (SERF) regime. A flat-frequency response from zero to 190 Hz was achieved, which is nearly a three-fold enhancement while maintaining sensitivity, 3 fT/Hz1/2 at 100 Hz. With the extension of the bandwidth, the linear correlation between measured signals and a magne-tocardiographic field synthesized for comparison was increased from 0.21 to 0.74. This result supports the feasibility of measuring weak biomagnetic signals containing multiple frequency components using a SERF atomic magnetometer under negative feedback.

  5. Morphology and local conductance of single crystalline Bi2Te3 thin films on mica.

    PubMed

    Rapacz, R; Balin, K; Wojtyniak, M; Szade, J

    2015-10-14

    The relation between surface morphology and local conductance was studied for single crystalline thin films of Bi2Te3 grown on mica. Atomic force microscopy and electron diffraction revealed the hexagonal order of the surface with quintuple layer steps and spiral islands. Furthermore, the experiments using contact mode AFM with conducting tip performed at room temperature revealed the high conductance of the surface, which was locally reduced due to changes in the local electronic structure at the defects (e.g. edges of the terraces). Contact current-voltage characteristics tested over the surface showed a linear behavior in every point, with the resistance significantly lower than the resistance of reference metallic samples (gold, platinum). We show that local conductivity AFM is a good technique to exploit the peculiar surface properties of topological insulators.

  6. Cold welding of copper nanowires with single-crystalline and twinned structures: A comparison study

    NASA Astrophysics Data System (ADS)

    Huang, Rao; Shao, Gui-Fang; Wen, Yu-Hua

    2016-09-01

    In this article, molecular simulations were adopted to explore the cold welding processes of copper nanowires with both single-crystalline and fivefold twinned structures. It was verified that the twinned nanowires exhibited enhanced strength but lowered elastic limit and ductility. Both nanowires could be successfully welded through rather small loadings, although their stress-strain responses toward compression were different. Meanwhile, more stress was accumulated in the twinned nanowire due to repulsive force of the twin boundaries against the nucleation and motions of dislocations. Moreover, by characterizing the structure evolutions in the welding process, it can be ascertained that perfect atomic order was finally built at the weld region in both nanowires. This comparison study will be of great importance to future mechanical processing of metallic nanowires.

  7. Spin pumping and Gilbert damping in atomically flat nanometric thick YIG|NM system

    NASA Astrophysics Data System (ADS)

    Alyahyaei, H. M.; Tang, Chi; Yang, Bowen; Shi, Jing

    2014-03-01

    Epitaxial nanometric thick ytrrium iron garnet (YIG) films grown on (111) and (110) gadolliun gallium garnet (GGG) substrates via PLD exhibit an atomically flat surface. This extremely flat surface with a roughness ~ 0.1 Å offers a more controlled study of the physical mechanism behind the newly observed damping in YIG|NM bilayer systems. Our bilayer systems consist of a 30 nm thick YIG film, either (111) or (110), and a non-magnetic layer, either beta-phase Ta or Pd, with thickness ranging from 0 to 20 nm. We have performed ferromagnetic resonance (FMR) experiments and observed systematic thickness dependence of the FMR linewidth. As the thickness of NM increases, the FMR linewidth increases rapidly and then slowly approaches saturation. The effect of the YIG surface on the Gilbert damping due to the magnetic proximity effect and on spin pumping in such bilayer systems will be discussed. The research is supported by NSF/EECS.

  8. Accelerating atomic-level protein simulations by flat-histogram techniques

    NASA Astrophysics Data System (ADS)

    Jónsson, Sigurður Ć.; Mohanty, Sandipan; Irbäck, Anders

    2011-09-01

    Flat-histogram techniques provide a powerful approach to the simulation of first-order-like phase transitions and are potentially very useful for protein studies. Here, we test this approach by implicit solvent all-atom Monte Carlo (MC) simulations of peptide aggregation, for a 7-residue fragment (GIIFNEQ) of the Cu/Zn superoxide dismutase 1 protein (SOD1). In simulations with 8 chains, we observe two distinct aggregated/non-aggregated phases. At the midpoint temperature, these phases coexist, separated by a free-energy barrier of height 2.7 kBT. We show that this system can be successfully studied by carefully implemented flat-histogram techniques. The frequency of barrier crossing, which is low in conventional canonical simulations, can be increased by turning to a two-step procedure based on the Wang-Landau and multicanonical algorithms.

  9. Epitaxial Growth of Zinc Oxide on Single Crystalline Gold Plates

    NASA Astrophysics Data System (ADS)

    Greenberg, Kathryn; Joo, John; Baram, Mor; Clarke, David; Hu, Evelyn

    2012-02-01

    Although metal-oxide interfaces are the critical components of many electronic and optical devices, it is rare to find epitaxial metal-oxide structures. We demonstrate for the first time, a method for the low temperature, epitaxial growth of zinc oxide (ZnO) on single crystalline gold plates. The gold plates, up to 100μm in width, are grown from a gold-surfactant complex. Even with the large lattice mismatch between (111) gold and (0001) ZnO, we are able to form epitaxial zinc oxide at 90^oC on top of the single crystal gold plates. This epitaxial growth is confirmed using transmission electron microscopy, electron diffraction, and electron backscatterer diffraction. Micro-photoluminescence is also performed to investigate the optical properties of the epitaxial zinc oxide. We remove the grown ZnO membranes from the gold plates using a stamping and etching process. These membranes can potentially be used to fabricate high quality microdisks and photonic crystals. The metal-oxide interfaces that we have fabricated may have the ability to be used in a number of technologically important applications, including as better electrical contacts and for improved light extraction from planar LED structures.

  10. Synthesis and magnetic properties of single-crystalline magnetite nanowires

    NASA Astrophysics Data System (ADS)

    Han, Qin; Liu, Zhenghui; Xu, Yingying; Zhang, Han

    2007-09-01

    By carefully controlling the reaction conditions, nanowires of Fe 3O 4 are directly acquired from nanowires of α-Fe 2O 3 in a reduced atmosphere at 410-430 °C. X-ray diffraction, Raman spectrum, and transmission electron microscopic analyses demonstrate that the product is single-crystalline Fe 3O 4. The nanowires have diameters of 40-90 nm and lengths of 10-20 μm, which are close to those of the pristine α-Fe 2O 3 nanowires. By studying different growth conditions, we find that hydrogen can push the conversion of the crystal structures, while temperature determines the chemical composition of the final products. The magnetic properties of as-prepared Fe 3O 4 nanowires are measured using a quantum design magnetic property measurement system. The nanowires show a ferrimagnetic behavior at room temperature and their magnetic properties are strongly influenced by surface and interface effects. The Verwey transition temperature ( TV=116 K) is found to be a little lower than that of bulk materials, which can be attributed to the small deviation from stoichiometry caused by the oxygen vacancies near the surfaces. Below 12 K, the nanowires show a spin-glass-like behavior owing to the disordered frozen magnetic state at the surfaces.

  11. Hydrogen Gas Sensors Fabricated on Atomically Flat 4H-SiC Webbed Cantilevers

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Spry, David J.; Trunek, Andrew J.; Evans, Laura J.; Chen, Liang-Yu; Hunter, Gary W.; Androjna, Drago

    2007-01-01

    This paper reports on initial results from the first device tested of a "second generation" Pt-SiC Schottky diode hydrogen gas sensor that: 1) resides on the top of atomically flat 4H-SiC webbed cantilevers, 2) has integrated heater resistor, and 3) is bonded and packaged. With proper selection of heater resistor and sensor diode biases, rapid detection of H2 down to concentrations of 20 ppm was achieved. A stable sensor current gain of 125 +/- 11 standard deviation was demonstrated during 250 hours of cyclic test exposures to 0.5% H2 and N2/air.

  12. Combined single-crystalline and polycrystalline CVD diamond substrates for diamond electronics

    SciTech Connect

    Vikharev, A. L. Gorbachev, A. M.; Dukhnovsky, M. P.; Muchnikov, A. B.; Ratnikova, A. K.; Fedorov, Yu. Yu.

    2012-02-15

    The fabrication of diamond substrates in which single-crystalline and polycrystalline CVD diamond form a single wafer, and the epitaxial growth of diamond films on such combined substrates containing polycrystalline and (100) single-crystalline CVD diamond regions are studied.

  13. Flat metallic surface gratings with sub-10 nm gaps controlled by atomic-layer deposition.

    PubMed

    Chen, Borui; Ji, Dengxin; Cheney, Alec; Zhang, Nan; Song, Haomin; Zeng, Xie; Thomay, Tim; Gan, Qiaoqiang; Cartwright, Alexander

    2016-09-16

    Atomic layer lithography is a recently reported new technology to fabricate deep-subwavelength features down to 1-2 nm, based on combinations of electron beam lithography (EBL) and atomic layer deposition (ALD). However, the patterning area is relatively small as limited by EBL, and the fabrication yield is not very high due to technical challenges. Here we report an improved procedure to fabricate flat metallic surfaces with sub-10 nm features based on ALD processes. To demonstrate the scalability of the new manufacturing method, we combine the ALD process with large area optical interference patterning, which is particularly promising for the development of practical applications for nanoelectronics and nanophotonics with extremely strong confinement of electromagnetic fields.

  14. Flat metallic surface gratings with sub-10 nm gaps controlled by atomic-layer deposition.

    PubMed

    Chen, Borui; Ji, Dengxin; Cheney, Alec; Zhang, Nan; Song, Haomin; Zeng, Xie; Thomay, Tim; Gan, Qiaoqiang; Cartwright, Alexander

    2016-09-16

    Atomic layer lithography is a recently reported new technology to fabricate deep-subwavelength features down to 1-2 nm, based on combinations of electron beam lithography (EBL) and atomic layer deposition (ALD). However, the patterning area is relatively small as limited by EBL, and the fabrication yield is not very high due to technical challenges. Here we report an improved procedure to fabricate flat metallic surfaces with sub-10 nm features based on ALD processes. To demonstrate the scalability of the new manufacturing method, we combine the ALD process with large area optical interference patterning, which is particularly promising for the development of practical applications for nanoelectronics and nanophotonics with extremely strong confinement of electromagnetic fields. PMID:27505713

  15. Flat metallic surface gratings with sub-10 nm gaps controlled by atomic-layer deposition

    NASA Astrophysics Data System (ADS)

    Chen, Borui; Ji, Dengxin; Cheney, Alec; Zhang, Nan; Song, Haomin; Zeng, Xie; Thomay, Tim; Gan, Qiaoqiang; Cartwright, Alexander

    2016-09-01

    Atomic layer lithography is a recently reported new technology to fabricate deep-subwavelength features down to 1-2 nm, based on combinations of electron beam lithography (EBL) and atomic layer deposition (ALD). However, the patterning area is relatively small as limited by EBL, and the fabrication yield is not very high due to technical challenges. Here we report an improved procedure to fabricate flat metallic surfaces with sub-10 nm features based on ALD processes. To demonstrate the scalability of the new manufacturing method, we combine the ALD process with large area optical interference patterning, which is particularly promising for the development of practical applications for nanoelectronics and nanophotonics with extremely strong confinement of electromagnetic fields.

  16. Flat metallic surface gratings with sub-10 nm gaps controlled by atomic-layer deposition

    NASA Astrophysics Data System (ADS)

    Chen, Borui; Ji, Dengxin; Cheney, Alec; Zhang, Nan; Song, Haomin; Zeng, Xie; Thomay, Tim; Gan, Qiaoqiang; Cartwright, Alexander

    2016-09-01

    Atomic layer lithography is a recently reported new technology to fabricate deep-subwavelength features down to 1–2 nm, based on combinations of electron beam lithography (EBL) and atomic layer deposition (ALD). However, the patterning area is relatively small as limited by EBL, and the fabrication yield is not very high due to technical challenges. Here we report an improved procedure to fabricate flat metallic surfaces with sub-10 nm features based on ALD processes. To demonstrate the scalability of the new manufacturing method, we combine the ALD process with large area optical interference patterning, which is particularly promising for the development of practical applications for nanoelectronics and nanophotonics with extremely strong confinement of electromagnetic fields.

  17. Silane-catalysed fast growth of large single-crystalline graphene on hexagonal boron nitride

    PubMed Central

    Tang, Shujie; Wang, Haomin; Wang, Hui Shan; Sun, Qiujuan; Zhang, Xiuyun; Cong, Chunxiao; Xie, Hong; Liu, Xiaoyu; Zhou, Xiaohao; Huang, Fuqiang; Chen, Xiaoshuang; Yu, Ting; Ding, Feng; Xie, Xiaoming; Jiang, Mianheng

    2015-01-01

    The direct growth of high-quality, large single-crystalline domains of graphene on a dielectric substrate is of vital importance for applications in electronics and optoelectronics. Traditionally, graphene domains grown on dielectrics are typically only ~1 μm with a growth rate of ~1 nm min−1 or less, the main reason is the lack of a catalyst. Here we show that silane, serving as a gaseous catalyst, is able to boost the graphene growth rate to ~1 μm min−1, thereby promoting graphene domains up to 20 μm in size to be synthesized via chemical vapour deposition (CVD) on hexagonal boron nitride (h-BN). Hall measurements show that the mobility of the sample reaches 20,000 cm2 V−1 s−1 at room temperature, which is among the best for CVD-grown graphene. Combining the advantages of both catalytic CVD and the ultra-flat dielectric substrate, gaseous catalyst-assisted CVD paves the way for synthesizing high-quality graphene for device applications while avoiding the transfer process. PMID:25757864

  18. Silane-catalysed fast growth of large single-crystalline graphene on hexagonal boron nitride.

    PubMed

    Tang, Shujie; Wang, Haomin; Wang, Hui Shan; Sun, Qiujuan; Zhang, Xiuyun; Cong, Chunxiao; Xie, Hong; Liu, Xiaoyu; Zhou, Xiaohao; Huang, Fuqiang; Chen, Xiaoshuang; Yu, Ting; Ding, Feng; Xie, Xiaoming; Jiang, Mianheng

    2015-03-11

    The direct growth of high-quality, large single-crystalline domains of graphene on a dielectric substrate is of vital importance for applications in electronics and optoelectronics. Traditionally, graphene domains grown on dielectrics are typically only ~1 μm with a growth rate of ~1 nm min(-1) or less, the main reason is the lack of a catalyst. Here we show that silane, serving as a gaseous catalyst, is able to boost the graphene growth rate to ~1 μm min(-1), thereby promoting graphene domains up to 20 μm in size to be synthesized via chemical vapour deposition (CVD) on hexagonal boron nitride (h-BN). Hall measurements show that the mobility of the sample reaches 20,000 cm(2) V(-1) s(-1) at room temperature, which is among the best for CVD-grown graphene. Combining the advantages of both catalytic CVD and the ultra-flat dielectric substrate, gaseous catalyst-assisted CVD paves the way for synthesizing high-quality graphene for device applications while avoiding the transfer process.

  19. Synthesis of single crystalline spinel LiMn2O4 nanowires for a lithium ion battery with high power density.

    PubMed

    Hosono, Eiji; Kudo, Tetsuichi; Honma, Itaru; Matsuda, Hirofumi; Zhou, Haoshen

    2009-03-01

    How to improve the specific power density of the rechargeable lithium ion battery has recently become one of the most attractive topics of both scientific and industrial interests. The spinel LiMn2O4 is the most promising candidate as a cathode material because of its low cost and nontoxicity compared with commercial LiCoO2. Moreover, nanostructured electrodes have been widely investigated to satisfy such industrial needs. However, the high-temperature sintering process, which is necessary for high-performance cathode materials based on high-quality crystals, leads the large grain size and aggregation of the nanoparticles which gives poor lithium ion battery performance. So there is still a challenge to synthesize a high-quality single-crystal nanostructured electrode. Among all of the nanostructures, a single crystalline nanowire is the most attractive morphology because the nonwoven fabric morphology constructed by the single crystalline nanowire suppresses the aggregation and grain growth at high temperature, and the potential barrier among the nanosize grains can be ignored. However, the reported single crystalline nanowire is almost the metal oxide with an anisotropic crystal structure because the cubic crystal structure such as LiMn2O4 cannot easily grow in the one-dimentional direction. Here we synthesized high-quality single crystalline cubic spinel LiMn2O4 nanowires based on a novel reaction method using Na0.44MnO2 nanowires as a self-template. These single crystalline spinel LiMn2O4 nanowires show high thermal stability because the nanowire structure is maintained after heating to 800 degrees C for 12 h and excellent performance at high rate charge-discharge, such as 20 A/g, with both a relative flat charge-discharge plateau and excellent cycle stability.

  20. Gallium Arsenide Layers Grown by Molecular Beam Epitaxy on Single Crystalline Germanium Islands on Insulator

    NASA Astrophysics Data System (ADS)

    Takai, Mikio; Tanigawa, Takaho; Minamisono, Tadanori; Gamo, Kenji; Namba, Susumu

    1984-05-01

    Gallium arsenide (GaAs) layers have successfully been grown by molecular beam epitaxy on single crystalline germanium (Ge) islands, recrystallized by zone melting with SiO2 capping layers, on thermally-oxidized Si-wafers. The GaAs layers, grown on the single crystalline Ge islands, show smooth surfaces without any grain-boundaries, while those, grown on the Ge islands with grain-boundaries and on the SiO2, have grain-boundaries. The GaAs layers on the single crystalline Ge islands emit photoluminescence, the intensity of which is almost comparable to that of GaAs layers on bulk Ge crystals.

  1. Variations in Crystalline Structures and Electrical Properties of Single Crystalline Boron Nitride Nanosheets.

    PubMed

    Aldalbahi, Ali; Zhou, Andrew Feng; Feng, Peter

    2015-01-01

    We report the studies of (1) the basic mechanism underlying the formation of defect-free, single crystalline boron nitride nanosheets (BNNSs) synthesized using pulsed laser plasma deposition (PLPD) technique, (2) the variation in the crystalline structure at the edges of the hexagonal boron nitride (h-BN) nanosheets, and (3) the basic electrical properties related to the BNNSs tunneling effect and electrical breakdown voltage. The nanoscale morphologies of BNNSs are characterized using scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM). The results show that each sample consisted of a number of transparent BNNSs that partially overlapped one another. Varying the deposition duration yielded different thicknesses of sample but did not affect the morphology, structure, and thickness of individual BNNSs pieces. Analysis of the SEM and HRTEM data revealed changes in the spatial period of the B3-N3 hexagonal structures and the interlayer distance at the edge of the BNNSs, which occurred due to the limited number of atomic layers and was confirmed further by x-ray diffraction (XRD) study. The experimental results clearly indicate that the values of the electrical conductivities of the super-thin BNNSs and the effect of temperature relied strongly on the direction of observation. PMID:26563901

  2. Synthesis of single-crystalline Zn metal nanowires utilizing cold-wall physical vapor deposition.

    PubMed

    Kast, Michael; Schroeder, Philipp; Hyun, Youn J; Pongratz, Peter; Bruückl, Hubert

    2007-08-01

    Zinc metal nanowires (NWs) of two different morphologies have been synthesized in a cold-wall physical vapor deposition (CWPVD) chamber at high vacuum conditions and growth temperatures of 150 degrees C. Substrates initially seeded by gold or platinum crystals show NWs of wool-like and/or unidirectional morphologies. Transmission electron microscopy (TEM) studies revealed that the rodlike NWs consist of single-crystalline Zn covered with a thin native oxide. NWs of wool-like morphology are suppressed using platinum as the seed metal. NW growth proceeds via vapor-solid (VS) kinetics without any catalyst particles on the wire tips. The highest observed growth rates exceed the Zn deposition rate by factors up to 860, indicating the dominant role of surface diffusion of Zn adatoms, also along the NWs. The surface diffusion length of Zn adatoms on the NW side facet is determined to be 39 mum. Direct impingement of precursor atoms on the NW tip is not significant for the growth process.

  3. Variations in Crystalline Structures and Electrical Properties of Single Crystalline Boron Nitride Nanosheets

    PubMed Central

    Aldalbahi, Ali; Zhou, Andrew Feng; Feng, Peter

    2015-01-01

    We report the studies of (1) the basic mechanism underlying the formation of defect-free, single crystalline boron nitride nanosheets (BNNSs) synthesized using pulsed laser plasma deposition (PLPD) technique, (2) the variation in the crystalline structure at the edges of the hexagonal boron nitride (h-BN) nanosheets, and (3) the basic electrical properties related to the BNNSs tunneling effect and electrical breakdown voltage. The nanoscale morphologies of BNNSs are characterized using scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM). The results show that each sample consisted of a number of transparent BNNSs that partially overlapped one another. Varying the deposition duration yielded different thicknesses of sample but did not affect the morphology, structure, and thickness of individual BNNSs pieces. Analysis of the SEM and HRTEM data revealed changes in the spatial period of the B3–N3 hexagonal structures and the interlayer distance at the edge of the BNNSs, which occurred due to the limited number of atomic layers and was confirmed further by x-ray diffraction (XRD) study. The experimental results clearly indicate that the values of the electrical conductivities of the super-thin BNNSs and the effect of temperature relied strongly on the direction of observation. PMID:26563901

  4. Ultrahigh strength single crystalline nanowhiskers grown by physical vapor deposition.

    PubMed

    Richter, Gunther; Hillerich, Karla; Gianola, Daniel S; Mönig, Reiner; Kraft, Oliver; Volkert, Cynthia A

    2009-08-01

    The strength of metal crystals is reduced below the theoretical value by the presence of dislocations or by flaws that allow easy nucleation of dislocations. A straightforward method to minimize the number of defects and flaws and to presumably increase its strength is to increase the crystal quality or to reduce the crystal size. Here, we describe the successful fabrication of high aspect ratio nanowhiskers from a variety of face-centered cubic metals using a high temperature molecular beam epitaxy method. The presence of atomically smooth, faceted surfaces and absence of dislocations is confirmed using transmission electron microscopy investigations. Tensile tests performed in situ in a focused-ion beam scanning electron microscope on Cu nanowhiskers reveal strengths close to the theoretical upper limit and confirm that the properties of nanomaterials can be engineered by controlling defect and flaw densities.

  5. Field emission from single-crystalline HfC nanowires

    SciTech Connect

    Yuan, Jinshi; Tang, Jie; Zhang Han; Shinya, Norio; Nakajima, Kiyomi; Qin, Lu-Chang

    2012-03-12

    Single HfC nanowire field emitter/electrode structures have been fabricated using nano-assembling and electron beam induced deposition. Field ion microscopy has been applied to study the atomic arrangement of facets formed on a field evaporation-modified HfC nanowire tip. Field evaporation and crystal form studies suggest that the {l_brace}111{r_brace} and {l_brace}110{r_brace} crystal planes have lower work functions, while the {l_brace}100{r_brace}, {l_brace}210{r_brace}, and {l_brace}311{r_brace} planes have higher work functions. Field emission measurement permits us to obtain that the work function of the {l_brace}111{r_brace} crystal plane is about 3.4 eV.

  6. Healing of graphene on single crystalline Ni(111) films

    SciTech Connect

    Zeller, Patrick; Wintterlin, Joost; Speck, Florian; Ostler, Markus; Weinl, Michael; Schreck, Matthias; Seyller, Thomas

    2014-11-10

    The annealing of graphene layers grown on 150 nm thick single crystal Ni(111) films was investigated in situ by low energy electron microscopy and photoemission electron microscopy. After growth, by means of chemical vapor deposition of ethylene, the graphene layers consist of several domains showing different orientations with respect to the underlying Ni surface and also of small bilayer areas. It is shown that, in a controlled process, the rotated domains can be transformed into lattice-aligned graphene, and the bilayer areas can be selectively dissolved, so that exclusively the aligned monolayer graphene is obtained. The ordering mechanism involves transport of C atoms across the surface and solution in the bulk.

  7. Lattice-Matched Semiconductor Layers on Single Crystalline Sapphire Substrate

    NASA Technical Reports Server (NTRS)

    Choi, Sang; King, Glen; Park, Yeonjoon

    2009-01-01

    SiGe is an important semiconductor alloy for high-speed field effect transistors (FETs), high-temperature thermoelectric devices, photovoltaic solar cells, and photon detectors. The growth of SiGe layer is difficult because SiGe alloys have different lattice constants from those of the common Si wafers, which leads to a high density of defects, including dislocations, micro-twins, cracks, and delaminations. This innovation utilizes newly developed rhombohedral epitaxy of cubic semiconductors on trigonal substrates in order to solve the lattice mismatch problem of SiGe by using trigonal single crystals like sapphire (Al2O3) as substrate to give a unique growth-orientation to the SiGe layer, which is automatically controlled at the interface upon sapphire (0001). This technology is different from previous silicon on insulator (SOI) or SGOI (SiGe on insulator) technologies that use amorphous SiO2 as the growth plane. A cubic semiconductor crystal is a special case of a rhombohedron with the inter-planar angle, alpha = 90 deg. With a mathematical transformation, all rhombohedrons can be described by trigonal crystal lattice structures. Therefore, all cubic lattice constants and crystal planes (hkl) s can be transformed into those of trigonal crystal parameters. These unique alignments enable a new opportunity of perfect lattice matching conditions, which can eliminate misfit dislocations. Previously, these atomic alignments were thought to be impossible or very difficult. With the invention of a new x-ray diffraction measurement method here, growth of cubic semiconductors on trigonal crystals became possible. This epitaxy and lattice-matching condition can be applied not only to SiGe (111)/sapphire (0001) substrate relations, but also to other crystal structures and other materials, including similar crystal structures which have pointgroup rotational symmetries by 120 because the cubic (111) direction has 120 rotational symmetry. The use of slightly miscut (less than

  8. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Structural and Electrical Properties of Single Crystalline Ga-Doped ZnO Thin Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Lu, Zhong-Lin; Zou, Wen-Qin; Xu, Ming-Xiang; Zhang, Feng-Ming; Du, You-Wei

    2009-11-01

    High-quality Ga-doped ZnO (ZnO:Ga) single crystalline films with various Ga concentrations are grown on a-plane sapphire substrates using molecular-beam epitaxy. The site configuration of doped Ga atoms is studied by means of x-ray absorption spectroscopy. It is found that nearly all Ga can substitute into ZnO lattice as electrically active donors, a generating high density of free carriers with about one electron per Ga dopant when the Ga concentration is no more than 2%. However, further increasing the Ga doping concentration leads to a decrease of the conductivity due to partial segregation of Ga atoms to the minor phase of the spinel ZnGa2O4 or other intermediate phase. It seems that the maximum solubility of Ga in the ZnO single crystalline film is about 2 at.% and the lowest resistivity can reach 1.92 × 10-4 Ω·cm at room temperature, close to the best value reported. In contrast to ZnO:Ga thin film with 1% or 2% Ga doping, the film with 4% Ga doping exhibits a metal semiconductor transition at 80 K. The scattering mechanism of conducting electrons in single crystalline ZnO:Ga thin film is discussed.

  9. Preparation of atomically flat rutile TiO2(001) surfaces for oxide film growth

    SciTech Connect

    Wang, Yang; Lee, Shinbuhm; Vilmercati, P.; Lee, Ho Nyung; Weitering, Hanno; Snijders, Paul C.

    2016-01-01

    The availability of low-index rutile TiO2 single crystal substrates with atomically flat surfaces is essential for enabling epitaxialgrowth of rutile transition metal oxide films. The high surface energy of the rutile (001) surface often leads to surface faceting, which precludes the sputter and annealing treatment commonly used for the preparation of clean and atomically flat TiO2(110) substrate surfaces. In this work, we reveal that stable and atomically flat rutile TiO2(001) surfaces can be prepared with an atomically ordered reconstructedsurface already during a furnace annealing treatment in air. We tentatively ascribe this result to the decrease in surface energy associated with the surface reconstruction, which removes the driving force for faceting. Despite the narrow temperature window where this morphology can initially be formed, we demonstrate that it persists in homoepitaxialgrowth of TiO2(001) thin films. The stabilization of surface reconstructions that prevent faceting of high-surface-energy crystal faces may offer a promising avenue towards the realization of a wider range of high quality epitaxial transition metal oxide heterostructures.

  10. Growth of single-crystalline Cu2O (111) film on ultrathin MgO modified α-Al2O3 (0001) substrate by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Li, Junqiang; Mei, Zengxia; Ye, Daqian; Liang, Huili; Liu, Yaoping; Du, Xiaolong

    2012-08-01

    We report the synthesis of Cu2O single crystalline films on the c-plane α-Al2O3 substrate by radio-frequency plasma assisted molecular beam epitaxy. An ultrathin MgO layer was adopted to modify the complex surface structure of sapphire (0001) and engineer the interfacial atomic matching between the epilayer and the substrate. The experimental results solidly proved the single crystallinity of cubic Cu2O (111) without twin crystals. A coincident match mode was proposed to explain the unusual in-plane orientation between strained MgO (111) and Cu2O (111). It was found that the crystal quality of Cu2O is very sensitive to the thickness of MgO layer, which is optimized to be ˜2 nm. The reason why MgO has a critical thickness in Cu2O single crystal growth was also tentatively discussed.

  11. Fabrication of surface plasmon resonators by nanoskiving single-crystalline gold microplates

    NASA Astrophysics Data System (ADS)

    Wiley, Benjamin J.; Lipomi, Darren J.; Bao, Jiming; Capasso, Federico; Whitesides, George M.

    2009-02-01

    This paper demonstrates the sectioning of chemically synthesized, single-crystalline microplates of gold with an ultramicrotome to produce single-crystalline nanowires. This method produces collinearly aligned nanostructures with small, regular changes in dimension with each consecutive cross-section. The diamond knife cuts cleanly through microplates 100 nm thick without bending the resulting nanowire, and cuts through the sharp edges of a crystal to generate nanoscale tips. This paper demonstrates that the smooth surface of the single-crystalline gold nanowires allows them to guide plasmons with lower loss than rough, polycrystalline nanowires, and that the sharp tips on the singlecrystalline nanowires serve as optical antenna that selectively couple light into the nanowire at the resonance frequency of the sharp tip.

  12. Formation of quasi-single crystalline porous ZnO nanostructures with a single large cavity.

    PubMed

    Cho, Seungho; Kim, Semi; Jung, Dae-Won; Lee, Kun-Hong

    2011-09-01

    We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space.

  13. Experimental and Theoretical Investigation of Crystallographic Orientation Dependence of Nanoscratching of Single Crystalline Copper

    PubMed Central

    Geng, Yanquan; Zhang, Junjie; Yan, Yongda; Yu, Bowen; Geng, Lin; Sun, Tao

    2015-01-01

    In the present work, we perform experiments and molecular dynamics simulations to elucidate the underlying deformation mechanisms of single crystalline copper under the load-controlled multi-passes nanoscratching using a triangular pyramidal probe. The correlation of microscopic deformation behavior of the material with macroscopically-observed machining results is revealed. Moreover, the influence of crystallographic orientation on the nanoscratching of single crystalline copper is examined. Our simulation results indicate that the plastic deformation of single crystalline Cu under the nanoscratching is exclusively governed by dislocation mechanisms. However, there is no glissile dislocation structure formed due to the probe oscillation under the load-controlled mode. Both experiments and MD simulations demonstrate that the machined surface morphologies in terms of groove depth and surface pile-up exhibit strong crystallographic orientation dependence, because of different geometries of activated slip planes cutting with free surfaces and strain hardening abilities associated with different crystallographic orientations. PMID:26147506

  14. {116} faceted anatase single-crystalline nanosheet arrays: facile synthesis and enhanced electrochemical performances

    NASA Astrophysics Data System (ADS)

    Li, Feng; Li, Xiaoning; Peng, Ranran; Zhai, Xiaofang; Yang, Shangfeng; Fu, Zhengping; Lu, Yalin

    2014-10-01

    Single-crystalline anatase TiO2 nanosheet arrays were synthesized on a transparent conductive fluorine-doped tin oxide (FTO) substrate with a unique one-step alcohol-thermal process. The nanosheets were nearly vertically grown on the FTO substrate along their <11&cmb.macr;0> zone, and they were dominated by {116} facets. The as-fabricated {116} faceted single-crystalline anatase nanosheet arrays exhibit a much higher reduction capacity and a much better electrochemical reversibility than both {001} faceted anatase single-crystalline nanosheet arrays and P25 film. The results indicate a promising application potential for the new material in the photoelectrochemical field.Single-crystalline anatase TiO2 nanosheet arrays were synthesized on a transparent conductive fluorine-doped tin oxide (FTO) substrate with a unique one-step alcohol-thermal process. The nanosheets were nearly vertically grown on the FTO substrate along their <11&cmb.macr;0> zone, and they were dominated by {116} facets. The as-fabricated {116} faceted single-crystalline anatase nanosheet arrays exhibit a much higher reduction capacity and a much better electrochemical reversibility than both {001} faceted anatase single-crystalline nanosheet arrays and P25 film. The results indicate a promising application potential for the new material in the photoelectrochemical field. Electronic supplementary information (ESI) available: Photo of the large area STNA-116, FESEM images of STNA-001 and STNA-116 with a series of growth time, the enlarged XRD pattern, the simulated SAED pattern, the reflectance spectra, the cyclic voltammograms of P25 on the FTO substrate. See DOI: 10.1039/c4nr04248d

  15. Single crystalline tantalum oxychloride microcubes: controllable synthesis, formation mechanism and enhanced photocatalytic hydrogen production activity.

    PubMed

    Tu, Hao; Xu, Leilei; Mou, Fangzhi; Guan, Jianguo

    2015-08-11

    Single crystalline microcubes of a new tantalum compound, tantalum oxychloride (TaO2.18Cl0.64), have been fabricated hydrothermally in a concentrated aqueous solution of hydrochloric acid and acetic acid. They contain a superstructure and exhibit remarkably enhanced photocatalytic activities for hydrogen production due to the improved light harvest and facilitated charge transport.

  16. Controllable growth of ultrathin BiFeO3 from finger-like nanostripes to atomically flat films.

    PubMed

    Feng, Yu; Wang, Can; Tian, Shilu; Zhou, Yong; Ge, Chen; Guo, Haizhong; He, Meng; Jin, Kuijuan; Yang, Guozhen

    2016-09-01

    BiFeO3 (BFO) ultrathin films with nominal thicknesses from 2 to 12 nm were grown with a SrRuO3 (SRO) buffer layer on TiO2-terminated (001) SrTiO3 (STO) substrates using pulsed laser deposition. The surface morphologies and domain configurations of the thin films were investigated using atomic force microscopy and piezoelectric force microscopy. Periodical one-dimensional finger-like nanostripes of BFO on the SRO covered STO substrates were observed. With increasing thickness, the BFO ultrathin films develop from the finger-like nanostripes to an atomically flat surface. The formation of the finger-like nanostructures of BFO is related to the atomic step or terrace structure of the substrate. The BFO nanostripes and the atomically flat thin films both show good ferroelectricity. The as-grown domain orientations of the BFO ultrathin films are ascribed to the chemical terminations at the surface of the SRO layer. These results indicate that the surface morphologies and the domain configurations of BFO ultrathin films can be artificially designed by using substrates with optimized terrace structures and chemical termination, and these films are potentially useful in multifunctional nanoelectronic devices. PMID:27454488

  17. Controllable growth of ultrathin BiFeO3 from finger-like nanostripes to atomically flat films

    NASA Astrophysics Data System (ADS)

    Feng, Yu; Wang, Can; Tian, Shilu; Zhou, Yong; Ge, Chen; Guo, Haizhong; He, Meng; Jin, Kuijuan; Yang, Guozhen

    2016-09-01

    BiFeO3 (BFO) ultrathin films with nominal thicknesses from 2 to 12 nm were grown with a SrRuO3 (SRO) buffer layer on TiO2-terminated (001) SrTiO3 (STO) substrates using pulsed laser deposition. The surface morphologies and domain configurations of the thin films were investigated using atomic force microscopy and piezoelectric force microscopy. Periodical one-dimensional finger-like nanostripes of BFO on the SRO covered STO substrates were observed. With increasing thickness, the BFO ultrathin films develop from the finger-like nanostripes to an atomically flat surface. The formation of the finger-like nanostructures of BFO is related to the atomic step or terrace structure of the substrate. The BFO nanostripes and the atomically flat thin films both show good ferroelectricity. The as-grown domain orientations of the BFO ultrathin films are ascribed to the chemical terminations at the surface of the SRO layer. These results indicate that the surface morphologies and the domain configurations of BFO ultrathin films can be artificially designed by using substrates with optimized terrace structures and chemical termination, and these films are potentially useful in multifunctional nanoelectronic devices.

  18. Atomically flat La-silicate/Si interface using tungsten carbide gate electrode with nano-sized grain

    SciTech Connect

    Tuokedaerhan, K.; Natori, K.; Iwai, H.; Kakushima, K. Kataoka, Y.; Nishiyama, A.; Sugii, N.; Wakabayashi, H.; Tsutsui, K.

    2014-01-13

    Interface properties of La-silicate gate dielectrics on Si substrates with W or nano-sized grain W{sub 2}C gate electrodes have been investigated. A low interface state density of 2.5 × 10{sup 11} cm{sup −2}/eV has been achieved with W{sub 2}C gate electrodes, which is one third of those with W gate electrode. An interface roughness of 0.33 nm with spatial frequency comparable to the grain size of W gate electrode has been observed. Besides, an atomically flat interface of 0.12 nm has been obtained with W{sub 2}C gate electrode. The origin of flat interface may be attributed to the elimination of inhomogeneous stress by grains in metal electrode.

  19. Single-crystalline Ni(OH)2 and NiO nanoplatelet arrays as supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Li, Jiangtian; Zhao, Wei; Huang, Fuqiang; Manivannan, Ayyakkannu; Wu, Nianqiang

    2011-12-01

    Vertically aligned Ni(OH)2 and NiO single-crystalline nanoplatelet arrays were directly grown on the fluorine-doped tin oxide (FTO) substrate by a simple hydrothermal method. The effects of the hydrothermal parameters on the morphology and crystal structure of the nanoarray film were investigated. Controlling the ammonia and persulfate concentrations was the key to controlling the morphology of the nanoarray film. The experimental results showed that the single-crystalline NiO nanoplatelet array was a promising candidate for the supercapacitor electrode. It exhibited a high specific capacitance, prompt charge/discharge rate, and good stability of cycling performance. It is believed that the vertically oriented aligned single-crystalline NiO nanoplatelet array is beneficial to the charge transfer in the electrode and to the ion transport in the solution during redox reaction.Vertically aligned Ni(OH)2 and NiO single-crystalline nanoplatelet arrays were directly grown on the fluorine-doped tin oxide (FTO) substrate by a simple hydrothermal method. The effects of the hydrothermal parameters on the morphology and crystal structure of the nanoarray film were investigated. Controlling the ammonia and persulfate concentrations was the key to controlling the morphology of the nanoarray film. The experimental results showed that the single-crystalline NiO nanoplatelet array was a promising candidate for the supercapacitor electrode. It exhibited a high specific capacitance, prompt charge/discharge rate, and good stability of cycling performance. It is believed that the vertically oriented aligned single-crystalline NiO nanoplatelet array is beneficial to the charge transfer in the electrode and to the ion transport in the solution during redox reaction. Electronic supplementary information (ESI) available: XRD patterns of Ni(OH)2 and NiO powders; SEM and TEM images of Ni(OH)2 and NiO nanoplatelet arrays; and electrochemical performances for NiO nanoarrays and powders. See

  20. Atomic Scale Flatness of Chemically Cleaned Silicon Surfaces Studied by Infrared Attenuated-Total-Reflection Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sawara, Kenichi; Yasaka, Tatsuhiro; Miyazaki, Seiichi; Hirose, Masataka

    1992-07-01

    Hydrogen-terminated Si(111) and Si(100) surfaces obtained by aqueous HF or pH-modified (pH{=}5.3) buffered-HF (BHF) treatments have been characterized by a Fourier transform infrared (FT-IR) attenuated-total-reflection (ATR) technique. The BHF treatment provides better surface flatness than the HF treatment. Pure water rinse is effective for improving the Si(111) surface flatness, while this is not the case for Si(100) because the pure water acts as an alkaline etchant and promotes the formation of (111) microfacets or microdefects on the (100) surface.

  1. Fabrication and temperature dependence of the resistance of single-crystalline Bi nanowires

    NASA Astrophysics Data System (ADS)

    Wang, X. F.; Zhang, J.; Shi, H. Z.; Wang, Y. W.; Meng, G. W.; Peng, X. S.; Zhang, L. D.; Fang, J.

    2001-04-01

    Single-crystalline Bi nanowires with diameters ranging from 20 to 70 nm were prepared by electrodeposition using nanoporous aluminum oxide membranes rather than the more usual track-etched polycarbonate membranes. X-ray diffraction and selected area electron diffraction investigations revealed that the nanowires are essentially single crystalline and highly oriented. The temperature dependence of zero-field resistance of different diameter nanowires indicated that these Bi nanowires undergo a semimetal-semiconductor transition due to two-dimensional quantum confinement effects. The resistance maximum was observed at 50 K in zero magnetic field for 20 nm Bi nanowires, while the resistance minimum at 258 K for 50 nm Bi nanowires, due to the quantum size effect.

  2. Single-Crystalline SrRuO3 Nanomembranes: A Platform for Flexible Oxide Electronics.

    PubMed

    Paskiewicz, Deborah M; Sichel-Tissot, Rebecca; Karapetrova, Evguenia; Stan, Liliana; Fong, Dillon D

    2016-01-13

    The field of oxide electronics has benefited from the wide spectrum of functionalities available to the ABO3 perovskites, and researchers are now employing defect engineering in single crystalline heterostructures to tailor properties. However, bulk oxide single crystals are not conducive to many types of applications, particularly those requiring mechanical flexibility. Here, we demonstrate the realization of an all-oxide, single-crystalline nanomembrane heterostructure. With a surface-to-volume ratio of 2 × 10(7), the nanomembranes are fully flexible and can be readily transferred to other materials for handling purposes or for new materials integration schemes. Using in situ synchrotron X-ray scattering, we find that the nanomembranes can bond to other host substrates near room temperature and demonstrate coupling between surface reactivity and electromechanical properties in ferroelectric nanomembrane systems. The synthesis technique described here represents a significant advancement in materials integration and provides a new platform for the development of flexible oxide electronics.

  3. Single crystalline SiGe layers on Si by solid phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lieten, R. R.; McCallum, J. C.; Johnson, B. C.

    2015-04-01

    We demonstrate a straightforward way to obtain single crystalline SiGe layers on silicon substrates. Amorphous SiGe layers, deposited by plasma enhanced chemical vapour deposition on Si, are transformed into single crystalline and smooth layers by solid phase epitaxy during annealing in a N2 atmosphere. The SiGe layers relax during the crystallization anneal and become slightly tensile strained during cooldown due to the thermal mismatch. The SiGe layers show excellent structural quality for compositions ranging from Ge- to Si-rich. The Ge content can be accurately estimated from the SiH4 to GeH4 flow ratio. Furthermore, the crystallization temperature decreases linearly with increasing Ge content from 725 °C for a-Si to 475 °C for a-Ge.

  4. Single-Crystalline SrRuO3 Nanomembranes: A Platform for Flexible Oxide Electronics

    SciTech Connect

    Fong, Dillon D.; Paskiewicz, Deborah M.; Sichel-Tissot, Rebecca; Stan, Liliana; Karapetrova, Evguenia

    2016-01-01

    The field of oxide electronics has benefited from the wide spectrum of functionalities available to the ABO3 perovskites, and researchers are now employing defect engineering in single crystalline heterostructures to tailor properties. However, bulk oxide single crystals are not conducive to many types of applications, particularly those requiring mechanical flexibility. Here, we demonstrate the realization of an all-oxide, single-crystalline nanomembrane heterostructure. With a surface-to-volume ratio of 2 × 107 , the nanomembranes are fully flexible and can be readily transferred to other materials for handling purposes or for new materials integration schemes. Using in situ synchrotron X-ray scattering, we find that the nanomembranes can bond to other host substrates near room temperature and demonstrate coupling between surface reactivity and electromechanical properties in ferroelectric nanomembrane systems. The synthesis technique described here represents a significant advancement in materials integration and provides a new platform for the development of flexible oxide electronics.

  5. Graphene-silicon layered structures on single-crystalline Ir(111) thin films

    SciTech Connect

    Que, Yande D.; Tao, Jing; Zhang, Yong; Wang, Yeliang L.; Wu, Lijun J.; Zhu, Yimei M.; Kim, Kisslinger; Weinl, Michael; Schreck, Matthias; Shen, Chengmin M.; Du, Shixuan X.; Liu, Yunqi Q.; Gao, H. -J.; Huang, Li; Xu, Wenyan Y.

    2015-01-20

    Epitaxial growth of graphene on transition metal crystals, such as Ru,⁽¹⁻³⁾ Ir,⁽⁴⁻⁶⁾ and Ni,⁽⁷⁾ provides large-area, uniform graphene layers with controllable defect density, which is crucial for practical applications in future devices. To decrease the high cost of single-crystalline metal bulks, single-crystalline metal films are strongly suggested as the substrates for epitaxial growth large-scale high-quality graphene.⁽⁸⁻¹⁰⁾ Moreover, in order to weaken the interactions of graphene with its metal host, which may result in a suppression of the intrinsic properties of graphene,⁽¹¹ ¹²⁾ the method of element intercalation of semiconductors at the interface between an epitaxial graphene layer and a transition metal substrate has been successfully realized.⁽¹³⁻¹⁶⁾

  6. Graphene-silicon layered structures on single-crystalline Ir(111) thin films

    DOE PAGESBeta

    Que, Yande D.; Tao, Jing; Zhang, Yong; Wang, Yeliang L.; Wu, Lijun J.; Zhu, Yimei M.; Kim, Kisslinger; Weinl, Michael; Schreck, Matthias; Shen, Chengmin M.; et al

    2015-01-20

    Epitaxial growth of graphene on transition metal crystals, such as Ru,⁽¹⁻³⁾ Ir,⁽⁴⁻⁶⁾ and Ni,⁽⁷⁾ provides large-area, uniform graphene layers with controllable defect density, which is crucial for practical applications in future devices. To decrease the high cost of single-crystalline metal bulks, single-crystalline metal films are strongly suggested as the substrates for epitaxial growth large-scale high-quality graphene.⁽⁸⁻¹⁰⁾ Moreover, in order to weaken the interactions of graphene with its metal host, which may result in a suppression of the intrinsic properties of graphene,⁽¹¹ ¹²⁾ the method of element intercalation of semiconductors at the interface between an epitaxial graphene layer and a transitionmore » metal substrate has been successfully realized.⁽¹³⁻¹⁶⁾« less

  7. GAGG:ce single crystalline films: New perspective scintillators for electron detection in SEM.

    PubMed

    Bok, Jan; Lalinský, Ondřej; Hanuš, Martin; Onderišinová, Zuzana; Kelar, Jakub; Kučera, Miroslav

    2016-04-01

    Single crystal scintillators are frequently used for electron detection in scanning electron microscopy (SEM). We report gadolinium aluminum gallium garnet (GAGG:Ce) single crystalline films as a new perspective scintillators for the SEM. For the first time, the epitaxial garnet films were used in a practical application: the GAGG:Ce scintillator was incorporated into a SEM scintillation electron detector and it showed improved image quality. In order to prove the GAGG:Ce quality accurately, the scintillation properties were examined using electron beam excitation and compared with frequently used scintillators in the SEM. The results demonstrate excellent emission efficiency of the GAGG:Ce single crystalline films together with their very fast scintillation decay useful for demanding SEM applications.

  8. Fast visible light photoelectric switch based on ultralong single crystalline V₂O₅ nanobelt.

    PubMed

    Lu, Jianing; Hu, Ming; Tian, Ye; Guo, Chuanfei; Wang, Chuang; Guo, Shengming; Liu, Qian

    2012-03-26

    A photoelectric switch with fast response to visible light (<200 μs), suitable photosensitivity and excellent repeatability is proposed based on the ultralong single crystalline V₂O₅ nanobelt, which are synthesized by chemical vapor deposition and its photoconductive mechanism can well be explained by small polaron hopping theory. Our results reveal that the switch has a great potential in next generation photodetectors and light-wave communications.

  9. Self-powered cardiac pacemaker enabled by flexible single crystalline PMN-PT piezoelectric energy harvester.

    PubMed

    Hwang, Geon-Tae; Park, Hyewon; Lee, Jeong-Ho; Oh, SeKwon; Park, Kwi-Il; Byun, Myunghwan; Park, Hyelim; Ahn, Gun; Jeong, Chang Kyu; No, Kwangsoo; Kwon, HyukSang; Lee, Sang-Goo; Joung, Boyoung; Lee, Keon Jae

    2014-07-23

    A flexible single-crystalline PMN-PT piezoelectric energy harvester is demonstrated to achieve a self-powered artificial cardiac pacemaker. The energy-harvesting device generates a short-circuit current of 0.223 mA and an open-circuit voltage of 8.2 V, which are enough not only to meet the standard for charging commercial batteries but also for stimulating the heart without an external power source. PMID:24740465

  10. Highly Polarized and Self-Waveguided Emission from Single-Crystalline Organic Nanobelts

    SciTech Connect

    Che, Yanke; Yang, Xiaomei; Balakrishnan, Kaushik; Zuo, Jianmin; Zang, Ling

    2009-09-15

    Well-defined single-crystalline nanobelts with strong fluorescence were fabricated from a perylene tetracarboxylic diimide molecule modified with specific side-chains that afford flip-flap stacking, rather than the common translated stacking, between the molecules along the long axis of the nanobelt. The nanobelts thus fabricated possess highly polarized, self-waveguided emission, making them ideal candidates for application in nanolasers and other angle-dependent optical nanodevices.

  11. Self-powered cardiac pacemaker enabled by flexible single crystalline PMN-PT piezoelectric energy harvester.

    PubMed

    Hwang, Geon-Tae; Park, Hyewon; Lee, Jeong-Ho; Oh, SeKwon; Park, Kwi-Il; Byun, Myunghwan; Park, Hyelim; Ahn, Gun; Jeong, Chang Kyu; No, Kwangsoo; Kwon, HyukSang; Lee, Sang-Goo; Joung, Boyoung; Lee, Keon Jae

    2014-07-23

    A flexible single-crystalline PMN-PT piezoelectric energy harvester is demonstrated to achieve a self-powered artificial cardiac pacemaker. The energy-harvesting device generates a short-circuit current of 0.223 mA and an open-circuit voltage of 8.2 V, which are enough not only to meet the standard for charging commercial batteries but also for stimulating the heart without an external power source.

  12. Three-dimensional bicomponent supramolecular nanoporous self-assembly on a hybrid all-carbon atomically flat and transparent platform.

    PubMed

    Li, Juan; Wieghold, Sarah; Öner, Murat Anil; Simon, Patrick; Hauf, Moritz V; Margapoti, Emanuela; Garrido, Jose A; Esch, Friedrich; Palma, Carlos-Andres; Barth, Johannes V

    2014-08-13

    Molecular self-assembly is a versatile nanofabrication technique with atomic precision en route to molecule-based electronic components and devices. Here, we demonstrate a three-dimensional, bicomponent supramolecular network architecture on an all-carbon sp(2)-sp(3) transparent platform. The substrate consists of hydrogenated diamond decorated with a monolayer graphene sheet. The pertaining bilayer assembly of a melamine-naphthalenetetracarboxylic diimide supramolecular network exhibiting a nanoporous honeycomb structure is explored via scanning tunneling microscopy initially at the solution-highly oriented pyrolytic graphite interface. On both graphene-terminated copper and an atomically flat graphene/diamond hybrid substrate, an assembly protocol is demonstrated yielding similar supramolecular networks with long-range order. Our results suggest that hybrid platforms, (supramolecular) chemistry and thermodynamic growth protocols can be merged for in situ molecular device fabrication. PMID:25115337

  13. Probing antiferromagnetism in NiMn/Ni/(Co)/Cu3Au(001) single-crystalline epitaxial thin films

    NASA Astrophysics Data System (ADS)

    Yaqoob Khan, M.; Wu, Chii-Bin; Erkovan, Mustafa; Kuch, Wolfgang

    2013-01-01

    Antiferromagnetism of equi-atomic single-crystalline NiMn thin film alloys grown on Ni/Cu3Au(001) is probed by means of magneto-optical Kerr effect (MOKE). Thickness-dependent coercivity (HC) enhancement of polar MOKE measurements in NiMn/Ni/Cu3Au(001) shows that ˜7 atomic monolayers (MLs) NiMn order antiferromagnetically at room temperature. It is found that NiMn can couple to out-of-plane (OoP) as well as in-plane (IP) magnetized Ni films, the latter stabilized by Co under-layer deposition. The antiferromagnetic (AFM) ordering temperature (TAFM) of NiMn coupled to OoP Ni is found to be much higher (up to 110 K difference) than in the IP case, for similar interfacial conditions. This is attributed to a magnetic proximity effect in which the ferromagnetic (FM) layer substantially influences TAFM of the adjacent AFM layer, and can be explained by either (i) a higher interfacial coupling strength and/or (ii) a thermally more stable NiMn spin structure when coupled to Ni magnetized in OoP direction than in IP. An exchange-bias effect could only be observed for the thickest NiMn film studied (35.7 ML); the exchange-bias field is higher in the OoP exchange-coupled system than in the IP one, possibly due to the same reason/s.

  14. Probing antiferromagnetism in NiMn/Ni/(Co)/Cu3Au(001) single-crystalline epitaxial thin films

    NASA Astrophysics Data System (ADS)

    Yaqoob Khan, M.; Wu, Chii-Bin; Kuch, Wolfgang

    2012-02-01

    Antiferromagnetism of equi-atomic single-crystalline NiMn thin film alloys grown on Ni/Cu3Au(001) is probed by means of magneto-optical Kerr effect (MOKE). Thickness-dependent coercivity enhancement of NiMn/Ni/Cu3Au(001) showed that 7 atomic monolayers (ML) NiMn order antiferromagnetically at room temperature. It is found that NiMn can couple to out-of-plane (OoP) as well as in-plane (IP) magnetized Ni, the latter stabilized by Co under-layer deposition. The antiferromagnetic (AFM) ordering temperature (TAFM) of NiMn coupled to OoP Ni is found to be much higher (up to 110 K) than in the IP case, for otherwise identical interfacial conditions. This is attributed to the `magnetic proximity effect' in which the ferromagnetic (FM) layer substantially influences the TAFM of the adjacent AFM layer and can be explained by either (i) a higher interfacial coupling strength or/and (ii) more thermally stable NiMn distorted spin structure when coupled to Ni magnetized in OoP direction than in IP. An exchange-bias effect could only be observed for the thickest NiMn film studied (35.7 ML); the exchange-bias field is higher in the OoP exchange-coupled system than in the IP one due to the same reason/s.

  15. Controlled vapor phase growth of single crystalline, two-dimensional GaSe crystals with high photoresponse.

    PubMed

    Li, Xufan; Lin, Ming-Wei; Puretzky, Alexander A; Idrobo, Juan C; Ma, Cheng; Chi, Miaofang; Yoon, Mina; Rouleau, Christopher M; Kravchenko, Ivan I; Geohegan, David B; Xiao, Kai

    2014-06-30

    Compared with their bulk counterparts, atomically thin two-dimensional (2D) crystals exhibit new physical properties, and have the potential to enable next-generation electronic and optoelectronic devices. However, controlled synthesis of large uniform monolayer and multi-layer 2D crystals is still challenging. Here, we report the controlled synthesis of 2D GaSe crystals on SiO2/Si substrates using a vapor phase deposition method. For the first time, uniform, large (up to ~60 μm in lateral size), single-crystalline, triangular monolayer GaSe crystals were obtained and their structure and orientation were characterized from atomic scale to micrometer scale. The size, density, shape, thickness, and uniformity of the 2D GaSe crystals were shown to be controllable by growth duration, growth region, growth temperature, and argon carrier gas flow rate. The theoretical modeling of the electronic structure and Raman spectroscopy demonstrate a direct-to-indirect bandgap transition and progressive confinement-induced bandgap shifts for 2D GaSe crystals. The 2D GaSe crystals show p-type semiconductor characteristics and high photoresponsivity (~1.7 A/W under white light illumination) comparable to exfoliated GaSe nanosheets. These 2D GaSe crystals are potentially useful for next-generation electronic and optoelectronic devices such as photodetectors and field-effect transistors.

  16. Controlled Vapor Phase Growth of Single Crystalline, Two-Dimensional GaSe Crystals with High Photoresponse

    SciTech Connect

    Li, Xufan; Lin, Ming-Wei; Zhang, Huidong; Puretzky, Alexander A; Idrobo Tapia, Juan C; Ma, Cheng; Chi, Miaofang; Yoon, Mina; Rouleau, Christopher M; Kravchenko, Ivan I; Geohegan, David B; Xiao, Kai

    2014-01-01

    Abstract Compared with their bulk counterparts, atomically thin two-dimensional (2D) crystals exhibit new physical properties, and have the potential to enable next-generation electronic and optoelectronic devices. However, controlled synthesis of large uniform monolayer and multi-layer 2D crystals is still challenging. Here, we report the controlled synthesis of 2D GaSe crystals on SiO2/Si substrates using a vapor phase deposition method. For the first time, uniform, large (up to ~60 m in lateral size), single-crystalline, triangular monolayer GaSe crystals were obtained and their atomic resolution structure were characterized. The size, density, shape, thickness, and uniformity of the 2D GaSe crystals were shown to be controllable by growth duration, growth region, growth temperature, and argon carrier gas flow rate. The theoretical modeling of the electronic structure and Raman spectroscopy demonstrate a direct-to-indirect bandgap transition and progressive confinement-induced bandgap shifts for 2D GaSe crystals. The 2D GaSe crystals show p-type semiconductor characteristics and high photoresponsivity (~1.7 A/W under white light illumination) comparable to exfoliated GaSe nanosheets. These 2D GaSe crystals are potentially useful for next-generation electronic and optoelectronic devices such as photodetectors and field-effect transistors.

  17. Room-temperature single-electron memory made by pulse-mode atomic force microscopy nano oxidation process on atomically flat α-alumina substrate

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kazuhiko; Gotoh, Yoshitaka; Maeda, Tatsuro; Dagata, John A.; Harris, James S.

    2000-01-01

    A single-electron memory was fabricated using the improved pulse-mode atomic force microscopy nano oxidation process which oxidized the surface of the thin titanium (Ti) metal on the atomically flat α-alumina (α-Al2O3) substrate and formed the narrow oxidized titanium (TiOx) line that works as a tunnel junction for the device. This single-electron memory consists of the multitunnel junction and a memory capacitance. The single-electron transistor, which works as an electrometer, was connected to the memory node of the single-electron memory to detect the potential change of the memory node by the injection of the individual electrons. The fabricated single-electron memory showed the hysteresis loop even at room temperature by the return trip of the memory bias when starting from 0 to 10 V and again coming back to 0 V. About 25 electrons were stored at the memory node.

  18. Epitaxial Growth of Atomically Flat Yttrium Iron Garnet Thin Films on Gadolinium Gallium Garnet by Pulse Laser Deposition

    NASA Astrophysics Data System (ADS)

    Lin, Tao; Tang, Chi; Shi, Jing

    2013-03-01

    Yttrium iron garnet (YIG) is a ferrimagnetic insulator which is useful for magneto-optical, microwave, and more recently spintronic devices. Pulsed laser deposition (PLD) has emerged as a preferred technique to deposit complex oxide thin films, heterostructures, and superlattices with high quality. Deposition of YIG films using PLD has been reported by several groups. The layer-by-layer growth mode has been achieved with a high laser repetition rate. No details about surface morphology were discussed. Here we report our approach to grow YIG films with thickness ranging from 10 to 100 nm on (110)- and (111)-oriented gadolinium gallium garnet (GGG) substrates. In both orientations, we have successfully grown epitaxial YIG thin films confirmed by the patterns of the reflection high-energy electron diffraction. The magnetic properties are measured by a vibrating sample magnetometer. The in-plane easy-axis coercivity is less than 1 Oe, while the perpendicular saturation field is ~ 2000 Oe. For both orientations, the atomic force microscopy images show that the YIG surface is extremely flat with roughness ~ 0.6Å. Flat terraces are found with the atomic step height in films with both orientations. This work paves the way to engineering anisotropy of the thin films for YIG-based magnetic devices. This work was supported in part by DMEA and DOE.

