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Sample records for inas nanoplates grown

  1. Ag-catalyzed InAs nanowires grown on transferable graphite flakes

    DEFF Research Database (Denmark)

    Meyer-Holdt, Jakob; Kanne, Thomas; Sestoft, Joachim E.

    2016-01-01

    on exfoliated graphite flakes by molecular beam epitaxy. Ag catalyzes the InAs nanowire growth selectively on the graphite flakes and not on the underlying InAs substrates. This allows for easy transfer of the flexible graphite flakes with as-grown nanowire ensembles to arbitrary substrates by a micro...

  2. Electrical characterisation of Sn doped InAs grown by MOVPE

    International Nuclear Information System (INIS)

    Shamba, P.; Botha, L.; Krug, T.; Venter, A.; Botha, J.R.

    2008-01-01

    The feasibility of tetraethyl tin (TESn) as an n-type dopant for InAs is investigated. The electrical properties of Sn doped InAs films grown on semi-insulating GaAs substrates by MOVPE are extensively studied as a function of substrate temperature, V/III ratio, substrate orientation and TESn flow rate. Results from this study show that Sn concentrations can be controlled over 2 orders of magnitude. The Sn doped InAs layers exhibit carrier concentrations between 2.7 x 10 17 and 4.7 x 10 19 cm -3 with 77 K mobilities ranging from 12 000 to 1300 cm 2 /Vs. Furthermore, the influence of the variation of these parameters on the structural properties of InAs are also reported. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. The Crystal structure of InAs nanorods grown onto Si[111] substrate

    Energy Technology Data Exchange (ETDEWEB)

    Davydok, Anton; Biermanns, Andreas; Pietsch, Ullrich [Festkoerperphysik, Universitaet Siegen, Walter-Flex-Str. 3,57072, Siegen (Germany); Breuer, Steffen; Dimakis, Manos; Geelhaar, Lutz [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2011-07-01

    Nanowires are of particular interest due to the ability to synthesize heterostructures in the nanometer range. It was found that nearly any AIIIBV semiconductor material can be grown as NWs onto another AIIIBV or group IV [111] substrate independent from lattice mismatch. We presented an X-ray characterization of InAs NRs on Si [111] grown by assist free MBE method. Lattice mismatch of this materials is 11%. For study of strain realizing we concentrated our research on initial stages of growth process investigating samples set with different growth time. Using synchrotron radiation we have performed experiments in symmetrical and asymmetrical out-of plane scattering geometry and grazing-incidence diffraction. Combining the results we were able to characterize the transition between silicon silicon substrate and InAs NWs. We find in-plane lattice mismatch of -0.18% close to the interface compared to InAs bulk material. With help of micro-focus setup we are able measure structural parameters of single NWs to determine the strain accomodation as function of NW size. In particular using asymmetric wurzite-sensitive reflections under coherent beam illumination we could quantify the number of stacking faults. In the talk we present details of the analysis and first simulation results.

  4. Wavelength tuning of InAs quantum dots grown on InP (100) by chemical-beam epitaxy

    International Nuclear Information System (INIS)

    Gong, Q.; Noetzel, R.; Veldhoven, P.J. van; Eijkemans, T.J.; Wolter, J.H.

    2004-01-01

    We report on an effective way to continuously tune the emission wavelength of InAs quantum dots (QDs) grown on InP (100) by chemical-beam epitaxy. The InAs QD layer is embedded in a GaInAsP layer lattice matched to InP. With an ultrathin GaAs layer inserted between the InAs QD layer and the GaInAsP buffer, the peak wavelength from the InAs QDs can be continuously tuned from above 1.6 μm down to 1.5 μm at room temperature. The major role of the thin GaAs layer is to greatly suppress the As/P exchange during the deposition of InAs and subsequent growth interruption under arsenic flux, as well as to consume the segregated surface In layer floating on the GaInAsP buffer layer

  5. Competitive emissions of InAs (QDs)/GaInAsP/InP grown by GSMBE

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Xiaowen [Huazhong University of Science and Technology, Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Wuhan (China); Chinese Academy of Sciences, National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Shanghai (China); Wang, Qi; Li, Senlin; Chen, C.Q. [Huazhong University of Science and Technology, Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Wuhan (China); Sun, Liaoxin; Luo, X.D.; Zhang, Bo [Chinese Academy of Sciences, National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Shanghai (China)

    2015-04-01

    In this letter, the optical properties of InAs (QDs)/GaInAsP on InP substrate grown by gas source molecular beam epitaxy are investigated. By measuring and analyzing the photoluminescence spectra of InAs (QDs)/GaInAsP/InP at different temperatures and excitation powers, the origin of each emission is verified. And it is found that, with the temperature increasing, the emission intensity of GaInAsP wetting layers decreases firstly (T < 150 K) and then increases from 160 K to room temperature. By analyzing the experimental results of three samples with different QDs' sizes, a competitive emission between InAs QDs and GaInAsP wetting layers is confirmed. (orig.)

  6. Three-dimensional mesoscale heterostructures of ZnO nanowire arrays epitaxially grown on CuGaO2 nanoplates as individual diodes.

    Science.gov (United States)

    Forticaux, Audrey; Hacialioglu, Salih; DeGrave, John P; Dziedzic, Rafal; Jin, Song

    2013-09-24

    We report a three-dimensional (3D) mesoscale heterostructure composed of one-dimensional (1D) nanowire (NW) arrays epitaxially grown on two-dimensional (2D) nanoplates. Specifically, three facile syntheses are developed to assemble vertical ZnO NWs on CuGaO2 (CGO) nanoplates in mild aqueous solution conditions. The key to the successful 3D mesoscale integration is the preferential nucleation and heteroepitaxial growth of ZnO NWs on the CGO nanoplates. Using transmission electron microscopy, heteroepitaxy was found between the basal planes of CGO nanoplates and ZnO NWs, which are their respective (001) crystallographic planes, by the observation of a hexagonal Moiré fringes pattern resulting from the slight mismatch between the c planes of ZnO and CGO. Careful analysis shows that this pattern can be described by a hexagonal supercell with a lattice parameter of almost exactly 11 and 12 times the a lattice constants for ZnO and CGO, respectively. The electrical properties of the individual CGO-ZnO mesoscale heterostructures were measured using a current-sensing atomic force microscopy setup to confirm the rectifying p-n diode behavior expected from the band alignment of p-type CGO and n-type ZnO wide band gap semiconductors. These 3D mesoscale heterostructures represent a new motif in nanoassembly for the integration of nanomaterials into functional devices with potential applications in electronics, photonics, and energy.

  7. Crystal-phase intergradation in InAs nanostructures grown by van der Waals heteroepitaxy on graphene

    Science.gov (United States)

    Choi, Ji Eun; Yoo, Jinkyoung; Lee, Donghwa; Hong, Young Joon; Fukui, Takashi

    2018-04-01

    This study demonstrates the crystal-phase intergradation of InAs nanostructures grown on graphene via van der Waals epitaxy. InAs nanostructures with diverse diameters are yielded on graphene. High-resolution transmission electron microscopy (HR-TEM) reveals two crystallographic features of (i) wurtzite (WZ)-to-zinc blende (ZB) intergradation along the growth direction of InAs nanostructures and (ii) an increased mean fraction of ZB according to diameter increment. Based on the HR-TEM observations, a crystal-phase intergradation diagram is depicted. We discuss how the formation of a WZ-rich phase during the initial growth stage is an effective way of releasing heterointerfacial stress endowed by the lattice mismatch of InAs/graphene for energy minimization in terms of less in-plane lattice mismatching between WZ-InAs and graphene. The WZ-to-ZB evolution is responsible for the attenuation of the bottom-to-top surface charge interaction as growth proceeds.

  8. X-ray characterization Si-doped InAs nanowires grown on GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Saqib, Muhammad; Biermanns, Andreas; Pietsch, Ullrich [Universitaet Siegen, Festkoerperphysik (Germany); Grap, Thomas; Lepsa, Mihail [Forschungszentrum Juelich, Institut fuer Bio- und Nanosysteme (Germany)

    2011-07-01

    Semiconductor nanowires (NW) are of particular interest due to the ability to synthesize single-crystalline 1D epitaxial structures and heterostructures in the nanometer range. However, many details of the growth mechanism are not well understood. In particular, understanding and control of doping mechanisms during NW growth are important issues for technological applications. In this contribution we present a x-ray diffraction study of the influence of Si-doping in InAs NWs grown on GaAs(111) substrates using In-assisted MBE growth. With the help of coplanar and asymmetric x-ray diffraction, we monitor the evolution of the lattice constants and structure of the InAs NWs as function of doping concentration. We observe that increasing the nominal doping concentration leads to the appearance of additional diffraction maxima corresponding to material whose vertical lattice parameter is 1% smaller than that of the undoped nanowires. Those lattice parameters can be attributed with alloy formation in the form of island like crystallites.

  9. Photoluminescence characteristics of InAs quantum dots grown by STM/MBE site-control technique

    Energy Technology Data Exchange (ETDEWEB)

    Nishikawa, S.; Kohmoto, S.; Nakamura, H.; Ishikawa, T.; Asakawa, K.; Wada, O. [Femtosecond Technology Research Association, Tsukuba, Ibaraki (Japan). FESTA Lab.

    2001-03-08

    This paper describes micro-photoluminescence (PL) analysis of site-controlled QDs (SCQDs) grown using a novel in-situ MBE growth technique in which sites of self-assembled InAs QDs are controlled by forming nanometer deposits using a scanning tunneling microscope (STM) probe. We found from the temperature dependence of PL that the carrier collection at QDs at low temperature is limited by carrier diffusion in the wetting layer. The analysis of PL data considering this effect has indicated that individual QDs grown have high crystalline quality in spite of the addition of an artificial STM process during growth. (orig.)

  10. Optical characterization of InAs quantum wells and dots grown radially on wurtzite InP nanowires

    International Nuclear Information System (INIS)

    Lindgren, David; Kawaguchi, Kenichi; Heurlin, Magnus; Borgström, Magnus T; Pistol, Mats-Erik; Samuelson, Lars; Gustafsson, Anders

    2013-01-01

    Correlated micro-photoluminescence (μPL) and cathodoluminescence (CL) measurements are reported for single core–shell InP–InAs wurtzite nanowires grown using metal–organic vapor phase epitaxy. Samples covering a radial InAs shell thickness of 1–12 ML were investigated. The effective masses for the wurtzite material were determined from the transition energy dependence of the InAs shell thickness, using a model based on linear deformation potential theory. InP cores with segments of mixed zincblende and wurtzite, on which quantum dots nucleated selectively, were also investigated. Narrow peaks were observed by μPL and the spatial origin of the emission was identified with CL imaging. (paper)

  11. Conformal spinel/layered heterostructures of Co3O4 shells grown on single-crystal Li-rich nanoplates for high-performance lithium-ion batteries

    Science.gov (United States)

    Xin, Yue; Lan, Xiwei; Chang, Peng; Huang, Yaqun; Wang, Libin; Hu, Xianluo

    2018-07-01

    Lithium-rich layered materials have received much attention because of their high specific capacity and high energy density. Unfortunately, they suffer from irreversible capacity loss, low initial Coulombic efficiency and poor cyclability. Here we report a facile co-precipitation method to synthesize uniform single-crystal Li-rich Li[Li0.2Mn0.54Ni0.13Co0.13]O2 nanoplates without using any template. Subsequently, a Co3O4 shell is in situ grown on the Li-rich nanoplates through a hydrothermal method, leading to spinel/layered heterostructures. The electrode made of conformal heterostructured Li-rich/Co3O4 nanoplates delivers a high discharge capacity of 296 mA h g-1 at 0.1 C with an initial Coulombic efficiency of 84%. The capacity retention reaches 83.2% with a discharge capacity of 223 mA h g-1 after 160 cycles at 0.2 C during the potential window ranging from 2.0 to 4.8 V. The enhanced electrochemical performance of the resulting Li-rich/Co3O4 nanoplates benefits from the unique conformal heterostructure as well as the electrochemically active LixCoOy generated between the reaction of Co3O4 shells and the extracted Li2O during charging/discharging processes.

  12. High uniformity of self-organized InAs quantum wires on InAlAs buffers grown on misoriented InP(001)

    International Nuclear Information System (INIS)

    Wang Yuanli; Jin, P.; Ye, X.L.; Zhang, C.L.; Shi, G.X.; Li, R.Y.; Chen, Y.H.; Wang, Z.G.

    2006-01-01

    Highly uniform InAs quantum wires (QWRs) have been obtained on the In 0.5 Al 0.5 As buffer layer grown on the InP substrate 8 (convolutionsign) off (001) towards (111) by molecular-beam epitaxy. The quasi-periodic composition modulation was spontaneously formed in the In 0.5 Al 0.5 As buffer layer on this misoriented InP (001). The width and period of the In-rich bands are about 10 and 40 nm, respectively. The periodic In-rich bands play a major role in the sequent InAs QWRs growth and the InAs QWRs are well positioned atop In-rich bands. The photoluminescence (PL) measurements showed a significant reduction in full width at half maximum and enhanced PL efficiency for InAs QWRs on misoriented InP(001) as compared to that on normal InP(001)

  13. Enhancement of optical properties of InAs quantum dots grown by using periodic arsine interruption

    International Nuclear Information System (INIS)

    Kim, Jungsub; Yang, Changjae; Sim, Uk; Lee, Jaeyel; Yoon, Euijoon; Lee, Youngsoo

    2009-01-01

    We investigated the morphological and optical properties of InAs quantum dots (QDs) grown by using periodic arsine interruption (PAI) and compared them with QDs grown conventionally. In the conventional growth, the formation of large islands was observed, which suppresses the nucleation and growth of QDs. Furthermore, the growth of capping layers was significantly degraded by these large islands. On the other hand, in the PAI growth, the formation of large islands was completely suppressed, resulting in the increase of the density and aspect ratio of QDs and the uniform growth of capping layers. As a result of photoluminescence (PL) measurements, we found that the emission efficiency was enhanced and the full-width-half-maximum was reduced to 32 meV. The temperature dependence of these optical properties also revealed the enhancement of the uniformity of QDs grown by the PAI method.

  14. STM/STS Measurements of Two-Dimensional Electronic States in Magnetic Fields at Epitaxially Grown InAs(111)A Surfaces

    International Nuclear Information System (INIS)

    Niimi, Y; Kanisawa, K; Kojima, H; Kambara, H; Hirayama, Y; Tarucha, S; Fukuyama, Hiroshi

    2007-01-01

    The local density of states (LDOS) at the epitaxially grown InAs surface on a GaAs substrate was studied at very low temperatures in magnetic fields up to 6 T by scanning tunneling microscopy and spectroscopy. We observed a series of peaks, associated with Landau quantization of the two-dimensional electron system (2DES), in the tunnel spectra just above the subband energy (-80 meV) of the 2DES. The intervals between the peaks are consistent with the estimation from the effective mass of the 2DES at the InAs surface. In a wider energy range, another type of oscillation which was independent of magnetic field was also observed. This oscillation can be explained by the energy dependence of the transmission probability of the tunneling current through the Schottky barrier formed at the interface between the InAs film and GaAs substrate

  15. Growth and electrical characterization of Zn-doped InAs and InAs1-xSbx

    International Nuclear Information System (INIS)

    Venter, A.; Shamba, P.; Botha, L.; Botha, J.R.

    2009-01-01

    The electrical properties of Zn doped InAs and InAsSb layers grown on semi-insulating GaAs by metal organic vapour phase epitaxy, using dimethyl zinc as the p-type dopant source, have been studied. The influence of dopant flow rate, V/III ratio and substrate orientation on the electrical properties of these InAs and InAs 1-x Sb x layers have been studied at a few appropriate growth temperatures. A promising group V source, tertiary butyl arsenic was used as an alternative to arsenic hydride in the case of InAs growth. The electrical properties of the InAs and InAs 1-x Sb x epitaxial layers were mainly studied by the Hall effect. However, surface accumulation in these materials results in deceptive Hall results being extracted. A two layer model (assuming the layer to consist of two parallel conducting paths viz. surface and bulk) has therefore been used to extract sensible transport properties. In addition, conventional Hall measurements ignores the high electron to hole mobility ratio in InAs and InAsSb leading to erroneous transport properties.

  16. Poly(vinylpyrrolidone)-Free Multistep Synthesis of Silver Nanoplates with Plasmon Resonance in the Near Infrared Range.

    Science.gov (United States)

    Khan, Assad U; Zhou, Zhengping; Krause, Joseph; Liu, Guoliang

    2017-11-01

    Herein, a poly(vinylpyrrolidone) (PVP)-free method is described for synthesizing Ag nanoplates that have localized surface plasmon resonance in the near-infrared (NIR) range. Citrate-capped Ag spherical nanoparticles are first grown into small Ag nanoplates that resonate in the range of 500-800 nm. The small Ag nanoplates are used as seeds to further grow into large Ag nanoplates with a lateral dimension of 100-600 nm and a plasmon resonance wavelength of 800-1660 nm and above. The number of growth steps can be increased as desired. Without introducing additional citrate into the solutions of small Ag nanoplate seeds, large Ag nanoplates can be synthesized within minutes. The entire synthesis is completely PVP free, which promotes the nanoparticle growth along the lateral direction to form large Ag nanoplates. The multistep growth and the minimum usage of citrate are essential for the fast growth of high-aspect-ratio Ag nanoplates resonating in the NIR range. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Inhomogeneous Si-doping of gold-seeded InAs nanowires grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Rolland, Chloe; Coinon, Christophe; Wallart, Xavier; Leturcq, Renaud [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d' Ascq Cedex (France); Caroff, Philippe [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d' Ascq Cedex (France); Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia)

    2013-06-03

    We have investigated in situ Si doping of InAs nanowires grown by molecular beam epitaxy from gold seeds. The effectiveness of n-type doping is confirmed by electrical measurements showing an increase of the electron density with the Si flux. We also observe an increase of the electron density along the nanowires from the tip to the base, attributed to the dopant incorporation on the nanowire facets whereas no detectable incorporation occurs through the seed. Furthermore, the Si incorporation strongly influences the lateral growth of the nanowires without giving rise to significant tapering, revealing the complex interplay between axial and lateral growth.

  18. Strain in GaAs / InAs core-shell nanowire heterostructures grown on GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Biermanns, Andreas; Davydok, Anton; Pietsch, Ullrich [Universitaet Siegen, Festkoerperphysik (Germany); Rieger, Torsten; Lepsa, Mihail Ion [Peter Gruenberg Institut 9, Forschungszentrum Juelich (Germany); JARA - Fundamentals of Future Information Technology (Germany)

    2012-07-01

    The growth of semiconductor nanowires (NWs) has attracted significant interest in recent years due to the possible fabrication of novel semiconductor devices for future electronic and opto-electronic applications. Compared to planar heterostructures, the nanowire approach offers an advantage regarding the possibility to form heterostructures between highly lattice mismatched systems, because the free surface of the nanowires allows to relieve the strain more efficiently. One particular way to form heterostructures in the NW geometry, is the fabrication of core-shell devices, in which a NW core is surrounded by a shell of different material. The understanding of the mutual strain between core and shell, as well as the relaxation behavior of the system are crucial for the fabrication of functional devices. In this contribution we report on first X-ray diffraction measurements of GaAs-core/InAs-shell nanowires grown on GaAs(111) by molecular beam epitaxy. Using symmetric- and grazing-incidence X-ray diffraction, the relaxation state of the InAs shell as well as the strain in the GaAs core are measured as function of the InAs shell thickness, showing a gradual relaxation behavior of the shell.

  19. Contactless electroreflectance and photoluminescence of InAs quantum dots with GaInNAs barriers grown on GaAs substrate

    International Nuclear Information System (INIS)

    Motyka, M.; Kudrawiec, R.; Misiewicz, J.; Pucicki, D.; Tlaczala, M.; Fischer, M.; Marquardt, B.; Forchel, A.

    2007-01-01

    InAs quantum dots (QDs) with GaInNAs barriers grown on (001) GaAs substrate by molecular beam epitaxy have been studied by contactless electroreflectance (CER) and photoluminescence (PL) spectroscopies. It has been observed that the overgrowth of self-organized InAs QDs with GaInNAs layers effectively tunes the QD emission to the 1.3 μm spectral region. In case of PL spectra only one peak related to QD emission has been observed. In the case of CER spectra, in addition to a CER feature corresponding to the QD ground state, a rich spectrum of CER resonances related to optical transitions in InAs/GaInNAs/GaAs QW has been observed. It has been concluded that the application of GaInNAs instead InGaAs leads to better control of emission wavelength from InAs QDs since strains in GaInNAs can be tuned from compressive to tensile. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. On the evolution of InAs thin films grown by molecular beam epitaxy on the GaAs(001) surface

    International Nuclear Information System (INIS)

    Grabowski, Jan

    2010-01-01

    Semiconductor nanostructures are currently of high interest for a wide variety of electronic and optoelectronic applications. A large number of devices, in particular for the optical data transmission in the long-wavelength range, essential in modern communication, are based on InAs/GaAs quantum dot (QD) structures. Though the properties of the InAs/GaAs QDs have been extensively studied, only little is known about the formation and structure of the wetting layer (WL) yet. In the present work, the pathway of the InAs WL evolution is studied in detail. For this purpose, InAs thin films in the range of one monolayer (ML) are deposited on the GaAs(001) surface by molecular beam epitaxy (MBE) and studied by reflection high energy electron diffraction (RHEED) and in particular by scanning tunneling microscopy (STM). The InAs thin films are grown in both typical growth regimes, on the GaAs-c(4 x 4) and the GaAs-β2(2 x 4) reconstructed surface, in a variety of thicknesses starting from submonolayers with 0.09 ML of InAs up to 1.65 ML of InAs exceeding the critical thickness for QD growth. In principle, three growth stages are found. At low InAs coverages, the indium adsorbs in agglomerations of typically eight In atoms at energetically preferable surface sites. In the STM images, the signatures of these In agglomerations appear with a clear bright contrast. A structural model for the initial formation of these signatures is presented, and its electronic and strain related properties are discussed. At an InAs coverage of about 0.67ML the initial surface transforms into a (4 x 3) reconstructed In 2/3 Ga 1/3 As ML and the detailed structure and strain properties of this surface are unraveled. On top of the InGaAs ML further deposited InAs forms a second layer, characterized by a typical zig-zag alignment of (2 x 4) reconstructed unit cells, with an alternating α2/α2-m configuration. In contrast to the previous surface reconstructions, where structural strain is

  1. On the evolution of InAs thin films grown by molecular beam epitaxy on the GaAs(001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Grabowski, Jan

    2010-12-14

    Semiconductor nanostructures are currently of high interest for a wide variety of electronic and optoelectronic applications. A large number of devices, in particular for the optical data transmission in the long-wavelength range, essential in modern communication, are based on InAs/GaAs quantum dot (QD) structures. Though the properties of the InAs/GaAs QDs have been extensively studied, only little is known about the formation and structure of the wetting layer (WL) yet. In the present work, the pathway of the InAs WL evolution is studied in detail. For this purpose, InAs thin films in the range of one monolayer (ML) are deposited on the GaAs(001) surface by molecular beam epitaxy (MBE) and studied by reflection high energy electron diffraction (RHEED) and in particular by scanning tunneling microscopy (STM). The InAs thin films are grown in both typical growth regimes, on the GaAs-c(4 x 4) and the GaAs-{beta}2(2 x 4) reconstructed surface, in a variety of thicknesses starting from submonolayers with 0.09 ML of InAs up to 1.65 ML of InAs exceeding the critical thickness for QD growth. In principle, three growth stages are found. At low InAs coverages, the indium adsorbs in agglomerations of typically eight In atoms at energetically preferable surface sites. In the STM images, the signatures of these In agglomerations appear with a clear bright contrast. A structural model for the initial formation of these signatures is presented, and its electronic and strain related properties are discussed. At an InAs coverage of about 0.67ML the initial surface transforms into a (4 x 3) reconstructed In{sub 2/3}Ga{sub 1/3}As ML and the detailed structure and strain properties of this surface are unraveled. On top of the InGaAs ML further deposited InAs forms a second layer, characterized by a typical zig-zag alignment of (2 x 4) reconstructed unit cells, with an alternating {alpha}2/{alpha}2-m configuration. In contrast to the previous surface reconstructions, where

  2. Growth and characterization of InAs quantum dots on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, L.; Ankudinov, A.; Bensing, F.; Wagner, J.; Wagner, V.; Geurts, J. [Wuerzburg Univ. (Germany). Lehrstuhl fuer Experimentelle Physik 3; Ade, G.; Hinze, P. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Waag, A. [Ulm Univ. (Germany). Abt. Halbleiterphysik

    2001-03-08

    We present a comprehensive investigation of molecular beam epitaxial (MBE) grown InAs quantum dots (QD) on silicon (001) and (111) by reflection high energy electron diffraction (RHEED) and Raman spectroscopy in UHV environment and ex-situ by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Two different ways were developed to prepare up to 10{sup 11} cm{sup -2} InAs QDs on Si(001). One is the conventional mode by exceeding a critical thickness of deposition at which 2D growth changes towards a 3D growth mode. A second way is a dewetting transition, induced by cooling an approximately 1 ML thin 2D InAs layer from growth temperature below a critical temperature at which RHEED indicates the formation of nanoislands. Samples grown in both manners show significant differences in morphology and shape though RHEED, TEM and Raman studies correspondingly indicate strain relaxation. On Si(111) InAs grows in the common temperature range for InAs growth ({proportional_to}400 C) in flat clusters separated by deep trenches. A previous passivation of the Si(111) surface with arsenic at {proportional_to}700 C on the other hand leads to the formation of large InAs nanocrystals. (orig.)

  3. A soft lithographic approach to fabricate InAs nanowire field-effect transistors

    DEFF Research Database (Denmark)

    Madsen, Morten; Lee, S. H.; Shin, S.-H.

    2018-01-01

    -down approach and an epitaxial layer transfer process, using MBE-grown ultrathin InAs as a source wafer. The width of the InAs nanowires was controlled using solvent-assisted nanoscale embossing (SANE), descumming, and etching processes. By optimizing these processes, NWs with a width less than 50 nm were...

  4. InAs film grown on Si(111) by metal organic vapor phase epitaxy

    International Nuclear Information System (INIS)

    Caroff, P; Jeppsson, M; Mandl, B; Wernersson, L-E; Wheeler, D; Seabaugh, A; Keplinger, M; Stangl, J; Bauer, G

    2008-01-01

    We report the successful growth of high quality InAs films directly on Si(111) by Metal Organic Vapor Phase Epitaxy. A nearly mirror-like and uniform InAs film is obtained at 580 0 C for a thickness of 2 μm. We measured a high value of the electron mobility of 5100 cm 2 /Vs at room temperature. The growth is performed using a standard two-step procedure. The influence of the nucleation layer, group V flow rate, and layer thickness on the electrical and morphological properties of the InAs film have been investigated. We present results of our studies by Atomic Force Microscopy, Scanning Electron Microscopy, electrical Hall/van der Pauw and structural X-Ray Diffraction characterization

  5. Effect of growth temperature on the morphology and phonon properties of InAs nanowires on Si substrates

    Directory of Open Access Journals (Sweden)

    Lei Wen

    2011-01-01

    Full Text Available Abstract Catalyst-free, vertical array of InAs nanowires (NWs are grown on Si (111 substrate using MOCVD technique. The as-grown InAs NWs show a zinc-blende crystal structure along a < 111 > direction. It is found that both the density and length of InAs NWs decrease with increasing growth temperatures, while the diameter increases with increasing growth temperature, suggesting that the catalyst-free growth of InAs NWs is governed by the nucleation kinetics. The longitudinal optical and transverse optical (TO mode of InAs NWs present a phonon frequency slightly lower than those of InAs bulk materials, which are speculated to be caused by the defects in the NWs. A surface optical mode is also observed for the InAs NWs, which shifts to lower wave-numbers when the diameter of NWs is decreased, in agreement with the theory prediction. The carrier concentration is extracted to be 2.25 × 1017 cm-3 from the Raman line shape analysis. A splitting of TO modes is also observed. PACS: 62.23.Hj; 81.07.Gf; 63.22.Gh; 61.46.Km

  6. Raman scattering investigation of Bi2Te3 hexagonal nanoplates prepared by a solvothermal process in the absence of NaOH

    International Nuclear Information System (INIS)

    Liang Yujie; Wang Wenzhong; Zeng Baoqing; Zhang Guling; Huang Jing; Li Jin; Li Te; Song Yangyang; Zhang Xiuyu

    2011-01-01

    Research highlights: → Hexagonal Bi 2 Te 3 thin nanoplates were synthesized by a simple solvothermal method. → Optical properties of the nanoplates were investigated by micro-Raman spectroscopy. → Infrared (IR) active mode (A 1u ) is greatly activated in Raman scattering spectrum. → Infrared (IR) active mode (A 1u ) shows up in Raman spectrum of hexagonal nanoplates. → Raman spectrum clearly shows crystal symmetry breaking of hexagonal nanoplates. - Abstract: Hexagonal Bi 2 Te 3 nanoplates were synthesized by a simple solvothermal process in the absence of NaOH. The composition, morphology and size of the as-prepared products were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Raman scattering optical properties of the as-prepared Bi 2 Te 3 nanoplates were investigated by micro-Raman spectroscopy. The Raman spectrum shows that infrared (IR) active mode (A 1u ), which must be odd parity and is Raman forbidden for bulk crystal due to its inversion symmetry, is greatly activated and shown up clearly in Raman scattering spectrum. We attribute the appearance of infrared active (A 1u ) in Raman spectrum to crystal symmetry breaking of Bi 2 Te 3 hexagonal nanoplates. The as-grown Bi 2 Te 3 hexagonal nanoplates, exhibiting novel Raman optical properties compared with bulk crystals, may find potential applications in thermoelectric devices.

  7. Homo- and heteroepitaxial growth behavior of upright InAs nanowires on InAs and GaAs substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Jens; Gottschalch, Volker; Paetzelt, Hendrik [Institut fuer Anorganische Chemie, Universitaet Leipzig, Johannesallee 29, D-04103 Leipzig (Germany); Wagner, Gerald [Institut fuer Kristallographie und Mineralogie, Universitaet Leipzig, Linnestr. 5, D-04103 Leipzig (Germany); Pietsch, Ulrich [Festkoerperphysik, Universitaet Siegen, D-57068 Siegen (Germany)

    2008-07-01

    Semiconductor nanowires (NW) acquire recently attraction because of promising new application fields in electronics and optoelectronic. We applied the vapor-liquid-solid mechanism with gold seeds in combination with low-pressure metal-organic vapor phase epitaxy (LP-MOVPE) to achieve replicable InAs NW growth with high growth rates. Since the initial alloying of the gold seeds with the substrate material plays a deciding role for the inceptive NW growth, InAs free standing nanowires were grown on GaAs(111)B substrate as well as on InAs/GaAs(111)B quasi-substrate. The influence of the MOVPE parameters will be discussed with respect to NW morphology and real-structure. A special focus will be set on the heteroepitaxial InAs NW growth on GaAs substrates. Gracing-incidence X-ray studies and transmission electron microscopy investigations revealed the existence of a thin Ga{sub x}In{sub 1-x}As graduated alloy layer with embedded crystalline gold alloy particles at the NW substrate interface. The effect of droplet composition on the VLS growth will be presented in a thermodynamic model.

  8. InAs quantum dots as charge storing elements for applications in flash memory devices

    Energy Technology Data Exchange (ETDEWEB)

    Islam, Sk Masiul; Biswas, Pranab [Materials Science Centre, Indian Institute of Technology, Kharagpur 721 302 (India); Banerji, P., E-mail: pallab@matsc.iitkgp.ernet.in [Materials Science Centre, Indian Institute of Technology, Kharagpur 721 302 (India); Chakraborty, S. [Applied Materials Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Sector-I, Kolkata 700 064 (India)

    2015-08-15

    Graphical abstract: - Highlights: • Catalyst-free growth of InAs quantum dots was carried out on high-k ZrO{sub 2}. • Memory device with InAs quantum dots as charge storage nodes are fabricated. • Superior memory window, low leakage and reasonably good retention were observed. • Carrier transport phenomena are explained in both program and erase operations. - Abstract: InAs quantum dots (QDs) were grown by metal organic chemical vapor deposition technique to use them as charge storage nodes. Uniform QDs were formed with average diameter 5 nm and height 5–10 nm with a density of 2 × 10{sup 11} cm{sup −2}. The QDs were grown on high-k dielectric layer (ZrO{sub 2}), which was deposited onto ultra-thin GaP passivated p-GaAs (1 0 0) substrate. A charge storage device with the structure Metal/ZrO{sub 2}/InAs QDs/ZrO{sub 2}/(GaP)GaAs/Metal was fabricated. The devices containing InAs QDs exhibit superior memory window, low leakage current density along with reasonably good charge retention. A suitable electronic band diagram corresponding to programming and erasing operations was proposed to explain the operation.

  9. Optical emission of InAs nanowires

    International Nuclear Information System (INIS)

    Möller, M; De Lima Jr, M M; Cantarero, A; Chiaramonte, T; Cotta, M A; Iikawa, F

    2012-01-01

    Wurtzite InAs nanowire samples grown by chemical beam epitaxy have been analyzed by photoluminescence spectroscopy. The nanowires exhibit two main optical emission bands at low temperatures. They are attributed to the recombination of carriers in quantum well structures, formed by zincblende–wurtzite alternating layers, and to the donor–acceptor pair. The blue-shift observed in the former emission band when the excitation power is increased is in good agreement with the type-II band alignment between the wurtzite and zincblende sections predicted by previous theoretical works. When increasing the temperature and the excitation power successively, an additional band attributed to the band-to-band recombination from wurtzite InAs appears. We estimated a lower bound for the wurtzite band gap energy of approximately 0.46 eV at low temperature. (paper)

  10. Optical emission of InAs nanowires

    Science.gov (United States)

    Möller, M.; de Lima, M. M., Jr.; Cantarero, A.; Chiaramonte, T.; Cotta, M. A.; Iikawa, F.

    2012-09-01

    Wurtzite InAs nanowire samples grown by chemical beam epitaxy have been analyzed by photoluminescence spectroscopy. The nanowires exhibit two main optical emission bands at low temperatures. They are attributed to the recombination of carriers in quantum well structures, formed by zincblende-wurtzite alternating layers, and to the donor-acceptor pair. The blue-shift observed in the former emission band when the excitation power is increased is in good agreement with the type-II band alignment between the wurtzite and zincblende sections predicted by previous theoretical works. When increasing the temperature and the excitation power successively, an additional band attributed to the band-to-band recombination from wurtzite InAs appears. We estimated a lower bound for the wurtzite band gap energy of approximately 0.46 eV at low temperature.

  11. Growth of InAs Quantum Dots on Germanium Substrate Using Metal Organic Chemical Vapor Deposition Technique

    Directory of Open Access Journals (Sweden)

    Tyagi Renu

    2009-01-01

    Full Text Available Abstract Self-assembled InAs quantum dots (QDs were grown on germanium substrates by metal organic chemical vapor deposition technique. Effects of growth temperature and InAs coverage on the size, density, and height of quantum dots were investigated. Growth temperature was varied from 400 to 450 °C and InAs coverage was varied between 1.40 and 2.35 monolayers (MLs. The surface morphology and structural characteristics of the quantum dots analyzed by atomic force microscope revealed that the density of the InAs quantum dots first increased and then decreased with the amount of InAs coverage; whereas density decreased with increase in growth temperature. It was observed that the size and height of InAs quantum dots increased with increase in both temperature and InAs coverage. The density of QDs was effectively controlled by growth temperature and InAs coverage on GaAs buffer layer.

  12. Compressive buckling of a rectangular nanoplate

    Science.gov (United States)

    Bochkarev, A. O.

    2018-05-01

    This paper considers the constitutive relations of the nanoplate theory with surface stresses taken into account according to the original or complete Gurtin-Murdoch (GM) model and according to the simplified strain-consistent GM model (which does not include any non-strain terms in the surface stress-strain relation). It is shown that the potential energy of a deformed nanoplate according to both GM models preserves the classical structure using the redefined elastic moduli (effective tangential and flexural elastic properties, which contain the characteristics of bulk phase and a surface). This allows to apply the known solutions and methods from macroplates to nanoplates. As example, it is shown that the critical load of the compressive buckling of a nanoplate according to the complete and strain-consistent GM models has the difference between two solutions no more than 1.5%.

  13. Alloy formation during InAs nanowire growth on GaAs(111)

    Energy Technology Data Exchange (ETDEWEB)

    Davydok, Anton; Saqib, Muhammad; Biermanns, Andreas; Pietsch, Ullrich [Festkoerperphysik, Universitaet Siegen (Germany); Rieger, Torsten; Grap, Thomas; Lepsa, Mihail [Peter Gruenberg Institut 9, Forschungszentrum Juelich (Germany); JARA - Fundamentals of Future Information Technology (Germany)

    2012-07-01

    The growth of semiconductor nanowires has attracted significant interest in recent years due to the possible fabrication of novel semiconductor devices for future electronic and opto-electronic applications. A possible way to obtain nanowires is the growth in molecular beam epitaxy on the (111)B oriented surface of the desired substrate, covered by a thin oxide layer. A crucial parameter in this method is the initial thickness of the oxide layer, often determined by an etching procedure. In this contribution, we report on the structural investigation of InAs nanowires grown on GaAs substrates covered by different oxide-layers using X-ray diffraction. In this contribution, we report on the structural investigation of InAs nanowires grown via an In droplet on GaAs substrates covered by different oxide layers using X-ray diffraction. Using a combination of symmetric and asymmetric X-ray diffraction, we observe that for growth on a defective oxide layer, alloy formation takes place and a large amount of InGaAs is formed, whereas for growth on an initially smooth oxide layer, only pure InAs is formed.

  14. Sorption of Triangular Silver Nanoplates on Polyurethane Foam

    Science.gov (United States)

    Furletov, A. A.; Apyari, V. V.; Garshev, A. V.; Volkov, P. A.; Tolmacheva, V. V.; Dmitrienko, S. G.

    2018-02-01

    The sorption of triangular silver nanoplates on polyurethane foam is investigated as a procedure for creating a nanocomposite sensing material for subsequent use in optical means of chemical analysis. Triangular silver nanoplates are synthesized and characterized, and a simple sorption technique for the formation of a composite material based on these nanoplates is proposed.

  15. Solution-processed n-ZnO nanorod/p-Co_3O_4 nanoplate heterojunction light-emitting diode

    International Nuclear Information System (INIS)

    Kim, Jong-Woo; Lee, Su Jeong; Biswas, Pranab; Lee, Tae Il; Myoung, Jae-Min

    2017-01-01

    Highlights: • The n-ZnO nanorods were epitaxially grown on p-Co_3O_4 nanoplates. • The heteroepitaxial p-n junction was fabricated by using hydrothermal process. • The LEDs emitted reddish-orange and violet light related to ZnO point defects. • The Co_3O_4 nanoplates function as a hole injection layer. • Junction between 1D NRs and 2D NPs provides a new approach to design nanostructures. - Abstract: A heterojunction light-emitting diode (LED) based on p-type cobalt oxide (Co_3O_4) nanoplates (NPs)/n-type zinc oxide (ZnO) nanorods (NRs) is demonstrated. Using a low-temperature aqueous solution process, the n-type ZnO NRs were epitaxially grown on Co_3O_4 NPs which were two-dimensionally assembled by a modified Langmuir-Blodgett process. The heterojunction LEDs exhibited a typical rectifying behavior with a turn-on voltage of about 2 V and emitted not only reddish-orange light at 610 nm but also violet light at about 400 nm. From the comparative analyses of electroluminescence and photoluminescence, it was determined that the reddish-orange light emission was related to the electronic transitions from zinc interstitials (Zn_i) to oxygen interstitials (O_i) or conduction-band minimum (CBM) to oxygen vacancies (V_O), and the violet light emission was attribute to the transition from CBM to valence-band maximum (VBM) or Zn_i to zinc vacancies (V_Z_n).

  16. Facile synthesis and characterization of hexagonal NbSe2 nanoplates

    International Nuclear Information System (INIS)

    Zhang, Xianghua; Zhang, Du; Tang, Hua; Ji, Xiaorui; Zhang, Yi; Tang, Guogang; Li, Changsheng

    2014-01-01

    Graphical abstract: - Highlights: • Uniform hexagonal NbSe 2 nanoplates were prepared by a simple solid state reaction. • The possible formation mechanism of the NbSe 2 nanoplates was discussed. • The formation of NbSe 2 nanoplates undergoes a series of phase transition. - Abstract: The NbSe 2 nanoplates with hexagonal morphology have been successfully prepared by a facile, environmentally friendly reaction in closed reactor at moderate temperature. The thermal (750 °C) solid-state reaction between the ball-milled mixture of micro-sized Nb and Se yielded a high yield of NbSe 2 nanoplates. The as-prepared products were characterized by XRD, EDS, and SEM. The results showed that the as-prepared products were hexagonal phase NbSe 2 nanoplates with uniform sizes and the formation of NbSe 2 nanoplates underwent a series of phase transition. On the basis of experimental results obtained at different temperatures, a reasonable reaction process and a formation mechanism were proposed. Moreover, the ball milling time played a crucial role in acquiring the homogeneous distribution nanoplates

  17. Formation of nanogaps in InAs nanowires by selectively etching embedded InP segments.

    Science.gov (United States)

    Schukfeh, M I; Storm, K; Hansen, A; Thelander, C; Hinze, P; Beyer, A; Weimann, T; Samuelson, L; Tornow, M

    2014-11-21

    We present a method to fabricate nanometer scale gaps within InAs nanowires by selectively etching InAs/InP heterostructure nanowires. We used vapor-liquid-solid grown InAs nanowires with embedded InP segments of 10-60 nm length and developed an etching recipe to selectively remove the InP segment. A photo-assisted wet etching process in a mixture of acetic acid and hydrobromic acid gave high selectivity, with accurate removal of InP segments down to 20 nm, leaving the InAs wire largely unattacked, as verified using scanning electron and transmission electron microscopy. The obtained nanogaps in InAs wires have potential as semiconducting electrodes to investigate electronic transport in nanoscale objects. We demonstrate this functionality by dielectrophoretically trapping 30 nm diameter gold nanoparticles into the gap.

  18. Formation of nanogaps in InAs nanowires by selectively etching embedded InP segments

    International Nuclear Information System (INIS)

    Schukfeh, M I; Hansen, A; Tornow, M; Storm, K; Thelander, C; Samuelson, L; Hinze, P; Weimann, T; Beyer, A

    2014-01-01

    We present a method to fabricate nanometer scale gaps within InAs nanowires by selectively etching InAs/InP heterostructure nanowires. We used vapor–liquid–solid grown InAs nanowires with embedded InP segments of 10–60 nm length and developed an etching recipe to selectively remove the InP segment. A photo-assisted wet etching process in a mixture of acetic acid and hydrobromic acid gave high selectivity, with accurate removal of InP segments down to 20 nm, leaving the InAs wire largely unattacked, as verified using scanning electron and transmission electron microscopy. The obtained nanogaps in InAs wires have potential as semiconducting electrodes to investigate electronic transport in nanoscale objects. We demonstrate this functionality by dielectrophoretically trapping 30 nm diameter gold nanoparticles into the gap. (paper)

  19. Growth-interruption-induced low-density InAs quantum dots on GaAs

    International Nuclear Information System (INIS)

    Li, L. H.; Alloing, B.; Chauvin, N.; Fiore, A.; Patriarche, G.

    2008-01-01

    We investigate the use of growth interruption to obtain low-density InAs quantum dots (QDs) on GaAs. The process was realized by Ostwald-type ripening of a thin InAs layer. It was found that the optical properties of the QDs as a function of growth interruption strongly depend on InAs growth rate. By using this approach, a low density of QDs (4 dots/μm 2 ) with uniform size distribution was achieved. As compared to QDs grown without growth interruption, a larger energy separation between the QD confined levels was observed, suggesting a situation closer to the ideal zero-dimensional system. Combining with an InGaAs capping layer such as In-rich QDs enable 1.3 μm emission at 4 K

  20. InAs nanocrystals on SiO2/Si by molecular beam epitaxy for memory applications

    International Nuclear Information System (INIS)

    Hocevar, Moiera; Regreny, Philippe; Descamps, Armel; Albertini, David; Saint-Girons, Guillaume; Souifi, Abdelkader; Gendry, Michel; Patriarche, Gilles

    2007-01-01

    We studied a memory structure based on InAs nanocrystals grown by molecular beam epitaxy directly on thermal SiO 2 on silicon. Both nanocrystal diameter and density can be controlled by growth parameters. Transmission electron microscopy analysis shows high crystallinity and low size dispersion. In an electrical test structure with a 3.5 nm tunnel oxide, we observed that 80% of the initial injected electrons remain stored in the InAs nanocrystals after 3 months and that the retention time for electrons in InAs nanocrystals is four orders of magnitude higher than in silicon nanocrystals

  1. Fe-contacts on InAs(100) and InP(100) characterised by conversion electron Mössbauer spectroscopy

    DEFF Research Database (Denmark)

    Damsgaard, Christian Danvad; Gunnlaugsson, H.P; Weyer, G.

    2005-01-01

    We have grown 4 nm thin films of Fe-57 on InAs(100) and InP(100) surfaces by use of MBE and studied the samples by Fe-57 conversion electron Mossbauer spectroscopy. In the case of InAs, the Mossbauer spectrum showed a sextet due to alpha-Fe and a further magnetically split component with slightly...

  2. Driven self-assembly of hard nanoplates on soft elastic shells

    International Nuclear Information System (INIS)

    Zhang Yao-Yang; Hua Yun-Feng; Deng Zhen-Yu

    2015-01-01

    The driven self-assembly behaviors of hard nanoplates on soft elastic shells are investigated by using molecular dynamics (MD) simulation method, and the driven self-assembly structures of adsorbed hard nanoplates depend on the shape of hard nanoplates and the bending energy of soft elastic shells. Three main structures for adsorbed hard nanoplates, including the ordered aggregation structures of hard nanoplates for elastic shells with a moderate bending energy, the collapsed structures for elastic shells with a low bending energy, and the disordered aggregation structures for hard shells, are observed. The self-assembly process of adsorbed hard nanoplates is driven by the surface tension of the elastic shell, and the shape of driven self-assembly structures is determined on the basis of the minimization of the second moment of mass distribution. Meanwhile, the deformations of elastic shells can be controlled by the number of adsorbed rods as well as the length of adsorbed rods. This investigation can help us understand the complexity of the driven self-assembly of hard nanoplates on elastic shells. (paper)

  3. Characterization of multilayer self-organized InAs quantum dot embedded waveguides at 1.3 and 1.5 μm

    NARCIS (Netherlands)

    Akca, I.B.; Dana, A.; Aydinli, A.; Rossetti, M.; Li, L.; Fiore, A.; Dagli, N.

    2007-01-01

    In this paper, we characterized the electro-optic coefficient and loss of multilayer InAs quantum dot laser structures at 1309 and 1515 nm. Quantum dot waveguides were grown by molecular beam epitaxy, where the active region is formed by three or five layers of self-assembled InAs QDs. Loss

  4. Superconducting proximity effect in MBE grown Nb-InAs junctions

    Science.gov (United States)

    Kan, Carolyn; Xue, Chi; Law, Stephanie; Eckstein, James

    2013-03-01

    Several proposals for the realization of Majorana fermions rely on excellent quality proximity coupling between a superconductor and a high-mobility semiconductor. We examine the long-range proximity coupling between MBE-grown InAs and in situ grown superconducting overlayers by fabricating transport devices, and investigate the effect of substrate choice and growth conditions on the quality of the MBE InAs. GaAs is commonly available as a high quality insulating substrate. Overcoming its lattice mismatch with InAs using GaSb and AlSb layers results in locally smooth terraced surfaces, but global spiral dislocation structures also appear and have a negative impact on the InAs mobility. Growing InAs on homoepitaxial GaSb results in improved morphology and increases the mean free path. We compare the proximity effect in devices made both ways. This material is based upon work supported by the U.S. Department of Energy, Division of Materials Sciences under Award No. DE-FG02 07ER46453, through the Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign.

  5. Effects of growth temperature and arsenic pressure on size distribution and density of InAs quantum dots on Si (001)

    International Nuclear Information System (INIS)

    Zhao, Z.M.; Hul'ko, O.; Kim, H.J.; Liu, J.; Shi, B.; Xie, Y.H.

    2005-01-01

    InAs self-assembled quantum dots (QDs) were grown on Si (001) substrates via molecular beam epitaxy. The size distribution and density of InAs QDs grown under different conditions were studied using plan-view transmission electron microscopy. Dot density was shown to strongly depend on arsenic beam equivalent pressure (BEP) ranging from 2.8x10 -5 to 1.2x10 -3 Pa. In contrast, dot density was nearly independent of substrate temperature from 295 to 410 deg. C under constant arsenic BEP, while broadening of size distribution was observed with increasing temperature. The mechanism accounting for some of the main features of the experimental observations is discussed. Finally, InAs quantum dots with optimized narrow size distribution and high density were grown at low arsenic BEP of 7.2 x10 -5 Pa and low temperature of 250 deg. C followed by annealing at arsenic BEP of 1.9 x10 -4 Pa and temperature of 410 deg. C

  6. GaAs structures with InAs and As quantum dots produced in a single molecular beam epitaxy process

    International Nuclear Information System (INIS)

    Nevedomskii, V. N.; Bert, N. A.; Chaldyshev, V. V.; Preobrazhenskii, V. V.; Putyato, M. A.; Semyagin, B. R.

    2009-01-01

    Epitaxial GaAs layers containing InAs semiconductor quantum dots and As metal quantum dots are grown by molecular beam epitaxy. The InAs quantum dots are formed by the Stranskii-Krastanow mechanism, whereas the As quantum dots are self-assembled in the GaAs layer grown at low temperature with a large As excess. The microstructure of the samples is studied by transmission electron microscopy. It is established that the As metal quantum dots formed in the immediate vicinity of the InAs semiconductor quantum dots are larger in size than the As quantum dots formed far from the InAs quantum dots. This is apparently due to the effect of strain fields of the InAs quantum dots upon the self-assembling of As quantum dots. Another phenomenon apparently associated with local strains around the InAs quantum dots is the formation of V-like defects (stacking faults) during the overgrowth of the InAs quantum dots with the GaAs layer by low-temperature molecular beam epitaxy. Such defects have a profound effect on the self-assembling of As quantum dots. Specifically, on high-temperature annealing needed for the formation of large-sized As quantum dots by Ostwald ripening, the V-like defects bring about the dissolution of the As quantum dots in the vicinity of the defects. In this case, excess arsenic most probably diffuses towards the open surface of the sample via the channels of accelerated diffusion in the planes of stacking faults.

  7. Synthesis and electrical properties of silver nanoplates for electronic applications

    Directory of Open Access Journals (Sweden)

    Xiong Nana

    2015-06-01

    Full Text Available In this paper, silver nanoplates of 100 to 500 nm size were synthesized by reduction of silver nitrate with N,Ndimethylformamide, using poly(vinylpyrolidone as a surfactant and ferric chloride as a controlling agent, at 120 to 160 °C for 5 to 24 hours. The influence of the concentration of ferric chloride, the reaction temperature and reaction time on the morphology of the product has been investigated by transmission electron microscopy, scanning electron microscopy and UV-Vis spectroscopy. The results indicated that the products obtained at the low reaction temperature and short reaction time in the presence of FeCl3 in the reaction solution were in the form of silver nanoplates, whose morphology was mainly triangular and hexagonal. In addition, the size and thickness of the nanoplates increased with increasing of the FeCl3 concentration. At a high reaction temperature and long reaction time, the truncated triangle and hexagonal nanoplates were mainly produced. Furthermore, the sintering behavior of nanoplates was studied and the results showed that sintering of the silver nanoplates started at 180 °C, and a typical sintering behavior was observed at higher temperatures. The incorporation of the silver nanoplates into the polymer matrix with micro-sized silver flakes led to an increase in the matrix resistivity in almost all cases, especially at high fractions and low curing temperatures. The curing temperature had an influence on the resistivity of the conductive adhesives filled with micro-sized silver flakes and silver nanoplates due to sintering of the silver nanoplates.

  8. Linear electro-optic coefficient in multilayer self-organized InAs quantum dot structures

    NARCIS (Netherlands)

    Akca, I.B.; Dana, A.; Aydinli, A.; Rossetti, M.; Li, L.; Dagli, N.; Fiore, A.

    2007-01-01

    The electro-optic coefficients of self-organized InAs quantum dot layers in molecular beam epitaxy grown laser structures in reverse bias have been investigated. Enhanced electrooptic coefficients compared to bulk GaAs were observed.

  9. Conductive atomic force microscopy study of InAs growth kinetics on vicinal GaAs (110)

    International Nuclear Information System (INIS)

    Tejedor, Paloma; Diez-Merino, Laura; Beinik, Igor; Teichert, Christian

    2009-01-01

    Conductive atomic force microscopy has been used to investigate the effect of atomic hydrogen and step orientation on the growth behavior of InAs on GaAs (110) misoriented substrates. Samples grown by conventional molecular beam epitaxy exhibit higher conductivity on [110]-multiatomic step edges, where preferential nucleation of InAs nanowires takes place by step decoration. On H-terminated substrates with triangular terraces bounded by [115]-type steps, three-dimensional InAs clusters grow selectively at the terrace apices as a result of a kinetically driven enhancement in upward mass transport via AsH x intermediate species and a reduction in the surface free energy.

  10. Positioning of self-assembled InAs quantum dots by focused ion beam implantation

    International Nuclear Information System (INIS)

    Mehta, M.

    2007-01-01

    Self-assembled quantum dots (QDs) are envisioned as building blocks for realization of novel nanoelectronic devices, for which the site-selective growth is highly desirable. This thesis presents a successful route toward selective positioning of self-assembled InAs QDs on patterned GaAs surface by combination of in situ focused ion beam (FIB) implantation and molecular beam epitaxy (MBE) technology. First, a buffer layer of GaAs was grown by MBE before a square array of holes with a pitch of 1-2 μm was fabricated by FIB implantation of Ga and In, ions respectively. Later, an in-situ annealing step followed by InAs deposition was performed. The InAs QDs were preferentially formed in the holes generated by FIB. The influence of ion dose, annealing parameters and InAs amount was investigated in this work. With optimized parameters, more than 50 % single dot occupancy per hole is achieved. Furthermore, the photoluminescence spectra from positioned QDs confirm their good optical quality. (orig.)

  11. Studies on the controlled growth of InAs nanostructures on scission surfaces

    International Nuclear Information System (INIS)

    Bauer, J.

    2006-01-01

    The aim of this thesis was the controlled alignment of self-assembled InAs nano-structures on a {110}-oriented surface. The surface is prestructured with the atomic precision offered by molecular beam epitaxy, using the cleaved edge overgrowth-technique. On all samples grown within this work, the epitaxial template in the first growth step was deposited on a (001)GaAs substrate, while the InAs-layer forming the nanostructures during the second growth step was grown on cleaved {110}-GaAs surfaces. Atomic Force Microscopy (AFM) investigations demonstrate the formation of quantum dot (QD)-like nanostructures on top of the AlAs-stripes. X-ray diffraction measurements on large arrays of aligned quantum dots demonstrate that the quantum dots are formed of pure InAs. First investigations on the optical properties of these nanostructures were done using microphotoluminescence-spectroscopy with both high spatial and spectral resolution. (orig.)

  12. Linear and Nonlinear Optical Properties of Micrometer-Scale Gold Nanoplates

    International Nuclear Information System (INIS)

    Liu Xiao-Lan; Peng Xiao-Niu; Yang Zhong-Jian; Li Min; Zhou Li

    2011-01-01

    Micrometer-scale gold nanoplates have been synthesized in high yield through a polyol process. The morphology, crystal structure and linear optical extinction of the gold nanoplates have been characterized. These gold nanoplates are single-crystalline with triangular, truncated triangular and hexagonal shapes, exhibiting strong surface plasmon resonance (SPR) extinction in the visible and near-infrared (NIR) region. The linear optical properties of gold nanoplates are also investigated by theoretical calculations. We further investigate the nonlinear optical properties of the gold nanoplates in solution by Z-scan technique. The nonlinear absorption (NLA) coefficient and nonlinear refraction (NLR) index are measured to be 1.18×10 2 cm/GW and −1.04×10 −3 cm 2 /GW, respectively. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  13. The enhanced alcohol-sensing response of ultrathin WO3 nanoplates

    International Nuclear Information System (INIS)

    Chen Deliang; Hou Xianxiang; Wen Hejing; Wang Yu; Wang Hailong; Zhang Rui; Lu Hongxia; Xu Hongliang; Guan Shaokang; Li Xinjian; Sun Jing; Gao Lian

    2010-01-01

    Chemical sensors based on semiconducting metal oxide nanocrystals are of academic and practical significance in industrial processing and environment-related applications. Novel alcohol response sensors using two-dimensional WO 3 nanoplates as active elements have been investigated in this paper. Single-crystalline WO 3 nanoplates were synthesized through a topochemical approach on the basis of intercalation chemistry (Chen et al 2008 Small 4 1813). The as-obtained WO 3 nanoplate pastes were coated on the surface of an Al 2 O 3 ceramic microtube with four Pt electrodes to measure their alcohol-sensing properties. The results show that the WO 3 nanoplate sensors are highly sensitive to alcohols (e.g., methanol, ethanol, isopropanol and butanol) at moderate operating temperatures (260-360 deg. C). For butanol, the WO 3 nanoplate sensors have a sensitivity of 31 at 2 ppm and 161 at 100 ppm, operating at 300 deg. C. For other alcohols, WO 3 nanoplate sensors also show high sensitivities: 33 for methanol at 300 ppm, 70 for ethanol at 200 ppm, and 75 for isopropanol at 200 ppm. The response and recovery times of the WO 3 nanoplate sensors are less than 15 s for all the test alcohols. A good linear relationship between the sensitivity and alcohol concentrations has been observed in the range of 2-300 ppm, whereas the WO 3 nanoparticle sensors have not shown such a linear relationship. The sensitivities of the WO 3 nanoplate sensors decrease and their response times become short when the operating temperatures increase. The enhanced alcohol-sensing performance could be attributed to the ultrathin platelike morphology, the high crystallinity and the loosely assembling structure of the WO 3 nanoplates, due to the advantages of the effective adsorption and rapid diffusion of the alcohol molecules.

  14. Solution-processed n-ZnO nanorod/p-Co{sub 3}O{sub 4} nanoplate heterojunction light-emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong-Woo; Lee, Su Jeong; Biswas, Pranab [Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of); Lee, Tae Il [Department of BioNano Technology, Gachon University, 1342 Seongnam Daero, Seongnam 13120 (Korea, Republic of); Myoung, Jae-Min, E-mail: jmmyoung@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of)

    2017-06-01

    Highlights: • The n-ZnO nanorods were epitaxially grown on p-Co{sub 3}O{sub 4} nanoplates. • The heteroepitaxial p-n junction was fabricated by using hydrothermal process. • The LEDs emitted reddish-orange and violet light related to ZnO point defects. • The Co{sub 3}O{sub 4} nanoplates function as a hole injection layer. • Junction between 1D NRs and 2D NPs provides a new approach to design nanostructures. - Abstract: A heterojunction light-emitting diode (LED) based on p-type cobalt oxide (Co{sub 3}O{sub 4}) nanoplates (NPs)/n-type zinc oxide (ZnO) nanorods (NRs) is demonstrated. Using a low-temperature aqueous solution process, the n-type ZnO NRs were epitaxially grown on Co{sub 3}O{sub 4} NPs which were two-dimensionally assembled by a modified Langmuir-Blodgett process. The heterojunction LEDs exhibited a typical rectifying behavior with a turn-on voltage of about 2 V and emitted not only reddish-orange light at 610 nm but also violet light at about 400 nm. From the comparative analyses of electroluminescence and photoluminescence, it was determined that the reddish-orange light emission was related to the electronic transitions from zinc interstitials (Zn{sub i}) to oxygen interstitials (O{sub i}) or conduction-band minimum (CBM) to oxygen vacancies (V{sub O}), and the violet light emission was attribute to the transition from CBM to valence-band maximum (VBM) or Zn{sub i} to zinc vacancies (V{sub Zn}).

  15. Mobility in excess of 106 cm2/V s in InAs quantum wells grown on lattice mismatched InP substrates

    Science.gov (United States)

    Hatke, A. T.; Wang, T.; Thomas, C.; Gardner, G. C.; Manfra, M. J.

    2017-10-01

    We investigate the transport properties of a two-dimensional electron gas residing in strained composite quantum wells of In0.75Ga0.25As/InAs/In0.75Ga0.25As cladded with In0.75Al0.25As barriers grown metamorphically on insulating InP substrates. By optimizing the widths of the In0.75Ga0.25As layers, the In0.75Al0.25As barrier, and the InAs quantum well, we demonstrate mobility in excess of 1 ×106 cm2/V s. Mobility vs. density data indicate that scattering is dominated by a residual three dimensional distribution of charged impurities. We extract the effective Rashba parameter and spin-orbit length for these composite quantum wells.

  16. Controlled growth of high-density CdS and CdSe nanorod arrays on selective facets of two-dimensional semiconductor nanoplates

    KAUST Repository

    Wu, Xue-Jun

    2016-03-14

    The rational synthesis of hierarchical three-dimensional nanostructures with specific compositions, morphologies and functionalities is important for applications in a variety of fields ranging from energy conversion and electronics to biotechnology. Here, we report a seeded growth approach for the controlled epitaxial growth of three types of hierarchical one-dimensional (1D)/two-dimensional (2D) nanostructures, where nanorod arrays of II-VI semiconductor CdS or CdSe are grown on the selective facets of hexagonal-shaped nanoplates, either on the two basal facets of the nanoplate, or on one basal facet, or on the two basal facets and six side facets. The seed engineering of 2D hexagonal-shaped nanoplates is the key factor for growth of the three resulting types of 1D/2D nanostructures. The wurtzite- and zinc-blende-type polymorphs of semiconductors are used to determine the facet-selective epitaxial growth of 1D nanorod arrays, resulting in the formation of different hierarchical three-dimensional (3D) nanostructures. © 2016 Macmillan Publishers Limited. All rights reserved.

  17. Formation of anodic layers on InAs (111)III. Study of the chemical composition

    Energy Technology Data Exchange (ETDEWEB)

    Valisheva, N. A., E-mail: valisheva@thermo.isp.nsc.ru; Tereshchenko, O. E. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Prosvirin, I. P.; Kalinkin, A. V. [Russian Academy of Sciences, Boreskov Institute of Catalysis, Siberian Branch (Russian Federation); Goljashov, V. A. [Novosibirsk State University (Russian Federation); Levtzova, T. A. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Bukhtiyarov, V. I. [Russian Academy of Sciences, Boreskov Institute of Catalysis, Siberian Branch (Russian Federation)

    2012-04-15

    The chemical composition of {approx}20-nm-thick anodic layers grown on InAs (111)III in alkaline and acid electrolytes containing or not containing NH{sub 4}F is studied by X-ray photoelectron spectroscopy. It is shown that the composition of fluorinated layers is controlled by the relation between the concentrations of fluorine and hydroxide ions in the electrolyte and by diffusion processes in the growing layer. Fluorine accumulates at the (anodic layer)/InAs interface. Oxidation of InAs in an acid electrolyte with a low oxygen content and a high NH{sub 4}F content brings about the formation of anodic layers with a high content of fluorine and elemental arsenic and the formation of an oxygen-free InF{sub x}/InAs interface. Fluorinated layers grown in an alkaline electrolyte with a high content of O{sup 2-} and/or OH{sup -} groups contain approximately three times less fluorine and consist of indium and arsenic oxyfluorides. No distinction between the compositions of the layers grown in both types of fluorine-free electrolytes is established.

  18. Ultraflat Au nanoplates as a new building block for molecular electronics.

    Science.gov (United States)

    Jeong, Wooseok; Lee, Miyeon; Lee, Hyunsoo; Lee, Hyoban; Kim, Bongsoo; Park, Jeong Young

    2016-05-27

    We demonstrate the charge transport properties of a self-assembled organic monolayer on Au nanoplates with conductive probe atomic force microscopy (CP-AFM). Atomically flat Au nanoplates, a few hundred micrometers on each side, that have only (111) surfaces, were synthesized using the chemical vapor transport method; these nanoplates were employed as the substrates for hexadecanethiol (HDT) self-assembled monolayers (SAMs). Atomic-scale high-resolution images show (√3 x √3) R30° molecular periodicity, indicating a well-ordered structure of the HDT on the Au nanoplates. We observed reduced friction and adhesion forces on the HDT SAMs on Au nanoplates, compared with Si substrates, which is consistent with the lubricating nature of HDT SAMs. The electrical properties, such as I-V characteristics and current as a function of load, were measured using CP-AFM. We obtained a tunneling decay constant (β) of 0.57 Å(-1), including through-bond (βtb = 0.99 Å(-1)) and through-space (βts = 1.36 Å(-1)) decay constants for the two-pathway model. This indicates that the charge transport properties of HDT SAMs on Au nanoplates are consistent with those on a Au (111) film, suggesting that SAMs on nanoplates can provide a new building block for molecular electronics.

  19. Few-Layer Nanoplates of Bi 2 Se 3 and Bi 2 Te 3 with Highly Tunable Chemical Potential

    KAUST Repository

    Kong, Desheng

    2010-06-09

    A topological insulator (TI) represents an unconventional quantum phase of matter with insulating bulk band gap and metallic surface states. Recent theoretical calculations and photoemission spectroscopy measurements show that group V-VI materials Bi2Se3, Bi2Te3, and Sb2Te3 are TIs with a single Dirac cone on the surface. These materials have anisotropic, layered structures, in which five atomic layers are covalently bonded to form a quintuple layer, and quintuple layers interact weakly through van der Waals interaction to form the crystal. A few quintuple layers of these materials are predicted to exhibit interesting surface properties. Different from our previous nanoribbon study, here we report the synthesis and characterizations of ultrathin Bi2Te3 and Bi2Se3 nanoplates with thickness down to 3 nm (3 quintuple layers), via catalyst-free vapor-solid (VS) growth mechanism. Optical images reveal thickness-dependent color and contrast for nanoplates grown on oxidized silicon (300 nm SiO2/Si). As a new member of TI nanomaterials, ultrathin TI nanoplates have an extremely large surface-to-volume ratio and can be electrically gated more effectively than the bulk form, potentially enhancing surface state effects in transport measurements. Low-temperature transport measurements of a single nanoplate device, with a high-k dielectric top gate, show decrease in carrier concentration by several times and large tuning of chemical potential. © 2010 American Chemical Society.

  20. Electron microscopy of GaAs-based structures with InAs and As quantum dots separated by an AlAs barrier

    International Nuclear Information System (INIS)

    Nevedomskiy, V. N.; Bert, N. A.; Chaldyshev, V. V.; Preobrazhenskiy, V. V.; Putyato, M. A.; Semyagin, B. R.

    2013-01-01

    Electron microscopy studies of GaAs-based structures grown by molecular beam epitaxy and containing arrays of semiconductor InAs quantum dots and metal As quantum dots are performed. The array of InAs quantum dots is formed by the Stranski-Krastanov mechanism and consists of vertically coupled pairs of quantum dots separated by a GaAs spacer 10 nm thick. To separate the arrays of semiconductor and metal quantum dots and to prevent diffusion-induced mixing, the array of InAs quantum dots is overgrown with an AlAs barrier layer 5 or 10 nm thick, after which a GaAs layer is grown at a comparatively low temperature (180°C). The array of As quantum dots is formed in an As-enriched layer of the low-temperature GaAs by means of post-growth annealing at 400–760°C for 15 min. It is established that the AlAs barrier layer has a surface profile corresponding to that of a subbarrier layer with InAs quantum dots. The presence of such a profile causes the formation of V-shaped structural defects upon subsequent overgrowth with the GaAs layer. Besides, it was obtained that AlAs layer is thinned over the InAs quantum dots tops. It is shown that the AlAs barrier layer in the regions between the InAs quantum dots effectively prevents the starting diffusion of excess As at annealing temperatures up to 600°C. However, the concentration of mechanical stresses and the reduced thickness of the AlAs barrier layer near the tops of the InAs quantum dots lead to local barrier breakthroughs and the diffusion of As quantum dots into the region of coupled pairs of InAs quantum dots at higher annealing temperatures

  1. Preparation of triangular and hexagonal silver nanoplates on the surface of quartz substrate

    International Nuclear Information System (INIS)

    Jia Huiying; Zeng Jianbo; An Jing; Song Wei; Xu Weiqing; Zhao Bing

    2008-01-01

    In this paper, triangular and hexagonal silver nanoplates were prepared on the surface of quartz substrate using photoreduction of silver ions in the presence of silver seeds. The obtained silver nanoplates were characterized by atomic force microscopy and UV-vis spectroscopy. It was found that the silver seeds played an important role in the formation of triangular and hexagonal silver nanoplates. By varying the irradiation time, nanoplates with different sizes and shapes could be obtained. The growth mechanism for triangular and hexagonal nanoplates prepared on quartz substrate was discussed

  2. Facile synthesis of porous Co3O4 nanoplates for supercapacitor ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Porous tricobalt tetraoxide (Co3O4) nanoplates with large aspect ratio have been obtained by annealing Co(OH)2 precursor nanoplates synthesized by a facile reflux method without the need for any template or surfactant. After the heat treatment, the as-obtained phase-pure Co3O4 nanoplates with a well- retained ...

  3. Light-induced reversible expansion of individual gold nanoplates

    Directory of Open Access Journals (Sweden)

    Jinsheng Lu

    2017-10-01

    Full Text Available Light-induced mechanical response of materials has been extensively investigated and widely utilized to convert light energy into mechanical energy directly. The metallic nanomaterials have excellent photothermal properties and show enormous potential in micromechanical actuators, etc. However, the photo-thermo-mechanical properties of individual metallic nanostructures have yet to be well investigated. Here, we experimentally demonstrate a way to realize light-induced reversible expansion of individual gold nanoplates on optical microfibers. The light-induced thermal expansion coefficient is obtained as 21.4 ± 4.6 ∼ 31.5 ± 4.2 μ·K-1 when the light-induced heating temperature of the gold nanoplates is 240 ∼ 490 °C. The photo-thermo-mechanical response time of the gold nanoplates is about 0.3 ± 0.1 s. This insight into the photo-thermo-mechanical properties of the gold nanoplates could deepen the understanding of the light-induced reversible expansion behavior in nanoscale and pave the way for applications based on this piezoelectric-like response, such as light-driven metallic micromotors.

  4. CuS nanoplates from ionic liquid precursors—Application in organic photovoltaic cells

    Science.gov (United States)

    Kim, Yohan; Heyne, Benjamin; Abouserie, Ahed; Pries, Christopher; Ippen, Christian; Günter, Christina; Taubert, Andreas; Wedel, Armin

    2018-05-01

    Hexagonal p-type semiconductor CuS nanoplates were synthesized via a hot injection method from bis(trimethylsilyl)sulfide and the ionic liquid precursor bis(N-dodecylpyridinium) tetrachloridocuprate(ii). The particles have a broad size distribution with diameters between 30 and 680 nm and well-developed crystal habits. The nanoplates were successfully incorporated into organic photovoltaic (OPV) cells as hole conduction materials. The power conversion efficiency of OPV cells fabricated with the nanoplates is 16% higher than that of a control device fabricated without the nanoplates.

  5. Random oriented hexagonal nickel hydroxide nanoplates grown on graphene as binder free anode for lithium ion battery with high capacity

    Science.gov (United States)

    Du, Yingjie; Ma, Hu; Guo, Mingxuan; Gao, Tie; Li, Haibo

    2018-05-01

    In this work, two-step method has been employed to prepare random oriented hexagonal hydroxide nanoplates on graphene (Ni(OH)2@G) as binder free anode for lithium ion battery (LIB) with high capacity. The morphology, microstructure, crystal phase and elemental bonding have been characterized. When evaluated as anode for LIB, the Ni(OH)2@G exhibited high initial discharge capacity of 1318 mAh/g at the current density of 50 mA/g. After 80 cycles, the capacity was maintained at 834 mAh/g, implying 63.3% remaining. Even the charge rate was increased to 2000 mA/g, an impressive capacity of 141 mAh/g can be obtained, indicating good rate capability. The superior LIB behavior of Ni(OH)2@G is ascribed to the excellent combination between Ni(OH)2 nanoplates and graphene via both covalent chemical bonding and van der Waals interactions.

  6. Synthesis of Dispersible Mesoporous Nitrogen-Doped Hollow Carbon Nanoplates with Uniform Hexagonal Morphologies for Supercapacitors.

