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Sample records for germanium nanowires bulk

  1. Germanium nanowires grown using different catalyst metals

    Energy Technology Data Exchange (ETDEWEB)

    Gouveia, R.C., E-mail: riama@ifsp.edu.br [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil); Área de Ciências, Instituto Federal de Educação Ciência e Tecnologia de São Paulo, Rua Américo Ambrósio, 269, Jd. Canaã, Sertãozinho, CEP 14169-263 (Brazil); Kamimura, H.; Munhoz, R.; Rodrigues, A.D. [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil); Leite, E.R. [Departamento de Química – LIEC, Universidade Federal de São Carlos, São Carlos, CEP 13565-905 (Brazil); Chiquito, A.J. [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil)

    2016-11-01

    Germanium nanowires have been synthesized by the well known vapor-liquid-solid growth mechanism using gold, silver, cooper, indium and nickel as catalyst metals. The influence of metal seeds on nanowires structural and electronic transport properties was also investigated. Electron microscopy images demonstrated that, despite differences in diameters, all nanowires obtained presented single crystalline structures. X-ray patterns showed that all nanowires were composed by germanium with a small amount of germanium oxide, and the catalyst metal was restricted at the nanowires' tips. Raman spectroscopy evidenced the long range order in the crystalline structure of each sample. Electrical measurements indicated that variable range hopping was the dominant mechanism in carrier transport for all devices, with similar hopping distance, regardless the material used as catalyst. Then, in spite of the differences in synthesis temperatures and nanowires diameters, the catalyst metals have not affected the composition and crystalline quality of the germanium nanowires nor the carrier transport in the germanium nanowire network devices. - Highlights: • Ge nanowires were grown by VLS method using Au, Ag, Cu, In and Ni as catalysts. • All nanowires presented high single crystalline quality and long range order. • Devices showed semiconducting behavior having VRH as dominant transport mechanism. • The metal catalyst did not influence structural properties or the transport mechanism.

  2. Promoting cell proliferation using water dispersible germanium nanowires.

    Directory of Open Access Journals (Sweden)

    Michael Bezuidenhout

    Full Text Available Group IV Nanowires have strong potential for several biomedical applications. However, to date their use remains limited because many are synthesised using heavy metal seeds and functionalised using organic ligands to make the materials water dispersible. This can result in unpredicted toxic side effects for mammalian cells cultured on the wires. Here, we describe an approach to make seedless and ligand free Germanium nanowires water dispersible using glutamic acid, a natural occurring amino acid that alleviates the environmental and health hazards associated with traditional functionalisation materials. We analysed the treated material extensively using Transmission electron microscopy (TEM, High resolution-TEM, and scanning electron microscope (SEM. Using a series of state of the art biochemical and morphological assays, together with a series of complimentary and synergistic cellular and molecular approaches, we show that the water dispersible germanium nanowires are non-toxic and are biocompatible. We monitored the behaviour of the cells growing on the treated germanium nanowires using a real time impedance based platform (xCELLigence which revealed that the treated germanium nanowires promote cell adhesion and cell proliferation which we believe is as a result of the presence of an etched surface giving rise to a collagen like structure and an oxide layer. Furthermore this study is the first to evaluate the associated effect of Germanium nanowires on mammalian cells. Our studies highlight the potential use of water dispersible Germanium Nanowires in biological platforms that encourage anchorage-dependent cell growth.

  3. A catalyst-free synthesis of germanium nanowires obtained by ...

    Indian Academy of Sciences (India)

    A catalyst-free innovative synthesis, by combined X-ray chemical vapour deposition and lowtemperature thermal treatments, which has not been applied since so far to the growth of germanium nanowires (Ge-NWs), produced high yields of the nanoproducts with theGeH4 reactant gas. Nanowires were grown on both ...

  4. Photoconductivity of Germanium Nanowire Arrays Incorporated in Anodic Aluminum Oxide

    International Nuclear Information System (INIS)

    Polyakov, B; Prikulis, J; Grigorjeva, L; Millers, D; Daly, B; Holmes, J D; Erts, D

    2007-01-01

    Photoconductivity of germanium nanowire arrays of 50 and 100 nm diameter incorporated into Anodic Aluminum Oxide (AAO) membranes illuminated with visible light is investigated. Photocurrent response to excitation radiation with time constants faster than 10 -4 s were governed by absorption of incident light by nanowires, while photokinetics with time constants of the order of 10 -3 s originates from the photoluminescence of the AAO matrix. Possible applications of nanowire arrays inside AAO as photoresistors are discussed

  5. Electrodeposition at room temperature of amorphous silicon and germanium nanowires in ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Martineau, F; Namur, K; Mallet, J; Delavoie, F; Troyon, M; Molinari, M [Laboratoire de Microscopies et d' Etude de Nanostructures (LMEN EA3799), Universite de Reims Champagne Ardennes (URCA), Reims Cedex 2 (France); Endres, F, E-mail: michael.molinari@univ-reims.fr [Institute of Particle Technology, Chair of Interface Processes, Clausthal University of Technology, D-36678 Clausthal-Zellerfeld (Germany)

    2009-11-15

    The electrodeposition at room temperature of silicon and germanium nanowires from the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P{sub 1,4}) containing SiCl{sub 4} as Si source or GeCl{sub 4} as Ge source is investigated by cyclic voltammetry. By using nanoporous polycarbonate membranes as templates, it is possible to reproducibly grow pure silicon and germanium nanowires of different diameters. The nanowires are composed of pure amorphous silicon or germanium. The nanowires have homogeneous cylindrical shape with a roughness of a few nanometres on the wire surfaces. The nanowires' diameters and lengths well match with the initial membrane characteristics. Preliminary photoluminescence experiments exhibit strong emission in the near infrared for the amorphous silicon nanowires.

  6. Tensile strained germanium nanowires measured by photocurrent spectroscopy and X-ray microdiffraction.

    Science.gov (United States)

    Guilloy, Kevin; Pauc, Nicolas; Gassenq, Alban; Gentile, Pascal; Tardif, Samuel; Rieutord, François; Calvo, Vincent

    2015-04-08

    Applying tensile strain in a single germanium crystal is a very promising way to tune its bandstructure and turn it into a direct band gap semiconductor. In this work, we stress vapor-liquid-solid grown germanium nanowires along their [111] axis thanks to the strain tranfer from a silicon nitride thin film by a microfabrication process. We measure the Γ-LH direct band gap transition by photocurrent spectrometry and quantify associated strain by X-ray Laue microdiffraction on beamline BM32 at the European Synchrotron Radiation Facility. Nanowires exhibit up to 1.48% strain and an absorption threshold down to 0.73 eV, which is in good agreement with theoretical computations for the Γ-LH transition, showing that the nanowire geometry is an efficient way of applying tensile uniaxial stress along the [111] axis of a germanium crystal.

  7. Solvent Vapor Growth of Axial Heterostructure Nanowires with Multiple Alternating Segments of Silicon and Germanium.

    Science.gov (United States)

    Flynn, Grace; Ramasse, Quentin M; Ryan, Kevin M

    2016-01-13

    Herein, we report the formation of multisegment Si-Ge axial heterostructure nanowires in a wet chemical synthetic approach. These nanowires are grown by the liquid injection of the respective silicon and germanium precursors into the vapor phase of an organic solvent in which a tin-coated stainless steel substrate is placed. The Si-Ge transition is obtained by sequential injection with the more difficult Ge-Si transition enabled by inclusion of a quench sequence in the reaction. This approach allows for alternating between pure Si and pure Ge segments along the entire nanowire length with good control of the respective segment dimensions. The multisegment heterostructure nanowires presented are Ge-Si, Si-Ge-Si, Ge-Si-Ge, Si-Ge-Si-Ge, and Si-Ge-Si-Ge-Si-Ge. The interfacial abruptness of the Ge to Si interface is also determined through the use of aberration corrected scanning transmission electron microscopy and electron energy loss spectroscopy.

  8. A catalyst-free synthesis of germanium nanowires obtained by ...

    Indian Academy of Sciences (India)

    2015-08-25

    Aug 25, 2015 ... Noteworthy, core–shell morphological architec- tures of germanium NWs, with a crystal core embedded in a less-ordered nanocrystalline or amorphous Ge-shell, have been reported, providing a broad-peak experimental. XRPD diffraction pattern [14]. The deposited materials on the upper substrate surface ...

  9. Lithium effects on the mechanical and electronic properties of germanium nanowires

    Science.gov (United States)

    González-Macías, A.; Salazar, F.; Miranda, A.; Trejo-Baños, A.; Pérez, L. A.; Carvajal, E.; Cruz-Irisson, M.

    2018-04-01

    Semiconductor nanowire arrays promise rapid development of a new generation of lithium (Li) batteries because they can store more Li atoms than conventional crystals due to their large surface areas. During the charge-discharge process, the electrodes experience internal stresses that fatigue the material and limit the useful life of the battery. The theoretical study of electronic and mechanical properties of lithiated nanowire arrays allows the designing of electrode materials that could improve battery performance. In this work, we present a density functional theory study of the electronic band structure, formation energy, binding energy, and Young’s modulus (Y) of hydrogen passivated germanium nanowires (H-GeNWs) grown along the [111] and [001] crystallographic directions with surface and interstitial Li atoms. The results show that the germanium nanowires (GeNWs) with surface Li atoms maintain their semiconducting behavior but their energy gap size decreases when the Li concentration grows. In contrast, the GeNWs can have semiconductor or metallic behavior depending on the concentration of the interstitial Li atoms. On the other hand, Y is an indicator of the structural changes that GeNWs suffer due to the concentration of Li atoms. For surface Li atoms, Y stays almost constant, whereas for interstitial Li atoms, the Y values indicate important structural changes in the GeNWs.

  10. Thermal Conductivity Suppression in Nanostructured Silicon and Germanium Nanowires

    Science.gov (United States)

    Özden, Ayberk; Kandemir, Ali; Ay, Feridun; Perkgöz, Nihan Kosku; Sevik, Cem

    2016-03-01

    The inherent low lattice thermal conductivity (TC) of semiconductor nanowires (s-NW) due to one-dimensional phonon confinement might provide a solution for the long-lasting figure-of-merit problem for highly efficient thermoelectric (TE) applications. Standalone diameter modulation or alloying of s-NW serve as a toolkit for TC control, but realizing the full potential of nanowires requires new atomic-scale designs, growth, characterization, and understanding of the physical mechanisms behind the structure-property (TC) relationship. Before undertaking time-consuming and expensive experimental work, molecular dynamics (MD) simulations serve as an excellent probe to investigate new designs and understand how nanostructures affect thermal transport properties through their capability to capture various phenomena such as phonon boundary scattering, phonon coherence resonance, and phonon backscattering. On the other hand, because different research groups use different structural and MD parameters in their simulations, it is rather difficult to make comparisons between different nanostructures and select appropriate ones for potential TE applications. Therefore, in this work, we systematically investigated pristine, core-shell (C-S), holey (H-N), superlattice (SL), sawtooth (ST), and superlattice sawtooth (SL-ST) nanowires with identical structural parameters. Specifically, we aim to compare the relative TC reduction achieved by these nanostructures with respect to pristine nanowires in order to propose the best structural design with the lowest lattice TC, using Green-Kubo method-based equilibrium molecular dynamics simulations at 300 K. Our results show that the TC can be minimized by changing specific parameters such as the core diameter and monolayer separation for C-S, H-N, and ST structures. In the case of SL structures, the TC is found to be independent of these parameters. However, surface roughness in the form of a ST morphology provides a TC value below 2 W

  11. Bulk and surface event identification in p-type germanium detectors

    Science.gov (United States)

    Yang, L. T.; Li, H. B.; Wong, H. T.; Agartioglu, M.; Chen, J. H.; Jia, L. P.; Jiang, H.; Li, J.; Lin, F. K.; Lin, S. T.; Liu, S. K.; Ma, J. L.; Sevda, B.; Sharma, V.; Singh, L.; Singh, M. K.; Singh, M. K.; Soma, A. K.; Sonay, A.; Yang, S. W.; Wang, L.; Wang, Q.; Yue, Q.; Zhao, W.

    2018-04-01

    The p-type point-contact germanium detectors have been adopted for light dark matter WIMP searches and the studies of low energy neutrino physics. These detectors exhibit anomalous behavior to events located at the surface layer. The previous spectral shape method to identify these surface events from the bulk signals relies on spectral shape assumptions and the use of external calibration sources. We report an improved method in separating them by taking the ratios among different categories of in situ event samples as calibration sources. Data from CDEX-1 and TEXONO experiments are re-examined using the ratio method. Results are shown to be consistent with the spectral shape method.

  12. One-dimensional hole gas in germanium/silicon nanowire heterostructures

    Science.gov (United States)

    Lu, Wei; Xiang, Jie; Timko, Brian P.; Wu, Yue; Lieber, Charles M.

    2005-07-01

    Two-dimensional electron and hole gas systems, enabled through band structure design and epitaxial growth on planar substrates, have served as key platforms for fundamental condensed matter research and high-performance devices. The analogous development of one-dimensional (1D) electron or hole gas systems through controlled growth on 1D nanostructure substrates, which could open up opportunities beyond existing carbon nanotube and nanowire systems, has not been realized. Here, we report the synthesis and transport studies of a 1D hole gas system based on a free-standing germanium/silicon (Ge/Si) core/shell nanowire heterostructure. Room temperature electrical transport measurements clearly show hole accumulation in undoped Ge/Si nanowire heterostructures, in contrast to control experiments on single-component nanowires. Low-temperature studies show well-controlled Coulomb blockade oscillations when the Si shell serves as a tunnel barrier to the hole gas in the Ge channel. Transparent contacts to the hole gas also have been reproducibly achieved by thermal annealing. In such devices, we observe conductance quantization at low temperatures, corresponding to ballistic transport through 1D subbands, where the measured subband energy spacings agree with calculations for a cylindrical confinement potential. In addition, we observe a “0.7 structure,” which has been attributed to spontaneous spin polarization, suggesting the universality of this phenomenon in interacting 1D systems. Lastly, the conductance exhibits little temperature dependence, consistent with our calculation of reduced backscattering in this 1D system, and suggests that transport is ballistic even at room temperature. Author contributions: W.L., J.X., and C.M.L. designed research; W.L. and J.X. performed research; B.P.T. and Y.W. contributed new reagents/analytic tools; W.L., J.X., and C.M.L. analyzed data; W.L., J.X., and C.M.L. wrote the paper; and B.P.T. and Y.W. developed growth of nanowire

  13. Thermal recrystallization of physical vapor deposition based germanium thin films on bulk silicon (100)

    KAUST Repository

    Hussain, Aftab M.

    2013-08-16

    We demonstrate a simple, low-cost, and scalable process for obtaining uniform, smooth surfaced, high quality mono-crystalline germanium (100) thin films on silicon (100). The germanium thin films were deposited on a silicon substrate using plasma-assisted sputtering based physical vapor deposition. They were crystallized by annealing at various temperatures ranging from 700 °C to 1100 °C. We report that the best quality germanium thin films are obtained above the melting point of germanium (937 °C), thus offering a method for in-situ Czochralski process. We show well-behaved high-κ /metal gate metal-oxide-semiconductor capacitors (MOSCAPs) using this film. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Vapor-liquid-solid growth of silicon and silicon germanium nanowires

    Science.gov (United States)

    Nimmatoori, Pramod

    2009-12-01

    Si and Si1-xGex nanowires are promising materials with potential applications in various disciplines of science and technology. Small diameter nanowires can act as model systems to study interesting phenomena such as tunneling that occur in the nanometer regime. Furthermore, technical challenges in fabricating nanoscale size devices from thin films have resulted in interest and research on nanowires. In this perspective, vertical integrated nanowire field effect transistors (VINFETs) fabricated from Si nanowires are promising devices that offer better control on device properties and push the transistor architecture into the third dimension potentially enabling ultra-high transistor density circuits. Transistors fabricated from Si/Si 1-xGex nanowires have also been proposed that can have high carrier mobility. In addition, the Si and Si1-xGe x nanowires have potential to be used in various applications such as sensing, thermoelectrics and solar cells. Despite having considerable potential, the understanding of the vapor-liquid-solid (VLS) mechanism utilized to fabricate these wires is still rudimentary. Hence, the objective of this thesis is to understand the effects of nanoscale size and the role of catalyst that mediates the wire growth on the growth rate of Si and Si1-xGe x nanowires and interfacial abruptness in Si/Si1-xGe x axial heterostructure nanowires. Initially, the growth and structural properties of Si nanowires with tight diameter distribution grown from 10, 20 and 50 nm Au particles dispersed on a polymer-modified substrate was studied. A nanoparticle application process was developed to disperse Au particles on the substrate surface with negligible agglomeration and sufficient density. The growth temperature and SiH4 partial pressure were varied to optimize the growth conditions amenable to VLS growth with smooth wire morphology and negligible Si thin film deposition on wire sidewalls. The Si nanowire growth rate was studied as a function of growth

  15. Strain distribution in single, suspended germanium nanowires studied using nanofocused x-rays

    DEFF Research Database (Denmark)

    Keplinger, Mario; Grifone, Raphael; Greil, Johannes

    2016-01-01

    illumination positions along the nanowire length results in corresponding strain components as well as the nanowire's tilting and bending. By using these findings we determined the complete strain state with the help of finite element modelling. The resulting information provides us with the possibility...... of evaluating the validity of the strain investigations following from Raman scattering experiments which are based on the assumption of purely uniaxial strain....

  16. Atomically abrupt silicon-germanium axial heterostructure nanowires synthesized in a solvent vapor growth system.

    Science.gov (United States)

    Geaney, Hugh; Mullane, Emma; Ramasse, Quentin M; Ryan, Kevin M

    2013-04-10

    The growth of Si/Ge axial heterostructure nanowires in high yield using a versatile wet chemical approach is reported. Heterostructure growth is achieved using the vapor zone of a high boiling point solvent as a reaction medium with an evaporated tin layer as the catalyst. The low solubility of Si and Ge within the Sn catalyst allows the formation of extremely abrupt heterojunctions of the order of just 1-2 atomic planes between the Si and Ge nanowire segments. The compositional abruptness was confirmed using aberration corrected scanning transmission electron microscopy and atomic level electron energy loss spectroscopy. Additional analysis focused on the role of crystallographic defects in determining interfacial abruptness and the preferential incorporation of metal catalyst atoms near twin defects in the nanowires.

  17. Near-Field Imaging of Free Carriers in ZnO Nanowires with a Scanning Probe Tip Made of Heavily Doped Germanium

    Science.gov (United States)

    Sakat, Emilie; Giliberti, Valeria; Bollani, Monica; Notargiacomo, Andrea; Pea, Marialilia; Finazzi, Marco; Pellegrini, Giovanni; Hugonin, Jean-Paul; Weber-Bargioni, Alexander; Melli, Mauro; Sassolini, Simone; Cabrini, Stefano; Biagioni, Paolo; Ortolani, Michele; Baldassarre, Leonetta

    2017-11-01

    A novel scanning probe tip made of heavily doped semiconductor is fabricated and used instead of standard gold-coated tips in infrared scattering-type near-field microscopy. Midinfrared near-field microscopy experiments are conducted on ZnO nanowires with a lateral resolution better than 100 nm, using tips made of heavily electron-doped germanium with a plasma frequency in the midinfrared (plasma wavelength of 9.5 μ m ). Nanowires embedded in a dielectric matrix are imaged at two wavelengths, 11.3 and 8.0 μ m , above and below the plasma wavelength of the tips. An opposite sign of the imaging contrasts between the nanowire and the dielectric matrix is observed at the two infrared wavelengths, indicating a clear role of the free-electron plasma in the heavily doped germanium tip in building the imaging contrast. Electromagnetic simulations with a multispherical dipole model accounting for the finite size of the tip are well consistent with the experiments. By comparison of the simulated and measured imaging contrasts, an estimate for the local free-carrier density in the investigated ZnO nanowires in the low 1019 cm-3 range is retrieved. The results are benchmarked against the scattering intensity and phase maps obtained on the same sample with a gold-coated probe tip in pseudoheterodyne detection mode.

  18. Self-assembled, nanowire network electrodes for depleted bulk heterojunction solar cells

    KAUST Repository

    Lan, Xinzheng

    2013-01-06

    Herein, a solution-processed, bottom-up-fabricated, nanowire network electrode is developed. This electrode features a ZnO template which is converted into locally connected, infiltratable, TiO2 nanowires. This new electrode is used to build a depleted bulk heterojunction solar cell employing hybrid-passivated colloidal quantum dots. The new electrode allows the application of a thicker, and thus more light-absorbing, colloidal quantum dot active layer, from which charge extraction of an efficiency comparable to that obtained from a thinner, planar device could be obtained. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Analysis of InAs-Si heterojunction nanowire tunnel FETs: Extreme confinement vs. bulk

    OpenAIRE

    Carrillo-Nuñez Hamilton; Luisier Mathieu; Schenk Andreas

    2015-01-01

    Abstract Extremely narrow and bulk like p type InAs–Si nanowire \\{TFETs\\} are studied using (i) a full band and atomistic quantum transport simulator based on the sp 3 d 5 s * tight binding model and (ii) a drift–diffusion \\{TCAD\\} tool. As (iii) option a two band model and the \\{WKB\\} approximation have been adapted to work in heterostructures through a careful choice of the imaginary dispersion. It is found that for ultra scaled InAs–Si nanowire TFETs the \\{WKB\\} approximation and the quant...

  20. Silicon-germanium nanowire tunnel-FETs with homo- and heterostructure tunnel junctions

    Science.gov (United States)

    Richter, S.; Blaeser, S.; Knoll, L.; Trellenkamp, S.; Fox, A.; Schäfer, A.; Hartmann, J. M.; Zhao, Q. T.; Mantl, S.

    2014-08-01

    Experimental results on tunneling field-effect transistors (TFETs) based on strained SiGe on SOI nanowire arrays are presented. A heterostructure SiGe/Si TFET with a vertical tunnel junction consisting of an in situ doped SiGe source and a Si channel with a minimum inverse subthreshold slope of 90 mV/dec is demonstrated. An increase in tunneling area results in higher on-current. The in situ doped heterojunction TFET shows great improvement compared to a homojunction SiGe on SOI nanowire design with implanted junctions. Temperature dependent measurements and device simulations are performed in order to analyze the tunnel transport mechanism in the devices.

  1. One-Dimensional Hole Gas in Germanium/Silicon Nanowire Heterostructures

    OpenAIRE

    Lu, Wei; Xiang, Jie; Timko, Brian P.; Wu, Yue; Lieber, Charles M.

    2005-01-01

    Two-dimensional electron and hole gas systems, enabled through band structure design and epitaxial growth on planar substrates, have served as key platforms for fundamental condensed matter research and high-performance devices. The analogous development of one-dimensional (1D) electron or hole gas systems through controlled growth on 1D nanostructure substrates, which could open up opportunities beyond existing carbon nanotube and nanowire systems, has not been realized. Here, we report the ...

  2. Analysis of InAs-Si heterojunction nanowire tunnel FETs: Extreme confinement vs. bulk

    Science.gov (United States)

    Carrillo-Nuñez, Hamilton; Luisier, Mathieu; Schenk, Andreas

    2015-11-01

    Extremely narrow and bulk-like p-type InAs-Si nanowire TFETs are studied using (i) a full-band and atomistic quantum transport simulator based on the sp3d5s∗ tight-binding model and (ii) a drift-diffusion TCAD tool. As (iii) option, a two-band model and the WKB approximation have been adapted to work in heterostructures through a careful choice of the imaginary dispersion. It is found that for ultra-scaled InAs-Si nanowire TFETs, the WKB approximation and the quantum transport results agree very well, suggesting that the former could be applied to larger hetero-TFET structures and considerably reduce the simulation time while keeping a high accuracy.

  3. Strain-induced structural defects and their effects on the electrochemical performances of silicon core/germanium shell nanowire heterostructures.

    Science.gov (United States)

    Lin, Yung-Chen; Kim, Dongheun; Li, Zhen; Nguyen, Binh-Minh; Li, Nan; Zhang, Shixiong; Yoo, Jinkyoung

    2017-01-19

    We report on strain-induced structural defect formation in core Si nanowires of a Si/Ge core/shell nanowire heterostructure and the influence of the structural defects on the electrochemical performances in lithium-ion battery anodes based on Si/Ge core/shell nanowire heterostructures. The induced structural defects consisting of stacking faults and dislocations in the core Si nanowire were observed for the first time. The generation of stacking faults in the Si/Ge core/shell nanowire heterostructure is observed to prefer settling in either only the Ge shell region or in both the Ge shell and Si core regions and is associated with the increase of the shell volume fraction. The relaxation of the misfit strain in the [112] oriented core/shell nanowire heterostructure leads to subsequent gliding of Shockley partial dislocations, preferentially forming the twins. The observation of crossover of defect formation is of great importance for understanding heteroepitaxy in radial heterostructures at the nanoscale and for building three dimensional heterostructures for the various applications. Furthermore, the effect of the defect formation on the nanomaterial's functionality is investigated using electrochemical performance tests. The Si/Ge core/shell nanowire heterostructures enhance the gravimetric capacity of lithium ion battery anodes under fast charging/discharging rates compared to Si nanowires. However, the induced structural defects hamper lithiation of the Si/Ge core/shell nanowire heterostructure.

  4. Effective mass approximation versus full atomistic model to calculate the output characteristics of a gate-all-around germanium nanowire field effect transistor (GAA-GeNW-FET)

    Science.gov (United States)

    Bayani, Amir Hossein; Voves, Jan; Dideban, Daryoosh

    2018-01-01

    Here, we compare the output characteristics of a gate-all-around germanium nanowire field effect transistor (GAA-GeNW-FET) with 2.36 nm2 square cross-section area using tight-binding (TB) sp3d5s∗ model (full atomistic model (FAM)) and effective mass approximation (EMA). Synopsys/QuantumWise Atomistix ToolKit (ATK) and Silvaco Atlas3D are used to consider the TB model and EMA, respectively. Results show that EMA predicted only one quantum state (QS) for quantum transport, whereas FAM predicted three QSs. A cosine function behavior is obtained by both methods for the first quantum state. The calculated bandgap value by EMA is almost twice smaller than that of the FAM. Also, a fluctuating current is predicted by both methods but in different oscillation values.

  5. Fabrication of a Silicon Nanowire on a Bulk Substrate by Use of a Plasma Etching and Total Ionizing Dose Effects on a Gate-All-Around Field-Effect Transistor

    Science.gov (United States)

    Moon, Dong-Il; Han, Jin-Woo; Meyyappan, Meyya

    2016-01-01

    The gate all around transistor is investigated through experiment. The suspended silicon nanowire for the next generation is fabricated on bulk substrate by plasma etching method. The scallop pattern generated by Bosch process is utilized to form a floating silicon nanowire. By combining anisotropic and istropic silicon etch process, the shape of nanowire is accurately controlled. From the suspended nanowire, the gate all around transistor is demonstrated. As the silicon nanowire is fully surrounded by the gate, the device shows excellent electrostatic characteristics.

  6. Separation and purification of no-carrier-added arsenic from bulk amounts of germanium for use in radiopharmaceutical labelling

    Energy Technology Data Exchange (ETDEWEB)

    Jahn, M.; Radchenko, V.; Roesch, F.; Jennewein, M. [Mainz Univ. (Germany). Inst. of Nuclear Chemsistry; Filosofov, D. [Joint Inst. for Nuclear Research, Dubna (Russian Federation). Lab. of Nuclear Problems; Hauser, H.; Eisenhut, M. [Deutsches Krebsforschungszentrum, Heidelberg (Germany). Radiopharmaceutical Chemistry

    2010-07-01

    Radioarsenic labelled radiopharmaceuticals could add special features to molecular imaging with positron emission tomography (PET). For example the long physical half-lives of {sup 72}As (T{sub 1/2}=26 h) and {sup 74}As (T{sub 1/2}=17.8 d) in conjunction with their high positron branching rates of 88% and 29%, respectively, allow the investigation of slow physiological or metabolical processes, like the enrichment and biodistribution of monoclonal antibodies in tumour tissue or the characterization of stem cell trafficking. A method for separation and purification of no-carrier-added (nca) arsenic from irradiated metallic germanium targets based on distillation and anion exchange is developed. It finally converts the arsenic into an {sup *}As(III) synthon in PBS buffer and pH 7 suitable for labelling of proteins via As-S bond formations. The method delivers radioarsenic in high purity with separation factors of 10{sup 6} from germanium and an overall yield from target to labelling synthon of > 40%. In a proof-of-principle experiment, the monoclonal antibody Bevacizumab, directed against the human VEGF receptor, was labelled with a radiochemical yield > 90% within 1 h at room temperature with nca {sup 72/74/77}As. (orig.)

  7. Ab initio study of point defects in PbSe and PbTe: Bulk and nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Wrasse, E. O. [Instituto de Física, Universidade Federal de Uberlândia, 38408-100, Uberlândia, MG, Brazil and Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS (Brazil); Venezuela, P. [Instituto de Física, Universidade Federal Fluminense, 24210-346, Niteroi, RJ (Brazil); Baierle, R. J., E-mail: rbaierle@smail.ufsm.br [Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS (Brazil)

    2014-11-14

    First principles investigations, within the spin-polarized density functional theory, are performed to study energetic stability and electronic properties of point defects (vacancies and antisites) in PbSe and PbTe: bulk and nanowire (NW). Our results show that the energetic stability of these defects is ruled by relaxation process. These defects have lower formation energies in the nanowire structures as compared to the bulk, being more stable in the surface of the NWs. We also show that in the bulk system only one charge state is stable, otherwise, due to the larger band gaps, more than one charge state may be stable in the NWs. In addition, we have investigated how the presence of intrinsic defects affects the electronic properties of bulk and NW systems. Vacancies give rise to new electronic states near to the edges of the valence and conduction bands while the energetic position of the electronic states from antisites depends on the charge state, being localized inside the band gap or near the edges of the valence or conduction bands. We discuss how these changes in the electronic properties due to intrinsic defects may affect the thermoelectric properties of PbSe and PbTe NWs.

  8. Transfer-less flexible and transparent high-κ/metal gate germanium devices on bulk silicon (100)

    KAUST Repository

    Nassar, Joanna M.

    2014-08-01

    Flexible wearable electronics have been of great interest lately for the development of innovative future technology for various interactive applications in the field of consumer electronics and advanced healthcare, offering the promise of low-cost, lightweight, and multifunctionality. In the pursuit of this trend, high mobility channel materials need to be investigated on a flexible platform, for the development of flexible high performance devices. Germanium (Ge) is one of the most attractive alternatives for silicon (Si) for high-speed computational applications, due its higher hole and electron mobility. Thus, in this work we show a cost effective CMOS compatible process for transforming conventional rigid Ge metal oxide semiconductor capacitors (MOSCAPS) into a mechanically flexible and semi-transparent platform. Devices exhibit outstanding bendability with a bending radius of 0.24 cm, and semi-transparency up to 30 %, varying with respect to the diameter size of the release holes array.

  9. Decoupling single nanowire mobilities limited by surface scattering and bulk impurity scattering

    International Nuclear Information System (INIS)

    Khanal, D. R.; Levander, A. X.; Wu, J.; Yu, K. M.; Liliental-Weber, Z.; Walukiewicz, W.; Grandal, J.; Sanchez-Garcia, M. A.; Calleja, E.

    2011-01-01

    We demonstrate the isolation of two free carrier scattering mechanisms as a function of radial band bending in InN nanowires via universal mobility analysis, where effective carrier mobility is measured as a function of effective electric field in a nanowire field-effect transistor. Our results show that Coulomb scattering limits effective mobility at most effective fields, while surface roughness scattering only limits mobility under very high internal electric fields. High-energy α particle irradiation is used to vary the ionized donor concentration, and the observed decrease in mobility and increase in donor concentration are compared to Hall effect results of high-quality InN thin films. Our results show that for nanowires with relatively high doping and large diameters, controlling Coulomb scattering from ionized dopants should be given precedence over surface engineering when seeking to maximize nanowire mobility.

  10. Enhanced thermoelectric properties in bulk nanowire heterostructure-based nanocomposites through minority carrier blocking.

    Science.gov (United States)

    Yang, Haoran; Bahk, Je-Hyeong; Day, Tristan; Mohammed, Amr M S; Snyder, G Jeffrey; Shakouri, Ali; Wu, Yue

    2015-02-11

    To design superior thermoelectric materials the minority carrier blocking effect in which the unwanted bipolar transport is prevented by the interfacial energy barriers in the heterogeneous nanostructures has been theoretically proposed recently. The theory predicts an enhanced power factor and a reduced bipolar thermal conductivity for materials with a relatively low doping level, which could lead to an improvement in the thermoelectric figure of merit (ZT). Here we show the first experimental demonstration of the minority carrier blocking in lead telluride-silver telluride (PbTe-Ag2Te) nanowire heterostructure-based nanocomposites. The nanocomposites are made by sintering PbTe-Ag2Te nanowire heterostructures produced in a highly scalable solution-phase synthesis. Compared with Ag2Te nanowire-based nanocomposite produced in similar method, the PbTe-Ag2Te nanocomposite containing ∼5 atomic % PbTe exhibits enhanced Seebeck coefficient, reduced thermal conductivity, and ∼40% improved ZT, which can be well explained by the theoretical modeling based on the Boltzmann transport equations when energy barriers for both electrons and holes at the heterostructure interfaces are considered in the calculations. For this p-type PbTe-Ag2Te nanocomposite, the barriers for electrons, that is, minority carriers, are primarily responsible for the ZT enhancement. By extending this approach to other nanostructured systems, it represents a key step toward low-cost solution-processable nanomaterials without heavy doping level for high-performance thermoelectric energy harvesting.

  11. Tunable conductivity in mesoporous germanium

    Science.gov (United States)

    Beattie, Meghan N.; Bioud, Youcef A.; Hobson, David G.; Boucherif, Abderraouf; Valdivia, Christopher E.; Drouin, Dominique; Arès, Richard; Hinzer, Karin

    2018-05-01

    Germanium-based nanostructures have attracted increasing attention due to favourable electrical and optical properties, which are tunable on the nanoscale. High densities of germanium nanocrystals are synthesized via electrochemical etching, making porous germanium an appealing nanostructured material for a variety of applications. In this work, we have demonstrated highly tunable electrical conductivity in mesoporous germanium layers by conducting a systematic study varying crystallite size using thermal annealing, with experimental conductivities ranging from 0.6 to 33 (×10‑3) Ω‑1 cm‑1. The conductivity of as-prepared mesoporous germanium with 70% porosity and crystallite size between 4 and 10 nm is shown to be ∼0.9 × 10‑3 Ω‑1 cm‑1, 5 orders of magnitude smaller than that of bulk p-type germanium. Thermal annealing for 10 min at 400 °C further reduced the conductivity; however, annealing at 450 °C caused a morphological transformation from columnar crystallites to interconnecting granular crystallites and an increase in conductivity by two orders of magnitude relative to as-prepared mesoporous germanium caused by reduced influence of surface states. We developed an electrostatic model relating the carrier concentration and mobility of p-type mesoporous germanium to the nanoscale morphology. Correlation within an order of magnitude was found between modelled and experimental conductivities, limited by variation in sample uniformity and uncertainty in void size and fraction after annealing. Furthermore, theoretical results suggest that mesoporous germanium conductivity could be tuned over four orders of magnitude, leading to optimized hybrid devices.

  12. Equivalence of the equilibrium and the nonequilibrium molecular dynamics methods for thermal conductivity calculations: From bulk to nanowire silicon

    Science.gov (United States)

    Dong, Haikuan; Fan, Zheyong; Shi, Libin; Harju, Ari; Ala-Nissila, Tapio

    2018-03-01

    Molecular dynamics (MD) simulations play an important role in studying heat transport in complex materials. The lattice thermal conductivity can be computed either using the Green-Kubo formula in equilibrium MD (EMD) simulations or using Fourier's law in nonequilibrium MD (NEMD) simulations. These two methods have not been systematically compared for materials with different dimensions and inconsistencies between them have been occasionally reported in the literature. Here we give an in-depth comparison of them in terms of heat transport in three allotropes of Si: three-dimensional bulk silicon, two-dimensional silicene, and quasi-one-dimensional silicon nanowire. By multiplying the correlation time in the Green-Kubo formula with an appropriate effective group velocity, we can express the running thermal conductivity in the EMD method as a function of an effective length and directly compare it to the length-dependent thermal conductivity in the NEMD method. We find that the two methods quantitatively agree with each other for all the systems studied, firmly establishing their equivalence in computing thermal conductivity.

  13. Electronic transport through Si nanowires: Role of bulk and surface disorder

    DEFF Research Database (Denmark)

    Markussen, Troels; Rurali, R.; Brandbyge, Mads

    2006-01-01

    on the situation a preferable method can be identified. Several numerical results are presented to illustrate the relative merits of the two methods. Our calculations of relaxed atomic structures and their conductance properties are based on density functional theory without introducing adjustable parameters. Two...... specific models of disorder are considered: Unpassivated, surface reconstructed SiNW's are perturbed by random on-site (Anderson) disorder whereas defects in hydrogen passivated wires are introduced by randomly removed H atoms. The unpassivated wires are very sensitive to disorder in the surface whereas...... bulk disorder has almost no influence. For the passivated wires, the scattering by the hydrogen vacancies is strongly energy dependent and for relatively long SiNW's (L > 200 nm) the resistance changes from the Ohmic to the localization regime within a 0.1-eV shift of the Fermi energy. This high...

  14. Proton beam simulation with MCNPX/CINDER'90: Germanium metal activation estimates below 30MeV relevant to the bulk production of arsenic radioisotopes.

    Science.gov (United States)

    Fassbender, M; Taylor, W; Vieira, D; Nortier, M; Bach, H; John, K

    2012-01-01

    Germanium metal targets encapsulated in Nb shells were irradiated in a proton beam. Proton and secondary neutron beam fluences as well as radionuclide activity formation were modeled using MCNPX in combination with CINDER90. Targets were chemically processed using distillation and anion exchange. Good agreement between the measured radiochemical yields and MCNPX/CINDER90 estimates was observed. A target of pentavalent (73,74)As radioarsenic for neutron activation studies was prepared. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. Semiconductor nanowires and templates for electronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Ying, Xiang

    2009-07-15

    This thesis starts by developing a platform for the organized growth of nanowires directly on a planar substrate. For this, a method to fabricate horizontal porous alumina membranes is studied. The second part of the thesis focuses on the study of nanowires. It starts by the understanding of the growth mechanisms of germanium nanowires and follows by the structural and electrical properties at the single nanowire level. Horizontally aligned porous anodic alumina (PAA) was used as a template for the nanowire synthesis. Three PAA arrangements were studied: - high density membranes - micron-sized fingers - multi-contacts Membranes formed by a high density of nanopores were obtained by anodizing aluminum thin films. Metallic and semiconducting nanowires were synthesized into the PAA structures via DC deposition, pulsed electro-depostion and CVD growth. The presence of gold, copper, indium, nickel, tellurium, and silicon nanowires inside PAA templates was verified by SEM and EDX analysis. Further, room-temperature transport measurements showed that the pores are completely filled till the bottom of the pores. In this dissertation, single crystalline and core-shell germanium nanowires are synthesized using indium and bismuth as catalyst in a chemical vapor deposition procedure with germane (GeH{sub 4}) as growth precursor. A systematic growth study has been performed to obtain high aspect-ratio germanium nanowires. The influence of the growth conditions on the final morphology and the crystalline structure has been determined via scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). In the case of indium catalyzed germanium nanowires, two different structures were identified: single crystalline and crystalline core-amorphous shell. The preferential growth axis of both kinds of nanowires is along the [110] direction. The occurrence of the two morphologies was found to only depend on the nanowire dimension. In the case of bismuth

  16. Facile Formation of High-quality InGaN/GaN Quantum-disks-in-Nanowires on Bulk-Metal Substrates for High-power Light-emitters

    KAUST Repository

    Zhao, Chao

    2016-01-08

    High-quality nitride materials grown on scalable and low-cost metallic substrates are considerably attractive for high-power light emitters. We demonstrate here, for the first time, the high-power red (705 nm) InGaN/GaN quantum-disks (Qdisks)-in-nanowire light-emitting diodes (LEDs) self-assembled directly on metal-substrate. The LEDs exhibited a low turn-on voltage of ~2 V without efficiency droop up to injection current of 500 mA (1.6 kA/cm2) at ~5 V. This is achieved through the direct growth and optimization of high-quality nanowires on titanium (Ti) coated bulk polycrystalline-molybdenum (Mo) substrates. We performed extensive studies on the growth mechanisms, obtained high-crystal-quality nanowires, and confirmed the epitaxial relationship between the cubic titanium nitride (TiN) transition layer and the hexagonal nanowires. The growth of nanowires on all-metal stack of TiN/Ti/Mo enables simultaneous implementation of n-metal contact, reflector and heat-sink, which greatly simplifies the fabrication process of high-power light emitters. Our work ushers in a practical platform for high-power nanowires light emitters, providing versatile solutions for multiple cross-disciplinary applications that are greatly enhanced by leveraging on the chemical stability of nitride materials, large specific surface of nanowires, chemical lift-off ready layer structures, and reusable Mo substrates.

  17. Nanowire Photovoltaic Devices

    Science.gov (United States)

    Forbes, David

    2015-01-01

    Firefly Technologies, in collaboration with the Rochester Institute of Technology and the University of Wisconsin-Madison, developed synthesis methods for highly strained nanowires. Two synthesis routes resulted in successful nanowire epitaxy: direct nucleation and growth on the substrate and a novel selective-epitaxy route based on nanolithography using diblock copolymers. The indium-arsenide (InAs) nanowires are implemented in situ within the epitaxy environment-a significant innovation relative to conventional semiconductor nanowire generation using ex situ gold nanoparticles. The introduction of these nanoscale features may enable an intermediate band solar cell while simultaneously increasing the effective absorption volume that can otherwise limit short-circuit current generated by thin quantized layers. The use of nanowires for photovoltaics decouples the absorption process from the current extraction process by virtue of the high aspect ratio. While no functional solar cells resulted from this effort, considerable fundamental understanding of the nanowire epitaxy kinetics and nanopatterning process was developed. This approach could, in principle, be an enabling technology for heterointegration of dissimilar materials. The technology also is applicable to virtual substrates. Incorporating nanowires onto a recrystallized germanium/metal foil substrate would potentially solve the problem of grain boundary shunting of generated carriers by restricting the cross-sectional area of the nanowire (tens of nanometers in diameter) to sizes smaller than the recrystallized grains (0.5 to 1 micron(exp 2).

  18. Enhancement of short-circuit current density in polymer bulk heterojunction solar cells comprising plasmonic silver nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yuzhao; Lin, Xiaofeng; Ou, Jiemei; Chen, Xudong, E-mail: cescxd@mail.sysu.edu.cn, E-mail: stszx@mail.sysu.edu.cn, E-mail: chenyj69@mail.sysu.edu.cn [Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education of China, Sun Yat-sen University, Guangzhou 510275 (China); Qing, Jian; Zhong, Zhenfeng; Zhou, Xiang, E-mail: cescxd@mail.sysu.edu.cn, E-mail: stszx@mail.sysu.edu.cn, E-mail: chenyj69@mail.sysu.edu.cn; Chen, Yujie, E-mail: cescxd@mail.sysu.edu.cn, E-mail: stszx@mail.sysu.edu.cn, E-mail: chenyj69@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Hu, Chenglong [Key Laboratory of Optoelectronic Chemical Materials and Devices of Ministry of Education, Jianghan University, Wuhan 430056 (China)

    2014-03-24

    We demonstrate that the influence of plasmonic effects based on silver nanowires (Ag NWs) on the characteristics of polymer solar cells (PSCs). The solution-processed Ag NWs are situated at the interface of anode buffer layer and active layer, which could enhance the performance especially the photocurrent of PSCs by scattering, localized surface plasmon resonance, and surface plasmon polaritons. Plasmonic effects are confirmed by the enhancement of extinction spectra, external quantum efficiency, and steady state photoluminescence. Consequently, the short-circuit current density (J{sub sc}) and power conversion efficiency enhance about 24% and 18%, respectively, under AM1.5 illumination when Ag NWs plasmonic nanostructure incorporated into PSCs.

  19. [Respective determination of inorganic germanium and germanium-132 in foods].

    Science.gov (United States)

    Chen, Q; Yang, H

    1998-02-01

    Inorganic germanium and carboxyethyl germanium sesquioxide (germanium-132) in health drinks were respectively determined by hydride generation-atomic fluorescence spectrometry (HG-AFS). The conditions of respective determination of inorganic germanium and germanium-132 in natural foods were preliminarily discussed.

  20. Solution synthesis of germanium nanocrystals

    Science.gov (United States)

    Gerung, Henry [Albuquerque, NM; Boyle, Timothy J [Kensington, MD; Bunge, Scott D [Cuyahoga Falls, OH

    2009-09-22

    A method for providing a route for the synthesis of a Ge(0) nanometer-sized material from. A Ge(II) precursor is dissolved in a ligand heated to a temperature, generally between approximately 100.degree. C. and 400.degree. C., sufficient to thermally reduce the Ge(II) to Ge(0), where the ligand is a compound that can bond to the surface of the germanium nanomaterials to subsequently prevent agglomeration of the nanomaterials. The ligand encapsulates the surface of the Ge(0) material to prevent agglomeration. The resulting solution is cooled for handling, with the cooling characteristics useful in controlling the size and size distribution of the Ge(0) materials. The characteristics of the Ge(II) precursor determine whether the Ge(0) materials that result will be nanocrystals or nanowires.

  1. Hazard assessment of germanium supplements.

    Science.gov (United States)

    Tao, S H; Bolger, P M

    1997-06-01

    Germanium-containing dietary supplements became popular in the 1970s in Japan and later in other countries, as elixirs for certain diseases (e.g., cancer and AIDS). Germanium is not an essential element. Its acute toxicity is low. However, at least 31 reported human cases linked prolonged intake of germanium products with renal failure and even death. Signs of kidney dysfunction, kidney tubular degeneration, and germanium accumulation were observed. Other adverse effects were anemia, muscle weakness, and peripheral neuropathy. Recovery of renal function is slow and incomplete even long after germanium intake was stopped. The total dose of ingested germanium (as dioxide, carboxyethyl germanium sesquioxide, germanium-lactate-citrate, or unspecified forms) varied from 15 to over 300 g; the exposure duration varied from 2 to 36 months. In laboratory animals, elevated germanium in tissues and impaired kidney and liver function were observed in a life-time drinking water (5 ppm germanium) study. Other toxicities associated with ingested germanium products in human cases were also demonstrated in animal studies with germanium dioxide and sometimes other germanium compounds. Based on the evidence of persistent renal toxicity associated with germanium dioxide, the lack of conclusive findings of differential nephrotoxicity of organic germanium compounds, and the possibility of contamination of the organic germanium products with inorganic germanium, it is clear that germanium products present a potential human health hazard.

  2. Near-infrared emission from mesoporous crystalline germanium

    Energy Technology Data Exchange (ETDEWEB)

    Boucherif, Abderraouf; Aimez, Vincent; Arès, Richard, E-mail: richard.ares@usherbrooke.ca [Institut Interdisciplinaire d’Innovation Technologique (3IT), Université de Sherbrooke, 3000 Boulevard Université, Sherbrooke, J1K OA5, Québec (Canada); Laboratoire Nanotechnologies Nanosystèmes (LN2)-CNRS UMI-3463, Université de Sherbrooke, 3000 Boulevard Université, Sherbrooke, J1K OA5, Québec (Canada); Korinek, Andreas [Canadian Centre for Electron Microscopy, Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada)

    2014-10-15

    Mesoporous crystalline germanium was fabricated by bipolar electrochemical etching of Ge wafer in HF-based electrolyte. It yields uniform mesoporous germanium layers composed of high density of crystallites with an average size 5-7 nm. Subsequent extended chemical etching allows tuning of crystallites size while preserving the same chemical composition. This highly controllable nanostructure exhibits photoluminescence emission above the bulk Ge bandgap, in the near-infrared range (1095-1360nm) with strong evidence of quantum confinement within the crystallites.

  3. Impact of screw and edge dislocations on the thermal conductivity of individual nanowires and bulk GaN: a molecular dynamics study.

    Science.gov (United States)

    Termentzidis, Konstantinos; Isaiev, Mykola; Salnikova, Anastasiia; Belabbas, Imad; Lacroix, David; Kioseoglou, Joseph

    2018-02-14

    We report the thermal transport properties of wurtzite GaN in the presence of dislocations using molecular dynamics simulations. A variety of isolated dislocations in a nanowire configuration are analyzed and found to considerably reduce the thermal conductivity while impacting its temperature dependence in a different manner. Isolated screw dislocations reduce the thermal conductivity by a factor of two, while the influence of edge dislocations is less pronounced. The relative reduction of thermal conductivity is correlated with the strain energy of each of the five studied types of dislocations and the nature of the bonds around the dislocation core. The temperature dependence of the thermal conductivity follows a physical law described by a T -1 variation in combination with an exponent factor that depends on the material's nature, type and the structural characteristics of the dislocation core. Furthermore, the impact of the dislocation density on the thermal conductivity of bulk GaN is examined. The variation and absolute values of the total thermal conductivity as a function of the dislocation density are similar for defected systems with both screw and edge dislocations. Nevertheless, we reveal that the thermal conductivity tensors along the parallel and perpendicular directions to the dislocation lines are different. The discrepancy of the anisotropy of the thermal conductivity grows with increasing density of dislocations and it is more pronounced for the systems with edge dislocations. Besides the fundamental insights of the presented results, these could also be used for the identification of the type of dislocations when one experimentally obtains the evolution of thermal conductivity with temperature since each type of dislocation has a different signature, or one could extract the density of dislocations with a simple measurement of thermal anisotropy.

  4. Technology CAD for germanium CMOS circuit

    Energy Technology Data Exchange (ETDEWEB)

    Saha, A.R. [Department of Electronics and ECE, IIT Kharagpur, Kharagpur-721302 (India)]. E-mail: ars.iitkgp@gmail.com; Maiti, C.K. [Department of Electronics and ECE, IIT Kharagpur, Kharagpur-721302 (India)

    2006-12-15

    Process simulation for germanium MOSFETs (Ge-MOSFETs) has been performed in 2D SILVACO virtual wafer fabrication (VWF) suite towards the technology CAD for Ge-CMOS process development. Material parameters and mobility models for Germanium were incorporated in simulation via C-interpreter function. We also report on the device design issues along with the DC and RF characterization of the bulk Ge-MOSFETs, AC parameter extraction and circuit simulation of Ge-CMOS. Simulation results are compared with bulk-Si devices. Simulations predict a cut-off frequency, f {sub T} of about 175 GHz for Ge-MOSFETs compared to 70 GHz for a similar gate-length Si MOSFET. For a single stage Ge-CMOS inverter circuit, a GATE delay of 0.6 ns is predicted.