  19. Integrated electro-optic devices of melt-processable single-crystalline organic films

    NASA Astrophysics Data System (ADS)

    Figi, Harry; Jazbinšek, Mojca; Hunziker, Christoph; Koechlin, Manuel; Günter, Peter

    2010-02-01

    Organic electro-optic (EO) materials are the materials of choice for high speed optical modulators with modulation frequencies greater than 100 GHz. This is due to the large EO effects observed and a low material dispersion of the dielectric constant resulting in a very small velocity mismatch between the optical and electrical waves. However, the implementation of organic materials into real devices has been hindered by several factors such as an insufficient long-term thermal and photochemical stability of the widely investigated poled polymers or the lack of available structuring techniques for the inherently superior organic EO crystalline materials. Here we report on the realization of integrated organic EO single-crystalline Mach-Zehnder modulators by a recently developed melt based channel growth technique. The main fabrication concept is to grow the organic EO singlecrystals from the melt directly in pre-structured and electroded waveguide channels, which were obtained by standard optical lithographic techniques and wafer bonding. By this method single crystal structure details with a size below 30 nm have been achieved and the growth of single-crystalline Mach-Zehnder modulators has been successfully demonstrated, where we have chosen DAT2 (2-(3-(2-(4-dimethylaminophenyl)vinyl)-5,5- dimethylcyclohex-2-enylidene)malononitrile) as EO material. The half-wave voltage × length product determined in the DAT2 based Mach-Zehnder modulators has been found to be 78 +/- 2 Vcm for TE-modes and 60 +/-1 Vcm for TM-modes at a wavelength of 1.55 μm. The accuracy and reproducibility of the process allowed also for the realization of the first EO single-crystalline microring resonator in an organic material.

  20. Dependence of Fracture Toughness on Crystallographic Orientation in Single-Crystalline Cubic (β) Silicon Carbide

    SciTech Connect

    Pharr, M.; Katoh, Y.; Bei, H.

    2006-01-01

    Along with other desirable properties, the ability of silicon carbide (SiC) to retain high strength after elevated temperature exposures to neutron irradiation renders it potentially applicable in fusion and advanced fission reactors. However, properties of the material such as room temperature fracture toughness must be thoroughly characterized prior to such practical applications. The objective of this work is to investigate the dependence of fracture toughness on crystallographic orientation for single-crystalline β-SiC. X-ray diffraction was first performed on the samples to determine the orientation of the crystal. Nanoindentation was used to determine a hardness of 39.1 and 35.2 GPa and elastic modulus of 474 and 446 GPa for the single-crystalline and polycrystalline samples, respectively. Additionally, crack lengths and indentation diagonals were measured via a Vickers micro-hardness indenter under a load of 100 gf for different crystallographic orientations with indentation diagonals aligned along fundamental cleavage planes. Upon examination of propagation direction of cracks, the cracks usually did not initiate and propagate from the corners of the indentation where the stresses are concentrated but instead from the indentation sides. Such cracks clearly moved along the {1 1 0} family of planes (previously determined to be preferred cleavage plane), demonstrating that the fracture toughness of SiC is comparatively so much lower along this set of planes that the lower energy required to cleave along this plane overpowers the stress-concentration at indentation corners. Additionally, fracture toughness in the <1 1 0> direction was 1.84 MPa·m1/2, lower than the 3.46 MPa·m1/2 measured for polycrystalline SiC (which can serve as an average of a spectrum of orientations), further demonstrating that single-crystalline β-SiC has a strong fracture toughness anisotropy.

  1. Investigation of the nonlinear refractive index of single-crystalline thin gold films and plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Goetz, Sebastian; Razinskas, Gary; Krauss, Enno; Dreher, Christian; Wurdack, Matthias; Geisler, Peter; Pawłowska, Monika; Hecht, Bert; Brixner, Tobias

    2016-04-01

    The nonlinear refractive index of plasmonic materials may be used to obtain nonlinear functionality, e.g., power-dependent switching. Here, we investigate the nonlinear refractive index of single-crystalline gold in thin layers and nanostructures on dielectric substrates. In a first step, we implement a z-scan setup to investigate ~100-µm-sized thin-film samples. We determine the nonlinear refractive index of fused silica, n 2(SiO2) = 2.9 × 10-20 m2/W, in agreement with literature values. Subsequent z-scan measurements of single-crystalline gold films reveal a damage threshold of 0.22 TW/cm2 and approximate upper limits of the real and imaginary parts of the nonlinear refractive index, | n 2'(Au)| < 1.2 × 10-16 m2/W and | n 2″(Au)| < 0.6 × 10-16 m2/W, respectively. To further determine possible effects of a nonlinear refractive index in plasmonic circuitry, interferometry is proposed as a phase-sensitive probe. In corresponding nanostructures, relative phase changes between two propagating near-field modes are converted to amplitude changes by mode interference. Power-dependent experiments using sub-10-fs near-infrared pulses and diffraction-limited resolution (NA = 1.4) reveal linear behavior up to the damage threshold (0.23 times relative to that of a solid single-crystalline gold film). An upper limit for the nonlinear power-dependent phase change between two propagating near-field modes is determined to Δ φ < 0.07 rad.

  2. Large-scale growth of millimeter-long single-crystalline ZnS nanobelts

    SciTech Connect

    Li Jianye Zhang Qi; An Lei; Qin Luchang; Liu Jie

    2008-11-15

    Millimeter-long single-crystalline hexagonal ZnS nanobelts were grown on specific locations on a wafer scale. This is the first time that the millimeter-scale ZnS nanobelt has been synthesized. The longest nanobelts are about 3 mm. The as-grown nanobelts were characterized by means of field emission scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction. The results indicate that the ultra-long nanobelts are pure single-crystalline hexagonal ZnS. There are two kinds of ZnS nanobelts existing in the products. One is the nanobelts that have two smooth sides and grow along the [0 0 1] longitudinal direction, and the other is the nanobelts that have one smooth side and one saw-teeth-like side, namely nanosaws, and grow along the [2 1 0] longitudinal direction. A vapor-liquid-solid mechanism is suggested for the lengthwise growth of the ZnS nanobelts (nanosaws) and a vapor-solid mechanism for the side direction growth of the saw-teeth of the nanosaws. - Graphical Abstract: Millimeter-long single-crystalline ZnS nanobelts were grown on specific locations on a large scale. There are two kinds of nanobelts in the products-one has two smooth sides, and the other has one smooth side and one saw-teeth-like side, namely nanosaws. Mechanisms for the longitudinal direction growth of the nanobelts/nanosaws and the side saw-teeth direction growth of the nanosaws are discussed.

  3. Enhanced photocatalytic efficiency in zirconia buffered n-NiO/p-NiO single crystalline heterostructures by nanosecond laser treatment

    NASA Astrophysics Data System (ADS)

    Molaei, R.; Bayati, M. R.; Alipour, H. M.; Nori, S.; Narayan, J.

    2013-06-01

    We report the formation of NiO based single crystalline p-n junctions with enhanced photocatalytic activity induced by pulsed laser irradiation. The NiO epilayers were grown on Si(001) substrates buffered with cubic yttria-stabilized zirconia (c-YSZ) by using pulsed laser deposition. The NiO/c-YSZ/Si heterostructures were subsequently laser treated by 5 pulses of KrF excimer laser (pulse duration = 25 × 10-9 s) at lower energies. Microstructural studies, conducted by X-ray diffraction (θ-2θ and φ techniques) and high resolution transmission electron microscope, showed a cube-on-cube epitaxial relationship at the c-YSZ/Si interface; the epitaxial relationship across the NiO/c-YSZ interface was established as NiO⟨111 ⟩||c-YSZ⟨001⟩ and in-plane NiO⟨110⟩||c-YSZ⟨100⟩. Electron microscopy studies showed that the interface between the laser annealed and the pristine region as well as the NiO/c-YSZ interface was atomically sharp and crystallographically continuous. The formation of point defects, namely oxygen vacancies and NiO, due to the coupling of the laser photons with the NiO epilayers was confirmed by XPS. The p-type electrical characteristics of the pristine NiO epilayers turned to an n-type behavior and the electrical conductivity was increased by one order of magnitude after laser treatment. Photocatalytic activity of the pristine (p-NiO/c-YSZ/Si) and the laser-annealed (n-NiO/p-NiO/c-YSZ/Si) heterostructures were assessed by measuring the decomposition rate of 4-chlorophenol under UV light. The photocatalytic reaction rate constants were determined to be 0.0059 and 0.0092 min-1 for the as-deposited and the laser-treated samples, respectively. The enhanced photocatalytic efficiency was attributed to the suppressed charge carrier recombination in the NiO based p-n junctions and higher electrical conductivity. Besides, the oxygen vacancies ease the adsorption of 4-chlorophenol, hydroxyl, and water molecules to the surface. Thus, n

  4. High mobility single crystalline ScN and single-orientation epitaxial YN on sapphire via magnetron sputtering

    SciTech Connect

    Gregoire, John M.; Kirby, Steven D.; Scopelianos, George E.; Dover, R. Bruce van; Lee, Felix H.

    2008-10-01

    The mechanical, chemical, and electronic properties of the lanthanoid nitrides give this class of materials many potential applications. While ScN research activity has sharply increased recently, investigations of growth methods for optimizing structural and, more importantly, electronic properties are still needed. YN has received some theoretical but very little experimental attention. We present results of x-ray diffraction and atomic force microscopy analyses of film structure as well as Hall effect measurements of electronic properties for sputter-deposited ScN and YN. Films are deposited at select values of sputter gas stoichiometry, gas pressure, and substrate temperature, and optimal values are suggested. Additionally, the role of deposition geometry is investigated. Grown under optimal conditions, ScN films are single crystalline and YN films are singly oriented with both nitrides exhibiting the same epitaxial relation to {alpha}-Al{sub 2}O{sub 3}(1102) substrates. Our films also exhibit the highest documented electron mobility for the respective materials, despite their high carrier concentration.

  5. Synthesis of single-crystalline anisotropic gold nano-crystals via chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Manna, Sohini; Kim, Jong Woo; Takahashi, Yukiko; Shpyrko, Oleg G.; Fullerton, Eric E.

    2016-05-01

    We report on a novel one-step catalyst-free, thermal chemical vapor deposition procedure to synthesize gold nanocrystals on silicon substrates. This approach yields single-crystal nanocrystals with various morphologies, such as prisms, icosahedrons, and five-fold twinned decahedrons. Our approach demonstrates that high-quality anisotropic crystals composed of fcc metals can be produced without the need for surfactants or templates. Compared with the traditional wet chemical synthesis processes, our method enables direct formation of highly pure and single crystalline nanocrystals on solid substrates which have applications in catalysis. We investigated the evolution of gold nanocrystals and established their formation mechanism.

  6. Wafer-size free-standing single-crystalline graphene device arrays

    NASA Astrophysics Data System (ADS)

    Li, Peng; Jing, Gaoshan; Zhang, Bo; Sando, Shota; Cui, Tianhong

    2014-08-01

    We report an approach of wafer-scale addressable single-crystalline graphene (SCG) arrays growth by using pre-patterned seeds to control the nucleation. The growth mechanism and superb properties of SCG were studied. Large array of free-standing SCG devices were realized. Characterization of SCG as nano switches shows excellent performance with life time (>22 000 times) two orders longer than that of other graphene nano switches reported so far. This work not only shows the possibility of producing wafer-scale high quality SCG device arrays but also explores the superb performance of SCG as nano devices.

  7. Structural and Optical Properties of Single Crystalline Bismuth Nanoparticles in Polymer

    NASA Astrophysics Data System (ADS)

    Kabir, Lutful; Mandal, Swapan K.

    We report here the structural and optical properties of Bi nanoparticles in polymer (polypyrrole) matrix. The nanoparticles are synthesized following a wet chemical route. The X-ray diffraction data clearly shows the growth of single crystalline Bi nanoparticles within the host polymer. The microstructure of the Bi nanoparticles obtained by transmission electron microscopy (TEM) reveals clearly the formation of spherical shaped nanoparticles of average size˜27 nm with a narrow size distribution. The optical absorption spectrum exhibits a distinct peak at 278 nm which is attributed to the surface plasmon band of Bi nanoparticles. The absorption spectrum is found to be described well following Mie theory.

  8. Multiple phase transitions in single-crystalline Na_{1-delta}FeAs.

    PubMed

    Chen, G F; Hu, W Z; Luo, J L; Wang, N L

    2009-06-01

    Specific heat, resistivity, susceptibility, and Hall coefficient measurements were performed on high-quality single-crystalline Na_{1-delta}FeAs. This compound is found to undergo three successive phase transitions at around 52, 41, and 23 K, which correspond to structural, magnetic, and superconducting transitions, respectively. The Hall effect result indicates the development of energy gap at low temperature due to the occurrence of spin-density-wave instability. Our results provide direct experimental evidence of the magnetic ordering in the nearly stoichiometric NaFeAs.

  9. Dissolution chemistry and biocompatibility of single-crystalline silicon nanomembranes and associated materials for transient electronics.

    PubMed

    Hwang, Suk-Won; Park, Gayoung; Edwards, Chris; Corbin, Elise A; Kang, Seung-Kyun; Cheng, Huanyu; Song, Jun-Kyul; Kim, Jae-Hwan; Yu, Sooyoun; Ng, Joanne; Lee, Jung Eun; Kim, Jiyoung; Yee, Cassian; Bhaduri, Basanta; Su, Yewang; Omennetto, Fiorenzo G; Huang, Yonggang; Bashir, Rashid; Goddard, Lynford; Popescu, Gabriel; Lee, Kyung-Mi; Rogers, John A

    2014-06-24

    Single-crystalline silicon nanomembranes (Si NMs) represent a critically important class of material for high-performance forms of electronics that are capable of complete, controlled dissolution when immersed in water and/or biofluids, sometimes referred to as a type of "transient" electronics. The results reported here include the kinetics of hydrolysis of Si NMs in biofluids and various aqueous solutions through a range of relevant pH values, ionic concentrations and temperatures, and dependence on dopant types and concentrations. In vitro and in vivo investigations of Si NMs and other transient electronic materials demonstrate biocompatibility and bioresorption, thereby suggesting potential for envisioned applications in active, biodegradable electronic implants.

  10. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings

    NASA Astrophysics Data System (ADS)

    Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew; Krishnan, Kannan M.

    2014-11-01

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe3O4 nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy.

  11. Magnetic anisotropy engineering: Single-crystalline Fe films on ion eroded ripple surfaces

    NASA Astrophysics Data System (ADS)

    Liedke, M. O.; Körner, M.; Lenz, K.; Grossmann, F.; Facsko, S.; Fassbender, J.

    2012-06-01

    We present a method to preselect the direction of an induced in-plane uniaxial magnetic anisotropy (UMA) in thin single-crystalline Fe films on MgO(001). Ion beam irradiation is used to modulate the MgO(001) surface with periodic ripples on the nanoscale. The ripple direction determines the orientation of the UMA, whereas the intrinsic cubic anisotropy of the Fe film is not affected. Thus, it is possible to superimpose an in-plane UMA with a precision of a few degrees—a level of control not reported so far that can be relevant for example in spintronics.

  12. Thin-film transistor fabricated in single-crystalline transparent oxide semiconductor.

    PubMed

    Nomura, Kenji; Ohta, Hiromichi; Ueda, Kazushige; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2003-05-23

    We report the fabrication of transparent field-effect transistors using a single-crystalline thin-film transparent oxide semiconductor, InGaO3(ZnO)5, as an electron channel and amorphous hafnium oxide as a gate insulator. The device exhibits an on-to-off current ratio of approximately 106 and a field-effect mobility of approximately 80 square centimeters per volt per second at room temperature, with operation insensitive to visible light irradiation. The result provides a step toward the realization of transparent electronics for next-generation optoelectronics. PMID:12764192

  13. Single-layer MoS{sub 2} roughness and sliding friction quenching by interaction with atomically flat substrates

    SciTech Connect

    Quereda, J.; Castellanos-Gomez, A.; Agraït, N.; Rubio-Bollinger, G.

    2014-08-04

    We experimentally study the surface roughness and the lateral friction force in single-layer MoS{sub 2} crystals deposited on different substrates: SiO{sub 2}, mica, and hexagonal boron nitride (h-BN). Roughness and sliding friction measurements are performed by atomic force microscopy. We find a strong dependence of the MoS{sub 2} roughness on the underlying substrate material, being h-BN the substrate which better preserves the flatness of the MoS{sub 2} crystal. The lateral friction also lowers as the roughness decreases, and attains its lowest value for MoS{sub 2} flakes on h-BN substrates. However, it is still higher than for the surface of a bulk MoS{sub 2} crystal, which we attribute to the deformation of the flake due to competing tip-to-flake and flake-to-substrate interactions.

  14. Free-Standing Two-Dimensional Single-Crystalline InSb Nanosheets.

    PubMed

    Pan, D; Fan, D X; Kang, N; Zhi, J H; Yu, X Z; Xu, H Q; Zhao, J H

    2016-02-10

    Growth of high-quality single-crystalline InSb layers remains challenging in material science. Such layered InSb materials are highly desired for searching for and manipulation of Majorana Fermions in solid state, a fundamental research task in physics today, and for development of novel high-speed nanoelectronic and infrared optoelectronic devices. Here, we report on a new route toward growth of single-crystalline, layered InSb materials. We demonstrate the successful growth of free-standing, two-dimensional InSb nanosheets on one-dimensional InAs nanowires by molecular-beam epitaxy. The grown InSb nanosheets are pure zinc-blende single crystals. The length and width of the InSb nanosheets are up to several micrometers and the thickness is down to ∼10 nm. The InSb nanosheets show a clear ambipolar behavior and a high electron mobility. Our work will open up new technology routes toward the development of InSb-based devices for applications in nanoelectronics, optoelectronics, and quantum electronics and for the study of fundamental physical phenomena. PMID:26788662

  15. Principle of direct van der Waals epitaxy of single-crystalline films on epitaxial graphene.

    PubMed

    Kim, Jeehwan; Bayram, Can; Park, Hongsik; Cheng, Cheng-Wei; Dimitrakopoulos, Christos; Ott, John A; Reuter, Kathleen B; Bedell, Stephen W; Sadana, Devendra K

    2014-09-11

    There are numerous studies on the growth of planar films on sp(2)-bonded two-dimensional (2D) layered materials. However, it has been challenging to grow single-crystalline films on 2D materials due to the extremely low surface energy. Recently, buffer-assisted growth of crystalline films on 2D layered materials has been introduced, but the crystalline quality is not comparable with the films grown on sp(3)-bonded three-dimensional materials. Here we demonstrate direct van der Waals epitaxy of high-quality single-crystalline GaN films on epitaxial graphene with low defectivity and surface roughness comparable with that grown on conventional SiC or sapphire substrates. The GaN film is released and transferred onto arbitrary substrates. The post-released graphene/SiC substrate is reused for multiple growth and transfer cycles of GaN films. We demonstrate fully functional blue light-emitting diodes (LEDs) by growing LED stacks on reused graphene/SiC substrates followed by transfer onto plastic tapes.

  16. Preparation and oxidation resistance of single crystalline β-Zn4Sb3

    NASA Astrophysics Data System (ADS)

    Liu, Hong-xia; Deng, Shu-ping; Li, De-cong; Shen, Lan-xian; Cheng, Feng; Wang, Jin-song; Deng, Shu-kang

    2016-11-01

    This study prepared a Zn-rich single crystal β-Zn4Sb3 using a Sn flux method based on the stoichiometric ratios of Zn4.4Sb3Sn3. The oxidation resistance of the sample was determined by exploring the effects of heat treatment in air on electrical transport properties and thermal stability, which is of practical importance in the application of the material at high temperatures. Results showed that the prepared sample possessed high electrical transport properties, with a high power factor of 1.67×10-3 W m-1 K-2 at 563 K. The heat treatment in air weakened the electrical conductivity of the single crystalline β-Zn4Sb3, whereas the Seebeck coefficients were rarely independent of the annealing condition. Eventually, the power factor obtained after the first heating at 523 K for 4 h became comparable to that of the as-prepared sample, although it decreased after the second heating at 573 K for 5 h. Nevertheless, the single crystalline β-Zn4Sb3 still possessed a good thermal stability after the heat treatment process.

  17. Large-scale growth of millimeter-long single-crystalline ZnS nanobelts

    NASA Astrophysics Data System (ADS)

    Li, Jianye; Zhang, Qi; An, Lei; Qin, Luchang; Liu, Jie

    2008-11-01

    Millimeter-long single-crystalline hexagonal ZnS nanobelts were grown on specific locations on a wafer scale. This is the first time that the millimeter-scale ZnS nanobelt has been synthesized. The longest nanobelts are about 3 mm. The as-grown nanobelts were characterized by means of field emission scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction. The results indicate that the ultra-long nanobelts are pure single-crystalline hexagonal ZnS. There are two kinds of ZnS nanobelts existing in the products. One is the nanobelts that have two smooth sides and grow along the [0 0 1] longitudinal direction, and the other is the nanobelts that have one smooth side and one saw-teeth-like side, namely nanosaws, and grow along the [2 1 0] longitudinal direction. A vapor-liquid-solid mechanism is suggested for the lengthwise growth of the ZnS nanobelts (nanosaws) and a vapor-solid mechanism for the side direction growth of the saw-teeth of the nanosaws.

  18. Direct growth of single-crystalline III–V semiconductors on amorphous substrates

    DOE PAGESBeta

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; et al

    2016-01-27

    The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V’s on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V’s of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. Themore » patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. In conclusion, the work presents an important advance towards universal integration of III–V’s on application-specific substrates by direct growth.« less

  19. Highly efficient electrochemical responses on single crystalline ruthenium-vanadium mixed metal oxide nanowires.

    PubMed

    Chun, Sung Hee; Choi, Hyun-A; Kang, Minkyung; Koh, Moonjee; Lee, Nam-Suk; Lee, Sang Cheol; Lee, Minyung; Lee, Youngmi; Lee, Chongmok; Kim, Myung Hwa

    2013-09-11

    Highly efficient single crystalline ruthenium-vanadium mixed metal oxide (Ru1-xVxO2, 0≤x≤1) nanowires were prepared on a SiO2 substrate and a commercial Au microelectrode for the first time through a vapor-phase transport process by adjusting the mixing ratios of RuO2 and VO2 precursors. Single crystalline Ru1-xVxO2 nanowires show homogeneous solid-solution characteristics as well as the distinct feature of having remarkably narrow dimensional distributions. The electrochemical observations of a Ru1-xVxO2 (x=0.28 and 0.66)-decorated Au microelectrode using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrate favorable charge-transfer kinetics of [Fe(CN)6]3-/4- and Ru(NH3)6(3+/2+) couples compared to that of a bare Au microelectrode. The catalytic activity of Ru1-xVxO2 for oxygen and H2O2 reduction at neutral pH increases as the fraction of vanadium increases within our experimental conditions, which might be useful in the area of biofuel cells and biosensors.

  20. Direct growth of single-crystalline III-V semiconductors on amorphous substrates.

    PubMed

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager Iii, Joel W; Chrzan, Daryl C; Javey, Ali

    2016-01-01

    The III-V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III-V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III-V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III-V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III-V's on application-specific substrates by direct growth. PMID:26813257

  1. Direct growth of single-crystalline III–V semiconductors on amorphous substrates

    PubMed Central

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager III, Joel W.; Chrzan, Daryl C.; Javey, Ali

    2016-01-01

    The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III–V's on application-specific substrates by direct growth. PMID:26813257

  2. Rare orbital glass state in single crystalline Y2Mo2O7

    NASA Astrophysics Data System (ADS)

    Silverstein, Harlyn; Zhou, Haidong; Hallas, Alannah; Gardner, Jason; Qiu, Yiming; Ehlers, Georg; Savici, Andrei; Yamani, Zahra; Gingras, Michel; Gaulin, Bruce; Fritsche, Katharina; Ross, Kate; Wiebe, Christopher

    2012-02-01

    Perhaps one of the most curious cases of frustrated pyrochlores, Y2Mo2O7 was first classified as a spin glass in 1986. Conventionally, spin glasses must exhibit some sort of chemical disorder although oxygen vacancies and Y-Mo site mixing is virtually absent in all studies to date. NMR and neutron PDF experiments show the presence of local disorder. While other studies have shown a lattice deformation occurring near Tg=22K, these distortions cannot be detected globally and may not be enough to explain the spin glass behavior. For 25 years, researchers have struggled to resolve spin glass theory with the data; the problem lies in that, until now, scientists have been unable to grow single crystal samples due to the oxidation of Mo^4+ to Mo^6+ at low temperatures. Here, we report the synthesis and characterization of the world's first single crystalline sample of Y2Mo2O7. Unlike powder samples, single crystalline Y2Mo2O7 heat capacity measurements show a T^2 dependence. Neutron scattering experiments show isotropic, broad, liquid-like collective modes and high-Q diffuse scattering characteristic of an orbital liquid to orbital glass transition at Tg.

  3. Principle of direct van der Waals epitaxy of single-crystalline films on epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Kim, Jeehwan; Bayram, Can; Park, Hongsik; Cheng, Cheng-Wei; Dimitrakopoulos, Christos; Ott, John A.; Reuter, Kathleen B.; Bedell, Stephen W.; Sadana, Devendra K.

    2014-09-01

    There are numerous studies on the growth of planar films on sp2-bonded two-dimensional (2D) layered materials. However, it has been challenging to grow single-crystalline films on 2D materials due to the extremely low surface energy. Recently, buffer-assisted growth of crystalline films on 2D layered materials has been introduced, but the crystalline quality is not comparable with the films grown on sp3-bonded three-dimensional materials. Here we demonstrate direct van der Waals epitaxy of high-quality single-crystalline GaN films on epitaxial graphene with low defectivity and surface roughness comparable with that grown on conventional SiC or sapphire substrates. The GaN film is released and transferred onto arbitrary substrates. The post-released graphene/SiC substrate is reused for multiple growth and transfer cycles of GaN films. We demonstrate fully functional blue light-emitting diodes (LEDs) by growing LED stacks on reused graphene/SiC substrates followed by transfer onto plastic tapes.

  4. Free-Standing Two-Dimensional Single-Crystalline InSb Nanosheets.

    PubMed

    Pan, D; Fan, D X; Kang, N; Zhi, J H; Yu, X Z; Xu, H Q; Zhao, J H

    2016-02-10

    Growth of high-quality single-crystalline InSb layers remains challenging in material science. Such layered InSb materials are highly desired for searching for and manipulation of Majorana Fermions in solid state, a fundamental research task in physics today, and for development of novel high-speed nanoelectronic and infrared optoelectronic devices. Here, we report on a new route toward growth of single-crystalline, layered InSb materials. We demonstrate the successful growth of free-standing, two-dimensional InSb nanosheets on one-dimensional InAs nanowires by molecular-beam epitaxy. The grown InSb nanosheets are pure zinc-blende single crystals. The length and width of the InSb nanosheets are up to several micrometers and the thickness is down to ∼10 nm. The InSb nanosheets show a clear ambipolar behavior and a high electron mobility. Our work will open up new technology routes toward the development of InSb-based devices for applications in nanoelectronics, optoelectronics, and quantum electronics and for the study of fundamental physical phenomena.

  5. Interdiffusion and stress development in single-crystalline Pd/Ag bilayers

    NASA Astrophysics Data System (ADS)

    Noah, Martin A.; Flötotto, David; Wang, Zumin; Mittemeijer, Eric J.

    2016-04-01

    Interdiffusion and stress evolution in single-crystalline Pd/single-crystalline Ag thin films were investigated by Auger electron spectroscopy sputter-depth profiling and in-situ X-ray diffraction, respectively. The concentration-dependent chemical diffusion coefficient, as well as the impurity diffusion coefficient of Ag in Pd could be determined in the low temperature range of 356 °C-455 °C. As a consequence of the similarity of the strong concentration-dependences of the intrinsic diffusion coefficients, the chemical diffusion coefficient varies only over three orders of magnitude over the whole composition range, despite the large difference of six orders of magnitude of the self-diffusion coefficients of Ag in Ag and Pd in Pd. It is shown that the Darken-Manning treatment should be adopted for interpretation of the experimental data; the Nernst-Planck treatment yielded physically unreasonable results. Apart from the development of compressive thermal stress, the development of stress in both sublayers separately could be ascribed to compositional stress (tensile in the Ag sublayer and compressive in the Pd sublayer) and dominant relaxation processes, especially in the Ag sublayer. The effect of these internal stresses on the values determined for the diffusion coefficients is shown to be negligible.

  6. Fabrication of single crystalline, uniaxial single domain Co nanowire arrays with high coercivity

    NASA Astrophysics Data System (ADS)

    Ramazani, A.; Almasi Kashi, M.; Montazer, A. H.

    2014-03-01

    Whilst Co nanorods with high coercivity were synthesized during recent years, they did not achieve the same results as for Co nanowires embedded in solid templates. In the present work, Co nanowire arrays (NWAs) with high coercivity were successfully fabricated in porous aluminum oxide template under optimum conditions by using pulsed ac electrodeposition technique. Magnetic properties and crystalline characteristics of the nanowires were investigated by hysteresis loop measurements, first-order reversal curve (FORC) analysis, X-ray diffraction (XRD), and selected area electron diffraction (SAED) patterns. Hysteresis loop measurements showed high coercivity of about 4.8 kOe at room temperature together with optimum squareness of 1, resulting in an increase of the previous maximum coercivity for Co NWAs up to 45%. XRD and SAED patterns revealed a single crystalline texture along the [0002] direction, indicating the large magnetocrystalline anisotropy. On the other hand, FORC analysis confirmed a single domain structure for the Co NWAs. In addition, the reversal mechanism of the single crystalline, single domain Co NWAs was studied which resulted in the fixed easy axis with a coherent rotation. Accordingly, these nanowires might offer promising applications in high density bit patterned media and low power logic devices.

  7. Fabrication of single crystalline, uniaxial single domain Co nanowire arrays with high coercivity

    SciTech Connect

    Ramazani, A. Almasi Kashi, M.; Montazer, A. H.

    2014-03-21

    Whilst Co nanorods with high coercivity were synthesized during recent years, they did not achieve the same results as for Co nanowires embedded in solid templates. In the present work, Co nanowire arrays (NWAs) with high coercivity were successfully fabricated in porous aluminum oxide template under optimum conditions by using pulsed ac electrodeposition technique. Magnetic properties and crystalline characteristics of the nanowires were investigated by hysteresis loop measurements, first-order reversal curve (FORC) analysis, X-ray diffraction (XRD), and selected area electron diffraction (SAED) patterns. Hysteresis loop measurements showed high coercivity of about 4.8 kOe at room temperature together with optimum squareness of 1, resulting in an increase of the previous maximum coercivity for Co NWAs up to 45%. XRD and SAED patterns revealed a single crystalline texture along the [0002] direction, indicating the large magnetocrystalline anisotropy. On the other hand, FORC analysis confirmed a single domain structure for the Co NWAs. In addition, the reversal mechanism of the single crystalline, single domain Co NWAs was studied which resulted in the fixed easy axis with a coherent rotation. Accordingly, these nanowires might offer promising applications in high density bit patterned media and low power logic devices.

  8. Solution-grown organic single-crystalline donor-acceptor heterojunctions for photovoltaics.

    PubMed

    Li, Hanying; Fan, Congcheng; Fu, Weifei; Xin, Huolin L; Chen, Hongzheng

    2015-01-12

    Organic single crystals are ideal candidates for high-performance photovoltaics due to their high charge mobility and long exciton diffusion length; however, they have not been largely considered for photovoltaics due to the practical difficulty in making a heterojunction between donor and acceptor single crystals. Here, we demonstrate that extended single-crystalline heterojunctions with a consistent donor-top and acceptor-bottom structure throughout the substrate can be simply obtained from a mixed solution of C60 (acceptor) and 3,6-bis(5-(4-n-butylphenyl)thiophene-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (donor). 46 photovoltaic devices were studied with the power conversion efficiency of (0.255±0.095)% under 1 sun, which is significantly higher than the previously reported value for a vapor-grown organic single-crystalline donor-acceptor heterojunction (0.007%). As such, this work opens a practical avenue for the study of organic photovoltaics based on single crystals.

  9. Probing the low thermal conductivity of single-crystalline porous Si nanowires

    NASA Astrophysics Data System (ADS)

    Zhao, Yunshan; Lina Yang Collaboration; Lingyu Kong Collaboration; Baowen Li Collaboration; John T L Thong Collaboration; Kedar Hippalgaonkar Collaboration

    Pore-like structures provide a novel way to reduce the thermal conductivity of silicon nanowires, compared to both smooth-surface VLS nanowires and rough EE nanowires. Because of enhanced phonon scattering with interface and decrease in phonon transport path, the porous nanostructures show reduction in thermal conductance by few orders of magnitude. It proves to be extremely challenging to evaluate porosity accurately in an experimental manner and further understand its effect on thermal transport. In this study, we use the newly developed electron-beam based micro-electrothermal device technique to study the porosity dependent thermal conductivity of mesoporous silicon nanowires that have single-crystalline scaffolding. Based on the Casino simulation, the power absorbed by the nanowire, coming from the loss of travelling electron energy, has a linear relationship with it cross section. The relationship has been verified experimentally as well. Monte Carlo simulation is carried out to theoretically predict the thermal conductivity of silicon nanowires with a specific value of porosity. These single-crystalline porous silicon nanowires show extremely low thermal conductivity, even below the amorphous limit. These structures together with our experimental techniques provide a particularly intriguing platform to understand the phonon transport in nanoscale and aid the performance improvement in future nanowires-based devices.

  10. Direct growth of single-crystalline III-V semiconductors on amorphous substrates

    NASA Astrophysics Data System (ADS)

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager, Joel W., III; Chrzan, Daryl C.; Javey, Ali

    2016-01-01

    The III-V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III-V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III-V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III-V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III-V's on application-specific substrates by direct growth.

  11. PbO networks composed of single crystalline nanosheets synthesized by a facile chemical precipitation method

    SciTech Connect

    Samberg, Joshua P.; Kajbafvala, Amir; Koolivand, Amir

    2014-03-01

    Graphical abstract: - Highlights: • Synthesis of PbO networks through a simple chemical precipitation route. • The synthesis method is rapid and low-cost. • Each network is composed of single crystalline PbO nanosheets. • A possible growth mechanism is proposed for synthesized PbO networks. - Abstract: For the field of energy storage, nanostructured lead oxide (PbO) shows immense potential for increased specific energy and deep discharge for lead acid battery technologies. In this work, PbO networks composed of single crystalline nanosheets were synthesized utilizing a simple, low cost and rapid chemical precipitation method. The PbO networks were prepared in a single reaction vessel from starting reagents of lead acetate dehydrate, ammonium hydroxide and deionized water. Lead acetate dehydrate was chosen as a reagent, as opposed to lead nitrate, to eliminate the possibility of nitrate contamination of the final product. X-ray diffraction (XRD) analysis, high resolution scanning electron microscopy (HRSEM) and high resolution transmission electron microscopy (HRTEM) analysis were used to characterize the synthesized PbO networks. The reproducible method described herein synthesized pure β-PbO (massicot) powders, with no byproducts. A possible formation mechanism for these PbO networks is proposed. The growth is found to proceed predominately in the 〈1 1 1〉 and 〈2 0 0〉 directions while being limited in the 〈0 1 1〉 direction.

  12. Single-crystalline CuGeO{sub 3} nanorods: Synthesis, characterization and properties

    SciTech Connect

    Wang, Fangfang; Xing, Yan; Su, Zhongmin; Song, Shuyan

    2013-07-15

    Graphical abstract: - Highlights: • Single crystalline CuGeO{sub 3} nanorods were prepared via a hydrothermal route. • The material exhibits greatly enhanced activity in photocatalytic degradation of dyes. • The magnetic susceptibility measurements indicate spin-Peierls transition properties. • CuGeO{sub 3} nanorods may be of potential application in future integrated optical devices. - Abstract: Single crystalline CuGeO{sub 3} nanorods with a diameter of 20–35 nm and a length up to 1 μm have been prepared via a facile hydrothermal route with the assistance of ethylenediamine. Some influencing factors such as the reaction time, reaction temperature, the volume of ethylenediamine were revealed to play crucial roles in the formation of the CuGeO{sub 3} nanorods. A possible growth mechanism was proposed based on the experimental results. Significantly, this is the first time that CuGeO{sub 3} was used as a photocatalyst for organic pollutant degradation under UV light irradiation. The reaction constant (k) of CuGeO{sub 3} nanorods was five times that of the sample prepared by solid-state reaction under UV light irradiation. Additionally, the optical and magnetic properties of CuGeO{sub 3} nanorods were systematically studied.

  13. Preservation of atomic flatness at SiO_2/Si(111) interface during furnace oxidation

    NASA Astrophysics Data System (ADS)

    Miyata, Noriyuki; Watanabe, Heiji; Ichikawa, Masakazu

    1998-03-01

    We used a scanning reflection electron microscopy (SREM) to study SiO_2/Si(111) interfaces formed by a furnace oxidation. Clean Si(111)-7x7 surfaces were slightly oxidized at 630^circC in ultrahigh-vacuum chamber (0.3 nm thick). Then SiO2 layers (2.5 - 48 nm) were grown by furnace oxidation under 1-atm O2 at 900^circC. In order to observe atomic-step images at thick-SiO_2/Si interfaces, as-grown SiO2 layers were chemically thinned by using dilute HF to less than 1 nm without exposure of the Si areas. SREM observation indicates that atomic steps on an initial Si surface are preserved at the SiO_2/Si interface and the interfacial steps do not move laterally even after 48-nm-thick oxidation. A profile analysis of reflection high-energy electron diffraction shows that the SiO_2/Si interface consists of islands which have a diameter of about 5 nm and monolayer depth. Our results indicate that the layer-by-layer oxidation caused by two-dimensional island nucleation proceeds under furnace oxidation.

  14. Photochemical Modification of Single Crystalline GaN Film Using n-Alkene with Different Carbon Chain Lengths as Biolinker.

    PubMed

    Wang, Chun; Zhuang, Hao; Huang, Nan; Heuser, Steffen; Schlemper, Christoph; Zhai, Zhaofeng; Liu, Baodan; Staedler, Thorsten; Jiang, Xin

    2016-06-14

    As a potential material for biosensing applications, gallium nitride (GaN) films have attracted remarkable attention. In order to construct GaN biosensors, a corresponding immobilization of biolinkers is of great importance in order to render a surface bioactive. In this work, two kinds of n-alkenes with different carbon chain lengths, namely allylamine protected with trifluoroacetamide (TFAAA) and 10-aminodec-1-ene protected with trifluoroacetamide (TFAAD), were used to photochemically functionalize single crystalline GaN films. The successful linkage of both TFAAA and TFAAD to the GaN films is confirmed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurement. With increased UV illumination time, the intensity of the secondary ions corresponding to the linker molecules initially increases and subsequently decreases in both cases. Based on the SIMS measurements, the maximum coverage of TFAAA is achieved after 14 h of UV illumination, while only 2 h is required in the case of TFAAD to reach the situation of a fully covered GaN surface. This finding leads to the conclusion that the reaction rate of TFAAD is significantly higher compared to TFAAA. Measurements by atomic force microscopy (AFM) indicate that the coverage of GaN films by a TFAAA layer leads to an increased surface roughness. The atomic terraces, which are clearly observable for the pristine GaN films, disappear once the surface is fully covered by a TFAAA layer. Such TFAAA layers will feature a homogeneous surface topography even for reaction times of 24 h. In contrast to this, TFAAD shows strong cross-polymerization on the surface, this is confirmed by optical microscopy. These results demonstrate that TFAAA is a more suitable candidate as biolinker in context of the GaN surfaces due to its improved controllability.

  15. Photochemical Modification of Single Crystalline GaN Film Using n-Alkene with Different Carbon Chain Lengths as Biolinker.

    PubMed

    Wang, Chun; Zhuang, Hao; Huang, Nan; Heuser, Steffen; Schlemper, Christoph; Zhai, Zhaofeng; Liu, Baodan; Staedler, Thorsten; Jiang, Xin

    2016-06-14

    As a potential material for biosensing applications, gallium nitride (GaN) films have attracted remarkable attention. In order to construct GaN biosensors, a corresponding immobilization of biolinkers is of great importance in order to render a surface bioactive. In this work, two kinds of n-alkenes with different carbon chain lengths, namely allylamine protected with trifluoroacetamide (TFAAA) and 10-aminodec-1-ene protected with trifluoroacetamide (TFAAD), were used to photochemically functionalize single crystalline GaN films. The successful linkage of both TFAAA and TFAAD to the GaN films is confirmed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurement. With increased UV illumination time, the intensity of the secondary ions corresponding to the linker molecules initially increases and subsequently decreases in both cases. Based on the SIMS measurements, the maximum coverage of TFAAA is achieved after 14 h of UV illumination, while only 2 h is required in the case of TFAAD to reach the situation of a fully covered GaN surface. This finding leads to the conclusion that the reaction rate of TFAAD is significantly higher compared to TFAAA. Measurements by atomic force microscopy (AFM) indicate that the coverage of GaN films by a TFAAA layer leads to an increased surface roughness. The atomic terraces, which are clearly observable for the pristine GaN films, disappear once the surface is fully covered by a TFAAA layer. Such TFAAA layers will feature a homogeneous surface topography even for reaction times of 24 h. In contrast to this, TFAAD shows strong cross-polymerization on the surface, this is confirmed by optical microscopy. These results demonstrate that TFAAA is a more suitable candidate as biolinker in context of the GaN surfaces due to its improved controllability. PMID:27217218

  16. Strain Anisotropies and Self-limiting Capacities in Single-crystalline 3D Silicon Microstructures: Models for High Energy Denisty Lithium-Ion Battery Anodes

    SciTech Connect

    Goldman, Jason L.; Long, Brandon R.; Gewirth, Andrew A.; Nuzzo, Ralph G

    2011-01-01

    This study examines the crystallographic anisotropy of strain evolution in model, single-crystalline silicon anode microstructures on electrochemical intercalation of lithium atoms. The 3D hierarchically patterned single- crystalline silicon microstructures used as model anodes were prepared using combined methods of photolithography and anisotropic dry and wet chemical etching. Silicon anodes, which possesses theoretically ten times the energy density by weight compared to conventional carbon anodes, reveal highly anisotropic but more importantly, variably recoverable crystallographic strains during cycling. Model strain-limiting silicon anode architectures that mitigate these impacts are highlighted. By selecting a specific design for the silicon anode microstructure, and exploiting the crystallographic anisotropy of strain evolution upon lithium intercalation to control the direction of volumetric expansion, the volume available for expansion and thus the charging capacity of these structures can be broadly varied. We highlight exemplary design rules for this self-strain-limited charging in which an anode can be variably optimized between capacity and stability. Strain-limited capacities ranging from 677 mAhg-1 to 2833 mAhg-1 were achieved by constraining the area available for volumetric expansion via the design rules of the microstructures.

  17. Robust ferromagnetism of single crystalline CoxZn1-xO (0.3 ≤ x ≤ 0.45) epitaxial films with high Co concentration

    NASA Astrophysics Data System (ADS)

    Cao, Qiang; Zhu, Dapeng; Fu, Maoxiang; Cai, Li; Yang, Ping; Li, Shuang; Zhu, Yinlian; Ma, Xiuliang; Liu, Guolei; Chen, Yanxue; Yan, Shishen; Mei, Liangmo; Wang, Xiaolin

    2016-08-01

    In contrast to conventional dilute magnetic semiconductors with concentrations of magnetic ions of just a few percent, here, we report the fabrication of epitaxial CoxZn1-xO single crystalline films with Co concentrations from x = 0.3 up to 0.45 by radio-frequency oxygen-plasma-assisted molecular beam epitaxy. The films retain their single crystalline wurtzite structure without any other crystallographic phase from precipitates, based on reflection high energy electron diffraction, X-ray diffraction, transmission electron microscopy, and Raman scattering. The results of X-ray diffraction, optical transmission spectroscopy, and in-situ X-ray photoelectron spectroscopy confirm the incorporation of Co2+ cations into the wurtzite lattice. The films exhibit robust ferromagnetism and the magneto-optical Kerr effect at room temperature. The saturation magnetization reaches 265 emu/cm3 at x = 0.45, which corresponds to the average magnetic moment of 1.5 μ B per Co atom.

  18. Generation and the role of dislocations in single-crystalline phase-change In2Se3 nanowires under electrical pulses

    NASA Astrophysics Data System (ADS)

    Mafi, Elham; Tao, Xin; Zhu, Wenguang; Gao, Yanfei; Wang, Chongmin; Gu, Yi

    2016-08-01

    We report the observation of the generation of dislocations in single-crystal phase-change In2Se3 nanowires under electrical pulses and the impact of these dislocations on electrical properties. Particularly, we correlated the atomic-scale structural characteristics with local electrical resistance variations, by performing transmission electron microscopy and scanning Kelvin probe microscopy on the same nanowires. By coupling the experimental results with first-principles density functional theory calculations, we show that the immobile dislocations are generated via vacancy condensations. Importantly, these dislocations lead to several orders of magnitude increase in the electrical resistance, while maintaining the single crystallinity of the lattice. These results significantly advance the fundamental understanding of the structure-property relation in this phase-change material under transient electrical excitations. From a practical perspective, the significant increase in the electrical resistance, driven by the formation of dislocations, can be exploited as a new electronic state in the single-crystalline phase in this phase-change material.

  19. Surface modification via wet chemical etching of single-crystalline silicon for photovoltaic application.

    PubMed

    Reshak, A H; Shahimin, M M; Shaari, S; Johan, N

    2013-11-01

    The potential of solar cells have not been fully tapped due to the lack of energy conversion efficiency. There are three important mechanisms in producing high efficiency cells to harvest solar energy; reduction of light reflectance, enhancement of light trapping in the cell and increment of light absorption. The current work represent studies conducted in surface modification of single-crystalline silicon solar cells using wet chemical etching techniques. Two etching types are applied; alkaline etching (KOH:IPA:DI) and acidic etching (HF:HNO3:DI). The alkaline solution resulted in anisotropic profile that leads to the formation of inverted pyramids. While acidic solution formed circular craters along the front surface of silicon wafer. This surface modification will leads to the reduction of light reflectance via texturizing the surface and thereby increases the short circuit current and conversion rate of the solar cells. PMID:24139943

  20. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings

    PubMed Central

    Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew

    2014-01-01

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe3O4 nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy. PMID:25422526

  1. Conically shaped single-crystalline diamond backing plates for a diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Krauss, G.; Reifler, H.; Steurer, W.

    2005-10-01

    Based on computer-aided design (CAD) and finite-element calculations (FEM), single-crystalline diamond backing plates were tailored as a replacement of beryllium for high-pressure diamond anvil cells with a focus on in-house single-crystal experiments. Although the modified cell has an opening angle of 90°, a very homogeneous stress distribution all over the backing plate was realized to avoid failure. The conically shaped backing plates work well in the targeted pressure range up to Mg2Co3Sn10.15 up to 9.69 GPa. The influence of simultaneous diffraction phenomena in the diamonds (diamond dips) is illustrated by single-counter and area-detector measurements using standard laboratory equipment.

  2. Exploring metamagnetism of single crystalline EuNiGe3 by neutron scattering

    NASA Astrophysics Data System (ADS)

    Fabrèges, X.; Gukasov, A.; Bonville, P.; Maurya, A.; Thamizhavel, A.; Dhar, S. K.

    2016-06-01

    We present here a neutron diffraction study, both in zero field and as a function of magnetic field, of the magnetic structure of the tetragonal intermetallic EuNiGe3 on a single crystalline sample. This material is known to undergo a cascade of transitions, first at 13.2 K towards an incommensurate modulated magnetic structure, then at 10.5 K to an antiferromagnetic structure. We show here that the low-temperature phase presents a spiral moment arrangement with wave vector k =(1/4 ,δ ,0 ) . For a magnetic field applied along the tetragonal c axis, the square root of the scattering intensity of the (1 0 1) reflection matches very well the complex metamagnetic behavior of the magnetization along c measured previously. For the magnetic field applied along the b axis, two magnetic transitions are observed below the transition to a fully polarized state.

  3. Four-fold symmetric anisotropic magnetoresistance of single-crystalline Ni(001) film

    SciTech Connect

    Xiao, X.; Li, J. X.; Ding, Z.; Wu, Y. Z.

    2015-11-28

    Temperature, current-direction, and film-thickness dependent anisotropic magnetoresistance measurements were performed on single-crystalline face-centered-cubic nickel films. An additional four-fold symmetry was confirmed besides the typical two-fold term even at room temperature. The angular-dependent longitudinal resistivity resolves into a two-fold term, which varies as a function of current direction, and a four-fold term, which is isotropically independent of current direction. The experimental results are interpreted well using an expression based on the phenomenological model. Both the two- and four-fold terms vary inversely proportional to film thickness, indicating that interfacial scattering can significantly influence the spin-dependent transport properties.

  4. Reduction in the thermal conductivity of single crystalline silicon by phononic crystal patterning.

    PubMed

    Hopkins, Patrick E; Reinke, Charles M; Su, Mehmet F; Olsson, Roy H; Shaner, Eric A; Leseman, Zayd C; Serrano, Justin R; Phinney, Leslie M; El-Kady, Ihab

    2011-01-12

    Phononic crystals (PnCs) are the acoustic wave equivalent of photonic crystals, where a periodic array of scattering inclusions located in a homogeneous host material causes certain frequencies to be completely reflected by the structure. In conjunction with creating a phononic band gap, anomalous dispersion accompanied by a large reduction in phonon group velocities can lead to a massive reduction in silicon thermal conductivity. We measured the cross plane thermal conductivity of a series of single crystalline silicon PnCs using time domain thermoreflectance. The measured values are over an order of magnitude lower than those obtained for bulk Si (from 148 W m(-1) K(-1) to as low as 6.8 W m(-1) K(-1)). The measured thermal conductivity is much smaller than that predicted by only accounting for boundary scattering at the interfaces of the PnC lattice, indicating that coherent phononic effects are causing an additional reduction to the cross plane thermal conductivity.

  5. Antibacterial activity of single crystalline silver-doped anatase TiO2 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangyu; Li, Meng; He, Xiaojing; Hang, Ruiqiang; Huang, Xiaobo; Wang, Yueyue; Yao, Xiaohong; Tang, Bin

    2016-05-01

    Well-ordered, one-dimensional silver-doped anatase TiO2 nanowire (AgNW) arrays have been prepared through a hydrothermal growth process on the sputtering-deposited AgTi layers. Electron microscope analyses reveal that the as-synthesized AgNW arrays exhibit a single crystalline phase with highly uniform morphologies, diameters ranging from 85 to 95 nm, and lengths of about 11 μm. Silver is found to be doped into TiO2 nanowire evenly and mainly exists in the zerovalent state. The AgNW arrays show excellent efficient antibacterial activity against Escherichia coli (E. coli), and all of the bacteria can be killed within 1 h. Additionally, the AgNW arrays can still kill E. coli after immersion for 60 days, suggesting the long-term antibacterial property. The technique reported here is environmental friendly for formation of silver-containing nanostructure without using any toxic organic solvents.

  6. Surface modification via wet chemical etching of single-crystalline silicon for photovoltaic application.

    PubMed

    Reshak, A H; Shahimin, M M; Shaari, S; Johan, N

    2013-11-01

    The potential of solar cells have not been fully tapped due to the lack of energy conversion efficiency. There are three important mechanisms in producing high efficiency cells to harvest solar energy; reduction of light reflectance, enhancement of light trapping in the cell and increment of light absorption. The current work represent studies conducted in surface modification of single-crystalline silicon solar cells using wet chemical etching techniques. Two etching types are applied; alkaline etching (KOH:IPA:DI) and acidic etching (HF:HNO3:DI). The alkaline solution resulted in anisotropic profile that leads to the formation of inverted pyramids. While acidic solution formed circular craters along the front surface of silicon wafer. This surface modification will leads to the reduction of light reflectance via texturizing the surface and thereby increases the short circuit current and conversion rate of the solar cells.

  7. Graphene Enhances Li Storage Capacity of Porous Single-crystalline Silicon Nanowires

    SciTech Connect

    Wang, X.; Han, W.

    2010-12-01

    We demonstrated that graphene significantly enhances the reversible capacity of porous silicon nanowires used as the anode in Li-ion batteries. We prepared our experimental nanomaterials, viz., graphene and porous single-crystalline silicon nanowires, respectively, using a liquid-phase graphite exfoliation method and an electroless HF/AgNO{sub 3} etching process. The Si porous nanowire/graphene electrode realized a charge capacity of 2470 mAh g{sup -1} that is much higher than the 1256 mAh g{sup -1} of porous Si nanowire/C-black electrode and 6.6 times the theoretical capacity of commercial graphite. This relatively high capacity could originate from the favorable charge-transportation characteristics of the combination of graphene with the porous Si 1D nanostructure.

  8. Finite-size scaling law in single-crystalline Fe3O4 hollow nanostructures

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoping; Wang, Jun; Gao, Miao

    2016-07-01

    Single-crystalline Fe3O4 hollow nanostructures (nanoring and nanotube) have been successfully synthesized by a hydrothermal method along with a heat treatment process. The temperature dependences of the magnetization of the hollow nanostructures were measured under a high vacuum ( < 9.5 × 10‑6 Torr) from 300K to 900K. The Curie temperatures of the nanoring and nanotube samples were found to decrease with decreasing the mean wall thickness. The Curie temperatures of the hollow magnetite nanostructures follow a finite-size scaling relation with the scaling exponent ν = 1.04 ± 0.03. By comparison with those of the zero-dimensional Fe3O4 particles and two-dimensional Fe3O4 films, we show that the scaling relation for our hollow nanostructures is in better agreement with the quasi-two-dimensional finite-size scaling law.

  9. Electronic structure and magnetic and transport properties of single-crystalline UN

    NASA Astrophysics Data System (ADS)

    Samsel-Czekała, M.; Talik, E.; de v. Du Plessis, P.; Troć, R.; Misiorek, H.; Sułkowski, C.

    2007-10-01

    The electronic structure (both valence band and 4f core level spectra) of the cubic monocompound UN in the paramagnetic state was studied by x-ray photoelectron spectroscopy. The experimental results are compared with the results of calculations employing full-potential local-orbital minimum-basis full relativistic method with the spin-orbit coupling included implicitly. The molar susceptibility of a single crystal of antiferromagnetic UN (TN=51K) is reported along three main crystallographic directions between 1.9 and 300K . The observed magnetic characteristics are in agreement with previous studies. The observed small anisotropy in the ordered region is discussed. Results of electronic structure, magnetoresistivity, thermoelectric power, and thermal conductivity as studied on single-crystalline specimens are given and discussed from the viewpoint of dual and spin-density-wave-like character of the 5f electrons.

  10. Synthesis and size-dependent magnetic properties of single-crystalline hematite nanodiscs

    NASA Astrophysics Data System (ADS)

    Bao, Liu; Yang, Heqing; Wang, Xuewen; Zhang, Fenghua; Shi, Ruyu; Liu, Bin; Wang, Lin; Zhao, Hua

    2011-08-01

    Single-crystalline α-Fe 2O 3 nanodiscs with diameters of 132-150 nm were synthesized by a facile and efficient hydrothermal reaction of FeCl 3 with NaH 2PO 4 and H 2O at 200 °C for 12 h. The diameters of the nanodiscs can be decreased to 91-112 and 78-92 nm by adding ethanol glycol into the hydrothermal system. The α-Fe 2O 3 nanodiscs are formed by the cooperative action of selective adsorption and etching of the phosphate ions. The as-synthesized α-Fe 2O 3 nanodiscs exhibit weak ferromagnetic behaviours. The remanent magnetization and coercivity of the nanodiscs with the diameters of 132-150 nm are 0.01743 emu g -1 and 214.8 Oe, respectively, and the remanent magnetization and coercivity decrease with deceasing the nanodisc size.

  11. Electromigration and potentiometry measurements of single-crystalline Ag nanowires under UHV conditions.

    PubMed

    Kaspers, M R; Bernhart, A M; Meyer Zu Heringdorf, F-J; Dumpich, G; Möller, R

    2009-07-01

    We report on in situ electromigration and potentiometry measurements on single-crystalline Ag nanowires under ultra-high vacuum (UHV) conditions, using a four-probe scanning tunnelling microscope (STM). The Ag nanowires are grown in place by self-organization on a 4° vicinal Si(001) surface. Two of the four available STM tips are used to contact the nanowire. The positioning of the tips is controlled by a scanning electron microscope (SEM). Potentiometry measurements on an Ag nanowire were carried out using a third tip to determine the resistance per length. During electromigration measurements current densities of up to 1 × 10(8) A cm(-2) could be achieved. We use artificially created notches in the wire to initiate electromigration and to control the location of the electromigration process. At the position of the notch, electromigration sets in and is observed quasi-continuously by the SEM.

  12. Electrochemical preparation of single-crystalline Cr 2O 3 from molten salts

    NASA Astrophysics Data System (ADS)

    Abe, Hideki; Nishida, Kenji; Imai, Motoharu; Kitazawa, Hideaki

    2004-06-01

    Single crystals of Cr 2O 3 have been grown by means of electrolysis on a 1:100 stoichiometric mixture of CrO 3 and cesium molybdate, Cs 2MoO 4, fused at 1000°C in an ambient atmosphere. Potentiometric measurements on the molten salts have shown the existence of a critical voltage of -320 mV below which hexagonal platelets-shaped single-crystalline Cr 2O 3 is grown on the surface of the working electrode. Coulometry measurements have revealed that the Cr ions are at their highest oxidation state of Cr +6 in the molten electrolyte, which suggests that the electric reduction of Cr +6 to Cr +3 drives the single-crystal growth of Cr 2O 3.

  13. Luminescent properties of Al2O3:Ce single crystalline films under synchrotron radiation excitation

    NASA Astrophysics Data System (ADS)

    Zorenko, Yu.; Zorenko, T.; Gorbenko, V.; Savchyn, V.; Voznyak, T.; Fabisiak, K.; Zhusupkalieva, G.; Fedorov, A.

    2016-09-01

    The paper is dedicated to study the luminescent and scintillation properties of the Al2O3:Ce single crystalline films (SCF) grown by LPE method onto saphire substrates from PbO based flux. The structural quality of SCF samples was investigated by XRD method. For characterization of luminescent properties of Al2O3:Ce SCFs the cathodoluminescence spectra, scintillation light yield (LY) and decay kinetics under excitation by α-particles of Pu239 source were used. We have found that the scintillation LY of Al2O3:Ce SCF samples is relatively large and can reach up to 50% of the value realized in the reference YAG:Ce SCF. Using the synchrotron radiation excitation in the 3.7-25 eV range at 10 K we have also determined the basic parameters of the Ce3+ luminescence in Al2O3 host.

  14. Molecular beam epitaxy of single crystalline GaN nanowires on a flexible Ti foil

    NASA Astrophysics Data System (ADS)

    Calabrese, Gabriele; Corfdir, Pierre; Gao, Guanhui; Pfüller, Carsten; Trampert, Achim; Brandt, Oliver; Geelhaar, Lutz; Fernández-Garrido, Sergio

    2016-05-01

    We demonstrate the self-assembled growth of vertically aligned GaN nanowire ensembles on a flexible Ti foil by plasma-assisted molecular beam epitaxy. The analysis of single nanowires by transmission electron microscopy reveals that they are single crystalline. Low-temperature photoluminescence spectroscopy demonstrates that in comparison to standard GaN nanowires grown on Si, the nanowires prepared on the Ti foil exhibit an equivalent crystalline perfection, a higher density of basal-plane stacking faults, but a reduced density of inversion domain boundaries. The room-temperature photoluminescence spectrum of the nanowire ensemble is not influenced or degraded by the bending of the substrate. The present results pave the way for the fabrication of flexible optoelectronic devices based on GaN nanowires on metal foils.