    Science.gov (United States)

    Cao, Jie; Jafta, Charl J; Gong, Jiang; Ran, Qidi; Lin, Xianzhong; Félix, Roberto; Wilks, Regan G; Bär, Marcus; Yuan, Jiayin; Ballauff, Matthias; Lu, Yan

    2016-11-02

    In this study, dispersible mesoporous nitrogen-doped hollow carbon nanoplates have been synthesized as a new anisotropic carbon nanostructure using gibbsite nanoplates as templates. The gibbsite-silica core-shell nanoplates were first prepared before the gibbsite core was etched away. Dopamine as carbon precursor was self-polymerized on the hollow silica nanoplates surface assisted by sonification, which not only favors a homogeneous polymer coating on the nanoplates but also prevents their aggregation during the polymerization. Individual silica-polydopamine core-shell nanoplates were immobilized in a silica gel in an insulated state via a silica nanocasting technique. After pyrolysis in a nanoconfine environment and elimination of silica, discrete and dispersible hollow carbon nanoplates are obtained. The resulted hollow carbon nanoplates bear uniform hexagonal morphology with specific surface area of 460 m 2 ·g -1 and fairly accessible small mesopores (∼3.8 nm). They show excellent colloidal stability in aqueous media and are applied as electrode materials for symmetric supercapacitors. When using polyvinylimidazolium-based nanoparticles as a binder in electrodes, the hollow carbon nanoplates present superior performance in parallel to polyvinylidene fluoride (PVDF) binder.

  7. The role of strain-driven in migration in the growth of self-assembled InAs quantum dots on InP

    CERN Document Server

    Yoon, S H; Lee, T W; Hwang, H D; Yoon, E J; Kim, Y D

    1999-01-01

    Self-assembled InAs quantum dots (SAQDs) were grown on InP by metalorganic chemical vapor deposition. The amount of excess InAs and the aspect ratio of the SAQD increased with temperature and V/III ratio. It is explained that the As/P exchange reaction at the surface played an important role in the kinetics of SAQD formation. Insertion of a lattice-matched InGaAs buffer layer suppressed the excess InAs formation, and lowered the aspect ratio. Moreover, the dots formed on InGaAs buffer layers were faceted, whereas those on InP were hemispherical, confirming the effect of the As/P exchange reaction. The shape of InAs quantum dots on InGaAs buffer layers was a truncated pyramid with four [136] facets and base edges parallel to directions.

  8. Self-templated synthesis of single-crystal and single-domain ferroelectric nanoplates

    KAUST Repository

    Chao, Chunying

    2012-08-15

    Free-standing single-crystal PbTiO 3 nanoplates (see picture) were synthesized by a facile hydrothermal method. A "self-templated" crystal growth is presumed to lead to the formation of the PbTiO 3 nanoplates, which have ferroelectric single-domain structures, whose polarization areas can be manipulated by writing and reading. The nanoplates are also effective catalysts for the oxidation of carbon monoxide. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Orientation dependent size effects in single crystalline anisotropic nanoplates with regard to surface energy

    International Nuclear Information System (INIS)

    Assadi, Abbas; Salehi, Manouchehr; Akhlaghi, Mehdi

    2015-01-01

    In this work, size dependent behavior of single crystalline normal and auxetic anisotropic nanoplates is discussed with consideration of material surface stresses via a generalized model. Bending of pressurized nanoplates and their fundamental resonant frequency are discussed for different crystallographic directions and anisotropy degrees. It is explained that the orientation effects are considerable when the nanoplates' edges are pinned but for clamped nanoplates, the anisotropy effect may be ignored. The size effects are the highest when the simply supported nanoplates are parallel to [110] direction but as the anisotropy gets higher, the size effects are reduced. The orientation effect is also discussed for possibility of self-instability occurrence in nanoplates. The results in simpler cases are compared with previous experiments for nanowires but with a correction factor. There are still some open questions for future studies. - Highlights: • Size effects in single crystalline anisotropic nanoplates are discussed. • A generalized model is established containing some physical assumptions. • Orientation dependent size effects due to material anisotropy are explained. • Bending, instability and frequencies are studied at normal/auxetic domain

  10. Direct Vapor Growth of Perovskite CsPbBr3 Nanoplate Electroluminescence Devices.

    Science.gov (United States)

    Hu, Xuelu; Zhou, Hong; Jiang, Zhenyu; Wang, Xiao; Yuan, Shuangping; Lan, Jianyue; Fu, Yongping; Zhang, Xuehong; Zheng, Weihao; Wang, Xiaoxia; Zhu, Xiaoli; Liao, Lei; Xu, Gengzhao; Jin, Song; Pan, Anlian

    2017-10-24

    Metal halide perovskite nanostructures hold great promises as nanoscale light sources for integrated photonics due to their excellent optoelectronic properties. However, it remains a great challenge to fabricate halide perovskite nanodevices using traditional lithographic methods because the halide perovskites can be dissolved in polar solvents that are required in the traditional device fabrication process. Herein, we report single CsPbBr 3 nanoplate electroluminescence (EL) devices fabricated by directly growing CsPbBr 3 nanoplates on prepatterned indium tin oxide (ITO) electrodes via a vapor-phase deposition. Bright EL occurs in the region near the negatively biased contact, with a turn-on voltage of ∼3 V, a narrow full width at half-maximum of 22 nm, and an external quantum efficiency of ∼0.2%. Moreover, through scanning photocurrent microscopy and surface electrostatic potential measurements, we found that the formation of ITO/p-type CsPbBr 3 Schottky barriers with highly efficient carrier injection is essential in realizing the EL. The formation of the ITO/p-type CsPbBr 3 Schottky diode is also confirmed by the corresponding transistor characteristics. The achievement of EL nanodevices enabled by directly grown perovskite nanostructures could find applications in on-chip integrated photonics circuits and systems.

  11. Effects of InAlAs strain reducing layer on the photoluminescence properties of InAs quantum dots embedded in InGaAs/GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Lingmin, E-mail: konglm@qq.com [School of Marine Science and Technology, Zhejiang Ocean University, Zhoushan 316000 (China); Sun, Wei [SEM School of Electromechanical Engineering, Weifang Engineering Vocational College, Qingzhou 262500 (China); Feng, Zhe Chuan, E-mail: zcfeng@nut.edu.tw [Institute of Photonics and Optoelectronics, Department of Electrical Engineering, and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 106-17, Taiwan (China); Xie, Sheng [School of Electronic and Information Engineering, Tianjin University, Tianjin 300072 (China); Zhou, Yunqing; Wang, Rui; Zhang, Cunxi; Zong, Zhaocun; Wang, Hongxia; Qiao, Qian [Department of Physics, Zhejiang Ocean University, Zhoushan 316000 (China); Wu, Zhengyun [Department of Physics, Xiamen University, Xiamen 361005 China (China)

    2014-07-01

    Two kinds of self-assembled quantum dots (QDs) embedded within InGaAs/GaAs quantum wells were grown by molecular beam epitaxy: one was capped with an InAlAs strain reducing (SR) layer, while the other was not. Their emission dynamics was investigated by time-resolved and temperature dependent (TD) photoluminescence (PL) measurements. A significant redshift can be observed in the emission peak position of InAs QDs with thin InAlAs SR cap layer, which results from SR effects. Different behaviors of the integrated PL intensity for the samples with or without InAlAs layer may be ascribed to the reduced carrier transition at higher temperature for the higher energy barrier of the InAlAs layer, and the TD mode of carrier migration. The PL decay time of quantum dots grown with InAlAs layer was much longer than that without the layer, which implies that the InAlAs layer with higher energy barrier may enhance the quantum restriction of carriers in InAs QDs. These observations are discussed from the viewpoint of strain compensation and potential barrier variation with SR layers. Our experiments also demonstrate that the main mode of carrier migration is quantum tunneling effect at lower temperature, while it is quantum transition at higher temperature. The results demonstrate the importance of InAlAs SR layer for the optical quality of InAs QDs. - Highlights: • InAs quantum dots (QDs) were grown on GaAs. • A thin InAlAs layer was grown on InAs QDs. • Temperature dependent photoluminescence (PL) and time-resolved PL were carried out. • Both a redshift and a double exponential decay of PL emission were generated by the InAlAs layer.

  12. Electron Spin Polarization and Detection in InAs Quantum Dots Through p-Shell Trions

    Science.gov (United States)

    2010-01-08

    optical control of spin states in quantum dots. II. EXPERIMENT The QD sample consists of 20 layers of InAs QDs, grown by molecular -beam epitaxy through...anisotropic 2D harmonic poten- tials. The electrons and holes are described by Fock- Darwin states harmonic oscillators with lateral sizes ax and ay in this

  13. A surface-chemistry study of barium ferrite nanoplates with DBSa-modified surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lisjak, Darja, E-mail: darja.lisjak@ijs.si [Jožef Stefan Institute, Ljubljana (Slovenia); Ovtar, Simona; Kovač, Janez [Jožef Stefan Institute, Ljubljana (Slovenia); Gregoratti, Luca; Aleman, Belen; Amati, Matteo [Elettra – Sincrotrone Trieste S.C.p.A. di interesse nazionale, Trieste (Italy); Fanetti, Mattia [University of Nova Gorica, Nova Gorica (Slovenia); Istituto Officina dei Materiali CNR, Area Science Park, Trieste (Italy); Makovec, Darko [Jožef Stefan Institute, Ljubljana (Slovenia)

    2014-06-01

    Barium ferrite (BaFe{sub 12}O{sub 19}) is a ferrimagnetic oxide with a high magnetocrystalline anisotropy that can be exploited in magnetically aligned ceramics or films for self-biased magnetic applications. Magnetic alignment of the films can be achieved by the directed assembly of barium ferrite nanoplates. In this investigation the nanoplates were synthesized hydrothermally and suspended in 1-butanol using dodecylbenzene sulphonic acid (DBSa) as a surfactant. They were then deposited in an electric or magnetic field on flat substrates and exhibited a significant preferential alignment in the plane of the substrate, allowing a differentiation between the analysis of their basal and side planes using scanning photoelectron microscopy with a lateral resolution down to 100 nm. The surface chemistry of the nanoplates was additionally studied with X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. For a comparison, bare barium ferrite nanoplates were also analyzed after decomposing the DBSa at 460 °C. The deviation of the surface chemistry from the stoichiometric composition was observed and the adsorption of the DBSa molecules on the nanoplates was confirmed with all three methods. Different types of bonding (physi- or chemisorption) were possible and considered with respect to the assembly of the barium ferrite nanoplates into anisotropic magnetic films.

  14. Self-templated synthesis of single-crystal and single-domain ferroelectric nanoplates

    KAUST Repository

    Chao, Chunying; Ren, Zhaohui; Zhu, Yihan; Xiao, Zhen; Liu, Zhenya; Xú , Gang; Mai, Jiangquan; Li, Xiang; Shen, Ge; Han, Gaorong

    2012-01-01

    Free-standing single-crystal PbTiO 3 nanoplates (see picture) were synthesized by a facile hydrothermal method. A "self-templated" crystal growth is presumed to lead to the formation of the PbTiO 3 nanoplates, which have ferroelectric single

  15. Growth and electrical characterization of Zn-doped InAs and InAs{sub 1-x}Sb{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Venter, A., E-mail: andre.venter@nmmu.ac.z [Department of Physics, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth (South Africa); Shamba, P.; Botha, L.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth (South Africa)

    2009-06-01

    The electrical properties of Zn doped InAs and InAsSb layers grown on semi-insulating GaAs by metal organic vapour phase epitaxy, using dimethyl zinc as the p-type dopant source, have been studied. The influence of dopant flow rate, V/III ratio and substrate orientation on the electrical properties of these InAs and InAs{sub 1-x}Sb{sub x} layers have been studied at a few appropriate growth temperatures. A promising group V source, tertiary butyl arsenic was used as an alternative to arsenic hydride in the case of InAs growth. The electrical properties of the InAs and InAs{sub 1-x}Sb{sub x} epitaxial layers were mainly studied by the Hall effect. However, surface accumulation in these materials results in deceptive Hall results being extracted. A two layer model (assuming the layer to consist of two parallel conducting paths viz. surface and bulk) has therefore been used to extract sensible transport properties. In addition, conventional Hall measurements ignores the high electron to hole mobility ratio in InAs and InAsSb leading to erroneous transport properties.

  16. The synthesis of high yield Au nanoplate and optimized optical properties

    Science.gov (United States)

    Ni, Yuan; Kan, Caixia; Xu, Juan; Liu, Yang

    2018-02-01

    The applications of Au nanoplates based on the tunable plasmon properties and enhanced electromagnetic field at the sharp tip and straight edges, have generated a great deal of interest in recent years, especially in the fields of the bio-chemical sensing and imaging. In this review, we focus on the synthesis of nanoscale platelike structures by multiple synthetic strategies (such as thermal solution method, seed-mediated method, seedless method, and some greener methods), and explore corresponding growth mechanism in different synthetic approaches. Other than to review the fabrication of Au nanoplates, the purification strategies are also discussed in order to support the applications in various fields. Modifying synthetic method to obtain well-defined nanoplates can tuned optical absorption from visible to near-infrared region. Moreover, the Au nanoplate dimers (vertex-to-vertex and edge-by-edge assemblies) can induce more specific plasmon properties and stronger localized field due to coupling of interparticles. Compared with 0D quasi-spherical nanoparticles and 1D nanorods, the 2D nanoplates can be applied as a good surface-enhanced Raman scattering (SERS) substrate because of the sharp corners and straight edges. This review will provide background information for the controllable synthesis of anisotropic nanoparticles and advance the application of coupled nanostructures.

  17. Label-free immunosensor based on Pd nanoplates for amperometric immunoassay of alpha-fetoprotein.

    Science.gov (United States)

    Wang, Huan; Li, He; Zhang, Yihe; Wei, Qin; Ma, Hongmin; Wu, Dan; Li, Yan; Zhang, Yong; Du, Bin

    2014-03-15

    In this paper, Pd nanoplates were used as a kind of electrode materials for fabrication of an electrochemical immunosensor, which was applied for detection of cancer biomarker alpha-fetoprotein (AFP). Thanks to the unique structure and properties of Pd nanoplates, the antibody of AFP (Ab) was effectively immobilized onto the surface of the Pd nanoplates modified glassy carbon electrode (GCE). Moreover, the good electrochemical properties of Pd nanoplates greatly improved the electronic transmission rate and enhanced the electrochemical signal, which led to an increase of the detection sensitivity. Based on the specific antibody-antigen interaction, a label-free immunosensor based on Pd nanoplates was developed for sensing of AFP. The current method allows us to detect AFP over a wide concentration range from 0.01 to 75.0 ng/mL with a detection limit of 4 pg/mL. The proposed immunosensor has been used to determine AFP in human serum with satisfactory results. © 2013 Elsevier B.V. All rights reserved.

  18. Self-assembled InAs quantum dots formed by molecular beam epitaxy at low temperature and postgrowth annealing

    NARCIS (Netherlands)

    Zhan, H.H.; Nötzel, R.; Hamhuis, G.J.; Eijkemans, T.J.; Wolter, J.H.

    2003-01-01

    Self-assembled InAs quantum dots are grown at low temperature (LT) by molecular beam epitaxy (MBE) on GaAs substrates. The growth is in situ monitored by reflection high-energy electron diffraction, and ex situ evaluated by atomic force microscopy for the morphological properties, and by

  19. Ultrasonic-assisted synthesis of monodisperse single-crystalline silver nanoplates and gold nanorings.

    Science.gov (United States)

    Jiang, Li-Ping; Xu, Shu; Zhu, Jian-Min; Zhang, Jian-Rong; Zhu, Jun-Jie; Chen, Hong-Yuan

    2004-09-20

    A simple sonochemical route was developed for the crystal growth of uniform silver nanoplates and ringlike gold nanocrystals in a N,N-dimethylformamide solution. The platelike structures were generated from the selective growth on different crystal planes in the presence of poly(vinylpyrrolidone) and the ultrasonic-assisted Ostwald ripening processes. The silver nanoplates in solution served as the templates for the synthesis of ringlike gold crystals via a displacement reaction. Both the silver nanoplates and gold nanorings were highly oriented single crystals with (111) planes as the basal planes. Copyright 2004 American Chemical Society

  20. Statistical optimization of synthesis procedure and characterization of europium (III) molybdate nano-plates

    Energy Technology Data Exchange (ETDEWEB)

    Pourmortazavi, Seied Mahdi [Malek Ashtar University of Technology, Faculty of Material and Manufacturing Technologies, P. O. Box 16765-3454, Tehran (Iran, Islamic Republic of); Rahimi-Nasrabadi, Mehdi [Imam Hossein University, Nano Science Center, Tehran (Iran, Islamic Republic of); Fazli, Yousef [Islamic Azad University, Department of Chemistry, Faculty of Science, Arak Branch, Arak (Iran, Islamic Republic of); Mohammad-Zadeh, Mohammad [Sabzevar University of Medical Sciences, Department of Physiology and Pharmacology, School of Medicine, Sabzevar (Iran, Islamic Republic of)

    2015-06-15

    Europium (III) molybdate nano-plates were synthesized in this work via chemical precipitation route involving adding of europium (III) ion solution to the aqueous solution of molybdate reagent. Effects of some reaction variables such as concentrations of europium and molybdate ions, flow rate of europium reagent, and reactor temperature on the diameter of the synthesized europium (III) molybdate nano-plates were experimentally investigated by orthogonal array design. The results showed that the size of europium (III) molybdate nano-plates can be optimized by adjusting the concentrations of europium (III) and molybdate ions, as well as the reactional temperature. Europium (III) molybdate nano-plates prepared under the optimum conditions were characterized by X-ray powder diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. (orig.)

  1. Polyol synthesis of silver nanoplates: The crystal growth mechanism based on a rivalrous adsorption

    International Nuclear Information System (INIS)

    Luo Xiaolin; Li Zongxiao; Yuan Chunlan; Chen Yashao

    2011-01-01

    Highlights: → Silver nanoplates have been successfully synthesized by polyol reduction in the presence of poly (vinylpyrrolidone) (PVP) and HNO 3 . → Due to the discovery of CN - ions in the solution, a mechanism for the anisotropic growth of silver nanoplates is systematically discussed. → TG, FT-IR and SERS were used to provide some direct evidences of rivalrous adsorption between PVP and CN - ions on the surface of the silver crystals. - Abstract: A polyol reducing approach has been applied to synthesize silver nanoplates with an average thickness of 50 nm and edge length of 3 μm in the presence of poly (vinylpyrrolidone) (PVP) and HNO 3 . X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscropy (TEM), and electron diffraction are used to characterize these silver nanoplates. Findings indicate that the nanoplates are single crystals and with their basal plane as (1 1 1) lattice plane. On the basis of the results from thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy, a crystal growth mechanism based on the rivalrous adsorption between PVP and CN - ions on the surface of silver nanoplates is supposed to explain the crystal anisotropic growth.

  2. The evidence for synthesis of truncated triangular silver nanoplates in the presence of CTAB

    International Nuclear Information System (INIS)

    He Xin; Zhao Xiujian; Chen Yunxia; Feng Jinyang

    2008-01-01

    Truncated triangular silver nanoplates were prepared by a solution-phase approach, which involved the seed-mediated growth of silver nanoparticles in the presence of cetyltrimethylammonium bromide (CTAB) at 40 deg. C. The result of X-ray diffraction indicates that the as-prepared nanoparticles are made of pure face centered cubic silver. Transmission electron microscopy and atomic force microscopy studies show that the truncated triangular silver nanoplates, with edge lengths of 50 ± 5 nm and thicknesses of 27 ± 3 nm, are oriented differently on substrates of a copper grid and a fresh mica flake. The corners of these nanoplates are round. The selected area electron diffraction analysis reveals that the silver nanoplates are single crystals with an atomically flat surface. We determine the holistic morphology of truncated triangular silver nanoplates through the above measurements with the aid of computer-aided 3D perspective images

  3. Electrochemical supercapacitors of cobalt hydroxide nanoplates grown on conducting cadmium oxide base-electrodes

    Directory of Open Access Journals (Sweden)

    Kailas K. Tehare

    2017-05-01

    Full Text Available Dopant-free and cost-effective sprayed cadmium oxide (CdO conducting base-electrodes, obtained at different concentrations (0.5, 1 and 1.5 M, characterized for their structures, morphologies and conductivities by using X-ray diffraction, scanning electron microscopy and electrical conductivity measurements, respectively, are employed as base-electrodes for growing cobalt hydroxide (Co(OH2 nanoplates using a simple electrodeposition method which further are envisaged for electrochemical supercapacitor application. Polycrystalline nature and mushroom-like plane-views are confirmed from the structure and morphology analyses. Both CdO and CdO–Co(OH2 electrodes reveal specific capacitances as high as 312 F g−1 and 1119 F g−1, respectively, in 0.1 M KOH electrolyte at 10 mV s−1 sweep rate. Optimized Co(OH2–CdO configuration electrode demonstrates energy density of 98.83 W h kg−1 and power density of 0.75 kW kg−1. In order to investigate the charge transfer kinematics electrochemical impedance measurements are carried out and explored.

  4. InaSAFE applications in disaster preparedness

    Science.gov (United States)

    Pranantyo, Ignatius Ryan; Fadmastuti, Mahardika; Chandra, Fredy

    2015-04-01

    Disaster preparedness activities aim to reduce the impact of disasters by being better prepared to respond when a disaster occurs. In order to better anticipate requirements during a disaster, contingency planning activities can be undertaken prior to a disaster based on a realistic disaster scenario. InaSAFE is a tool that can inform this process. InaSAFE is a free and open source software that estimates the impact to people and infrastructure from potential hazard scenarios. By using InaSAFE, disaster managers can develop scenarios of disaster impacts (people and infrastructures affected) to inform their contingency plan and emergency response operation plan. While InaSAFE provides the software framework exposure data and hazard data are needed as inputs to run this software. Then InaSAFE can be used to forecast the impact of the hazard scenario to the exposure data. InaSAFE outputs include estimates of the number of people, buildings and roads are affected, list of minimum needs (rice and clean water), and response checklist. InaSAFE is developed by Indonesia's National Disaster Management Agency (BNPB) and the Australian Government, through the Australia-Indonesia Facility for Disaster Reduction (AIFDR), in partnership with the World Bank - Global Facility for Disaster Reduction and Recovery (GFDRR). This software has been used in many parts of Indonesia, including Padang, Maumere, Jakarta, and Slamet Mountain for emergency response and contingency planning.

  5. Enhanced photoactivity from single-crystalline SrTaO2N nanoplates synthesized by topotactic nitridation

    International Nuclear Information System (INIS)

    Fu, Jie; Skrabalak, Sara E.

    2017-01-01

    There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often give enhanced photoactivity. Herein, single-crystalline SrTaO 2 N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, in which single-crystalline SrTaO 2 N nanoplates form by topotactic nitridation of aerosol-prepared Sr 2 Ta 2 O 7 nanoplates and SrTaO 2 N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO 2 N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1 % for OER compared to the polyhedra (AQE: 1.6 %) and SrTaO 2 N polycrystals (AQE: 0.6 %). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Enhanced Photoactivity from Single-Crystalline SrTaO2 N Nanoplates Synthesized by Topotactic Nitridation.

    Science.gov (United States)

    Fu, Jie; Skrabalak, Sara E

    2017-11-06

    There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often give enhanced photoactivity. Herein, single-crystalline SrTaO 2 N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, in which single-crystalline SrTaO 2 N nanoplates form by topotactic nitridation of aerosol-prepared Sr 2 Ta 2 O 7 nanoplates and SrTaO 2 N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO 2 N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1 % for OER compared to the polyhedra (AQE: 1.6 %) and SrTaO 2 N polycrystals (AQE: 0.6 %). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Nonlocal microstructure-dependent dynamic stability of refined porous FG nanoplates in hygro-thermal environments

    Science.gov (United States)

    Reza Barati, Mohammad

    2017-10-01

    Based on the generalized nonlocal strain gradient theory (NSGT), dynamic modeling and analysis of nanoporous inhomogeneous nanoplates is presented. Therefore, it is possible to capture both stiffness-softening and stiffness-hardening effects for a more accurate dynamic analysis of nanoplates. The nanoplate is in hygro-thermal environments and is subjected to an in-plane harmonic load. Porosities are incorporated to the model based on a modified rule of mixture. Modeling of the porous nanoplate is conducted according to a refined four-variable plate theory with fewer field variables than in the first-order plate theory. The governing equations and related classical and nonclassical boundary conditions are derived based on Hamilton's principle. These equations are solved for hinged nanoplates via Galerkin's method. It is shown that porosities, moisture rise, temperature rise, nonlocal parameter, strain gradient parameter, material gradation, elastic foundation and uniform dynamic load have a remarkable influence on the dynamic behavior of nanoscale plates.

  8. Liquid-liquid interface assisted synthesis of size- and thickness-controlled Ag nanoplates

    International Nuclear Information System (INIS)

    Jin Mingshang; Kuang Qin; Han Xiguang; Xie Shuifen; Xie Zhaoxiong; Zheng Lansun

    2010-01-01

    Here we proposed a synthetic method of high-purity Ag nanoplates by the reduction of aqueous Ag + ions at the aqueous-organic interface with the reductant ferrocene. We demonstrated that the as-prepared Ag nanoplates can be widely tunable from 600 nm to 7 μm in size and from 10 to 35 nm in thickness, simply by adjusting the component of organic phase. To our knowledge, there are few methods to tailor the size and the thickness of metal nanoplates in such a large range although many efforts have been made aiming to realize it. Our proposed synthetic strategy is rapid, template-free, seed-less, and high-yield, and could be applied to synthesize analogous two-dimensional nanostructures of other noble metals, such as Pt, Au, and Pd. - Graphical abstract: High-purity Ag nanoplates were synthesized by the reduction of aqueous Ag + ions at the aqueous-organic interface with the reductant ferrocene, the size and thickness of which were widely tunable.

  9. Fabrication of Self-Standing Silver Nanoplate Arrays by Seed-Decorated Electrochemical Route and Their Structure-Induced Properties

    Directory of Open Access Journals (Sweden)

    Guangqiang Liu

    2013-01-01

    Full Text Available We present an electrochemical route to synthesize silver nanoplates on seed-decorated Indium tin oxide (ITO glass substrate. The nanoplates are several tens of to several hundred nanometers in dimension. The density of nanoplates covered on the substrate can be controlled well by adjusting the amounts of seed. All the nanoplates are standing on the substrate uniformly even at very high density. Silver nanoplate arrays displayed an extraordinary superhydrophobicity after chemical modification and can serve as highly active surface-enhanced Raman scattering (SERS substrates for microdetection. The arrays can also be used as electrodes for electrochemical capacitor with high power density.

  10. One-Pot Synthesis of Cu2ZnSnSe4 Nanoplates and their Visible-Light-Driven Photocatalytic Activity

    Science.gov (United States)

    Han, Zhenzhen; Li, Nan; Shi, Aihua; Wang, Haohua; Ma, Feng; Lv, Yi; Wu, Rongqian

    2018-01-01

    A SeO2 ethanol solution as the facile precursor has been used for the preparation of quaternary Cu2ZnSnSe4 (CZTSe) nanoplates. Monodispersed single-phase CZTSe nanoplates have been prepared successfully by a facile one-pot thermal chemical method. The as-prepared CZTSe nanoplates show uniform morphology with a bandgap of 1.4 eV. As a proof of concept, the CZTSe nanoplates have been used as a visible-light-driven photocatalyst for Rhodamine B dye degradation and show high photocatalytic activity and stability. The excellent dye removal is mainly ascribed to the efficient light utilization of CZTSe nanoplates.

  11. Growth patterns of self-assembled InAs quantum dots near the two-dimensional to three-dimensional transition

    Science.gov (United States)

    Colocci, M.; Bogani, F.; Carraresi, L.; Mattolini, R.; Bosacchi, A.; Franchi, S.; Frigeri, P.; Rosa-Clot, M.; Taddei, S.

    1997-06-01

    Self-assembled InAs quantum dots have been grown by molecular beam epitaxy in such a way as to obtain a continuous variation of InAs coverages across the wafer. Structured photoluminescence spectra are observed after excitation of a large number of dots; deconvolution into Gaussian components yields narrow emission bands (full width at half-maximum 20-30 meV) separated in energy by an average spacing of 30-40 meV. We ascribe the individual bands of the photoluminescence spectra after low excitation to families of dots with similar shapes and with heights differing by one monolayer, as strongly supported by numerical calculations of the fundamental electronic transitions in quantum dot structures.

  12. Graphene nanoplate-MnO2 composites for supercapacitors: a controllable oxidation approach

    Science.gov (United States)

    Huang, Huajie; Wang, Xin

    2011-08-01

    Graphene nanoplate-MnO2 composites have been synthesized by oxidising part of the carbon atoms in the framework of graphene nanoplates at ambient temperature. The composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). It was found that the oxidation extent of the carbon atoms in the graphene framework in these composites was dependent on the reaction time, which also influenced their microstructure, morphology and electrochemical properties. Compared with MnO2 nanolamellas, the nanocomposite prepared with a reaction time of 3 h reveals better electrochemical properties as a supercapacitor electrode material.Graphene nanoplate-MnO2 composites have been synthesized by oxidising part of the carbon atoms in the framework of graphene nanoplates at ambient temperature. The composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). It was found that the oxidation extent of the carbon atoms in the graphene framework in these composites was dependent on the reaction time, which also influenced their microstructure, morphology and electrochemical properties. Compared with MnO2 nanolamellas, the nanocomposite prepared with a reaction time of 3 h reveals better electrochemical properties as a supercapacitor electrode material. Electronic supplementary information (ESI) available: Fig. S1, AFM image (5 μm × 5 μm) of graphene nanoplate-MnO2 composite obtained at 3 h; Fig. S2, nitrogen adsorption/desorption isotherm of graphene nanoplate-MnO2 composite obtained at 3 h. See DOI: 10.1039/c1nr10229j

  13. X-ray investigation of the interface structure of free standing InAs nanowires grown on GaAs[ anti 1 anti 1 anti 1]{sub B}

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Jens; Gottschalch, Volker; Wagner, Gerald [Universitaet Leipzig, Halbleiterchemie, Leipzig (Germany); Pietsch, Ullrich; Davydok, Anton; Biermanns, Andreas [Universitaet Siegen, Festkoerperphysik, Siegen (Germany); Grenzer, Joerg [Forschungszentrum Rossendorf, Institut fuer Ionenstrahlphysik und Materialforschung, Dresden (Germany)

    2009-09-15

    The heteroepitaxial growth process of InAs nanowires (NW) on GaAs[ anti 1 anti 1 anti 1]{sub B} substrate was investigated by X-ray grazing-incidence diffraction using synchrotron radiation. For crystal growth we applied the vapor-liquid-solid (VLS) growth mechanism via gold seeds. The general sample structure was extracted from various electron microscopic and X-ray diffraction experiments. We found a closed Ga{sub x}In{sub 1-x} As graduated alloy layer at the substrate to NW interface which was formed in the initial stage of VLS growth with a Au-Ga-In liquid alloy. With ongoing growth time a transition from this VLS layer growth to the conventional VLS NW growth was observed. The structural properties of both VLS grown crystal types were examined. Furthermore, we discuss the VLS layer growth process. (orig.)

  14. Formation of Silver Nanoplates Layer on Amino Group Grafted Silica Coatings

    Directory of Open Access Journals (Sweden)

    Jurgis PILIPAVICIUS

    2016-05-01

    Full Text Available In this study the self-arrangement of Ag nanoplates on (3-Aminopropyltriethoxysilane (APTES silanized silica coatings was investigated. Silica coatings were made by sol-gel method and silanized in two different ways. The first one includes silanization in acidic 2-propanol solution, the other one – in dry toluene. Coatings were silanized by using different amounts of APTES in case of silanization in 2-propanol. Silver nanoplates layer of functionalized silica coatings was obtained via self-assembly. Coatings were investigated by atomic force microscopy (AFM, water contact angle measurements (CA, FT-IR analysis, and scanning electron microscopy (SEM. Research showed that dense Ag nanoplates arrangement occurs when there is a high amount of amino groups on the surface.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.8405

  15. Improvement of the optical quality of site-controlled InAs quantum dots by a double stack growth technique in wet-chemically etched holes

    Energy Technology Data Exchange (ETDEWEB)

    Pfau, Tino Johannes; Gushterov, Aleksander; Reithmaier, Johann-Peter [Technische Physik, INA, Universitaet Kassel (Germany); Cestier, Isabelle; Eisenstein, Gadi [Electrical Engineering Dept., Technion, Haifa (Israel); Linder, Evgany; Gershoni, David [Solid State Institute and Physics Dept., Technion, Haifa (Israel)

    2010-07-01

    The optimization of the wet-chemically etching of holes and a special MBE growth stack technique allows enlarging the site-control of low density InAs QDs on GaAs substrates up to a buffer layer thickness of 55 nm. The strain of InAs QDs, grown in the etched holes, reduces the hole closing, so that a pre-patterned surface is conserved for the second QD layer. The distance of 50 nm GaAs between the two QD layers exceeds drastically the maximum vertical alignment based on pure strain coupling (20 nm). Compared to stacks with several QD layers, this method avoids electronic coupling between the different QD layers and reduces the problems to distinguish the dots of different layers optically. Confocal microphotoluminescence reveals a significant diminution of the low temperature photoluminescence linewidth of the second InAs QD layer to an average value of 505{+-}53 {mu}eV and a minimum width of 460 {mu}eV compared to 2 to 4 meV for QDs grown on thin buffer layers. The increase of the buffer layer thickness decreases the influence of the surface defects caused by prepatterning.

  16. New process for high optical quality InAs quantum dots grown on patterned GaAs(001) substrates

    NARCIS (Netherlands)

    Alonso-González, Pablo; González, Luisa; González, Yolanda; Fuster, David; Fernández-Martinez, Ivan; Martin-Sánchez, Javier; Abelmann, Leon

    2007-01-01

    This work presents a selective ultraviolet (UV)-ozone oxidation-chemical etching process that has been used, in combination with laser interference lithography (LIL), for the preparation of GaAs patterned substrates. Further molecular beam epitaxy (MBE) growth of InAs results in ordered InAs/GaAs

  17. Electrical characterization of InAs thin films

    Energy Technology Data Exchange (ETDEWEB)

    Botha, L.; Shamba, P.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2008-07-01

    It is known that parallel conduction as a result of surface and /or interface charge accumulation significantly shields the bulk electrical properties of InAs thin films when characterized using Hall measurements. This parallel conduction in InAs can be modeled by using the two-layer model of Nedoluha and Koch [Zeitschrift fuer Physik 132, 608 (1952)]; where an InAs epilayer is treated as consisting of two conductors connected in parallel viz. a bulk and a surface layer. Here, this two-layer model is used to simulate Hall coefficient and conductivity data of InAs thin films ranging from strongly n-doped (n=10{sup 18} cm{sup -3}) to strongly p-doped (p{proportional_to}10{sup 19} cm{sup -3}) material. Conventional Hall approximations, i.e. those that assume uniform conduction from a single band, are then used to predict the apparent carrier concentration and mobility that will be determined from conventional Hall measurements, with the aim of illustrating the error of such a simplified analysis of InAs Hall data. Results show that, in addition to ignoring parallel conduction, the approximations of conventional Hall data analysis have a further inadequacy for p-type InAs, in that the high electron to hole mobility ratio in InAs is not taken into account. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Electrical characterization of InAs thin films

    International Nuclear Information System (INIS)

    Botha, L.; Shamba, P.; Botha, J.R.

    2008-01-01

    It is known that parallel conduction as a result of surface and /or interface charge accumulation significantly shields the bulk electrical properties of InAs thin films when characterized using Hall measurements. This parallel conduction in InAs can be modeled by using the two-layer model of Nedoluha and Koch [Zeitschrift fuer Physik 132, 608 (1952)]; where an InAs epilayer is treated as consisting of two conductors connected in parallel viz. a bulk and a surface layer. Here, this two-layer model is used to simulate Hall coefficient and conductivity data of InAs thin films ranging from strongly n-doped (n=10 18 cm -3 ) to strongly p-doped (p∝10 19 cm -3 ) material. Conventional Hall approximations, i.e. those that assume uniform conduction from a single band, are then used to predict the apparent carrier concentration and mobility that will be determined from conventional Hall measurements, with the aim of illustrating the error of such a simplified analysis of InAs Hall data. Results show that, in addition to ignoring parallel conduction, the approximations of conventional Hall data analysis have a further inadequacy for p-type InAs, in that the high electron to hole mobility ratio in InAs is not taken into account. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Enhanced photoactivity from single-crystalline SrTaO{sub 2}N nanoplates synthesized by topotactic nitridation

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Jie; Skrabalak, Sara E. [Department of Chemistry, Indiana University, Bloomington, IN (United States)

    2017-11-06

    There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often give enhanced photoactivity. Herein, single-crystalline SrTaO{sub 2}N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, in which single-crystalline SrTaO{sub 2}N nanoplates form by topotactic nitridation of aerosol-prepared Sr{sub 2}Ta{sub 2}O{sub 7} nanoplates and SrTaO{sub 2}N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO{sub 2}N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1 % for OER compared to the polyhedra (AQE: 1.6 %) and SrTaO{sub 2}N polycrystals (AQE: 0.6 %). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Van der Waals epitaxy and photoresponse of hexagonal tellurium nanoplates on flexible mica sheets.

    Science.gov (United States)

    Wang, Qisheng; Safdar, Muhammad; Xu, Kai; Mirza, Misbah; Wang, Zhenxing; He, Jun

    2014-07-22

    Van der Waals epitaxy (vdWE) is of great interest due to its extensive applications in the synthesis of ultrathin two-dimensional (2D) layered materials. However, vdWE of nonlayered functional materials is still not very well documented. Here, although tellurium has a strong tendency to grow into one-dimensional nanoarchitecture due to its chain-like structure, we successfully realize 2D hexagonal tellurium nanoplates on flexible mica sheets via vdWE. Chemically inert mica surface is found to be crucial for the lateral growth of hexagonal tellurium nanoplates since it (1) facilitates the migration of tellurium adatoms along mica surface and (2) allows a large lattice mismatch. Furthermore, 2D tellurium hexagonal nanoplates-based photodetectors are in situ fabricated on flexible mica sheets. Efficient photoresponse is obtained even after bending the device for 100 times, indicating 2D tellurium hexagonal nanoplates-based photodetectors on mica sheets have a great application potential in flexible and wearable optoelectronic devices. We believe the fundamental understanding of vdWE effect on the growth of 2D tellurium hexagonal nanoplate can pave the way toward leveraging vdWE as a useful channel to realize the 2D geometry of other nonlayered materials.

  1. Direct evidence of strain transfer for InAs island growth on compliant Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Marçal, L. A. B.; Magalhães-Paniago, R.; Malachias, Angelo, E-mail: angeloms@fisica.ufmg.br [Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, CEP 31270-901, Belo Horizonte (Brazil); Richard, M.-I. [European Synchrotron (ESRF), ID01 beamline, CS 40220, 38043 Grenoble Cedex 9 (France); Aix-Marseille University, IM2NP-CNRS, Faculté des Sciences de St Jérôme, 13397 Marseille (France); Cavallo, F. [Center for High Technology Materials, University of New Mexico, 1313 Goddard St., Albuquerque, New Mexico 87106 (United States); University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706 (United States); Lagally, M. G. [University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706 (United States); Schmidt, O. G. [Institute for Integrative Nanosciences, IFW-Dresden, D-01171 Dresden (Germany); Schülli, T. Ü. [European Synchrotron (ESRF), ID01 beamline, CS 40220, 38043 Grenoble Cedex 9 (France); Deneke, Ch. [Laboratório Nacional de Nanotecnologia (LNNano/CNPEM), C.P. 6192, CEP 13083-970, Campinas (Brazil)

    2015-04-13

    Semiconductor heteroepitaxy on top of thin compliant layers has been explored as a path to make inorganic electronics mechanically flexible as well as to integrate materials that cannot be grown directly on rigid substrates. Here, we show direct evidences of strain transfer for InAs islands on freestanding Si thin films (7 nm). Synchrotron X-ray diffraction measurements using a beam size of 300 × 700 nm{sup 2} can directly probe the strain status of the compliant substrate underneath deposited islands. Using a recently developed diffraction mapping technique, three-dimensional reciprocal space maps were reconstructed around the Si (004) peak for specific illuminated positions of the sample. The strain retrieved was analyzed using continuous elasticity theory via Finite-element simulations. The comparison of experiment and simulations yields the amount of strain from the InAs islands, which is transferred to the compliant Si thin film.

  2. Fermi energy dependence of the optical emission in core/shell InAs nanowire homostructures

    Science.gov (United States)

    Möller, M.; Oliveira, D. S.; Sahoo, P. K.; Cotta, M. A.; Iikawa, F.; Motisuke, P.; Molina-Sánchez, A.; de Lima, M. M., Jr.; García-Cristóbal, A.; Cantarero, A.

    2017-07-01

    InAs nanowires grown by vapor-liquid-solid (VLS) method are investigated by photoluminescence. We observe that the Fermi energy of all samples is reduced by ˜20 meV when the size of the Au nanoparticle used for catalysis is increased from 5 to 20 nm. Additional capping with a thin InP shell enhances the optical emission and does not affect the Fermi energy. The unexpected behavior of the Fermi energy is attributed to the differences in the residual donor (likely carbon) incorporation in the axial (low) and lateral (high incorporation) growth in the VLS and vapor-solid (VS) methods, respectively. The different impurity incorporation rate in these two regions leads to a core/shell InAs homostructure. In this case, the minority carriers (holes) diffuse to the core due to the built-in electric field created by the radial impurity distribution. As a result, the optical emission is dominated by the core region rather than by the more heavily doped InAs shell. Thus, the photoluminescence spectra and the Fermi energy become sensitive to the core diameter. These results are corroborated by a theoretical model using a self-consistent method to calculate the radial carrier distribution and Fermi energy for distinct diameters of Au nanoparticles.

  3. Surface effects on anti-plane shear waves propagating in magneto-electro-elastic nanoplates

    International Nuclear Information System (INIS)

    Wu, Bin; Zhang, Chunli; Chen, Weiqiu; Zhang, Chuanzeng

    2015-01-01

    Material surfaces may have a remarkable effect on the mechanical behavior of magneto-electro-elastic (or multiferroic) structures at nanoscale. In this paper, a surface magneto-electro-elasticity theory (or effective boundary condition formulation), which governs the motion of the material surface of magneto-electro-elastic nanoplates, is established by employing the state-space formalism. The properties of anti-plane shear (SH) waves propagating in a transversely isotropic magneto-electro-elastic plate with nanothickness are investigated by taking surface effects into account. The size-dependent dispersion relations of both antisymmetric and symmetric SH waves are presented. The thickness-shear frequencies and the asymptotic characteristics of the dispersion relations considering surface effects are determined analytically as well. Numerical results show that surface effects play a very pronounced role in elastic wave propagation in magneto-electro-elastic nanoplates, and the dispersion properties depend strongly on the chosen surface material parameters of magneto-electro-elastic nanoplates. As a consequence, it is possible to modulate the waves in magneto-electro-elastic nanoplates through surface engineering. (paper)

  4. InAs quantum dot growth on AlxGa1−xAs by metalorganic vapor phase epitaxy for intermediate band solar cells

    International Nuclear Information System (INIS)

    Jakomin, R.; Kawabata, R. M. S.; Souza, P. L.; Mourão, R. T.; Pires, M. P.; Micha, D. N.; Xie, H.; Fischer, A. M.; Ponce, F. A.

    2014-01-01

    InAs quantum dot multilayers have been grown using Al x Ga 1−x As spacers with dimensions and compositions near the theoretical values for optimized efficiencies in intermediate band photovoltaic cells. Using an aluminium composition of x = 0.3 and InAs dot vertical dimensions of 5 nm, transitions to an intermediate band with energy close to the ideal theoretical value have been obtained. Optimum size uniformity and density have been achieved by capping the quantum dots with GaAs following the indium-flush method. This approach has also resulted in minimization of crystalline defects in the epilayer structure

  5. Hexagonal-like Nb2O5 Nanoplates-Based Photodetectors and Photocatalyst with High Performances

    Science.gov (United States)

    Liu, Hui; Gao, Nan; Liao, Meiyong; Fang, Xiaosheng

    2015-01-01

    Ultraviolet (UV) photodetectors are important tools in the fields of optical imaging, environmental monitoring, and air and water sterilization, as well as flame sensing and early rocket plume detection. Herein, hexagonal-like Nb2O5 nanoplates are synthesized using a facile solvothermal method. UV photodetectors based on single Nb2O5 nanoplates are constructed and the optoelectronic properties have been probed. The photodetectors show remarkable sensitivity with a high external quantum efficiency (EQE) of 9617%, and adequate wavelength selectivity with respect to UV-A light. In addition, the photodetectors exhibit robust stability and strong dependence of photocurrent on light intensity. Also, a low-cost drop-casting method is used to fabricate photodetectors based on Nb2O5 nanoplate film, which exhibit singular thermal stability. Moreover, the hexagonal-like Nb2O5 nanoplates show significantly better photocatalytic performances in decomposing Methylene-blue and Rhdamine B dyes than commercial Nb2O5.

  6. Synthesis and optical properties of CuS nanoplate-based architectures by a solvothermal method

    International Nuclear Information System (INIS)

    Li Fei; Kong Tao; Bi Wentuan; Li Dachang; Li Zhen; Huang Xintang

    2009-01-01

    The controlled synthesis of copper sulfide (CuS) nanoplate-based architectures in different solvents has been realized at low cost by simply reaction of Cu(NO 3 ) 2 .3H 2 O and S under solvothermal conditions without the use of any template. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectrometer and fluorescence measurement were used to characterize the products. The products were all in hexagonal phase with high crystallinity and the morphology was significantly influenced by the solvents. The CuS products synthesized in dimethylformamide (DMF) were nanoplates and the samples prepared in ethanol were flower-like morphology composed of large numbers of nanoplates, but those synthesized in ethylene glycol (EG) were CuS architectures with high symmetry made up of several nanoplates arranged in a certain mode. The optical properties were investigated and the growth mechanisms of these CuS crystals were also proposed.

  7. Elastic properties and electron transport in InAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Migunov, Vadim

    2013-02-22

    The electron transport and elastic properties of InAs nanowires grown by chemical vapor deposition on InAs (001) substrate were studied experimentally, in-situ in a transmission electron microscope (TEM). A TEM holder allowing the measurement of a nanoforce while simultaneous imaging nanowire bending was used. Diffraction images from local areas of the wire were recorded to correlate elastic properties with the atomic structure of the nanowires. Another TEM holder allowing the application of electrical bias between the nanowire and an apex of a metallic needle while simultaneous imaging the nanowire in TEM or performing electron holography was used to detect mechanical vibrations in mechanical study or holographical observation of the nanowire inner potential in the electron transport studies. The combination of the scanning probe methods with TEM allows to correlate the measured electric and elastic properties of the nanowires with direct identification of their atomic structure. It was found that the nanowires have different atomic structures and different stacking fault defect densities that impacts critically on the elastic properties and electric transport. The unique methods, that were applied in this work, allowed to obtain dependencies of resistivity and Young's modulus of left angle 111 right angle -oriented InAs nanowires on defect density and diameter. It was found that the higher is the defect density the higher are the resistivity and the Young's modulus. Regarding the resistivity, it was deduced that the stacking faults increase the scattering of the electrons in the nanowire. These findings are consistent with the literature, however, the effect described by the other groups is not so pronounced. This difference can be attributed to the significant incompleteness of the physical models used for the data analysis. Regarding the elastic modulus, there are several mechanisms affecting the elasticity of the nanowires discussed in the thesis. It

  8. Designing Tripodal and Triangular Gadolinium Oxide Nanoplates and Self-Assembled Nanofibrils as Potential Multimodal Bioimaging Probes

    Energy Technology Data Exchange (ETDEWEB)

    Paik, T; Gordon, TR; Prantner, AM; Yun, H; Murray, CB

    2013-03-01

    Here, we report the shape-controlled synthesis of tripodal and triangular gadolinium oxide (Gd2O3) nanoplates. In the presence of lithium ions, the shape of the nanocrystals is readily controlled by tailoring reaction parameters such as temperature and time. We observe that the morphology transforms from an initial tripodal shape to a triangular shape with increasing reaction time or elevated temperatures. Highly uniform Gd2O3 nanoplates are self-assembled into nanofibril-like liquid-crystalline superlattices with long-range orientational and positional order. In addition, shape-directed self-assemblies are investigated by tailoring the aspect ratio of the arms of the Gd2O3 nanoplates. Due to a strong paramagnetic response, Gd2O3 nanocrystals are excellent candidates for MRI contrast agents and also can be doped with rare-earth ions to form nanophosphors, pointing to their potential in multimodal imaging. In this work, we investigate the MR relaxometry at high magnetic fields (9,4 and 14.1 T) and the optical properties including near-IR to visible upconversion luminescence and X-ray excited optical luminescence of doped Gd2O3 nanoplates. The complex shape of Gd2O3 nanoplates, coupled with their magnetic properties and their ability to phosphoresce under NIR or X-ray excitation which penetrate deep into tissue, makes these nanoplates a promising platform for multimodal imaging in biomedical applications.

  9. Comparison of Surface-enhanced Raman Scattering Spectra of Two Kinds of Silver Nanoplate Films

    Institute of Scientific and Technical Information of China (English)

    TAO Jin-long; TANG Bin; XU Shu-ping; PAN Ling-yun; XU Wei-qing

    2012-01-01

    Surface-enhanced Raman scattering(SERS) spectra of different silver nanoplate self-assembled films at different excitation wavelengths were fairly compared.Shape conversion from silver nanoprisms to nanodisks on slides was in situ carried out.The SERS spectra of 4-mercaptopyridine(4-MPY) on these anisotropic silver nanoparticle self-assembled films present that strong enhancement appeared when the excitation line and the surface plasmon resonance(SPR) band of silver substrate overlapped.In this model,the influence of the crystal planes of silver nanoplates on SERS enhancement could be ignored because the basal planes were nearly unchanged in two kinds of silver nanoplate self-assembled films.

  10. Size-dependent free vibration and dynamic analyses of piezo-electro-magnetic sandwich nanoplates resting on viscoelastic foundation

    Science.gov (United States)

    Arefi, Mohammad; Zenkour, Ashraf M.

    2017-09-01

    In this paper, size-dependent free vibration analysis of a sandwich nanoplate is presented. The sandwich nanoplate is including an elastic nano core and two piezo-electro-magnetic face-sheets as sensor and actuator actuated by electric and magnetic potentials. The sandwich nanoplate is resting on visco-Pasternak's foundation. Hamilton's principle is employed to derive the governing equations of motion based on Kirchhoff plate and nonlocal elasticity theory. The numerical results are presented to study the influence of important parameters of the problem such as applied electric and magnetic potentials, nonlocal parameter and visco-Pasternak's parameters. Furthermore, the influence of various boundary conditions is discussed on the vibration characteristics of the sandwich nanoplate.

  11. Studies on the controlled growth of InAs nanostructures on scission surfaces; Untersuchungen zum kontrollierten Wachstum von InAs-Nanostrukturen auf Spaltflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, J.

    2006-01-15

    The aim of this thesis was the controlled alignment of self-assembled InAs nano-structures on a {l_brace}110{r_brace}-oriented surface. The surface is prestructured with the atomic precision offered by molecular beam epitaxy, using the cleaved edge overgrowth-technique. On all samples grown within this work, the epitaxial template in the first growth step was deposited on a (001)GaAs substrate, while the InAs-layer forming the nanostructures during the second growth step was grown on cleaved {l_brace}110{r_brace}-GaAs surfaces. Atomic Force Microscopy (AFM) investigations demonstrate the formation of quantum dot (QD)-like nanostructures on top of the AlAs-stripes. X-ray diffraction measurements on large arrays of aligned quantum dots demonstrate that the quantum dots are formed of pure InAs. First investigations on the optical properties of these nanostructures were done using microphotoluminescence-spectroscopy with both high spatial and spectral resolution. (orig.)

  12. Facile Br- assisted hydrothermal synthesis of Bi2MoO6 nanoplates with enhanced visible-light photocatalytic activity

    International Nuclear Information System (INIS)

    Zhang, Peng; Teng, Xiaoxu; Liu, Dongsheng; Fu, Liang; Xie, Hualin; Zhang, Guoqing; Ding, Shimin

    2017-01-01

    Bi 2 MoO 6 nanoplates have been controllably synthesized via a facile hydrothermal process with the assistance of Br - containing surfactant cetyltrimethylammonium bromide (CTAB) or KBr. A remarkable enhancement in the visible-light-driven photocatalytic degradation of Rhodamine B was observed. It was found that reaction temperature and surfactant play crucial roles in the formation and properties of the Bi 2 MoO 6 nanoplates. The best results as photocatalyst were obtained with the sample hydrothermally synthesized at 150 C with the assistance of CTAB. The improved photocatalytic performance could be ascribed to the {001}-oriented nanostructure of the Bi 2 MoO 6 nanoplates. KBr-templated Bi 2 MoO 6 nanoplates also showed better photocatalytic efficiency compared with that of flower-like Bi 2 MoO 6 but inferior to that of CTAB-templated Bi 2 MoO 6 nanoplates. (orig.)

  13. The investigation of alloy formation during InAs nanowires growth on GaAs (111)B substrate

    Energy Technology Data Exchange (ETDEWEB)

    Saqib, Muhammad; Biermanns, Andreas; Davydok, Anton; Pietsch, Ullrich [Festkoerperphysik, Universitaet Siegen, Walter-Flex-Str. 3, Siegen 57072 (Germany); Rieger, Torsten; Grap, Thomas; Lepsa, Mihail [Peter Gruenberg Institute (PGI-9), Forschungzentrum Juelich, Juelich 52425 (Germany)

    2013-07-01

    A possible way to obtain nanowires is the growth in molecular beam epitaxy (MBE) on the (111) oriented surface of the desired substrate, covered by a thin oxide layer. A crucial parameter in this method is the initial thickness of the oxide layer, often determined by an etching procedure. In this contribution, we report on the structural investigation of two different series (etched and unetched) of NWs samples. Vertically aligned InAs nanowires (NWs) doped with Si were self-assisted grown by molecular beam epitaxy on GaAs [111]B substrates covered with a thin SiO{sub x} layer. Using a combination of symmetric and asymmetric X-ray diffraction we study the influence of Si supply on the growth process and nanostructure formation. We find that the number of parasitic crystallites grown between the NWs increases with increasing Si flux. In addition, we observe the formation of a Ga{sub 0.2}In{sub 0.8}As alloy if the growth is performed on samples covered by a defective (etched) oxide layer. This alloy formation is observed within the crystallites and not within the nanowires. The Gallium concentration is determined from the lattice mismatch of the crystallites relative to the InAs nanowires. No alloy formation is found for samples with faultless oxide layers.

  14. Tuning of Rashba/Dresselhaus Spin Splittings by Inserting Ultra-Thin InAs Layers at Interfaces in Insulating GaAs/AlGaAs Quantum Wells.

    Science.gov (United States)

    Yu, Jinling; Zeng, Xiaolin; Cheng, Shuying; Chen, Yonghai; Liu, Yu; Lai, Yunfeng; Zheng, Qiao; Ren, Jun

    2016-12-01

    The ratio of Rashba and Dresselhaus spin splittings of the (001)-grown GaAs/AlGaAs quantum wells (QWs), investigated by the spin photocurrent spectra induced by circular photogalvanic effect (CPGE) at inter-band excitation, has been effectively tuned by changing the well width of QWs and by inserting a one-monolayer-thick InAs layer at interfaces of GaAs/AlGaAs QWs. Reflectance difference spectroscopy (RDS) is also employed to study the interface asymmetry of the QWs, whose results are in good agreement with that obtained by CPGE measurements. It is demonstrated that the inserted ultra-thin InAs layers will not only introduce structure inversion asymmetry (SIA), but also result in additional interface inversion asymmetry (IIA), whose effect is much stronger in QWs with smaller well width. It is also found that the inserted InAs layer brings in larger SIA than IIA. The origins of the additional SIA and IIA introduced by the inserted ultra-thin InAs layer have been discussed.

  15. Wave propagation analysis of a size-dependent magneto-electro-elastic heterogeneous nanoplate

    Science.gov (United States)

    Ebrahimi, Farzad; Dabbagh, Ali; Reza Barati, Mohammad

    2016-12-01

    The analysis of the wave propagation behavior of a magneto-electro-elastic functionally graded (MEE-FG) nanoplate is carried out in the framework of a refined higher-order plate theory. In order to take into account the small-scale influence, the nonlocal elasticity theory of Eringen is employed. Furthermore, the material properties of the nanoplate are considered to be variable through the thickness based on the power-law form. Nonlocal governing equations of the MEE-FG nanoplate have been derived using Hamilton's principle. The results of the present study have been validated by comparing them with previous researches. An analytical solution of governing equations is performed to obtain wave frequencies, phase velocities and escape frequencies. The effect of different parameters, such as wave number, nonlocal parameter, gradient index, magnetic potential and electric voltage on the wave dispersion characteristics of MEE-FG nanoscale plates is studied in detail.

  16. Size-dependent electro-magneto-elastic bending analyses of the shear-deformable axisymmetric functionally graded circular nanoplates

    Science.gov (United States)

    Arefi, Mohammad; Zenkour, Ashraf M.

    2017-10-01

    This paper develops nonlocal elasticity equations and magneto-electro-elastic relations to size-dependent electro-magneto-elastic bending analyses of the functionally graded axisymmetric circular nanoplates based on the first-order shear deformation theory. All material properties are graded along the thickness direction based on exponential varying. It is assumed that a circular nanoplate is made from piezo-magnetic materials. The energy method and Ritz approach is employed for the derivation of governing equations of electro-magneto-elastic bending and the solution of the problem, respectively. The nanoplate is subjected to applied electric and magnetic potentials at top and transverse loads while it is rested on Pasternak's foundation. Some important numerical results are presented in various figures to show the influence of applied electric and magnetic potentials, small scale parameter and inhomogeneous index of an exponentially graded nanoplate.

  17. Room-temperature synthesis of gold nanoparticles and nanoplates using Shewanella algae cell extract

    International Nuclear Information System (INIS)

    Ogi, Takashi; Saitoh, Norizoh; Nomura, Toshiyuki; Konishi, Yasuhiro

    2010-01-01

    Biosynthesis of spherical gold nanoparticles and gold nanoplates was achieved at room temperature and pH 2.8 when cell extract from the metal-reducing bacterium Shewanella algae was used as both a reducing and shape-controlling agent. Cell extract, prepared by sonicating a suspension of S. algae cells, was capable of reducing 1 mol/m 3 aqueous AuCl 4 - ions into elemental gold within 10 min when H 2 gas was provided as an electron donor. The time interval lapsed since the beginning of the bioreductive reaction was found to be an important factor in controlling the morphology of biogenic gold nanoparticles. After 1 h, there was a large population of well-dispersed, spherical gold nanoparticles with a mean size of 9.6 nm. Gold nanoplates with an edge length of 100 nm appeared after 6 h, and 60% of the total nanoparticle population was due to gold nanoplates with an edge length of 100-200 nm after 24 h. The yield of gold nanoplates prepared with S. algae extract was four times higher than that prepared with resting cells of S. algae. The resulting biogenic gold nanoparticle suspensions showed a large variation in color, ranging from pale pink to purple due to changes in nanoparticle morphology.

  18. Room-temperature synthesis of gold nanoparticles and nanoplates using Shewanella algae cell extract

    Energy Technology Data Exchange (ETDEWEB)

    Ogi, Takashi; Saitoh, Norizoh; Nomura, Toshiyuki; Konishi, Yasuhiro, E-mail: yasuhiro@chemeng.osakafu-u.ac.j [Osaka Prefecture University, Department of Chemical Engineering (Japan)

    2010-09-15

    Biosynthesis of spherical gold nanoparticles and gold nanoplates was achieved at room temperature and pH 2.8 when cell extract from the metal-reducing bacterium Shewanella algae was used as both a reducing and shape-controlling agent. Cell extract, prepared by sonicating a suspension of S. algae cells, was capable of reducing 1 mol/m{sup 3} aqueous AuCl{sub 4}{sup -} ions into elemental gold within 10 min when H{sub 2} gas was provided as an electron donor. The time interval lapsed since the beginning of the bioreductive reaction was found to be an important factor in controlling the morphology of biogenic gold nanoparticles. After 1 h, there was a large population of well-dispersed, spherical gold nanoparticles with a mean size of 9.6 nm. Gold nanoplates with an edge length of 100 nm appeared after 6 h, and 60% of the total nanoparticle population was due to gold nanoplates with an edge length of 100-200 nm after 24 h. The yield of gold nanoplates prepared with S. algae extract was four times higher than that prepared with resting cells of S. algae. The resulting biogenic gold nanoparticle suspensions showed a large variation in color, ranging from pale pink to purple due to changes in nanoparticle morphology.

  19. Transmission electron microscopy study of vertical quantum dots molecules grown by droplet epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Maldonado, D., E-mail: david.hernandez@uca.es [Departamento de Ciencia de los Materiales e I.M. y Q.I., Facultad de Ciencias, Universidad de Cadiz, Campus Rio San Pedro, s/n, 11510 Puerto Real, Cadiz (Spain); Herrera, M.; Sales, D.L. [Departamento de Ciencia de los Materiales e I.M. y Q.I., Facultad de Ciencias, Universidad de Cadiz, Campus Rio San Pedro, s/n, 11510 Puerto Real, Cadiz (Spain); Alonso-Gonzalez, P.; Gonzalez, Y.; Gonzalez, L. [Instituto de Microelectronica de Madrid (CNM-CSIC), Isaac Newton 8 (PTM), 28760 Tres Cantos, Madrid (Spain); Pizarro, J.; Galindo, P.L. [Departamento de Lenguajes y Sistemas Informaticos, CASEM, Universidad de Cadiz, Campus Rio San Pedro, s/n, 11510 Puerto Real, Cadiz (Spain); Molina, S.I. [Departamento de Ciencia de los Materiales e I.M. y Q.I., Facultad de Ciencias, Universidad de Cadiz, Campus Rio San Pedro, s/n, 11510 Puerto Real, Cadiz (Spain)

    2010-07-01

    The compositional distribution of InAs quantum dots grown by molecular beam epitaxy on GaAs capped InAs quantum dots has been studied in this work. Upper quantum dots are nucleated preferentially on top of the quantum dots underneath, which have been nucleated by droplet epitaxy. The growth process of these nanostructures, which are usually called as quantum dots molecules, has been explained. In order to understand this growth process, the analysis of the strain has been carried out from a 3D model of the nanostructure built from transmission electron microscopy images sensitive to the composition.

  20. Transmission electron microscopy study of vertical quantum dots molecules grown by droplet epitaxy

    International Nuclear Information System (INIS)

    Hernandez-Maldonado, D.; Herrera, M.; Sales, D.L.; Alonso-Gonzalez, P.; Gonzalez, Y.; Gonzalez, L.; Pizarro, J.; Galindo, P.L.; Molina, S.I.

    2010-01-01

    The compositional distribution of InAs quantum dots grown by molecular beam epitaxy on GaAs capped InAs quantum dots has been studied in this work. Upper quantum dots are nucleated preferentially on top of the quantum dots underneath, which have been nucleated by droplet epitaxy. The growth process of these nanostructures, which are usually called as quantum dots molecules, has been explained. In order to understand this growth process, the analysis of the strain has been carried out from a 3D model of the nanostructure built from transmission electron microscopy images sensitive to the composition.

  1. Electrical transport properties of large, individual NiCo{sub 2}O{sub 4} nanoplates

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Linfeng; Wu, Limin; Hu, Xinhua; Fang, Xiaosheng [Department of Materials Science, Fudan University, Shanghai (China); Liao, Meiyong [Optical and Electronic Materials Unit, National Institute for Materials Science (NIMS), Namiki, Tsukuba, Ibaraki (Japan)

    2012-03-07

    Understanding the electrical transport properties of individual semiconductor nanostructures is crucial to advancing their practical applications in high-performance nanodevices. Large-sized individual nanostructures with smooth surfaces are preferred because they can be easily made into nanodevices using conventional photolithography procedures rather than having to rely on costly and complex electron-beam lithography techniques. In this study, micrometer-sized NiCo{sub 2}O{sub 4} nanoplates are successfully prepared from their corresponding hydroxide precursor using a quasi-topotactic transformation. The Co/Ni atomic arrangement shows no changes during the transformation from the rhombohedral LDH precursor (space group R anti 3 m) to the cubic NiCo{sub 2}O{sub 4} spinel (space group Fd anti 3 m), and the nanoplate retains its initial morphology during the conversion process. In particular, electrical transport within an individual NiCo{sub 2}O{sub 4} nanoplate is further investigated. The mechanisms of electrical conduction in the low-temperature range (T < 100 K) can be explained in terms of the Mott's variable-range hopping model. At high temperatures (T > 100 K), both the variable-range hopping and nearest-neighbor hopping mechanisms contribute to the electrical transport properties of the NiCo{sub 2}O{sub 4} nanoplate. These initial results will be useful to understanding the fundamental characteristics of these nanoplates and to designing functional nanodevices from NiCo{sub 2}O{sub 4} nanostructures. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Size-dependent thermal stability analysis of graded piezomagnetic nanoplates on elastic medium subjected to various thermal environments

    Science.gov (United States)

    Ebrahimi, Farzad; Barati, Mohammad Reza

    2016-10-01

    This paper investigates the thermal stability of magneto-electro-thermo-elastic functionally graded (METE-FG) nanoplates based on the nonlocal theory and a refined plate model. The METE-FG nanoplate is subjected to the external electric potential, magnetic potential and different temperature rises. Interaction of elastic medium with the METE-FG nanoplate is modeled via Winkler-Pasternak foundation model. The governing equations are derived by using the Hamilton principle and solved by using an analytical method to determine the critical buckling temperatures. To verify the validity of the developed model, the results of the present work are compared with those available in the literature. A detailed parametric study is conducted to study the influences of the nonlocal parameter, foundation parameters, temperature rise, external electric and magnetic potentials on the size-dependent thermal buckling characteristics of METE-FG nanoplates.

  3. [Fluorescence Resonance Energy Transfer Detection of Cobalt Ions by Silver Triangular Nanoplates and Rhodamine 6G].

    Science.gov (United States)

    Zhang, Xiu-qing; Peng, Jun; Ling, Jian; Liu, Chao-juan; Cao, Qiu-e; Ding, Zhong-tao

    2015-04-01

    In the present paper, the authors studied fluorescence resonance energy transfer (FRET) phenomenon between silver triangular nanoplates and bovine serum albumin (BSA)/Rhodamine 6G fluorescence complex, and established a fluorescence method for the detection of cobalt ions. We found that when increasing the silver triangular nanoplates added to certain concentrations of fluorescent bovine serum albumin (BSA)/Rhodamine 6G complex, the fluorescence of Rhodamine 6G would be quenched up to 80% due to the FRET between the quencher and donor. However, in the presence of cobalt ions, the disassociation of the fluorescent complex from silver triangular nanoplates occurred and the fluorescence of the Rhodamine 6G recovered. The recovery of fluorescence intensity rate (I/I0) has a good relationship with the cobalt ion concentration (cCO2+) added. Thus, the authors developed a fluorescence method for the detection of cobalt ions based on the FRET of silver triangular nanoplates and Rhodamine 6G.

  4. Growth and quantum transport properties of vertical Bi2Se3 nanoplate films on Si substrates.

    Science.gov (United States)

    Li, M Z; Wang, Z H; Yang, L; Pan, D S; Li, Da; Gao, Xuan; Zhang, Zhi-Dong

    2018-05-14

    Controlling the growth direction (planar vs. vertical) and surface-to-bulk ratio can lead to lots of unique properties for two-dimensional (2D) layered materials. We report a simple method to fabricate continuous films of vertical Bi2Se3 nanoplates on Si substrate and investigate the quantum transport properties of such films. In contrast to (001) oriented planar Bi2Se3 nanoplate film, vertical Bi2Se3 nanoplate films are enclosed by (015) facets, which possess high surface-to-bulk ratio that can enhance the quantum transport property of topological surface states. And by controlling the compactness of vertical Bi2Se3 nanoplates, we realized an effective tuning of the weak antilocalization (WAL) effect from topological surface states in Bi2Se3 films. Our work paves a way for exploring the unique transport properties of this unconventional structure topological insulator film. © 2018 IOP Publishing Ltd.

  5. Synthesis of ultrathin face-centered-cubic Au@Pt and Au@Pd core-shell nanoplates from hexagonal-close-packed Au square sheets

    KAUST Repository

    Fan, Zhanxi

    2015-03-17

    The synthesis of ultrathin face-centered-cubic (fcc) Au@Pt rhombic nanoplates is reported through the epitaxial growth of Pt on hexagonal-close-packed (hcp) Au square sheets (AuSSs). The Pt-layer growth results in a hcp-to-fcc phase transformation of the AuSSs under ambient conditions. Interestingly, the obtained fcc Au@Pt rhombic nanoplates demonstrate a unique (101)f orientation with the same atomic arrangement extending from the Au core to the Pt shell. Importantly, this method can be extended to the epitaxial growth of Pd on hcp AuSSs, resulting in the unprecedented formation of fcc Au@Pd rhombic nanoplates with (101)f orientation. Additionally, a small amount of fcc (100)f-oriented Au@Pt and Au@Pd square nanoplates are obtained with the Au@Pt and Au@Pd rhombic nanoplates, respectively. We believe that these findings will shed new light on the synthesis of novel noble bimetallic nanostructures. Phase change: Ultrathin Au@Pt and Au@Pd core-shell nanoplates were prepared from Au square sheets. A phase transformation from hexagonal close-packed (hcp) to face-centered cubic (fcc) is observed upon coating the hcp Au square sheets with Pt or Pd under ambient conditions. The prepared fcc Au@Pt and Au@Pd rhombic nanoplates demonstrate unique (101)f orientation (picture shows a typical fcc Au@Pt rhombic nanoplate). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. In situ doping of catalyst-free InAs nanowires with Si: Growth, polytypism, and local vibrational modes of Si

    Energy Technology Data Exchange (ETDEWEB)

    Dimakis, Emmanouil; Ramsteiner, Manfred; Huang, Chang-Ning; Trampert, Achim; Riechert, Henning; Geelhaar, Lutz [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Davydok, Anton; Biermanns, Andreas; Pietsch, Ullrich [Festkörperphysik, Universität Siegen, Walter-Flex-Str. 3, 57072 Siegen (Germany)

    2013-09-30

    Growth and structural aspects of the in situ doping of InAs nanowires with Si have been investigated. The nanowires were grown catalyst-free on Si(111) substrates by molecular beam epitaxy. The supply of Si influenced the growth kinetics, affecting the nanowire dimensions, but not the degree of structural polytypism, which was always pronounced. As determined by Raman spectroscopy, Si was incorporated as substitutional impurity exclusively on In sites, which makes it a donor. Previously unknown Si-related Raman peaks at 355 and 360 cm{sup −1} were identified, based on their symmetry properties in polarization-dependent measurements, as the two local vibrational modes of an isolated Si impurity on In site along and perpendicular, respectively, to the c-axis of the wurtzite InAs crystal.

  7. Selective Magnetic Evolution of MnxFe1-xO Nanoplates

    KAUST Repository

    Song, Hyon-Min

    2015-04-27

    Iron-manganese oxide (MnxFe1-xO) nanoplates were prepared by thermal decomposition method. Irregular development of crystalline phases was observed with the increase of annealing temperature. Magnetic properties are in accordance with their respective crystalline phases, and the selective magnetic evolution from their rich magnetism of MnxFe1-xO and MnFe2O4 is achieved by controlling the annealing conditions. Rock-salt structure of MnxFe1-xO (space group Fm-3m) is observed in as-synthesized nanoplates, while MnFe2O4 and MnxFe1-xO with significant magnetic interactions between them are observed at 380 °C. In nanoplates annealed at 450 °C, soft ferrites of Mn0.48Fe2.52O4 with MnxFe1-xO are observed. It is assumed that the differential and early development of crystalline phase of MnxFe1-xO, and the inhomogeneous cation mixing between Mn and Fe cause this rather extraordinary magnetic development. In particular, the prone nature of divalent metal oxides to cation vacancy and the prolonged annealing time of 15 hours which enables ordering are also thought to contribute to these irregularities.

  8. Selective Magnetic Evolution of MnxFe1-xO Nanoplates

    KAUST Repository

    Song, Hyon-Min; Zink, Jeffrey I.; Khashab, Niveen M.