  5. Technology CAD for germanium CMOS circuit

    International Nuclear Information System (INIS)

    Saha, A.R.; Maiti, C.K.

    2006-01-01

    Process simulation for germanium MOSFETs (Ge-MOSFETs) has been performed in 2D SILVACO virtual wafer fabrication (VWF) suite towards the technology CAD for Ge-CMOS process development. Material parameters and mobility models for Germanium were incorporated in simulation via C-interpreter function. We also report on the device design issues along with the DC and RF characterization of the bulk Ge-MOSFETs, AC parameter extraction and circuit simulation of Ge-CMOS. Simulation results are compared with bulk-Si devices. Simulations predict a cut-off frequency, f T of about 175 GHz for Ge-MOSFETs compared to 70 GHz for a similar gate-length Si MOSFET. For a single stage Ge-CMOS inverter circuit, a GATE delay of 0.6 ns is predicted

  6. The germination of germanium

    Science.gov (United States)

    Burdette, Shawn C.; Thornton, Brett F.

    2018-02-01

    Shawn C. Burdette and Brett F. Thornton explore how germanium developed from a missing element in Mendeleev's periodic table to an enabler for the information age, while retaining a nomenclature oddity.

  7. Germanium and indium

    Science.gov (United States)

    Shanks, W.C. Pat; Kimball, Bryn E.; Tolcin, Amy C.; Guberman, David E.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    Germanium and indium are two important elements used in electronics devices, flat-panel display screens, light-emitting diodes, night vision devices, optical fiber, optical lens systems, and solar power arrays. Germanium and indium are treated together in this chapter because they have similar technological uses and because both are recovered as byproducts, mainly from copper and zinc sulfides.The world’s total production of germanium in 2011 was estimated to be 118 metric tons. This total comprised germanium recovered from zinc concentrates, from fly ash residues from coal burning, and from recycled material. Worldwide, primary germanium was recovered in Canada from zinc concentrates shipped from the United States; in China from zinc residues and coal from multiple sources in China and elsewhere; in Finland from zinc concentrates from the Democratic Republic of the Congo; and in Russia from coal.World production of indium metal was estimated to be about 723 metric tons in 2011; more than one-half of the total was produced in China. Other leading producers included Belgium, Canada, Japan, and the Republic of Korea. These five countries accounted for nearly 95 percent of primary indium production.Deposit types that contain significant amounts of germanium include volcanogenic massive sulfide (VMS) deposits, sedimentary exhalative (SEDEX) deposits, Mississippi Valley-type (MVT) lead-zinc deposits (including Irish-type zinc-lead deposits), Kipushi-type zinc-lead-copper replacement bodies in carbonate rocks, and coal deposits.More than one-half of the byproduct indium in the world is produced in southern China from VMS and SEDEX deposits, and much of the remainder is produced from zinc concentrates from MVT deposits. The Laochang deposit in Yunnan Province, China, and the VMS deposits of the Murchison greenstone belt in Limpopo Province, South Africa, provide excellent examples of indium-enriched deposits. The SEDEX deposits at Bainiuchang, China (located in

  8. Lattice dislocation in Si nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Omar, M.S., E-mail: dr_m_s_omar@yahoo.co [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq); Taha, H.T. [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq)

    2009-12-15

    Modified formulas were used to calculate lattice thermal expansion, specific heat and Bulk modulus for Si nanowires with diameters of 115, 56, 37 and 22 nm. From these values and Gruneisen parameter taken from reference, mean lattice volumes were found to be as 20.03 A{sup 3} for the bulk and 23.63, 29.91, 34.69 and 40.46 A{sup 3} for Si nanowire diameters mentioned above, respectively. Their mean bonding length was calculated to be as 0.235 nm for the bulk and 0.248, 0.269, 0.282 and 0.297 nm for the nanowires diameter mentioned above, respectively. By dividing the nanowires diameter on the mean bonding length, number of layers per each nanowire size was found to be as 230, 104, 65 and 37 for the diameters mentioned above, respectively. Lattice dislocations in 22 nm diameter wire were found to be from 0.00324 nm for the 1st central lattice to 0.2579 nm for the last surface lattice. Such dislocation was smaller for larger wire diameters. Dislocation concentration found to change in Si nanowires according to the proportionalities of surface thickness to nanowire radius ratios.

  9. Calibration of germanium detectors

    International Nuclear Information System (INIS)

    Bjurman, B.; Erlandsson, B.

    1985-01-01

    This paper describes problems concerning the calibration of germanium detectors for the measurement of gamma-radiation from environmental samples. It also contains a brief description of some ways of reducing the uncertainties concerning the activity determination. These uncertainties have many sources, such as counting statistics, full energy peak efficiency determination, density correction and radionuclide specific-coincidence effects, when environmental samples are investigated at close source-to-detector distances

  10. Hafnium germanium telluride

    Science.gov (United States)

    Jang, Gyung-Joo; Yun, Hoseop

    2008-01-01

    The title hafnium germanium telluride, HfGeTe4, has been synthesized by the use of a halide flux and structurally characterized by X-ray diffraction. HfGeTe4 is isostructural with stoichiometric ZrGeTe4 and the Hf site in this compound is also fully occupied. The crystal structure of HfGeTe4 adopts a two-dimensional layered structure, each layer being composed of two unique one-dimensional chains of face-sharing Hf-centered bicapped trigonal prisms and corner-sharing Ge-centered tetra­hedra. These layers stack on top of each other to complete the three-dimensional structure with undulating van der Waals gaps. PMID:21202163

  11. Hafnium germanium telluride

    Directory of Open Access Journals (Sweden)

    Hoseop Yun

    2008-05-01

    Full Text Available The title hafnium germanium telluride, HfGeTe4, has been synthesized by the use of a halide flux and structurally characterized by X-ray diffraction. HfGeTe4 is isostructural with stoichiometric ZrGeTe4 and the Hf site in this compound is also fully occupied. The crystal structure of HfGeTe4 adopts a two-dimensional layered structure, each layer being composed of two unique one-dimensional chains of face-sharing Hf-centered bicapped trigonal prisms and corner-sharing Ge-centered tetrahedra. These layers stack on top of each other to complete the three-dimensional structure with undulating van der Waals gaps.

  12. Nitrogen in germanium

    Science.gov (United States)

    Chambouleyron, I.; Zanatta, A. R.

    1998-07-01

    The known properties of nitrogen as an impurity in, and as an alloy element of, the germanium network are reviewed in this article. Amorphous and crystalline germanium-nitrogen alloys are interesting materials with potential applications for protective coatings and window layers for solar conversion devices. They may also act as effective diffusion masks for III-V electronic devices. The existing data are compared with similar properties of other group IV nitrides, in particular with silicon nitride. To a certain extent, the general picture mirrors the one found in Si-N systems, as expected from the similar valence structure of both elemental semiconductors. However, important differences appear in the deposition methods and alloy composition, the optical properties of as grown films, and the electrical behavior of nitrogen-doped amorphous layers. Structural studies are reviewed, including band structure calculations and the energies of nitrogen-related defects, which are compared with experimental data. Many important aspects of the electronic structure of Ge-N alloys are not yet completely understood and deserve a more careful investigation, in particular the structure of defects associated with N inclusion. The N doping of the a-Ge:H network appears to be very effective, the activation energy of the most effectively doped samples becoming around 120 meV. This is not the case with N-doped a-Si:H, the reasons for the difference remaining an open question. The lack of data on stoichiometric β-Ge3N4 prevents any reasonable assessment on the possible uses of the alloy in electronic and ceramic applications.

  13. Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, Frank; Schiek, Manuela; Al-Shamery, Katharina

    Single crystalline nanowires from fluorescing organic molecules like para-phenylenes or thiophenes are supposed to become key elements in future integrated optoelectronic devices [1]. For a sophisticated design of devices based on nanowires the basic principles of the nanowire formation have...... to be well understood [2]. Nanowires from para-phenylenes, from ®-thiophenes, and from phenylene/thiophene co-oligomers, Fig. 1, are investigated exemplarily. Epitaxy and electrostatic interactions determine the microscopic growth mechanism, whereas kinetics ascertains the macroscopic habit. Results from...

  14. Optical properties of Germanium nanoparticles synthesized by pulsed laser ablation in acetone

    Directory of Open Access Journals (Sweden)

    Saikiran eVadavalli

    2014-10-01

    Full Text Available Germanium (Ge nanoparticles (NPs are synthesized by means of pulsed laser ablation of bulk germanium target immersed in acetone with ns laser pulses at different pulse energies. The fabricated NPs are characterized by employing different techniques such as UV-visible absorption spectroscopy, photoluminescence, micro-Raman spectroscopy, transmission electron microscopy (TEM and field emission scanning electron microscopy (FESEM. The mean size of the Ge NPs is found to vary from few nm to 40 nm with the increase in laser pulse energy. Shift in the position of the absorption spectra is observed and also the photoluminescence peak shift is observed due to quantum confinement effects. High resolution TEM combined with micro-Raman spectroscopy confirms the crystalline nature of the generated germanium nanoparticles. The formation of various sizes of germanium NPs at different laser pulse energies is evident from the asymmetry in the Raman spectra and the shift in its peak position towards the lower wavenumber side. The FESEM micrographs confirm the formation of germanium micro/nanostructures at the laser ablated position of the bulk germanium. In particular, the measured NP sizes from the micro-Raman phonon quantum confinement model are found in good agreement with TEM measurements of Ge NPs.

  15. [Effects of Germanium Concentrations on Germanium Accumulation and Biotransformation of Polysaccarified Germanium in Cordyceps militaris].

    Science.gov (United States)

    Wang, Ju-feng; Li, Hu-ming; Yang, Dao-de

    2015-11-01

    To study the effects of Germanium (Ge) concentration on Ge accumulation and biotransformation of polysaccarified Ge (PG) in Cordyceps militaris. Solid and liquid culture were used in this study. In the solid culture conditions, when the Ge concentration of medium was 200 mg/L, the sporophore biomass of Cordyceps militaris was the maximum; and when Ge concentration was 300 mg/L,the amount of biotransformation of PG in sporophore was the highest; and when the Ge concentration is 250 mg/L, conversion rate of organic germanium (OG) in sporophore reached the highest value. In the liquid culture conditions, when the Ge concentration was 250 mg/L, the mycelium biomass of Cordyceps militaris was the maximum; and when Ge concentration was 150 mg/L, the amount of organic conversion of PG in mycelium was the most; and conversion rate of OG in mycelium was the highest in media with the Ge concentration of 200 mg/L. This study showed the germanium concentrations in 150 - 300 mg/L was more suitable for Ge accumulation and biotransformation of PG in Cordyceps militaris. In general, the biotransformation capacity to germanium of sporophore was stronger than that of mycelium of Cordyceps militaris. Germanium can significantly affect Ge accumulation and biotransformation of PG in Cordyceps militaris (P Cordyceps militaris.

  16. Superconductive silicon nanowires using gallium beam lithography.

    Energy Technology Data Exchange (ETDEWEB)

    Henry, Michael David; Jarecki, Robert Leo,

    2014-01-01

    This work was an early career LDRD investigating the idea of using a focused ion beam (FIB) to implant Ga into silicon to create embedded nanowires and/or fully suspended nanowires. The embedded Ga nanowires demonstrated electrical resistivity of 5 m-cm, conductivity down to 4 K, and acts as an Ohmic silicon contact. The suspended nanowires achieved dimensions down to 20 nm x 30 nm x 10 m with large sensitivity to pressure. These structures then performed well as Pirani gauges. Sputtered niobium was also developed in this research for use as a superconductive coating on the nanowire. Oxidation characteristics of Nb were detailed and a technique to place the Nb under tensile stress resulted in the Nb resisting bulk atmospheric oxidation for up to years.

  17. Carrier multiplication in germanium nanocrystals

    NARCIS (Netherlands)

    Saeed, S.; de Weerd, C.; Stallinga, P.; Spoor, F.C.M.; Houtepen, A.J.; Siebbeles, L.D.A.; Gregorkiewicz, T.

    2015-01-01

    Carrier multiplication is demonstrated in a solid-state dispersion of germanium nanocrystals in a silicon-dioxide matrix. This is performed by comparing ultrafast photo-induced absorption transients at different pump photon energies below and above the threshold energy for this process. The average

  18. Failure mechanisms and electromechanical coupling in semiconducting nanowires

    Directory of Open Access Journals (Sweden)

    Peng B.

    2010-06-01

    Full Text Available One dimensional nanostructures, like nanowires and nanotubes, are increasingly being researched for the development of next generation devices like logic gates, transistors, and solar cells. In particular, semiconducting nanowires with a nonsymmetric wurtzitic crystal structure, such as zinc oxide (ZnO and gallium nitride (GaN, have drawn immense research interests due to their electromechanical coupling. The designing of the future nanowire-based devices requires component-level characterization of individual nanowires. In this paper, we present a unique experimental set-up to characterize the mechanical and electromechanical behaviour of individual nanowires. Using this set-up and complementary atomistic simulations, mechanical properties of ZnO nanowires and electromechanical properties of GaN nanowires were investigated. In ZnO nanowires, elastic modulus was found to depend on nanowire diameter decreasing from 190 GPa to 140 GPa as the wire diameter increased from 5 nm to 80 nm. Inconsistent failure mechanisms were observed in ZnO nanowires. Experiments revealed a brittle fracture, whereas simulations using a pairwise potential predicted a phase transformation prior to failure. This inconsistency is addressed in detail from an experimental as well as computational perspective. Lastly, in addition to mechanical properties, preliminary results on the electromechanical properties of gallium nitride nanowires are also reported. Initial investigations reveal that the piezoresistive and piezoelectric behaviour of nanowires is different from bulk gallium nitride.

  19. Nanowire Optoelectronics

    OpenAIRE

    Wang Zhihuan; Nabet Bahram

    2015-01-01

    Semiconductor nanowires have been used in a variety of passive and active optoelectronic devices including waveguides, photodetectors, solar cells, light-emitting diodes (LEDs), lasers, sensors, and optical antennas. We review the optical properties of these nanowires in terms of absorption, guiding, and radiation of light, which may be termed light management. Analysis of the interaction of light with long cylindrical/hexagonal structures with ...

  20. Nanowire Lasers

    Directory of Open Access Journals (Sweden)

    Couteau C.

    2015-05-01

    Full Text Available We review principles and trends in the use of semiconductor nanowires as gain media for stimulated emission and lasing. Semiconductor nanowires have recently been widely studied for use in integrated optoelectronic devices, such as light-emitting diodes (LEDs, solar cells, and transistors. Intensive research has also been conducted in the use of nanowires for subwavelength laser systems that take advantage of their quasione- dimensional (1D nature, flexibility in material choice and combination, and intrinsic optoelectronic properties. First, we provide an overview on using quasi-1D nanowire systems to realize subwavelength lasers with efficient, directional, and low-threshold emission. We then describe the state of the art for nanowire lasers in terms of materials, geometry, andwavelength tunability.Next,we present the basics of lasing in semiconductor nanowires, define the key parameters for stimulated emission, and introduce the properties of nanowires. We then review advanced nanowire laser designs from the literature. Finally, we present interesting perspectives for low-threshold nanoscale light sources and optical interconnects. We intend to illustrate the potential of nanolasers inmany applications, such as nanophotonic devices that integrate electronics and photonics for next-generation optoelectronic devices. For instance, these building blocks for nanoscale photonics can be used for data storage and biomedical applications when coupled to on-chip characterization tools. These nanoscale monochromatic laser light sources promise breakthroughs in nanophotonics, as they can operate at room temperature, can potentially be electrically driven, and can yield a better understanding of intrinsic nanomaterial properties and surface-state effects in lowdimensional semiconductor systems.

  1. Individually grown cobalt nanowires as magnetic force microscopy probes.

    Science.gov (United States)

    Alotaibi, Shuaa; Samba, Joshua; Pokharel, Sabin; Lan, Yucheng; Uradu, Kelechi; Afolabi, Ayodeji; Unlu, Ilyas; Basnet, Gobind; Aslan, Kadir; Flanders, Bret N; Lisfi, Abdellah; Ozturk, Birol

    2018-02-26

    AC electric fields were utilized in the growth of individual high-aspect ratio cobalt nanowires from simple salt solutions using the Directed Electrochemical Nanowire Assembly method. Nanowire diameters were tuned from the submicron scale to 40 nm by adjusting the AC voltage frequency and the growth solution concentration. The structural properties of the nanowires, including shape and crystallinity, were identified using electron microscopy. Hysteresis loops obtained along different directions of an individual nanowire using vibrating sample magnetometry showed that the magnetocrystalline anisotropy energy has the same order of magnitude as the shape anisotropy energy. Additionally, the saturation magnetization of an individual cobalt nanowire was estimated to be close to the bulk single crystal value. A small cobalt nanowire segment was grown from a conductive atomic force microscope cantilever tip that was utilized in magnetic force microscopy (MFM) imaging. The fabricated MFM tip provided moderate quality magnetic images of an iron-cobalt thin-film sample.

  2. A catalyst-free synthesis of germanium nanowires obtained by ...

    Indian Academy of Sciences (India)

    2015-08-25

    Aug 25, 2015 ... atomic X-ray fluorescence and transmission electron microscopies, X-ray powder diffraction diffractometry, ther- mogravimetric analysis with ... ent technical devices, e.g., diodes [1], transistors [2], pho- tovoltaic panels [3], laser [4], ... of 250 kV and a current of 10 mA were applied in the. X-ray generator tube ...

  3. Strained silicon and silicon germanium nanowire tunnel FETs and inverters

    OpenAIRE

    Richter, Simon

    2014-01-01

    Reducing power consumption is an important issue for integrated circuits in portable devices relying on batteries and systems without external power supply. Scaling of the supply voltage VDD in integrated circuits is a powerful tool for reducing the power consumption, due to the quadratic dependence on VDD. MOSFETs, however, exhibit a fundamental limitation for the drain current increase per applied gate voltage difference. The tunnel field-effect transistor (TFET) provides the ability for be...

  4. Nanoscale contact engineering for Silicon/Silicide nanowire devices

    Science.gov (United States)

    Lin, Yung-Chen

    Metal silicides have been used in silicon technology as contacts to achieve high device performance and desired device functions. The growth and applications of silicide materials have recently attracted increasing interest for nanoscale device applications. Nanoscale silicide materials have been demonstrated with various synthetic approaches. Solid state reaction wherein high quality silicides form through diffusion of metal atoms into silicon nano-templates and the subsequent phase transformation caught significant attention for the fabrication of nanoscale Si devices. Very interestingly, studies on the diffusion and phase transformation processes at nanoscale have indicated possible deviations from the bulk and the thin film system. Here we studied growth kinetics, electronic properties and device applications of nanoscale silicides formed through solid state reaction. We have grown single crystal PtSi nanowires and PtSi/Si/PtSi nanowire heterostructures through solid state reaction. TEM studies show that the heterostructures have atomically sharp interfaces free of defects. Electrical measurement of PtSi nanowires shows a low resistivity of ˜28.6 μΩ·cm and a high breakdown current density beyond 108 A/cm2. Furthermore, using single-crystal PtSi/Si/PtSi nanowire heterostructures with atomically clean interfaces, we have fabricated p-channel enhancement mode transistors with the best reported performance for intrinsic silicon nanowires to date. In our results, silicide can provide a clean and no Fermi level pinning interface and then silicide can form Ohmic-contact behavior by replacing the source/drain metal with PtSi. It has been proven by our experiment by contacting PtSi with intrinsic Si nanowires (no extrinsic doping) to achieve high performance p-channel device. By utilizing the same approach, single crystal MnSi nanowires and MnSi/Si/MnSi nanowire heterojunction with atomically sharp interfaces can also been grown. Electrical transport studies on Mn

  5. Electronic Structure of Cdse Nanowires Terminated With Gold ...

    African Journals Online (AJOL)

    Cadmium selenide nanowires in the wurtzite bulk phase, connected to gold electrodes are studied using local density approximation. The short wire is fully metalized by metal-induced gap states. For longer wires, a gap similar to that in bare cadmium selenide nanowires is observed near the center while sub-gap structure ...

  6. Electrical Spin Injection and Transport in Germanium (Preprint)

    Science.gov (United States)

    2011-01-01

    spin functionality into semiconductor-based field effect transistors (spin-FET) [3-5] is considered as one of the approaches to overcome the ultimate...inversion symmetry [13]. Liu et al. [14] reported the spin diffusion length in Ge nanowires (NW) based on local magnetoresistance (MR) between two Co...injection to bulk 3 Ge by using an epitaxially grown Fe/MgO/n-Ge tunnel junction. The spin dependent properties of Ge are characterized by the non-local

  7. Harmonic Lattice Dynamics of Germanium

    International Nuclear Information System (INIS)

    Nelin, G.

    1974-01-01

    The phonon dispersion relations of the Δ-, Λ-, and Σ-directions of germanium at 80 K are analysed in terms of current harmonic lattice dynamical models. On the basis of this experience, a new model is proposed which gives a unified account of the strong points of the previous models. The principal elements of the presented theory are quasiparticle bond charges combined with a valence force field

  8. Harmonic Lattice Dynamics of Germanium

    Energy Technology Data Exchange (ETDEWEB)

    Nelin, G.

    1974-07-01

    The phonon dispersion relations of the DELTA-, LAMBDA-, and SIGMA-directions of germanium at 80 K are analysed in terms of current harmonic lattice dynamical models. On the basis of this experience, a new model is proposed which gives a unified account of the strong points of the previous models. The principal elements of the presented theory are quasiparticle bond charges combined with a valence force field.

  9. Study on the local atomic structure of germanium in organic germanium compounds by EXAFS

    Science.gov (United States)

    Wang, Yin-song; Wu, Zhong-hua; Shi, Yun-tian; Wang, Yong-jie

    1999-04-01

    Organic germanium compounds have been extensively applied in medicine as tonics. In this paper, the local structures of two organic germanium compounds, carboxyethylgermanium sesquioxide and polymeric germanium glutamate, were determined by EXAFS. The structure parameters including coordination numbers and bond lengths were reported, and possible structure patterns were discussed.

  10. Point contact germanium detectors at 500 eVee threshold for light dark matter searches

    Science.gov (United States)

    Soma, Arun Kumar; Li, Hau-Bin; Lin, Shin-Ted; Wong, Henry Tsz-King; TEXONO Collaboration

    2016-04-01

    Germanium detectors with sub-keV sensitivities can probe low-mass WIMP Dark Matter. This experimental approach is pursued at Kuo-Sheng Neutrino Laboratory (KSNL) in Taiwan and at China Jinping Underground Laboratory (CJPL) in China via TEXONO and CDEX programs, respectively. The highlights of R&D efforts on point contact germanium detectors and in particular the differentiation of surface and bulk events by pulse shape analysis are described. The latest results on WIMP-nucleon scattering cross-sections are also presented. Some of the allowed parameter space implied by other experiments are probed and excluded.

  11. Hydrothermal synthesis of bismuth germanium oxide

    Science.gov (United States)

    Boyle, Timothy J.

    2016-12-13

    A method for the hydrothermal synthesis of bismuth germanium oxide comprises dissolving a bismuth precursor (e.g., bismuth nitrate pentahydrate) and a germanium precursor (e.g., germanium dioxide) in water and heating the aqueous solution to an elevated reaction temperature for a length of time sufficient to produce the eulytite phase of bismuth germanium oxide (E-BGO) with high yield. The E-BGO produced can be used as a scintillator material. For example, the air stability and radioluminescence response suggest that the E-BGO can be employed for medical applications.

  12. Structural and electronic properties of AlX (X = P, As, Sb) nanowires: Ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Anurag, E-mail: anurags@iiitm.ac.in [Advanced Materials Research Group, Computational Nanoscience and Technology Laboratory, ABV-Indian Institute of Information Technology and Management, Gwalior 474015 (India); Tyagi, Neha [Advanced Materials Research Group, Computational Nanoscience and Technology Laboratory, ABV-Indian Institute of Information Technology and Management, Gwalior 474015 (India)

    2012-11-15

    Present paper discusses the structural stability and electronic properties of AlX (X = P, As and Sb) nanowires in its linear, zigzag, ladder, square and hexagonal type atomic configurations. The structural optimization has been performed in self consistence manner by using generalized gradient approximation with revised Perdew, Burke and Ernzerhof type parameterization. The study observes that in all the three nanowires, the square shaped atomic configuration is the most stable one. The calculated electronic band structures and density of states profile confirms the semiconducting behaviour of linear and zigzag shaped nanowires of AlP, whereas for AlAs and AlSb nanowires are metallic. The ground state properties have also been analysed in terms of bond length, bulk modulus and pressure derivative for all the nanowires along with their bulk counterpart. The lower bulk modulus of all the linear shaped geometries of AlX nanowires in comparison to its bulk counterpart indicates softening of the material at reduced dimension. -- Graphical abstract: Figure-Electronic band structure of zigzag shaped AlP nanowire. The present electronic band structures of zigzag and linear shaped AlP nanowires are showing a clear band gap at {Gamma} point, however others (AlAs and AlSb) in zigzag as well as in linear shape show metallic behaviour. Highlights: Black-Right-Pointing-Pointer Stability analysis of five geometries of AlX (X = P, As and Sb) nanowires studied. Black-Right-Pointing-Pointer Square shaped geometry of AlX nanowires is most stable. Black-Right-Pointing-Pointer Linear and zigzag shaped AlP nanowires are semiconducting. Black-Right-Pointing-Pointer Bulk moduli of all the linear nanowires are lower than their bulk counterpart. Black-Right-Pointing-Pointer Lower bulk moduli defends the softening of material.

  13. Theory of second-harmonic generation in silica nanowires

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2010-01-01

    The possibility of second-harmonic generation based on surface dipole and bulk multipole nonlinearities in silica nanowires is investigated numerically. Both circular and microstructured nanowires are considered. Phase matching is provided by propagating the pump field in the fundamental mode......, while generating the second harmonic in one of the modes of the LP11 multiplet. This is shown to work in both circular and microstructured nanowires, although only one of the LP11 modes can be phase-matched in the microstructure. The prospect of obtaining large conversion efficiencies in silica......-based nanowires is critically discussed, based on simulations of second-harmonic generation in nanowires with a fluctuating phase-matching wavelength. It is concluded that efficient wavelength conversion will either require strong improvements in the nanowire uniformity, or an increase of the second...

  14. Design and Characterisation of III-V Semiconductor Nanowire Lasers

    Science.gov (United States)

    Saxena, Dhruv

    The development of small, power-efficient lasers underpins many of the technologies that we utilise today. Semiconductor nanowires are promising for miniaturising lasers to even smaller dimensions. III-V semiconductors, such as Gallium Arsenide (GaAs) and Indium Phosphide (InP), are the most widely used materials for optoelectronic devices and so the development of nanowire lasers based on these materials is expected to have technologically significant outcomes. This PhD dissertation presents a comprehensive study of the design of III-V semiconductor nanowire lasers, with bulk and quantum confined active regions. Based on the design, various III-V semiconductor nanowire lasers are demonstrated, namely, GaAs nanowire lasers, GaAs/AlGaAs multi-quantum well (MQW) nanowire lasers and InP nanowire lasers. These nanowire lasers are shown to operate at room temperature, have low thresholds, and lase from different transverse modes. The structural and optoelectronic quality of nanowire lasers are characterised via electron microscopy and photoluminescence spectroscopic techniques. Lasing is characterised in all these devices by optical pumping. The lasing characteristics are analysed by rate equation modelling and the lasing mode(s) in these devices is characterised by threshold gain modelling, polarisation measurements and Fourier plane imaging. Firstly, GaAs nanowire lasers that operate at room temperature are demonstrated. This is achieved by determining the optimal nanowire diameter to reduce threshold gain and by passivating nanowires to improve their quantum efficiency (QE). High-quality surface passivated GaAs nanowires of suitable diameters are grown. The growth procedure is tailored to improve both QE and structural uniformity of nanowires. Room-temperature lasing is demonstrated from individual nanowires and lasing is characterised to be from TM01 mode by threshold gain modelling. To lower threshold even further, nanowire lasers with GaAs/AlGaAs coaxial multi

  15. Designing and building nanowires: directed nanocrystal self-assembly into radically branched and zigzag PbS nanowires

    International Nuclear Information System (INIS)

    Xu Fan; Ma Xin; Gerlein, L Felipe; Cloutier, Sylvain G

    2011-01-01

    Lead sulfide nanowires with controllable optoelectronic properties would be promising building blocks for various applications. Here, we report the hot colloidal synthesis of radically branched and zigzag nanowires through self-attachment of star-shaped and octahedral nanocrystals in the presence of multiple surfactants. We obtained high-quality single-crystal nanowires with uniform diameter along the entire length, and the size of the nanowire can be tuned by tailoring the reaction parameters. This slow oriented attachment provides a better understanding of the intricacies of this complex nanocrystal assembly process. Meanwhile, these self-assembled nanowire structures have appealing lateral conformations with narrow side arms or highly faceted edges, where strong quantum confinement can occur. Consequently, the single-crystal nanowire structures exhibit strong photoluminescence in the near-infrared region with a large blue-shift compared to the bulk material.

  16. Influence of channel material properties on performance of nanowire transistors

    Science.gov (United States)

    Razavi, Pedram; Fagas, Giorgos; Ferain, Isabelle; Yu, Ran; Das, Samaresh; Colinge, Jean-Pierre

    2012-06-01

    The performance of germanium and silicon inversion-mode and junctionless nanowire field-effect transistors are investigated using three-dimensional quantum mechanical simulations in the ballistic transport regime and within the framework of effective-mass theory for different channel materials and orientations. Our study shows that junctionless nanowire transistors made using n-type Ge or Si nanowires as a channel material are more immune to short-channel effects than conventional inversion-mode nanowire field-effect transistors. As a result, these transistors present smaller subthreshold swing, less drain-induced barrier-lowering, lower source-to-drain tunneling, and higher Ion/Ioff ratio for the same technology node and low standby power technologies. We also show that the short-channel characteristics of Ge and Si junctionless nanowire transistors, unlike the inversion-mode nanowire transistors, are very similar. The results are explained through a detailed analysis on the effect of the channel crystallographic orientation, effective masses, and dielectric constant on electrical characteristics.

  17. Boron carbide nanowires: Synthesis and characterization

    Science.gov (United States)

    Guan, Zhe

    Bulk boron carbide has been widely used in ballistic armored vest and the property characterization has been heavily focused on mechanical properties. Even though boron carbides have also been projected as a promising class of high temperature thermoelectric materials for energy harvesting, the research has been limited in this field. Since the thermal conductivity of bulk boron carbide is still relatively high, there is a great opportunity to take advantage of the nano effect to further reduce it for better thermoelectric performance. This dissertation work aims to explore whether improved thermoelectric performance can be found in boron carbide nanowires compared with their bulk counterparts. This dissertation work consists of four main parts. (1) Synthesis of boron carbide nanowires. Boron carbide nanowires were synthesized by co-pyrolysis of diborane and methane at low temperatures (with 879 °C as the lowest) in a home-built low pressure chemical vapor deposition (LPCVD) system. The CVD-based method is energy efficient and cost effective. The as-synthesized nanowires were characterized by electron microscopy extensively. The transmission electron microscopy (TEM) results show the nanowires are single crystalline with planar defects. Depending on the geometrical relationship between the preferred growth direction of the nanowire and the orientation of the defects, the as-synthesized nanowires could be further divided into two categories: transverse fault (TF) nanowires grow normal to the defect plane, while axial fault (AF) ones grow within the defect plane. (2) Understanding the growth mechanism of as-synthesized boron carbide nanowires. The growth mechanism can be generally considered as the famous vapor-liquid-solid (VLS) mechanism. TF and AF nanowires were found to be guided by Ni-B catalysts of two phases. A TF nanowire is lead by a hexagonal phase catalyst, which was proved to be in a liquid state during reaction. While an AF nanowires is catalyzed by a

  18. Purcell effect for finite-length metal-coated and metal nanowires

    DEFF Research Database (Denmark)

    Filonenko, Konstantin V.; Willatzen, Morten; Bordo, Vladimir G.

    2014-01-01

    We investigate the modification (enhancement and suppression) of the spontaneous emission rate of a dipole emitter in two configurations: inside a finite-length semiconductor nanowire surrounded by bulk metal and in the vicinity of a finite metal nanowire. Our analysis is based on a first......-principle approach, which is reduced to a seminumeric one in the limit of large nanowire aspect ratios. The numerical calculations are carried out for an emitter in a GaAs nanowire embedded in Ag or Au and for that nearby an Ag or Au nanowire in vacuum or dielectric. We consider in detail the Purcell and β factors...

  19. Zone refining high-purity germanium

    International Nuclear Information System (INIS)

    Hubbard, G.S.; Haller, E.E.; Hansen, W.L.

    1977-10-01

    The effects of various parameters on germanium purification by zone refining have been examined. These parameters include the germanium container and container coatings, ambient gas and other operating conditions. Four methods of refining are presented which reproducibly yield 3.5 kg germanium ingots from which high purity (vertical barN/sub A/ - N/sub D/vertical bar less than or equal to2 x 10 10 cm -3 ) single crystals can be grown. A qualitative model involving binary and ternary complexes of Si, O, B, and Al is shown to account for the behavior of impurities at these low concentrations

  20. Silicon and Germanium Nanostructures for Photovoltaic Applications: Ab-Initio Results

    Directory of Open Access Journals (Sweden)

    Pulci Olivia

    2010-01-01

    Full Text Available Abstract Actually, most of the electric energy is being produced by fossil fuels and great is the search for viable alternatives. The most appealing and promising technology is photovoltaics. It will become truly mainstream when its cost will be comparable to other energy sources. One way is to significantly enhance device efficiencies, for example by increasing the number of band gaps in multijunction solar cells or by favoring charge separation in the devices. This can be done by using cells based on nanostructured semiconductors. In this paper, we will present ab-initio results of the structural, electronic and optical properties of (1 silicon and germanium nanoparticles embedded in wide band gap materials and (2 mixed silicon-germanium nanowires. We show that theory can help in understanding the microscopic processes important for devices performances. In particular, we calculated for embedded Si and Ge nanoparticles the dependence of the absorption threshold on size and oxidation, the role of crystallinity and, in some cases, the recombination rates, and we demonstrated that in the case of mixed nanowires, those with a clear interface between Si and Ge show not only a reduced quantum confinement effect but display also a natural geometrical separation between electron and hole.

  1. Piezoresistive effect in top-down fabricated silicon nanowires

    DEFF Research Database (Denmark)

    Reck, Kasper; Richter, Jacob; Hansen, Ole

    2008-01-01

    resistor, each with integrated contacts for electrical 4-point measurements. We show an increase in the piezoresistive effect of 633% compared to bulk silicon. Preliminary temperature measurements indicate a larger temperature dependence of silicon nanowires, compared to bulk silicon. An increase of up...

  2. Silicon Germanium Quantum Well Solar Cell Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Quantum-well structures embodied on single crystal silicon germanium drastically enhanced carrier mobilities.  The cell-to-cell circuits of quantum-well PV...

  3. Metal induced crystallization of silicon germanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gjukic, M.

    2007-05-15

    In the framework of this thesis the applicability of the aluminium-induced layer exchange on binary silicon germanium alloys was studied. It is here for the first time shown that polycrstalline silicon-germanium layers can be fabricated over the whole composition range by the aluminium-induced layer exchange. The experimental results prove thet the resulting material exhibits a polycrystalline character with typocal grain sizes of 10-100 {mu}m. Raman measurements confirm that the structural properties of the resulting layers are because of the large crystallites more comparable with monocrystalline than with nano- or microcrystalline silicon-germanium. The alloy ratio of the polycrystalline layer correspondes to the chemical composition of the amorphous starting layer. The polycrystalline silicon-germanium layers possess in the range of the interband transitions a reflection spectrum, as it is otherwise only known from monocrystalline reference layers. The improvement of the absorption in the photovoltaically relevant spectral range aimed by the application of silicon-germanium could be also proved by absorption measurments. Strongly correlated with the structural properties of the polycrystalline layers and the electronic band structure resulting from this are beside the optical properties also the electrical properties of the material, especially the charge-carrier mobility and the doping concentration. For binary silicon-germanium layers the hole concentration of about 2 x 10{sup 18} cm{sup -3} for pure silicon increrases to about 5 x 10{sup 20} cm{sub -3} for pure germanium. Temperature-resolved measurements were applied in order to detect doping levels respectively semiconductor-metal transitions. In the last part of the thesis the hydrogen passivation of polycrystalline thin silicon-germanium layers, which were fabricated by means of aluminium-induced layer exchange, is treated.

  4. Nanowire Optoelectronics

    Directory of Open Access Journals (Sweden)

    Wang Zhihuan

    2015-12-01

    Full Text Available Semiconductor nanowires have been used in a variety of passive and active optoelectronic devices including waveguides, photodetectors, solar cells, light-emitting diodes (LEDs, lasers, sensors, and optical antennas. We review the optical properties of these nanowires in terms of absorption, guiding, and radiation of light, which may be termed light management. Analysis of the interaction of light with long cylindrical/hexagonal structures with subwavelength diameters identifies radial resonant modes, such as Leaky Mode Resonances, or Whispering Gallery modes. The two-dimensional treatment should incorporate axial variations in “volumetric modes,”which have so far been presented in terms of Fabry–Perot (FP, and helical resonance modes. We report on finite-difference timedomain (FDTD simulations with the aim of identifying the dependence of these modes on geometry (length, width, tapering, shape (cylindrical, hexagonal, core–shell versus core-only, and dielectric cores with semiconductor shells. This demonstrates how nanowires (NWs form excellent optical cavities without the need for top and bottommirrors. However, optically equivalent structures such as hexagonal and cylindrical wires can have very different optoelectronic properties meaning that light management alone does not sufficiently describe the observed enhancement in upward (absorption and downward transitions (emission of light inNWs; rather, the electronic transition rates should be considered. We discuss this “rate management” scheme showing its strong dimensional dependence, making a case for photonic integrated circuits (PICs that can take advantage of the confluence of the desirable optical and electronic properties of these nanostructures.

  5. AC surface photovoltage of indium phosphide nanowire networks

    Energy Technology Data Exchange (ETDEWEB)

    Lohn, Andrew J.; Kobayashi, Nobuhiko P. [California Univ., Santa Cruz, CA (United States). Baskin School of Engineering; California Univ., Santa Cruz, CA (US). Nanostructured Energy Conversion Technology and Research (NECTAR); NASA Ames Research Center, Moffett Field, CA (United States). Advanced Studies Laboratories

    2012-06-15

    Surface photovoltage is used to study the dynamics of photogenerated carriers which are transported through a highly interconnected three-dimensional network of indium phosphide nanowires. Through the nanowire network charge transport is possible over distances far in excess of the nanowire lengths. Surface photovoltage was measured within a region 10.5-14.5 mm from the focus of the illumination, which was chopped at a range of frequencies from 15 Hz to 30 kHz. Carrier dynamics were modeled by approximating the nanowire network as a thin film, then fitted to experiment suggesting diffusion of electrons and holes at approximately 75% of the bulk value in InP but with significantly reduced built-in fields, presumably due to screening by nanowire surfaces. (orig.)

  6. Electrical transport and thermoelectric properties of boron carbide nanowires

    Science.gov (United States)

    Kirihara, Kazuhiro; Mukaida, Masakazu; Shimizu, Yoshiki

    2017-04-01

    The electrical transport and thermoelectric property of boron carbide nanowires synthesized by a carbothermal method are reported. It is demonstrated that the nanowires achieve a higher Seebeck coefficient and power factor than those of the bulk samples. The conduction mechanism of the nanowires at low temperatures below 300 K is different from that of the sintered-polycrystalline and single-crystal bulk samples. In a temperature range of 200-450 K, there is a crossover between electrical conduction by variable-range hopping and phonon-assisted hopping. The inhomogeneous carbon concentration and planar defects, such as twins and stacking faults, in the nanowires are thought to modify the bonding nature and electronic structure of the boron carbide crystal substantially, causing differences in the electrical conductivity and Seebeck coefficient. The effect of boundary scattering of phonon at nanostructured surface on the thermal conductivity reduction is discussed.

  7. Bulk photoemission from metal films and nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ikhsanov, R Sh [Research Institute of Scientific Instruments, ' Rosatom' ' State Atomic Energy Corporation (Russian Federation); Babicheva, V E [Technical University of Denmark (Denmark); Protsenko, I E; Uskov, A V [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Guzhva, M E [St. Petersburg State Politechnical University, St. Petersburg (Russian Federation)

    2015-01-31

    Internal emission of photoelectrons from metal films and nanoparticles (nanowires and nanospheres) into a semiconductor matrix is studied theoretically by taking into account the jump of the effective electron mass at the metal – semiconductor interface and the cooling effect of hot electrons due to electron – electron collisions in the metal. The internal quantum efficiency of photoemission for the film and nanoparticles of two types (nanospheres and nanowires) is calculated. It is shown that the reduction of the effective mass of the electron during its transition from metal to semiconductor may lead to a significant (orders of magnitude and higher) decrease in the internal quantum efficiency of bulk photoemission. (nanostructures)

  8. Creating ligand-free silicon germanium alloy nanocrystal inks.

    Science.gov (United States)

    Erogbogbo, Folarin; Liu, Tianhang; Ramadurai, Nithin; Tuccarione, Phillip; Lai, Larry; Swihart, Mark T; Prasad, Paras N

    2011-10-25

    Particle size is widely used to tune the electronic, optical, and catalytic properties of semiconductor nanocrystals. This contrasts with bulk semiconductors, where properties are tuned based on composition, either through doping or through band gap engineering of alloys. Ideally, one would like to control both size and composition of semiconductor nanocrystals. Here, we demonstrate production of silicon-germanium alloy nanoparticles by laser pyrolysis of silane and germane. We have used FTIR, TEM, XRD, EDX, SEM, and TOF-SIMS to conclusively determine their structure and composition. Moreover, we show that upon extended sonication in selected solvents, these bare nanocrystals can be stably dispersed without ligands, thereby providing the possibility of using them as an ink to make patterned films, free of organic surfactants, for device fabrication. The engineering of these SiGe alloy inks is an important step toward the low-cost fabrication of group IV nanocrystal optoelectronic, thermoelectric, and photovoltaic devices.

  9. Denuded Zone Formation in Germanium Codoped Heavily Phosphorus-Doped Czochralski Silicon

    Science.gov (United States)

    Lin, Li-Xia; Chen, Jia-He; Wu, Peng; Zeng, Yu-Heng; Ma, Xiang-Yang; Yang, De-Ren

    2011-03-01

    The formation of a denuded zone (DZ) by conventional furnace annealing (CFA) and rapid thermal annealing (RTA) based denudation processing is investigated and the gettering of copper (Cu) atoms in germanium co-doped heavily phosphorus-doped Czochralski (GHPCZ) silicon wafers is evaluated. It is suggested that both a good quality defect-free DZ with a suitable width in the sub-surface area and a high density bulk micro-defect (BMD) region could be formed in heavily phosphorus-doped Czochralski (HPCZ) silicon and GHPCZ silicon wafers. This is ascribed to the formation of phosphorus-vacancy (P-V) related complexes and germanium-vacancy (GeV) related complexes. Compared with HPCZ silicon, the DZ width is wider in the GHPCZ silicon sample with CFA-based denudation processing but narrower in the one with two-step RTA pretreatments. These phenomena are ascribed to the enhancing effect of germanium on oxygen out-diffusion movement and oxygen precipitate nucleation, respectively. Furthermore, fairly clean DZs near the surface remain in both the HPCZ and GHPCZ silicon wafers after Cu in-diffusion, except for the HPCZ silicon wafer which underwent denudation processing with a CFA pretreatment, suggesting that germanium doping could improve the gettering of Cu contamination.

  10. Germanium content in Polish hard coals

    Directory of Open Access Journals (Sweden)

    Makowska Dorota

    2016-01-01

    Full Text Available Due to the policy of the European Union, it is necessary to search for new sources of scarce raw materials. One of these materials is germanium, listed as a critical element. This semi-metal is widely used in the electronics industry, for example in the production of semiconductors, fibre optics and solar cells. Coal and fly ash from its combustion and gasification for a long time have been considered as a potential source of many critical elements, particularly germanium. The paper presents the results of germanium content determination in the Polish hard coal. 23 coal samples of various coal ranks were analysed. The samples were collected from 15 mines of the Upper Silesian Coal Basin and from one mine of the Lublin Coal Basin. The determination of germanium content was performed with the use of Atomic Absorption Spectrometry with Electrothermal Atomization (GFAAS. The investigation showed that germanium content in the analysed samples was at least twice lower than the average content of this element in the hard coals analysed so far and was in the range of 0.08 ÷ 1.28 mg/kg. Moreover, the content of Ge in the ashes from the studied coals does not exceed 15 mg/kg, which is lower than the average value of Ge content in the coal ashes. The highest content of this element characterizes coals of the Lublin Coal Basin and young coals type 31 from the Vistula region. The results indicate a low utility of the analysed coal ashes as a source of the recovery of germanium. On the basis of the analyses, the lack of the relationship between the content of the element and the ash content in the tested coals was noted. For coals of the Upper Silesian Coal Basin, the relationship between the content of germanium in the ashes and the depth of the seam was observed.

  11. Magnetic and superconducting nanowires

    DEFF Research Database (Denmark)

    Piraux, L.; Encinas, A.; Vila, L.

    2005-01-01

    magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also...

  12. Stability of Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, F.; Schiek, M.; Wallmann, I.

    2011-01-01

    atomic force microscopy (AFM). Aging experiments under ambient conditions already show substantial morphological changes. Nanoscopic organic clusters, which initially coexist with the nanowires, vanish within hours. Thermal annealing of nanowire samples leads to even more pronounced morphology changes...

  13. Resonant features of the terahertz generation in semiconductor nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Trukhin, V. N., E-mail: valera.truchin@mail.ioffe.ru [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Bouravleuv, A. D. [Russian Academy of Sciences, St. Petersburg Academic University—Nanotechnology Research and Education Centre (Russian Federation); Mustafin, I. A. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Cirlin, G. E. [Russian Academy of Sciences, St. Petersburg Academic University—Nanotechnology Research and Education Centre (Russian Federation); Kuritsyn, D. I.; Rumyantsev, V. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Morosov, S. V. [Russian Academy of Sciences, St. Petersburg Academic University—Nanotechnology Research and Education Centre (Russian Federation); Kakko, J. P.; Huhtio, T.; Lipsanen, H. [Aalto University, Department of Micro- and Nanosciences, Micronova (Finland)

    2016-12-15

    The paper presents the results of experimental studies of the generation of terahertz radiation in periodic arrays of GaAs nanowires via excitation by ultrashort optical pulses. It is found that the generation of THz radiation exhibits resonant behavior due to the resonant excitation of cylindrical modes in the nanowires. At the optimal geometric parameters of the nanowire array, the generation efficiency is found to be higher than that for bulk p-InAs, which is one of the most effective coherent terahertz emitters.

  14. Vertically Integrated Multiple Nanowire Field Effect Transistor.

    Science.gov (United States)

    Lee, Byung-Hyun; Kang, Min-Ho; Ahn, Dae-Chul; Park, Jun-Young; Bang, Tewook; Jeon, Seung-Bae; Hur, Jae; Lee, Dongil; Choi, Yang-Kyu

    2015-12-09

    A vertically integrated multiple channel-based field-effect transistor (FET) with the highest number of nanowires reported ever is demonstrated on a bulk silicon substrate without use of wet etching. The driving current is increased by 5-fold due to the inherent vertically stacked five-level nanowires, thus showing good feasibility of three-dimensional integration-based high performance transistor. The developed fabrication process, which is simple and reproducible, is used to create multiple stiction-free and uniformly sized nanowires with the aid of the one-route all-dry etching process (ORADEP). Furthermore, the proposed FET is revamped to create nonvolatile memory with the adoption of a charge trapping layer for enhanced practicality. Thus, this research suggests an ultimate design for the end-of-the-roadmap devices to overcome the limits of scaling.

  15. Nanotubes and nanowires

    Indian Academy of Sciences (India)

    Unknown

    nanotubes are likely to be useful as nanochips since they exhibit diode properties at the junction. By making use of carbon nanotubes, nanowires of metals, metal oxides and GaN have been obtained. Both the oxide and GaN nanowires are single crystalline. Gold nanowires exhibit plasmon bands varying markedly with.

  16. Method of beryllium implantation in germanium substrate

    International Nuclear Information System (INIS)

    Kagawa, S.; Baba, Y.; Kaneda, T.; Shirai, T.

    1983-01-01

    A semiconductor device is disclosed, as well as a method for manufacturing it in which ions of beryllium are implanted into a germanium substrate to form a layer containing p-type impurity material. There after the substrate is heated at a temperature in the range of 400 0 C. to 700 0 C. to diffuse the beryllium ions into the substrate so that the concentration of beryllium at the surface of the impurity layer is in the order of 10 17 cm- 3 or more. In one embodiment, a p-type channel stopper is formed locally in a p-type germanium substrate and an n-type active layer is formed in a region surrounded by, and isolated from, the channel stopper region. In another embodiment, a relatively shallow p-type active layer is formed at one part of an n-type germanium substrate and p-type guard ring regions are formed surrounding, and partly overlapping said p-type active layer. In a further embodiment, a p-type island region is formed at one part of an n-type germanium substrate, and an n-type region is formed within said p-type region. In these embodiments, the p-type channel stopper region, p-type guard ring regions and the p-type island region are all formed by implanting ions of beryllium into the germanium substrate

  17. Phase diagram of germanium telluride encapsulated in carbon nanotubes from first-principles searches

    Science.gov (United States)

    Wynn, Jamie M.; Medeiros, Paulo V. C.; Vasylenko, Andrij; Sloan, Jeremy; Quigley, David; Morris, Andrew J.