  15. High-Quality Single Crystalline Ge(111) Growth on Si(111) Substrates by Solid Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Sun, Bing; Chang, Hu-Dong; Lu, Li; Liu, Hong-Gang; Wu, De-Xin

    2012-03-01

    Heterogeneous integration of crystalline Ge layers on cleaned and H-terminated Si(111) substrates are demonstrated by employing a combination of e-beam evaporation and solid phase epitaxy techniques. High-quality single crystalline Ge(111) layers on Si(111) substrates with a smooth Ge surface and an abrupt interface between Ge and Si are obtained. An XRD rocking curve scan of the Ge(111) diffraction peak shows a FWHM of only 260 arcsec for a 50-nm-thick Ge layer annealed at 600°C with a ramp-up rate of 20°C/s and a holding time of 1 min. The AFM images exhibit that the rms surface roughness of all the crystalline Ge layers are less than 2.1 nm.

  16. Carrier Transport Mechanism in Single Crystalline Organic Semiconductor Thin Film Elucidated by Visualized Carrier Motion.

    PubMed

    Matsubara, Kohei; Abe, Kentaro; Manaka, Takaaki; Iwamoto, Mitsumasa

    2016-04-01

    Time-resolved microscopic second harmonic generation (TRM-SHG) measurement was conducted to evaluate temperature dependence of the anisotropic carrier transport process in 6,13-Bis(triisopropylsilylethynyl) (TIPS) pentacene single crystalline domains for two orthogonal directions. Enhancement of the electric field induced SHG (EFI-SHG) signal at the electrode edge at low temperature suggests the presence of potential drop in the injection process. We directly evaluated temperature dependence of the carrier mobility by taking into account the potential drop, and concluded that the Marcus theory is appropriate to interpret the carrier transport in anisotropic TIPS pentacene thin film. TRM-SHG method is a facile and effective way to directly visualize transport process in anisotropic materials and to evaluate injection and transport processes simultaneously. PMID:27451638

  17. Electrode engineering for improving resistive switching performance in single crystalline CeO2 thin films

    NASA Astrophysics Data System (ADS)

    Liao, Zhaoliang; Gao, Peng; Meng, Yang; Fu, Wangyang; Bai, Xuedong; Zhao, Hongwu; Chen, Dongmin

    2012-06-01

    We have studied the electrode effect on the resistive switching behavior in the single crystalline films of CeO2 grown on Nb-SrTiO3. The fabricated devices with the top electrode made of non-reactive metals (Ag, Au, Pt) show bipolar resistive switching but are volatile. In contrast, the devices with top electrodes made of reactive metals (Al, Ta, Ti) present different bipolar resistive switching direction and are non-volatile, with Ta one having the best in OFF/ON switching ratio. The devices with these kinds of electrodes also exhibit remarkably different rectification behavior because of the difference of electrode/CeO2 interface formation. These results demonstrate that it is possible to improve the performance of resistive switching by electrode engineering.

  18. Interfacial electronic transport phenomena in single crystalline Fe-MgO-Fe thin barrier junctions

    SciTech Connect

    Gangineni, R. B.; Negulescu, B.; Baraduc, C.; Gaudin, G.

    2014-05-05

    Spin filtering effects in nano-pillars of Fe-MgO-Fe single crystalline magnetic tunnel junctions are explored with two different sample architectures and thin MgO barriers (thickness: 3–8 monolayers). The two architectures, with different growth and annealing conditions of the bottom electrode, allow tuning the quality of the bottom Fe/MgO interface. As a result, an interfacial resonance states (IRS) is observed or not depending on this interface quality. The IRS contribution, observed by spin polarized tunnel spectroscopy, is analyzed as a function of the MgO barrier thickness. Our experimental findings agree with theoretical predictions concerning the symmetry of the low energy (0.2 eV) interfacial resonance states: a mixture of Δ{sub 1}-like and Δ{sub 5}-like symmetries.

  19. Molten salt synthesis of single-crystalline K2Ti6O13 annular nanostructures.

    PubMed

    Zhang, Xianke; Tang, Shaolong; Yu, Jiangying; Zhai, Lin; Shi, Yangguang; Deng, Yu; Du, Youwei

    2010-08-01

    Single-crystalline K2Ti6O13 ring-like structures have been synthesized via a simple molten salt method without any templates and surfactants. The annular structures have several different types, such as nanoring, wheel-like and diskette-like ring. Each type of rings was characterized individually by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). These annular structures are formed by the loop-by-loop self-coiling of K2Ti6O13 nanobelts in the ring plane. The driving force of self-coiling is suggested to minimize the local electrostatic energy introduced by spontaneous polarization.

  20. Measuring the mobility of single crystalline wires and its dependence on temperature and carrier density.

    PubMed

    Amorim, Cleber A; Berengue, Olivia M; Kamimura, Hanay; Leite, Edson R; Chiquito, Adenilson J

    2011-05-25

    Kinetic transport parameters are fundamental for the development of electronic nanodevices. We present new results for the temperature dependence of mobility and carrier density in single crystalline In(2)O(3) samples and the method of extraction of these parameters which can be extended to similar systems. The data were obtained using a conventional Hall geometry and were quantitatively described by the semiconductor transport theory characterizing the electron transport as being controlled by the variable range hopping mechanism. A comprehensive analysis is provided showing the contribution of ionized impurities (low temperatures) and acoustic phonon (high temperatures) scattering mechanisms to the electron mobility. The approach presented here avoids common errors in kinetic parameter extraction from field effect data, serving as a versatile platform for direct investigation of any nanoscale electronic materials.

  1. Formation and Stabilization of Single-Crystalline Metastable AuGe Phases in Ge Nanowires

    SciTech Connect

    Sutter, E.; Sutter, P.

    2011-07-22

    We use in situ observations by variable temperature transmission electron microscopy on AuGe alloy drops at the tips of Ge nanowires (NWs) with systematically varying composition to demonstrate the controlled formation of metastable solid phases integrated in NWs. The process, which operates in the regime of vapor-liquid-solid growth, involves a size-dependent depression of the alloy liquidus at the nanoscale that leads to extremely Ge-rich AuGe melts at low temperatures. During slow cooling, these liquid AuGe alloy drops show pronounced departures from equilibrium, i.e., a frustrated phase separation of Ge into the adjacent solid NW, and ultimately crystallize as single-crystalline segments of metastable {gamma}-AuGe. Our findings demonstrate a general avenue for synthesizing NW heterostructures containing stable and metastable solid phases, applicable to a wide range of materials of which NWs form by the vapor-liquid-solid method.

  2. Single-crystalline δ-Ni2Si nanowires with excellent physical properties.

    PubMed

    Chiu, Wen-Li; Chiu, Chung-Hua; Chen, Jui-Yuan; Huang, Chun-Wei; Huang, Yu-Ting; Lu, Kuo-Chang; Hsin, Cheng-Lun; Yeh, Ping-Hung; Wu, Wen-Wei

    2013-01-01

    In this article, we report the synthesis of single-crystalline nickel silicide nanowires (NWs) via chemical vapor deposition method using NiCl2·6H2O as a single-source precursor. Various morphologies of δ-Ni2Si NWs were successfully acquired by controlling the growth conditions. The growth mechanism of the δ-Ni2Si NWs was thoroughly discussed and identified with microscopy studies. Field emission measurements show a low turn-on field (4.12 V/μm), and magnetic property measurements show a classic ferromagnetic characteristic, which demonstrates promising potential applications for field emitters, magnetic storage, and biological cell separation. PMID:23782805

  3. Single-crystalline δ-Ni2Si nanowires with excellent physical properties

    PubMed Central

    2013-01-01

    In this article, we report the synthesis of single-crystalline nickel silicide nanowires (NWs) via chemical vapor deposition method using NiCl2·6H2O as a single-source precursor. Various morphologies of δ-Ni2Si NWs were successfully acquired by controlling the growth conditions. The growth mechanism of the δ-Ni2Si NWs was thoroughly discussed and identified with microscopy studies. Field emission measurements show a low turn-on field (4.12 V/μm), and magnetic property measurements show a classic ferromagnetic characteristic, which demonstrates promising potential applications for field emitters, magnetic storage, and biological cell separation. PMID:23782805

  4. Laser ablation of single-crystalline silicon by radiation of pulsed frequency-selective fiber laser

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

    2015-07-01

    We have studied the process of destruction of the surface of a single-crystalline silicon wafer scanned by the beam of a pulsed ytterbium-doped fiber laser radiation with a wavelength of λ = 1062 nm. It is established that the laser ablation can proceed without melting of silicon and the formation of a plasma plume. Under certain parameters of the process (radiation power, beam scan velocity, and beam overlap density), pronounced oxidation of silicon microparticles with the formation of a characteristic loose layer of fine powdered silicon dioxide has been observed for the first time. The range of lasing and beam scanning regimes in which the growth of SiO2 layer takes place is determined.

  5. Diameter-dependent thermoelectric figure of merit in single-crystalline Bi nanowires

    NASA Astrophysics Data System (ADS)

    Kim, Jeongmin; Lee, Seunghyun; Brovman, Yuri M.; Kim, Philip; Lee, Wooyoung

    2015-03-01

    The diameter-dependent thermoelectric properties of individual single-crystalline Bi nanowires grown by the on-film formation of nanowires method have been investigated. The electrical resistivity, Seebeck coefficient, and thermal conductivity were measured as functions of the nanowire diameter using an individual nanowire device. The thermoelectric figure of merit (ZT) calculated from the measured thermoelectric properties shows an increase from the bulk value to a maximum value of 0.28 at 109 nm-diameter, followed by a decrease upon further decreasing the diameter. This non-monotonic diameter dependence of ZT in Bi nanowires reveals simultaneous positive and negative contributions to the thermoelectric efficiency, driven by the change in intrinsic properties, which originates from the diameter-dependent classical and quantum size effects.The diameter-dependent thermoelectric properties of individual single-crystalline Bi nanowires grown by the on-film formation of nanowires method have been investigated. The electrical resistivity, Seebeck coefficient, and thermal conductivity were measured as functions of the nanowire diameter using an individual nanowire device. The thermoelectric figure of merit (ZT) calculated from the measured thermoelectric properties shows an increase from the bulk value to a maximum value of 0.28 at 109 nm-diameter, followed by a decrease upon further decreasing the diameter. This non-monotonic diameter dependence of ZT in Bi nanowires reveals simultaneous positive and negative contributions to the thermoelectric efficiency, driven by the change in intrinsic properties, which originates from the diameter-dependent classical and quantum size effects. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06412g

  6. Growth of single crystalline TaON on yttria-stabilized zirconia (YSZ)

    SciTech Connect

    Tao, Junguang Chai, J.W.; Wong, L.M.; Zhang, Z.; Pan, J.S.; Wang, S.J.

    2013-08-15

    Owing to its high stability in aqueous solution and high quantum efficiency, tantalum based oxyntride (TaON) has attracted increasing attentions for application as visible light photocatalyst. However, despite the recent progress in photocatalytic studies, its bulk charge transport mechanisms are yet to be discovered because of the lack of single crystal sample. In this paper, high quality single crystalline TaON(100) thin film was prepared on cubic YSZ(100) surface by reactive RF magnetron sputtering to avail the understandings of charge transport mechanism so as to improve the device efficiency. The stoichiometry, crystal phase and structure were examined in situ by x-ray photoelectron spectroscopy (XPS) and ex situ by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The TaON film crystallizes in monoclinic β-phase with its [010]/[001] directions aligned to those of the substrate. The small band gap of 2.5 eV as well as the high structure perfection suggests better performance for visible light water splitting. The method can be used to prepare other surface orientations to elucidate fundamental surface structure dependent photoactivities. - Graphical abstract: Structure of single crystalline β-TaON and its diffraction pole figure. Highlights: • High quality single crystal TaON(100) thin film were grown on YSZ(100) surface. • β-phase monoclinic TaON film is formed. • Its [010]/[001] directions are aligned to those of the substrate. • The small band gap and structure perfection suggest visible light photo-activity.

  7. Van der Waals Epitaxial Growth of Two-Dimensional Single-Crystalline GaSe Domains on Graphene.

    PubMed

    Li, Xufan; Basile, Leonardo; Huang, Bing; Ma, Cheng; Lee, Jaekwang; Vlassiouk, Ivan V; Puretzky, Alexander A; Lin, Ming-Wei; Yoon, Mina; Chi, Miaofang; Idrobo, Juan C; Rouleau, Christopher M; Sumpter, Bobby G; Geohegan, David B; Xiao, Kai

    2015-08-25

    Two-dimensional (2D) van der Waals (vdW) heterostructures are a family of artificially structured materials that promise tunable optoelectronic properties for devices with enhanced functionalities. Compared to transferring, direct epitaxy of vdW heterostructures is ideal for clean interlayer interfaces and scalable device fabrication. Here we report the synthesis and preferred orientations of 2D GaSe atomic layers on graphene (Gr) by vdW epitaxy. GaSe crystals are found to nucleate predominantly on random wrinkles or grain boundaries of graphene, share a preferred lattice orientation with underlying graphene, and grow into large (tens of micrometers) irregularly shaped, single-crystalline domains. The domains are found to propagate with triangular edges that merge into the large single crystals during growth. Electron diffraction reveals that approximately 50% of the GaSe domains are oriented with a 10.5 ± 0.3° interlayer rotation with respect to the underlying graphene. Theoretical investigations of interlayer energetics reveal that a 10.9° interlayer rotation is the most energetically preferred vdW heterostructure. In addition, strong charge transfer in these GaSe/Gr vdW heterostructures is predicted, which agrees with the observed enhancement in the Raman E(2)1g band of monolayer GaSe and highly quenched photoluminescence compared to GaSe/SiO2. Despite the very large lattice mismatch of GaSe/Gr through vdW epitaxy, the predominant orientation control and convergent formation of large single-crystal flakes demonstrated here is promising for the scalable synthesis of large-area vdW heterostructures for the development of new optical and optoelectronic devices.

  8. Van der Waals Epitaxial Growth of Two-Dimensional Single-Crystalline GaSe Domains on Graphene.

    PubMed

    Li, Xufan; Basile, Leonardo; Huang, Bing; Ma, Cheng; Lee, Jaekwang; Vlassiouk, Ivan V; Puretzky, Alexander A; Lin, Ming-Wei; Yoon, Mina; Chi, Miaofang; Idrobo, Juan C; Rouleau, Christopher M; Sumpter, Bobby G; Geohegan, David B; Xiao, Kai

    2015-08-25

    Two-dimensional (2D) van der Waals (vdW) heterostructures are a family of artificially structured materials that promise tunable optoelectronic properties for devices with enhanced functionalities. Compared to transferring, direct epitaxy of vdW heterostructures is ideal for clean interlayer interfaces and scalable device fabrication. Here we report the synthesis and preferred orientations of 2D GaSe atomic layers on graphene (Gr) by vdW epitaxy. GaSe crystals are found to nucleate predominantly on random wrinkles or grain boundaries of graphene, share a preferred lattice orientation with underlying graphene, and grow into large (tens of micrometers) irregularly shaped, single-crystalline domains. The domains are found to propagate with triangular edges that merge into the large single crystals during growth. Electron diffraction reveals that approximately 50% of the GaSe domains are oriented with a 10.5 ± 0.3° interlayer rotation with respect to the underlying graphene. Theoretical investigations of interlayer energetics reveal that a 10.9° interlayer rotation is the most energetically preferred vdW heterostructure. In addition, strong charge transfer in these GaSe/Gr vdW heterostructures is predicted, which agrees with the observed enhancement in the Raman E(2)1g band of monolayer GaSe and highly quenched photoluminescence compared to GaSe/SiO2. Despite the very large lattice mismatch of GaSe/Gr through vdW epitaxy, the predominant orientation control and convergent formation of large single-crystal flakes demonstrated here is promising for the scalable synthesis of large-area vdW heterostructures for the development of new optical and optoelectronic devices. PMID:26202730

  9. Macroscopic Quantum Tunneling in a Bi2Sr2CaCu2O8+δ Single Crystalline Whisker

    NASA Astrophysics Data System (ADS)

    Kubo, Yuimaru; Takahide, Yamaguchi; Ueda, Shinya; Takano, Yoshihiko; Ootuka, Youiti

    2010-06-01

    Macroscopic quantum tunneling (MQT) has been observed in an intrinsic Josephson junction (IJJ) stack of a Bi2Sr2CaCu2O8+δ (BSCCO) single crystalline whisker with high precision using a home made setup. The cross-over temperature between thermal activation and MQT was about 260 mK, and the Josephson plasma frequency was estimated to be 86 GHz. Both the thermal escape theory and the MQT theory are consistent with the experiments. These facts strongly suggest that single crystalline BSCCO whiskers are high enough quality to be used as intrinsic Josephson quantum devices such as intrinsic Josephson phase qubits. This is the first demonstration of MQT in BSCCO single crystalline whiskers.

  10. Microwave synthesis of single-crystalline perovskite BiFeO{sub 3} nanocubes for photoelectrode and photocatalytic applications

    SciTech Connect

    Joshi, Upendra A.; Jang, Jum Suk; Borse, Pramod H.; Lee, Jae Sung

    2008-06-16

    A simple microwave synthesis procedure has been developed for the single-crystalline perovskite nanocubes composed of bismuth ferrite (BiFeO{sub 3}). Typical nanocubes had sizes ranging from 50 to 200 nm. The single-crystalline nature of nanocubes was confirmed by high resolution transmission electron microscopy and selected area electron diffraction pattern. X-ray diffraction pattern showed the rhombohedral phase with R3c space group. The material showed photoinduced water oxidation activity in both photoelectrochemical and photocatalytic modes. It could become a useful material for photoelectrode and photocatalytic applications.

  11. Magnetic property and microstructure of single crystalline Nd2Fe14B ultrafine particles ball milled from HDDR powders

    NASA Astrophysics Data System (ADS)

    Li, W. F.; Hu, X. C.; Cui, B. Z.; Yang, J. B.; Han, J. Z.; Hadjipanayis, G. C.

    2013-08-01

    In this work we report the microstructure and magnetic property of single crystalline Nd2Fe14B ultrafine particles ball milled from HDDR Nd-Fe-B alloys. The average size of the particles is 283 nm, and TEM observation reveals that these particles are single crystalline. The coercivity of these particles is 6.0 kOe, which is much higher than that of the particles ball milled from sintered and hot pressed Nd-Fe-B magnets. Micromagnetic analysis shows that the coercivity degradation is caused by surface damage during ball milling.

  12. Fast growth of inch-sized single-crystalline graphene from a controlled single nucleus on Cu-Ni alloys

    NASA Astrophysics Data System (ADS)

    Wu, Tianru; Zhang, Xuefu; Yuan, Qinghong; Xue, Jiachen; Lu, Guangyuan; Liu, Zhihong; Wang, Huishan; Wang, Haomin; Ding, Feng; Yu, Qingkai; Xie, Xiaoming; Jiang, Mianheng

    2016-01-01

    Wafer-scale single-crystalline graphene monolayers are highly sought after as an ideal platform for electronic and other applications. At present, state-of-the-art growth methods based on chemical vapour deposition allow the synthesis of one-centimetre-sized single-crystalline graphene domains in ~12 h, by suppressing nucleation events on the growth substrate. Here we demonstrate an efficient strategy for achieving large-area single-crystalline graphene by letting a single nucleus evolve into a monolayer at a fast rate. By locally feeding carbon precursors to a desired position of a substrate composed of an optimized Cu-Ni alloy, we synthesized an ~1.5-inch-large graphene monolayer in 2.5 h. Localized feeding induces the formation of a single nucleus on the entire substrate, and the optimized alloy activates an isothermal segregation mechanism that greatly expedites the growth rate. This approach may also prove effective for the synthesis of wafer-scale single-crystalline monolayers of other two-dimensional materials.

  13. Nb-doped single crystalline MoS{sub 2} field effect transistor

    SciTech Connect

    Das, Saptarshi E-mail: das@anl.gov; Demarteau, Marcellinus; Roelofs, Andreas

    2015-04-27

    We report on the demonstration of a p-type, single crystalline, few layer MoS{sub 2} field effect transistor (FET) using Niobium (Nb) as the dopant. The doping concentration was extracted and determined to be ∼3 × 10{sup 19}/cm{sup 3}. We also report on bilayer Nb-doped MoS{sub 2} FETs with ambipolar conduction. We found that the current ON-OFF ratio of the Nb-doped MoS{sub 2} FETs changes significantly as a function of the flake thickness. We attribute this experimental observation to bulk-type electrostatic effect in ultra-thin MoS{sub 2} crystals. We provide detailed analytical modeling in support of our claims. Finally, we show that in the presence of heavy doping, even ultra-thin 2D-semiconductors cannot be fully depleted and may behave as a 3D material when used in transistor geometry. Our findings provide important insights into the doping constraints of 2D materials, in general.

  14. Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors.

    PubMed

    Stoesser, Anna; von Seggern, Falk; Purohit, Suneeti; Nasr, Babak; Kruk, Robert; Dehm, Simone; Di Wang; Hahn, Horst; Dasgupta, Subho

    2016-10-14

    Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm(2) V(-1) s(-1). PMID:27609560

  15. Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors

    NASA Astrophysics Data System (ADS)

    Stoesser, Anna; von Seggern, Falk; Purohit, Suneeti; Nasr, Babak; Kruk, Robert; Dehm, Simone; Wang, Di; Hahn, Horst; Dasgupta, Subho

    2016-10-01

    Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm2 V-1 s-1.

  16. Growth and mechanisms of enamel-like hierarchical nanostructures on single crystalline hydroxyapatite micro-ribbons.

    PubMed

    Ma, Guobin; Liu, Xiang Yang; Wang, Mu

    2011-06-01

    In vitro growth of enamel-like microstructured hydroxyapatite (HAP) crystals is highly expected for developing novel biomaterials/scaffolds. It is also essential for a clearer understanding of in vivo biomineralization process. In this paper, hierarchical HAP structures are controllably fabricated by growth of nanocrystals on single crystalline micro-ribbon substrates in vitro at biophysical conditions. HAP crystals grown on the substrate change from disordered aggregations of nano-flakes to well-oriented nano-needles, branched bundles of nano-needles, and finally highly porous aggregates, with increase of F- concentrations. The flexibility of the size, morphology, and microstructure control highlights a method to produce hierarchical HAP structures for potential applications in dental restoration or bone implant. We demonstrate that the mutual effects of F- on the crystallinity of HAP and on the supersaturation of the solutions control the morphology and assembly properties of the products. Moreover, the products excellently mimic real tooth enamel structures formed with different F- intakes. The work represents an appropriate simplified model system for an in-depth understanding of the microscopic mechanisms of the effects of F- on enamel growth, and the relationship of enamel microstructures and dental diseases.

  17. Enhanced piezoelectric properties of vertically aligned single-crystalline NKN nano-rod arrays.

    PubMed

    Kang, Min-Gyu; Oh, Seung-Min; Jung, Woo-Suk; Moon, Hi Gyu; Baek, Seung-Hyub; Nahm, Sahn; Yoon, Seok-Jin; Kang, Chong-Yun

    2015-05-08

    Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures.

  18. Single-crystalline ZnO sheet Source-Gated Transistors

    PubMed Central

    Dahiya, A. S.; Opoku, C.; Sporea, R. A.; Sarvankumar, B.; Poulin-Vittrant, G.; Cayrel, F.; Camara, N.; Alquier, D.

    2016-01-01

    Due to their fabrication simplicity, fully compatible with low-cost large-area device assembly strategies, source-gated transistors (SGTs) have received significant research attention in the area of high-performance electronics over large area low-cost substrates. While usually based on either amorphous or polycrystalline silicon (α-Si and poly-Si, respectively) thin-film technologies, the present work demonstrate the assembly of SGTs based on single-crystalline ZnO sheet (ZS) with asymmetric ohmic drain and Schottky source contacts. Electrical transport studies of the fabricated devices show excellent field-effect transport behaviour with abrupt drain current saturation (IDSSAT) at low drain voltages well below 2 V, even at very large gate voltages. The performance of a ZS based SGT is compared with a similar device with ohmic source contacts. The ZS SGT is found to exhibit much higher intrinsic gain, comparable on/off ratio and low off currents in the sub-picoamp range. This approach of device assembly may form the technological basis for highly efficient low-power analog and digital electronics using ZnO and/or other semiconducting nanomaterial. PMID:26757945

  19. Single-crystalline ZnO sheet Source-Gated Transistors.

    PubMed

    Dahiya, A S; Opoku, C; Sporea, R A; Sarvankumar, B; Poulin-Vittrant, G; Cayrel, F; Camara, N; Alquier, D

    2016-01-01

    Due to their fabrication simplicity, fully compatible with low-cost large-area device assembly strategies, source-gated transistors (SGTs) have received significant research attention in the area of high-performance electronics over large area low-cost substrates. While usually based on either amorphous or polycrystalline silicon (α-Si and poly-Si, respectively) thin-film technologies, the present work demonstrate the assembly of SGTs based on single-crystalline ZnO sheet (ZS) with asymmetric ohmic drain and Schottky source contacts. Electrical transport studies of the fabricated devices show excellent field-effect transport behaviour with abrupt drain current saturation (IDS(SAT)) at low drain voltages well below 2 V, even at very large gate voltages. The performance of a ZS based SGT is compared with a similar device with ohmic source contacts. The ZS SGT is found to exhibit much higher intrinsic gain, comparable on/off ratio and low off currents in the sub-picoamp range. This approach of device assembly may form the technological basis for highly efficient low-power analog and digital electronics using ZnO and/or other semiconducting nanomaterial. PMID:26757945

  20. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life

    SciTech Connect

    Cao, Yuliang; Xiao, Lifen; Wang, Wei; Choi, Daiwon; Nie, Zimin; Yu, Jianguo; Saraf, Laxmikant V.; Yang, Zhenguo; Liu, Jun

    2011-07-26

    Single crystalline Na4Mn9O18 nanowires were synthesized via pyrolysis of polyacrylate salt precursors prepared by in-situ polymerization of the metal salts and acrylate acid, followed by calcinations at an appropriate temperature to achieve good crystalline structure and uniform nanowire morphology with an average diameter of 50 nm. The Na4Mn9O18 nanowires have shown a high, reversible, and near theoretical sodium ion insertion capacity (128 mA h g-1 at 0.1C), excellent long cyclability (77% capacity retention for 1000 cycles at 0.5 C), along with good rate capability. Good capacity and charge-discharge stability are also observed for full cell experiments using a pyrolyzed carbon as the anode, therefore demonstrating the potential of these materials for sodium-ion batteries for large scale energy storage. Furthermore, this research shows that a good crystallinity and small particles are required to enhance the Na-ion diffusion and increase the stability of the electrode materials for long charge-discharge cycles.

  1. Single-crystalline ZnO sheet Source-Gated Transistors

    NASA Astrophysics Data System (ADS)

    Dahiya, A. S.; Opoku, C.; Sporea, R. A.; Sarvankumar, B.; Poulin-Vittrant, G.; Cayrel, F.; Camara, N.; Alquier, D.

    2016-01-01

    Due to their fabrication simplicity, fully compatible with low-cost large-area device assembly strategies, source-gated transistors (SGTs) have received significant research attention in the area of high-performance electronics over large area low-cost substrates. While usually based on either amorphous or polycrystalline silicon (α-Si and poly-Si, respectively) thin-film technologies, the present work demonstrate the assembly of SGTs based on single-crystalline ZnO sheet (ZS) with asymmetric ohmic drain and Schottky source contacts. Electrical transport studies of the fabricated devices show excellent field-effect transport behaviour with abrupt drain current saturation (IDSSAT) at low drain voltages well below 2 V, even at very large gate voltages. The performance of a ZS based SGT is compared with a similar device with ohmic source contacts. The ZS SGT is found to exhibit much higher intrinsic gain, comparable on/off ratio and low off currents in the sub-picoamp range. This approach of device assembly may form the technological basis for highly efficient low-power analog and digital electronics using ZnO and/or other semiconducting nanomaterial.

  2. Enzyme-modified field effect transistors based on surface-conductive single-crystalline diamond.

    PubMed

    Härtl, Andreas; Baur, Barbara; Stutzmann, Martin; Garrido, Jose A

    2008-09-01

    Enzyme-modified field effect transistors (ENFETs) were realized using surface-conductive single-crystalline diamond films. The enzymes penicillinase and acetylcholinesterase were immobilized onto the active area of diamond-based electrolytic solution gated FETs, using different organic linker molecules and cross-linking chemistries. The active area of the devices was patterned to generate enzyme-modified regions next to surface-conductive regions. Penicillinase was chosen as a robust model system, but the main focus of the present paper is on acetylcholinesterase, an enzyme essential for many neuronal signal transduction processes. All the different ENFETs show a clear and specific response to the corresponding substrate, penicillin and acetylcholine. The device response is based on the pH sensitivity of the surface-conductive active area and is enabled by the local pH change induced during the enzymatic reaction. The devices demonstrate promising stability and characteristic variations of the enzymatic activity with measurement conditions. Furthermore, the results from the ENFET measurements were compared with the results of spectrophotometric experiments, carried out with enzymes immobilized on diamond substrates and also with free enzymes in solution. This allows an analysis of the enzyme kinetics, as well as qualitative comparison of the different functionalization methods employed in this study.

  3. Nanometre-thick single-crystalline nanosheets grown at the water–air interface

    PubMed Central

    Wang, Fei; Seo, Jung-Hun; Luo, Guangfu; Starr, Matthew B.; Li, Zhaodong; Geng, Dalong; Yin, Xin; Wang, Shaoyang; Fraser, Douglas G.; Morgan, Dane; Ma, Zhenqiang; Wang, Xudong

    2016-01-01

    To date, the preparation of free-standing 2D nanomaterials has been largely limited to the exfoliation of van der Waals solids. The lack of a robust mechanism for the bottom-up synthesis of 2D nanomaterials from non-layered materials has become an obstacle to further explore the physical properties and advanced applications of 2D nanomaterials. Here we demonstrate that surfactant monolayers can serve as soft templates guiding the nucleation and growth of 2D nanomaterials in large area beyond the limitation of van der Waals solids. One- to 2-nm-thick, single-crystalline free-standing ZnO nanosheets with sizes up to tens of micrometres are synthesized at the water–air interface. In this process, the packing density of surfactant monolayers adapts to the sub-phase metal ions and guides the epitaxial growth of nanosheets. It is thus named adaptive ionic layer epitaxy (AILE). The electronic properties of ZnO nanosheets and AILE of other materials are also investigated. PMID:26786708

  4. Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors.

    PubMed

    Stoesser, Anna; von Seggern, Falk; Purohit, Suneeti; Nasr, Babak; Kruk, Robert; Dehm, Simone; Di Wang; Hahn, Horst; Dasgupta, Subho

    2016-10-14

    Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm(2) V(-1) s(-1).

  5. Surface Engineering of Copper Foils for Growing Centimeter-Sized Single-Crystalline Graphene.

    PubMed

    Lin, Li; Li, Jiayu; Ren, Huaying; Koh, Ai Leen; Kang, Ning; Peng, Hailin; Xu, H Q; Liu, Zhongfan

    2016-02-23

    The controlled growth of high-quality graphene on a large scale is of central importance for applications in electronics and optoelectronics. To minimize the adverse impacts of grain boundaries in large-area polycrystalline graphene, the synthesis of large single crystals of monolayer graphene is one of the key challenges for graphene production. Here, we develop a facile surface-engineering method to grow large single-crystalline monolayer graphene by the passivation of the active sites and the control of graphene nucleation on copper surface using the melamine pretreatment. Centimeter-sized hexagonal single-crystal graphene domains were successfully grown, which exhibit ultrahigh carrier mobilities exceeding 25,000 cm(2) V(-1) s(-1) and quantum Hall effects on SiO2 substrates. The underlying mechanism of melamine pretreatments were systematically investigated through elemental analyses of copper surface in the growth process of large single-crystals. This present work provides a surface design of a catalytic substrate for the controlled growth of large-area graphene single crystals.

  6. Enhanced piezoelectric properties of vertically aligned single-crystalline NKN nano-rod arrays

    PubMed Central

    Kang, Min-Gyu; Oh, Seung-Min; Jung, Woo-Suk; Gyu Moon, Hi; Baek, Seung-Hyub; Nahm, Sahn; Yoon, Seok-Jin; Kang, Chong-Yun

    2015-01-01

    Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures. PMID:25955763

  7. Temperature dependent van der Pauw-Hall measurements on sodium doped single crystalline cadmium telluride

    SciTech Connect

    Ahmad, Faisal R.

    2015-03-21

    In this report, results of the temperature dependent electrical conductivity measurements conducted on single crystalline cadmium telluride (CdTe), containing sodium (Na) impurities are presented and discussed. The electrical conductivity measurements were conducted using an apparatus that allowed the implementation of a standard van der Pauw-Hall effect technique through which the electrical resistivity, concentration of majority carriers, as well as the carrier mobility were determined for temperatures ranging between 24 K and 350 K. Over this temperature range, the electrical resistivity was observed to change by 7 orders of magnitude. Hall measurements showed that the hole concentration at 300 K was ∼3 × 10{sup 15 }cm{sup –3} and the hole mobility at the same temperature was ∼80 cm{sup 2}/V s. Measuring the concentration of holes as a function of the sample temperature enabled the estimation of the acceptor energy level with respect to the valence band maximum to be ∼60 meV. The same data also revealed the potential presence of a compensating donor level. Furthermore, the hole mobility was also analyzed over the entire temperature range and the data revealed that above 100 K, the carrier mobility was dominated by the scattering of holes from lattice vibrations.

  8. High-Operation-Temperature Plasmonic Nanolasers on Single-Crystalline Aluminum.

    PubMed

    Chou, Yu-Hsun; Wu, Yen-Mo; Hong, Kuo-Bin; Chou, Bo-Tsun; Shih, Jheng-Hong; Chung, Yi-Cheng; Chen, Peng-Yu; Lin, Tzy-Rong; Lin, Chien-Chung; Lin, Sheng-Di; Lu, Tien-Chang

    2016-05-11

    The recent development of plasmonics has overcome the optical diffraction limit and fostered the development of several important components including nanolasers, low-operation-power modulators, and high-speed detectors. In particular, the advent of surface-plasmon-polariton (SPP) nanolasers has enabled the development of coherent emitters approaching the nanoscale. SPP nanolasers widely adopted metal-insulator-semiconductor structures because the presence of an insulator can prevent large metal loss. However, the insulator is not necessary if permittivity combination of laser structures is properly designed. Here, we experimentally demonstrate a SPP nanolaser with a ZnO nanowire on the as-grown single-crystalline aluminum. The average lasing threshold of this simple structure is 20 MW/cm(2), which is four-times lower than that of structures with additional insulator layers. Furthermore, single-mode laser operation can be sustained at temperatures up to 353 K. Our study represents a major step toward the practical realization of SPP nanolasers. PMID:27089144

  9. Fabrications and application of single crystalline GaN for high-performance deep UV photodetectors

    NASA Astrophysics Data System (ADS)

    Velazquez, R.; Aldalbahi, A.; Rivera, M.; Feng, P.

    2016-08-01

    High-quality single crystalline Gallium Nitride (GaN) semiconductor has been synthesized using molecule beam epitaxy (MBE) technique for development of high-performance deep ultraviolet (UV) photodetectors. Thickness of the films was estimated by using surface profile meter and scanning electron microscope. Electronic states and elemental composition of the films were obtained using Raman scattering spectroscopy. The orientation, crystal structure and phase purity of the films were examined using a Siemens x-ray diffractometer radiation. The surface microstructure was studied using high resolution scanning electron microscopy (SEM). Two types of metal pairs: Al-Al, Al-Cu or Cu-Cu were used for interdigital electrodes on GaN film in order to examine the Schottky properties of the GaN based photodetector. The characterizations of the fabricated prototype include the stability, responsivity, response and recovery times. Typical time dependent photoresponsivity by switching different UV light source on and off five times for each 240 seconds at a bias of 2V, respectively, have been obtained. The detector appears to be highly sensitive to various UV wavelengths of light with very stable baseline and repeatability. The obtained photoresponsivity was up to 354 mA/W at the bias 2V. Higher photoresponsivity could be obtained if higher bias was applied but it would unavoidably result in a higher dark current. Thermal effect on the fabricated GaN based prototype was discussed.

  10. Single-crystalline, wormlike hematite photoanodes for efficient solar water splitting

    PubMed Central

    Kim, Jae Young; Magesh, Ganesan; Youn, Duck Hyun; Jang, Ji-Wook; Kubota, Jun; Domen, Kazunari; Lee, Jae Sung

    2013-01-01

    A hematite photoanode showing a stable, record-breaking performance of 4.32 mA/cm2 photoelectrochemical water oxidation current at 1.23 V vs. RHE under simulated 1-sun (100 mW/cm2) irradiation is reported. This photocurrent corresponds to ca. 34% of the maximum theoretical limit expected for hematite with a band gap of 2.1 V. The photoanode produced stoichiometric hydrogen and oxygen gases in amounts close to the expected values from the photocurrent. The hematitle has a unique single-crystalline “wormlike” morphology produced by in-situ two-step annealing at 550°C and 800°C of β-FeOOH nanorods grown directly on a transparent conducting oxide glass via an all-solution method. In addition, it is modified by platinum doping to improve the charge transfer characteristics of hematite and an oxygen-evolving co-catalyst on the surface. PMID:24045290

  11. Size- and structure-dependence of thermal and mechanical behaviors of single-crystalline and polytypic superlattice ZnS nanowires

    SciTech Connect

    Moon, Junghwan; Cho, Maenghyo; Zhou, Min

    2015-06-07

    Molecular dynamics (MD) simulations are carried out to study the thermal and mechanical behaviors of single-crystalline wurtzite (WZ), zinc-blende (ZB), and polytypic superlattice ZnS nanowires containing alternating WZ and ZB regions with thicknesses between 1.85 nm and 29.62 nm under tensile loading. The wires analyzed have diameters between 1.77 nm and 5.05 nm. The Green-Kubo method is used to calculate the thermal conductivity of the wires at different deformed states. A non-equilibrium MD approach is used to analyze the thermal transport behavior at the interfaces between different structural regions in the superlattice nanowires (SLNWs). The Young's modulus and thermal conductivity of ZB nanowires are approximately 2%–12% and 23%–35% lower than those of WZ nanowires, respectively. The lower initial residual compressive stress due to higher irregularity of surface atoms causes the Young's modulus of ZB nanowires to be lower. The dependence of the thermal conductivity on structure comes from differences in phonon group velocities associated with the different wires. The thermal conductivity of polytypic superlattice nanowires is up to 55% lower than that of single-crystalline nanowires, primarily because of phonon scattering at the interfaces and the resulting lower effective phonon mean free paths for each structural region. As the periodic lengths (1.85–29.62 nm) and specimen lengths (14.81–59.24 nm) of SLNWs decrease, these effects become more pronounced, causing the thermal conductivity to further decrease by up to 30%.

  12. Preparation of highly ordered growth of single-crystalline Gd{sub 2}O{sub 2}S:Eu{sup 3+} nanostructures

    SciTech Connect

    Thirumalai, J.; Chandramohan, R.; Vijayan, T.A.; Somasundaram, R.M.

    2011-02-15

    Graphical abstract: Fabrication of highly ordered single-crystalline Gd{sub 2}O{sub 2}S:Eu{sup 3+} nanostructures over a porous anodized aluminum oxide (AAO) template via hydrothermal method is described. Well aligned non-collapsed Gd{sub 2}O{sub 2}S:Eu{sup 3+} nanostructures are ideal functional components for next generation luminescent devices. Research highlights: {yields} Synthesis of highly ordered Gd{sub 2}O{sub 2}S:Eu{sup 3+} nanotubes, nanorods and nanoflowers. {yields} Using template-assisted (AAO) hydrothermal method. {yields} Well aligned nanostructures for next generation luminescent devices. {yields} Detailed structural, morphology and the phase composition were studied. -- Abstract: A simple and facile template-assisted hydrothermal route has been demonstrated for the shape-selective preparation of highly ordered single-crystalline Gd{sub 2}O{sub 2}S:Eu{sup 3+} nanostructures, such as nanotubes, nanorods and nanoflowers. These fabricated nanostructures possess desirable atomic structures, surfaces, morphologies and properties to meet the growing demands and specific requirements of new technologies. The concentration of precursor chemicals, the temperature, the reaction time, and the use of a capping agent are key factors in the morphological control of Gd{sub 2}O{sub 2}S:Eu{sup 3+} nanostructures. The morphology and the phase composition of the prepared nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy disperse spectroscopy (EDS) and photoluminescence (PL). We believe this technique will be readily adopted in realizing other forms of various nanostructured materials.

  13. Recovery Act : Near-Single-Crystalline Photovoltaic Thin Films on Polycrystalline, Flexible Substrates

    SciTech Connect

    Venkat Selvamanickam; Alex Freundlich

    2010-11-29

    III-V photovoltaics have exhibited efficiencies above 40%, but have found only a limited use because of the high cost of single crystal substrates. At the other end of the spectrum, polycrystalline and amorphous thin film solar cells offer the advantage of low-cost fabrication, but have not yielded high efficiencies. Our program is based on single-crystalline-like thin film photovoltaics on polycrystalline substrates using biaxially-textured templates made by Ion Beam-Assisted Deposition (IBAD). MgO templates made by IBAD on flexible metal substrate have been successfully used for epitaxial growth of germanium films. In spite of a 4.5% lattice mismatch, heteroepitaxial growth of Ge was achieved on CeO2 that was grown on IBAD MgO template. Room temperature optical bandgap of the Ge films was identified at 0.67 eV indicating minimal residual strain. Refraction index and extinction coefficient values of the Ge films were found to match well with that measured from a reference Ge single crystal. GaAs has been successfully grown epitaxially on Ge on metal substrate by molecular beam epitaxy. RHEED patterns indicate self annihilation of antiphase boundaries and the growth of a single domain GaAs. The GaAs is found to exhibit strong photoluminescence signal and, an existence of a relatively narrow (FWHM~20 meV) band-edge excitons measured in this film indicates a good optoelectronic quality of deposited GaAs. While excellent epitaxial growth has been achieved in GaAs on flexible metal substrates, the defect density of the films as measured by High Resolution X-ray Diffraction and etch pit experiments showed a high value of 5 * 10^8 per cm^2. Cross sectional transmission electron microscopy of the multilayer architecture showed concentration of threading dislocations near the germanium-ceria interface. The defect density was found decrease as the Ge films were made thicker. The defects appear to originate from the MgO layer presumably because of large lattice mismatches

  14. Phase-controlled solvothermal synthesis and characterization of nickel sulfides with good single crystalline nature

    SciTech Connect

    Chen Shuguang; Zeng Kai; Li Haibin; Li Fujin

    2011-08-15

    Dispersed rhombohedral NiS rods with high aspect ratios and rhombic dodecahedron-like cubic NiS{sub 2} crystals were prepared by solvothermal routes using NiCl{sub 2}.6H{sub 2}O and Na{sub 2}S{sub 2}O{sub 3}.5H{sub 2}O as reagents and ethylenediamine as a solvent, and 3D blossoming flower-like rhombohedral NiS microstructures were synthesized using different sulfur sources of thiourea. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy dispersion spectrometry and selected area electronic diffraction. All the products were pure and had good single crystalline nature. The synthesis parameters were of great importance on the purity and morphology of the products. The possible growth mechanisms have been discussed based on the analyses of the effects of sulfur sources and solvent on the crystal structures and detailed configurations of the products. The present work is likely to help the phase-controlled synthesis of other metal chalcogenides. - Graphical abstract: Rhombohedral NiS dispersed rods and 3D flower-like microstructures are evolved from dispersed nucleus and aggregate of nucleus, respectively, and the cross-sections of such rods are in equilateral triangle-like shape. Highlights: > 3D blossoming flower-like r-NiS microstructures are obtained. > Equilateral triangle-like cross-sections of r-NiS rods are observed. > Approach based on XRD analysis to phase-controlled synthesis is presented.

  15. Specific heat and magnetic properties of single-crystalline ZnxDyyCrzSe4 spinels

    NASA Astrophysics Data System (ADS)

    Jendrzejewska, Izabela; Groń, Tadeusz; Maciążek, Ewa; Duda, Henryk; Kubisztal, Marian; Ślebarski, Andrzej; Pietrasik, Ewa; Fijałkowski, Marcin

    2016-06-01

    The crystal structure, magnetic isotherm, magnetic susceptibility, electrical conductivity and specific heat measurements for single-crystalline ZnxDyyCrzSe4 (where x+y+z≈3) spinels are presented. A semiconducting behavior with the activation energy of 0.53 eV, an antiferromagnetic order with a Néel temperature TN=22 K and a strong ferromagnetic exchange evidenced by a positive Curie-Weiss temperature θ=79, 71 and 70 K with increasing Dy-content in the sequence 0.05, 0.13 and 0.19 were established. Below TN the magnetic field dependence of magnetization, M(H), shows two peaks at critical fields Hc1 and Hc2. The values of Hc1 decrease slightly with temperature, especially for the larger Dy-content, while the values of Hc2 drop rapidly with temperature. The magnetic contribution to the specific heat displays a sharp peak at TN, which is strongly shifted to much lower temperatures in the applied magnetic fields. Similar behavior was found for the temperature dependence of the specific heat C(T) plotted as C(T)/T vs. T. The value of the magnetic and phonon contribution to the entropy at TN and at H=0 is only ∼4.8, ∼4.4 and ∼4.2 J mol-1 K-1/Cr3+ for y=0.05, 0.13 and 0.19, respectively, much lower than the average magnetic contribution Sm=(z/2)Rln(2S+1)=12.33 J mol-1 K-1/Cr3+ calculated for Cr3+ ion with S=3/2, as the dysprosium one is paramagnetic.

  16. Vertical Single-Crystalline Organic Nanowires on Graphene: Solution-Phase Epitaxy and Optical Microcavities.

    PubMed

    Zheng, Jian-Yao; Xu, Hongjun; Wang, Jing Jing; Winters, Sinéad; Motta, Carlo; Karademir, Ertuğrul; Zhu, Weigang; Varrla, Eswaraiah; Duesberg, Georg S; Sanvito, Stefano; Hu, Wenping; Donegan, John F

    2016-08-10

    Vertically aligned nanowires (NWs) of single crystal semiconductors have attracted a great deal of interest in the past few years. They have strong potential to be used in device structures with high density and with intriguing optoelectronic properties. However, fabricating such nanowire structures using organic semiconducting materials remains technically challenging. Here we report a simple procedure for the synthesis of crystalline 9,10-bis(phenylethynyl) anthracene (BPEA) NWs on a graphene surface utilizing a solution-phase van der Waals (vdW) epitaxial strategy. The wires are found to grow preferentially in a vertical direction on the surface of graphene. Structural characterization and first-principles ab initio simulations were performed to investigate the epitaxial growth and the molecular orientation of the BPEA molecules on graphene was studied, revealing the role of interactions at the graphene-BPEA interface in determining the molecular orientation. These free-standing NWs showed not only efficient optical waveguiding with low loss along the NW but also confinement of light between the two end facets of the NW forming a microcavity Fabry-Pérot resonator. From an analysis of the optical dispersion within such NW microcavities, we observed strong slowing of the waveguided light with a group velocity reduced to one-tenth the speed of light. Applications of the vertical single-crystalline organic NWs grown on graphene will benefit from a combination of the unique electronic properties and flexibility of graphene and the tunable optical and electronic properties of organic NWs. Therefore, these vertical organic NW arrays on graphene offer the potential for realizing future on-chip light sources. PMID:27438189

  17. Enhanced non-volatile resistive switching in suspended single-crystalline ZnO nanowire with controllable multiple states

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Pang, Wei; Zhang, Qing; Chen, Yan; Chen, Xuejiao; Feng, Zhihong; Yang, Jianhua; Zhang, Daihua

    2016-08-01

    Resistive switching nanostructures are a promising candidate for next-generation non-volatile memories. In this report, we investigate the switching behaviors of single-crystalline ZnO nanowires suspended in air. They exhibit significantly higher current density, lower switching voltage, and more pronounced multiple conductance states compared to nanowires in direct contact with substrate. We attribute the effect to enhanced Joule heating efficiency, reduced surface scattering, and more significantly, the positive feedback established between the current density and local temperature in the suspended nanowires. The proposed mechanism has been quantitatively examined by finite element simulations. We have also demonstrated an innovative approach to initiating the current–temperature mutual enhancement through illumination by ultraviolet light, which further confirmed our hypothesis and enabled even greater enhancement. Our work provides further insight into the resistive switching mechanism of single-crystalline one-dimensional nanostructures, and suggests an effective means of performance enhancement and device optimization.

  18. Enhanced non-volatile resistive switching in suspended single-crystalline ZnO nanowire with controllable multiple states

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Pang, Wei; Zhang, Qing; Chen, Yan; Chen, Xuejiao; Feng, Zhihong; Yang, Jianhua; Zhang, Daihua

    2016-08-01

    Resistive switching nanostructures are a promising candidate for next-generation non-volatile memories. In this report, we investigate the switching behaviors of single-crystalline ZnO nanowires suspended in air. They exhibit significantly higher current density, lower switching voltage, and more pronounced multiple conductance states compared to nanowires in direct contact with substrate. We attribute the effect to enhanced Joule heating efficiency, reduced surface scattering, and more significantly, the positive feedback established between the current density and local temperature in the suspended nanowires. The proposed mechanism has been quantitatively examined by finite element simulations. We have also demonstrated an innovative approach to initiating the current-temperature mutual enhancement through illumination by ultraviolet light, which further confirmed our hypothesis and enabled even greater enhancement. Our work provides further insight into the resistive switching mechanism of single-crystalline one-dimensional nanostructures, and suggests an effective means of performance enhancement and device optimization.

  19. Generation of single-crystalline domain in nano-scale silicon pillars by near-field short pulsed laser

    NASA Astrophysics Data System (ADS)

    In, Jung Bin; Xiang, Bin; Hwang, David J.; Ryu, Sang-Gil; Kim, Eunpa; Yoo, Jae-Hyuck; Dubon, Oscar; Minor, Andrew M.; Grigoropoulos, Costas P.

    2014-01-01

    We observe laser-induced grain morphology change in silicon nanopillars under a transmission electron microscopy (TEM) environment. We couple the TEM with a near-field scanning optical microscopy pulsed laser processing system. This novel combination enables immediate scrutiny on the grain morphologies that the pulsed laser irradiation produces. We find unusual transformation of the tip of the amorphous or polycrystalline silicon pillar into a single crystalline domain via melt-mediated crystallization. On the basis of the three-dimensional finite difference simulation result and the dark field TEM data, we propose that the creation of the distinct single crystalline tip originates from the dominant grain growth initiated at the apex of the non-planar liquid-solid interface. Our microscopic observation provides a fundamental basis for laser-induced conversion of amorphous nanostructures into coarse-grained crystals.

  20. High-quality single crystalline NiO with twin phases grown on sapphire substrate by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Uchida, Kazuo; Yoshida, Ken-ichi; Zhang, Dongyuan; Koizumi, Atsushi; Nozaki, Shinji

    2012-12-01

    High-quality single crystalline twin phase NiO grown on sapphire substrates by metalorganic vapor phase epitaxy is reported. X-ray rocking curve analysis of NiO films grown at different temperatures indicates a minimum full width at half maximum of the cubic (111) diffraction peak of 0.107° for NiO film grown at as low as 550 °C. Detailed microstructural analysis by Φ scan X-ray diffraction and transmission electron microscopy reveal that the NiO film consists of large single crystalline domains with two different crystallographic orientations which are rotated relative to each other along the [111] axis by 60°. These single crystal domains are divided by the twin phase boundaries.

  1. Single crystalline InAsxSb1-x grown on (100) InSb substrate by liquid phase epitaxy

    NASA Astrophysics Data System (ADS)

    Sun, Changhong; Hu, Shuhong; Wang, Qiwei; Qiu, Feng; Lv, Yingfei; Deng, Huiyong; Sun, Yan; Dai, Ning

    2012-10-01

    Single crystalline InAs0.016Sb0.984 film has been successfully grown on (100) InSb substrate by LPE method. A large supercooling (ΔT = 15 °C) had been used to prevent substrate from dissolving into the epilayer. High resolution X-ray diffraction (HRXRD) measurement was used to characterize the crystal quality of the film. Only (200) and (400) peaks were observed from the XRD spectrum, indicating that the film was single crystalline with (100) orientation. The Fourier transform infrared (FTIR) transmission spectrum of the film at room temperature revealed 7.77 μm cut-off wavelength of the film. The lattice dynamics of the epilayer was studied by Raman scattering, suggests two-mode behavior of the optical phonons.

  2. Formation of single crystalline tellurium supersaturated silicon pn junctions by ion implantation followed by pulsed laser melting

    NASA Astrophysics Data System (ADS)

    Xiyuan, Wang; Yongguang, Huang; Dewei, Liu; Xiaoning, Zhu; Xiao, Cui; Hongliang, Zhu

    2013-06-01

    Pn junctions based on single crystalline tellurium supersaturated silicon were formed by ion implantation followed by pulsed laser melting (PLM). P type silicon wafers were implanted with 245 keV 126Te+ to a dose of 2 × 1015 ions/cm2, after a PLM process (248 nm, laser fluence of 0.30 and 0.35 J/cm2, 1-5 pulses, duration 30 ns), an n+ type single crystalline tellurium supersaturated silicon layer with high carrier density (highest concentration 4.10 × 1019 cm-3, three orders of magnitude larger than the solid solution limit) was formed, it shows high broadband optical absorption from 400 to 2500 nm. Current—voltage measurements were performed on these diodes under dark and one standard sun (AM 1.5), and good rectification characteristics were observed. For present results, the samples with 4-5 pulses PLM are best.

  3. Single-Crystalline Aluminum Nanostructures on a Semiconducting GaAs Substrate for Ultraviolet to Near-Infrared Plasmonics.

    PubMed

    Liu, Hsuan-Wei; Lin, Fan-Cheng; Lin, Shi-Wei; Wu, Jau-Yang; Chou, Bo-Tsun; Lai, Kuang-Jen; Lin, Sheng-Di; Huang, Jer-Shing

    2015-04-28

    Aluminum, as a metallic material for plasmonics, is of great interest because it extends the applications of surface plasmon resonance into the ultraviolet (UV) region and is superior to noble metals in natural abundance, cost, and compatibility with modern semiconductor fabrication processes. Ultrasmooth single-crystalline metallic films are beneficial for the fabrication of high-definition plasmonic nanostructures, especially complex integrated nanocircuits. The absence of surface corrugation and crystal boundaries also guarantees superior optical properties and applications in nanolasers. Here, we present UV to near-infrared plasmonic resonance of single-crystalline aluminum nanoslits and nanoholes. The high-definition nanostructures are fabricated with focused ion-beam milling into an ultrasmooth single-crystalline aluminum film grown on a semiconducting GaAs substrate with a molecular beam epitaxy method. The single-crystalline aluminum film shows improved reflectivity and reduced two-photon photoluminescence (TPPL) due to the ultrasmooth surface. Both linear scattering and nonlinear TPPL are studied in detail. The nanoslit arrays show clear Fano-like resonance, and the nanoholes are found to support both photonic modes and localized surface plasmon resonance. We also found that TPPL generation is more efficient when the excitation polarization is parallel rather than perpendicular to the edge of the aluminum film. Such a counterintuitive phenomenon is attributed to the high refractive index of the GaAs substrate. We show that the polarization of TPPL from aluminum preserves the excitation polarization and is independent of the crystal orientation of the film or substrate. Our study gains insight into the optical property of aluminum nanostructures on a high-index semiconducting GaAs substrate and illustrates a practical route to implement plasmonic devices onto semiconductors for future hybrid nanodevices.

  4. Dynamic response of single crystalline copper subjected to quasi-isentropic laser and gas-gun driven loading

    SciTech Connect

    Meyers, M; Jarmakani, H; McNaney, J; Schneider, M; Nguyen, J; Kad, B

    2006-05-22

    Single crystalline copper was subjected to quasi-isentropic compression via gas-gun and laser loading at pressures between 18 GPa and 59 GPa. The deformation substructure was analyzed via transmission electron microscopy (TEM). Twins and laths were evident at the highest pressures, and stacking faults and dislocation cells in the intermediate and lowest pressures, respectively. The Preston-Tonks-Wallace (PTW) constitutive description was used to model the slip-twinning process in both cases.

  5. Approaching the alloy limit of thermal conductivity in single-crystalline Si-based thermoelectric nanocomposites: A molecular dynamics investigation

    PubMed Central

    Guo, Ruiqiang; Huang, Baoling

    2015-01-01

    Single-crystalline Si-based nanocomposites have become promising candidates for thermoelectric applications due to their prominent merits. Reducing the thermal conductivity κ without deteriorating the electrical properties is the key to improve their performance. Through non-equilibrium molecular dynamics simulations, we show that κ of single-crystalline Si-based nanocomposites can be reduced to the alloy limit by embedding various nanoinclusions of similar lattice constants but different lattice orientations or space symmetries with respect to the matrix. The surprisingly low κ is mainly due to the large acoustic phonon density of states mismatch caused by the destruction of lattice periodicity at the interfaces between the nanoinclusions and matrix, which leads to the substantial reduction of phonon group velocity and relaxation time, as well as the enhancement of phonon localization. The resulting κ is also temperature-insensitive due to the dominance of boundary scattering. The increase in thermal resistance induced by lattice structure mismatch mainly comes from the nanoinclusions and the channels between them and is caused by the enhanced boundary scattering at the interfaces parallel to the heat flux. Approaching the alloy limit of κ with potentially improved electrical properties by fillers will remarkably improve ZT of single-crystalline Si-based nanocomposites and extend their application. PMID:25851401

  6. Anisotropic thermodynamic and transport properties of single-crystalline CaKFe4As4

    DOE PAGESBeta

    Meier, W. R.; Kong, T.; Kaluarachchi, U. S.; Taufour, V.; Jo, N. H.; Drachuck, G.; Böhmer, A. E.; Saunders, S. M.; Sapkota, A.; Kreyssig, A.; et al

    2016-08-01

    We grew single-crystalline, single-phase CaKFe4As4 out of a high-temperature, quaternary melt. Temperature-dependent measurements of x-ray diffraction, anisotropic electrical resistivity, elastoresistivity, thermoelectric power, Hall effect, magnetization, and specific heat, combined with field-dependent measurements of electrical resistivity and field and pressure-dependent measurements of magnetization indicate that CaKFe4As4 is an ordered, stoichiometric, Fe-based superconductor with a superconducting critical temperature, Tc=35.0±0.2 K. Other than superconductivity, there is no indication of any other phase transition for 1.8K≤T≤300 K. All of these thermodynamic and transport data reveal striking similarities to those found for optimally or slightly overdoped (Ba1-xKx)Fe2As2, suggesting that stoichiometric CaKFe4As4 is intrinsically close to what is referred to as “optimal-doped” on a generalized, Fe-based superconductor, phase diagram. Furthermore, the anisotropic superconducting upper critical field, Hc2(T), of CaKFe4As4 was determined up to 630 kOe. The anisotropy parameter γ(T)=Hmore » $$⊥\\atop{c2}$$/H$$∥\\atop{c2}$$, for H applied perpendicular and parallel to the c axis, decreases from ≃2.5 at Tc to ≃1.5 at 25 K, which can be explained by interplay of paramagnetic pair breaking and orbital effects. The slopes of dH$$∥\\atop{c2}$$/dT≃-44 kOe/K and dH$$⊥\\atop{c2}$$/dT≃-109 kOe/K at Tc yield an electron mass anisotropy of m⊥/m∥≃1/6 and short Ginzburg-Landau coherence lengths ξ∥(0)≃5.8Å and ξ⊥(0)≃14.3Å. Finally, the value of H$$⊥\\atop{c2}$$(0) can be extrapolated to ≃920 kOe, well above the BCS paramagnetic limit.« less

  7. Anisotropic thermodynamic and transport properties of single-crystalline CaKFe4As4

    NASA Astrophysics Data System (ADS)

    Meier, W. R.; Kong, T.; Kaluarachchi, U. S.; Taufour, V.; Jo, N. H.; Drachuck, G.; Böhmer, A. E.; Saunders, S. M.; Sapkota, A.; Kreyssig, A.; Tanatar, M. A.; Prozorov, R.; Goldman, A. I.; Balakirev, Fedor F.; Gurevich, Alex; Bud'ko, S. L.; Canfield, P. C.