    2015-01-01

    Iron-manganese oxide (MnxFe1-xO) nanoplates were prepared by thermal decomposition method. Irregular development of crystalline phases was observed with the increase of annealing temperature. Magnetic properties are in accordance with their respective crystalline phases, and the selective magnetic evolution from their rich magnetism of MnxFe1-xO and MnFe2O4 is achieved by controlling the annealing conditions. Rock-salt structure of MnxFe1-xO (space group Fm-3m) is observed in as-synthesized nanoplates, while MnFe2O4 and MnxFe1-xO with significant magnetic interactions between them are observed at 380 °C. In nanoplates annealed at 450 °C, soft ferrites of Mn0.48Fe2.52O4 with MnxFe1-xO are observed. It is assumed that the differential and early development of crystalline phase of MnxFe1-xO, and the inhomogeneous cation mixing between Mn and Fe cause this rather extraordinary magnetic development. In particular, the prone nature of divalent metal oxides to cation vacancy and the prolonged annealing time of 15 hours which enables ordering are also thought to contribute to these irregularities.

  9. Vibration analysis of orthotropic circular and elliptical nano-plates embedded in elastic medium based on nonlocal Mindlin plate theory and using Galerkin method

    International Nuclear Information System (INIS)

    Anjomshoa, Amin; Tahani, Masoud

    2016-01-01

    In the present study a continuum model based on the nonlocal elasticity theory is developed for free vibration analysis of embedded ortho tropic thick circular and elliptical nano-plates rested on an elastic foundation. The elastic foundation is considered to behave like a Pasternak type of foundations. Governing equations for vibrating nano-plate are derived according to the Mindlin plate theory in which the effects of shear deformations of nano-plate are also included. The Galerkin method is then employed to obtain the size dependent natural frequencies of nano-plate. The solution procedure considers the entire nano-plate as a single super-continuum element. Effect of nonlocal parameter, lengths of nano-plate, aspect ratio, mode number, material properties, thickness and foundation on circular frequencies are investigated. It is seen that the nonlocal frequencies of the nano-plate are smaller in comparison to those from the classical theory and this is more pronounced for small lengths and higher vibration modes. It is also found that as the aspect ratio increases or the nanoplate becomes more elliptical, the small scale effect on natural frequencies increases. Further, it is observed that the elastic foundation decreases the influence of nonlocal parameter on the results. Since the effect of shear deformations plays an important role in vibration analysis and design of nano-plates, by predicting smaller values for fundamental frequencies, the study of these nano-structures using thick plate theories such as Mindlin plate theory is essential.

  10. Dynamic analysis of isotropic nanoplates subjected to moving load using state-space method based on nonlocal second order plate theory

    Energy Technology Data Exchange (ETDEWEB)

    Nami, Mohammad Rahim [Shiraz University, Shiraz, Iran (Iran, Islamic Republic of); Janghorban, Maziar [Islamic Azad University, Marvdash (Iran, Islamic Republic of)

    2015-06-15

    In this work, dynamic analysis of rectangular nanoplates subjected to moving load is presented. In order to derive the governing equations of motion, second order plate theory is used. To capture the small scale effects, the nonlocal elasticity theory is adopted. It is assumed that the nanoplate is subjected to a moving concentrated load with the constant velocity V in the x direction. To solve the governing equations, state-space method is used to find the deflections of rectangular nanoplate under moving load. The results obtained here reveal that the nonlocality has significant effect on the deflection of rectangular nanoplate subjected to moving load.

  11. Femtosecond upconverted photocurrent spectroscopy of InAs quantum nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Yasuhiro [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Tex, David M.; Kanemitsu, Yoshihiko, E-mail: kanemitu@scl.kyoto-u.ac.jp [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Japan Science and Technology Agency, CREST, Kyoto University, Uji, Kyoto 611-0011 (Japan); Kamiya, Itaru [Toyota Technological Institute, Nagoya, Aichi 468-8511 (Japan)

    2015-07-06

    The carrier upconversion dynamics in InAs quantum nanostructures are studied for intermediate-band solar-cell applications via ultrafast photoluminescence and photocurrent (PC) spectroscopy based on femtosecond excitation correlation (FEC) techniques. Strong upconverted PC-FEC signals are observed under resonant excitation of quantum well islands (QWIs), which are a few monolayer-thick InAs quantum nanostructures. The PC-FEC signal typically decays within a few hundred picoseconds at room temperature, which corresponds to the carrier lifetime in QWIs. The photoexcited electron and hole lifetimes in InAs QWIs are evaluated as functions of temperature and laser fluence. Our results provide solid evidence for electron–hole–hole Auger process, dominating the carrier upconversion in InAs QWIs at room temperature.

  12. Characterization and supercapacitor application of coin-like β-nickel hydroxide nanoplates

    International Nuclear Information System (INIS)

    Li Hongliang; Liu Suqin; Huang Chenghuan; Zhou Zhi; Li Yanhua; Fang Dong

    2011-01-01

    Coin-like nickel hydroxide nanoplates are synthesized via a simple coordination homogeneous precipitation method. The structure and morphology of as-prepared products are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and scanning electron microscopy. It is demonstrated that the products are typical β-nickel hydroxide with bunches coin-like nanoplates morphology. The electrochemical properties of coin-like β-Ni(OH) 2 are examined by cyclic voltammetric, chronopotentiometry and electrochemical impedance spectroscope. Cyclic voltammetric studies show that the electrodes have good reversibility. A specific capacitance of 1532 F g −1 is obtained at a charge/discharge current density of 0.2 A g −1 .

  13. Polarized and resonant Raman spectroscopy on single InAs nanowires

    Science.gov (United States)

    Möller, M.; de Lima, M. M., Jr.; Cantarero, A.; Dacal, L. C. O.; Madureira, J. R.; Iikawa, F.; Chiaramonte, T.; Cotta, M. A.

    2011-08-01

    We report polarized Raman scattering and resonant Raman scattering studies on single InAs nanowires. Polarized Raman experiments show that the highest scattering intensity is obtained when both the incident and analyzed light polarizations are perpendicular to the nanowire axis. InAs wurtzite optical modes are observed. The obtained wurtzite modes are consistent with the selection rules and also with the results of calculations using an extended rigid-ion model. Additional resonant Raman scattering experiments reveal a redshifted E1 transition for InAs nanowires compared to the bulk zinc-blende InAs transition due to the dominance of the wurtzite phase in the nanowires. Ab initio calculations of the electronic band structure for wurtzite and zinc-blende InAs phases corroborate the observed values for the E1 transitions.

  14. Solvothermal synthesis of LiFePO4 nanoplates with (010) plane and the uniform carbon coated on their surface by esterification reaction

    International Nuclear Information System (INIS)

    Ma, Zhipeng; Shao, Guangjie; Wang, Xu; Song, Jianjun; Wang, Guiling; Liu, Tingting

    2014-01-01

    A facile solvothermal synthesis and esterification reaction combined with a high temperature calcination technique has been developed to prepare the uniform carbon coating LiFePO 4 nanoplates. The carbon coating LiFePO 4 nanoplates are investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), galvanostatic intermittent titration technique (GITT) and galvanostatic charge–discharge test. A reasonable growth mechanism of LiFePO 4 nanoplates is proposed on the basis of time dependent experimental results. The results show that each nanoplate is a LiFePO 4 single crystal with the large (010) plane. According to Raman spectroscopy analysis, carbon is uniformly coated on the surface of LiFePO 4 nanoplates. Electrochemical test results also indicate that the carbon coating LiFePO 4 nanoplates exhibit a high reversible specific capacity of 144.8 mAh g −1 at 0.5 C and 116.9 mAh g −1 under lower discharging rate at −20 °C. - Highlights: • LiFePO 4 nanoplates prepared by facile solvothermal synthesis expose large (010) plane. • The polyester network formed by the esterification reaction could entirely wrap LiFePO 4 . • The polyester wrapped on the surface of LiFePO 4 transformed into the uniform carbon layer after calcination. • LiFePO 4 /C nanoplates have good high-rate and low-temperature performance

  15. InAs quantum dot growth on Al{sub x}Ga{sub 1−x}As by metalorganic vapor phase epitaxy for intermediate band solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Jakomin, R., E-mail: robertojakomin@xerem.ufrj.br [Campus de Xerém, Universidade Federal do Rio de Janeiro, UFRJ, Duque de Caxias-RJ (Brazil); Campus de Xerém, Universidade Federal do Rio de Janeiro, UFRJ, Duque de Caxias-RJ (Brazil); Kawabata, R. M. S.; Souza, P. L. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutoires–DISSE–PUC-Rio, RJ (Brazil); Pontificia Universidade Católica do Rio de Janeiro, Marques de São Vicente 225, Rio de Janeiro, 22452-900 RJ (Brazil); Mourão, R. T.; Pires, M. P. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutoires–DISSE–PUC-Rio, RJ (Brazil); Instituto de Física, Universidade Federal do Rio de Janeiro, UFRJ, Rio de Janeiro-RJ (Brazil); Micha, D. N. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutoires–DISSE–PUC-Rio, RJ (Brazil); Instituto de Física, Universidade Federal do Rio de Janeiro, UFRJ, Rio de Janeiro-RJ (Brazil); Coordenação de Licenciatura em Física, CEFET/RJ, Petrópolis-RJ (Brazil); Xie, H.; Fischer, A. M.; Ponce, F. A. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)

    2014-09-07

    InAs quantum dot multilayers have been grown using Al{sub x}Ga{sub 1−x}As spacers with dimensions and compositions near the theoretical values for optimized efficiencies in intermediate band photovoltaic cells. Using an aluminium composition of x = 0.3 and InAs dot vertical dimensions of 5 nm, transitions to an intermediate band with energy close to the ideal theoretical value have been obtained. Optimum size uniformity and density have been achieved by capping the quantum dots with GaAs following the indium-flush method. This approach has also resulted in minimization of crystalline defects in the epilayer structure.

  16. Strain engineering of quantum dots for long wavelength emission: Photoluminescence from self-assembled InAs quantum dots grown on GaAs(001) at wavelengths over 1.55 μm

    International Nuclear Information System (INIS)

    Shimomura, K.; Kamiya, I.

    2015-01-01

    Photoluminescence (PL) at wavelengths over 1.55 μm from self-assembled InAs quantum dots (QDs) grown on GaAs(001) is observed at room temperature (RT) and 4 K using a bilayer structure with thin cap. The PL peak has been known to redshift with decreasing cap layer thickness, although accompanying intensity decrease and peak broadening. With our strain-controlled bilayer structure, the PL intensity can be comparable to the ordinary QDs while realizing peak emission wavelength of 1.61 μm at 4 K and 1.73 μm at RT. The key issue lies in the control of strain not only in the QDs but also in the cap layer. By combining with underlying seed QD layer, we realize strain-driven bandgap engineering through control of strain in the QD and cap layers

  17. Strain engineering of quantum dots for long wavelength emission: Photoluminescence from self-assembled InAs quantum dots grown on GaAs(001) at wavelengths over 1.55 μm

    Energy Technology Data Exchange (ETDEWEB)

    Shimomura, K., E-mail: sd12502@toyota-ti.ac.jp; Kamiya, I., E-mail: kamiya@toyota-ti.ac.jp [Toyota Technological Institute 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan)

    2015-02-23

    Photoluminescence (PL) at wavelengths over 1.55 μm from self-assembled InAs quantum dots (QDs) grown on GaAs(001) is observed at room temperature (RT) and 4 K using a bilayer structure with thin cap. The PL peak has been known to redshift with decreasing cap layer thickness, although accompanying intensity decrease and peak broadening. With our strain-controlled bilayer structure, the PL intensity can be comparable to the ordinary QDs while realizing peak emission wavelength of 1.61 μm at 4 K and 1.73 μm at RT. The key issue lies in the control of strain not only in the QDs but also in the cap layer. By combining with underlying seed QD layer, we realize strain-driven bandgap engineering through control of strain in the QD and cap layers.

  18. INA-Rxiv: The Missing Puzzle in Indonesia’s Scientific Publishing Workflow

    Science.gov (United States)

    Rahim, R.; Irawan, D. E.; Zulfikar, A.; Hardi, R.; Arliman S, L.; Gultom, E. R.; Ginting, G.; Wahyuni, S. S.; Mesran, M.; Mahjudin, M.; Saputra, I.; Waruwu, F. T.; Suginam, S.; Buulolo, E.; Abraham, J.

    2018-04-01

    INA-Rxiv is the first Indonesia preprint server marking the new development initiated by the open science community. This study aimed at describing the development of INA-Rxiv and its conversations. It usedanalyzer of Inarxiv.id, WhatsApp Group Analyzer, and Twitter Analytics as the tools for data analysis complemented with observation.The results showed that INA-Rxiv users are growing because of the numerous discussions in social media, e.g.WhatsApp,as well as some other positive response of writers who have been using INA- Rxiv. The perspective of growth mindset and the implication of INA-Rxiv movement for filling up the gap in accelerating scientific dissemination process are presented at the end of this article.

  19. 22 CFR 40.68 - Aliens subject to INA 222(g).

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Aliens subject to INA 222(g). 40.68 Section 40... § 40.68 Aliens subject to INA 222(g). An alien who, under the provisions of INA 222(g), has voided a... new nonimmigrant visa unless the alien complies with the requirements in 22 CFR 41.101 (b) or (c...

  20. Investigating dynamic characteristics of porous double-layered FG nanoplates in elastic medium via generalized nonlocal strain gradient elasticity

    Science.gov (United States)

    Reza Barati, Mohammad

    2017-09-01

    For the first time, a vibrating porous double-nanoplate system under in-plane periodic loads is modeled via the generalized nonlocal strain gradient theory (NSGT). Based on the proposed theory, one can examine both stiffness-softening and stiffness-hardening effects for a more accurate analysis of nanoplates. Nanopores or nanovoids are incorporated to the model based on a modified rule of mixture. Modeling of porous double-layered nanoplate is conducted according to a refined four-variable plate theory with fewer field variables than first-order plate theory. The governing equations and related classical and nonclassical boundary conditions are derived based on Hamilton's principle. These equations are solved for hinged nanoplates via Galerkin's method. It is shown that porosities, nonlocal parameter, strain gradient parameter, material gradation, interlayer stiffness, elastic foundation, side-to-thickness and aspect ratios have a notable impact on the vibration behavior of nanoporous materials.

  1. Electrical transport properties of nanoplates shaped tungsten oxide embedded poly(vinyl-alcohol) film

    Science.gov (United States)

    Das, Amit Kumar; Chatterjee, Piyali; Meikap, Ajit Kumar

    2018-04-01

    Tungsten oxide (WO3) nanoplates have been synthesized via hydrothermal method. The average crystallite size of the nanoplates is 28.9 ± 0.5 nm. The direct and indirect band gap of WO3 is observed. The AC conductivity of PVA-WO3 composite film has been observed and carrier transport mechanism follows correlated barrier hopping model. The maximum barrier height of the composite film is 0.1 eV. The electric modulus reflects the non-Debye type behaviour of relaxation time which is simulated by Kohlrausch-Willims-Watts (KWW) function.

  2. Spin Injection, Manipulation, and Detection, in InAs Nanodevices

    Science.gov (United States)

    Jones, G. M.; Jonker, B. T.; Bennett, B. R.; Meyer, J. R.; Twigg, M. E.; Reinecke, T. L.; Park, D.; Pereverzev, S. V.; Badescu, C. S.; Li, C. H.; Hanbicki, A. T.; van'terve, O.; Vurgaftman, I.

    2008-03-01

    In this talk the authors will discuss their progress using InAs heterostructures to produce spin-polarized injection and detection, as well as manipulation of coherent spin-polarized electrons for a spin-based FET (SpinFET). High-quality n-type InAs heterostructures demonstrate many favorable characteristics necessary to the study of spin dynamics, including 2DEG's with small effective mass (m* = 0.023) and large g-factor (g = -15). Previously, high-mobility InAs heterostructures have been demonstrated in which electrons pass ballistically over hundreds of nanometers up to room temperature. Our devices seek to exploit the strong Spin-Orbit effect present in InAs to manipulate coherent spin-polarized electrons during transport, by producing perpendicular electric field using isolated top-gates fabricated over the electron transport region.

  3. Defects and Interfaces on PtPb Nanoplates Boost Fuel Cell Electrocatalysis.

    Science.gov (United States)

    Sun, Yingjun; Liang, Yanxia; Luo, Mingchuan; Lv, Fan; Qin, Yingnan; Wang, Lei; Xu, Chuan; Fu, Engang; Guo, Shaojun

    2018-01-01

    Nanostructured Pt is the most efficient single-metal catalyst for fuel cell technology. Great efforts have been devoted to optimizing the Pt-based alloy nanocrystals with desired structure, composition, and shape for boosting the electrocatalytic activity. However, these well-known controls still show the limited ability in maximizing the Pt utilization efficiency for achieving more efficient fuel cell catalysis. Herein, a new strategy for maximizing the fuel cell catalysis by controlling/tuning the defects and interfaces of PtPb nanoplates using ion irradiation technique is reported. The defects and interfaces on PtPb nanoplates, controlled by the fluence of incident C + ions, make them exhibit the volcano-like electrocatalytic activity for methanol oxidation reaction (MOR), ethanol oxidation reaction (EOR), and oxygen reduction reaction (ORR) as a function of ion irradiation fluence. The optimized PtPb nanoplates with the mixed structure of dislocations, subgrain boundaries, and small amorphous domains are the most active for MOR, EOR, and ORR. They can also maintain high catalytic stability in acid solution. This work highlights the impact and significance of inducing/controlling the defects and interfaces on Pt-based nanocrystals toward maximizing the catalytic performance by advanced ion irradiation strategy. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Facile Br{sup -} assisted hydrothermal synthesis of Bi{sub 2}MoO{sub 6} nanoplates with enhanced visible-light photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Peng [Yangtze Normal University, Chongqing Key Laboratory of Inorganic Special Functional Materials, Chongqing (China); Yangtze Normal University, College of Chemistry and Chemical Engineering, Chongqing (China); Teng, Xiaoxu; Liu, Dongsheng; Fu, Liang; Xie, Hualin [Yangtze Normal University, College of Chemistry and Chemical Engineering, Chongqing (China); Zhang, Guoqing [Yangtze Normal University, Chongqing Key Laboratory of Inorganic Special Functional Materials, Chongqing (China); Ding, Shimin [Yangtze Normal University, Collaborative Innovation Center for Green Development in Wuling Mountain Areas, Chongqing (China)

    2017-10-15

    Bi{sub 2}MoO{sub 6} nanoplates have been controllably synthesized via a facile hydrothermal process with the assistance of Br{sup -} containing surfactant cetyltrimethylammonium bromide (CTAB) or KBr. A remarkable enhancement in the visible-light-driven photocatalytic degradation of Rhodamine B was observed. It was found that reaction temperature and surfactant play crucial roles in the formation and properties of the Bi{sub 2}MoO{sub 6} nanoplates. The best results as photocatalyst were obtained with the sample hydrothermally synthesized at 150 C with the assistance of CTAB. The improved photocatalytic performance could be ascribed to the {001}-oriented nanostructure of the Bi{sub 2}MoO{sub 6} nanoplates. KBr-templated Bi{sub 2}MoO{sub 6} nanoplates also showed better photocatalytic efficiency compared with that of flower-like Bi{sub 2}MoO{sub 6} but inferior to that of CTAB-templated Bi{sub 2}MoO{sub 6} nanoplates. (orig.)

  5. Women Fellows of INAE | Women in Science | Initiatives | Indian ...

    Indian Academy of Sciences (India)

    Women Fellows of INAE. INAE - Indian National Academy of Engineering. Ms. Alpa Sheth Civil Engineering. Prof. Bharathi Bhat Electronics & Communication Engineering. Prof. Dipanwita Roy Chowdhury Computer Engineering and Information Technology. Prof. Kamala Krithivasan Computer Engineering and Information ...

  6. Anisotropic localized surface plasmon resonances in CuS nanoplates prepared by size-selective precipitation

    Science.gov (United States)

    Hamanaka, Yasushi; Yamada, Kaoru; Hirose, Tatsunori; Kuzuya, Toshihiro

    2018-05-01

    CuS nanoplates were synthesized by a colloidal method and separated into four fractions of nanoplates with different aspect ratios by a size-selective precipitation. In addition to a strong near infrared absorption band ascribed to the in-plane mode of the localized surface plasmon resonance (LSPR), we found a weak absorption band on the high frequency tail of the in-plane LSPR band. The frequency of the weak absorption band was almost constant and independent of the aspect ratio, while the in-plane LSPR band exhibited a strong aspect ratio dependence. These characteristics suggested that the weak absorption band is ascribed to the out-of-plane LSPR. Although the out-of-plane LSPR was expected to be difficult to observe for CuS nanoplates due to its low intensity and overlap with the strong in-plane resonance, we could successfully identify the out-of-plane mode by reducing the width of the size distribution and spectral broadening caused thereby.

  7. Electronic structure of GaAs with InAs (001) monolayer

    International Nuclear Information System (INIS)

    Tit, N.; Peressi, M.

    1995-04-01

    The effect on the electronic structure of an InAs monomolecular plane inserted in bulk GaAs is investigated theoretically. The (InAs) 1 (GaAs) n (001) strained superlattice is studied via ab-initio self-consistent pseudopotential calculations. Both electrons and holes are localized nearby the inserted InAs monolayer, which therefore acts as a quantum well for all the charge carriers. The small thickness of the inserted InAs slab is responsible of high confinement energies for the charge carriers, and therefore the interband electron-heavy-hole transition energy is close to the energy gap of the bulk GaAs, in agreement with recent experimental data. (author). 18 refs, 4 figs

  8. Growth and characterization of InAs columnar quantum dots on GaAs substrate

    International Nuclear Information System (INIS)

    Li, L. H.; Patriarche, G.; Rossetti, M.; Fiore, A.

    2007-01-01

    The growth of InAs columnar quantum dots (CQDs) on GaAs substrates by molecular beam epitaxy was investigated. The CQDs were formed by depositing a 1.8 monolayer (ML) InAs seed dot layer and a short period GaAs/InAs superlattice (SL). It was found that the growth of the CQDs is very sensitive to growth interruption (GI) and growth temperature. Both longer GI and higher growth temperature impact the size dispersion of the CQDs, which causes the broadening of photoluminescence (PL) spectrum and the presence of the additional PL peak tails. By properly choosing the GI and the growth temperature, CQDs including GaAs (3 ML)/InAs (0.62 ML) SL with period number up to 35 without plastic relaxation were grown. The corresponding equivalent thickness of the SL is 41 nm which is two times higher than the theoretical critical thickness of the strained InGaAs layer with the same average In composition of 16%. The increase of the critical thickness is partially associated with the formation of the CQDs. Based on a five-stack CQD active region, laser diodes emitting around 1120 nm at room temperature were demonstrated, indicating a high material quality. CQDs with nearly isotropic cross section (20 nmx20 nm dimensions) were formed by depositing a 16-period GaAs (3 ML)/InAs (0.62 ML) SL on an InAs seed dot layer, indicating the feasibility of artificial shape engineering of QDs. Such a structure is expected to be very promising for polarization insensitive device applications, such as semiconductor optical amplifiers

  9. Komunikační mix Svatebního salonu INA

    OpenAIRE

    Rybníčková, Michala

    2015-01-01

    Rybníčková, M. Marketing mix for Wedding Boutique INA. Bachelor thesis, Brno: Mendel university in Brno, 2015 This Bechelor thesis focuses on the marketing mix for the company Wedding Boutique INA. Survey results are used to evaluate the effectiveness of marketing tools currently used by INA. Furthermore, the results are used to recommend improvements to the marketing mix. Thesis also includes calculation of costs and scheduling for the year 2015.

  10. Longer than 1.9 μm photoluminescence emission from InAs quantum structure on GaAs (001) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ke; Ma, Wenquan, E-mail: wqma@semi.ac.cn; Huang, Jianliang; Zhang, Yanhua; Cao, Yulian; Huang, Wenjun; Luo, Shuai; Yang, Tao [Institute of Semiconductors, Chinese Academy of Sciences, Qinghua East Road A 35, Beijing 100083 (China)

    2015-07-27

    We report on photoluminescence (PL) emission with long wavelength for quantum structure by the sub-monolayer (SML) growth technique on GaAs (001) substrate. It is found that the PL emission wavelength can be controlled by controlling the SML InAs deposition amount. At 12 K, the PL peak position of the grown samples changes from about 1.66 to 1.78 μm. At 120 K, the PL emission of a sample reaches 1.91 μm. The physical mechanism responsible for the measured long wavelength PL emission may be related to strong In segregation and intermixing effects occurred in the structure grown by SML growth technique.

  11. Selenium-assisted controlled growth of graphene–Bi_2Se_3 nanoplates hybrid Dirac materials by chemical vapor deposition

    International Nuclear Information System (INIS)

    Sun, Zhencui; Man, Baoyuan; Yang, Cheng; Liu, Mei; Jiang, Shouzhen; Zhang, Chao; Zhang, Jiaxin; Liu, Fuyan; Xu, Yuanyuan

    2016-01-01

    Graphical abstract: - Highlights: • We synthesize the graphene–Bi_2Se_3 nanoplates hybrid Dirac materials via CVD. • The Se seed layer impels the Bi_2Se_3 plates growing along the lateral direction. • The Se seed layer can supply enough Se atoms to fill the Se vacancies. • The Se seed layer can effectively avoid the interaction of Bi_2Se_3 and the graphene. • The Se seed layer can be used to control the density of the Bi_2Se_3 nanoplates. - Abstract: Se seed layers were used to synthesize the high-quality graphene–Bi_2Se_3 nanoplates hybrid Dirac materials via chemical vapor deposition (CVD) method. The morphology, crystallization and structural properties of the hybrid Dirac materials were characterized by SEM, EDS, Raman, XRD, AFM and HRTEM. The measurement results verify that the Se seed layer on the graphene surface can effectively saturate the surface dangling bonds of the graphene, which not only impel the uniform Bi_2Se_3 nanoplates growing along the horizontal direction but also can supply enough Se atoms to fill the Se vacancies. We also demonstrate the Se seed layer can effectively avoid the interaction of Bi_2Se_3 and the graphene. Further experiments testify the different Se seed layer on the graphene surface can be used to control the density of the Bi_2Se_3 nanoplates.

  12. Study of Structural, Morphological and Optical Properties of Magnesium Hydroxide Nanoplates Synthesized by Precipitation Route

    Directory of Open Access Journals (Sweden)

    S. yousefi

    2018-03-01

    Full Text Available In this paper, high purity magnesium hydroxide nanoplates were successfully synthesized by using brine rich in magnesium ions as precursor and NaOH as precipitating agent without using dispersant agent in the room temoerature. The study and characterization of various properties of obtained nanopowder was carried out by X-Ray Diffraction (XRD, Field Emission Scanning Electron Microscopy (FESEM, Energy Dispersive X-ray Fluorescence Spectrometer (EDX, Fourier Transform Infrared Spectrophotometer (FTIR and Ultraviolet–visible spectroscopy (UV-Vis. The FESEM and XRD analysis results showed that magnesium hydroxide powder had nanoplates with the average crystallite size 17.1nm and no impurity; that was in agreement with the result of EDX and FTIR perfectly. Furthermore, optical characteristics of magnesium hydroxide nanoplates by UV-Vis spectroscopy showed an optical band gap of 5.5 eV. This wide band gap can be a useful innovation in optoelectronic sub-micron devices.

  13. Effective Chemical Route to 2D Nanostructured Silicon Electrode Material: Phase Transition from Exfoliated Clay Nanosheet to Porous Si Nanoplate

    International Nuclear Information System (INIS)

    Adpakpang, Kanyaporn; Patil, Sharad B.; Oh, Seung Mi; Kang, Joo-Hee; Lacroix, Marc; Hwang, Seong-Ju

    2016-01-01

    Graphical abstract: Effective morphological control of porous silicon 2D nanoplate can be achieved by the magnesiothermically-induced phase transition of exfoliated silicate clay nanosheets. The promising lithium storage performance of the obtained silicon materials with huge capacity and excellent rate characteristics underscores the prime importance of porously 2D nanostructured morphology of silicon. - Highlights: • 2D nanostructured silicon electrode materials are successfully synthesized via the magnesiothermically-induced phase transition of exfoliated clay 2D nanosheets. • High discharge capacity and rate capability are achieved from the 2D nanoplates of silicon. • Silicon 2D nanoplates can enhance both Li"+ diffusion and charge-transfer kinetics. • 2D nanostructured silicon is beneficial for the cycling stability by minimizing the volume change during lithiation-delithiation. - Abstract: An efficient and economical route for the synthesis of porous two-dimensional (2D) nanoplates of silicon is developed via the magnesiothermically-induced phase transition of exfoliated clay 2D nanosheets. The magnesiothermic reaction of precursor clay nanosheets prepared by the exfoliation and restacking with Mg"2"+ cations yields porous 2D nanoplates of elemental silicon. The variation in the Mg:SiO_2 ratio has a significant effect on the porosity and connectivity of silicon nanoplates. The porous silicon nanoplates show a high discharge capacity of 2000 mAh g"−"1 after 50 cycles. Of prime importance is that this electrode material still retains a large discharge capacity at higher C-rates, which is unusual for the elemental silicon electrode. This is mainly attributed to the improved diffusion of lithium ions, charge-transfer kinetics, and the preservation of the electrical connection of the porous 2D plate-shaped morphology. This study highlights the usefulness of clay mineral as an economical and scalable precursor of high-performance silicon electrodes with

  14. Progress in low light-level InAs detectors- towards Geiger-mode detection

    Science.gov (United States)

    Tan, Chee Hing; Ng, Jo Shien; Zhou, Xinxin; David, John; Zhang, Shiyong; Krysa, Andrey

    2017-05-01

    InAs avalanche photodiodes (APDs) can be designed such that only electrons are allowed to initiate impact ionization, leading to the lowest possible excess noise factor. Optimization of wet chemical etching and surface passivation produced mesa APDs with bulk dominated dark current and responsivity that are comparable and higher, respectively, than a commercial InAs detector. Our InAs electron-APDs also show high stability with fluctuation of 0.1% when operated at a gain of 11.2 over 60 s. These InAs APDs can detect very weak signal down to 35 photons per pulse. Fabrication of planar InAs by Be implantation produced planar APDs with bulk dominated dark current. Annealing at 550 °C was necessary to remove implantation damage and to activate Be dopants. Due to minimal diffusion of Be, thick depletion of 8 μm was achieved. Since the avalanche gain increases exponentially with the thickness of avalanche region, our planar APD achieved high gain > 300 at 200 K. Our work suggest that both mesa and planar InAs APDs can exhibit high gain. When combined with a suitable preamplifier, single photon detection using InAs electron-APDs could be achieved.

  15. High Curie temperature Bi(1.85)Mn(0.15)Te3 nanoplates.

    Science.gov (United States)

    Cheng, Lina; Chen, Zhi-Gang; Ma, Song; Zhang, Zhi-dong; Wang, Yong; Xu, Hong-Yi; Yang, Lei; Han, Guang; Jack, Kevin; Lu, Gaoqing Max; Zou, Jin

    2012-11-21

    Bi(1.85)Mn(0.15)Te(3) hexagonal nanoplates with a width of ~200 nm and a thickness of ~20 nm were synthesized using a solvothermal method. According to the structural characterization and compositional analysis, the Mn(2+) and Mn(3+) ions were found to substitute Bi(3+) ions in the lattice. High-level Mn doping induces significant lattice distortion and decreases the crystal lattice by 1.07% in the a axis and 3.18% in the c axis. A high ferromagnetic state with a Curie temperature of ~45 K is observed in these nanoplates due to Mn(2+) and Mn(3+) ion doping, which is a significant progress in the field of electronics and spintronics.

  16. Highly Reversible Lithium-ions Storage of Molybdenum Dioxide Nanoplates for High Power Lithium-ion Batteries.

    Science.gov (United States)

    Liu, Xiaolin; Yang, Jun; Hou, Wenhua; Wang, Jiulin; Nuli, Yanna

    2015-08-24

    Herein, MoO2 nanoplates have been facilely prepared through a hydrothermal process by using MoO3 microbelts as the intercalation host. The obtained MoO2 nanoplates manifest excellent electrochemical properties when the discharge cutoff voltage is simply set at 1.0 V to preclude the occurrence of conversion reactions. Its initial reversible capacity reaches 251 mAh g(-1), which is larger than that of Li4Ti5O12 , at a current rate of 0.2 C. The average capacity decay is only 0.0465 mAh g(-1) per cycle, with a coulombic efficiency of 99.5% (from the 50th cycle onward) for 2000 cycles at 1 C. Moreover, this MoO2 electrode demonstrates an outstanding high power performance. When the current rate is increased from 0.2 to 50 C, about 54% of the capacity is retained. The superior electrochemical performance can be attributed to the metallic conductivity of MoO2, short Li(+) diffusion distance in the nanoplates, and reversible crystalline phase conversion of the addition-type reaction of MoO2. The prepared MoO2 nanoplates may hopefully replace their currently used analogues, such as Li4Ti5O12 , in high power lithium-ion batteries. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. X-ray diffraction analysis of InAs nanowires

    International Nuclear Information System (INIS)

    Davydok, Anton

    2013-01-01

    Semiconductor nanowires have attracted great interest as building blocks for future electronic and optoelectronic devices. The variability of the growth process opens the opportunity to control and combine the various properties tailoring for specific application. It was shown that the electrical and optical characteristics of the nanowires are strongly connected with their structure. Despite intensive research in this field, the growth process is still not fully understood. In particular, extensive real structure investigations are required. Most of the reports dedicated on the structural researches are based on the results of scanning electron microscopy (SEM) or transmission electron microscopy (TEM). SEM provides an image of the surface with nanostructures and is mainly used to describe the morphology of the sample, but it does not bring information about the internal structure, phase composition and defect structure. At the same time, the internal structure can be examined by TEM down to atomic scale. TEM image of good quality are very expensive due to the efforts in sample preparation and in localisation of a single object. All these aspects make the statistical structural analysis difficult. In the present work, X-ray diffraction analysis has been applied for structural investigation of InAs nanowires grown by different techniques. Using various X-ray diffraction geometries, the nanowire systems were investigated in terms of the lattice parameters, phase composition, strains and displacement fields and stacking defects. In particular, realizing grazing incidence diffraction and controlling the penetration depth of X-ray beam, we characterized sample series grown by Au-assisted metal organic phase epitaxy on GaAs [111]B substrate with different growth time. According to the results of SEM and X-ray investigations, a model of the growth process has been proposed. A more detailed analysis was performed on InAs nanowires grown by molecular beam epitaxy (MBE) on

  18. Identification of Ina proteins from Fusarium acuminatum

    Science.gov (United States)

    Scheel, Jan Frederik; Kunert, Anna Theresa; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine

    2015-04-01

    Freezing of water above -36° C is based on ice nucleation activity (INA) mediated by ice nucleators (IN) which can be of various origins. Beside mineral IN, biological particles are a potentially important source of atmospheric IN. The best-known biological IN are common plant-associated bacteria. The IN activity of these bacteria is induced by a surface protein on the outer cell membrane, which is fully characterized. In contrast, much less is known about the nature of fungal IN. The fungal genus Fusarium is widely spread throughout the earth. It belongs to the Ascomycota and is one of the most severe fungal pathogens. It can affect a variety of organisms from plants to animals including humans. INA of Fusarium was already described about 30 years ago and INA of Fusarium as well as other fungal genera is assumed to be mediated by proteins or at least to contain a proteinaceous compound. Although many efforts were made the precise INA machinery of Fusarium and other fungal species including the proteins and their corresponding genes remain unidentified. In this study preparations from living fungal samples of F. acuminatum were fractionated by liquid chromatography and IN active fractions were identified by freezing assays. SDS-page and de novo sequencing by mass spectrometry were used to identify the primary structure of the protein. Preliminary results show that the INA protein of F. acuminatum is contained in the early size exclusion chromatography fractions indicating a high molecular size. Moreover we could identify a single protein band from IN active fractions at 130-145 kDa corresponding to sizes of IN proteins from bacterial species. To our knowledge this is for the first time an isolation of a single protein from in vivo samples, which can be assigned as IN active from Fusarium.

  19. ZnO nanorods/ZnS.(1,6-hexanediamine)0.5 hybrid nanoplates hierarchical heteroarchitecture with improved electrochemical catalytic properties for hydrazine

    Science.gov (United States)

    Wu, Zhengcui; Wu, Yaqin; Pei, Tonghui; Wang, Huan; Geng, Baoyou

    2014-02-01

    Novel hierarchical heteronanostructures of ZnO nanorods/ZnS.(HDA)0.5 (HDA = 1,6-hexanediamine) hybrid nanoplates on a zinc substrate are successfully synthesized on a large scale by combining hydrothermal growth (for ZnO nanorods) and liquid chemical conversion (for ZnS.(HDA)0.5 nanoplates) techniques. The formation of ZnS.(HDA)0.5 hybrid nanoplates branches takes advantage of the preferential binding of 1,6-hexanediamine on specific facets of ZnS, which makes the thickening rate much lower than the lateral growth rate. The ZnS.(HDA)0.5 hybrid nanoplates have a layered structure with 1,6-hexanediamine inserted into interlayers of wurtzite ZnS through the bonding of nitrogen. The number density and thickness of the secondary ZnS.(HDA)0.5 nanoplates can be conveniently engineered by variation of the sulfur source and straightforward adjustment of reactant concentrations such as 1,6-hexanediamine and the sulfur source. The fabricated ZnO/ZnS.(HDA)0.5 heteronanostructures show improved electrochemical catalytic properties for hydrazine compared with the primary ZnO nanorods. Due to its simplicity and efficiency, this approach could be similarly used to fabricate varieties of hybrid heterostructures made of materials with an intrinsic large lattice mismatch.Novel hierarchical heteronanostructures of ZnO nanorods/ZnS.(HDA)0.5 (HDA = 1,6-hexanediamine) hybrid nanoplates on a zinc substrate are successfully synthesized on a large scale by combining hydrothermal growth (for ZnO nanorods) and liquid chemical conversion (for ZnS.(HDA)0.5 nanoplates) techniques. The formation of ZnS.(HDA)0.5 hybrid nanoplates branches takes advantage of the preferential binding of 1,6-hexanediamine on specific facets of ZnS, which makes the thickening rate much lower than the lateral growth rate. The ZnS.(HDA)0.5 hybrid nanoplates have a layered structure with 1,6-hexanediamine inserted into interlayers of wurtzite ZnS through the bonding of nitrogen. The number density and thickness of the

  20. A nonlocal continuum model for the biaxial buckling analysis of composite nanoplates with shape memory alloy nanowires

    Science.gov (United States)

    Farajpour, M. R.; Shahidi, A. R.; Farajpour, A.

    2018-03-01

    In this study, the buckling behavior of a three-layered composite nanoplate reinforced with shape memory alloy (SMA) nanowires is examined. Whereas the upper and lower layers are reinforced with typical nanowires, SMA nanoscale wires are used to strengthen the middle layer of the system. The composite nanoplate is assumed to be under the action of biaxial compressive loading. A scale-dependent mathematical model is presented with the consideration of size effects within the context of the Eringen’s nonlocal continuum mechanics. Using the one-dimensional Brinson’s theory and the Kirchhoff theory of plates, the governing partial differential equations of SMA nanowire-reinforced hybrid nanoplates are derived. Both lateral and longitudinal deflections are taken into consideration in the theoretical formulation and method of solution. In order to reduce the governing differential equations to their corresponding algebraic equations, a discretization approach based on the differential quadrature method is employed. The critical buckling loads of the hybrid nanosystem with various boundary conditions are obtained with the use of a standard eigenvalue solver. It is found that the stability response of SMA composite nanoplates is strongly sensitive to the small scale effect.

  1. Selective area growth of InAs nanowires from SiO2/Si(1 1 1) templates direct-written by focused helium ion beam technology

    Science.gov (United States)

    Yang, Che-Wei; Chen, Wei-Chieh; Chou, Chieh; Lin, Hao-Hsiung

    2018-02-01

    We report on the selective area growth of InAs nanowires on patterned SiO2/Si (1 1 1) nano-holes, prepared by focused helium ion beam technology. We used a single spot mode, in which the focused helium ion beam was fixed on a single point with a He+-ion dosage, ranging from 1.5 pC to 8 pC, to drill the nano-holes. The smallest hole diameter achieved is ∼8 nm. We found that low He+-ion dosage is able to facilitate the nucleation of (1 1 1)B InAs on the highly mismatched Si, leading to the vertical growth of InAs nanowires (NWs). High He-ion dosage, on the contrary, severely damaged Si surface, resulting in tilted and stripe-like NWs. In addition to titled NW grown from (1 1 1)A InAs domain, a new titled growth direction due to defect induced twinning was observed. Cross-sectional TEM images of vertical NWs show mixed wurtizite (WZ) and zincblende (ZB) phases, while WZ phase dominants. The stacking faults resulting from the phase change is proportional to NW diameter, suggesting that the critical diameter of phase turning is larger than 110 nm, the maximum diameter of our NWs. Period of misfit dislocation at the InAs/Si interface of vertical NW is also found larger than the theoretical value when the diameter of heterointerface is smaller than 50 nm, indicating that the small contact area is able to accommodate the large lattice and thermal mismatch between InAs and Si.

  2. New process for high optical quality InAs quantum dots grown on patterned GaAs(001) substrates

    International Nuclear Information System (INIS)

    Alonso-Gonzalez, Pablo; Gonzalez, Luisa; Gonzalez, Yolanda; Fuster, David; Fernandez-Martinez, Ivan; Martin-Sanchez, Javier; Abelmann, Leon

    2007-01-01

    This work presents a selective ultraviolet (UV)-ozone oxidation-chemical etching process that has been used, in combination with laser interference lithography (LIL), for the preparation of GaAs patterned substrates. Further molecular beam epitaxy (MBE) growth of InAs results in ordered InAs/GaAs quantum dot (QD) arrays with high optical quality from the first layer of QDs formed on the patterned substrate. The main result is the development of a patterning technology that allows the engineering of customized geometrical displays of QDs with the same optical quality as those formed spontaneously on flat non-patterned substrates

  3. Growth and optical characteristics of InAs quantum dot structures with tunnel injection quantum wells for 1.55 μ m high-speed lasers

    Science.gov (United States)

    Bauer, Sven; Sichkovskyi, Vitalii; Reithmaier, Johann Peter

    2018-06-01

    InP based lattice matched tunnel injection structures consisting of a InGaAs quantum well, InAlGaAs barrier and InAs quantum dots designed to emit at 1.55 μ m were grown by molecular beam epitaxy and investigated by photoluminescence spectroscopy and atomic force microscopy. The strong influence of quantum well and barrier thicknesses on the samples emission properties at low and room temperatures was investigated. The phenomenon of a decreased photoluminescence linewidth of tunnel injection structures compared to a reference InAs quantum dots sample could be explained by the selection of the emitting dots through the tunneling process. Morphological investigations have not revealed any effect of the injector well on the dot formation and their size distribution. The optimum TI structure design could be defined.

  4. Surface roughness induced electron mobility degradation in InAs nanowires

    International Nuclear Information System (INIS)

    Wang Fengyun; Yip, Sen Po; Han, Ning; Fok, KitWa; Lin, Hao; Hou, Jared J; Dong, Guofa; Hung, Tak Fu; Chan, K S; Ho, Johnny C

    2013-01-01

    In this work, we present a study of the surface roughness dependent electron mobility in InAs nanowires grown by the nickel-catalyzed chemical vapor deposition method. These nanowires have good crystallinity, well-controlled surface morphology without any surface coating or tapering and an excellent peak field-effect mobility up to 15 000 cm 2 V −1 s −1 when configured into back-gated field-effect nanowire transistors. Detailed electrical characterizations reveal that the electron mobility degrades monotonically with increasing surface roughness and diameter scaling, while low-temperature measurements further decouple the effects of surface/interface traps and phonon scattering, highlighting the dominant impact of surface roughness scattering on the electron mobility for miniaturized and surface disordered nanowires. All these factors suggest that careful consideration of nanowire geometries and surface condition is required for designing devices with optimal performance. (paper)

  5. Hydroxyapatite coatings with oriented nanoplate and nanorod arrays: Fabrication, morphology, cytocompatibility and osteogenic differentiation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei [The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, Shanghai Normal University, Shanghai 200234 (China); Tian, Bo [Shanghai Key Laboratory of Orthopedic Implant, Department of Orthopedic Surgery, Shanghai Ninth People' s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011 (China); Lei, Yong; Ke, Qin-Fei [The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, Shanghai Normal University, Shanghai 200234 (China); Zhu, Zhen-An, E-mail: zhuzhenan2006@126.com [Shanghai Key Laboratory of Orthopedic Implant, Department of Orthopedic Surgery, Shanghai Ninth People' s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011 (China); Guo, Ya-Ping, E-mail: ypguo@shnu.edu.cn [The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, Shanghai Normal University, Shanghai 200234 (China)

    2016-10-01

    Hydroxyapatite (HA) crystals exhibit rod-like shape with c-axis orientation and plate-like shape with a(b)-axis orientation in vertebrate bones and tooth enamel surfaces, respectively. Herein, we report the synthesis of HA coatings with the oriented nanorod arrays (RHACs) and HA coatings with oriented nanoplate arrays (PHACs) by using bioglass coatings as sacrificial templates. After soaking in simulated body fluid (SBF) at 120 °C, the bioglass coatings are hydrothermally converted into the HA coatings via a dissolution-precipitation reaction. If the Ca/P ratios in SBF are 2.50 and 1.25, the HA crystals on the coatings are oriented nanorod arrays and oriented nanoplate arrays, respectively. Moreover, the bioglass coatings are treated with SBF at 37 °C, plate-like HA coatings with a low crystallinity (SHACs) are prepared. As compared with the Ti6Al4V and SHACs, the human bone marrow stromal cells (hBMSCs) on the RHACs and PHACs have better cell adhesion, spreading, proliferation and osteogenic differentiation because of their moderately hydrophilic surfaces and similar chemical composition, morphology and crystal orientation to human hard tissues. Notably, the morphologies of HA crystals have no obvious effects on cytocompatibility and osteogenic differentiation. Hence, the HA coatings with oriented nanoplate arrays or oriented nanorod arrays have a great potential for orthopedic applications. - Highlights: • We prepare hydroxyapatite coatings with oriented nanoplate and nanorod arrays. • Hydroxyapatite coatings are in situ converted from bioglass coatings. • Hydroxyapatite coatings have good cytocompatibility and osteogenic differentiation. • Oriented hydroxyapatite coatings are used for orthopedic implants.

  6. Hydroxyapatite coatings with oriented nanoplate and nanorod arrays: Fabrication, morphology, cytocompatibility and osteogenic differentiation

    International Nuclear Information System (INIS)

    Chen, Wei; Tian, Bo; Lei, Yong; Ke, Qin-Fei; Zhu, Zhen-An; Guo, Ya-Ping

    2016-01-01

    Hydroxyapatite (HA) crystals exhibit rod-like shape with c-axis orientation and plate-like shape with a(b)-axis orientation in vertebrate bones and tooth enamel surfaces, respectively. Herein, we report the synthesis of HA coatings with the oriented nanorod arrays (RHACs) and HA coatings with oriented nanoplate arrays (PHACs) by using bioglass coatings as sacrificial templates. After soaking in simulated body fluid (SBF) at 120 °C, the bioglass coatings are hydrothermally converted into the HA coatings via a dissolution-precipitation reaction. If the Ca/P ratios in SBF are 2.50 and 1.25, the HA crystals on the coatings are oriented nanorod arrays and oriented nanoplate arrays, respectively. Moreover, the bioglass coatings are treated with SBF at 37 °C, plate-like HA coatings with a low crystallinity (SHACs) are prepared. As compared with the Ti6Al4V and SHACs, the human bone marrow stromal cells (hBMSCs) on the RHACs and PHACs have better cell adhesion, spreading, proliferation and osteogenic differentiation because of their moderately hydrophilic surfaces and similar chemical composition, morphology and crystal orientation to human hard tissues. Notably, the morphologies of HA crystals have no obvious effects on cytocompatibility and osteogenic differentiation. Hence, the HA coatings with oriented nanoplate arrays or oriented nanorod arrays have a great potential for orthopedic applications. - Highlights: • We prepare hydroxyapatite coatings with oriented nanoplate and nanorod arrays. • Hydroxyapatite coatings are in situ converted from bioglass coatings. • Hydroxyapatite coatings have good cytocompatibility and osteogenic differentiation. • Oriented hydroxyapatite coatings are used for orthopedic implants.

  7. Nonlocal free vibration in the pre- and post-buckled states of magneto-electro-thermo elastic rectangular nanoplates with various edge conditions

    Science.gov (United States)

    Ansari, R.; Gholami, R.

    2016-09-01

    Considering the small scale effect together with the influences of transverse shear deformation, rotary inertia and the magneto-electro-thermo-mechanical coupling, the linear free vibration of magneto-electro-thermo-elastic (METE) rectangular nanoplates with various edge supports in pre- and post-buckled states is investigated herein. It is assumed that the METE nanoplate is subjected to the external in-plane compressive loads in combination with magnetic, electric and thermal loads. The Mindlin plate theory, von Kármán hypothesis and the nonlocal theory are utilized to develop a size-dependent geometrically nonlinear plate model for describing the size-dependent linear and nonlinear mechanical characteristics of moderately thick METE rectangular nanoplates. The nonlinear governing equations and the corresponding boundary conditions are derived using Hamilton’s principle which are then discretized via the generalized differential quadrature method. The pseudo-arc length continuation approach is used to obtain the equilibrium postbuckling path of METE nanoplates. By the obtained postbuckling response, and taking a time-dependent small disturbance around the buckled configuration, and inserting them into the nonlinear governing equations, an eigenvalue problem is achieved from which the frequencies of pre- and post-buckled METE nanoplates can be calculated. The effects of nonlocal parameter, electric, magnetic and thermal loadings, length-to-thickness ratio and different boundary conditions on the free vibration response of METE rectangular nanoplates in the pre- and post-buckled states are highlighted.

  8. Sensing the facet orientation in silver nano-plates using scanning Kelvin probe microscopy in air

    Energy Technology Data Exchange (ETDEWEB)

    Abdellatif, M.H. [Department of Nanostructures, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Physics Department, National Research Center, Elbehoos st., 12622, Dokki, Giza (Egypt); Salerno, M., E-mail: marco.salerno@iit.it [Department of Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Polovitsyn, Anatolii [Department of Nanochemistry, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Dipartimentodi Fisica, Università di Genova, via Dodecaneso 33, I-16146 Genova (Italy); Marras, Sergio [Department of Nanochemistry, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); De Angelis, Francesco [Department of Nanostructures, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy)

    2017-05-01

    Highlights: • The surface potential of drop cast nanocrystals was measured by SKPM in ambient air. • The nanocrystal facet work function was derived by theory. • By comparing theory and experiment we distinguished the nanocrystal facets. • Nanocrystal facet control is of practical interest for optoelectronic devices. - Abstract: The work function of nano-materials is important for a full characterization of their electronic properties. Because the band alignment, band bending and electronic noise are very sensitive to work function fluctuations, the dependence of the work function of nano-scale crystals on facet orientation can be a critical issue in optimizing optoelectronic devices based on these materials. We used scanning Kelvin probe microscopy to assess the local work function on samples of silver nano-plates at sub-micrometric spatial resolution. With the appropriate choice of the substrate and based on statistical analysis, it was possible to distinguish the surface potential of the different facets of silver nano-plates even if the measurements were done in ambient conditions without the use of vacuum. A phenomenological model was used to calculate the differences of facet work function of the silver nano-plates and the corresponding shift in Fermi level. This theoretical prediction and the experimentally observed difference in surface potential on the silver nano-plates were in good agreement. Our results show the possibility to sense the nano-crystal facets by appropriate choice of the substrate in ambient conditions.

  9. Sensing the facet orientation in silver nano-plates using scanning Kelvin probe microscopy in air

    International Nuclear Information System (INIS)

    Abdellatif, M.H.; Salerno, M.; Polovitsyn, Anatolii; Marras, Sergio; De Angelis, Francesco

    2017-01-01

    Highlights: • The surface potential of drop cast nanocrystals was measured by SKPM in ambient air. • The nanocrystal facet work function was derived by theory. • By comparing theory and experiment we distinguished the nanocrystal facets. • Nanocrystal facet control is of practical interest for optoelectronic devices. - Abstract: The work function of nano-materials is important for a full characterization of their electronic properties. Because the band alignment, band bending and electronic noise are very sensitive to work function fluctuations, the dependence of the work function of nano-scale crystals on facet orientation can be a critical issue in optimizing optoelectronic devices based on these materials. We used scanning Kelvin probe microscopy to assess the local work function on samples of silver nano-plates at sub-micrometric spatial resolution. With the appropriate choice of the substrate and based on statistical analysis, it was possible to distinguish the surface potential of the different facets of silver nano-plates even if the measurements were done in ambient conditions without the use of vacuum. A phenomenological model was used to calculate the differences of facet work function of the silver nano-plates and the corresponding shift in Fermi level. This theoretical prediction and the experimentally observed difference in surface potential on the silver nano-plates were in good agreement. Our results show the possibility to sense the nano-crystal facets by appropriate choice of the substrate in ambient conditions.

  10. Synthesis of ultrathin face-centered-cubic Au@Pt and Au@Pd core-shell nanoplates from hexagonal-close-packed Au square sheets

    KAUST Repository

    Fan, Zhanxi; Zhu, Yihan; Huang, Xiao; Han, Yu; Wang, Qingxiao; Liu, Qing; Huang, Ying; Gan, Chee Lip; Zhang, Hua

    2015-01-01

    @Pd rhombic nanoplates, respectively. We believe that these findings will shed new light on the synthesis of novel noble bimetallic nanostructures. Phase change: Ultrathin Au@Pt and Au@Pd core-shell nanoplates were prepared from Au square sheets. A phase

  11. Hydrothermal synthesis of p-type nanocrystalline NiO nanoplates for high response and low concentration hydrogen gas sensor application

    KAUST Repository

    Nakate, Umesh T.; Lee, Gun Hee; Ahmad, Rafiq; Patil, Pramila; Bhopate, Dhanaji P.; Hahn, Y.B.; Yu, Y.T.; Suh, Eun-kyung

    2018-01-01

    High quality nanocrystalline NiO nanoplates were synthesized using surfactant and template free hydrothermal route. The gas sensing properties of NiO nanoplates were investigated. The nanoplates morphology of NiO with average thickness ~20 nm and diameter ~100 nm has been confirmed by FE-SEM and TEM. Crystalline quality of NiO has been studied using HRTEM and SAED techniques. Structural properties and elemental compositions have been analysed by XRD and energy dispersive spectrometer (EDS) respectively. The detailed investigation of structural parameters has been carried out. The optical properties of NiO were analyzed from UV-Visible and photoluminescence spectra. NiO nanoplates have good selectivity towards hydrogen (H2) gas. The lowest H2 response of 3% was observed at 2 ppm, whereas 90% response was noted for 100 ppm at optimized temperature of 200 °C with response time 180 s. The H2 responses as functions of different operating temperature as well as gas concentrations have been studied along with sensor stability. The hydrogen sensing mechanism was also elucidated.

  12. Hydrothermal synthesis of p-type nanocrystalline NiO nanoplates for high response and low concentration hydrogen gas sensor application

    KAUST Repository

    Nakate, Umesh T.

    2018-05-30

    High quality nanocrystalline NiO nanoplates were synthesized using surfactant and template free hydrothermal route. The gas sensing properties of NiO nanoplates were investigated. The nanoplates morphology of NiO with average thickness ~20 nm and diameter ~100 nm has been confirmed by FE-SEM and TEM. Crystalline quality of NiO has been studied using HRTEM and SAED techniques. Structural properties and elemental compositions have been analysed by XRD and energy dispersive spectrometer (EDS) respectively. The detailed investigation of structural parameters has been carried out. The optical properties of NiO were analyzed from UV-Visible and photoluminescence spectra. NiO nanoplates have good selectivity towards hydrogen (H2) gas. The lowest H2 response of 3% was observed at 2 ppm, whereas 90% response was noted for 100 ppm at optimized temperature of 200 °C with response time 180 s. The H2 responses as functions of different operating temperature as well as gas concentrations have been studied along with sensor stability. The hydrogen sensing mechanism was also elucidated.

  13. Synthesis and characterization of NiCo_2O_4 nanoplates as efficient electrode materials for electrochemical supercapacitors

    International Nuclear Information System (INIS)

    Kim, Taehyun; Ramadoss, Ananthakumar; Saravanakumar, Balasubramaniam; Veerasubramani, Ganesh Kumar; Kim, Sang Jae

    2016-01-01

    Highlights: • NiCo_2O_4 nanoplates were synthesized through a facile approach. • The NiCo_2O_4 nanoplates electrode material exhibit a specific capacitance of 332 F g"−"1 at 5 mV s"−"1. • The fabricated NiCo_2O_4 electrode reveals 86% retention of initial capacitance after 2000 cycles. - Abstract: In the present work, NiCo_2O_4 nanoplates were prepared by a facile, low temperature, hydrothermal method, followed by thermal annealing and used supercapacitor applications. The physico-chemical characterization of as-prepared materials were investigated by means of X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR) and field emission scanning electron microscopy (FE-SEM). The electrochemical measurements demonstrate that the NiCo_2O_4 nanoplates electrode (NC-5) exhibits a high specific capacitance of 332 F g"−"1 at a scan rate of 5 mV s"−"1 and also retained about 86% of the initial specific capacitance value even after 2000 cycles at a current density of 2.5 A g"−"1. These results suggest that the fabricated electrode material has huge potential as a novel electrode material for electrochemical capacitors.

  14. Inhibition of growth of S. epidermidis by hydrothermally synthesized ZnO nanoplates

    Science.gov (United States)

    Abinaya, C.; Mayandi, J.; Osborne, J.; Frost, M.; Ekstrum, C.; Pearce, J. M.

    2017-07-01

    The antibacterial effect of zinc oxide (ZnO#1) as prepared and annealed (ZnO#2) at 400 °C, Cu doped ZnO (CuZnO), and Ag doped ZnO (AgZnO) nanoplates on Staphylococcus epidermidis was investigated for the inhibition and inactivation of cell growth. The results shows that pure ZnO and doped ZnO samples exhibited antibacterial activity against Staphylococcus epidermidis (S. epidermidis) as compared to tryptic soy broth (TSB). Also it is observed that S. epidermidis was extremely sensitive to treatment with ZnO nanoplates and it is clear that the effect is not purely depend on Cu/Ag. Phase identification of a crystalline material and unit cell dimensions were studied by x-ray powder diffraction (XRD). The scanning electron microscopy (SEM) provides information on sample’s surface topography and the EDX confirms the presence of Zn, O, Cu and Ag. X-ray photo-electron spectroscopy (XPS) was used to analyze the elemental composition and electronic state of the elements that exist within the samples. These studies confirms the formation of nanoplates and the presence of Zn, O, Ag, Cu with the oxidation states  +2, -2, 0 and  +2 respectively. These results indicates promising antibacterial applications of these ZnO-based nanoparticles synthesized with low-cost hydrothermal methods.

  15. Infrared reflection spectra of multilayer epitaxial heterostructures with embedded InAs and GaAs layers

    International Nuclear Information System (INIS)

    Seredin, P. V.; Domashevskaya, E. P.; Lukin, A. N.; Arsent'ev, I. N.; Vinokurov, D. A.; Tarasov, I. S.

    2008-01-01

    The effect of the thickness of embedded InAs and GaAs layers on the infrared reflection spectra of lattice vibrations for AlInAs/InAs/AlInAs, InGaAs/GaAs/InGaAs, and AlInAs/InGaAs/GaAs/InGaAs/AlInAs multilayer epitaxial heterostructures grown by MOC hydride epitaxy on InP (100) substrates is studied. Relative stresses emerging in the layers surrounding the embedded layers with variation in the number of monolayers from which the quantum dots are formed and with variation the thickness of the layers themselves surrounding the embedded layers are evaluated.

  16. Evaluation of pulmonary and systemic toxicity following lung exposure to graphite nanoplates: a member of the graphene-based nanomaterial family.

    Science.gov (United States)

    Roberts, Jenny R; Mercer, Robert R; Stefaniak, Aleksandr B; Seehra, Mohindar S; Geddam, Usha K; Chaudhuri, Ishrat S; Kyrlidis, Angelos; Kodali, Vamsi K; Sager, Tina; Kenyon, Allison; Bilgesu, Suzan A; Eye, Tracy; Scabilloni, James F; Leonard, Stephen S; Fix, Natalie R; Schwegler-Berry, Diane; Farris, Breanne Y; Wolfarth, Michael G; Porter, Dale W; Castranova, Vincent; Erdely, Aaron

    2016-06-21

    Graphene, a monolayer of carbon, is an engineered nanomaterial (ENM) with physical and chemical properties that may offer application advantages over other carbonaceous ENMs, such as carbon nanotubes (CNT). The goal of this study was to comparatively assess pulmonary and systemic toxicity of graphite nanoplates, a member of the graphene-based nanomaterial family, with respect to nanoplate size. Three sizes of graphite nanoplates [20 μm lateral (Gr20), 5 μm lateral (Gr5), and m(2). At the low dose, none of the Gr materials induced toxicity. At the high dose, Gr20 and Gr5 exposure increased indices of lung inflammation and injury in lavage fluid and tissue gene expression to a greater degree and duration than Gr1 and CB. Gr5 and Gr20 showed no or minimal lung epithelial hypertrophy and hyperplasia, and no development of fibrosis by 2 months post-exposure. In addition, the aorta and liver inflammatory and acute phase genes were transiently elevated in Gr5 and Gr20, relative to Gr1. Pulmonary and systemic toxicity of graphite nanoplates may be dependent on lateral size and/or surface reactivity, with the graphite nanoplates > 5 μm laterally inducing greater toxicity which peaked at the early time points post-exposure relative to the 1-2 μm graphite nanoplate.

  17. ZnO nanorods/ZnS·(1,6-hexanediamine)(0.5) hybrid nanoplates hierarchical heteroarchitecture with improved electrochemical catalytic properties for hydrazine.

    Science.gov (United States)

    Wu, Zhengcui; Wu, Yaqin; Pei, Tonghui; Wang, Huan; Geng, Baoyou

    2014-03-07

    Novel hierarchical heteronanostructures of ZnO nanorods/ZnS·(HDA)0.5 (HDA = 1,6-hexanediamine) hybrid nanoplates on a zinc substrate are successfully synthesized on a large scale by combining hydrothermal growth (for ZnO nanorods) and liquid chemical conversion (for ZnS·(HDA)0.5 nanoplates) techniques. The formation of ZnS·(HDA)0.5 hybrid nanoplates branches takes advantage of the preferential binding of 1,6-hexanediamine on specific facets of ZnS, which makes the thickening rate much lower than the lateral growth rate. The ZnS·(HDA)0.5 hybrid nanoplates have a layered structure with 1,6-hexanediamine inserted into interlayers of wurtzite ZnS through the bonding of nitrogen. The number density and thickness of the secondary ZnS·(HDA)0.5 nanoplates can be conveniently engineered by variation of the sulfur source and straightforward adjustment of reactant concentrations such as 1,6-hexanediamine and the sulfur source. The fabricated ZnO/ZnS·(HDA)0.5 heteronanostructures show improved electrochemical catalytic properties for hydrazine compared with the primary ZnO nanorods. Due to its simplicity and efficiency, this approach could be similarly used to fabricate varieties of hybrid heterostructures made of materials with an intrinsic large lattice mismatch.

  18. Fabrication of nanoplate resonating structures via micro-masonry

    International Nuclear Information System (INIS)

    Bhaswara, A; Legrand, B; Mathieu, F; Nicu, L; Leichle, T; Keum, H; Rhee, S; Kim, S

    2014-01-01

    Advantages of using nanoscale membrane and plate resonators over more common cantilever shapes include higher quality factor (Q factor) for an equivalent mass and better suitability to mass sensing applications in fluid. Unfortunately, the current fabrication methods used to obtain such membranes and plates are limited in terms of materials and thickness range, and can potentially cause stiction. This study presents a new method to fabricate nanoplate resonating structures based on micro-masonry, which is the advanced form of the transfer printing technique. Nanoplate resonators were fabricated by transfer printing 0.34 µm thick square-shaped silicon plates by means of polydimethylsiloxane microtip stamps on top of silicon oxide base structures displaying 20 µm diameter cavities, followed by a thermal annealing step to create a rigid bond. Typical resulting suspended structures display vibration characteristics, i.e. a resonance frequency of a few MHz and Q factors above 10 in air at atmospheric pressure, which are in accordance with theory. Moreover, the presented fabrication method enables the realization of multiple suspended structures in a single step and on the same single base, without mechanical crosstalk between the resonators. This work thus demonstrates the suitability and the advantages of the micro-masonry technique for the fabrication of plate resonators for mass sensing purpose. (paper)

  19. Towards quantitative three-dimensional characterisation of buried InAs quantum dots

    DEFF Research Database (Denmark)

    Kadkhodazadeh, Shima; Semenova, Elizaveta; Schubert, Martin

    2011-01-01

    InAs quantum dots grown on InP or InGaAsP are used for optical communication applications operating in the 1.3 – 1.55 μm wavelength range. It is generally understood that the optical properties of such dots are highly dependent on their structural and chemical profiles. However, morphological...... and compositional measurements of quantum dots using transmission electron microscopy can be ambiguous because the recorded signal is usually a projection through the thickness of the specimen. Here, we discuss the application of scanning transmission electron microscopy tomography to the morphological and chemical...... characterisation of surface and buried quantum dots. We highlight some of the challenges involved and introduce a new specimen preparation method for creating needle-shaped specimens that each contain multiple dots and are suitable for both scanning transmission electron microscopy tomography and atom probe...

  20. Towards quantitative three-dimensional characterisation of buried InAs quantum dots

    International Nuclear Information System (INIS)

    Kadkhodazadeh, S; Dunin-Borkowski, R E; Semenova, E S; Schubert, M; Yvind, K; Thuvander, M; Stiller, K M

    2011-01-01

    InAs quantum dots grown on InP or InGaAsP are used for optical communication applications operating in the 1.3 – 1.55 μm wavelength range. It is generally understood that the optical properties of such dots are highly dependent on their structural and chemical profiles. However, morphological and compositional measurements of quantum dots using transmission electron microscopy can be ambiguous because the recorded signal is usually a projection through the thickness of the specimen. Here, we discuss the application of scanning transmission electron microscopy tomography to the morphological and chemical characterisation of surface and buried quantum dots. We highlight some of the challenges involved and introduce a new specimen preparation method for creating needle-shaped specimens that each contain multiple dots and are suitable for both scanning transmission electron microscopy tomography and atom probe tomography.

  1. 20 CFR 668.860 - What cash management procedures apply to INA grant funds?

    Science.gov (United States)

    2010-04-01

    ... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false What cash management procedures apply to INA... Administrative Requirements § 668.860 What cash management procedures apply to INA grant funds? INA grantees must... implement the Cash Management Improvement Act, found at 31 CFR part 205, apply by law to most recipients of...

  2. La costituzione dell’INA e il monopolio statale delle assicurazioni (1912-1922 = The constitution of INA and the state monopoly of insurance (1912-1922

    Directory of Open Access Journals (Sweden)

    Serena Potito

    2012-07-01

    Full Text Available Il saggio –basato principalmente su documenti attualmente conservati presso l’Archivio Storico dell’INA, a Roma– esamina le vicende legate alla nascita dell’Istituto, costituito in un regime transitorio di monopolio relativo nel settore delle assicurazioni sulla vita.A causa del suo significato economico e politico, questa speciale forma di monopolio statale diede luogo a molte reazioni nell’ambito finanziario e politico nazionale, pertanto l’INA iniziò i primi anni di attività in una situazione conflittuale ed incerta.Il saggio inoltre approfondisce le ripercussioni sul mercato assicurativo internazionale in seguito alla nascita dell’INA.Durante il decennio di monopolio parziale dell’Istituto nel settore delle assicurazioni sulla vita (1912-1922, le compagnie di assicurazione straniere ritennero compromessi i loro interessi finanziari nel mercato italiano, e lo osteggiarono fino al 1923, quando una nuova legge riformò il mercato assicurativo sulla vita, abolendo il regime di monopolio.The essay –mainly based on documents actually preserved in the Historical Archives of INA, in Rome– examines the events connected with the foundation of the Institute, established in a transient condition of partial monopoly system in life insurance sector. Because of its economic and political meaning, this special form of state monopoly gave rise to many reactions in the financial and political national context, and so INA started its first years of activity in a troubled and unstable situation. The essay also discusses about the repercussions on international insurance market in consequence of the foundation of INA.During the ten-year perior of partial monopoly of the Institute in life insurance sector (1912-1922, foreign insurance companies deemed their financial interest in Italian market jeopardized, and contrasted with it until 1923, when a new act reformed life insurance market, abrogating monopoly system. 

  3. Facile design and synthesis of Li-rich nanoplates cathodes with habit-tuned crystal for lithium ion batteries

    Science.gov (United States)

    Li, Jili; Jia, Tiekun; Liu, Kai; Zhao, Junwei; Chen, Jian; Cao, Chuanbao

    2016-11-01

    Li-ion batteries with high-energy and high-power density are pursued to apply in the electronic vehicles and renewable energy storage systems. In this work, layered Li-rich transition-metal oxide cathode Li1.2Ni0.2Mn0.6O2 nanoplates with enhanced growth of {010} planes (LNMO-NP) is successfully synthesized through a facile and versatile strategy. Ethylene glycol plays an important role in the formation of LNMO-NP nanoplates with {010} electrochemically active surface planes exposure. As cathode for Li-ion batteries, LNMO-NP demonstrates a high specific discharge capacity of 270.2 mAh g-1 at 0.1 C (1 C = 300 mA g-1) and an excellent rate capability. The good electrochemical performance can be attributed to the nanoplates with the growth of {010} electrochemically active planes which is in favor of Li+ intercalation/deintercalation.

  4. Photoreflectance study of InAs ultrathin layer embedded in Si-delta-doped GaAs/AlGaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Dhifallah, I., E-mail: ines.dhifallah@gmail.co [Laboratoire de Photovoltaique, des Semiconducteurs et des Nanostructures, Centre de Recherche et des Technologies de l' energie, BP 95 Hammam-Lif 2050 (Tunisia); Daoudi, M.; Bardaoui, A. [Laboratoire de Photovoltaique, des Semiconducteurs et des Nanostructures, Centre de Recherche et des Technologies de l' energie, BP 95 Hammam-Lif 2050 (Tunisia); Eljani, B. [Unite de recherche sur les Hetero-Epitaxie et Applications, Faculte des Sciences de Monastir (Tunisia); Ouerghi, A. [Laboratoire de Photonique et de Nanostructures, CNRS Route de Nozay 91 46a0, Marcoussis (France); Chtourou, R. [Laboratoire de Photovoltaique, des Semiconducteurs et des Nanostructures, Centre de Recherche et des Technologies de l' energie, BP 95 Hammam-Lif 2050 (Tunisia)

    2011-05-15

    Photoreflectance and photoluminescence studies were performed to characterize InAs ultrathin layer embedded in Si-delta-doped GaAs/AlGaAs high electron mobility transistors. These structures were grown by Molecular Beam Epitaxy on (1 0 0) oriented GaAs substrates with different silicon-delta-doped layer densities. Interband energy transitions in the InAs ultrathin layer quantum well were observed below the GaAs band gap in the photoreflectance spectra, and assigned to electron-heavy-hole (E{sub e-hh}) and electron-light-hole (E{sub e-lh}) fundamental transitions. These transitions were shifted to lower energy with increasing silicon-{delta}-doping density. This effect is in good agreement with our theoretical results based on a self-consistent solution of the coupled Schroedinger and Poisson equations and was explained by increased escape of photogenerated carriers and enhanced Quantum Confined Stark Effect in the Si-delta-doped InAs/GaAs QW. In the photoreflectance spectra, not only the channel well interband energy transitions were observed, but also features associated with the GaAs and AlGaAs bulk layers located at about 1.427 and 1.8 eV, respectively. By analyzing the Franz-Keldysh Oscillations observed in the spectral characteristics of Si-{delta}-doped samples, we have determined the internal electric field introduced by ionized Si-{delta}-doped centers. We have observed an increase in the electric field in the InAs ultrathin layer with increasing silicon content. The results are explained in terms of doping dependent ionized impurities densities and surface charges. - Research highlights: {yields} Studying HEMTs structures with different silicon doping content. {yields} An increase of the electric field in the InAs layer with increasing Si content. {yields} The interband energy transitions in the HEMTs structures have been obtained from PR. {yields} Experimental and theoretical values of transitions energies were in good agreement.

  5. Photoreflectance study of InAs ultrathin layer embedded in Si-delta-doped GaAs/AlGaAs quantum wells

    International Nuclear Information System (INIS)

    Dhifallah, I.; Daoudi, M.; Bardaoui, A.; Eljani, B.; Ouerghi, A.; Chtourou, R.