    2017-12-01

    Germanium telluride has attracted great research interest, primarily because of its phase-change properties. We have developed a general scheme, based on the ab initio random structure searching (AIRSS) method, for predicting the structures of encapsulated nanowires, and using this we predict a number of thermodynamically stable structures of GeTe nanowires encapsulated inside carbon nanotubes of radii under 9 Å . We construct the phase diagram of encapsulated GeTe, which provides quantitative predictions about the energetic favorability of different filling structures as a function of the nanotube radius, such as the formation of a quasi-one-dimensional rock-salt-like phase inside nanotubes of radii between 5.4 and 7.9 Å . Simulated TEM images of our structures show excellent agreement between our results and experimental TEM imagery. We show that, for some nanotubes, the nanowires undergo temperature-induced phase transitions from one crystalline structure to another due to vibrational contributions to the free energy, which is a first step toward nano-phase-change memory devices.

  18. Photoelectrochemical reduction of carbon dioxide using Ge doped GaN nanowire photoanodes

    Directory of Open Access Journals (Sweden)

    Yichen Wang

    2015-11-01

    Full Text Available We report on the direct conversion of carbon dioxide (CO2 in a photoelectrochemical cell consisting of germanium doped gallium nitride nanowire anode and copper (Cu cathode. Various products including methane (CH4, carbon monoxide (CO, and formic acid (HCOOH were observed under light illumination. A Faradaic efficiency of ∼10% was measured for HCOOH. Furthermore, this photoelectrochemical system showed enhanced stability for 6 h CO2 reduction reaction on low cost, large area Si substrates.

  19. Front End Spectroscopy ASIC for Germanium Detectors

    Science.gov (United States)

    Wulf, Eric

    Large-area, tracking, semiconductor detectors with excellent spatial and spectral resolution enable exciting new access to soft (0.2-5 MeV) gamma-ray astrophysics. The improvements from semiconductor tracking detectors come with the burden of high density of strips and/or pixels that require high-density, low-power, spectroscopy quality readout electronics. CMOS ASIC technologies are a natural fit to this requirement and have led to high-quality readout systems for all current semiconducting tracking detectors except for germanium detectors. The Compton Spectrometer and Imager (COSI), formerly NCT, at University of California Berkeley and the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) at Goddard Space Flight Center utilize germanium cross-strip detectors and are on the forefront of NASA's Compton telescope research with funded missions of long duration balloon flights. The development of a readout ASIC for germanium detectors would allow COSI to replace their discrete electronics readout and would enable the proposed Gamma-Ray Explorer (GRX) mission utilizing germanium strip-detectors. We propose a 3-year program to develop and test a germanium readout ASIC to TRL 5 and to integrate the ASIC readout onto a COSI detector allowing a TRL 6 demonstration for the following COSI balloon flight. Our group at NRL led a program, sponsored by another government agency, to produce and integrate a cross-strip silicon detector ASIC, designed and fabricated by Dr. De Geronimo at Brookhaven National Laboratory. The ASIC was designed to handle the large (>30 pF) capacitance of three 10 cm^2 detectors daisy-chained together. The front-end preamplifier, selectable inverter, shaping times, and gains make this ASIC compatible with a germanium cross-strip detector as well. We therefore have the opportunity and expertise to leverage the previous investment in the silicon ASIC for a new mission. A germanium strip detector ASIC will also require precise timing of the signals at

  20. Growth Mechanism of Nanowires: Ternary Chalcogenides

    Science.gov (United States)

    Singh, N. B.; Coriell, S. R.; Hopkins, R. H.; Su, Ching Hua; Arnold, B.; Choa, Fow-Sen; Cullum, Brian

    2016-01-01

    In the past two decades there has been a large rise in the investment and expectations for nanotechnology use. Almost every area of research has projected improvements in sensors, or even a promise for the emergence of some novel device technologies. For these applications major focuses of research are in the areas of nanoparticles and graphene. Although there are some near term applications with nanowires in photodetectors and other low light detectors, there are few papers on the growth mechanism and fabrication of nanowire-based devices. Semiconductor nanowires exhibit very favorable and promising optical properties, including high transparency and a several order of magnitude better photocurrent than thin film and bulk materials. We present here an overview of the mechanism of nanowire growth from the melt, and some preliminary results for the thallium arsenic selenide material system. Thallium arsenic selenide (TAS) is a multifunctional material combining excellent acousto-optical, nonlinear and radiation detection properties. We observed that small units of (TAS) nanocubes arrange and rearrange at moderate melt undercooling to form the building block of a nanowire. In some cases very long wires (less than mm) are formed. Since we avoided the catalyst, we observed self-nucleation and uncontrolled growth of wires from different places.

  1. Nanofabrication of structures for the study of nanowire doping

    Science.gov (United States)

    Eichfeld, Chad

    characterized by electron microscopy and found to be single crystal and to grow oriented to the growth substrate. 4-pt electrical resistivity measurements of the silicon nanowires were made. The resistivity measured ranged from of 0.005-0.017 O-cm, corresponding to an impurity concentration 7 x 1018 to 2 x 1019 cm-3 assuming bulk mobility. Calculations show that possible error from depletion at the surface has only a small effect on the calculated resistivity for a 100 nm diameter nanowire at this high of a doping concentration. The results of LEAP metrology analysis of the Al catalyzed nanowires show an estimated Al concentration of 0.4 atomic percent or 2 x 1020 cm-3 about 200 nm from the nanowire tip, where the concentration appears to have leveled out. This value is higher than would be expected from the solubility published for Al.

  2. Neutron-transmutation-doped germanium bolometers

    International Nuclear Information System (INIS)

    Palaio, N.P.; Rodder, M.; Haller, E.E.; Kreysa, E.

    1983-02-01

    Six slices of ultra-pure germanium were irradiated with thermal neutron fluences between 7.5 x 10 16 and 1.88 x 10 18 cm - 2 . After thermal annealing the resistivity was measured down to low temperatures ( 0 exp(δ/T) in the hopping conduction regime. Also, several junction FETs were tested for noise performance at room temperature and in an insulating housing in a 4.2K cryostat. These FETs will be used as first stage amplifiers for neutron-transmutation-doped germanium bolometers

  3. GRAN SASSO: Enriched germanium in action

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    Two large crystals of carefully enriched germanium, one weighing 1 kilogram and the other 2.9 kilograms, and worth many millions of dollars, are being carefully monitored in the Italian Gran Sasso Laboratory in the continuing search for neutrinoless double beta decay

  4. Characterization of nanocrystalline silicon germanium film and ...

    African Journals Online (AJOL)

    The nanocrystalline silicon-germanium films (Si/Ge) and Si/Ge nanotubes have low band gaps and high carrier mobility, thus offering appealing potential for absorbing gas molecules. Interaction between hydrogen molecules and bare as well as functionalized Si/Ge nanofilm and nanotube was investigated using Monte ...

  5. Single-Crystal Germanium Core Optoelectronic Fibers

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Xiaoyu [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA; Page, Ryan L. [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA; Chaudhuri, Subhasis [Department of Chemistry, Pennsylvania State University, University Park PA 16802 USA; Liu, Wenjun [Advanced Photon Source, Argonne National Laboratory, Argonne IL 60439 USA; Yu, Shih-Ying [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA; Mohney, Suzanne E. [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA; Badding, John V. [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA; Department of Chemistry, Pennsylvania State University, University Park PA 16802 USA; Department of Physics, Pennsylvania State University, University Park PA 16802 USA; Gopalan, Venkatraman [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA

    2016-09-19

    Synthesis and fabrication of high-quality, small-core single-crystal germanium fibers that are photosensitive at the near-infrared and have low optical losses ≈1 dB cm-1 at 2 μm are reported. These fibers have potential applications in fiber-based spectroscopic imaging, nonlinear optical devices, and photodetection at the telecommunication wavelengths.

  6. Filtering microphonics in dark matter germanium experiments

    International Nuclear Information System (INIS)

    Morales, J.; Garcia, E.; Ortiz de Solorzano, A.; Morales, A.; Nunz-Lagos, R.; Puimedon, J.; Saenz, C.; Villar, J.A.

    1992-01-01

    A technique for reducing the microphonic noise in a germanium spectrometer used in dark matter particles searches is described. Filtered energy spectra, corresponding to 48.5 kg day of data in a running experiment in the Canfranc tunnel are presented. Improvements of this filtering procedure with respect to the method of rejecting those events not distributed evenly in time are also discussed. (orig.)

  7. Silicon Germanium Quantum Well Thermoelectrics

    Science.gov (United States)

    Davidson, Anthony Lee, III

    Today's growing energy demands require new technologies to provide high efficiency clean energy. Thermoelectrics that convert heat to electrical energy directly can provide a method for the automobile industry to recover waste heat to power vehicle electronics, hence improving fuel economy. If large enough efficiencies can be obtained then the internal combustion engine could even be replaced. Exhaust temperature for automotive application range from 400 to 800 K. In this temperature range the current state of the art materials are bulk Si1-xGex alloys. By alternating layers of Si and Si1-xGex alloy device performance may be enhanced through quantum well effects and variations in material thermal properties. In this study, superlattices designed for in-plane operation with varying period and crystallinity are examined to determine the effect on electrical and thermal properties. In-plane electrical resistivity of these materials was found to be below the bulk material at a similar doping at room temperature, confirming the role of quantum wells in electron transport. As period is reduced in the structures boundary scattering limits electron propagation leading to increased resistivity. The Seebeck coefficient measured at room temperature is higher than the bulk material, additionally lending proof to the effects of quantum wells. When examining cross-plane operation the low doping in the Si layers of the device produce high resistivity resulting from boundary scattering. Thermal conductivity was measured from 77 K up to 674 K and shows little variation due to periodicity and temperature, however an order of magnitude reduction over bulk Si1-xGex is shown in all samples. A model is developed that suggests a combination of phonon dispersion effects and strong boundary scattering. Further study of the phonon dispersion effects was achieved through the examination of the heat capacity by combining thermal diffusivity with thermal conductivity. All superlattices show a

  8. Superlattice nanowire pattern transfer (SNAP).

    Science.gov (United States)

    Heath, James R

    2008-12-01

    During the past 15 years or so, nanowires (NWs) have emerged as a new and distinct class of materials. Their novel structural and physical properties separate them from wires that can be prepared using the standard methods for manufacturing electronics. NW-based applications that range from traditional electronic devices (logic and memory) to novel biomolecular and chemical sensors, thermoelectric materials, and optoelectronic devices, all have appeared during the past few years. From a fundamental perspective, NWs provide a route toward the investigation of new physics in confined dimensions. Perhaps the most familiar fabrication method is the vapor-liquid-solid (VLS) growth technique, which produces semiconductor nanowires as bulk materials. However, other fabrication methods exist and have their own advantages. In this Account, I review a particular class of NWs produced by an alternative method called superlattice nanowire pattern transfer (SNAP). The SNAP method is distinct from other nanowire preparation methods in several ways. It can produce large NW arrays from virtually any thin-film material, including metals, insulators, and semiconductors. The dimensions of the NWs can be controlled with near-atomic precision, and NW widths and spacings can be as small as a few nanometers. In addition, SNAP is almost fully compatible with more traditional methods for manufacturing electronics. The motivation behind the development of SNAP was to have a general nanofabrication method for preparing electronics-grade circuitry, but one that would operate at macromolecular dimensions and with access to a broad materials set. Thus, electronics applications, including novel demultiplexing architectures; large-scale, ultrahigh-density memory circuits; and complementary symmetry nanowire logic circuits, have served as drivers for developing various aspects of the SNAP method. Some of that work is reviewed here. As the SNAP method has evolved into a robust nanofabrication

  9. Advances in nanowire bioelectronics

    Science.gov (United States)

    Zhou, Wei; Dai, Xiaochuan; Lieber, Charles M.

    2017-01-01

    Semiconductor nanowires represent powerful building blocks for next generation bioelectronics given their attractive properties, including nanometer-scale footprint comparable to subcellular structures and bio-molecules, configurable in nonstandard device geometries readily interfaced with biological systems, high surface-to-volume ratios, fast signal responses, and minimum consumption of energy. In this review article, we summarize recent progress in the field of nanowire bioelectronics with a focus primarily on silicon nanowire field-effect transistor biosensors. First, the synthesis and assembly of semiconductor nanowires will be described, including the basics of nanowire FETs crucial to their configuration as biosensors. Second, we will introduce and review recent results in nanowire bioelectronics for biomedical applications ranging from label-free sensing of biomolecules, to extracellular and intracellular electrophysiological recording.

  10. From nanodiamond to nanowires.

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, A.; Materials Science Division

    2005-01-01

    Recent advances in the fabrication and characterization of semiconductor and metallic nanowires are proving very successful in meeting the high expectations of nanotechnologists. Although the nanoscience surrounding sp{sup 3} bonded carbon nanotubes has continued to flourish over recent years the successful synthesis of the sp{sup 3} analogue, diamond nanowires, has been limited. This prompts questions as to whether diamond nanowires are fundamentally unstable. By applying knowledge obtained from examining the structural transformations in nanodiamond, a framework for analyzing the structure and stability of diamond nanowires may be established. One possible framework will be discussed here, supported by results of ab initio density functional theory calculations used to study the structural relaxation of nanodiamond and diamond nanowires. The results show that the structural stability and electronic properties of diamond nanowires are dependent on the surface morphology, crystallographic direction of the principal axis, and the degree of surface hydrogenation.

  11. Template-assisted electrodeposition of indium–antimony nanowires – Comparison of electrochemical methods

    Energy Technology Data Exchange (ETDEWEB)

    Hnida, Katarzyna, E-mail: hnida@chemia.uj.edu.pl [Department of Physical Chemistry and Electrochemistry, Jagiellonian University, Ingardena 3, 30060 Krakow (Poland); Mech, Justyna [Faculty of Non-Ferrous Metals, AGH University of Science and Technology, Al. A. Mickiewicza 30, 30059 Krakow (Poland); Sulka, Grzegorz D. [Department of Physical Chemistry and Electrochemistry, Jagiellonian University, Ingardena 3, 30060 Krakow (Poland)

    2013-12-15

    Indium antimonide (InSb) is a III–V compound semiconductor that in a form of nanowires can possess improved thermoelectrical and optical properties compared to the corresponding bulk crystal. Here, we applied three electrodeposition techniques for a fast and inexpensive template-assisted fabrication of InSb nanowires from a sodium citrate-citric acid solution at room temperature. The home-made anodic aluminum oxide (AAO) templates with the pore diameter of 100 nm were used. InSb nanowires were synthesized by potentiostatic, galvanostatic and periodic pulse reverse techniques. The morphology, composition and crystallinity of as-obtained and annealed nanowires were investigated and compared with the literature data. It was found that the potentiostatic and pulse reverse methods gave crystalline nanowires. On the other hand, the constant current density deposition results in a partially amorphous nanowire material.

  12. Optical Sensing with Simultaneous Electrochemical Control in Metal Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Janos Vörös

    2010-11-01

    Full Text Available This work explores the alternative use of noble metal nanowire systems in large-scale array configurations to exploit both the nanowires’ conductive nature and localized surface plasmon resonance (LSPR. The first known nanowire-based system has been constructed, with which optical signals are influenced by the simultaneous application of electrochemical potentials. Optical characterization of nanowire arrays was performed by measuring the bulk refractive index sensitivity and the limit of detection. The formation of an electrical double layer was controlled in NaCl solutions to study the effect of local refractive index changes on the spectral response. Resonance peak shifts of over 4 nm, a bulk refractive index sensitivity up to 115 nm/RIU and a limit of detection as low as 4.5 × 10−4 RIU were obtained for gold nanowire arrays. Simulations with the Multiple Multipole Program (MMP confirm such bulk refractive index sensitivities. Initial experiments demonstrated successful optical biosensing using a novel form of particle-based nanowire arrays. In addition, the formation of an ionic layer (Stern-layer upon applying an electrochemical potential was also monitored by the shift of the plasmon resonance.

  13. Shear-driven phase transformation in silicon nanowires

    Science.gov (United States)

    Vincent, L.; Djomani, D.; Fakfakh, M.; Renard, C.; Belier, B.; Bouchier, D.; Patriarche, G.

    2018-03-01

    We report on an unprecedented formation of allotrope heterostructured Si nanowires by plastic deformation based on applied radial compressive stresses inside a surrounding matrix. Si nanowires with a standard diamond structure (3C) undergo a phase transformation toward the hexagonal 2H-allotrope. The transformation is thermally activated above 500 °C and is clearly driven by a shear–stress relief occurring in parallel shear bands lying on {115} planes. We have studied the influence of temperature and axial orientation of nanowires. The observations are consistent with a martensitic phase transformation, but the finding leads to clear evidence of a different mechanism of deformation-induced phase transformation in Si nanowires with respect to their bulk counterpart. Our process provides a route to study shear-driven phase transformation at the nanoscale in Si.

  14. Oligo and Poly-thiophene/Zno Hybrid Nanowire Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Briseno, Alejandro L.; Holcombe, Thomas W.; Boukai, Akram I.; Garnett, Erik C.; Shelton, Steve W.; Frechet, Jean J. M.; Yang, Peidong

    2009-11-03

    We demonstrate the basic operation of an organic/inorganic hybrid single nanowire solar cell. End-functionalized oligo- and polythiophenes were grafted onto ZnO nanowires to produce p-n heterojunction nanowires. The hybrid nanostructures were characterized via absorption and electron microscopy to determine the optoelectronic properties and to probe the morphology at the organic/inorganic interface. Individual nanowire solar cell devices exhibited well-resolved characteristics with efficiencies as high as 0.036percent, Jsc = 0.32 mA/cm2, Voc = 0.4 V, and a FF = 0.28 under AM 1.5 illumination with 100 mW/cm2 light intensity. These individual test structures will enable detailed analysis to be carried out in areas that have been difficult to study in bulk heterojunction devices.

  15. InGaN/GaN Nanowire LEDs and Lasers

    KAUST Repository

    Zhao, Chao

    2016-01-01

    The large specific surface, and the associated high density of surface states was found to limit the light output power and quantum efficiency of nanowire-array devices, despite their potential for addressing the “green-gap” and efficiency-droop issues. The phonon and carrier confinement in nanowires also led to junction heating, and reduced heat dissipation. In this paper, we will present our studies on effective surface states passivation in InGaN/GaN quantum-disks (Qdisks)-in-nanowire light-emitting diodes (LEDs) and lasers grown on silicon (Si), as well as our recent work on nanowires LEDs grown on bulk-metal, a non-conventional substrate.

  16. Direct Observation of Acoustic Oscillations in InAs Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Mariager, Simon O.; Khakhulin, Dmitry; Lemke, Henrik T.; Kjær, Kasper S.; Guerin, Laurent; Nuccio, Laura; Sørensen, Claus B.; Nielsen, Martin M.; Feidenhans’l, Robert (Copenhagen); (ESRF)

    2010-09-02

    Time-resolved X-ray diffraction and optical reflectivity are used to directly measure three different acoustic oscillations of InAs nanowires. The oscillations are excited by a femtosecond laser pulse and evolve at three different time scales. We measure the absolute scale of the initial radial expansion of the fundamental breathing eigenmode and determine the frequency by transient optical reflectivity. For the extensional eigenmode we measure the oscillations of the average radial and axial lattice constants and determine the amplitude of oscillations and the average extension. Finally we observe a bending motion of the nanowires. The frequencies of the eigenmodes are in good agreements with predictions made by continuum elasticity theory and we find no difference in the speed of sound between the wurtzite nanowires and cubic bulk crystals, but the measured strain is influenced by the interaction between different modes. The wurtzite crystal structure of the nanowires however has an anisotropic thermal expansion.

  17. Enhanced absorption and cavity effects of three-photon pumped ZnO nanowires

    Science.gov (United States)

    Hollinger, Richard; Samsonova, Zhanna; Gupta, Dishiti; Spielmann, Christian; Röder, Robert; Trefflich, Lukas; Ronning, Carsten; Kartashov, Daniil

    2017-11-01

    Semiconductor nanowire (NW) lasers attract a lot of attention as potential elements of nanophotonic circuits and lab-on-a chip devices. Here, we report on the experimental investigation of stimulated near ultraviolet (NUV) emission, pumped by three-photon absorption from near infrared femtosecond laser pulses, from ZnO NW arrays of different morphologies and compare it to the bulk. The spectrally and temporally resolved measurements of the NUV emission show both strong enhancements in the absorption and emission properties of the nanowire arrays compared to bulk samples. Thus, we determine a many times higher three-photon absorption in the nanostructure morphology compared to the bulk material. Furthermore, the threshold pumping intensity for stimulated emission in a vertically oriented nanowire array is twice lower and the emission onset time is shorter than in randomly oriented arrays, revealing strong influence of the macroscopic nanowire arrangement.

  18. Comparison of organic and inorganic germanium compounds in cellular radiosensitivity and preparation of germanium nanoparticles as a radiosensitizer.

    Science.gov (United States)

    Lin, Ming-Hsing; Hsu, Tzu-Sheng; Yang, Pei-Ming; Tsai, Meng-Yen; Perng, Tsong-Pyng; Lin, Lih-Yuan

    2009-03-01

    The aim of this work is to compare the radiosensitizing effect between organic and inorganic germanium compounds and to investigate whether nanometer-sized germanium particles can act as radiosensitizers. Bis (2-carboxyethylgermanium) sesquioxide (Ge-132), germanium oxide (GeO(2)) and germanium nanoparticles were used in this study. Cell viability was determined by clonogenic survival assay. Cellular DNA damage was evaluated by alkaline comet assay, confocal microscopy and the cellular level of phospho-histone H2AX (gamma-H2AX). Nanometer-sized germanium particles were fabricated. They have a similar radiosensitizing effect as that of GeO(2). Conversely, Ge-132 did not enhance the radiosensitivity of cells. Comet assay was employed to evaluate the level of DNA damage and confirmed that inorganic germanium compounds enhanced cellular radiosensitivity. Notably, the comet assay indicated that the nanoparticle itself caused a higher level of DNA damage. The possibility that germanium nanoparticles per se caused DNA damage was ruled out when the cellular level of gamma-H2AX was examined. We demonstrated that inorganic but not organic germanium compounds exerted radiosensitizing effect in cells. Nanometer-sized germanium particles were fabricated and were able to enhance the radiosensitivity of cells. Confounding effect may occur when comet assay is used to estimate the level of DNA damage in the presence of germanium nanoparticles.

  19. Quantum ion-acoustic wave oscillations in metallic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, Afshin, E-mail: a.moradi@kut.ac.ir [Department of Engineering Physics, Kermanshah University of Technology, Kermanshah, Iran and Department of Nano Sciences, Institute for Studies in Theoretical Physics and Mathematics (IPM), Tehran (Iran, Islamic Republic of)

    2015-05-15

    The low-frequency electrostatic waves in metallic nanowires are studied using the quantum hydrodynamic model, in which the electron and ion components of the system are regarded as a two-species quantum plasma system. The Poisson equation as well as appropriate quantum boundary conditions give the analytical expressions of dispersion relations of the surface and bulk quantum ion-acoustic wave oscillations.

  20. Vacancy-indium clusters in implanted germanium

    KAUST Repository

    Chroneos, Alexander I.

    2010-04-01

    Secondary ion mass spectroscopy measurements of heavily indium doped germanium samples revealed that a significant proportion of the indium dose is immobile. Using electronic structure calculations we address the possibility of indium clustering with point defects by predicting the stability of indium-vacancy clusters, InnVm. We find that the formation of large clusters is energetically favorable, which can explain the immobility of the indium ions. © 2010 Elsevier B.V. All rights reserved.

  1. Silicon Germanium Cryogenic Low Noise Amplifiers

    Science.gov (United States)

    Bardin, J. C.; Montazeri, S.; Chang, Su-Wei

    2017-05-01

    Silicon germanium heterojunction bipolar transistors have emerged in the last decade as an excellent option for use in cryogenic low noise amplifiers. This paper begins with a review of the critical developments that have led to today’s cryogenic low noise amplifiers. Next, recent work focused on minimizing the power consumption of SiGe cryogenic amplifiers is presented. Finally, open issues related to the cryogenic noise properties of SiGe HBTs are discussed.

  2. Nanowire Growth for Photovoltaics

    DEFF Research Database (Denmark)

    Holm, Jeppe Vilstrup

    Solar cells commercial success is based on an efficiency/cost calculation. Nanowire solar cells is one of the foremost candidates to implement third generation photo voltaics, which are both very efficient and cheap to produce. This thesis is about our progress towards commercial nanowire solar c...

  3. Semiconductor Nanowires: Defects Update

    Science.gov (United States)

    Kavanagh, Karen L.

    2008-05-01

    Structural defects commonly observed in semiconducting nanowires by electron microscopy will be reviewed and their origins discussed. Their effects on electrical and optical properties will be illustrated with examples from GaSb, InAs, and ZnSe nanowires grown by MOCVD and MBE.

  4. Topological Insulator Nanowires and Nanoribbons

    KAUST Repository

    Kong, Desheng

    2010-01-13

    Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi2Se3 material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi2Se5 nanomaterials with a variety of morphologies. The synthesis of Bi 2Se5 nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [1120] direction with a rectangular cross-section and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with ∼ 1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitais to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states. © 2010 American Chemical Society.

  5. [Absolute and relative bioavailability of germanium in the rabbit].

    Science.gov (United States)

    Anger, F S; Anger, J P; Sado, P A; Chevanne, F

    1994-01-01

    The debated consumption of germanium suggested the authors to compare biopharmaceutical parameters of germanium oxide and germanium sesquioxide. A first evaluation, in rabbit, has been based on Germanium blood levels determined by atomic absorption spectrometry, after cross administration of both products by the I.V. and oral routes. When given orally, the apparent oxide bioavailability is very low (about 10%) but better than that of the sesquioxide. That difference could result from differences of disposition parameters of both products, which have to be studied late.

  6. Nanowire Growth for Photovoltaics

    DEFF Research Database (Denmark)

    Holm, Jeppe Vilstrup

    consisting of a single, vertical, gallium arsenide(GaAs) nanowire grown on silicon with a radial p-i-n-junction. The average concentration was ~8, and the peak concentration was ~12. By increasing the number of junctions in solar cells, they can extract more energy per absorbed photon. In ideal multi...... of the nanowires, some of which were removed from their growth substrate and turned into single nanowire solar cells (SNWSC). The best device showed a conversion efficiency of 6.8% under 1.5AMG 1-sun illumination. In order to improve the efficiency a surface passivating shell consisting of highly doped, wide......Solar cells commercial success is based on an efficiency/cost calculation. Nanowire solar cells is one of the foremost candidates to implement third generation photo voltaics, which are both very efficient and cheap to produce. This thesis is about our progress towards commercial nanowire solar...

  7. Amorphous germanium as an electron or hole blocking contact on high-purity germanium detectors

    International Nuclear Information System (INIS)

    Hansen, W.L.; Haller, E.E.

    1976-10-01

    Experiments were performed in an attempt to make thin n + contacts on high-purity germanium by the solid phase/sup 1)/ epitaxial regrowth of arsenic doped amorphous germanium. After cleaning the crystal surface with argon sputtering and trying many combinations of layers, it was not found possible to induce recrystallization below 400 0 C. However, it was found that simple thermally evaporated amorphous Ge made fairly good electron or hole blocking contacts. Excellent spectrometers have been made with amorphous Ge replacing the n + contact. As presently produced, the amorphous Ge contact diodes show a large variation in high-voltage leakage current

  8. Strain and thermal conductivity in ultrathin suspended silicon nanowires

    Science.gov (United States)

    Fan, Daniel; Sigg, Hans; Spolenak, Ralph; Ekinci, Yasin

    2017-09-01

    We report on the uniaxial strain and thermal conductivity of well-ordered, suspended silicon nanowire arrays between 10 to 20 nm width and 22 nm half-pitch, fabricated by extreme-ultraviolet (UV) interference lithography. Laser-power-dependent Raman spectroscopy showed that nanowires connected monolithically to the bulk had a consistent strain of ˜0.1 % , whereas nanowires clamped by metal exhibited variability and high strain of up to 2.3%, having implications in strain engineering of nanowires. The thermal conductivity at room temperature was measured to be ˜1 W /m K for smooth nanowires and ˜0.1 W /m K for rougher ones, similar to results by other investigators. We found no modification of the bulk properties in terms of intrinsic scattering, and therefore, the decrease in thermal conductivity is mainly due to boundary scattering. Different types of surface roughness, such as constrictions and line-edge roughness, may play roles in the scattering of phonons of different wavelengths. Such low thermal conductivities would allow for very efficient thermal energy harvesting, approaching and passing values achieved by state-of-the-art thermoelectric materials.

  9. Measurement of carrier mobility in silicon nanowires.

    Science.gov (United States)

    Gunawan, Oki; Sekaric, Lidija; Majumdar, Amlan; Rooks, Michael; Appenzeller, Joerg; Sleight, Jeffrey W; Guha, Supratik; Haensch, Wilfried

    2008-06-01

    We report the first direct capacitance measurements of silicon nanowires (SiNWs) and the consequent determination of field carrier mobilities in undoped-channel SiNW field-effect transistors (FETs) at room temperature. We employ a two-FET method for accurate extraction of the intrinsic channel resistance and intrinsic channel capacitance of the SiNWs. The devices used in this study were fabricated using a top-down method to create SiNW FETs with up to 1000 wires in parallel for increasing the raw capacitance while maintaining excellent control on device dimensions and series resistance. We found that, compared with the universal mobility curves for bulk silicon, the electron and hole mobilities in nanowires are comparable to those of the surface orientation that offers a lower mobility.

  10. Growth Mechanism of Nanowires: Binary and Ternary Chalcogenides

    Science.gov (United States)

    Singh, N. B.; Coriell, S. R.; Su, Ching-Hua; Hopkins, R. H.; Arnold, B.; Choa, Fow-Sen; Cullum, Brian

    2016-01-01

    Semiconductor nanowires exhibit very exciting optical and electrical properties including high transparency and a several order of magnitude better photocurrent than thin film and bulk materials. We present here the mechanism of nanowire growth from the melt-liquid-vapor medium. We describe preliminary results of binary and ternary selenide materials in light of recent theories. Experiments were performed with lead selenide and thallium arsenic selenide systems which are multifunctional material and have been used for detectors, acousto-optical, nonlinear and radiation detection applications. We observed that small units of nanocubes and elongated nanoparticles arrange and rearrange at moderate melt undercooling to form the building block of a nanowire. Since we avoided the catalyst, we observed self-nucleation and uncontrolled growth of wires from different places. Growth of lead selenide nanowires was performed by physical vapor transport method and thallium arsenic selenide nanowire by vapor-liquid-solid (VLS) method. In some cases very long wires (>mm) are formed. To achieve this goal experiments were performed to create situation where nanowires grew on the surface of solid thallium arsenic selenide itself.

  11. Electrochemically deposited BiTe-based nanowires for thermoelectric applications

    Energy Technology Data Exchange (ETDEWEB)

    Ng, Inn-Khuan; Kok, Kuan-Ying; Rahman, Che Zuraini Che Ab; Saidin, Nur Ubaidah; Ilias, Suhaila Hani; Choo, Thye-Foo [Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor Darul Ehsan (Malaysia)

    2014-02-12

    Nanostructured materials systems such as thin-films and nanowires (NWs) are promising for thermoelectric power generation and refrigeration compared to traditional counterparts in bulk, due to their enhanced thermoelectric figures-of-merit. BiTe and its derivative compounds, in particular, are well-known for their near-room temperature thermoelectric performance. In this work, both the binary and ternary BiTe-based nanowires namely, BiTe and BiSbTe, were synthesized using template-assisted electrodeposition. Diameters of the nanowires were controlled by the pore sizes of the anodised alumina (AAO) templates used. Systematic study on the compositional change as a function of applied potential was carried out via Linear Sweep Voltanmetry (LSV). Chemical compositions of the nanowires were studied using Energy Dispersive X-ray Spectrometry (EDXS) and their microstructures evaluated using diffraction and imaging techniques. Results from chemical analysis on the nanowires indicated that while the Sb content in BiSbTe nanowires increased with more negative deposition potentials, the formation of Te{sup 0} and Bi{sub 2}Te{sub 3} were favorable at more positive potentials.

  12. Enhanced thermoelectric performance of rough silicon nanowires

    Science.gov (United States)

    Hochbaum, Allon I.; Chen, Renkun; Delgado, Raul Diaz; Liang, Wenjie; Garnett, Erik C.; Najarian, Mark; Majumdar, Arun; Yang, Peidong

    2008-01-01

    Approximately 90 per cent of the world's power is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30-40 per cent efficiency, such that roughly 15terawatts of heat is lost to the environment. Thermoelectric modules could potentially convert part of this low-grade waste heat to electricity. Their efficiency depends on the thermoelectric figure of merit ZT of their material components, which is a function of the Seebeck coefficient, electrical resistivity, thermal conductivity and absolute temperature. Over the past five decades it has been challenging to increase ZT>1, since the parameters of ZT are generally interdependent. While nanostructured thermoelectric materials can increase ZT>1 (refs 2-4), the materials (Bi, Te, Pb, Sb, and Ag) and processes used are not often easy to scale to practically useful dimensions. Here we report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20-300nm in diameter. These nanowires have Seebeck coefficient and electrical resistivity values that are the same as doped bulk Si, but those with diameters of about 50nm exhibit 100-fold reduction in thermal conductivity, yielding ZT = 0.6 at room temperature. For such nanowires, the lattice contribution to thermal conductivity approaches the amorphous limit for Si, which cannot be explained by current theories. Although bulk Si is a poor thermoelectric material, by greatly reducing thermal conductivity without much affecting the Seebeck coefficient and electrical resistivity, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.

  13. Silicon nanowire hybrid photovoltaics

    KAUST Repository

    Garnett, Erik C.

    2010-06-01

    Silicon nanowire Schottky junction solar cells have been fabricated using n-type silicon nanowire arrays and a spin-coated conductive polymer (PEDOT). The polymer Schottky junction cells show superior surface passivation and open-circuit voltages compared to standard diffused junction cells with native oxide surfaces. External quantum efficiencies up to 88% were measured for these silicon nanowire/PEDOT solar cells further demonstrating excellent surface passivation. This process avoids high temperature processes which allows for low-cost substrates to be used. © 2010 IEEE.

  14. Germanium: From Its Discovery to SiGe Devices

    Energy Technology Data Exchange (ETDEWEB)

    Haller, E.E.

    2006-06-14

    Germanium, element No.32, was discovered in 1886 by Clemens Winkler. Its first broad application was in the form of point contact Schottky diodes for radar reception during WWII. The addition of a closely spaced second contact led to the first all-solid-state electronic amplifier device, the transistor. The relatively low bandgap, the lack of a stable oxide and large surface state densities relegated germanium to the number 2 position behind silicon. The discovery of the lithium drift process, which made possible the formation of p-i-n diodes with fully depletable i-regions several centimeters thick, led germanium to new prominence as the premier gamma-ray detector. The development of ultra-pure germanium yielded highly stable detectors which have remained unsurpassed in their performance. New acceptors and donors were discovered and the electrically active role of hydrogen was clearly established several years before similar findings in silicon. Lightly doped germanium has found applications as far infrared detectors and heavily Neutron Transmutation Doped (NTD) germanium is used in thermistor devices operating at a few milliKelvin. Recently germanium has been rediscovered by the silicon device community because of its superior electron and hole mobility and its ability to induce strains when alloyed with silicon. Germanium is again a mainstream electronic material.

  15. Aerosol assisted chemical vapour deposition of germanium thin ...

    Indian Academy of Sciences (India)

    films were characterized by XRD, SEM and EDS measurements. Their electrical properties were assessed by current–voltage (I–V) characterization. Keywords. Organogermanium; germanium thin films; AACVD; XRD. 1. Introduction. Germanium has gained a renewed interest in electronics industry due to its lower bandgap ...

  16. Effects of electronically neutral impurities on muonium in germanium

    International Nuclear Information System (INIS)

    Clawson, C.W.; Crowe, K.M.; Haller, E.E.; Rosenblum, S.S.; Brewer, J.H.

    1983-04-01

    Low-temperature measurements of muonium parameters in various germanium crystals have been performed. We have measured crystals with different levels of neutral impurities, with and without dislocations, and with different annealing histories. The most striking result is the apparent trapping of Mu by silicon impurities in germanium

  17. Ultraviolet-light-induced processes in germanium-doped silica

    DEFF Research Database (Denmark)

    Kristensen, Martin

    2001-01-01

    A model is presented for the interaction of ultraviolet (UV) light with germanium-doped silica glass. It is assumed that germanium sites work as gates for transferring the excitation energy into the silica. In the material the excitation induces forbidden transitions to two different defect states...

  18. Frenkel pairs in germanium and silicon (review)

    International Nuclear Information System (INIS)

    Emtsev, V.V.; Mashovets, T.V.; Mikhnovich, V.V.

    1992-01-01

    A state-of-the-art review is given of the properties of primary structure defects (Frenkel pairs) in silicon and geramanium. The process of formation of Frenkel pairs under conditions of irradiation with electrons or with γrays of ∼1 MeV energy at temperatures 4.2-300 K is considered. Approximate calculations are made of the energy of the interaction of the Frenkel pair components, vacancies (V) and interstitial atoms (I), in the approximation of an anisotropic elastic continuum subject to the electrostatic and elastic interactions. It is shown that the contribution of the flexoelectric effect may be considerable and should be allowed for in estimating the energy of the electrostatic interaction between V and I in those cases when one or both Frenkel pair components are electrically neutral. The mobility of V and I is considered, including the mobility during irradiation, and the energy spectra of vacancies and interstitials are discussed. The dependence of the probability of annihilation of homogeneous V and I on a whole range of parameters (temperature and intensity of irradiation, impurity composition of the irradiated material, densities of equilibrium and nonequilibrium carriers) is considered. An analysis of this dependence makes it possible to interpret qualitatively a complex nonmonotonic dependence of the efficiency of formation of primary and secondary (including impurity atoms) defects on the irradiation temperature and the radiation intensity and on the type of conduction of germanium. A nomogram is plotted for describing the dependence of the efficiency of defect formation in n-type germanium at 300 K on the radiation intensity and on the concentration of group V donors. It is shown that metastable Frenkel pairs are not observed in silicon, whereas germanium represents a unique opportunity for detecting such metastable pairs in an elemental semiconductor with the covalent type of binding. 68 refs., 7 figs., 2 tabs

  19. MAJORANA Collaboration's Experience with Germanium Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Mertens, S. [Lawrence Berkeley National Laboratory (LBNL); Abgrall, N. [Lawrence Berkeley National Laboratory (LBNL); Avignone, III, F. T. [University of South Carolina/Oak Ridge National Laboratory (ORNL); Barabash, A.S. [Institute of Theoretical & Experimental Physics (ITEP), Moscow, Russia; Bertrand, F. E. [Oak Ridge National Laboratory (ORNL); Efremenko, Yuri [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Galindo-Uribarri, A [Oak Ridge National Laboratory (ORNL); Radford, D. C. [Oak Ridge National Laboratory (ORNL); Romero-Romero, E. [UTK/ORNL; Varner, R. L. [Oak Ridge National Laboratory (ORNL); White, B. R. [Oak Ridge National Laboratory (ORNL); Wilkerson, J. F. [UNC/Triangle Univ. Nucl. Lab, Durham, NC/ORNL; Yu, C.-H. [Oak Ridge National Laboratory (ORNL); Majorana, [MAJORANA Collaboration

    2015-01-01

    The goal of the Majorana Demonstrator project is to search for 0v beta beta decay in Ge-76. Of all candidate isotopes for 0v beta beta, Ge-76 has some of the most favorable characteristics. Germanium detectors are a well established technology, and in searches for 0v beta beta, the high purity germanium crystal acts simultaneously as source and detector. Furthermore, p-type germanium detectors provide excellent energy resolution and a specially designed point contact geometry allows for sensitive pulse shape discrimination. This paper will summarize the experiences the MAJORANA collaboration made with enriched germanium detectors manufactured by ORTEC (R)(R). The process from production, to characterization and integration in MAJORANA mounting structure will be described. A summary of the performance of all enriched germanium detectors will be given.

  20. Temperature dependence of the infrared optical constants of germanium films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Dandan, E-mail: ldd6162@163.com; Liu, Huasong; Jiang, Chenghui; Leng, Jian; Zhang, Yanmin; Zhao, Zhihong; Zhuang, Kewen; Jiang, Yugang; Ji, Yiqin

    2015-10-01

    High-temperature transmittance spectrum of germanium films was obtained by a Fourier Transform infrared spectroscopy with a high-temperature accessory. The optical constants were determined by transmittance spectrum fitting with a Gaussian oscillator as the dispersion model. The analysis results showed that both the refractive index and extinction coefficient increased with the increasing temperature. The square of the refractive index increased linearly with the increasing temperature. The higher the temperature was, the faster the absorption coefficient increased. The germanium films were deposited on chemical vapor deposition ZnS substrates by ion-beam-assisted deposition. The region of temperature was between room temperature and 773 K, and the analysis spectrum was between 2000 nm and 5000 nm. - Highlights: • Temperature dependence of transmittance spectrum of Germanium films • Temperature properties of refractive index of Germanium films • Temperature properties of absorption coefficient of Germanium films.

  1. Array of germanium detectors for nuclear safeguards

    International Nuclear Information System (INIS)

    Moss, C.E.; Bernard, W.; Dowdy, E.J.; Garcia, C.; Lucas, M.C.; Pratt, J.C.

    1983-01-01

    Our gamma-ray spectrometer system, designed for field use, offers high efficiency and high resolution for safeguards applications. The system consists of three 40% high-purity germanium detectors and a LeCroy 3500 data-acquisition system that calculates a composite spectrum for the three detectors. The LeCroy 3500 mainframe can be operated remotely from the detector array with control exercised through moderns and the telephone system. System performance with a mixed source of 125 Sb, 154 Eu, and 155 Eu confirms the expected efficiency of 120% with an overall resolution that is between the resolution of the best detector and that of the worst

  2. Tensile strain mapping in flat germanium membranes

    Energy Technology Data Exchange (ETDEWEB)

    Rhead, S. D., E-mail: S.Rhead@warwick.ac.uk; Halpin, J. E.; Myronov, M.; Patchett, D. H.; Allred, P. S.; Wilson, N. R.; Leadley, D. R. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Shah, V. A. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Department of Engineering, University of Warwick, Coventry, CV4 7AL (United Kingdom); Kachkanov, V.; Dolbnya, I. P. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE (United Kingdom); Reparaz, J. S. [ICN2 - Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) (Spain); Sotomayor Torres, C. M. [ICN2 - Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) (Spain)

    2014-04-28

    Scanning X-ray micro-diffraction has been used as a non-destructive probe of the local crystalline quality of a thin suspended germanium (Ge) membrane. A series of reciprocal space maps were obtained with ∼4 μm spatial resolution, from which detailed information on the strain distribution, thickness, and crystalline tilt of the membrane was obtained. We are able to detect a systematic strain variation across the membranes, but show that this is negligible in the context of using the membranes as platforms for further growth. In addition, we show evidence that the interface and surface quality is improved by suspending the Ge.

  3. Tensile strain mapping in flat germanium membranes

    International Nuclear Information System (INIS)

    Rhead, S. D.; Halpin, J. E.; Myronov, M.; Patchett, D. H.; Allred, P. S.; Wilson, N. R.; Leadley, D. R.; Shah, V. A.; Kachkanov, V.; Dolbnya, I. P.; Reparaz, J. S.; Sotomayor Torres, C. M.

    2014-01-01

    Scanning X-ray micro-diffraction has been used as a non-destructive probe of the local crystalline quality of a thin suspended germanium (Ge) membrane. A series of reciprocal space maps were obtained with ∼4 μm spatial resolution, from which detailed information on the strain distribution, thickness, and crystalline tilt of the membrane was obtained. We are able to detect a systematic strain variation across the membranes, but show that this is negligible in the context of using the membranes as platforms for further growth. In addition, we show evidence that the interface and surface quality is improved by suspending the Ge

  4. Silicon germanium mask for deep silicon etching

    KAUST Repository

    Serry, Mohamed

    2014-07-29

    Polycrystalline silicon germanium (SiGe) can offer excellent etch selectivity to silicon during cryogenic deep reactive ion etching in an SF.sub.6/O.sub.2 plasma. Etch selectivity of over 800:1 (Si:SiGe) may be achieved at etch temperatures from -80 degrees Celsius to -140 degrees Celsius. High aspect ratio structures with high resolution may be patterned into Si substrates using SiGe as a hard mask layer for construction of microelectromechanical systems (MEMS) devices and semiconductor devices.

  5. Self-induced growth of vertical GaN nanowires on silica

    International Nuclear Information System (INIS)

    Kumaresan, V; Largeau, L; Oehler, F; Mauguin, O; Glas, F; Gogneau, N; Harmand, J-C; Zhang, H; Tchernycheva, M

    2016-01-01

    We study the self-induced growth of GaN nanowires on silica. Although the amorphous structure of this substrate offers no possibility of an epitaxial relationship, the nanowires are remarkably aligned with the substrate normal whereas, as expected, their in-plane orientation is random. Their structural and optical characteristics are compared to those of GaN nanowires grown on standard crystalline Si (111) substrates. The polarity inversion domains are much less frequent, if not totally absent, in the nanowires grown on silica, which we find to be N-polar. This work demonstrates that high-quality vertical GaN nanowires can be elaborated without resorting to bulk crystalline substrates. (paper)

  6. Dimensional effects in semiconductor nanowires; Dimensionseffekte in Halbleiternanodraehten

    Energy Technology Data Exchange (ETDEWEB)

    Stichtenoth, Daniel

    2008-06-23

    Nanomaterials show new physical properties, which are determined by their size and morphology. These new properties can be ascribed to the higher surface to volume ratio, to quantum size effects or to a form anisotropy. They may enable new technologies. The nanowires studied in this work have a diameter of 4 to 400 nm and a length up to 100 {mu}m. The semiconductor material used is mainly zinc oxide (ZnO), zinc sulfide (ZnS) and gallium arsenide (GaAs). All nanowires were synthesized according to the vapor liquid solid mechanism, which was originally postulated for the growth of silicon whiskers. Respective modifications for the growth of compound semiconductor nanowires are discussed. Detailed luminescence studies on ZnO nanowires with different diameters show pronounced size effects which can be attributed to the origins given above. Similar to bulk material, a tuning of the material properties is often essential for a further functionalization of the nanowires. This is typical realized by doping the source material. It becomes apparent, that a controlled doping of nanowires during the growth process is not successful. Here an alternative method is chosen: the doping after the growth by ion implantation. However, the doping by ion implantation goes always along with the creation of crystal defects. The defects have to be annihilated in order to reach an activation of th introduced dopants. At high ion fluences and ion masses the sputtering of surface atoms becomes more important. This results in a characteristic change in the morphology of the nanowires. In detail, the doping of ZnO and ZnS nanowires with color centers (manganese and rare earth elements) is demonstrated. Especially, the intra 3d luminescence of manganese implanted ZnS nanostructures shows a strong dependence of the nanowire diameter and morphology. This dependence can be described by expanding Foersters model (which describes an energy transfer to the color centers) by a dimensional parameter

  7. Porous Silicon Nanowires

    Science.gov (United States)

    Qu, Yongquan; Zhou, Hailong; Duan, Xiangfeng

    2011-01-01

    In this minreview, we summarize recent progress in the synthesis, properties and applications of a new type of one-dimensional nanostructures — single crystalline porous silicon nanowires. The growth of porous silicon nanowires starting from both p- and n-type Si wafers with a variety of dopant concentrations can be achieved through either one-step or two-step reactions. The mechanistic studies indicate the dopant concentration of Si wafers, oxidizer concentration, etching time and temperature can affect the morphology of the as-etched silicon nanowires. The porous silicon nanowires are both optically and electronically active and have been explored for potential applications in diverse areas including photocatalysis, lithium ion battery, gas sensor and drug delivery. PMID:21869999

  8. Biofunctionalized Magnetic Nanowires

    KAUST Repository

    Kosel, Jurgen

    2013-12-19

    Magnetic nanowires can be used as an alternative method overcoming the limitations of current cancer treatments that lack specificity and are highly cytotoxic. Nanowires are developed so that they selectively attach to cancer cells via antibodies, potentially destroying them when a magnetic field induces their vibration. This will transmit a mechanical force to the targeted cells, which is expected to induce apoptosis on the cancer cells.

  9. Engineering Nanostructural Routes for Enhancing Thermoelectric Performance: Bulk to Nanoscale.

    Science.gov (United States)

    Mohanraman, Rajeshkumar; Lan, Tian-Wey; Hsiung, Te-Chih; Amada, Dedi; Lee, Ping-Chung; Ou, Min-Nan; Chen, Yang-Yuan

    2015-01-01

    Thermoelectricity is a very important phenomenon, especially its significance in heat-electricity conversion. If thermoelectric devices can be effectively applied to the recovery of the renewable energies, such as waste heat and solar energy, the energy shortage, and global warming issues may be greatly relieved. This review focusses recent developments on the thermoelectric performance of a low-dimensional material, bulk nanostructured materials, conventional bulk materials etc. Particular emphasis is given on, how the nanostructure in nanostructured composites, confinement effects in one-dimensional nanowires and doping effects in conventional bulk composites plays an important role in ZT enhancement.

  10. Efficient Organic/Inorganic Hybrid Solar Cell Integrating Polymer Nanowires and Inorganic Nanotetrapods

    OpenAIRE

    Xu, Weizhe; Tan, Furui; Liu, Xiansheng; Zhang, Weifeng; Qu, Shengchun; Wang, Zhijie; Wang, Zhanguo

    2017-01-01

    Constructing a highly efficient bulk-heterojunction is of critical importance to the hybrid organic/inorganic solar cells. Here in this work, we introduce a novel hybrid architecture containing P3HT nanowire and CdSe nanotetrapod as bicontinuous charge channels for holes and electrons, respectively. Compared to the traditionally applied P3HT molecules, the well crystallized P3HT nanowires qualify an enhanced light absorption at the long wavelength as well as strengthened charge carrier transp...

  11. Electromechanically cooled germanium radiation detector system

    International Nuclear Information System (INIS)

    Lavietes, Anthony D.; Joseph Mauger, G.; Anderson, Eric H.