    2016-08-01

    Single-crystalline, single-phase CaKFe4As4 has been grown out of a high-temperature, quaternary melt. Temperature-dependent measurements of x-ray diffraction, anisotropic electrical resistivity, elastoresistivity, thermoelectric power, Hall effect, magnetization, and specific heat, combined with field-dependent measurements of electrical resistivity and field and pressure-dependent measurements of magnetization indicate that CaKFe4As4 is an ordered, stoichiometric, Fe-based superconductor with a superconducting critical temperature, Tc=35.0 ±0.2 K. Other than superconductivity, there is no indication of any other phase transition for 1.8 K≤T ≤300 K. All of these thermodynamic and transport data reveal striking similarities to those found for optimally or slightly overdoped (Ba1 -xKx )Fe2As2 , suggesting that stoichiometric CaKFe4As4 is intrinsically close to what is referred to as "optimal-doped" on a generalized, Fe-based superconductor, phase diagram. The anisotropic superconducting upper critical field, Hc 2(T ) , of CaKFe4As4 was determined up to 630 kOe. The anisotropy parameter γ (T ) =Hc2 ⊥/Hc2 ∥ , for H applied perpendicular and parallel to the c axis, decreases from ≃2.5 at Tc to ≃1.5 at 25 K, which can be explained by interplay of paramagnetic pair breaking and orbital effects. The slopes of d Hc2 ∥/d T ≃-44 kOe/K and d Hc2 ⊥/d T ≃-109 kOe/K at Tc yield an electron mass anisotropy of m⊥/m∥≃1 /6 and short Ginzburg-Landau coherence lengths ξ∥(0 ) ≃5.8 Å and ξ⊥(0 ) ≃14.3 Å . The value of Hc2 ⊥(0 ) can be extrapolated to ≃920 kOe, well above the BCS paramagnetic limit.

  8. Structure, morphology, and magnetic properties of Fe nanoparticles deposited onto single-crystalline surfaces

    PubMed Central

    Kleibert, Armin; Rosellen, Wolfgang; Getzlaff, Mathias

    2011-01-01

    Summary Background: Magnetic nanostructures and nanoparticles often show novel magnetic phenomena not known from the respective bulk materials. In the past, several methods to prepare such structures have been developed – ranging from wet chemistry-based to physical-based methods such as self-organization or cluster growth. The preparation method has a significant influence on the resulting properties of the generated nanostructures. Taking chemical approaches, this influence may arise from the chemical environment, reaction kinetics and the preparation route. Taking physical approaches, the thermodynamics and the kinetics of the growth mode or – when depositing preformed clusters/nanoparticles on a surface – the landing kinetics and subsequent relaxation processes have a strong impact and thus need to be considered when attempting to control magnetic and structural properties of supported clusters or nanoparticles. Results: In this contribution we focus on mass-filtered Fe nanoparticles in a size range from 4 nm to 10 nm that are generated in a cluster source and subsequently deposited onto two single crystalline substrates: fcc Ni(111)/W(110) and bcc W(110). We use a combined approach of X-ray magnetic circular dichroism (XMCD), reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) to shed light on the complex and size-dependent relation between magnetic properties, crystallographic structure, orientation and morphology. In particular XMCD reveals that Fe particles on Ni(111)/W(110) have a significantly lower (higher) magnetic spin (orbital) moment compared to bulk iron. The reduced spin moments are attributed to the random particle orientation being confirmed by RHEED together with a competition of magnetic exchange energy at the interface and magnetic anisotropy energy in the particles. The RHEED data also show that the Fe particles on W(110) – despite of the large lattice mismatch between iron and tungsten – are

  9. Conducting LaAlO3/SrTiO3 heterointerfaces on atomically-flat substrates prepared by deionized-water

    PubMed Central

    Connell, J. G.; Nichols, J.; Gruenewald, J. H.; Kim, D.-W.; Seo, S. S. A.

    2016-01-01

    We have investigated how the recently-developed water-leaching method for atomically-flat SrTiO3 (STO) substrates affects the transport properties of LaAlO3 (LAO) and STO heterointerfaces. Using pulsed laser deposition at identical growth conditions, we have synthesized epitaxial LAO thin-films on two different STO substrates, which are prepared by water-leaching and buffered hydrofluoric acid (BHF) etching methods. The structural, transport, and optical properties of LAO/STO heterostructures grown on water-leached substrates show the same high-quality as the samples grown on BHF-etched substrates. These results indicate that the water-leaching method can be used to grow complex oxide heterostructures with atomically well-defined heterointerfaces without safety concerns. PMID:27033248

  10. Conducting LaAlO3/SrTiO3 heterointerfaces on atomically-flat substrates prepared by deionized-water

    NASA Astrophysics Data System (ADS)

    Connell, J. G.; Nichols, J.; Gruenewald, J. H.; Kim, D.-W.; Seo, S. S. A.

    2016-04-01

    We have investigated how the recently-developed water-leaching method for atomically-flat SrTiO3 (STO) substrates affects the transport properties of LaAlO3 (LAO) and STO heterointerfaces. Using pulsed laser deposition at identical growth conditions, we have synthesized epitaxial LAO thin-films on two different STO substrates, which are prepared by water-leaching and buffered hydrofluoric acid (BHF) etching methods. The structural, transport, and optical properties of LAO/STO heterostructures grown on water-leached substrates show the same high-quality as the samples grown on BHF-etched substrates. These results indicate that the water-leaching method can be used to grow complex oxide heterostructures with atomically well-defined heterointerfaces without safety concerns.

  11. Realization of atomically flat steps and terraces like surface of SrTiO3 (001) single crystal by hot water etching and high temperature annealing

    NASA Astrophysics Data System (ADS)

    Prakash, Bhanu; Chakraverty, S.

    2015-07-01

    We have successfully prepared atomically flat single-terminated SrTiO3(001) surface using a mild and reproducible etching technique combined with high temperature annealing. To achieve single terminated surface, deionised water at 60 °C was used to selectively etch SrO composites from the substrate surface. A clear step-and-terrace like surface morphology is observed by subsequent air annealing at 1000 °C. Atomic Force Microscopy suggests the step height (~0.4 nm) corresponding to the lattice parameter of SrTiO3, which confirms the formation of single-terminated surface. This chemical-free mild etching technique might be useful to prepare single-terminated surface, especially for the perovskites containing reactive elements.

  12. Ripple formation on atomically flat cleaved Si surface with roughness of 0.038 nm rms by low-energy Ar{sup 1+} ion bombardment

    SciTech Connect

    Pahlovy, Shahjada A.; Mahmud, S. F.; Yanagimoto, K.; Miyamoto, I.

    2011-03-15

    The authors have conducted research regarding ripple formation on an atomically flat cleaved Si surface by low-energy Ar{sup +} ion bombardment. The cleaved atomically flat and smooth plane of a Si wafer was obtained by cutting vertically against the orientation of a Si (100) wafer. Next, the cleaved surface was sputtered by a 1 keV Ar{sup +} ion beam at ion-incidence angles of 0 deg., 60 deg., 70 deg., and 80 deg. The results confirm the successful ripple formation at ion-incidence angles of 60 deg. - 80 deg. and that the wavelength of the ripples increases with the increase of the ion-incidence angle, as well as the inverse of ion doses. The direction of the ripple also changes from perpendicular to parallel to the projection of the ion-beam direction along the surface with the increasing ion-incidence angle. The authors have also observed the dose effects on surface roughness of cleaved Si surface at the ion-incidence angle of 60 deg., where the surface roughness increases with the increased ion dose. Finally, to understand the roughening mechanism, the authors studied the scaling behavior, measured the roughness exponent {alpha}, and compared the evolution of scaling regimes with Cuerno's one-dimensional simulation results.

  13. High quality single atomic layer deposition of hexagonal boron nitride on single crystalline Rh(111) four-inch wafers

    NASA Astrophysics Data System (ADS)

    Hemmi, A.; Bernard, C.; Cun, H.; Roth, S.; Klöckner, M.; Kälin, T.; Weinl, M.; Gsell, S.; Schreck, M.; Osterwalder, J.; Greber, T.

    2014-03-01

    The setup of an apparatus for chemical vapor deposition (CVD) of hexagonal boron nitride (h-BN) and its characterization on four-inch wafers in ultra high vacuum (UHV) environment is reported. It provides well-controlled preparation conditions, such as oxygen and argon plasma assisted cleaning and high temperature annealing. In situ characterization of a wafer is accomplished with target current spectroscopy. A piezo motor driven x-y stage allows measurements with a step size of 1 nm on the complete wafer. To benchmark the system performance, we investigated the growth of single layer h-BN on epitaxial Rh(111) thin films. A thorough analysis of the wafer was performed after cutting in atmosphere by low energy electron diffraction, scanning tunneling microscopy, and ultraviolet and X-ray photoelectron spectroscopies. The apparatus is located in a clean room environment and delivers high quality single layers of h-BN and thus grants access to large area UHV processed surfaces, which had been hitherto restricted to expensive, small area single crystal substrates. The facility is versatile enough for customization to other UHV-CVD processes, e.g., graphene on four-inch wafers.

  14. High quality single atomic layer deposition of hexagonal boron nitride on single crystalline Rh(111) four-inch wafers

    SciTech Connect

    Hemmi, A.; Bernard, C.; Cun, H.; Roth, S.; Klöckner, M.; Kälin, T.; Osterwalder, J.; Greber, T.; Weinl, M.; Gsell, S.; Schreck, M.

    2014-03-15

    The setup of an apparatus for chemical vapor deposition (CVD) of hexagonal boron nitride (h-BN) and its characterization on four-inch wafers in ultra high vacuum (UHV) environment is reported. It provides well-controlled preparation conditions, such as oxygen and argon plasma assisted cleaning and high temperature annealing. In situ characterization of a wafer is accomplished with target current spectroscopy. A piezo motor driven x-y stage allows measurements with a step size of 1 nm on the complete wafer. To benchmark the system performance, we investigated the growth of single layer h-BN on epitaxial Rh(111) thin films. A thorough analysis of the wafer was performed after cutting in atmosphere by low energy electron diffraction, scanning tunneling microscopy, and ultraviolet and X-ray photoelectron spectroscopies. The apparatus is located in a clean room environment and delivers high quality single layers of h-BN and thus grants access to large area UHV processed surfaces, which had been hitherto restricted to expensive, small area single crystal substrates. The facility is versatile enough for customization to other UHV-CVD processes, e.g., graphene on four-inch wafers.

  15. Dissociative adsorption of molecular deuterium and thermal stability onto hydrogenated, bare and ion beam damaged poly- and single crystalline diamond surfaces

    NASA Astrophysics Data System (ADS)

    Michaelson, Sh.; Chandran, M.; Zalkind, S.; Shamir, N.; Akhvlediani, R.; Hoffman, A.

    2015-12-01

    In this work we report on dissociative adsorption of deuterium (D2) on bare, hydrogenated and ion beam bombarded polycrystalline and single crystalline diamond surfaces. Polycrystalline diamond films with an average grain size of ~ 300 nm were deposited on silicon substrates by hot filament chemical vapor deposition technique from methane/hydrogen gas mixture. Deposited films were characterized using Raman spectroscopy, atomic force microscopy and scanning electron microscopy to estimate the phase composition and microstructure. High resolution electron energy loss spectroscopy and direct recoil spectrometry were used to study hydrogen (deuterium) bonding configuration of the upper surface region. Near surface amorphization was achieved by 1 keV Ar+ implantation at ~ 1 × 1015 ions/cm2 at room temperature (RT). As deposited and Ar+ bombarded films are annealed to 500-1000 °C in ultra-high vacuum conditions and also under D2 partial pressure of 5 × 10- 6 Torr. For comparison, key experiments were repeated on the single crystal (100) diamond. Our results clearly show the preferential dissociative adsorption of D2 on low hybridized carbon (sp/sp2) states with activation temperature as low as RT, but with a lower thermal stability compared to pure diamond Csbnd D bonds.

  16. Experimental investigation of off-stoichiometry and 3d transition metal (Mn, Ni, Cu)-substitution in single-crystalline FePt thin films

    NASA Astrophysics Data System (ADS)

    Ono, Takuya; Nakata, Hitoshi; Moriya, Tomohiro; Kikuchi, Nobuaki; Okamoto, Satoshi; Kitakami, Osamu; Shimatsu, Takehito

    2016-05-01

    In L10 (fct)-FePt thin films, both tuning Fe and Pt concentrations and substitution with third-metal were studied for magnetic characteristic optimization. We investigated single-crystalline FePt-X (X = Mn, Ni, Cu) thin films grown epitaxially on MgO(001) substrates at a substrate temperature of 350 °C by changing Fe, Pt, and X contents, and explored the effects of off-stoichiometry and 3d-metal-substitution. The magnetic moment per atom (m) of FePt-X films as a function of the effective number of valence electrons (neff) in 3d metal sites follows the Slater-Pauling-type trend, by which m decreases by the neff deviation from neff = 8, independently of the X metal and the Pt concentration. The magnetic anisotropy (Ku) exhibits neff dependence similar to m. This trend was almost independent of the Pt concentration after compensation using the theoretical prediction on the relation between Ku and Fe/Pt concentrations. Such a trend has been proved for stoichiometric FePt-X films, but it was clarified as robust against off-stoichiometry. The compensated Ku ( Ku comp ) of FePt-Mn and FePt-Cu followed a similar trend to that predicted by the rigid-band model, although the Ku comp of the FePt-Mn thin films dropped more rapidly than the rigid band calculation. However, it followed the recent first-principles calculation.

  17. Investigation of electrically-active deep levels in single-crystalline diamond by particle-induced charge transient spectroscopy

    NASA Astrophysics Data System (ADS)

    Kada, W.; Kambayashi, Y.; Ando, Y.; Onoda, S.; Umezawa, H.; Mokuno, Y.; Shikata, S.; Makino, T.; Koka, M.; Hanaizumi, O.; Kamiya, T.; Ohshima, T.

    2016-04-01

    To investigate electrically-active deep levels in high-resistivity single-crystalline diamond, particle-induced charge transient spectroscopy (QTS) techniques were performed using 5.5 MeV alpha particles and 9 MeV carbon focused microprobes. For unintentionally-doped (UID) chemical vapor deposition (CVD) diamond, deep levels with activation energies of 0.35 eV and 0.43 eV were detected which correspond to the activation energy of boron acceptors in diamond. The results suggested that alpha particle and heavy ion induced QTS techniques are the promising candidate for in-situ investigation of deep levels in high-resistivity semiconductors.

  18. Synthesis and magnetic properties of single-crystalline Na2-xMn8O16 nanorods

    PubMed Central

    2011-01-01

    The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time. The nanorods were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and a superconducting quantum interference device magnetometer. The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures. The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods. PMID:21711626

  19. Motion, collision and annihilation of polarization vortex pair in single crystalline BaTiO3 thin film

    NASA Astrophysics Data System (ADS)

    Tian, Xianbao; Yang, Xinhua; Wang, Peng; Peng, Di

    2013-12-01

    Domain evolution of a single crystalline BaTiO3 thin film, initially possessing two vortex-antivortex pairs, placed under compressive displacement loading with a constant strain rate, is simulated using a molecular dynamics method based on the shell model. The evolution details, including the relative motion and collision between the vortices and antivortices and their annihilation, are carefully observed, and both the movement velocity and the equilibrium time after annihilation are estimated. When the vortex-antivortex pairs annihilate, the polarization configuration evolves into a 180° domain structure. These distinctive domain evolution characteristics could open up opportunities for designing ferroelectric nanodevices.

  20. Current-direction dependence of the transport properties in single-crystalline face-centered-cubic cobalt films

    SciTech Connect

    Xiao, X.; Liang, J. H.; Chen, B. L.; Li, J. X.; Ding, Z.; Wu, Y. Z.; Ma, D. H.

    2015-07-28

    Face-centered-cubic cobalt films are epitaxially grown on insulating LaAlO{sub 3}(001) substrates by molecular beam epitaxy. Transport measurements are conducted in different current directions relative to the crystal axes. We find that the temperature dependent anisotropic magnetoresistance ratio strongly depends on the current direction. However, the anomalous Hall effect shows isotropic behavior independent of the current direction. Our results demonstrate the interplay between the current direction and the crystalline lattice in single-crystalline ferromagnetic films. A phenomenological analysis is presented to interpret the experimental data.

  1. Single-crystalline MFe(2)O(4) nanotubes/nanorings synthesized by thermal transformation process for biological applications.

    PubMed

    Fan, Hai-Ming; Yi, Jia-Bao; Yang, Yi; Kho, Kiang-Wei; Tan, Hui-Ru; Shen, Ze-Xiang; Ding, Jun; Sun, Xiao-Wei; Olivo, Malini Carolene; Feng, Yuan-Ping

    2009-09-22

    We report a general thermal transformation approach to synthesize single-crystalline magnetic transition metal oxides nanotubes/nanorings including magnetite Fe(3)O(4), maghematite gamma-Fe(2)O(3), and ferrites MFe(2)O(4) (M = Co, Mn, Ni, Cu) using hematite alpha-Fe(2)O(3) nanotubes/nanorings template. While the straightforward reduction or reduction-oxides process was employed to produce Fe(3)O(4) and gamma-Fe(2)O(3), the alpha-Fe(2)O(3)/M(OH)(2) core/shell nanostructure was used as precursor to prepare MFe(2)O(4) nanotubes via MFe(2)O(4-x) (0 < x < 1) intermediate. The transformed ferrites nanocrystals retain the hollow structure and single-crystalline nature of the original templates. However, the crystallographic orientation-relationships of cubic spinel ferrites and trigonal hematite show strong correlation with their morpologies. The hollow-structured MFe(2)O(4) nanocrystals with tunable size, shape, and composition have exhibited unique magnetic properties. Moreover, they have been demonstrated as a highly effective peroxidase mimic catalysts for laboratory immunoassays or as a universal nanocapsules hybridized with luminescent QDs for magnetic separation and optical probe of lung cancer cells, suggesting that these biocompatible magnetic nanotubes/nanorings have great potential in biomedicine and biomagnetic applications.

  2. Single crystalline Co3O4 nanocrystals exposed with different crystal planes for Li-O2 batteries.

    PubMed

    Su, Dawei; Dou, Shixue; Wang, Guoxiu

    2014-08-29

    Single crystalline Co3O4 nanocrystals exposed with different crystal planes were synthesised, including cubic Co3O4 nanocrystals enclosed by {100} crystal planes, pseudo octahedral Co3O4 enclosed by {100} and {110} crystal planes, Co3O4 nanosheets exposed by {110} crystal planes, hexagonal Co3O4 nanoplatelets exposed with {111} crystal planes, and Co3O4 nanolaminar exposed with {112} crystal planes. Well single crystalline features of these Co3O4 nanocrystals were confirmed by FESEM and HRTEM analyses. The electrochemical performance for Li-O2 batteries shows that Co3O4 nanocrystals can significantly reduce the discharge-charge over-potential via the effect on the oxygen evolution reaction (OER). From the comparison on their catalytic performances, we found that the essential factor to promote the oxygen evolution reactions is the surface crystal planes of Co3O4 nanocrystals, namely, crystal planes-dependent process. The correlation between different Co3O4 crystal planes and their effect on reducing charge-discharge over-potential was established: {100} < {110} < {112} < {111}.

  3. One-dimensional single-crystalline bismuth oxide micro/nanoribbons: morphology-controlled synthesis and luminescent properties.

    PubMed

    Ling, B; Sun, X W; Zhao, J L; Shen, Y Q; Dong, Z L; Sun, L D; Li, S F; Zhang, S

    2010-12-01

    Based on a facile vapor-phase transport method without any catalyst and template, one-dimensional single-crystalline bismuth oxide (Bi2O3) micro/nanoribbons were fabricated on silicon substrates in large quantities and morphology-controlled fabrication of Bi2O3 was achieved from a single precursor. The widths of Bi2O3 ribbons varied from 0.2 to 20 microm depending on the deposition temperatures. The thickness was in the range of 0.1-2 microm and the length reached several hundred micrometers and even millimeter range. The detailed composition and structural analysis confirmed the single-crystalline nature of alpha-Bi2O3 micro/nanoribbons with monoclinic structure. The photoluminescence spectrum of a single Bi2O3 ribbon showed a broadband emission from 450 to 750 nm in the visible region, consisting two peaks located at 589 and 697 nm which were primarily originated from the impurity ions and crystal defects. A self-catalyzed vapor-solid model was proposed to account for the growth mechanism of Bi2O3 ribbons with different morphologies. PMID:21121334

  4. Towards intrinsic graphene biosensor: A label-free, suspended single crystalline graphene sensor for multiplex lung cancer tumor markers detection.

    PubMed

    Li, Peng; Zhang, Bo; Cui, Tianhong

    2015-10-15

    Graphene biosensors reported so far are based on polycrystalline graphene flakes which are anchored on supporting substrates. The influence of grain boundary and the scattering from substrate drastically degrade the properties of graphene and conceal the performance of intrinsic graphene as a sensor. Here we report a label-free biosensor based on suspended single crystalline graphene (SCG), which can get rid of grain boundary and substrate scattering, revealing the biosensing mechanism of intrinsic graphene for the first time. Monolayer SCG flakes were derived from low pressure chemical vapor deposition (LPCVD) method. Multiplex detection of three different lung cancer tumor markers was realized. The suspended structure can largely improve the sensitivity and detection limit (0.1 pg/ml) of the sensor, and the single crystalline nature of SCG enable the biosensor to have superior uniformity compared to polycrystalline ones. The SCG sensors exhibit superb specificity and large linear detection range from 1 pg/ml to 1 μg/ml, showing the prominent advantages of graphene as a sensing material.

  5. Effect of nitridation surface treatment on silicon (1 1 1) substrate for the growth of high quality single-crystalline GaN hetero-epitaxy layer by MOCVD

    NASA Astrophysics Data System (ADS)

    Rahman, Mohd Nazri Abd.; Yusuf, Yusnizam; Mansor, Mazwan; Shuhaimi, Ahmad

    2016-01-01

    A single-crystalline with high quality of gallium nitride epilayers was grown on silicon (1 1 1) substrate by metal organic chemical vapor deposition. The process of nitridation surface treatment was accomplished on silicon (1 1 1) substrate by flowing the ammonia gaseous. Then, it was followed by a thin aluminum nitride nucleation layer, aluminum nitride/gallium nitride multi-layer and a thick gallium nitride epilayer. The influence of in situ nitridation surface treatment on the crystallinity quality of gallium nitride epilayers was studied by varying the nitridation times at 40, 220 and 400 s, respectively. It was shown that the nitridation times greatly affect the structural properties of the grown top gallium nitride epilayer on silicon (1 1 1) substrate. In the (0 0 0 2) and (1 0 1 bar 2) X-ray rocking curve analysis, a narrower value of full width at half-maximum has been obtained as the nitridation time increased. This is signifying the reduction of dislocation density in the gallium nitride epilayer. This result was supported by the value of bowing and root mean square roughness measured by surface profilometer and atomic force microscopy. Furthermore, a crack-free gallium nitride surface with an abrupt cross-sectional structure that observed using field effect scanning electron microscopy was also been obtained. The phi-scan curve of asymmetric gallium nitride proved the top gallium nitride epilayer exhibited a single-crystalline structure.

  6. Survival of hydrogen anions near atomically flat metal surfaces: Band gap confinement and image state recapture effects

    NASA Astrophysics Data System (ADS)

    Schmitz, Andrew; Shaw, John; Chakraborty, Himadri; Thumm, Uwe

    2010-03-01

    Resonant charge transfer (RCT) between ions and surfaces is a key intermediate step in surface-chemical processes as well as in micro- and nano-fabrications on the surface. The RCT process in the collision of hydrogen anions with metal surfaces is described within a wave packet propagation methodology using Crank-Nicholson algorithm [1]. The ion-survival probability is found to strongly enhance at two different ion velocities perpendicular to the surface. The low velocity enhancement is induced from a dynamical confinement of the ion level inside the band gap, while the high velocity enhancement emerges owing to the recapture from transiently populated image states [2]. These structures are found to be somewhat sensitive to the ion's distance of closest approach to the surface and the choice of inter-atomic potentials between the ion and the surface atoms. [1] Chakraborty et al., Phys. Rev. A 70, 052903 (2004); [2] Schmitz et al., Phys. Rev. A (submitted).

  7. Magnetic properties of single-crystalline UCu[sub 3]Al[sub 2

    SciTech Connect

    Nakotte, H.; Brueck, E.; Brabers, J.H.V.J.; Prokes, K.; de Boer, F.R. . Van der Waals Lab.); Sechovsky, V. . Dept. of Metal Physics); Buschow, K.H.J. ); Andreev, A.V. ); Robinson, R.A.; Purwanto, A. (Los Alamos National Lab., NM (Unite

    1993-01-01

    UCu[sub 3]Al[sub 2] crystallizes in an ordered variant of the hexagonal CaCu[sub 5] structure. By neutron powder-diffraction, the U atoms were found to occupy the la sites, while the 2c sites are occupied by Cu atoms only and a random occupation of the 3g sites by the remaining Cu and Al is found. The magnetic susceptibility, measured on a single crystal grown by the Czochralski tri-arc technique, is found to be maximal within the hexagonal basal plane with a maximum at about 10 K. For fields applied within the basal plane, the magnetization at 4.2 K exhibits a slight S-shape starting slightly below 15 T. No such anomalies are found for fields applied along the c-axis where the magnetic response is found to be much lower. No additional magnetic peaks, which could be related with long-range antiferromagnetic ordering, were detected in the neutron powder-patterns at low temperatures.

  8. Magnetic properties of single-crystalline UCu{sub 3}Al{sub 2}

    SciTech Connect

    Nakotte, H.; Brueck, E.; Brabers, J.H.V.J.; Prokes, K.; de Boer, F.R.; Sechovsky, V.; Buschow, K.H.J.; Andreev, A.V.; Robinson, R.A.; Purwanto, A.; Lynn, J.W.

    1993-07-01

    UCu{sub 3}Al{sub 2} crystallizes in an ordered variant of the hexagonal CaCu{sub 5} structure. By neutron powder-diffraction, the U atoms were found to occupy the la sites, while the 2c sites are occupied by Cu atoms only and a random occupation of the 3g sites by the remaining Cu and Al is found. The magnetic susceptibility, measured on a single crystal grown by the Czochralski tri-arc technique, is found to be maximal within the hexagonal basal plane with a maximum at about 10 K. For fields applied within the basal plane, the magnetization at 4.2 K exhibits a slight S-shape starting slightly below 15 T. No such anomalies are found for fields applied along the c-axis where the magnetic response is found to be much lower. No additional magnetic peaks, which could be related with long-range antiferromagnetic ordering, were detected in the neutron powder-patterns at low temperatures.

  9. Single crystalline monoclinic La0.7Sr0.3MnO3 nanowires with high temperature ferromagnetism

    SciTech Connect

    Carretero-Genevrier, Adrian; Gazquez Alabart, Jaume; Idrobo Tapia, Juan C; Oro, Judith; Arbiol, Jordi; Varela del Arco, Maria; Ferain, Etienne; Rodriguez-Carvajal, Juan; Puig, Teresa; Mestres, Narcis; Obradors, Xavier

    2011-01-01

    Porous mixed-valent manganese oxides are a group of multifunctional materials that can be used as molecular sieves, catalysts, battery materials, and gas sensors. However, material properties and thus activity can vary significantly with different synthesis methods or process conditions, such as temperature and time. Here, we report on a new synthesis route for MnO{sub 2} and LaSr-doped molecular sieve single crystalline nanowires based on a solution chemistry methodology combined with the use of nanoporous polymer templates supported on top of single crystalline substrates. Because of the confined nucleation in high aspect ratio nanopores and of the high temperatures attained, new structures with novel physical properties have been produced. During the calcination process, the nucleation and crystallization of {var_epsilon}-MnO{sub 2} nanoparticles with a new hexagonal structure is promoted. These nanoparticles generated up to 30 {mu}m long and flexible hexagonal nanowires at mild growth temperatures (T{sub g} = 700 C) as a consequence of the large crystallographic anisotropy of {var_epsilon}-MnO{sub 2}. The nanocrystallites of MnO{sub 2} formed at low temperatures serve as seeds for the growth of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} nanowires at growth temperatures above 800 C, through the diffusion of La and Sr into the empty 1D-channels of {var_epsilon}-MnO{sub 2}. Our particular growth method has allowed the synthesis of single crystalline molecular sieve (LaSr-2 x 4) monoclinic nanowires with composition La{sub 0.7}Sr{sub 0.3}MnO{sub 3} and with ordered arrangement of La{sup 3+} and Sr{sup 2+} cations inside the 1D-channels. These nanowires exhibit ferromagnetic ordering with strongly enhanced Curie temperature (T{sub c} > 500 K) that probably results from the new crystallographic order and from the mixed valence of manganese.

  10. Formation of single-crystalline CuS at the organic-aqueous interface.

    PubMed

    Maiti, Santanu; Sanyal, Milan K; Varghese, Neenu; Satpati, Biswarup; Dasgupta, Dipak; Daillant, Jean; Carriere, David; Konovolov, Oleg; Rao, C N R

    2013-10-01

    We report here the results of a study to understand the formation mechanism of single crystals of the transition metal chalcogenide, CuS, at the water-toluene interface through an interfacial reaction. Systematic measurements carried out using synchrotron x-ray scattering, electron microscopy, atomic force microscopy and calorimetric techniques clearly show that nano-crystallites of CuS form within a few minutes at the interface as the reagents are brought from the organic (upper) and aqueous (lower) layers to the interface, then crystallization of CuS proceeds over a few hours only by reorganization, despite the large excess available in both upper and lower liquid phases. The interface confinement and passivation by organics is critical here in the formation of single crystals having sizes of 6 and 200 nm along the normal and in-plane directions of the liquid-liquid interface.

  11. Preservation of atomic flatness at SiO2/Si(111) interfaces during thermal oxidation in a furnace

    NASA Astrophysics Data System (ADS)

    Miyata, Noriyuki; Watanabe, Heiji; Ichikawa, Masakazu

    1998-04-01

    SiO2/Si(111) interfaces formed by a furnace oxidation are studied by a scanning reflection electron microscopy (SREM). SREM observation indicates that the initial atomic steps on a Si(111) surface are preserved at the SiO2/Si interface and the interfacial steps do not move laterally even after 48-nm-thick oxidation. A profile analysis of reflection high-energy electron diffraction shows that the SiO2/Si interface consists of islands which have a diameter of about 5 nm and monolayer depth. Our results indicate that the layer-by-layer oxidation caused by two-dimensional island nucleation proceeds under furnace oxidation.

  12. Direct writing of continuous and discontinuous sub-wavelength periodic surface structures on single-crystalline silicon using femtosecond laser

    SciTech Connect

    Kuladeep, Rajamudili; Sahoo, Chakradhar; Narayana Rao, Desai E-mail: dnr-laserlab@yahoo.com

    2014-06-02

    Laser-induced ripples or uniform arrays of continuous near sub-wavelength or discontinuous deep sub-wavelength structures are formed on single-crystalline silicon (Si) by femtosecond (fs) laser direct writing technique. Laser irradiation was performed on Si wafers at normal incidence in air and by immersing them in dimethyl sulfoxide using linearly polarized Ti:sapphire fs laser pulses of ∼110 fs pulse duration and ∼800 nm wavelength. Morphology studies of laser written surfaces reveal that sub-wavelength features are oriented perpendicular to laser polarization, while their morphology and spatial periodicity depend on the surrounding dielectric medium. The formation mechanism of the sub-wavelength features is explained by interference of incident laser with surface plasmon polaritons. This work proves the feasibility of fs laser direct writing technique for the fabrication of sub-wavelength features, which could help in fabrication of advanced electro-optic devices.

  13. Thin single-crystalline Bi2(Te1-xSex)3 ternary nanosheets synthesized by a solvothermal technique

    NASA Astrophysics Data System (ADS)

    Guo, Jing; Jian, Jikang; Zhang, Zhihua; Wu, Rong; Li, Jin; Sun, Yanfei

    2016-01-01

    Bi2(Te1-xSex)3 ternary nanosheets have been successfully synthesized through a facile solvothermal technique using diethylenetriamine as solvent, where x can vary from 0 to 1. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) indicate that the as-synthesized Bi2(Te1-xSex)3 samples are nanosheets with rhombohedral structure, and the thickness of the nanosheets can be as thin as several nanometers. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) reveal that the nanosheets are single crystalline with a rhombohedral structure. Energy disperse spectroscopy (EDS) and XRD analysis by Vegard's law confirm that the ternary Bi2(Te1-xSex)3 nanosheets have been obtained here. The growth of the nanosheets is discussed based on an amine-based molecular template mechanism that has been employed to synthesize some other metal chalcogenides.

  14. The unusually high Tc in rare-earth-doped single crystalline CaFe2As2

    NASA Astrophysics Data System (ADS)

    Wei, Fengyan; Lv, Bing; Deng, Liangzi; Meen, James K.; Xue, Yu-Yi; Chu, Ching-Wu

    2014-08-01

    In rare-earth-doped single crystalline CaFe2As2, the mysterious small volume fraction which superconducts up to 49 K, much higher than the bulk Tc ~ 30 s K, has prompted a long search for a hidden variable that could enhance the Tc by more than 30% in iron-based superconductors of the same structure. Here we report a chemical, structural and magnetic study of CaFe2As2 systematically doped with La, Ce, Pr and Nd. Coincident with the high Tc phase, we find extreme magnetic anisotropy, accompanied by an unexpected doping-independent Tc and equally unexpected superparamagnetic clusters associated with As vacancies. These observations lead us to conjecture that the tantalizing Tc enhancement may be associated with naturally occurring chemical interfaces and may thus provide a new paradigm in the search for superconductors with higher Tc.

  15. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe{sub 3}O{sub 4} nanoparticle rings

    SciTech Connect

    Takeno, Yumu; Murakami, Yasukazu E-mail: kannanmk@uw.edu; Shindo, Daisuke; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Ferguson, R. Matthew; Krishnan, Kannan M. E-mail: kannanmk@uw.edu

    2014-11-03

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe{sub 3}O{sub 4} nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy.

  16. Single-crystalline LiFePO4 nanosheets for high-rate Li-ion batteries.

    PubMed

    Zhao, Yu; Peng, Lele; Liu, Borui; Yu, Guihua

    2014-05-14

    The lithiation/delithiation in LiFePO4 is highly anisotropic with lithium-ion diffusion being mainly confined to channels along the b-axis. Controlling the orientation of LiFePO4 crystals therefore plays an important role for efficient mass transport within this material. We report here the preparation of single crystalline LiFePO4 nanosheets with a large percentage of highly oriented {010} facets, which provide the highest pore density for lithium-ion insertion/extraction. The LiFePO4 nanosheets show a high specific capacity at low charge/discharge rates and retain significant capacities at high C-rates, which may benefit the development of lithium batteries with both favorable energy and power density.

  17. Single-Crystalline cooperite (PtS): Crystal-Chemical characterization, ESR spectroscopy, and {sup 195}Pt NMR spectroscopy

    SciTech Connect

    Rozhdestvina, V. I. Ivanov, A. V.; Zaremba, M. A.; Antsutkin, O. N.; Forsling, W.

    2008-05-15

    Single-crystalline cooperite (PtS) with a nearly stoichiometric composition was characterized in detail by X-ray diffraction, electron-probe X-ray microanalysis, and high-resolution scanning electron microscopy. For the first time it was demonstrated that {sup 195}Pt static and MAS NMR spectroscopy can be used for studying natural platinum minerals. The {sup 195}Pt chemical-shift tensor of cooperite was found to be consistent with the axial symmetry and is characterized by the following principal values: {delta}{sub xx} = -5920 ppm, {delta}{sub yy} = -3734 ppm, {delta}{sub zz} = +4023 ppm, and {delta}{sub iso} = -1850 ppm. According to the ESR data, the samples of cooperite contain copper(II), which is adsorbed on the surface during the layer-by-layer crystal growth and is not involved in the crystal lattice.

  18. Synthesis of one-molecule-thick single-crystalline nanosheets of energetic material for high-sensitive force sensor.

    PubMed

    Yang, Guangcheng; Hu, Hailong; Zhou, Yong; Hu, Yingjie; Huang, Hui; Nie, Fude; Shi, Weimei

    2012-01-01

    Energetic material is a reactive substance that contains a great amount of potential energy, which is extremely sensitive to external stimuli like force. In this work, one-molecule-thick single-crystalline nanosheets of energetic material were synthesized. Very small force applied on the nanosheet proves to lead to the rotation of the tilted nitro groups, and subsequently change of current of the nanosheet. We apply this principle to design high-sensitive force sensor. A theoretical model of force-current dependence was established based on the nanosheets' molecular packing structure model that was well supported with the high resolution XPS, AFM analysis results. An ultra-low-force with range of several picoNewton to several nanoNewton can be measured by determination of corresponding current value.

  19. Molecular-dynamics simulations of stacking-fault-induced dislocation annihilation in prestrained ultrathin single-crystalline copper films

    SciTech Connect

    Kolluri, Kedarnath; Gungor, M. Rauf; Maroudas, Dimitrios

    2009-05-01

    We report results of large-scale molecular-dynamics simulations of dynamic deformation under biaxial tensile strain of prestrained single-crystalline nanometer-scale-thick face-centered cubic (fcc) copper films. Our results show that stacking faults, which are abundantly present in fcc metals, may play a significant role in the dissociation, cross slip, and eventual annihilation of dislocations in small-volume structures of fcc metals. The underlying mechanisms are mediated by interactions within and between extended dislocations that lead to annihilation of Shockley partial dislocations or formation of perfect dislocations. Our findings demonstrate dislocation starvation in small-volume structures with ultrathin film geometry, governed by a mechanism other than dislocation escape to free surfaces, and underline the significant role of geometry in determining the mechanical response of metallic small-volume structures.

  20. Vapor-phase hydrothermal transformation of HTiOF3 intermediates into {001} faceted anatase single-crystalline nanosheets.

    PubMed

    Liu, Porun; Wang, Yun; Zhang, Haimin; An, Taicheng; Yang, Huagui; Tang, Zhiyong; Cai, Weiping; Zhao, Huijun

    2012-12-01

    For the first time, a facile, one-pot hydrofluoric acid vapor-phase hydrothermal (HF-VPH) method is demonstrated to directly grow single-crystalline anatase TiO(2) nanosheets with 98.2% of exposed {001} faceted surfaces on the Ti substrate via a distinctive two-stage formation mechanism. The first stage produces a new intermediate crystal (orthorhombic HTiOF(3) ) that is transformed into anatase TiO(2) nanosheets during the second stage. The findings reveal that the HF-VPH reaction environment is unique and differs remarkably from that of liquid-phase hydrothermal processes. The uniqueness of the HF-VPH conditions can be readily used to effectively control the nanostructure growth. PMID:22903795

  1. Superconducting single crystalline YBa2Cu3O7- δ on SrTiO3 buffered Si (100)

    NASA Astrophysics Data System (ADS)

    Jahangir Moghadam, Mohammadreza; Ahmadi Majlan, Kamyar; Zhang, Hao; Shen, Xuan; Chrysler, Matthew; Conlin, Patrick; Hensley, Ricky; Su, Dong; Wei, John; Ngai, Joseph

    2015-03-01

    The growth of crystalline oxides on semiconductors enables new functionalities to be integrated with semiconducting technologies. Here, thin films of optimally-doped (001)-oriented YBa2Cu3O7- δ are epitaxially integrated on silicon (001) through growth on a SrTiO3 buffer. The former is grown using pulsed-laser deposition and the latter is grown on Si using oxide molecular beam epitaxy. The single crystal nature of the SrTiO3 buffer enables very high transition temperatures to be achieved. For a 30 nm thick SrTiO3 buffer, YBa2Cu3O7- δ films exhibiting a transition temperature of ~ 95 K, and a narrow transition width (<5 K) are achieved. The integration of single crystalline YBa2Cu3O7- δ on Si (001) paves the way for the potential exploration of cuprate materials in a variety of applications.

  2. Morphology evolution of single-crystalline hematite nanocrystals: magnetically recoverable nanocatalysts for enhanced facet-driven photoredox activity

    NASA Astrophysics Data System (ADS)

    Patra, Astam K.; Kundu, Sudipta K.; Bhaumik, Asim; Kim, Dukjoon

    2015-12-01

    We have developed a new green chemical approach for the shape-controlled synthesis of single-crystalline hematite nanocrystals in aqueous medium. FESEM, HRTEM and SAED techniques were used to determine the morphology and crystallographic orientations of each nanocrystal and its exposed facets. PXRD and HRTEM techniques revealed that the nanocrystals are single crystalline in nature; twins and stacking faults were not detected in these nanocrystals. The structural, vibrational, and electronic spectra of these nanocrystals were highly dependent on their shape. Different shaped hematite nanocrystals with distinct crystallographic planes have been synthesized under similar reaction conditions, which can be desired as a model for the purpose of properties comparison with the nanocrystals prepared under different reaction conditions. Here we investigated the photocatalytic performance of these different shaped-nanocrystals for methyl orange degradation in the presence of white light (λ > 420 nm). In this study, we found that the density of surface Fe3+ ions in particular facets was the key factor for the photocatalytic activity and was higher on the bitruncated-dodecahedron shape nanocrystals by coexposed {104}, {100} and {001} facets, attributing to higher catalytic activity. The catalytic activity of different exposed facet nanocrystals were as follows: {104} + {100} + {001} (bitruncated-dodecahedron) > {101} + {001} (bitruncated-octahedron) > {001} + {110} (nanorods) > {012} (nanocuboid) which provided the direct evidence of exposed facet-driven photocatalytic activity. The nanocrystals were easily recoverable using an external magnet and reused at least six times without significant loss of its catalytic activity.We have developed a new green chemical approach for the shape-controlled synthesis of single-crystalline hematite nanocrystals in aqueous medium. FESEM, HRTEM and SAED techniques were used to determine the morphology and crystallographic orientations of

  3. Simple and rapid green synthesis of micrometer scale single crystalline gold nanoplates using chitosan as the reducing agent

    NASA Astrophysics Data System (ADS)

    Alex, Saji; Tian, Kun; Teng, Shiang; Siegel, Gene; Tiwari, Ashutosh

    2014-11-01

    A simple, rapid and green chemical method for the synthesis of single crystalline gold nanoplates of several micrometeres in size has been demonstrated. The synthesis involved the reduction of HAuCl4 in aqueous solution using low molecular weight chitosan at boiling temperature for 25 min. The [Au3+]:[chitosan] molar ratio plays an important role in the formation of gold nanoplates and found that an optimized molar ratio in the range of 80 to 125 was suitable for the formation of nanoplates. The size and morphology of the nanoplates can be tuned by adjusting the molar ratio. In this process, the chitosan functions both as a reducing as well as a stabilizing agent and no other special agents were added to induce the nanoplate formation. The obtained nanoplates were single crystals with (1 1 1) planes as the basal planes with shapes of hexagonal, triangular, or truncated triangular plates.

  4. Influence of crystal orientation and ion bombardment on the nitrogen diffusivity in single-crystalline austenitic stainless steel

    SciTech Connect

    Martinavicius, A.; Abrasonis, G.; Moeller, W.

    2011-10-01

    The nitrogen diffusivity in single-crystalline AISI 316L austenitic stainless steel (ASS) during ion nitriding has been investigated at different crystal orientations ((001), (110), (111)) under variations of ion flux (0.3-0.7 mA cm{sup -2}), ion energy (0.5-1.2 keV), and temperature (370-430 deg. C). The nitrogen depth profiles obtained from nuclear reaction analysis are in excellent agreement with fits using the model of diffusion under the influence of traps, from which diffusion coefficients were extracted. At fixed ion energy and flux, the diffusivity varies by a factor up to 2.5 at different crystal orientations. At (100) orientation, it increases linearly with increasing ion flux or energy. The findings are discussed on the basis of atomistic mechanisms of interstitial diffusion, potential lattice distortions, local decomposition, and ion-induced lattice vibrational excitations.

  5. Influence of crystal orientation and ion bombardment on the nitrogen diffusivity in single-crystalline austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Martinavičius, A.; Abrasonis, G.; Möller, W.

    2011-10-01

    The nitrogen diffusivity in single-crystalline AISI 316L austenitic stainless steel (ASS) during ion nitriding has been investigated at different crystal orientations ((001), (110), (111)) under variations of ion flux (0.3-0.7 mA cm-2), ion energy (0.5-1.2 keV), and temperature (370-430 °C). The nitrogen depth profiles obtained from nuclear reaction analysis are in excellent agreement with fits using the model of diffusion under the influence of traps, from which diffusion coefficients were extracted. At fixed ion energy and flux, the diffusivity varies by a factor up to 2.5 at different crystal orientations. At (100) orientation, it increases linearly with increasing ion flux or energy. The findings are discussed on the basis of atomistic mechanisms of interstitial diffusion, potential lattice distortions, local decomposition, and ion-induced lattice vibrational excitations.

  6. Constructing MnO2/single crystalline ZnO nanorod hybrids with enhanced photocatalytic and antibacterial activity

    NASA Astrophysics Data System (ADS)

    Yu, Weiwei; Liu, Tiangui; Cao, Shiyi; Wang, Chen; Chen, Chuansheng

    2016-07-01

    In order to improve the photocatalytic and antibacterial activity of ZnO nanorods, ZnO nanorods decorated with MnO2 nanoparticles (MnO2/ZnO nanorod hybrids) were prepared by using microwave assisted coprecipitation method under the influence of hydrogen peroxide, and the structure, photocatalytic activity and antibacterial property of the products were studied. Experimental results indicated that MnO2 nanoparticles are decorated on the surface of single crystalline ZnO nanorods. Moreover, the resultant MnO2/ZnO nanorod hybrids have been proven to possess good photocatalytic and antibacterial activity, which their degradated efficiency for Rhodamin B (RhB) is twice as the pure ZnO nanorods. Enhancement for photocatalytic and antibacterial activity is mainly attributed to the low band gap energy and excellent electrochemical properties of MnO2 nanoparticles.

  7. Hydrothermal synthesis, characterizations and photoluminescence study of single crystalline hexagonal ZnO nanorods with three dimensional flowerlike microstructures

    NASA Astrophysics Data System (ADS)

    Kale, Rohidas B.; Hsu, Yung-Jung; Lin, Yi-Feng; Lu, Shih-Yuan

    2014-05-01

    A simple, low-cost, and environmentally benign hydrothermal approach has been successfully developed to synthesize uniform, large-scale well-crystallized ZnO nanorods with different aspect ratios that were united together to form three dimensional (3D) flowerlike structures. The method involved direct growth of ZnO 3D microstructures using aqueous solution of Zn(CH3COO)2 as the precursor and NaOH to adjust the pH of resultant solution. Surfactants or templates were not used during the entire synthetic process. Moreover, the morphology evolution of the ZnO nanorods with reaction time suggests a recrystallization-dissolution-growth mechanism that continuously takes place for prolonged interval of time. The XRD pattern of the as-grown ZnO nanorods and relevant analyses confirm the well crystallized hexagonal structure of the ZnO microstructures and no evidence of any other impurity phases. SEM observations reveal that the ZnO product grew in the form of nanorods that were united together to form 3D flowerlike morphology. The high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) shows that the ZnO nanorods were single crystalline and grew along the c-axis of the crystal plane. PL measurements of the as-synthesized nanorods exhibit excellent excitation features and strong band-edge UV luminescence even at room temperature. The uniform single crystalline, defect free, and high aspect ratio nanorods may find promising applications in optoelectronics and photo-catalysts. The growth habit of ZnO crystal is also illustrated. This method is suitable for large-scale production of ZnO microstructures and could be extended for syntheses of other metal oxides.

  8. Construction of single-crystalline supramolecular networks of perchlorinated hexa-peri-hexabenzocoronene on Au(111)

    SciTech Connect

    Zhang, Yi; Zhang, Yanfang; Li, Geng; Lu, Jianchen; Du, Shixuan E-mail: hjgao@iphy.ac.cn; Gao, Hong-Jun E-mail: hjgao@iphy.ac.cn; Lin, Xiao; Tan, Yuanzhi; Feng, Xinliang; Müllen, Klaus

    2015-03-14

    The self-assembly of the perchlorinated hexa-peri-hexabenzocoronene (PCHBC) molecules on Au(111) has been studied by a low temperature scanning tunneling microscopy (STM) combining with density functional theory based first principle calculations. Highly ordered supramolecular networks with single domains limited by the terraces are formed on Au(111) substrate. High resolution images of the PCHBC molecules, confirmed by first principle simulations, are obtained. It reveals the close-packed arrangement of the PCHBC molecules on Au(111). The calculated charge distribution of PCHBC molecules shows the existence of attractive halogen–halogen interaction between neighboring molecules. Compared with the disordered adsorption of hexa-peri-hexabenzocoronene on Au(111), we conclude that the formation of attractive ClCl interactions between neighbors is the key factor to form the highly ordered, close-packed networks. Due to the steric hindrance resulted from the peripheral chlorine atoms, the PCHBC molecule is contorted and forms the doubly concave conformation, which is different from the hexa-peri-hexabenzocoronene with a planar structure. By using this supramolecular network as a template, we deposited C{sub 60} molecules on it at room temperature with low coverage. The STM images taken at low temperature show that the C{sub 60} molecules are mono-dispersed on the networks and adsorb on top of the PCHBC molecules, forming a typical concave-convex host-guest system.

  9. Real-time observation of the swelling and hydrolysis of a single crystalline cellulose fiber catalyzed by cellulase 7B from Trichoderma reesei.

    PubMed

    Wang, Jingpeng; Quirk, Amanda; Lipkowski, Jacek; Dutcher, John R; Hill, Christopher; Mark, Adam; Clarke, Anthony J

    2012-06-26

    The biodegradation of cellulose involves the enzymatic action of cellulases (endoglucanases), cellobiohydrolases (exoglucanases), and β-glucosidases that act synergistically. The rate and efficiency of enzymatic hydrolysis of crystalline cellulose in vitro decline markedly with time, limiting the large-scale, cost-effective production of cellulosic biofuels. Several factors have been suggested to contribute to this phenomenon, but there is considerable disagreement regarding the relative importance of each. These earlier investigations were hampered by the inability to observe the disruption of crystalline cellulose and its subsequent hydrolysis directly. Here, we show the application of high-resolution atomic force microscopy to observe the swelling of a single crystalline cellulose fiber and its-hydrolysis in real time directly as catalyzed by a single cellulase, the industrially important cellulase 7B from Trichoderma reesei. Volume changes, the root-mean-square roughness, and rates of hydrolysis of the surfaces of single fibers were determined directly from the images acquired over time. Hydrolysis dominated the early stage of the experiment, and swelling dominated the later stage. The high-resolution images revealed that the combined action of initial hydrolysis followed by swelling exposed individual microfibrils and bundles of microfibrils, resulting in the loosening of the fiber structure and the exposure of microfibrils at the fiber surface. Both the hydrolysis and swelling were catalyzed by the native cellulase; under the same conditions, its isolated carbohydrate-binding module did not cause changes to crystalline cellulose. We anticipate that the application of our AFM-based analysis on other cellulolytic enzymes, alone and in combination, will provide significant insight into the process of cellulose biodegradation and greatly facilitate its application for the efficient and economical production of cellulosic ethanol.

  10. Phase transformation between Cu(In,Sn){sub 2} and Cu{sub 2}(In,Sn) compounds formed on single crystalline Cu substrate during solid state aging

    SciTech Connect

    Tian, Feifei; Liu, Zhi-Quan Guo, Jingdong

    2014-01-28

    Interfacial reactions between eutectic SnIn and single crystalline Cu during solid-state aging at low temperature were investigated systematically. Three types of phase transformations between Cu(In,Sn){sub 2} layer and Cu{sub 2}(In,Sn) layer were observed, which are Cu(In,Sn){sub 2} grows and Cu{sub 2}(In,Sn) consumes at 40 °C, Cu(In,Sn){sub 2} and Cu{sub 2}(In,Sn) grow simultaneously at 60 °C, as well as Cu(In,Sn){sub 2} consumes and Cu{sub 2}(In,Sn) grows at 80 and 100 °C. According to physicochemical approach, the chemical reactions at Cu/Cu{sub 2}(In,Sn)/Cu(In,Sn){sub 2}/SnIn interfaces were discussed in detail. It was concluded that the diffusion ability of Cu and In atoms dominated different phase transformations. When diffusion constants k{sub 1In2} > 8/3k{sub 1Cu2} Cu(In,Sn){sub 2} will grow, and if k{sub 1Cu2} ≫ k{sub 1In2} Cu{sub 2}(In,Sn) will grow. Both Cu(In,Sn){sub 2} and Cu{sub 2}(In,Sn) can grow in the condition of k{sub 1In2} ≈ k{sub 1Cu2}. The values of k{sub 1Cu2} and k{sub 1In2} at different temperatures on (100)Cu and (111)Cu substrate were also calculated or estimated by analyzing the growth kinetics of the compound layers.

  11. High mobility single-crystalline-like GaAs thin films on inexpensive flexible metal substrates by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Dutta, P.; Rathi, M.; Zheng, N.; Gao, Y.; Yao, Y.; Martinez, J.; Ahrenkiel, P.; Selvamanickam, V.

    2014-09-01

    We demonstrate heteroepitaxial growth of single-crystalline-like n and p-type doped GaAs thin films on inexpensive, flexible, and light-weight metal foils by metal-organic chemical vapor deposition. Single-crystalline-like Ge thin film on biaxially textured templates made by ion beam assisted deposition on metal foil served as the epitaxy enabling substrate for GaAs growth. The GaAs films exhibited strong (004) preferred orientation, sharp in-plane texture, low grain misorientation, strong photoluminescence, and a defect density of ˜107 cm-2. Furthermore, the GaAs films exhibited hole and electron mobilities as high as 66 and 300 cm2/V-s, respectively. High mobility single-crystalline-like GaAs thin films on inexpensive metal substrates can pave the path for roll-to-roll manufacturing of flexible III-V solar cells for the mainstream photovoltaics market.

  12. Defect evolution in single crystalline tungsten following low temperature and low dose neutron irradiation

    DOE PAGESBeta

    Hu, Xunxiang; Koyanagi, Takaaki; Fukuda, Makoto; Katoh, Yutai; Wirth, Brian D; Snead, Lance Lewis

    2016-01-01

    The tungsten plasma-facing components of fusion reactors will experience an extreme environment including high temperature, intense particle fluxes of gas atoms, high-energy neutron irradiation, and significant cyclic stress loading. Irradiation-induced defect accumulation resulting in severe thermo-mechanical property degradation is expected. For this reason, and because of the lack of relevant fusion neutron sources, the fundamentals of tungsten radiation damage must be understood through coordinated mixed-spectrum fission reactor irradiation experiments and modeling. In this study, high-purity (110) single-crystal tungsten was examined by positron annihilation spectroscopy and transmission electron microscopy following low-temperature (~90 °C) and low-dose (0.006 and 0.03 dpa) mixed-spectrum neutronmore » irradiation and subsequent isochronal annealing at 400, 500, 650, 800, 1000, 1150, and 1300 °C. The results provide insights into microstructural and defect evolution, thus identifying the mechanisms of different annealing behavior. Following 1 h annealing, ex situ characterization of vacancy defects using positron lifetime spectroscopy and coincidence Doppler broadening was performed. The vacancy cluster size distributions indicated intense vacancy clustering at 400 °C with significant damage recovery around 1000 °C. Coincidence Doppler broadening measurements confirm the trend of the vacancy defect evolution, and the S–W plots indicate that only a single type of vacancy cluster is present. Furthermore, transmission electron microscopy observations at selected annealing conditions provide supplemental information on dislocation loop populations and visible void formation. This microstructural information is consistent with the measured irradiation-induced hardening at each annealing stage. This provides insight into tungsten hardening and embrittlement due to irradiation-induced matrix defects.« less

  13. Defect evolution in single crystalline tungsten following low temperature and low dose neutron irradiation

    SciTech Connect

    Hu, Xunxiang; Koyanagi, Takaaki; Fukuda, Makoto; Katoh, Yutai; Wirth, Brian D; Snead, Lance Lewis

    2016-01-01

    The tungsten plasma-facing components of fusion reactors will experience an extreme environment including high temperature, intense particle fluxes of gas atoms, high-energy neutron irradiation, and significant cyclic stress loading. Irradiation-induced defect accumulation resulting in severe thermo-mechanical property degradation is expected. For this reason, and because of the lack of relevant fusion neutron sources, the fundamentals of tungsten radiation damage must be understood through coordinated mixed-spectrum fission reactor irradiation experiments and modeling. In this study, high-purity (110) single-crystal tungsten was examined by positron annihilation spectroscopy and transmission electron microscopy following low-temperature (~90 °C) and low-dose (0.006 and 0.03 dpa) mixed-spectrum neutron irradiation and subsequent isochronal annealing at 400, 500, 650, 800, 1000, 1150, and 1300 °C. The results provide insights into microstructural and defect evolution, thus identifying the mechanisms of different annealing behavior. Following 1 h annealing, ex situ characterization of vacancy defects using positron lifetime spectroscopy and coincidence Doppler broadening was performed. The vacancy cluster size distributions indicated intense vacancy clustering at 400 °C with significant damage recovery around 1000 °C. Coincidence Doppler broadening measurements confirm the trend of the vacancy defect evolution, and the S–W plots indicate that only a single type of vacancy cluster is present. Furthermore, transmission electron microscopy observations at selected annealing conditions provide supplemental information on dislocation loop populations and visible void formation. This microstructural information is consistent with the measured irradiation-induced hardening at each annealing stage. This provides insight into tungsten hardening and embrittlement due to irradiation-induced matrix defects.

  14. Defect evolution in single crystalline tungsten following low temperature and low dose neutron irradiation

    NASA Astrophysics Data System (ADS)

    Hu, Xunxiang; Koyanagi, Takaaki; Fukuda, Makoto; Katoh, Yutai; Snead, Lance L.; Wirth, Brian D.

    2016-03-01

    The tungsten plasma-facing components of fusion reactors will experience an extreme environment including high temperature, intense particle fluxes of gas atoms, high-energy neutron irradiation, and significant cyclic stress loading. Irradiation-induced defect accumulation resulting in severe thermo-mechanical property degradation is expected. For this reason, and because of the lack of relevant fusion neutron sources, the fundamentals of tungsten radiation damage must be understood through coordinated mixed-spectrum fission reactor irradiation experiments and modeling. In this study, high-purity (110) single-crystal tungsten was examined by positron annihilation spectroscopy and transmission electron microscopy following low-temperature (∼90 °C) and low-dose (0.006 and 0.03 dpa) mixed-spectrum neutron irradiation and subsequent isochronal annealing at 400, 500, 650, 800, 1000, 1150, and 1300 °C. The results provide insights into microstructural and defect evolution, thus identifying the mechanisms of different annealing behavior. Following 1 h annealing, ex situ characterization of vacancy defects using positron lifetime spectroscopy and coincidence Doppler broadening was performed. The vacancy cluster size distributions indicated intense vacancy clustering at 400 °C with significant damage recovery around 1000 °C. Coincidence Doppler broadening measurements confirm the trend of the vacancy defect evolution, and the S-W plots indicate that only a single type of vacancy cluster is present. Furthermore, transmission electron microscopy observations at selected annealing conditions provide supplemental information on dislocation loop populations and visible void formation. This microstructural information is consistent with the measured irradiation-induced hardening at each annealing stage, providing insight into tungsten hardening and embrittlement due to irradiation-induced matrix defects.

  15. Spin-related thermoelectric conversion in lateral spin-valve devices with single-crystalline Co2FeSi electrodes

    NASA Astrophysics Data System (ADS)

    Yamasaki, Kento; Oki, Soichiro; Yamada, Shinya; Kanashima, Takeshi; Hamaya, Kohei

    2015-04-01

    We demonstrate the conversion between a heat current and a spin current in Cu-based lateral spin valves (LSVs) with single-crystalline Co2FeSi (CFS) electrodes. We can observe the thermally induced spin injection from CFS into Cu resulting from the spin-dependent Seebeck effect, and the heat current generated by the spin-dependent Peltier effect can be detected even in the LSV structures. This study is an important step toward understanding heat-spin conversion in single-crystalline materials with various electronic band structures.

  16. Atomically Precise Growth of Catalytically Active Cobalt Sulfide on Flat Surfaces and within a Metal-Organic Framework via Atomic Layer Deposition.