    2011-01-01

    Photoreflectance and photoluminescence studies were performed to characterize InAs ultrathin layer embedded in Si-delta-doped GaAs/AlGaAs high electron mobility transistors. These structures were grown by Molecular Beam Epitaxy on (1 0 0) oriented GaAs substrates with different silicon-delta-doped layer densities. Interband energy transitions in the InAs ultrathin layer quantum well were observed below the GaAs band gap in the photoreflectance spectra, and assigned to electron-heavy-hole (E e-hh ) and electron-light-hole (E e-lh ) fundamental transitions. These transitions were shifted to lower energy with increasing silicon-δ-doping density. This effect is in good agreement with our theoretical results based on a self-consistent solution of the coupled Schroedinger and Poisson equations and was explained by increased escape of photogenerated carriers and enhanced Quantum Confined Stark Effect in the Si-delta-doped InAs/GaAs QW. In the photoreflectance spectra, not only the channel well interband energy transitions were observed, but also features associated with the GaAs and AlGaAs bulk layers located at about 1.427 and 1.8 eV, respectively. By analyzing the Franz-Keldysh Oscillations observed in the spectral characteristics of Si-δ-doped samples, we have determined the internal electric field introduced by ionized Si-δ-doped centers. We have observed an increase in the electric field in the InAs ultrathin layer with increasing silicon content. The results are explained in terms of doping dependent ionized impurities densities and surface charges. - Research highlights: → Studying HEMTs structures with different silicon doping content. → An increase of the electric field in the InAs layer with increasing Si content. → The interband energy transitions in the HEMTs structures have been obtained from PR. → Experimental and theoretical values of transitions energies were in good agreement.

  6. In situ synthesis of Bi2S3 sensitized WO3 nanoplate arrays with less interfacial defects and enhanced photoelectrochemical performance

    Science.gov (United States)

    Liu, Canjun; Yang, Yahui; Li, Wenzhang; Li, Jie; Li, Yaomin; Chen, Qiyuan

    2016-03-01

    In this study, Bi2S3 sensitive layer has been grown on the surface of WO3 nanoplate arrays via an in situ approach. The characterization of samples were carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and ultraviolet-visible absorption spectroscopy (UV-vis). The results show that the Bi2S3 layer is uniformly formed on the surface of WO3 nanoplates and less interfacial defects were observed in the interface between the Bi2S3 and WO3. More importantly, the Bi2S3/WO3 films as photoanodes for photoelectrochemical (PEC) cells display the enhanced PEC performance compared with the Bi2S3/WO3 films prepared by a sequential ionic layer adsorption reaction (SILAR) method. In order to understand the reason for the enhanced PEC properties, the electron transport properties of the photoelectrodes were studied by using the transient photocurrent spectroscopy and intensity modulated photocurrent spectroscopy (IMPS). The Bi2S3/WO3 films prepared via an in situ approach have a greater transient time constant and higher electron transit rate. This is most likely due to less interfacial defects for the Bi2S3/WO3 films prepared via an in situ approach, resulting in a lower resistance and faster carrier transport in the interface between WO3 and Bi2S3.

  7. Wet-chemical passivation of InAs: toward surfaces with high stability and low toxicity.

    Science.gov (United States)

    Jewett, Scott A; Ivanisevic, Albena

    2012-09-18

    In a variety of applications where the electronic and optical characteristics of traditional, siliconbased materials are inadequate, recently researchers have employed semiconductors made from combinations of group III and V elements such as InAs. InAs has a narrow band gap and very high electron mobility in the near-surface region, which makes it an attractive material for high performance transistors, optical applications, and chemical sensing. However, silicon-based materials remain the top semiconductors of choice for biological applications, in part because of their relatively low toxicity. In contrast to silicon, InAs forms an unstable oxide layer under ambient conditions, which can corrode over time and leach toxic indium and arsenic components. To make InAs more attractive for biological applications, researchers have investigated passivation, chemical and electronic stabilization, of the surface by adlayer adsorption. Because of the simplicity, low cost, and flexibility in the type of passivating molecule used, many researchers are currently exploring wet-chemical methods of passivation. This Account summarizes much of the recent work on the chemical passivation of InAs with a particular focus on the chemical stability of the surface and prevention of oxide regrowth. We review the various methods of surface preparation and discuss how crystal orientation affects the chemical properties of the surface. The correct etching of InAs is critical as researchers prepare the surface for subsequent adlayer adsorption. HCl etchants combined with a postetch annealing step allow the tuning of the chemical properties in the near-surface region to either arsenic- or indium-rich environments. Bromine etchants create indium-rich surfaces and do not require annealing after etching; however, bromine etchants are harsh and potentially destructive to the surface. The simultaneous use of NH(4)OH etchants with passivating molecules prevents contact with ambient air that can

  8. Fabrication and optical properties of multishell InAs quantum dots on GaAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Xin; Zhang, Xia, E-mail: xzhang@bupt.edu.cn; Li, Junshuai; Cui, Jiangong; Ren, Xiaomin [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China)

    2015-02-07

    Hybrid nanostructures combining nanowires with quantum dots promote the development of nanoelectronic and nanophotonic devices with integrated functionalities. In this work, we present a complex nanostructure with multishell quantum dots grown on nanowires. 1–4 shells of Stranski-Krastanov InAs quantum dots are grown on the sidewalls of GaAs nanowires by metal organic chemical vapor deposition. Different dot shells are separated by 8 nm GaAs spacer shells. With increasing the number of shells, the quantum dots become sparser and tend to align in one array, which is caused by the shrinkage of facets on which dots prefer to grow as well as the strain fields produced by the lower set of dots which influences the migration of In adatoms. The size of quantum dots increases with the increase of shell number due to enhanced strain fields coupling. The spectra of multishell dots exhibit multiwavelength emission, and each peak corresponds to a dot shell. This hybrid structure may serve as a promising element in nanowire intermediate band solar cells, infrared nanolasers, and photodetectors.

  9. A modified gradient approach for the growth of low-density InAs quantum dot molecules by molecular beam epitaxy

    Science.gov (United States)

    Sharma, Nandlal; Reuter, Dirk

    2017-11-01

    Two vertically stacked quantum dots that are electronically coupled, so called quantum dot molecules, are of great interest for the realization of solid state building blocks for quantum communication networks. We present a modified gradient approach to realize InAs quantum dot molecules with a low areal density so that single quantum dot molecules can be optically addressed. The individual quantum dot layers were prepared by solid source molecular beam epitaxy depositing InAs on GaAs(100). The bottom quantum dot layer has been grown without substrate rotation resulting in an In-gradient across the surface, which translated into a density gradient with low quantum dot density in a certain region of the wafer. For the top quantum dot layer, separated from the bottom quantum dot layer by a 6 nm thick GaAs barrier, various InAs amounts were deposited without an In-gradient. In spite of the absence of an In-gradient, a pronounced density gradient is observed for the top quantum dots. Even for an In-amount slightly below the critical thickness for a single dot layer, a density gradient in the top quantum dot layer, which seems to reproduce the density gradient in the bottom layer, is observed. For more or less In, respectively, deviations from this behavior occur. We suggest that the obvious influence of the bottom quantum dot layer on the growth of the top quantum dots is due to the strain field induced by the buried dots.

  10. Nonlocal strain gradient based wave dispersion behavior of smart rotating magneto-electro-elastic nanoplates

    Science.gov (United States)

    Ebrahimi, Farzad; Dabbagh, Ali

    2017-02-01

    Main object of the present research is an exact investigation of wave propagation responses of smart rotating magneto-electro-elastic (MEE) graded nanoscale plates. In addition, effective material properties of functionally graded (FG) nanoplate are presumed to be calculated using the power-law formulations. Also, it has been tried to cover both softening and stiffness-hardening behaviors of nanostructures by the means of employing nonlocal strain gradient theory (NSGT). Due to increasing the accuracy of the presented model in predicting shear deformation effects, a refined higher-order plate theory is introduced. In order to cover the most enormous circumstances, maximum amount of load generated by plate’s rotation is considered. Furthermore, utilizing a developed form of Hamilton’s principle, containing magneto-electric effects, the nonlocal governing equations of MEE-FG rotating nanoplates are derived. An analytical solution is obtained to solve the governing equations and validity of the solution method is proven by comparing results from present method with those of former attempts. At last, outcomes are plotted in the framework of some figures to show the influences of various parameters such as wave number, nonlocality, length scale parameter, magnetic potential, electric voltage, gradient index and angular velocity on wave frequency, phase velocity and escape frequency of the examined nanoplate.

  11. Synthesis of a mesoporous single crystal Ga2O3 nanoplate with improved photoluminescence and high sensitivity in detecting CO.

    Science.gov (United States)

    Yan, Shicheng; Wan, Lijuan; Li, Zhaosheng; Zhou, Yong; Zou, Zhigang

    2010-09-14

    A new approach is proposed to synthesize a mesoporous single crystal Ga(2)O(3) nanoplate by heating a single crystal nanoplate of GaOOH, which involves an ion exchange between KGaO(2) and CH(3)COOH at room temperature for the formation of GaOOH and pseudomorphic and topotactic phase transformation from GaOOH to Ga(2)O(3).

  12. Electronic and optical properties of graphene-like InAs: An ab initio study

    Science.gov (United States)

    Sohrabi, Leila; Boochani, Arash; Ali Sebt, S.; Mohammad Elahi, S.

    2018-03-01

    The present work initially investigates structural, optical, and electronic properties of graphene-like InAs by using the full potential linear augmented plane wave method in the framework of density functional theory and is then compared with the bulk Indium Arsenide in the wurtzite phase. The lattice parameters are optimized with GGA-PBE and LDA approximations for both 2D- and 3D-InAs. In order to study the electronic properties of graphene-like InAs and bulk InAs in the wurtzite phase, the band gap is calculated by GGA-PBG and GGA-EV approximations. Moreover, optical parameters of graphene-like InAs and bulk InAs such as the real and imaginary parts of dielectric function, electron energy loss function, refractivity, extinction and absorption coefficients, and optical conductivity are investigated. Plasmonic frequencies of 2D- and 3D-InAs are also calculated by using maximum electron energy loss function and the roots of the real part of the dielectric function.

  13. On the thermal growth and properties of doped TiO2 and In2O3 elongated nanostructures and nanoplates

    International Nuclear Information System (INIS)

    Cremades, A.; Herrera, M.; Bartolomé, J.; Vásquez, G.C.; Maestre, D.; Piqueras, J.

    2014-01-01

    In this work, the driving forces behind the growth mechanisms of In 2 O 3 and TiO 2 micro- and nano-structures grown by an evaporation–solidification method are discussed. Effective or limited doping incorporation and its influence on the growth and morphology of the low dimensional structures are also assessed. A dislocation driven growth mechanism is proposed for indium oxide, indium tin oxide (ITO) and zinc doped indium oxide (IZO) nanowires. This growth mechanism is extended to the growth of IZO nano-plates. On the other hand, different low dimensional TiO 2 morphologies, mainly nanowires, needles, and bidimensional leaf-like nanostructures, have been obtained by an anisotropic induced growth. By introducing Cr in the precursor mixture, needles are formed showing stepped lateral faces related to oxygen defect stoichiometry areas as observed by EDS mapping

  14. Synthesis of α-MoO3 nanoplates using organic aliphatic acids and investigation of sunlight enhanced photodegradation of organic dyes

    International Nuclear Information System (INIS)

    Kumar, V. Vinod; Gayathri, K.; Anthony, Savarimuthu Philip

    2016-01-01

    Graphical abstract: Thermodynamically stable α-MoO 3 nanoplates and nanorods were synthesized using organic structure controlling agents and demonstrated sun light enhanced photocatalytic degradation of methylene blue (MB) and rhodamine blue (Rh-B) dyes in aqueous solution. - Highlights: • α-MoO 3 hexagonal nanoplates using organic structure controlling agents. • Tunable optical band gap of MoO 3 . • Demonstrated strong sun light mediated enhanced photodegradation of methylene blue and rhodamine blue. • Photodegradation did not use any other external oxidizing agents. - Abstract: Thermodynamically stable α-MoO 3 nanoplates were synthesized using organic aliphatic acids as structure controlling agents and investigated photocatalytic degradation of methylene blue (MB) and rhodamine blue (Rh-B) in presence of sun light. Three different organic aliphatic acids, citric acid (CA), tartaric acid (TA) and ethylene diamine tetra-acetic acid (EDTA), were employed to control morphologies. CA and TA predominantly produced extended hexagonal plates where EDTA gave nanorods as well as nanoplates. PXRD studies confirmed the formation of α-MoO 3 nanoparticles. HR-TEM and FE-SEM reveal the formation of plate morphologies with 20–40 nm thickness, 50–100 nm diameter and 600 nm lengths. The different morphologies of α-MoO 3 nanoparticles lead to the tunable optical band gap between 2.80 and 2.98 eV which was obtained from diffused reflectance spectra (DRS). Interestingly, the synthesized α-MoO 3 nanoplates exhibited strong photocatalytic degradation of MB and Rh-B up to 99% in presence of sun light without using any oxidizing agents.

  15. The influence of atmosphere on performance of pure-phase WZ and ZB InAs nanowire transistors.

    Science.gov (United States)

    Ullah, Abu Rifat; Joyce, Hannah J; Tan, Hoe; Jagadish, Chennupati; Micolich, Adam P

    2017-09-21

    We compare the characteristics of phase-pure MOCVD grown ZB and WZ InAs nanowire transistors in several atmospheres: air, dry pure N2 and O2, and N2 bubbled through liquid H2O and alcohols to identify whether phase-related structural/surface differences affect their response. Both WZ and ZB give poor gate characteristics in dry state. Adsorption of polar species reduces off-current by 2-3 orders of magnitude, increases on-off ratio and significantly reduces sub-threshold slope. The key difference is the greater sensitivity of WZ to low adsorbate level. We attribute this to facet structure and its influence on the separation between conduction electrons and surface adsorption sites. We highlight the important role adsorbed species play in nanowire device characterisation. WZ is commonly thought superior to ZB in InAs nanowire transistors. We show this is an artefact of the moderate humidity found in ambient laboratory conditions: WZ and ZB perform equally poorly in the dry gas limit yet equally well in the wet gas limit. We also highlight the vital role density-lowering disorder has in improving gate characteristics, be it stacking faults in mixed-phase WZ or surface adsorbates in pure-phase nanowires. © 2017 IOP Publishing Ltd.

  16. Ultrathin NiO/NiFe2O4 Nanoplates Decorated Graphene Nanosheets with Enhanced Lithium Storage Properties

    International Nuclear Information System (INIS)

    Du, Dejian; Yue, Wenbo; Fan, Xialu; Tang, Kun; Yang, Xiaojing

    2016-01-01

    Highlights: • Ultrathin NiO/NiFe 2 O 4 nanoplates derived from NiFe layered double hydroxides are fabricated on the graphene. • NiO/NiFe 2 O 4 nanoplates on the graphene show superior electrochemical performance compared to pure NiO/NiFe 2 O 4 aggregates. • The effects of the content and the particle size/component of NiO/NiFe 2 O 4 on the electrochemical performances are studied. • Graphene-encapsulated NiO/NiFe 2 O 4 is prepared and shows slightly decreased performance compared to graphene-based composite. - Abstract: As anode materials for lithium-ion batteries, bicomponent metal oxide composites show high reversible capacities; but the morphology and particle size of the composites are hardly controllable, which may reduce their electrochemical properties. In this work, ultrathin NiO/NiFe 2 O 4 nanoplates with a diameter of 5 ∼ 7 nm and a thickness of ∼2 nm are controllably fabricated on the graphene derived from NiFe layered double hydroxides (NiFe-LDHs), and exhibit superior electrochemical performance compared to pure NiO/NiFe 2 O 4 aggregates without graphene. The nanosized NiO and NiFe 2 O 4 plates are separated from each other and the graphene substrate can prevent the aggregation of NiO/NiFe 2 O 4 as well as enhance the electronic conductivity of the composite, which is beneficial to improving the electrochemical performance. Moreover, the effects of the content and the particle size/component of NiO/NiFe 2 O 4 on the electrochemical performances are also studied in order to achieve optimal performance. Ultrathin NiO/NiFe 2 O 4 nanoplates are further encapsulated by graphene nanosheets and show slightly decreased performance compared to those supported by graphene nanosheets. The different electrochemical behaviors of graphene-containing composites may be attributed to the different interactions between graphene nanosheets and NiO/NiFe 2 O 4 nanoplates.

  17. Jezdecké stezky v kraji Vysočina

    OpenAIRE

    Bendeová, Tereza

    2014-01-01

    This bachelor thesis discusses the topic of riding trails in the Vysočina region. At the beginning I discuss the role of equestrian tourism in the Czech Republic. There are briefly described origins and conditions of riding trails in the regions and also the list of the public support and grants for development of equestrian tourism. The next part focuses on chosen region and characterizes its natural and cultural heritage. There are also described several trails through the Vysočina region. ...

  18. Visualizing Carrier Transport in Metal Halide Perovskite Nanoplates via Electric Field Modulated Photoluminescence Imaging.

    Science.gov (United States)

    Hu, Xuelu; Wang, Xiao; Fan, Peng; Li, Yunyun; Zhang, Xuehong; Liu, Qingbo; Zheng, Weihao; Xu, Gengzhao; Wang, Xiaoxia; Zhu, Xiaoli; Pan, Anlian

    2018-05-09

    Metal halide perovskite nanostructures have recently been the focus of intense research due to their exceptional optoelectronic properties and potential applications in integrated photonics devices. Charge transport in perovskite nanostructure is a crucial process that defines efficiency of optoelectronic devices but still requires a deep understanding. Herein, we report the study of the charge transport, particularly the drift of minority carrier in both all-inorganic CsPbBr 3 and organic-inorganic hybrid CH 3 NH 3 PbBr 3 perovskite nanoplates by electric field modulated photoluminescence (PL) imaging. Bias voltage dependent elongated PL emission patterns were observed due to the carrier drift at external electric fields. By fitting the drift length as a function of electric field, we obtained the carrier mobility of about 28 cm 2 V -1 S -1 in the CsPbBr 3 perovskite nanoplate. The result is consistent with the spatially resolved PL dynamics measurement, confirming the feasibility of the method. Furthermore, the electric field modulated PL imaging is successfully applied to the study of temperature-dependent carrier mobility in CsPbBr 3 nanoplates. This work not only offers insights for the mobile carrier in metal halide perovskite nanostructures, which is essential for optimizing device design and performance prediction, but also provides a novel and simple method to investigate charge transport in many other optoelectronic materials.

  19. Silver nanoplates with ground or metastable structures obtained from template-free two-phase aqueous/organic synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Zhelev, Doncho V., E-mail: dontcho.jelev@nih.gov; Zheleva, Tsvetanka S. [Army Research Laboratory, 2800 Adelphi, Maryland 20783 (United States)

    2014-01-28

    Silver has unique electrical, catalytic, and plasmonic characteristics and has been widely sought for fabrication of nanostructures. The properties of silver nanostructures are intimately coupled to the structure of silver crystals. Two crystal structures are known for silver: the stable (ground) state cubic face centered 3C-Ag structure and the metastable hexagonal 4H-Ag structure. Recently, Chackraborty et al. [J. Phys.: Condens. Matter 23, 325401 (2011)] discovered a low density, highly reactive metastable hexagonal 2H-Ag structure accessible during electrodeposition of silver nanowires in porous anodic alumina templates. This 2H-Ag structure has enhanced electrical and catalytic characteristics. In the present work we report template-free synthesis of silver nanoplates with the metastable 2H-Ag crystal structure, which appears together with the ground 3C-Ag and the metastable 4H-Ag structures in a two-phase solution synthesis with citric acid as the capping agent. The capacity of citric acid to stabilize both the stable and the metastable structures is explained by its preferential binding to the close packed facets of Ag crystals, which are the (111) planes for 3C-Ag and the (0001) planes for 4H-Ag and 2H-Ag. Nanoplate morphology and structure are characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The synthesized nanoplates have thickness from 15 to 17 nm and edge length from 1 to 10 μm. Transmission electron microscopy selected area electron diffraction is used to uniquely identify and distinguish between nanoplates with 2H-Ag or 4H-Ag or 3C-Ag structures.

  20. Enhanced visible-light activities for PEC water reduction of CuO nanoplates by coupling with anatase TiO2 and mechanism

    International Nuclear Information System (INIS)

    Li, Zhijun; Qu, Yang; He, Guangwen; Humayun, Muhammad; Chen, Shuangying; Jing, Liqiang

    2015-01-01

    Graphical abstract: - Highlights: • CuO nanoplates were successfully prepared as photocathodes for PEC water reduction. • Visible-light activity for PEC water reduction is improved after coupling with TiO 2 . • Improved PEC performance is attributed to the enhanced visible-excited charge separation. • Enhanced charge separation results from high-energy electron transfer from CuO to TiO 2 . - Abstract: CuO nanoplates were prepared by a feasible hydrothermal method, and then utilized as photocathodes for photoelectrochemical (PEC) water reduction in a neutral medium under visible-light irradiation. It is clearly demonstrated that the visible-light activities of the resulting nanoplates for PEC water reduction could be greatly improved after coupling with a proper amount of nanocrystalline anatase TiO 2 . This is attributed to the enhanced charge separation in the fabricated TiO 2 /CuO nanoplate composites mainly based on the atmosphere-controlled steady-state surface photovoltage spectra. Moreover, it is suggested that the enhanced charge separation resulted from the transfer of visible-light-excited high-energy electrons from CuO to TiO 2 as confirmed from the single-wavelength PEC behavior

  1. Size-dependent bending, buckling and vibration of higher-order shear deformable magneto-electro-thermo-elastic rectangular nanoplates

    Science.gov (United States)

    Gholami, Raheb; Ansari, Reza; Gholami, Yousef

    2017-06-01

    The aim of the present study is to propose a unified size-dependent higher-order shear deformable plate model for magneto-electro-thermo-elastic (METE) rectangular nanoplates by adopting the nonlocal elasticity theory to capture the size effect, and by utilizing a generalized shape function to consider the effects of transverse shear deformation and rotary inertia. By considering various shape functions, the proposed plate model can be reduced to the nonlocal plate model based upon the Kirchhoff, Mindlin and Reddy plate theories, as well as the parabolic, trigonometric, hyperbolic and exponential shear deformation plate theories. The governing equations of motion and corresponding boundary conditions of METE nanoplates subjected to external in-plane, transverse loads as well as magnetic, electric and thermal loadings, are obtained using Hamilton’s principle. Then, as in some case studies, the static bending, buckling, and free vibration characteristics of simply-supported METE rectangular nanoplates are investigated based upon the Navier solution approach. Numerical results are provided in order to investigate the influences of various parameters including the nondimensional nonlocal parameter, type of transverse loading, temperature change, applied voltage, and external magnetic potential on the mechanical behaviors of METE nanoplates. Furthermore, comparisons are made between the results predicted by different nonlocal plate models by utilizing the developed unified nonlocal plate model and selecting the associated shape functions. It is illustrated that by using the presented unified nonlocal plate model, the development of a nonlocal plate model based upon any existing higher-order shear deformable plate theory is a simple task.

  2. Shape transformation of silver nanospheres to silver nanoplates induced by redox reaction of hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Parnklang, Tewarak; Lamlua, Banjongsak; Gatemala, Harnchana; Thammacharoen, Chuchaat [Department of Chemistry, Faculty of Science, Chulalongkorn University, 254 Phyathai Road, Patumwan, Bangkok 10330 (Thailand); Kuimalee, Surasak [Industrial Chemistry and Textile Technology Programme, Faculty of Science, Maejo University, Chiang Mai 50290 (Thailand); Lohwongwatana, Boonrat [Metallurgical Engineering Department, Faculty of Engineering, Chulalongkorn University, 254 Phyathai Road, Patumwan, Bangkok 10330 (Thailand); Ekgasit, Sanong, E-mail: sanong.e@chula.ac.th [Department of Chemistry, Faculty of Science, Chulalongkorn University, 254 Phyathai Road, Patumwan, Bangkok 10330 (Thailand)

    2015-03-01

    In this paper we demonstrate a simple and rapid shape transformation of silver nanospheres (AgNSs) to silver nanoplates (AgNPls) using the oxidation and reduction capabilities of hydrogen peroxide. AgNPls having tunable surface plasmon resonance across the visible region with average size of 40–100 nm and thickness of 10–15 nm can be fabricated within 2 min simply by adding H{sub 2}O{sub 2} into a colloid of AgNSs with average particle size of 7 nm. The efficiency of H{sub 2}O{sub 2} as a shape-transforming agent depends strongly on its concentration, pH of the AgNS colloid, and the employed stabilizers. H{sub 2}O{sub 2} oxidizes AgNSs to silver ions while concertedly reduces silver ions to silver atom necessary for the growth of AgNPls. The shape transformation reaction was conducted at a relatively low concentration of H{sub 2}O{sub 2} in order to minimize the oxidative dissolution while facilitating kinetically controlled growth of AgNPls under a near neutral pH. Polyvinyl-pyrrolidone is an effective steric stabilizer preventing aggregation while assisting the growth of AgNPls. Trisodium citrate inhibits the formation of AgNPls under the H{sub 2}O{sub 2} reduction as it forms a stable complex with silver ions capable of withstanding the weakly reducing power of H{sub 2}O{sub 2}. After a complete consumption of AgNSs, large nanoplates grows with an expense of smaller nanoplates. The growth continues until H{sub 2}O{sub 2} is exhausted. A high concentration H{sub 2}O{sub 2} promotes catalytic decomposition of H{sub 2}O{sub 2} on the surface of AgNSs and oxidative dissolution of AgNSs without a formation of AgNPls. - Graphical abstract: Proposed mechanism for the shape transformation of AgNSs to AgNPls induced by the oxidation/reduction of H{sub 2}O{sub 2}. - Highlights: • Rapid shape transformation of silver nanospheres to nanoplates by H{sub 2}O{sub 2}. • Structural change completes in 2 min with a yellow-to-blue color change. • Selective fabrication of

  3. Synthesis and characterization of NiCo{sub 2}O{sub 4} nanoplates as efficient electrode materials for electrochemical supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Taehyun [Nanomaterials and System Lab, Department of Mechatronics Engineering, Engineering College, Jeju National University, Jeju 690-756 (Korea, Republic of); Ramadoss, Ananthakumar [Nanomaterials and System Lab, Faculty of Applied Energy System, Science and Engineering College, Jeju National University, Jeju 690-756 (Korea, Republic of); Saravanakumar, Balasubramaniam; Veerasubramani, Ganesh Kumar [Nanomaterials and System Lab, Department of Mechatronics Engineering, Engineering College, Jeju National University, Jeju 690-756 (Korea, Republic of); Kim, Sang Jae, E-mail: kimsangj@jejunu.ac.kr [Nanomaterials and System Lab, Department of Mechatronics Engineering, Engineering College, Jeju National University, Jeju 690-756 (Korea, Republic of); Nanomaterials and System Lab, Faculty of Applied Energy System, Science and Engineering College, Jeju National University, Jeju 690-756 (Korea, Republic of)

    2016-05-01

    Highlights: • NiCo{sub 2}O{sub 4} nanoplates were synthesized through a facile approach. • The NiCo{sub 2}O{sub 4} nanoplates electrode material exhibit a specific capacitance of 332 F g{sup −1} at 5 mV s{sup −1}. • The fabricated NiCo{sub 2}O{sub 4} electrode reveals 86% retention of initial capacitance after 2000 cycles. - Abstract: In the present work, NiCo{sub 2}O{sub 4} nanoplates were prepared by a facile, low temperature, hydrothermal method, followed by thermal annealing and used supercapacitor applications. The physico-chemical characterization of as-prepared materials were investigated by means of X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR) and field emission scanning electron microscopy (FE-SEM). The electrochemical measurements demonstrate that the NiCo{sub 2}O{sub 4} nanoplates electrode (NC-5) exhibits a high specific capacitance of 332 F g{sup −1} at a scan rate of 5 mV s{sup −1} and also retained about 86% of the initial specific capacitance value even after 2000 cycles at a current density of 2.5 A g{sup −1}. These results suggest that the fabricated electrode material has huge potential as a novel electrode material for electrochemical capacitors.

  4. Hall and thermoelectric evaluation of p-type InAs

    Energy Technology Data Exchange (ETDEWEB)

    Wagener, M.C., E-mail: magnus.wagener@nmmu.ac.z [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Wagener, V.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2009-12-15

    This paper compares the galvanometric and thermoelectric evaluation of the electrical characteristics of narrow gap semiconductors. In particular, the influence of a surface inversion layer is incorporated into the analysis of the temperature-dependent Hall and thermoelectric measurements of p-type InAs. The temperature at which the Seebeck coefficient of p-type material changes sign is shown to be unaffected by the presence of degenerate conduction paths. This finding consequently facilitated the direct determination of the acceptor density of lightly doped thin film InAs.

  5. Hall and thermoelectric evaluation of p-type InAs

    International Nuclear Information System (INIS)

    Wagener, M.C.; Wagener, V.; Botha, J.R.

    2009-01-01

    This paper compares the galvanometric and thermoelectric evaluation of the electrical characteristics of narrow gap semiconductors. In particular, the influence of a surface inversion layer is incorporated into the analysis of the temperature-dependent Hall and thermoelectric measurements of p-type InAs. The temperature at which the Seebeck coefficient of p-type material changes sign is shown to be unaffected by the presence of degenerate conduction paths. This finding consequently facilitated the direct determination of the acceptor density of lightly doped thin film InAs.

  6. The fabrication of highly conductive and flexible Ag patterning through baking Ag nanosphere-nanoplate hybrid ink at a low temperature of 100 °C

    Science.gov (United States)

    Han, Y. D.; Zhang, S. M.; Jing, H. Y.; Wei, J.; Bu, F. H.; Zhao, L.; Lv, X. Q.; Xu, L. Y.

    2018-04-01

    With the aim of developing highly conductive ink for flexible electronics on heat-sensitive substrates, Ag nanospheres and nanoplates were mixed to synthesize hybrid inks. Five kinds of hybrid ink and two types of pure ink were written to square shape on Epson photo paper using rollerball pens, and sintered at a low temperature (100 °C). The microstructure, electrical resistivity, surface porosity, hardness and flexibility of silver patterns were systematically investigated and compared. It was observed that the optimal mixing ratio of nanospheres and nanoplates was 1:1, which equipped the directly written pattern with excellent electrical and mechanical properties. The electrical resistivity was 0.103 μΩ · m, only 6.5 times that of bulk silver. The enhancement compared to pure silver nanospheres or nanoplates based ink was due to the combined action of nanospheres and nanoplates. This demonstrates a valuable way to prepare Ag nanoink with good performance for printed/written electronics.

  7. The fabrication of highly conductive and flexible Ag pattern through baking Ag nanospheres - nanoplates hybrid ink at a low temperature of 100°C.

    Science.gov (United States)

    Han, Y D; Zhang, Siming; Jing, H Y; Wei, Jun; Bu, Fanhui; Zhao, Lei; Lv, Xiaoqing; Xu, L Y

    2018-01-24

    With the aim of developing highly conductive ink for flexible electronics on heat-sensitive substrates, Ag nanospheres and nanoplates were mixed to synthesize hybrid inks. Five kinds of hybrid ink and two types of pure ink were written to square shape on Epson photo paper using rollerball pens and sintered at a low temperature (100℃). The microstructure, electrical resistivity, surface porosity, hardness and flexibility of silver patterns were systematically investigated and compared. It was observed that the optimal mixing ratio of nanospheres and nanoplates was 1:1, which equipped the directly written pattern with excellent electrical and mechanical properties. The electrical resistivity was 0.103 μΩ·m, which was only 6.5 times of bulk silver. The enhancement compared to pure silver nanospheres or nanoplates based ink was owing to the combined action of nanospheres and nanoplates. It was a valued way to prepare Ag nanoink with good performance for printed/written electronics. © 2018 IOP Publishing Ltd.

  8. The influence of atmosphere on the performance of pure-phase WZ and ZB InAs nanowire transistors

    Science.gov (United States)

    Ullah, A. R.; Joyce, H. J.; Tan, H. H.; Jagadish, C.; Micolich, A. P.

    2017-11-01

    We compare the characteristics of phase-pure MOCVD grown ZB and WZ InAs nanowire transistors in several atmospheres: air, dry pure N2 and O2, and N2 bubbled through liquid H2O and alcohols to identify whether phase-related structural/surface differences affect their response. Both WZ and ZB give poor gate characteristics in dry state. Adsorption of polar species reduces off-current by 2-3 orders of magnitude, increases on-off ratio and significantly reduces sub-threshold slope. The key difference is the greater sensitivity of WZ to low adsorbate level. We attribute this to facet structure and its influence on the separation between conduction electrons and surface adsorption sites. We highlight the important role adsorbed species play in nanowire device characterisation. WZ is commonly thought superior to ZB in InAs nanowire transistors. We show this is an artefact of the moderate humidity found in ambient laboratory conditions: WZ and ZB perform equally poorly in the dry gas limit yet equally well in the wet gas limit. We also highlight the vital role density-lowering disorder has in improving gate characteristics, be it stacking faults in mixed-phase WZ or surface adsorbates in pure-phase nanowires.

  9. Spin effects in InAs self-assembled quantum dots

    Directory of Open Access Journals (Sweden)

    Brasil Maria

    2011-01-01

    Full Text Available Abstract We have studied the polarized resolved photoluminescence in an n-type resonant tunneling diode (RTD of GaAs/AlGaAs which incorporates a layer of InAs self-assembled quantum dots (QDs in the center of a GaAs quantum well (QW. We have observed that the QD circular polarization degree depends on applied voltage and light intensity. Our results are explained in terms of the tunneling of minority carriers into the QW, carrier capture by InAs QDs and bias-controlled density of holes in the QW.

  10. Platinum(iv) prodrug conjugated Pd@Au nanoplates for chemotherapy and photothermal therapy

    Science.gov (United States)

    Shi, Saige; Chen, Xiaolan; Wei, Jingping; Huang, Yizhuan; Weng, Jian; Zheng, Nanfeng

    2016-03-01

    Owing to the excellent near infrared (NIR) light absorption and efficient passive targeting toward tumor tissue, two-dimensional (2D) core-shell PEGylated Pd@Au nanoplates have great potential in both photothermal therapy and drug delivery systems. In this work, we successfully conjugate Pd@Au nanoplates with a platinum(iv) prodrug c,c,t-[Pt(NH3)2Cl2(O2CCH2CH2CO2H)2] to obtain a nanocomposite (Pd@Au-PEG-Pt) for combined photothermal-chemotherapy. The prepared Pd@Au-PEG-Pt nanocomposite showed excellent stability in physiological solutions and efficient Pt(iv) prodrug loading. Once injected into biological tissue, the Pt(iv) prodrug was easily reduced by physiological reductants (e.g. ascorbic acid or glutathione) into its cytotoxic and hydrophilic Pt(ii) form and released from the original nanocomposite, and the NIR laser irradiation could accelerate the release of Pt(ii) species. More importantly, Pd@Au-PEG-Pt has high tumor accumulation (29%ID per g), which makes excellent therapeutic efficiency at relatively low power density possible. The in vivo results suggested that, compared with single therapy the combined thermo-chemotherapy treatment with Pd@Au-PEG-Pt resulted in complete destruction of the tumor tissue without recurrence, while chemotherapy using Pd@Au-PEG-Pt without irradiation or photothermal treatment using Pd@Au-PEG alone did not. Our work highlights the prospects of a feasible drug delivery strategy of the Pt prodrug by using 2D Pd@Au nanoplates as drug delivery carriers for multimode cancer treatment.Owing to the excellent near infrared (NIR) light absorption and efficient passive targeting toward tumor tissue, two-dimensional (2D) core-shell PEGylated Pd@Au nanoplates have great potential in both photothermal therapy and drug delivery systems. In this work, we successfully conjugate Pd@Au nanoplates with a platinum(iv) prodrug c,c,t-[Pt(NH3)2Cl2(O2CCH2CH2CO2H)2] to obtain a nanocomposite (Pd@Au-PEG-Pt) for combined photothermal-chemotherapy. The

  11. 20 CFR 668.710 - What planning documents must an INA grantee submit?

    Science.gov (United States)

    2010-04-01

    ... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false What planning documents must an INA grantee... Planning/Funding Process § 668.710 What planning documents must an INA grantee submit? Each grantee... participant services and expenditures covering the two-year planning cycle. We will, in consultation with the...

  12. Nanoparticle-mediated nonclassical crystal growth of sodium fluorosilicate nanowires and nanoplates

    Directory of Open Access Journals (Sweden)

    Hongxia Li

    2011-12-01

    Full Text Available We observed nonclassical crystal growth of the sodium fluorosilicate nanowires, nanoplates, and hierarchical structures through self-assembly and aggregation of primary intermediate nanoparticles. Unlike traditional ion-by-ion crystallization, the primary nanoparticles formed first and their subsequent self-assembly, fusion, and crystallization generated various final crystals. These findings offer direct evidences for the aggregation-based crystallization mechanism.

  13. The fabrication of highly conductive and flexible Ag patterning through baking Ag nanosphere-nanoplate hybrid ink at a low temperature of 100 °C.

    Science.gov (United States)

    Han, Y D; Zhang, S M; Jing, H Y; Wei, J; Bu, F H; Zhao, L; Lv, X Q; Xu, L Y

    2018-02-12

    With the aim of developing highly conductive ink for flexible electronics on heat-sensitive substrates, Ag nanospheres and nanoplates were mixed to synthesize hybrid inks. Five kinds of hybrid ink and two types of pure ink were written to square shape on Epson photo paper using rollerball pens, and sintered at a low temperature (100 °C). The microstructure, electrical resistivity, surface porosity, hardness and flexibility of silver patterns were systematically investigated and compared. It was observed that the optimal mixing ratio of nanospheres and nanoplates was 1:1, which equipped the directly written pattern with excellent electrical and mechanical properties. The electrical resistivity was 0.103 μΩ · m, only 6.5 times that of bulk silver. The enhancement compared to pure silver nanospheres or nanoplates based ink was due to the combined action of nanospheres and nanoplates. This demonstrates a valuable way to prepare Ag nanoink with good performance for printed/written electronics.

  14. Formation Mechanism and Gas-Sensing Performance of La/ZnO Nanoplates Synthesized by a Facile Hydrothermal Method

    Science.gov (United States)

    Li, Yan; Chen, Li-Li; Lian, Xiao-Xue; Li, Jiao

    2018-03-01

    La/ZnO nanoplates were successfully synthesized by a facile hydrothermal method. The structure and morphology of the products were characterized using x-ray diffraction and scanning electron microscopy. The gas-sensing properties of the as-prepared La/ZnO were also tested with a series of target gases, and a possible gas sensing mechanism was discussed. The results show that the as-prepared La/ZnO nanoparticles are mainly composde of a wurtzite ZnO and a little La2O3 phase with face-centered structure, showing a uniform plate-like morphology with a thickness of about 50 nm. The La/ZnO nanoplate-based sensors display a significantly better sensing performance than pure ZnO for the detection of acetone and ethanol. The 3 mol.% La/ZnO sensor shows high sensitivity (127) to 200 ppm acetone at a low working temperature (330°C), and 120-200 ppm ethanol at 300°C. Moreover, its response and recovery time for acetone and ethanol were 3 s and 4 s, 18 s and 11 s, respectively. This work demonstrates that La/ZnO nanoplate-based sensors have potential applications as practical sensors for acetone and ethanol.

  15. Structure, interface abruptness and strain relaxation in self-assisted grown InAs/GaAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Frigeri, Cesare, E-mail: frigeri@imem.cnr.it [CNR-IMEM Institute, Parma (Italy); Scarpellini, David [L–NESS and Dept. Materials Science, University of Milano Bicocca, Milano (Italy); Department of Industrial Engineering University of Rome Tor Vergata, Rome (Italy); Fedorov, Alexey [LNESS and CNR-IFN, Como (Italy); Bietti, Sergio; Somaschini, Claudio [L–NESS and Dept. Materials Science, University of Milano Bicocca, Milano (Italy); Grillo, Vincenzo [CNR-IMEM Institute, Parma (Italy); CNR-S3-NANO Center, Modena (Italy); Esposito, Luca; Salvalaglio, Marco; Marzegalli, Anna; Montalenti, Francesco [L–NESS and Dept. Materials Science, University of Milano Bicocca, Milano (Italy); Sanguinetti, Stefano [L–NESS and Dept. Materials Science, University of Milano Bicocca, Milano (Italy); LNESS and CNR-IFN, Como (Italy)

    2017-02-15

    Highlights: • We study 2 critical issues (interface abruptness and strain release) in InAs/GaAs NWs. • Structural and chemical interface sharpness ≤1.5 nm, better than in previous reports. • Simultaneous elastic and plastic relaxation is shown that agrees with FEM simulations. • Structural, chemical and strain release investigations were performed by STEM. • New MBE self-seeded method whereby InAs is grown by splitting In and As depositions. - Abstract: The structure, interface abruptness and strain relaxation in InAs/GaAs nanowires grown by molecular beam epitaxy in the Ga self-catalysed mode on (111) Si have been investigated by transmission electron microscopy. The nanowires had the zincblende phase. The InAs/GaAs interface was atomically and chemically sharp with a width around 1.5 nm, i.e. significantly smaller than previously reported values. This was achieved by the consumption of the Ga droplet and formation of a flat top facet of the GaAs followed by the growth of InAs by splitting the depositions of In and As. Both elastic and plastic strain relaxation took place simultaneously. Experimental TEM results about strain relaxation very well agree with linear elasticity theory calculations by the finite element methods.

  16. Structure, interface abruptness and strain relaxation in self-assisted grown InAs/GaAs nanowires

    International Nuclear Information System (INIS)

    Frigeri, Cesare; Scarpellini, David; Fedorov, Alexey; Bietti, Sergio; Somaschini, Claudio; Grillo, Vincenzo; Esposito, Luca; Salvalaglio, Marco; Marzegalli, Anna; Montalenti, Francesco; Sanguinetti, Stefano

    2017-01-01

    Highlights: • We study 2 critical issues (interface abruptness and strain release) in InAs/GaAs NWs. • Structural and chemical interface sharpness ≤1.5 nm, better than in previous reports. • Simultaneous elastic and plastic relaxation is shown that agrees with FEM simulations. • Structural, chemical and strain release investigations were performed by STEM. • New MBE self-seeded method whereby InAs is grown by splitting In and As depositions. - Abstract: The structure, interface abruptness and strain relaxation in InAs/GaAs nanowires grown by molecular beam epitaxy in the Ga self-catalysed mode on (111) Si have been investigated by transmission electron microscopy. The nanowires had the zincblende phase. The InAs/GaAs interface was atomically and chemically sharp with a width around 1.5 nm, i.e. significantly smaller than previously reported values. This was achieved by the consumption of the Ga droplet and formation of a flat top facet of the GaAs followed by the growth of InAs by splitting the depositions of In and As. Both elastic and plastic strain relaxation took place simultaneously. Experimental TEM results about strain relaxation very well agree with linear elasticity theory calculations by the finite element methods.

  17. Intense luminescence emission from rare-earth-doped MoO3 nanoplates and lamellar crystals for optoelectronic applications

    International Nuclear Information System (INIS)

    Vila, M; Díaz-Guerra, C; Jerez, D; Piqueras, J; Lorenz, K; Alves, E

    2014-01-01

    Strong and stable room-temperature photoluminescence (PL) emission is achieved in MoO 3 nanoplates and lamellar crystals doped with Er and Eu by ion implantation and subsequent annealing. Micro-Raman and PL spectroscopy reveal that optical activation of the rare earth ions and recovery of the original MoO 3 structure are achieved for shorter annealing treatments and for lower temperatures in nanoplates, as compared with lamellar crystals. Er seems to be more readily incorporated into optically active sites in the oxide lattice than Eu. The influence of the dimensionality of the host sample on the characteristics of the PL emission of both rare earth dopants is addressed. (paper)

  18. Characterization by Raman scattering, x-ray diffraction, and transmission electron microscopy of (AlAs)m(InAs)m short period superlattices grown by migration enhanced epitaxy

    DEFF Research Database (Denmark)

    Bradshaw, J.; Song, X.J.; Shealy, J.R.

    1992-01-01

    We report growth of (InAs)1(AlAs)1 and (InAs)2(AlAs)2 strained layer superlattices by migration enhanced epitaxy. The samples were grown on InP (001) substrates and characterized by Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. Satellite peaks in the x-ray data...... confirm the intended periodicity and indicate the presence of some disorder in the monolayer sample. The energies of the zone folded and quantum confined optic phonons are in reasonable agreement with calculations based on one-dimensional elastic continuum and linear chain models. Journal of Applied...

  19. 2-D modeling of dual-mode acoustic phonon excitation of a triangular nanoplate

    International Nuclear Information System (INIS)

    Tai, Po-Tse; Yu, Pyng; Tang, Jau

    2010-01-01

    Graphical abstract: Modeling the lattice dynamics of a triangular plate with the arrows indicating the direction of impulsive thermal stress. We investigated ultrafast structural dynamics of triangular nanoplates based on 2-D Fermi-Pasta-Ulam model to explain coherent acoustic phonon excitation in nanoprisms. - Abstract: In this theoretical work, we investigated coherent phonon excitation of a triangular nanoplate based on 2-D Fermi-Pasta-Ulam lattice model. Based on the two-temperature model commonly used in description of laser heating of metals, we considered two kinds of forces related to electronic and lattice stresses. Based on extensive simulation and analysis, we identified two major planar phonon modes, namely, a standing wave mode related to the triangle bisector and another mode corresponding to half of the side length. This work elucidates the roles of laser-induced electronic stress and lattice stress in controlling the initial phase and the amplitude ratio between these two phonon modes.

  20. Spectroscopic properties of triangular silver nanoplates immobilized on polyelectrolyte multilayer-modified glass substrates

    Science.gov (United States)

    Rabor, Janice B.; Kawamura, Koki; Muko, Daiki; Kurawaki, Junichi; Niidome, Yasuro

    2017-07-01

    Fabrication of surface-immobilized silver nanostructures with reproducible plasmonic properties by dip-coating technique is difficult due to shape alteration. To address this challenge, we used a polyelectrolyte multilayer to promote immobilization of as-received triangular silver nanoplates (TSNP) on a glass substrate through electrostatic interaction. The substrate-immobilized TSNP were characterized by absorption spectrophotometry and scanning electron microscopy. The bandwidth and peak position of localized surface plasmon resonance (LSPR) bands can be tuned by simply varying the concentration of the colloidal solution and immersion time. TSNP immobilized from a higher concentration of colloidal solution with longer immersion time produced broadened LSPR bands in the near-IR region, while a lower concentration with shorter immersion time produced narrower bands in the visible region. The shape of the nanoplates was retained even at long immersion time. Analysis of peak positions and bandwidths also revealed the point at which the main species of the immobilization had been changed from isolates to aggregates.

  1. Metalorganic vapour epitaxial growth and infrared characterisation of InAsSb and InAs on InAs substrates

    CSIR Research Space (South Africa)

    Baisitse, TR

    2006-07-01

    Full Text Available Motivation for the research: Interest exists in III-V semiconducting materials (InAs, GaSb, InSb and related alloys) for the detection of infrared radiation; Such materials could be used as alternatives for future infrared detectors and various...

  2. 3D hierarchical porous cobalt monoxide nanoplates with a book-like structure derived from Co(CO3)0.5(OH)·0.11H2O: two-steps oriented attachment and high-performance asymmetric supercapacitors

    Science.gov (United States)

    Xiao, Yuanhua; Zhao, Xiaobing; Jin, Qingxian; Su, Dangcheng; Wang, Xuezhao; Wu, Shide; Zhou, Liming; Fang, Shaoming

    2017-10-01

    3D Hierarchical porous cobalt monoxide (CoO) nanoplates with a book-like structure derive from Co(CO3)0.5(OH)·0.11H2O by a two-steps oriented attachment mechanism in the solvothermal process. Firstly, nanoplates are formed by oriented attachment of nanorods. Secondly, new nanoplates could be generated on the old nanoplates by a sloped oriented attachment of nanorods with the based nanoplates shape into a 3D hierarchical book-like structure. The CoO nanoplates show superior specific capacitance about 1221.7 F g-1 at 1 A g-1 to most of the Co-based supercapacitor materials up to date. An asymmetric supercapacitor (ASC) based on positive electrode CoO and negative electrode active carbon (AC) exhibits an excellent energy density of 50.1 Wh kg-1 at a power density of 589 W kg-1 and gets a satisfactory cycling stability (86.3% of its initial capacitance retention at 10 A g-1 over 10 000 cycles).

  3. On the thermal growth and properties of doped TiO{sub 2} and In{sub 2}O{sub 3} elongated nanostructures and nanoplates

    Energy Technology Data Exchange (ETDEWEB)

    Cremades, A. [Departamento de Física de Materiales, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Herrera, M. [Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Ensenada (Mexico); Bartolomé, J.; Vásquez, G.C. [Departamento de Física de Materiales, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Maestre, D., E-mail: davidmaestre@fis.ucm.es [Departamento de Física de Materiales, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Piqueras, J. [Departamento de Física de Materiales, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid (Spain)

    2014-11-15

    In this work, the driving forces behind the growth mechanisms of In{sub 2}O{sub 3} and TiO{sub 2} micro- and nano-structures grown by an evaporation–solidification method are discussed. Effective or limited doping incorporation and its influence on the growth and morphology of the low dimensional structures are also assessed. A dislocation driven growth mechanism is proposed for indium oxide, indium tin oxide (ITO) and zinc doped indium oxide (IZO) nanowires. This growth mechanism is extended to the growth of IZO nano-plates. On the other hand, different low dimensional TiO{sub 2} morphologies, mainly nanowires, needles, and bidimensional leaf-like nanostructures, have been obtained by an anisotropic induced growth. By introducing Cr in the precursor mixture, needles are formed showing stepped lateral faces related to oxygen defect stoichiometry areas as observed by EDS mapping.

  4. Improved electrochemical performances of binder-free CoMoO4 nanoplate arrays@Ni foam electrode using redox additive electrolyte

    Science.gov (United States)

    Veerasubramani, Ganesh Kumar; Krishnamoorthy, Karthikeyan; Kim, Sang Jae

    2016-02-01

    Herein, we are successfully prepared cobalt molybdate (CoMoO4) grown on nickel foam as a binder free electrode by hydrothermal approach for supercapacitors and improved their electrochemical performances using potassium ferricyanide (K3Fe(CN)6) as redox additive. The formation of CoMoO4 on Ni foam with high crystallinity is confirmed using XRD, Raman, and XPS measurements. The nanoplate arrays (NPAs) of CoMoO4 are uniformly grown on Ni foam which is confirmed by FE-SEM analysis. The prepared binder-free CoMoO4 NPAs achieved maximum areal capacity of 227 μAh cm-2 with KOH electrolyte at 2.5 mA cm-2. This achieved areal capacity is further improved about three times using the addition of K3Fe(CN)6 as redox additive. The increased electrochemical performances of CoMoO4 NPAs on Ni foam electrode via redox additive are discussed in detail and the mechanism has been explored. Moreover, the assembled CoMoO4 NPAs on Ni foam//activated carbon asymmetric supercapacitor device with an extended operating voltage window of 1.5 V exhibits an excellent performances such as high energy density and cyclic stability. The overall performances of binder-free CoMoO4 NPAs on Ni foam with redox additives suggesting their potential use as positive electrode material for high performance supercapacitors.

  5. The influence of magnetic interactions and shape anisotropy on the alignment and assembly of BaFe{sub 12}O{sub 19} and Er{sub 2}O{sub 3} nanoplates

    Energy Technology Data Exchange (ETDEWEB)

    Lisjak, Darja, E-mail: darja.lisjak@ijs.si

    2014-11-14

    Magnetically anisotropic material with useful properties can be obtained when the barium ferrite (BaFe{sub 12}O{sub 19}) plates are aligned in a single plane. We studied the influence of the magnetic forces and the shape anisotropy on the alignment of barium ferrite nanoparticles. Nanoplates with diameters of 10–350 nm and diameter-to-thickness ratios of 3–30 were synthesized hydrothermally and stabilized in 1-butanol with dodecylbenzene sulphonic acid. The nanoplates were then deposited from the suspension on gold-coated substrates and dried with or without an applied magnetic field. In both cases the nanoplates aligned preferentially in the plane of the substrate, as evidenced by the scanning electron microscopy observations. To compare the influence of the magnetic field and the magnetic dipole–dipole interactions with that of the nanoparticle shape anisotropy, the alignment of paramagnetic erbium oxide (Er{sub 2}O{sub 3}) nanoplates was also studied. A lower degree of alignment was obtained with the erbium oxide than with the barium ferrite nanoplates. Barium ferrite films with a minimum orientation of 90% were prepared from the deposits after sintering at 1150 °C for 5 h. A comparable alignment of the erbium oxide films was induced hydrodynamically during the electrophoretic deposition. - Highlights: • Aligned deposits from BaFe{sub 12}O{sub 19} and Er{sub 2}O{sub 3} were prepared. • The magnetic interactions prevail over the shape anisotropy effect. • The alignment of the BaFe{sub 12}O{sub 19} nanoplates was obtained by drying a suspension. • The alignment of Er{sub 2}O{sub 3} nanoplates was obtained only by electrophoretic deposition.

  6. 20 CFR 668.650 - Can INA grantees exclude segments of the eligible population?

    Science.gov (United States)

    2010-04-01

    ... eligible population? 668.650 Section 668.650 Employees' Benefits EMPLOYMENT AND TRAINING ADMINISTRATION... population? (a) No, INA grantees cannot exclude segments of the eligible population. INA grantees must document in their Two Year Plan that a system is in place to afford all members of the eligible population...

  7. Effect of GaAs interlayer thickness variations on the optical properties of multiple InAs QD structure

    International Nuclear Information System (INIS)

    Park, C.Y.; Park, K.W.; Kim, J.M.; Lee, Y.T.

    2009-01-01

    Multiple InAs/GaAs self-assembled quantum dots (QDs) with vertically stacked structure are grown by molecular beam epitaxy and the effects of GaAs interlayer thickness variation on optical properties are studied. The growth conditions are optimized by in-situ RHEED, AFM, and PL measurement. The five InAs QD layers are embedded in GaAs and Al0.3Ga0.7As layer. The PL intensity is increased with increasing GaAs interlayer thickness. The thin GaAs interlayer has strain field, the strain-induced intermixing of indium atoms in the InAs QDs (blue-shift) can overcompensate for the effect on the increased QD size (red-shift) (H. Heidemeyer et al. Appl. Phys. Lett. 80, 1544 (2002); T. Nakaoka et al. J. Appl. Phys. Lett. 96, 150 (2004)[1, 2], respectively). For the interlayer thickness larger than about 7 nm, the blue-shifts are correlated to the dominant high-energy excited state transitions due to the successive state filling of the ground and higher excited states in the QDs. The energy separation of double PL peaks, originated from two different excited states, was kept at around 50 meV at room temperature. A possible mechanism concerning this phenomenon is also discussed. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Current–Voltage Characterization of Individual As-Grown Nanowires Using a Scanning Tunneling Microscope

    Science.gov (United States)

    2013-01-01

    Utilizing semiconductor nanowires for (opto)electronics requires exact knowledge of their current–voltage properties. We report accurate on-top imaging and I–V characterization of individual as-grown nanowires, using a subnanometer resolution scanning tunneling microscope with no need for additional microscopy tools, thus allowing versatile application. We form Ohmic contacts to InP and InAs nanowires without any sample processing, followed by quantitative measurements of diameter dependent I–V properties with a very small spread in measured values compared to standard techniques. PMID:24059470

  9. Current-voltage characterization of individual as-grown nanowires using a scanning tunneling microscope.

    Science.gov (United States)

    Timm, Rainer; Persson, Olof; Engberg, David L J; Fian, Alexander; Webb, James L; Wallentin, Jesper; Jönsson, Andreas; Borgström, Magnus T; Samuelson, Lars; Mikkelsen, Anders

    2013-11-13

    Utilizing semiconductor nanowires for (opto)electronics requires exact knowledge of their current-voltage properties. We report accurate on-top imaging and I-V characterization of individual as-grown nanowires, using a subnanometer resolution scanning tunneling microscope with no need for additional microscopy tools, thus allowing versatile application. We form Ohmic contacts to InP and InAs nanowires without any sample processing, followed by quantitative measurements of diameter dependent I-V properties with a very small spread in measured values compared to standard techniques.

  10. Awareness of the Vysočina Regional Food Labels With Context of Their Media Presence

    Directory of Open Access Journals (Sweden)

    Martina Chalupová

    2016-01-01

    Full Text Available The article presents results of research study that focused on the recognition of the Vysočina regional labels among the consumers in the region in connection with media analysis about the topic. Research among consumers was conducted in each district of Vysočina Region (Jihlava, Žďár nad Sázavou, Třebíč, Havlíčkův Brod and Pelhřimov by interviewing a sample of 819 respondents, selected by quota sampling methods. The research was aimed at analysing the ability of respondents to recognise and differentiate two existing regional labels VYSOČINA Regional Product®, Regional Food Vysočina Region and also nonexistent brand From Our Region Vysočina, created by authors. Data have been processed with correspondence analysis and showed that respondents connect different characteristics with the labels. Media analysis of the Vysočina regional labels revealed that media may help building awareness about the labels but they do not shape respondents’ views on them. Examining the link between the frequency of different types of information in media and their potential impact on the labels’ pereception by consumers have shown distorted image. Stronger consensus between research and media analysis have been examined only on importance of products’ origin, which can be viewed as a logical inference from the name of the labels.

  11. INA's Preparations for Liberalised Energy Market and Privatisation

    International Nuclear Information System (INIS)

    Dragicevic, T.; Kolundzic, S.

    2001-01-01

    Before opening of the market, energy entities must carry out numerous preparations in order to be ready for challenges of a competitive environment. Some preparations refer to legal and organisational issues, but many of them encompass reengineering of business processes, cost reduction schemes and various improvement measures aimed at maintenance or acquisition of a competitive advantage. INA is actively pursuing some of the above measures, but now, by the end of 2001, we also have to deal with preparations for privatisation. These two processes have some important common elements, competitiveness being certainly one of them. INA must work toward improving its competitive strength in the gas sector, in refining, in marketing of oil products, but also in various supporting activities. However, there are constraints that we have to observe, mainly related to social issues.(author)

  12. Silver nanoplates-based colorimetric iodide recognition and sensing using sodium thiosulfate as a sensitizer

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Xinyan; Chen, Shu, E-mail: chenshumail@gmail.com; Tang, Jian; Xiong, Yuan; Long, Yunfei, E-mail: l_yunfei927@163.com

    2014-05-01

    Highlights: • A new colorimetric iodide detection strategy based on triangular Ag nanoplate. • Sodium thiosulfate performed as a sensitizer. • Formation of insoluble AgI on the surface of Ag nanoplate. • This method has the advantages of good selectivity and high sensitivity. Abstract: A colorimetric method for the recognition and sensing of iodide ions (I⁻) has been developed by utilizing the reactions between triangular silver nanoplates (TAg-NPs) and I⁻ in the presence of sodium thiosulfate (Na₂S₂O₃). Specifically, I⁻ together with Na₂S₂O₃ can induce protection of TAg-NPs owing to the formation of insoluble AgI, as confirmed by the high-resolution transmission electron microscopy (HRTEM). In the absence of Na₂S₂O₃, the etching reactions on TAg-NPs were observed not only by I⁻ but also other halides ions. The Na₂S₂O₃ plays as a sensitizer in this system, which improved the selectivity and sensitivity. The desired colorimetric detection can be achieved by measuring the change of the absorption peak wavelength corresponding to localized surface plasmon resonance (LSPR) with UV–vis spectrophotometer or recognized by naked eye observation. The results show that the shift of the maximum absorption wavelength (Δλ) of the TAg-NPs/Na₂S₂O₃/I⁻ mixture was proportional to the concentration of I⁻ in the range 1.0 × 10⁻⁹–1.0 × 10⁻⁶ mol L⁻¹. Moreover, no other ions besides I⁻ can induce an eye discernible color change as low as 1.0 × 10⁻⁷ mol L⁻¹. Finally, this method was successfully applied for I⁻ determination in kelp samples.

  13. Preparation of novel silver nanoplates/graphene composite and their application in vanillin electrochemical detection

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Linhong [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Hou, Keyu; Jia, Xiao [Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Pan, Haibo, E-mail: hbpan@fzu.edu.cn [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Du, Min [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China)

    2014-05-01

    Hexagonal Ag nanoplates (NPs) were synthesized by polyvinylpyrrolidone (PVP) and trisodium citrate (TSC) which selectively absorbed to Ag (100) and Ag (111) surfaces, then were anchored to graphene (GN) to form novel Ag NPs/GN composite. The thickness of Ag NPs is ∼ 4 nm and the length is 18–66 nm. Transmission electron microscopy (TEM) image shows that the plates are f-c-c crystals containing {111} facets on their two planar surfaces. Zeta potential indicated that the surface of Ag NPs/GN is negatively charged while vanillin is positively charged. Thus Ag NPs/GN modified on glass carbon electrodes (GCE) allowed abundant adsorption for vanillin and electron transfer between vanillin and Ag NPs/GN/GCE. Square wave voltammetry (SWV) results indicated that the over potential on Ag NPs/GN/GCE negatively shifts 52 mV than that on Ag NPs/GCE. Ag NPs/GN with enhanced surface area and good conductivity exhibited an excellent electrocatalytic activity toward the oxidation of vanillin. The corresponding linear range was estimated to be from 2 to 100 μM (R{sup 2} = 0.998), and the detection limit is 3.32 × 10{sup −7} M (S/N = 3). The as-prepared vanillin sensor exhibits good selectivity and potential application in practical vanillin determination. - Highlights: • Hexagonal Ag nanoplates were synthesized by controlling of PVP and trisodium citrate. • Ag nanoplates/GN composite allowed adsorption and electron transfer of vanillin. • The composite with good dispersion exhibits enhanced surface area and good catalysis. • Vanillin on the Ag NPs/GN/GCE shows high sensitivity and selectivity.

  14. Preparation of novel silver nanoplates/graphene composite and their application in vanillin electrochemical detection

    International Nuclear Information System (INIS)

    Huang, Linhong; Hou, Keyu; Jia, Xiao; Pan, Haibo; Du, Min

    2014-01-01

    Hexagonal Ag nanoplates (NPs) were synthesized by polyvinylpyrrolidone (PVP) and trisodium citrate (TSC) which selectively absorbed to Ag (100) and Ag (111) surfaces, then were anchored to graphene (GN) to form novel Ag NPs/GN composite. The thickness of Ag NPs is ∼ 4 nm and the length is 18–66 nm. Transmission electron microscopy (TEM) image shows that the plates are f-c-c crystals containing {111} facets on their two planar surfaces. Zeta potential indicated that the surface of Ag NPs/GN is negatively charged while vanillin is positively charged. Thus Ag NPs/GN modified on glass carbon electrodes (GCE) allowed abundant adsorption for vanillin and electron transfer between vanillin and Ag NPs/GN/GCE. Square wave voltammetry (SWV) results indicated that the over potential on Ag NPs/GN/GCE negatively shifts 52 mV than that on Ag NPs/GCE. Ag NPs/GN with enhanced surface area and good conductivity exhibited an excellent electrocatalytic activity toward the oxidation of vanillin. The corresponding linear range was estimated to be from 2 to 100 μM (R 2 = 0.998), and the detection limit is 3.32 × 10 −7 M (S/N = 3). The as-prepared vanillin sensor exhibits good selectivity and potential application in practical vanillin determination. - Highlights: • Hexagonal Ag nanoplates were synthesized by controlling of PVP and trisodium citrate. • Ag nanoplates/GN composite allowed adsorption and electron transfer of vanillin. • The composite with good dispersion exhibits enhanced surface area and good catalysis. • Vanillin on the Ag NPs/GN/GCE shows high sensitivity and selectivity

  15. Bending analysis of embedded nanoplates based on the integral formulation of Eringen's nonlocal theory using the finite element method

    Science.gov (United States)

    Ansari, R.; Torabi, J.; Norouzzadeh, A.

    2018-04-01

    Due to the capability of Eringen's nonlocal elasticity theory to capture the small length scale effect, it is widely used to study the mechanical behaviors of nanostructures. Previous studies have indicated that in some cases, the differential form of this theory cannot correctly predict the behavior of structure, and the integral form should be employed to avoid obtaining inconsistent results. The present study deals with the bending analysis of nanoplates resting on elastic foundation based on the integral formulation of Eringen's nonlocal theory. Since the formulation is presented in a general form, arbitrary kernel functions can be used. The first order shear deformation plate theory is considered to model the nanoplates, and the governing equations for both integral and differential forms are presented. Finally, the finite element method is applied to solve the problem. Selected results are given to investigate the effects of elastic foundation and to compare the predictions of integral nonlocal model with those of its differential nonlocal and local counterparts. It is found that by the use of proposed integral formulation of Eringen's nonlocal model, the paradox observed for the cantilever nanoplate is resolved.

  16. GaAs metal-oxide-semiconductor based non-volatile flash memory devices with InAs quantum dots as charge storage nodes

    Energy Technology Data Exchange (ETDEWEB)

    Islam, Sk Masiul, E-mail: masiulelt@gmail.com; Chowdhury, Sisir; Sarkar, Krishnendu; Nagabhushan, B.; Banerji, P. [Materials Science Centre, Indian Institute of Technology, Kharagpur 721 302 (India); Chakraborty, S. [Applied Materials Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Sector-I, Kolkata 700 064 (India); Mukherjee, Rabibrata [Department of Chemical Engineering, Indian Institute of Technology, Kharagpur 721302 (India)

    2015-06-24

    Ultra-thin InP passivated GaAs metal-oxide-semiconductor based non-volatile flash memory devices were fabricated using InAs quantum dots (QDs) as charge storing elements by metal organic chemical vapor deposition technique to study the efficacy of the QDs as charge storage elements. The grown QDs were embedded between two high-k dielectric such as HfO{sub 2} and ZrO{sub 2}, which were used for tunneling and control oxide layers, respectively. The size and density of the QDs were found to be 5 nm and 1.8×10{sup 11} cm{sup −2}, respectively. The device with a structure Metal/ZrO{sub 2}/InAs QDs/HfO{sub 2}/GaAs/Metal shows maximum memory window equivalent to 6.87 V. The device also exhibits low leakage current density of the order of 10{sup −6} A/cm{sup 2} and reasonably good charge retention characteristics. The low value of leakage current in the fabricated memory device is attributed to the Coulomb blockade effect influenced by quantum confinement as well as reduction of interface trap states by ultra-thin InP passivation on GaAs prior to HfO{sub 2} deposition.

  17. Microwave Synthesis of Zinc Hydroxy Sulfate Nanoplates and Zinc Oxide Nanorods in the Classroom

    Science.gov (United States)

    Dziedzic, Rafal M.; Gillian-Daniel, Anne Lynn; Peterson, Greta M.; Martínez-Herna´ndez, Kermin J.

    2014-01-01

    In this hands-on, inquiry-based lab, high school and undergraduate students learn about nanotechnology by synthesizing their own nanoparticles in a single class period. This simple synthesis of zinc oxide nanorods and zinc hydroxy sulfate nanoplates can be done in 15 min using a household microwave oven. Reagent concentration, reaction…

  18. Channeling study of laser-induced defect generation in InP and InAs

    International Nuclear Information System (INIS)

    Burdel', K.K.; Kashkarov, P.K.; Timoshenko, V.Yu.; Chechenin, N.G.

    1992-01-01

    Damage production in InP and InAs single crystals induced by a ruby-laser pulse irradiation with τ p =20 ms in the energy density region W=0.05-1.0 J/cm 2 is studied by the channeling and Rutherford backscattering techniques. The defect generation threshold was determined to be equal to 0.2 J/cm 2 and 0.55 J/cm 2 for InP and InAs crystals, respectively. Stoichiometric defects in InP crystals were observed at W>=0.5 J/cm 2 . The temperature fields in InP and InAs under laser irradiation were calculated. The experimental observations are considered as a result of a selective evaporation of the components from the melt

  19. Crystallographic Habit Tuning of Li2MnSiO4 Nanoplates for High-Capacity Lithium Battery Cathodes.

    Science.gov (United States)

    Ding, Zhengping; Feng, Yiming; Zhang, Datong; Ji, Ran; Chen, Libao; Ivey, Douglas G; Wei, Weifeng

    2018-02-21

    Li 2 MnSiO 4 has attracted significant attention as a cathode material for lithium ion batteries because of its high theoretical capacity (330 mA h g -1 with two Li + ions per formula unit), low cost, and environmentally friendly nature. However, its intrinsically poor Li diffusion, low electronic conductivity, and structural instability preclude its use in practical applications. Herein, elongated hexagonal prism-shaped Li 2 MnSiO 4 nanoplates with preferentially exposed {001} and {210} facets have been successfully synthesized via a solvothermal method. Density functional theory calculations and experimental characterization reveal that the formation mechanism involves the decomposition of solid precursors to nanosheets, self-assembly into nanoplates, and Ostwald ripening. Hydroxyl-containing solvents such as ethylene glycol and diethylene glycol play a crucial role as capping agents in tuning the preferential growth. Li 2 MnSiO 4 @C nanoplates demonstrate a near theoretical discharge capacity of 326.7 mA h g -1 at 0.05 C (1 C = 160 mA h g -1 ), superior rate capability, and good cycling stability. The enhanced electrochemical performance is ascribed to the electrochemically active {001} and {210} exposed facets, which provide short and fast Li + diffusion pathways along the [001] and [100] axes, a conformal carbon nanocoating, and a nanoscaled platelike structure, which offers a large electrode/electrolyte contact interface for Li + extraction/insertion processes.

  20. Static stability analysis of smart magneto-electro-elastic heterogeneous nanoplates embedded in an elastic medium based on a four-variable refined plate theory

    Science.gov (United States)

    Ebrahimi, Farzad; Barati, Mohammad Reza

    2016-10-01

    In this article, a nonlocal four-variable refined plate theory is developed to examine the buckling behavior of nanoplates made of magneto-electro-elastic functionally graded (MEE-FG) materials resting on Winkler-Pasternak foundation. Material properties of nanoplate change in spatial coordinate based on power-law distribution. The nonlocal governing equations are deduced by employing the Hamilton principle. For various boundary conditions, the analytical solutions of nonlocal MEE-FG plates for buckling problem will be obtained based on an exact solution approach. Finally, dependency of buckling response of MEE-FG nanoplate on elastic foundation parameters, magnetic potential, external electric voltage, various boundary conditions, small scale parameter, power-law index, plate side-to-thickness ratio and aspect ratio will be figure out. These results can be advantageous for the mechanical analysis and design of intelligent nanoscale structures constructed from magneto-electro-thermo-elastic functionally graded materials.

  1. Competitive growth mechanisms of InAs quantum dots on InxGa1-xAs layer during post growth interruption

    International Nuclear Information System (INIS)

    Yang, Changjae; Kim, Jungsub; Sim, Uk; Lee, Jaeyel; Choi, Won Jun; Yoon, Euijoon

    2010-01-01

    We investigated the effect of the post growth interruption (GI) on InAs quantum dots (QDs) grown on In x Ga 1-x As strained buffer layers (SBL). When QDs were grown on the 5 and 10% In content SBLs by using post GI, the size of QDs increased as its density decreased. Based on the 50 meV red-shift of PL in these cases, the transport of materials between QDs leads to the increase of QD size with maintaining its composition during the post GI. On the other hand, when using SBLs with the 15 and 20% In contents, the size of QDs increased, but its density was a little reduced. In addition, PL results were observed blue-shifted by about 20 meV and 2 meV, respectively. Considering the interruption of source gases during the post GI, these observations are strong evidence of the Ga incorporation from 15 and 20% In content SBLs. Therefore, these results imply that the dominant mechanism which increases the size of QDs during the post GI depends on the growth condition of SBL.

  2. Reactive ion etching of GaSb, (Al,Ga)Sb, and InAs for novel device applications

    International Nuclear Information System (INIS)

    LaTulipe, D.C.; Frank, D.J.; Munekata, H.