    1999-01-01

    We have successfully developed and fielded an electromechanically cooled germanium radiation detector (EMC-HPGe) at Lawrence Livermore National Laboratory (LLNL). This detector system was designed to provide optimum energy resolution, long lifetime, and extremely reliable operation for unattended and portable applications. For most analytical applications, high purity germanium (HPGe) detectors are the standard detectors of choice, providing an unsurpassed combination of high energy resolution performance and exceptional detection efficiency. Logistical difficulties associated with providing the required liquid nitrogen (LN) for cooling is the primary reason that these systems are found mainly in laboratories. The EMC-HPGe detector system described in this paper successfully provides HPGe detector performance in a portable instrument that allows for isotopic analysis in the field. It incorporates a unique active vibration control system that allows the use of a Sunpower Stirling cycle cryocooler unit without significant spectral degradation from microphonics. All standard isotopic analysis codes, including MGA and MGA++, GAMANL, GRPANL and MGAU, typically used with HPGe detectors can be used with this system with excellent results. Several national and international Safeguards organisations including the International Atomic Energy Agency (IAEA) and U.S. Department of Energy (DOE) have expressed interest in this system. The detector was combined with custom software and demonstrated as a rapid Field Radiometric Identification System (FRIS) for the U.S. Customs Service . The European Communities' Safeguards Directorate (EURATOM) is field-testing the first Safeguards prototype in their applications. The EMC-HPGe detector system design, recent applications, and results will be highlighted

  12. High-purity germanium crystal growing

    International Nuclear Information System (INIS)

    Hansen, W.L.; Haller, E.E.

    1982-10-01

    The germanium crystals used for the fabrication of nuclear radiation detectors are required to have a purity and crystalline perfection which is unsurpassed by any other solid material. These crystals should not have a net electrically active impurity concentration greater than 10 10 cm - 3 and be essentially free of charge trapping defects. Such perfect crystals of germanium can be grown only because of the highly favorable chemical and physical properties of this element. However, ten years of laboratory scale and commercial experience has still not made the production of such crystals routine. The origin and control of many impurities and electrically active defect complexes is now fairly well understood but regular production is often interrupted for long periods due to the difficulty of achieving the required high purity or to charge trapping in detectors made from crystals seemingly grown under the required conditions. The compromises involved in the selection of zone refining and crystal grower parts and ambients is discussed and the difficulty in controlling the purity of key elements in the process is emphasized. The consequences of growing in a hydrogen ambient are discussed in detail and it is shown how complexes of neutral defects produce electrically active centers

  13. Thermal conductivity measurement of Ge-Si{sub x}Ge{sub 1-x} core-shell nanowires using suspended microdevices

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hyun Joon; Seol Jae Hun [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of); Nah, Jung Hyo [Chonnam National University, Gwangju (Korea, Republic of); Tutuc, Emanuel [The University of Texas at Austin, Austin (Korea, Republic of)

    2015-10-15

    Theoretical calculations suggest that the thermoelectric figure of merit (ZT) can be improved by introducing a core-shell heterostructure to a semiconductor nanowire because of the reduced thermal conductivity of the nanowire. To experimentally verify the decrease in thermal conductivity in core-shell nanowires, the thermal conductivity of Ge-SixGe1-x core-shell nanowires grown by chemical vapor deposition (CVD) was measured using suspended microdevices. The silicon composition (Xsi) in the shells was measured to be about 0.65, and the remainder of the germanium in the shells was shown to play a role in decreasing defects originating from the lattice mismatch between the cores and shells. In addition to the standard four-point current- voltage (I-V) measurement, the measurement configuration based on the Wheatstone bridge was attempted to enhance the measurement sensitivity. The measured thermal conductivity values are in the range of 9-13 W/mK at room temperature and are lower by approximately 30 than that of a germanium nanowire with a comparable diameter.

  14. Effect of magnetic field on the mechanical properties of magnetostrictive iron-gallium nanowires

    International Nuclear Information System (INIS)

    Downey, Patrick R.; Flatau, Alison B.; McGary, Patrick D.; Stadler, Bethanie J. H.

    2008-01-01

    This study experimentally investigates the elastic properties of individual iron-gallium nanowires with and without an applied magnetic bias field. The experiments were conducted with a custom manipulator stage designed for use within a scanning electron microscope, where nanowires were mechanically tested both statically and dynamically. Experiments were also performed in the presence of a 20 Oe dc magnetic field in order to identify any variation in wire properties. The results suggest that iron-gallium nanowires possess an elastic modulus very similar to the macroscale value, tensile strengths of more than double the bulk material, and minor magnetic field induced stiffening at low stresses

  15. Site-selective fabrication of conducting molecular nanowires based on electrocrystallization

    International Nuclear Information System (INIS)

    Hasegawa, H.; Kubota, T.; Mashiko, S.

    2005-01-01

    We have grown nanowires in a selective position by using an electrochemical process and alternating current. Nanoscale electrocrystallization was carried out in an axially substituted phthalocyanine solution using substrates with two electrodes formed by photolithography. The growth area was limited to the narrowest part of the gap between the tips of the electrodes by using tapered electrodes. The nanowires obtained had a width of approximately 100 nm and a length of more than 1 μm. Analysis of the selected-area electron diffraction pattern showed that the nanowire structure was identical to that of bulk crystal

  16. Using Nanowires To Extract Excitons from a Nanocrystal Solid

    Energy Technology Data Exchange (ETDEWEB)

    Dorn, August; Strasfeld, David B.; Harris, Daniel K.; Han, Hee-Sun; Bawendi, Moungi G.

    2011-11-22

    Synthetic methods yielding highly uniform colloidal semiconductor nanocrystals with controlled shapes and sizes are now available for many materials. These methods have enabled geometrical control of optical properties, which are difficult or impossible to achieve in conventional bulk solids. However, incorporating nanocrystals efficiently into photodetectors remains challenging because of the low charge carrier mobilities typical of nanocrystal solids. Here we present an approach based on exciton energy transfer from CdSe/CdS core/shell nanocrystals to embedded CdSe nanowires. By combining the wide electronic tunability of nanocrystals with the excellent one-dimensional charge transport characteristics obtainable in nanowires, we are able to increase photocurrent extraction from a nanocrystal solid by 2–3 orders of magnitude. Furthermore, we correlate local device morphology with optoelectronic functionality by measuring the local photocurrent response in a scanning confocal microscope. We also discuss how nancocrystal/nanowire hybrid devices could be used in particle detector systems.

  17. Topological Insulator Nanowires and Nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Kong, D.S.

    2010-06-02

    Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi{sub 2}Se{sub 3} material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi{sub 2}Se{sub 3} nanomaterials with a variety of morphologies. The synthesis of Bi{sub 2}Se{sub 3} nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [11-20] direction with a rectangular crosssection and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with {approx}1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitals to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states.

  18. Solution-processed core-shell nanowires for efficient photovoltaic cells.

    Science.gov (United States)

    Tang, Jinyao; Huo, Ziyang; Brittman, Sarah; Gao, Hanwei; Yang, Peidong

    2011-08-21

    Semiconductor nanowires are promising for photovoltaic applications, but, so far, nanowire-based solar cells have had lower efficiencies than planar cells made from the same materials, even allowing for the generally lower light absorption of nanowires. It is not clear, therefore, if the benefits of the nanowire structure, including better charge collection and transport and the possibility of enhanced absorption through light trapping, can outweigh the reductions in performance caused by recombination at the surface of the nanowires and at p-n junctions. Here, we fabricate core-shell nanowire solar cells with open-circuit voltage and fill factor values superior to those reported for equivalent planar cells, and an energy conversion efficiency of ∼5.4%, which is comparable to that of equivalent planar cells despite low light absorption levels. The device is made using a low-temperature solution-based cation exchange reaction that creates a heteroepitaxial junction between a single-crystalline CdS core and single-crystalline Cu2S shell. We integrate multiple cells on single nanowires in both series and parallel configurations for high output voltages and currents, respectively. The ability to produce efficient nanowire-based solar cells with a solution-based process and Earth-abundant elements could significantly reduce fabrication costs relative to existing high-temperature bulk material approaches.

  19. Oxygen defect processes in silicon and silicon germanium

    KAUST Repository

    Chroneos, A.

    2015-06-18

    Silicon and silicon germanium are the archetypical elemental and alloy semiconductor materials for nanoelectronic, sensor, and photovoltaic applications. The investigation of radiation induced defects involving oxygen, carbon, and intrinsic defects is important for the improvement of devices as these defects can have a deleterious impact on the properties of silicon and silicon germanium. In the present review, we mainly focus on oxygen-related defects and the impact of isovalent doping on their properties in silicon and silicon germanium. The efficacy of the isovalent doping strategies to constrain the oxygen-related defects is discussed in view of recent infrared spectroscopy and density functional theory studies.

  20. Electronic states of germanium grown under micro-gravity condition

    Energy Technology Data Exchange (ETDEWEB)

    Sugahara, A. [Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)]. E-mail: sugahara@tsurugi.phys.sci.osaka-u.ac.jp; Ogawa, T. [Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Fujii, K. [Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Ohyama, T. [Liberal Arts, Fukui University of Technology, 3-6-1 Gakuen, Fukui, Fukui 910-8505 (Japan); Nakata, J. [Kyoto Semiconductor Corp. 418-9 Yodo Saime-cho, Fushimi-ku, Kyoto 613-0915 (Japan)

    2006-04-01

    Magneto-optical absorption measurements of Sb-doped germaniums grown under micro-gravity condition were carried out to investigate the influence of the gravity on crystal growth, using far-infrared laser and microwave. For comparison, we prepared two germanium crystals grown in the same conditions except the gravity conditions. In spite of the quite short growth period, the germanium grown under micro-gravity has a quite good quality. The lineshape analysis of Zeeman absorption peaks due to donor electrons indicates the existence of residual thermal acceptors.

  1. Band structure analysis in SiGe nanowires

    International Nuclear Information System (INIS)

    Amato, Michele; Palummo, Maurizia; Ossicini, Stefano

    2012-01-01

    One of the main challenges for Silicon-Germanium nanowires (SiGe NWs) electronics is the possibility to modulate and engine their electronic properties in an easy way, in order to obtain a material with the desired electronic features. Diameter and composition constitute two crucial ways for the modification of the band gap and of the band structure of SiGe NWs. Within the framework of density functional theory we present results of ab initio calculations regarding the band structure dependence of SiGe NWs on diameter and composition. We point out the main differences with respect to the case of pure Si and Ge wires and we discuss the particular features of SiGe NWs that are useful for future technological applications.

  2. Band structure analysis in SiGe nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Amato, Michele [' Centro S3' , CNR-Istituto Nanoscienze, via Campi 213/A, 41100 Modena (Italy); Dipartimento di Scienze e Metodi dell' Ingegneria, Universita di Modena e Reggio Emilia, via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia (Italy); Palummo, Maurizia [European Theoretical Spectroscopy Facility (ETSF) (Italy); CNR-INFM-SMC, Dipartimento di Fisica, Universita di Roma, ' Tor Vergata' , via della Ricerca Scientifica 1, 00133 Roma (Italy); Ossicini, Stefano, E-mail: stefano.ossicini@unimore.it [' Centro S3' , CNR-Istituto Nanoscienze, via Campi 213/A, 41100 Modena (Italy) and Dipartimento di Scienze e Metodi dell' Ingegneria, Universita di Modena e Reggio Emilia, via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia (Italy) and European Theoretical Spectroscopy Facility - ETSF (Italy) and Centro Interdipartimentale ' En and Tech' , Universita di Modena e Reggio Emilia, via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia (Italy)

    2012-06-05

    One of the main challenges for Silicon-Germanium nanowires (SiGe NWs) electronics is the possibility to modulate and engine their electronic properties in an easy way, in order to obtain a material with the desired electronic features. Diameter and composition constitute two crucial ways for the modification of the band gap and of the band structure of SiGe NWs. Within the framework of density functional theory we present results of ab initio calculations regarding the band structure dependence of SiGe NWs on diameter and composition. We point out the main differences with respect to the case of pure Si and Ge wires and we discuss the particular features of SiGe NWs that are useful for future technological applications.

  3. Energy harvesting performance of piezoelectric ceramic and polymer nanowires.

    Science.gov (United States)

    Crossley, Sam; Kar-Narayan, Sohini

    2015-08-28

    Energy harvesting from ubiquitous ambient vibrations is attractive for autonomous small-power applications and thus considerable research is focused on piezoelectric materials as they permit direct inter-conversion of mechanical and electrical energy. Nanogenerators (NGs) based on piezoelectric nanowires are particularly attractive due to their sensitivity to small-scale vibrations and may possess superior mechanical-to-electrical conversion efficiency when compared to bulk or thin-film devices of the same material. However, candidate piezoelectric nanowires have hitherto been predominantly analyzed in terms of NG output (i.e. output voltage, output current and output power density). Surprisingly, the corresponding dynamical properties of the NG, including details of how the nanowires are mechanically driven and its impact on performance, have been largely neglected. Here we investigate all realizable NG driving contexts separately involving inertial displacement, applied stress T and applied strain S, highlighting the effect of driving mechanism and frequency on NG performance in each case. We argue that, in the majority of cases, the intrinsic high resonance frequencies of piezoelectric nanowires (∼tens of MHz) present no barrier to high levels of NG performance even at frequencies far below resonance (materials properties, for comparing piezoelectric NG performance under strain-driven and stress-driven conditions respectively. These figures of merit permit, for the first time, a general comparison of piezoelectric nanowires for NG applications that takes into account the nature of the mechanical excitation. We thus investigate the energy harvesting performance of prototypical piezoelectric ceramic and polymer nanowires. We find that even though ceramic and polymer nanowires have been found, in certain cases, to have similar energy conversion efficiencies, ceramics are more promising in strain-driven NGs while polymers are more promising for stress-driven NGs

  4. Low frequency noise sources and mechanisms in semiconductor nanowire transistors

    Science.gov (United States)

    Delker, Collin James

    Semiconductor nanowires are attractive candidates for use in future high-speed electronics, transparent/flexible devices, and chemical sensors. Among other materials, III-V semiconductors have gained considerable interest for their high bulk mobility and low band gap, making them promising for high-speed nanoscale devices. However, nanowire devices also exhibit high levels of low-frequency noise due to their low band gap and high surface-to-volume ratio. The sources and mechanisms of this noise must be understood and controlled in order to realize practical applications of nanowire electronics. This work seeks to understand the underlying noise mechanisms of nanowire transistors in order discover ways to reduce noise levels. It also demonstrates how noise can provide a spectroscopy for analyzing device quality. Most traditional noise studies tend to apply standard MOSFET models to nanowire noise and transport, which lump together all possible independent noise sources in a nanowire, ignoring effects of the contacts or multiple gates, and could lead to misestimation of the noise figures for a device. This work demonstrates how noise in a nanowire transistor can stem from the channel, ungated access regions, metal- semiconductor contacts, and tunnel barriers, all independently adding to the total noise. Each source of noise can contribute and may dominate the overall noise behavior under certain bias regimes and temperatures, as demonstrated in this work through various device structures and measurements. For example, the contacts can influence noise even below the threshold voltage under certain conditions, emphasizing the need for high-quality metal-semiconductor interface technology.

  5. Germanium detectors and natural radioactivity in food

    Energy Technology Data Exchange (ETDEWEB)

    Garbini, Lucia [Max-Planck-Institut fuer Physik, Muenchen (Germany); Collaboration: GeDet-Collaboration

    2013-07-01

    Potassium is a very important mineral for many physiological processes, like fluid balance, protein synthesis and signal transmission in nerves. Many aliments like raisins, bananas or chocolate contain potassium. Natural potassium contains 0.012% of the radioactive isotope Potassium 40. This isotope decays via β{sup +} decay into a metastable state of Argon 40, which reaches its ground state emitting a gamma of 1460 keV. A commercially produced Germanium detector has been used to measure the energy spectra of different selected food samples. It was calibrated with KCl and potassium contents were extracted. Results verify the high potassium content of commonly recommended food samples. However, the measurement quantitatively differ from the expectations in several cases. One of the most interesting results concerns chocolate bars with different percentages of cacao.

  6. Whispering gallery germanium-on-silicon photodetector.

    Science.gov (United States)

    Su, Zhan; Hosseini, Ehsan Shah; Timurdogan, Erman; Sun, Jie; Moresco, Michele; Leake, Gerald; Adam, Thomas N; Coolbaugh, Douglas D; Watts, Michael R

    2017-08-01

    We design and demonstrate, to the best of our knowledge, the first whispering gallery germanium-on-silicon photodetector with evanescent coupling from a silicon bus waveguide in a CMOS-compatible process. The small footprint (63.6  μm 2 ), high responsivity (∼1.04  A/W at 1530 nm), low bias voltage (-1  V), low dark current (2.03 nA), and large optoelectric bandwidth (32.9 GHz) of the detector enable simultaneous wavelength filtering and power detection, ideal for handling large network data traffic. In addition, with the resonant nature of the detector, we also optimize the design to enable long-wavelength detection, achieving a separate device with a detection range of up to 1630 nm with a >0.45  A/W responsivity, making it an important building block for optical communication networks.

  7. Scalable, epitaxy-free fabrication of super-absorbing sparse III-V nanowire arrays for photovoltaic applications (Conference Presentation)

    Science.gov (United States)

    Cheng, Wen-Hui; Fountaine, Katherine T.; Bukowsky, Colton R.; Atwater, Harry A.

    2016-09-01

    III-V compound semiconductor nanowire arrays are promising candidates for photovoltaics applications due to their high volumetric absorption. Uniform nanowire arrays exhibit high absorption at certain wavelengths due to strong coupling into lossy waveguide modes. Previously, simulations predicted near-unity, broadband absorption in sparse semiconductor nanowire arrays (Polymer-embedded wires are removed from the bulk InP substrate by a mechanical method that facilitates extensive reuse of a single bulk InP wafer to synthesize many polymer-embedded nanowire array thin films. Arrays containing multiple nanowire radii and tapered nanowires were successfully fabricated. For both designs, the polymer-embedded arrays achieved 90% broadband absorption (λ=400-900 nm) in less than 100 nm planar equivalence of InP. The addition of a silver back reflector increased this broadband absorption to 95%. The repeatable process of imprinting, etching and peeling to obtain many nanowire arrays from one single wafer represents an economical manufacturing route for high efficiency III-V photovoltaics. [1] K.T. Fountaine, C.G. Kendall, Harry A. Atwater, "Near-unity broadband absorption designs for semiconducting nanowire arrays via localized radial mode excitation," Opt. Exp. (2014).

  8. Growth and Raman spectroscopy studies of gold-free catalyzed semiconductor nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Zardo, Ilaria

    2010-12-15

    , enabled us to address the variation of the intensity of the scattered radiation along the nanowire length to the variation of the crystalline fraction. As well, the shift in frequency of the mode related to the crystalline Ge was attributed to phonon confinement effects. Spatially resolved Raman spectroscopy experiments were realized on single GaAs nanowires. Polarization dependent Raman scattering experiments enabled us to determine the Raman selection rules for zinc-blende GaAs nanowires. They were found to be modified with respect to the bulk. A component of the scattered light with respect to bulk GaAs is suppressed, due to the dielectric mismatch of a cylinder of nanoscale dimensions. Spatially resolved Raman spectroscopy experiments were realized on single zinc- blende/wurtzite GaAs nanowires, with different wurtzite content. The Raman spectrum of wurtzite GaAs was measured for the first time and the symmetry of the corresponding modes was determined by polarization dependent scattering experiments. The E{sub 1} - A{sub 1} splitting due to anisotropy of the crystal in wurtzite GaAs nanowires was found. The presence of strain along the zinc-blende/wurtzite nanowires was studied. Light scattering experiments on zinc-blende GaAs nanowires under hydrostatic pressure up to 20 GPa were realized with the use of a diamond anvil cell. The resonance profile of the 2LO mode suggests a stronger Froehlich coupling. The Grueneisen parameters were also found to be different from those obtained from bulk GaAs. Finally, there is evidence for a structural transition for P>16 GPa. (orig.)

  9. Selective formation of tungsten nanowires

    Directory of Open Access Journals (Sweden)

    Bien Daniel

    2011-01-01

    Full Text Available Abstract We report on a process for fabricating self-aligned tungsten (W nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions.

  10. Hierarchical magnetic assembly of nanowires

    International Nuclear Information System (INIS)

    Hangarter, Carlos M; Rheem, Youngwoo; Yoo, Bongyoung; Yang, Eui-Hyeok; Myung, Nosang V

    2007-01-01

    Magnetic alignment is reported as a facile technique for assembling nanowires into hierarchical structures. Cross junction and T junction nanowire networks are demonstrated using a sequential alignment technique on unpatterned substrates and predefined lithographically patterned ferromagnetic electrodes. The formation of T junctions prevails as nanowires from the first alignment behave as ferromagnetic electrodes under the external magnetic field of the second alignment. The presence of prefabricated ferromagnetic electrodes dominates dipole interactions of localized nanowires for preferential alignment. Application of a magnetic field from a cylindrical coaxial magnet has also been utilized to form radially aligned nanowires. The magnetic field of the coaxial cylindrical magnet produced a dense, concentric nanowire configuration at the centre of the magnetic field as a consequence of the radial field gradient, and sparse nanowire arrangements in the peripheral field, which were utilized as interconnects with a concentric electrode design

  11. Lattice site and thermal stability of transition metals in germanium

    CERN Document Server

    Augustyns, Valérie; Pereira, Lino

    Although the first transistor was based on germanium, current chip technology mainly uses silicon due to its larger abundance, a lower price and higher quality silicon-oxide. However, a very important goal in microelectronics is to obtain faster integrated circuits. The advantages of germanium compared to silicon (e.g. a higher mobility of the charge carriers) motivates further research on germanium based materials. Semiconductor doping (e.g. introducing impurities into silicon and germanium in order to alter - and control - their properties) can be done by ion implantation or by in situ doping, whereby the host material is doped during growth. This thesis focuses on introducing dopants by ion implantation. The implantation as well as the subsequent measurements were performed in ISOLDE (CERN) using the emission channeling technique. Although ion implantation generates undesired defects in the host material (e.g. vacancies), such damage can be reduced by performing the implantation at an elevated temperature....

  12. Electrodeposition of Cobalt Nanowires

    International Nuclear Information System (INIS)

    Ahn, Sungbok; Hong, Kimin

    2013-01-01

    We developed an electroplating process of cobalt nanowires of which line-widths were between 70 and 200 nm. The plating electrolyte was made of CoSO 4 and an organic additive, dimethyldithiocarbamic acid ester sodium salt (DAESA). DAESA in plating electrolytes had an accelerating effect and reduced the surface roughness of plated cobalt thin films. We obtained void-free cobalt nanowires when the plating current density was 6.25 mA/cm 2 and DAESA concentration was 1 mL/L

  13. Protective infrared antireflection coating based on sputtered germanium carbide

    Science.gov (United States)

    Gibson, Des; Waddell, Ewan; Placido, Frank

    2011-09-01

    This paper describes optical, durablility and environmental performance of a germanium carbide based durable antireflection coating. The coating has been demonstrated on germanium and zinc selenide infra-red material however is applicable to other materials such as zinc sulphide. The material is deposited using a novel reactive closed field magnetron sputtering technique, offering significant advantages over conventional evaporation processes for germanium carbide such as plasma enhanced chemical vapour deposition. The sputtering process is "cold", making it suitable for use on a wide range of substrates. Moreover, the drum format provide more efficient loading for high throughput production. The use of the closed field and unbalanced magnetrons creates a magnetic confinement that extends the electron mean free path leading to high ion current densities. The combination of high current densities with ion energies in the range ~30eV creates optimum thin film growth conditions. As a result the films are dense, spectrally stable, supersmooth and low stress. Films incorporate low hydrogen content resulting in minimal C-H absorption bands within critical infra-red passbands such as 3 to 5um and 8 to 12um. Tuning of germanium carbide (Ge(1-x)Cx) film refractive index from pure germanium (refractive index 4) to pure germanium carbide (refractive index 1.8) will be demonstrated. Use of film grading to achieve single and dual band anti-reflection performance will be shown. Environmental and durability levels are shown to be suitable for use in harsh external environments.

  14. Localisation of spin orbit coupling in silicon-germanium alloys

    International Nuclear Information System (INIS)

    Vincent, J.K.

    2002-01-01

    The validity of the standard method of treating silicon-germanium alloy systems - the virtual crystal approximation - is studied. The largest difference between the properties of silicon and germanium is the Γ-point spin orbit coupling (0.04 eV in silicon and 0.29 eV in germanium). As the spin orbit potential is delta function like it might be expected that simply smearing out the potential to an average in the alloy is not appropriate. Calculations using k · p theory and the Empirical Pseudopotential method are performed to compare the density of states, bandstructure and dielectric function of supercell based silicon-germanium alloys with an averaged out (virtual crystal) spin orbit coupling potential and with the situation when the potential is localised at the germanium sites. In general it was found that the virtual crystal approximation holds for silicon-germanium as the localisation of the spin orbit potential caused only small changes in the energy levels of the system. However the effect would become potentially significant for a larger difference in the spin orbit coupling of the two alloyed materials. (author)

  15. Method of fabricating germanium and gallium arsenide devices

    Science.gov (United States)

    Jhabvala, Murzban (Inventor)

    1990-01-01

    A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium by either molecular beam epitaxy (MBE) or by metal-organic chemical vapor deposition (MOCVD). The method involves: depositing a layer of doped or undoped silicon dioxide on a germanium or gallium arsenide wafer or substrate, selectively removing the silicon dioxide layer to define one or more surface regions for a device to be fabricated thereon, growing a matched epitaxial layer of doped germanium or gallium arsenide of an appropriate thickness using MBE or MOCVD techniques on both the silicon dioxide layer and the defined one or more regions; and etching the silicon dioxide and the epitaxial material on top of the silicon dioxide to leave a matched epitaxial layer of germanium or gallium arsenide on the germanium or gallium arsenide substrate, respectively, and upon which a field effect device can thereafter be formed.

  16. Room temperature ferromagnetic Cr doped Ge/GeOx core-shell nanowires.

    Science.gov (United States)

    Katkar, Amar S; Gupta, Shobhnath P; Seikh, Md Motin; Chen, Lih-Juann; Walke, Pravin S

    2018-03-19

    The Cr doped tunable thickness core-shell Ge/GeOx nanowires were synthesized and characterized using X-ray diffraction, FESEM, TEM, EDS, XPS and magnetization studies. The shell thickness increases with the increase in synthesis temperature. The presence of metallic Cr and Cr3+ in core-shell structure was confirmed from XPS study. The magnetic property is highly sensitive to the core-shell thickness and intriguing room temperature ferromagnetism is realized only in core-shell nanowires. The magnetization decreases with increase in shell thickness and practically ceases to exist when there is no core. These nanowires shows high Curie temperature (TC>300 K) remarkably with the dominating values of its magnetic remanence (MR) and coercivity (HC) as compared to germanium dilute magnetic semiconductor nanomaterials. We believe that our finding on these Cr doped Ge/GeOX core-shell nanowires have potential to use as a hard magnet for forthcoming spintronic devices, owing to their higher characteristic values of FM ordering. © 2018 IOP Publishing Ltd.

  17. Plasmon modes of metallic nanowires including quantum nonlocal effects

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, Afshin, E-mail: a.moradi@kut.ac.ir [Department of Engineering Physics, Kermanshah University of Technology, Kermanshah, Iran and Department of Nano Sciences, Institute for Studies in Theoretical Physics and Mathematics (IPM), Tehran (Iran, Islamic Republic of)

    2015-03-15

    The properties of electrostatic surface and bulk plasmon modes of cylindrical metallic nanowires are investigated, using the quantum hydrodynamic theory of plasmon excitation which allows an analytical study of quantum tunneling effects through the Bohm potential term. New dispersion relations are obtained for each type of mode and their differences with previous treatments based on the standard hydrodynamic model are analyzed in detail. Numerical results show by considering the quantum effects, as the value of wave number increases, the surface modes are slightly red-shifted first and then blue-shifted while the bulk modes are blue-shifted.

  18. X-ray diffraction from single GaAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Biermanns, Andreas

    2012-11-12

    In recent years, developments in X-ray focussing optics have allowed to produce highly intense, coherent X-ray beams with spot sizes in the range of 100 nm and below. Together with the development of new experimental stations, X-ray diffraction techniques can now be applied to study single nanometer-sized objects. In the present work, X-ray diffraction is applied to study different aspects of the epitaxial growth of GaAs nanowires. Besides conventional diffraction methods, which employ X-ray beams with dimensions of several tens of {mu}m, special emphasis lies on the use of nanodiffraction methods which allow to study single nanowires in their as-grown state without further preparation. In particular, coherent X-ray diffraction is applied to measure simultaneously the 3-dimensional shape and lattice parameters of GaAs nanowires grown by metal-organic vapor phase epitaxy. It is observed that due to a high density of zinc-blende rotational twins within the nanowires, their lattice parameter deviates systematically from the bulk zinc-blende phase. In a second step, the initial stage in the growth of GaAs nanowires on Si (1 1 1) surfaces is studied. This nanowires, obtained by Ga-assisted growth in molecular beam epitaxy, grow predominantly in the cubic zinc-blende structure, but contain inclusions of the hexagonal wurtzite phase close to their bottom interface. Using nanodiffraction methods, the position of the different structural units along the growth axis is determined. Because the GaAs lattice is 4% larger than silicon, these nanowires release their lattice mismatch by the inclusion of dislocations at the interface. Whereas NWs with diameters below 50 nm are free of strain, a rough interface structure in nanowires with diameters above 100 nm prevents a complete plastic relaxation, leading to a residual strain at the interface that decays elastically along the growth direction. Finally, measurements on GaAs-core/InAs-shell nanowire heterostructures are presented

  19. Probing the carrier concentration profiles in phosphorus-implanted germanium using infrared spectroscopic ellipsometry

    Science.gov (United States)

    D'Costa, Vijay Richard; Yeo, Yee-Chia

    2015-02-01

    Spectroscopic ellipsometry with photon energy in the 0.045-0.65 eV range was used to investigate germanium samples implanted with 30 keV phosphorus ions and annealed at 700 °C. The infrared response of implanted layers is dominated by free carrier absorption which is modeled using a Drude oscillator. The carrier concentration profiles were modeled using an error function, and compared with those obtained by electrochemical capacitance-voltage profiling and secondary ion mass spectrometry. In the flat region of the carrier concentration profile, average carrier concentration and mobility of 1.40 × 1019 cm-3 and 336 cm2V-1s-1, respectively, were obtained. A phosphorus diffusivity of ˜1.2 × 10-13 cm2/s was obtained. The mobility versus carrier concentration relationships obtained for the implanted samples are close to the empirical relationship for bulk Ge.

  20. Synthesis and Characterization of ZnO/ZnS Core/Shell Nanowires

    Directory of Open Access Journals (Sweden)

    Taher Ghrib

    2014-01-01

    Full Text Available ZnO nanowires of approximately 3 µm length and 200 nm diameter are prepared and implanted vertically on substrate glass which is coated with thin layer of ITO which is too covered with bulk ZnO thin layer via electrodeposition process by cyclic voltammetry-chronoamperometry and with a chemical process that is described later; we have synthesized a ZnS nanolayer. ZnO/ZnS core/shell nanowires are formed by ZnO nanowires core surrounded by a very thin layer of porous ZnS shell principally constituted with a crystal which is about 15–20 nm in diameter. In the method, ZnS nanoparticles were prepared by reaction of ZnO nanowires with Na2S in aqueous solution at low temperature and also we have discussed the growth mechanism of ZnO/ZnS nanowires. The morphology, structure, and composition of the obtained nanostructures were obtained by using X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscopy (TEM, and X-ray photoelectron spectroscopy (XPS. For the structure, SEM and XRD measurements indicated that the as-grown ZnO nanowires microscale was of hexagonal wurtzite phase with a high crystalline quality, and TEM shows that the ZnS is uniformly distributed on the surface of the ZnO nanowires.

  1. Electronic transport properties of one dimensional lithium nanowire using density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Anil, E-mail: anil-t2001@yahoo.com [Department of Physics, Govt. P.G. College Solan, Himachal Pradesh, India 173212 (India); Kumar, Arun [Department of Physics, Govt. P.G. College Banjar, Himachal Pradesh (India); Chandel, Surjeet [Department of Physics, Govt. P.G. College Bilaspur, Himachal Pradesh (India); Ahluwalia, P. K. [Department of Physics, Himachal Pradesh University Shimla, Himachal Pradesh, India 171005 (India)

    2015-05-15

    Single nanowire electrode devices are a unique platform for studying as energy storage devices. Lithium nanowire is of much importance in lithium ion batteries and therefore has received a great deal of attention in past few years. In this paper we investigated structural and electronic transport properties of Li nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Li nanowire are investigated theoretically. The calculations are performed in two steps: first an optimized geometry for Li nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations correspondingly. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Agreement of bulk properties of Li with experimental values make the study of electronic and transport properties in lithium nanowires interesting because they are promising candidates as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Li nano wire indicates that Li nanowire can be used as an electrode device.

  2. Synthesis and magnetotransport studies of single nickel-rich NiFe nanowire

    International Nuclear Information System (INIS)

    Rheem, Y; Yoo, B-Y; Koo, B K; Beyermann, W P; Myung, N V

    2007-01-01

    One of the main concerns in the preparation of alloy nanowires is the ability to synthesize compositionally uniform nanowires along the axis. Since most of the conventional mild acidic permalloy (Ni 80 Fe 20 ) electroplating baths consist of an extremely low concentration of Fe ions compared with Ni ions, the electrodeposition of iron is controlled by mass transfer, which leads to a significant change in the composition along the axis of the nanowire. To overcome this obstacle, we developed a new acidic chloride electrolyte with a high concentration of Fe and Ni ions to electrodeposit homogeneous nanowires. After synthesizing nanowires, the temperature dependent magneto- and electro-transport properties of individual nanowires were investigated. The temperature coefficient of resistance of a nanowire is much lower than the bulk counterpart, which might be attributed to a higher residual resistivity. The magnetoresistance shows a typical anisotropic magnetoresistance behaviour where the maximum anisotropic magnetoresistance ratio decreased with increasing temperature. The angular dependence of the magnetization switching field indicated that curling is the magnetization reversal mode at all temperatures

  3. Fabrication and optical properties of TiO sub 2 nanowire arrays made by sol-gel electrophoresis deposition into anodic alumina membranes

    CERN Document Server

    Lin, Y; Yuan, X Y; Xie, T; Zhang, L D

    2003-01-01

    Ordered TiO sub 2 nanowire arrays have been successfully fabricated into the nanochannels of a porous anodic alumina membrane by sol-gel electrophoretic deposition. After annealing at 500 deg. C, the TiO sub 2 nanowire arrays and the individual nanowires were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and x-ray diffraction (XRD). SEM and TEM images show that these nanowires are dense and continuous with a uniform diameter throughout their entire length. XRD and SAED analysis together indicate that these TiO sub 2 nanowires crystallize in the anatase polycrystalline structure. The optical absorption band edge of TiO sub 2 nanowire arrays exhibits a blue shift with respect of that of the bulk TiO sub 2 owing to the quantum size effect.

  4. Surface Hydrogen Enables Subeutectic Vapor-Liquid-Solid Semiconductor Nanowire Growth.

    Science.gov (United States)

    Sivaram, Saujan V; Hui, Ho Yee; de la Mata, María; Arbiol, Jordi; Filler, Michael A

    2016-11-09

    Vapor-liquid-solid nanowire growth below the bulk metal-semiconductor eutectic temperature is known for several systems; however, the fundamental processes that govern this behavior are poorly understood. Here, we show that hydrogen atoms adsorbed on the Ge nanowire sidewall enable AuGe catalyst supercooling and control Au transport. Our approach combines in situ infrared spectroscopy to directly and quantitatively determine hydrogen atom coverage with a "regrowth" step that allows catalyst phase to be determined with ex situ electron microscopy. Maintenance of a supercooled catalyst with only hydrogen radical delivery confirms the centrality of sidewall chemistry. This work underscores the importance of the nanowire sidewall and its chemistry on catalyst state, identifies new methods to regulate catalyst composition, and provides synthetic strategies for subeutectic growth in other nanowire systems.

  5. 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.

  6. Ab initio design of nanostructures for solar energy conversion: a case study on silicon nitride nanowire.

    Science.gov (United States)

    Pan, Hui

    2014-01-01

    Design of novel materials for efficient solar energy conversion is critical to the development of green energy technology. In this work, we present a first-principles study on the design of nanostructures for solar energy harvesting on the basis of the density functional theory. We show that the indirect band structure of bulk silicon nitride is transferred to direct bandgap in nanowire. We find that intermediate bands can be created by doping, leading to enhancement of sunlight absorption. We further show that codoping not only reduces the bandgap and introduces intermediate bands but also enhances the solubility of dopants in silicon nitride nanowires due to reduced formation energy of substitution. Importantly, the codoped nanowire is ferromagnetic, leading to the improvement of carrier mobility. The silicon nitride nanowires with direct bandgap, intermediate bands, and ferromagnetism may be applicable to solar energy harvesting.

  7. Strained Silicon and Silicon-GermaniumNanowire Tunnel FETs and Inverters

    OpenAIRE

    Richter, Simon

    2014-01-01

    Reducing power consumption is an important issue for integrated circuits in portable devicesrelying on batteries and systems without external power supply. Scaling of the supply voltageVDD in integrated circuits is a powerful tool for reducing the power consumption, due to thequadratic dependence on VDD. MOSFETs, however, exhibit a fundamental limitation forthe drain current increase per applied gate voltage difference. The tunnel field-effect transistor(TFET) provides the ability for beating...

  8. Germanium CMOS potential from material and process perspectives: Be more positive about germanium

    Science.gov (United States)

    Toriumi, Akira; Nishimura, Tomonori

    2018-01-01

    CMOS miniaturization is now approaching the sub-10 nm level, and further downscaling is expected. This size scaling will end sooner or later, however, because the typical size is approaching the atomic distance level in crystalline Si. In addition, it is said that electron transport in FETs is ballistic or nearly ballistic, which means that the injection velocity at the virtual source is a physical parameter relevant for estimating the driving current. Channel-materials with higher carrier mobility than Si are nonetheless needed, and the carrier mobility in the channels is a parameter important with regard to increasing the injection velocity. Although the density of states in the channel has not been discussed often, it too is relevant for estimating the channel current. Both the mobility and the density of states are in principle related to the effective mass of the carrier. From this device physics viewpoint, we expect germanium (Ge) CMOS to be promising for scaling beyond the Si CMOS limit because the bulk mobility values of electrons and holes in Ge are much higher than those of electrons and holes in Si, and the electron effective mass in Ge is not much less than that in III-V compounds. There is a debate that Ge should be used for p-MOSFETs and III-V compounds for n-MOSFETs, but considering that the variability or nonuniformity of the FET performance in today’s CMOS LSIs is a big challenge, it seems that much more attention should be paid to the simplicity of the material design and of the processing steps. Nevertheless, Ge faces a number of challenges even in case that only the FET level is concerned. One of the big problems with Ge CMOS technology has been its poor performance in n-MOSFETs. While the hole mobility in p-FETs has been improved, the electron mobility in the inversion layer of Ge FETs remains a serious concern. If this is due to the inherent properties of Ge, only p-MOSFETs might be used for device applications. To make Ge CMOS devices

  9. Energy harvesting performance of piezoelectric ceramic and polymer nanowires

    Science.gov (United States)

    Crossley, Sam; Kar-Narayan, Sohini

    2015-08-01

    Energy harvesting from ubiquitous ambient vibrations is attractive for autonomous small-power applications and thus considerable research is focused on piezoelectric materials as they permit direct inter-conversion of mechanical and electrical energy. Nanogenerators (NGs) based on piezoelectric nanowires are particularly attractive due to their sensitivity to small-scale vibrations and may possess superior mechanical-to-electrical conversion efficiency when compared to bulk or thin-film devices of the same material. However, candidate piezoelectric nanowires have hitherto been predominantly analyzed in terms of NG output (i.e. output voltage, output current and output power density). Surprisingly, the corresponding dynamical properties of the NG, including details of how the nanowires are mechanically driven and its impact on performance, have been largely neglected. Here we investigate all realizable NG driving contexts separately involving inertial displacement, applied stress T and applied strain S, highlighting the effect of driving mechanism and frequency on NG performance in each case. We argue that, in the majority of cases, the intrinsic high resonance frequencies of piezoelectric nanowires (∼tens of MHz) present no barrier to high levels of NG performance even at frequencies far below resonance (ceramic and polymer nanowires. We find that even though ceramic and polymer nanowires have been found, in certain cases, to have similar energy conversion efficiencies, ceramics are more promising in strain-driven NGs while polymers are more promising for stress-driven NGs. Our work offers a viable means of comparing NG materials and devices on a like-for-like basis that may be useful for designing and optimizing nanoscale piezoelectric energy harvesters for specific applications.

  10. Semiconductor Nanowires: Epitaxy and Applications

    OpenAIRE

    Mårtensson, Thomas

    2008-01-01

    Semiconductor nanowires are nanoscale objects formed by bottom-up synthesis. In recent years their unique properties have been exploited in fields such as electronics, photonics, sensors and the life sciences. In this work, the epitaxial growth of nanowires and their applications were studied. Heteroepitaxial growth of III-V nanowires on silicon substrates was demonstrated. This may enable direct band gap materials for optoelectronic devices, as well as high-mobility, low-contact resis...

  11. Optical transmissivity of metallic nanowires

    Science.gov (United States)

    Nairat, Mazen S.

    2017-08-01

    Optical transmissivity and reflectivity of one dimensional array of metallic nanowires embedded in transparent dielectric is characterized. i employ wave optics simulation to analyze the optical field distribution in both the dielectric and the nanowires. The results indicate that the transmissivity and reflectivity depend on the polarization states of the incident light. The metallic nanowires matrix transmit in-plane polarization but block light out at of-plane polarization.

  12. Theoretical Investigations of the Hexagonal Germanium Carbonitride

    Directory of Open Access Journals (Sweden)

    Xinhai Yu

    2018-04-01

    Full Text Available The structural, mechanical, elastic anisotropic, and electronic properties of hexagonal germanium carbonitride (h-GeCN are systematically investigated using the first-principle calculations method with the ultrasoft pseudopotential scheme in the frame of generalized gradient approximation in the present work. The h-GeCN are mechanically and dynamically stable, as proved by the elastic constants and phonon spectra, respectively. The h-GeCN is brittle because the ratio B/G and Poisson’s ratio v of the h-GeCN are less than 1.75 and 0.26, respectively. For h-GeCN, from brittleness to ductility, the transformation pressures are 5.56 GPa and 5.63 GPa for B/G and Poisson’s ratio v, respectively. The h-GeCN exhibits the greater elastic anisotropy in Young’s modulus and the sound velocities. In addition, the calculated band structure of h-GeCN reveals that there is no band gap for h-GeCN with the HSE06 hybrid functional, so the h-GeCN is metallic.

  13. Tunnel current across linear homocatenated germanium chains

    International Nuclear Information System (INIS)

    Matsuura, Yukihito

    2014-01-01

    The electronic transport properties of germanium oligomers catenating into linear chains (linear Ge chains) have been theoretically studied using first principle methods. The conduction mechanism of a Ge chain sandwiched between gold electrodes was analyzed based on the density of states and the eigenstates of the molecule in a two-probe environment. Like that of silicon chains (Si chains), the highest occupied molecular orbital of Ge chains contains the extended σ-conjugation of Ge 4p orbitals at energy levels close to the Fermi level; this is in contrast to the electronic properties of linear carbon chains. Furthermore, the conductance of a Ge chain is expected to decrease exponentially with molecular length L. The decay constant β, which is defined as e −βL , of a Ge chain is similar to that of a Si chain, whereas the conductance of the Ge chains is higher than that of Si chains even though the Ge–Ge bond length is longer than the Si–Si bond length

  14. Optical Spectroscopy of Single Nanowires

    OpenAIRE

    Trägårdh, Johanna

    2008-01-01

    This thesis describes optical spectroscopy on III-V semiconductor nanowires. The nanowires were grown by metal-organic vapor phase epitaxy (MOVPE) and chemical beam epitaxy (CBE). Photoluminescence and photocurrent spectroscopy are used as tools to investigate issues such as the size of the band gap, the effects of surface states, and the charge carrier transport in core-shell nanowires. The band gap of InAs1-xPx nanowires with wurtzite crystal structure is measured as a function of ...

  15. A Low Noise 64x64 Germanium Array for Far IR Astronomy Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develope a 64x64 far infrared germanium focal-plane array with the following key design features: 1- Four top-illuminated, 32x32 germanium sub-arrays...

  16. [Determination of GeO2 in germanium-132 by phenylfuorone].

    Science.gov (United States)

    Dong, Y; Shen, H

    1999-08-01

    Inorganic (GeO2) in carboxyethyl germanium sesquioxide (germanium-132) was determined by phenylfuorone spectrometry. The method is convenient and has good precision and accuracy. The recovery of GeO2 is 93%-107%.

  17. Analytical product study of germanium-containing medicine by different ICP-MS applications

    NARCIS (Netherlands)

    Krystek, Petra; Ritsema, Rob

    2004-01-01

    For several years organo-germanium containing medicine has been used for special treatments of e.g. cancer and AIDS. The active substances contain germanium as beta-carboxyethylgermanium sesquioxide ((GeCH2CH 2COO-H)2O3/"Ge-132"), spirogermanium, germanium-lactate-citrate or unspecified forms. For

  18. Nanowire Field-Effect Transistors : Sensing Simplicity?

    NARCIS (Netherlands)

    Mescher, M.

    2014-01-01

    Silicon nanowires are structures made from silicon with at least one spatial dimension in the nanometer regime (1-100 nm). From these nanowires, silicon nanowire field-effect transistors can be constructed. Since their introduction in 2001 silicon nanowire field-effect transistors have been studied

  19. Long Silver Nanowires Synthesis by Pulsed Electrodeposition

    Directory of Open Access Journals (Sweden)

    M.R. Batevandi

    2015-09-01

    Full Text Available Silver nanowires were pulse electrodeposited into nanopore anodic alumina oxide templates. The effects of continuous and pulse electrodeposition waveform on the microstructure properties of the nanowire arrays were studied. It is seen that the microstructure of nanowire is depend to pulse condition. The off time duration of pulse waveform enables to control the growth direction of Ag nanowires.

  20. Bulk oil clauses

    International Nuclear Information System (INIS)

    Gough, N.

    1993-01-01

    The Institute Bulk Oil Clauses produced by the London market and the American SP-13c Clauses are examined in detail in this article. The duration and perils covered are discussed, and exclusions, adjustment clause 15 of the Institute Bulk Oil Clauses, Institute War Clauses (Cargo), and Institute Strikes Clauses (Bulk Oil) are outlined. (UK)

  1. 19 CFR 149.4 - Bulk and break bulk cargo.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 2 2010-04-01 2010-04-01 false Bulk and break bulk cargo. 149.4 Section 149.4... TREASURY (CONTINUED) IMPORTER SECURITY FILING § 149.4 Bulk and break bulk cargo. (a) Bulk cargo exempted.... (b) Break bulk cargo exempted from time requirement. For break bulk cargo that is exempt from the...

  2. Aging of Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, Frank; Schiek, Manuela; Osadnik, Andreas

    2012-01-01

    Organic semiconductors formed by epitaxial growth from small molecules such as the para-phenylenes or squaraines promise a vast application potential as the active ingredient in electric and optoelectronic devices. Their self-organization into organic nanowires or "nanofibers" adds a peculiar...... attribute, making them especially interesting for light generation in OLEDs and for light-harvesting devices such as solar cells. Functionalization of the molecules allows the customization of optical and electrical properties. However, aging of the wires might lead to a considerable decrease in device...... performance over time. In this study the morphological stability of organic nanoclusters and nanowires from the methoxy functionalized quaterphenylene, 4,4'''dimethoxy-1,1':4',1''4'',1'''-quaterphenylene (MOP4), is investigated in detail. Aging experiments conducted by atomic force microscopy under ambient...

  3. Silicon nanowire transistors

    CERN Document Server

    Bindal, Ahmet

    2016-01-01

    This book describes the n and p-channel Silicon Nanowire Transistor (SNT) designs with single and dual-work functions, emphasizing low static and dynamic power consumption. The authors describe a process flow for fabrication and generate SPICE models for building various digital and analog circuits. These include an SRAM, a baseband spread spectrum transmitter, a neuron cell and a Field Programmable Gate Array (FPGA) platform in the digital domain, as well as high bandwidth single-stage and operational amplifiers, RF communication circuits in the analog domain, in order to show this technology’s true potential for the next generation VLSI. Describes Silicon Nanowire (SNW) Transistors, as vertically constructed MOS n and p-channel transistors, with low static and dynamic power consumption and small layout footprint; Targets System-on-Chip (SoC) design, supporting very high transistor count (ULSI), minimal power consumption requiring inexpensive substrates for packaging; Enables fabrication of different types...

  4. Characterisation of a Broad Energy Germanium (BEGe) detector

    Energy Technology Data Exchange (ETDEWEB)

    Barrientos, D., E-mail: diego_barrientos@usal.es [Laboratorio de Radiaciones Ionizantes, University of Salamanca (Spain); Boston, A.J.; Boston, H.C. [Nuclear Physics Group, University of Liverpool (United Kingdom); Quintana, B.; Sagrado, I.C. [Laboratorio de Radiaciones Ionizantes, University of Salamanca (Spain); Unsworth, C.; Moon, S.; Cresswell, J.R. [Nuclear Physics Group, University of Liverpool (United Kingdom)

    2011-08-21

    Characterisation of Germanium detectors used for gamma-ray tracking or medical imaging is one of the current goals in the Nuclear physics community. Good knowledge of detector response to different gamma radiations is needed for this purpose. In order to develop this task, Pulse Shape Analysis (PSA) techniques have been developed for different detector geometries or setups. In this work, we present the results of the application of PSA for a Canberra Broad Energy Germanium (BEGe) detector. This detector was scanned across its front and bottom face using a fully digital data acquisition system; allowing to record detector charge pulse shapes from well defined positions with collimated sources of {sup 241}Am, {sup 22}Na and {sup 137}Cs. With the study of the data acquired, characteristics of the inner detector geometry like crystal limits or positions of contact and isolate can be found, as well as the direction of the axes for the Germanium crystal.