    PubMed

    Peters, Aaron W; Li, Zhanyong; Farha, Omar K; Hupp, Joseph T

    2015-08-25

    Atomic layer deposition (ALD) has been employed as a new synthetic route to thin films of cobalt sulfide on silicon and fluorine-doped tin oxide platforms. The self-limiting nature of the stepwise synthesis is established through growth rate studies at different pulse times and temperatures. Additionally, characterization of the materials by X-ray diffraction and X-ray photoelectron spectroscopy indicates that the crystalline phase of these films has the composition Co9S8. The nodes of the metal-organic framework (MOF) NU-1000 were then selectively functionalized with cobalt sulfide via ALD in MOFs (AIM). Spectroscopic techniques confirm uniform deposition of cobalt sulfide throughout the crystallites, with no loss in crystallinity or porosity. The resulting material, CoS-AIM, is catalytically active for selective hydrogenation of m-nitrophenol to m-aminophenol, and outperforms the analogous oxide AIM material (CoO-AIM) as well as an amorphous CoSx reference material. These results reveal AIM to be an effective method of incorporating high surface area and catalytically active cobalt sulfide in metal-organic frameworks.

  17. Atomically Precise Growth of Catalytically Active Cobalt Sulfide on Flat Surfaces and within a Metal-Organic Framework via Atomic Layer Deposition.

    PubMed

    Peters, Aaron W; Li, Zhanyong; Farha, Omar K; Hupp, Joseph T

    2015-08-25

    Atomic layer deposition (ALD) has been employed as a new synthetic route to thin films of cobalt sulfide on silicon and fluorine-doped tin oxide platforms. The self-limiting nature of the stepwise synthesis is established through growth rate studies at different pulse times and temperatures. Additionally, characterization of the materials by X-ray diffraction and X-ray photoelectron spectroscopy indicates that the crystalline phase of these films has the composition Co9S8. The nodes of the metal-organic framework (MOF) NU-1000 were then selectively functionalized with cobalt sulfide via ALD in MOFs (AIM). Spectroscopic techniques confirm uniform deposition of cobalt sulfide throughout the crystallites, with no loss in crystallinity or porosity. The resulting material, CoS-AIM, is catalytically active for selective hydrogenation of m-nitrophenol to m-aminophenol, and outperforms the analogous oxide AIM material (CoO-AIM) as well as an amorphous CoSx reference material. These results reveal AIM to be an effective method of incorporating high surface area and catalytically active cobalt sulfide in metal-organic frameworks. PMID:26241521

  18. Improvements in Optical Properties of Semipolar r-Plane GaN Films Grown Using Atomically Flat ZnO Substrates and Room-Temperature Epitaxial Buffer Layers

    NASA Astrophysics Data System (ADS)

    Kobayashi, Atsushi; Kawano, Satoshi; Ueno, Kohei; Ohta, Jitsuo; Fujioka, Hiroshi

    2010-10-01

    We have investigated the structural and optical properties of semipolar r-plane GaN{1102} films grown on nearly-lattice-matched ZnO substrates with room-temperature (RT) epitaxial GaN buffer layers, putting special emphasis on the effect of surface treatment of the ZnO substrates. The full-width at half-maximum values of X-ray rocking curves for 1-µm-thick r-plane GaN layers grown at 700 °C on these RT-buffer layers, as measured using various X-ray incidence geometries, are in a range from 313 to 598 arcsec. Photoluminescence peaks attributable to structural defects in the r-plane GaN films have been shown to be reduced, and the near-band-edge emission has been enhanced by approximately 5 times by the use of atomically-flat r-plane ZnO substrates prepared by high-temperature annealing in air inside a box made of ZnO.

  19. Properties of isolated single crystalline and textured polycrystalline nano/sub-micrometre Nd2Fe14B particles obtained from milling of HDDR powder

    NASA Astrophysics Data System (ADS)

    Pal, S. K.; Güth, K.; Woodcock, T. G.; Schultz, L.; Gutfleisch, O.

    2013-09-01

    Textured, polycrystalline Nd2Fe14B powders, produced by dynamic hydrogenation disproportionation desorption and recombination (d-HDDR) were further processed by wet and surfactant-assisted ball milling. After 4 h of milling at 400 rpm in absolute ethanol and heptane + oleic acid, the polycrystalline d-HDDR particles had disintegrated, via intergranular fracture, into the individual grains i.e. isolated single crystalline particles of size 200 to 500 nm. An excellent degree of alignment was produced in the single crystalline particles using an applied magnetic field. This was reflected in the remanence of the field-aligned single crystalline powder (148.1 emu g-1) which was far higher than that of field-aligned un-milled d-HDDR powder (119.5 emu g-1). Milling the single crystalline powder further at 800 rpm in the same media produced polycrystalline flakes of size 0.2 to 1.0 µm. The polycrystalline flakes showed (0 0 l) in-plane texture and thus oriented edge to edge in an applied field.

  20. Ti3+-self doped brookite TiO2 single-crystalline nanosheets with high solar absorption and excellent photocatalytic CO2 reduction

    NASA Astrophysics Data System (ADS)

    Xin, Xiaoye; Xu, Tao; Wang, Lan; Wang, Chuanyi

    2016-03-01

    Black brookite TiO2 single-crystalline nanosheets with outstanding photocatalytic activity toward CO2 reduction is prepared by a facile oxidation-based hydrothermal reaction method combined with post-annealing treatment. Large amount of Ti3+ defects are introduced into the bulk of brookite nanoparticles, which increases the solar energy absorption and enhances the photocatalytic activity.

  1. Ti3+-self doped brookite TiO2 single-crystalline nanosheets with high solar absorption and excellent photocatalytic CO2 reduction

    PubMed Central

    Xin, Xiaoye; Xu, Tao; Wang, Lan; Wang, Chuanyi

    2016-01-01

    Black brookite TiO2 single-crystalline nanosheets with outstanding photocatalytic activity toward CO2 reduction is prepared by a facile oxidation-based hydrothermal reaction method combined with post-annealing treatment. Large amount of Ti3+ defects are introduced into the bulk of brookite nanoparticles, which increases the solar energy absorption and enhances the photocatalytic activity. PMID:27021203

  2. Synthesis of single-crystalline spinel LiMn2 O4 Nanorods for lithium-ion batteries with high rate capability and long cycle life.

    PubMed

    Xie, Xiuqiang; Su, Dawei; Sun, Bing; Zhang, Jinqiang; Wang, Chengyin; Wang, Guoxiu

    2014-12-15

    The long-standing challenge associated with capacity fading of spinel LiMn2 O4 cathode material for lithium-ion batteries is investigated. Single-crystalline spinel LiMn2 O4 nanorods were successfully synthesized by a template-engaged method. Porous Mn3 O4 nanorods were used as self-sacrificial templates, into which LiOH was infiltrated by a vacuum-assisted impregnation route. When used as cathode materials for lithium-ion batteries, the spinel LiMn2 O4 nanorods exhibited superior long cycle life owing to the one-dimensional nanorod structure, single-crystallinity, and Li-rich effect. LiMn2 O4 nanorods retained 95.6 % of the initial capacity after 1000 cycles at 3C rate. In particular, the nanorod morphology of the spinel LiMn2 O4 was well-preserved after a long-term cycling, suggesting the ultrahigh structural stability of the single crystalline spinel LiMn2 O4 nanorods. This result shows the promising applications of single-crystalline spinel LiMn2 O4 nanorods as cathode materials for lithium-ion batteries with high rate capability and long cycle life.

  3. Temperature dependent exchange bias training effect in single-crystalline BiFeO{sub 3}/Co bilayers

    SciTech Connect

    He, M. C.; You, B.; Tu, H. Q.; Rui, W. B.; Gao, Y.; Zhang, Y. Q.; Sheng, Y.; Xu, Q. Y. E-mail: jdu@nju.edu.cn; Xu, Y. B.; Du, J. E-mail: jdu@nju.edu.cn

    2015-05-07

    Single-crystalline BiFeO{sub 3} (BFO)/Co bilayers were prepared by combined pulsed laser deposition and magnetron sputtering on (001) SrTiO{sub 3} substrates. Exchange bias (EB) and accompanying training effect have been studied as a function of temperature (T) between 5 K and 300 K. A non-monotonic exchange field variation with sharp increase below 100 K has been observed. In the meanwhile, strong training effect was recorded when T < 100 K and it weakens monotonically with increasing T up to 300 K. These temperature dependent EB and training effect may be caused by the uncompensated spins in both the interfacial spin-glass (SG) phase at low temperature and the antiferromagnetic BFO layer at higher temperature. The low temperature EB training results can be well fitted by a modified Binek's model considering asymmetric changes of the pinning SG spins at the descending and the ascending branches.

  4. 3D spin-flop transition in enhanced 2D layered structure single crystalline TlCo2Se2.

    PubMed

    Jin, Z; Xia, Z-C; Wei, M; Yang, J-H; Chen, B; Huang, S; Shang, C; Wu, H; Zhang, X-X; Huang, J-W; Ouyang, Z-W

    2016-10-01

    The enhanced 2D layered structure single crystalline TlCo2Se2 has been successfully fabricated, which exhibits field-induced 3D spin-flop phase transitions. In the case of the magnetic field parallel to the c-axis (B//c), the applied magnetic field induces the evolution of the noncollinear helical magnetic coupling into a ferromagnetic (FM) state with all the magnetization of the Co ion parallel to the c-axis. A striking variation of the field-induced strain within the ab-plane is noticed in the magnetic field region of 20-30 T. In the case of the magnetic field perpendicular to the c-axis (B  ⊥  c), the inter-layer helical antiferromagnetic (AFM) coupling may transform to an initial canted AFM coupling, and then part of it transforms to an intermediate metamagnetic phase with the alignment of two-up-one-down Co magnetic moments and finally to an ultimate FM coupling in higher magnetic fields. The robust noncollinear AFM magnetic coupling is completely destroyed above 30 T. In combination with the measurements of magnetization, magnetoresistance and field-induced strain, a complete magnetic phase diagram of the TlCo2Se2 single crystal has been depicted, demonstrating complex magnetic structures even though the crystal geometry itself gives no indication of the magnetic frustration. PMID:27485370

  5. Detachment of CVD-grown graphene from single crystalline Ni films by a pure gas phase reaction

    NASA Astrophysics Data System (ADS)

    Zeller, Patrick; Henß, Ann-Kathrin; Weinl, Michael; Diehl, Leo; Keefer, Daniel; Lippmann, Judith; Schulz, Anne; Kraus, Jürgen; Schreck, Matthias; Wintterlin, Joost

    2016-11-01

    Despite great previous efforts there is still a high need for a simple, clean, and upscalable method for detaching epitaxial graphene from the metal support on which it was grown. We present a method based on a pure gas phase reaction that is free of solvents and polymer supports and avoids mechanical transfer steps. The graphene was grown on 150 nm thick, single crystalline Ni(111) films on Si(111) wafers with YSZ buffer layers. Its quality was monitored by using low energy electron diffraction and scanning tunneling microscopy. The gas phase etching uses a chemical transport reaction, the so-called Mond process, based on the formation of gaseous nickel tetracarbonyl in ~ 1 bar of CO at ~ 75 °C and by adding small amounts of sulfide catalysts. X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy were used to characterize the detached graphene. It was found that the method successfully removes the nickel from underneath the graphene layer, so that the graphene lies on the insulating oxide buffer layer. Small residual particles of nickel sulfide and cracks in the obtained graphene layer were identified. The defect concentrations were comparable to graphene samples obtained by wet chemical etching and by the bubbling transfer.

  6. TEA-assisted synthesis of single-crystalline Mn3O4 octahedrons and their magnetic properties

    NASA Astrophysics Data System (ADS)

    Li, Li; Liang, Jun; Kang, Hui; Fang, Junzhuo; Luo, Min; Jin, Xiaoyong

    2012-11-01

    Well-defined Mn3O4 octahedrons were synthesized by a facile triethanolamine (TEA)-assisted route under mild hydrothermal conditions. The chemical compositions and morphologies of the as-prepared samples were characterized in detail by power X-ray diffraction (XRD), fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), and field emission scanning electron microscopy (FE-SEM). The possible reaction mechanism and growth mechanism was discussed to elucidate the formation of the single-crystalline Mn3O4 octahedrons. The amounts of TEA and NaOH played important roles in controlling the morphology of the final products. Besides, the magnetic property was tested by a vibrating sample magnetometer (VSM), and the as-obtained sample exhibit ferrimagnetic behavior at low temperature and normal paramagnetic behavior at room temperature. The method can be easily controlled and expected to be applicable for the large-scale preparation of the Mn3O4 octahedrons.

  7. Growth mechanism of single-crystalline NiO thin films grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Roffi, Teuku Muhammad; Nozaki, Shinji; Uchida, Kazuo

    2016-10-01

    Nickel oxide (NiO) thin films were grown by atmospheric-pressure metal organic chemical vapor deposition (APMOCVD). Growth was carried out using various growth parameters, including the growth temperature, the input precursor (O2/Ni) ratio, and the type of substrate material. Effects of the growth parameters on the structural and electrical properties of the films were investigated. X-ray diffraction analysis revealed that the crystal structure and quality were strongly affected by the growth temperature and the type of substrate material. At an optimized growth temperature, single-crystalline NiO films were grown on MgO(100) and MgO(111) substrates in a cube-on-cube orientation relationship, while on an Al2O3(001) substrate, the film was grown in the NiO[111] direction. The use of MgO substrates successfully suppressed the formation of twin defects, which have been frequently reported in the growth of NiO. The difference in the formation of the twin defects on MgO and Al2O3 substrates was discussed. It was observed that the resistivity dependence on crystal quality was affected by the choice of substrate material. The effects of the precursor ratio on the transmittance and resistivity of the films were also investigated. Improved transparency in the visible wavelength region and higher conductivity were found in films grown with higher O2/Ni ratios.

  8. Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys

    DOE PAGESBeta

    Lu, Chenyang; Jin, Ke; Béland, Laurent K.; Zhang, Feifei; Yang, Taini; Qiao, Liang; Zhang, Yanwen; Bei, Hongbin; Christen, Hans M.; Stoller, Roger E.; et al

    2016-02-01

    We report that energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters farmore » exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance.« less

  9. Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys.

    PubMed

    Lu, Chenyang; Jin, Ke; Béland, Laurent K; Zhang, Feifei; Yang, Taini; Qiao, Liang; Zhang, Yanwen; Bei, Hongbin; Christen, Hans M; Stoller, Roger E; Wang, Lumin

    2016-01-01

    Energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters far exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance.

  10. Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys.

    PubMed

    Lu, Chenyang; Jin, Ke; Béland, Laurent K; Zhang, Feifei; Yang, Taini; Qiao, Liang; Zhang, Yanwen; Bei, Hongbin; Christen, Hans M; Stoller, Roger E; Wang, Lumin

    2016-01-01

    Energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters far exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance. PMID:26829570

  11. Perovskite Solar Cells with Near 100% Internal Quantum Efficiency Based on Large Single Crystalline Grains and Vertical Bulk Heterojunctions

    DOE PAGESBeta

    Yang, Bin; Dyck, Ondrej; Poplawsky, Jonathan; Keum, Jong; Puretzky, Alexander; Das, Sanjib; Ivanov, Ilia; Rouleau, Christopher; Duscher, Gerd; Geohegan, David; et al

    2015-07-09

    Grain boundaries (GBs) as defects in the crystal lattice detrimentally impact the power conversion efficiency (PCE) of polycrystalline solar cells, particularly in recently emerging hybrid perovskites where non-radiative recombination processes lead to significant carrier losses. Here, the beneficial effects of activated vertical GBs are demonstrated by first growing large, vertically-oriented methylammonium lead tri-iodide (CH3NH3PbI3) single-crystalline grains. We show that infiltration of p-type doped 2 -7,7 -tetrakis(N,Ndi-p-methoxyphenylamine)-9,9-spirobifluorene (Spiro-OMeTAD) into CH3NH3PbI3 films along the GBs creates space charge regions to suppress non-radiative recombination and enhance carrier collection efficiency. Solar cells with such activated GBs yielded average PCE of 16.3 ± 0.9%, whichmore » are among the best solution-processed perovskite devices. As an important alternative to growing ideal CH3NH3PbI3 single crystal films, which is difficult to achieve for such fast-crystallizing perovskites, activating GBs paves a way to design a new type of bulk heterojunction hybrid perovskite photovoltaics toward theoretical maximum PCE.« less

  12. Specific Heat of Single Crystalline Nd0.5Sr0.5MnO3

    NASA Astrophysics Data System (ADS)

    Sanchez, Carlos; Aguilar, Victor; Bernal, Oscar; Zhao, Guo-Meng

    2014-03-01

    Substantial studies of magnetization and specific heat on Nd0.5Sr0.5MnO3 have demonstrated the existence of a charge ordering (CO), ferromagnetic (FM), antiferromagnetic (AFM) transitions. In this work, the specific heat of two single crystalline Nd0.5Sr0.5MnO3 samples, one containing 16O and the other highly concentrated 18O, was measured as a function of temperature, from 3K to 300K, at both zero and 50 kOe applied field. Measurements were done using a Quantum Design Physical Property Measurement System (PPMS) with Specific Heat option. The FM transition was found to depend on the isotope mass, which seems to agree with previous works. The CO transitions was observed as a sharp peak at the CO temperature (Tco), which seems to depend strongly on field, oxygen isotope mass, and thermal cycling history. Work Supported by NSF-DMR 1105380. CSU-LSAMP is supported by the National Science Foundation under Grant # HRD-1302873 and the CSU Office of the Chancellor.

  13. Single crystalline VO2 nanosheets: A cathode material for sodium-ion batteries with high rate cycling performance

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Jiang, Bo; Hu, Liwen; Lin, Zheshuai; Hou, Jungang; Jiao, Shuqiang

    2014-03-01

    In recent years, with the growing demands for large-scale applications of rechargeable batteries, the eco-friendly sodium-ion batteries with low price and high charge-discharge rates have attracted much attention. In this work, using a simple hydrothermal process, we successfully synthesize single crystalline VO2 parallel ultrathin nanosheets for the cathode material in sodium-ion batteries. Combined the XRD, XPS, electrochemical measurements with the first-principles simulations, the charge-discharge performance and the mechanism of Na insertion and extraction into/from the VO2 structure have systematically studied. The results reveal that the NaxVO2 products possess semiconductor properties and the interlayer distance almost keeps constant during charge and discharge process, which is beneficial to the transmission of Na ions. The charge and discharge process occurs between Na0.3VO2 and NaVO2. Even at a large current density of 500 mA g-1, the discharge capacity can still keep at 108 mAh g-1. As a cathode material for sodium-ion batteries, the results are outstanding and provide a possibility of large-scale applications for rechargeable sodium-ion batteries.

  14. Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys

    NASA Astrophysics Data System (ADS)

    Lu, Chenyang; Jin, Ke; Béland, Laurent K.; Zhang, Feifei; Yang, Taini; Qiao, Liang; Zhang, Yanwen; Bei, Hongbin; Christen, Hans M.; Stoller, Roger E.; Wang, Lumin

    2016-02-01

    Energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters far exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance.

  15. Ellipsometric study of the polysilicon/thin oxide/single-crystalline silicon structure and its change upon annealing

    NASA Astrophysics Data System (ADS)

    Petrik, P.; Lohner, T.; Fried, M.; Gyulai, J.; Boell, U.; Berger, R.; Lehnert, W.

    2002-09-01

    Polysilicon/thin oxide/single-crystalline silicon structures used as emitters of bipolar transistors were measured using spectroscopic ellipsometry. The thin SiOx layer was deposited on the substrate in a rapid thermal processing chamber, then polysilicon was deposited, implanted with As, and annealed. During annealing the SiOx layer dissolves to islands retarding the diffusion of As, which results in a shallow p-n junction. The process--and as a consequence, the device performance--depends sensitively on the thickness of the oxide layer. We developed optical models to measure the thickness of the SiOx layer at each process step, i.e., after SiOx deposition, after polysilicon deposition, and after annealing. The structure, the surface quality, and the homogeneity of the polysilicon layers were obtained from the same optical model. The thickness of the initially 0.76-0.86 nm SiOx layer decreased to the detection limit of about 0.2 nm during annealing, together with a significant crystallization of the deposited amorphous Si resulting in a perfectly smooth surface with a native oxide layer. The uncertainty of the measurement of the SiOx layer after annealing was typically 0.2 nm even below the polysilicon layer of about 150 nm. Our results show that ellipsometry is a proper tool for the measurement of the thickness of the buried SiOx boundary layer, which can be applied as an in line or in situ measurement as well.

  16. Application of single-crystalline PMN-PT and PIN-PMN-PT in high-performance pyroelectric detectors.

    PubMed

    Yu, Ping; Ji, Yadong; Neumann, Norbert; Lee, Sang-Goo; Luo, Hasou; Es-Souni, Mohammed

    2012-09-01

    The suitability for use in pyroelectric detectors of single-crystalline doped and undoped lead indium niobate-lead magnesium niobate-lead titanate was tested and compared with high-quality Mn-doped lead magnesium niobate-lead titanate and standard lithium tantalate. Pyroelectric and dielectric measurements confirmed an increased processing and operating temperature range because of the higher phase transitions of lead indium niobate-lead magnesium niobate-lead titanate. Pyroelectric coefficients of 705 to 770 μC/m(2)K were obtained with doped and undoped lead indium niobate-lead magnesium niobate-lead titanate, which are about 70% to 80% of the pyroelectric coefficient of lead magnesium niobate-lead titanate but 4 times higher than standard lithium tantalate. Manganese doping has been proved as a solution to decrease the dielectric loss of lead magnesium niobate-lead titanate and it also works well for lead indium niobate-lead magnesium niobate-lead titanate. An outstanding specific detectivity D* of about 1.1 · 10(9) cm·Hz(1/2)/W was achieved at a frequency of 2 Hz for Mn-doped lead magnesium niobate-based detectors. PMID:23007771

  17. Selective oxidation and internal nitridation during high-temperature exposure of single-crystalline nickel-base superalloys

    SciTech Connect

    Krupp, U.; Christ, H.J.

    2000-01-01

    The process of internal nitridation of the three commercial single-crystalline nickel-base superalloys CMSX-2, CMSX-6, and SRR99 has been studied in air and oxygen-free nitrogen atmospheres at 800 C to 1,100 C using thermogravimetric techniques supplemented by extensive microstructural examinations. Non-protective oxide formation, particularly cracking and spalling at edges or curved surfaces, enables nitrogen to penetrate into the alloy leading to the precipitation of stable Ti and Al nitrides. The high-temperature corrosion behavior of the superalloys studied is strongly affected by composition differences between dendritic and interdendritic areas due to segregation resulting in an inhomogeneous internal precipitation zone. Furthermore, the stability of the strengthening {radical} phase (N3i(Al, Ti, Ta)) in front of the growing internal-nitridation zone was observed to depend clearly on the alloy composition. Therefore, the near-surface area of the alloys can be weakened by {radical} depletion and by embrittlement resulting from internal-nitride precipitation. The results obtained on the nickel-base superalloys are discussed, taking into account the results of a computer-based simulation of internal-corrosion processes. Furthermore, results on Ni-base model alloys of the system Ni-Cr-Al-Ti provided information on the role of the alloy composition. It was found that a higher Cr concentration seems to increase the nitrogen solubility and diffusion in Ni-base alloys.

  18. 3D spin-flop transition in enhanced 2D layered structure single crystalline TlCo2Se2

    NASA Astrophysics Data System (ADS)

    Jin, Z.; Xia, Z.-C.; Wei, M.; Yang, J.-H.; Chen, B.; Huang, S.; Shang, C.; Wu, H.; Zhang, X.-X.; Huang, J.-W.; Ouyang, Z.-W.

    2016-10-01

    The enhanced 2D layered structure single crystalline TlCo2Se2 has been successfully fabricated, which exhibits field-induced 3D spin-flop phase transitions. In the case of the magnetic field parallel to the c-axis (B//c), the applied magnetic field induces the evolution of the noncollinear helical magnetic coupling into a ferromagnetic (FM) state with all the magnetization of the Co ion parallel to the c-axis. A striking variation of the field-induced strain within the ab-plane is noticed in the magnetic field region of 20-30 T. In the case of the magnetic field perpendicular to the c-axis (B  ⊥  c), the inter-layer helical antiferromagnetic (AFM) coupling may transform to an initial canted AFM coupling, and then part of it transforms to an intermediate metamagnetic phase with the alignment of two-up-one-down Co magnetic moments and finally to an ultimate FM coupling in higher magnetic fields. The robust noncollinear AFM magnetic coupling is completely destroyed above 30 T. In combination with the measurements of magnetization, magnetoresistance and field-induced strain, a complete magnetic phase diagram of the TlCo2Se2 single crystal has been depicted, demonstrating complex magnetic structures even though the crystal geometry itself gives no indication of the magnetic frustration.

  19. Perovskite Solar Cells with Near 100% Internal Quantum Efficiency Based on Large Single Crystalline Grains and Vertical Bulk Heterojunctions

    SciTech Connect

    Yang, Bin; Dyck, Ondrej; Poplawsky, Jonathan; Keum, Jong; Puretzky, Alexander; Das, Sanjib; Ivanov, Ilia; Rouleau, Christopher; Duscher, Gerd; Geohegan, David; Xiao, Kai

    2015-07-09

    Grain boundaries (GBs) as defects in the crystal lattice detrimentally impact the power conversion efficiency (PCE) of polycrystalline solar cells, particularly in recently emerging hybrid perovskites where non-radiative recombination processes lead to significant carrier losses. Here, the beneficial effects of activated vertical GBs are demonstrated by first growing large, vertically-oriented methylammonium lead tri-iodide (CH3NH3PbI3) single-crystalline grains. We show that infiltration of p-type doped 2 -7,7 -tetrakis(N,Ndi-p-methoxyphenylamine)-9,9-spirobifluorene (Spiro-OMeTAD) into CH3NH3PbI3 films along the GBs creates space charge regions to suppress non-radiative recombination and enhance carrier collection efficiency. Solar cells with such activated GBs yielded average PCE of 16.3 ± 0.9%, which are among the best solution-processed perovskite devices. As an important alternative to growing ideal CH3NH3PbI3 single crystal films, which is difficult to achieve for such fast-crystallizing perovskites, activating GBs paves a way to design a new type of bulk heterojunction hybrid perovskite photovoltaics toward theoretical maximum PCE.

  20. Magnetization reversal process in Fe/Si (001) single-crystalline film investigated by planar Hall effect

    NASA Astrophysics Data System (ADS)

    Ye, Jun; He, Wei; Hu, Bo; Tang, Jin; Zhang, Yong-Sheng; Zhang, Xiang-Qun; Chen, Zi-Yu; Cheng, Zhao-Hua

    2015-02-01

    A planar Hall effect (PHE) is introduced to investigate the magnetization reversal process in single-crystalline iron film grown on a Si (001) substrate. Owing to the domain structure of iron film and the characteristics of PHE, the magnetization switches sharply in an angular range of the external field for two steps of 90° domain wall displacement and one step of 180° domain wall displacement near the easy axis, respectively. However, the magnetization reversal process near the hard axis is completed by only one step of 90° domain wall displacement and then rotates coherently. The magnetization reversal process mechanism near the hard axis seems to be a combination of coherent rotation and domain wall displacement. Furthermore, the domain wall pinning energy and uniaxial magnetic anisotropy energy can also be derived from the PHE measurement. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB921801 and 2012CB933102), the National Natural Science Foundation of China (Grant Nos. 11374350, 11034004, 11274361, 11274033, 11474015, and 61227902), and the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20131102130005).

  1. Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys

    PubMed Central

    Lu, Chenyang; Jin, Ke; Béland, Laurent K.; Zhang, Feifei; Yang, Taini; Qiao, Liang; Zhang, Yanwen; Bei, Hongbin; Christen, Hans M.; Stoller, Roger E.; Wang, Lumin

    2016-01-01

    Energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters far exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance. PMID:26829570

  2. A facile strategy to fabricate high-quality single crystalline brookite TiO2 nanoarrays and their photoelectrochemical properties

    NASA Astrophysics Data System (ADS)

    Choi, Mingi; Yong, Kijung

    2014-10-01

    Vertically aligned high-quality single crystalline brookite TiO2 nanoarrays were synthesized for the first time using an environmentally benign one-step hydrothermal reaction. They have a unique bullet-shaped structure which has a length of 700-1000 nm and a width of 150-250 nm with a sharpened tip structure. By adjusting the concentration of NaOH in hydrothermal reaction, we could also synthesize other types of TiO2 nanostructures including anatase TiO2 nanotubes/nanowires. The morphologies and crystal structures of the products were confirmed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Their vertically aligned structures facilitate their application as photoanodes in photoelectrochemical cells, and the photoelectrochemical properties such as photocurrent density and open circuit voltage were measured in a three-electrode electrochemical cell with TiO2 nanoarrays, Ag/AgCl and a Pt flag as the working, reference and counter electrodes, respectively, incorporating a 0.1 M NaOH electrolyte solution. The fabricated brookite TiO2 nanoarrays exhibited a highly enhanced photocurrent density and a longer electron lifetime compared with anatase TiO2 nanoarrays with similar lengths.Vertically aligned high-quality single crystalline brookite TiO2 nanoarrays were synthesized for the first time using an environmentally benign one-step hydrothermal reaction. They have a unique bullet-shaped structure which has a length of 700-1000 nm and a width of 150-250 nm with a sharpened tip structure. By adjusting the concentration of NaOH in hydrothermal reaction, we could also synthesize other types of TiO2 nanostructures including anatase TiO2 nanotubes/nanowires. The morphologies and crystal structures of the products were confirmed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Their vertically aligned structures facilitate their application as photoanodes in photoelectrochemical

  3. Well-Defined Nanostructured, Single-Crystalline TiO2 Electron Transport Layer for Efficient Planar Perovskite Solar Cells.

    PubMed

    Choi, Jongmin; Song, Seulki; Hörantner, Maximilian T; Snaith, Henry J; Park, Taiho

    2016-06-28

    An electron transporting layer (ETL) plays an important role in extracting electrons from a perovskite layer and blocking recombination between electrons in the fluorine-doped tin oxide (FTO) and holes in the perovskite layers, especially in planar perovskite solar cells. Dense TiO2 ETLs prepared by a solution-processed spin-coating method (S-TiO2) are mainly used in devices due to their ease of fabrication. Herein, we found that fatal morphological defects at the S-TiO2 interface due to a rough FTO surface, including an irregular film thickness, discontinuous areas, and poor physical contact between the S-TiO2 and the FTO layers, were inevitable and lowered the charge transport properties through the planar perovskite solar cells. The effects of the morphological defects were mitigated in this work using a TiO2 ETL produced from sputtering and anodization. This method produced a well-defined nanostructured TiO2 ETL with an excellent transmittance, single-crystalline properties, a uniform film thickness, a large effective area, and defect-free physical contact with a rough substrate that provided outstanding electron extraction and hole blocking in a planar perovskite solar cell. In planar perovskite devices, anodized TiO2 ETL (A-TiO2) increased the power conversion efficiency by 22% (from 12.5 to 15.2%), and the stabilized maximum power output efficiency increased by 44% (from 8.9 to 12.8%) compared with S-TiO2. This work highlights the importance of the ETL geometry for maximizing device performance and provides insights into achieving ideal ETL morphologies that remedy the drawbacks observed in conventional spin-coated ETLs.

  4. Sonochemical synthesis and luminescence properties of single-crystalline BaF{sub 2}:Eu{sup 3+} nanospheres

    SciTech Connect

    Zhu Ling; Meng Jian; Cao Xueqiang

    2007-11-15

    BaF{sub 2} nanocrystals doped with 5.0 mol% Eu{sup 3+} has been successfully synthesized via a facile, quick and efficient ultrasonic solution route employing the reactions between Ba(NO{sub 3}){sub 2}, Eu(NO{sub 3}){sub 3} and KBF{sub 4} under ambient conditions. The product was characterized via X-ray powder diffraction (XRD), scanning electron micrographs (SEM), transmission electron microscopy (TEM), high-resolution transmission electron micrographs (HRTEM), selected area electron diffraction (SAED) and photoluminescence (PL) spectra. The ultrasonic irradiation has a strong effect on the morphology of the BaF{sub 2}:Eu{sup 3+} particles. The caddice-sphere-like particles with an average diameter of 250 nm could be obtained with ultrasonic irradiation, whereas only olive-like particles were produced without ultrasonic irradiation. The results of XRD indicate that the obtained BaF{sub 2}:Eu{sup 3+} nanospheres crystallized well with a cubic structure. The PL spectrum shows that the BaF{sub 2}:Eu{sup 3+} nanospheres has the characteristic emission of Eu{sup 3+5}D{sub 0}-{sup 7}F{sub J} (J=1-4) transitions, with the magnetic dipole {sup 5}D{sub 0}-{sup 7}F{sub 1} allowed transition (590 nm) being the most prominent emission line. - Graphical abstract: Single-crystalline BaF{sub 2}:Eu{sup 3+} (5.0 mol% Eu{sup 3+}) caddice spheres has been successfully synthesized via a facile, quick and efficient ultrasonic solution route employing the reactions between Ba(NO{sub 3}){sub 2}, Eu(NO{sub 3}){sub 3} and KBF{sub 4} under ambient conditions. This simple and unique synthetic method without any template or surfactant, which avoids the subsequent complicated workup procedures for the removal of the template or surfactant, has a potential advantage for synthesis of material with novel morphology.

  5. Nonaqueous sol-gel synthesis and growth mechanism of single crystalline TiO{sub 2} nanorods with high photocatalytic activity

    SciTech Connect

    Jia Huimin; Zheng Zhi; Zhao Hongxiao; Zhang Lizhi; Zou Zhigang

    2009-06-03

    In this paper, we report on a nonaqueous synthesis of single crystalline anatase TiO{sub 2} nanorods by reaction between TiCl{sub 4} and benzyl alcohol at a low temperature of 80 deg. C. The resulting samples were characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, nitrogen adsorption, X-ray photoelectron spectrometry and UV-vis diffuse reflectance spectroscopy. We proposed that the TiO{sub 2} nanorods were formed through an oriented attachment mechanism. More importantly, these single crystalline anatase TiO{sub 2} nanorods exhibited significantly higher photocatalytic activities than commercial photocatalyst P25. This study provides an environmentally friendly and economic approach to produce highly active TiO{sub 2} photocatalyst.

  6. Formation of hollow and mesoporous structures in single-crystalline microcrystals of metal-organic frameworks via double-solvent mediated overgrowth.

    PubMed

    Chou, Lien-Yang; Hu, Pan; Zhuang, Jia; Morabito, Joseph V; Ng, Ka Chon; Kao, Ya-Chuan; Wang, Shao-Chun; Shieh, Fa-Kuen; Kuo, Chun-Hong; Tsung, Chia-Kuang

    2015-12-14

    The creation of hierarchical porosity in metal-organic frameworks (MOFs) could benefit various applications of MOFs such as gas storage and separation. Having single-crystalline microcrystals instead of poly-crystalline composites is critical for these potential applications of MOFs with hierarchical porosity. We developed a room temperature synthetic method to generate uniform hollow and mesoporous zeolitic imidazolate framework-8 (ZIF-8) microcrystals with a single-crystalline structure via overgrowing a ZIF-8 shell in methanol solution on a ZIF-8 core with water adsorbed in the pores. The cavities formed as a result of the different solvent micro-environment. This double-solvent mediated overgrowth method could be applied to prepare other MOFs with hierarchical porosity.

  7. Improvement of electroluminescence performance by integration of ZnO nanowires and single-crystalline films on ZnO/GaN heterojunction

    SciTech Connect

    Shi, Zhifeng; Zhang, Yuantao Cui, Xijun; Wu, Bin; Zhuang, Shiwei; Yang, Fan; Zhang, Baolin; Du, Guotong; Yang, Xiaotian

    2014-03-31

    Heterojunction light-emitting diodes based on n-ZnO nanowires/ZnO single-crystalline films/p-GaN structure have been demonstrated for an improved electroluminescence performance. A highly efficient ultraviolet emission was observed under forward bias. Compared with conventional n-ZnO/p-GaN structure, high internal quantum efficiency and light extraction efficiency were simultaneously considered in the proposed diode. In addition, the diode can work continuously for ∼10 h with only a slight degradation in harsh environments, indicating its good reliability and application prospect in the future. This route opens possibilities for the development of advanced nanoscale devices in which the advantages of ZnO single-crystalline films and nanostructures can be integrated together.

  8. Formation of hollow and mesoporous structures in single-crystalline microcrystals of metal-organic frameworks via double-solvent mediated overgrowth

    NASA Astrophysics Data System (ADS)

    Chou, Lien-Yang; Hu, Pan; Zhuang, Jia; Morabito, Joseph V.; Ng, Ka Chon; Kao, Ya-Chuan; Wang, Shao-Chun; Shieh, Fa-Kuen; Kuo, Chun-Hong; Tsung, Chia-Kuang

    2015-11-01

    The creation of hierarchical porosity in metal-organic frameworks (MOFs) could benefit various applications of MOFs such as gas storage and separation. Having single-crystalline microcrystals instead of poly-crystalline composites is critical for these potential applications of MOFs with hierarchical porosity. We developed a room temperature synthetic method to generate uniform hollow and mesoporous zeolitic imidazolate framework-8 (ZIF-8) microcrystals with a single-crystalline structure via overgrowing a ZIF-8 shell in methanol solution on a ZIF-8 core with water adsorbed in the pores. The cavities formed as a result of the different solvent micro-environment. This double-solvent mediated overgrowth method could be applied to prepare other MOFs with hierarchical porosity.The creation of hierarchical porosity in metal-organic frameworks (MOFs) could benefit various applications of MOFs such as gas storage and separation. Having single-crystalline microcrystals instead of poly-crystalline composites is critical for these potential applications of MOFs with hierarchical porosity. We developed a room temperature synthetic method to generate uniform hollow and mesoporous zeolitic imidazolate framework-8 (ZIF-8) microcrystals with a single-crystalline structure via overgrowing a ZIF-8 shell in methanol solution on a ZIF-8 core with water adsorbed in the pores. The cavities formed as a result of the different solvent micro-environment. This double-solvent mediated overgrowth method could be applied to prepare other MOFs with hierarchical porosity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06532a

  9. Porous and single-crystalline ZnO nanobelts: fabrication with annealing precursor nanobelts, and gas-sensing and optoelectronic performance

    NASA Astrophysics Data System (ADS)

    Jin, Xiao-Bo; Li, Yi-Xiang; Su, Yao; Guo, Zheng; Gu, Cui-Ping; Huang, Jia-Rui; Meng, Fan-Li; Huang, Xing-Jiu; Li, Min-Qiang; Liu, Jin-Huai

    2016-09-01

    Porous and single-crystalline ZnO nanobelts have been prepared through annealing precursors of ZnSe · 0.5N2H4 well-defined and smooth nanobelts, which have been synthesized via a simple hydrothermal method. The composition and morphology evolutions with the calcination temperatures have been investigated in detail for as-prepared precursor nanobelts, suggesting that they can be easily transformed into ZnO nanobelts by preserving their initial morphology via calcination in air. In contrast, the obtained ZnO nanobelts are densely porous, owing to the thermal decomposition and oxidization of the precursor nanobelts. More importantly, the achieved porous ZnO nanobelts are single-crystalline, different from previously reported ones. Motivated by the intrinsic properties of the porous structure and good electronic transporting ability of single crystals, their gas-sensing performance has been further explored. It is demonstrated that porous ZnO single-crystalline nanobelts exhibit high response and repeatability toward volatile organic compounds, such as ethanol and acetone, with a short response/recovery time. Furthermore, their optoelectronic behaviors indicate that they can be promisingly employed to fabricate photoelectrochemical sensors.

  10. Pulsed laser deposition of single-crystalline Cu7In3/CuIn0.8Ga0.2Se2 core/shell nanowires

    PubMed Central

    2014-01-01

    Single-crystalline Cu7In3/CuIn0.8Ga0.2Se2 (CI/CIGS) core/shell nanowires are fabricated by pulsed laser deposition with Ni nanoparticles as catalyst. The CI/CIGS core/shell nanowires are made up of single-crystalline CI cores surrounded by single-crystalline CIGS shells. The CI/CIGS nanowires are grown at a considerably low temperature (350°C ~ 450°C) by vapor-liquid-solid mode combined with vapor-solid mode. The distribution density of the nanowires increases with the increasing of the deposition duration, and the substrate temperature determines the lengths of the nanowires. The U-V absorption spectra of the CIGS thin films with and without the CI/CIGS core/shell nanowires demonstrate that the CI/CIGS nanowires can remarkably enhance the absorption of CIGS thin films in the spectrum range of 300 to 900 nm. PACS 61.46. + w; 61.41.e; 81.15.Fg; 81.07.b PMID:25520597

  11. Facile synthesis of porous single crystalline ZnO nanoplates and their application in photocatalytic reduction of Cr(VI) in the presence of phenol.

    PubMed

    Jin, Zhen; Zhang, Yong-Xing; Meng, Fan-Li; Jia, Yong; Luo, Tao; Yu, Xin-Yao; Wang, Jin; Liu, Jin-Huai; Huang, Xing-Jiu

    2014-07-15

    Porous single crystalline ZnO nanoplates were successfully synthesized through a facile and cost-effective hydrothermal process at low temperature condition, followed by annealing of the zinc carbonate hydroxide hydrate precursors. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) measurements. The porous single crystalline ZnO nanoplates are with 12nm thickness and pore ranging from 10nm to several tens of nanometers. The porous structure of the ZnO nanoplates caused large amount of surface defects which worked as photogenerated holes' shallow trappers and largely restrained the recombination of photogenerated electrons and holes, resulting in a significantly high photocatalytic activity and durability toward the photoreduction of Cr(VI) under UV irradiation. Moreover, a synergistic effect, that is, increased photocatalytic reduction of Cr(VI) and degradation of phenol, can be observed. Furthermore, the synergistic photocatalytic mechanism has also been discussed. Those results present an enlightenment to employ porous single crystalline nanomaterials to remove Cr(VI) and organic pollutants simultaneously.

  12. High mobility single-crystalline-like GaAs thin films on inexpensive flexible metal substrates by metal-organic chemical vapor deposition

    SciTech Connect

    Dutta, P. Rathi, M.; Gao, Y.; Yao, Y.; Selvamanickam, V.; Zheng, N.; Ahrenkiel, P.; Martinez, J.

    2014-09-01

    We demonstrate heteroepitaxial growth of single-crystalline-like n and p-type doped GaAs thin films on inexpensive, flexible, and light-weight metal foils by metal-organic chemical vapor deposition. Single-crystalline-like Ge thin film on biaxially textured templates made by ion beam assisted deposition on metal foil served as the epitaxy enabling substrate for GaAs growth. The GaAs films exhibited strong (004) preferred orientation, sharp in-plane texture, low grain misorientation, strong photoluminescence, and a defect density of ∼10{sup 7 }cm{sup −2}. Furthermore, the GaAs films exhibited hole and electron mobilities as high as 66 and 300 cm{sup 2}/V-s, respectively. High mobility single-crystalline-like GaAs thin films on inexpensive metal substrates can pave the path for roll-to-roll manufacturing of flexible III-V solar cells for the mainstream photovoltaics market.

  13. Porous and single-crystalline ZnO nanobelts: fabrication with annealing precursor nanobelts, and gas-sensing and optoelectronic performance.

    PubMed

    Jin, Xiao-Bo; Li, Yi-Xiang; Su, Yao; Guo, Zheng; Gu, Cui-Ping; Huang, Jia-Rui; Meng, Fan-Li; Huang, Xing-Jiu; Li, Min-Qiang; Liu, Jin-Huai

    2016-09-01

    Porous and single-crystalline ZnO nanobelts have been prepared through annealing precursors of ZnSe · 0.5N2H4 well-defined and smooth nanobelts, which have been synthesized via a simple hydrothermal method. The composition and morphology evolutions with the calcination temperatures have been investigated in detail for as-prepared precursor nanobelts, suggesting that they can be easily transformed into ZnO nanobelts by preserving their initial morphology via calcination in air. In contrast, the obtained ZnO nanobelts are densely porous, owing to the thermal decomposition and oxidization of the precursor nanobelts. More importantly, the achieved porous ZnO nanobelts are single-crystalline, different from previously reported ones. Motivated by the intrinsic properties of the porous structure and good electronic transporting ability of single crystals, their gas-sensing performance has been further explored. It is demonstrated that porous ZnO single-crystalline nanobelts exhibit high response and repeatability toward volatile organic compounds, such as ethanol and acetone, with a short response/recovery time. Furthermore, their optoelectronic behaviors indicate that they can be promisingly employed to fabricate photoelectrochemical sensors. PMID:27454792

  14. Pulsed laser deposition of single-crystalline Cu7In3/CuIn0.8Ga0.2Se2 core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Zhao, Yu; Li, Hui; Zhu, Yan-Yan; Guan, Lei-Lei; Li, Yan-Li; Sun, Jian; Ying, Zhi-Feng; Wu, Jia-Da; Xu, Ning

    2014-12-01

    Single-crystalline Cu7In3/CuIn0.8Ga0.2Se2 (CI/CIGS) core/shell nanowires are fabricated by pulsed laser deposition with Ni nanoparticles as catalyst. The CI/CIGS core/shell nanowires are made up of single-crystalline CI cores surrounded by single-crystalline CIGS shells. The CI/CIGS nanowires are grown at a considerably low temperature (350°C ~ 450°C) by vapor-liquid-solid mode combined with vapor-solid mode. The distribution density of the nanowires increases with the increasing of the deposition duration, and the substrate temperature determines the lengths of the nanowires. The U-V absorption spectra of the CIGS thin films with and without the CI/CIGS core/shell nanowires demonstrate that the CI/CIGS nanowires can remarkably enhance the absorption of CIGS thin films in the spectrum range of 300 to 900 nm.

  15. Reviews Opera: Doctor Atomic DVD: Doctor Atomic Equipment: Digital stopclock with external trigger Book: I Cyborg Book: Flat Earth: The History of an Infamous Idea Book: Mere Thermodynamics Book: CGP revision guides Book: Hiding the Elephant: How Magicians Invented the Impossible Book: Back of the Envelope Physics Web Watch

    NASA Astrophysics Data System (ADS)

    2009-07-01

    WE RECOMMEND Doctor Atomic The new Doctor Atomic opera provkes discussion on ethics I Cyborg The world's first human cyborg shares his life story in I Cyborg Flat Earth: The History of an Infamous Idea Flat Earth gives us a different perspective on creationism Mere Thermodynamics An introductory text on the three laws CGP revision guides This revision guide suits all courses and every pocket Hiding the Elephant: How Magicians Invented the Impossible The mystery of many illusions are solved in this book Back of the Envelope Physics This reference deserves a place on your bookshelf WORTH A LOOK Doctor Atomic The DVD doesn't do justice to the live performance Digital stopclock with external trigger Use these stopclocks when you need an external trigger WEB WATCH Webcasts reach out to an online audience

  16. Flat minima.

    PubMed

    Hochreiter, S; Schmidhuber, J

    1997-01-01

    We present a new algorithm for finding low-complexity neural networks with high generalization capability. The algorithm searches for a "flat" minimum of the error function. A flat minimum is a large connected region in weight space where the error remains approximately constant. An MDL-based, Bayesian argument suggests that flat minima correspond to "simple" networks and low expected overfitting. The argument is based on a Gibbs algorithm variant and a novel way of splitting generalization error into underfitting and overfitting error. Unlike many previous approaches, ours does not require gaussian assumptions and does not depend on a "good" weight prior. Instead we have a prior over input-output functions, thus taking into account net architecture and training set. Although our algorithm requires the computation of second-order derivatives, it has backpropagation's order of complexity. Automatically, it effectively prunes units, weights, and input lines. Various experiments with feedforward and recurrent nets are described. In an application to stock market prediction, flat minimum search outperforms conventional backprop, weight decay, and "optimal brain surgeon/optimal brain damage".

  17. Charlie Flats

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image from the Mars Exploration Rover Opportunity's panoramic camera shows a region of the rock outcrop at Meridiani Planum, Mars, dubbed 'Charlie Flats.' This region is a rich science target for Opportunity because it contains a diverse assortment of small grains, pebbles and spherules, as well as both dark and light soil deposits. The area seen here measures approximately 0.6 meters (2 feet) across. The smallest grains visible in this image are only a few millimeters in size. The approximate true color image was acquired on Sol 20 of Opportunity's mission with panoramic camera filters red, green and blue. [figure removed for brevity, see original site] Click on image for larger view Charlie Flats Spectra The chart above shows examples of spectra, or light wave patterns, extracted from the region of the Meridiani Planum rock outcrop dubbed 'Charlie Flats,' a rich science target for the Mars Exploration Rover Opportunity. The spectra were extracted from the similarly colored regions in the image on the left, taken by the rover's panoramic camera. The green circle identifies a bright, dust-like soil deposit. The red circle identifies a dark soil region. The yellow identifies a small, angular rock chip with a strong near-infrared band. The pink identifies a sphere-shaped pebble with a different strong near-infrared band. The cyan circle shows a dark, grayish pebble.

  18. Single crystalline YAG:Ce phosphor for powerful solid-state sources of white light. The influence of production conditions on luminescence properties and lighting characteristics

    NASA Astrophysics Data System (ADS)

    Nizhankovskyi, S. V.; Tan'ko, A. V.; Savvin, Yu. N.; Krivonogov, S. I.; Budnikov, A. T.; Voloshin, A. V.

    2016-06-01

    It is shown that the spectral properties and spatial distribution of LED radiation with a YAG:Ce single crystalline luminescent converter significantly depend on the morphology of the converter surface. The variation of surface roughness enables one to obtain a light source with a wide range of color characteristics. As a result of optimization of converter parameters we demonstrate a possibility of creating a white light LED with correlated color temperature TCC ~ 5000-6500 K and color rendering index CRI ≈ 60-70.

  19. Observation of intrinsic Josephson effects in tetragonally synthesized single-crystalline NdBa2Cu3O6.65 films grown by tri-phase epitaxy

    NASA Astrophysics Data System (ADS)

    Yun, Kyung Sung; Hatano, Takeshi; Arisawa, Shunichi; Ishii, Akira; Wang, Huabing; Yamashita, Tsutomu; Iguchi, Ienari; Kawasaki, Masashi; Koinuma, Hideomi

    2008-07-01

    In this work twin-free tetragonal NdBa2Cu3O7-δ films were fabricated that exhibited superconductivity with sufficient anisotropy which produced intrinsic Josephson junction (IJJ) characteristics in the films. The intrinsic Josephson effects (IJEs) were observed in oxygen-deficient single-crystalline NdBa2Cu3O6.65 (NBCO) films grown on SrTiO3 (STO) substrates, using tri-phase epitaxy (TPE). The single-crystalline nature of NBCO films on well-matched STO substrates, and the precisely controlled oxygen content of the films, lead to the IJEs of the thin films. Furthermore, the films exhibit high anisotropy and clear multiple-branch structures, with hysteresis observed in the current-voltage characteristics. Periodic Josephson vortex-flow resistance oscillations were also observed for a magnetic field higher than 64 kOe, which was applied normal to the junctions. These results strongly support the single-crystal nature of TPE films, which play an important role in both the fundamental study and the practical applications of high-frequency devices.

  20. Dimensionally modulated, single-crystalline LiMPO4 (M= Mn, Fe, Co, and Ni) with nano-thumblike shapes for high-power energy storage.

    PubMed

    Vadivel Murugan, A; Muraliganth, T; Ferreira, P J; Manthiram, A

    2009-02-01

    We demonstrate an efficient and rapid microwave irradiated solvothermal method to prepare nanostructured lithium metal phosphates LiMPO(4) (M = Mn, Fe, Co, and Ni) within a short reaction time (5-15 min) at temperatures as low as 300 degrees C without requiring any post annealing at elevated temperatures. The highly viscous, high-boiling tetraethyleneglycol used as the solvent not only provides a reducing atmosphere to prevent the oxidation of M(2+) to M(3+) but also inhibits the agglomeration of the nanoparticles formed. The enhanced reaction rates facilitated by the dielectric volumetric heating of the microwave absorbing reactants led to the formation of highly crystalline, phase-pure LiMPO(4) powders. The samples are characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM), and electrochemical measurements in lithium cells. High-resolution TEM studies reveal the formation of single-crystalline LiMPO(4) with nano-thumblike shapes. The dimensionally modulated nano-thumblike shapes with the lithium diffusion direction (b axis) along the shorter dimension are particularly beneficial to achieve high-power capability in lithium ion cells. Subsequent networking of the single-crystalline LiMPO(4) nano-thumps with multiwalled carbon nanotubes by a simple solution-based mixing at ambient temperatures to overcome the electronic conductivity limitations offers excellent electrochemical performance in lithium ion cells. PMID:19125669

  1. Isotropic plasticity of β-type Ti-29Nb-13Ta-4.6Zr alloy single crystals for the development of single crystalline β-Ti implants

    NASA Astrophysics Data System (ADS)

    Hagihara, Koji; Nakano, Takayoshi; Maki, Hideaki; Umakoshi, Yukichi; Niinomi, Mitsuo

    2016-07-01

    β-type Ti-29Nb-13Ta-4.6Zr alloy is a promising novel material for biomedical applications. We have proposed a ‘single crystalline β-Ti implant’ as new hard tissue replacements for suppressing the stress shielding by achieving a drastic reduction in the Young’s modulus. To develop this, the orientation dependence of the plastic deformation behavior of the Ti-29Nb-13Ta-4.6Zr single crystal was first clarified. Dislocation slip with a Burgers vector parallel to <111> was the predominant deformation mode in the wide loading orientation. The orientation dependence of the yield stress due to <111> dislocations was small, in contrast to other β-Ti alloys. In addition, {332} twin was found to be operative at the loading orientation around [001]. The asymmetric features of the {332} twin formation depending on the loading orientation could be roughly anticipated by their Schmid factors. However, the critical resolved shear stress for the {332} twins appeared to show orientation dependence. The simultaneous operation of <111> slip and {332} twin were found to be the origin of the good mechanical properties with excellent strength and ductility. It was clarified that the Ti-29Nb-13Ta-4.6Zr alloy single crystal shows the “plastically almost-isotropic and elastically highly-anisotropic” nature, that is desirable for the development of ‘single crystalline β-Ti implant’.

  2. Isotropic plasticity of β-type Ti-29Nb-13Ta-4.6Zr alloy single crystals for the development of single crystalline β-Ti implants

    PubMed Central

    Hagihara, Koji; Nakano, Takayoshi; Maki, Hideaki; Umakoshi, Yukichi; Niinomi, Mitsuo

    2016-01-01

    β-type Ti-29Nb-13Ta-4.6Zr alloy is a promising novel material for biomedical applications. We have proposed a ‘single crystalline β-Ti implant’ as new hard tissue replacements for suppressing the stress shielding by achieving a drastic reduction in the Young’s modulus. To develop this, the orientation dependence of the plastic deformation behavior of the Ti-29Nb-13Ta-4.6Zr single crystal was first clarified. Dislocation slip with a Burgers vector parallel to <111> was the predominant deformation mode in the wide loading orientation. The orientation dependence of the yield stress due to <111> dislocations was small, in contrast to other β-Ti alloys. In addition, {332} twin was found to be operative at the loading orientation around [001]. The asymmetric features of the {332} twin formation depending on the loading orientation could be roughly anticipated by their Schmid factors. However, the critical resolved shear stress for the {332} twins appeared to show orientation dependence. The simultaneous operation of <111> slip and {332} twin were found to be the origin of the good mechanical properties with excellent strength and ductility. It was clarified that the Ti-29Nb-13Ta-4.6Zr alloy single crystal shows the “plastically almost-isotropic and elastically highly-anisotropic” nature, that is desirable for the development of ‘single crystalline β-Ti implant’. PMID:27417073

  3. Quantum criticality in single crystalline YFe2 Al10 determined from zero-field and longitudinal-field muon spin relaxation

    NASA Astrophysics Data System (ADS)

    Huang, Kevin; Tan, Cheng; Zhang, Jian; Ding, Zhaofeng; Maclaughlin, Douglas; Bernal, Oscar; Ho, Pei-Chun; Wu, Liusuo; Aronson, Meigan; Shu, Lei

    Muon spin relaxation (μSR) measurements were performed on single crystalline YFe2Al10 down to 19 mK and in magnetic fields up to ~100 Oe. Zero-field- μSR measurements showed no evidence of magnetic order down to 19 mK, consistent with previous measurements. However, we also find that the depolarization rate Λ is temperature independent above 1 K but increases in an exponential behavior for T < 1 K. Longitudinal-field μSR measurements also reveals a time-field scaling where G (t , H) = G (t /Hγ), with γ = 0.67. This is further confirmed from the magnetic field dependence of Λ, which finds Λ (H) ~H0. 67 at 19 mK. This is further evidence that single crystalline YFe2Al10 is in close proximity to a ferromagnetic quantum critical point. The research performed in this study was supported by the National NSF of China under Grant No. 11474060 and STCSM of China (No. 15XD1500200). Work at CSULA funded by NSF/DMR-1105380. Research at CSU-Fresno is supported by NSF DMR-1506677.

  4. Synthesis, structural and electronic properties of monodispersed self-organized single crystalline nanobricks of isocubanite CuFe{sub 2}S{sub 3}

    SciTech Connect

    Lyubutin, Igor S.; Lin, Chun-Rong; Starchikov, Sergey S.; Siao, Yu-Jhan; Tseng, Yaw-Teng

    2015-01-15

    The nanoparticles with a pure cubic phase of isocubanite CuFe{sub 2}S{sub 3} are successfully synthesized for the first time. The particles are self-organized into the single crystalline nanocomposites with a shape of “bricks” which are well ordered in a certain anisotropic orientation. All bricks have nearly the same shape and dimensions and may be considered as monodispersed nanobricks. Magnetic measurements show paramagnetic behavior of the compound down to 4.2 K with the antiferromagnetic correlation between iron ions. An average magnetic moment is about 2.8–3.0 μ{sub B} per formula unit CuFe{sub 2}S{sub 3}. Mössbauer spectroscopy data reveal that the ferric ions in isocubanite are in the high-spin state (spin S=5/2) whereas the ferrous ions are in the intermediate-spin state (S=1). The Fe{sup 3+} and Fe{sup 2+} ions are distributed randomly over tetrahedral sites and the electron exchange between these ions is absent. This can explain nonmagnetic behavior of isocubanite. In the suggested method, the combined nanocomposites containing the magnetic chalcopyrite CuFeS{sub 2} and the nonmagnetic isocubanite CuFe{sub 2}S{sub 3} can be synthesized in a certain sequence. Such composites could be useful for the applied nanotechnology. - Graphical abstract: Self-organized single crystalline “nanobricks” of isocubanite CuFe{sub 2}S{sub 3} synthesized by a thermal pyrolysis method. - Highlights: • Self-organized single crystalline “nanobricks” of CuFe{sub 2}S{sub 3} were synthesized. • All bricks are nearly monodispersed and well-ordered in a certain anisotropic orientation. • XRD, HRTEM, magnetic measurements and Mössbauer spectroscopy were used for characterization. • Nanobricks are paramagnetic down to 4.2 K with effective magnetic moment about 3.0 μ{sub B} per f.u. • Mössbauer spectroscopy data indicate different spin states of Fe{sup 2+} and Fe{sup 3+} ions.