    1991-01-01

    Although a variety of novel device proposals for GaSb/(Al,Ga)Sb/InAs heterostructures have been made, relatively little is known about processing these materials. The authors of this paper have studied the reactive ion etching characteristics of GaSb, (Al,Ga)Sb, and InAs in both methane/hydrogen and chlorine gas chemistries. At conditions similar to those reported elsewhere for RIE of InP and GaAs in CH 4 /H 2 , the etch rate of (Al,Ga)Sb was found to be near zero, while GaSb and InAs etched at 200 Angstrom/minute. Under conditions where the etch mechanism is primarily physical sputtering, the three compounds etch at similar rates. Etching in Cl 2 was found to yield anistropic profiles, with the etch rate of (Al,Ga)Sb increasing with Al mole fraction, while InAs remains unetched. Damage to the InAs stop layer was investigated by sheet resistance and mobility measurements. These etching techniques were used to fabricate a novel InAs- channel FET composed of these materials. Several scanning electron micrographs of etching results are shown along with preliminary electrical characteristics

  3. Design, fabrication and structural optimization of tubular carbon/Kevlar®/PMMA/graphene nanoplate composite for bone fixation prosthesis.

    Science.gov (United States)

    Nasiri, F; Ajeli, S; Semnani, D; Jahanshahi, M; Emadi, R

    2018-05-02

    The present work investigates the mechanical properties of tubular carbon/Kevlar ® composite coated with poly(methyl methacrylate)/graphene nanoplates as used in the internal fixation of bones. Carbon fibers are good candidates for developing high-strength biomaterials and due to better stress transfer and electrical properties, they can enhance tissue formation. In order to improve carbon brittleness, ductile Kevlar ® was added to the composite. The tubular carbon/Kevlar ® composites have been prepared with tailorable braiding technology by changing the fiber pattern and angle in the composite structure and the number of composite layers. Fuzzy analyses are used for optimizing the tailorable parameters of 80 prepared samples and then mechanical properties of selected samples are discussed from the viewpoint of mechanical properties required for a bone fixation device. Experimental results showed that with optimizing braiding parameters the desired composite structure with mechanical properties close to bone properties could be produced. Results showed that carbon/Kevlar ® braid's physical properties, fiber composite distribution and diameter uniformity resulted in matrix uniformity, which enhanced strength and modulus due to better ability for distributing stress on the composite. Finally, as graphene nanoplates demonstrated their potential properties to improve wound healing intended for bone replacement, so reinforcing the PMMA matrix with graphene nanoplates enhanced the composite quality, for use as an implant.

  4. Past and Present Development of INA's Liberalisation and Privatisation

    International Nuclear Information System (INIS)

    Lesic, A.; Stimac, B.

    2001-01-01

    The paper deals with the historical development aspects of the Croatian oil and gas industry INA. It describes the period from the very start of oil and gas production to the data of establishment of the Croatian state and afterwards. Some important milestones and political and economic events that impacted the development of the Croatian oil industry are described and commented, including changes toward liberalisation and privatisation of the oil and gas sector. The paper emphasises the role of INA in the Croatian economy and proposes some solutions for the liberalisation process and privatisation of the company that could prevent undesirable effects of privatisation and protect the interests of Croatia in the energy sector which is one of the main sectors of economy having influence on other production and service sectors and their competitiveness.(author)

  5. The presence of INA proteins on the surface of single cells of Pseudomonas syringae R10.79 isolated from rain

    Science.gov (United States)

    Šantl-Temkiv, Tina; Ling, Meilee; Holm, Stine; Finster, Kai; Boesen, Thomas

    2016-04-01

    One of the important open questions in atmospheric ice nucleation is the impact of bioaerosols on the ice content of mix phase clouds (DeMott and Prenni 2010). Biogenic ice nuclei have a unique capacity of facilitating ice formation at temperatures between -1 and -10 °C. The model biogenic ice nuclei are produced by a few species of plant-surface bacteria, such as Pseudomonas syringae, that are commonly transported through the atmosphere. These bacterial species have highly specialized proteins, the so-called ice nucleation active (INA) proteins, which are exposed at the outer membrane surface of the cell where they promote ice particle formation. The mechanisms behind the onset of INA protein synthesis in single bacterial cells are not well understood. We performed a laboratory study in order to (i) investigate the presence of INA proteins on single bacterial cells and (ii) understand the conditions that induce INA protein production. We previously isolated an INA-positive strain of Pseudomonas syringae from rain samples collected in Denmark. Bacterial cells initiated ice nucleation activity at temperatures ≤-2°C and the cell fragments at temperatures ≤-8°C (Šantl-Temkiv et al 2015). We determined the amino-acid sequence of the INA protein and used the sequence to produce custom-made antibodies (GenScript, Germany). These antibodies were used to specifically stain and visualize the INA protein on the surfaces of single cells, which can then be quantified by a technique called flow cytometry. The synthesis of INA proteins by individual cells was followed during a batch growth experiment. An unusually high proportion of cells that were adapting to the new conditions prior to growth produced INA proteins (~4.4% of all cells). A smaller fraction of actively growing cells was carrying INA proteins (~1.2 % of all cells). The cells that stopped growing due to unfavorable conditions had the lowest fraction of cells carrying INA proteins (~0.5 % of all cells). To

  6. Detection of hydrogen peroxide and glucose by using Tb2(MoO4)3 nanoplates as peroxidase mimics

    Science.gov (United States)

    Rahimi-Nasrabadi, Mehdi; Mizani, Farhang; Hosseini, Morteza; Keihan, Amir Homayoun; Ganjali, Mohammad Reza

    2017-11-01

    Tb2(MoO4)3 nanostructures are demonstrated for the first time to have an intrinsic peroxidase-like activity. Tb2(MoO4)3 nanoplates could efficiently catalyse the oxidation of 3,3‧,5,5‧-tetramethylbenzidine (TMB) to generate a blue dye (with an absorbance maximum at 652 nm) in the presence of H2O2. Based on the highly efficient catalytic of Tb2(MoO4)3 nanoplates, a novel system for optical determination of H2O2 and glucose was successfully established under optimized conditions. The assay had 0.0.08 μM and 0.1 μM detection limit for H2O2 and glucose, respectively. In our opinion, this enzyme mimetic has a potential to use in other oxidase based assays.

  7. Free vibration analysis of a rotary smart two directional functionally graded piezoelectric material in axial symmetry circular nanoplate

    Science.gov (United States)

    Mahinzare, Mohammad; Ranjbarpur, Hosein; Ghadiri, Majid

    2018-02-01

    In this article, free vibration of a rotating circular nanoplate made of two directional functionally graded piezo materials (two directional FGPM) is modeled based on the first shear deformation theory (FSDT). Based on the power-law model, electro-elastic properties of two directional FGP rotating circular nanoplates are supposed to change continuously along the thickness and radius. Employing the modified couple stress theory, the small size effect of the equations of the plate is considered. The governing equations of the first shear deformation theory (FSDT) for the studied plate are obtained based on Hamilton's principle; these equations are solved using differential quadrature method (DQM). It is shown that the vibration behavior of the plate is significantly affected by angular velocity, external electric voltage, size dependency and power-law index (thickness and radial directions).

  8. Structural and optical characterization and efficacy of hydrothermal synthesized Cu and Ag doped zinc oxide nanoplate bactericides

    Energy Technology Data Exchange (ETDEWEB)

    Abinaya, C.; Marikkannan, M.; Manikandan, M. [Department of Materials Science, School of Chemistry, Madurai Kamaraj University, Madurai, 625 021, Tamil Nadu (India); Mayandi, J., E-mail: jeyanthinath@yahoo.co.in [Department of Materials Science, School of Chemistry, Madurai Kamaraj University, Madurai, 625 021, Tamil Nadu (India); Department of Materials Science and Engineering, Michigan Technological University, Houghton, 49931 1295, MI (United States); Suresh, P.; Shanmugaiah, V. [Department of Microbial Technology, School of Biological Sciences, Madurai Kamaraj University, Madurai, 625 021, Tamil Nadu (India); Ekstrum, C. [Department of Materials Science and Engineering, Michigan Technological University, Houghton, 49931 1295, MI (United States); Pearce, J.M. [Department of Materials Science and Engineering, Michigan Technological University, Houghton, 49931 1295, MI (United States); Department of Electrical & Computer Engineering, Michigan Technological University, Houghton, 49931 1295, MI (United States)

    2016-12-01

    This study reports on a novel synthesis of pure zinc oxide and both Cu and Ag doped ZnO nanoplates using a simple and low-cost hydrothermal method. The structural and optical properties of the nanoplates were quantified and the materials were tested for antibacterial activity. X-ray diffraction revealed the formation of the wurtzite phase of ZnO and scanning and transmission electron microscopy showed the formation of randomly oriented ZnO nanoplates, having a thickness less than 80 nm and diameter less than 350 nm. The elemental analyses of both the pure and doped samples were evaluated by energy dispersive X-ray spectrometry. The FTIR spectra of ZnO nanomaterials showed the predictable bands at 3385 cm{sup −1} (O−H stretching), 1637 cm{sup −1} (stretching vibration of H{sub 2}O), 400 cm{sup −1}–570 cm{sup −1} (M−O stretching). The as synthesized samples showed a strong absorption peak in the UV region (∼376 nm) and a near band edge emission at 392 nm with some defect peaks in the visible region. From the XPS spectra the oxidation states of Zn, Cu and Ag were found to be +2, +2 and 0 respectively. Escherichia coli, Staphylococcus aureus and Salmonella typhi bacteria were used to evaluate the antibacterial activity of undoped and doped ZnO. Ag doped ZnO exhibited low minimum inhibitory concentration (MIC) values as 40 μg/ml for E. coli and S. aureus and 20 μg/ml for S. typhi, which are comparable to commercial antibiotics without optimization. Further, these chemically modified nanoparticles will be applicable in the development of medicine to control the spread and infection of a variety of bacterial strains. - Highlights: • Distinct ZnO nanoplates were successfully synthesized by facile hydrothermal method. • Cu and Ag doped ZnO exhibits significant destruction of bacteria with low MIC value. • Ag:ZnO has a noteworthy bactericidal effect against E. coli, S. aureus &S. typhi. • It projects that, a feasible low cost industrial process can

  9. Thermo-magnetic field effects on the wave propagation behavior of smart magnetostrictive sandwich nanoplates

    Science.gov (United States)

    Ebrahimi, Farzad; Dabbagh, Ali

    2018-03-01

    In this paper, a three-variable plate model is utilized to explore the wave propagation problem of smart sandwich nanoplates made of a magnetostrictive core and ceramic face sheets while subjected to thermo-magnetic loading. Herein, the magnetostriction effect is considered and controlled via a feedback control system. The nanoplate is supposed to be embedded on a visco-Pasternak elastic substrate. The kinematic relations are derived based on the Kirchhoff plate theory; also, combining these obtained equations with Hamilton's principle, the local equations of motion are achieved. According to a nonlocal strain gradient theory (NSGT), the small-scale influences are covered precisely by introducing two scale coefficients. Afterwards, the nonlocal governing equations are derived coupling the local equations with those of the NSGT. Applying an analytical solution, the wave frequency and phase velocity of the propagated waves can be gathered solving an eigenvalue problem. On the other hand, accuracy and efficiency of the presented model are verified by setting a comparison between the obtained results with those of previous published researches. Effects of different variants are plotted in some figures and the highlights are discussed in detail.

  10. Etching and oxidation of InAs in planar inductively coupled plasma

    Energy Technology Data Exchange (ETDEWEB)

    Dultsev, F.N., E-mail: fdultsev@thermo.isp.nsc.ru [Institute of Semiconductor Physics SB RAS, Lavrentiev av. 13, Novosibirsk 630090 (Russian Federation); Kesler, V.G. [Institute of Semiconductor Physics SB RAS, Lavrentiev av. 13, Novosibirsk 630090 (Russian Federation)

    2009-10-15

    The surface of InAs (1 1 1)A was investigated under plasmachemical etching in the gas mixture CH{sub 4}/H{sub 2}/Ar. Etching was performed using the RF (13.56 MHz) and ICP plasma with the power 30-150 and 50-300 W, respectively; gas pressure in the reactor was 3-10 mTorr. It was demonstrated that the composition of the subsurface layer less than 5 nm thick changes during plasmachemical etching. A method of deep etching of InAs involving ICP plasma and hydrocarbon based chemistry providing the conservation of the surface relief is proposed. Optimal conditions and the composition of the gas phase for plasmachemical etching ensuring acceptable etch rates were selected.

  11. Etching and oxidation of InAs in planar inductively coupled plasma

    Science.gov (United States)

    Dultsev, F. N.; Kesler, V. G.

    2009-10-01

    The surface of InAs (1 1 1)A was investigated under plasmachemical etching in the gas mixture CH 4/H 2/Ar. Etching was performed using the RF (13.56 MHz) and ICP plasma with the power 30-150 and 50-300 W, respectively; gas pressure in the reactor was 3-10 mTorr. It was demonstrated that the composition of the subsurface layer less than 5 nm thick changes during plasmachemical etching. A method of deep etching of InAs involving ICP plasma and hydrocarbon based chemistry providing the conservation of the surface relief is proposed. Optimal conditions and the composition of the gas phase for plasmachemical etching ensuring acceptable etch rates were selected.

  12. Etching and oxidation of InAs in planar inductively coupled plasma

    International Nuclear Information System (INIS)

    Dultsev, F.N.; Kesler, V.G.

    2009-01-01

    The surface of InAs (1 1 1)A was investigated under plasmachemical etching in the gas mixture CH 4 /H 2 /Ar. Etching was performed using the RF (13.56 MHz) and ICP plasma with the power 30-150 and 50-300 W, respectively; gas pressure in the reactor was 3-10 mTorr. It was demonstrated that the composition of the subsurface layer less than 5 nm thick changes during plasmachemical etching. A method of deep etching of InAs involving ICP plasma and hydrocarbon based chemistry providing the conservation of the surface relief is proposed. Optimal conditions and the composition of the gas phase for plasmachemical etching ensuring acceptable etch rates were selected.

  13. Exciton radiative lifetime in sub-monlayer and stranskii-Krastanow grown InGaAs/GaAs quantum dots

    DEFF Research Database (Denmark)

    Xu, Zhangcheng; Zhang, Yating; Tackeuchi, Atsushi

    radiative lifetime rad [4]. Here, we compare the exciton radiative lifetime of SML-grown and SK-grown InGaAs/GaAs QDs at 10 K, via time-resolved photoluminescence (PL). The SML-QDs, were formed by 10 cycles of alternate deposition of 0.5 monolayer (ML) InAs and 2.5 ML GaAs, at 500 °C. The SK-QDs were...... formed by depositing 4.1 ML In0.6Ga0.4As on GaAs. The PL spectra indicate that the SML-QDs show better uniformity than the SK-QDs. Transient PL for SML and SK QDs at 10 K, where the PL decay time d is dominated by the exciton radiative lifetime, show d = 90 ps for SML-QDs which is much shorter than...

  14. Sensing Responses Based on Transfer Characteristics of InAs Nanowire Field-Effect Transistors

    Science.gov (United States)

    Savelyev, Igor; Blumin, Marina; Wang, Shiliang; Ruda, Harry E.

    2017-01-01

    Nanowire-based field-effect transistors (FETs) have demonstrated considerable promise for a new generation of chemical and biological sensors. Indium arsenide (InAs), by virtue of its high electron mobility and intrinsic surface accumulation layer of electrons, holds properties beneficial for creating high performance sensors that can be used in applications such as point-of-care testing for patients diagnosed with chronic diseases. Here, we propose devices based on a parallel configuration of InAs nanowires and investigate sensor responses from measurements of conductance over time and FET characteristics. The devices were tested in controlled concentrations of vapour containing acetic acid, 2-butanone and methanol. After adsorption of analyte molecules, trends in the transient current and transfer curves are correlated with the nature of the surface interaction. Specifically, we observed proportionality between acetic acid concentration and relative conductance change, off current and surface charge density extracted from subthreshold behaviour. We suggest the origin of the sensing response to acetic acid as a two-part, reversible acid-base and redox reaction between acetic acid, InAs and its native oxide that forms slow, donor-like states at the nanowire surface. We further describe a simple model that is able to distinguish the occurrence of physical versus chemical adsorption by comparing the values of the extracted surface charge density. These studies demonstrate that InAs nanowires can produce a multitude of sensor responses for the purpose of developing next generation, multi-dimensional sensor applications. PMID:28714903

  15. Geometric factors in the magnetoresistance of n-doped InAs epilayers

    KAUST Repository

    Sun, Jian

    2013-11-27

    We investigate the magnetoresistance (MR) effect in n-doped InAs and InAs/metal hybrid devices with geometries tailored to elucidate the physical mechanism and the role of geometry in the MR. Despite the isotropic Fermi surface in InAs, we observe a strong intrinsic MR in the InAs epilayer due to the existence of a surface conducting layer. Experimental comparison confirms that the extraordinary MR in the InAs/metal hybrids outperforms the orbital MR in the Corbino disk in terms of both the MR ratio and the magnetic field resolution. The results also indicate the advantage of a two-contact configuration in the hybrid devices over a four-contact one with respect to the magnetic field resolution. This is in contrast to previously reported results, where performance was evaluated in terms of the MR ratio and a four-contact configuration was found to be optimal. By applying Kohler\\'s rule, we find that at temperatures above 75 K the extraordinary MR violates Kohler\\'s rule, due to multiple relaxation rates, whereas the orbital MR obeys it. This finding can be used to distinguish the two geometric effects, the extraordinary MR and the orbital MR, from each other.

  16. Critical surface phase of α2(2 × 4) reconstructed zig-zag chains on InAs(001)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xiang [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China); Zhou, Xun [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China); School of Physics and Electronics Science, Guizhou Normal University, Guizhou, Guiyang 550001 (China); Wang, Ji-Hong [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China); Luo, Zi-Jiang [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China); School of Education Administration, Guizhou University of Finance and Economics, Guizhou, Guiyang 550004 (China); Zhou, Qing; Liu, Ke; Hu, Ming-Zhe [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China); Ding, Zhao, E-mail: zding@gzu.edu.cn [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China)

    2014-07-01

    The critical condition for InAs(001) surface phase transition has been studied, the surface phase transition of InAs(001) showed discontinuity with hysteresis cycle as a function of substrate temperature. A mixed reconstruction surface and zig-zag chain α2(2 × 4) reconstruction surface have been observed by scanning tunneling microscopy. Considering the interaction and dynamics of surface arsenic atoms, the zig-zag chains of α2(2 × 4) reconstruction were found to be actually caused by the selective adsorption and desorption of surface arsenic dimers, they played a critical role in the surface phase transition between (2 × 4) and (4 × 2). - Highlights: • Discontinuous surface phase transition phenomena on the flat InAs(001) surface • Nanoscale InAs(001) surface observed by scanning tunneling microscopy • “Zig-Zag” chains of α2(2 × 4) reconstruction • Critical role in the surface phase transition between (2 × 4) and (4 × 2)

  17. Critical surface phase of α2(2 × 4) reconstructed zig-zag chains on InAs(001)

    International Nuclear Information System (INIS)

    Guo, Xiang; Zhou, Xun; Wang, Ji-Hong; Luo, Zi-Jiang; Zhou, Qing; Liu, Ke; Hu, Ming-Zhe; Ding, Zhao

    2014-01-01

    The critical condition for InAs(001) surface phase transition has been studied, the surface phase transition of InAs(001) showed discontinuity with hysteresis cycle as a function of substrate temperature. A mixed reconstruction surface and zig-zag chain α2(2 × 4) reconstruction surface have been observed by scanning tunneling microscopy. Considering the interaction and dynamics of surface arsenic atoms, the zig-zag chains of α2(2 × 4) reconstruction were found to be actually caused by the selective adsorption and desorption of surface arsenic dimers, they played a critical role in the surface phase transition between (2 × 4) and (4 × 2). - Highlights: • Discontinuous surface phase transition phenomena on the flat InAs(001) surface • Nanoscale InAs(001) surface observed by scanning tunneling microscopy • “Zig-Zag” chains of α2(2 × 4) reconstruction • Critical role in the surface phase transition between (2 × 4) and (4 × 2)

  18. Pathogenic and Ice-Nucleation Active (INA) Bacteria causing Dieback of Willows in Short Rotation Forestry

    Energy Technology Data Exchange (ETDEWEB)

    Nejad, Pajand

    2005-03-01

    To find out whether bacteria isolated from diseased plant parts can be the main causal agent for the dieback appearing in Salix energy forestry plantations in Sweden during the last few years, and if the joint effects of bacteria and frost injury are synergistic, extensive sampling of shoots from diseased Salix plants was performed. We performed several laboratory and greenhouse investigations and used evaluation techniques on the functions of the Ice-Nucleation Active (INA) bacteria. We carried out a comparison between spring and autumn bacterial communities isolated from within (endophytically) and surface (epiphytically) plant tissues of Salix viminalis. Seasonal variation of bacteria in willow clones with different levels of frost sensitivity and symptoms of bacterial damage was also investigated. We further focussed on possible effect of fertilisation and nutrient availability on the bacterial community in relation to plant dieback in Estonian willow plantations. The identification and detection of INA bacteria which cause damage in combination with frost to willow (Salix spp) plants in late fall, winter and spring was performed using BIOLOG MicroPlate, biochemical tests, selective INA primers and 16S rDNA analysis. To distinguish the character for differentiation between these bacteria morphologically and with respect to growing ability different culture media were used. We studied the temperature, at which ice nucleation occurred for individual bacteria, estimated the population of INA bacteria, effect of growth limiting factors, and evaluated the effect of chemical and physical agents for disruption and possible inhibition of INA among individual bacterial strains. The concentration of carbon, nitrogen and phosphorus on INA is discussed. We demonstrate that among the bacterial isolates recovered from the willow plantations, there were many that were capable of ice nucleation at temperatures between -2 and -10 deg C, many that were capable of inducing a

  19. Electronic Structures of Strained InAs x P1-x by Density Functional Theory.

    Science.gov (United States)

    Lee, Seung Mi; Kim, Min-Young; Kim, Young Heon

    2018-09-01

    We investigated the effects of strain on the electronic structures of InAsxP1-x using quantum mechanical density functional theory calculations. The electronic band gap and electron effective mass decreased with the increase of the uniaxial tensile strain along the [0001] direction of wurtzite InAs0.75P0.25. Therefore, faster electron movements are expected. These theoretical results are in good agreement with the experimental measurements of InAs0.75P0.25 nanowire.

  20. InAs migration on released, wrinkled InGaAs membranes used as virtual substrate

    International Nuclear Information System (INIS)

    Filipe Covre da Silva, S; Lanzoni, E M; De Araujo Barboza, V; Deneke, Ch; Malachias, A; Kiravittaya, S

    2014-01-01

    Partly released, relaxed and wrinkled InGaAs membranes are used as virtual substrates for overgrowth with InAs. Such samples exhibit different lattice parameters for the unreleased epitaxial parts, the released flat, back-bond areas and the released wrinkled areas. A large InAs migration towards the released membrane is observed with a material accumulation on top of the freestanding wrinkles during overgrowth. A semi-quantitative analysis of the misfit strain shows that the material migrates to the areas of the sample with the lowest misfit strain, which we consider as the areas of the lowest chemical potential of the surface. Material migration is also observed for the edge-supported, freestanding InGaAs membranes found on these samples. Our results show that the released, wrinkled nanomembranes offer a growth template for InAs deposition that fundamentally changes the migration behavior of the deposited material on the growth surface. (paper)

  1. Single-photon generation with InAs quantum dots

    International Nuclear Information System (INIS)

    Santori, Charles; Fattal, David; Vuckovic, Jelena; Solomon, Glenn S; Yamamoto, Yoshihisa

    2004-01-01

    Single-photon generation using InAs quantum dots in pillar microcavities is described. The effects on performance of the excitation wavelength and polarization, and the collection bandwidth and polarization, are studied in detail. The efficiency and photon state purity of these devices have been measured, and issues affecting these parameters are discussed. Prospects for improved devices are also discussed

  2. Correlation between the Montreal Cognitive Assessment-Indonesian Version (Moca-INA) and the Mini-Mental State Examination (MMSE) in Elderly.

    Science.gov (United States)

    Rambe, Aldy Safruddin; Fitri, Fasihah Irfani

    2017-12-15

    As the rapid growth of the elderly population and the increased prevalence of Alezheimer's Disease and related disorders, there is an increasing need for effective cognitive screening. The Mini Mental State Examination (MMSE) is the most frequently used screening test of cognitive impairment because of its convenience. The Montreal Cognitive Assessment-Indonesian Version (MoCA-INA) has been validated and recently been used as a cognitive screening tool. The aim of this study was to compare the MMSE and MoCA-INA scores and to determine the correlation between the MMSE and MoCA-INA scores in elderly. This was a cross-sectional study including 83 elderly subjects from November 2016 until June 2017. We performed MMSE and MoCA-INA for assessment of cognitive function and the time between each test was at least 30 minutes. The study included 83 subjects which were consisted of 46 (55.4%) males and 37 (44.6%) females. The mean age was 69.19 ± 4.23 ranging from 65 to 79 years old. The average MMSE scores was 24.96 ± 3.38 (range 14 to 30). The average MoCA-INA scores was 21.06 ± 4.56 (range 5 to 30). The Pearson correlation coefficient between the scores was 0.71 (p<0.005). There were no significant differences of both scores based on history of hypertension, diabetes mellitus and previous stroke, but there was a significant difference in MMSE scores based on level of education. The MoCA-INA score showed a good correlation with the MMSE score. Both tests showed comparable results but MoCA-INA showed lower average with wider range of scores.

  3. Surface Preparation of InAs (110 Using Atomic Hydrogen

    Directory of Open Access Journals (Sweden)

    T.D. Veal

    2002-06-01

    Full Text Available Atomic hydrogen cleaning has been used to produce structurally and electronically damage-free InAs(110 surfaces.  X-ray photoelectron spectroscopy (XPS was used to obtain chemical composition and chemical state information about the surface, before and after the removal of the atmospheric contamination. Low energy electron diffraction (LEED and high-resolution electron-energy-loss spectroscopy (HREELS were also used, respectively, to determine the surface reconstruction and degree of surface ordering, and to probe the adsorbed contaminant vibrational modes and the collective excitations of the clean surface. Clean, ordered and stoichiometric  InAs(110-(1×1 surfaces were obtained by exposure to thermally generated atomic hydrogen at a substrate temperature as low as 400ºC.  Semi-classical dielectric theory analysis of HREEL spectra of the phonon and plasmon excitations of the clean surface indicate that no electronic damage or dopant passivation were induced by the surface preparation method.

  4. Nonlocal vibration and biaxial buckling of double-viscoelastic-FGM-nanoplate system with viscoelastic Pasternak medium in between

    Energy Technology Data Exchange (ETDEWEB)

    Liu, J.C. [College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058 (China); Zhang, Y.Q., E-mail: cyqzhang@zju.edu.cn [College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058 (China); State Key Laboratory of Mechanical Structural Strength and Vibration, Xi' an Jiaotong University, Xi' an 710049 (China); Fan, L.F. [College of Architecture and Civil Engineering, Beijing University of Technology, Beijing 100084 (China)

    2017-04-11

    The general equation for transverse vibration of double-viscoelastic-FGM-nanoplate system with viscoelastic Pasternak medium in between and each nanoplate subjected to in-plane edge loads is formulated on the basis of the Eringen's nonlocal elastic theory and the Kelvin model. The factors of the structural damping, medium damping, small size effect, loading ratio, and Winkler modulus and shear modulus of the medium are incorporated in the formulation. Based on the Navier's method, the analytical solutions for vibrational frequency and buckling load of the system with simply supported boundary conditions are obtained. The influences of these factors on vibrational frequency and buckling load of the system are discussed. It is demonstrated that the vibrational frequency of the system for the out-of-phase vibration is dependent upon the structural damping, small size effect and viscoelastic Pasternak medium, whereas the vibrational frequency for the in-phase vibration is independent of the viscoelastic Pasternak medium. While the buckling load of the system for the in-phase buckling case has nothing to do with the viscoelastic Pasternak medium, the buckling load for the out-of-phase case is related to the small size effect, loading ratio and Pasternak medium. - Highlights: • Vibration of double-viscoelastic-FGM-nanoplate system under in-plane edge loads is investigated. • Biaxial buckling of the system with simply supported boundary conditions is analyzed. • Explicit expression for the vibrational frequency and buckling load is obtained. • Impacts of viscoelastic Pasternak medium on vibrational frequency and buckling load are discussed. • Influences of structural damping, small size effect and loading ratio are also considered.

  5. Synthesis of Mesoporous Single Crystal Co(OH)2 Nanoplate and Its Topotactic Conversion to Dual-Pore Mesoporous Single Crystal Co3O4.

    Science.gov (United States)

    Jia, Bao-Rui; Qin, Ming-Li; Li, Shu-Mei; Zhang, Zi-Li; Lu, Hui-Feng; Chen, Peng-Qi; Wu, Hao-Yang; Lu, Xin; Zhang, Lin; Qu, Xuan-Hui

    2016-06-22

    A new class of mesoporous single crystalline (MSC) material, Co(OH)2 nanoplates, is synthesized by a soft template method, and it is topotactically converted to dual-pore MSC Co3O4. Most mesoporous materials derived from the soft template method are reported to be amorphous or polycrystallined; however, in our synthesis, Co(OH)2 seeds grow to form single crystals, with amphiphilic block copolymer F127 colloids as the pore producer. The single-crystalline nature of material can be kept during the conversion from Co(OH)2 to Co3O4, and special dual-pore MSC Co3O4 nanoplates can be obtained. As the anode of lithium-ion batteries, such dual-pore MSC Co3O4 nanoplates possess exceedingly high capacity as well as long cyclic performance (730 mAh g(-1) at 1 A g(-1) after the 350th cycle). The superior performance is because of the unique hierarchical mesoporous structure, which could significantly improve Li(+) diffusion kinetics, and the exposed highly active (111) crystal planes are in favor of the conversion reaction in the charge/discharge cycles.

  6. Characterisation of InAs-based epilayers by FTIR spectroscopy

    CSIR Research Space (South Africa)

    Baisitse, TR

    2008-01-01

    Full Text Available In this paper, infrared reflectance spectroscopy was employed to extract information on the optical and electrical properties of metal organic vapour phase epitaxial (MOVPE) grown InAs and InAsSb epilayers. These epitaxial layers were grown on InAs...

  7. In situ catalytic synthesis of high-graphitized carbon-coated LiFePO4 nanoplates for superior Li-ion battery cathodes.

    Science.gov (United States)

    Ma, Zhipeng; Fan, Yuqian; Shao, Guangjie; Wang, Guiling; Song, Jianjun; Liu, Tingting

    2015-02-04

    The low electronic conductivity and one-dimensional diffusion channel along the b axis for Li ions are two major obstacles to achieving high power density of LiFePO4 material. Coating carbon with excellent conductivity on the tailored LiFePO4 nanoparticles therefore plays an important role for efficient charge and mass transport within this material. We report here the in situ catalytic synthesis of high-graphitized carbon-coated LiFePO4 nanoplates with highly oriented (010) facets by introducing ferrocene as a catalyst during thermal treatment. The as-obtained material exhibits superior performances for Li-ion batteries at high rate (100 C) and low temperature (-20 °C), mainly because of fast electron transport through the graphitic carbon layer and efficient Li(+)-ion diffusion through the thin nanoplates.

  8. CuCo2O4 nanoplate film as a low-cost, highly active and durable catalyst towards the hydrolytic dehydrogenation of ammonia borane for hydrogen production

    Science.gov (United States)

    Liu, Quanbing; Zhang, Shengjie; Liao, Jinyun; Feng, Kejun; Zheng, Yuying; Pollet, Bruno G.; Li, Hao

    2017-07-01

    Catalytic dehydrogenation of ammonia borane is one of the most promising routes for the production of clean hydrogen as it is seen as a highly efficient and safe method. However, its large-scale industrial application is either limited by the high cost of the catalyst (usually a noble metal based catalyst) or by the low activity and poor reusability (usually a non-noble metal catalyst). In this study, we have successfully prepared three low-cost CuCo2O4 nanocatalysts, namely: (i) Ti supported CuCo2O4 film made of CuCo2O4 nanoplates, (ii) Ti supported CuCo2O4 film made of CuCo2O4 nanosheets, and (iii) unsupported CuCo2O4 nanoparticles. Among the three catalysts used for the hydrolytic dehydrogeneration of ammonia borane, the CuCo2O4 nanoplate film exhibits the highest catalytic activity with a turnover frequency (TOF) of ∼44.0 molhydrogen min-1 molcat-1. This is one of the largest TOF value for noble-metal-free catalysts ever reported in the literature. Moreover, the CuCo2O4 nanoplate film almost keeps its original catalytic activity after eight cycles, indicative of its high stability and good reusability. Owing to its advantages, the CuCo2O4 nanoplate film can be a promising catalyst for the hydrolytic dehydrogenation of ammonia borane, which may find important applications in the field of hydrogen energy.

  9. Aqueous supercapacitors of high energy density based on MoO3 nanoplates as anode material.

    Science.gov (United States)

    Tang, Wei; Liu, Lili; Tian, Shu; Li, Lei; Yue, Yunbo; Wu, Yuping; Zhu, Kai

    2011-09-28

    MoO(3) nanoplates were prepared as anode material for aqueous supercapacitors. They can deliver a high energy density of 45 W h kg(-1) at 450 W kg(-1) and even maintain 29 W h kg(-1) at 2 kW kg(-1) in 0.5 M Li(2)SO(4) aqueous electrolyte. These results present a new direction to explore non-carbon anode materials.

  10. On the processing of InAs and InSb photodiode applications

    Energy Technology Data Exchange (ETDEWEB)

    Odendaal, V.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, PO Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Auret, F.D. [Department of Physics, University of Pretoria, Lynnwood road, Hillcrest, Pretoria 0002 (South Africa)

    2008-07-01

    In this paper, potential methods for the surface passivation of InSb and InAs material, covering both compositional extremes of the promising narrow band gap semiconductor InAsSb, are evaluated. Surface states, mostly due to dangling bonds and exposure to the atmosphere, create generation-recombination centres that negatively influence the dark current, stability, efficiency and related noise characteristics of photosensitive devices fabricated from these materials. The effect of various surface treatments, including sulphuric acid based etching, lactic acid based etching, KOH anodising and Na{sub 2}S anodising, on the relative number of surface states is deduced by evaluating the capacitance versus voltage characteristics of metal-insulator-semiconductor structures fabricated on InAs and InSb. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. On the processing of InAs and InSb photodiode applications

    International Nuclear Information System (INIS)

    Odendaal, V.; Botha, J.R.; Auret, F.D.

    2008-01-01

    In this paper, potential methods for the surface passivation of InSb and InAs material, covering both compositional extremes of the promising narrow band gap semiconductor InAsSb, are evaluated. Surface states, mostly due to dangling bonds and exposure to the atmosphere, create generation-recombination centres that negatively influence the dark current, stability, efficiency and related noise characteristics of photosensitive devices fabricated from these materials. The effect of various surface treatments, including sulphuric acid based etching, lactic acid based etching, KOH anodising and Na 2 S anodising, on the relative number of surface states is deduced by evaluating the capacitance versus voltage characteristics of metal-insulator-semiconductor structures fabricated on InAs and InSb. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Controllable synthesis of Bi{sub 2}WO{sub 6} nanoplate self-assembled hierarchical erythrocyte microspheres via a one-pot hydrothermal reaction with enhanced visible light photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhenya; Huang, Lin; Xie, Yanyu; Lin, Zheguan; Fan, Yunyan; Liu, Dan; Chen, Lu; Zhang, Zizhong, E-mail: z.zhang@fzu.edu.cn; Wang, Xuxu

    2017-05-01

    Highlights: • Bi{sub 2}WO{sub 6} hierarchical erythrocyte structure was designed by F{sup −}-assisted one-pot reaction. • Erythrocyte structure enhanced the visible-light photocatalytic activity of Bi{sub 2}WO{sub 6}. • Superoxide radical anions and h{sup +} were the main active species for RhB degradation. - Abstract: This work provides a simple approach of the F{sup −}-assisted one-pot hydrothermal reaction to successfully synthesize Bi{sub 2}WO{sub 6} hierarchical erythrocyte microspheres. The importance role of F{sup −} was systematically investigated by comparing different type of halogen ions, hydrothermal temperature and time. The possible growth mechanism of Bi{sub 2}WO{sub 6} hierarchical structures was proposed. The hierarchical erythrocytes were formed through the well-ordered and oriented self-assembly of thin Bi{sub 2}WO{sub 6} nanoplate primary subunits. F{sup −} ions were absorbed on Bi{sub 2}WO{sub 6} nanoplate surface to suppress the nanoplate stack but to induce a self-assembly through the edge interaction of Bi{sub 2}WO{sub 6} nanoplates into erythrocyte-like hierarchical microspheres superstructures. This erythrocyte structure narrowed the band gap energy and enhanced the visible-light photocatalytic activity of Bi{sub 2}WO{sub 6}. Moreover, superoxide radical anions and h{sup +} were revealed as the main active species responding for the RhB degradation on Bi{sub 2}WO{sub 6} under visible light irradiation.

  13. Ultrathin Layered SnSe Nanoplates for Low Voltage, High-Rate, and Long-Life Alkali-Ion Batteries.

    Science.gov (United States)

    Wang, Wei; Li, Peihao; Zheng, Henry; Liu, Qiao; Lv, Fan; Wu, Jiandong; Wang, Hao; Guo, Shaojun

    2017-12-01

    2D electrode materials with layered structures have shown huge potential in the fields of lithium- and sodium-ion batteries. However, their poor conductivity limits the rate performance and cycle stability of batteries. Herein a new colloid chemistry strategy is reported for making 2D ultrathin layered SnSe nanoplates (SnSe NPs) for achieving more efficient alkali-ion batteries. Due to the effect of weak Van der Waals forces, each semiconductive SnSe nanoplate stacks on top of each other, which can facilitate the ion transfer and accommodate volume expansion during the charge and discharge process. This unique structure as well as the narrow-bandgap semiconductor property of SnSe simultaneously meets the requirements of achieving fast ionic and electronic conductivities for alkali-ion batteries. They exhibit high capacity of 463.6 mAh g -1 at 0.05 A g -1 for Na-ion batteries and 787.9 mAh g -1 at 0.2 A g -1 for Li-ion batteries over 300 cycles, and also high stability for alkali-ion batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. 99mTc-MIBI/123I-Na subtraction scanning for localized parathyroid adenoma in patients with asymptomatic/mild primary hyperparathyroidism

    International Nuclear Information System (INIS)

    Tanaka, Yuji; Funahashi, Hiroomi; Imai, Tsuneo

    1996-01-01

    Primary hyperparathyroidism is most commonly detected as a mild elevation of the serum calcium concentration. In the present study, the utility of 99m Tc-methoxyisobutylisonitrile (MIBI) imaging before initial surgery was evaluated for localizing abnormal parathyroid glands in patients with asymptomatic and mild primary hyperparathyroidism. The results were compared with those of thallium-technetium subtraction scanning (TTSS). 99m Tc-MIBI/ 123 I-Na subtraction scanning was performed in 11 patients, and TTSS was performed in 10 of them. The sensitivity was 100% and the positive predictive value was 92% for 99m Tc-MIBI/ 123 I-Na, while the sensitivity was 50% and the positive predictive value was 100% for TTSS. The smallest gland detected weighed 85 mg in 99m Tc-MIBI/ 123 I-Na, and 570 mg in TTSS. There was a difference between the median weight of adenomas which were detected by 99m Tc-MIBI/ 123 I-Na (754 mg), and those which were detected by TTSS (1,195 mg). These results suggest that TTSS parathyroid scintigraphy could give way to 99m Tc-MIBI/ 123 I-Na parathyroid scintigraphy for improved detection of low-weight abnormal parathyroid glands. (author)

  15. InP and InAs nanowires hetero- and homojunctions: energetic stability and electronic properties.

    Science.gov (United States)

    Dionízio Moreira, M; Venezuela, P; Miwa, R H

    2010-07-16

    We performed an ab initio total energy investigation, within the density functional theory, of the energetic stability and the electronic properties of hydrogenated InAs/InP nanowire (NW) heterojunctions, as well as InAs and InP homojunctions composed of different structural arrangements, zinc-blend (zb) and wurtzite (w). For InAs/InP NW heterojunctions our results indicate that w and zb NW heterojunctions are quite similar, energetically, for thin NWs. We also examined the robustness of the abrupt interface through an atomic swap at the InAs/InP interface. Our results support the formation of abrupt (non-abrupt) interfaces in w (zb) InAs/InP heterojunctions. Concerning InAs/InP NW-SLs, our results indicate a type-I band alignment, with the energy barrier at the InP layers, in accordance with experimental works. For InAs or InP zb/w homojunctions, we also found a type-I band alignment for thin NWs, however, on increasing the NW diameter both InAs and InP homojunctions exhibit a type-II band alignment.

  16. InP and InAs nanowires hetero- and homojunctions: energetic stability and electronic properties

    International Nuclear Information System (INIS)

    Dionizio Moreira, M; Venezuela, P; Miwa, R H

    2010-01-01

    We performed an ab initio total energy investigation, within the density functional theory, of the energetic stability and the electronic properties of hydrogenated InAs/InP nanowire (NW) heterojunctions, as well as InAs and InP homojunctions composed of different structural arrangements, zinc-blend (zb) and wurtzite (w). For InAs/InP NW heterojunctions our results indicate that w and zb NW heterojunctions are quite similar, energetically, for thin NWs. We also examined the robustness of the abrupt interface through an atomic As↔P swap at the InAs/InP interface. Our results support the formation of abrupt (non-abrupt) interfaces in w (zb) InAs/InP heterojunctions. Concerning InAs/InP NW-SLs, our results indicate a type-I band alignment, with the energy barrier at the InP layers, in accordance with experimental works. For InAs or InP zb/w homojunctions, we also found a type-I band alignment for thin NWs, however, on increasing the NW diameter both InAs and InP homojunctions exhibit a type-II band alignment.

  17. Charge pumping in InAs nanowires by surface acoustic waves

    NARCIS (Netherlands)

    Roddaro, Stefano; Strambini, Elia; Romeo, Lorenzo; Piazza, Vincenzo; Nilsson, Kristian; Samuelson, Lars; Beltram, Fabio

    2010-01-01

    We investigate the interaction between surface acoustic waves on a piezoelectric LiNbO3 substrate and charge carriers in InAs nanowire transistors. Interdigital transducers are used to excite electromechanical waves on the chip surface and their influence on the transport in the nanowire devices is

  18. In situ study of the formation kinetics of InSb quantum dots grown in an InAs(Sb) matrix

    International Nuclear Information System (INIS)

    Semenov, A. N.; Lyublinskaya, O. G.; Solov’ev, V. A.; Mel’tser, B. Ya.; Ivanov, S. V.

    2008-01-01

    Formation of InSb quantum dots grown in an InAs matrix by molecular-beam epitaxy that does not involve forced deposition of InSb is studied. Detection of intensity oscillations in the reflection of high-energy electron diffraction patterns was used to study in situ the kinetics of the formation of InSb quantum dots and an InAsSb wetting layer. The effects of the substrate temperature, the shutter operation sequence, and the introduction of growth interruptions on the properties of the array of InSb quantum dots are examined. Introduction of a growth interruption immediately after completing the exposure of the InAs surface to the antimony flux leads to a reduction in the nominal thickness of InSb and to an enhancement in the uniformity of the quantum-dot array. It is shown that, in the case of deposition of submonolayer-thickness InSb/InAs quantum dots, the segregation layer of InAsSb plays the role of the wetting layer. The Sb segregation length and segregation ratio, as well as their temperature dependences, are determined.

  19. Diameter dependence of the thermal conductivity of InAs nanowires

    NARCIS (Netherlands)

    Swinkels, M.Y.; van Delft, M.R.; Oliveira, D.S.; Cavalli, A.; Zardo, I.; van der Heijden, R.W.; Bakkers, E.P.A.M.

    2015-01-01

    The diameter dependence of the thermal conductivity of InAs nanowires in the range of 40–1500 nm has been measured. We demonstrate a reduction in thermal conductivity of 80% for 40 nm nanowires, opening the way for further design strategies for nanoscaled thermoelectric materials. Furthermore, we

  20. Electrical properties of undoped and doped MOVPE-grown InAsSb

    CSIR Research Space (South Africa)

    Krug, T

    2006-01-01

    Full Text Available ) Simulation Figure 1: Reflectance spectrum of M3007, together with computer simulation result. d T (K) ns (cm-3) nb (cm-3) n (cm-3) µs (cm2/Vs) µb (cm2/Vs) µ (cm2/Vs) 16µm 80 3×1018 3×1014 1×1016 5×103 1×105 2×104 22µm 81 1×1018 2×1014 3...×1015 7×103 1×105 3×104 17µma 77 1×1017 2×1014 - 2×104 2×105 - a Carrier concentration and mobility given in Wang et al [10] for a 17µm InAs film grown on GaAs by molecular beam epitaxy. These results were obtained using cyclotron resonance...

  1. Ag loaded WO_3 nanoplates for efficient photocatalytic degradation of sulfanilamide and their bactericidal effect under visible light irradiation

    International Nuclear Information System (INIS)

    Zhu, Wenyu; Liu, Jincheng; Yu, Shuyan; Zhou, Yan; Yan, Xiaoli

    2016-01-01

    Highlights: • WO_3/Ag heterogeneous composites were fabricated with simply photo-reduction method. • Property changes due to Ag loading were systematically studied. • WO_3/Ag composites efficiently degraded sulfanilamide under visible light irradiation. • WO_3/Ag composites exhibited bactericidal effectS under visible light irradiation. - Abstract: Sulfonamides (SAs) are extensively used antibiotics and their residues in the water bodies propose potential threat to the public. In this study, degradation efficiency of sulfanilamide (SAM), which is the precursor of SAs, using WO_3 nanoplates and their Ag heterogeneous as photocatalysts was investigated. WO_3 nanoplates with uniform size were synthesized by a facile one step hydrothermal method. Different amount of Ag nanoparticles (Ag NPs) were loaded onto WO_3 nanoplates using a photo-reduction method to generate WO_3/Ag composites. The physio-chemical properties of synthesized nanomaterials were systematically characterized. Photodegradation of SAM by WO_3 and WO_3/Ag composites was conducted under visible light irradiation. The results show that WO_3/Ag composites performed much better than pure WO_3 where the highest removal rate was 96.2% in 5 h. Ag as excellent antibacterial agent also endows certain antibacterial efficiency to WO_3, and 100% removal efficiency against Escherichia Coli and Bacillus subtilis could be achieved in 2 h under visible light irradiation for all three WO_3/Ag composites synthesized. The improved performance in terms of SAM degradation and antibacterial activity of WO_3/Ag can be attributed to the improved electron-hole pair separation rate where Ag NPs act as effective electron trapper during the photocatalytic process.

  2. Growth and anisotropic transport properties of self-assembled InAs nanostructures in InP

    International Nuclear Information System (INIS)

    Bierwagen, O.

    2007-01-01

    Self-assembled InAs nanostructures in InP, comprising quantum wells, quantum wires, and quantum dots, are studied in terms of their formation and properties. In particular, the structural, optical, and anisotropic transport properties of the nanostructures are investigated. The focus is a comprehending exploration of the anisotropic in-plane transport in large ensembles of laterally coupled InAs nanostructures. The self-assembled Stranski-Krastanov growth of InAs nanostructures is studied by gas-source molecular beam epitaxy on both nominally oriented and vicinal InP(001). Optical polarization of the interband transitions arising from the nanostructure type is demonstrated by photoluminescence and transmission spectroscopy. The experimentally convenient four-contact van der Pauw Hall measurement of rectangularly shaped semiconductors, usually applied to isotropic systems, is extended to yield the anisotropic transport properties. Temperature dependent transport measurements are performed in large ensembles of laterally closely spaced nanostructures. The transport of quantum wire-, quantum dash- and quantum dot containing samples is highly anisotropic with the principal axes of conductivity aligned to the directions. The direction of higher mobility is [ anti 110], which is parallel to the direction of the quantum wires. In extreme cases, the anisotropies exceed 30 for electrons, and 100 for holes. The extreme anisotropy for holes is due to diffusive transport through extended states in the [ anti 110], and hopping transport through laterally localized states in the [110] direction, within the same sample. A novel 5-terminal electronic switching device based on gate-controlled transport anisotropy is proposed. The gate-control of the transport anisotropy in modulation-doped, self-organized InAs quantum wires embedded in InP is demonstrated. (orig.)

  3. Growth and anisotropic transport properties of self-assembled InAs nanostructures in InP

    Energy Technology Data Exchange (ETDEWEB)

    Bierwagen, O.

    2007-12-20

    Self-assembled InAs nanostructures in InP, comprising quantum wells, quantum wires, and quantum dots, are studied in terms of their formation and properties. In particular, the structural, optical, and anisotropic transport properties of the nanostructures are investigated. The focus is a comprehending exploration of the anisotropic in-plane transport in large ensembles of laterally coupled InAs nanostructures. The self-assembled Stranski-Krastanov growth of InAs nanostructures is studied by gas-source molecular beam epitaxy on both nominally oriented and vicinal InP(001). Optical polarization of the interband transitions arising from the nanostructure type is demonstrated by photoluminescence and transmission spectroscopy. The experimentally convenient four-contact van der Pauw Hall measurement of rectangularly shaped semiconductors, usually applied to isotropic systems, is extended to yield the anisotropic transport properties. Temperature dependent transport measurements are performed in large ensembles of laterally closely spaced nanostructures. The transport of quantum wire-, quantum dash- and quantum dot containing samples is highly anisotropic with the principal axes of conductivity aligned to the <110> directions. The direction of higher mobility is [ anti 110], which is parallel to the direction of the quantum wires. In extreme cases, the anisotropies exceed 30 for electrons, and 100 for holes. The extreme anisotropy for holes is due to diffusive transport through extended states in the [ anti 110], and hopping transport through laterally localized states in the [110] direction, within the same sample. A novel 5-terminal electronic switching device based on gate-controlled transport anisotropy is proposed. The gate-control of the transport anisotropy in modulation-doped, self-organized InAs quantum wires embedded in InP is demonstrated. (orig.)

  4. Carrier dynamics in InAs quantum dots embedded in InGaAs/GaAs multi quantum well structures

    International Nuclear Information System (INIS)

    Espinola, J L Casas; Dybic, M; Ostapenko, S; Torchynska, T V; Polupan, G

    2007-01-01

    Ground and multi excited state photoluminescence, as well as its temperature dependence, in InAs quantum dots embedded in symmetric In x Ga 1-x As/GaAs (x = 0.15) quantum wells (DWELL) have been investigated. The solution of the set of rate equations for exciton dynamics (relaxation into QWs or QDs and thermal escape) solved by us earlier is used for analysis the variety of thermal activation energies of photoluminescence thermal quenching for ground and multi excited states of InAs QDs. The obtained solutions were used at the discussion of the variety of activation energies of PL thermal quenching in InAs QDs. It is revealed three different regimes of thermally activated quenching of the QD PL intensity. These three regimes were attributed to thermal escape of excitons: i) from the high energy excited states of InAs QDs into the WL with follows exciton re-localization; ii) from the In x Ga 1-x As QWs into the GaAs barrier and iii) from the WL into the GaAs barrier with their subsequent nonradiative recombination in GaAs barrier

  5. Calculation of Nonlinear Thermoelectric Coefficients of InAs1-xSbx Using Monte Carlo Method

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghian, RB; Bahk, JH; Bian, ZX; Shakouri, A

    2011-12-28

    It was found that the nonlinear Peltier effect could take place and increase the cooling power density when a lightly doped thermoelectric material is under a large electrical field. This effect is due to the Seebeck coefficient enhancement from an electron distribution far from equilibrium. In the nonequilibrium transport regime, the solution of the Boltzmann transport equation in the relaxation-time approximation ceases to apply. The Monte Carlo method, on the other hand, proves to be a capable tool for simulation of semiconductor devices at small scales as well as thermoelectric effects with local nonequilibrium charge distribution. InAs1-xSb is a favorable thermoelectric material for nonlinear operation owing to its high mobility inherited from the binary compounds InSb and InAs. In this work we report simulation results on the nonlinear Peltier power of InAs1-xSb at low doping levels, at room temperature and at low temperatures. The thermoelectric power factor in nonlinear operation is compared with the maximum value that can be achieved with optimal doping in the linear transport regime.

  6. Rapid optical determination of topological insulator nanoplate thickness and oxidation

    Directory of Open Access Journals (Sweden)

    Fan Yang

    2017-01-01

    Full Text Available The stability of 2D antimony telluride (Sb2Te3 nanoplates in ambient conditions is elucidated. These materials exhibit an anisotropic oxidation mode, and CVD synthesized samples oxidize at a much faster rate than exfoliated samples investigated in previous studies. Optical measurement techniques are introduced to rapidly measure the oxidation modes and thickness of 2D materials. Auger characterization were conducted to confirm that oxygen replaces tellurium as opposed to antimony under ambient conditions. No surface morphology evolution was detected in AFM before and after exposure to air. These techniques were employed to determine the origin of the thickness dependent color change effect in Sb2Te3. It is concluded that this effect is a combination of refractive index change due to oxidation and Fresnel effects.

  7. Reconstruction of an InAs nanowire using geometric tomography

    DEFF Research Database (Denmark)

    Pennington, Robert S.; König, Stefan; Alpers, Andreas

    Geometric tomography and conventional algebraic tomography algorithms are used to reconstruct cross-sections of an InAs nanowire from a tilt series of experimental annular dark-field images. Both algorithms are also applied to a test object to assess what factors affect the reconstruction quality....... When using the present algorithms, geometric tomography is faster, but artifacts in the reconstruction may be difficult to recognize....

  8. Adding GaAs Monolayers to InAs Quantum-Dot Lasers on (001) InP

    Science.gov (United States)

    Qiu, Yueming; Chacon, Rebecca; Uhl, David; Yang, Rui

    2005-01-01

    In a modification of the basic configuration of InAs quantum-dot semiconductor lasers on (001)lnP substrate, a thin layer (typically 1 to 2 monolayer thick) of GaAs is incorporated into the active region. This modification enhances laser performance: In particular, whereas it has been necessary to cool the unmodified devices to temperatures of about 80 K in order to obtain lasing at long wavelengths, the modified devices can lase at wavelengths of about 1.7 microns or more near room temperature. InAs quantum dots self-assemble, as a consequence of the lattice mismatch, during epitaxial deposition of InAs on ln0.53Ga0.47As/lnP. In the unmodified devices, the quantum dots as thus formed are typically nonuniform in size. Strainenergy relaxation in very large quantum dots can lead to poor laser performance, especially at wavelengths near 2 microns, for which large quantum dots are needed. In the modified devices, the thin layers of GaAs added to the active regions constitute potential-energy barriers that electrons can only penetrate by quantum tunneling and thus reduce the hot carrier effects. Also, the insertion of thin GaAs layer is shown to reduce the degree of nonuniformity of sizes of the quantum dots. In the fabrication of a batch of modified InAs quantum-dot lasers, the thin additional layer of GaAs is deposited as an interfacial layer in an InGaAs quantum well on (001) InP substrate. The device as described thus far is sandwiched between InGaAsPy waveguide layers, then further sandwiched between InP cladding layers, then further sandwiched between heavily Zn-doped (p-type) InGaAs contact layer.

  9. Emission and elastic strain in InGaAs/GaAs quantum wells with embedded InAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Vega-Macotela, L.G.; Polupan, G. [ESIME - Instituto Politecnico Nacional, Mexico D.F. 07738 (Mexico); Shcherbyna, Ye. [National Technical University-' ' KPI' ' , Kiev 03057 (Ukraine)

    2012-07-15

    Photoluminescence (PL) spectra have been studied in the symmetric GaAs/In{sub 0.15}Ga{sub 0.85}As/GaAs quantum wells (QWs) with embedded InAs quantum dots (QDs), grown at different temperatures from the range 470-535 C. The increase of QD growth temperature is accompanied by decreasing the QD surface density and the enlargement of QD lateral diameters. Simultaneously the variation of the PL intensity and PL peak positions none monotonously have been detected. To understand the reason of the variation of PL intensity and peak positions the PL temperature dependences and the X-ray diffraction (XRD) at low angles (1.75-1.92 ) have been studied. The fitting procedure is applied to analysis the temperature shift of PL peak positions. Fitting has been done on the base of empirical expression for the band gap shrinkage that uses the Einstein temperature parameter. The character non monotonous for the Ga/In inter diffusion versus QD growth temperatures has been revealed. The XRD study has detected the high intensity peaks that corresponds to the diffraction of X-ray beam from the (311) crystal planes in GaAs QWs. The position of XRD peaks in the structures with QD grown at 490-510 C is very close to the angles related to the diffraction from (311) planes in the bulk GaAs. In QD structures with QD grown at 470 and 525-535 C the (311) XRD peaks shift to the higher diffraction angles that testifies on the essential compressive strains in these structures. The reason of the variation non monotonously of elastic strain versus QD densities has been discussed (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Quantum efficiency and oscillator strength of site-controlled InAs quantum dots

    DEFF Research Database (Denmark)

    Albert, F.; Stobbe, Søren; Schneider, C.

    2010-01-01

    We report on time-resolved photoluminescence spectroscopy to determine the oscillator strength (OS) and the quantum efficiency (QE) of site-controlled InAs quantum dots nucleating on patterned nanoholes. These two quantities are determined by measurements on site-controlled quantum dot (SCQD...

  11. Quantum Dots obtained by LPE from under-saturated In-As liquid phases on GaAs substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz F E; Mishurnyi V; Gorbatchev A; De Anda F [Universidad Autonoma de San Luis Potosi, Instituto de Investigacion en Comunicacion Optica, Av. Karacorum 1470, Col. Lomas 4a Sec., CP 78210San Luis PotosI (Mexico); Prutskij T, E-mail: fcoe_ov@prodigy.net.mx, E-mail: andre@cactus.iico.uaslp.mx [BUAP, Instituto de Ciencias, Apartado Postal 207, 72000, Puebla (Mexico)

    2011-01-01

    In this work we inform about quantum dots (QD) obtained by Liquid Phase Epitaxy (LPE) on GaAs substrates from under-saturated In-As liquid phases. In our processes, we have prepared saturated In-rich liquid phases by dissolving an InAs wafer at one of the temperatures interval from 450 to 414 C for 60 minutes. The contact between In-As liquid phase and the GaAs substrate was always done at a constant temperature of 444 C for 5 seconds. Thus, the growth temperature for most of the samples was higher than the liquidus temperature. We think that the growth driving force is related to a transient process that occurs when the system is trying to reach equilibrium. Under the atom force microscope (AFM) we have observed nano-islands on the surfaces of the samples obtained from under-saturated liquid phases prepared at 438, 432 and 426 C. The 25 K photoluminescence spectrum shows a peak at a 1.33 eV, in addition to the GaAs related line.

  12. Rapid adsorption properties of flower-like BiOI nanoplates synthesized via a simple EG-assisted solvothermal process

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bin; Ji, Guangbin, E-mail: gbji@nuaa.edu.cn [Nanjing University of Aeronautics and Astronautics, College of Materials Science and Technology (China); Gondal, M. A. [King Fahd University of Petroleum and Minerals, Physics Department (Saudi Arabia); Liu, Yousong; Zhang, Xingmiao; Chang, Xiaofeng; Li, Nianwu [Nanjing University of Aeronautics and Astronautics, College of Materials Science and Technology (China)

    2013-07-15

    Uniform well-crystallized flower-like BiOI nanoplates contained 3.7 nm mesopores, which may be attributed to the internanosheet spaces of BiOI with maximum pore diameters of about 30 nm, were successfully synthesized via a simple ethylene glycol-assisted solvothermal method. The as-prepared porous BiOI nanoplates exhibited excellent adsorption ability, and the saturated extent of adsorption of BiOI over an RhB solution was as high as 197 mg/g, which is much higher than those for BiOCl and BiOBr prepared via the same method and with a similar surface area. The probable adsorption mechanism could have originated from the interaction between the I atom in BiOI and a proton in RhB at different pH values and temperatures. With visible light irradiation ({lambda} > 420 nm), 80 % of the RhB was degraded in 4 h, while BiOI still demonstrated reasonably outstanding photocatalytic ability under green light ({lambda} = 550 {+-} 15 nm) because of its low-energy gap (1.72 eV). The degradation test for BiOI under irradiation at {lambda} = 550 {+-} 15 nm is an excellent achievement for field applications because the catalyst can be applied in solar irradiation to remove organic pollutants, which may be of great value BiOI complex.

  13. A colorimetric method for highly sensitive and accurate detection of iodide by finding the critical color in a color change process using silver triangular nanoplates

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiu-Hua; Ling, Jian, E-mail: lingjian@ynu.edu.cn; Peng, Jun; Cao, Qiu-E., E-mail: qecao@ynu.edu.cn; Ding, Zhong-Tao; Bian, Long-Chun

    2013-10-10

    Graphical abstract: -- Highlights: •Demonstrated a new colorimetric strategy for iodide detection by silver nanoplates. •The colorimetric strategy is to find the critical color in a color change process. •The colorimetric strategy is more accurate and sensitive than common colorimetry. •Discovered a new morphological transformation phenomenon of silver nanoplates. -- Abstract: In this contribution, we demonstrated a novel colorimetric method for highly sensitive and accurate detection of iodide using citrate-stabilized silver triangular nanoplates (silver TNPs). Very lower concentration of iodide can induce an appreciable color change of silver TNPs solution from blue to yellow by fusing of silver TNPs to nanoparticles, as confirmed by UV–vis absorption spectroscopy and transmission electron microscopy (TEM). The principle of this colorimetric assay is not an ordinary colorimetry, but a new colorimetric strategy by finding the critical color in a color change process. With this strategy, 0.1 μM of iodide can be recognized within 30 min by naked-eyes observation, and lower concentration of iodide down to 8.8 nM can be detected using a spectrophotometer. Furthermore, this high sensitive colorimetric assay has good accuracy, stability and reproducibility comparing with other ordinary colorimetry. We believe this new colorimetric method will open up a fresh insight of simple, rapid and reliable detection of iodide and can find its future application in the biochemical analysis or clinical diagnosis.

  14. A colorimetric method for highly sensitive and accurate detection of iodide by finding the critical color in a color change process using silver triangular nanoplates

    International Nuclear Information System (INIS)

    Yang, Xiu-Hua; Ling, Jian; Peng, Jun; Cao, Qiu-E.; Ding, Zhong-Tao; Bian, Long-Chun

    2013-01-01

    Graphical abstract: -- Highlights: •Demonstrated a new colorimetric strategy for iodide detection by silver nanoplates. •The colorimetric strategy is to find the critical color in a color change process. •The colorimetric strategy is more accurate and sensitive than common colorimetry. •Discovered a new morphological transformation phenomenon of silver nanoplates. -- Abstract: In this contribution, we demonstrated a novel colorimetric method for highly sensitive and accurate detection of iodide using citrate-stabilized silver triangular nanoplates (silver TNPs). Very lower concentration of iodide can induce an appreciable color change of silver TNPs solution from blue to yellow by fusing of silver TNPs to nanoparticles, as confirmed by UV–vis absorption spectroscopy and transmission electron microscopy (TEM). The principle of this colorimetric assay is not an ordinary colorimetry, but a new colorimetric strategy by finding the critical color in a color change process. With this strategy, 0.1 μM of iodide can be recognized within 30 min by naked-eyes observation, and lower concentration of iodide down to 8.8 nM can be detected using a spectrophotometer. Furthermore, this high sensitive colorimetric assay has good accuracy, stability and reproducibility comparing with other ordinary colorimetry. We believe this new colorimetric method will open up a fresh insight of simple, rapid and reliable detection of iodide and can find its future application in the biochemical analysis or clinical diagnosis

  15. Ag loaded WO{sub 3} nanoplates for efficient photocatalytic degradation of sulfanilamide and their bactericidal effect under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Wenyu [School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141 (Singapore); Liu, Jincheng, E-mail: JCLIU@ntu.edu.sg [School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Current address: Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510009 (China); Yu, Shuyan; Zhou, Yan [School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141 (Singapore); Yan, Xiaoli, E-mail: XLYAN@ntu.edu.sg [School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Current address: Environmental and Water Technology Centre of Innovation, Ngee Ann Polytechnic, 535 Clementi Road, Singapore 599489 (Singapore)

    2016-11-15

    Highlights: • WO{sub 3}/Ag heterogeneous composites were fabricated with simply photo-reduction method. • Property changes due to Ag loading were systematically studied. • WO{sub 3}/Ag composites efficiently degraded sulfanilamide under visible light irradiation. • WO{sub 3}/Ag composites exhibited bactericidal effectS under visible light irradiation. - Abstract: Sulfonamides (SAs) are extensively used antibiotics and their residues in the water bodies propose potential threat to the public. In this study, degradation efficiency of sulfanilamide (SAM), which is the precursor of SAs, using WO{sub 3} nanoplates and their Ag heterogeneous as photocatalysts was investigated. WO{sub 3} nanoplates with uniform size were synthesized by a facile one step hydrothermal method. Different amount of Ag nanoparticles (Ag NPs) were loaded onto WO{sub 3} nanoplates using a photo-reduction method to generate WO{sub 3}/Ag composites. The physio-chemical properties of synthesized nanomaterials were systematically characterized. Photodegradation of SAM by WO{sub 3} and WO{sub 3}/Ag composites was conducted under visible light irradiation. The results show that WO{sub 3}/Ag composites performed much better than pure WO{sub 3} where the highest removal rate was 96.2% in 5 h. Ag as excellent antibacterial agent also endows certain antibacterial efficiency to WO{sub 3}, and 100% removal efficiency against Escherichia Coli and Bacillus subtilis could be achieved in 2 h under visible light irradiation for all three WO{sub 3}/Ag composites synthesized. The improved performance in terms of SAM degradation and antibacterial activity of WO{sub 3}/Ag can be attributed to the improved electron-hole pair separation rate where Ag NPs act as effective electron trapper during the photocatalytic process.

  16. Mg-doped hydroxyapatite nanoplates for biomedical applications: A surfactant assisted microwave synthesis and spectroscopic investigations

    International Nuclear Information System (INIS)

    Mishra, Vijay Kumar; Bhattacharjee, Birendra Nath; Parkash, Om; Kumar, Devendra; Rai, Shyam Bahadur

    2014-01-01

    Highlights: • Microwave irradiation technique: employed for the synthesis of Mg-HAp nanoplates. • Surfactant (EDTA) assisted synthesis of Mg-HAp. • FT-IR and Raman analysis of functional groups of Mg-HAp. - Abstract: Nanoplates of Mg doped hydroxyapatite (Mg-HAp) were derived successfully and rapidly via microwave irradiation technique. Hydroxyapatite (HAp) is the hard tissues and main inorganic component in mammals. Different nanostructures of HAp exist in different parts of human bone but nanorods are very common due to its intrinsic nature to grow in rode-like structure under physiological as well as under applied ambient conditions in laboratory. On the addition of Mg at very low level (0.06 mol%) in pure HAp results the formation of 2-D plate-like nanostructures rather than rod-like which is the matter of interest. In this attempt our efforts have been focused on the study of effect of Mg incorporation on structural and spectroscopic properties of HAp prepared via microwave irradiation technique. This technique is preferred due to several advantages viz. very fast as well as homogeneous heating, time/energy saving and eco-friendliness. The calcium nitrate tetrahydrate (Ca(NO 3 ) 2 ⋅4H 2 O)) as a source of calcium, magnesium nitrate hexahydrate (Mg(NO 3 ) 2 ⋅6H 2 O) as a source of magnesium, disodium hydrogen phosphate dihydrate (NaH 2 PO 4 ⋅2H 2 O) as a source of phosphorous and sodium ethylene diamine tetra acetate (NaEDTA) as a surfactant were used as starting reagents. Sodium hydroxide (NaOH) pellets were employed to adjust the pH value of final solution. The solution of fixed pH value was kept into the microwave oven generating waves of frequency 2.45 GHz (water absorption frequency) and power 750 W for 8 min. The precipitate thus obtained was washed, centrifuged and then dried at 100 °C for 2 h. Dried powder was then calcined at 700 °C for 2 h. The bright white powder thus obtained was characterized structurally using X-ray diffraction and

  17. Mg-doped hydroxyapatite nanoplates for biomedical applications: A surfactant assisted microwave synthesis and spectroscopic investigations

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Vijay Kumar [Department of Physics, Faculty of Science, Banaras Hindu University, Varanasi 221005 (India); Bhattacharjee, Birendra Nath; Parkash, Om [Department of Ceramic Engineering, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Kumar, Devendra, E-mail: devendra.cer@iitbhu.ac.in [Department of Ceramic Engineering, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Rai, Shyam Bahadur, E-mail: sbrai49@yahoo.co.in [Department of Physics, Faculty of Science, Banaras Hindu University, Varanasi 221005 (India)

    2014-11-25

    Highlights: • Microwave irradiation technique: employed for the synthesis of Mg-HAp nanoplates. • Surfactant (EDTA) assisted synthesis of Mg-HAp. • FT-IR and Raman analysis of functional groups of Mg-HAp. - Abstract: Nanoplates of Mg doped hydroxyapatite (Mg-HAp) were derived successfully and rapidly via microwave irradiation technique. Hydroxyapatite (HAp) is the hard tissues and main inorganic component in mammals. Different nanostructures of HAp exist in different parts of human bone but nanorods are very common due to its intrinsic nature to grow in rode-like structure under physiological as well as under applied ambient conditions in laboratory. On the addition of Mg at very low level (0.06 mol%) in pure HAp results the formation of 2-D plate-like nanostructures rather than rod-like which is the matter of interest. In this attempt our efforts have been focused on the study of effect of Mg incorporation on structural and spectroscopic properties of HAp prepared via microwave irradiation technique. This technique is preferred due to several advantages viz. very fast as well as homogeneous heating, time/energy saving and eco-friendliness. The calcium nitrate tetrahydrate (Ca(NO{sub 3}){sub 2}⋅4H{sub 2}O)) as a source of calcium, magnesium nitrate hexahydrate (Mg(NO{sub 3}){sub 2}⋅6H{sub 2}O) as a source of magnesium, disodium hydrogen phosphate dihydrate (NaH{sub 2}PO{sub 4}⋅2H{sub 2}O) as a source of phosphorous and sodium ethylene diamine tetra acetate (NaEDTA) as a surfactant were used as starting reagents. Sodium hydroxide (NaOH) pellets were employed to adjust the pH value of final solution. The solution of fixed pH value was kept into the microwave oven generating waves of frequency 2.45 GHz (water absorption frequency) and power 750 W for 8 min. The precipitate thus obtained was washed, centrifuged and then dried at 100 °C for 2 h. Dried powder was then calcined at 700 °C for 2 h. The bright white powder thus obtained was characterized

  18. 2-D modeling of dual-mode acoustic phonon excitation of a triangular nanoplate

    Science.gov (United States)

    Tai, Po-Tse; Yu, Pyng; Tang, Jau

    2010-08-01

    In this theoretical work, we investigated coherent phonon excitation of a triangular nanoplate based on 2-D Fermi-Pasta-Ulam lattice model. Based on the two-temperature model commonly used in description of laser heating of metals, we considered two kinds of forces related to electronic and lattice stresses. Based on extensive simulation and analysis, we identified two major planar phonon modes, namely, a standing wave mode related to the triangle bisector and another mode corresponding to half of the side length. This work elucidates the roles of laser-induced electronic stress and lattice stress in controlling the initial phase and the amplitude ratio between these two phonon modes.

  19. Stress evolution during growth of InAs on GaAs measured by an in-situ cantilever beam setup

    Energy Technology Data Exchange (ETDEWEB)

    Hu Dongzhi

    2007-02-13

    The influence of stress on the growth of InAs on GaAs(001) by molecular beam epitaxy (MBE) is investigated in this thesis. Film force curves were measured for InAs deposition under As-rich as well as In-rich growth conditions. The growth under As-rich conditions proceeds in the Stranski- Krastanov growth mode, meaning that quantum dots are formed after the initial growth of a wetting layer. During subsequent growth interruptions or intentional annealing at the growth temperature, the quantum dots undergo ripening. This growth mode of InAs films and the subsequent annealing behavior were studied in detail in this thesis. To understand the influence of strain on the growth mechanisms, the film force curves were analyzed and correlated to the morphological evolution of the InAs films during deposition and especially during annealing. Models were developed to fit and explain the relaxation of the film force measured during the annealing of InAs quantum dots. At temperatures lower than 470 C, quantum dots undergo standard Ostwald ripening. Different mechanisms, such as kinetic and diffusion limited, determine the ripening process. Fits of models based on these mechanisms to the film force relaxation curves, show, that although the relaxation curve for annealing at 440 C can be fitted reasonably well with all the models, the model describing ripening limited by the diffusion along dot boundaries yields a slightly better fit. The relaxation curves obtained at 455 C and 470 C can be fitted very well only with the model in which the ripening is controlled by the attachment/detachment of atoms on the dot surface. Annealing of quantum dots at temperatures higher than 500 C shows a very different behavior. Atomic force microscopy images reveal that the quantum dots ripen first and then dissolve after 450 s-600 s annealing. (orig.)