  5. Germane facts about germanium sesquioxide: II. Scientific error and misrepresentation.

    Science.gov (United States)

    Kaplan, Bonnie J; Andrus, G Merrill; Parish, W Wesley

    2004-04-01

    The preceding paper reviewed the anticancer properties and safety of bis (2-carboxyethylgermanium) sesquioxide (CEGS). An examination of those data leads one to question why this information has not stimulated clinical trials in patients with cancer. The answer is discussed in this paper, which traces the history to an error published in the scientific literature in 1987. The reliance by subsequent authors on secondary sources, citing only the error and not the correction published in 1988, constitutes part of the explanation of why CEGS has been neglected. A second factor is also considered: careless reporting about any germanium-based compound as if the many thousands of germanium compounds were all the same. This combination of a publication error, careless writing, and the reliance on secondary sources appears to be responsible for the neglect of the potential clinical use of this unique germanium compound.

  6. Transport in silicon-germanium heterostructures

    International Nuclear Information System (INIS)

    Chrastina, Daniel

    2001-01-01

    The work presented here describes the electrical characterization of n- and p-type strained silicon-germanium systems. Theories of quantum transport m low magnetic fields at low temperature are discussed m terms of weak-localization: the traditional theory is shown not to account for the dephasing in a 2-dimensional hole gas behaving in a metallic manner and emergent alternative theories, while promising, require refinement. The mobility as a function of sheet density is measured in a p-type pseudomorphic Si 0.5 Ge 0.5 across the temperature range 350mK-282K; it is shown that calculations of the mobility based on semi-classical scattering mechanisms fail below 10K where quantum transport effects become relevant. A room temperature Hall scattering factor has been extracted. A new functional form has been presented to fit the resistivity as a function of temperature, below 20K: traditional theories of screening and weak localization appear not to be applicable. It is also demonstrated that simple protection circuitry is essential if commercial-scale devices are to be meaningfully investigated. Mobility spectrum analysis is performed on an n-type strained-silicon device. Established analysis methods are discussed and a new method is presented based on the Bryan's Algorithm approach to maximum entropy. The breakdown of the QHE is also investigated: the critical current density compares well to that predicted by an existing theory. Finally, devices in which both electron and hole gases can be induced are investigated. However, it is shown that the two cannier species never co-exist. Design rules are presented which may allow more successful structures to be created. Results are presented which demonstrate the success and the utility of implanted contacts which selectively reach different regions of the structure. (author)

  7. Quantum transport in semiconductor nanowires

    NARCIS (Netherlands)

    Van Dam, J.

    2006-01-01

    This thesis describes a series of experiments aimed at understanding the low-temperature electrical transport properties of semiconductor nanowires. The semiconductor nanowires (1-100 nm in diameter) are grown from nanoscale gold particles via a chemical process called vapor-liquid-solid (VLS)

  8. Proton loss by nuclear inelastic interactions in germanium

    International Nuclear Information System (INIS)

    Carlson, R.F.; Cox, A.J.; Abegg, R.; Davison, N.E.; Hasell, D.K.; McCamis, R.H.; Nasr, T.N.; Van Oers, W.T.H.; Manitoba Univ., Winnipeg

    1981-01-01

    The probability of protons undergoing nuclear inelastic interactions while stopping in germanium has been measured in a direct counting experiment using protons with energies between 25 and 49 MeV incident on a germanium detector. These values have been determined to an accuracy of approximately +-2%. Calculatins of the proton reaction probability over the incident energy range 20-150 MeV have also been made, using previously reported proton total reaction cross sections. The experimental and calculated results agree to within +-1.8%. (orig.)

  9. Quantitative spectrographic determination of traces of germanium in lignite

    International Nuclear Information System (INIS)

    Martin, M.; Roca, M.

    1972-01-01

    A burning technique in a d.c. arc at 10 amp has been employed. The standards have been prepared from a natural lignite with a low germanium content. In order to enhance sensitivity, AgCl, K 2 SO 4 , CuF 2 , Sb 2 S 3 and Bi 2 S 3 have been tested as sweeping materials. Using 2% CuF 2 a detection limit of 1 ppm germanium is attainable. Bi, Cu, Sb and Sn have been studied as internal standards: the former leads to the, highest precision (1 6%. Results show good agreement with those obtained by the addition method. (Author) 6 refs

  10. In vitro binding of germanium to proteins of rice shoots

    International Nuclear Information System (INIS)

    Matsumoto, Hideaki; Takahashi, Eiichi

    1976-01-01

    The possibility of in vitro binding between proteins of rice shoots and germanium (Ge) was investigated. The proteins in mixtures of aqueous extracts of rice shoots and radioactive germanium ( 68 GeO 2 ) were fractionated. The binding of radioactivity to the proteins was observed even after 5 successive fractionation steps from the original mixtures. At the final fractionation step using polyacrylamide gel electrophoresis, a constant proportionality between protein concentration and associated radioactivity was found in most samples although not all. These results indicate that the binding of 68 Ge to proteins is not due to the simple adsorption by proteins. (auth.)

  11. Self-diffusion in single crystalline silicon nanowires

    Science.gov (United States)

    Südkamp, T.; Hamdana, G.; Descoins, M.; Mangelinck, D.; Wasisto, H. S.; Peiner, E.; Bracht, H.

    2018-04-01

    Self-diffusion experiments in single crystalline isotopically controlled silicon nanowires with diameters of 70 and 400 nm at 850 and 1000 °C are reported. The isotope structures were first epitaxially grown on top of silicon substrate wafers. Nanowires were subsequently fabricated using a nanosphere lithography process in combination with inductively coupled plasma dry reactive ion etching. Three-dimensional profiling of the nanosized structure before and after diffusion annealing was performed by means of atom probe tomography (APT). Self-diffusion profiles obtained from APT analyses are accurately described by Fick's law for self-diffusion. Data obtained for silicon self-diffusion in nanowires are equal to the results reported for bulk silicon crystals, i.e., finite size effects and high surface-to-volume ratios do not significantly affect silicon self-diffusion. This shows that the properties of native point defects determined from self-diffusion in bulk crystals also hold for nanosized silicon structures with diameters down to 70 nm.

  12. Distinct local structure of nanoparticles and nanowires of V2O5 probed by x-ray absorption spectroscopy

    Science.gov (United States)

    Joseph, B.; Iadecola, A.; Maugeri, L.; Bendele, M.; Okubo, M.; Li, H.; Zhou, H.; Mizokawa, T.; Saini, N. L.

    2013-12-01

    We have used V K-edge x-ray absorption spectroscopy to study local structures of bulk, nanoparticles and nanowires of V2O5. The extended x-ray absorption fine structure measurements show different local displacements in the three morphologically different V2O5 samples. It is found that the nanowires have a significantly ordered chain structure in comparison to the V2O5 bulk. In contrast, nanoparticles have larger interlayer disorder. The x-ray absorption near-edge structure spectra show different electronic structure that appears to be related with the local atomic disorder in the three V2O5 samples.

  13. Investigation of vibration spectrum ferroelectric semiconductor SbSBr nanowire

    International Nuclear Information System (INIS)

    Audzijonis, A.; Zigas, L.; Kvedaravicius, A.; Sereika, R.; Zaltauskas, R.; Cerskus, A

    2010-01-01

    The temperature dependence of vibration spectra of one SbSBr chain (nanowire) in the direction of the c(z)-axis has been calculated in quasiharmonic approximation by diagonalization of dynamical matrix. The vibrational frequencies in the direction of c(z)-axis have been derived by fitting of the experimental low-frequency ω s 2 of soft infrared (IR) mode of bulk-size SbSBr with the theoretical quasiharmonic low-frequency ω 2 of SbSBr nanowires. In this work the nature of anharmonism and temperature dependence of force constants between atoms in SbSBr crystal along c(z)-axis have been discussed. The anharmonism of all soft (at BZ k=0) modes has been created by the interaction between phonons.

  14. Low temperature phonon boundary scattering in slightly rough Silicon nanowires

    Science.gov (United States)

    Ghossoub, Marc; Valavala, Krishna; Seong, Myunghoon; Azeredo, Bruno; Sadhu, Jyothi S.; Sinha, Sanjiv

    2013-03-01

    Nanostructured materials have lower thermal conductivities than the bulk and are promising candidates for thermoelectric applications. In particular, measurements on single silicon nanowires show a reduction in thermal conductivity below the Casimir limit. This reduction increases with surface roughness but the trend and its connection to phonon boundary scattering are still elusive. Here, we measure the thermal conductivity of single silicon nanowires fabricated using metal-assisted chemical etching. High resolution TEM imaging shows crystalline wires with slightly rough surfaces. Their statistical correlation lengths (5-15 nm) and RMS heights (0.8-1.5 nm) are in a range where perturbation-based wave scattering theory is still applicable. We use the thermal conductivity data to extract the frequency dependence of phonon boundary scattering at low temperatures (10-40 K) and show agreement with multiple scattering theory. This work provides insight into enhancing the thermoelectric performance of nanostructures.

  15. Spin-Orbit Torques in Co/Pd Multilayer Nanowires

    KAUST Repository

    Jamali, Mahdi

    2013-12-09

    Current induced spin-orbit torques have been studied in ferromagnetic nanowires made of 20 nm thick Co/Pd multilayers with perpendicular magnetic anisotropy. Using Hall voltage and lock-in measurements, it is found that upon injection of an electric current both in-plane (Slonczewski-like) and perpendicular (fieldlike) torques build up in the nanowire. The torque efficiencies are found to be as large as 1.17 and 5 kOe at 108  A/cm2 for the in-plane and perpendicular components, respectively, which is surprisingly comparable to previous studies in ultrathin (∼1  nm) magnetic bilayers. We show that this result cannot be explained solely by spin Hall effect induced torque at the outer interfaces, indicating a probable contribution of the bulk of the Co/Pd multilayer.

  16. Dislocation multiplication rate in the early stage of germanium plasticity

    Czech Academy of Sciences Publication Activity Database

    Fikar, J.; Dupas, Corinne; Kruml, Tomáš; Jacques, A.; Martin, J. L.

    400-401, - (2005), s. 431-434 ISSN 0921-5093. [Dislocations 2004. La Colle-sur-Loup, 13.09.2004-17.09.2004] Institutional research plan: CEZ:AV0Z2041904 Keywords : dislocation multiplication * germanium * constitutive modelling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.347, year: 2005

  17. Synthesis and characterization of germanium monosulphide (GeS)

    Indian Academy of Sciences (India)

    This paper reports the growth of germanium monosulphide (GeS) single crystals by vapour phase technique using different transporting agents. The single crystallinity and composition of the grown crystals have been verified by transmission electron microscopy (TEM) and energy dispersive analysis of X-rays (EDAX) ...

  18. Direct observations of the vacancy and its annealing in germanium

    DEFF Research Database (Denmark)

    Slotte, J.; Kilpeläinen, S.; Tuomisto, F.

    2011-01-01

    Weakly n-type doped germanium has been irradiated with protons up to a fluence of 3×1014 cm-2 at 35 K and 100 K in a unique experimental setup. Positron annihilation measurements show a defect lifetime component of 272±4 ps at 35 K in in situ positron lifetime measurements after irradiation at 100...

  19. Microwave Faraday effect in n-type germanium

    NARCIS (Netherlands)

    Bouwknegt, A.; Volger, J.

    The Faraday rotation, ellipticity and the accompanying magneto-absorption were determined from measurements with the crossed wave guide coupler device, at room temperature, at 24.9 GHz. The complex conductivity tensor elements of n-type germanium were deduced from this complete Faraday effect, with

  20. Synthesis and characterization of germanium monosulphide (GeS ...

    Indian Academy of Sciences (India)

    This paper reports the growth of germanium monosulphide (GeS) single crystals by vapour phase technique using different transporting agents. The single crystallinity and composition of the grown crystals have been verified by transmission electron microscopy (TEM) and energy dispersive analysis of X-rays (EDAX) ...

  1. Effect of normal processes on thermal conductivity of germanium ...

    Indian Academy of Sciences (India)

    Abstract. The effect of normal scattering processes is considered to redistribute the phonon momentum in (a) the same phonon branch – KK-S model and (b) between differ- ent phonon branches – KK-H model. Simplified thermal conductivity relations are used to estimate the thermal conductivity of germanium, silicon and ...

  2. Solution-processable white-light-emitting germanium nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Shirahata, Naoto, E-mail: SHIRAHATA.Naoto@nims.go.jp [International Center for Materials Nanoarchitectonics (WPI-MANA), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)

    2014-06-01

    This paper describes an efficient chemical route for the synthesis of visible light emitting nanocrystals of germanium (ncGe). The synthesis started by heating Ge(II) iodide at 300 °C in argon atmosphere. Spectroscopic characterizations confirmed the formation of diamond cubic lattice structures of ncGe. By grafting hydrophobic chains on the ncGe surface, the dispersions in nonpolar solvents of the ncGe became very stable. The as-synthesized ncGe showed the bluish white photoluminescence (PL) feature, but it was found that the PL spectrum is composed of many different emission spectra. Therefore, the color-tuning of white light emission is demonstrated through the witting removal of extra ncGe with unfavorable emission feature by making full use of column chromatographic techniques. - Highlights: • Visible light emitting nanocrystals of germanium was synthesized by chemical reduction of germanium iodide. • White light emission was achieved by control over size distribution of germanium nanocrystals. • Tuning the color of white light was achieved by separation of nanocrystals by emission.

  3. Noise and oscillations in gold-doped germanium photodiodes

    NARCIS (Netherlands)

    Bolwijn, P.T.; Rijst, C. v. d.; Ast, W.G. van; Lam, T.

    Considerable noise effects in excess of shot noise and oscillations found in commercially available, gold-doped germanium photodiodes have been investigated. The noise and oscillation effects occur in the photocurrent of reversely biased diodes at temperatures below about 100°K. The dependence of

  4. Effect of normal processes on thermal conductivity of germanium ...

    Indian Academy of Sciences (India)

    The effect of normal scattering processes is considered to redistribute the phonon momentum in (a) the same phonon branch – KK-S model and (b) between different phonon branches – KK-H model. Simplified thermal conductivity relations are used to estimate the thermal conductivity of germanium, silicon and diamond ...

  5. Composite germanium monochromators - results for the TriCS

    Energy Technology Data Exchange (ETDEWEB)

    Schefer, J.; Fischer, S.; Boehm, M.; Keller, L.; Horisberger, M.; Medarde, M.; Fischer, P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Composite germanium monochromators are in the beginning of their application in neutron diffraction. We show here the importance of the permanent quality control with neutrons on the example of the 311 wafers which will be used on the single crystal diffractometer TriCS at SINQ. (author) 2 figs., 3 refs.

  6. Active noise canceling system for mechanically cooled germanium radiation detectors

    Science.gov (United States)

    Nelson, Karl Einar; Burks, Morgan T

    2014-04-22

    A microphonics noise cancellation system and method for improving the energy resolution for mechanically cooled high-purity Germanium (HPGe) detector systems. A classical adaptive noise canceling digital processing system using an adaptive predictor is used in an MCA to attenuate the microphonics noise source making the system more deployable.

  7. Cosmogenic activation in germanium double beta decay experiments

    International Nuclear Information System (INIS)

    Cebrian, S; Amare, J; Beltran, B; Carmona, J M; GarcIa, E; Gomez, H; Irastorza, I G; Luzon, G; MartInez, M; Morales, J; Solorzano, A Ortiz de; Pobes, C; Puimedon, J; Rodriguez, A; Ruz, J; Sarsa, M L; Torres, L; Villar, J A

    2006-01-01

    A new estimate of the production rates of several long-lived isotopes cosmogenically induced in germanium is presented, paying attention to those products relevant in Double Beta Decay searches. Special care has been taken in the selection of reliable excitation functions

  8. Cosmogenic activation in germanium double beta decay experiments

    Energy Technology Data Exchange (ETDEWEB)

    Cebrian, S; Amare, J; Beltran, B; Carmona, J M; GarcIa, E; Gomez, H; Irastorza, I G; Luzon, G; MartInez, M; Morales, J; Solorzano, A Ortiz de; Pobes, C; Puimedon, J; Rodriguez, A; Ruz, J; Sarsa, M L; Torres, L; Villar, J A [Laboratorio de Fisica Nuclear y Altas Energias, Universidad de Zaragoza, 50009 (Spain)

    2006-05-15

    A new estimate of the production rates of several long-lived isotopes cosmogenically induced in germanium is presented, paying attention to those products relevant in Double Beta Decay searches. Special care has been taken in the selection of reliable excitation functions.

  9. Inhomogeneous electron distribution in InN nanowires: Influence on the optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Molina-Sanchez, A.; Garro, N.; Garcia-Cristobal, A.; Cantarero, A. [Instituto de Ciencia de los Materiales, Universidad de Valencia (Spain); Segura-Ruiz, J. [European Synchrotron Radiation Facility, Experiments Div., Grenoble (France); Iikawa, F. [Instituto de Fisica Gleb Wataghin - Unicamp, CP 6165, Campinas (Brazil); Denker, C.; Malindretos, J.; Rizzi, A. [IV. Physikalisches Institut, Georg-August Universitaet Goettingen (Germany)

    2012-03-15

    In this work, we study theoretically and experimentally the influence of the surface electron accumulation on the optical properties of InN nanowires. For this purpose, the photoluminescence and photoluminescence excitation spectra have been measured for a set of self-assembled InN NWs grown under different conditions. The photoluminescence excitation experimental lineshapes have been reproduced by a self-consistent calculation of the absorption in a cylindrical InN nanowires. With the self-consistent model we can explore how the optical absorption depends on nanowires radius and doping concentration. Our model solves the Schroedinger equation for a cylindrical nanowire of infinite length, assuming a parabolic conduction band. The columnar geometry introduces effects in both the electron density and in the self-consistent conduction band profile, with no equivalence in planar layer. On the other hand, the differences in the photoluminescence excitation spectra are related to the inhomogeneous electron distribution inside the nanowires, caused by a bulk donor concentration and a two-dimensional density of ionized surface states. For nanowire radii larger than 30 nm, such concentrations modify the absorption edge and the lineshape, respectively, and can be determined from the comparison with the experimental data (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Dangling-bond defects and hydrogen passivation in germanium

    Science.gov (United States)

    Weber, Justin R.

    2008-03-01

    The application of germanium in complementary metal-oxide semiconductor (CMOS) technology is hampered by high interface-state densities, the microscopic origin of which has remained elusive. Using first-principles calculations, we have investigated the atomic and electronic structure of prototype germanium dangling-bond defects [1]. The computational approach is based on density functional theory, and in order to overcome band-gap problems we have also performed quasiparticle calculations based on the GW approach. Surprisingly, the germanium dangling bonds give rise to electronic levels below the valence-band maximum. They therefore occur exclusively in the negative charge state, explaining why they have eluded observation with electron spin resonance. The associated fixed charge is likely responsible for threshold-voltage shifts and poor performance of n-channel transistors. At silicon/silicon dioxide interfaces, hydrogen is successfully used to passivate dangling-bond defects. We have therefore also investigated the interaction of hydrogen with germanium. In contrast to silicon and other semiconductors in which hydrogen behaves as an amphoteric impurity, interstitial hydrogen in germanium is stable only in the negative charge state, i.e., it behaves exclusively as an acceptor. Passivation of dangling bonds by hydrogen will therefore be ineffective, again explaining experimental observations. Other cases where unusual interfacial defects and problems with hydrogen passivation may occur will be discussed. Work performed in collaboration with A. Janotti, P. Rinke, and C. G. Van de Walle, and supported by the Semiconductor Research Corporation. 1. J. R. Weber, A. Janotti, P. Rinke, and C. G. Van de Walle, Appl. Phys. Lett. 91, 142101 (2007).

  11. Germanium detector studies in the framework of the GERDA experiment

    Energy Technology Data Exchange (ETDEWEB)

    Budjas, Dusan

    2009-05-06

    The GERmanium Detector Array (GERDA) is an ultra-low background experiment under construction at Laboratori Nazionali del Gran Sasso. GERDA will search for {sup 76}Ge neutrinoless double beta decay with an aim for 100-fold reduction in background compared to predecessor experiments. This ambition necessitates innovative design approaches, strict selection of low-radioactivity materials, and novel techniques for active background suppression. The core feature of GERDA is its array of germanium detectors for ionizing radiation, which are enriched in {sup 76}Ge. Germanium detectors are the central theme of this dissertation. The first part describes the implementation, testing, and optimisation of Monte Carlo simulations of germanium spectrometers, intensively involved in the selection of low-radioactivity materials. The simulations are essential for evaluations of the gamma ray measurements. The second part concerns the development and validation of an active background suppression technique based on germanium detector signal shape analysis. This was performed for the first time using a BEGe-type detector, which features a small read-out electrode. As a result of this work, BEGe is now one of the two detector technologies included in research and development for the second phase of the GERDA experiment. A suppression of major GERDA backgrounds is demonstrated, with (0.93{+-}0.08)% survival probability for events from {sup 60}Co, (21{+-}3)% for {sup 226}Ra, and (40{+-}2)% for {sup 228}Th. The acceptance of {sup 228}Th double escape events, which are analogous to double beta decay, was kept at (89{+-}1)%. (orig.)

  12. Pulse shapes and surface effects in segmented germanium detectors

    Energy Technology Data Exchange (ETDEWEB)

    Lenz, Daniel

    2010-03-24

    It is well established that at least two neutrinos are massive. The absolute neutrino mass scale and the neutrino hierarchy are still unknown. In addition, it is not known whether the neutrino is a Dirac or a Majorana particle. The GERmanium Detector Array (GERDA) will be used to search for neutrinoless double beta decay of {sup 76}Ge. The discovery of this decay could help to answer the open questions. In the GERDA experiment, germanium detectors enriched in the isotope {sup 76}Ge are used as source and detector at the same time. The experiment is planned in two phases. In the first, phase existing detectors are deployed. In the second phase, additional detectors will be added. These detectors can be segmented. A low background index around the Q value of the decay is important to maximize the sensitivity of the experiment. This can be achieved through anti-coincidences between segments and through pulse shape analysis. The background index due to radioactive decays in the detector strings and the detectors themselves was estimated, using Monte Carlo simulations for a nominal GERDA Phase II array with 18-fold segmented germanium detectors. A pulse shape simulation package was developed for segmented high-purity germanium detectors. The pulse shape simulation was validated with data taken with an 19-fold segmented high-purity germanium detector. The main part of the detector is 18-fold segmented, 6-fold in the azimuthal angle and 3-fold in the height. A 19th segment of 5mm thickness was created on the top surface of the detector. The detector was characterized and events with energy deposited in the top segment were studied in detail. It was found that the metalization close to the end of the detector is very important with respect to the length of the of the pulses observed. In addition indications for n-type and p-type surface channels were found. (orig.)

  13. Optical Binding of Nanowires

    Czech Academy of Sciences Publication Activity Database

    Simpson, Stephen Hugh; Zemánek, Pavel; Marago, O.M.; Jones, P.H.; Hanna, S.

    2017-01-01

    Roč. 17, č. 6 (2017), s. 3485-3492 ISSN 1530-6984 R&D Projects: GA ČR GB14-36681G Grant - others:AV ČR(CZ) CNR-16-12 Program:Bilaterální spolupráce Institutional support: RVO:68081731 Keywords : optical binding nanowires * Brownian motion * self -organization * non-equilibrium thermodynamics * non-equilibrium steady state * spin-orbit coupling * emergent phenomena Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 12.712, year: 2016

  14. Superconductivity in nanowires

    CERN Document Server

    Bezryadin, Alexey

    2012-01-01

    The importance and actuality of nanotechnology is unabated and will be for years to come. A main challenge is to understand the various properties of certain nanostructures, and how to generate structures with specific properties for use in actual applications in Electrical Engineering and Medicine.One of the most important structures are nanowires, in particular superconducting ones. They are highly promising for future electronics, transporting current without resistance and at scales of a few nanometers. To fabricate wires to certain defined standards however, is a major challenge, and so i

  15. Hybrid functional calculated optical and electronic structures of thin anatase TiO2 nanowires with organic dye adsorbates

    International Nuclear Information System (INIS)

    Ünal, Hatice; Gunceler, Deniz; Gülseren, Oğuz; Ellialtıoğlu, Şinasi; Mete, Ersen

    2015-01-01

    Highlights: • Size effect on the band gap features of thin anatase (0 0 1) and (1 0 1) nanowires calculated at the screened Coulomb hybrid DFT approach. • HSE-optimized structures of coumarin and donor-pi-acceptor type C2-1 dye adsorbates on anatase (0 0 1) and (1 0 1) nanowires. • HSE charge density distributions of frontier states of dye-nanowire systems. • HSE + PCM calculations for C2-1 and coumarin on anatase nanowires including nonlinear solvation environment effects. • Optical properties of dye + nanowire combined systems. - Abstract: The electronic and optical properties of thin anatase TiO 2 (1 0 1) and (0 0 1) nanowires have been investigated using the screened Coulomb hybrid density functional calculations. For the bare nanowires with sub-nanometer diameters, the calculated band gaps are larger relative to the bulk values due to size effects. The role of organic light harvesting sensitizers on the absorption characteristics of the anatase nanowires has been examined using the hybrid density functional method incorporating partial exact exchange with range separation. For the lowest lying excitations, directional charge redistribution of tetrahydroquinoline (C2-1) dye shows a remarkably different profile in comparison to a simple molecule which is chosen as the coumarin skeleton. The binding modes and the adsorption energies of C2-1 dye and coumarin core on the anatase nanowires have been studied including non-linear solvation effetcs. The calculated optical and electronic properties of the nanowires with these two different types of sensitizers have been interpreted in terms of their electron–hole generation, charge carrier injection and recombination characteristics.

  16. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

    Fu, Xin; Jiang, Jun; Liu, Chao; Yuan, Jun

    2009-09-09

    Chemical composition and crystal structure of fivefold twinned boron carbide nanowires have been determined by electron energy-loss spectroscopy and electron diffraction. The fivefold cyclic twinning relationship is confirmed by systematic axial rotation electron diffraction. Detailed chemical analysis reveals a carbon-rich boron carbide phase. Such boron carbide nanowires are potentially interesting because of their intrinsic hardness and high temperature thermoelectric property. Together with other boron-rich compounds, they may form a set of multiply twinned nanowire systems where the misfit strain could be continuously tuned to influence their mechanical properties.

  17. Energy harvesting performance of piezoelectric ceramic and polymer nanowires

    International Nuclear Information System (INIS)

    Crossley, Sam; Kar-Narayan, Sohini

    2015-01-01

    Energy harvesting from ubiquitous ambient vibrations is attractive for autonomous small-power applications and thus considerable research is focused on piezoelectric materials as they permit direct inter-conversion of mechanical and electrical energy. Nanogenerators (NGs) based on piezoelectric nanowires are particularly attractive due to their sensitivity to small-scale vibrations and may possess superior mechanical-to-electrical conversion efficiency when compared to bulk or thin-film devices of the same material. However, candidate piezoelectric nanowires have hitherto been predominantly analyzed in terms of NG output (i.e. output voltage, output current and output power density). Surprisingly, the corresponding dynamical properties of the NG, including details of how the nanowires are mechanically driven and its impact on performance, have been largely neglected. Here we investigate all realizable NG driving contexts separately involving inertial displacement, applied stress T and applied strain S, highlighting the effect of driving mechanism and frequency on NG performance in each case. We argue that, in the majority of cases, the intrinsic high resonance frequencies of piezoelectric nanowires (∼tens of MHz) present no barrier to high levels of NG performance even at frequencies far below resonance (<1 kHz) typically characteristic of ambient vibrations. In this context, we introduce vibrational energy harvesting (VEH) coefficients η S and η T , based on intrinsic materials properties, for comparing piezoelectric NG performance under strain-driven and stress-driven conditions respectively. These figures of merit permit, for the first time, a general comparison of piezoelectric nanowires for NG applications that takes into account the nature of the mechanical excitation. We thus investigate the energy harvesting performance of prototypical piezoelectric ceramic and polymer nanowires. We find that even though ceramic and polymer nanowires have been found, in

  18. Growth and Physical Property Study of Single Nanowire (Diameter ~45 nm of Half Doped Manganite

    Directory of Open Access Journals (Sweden)

    Subarna Datta

    2013-01-01

    Full Text Available We report here the growth and characterization of functional oxide nanowire of hole doped manganite of La0.5Sr0.5MnO3 (LSMO. We also report four-probe electrical resistance measurement of a single nanowire of LSMO (diameter ~45 nm using focused ion beam (FIB fabricated electrodes. The wires are fabricated by hydrothermal method using autoclave at a temperature of 270 °C. The elemental analysis and physical property like electrical resistivity are studied at an individual nanowire level. The quantitative determination of Mn valency and elemental mapping of constituent elements are done by using Electron Energy Loss Spectroscopy (EELS in the Transmission Electron Microscopy (TEM mode. We address the important issue of whether as a result of size reduction the nanowires can retain the desired composition, structure, and physical properties. The nanowires used are found to have a ferromagnetic transition (TC at around 325 K which is very close to the bulk value of around 330 K found in single crystal of the same composition. It is confirmed that the functional behavior is likely to be retained even after size reduction of the nanowires to a diameter of 45 nm. The electrical resistivity shows insulating behavior within the measured temperature range which is similar to the bulk system.

  19. Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

    Science.gov (United States)

    Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

    2011-12-23

    Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Interactions between semiconductor nanowires and living cells.

    Science.gov (United States)

    Prinz, Christelle N

    2015-06-17

    Semiconductor nanowires are increasingly used for biological applications and their small dimensions make them a promising tool for sensing and manipulating cells with minimal perturbation. In order to interface cells with nanowires in a controlled fashion, it is essential to understand the interactions between nanowires and living cells. The present paper reviews current progress in the understanding of these interactions, with knowledge gathered from studies where living cells were interfaced with vertical nanowire arrays. The effect of nanowires on cells is reported in terms of viability, cell-nanowire interface morphology, cell behavior, changes in gene expression as well as cellular stress markers. Unexplored issues and unanswered questions are discussed.

  1. Actuation of polypyrrole nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Alexander S; Peteu, Serban F; Ly, James V; Requicha, Aristides A G; Thompson, Mark E; Zhou Chongwu [Laboratory for Molecular Robotics, University of Southern California, Los Angeles, CA 90089 (United States)], E-mail: requicha@usc.edu

    2008-04-23

    Nanoscale actuators are essential components of the NEMS (nanoelectromechanical systems) and nanorobots of the future, and are expected to become a major area of development within nanotechnology. This paper demonstrates for the first time that individual polypyrrole (PPy) nanowires with diameters under 100 nm exhibit actuation behavior, and therefore can potentially be used for constructing nanoscale actuators. PPy is an electroactive polymer which can change volume on the basis of its oxidation state. PPy-based macroscale and microscale actuators have been demonstrated, but their nanoscale counterparts have not been realized until now. The research reported here answers positively the fundamental question of whether PPy wires still exhibit useful volume changes at the nanoscale. Nanowires with a 50 nm diameter and a length of approximately 6 {mu}m, are fabricated by chemical polymerization using track-etched polycarbonate membranes as templates. Their actuation response as a function of oxidation state is investigated by electrochemical AFM (atomic force microscopy). An estimate of the minimum actuation force is made, based on the displacement of the AFM cantilever.

  2. Electric Conductivity of Phosphorus Nanowires

    International Nuclear Information System (INIS)

    Jing-Xiang, Zhang; Hui, Li; Xue-Qing, Zhang; Kim-Meow, Liew

    2009-01-01

    We present the structures and electrical transport properties of nanowires made from different strands of phosphorus chains encapsulated in carbon nanotubes. Optimized by density function theory, our results indicate that the conductance spectra reveal an oscillation dependence on the size of wires. It can be seen from the density of states and current-voltage curves that the structure of nanowires affects their properties greatly. Among them, the DNA-like double-helical phosphorus nanowire exhibits the distinct characteristic of an approximately linear I – V relationship and has a higher conductance than others. The transport properties of phosphorus nanowires are highly correlated with their microstructures. (condensed matter: structure, mechanical and thermal properties)

  3. Semiconductor nanowires: optics and optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, R. [University of Pennsylvania, Department of Materials Science and Engineering, Philadelphia, PA (United States); Lieber, C.M. [Harvard University, Department of Chemistry and Chemical Biology, and Division of Engineering Applied Sciences, Cambridge, MA (United States)

    2006-11-15

    Single crystalline semiconductor nanowires are being extensively investigated due to their unique electronic and optical properties and their potential use in novel electronic and photonic devices. The unique properties of nanowires arise owing to their anisotropic geometry, large surface to volume ratio, and carrier and photon confinement in two dimensions (1D system). Currently, tremendous efforts are being devoted to rational synthesis of nanowire structures with control over their composition, structure, dopant concentration, characterization, fundamental properties, and assembly into functional devices. In this article we will review the progress made in the area of nanowire optics and optoelectronic devices, including diodes, lasers, detectors, and waveguides, and will outline the general challenges that must be overcome and some potential solutions in order to continue the exponential progress in this exciting area of research. (orig.)

  4. Endotaxial silicide nanowires: A review

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, P.A., E-mail: peter.bennett@asu.edu [Physics Department, Arizona State University, Tempe, AZ 85287 (United States); School of Materials, Arizona State University, Tempe, AZ 85287 (United States); He, Zhian [School of Materials, Arizona State University, Tempe, AZ 85287 (United States); Smith, David J. [Physics Department, Arizona State University, Tempe, AZ 85287 (United States); School of Materials, Arizona State University, Tempe, AZ 85287 (United States); Ross, F.M. [IBM T. J. Watson Research Center, Yorktown Heights NY 10598 (United States)

    2011-10-03

    We review the topic of self-assembled endotaxial silicide nanowires on silicon. Crystallographic orientation, lattice mismatch and average dimensions are discussed for a variety of systems including Ti, Mn, Fe, Co, Ni, Pt and several rare earths on Si(100), Si(111) and Si(110) surfaces. In situ observations of growth dynamics support a constant-shape growth model, in which length, width and thickness all change in proportion as the nanowire grows, with thermally activated, facet-dependent rates.

  5. Silicon nanowires: structure and properties

    International Nuclear Information System (INIS)

    Nezhdanov, A.V.; Mashin, A.I.; Razuvaev, A.G.; Ershov, A.V.; Ignatov, S.K.

    2006-01-01

    An attempt to grow silicon nanowires has been made by electron beam evaporation on highly oriented pyrolytic substrate. Needle-like objects are located along the normal to a substrate (density 2 x 10 11 cm -2 ). For modeling quasi-one-dimensional objects calculations of nuclear structure and energy spectra have been accomplished. A fullerene-like structure Si 24 is proposed as a basic atomic configuration of silicon nanowires [ru

  6. Electron transport in silicon nanowires having different cross-sections

    Directory of Open Access Journals (Sweden)

    Muscato Orazio

    2016-06-01

    Full Text Available Transport phenomena in silicon nanowires with different cross-section are investigated using an Extended Hydrodynamic model, coupled to the Schrödinger-Poisson system. The model has been formulated by closing the moment system derived from the Boltzmann equation on the basis of the maximum entropy principle of Extended Thermodynamics, obtaining explicit closure relations for the high-order fluxes and the production terms. Scattering of electrons with acoustic and non polar optical phonons have been taken into account. The bulk mobility is evaluated for square and equilateral triangle cross-sections of the wire.

  7. Effects of electronic correlation, physical structure, and surface termination on the electronic structure of V2O3 nanowires

    Science.gov (United States)

    Tiano, Amanda L.; Li, Jing-bin; Sutter, Eli; Wong, Stanislaus S.; Fernández-Serra, M.-V.

    2012-09-01

    We report on a density functional theory (DFT) study of the electronic structure of vanadium sesquioxide (V2O3) in both bulk and nanowire form. In particular, our study focuses on the role of spin polarization and electronic correlations, as computed within the local (spin) density approximation (L(S)DA) and the LDA+U formalism. As expected for a mean-field approach such as DFT, our optimized bulk V2O3 structure is shown to be metallic in nature, while an adequate choice of the Hubbard U parameter (U = 4 eV) is enough to open the band gap, making the system insulating. However, this formalism predicts a nonmagnetic insulator, as opposed to the experimentally observed antiferromagnetic structure, to be the ground state. The electronic structure of the V2O3 nanowire system is more complex, and it strongly depends on the surface termination of the structures. Our results show that non-spin-polarized LDA calculations of 001-grown nanowires are metallic in nature. However, LSDA predicts that some surface terminations are half-metals, with a large band gap opening for one of the spins. When LSDA+U was used to study the nanowire model with a closed-shell oxygen surface termination, we observe insulating behavior with no net magnetic moment, with a 104 meV band gap. This is consistent with the experimentally observed gap recently reported in the literature for similar wires. To experimentally address the surface structure of these nanowires, we perform surface specific nano-Auger electron spectroscopy on as-synthesized V2O3 nanowires. Our experimental results show a higher O:V peak ratio (1.93:1) than expected for pure V2O3, thereby suggesting higher oxygen content at the surface of the nanowires. From our results, we conclude that oxygen termination is likely the termination for our as-synthesized V2O3 nanowires.

  8. Structural and tunneling properties of Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2013-12-06

    We investigate the electronic structure and electron transport properties of Si nanowires attached to Au electrodes from first principles using density functional theory and the nonequilibrium Green\\'s function method. We systematically study the dependence of the transport properties on the diameter of the nanowires, on the growth direction, and on the length. At the equilibrium Au-nanowire distance we find strong electronic coupling between the electrodes and nanowires, which results in a low contact resistance. With increasing nanowire length we study the transition from metallic to tunneling conductance for small applied bias. For the tunneling regime we investigate the decay of the conductance with the nanowire length and rationalize the results using the complex band structure of the pristine nanowires. The conductance is found to depend strongly on the growth direction, with nanowires grown along the ⟨110⟩ direction showing the smallest decay with length and the largest conductance and current.

  9. Silver nanowires - unique templates for functional nanostructures

    Science.gov (United States)

    Sun, Yugang

    2010-09-01

    This feature article reviews the synthesis and application of silver nanowires with the focus on a polyol process that is capable of producing high quality silver nanowires with high yield. The as-synthesized silver nanowires can be used as both physical templates for the synthesis of metal/dielectric core/shell nanowires and chemical templates for the synthesis of metal nanotubes as well as semiconductor nanowires. Typical examples including Ag/SiO2 coaxial nanocables, single- and multiple-walled nanotubes made of Au-Ag alloy, AgCl nanowires and AgCl/Au core/shell nanowires are discussed in detail to illustrate the versatility of nanostructures derived from silver nanowire templates. Novel properties associated with these one-dimensional nanostructures are also briefly discussed to shed the light on their potential applications in electronics, photonics, optoelectronics, catalysis, and medicine.

  10. Nonlocal Optical Response of Plasmonic Nanowire Metamaterials

    Science.gov (United States)

    2014-01-01

    can be expressed as the product = ()()(). Making this substitution, the differential equation can then be written as 1 ...nanowire geometry and solution method. 61 52 Transmission and reflection of the nanowire metamaterial are now compared for full- vectorial

  11. Thermal conductivity reduction in silicon fishbone nanowires.

    Science.gov (United States)

    Maire, Jeremie; Anufriev, Roman; Hori, Takuma; Shiomi, Junichiro; Volz, Sebastian; Nomura, Masahiro

    2018-03-13

    Semiconductor nanowires are potential building blocks for future thermoelectrics because of their low thermal conductivity. Recent theoretical works suggest that thermal conductivity of nanowires can be further reduced by additional constrictions, pillars or wings. Here, we experimentally study heat conduction in silicon nanowires with periodic wings, called fishbone nanowires. We find that like in pristine nanowires, the nanowire cross-section controls thermal conductivity of fishbone nanowires. However, the periodic wings further reduce the thermal conductivity. Whereas an increase in the wing width only slightly affects the thermal conductivity, an increase in the wing depth clearly reduces thermal conductivity, and this reduction is stronger in the structures with narrower nanowires. Our experimental data is supported by the Callaway-Holland model, finite element modelling and phonon transport simulations.

  12. Debye–Einstein approximation approach to calculate the lattice specific heat and related parameters for a Si nanowire

    Directory of Open Access Journals (Sweden)

    A. KH. Alassafee

    2017-11-01

    Full Text Available The modified Debye–Einstein approximation model is used to calculate nanoscale size-dependent values of Gruneisen parameters and lattice specific heat capacity for Si nanowires. All parameters forming the model, including Debye temperatures, bulk moduli, the lattice thermal expansion and the lattice volume, are calculated according to their nanoscale size dependence. Values for lattice volume Gruneisen parameters increase with the decrease of the nanowires’ diameter, while all other parameters decrease. The nanosize dependence of lattice thermal parameters agree with other reported theoretical results. Keywords: Lattice specific heat capacity, Gruneisen parameter, Debye–Einstein model, Si nanowires

  13. Multifunctional Magnetic Nanowires for Biomagnetic Interfacing Concepts

    Science.gov (United States)

    2006-07-14

    1 Final Performance Report Multifunctional Magnetic Nanowires for Biomagnetic Interfacing Concepts AFOSR Agreement Number F49620-02-1-0307 July 14...AND DATES COVERED Final report covering 06/15/02 –12/15/05 4. TITLE AND SUBTITLE Multifunctional Magnetic Nanowires for Biomagnetic Interfacing...nanowires for biomagnetic applications. These include (i) tuning of magnetic and other physical properties of nanowires, (ii) selective

  14. Semiconducting silicon nanowires for biomedical applications

    CERN Document Server

    Coffer, JL

    2014-01-01

    Biomedical applications have benefited greatly from the increasing interest and research into semiconducting silicon nanowires. Semiconducting Silicon Nanowires for Biomedical Applications reviews the fabrication, properties, and applications of this emerging material. The book begins by reviewing the basics, as well as the growth, characterization, biocompatibility, and surface modification, of semiconducting silicon nanowires. It goes on to focus on silicon nanowires for tissue engineering and delivery applications, including cellular binding and internalization, orthopedic tissue scaffol

  15. Controlling nanowire emission profile using conical taper

    DEFF Research Database (Denmark)

    Gregersen, Niels; Nielsen, Torben Roland; Mørk, Jesper

    2008-01-01

    The influence of a conical taper on nanowire light emission is studied. For nanowires with divergent output beams, the introduction of tapers improves the emission profile and increase the collection efficiency of the detection optics.......The influence of a conical taper on nanowire light emission is studied. For nanowires with divergent output beams, the introduction of tapers improves the emission profile and increase the collection efficiency of the detection optics....

  16. Acoustic absorption by the electron-hole liquid in germanium

    International Nuclear Information System (INIS)

    Hansen, A.D.A.

    1977-11-01

    The absorption of ultrasonic acoustic waves by the electron-hole liquid that may be created in germanium at liquid helium temperatures by intense optical excitation was studied. This is a degenerate compensated Fermi liquid that exhibits the behavior of both classical dynamics in a force field, and quantum phenomena in a magnetic field. Results of theoretical and experimental studies of the interaction of the mobile liquid with a travelling acoustic wave force field, the attenuation of the wave due to energy-dissipative processes coupling the liquid to the crystal lattice, and the effect of a moderately strong magnetic field on the dynamic behavior of the system are presented. In unstrained germanium the electron-hole liquid (EHL) is known to be condensed into small droplets of radius approx. 5 μm; the creation of an EHL energy well by the application of an inhomogeneous stress causes the liquid to be aggregated into a macroscopically large volume

  17. Acoustic absorption by the electron-hole liquid in germanium

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, A.D.A.

    1977-11-01

    The absorption of ultrasonic acoustic waves by the electron-hole liquid that may be created in germanium at liquid helium temperatures by intense optical excitation was studied. This is a degenerate compensated Fermi liquid that exhibits the behavior of both classical dynamics in a force field, and quantum phenomena in a magnetic field. Results of theoretical and experimental studies of the interaction of the mobile liquid with a travelling acoustic wave force field, the attenuation of the wave due to energy-dissipative processes coupling the liquid to the crystal lattice, and the effect of a moderately strong magnetic field on the dynamic behavior of the system are presented. In unstrained germanium the electron-hole liquid (EHL) is known to be condensed into small droplets of radius approx. 5 ..mu..m; the creation of an EHL energy well by the application of an inhomogeneous stress causes the liquid to be aggregated into a macroscopically large volume.

  18. Synthesis and Gas Phase Thermochemistry of Germanium-Containing Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Classen, Nathan Robert [Iowa State Univ., Ames, IA (United States)

    2002-01-01

    The driving force behind much of the work in this dissertation was to gain further understanding of the unique olefin to carbene isomerization observed in the thermolysis of 1,1-dimethyl-2-methylenesilacyclobutane by finding new examples of it in other silicon and germanium compounds. This lead to the examination of a novel phenylmethylenesilacyclobut-2-ene, which did not undergo olefin to carbene rearrangement. A synthetic route to methylenegermacyclobutanes was developed, but the methylenegermacyclobutane system exhibited kinetic instability, making the study of the system difficult. In any case the germanium system decomposed through a complex mechanism which may not include olefin to carbene isomerization. However, this work lead to the study of the gas phase thermochemistry of a series of dialkylgermylene precursors in order to better understand the mechanism of the thermal decomposition of dialkylgermylenes. The resulting dialkylgermylenes were found to undergo a reversible intramolecular β C-H insertion mechanism.

  19. Mechanically-cooled germanium detector using two stirling refrigerators

    International Nuclear Information System (INIS)

    Katagiri, Masaki; Kobayashi, Yoshii; Takahashi, Koji

    1996-01-01

    In this paper, we present a developed mechanically-cooled germanium gamma-ray detector using Stirling refrigerators. Two Stirling refrigerators having cooling faculty of 1.5W at 80K were used to cool down a germanium detector element to 77K instead of a dewar containing liquid nitrogen. An 145cm 3 (56.0mmf x 59.1 mml) closed-end Ge(I) detector having relative detection efficiency of 29.4% was attached at the refrigerators. The size of the detector was 60cml x 15cmh x 15cmw. The lowest cooling temperature, 70K was obtained after 8 hours operation. The energy resolutions for 1.33MeV gamma-rays and for pulser signals were 2.43keV and 1.84keV at an amplifier shaping time of 2μsec, respectively

  20. Development of neutron-transmutation-doped germanium bolometer material

    International Nuclear Information System (INIS)

    Palaio, N.P.

    1983-08-01

    The behavior of lattice defects generated as a result of the neutron-transmutation-doping of germanium was studied as a function of annealing conditions using deep level transient spectroscopy (DLTS) and mobility measurements. DLTS and variable temperature Hall effect were also used to measure the activation of dopant impurities formed during the transmutation process. In additioon, a semi-automated method of attaching wires on to small chips of germanium ( 3 ) for the fabrication of infrared detecting bolometers was developed. Finally, several different types of junction field effect transistors were tested for noise at room and low temperature (approx. 80 K) in order to find the optimum device available for first stage electronics in the bolometer signal amplification circuit

  1. The Future of Low Temperature Germanium as Dark Matter Detectors

    CERN Multimedia

    CERN. Geneva

    2009-01-01

    The Weakly Interactive Massive Particles (WIMPs) represent one of the most attractive candidates for the dark matter in the universe. With the combination of experiments attempting to detect WIMP scattering in the laboratory, of searches for their annihilation in the cosmos and of their potential production at the LHC, the next five years promise to be transformative. I will review the role played so far by low temperature germanium detectors in the direct detection of WIMPs. Because of its high signal to noise ratio, the simultaneous measurement of athermal phonons and ionization is so far the only demonstrated approach with zero-background. I will argue that this technology can be extrapolated to a target mass of the order of a tonne at reasonable cost and can keep playing a leading role, complementary to noble liquid technologies. I will describe in particular GEODM, the proposed Germanium Observatory for Dark Matter at the US Deep Underground Science and Engineering Laboratory (DUSEL).

  2. Germanium-doped gallium phosphide obtained by neutron irradiation

    Science.gov (United States)

    Goldys, E. M.; Barczynska, J.; Godlewski, M.; Sienkiewicz, A.; Heijmink Liesert, B. J.

    1993-08-01

    Results of electrical, optical, electron spin resonance and optically detected magnetic resonance studies of thermal neutron irradiated and annealed at 800 °C n-type GaP are presented. Evidence is found to support the view that the main dopant introduced via transmutation of GaP, germanium, occupies cation sites and forms neutral donors. This confirms the possibility of neutron transmutation doping of GaP. Simultaneously, it is shown that germanium is absent at cation sites. Presence of other forms of Ge-related defects is deduced from luminescence and absorption data. Some of them are tentatively identified as VGa-GeGa acceptors leading to the self-compensation process. This observation means that the neutron transmutation as a doping method in application to GaP is not as efficient as for Si.

  3. Heterogeneous metal-oxide nanowire micro-sensor array for gas sensing

    Science.gov (United States)

    DeMeo, Dante; MacNaughton, Sam; Wang, Zhilong; Zhang, Xinjie; Sonkusale, Sameer; Vandervelde, Thomas E.

    2014-04-01

    Vanadium oxide, manganese oxide, tungsten oxide, and nickel oxide nanowires were investigated for their applicability as chemiresistive gas sensors. Nanowires have excellent surface-to-volume ratios which yield higher sensitivities than bulk materials. Sensing elements consisting of these materials were assembled in an array to create an electronic nose platform. Dielectrophoresis was used to position the nanomaterials onto a microfabricated array of electrodes, which was subsequently mounted onto a leadless chip carrier and printed circuit board for rapid testing. Samples were tested in an enclosed chamber with vapors of acetone, isopropanol, methanol, and aqueous ammonia. The change in resistance of each assembly was measured. Responses varied between nanowire compositions, each demonstrating unique and repeatable responses to different gases; this enabled direct detection of the gases from the ensemble response. Sensitivities were calculated based on the fractional resistance change in a saturated environment and ranged from 6 × 10-4 to 2 × 10-5%change ppm-1.

  4. Ammonium vanadate@polypyrrole@manganese dioxide nanowire arrays with enhanced reversible lithium storage

    Science.gov (United States)

    Wang, Chang; Liu, Hui; Jiang, Ming; Wang, Yingde; Liu, Ruina; Luo, Zhiping; Liu, Xiaoqing; Xu, Weilin; Xiong, Chuanxi; Fang, Dong

    2017-09-01

    Design and fabrication of novel optimized electrode materials are important for the development of new batteries for energy storage applications. Herein, we report on a hierarchical bulk electrode material with a tailored nanostructure that which consists of three components: a NH4V4O10 nanowire as an active skeleton, an intermediate polymer layer (polypyrrole, PPy), and a metal oxide layer (MnO2) as the outside shell. The NH4V4O10-PPy-MnO2 nanowires exhibit present higher capacitance than that of the simple NH4V4O10-PPy core@shell or NH4V4O10 nanowires. The structure of double shells of combined PPy and MnO2 is a key factor in enhancing their electrochemical performance including high specific capacitance and excellent cycling stability. Our V-based core@shell@shell structure can serve as freestanding, compressible electrodes for various energy devices.