  5. Smoothing single-crystalline SiC surfaces by reactive ion etching using pure NF{sub 3} and NF{sub 3}/Ar mixture gas plasmas

    SciTech Connect

    Tasaka, Akimasa; Kotaka, Yuki; Oda, Atsushi; Saito, Morihiro; Tojo, Tetsuro; Inaba, Minoru

    2014-09-01

    In pure NF{sub 3} plasma, the etching rates of four kinds of single-crystalline SiC wafer etched at NF{sub 3} pressure of 2 Pa were the highest and it decreased with an increase in NF{sub 3} pressure. On the other hand, they increased with an increase in radio frequency (RF) power and were the highest at RF power of 200 W. A smooth surface was obtained on the single-crystalline 4H-SiC after reactive ion etching at NF{sub 3}/Ar gas pressure of 2 Pa and addition of Ar to NF{sub 3} plasma increased the smoothness of SiC surface. Scanning electron microscopy observation revealed that the number of pillars decreased with an increase in the Ar-concentration in the NF{sub 3}/Ar mixture gas. The roughness factor (R{sub a}) values were decreased from 51.5 nm to 25.5 nm for the As-cut SiC, from 0.25 nm to 0.20 nm for the Epi-SiC, from 5.0 nm to 0.7 nm for the Si-face mirror-polished SiC, and from 0.20 nm to 0.16 nm for the C-face mirror-polished SiC by adding 60% Ar to the NF{sub 3} gas. Both the R{sub a} values of the Epi- and the C-face mirror-polished wafer surfaces etched using the NF{sub 3}/Ar (40:60) plasma were similar to that treated with mirror polishing, so-called the Catalyst-Referred Etching (CARE) method, with which the lowest roughness of surface was obtained among the chemical mirror polishing methods. Etching duration for smoothing the single-crystalline SiC surface using its treatment was one third of that with the CARE method.

  6. Van der Waals epitaxial growth of two-dimensional single-crystalline GaSe domains on graphene

    DOE PAGESBeta

    Li, Xufan; Basile, Leonardo; Huang, Bing; Ma, Cheng; Lee, Jaekwang; Vlassiouk, Ivan V.; Puretzky, Alexander A.; Lin, Ming -Wei; Chi, Miaofang; Idrobo Tapia, Juan Carlos; et al

    2015-07-22

    Two-dimensional (2D) van der Waals (vdW) heterostructures are a family of artificially-structured materials that promise tunable optoelectronic properties for devices with enhanced functionalities. Compared to stamping, direct epitaxy of vdW heterostructures is ideal for clean interlayer interfaces and scalable device fabrication. Here, we explore the synthesis and preferred orientations of 2D GaSe atomic layers on graphene (Gr) by vdW epitaxy. Guided by the wrinkles on graphene, GaSe nuclei form that share a predominant lattice orientation. Due to vdW epitaxial growth many nuclei grow as perfectly aligned crystals and coalesce to form large (tens of microns), single-crystal flakes. Through theoretical investigationsmore » of interlayer energetics, and measurements of preferred orientations by atomic-resolution STEM and electron diffraction, a 10.9 interlayer rotation of the GaSe lattice with respect to the underlying graphene is found to be the most energetically preferred vdW heterostructure with the largest binding energy and the longest-range ordering. These GaSe/Gr vdW heterostructures exhibit an enhanced Raman E21g band of monolayer GaSe along with highly-quenched photoluminescence due to strong charge transfer. Despite the very large lattice mismatch of GaSe/Gr through vdW epitaxy, the predominant orientation control and convergent formation of large single-crystal flakes demonstrated here is promising for the scalable synthesis of large-area vdW heterostructures for the development of new optical and optoelectronic devices.« less

  7. Van der Waals epitaxial growth of two-dimensional single-crystalline GaSe domains on graphene

    SciTech Connect

    Li, Xufan; Basile, Leonardo; Huang, Bing; Ma, Cheng; Lee, Jaekwang; Vlassiouk, Ivan V.; Puretzky, Alexander A.; Lin, Ming -Wei; Chi, Miaofang; Idrobo Tapia, Juan Carlos; Rouleau, Christopher M.; Sumpter, Bobby G.; Yoon, Mina; Geohegan, David B.; Xiao, Kai

    2015-07-22

    Two-dimensional (2D) van der Waals (vdW) heterostructures are a family of artificially-structured materials that promise tunable optoelectronic properties for devices with enhanced functionalities. Compared to stamping, direct epitaxy of vdW heterostructures is ideal for clean interlayer interfaces and scalable device fabrication. Here, we explore the synthesis and preferred orientations of 2D GaSe atomic layers on graphene (Gr) by vdW epitaxy. Guided by the wrinkles on graphene, GaSe nuclei form that share a predominant lattice orientation. Due to vdW epitaxial growth many nuclei grow as perfectly aligned crystals and coalesce to form large (tens of microns), single-crystal flakes. Through theoretical investigations of interlayer energetics, and measurements of preferred orientations by atomic-resolution STEM and electron diffraction, a 10.9 interlayer rotation of the GaSe lattice with respect to the underlying graphene is found to be the most energetically preferred vdW heterostructure with the largest binding energy and the longest-range ordering. These GaSe/Gr vdW heterostructures exhibit an enhanced Raman E21g band of monolayer GaSe along with highly-quenched photoluminescence due to strong charge transfer. Despite the very large lattice mismatch of GaSe/Gr through vdW epitaxy, the predominant orientation control and convergent formation of large single-crystal flakes demonstrated here is promising for the scalable synthesis of large-area vdW heterostructures for the development of new optical and optoelectronic devices.

  8. Single crystalline Er{sub 2}O{sub 3}:sapphire films as potentially high-gain amplifiers at telecommunication wavelength

    SciTech Connect

    Kuznetsov, A. S.; Sadofev, S.; Schäfer, P.; Kalusniak, S.; Henneberger, F.

    2014-11-10

    Single crystalline thin films of Er{sub 2}O{sub 3}, demonstrating efficient 1.5 μm luminescence of Er{sup 3+} at room temperature were grown on Al{sub 2}O{sub 3} substrate by molecular beam epitaxy. The absorption coefficient at 1.536 μm was found to reach 270 cm{sup −1} translating in a maximal possible gain of 1390 dBcm{sup −1}. In conjunction with the 10% higher refractive index as compared to Al{sub 2}O{sub 3}, this opens the possibility to use Er{sub 2}O{sub 3}:sapphire films as short-length waveguide amplifiers in telecommunication.

  9. Single-Crystalline CaMoO3 and SrMoO3 Films Grown by Pulsed Laser Deposition in a Reductive Atmosphere

    NASA Astrophysics Data System (ADS)

    Radetinac, Aldin; Takahashi, Kei S.; Alff, Lambert; Kawasaki, Masashi; Tokura, Yoshinori

    2010-07-01

    Single-crystalline thin films of CaMoO3 and SrMoO3 with a Mo4+ state perovskite structure have been epitaxially grown by pulsed-laser deposition from Mo6+ state ceramic targets. Phase-pure films were obtained on nearly lattice-matched perovskite substrates using argon gas flow during the deposition. Transport properties of the films are consistent with those of paramagnetic and metallic phases, whereas the residual resistivities are far lower than those reported previously for films and bulk polycrystals. These results indicate that this growth method can be useful for exploring the interfaces and junction properties of 4d and 5d transition metal oxides that are unstable in a conventional oxidative atmosphere.

  10. Magnetic and Mössbauer characterization of the magnetic properties of single-crystalline sub-micron sized Bi₂Fe₄O₉ cubes

    SciTech Connect

    Papaefthymiou, Georgia C.; Wong, Stanislaus S.; Viescas, Arthur J.; Le Breton, Jean-Marie; Chiron, Hubert; Juraszek, Jean; Park, Tae-Jin

    2014-11-25

    Magnetic and Mössbauer characterization of single crystalline, sub-micron sized Bi₂Fe₄O₉ cubes has been performed using SQUID magnetometry and transmission Mössbauer spectroscopy in the temperature range of 4.2 K ≤ T ≤ 300 K. A broad magnetic phase transition from the paramagnetic to the anti-ferromagnetic state is observed below 250 K, with the Mössbauer spectra exhibiting a superposition of magnetic, collapsed and quadrupolar spectra in the transition region of 200 K < T < 245 K. Room temperature Mössbauer spectra obtained in transmission geometry are identical to those recorded in back-scattering geometry via conversion electron Mössbauer spectroscopy, indicating the absence of strain at the surface. A small hysteresis loop is observed in SQUID measurements at 5 K, attributable to the presence of weak-ferromagnetism arising from the canting of Fe³⁺ ion sublattices in the antiferromagnetic matrix.

  11. Kinetics aspects of initial stage thin γ-Al2O3 film formation on single crystalline β-NiAl (110)

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongfan; Jung, Keeyoung; Li, Long; Yang, Judith C.

    2012-02-01

    The growth kinetics and mechanisms of thermally-grown thin γ-Al2O3 film at 650 °C in air on single-crystalline β-NiAl (110) was characterized via transmission electron microscopy, X-ray diffractometry, and thermo-gravimetric analyses. The oxidation kinetics as a function of thickness was gradually changing from an inverse-logarithmic to parabolic behavior across the "intermediate thickness regime" as the oxide thickness increases. To define the boundaries of the three thickness regimes, the high field approximation (x1) and Debye-Hückel length (LD) were determined using the existing theoretical kinetics models combined with experimentally measured data. All the relevant constants for each rate law at the three thickness regimes were also experimentally determined to quantitatively describe the initial stage growth kinetics.

  12. Distinct magnetism in ultrathin epitaxial NiFe2O4 films on MgAl2O4 and SrTiO3 single crystalline substrates

    NASA Astrophysics Data System (ADS)

    Foerster, Michael; Rebled, José Manuel; Estradé, Sònia; Sánchez, Florencio; Peiró, Francesca; Fontcuberta, Josep

    2011-10-01

    Spinel ferrites are being considered for advanced spintronic applications. Here, we report on the magnetic properties of ultrathin (3-37 nm) epitaxial films of NiFe2O4 (NFO) on MgAl2O4 (MAO) and SrTiO3 (STO) single crystalline substrates. It is found that NFO films on STO display superparamagnetic response down to 50 K, whereas films grown on MAO display ferrimagnetic response up to room temperature. Microstructural information indicates that this distinct response can be attributed to the different growth mechanisms of the spinel ferrite on the isostructural MAO substrate (two-dimensional growth) and the perovskite STO (Volmer-Weber three-dimensional growth). We discuss the reasons for this distinct behavior and its relevance for the integration of ferrites in epitaxial heterostructures for tunnel devices.

  13. Epitaxial growth of large area single-crystalline few-layer MoS2 with high space charge mobility of 192 cm2 V-1 s-1

    NASA Astrophysics Data System (ADS)

    Ma, Lu; Nath, Digbijoy N.; Lee, Edwin W.; Lee, Choong Hee; Yu, Mingzhe; Arehart, Aaron; Rajan, Siddharth; Wu, Yiying

    2014-08-01

    We report on the vapor-solid growth of single crystalline few-layer MoS2 films on (0001)-oriented sapphire with excellent structural and electrical properties over centimeter length scale. High-resolution X-ray diffraction scans indicated that the films had good out-of-plane ordering and epitaxial registry. A carrier density of ˜2 × 1011 cm-2 and a room temperature mobility of 192 cm2/Vs were extracted from space-charge limited transport regime in the films. The electron mobility was found to exhibit in-plane anisotropy with a ratio of ˜1.8. Theoretical estimates of the temperature-dependent electron mobility including optical phonon, acoustic deformation potential, and remote ionized impurity scattering were found to satisfactorily match the measured data. The synthesis approach reported here demonstrates the feasibility of device quality few-layer MoS2 films with excellent uniformity and high quality.

  14. Single crystalline Pr{sub 2-x}Y{sub x}O{sub 3} (x=0-2) dielectrics on Si with tailored electronic and crystallographic structure

    SciTech Connect

    Seifarth, O.; Schubert, M. A.; Giussani, A.; Schroeder, T.; Klenov, D. O.; Schmeisser, D.

    2010-11-15

    Crystalline oxides on Si with tailored electronic and crystallographic properties are of importance for the integration of functional oxides or alternative semiconductors to enable novel device concepts in Si microelectronics. We present an electronic band gap study of single crystalline Pr{sub 2-x}Y{sub x}O{sub 3} (0{<=}x{<=}2) heterostructures on Si(111). The perfect solubility of the isomorphic bixbyites Pr{sub 2}O{sub 3} and Y{sub 2}O{sub 3} during molecular beam epitaxy thin film growth on Si enables a linear band gap tuning. Special focus is devoted to the determination of the electronic band offsets across the dielectric/Si interface. In addition, the composition x allows to control the crystallographic lattice parameter where, for example, Pr{sub 0.8}Y{sub 1.2}O{sub 3} enables the growth of fully lattice matched oxide heterostructures on Si.

  15. A hierarchical nanostructure consisting of amorphous MnO 2, Mn 3O 4 nanocrystallites, and single-crystalline MnOOH nanowires for supercapacitors

    NASA Astrophysics Data System (ADS)

    Hu, Chi-Chang; Hung, Ching-Yun; Chang, Kuo-Hsin; Yang, Yi-Lin

    In this communication, a porous hierarchical nanostructure consisting of amorphous MnO 2 (a-MnO 2), Mn 3O 4 nanocrystals, and single-crystalline MnOOH nanowires is designed for the supercapacitor application, which is prepared by a simple two-step electrochemical deposition process. Because of the gradual co-transformation of Mn 3O 4 nanocrystals and a-MnO 2 nanorods into an amorphous manganese oxide, the cycle stability of a-MnO 2 is obviously enhanced by adding Mn 3O 4. This unique ternary oxide nanocomposite with 100-cycle CV activation exhibits excellent capacitive performances, i.e., excellent reversibility, high specific capacitances (470 F g -1 in CaCl 2), high power property, and outstanding cycle stability. The highly porous microstructures of this composite before and after the 10,000-cycle CV test are examined by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

  16. Hierarchical hollow microflowers constructed from mesoporous single crystalline CoMn2O4 nanosheets for high performance anode of lithium ion battery

    NASA Astrophysics Data System (ADS)

    Zhang, Lixin; He, Guofeng; Lei, Shiwen; Qi, Guisheng; Jiu, Hongfang; Wang, Juan

    2016-09-01

    Hierarchical hollow microflowers constructed from mesoporous single crystalline CoMn2O4 nanosheets were synthesized by a solvothermal route followed by calcination in air. It was found that the amount of deionized water plays a key role in the formation of the well-defined hierarchical hollow structure. A possible formation mechanism of the hierarchical hollow microflowers is proposed based on the time-dependent experimental results. In addition, the unique structure of CoMn2O4 microflowers exhibits superior electrochemical performances with an initial discharge specific capacity of 1024 mA h g-1 at 1000 mA g-1 and remains at 650 mA h g-1 with a coulombic efficiency of 98.7% after 500 cycles.

  17. Zero lattice mismatch and twin-free single crystalline ScN buffer layers for GaN growth on silicon

    SciTech Connect

    Lupina, L.; Zoellner, M. H.; Dietrich, B.; Capellini, G.; Niermann, T.; Lehmann, M.; Thapa, S. B.; Haeberlen, M.; Storck, P.; Schroeder, T.

    2015-11-16

    We report the growth of thin ScN layers deposited by plasma-assisted molecular beam epitaxy on Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3}/Si(111) substrates. Using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we find that ScN films grown at 600 °C are single crystalline, twin-free with rock-salt crystal structure, and exhibit a direct optical band gap of 2.2 eV. A high degree of crystalline perfection and a very good lattice matching between ScN and GaN (misfit < 0.1%) makes the ScN/Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3} buffer system a very promising template for the growth of high quality GaN layers on silicon.

  18. New method of verificating optical flat flatness

    NASA Astrophysics Data System (ADS)

    Sun, Hao; Li, Xueyuan; Han, Sen; Zhu, Jianrong; Guo, Zhenglai; Fu, Yuegang

    2014-11-01

    Optical flat is commonly used in optical testing instruments, flatness is the most important parameter of forming errors. As measurement criteria, optical flat flatness (OFF) index needs to have good precision. Current measurement in China is heavily dependent on the artificial visual interpretation, through discrete points to characterize the flatness. The efficiency and accuracy of this method can not meet the demand of industrial development. In order to improve the testing efficiency and accuracy of measurement, it is necessary to develop an optical flat verification system, which can obtain all surface information rapidly and efficiently, at the same time, in accordance with current national metrological verification procedures. This paper reviews current optical flat verification method and solves the problems existing in previous test, by using new method and its supporting software. Final results show that the new system can improve verification efficiency and accuracy, by comparing with JJG 28-2000 metrological verification procedures method.

  19. Yolk-shell, hollow, and single-crystalline ZnCo(2)O(4) powders: preparation using a simple one-pot process and application in lithium-ion batteries.

    PubMed

    Choi, Seung Ho; Kang, Yun Chan

    2013-11-01

    The electrochemical properties of yolk-shell-structured, multi-component, transition-metal oxides have not yet been properly compared to those of hollow-structured or nanoscale powders. In this study, yolk-shell, hollow, and single-crystalline ZnCo2 O4 powders with uniform compositions are prepared by using simple gas-phase reaction methods. Double-shelled ZnCo2 O4 yolk-shell powder is prepared directly from the spray solution by using spray pyrolysis. Single-crystalline ZnCo2 O4 nanopowder is prepared by means of flame spray pyrolysis. The yolk-shell ZnCo2 O4 powder shows higher charge and discharge capacities than the hollow and single-crystalline powders. The yolk-shell, hollow, and single-crystalline ZnCo2 O4 powders deliver discharge capacities of 753, 586, and 206 mAh g(-1) , respectively, after 200 cycles at a charge/discharge rate of 3 A g(-1) , and the corresponding capacity retentions measured after the first cycle are 99, 74, and 27 %, respectively. The yolk-shell ZnCo2 O4 powders are structurally stable during cycling and have good electrochemical properties even at high current densities. PMID:23908071

  20. Designing Au Surface-Modified Nanoporous-Single-Crystalline SrTiO3 to Optimize Diffusion of Surface Plasmon Resonance-Induce Photoelectron toward Enhanced Visible-Light Photoactivity.

    PubMed

    Lu, Da; Ouyang, Shuxin; Xu, Hua; Li, Dewang; Zhang, Xueliang; Li, Yunxiang; Ye, Jinhua

    2016-04-13

    Nanoporous single-crystalline SrTiO3 is fabricated at a low temperature of 60 °C via a novel approach of sol-gel alkali-dissolution-exothermal reaction. The plasmon-active metal Au is loaded on the nanoporous single-crystalline SrTiO3 material to construct a new kind of plasmonic photocatalyst. Due to the single-crystalline nature and the space confinement effect of pores for Au growing, not only the promoted diffusion efficiency of surface plasmon resonance (SPR)-induce photoelectron is achieved, but also the diffusion region are well optimized via changing the loading amount of Au. Therefore, an optimal sample with 4.8 wt % Au loading exhibits a more than 40-fold photoactivity enhancement under visible-light irradiation compared to the common nanosized SrTiO3 (a commercially available sample) loaded with 5.3 wt % Au which was prepared under the same condition. Furthermore, combining the special nanostructure of Au surface-modified nanoporous-single-crystalline SrTiO3 with photocatalytic properties, estimation of the diffusion mean free path of SPR-induce photoelectron can be achieved. This study proposes an alternative approach to enhance the photoactivity of plasmonic photocatalyst via fine designing the semiconductor substrate. PMID:27007490

  1. Low-temperature growth and characterization of single crystalline ZnO nanorod arrays using a catalyst-free inductively coupled plasma-metal organic chemical vapor deposition.

    PubMed

    Jeong, Sang-Hun; Lee, Chang-Bae; Moon, Won-Jin; Song, Ho-Jun

    2008-10-01

    Vertically aligned ZnO nanorod arrays have been synthesized on c-plane sapphires at a low temperature of 400 degrees C using catalyst-free inductively coupled plasma (ICP) metal organic chemical vapor deposition (MOCVD) technique by varying the ICP powers. Diameters of the ZnO nanorods changed from 200 nm to 400 nm as the ICP power increased from 200 to 400 Watt. TEM and XRD investigations indicated that the ZnO nanorod arrays grown at ICP powers above 200 Watt had a homogeneous in-plane alignment and single crystalline nature. PL study at room temperature (RT) and 6 K confirmed that the ZnO nanorod arrays in the present study are of high optical quality as well as good crystalline quality, showing only exciton-related emission peaks without any trace of defect-related deep level emissions in visible range. The blueshift of exciton emission peak in RTPL spectra was also found as rod diameter decreased and it is deduced that this shift in emission energy may be due to the surface resonance effect resulted from the increased surface-to-volume ratio, based on the observation and behavior of the surface exciton (SX) emission in the high-resolution 6 K PL spectra. PMID:19198399

  2. Highly enhanced acetone sensing performances of porous and single crystalline ZnO nanosheets: high percentage of exposed (100) facets working together with surface modification with Pd nanoparticles.

    PubMed

    Xiao, Yuanhua; Lu, Lingzhen; Zhang, Aiqin; Zhang, Yonghui; Sun, Li; Huo, Lei; Li, Feng

    2012-08-01

    Porous and single crystalline ZnO nanosheets, which were synthesized by annealing hydrozincite Zn(5)(CO(3))(2)(OH)(6) nanoplates produced with a water/ethylene glycol solvothermal method, are used as building blocks to construct functional Pd-ZnO nanoarchitectures together with Pd nanoparticles based on a self-assembly approach. Chemical sensing performances of the ZnO nanosheets were investigated carefully before and after their surface modification with Pd nanoparticles. It was found that the chemical sensors made with porous ZnO nanosheets exhibit high selectivity and quick response for detecting acetone, because of the 2D ZnO nanocrystals exposed in (100) facets at high percentage. The performances of the acetone sensors can be further improved dramatically, after the surfaces of ZnO nanosheets are modified with Pd nanoparticles. Novel acetone sensors with enhanced response, selectivity and stability have been fabricated successfully by using nanoarchitectures consisting of ZnO nanosheets and Pd nanoparticles.

  3. Magnetic and Mössbauer characterization of the magnetic properties of single-crystalline sub-micron sized Bi₂Fe₄O₉ cubes

    DOE PAGESBeta

    Papaefthymiou, Georgia C.; Wong, Stanislaus S.; Viescas, Arthur J.; Le Breton, Jean-Marie; Chiron, Hubert; Juraszek, Jean; Park, Tae-Jin

    2014-11-25

    Magnetic and Mössbauer characterization of single crystalline, sub-micron sized Bi₂Fe₄O₉ cubes has been performed using SQUID magnetometry and transmission Mössbauer spectroscopy in the temperature range of 4.2 K ≤ T ≤ 300 K. A broad magnetic phase transition from the paramagnetic to the anti-ferromagnetic state is observed below 250 K, with the Mössbauer spectra exhibiting a superposition of magnetic, collapsed and quadrupolar spectra in the transition region of 200 K < T < 245 K. Room temperature Mössbauer spectra obtained in transmission geometry are identical to those recorded in back-scattering geometry via conversion electron Mössbauer spectroscopy, indicating the absence ofmore » strain at the surface. A small hysteresis loop is observed in SQUID measurements at 5 K, attributable to the presence of weak-ferromagnetism arising from the canting of Fe³⁺ ion sublattices in the antiferromagnetic matrix.« less

  4. Anion-Exchange Induced Strong π-π Interactions in Single Crystalline Naphthalene Diimide for Nitroexplosive Sensing: An Electronic Prototype for Visual on-Site Detection.

    PubMed

    Kalita, Anamika; Hussain, Sameer; Malik, Akhtar Hussain; Barman, Ujjwol; Goswami, Namami; Iyer, Parameswar Krishnan

    2016-09-28

    A new derivative of naphthalene diimide (NDMI) was synthesized that displayed optical, electrical, and visual changes exclusively for the most widespread nitroexplosive and highly water-soluble toxicant picric acid (PA) due to strong π-π interactions, dipole-charge interaction, and a favorable ground state electron transfer process facilitated by Coulombic attraction. The sensing mechanism and interaction between NDMI with PA is demonstrated via X-ray diffraction analysis, (1)H NMR studies, cyclic voltammetry, UV-visible/fluorescence spectroscopy, and lifetime measurements. Single crystal X-ray structure of NDMI revealed the formation of self-assembled crystalline network assisted by noncovalent C-H···I interactions that get disrupted upon introducing PA as a result of anion exchange and strong π-π stacking between NDMI and PA. Morphological studies of NDMI displayed large numbers of single crystalline microrods along with some three-dimensional (3D) daisy-like structures which were fabricated on Al-coated glass substrate to construct a low-cost two terminal sensor device for realizing vapor mode detection of PA at room temperature and under ambient conditions. Furthermore, an economical and portable electronic prototype was developed for visual and on-site detection of PA vapors under exceptionally realistic conditions.

  5. Small-angle neutron scattering measurements of hydrogen and deuterium trapping at dislocations in deformed single-crystalline Pd at low temperature

    SciTech Connect

    Heuser, Brent J.; JU, H. S.

    2011-01-01

    Small-angle neutron scattering (SANS) measurements of hydrogen and deuterium trapped at dislocation defects in deformed single-crystalline Pd have been performed at 15, 100, and 200 K at total interstitial solute concentrations of order 10 3. This work supports recent incoherent inelastic neutron scattering measurements of the vibrational density of states of trapped hydrogen under similar concentration-temperature conditions [Heuser et al., Phys. Rev. B 78, 214101 (2008)]. The measured net absolute macroscopic differential scattering cross sections have been fitted with a cylindrical form factor representing solute-decorated dislocation line segments. Generally, very little difference in the measured cross sections was observed with temperature for a given solute type, while a significant change was observed between hydrogen- and deuterium-loaded samples. The latter difference is understood within a cross-section model that takes into account the local lattice dilatation associated with solute segregation at dislocations. The application of the model cross section to the net PdH0.0013 SANS response yields an effective trapping radius of R 10 A and dislocation density of d 1010 cm 2. Analysis of the SANS response allowed the local trapped solute concentration ( 0.5 [H]/[Pd]) and volumetric dilatation (/ 1.1) to be determined with the constraint that the system locally satisfies the known lattice expansion of Pd hydride (i.e., Vegard s law).

  6. Three-Dimensional Cu Foam-Supported Single Crystalline Mesoporous Cu2O Nanothorn Arrays for Ultra-Highly Sensitive and Efficient Nonenzymatic Detection of Glucose.

    PubMed

    Dong, Chaoqun; Zhong, Hua; Kou, Tianyi; Frenzel, Jan; Eggeler, Gunther; Zhang, Zhonghua

    2015-09-16

    Highly sensitive and efficient biosensors play a crucial role in clinical, environmental, industrial, and agricultural applications, and tremendous efforts have been dedicated to advanced electrode materials with superior electrochemical activities and low cost. Here, we report a three-dimensional binder-free Cu foam-supported Cu2O nanothorn array electrode developed via facile electrochemistry. The nanothorns growing in situ along the specific direction of <011> have single crystalline features and a mesoporous surface. When being used as a potential biosensor for nonenzyme glucose detection, the hybrid electrode exhibits multistage linear detection ranges with ultrahigh sensitivities (maximum of 97.9 mA mM(-1) cm(-2)) and an ultralow detection limit of 5 nM. Furthermore, the electrode presents outstanding selectivity and stability toward glucose detection. The distinguished performances endow this novel electrode with powerful reliability for analyzing human serum samples. These unprecedented sensing characteristics could be ascribed to the synergistic action of superior electrochemical catalytic activity of nanothorn arrays with dramatically enhanced surface area and intimate contact between the active material (Cu2O) and current collector (Cu foam), concurrently supplying good conductivity for electron/ion transport during glucose biosensing. Significantly, our findings could guide the fabrication of new metal oxide nanostructures with well-organized morphologies and unique properties as well as low materials cost. PMID:26305112

  7. Magnetic property and phase diagram of single-crystalline over-doped Ba1-xKxFe2As2

    NASA Astrophysics Data System (ADS)

    Li, Yu; Zhang, Chenglin; Dai, Pengcheng

    2013-03-01

    Sizable single-crystalline samples of hole-doped Ba1-xKxFe2As2 with x > 0.4 have been grown and characterized via magnetic measurements. Tc of our samples decreases from that of optimal doping as doping rate of K increases. Sharp transitions in M(T) curves indicate high quality of our sizable crystals which has never succeeded in over-doped region due to extreme nonhomogeneous property of this kind of material. With increasing K content, electron Fermi surface diminishing and nesting between hole FS and electron FS disappearing consequently, it is predicted that there exists a transition from s-wave superconducting state to d-wave yet without sufficient experimental evidences. Our results made it possible to further study on the hole-overdoped Ba1-xKxFe2As2 series and provide a significant platform to test and verify these current theories and understand the underlying pairing mechanism in iron-based superconductors.

  8. Development and Progress in Bulk c-Plane AlN Single-Crystalline Template Growth for Large-Area Native Seeds

    NASA Astrophysics Data System (ADS)

    Radhakrishnan Sumathi, R.; Gille, Peter

    2013-08-01

    28-mm diameter free-standing AlN substrates were obtained from single crystalline templates grown hetero-epitaxially on (0001) SiC substrates by the sublimation method. The grown template crystals have fairly high structural quality with X-ray rocking curve FWHM values of 120 and 200 arcsec for symmetric and asymmetric reflections, respectively and an average etch pit density of about 5×105 cm-2. In Raman spectroscopy, the E2(high) phonon mode peak FWHM is 18 cm-1 and its position shift shows a very low tensile strain of ˜1.5×10-4 in the crystals. The presence of Si and C impurity-related local vibrational modes is observed. These impurities might be responsible for lowering the optical absorption band edge to 4.3 eV. Homo-epitaxial growth of 5-mm-thick bulk crystals, using 10 mm diameter seeds prepared from these templates demonstrates their suitability as native seeds for further growth.

  9. Development and Progress in Bulk c-Plane AlN Single-Crystalline Template Growth for Large-Area Native Seeds

    NASA Astrophysics Data System (ADS)

    Sumathi, R. Radhakrishnan; Gille, Peter

    2013-08-01

    28-mm diameter free-standing AlN substrates were obtained from single crystalline templates grown hetero-epitaxially on (0001) SiC substrates by the sublimation method. The grown template crystals have fairly high structural quality with X-ray rocking curve FWHM values of 120 and 200 arcsec for symmetric and asymmetric reflections, respectively and an average etch pit density of about 5× 105 cm-2. In Raman spectroscopy, the E2(high) phonon mode peak FWHM is 18 cm-1 and its position shift shows a very low tensile strain of ˜1.5× 10-4 in the crystals. The presence of Si and C impurity-related local vibrational modes is observed. These impurities might be responsible for lowering the optical absorption band edge to 4.3 eV. Homo-epitaxial growth of 5-mm-thick bulk crystals, using 10 mm diameter seeds prepared from these templates demonstrates their suitability as native seeds for further growth.

  10. Low-temperature growth and characterization of single crystalline ZnO nanorod arrays using a catalyst-free inductively coupled plasma-metal organic chemical vapor deposition.

    PubMed

    Jeong, Sang-Hun; Lee, Chang-Bae; Moon, Won-Jin; Song, Ho-Jun

    2008-10-01

    Vertically aligned ZnO nanorod arrays have been synthesized on c-plane sapphires at a low temperature of 400 degrees C using catalyst-free inductively coupled plasma (ICP) metal organic chemical vapor deposition (MOCVD) technique by varying the ICP powers. Diameters of the ZnO nanorods changed from 200 nm to 400 nm as the ICP power increased from 200 to 400 Watt. TEM and XRD investigations indicated that the ZnO nanorod arrays grown at ICP powers above 200 Watt had a homogeneous in-plane alignment and single crystalline nature. PL study at room temperature (RT) and 6 K confirmed that the ZnO nanorod arrays in the present study are of high optical quality as well as good crystalline quality, showing only exciton-related emission peaks without any trace of defect-related deep level emissions in visible range. The blueshift of exciton emission peak in RTPL spectra was also found as rod diameter decreased and it is deduced that this shift in emission energy may be due to the surface resonance effect resulted from the increased surface-to-volume ratio, based on the observation and behavior of the surface exciton (SX) emission in the high-resolution 6 K PL spectra.

  11. Growth of aligned single-crystalline rutile TiO2 nanowires on arbitrary substrates and their application in dye-sensitized solar cells

    SciTech Connect

    Kumar, Akshay; Madaria, Anuj R.; Zhou, Chongwu

    2010-05-06

    TiO{sub 2} is a wide band gap semiconductor with important applications in photovoltaic cells and photocatalysis. In this paper, we report synthesis of single-crystalline rutile phase TiO{sub 2} nanowires on arbitrary substrates, including fluorine-doped tin oxide (FTO), glass slides, tin-doped indium oxide (ITO), Si/SiO{sub 2}, Si(100), Si(111), and glass rods. By controlling the growth parameters such as growth temperature, precursor concentrations, and so forth, we demonstrate that anisotropic growth of TiO{sub 2} is possible leading to various morphologies of nanowires. Optimization of the growth recipe leads to well-aligned vertical array of TiO{sub 2} nanowires on both FTO and glass substrates. Effects of various titanium precursors on the growth kinetics, especially on the growth rate of nanowires, are also studied. Finally, application of vertical array of TiO{sub 2} nanowires on FTO as the photoanode is demonstrated in dye-sensitized solar cell with an efficiency of 2.9 ± 0.2%.

  12. Single-crystalline Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} detectors for direct detection of microwave radiation

    SciTech Connect

    Li, M. Winkler, D.; Yurgens, A.

    2015-04-13

    We test radiation detectors made from single-crystalline Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} flakes put on oxidized Si substrates. The 100-nm-thick flakes are lithographically patterned into 4×12 μm{sup 2} large rectangles embedded in thin-film log-spiral antennas. The SiO{sub 2} layer weakens the thermal link between the flakes and the bath. Two modes of radiation detection have been observed. For a bolometric type of sensors a responsivity of ∼300 V/W and a noise equivalent power of 30 nW/√(Hz) has been deduced at 70 K. Much more sensitive is the non-bolometric device showing characteristics similar to a Golay-type detector while being at least a thousand times faster. Making smaller (sub-μm) structures is expected to significantly improve the performance of these devices and makes them very competitive among other microwave and terahertz detectors.

  13. Front Side Metallization of n- and p-Type, High-Efficiency, Single-Crystalline Si Solar Cells: Assessing the Temperature-Dependent Series Resistance

    NASA Astrophysics Data System (ADS)

    Willsch, Benjamin; Kumar, Praveen; Eibl, Oliver

    2016-06-01

    The series resistance of high-quality, single crystalline p-type and n-type solar cells was measured in a temperature range between 80 K and room temperature. Among one cell type ( n or p), cells were processed identically. Only the processing of the front side metallization was varied by using different processing conditions and screen printing pastes. High-efficiency n- ( η = 20.0%) and p-type ( η = 18.0%) cells yielded similar contact and series resistance and common features of the microstructure of the front side contact, i.e. a glass layer containing Ag colloids with typical diameters of 5-200 nm. Temperature-dependent current voltage curves ( I- V curves) were acquired and evaluated with respect to the series resistance by using two different methods yielding different results. On average the series resistance follows the trends of the contact resistance of the front side metallization determined at room temperature. Optimally processed cells yielded series resistances of less than 25 mΩ cm2 (method #1) both for n- and p-type cells. It could be shown that the series resistance reflected the processing conditions and paste properties and yielded similar temperature dependence for p- and n-type cells with small contact resistance. Therefore, the relevant current paths of high-efficiency n- and p-type cells appear to be similar in the front side metallization and include the glass layer which contains a high density of Ag colloids.

  14. Direct observation of intrinsic piezoelectricity of Pb(Zr,Ti)O{sub 3} by time-resolved x-ray diffraction measurement using single-crystalline films

    SciTech Connect

    Fujisawa, Takashi; Ehara, Yoshitaka; Yasui, Shintaro; Kamo, Takafumi; Funakubo, Hiroshi; Yamada, Tomoaki; Sakata, Osami

    2014-07-07

    Lead zirconate titanate, Pb(Zr,Ti)O{sub 3} or PZT, is one of the most widely investigated ferroelectric and piezoelectric materials due to its superior properties. However, the intrinsic properties of PZT have not been directly measured due to the lack of fabrication of single crystals even though a basic understanding of intrinsic properties has been of interest developing lead-free piezoelectric materials. We demonstrated the direct observation of the intrinsic piezoelectric property by means of the detection of electric-field induced crystal lattice distortion of thick Pb(Zr{sub 0.35}Ti{sub 0.65})O{sub 3} single-crystalline films with single polar-axis orientation and negligible residual strain using the time-resolved X-ray diffraction (XRD) together with the polarization response. Consequently, the effective converse piezoelectric response was experimentally revealed; hence, the electrostrictive coefficient, which is the conversion coefficient between the electrical and mechanical response, was determined. The obtained effective electrostrictive coefficient was 5.2–6.3 × 10{sup −2} m{sup 4}/C{sup 2}, which agrees with theoretical prediction.

  15. Direct observation of intrinsic piezoelectricity of Pb(Zr,Ti)O3 by time-resolved x-ray diffraction measurement using single-crystalline films

    NASA Astrophysics Data System (ADS)

    Fujisawa, Takashi; Ehara, Yoshitaka; Yasui, Shintaro; Kamo, Takafumi; Yamada, Tomoaki; Sakata, Osami; Funakubo, Hiroshi

    2014-07-01

    Lead zirconate titanate, Pb(Zr,Ti)O3 or PZT, is one of the most widely investigated ferroelectric and piezoelectric materials due to its superior properties. However, the intrinsic properties of PZT have not been directly measured due to the lack of fabrication of single crystals even though a basic understanding of intrinsic properties has been of interest developing lead-free piezoelectric materials. We demonstrated the direct observation of the intrinsic piezoelectric property by means of the detection of electric-field induced crystal lattice distortion of thick Pb(Zr0.35Ti0.65)O3 single-crystalline films with single polar-axis orientation and negligible residual strain using the time-resolved X-ray diffraction (XRD) together with the polarization response. Consequently, the effective converse piezoelectric response was experimentally revealed; hence, the electrostrictive coefficient, which is the conversion coefficient between the electrical and mechanical response, was determined. The obtained effective electrostrictive coefficient was 5.2-6.3 × 10-2 m4/C2, which agrees with theoretical prediction.

  16. Meniscus-force-mediated layer transfer technique using single-crystalline silicon films with midair cavity: Application to fabrication of CMOS transistors on plastic substrates

    NASA Astrophysics Data System (ADS)

    Sakaike, Kohei; Akazawa, Muneki; Nakagawa, Akitoshi; Higashi, Seiichiro

    2015-04-01

    A novel low-temperature technique for transferring a silicon-on-insulator (SOI) layer with a midair cavity (supported by narrow SiO2 columns) by meniscus force has been proposed, and a single-crystalline Si (c-Si) film with a midair cavity formed in dog-bone shape was successfully transferred to a poly(ethylene terephthalate) (PET) substrate at its heatproof temperature or lower. By applying this proposed transfer technique, high-performance c-Si-based complementary metal-oxide-semiconductor (CMOS) transistors were successfully fabricated on the PET substrate. The key processes are the thermal oxidation and subsequent hydrogen annealing of the SOI layer on the midair cavity. These processes ensure a good MOS interface, and the SiO2 layer works as a “blocking” layer that blocks contamination from PET. The fabricated n- and p-channel c-Si thin-film transistors (TFTs) on the PET substrate showed field-effect mobilities of 568 and 103 cm2 V-1 s-1, respectively.

  17. High-Performance Fully Nanostructured Photodetector with Single-Crystalline CdS Nanotubes as Active Layer and Very Long Ag Nanowires as Transparent Electrodes.

    PubMed

    An, Qinwei; Meng, Xianquan; Sun, Pan

    2015-10-21

    Long and single-crystalline CdS nanotubes (NTs) have been prepared via a physical evaporation process. A metal-semiconductor-metal full-nanostructured photodetector with CdS NTs as active layer and Ag nanowires (NWs) of low resistivity and high transmissivity as electrodes has been fabricated and characterized. The CdS NTs-based photodetectors exhibit high performance, such as lowest dark currents (0.19 nA) and high photoresponse ratio (Ilight/Idark ≈ 4016) (among CdS nanostructure network photodetectors and NTs netwok photodetectors reported so far) and very low operation voltages (0.5 V). The photoconduction mechanism, including the formation of a Schottky barrier at the interface of Ag NW and CdS NTs and the effect of oxygen adsorption process on the Schottky barrier has also been provided in detail based on the studies of CdS NTs photodetector in air and vacuum. Furthermore, CdS NTs photodetector exhibits an enhanced photosensitivity as compared with CdS NWs photodetector. The enhancement in performance is dependent on the larger surface area of NTs adsorbing more oxygen in air and the microcavity structure of NTs with higher light absorption efficiency and external quantum efficiency. It is believed that CdS NTs can potentially be useful in the designs of 1D CdS-based optoelectronic devices and solar cells.

  18. Highly Ordered Single Crystalline Nanowire Array Assembled Three-Dimensional Nb3O7(OH) and Nb2O5 Superstructures for Energy Storage and Conversion Applications.

    PubMed

    Zhang, Haimin; Wang, Yun; Liu, Porun; Chou, Shu Lei; Wang, Jia Zhao; Liu, Hongwei; Wang, Guozhong; Zhao, Huijun

    2016-01-26

    Three-dimensional (3D) metal oxide superstructures have demonstrated great potentials for structure-dependent energy storage and conversion applications. Here, we reported a facile hydrothermal method for direct growth of highly ordered single crystalline nanowire array assembled 3D orthorhombic Nb3O7(OH) superstructures and their subsequent thermal transformation into monoclinic Nb2O5 with well preserved 3D nanowire superstructures. The performance of resultant 3D Nb3O7(OH) and Nb2O5 superstructures differed remarkably when used for energy conversion and storage applications. The thermally converted Nb2O5 superstructures as anode material of lithium-ion batteries (LiBs) showed higher capacity and excellent cycling stability compared to the Nb3O7(OH) superstructures, while directly hydrothermal grown Nb3O7(OH) nanowire superstructure film on FTO substrate as photoanode of dye-sensitized solar cells (DSSCs) without the need for further calcination exhibited an overall light conversion efficiency of 6.38%, higher than that (5.87%) of DSSCs made from the thermally converted Nb2O5 film. The high energy application performance of the niobium-based nanowire superstructures with different chemical compositions can be attributed to their large surface area, superior electron transport property, and high light utilization efficiency resulting from a 3D superstructure, high crystallinity, and large sizes. The formation process of 3D nanowire superstructures before and after thermal treatment was investigated and discussed based on our theoretical and experimental results. PMID:26579783

  19. Unusually high critical current of clean P-doped BaFe{sub 2}As{sub 2} single crystalline thin film

    SciTech Connect

    Kurth, F. Engelmann, J.; Schultz, L.; Tarantini, C.; Jaroszynski, J.; Grinenko, V.; Reich, E.; Hühne, R.; Hänisch, J.; Mori, Y.; Sakagami, A.; Kawaguchi, T.; Ikuta, H.; Holzapfel, B.; Iida, K.

    2015-02-16

    Microstructurally clean, isovalently P-doped BaFe{sub 2}As{sub 2} (Ba-122) single crystalline thin films have been prepared on MgO (001) substrates by molecular beam epitaxy. These films show a superconducting transition temperature (T{sub c}) of over 30 K although P content is around 0.22, which is lower than the optimal one for single crystals (i.e., 0.33). The enhanced T{sub c} at this doping level is attributed to the in-plane tensile strain. The strained film shows high transport self-field critical current densities (J{sub c}) of over 6 MA/cm{sup 2} at 4.2 K, which are among the highest for Fe based superconductors (FeSCs). In-field J{sub c} exceeds 0.1 MA/cm{sup 2} at μ{sub 0}H=35 T for H‖ab and μ{sub 0}H=18 T for H‖c at 4.2 K, respectively, in spite of moderate upper critical fields compared to other FeSCs with similar T{sub c}. Structural investigations reveal no defects or misoriented grains pointing to strong pinning centers. We relate this unexpected high J{sub c} to a strong enhancement of the vortex core energy at optimal T{sub c}, driven by in-plane strain and doping. These unusually high J{sub c} make P-doped Ba-122 very favorable for high-field magnet applications.

  20. Single crystalline Sc2O3/Y2O3 heterostructures as novel engineered buffer approach for GaN integration on Si (111)

    NASA Astrophysics Data System (ADS)

    Tarnawska, L.; Giussani, A.; Zaumseil, P.; Schubert, M. A.; Paszkiewicz, R.; Brandt, O.; Storck, P.; Schroeder, T.

    2010-09-01

    The preparation of GaN virtual substrates on Si wafers via buffer layers is intensively pursued for high power/high frequency electronics as well as optoelectronics applications. Here, GaN is integrated on the Si platform by a novel engineered bilayer oxide buffer, namely, Sc2O3/Y2O3, which gradually reduces the lattice misfit of ˜-17% between GaN and Si. Single crystalline GaN(0001)/Sc2O3(111)/Y2O3(111)/Si(111) heterostructures were prepared by molecular beam epitaxy and characterized ex situ by various techniques. Laboratory-based x-ray diffraction shows that the epitaxial Sc2O3 grows fully relaxed on the Y2O3/Si(111) support, creating a high quality template for subsequent GaN overgrowth. The high structural quality of the Sc2O3 film is demonstrated by the fact that the concentration of extended planar defects in the preferred {111} slip planes is below the detection limit of synchrotron based diffuse x-ray scattering studies. Transmission electron microscopy (TEM) analysis reveal that the full relaxation of the -7% lattice misfit between the isomorphic oxides is achieved by a network of misfit dislocations at the Sc2O3/Y2O3 interface. X-ray reflectivity and TEM prove that closed epitaxial GaN layers as thin as 30 nm can be grown on these templates. Finally, the GaN thin film quality is studied using a detailed Williamson-Hall analysis.

  1. On-Demand Guided Bone Regeneration with Microbial Protection of Ornamented SPU Scaffold with Bismuth-Doped Single Crystalline Hydroxyapatite: Augmentation and Cartilage Formation.

    PubMed

    Selvakumar, M; Srivastava, Priyanka; Pawar, Harpreet Singh; Francis, Nimmy K; Das, Bodhisatwa; Sathishkumar, G; Subramanian, Bhuvaneshwaran; Jaganathan, Saravana Kumar; George, Gibin; Anandhan, S; Dhara, Santanu; Nando, Golok B; Chattopadhyay, Santanu

    2016-02-17

    Guided bone regeneration (GBR) scaffolds are futile in many clinical applications due to infection problems. In this work, we fabricated GBR with an anti-infective scaffold by ornamenting 2D single crystalline bismuth-doped nanohydroxyapatite (Bi-nHA) rods onto segmented polyurethane (SPU). Bi-nHA with high aspect ratio was prepared without any templates. Subsequently, it was introduced into an unprecedented synthesized SPU matrix based on dual soft segments (PCL-b-PDMS) of poly(ε-caprolactone) (PCL) and poly(dimethylsiloxane) (PDMS), by an in situ technique followed by electrospinning to fabricate scaffolds. For comparison, undoped pristine nHA rods were also ornamented into it. The enzymatic ring-opening polymerization technique was adapted to synthesize soft segments of PCL-b-PDMS copolymers of SPU. Structure elucidation of the synthesized polymers is done by nuclear magnetic resonance spectroscopy. Sparingly, Bi-nHA ornamented scaffolds exhibit tremendous improvement (155%) in the mechanical properties with excellent antimicrobial activity against various human pathogens. After confirmation of high osteoconductivity, improved biodegradation, and excellent biocompatibility against osteoblast cells (in vitro), the scaffolds were implanted in rabbits by subcutaneous and intraosseous (tibial) sites. Various histological sections reveal the signatures of early cartilage formation, endochondral ossification, and rapid bone healing at 4 weeks of the critical defects filled with ornamented scaffold compared to SPU scaffold. This implies osteogenic potential and ability to provide an adequate biomimetic microenvironment for mineralization for GBR of the scaffolds. Organ toxicity studies further confirm that no tissue architecture abnormalities were observed in hepatic, cardiac, and renal tissue sections. This finding manifests the feasibility of fabricating a mechanically adequate nanofibrous SPU scaffold by a biomimetic strategy and the advantages of Bi

  2. Thermal conductivity measurements of single-crystalline bismuth nanowires by the four-point-probe 3-ω technique at low temperatures.

    PubMed

    Lee, Seung-Yong; Kim, Gil-Sung; Lee, Mi-Ri; Lim, Hyuneui; Kim, Wan-Doo; Lee, Sang-Kwon

    2013-05-10

    We have successfully investigated the thermal conductivity (κ) of single-crystalline bismuth nanowires (BiNWs) with [110] growth direction, via a straightforward and powerful four-point-probe 3-ω technique in the temperature range 10-280 K. The BiNWs, which are well known as the most effective material for thermoelectric (TE) device applications, were synthesized by compressive thermal stress on a SiO2/Si substrate at 250-270 °C for 10 h. To understand the thermal transport mechanism of BiNWs, we present three kinds of experimental technique as follows, (i) a manipulation of a single BiNW by an Omni-probe in a focused ion beam (FIB), (ii) a suspended bridge structure integrating a four-point-probe chip by micro-fabrication to minimize the thermal loss to the substrate, and (iii) a simple 3-ω technique system setup. We found that the thermal transport of BiNWs is highly affected by boundary scattering of both phonons and electrons as the dominant heat carriers. The thermal conductivity of a single BiNW (d ~ 123 nm) was estimated to be ~2.9 W m(-1) K(-1) at 280 K, implying lower values compared to the thermal conductivity of the bulk (~11 W m(-1) K(-1) at 280 K). It was noted that this reduction in the thermal conductivity of the BiNWs could be due to strongly enhanced phonon-boundary scattering at the surface of the BiNWs. Furthermore, we present temperature-dependent (10-280 K) thermal conductivity of the BiNWs using the 3-ω technique.

  3. Cation self-diffusion of 44Ca, 88Y, and 96Zr in single-crystalline calcia- and yttria-doped zirconia

    NASA Astrophysics Data System (ADS)

    Kilo, M.; Taylor, M. A.; Argirusis, Ch.; Borchardt, G.; Lesage, B.; Weber, S.; Scherrer, S.; Scherrer, H.; Schroeder, M.; Martin, M.

    2003-12-01

    Self-diffusion of calcium, yttrium, and zirconium in single-crystalline YSZ and CSZ (YSZ: yttria-stabilized zirconia; containing 10 to 32 mol % Y2O3; CSZ: calcia-stabilized zirconia; containing 11 and 17 mol % CaO) was measured at temperatures between 960 and 1700 °C. For zirconium and calcium diffusion, the stable isotopes 44Ca and 96Zr were used as tracers and the samples were analyzed with secondary ion mass spectrometry. In the case of yttrium diffusion, the radioactive tracer 88Y was used and an abrasive sectioning technique was applied. Zirconium bulk diffusion is slower than yttrium and calcium bulk diffusion, and there is a nearly linear correlation of diffusion coefficient with cation radius. In YSZ, zirconium and yttrium bulk diffusivity are maximum for a stabilizer content of 10-11 mol %, while in CSZ both calcium and zirconium tracer diffusion are independent of the calcium content. The activation enthalpy of yttrium stabilizer bulk diffusion (4.2 eV) is, as in CSZ, slightly smaller than for zirconium bulk diffusion (4.5 eV). The yttrium dislocation pipe diffusivity is five to six orders of magnitude faster than the bulk diffusivity, and its activation enthalpy (3.5 eV) is also smaller than that of the bulk diffusion. From the activation enthalpy and from the concentration dependence of the cation bulk diffusion, it is concluded that the cation diffusion occurs either via free vacancies (VZr4' in YSZ) or via bound vacancies ([VZr4'-2VO2•]x in CSZ).

  4. Growth, structure, and magnetism of single-crystalline NixMn100-x films and NiMn/Co bilayers on Cu(001)

    NASA Astrophysics Data System (ADS)

    Tieg, C.; Kuch, W.; Wang, S. G.; Kirschner, J.

    2006-09-01

    The growth and structure of single-crystalline NixMn100-x films on Cu(001) were studied for concentrations of x⩾13 and thicknesses of 0 15 monolayer (ML). Medium energy electron diffraction (MEED) curves revealed a layer-by-layer growth mode at a substrate temperature of T=300K for alloy films with 40

  5. MAMA NUV Flats

    NASA Astrophysics Data System (ADS)

    Sana, Hugues

    2013-10-01

    This program is aimed at obtaining NUV-MAMA flat-field observations for the construction of pixel-to-pixel flats {p-flats} with a SNR of 100 per binned pixel. The flats are obtained with the DEUTERIUM-lamp and the MR grisms G230M. The actual choice of central wavelength and slit combination depends on the observed count level within each exposure.Note that STIS NUV-MAMA flats are taken every other cycles{i.e. during odd number cycles} in order to not drain the DEUTERIUMlamp lifetime.

  6. MAMA NUV Flats

    NASA Astrophysics Data System (ADS)

    Mason, Elena

    2011-10-01

    This program is aimed at obtaining NUV-MAMA flat-field observations for the construction of pixel-to-pixel flats {p-flats} with a SNR of 100 per binned pixel. The flats are obtained with the DEUTERIUM-lamp and the MR grisms G230M. The actual choice of central wavelength and slit combination depends on the observed count level within each exposure.Note that STIS NUV-MAMA flats are taken every other cycles{i.e. during odd number cycles} in order to not drain the DEUTERIUMlamp lifetime.

  7. Graphene folding on flat substrates

    SciTech Connect

    Chen, Xiaoming; Zhao, Yadong; Ke, Changhong; Zhang, Liuyang; Wang, Xianqiao

    2014-10-28

    We present a combined experimental-theoretical study of graphene folding on flat substrates. The structure and deformation of the folded graphene sheet are experimentally characterized by atomic force microscopy. The local graphene folding behaviors are interpreted based on nonlinear continuum mechanics modeling and molecular dynamics simulations. Our study on self-folding of a trilayer graphene sheet reports a bending stiffness of about 6.57 eV, which is about four times the reported values for monolayer graphene. Our results reveal that an intriguing free sliding phenomenon occurs at the interlayer van der Waals interfaces during the graphene folding process. This work demonstrates that it is a plausible venue to quantify the bending stiffness of graphene based on its self-folding conformation on flat substrates. The findings reported in this work are useful to a better understanding of the mechanical properties of graphene and in the pursuit of its applications.

  8. MAMA FUV Flats

    NASA Astrophysics Data System (ADS)

    Mason, Elena

    2012-10-01

    This program aims at obtaining FUV-MAMA flat-field observations to create a new p-flats with a SNR of 100 per {low resolution} pixel. The flats are obtained with the Krypton-lamp and the MR grating G140M, similarly to the cycle 17 and 18 programs. However the exact instrument setup {slit width and central wavelength} might change depending on the desired count level {which will be close to the internally allowed global rate limit}.

  9. Large-area alignment of tungsten oxide nanowires over flat and patterned substrates for room-temperature gas sensing.

    PubMed

    Cheng, Wei; Ju, Yanrui; Payamyar, Payam; Primc, Darinka; Rao, Jingyi; Willa, Christoph; Koziej, Dorota; Niederberger, Markus

    2015-01-01

    Alignment of nanowires over a large area of flat and patterned substrates is a prerequisite to use their collective properties in devices such as gas sensors. In this work, uniform single-crystalline ultrathin W18 O49 nanowires with diameters less than 2 nm and aspect ratios larger than 100 have been synthesized, and, despite their flexibility, assembled into thin films with high orientational order over a macroscopic area by the Langmuir-Blodgett technique. Alignment of the tungsten oxide nanowires was also possible on top of sensor substrates equipped with electrodes. Such sensor devices were found to exhibit outstanding sensitivity to H2 at room temperature. PMID:25412600

  10. CESAR at Poker Flat

    NASA Astrophysics Data System (ADS)

    Matsiev, D.; Slanger, T. G.; Hedin, J.

    2015-12-01

    The Compact Echelle Spectrograph for Aeronomic Research (CESAR) has been sited at Poker Flat Research Range since November 2013, collecting data over two seasons of the nightglow and the aurora. CESAR has operated with a field of view of seven degrees in the zenith direction, with a resolution of 5000, although a resolution three times greater is available. So far, data collection times have been in the range of 20 minutes, while the wavelength range used has been 500-1050 nm. Detailed studies of a number of optical features have been carried out. 1) It is demonstrated that the v = 2 level of the O2(b) state is best studied by using the weak b-X 2-1 band near 697 nm, it being free of auroral contamination. 2) Similarly, the best uncontaminated feature of the N2+ Meinel system is the complex A-X 0-1 band, which has been accurately simulated for the first time [Dubowsky and McCall, private communication, 2014]. 3) The N(2P-2D) quartet of lines near 1040 nm is an important auroral feature, being the N-atom equivalent of the oxygen green line. These lines are uncontaminated in many of our spectra. For lower altitude auroral excitation, there may be some overlap with the N2 First Positive 0-0 band [Pendleton et al, 1989]. 4) Time series on the O+(2P-2D) lines near 732-733 nm have been studied, showing variable background emission in this region depending on auroral type. Information on OH Meinel band lines is available throughout the region studied, and there is substantial evidence from sky spectra (Keck, VLT) that the attempt to extract kinetic temperatures from OH intensity distributions is strongly influenced by non-LTE effects [Cosby and Slanger, 2007; Noll et al, 2014].

  11. Flat Pack Toy Design

    ERIC Educational Resources Information Center

    Hutcheson, Brian

    2007-01-01

    In this article, the author introduces the concept of flat pack toys. Flat pack toys are designed using a template on a single sheet of letter-sized card stock paper. Before being cut out and built into a three-dimensional toy, they are scanned into the computer and uploaded to a website. With the template accessible from the website, anyone with…

  12. FLATs: Warming Up - continuation

    NASA Astrophysics Data System (ADS)

    Calzetti, Daniela

    1997-07-01

    The purpose of this proposal is to monitor the flat fields during the interval between the end of science observations and the exhaustion of cryogen and subsequent warming of the dewar to > 100K. These flats will provide a monitor for particulate comtamination {GROT} and detector lateral position {from the coronagraphic spot and FDA vignetting}. They will provide some measure of relative {flat field} and absolute QE variation as a function of temperature. When stars are visible they might provide a limited degree of focus determination.

  13. FLATs: Warming Up

    NASA Astrophysics Data System (ADS)

    Calzetti, Daniela

    1997-07-01

    The purpose of this proposal is to monitor the flat fields during the interval between the end of science observations and the exhaustion of cryogen and subsequent warming of the dewar to > 100K. These flats will provide a monitor for particulate comtamination {GROT} and detector lateral position {from the coronagraphic spot and FDA vignetting}. They will provide some measure of relative {flat field} and absolute QE variation as a function of temperature. When stars are visible they might provide a limited degree of focus determination.

  14. Flat plate solar oven

    SciTech Connect

    Parikh, M.

    1981-01-01

    The construction of an Indian Rs. 186 (US $20.33) flat-plate solar oven is described. Detailed drawings are provided and relevant information on cooking times and temperature for different foods is given.

  15. ZnO layers deposited by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Pécz, B.; Baji, Zs; Lábadi, Z.; Kovács, A.

    2013-11-01

    The structure of 40 nm thick epitaxial ZnO layers grown on single crystalline sapphire and GaN substrates by atomic layer deposition has been studied using transmission electron microscopy. The growth is carried out between 150°C and 300°C without any buffer layer using di-ethyl zinc and water precursors. The ZnO layer on sapphire is found to be polycrystalline, which is probably due to the large misfit (~15 %) and the relatively low deposition temperature. However, the small misfit (~1.8 %) between the ZnO layer that is deposited on GaN at 300°C resulted in a high quality single crystalline layer.

  16. Single-crystalline Li4Ti5O12 nanorods and their application in high rate capability Li4Ti5O12/LiMn2O4 full cells

    NASA Astrophysics Data System (ADS)

    Xi, Liu Jiang; Wang, Hong Kang; Yang, Shi Liu; Ma, Ru Guang; Lu, Zhou Guang; Cao, Chen Wei; Leung, Kwan Lan; Deng, Jian Qiu; Rogach, Andrey L.; Chung, C. Y.

    2013-11-01

    Single-crystalline Li4Ti5O12 nanorods have been successfully prepared through a molten salt method, followed by a precipitation method, and characterized with X-ray powder diffractometry, field-emission scanning electron microscopy, and transmission electron microscope. Their electrochemical properties have been studied by charge/discharge cycling and cyclic voltammetry. The results show that the single-crystalline Li4Ti5O12 nanorods reveal high capacity, excellent rate capability and cycle stability. The discharge capacity up to 176.4 mAh g-1 at 0.1 C rate is achieved. When tested at 10 C rate, the first discharge capacity reaches 135.9 mAh g-1, and the capacity retention is more than 61.5% after 1500 cycles. Furthermore, high rate capability Li4Ti5O12/LiMn2O4 full cells have been made using Li4Ti5O12 nanorods as the negative electrode, which display superior cycle stability at high rate. The discharge capacity and the mass energy density sequentially reach 40 mAh g-1 and 86.4 Wh kg-1 at 10 C rate, while the capacity retention is about 60% after 1000 cycles.