  20. Stress evolution during growth of InAs on GaAs measured by an in-situ cantilever beam setup

    International Nuclear Information System (INIS)

    Hu Dongzhi

    2007-01-01

    The influence of stress on the growth of InAs on GaAs(001) by molecular beam epitaxy (MBE) is investigated in this thesis. Film force curves were measured for InAs deposition under As-rich as well as In-rich growth conditions. The growth under As-rich conditions proceeds in the Stranski- Krastanov growth mode, meaning that quantum dots are formed after the initial growth of a wetting layer. During subsequent growth interruptions or intentional annealing at the growth temperature, the quantum dots undergo ripening. This growth mode of InAs films and the subsequent annealing behavior were studied in detail in this thesis. To understand the influence of strain on the growth mechanisms, the film force curves were analyzed and correlated to the morphological evolution of the InAs films during deposition and especially during annealing. Models were developed to fit and explain the relaxation of the film force measured during the annealing of InAs quantum dots. At temperatures lower than 470 C, quantum dots undergo standard Ostwald ripening. Different mechanisms, such as kinetic and diffusion limited, determine the ripening process. Fits of models based on these mechanisms to the film force relaxation curves, show, that although the relaxation curve for annealing at 440 C can be fitted reasonably well with all the models, the model describing ripening limited by the diffusion along dot boundaries yields a slightly better fit. The relaxation curves obtained at 455 C and 470 C can be fitted very well only with the model in which the ripening is controlled by the attachment/detachment of atoms on the dot surface. Annealing of quantum dots at temperatures higher than 500 C shows a very different behavior. Atomic force microscopy images reveal that the quantum dots ripen first and then dissolve after 450 s-600 s annealing. (orig.)

  1. Fabrication of GaAs/Al0.3Ga0.7As multiple quantum well nanostructures on (100) si substrate using a 1-nm InAs relief layer.

    Science.gov (United States)

    Oh, H J; Park, S J; Lim, J Y; Cho, N K; Song, J D; Lee, W; Lee, Y J; Myoung, J M; Choi, W J

    2014-04-01

    Nanometer scale thin InAs layer has been incorporated between Si (100) substrate and GaAs/Al0.3Ga0.7As multiple quantum well (MQW) nanostructure in order to reduce the defects generation during the growth of GaAs buffer layer on Si substrate. Observations based on atomic force microscopy (AFM) and transmission electron microscopy (TEM) suggest that initiation and propagation of defect at the Si/GaAs interface could be suppressed by incorporating thin (1 nm in thickness) InAs layer. Consequently, the microstructure and resulting optical properties improved as compared to the MQW structure formed directly on Si substrate without the InAs layer. It was also observed that there exists some limit to the desirable thickness of the InAs layer since the MQW structure having thicker InAs layer (4 nm-thick) showed deteriorated properties.

  2. Characterisation of InAs-based epilayers by FTIR spectroscopy

    International Nuclear Information System (INIS)

    Baisitse, T.R.; Forbes, A.; Katumba, G.; Botha, J.R.; Engelbrecht, J.A.A.

    2008-01-01

    In this paper, infrared reflectance spectroscopy was employed to extract information on the optical and electrical properties of metal organic vapour phase epitaxial (MOVPE) grown InAs and InAsSb epilayers. These epitaxial layers were grown on InAs and GaAs substrates and characterised by infrared reflectance spectroscopy and Hall measurements. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Upotreba začina u proizvodnji tradicionalnih sireva

    OpenAIRE

    Josipović, Renata; Markov, Ksenija; Frece, Jadranka; Stanzer, Damir; Cvitković, Ante; Mrvčić, Jasna

    2016-01-01

    Sir je visoko cijenjeni mliječni proizvod u mnogim zemljama svijeta, a posebna pažnja pridaje se tradicionalnim sirevima, koji nisu samo hrana već i dio kulture i obilježja neke zemlje. Zahvaljujući zemljopisnom položaju i klimatsko-vegetacijskoj raznolikosti Republike Hrvatske, u pojedinim regijama razvijena je proizvodnja različitih tradicionalnih sireva uz upotrebu začina. Kod proizvodnje sireva sa začinima, začini se dodaju ili u sir koji se potom oblikuje, ili se sir omata lišćem začinsk...

  4. Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots

    Directory of Open Access Journals (Sweden)

    Lin Chien-Hung

    2011-01-01

    Full Text Available Abstract In this report, the influence of the intrinsic transitions between bound-to-delocalized states (crossed states or quasicontinuous density of electron-hole states on photoluminescence excitation (PLE spectra of InAs quantum dots (QDs was investigated. The InAs QDs were different in size, shape, and number of bound states. Results from the PLE spectroscopy at low temperature and under a high magnetic field (up to 14 T were compared. Our findings show that the profile of the PLE resonances associated with the bound transitions disintegrated and broadened. This was attributed to the coupling of the localized QD excited states to the crossed states and scattering of longitudinal acoustical (LA phonons. The degree of spectral linewidth broadening was larger for the excited state in smaller QDs because of the higher crossed joint density of states and scattering rate.

  5. LiNi1/3Co1/3Mn1/3O2 nanoplates with {010} active planes exposing prepared in polyol medium as a high-performance cathode for Li-ion battery.

    Science.gov (United States)

    Li, Jili; Yao, Ruimin; Cao, Chuanbao

    2014-04-09

    As we know, Li(+)-ion transport in layered LiNi1/3Co1/3Mn1/3O2 (NCM) is through two-dimensional channels parallel to the Li(+)-ion layers that are indexed as {010} active planes. In this paper, NCM nanoplates with exposed {010} active facets are synthesized in a polyol medium (ethylene glycol) and characterized by XRD, XPS, SEM, and HR-TEM. In addition, the effects of reaction conditions on the morphologies, structures and electrochemical performances are also evaluated. The results show that more {010} facets can be exposed with the thickness of NCM nanoplates increasing which can lead to more channels for Li(+)-ion migration. However, when the annealing temperatures exceed 900 °C, many new crystal planes grow along the thickness direction covering the {010} facets. In all of the NCM nanoplates obtained at different conditions, the NCM nanoplates calcined at 850 °C for 12 h (NCM-850-12H) display a high initial discharge capacity of 207.6 mAh g(-1) at 0.1 C (1 C = 200 mA g(-1)) between 2.5 and 4.5 V higher than most of NCM materials as cathodes for lithium ion batteries. The discharge capacities of NCM-850-12H are 169.8, 160.5, and 149.3 mAh g(-1) at 2, 5, and 7 C, respectively, illustrating the excellent rate capability. The superior electrochemical performance of NCM-850-12H cathode can be attributed to more {010} active planes exposure.

  6. Molecular dynamics growth modeling of InAs1-xSbx-based type-II superlattice

    Science.gov (United States)

    Ciani, Anthony J.; Grein, Christoph H.; Irick, Barry; Miao, Maosheng; Kioussis, Nicholas

    2017-09-01

    Type-II strained-layer superlattices (T2SL) based on InAs1-xSbx are a promising photovoltaic detector material technology for thermal imaging; however, Shockley-Read-Hall recombination and generation rates are still too high for thermal imagers based on InAs1-xSbx T2SL to reach their ideal performance. Molecular dynamics simulations using the Stillinger-Weber (SW) empirical potentials are a useful tool to study the growth of tetrahedral coordinated crystals and the nonequilibrium formation of defects within them, including the long-range effects of strain. SW potentials for the possible atomic interactions among {Ga, In, As, Sb} were developed by fitting to ab initio calculations of elastically distorted zinc blende and diamond unit cells. The SW potentials were tested against experimental observations of molecular beam epitaxial (MBE) growth and then used to simulate the MBE growth of InAs/InAs0.5Sb0.5 T2SL on GaSb substrates over a range of processes parameters. The simulations showed and helped to explain Sb cross-incorporation into the InAs T2SL layers, Sb segregation within the InAsSb layers, and identified medium-range defect clusters involving interstitials and their induction of interstitial-vacancy pairs. Defect formation was also found to be affected by growth temperature and flux stoichiometry.

  7. Increasing the quantum efficiency of GaAs solar cells by embedding InAs quantum dots

    Science.gov (United States)

    Salii, R. A.; Mintairov, S. A.; Nadtochiy, A. M.; Payusov, A. S.; Brunkov, P. N.; Shvarts, M. Z.; Kalyuzhnyy, N. A.

    2016-11-01

    Development of Metalorganic Vapor Phase Epitaxy (MOVPE) technology of InAs quantum dots (QDs) in GaAs for photovoltaic applications is presented. The growth peculiarities in InAs-GaAs lattice-mismatched system were considered. The photoluminescence (PL) intensity dependences on different growth parameters were obtained. The multimodal distribution of QDs by sizes was found using AFM and PL methods. GaAs solar cell nanoheterostructures with imbedded QD arrays were designed and obtained. Ones have been demonstrated a significant increase of quantum efficiency and photogenerated current of QD solar cells due to photo effect in InAs QD array (0.59 mA/cm2 for AM1.5D and 82 mA/cm2 for AM0).

  8. Temperature dependence of the transport properties of spin field-effect transistors built with InAs and Si channels

    Science.gov (United States)

    Osintsev, D.; Sverdlov, V.; Stanojević, Z.; Makarov, A.; Selberherr, S.

    2012-05-01

    We study the transport properties of the Datta-Das spin field-effect transistor built on InAs and Si. First, we demonstrate that the amplitude of the magnetoresistance oscillations as a function of the band mismatch between the ferromagnetic contacts and the semiconductor channel made of InAs decreases dramatically with increasing temperature. A shorter InAs channel is needed to create an InAs-based SpinFET which will operate at higher temperatures. Second, we show that the [1 0 0] orientation of the fin is preferable for silicon SpinFETs due to stronger modulation of the conductance as a function of spin-orbit interaction and magnetic field. Short silicon fins can be used for current modulation as a function of the conduction band mismatch between the channel and the ferromagnetic contacts only at relatively low temperatures. In contrast, longer silicon channels allow a TMR modulation at room temperature by changing the strength of the spin-orbit interaction through the gate bias.

  9. Temperature effect on the growth of Au-free InAs and InAs/GaSb heterostructure nanowires on Si substrate by MOCVD

    Science.gov (United States)

    Kakkerla, Ramesh Kumar; Anandan, Deepak; Hsiao, Chih-Jen; Yu, Hung Wei; Singh, Sankalp Kumar; Chang, Edward Yi

    2018-05-01

    We demonstrate the growth of vertically aligned Au-free InAs and InAs/GaSb heterostructure nanowires on Si (1 1 1) substrate by Metal Organic Chemical Vapor Deposition (MOCVD). The effect of growth temperature on the morphology and growth rate of the InAs and InAs/GaSb heterostructure nanowires (NWs) is investigated. Control over diameter and length of the InAs NWs and the GaSb shell thickness was achieved by using growth temperature. As the GaSb growth temperature increase, GaSb radial growth rate increases due to the increase in alkyl decomposition at the substrate surface. Diffusivity of the adatoms increases as the GaSb growth temperature increase which results in tapered GaSb shell growth. Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) measurements revealed that the morphology and shell thickness can be tuned by the growth temperature. Electron microscopy also shows the formation of GaSb both in radial and axial directions outside the InAs NW core can be controlled by the growth temperature. This study demonstrates the control over InAs NWs growth and the GaSb shell thickness can be achieved through proper growth temperature control, such technique is essential for the growth of nanowire for future nano electronic devices, such as Tunnel FET.

  10. Self-assembly of palladium nanoparticles: Synthesis of nanobelts, nanoplates and nanotrees using vitamin B1 and their application in carbon-carbon coupling reactions

    Science.gov (United States)

    An environmentally friendly one-step method to synthesize palladium (Pd) nanobelts, nanoplates and nanotrees using vitamin B1 without using any special capping agents at room temperature is described. This greener method, which uses water as benign solvent and vitamin B1 as a red...

  11. Cathodoluminescence imaging and spectroscopy of excited states in InAs self-assembled quantum dots

    International Nuclear Information System (INIS)

    Khatsevich, S.; Rich, D.H.; Kim, Eui-Tae; Madhukar, A.

    2005-01-01

    We have examined state filling and thermal activation of carriers in buried InAs self-assembled quantum dots (SAQDs) with excitation-dependent cathodoluminescence (CL) imaging and spectroscopy. The InAs SAQDs were formed during molecular-beam epitaxial growth of InAs on undoped planar GaAs (001). The intensities of the ground- and excited-state transitions were analyzed as a function of temperature and excitation density to study the thermal activation and reemission of carriers. The thermal activation energies associated with the thermal quenching of the luminescence were measured for ground- and excited-state transitions of the SAQDs, as a function of excitation density. By comparing these activation energies with the ground- and excited-state transition energies, we have considered various processes that describe the reemission of carriers. Thermal quenching of the intensity of the QD ground- and first excited-state transitions at low excitations in the ∼230-300-K temperature range is attributed to dissociation of excitons from the QD states into the InAs wetting layer. At high excitations, much lower activation energies of the ground and excited states are obtained, suggesting that thermal reemission of single holes from QD states into the GaAs matrix is responsible for the observed temperature dependence of the QD luminescence in the ∼230-300-K temperature range. The dependence of the CL intensity of the ground-and first excited-state transition on excitation density was shown to be linear at all temperatures at low-excitation density. This result can be understood by considering that carriers escape and are recaptured as excitons or correlated electron-hole pairs. At sufficiently high excitations, state-filling and spatial smearing effects are observed together with a sublinear dependence of the CL intensity on excitation. Successive filling of the ground and excited states in adjacent groups of QDs that possess different size distributions is assumed to

  12. Energy Band Structure Studies Of Zinc-Blende GaAs and InAs ...

    African Journals Online (AJOL)

    A self-consistent calculation of the structural and electronic properties of zinc blende GaAs and InAs has been carried out. The calculations were done using the full potential-linearized augmented plane wave (FPLAPW) method within the density functional theory (DFT). The exchange-correlation energy used is the ...

  13. Intermediate band solar cell simulation use InAs quantum dot in GaAs

    International Nuclear Information System (INIS)

    Hendra P, I. B.; Rahayu, F.; Sahdan, M. F.; Darma, Y.

    2015-01-01

    Intermediate band solar cell (IBSC) has become a new approach in increasing solar cell efficiency significantly. One way to create intermediate band is by proposing quantum dots (QD) technology. One of the important aspects in utilizing IBSC is the absorption of light. In this work we simulated the influence of QD arrangement in order to increase absorption coefficient and solar cell efficiency. We also simulated the influence of QD size to capture a wider light spectrum. We present a simple calculation method with low computing power demand. Results show that the increasing in quantum dot size can increase in capturing wider spectrum of light. Arrangement InAs QD in bulk material GaAs can capture wider spectrum of light and increase the absorption coefficient. The arrangement InAs QD 2 nm in GaAs bulk can increase solar cell efficiency up to 49.68%

  14. The photoluminescence decay time of self-assembled InAs quantum dots covered by InGaAs layers

    International Nuclear Information System (INIS)

    Shu, G W; Wang, C K; Wang, J S; Shen, J L; Hsiao, R S; Chou, W C; Chen, J F; Lin, T Y; Ko, C H; Lai, C M

    2006-01-01

    The temperature dependence of the time-resolved photoluminescence (PL) of self-assembled InAs quantum dots (QDs) with InGaAs covering layers was investigated. The PL decay time increases with temperature from 50 to 170 K, and then decreases as the temperature increases further above 170 K. A model based on the phonon-assisted transition between the QD ground state and the continuum state is used to explain the temperature dependence of the PL decay time. This result suggests that the continuum states are important in the carrier capture in self-assembled InAs QDs

  15. Time-resolved x-ray diffraction measurements of high-density InAs quantum dots on Sb/GaAs layers and the suppression of coalescence by Sb-irradiated growth interruption

    International Nuclear Information System (INIS)

    Kakuda, Naoki; Yamaguchi, Koichi; Kaizu, Toshiyuki; Takahasi, Masamitu; Fujikawa, Seiji

    2010-01-01

    Self-assembly of high-density InAs quantum dots (QDs) on Sb-irradiated GaAs buffer layers was observed in-situ by a time-resolved X-ray diffraction (XRD) technique using a combination of XRD and molecular beam epitaxy. Evolution of dot height and lattice constant was analyzed during InAs QD growth and subsequent growth interruption (GI), and as a result, dislocated giant dots due to coalescence and coherent dots were separately evaluated. An Sb-irradiated GI (Sb-GI) method to be applied after InAs growth was attempted for the suppression of coalescence. Using this method, the XRD intensity of giant dots decreased, and the photoluminescence intensity of InAs QDs was enhanced. High-density InAs QDs without giant dots were produced by using the combination of the QD growth on the Sb-irradiated GaAs buffer layers and the Sb-GI. (author)

  16. Demonstration of GaAsSb/InAs nanowire backward diodes grown using position-controlled vapor-liquid-solid method

    Science.gov (United States)

    Kawaguchi, Kenichi; Takahashi, Tsuyoshi; Okamoto, Naoya; Sato, Masaru

    2018-02-01

    p-GaAsSb/n-InAs type-II nanowire (NW) diodes were fabricated using the position-controlled vapor-liquid-solid growth method. InAs and GaAsSb NW segments were grown vertically on GaAs(111)B substrates with the assistance of Au catalysts. Transmission electron microscopy-energy-dispersive X-ray spectroscopy analysis revealed that the GaAsSb segments have an Sb content of 40%, which is sufficient to form a tunnel heterostructure. Scanning capacitance microscope images clearly indicated the formation of a p-n junction in the NWs. Backward diode characteristics, that is, current flow toward negative bias originating from a tunnel current and current suppression toward positive bias by a heterobarrier, were demonstrated.

  17. Nonlinear refraction at the absorption edge in InAs.

    Science.gov (United States)

    Poole, C D; Garmire, E

    1984-08-01

    The results of measurements of nonlinear refraction at the absorption edge in InAs between 68 and 90 K taken with an HF laser are compared with those of a band-gap resonant model in which the contribution of the light-hole band is included and found to account for more than 40% of the observed nonlinear refraction. A generalized expression for the nonlinear index is derived by using the complete Fermi-Dirac distribution function. Good agreement between theory and experiment is obtained, with no free parameters.

  18. Quantification of Discrete Oxide and Sulfur Layers on Sulfur-Passivated InAs by XPS

    National Research Council Canada - National Science Library

    Petrovykh, D. Y; Sullivan, J. M; Whitman, L. J

    2005-01-01

    .... The S-passivated InAs(001) surface can be modeled as a sulfur-indium-arsenic layer-cake structure, such that characterization requires quantification of both arsenic oxide and sulfur layers that are at most a few monolayers thick...

  19. High tunability and superluminescence in InAs mid-infrared light emitting diodes

    International Nuclear Information System (INIS)

    Sherstnev, V.V.; Krier, A.; Hill, G.

    2002-01-01

    We report on the observation of super luminescence and high spectral current tunability (181 nm) of InAs light emitting diodes operating at 3.0 μm. The source is based on an optical whispering gallery mode which is generated near the edges of the mesa and which is responsible for the superluminescence. (author)

  20. Wet etch methods for InAs nanowire patterning and self-aligned electrical contacts

    Science.gov (United States)

    Fülöp, G.; d'Hollosy, S.; Hofstetter, L.; Baumgartner, A.; Nygård, J.; Schönenberger, C.; Csonka, S.

    2016-05-01

    Advanced synthesis of semiconductor nanowires (NWs) enables their application in diverse fields, notably in chemical and electrical sensing, photovoltaics, or quantum electronic devices. In particular, indium arsenide (InAs) NWs are an ideal platform for quantum devices, e.g. they may host topological Majorana states. While the synthesis has been continously perfected, only a few techniques have been developed to tailor individual NWs after growth. Here we present three wet chemical etch methods for the post-growth morphological engineering of InAs NWs on the sub-100 nm scale. The first two methods allow the formation of self-aligned electrical contacts to etched NWs, while the third method results in conical shaped NW profiles ideal for creating smooth electrical potential gradients and shallow barriers. Low temperature experiments show that NWs with etched segments have stable transport characteristics and can serve as building blocks of quantum electronic devices. As an example we report the formation of a single electrically stable quantum dot between two etched NW segments.

  1. Static and low frequency noise characterization of ultra-thin body InAs MOSFETs

    Science.gov (United States)

    Karatsori, T. A.; Pastorek, M.; Theodorou, C. G.; Fadjie, A.; Wichmann, N.; Desplanque, L.; Wallart, X.; Bollaert, S.; Dimitriadis, C. A.; Ghibaudo, G.

    2018-05-01

    A complete static and low frequency noise characterization of ultra-thin body InAs MOSFETs is presented. Characterization techniques, such as the well-known Y-function method established for Si MOSFETs, are applied in order to extract the electrical parameters and study the behavior of these research grade devices. Additionally, the Lambert-W function parameter extraction methodology valid from weak to strong inversion is also used in order to verify its applicability in these experimental level devices. Moreover, a low-frequency noise characterization of the UTB InAs MOSFETs is presented, revealing carrier trapping/detrapping in slow oxide traps and remote Coulomb scattering as origin of 1/f noise, which allowed for the extraction of the oxide trap areal density. Finally, Lorentzian-like noise is also observed in the sub-micron area devices and attributed to both Random Telegraph Noise from oxide individual traps and g-r noise from the semiconductor interface.

  2. Surface morphology and electronic structure of halogen etched InAs (1 1 1)

    Energy Technology Data Exchange (ETDEWEB)

    Eassa, N., E-mail: nashwa.eassa@nmmu.ac.za [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Murape, D.M. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Betz, R. [Department of Chemistry, Nelson Mandela Metropolitan University (South Africa); Neethling, J.H.; Venter, A.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2012-05-15

    The reaction of halogen-based etchants with n-InAs (1 1 1)A and the resulting surface morphology and surface electronic structure are investigated using field emission scanning electron microscopy and Raman spectroscopy. Using the intensity ratio of the unscreened longitudinal optical (LO) phonon to the transverse optical (TO) phonon in the Raman spectrum, a significant reduction in band bending is deduced after exposure of the InAs surface to HCl:H{sub 2}O, Br-methanol and I-ethanol for moderate times and concentrations. These procedures also lead to smooth and defect-free InAs surfaces. The improvements in surface properties are reversed, however, if the concentrations of the etchants are increased or the etch time is too long. In the worst cases, pit formation and inverted pyramids with {l_brace}1 1 1{r_brace} side facets are observed. The influence of the etchant concentration and etch time on the morphological and electronic properties of the etched surfaces is reported.

  3. Surface morphology and electronic structure of halogen etched InAs (1 1 1)

    International Nuclear Information System (INIS)

    Eassa, N.; Murape, D.M.; Betz, R.; Neethling, J.H.; Venter, A.; Botha, J.R.

    2012-01-01

    The reaction of halogen-based etchants with n-InAs (1 1 1)A and the resulting surface morphology and surface electronic structure are investigated using field emission scanning electron microscopy and Raman spectroscopy. Using the intensity ratio of the unscreened longitudinal optical (LO) phonon to the transverse optical (TO) phonon in the Raman spectrum, a significant reduction in band bending is deduced after exposure of the InAs surface to HCl:H 2 O, Br–methanol and I–ethanol for moderate times and concentrations. These procedures also lead to smooth and defect-free InAs surfaces. The improvements in surface properties are reversed, however, if the concentrations of the etchants are increased or the etch time is too long. In the worst cases, pit formation and inverted pyramids with {1 1 1} side facets are observed. The influence of the etchant concentration and etch time on the morphological and electronic properties of the etched surfaces is reported.

  4. Reconstruction of an InAs nanowire using geometric and algebraic tomography

    International Nuclear Information System (INIS)

    Pennington, R S; Boothroyd, C B; König, S; Alpers, A; Dunin-Borkowski, R E

    2011-01-01

    Geometric tomography and conventional algebraic tomography algorithms are used to reconstruct cross-sections of an InAs nanowire from a tilt series of experimental annular dark-field images. Both algorithms are also applied to a test object to assess what factors affect the reconstruction quality. When using the present algorithms, geometric tomography is faster, but artifacts in the reconstruction may be difficult to recognize.

  5. Reconstruction of an InAs nanowire using geometric and algebraic tomography

    DEFF Research Database (Denmark)

    Pennington, Robert S.; König, S.; Alpers, A.

    2011-01-01

    Geometric tomography and conventional algebraic tomography algorithms are used to reconstruct cross-sections of an InAs nanowire from a tilt series of experimental annular dark-field images. Both algorithms are also applied to a test object to assess what factors affect the reconstruction quality....... When using the present algorithms, geometric tomography is faster, but artifacts in the reconstruction may be difficult to recognize....

  6. Coherent dynamics of excitons in a stack of self-assembled InAs quantum dots at 1.5-μm waveband

    International Nuclear Information System (INIS)

    Ishi-Hayase, J.; Akahane, K.; Yamamoto, N.; Kujiraoka, M.; Inoue, J.; Ema, K.; Tsuchiya, M.; Sasaki, M.

    2006-01-01

    We investigate the excitonic dephasing in a stack of self-assembled quantum dots (SAQDs) by using a four-wave-mixing (FWM) technique performed in the optical telecomm-fiber wavelength region at 6 K. A sample used in our experiment is a 150-layer stack of InAs SAQDs embedded in InGaAlAs grown on InP(3 1 1)B substrate fabricated by molecular beam epitaxy. By using a novel strain-controlled technique, the resonant wavelength of the exciton ground state (GS) ranges from 1.25 to 1.5 μm which is much longer than that in typical In(Ga)As SAQDs. In the weak excitation region, the intrinsic dephasing time of excitons at the excitation wavelength of 1.43 μm reaches 770 ps which is much longer than that in most SAQDs with the resonant wavelength of <1 μm. We also find a strong anisotoropy of the signal intensity with respect to the crystal axis attributed to the orientation of InP(3 1 1)B substrate and the elongated shape of QDs

  7. Critical Temperature for the Conversion from Wurtzite to Zincblende of the Optical Emission of InAs Nanowires

    KAUST Repository

    Rota, Michele B.

    2017-07-12

    One hour annealing at 300 degrees C changes the optical emission characteristics of InAs nanowires (NWs) from the wurtzite (WZ) phase into that of zincblende (ZB). These results are accounted for by the conversion of a small fraction of the NW WZ metastable structure into the stable ZB structure. Several paths toward the polytype transformation in the configuration space are also demonstrated using first-principles calculations. For lower annealing temperatures, emission which is likely related to WZ polytypes is observed at energies that agree with theoretical predictions. These results demonstrate severe constraints on thermal processes to which devices made from InAs WZ NWs can be exposed.

  8. Arsenic flux dependence of island nucleation on InAs(001)

    International Nuclear Information System (INIS)

    Grosse, Frank; Barvosa-Carter, William; Zinck, Jenna; Wheeler, Matthew; Gyure, Mark F.

    2002-01-01

    The initial stages of InAs(001) homoepitaxial growth are investigated using a combination of kinetic Monte Carlo simulations based on ab initio density functional theory and scanning tunneling microscopy. In the two dimensional island nucleation mode investigated, the island number density is found to decrease with increasing As. This behavior is explained by a suppression of the effective In-adatom density leading to a reduction in island nucleation. The relevant microscopic processes responsible for this reduction are identified

  9. Functional display of ice nucleation protein InaZ on the surface of bacterial ghosts.

    Science.gov (United States)

    Kassmannhuber, Johannes; Rauscher, Mascha; Schöner, Lea; Witte, Angela; Lubitz, Werner

    2017-09-03

    In a concept study the ability to induce heterogeneous ice formation by Bacterial Ghosts (BGs) from Escherichia coli carrying ice nucleation protein InaZ from Pseudomonas syringae in their outer membrane was investigated by a droplet-freezing assay of ultra-pure water. As determined by the median freezing temperature and cumulative ice nucleation spectra it could be demonstrated that both the living recombinant E. coli and their corresponding BGs functionally display InaZ on their surface. Under the production conditions chosen both samples belong to type II ice-nucleation particles inducing ice formation at a temperature range of between -5.6 °C and -6.7 °C, respectively. One advantage for the application of such BGs over their living recombinant mother bacteria is that they are non-living native cell envelopes retaining the biophysical properties of ice nucleation and do no longer represent genetically modified organisms (GMOs).

  10. Shubnikov-de Haas effect study of InAs after transmutation doping at low temperatures

    International Nuclear Information System (INIS)

    Gerstenberg, H.; Mueller, P.

    1990-01-01

    Degenerate InAs single crystals have been irradiated by thermal neutrons below 6 K. The Shubnikov-de Haas effect and the electrical resistivity have been measured as a function of the neutron dose and the annealing temperature. The effects of transmutation doping and simultaneous introduction of lattice defects have been analysed in terms of the conduction electron density and the scattering rates τ ρ -1 - ρne 2 /m * and τ x -1 2πkub(B)X/h/2π (where X is the Dingle temperature). The measured conduction electron density after irradiation and thermal annealing agreed well with the values calculated from the experimental and materials parameters. The effects of radiation damage may qualitatively be explained assuming neutral In vacancies to be the most common type of defect in thermal-neutron-irradiated InAs. A comparison with similar experiments on InSb is given. (author)

  11. High-density InAs/GaAs{sub 1−x}Sb{sub x} quantum-dot structures grown by molecular beam epitaxy for use in intermediate band solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Debnath, M. C., E-mail: mdebnath@cnsi.ucla.edu [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, Oklahoma 73019 (United States); California NanoSystems Institute and Electrical Engineering Department, University of California-Los Angeles (UCLA), Los Angeles, California 90095 (United States); Mishima, T. D.; Santos, M. B.; Cheng, Y.; Whiteside, V. R.; Sellers, I. R. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, Oklahoma 73019 (United States); Hossain, K. [Amethyst Research, Inc., 123 Case Circle, Ardmore, Oklahoma 73401 (United States); Laghumavarapu, R. B.; Liang, B. L.; Huffaker, D. L. [California NanoSystems Institute and Electrical Engineering Department, University of California-Los Angeles (UCLA), Los Angeles, California 90095 (United States)

    2016-03-21

    InAs quantum-dot structures were grown using a GaAs{sub 1−x}Sb{sub x} matrix on a GaAs(001) substrate. The use of GaAs{sub 1−x}Sb{sub x} for the buffer and cap layers effectively suppressed coalescence between dots and significantly increased the dot density. The highest density (∼3.5 × 10{sup 11}/cm{sup 2}) was obtained for a nominal 3.0 monolayer deposition of InAs with an Sb composition of x = 13–14% in the GaAs{sub 1−x}Sb{sub x} matrix. When the Sb composition was increased to 18%, the resulting large photoluminescent red shift (∼90 meV) indicated the release of compressive strain inside the quantum dots. For x > 13%, we observed a significant decrease in photoluminescence intensity and an increase in the carrier lifetime (≥4.0 ns). This is attributed to the type-II band alignment between the quantum dots and matrix material.

  12. Supercurrent through a spin-split quasi-ballistic point contact in an InAs nanowire

    DEFF Research Database (Denmark)

    Saldaña, J. C. Estrada; Žitko, R.; Cleuziou, J. P.

    2018-01-01

    We study the superconducting proximity effect in an InAs nanowire contacted by Ta-based superconducting electrodes. Using local bottom gates, we control the potential landscape along the nanowire, tuning its conductance to a quasi-ballistic regime. At high magnetic field ($B$), we observe...

  13. Comparison between mini mental state examination (MMSE) and Montreal cognitive assessment Indonesian version (MoCA-Ina) as an early detection of cognitive impairments in post-stroke patients

    Science.gov (United States)

    Lestari, S.; Mistivani, I.; Rumende, C. M.; Kusumaningsih, W.

    2017-08-01

    Mild cognitive impairment (MCI) is defined as cognitive impairment that may never develop into dementia. Cognitive impairment is one long-term complication of a stroke. The Mini Mental State Examination (MMSE), which is commonly used as a screening tool for cognitive impairment, has a low sensitivity to detect cognitive impairment, especially MCI. Alternatively, the Montreal Cognitive Assessment Indonesian version (MoCA-Ina) has been reported to have a higher sensitivity than the MMSE. The aim of this study was to compare the proportion of MCI identified between the MMSE and MoCA-Ina in stroke patients. This was a cross-sectional study of stroke outpatients who attended the Polyclinic Neuromuscular Division, Rehabilitation Department, and Polyclinic Stroke, Neurology Department Cipto Mangunkusumo General Hospital, Jakarta. The proportion of MCI identified using the MMSE was 31.03% compared to 72.41% when using the MoCA-Ina. This difference was statistically significant (Fisher’s exact test, p = 0.033). The proportion of MCI in stroke patients was higher when using the MoCA-Ina compared to the MMSE. The MoCA-Ina should be used as an alternative in the early detection of MCI in stroke patients, especially those undergoing rehabilitation.

  14. In situ surface and interface study of crystalline (3×1)-O on InAs

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Xiaoye, E-mail: xxq102020@utdallas.edu; Wallace, Robert M., E-mail: rmwallace@utdallas.edu [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States); Wang, Wei-E.; Rodder, Mark S. [Advanced Logic Lab, Samsung Semiconductor, Inc., Austin, Texas 78754 (United States)

    2016-07-25

    The oxidation behavior of de-capped InAs (100) exposed to O{sub 2} gas at different temperatures is investigated in situ with high resolution of monochromatic x-ray photoelectron spectroscopy and low energy electron diffraction. The oxide chemical states and structure change dramatically with the substrate temperature. A (3 × 1) crystalline oxide layer on InAs is generated in a temperature range of 290–330 °C with a coexistence of In{sub 2}O and As{sub 2}O{sub 3}. The stability of the crystalline oxide upon the atomic layer deposition (ALD) of HfO{sub 2} is studied as well. It is found that the generated (3 × 1) crystalline oxide is stable upon ALD HfO{sub 2} growth at 100 °C.

  15. Transport and performance of a gate all around InAs nanowire transistor

    International Nuclear Information System (INIS)

    Alam, Khairul

    2009-01-01

    The transport physics and performance metrics of a gate all around an InAs nanowire transistor are studied using a three-dimensional quantum simulation. The transistor action of an InAs nanowire transistor occurs by modulating the transmission coefficient of the device. This action is different from a conventional metal-oxide-semiconductor field effect transistor, where the transistor action occurs by modulating the charge in the channel. The device has 82% tunneling current in the off-state and 81% thermal current in the on-state. The two current components become equal at a gate bias at which an approximate source-channel flat-band condition is achieved. Prior to this gate bias, the tunneling current dominates and the thermal current dominates beyond it. The device has an on/off current ratio of 7.84 × 10 5 and an inverse subthreshold slope of 63 mV dec −1 . The transistor operates in the quantum capacitance limit with a normalized transconductance value of 14.43 mS µm −1 , an intrinsic switching delay of 90.1675 fs, and an intrinsic unity current gain frequency of 6.8697 THz

  16. Study of electron transport in n-type InAs substrate by Monte Carlo ...

    African Journals Online (AJOL)

    It is therefore an iterative process made up from a whole coasting flights stopped by acoustics interactions, polar and non polar optics, piezoelectric, inter-valley, impurity, ionization and surface. By applying this method to the III-V material, case of InAs, we have described the behavior of the carriers from dynamic and ...

  17. ODNOS ZAPOSLENIH V VRTCU DO ZDRAVEGA NAČINA ŽIVLJENJA

    OpenAIRE

    Cesarec, Anja

    2009-01-01

    Diplomsko delo predstavlja temo odnos zaposlenih v vrtcu do zdravega načina življenja. Predstavili smo zdravje, dejavnike, ki vplivajo na stopnjo zdravja in dejavnike, ki vplivajo na življenjski slog, kot so kajenje tobaka, način prehranjevanja, telesno aktivnost, uživanje nedovoljenih drog in alkohola ter stres. Posebno poglavje pa je namenjeno skrbi za zdrav način življenja. V empiričnem delu so predstavljeni rezultati raziskave, narejene v vrtcu Rogaška Slatina, enota Izvir. V raziskavo, k...

  18. High-Pressure-Induced Comminution and Recrystallization of CH3 NH3 PbBr3 Nanocrystals as Large Thin Nanoplates.

    Science.gov (United States)

    Yin, Tingting; Fang, Yanan; Chong, Wee Kiang; Ming, Koh Teck; Jiang, Shaojie; Li, Xianglin; Kuo, Jer-Lai; Fang, Jiye; Sum, Tze Chien; White, Timothy J; Yan, Jiaxu; Shen, Ze Xiang

    2018-01-01

    High pressure (HP) can drive the direct sintering of nanoparticle assemblies for Ag/Au, CdSe/PbS nanocrystals (NCs). Instead of direct sintering for the conventional nanocrystals, this study experimentally observes for the first time high-pressure-induced comminution and recrystallization of organic-inorganic hybrid perovskite nanocrystals into highly luminescent nanoplates with a shorter carrier lifetime. Such novel pressure response is attributed to the unique structural nature of hybrid perovskites under high pressure: during the drastic cubic-orthorhombic structural transformation at ≈2 GPa, (301) the crystal plane fully occupied by organic molecules possesses a higher surface energy, triggering the comminution of nanocrystals into nanoslices along such crystal plane. Beyond bulk perovskites, in which pressure-induced modifications on crystal structures and functional properties will disappear after pressure release, the pressure-formed variants, i.e., large (≈100 nm) and thin (perovskite nanoplates, are retained and these exhibit simultaneous photoluminescence emission enhancing (a 15-fold enhancement in the photoluminescence) and carrier lifetime shortening (from ≈18.3 ± 0.8 to ≈7.6 ± 0.5 ns) after releasing of pressure from 11 GPa. This pressure-induced comminution of hybrid perovskite NCs and a subsequent amorphization-recrystallization treatment offer the possibilities of engineering the advanced hybrid perovskites with specific properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Self-Assembled InAs Nanowires as Optical Reflectors

    Directory of Open Access Journals (Sweden)

    Francesco Floris

    2017-11-01

    Full Text Available Subwavelength nanostructured surfaces are realized with self-assembled vertically-aligned InAs nanowires, and their functionalities as optical reflectors are investigated. In our system, polarization-resolved specular reflectance displays strong modulations as a function of incident photon energy and angle. An effective-medium model allows one to rationalize the experimental findings in the long wavelength regime, whereas numerical simulations fully reproduce the experimental outcomes in the entire frequency range. The impact of the refractive index of the medium surrounding the nanostructure assembly on the reflectance was estimated. In view of the present results, sensing schemes compatible with microfluidic technologies and routes to innovative nanowire-based optical elements are discussed.

  20. Study of a MHEMT heterostructure with an In0.4Ga0.6As channel MBE-grown on a GaAs substrate using reciprocal space mapping

    International Nuclear Information System (INIS)

    Aleshin, A. N.; Bugaev, A. S.; Ermakova, M. A.; Ruban, O. A.

    2015-01-01

    The crystallographic characteristics of the design elements of a metamorphic high-electron-mobility (MHEMT) heterostructure with an In 0.4 Ga 0.6 As channel are determined based on reciprocal space mapping. The heterostructure is grown by molecular beam epitaxy on the vicinal surface of a GaAs substrate with a deviation angle from the (001) plane of 2° and consists of a stepped metamorphic buffer containing six layers including an inverse step, a high-temperature buffer layer with constant composition, and active HEMT layers. The InAs content in the layers of the metamorphic buffer is varied from 0.1 to 0.48. Reciprocal space maps are constructed for the (004) symmetric reflection and (224)+ asymmetric reflection. It is found that the heterostructure layers are characterized both by a tilt angle relative to the plane of the (001) substrate and a rotation angle around the [001] axis. The tilt angle of the layer increases as the InAs concentration in the layer increases. It is shown that a high-temperature buffer layer of constant composition has the largest degree of relaxation compared with all other layers of the heterostructure

  1. Controlling the size of InAs quantum dots on Si1-xGex/Si(0 0 1) by metalorganic vapor-phase epitaxy

    International Nuclear Information System (INIS)

    Kawaguchi, Kenichi; Ebe, Hiroji; Ekawa, Mitsuru; Sugama, Akio; Arakawa, Yasuhiko

    2009-01-01

    The formation of III-V InAs quantum dots (QDs) on group-IV Si 1-x Ge x /Si(0 0 1) was investigated by metalorganic vapor-phase epitaxy. Two types of QDs, round-shaped QDs and giant QDs elongated in the [1 1 0] or [1,-1,0] direction, were observed in a growth condition of low V/III ratios. An increase in the V/III ratio and AsH 3 preflow during the cooling process was found to suppress the formation of giant QDs. It was considered that replacing the H-stabilized SiGe surface with the As-stabilized surface was necessary for increasing the QD nucleation. The size and density of InAs QDs on SiGe were controllable as well as that on III-V semiconductor buffer layers, and InAs QDs with a density as high as 5 x 10 10 cm -2 were obtained.

  2. Composition, morphology and surface recombination rate of HCl-isopropanol treated and vacuum annealed InAs(1 1 1)A surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kesler, V.G., E-mail: kesler@isp.nsc.ru [Institute of Semiconductor Physics SB RAS, Lavrentiev av., 13, Novosibirsk 630090 (Russian Federation); Seleznev, V.A.; Kovchavtsev, A.P.; Guzev, A.A. [Institute of Semiconductor Physics SB RAS, Lavrentiev av., 13, Novosibirsk 630090 (Russian Federation)

    2010-05-01

    X-ray photoelectron spectroscopy and atomic force microscopy were used to examine the chemical composition and surface morphology of InAs(1 1 1)A surface chemically etched in isopropanol-hydrochloric acid solution (HCl-iPA) and subsequently annealed in vacuum in the temperature range 200-500 deg. C. Etching for 2-30 min resulted in the formation of 'pits' and 'hillocks' on the sample surface, respectively 1-2 nm deep and high, with lateral dimensions 50-100 nm. The observed local formations, whose density was up to 3 x 10{sup 8} cm{sup -2}, entirely vanished from the surface after the samples were vacuum-annealed at temperatures above 300 deg. C. Using a direct method, electron beam microanalysis, we have determined that the defects of the hillock type includes oxygen and excessive As, while the 'pits' proved to be identical in their chemical composition to InAs. Vacuum anneals were found to cause a decrease in As surface concentration relative to In on InAs surface, with a concomitant rise of surface recombination rate.

  3. Composition, morphology and surface recombination rate of HCl-isopropanol treated and vacuum annealed InAs(1 1 1)A surfaces

    Science.gov (United States)

    Kesler, V. G.; Seleznev, V. A.; Kovchavtsev, A. P.; Guzev, A. A.

    2010-05-01

    X-ray photoelectron spectroscopy and atomic force microscopy were used to examine the chemical composition and surface morphology of InAs(1 1 1)A surface chemically etched in isopropanol-hydrochloric acid solution (HCl-iPA) and subsequently annealed in vacuum in the temperature range 200-500 °C. Etching for 2-30 min resulted in the formation of "pits" and "hillocks" on the sample surface, respectively 1-2 nm deep and high, with lateral dimensions 50-100 nm. The observed local formations, whose density was up to 3 × 10 8 cm -2, entirely vanished from the surface after the samples were vacuum-annealed at temperatures above 300 °C. Using a direct method, electron beam microanalysis, we have determined that the defects of the hillock type includes oxygen and excessive As, while the "pits" proved to be identical in their chemical composition to InAs. Vacuum anneals were found to cause a decrease in As surface concentration relative to In on InAs surface, with a concomitant rise of surface recombination rate.

  4. Composition, morphology and surface recombination rate of HCl-isopropanol treated and vacuum annealed InAs(1 1 1)A surfaces

    International Nuclear Information System (INIS)

    Kesler, V.G.; Seleznev, V.A.; Kovchavtsev, A.P.; Guzev, A.A.

    2010-01-01

    X-ray photoelectron spectroscopy and atomic force microscopy were used to examine the chemical composition and surface morphology of InAs(1 1 1)A surface chemically etched in isopropanol-hydrochloric acid solution (HCl-iPA) and subsequently annealed in vacuum in the temperature range 200-500 deg. C. Etching for 2-30 min resulted in the formation of 'pits' and 'hillocks' on the sample surface, respectively 1-2 nm deep and high, with lateral dimensions 50-100 nm. The observed local formations, whose density was up to 3 x 10 8 cm -2 , entirely vanished from the surface after the samples were vacuum-annealed at temperatures above 300 deg. C. Using a direct method, electron beam microanalysis, we have determined that the defects of the hillock type includes oxygen and excessive As, while the 'pits' proved to be identical in their chemical composition to InAs. Vacuum anneals were found to cause a decrease in As surface concentration relative to In on InAs surface, with a concomitant rise of surface recombination rate.

  5. Jačina sveze adhezijskih materijala na tvrda zubna tkiva

    OpenAIRE

    Žagar, Polona

    2017-01-01

    Adhezija se odnosi na povezivanje atoma i molekula na kontaktnim površinama različitih materijala. Adhezijske sustave možemo podjeliti prema interakciji sa tvrdim zubnim tkivima na jetkajuće ispirajuće, samojetkajuće i staklenoionomerne sustave. Univerzalni adhezivi su najnovija generacija adheziva na tržištu. Mogu se koristiti kao jetkajući ispirajući i samojetkajući sustavi. U ovom radu je ispitivana jačina adhezijske sveze s caklinom jetkajuće ispirajućim i univerzalnim adheziv...

  6. Absorption coefficients for interband optical transitions in a strained InAs1−xPx/InP quantum wire

    International Nuclear Information System (INIS)

    Saravanan, S.; John Peter, A.; Lee, Chang Woo

    2014-01-01

    Excitons confined in an InAs 1−x P x /InP (x=0.2) quantum well wire are studied in the presence of magnetic field strength. Numerical calculations are carried out using variational approach within the single band effective mass approximation. The compressive strain contribution to the confinement potential is included throughout the calculations. The energy difference of the ground and the first excited state is investigated in the influence of magnetic field strength taking into account the geometrical confinement effect. The magnetic field induced optical band as a function of wire radius is investigated in the InAs 0.8 P 0.2 /InP quantum well wire. The valence-band anisotropy is included in our theoretical model by employing different hole masses in different spatial directions. The optical gain as a function of incident photon energy is computed in the presence of magnetic field strength. The corresponding 1.55 μm wavelength is achieved for 40 Å InAs 0.8 P 0.2 /InP quantum well wire. We hope that the results could be used for the potential applications in fiber optic communications. -- Highlights: • Magnetic field induced excitons confined in a InAs 1−x P x /InP (x=0.2) quantum well wire are studied. • The compressive strain is included throughout the calculations. • The energy difference of the ground and the first excited state is investigated in the presence of magnetic field strength. • The magnetic field induced optical band with the geometrical confinement is studied. • The optical gain with the photon energy is computed in the presence of magnetic field strength

  7. EG-Assisted Synthesis and Electrochemical Performance of Ultrathin Carbon-Coated LiMnPO4 Nanoplates as Cathodes in Lithium Ion Batteries

    Directory of Open Access Journals (Sweden)

    Liwei Su

    2015-01-01

    Full Text Available Ultrathin carbon-coated LiMnPO4 (ULMP/C nanoplates were prepared through an ethylene glycol- (EG- assisted pyrolysis method. Different from most of LiMnPO4/C works, the obtained ULMP/C possessed relatively small particle size (less than 50 nm in thickness and preferable carbon coating (~1 nm in thickness, 2 wt.%. As a reference, LiMnPO4/C (LMP/C composites were also fabricated via the traditional hydrothermal method. X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscopy (TEM, energy dispersive X-ray spectroscopy (EDS, thermogravimetric analysis (TG, galvanostatic charge-discharge, and cyclic voltammetry (CV were performed to characterize the crystalline phase, morphology, structure, carbon content, and electrochemical behaviors of samples. The electrochemical performance of bare and carbon-coated LiMnPO4 was evaluated as cathodes in lithium ion batteries. As a result, the obtained ULMP/C nanoplates demonstrated much higher reversible capacities (110.9 mAh g−1 after 50 cycles at 0.1 C and rate performances than pure LMP and LMP/C composites. This facile and efficient EG-assisted pyrolysis method can enlighten us on exploiting advanced routes to modify active materials with ultrathin and homogeneous carbon layers.

  8. Thermal conductivity of InAs quantum dot stacks using AlAs strain compensating layers on InP substrate

    International Nuclear Information System (INIS)

    Salman, S.; Folliot, H.; Le Pouliquen, J.; Chevalier, N.; Rohel, T.; Paranthoën, C.; Bertru, N.; Labbé, C.; Letoublon, A.; Le Corre, A.

    2012-01-01

    Highlights: ► The thermal conductivity of InAs on InP (1 1 3)B quantum dots stacks is measured. ► The growth of a close stack of 100 layers of InAs using AlAs strain compensating layers is presented. ► New data on the thermal conductivity of InP n-doped susbtrate are given. - Abstract: The growth and thermal conductivity of InAs quantum dot (QD) stacks embedded in GaInAs matrix with AlAs compensating layers deposited on (1 1 3)B InP substrate are presented. The effect of the strain compensating AlAs layer is demonstrated through Atomic Force Microscopy (AFM) and X-ray diffraction structural analysis. The thermal conductivity (2.7 W/m K at 300 K) measured by the 3ω method reveals to be clearly reduced in comparison with a bulk InGaAs layer (5 W/m K). In addition, the thermal conductivity measurements of S doped InP substrates and the SiN insulating layer used in the 3ω method in the 20–200 °C range are also presented. An empirical law is proposed for the S doped InP substrate, which slightly differs from previously presented results.

  9. Simulation of quantum dots size and spacing effect for intermediate band solar cell application based on InAs quantum dots arrangement in GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Hendra, P. I. B., E-mail: ib.hendra@gmail.com; Rahayu, F., E-mail: ib.hendra@gmail.com; Darma, Y., E-mail: ib.hendra@gmail.com [Physical Vapor Deposition Laboratory, Physics of Material Electronics Research, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia)

    2014-03-24

    Intermediate band solar cell (IBSC) has become a promising technology in increasing solar cell efficiency. In this work we compare absorption coefficient profile between InAs quantum dots with GaAs bulk. We calculate the efficiency of GaAs bulk and GaAs doped with 2, 5, and 10 nm InAs quantum dot. Effective distances in quantum dot arrangement based on electron tunneling consideration were also calculated. We presented a simple calculation method with low computing power demand. Results showed that arrangement of quantum dot InAs in GaAs can increase solar cell efficiency from 23.9 % initially up to 60.4%. The effective distance between two quantum dots was found 2 nm in order to give adequate distance to prevent electron tunneling and wave functions overlap.

  10. Spin interactions in InAs quantum dots

    Science.gov (United States)

    Doty, M. F.; Ware, M. E.; Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Gammon, D.; Ponomarev, I. V.; Reinecke, T. L.; Korenev, V. L.

    2006-03-01

    Fine structure splittings in optical spectra of self-assembled InAs quantum dots (QDs) generally arise from spin interactions between particles confined in the dots. We present experimental studies of the fine structure that arises from multiple charges confined in a single dot [1] or in molecular orbitals of coupled pairs of dots. To probe the underlying spin interactions we inject particles with a known spin orientation (by using polarized light to perform photoluminescence excitation spectroscopy experiments) or use a magnetic field to orient and/or mix the spin states. We develop a model of the spin interactions that aids in the development of quantum information processing applications based on controllable interactions between spins confined to QDs. [1] Polarized Fine Structure in the Photoluminescence Excitation Spectrum of a Negatively Charged Quantum Dot, Phys. Rev. Lett. 95, 177403 (2005)

  11. Stimulated Emission from InAs (GaAs Monolayers Stacks Embedded in Al0.33Ga0.67As Ective Region

    Directory of Open Access Journals (Sweden)

    Dusan Pudis

    2002-01-01

    Full Text Available Our study is focused on the optical and electronic properties of InAs (GaAs monolayers embedded in Al0.33GA0.67As barrier layers investigated by temperature dependencies of electroluminescence spectra. The experimental results obtained from low temperature electroluminescence measurements of InAs (GaAs/Al0.33GA0.67As revealed the excellent emission spectra in the visib le range 630-690 nm. The stimulated emission from these structures across their cleavage planes has been observed at low  temperatures what is highly interesting for potential device applications.

  12. Spin Qubits in GaAs Heterostructures and Gating of InAs Nanowires for Lowtemperature Measurements

    DEFF Research Database (Denmark)

    Nissen, Peter Dahl

    of the contenders in the race to build a large-scale quantum computer, is such a component, and research aiming to build, manipulate and couple spin qubits is looking at many materials systems to nd one where the requirements for fast control and long coherence time can be combined with ecient coupling between...... distant qubits. This thesis presents electric measurement on two of the materials systems currently at the forefront of the spin qubit race, namely InAs nanowires and GaAs/AlGaAs heterostructures. For the InAs nanowires we investigate dierent gating geometries towards the goal of dening stable quantum...... electrodes induces tunable barriers of up to 0:25 eV. From the temperature dependence of the conductance, the barrier height is extracted and mapped as a function of gate voltage. Top and bottom gates are similar to each other in terms of electrostatic couplings (lever arms 0:10:2 eV=V) and threshold...

  13. Comparative study of porosification in InAs, InP, ZnSe and ZnCdS

    International Nuclear Information System (INIS)

    Monaico, Eduard; Tiginyanu, Ion; Nielsch, Kornelius; Ursaki, Veaceslav; Colibaba, Gleb; Nedeoglo, Dmitrii; Cojocaru, Ala; Foell Helmut

    2013-01-01

    We report on a comparative study of the pore growth during anodization of a narrow-bandgap III-V compound (InAs), a medium-bandgap III-V one (InP) and wide-bandgap II-VI semiconductors (ZnSe and Zn 0,4 Cd 0,6 S). According to the obtained results, the morphology of the porous layers can be controlled by the composition of the electrolyte and the applied electrochemical parameters. It was evidenced that in the narrow bandgap semiconductor InAs it is difficult to control the mechanism of pore growth. Both current line oriented pores and crystallographically oriented pores were produced in the medium-bandgap material InP. The electrochemical nanostructuring of wide-bandgap semiconductors realized in single crystalline high conductivity samples evidenced only current-line oriented pores. This behavior is explained in terms of difference in the values of electronegativity of the constituent atoms and the degree of ionicity. (authors)

  14. Crystalline mesoporous tungsten oxide nanoplate monoliths synthesized by directed soft template method for highly sensitive NO2 gas sensor applications

    International Nuclear Information System (INIS)

    Hoa, Nguyen Duc; Duy, Nguyen Van; Hieu, Nguyen Van

    2013-01-01

    Graphical abstract: Display Omitted Highlights: ► Mesoporous WO 3 nanoplate monoliths were obtained by direct templating synthesis. ► Enable effective accession of the analytic molecules for the sensor applications. ► The WO 3 sensor exhibited a high performance to NO 2 gas at low temperature. -- Abstract: Controllable synthesis of nanostructured metal oxide semiconductors with nanocrystalline size, porous structure, and large specific surface area is one of the key issues for effective gas sensor applications. In this study, crystalline mesoporous tungsten oxide nanoplate-like monoliths with high specific surface areas were obtained through instant direct-templating synthesis for highly sensitive nitrogen dioxide (NO 2 ) sensor applications. The copolymer soft template was converted into a solid carbon framework by heat treatment in an inert gas prior to calcinations in air to sustain the mesoporous structure of tungsten oxide. The multidirectional mesoporous structures of tungsten oxide with small crystalline size, large specific surface area, and superior physical characteristics enabled the rapid and effective accession of analytic gas molecules. As a result, the sensor response was enhanced and the response and recovery times were reduced, in which the mesoporous tungsten oxide based gas sensor exhibited a superior response of 21,155% to 5 ppm NO 2 . In addition, the developed sensor exhibited selective detection of low NO 2 concentration in ammonia and ethanol at a low temperature of approximately 150 °C.

  15. Direct Identification of Atomic-Like Electronic Levels in InAs Nano crystal Quantum Dots

    International Nuclear Information System (INIS)

    Millo, O.; Katz, D.

    1999-01-01

    The size dependent level structure of InAs nano crystals in the range 2-7 nm in diameter is investigated using both tunneling and optical spectroscopies. The tunneling measurements are performed using a cryogenic scanning tunneling microscope on individual nano crystals that, are attached to a gold substrate via dithiol molecules. The tunneling I-V characteristics manifest an interplay between single electron charging and quantum size effects. We are able to directly identify quantum confined states of isolated InAs nano crystals having s and p symmetries. These states are observed in the I-V curves as two and six-fold single electron charging multiplets. Excellent agreement is found between the strongly allowed optical transitions [1] and the spacing of levels detected in the tunneling experiment. This correlation provides new information on the quantum-dot level structure, from which we conclude that the top-most valence band state has both s and p characteristics. The interplay between level structure singles electron charging of the nano crystals obeys an atomic-like Aufbau sequential electron level occupation

  16. Analysis and optimization of RC delay in vertical nanoplate FET

    Science.gov (United States)

    Woo, Changbeom; Ko, Kyul; Kim, Jongsu; Kim, Minsoo; Kang, Myounggon; Shin, Hyungcheol

    2017-10-01

    In this paper, we have analyzed short channel effects (SCEs) and RC delay with Vertical nanoplate FET (VNFET) using 3-D Technology computer-aided design (TCAD) simulation. The device is based on International Technology Road-map for Semiconductor (ITRS) 2013 recommendations, and it has initially gate length (LG) of 12.2 nm, channel thickness (Tch) of 4 nm, and spacer length (LSD) of 6 nm. To obtain improved performance by reducing RC delay, each dimension is adjusted (LG = 12.2 nm, Tch = 6 nm, LSD = 11.9 nm). It has each characteristic in this dimension (Ion/Ioff = 1.64 × 105, Subthreshold swing (S.S.) = 73 mV/dec, Drain-induced barrier lowering (DIBL) = 60 mV/V, and RC delay = 0.214 ps). Furthermore, with long shallow trench isolation (STI) length and thick insulator thickness (Ti), we can reduce RC delay from 0.214 ps to 0.163 ps. It is about a 23.8% reduction. Without decreasing drain current, there is a reduction of RC delay as reducing outer fringing capacitance (Cof). Finally, when source/drain spacer length is set to be different, we have verified RC delay to be optimum.

  17. Liquid phase epitaxy of abrupt junctions in InAs and studies of injection radiative tunneling processes

    International Nuclear Information System (INIS)

    Bull, D.J.

    1977-01-01

    The p-n junction in a InAs crystal, by liquid phase epitaxy is obtained. The processes of injection and tunneling radiative recombination by emitted radiation from active region of p-n junction for low injection current are studied. (M.C.K.) [pt

  18. Atomic structures of a monolayer of AlAs, GaAs, and InAs on Si(111)

    International Nuclear Information System (INIS)

    Lee, Geunjung; Yoon, Younggui

    2010-01-01

    We study atomic structures of a monolayer of AlAs, GaAs, and InAs on a Si(111) substrate from first-principles. The surface with the stacking sequence of ...SiSiMAsSiAs is energetically more stable than the surface with the stacking sequence of ...SiSiSiAsMAs, where M is Al, Ga, or In. The atomic structure of the three top layers of the low-energy surfaces are quite robust, irrespective of M, and the atomic structure of the AlAsSiAs terminated surface and that of the GaAsSiAs terminated surface are very similar. For the high-energy AsMAs terminated surfaces, the broken local tetrahedral symmetry plays an important role in the atomic structures. The calculated atomic structures of InAs on the Si(111) substrate depart most from the structure of crystalline Si.

  19. Seeded growth of InP and InAs quantum rods using indium acetate and myristic acid

    International Nuclear Information System (INIS)

    Shweky, Itzhak; Aharoni, Assaf; Mokari, Taleb; Rothenberg, Eli; Nadler, Moshe; Popov, Inna; Banin, Uri

    2006-01-01

    A synthesis of soluble III-V semiconductor quantum rods using gold nanoparticles to direct and catalyze one-dimensional growth is developed. The growth takes place via the solution-liquid-solid (SLS) mechanism where proper precursors are injected into a coordinating solvent. We report the synthesis of InP nanorods using indium acetate and myristic acid with gold nanoparticles as the catalysts in the SLS growth mode. A similar route was successfully developed for the growth of InAs nanorods. We find that the amount of Au catalyst in the reaction is an important parameter to achieve shape control. Transmission electron microscope (TEM) images of InP and InAs nanocrystals revealed that the crystals are mostly rod-shaped, and provide strong evidence for Au presence in one edge. The rods were characterized structurally using X-ray diffraction and high-resolution TEM and optically by absorption and photoluminescence

  20. Hydrothermal Synthesis, Characterization, and Optical Properties of Ce Doped Bi2MoO6 Nanoplates

    Directory of Open Access Journals (Sweden)

    Anukorn Phuruangrat

    2014-01-01

    Full Text Available Undoped and Ce doped Bi2MoO6 samples were synthesized by hydrothermal reaction at 180°C for 20 h. Phase, morphology, atomic vibration, and optical properties were characterized by X-ray powder diffraction (XRD, X-ray photoelectron spectroscopy (XPS, Raman spectrophotometry, Fourier transform infrared (FTIR spectroscopy, scanning electron microscopy (SEM, transmission electron microscopy (TEM, selected area electron diffraction (SAED, and UV-visible spectroscopy. In this research, the products were orthorhombic Bi2MoO6 nanoplates with the growth direction along the [0b0], including the asymmetric and symmetric stretching and bending modes of Bi–O and Mo–O. Undoped and Ce doped Bi2MoO6 samples show a strong absorption in the UV region.

  1. InAs nanowire formation on InP(001)

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  2. Growth of InAs Wurtzite Nanocrosses from Hexagonal and Cubic Basis

    DEFF Research Database (Denmark)

    Krizek, Filip; Kanne, Thomas; Razmadze, Davydas

    2017-01-01

    . Two methods use conventional wurtzite nanowire arrays as a 6-fold hexagonal basis for growing single crystal wurtzite nanocrosses. A third method uses the 2-fold cubic symmetry of (100) substrates to form well-defined coherent inclusions of zinc blende in the center of the nanocrosses. We show......Epitaxially connected nanowires allow for the design of electron transport experiments and applications beyond the standard two terminal device geometries. In this Letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the vapor-liquid-solid mechanism...

  3. CTAB assisted synthesis of tungsten oxide nanoplates as an efficient low temperature NOX sensor

    Science.gov (United States)

    Mehta, Swati S.; Tamboli, Mohaseen S.; Mulla, Imtiaz S.; Suryavanshi, Sharad S.

    2018-02-01

    Tungsten oxide nanoplates with porous morphology were effectively prepared by acidification using CTAB (HexadeCetyltrimethyl ammonium bromide) as a surfactant. For characterization, the synthesized materials were subjected to X-Ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), UV-Visible spectroscopy (UV-Vis) and surface area (BET) measurements. The morphology and size of the particles were controlled by solution acidity. The BET results confirmed that the materials are well crystallized and mesoporous in nature. The nanocrystalline powder was used to prepare thick films by screen printing on alumina substrate for the investigation of gas sensing properties. The gas response measurements revealed that the samples acidified using 10 M H2SO4 exhibits highest response of 91% towards NOX at optimum temperature of 200 °C for 100 ppm, and it also exhibits 35% response at room temperature.

  4. Comparison of the reactivity of alkyl and alkyl amine precursors with native oxide GaAs(100) and InAs(100) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Henegar, A.J., E-mail: henegar1@umbc.edu; Gougousi, T., E-mail: gougousi@umbc.edu

    2016-12-30

    Graphical abstract: The interaction of the native oxides of GaAs(100) and InAs(100) with alkyl (trimethyl aluminum) and alkyl amine (tetrakis dimethylamino titanium) precursors during thermal atomic layer deposition (ALD) of Al{sub 2}O{sub 3} and TiO{sub 2} is compared. Al{sub 2}O{sub 3} if found to be a significantly better barrier against the transport of the surface native oxide during the film deposition as well as after post-deposition heat treatment. This superior blocking ability also limits the removal of the native oxides during the Al{sub 2}O{sub 3} ALD process. - Highlights: • Native oxide diffusion is required for continuous native oxide removal. • The diffusion barrier capabilities of Al{sub 2}O{sub 3} limits native oxide removal during ALD. • Arsenic oxide exhibits higher mobility from InAs compared to GaAs substrates. • Oxygen scavenging from the surface by trimethyl aluminum is confirmed. - Abstract: In this manuscript we compare the interaction of alkyl (trimethyl aluminum) and alkyl amine (tetrakis dimethylamino titanium) precursors during thermal atomic layer deposition with III-V native oxides. For that purpose we deposit Al{sub 2}O{sub 3} and TiO{sub 2}, using H{sub 2}O as the oxidizer, on GaAs(100) and InAs(100) native oxide surfaces. We find that there are distinct differences in the behavior of the two films. For the Al{sub 2}O{sub 3} ALD very little native oxide removal happens after the first few ALD cycles while the interaction of the alkyl amine precursor for TiO{sub 2} and the native oxides continues well after the surface has been covered with 2 nm of TiO{sub 2}. This difference is traced to the superior properties of Al{sub 2}O{sub 3} as a diffusion barrier. Differences are also found in the behavior of the arsenic oxides of the InAs and GaAs substrates. The arsenic oxides from the InAs surface are found to mix more efficiently in the growing dielectric film than those from the GaAs surface. This difference is attributed to

  5. Comparison of the reactivity of alkyl and alkyl amine precursors with native oxide GaAs(100) and InAs(100) surfaces

    International Nuclear Information System (INIS)

    Henegar, A.J.; Gougousi, T.

    2016-01-01

    Graphical abstract: The interaction of the native oxides of GaAs(100) and InAs(100) with alkyl (trimethyl aluminum) and alkyl amine (tetrakis dimethylamino titanium) precursors during thermal atomic layer deposition (ALD) of Al_2O_3 and TiO_2 is compared. Al_2O_3 if found to be a significantly better barrier against the transport of the surface native oxide during the film deposition as well as after post-deposition heat treatment. This superior blocking ability also limits the removal of the native oxides during the Al_2O_3 ALD process. - Highlights: • Native oxide diffusion is required for continuous native oxide removal. • The diffusion barrier capabilities of Al_2O_3 limits native oxide removal during ALD. • Arsenic oxide exhibits higher mobility from InAs compared to GaAs substrates. • Oxygen scavenging from the surface by trimethyl aluminum is confirmed. - Abstract: In this manuscript we compare the interaction of alkyl (trimethyl aluminum) and alkyl amine (tetrakis dimethylamino titanium) precursors during thermal atomic layer deposition with III-V native oxides. For that purpose we deposit Al_2O_3 and TiO_2, using H_2O as the oxidizer, on GaAs(100) and InAs(100) native oxide surfaces. We find that there are distinct differences in the behavior of the two films. For the Al_2O_3 ALD very little native oxide removal happens after the first few ALD cycles while the interaction of the alkyl amine precursor for TiO_2 and the native oxides continues well after the surface has been covered with 2 nm of TiO_2. This difference is traced to the superior properties of Al_2O_3 as a diffusion barrier. Differences are also found in the behavior of the arsenic oxides of the InAs and GaAs substrates. The arsenic oxides from the InAs surface are found to mix more efficiently in the growing dielectric film than those from the GaAs surface. This difference is attributed to lower native oxide stability as well as an initial diffusion path formation by the indium oxides.

  6. Self-assembled monolayers of alkyl-thiols on InAs: A Kelvin probe force microscopy study

    Science.gov (United States)

    Szwajca, A.; Wei, J.; Schukfeh, M. I.; Tornow, M.

    2015-03-01

    We report on the preparation and characterization of self-assembled monolayers from aliphatic thiols with different chain length and termination on InAs (100) planar surfaces. This included as first step the development and investigation of a thorough chemical InAs surface preparation step using a dedicated bromine/NH4OH-based etching process. Ellipsometry, contact angle measurements and atomic force microscopy (AFM) indicated the formation of smooth, surface conforming monolayers. The molecular tilt angles were obtained as 30 ± 10° with respect to the surface normal. Kelvin probe force microscopy (KPFM) measurements in hand with Parameterized Model number 5 (PM5) calculations of the involved molecular dipoles allowed for an estimation of the molecular packing densities on the surface. We obtained values of up to n = 1014 cm- 2 for the SAMs under study. These are close to what is predicted from a simple geometrical model that would calculate a maximum density of about n = 2.7 × 1014 cm- 2. We take this as additional conformation of the substrate smoothness and quality of our InAs-SAM hybrid layer systems.

  7. Critical Temperature for the Conversion from Wurtzite to Zincblende of the Optical Emission of InAs Nanowires

    KAUST Repository

    Rota, Michele B.; Ameruddin, Amira S.; Wong-Leung, Jennifer; Belabbes, Abderrezak; Gao, Qiang; Miriametro, Antonio; Mura, Francesco; Tan, Hark Hoe; Polimeni, Antonio; Bechstedt, Friedhelm; Jagadish, Chennupati; Capizzi, Mario

    2017-01-01

    One hour annealing at 300 degrees C changes the optical emission characteristics of InAs nanowires (NWs) from the wurtzite (WZ) phase into that of zincblende (ZB). These results are accounted for by the conversion of a small fraction of the NW WZ

  8. Formation of InAs/GaAs quantum dots from a subcritical InAs wetting layer: A reflection high-energy electron diffraction and theoretical study

    International Nuclear Information System (INIS)

    Song, H. Z.; Usuki, T.; Nakata, Y.; Yokoyama, N.; Sasakura, H.; Muto, S.

    2006-01-01

    InAs/GaAs quantum dots (QD's) are formed by postgrowth annealing of an InAs wetting layer thinner than the critical thickness for the transition from two- (2D) to three-dimensional (3D) growth mode. Reflection high energy electron diffraction is used to monitor the QD formation. Based on a mean-field theory [Phys. Rev. Lett. 79, 897 (1997)], the time evolution of total QD's volume, first increasing and finally saturating, is well explained by precursors forming during wetting layer growth and converting into nucleated QD's after growth stop. Both the saturation QD's volume and the QD nucleation rate depend exponentially on the InAs coverage. These behaviors and their temperature and InAs growth rate dependences are essentially understandable in the frame of the mean-field theory. Similar analysis to conventional QD growth suggests that the often observed significant mass transport from wetting layer to QD's can be ascribed to the precursors existing before 2D-3D growth mode transition

  9. Self-Assembly of Bi2Te3-Nanoplate/Graphene-Nanosheet Hybrid by One-Pot Route and Its Improved Li-Storage Properties

    Directory of Open Access Journals (Sweden)

    Xinbing Zhao

    2012-07-01

    Full Text Available A sandwich structured Bi2Te3-nanoplates/graphene-nanosheet (Bi2Te3/G hybrid has been synthesized by a facile in situ solvothermal route and has been investigated as a potential anode material for Li-ion batteries. Bi2Te3 grows during the solvothermal process with the simultaneous reduction of graphite oxide into graphene. The in situ formation process of the hybrid has been investigated by X-ray diffraction and X-ray photoelectron spectra. The Li-storage mechanism and performance of Bi2Te3/G and bare Bi2Te3 have been studied by galvanostatic cycling and cyclic voltammetry. The Bi2Te3/G sandwich exhibits an obviously improved cycling stability compared to bare Bi2Te3. The enhancement in electrochemical performance can be attributed to the combined conducting, confining and dispersing effects of graphene for Bi2Te3 nanoplates and to the self-assembled sandwich structure.

  10. Steering of quantum waves: Demonstration of Y-junction transistors using InAs quantum wires

    Science.gov (United States)

    Jones, Gregory M.; Qin, Jie; Yang, Chia-Hung; Yang, Ming-Jey

    2005-06-01

    In this paper we demonstrate using an InAs quantum wire Y-branch switch that the electron wave can be switched to exit from the two drains by a lateral gate bias. The gating modifies the electron wave functions as well as their interference pattern, causing the anti-correlated, oscillatory transconductances. Our result suggests a new transistor function in a multiple-lead ballistic quantum wire system.