  5. "High Quantum Efficiency of Band-Edge Emission from ZnO Nanowires"

    Energy Technology Data Exchange (ETDEWEB)

    GARGAS, DANIEL; GAO, HANWEI; WANG, HUNGTA; PEIDONG, YANG

    2010-12-01

    External quantum efficiency (EQE) of photoluminescence as high as 20 percent from isolated ZnO nanowires were measured at room temperature. The EQE was found to be highly dependent on photoexcitation density, which underscores the importance of uniform optical excitation during the EQE measurement. An integrating sphere coupled to a microscopic imaging system was used in this work, which enabled the EQE measurement on isolated ZnO nanowires. The EQE values obtained here are significantly higher than those reported for ZnO materials in forms of bulk, thin films or powders. Additional insight on the radiative extraction factor of one-dimensional nanostructures was gained by measuring the internal quantum efficiency of individual nanowires. Such quantitative EQE measurements provide a sensitive, noninvasive method to characterize the optical properties of low-dimensional nanostructures and allow tuning of synthesis parameters for optimization of nanoscale materials.

  6. Electronic and structural properties of ultrathin tungsten nanowires and nanotubes by density functional theory calculation

    International Nuclear Information System (INIS)

    Sun, Shih-Jye; Lin, Ken-Huang; Li, Jia-Yun; Ju, Shin-Pon

    2014-01-01

    The simulated annealing basin-hopping method incorporating the penalty function was used to predict the lowest-energy structures for ultrathin tungsten nanowires and nanotubes of different sizes. These predicted structures indicate that tungsten one-dimensional structures at this small scale do not possess B.C.C. configuration as in bulk tungsten material. In order to analyze the relationship between multi-shell geometries and electronic transfer, the electronic and structural properties of tungsten wires and tubes including partial density of state and band structures which were determined and analyzed by quantum chemistry calculations. In addition, in order to understand the application feasibility of these nanowires and tubes on nano-devices such as field emitters or chemical catalysts, the electronic stability of these ultrathin tungsten nanowires was also investigated by density functional theory calculations.

  7. Nanowire resonant tunneling diodes

    Science.gov (United States)

    Björk, M. T.; Ohlsson, B. J.; Thelander, C.; Persson, A. I.; Deppert, K.; Wallenberg, L. R.; Samuelson, L.

    2002-12-01

    Semiconductor heterostructures and their implementation into electronic and photonic devices have had tremendous impact on science and technology. In the development of quantum nanoelectronics, one-dimensional (1D) heterostructure devices are receiving a lot of interest. We report here functional 1D resonant tunneling diodes obtained via bottom-up assembly of designed segments of different semiconductor materials in III/V nanowires. The emitter, collector, and the central quantum dot are made from InAs and the barrier material from InP. Ideal resonant tunneling behavior, with peak-to-valley ratios of up to 50:1 and current densities of 1 nA/μm2 was observed at low temperatures.

  8. Indium Arsenide Nanowires

    DEFF Research Database (Denmark)

    Madsen, Morten Hannibal

    is presented. A series of experiments with formation of a droplet on top of the wires has been carried out and pyramidal shaped structures at the NW top with pure zinc blende crystal structure are observed. A novel in-situ experiment with fabrication of NWs and simultanous characterization using x......This thesis is about growth of Au-assisted and self-assisted InAs nanowires (NWs). The wires are synthesized using a solid source molecular beam epitaxy (MBE) system and characterized with several techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x......-ray diffraction is performed with a MBE system attached to a synchrotron beam line. The evolution in crystal structure is monitored for different growth conditions and can be correlated to post growth analysis in TEM. This type of studies gives much more detailed information on formation of the crystal structure...

  9. Bandwidth improvement for germanium photodetector using wire bonding technology.

    Science.gov (United States)

    Chen, Guanyu; Yu, Yu; Deng, Shupeng; Liu, Lei; Zhang, Xinliang

    2015-10-05

    We demonstrate an ultrahigh speed germanium photodetector by introducing gold wires into the discrete ground electrodes with standard wire bonding technology. To engineer the parasitic parameter, the physical dimension of the gold wire used for wire bonding is specially designed with an inductance of about 450 pH. Simulation and experimental results show that the bandwidth of the photodetector can be effectively extended from less than 30 GHz to over 60 GHz.

  10. Strain-induced changes to the electronic structure of germanium

    KAUST Repository

    Tahini, H. A.

    2012-04-17

    Density functional theory calculations (DFT) are used to investigate the strain-induced changes to the electronic structure of biaxially strained (parallel to the (001), (110) and (111) planes) and uniaxially strained (along the [001], [110] and [111] directions) germanium (Ge). It is calculated that a moderate uniaxial strain parallel to the [111] direction can efficiently transform Ge to a direct bandgap material with a bandgap energy useful for technological applications. © 2012 IOP Publishing Ltd.

  11. Fabrication techniques for reverse electrode coaxial germanium nuclear radiation detectors

    International Nuclear Information System (INIS)

    Hansen, W.L.; Haller, E.E.

    1980-11-01

    Germanium detectors with reverse polarity coaxial electrodes have been shown to exhibit improved resistance to radiation damage as compared with conventional electrode devices. However, the production of reverse electrode devices involves the development of new handling and fabrication techniques which has limited their wider application. We have developed novel techniques which lead to a device which is simple to fabricate, environmentally passivated and surface state adjusted

  12. Strain-induced changes to the electronic structure of germanium.

    Science.gov (United States)

    Tahini, H; Chroneos, A; Grimes, R W; Schwingenschlögl, U; Dimoulas, A

    2012-05-16

    Density functional theory calculations (DFT) are used to investigate the strain-induced changes to the electronic structure of biaxially strained (parallel to the (001), (110) and (111) planes) and uniaxially strained (along the [001], [110] and [111] directions) germanium (Ge). It is calculated that a moderate uniaxial strain parallel to the [111] direction can efficiently transform Ge to a direct bandgap material with a bandgap energy useful for technological applications.

  13. Determination of carbon and nitrogen in silicon and germanium

    International Nuclear Information System (INIS)

    Gebauhr, W.; Martin, J.

    1975-01-01

    The essential aim of this study is to examine the various technical and economic problems encountered in the determination of carbon and nitrogen in silicon and germanium, for this is in a way an extension of the discussion concerning the presence of oxygen in these two elements. The greater part of the study is aimed at drawing up a catalogue of the methods of analysis used and of the results obtained so far

  14. The germanium wall of the GEM detector system GEM Collaboration

    International Nuclear Information System (INIS)

    Betigeri, M.; Biakowski, E.; Bojowald, H.; Budzanowski, A.; Chatterjee, A.; Drochner, M.; Ernst, J.; Foertsch, S.; Freindl, L.; Frekers, D.; Garske, W.; Grewer, K.; Hamacher, A.; Igel, S.; Ilieva, J.; Jarczyk, L.; Jochmann, M.; Kemmerling, G.; Kilian, K.; Kliczewski, S.; Klimala, W.; Kolev, D.; Kutsarova, T.; Lieb, J.; Lippert, G.; Machner, H.; Magiera, A.; Nann, H.; Pentchev, L.; Plendl, H.S.; Protic, D.; Razen, B.; Rossen, P. von; Roy, B.J.; Siudak, R.; Smyrski, J.; Srikantiah, R.V.; Strzakowski, A.; Tsenov, R.; Zolnierczuk, P.A.; Zwoll, K.

    1999-01-01

    A stack of annular detectors made of high-purity germanium was developed. The detectors are position sensitive with radial structures. The first one ('Quirl') is double-sided position sensitive defining 40,000 pixels, the following three (E1, E2 and E3) have 32 wedges each. The Quirl acts as tracker while the other three act as calorimeter. The stack was successfully operated in meson production reactions close to threshold

  15. Characterization of the sub-keV Germanium detector

    Science.gov (United States)

    Singh, M. K.; Singh, Manoj K.; Sharma, V.; Singh, L.; Singh, V.; Subrahmanyam, V. S.; Soma, A. K.; Kiran Kumar, G.; Wong, H. T.

    2018-03-01

    Germanium ionization detectors having sensitivities as low as 100 eV open new windows for the studies of neutrino and dark matter physics. This novel detector demands overcoming several challenges at both hardware and software levels. The amplitude of physics signals is comparable to those due to fluctuations of the pedestal electronic noise in low energy range. Therefore, it is important to study the low energy calibration properly. In this article, we focus on the optimization of the calibration scheme.

  16. Photoluminescent polysaccharide-coated germanium(IV) oxide nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Lobaz, Volodymyr; Rabyk, Mariia; Pánek, Jiří; Doris, E.; Nallet, F.; Štěpánek, Petr; Hrubý, Martin

    2016-01-01

    Roč. 294, č. 7 (2016), s. 1225-1235 ISSN 0303-402X R&D Projects: GA MŠk(CZ) 7AMB14FR027; GA ČR(CZ) GA13-08336S; GA MZd(CZ) NV15-25781A Institutional support: RVO:61389013 Keywords : germanium oxide nanoparticles * polysaccharide coating * photoluminescent label Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.723, year: 2016

  17. Optical properties of silicon germanium waveguides at telecommunication wavelengths.

    Science.gov (United States)

    Hammani, Kamal; Ettabib, Mohamed A; Bogris, Adonis; Kapsalis, Alexandros; Syvridis, Dimitris; Brun, Mickael; Labeye, Pierre; Nicoletti, Sergio; Richardson, David J; Petropoulos, Periklis

    2013-07-15

    We present a systematic experimental study of the linear and nonlinear optical properties of silicon-germanium (SiGe) waveguides, conducted on samples of varying cross-sectional dimensions and Ge concentrations. The evolution of the various optical properties for waveguide widths in the range 0.3 to 2 µm and Ge concentrations varying between 10 and 30% is considered. Finally, we comment on the comparative performance of the waveguides, when they are considered for nonlinear applications at telecommunications wavelengths.

  18. Diffusion of tin in germanium: A GGA+U approach

    KAUST Repository

    Tahini, H. A.

    2011-10-18

    Density functional theory calculations are used to investigate the formation and diffusion of tin-vacancy pairs (SnV) in germanium(Ge). Depending upon the Fermi energy, SnV pairs can form in neutral, singly negative, or doubly negative charged states. The activation energies of diffusion, also as function of the Fermi energy, are calculated to lie between 2.48-3.65 eV, in agreement with and providing an interpretation of available experimental work.

  19. The investigation of germanium based compounds, transition metals and isoflavones within foods

    OpenAIRE

    Dowling, Stephen

    2010-01-01

    The body of work here looks not only at how germanium was present in foods but also the ascertainment of chelation behaviour of germanium compounds and also transition metals with flavonoids. The chelation of germanium with flavonoids, or particularly isoflavones, is a completely novel area and gave some interesting results for chelation with isoflavones with transition metals, an area of research that was completely underexploited until recently. (refer to appendix 1) The Fourier Tran...

  20. An environmentally-friendly vacuum reduction metallurgical process to recover germanium from coal fly ash

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lingen; Xu, Zhenming, E-mail: zmxu@sjtu.edu.cn

    2016-07-15

    Highlights: • An environmental friendly vacuum reduction metallurgical process is proposed. • Rare and valuable metal germanium from coal fly ash is recycled. • Residues are not a hazardous material and can be further recycled. • A germanium recovery ratio of 94.64% is obtained in pilot scale experiments. - Abstract: The demand for germanium in the field of semiconductor, electronics, and optical devices is growing rapidly; however, the resources of germanium are scarce worldwide. As a secondary material, coal fly ash could be further recycled to retrieve germanium. Up to now, the conventional processes to recover germanium have two problems as follows: on the one hand, it is difficult to be satisfactory for its economic and environmental effect; on the other hand, the recovery ratio of germanium is not all that could be desired. In this paper, an environmentally-friendly vacuum reduction metallurgical process (VRMP) was proposed to recover germanium from coal fly ash. The results of the laboratory scale experiments indicated that the appropriate parameters were 1173 K and 10 Pa with 10 wt% coke addition for 40 min, and recovery ratio germanium was 93.96%. On the basis of above condition, the pilot scale experiments were utilized to assess the actual effect of VRMP for recovery of germanium with parameter of 1473 K, 1–10 Pa and heating time 40 min, the recovery ratio of germanium reached 94.64%. This process considerably enhances germanium recovery, meanwhile, eliminates much of the water usage and residue secondary pollution compared with other conventional processes.

  1. Corrosion detection of nanowires by magnetic sensors

    KAUST Repository

    Kosel, Jürgen

    2017-10-05

    Disclosed are various embodiments related to a corrosion detection device for detecting corrosive environments. A corrosion detection device comprises a magnetic sensor and at least one magnetic nanowire disposed on the magnetic sensor. The magnetic sensor is configured to detect corrosion of the one or more magnetic nanowires based at least in part on a magnetic field of the one or more magnetic nanowires.

  2. Evaluation of peak-to-total ratio for germanium detectors

    International Nuclear Information System (INIS)

    Watanabe, Tamaki; Oi, Yoshihiro; Taki, Mitsumasa; Kawasaki, Katsuya; Yoshida, Makoto

    1999-01-01

    An equation for the peak-to-total ratio, P, of a germanium detector is proposed in the following form. P=ε p /ε t +a(V/A)+b(V/A) 2 /2 where ε p /ε t is the ratio of the photoelectric to the total detection efficiency for a germanium detector, V/A is the volume-to-surface ratio of the detector, and the parameters of a and b are experimentally given as a function of incident photon energy. The first term in the right side of the equation expresses the fractional single photoelectric-to-total interaction between photons and the detector. The second and third terms correspond to the multiple interactions. The peak-to-total ratios for the germanium detector with a sensitive volume up to 200 cm 3 were calculated by the equation. They coincide with the experimental values to within an uncertainty of several percent in the energy region 0.3-3 MeV

  3. Testing CuO nanowires as a novel X-ray to electron converter for gas-filled radiation detectors

    Science.gov (United States)

    Zarei, H.; Saramad, S.; Razaghi, S.

    2017-10-01

    Nanowires, due to their special physical properties and also high surface to volume ratio, can have considerable applications in designing and development of novel nanodevices. For the radiation shielding, higher absorption coefficient of nanostructures in comparison to bulk ones is an advantage. In gas detectors, designing a proper converter that absorbs higher energy of gamma and X-rays and convert it to more free electrons is one of the major problems. Since the nanowires have higher surface to volume ratio in comparison to the bulk one, so it is expected that by optimizing the thickness, the generated electrons can have higher chance to escape from the surface. In this work, the random CuO nanowires with diameter of 40 nm are deposited on thin glass slide. This nanostructure with different thicknesses are tested by plastic and CsI scintillators by X-ray tube with HVs in the range of 16 to 25 kV. The results show that for the same thickness, the CuO nanowires can release electrons six times more than the bulk ones and for the same energy the optimum QE of nanoconverter can be three times greater than the bulk converter. This novel nanoconverter with higher detection efficiency can have applications in high energy physics, medical imaging and also astronomy.

  4. Growth and properties of low-dimensional III-V semiconductor nanowire heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Heiss, Martin

    2010-08-25

    symmetry from cubic zinc-blende to hexagonal wurtzite structure, while the chemical composition of the material remains constant. The GaAs nanowires synthesized with the Au-free technique can be grown under conditions where a statistical wurtzite/zinc-blende polytypism occurs. A novel method for the direct correlation at the nanoscale of structural and optical properties of single GaAs nanowires is developed in order to characterize the resulting statistically distributed quantum heterostructures. Nanowires consisting of {approx}100% wurtzite and nanowires presenting zinc-blende/wurtzite polytypism are studied by photoluminescence spectroscopy and Transmission Electron Microscopy. The photoluminescence of wurtzite GaAs is found to be consistent with a bulk wurtzite band gap of 1.50 eV, slightly smaller compared to the zinc-blende GaAs band gap. In the polytypic nanowires, it is shown that the regions that are predominantly composed of either zinc-blende or wurtzite phase show photoluminescence emission close to the according bulk band gaps, while regions composed of a non periodic superlattice of wurtzite and zinc-blende phases exhibit a redshift of the photoluminescence spectra as low as 1.455 eV. The dimensions of the quantum heterostructures are correlated with the light emission, allowing us to estimate the band offsets of {delta}E{sub CB}=53{+-}20 meV and {delta}E{sub VB}=76{+-}12 meV between the two crystalline phases. These results are in excellent agreement with recent theoretical band structure calculations. (orig.)

  5. Interdigitated design of a thermoelectric microgenerator based on silicon nanowire arrays

    Science.gov (United States)

    Donmez, I.; Salleras, M.; Calaza, C.; Santos, J. D.; Gadea, G.; Morata, A.; Dávila, D.; Tarancón, A.; Fonseca, L.

    2015-05-01

    Silicon nanowires thermoelectric properties are much better than those of silicon bulk. Taking advantage of silicon microfabrication techniques and compatibilizing the device fabrication with the CVD-VLS silicon nanowire growth, we present a thermoelectric microgenerator based on silicon nanowire arrays with interdigitated structures which enhance the power density compared to previous designs presented by the authors. The proposed design features a thermally isolated silicon platform on the silicon device layer of an SOI silicon wafer. This silicon platform has vertical walls exposing thermoelectric generator is unileg, which means that only one type of semiconductor is used, and the second connection is made through a metal. In addition, to improve the thermal isolation of the silicon platform, multiple trenches of silicon nanowire arrays are used, up to a maximum of nine. After packaging the device with nanowires, we are able to measure the Seebeck voltage and the power obtained with different operation modes: harvesting mode, where the bottom device is heated up, and the silicon platform is cooled down by natural or forced convection, and test mode, where a heater integrated on the silicon platform is used to produce a thermal gradient.

  6. Revealing ultralarge and localized elastic lattice strains in Nb nanowires embedded in NiTi matrix.

    Science.gov (United States)

    Zang, Ketao; Mao, Shengcheng; Cai, Jixiang; Liu, Yinong; Li, Haixin; Hao, Shijie; Jiang, Daqiang; Cui, Lishan

    2015-12-02

    Freestanding nanowires have been found to exhibit ultra-large elastic strains (4 to 7%) and ultra-high strengths, but exploiting their intrinsic superior mechanical properties in bulk forms has proven to be difficult. A recent study has demonstrated that ultra-large elastic strains of ~6% can be achieved in Nb nanowires embedded in a NiTi matrix, on the principle of lattice strain matching. To verify this hypothesis, this study investigated the elastic deformation behavior of a Nb nanowire embedded in NiTi matrix by means of in situ transmission electron microscopic measurement during tensile deformation. The experimental work revealed that ultra-large local elastic lattice strains of up to 8% are induced in the Nb nanowire in regions adjacent to stress-induced martensite domains in the NiTi matrix, whilst other parts of the nanowires exhibit much reduced lattice strains when adjacent to the untransformed austenite in the NiTi matrix. These observations provide a direct evidence of the proposed mechanism of lattice strain matching, thus a novel approach to designing nanocomposites of superior mechanical properties.

  7. Mapping the local structure of nanowires

    DEFF Research Database (Denmark)

    Persson, Johan Mikael; Wagner, Jakob Birkedal

    2013-01-01

    The crystallographic and compositional structure of heterostructured semiconductor nanowires has been studied by means of transmission electron microscopy. The native geometry of the studied InP-GaAs nanowires (80-100 nm in diameter) is in general too thick for reliable high-resolution TEM imaging....... Nano Beam Electron Diffraction (NBED) is shown to be a powerful technique to reveal strain near the interface of compositional change in heterostructured semiconductor nanowires. Furthermore, the relative orientation of the nanowires is studied by means of NBED revealing the nanowires to be very...

  8. Micromagnetic simulations of cylindrical magnetic nanowires

    KAUST Repository

    Ivanov, Yurii P.

    2015-05-27

    This chapter reviews micromagnetic simulations of cylindrical magnetic nanowires and their ordered arrays. It starts with a description of the theoretical background of micromagnetism. The chapter discusses main magnetization reversal modes, domain wall types, and state diagrams in cylindrical nanowires of different types and sizes. The results of the hysteresis process in individual nanowires and nanowire arrays also are presented. Modeling results are compared with experimental ones. The chapter also discusses future trends in nanowire applications in relation to simulations, such as current-driven dynamics, spintronics, and spincaloritronics. The main micromagnetic programs are presented and discussed, together with the corresponding links.

  9. Electronic Structure of Silicon Nanowires Matrix from Ab Initio Calculations.

    Science.gov (United States)

    Monastyrskii, Liubomyr S; Boyko, Yaroslav V; Sokolovskii, Bogdan S; Potashnyk, Vasylyna Ya

    2016-12-01

    An investigation of the model of porous silicon in the form of periodic set of silicon nanowires has been carried out. The electronic energy structure was studied using a first-principle band method-the method of pseudopotentials (ultrasoft potentials in the basis of plane waves) and linearized mode of the method of combined pseudopotentials. Due to the use of hybrid exchange-correlation potentials (B3LYP), the quantitative agreement of the calculated value of band gap in the bulk material with experimental data is achieved. The obtained results show that passivation of dangling bonds with hydrogen atoms leads to substantial transformation of electronic energy structure. At complete passivation of the dangling silicon bonds by hydrogen atoms, the band gap value takes the magnitude which substantially exceeds that for bulk silicon. The incomplete passivation gives rise to opposite effect when the band gap value decreases down the semimetallic range.

  10. Photoelectrochemistry of Semiconductor Nanowire Arrays

    Energy Technology Data Exchange (ETDEWEB)

    Mallouk, Thomas E; Redwing, Joan M

    2009-11-10

    This project supported research on the growth and photoelectrochemical characterization of semiconductor nanowire arrays, and on the development of catalytic materials for visible light water splitting to produce hydrogen and oxygen. Silicon nanowires were grown in the pores of anodic aluminum oxide films by the vapor-liquid-solid technique and were characterized electrochemically. Because adventitious doping from the membrane led to high dark currents, silicon nanowire arrays were then grown on silicon substrates. The dependence of the dark current and photovoltage on preparation techniques, wire diameter, and defect density was studied for both p-silicon and p-indium phosphide nanowire arrays. The open circuit photovoltage of liquid junction cells increased with increasing wire diameter, reaching 350 mV for micron-diameter silicon wires. Liquid junction and radial p-n junction solar cells were fabricated from silicon nano- and microwire arrays and tested. Iridium oxide cluster catalysts stabilized by bidentate malonate and succinate ligands were also made and studied for the water oxidation reaction. Highlights of this project included the first papers on silicon and indium phosphide nanowire solar cells, and a new procedure for making ligand-stabilized water oxidation catalysts that can be covalently linked to molecular photosensitizers or electrode surfaces.

  11. In situ biasing and off-axis electron holography of a ZnO nanowire

    Science.gov (United States)

    den Hertog, Martien; Donatini, Fabrice; McLeod, Robert; Monroy, Eva; Sartel, Corinne; Sallet, Vincent; Pernot, Julien

    2018-01-01

    Quantitative characterization of electrically active dopants and surface charges in nano-objects is challenging, since most characterization techniques using electrons [1-3], ions [4] or field ionization effects [5-7] study the chemical presence of dopants, which are not necessarily electrically active. We perform cathodoluminescence and voltage contrast experiments on a contacted and biased ZnO nanowire with a Schottky contact and measure the depletion length as a function of reverse bias. We compare these results with state-of-the-art off-axis electron holography in combination with electrical in situ biasing on the same nanowire. The extension of the depletion length under bias observed in scanning electron microscopy based techniques is unusual as it follows a linear rather than square root dependence, and is therefore difficult to model by bulk equations or finite element simulations. In contrast, the analysis of the axial depletion length observed by holography may be compared with three-dimensional simulations, which allows estimating an n-doping level of 1 × 1018 cm-3 and negative sidewall surface charge of 2.5 × 1012 cm-2 of the nanowire, resulting in a radial surface depletion to a depth of 36 nm. We found excellent agreement between the simulated diameter of the undepleted core and the active thickness observed in the experimental data. By combining TEM holography experiments and finite element simulation of the NW electrostatics, the bulk-like character of the nanowire core is revealed.

  12. Monolithic carbon structures including suspended single nanowires and nanomeshes as a sensor platform.

    Science.gov (United States)

    Lim, Yeongjin; Heo, Jeong-Il; Madou, Marc; Shin, Heungjoo

    2013-11-20

    With the development of nanomaterial-based nanodevices, it became inevitable to develop cost-effective and simple nanofabrication technologies enabling the formation of nanomaterial assembly in a controllable manner. Herein, we present suspended monolithic carbon single nanowires and nanomeshes bridging two bulk carbon posts, fabricated in a designed manner using two successive UV exposure steps and a single pyrolysis step. The pyrolysis step is accompanied with a significant volume reduction, resulting in the shrinkage of micro-sized photoresist structures into nanoscale carbon structures. Even with the significant elongation of the suspended carbon nanowire induced by the volume reduction of the bulk carbon posts, the resultant tensional stress along the nanowire is not significant but grows along the wire thickness; this tensional stress gradient and the bent supports of the bridge-like carbon nanowire enhance structural robustness and alleviate the stiction problem that suspended nanostructures frequently experience. The feasibility of the suspended carbon nanostructures as a sensor platform was demonstrated by testing its electrochemical behavior, conductivity-temperature relationship, and hydrogen gas sensing capability.

  13. Electrically Injected UV-Visible Nanowire Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Wang, George T.; Li, Changyi; Li, Qiming; Liu, Sheng; Wright, Jeremy Benjamin; Brener, Igal; Luk, Ting -Shan; Chow, Weng W.; Leung, Benjamin; Figiel, Jeffrey J.; Koleske, Daniel D.; Lu, Tzu-Ming

    2015-09-01

    There is strong interest in minimizing the volume of lasers to enable ultracompact, low-power, coherent light sources. Nanowires represent an ideal candidate for such nanolasers as stand-alone optical cavities and gain media, and optically pumped nanowire lasing has been demonstrated in several semiconductor systems. Electrically injected nanowire lasers are needed to realize actual working devices but have been elusive due to limitations of current methods to address the requirement for nanowire device heterostructures with high material quality, controlled doping and geometry, low optical loss, and efficient carrier injection. In this project we proposed to demonstrate electrically injected single nanowire lasers emitting in the important UV to visible wavelengths. Our approach to simultaneously address these challenges is based on high quality III-nitride nanowire device heterostructures with precisely controlled geometries and strong gain and mode confinement to minimize lasing thresholds, enabled by a unique top-down nanowire fabrication technique.

  14. Methods for synthesizing metal oxide nanowires

    Science.gov (United States)

    Sunkara, Mahendra Kumar; Kumar, Vivekanand; Kim, Jeong H.; Clark, Ezra Lee

    2016-08-09

    A method of synthesizing a metal oxide nanowire includes the steps of: combining an amount of a transition metal or a transition metal oxide with an amount of an alkali metal compound to produce a mixture; activating a plasma discharge reactor to create a plasma discharge; exposing the mixture to the plasma discharge for a first predetermined time period such that transition metal oxide nanowires are formed; contacting the transition metal oxide nanowires with an acid solution such that an alkali metal ion is exchanged for a hydrogen ion on each of the transition metal oxide nanowires; and exposing the transition metal oxide nanowires to the plasma discharge for a second predetermined time period to thermally anneal the transition metal oxide nanowires. Transition metal oxide nanowires produced using the synthesis methods described herein are also provided.

  15. Synthesis, surface properties and antimicrobial activity of some germanium nonionic surfactants.

    Science.gov (United States)

    Zaki, Mohamed F; Tawfik, Salah M

    2014-01-01

    Esterification reaction between different fatty acid namely; lauric, stearic, oleic and linoleic acids and polyethylene glycol-400 were performed. The produced polyethylene glycol ester were reacted with p-amine benzoic acid followed by condensation reaction with germanium dioxide in presence of sodium carbonate to form desired germinate surfactants. The chemical structures of the synthesized surfactants were determined using different spectra tools. The surface parameter including: the critical micelle concentration (CMC), effectiveness (π(cmc)), efficiency (Pc20), maximum surface excess (Γ(max)) and minimum surface area (A(min)), were calculated from the surface tension measurements. The synthesized surfactants showed higher surface activity. The thermodynamic parameters showed that adsorption and micellization processes are spontaneous. It is clear that the synthesized nonionic surfactants showed their tendency towards adsorption at the interfaces and also micellization in the bulk of their solutions. The synthesized surfactants were tested against different strain of bacteria using inhibition zone diameters. The synthesized surfactants showed good antimicrobial activities against the tested microorganisms including Gram positive, Gram negative as well as fungi. The promising inhibition efficiency of these compounds against the sulfate reducing bacteria facilitates them to be applicable as new categories of sulfate reducing bacteria biocides.

  16. Optical biosensor based on silicon nanowire ridge waveguide

    Science.gov (United States)

    Gamal, Rania; Ismail, Yehia; Swillam, Mohamed A.

    2015-02-01

    Optical biosensors present themselves as an attractive solution for integration with the ever-trending lab-on-a-chip devices. This is due to their small size, CMOS compatibility, and invariance to electromagnetic interference. Despite their many benefits, typical optical biosensors rely on evanescent field detection, where only a small portion of the light interacts with the analyte. We propose to use a silicon nanowire ridge waveguide (SNRW) for optical biosensing. This structure is comprised of an array of silicon nanowires, with the envelope of a ridge, on an insulator substrate. The SNRW maximizes the overlap between the analyte and the incident light wave by introducing voids to the otherwise bulk structure, and strengthens the contribution of the material under test to the overall modal effective index will greatly augment the sensitivity. Additionally, the SNRW provides a fabrication convenience as it covers the entire substrate, ensuring that the etching process would not damage the substrate. FDTD simulations were conducted and showed that the percentage change in the effective index due to a 1% change in the surrounding environment was more than 170 times the amount of change perceived in an evanescent detection based bulk silicon ridge waveguide.

  17. Ion-beam induced structure modifications in amorphous germanium; Ionenstrahlinduzierte Strukturmodifikationen in amorphem Germanium

    Energy Technology Data Exchange (ETDEWEB)

    Steinbach, Tobias

    2012-05-03

    Object of the present thesis was the systematic study of ion-beam induced structure modifications in amorphous germanium (a-Ge) layers due to low- (LEI) and high-energetic (SHI) ion irradiation. The LEI irradiation of crystalline Ge (c-Ge) effects because the dominating nuclear scattering of the ions on the solid-state atoms the formation of a homogeneous a-Ge Layer. Directly on the surface for fluences of two orders of magnitude above the amorphization fluence the formation of stable cavities independently on the irradiation conditions was observed. For the first time for the ion-beam induced cavity formation respectively for the steady expansion of the porous layer forming with growing fluence a linear dependence on the energy {epsilon}{sub n} deposed in nuclear processes was detected. Furthermore the formation of buried cavities was observed, which shows a dependence on the type of ions. While in the c-Ge samples in the range of the high electronic energy deposition no radiation defects, cavities, or plastic deformations were observed, the high electronic energy transfer in the 3.1 {mu}m thick pre-amorphized a-Ge surface layers leads to the formation of randomly distributed cavities. Basing on the linear connection between cavity-induced vertical volume expansion and the fluence determined for different energy transfers for the first time a material-specific threshold value of {epsilon}{sub e}{sup HRF}=(10.5{+-}1.0) kev nm{sup -1} was determined, above which the ion-beam induced cavity formation in a-Ge sets on. The anisotropic plastic deformation of th a-Ge layer superposed at inclined SHI irradiation on the cavity formation was very well described by an equation derived from the viscoelastic Maxwell model, but modified under regardment of the experimental results. The positive deformation yields determined thereby exhibit above a threshold value for the ion-beam induced plastic deformation {epsilon}{sub e}{sup S{sub a}}=(12{+-}2) keV nm{sup -1} for the first

  18. Optical absorption of silicon nanowires

    International Nuclear Information System (INIS)

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stiévenard, D.; Lévêque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B.

    2012-01-01

    We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

  19. Tunneling magnetoresistance in Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2016-11-09

    We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green\\'s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

  20. Electrochemical synthesis of multisegmented nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Kok, Kuan-Ying; Ng, Inn-Khuan; Saidin, Nur Ubaidah [Malaysian Nuclear Agency, Bangi, 43000 Kajang (Malaysia)

    2012-11-27

    Electrochemical deposition has emerged as a promising route for nanostructure fabrication in recent years due to the many inherent advantages it possesses. This study focuses on the synthesis of high-aspect-ratio multisegmented Au/Ni nanowires using template-directed sequential electrochemical deposition techniques. By selectively removing the Ni segments in the nanowires, high-yield of pure gold nanorods of predetermined lengths was obtained. Alternatively, the sacrificial Ni segments in the nanowires can be galvanically displaced with Bi and Te to form barbells structures with Bi{sub x}Te{sub y} nanotubes attached to neighbouring gold segments. Detailed studies on the nanostructures obtained were carried out using various microscopy, diffraction and probebased techniques for structural, morphological and chemical characterizations.

  1. Preparation of electrodeposited cobalt nanowires

    Directory of Open Access Journals (Sweden)

    Valeska da Rocha Caffarena

    2006-06-01

    Full Text Available Nanostructured magnetic materials have great interest because of their applications in high-density magnetic information storage and for magnetic sensors. The electrodeposition of materials into porous alumina arrays is a suitable technique to produce nanomaterials, since highly ordered uniform nanomaterials can be obtained simply and cheaply. In this work, template-assisted Co nanowire arrays were prepared by electrodeposition into nanometer-sized pores of an alumite film using a two-electrode electrochemical cell. The Co nanowires were electrodeposited from a solution of 400 g/L of CoSO4.7H2O and 40 g/L of H3BO3. The morphology of the samples was investigated by means of TEM and AFM. The structural characteristic of the samples was examined using XRD, EDX and FTIR, which confirm the cobalt nanowire formation.

  2. Understanding the Room Temperature Ferromagnetism in GaN Nanowires with Pd Doping

    Energy Technology Data Exchange (ETDEWEB)

    Manna, S; De, S K, E-mail: mannaju@gmail [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

    2011-04-01

    We report the first synthesis and characterization of 4d transition metal palladium-doped GaN nanowires (NWs). Room temperature ferromagnetism has been observed in high quality Vapor Liquid Solid (VLS) epitaxy grown undoped n-type GaN nanowires. It was proposed that this type of magnetism is due to defects which are not observed in Bulk GaN because of large formation energy of defects in bulk GaN. Here we have successfully doped 4d transition metal Pd in GaN NWs. We find fairly strong and long-range ferromagnetic coupling between Pd substituted for Ga in GaN . The results suggest that 4d metals such as Pd may also be considered as candidates for ferromagnetic dopants in semiconductors.

  3. On solid bulk liquefaction

    OpenAIRE

    Fkhir, Moustafa

    2016-01-01

    Solid bulk cargoes, such as nickel ore and iron ore, have a tendency to liquefy. Such goods can transform from hard to liquid state very rapidly leaving no time for the master or crew to do anything but face their imminent fate. The liquefaction of solid bulk cargoes has claimed many seafarers’ lives and dozens of ships. The moisture content present in these cargoes can be dramatically increased to unsafe limits by the mere reason of the vessel’s rolling on waves. In response to the alarming ...

  4. Role of surface on the size-dependent mechanical properties of copper nanowire under tensile load: A molecular dynamics simulation

    International Nuclear Information System (INIS)

    Liu, Wei-Ting; Hsiao, Chun-I.; Hsu, Wen-Dung

    2014-01-01

    In this study we have used atomistic simulations to investigate the role of surface on the size-dependent mechanical properties of nanowires. In particular, we have performed computational investigation on single crystal face-centered cubic copper nano-wires with diameters ranging from 2 to 20 nm. The wire axis for all the nanowires are considered along the [0 0 1] direction. Characterization of the initial optimized structures revealed clear differences in interatomic spacing, stress, and potential energy in all the nanowires. The mechanical properties with respect to wire diameter are evaluated by applying tension along the [0 0 1] direction until yielding. We have discussed the stress–strain relationships, Young's modulus, and the variation in potential energy from surface to the center of the wire for all the cases. Our results indicate that the mechanical response (including yield strain, Young's modulus, and resilience) is directly related to the proportion of surface to bulk type atoms present in each nanowire. Thus the size-dependent mechanical properties of single crystal copper nanowire within elastic region are attributed to the surface to volume ratio (surface effect). Using the calculated response, we have formulated a mathematical relationship, which predicts the nonlinear correlation between the mechanical properties and the diameter of the wire.

  5. Crystal phase-based epitaxial growth of hybrid noble metal nanostructures on 4H/fcc Au nanowires

    Science.gov (United States)

    Lu, Qipeng; Wang, An-Liang; Gong, Yue; Hao, Wei; Cheng, Hongfei; Chen, Junze; Li, Bing; Yang, Nailiang; Niu, Wenxin; Wang, Jie; Yu, Yifu; Zhang, Xiao; Chen, Ye; Fan, Zhanxi; Wu, Xue-Jun; Chen, Jinping; Luo, Jun; Li, Shuzhou; Gu, Lin; Zhang, Hua

    2018-03-01

    Crystal-phase engineering offers opportunities for the rational design and synthesis of noble metal nanomaterials with unusual crystal phases that normally do not exist in bulk materials. However, it remains a challenge to use these materials as seeds to construct heterometallic nanostructures with desired crystal phases and morphologies for promising applications such as catalysis. Here, we report a strategy for the synthesis of binary and ternary hybrid noble metal nanostructures. Our synthesized crystal-phase heterostructured 4H/fcc Au nanowires enable the epitaxial growth of Ru nanorods on the 4H phase and fcc-twin boundary in Au nanowires, resulting in hybrid Au-Ru nanowires. Moreover, the method can be extended to the epitaxial growth of Rh, Ru-Rh and Ru-Pt nanorods on the 4H/fcc Au nanowires to form unique hybrid nanowires. Importantly, the Au-Ru hybrid nanowires with tunable compositions exhibit excellent electrocatalytic performance towards the hydrogen evolution reaction in alkaline media.

  6. Carrier Dynamics and Band Structure in InGaAs and InGaAs/InP Nanowires

    Science.gov (United States)

    Linser, Samuel; Shojaei, Iraj; Jnawali, Giriraj; Wickramasuriya, Nadeeka; Jackson, Howard; Smith, Leigh; Ameruddin, Amira; Caroff, Philippe; Tan, Hoe; Jagadish, Chennupati

    We use transient Rayleigh scattering (TRS) measurements to explore the electronic energy structure of wurtzite InGaAs nanowires. We studied single core-only InGaAs nanowires as well as strained core-shell InGaAs-InP heterostructures at 300 K and 10 K, with probe photon energies in the near-infrared from 0.79 to 1.16 eV. We report a factor of four enhancement of the typical lifetime of excited states in the core-shell nanowires (500 ps) when compared to the core-only nanowires (125 ps). We observe a clear band-edge-like structure in the core-shell wires at energies of 0.98 eV at 10 K and 0.88 eV at 300 K. In both cases, this structure is at a significantly higher energy than the reported bandgap of bulk zincblende InGaAs of the same nominal composition as our nanowires. We also present a phenomenological fitting model of our TRS spectra which provides insight into the cooling dynamics of the electron-hole plasma within a single photo-excited nanowire. We acknowledge the financial support of the NSF through Grants DMR 1507844, DMR 1531373 and ECCS 1509706, and the financial support of the Australian Research Council.

  7. Indium Arsenide Nanowires

    DEFF Research Database (Denmark)

    Madsen, Morten Hannibal

    This thesis is about growth of Au-assisted and self-assisted InAs nanowires (NWs). The wires are synthesized using a solid source molecular beam epitaxy (MBE) system and characterized with several techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ...... tumor cells (CTCs) have been fabricated. The CTC concentration is extremely low and highly effective devices for capturing the CTCs may improve the treatment of cancer patients....... is presented. A series of experiments with formation of a droplet on top of the wires has been carried out and pyramidal shaped structures at the NW top with pure zinc blende crystal structure are observed. A novel in-situ experiment with fabrication of NWs and simultanous characterization using x...... and its dependence on growth parameters. By fabricating the NWs on silicon-on-insulator substrates we demonstrate electrically addressable NWs that are still standing vertically on the substrate and can potentially be used for intra-cellular recordings. Devices for biological experiments using vertically...

  8. Oriented bottom-up growth of armchair graphene nanoribbons on germanium

    Science.gov (United States)

    Arnold, Michael Scott; Jacobberger, Robert Michael

    2016-03-15

    Graphene nanoribbon arrays, methods of growing graphene nanoribbon arrays and electronic and photonic devices incorporating the graphene nanoribbon arrays are provided. The graphene nanoribbons in the arrays are formed using a scalable, bottom-up, chemical vapor deposition (CVD) technique in which the (001) facet of the germanium is used to orient the graphene nanoribbon crystals along the [110] directions of the germanium.

  9. "Understanding" cosmological bulk viscosity

    OpenAIRE

    Zimdahl, Winfried

    1996-01-01

    A universe consisting of two interacting perfect fluids with the same 4-velocity is considered. A heuristic mean free time argument is used to show that the system as a whole cannot be perfect as well but neccessarily implies a nonvanishing bulk viscosity. A new formula for the latter is derived and compared with corresponding results of radiative hydrodynamics.

  10. Nephrotoxicity in humans by the ultratrace element germanium.

    Science.gov (United States)

    Schauss, A G

    1991-01-01

    Acute renal failure (ARF) or renal dysfunction (RD) associated with germanium-induced nephrotoxicity has been reported in 18 patients since 1982. In 2 of these cases the patients died of acute renal and cardiogenic failure. In 17 of 18 cases biopsies showed vacuolar degeneration in renal tubular epithelial cells in the absence of glomerular changes, without proteinuria or hematuria. Accumulated elemental Ge intake in 17 patients over a period of 4 to 36 months ranged between 16 and 328 g, or more than 100 to 2000 times the average estimated dietary intake of Ge for man (1.5 mg/d; range 0.40 to 3.40 mg/d). The biological half-life of Ge is 4.5 days for kidneys, the highest retention level of any organ. The mean concentration of Ge in healthy adult kidneys is 9.0 mg/kg wet weight. In 3 patients studied with Ge-induced RD or ARF, urinary Ge excretion was 9, 15, and 60 ng/mL, compared to greater than 5 ng/mL in healthy controls, and remained elevated even 12 months after discontinuing supplemental Ge intake. The mechanism for Ge-induced nephrotoxicity remains unknown, although the suspected cause is the inorganic Ge salts, such as germanium dioxide. Sufficient evidence for a role of organogermanium compounds, such as carboxyethyl germanium sesquioxide or citrate-lactate germanate, in Ge-induced nephrotoxicity remains lacking. The recent introduction of over-the-counter Ge "nutritional" supplements in some countries increases the risk of additional cases of Ge-induced nephrotoxicity, especially if appreciable levels of inorganic Ge salts are present and consumed for long periods (greater than 3 months) at levels above the average daily estimated dietary intake for Ge.(ABSTRACT TRUNCATED AT 250 WORDS)

  11. A crystalline germanium flexible thin-film transistor

    Science.gov (United States)

    Higashi, H.; Nakano, M.; Kudo, K.; Fujita, Y.; Yamada, S.; Kanashima, T.; Tsunoda, I.; Nakashima, H.; Hamaya, K.

    2017-11-01

    We experimentally demonstrate a flexible thin-film transistor (TFT) with (111)-oriented crystalline germanium (Ge) layers grown by a gold-induced crystallization method. Accumulation-mode metal source/drain p-channel Ge TFTs are fabricated on a polyimide film at ≤ 400 ° C . A field-effect mobility (μFE) of 10.7 cm2/Vs is obtained, meaning the highest μFE in the p-TFTs fabricated at ≤ 400 ° C on flexible plastic substrates. This study will lead to high-performance flexible electronics based on an inorganic-semiconductor channel.

  12. Performance of the Ultra-High Rate Germanium (UHRGe) System

    Energy Technology Data Exchange (ETDEWEB)

    Fast, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Dion, Michael P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Rodriguez, Douglas C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); VanDevender, Brent A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wood, Lynn S. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wright, Michael E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-12-01

    This report describes the final performance achieved with the detector system developed for the Ultra High Rate Germanium (UHRGe) project. The system performance has been evaluated at low, moderate and high rates and includes the performance of real-time analysis algorithms running in the FPGA of the data acquisition system. This performance is compared to that of offline analyses of streaming waveform data collected with the same data acquisition system the performance of a commercial Multi-Channel Analyzer designed for high-resolution spectroscopy applications, the Canberra LYNX.

  13. Point defect engineering strategies to retard phosphorous diffusion in germanium.

    Science.gov (United States)

    Tahini, H A; Chroneos, A; Grimes, R W; Schwingenschlögl, U; Bracht, H

    2013-01-07

    The diffusion of phosphorous in germanium is very fast, requiring point defect engineering strategies to retard it in support of technological application. Density functional theory corroborated with hybrid density functional calculations are used to investigate the influence of the isovalent codopants tin and hafnium in the migration of phosphorous via the vacancy-mediated diffusion process. The migration energy barriers for phosphorous are increased significantly in the presence of oversized isovalent codopants. Therefore, it is proposed that tin and in particular hafnium codoping are efficient point defect engineering strategies to retard phosphorous migration.

  14. Self-absorption corrections for well-type germanium detectors

    International Nuclear Information System (INIS)

    Appleby, P.G.; Richardson, N.; Nolan, P.J.

    1992-01-01

    Corrections for self-absorption are of vital importance to accurate determination by gamma spectrometry of radionuclides such as 210 Pb, 241 Am and 234 Th which emit low energy gamma radiation. A simple theoretical model for determining the necessary corrections for well-type germanium detectors is presented. In this model, self-absorption factors are expressed in terms of the mass attenuation coefficient of the sample and a parameter characterising the well geometry. Experimental measurements of self-absorption are used to evaluate the model and to determine a semi-empirical algorithm for improved estimates of the geometrical parameter. (orig.)

  15. Liquid-helium scintillation detection with germanium photodiodes

    International Nuclear Information System (INIS)

    Luke, P.N.; Haller, E.E.; Steiner, H.M.

    1982-05-01

    Special high-purity germanium photodiodes have been developed for the direct detection of vacuum ultraviolet scintillations in liquid helium. The photodiodes are immersed in the liquid helium, and scintillations are detected through one of the bare sides of the photodiodes. Test results with scintillation photons produced by 5.3-MeV α particles are presented. The use of these photodiodes as liquid-helium scintillation detectors may offer substantial improvements over the alternate detection method requiring the use of wavelength shifters and photomultiplier tubes

  16. Multiple pulse traveling wave excitation of neon-like germanium

    International Nuclear Information System (INIS)

    Moreno, J. C.; Nilsen, J.; Silva, L. B. da

    1995-01-01

    Traveling wave excitation has been shown to significantly increase the output intensity of the neon-like germanium x-ray laser. The driving laser pulse consisted of three 100 ps Gaussian laser pulses separated by 400 ps. Traveling wave excitation was employed by tilting the wave front of the driving laser by 45 degrees to match the propagation speed of the x-ray laser photons along the length of the target. We show results of experiments with the traveling wave, with no traveling wave, and against the traveling wave and comparisons to a numerical model. Gain was inferred from line intensity measurements at two lengths

  17. Effect of germanium dioxide on growth of Spirulina platensis

    Science.gov (United States)

    Cao, Ji-Xiang

    1996-12-01

    This study on the effect of different concentrations of germanium dioxide (GeO2) on the specific growth rate (SGR), pigment contents, protein content and amino acid composition of Spirulina platensis showed that Ge was not the essential element of this alga; that GeO2 could speed up growth and raise protein content of S. platensis, and could possibly influence the photosynthesis system. The concentration range of GeO2 beneficial to growth of S. platensis is from 5 100mg/l. GeO2 is proposed to be utilized to remove contamination by Chlorella spp. usually occurring in the cultivation of Spirulina.

  18. Point defect engineering strategies to retard phosphorous diffusion in germanium

    KAUST Repository

    Tahini, H. A.

    2013-01-01

    The diffusion of phosphorous in germanium is very fast, requiring point defect engineering strategies to retard it in support of technological application. Density functional theory corroborated with hybrid density functional calculations are used to investigate the influence of the isovalent codopants tin and hafnium in the migration of phosphorous via the vacancy-mediated diffusion process. The migration energy barriers for phosphorous are increased significantly in the presence of oversized isovalent codopants. Therefore, it is proposed that tin and in particular hafnium codoping are efficient point defect engineering strategies to retard phosphorous migration. © the Owner Societies 2013.

  19. High frequency III-V nanowire MOSFETs

    Science.gov (United States)

    Lind, Erik

    2016-09-01

    III-V nanowire transistors are promising candidates for very high frequency electronics applications. The improved electrostatics originating from the gate-all-around geometry allow for more aggressive scaling as compared with planar field-effect transistors, and this can lead to device operation at very high frequencies. The very high mobility possible with In-rich devices can allow very high device performance at low operating voltages. GaN nanowires can take advantage of the large band gap for high voltage operation. In this paper, we review the basic physics and device performance of nanowire field- effect transistors relevant for high frequency performance. First, the geometry of lateral and vertical nanowire field-effect transistors is introduced, with special emphasis on the parasitic capacitances important for nanowire geometries. The basic important high frequency transistor metrics are introduced. Secondly, the scaling properties of gate-all-around nanowire transistors are introduced, based on geometric length scales, demonstrating the scaling possibilities of nanowire transistors. Thirdly, to model nanowire transistor performance, a two-band non-parabolic ballistic transistor model is used to efficiently calculate the current and transconductance as a function of band gap and nanowire size. The intrinsic RF metrics are also estimated. Finally, experimental state-of-the-art nanowire field-effect transistors are reviewed and benchmarked, lateral and vertical transistor geometries are explored, and different fabrication routes are highlighted. Lateral devices have demonstrated operation up to 350 GHz, and vertical devices up to 155 GHz.