  17. Disorder-driven non-Fermi liquid behavior in single-crystalline Ce2Co0.8Si3.2.

    PubMed

    Szlawska, M; Kaczorowski, D

    2014-01-01

    A single crystal of the Ce-based ternary silicide Ce2Co0.8Si3.2, which crystallizes with a hexagonal AlB2-type related structure, was studied by means of magnetization, resistivity and heat capacity measurements. The compound was characterized as a Kondo paramagnet down to 0.4 K. Its low-temperature behavior is dominated by distinct non-Fermi liquid features, most likely arising due to structural disorder in the nonmagnetic-atom sublattice. PMID:24292411

  18. Flat Top & rocky terrain

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Flat Top, the rectangular rock at lower right, is part of a stretch of rocky terrain in this image, taken by the deployed Imager for Mars Pathfinder (IMP) on Sol 3. Dust has accumulated on the top of Flat Top, but is not present on the sides due to the steep angles of the rock. This dust may have been placed by dust storms moving across the Martian surface. Flat Top has been studied using several different color filters on the IMP camera.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C.

  19. Growth, structural and optical characterizations of LiLa{sub (1-x)}Eu{sub x}(WO{sub 4}){sub 2} single-crystalline fibers by the micro-pulling-down method

    SciTech Connect

    Moraes, Jair Ricardo de

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Transparent and uniform LiLa{sub (1-x)}Eu{sub x}(WO{sub 4}){sub 2} single-crystalline fibers were grown by the micro-pulling-down method. Black-Right-Pointing-Pointer Alkali and rare earth ionic radii influence the pulling rate on the growth. Black-Right-Pointing-Pointer Eu incorporation in LiLa(WO{sub 4}){sub 2} induces local distortions in the crystalline lattice. Black-Right-Pointing-Pointer LiLa{sub (1-x)}Eu{sub x}(WO{sub 4}){sub 2} single-crystalline fibers present intense red emission under 395 nm excitation. Black-Right-Pointing-Pointer Concentration quenching observed in the emission around 20 mol% of Eu doping. -- Abstract: Transparent and uniform LiLa{sub (1-x)}Eu{sub x}(WO{sub 4}){sub 2} single-crystalline fibers where x = 0.005, 0.01, 0.03, 0.05, 0.07, 0.1, 0.15, 0.2, 0.25 and 1.0, with an average of 20-40 mm length were obtained by the micro-pulling-down method aiming structural and optical characterization. The optimum pulling rate was found to depend on the difference between alkali and rare earth ionic radii. Rietveld analysis from X-ray diffraction data and excitation spectroscopy at room temperature were applied to investigate the lattice changes due to the Eu{sup 3+} incorporation in the host. LiLa{sub (1-x)}Eu{sub x}(WO{sub 4}){sub 2} crystal fibers present red emission due to the electric dipole {sup 5}D{sub 0} {yields} {sup 7}F{sub 2} transition under 395 nm excitation showing a concentration quenching around 20 mol% of doping. The excitation spectra of the {sup 7}F{sub 0} {yields} {sup 5}D{sub 0} transition show small changes in the Eu{sup 3+} surroundings as function of dopant concentration.

  20. Flat Focusing Mirror

    PubMed Central

    Cheng, Y. C.; Kicas, S.; Trull, J.; Peckus, M.; Cojocaru, C.; Vilaseca, R.; Drazdys, R.; Staliunas, K.

    2014-01-01

    The control of spatial propagation properties of narrow light beams such as divergence, focusing or imaging are main objectives in optics and photonics. In this letter, we propose and demonstrate experimentally a flat focusing mirror, based on an especially designed dielectric structure without any optical axis. More generally, it also enables imaging any light pattern in reflection. The flat focusing mirror with a transversal invariance can largely increase the applicability of structured photonic materials for light beam propagation control in small-dimension photonic circuits. PMID:25228358

  1. Holograms of Flat Space

    NASA Astrophysics Data System (ADS)

    Bagchi, Arjun; Grumiller, Daniel

    2013-07-01

    The holographic principle has a concrete realization in the Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence. If this principle is a true fact about quantum gravity then it must also hold beyond AdS/CFT. In this paper, we address specifically holographic field theory duals of gravitational theories in asymptotically flat spacetimes. We present some evidence of our recent conjecture that three-dimensional (3d) conformal Chern-Simons gravity (CSG) with flat space boundary conditions is dual to an extremal CFT.

  2. Is flat fair?

    SciTech Connect

    Bunzl, Martin

    2010-07-15

    Dynamic pricing holds out the promise of shifting peak demand as well as reducing overall demand. But it also raises thorny issues of fairness. All practical pricing systems involve tradeoffs between equity and efficiency. I examine the circumstances under which equity ought to be allowed to trump efficiency and whether or not this constitutes a defense of flat pricing. (author)

  3. Flat conductor cable applications

    NASA Technical Reports Server (NTRS)

    Angele, W.

    1972-01-01

    Some of the numerous applications of flat conductor cable (FCC) systems are briefly described. Both government and commercial uses were considered, with applications designated as either aerospace, military, or commercial. The number and variety of ways in which FCC is being applied and considered for future designs are illustrated.

  4. Multilayer flat electrical cable

    NASA Technical Reports Server (NTRS)

    Silverman, P. G.

    1973-01-01

    Flat electrical cable is lightweight, flexible over wide temperature range, withstands continuous exposure to high levels of nuclear radiation, and can carry high currents with minimum of temperature rise. Its magnetic cleanliness is equal to or better than twisted pair of wires, and it can be terminated in conventional electrical connector.

  5. Fabricating metal-oxide-semiconductor field-effect transistors on a polyethylene terephthalate substrate by applying low-temperature layer transfer of a single-crystalline silicon layer by meniscus force

    NASA Astrophysics Data System (ADS)

    Sakaike, Kohei; Akazawa, Muneki; Nakamura, Shogo; Higashi, Seiichiro

    2013-12-01

    A low-temperature local-layer technique for transferring a single-crystalline silicon (c-Si) film by using a meniscus force was proposed, and an n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) was fabricated on polyethylene terephthalate (PET) substrate. It was demonstrated that it is possible to transfer and form c-Si films in the required shape at the required position on PET substrates at extremely low temperatures by utilizing a meniscus force. The proposed technique for layer transfer was applied for fabricating high-performance c-Si MOSFETs on a PET substrate. The fabricated MOSFET showed a high on/off ratio of more than 108 and a high field-effect mobility of 609 cm2 V-1 s-1.

  6. Understanding hydrothermal transformation from Mn2O3 particles to Na0.55Mn2O4·1.5H2O nanosheets, nanobelts, and single crystalline ultra-long Na4Mn9O18 nanowires

    PubMed Central

    Park, Yohan; Woo Lee, Sung; Kim, Ki Hyeon; Min, Bong-Ki; Kumar Nayak, Arpan; Pradhan, Debabrata; Sohn, Youngku

    2015-01-01

    Manganese oxides are one of the most valuable materials for batteries, fuel cells and catalysis. Herein, we report the change in morphology and phase of as-synthesized Mn2O3 by inserting Na+ ions. In particular, Mn2O3 nanoparticles were first transformed to 2 nm thin Na0.55Mn2O4·1.5H2O nanosheets and nanobelts via hydrothermal exfoliation and Na cation intercalation, and finally to sub-mm ultra-long single crystalline Na4Mn9O18 nanowires. This paper reports the morphology and phase-dependent magnetic and catalytic (CO oxidation) properties of the as-synthesized nanostructured Na intercalated Mn-based materials. PMID:26667348

  7. Room temperature ferromagnetic properties of epitaxial (111) Y0.225Sr0.775CoO3-δ thin film grown on single crystalline (111) MgO substrate

    NASA Astrophysics Data System (ADS)

    Seo, Jeongdae; Ahn, Yoonho; Yeog Son, Jong

    2015-08-01

    Epitaxial (111) Y0.225Sr0.775CoO3-δ (YSCO) thin films were deposited on single crystalline (111) MgO substrates by a pulsed laser deposition method. The YSCO thin film exhibited room temperature ferromagnetism with a remanent magnetization of 1.5×10-5 emu. The magnetic force microscopy (MFM) study revealed that the YSCO thin film had a mosaic MFM domain structure. The comparison of domain wall energy for the YSCO and PZT indicates that the large domain wall energy induce the large domain size, though the large magnetization value reduce the magnetic domain size in the case of Co. According to the optical conductivity analysis by spectroscopic ellipsometry, it is inferred that the transition from the intermediate spin state to the high spin state of the YSCO thin film is attributed to the ferromagnetism of the Co4+ ion.

  8. Fabricating metal-oxide-semiconductor field-effect transistors on a polyethylene terephthalate substrate by applying low-temperature layer transfer of a single-crystalline silicon layer by meniscus force

    SciTech Connect

    Sakaike, Kohei; Akazawa, Muneki; Nakamura, Shogo; Higashi, Seiichiro

    2013-12-02

    A low-temperature local-layer technique for transferring a single-crystalline silicon (c-Si) film by using a meniscus force was proposed, and an n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) was fabricated on polyethylene terephthalate (PET) substrate. It was demonstrated that it is possible to transfer and form c-Si films in the required shape at the required position on PET substrates at extremely low temperatures by utilizing a meniscus force. The proposed technique for layer transfer was applied for fabricating high-performance c-Si MOSFETs on a PET substrate. The fabricated MOSFET showed a high on/off ratio of more than 10{sup 8} and a high field-effect mobility of 609 cm{sup 2} V{sup −1} s{sup −1}.

  9. Optical Lithography on non-flat surfaces; A Case Study

    NASA Astrophysics Data System (ADS)

    Moore, Clayton; Newton, Conrad; Geerts, Wilhelmus; Palmer, Daniel; Tamir, Dan

    2008-10-01

    Only a few studies of optical lithography on non-flat substrates have been reported. Most of these systems only work on polished very well defined substrates. For example, Ball Semiconductor developed a system for projection lithography on polished spherical balls of 1 mm diameter. We propose a system that works on an arbitrary surface and enables lithography on a wide variety of substrates including the wings of insects or a single crystalline grain of a ceramic sample. The system consists of a computer controlled laser beam that is focused through an optical microscope on an XY-table. The size of the beam can be changed by varying the size of the aperture or the change of the objective. The focus of the microscope can be automatically adjusted enabling to follow the 3D profile of the sample's surface. The laser intensity is automatically adjusted to keep the dose constant as the samples profile and the speed of the xy-table very. A cross-compiler, which utilizes principles of computer graphics to figure the required exposure parameters based on the surface of the object was developed. It accepts a text file, a vector based graphic file, or a raster image and generates a file with instructions for the laser beam writer.

  10. Landau-Zener Bloch Oscillations with Perturbed Flat Bands.

    PubMed

    Khomeriki, Ramaz; Flach, Sergej

    2016-06-17

    Sinusoidal Bloch oscillations appear in band structures exposed to external fields. Landau-Zener (LZ) tunneling between different bands is usually a counteracting effect limiting Bloch oscillations. Here we consider a flat band network with two dispersive and one flat band, e.g., for ultracold atoms and optical waveguide networks. Using external synthetic gauge and gravitational fields we obtain a perturbed yet gapless band structure with almost flat parts. The resulting Bloch oscillations consist of two parts-a fast scan through the nonflat part of the dispersion structure, and an almost complete halt for substantial time when the atomic or photonic wave packet is trapped in the original flat band part of the unperturbed spectrum, made possible due to LZ tunneling.

  11. Landau-Zener Bloch Oscillations with Perturbed Flat Bands.

    PubMed

    Khomeriki, Ramaz; Flach, Sergej

    2016-06-17

    Sinusoidal Bloch oscillations appear in band structures exposed to external fields. Landau-Zener (LZ) tunneling between different bands is usually a counteracting effect limiting Bloch oscillations. Here we consider a flat band network with two dispersive and one flat band, e.g., for ultracold atoms and optical waveguide networks. Using external synthetic gauge and gravitational fields we obtain a perturbed yet gapless band structure with almost flat parts. The resulting Bloch oscillations consist of two parts-a fast scan through the nonflat part of the dispersion structure, and an almost complete halt for substantial time when the atomic or photonic wave packet is trapped in the original flat band part of the unperturbed spectrum, made possible due to LZ tunneling. PMID:27367392

  12. Dislocation “Bubble-Like-Effect” and the Ambient Temperature Super-plastic Elongation of Body-centred Cubic Single Crystalline Molybdenum

    PubMed Central

    Lu, Yan; Xiang, Sisi; Xiao, Lirong; Wang, Lihua; Deng, Qingsong; Zhang, Ze; Han, Xiaodong

    2016-01-01

    With our recently developed deformation device, the in situ tensile tests of single crystal molybdenum nanowires with various size and aspect ratio were conducted inside a transmission electron microscope (TEM). We report an unusual ambient temperature (close to room temperature) super-plastic elongation above 127% on single crystal body-centred cubic (bcc) molybdenum nanowires with an optimized aspect ratio and size. A novel dislocation “bubble-like-effect” was uncovered for leading to the homogeneous, large and super-plastic elongation strain in the bcc Mo nanowires. The dislocation bubble-like-effect refers to the process of dislocation nucleation and annihilation, which likes the nucleation and annihilation process of the water bubbles. A significant plastic deformation dependence on the sample’s aspect ratio and size was revealed. The atomic scale TEM observations also demonstrated that a single crystal to poly-crystal transition and a bcc to face-centred cubic phase transformation took place, which assisted the plastic deformation of Mo in small scale. PMID:26956918

  13. COS NUV Flat Fields

    NASA Astrophysics Data System (ADS)

    Mason, Elena

    2011-10-01

    This program aims at obtaining COS NUV-MAMA flat-field observations for monitoring purpose only.The program uses the internal deuterium lamp and the MR grism G185M {at the central wavelengths 1835, 1850 and 1864 A}, as during thermal vacuum testing and SMOV4. The estimated SNR reached at the end of the program {13 hr integration during 10 orbits} is 20-25 per 3x3 pixel.

  14. Flat-plate heat pipe

    NASA Technical Reports Server (NTRS)

    Marcus, B. D.; Fleischman, G. L. (Inventor)

    1977-01-01

    Flat plate (vapor chamber) heat pipes were made by enclosing metal wicking between two capillary grooved flat panels. These heat pipes provide a unique configuration and have good capacity and conductance capabilities in zero gravity. When these flat plate vapor chamber heat pipes are heated or cooled, the surfaces are essentially isothermal, varying only 3 to 5 C over the panel surface.

  15. Temperature-modulated annealing of c-plane sapphire for long-range-ordered atomic steps

    NASA Astrophysics Data System (ADS)

    Yatsui, Takashi; Kuribara, Kazunori; Sekitani, Tsuyoshi; Someya, Takao; Yoshimoto, Mamoru

    2016-03-01

    High-quality single-crystalline sapphire is used to prepare various semiconductors because of its thermal stability. Here, we applied the tempering technique, which is well known in the production of chocolate, to prepare a sapphire substrate. Surprisingly, we successfully realised millimetre-range ordering of the atomic step of the sapphire substrate. We also obtained a sapphire atomic step with nanometre-scale uniformity in the terrace width and atomic-step height. Such sapphire substrates will find applications in the preparation of various semiconductors and devices.

  16. Flat conductor cable commercialization project

    NASA Technical Reports Server (NTRS)

    Hogarth, P.; Wadsworth, E.

    1977-01-01

    An undercarpet flat conductor cable and a baseboard flat conductor cable system were studied for commercialization. The undercarpet system is designed for use in office and commercial buildings. It employs a flat power cable, protected by a grounded metal shield, that terminates in receptacles mounted on the floor. It is designed to interface with a flat conductor cable telephone system. The baseboard system consists of a flat power cable mounted in a plastic raceway; both the raceway and the receptacles are mounted on the surface of the baseboard. It is designed primarily for use in residential buildings, particularly for renovation and concrete and masonry construction.

  17. Growth and luminescent properties of scintillators based on the single crystalline films of Lu{sub 3−x}Gd{sub x}Al{sub 5}O{sub 12}:Ce garnet

    SciTech Connect

    Zorenko, Yu; Gorbenko, V.; Vasylkiv, Ja; Zelenyj, A.; Fedorov, A.; Kucerkova, R.; Mares, J.A.; Nikl, M.; Bilski, P.; Twardak, A.

    2015-04-15

    Highlights: • Single crystalline films of Lu{sub 3−x}Gd{sub x}Al{sub 5}O{sub 12} garnets at x = 0 ÷ 3.0 were grown by LPE method onto YAG substrates. • Lattice constant of Lu{sub 3−}Gd{sub x}Al{sub 5}O{sub 12}:Ce film and the misfit m between films and YAG substrate changed linearly with increasing of Gd content. • Effective Gd{sup 3+}–Ce{sup 3+} energy transfer occurs in the Lu{sub 3−x}Gd{sub x}Al{sub 5}O{sub 12}:Ce films. • Best scintillation light yield is observed in the Lu{sub 3}Al{sub 5}O{sub 12}:Ce and Lu{sub 2.4}Gd{sub 0.6}Al{sub 5}O{sub 12}:Ce films. • Increase of the Gd content in x = 1.5–2.5 range results in decreasing the scintillation LY of Lu{sub 3−x}Gd{sub x}Al{sub 5}O{sub 12}:Ce films. - Abstract: The work is related to the growth of scintillators based on the single crystalline films (SCF) of Ce{sup 3+} doped Lu{sub 3−}Gd{sub x}Al{sub 5}O{sub 12} mixed rare-earth garnets by Liquid Phase Epitaxy (LPE) method. We have shown, that full set of Lu{sub 3−}Gd{sub x}Al{sub 5}O{sub 12} SCFs with x values ranging from 0 to 3.0 can be successfully crystallized by the LPE method onto Y{sub 3}Al{sub 5}O{sub 12} (YAG) substrates from the melt-solutions based on PbO-B{sub 2}O{sub 3} flux. The absorption, X-ray excited luminescence, photoluminescence, thermoluminescence and light yield measurements, the latter under excitation by α-particles of {sup 239}Pu and {sup 241}Am radioisotopes, were applied for their characterization.

  18. Wedge and Flat Top

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Flat Top, the rectangular rock at right, is part of a stretch of rocky terrain in this image, taken by the deployed Imager for Mars Pathfinder (IMP) on Sol 3. Dust has accumulated on the top of Flat Top, but is not present on the sides due to the steep angles of the rock. This dust may have been placed by dust storms moving across the Martian surface. The rock dubbed 'Wedge' is at left. The objects have been studied using several different color filters on the IMP camera.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

  19. Epitaxial growth of large area single-crystalline few-layer MoS{sub 2} with high space charge mobility of 192 cm{sup 2} V{sup −1} s{sup −1}

    SciTech Connect

    Ma, Lu; Yu, Mingzhe; Wu, Yiying E-mail: wu@chemistry.ohio-state.edu; Nath, Digbijoy N.; Lee, Edwin W.; Lee, Choong Hee; Arehart, Aaron; Rajan, Siddharth E-mail: wu@chemistry.ohio-state.edu

    2014-08-18

    We report on the vapor-solid growth of single crystalline few-layer MoS{sub 2} films on (0001)-oriented sapphire with excellent structural and electrical properties over centimeter length scale. High-resolution X-ray diffraction scans indicated that the films had good out-of-plane ordering and epitaxial registry. A carrier density of ∼2 × 10{sup 11 }cm{sup −2} and a room temperature mobility of 192 cm{sup 2}/Vs were extracted from space-charge limited transport regime in the films. The electron mobility was found to exhibit in-plane anisotropy with a ratio of ∼1.8. Theoretical estimates of the temperature-dependent electron mobility including optical phonon, acoustic deformation potential, and remote ionized impurity scattering were found to satisfactorily match the measured data. The synthesis approach reported here demonstrates the feasibility of device quality few-layer MoS{sub 2} films with excellent uniformity and high quality.

  20. Single-crystalline EuF3 hollow hexagonal microdisks: synthesis and application as a background-free matrix for MALDI-TOF-MS analysis of small molecules and polyethylene glycols.

    PubMed

    Chen, Zhiming; Geng, Zhirong; Shao, Dalin; Mei, Yuhua; Wang, Zhilin

    2009-09-15

    Single-crystalline EuF(3) hexagonal microdisks with hollow interior were fabricated to serve as a background-free matrix for analysis of small molecules and polyethylene glycols (PEGs) by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The long-lived excited state of europium ions can transfer energy to high-energy vibrations of organic molecules, which provides the potential technological application in MALDI-TOF-MS analysis of small molecules and PEGs. The efficiency of the hollow microdisks as a novel matrix of low molecular weight compounds was verified by analysis of small peptide, amino acid, organic compounds, and hydroxypropyl beta-cyclodextrin (HP-beta-CD). The advantage of this matrix in comparison with alpha-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB) was demonstrated by MALDI-TOF-MS analysis of an amino acid mixture and a peptide mixture. This matrix is successfully used for analysis of PEGs (PEG 2000, PEG 4000, PEG 8000, PEG 15000, and PEG 30000), suggesting a potential for monitoring reactions and for synthetic polymer quality control. The upper limit of detectable mass range was approximately 35,000 Da (PEG 30000). It is believed that this work will not only offer a new technique for high-speed analysis of small molecules and PEGs but also open a new field for applications of rare earth fluorides.

  1. Ion-irradiation-assisted phase selection in single crystalline Fe7Pd3 ferromagnetic shape memory alloy thin films: from fcc to bcc along the Nishiyama-Wassermann path.

    PubMed

    Arabi-Hashemi, A; Mayr, S G

    2012-11-01

    When processing Fe-Pd ferromagnetic shape memory thin films, selection of the desired phases and their transformation temperatures constitutes one of the largest challenges from an application point of view. In the present contribution we demonstrate that irradiation with 1.8 MeV Kr(+) ions is the method of choice to achieve this goal: Single crystalline Fe(7)Pd(3) thin films that are grown with molecular beam epitaxy on MgO (001) substrates and subsequently irradiated with ions reveal a phase transformation along the whole phase transformation path ranging from fcc austenite to bcc martensite. While for 10(14) ions/cm(2) a fcc-fct phase transformation is observed, increasing the fluence to 5 × 10(14) ions/cm(2) and 5 × 10(15) ions/cm(2) leads to a phase transformation to the bcc phase. Pole figure measurements reveal an orientation relationship for the fcc-bcc phase transformation according to Nishiyama and Wassermann.

  2. In situ direct growth of single crystalline metal (Co, Ni) selenium nanosheets on metal fibers as counter electrodes toward low-cost, high-performance fiber-shaped dye-sensitized solar cells.

    PubMed

    Chen, Liang; Yin, Hexing; Zhou, Yong; Dai, Hui; Yu, Tao; Liu, Jianguo; Zou, Zhigang

    2016-01-28

    Highly crystalline metal (Co, Ni) selenium (Co0.85Se or Ni0.85Se) nanosheets were in situ grown on metal (Co, Ni) fibers (M-M0.85Se). Both M-M0.85Se (Co-Co0.85Se and Ni-Ni0.85Se) fibers prove to function as excellent, low-cost counter electrodes (CEs) in fiber-shaped dye-sensitized solar cells (FDSSCs) with high power conversion efficiency (Co-Co0.85Se 6.55% and Ni-Ni0.85Se 7.07%), comparable or even superior to a Pt fiber CE (6.54%). The good performance of the present Pt-free CE-based solar cell was believed to originate from: (1) the intrinsic electrocatalytic properties of the single-crystalline M-M0.85Se; (2) the enough void space among M0.85Se nanosheets that allows easier redox ion diffusion; (3) the two-dimensional morphology that provides a large contact area between the CE catalytic material and electrolyte; (4) in situ direct growth of the M0.85Se on metal fibers that renders good electrical contact between the active material and the electron collector.

  3. Detection and imaging of the oxygen deficiency in single crystalline YBa{sub 2}Cu{sub 3}O{sub 7−δ} thin films using a scanning positron beam

    SciTech Connect

    Reiner, M.; Gigl, T.; Hugenschmidt, C.; Jany, R.; Hammerl, G.

    2015-03-16

    Single crystalline YBa{sub 2}Cu{sub 3}O{sub 7−δ} (YBCO) thin films were grown by pulsed laser deposition in order to probe the oxygen deficiency δ using a mono-energetic positron beam. The sample set covered a large range of δ (0.191 < δ < 0.791) yielding a variation of the critical temperature T{sub c} between 25 and 90 K. We found a linear correlation between the Doppler broadening of the positron electron annihilation line and δ determined by X-ray diffraction. Ab-initio calculations have been performed in order to exclude the presence of Y vacancies and to ensure the negligible influence of potentially present Ba or Cu vacancies to the found correlation. Moreover, scanning with the positron beam allowed us to analyze the spatial variation of δ, which was found to fluctuate with a standard deviation of up to 0.079(5) within a single YBCO film.

  4. Superconducting properties of single crystalline FeTe{sub 1-x}Se{sub x} (x = 0, 0.15, 0.25, 0.35, 0.40 and 0.50)

    SciTech Connect

    Sudesh,; Kumar, R.; Varma, G. D.

    2015-06-24

    In this paper we have grown single crystalline samples of Se-doped FeTe compound using self-flux technique and studied the structural and electrical transport properties of the as-grown crystals. The samples have been grown with compositions FeTe{sub 1-x}Se{sub x} (x = 0, 0.15, 0.25, 0.35, 0.40 and 0.50). The as-grown samples are then investigated for their structural and superconducting properties by means of X-ray diffraction and physical property measurements. The XRD results of powdered samples reveal a single (tetragonal) phase with space group symmetry P4/nmm for all the samples. The lattice parameters are observed to reduce with increase of Se-doping at Te-site. Highest H{sub c2}(0) (∼180 T) value has been observed for FeTe{sub 0.5}Se{sub 0.5} sample.

  5. Novel porous single-crystalline ZnO nanosheets fabricated by annealing ZnS(en)0.5 (en = ethylenediamine) precursor. Application in a gas sensor for indoor air contaminant detection.

    PubMed

    Liu, Jinyun; Guo, Zheng; Meng, Fanli; Luo, Tao; Li, Minqiang; Liu, Jinhuai

    2009-03-25

    Novel single-crystalline ZnO nanosheets with porous structure have been fabricated by annealing ZnS(en)(0.5) (en = ethylenediamine) complex precursor. The morphology and structure observations performed by field emission scanning electronic microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) indicate that numerous mesopores with a diameter of about 26.1 nm distribute all through each nanosheet with a high density. The transformation of structure and composition of samples obtained during thermal treatment processes were investigated by x-ray diffraction (XRD), x-ray photoelectron spectrometry (XPS), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) absorption spectroscopy. The formation mechanism of the porous structure is proposed. For indoor air contaminant detection in which formaldehyde and ammonia are employed as target gases, the as-prepared ZnO nanosheets were applied for the fabrication of gas sensors. It was found that the as-fabricated sensors not only exhibit highly sensitive performance, e.g., high gas-sensing responses, short response and recovery time, but also possess significant long-term stability. It is indicated that these ZnO nanostructures could promisingly be applied in electronic devices for environmental evaluation.

  6. Magnetotransport of single crystalline NbAs

    SciTech Connect

    Ghimire, N. J.; Luo, Yongkang; Neupane, M.; Williams, D. J.; Bauer, E. D.; Ronning, F.

    2015-03-27

    We report transport measurement in zero and applied magnetic field on a single crystal of NbAs. Transverse and longitudinal magnetoresistance in the plane of this tetragonal structure does not saturate up to 9 T. In the transverse configuration (H ∥ c, I ⊥ c) it is 230,000% at 2 K. The Hall coefficient changes sign from hole-like at room temperature to electron-like below ~150 K. The electron carrier density and mobility calculated at 2 K based on a single band approximation are 1.8 × 1019 cm-3 and 3.5 × 105 cm2/Vs, respectively. These values are similar to reported values for TaAs and NbP, and further emphasize that this class of noncentrosymmetric, transition-metal monopnictides is a promising family to explore the properties of Weyl semimetals and the consequences of their novel electronic structure.

  7. Magnetotransport of single crystalline NbAs

    DOE PAGESBeta

    Ghimire, N. J.; Luo, Yongkang; Neupane, M.; Williams, D. J.; Bauer, E. D.; Ronning, F.

    2015-03-27

    We report transport measurement in zero and applied magnetic field on a single crystal of NbAs. Transverse and longitudinal magnetoresistance in the plane of this tetragonal structure does not saturate up to 9 T. In the transverse configuration (H ∥ c, I ⊥ c) it is 230,000% at 2 K. The Hall coefficient changes sign from hole-like at room temperature to electron-like below ~150 K. The electron carrier density and mobility calculated at 2 K based on a single band approximation are 1.8 × 1019 cm-3 and 3.5 × 105 cm2/Vs, respectively. These values are similar to reported values formore » TaAs and NbP, and further emphasize that this class of noncentrosymmetric, transition-metal monopnictides is a promising family to explore the properties of Weyl semimetals and the consequences of their novel electronic structure.« less

  8. 13. AERIAL VIEW OF THE ROCKY FLATS PLANT FROM DIRECTLY ...

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

    13. AERIAL VIEW OF THE ROCKY FLATS PLANT FROM DIRECTLY OVERHEAD IN 1954. IN 1950, DOW CHEMICAL COMPANY WAS CHOSEN BY THE ATOMIC ENERGY COMMISSION TO ESTABLISH THE ROCKY FLATS PLANT AS AN ATOMIC BOMB TRIGGER FABRICATION FACILITY. THE CRITERIA FOR SITING SUCH A PLANT INCLUDED A LOCATION WEST OF THE MISSISSIPPI, NORTH OF TEXAS, SOUTH OF THE NORTHERN BORDER OF COLORADO, AND EAST OF UTAH; A DRY MODERATE CLIMATE; A SUPPORTING POPULATION OF AT LEAST 25,000 PEOPLE; AND ACCESSIBILITY FROM LOS ALAMOS, NM, CHICAGO, IL, AND ST. LOUIS, MO. TWENTY-ONE AREAS IN THE UNITED STATES WERE SUGGESTED; SEVEN LOCATIONS WERE SCREENED IN THE DENVER AREA. THIS FOUR-SQUARE MILE AREA WAS SELECTED AND CONSTRUCTION BEGAN IN 1951 (8/31/54). - Rocky Flats Plant, Bounded by Indiana Street & Routes 93, 128 & 72, Golden, Jefferson County, CO

  9. 26. AERIAL VIEW OF THE ROCKY FLATS PLANT LOOKING NORTHEAST. ...

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

    26. AERIAL VIEW OF THE ROCKY FLATS PLANT LOOKING NORTHEAST. IN 1951, A GOOD FRIDAY ISSUE OF THE DENVER POST ANNOUNCED THE ATOMIC ENERGY COMMISSION'S PLANS TO BUILD THE ROCKY FLATS PLANT. UNDER THE HEADLINE 'THERE'S GOOD NEWS TODAY.' POLITICAL LEADERS EXPRESSED GREAT PRIDE IN THE CHOICE OF THE DENVER-BOULDER AREA AS THE SITE FOR AN ATOMIC PLANT AS QUOTED IN THE ROCKY MOUNTAIN NEWS: 'WE ARE PROUD THAT THE AREA HAS BEEN CHOSEN FOR ANOTHER IMPORTANT CONTRIBUTION TO THE NATION'S STRENGTH AND FUTURE SECURITY.' BY THE MID 1970S, PUBLIC OPINION OF THE SITE HAD CHANGED (5/4/78). - Rocky Flats Plant, Bounded by Indiana Street & Routes 93, 128 & 72, Golden, Jefferson County, CO

  10. Is classical flat Kasner spacetime flat in quantum gravity?

    NASA Astrophysics Data System (ADS)

    Singh, Parampreet

    2016-05-01

    Quantum nature of classical flat Kasner spacetime is studied using effective spacetime description in loop quantum cosmology (LQC). We find that even though the spacetime curvature vanishes at the classical level, nontrivial quantum gravitational effects can arise. For the standard loop quantization of Bianchi-I spacetime, which uniquely yields universal bounds on expansion and shear scalars and results in a generic resolution of strong singularities, we find that a flat Kasner metric is not a physical solution of the effective spacetime description, except in a limit. The lack of a flat Kasner metric at the quantum level results from a novel feature of the loop quantum Bianchi-I spacetime: quantum geometry induces nonvanishing spacetime curvature components, making it not Ricci flat even when no matter is present. The noncurvature singularity of the classical flat Kasner spacetime is avoided, and the effective spacetime transits from a flat Kasner spacetime in asymptotic future, to a Minkowski spacetime in asymptotic past. Interestingly, for an alternate loop quantization which does not share some of the fine features of the standard quantization, flat Kasner spacetime with expected classical features exists. In this case, even with nontrivial quantum geometric effects, the spacetime curvature vanishes. These examples show that the character of even a flat classical vacuum spacetime can alter in a fundamental way in quantum gravity and is sensitive to the quantization procedure.

  11. Graphene nanoribbons production from flat carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Melo, W. S.; Guerini, S.; Diniz, E. M.

    2015-11-01

    Graphene nanoribbons are of great interest for pure and applied sciences due to their unique properties which depend on the nanoribbon edges, as, for example, energy gap and antiferromagnetic coupling. Nevertheless, the synthesis of nanoribbons with well-defined edges remains a challenge. To collaborate with this subject, here we propose a new route for the production of graphene nanoribbons from flat carbon nanotubes filled with a one-dimensional chain of Fe atoms by first principles calculations based on density functional theory. Our results show that Fe-filled flat carbon nanotubes are energetically more stable than non flattened geometries. Also we find that by hydrogenation or oxygenation of the most curved region of the Fe-filled flat armchair carbon nanotube, it occurred a spontaneous production of zigzag graphene nanoribbons which have metallic or semiconducting behavior depending on the edge and size of the graphene nanoribbon. Such findings can be used to create a new method of synthesis of regular-edge carbon nanoribbons.

  12. Graphene nanoribbons production from flat carbon nanotubes

    SciTech Connect

    Melo, W. S.; Guerini, S.; Diniz, E. M.

    2015-11-14

    Graphene nanoribbons are of great interest for pure and applied sciences due to their unique properties which depend on the nanoribbon edges, as, for example, energy gap and antiferromagnetic coupling. Nevertheless, the synthesis of nanoribbons with well-defined edges remains a challenge. To collaborate with this subject, here we propose a new route for the production of graphene nanoribbons from flat carbon nanotubes filled with a one-dimensional chain of Fe atoms by first principles calculations based on density functional theory. Our results show that Fe-filled flat carbon nanotubes are energetically more stable than non flattened geometries. Also we find that by hydrogenation or oxygenation of the most curved region of the Fe-filled flat armchair carbon nanotube, it occurred a spontaneous production of zigzag graphene nanoribbons which have metallic or semiconducting behavior depending on the edge and size of the graphene nanoribbon. Such findings can be used to create a new method of synthesis of regular-edge carbon nanoribbons.

  13. SDO FlatSat Facility

    NASA Technical Reports Server (NTRS)

    Amason, David L.

    2008-01-01

    The goal of the Solar Dynamics Observatory (SDO) is to understand and, ideally, predict the solar variations that influence life and society. It's instruments will measure the properties of the Sun and will take hifh definition images of the Sun every few seconds, all day every day. The FlatSat is a high fidelity electrical and functional representation of the SDO spacecraft bus. It is a high fidelity test bed for Integration & Test (I & T), flight software, and flight operations. For I & T purposes FlatSat will be a driver to development and dry run electrical integration procedures, STOL test procedures, page displays, and the command and telemetry database. FlatSat will also serve as a platform for flight software acceptance and systems testing for the flight software system component including the spacecraft main processors, power supply electronics, attitude control electronic, gimbal control electrons and the S-band communications card. FlatSat will also benefit the flight operations team through post-launch flight software code and table update development and verification and verification of new and updated flight operations products. This document highlights the benefits of FlatSat; describes the building of FlatSat; provides FlatSat facility requirements, access roles and responsibilities; and, and discusses FlatSat mechanical and electrical integration and functional testing.

  14. Absolute calibration of optical flats

    DOEpatents

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  15. Microgap flat panel display

    DOEpatents

    Wuest, Craig R.

    1998-01-01

    A microgap flat panel display which includes a thin gas-filled display tube that utilizes switched X-Y "pixel" strips to trigger electron avalanches and activate a phosphor at a given location on a display screen. The panel utilizes the principal of electron multiplication in a gas subjected to a high electric field to provide sufficient electron current to activate standard luminescent phosphors located on an anode. The X-Y conductive strips of a few micron widths may for example, be deposited on opposite sides of a thin insulating substrate, or on one side of the adjacent substrates and function as a cathode. The X-Y strips are separated from the anode by a gap filled with a suitable gas. Electrical bias is selectively switched onto X and Y strips to activate a "pixel" in the region where these strips overlap. A small amount of a long-lived radioisotope is used to initiate an electron avalanche in the overlap region when bias is applied. The avalanche travels through the gas filled gap and activates a luminescent phosphor of a selected color. The bias is adjusted to give a proportional electron multiplication to control brightness for given pixel.

  16. Microgap flat panel display

    DOEpatents

    Wuest, C.R.

    1998-12-08

    A microgap flat panel display is disclosed which includes a thin gas-filled display tube that utilizes switched X-Y ``pixel`` strips to trigger electron avalanches and activate a phosphor at a given location on a display screen. The panel utilizes the principal of electron multiplication in a gas subjected to a high electric field to provide sufficient electron current to activate standard luminescent phosphors located on an anode. The X-Y conductive strips of a few micron widths may for example, be deposited on opposite sides of a thin insulating substrate, or on one side of the adjacent substrates and function as a cathode. The X-Y strips are separated from the anode by a gap filled with a suitable gas. Electrical bias is selectively switched onto X and Y strips to activate a ``pixel`` in the region where these strips overlap. A small amount of a long-lived radioisotope is used to initiate an electron avalanche in the overlap region when bias is applied. The avalanche travels through the gas filled gap and activates a luminescent phosphor of a selected color. The bias is adjusted to give a proportional electron multiplication to control brightness for given pixel. 6 figs.

  17. Flat-space chiral gravity.

    PubMed

    Bagchi, Arjun; Detournay, Stéphane; Grumiller, Daniel

    2012-10-12

    We provide the first evidence for a holographic correspondence between a gravitational theory in flat space and a specific unitary field theory in one dimension lower. The gravitational theory is a flat-space limit of topologically massive gravity in three dimensions at a Chern-Simons level of k=1. The field theory is a chiral two-dimensional conformal field theory with a central charge of c=24. PMID:23102291

  18. The model case of an oxygen storage catalyst - non-stoichiometry, point defects and electrical conductivity of single crystalline CeO2-ZrO2-Y2O3 solid solutions.

    PubMed

    Eufinger, Jens-Peter; Daniels, Maximilian; Schmale, Kerstin; Berendts, Stefan; Ulbrich, Gregor; Lerch, Martin; Wiemhöfer, Hans-Dieter; Janek, Jürgen

    2014-12-14

    The ternary solid solution CeO2-ZrO2 is known for its superior performance as an oxygen storage catalyst in exhaust gas catalysis (e.g. TWC), although the defect chemical background of these outstanding properties is not fully understood quantitatively. Here, a comprehensive experimental study is reported regarding defects and defect-related transport properties of cubic stabilized single crystalline (CexZr1-x)0.8Y0.2O1.9-δ (0 ≤x≤ 1) solid solutions as a model system for CeO2-ZrO2. The constant fraction of yttria was chosen in order to fix a defined concentration of oxygen vacancies and to stabilize the cubic fluorite-type lattice for all Ce/Zr ratios. Measurements of the total electrical conductivity, the partial electronic conductivity, the ionic transference number and the non-stoichiometry (oxygen deficiency, oxygen storage capacity) were performed in the oxygen partial pressure range -25 < lg pO2/bar < 0 and for temperatures between 500 °C and 750 °C. The total conductivity at low pO2 is dominated by electronic transport. A strong deviation from the widely accepted ideal solution based point defect model was observed. An extended point defect model was developed using defect activities rather than concentrations in order to describe the point defect reactions in CeO2-ZrO2-Y2O3 properly. It served to obtain good quantitative agreement with the measured data. By a combination of values for non-stoichiometries and for electronic conductivities, the electron mobility could be calculated as a function of pO2, ranging between 10(-2) cm(2) V(-1) s(-1) and 10(-5) cm(2) V(-1) s(-1). Finally, the origin of the high oxygen storage capacity and superior catalytic promotion performance at a specific ratio of n(Ce)/n(Zr) ≈ 1 was attributed to two main factors: (1) a strongly enhanced electronic conductivity in the high and medium pO2 range qualifies the material to be a good mixed conductor, which is essential for a fast oxygen exchange and (2) the equilibrium

  19. Wafer-Size and Single-Crystal MoSe2 Atomically Thin Films Grown on GaN Substrate for Light Emission and Harvesting.

    PubMed

    Chen, Zuxin; Liu, Huiqiang; Chen, Xuechen; Chu, Guang; Chu, Sheng; Zhang, Hang

    2016-08-10

    Two-dimensional (2D) atomic-layered semiconductors are important for next-generation electronics and optoelectronics. Here, we designed the growth of an MoSe2 atomic layer on a lattice-matched GaN semiconductor substrate. The results demonstrated that the MoSe2 films were less than three atomic layers thick and were single crystalline of MoSe2 over the entire GaN substrate. The ultrathin MoSe2/GaN heterojunction diode demonstrated ∼850 nm light emission and could also be used in photovoltaic applications. PMID:27409977

  20. Wafer-Size and Single-Crystal MoSe2 Atomically Thin Films Grown on GaN Substrate for Light Emission and Harvesting.

    PubMed

    Chen, Zuxin; Liu, Huiqiang; Chen, Xuechen; Chu, Guang; Chu, Sheng; Zhang, Hang

    2016-08-10

    Two-dimensional (2D) atomic-layered semiconductors are important for next-generation electronics and optoelectronics. Here, we designed the growth of an MoSe2 atomic layer on a lattice-matched GaN semiconductor substrate. The results demonstrated that the MoSe2 films were less than three atomic layers thick and were single crystalline of MoSe2 over the entire GaN substrate. The ultrathin MoSe2/GaN heterojunction diode demonstrated ∼850 nm light emission and could also be used in photovoltaic applications.

  1. Half-flat quantum hair

    NASA Astrophysics Data System (ADS)

    García-Compeán, Hugo; Loaiza-Brito, Oscar; Martínez-Merino, Aldo; Santos-Silva, Roberto

    2014-02-01

    By wrapping D3-branes over 3-cycles on a half-flat manifold, we construct an effective supersymmetric black hole in the N=2 low-energy theory in four dimensions. Specifically, we find that the torsion cycles present in a half-flat compactification, corresponding to the mirror symmetric image of electric Neveu-Schwarz flux on a Calabi-Yau manifold, manifest in the half-flat black hole as quantum hair. We compute the electric and magnetic charges related to the quantum hair and also the mass contribution to the effective black hole. We find that by wrapping a number of D3-branes equal to the order of the discrete group associated to the torsional part of the half-flat homology, the effective charge and mass terms vanish. We compute the variation of entropy and the corresponding temperature associated with the loss of quantum hair. We also comment on the equivalence between canceling Freed-Witten anomaly and the assumption of self-duality for the 5-form field strength. Finally from a K-theoretical perspective, we compute the presence of discrete Ramond-Ramond charge of D-branes wrapping torsional cycles in a half-flat manifold.

  2. The Fallacies of Flatness: Thomas Friedman's "The World Is Flat"

    ERIC Educational Resources Information Center

    Abowitz, Kathleen Knight; Roberts, Jay

    2007-01-01

    Thomas Friedman's best-selling "The World is Flat" has exerted much influence in the west by providing both an accessible analysis of globalization and its economic and social effects, and a powerful cultural metaphor for globalization. In this review, we more closely examine Friedman's notion of the social contract, the moral center of his…

  3. Automatic Flatness Control of Cold Rolling Mill

    NASA Astrophysics Data System (ADS)

    Anbe, Yoshiharu; Sekiguchi, Kunio

    One of the subjects of cold rolling is a flatness of the rolled strip. Conventionally, measured strip flatness was approximated by polynomial (2th, 4th, 6th) equation across the entire strip width. This made it difficult to deal with desired loose edge or any desired flatness across the entire strip width. Also conventional flatness control was done for the entire strip width, so if there is a different flatness error among drive side and work side, conventional flatness control can not control properly. We propose independent strip flatness control among drive side and work side, and also automatic flatness control (AFC) system with arbitrary desired strip flatness. Also some applied results to cold mill are shown.

  4. Atomic mechanisms governing the elastic limit and the incipient plasticity of bending Si nanowires.

    PubMed

    Zheng, Kun; Han, Xiaodong; Wang, Lihua; Zhang, Yuefei; Yue, Yonghai; Qin, Yan; Zhang, Xiaona; Zhang, Ze

    2009-06-01

    Individual single-crystalline Si nanowires (NWs) were bent by forming loops or arcs with different radius. Positional-resolved atomic level strain distribution (PRALSD) along both of the radial and axial directions were calculated and mapped directly from the atomic-resolution strained high-resolution electron microscopy (HREM) images of the bent Si NWs. For the first time, the neutral-strain axis shifted from the compressive zone to the tensile region was directly demonstrated from the PRALSD along the radial direction. Bending-induced ripple-buckling of the bent Si NW was observed and a significant strain variation along the bending axial direction in the compressive region was revealed. The tensile surface atomic steps and the compressive buckling are the physical origin of the asymmetric tensile-compressive properties of postelastic instabilities and the incipient plasticity. Both of the tensile surface atomic-steps and the compressive buckling initiated versatile ductile plastic dislocation events.

  5. Laser illuminated flat panel display

    SciTech Connect

    Veligdan, J.T.

    1995-12-31

    A 10 inch laser illuminated flat panel Planar Optic Display (POD) screen has been constructed and tested. This POD screen technology is an entirely new concept in display technology. Although the initial display is flat and made of glass, this technology lends itself to applications where a plastic display might be wrapped around the viewer. The display screen is comprised of hundreds of planar optical waveguides where each glass waveguide represents a vertical line of resolution. A black cladding layer, having a lower index of refraction, is placed between each waveguide layer. Since the cladding makes the screen surface black, the contrast is high. The prototype display is 9 inches wide by 5 inches high and approximately I inch thick. A 3 milliwatt HeNe laser is used as the illumination source and a vector scanning technique is employed.

  6. Parallel spinors on flat manifolds

    NASA Astrophysics Data System (ADS)

    Sadowski, Michał

    2006-05-01

    Let p(M) be the dimension of the vector space of parallel spinors on a closed spin manifold M. We prove that every finite group G is the holonomy group of a closed flat spin manifold M(G) such that p(M(G))>0. If the holonomy group Hol(M) of M is cyclic, then we give an explicit formula for p(M) another than that given in [R.J. Miatello, R.A. Podesta, The spectrum of twisted Dirac operators on compact flat manifolds, Trans. Am. Math. Soc., in press]. We answer the question when p(M)>0 if Hol(M) is a cyclic group of prime order or dim⁡M≤4.

  7. Warped Ricci-flat reductions

    NASA Astrophysics Data System (ADS)

    Colgáin, E. Ó.; Sheikh-Jabbari, M. M.; Vázquez-Poritz, J. F.; Yavartanoo, H.; Zhang, Z.

    2014-08-01

    We present a simple class of warped-product vacuum (Ricci-flat) solutions to ten- and eleven-dimensional supergravity, where the internal space is flat and noncompact and the warp factor supports de Sitter (dS) and anti-de Sitter (AdS) vacua, in addition to trivial Minkowski vacua with compact internal spaces. We outline the construction of consistent Kaluza-Klein reductions and show that, although our vacuum solutions are nonsupersymmetric, these are closely related to the bosonic part of well-known maximally supersymmetric reductions on spheres. We comment on the stability of our solutions, noting that (A)dS3 vacua pass routine stability tests.

  8. Investigation of structural and optical properties of GaN on flat and porous silicon

    NASA Astrophysics Data System (ADS)

    Abud, Saleh H.; Selman, Abbas M.; Hassan, Z.

    2016-09-01

    In this work, gallium nitride (GaN) layers were successfully grown on Flat-Si and porous silicon (PSi) using a radio frequency-magnetron sputtering system. Field emission scanning electron microscopy and atomic force microscopy images showed that the grown film on Flat-Si had smoother surface, even though there were some cracks on it. Furthermore, the X-ray diffraction measurements showed that the peak intensity of all the grown layers on PSi was higher than that of the grown layer on Flat-Si. Our detailed observation showed that PSi is a promising substrate to obtain GaN films.

  9. Corrugated cover plate for flat plate collector

    DOEpatents

    Hollands, K. G. Terry; Sibbitt, Bruce

    1978-01-01

    A flat plate radiant energy collector is providing having a transparent cover. The cover has a V-corrugated shape which reduces the amount of energy reflected by the cover away from the flat plate absorber of the collector.

  10. Fluctuations along supersymmetric flat directions during inflation

    NASA Astrophysics Data System (ADS)

    Enqvist, Kari; Figueroa, Daniel G.; Rigopoulos, Gerasimos

    2012-01-01

    We consider a set of scalar fields, consisting of a single flat direction and one or several non-flat directions. We take our cue from the MSSM, considering separately D-flat and F-flat directions, but our results apply to any supersymmetric scenario containing flat directions. We study the field fluctuations during pure de Sitter inflation, following the evolution of the infrared modes by numerically solving the appropriate Langevin equations. We demonstrate that for the Standard Model U(1)Y, SU(2)L or SU(3)c gauge couplings, as well as for large enough Yukawa couplings, the fluctuations along the non-flat directions effectively block the fluctuations along the flat directions. The usual expected behaviour langlephi2rangleproptoN, with N the number of e-folds, may be strongly violated, depending on the coupling strengths. As a consequence, those cosmological considerations, which are derived assuming that during inflation flat directions fluctuate freely, should be revised.

  11. Flat heat pipe design, construction, and analysis

    SciTech Connect

    Voegler, G.; Boughey, B.; Cerza, M.; Lindler, K.W.

    1999-08-02

    This paper details the design, construction and partial analysis of a low temperature flat heat pipe in order to determine the feasibility of implementing flat heat pipes into thermophotovoltaic (TPV) energy conversion systems.

  12. Flat panel planar optic display

    SciTech Connect

    Veligdan, J.T.

    1994-11-01

    A prototype 10 inch flat panel Planar Optic Display, (POD), screen has been constructed and tested. This display screen is comprised of hundreds of planar optic class sheets bonded together with a cladding layer between each sheet where each glass sheet represents a vertical line of resolution. The display is 9 inches wide by 5 inches high and approximately 1 inch thick. A 3 milliwatt HeNe laser is used as the illumination source and a vector scanning technique is employed.

  13. Residue management at Rocky Flats

    SciTech Connect

    Olencz, J.

    1995-12-31

    Past plutonium production and manufacturing operations conducted at the Rocky Flats Environmental Technology Site (RFETS) produced a variety of plutonium-contaminated by-product materials. Residues are a category of these materials and were categorized as {open_quotes}materials in-process{close_quotes} to be recovered due to their inherent plutonium concentrations. In 1989 all RFETS plutonium production and manufacturing operations were curtailed. This report describes the management of plutonium bearing liquid and solid wastes.

  14. Flat space physics from holography

    SciTech Connect

    Bousso, Raphael

    2004-02-06

    We point out that aspects of quantum mechanics can be derived from the holographic principle, using only a perturbative limit of classical general relativity. In flat space, the covariant entropy bound reduces to the Bekenstein bound. The latter does not contain Newton's constant and cannot operate via gravitational backreaction. Instead, it is protected by--and in this sense, predicts--the Heisenberg uncertainty principle.

  15. 49 CFR 231.6 - Flat cars.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Flat cars. 231.6 Section 231.6 Transportation... TRANSPORTATION RAILROAD SAFETY APPLIANCE STANDARDS § 231.6 Flat cars. (Cars with sides 12 inches or less above the floor may be equipped the same as flat cars.) (a) Hand brakes—(1) Number. Same as specified...

  16. 49 CFR 231.6 - Flat cars.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Flat cars. 231.6 Section 231.6 Transportation... TRANSPORTATION RAILROAD SAFETY APPLIANCE STANDARDS § 231.6 Flat cars. (Cars with sides 12 inches or less above the floor may be equipped the same as flat cars.) (a) Hand brakes—(1) Number. Same as specified...

  17. 49 CFR 231.6 - Flat cars.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 4 2012-10-01 2012-10-01 false Flat cars. 231.6 Section 231.6 Transportation... TRANSPORTATION RAILROAD SAFETY APPLIANCE STANDARDS § 231.6 Flat cars. (Cars with sides 12 inches or less above the floor may be equipped the same as flat cars.) (a) Hand brakes—(1) Number. Same as specified...

  18. 49 CFR 231.6 - Flat cars.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Flat cars. 231.6 Section 231.6 Transportation... TRANSPORTATION RAILROAD SAFETY APPLIANCE STANDARDS § 231.6 Flat cars. (Cars with sides 12 inches or less above the floor may be equipped the same as flat cars.) (a) Hand brakes—(1) Number. Same as specified...

  19. Flat mites of the world - Edition 2

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Flat Mites of the World has an interactive key, fact sheets, descriptions, and images to aid in the identification of flat mites (Acari: Trombidiformes: Tetranychoidea: Tenuipalpidae) worldwide. The tool will help identify 36 genera of flat mites, including specific diagnostics for 13 species of...

  20. 49 CFR 231.6 - Flat cars.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Flat cars. 231.6 Section 231.6 Transportation... TRANSPORTATION RAILROAD SAFETY APPLIANCE STANDARDS § 231.6 Flat cars. (Cars with sides 12 inches or less above the floor may be equipped the same as flat cars.) (a) Hand brakes—(1) Number. Same as specified...

  1. An extension to flat band ferromagnetism

    NASA Astrophysics Data System (ADS)

    Gulacsi, M.; Kovacs, G.; Gulacsi, Z.

    2014-11-01

    From flat band ferromagnetism, we learned that the lowest energy half-filled flat band gives always ferromagnetism if the localized Wannier states on the flat band satisfy the connectivity condition. If the connectivity conditions are not satisfied, ferromagnetism does not appear. We show that this is not always the case namely, we show that ferromagnetism due to flat bands can appear even if the connectivity condition does not hold due to a peculiar behavior of the band situated just above the flat band.

  2. Engineering flat electronic bands in quasiperiodic and fractal loop geometries

    NASA Astrophysics Data System (ADS)

    Nandy, Atanu; Chakrabarti, Arunava

    2015-11-01

    Exact construction of one electron eigenstates with flat, non-dispersive bands, and localized over clusters of various sizes is reported for a class of quasi-one-dimensional looped networks. Quasiperiodic Fibonacci and Berker fractal geometries are embedded in the arms of the loop threaded by a uniform magnetic flux. We work out an analytical scheme to unravel the localized single particle states pinned at various atomic sites or over clusters of them. The magnetic field is varied to control, in a subtle way, the extent of localization and the location of the flat band states in energy space. In addition to this we show that an appropriate tuning of the field can lead to a re-entrant behavior of the effective mass of the electron in a band, with a periodic flip in its sign.

  3. Investigation of pellicle influence on reticle flatness

    NASA Astrophysics Data System (ADS)

    Lee, Christopher; Racette, Kenneth; Barrett, Monica

    2005-06-01

    In lithography systems, the need for increased resolution requires larger numerical apertures and shorter illumination wavelengths. Both of these requirements cause a reduction in the system"s depth of focus resulting in the need for flatter photomasks with specifications under 0.5 micron. Currently the mask blank substrates are measured after polishing, and all subsequent process steps are assumed to have little or no impact on the final mask flatness. With today"s ever tightening flatness requirements, this assumption can no longer be taken for granted. This paper investigates the distortions seen at the reticle surface induced by the mounting of a standard optical pellicle frame to the photomask and relates these distortions to the pellicle frame flatness. The experiment involves using a set of mask blanks that are better than 0.5 micron flatness with similar form errors before attaching the pellicle. Two groups of pellicles are used to create two distinct frame flatness populations: one set assumed to be within specification as purchased; and a second set of pellicles that are intentionally distorted. Mask flatness is compared before and after mounting the pellicles, and all frames are measured for flatness. Correlation between the frame flatness and form to the measured distortion on the reticle surface are made and discussed, and a practical guideline for selecting an appropriate blank flatness and pellicle flatness to achieve the desired reticle flatness is suggested.

  4. Characterizing silicon intercalated graphene grown epitaxially on Ir films by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Wang, Ye-Liang; Que, Yan-De; Gao, Hong-Jun

    2015-07-01

    An efficient method based on atomic force microscopy (AFM) has been developed to characterize silicon intercalated graphene grown on single crystalline Ir(111) thin films. By combining analyses of the phase image, force curves, and friction-force mapping, acquired by AFM, the locations and coverages of graphene and silicon oxide can be well distinguished. We can also demonstrate that silicon atoms have been successfully intercalated between graphene and the substrate. Our method gives an efficient and simple way to characterize graphene samples with interacted atoms and is very helpful for future applications of graphene-based devices in the modern microelectronic industry, where AFM is already widely used. Project supported by the National Basic Research Program of China (Grant Nos. 2013CBA01600 and 2011CB932700), the National Natural Science Foundation of China (Grant Nos. 61222112, 61390501 and 51325204), and Chinese Academy of Sciences (Grant Nos. 1731300500015 and XDB07030100).

  5. Flat Subduction and Dynamic Topography

    NASA Astrophysics Data System (ADS)

    Lithgow-Bertelloni, C. R.; Dávila, F. M.; Eakin, C. M.; Crameri, F.

    2014-12-01

    Mantle dynamics manifests at the surface via the horizontal motions of plates and the vertical deflections that influence topography and the non-hydrostatic geoid. The pioneering work of Mitrovica et al. (1989) and Gurnis (1990) on this dynamic topography revolutionized our understanding of sedimentary basin formation, sea level changes and continental flooding. The temporal evolution of subduction can explain the migration of basins and even the drainage reversal of the Amazon (Shephard et al., 2012; Eakin et al., 2014). Until recently, flat subduction has been seen as enhancing downward deflection of the overriding plate and increasing flooding. However, this interpretation depends crucially on the details of the morphology and density structure of the slab, which controls the loci and amplitude of the deflection. We tend to ignore morphological details in mantle dynamics because flow can smooth out short wavelength variations. We have shown instead that details matter! Using South America as a natural laboratory because of the large changes in morphology of the Nazca slab along strike, we show that downward deflection of the overriding plate and hence basin formation, do not occur over flat segments but at the leading edge, where slabs plunge back into the mantle. This is true in both Argentina and Peru. The temporal evolution from a 'normally' dipplng slab to a flat slab leads to uplift over flat segments rather than enhanced subsidence. Critical for this result is the use of a detailed morphological model of the present-day Nazca slab with a spatial resolution of 50-100 km and based on relocated seismicity and magnetotelluric results. The density structure of the slab, due to age and the presence of overthickened crust from aseismic ridge subduction is essential. Overthickened crust leads to buoyant slabs. We reproduce formation and deposition of the Acres-Solimoes basin and the evolution of the Amazon drainage basin in Peru as well as the Mar Chiquita

  6. Growth of iron cobalt oxides by atomic layer deposition.

    PubMed

    Lie, Martin; Barnholt Klepper, Karina; Nilsen, Ola; Fjellvåg, Helmer; Kjekshus, Arne

    2008-01-14

    Thin films of iron cobalt oxides with spinel-type structure are made by the atomic layer deposition (ALD) technique using Fe(thd)3 (Hthd = 2,2,6,6-tetramethylheptane-3,5-dione), Co(thd)2, and ozone as precursors. Pulse parameters for ALD-type growth are established and such growth can be achieved at deposition temperatures between 185 and 310 degrees C. Films have been deposited on amorphous soda-lime glass and single-crystalline substrates of Si(100), MgO(100), and alpha-Al2O3(001) which all provide crystalline films, but with various orientations and crystallite sizes. Application of an external magnetic field during the film growth does not influence film growth characteristics (growth rate, crystallinity, topography etc.). Magnetization data are reported for phase-pure films of spinel-type structure with composition Fe2CoO4.