  11. Enhanced Photoelectrocatalytic Activity of BiOI Nanoplate-Zinc Oxide Nanorod p-n Heterojunction.

    Science.gov (United States)

    Kuang, Pan-Yong; Ran, Jing-Run; Liu, Zhao-Qing; Wang, Hong-Juan; Li, Nan; Su, Yu-Zhi; Jin, Yong-Gang; Qiao, Shi-Zhang

    2015-10-19

    The development of highly efficient and robust photocatalysts has attracted great attention for solving the global energy crisis and environmental problems. Herein, we describe the synthesis of a p-n heterostructured photocatalyst, consisting of ZnO nanorod arrays (NRAs) decorated with BiOI nanoplates (NPs), by a facile solvothermal method. The product thus obtained shows high photoelectrochemical water splitting performance and enhanced photoelectrocatalytic activity for pollutant degradation under visible light irradiation. The p-type BiOI NPs, with a narrow band gap, not only act as a sensitizer to absorb visible light and promote electron transfer to the n-type ZnO NRAs, but also increase the contact area with organic pollutants. Meanwhile, ZnO NRAs provide a fast electron-transfer channel, thus resulting in efficient separation of photoinduced electron-hole pairs. Such a p-n heterojunction nanocomposite could serve as a novel and promising catalyst in energy and environmental applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Uniform Fe{sub 3}O{sub 4} microflowers hierarchical structures assembled with porous nanoplates as superior anode materials for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaoliang [Institute of Electrostatic & Electromagnetic Protection, Mechanical Engineering College, Shijiazhuang 050003 (China); Liu, Yanguo [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China); Arandiyan, Hamidreza [Particles and Catalysis Research Group, School of Chemical Engineering, The University of New South Wales, Sydney, New South Wales 2052 (Australia); Yang, Hongping; Bai, Lu; Mujtaba, Jawayria [Beijing National Center for Electron Microscopy, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Wang, Qingguo; Liu, Shanghe [Institute of Electrostatic & Electromagnetic Protection, Mechanical Engineering College, Shijiazhuang 050003 (China); Sun, Hongyu, E-mail: hyltsun@gmail.com [Beijing National Center for Electron Microscopy, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Department of Micro- and Nanotechnology, Technical University of Denmark, 2800 Kongens Lyngby (Denmark)

    2016-12-15

    Highlights: • Uniform Fe{sub 3}O{sub 4} microflowers hierarchical structures were successfully prepared. • The Fe{sub 3}O{sub 4} microflowers are assembled with porous nanoplates. • Hollow Fe{sub 3}O{sub 4} microspheres exhibit better lithium storage properties than Fe{sub 3}O{sub 4} microspheres. • The good lithium storage properties are attributed to the special structural nature. - Abstract: Uniform Fe{sub 3}O{sub 4} microflowers assembled with porous nanoplates were successfully synthesized by a solvothermal method and subsequent annealing process. The structural and compositional analysis of the Fe{sub 3}O{sub 4} microflowers were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The Bruauer–Emmett–Teller (BET) specific surface area was calculated by the nitrogen isotherm curve and pore size distribution of Fe{sub 3}O{sub 4} microflowers was determined by the Barret–Joyner–Halenda (BJH) method. When evaluated as anode material for lithium-ion batteries, the as-prepared Fe{sub 3}O{sub 4} microflowers electrodes delivered superior capacity, better cycling stability and rate capability than that of Fe{sub 3}O{sub 4} microspheres electrodes. The improved electrochemical performance was attributed to the microscale flowerlike architecture and the porous sheet structural nature.

  13. Intrinsic quantum dots in InAs nanowires

    International Nuclear Information System (INIS)

    Weis, Karl Martin Darius

    2013-01-01

    This work deals with InAs nanowire field effect transistors in back gate configuration. In such devices, quantum dots can form at low temperatures in the order of magnitude of a few Kelvin. These dots are henceforth referred to as intrinsic as they are not intentionally defined by electrodes. For the interpretation of their stability diagrams, a thorough knowledge of the structure and transport properties of the nanowires is required. Therefore, first of all, the influence of growth method and doping on the transport properties is studied at room temperature. The wires are grown by two types of metal-organic vapour phase epitaxy: a selective-area (SA-MOVPE) and an Au-catalyzed vapour-liquid-solid method (VLS-MOVPE). Transport data shows that the background doping of VLS-MOVPE wires is higher than for SA-MOVPE wires, but the variability of the transport properties is lower. The polytypism of the SA-MOVPE wires (they are composed of wurtzite and zinc blende segments) is a possible explanation for the second observation. Furthermore, it is shown that the measured transport properties significantly depend on the dielectric environment of the nanowires and on the way the electrical measurements are done (two- or four-terminal configuration). The conductivity is tunable via doping and the gate voltage. Conductivity measurements in the temperature range from 10 K to 300 K show that different transport regimes can occur (partially metallic behaviour for sufficiently high conductivity, otherwise purely semiconducting behaviour). This is attributed to different positions of the Fermi level and thus, a different effect of potential fluctuations. If conductivity and temperature are sufficiently low, the onset of Coulomb blockade is observed for semiconducting samples. It is even possible to tune the very same sample to different regimes via the gate voltage. The semiconducting behaviour observed in many samples contradicts the Thomas-Fermi theory. This is attributed to the

  14. The third order nonlinear susceptibility of InAs at infrared region

    International Nuclear Information System (INIS)

    Musayev, M.A.

    2008-01-01

    Nonlinear susceptibilities of the third order and coefficient of nonlinear absorption in InAs n-type with a different degree of a doping have been measured. The values of the third order nonlinear susceptibilities have derived from these measurements essentially exceed the values calculated on the basis of model featuring nonlinear susceptibility of electrons, being in conduction-band nonparabolicity. It has been shown that the observable discrepancy has been eliminated, if in calculation a dissipation of energy of electrons has been considered. Growth of efficiency at four-wave mixingin narrow-gap semiconductors has been restricted to nonlinear absorption of interacting waves

  15. INFLUENCE OF LOW-ENERGY AR-SPUTTERING ON THE ELECTRONIC-PROPERTIES OF INAS-BASED QUANTUM-WELL STRUCTURES

    NARCIS (Netherlands)

    Magnee, P.H.C.; den Hartog, S.G.; Wees, B.J.van; Klapwijk, T.M; van de Graaf, W.; Borghs, G.

    1995-01-01

    The influence of low energy (80-500 eV) Ar-ion milling cleaning techniques on InAs based quantum well structures is investigated. It is found that both etching with a Kaufmann source and sputter-etching with a rf-plasma enhances the electron density and reduces the mobility. An anneal at 180 degrees

  16. Synthesis of core-shell hematite (α-Fe2O3) nanoplates: Quantitative analysis of the particle structure and shape, high coercivity and low cytotoxicity

    Science.gov (United States)

    Tadic, Marin; Kopanja, Lazar; Panjan, Matjaz; Kralj, Slavko; Nikodinovic-Runic, Jasmina; Stojanovic, Zoran

    2017-05-01

    Hematite core-shell nanoparticles with plate-like morphology were synthesized using a one-step hydrothermal synthesis. An XRPD analysis indicates that the sample consist of single-phase α-Fe2O3 nanoparticles. SEM and TEM measurements show that the hematite sample is composed of uniform core-shell nanoplates with 10-20 nm thickness, 80-100 nm landscape dimensions (aspect ratio ∼5) and 3-4 nm thickness of the surface shells. We used computational methods for the quantitative analysis of the core-shell particle structure and circularity shape descriptor for the quantitative shape analysis of the nanoparticles from TEM micrographs. The calculated results indicated that a percentage of the shell area in the nanoparticle area (share [%]) is significant. The determined values of circularity in the perpendicular and oblique perspective clearly show shape anisotropy of the nanoplates. The magnetic properties revealed the ferromagnetic-like properties at room temperature with high coercivity HC = 2340 Oe, pointing to the shape and surface effects. These results signify core-shell hematite nanoparticles' for practical applications in magnetic devices. The synthesized hematite plate-like nanoparticles exhibit low cytotoxicity levels on the human lung fibroblasts (MRC5) cell line demonstrating the safe use of these nanoparticles for biomedical applications.

  17. Two-color single-photon emission from InAs quantum dots: toward logic information management using quantum light.

    Science.gov (United States)

    Rivas, David; Muñoz-Matutano, Guillermo; Canet-Ferrer, Josep; García-Calzada, Raúl; Trevisi, Giovanna; Seravalli, Luca; Frigeri, Paola; Martínez-Pastor, Juan P

    2014-02-12

    In this work, we propose the use of the Hanbury-Brown and Twiss interferometric technique and a switchable two-color excitation method for evaluating the exciton and noncorrelated electron-hole dynamics associated with single photon emission from indium arsenide (InAs) self-assembled quantum dots (QDs). Using a microstate master equation model we demonstrate that our single QDs are described by nonlinear exciton dynamics. The simultaneous detection of two-color, single photon emission from InAs QDs using these nonlinear dynamics was used to design a NOT AND logic transference function. This computational functionality combines the advantages of working with light/photons as input/output device parameters (all-optical system) and that of a nanodevice (QD size of ∼ 20 nm) while also providing high optical sensitivity (ultralow optical power operational requirements). These system features represent an important and interesting step toward the development of new prototypes for the incoming quantum information technologies.

  18. Design of a multivariable controller for a CANDU 600 MWe nuclear power plant using the INA method

    International Nuclear Information System (INIS)

    Roy, N.; Boisvert, J.; Mensah, S.

    1984-04-01

    The development of large and complex nuclear and process plants requires high-performance control systems, designed with rigorous multivariable techniques. This work is part of an analytical study demonstrating the real potential of multivariable methods. It covers every step in the design of a multi-variable controller for a Gentilly-2 type CANDU 600 MWe nuclear power plant using the Inverse Nyquist Array (INA) method. First the linear design model and its preliminary modifications are described. The design tools are reviewed and the operations required to achieve open-loop diagonal dominance are thoroughly described. Analysis of the closed-loop system is then performed and a feedback matrix is selected to meet the design specifications. The performance of the controller on the linear model is verified by simulation. Finally, the controller is implemented on the reference non-linear model to assess its overall performance. The results show that the INA method can be used successfully to design controllers for large and complex systems

  19. Crystalline mesoporous tungsten oxide nanoplate monoliths synthesized by directed soft template method for highly sensitive NO{sub 2} gas sensor applications

    Energy Technology Data Exchange (ETDEWEB)

    Hoa, Nguyen Duc, E-mail: ndhoa@itims.edu.vn [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST) (Viet Nam); Duy, Nguyen Van [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST) (Viet Nam); Hieu, Nguyen Van, E-mail: hieu@itims.edu.vn [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST) (Viet Nam)

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Mesoporous WO{sub 3} nanoplate monoliths were obtained by direct templating synthesis. ► Enable effective accession of the analytic molecules for the sensor applications. ► The WO{sub 3} sensor exhibited a high performance to NO{sub 2} gas at low temperature. -- Abstract: Controllable synthesis of nanostructured metal oxide semiconductors with nanocrystalline size, porous structure, and large specific surface area is one of the key issues for effective gas sensor applications. In this study, crystalline mesoporous tungsten oxide nanoplate-like monoliths with high specific surface areas were obtained through instant direct-templating synthesis for highly sensitive nitrogen dioxide (NO{sub 2}) sensor applications. The copolymer soft template was converted into a solid carbon framework by heat treatment in an inert gas prior to calcinations in air to sustain the mesoporous structure of tungsten oxide. The multidirectional mesoporous structures of tungsten oxide with small crystalline size, large specific surface area, and superior physical characteristics enabled the rapid and effective accession of analytic gas molecules. As a result, the sensor response was enhanced and the response and recovery times were reduced, in which the mesoporous tungsten oxide based gas sensor exhibited a superior response of 21,155% to 5 ppm NO{sub 2}. In addition, the developed sensor exhibited selective detection of low NO{sub 2} concentration in ammonia and ethanol at a low temperature of approximately 150 °C.

  20. Nano-scale mass sensor based on the vibration analysis of a magneto-electro-elastic nanoplate resting on a visco-Pasternak substrate

    Science.gov (United States)

    Khanmirza, E.; Jamalpoor, A.; Kiani, A.

    2017-10-01

    In this paper, a magneto-electro-elastic nanoplate resting on a visco-Pasternak medium with added concentrated nanoparticles is presented as a mass nanosensor according to the vibration analysis. The MEE nanoplate is supposed to be subject to external electric voltage and magnetic potential. In order to take into account the size effect on the sensitivity of the sensor, the nonlocal elasticity theory in conjunction with the Kirchhoff plate theory is applied. Partial differential equations are derived by implementing Hamilton's variational principle. Equilibrium equations were solved analytically to determine an explicit closed-form statement for both the damped frequency shift and the relative damped frequency shift using Navier's approach. A genetic algorithm (GA) is employed to achieve the optimal added nanoparticle location to gain the most sensitivity performance of the nanosensor. Numerical studies are performed to illustrate the variation of the sensitivity property corresponding to various values of the number of attached nanoparticles, the mass of each nanoparticle, the nonlocal parameter, external electric voltage and magnetic potential, the aspect ratio, and visco-Pasternak parameters. Some numerical outcomes of this paper show that the minimum value of the damped frequency shift occurs for a certain value of the length-to-thickness ratio. Also, it is shown that the external magnetic and external electric potentials have a different effect on the sensitivity property. It is anticipated that the results reported in this work can be considered as a benchmark in future micro-structures issues.

  1. BIAYA KLAIM INA CBGS DAN BIAYA RIIL PENYAKIT KATASTROPIK RAWAT INAP PESERTA JAMKESMAS DI RUMAH SAKIT STUDI DI 10 RUMAH SAKIT MILIK KEMENTERIAN KESEHATAN JANUARI–MARET 2012

    Directory of Open Access Journals (Sweden)

    Wasis Budiarto

    2013-08-01

    Full Text Available Latar belakang: Implementasi sistem INA-CBGs bagi pasien penyakit katastropik (jantung, kanker, stroke peserta Jamkesmas di rumah sakit, memberikan konsekuensi di satu pihak bahwa penyakit katastropik merupakan ancaman terhadap membengkaknya pembiayaan Jamkesmas di masa datang, sedangkan di pihak lain, rumah sakit merasakan bahwa biaya penggantian klaim INA CBGs lebih rendah dari tarif yang berlaku dirumah sakit. Tujuan: Tujuan penelitian ini untuk memperoleh gambaran biaya pengobatan penyakit katastropik dan perbandingan pembiayaan klaim berdasarkan INA-DRGs dengan biaya pengobatan riil penyakit katastropik dirumah sakit. Jenis penelitian adalah deskriptif menurut perspektif rumah sakit. Metode: Metode pengambilan data dilakukan secara retrospektif yang diambil dari penelusuran dokumen catatan medik pasien penyakit katastropik di 10 rumah sakit selama 3 bulan (Januari–Maret 2012. Analisis data dilakukan secara deskriptif. Hasil: Hasil penelitian menunjukkan bahwa pasien Jamkesmas yang dirawat dengan kasus katastropik terdiri dari penyakit jantung sebesar37,11%, penyakit kanker 23,54% dan sisanya sebesar 39,35% pasien penyakit stroke. Kesimpulan: Biaya pengobatan rawat inap berdasarkan tarif rumah sakit kelas A jauh lebih besar dibandingkan kelas B dan RS Khusus, biaya klaim berdasarkan INA-CBGs jauh lebih besar di rumah sakit kelas A dibanding kelas B dan RS Khusus. Komponen biaya yang banyak peruntukannya adalah biaya akomodasi, tindakan ruangan, pemeriksaan laboratorium, tindakan intervensi nonbedah untuk jantung, tindakan operasi untuk kanker serta biaya obat-obatan. Biaya penggantian klaim penyakit katastropik berdasarkan INA CBGs lebih besar dibandingkan dengan biaya riil berdasarkan tarif rumah sakit, sehingga untuk penyakit katastropik rumah sakit tidak merugi. Untuk itu pelaksanaan kebijakan rujukan berjenjang bagi peserta Jamkesmas harus diawasi secara ketat sehingga pelayanan kesehatan bagi penduduk miskin menjadi lebih terjamin

  2. Making Mn substitutional impurities in InAs using a scanning tunneling microscope.

    Science.gov (United States)

    Song, Young Jae; Erwin, Steven C; Rutter, Gregory M; First, Phillip N; Zhitenev, Nikolai B; Stroscio, Joseph A

    2009-12-01

    We describe in detail an atom-by-atom exchange manipulation technique using a scanning tunneling microscope probe. As-deposited Mn adatoms (Mn(ad)) are exchanged one-by-one with surface In atoms (In(su)) to create a Mn surface-substitutional (Mn(In)) and an exchanged In adatom (In(ad)) by an electron tunneling induced reaction Mn(ad) + In(su) --> Mn(In) + In(ad) on the InAs(110) surface. In combination with density-functional theory and high resolution scanning tunneling microscopy imaging, we have identified the reaction pathway for the Mn and In atom exchange.

  3. Nonlinear absorption and receptivity of the third order in InAs infrared region

    International Nuclear Information System (INIS)

    Musayev, M.A.

    2005-01-01

    Nonlinear absorption and receptivity of the third order and coefficient nonlinear absorption in InAs n-type with different degree of alloying was measured. Obtained score considerably exceed sense, calculated on the basis of the models describing nonlinear receptivity of electrons, situated in the nonparabolic area of conductivity. It was shown that, observable deviations withdraw; if in the calculation apply energy dissipation of electrons. Growth of the efficiency under four-wave interaction in low-energy-gap semiconductors confines nonlinear absorption of interacting waves

  4. Effect of surface density silver nanoplate films toward surface-enhanced Raman scattering enhancement for bisphenol A detection

    Science.gov (United States)

    Bakar, N. A.; Salleh, M. M.; Umar, A. A.; Shapter, J. G.

    2018-03-01

    This paper reports a study on surface-enhanced Raman scattering (SERS) phenomenon of triangular silver nanoplate (NP) films towards bisphenol A (BPA) detection. The NP films were prepared using self-assembly technique with four different immersion times; 1 hour, 2 hours, 5 hours, and 8 hours. The SERS measurement was studied by observing the changes in Raman spectra of BPA after BPA absorbed on the NP films. It was found that the Raman intensity of BPA peaks was enhanced by using the prepared SERS substrates. This is clearly indicated that these SERS silver substrates are suitable to sense industrial chemical and potentially used as SERS detector. However, the rate of SERS enhancement is depended on the distribution of NP on the substrate surface.

  5. Theoretical interpretation of the electron mobility behavior in InAs nanowires

    International Nuclear Information System (INIS)

    Marin, E. G.; Ruiz, F. G.; Godoy, A.; Tienda-Luna, I. M.; Martínez-Blanque, C.; Gámiz, F.

    2014-01-01

    This work studies the electron mobility in InAs nanowires (NWs), by solving the Boltzmann Transport Equation under the Momentum Relaxation Time approximation. The numerical solver takes into account the contribution of the main scattering mechanisms present in III-V compound semiconductors. It is validated against experimental field effect-mobility results, showing a very good agreement. The mobility dependence on the nanowire diameter and carrier density is analyzed. It is found that surface roughness and polar optical phonons are the scattering mechanisms that mainly limit the mobility behavior. Finally, we explain the origin of the oscillations observed in the mobility of small NWs at high electric fields.

  6. Theoretical interpretation of the electron mobility behavior in InAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Marin, E. G., E-mail: egmarin@ugr.es; Ruiz, F. G., E-mail: franruiz@ugr.es; Godoy, A.; Tienda-Luna, I. M.; Martínez-Blanque, C.; Gámiz, F. [Departamento de Electrónica y Tecnología de los Computadores, Facultad de Ciencias, Universidad de Granada, Av. Fuentenueva S/N, 18071 Granada (Spain)

    2014-11-07

    This work studies the electron mobility in InAs nanowires (NWs), by solving the Boltzmann Transport Equation under the Momentum Relaxation Time approximation. The numerical solver takes into account the contribution of the main scattering mechanisms present in III-V compound semiconductors. It is validated against experimental field effect-mobility results, showing a very good agreement. The mobility dependence on the nanowire diameter and carrier density is analyzed. It is found that surface roughness and polar optical phonons are the scattering mechanisms that mainly limit the mobility behavior. Finally, we explain the origin of the oscillations observed in the mobility of small NWs at high electric fields.

  7. Influence of polymer swelling and dissolution into food simulants on the release of graphene nanoplates and carbon nanotubes from poly(lactic) acid and polypropylene composite films

    OpenAIRE

    Velichkova, Hristiana; Petrova, Ivanka; Kotsilkov, Stanislav; Ivanov, Evgeni; Vitanov, Nikolay K.; Kotsilkova, Rumiana

    2017-01-01

    The study compared the effects of swelling and dissolution of a matrix polymer by food simulants on the release of graphene nanoplates (GNPs) and multiwall carbon nanotubes (MWCNTs) from poly(lactic) acid (PLA) and polypropylene (PP) composite films. The total migration was determined gravimetrically in the ethanol and acetic acid food simulants at different time and temperature conditions, while migrants were detected by laser diffraction analysis and transmission electron microscopy. Swelli...

  8. Hierarchical Li1.2 Ni0.2 Mn0.6 O2 nanoplates with exposed {010} planes as high-performance cathode material for lithium-ion batteries.

    Science.gov (United States)

    Chen, Lai; Su, Yuefeng; Chen, Shi; Li, Ning; Bao, Liying; Li, Weikang; Wang, Zhao; Wang, Meng; Wu, Feng

    2014-10-22

    Hierarchical Li1.2 Ni0.2 Mn0.6 O2 nanoplates with exposed {010} planes are designed and synthesized. In combination with the advantages from the hierarchical archi-tecture and the exposed electrochemically active {010} planes of layered materials, this material satisfies both efficient ion and electron transport and thus shows superior rate capability and excellent cycling stability. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Fast Synthesis of Gibbsite Nanoplates and Process Optimization using Box-Behnken Experimental Design

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xin; Zhang, Xianwen; Graham, Trenton R.; Pearce, Carolyn I.; Mehdi, Beata L.; N' Diaye, Alpha T.; Kerisit, Sebastien N.; Browning, Nigel D.; Clark, Sue B.; Rosso, Kevin M.

    2017-10-26

    Developing the ability to synthesize compositionally and morphologically well-defined gibbsite particles at the nanoscale with high yield is an ongoing need that has not yet achieved the level of rational design. Here we report optimization of a clean inorganic synthesis route based on statistical experimental design examining the influence of Al(OH)3 gel precursor concentration, pH, and aging time at temperature. At 80 oC, the optimum synthesis conditions of gel concentration at 0.5 M, pH at 9.2, and time at 72 h maximized the reaction yield up to ~87%. The resulting gibbsite product is composed of highly uniform euhedral hexagonal nanoplates within a basal plane diameter range of 200-400 nm. The independent roles of key system variables in the growth mechanism are considered. On the basis of these optimized experimental conditions, the synthesis procedure, which is both cost-effective and environmentally friendly, has the potential for mass production scale-up of high quality gibbsite material for various fundamental research and industrial applications.

  10. The Effect of INA [(R)-1-O-(1-Pyrenylmethyl)Glycerol] Insertions on the Structure and Biological Activity of a G-Quadruplex from a Critical Kras G-Rich Sequence

    DEFF Research Database (Denmark)

    Cogoi, Susanna; Paramasivan, Manikandan; Xodo, Luigi E.

    2007-01-01

    Quadruplex-forming oligonucleotides containing INA [(R)-1-O-(1-pyrenylmethyl)glycerol] insertions have been designed and studied for their capacity to inhibit the expression of the KRAS oncogene in pancreatic adenocarcinoma cells. It is found that INA can influence the folding topology of the G-q...

  11. Auger recombination in p-type InAs and in Gasub(x)Insub(1-x)As solid solutions

    International Nuclear Information System (INIS)

    Zotova, N.V.; Yassievich, I.N.

    1977-01-01

    The probability of the Auger recombination in p-type semiconductors, which is accompanied by transition of the second hole into the zone, splitted by spin-orbital interaction, was calculated. The above process is effective when the energy of spin-orbital splitting off Δ is close to the forbidden zone energy Esub(g), which takes place in the case of InAs, GaSb and solid solutions based on these compounds. The calculation is performed for the non-degenerate hole gas at a finite difference of Esub(g) - Δ. By means of the study of radiative recombination in InAs and Gasub(x)Insub(1-x)As solid solutions with small contents of GaAs (0 17 cm -3 . It is found that the quantum yield of radiative recombination increases sharply in Gasub(x)Insub(1-x)As solid solutions with the increase of x, which is associated with the increase of the difference of Esub(g) - Δ; the radiative recombination intensity increases in correspondence with the theoretical calculation made

  12. SnS{sub 2} nanoplates embedded in 3D interconnected graphene network as anode material with superior lithium storage performance

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Hongli [Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105 (China); Qi, Xiang, E-mail: xqi@xtu.edu.cn [Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105 (China); Han, Weijia; Ren, Long; Liu, Yundan [Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105 (China); Wang, Xingyan, E-mail: xywangxtu@163.com [Department of Environmental Science and Engineering, College of Chemical Engineering, Xiangtan University, Xiangtan 411105 (China); Zhong, Jianxin [Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105 (China)

    2015-11-15

    Graphical abstract: Schematic formation process of 3D interconnected SnS{sub 2}/graphene composite, and its superior lithium storage performance. - Highlights: • 3D graphene network embedded with SnS{sub 2} is synthesized by a facile two-step method. • This structure produces a synergistic effect between graphene and SnS{sub 2} nanoplates. • High capacity, excellent cycle performance and good rate capability are achieved. - Abstract: Three-dimensional (3D) interconnected graphene network embedded with uniformly distributed tin disulfide (SnS{sub 2}) nanoplates was prepared by a facile two-step method. The microstructures and morphologies of the SnS{sub 2}/graphene nanocomposite (SSG) are experimentally confirmed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Using the as-prepared SSG as an anode material for lithium batteries, its electrochemical performances were investigated by cyclic voltammograms (CV), charge/discharge tests, galvanostatic cycling performance and AC impedance spectroscopy. The results demonstrate that the as-prepared SSG exhibits excellent cycling performance with a capacity of 1060 mAh g{sup −1} retained after 200 charge/discharge cycles at a current density of 100 mA g{sup −1}, also a superior rate capability of 670 mAh g{sup −1} even at such a high current density of 2000 mA g{sup −1}. This favorable performance can be attributed to the unique 3D interconnected architecture with great electro-conductivity and its intimate contact with SnS{sub 2}. Our results indicate a potential application of this novel 3D SnS{sub 2}/graphene nanocomposite in lithium-ion battery.

  13. Direct radiocarbon dates for Vindija G1 and Velika Pećina Late Pleistocene hominid remains

    Science.gov (United States)

    Smith, Fred H.; Trinkaus, Erik; Pettitt, Paul B.; Karavanić, Ivor; Paunović, Maja

    1999-01-01

    New accelerator mass spectrometry radiocarbon dates taken directly on human remains from the Late Pleistocene sites of Vindija and Velika Pećina in the Hrvatsko Zagorje of Croatia are presented. Hominid specimens from both sites have played critical roles in the development of current perspectives on modern human evolutionary emergence in Europe. Dates of ≈28 thousand years (ka) before the present (B.P.) and ≈29 ka B.P. for two specimens from Vindija G1 establish them as the most recent dated Neandertals in the Eurasian range of these archaic humans. The human frontal bone from Velika Pećina, generally considered one of the earliest representatives of modern humans in Europe, dated to ≈5 ka B.P., rendering it no longer pertinent to discussions of modern human origins. Apart from invalidating the only radiometrically based example of temporal overlap between late Neandertal and early modern human fossil remains from within any region of Europe, these dates raise the question of when early modern humans first dispersed into Europe and have implications for the nature and geographic patterning of biological and cultural interactions between these populations and the Neandertals. PMID:10535913

  14. Spin-lattice relaxation times and knight shift in InSb and InAs

    International Nuclear Information System (INIS)

    Braun, P.; Grande, S.

    1976-01-01

    For a dominant contact interaction between nuclei and conduction electrons the relaxation rate is deduced. The extreme cases of degenerate and non-degenerate semiconductors are separately discussed. At strong degeneracy the product of the Knight shift and relaxation time gives the Korringa relation for metals. Measurements of the NMR spin-lattice relaxation times of 115 InSb and 115 InAs were made between 4.2 and 300 K for strongly degenerated samples. The different relaxation mechanisms are discussed and the experimental and theoretical results are compared. (author)

  15. Unit Cell Structure of Crystal Polytypes in InAs and InSb Nanowires

    DEFF Research Database (Denmark)

    Kriegner, Dominik; Panse, Christian; Mandl, Bernhard

    2011-01-01

    The atomic distances in hexagonal polytypes of III−V compound semiconductors differ from the values expected from simply a change of the stacking sequence of (111) lattice planes. While these changes were difficult to quantify so far, we accurately determine the lattice parameters of zinc blende......, wurtzite, and 4H polytypes for InAs and InSb nanowires, using X-ray diffraction and transmission electron microscopy. The results are compared to density functional theory calculations. Experiment and theory show that the occurrence of hexagonal bilayers tends to stretch the distances of atomic layers...

  16. Direct-Bandgap InAs Quantum-Dots Have Long-Range Electron--Hole Exchange Whereas Indirect Gap Si Dots Have Short-Range Exchange

    International Nuclear Information System (INIS)

    Juo, J.W.; Franceschetti, A.; Zunger, A.

    2009-01-01

    Excitons in quantum dots manifest a lower-energy spin-forbidden 'dark' state below a spin-allowed 'bright' state; this splitting originates from electron-hole (e-h) exchange interactions, which are strongly enhanced by quantum confinement. The e-h exchange interaction may have both a short-range and a long-range component. Calculating numerically the e-h exchange energies from atomistic pseudopotential wave functions, we show here that in direct-gap quantum dots (such as InAs) the e-h exchange interaction is dominated by the long-range component, whereas in indirect-gap quantum dots (such as Si) only the short-range component survives. As a result, the exciton dark/bright splitting scales as 1/R 2 in InAs dots and 1/R 3 in Si dots, where R is the quantum-dot radius.

  17. Nonlinear absorption and transmission properties of Ge, Te and InAs using tuneable IR FEL

    Energy Technology Data Exchange (ETDEWEB)

    Amirmadhi, F.; Becker, K.; Brau, C.A. [Vanderbilt Univ., Nashville, TN (United States)

    1995-12-31

    Nonlinear absorption properties of Ge, Te and InAs are being investigated using the transmission of FEL optical pulses through these semiconductors (z-scan method). Wavelength, intensity and macropulse dependence are used to differentiate between two-photon and free-carrier absorption properties of these materials. Macropulse dependence is resolved by using a Pockles Cell to chop the 4-{mu}s macropulse down to 100 ns. Results of these experiments will be presented and discussed.

  18. 20 CFR 668.700 - What process must an INA grantee use to plan its employment and training services?

    Science.gov (United States)

    2010-04-01

    ... it uses to plan other activities and services. (b) However, in the process of preparing its Two Year... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false What process must an INA grantee use to plan its employment and training services? 668.700 Section 668.700 Employees' Benefits EMPLOYMENT AND...

  19. Mieloencefalite protozoária eqüina (Relato de caso.

    Directory of Open Access Journals (Sweden)

    R. C. Gonçalves

    2005-03-01

    Full Text Available RESUMO :O objetivo deste trabalho foi relatar um caso de mieloencefalite protozoária eqüina no Estado de São Paulo, Brasil. O diagnóstico se baseou nos sinais clínicos, no resultado positivo para anticorpos contra Sarcocystis neurona no soro e no líquor pela técnica de Western blot. Palavras chave: Mieloencefalite, Sarcocystis neurona, eqüinos. SUMMARY: The purpose of this work was to present a case of equine protozoal myeloencephalitis (EPM in the State of São Paulo, Brazil. The diagnosis was based on the clinical sings, the positive results of the serum and cerebrospinal fluid analysis (Western blot for antibodies against Sarcocystis neurona. Keywords: Myeloencephalitis, Sarcocystis neurona,

  20. Shape analysis of single and stacked InAs quantum dots at the atomic level by cross-sectional STM

    NARCIS (Netherlands)

    Bruls, D.M.; Vugs, J.W.A.M.; Koenraad, P.M.; Skolnick, M.S.; Hopkinson, M.; Wolter, J.H.; Miura, N.; Ando, T.

    2001-01-01

    We present a study of InAs self-assembled quantum dots in GaAs by cross-sectional scanning tunneling microscopy (X-STM). Our results shows that the dots consist of an JnGaAs alloy and that the indium content increases towards the top. The analysis of the height versus base length relation obtained

  1. Degree of functionalization and stability of fluorine groups fixed to carbon nanotubes and graphite nanoplates by CF{sub 4} microwave plasma

    Energy Technology Data Exchange (ETDEWEB)

    Abdelkader-Fernández, V.K.; Morales-Lara, F. [Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain); Melguizo, M.; García-Gallarín, C.; López-Garzón, R.; Godino-Salido, M.L. [Departamento de Química Inorgánica y Orgánica, Facultad de Ciencias Experimentales, Universidad de Jaén, 23071 Jaén (Spain); López-Garzón, F.J., E-mail: flopez@ugr.es [Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain); Domingo-García, M.; Pérez-Mendoza, M.J. [Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain)

    2015-12-01

    Highlights: • The surface area of GNPs and MWCNTs determines the degree of fluorination by plasma. • Fluorine is bound to carbon atoms in up to eight chemical environments. • The stability of the fluorine groups varies in a wide range of temperature. • The electronic properties of MWCNTs are changed as a consequence of fluorination. • The textural characteristics of the materials are not changed after fluorination. - Abstract: The fluorination of graphite nanoplates (GNPs) and multi-wall carbon nanotubes (MWCNTs) by CF{sub 4} cold plasma is reported. The aim is to analyze the influence of the textural characteristics in the degree of fluorination and in the thermal stability of the fluorine groups. We have used thermal programmed desorption which clearly discriminates the nature of the desorbing species and their stability. The degree of fluorination of both materials is similar up to 20 min of treatment and then it decreases in GNPs at longer treatments. Nevertheless, the fluorine content in MWCNTs keeps increasing after 45 min. This different evolution of the fluorination degree with the time is related to the surface areas. The fluorine bonding is produced not only in defects and irregularities but also on the external graphene sheets of both materials, and it results in up to eight different chemical environments having different thermal stabilities from 150 °C up to temperatures higher than 900 °C. The fluorination increases the electronic states near the Fermi level of the nanotubes whereas it does not affect the electronic properties of graphite nanoplates. It is shown that no intercalation compounds are formed and that the textural characteristics of the materials remain unchanged after fluorination.

  2. Solução concentrada de albumina eqüina na fluidoterapia em eqüinos com desidratação leve a moderada

    OpenAIRE

    Belli,C.B.; Michima,L.E.S.; Latorre,S.M.; Fernandes,W.R.

    2008-01-01

    Avaliou-se o efeito da solução concentrada de albumina eqüina diluída a 5% em solução fisiológica (SF) durante fluidoterapia em eqüinos, após indução de desidratação leve a moderada, utilizando-se cinco eqüinos adultos, sem alterações clínicas. Cada animal passou por dois protocolos de fluidoterapia: apenas com SF (metade sob pressão e metade em fluxo contínuo - grupo-controle); com solução de albumina eqüina e SF (apenas em fluxo contínuo - grupo experimental). Avaliaram-se peso, exame físic...

  3. Self-assembled InAs quantum dots. Properties, modification and emission processes

    International Nuclear Information System (INIS)

    Schramm, A.

    2007-01-01

    In this thesis, structural, optical as well as electronic properties of self-assembled InAs quantum dots (QD) were studied by means of atomic force microscopy (AFM), photoluminescence (PL), capacitance spectroscopy (CV) and capacitance transient spectroscopy (DLTS). The quantum dots were grown with molecular beam epitaxy (MBE) and embedded in Schottky diodes for electrical characterization. In this work growth aspects as well as the electronic structures of QD were discussed. By varying the QD growth parameters it is possible to control the structural, and thus the optical and electronic properties of QD. Two methods are presented. Adjusting the QD growth temperature leads either to small QD with a high areal density or to high QDs with a low density. The structural changes of the QD are reflected in the changes of the optical and electronic properties. The second method is to introduce a growth interruption after capping the QD with thin cap layers. It was shown that capping with AlAs leads to a well-developed alternative to control the QD height and thus the ground-state energies of the QD. A post-growth method modifying the QD properties ist rapid thermal annealing (RTA). Raising the RTA temperature causes a lifting of the QD energy states with respect to the GaAs band edge energy due to In/Ga intermixing processes. A further main part of this work covers the emission processes of charge carriers in QD. Thermal emission, thermally assisted tunneling, and pure tunneling emission are studied by capacitance transient spectroscopy techniques. In DLTS experiments a strong impact of the electric field on the activation energies of electrons was found interfering the correct determination of the QD level energies. This behaviour can be explained by a thermally assisted tunneling model. A modified model taking the Coulomb interaction of occupied QD into account describes the emission rates of the electrons. In order to avoid several emission pathes in the experiments

  4. ZIF-8 derived hexagonal-like α-Fe2O3/ZnO/Au nanoplates with tunable surface heterostructures for superior ethanol gas-sensing performance

    Science.gov (United States)

    Chen, Ying; Li, Hui; Ma, Qian; Che, Quande; Wang, Junpeng; Wang, Gang; Yang, Ping

    2018-05-01

    A series of hexagonal-like α-Fe2O3/ZnO/Au nanoplate heterostructures with tunable morphologies and superior ethanol gas-sensing performance were successfully synthesized via the facile multi-step reaction processes. Hexagonal-like α-Fe2O3 nanoplates with uniform size around 150 nm are employed as new sensor substrates for loading the well-distributed ZnO and Au nanoparticles with adjustable size distribution on the different surfaces. Brunauer-EmmeQ-Teller (BET) surface areas of α-Fe2O3 and α-Fe2O3/ZnO samples are evaluated to be 37.94 and 61.27 m2/g, respectively, while α-Fe2O3/ZnO/Au composites present the highest value of 79.08 m2/g. These α-Fe2O3-based functional materials can exhibit outstanding sensing properties to ethanol. When the ethanol concentration is 100 ppm, the response value of α-Fe2O3/ZnO/Au composites can reach up to 170, which is 14.6 and 80.3 times higher than that of α-Fe2O3/ZnO and pure α-Fe2O3, respectively. The recycling stability and long-time effectiveness can be availably maintained within 30 days, as well as the response and recovery times are shortened to 4 and 5 s, respectively. Significantly, the response value of α-Fe2O3/ZnO/Au composite is still up to 63 at an operating temperature of 280 °C even though the ethanol concentration decreases to 10 ppm. The enhanced gas sensing mechanism would be focused on the synergistic effects of phase compositions, surface heterogeneous structures, large specific surface area, and the selective depositions of Au nanoparticles in α-Fe2O3/ZnO/Au sensors. The synergistic effect of different surface heterostructures referring to α-Fe2O3/Au and α-Fe2O3/ZnO/Au and their novel electron transport processes on the surfaces are first investigated and discussed in details. It is expected that hexagonal-like α-Fe2O3/ZnO/Au nanoplate heterostructures with excellent sensing performance can be the promising highly-sensitive materials in the actual application for monitoring and detecting ethanol.

  5. Efficiency enhancement of ZnO nanostructure assisted Si solar cell based on fill factor enlargement and UV-blue spectral down-shifting

    International Nuclear Information System (INIS)

    Gholizadeh, A; Reyhani, A; Mortazavi, S Z; Parvin, P

    2017-01-01

    ZnO nanostructures (including nano-plates and nano-rods (NRs)) are grown in various temperatures and Ar/O 2 flow rates using thermal chemical vapor deposition, which affect the structure, nano-plate/NR population, and the quality of ZnO nanostructures. X-ray diffraction (XRD) attests that the peak intensity of the crystallographic plane (1 0 0) is correlated to nano-plate abundance. Moreover, optical properties elucidate that the population of nano-plates in samples strongly affect the band gap, binding energy of the exciton, and UV–visible (UV–vis) absorption and spectral luminescence emissions. In fact, the exciton binding energy reduces from ∼100 to 80 meV when the population of nano-plates increases in samples. Photovoltaic characteristics based on the drop-casting on Si solar cells reveals three dominant factors, namely, the equivalent series resistance, decreasing reflectance, and down-shifting, in order to scale up the absolute efficiency by 3%. As a consequence, the oxygen vacancies in ZnO nanostructures give rise to the down-shifting and increase of free-carriers, leading to a reduction in the equivalent series resistance and an enlargement of fill factor. To obtain a larger I sc , reduction of spectral reflectance is essential; however, the down-shifting process is shown to be dominant by lessening the surface electron-hole recombination rate over the UV–blue spectral range. (paper)

  6. Efficiency enhancement of ZnO nanostructure assisted Si solar cell based on fill factor enlargement and UV-blue spectral down-shifting

    Science.gov (United States)

    Gholizadeh, A.; Reyhani, A.; Parvin, P.; Mortazavi, S. Z.

    2017-05-01

    ZnO nanostructures (including nano-plates and nano-rods (NRs)) are grown in various temperatures and Ar/O2 flow rates using thermal chemical vapor deposition, which affect the structure, nano-plate/NR population, and the quality of ZnO nanostructures. X-ray diffraction (XRD) attests that the peak intensity of the crystallographic plane (1 0 0) is correlated to nano-plate abundance. Moreover, optical properties elucidate that the population of nano-plates in samples strongly affect the band gap, binding energy of the exciton, and UV-visible (UV-vis) absorption and spectral luminescence emissions. In fact, the exciton binding energy reduces from ~100 to 80 meV when the population of nano-plates increases in samples. Photovoltaic characteristics based on the drop-casting on Si solar cells reveals three dominant factors, namely, the equivalent series resistance, decreasing reflectance, and down-shifting, in order to scale up the absolute efficiency by 3%. As a consequence, the oxygen vacancies in ZnO nanostructures give rise to the down-shifting and increase of free-carriers, leading to a reduction in the equivalent series resistance and an enlargement of fill factor. To obtain a larger I sc, reduction of spectral reflectance is essential; however, the down-shifting process is shown to be dominant by lessening the surface electron-hole recombination rate over the UV-blue spectral range.

  7. ISTRAŽIVANJE ZAGAĐENOSTI MESA, RADNIH POVRŠINA I PRIBORA BAKTERIJAMA RODA PROTEUS

    OpenAIRE

    Hadžiosmanović, Mirza; Živković, Josip; Trešćec, Aida

    1992-01-01

    Istraživan je stupanj zagađenja sirovina i radnih površina tijekom proizvodnje mesnih prerađevina bakterijama roda Proteus. Rezultati su pokazali da je meso peradi zagađeno vrstama roda Proteus u količini od 8,8%, svježe goveđe meso 7,8 % a polutrajne i obarene kobasice neposredno nakon proizvoodnje u količini od 2,8 %. Rezultati pretraga brisova s proizvodnih linija pokazuju da je pripadnika roda Proteus najviše u kobasičarnici (14,6 %), na liniji prerade svinja (11,8 %), goveda (10,9 %), a ...

  8. Electronic properties of GaAs, InAs and InP nanowires studied by terahertz spectroscopy

    International Nuclear Information System (INIS)

    Joyce, Hannah J; Docherty, Callum J; Lloyd-Hughes, James; Herz, Laura M; Johnston, Michael B; Gao Qiang; Tan, H Hoe; Jagadish, Chennupati

    2013-01-01

    We have performed a comparative study of ultrafast charge carrier dynamics in a range of III–V nanowires using optical pump–terahertz probe spectroscopy. This versatile technique allows measurement of important parameters for device applications, including carrier lifetimes, surface recombination velocities, carrier mobilities and donor doping levels. GaAs, InAs and InP nanowires of varying diameters were measured. For all samples, the electronic response was dominated by a pronounced surface plasmon mode. Of the three nanowire materials, InAs nanowires exhibited the highest electron mobilities of 6000 cm 2 V −1 s −1 , which highlights their potential for high mobility applications, such as field effect transistors. InP nanowires exhibited the longest carrier lifetimes and the lowest surface recombination velocity of 170 cm s −1 . This very low surface recombination velocity makes InP nanowires suitable for applications where carrier lifetime is crucial, such as in photovoltaics. In contrast, the carrier lifetimes in GaAs nanowires were extremely short, of the order of picoseconds, due to the high surface recombination velocity, which was measured as 5.4 × 10 5   cm s −1 . These findings will assist in the choice of nanowires for different applications, and identify the challenges in producing nanowires suitable for future electronic and optoelectronic devices. (paper)

  9. Shape-Dependent Electrocatalytic Reduction of CO2 to CO on Triangular Silver Nanoplates.

    Science.gov (United States)

    Liu, Subiao; Tao, Hongbiao; Zeng, Li; Liu, Qi; Xu, Zhenghe; Liu, Qingxia; Luo, Jing-Li

    2017-02-15

    Electrochemical reduction of CO 2 (CO 2 RR) provides great potential for intermittent renewable energy storage. This study demonstrates a predominant shape-dependent electrocatalytic reduction of CO 2 to CO on triangular silver nanoplates (Tri-Ag-NPs) in 0.1 M KHCO 3 . Compared with similarly sized Ag nanoparticles (SS-Ag-NPs) and bulk Ag, Tri-Ag-NPs exhibited an enhanced current density and significantly improved Faradaic efficiency (96.8%) and energy efficiency (61.7%), together with a considerable durability (7 days). Additionally, CO starts to be observed at an ultralow overpotential of 96 mV, further confirming the superiority of Tri-Ag-NPs as a catalyst for CO 2 RR toward CO formation. Density functional theory calculations reveal that the significantly enhanced electrocatalytic activity and selectivity at lowered overpotential originate from the shape-controlled structure. This not only provides the optimum edge-to-corner ratio but also dominates at the facet of Ag(100) where it requires lower energy to initiate the rate-determining step. This study demonstrates a promising approach to tune electrocatalytic activity and selectivity of metal catalysts for CO 2 RR by creating optimal facet and edge site through shape-control synthesis.

  10. Ballistic One-Dimensional InAs Nanowire Cross-Junction Interconnects.

    Science.gov (United States)

    Gooth, Johannes; Borg, Mattias; Schmid, Heinz; Schaller, Vanessa; Wirths, Stephan; Moselund, Kirsten; Luisier, Mathieu; Karg, Siegfried; Riel, Heike

    2017-04-12

    Coherent interconnection of quantum bits remains an ongoing challenge in quantum information technology. Envisioned hardware to achieve this goal is based on semiconductor nanowire (NW) circuits, comprising individual NW devices that are linked through ballistic interconnects. However, maintaining the sensitive ballistic conduction and confinement conditions across NW intersections is a nontrivial problem. Here, we go beyond the characterization of a single NW device and demonstrate ballistic one-dimensional (1D) quantum transport in InAs NW cross-junctions, monolithically integrated on Si. Characteristic 1D conductance plateaus are resolved in field-effect measurements across up to four NW-junctions in series. The 1D ballistic transport and sub-band splitting is preserved for both crossing-directions. We show that the 1D modes of a single injection terminal can be distributed into multiple NW branches. We believe that NW cross-junctions are well-suited as cross-directional communication links for the reliable transfer of quantum information as required for quantum computational systems.

  11. A Brief History of INA and ICOH SCNP: International Neurotoxicology Association and International Congress on Occupational Health Scientific Committee on Neurotoxicology and Psychophysiology

    Science.gov (United States)

    Two international scientific societies dedicated to research in neurotoxicology and neurobehavioral toxicology are the International Neurotoxicology Association (INA) and the International Congress on Occupational Health International Symposium on Neurobehavioral Methods and Effe...

  12. ANALYSIS OF INA-CBG’S FARE AND GOVERNOR REGULATION FAREON SURGERY AT INPATIENT ROOM OF UNDATA REGIONAL PUBLIC HOSPITAL IN PALU

    Directory of Open Access Journals (Sweden)

    Muh. Ryman Napirah

    2016-03-01

    Full Text Available Aim: In order to determine the fares of surgery, there are two types of fares used by hospitals namely Indonesian Case Based Groups fare (INA-CBG s and Governor Regulation fare. This study aimed to identify and analyze both types of fares in orthopedic surgery, general, eyes, midwifery, mouth, ENT, urology at inpatient room of Undata Regional Public Hospital in Palu during year 2014. Method: This was a quantitative study with descriptive approach with 46 cases as the number of surgery. Data were collected through observation and analysis of secondary data were gotten from medical record, pharmaceutical installation of IBS/IDR, inpatient therapy room (Matahari, Aster, and Teratai pavilions and cashier of inpatient room in form of cost details and patient data from January to December 2014. Data Presentation was formed on tables, where the existing fares are grouped based on the component of each cost then summed and calculated the deviation between the two types of fares. Results: This study indicated that orthopedic surgery with deviation of Rp 11.311.365, general surgery with deviation of Rp 6.438.409, eyes surgery with deviation of Rp 45.173.741, midwifery surgery with deviation of Rp 6.645.765, oral surgery with deviation of Rp 6.105.659, and urological surgery with deviation of Rp. 3.809.959. Conclusion: It can be concluded that INA-CBG's fares are higher than Governor Regulation fares except orthopedic surgery, where the Governor Regulation faresare higher than INA-CBG’s fares.

  13. Cleaved-edge overgrowth of aligned quantum dots on strained layers of InGaAs

    International Nuclear Information System (INIS)

    Wasserman, D.; Lyon, S.A.

    2004-01-01

    Strain aligned InAs quantum dots were grown on the cleaved edges of first growth samples containing strained In x Ga (1-x) As layers of varying thickness and indium fraction. The formation of the cleaved-edge quantum dots was observed by means of atomic force microscopy. 100% linear alignment of InAs quantum dots over the InGaAs strain layers of the first growth sample is demonstrated. Linear density of the aligned dots was found to depend on the properties of the underlying InGaAs strain layers. Vertical alignment of an additional InAs quantum dot layer over the buried, linearly aligned, initial dot layer was observed for thin GaAs spacer layers

  14. Determination of the burn-up in fuels of the MTR type by means of gamma spectroscopy with crystal of INa(Tl)

    International Nuclear Information System (INIS)

    Kestelman, A.J.

    1988-01-01

    One of the responsibilities of the Laboratory of Analysis by Neutronic Activation of the RA-6 reactor is to determine the burn-up in fuels of the MTR type. In order to gain experience, up to the arrival of the hyperpure Germanium detector (HPGe) to be used in normal operation, preliminary measurements with a crystal of INa(Tl) were made. The fuel elements used are originated in the RA-3 reactor, with a decay superior to the thirteen years. For this reason, the unique visible photoelectric peak is the one of Cs-137, owing to the low resolution of the INa(Tl). After preliminary measurements, the profiles of burn-up, rectified by attenuation, were measured. Once the efficiency of the detector was determined, the calculation of the burn-up was made; for the element No. 144, a value of 21.6 ± 2.9 g was obtained to be compared with the value 21.9 g which was the evaluation made by the operators. (Author) [es

  15. Influence of nitrogen on the growth and the properties of InAs quantum dots

    International Nuclear Information System (INIS)

    Schumann, O.

    2004-01-01

    This work investigates the influence of nitrogen incorporation on the growth and the optical properties of InAs quantum dots on GaAs(001) substrates. On the basis of systematic growth interruptions it was shown that the large quantum dots nucleate at dislocations, which are already formed during the growth of the wetting layer. After solving the growth problems, the influence of different combinations of matrix layers on the structural and optical properties of the quantum dots was investigated in the second part of this work. The strain and bandgap of these layers were varied systematically. (orig.)

  16. Prediction of phonon thermal transport in thin GaAs, InAs and InP nanowires by molecular dynamics simulations: influence of the interatomic potential

    Energy Technology Data Exchange (ETDEWEB)

    Carrete, J; Longo, R C; Gallego, L J, E-mail: jesus.carrete@usc.es [Departamento de Fisica de la Materia Condensada, Facultad de Fisica, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela (Spain)

    2011-05-06

    A number of different potentials are currently being used in molecular dynamics simulations of semiconductor nanostructures. Confusion can arise if an inappropriate potential is used. To illustrate this point, we performed direct molecular dynamics simulations to predict the room temperature lattice thermal conductivity {lambda} of thin GaAs, InAs and InP nanowires. In each case, simulations performed using the classical Harrison potential afforded values of {lambda} about an order of magnitude smaller than those obtained using more elaborate potentials (an Abell-Tersoff, as parameterized by Hammerschmidt et al for GaAs and InAs, and a potential of Vashishta type for InP). These results will be a warning to those wishing to use computer simulations to orient the development of quasi-one-dimensional systems as heat sinks or thermoelectric devices.

  17. Controlled tuning of the radiative lifetime in InAs self-assembled quantum dots through vertical ordering

    Science.gov (United States)

    Colocci, M.; Vinattieri, A.; Lippi, L.; Bogani, F.; Rosa-Clot, M.; Taddei, S.; Bosacchi, A.; Franchi, S.; Frigeri, P.

    1999-01-01

    Multilayer structures of InAs quantum dots have been studied by means of photoluminescence techniques. A strong increase of the radiative lifetime with increasing number of stacked dot layers has been observed at low temperatures. Moreover, a strong temperature dependence of the radiative lifetime, which is not present in the single layer samples, has been found in the multistacked structures. The observed effects are nicely explained as a consequence of the electronic coupling between electrons and holes induced by vertical ordering.

  18. Experimental Methods for Implementing Graphene Contacts to Finite Bandgap Semiconductors

    DEFF Research Database (Denmark)

    Meyer-Holdt, Jakob

    Present Ph.D. thesis describes my work on implanting graphene as electrical contact to finite bandgap semiconductors. Different transistor architectures, types of graphene and finite bandgap semiconductors have been employed. The device planned from the beginning of my Ph.D. fellowship...... contacts to semiconductor nanowires, more specifically, epitaxially grown InAs nanowires. First, we tried a top down method where CVD graphene was deposited on substrate supported InAs nanowires followed by selective graphene ashing to define graphene electrodes. While electrical contact between...

  19. Environmentally benign and scalable synthesis of LiFePO4 nanoplates with high capacity and excellent rate cycling performance for lithium ion batteries

    International Nuclear Information System (INIS)

    Zhao, Chunsong; Wang, Lu-Ning; Chen, Jitao; Gao, Min

    2017-01-01

    Highlights: •LiFePO 4 precursors were successfully prepared in pure water phase under atmosphere. •LiFePO 4 nanostructures were also regenerated by recycling filtrate. •LiFePO 4 /C delivers high discharge capacity of 160 mAh g −1 at 0.2 C and high rate capacity of 107 mAh g −1 at 20C. •LiFePO 4 /C delivers a capacity retention rate closed to 97% after 240 cycles at 20C. -- Abstract: An economical and scalable synthesis route of LiFePO 4 nanoplate precursors is successfully prepared in pure water phase under atmosphere without employing environmentally toxic surfactants or high temperature and high pressure compared with traditional hydrothermal or solvothermal methods, which also involves recycling the filtrate to regenerate LiFePO 4 nanoplate precursors and collecting by-product Na 2 SO 4 . The LiFePO 4 precursors present a plate-like morphology with mean thickness and length of 50–100 and 100–300 nm, respectively. After carbon coating, the LiFePO 4 /C nanoparticles with particle size around 200 nm can be observed which exhibit a high discharge capacity of 160 mAh g −1 at 0.2 C and 107 mAh g −1 at 20 C. A high capacity retention closed to 91% can be reached after 500 cycles even at a high current rate of 20C with coulombic efficiency of 99.5%. This work suggests a simple, economic and environmentally benign method in preparation of LiFePO 4 /C cathode material for power batteries that would be feasible for large scale industrial production.

  20. Combined vertically correlated InAs and GaAsSb quantum dots separated by triangular GaAsSb barrier

    Czech Academy of Sciences Publication Activity Database

    Hospodková, Alice; Oswald, Jiří; Pangrác, Jiří; Zíková, Markéta; Kubištová, Jana; Komninou, Ph.; Kioseoglou, J.; Kuldová, Karla; Hulicius, Eduard

    2013-01-01

    Roč. 114, č. 17 (2013), "174305-1"-"174305-5" ISSN 0021-8979 R&D Projects: GA ČR GA13-15286S; GA MŠk 7AMB12GR034; GA MŠk(CZ) LM2011026 Institutional support: RVO:68378271 Keywords : quantum dots * metal-organic vapor phase epitaxy * InAs * GaAs * GaAsSb Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.185, year: 2013

  1. Self-assembly of InAs and Si/Ge quantum dots on structured surfaces

    International Nuclear Information System (INIS)

    Patella, F; Sgarlata, A; Arciprete, F; Nufris, S; Szkutnik, P D; Placidi, E; Fanfoni, M; Motta, N; Balzarotti, A

    2004-01-01

    We discuss the self-aggregation process of InAs and Si-Ge quantum dots (QDs) on natural and patterned GaAs(001) and Si(001) and Si(111) surfaces, with reference to our recent studies with scanning tunnelling and atomic force microscopy and current experimental and theoretical works. Various methods for obtaining naturally structured surfaces are briefly surveyed, as the patterning formed by the surface instability and by the strain in mismatched heteroepitaxy, and the latest methods of pre-patterning and growth at selected sites are discussed. Basic topics are also addressed that determine the final morphology of QDs, such as the wetting layer formation, the elastic strain field and the two-dimensional to three-dimensional phase transition

  2. Heterostructures on the basis of GaAs with quantum points of InAs for photo-electric transformers

    Directory of Open Access Journals (Sweden)

    Maronchuk I. E.

    2008-12-01

    Full Text Available Heterostructures based on GaAs with InAs quantum dots obtained in the process of liquid-phase epitaxy by the method of pulse cooling of saturated solution in indium or heterostructures containing quantum dots in the area of the p–n-junction were much worse than control solar cells manufactured on the same structures but without quantum dots. Solar cells containing quantum dots in the p-region were slightly better than control solar cells.

  3. Understanding the crystallization mechanism of delafossite CuGaO2 for controlled hydrothermal synthesis of nanoparticles and nanoplates.

    Science.gov (United States)

    Yu, Mingzhe; Draskovic, Thomas I; Wu, Yiying

    2014-06-02

    The delafossite CuGaO2 is an important p-type transparent conducting oxide for both fundamental science and industrial applications. An emerging application is for p-type dye-sensitized solar cells. Obtaining delafossite CuGaO2 nanoparticles is challenging but desirable for efficient dye loading. In this work, the phase formation and crystal growth mechanism of delafossite CuGaO2 under low-temperature (mechanism to explain the formation of large CuGaO2 nanoplates. Importantly, by suppressing this OA process, delafossite CuGaO2 nanoparticles that are 20 nm in size were successfully synthesized for the first time. Moreover, considering the structural and chemical similarities between the Cu-based delafossite series compounds, the understanding of the hydrothermal chemistry and crystallization mechanism of CuGaO2 should also benefit syntheses of other similar delafossites such as CuAlO2 and CuScO2.

  4. Strain, size and composition of InAs quantum sticks, embedded in InP, determined via X-ray anomalous diffraction and diffraction anomalous fine structure in grazing incidence

    International Nuclear Information System (INIS)

    Letoublon, A.; Favre-Nicolin, V.; Renevier, H.; Proietti, M.G.; Monat, C.; Gendry, M.; Marty, O.; Priester, C.

    2005-01-01

    We report on the study of strain, size and composition of small-size encapsulated semiconductor nanostructures. We show that the partial structure factor of As atoms in InAs stick-like nanostructures (quantum sticks), embedded in InP, can be directly extracted from grazing incidence anomalous X-ray diffraction maps at the As K-edge. We have recovered the average height and strain of the islands and determined their composition. The average height of the quantum sticks (QSs), as deduced from the width of the structure factor profile is 2.54 nm. The InAs out of plane deformation, relative to InP, is equal to 6.1%. Fixed-Q anomalous diffraction spectra, measured at the As K-edge, in grazing incidence provide clear evidence of pure InAs QSs. This is confirmed by the analysis of the diffraction anomalous fine structure (DAFS) that also gives a direct way to recover the strain accomodation inside the quantum sticks. Finite difference method calculations reproduce well the diffraction data. Chemical mixing at interfaces is at most 1 ML. This paper shows that ultimate application of anomalous diffraction and DAFS together with reciprocal space maps is a powerful method to sudy the structural properties of nanostructures

  5. Effects of Particle Size and Surface Chemistry on the Dispersion of Graphite Nanoplates in Polypropylene Composites

    Directory of Open Access Journals (Sweden)

    Raquel M. Santos

    2018-02-01

    Full Text Available Carbon nanoparticles tend to form agglomerates with considerable cohesive strength, depending on particle morphology and chemistry, thus presenting different dispersion challenges. The present work studies the dispersion of three types of graphite nanoplates (GnP with different flake sizes and bulk densities in a polypropylene melt, using a prototype extensional mixer under comparable hydrodynamic stresses. The nanoparticles were also chemically functionalized by covalent bonding polymer molecules to their surface, and the dispersion of the functionalized GnP was studied. The effects of stress relaxation on dispersion were also analyzed. Samples were removed along the mixer length, and characterized by microscopy and dielectric spectroscopy. A lower dispersion rate was observed for GnP with larger surface area and higher bulk density. Significant re-agglomeration was observed for all materials when the deformation rate was reduced. The polypropylene-functionalized GnP, characterized by increased compatibility with the polymer matrix, showed similar dispersion effects, albeit presenting slightly higher dispersion levels. All the composites exhibit dielectric behavior, however, the alternate current (AC conductivity is systematically higher for the composites with larger flake GnP.

  6. Narrow ridge waveguide high power single mode 1.3-μm InAs/InGaAs ten-layer quantum dot lasers

    Directory of Open Access Journals (Sweden)

    Cao Q

    2007-01-01

    Full Text Available AbstractTen-layer InAs/In0.15Ga0.85As quantum dot (QD laser structures have been grown using molecular beam epitaxy (MBE on GaAs (001 substrate. Using the pulsed anodic oxidation technique, narrow (2 μm ridge waveguide (RWG InAs QD lasers have been fabricated. Under continuous wave operation, the InAs QD laser (2 × 2,000 μm2 delivered total output power of up to 272.6 mW at 10 °C at 1.3 μm. Under pulsed operation, where the device heating is greatly minimized, the InAs QD laser (2 × 2,000 μm2 delivered extremely high output power (both facets of up to 1.22 W at 20 °C, at high external differential quantum efficiency of 96%. Far field pattern measurement of the 2-μm RWG InAs QD lasers showed single lateral mode operation.

  7. Pressure dependence of photoluminescence of InAs/InP self-assembled quantum wires

    International Nuclear Information System (INIS)

    Ruiz-Castillo, M.; Segura, A.; Sans, J.A.; Martinez-Pastor, J.; Fuster, D.; Gonzalez, Y.; Gonzalez, L.

    2007-01-01

    This paper investigates the electronic structure of self-assembled InAs quantum wires (QWrs), grown under different conditions by molecular beam epitaxy on InP, by means of photoluminescence measurements under pressure. In samples with regularly distributed QWrs, room pressure photoluminescence spectra consist of a broad band centred at about 0.85 eV, which can be easily de-convoluted in a few Gaussian peaks. In samples with isolated QWrs, photoluminescence spectra exhibit up to four clearly resolved bands. Applying hydrostatic pressure, the whole emission band monotonously shifts towards higher photon energies with pressure coefficients ranging from 72 to 98 meV/GPa. In contrast to InAs quantum dots on GaAs, quantum wires photoluminescence is observed up to 10 GPa, indicating that InAs QWrs are metastable well above pressure at which bulk InAs undergoes a phase transition to the rock-salt phase (7 GPa). (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Effects of buffer layer on the structural and electrical properties of InAsSb epilayers grown on GaAs(001)

    International Nuclear Information System (INIS)

    Jayavel, P.; Nakamura, S.; Koyama, T.; Hayakawa, Y.

    2006-01-01

    InAsSb ternary epilayers with arsenic composition of 0.5 have been grown on GaAs(001) substrates. Linear-graded and step-graded InAsSb buffer layers with an InSb layer have been used to relax lattice mismatch between the epilayer and substrate. X-ray diffraction results of the epilayers indicate that an enhancement in the peak intensity of the buffer layer samples is due to improved crystalline quality of the epilayers. We find that the growth technique of the buffer layer strongly influences the surface morphology and roughness of the epilayer. Hall effect measurements of the step-graded buffer layer samples show an order of magnitude higher electron mobility than the direct and linear-graded buffer layer samples. These results demonstrate that high crystalline quality and electron mobility of the InAs 0.5 Sb 0.5 ternary epilayers can be achieved by using the step-graded InAsSb buffer layers. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Digitally grown AlInAsSb for high gain separate absorption, grading, charge, and multiplication avalanche photodiodes

    Science.gov (United States)

    Lyu, Yuexi; Han, Xi; Sun, Yaoyao; Jiang, Zhi; Guo, Chunyan; Xiang, Wei; Dong, Yinan; Cui, Jie; Yao, Yuan; Jiang, Dongwei; Wang, Guowei; Xu, Yingqiang; Niu, Zhichuan

    2018-01-01

    We report on the growth of high quality GaSb-based AlInAsSb quaternary alloy by molecular beam epitaxy (MBE) to fabricate avalanche photodiodes (APDs). By means of high resolution X-ray diffraction (HRXRD) and scanning transmission electron microscope (STEM), phase separation phenomenon of AlInAsSb random alloy with naturally occurring vertical superlattice configuration was demonstrated. To overcome the tendency for phase segregation while maintaining a highly crystalline film, a digital alloy technique with migration-enhanced epitaxy growth method was employed, using a shutter sequence of AlSb, AlAs, AlSb, Sb, In, InAs, In, Sb. AlInAsSb digital alloy has proved to be reproducible and consistent with single phase, showing sharp satellite peaks on HRXRD rocking curve and smooth surface morphology under atomic force microscopy (AFM). Using optimized digital alloy, AlInAsSb separate absorption, grading, charge, and multiplication (SAGCM) APD was grown and fabricated. At room temperature, the device showed high performance with low dark current density of ∼14.1 mA/cm2 at 95% breakdown and maximum stable gain before breakdown as high as ∼200, showing the potential for further applications in optoelectronic devices.

  10. Ab initio calculations of indium arsenide in the wurtzite phase: structural, electronic and optical properties

    International Nuclear Information System (INIS)

    Dacal, Luis C O; Cantarero, A

    2014-01-01

    Most III–V semiconductors, which acquire the zinc-blende phase as bulk materials, adopt the metastable wurtzite phase when grown in the form of nanowires. These are new semiconductors with new optical properties, in particular, a different electronic band gap when compared with that grown in the zinc-blende phase. The electronic gap of wurtzite InAs at the Γ–point of the Brillouin zone (E 0 gap) has been recently measured, E 0 =0.46 eV at low temperature. The electronic gap at the A–point of the Brillouin zone (equivalent to the L–point in the zinc-blende structure, E 1 ) has also been obtained recently based on a resonant Raman scattering experiment. In this work, we calculate the band structure of InAs in the zinc-blende and wurtzite phases, using the full potential linearized augmented plane wave method, including spin-orbit interaction. The electronic band gap has been improved through the modified Becke–Johnson exchange-correlation potential. Both the E 0 and E 1 gaps agree very well with the experiment. From the calculations, a crystal field splitting of 0.122 eV and a spin-orbit splitting of 0.312 eV (the experimental value in zinc-blende InAs is 0.4 eV) has been obtained. Finally, we calculate the dielectric function of InAs in both the zinc-blende and wurtzite phases and a comparative discussion is given. (paper)

  11. Ab initio calculations of indium arsenide in the wurtzite phase: structural, electronic and optical properties

    Science.gov (United States)

    Dacal, Luis C. O.; Cantarero, A.

    2014-03-01

    Most III-V semiconductors, which acquire the zinc-blende phase as bulk materials, adopt the metastable wurtzite phase when grown in the form of nanowires. These are new semiconductors with new optical properties, in particular, a different electronic band gap when compared with that grown in the zinc-blende phase. The electronic gap of wurtzite InAs at the \\Gamma -point of the Brillouin zone ({{E}_{0}} gap) has been recently measured, {{E}_{0}}=0.46 eV at low temperature. The electronic gap at the A-point of the Brillouin zone (equivalent to the L-point in the zinc-blende structure, {{E}_{1}}) has also been obtained recently based on a resonant Raman scattering experiment. In this work, we calculate the band structure of InAs in the zinc-blende and wurtzite phases, using the full potential linearized augmented plane wave method, including spin-orbit interaction. The electronic band gap has been improved through the modified Becke-Johnson exchange-correlation potential. Both the {{E}_{0}} and {{E}_{1}} gaps agree very well with the experiment. From the calculations, a crystal field splitting of 0.122 eV and a spin-orbit splitting of 0.312 eV (the experimental value in zinc-blende InAs is 0.4 eV) has been obtained. Finally, we calculate the dielectric function of InAs in both the zinc-blende and wurtzite phases and a comparative discussion is given.

  12. Fabrication of a complex InAs ring-and-dot structure by droplet epitaxy

    International Nuclear Information System (INIS)

    Noda, Takeshi; Mano, Takaaki

    2008-01-01

    An InAs ring structure accompanying the formation of quantum dots (QDs) was fabricated on (1 0 0)GaAs using droplet epitaxy. The QDs were located in the vicinity of the ring, due to the diffusion of In atoms from the In droplets. In addition, the dots were found to have distributed elliptically and preferentially along the [0 1 1] direction, implying that In itself prefers to diffuse along the [0 1 1] direction, which is the opposite of the favorable diffusion orientation of group III atoms on (1 0 0)GaAs under a commonly used As-stabilized growth condition. This is the first observation of a ring structure accompanying the formation of quantum dots in droplet epitaxy

  13. Co-Immobilization of Proteins and DNA Origami Nanoplates to Produce High-Contrast Biomolecular Nanoarrays.

    Science.gov (United States)

    Hager, Roland; Burns, Jonathan R; Grydlik, Martyna J; Halilovic, Alma; Haselgrübler, Thomas; Schäffler, Friedrich; Howorka, Stefan

    2016-06-01

    The biofunctionalization of nanopatterned surfaces with DNA origami nanostructures is an important topic in nanobiotechnology. An unexplored challenge is, however, to co-immobilize proteins with DNA origami at pre-determined substrate sites in high contrast relative to the nontarget areas. The immobilization should, in addition, preferably be achieved on a transparent substrate to allow ultrasensitive optical detection. If successful, specific co-binding would be a step towards stoichiometrically defined arrays with few to individual protein molecules per site. Here, we successfully immobilize with high specificity positively charged avidin proteins and negatively charged DNA origami nanoplates on 100 nm-wide carbon nanoislands while suppressing undesired adsorption to surrounding nontarget areas. The arrays on glass slides achieve unprecedented selectivity factors of up to 4000 and allow ultrasensitive fluorescence read-out. The co-immobilization onto the nanoislands leads to layered biomolecular architectures, which are functional because bound DNA origami influences the number of capturing sites on the nanopatches for other proteins. The novel hybrid DNA origami-protein nanoarrays allow the fabrication of versatile research platforms for applications in biosensing, biophysics, and cell biology, and, in addition, represent an important step towards single-molecule protein arrays. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Constructed ILs coated porous magnetic nickel cobaltate hexagonal nanoplates sensing materials for the simultaneous detection of cumulative toxic metals

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Yuanyuan; Zhang, Lei, E-mail: zhanglei63@126.com

    2017-07-05

    Highlights: • A novel sensor material based on ionic liquids@nickel cobaltate was constructed. • Various morphologies of NiCo{sub 2}O{sub 4} were synthesized for electrocatalytic comparison. • ILs@NiCo{sub 2}O{sub 4}-P was used to detect cumulative toxic metals for the first time. • The sensor displayed well reproducibility, excellent selectivity and sensitivity. • The method was applied to detect practical samples with satisfactory results. - Abstract: The different morphologies of magnetic nickel cobaltate (NiCo{sub 2}O{sub 4}) electrocatalysts, consisting of nanoparticles (NiCo{sub 2}O{sub 4}-N), nanoplates (NiCo{sub 2}O{sub 4}-P) and microspheres (NiCo{sub 2}O{sub 4}-S) were fabricated. It was found that the electrocatalytic properties of the sensing materials were strongly dependent on morphology and specific surface area. The porous NiCo{sub 2}O{sub 4} hexagonal nanoplates coupled with ILs as modified materials (ILs@NiCo{sub 2}O{sub 4}-P) for the simultaneous determination of thallium (Tl{sup +}), lead (Pb{sup 2+}) and copper (Cu{sup 2+}), exhibited high sensitivity, long-time stability and good repeatability. The enhanced electrocatalytic activity was attributed to relatively large specific surface area, excellent electronic conductivity, and unique porous nanostructure. The analytical performance of the constructed electrode on detection of Tl{sup +}, Pb{sup 2+} and Cu{sup 2+} was examined using differential pulse anodic stripping voltammetry (DPASV). Under optimal conditions, the electrode showed a good linear response to Tl{sup +}, Pb{sup 2+}and Cu{sup 2+} in the concentration range of 0.1–100.0, 0.1–100.0 and 0.05–100.0 μg/L, respectively. The detection limits (S/N = 3) were 0.046, 0.034 and 0.029 μg/L for Tl{sup +}, Pb{sup 2+} and Cu{sup 2+}, respectively. The fabricated sensor was successfully applied to detect trace Tl{sup +}, Pb{sup 2+} and Cu{sup 2+} in various water and soil samples with satisfactory results. Hence, this work

  15. Studying the InAs quantum points on the vicinal surface of a GaAs crystal by the atomic force microscopy

    CERN Document Server

    Evtikhiev, V P; Kotelnikov, E Y; Matveentsev, A V; Titkov, A N; Shkolnik, A S

    2002-01-01

    The methodology for processing the images, obtained through the atomic force microscopy, is proposed. It is shown by the concrete example, how the parameters of the InAs clusters on the vicinal surface of the GaAs crystal are determined. This makes it possible to calculate the energy levels of the electrons and holes in the quantum point with application of the previously developed cluster spherical model

  16. Anisotropic transport properties of quasiballistic InAs nanowires under high magnetic field

    Science.gov (United States)

    Vigneau, Florian; Zeng, Zaiping; Escoffier, Walter; Caroff, Philippe; Leturcq, Renaud; Niquet, Yann-Michel; Raquet, Bertrand; Goiran, Michel

    2018-03-01

    The magnetoconductance of a long channel InAs nanowire based field effect transistor in the quasiballistic regime under large magnetic field is investigated. The quasi-1D nanowire is fully characterized by a bias voltage spectroscopy and measurements under magnetic field up to 50 T applied either perpendicular or parallel to the nanowire axis lifting the spin and orbital degeneracies of the subbands. Under normal magnetic field, the conductance shows quantized steps due to the backscattering reduction and a decrease due to depopulation of the 1D modes. Under axial magnetic field, a quasioscillatory behavior is evidenced due to the coupling of the magnetic field with the angular momentum of the wave function. In addition the formation of cyclotron orbits is highlighted under high magnetic field. The experimental results are compared with theoretical calculation of the 1D band structure and related parameters.