  20. Cleaved-Coupled Nanowire Lasers

    Science.gov (United States)

    2013-01-15

    nanowires with a 40-nm gap show significant modulation of the threshold gain among different lasing modes (Fig. 4, blue dia- monds ). Within the...spectrometer (Princeton Instruments/Acton) equipped with a 1,200-groove/mm grating blazed at 300 nm and a liquid N2-cooled charge-coupled device. The

  1. Photonic nanowires for quantum optics

    DEFF Research Database (Denmark)

    Munsch, M.; Claudon, J.; Bleuse, J.

    Photonic nanowires (PWs) are simple dielectric structures for which a very efficient and broadband spontaneous emission (SE) control has been predicted [1]. Recently, a single photon source featuring a record high efficiency was demonstrated using this geometry [2]. Using time-resolved micro-phot...

  2. Optical properties of semiconducting nanowires

    NARCIS (Netherlands)

    Vugt, L.K. van

    2007-01-01

    Semiconductor nanowires of high purity and crystallinity hold promise as building blocks for opto-electronical devices at the nanoscale.. They are commonly grown via a Vapor-Liquid-Solid (VLS) mechanism in which metal (nano) droplets collect the semiconductor precursors to form a solution which,

  3. Tunneling and Transport in Nanowires

    International Nuclear Information System (INIS)

    Goldman, Allen M.

    2016-01-01

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO 3 . The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  4. Tunneling and Transport in Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Goldman, Allen M. [Univ. of Minnesota, Minneapolis, MN (United States)

    2016-08-16

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO3. The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  5. Electron Transport in Si Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ramayya, E [Arizona State University, Tempe, AZ (United States); Vasileska, D [Arizona State University, Tempe, AZ (United States); Goodnick, S M [Arizona State University, Tempe, AZ (United States); Knezevic, I [University of Wisconsin, Madison, WI (United States)

    2006-05-15

    We investigate electron transport in silicon nanowires taking into account acoustic, non-polar optical phonons and surface/interface roughness scattering. We find that at very high transverse fields the reduced density of final states to which the carriers can scatter into gives rise to a reduced influence of interface-roughness scattering, which is promising result from a fabrication point of view.

  6. Morphology of living cells cultured on nanowire arrays with varying nanowire densities and diameters.

    Science.gov (United States)

    Li, Zhen; Persson, Henrik; Adolfsson, Karl; Oredsson, Stina; Prinz, Christelle N

    2018-04-02

    Vertical nanowire arrays are increasingly investigated for their applications in steering cell behavior. The geometry of the array is an important parameter, which influences the morphology and adhesion of cells. Here, we investigate the effects of array geometry on the morphology of MCF7 cancer cells and MCF10A normal-like epithelial cells. Different gallium phosphide nanowire array-geometries were produced by varying the nanowire density and diameter. Our results show that the cell size is smaller on nanowires compared to flat gallium phosphide. The cell area decreases with increasing the nanowire density on the substrate. We observed an effect of the nanowire diameter on MCF10A cells, with a decreased cell area on 40 nm diameter nanowires, compared to 60 and 80 nm diameter nanowires in high-density arrays. The focal adhesion morphology depends on the extent to which cells are contacting the substrate. For low nanowire densities and diameters, cells are lying on the substrate and we observed large focal adhesions at the cell edges. In contrast, for high nanowire densities and diameters, cells are lying on top of the nanowires and we observed point-like focal adhesions distributed over the whole cell. Our results constitute a step towards the ability to fine-tune cell behavior on nanowire arrays.

  7. Effect of ion-plated films of germanium and silicon on friction, wear, and oxidation of 52100 bearing steel

    Science.gov (United States)

    Buckley, D. H.; Spalvins, T.

    1977-01-01

    Friction and wear experiments were conducted with ion plated films of germanium and silicon on the surface of 52100 bearing steel both dry and in the presence of mineral oil. Both silicon and germanium were found to reduce wear, with germanium being more effective than silicon. An optimum film thickness of germanium for minimum wear without surface crack formation was found to be approximately 400 nanometers (4000 A). The presence of silicon and germanium on the 52100 bearing steel surface improved resistance to oxidation.

  8. Facile Synthesis of Ultrafine Hematite Nanowire Arrays in Mixed Water-Ethanol-Acetic Acid Solution for Enhanced Charge Transport and Separation.

    Science.gov (United States)

    Wang, Jian; Wang, Menglong; Zhang, Tao; Wang, Zhiqiang; Guo, Penghui; Su, Jinzhan; Guo, Liejin

    2018-04-03

    Nanostructure engineering is of great significance for semiconductor electrode to achieve high photoelectrochemical performance. Herein, we report a novel strategy to fabricate ultrafine hematite (α-Fe 2 O 3 ) nanowire arrays in a mixed water-ethanol-acetic acid (WEA) solvent. To the best of our knowledge, this is the first report on direct growth of ultrafine (∼10 nm) α-Fe 2 O 3 nanowire arrays on fluorine-doped tin oxide substrates through solution-based fabrication process. The effect of WEA ratio on the morphology of nanowires has been systematically studied to understand the formation mechanism. Photoelectrochemical measurements were conducted on both Ti-treated α-Fe 2 O 3 nanowire and nanorod photoelectrodes. It reveals that α-Fe 2 O 3 nanowire electrode has higher photocurrent and charge separation efficiencies than nanorod electrode if the carrier concentration and space-charge carrier width are in the same order of magnitude. Normalized by electrochemically active surface area, the Ti-treated α-Fe 2 O 3 nanowire electrode obtains 6.4 times higher specific photocurrent density than nanorod electrode. This superiority of nanowires arises from the higher bulk and surface charge separation efficiencies, which could be partly attributed to reduced distance that holes must transfer to reach the semiconductor-liquid junction.

  9. Magnetostatic Interaction in Fe-Co Nanowires

    Directory of Open Access Journals (Sweden)

    Laura Elbaile

    2012-01-01

    Full Text Available Arrays of Fe-Co alloy nanowires with diameter around 35 nm and several micrometers in length have been synthesized by codepositing Fe and Co into porous anodic alumina. The morphology, structure, and magnetic properties of the nanowires (hysteresis loops and remanence curves were characterized by SEM, TEM, X-ray diffraction (XRD, and VSM, respectively. The XRD patterns indicate that the Fe-Co nanowires present a body-centered cubic (bcc structure and a preferred (110 orientation perpendicular to the template surface. From the hysteresis loops obtained with the magnetic field applied in the axis direction of the nanowires, we can observe that the coercive field slightly decreases when the nanowire length increases. This magnetic behaviour is analyzed considering the shape anisotropy and the dipolar interactions among nanowires.

  10. Cadmium zinc telluride (CZT) nanowire sensors for detection of low energy gamma-ray detection

    Science.gov (United States)

    Gandhi, T.; Raja, K. S.; Misra, M.

    2008-04-01

    Bulk single crystals of CdZnTe compound semiconductor is used for room temperature radiation detection in commercial radiation sensors. A large volume of detector material with low defect density is required for increasing the detection efficiency. Manufacture of such a bulky detector-quality material with low defect density is expensive. In this communication, synthesis of nanowires arrays of CdZnTe that can be used for detecting low energy radiation is reported for the first time. CdZnTe ternary compound semiconductor, referred as CZT, was electrodeposited in the form of nanowires onto a TiO II nanotubular template in non-aqueous electrolytes using a pulse-reverse process at 130 °C. Very high electrical resistivity of the CZT nanowires (in the order of 10 10 Ω-cm) was obtained. Such a high resistivity was attributed to the presence of deep defect states such as cadmium vacancies created by the anodic cycle of the pulse-reverse electrodeposition process. Stacks of series connected CZT nanowire arrays were impressed with different bias potentials. The leakage current was in the order of tens of PicoAmperes. When exposed to a radiation source (Am -241, 60 keV), the current flow in the circuit increased. The preliminary results indicate that the CZT nanowire arrays can be used as radiation detector materials at room temperature with a much low bias potential (0.7 - 2.3 V) as against 300 - 500 V applied to the bulk detector materials.

  11. Structural and electronic properties of hybrid silicon-germanium nanosheets

    Directory of Open Access Journals (Sweden)

    F. L. Pérez Sánchez

    2014-12-01

    Full Text Available Using first principles molecular calculations, based on the Density Functional Theory (DFT, structural and electronic properties of hybrid graphene—like silicon—germanium circular nanosheets of hexagonal symmetry are investigated. The exchange—correlation functional of Perdew—Wang (PW in the local spin density approximation (LSDA based on the pseudopotentials of Dolg—Bergnre is applied. The finite extension nanosheets are represented by the CnHm—like cluster model with mono—hydrogenated armchair edges. Changes of the physicochemical properties were analyzed to learn on the chemical composition. We have obtained that the corrugation of the hybrid nanosheets is maintained (with respect to the pristine nanosheets of Ge and Si and is more pronounced when there is a high percentage of germanium. Moreover, hybrid nanosheets have ionic bonds (polarity in the interval from 0.18 to 0.77 D and exhibit a semimetal behavior. Three types of chemical compositions are considered: 1 the one—one relationship, 2 formation of Ge dimers and 3 formation of Ge hexagons. In each case it is observed an increase in the chemical reactivity. Finally, analyzing the work function we conclude that in cases 1 and 2 the chemical compositions improve the efficiency of the field emission and thereby they could expand the scope of nanotechnology applications.

  12. Germanium-76 Isotope Separation by Cryogenic Distillation. Final Report

    International Nuclear Information System (INIS)

    Stohler, Eric

    2007-01-01

    The current separation method for Germanium isotopes is electromagnetic separation using Calutrons. The Calutrons have the disadvantage of having a low separation capacity and a high energy cost to achieve the separation. Our proposed new distillation method has the advantage that larger quantities of Germanium isotopes can be separated at a significantly lower cost and in a much shorter time. After nine months of operating the column that is 1.5 meter in length, no significant separation of the isotopes has been measured. We conclude that the length of the column we have been using is too short. In addition, other packing material than the 0.16 inch Propak, 316 ss Protruded metal packing that we used in the column, should be evaluated which may have a better separation factor than the 0.16 inch Propak, 316 ss Protruded metal packing that has been used. We conclude that a much longer column - a minimum of 50 feet length - should be built and additional column packing should be tested to verify that isotopic separation can be achieved by cryogenic distillation. Even a longer column than 50 feet would be desirable.

  13. An ultralow background germanium gamma-ray spectrometer

    International Nuclear Information System (INIS)

    Reeves, R.H.; Brodzinski, R.L.; Hensley, W.K.; Ryge, P.

    1984-01-01

    The monitoring of minimum detectable activity is becoming increasingly important as environmental concerns and regulations require more sensitive measurement of the radioactivity levels in the workplace and the home. In measuring this activity, however, the background becomes one of the limiting factors. Anticoincidence systems utilizing both NaI(T1) and plastic scintillators have proven effective in reducing some components of the background, but radiocontaminants in the various regions of these systems have limited their effectiveness, and their cost is often prohibitive. In order to obtain a genuinely low background detector system, all components must be free of detectable radioactivity, and the cosmic ray produced contribution must be significantly reduced. Current efforts by the authors to measure the double beta decay of Germanium 76 as predicted by Grand Unified Theories have resulted in the development of a high resolution germanium diode gamma spectrometer with an exceptionally low background. This paper describes the development of this system, outlines the configuration and operation of its preamplifier, linear amplifier, analog-to-digital converter, 4096-channel analyzer, shielding consisting of lead-sandwiched plastic scintillators wrapped in cadmium foil, photomultiplier, and its pulse generator and discriminator, and then discusses how the system can be utilized to significantly reduce the background in high resolution photon spectrometers at only moderate cost

  14. NTD germanium: a novel material for low-temperature bolometers

    International Nuclear Information System (INIS)

    Haller, E.E.; Palaio, N.P.; Rodder, M.; Hansen, W.L.; Kreysa, E.

    1982-06-01

    Six samples of ultra-pure (absolute value N/sub A/ - N/sub D/ absolute value less than or equal to 10 11 cm -3 ), single-crystal germanium have been neutron transmutation doped with neutron doses between 7.5 x 10 16 and 1.88 x 10 18 cm -2 . After thermal annealing at 400 0 C for six hours in a pure argon atmosphere, the samples have been characterized with Hall effect and resistivity measurements between 300 and 0.3 K. Our results show that the resistivity in the low temperature, hopping conduction regime can be approximated with rho = rho 0 exp(Δ/T). The three more heavily doped samples show values for rho 0 and Δ ranging from 430 to 3.3 Ω cm and from 4.9 to 2.8 K, respectively. The excellent reproducibility of neutron transmutation doping and the values of rho 0 and Δ make NTD Ge a prime candidate for the fabrication of low temperature, low noise bolometers. The large variation in the tabulated values of the thermal neutron cross sections for the different germanium isotopes makes it clear that accurate measurements of these cross-sections for well defined neutron energy spectra would be highly desirable

  15. Study and characterization of porous germanium for radiometric measurements

    Energy Technology Data Exchange (ETDEWEB)

    Akkari, E.; Benachour, Z.; Touayar, O.; Benbrahim, J. [Activites de Recherche, Metrologie des Rayonnements, Institut National des Sciences Appliquees et de Technologie, INSAT, Tunis (Tunisia); Aouida, S.; Bessais, B. [Laboratoire de Nanomateriaux et des Systemes de l' Energie, LaNSE, Centre de Recherche et des Technologies de l' Energie, CRTEn, Hammam-Lif (Tunisia)

    2009-07-15

    The aim of this article is to study and realize a new detector based on a porous germanium (pGe) photodiode to be used as a standard for radiometric measurement in the wavelength region between 800 nm and 1700 nm. We present the development and characterization of a porous structure realized on a single-crystal substrate of p-type germanium (Ga doped) and of crystallographic orientation (100). The obtained structure allows, on the one hand, to trap the incident radiation, and on the other hand, to minimize the fluctuations of the front-face reflection coefficient of the photodiode. The first studies thus made show that it is possible to optimize, respectively, the electrical current density and the electrochemical operation time necessary for obtaining exploitable porous structures. The obtained results show that for 50 mA/cm{sup 2} and 5 min as operational parameters, we obtain a textured aspect of the porous samples that present a pyramidal form. The reflectivity study of the front surface shows a constant value of around 38% in a spectral range between 800 nm and 1700 nm approximately. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Micromegas in a bulk

    International Nuclear Information System (INIS)

    Giomataris, I.; De Oliveira, R.; Andriamonje, S.; Aune, S.; Charpak, G.; Colas, P.; Fanourakis, G.; Ferrer, E.; Giganon, A.; Rebourgeard, Ph.; Salin, P.

    2006-01-01

    In this paper, we present a novel way to manufacture the bulk Micromegas detector. A simple process based on the Printed Circuit Board (PCB) technology is employed to produce the entire sensitive detector. Such a fabrication process could be extended to very large area detectors made by the industry. The low cost fabrication together with the robustness of the electrode materials will make it attractive for several applications ranging from particle physics and astrophysics to medicine

  17. Magnetic crossover effect in Nickel nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Ghaddar, A. [Laboratoire de Magnetisme de Bretagne, CNRS-FRE 3117, C.S. 93837, 29238 Brest, Cedex (France); Gloaguen, F. [Laboratoire de Chimie, Electrochimie Moleculaire et Chimie Analytique, CNRS-UMR 6521, C. S. 93837 Brest Cedex 3 (France); Gieraltowski, J. [Laboratoire de Magnetisme de Bretagne, CNRS-FRE 3117, C.S. 93837, 29238 Brest, Cedex (France); Tannous, C., E-mail: tannous@univ-brest.f [Laboratoire de Magnetisme de Bretagne, CNRS-FRE 3117, C.S. 93837, 29238 Brest, Cedex (France)

    2011-05-01

    A crossover effect in the magnetic reversal mechanism within arrays of Nickel nanowires whose diameter varies from 15 to 100 nm is observed around 50 nm. Hysteresis loops and FMR measurements confirm that nanowire diameter controls effectively the nanowire easy axis as well as the magnetization reversal mechanism. This might be very interesting for spintronic devices based on current-induced domain motion such as non-volatile magnetic memory elements (MRAM) and low Ohmic loss devices.

  18. Enhanced ionized impurity scattering in nanowires

    Science.gov (United States)

    Oh, Jung Hyun; Lee, Seok-Hee; Shin, Mincheol

    2013-06-01

    The electronic resistivity in silicon nanowires is investigated by taking into account scattering as well as the donor deactivation from the dielectric mismatch. The effects of poorly screened dopant atoms from the dielectric mismatch and variable carrier density in nanowires are found to play a crucial role in determining the nanowire resistivity. Using Green's function method within the self-consistent Born approximation, it is shown that donor deactivation and ionized impurity scattering combined with the charged interface traps successfully to explain the increase in the resistivity of Si nanowires while reducing the radius, measured by Björk et al. [Nature Nanotech. 4, 103 (2009)].

  19. Diluted magnetic semiconductor nanowires exhibiting magnetoresistance

    Science.gov (United States)

    Yang, Peidong [El Cerrito, CA; Choi, Heonjin [Seoul, KR; Lee, Sangkwon [Daejeon, KR; He, Rongrui [Albany, CA; Zhang, Yanfeng [El Cerrito, CA; Kuykendal, Tevye [Berkeley, CA; Pauzauskie, Peter [Berkeley, CA

    2011-08-23

    A method for is disclosed for fabricating diluted magnetic semiconductor (DMS) nanowires by providing a catalyst-coated substrate and subjecting at least a portion of the substrate to a semiconductor, and dopant via chloride-based vapor transport to synthesize the nanowires. Using this novel chloride-based chemical vapor transport process, single crystalline diluted magnetic semiconductor nanowires Ga.sub.1-xMn.sub.xN (x=0.07) were synthesized. The nanowires, which have diameters of .about.10 nm to 100 nm and lengths of up to tens of micrometers, show ferromagnetism with Curie temperature above room temperature, and magnetoresistance up to 250 Kelvin.

  20. Inelasticity and precipitation of germanium from a solid solution in Al-Ge binary alloys

    Science.gov (United States)

    Kardashev, B. K.; Korchunov, B. N.; Nikanorov, S. P.; Osipov, V. N.

    2015-08-01

    The influence of precipitation of germanium atoms in a solid solution on the dependence of the inelasticity characteristics on the germanium content in aluminum-germanium alloys prepared by directional crystallization has been studied. It has been shown that the Young's modulus defect, the amplitude-dependent decrement, and the microplastic flow stress at a specified cyclic strain amplitude have extreme values at the eutectic germanium content in the alloy. The eutectic composition of the alloy undergoes a ductilebrittle transition. It has been found that there is a correlation between the dependences of the Young's modulus defect, amplitude-dependent decrement, microplastic flow stress, and specific entropy of the exothermal process of germanium precipitation on the germanium content in the hypoeutectic alloy. The concentration dependences of the inelasticity characteristics and their changes after annealing have been explained by the change in the resistance to the motion of intragrain dislocations due to different structures of the Guinier-Preston zones formed during the precipitation of germanium atoms.

  1. High Performance Bulk Thermoelectric Materials

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Zhifeng [Boston College, Chestnut Hill, MA (United States)

    2013-03-31

    Over 13 plus years, we have carried out research on electron pairing symmetry of superconductors, growth and their field emission property studies on carbon nanotubes and semiconducting nanowires, high performance thermoelectric materials and other interesting materials. As a result of the research, we have published 104 papers, have educated six undergraduate students, twenty graduate students, nine postdocs, nine visitors, and one technician.

  2. Analytical product study of germanium-containing medicine by different ICP-MS applications.

    Science.gov (United States)

    Krystek, Petra; Ritsema, Rob

    2004-01-01

    For several years organo-germanium containing medicine has been used for special treatments of e.g. cancer and AIDS. The active substances contain germanium as beta-carboxyethylgermanium sesquioxide ((GeCH2CH2COOH)203/"Ge-132"), spirogermanium, germanium-lactate-citrate or unspecified forms. For humans, germanium is not essential and in general the toxicity of the mentioned organo-germanium compounds is low. Acute and chronic toxic effects of inorganic germanium dioxide have been demonstrated. It is obvious that especially inorganic germanium has a higher potential of negative effects. Therefore, a widespread analytical product control is indispensable. Inductively coupled plasma mass spectrometry (ICP-MS) is the preferred technique and different applications were developed for controlling various parameters: (i) A speciation method using high performance liquid chromatography (HPLC) coupled with quadrupole (Q-) ICP-MS was developed for the identification of organo-germanium species in medicine. (ii) The nuclear magnetic resonance (NMR) technique was applied to confirm the molecular structure and to determine the molecule concentration. (iii) The total concentration of germanium in the medicine was determined in the diluted sample by high resolution (HR-) ICP-MS. (iv) For a general overview, a multi-element screening method of 56 elements with HR-ICP-MS was developed. The semi-quantitative mode was used for quantification and elements of higher abundance are reported. (v) Investigations about matrix-based interferences on masses of isotopes, which are generally determinable without remarkable problems. Isotopes like e.g. 85Rb, 88Sr, 89y, 90Zr, 93Nb and the isotopes of Ba are strongly interfered by different Ge-based molecules and need to be analysed in a higher resolution mode than used for other common matrices.

  3. Single nanowire electrode electrochemistry of silicon anode by in situ atomic force microscopy: solid electrolyte interphase growth and mechanical properties.

    Science.gov (United States)

    Liu, Xing-Rui; Deng, Xin; Liu, Ran-Ran; Yan, Hui-Juan; Guo, Yu-Guo; Wang, Dong; Wan, Li-Jun

    2014-11-26

    Silicon nanowires (SiNWs) have attracted great attention as promising anode materials for lithium ion batteries (LIBs) on account of their high capacity and improved cyclability compared with bulk silicon. The interface behavior, especially the solid electrolyte interphase (SEI), plays a significant role in the performance and stability of the electrodes. We report herein an in situ single nanowire atomic force microscopy (AFM) method to investigate the interface electrochemistry of silicon nanowire (SiNW) electrode. The morphology and Young's modulus of the individual SiNW anode surface during the SEI growth were quantitatively tracked. Three distinct stages of the SEI formation on the SiNW anode were observed. On the basis of the potential-dependent morphology and Young's modulus evolution of SEI, a mixture-packing structural model was proposed for the SEI film on SiNW anode.

  4. Semiclassical Monte Carlo simulation studies of spin dephasing in InP and InSb nanowires

    Directory of Open Access Journals (Sweden)

    Ashish Kumar

    2012-03-01

    Full Text Available We use semiclassical Monte Carlo approach to investigate spin polarized transport in InP and InSb nanowires. D’yakonov-Perel (DP relaxation and Elliott-Yafet (EY relaxation are the two main relaxation mechanisms for spin dephasing in III-V channels. The DP relaxation occurs because of bulk inversion asymmetry (Dresselhaus spin-orbit interaction and structural inversion asymmetry (Rashba spin-orbit interaction. The injection polarization direction studied is that along the length of the channel. The dephasing rate is found to be very strong for InSb as compared to InP which has larger spin dephasing lengths. The ensemble averaged spin components vary differently for both InP and InSb nanowires. The steady state spin distribution also shows a difference between the two III-V nanowires.

  5. Nano-Angle Resolved Photoemission Spectroscopy on Topological insulator Sb2Te3 nanowires responsible of quantum transport

    Science.gov (United States)

    Avila, José; Chen, Chaoyu; Arango, Yulieth C.; Huang, Liubing; Grützmacher, Detlev; Lüth, Hans; Lu, J. Grace; Schäpers, Thomas; Asensio, Maria C.

    2017-06-01

    Using high-resolution Nano-Angle Resolved Photoemission Spectroscopy (Nano-ARPES), we have determined the electronic structure of the surface and bulk states of topological insulator Sb2Te3 nanowires, which have been also characterized by magnetoresistance measurements. The observed Aharonov-Bohm-type oscillations could be unambiguously related to the transport by topological protected surface states directly recorded by photoemission. We have measured Nano-ARPES on individual nanowires of a few nanometers wide to provide direct evidence of the existence of the nontrivial topological surface states, as well as their doping. Our findings are consistent with theoretical predictions and confirm that the surface states of intrinsically doped unidimensional topological insulator nanowires are responsible for the quantum transport.

  6. Single crystalline PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices.

    Science.gov (United States)

    Lin, Yung-Chen; Lu, Kuo-Chang; Wu, Wen-Wei; Bai, Jingwei; Chen, Lih J; Tu, K N; Huang, Yu

    2008-03-01

    We report the formation of PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices from such heterostructures. Scanning electron microscopy studies show that silicon nanowires can be converted into PtSi nanowires through controlled reactions between lithographically defined platinum pads and silicon nanowires. High-resolution transmission electron microscopy studies show that PtSi/Si/PtSi heterostructure has an atomically sharp interface with epitaxial relationships of Si[110]//PtSi[010] and Si(111)//PtSi(101). Electrical measurements show that the pure PtSi nanowires have low resistivities approximately 28.6 microOmega.cm and high breakdown current densities>1x10(8) A/cm2. Furthermore, using single crystal PtSi/Si/PtSi nanowire heterostructures with atomically sharp interfaces, we have fabricated high-performance nanoscale field-effect transistors from intrinsic silicon nanowires, in which the source and drain contacts are defined by the metallic PtSi nanowire regions, and the gate length is defined by the Si nanowire region. Electrical measurements show nearly perfect p-channel enhancement mode transistor behavior with a normalized transconductance of 0.3 mS/microm, field-effect hole mobility of 168 cm2/V.s, and on/off ratio>10(7), demonstrating the best performing device from intrinsic silicon nanowires.

  7. Diffusion or bulk flow

    DEFF Research Database (Denmark)

    Schulz, Alexander

    2015-01-01

    assimilate movement includes an apoplasmic step, this mode is called apoplasmic loading. Well established is also the polymer-trap loading mode, where the phloem-transport sugars are raffinose-family oligomers in herbaceous plants. Also this mode depends on the investment of energy, here for sugar...... is currently matter of discussion, called passive symplasmic loading. Based on the limited material available, this review compares the different loading modes and suggests that diffusion is the driving force in apoplasmic loaders, while bulk flow plays an increasing role in plants having a continuous...

  8. In Situ Study of Noncatalytic Metal Oxide Nanowire Growth

    DEFF Research Database (Denmark)

    Rackauskas, Simas; Jiang, Hua; Wagner, Jakob Birkedal

    2014-01-01

    The majority of the nanowire synthesis methods utilize catalyst particles to guide the nanowire geometry. In contrast, catalyst-free methods are attractive for facile fabrication of pure nanowires without the need for catalyst preparation. Nonetheless, how nanowire growth is guided without...

  9. Synthesis and evaluation of germanium organometallic compounds as precursors for chemical vapor deposition (CVD) and for obtaining nanoparticles of elemental germanium

    International Nuclear Information System (INIS)

    Ballestero Martinez, Ernesto

    2014-01-01

    The interest in the development of materials having applications such as electronics areas or biomarkers has affected the synthesis of new compounds based on germanium. This element has had two common oxidation states, +4 and +2, of them, +2 oxidation state has been the least studied and more reactive. Additionally, compounds of germanium (II) have had similarities with carbenes regarding the chemical acid-base Lewis. The preparation of compounds of germanium (II) with ligands β-decimations has enabled stabilization of new chemical functionalities and, simultaneously, provided interesting thermal properties to develop new preparation methodologies of materials with novel properties. The preparation of amides germanium(II) L'Ge(NHPh) [1, L' = {HC (CMeN-2,4,6-Me 3 C 6 H 2 ) 2 }], L'Ge(4-NHPy) [2] L'Ge(2-NHPy) [3] and LGe(2-NHPy) [4, L = {HC(CMeN-2,6- i Pr 2 C 6 H 3 ) 2 }]; the structural chemical composition were determined using techniques such as nuclear magnetic resonance ( 1 H, 13 C), other techniques are treated: elemental analysis, melting point, infrared spectroscopy, X-ray diffraction of single crystal and thermal gravimetric analysis (TGA). The TGA has showed that 4-1 have experimented a thermal decomposition; therefore, these compounds could be considered as potential starting materials for obtaining germanium nitride (GeN x ). Certainly, the availability of nitrogen coordinating atoms in the chemical composition in 2-4 have been interesting because it could act as ligands in reactions with transition metal complexes. That way, information could be obtained at the molecular level for some reactions and interactions that in surface chemistry have used similar link sites, for example, chemical functionalization of silicon and germanium substrates. The synthesis and structural characterization of germanium chloride compound(II) L''GeCl [5, L'' = HC{(CMe) (N-2,6-Me 2 C 6 H 3 )} 2 ], which could be used later for the

  10. Hybrid Solar Cells Based on Silicon Nanowire Arrays for Remote Chemical Sensing

    Directory of Open Access Journals (Sweden)

    Joël DAVENAS

    2014-05-01

    Full Text Available Disordered arrays of silicon nanowires have been produced by the OAG technique. The UV-visible absorption spectrum of the SiNWs shows a main increase of the absorption extending in the near infrared and similar absorption than bulk crystalline silicon below 400 nm. T EMT simulation of the UV absorption of silicon nanowires predicts a main optical absorption for a nanowire orientation parallel to the electric field vector of the incident light, as expected for SiNW lying with a dominant orientation parallel to the substrate. The enhanced optical absorption tail extending above 400 nm has been attributed to the combination of band gap opening shown by the PL emission and high densities of silicon surface states at high surface/volume ratio. Hybrid solar cells have been fabricated through the dispersion of silicon nanowires in a poly(3-hexylthiophene thin film leading to a 1.14 % conversion yield, which was increased to 3.04 % upon SiNW surface functionalization, opening new perspectives for self sufficient power supplies applicable to remote sensing.

  11. Vertical nanowire heterojunction devices based on a clean Si/Ge interface.

    Science.gov (United States)

    Chen, Lin; Fung, Wayne Y; Lu, Wei

    2013-01-01

    Different vertical nanowire heterojunction devices were fabricated and tested based on vertical Ge nanowires grown epitaxially at low temperatures on (111) Si substrates with a sharp and clean Si/Ge interface. The nearly ideal Si/Ge heterojuctions with controlled and abrupt doping profiles were verified through material analysis and electrical characterizations. In the nSi/pGe heterojunction diode, an ideality factor of 1.16, subpicoampere reverse saturation current, and rectifying ratio of 10(6) were obtained, while the n+Si/p+Ge structure leads to Esaki tunnel diodes with a high peak tunneling current of 4.57 kA/cm(2) and negative differential resistance at room temperature. The large valence band discontinuity between the Ge and Si in the nanowire heterojunctions was further verified in the p+Si/pGe structure, which shows a rectifying behavior instead of an Ohmic contact and raises an important issue in making Ohmic contacts to heterogeneously integrated materials. A raised Si/Ge structure was further developed using a self-aligned etch process, allowing greater freedom in device design for applications such as the tunneling field-effect transistor (TFET). All measurement data can be well-explained and fitted with theoretical models with known bulk properties, suggesting that the Si/Ge nanowire system offers a very clean heterojunction interface with low defect density, and holds great potential as a platform for future high-density and high-performance electronics.

  12. Suspended tungsten-based nanowires with enhanced mechanical properties grown by focused ion beam induced deposition

    Science.gov (United States)

    Córdoba, Rosa; Lorenzoni, Matteo; Pablo-Navarro, Javier; Magén, César; Pérez-Murano, Francesc; María De Teresa, José

    2017-11-01

    The implementation of three-dimensional (3D) nano-objects as building blocks for the next generation of electro-mechanical, memory and sensing nano-devices is at the forefront of technology. The direct writing of functional 3D nanostructures is made feasible by using a method based on focused ion beam induced deposition (FIBID). We use this technique to grow horizontally suspended tungsten nanowires and then study their nano-mechanical properties by three-point bending method with atomic force microscopy. These measurements reveal that these nanowires exhibit a yield strength up to 12 times higher than that of the bulk tungsten, and near the theoretical value of 0.1 times the Young’s modulus (E). We find a size dependence of E that is adequately described by a core-shell model, which has been confirmed by transmission electron microscopy and compositional analysis at the nanoscale. Additionally, we show that experimental resonance frequencies of suspended nanowires (in the MHz range) are in good agreement with theoretical values. These extraordinary mechanical properties are key to designing electro-mechanically robust nanodevices based on FIBID tungsten nanowires.

  13. Nanowire NMOS Logic Inverter Characterization.

    Science.gov (United States)

    Hashim, Yasir

    2016-06-01

    This study is the first to demonstrate characteristics optimization of nanowire N-Channel Metal Oxide Semiconductor (NW-MOS) logic inverter. Noise margins and inflection voltage of transfer characteristics are used as limiting factors in this optimization. A computer-based model used to produce static characteristics of NW-NMOS logic inverter. In this research two circuit configuration of NW-NMOS inverter was studied, in first NW-NMOS circuit, the noise margin for (low input-high output) condition was very low. For second NMOS circuit gives excellent noise margins, and results indicate that optimization depends on applied voltage to the inverter. Increasing gate to source voltage with (2/1) nanowires ratio results better noise margins. Increasing of applied DC load transistor voltage tends to increasing in decreasing noise margins; decreasing this voltage will improve noise margins significantly.

  14. Reliability assessment of germanium gate stacks with promising initial characteristics

    Science.gov (United States)

    Lu, Cimang; Lee, Choong Hyun; Nishimura, Tomonori; Nagashio, Kosuke; Toriumi, Akira

    2015-02-01

    This work reports on the reliability assessment of germanium (Ge) gate stacks with promising initial electrical properties, with focus on trap generation under a constant electric stress field (Estress). Initial Ge gate stack properties do not necessarily mean highly robust reliability when it is considered that traps are newly generated under high Estress. A small amount of yttrium- or scandium oxide-doped GeO2 (Y-GeO2 or Sc-GeO2, respectively) significantly reduces trap generation in Ge gate stacks without deterioration of the interface. This is explained by the increase in the average coordination number (Nav) of the modified GeO2 network that results from the doping.

  15. Long-wavelength germanium photodetectors by ion implantation

    International Nuclear Information System (INIS)

    Wu, I.C.; Beeman, J.W.; Luke, P.N.; Hansen, W.L.; Haller, E.E.

    1990-11-01

    Extrinsic far-infrared photoconductivity in thin high-purity germanium wafers implanted with multiple-energy boron ions has been investigated. Initial results from Fourier transform spectrometer(FTS) measurements have demonstrated that photodetectors fabricated from this material have an extended long-wavelength threshold near 192μm. Due to the high-purity substrate, the ability to block the hopping conduction in the implanted IR-active layer yields dark currents of less than 100 electrons/sec at temperatures below 1.3 K under an operating bias of up to 70 mV. Optimum peak responsivity and noise equivalent power (NEP) for these sensitive detectors are 0.9 A/W and 5 x 10 -16 W/Hz 1/2 at 99 μm, respectively. The dependence of the performance of devices on the residual donor concentration in the implanted layer will be discussed. 12 refs., 4 figs

  16. Radiation-enhanced self- and boron diffusion in germanium

    DEFF Research Database (Denmark)

    Schneider, S.; Bracht, H.; Klug, J.N.

    2013-01-01

    and the interstitialcy and dissociative diffusion mechanisms. The numerical simulations ascertain concentrations of Ge interstitials and B-interstitial pairs that deviate by several orders of magnitude from their thermal equilibrium values. The dominance of self-interstitial related defects under irradiation leads......We report experiments on proton radiation-enhanced self- and boron (B) diffusion in germanium (Ge) for temperatures between 515 ∘ C and 720 ∘ C. Modeling of the experimental diffusion profiles measured by means of secondary ion mass spectrometry is achieved on the basis of the Frenkel pair reaction...... to an enhanced self- and B diffusion in Ge. Analysis of the experimental profiles yields data for the diffusion of self-interstitials (I ) and the thermal equilibrium concentration of BI pairs in Ge. The temperature dependence of these quantities provides the migration enthalpy of I and formation enthalpy of BI...

  17. Germanium Nitride Interfacial Layer for Chalcogenide Random Access Memory Applications

    Science.gov (United States)

    Shen, Jie; Liu, Bo; Song, Zhitang; Xu, Cheng; Rao, Feng; Liang, Shuang; Feng, Songlin; Chen, Bomy

    2008-01-01

    This work reports on the performance improvement of a chalcogenide random access memory device by applying germanium nitride as an interfacial layer. The device with an 8-nm-thick GeN film was fabricated using standard 0.18 µm complementary metal oxide semiconductor technology. The as-deposited GeN is in the amorphous state and has a smooth surface. An electrical test showed that this N-deficient layer induces a lower threshold voltage during the operation. It is believed that the reduction mainly originated from the excellent interfacial properties, high electrical resistivity, and low thermal conductivity of GeN, which is would be a prospective interfacial material in CRAM devices.

  18. Anomalous compression behavior of germanium during phase transformation

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Xiaozhi [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Tan, Dayong [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Guangzhou Institute of Geochemistry, Chinese Academic of Sciences, Guangzhou 510640 (China); Ren, Xiangting [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Yang, Wenge, E-mail: yangwg@hpstar.ac.cn, E-mail: duanweihe@scu.edu.cn [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); He, Duanwei, E-mail: yangwg@hpstar.ac.cn, E-mail: duanweihe@scu.edu.cn [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Institute of Fluid Physics and National Key Laboratory of Shockwave and Detonation Physic, China Academy of Engineering Physics, Mianyang 621900 (China); Mao, Ho-Kwang [Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 (United States)

    2015-04-27

    In this article, we present the abnormal compression and plastic behavior of germanium during the pressure-induced cubic diamond to β-tin structure transition. Between 8.6 GPa and 13.8 GPa, in which pressure range both phases are co-existing, first softening and followed by hardening for both phases were observed via synchrotron x-ray diffraction and Raman spectroscopy. These unusual behaviors can be interpreted as the volume misfit between different phases. Following Eshelby, the strain energy density reaches the maximum in the middle of the transition zone, where the switch happens from softening to hardening. Insight into these mechanical properties during phase transformation is relevant for the understanding of plasticity and compressibility of crystal materials when different phases coexist during a phase transition.

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

    Energy Technology Data Exchange (ETDEWEB)

    Higashi, H.; Yamada, S.; Kanashima, T.; Hamaya, K., E-mail: hamaya@ee.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Kasahara, K.; Park, J.-H.; Miyao, M. [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Kudo, K.; Okamoto, H.; Moto, K.; Tsunoda, I. [Kumamoto National College of Technology, 2659-2 Suya, Koshi, Kumamoto 861-1102 (Japan)

    2015-01-26

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

  20. Formation of Tensilely Strained Germanium-on-Insulator

    Science.gov (United States)

    Hoshi, Yusuke; Sawano, Kentarou; Hamaya, Kohei; Miyao, Masanobu; Shiraki, Yasuhiro

    2012-01-01

    We fabricate a high-quality germanium-on-insulator (GOI) with tensile strain by combining the wafer bonding of a strained Ge grown on a Si substrate and an oxidized Si substrate and the selective etching of Si. The obtained 300-nm-thick strained GOI shows a smooth surface with RMS roughness of 0.15 nm and no dislocation is detected by cross-sectional transmission electron microscopy (XTEM). The tensile strain of 0.19% induced in the GOI is found to be maintained throughout the fabrication process. This suggests that the fabricated strained GOI has a high potential as an essential platform for high-performance electronic and optical devices.

  1. Gamma ray polarimetry using a position sensitive germanium detector

    CERN Document Server

    Kroeger, R A; Kurfess, J D; Phlips, B F

    1999-01-01

    Imaging gamma-ray detectors make sensitive polarimeters in the Compton energy regime by measuring the scatter direction of gamma rays. The principle is to capitalize on the angular dependence of the Compton scattering cross section to polarized gamma rays and measure the distribution of scatter directions within the detector. This technique is effective in a double-sided germanium detector between roughly 50 keV and 1 MeV. This paper reviews device characteristics important to the optimization of a Compton polarimeter, and summarizes measurements we have made using a device with a 5x5 cm active area, 1 cm thickness, and strip-electrodes on a 2 mm pitch.

  2. DNA hybridization on silicon nanowires

    International Nuclear Information System (INIS)

    Singh, Shalini; Zack, Jyoti; Kumar, Dinesh; Srivastava, S.K.; Govind; Saluja, Daman; Khan, M.A.; Singh, P.K.

    2010-01-01

    Nanowire-based detection strategies provide promising new routes to bioanalysis and indeed are attractive to conventional systems because of their small size, high surface-to-volume ratios, electronic, and optical properties. A sequence-specific detection of single-stranded oligonucleotides using silicon nanowires (SiNWs) is demonstrated. The surface of the SiNWs is functionalized with densely packed organic monolayer via hydrosilylation for covalent attachment. Subsequently, deoxyribonucleic acid (DNA) is immobilized to recognize the complementary target DNA. The biomolecular recognition properties of the nanowires are tested via hybridization with γ P 32 tagged complementary and non-complementary DNA oligonucleotides, showing good selectivity and reversibility. No significant non-specific binding to the incorrect sequences is observed. X-ray photoelectron spectroscopy, fluorescence imaging, and nanodrop techniques are used to characterize the modified SiNWs and covalent attachment with DNA. The results show that SiNWs are excellent substrates for the absorption, stabilization and detection of DNA sequences and could be used for DNA microarrays and micro fabricated SiNWs DNA sensors.

  3. Angular Magnetoresistance of Nanowires with Alternating Cobalt and Nickel Segments

    KAUST Repository

    Mohammed, Hanan

    2017-06-22

    Magnetization reversal in segmented Co/Ni nanowires with varying number of segments was studied using angular Magnetoresistance (MR) measurements on isolated nanowires. The MR measurements offer an insight into the pinning of domain walls within the nanowires. Angular MR measurements were performed on nanowires with two and multiple segments by varying the angle between the applied magnetic field and nanowire (−90° ≤θ≤90°). The angular MR measurements reveal that at lower values of θ the switching fields are nearly identical for the multisegmented and two-segmented nanowires, whereas at higher values of θ, a decrease in the switching field is observed in the case of two segmented nanowires. The two segmented nanowires generally exhibit a single domain wall pinning event, whereas an increased number of pinning events are characteristic of the multisegmented nanowires at higher values of θ. In-situ magnetic force microscopy substantiates reversal by domain wall nucleation and propagation in multisegmented nanowires.

  4. Pulsed laser deposition of aluminum nitride nanowires

    Science.gov (United States)

    Yunusova, N. R.; Kargin, N. I.; Ryndya, S. M.; Gusev, A. S.; Antonenko, S. V.; Timofeev, A. A.

    2018-01-01

    The possibility of AlN nanowires deposition on single-crystal silicon substrates by pulsed laser deposition in vacuum is shown in this work. Experimental samples were investigated by scanning electron microscopy and infrared Fourier spectroscopy. It is shown that the possible mechanism for the AlN nanowires formation is the "vapor-liquid-crystal" mechanism.

  5. Functionalization of magnetic nanowires by charged biopolymers

    DEFF Research Database (Denmark)

    Magnin, D.; Callegari, V.; Mátéfi-Tempfli, Stefan

    2008-01-01

    We report on a facile method for the preparation of biocompatible and bioactive magnetic nanowires. The method consists of the direct deposition of polysaccharides by layer-by-layer (LbL) assembly onto a brush of metallic nanowires; obtained by electrodeposition of the metal within the nanopores ...

  6. Optical properties of nanowire metamaterials with gain

    DEFF Research Database (Denmark)

    Isidio de Lima, Joaquim Junior; Adam, Jost; Rego, Davi

    2016-01-01

    The transmittance, reflectance and absorption of a nanowire metamaterial with optical gain are numerically simulated and investigated. It is assumed that the metamaterial is represented by aligned silver nanowires embedded into a semiconductor matrix, made of either silicon or gallium phosphide...

  7. Moessbauer study of Fe-Co nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Chen Ziyu [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou (China)]. E-mail: chenzy@lzu.edu.cn; Zhan Qingfeng; Xue Desheng; Li Fashen [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou (China); Zhou Xuezhi; Kunkel, Henry; Williams, Gwyn [Department of Physics and Astronomy, the University of Manitoba (Canada)

    2002-01-28

    Arrays of Fe{sub 1-x}Co{sub x} (0.0{<=}x{<=}0.92) nanowires have been prepared by an electrochemical process, co-depositing Fe and Co atoms into the pores of anodic aluminium; their compositions were determined by atomic absorption spectroscopy. Transmission electron microscope results show that the nanowires are regularly spaced and uniform in shape with lengths of about 7.5 {mu}m and diameters of 20 nm. The x-ray diffraction indicates a texture in the deposited nanowires. For the composition below 82 at.% cobalt, the nanowires had a body-centred-cubic structure with a [110] preferred orientation. For the 92 at.% cobalt sample, the alloy exhibited a mixture of bcc and face-centred-cubic structure. The room temperature {sup 57}Fe Moessbauer spectra of the arrays of Fe{sub 1-x}Co{sub x} nanowires have second and fifth absorption lines of the six-line pattern with almost zero intensity, indicating that the internal magnetic field in the nanowires lies along the long axis of the nanowire. The maximum values of the hyperfine field (B{sub hf} 36.6{+-}0.1 T) and isomer shift (IS=0.06{+-}0.01 mm s-1) occur for 44 at.% cobalt. The variations of the isomer shift and the linewidths with composition indicate that the Fe{sub 1-x}Co{sub x} alloy nanowires around the equiatomic composition are in an atomistic disordered state. (author)

  8. High-Performance Single Nanowire Tunnel Diodes

    DEFF Research Database (Denmark)

    Wallentin, Jesper; Persson, Johan Mikael; Wagner, Jakob Birkedal

    2010-01-01

    We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27...

  9. Embedding Ba Monolayers and Bilayers in Boron Carbide Nanowires.

    Science.gov (United States)

    Yu, Zhiyang; Luo, Jian; Shi, Baiou; Zhao, Jiong; Harmer, Martin P; Zhu, Jing

    2015-11-26

    Aberration corrected high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) was employed to study the distribution of barium atoms on the surfaces and in the interiors of boron carbide based nanowires. Barium based dopants, which were used to control the crystal growth, adsorbed to the surfaces of the boron-rich crystals in the form of nanometer-thick surficial films (a type of surface complexion). During the crystal growth, these dopant-based surface complexions became embedded inside the single crystalline segments of fivefold boron-rich nanowires collectively, where they were converted to more ordered monolayer and bilayer modified complexions. Another form of bilayer complexion stabilized at stacking faults has also been identified. Numerous previous works suggested that dopants/impurities tended to segregate at the stacking faults or twinned boundaries. In contrast, our study revealed the previously-unrecognized possibility of incorporating dopants and impurities inside an otherwise perfect crystal without the association to any twin boundary or stacking fault. Moreover, we revealed the amount of barium dopants incorporated was non-equilibrium and far beyond the bulk solubility, which might lead to unique properties.

  10. Orbital Contributions to the Electron g Factor in Semiconductor Nanowires

    Science.gov (United States)

    Winkler, Georg W.; Varjas, Dániel; Skolasinski, Rafal; Soluyanov, Alexey A.; Troyer, Matthias; Wimmer, Michael

    2017-07-01

    Recent experiments on Majorana fermions in semiconductor nanowires [S. M. Albrecht, A. P. Higginbotham, M. Madsen, F. Kuemmeth, T. S. Jespersen, J. Nygård, P. Krogstrup, and C. M. Marcus, Nature (London) 531, 206 (2016), 10.1038/nature17162] revealed a surprisingly large electronic Landé g factor, several times larger than the bulk value—contrary to the expectation that confinement reduces the g factor. Here we assess the role of orbital contributions to the electron g factor in nanowires and quantum dots. We show that an L .S coupling in higher subbands leads to an enhancement of the g factor of an order of magnitude or more for small effective mass semiconductors. We validate our theoretical finding with simulations of InAs and InSb, showing that the effect persists even if cylindrical symmetry is broken. A huge anisotropy of the enhanced g factors under magnetic field rotation allows for a straightforward experimental test of this theory.

  11. Size-effect features on the magnetothermopower of bismuth nanowires

    International Nuclear Information System (INIS)

    Condrea, E.; Nicorici, A.

    2011-01-01

    Full text: In this work we have studied the magnetic field dependence of the thermopower (TEP) and resistance of glass-coated Bi wires with diameter (d) from 100 nm to at 1.5 μm below 80 K. Nanowires have anomalously large values of the thermopower (+100 μV K.1) and relatively high effective resistivities, but their frequencies of SdH oscillations remain those of bulk Bi. The TEP stays positive in longitudinal magnetic fields up to 15 T, where the surface scattering of charge carriers is negligible. Our analysis shows that the anomalous thermopower has a diffusion origin and is a consequence of the microstructure rather than the result of the strong scattering of electrons by the wire walls. The intensities of field at which the size-effect features appear on the magnetothermopower curves correspond to a value at which the diameter of the hole cyclotron orbit equals d. Size-effect features were observed only for set of nanowires with d = 100-350 nm, where diffusion TEP is dominant. The contribution of the phonon-drag effect was observed in a wire with diameter larger than 400 nm and becomes dominant at diameter of 1 μm. (authors)

  12. Bulk-Fill Resin Composites

    DEFF Research Database (Denmark)

    Benetti, Ana Raquel; Havndrup-Pedersen, Cæcilie; Honoré, Daniel

    2015-01-01

    the restorative procedure. The aim of this study, therefore, was to compare the depth of cure, polymerization contraction, and gap formation in bulk-fill resin composites with those of a conventional resin composite. To achieve this, the depth of cure was assessed in accordance with the International Organization...... for Standardization 4049 standard, and the polymerization contraction was determined using the bonded-disc method. The gap formation was measured at the dentin margin of Class II cavities. Five bulk-fill resin composites were investigated: two high-viscosity (Tetric EvoCeram Bulk Fill, SonicFill) and three low......-viscosity (x-tra base, Venus Bulk Fill, SDR) materials. Compared with the conventional resin composite, the high-viscosity bulk-fill materials exhibited only a small increase (but significant for Tetric EvoCeram Bulk Fill) in depth of cure and polymerization contraction, whereas the low-viscosity bulk...

  13. Germanium microstrip detectors with 50 and 100 μm pitch

    International Nuclear Information System (INIS)

    Amendolia, S.R.; Bedeschi, F.; Bertolucci, E.; Bettoni, D.; Bosisio, L.; Bottigli, U.; Bradaschia, C.; Dell'Orso, M.; Fidecaro, F.; Foa, L.; Focardi, E.; Giannetti, P.; Giorgi, M.A.; Marrocchesi, P.S.; Menzione, A.; Raso, G.; Ristori, L.; Scribano, A.; Stefanini, A.; Tenchini, R.; Tonelli, G.; Triggiani, G.; Haller, E.E.; Hansen, W.L.; Luke, P.N.