  7. Closing Rocky Flats by 2006

    SciTech Connect

    Tuor, N. R.; Schubert, A. L.

    2002-02-26

    Safely accelerating the closure of Rocky Flats to 2006 is a goal shared by many: the State of Colorado, the communities surrounding the site, the U.S. Congress, the Department of Energy, Kaiser-Hill and its team of subcontractors, the site's employees, and taxpayers across the country. On June 30, 2000, Kaiser-Hill (KH) submitted to the Department of Energy (DOE), KH's plan to achieve closure of Rocky Flats by December 15, 2006, for a remaining cost of $3.96 billion (February 1, 2000, to December 15, 2006). The Closure Project Baseline (CPB) is the detailed project plan for accomplishing this ambitious closure goal. This paper will provide a status report on the progress being made toward the closure goal. This paper will: provide a summary of the closure contract completion criteria; give the current cost and schedule variance of the project and the status of key activities; detail important accomplishments of the past year; and discuss the challenges ahead.

  8. An Atomic-Scale X-ray View of Functional Oxide Films

    NASA Astrophysics Data System (ADS)

    Tung, I.-Cheng

    atomically controlled synthesis of single-crystalline La3Ni2O7. By building upon this knowledge, I have completed the first to date study of in situ surface X-ray scattering during homoepitaxial MBE growth of SrTiO3, which demonstrates codeposition is consistent with a 2D island growth mode with SrTiO3 islands, but shuttered deposition proceeds by the growth of SrO islands which then restructure into atomically flat SrTiO3 layer during the deposition of the TiO2. From this point, we have conducted a detailed microscopic study of epitaxial LaNiO3 ultrathin films grown on SrTiO3 (001) by using reactive MBE with in situ surface X-ray diffraction and ex situ soft XAS to explore the influence of polar mismatch on the resulting structural and electronic properties. Overall, this thesis highlights the power of artificial confinement to harness control over competing phases in complex oxides with atomic-scale precision.

  9. Stochastic approach to flat direction during inflation

    SciTech Connect

    Kawasaki, Masahiro; Takesako, Tomohiro E-mail: takesako@icrr.u-tokyo.ac.jp

    2012-08-01

    We revisit the time evolution of a flat and non-flat direction system during inflation. In order to take into account quantum noises in the analysis, we base on stochastic formalism and solve coupled Langevin equations numerically. We focus on a class of models in which tree-level Hubble-induced mass is not generated. Although the non-flat directions can block the growth of the flat direction's variance in principle, the blocking effects are suppressed by the effective masses of the non-flat directions. We find that the fate of the flat direction during inflation is determined by one-loop radiative corrections and non-renormalizable terms as usually considered, if we remove the zero-point fluctuation from the noise terms.

  10. RAYWOOD FLAT ROADLESS AREAS, CALIFORNIA.

    USGS Publications Warehouse

    Matti, Jonathan C.; Iverson, Stephen R.

    1984-01-01

    The Raywood Flat Roadless Areas are situated adjacent to the San Gorgonio Wilderness in the southeastern San Bernardino Mountains, southern California. Geologic, geochemical, and geophysical studies, together with an investigation of mines and prospects, indicate that there is little likelihood for the occurrence of metallic mineral or energy resources in the roadless areas. In the eastern part of the roadless areas, a geochemical survey shows slightly anomalous amounts of lead, copper, molybdenum, tin, and bismuth and suggests that there are small and scattered occurrences of these metals in the bedrock. The inferred mineral occurrences lack the characteristics associated with metal concentrations that would identify resources. Marble and other construction materials occur in the area.

  11. Spirit's View from 'Engineering Flats'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Figure 1 [figure removed for brevity, see original site] Figure 2

    This 360-degree view from a site dubbed 'Engineering Flats' combines several frames taken by the navigation camera on NASA's Mars Exploration Rover Spirit during the rover's 182nd martian day, or sol (July 7, 2004). Spirit had driven to this spot in the 'Columbia Hills' for four sols of engineering work on its right front wheel and a recalibration of positioning accuracy for tools on its robotic arm. The wheel tracks just beyond the rover's shadow indicate where Spirit had spent the preceding three weeks examining rocks in and near 'Hank's Hollow.' The view is presented in a cylindrical projection with geometric seam correction.

    Figure 1 is the left-eye view of a stereo pair and Figure 2 is the right-eye view of a stereo pair.

  12. Flat laminated microbial mat communities

    NASA Astrophysics Data System (ADS)

    Franks, Jonathan; Stolz, John F.

    2009-10-01

    Flat laminated microbial mats are complex microbial ecosystems that inhabit a wide range of environments (e.g., caves, iron springs, thermal springs and pools, salt marshes, hypersaline ponds and lagoons, methane and petroleum seeps, sea mounts, deep sea vents, arctic dry valleys). Their community structure is defined by physical (e.g., light quantity and quality, temperature, density and pressure) and chemical (e.g., oxygen, oxidation/reduction potential, salinity, pH, available electron acceptors and donors, chemical species) parameters as well as species interactions. The main primary producers may be photoautotrophs (e.g., cyanobacteria, purple phototrophs, green phototrophs) or chemolithoautophs (e.g., colorless sulfur oxidizing bacteria). Anaerobic phototrophy may predominate in organic rich environments that support high rates of respiration. These communities are dynamic systems exhibiting both spatial and temporal heterogeneity. They are characterized by steep gradients with microenvironments on the submillimeter scale. Diel oscillations in the physical-chemical profile (e.g., oxygen, hydrogen sulfide, pH) and species distribution are typical for phototroph-dominated communities. Flat laminated microbial mats are often sites of robust biogeochemical cycling. In addition to well-established modes of metabolism for phototrophy (oxygenic and non-oxygenic), respiration (both aerobic and anaerobic), and fermentation, novel energetic pathways have been discovered (e.g., nitrate reduction couple to the oxidation of ammonia, sulfur, or arsenite). The application of culture-independent techniques (e.g., 16S rRNA clonal libraries, metagenomics), continue to expand our understanding of species composition and metabolic functions of these complex ecosystems.

  13. Flat conductor cable design, manufacture, and installation

    NASA Technical Reports Server (NTRS)

    Angele, W.; Hankins, J. D.

    1973-01-01

    Pertinent information for hardware selection, design, manufacture, and quality control necessary for flat conductor cable interconnecting harness application is presented. Comparisons are made between round wire cable and flat conductor cable. The flat conductor cable interconnecting harness systems show major cost, weight, and space savings, plus increased system performance and reliability. The design application section includes electrical characteristics, harness design and development, and a full treatise on EMC considerations. Manufacturing and quality control sections pertain primarily to the developed conductor-contact connector system and special flat conductor cable to round wire cable transitions.

  14. Atomic polarizabilities

    SciTech Connect

    Safronova, M. S.; Mitroy, J.; Clark, Charles W.; Kozlov, M. G.

    2015-01-22

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

  15. 40 CFR 230.42 - Mud flats.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Mud flats. 230.42 Section 230.42 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN DUMPING SECTION 404(b)(1... are inundated, wind and wave action may resuspend bottom sediments. Coastal mud flats are exposed...

  16. 40 CFR 230.42 - Mud flats.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Mud flats. 230.42 Section 230.42 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN DUMPING SECTION 404(b)(1... are inundated, wind and wave action may resuspend bottom sediments. Coastal mud flats are exposed...

  17. Fluctuations along supersymmetric flat directions during inflation

    SciTech Connect

    Enqvist, Kari; Figueroa, Daniel G.; Rigopoulos, Gerasimos E-mail: daniel.figueroa@helsinki.fi

    2012-01-01

    We consider a set of scalar fields, consisting of a single flat direction and one or several non-flat directions. We take our cue from the MSSM, considering separately D-flat and F-flat directions, but our results apply to any supersymmetric scenario containing flat directions. We study the field fluctuations during pure de Sitter inflation, following the evolution of the infrared modes by numerically solving the appropriate Langevin equations. We demonstrate that for the Standard Model U(1){sub Y}, SU(2){sub L} or SU(3){sub c} gauge couplings, as well as for large enough Yukawa couplings, the fluctuations along the non-flat directions effectively block the fluctuations along the flat directions. The usual expected behaviour (φ{sup 2})∝N, with N the number of e-folds, may be strongly violated, depending on the coupling strengths. As a consequence, those cosmological considerations, which are derived assuming that during inflation flat directions fluctuate freely, should be revised.

  18. Lunar Reconnaissance Orbiter FlatSat

    NASA Technical Reports Server (NTRS)

    Wright, Michael

    2008-01-01

    This viewgraph presentation reviews the use of FlatSat as a platform for use during flight integration and testing (I&T) of the Lunar Reconnaissance Orbiter (LRO). Included in the presentations are requirements for the facility, a diagram of the LRO FlatSat lab, and discussion of the operational documentation, facility scheduling, and issues and lessons learned.

  19. How is WFPC flat field made

    NASA Technical Reports Server (NTRS)

    Hsu, J.-C.; Ritchie, C. E.

    1992-01-01

    An algorithm developed by the WFPC IDT to generate flat fields from Earth streak exposures is now implemented in STSDAS. We explain in detail how this algorithm works and possible deficiencies. We also present two associated tools which can be used to modify the flat field obtained from the standard procedure.

  20. The flat antenna - Now a reality

    NASA Astrophysics Data System (ADS)

    Wells, Daniel R.

    1989-09-01

    A practical, high-performance, low-cost, consumer-oriented flat antenna is described. Advantages of the flat antenna include a thin profile which is less obtrusive than a parabolic dish, features less expensive shipping and installation costs due to its light weight, has the ability to squint the beam, and has improved aperture control for sidelobe suppression. R&D focuses on development of monolithic microwave integrated circuts which will be embedded into the array, thus adding the potential features of amenability to integrated electronics (which will improve noise performance and avoid the necessity of appending an external low-noise converter), and electronic steerability to the list of flat antenna advantages. The basic construction of the flat panel and the intended market for the first flat antennas and the subsequent effect on product design are discussed. Initial market results in Japan, and planned development of European and American markets are discussed.

  1. Nonperturbative decay of supersymmetric flat directions

    SciTech Connect

    Guemruekcueoglu, A. Emir; Peloso, Marco; Sexton, Matthew; Olive, Keith A.

    2008-09-15

    We compute the nonperturbative decay of supersymmetric flat directions due to their D-term potential. Flat directions can develop large vacuum expectation values during inflation, and, if they are long-lived, this can strongly affect the reheating and thermalization stages after the inflation. We study a generic system of two U(1) or SU(2) flat directions which are cosmologically evolving after inflation. After proper gauge fixing, we show that the excitations of the fields around this background can undergo exponential amplification, at the expense of the energy density of the flat directions. We compute this effect for several values of the masses and the initial vacuum expectation values of the two flat directions, through a combination of analytical methods and extensive numerical simulations.

  2. Phase decomposition and ordering in Ni-11.3 at.% Ti studied with atom probe tomography.

    PubMed

    Al-Kassab, T; Kompatscher, M; Kirchheim, R; Kostorz, G; Schönfeld, B

    2014-09-01

    The decomposition behavior of Ni-rich Ni-Ti was reassessed using Tomographic Atom Probe (TAP) and Laser Assisted Wide Angle Tomographic Atom Probe. Single crystalline specimens of Ni-11.3 at.% Ti were investigated, the states selected from the decomposition path were the metastable γ″ and γ' states introduced on the basis of small-angle neutron scattering (SANS) and the two-phase model for evaluation. The composition values of the precipitates in these states could not be confirmed by APT data as the interface of the ordered precipitates may not be neglected. The present results rather suggest to apply a three-phase model for the interpretation of SANS measurements, in which the width of the interface remains nearly unchanged and the L12 structure close to 3:1 stoichiometry is maintained in the core of the precipitates from the γ″ to the γ' state.

  3. Layer matching epitaxy of NiO thin films on atomically stepped sapphire (0001) substrates

    PubMed Central

    Yamauchi, Ryosuke; Hamasaki, Yosuke; Shibuya, Takuto; Saito, Akira; Tsuchimine, Nobuo; Koyama, Koji; Matsuda, Akifumi; Yoshimoto, Mamoru

    2015-01-01

    Thin-film epitaxy is critical for investigating the original properties of materials. To obtain epitaxial films, careful consideration of the external conditions, i.e. single-crystal substrate, temperature, deposition pressure and fabrication method, is significantly important. In particular, selection of the single-crystal substrate is the first step towards fabrication of a high-quality film. Sapphire (single-crystalline α-Al2O3) is commonly used in industry as a thin-film crystal-growth substrate, and functional thin-film materials deposited on sapphire substrates have found industrial applications. However, while sapphire is a single crystal, two types of atomic planes exist in accordance with step height. Here we discuss the need to consider the lattice mismatch for each of the sapphire atomic layers. Furthermore, through cross-sectional transmission electron microscopy analysis, we demonstrate the uniepitaxial growth of cubic crystalline thin films on bistepped sapphire (0001) substrates. PMID:26402241

  4. Rocky Flats Beryllium Health Surveillance.

    PubMed

    Stange, A W; Furman, F J; Hilmas, D E

    1996-10-01

    The Rocky Flats Beryllium Health Surveillance Program (BHSP), initiated in June 1991, was designed to provide medical surveillance for current and former employees exposed to beryllium. The BHSP identifies individuals who have developed beryllium sensitivity using the beryllium lymphocyte proliferation test (BeLPT). A detailed medical evaluation to determine the prevalence of chronic beryllium disease (CBD) is offered to individuals identified as beryllium sensitized or to those who have chest X-ray changes suggestive of CBD. The BHSP has identified 27 cases of CBD and another 74 cases of beryllium sensitization out of 4268 individuals tested. The distribution of BeLPT values for normal, sensitized, and CBD-identified individuals is described. Based on the information collected during the first 3 1/3 years of the BHSP, the BeLPT is the most effective means for the early identification of beryllium-sensitized individuals and to identify individuals who may have CBD. The need for BeLPT retesting is demonstrated through the identification of beryllium sensitization in individuals who previously tested normal. Posterior/anterior chest X-rays were not effective in the identification of CBD. PMID:8933045

  5. Flat optics with designer metasurfaces.

    PubMed

    Yu, Nanfang; Capasso, Federico

    2014-02-01

    Conventional optical components such as lenses, waveplates and holograms rely on light propagation over distances much larger than the wavelength to shape wavefronts. In this way substantial changes of the amplitude, phase or polarization of light waves are gradually accumulated along the optical path. This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam. Metasurfaces are generally created by assembling arrays of miniature, anisotropic light scatterers (that is, resonators such as optical antennas). The spacing between antennas and their dimensions are much smaller than the wavelength. As a result the metasurfaces, on account of Huygens principle, are able to mould optical wavefronts into arbitrary shapes with subwavelength resolution by introducing spatial variations in the optical response of the light scatterers. Such gradient metasurfaces go beyond the well-established technology of frequency selective surfaces made of periodic structures and are extending to new spectral regions the functionalities of conventional microwave and millimetre-wave transmit-arrays and reflect-arrays. Metasurfaces can also be created by using ultrathin films of materials with large optical losses. By using the controllable abrupt phase shifts associated with reflection or transmission of light waves at the interface between lossy materials, such metasurfaces operate like optically thin cavities that strongly modify the light spectrum. Technology opportunities in various spectral regions and their potential advantages in replacing existing optical components are discussed.

  6. Communication: Two types of flat-planes conditions in density functional theory

    NASA Astrophysics Data System (ADS)

    Yang, Xiaotian Derrick; Patel, Anand H. G.; Miranda-Quintana, Ramón Alain; Heidar-Zadeh, Farnaz; González-Espinoza, Cristina E.; Ayers, Paul W.

    2016-07-01

    Using results from atomic spectroscopy, we show that there are two types of flat-planes conditions. The first type of flat-planes condition occurs when the energy as a function of the number of electrons of each spin, Nα and Nβ, has a derivative discontinuity on a line segment where the number of electrons, Nα + Nβ, is an integer. The second type of flat-planes condition occurs when the energy has a derivative discontinuity on a line segment where the spin polarization, Nα - Nβ, is an integer, but does not have a discontinuity associated with an integer number of electrons. Type 2 flat planes are rare—we observed just 15 type 2 flat-planes conditions out of the 4884 cases we tested—but their mere existence has implications for the design of exchange-correlation energy density functionals. To facilitate the development of functionals that have the correct behavior with respect to both fractional number of electrons and fractional spin polarization, we present a dataset for the chromium atom and its ions that can be used to test new functionals.

  7. Communication: Two types of flat-planes conditions in density functional theory.

    PubMed

    Yang, Xiaotian Derrick; Patel, Anand H G; Miranda-Quintana, Ramón Alain; Heidar-Zadeh, Farnaz; González-Espinoza, Cristina E; Ayers, Paul W

    2016-07-21

    Using results from atomic spectroscopy, we show that there are two types of flat-planes conditions. The first type of flat-planes condition occurs when the energy as a function of the number of electrons of each spin, Nα and Nβ, has a derivative discontinuity on a line segment where the number of electrons, Nα + Nβ, is an integer. The second type of flat-planes condition occurs when the energy has a derivative discontinuity on a line segment where the spin polarization, Nα - Nβ, is an integer, but does not have a discontinuity associated with an integer number of electrons. Type 2 flat planes are rare-we observed just 15 type 2 flat-planes conditions out of the 4884 cases we tested-but their mere existence has implications for the design of exchange-correlation energy density functionals. To facilitate the development of functionals that have the correct behavior with respect to both fractional number of electrons and fractional spin polarization, we present a dataset for the chromium atom and its ions that can be used to test new functionals.

  8. Particle detection on flat surfaces

    NASA Astrophysics Data System (ADS)

    van der Donck, Jacques; Snel, Rob; Stortelder, Jetske; Abutan, Alfred; Oostrom, Sjoerd; van Reek, Sander; van der Zwan, Bert; van der Walle, Peter

    2011-04-01

    Since 2006 EUV Lithographic tools have been available for testing purposes giving a boost to the development of fab infrastructure for EUV masks. The absence of a pellicle makes the EUV reticles extremely vulnerable to particles. Therefore, the fab infrastructure for masks must meet very strict particle requirements. It is expected that all new equipment must be qualified on particles before it can be put into operation. This qualification requirement increases the need for a low cost method for particle detection on mask substrates. TNO developed its fourth generation particle scanner, the Rapid Nano. This scanner is capable of detecting nanometer sized particles on flat surfaces. The particle detection is based on dark field imaging techniques and fast image processing. The tool was designed for detection of a single added particle in a handling experiment over a reticle sized substrate. Therefore, the Rapid Nano is very suitable for the validation of particle cleanliness of equipment. During the measurement, the substrate is protected against particle contamination by placing it in a protective environment. This environment shields the substrate from all possible contamination source in the Nano Rapid (stages, elevator, cabling). The imaging takes place through a window in the protective cover. The geometry of the protective environment enables large flexibility in substrate shape and size. Particles can be detected on substrates varying from 152 x 152 mm mask substrates to wafers up to 200 mm. PSL particles of 50 nm were detected with signal noise ratio of 26. Larger particles had higher signal noise ratios. By individually linking particles in two measurements the addition of particles can be detected. These results show that the Rapid Nano is capable of detecting particles of 50 nm and larger of a full reticle substrate.

  9. 2. VIEW IN ROOM 111, ATOMIC ABSORPTION BERYLLIUM ANALYSIS LABORATORY. ...

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

    2. VIEW IN ROOM 111, ATOMIC ABSORPTION BERYLLIUM ANALYSIS LABORATORY. AIR FILTERS AND SWIPES ARE DISSOLVED WITH ACIDS AND THE REMAINING RESIDUES ARE SUSPENDED IN NITRIC ACID SOLUTION. THE SOLUTION IS PROCESSED THROUGH THE ATOMIC ABSORPTION SPECTROPHOTOMETER TO DETECT THE PRESENCE AND LEVELS OF BERYLLIUM. - Rocky Flats Plant, Health Physics Laboratory, On Central Avenue between Third & Fourth Streets, Golden, Jefferson County, CO

  10. Rocky Flats ash test procedure (sludge stabilization)

    SciTech Connect

    Winstead, M.L.

    1995-09-14

    Rocky Flats Ash items have been identified as the next set of materials to be stabilized. This test is being run to determine charge sizes and soak times to completely stabilize the Rocky Flats Ash items. The information gathered will be used to generate the heating rampup cycle for stabilization. This test will also gain information on the effects of the glovebox atmosphere (moisture) on the stabilized material. This document provides instructions for testing Rocky Flats Ash in the HC-21C muffle furnace process.

  11. Atomic supersymmetry

    NASA Technical Reports Server (NTRS)

    Kostelecky, V. Alan

    1993-01-01

    Atomic supersymmetry is a quantum-mechanical supersymmetry connecting the properties of different atoms and ions. A short description of some established results in the subject are provided and a few recent developments are discussed including the extension to parabolic coordinates and the calculation of Stark maps using supersymmetry-based models.

  12. Atomic Calligraphy

    NASA Astrophysics Data System (ADS)

    Imboden, Matthias; Pardo, Flavio; Bolle, Cristian; Han, Han; Tareen, Ammar; Chang, Jackson; Christopher, Jason; Corman, Benjamin; Bishop, David

    2013-03-01

    Here we present a MEMS based method to fabricate devices with a small number of atoms. In standard semiconductor fabrication, a large amount of material is deposited, after which etching removes what is not wanted. This technique breaks down for structures that approach the single atom limit, as it is inconceivable to etch away all but one atom. What is needed is a bottom up method with single or near single atom precision. We demonstrate a MEMS device that enables nanometer position controlled deposition of gold atoms. A digitally driven plate is swept as a flux of gold atoms passes through an aperture. Appling voltages on four comb capacitors connected to the central plate by tethers enable nanometer lateral precision in the xy plane over 15x15 sq. microns. Typical MEMS structures have manufacturing resolutions on the order of a micron. Using a FIB it is possible to mill apertures as small as 10 nm in diameter. Assuming a low incident atomic flux, as well as an integrated MEMS based shutter with microsecond response time, it becomes possible to deposit single atoms. Due to their small size and low power consumption, such nano-printers can be mounted directly in a cryogenic system at ultrahigh vacuum to deposit clean quench condensed metallic structures.

  13. Anthropogenic plutonium in the North Jiangsu tidal flats of the Yellow Sea in China.

    PubMed

    Liu, Zhiyong; Zheng, Jian; Pan, Shaoming; Gao, Jianhua

    2013-08-01

    The (239+240)Pu activities and (240)Pu/(239)Pu atom ratios were analyzed using a double-focusing SF-ICP-MS for sediment core samples obtained in 2007-2008 from the North Jiangsu tidal flats in the Yellow Sea in China. Particular attention was focused on the (240)Pu/(239)Pu atom ratios in the sediment to identify the origins of Pu isotopes. The profiles of (239+240)Pu activities in the sediment cores are similar to those of the (137)Cs activities. The (240)Pu/(239)Pu atom ratios in the tidal flats showed typical global fallout values, indicating that this area did not receive the possible early direct close-in fallout or oceanic current transported Pu from the Pacific Proving Grounds (PPG). If any, the contribution of the PPG source Pu to the total Pu inventory is negligible. This is different from the sediments in the Yangtze River estuary in the East China Sea, where the PPG source Pu contributed ca. 45 % to the total inventory. In addition, the observation of the global fallout origin Pu in the North Jiangsu tidal flats indicated that the nuclear power plant in the region was not causing any alteration/contamination to the (240)Pu/(239)Pu atom ratios. The (239+240)Pu and (137)Cs activities/inventories in the sediment cores showed correlation to the mean clay sediment compositions (fine particles) in the tidal flats. Therefore, mud deposits are served as sinks for the anthropogenic radionuclides in the tidal flats and the Yellow Sea. Integrated with the previously reported spatial distributions of (239+240)Pu and (137)Cs activities in the surface sediments of the Yellow Sea, the mechanism of Pu transport with the ocean currents and the scavenging characteristics in the Yellow Sea were discussed.

  14. Anthropogenic plutonium in the North Jiangsu tidal flats of the Yellow Sea in China.

    PubMed

    Liu, Zhiyong; Zheng, Jian; Pan, Shaoming; Gao, Jianhua

    2013-08-01

    The (239+240)Pu activities and (240)Pu/(239)Pu atom ratios were analyzed using a double-focusing SF-ICP-MS for sediment core samples obtained in 2007-2008 from the North Jiangsu tidal flats in the Yellow Sea in China. Particular attention was focused on the (240)Pu/(239)Pu atom ratios in the sediment to identify the origins of Pu isotopes. The profiles of (239+240)Pu activities in the sediment cores are similar to those of the (137)Cs activities. The (240)Pu/(239)Pu atom ratios in the tidal flats showed typical global fallout values, indicating that this area did not receive the possible early direct close-in fallout or oceanic current transported Pu from the Pacific Proving Grounds (PPG). If any, the contribution of the PPG source Pu to the total Pu inventory is negligible. This is different from the sediments in the Yangtze River estuary in the East China Sea, where the PPG source Pu contributed ca. 45 % to the total inventory. In addition, the observation of the global fallout origin Pu in the North Jiangsu tidal flats indicated that the nuclear power plant in the region was not causing any alteration/contamination to the (240)Pu/(239)Pu atom ratios. The (239+240)Pu and (137)Cs activities/inventories in the sediment cores showed correlation to the mean clay sediment compositions (fine particles) in the tidal flats. Therefore, mud deposits are served as sinks for the anthropogenic radionuclides in the tidal flats and the Yellow Sea. Integrated with the previously reported spatial distributions of (239+240)Pu and (137)Cs activities in the surface sediments of the Yellow Sea, the mechanism of Pu transport with the ocean currents and the scavenging characteristics in the Yellow Sea were discussed. PMID:23264060

  15. Flatness Control Using Roll Coolant Based on Predicted Flatness Variation in Cold Rolling Mills

    NASA Astrophysics Data System (ADS)

    Dohmae, Yukihiro; Okamura, Yoshihide

    Flatness control for cold rolling mills is one of the important technologies for improving of product quality and productivity. In particular, poor flatness leads to strip tearing in the extreme case and, moreover, it significantly reduces productivity. Therefore, various flatness control system has been developed. The main actuators for flatness control are classified into two types; one is mechanical equipment such as roll bender, the other is roll coolant, which controls thermal expansion of roll. Flatness variation such as center buckle or edge wave is mainly controlled by mechanical actuator which has high response characteristics. On another front, flatness variation of local zone can be controlled by roll coolant although one's response is lower than the response of mechanical actuator. For accomplishing good flatness accuracy in cold rolling mills, it is important to improve the performance of coolant control moreover. In this paper, a new coolant control method based on flatness variation model is described. In proposed method, the state of coolant spray on or off is selected to minimize the flatness deviation by using predicted flatness variation. The effectiveness of developed system has been demonstrated by application in actual plant.

  16. The manufacture of flat conductor cable

    NASA Technical Reports Server (NTRS)

    Angele, W.

    1974-01-01

    The major techniques are described for fabricating flat conductor cable (FCC). Various types of FCC, including unshielded, shielded, power, and signal, in both existing and conceptual constructions, are covered.

  17. 40 CFR 230.42 - Mud flats.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... extremely low tides and inundated at high tides with the water table at or near the surface of the substrate... dewater the mud flat or disrupt periodic inundation, resulting in an increase in the rate of erosion...

  18. 40 CFR 230.42 - Mud flats.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... extremely low tides and inundated at high tides with the water table at or near the surface of the substrate... dewater the mud flat or disrupt periodic inundation, resulting in an increase in the rate of erosion...

  19. 40 CFR 230.42 - Mud flats.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... extremely low tides and inundated at high tides with the water table at or near the surface of the substrate... dewater the mud flat or disrupt periodic inundation, resulting in an increase in the rate of erosion...

  20. Rocky Flats Ash test procedure (sludge stabilization)

    SciTech Connect

    Funston, G.A.

    1995-06-14

    Rocky Flats Ash items have been identified as the next set of materials to be stabilized. This test is being run to determine charge sizes and soak times to completely stabilize the Rocky Flats Ash items. The information gathered will be used to generate the heating rampup cycle for stabilization. The test will provide information to determine charge sizes, soak times and mesh screen sizes (if available at time of test) for stabilization of Rocky Flats Ash items to be processed in the HC-21C Muffle Furnace Process. Once the charge size and soak times have been established, a program for the temperature controller of the HC-21C Muffle Furnace process will be generated for processing Rocky Flats Ash.

  1. Flat-package DIP handling tool

    NASA Technical Reports Server (NTRS)

    Angelou, E.; Fraser, R.

    1977-01-01

    Device, using magnetic attraction, can facilitate handling of integrated-circuit flat packages and prevent contamination and bent leads. Tool lifts packages by their cases and releases them by operation of manual plunger.

  2. High-energy-density flat flexible capacitors

    NASA Technical Reports Server (NTRS)

    Parker, R. D.; Zelik, J. A.

    1979-01-01

    Manufacturing technique produces flat flexible capacitors of energy density greater than 0.1 J/g. Exposure of some of metalized surface of each layer provides sufficient film surface to ensure good electrical connection to each layer of capacitor.

  3. Combined load test apparatus for flat panels

    NASA Astrophysics Data System (ADS)

    McWithey, Robert R.; Martin, Carl J., Jr.; Cerro, Jeffrey A.

    1992-04-01

    Future hypersonic aircraft such as the National Aero-Space Plane and a high speed civil transport will require the design and use of efficient, highly-loaded, flat structural panels to achieve mission requirements. These panels will be subjected to severe combinations of in-plane mechanical distributed loads (i.e., normal loads in two perpendicular directions plus a shear load), in addition to pressure and thermal loads. A testing apparatus is provided for applying uniform combined in-plane stresses to a flat panel containing an interior test area. Actuators cause two sets of load rods to apply loads to the edge of the flat panel. The first set applies loads which are perpendicular to and independent of the loads applied by the second set. The loads are applied according to a cosine load distribution to obtain a uniform stress field within the test area. The flat panel may be rotated with respect to the applied loads to obtain a wide range of combined stresses in the test area. Movement outside the plane of the flat panel may be selectively prevented by connecting the flat panel to a restraining disk by support rods. The support rods then define the test area. A thermal load may be applied to one side of the flat panel and a pressure load may be applied to the other side. The novelty of this method is found in providing a testing apparatus which allows mechanical, thermal and pressure loads to be applied simultaneously to a flat panel for testing purposes.

  4. Flat panel ferroelectric electron emission display system

    DOEpatents

    Sampayan, S.E.; Orvis, W.J.; Caporaso, G.J.; Wieskamp, T.F.

    1996-04-16

    A device is disclosed which can produce a bright, raster scanned or non-raster scanned image from a flat panel. Unlike many flat panel technologies, this device does not require ambient light or auxiliary illumination for viewing the image. Rather, this device relies on electrons emitted from a ferroelectric emitter impinging on a phosphor. This device takes advantage of a new electron emitter technology which emits electrons with significant kinetic energy and beam current density. 6 figs.

  5. Flat panel ferroelectric electron emission display system

    DOEpatents

    Sampayan, Stephen E.; Orvis, William J.; Caporaso, George J.; Wieskamp, Ted F.

    1996-01-01

    A device which can produce a bright, raster scanned or non-raster scanned image from a flat panel. Unlike many flat panel technologies, this device does not require ambient light or auxiliary illumination for viewing the image. Rather, this device relies on electrons emitted from a ferroelectric emitter impinging on a phosphor. This device takes advantage of a new electron emitter technology which emits electrons with significant kinetic energy and beam current density.

  6. High performance flat plate solar collector

    NASA Technical Reports Server (NTRS)

    Lansing, F. L.; Reynolds, R.

    1976-01-01

    The potential use of porous construction is presented to achieve efficient heat removal from a power producing solid and is applied to solar air heaters. Analytical solutions are given for the temperature distribution within a gas-cooled porous flat plate having its surface exposed to the sun's energy. The extracted thermal energy is calculated for two different types of plate transparency. Results show the great improvement in performance obtained with porous flat plate collectors as compared with analogous nonporous types.

  7. Topological properties of flat electroencephalography's state space

    NASA Astrophysics Data System (ADS)

    Ken, Tan Lit; Ahmad, Tahir bin; Mohd, Mohd Sham bin; Ngien, Su Kong; Suwa, Tohru; Meng, Ong Sie

    2016-02-01

    Neuroinverse problem are often associated with complex neuronal activity. It involves locating problematic cell which is highly challenging. While epileptic foci localization is possible with the aid of EEG signals, it relies greatly on the ability to extract hidden information or pattern within EEG signals. Flat EEG being an enhancement of EEG is a way of viewing electroencephalograph on the real plane. In the perspective of dynamical systems, Flat EEG is equivalent to epileptic seizure hence, making it a great platform to study epileptic seizure. Throughout the years, various mathematical tools have been applied on Flat EEG to extract hidden information that is hardly noticeable by traditional visual inspection. While these tools have given worthy results, the journey towards understanding seizure process completely is yet to be succeeded. Since the underlying structure of Flat EEG is dynamic and is deemed to contain wealthy information regarding brainstorm, it would certainly be appealing to explore in depth its structures. To better understand the complex seizure process, this paper studies the event of epileptic seizure via Flat EEG in a more general framework by means of topology, particularly, on the state space where the event of Flat EEG lies.

  8. Flat H Frangible Joint Evolution

    NASA Technical Reports Server (NTRS)

    Diegelman, Thomas E.; Hinkel, Todd J.; Benjamin, Andrew; Rochon, Brian V.; Brown, Christopher W.

    2016-01-01

    Space vehicle staging and separation events require pyrotechnic devices. They are single-use mechanisms that cannot be tested, nor can failure-tolerant performance be demonstrated in actual flight articles prior to flight use. This necessitates the implementation of a robust design and test approach coupled with a fully redundant, failure-tolerant explosive mechanism to ensure that the system functions even in the event of a single failure. Historically, NASA has followed the single failure-tolerant (SFT) design philosophy for all human-rated spacecraft, including the Space Shuttle Program. Following the end of this program, aerospace companies proposed building the next generation human-rated vehicles with off-the-shelf, non-redundant, zero-failure-tolerant (ZFT) separation systems. Currently, spacecraft and launch vehicle providers for both the Orion and Commercial Crew Programs (CCPs) plan to deviate from the heritage safety approach and NASA's SFT human rating requirements. Both programs' partners have base-lined ZFT frangible joints for vehicle staging and fairing separation. These joints are commercially available from pyrotechnic vendors. Non-human-rated missions have flown them numerous times. The joints are relatively easy to integrate structurally within the spacecraft. In addition, the separation event is debris free, and the resultant pyro shock is lower than that of other design solutions. It is, however, a serious deficiency to lack failure tolerance. When used for critical applications on human-rated vehicles, a single failure could potentially lead to loss of crew (LOC) or loss of mission (LOM)). The Engineering and Safety & Mission Assurance directorates within the NASA Johnson Space Center took action to address this safety issue by initiating a project to develop a fully redundant, SFT frangible joint design, known as the Flat H. Critical to the ability to retrofit on launch vehicles being developed, the SFT mechanisms must fit within the same

  9. Hydrogen diffusion and stabilization in single-crystal VO2 micro/nanobeams by direct atomic hydrogenation.

    PubMed

    Lin, Jian; Ji, Heng; Swift, Michael W; Hardy, Will J; Peng, Zhiwei; Fan, Xiujun; Nevidomskyy, Andriy H; Tour, James M; Natelson, Douglas

    2014-09-10

    We report measurements of the diffusion of atomic hydrogen in single crystalline VO2 micro/nanobeams by direct exposure to atomic hydrogen, without catalyst. The atomic hydrogen is generated by a hot filament, and the doping process takes place at moderate temperature (373 K). Undoped VO2 has a metal-to-insulator phase transition at ∼340 K between a high-temperature, rutile, metallic phase and a low-temperature, monoclinic, insulating phase with a resistance exhibiting a semiconductor-like temperature dependence. Atomic hydrogenation results in stabilization of the metallic phase of VO2 micro/nanobeams down to 2 K, the lowest point we could reach in our measurement setup. Optical characterization shows that hydrogen atoms prefer to diffuse along the c axis of rutile (a axis of monoclinic) VO2, along the oxygen "channels". Based on observing the movement of the hydrogen diffusion front in single crystalline VO2 beams, we estimate the diffusion constant for hydrogen along the c axis of the rutile phase to be 6.7 × 10(-10) cm(2)/s at approximately 373 K, exceeding the value in isostructural TiO2 by ∼38×. Moreover, we find that the diffusion constant along the c axis of the rutile phase exceeds that along the equivalent a axis of the monoclinic phase by at least 3 orders of magnitude. This remarkable change in kinetics must originate from the distortion of the "channels" when the unit cell doubles along this direction upon cooling into the monoclinic structure. Ab initio calculation results are in good agreement with the experimental trends in the relative kinetics of the two phases. This raises the possibility of a switchable membrane for hydrogen transport.

  10. Kinetic Atom.

    ERIC Educational Resources Information Center

    Wilson, David B.

    1981-01-01

    Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)

  11. Acting Atoms.

    ERIC Educational Resources Information Center

    Farin, Susan Archie

    1997-01-01

    Describes a fun game in which students act as electrons, protons, and neutrons. This activity is designed to help students develop a concrete understanding of the abstract concept of atomic structure. (DKM)

  12. Dynamics of DNA Chains on Flat and Patterned Surfaces

    NASA Astrophysics Data System (ADS)

    Li, Bingquan; Xiaohua, Fang; Seo, Young-Soo; Samuilov, Vladimir; Rafailovich, Miriam; Sokolov, Jonathan

    2003-03-01

    The electrophoresis of DNA chains on flat silicon and patterned surfaces was studied by Confocal Fluorescence Microscopy and Atomic Force Microscopy. Solutions of lambda DNA of 48,502 bp and Schizosaccharomyces pombe (S. pombe) of 3 6 Mb were deposited on different surfaces. The surfaces were chemically modified to be hydrophilic or SAM-covered and the patterns were produced over length scales from nano to micro size in the form of gratings or square arrays. The interaction with the surface and mobility of DNA chains depended on the surface chemistry, topography and ion concentration of buffer. The motion of individual chains in the electric field was analyzed both in terms of the dimensions and orientation of the pattern structure. Supported by NSF-MRSEC program (DMR-9632525)

  13. Rocky Flats Compliance Program; Technology summary

    SciTech Connect

    1994-02-01

    The Department of Energy (DOE) established the Office of Technology Development (EM-50) (OTD) as an element of Environmental Restoration and Waste Management (EM) in November 1989. The primary objective of the Office of Technology Development, Rocky Flats Compliance Program (RFCP), is to develop altemative treatment technologies for mixed low-level waste (wastes containing both hazardous and radioactive components) to use in bringing the Rocky Flats Plant (RFP) into compliance with Federal and state regulations and agreements. Approximately 48,000 cubic feet of untreated low-level mixed waste, for which treatment has not been specified, are stored at the RFP. The cleanup of the Rocky Flats site is driven by agreements between DOE, the Environmental Protection Agency (EPA), and the Colorado Department of Health (CDH). Under these agreements, a Comprehensive Treatment and Management Plan (CTMP) was drafted to outline the mechanisms by which RFP will achieve compliance with the regulations and agreements. This document describes DOE`s strategy to treat low-level mixed waste to meet Land Disposal Restrictions and sets specific milestones related to the regulatory aspects of technology development. These milestones detail schedules for the development of technologies to treat all of the mixed wastes at the RFP. Under the Federal Facilities Compliance Act (FFCA), the CTMP has been incorporated into Rocky Flats Plant Conceptual Site Treatment Plan (CSTP). The CSTP will become the Rocky Flats Plant site Treatment Plan in 1995 and will supersede the CTMP.

  14. Cosmic strings from supersymmetric flat directions

    SciTech Connect

    Cui Yanou; Morrissey, David E.; Martin, Stephen P.; Wells, James D.

    2008-02-15

    Flat directions are a generic feature of the scalar potential in supersymmetric gauge field theories. They can arise, for example, from D-terms associated with an extra Abelian gauge symmetry. Even when supersymmetry is broken softly, there often remain directions in the scalar field space along which the potential is almost flat. Upon breaking a gauge symmetry along one of these almost-flat directions, cosmic strings may form. Relative to the standard cosmic string picture based on the Abelian Higgs model, these flat-direction cosmic strings have the extreme type-I properties of a thin gauge core surrounded by a much wider scalar field profile. We perform a comprehensive study of the microscopic, macroscopic, and observational characteristics of this class of strings. We find many differences from the standard string scenario, including stable higher winding-mode strings, the dynamical formation of higher mode strings from lower ones, and a resultant multitension scaling string network in the early universe. These strings are only moderately constrained by current observations, and their gravitational wave signatures may be detectable at future gravity wave detectors. Furthermore, there is the interesting but speculative prospect that the decays of cosmic string loops in the early universe could be a source of ultrahigh-energy cosmic rays or nonthermal dark matter. We also compare the observational signatures of flat-direction cosmic strings with those of ordinary cosmic strings as well as (p,q) cosmic strings motivated by superstring theory.

  15. A single crystalline porphyrinic titanium metal–organic framework

    SciTech Connect

    Yuan, Shuai; Liu, Tian -Fu; Feng, Dawei; Tian, Jian; Wang, Kecheng; Qin, Junsheng; Zhang, Qiang; Chen, Ying -Pin; Bosch, Mathieu; Zou, Lanfang; Teat, Simon J.; Dalgarno, Scott J.; Zhou, Hong -Cai

    2015-04-28

    We successfully assembled the photocatalytic titanium-oxo cluster and photosensitizing porphyrinic linker into a metal–organic framework (MOF), namely PCN-22. A preformed titanium-oxo carboxylate cluster is adopted as the starting material to judiciously control the MOF growth process to afford single crystals. This synthetic method is useful to obtain highly crystalline titanium MOFs, which has been a daunting challenge in this field. Moreover, PCN-22 demonstrated permanent porosity and photocatalytic activities toward alcohol oxidation.

  16. Positioning and joining of organic single-crystalline wires

    NASA Astrophysics Data System (ADS)

    Wu, Yuchen; Feng, Jiangang; Jiang, Xiangyu; Zhang, Zhen; Wang, Xuedong; Su, Bin; Jiang, Lei

    2015-03-01

    Organic single-crystal, one-dimensional materials can effectively carry charges and/or excitons due to their highly ordered molecule packing, minimized defects and eliminated grain boundaries. Controlling the alignment/position of organic single-crystal one-dimensional architectures would allow on-demand photon/electron transport, which is a prerequisite in waveguides and other optoelectronic applications. Here we report a guided physical vapour transport technique to control the growth, alignment and positioning of organic single-crystal wires with the guidance of pillar-structured substrates. Submicrometre-wide, hundreds of micrometres long, highly aligned, organic single-crystal wire arrays are generated. Furthermore, these organic single-crystal wires can be joined within controlled angles by varying the pillar geometries. Owing to the controllable growth of organic single-crystal one-dimensional architectures, we can present proof-of-principle demonstrations utilizing joined wires to allow optical waveguide through small radii of curvature (internal angles of ~90-120°). Our methodology may open a route to control the growth of organic single-crystal one-dimensional materials with potential applications in optoelectronics.

  17. Single-crystalline InI—Material for infrared optics

    NASA Astrophysics Data System (ADS)

    Fedorov, P. P.; Kuznetsov, S. V.; Chuvilina, E. L.; Gasanov, A. A.; Plotnichenko, V. G.; Popov, P. A.; Matovnikov, A. V.; Osiko, V. V.

    2016-06-01

    The Bridgman-Stockbarger method is used for growing InI single crystals. The crystals are characterized by a perfect cleavage along (0k0). The long-wave IR transmission boundary amounts to 51 µm. For the first time, the thermal capacity and thermal conductivity are measured in the intervals of 80-300 and 50-300 K, respectively. The crystals have a high thermal capacity and a low thermal conductivity ( C = 52.7 J/(mol K) and k = 0.58 W/(m K) at 300 K).

  18. Thin single-crystalline silicon solar cells for space applications

    NASA Astrophysics Data System (ADS)

    Nijs, J.; Caymax, M.; Acke, P.; Roggen, J.; Lambrechts, M.; Gravesen, P.

    1986-11-01

    A technology to perform etching after the formation of the solar cell, using epitaxial deposition of the active layer of the cell combined with an etch stop technique is proposed. This can result in highly efficient silicon solar cells with thicknesses down to 10 microns.

  19. Optical cavity modes of a single crystalline zinc oxide microsphere.

    PubMed

    Moirangthem, Rakesh Singh; Cheng, Pi-Ju; Chien, Paul Ching-Hang; Ngo, Buu Trong Huynh; Chang, Shu-Wei; Tien, Chung-Hao; Chang, Yia-Chung

    2013-02-11

    A detailed study on the optical cavity modes of zinc oxide microspheres under the optical excitation is presented. The zinc oxide microspheres with diameters ranging from 1.5 to 3.0 µm are prepared using hydrothermal growth technique. The photoluminescence measurement of a single microsphere shows prominent resonances of whispering gallery modes at room temperature. The experimentally observed whispering gallery modes in the photoluminescence spectrum are compared with theoretical calculations using analytical and finite element methods in order to clarify resonance properties of these modes. The comparison between theoretical analysis and experiment suggests that the dielectric constant of the ZnO microsphere is somewhat different from that for bulk ZnO. The sharp resonances of whispering gallery modes in zinc oxide microspheres cover the entire visible window. They may be utilized in realizations of optical resonators, light emitting devices, and lasers for future chip integrations with micro/nano optoelectronic circuits, and developments of optical biosensors. PMID:23481759

  20. Deformation compatibility in a single crystalline Ni superalloy

    PubMed Central

    Zhang, Tiantian; Dunne, Fionn P. E.

    2016-01-01

    Deformation in materials is often complex and requires rigorous understanding to predict engineering component lifetime. Experimental understanding of deformation requires utilization of advanced characterization techniques, such as high spatial resolution digital image correlation (HR-DIC) and high angular resolution electron backscatter diffraction (HR-EBSD), combined with clear interpretation of their results to understand how a material has deformed. In this study, we use HR-DIC and HR-EBSD to explore the mechanical behaviour of a single-crystal nickel alloy and to highlight opportunities to understand the complete deformations state in materials. Coupling of HR-DIC and HR-EBSD enables us to precisely focus on the extent which we can access the deformation gradient, F, in its entirety and uncouple contributions from elastic deformation gradients, slip and rigid body rotations. Our results show a clear demonstration of the capabilities of these techniques, found within our experimental toolbox, to underpin fundamental mechanistic studies of deformation in polycrystalline materials and the role of microstructure. PMID:26997901

  1. Atomic research

    NASA Technical Reports Server (NTRS)

    Hadaway, James B.; Connatser, Robert; Cothren, Bobby; Johnson, R. B.

    1993-01-01

    Work performed by the University of Alabama in Huntsville's (UAH) Center for Applied Optics (CAO) entitled Atomic Research is documented. Atomic oxygen (AO) effects on materials have long been a critical concern in designing spacecraft to withstand exposure to the Low Earth Orbit (LEO) environment. The objective of this research effort was to provide technical expertise in the design of instrumentation and experimental techniques for analyzing materials exposed to atomic oxygen in accelerated testing at NASA/MSFC. Such testing was required to answer fundamental questions concerning Space Station Freedom (SSF) candidate materials and materials exposed to atomic oxygen aboard the Long-Duration Exposure Facility (LDEF). The primary UAH task was to provide technical design, review, and analysis to MSFC in the development of a state-of-the-art 5eV atomic oxygen beam facility required to simulate the RAM-induced low earth orbit (LEO) AO environment. This development was to be accomplished primarily at NASA/MSFC. In support of this task, contamination effects and ultraviolet (UV) simulation testing was also to be carried out using NASA/MSFC facilities. Any materials analysis of LDEF samples was to be accomplished at UAH.

  2. Actuated atomizer

    NASA Technical Reports Server (NTRS)

    Tilton, Charles (Inventor); Weiler, Jeff (Inventor); Palmer, Randall (Inventor); Appel, Philip (Inventor)

    2008-01-01

    An actuated atomizer is adapted for spray cooling or other applications wherein a well-developed, homogeneous and generally conical spray mist is required. The actuated atomizer includes an outer shell formed by an inner ring; an outer ring; an actuator insert and a cap. A nozzle framework is positioned within the actuator insert. A base of the nozzle framework defines swirl inlets, a swirl chamber and a swirl chamber. A nozzle insert defines a center inlet and feed ports. A spool is positioned within the coil housing, and carries the coil windings having a number of turns calculated to result in a magnetic field of sufficient strength to overcome the bias of the spring. A plunger moves in response to the magnetic field of the windings. A stop prevents the pintle from being withdrawn excessively. A pintle, positioned by the plunger, moves between first and second positions. In the first position, the head of the pintle blocks the discharge passage of the nozzle framework, thereby preventing the atomizer from discharging fluid. In the second position, the pintle is withdrawn from the swirl chamber, allowing the atomizer to release atomized fluid. A spring biases the pintle to block the discharge passage. The strength of the spring is overcome, however, by the magnetic field created by the windings positioned on the spool, which withdraws the plunger into the spool and further compresses the spring.

  3. High sensitivity flat SiO2 fibres for medical dosimetry

    NASA Astrophysics Data System (ADS)

    Abdul Sani, Siti. F.; Alalawi, Amani I.; Azhar, Hairul A. R.; Amouzad Mahdiraji, Ghafour; Tamchek, Nizam; Nisbet, A.; Maah, M. J.; Bradley, D. A.

    2014-11-01

    We describe investigation of a novel undoped flat fibre fabricated for medical radiation dosimetry. Using high energy X-ray beams generated at a potential of 6 MV, comparison has been made of the TL yield of silica flat fibres, TLD-100 chips and Ge-doped silica fibres. The flat fibres provide competitive TL yield to that of TLD-100 chips, being some 100 times that of the Ge-doped fibres. Pt-coated flat fibres have then been used to increase photoelectron production and hence local dose deposition, obtaining significant increase in dose sensitivity over that of undoped flat fibres. Using 250 kVp X-ray beams, the TL yield reveals a progressive linear increase in dose for Pt thicknesses from 20 nm up to 80 nm. The dose enhancement factor (DEF) of (0.0150±0.0003) nm-1 Pt is comparable to that obtained using gold, agreeing at the 1% level with the value expected on the basis of photoelectron generation. Finally, X-ray photoelectron spectroscopy (XPS) has been employed to characterize the surface oxidation state of the fibre medium. The charge state of Si2p was found to lie on 103.86 eV of binding energy and the atomic percentage obtained from the XPS analysis is 22.41%.

  4. Band flatness optimization through complex analysis

    NASA Astrophysics Data System (ADS)

    Lee, Ching Hua; Arovas, Daniel P.; Thomale, Ronny

    2016-04-01

    Narrow-band electron systems are particularly likely to exhibit correlated many-body phases driven by interaction effects. Examples include magnetic materials, heavy-fermion systems, and topological phases such as fractional quantum Hall states and their lattice-based cousins, the fractional Chern insulators (FCIs). Here we discuss the problem of designing models with optimal band flatness, subject to constraints on the range of electron hopping. In particular, we show how the imaginary gap, which serves as a proxy for band flatness, can be optimized by appealing to Rouché's theorem, a familiar result from complex analysis. This leads to an explicit construction which we illustrate through its application to two-band FCI models with nontrivial topology (i.e., nonzero Chern numbers). We show how the imaginary-gap perspective leads to an elegant geometric picture of how topological properties can obstruct band flatness in systems with finite-range hopping.

  5. Bubble nucleation for flat potential barriers

    NASA Astrophysics Data System (ADS)

    Jensen, Lars Gerhard; Steinhardt, Paul Joseph

    1989-05-01

    We have studied false vacuum decay for effective potentials in which the false vacuum is separated from the true vacuum by a ``flat'' potential barrier. By flat, we mean that, near the top of the barrier, the potential varies quartically, rather than quadratically with the field (to leading order). We have discovered several new types of bubble solutions. One type reduces in the flat space-time limit to the mathematical solution introduced by Lee and Weinberg to describe ``tunneling without barriers.'' Based on our analysis, though, we propose a significantly different interpretation of the curved space solution. We numerically study these solutions (plus the Hawking-Moss solution) for a toy model to examine how the dominant tunneling mode may change as a function of parameters. We propose a variant of the new inflationary scenario based on these results.

  6. Solid waste recycling programs at Rocky Flats

    SciTech Connect

    Millette, R.L.; Blackman, T.E.; Shepard, M.D.

    1994-12-31

    The Rocky Flats (RFP) recycling programs for solid waste materials have been in place for over ten years. Within the last three years, the programs were centralized under the direction of the Rocky Flats Waste Minimization department, with the assistance of various plant organizations (e.g., Trucking, Building Services, Regulated Waste Operations, property Utilization and Disposal and Security). Waste Minimization designs collection and transportation systems for recyclable materials and evaluates recycling markets for opportunities to add new commodities to the existing programs. The Waste Minimization department also promotes employee participation in the Rocky Flats Recycling Programs, and collects all recycling data for publication. A description of the program status as of January 1994 is given.

  7. High temperature solder device for flat cables

    NASA Technical Reports Server (NTRS)

    Haehner, Carl L. (Inventor)

    1992-01-01

    A high temperature solder device for flat cables includes a microwelder, an anvil which acts as a heat sink and supports a flexible flat ribbon cable that is to be connected to a multiple pin connector. The microwelder is made from a modified commercially available resistance welding machine such as the Split Tip Electrode microwelder by Weltek, which consists of two separate electrode halves with a removable dielectric spacer in between. The microwelder is not used to weld the items together, but to provide a controlled compressive force on, and energy pulse to, a solder preform placed between a pin of the connector and a conductor of the flexible flat ribbon cable. When the microwelder is operated, an electric pulse will flow down one electrode, through the solder preform and back up the other electrode. This pulse of electrical energy will cause the solder preform to heat up and melt, joining the pin and conductor.

  8. Atom Interferometry

    SciTech Connect

    Kasevich, Mark

    2008-05-08

    Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton's constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gyroscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be used to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

  9. Atom Interferometry

    SciTech Connect

    Mark Kasevich

    2008-05-07

    Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton’s constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gryoscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be sued to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

  10. Atom Interferometry

    ScienceCinema

    Mark Kasevich

    2016-07-12

    Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton’s constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gryoscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be sued to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

  11. Atomic Structure of Self-Assembled Monolayer of Thiolates on a Tetragonal Au92 Nanocrystal.

    PubMed

    Zeng, Chenjie; Liu, Chong; Chen, Yuxiang; Rosi, Nathaniel L; Jin, Rongchao

    2016-07-20

    Unveiling the ligand binding mode on the crystalline surfaces is important for deciphering the long-standing structural enigma in self-assembled monolayers (SAMs). Here, the binding and patterning structures of thiolates (SR) on the Au(100) crystalline facet are revealed on the basis of the atomic structure of a highly regular, single crystalline Au92(SR)44 nanocrystal. The six exposed facets of this tetragonal nanocrystal give rise to six pieces of "nanoSAMs". We found that thiolates bind to the planar (100) facets of the nanocrystal via a simple bridge-like mode and are assembled into an overlayer with c(2 × 2) symmetry. The Au-S binding mode and translational symmetry in the kernel and on the surface of the Au92 nanocrystal can be generalized infinitely to construct the bulk two-dimensional SAMs and various tetragonal nanocrystals.

  12. Silicon nanowire transistors with a channel width of 4 nm fabricated by atomic force microscope nanolithography.

    PubMed

    Martinez, J; Martínez, R V; Garcia, R

    2008-11-01

    The emergence of an ultrasensitive sensor technology based on silicon nanowires requires both the fabrication of nanoscale diameter wires and the integration with microelectronic processes. Here we demonstrate an atomic force microscopy lithography that enables the reproducible fabrication of complex single-crystalline silicon nanowire field-effect transistors with a high electrical performance. The nanowires have been carved from a silicon-on-insulator wafer by a combination of local oxidation processes with a force microscope and etching steps. We have fabricated and measured the electrical properties of a silicon nanowire transistor with a channel width of 4 nm. The flexibility of the nanofabrication process is illustrated by showing the electrical performance of two nanowire circuits with different geometries. The fabrication method is compatible with standard Si CMOS processing technologies and, therefore, can be used to develop a wide range of architectures and new microelectronic devices.

  13. Issues evaluation process at Rocky Flats Plant

    SciTech Connect

    Smith, L.C.

    1992-04-16

    This report describes the issues evaluation process for Rocky Flats Plant as established in July 1990. The issues evaluation process was initiated February 27, 1990 with a Charter and Process Overview for short-term implementation. The purpose of the process was to determine the projects required for completion before the Phased Resumption of Plutonium Operations. To determine which projects were required, the issues evaluation process and emphasized risk mitigation, based on a ranking system. The purpose of this report is to document the early design of the issues evaluation process to record the methodologies used that continue as the basis for the ongoing Issues Management Program at Rocky Flats Plant.

  14. Flat phase of quantum polymerized membranes

    NASA Astrophysics Data System (ADS)

    Coquand, O.; Mouhanna, D.

    2016-09-01

    We investigate the flat phase of quantum polymerized phantom membranes by means of a nonperturbative renormalization group approach. We first implement this formalism for general quantum polymerized membranes and derive the flow equations that encompass both quantum and thermal fluctuations. We then deduce and analyze the flow equations relevant to study the flat phase and discuss their salient features: quantum to classical crossover and, in each of these regimes, strong to weak coupling crossover. We finally illustrate these features in the context of free-standing graphene physics.

  15. 8. Asymptotically Flat and Regular Cauchy Data

    NASA Astrophysics Data System (ADS)

    Dain, Sergio

    I describe the construction of a large class of asymptotically flat initial data with non-vanishing mass and angular momentum for which the metric and the extrinsic curvature have asymptotic expansions at space-like infinity in terms of powers of a radial coordinate. I emphasize the motivations and the main ideas behind the proofs.

  16. Promoting Employability in a "Flat" World

    ERIC Educational Resources Information Center

    Parker, Polly

    2008-01-01

    T. L. Friedman (2005) described a "flat" world platform where competition and collaboration take place in real time among people all over the planet. Implications exist for people to assume responsibility for managing their own careers and ensuring their own security in a global economy. This article addresses those challenges from both the…

  17. Conformally flat polytropes for anisotropic matter

    NASA Astrophysics Data System (ADS)

    Herrera, L.; Di Prisco, A.; Barreto, W.; Ospino, J.

    2014-12-01

    We analyze in detail conformally flat spherically symmetric fluid distributions, satisfying a polytropic equation of state. Among the two possible families of relativistic polytropes, only one contains models which satisfy all the required physical conditions. The ensuing configurations are necessarily anisotropic and show interesting physical properties. Prospective applications of the presented models to the study of super-Chandrasekhar white dwarfs, are discussed.

  18. Mass Distributions Implying Flat Galactic Rotation Curves

    ERIC Educational Resources Information Center

    Keeports, David

    2010-01-01

    The rotational speeds of stars in the disc of a spiral galaxy are virtually independent of the distances of the stars from the centre of the galaxy. In common parlance, the stellar speed versus distance plot known as a galactic rotation curve is by observation typically nearly flat. This observation provides strong evidence that most galactic…

  19. Neal Lane: Science in a Flat World

    SciTech Connect

    Neal Lane

    2006-09-12

    Lane discusses the changes that have taken place in the world since World War II that have made it "flatter," referring to Thomas L. Friedman's book, The World is Flat. Friedman's main premise is that inexpensive telecommunications is bringing about unhampered international competition, the demise of economic stability, and a trend toward outsourcing services, such as computer programming, engineering and science research.

  20. Neal Lane: Science in a Flat World

    ScienceCinema

    Neal Lane

    2016-07-12

    Lane discusses the changes that have taken place in the world since World War II that have made it "flatter," referring to Thomas L. Friedman's book, The World is Flat. Friedman's main premise is that inexpensive telecommunications is bringing about unhampered international competition, the demise of economic stability, and a trend toward outsourcing services, such as computer programming, engineering and science research.