  17. Strong composition-dependent disorder in InAs1-xNx alloys

    International Nuclear Information System (INIS)

    Benaissa, H.; Zaoui, A.; Ferhat, M.

    2009-01-01

    We investigate the main causes of disorder in the InAs 1-x N x alloys (x = 0, 0.03125, 0.0625, 0.09375, 0.125, 0.25, 0.5, 0.75, 0.875, 0.90625, 0.9375, 0.96875 and 1). The calculation is based on the density-functional theory in the local-density approximation. We use a plane wave-expansion non-norm conserving ab initio Vanderbilt pseudopotentials. To avoid the difficulty of considering the huge number of atomic configurations, we use an appropriate strategy in which we consider four configurations for a given composition where the N atoms are not randomly distributed. We mainly show that the band gap decreases (increases) rapidly with increasing (decreasing) compositions of N. As a consequence the optical band gap bowing is found to be strong and composition dependent. The obtained compounds, from these alloys, may change from semi-conducting to metal (passing to a negative bowing) and could be useful for device applications, especially at certain composition.

  18. Probing into hybrid organic-molecule and InAs quantum-dots nanosystem with multistacked dots-in-a-well units

    Science.gov (United States)

    Chen, Miaoxiang; Kobashi, Kazufumi

    2012-09-01

    Hybridizing air-stable organic-molecules with advanced III-V semiconductor quantum-dots (QDs) structures can be utilized to create a new generation of biochemical sensing devices. In order to enhance their optical performances, the active regions in these QDs structures commonly consist of multistacked dots-in-a-well (DWELL) units. The effects of grafted molecules on the performances of the QDs structures with multistacked DWELLs, however, still remain unclear. Here, we show the significant improvements in the optical properties of InAs QDs in a hybrid nanosystem obtained by grafting biocompatible diazonium salt compound (amine donor) atop InAs QDs structure. Since its interface between the QDs structure and molecular monolayer retains an uncontaminated and non-oxidized condition, the nanosystem is an ideal platform to study the intrinsic properties of charge-carrier transport inside the system. Because of the complexity of the energy-levels in the QDs structure due to the existing surface QDs and DWELLs, selective excitation wavelengths (400, 633, and 885 nm, respectively) with different photo-energies are used to exactly analyze the complete charging mechanism in these QDs. A clear view of charge-carrier transfer inside the nanosystem is revealed by employing photoluminescence technique under selective-wavelength excitations. The present work provides new quantitative evidences for exploiting inorganic QDs applications in complex biological systems.

  19. Probing into hybrid organic-molecule and InAs quantum-dots nanosystem with multistacked dots-in-a-well units

    Energy Technology Data Exchange (ETDEWEB)

    Chen Miaoxiang [Department of Micro- and Nano technology, Technical University of Denmark, Orsteds Plads, 2800 Kgs. Lyngby (Denmark); Kobashi, Kazufumi [Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

    2012-09-15

    Hybridizing air-stable organic-molecules with advanced III-V semiconductor quantum-dots (QDs) structures can be utilized to create a new generation of biochemical sensing devices. In order to enhance their optical performances, the active regions in these QDs structures commonly consist of multistacked dots-in-a-well (DWELL) units. The effects of grafted molecules on the performances of the QDs structures with multistacked DWELLs, however, still remain unclear. Here, we show the significant improvements in the optical properties of InAs QDs in a hybrid nanosystem obtained by grafting biocompatible diazonium salt compound (amine donor) atop InAs QDs structure. Since its interface between the QDs structure and molecular monolayer retains an uncontaminated and non-oxidized condition, the nanosystem is an ideal platform to study the intrinsic properties of charge-carrier transport inside the system. Because of the complexity of the energy-levels in the QDs structure due to the existing surface QDs and DWELLs, selective excitation wavelengths (400, 633, and 885 nm, respectively) with different photo-energies are used to exactly analyze the complete charging mechanism in these QDs. A clear view of charge-carrier transfer inside the nanosystem is revealed by employing photoluminescence technique under selective-wavelength excitations. The present work provides new quantitative evidences for exploiting inorganic QDs applications in complex biological systems.

  20. Bond-Length Distortions in Strained Semiconductor Alloys

    International Nuclear Information System (INIS)

    Woicik, J.C.; Pellegrino, J.G.; Steiner, B.; Miyano, K.E.; Bompadre, S.G.; Sorensen, L.B.; Lee, T.; Khalid, S.

    1997-01-01

    Extended x-ray absorption fine structure measurements performed at In-K edge have resolved the outstanding issue of bond-length strain in semiconductor-alloy heterostructures. We determine the In-As bond length to be 2.581±0.004 Angstrom in a buried, 213 Angstrom thick Ga 0.78 In 0.22 As layer grown coherently on GaAs(001). This bond length corresponds to a strain-induced contraction of 0.015±0.004 Angstrom relative to the In-As bond length in bulk Ga 1-x In x As of the same composition; it is consistent with a simple model which assumes a uniform bond-length distortion in the epilayer despite the inequivalent In-As and Ga-As bond lengths. copyright 1997 The American Physical Society

  1. High Performance InAs/In0.53Ga0.23Al0.24As/InP Quantum Dot 1.55 um Tunnel Injection Laser

    KAUST Repository

    Bhowmick, Sishir; Baten, Md Zunaid; Bhattacharya, Pallab K.; Frost, Thomas; Ooi, Boon S.

    2014-01-01

    The characteristics of 1.55 ? InAs self-organized quantum-dot lasers, grown on (001) InP substrates by molecular beam epitaxy, have been investigated. Modulation doping of the dots with holes and tunnel injection of electrons have been incorporated

  2. Isolation, Fractionation and Characterization of Catalase from Neurospora crassa (InaCC F226)

    Science.gov (United States)

    Suryani; Ambarsari, L.; Lindawati, E.

    2017-03-01

    Catalase from Indigenous isolate Neurospora crassa InaCC F226 has been isolated, fractionated and characterized. Production of catalase by Neurospora crassa was done by using PDA medium (Potato Dextrosa Agar) and fractionated with ammonium sulphate with 20-80% saturation. Fraction 60% was optimum saturation of ammonium sulphate and had highest specific activity 3339.82 U/mg with purity 6.09 times, total protein 0.920 mg and yield 88.57%. The optimum pH and temperature for catalase activity were at 40°C and pH 7.0, respectively. The metal ions that stimulated catalase activity acted were Ca2+, Mn2+ and Zn2+, and inhibitors were EDTA, Mg2+ and Cu2+. Based on Km and Vmax values were 0.2384 mM and 13.3156 s/mM.

  3. Rectangular coordination polymer nanoplates: large-scale, rapid synthesis and their application as a fluorescent sensing platform for DNA detection.

    Directory of Open Access Journals (Sweden)

    Yingwei Zhang

    Full Text Available In this paper, we report on the large-scale, rapid synthesis of uniform rectangular coordination polymer nanoplates (RCPNs assembled from Cu(II and 4,4'-bipyridine for the first time. We further demonstrate that such RCPNs can be used as a very effective fluorescent sensing platform for multiple DNA detection with a detection limit as low as 30 pM and a high selectivity down to single-base mismatch. The DNA detection is accomplished by the following two steps: (1 RCPN binds dye-labeled single-stranded DNA (ssDNA probe, which brings dye and RCPN into close proximity, leading to fluorescence quenching; (2 Specific hybridization of the probe with its target generates a double-stranded DNA (dsDNA which detaches from RCPN, leading to fluorescence recovery. It suggests that this sensing system can well discriminate complementary and mismatched DNA sequences. The exact mechanism of fluorescence quenching involved is elucidated experimentally and its use in a human blood serum system is also demonstrated successfully.

  4. Measurements of the spin-orbit interaction and Landé g factor in a pure-phase InAs nanowire double quantum dot in the Pauli spin-blockade regime

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jiyin; Huang, Shaoyun, E-mail: hqxu@pku.edu.cn, E-mail: syhuang@pku.edu.cn; Lei, Zijin [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Pan, Dong; Zhao, Jianhua [State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Xu, H. Q., E-mail: hqxu@pku.edu.cn, E-mail: syhuang@pku.edu.cn [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Division of Solid State Physics, Lund University, Box 118, S-22100 Lund (Sweden)

    2016-08-01

    We demonstrate direct measurements of the spin-orbit interaction and Landé g factors in a semiconductor nanowire double quantum dot. The device is made from a single-crystal pure-phase InAs nanowire on top of an array of finger gates on a Si/SiO{sub 2} substrate and the measurements are performed in the Pauli spin-blockade regime. It is found that the double quantum dot exhibits a large singlet-triplet energy splitting of Δ{sub ST} ∼ 2.3 meV, a strong spin-orbit interaction of Δ{sub SO} ∼ 140 μeV, and a large and strongly level-dependent Landé g factor of ∼12.5. These results imply that single-crystal pure-phase InAs nanowires are desired semiconductor nanostructures for applications in quantum information technologies.

  5. The influence of post-growth annealing on the optical properties of InAs quantum dot chains grown on pre-patterned GaAs(100)

    International Nuclear Information System (INIS)

    Hakkarainen, T V; Polojärvi, V; Schramm, A; Tommila, J; Guina, M

    2012-01-01

    We report on the effect of post-growth thermal annealing of [011]-, [01 1-bar ]-, and [010]-oriented quantum dot chains grown by molecular beam epitaxy on GaAs(100) substrates patterned by UV-nanoimprint lithography. We show that the quantum dot chains experience a blueshift of the photoluminescence energy, spectral narrowing, and a reduction of the intersubband energy separation during annealing. The photoluminescence blueshift is more rapid for the quantum dot chains than for self-assembled quantum dots that were used as a reference. Furthermore, we studied polarization resolved photoluminescence and observed that annealing reduces the intrinsic optical anisotropy of the quantum dot chains and the self-assembled quantum dots. (paper)

  6. In situ oxidation and reduction of triangular nickel nanoplates via environmental transmission electron microscopy

    KAUST Repository

    LAGROW, A.P.

    2017-08-29

    Understanding the oxidation and reduction mechanisms of transition metals, such as nickel (Ni), is important for their use in industrial applications of catalysis. A powerful technique for investigating the redox reactive species is in situ environmental transmission electron microscopy (ETEM), where oxidation and reduction can be tracked in real time. One particular difficulty in understanding the underlying reactions is understanding the underlying morphology of the starting structure in a reaction, in particular the defects contained in the material, and the exposed surface facets. Here-in, we use a colloidal nanoparticle synthesis in a continuous flow reactor to form nanoplates of nickel coated with oleylamine as a capping agent. We utilise an in situ heating procedure at 300 °C in vacuum to remove the oleylamine ligands, and then oxidise the Ni nanoparticles at 25 °C with 2 Pa oxygen, and follow the nanoparticles initial oxidation. After that, the nanoparticles are oxidised at 200 and 300 °C, making the size of the oxide shell increase to ∼4 nm. The oxide shell could be reduced under 2 Pa hydrogen at 500 °C to its initial size of ∼1 nm. High temperature oxidation encouraged the nanoparticles to form pure NiO nanoparticles, which occurred via the Kirkendall effect leading to hollowing and void formation.

  7. In situ oxidation and reduction of triangular nickel nanoplates via environmental transmission electron microscopy

    KAUST Repository

    LAGROW, A.P.; AlYami, Noktan; LLOYD, D.C.; Bakr, Osman; BOYES, E.D.; GAI, P.L.

    2017-01-01

    Understanding the oxidation and reduction mechanisms of transition metals, such as nickel (Ni), is important for their use in industrial applications of catalysis. A powerful technique for investigating the redox reactive species is in situ environmental transmission electron microscopy (ETEM), where oxidation and reduction can be tracked in real time. One particular difficulty in understanding the underlying reactions is understanding the underlying morphology of the starting structure in a reaction, in particular the defects contained in the material, and the exposed surface facets. Here-in, we use a colloidal nanoparticle synthesis in a continuous flow reactor to form nanoplates of nickel coated with oleylamine as a capping agent. We utilise an in situ heating procedure at 300 °C in vacuum to remove the oleylamine ligands, and then oxidise the Ni nanoparticles at 25 °C with 2 Pa oxygen, and follow the nanoparticles initial oxidation. After that, the nanoparticles are oxidised at 200 and 300 °C, making the size of the oxide shell increase to ∼4 nm. The oxide shell could be reduced under 2 Pa hydrogen at 500 °C to its initial size of ∼1 nm. High temperature oxidation encouraged the nanoparticles to form pure NiO nanoparticles, which occurred via the Kirkendall effect leading to hollowing and void formation.

  8. Preparation of novel silver nanoplates/graphene composite and their application in vanillin electrochemical detection.

    Science.gov (United States)

    Huang, Linhong; Hou, Keyu; Jia, Xiao; Pan, Haibo; Du, Min

    2014-05-01

    Hexagonal Ag nanoplates (NPs) were synthesized by polyvinylpyrrolidone (PVP) and trisodium citrate (TSC) which selectively absorbed to Ag (100) and Ag (111) surfaces, then were anchored to graphene (GN) to form novel Ag NPs/GN composite. The thickness of Ag NPs is ~4 nm and the length is 18-66 nm. Transmission electron microscopy (TEM) image shows that the plates are f-c-c crystals containing {111} facets on their two planar surfaces. Zeta potential indicated that the surface of Ag NPs/GN is negatively charged while vanillin is positively charged. Thus Ag NPs/GN modified on glass carbon electrodes (GCE) allowed abundant adsorption for vanillin and electron transfer between vanillin and Ag NPs/GN/GCE. Square wave voltammetry (SWV) results indicated that the over potential on Ag NPs/GN/GCE negatively shifts 52 mV than that on Ag NPs/GCE. Ag NPs/GN with enhanced surface area and good conductivity exhibited an excellent electrocatalytic activity toward the oxidation of vanillin. The corresponding linear range was estimated to be from 2 to 100 μM (R(2)=0.998), and the detection limit is 3.32×10(-7) M (S/N=3). The as-prepared vanillin sensor exhibits good selectivity and potential application in practical vanillin determination. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Adsorbed layers on (111)InAs faces in contact with In-As-Cl-H gas phase, and the possibility of phase transitions in the adsorbed layers

    Science.gov (United States)

    Chernov, A. A.; Ruzaikin, M. P.

    1981-04-01

    Adsorption of various species existing in the In-As-Cl-H CVD gaseous system on both InAs (111) faces is considered. Arsenic is supposed to be adsorbed in the form of triangles As 3 and tetrahedrons As 4, each of them occupying 3 atomic sites above In or As atoms on (111)In or (111)As, respectively. The system of polyatomic adsorption equations was used to find the coverages of the faces by various species. Admolecule-surface bond strengths are taken to be equal to the ones for the single bonds in molecules. Pauling electronegativities were used to find the effective charges of the atoms in the adsorption layer. Thus, the dipole moments of adsorbed molecules which arise are directed along the In-As bonds in the InAs lattice. With this geometry, the calculated electrostatic dipole-dipole attraction between InCl molecules forming a dense layer on (111)As exceeds 12 kcal/mol. Thus, condensation of the two-dimensional gas of adsorbed InCl molecules should be expected. Corresponding S-shape isotherms θ( P) are calculated for different As 3 vapor pressures, θ and P being the surface coverage and bulk vapor pressure of InCl. Intervals of {InCl 3}/{H 2} ratios at different temperatures where the two-dimensional condensation may occur, are presented for realistic CVD conditions. Two-dimensional condensation may result in sharp changes in kinetic coefficient and thus in autho-oscillations in growth rate and doping level creating periodic superstructures. Nucleation and CVD growth processes are discussed.

  10. Deterministic self-organization: Ordered positioning of InAs quantum dots by self-organized anisotropic strain engineering on patterned GaAs(311)B

    International Nuclear Information System (INIS)

    Selcuk, E.; Hamhuis, G.J.; Noetzel, R.

    2009-01-01

    Laterally ordered InGaAs quantum dot (QD) arrays, InAs QD molecules, and single InAs QDs in a spot-like periodic arrangement are created by self-organized anisotropic strain engineering of InGaAs/GaAs superlattice (SL) templates on planar GaAs (311)B substrates in molecular beam epitaxy. On shallow- and deep-patterned substrates the respectively generated steps and facets guide the self-organization process during SL template formation to create more complex ordering such as periodic stripes, depending on pattern design. Here we demonstrate for patterns such as shallow- and deepetched round holes and deep-etched zigzag mesas that the self-organized periodic arrangement of QD molecules and single QDs is spatially locked to the pattern sidewalls and corners. This extends the concept of guided self-organization to deterministic self-organization. Absolute position control of the QDs is achieved without one-to-one pattern definition. This guarantees the excellent arrangement control of the ordered QD molecules and single QDs with strong photoluminescence emission up to room temperature, which is required for future quantum functional devices. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Atomic scale characterization of ion-induced amorphization of GaAs and InAs using PAC spectroscopy

    International Nuclear Information System (INIS)

    Dogra, R.; Byrne, A.P.; Ridgway, M.C.

    2005-01-01

    Single crystals of GaAs (100) and InAs (100) were implanted with 1-7 MeV 74 Ge ions over a wide dose range at liquid nitrogen temperature. The implanted substrates were investigated with respect to the damage production by means of perturbed angular correlation spectroscopy based upon hyperfine interactions of nuclear electromagnetic moments of probe nuclei with extra-nuclear fields. The perturbed angular correlation measurements were performed at room temperature utilizing the 111 In/Cd radioisotope probe nuclei. The crystalline, disordered and amorphous probe environments were identified from the measurements. The defect production is described within the framework of different amorphization models. (author). 6 refs., 2 figs

  12. Magnetic-field-induced Fermi-edge singularity in the tunneling current through an InAs self-assembled quantum dot

    International Nuclear Information System (INIS)

    Khanin, Yu. N.; Vdovin, E. E.; Eaves, L.; Larkin, I. A.; Patane, A.; Makarovskii, O. N.; Henini, M.

    2007-01-01

    The results of the investigation of tunneling transport through a GaAs/(AlGa)As/GaAs single-barrier heterostructure containing InAs self-assembled quantum dots at low temperatures are reported. An anomalous increase in the tunneling current through the quantum dots has been observed in the presence of a magnetic field both parallel and perpendicular to the current. This increase is a manifestation of a Fermi-edge singularity appearing in the current due to the interaction of a tunneling electron with the electron gas in an emitter

  13. Size dependence of the wavefunction of self-assembled InAs quantum dots from time-resolved optical measurements

    DEFF Research Database (Denmark)

    Johansen, Jeppe; Stobbe, Søren; Nikolaev, Ivan S.

    2008-01-01

    and a theoretical model, we determine the striking dependence of the overlap of the electron and hole wavefunctions on the quantum dot size. We conclude that the optical quality is best for large quantum dots, which is important in order to optimally tailor quantum dot emitters for, e.g., quantum electrodynamics......The radiative and nonradiative decay rates of InAs quantum dots are measured by controlling the local density of optical states near an interface. From time-resolved measurements, we extract the oscillator strength and the quantum efficiency and their dependence on emission energy. From our results...

  14. Two-Carrier Transport Induced Hall Anomaly and Large Tunable Magnetoresistance in Dirac Semimetal Cd3As2 Nanoplates.

    Science.gov (United States)

    Li, Cai-Zhen; Li, Jin-Guang; Wang, Li-Xian; Zhang, Liang; Zhang, Jing-Min; Yu, Dapeng; Liao, Zhi-Min

    2016-06-28

    Cd3As2 is a model material of Dirac semimetal with a linear dispersion relation along all three directions in the momentum space. The unique band structure of Cd3As2 is made with both Dirac and topological properties. It can be driven into a Weyl semimetal by symmetry breaking or a topological insulator by enhancing the spin-orbit coupling. Here we report the temperature and gate voltage-dependent magnetotransport properties of Cd3As2 nanoplates with Fermi level near the Dirac point. The Hall anomaly demonstrates the two-carrier transport accompanied by a transition from n-type to p-type conduction with decreasing temperature. The carrier-type transition is explained by considering the temperature-dependent spin-orbit coupling. The magnetoresistance exhibits a large nonsaturating value up to 2000% at high temperatures, which is ascribed to the electron-hole compensation in the system. Our results are valuable for understanding the experimental observations related to the two-carrier transport in Dirac/Weyl semimetals, such as Na3Bi, ZrTe5, TaAs, NbAs, and HfTe5.

  15. Ambient temperature dependence on emission spectrum of InAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, C.Y.; Yoon, S.F. [School of Electrical and Electronic Engineering, Nanyang Technological University (Singapore); Chua, S.J. [Institute of Materials Research and Engineering, Faculty of Engineering (Singapore)

    2009-04-15

    Semiconductor superluminescent diodes (SLDs) are important broadband light source for fiber optic gyroscope and biomedical imaging. Quantum dots (QDs) have been proposed to be the best candidate for broadband light sources due to the inhomogeneous broadening of the gain spectrum as a result of the inherited size inhomogeneity of the self-assembled QD growth. In this work, the effect of ambient temperature (25-100 C) on the emission spectrum of InAs QDs with wideband emission was investigated. It was found that the full-width at half-maximum (FWHM) of the photoluminescence (PL) spectra remains more than 125 nm throughout the temperature range, and the redshift as function of temperature is approximately 0.27 meV/K. Activation energy of 270 meV is extracted from the Arrhenius plot and the PL quenching at high temperature is attributed to thermally induced carriers escaping out of the In{sub 0.15}Ga{sub 0.85}As strain-reducing layer. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. GaAsSb-capped InAs QD type-II solar cell structures improvement by composition profiling of layers surrounding QD

    Czech Academy of Sciences Publication Activity Database

    Hospodková, Alice; Vyskočil, Jan; Zíková, Markéta; Oswald, Jiří; Pangrác, Jiří; Petříček, Otto

    2017-01-01

    Roč. 4, č. 2 (2017), s. 1-8, č. článku 025502. ISSN 2053-1591 R&D Projects: GA ČR(CZ) GP14-21285P; GA MŠk(CZ) LO1603 Institutional support: RVO:68378271 Keywords : GaAsSb * InAs * InGaAs * quantum dot * solar cells * MOVPE Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.068, year: 2016

  17. Formation of the InAs-, InSb-, GaAs-, and GaSb-polished surface

    Science.gov (United States)

    Levchenko, Iryna; Tomashyk, Vasyl; Stratiychuk, Iryna; Malanych, Galyna; Korchovyi, Andrii; Kryvyi, Serhii; Kolomys, Oleksandr

    2018-04-01

    The features of the InAs, InSb, GaAs, and GaSb ultra-smooth surface have been investigated using chemical-mechanical polishing with the (NH4)2Cr2O7-HBr-CH2(OH)CH2(OH)-etching solutions. The etching rate of the semiconductors has been measured as a function of the solution saturation by organic solvent (ethylene glycol). It was found that mechanical effect significantly increases the etching rate from 1.5 to 57 µm/min, and the increase of the organic solvent concentration promotes the decrease of the damaged layer-removing rate. According to AFM, RS, HRXRD results, the treatment with the (NH4)2Cr2O7-HBr-ethylene glycol solutions produces the clean surface of the nanosize level (R a < 0.5 nm).

  18. InAs0.45P0.55/InP strained multiple quantum wells intermixed by inductively coupled plasma etching

    International Nuclear Information System (INIS)

    Cao, Meng; Wu, Hui-Zhen; Lao, Yan-Feng; Cao, Chun-Fang; Liu, Cheng

    2009-01-01

    The intermixing effect on InAs 0.45 P 0.55 /InP strained multiple quantum wells (SMQWs) by inductively coupled plasma (ICP) etching and rapid thermal annealing (RTA) is investigated. Experiments show that the process of ICP etching followed RTA induces the blue shift of low temperature photoluminescence (PL) peaks of QWs. With increasing etching depth, the PL intensities are firstly enhanced and then diminished. This phenomenon is attributed to the variation of surface roughness and microstructure transformation inside the QW structure during ICP processing.

  19. Time evolution studies of laser induced chemical changes in InAs nanowire using Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Suparna; Aggarwal, R.; Kumari Gupta, Vandna; Ingale, Alka [Laser Physics Application Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, MP (India)

    2014-07-07

    We report the study of time evolution of chemical changes on the surface of an InAs nanowire (NW) on laser irradiation in different power density regime, using Raman spectroscopy for a time span of 8–16 min. Mixture of metastable oxides like InAsO{sub 4,} As{sub 2}O{sub 3} are formed upon oxidation, which are reflected as sharp Raman peaks at ∼240–254 and 180–200 cm{sup −1}. Evidence of removal of arsenic layer by layer is also observed at higher power density. Position controlled laser induced chemical modification on a nanometer scale, without changing the core of the NW, can be useful for NW based device fabrication.

  20. Defect properties of InGaAsN layers grown as sub-monolayer digital alloys by molecular beam epitaxy

    Science.gov (United States)

    Baranov, Artem I.; Gudovskikh, Alexander S.; Kudryashov, Dmitry A.; Lazarenko, Alexandra A.; Morozov, Ivan A.; Mozharov, Alexey M.; Nikitina, Ekaterina V.; Pirogov, Evgeny V.; Sobolev, Maxim S.; Zelentsov, Kirill S.; Egorov, Anton Yu.; Darga, Arouna; Le Gall, Sylvain; Kleider, Jean-Paul

    2018-04-01

    The defect properties of InGaAsN dilute nitrides grown as sub-monolayer digital alloys (SDAs) by molecular beam epitaxy for photovoltaic application were studied by space charge capacitance spectroscopy. Alloys of i-InGaAsN (Eg = 1.03 eV) were lattice-matched grown on GaAs wafers as a superlattice of InAs/GaAsN with one monolayer of InAs (solar cells. Low p-type background doping was demonstrated at room temperature in samples with InGaAsN layers 900 nm and 1200 nm thick (less 1 × 1015 cm-3). According to admittance spectroscopy and deep-level transient spectroscopy measurements, the SDA approach leads to defect-free growth up to a thickness of 900 nm. An increase in thickness to 1200 nm leads to the formation of non-radiative recombination centers with an activation energy of 0.5 eV (NT = 8.4 × 1014 cm-3) and a shallow defect level at 0.20 eV. The last one leads to the appearance of additional doping, but its concentration is low (NT = 5 × 1014 cm-3) so it does not affect the photoelectric properties. However, further increase in thickness to 1600 nm, leads to significant growth of its concentration to (3-5) × 1015 cm-3, while the concentration of deep levels becomes 1.3 × 1015 cm-3. Therefore, additional free charge carriers appearing due to ionization of the shallow level change the band diagram from p-i-n to p-n junction at room temperature. It leads to a drop of the external quantum efficiency due to the effect of pulling electric field decrease in the p-n junction and an increased number of non-radiative recombination centers that negatively impact lifetimes in InGaAsN.

  1. Supercapacitors Based on Reduced Graphene Oxide Nanofibers Supported Ni(OH)2 Nanoplates with Enhanced Electrochemical Performance.

    Science.gov (United States)

    Zhang, Chaoqi; Chen, Qidi; Zhan, Hongbing

    2016-09-07

    Pseudocapacitive materials are critical to the development of supercapacitors but usually suffer from poor conductivity and bad cycling property. Here, we describe the production of novel graphene oxide nanofibers (GONFs) via a partial oxidization and exfoliation method and concurrently report that highly crystallized Ni(OH)2 nanoplates uniformly grow on reduced GONFs' outer graphene nanosheets through the hydrothermal method. Because of their unique structure with high electric conductivity, the rGONF/Ni(OH)2 composite exhibits superior specific capacitance (SC), favorable rate capability and enhanced cycling stability relative to other composites or hybrids, e.g., 1433 F g(-1) at 5 mV s(-1) scan rate, 986 F g(-1) at 40 mV s(-1), and 90.5% capacitance retention after 2000 cycles, and as-fabricated rGONF/Ni(OH)2//active carbon asymmetric supercapacitor (ASC) exhibits a remarkable energy density and a 85.3% high retention (44.1 Wh kg(-1) at 467 W kg(-1) and 37.6 Wh kg(-1) at 3185 W kg(-1)) with a wide potential window of 0-1.7 V. Therefore, this study shows that rGONFs offers an exciting opportunity as substrate materials for supercapacior applications and opens up a new pathway for design and manufacture of novel supercapacitor electrode materials.

  2. Cooperative self-construction and enhanced optical absorption of nanoplates-assembled hierarchical Bi2WO6 flowers

    International Nuclear Information System (INIS)

    Liu Shengwei; Yu Jiaguo

    2008-01-01

    Bi 2 WO 6 hierarchical multilayered flower-like assemblies are fabricated on a large scale by a simple hydrothermal method in the presence of polymeric poly(sodium 4-styrenesulfonate). Such 3D Bi 2 WO 6 assemblies are constructed from orderly arranged 2D layers, which are further composed of a large number of interconnected nanoplates with a mean side length of ca. 50 nm. The bimodal mesopores associated with such hierarchical assembly exhibit peak mesopore size of ca. 4 nm for the voids within a layer, and peak mesopore size of ca. 40 nm corresponding to the interspaces between stacked layers, respectively. The formation process is discussed on the basis of the results of time-dependent experiments, which support a novel 'coupled cooperative assembly and localized ripening' formation mechanism. More interestingly, we have noticed that the collective effect related to such hierarchical assembly induces a significantly enhanced optical absorbance in the UV-visible region. This work may shed some light on the design of complex architectures and exploitation of their potential applications. - Graphical abstract: Bi 2 WO 6 hierarchical multilayered flower-like assemblies are fabricated on a large scale by a simple hydrothermal method in the presence of polymeric poly(sodium 4-styrenesulfonate)

  3. Improved Saturation Performance in High Speed Waveguide Photodetectors at 1.3 ??sing an Asymmetric InA1GaAs/InGaAsP Structure

    Science.gov (United States)

    Vang, T. A.; Davis, L.; Keo, S.; Forouhar, S. F.

    1996-01-01

    Waveguide photodetector (WGPD) results have recently been presented demonstrating the very large bandwidth-efficiency product potential of these devices. Improved saturation and linearity characteristics are realized in waveguide p-i-n photodetectors at 1.3 ??y using an asymmetric cladding structure with InA1GaAs/InGaAsP in the anode and InGaAsP in the cathode.

  4. Growth of InAs/InP core-shell nanowires with various pure crystal structures.

    Science.gov (United States)

    Gorji Ghalamestani, Sepideh; Heurlin, Magnus; Wernersson, Lars-Erik; Lehmann, Sebastian; Dick, Kimberly A

    2012-07-20

    We have studied the epitaxial growth of an InP shell on various pure InAs core nanowire crystal structures by metal-organic vapor phase epitaxy. The InP shell is grown on wurtzite (WZ), zinc-blende (ZB), and {111}- and {110}-type faceted ZB twin-plane superlattice (TSL) structures by tuning the InP shell growth parameters and controlling the shell thickness. The growth results, particularly on the WZ nanowires, show that homogeneous InP shell growth is promoted at relatively high temperatures (∼500 °C), but that the InAs nanowires decompose under the applied conditions. In order to protect the InAs core nanowires from decomposition, a short protective InP segment is first grown axially at lower temperatures (420-460 °C), before commencing the radial growth at a higher temperature. Further studies revealed that the InP radial growth rate is significantly higher on the ZB and TSL nanowires compared to WZ counterparts, and shows a strong anisotropy in polar directions. As a result, thin shells were obtained during low temperature InP growth on ZB structures, while a higher temperature was used to obtain uniform thick shells. In addition, a schematic growth model is suggested to explain the basic processes occurring during the shell growth on the TSL crystal structures.

  5. Growth of InAs/InP core–shell nanowires with various pure crystal structures

    International Nuclear Information System (INIS)

    Gorji Ghalamestani, Sepideh; Heurlin, Magnus; Lehmann, Sebastian; Dick, Kimberly A; Wernersson, Lars-Erik

    2012-01-01

    We have studied the epitaxial growth of an InP shell on various pure InAs core nanowire crystal structures by metal–organic vapor phase epitaxy. The InP shell is grown on wurtzite (WZ), zinc-blende (ZB), and {111}- and {110}-type faceted ZB twin-plane superlattice (TSL) structures by tuning the InP shell growth parameters and controlling the shell thickness. The growth results, particularly on the WZ nanowires, show that homogeneous InP shell growth is promoted at relatively high temperatures (∼500 °C), but that the InAs nanowires decompose under the applied conditions. In order to protect the InAs core nanowires from decomposition, a short protective InP segment is first grown axially at lower temperatures (420–460 °C), before commencing the radial growth at a higher temperature. Further studies revealed that the InP radial growth rate is significantly higher on the ZB and TSL nanowires compared to WZ counterparts, and shows a strong anisotropy in polar directions. As a result, thin shells were obtained during low temperature InP growth on ZB structures, while a higher temperature was used to obtain uniform thick shells. In addition, a schematic growth model is suggested to explain the basic processes occurring during the shell growth on the TSL crystal structures. (paper)

  6. Fabrication of manganese dioxide nanoplates anchoring on biomass-derived cross-linked carbon nanosheets for high-performance asymmetric supercapacitors

    Science.gov (United States)

    Li, Yiju; Yu, Neng; Yan, Peng; Li, Yuguang; Zhou, Xuemei; Chen, Shuangling; Wang, Guiling; Wei, Tong; Fan, Zhuangjun

    2015-12-01

    In this paper, MnO2 nanoplates loading on biomass-derived cross-linked carbon nanosheets have been prepared by a two-step synthesis. At first, the cross-linked carbon nanosheets derived from willow catkin are synthesized by one-step pyrolysis and activation method, then the MnO2 anchored cross-linked carbon nanosheets is prepared via in-situ hydrothermal deposition. The asymmetric supercapacitor with terrific energy and power density is assembled by employing the MnO2 anchored cross-linked carbon nanosheets as the positive electrode and the cross-linked carbon nanosheets as the negative electrode in a 1 M Na2SO4 electrolyte. The asymmetric supercapacitor displays a high energy density of 23.6 Wh kg-1 at a power density of 188.8 W kg-1 within a wide voltage rage of 0-1.9 V. In addition, the asymmetric supercapacitor exhibits excellent cycling stability with only 1.4% capacitance loss after 10000 cycles at 1 A g-1. These discoveries open up the prospect of biomass/biowaste derived carbon-based composites for high-voltage asymmetric supercapacitors with superb energy and power density performance.

  7. Controlled synthesis, formation mechanism, and carbon oxidation properties of Ho{sub 2}Cu{sub 2}O{sub 5} nanoplates prepared with a coordination-complex method

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Rui [School of Resources and Materials, Northeastern University at Qinhuangdao 066004 (China); School of Metallurgy, Northeastern University, Shenyang 110004 (China); You, Junhua [School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110870 (China); Han, Fei; Li, Chaoyang; Zheng, Guiyuan; Xiao, Weicheng [School of Resources and Materials, Northeastern University at Qinhuangdao 066004 (China); Liu, Xuanwen, E-mail: lxw@mail.neuq.edu.cn [School of Resources and Materials, Northeastern University at Qinhuangdao 066004 (China); School of Metallurgy, Northeastern University, Shenyang 110004 (China)

    2017-02-28

    Highlights: • The crystallization mechanism relies on Ho{sup 3+} and Cu{sup 2+} diffusion. • The Ho{sub 2}Cu{sub 2}O{sub 5} particles are refined by the coordination complex method under N{sub 2} environment. • The catalytic oxidation activity of Ho{sub 2}Cu{sub 2}O{sub 5} samples for carbon is enhanced. - Abstract: Ho{sub 2}Cu{sub 2}O{sub 5} nanoplates with perovskite structures were synthesized via a simple solution method (SSM) and a coordination-complex method (CCM) using [HoCu(3,4-pdc){sub 2}(OAc)(H{sub 2}O){sub 3}]·8H{sub 2}O (L = 3,4-pyridinedicarboxylic acid) as a precursor. The CCM was also performed in an N{sub 2} environment (CCMN) under various calcination conditions. The crystallization processes were characterized using X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. Ho{sub 2}Cu{sub 2}O{sub 5} formed through the diffusion of CuO into Ho{sub 2}O{sub 3} particles. Cu{sup 2+} diffused faster than Ho{sup 3+} during this process. The initial products of CCMN (along with the thermal decomposition products) were initially laminarized in the N{sub 2} atmosphere, which prevented the growth of CuO particles and decreased the size of the Ho{sub 2}Cu{sub 2}O{sub 5} particles. The final Ho{sub 2}Cu{sub 2}O{sub 5} particles from CCMN had a nanoplate morphology with an average thickness of 75 nm. The decomposition of organic molecules and protection from N{sub 2} played important roles in determining the morphology of the resulting Ho{sub 2}Cu{sub 2}O{sub 5}. The catalytic oxidation activity of Ho{sub 2}Cu{sub 2}O{sub 5} samples for carbon was characterized using a specific surface area measurement and thermogravimetric analysis, which revealed that the samples produced by CCMN had the highest catalytic activity.

  8. Quantum Confined Semiconductors

    Science.gov (United States)

    2015-02-01

    scattering mechanisms ( acoustic , piezoelectric, polar and non-polar optical) and the ionized impurity scattering. Since InAs and GaSb are binary... pyrometer referenced at GaSb oxide desorption temperature of 530 C. Figure 6a plots the 10 K carrier densities as a function of Tg. The SLs grown

  9. Specific features of electroluminescence in heterostructures with InSb quantum dots in an InAs matrix

    Energy Technology Data Exchange (ETDEWEB)

    Parkhomenko, Ya. A.; Ivanov, E. V.; Moiseev, K. D., E-mail: mkd@iropt2.ioffe.rssi.ru [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2013-11-15

    The electrical and electroluminescence properties of a single narrow-gap heterostructure based on a p-n junction in indium arsenide, containing a single layer of InSb quantum dots in the InAs matrix, are studied. The presence of quantum dots has a significant effect on the shape of the reverse branch of the current-voltage characteristic of the heterostructure. Under reverse bias, the room-temperature electroluminescence spectra of the heterostructure with quantum dots, in addition to a negative-luminescence band with a maximum at the wavelength {lambda} = 3.5 {mu}m, contained a positive-luminescence emission band at 3.8 {mu}m, caused by radiative transitions involving localized states of quantum dots at the type-II InSb/InAs heterointerface.

  10. Electrical characterization of InAs/GaAs (110) nanostructures by conductive atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Beinik, Igor; Teichert, Christian [Institute of Physics, Montanuniversitaet Leoben (Austria); Diez-Merino, Laura; Tejedor, Paloma [Instituto de Ciencia de Materiales de Madrid (Spain). CSIC

    2009-07-01

    Self-assembled InAs quantum dots and wires have been studied over many years and still they are of great interest for application in nanoelectronics, high-speed spintronic devices, etc. Samples for our investigation were grown by molecular beam epitaxy on misoriented (110) GaAs substrates. Conductive Atomic Force Microscopy (C-AFM) technique was used to study the surface topography and conductivity simultaneously. Comparison of the corresponding cross-section profiles indicated that InAs nucleation takes place on the[1-10]-oriented step bunches, forming 3 nm-high and up to 70 nm-wide wires of variable length. On the other hand,[1-12]-type steps very rarely appeared to be decorated by InAs, also in agreement with previous TEM studies. The presented results prove that C-AFM technique might be successfully applied as a tool for investigation of electrical properties in III-V quantum dots and wires on the nanometer scale.

  11. Improved optical properties of InAs quantum dots for intermediate band solar cells by suppression of misfit strain relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Xie, H. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, Arizona 85287-6106 (United States); Prioli, R. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Departamento de Física, Pontificia Universidade Católica do Rio de Janeiro, Marques de São Vicente 225, Rio de Janeiro 22452-900 RJ (Brazil); Fischer, A. M.; Ponce, F. A., E-mail: ponce@asu.edu [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Kawabata, R. M. S.; Pinto, L. D.; Souza, P. L. [LabSem, CETUC, Pontificia Universidade Católica do Rio de Janeiro, Marques de São Vicente 225, Rio de Janeiro 22452-900 RJ (Brazil); Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Jakomin, R. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Campus de Xerem, UFRJ, Duque de Caxias-RJ (Brazil); Pires, M. P. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Instituto de Física, UFRJ, Rio de Janeiro-RJ (Brazil)

    2016-07-21

    The properties of InAs quantum dots (QDs) have been studied for application in intermediate band solar cells. It is found that suppression of plastic relaxation in the QDs has a significant effect on the optoelectronic properties. Partial capping plus annealing is shown to be effective in controlling the height of the QDs and in suppressing plastic relaxation. A force balancing model is used to explain the relationship between plastic relaxation and QD height. A strong luminescence has been observed from strained QDs, indicating the presence of localized states in the desired energy range. No luminescence has been observed from plastically relaxed QDs.

  12. Structural Disorder in Colloidal InAs and CdSe Nanocrystals Observed by X-Ray Absorption Near-Edge Spectroscopy

    International Nuclear Information System (INIS)

    Hamad, K.S.; Hamad, K.S.; Roth, R.; Roth, R.; Rockenberger, J.; Rockenberger, J.; Alivisatos, A.P.; Alivisatos, A.P.; Buuren, T. van

    1999-01-01

    We report the observation of size dependent structural disorder by x-ray absorption near-edge spectroscopy (XANES) in InAs and CdSe nanocrystals 17 - 80 Angstrom in diameter. XANES of the In and Cd M 4,5 edges yields features that are sharp for the bulk solid but broaden considerably as the size of the particle decreases. FEFF7 multiple-scattering simulations reproduce the size dependent broadening of the spectra if a bulklike surface reconstruction of a spherical nanocrystal model is included. This illustrates that XANES is sensitive to the structure of the entire nanocrystal including the surface. copyright 1999 The American Physical Society

  13. Tricobalt tetroxide nanoplate arrays on flexible conductive fabric substrate: Facile synthesis and application for electrochemical supercapacitors

    Science.gov (United States)

    Nagaraju, Goli; Ko, Yeong Hwan; Yu, Jae Su

    2015-06-01

    Tricobalt tetroxide (Co3O4) nanoplate arrays (NPAs) were synthesized on flexible conductive fabric substrate (FCFs) by a facile two-electrode system based electrochemical deposition method, followed by a simple heat treatment process. Initially, cobalt hydroxide (Co(OH)2) NPAs were electrochemically deposited on FCFs by applying an external voltage of -1.5 V for 30 min. Then, the Co3O4 NPAs on FCFs was obtained by thermal treatment of as-deposited Co(OH)2 NPAs on FCFs at 200 °C for 2 h. From the analysis of morphological and crystal properties, the Co3O4 NPAs were well integrated and uniformly covered over the entire surface of substrate with good crystallinity in the cubic phase. Additionally, the fabricated sample was directly used as a binder-free electrode to examine the feasibility for electrochemical supercapacitors using cyclic voltammetry and galvanic charge-discharge measurements in 1 M KOH electrolyte solution. The Co3O4 NPAs coated FCFs electrode exhibited a maximum specific capacitance of 145.6 F/g at a current density of 1 A/g and an excellent rate capability after 1000 cycles at a current density of 3 A/g. This facile fabrication method for integrating the Co3O4 nanostructures on FCFs could be a promising approach for advanced flexible electronic and energy-storage device applications.

  14. Highly sensitive detection of bovine serum albumin based on the aggregation of triangular silver nanoplates

    Science.gov (United States)

    Zhang, Ling Ling; Ma, Fang Fang; Kuang, Yang Fang; Cheng, Shu; Long, Yun Fei; Xiao, Qiu Guo

    2016-02-01

    A simple, fast and highly sensitive spectrophotometric method for the determination of bovine serum albumin (BSA) has been developed based on the interactions between triangular silver nanoplates (TAgNPs) and BSA in the presence of Britton-Robison buffer solution (BR). Particularly, the wavelength of absorption maximum (λmax) of TAgNPs is red shifted in the presence of BSA together with Britton-Robinson buffer solution (BR, pH = 2.56), and the color of the solution changed from blue to light blue. This may be due to the interactions between BSA molecules on the surface of TAgNPs through electrostatic forces, hydrogen bonds, hydrophobic effects and van der Waals forces at pH 2.56, which leads to the aggregation of TAgNPs. The determination of BSA was achieved by measuring the change of λmax corresponding to localized surface plasmon resonance (LSPR) from UV-visible spectrophotometry. It was found that the shift value in the wavelength of absorption maximum (Δλ, the difference in absorption maxima of the TAgNPs/BSA/BR mixture and the TAgNPs/BR mixture) was proportionate to the concentration of BSA in the range of 1.0 ng mL- 1 to 100.0 ng mL- 1 with the correlation coefficient of r = 0.9969. The detection limit (3 σ/k) for BSA was found to be as low as 0.5 ng mL- 1.

  15. Complex laterally ordered InGaAs and InAs quantum dots by guided self-organized anisotropic strain engineering on artificially patterned GaAs (3 1 1)B substrates

    NARCIS (Netherlands)

    Selçuk, E.; Hamhuis, G.J.; Nötzel, R.

    2009-01-01

    Self-organized anisotropic strain engineering is combined with growth on artificially patterned GaAs (3 1 1)B substrates to realize complex lateral ordering of InGaAs and InAs quantum dots (QDs) guided by steps and facets generated along the pattern sidewalls. Depending on the pattern design, size,

  16. Quantitative strain mapping of InAs/InP quantum dots with 1 nm spatial resolution using dark field electron holography

    DEFF Research Database (Denmark)

    Cooper, David; Rouviere, Jean-Luc; Béché, Armand

    2011-01-01

    The optical properties of semiconductor quantum dots are greatly influenced by their strain state. Dark field electron holography has been used to measure the strain in InAs quantum dots grown in InP with a spatial resolution of 1 nm. A strain value of 5.4%60.1% has been determined which...

  17. Physical properties of metal–insulator–semiconductor structures based on n-GaAs with InAs quantum dots deposited onto the surface of an n-GaAs layer

    Energy Technology Data Exchange (ETDEWEB)

    Tikhov, S. V.; Gorshkov, O. N.; Koryazhkina, M. N., E-mail: mahavenok@mail.ru; Kasatkin, A. P.; Antonov, I. N.; Vihrova, O. V.; Morozov, A. I. [Lobachevsky State University of Nizhny Novgorod (NNSU) (Russian Federation)

    2016-12-15

    The properties of metal–insulator–semiconductor (MIS) structures based on n-GaAs in which silicon oxide and yttria-stabilized zirconia and hafnia are used as the insulator containing InAs quantum dots, which are embedded at the insulator/n-GaAs interface, are investigated. The structures manifest the resistive switching and synaptic behavior.

  18. Low temperature transport in p-doped InAs nanowires

    DEFF Research Database (Denmark)

    Upadhyay, Shivendra; Jespersen, Thomas Sand; Madsen, Morten Hannibal

    2013-01-01

    We present low temperature electrical measurements of p-type Indium Arsenide nanowires grown via molecular beam epitaxy using Beryllium as a dopant. Growth of p-type wires without stacking faults is demonstrated. Devices in field-effect geometries exhibit ambipolar behavior, and the temperature...

  19. Preparation of InAs(0 0 1) surface for spin injection via a chemical route

    International Nuclear Information System (INIS)

    Singh, L J; Oliver, R A; Barber, Z H; Eustace, D A; McComb, D W; Clowes, S K; Gilbertson, A M; Magnus, F; Branford, W R; Cohen, L F; Buckle, L; Buckle, P D; Ashley, T

    2007-01-01

    A wet chemical surface treatment for InAs epilayers is investigated to remove the native semiconductor oxide prior to growth of a MgO tunnel barrier and Co ferromagnetic electrode by dc magnetron sputtering. Use of a HCl etch followed by (NH 4 ) 2 S as the pre-growth surface treatment resulted in pinhole-like features in the tunnel barrier, as observed by conducting atomic force microscopy, but this detrimental effect is avoided if the etch procedure is repeated twice. High resolution transmission electron microscopy revealed that the etched samples had uniform tunnel barriers and reducing the growth temperature of the barrier from 200 to 100 0 C significantly improved the abruptness of the semiconductor/barrier interface. Electrical characterization of barrier properties illustrated that all the etched samples showed parabolic differential conductance curves indicative of tunnelling behaviour at 300 K

  20. Axial strain in GaAs/InAs core-shell nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Biermanns, Andreas; Pietsch, Ullrich [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany); Rieger, Torsten; Gruetzmacher, Detlev; Ion Lepsa, Mihail [Peter Gruenberg Institute (PGI-9), Forschungszentrum, 52425 Juelich (Germany); JARA-Fundamentals of Future Information Technology, 52425 Juelich (Germany); Bussone, Genziana [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany); ESRF, 6 rue Jules Horowitz, BP220, F-38043 Grenoble Cedex (France)

    2013-01-28

    We study the axial strain relaxation in GaAs/InAs core-shell nanowire heterostructures grown by molecular beam epitaxy. Besides a gradual strain relaxation of the shell material, we find a significant strain in the GaAs core, increasing with shell thickness. This strain is explained by a saturation of the dislocation density at the core-shell interface. Independent measurements of core and shell lattice parameters by x-ray diffraction reveal a relaxation of 93% in a 35 nm thick InAs shell surrounding cores of 80 nm diameter. The compressive strain of -0.5% compared to bulk InAs is accompanied by a tensile strain up to 0.9% in the GaAs core.

  1. Facile synthesis of CuSe nanoparticles and high-quality single-crystal two-dimensional hexagonal nanoplatelets with tunable near-infrared optical absorption

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yimin [State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Korolkov, Ilia [Laboratory of Glasses and Ceramics, Institute of Chemistry, CNRS-Université de Rennes I, Campus de Beaulieu, 35042 Rennes Cedex (France); Qiao, Xvsheng [State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Zhang, Xianghua [Laboratory of Glasses and Ceramics, Institute of Chemistry, CNRS-Université de Rennes I, Campus de Beaulieu, 35042 Rennes Cedex (France); Wan, Jun; Fan, Xianping [State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2016-06-15

    A rapid injection approach is used to synthesize the copper selenide nanoparticles and two-dimensional single crystal nanoplates. This technique excludes the use of toxic or expensive materials, increasing the availability of two-dimensional binary chalcogenide semiconductors. The structure of the nanocrystals has been studied and the possible formation mechanism of the nanoplates has been proposed. The optical absorption showed that the nanoplates demonstrated wide and tuneable absorption band in the visible and near infrared region. These nanoplates could be interesting for converting solar energy and for nanophotonic devices operating in the near infrared. - Graphical abstract: TEM images of the copper selenides nanoparticles and nanoplates synthesized at 180 °C for 0 min, 10 min, 60 min. And the growth mechanism of the copper selenide nanoplates via the “oriented attachment”. Display Omitted - Highlights: • CuSe nanoparticles and nanoplates are synthesized by a rapid injection approach. • CuSe band gap can be widely tuned simply by modifying the synthesized time. • Al{sup 3+} ions have a significant impact on the growth rate of the nanoplates. • Growth mechanism of the CuSe nanoplates is based on the “oriented attachment”.

  2. Skin cancer full-grown from scar

    International Nuclear Information System (INIS)

    Zikiryakhodjaev, D.Z.; Sanginov, D.R.

    2001-01-01

    In this chapter authors investigate the peculiarities of skin cancer full-grown from scar, the theory of it's descent, quote some statistical data on skin cancer full-grown from scar and variety clinical forms of skin cancer full-grown from scar was shown, quote some methods of treatment

  3. An efficient atomistic quantum mechanical simulation on InAs band-to-band tunneling field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhi [State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Jiang, Xiang-Wei; Li, Shu-Shen [State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wang, Lin-Wang, E-mail: lwwang@lbl.gov [Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2014-03-24

    We have presented a fully atomistic quantum mechanical simulation method on band-to-band tunneling (BTBT) field-effect transistors (FETs). Our simulation approach is based on the linear combination of bulk band method with empirical pseudopotentials, which is an atomist method beyond the effective-mass approximation or k.p perturbation method, and can be used to simulate real-size devices (∼10{sup 5} atoms) efficiently (∼5 h on a few computational cores). Using this approach, we studied the InAs dual-gate BTBT FETs. The I-V characteristics from our approach agree very well with the tight-binding non-equilibrium Green's function results, yet our method costs much less computationally. In addition, we have studied ways to increase the tunneling current and analyzed the effects of different mechanisms for that purpose.

  4. An efficient atomistic quantum mechanical simulation on InAs band-to-band tunneling field-effect transistors

    International Nuclear Information System (INIS)

    Wang, Zhi; Jiang, Xiang-Wei; Li, Shu-Shen; Wang, Lin-Wang

    2014-01-01

    We have presented a fully atomistic quantum mechanical simulation method on band-to-band tunneling (BTBT) field-effect transistors (FETs). Our simulation approach is based on the linear combination of bulk band method with empirical pseudopotentials, which is an atomist method beyond the effective-mass approximation or k.p perturbation method, and can be used to simulate real-size devices (∼10 5 atoms) efficiently (∼5 h on a few computational cores). Using this approach, we studied the InAs dual-gate BTBT FETs. The I-V characteristics from our approach agree very well with the tight-binding non-equilibrium Green's function results, yet our method costs much less computationally. In addition, we have studied ways to increase the tunneling current and analyzed the effects of different mechanisms for that purpose

  5. Structural and electrooptical characteristics of quantum dots emitting at 1.3 μm on gallium arsenide

    DEFF Research Database (Denmark)

    Fiore, A.; Oesterle, U.; Stanley, R.P.

    2001-01-01

    We present a comprehensive study of the structural and emission properties of self-assembled InAs quantum dots emitting at 1.3 mum. The dots are grown by molecular beam epitaxy on gallium arsenide substrates. Room-temperature emission at 1.3 mum is obtained by embedding the dots in an InGaAs layer...

  6. Influência da heparina sódica na ocorrência de laminite eqüina induzida por sobrecarga de carboidratos

    OpenAIRE

    Martins Filho,L.P.; Fagliari,J.J.; Moraes,J.R.E.; Sampaio,R.C.; Oliveira,J.A.; Lacerda Neto,J.C.

    2008-01-01

    Avaliou-se a eficiência da infusão intravenosa de heparina sódica (100UI/kg/8h, a partir de 24h após o fornecimento de carboidrato, até completar 48h) no controle da laminite eqüina experimentalmente induzida por sobrecarga de carboidrato (17,6g de amido de milho/kg de peso corpóreo). Foram utilizados 15 eqüinos adultos, distribuídos em três grupos experimentais: GI (grupo-controle); GII (grupo laminite) e GIII (grupo laminite+heparina). Posteriormente ao fornecimento de carboidrato, os anima...

  7. Homoclinic behaviors and chaotic motions of double layered viscoelastic nanoplates based on nonlocal theory and extended Melnikov method

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu; Wang, Yi-Ze [School of Astronautics, Harbin Institute of Technology, P. O. Box 137, Harbin 150001 (China); Li, Feng-Ming, E-mail: fmli@bjut.edu.cn [School of Astronautics, Harbin Institute of Technology, P. O. Box 137, Harbin 150001 (China); College of Mechanical Engineering, Beijing University of Technology, Beijing 100124 (China)

    2015-06-15

    The nonlinear dynamical equations are established for the double layered viscoelastic nanoplates (DLNP) subjected to in-plane excitation based on the nonlocal theory and von Kármán large deformation theory. The extended high dimensional homoclinic Melnikov method is employed to study the homoclinic phenomena and chaotic motions for the parametrically excited DLNP system. The criteria for the homoclinic transverse intersection for both the asynchronous and synchronous buckling cases are proposed. Lyapunov exponents and phase portraits are obtained to verify the Melnikov-type analysis. The influences of structural parameters on the transverse homoclinic orbits and homoclinic bifurcation sets are discussed for the two buckling cases. Some novel phenomena are observed in the investigation. It should be noticed that the nonlocal effect on the homoclinic behaviors and chaotic motions is quite remarkable. Hence, the small scale effect should be taken into account for homoclinic and chaotic analysis for nanostructures. It is significant that the nonlocal effect on the homoclinic phenomena for the asynchronous buckling case is quite different from that for the synchronous buckling case. Moreover, due to the van der Walls interaction between the layers, the nonlocal effect on the homoclinic behaviors and chaotic motions for high order mode is rather tiny under the asynchronous buckling condition.

  8. Homoclinic behaviors and chaotic motions of double layered viscoelastic nanoplates based on nonlocal theory and extended Melnikov method.

    Science.gov (United States)

    Wang, Yu; Li, Feng-Ming; Wang, Yi-Ze

    2015-06-01

    The nonlinear dynamical equations are established for the double layered viscoelastic nanoplates (DLNP) subjected to in-plane excitation based on the nonlocal theory and von Kármán large deformation theory. The extended high dimensional homoclinic Melnikov method is employed to study the homoclinic phenomena and chaotic motions for the parametrically excited DLNP system. The criteria for the homoclinic transverse intersection for both the asynchronous and synchronous buckling cases are proposed. Lyapunov exponents and phase portraits are obtained to verify the Melnikov-type analysis. The influences of structural parameters on the transverse homoclinic orbits and homoclinic bifurcation sets are discussed for the two buckling cases. Some novel phenomena are observed in the investigation. It should be noticed that the nonlocal effect on the homoclinic behaviors and chaotic motions is quite remarkable. Hence, the small scale effect should be taken into account for homoclinic and chaotic analysis for nanostructures. It is significant that the nonlocal effect on the homoclinic phenomena for the asynchronous buckling case is quite different from that for the synchronous buckling case. Moreover, due to the van der Walls interaction between the layers, the nonlocal effect on the homoclinic behaviors and chaotic motions for high order mode is rather tiny under the asynchronous buckling condition.

  9. An efficient p-n heterojunction photocatalyst constructed from a coordination polymer nanoplate and a partically reduced graphene oxide for visible-light hydrogen production.

    Science.gov (United States)

    Xu, Xinxin; Lu, Tingting; Liu, Xiaoxia; Wang, Xiuli

    2015-10-05

    A new p-n heterojunction photocatalyst has been synthesized successfully through chemical-bond-mediated combination of coordination polymer nanoplates (CPNPs) and partially reduced graphene oxide (PRGO) with a simple colloidal blending process. Photocatalytic H2 production by the p-n heterojunction photocatalyst PRGO/CPNP was investigated under visible-light irradiation, which illustrates that PRGO/CPNP exhibits a much higher photocatalytic H2 production rate than neat the CPNPs. The improvement of this photocatalytic property can be attributed to the inner electrical field formed in the p-n heterojunction, which impedes recombination of photogenerated electrons and holes. In PRGO/CPNP, the existence of the p-n heterojunction has been confirmed by electrochemical methods clearly. For PRGO/CPNP, the reductive degree of the PRGO has a great influence on the H2 production rate and an ideal condition to get a PRGO/CPNP photocatalyst with higher performance has been obtained. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Magnetic and electrical properties of zincblende CrAs

    International Nuclear Information System (INIS)

    Chen Peng; Takamura, K

    2008-01-01

    This paper reports that 9 nm zincblende CrAs is grown by molecular-beam epitaxy on InAs buffer layer. The zb-CrAs shows ferromagnetism at room temperature and the total magnetic moment 3.09 ± 0.15 μ B per CrAs unit. The temperature dependence of zb-CrAs resistance R shows metallic behaviour

  11. Evidence that an internal carbonic anhydrase is present in 5% CO2-grown and air-grown Chlamydomonas

    International Nuclear Information System (INIS)

    Moroney, J.V.; Togasaki, R.K.; Husic, H.D.; Tolbert, N.E.

    1987-01-01

    Inorganic carbon (C/sub i/) uptake was measured in wild-type cells of Chlamydomonas reinhardtii, and in cia-3, a mutant strain of C. reinhardtii that cannot grow with air levels of CO 2 . Both air-grown cells, that have a CO 2 concentrating system, and 5% CO 2 -grown cells that do not have this system, were used. When the external pH was 5.1 or 7.3, air-grown, wild-type cells accumulated inorganic carbon (C/sub i/) and this accumulation was enhanced when the permeant carbonic anhydrase inhibitor, ethoxyzolamide, was added. When the external pH was 5.1, 5% CO 2 -grown cells also accumulated some C/sub i/, although not as much as air-grown cells and this accumulation was stimulated by the addition of ethoxyzolamide. At the same time, ethoxyzolamide inhibited CO 2 fixation by high CO 2 -grown, wild-type cells at both pH 5.1 and 7.3. These observations imply that 5% CO 2 -grown, wild-type cells, have a physiologically important internal carbonic anhydrase, although the major carbonic anhydrase located in the periplasmic space is only present in air-grown cells. Inorganic carbon uptake by cia-3 cells supported this conclusion. This mutant strain, which is thought to lack an internal carbonic anhydrase, was unaffected by ethoxyzolamide at pH 5.1. Other physiological characteristics of cia-3 resemble those of wild-type cells that have been treated with ethoxyzolamide. It is concluded that an internal carbonic anhydrase is under different regulatory control than the periplasmic carbonic anhydrase

  12. Ordered quantum-ring chains grown on a quantum-dot superlattice template

    International Nuclear Information System (INIS)

    Wu Jiang; Wang, Zhiming M.; Holmes, Kyland; Marega, Euclydes; Mazur, Yuriy I.; Salamo, Gregory J.

    2012-01-01

    One-dimensional ordered quantum-ring chains are fabricated on a quantum-dot superlattice template by molecular beam epitaxy. The quantum-dot superlattice template is prepared by stacking multiple quantum-dot layers and quantum-ring chains are formed by partially capping quantum dots. Partially capping InAs quantum dots with a thin layer of GaAs introduces a morphological change from quantum dots to quantum rings. The lateral ordering is introduced by engineering the strain field of a multi-layer InGaAs quantum-dot superlattice.

  13. InAs(Sb) quantum dots grown on GaAs by MBE

    International Nuclear Information System (INIS)

    Sallet, V.; Patriarche, G.; Mauguin, O.; Largeau, L.; Travers, L.

    2006-01-01

    The MBE growth of InAs(Sb)/GaAs quantum dots is investigated. Photoluminescence shows a slight red-shift of the emission wavelength from 1.15 to 1.24 μm (InAs 0.95 Sb 0.05 dots). Attempts to incorporate higher concentrations of antimony lead to a poor optical quality and, occasionally, to a blue-shift. Trans-mission electron microscopy observations are discussed considering the surfactant effect of antimony. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Characterization of highly stacked InAs quantum dot layers on InP substrate for a planar saturable absorber at 1.5 μm band

    International Nuclear Information System (INIS)

    Inoue, Jun; Akahane, Kouichi; Yamamoto, Naokatsu; Isu, Toshiro; Tsuchiya, Masahiro

    2006-01-01

    We examined the absorption saturation properties in the 1.5 μm band of novel highly stacked InAs quantum dot layers. The transmission change at vertical incidence based on the saturable absorption of the quantum dots was more than 1%. This value is as large as the reflection changes of previously reported 1-μm-band quantum dot saturable absorber with interference enhancement. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. The polarization response in InAs quantum dots: theoretical correlation between composition and electronic properties

    International Nuclear Information System (INIS)

    Usman, Muhammad; O’Reilly, Eoin P; Tasco, Vittorianna; Todaro, Maria Teresa; De Giorgi, Milena; Passaseo, Adriana; Klimeck, Gerhard

    2012-01-01

    III–V growth and surface conditions strongly influence the physical structure and resulting optical properties of self-assembled quantum dots (QDs). Beyond the design of a desired active optical wavelength, the polarization response of QDs is of particular interest for optical communications and quantum information science. Previous theoretical studies based on a pure InAs QD model failed to reproduce experimentally observed polarization properties. In this work, multi-million atom simulations are performed in an effort to understand the correlation between chemical composition and polarization properties of QDs. A systematic analysis of QD structural parameters leads us to propose a two-layer composition model, mimicking In segregation and In–Ga intermixing effects. This model, consistent with mostly accepted compositional findings, allows us to accurately fit the experimental PL spectra. The detailed study of QD morphology parameters presented here serves as a tool for using growth dynamics to engineer the strain field inside and around the QD structures, allowing tuning of the polarization response. (paper)

  16. Weak Antilocalization in Bi 2 (Se x Te 1– x ) 3 Nanoribbons and Nanoplates

    KAUST Repository

    Cha, Judy J.; Kong, Desheng; Hong, Seung-Sae; Analytis, James G.; Lai, Keji; Cui, Yi

    2012-01-01

    Studying the surface states of Bi 2Se 3 and Bi 2Te 3 topological insulators has proven challenging due to the high bulk carrier density that masks the surface states. Ternary compound Bi 2(Se xTe 1-x) 3 may present a solution to the current materials challenge by lowering the bulk carrier mobility significantly. Here, we synthesized Bi 2(Se xTe 1-x) 3 nanoribbons and nanoplates via vapor-liquid-solid and vapor-solid growth methods where the atomic ratio x was controlled by the molecular ratio of Bi 2Se 3 to Bi 2Te 3 in the source mixture and ranged between 0 and 1. For the whole range of x, the ternary nanostructures are single crystalline without phase segregation, and their carrier densities decrease with x. However, the lowest electron density is still high (∼10 19 cm -3) and the mobility low, suggesting that the majority of these carriers may come from impurity states. Despite the high carrier density, weak antilocalization (WAL) is clearly observed. Angle-dependent magnetoconductance study shows that an appropriate magnetic field range is critical to capture a true, two-dimensional (2D) WAL effect, and a fit to the 2D localization theory gives α of -0.97, suggesting its origin may be the topological surface states. The power law dependence of the dephasing length on temperature is ∼T -0.49 within the appropriate field range (∼0.3 T), again reflecting the 2D nature of the WAL. Careful analysis on WAL shows how the surface states and the bulk/impurity states may interact with each other. © 2012 American Chemical Society.

  17. Weak Antilocalization in Bi 2 (Se x Te 1– x ) 3 Nanoribbons and Nanoplates

    KAUST Repository

    Cha, Judy J.

    2012-02-08

    Studying the surface states of Bi 2Se 3 and Bi 2Te 3 topological insulators has proven challenging due to the high bulk carrier density that masks the surface states. Ternary compound Bi 2(Se xTe 1-x) 3 may present a solution to the current materials challenge by lowering the bulk carrier mobility significantly. Here, we synthesized Bi 2(Se xTe 1-x) 3 nanoribbons and nanoplates via vapor-liquid-solid and vapor-solid growth methods where the atomic ratio x was controlled by the molecular ratio of Bi 2Se 3 to Bi 2Te 3 in the source mixture and ranged between 0 and 1. For the whole range of x, the ternary nanostructures are single crystalline without phase segregation, and their carrier densities decrease with x. However, the lowest electron density is still high (∼10 19 cm -3) and the mobility low, suggesting that the majority of these carriers may come from impurity states. Despite the high carrier density, weak antilocalization (WAL) is clearly observed. Angle-dependent magnetoconductance study shows that an appropriate magnetic field range is critical to capture a true, two-dimensional (2D) WAL effect, and a fit to the 2D localization theory gives α of -0.97, suggesting its origin may be the topological surface states. The power law dependence of the dephasing length on temperature is ∼T -0.49 within the appropriate field range (∼0.3 T), again reflecting the 2D nature of the WAL. Careful analysis on WAL shows how the surface states and the bulk/impurity states may interact with each other. © 2012 American Chemical Society.

  18. Self-assembled InAs quantum dots. Properties, modification and emission processes; Selbstorganisierte InAs-Quantenpunkte. Eigenschaften, Modifizierung und Emissionsprozesse

    Energy Technology Data Exchange (ETDEWEB)

    Schramm, A.

    2007-09-06

    In this thesis, structural, optical as well as electronic properties of self-assembled InAs quantum dots (QD) were studied by means of atomic force microscopy (AFM), photoluminescence (PL), capacitance spectroscopy (CV) and capacitance transient spectroscopy (DLTS). The quantum dots were grown with molecular beam epitaxy (MBE) and embedded in Schottky diodes for electrical characterization. In this work growth aspects as well as the electronic structures of QD were discussed. By varying the QD growth parameters it is possible to control the structural, and thus the optical and electronic properties of QD. Two methods are presented. Adjusting the QD growth temperature leads either to small QD with a high areal density or to high QDs with a low density. The structural changes of the QD are reflected in the changes of the optical and electronic properties. The second method is to introduce a growth interruption after capping the QD with thin cap layers. It was shown that capping with AlAs leads to a well-developed alternative to control the QD height and thus the ground-state energies of the QD. A post-growth method modifying the QD properties ist rapid thermal annealing (RTA). Raising the RTA temperature causes a lifting of the QD energy states with respect to the GaAs band edge energy due to In/Ga intermixing processes. A further main part of this work covers the emission processes of charge carriers in QD. Thermal emission, thermally assisted tunneling, and pure tunneling emission are studied by capacitance transient spectroscopy techniques. In DLTS experiments a strong impact of the electric field on the activation energies of electrons was found interfering the correct determination of the QD level energies. This behaviour can be explained by a thermally assisted tunneling model. A modified model taking the Coulomb interaction of occupied QD into account describes the emission rates of the electrons. In order to avoid several emission pathes in the experiments

  19. Photoresponse and Field Effect Transport Studies in InAsP-InP Core-Shell Nanowires

    Science.gov (United States)

    Lee, Rochelle; Jo, Min Hyeok; Kim, TaeWan; Kim, Hyo Jin; Kim, Doo Gun; Shin, Jae Cheol

    2018-05-01

    A ternary InAsyP1-y alloy is suitable for an application to near-infrared (NIR) optical devices as their direct bandgap energy covers the entire NIR band. A nanowire (NW) system allows an epitaxial integration of InAsyP1-y alloy on any type of substrate since the lattice mismatch strain can be relieved through the NW sidewall. Nevertheless, the very large surface to volume ratio feature of the NWs leads to enormous surface states which are susceptible to surface recombination of free carriers. Here, ternary InAs0.75P0.25 NWs are grown with InP passivation layer (i.e., core-shell structure) to minimize the influence of the surface states, thus increasing their optical and electrical properties. A photoresponse study was achieved through the modeled band structure of the grown NWs. The model and experimental results suggest that 5-nm-thick InP shell efficiently passivates the surface states of the InAs0.75P0.25 NWs. The fabricated core-shell photodetectors and field-effect transistors exhibit improved photoresponse and transport properties compared to its counterpart core-only structure.

  20. Photoresponse and Field Effect Transport Studies in InAsP-InP Core-Shell Nanowires

    Science.gov (United States)

    Lee, Rochelle; Jo, Min Hyeok; Kim, TaeWan; Kim, Hyo Jin; Kim, Doo Gun; Shin, Jae Cheol

    2018-03-01

    A ternary InAsyP1-y alloy is suitable for an application to near-infrared (NIR) optical devices as their direct bandgap energy covers the entire NIR band. A nanowire (NW) system allows an epitaxial integration of InAsyP1-y alloy on any type of substrate since the lattice mismatch strain can be relieved through the NW sidewall. Nevertheless, the very large surface to volume ratio feature of the NWs leads to enormous surface states which are susceptible to surface recombination of free carriers. Here, ternary InAs0.75P0.25 NWs are grown with InP passivation layer (i.e., core-shell structure) to minimize the influence of the surface states, thus increasing their optical and electrical properties. A photoresponse study was achieved through the modeled band structure of the grown NWs. The model and experimental results suggest that 5-nm-thick InP shell efficiently passivates the surface states of the InAs0.75P0.25 NWs. The fabricated core-shell photodetectors and field-effect transistors exhibit improved photoresponse and transport properties compared to its counterpart core-only structure.