    1984-01-01

    Multi-electrode germanium detectors are being used as an active target for decay path measurements of charmed mesons. The procedure used to fabricate such detectors is described and a brief analysis of their performance is given. (orig.)

  14. Silicon-Germanium Front-End Electronics for Space-Based Radar Applications

    Data.gov (United States)

    National Aeronautics and Space Administration — Over the past two decades, Silicon-Germanium (SiGe) heterojunction bipolar transistor (HBT) technology has emerged as a strong platform for high-frequency...

  15. Induced Radioactivity Measured in a Germanium Detector After a Long Duration Balloon Flight

    Science.gov (United States)

    Starr, R.; Evans, L. G.; Floyed, S. R.; Drake, D. M.; Feldman, W. C.; Squyres, S. W.; Rester, A. C.

    1997-01-01

    A 13-day long duration balloon flight carrying a germanium detector was flown from Williams Field, Antartica in December 1992. After recovery of the payload the activity induced in the detector was measured.

  16. An Implant-Passivated Blocked Impurity Band Germanium Detector for the Far Infrared, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to investigate the feasibility of fabricating a germanium blocked-impurity-band (BIB) detector using a novel process which will enable us to: 1- fabricate...

  17. An Implant-Passivated Blocked Impurity Band Germanium Detector for the Far Infrared, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to fabricate a germanium blocked-impurity-band (BIB) detector using a novel process which will enable us to: 1- fabricate a suitably-doped active layer...

  18. High-frequency electromagnetic radiation of germanium crystals in magnetic fields

    Directory of Open Access Journals (Sweden)

    G.V. Milenin

    2017-07-01

    Full Text Available The cyclotron radiation of plasma of thermal carriers of germanium crystals, which is not in the state of thermodynamic equilibrium with semiconductor, has been experimentally confirmed.

  19. An Implant-Passivated Blocked Impurity Band Germanium Detector for the Far Infrared Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to investigate the feasibility of fabricating a germanium blocked-impurity-band (BIB) detector using a novel process which will enable us to: 1- fabricate...

  20. An Implant-Passivated Blocked Impurity Band Germanium Detector for the Far Infrared Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to fabricate a germanium blocked-impurity-band (BIB) detector using a novel process which will enable us to: 1- fabricate a suitably-doped active layer...

  1. Nonthermal plasma synthesis of size-controlled, monodisperse, freestanding germanium nanocrystals

    International Nuclear Information System (INIS)

    Gresback, Ryan; Holman, Zachary; Kortshagen, Uwe

    2007-01-01

    Germanium nanocrystals may be of interest for a variety of electronic and optoelectronic applications including photovoltaics, primarily due to the tunability of their band gap from the infrared into the visible range of the spectrum. This letter discusses the synthesis of monodisperse germanium nanocrystals via a nonthermal plasma approach which allows for precise control of the nanocrystal size. Germanium crystals are synthesized from germanium tetrachloride and hydrogen entrained in an argon background gas. The crystal size can be varied between 4 and 50 nm by changing the residence times of crystals in the plasma between ∼30 and 440 ms. Adjusting the plasma power enables one to synthesize fully amorphous or fully crystalline particles with otherwise similar properties

  2. A Low Noise 64x64 Germanium Array for Far IR Astronomy, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to investigate the feasibility of developing a 64x64 far infrared germanium focal-plane array with the following key design features: 1- Four...

  3. Probing spin helical surface states in topological HgTe nanowires

    Science.gov (United States)

    Ziegler, J.; Kozlovsky, R.; Gorini, C.; Liu, M.-H.; Weishäupl, S.; Maier, H.; Fischer, R.; Kozlov, D. A.; Kvon, Z. D.; Mikhailov, N.; Dvoretsky, S. A.; Richter, K.; Weiss, D.

    2018-01-01

    Nanowires with helical surface states represent key prerequisites for observing and exploiting phase-coherent topological conductance phenomena, such as spin-momentum locked quantum transport or topological superconductivity. We demonstrate in a joint experimental and theoretical study that gated nanowires fabricated from high-mobility strained HgTe, known as a bulk topological insulator, indeed preserve the topological nature of the surface states, that moreover extend phase-coherently across the entire wire geometry. The phase-coherence lengths are enhanced up to 5 μ m when tuning the wires into the bulk gap, so as to single out topological transport. The nanowires exhibit distinct conductance oscillations, both as a function of the flux due to an axial magnetic field and of a gate voltage. The observed h /e -periodic Aharonov-Bohm-type modulations indicate surface-mediated quasiballistic transport. Furthermore, an in-depth analysis of the scaling of the observed gate-dependent conductance oscillations reveals the topological nature of these surface states. To this end we combined numerical tight-binding calculations of the quantum magnetoconductance with simulations of the electrostatics, accounting for the gate-induced inhomogeneous charge carrier densities around the wires. We find that helical transport prevails even for strongly inhomogeneous gating and is governed by flux-sensitive high-angular momentum surface states that extend around the entire wire circumference.

  4. Growth and structural characterization of III-V semiconductor nanowires

    OpenAIRE

    Rieger, Torsten

    2015-01-01

    In this thesis, the growth and structural properties of III-V semiconductor nanowires and nanowire heterostructures are studied. These nanowires represent structures suitable for both fundamental physics and applications in electronic devices such as (tunnel) field effect transistors. The III-V nanowires are grown with molecular beam epitaxy, high κ dielectric layers are deposited conformally around the nanowires by atomic layer deposition. The morphological and structural characteristics of ...

  5. Diamond nanowires: fabrication, structure, properties, and applications.

    Science.gov (United States)

    Yu, Yuan; Wu, Liangzhuan; Zhi, Jinfang

    2014-12-22

    C(sp(3) )C-bonded diamond nanowires are wide band gap semiconductors that exhibit a combination of superior properties such as negative electron affinity, chemical inertness, high Young's modulus, the highest hardness, and room-temperature thermal conductivity. The creation of 1D diamond nanowires with their giant surface-to-volume ratio enhancements makes it possible to control and enhance the fundamental properties of diamond. Although theoretical comparisons with carbon nanotubes have shown that diamond nanowires are energetically and mechanically viable structures, reproducibly synthesizing the crystalline diamond nanowires has remained challenging. We present a comprehensive, up-to-date review of diamond nanowires, including a discussion of their synthesis along with their structures, properties, and applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Nanowire-decorated microscale metallic electrodes

    DEFF Research Database (Denmark)

    Vlad, A.; Mátéfi-Tempfli, M.; Antohe, V.A.

    2008-01-01

    of lithographically defined metallic microelectrodes. The anodization of the aluminum permits electroplating only on top of the metallic electrodes, leading to the nanowire patterns having the same shape as the underlying metallic tracks. The variation in the fabricated structures between the patterned and non......The fabrication of metallic nanowire patterns within anodic alumina oxide (AAO) membranes on top of continuous conducting substrates are discussed. The fabrication protocol is based on the realization of nanowire patterns using supported nanoporous alumina templates (SNAT) prepared on top......-patterned substrates can be interpreted in terms of different behavior during anodization. The improved quality of fabricated nanowire patterns is clearly demonstrated by the SEM imaging and the uniform growth of nanowires inside the alumina template is observed without any significant height variation....

  7. Nanowires, nanostructures and devices fabricated therefrom

    Science.gov (United States)

    Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

    2005-04-19

    One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

  8. Synthesis and properties of antimonide nanowires

    Science.gov (United States)

    Mattias Borg, B.; Wernersson, Lars-Erik

    2013-05-01

    Antimonide semiconductors are suitable for low-power electronics and long-wavelength optoelectronic applications. In recent years research on antimonide nanowires has become a rapidly growing field, and nano-materials have promising applications in fundamental physics research, for tunnel field-effect transistors, and long-wavelength detectors. In this review, we give an overview of the field of antimonide nanowires, beginning with a description of the synthesis of these nano-materials. Here we summarize numerous reports on antimonide nanowire growth, with the aim to give an overall picture of the distinctive properties of antimonide nanowire synthesis. Secondly, we review the data on the physical properties and emerging applications for antimonide nanowires, focusing on applications in electronics and optics.

  9. Multisegment CdTe nanowire homojunction photodiode

    International Nuclear Information System (INIS)

    Matei, Elena; Enculescu, Ionut; Ion, Lucian; Antohe, Stefan; Neumann, Reinhard

    2010-01-01

    Electrochemical deposition in nanoporous ion track membranes is used for the preparation of multisegment CdTe-homojunction diode nanowires. Our study is based on the fact that the deposition overpotential strongly influences the composition of the compound semiconductor nanowires. Therefore, the transport behavior of the nanowire devices can be tailored by appropriately choosing a certain sequence of electrodeposition potentials. The wires were characterized using scanning electron microscopy, energy dispersive x-ray analysis, optical spectroscopy and x-ray diffraction. The current-voltage characteristics measured prove that, by appropriately choosing the voltage pulse pattern, one can fabricate nanowires with ohmic or rectifying behavior. The semiconducting nanowires are sensitive to light, their spectral sensitivity being characteristic of CdTe. The preparation of functional nanostructures in such a simple approach provides, as a major advantage, an increase in the process reproducibility and opens a wide field of potential optoelectronic applications.

  10. Electrospun ZnO nanowire plantations in the electron transport layer for high-efficiency inverted organic solar cells.

    Science.gov (United States)

    Elumalai, Naveen Kumar; Jin, Tan Mein; Chellappan, Vijila; Jose, Rajan; Palaniswamy, Suresh Kumar; Jayaraman, Sundaramurthy; Raut, Hemant Kumar; Ramakrishna, Seeram

    2013-10-09

    Inverted bulk heterojunction organic solar cells having device structure ITO/ZnO/poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C61 butyric acid methyl ester (PCBM) /MoO3/Ag were fabricated with high photoelectric conversion efficiency and stability. Three types of devices were developed with varying electron transporting layer (ETL) ZnO architecture. The ETL in the first type was a sol-gel-derived particulate film of ZnO, which in the second and third type contained additional ZnO nanowires of varying concentrations. The length of the ZnO nanowires, which were developed by the electrospinning technique, extended up to the bulk of the photoactive layer in the device. The devices those employed a higher loading of ZnO nanowires showed 20% higher photoelectric conversion efficiency (PCE), which mainly resulted from an enhancement in its fill factor (FF). Charge transport characteristic of the device were studied by transient photovoltage decay and charge extraction by linearly increasing voltage techniques. Results show that higher PCE and FF in the devices employed ZnO nanowire plantations resulted from improved charge collection efficiency and reduced recombination rate.

  11. Precise Placement of Metallic Nanowires on a Substrate by Localized Electric Fields and Inter-Nanowire Electrostatic Interaction

    Directory of Open Access Journals (Sweden)

    U Hyeok Choi

    2017-10-01

    Full Text Available Placing nanowires at the predetermined locations on a substrate represents one of the significant hurdles to be tackled for realization of heterogeneous nanowire systems. Here, we demonstrate spatially-controlled assembly of a single nanowire at the photolithographically recessed region at the electrode gap with high integration yield (~90%. Two popular routes, such as protruding electrode tips and recessed wells, for spatially-controlled nanowire alignment, are compared to investigate long-range dielectrophoretic nanowire attraction and short-range nanowire-nanowire electrostatic interaction for determining the final alignment of attracted nanowires. Furthermore, the post-assembly process has been developed and tested to make a robust electrical contact to the assembled nanowires, which removes any misaligned ones and connects the nanowires to the underlying electrodes of circuit.

  12. A Complete Physical Germanium-on-Silicon Quantum Dot Self-Assembly Process

    OpenAIRE

    Alkhatib, Amro; Nayfeh, Ammar

    2013-01-01

    Achieving quantum dot self-assembly at precise pre-defined locations is of vital interest. In this work, a novel physical method for producing germanium quantum dots on silicon using nanoindentation to pre-define nucleation sites is described. Self-assembly of ordered ~10?nm height germanium quantum dot arrays on silicon substrates is achieved. Due to the inherent simplicity and elegance of the proposed method, the results describe an attractive technique to manufacture semiconductor quantum ...

  13. Semiconductor nanowires for photovoltaic and photoelectrochemical energy conversion

    Energy Technology Data Exchange (ETDEWEB)

    Dasgupta, Neil; Yang, Peidong

    2013-01-23

    Semiconductor nanowires (NW) possess several beneficial properties for efficient conversion of solar energy into electricity and chemical energy. Due to their efficient absorption of light, short distances for minority carriers to travel, high surface-to-volume ratios, and the availability of scalable synthesis methods, they provide a pathway to address the low cost-to-power requirements for wide-scale adaptation of solar energy conversion technologies. Here we highlight recent progress in our group towards implementation of NW components as photovoltaic and photoelectrochemical energy conversion devices. An emphasis is placed on the unique properties of these one-dimensional (1D) structures, which enable the use of abundant, low-cost materials and improved energy conversion efficiency compared to bulk devices.

  14. Bulk material handling system

    Science.gov (United States)

    Kleysteuber, William K.; Mayercheck, William D.

    1979-01-01

    This disclosure relates to a bulk material handling system particularly adapted for underground mining and includes a monorail supported overhead and carrying a plurality of conveyors each having input and output end portions with the output end portion of a first of the conveyors positioned above an input end portion of a second of the conveyors, a device for imparting motion to the conveyors to move the material from the input end portions toward the output end portions thereof, a device for supporting at least one of the input and output end portions of the first and second conveyors from the monorail, and the supporting device including a plurality of trolleys rollingly supported by the monorail whereby the conveyors can be readily moved therealong.

  15. Creating bulk nanocrystalline metal.

    Energy Technology Data Exchange (ETDEWEB)

    Fredenburg, D. Anthony (Georgia Institute of Technology, Atlanta, GA); Saldana, Christopher J. (Purdue University, West Lafayette, IN); Gill, David D.; Hall, Aaron Christopher; Roemer, Timothy John (Ktech Corporation, Albuquerque, NM); Vogler, Tracy John; Yang, Pin

    2008-10-01

    Nanocrystalline and nanostructured materials offer unique microstructure-dependent properties that are superior to coarse-grained materials. These materials have been shown to have very high hardness, strength, and wear resistance. However, most current methods of producing nanostructured materials in weapons-relevant materials create powdered metal that must be consolidated into bulk form to be useful. Conventional consolidation methods are not appropriate due to the need to maintain the nanocrystalline structure. This research investigated new ways of creating nanocrystalline material, new methods of consolidating nanocrystalline material, and an analysis of these different methods of creation and consolidation to evaluate their applicability to mesoscale weapons applications where part features are often under 100 {micro}m wide and the material's microstructure must be very small to give homogeneous properties across the feature.

  16. Bulk muscles, loose cables.

    Science.gov (United States)

    Liyanage, Chamari R D G; Kodali, Venkata

    2014-10-17

    The accessibility and usage of body building supplements is on the rise with stronger internet marketing strategies by the industry. The dangers posed by the ingredients in them are underestimated. A healthy young man came to the emergency room with palpitations and feeling unwell. Initial history and clinical examination were non-contributory to find the cause. ECG showed atrial fibrillation. A detailed history for any over the counter or herbal medicine use confirmed that he was taking supplements to bulk muscle. One of the components in these supplements is yohimbine; the onset of symptoms coincided with the ingestion of this product and the patient is symptom free after stopping it. This report highlights the dangers to the public of consuming over the counter products with unknown ingredients and the consequential detrimental impact on health. 2014 BMJ Publishing Group Ltd.

  17. Axial InGaAs/GaAs nanowire separate absorption-multiplication avalanche photodetectors (Conference Presentation)

    Science.gov (United States)

    Huffaker, Diana L.

    2017-05-01

    In0.53Ga0.47As/InP single photon avalanche detectors (SPADs) have a high photon detection efficiency in the near-IR, however the dark count rate is prohibitively high at room temperature. A nanowire-based In0.3Ga0.7As/GaAs SPAD can significantly reduce the DCR through a nearly three order of magnitude reduction in bulk InGaAs volume, as well as by reducing the indium composition for operation at 1064 nm. As a first step, we have successfully grown axial InGaAs/GaAs heterostructures using catalyst-free selective-area epitaxy. We will present the electrical characterization of a vertically oriented nanowire array InGaAs/GaAs SPADs operating at 1064 nm and use 3-dimensional modeling to aid in the analysis.

  18. Thermal conductivity engineering in width-modulated silicon nanowires and thermoelectric efficiency enhancement

    Science.gov (United States)

    Zianni, Xanthippi

    2018-03-01

    Width-modulated nanowires have been proposed as efficient thermoelectric materials. Here, the electron and phonon transport properties and the thermoelectric efficiency are discussed for dimensions above the quantum confinement regime. The thermal conductivity decreases dramatically in the presence of thin constrictions due to their ballistic thermal resistance. It shows a scaling behavior upon the width-modulation rate that allows for thermal conductivity engineering. The electron conductivity also decreases due to enhanced boundary scattering by the constrictions. The effect of boundary scattering is weaker for electrons than for phonons and the overall thermoelectric efficiency is enhanced. A ZT enhancement by a factor of 20-30 is predicted for width-modulated nanowires compared to bulk silicon. Our findings indicate that width-modulated nanostructures are promising for developing silicon nanostructures with high thermoelectric efficiency.

  19. Ultradense, Deep Subwavelength Nanowire Array Photovoltaics As Engineered Optical Thin Films

    KAUST Repository

    Tham, Douglas

    2010-11-10

    A photovoltaic device comprised of an array of 20 nm wide, 32 nm pitch array of silicon nanowires is modeled as an optical material. The nanowire array (NWA) has characteristic device features that are deep in the subwavelength regime for light, which permits a number of simplifying approximations. Using photocurrent measurements as a probe of the absorptance, we show that the NWA optical properties can be accurately modeled with rigorous coupled-wave analysis. The densely structured NWAs behave as homogeneous birefringent materials into the ultraviolet with effective optical properties that are accurately modeled using the dielectric functions of bulk Si and SiO 2, coupled with a physical model for the NWA derived from ellipsometry and transmission electron microscopy. © 2010 American Chemical Society.

  20. Microwave-assisted synthesis of WS2 nanowires through tetrathiotungstate precursors

    Directory of Open Access Journals (Sweden)

    Pravas Kumar Panigrahi and Amita Pathak

    2008-01-01

    Full Text Available Tungsten disulfide (WS2 nanowires have been synthesized through a microwave-assisted chemical route that uses tungstic acid, elemental sulfur and monoethanolamine as starting reagents for obtaining a precursor solution of tetrathiotungstate ions. Acidification of the precursor solution yields amorphous precipitates, which lead to the formation of nanowires of WS2 with thickness of about 5–10 nm when heated at 750 °C under argon atmosphere for 1.5 h. Phase and the microstructure of the prepared powders have been investigated through x-ray powder diffraction and high-resolution transmission electron microscopy, respectively. Optical absorption of the WS2 powders reveals a red shift of the exciton bands compared to bulk WS2.

  1. An antioxidant nanozyme that uncovers the cytoprotective potential of vanadia nanowires

    Science.gov (United States)

    Vernekar, Amit A.; Sinha, Devanjan; Srivastava, Shubhi; Paramasivam, Prasath U.; D'Silva, Patrick; Mugesh, Govindasamy

    2014-11-01

    Nanomaterials with enzyme-like properties has attracted significant interest, although limited information is available on their biological activities in cells. Here we show that V2O5 nanowires (Vn) functionally mimic the antioxidant enzyme glutathione peroxidase by using cellular glutathione. Although bulk V2O5 is known to be toxic to the cells, the property is altered when converted into a nanomaterial form. The Vn nanozymes readily internalize into mammalian cells of multiple origin (kidney, neuronal, prostate, cervical) and exhibit robust enzyme-like activity by scavenging the reactive oxygen species when challenged against intrinsic and extrinsic oxidative stress. The Vn nanozymes fully restore the redox balance without perturbing the cellular antioxidant defense, thus providing an important cytoprotection for biomolecules against harmful oxidative damage. Based on our findings, we envision that biocompatible Vn nanowires can provide future therapeutic potential to prevent ageing, cardiac disorders and several neurological conditions, including Parkinson’s and Alzheimer’s disease.

  2. Confinement-guided shaping of semiconductor nanowires and nanoribbons: "writing with nanowires".

    Science.gov (United States)

    Pevzner, Alexander; Engel, Yoni; Elnathan, Roey; Tsukernik, Alexander; Barkay, Zahava; Patolsky, Fernando

    2012-01-11

    To fully exploit their full potential, new semiconductor nanowire building blocks with ab initio controlled shapes are desired. However, and despite the great synthetic advances achieved, the ability to control nanowire's geometry has been significantly limited. Here, we demonstrate a simple confinement-guided nanowire growth method that enables to predesign not only the chemical and physical attributes of the synthesized nanowires but also allows a perfect and unlimited control over their geometry. Our method allows the synthesis of semiconductor nanowires in a wide variety of two-dimensional shapes such as any kinked (different turning angles), sinusoidal, linear, and spiral shapes, so that practically any desired geometry can be defined. The shape-controlled nanowires can be grown on almost any substrate such as silicon wafer, quartz and glass slides, and even on plastic substrates (e.g., Kapton HN). © 2011 American Chemical Society

  3. Microfabricated Bulk Piezoelectric Transformers

    Science.gov (United States)

    Barham, Oliver M.

    Piezoelectric voltage transformers (PTs) can be used to transform an input voltage into a different, required output voltage needed in electronic and electro- mechanical systems, among other varied uses. On the macro scale, they have been commercialized in electronics powering consumer laptop liquid crystal displays, and compete with an older, more prevalent technology, inductive electromagnetic volt- age transformers (EMTs). The present work investigates PTs on smaller size scales that are currently in the academic research sphere, with an eye towards applications including micro-robotics and other small-scale electronic and electromechanical sys- tems. PTs and EMTs are compared on the basis of power and energy density, with PTs trending towards higher values of power and energy density, comparatively, indicating their suitability for small-scale systems. Among PT topologies, bulk disc-type PTs, operating in their fundamental radial extension mode, and free-free beam PTs, operating in their fundamental length extensional mode, are good can- didates for microfabrication and are considered here. Analytical modeling based on the Extended Hamilton Method is used to predict device performance and integrate mechanical tethering as a boundary condition. This model differs from previous PT models in that the electric enthalpy is used to derive constituent equations of motion with Hamilton's Method, and therefore this approach is also more generally applica- ble to other piezoelectric systems outside of the present work. Prototype devices are microfabricated using a two mask process consisting of traditional photolithography combined with micropowder blasting, and are tested with various output electri- cal loads. 4mm diameter tethered disc PTs on the order of .002cm. 3 , two orders smaller than the bulk PT literature, had the followingperformance: a prototype with electrode area ratio (input area / output area) = 1 had peak gain of 2.3 (+/- 0.1), efficiency of 33 (+/- 0

  4. Role of surface on the size-dependent mechanical properties of copper nano-wire under tensile load: A molecular dynamics simulation

    Science.gov (United States)

    Liu, Wei-Ting; Hsiao, Chun-I.; Hsu, Wen-Dung

    2014-01-01

    In this study we have used atomistic simulations to investigate the role of surface on the size-dependent mechanical properties of nano-wires. In particular, we have performed computational investigation on single crystal face-centered cubic copper nano-wires with diameters ranging from 2 to 20 nm. The wire axis for all the nano-wires are considered along the [0 0 1] direction. Characterization of the initial optimized structures revealed clear differences in interatomic spacing, stress, and potential energy in all the nano-wires. The mechanical properties with respect to wire diameter are evaluated by applying tension along the [0 0 1] direction until yielding. We have discussed the stress-strain relationships, Young's modulus, and the variation in potential energy from surface to the center of the wire for all the cases. Our results indicate that the mechanical response (including yield strain, Young's modulus, and resilience) is directly related to the proportion of surface to bulk type atoms present in each nano-wire. Thus the size-dependent mechanical properties of single crystal copper nano-wire within elastic region are attributed to the surface to volume ratio (surface effect). Using the calculated response, we have formulated a mathematical relationship, which predicts the nonlinear correlation between the mechanical properties and the diameter of the wire.

  5. Developing bulk exchange spring magnets

    Science.gov (United States)

    Mccall, Scott K.; Kuntz, Joshua D.

    2017-06-27

    A method of making a bulk exchange spring magnet by providing a magnetically soft material, providing a hard magnetic material, and producing a composite of said magnetically soft material and said hard magnetic material to make the bulk exchange spring magnet. The step of producing a composite of magnetically soft material and hard magnetic material is accomplished by electrophoretic deposition of the magnetically soft material and the hard magnetic material to make the bulk exchange spring magnet.

  6. Diamond nanowires: a novel platform for electrochemistry and matrix-free mass spectrometry.

    Science.gov (United States)

    Szunerits, Sabine; Coffinier, Yannick; Boukherroub, Rabah

    2015-05-27

    Over the last decades, carbon-based nanostructures have generated a huge interest from both fundamental and technological viewpoints owing to their physicochemical characteristics, markedly different from their corresponding bulk states. Among these nanostructured materials, carbon nanotubes (CNTs), and more recently graphene and its derivatives, hold a central position. The large amount of work devoted to these materials is driven not only by their unique mechanical and electrical properties, but also by the advances made in synthetic methods to produce these materials in large quantities with reasonably controllable morphologies. While much less studied than CNTs and graphene, diamond nanowires, the diamond analogue of CNTs, hold promise for several important applications. Diamond nanowires display several advantages such as chemical inertness, high mechanical strength, high thermal and electrical conductivity, together with proven biocompatibility and existence of various strategies to functionalize their surface. The unique physicochemical properties of diamond nanowires have generated wide interest for their use as fillers in nanocomposites, as light detectors and emitters, as substrates for nanoelectronic devices, as tips for scanning probe microscopy as well as for sensing applications. In the past few years, studies on boron-doped diamond nanowires (BDD NWs) focused on increasing their electrochemical active surface area to achieve higher sensitivity and selectivity compared to planar diamond interfaces. The first part of the present review article will cover the promising applications of BDD NWS for label-free sensing. Then, the potential use of diamond nanowires as inorganic substrates for matrix-free laser desorption/ionization mass spectrometry, a powerful label-free approach for quantification and identification of small compounds, will be discussed.

  7. Diamond Nanowires: A Novel Platform for Electrochemistry and Matrix-Free Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Sabine Szunerits

    2015-05-01

    Full Text Available Over the last decades, carbon-based nanostructures have generated a huge interest from both fundamental and technological viewpoints owing to their physicochemical characteristics, markedly different from their corresponding bulk states. Among these nanostructured materials, carbon nanotubes (CNTs, and more recently graphene and its derivatives, hold a central position. The large amount of work devoted to these materials is driven not only by their unique mechanical and electrical properties, but also by the advances made in synthetic methods to produce these materials in large quantities with reasonably controllable morphologies. While much less studied than CNTs and graphene, diamond nanowires, the diamond analogue of CNTs, hold promise for several important applications. Diamond nanowires display several advantages such as chemical inertness, high mechanical strength, high thermal and electrical conductivity, together with proven biocompatibility and existence of various strategies to functionalize their surface. The unique physicochemical properties of diamond nanowires have generated wide interest for their use as fillers in nanocomposites, as light detectors and emitters, as substrates for nanoelectronic devices, as tips for scanning probe microscopy as well as for sensing applications. In the past few years, studies on boron-doped diamond nanowires (BDD NWs focused on increasing their electrochemical active surface area to achieve higher sensitivity and selectivity compared to planar diamond interfaces. The first part of the present review article will cover the promising applications of BDD NWS for label-free sensing. Then, the potential use of diamond nanowires as inorganic substrates for matrix-free laser desorption/ionization mass spectrometry, a powerful label-free approach for quantification and identification of small compounds, will be discussed.

  8. Thermal stability of iron silicide nanowires epitaxially grown on Si(110) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Zhi-Qiang, E-mail: zouzhq@shanghaitech.edu.cn [School of Physical Science and Technology, ShanghaiTech University, 100 Haike Road, Pudong, Shanghai, 201210 (China); Li, Xu; Liu, Xiao-Yong; Shi, Kai-Juan; Guo, Xin-Qiu [Analytical and Testing Center, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)

    2017-03-31

    Highlights: • The α-FeSi{sub 2} nanowires epitaxially grown on Si(110) can be stable up to 750 °C. • The stable temperature of the nanowires is much lower than that of the bulk α-FeSi{sub 2} due to their small size and high relative surface area. • With increasing annealing temperature, the α-FeSi{sub 2} nanowires undergo an Ostwald ripening process and transform into large β-FeSi{sub 2} nanorods or three-dimensional nanocrystals. • The reduction in surface energy drives the transformation from metallic α-FeSi{sub 2} phase to semiconducting β-FeSi{sub 2} phase. - Abstract: Metallic α-FeSi{sub 2} nanowires (NWs) are epitaxially grown on Si(110) at 650 °C. Their evolution as a function of annealing temperature has been studied in situ by scanning tunneling microscopy. The NWs are stable up to 750 °C, which is much lower than that of the bulk α-FeSi{sub 2}. With further increasing the annealing temperature, some NWs begin to shrink in length and transform into wider and higher semiconducting β-FeSi{sub 2} nanorods or three-dimensional (3D) islands at 925 °C. The phase transformation is driven by the reduction in surface energy. On the other hand, some α-FeSi{sub 2} NWs begin to dissolve and become thinner until disappearing. The growth of the β-FeSi{sub 2} nanorods or 3D nanocrystals follows the Ostwald ripening mechanism, i.e., the large islands grow in size at the expense of the small ones. X-ray photoelectron spectroscopy study shows that the Fe 2p peaks of β-FeSi{sub 2} nanocrystals exhibit a negative shift of 0.2 eV with respect to the α-FeSi{sub 2} NWs.

  9. Highly integrated synthesis of heterogeneous nanostructures on nanowire heater array.

    Science.gov (United States)

    Jin, Chun Yan; Yun, Jeonghoon; Kim, Jung; Yang, Daejong; Kim, Dong Hwan; Ahn, Jae Hyuk; Lee, Kwang-Cheol; Park, Inkyu

    2014-11-06

    We have proposed a new method for the multiplexed synthesis of heterogeneous nanostructures using a top-down fabricated nanowire heater array. Hydrothermally synthesized nanostructures can be grown only on the heated nanowire through nanoscale temperature control using a Joule heated nanowire. We have demonstrated the selective synthesis of zinc oxide (ZnO) nanowires and copper oxide (CuO) nanostructures, as well as their surface modification with noble metal nanoparticles, using a nanowire heater array. Furthermore, we could fabricate an array of heterogeneous nanostructures via Joule heating of individual nanowire heaters and changing of the precursor solutions in a sequential manner. We have formed a parallel array of palladium (Pd) coated ZnO nanowires and gold (Au) coated ZnO nanowires, as well as a parallel array of ZnO nanowires and CuO nanospikes, in the microscale region by using the developed method.

  10. TiO2 nanowire-templated hierarchical nanowire network as water-repelling coating

    Science.gov (United States)

    Hang, Tian; Chen, Hui-Jiuan; Xiao, Shuai; Yang, Chengduan; Chen, Meiwan; Tao, Jun; Shieh, Han-ping; Yang, Bo-ru; Liu, Chuan

    2017-01-01

    Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials. PMID:29308265

  11. TiO2 nanowire-templated hierarchical nanowire network as water-repelling coating

    Science.gov (United States)

    Hang, Tian; Chen, Hui-Jiuan; Xiao, Shuai; Yang, Chengduan; Chen, Meiwan; Tao, Jun; Shieh, Han-ping; Yang, Bo-ru; Liu, Chuan; Xie, Xi

    2017-12-01

    Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials.

  12. Optical properties of heavily doped GaAs nanowires and electroluminescent nanowire structures.

    Science.gov (United States)

    Lysov, A; Offer, M; Gutsche, C; Regolin, I; Topaloglu, S; Geller, M; Prost, W; Tegude, F-J

    2011-02-25

    We present GaAs electroluminescent nanowire structures fabricated by metal organic vapor phase epitaxy. Electroluminescent structures were realized in both axial pn-junctions in single GaAs nanowires and free-standing nanowire arrays with a pn-junction formed between nanowires and substrate, respectively. The electroluminescence emission peak from single nanowire pn-junctions at 10 K was registered at an energy of around 1.32 eV and shifted to 1.4 eV with an increasing current. The line is attributed to the recombination in the compensated region present in the nanowire due to the memory effect of the vapor-liquid-solid growth mechanism. Arrayed nanowire electroluminescent structures with a pn-junction formed between nanowires and substrate demonstrated at 5 K a strong electroluminescence peak at 1.488 eV and two shoulder peaks at 1.455 and 1.519 eV. The main emission line was attributed to the recombination in the p-doped GaAs. The other two lines correspond to the tunneling-assisted photon emission and band-edge recombination in the abrupt junction, respectively. Electroluminescence spectra are compared with the micro-photoluminescence spectra taken along the single p-, n- and single nanowire pn-junctions to find the origin of the electroluminescence peaks, the distribution of doping species and the sharpness of the junctions.

  13. Fabrication of nanowires and nanostructures

    DEFF Research Database (Denmark)

    Mátéfi-Tempfli, Stefan; Mátéfi-Tempfli, M.; Piraux, L.

    2009-01-01

    We report on different approaches that we have adopted and developed for the fabrication of nanowires and nanostructures. Methods based on template synthesis and on self organization seem to be the most promising for the fabrication of nanomaterials and nanostructures due to their easiness and low...... cost. The development of a supported nanoporous alumina template and the possibility of using this template to combine electrochemical synthesis with lithographic methods open new ways for the fabrication of complex nanostructures. The numerous advantages of the supported template and its compatibility...

  14. Polyaniline-coated silver nanowires

    Czech Academy of Sciences Publication Activity Database

    Bober, Patrycja; Stejskal, Jaroslav; Trchová, Miroslava; Hromádková, Jiřina; Prokeš, J.

    2010-01-01

    Roč. 70, č. 9 (2010), s. 656-662 ISSN 1381-5148 R&D Projects: GA MŠk LA09028; GA ČR GA202/09/1626; GA ČR GA203/08/0686; GA AV ČR IAA100500902; GA AV ČR IAA400500905; GA AV ČR KAN200520704 Institutional research plan: CEZ:AV0Z40500505 Keywords : conducting polymer * conductivity * nanowire Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.546, year: 2010

  15. Nanodevices based on silicon nanowires.

    Science.gov (United States)

    Wan, Yuting; Sha, Jian; Chen, Bo; Fang, Yanjun; Wang, Zongli; Wang, Yewu

    2009-01-01

    Silicon nanowires (SiNWs) have been demonstrated as one of the promising building blocks for future nanodevices such as field effect transistors, solar cells, sensors and lithium battery; much progress has been made in this field during last decades. In this review paper, the synthesis and physical properties of SiNWs are introduced briefly. Significant advances of SiNWs-related nanodevices reported in recent literature and registered patents are reviewed. The latest development and prospects of SiNWs-related nanodevices are also discussed.

  16. n-Heptyl xanthate adsorption on a ZnS layer synthesized on germanium: an in situ attenuated total reflection IR study.

    Science.gov (United States)

    Fredriksson, Andreas; Larsson, Margareta L; Holmgren, Allan

    2005-06-01

    Adsorption of n-heptyl xanthate on synthesized zinc sulfide was followed in situ by monitoring the methylene absorption band at 2925 cm(-1). The zinc sulfide surface used in the adsorption experiments was synthesized on a germanium internal reflection element using the chemical bath deposition method. Characterization of the adsorbent surface was performed by X-ray photoelectron spectroscopy. The time needed to reach adsorption equilibrium varied with the initial concentration of the aqueous potassium heptyl xanthate solution. The amount of adsorbed xanthate ions increased with the concentration of the solution within the range studied (10 microM-50 mM). The experimental data are reasonably well described by the Langmuir adsorption isotherm. Polarized infrared attenuated total reflection (ATR) was used to determine the average orientation of the heptyl chains by measuring the absorbance of the infrared beam polarized perpendicularly and parallely to the plane of incidence. Measured absorbances were corrected for contribution from heptyl xanthate in bulk solution.

  17. Optical Properties of Rotationally Twinned Nanowire Superlattices

    DEFF Research Database (Denmark)

    Bao, Jiming; Bell, David C.; Capasso, Federico

    2008-01-01

    blende InP nanowires. We have constructed the energy band diagram of the resulting multiquantum well heterostructure and have performed detailed quantum mechanical calculations of the electron and hole wave functions. The excitation power dependent blue-shift of the photoluminescence can be explained...... a heterostructure in a chemically homogeneous nanowire material and alter in a major way its optical properties opens new possibilities for band-structure engineering.......We have developed a technique so that both transmission electron microscopy and microphotoluminescence can be performed on the same semiconductor nanowire over a large range of optical power, thus allowing us to directly correlate structural and optical properties of rotationally twinned zinc...

  18. Antimonide Heterostructure Nanowires - Growth, Physics and Devices

    OpenAIRE

    Borg, Mattias

    2012-01-01

    This thesis investigates the growth and application of antimonide heterostructure nanowires for low-power electronics. In the first part of the thesis, GaSb, InSb and InAsSb nanowire growth is presented, and the distinguishing features of the growth are described. It is found that the presence of Sb results in more than 50 at. % group-III concentration in the Au seed particle on top of the nanowires. It is further concluded that the effective V/III ratio inside the seed particle is reduced co...

  19. Growth of HgTe nanowires

    Science.gov (United States)

    Selvig, E.; Hadzialic, S.; Skauli, T.; Steen, H.; Hansen, V.; Trosdahl-Iversen, L.; van Rheenen, A. D.; Lorentzen, T.; Haakenaasen, R.

    2006-09-01

    HgTe nanowires nucleated by Au particles have been grown on Si and GaAs substrates by molecular beam epitaxy. The wires are polycrystalline. They evolve from crooked to straight during growth and have rounded to rectangular cross-sections. The widths are in the range 20-500 nm, with lengths up to 4 μm. The height of the nanowires is typically less than the width. The nanowires have been characterized by scanning electron microscopy, x-ray photoelectron spectroscopy, transmission electron microscopy and atomic force microscopy. The effects of substrate material, substrate preparation and growth conditions have been investigated.

  20. Rare earth silicide nanowires on silicon surfaces

    International Nuclear Information System (INIS)

    Wanke, Martina

    2008-01-01

    The growth, structure and electronic properties of rare earth silicide nanowires are investigated on planar and vicinal Si(001) und Si(111) surfaces with scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and angle-resolved photoelectron spectroscopy (ARPES). On all surfaces investigated within this work hexagonal disilicides are grown epitaxially with a lattice mismatch of -2.55% up to +0.83% along the hexagonal a-axis. Along the hexagonal c-axis the lattice mismatch is essentially larger with 6.5%. On the Si(001)2 x 1 surface two types of nanowires are grown epitaxially. The socalled broad wires show a one-dimensional metallic valence band structure with states crossing the Fermi level. Along the nanowires two strongly dispersing states at the anti J point and a strongly dispersing state at the anti Γ point can be observed. Along the thin nanowires dispersing states could not be observed. Merely in the direction perpendicular to the wires an intensity variation could be observed, which corresponds to the observed spacial structure of the thin nanowires. The electronic properties of the broad erbium silicide nanowires are very similar to the broad dysprosium silicide nanowires. The electronic properties of the DySi 2 -monolayer and the Dy 3 Si 5 -multilayer on the Si(111) surface are investigated in comparison to the known ErSi 2 /Si(111) and Er 3 Si 5 /Si(111) system. The positions and the energetic locations of the observed band in the surface Brillouin zone will be confirmed for dysprosium. The shape of the electron pockets in the vector k parallel space is elliptical at the anti M points, while the hole pocket at the anti Γ point is showing a hexagonal symmetry. On the Si(557) surface the structural and electronic properties depend strongly on the different preparation conditions likewise, in particular on the rare earth coverage. At submonolayer coverage the thin nanowires grow in wide areas of the sample surface, which are oriented

  1. Boron carbide nanowires with uniform CNx coatings

    Science.gov (United States)

    Zhang, H. Z.; Wang, R. M.; You, L. P.; Yu, J.; Chen, H.; Yu, D. P.; Chen, Y.

    2007-01-01

    Boron carbide nanowires with uniform carbon nitride coating layers were synthesized on a silicon substrate using a simple thermal process. The structure and morphology of the as-synthesized nanowires were characterized using x-ray diffraction, scanning and transmission electron microscopy and electron energy loss spectroscopy. A correlation between the surface smoothness of the nanowire sidewalls and their lateral sizes has been observed and it is a consequence of the anisotropic formation of the coating layers. A growth mechanism is also proposed for these growth phenomena.

  2. Fabrication and properties of silicon carbide nanowires

    Science.gov (United States)

    Shim, Hyun Woo

    2008-12-01

    Silicon carbide (SiC), with excellent electrical, thermal, and mechanical properties, is a promising material candidate for future devices such as high-temperature electronics and super-strong lightweight structures. Combined with superior intrinsic properties, the nanomaterials of SiC show further advantages thanks to nanoscale effects. This thesis reports the growth mechanism, the self-integration, and the friction of SiC nanowires. The study involves nanowires fabrication using thermal evaporation, structure characterization using electron microscopy, friction measurement, and theoretical modeling. The study on nanowire growth mechanism requires understanding of the surfaces and interfaces of nanowire crystal. The catalyzed growth of SiC nanowires involves interfaces between source vapor, catalytic liquid, and nanowire solid. Our experimental observation includes the periodical twinning in a faceted SiC nanowire and three stage structure transitions during the growth. The proposed theoretical model shows that such phenomenon is the result of surface energy minimization process during the catalytic growth. Surface interactions also exist between nanowires, leading to their self-integration. Our parametric growth study reveals novel self-integration of SiC-SiO 2 core-shell nanowires as a result of SiO2 joining. Attraction between nanowires through van der Waals force and enhanced SiO2 diffusion at high temperature transform individual nanowires to the integrated nanojunctions, nanocables, and finally nanowebs. We also show that such joining process becomes effective either during growth or by annealing. The solid friction is a result of the interaction between two solid surfaces, and it depends on the adhesion and the deformation of two contacting solids among other factors. Having strong adhesion as shown from gecko foot-hairs, nanostructured materials should also have strong friction; this study is the first to investigate friction of nanostructures under

  3. Semiconductor Nanowires for Photoelectrochemical Water Splitting

    Science.gov (United States)

    Hwang, Yun Jeong

    Photolysis of water with semiconductor materials has been investigated intensely as a clean and renewable energy resource by storing solar energy in chemical bonds such as hydrogen. One-dimensional (1D) nanostructures such as nanowires can provide several advantages for photoelectrochemical (PEC) water splitting due to their high surface areas and excellent charge transport and collection efficiency. This dissertation discusses various nanowire photoelectrodes for single or dual semiconductor systems, and their linked PEC cells for self-driven water splitting. After an introduction of solar water splitting in the first chapter, the second chapter demonstrates water oxidative activities of hydrothermally grown TiO2 nanowire arrays depending on their length and surface properties. The photocurrents with TiO2 nanowire arrays approach saturation due to their poor charge collection efficiency with longer nanowires despite increased photon absorption efficiency. Epitaxial grains of rutile atomic layer deposition (ALD) shell on TiO2 nanowire increase the photocurrent density by 1.5 times due to improved charge collection efficiency especially in the short wavelength region. Chapter three compares the photocurrent density of the planar Si and Si nanowire arrays coated by anatase ALD TiO 2 thin film as a model system of a dual bandgap system. The electroless etched Si nanowire coated by ALD TiO2 (Si EENW/TiO2) shows 2.5 times higher photocurrent density due to lower reflectance and higher surface area. Also, this chapter illustrates that n-Si/n-TiO2 heterojunction is a promising structure for the photoanode application of a dual semiconductor system, since it can enhance the photocurrent density compared to p-Si/n-TiO 2 junction with the assistance of bend banding at the interface. Chapter four demonstrates the charge separation and transport of photogenerated electrons and holes within a single asymmetric Si/TiO2 nanowire. Kelvin probe force microscopy measurements show

  4. Thermal stability of germanium-tin (GeSn) fins

    Science.gov (United States)

    Lei, Dian; Lee, Kwang Hong; Bao, Shuyu; Wang, Wei; Masudy-Panah, Saeid; Tan, Chuan Seng; Tok, Eng Soon; Gong, Xiao; Yeo, Yee-Chia

    2017-12-01

    We investigate the thermal stability of germanium-tin (Ge1-xSnx) fins under rapid thermal annealing in N2 ambient. The Ge1-xSnx fins were formed on a GeSn-on-insulator substrate and were found to be less thermally stable than blanket Ge1-xSnx films. The morphology change and material quality of the annealed Ge1-xSnx fin are investigated using scanning electron microscopy, Raman spectroscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electron energy loss spectroscopy. Obvious degradation of crystalline quality of the Ge0.96Sn0.04 fin was observed, and a thin Ge layer was formed on the SiO2 surface near the Ge0.96Sn0.04 fin region after 500 °C anneal. A model was proposed to explain the morphology change of the Ge0.96Sn0.04 fin.

  5. Photoconductivity in Transition Metal Doped Bismuth Germanium Oxide

    Science.gov (United States)

    Newkirk, Nolan M.; McCullough, J. S.; Martin, J. J.

    1999-10-01

    Bismuth germanium oxide (BGO) is a photorefractive material that has potential for a number of applications. We are investigating the possibility of tailoring it for specific uses by doping with 3d-ions. . Anti-site bismuth is a native defect in melt-grown BGO. This amphoteric defect dominates the photo-response of undoped BGO and plays a role in transition metal doped samples. The majority of the 3d-ions go into the tetrahedrally bonded Ge-site; thus, Cr would be expected to be in a 4+ state. Instead, it gives up an electron to the anti-site Bi and is in a 5+ state. Strongly persistent photorefractive gratings are observed in BGO:Cr. Photoconductivity measurements were performed on undoped BGO, BGO:V, and BGO:Cr before and after the samples were exposed to 442 nm light. The photoconductivity response roughly matched the optical absorption spectra of the samples. The exposed samples showed additional photo-induced absorption bands and much stronger photocurrents in the same spectral regions. The exposure to blue light appears to convert Cr from the 5+ state to the 4+state.

  6. Germane facts about germanium sesquioxide: I. Chemistry and anticancer properties.

    Science.gov (United States)

    Kaplan, Bonnie J; Parish, W Wesley; Andrus, G Merrill; Simpson, J Steven A; Field, Catherine J

    2004-04-01

    This paper reviews the history, chemistry, safety, toxicity, and anticancer effects of the organogermanium compound bis (2-carboxyethylgermanium) sesquioxide (CEGS). A companion review follows, discussing the inaccuracies in the scientific record that have prematurely terminated research on clinical uses of CEGS. CEGS is a unique organogermanium compound first made by Mironov and coworkers in Russia and, shortly thereafter, popularized by Asai and his colleagues in Japan. Low concentrations of germanium occur in nearly all soils, plants and animal life; natural occurrence of the CEGS form is postulated but not yet demonstrated. The literature demonstrating its anticancer effect is particularly strong: CEGS induces interferon-gamma (IFN-gamma), enhances natural killer cell activity, and inhibits tumor and metastatic growth--effects often detectable after a single oral dose. In addition, oral consumption of CEGS is readily assimilated and rapidly cleared from the body without evidence of toxicity. Given these findings, the absence of human clinical trials of CEGS is unexpected. Possible explanations of why the convincing findings from animal research have not been used to support clinical trials are discussed. Clinical trials on CEGS are recommended.

  7. Thermal stability of simple tetragonal and hexagonal diamond germanium

    Science.gov (United States)

    Huston, L. Q.; Johnson, B. C.; Haberl, B.; Wong, S.; Williams, J. S.; Bradby, J. E.

    2017-11-01

    Exotic phases of germanium, that form under high pressure but persist under ambient conditions, are of technological interest due to their unique optical and electrical properties. The thermal evolution and stability of two of these exotic Ge phases, the simple tetragonal (st12) and hexagonal diamond (hd) phases, are investigated in detail. These metastable phases, formed by high pressure decompression in either a diamond anvil cell or by nanoindentation, are annealed at temperatures ranging from 280 to 320 °C for st12-Ge and 200 to 550 °C for hd-Ge. In both cases, the exotic phases originated from entirely pure Ge precursor materials. Raman microspectroscopy is used to monitor the phase changes ex situ following annealing. Our results show that hd-Ge synthesized via a pure form of a-Ge first undergoes a subtle change in structure and then an irreversible phase transformation to dc-Ge with an activation energy of (4.3 ± 0.2) eV at higher temperatures. St12-Ge was found to transform to dc-Ge with an activation energy of (1.44 ± 0.08) eV. Taken together with results from previous studies, this study allows for intriguing comparisons with silicon and suggests promising technological applications.

  8. gamma-ray tracking in germanium the backtracking method

    CERN Document Server

    Marel, J V D

    2002-01-01

    In the framework of a European TMR network project the concept for a gamma-ray tracking array is being developed for nuclear physics spectroscopy in the energy range of approx 10 keV up to several MeV. The tracking array will consist of a large number of position-sensitive germanium detectors in a spherical geometry around a target. Due to the high segmentation, a Compton scattered gamma-ray will deposit energy in several different segments. A method has been developed to reconstruct the tracks of multiple coincident gamma-rays and to find their initial energies. By starting from the final point the track can be reconstructed backwards to the origin with the help of the photoelectric and Compton cross-sections and the Compton scatter formula. Every reconstructed track is given a figure of merit, thus allowing suppression of wrongly reconstructed tracks and gamma-rays that have scattered out of the detector system. This so-called backtracking method has been tested on simulated events in a shell-like geometry ...

  9. Etching of germanium-tin using ammonia peroxide mixture

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Yuan; Ong, Bin Leong; Wang, Wei; Gong, Xiao; Liang, Gengchiau; Yeo, Yee-Chia, E-mail: yeo@ieee.org [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Zhang, Zheng; Pan, Jisheng [Institute of Material Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, #08-03, Innovis, Singapore 138634 (Singapore); Tok, Eng-Soon [Department of Physics, National University of Singapore, Singapore 117551 (Singapore)

    2015-12-28

    The wet etching of germanium-tin (Ge{sub 1-x}Sn{sub x}) alloys (4.2% < x < 16.0%) in ammonia peroxide mixture (APM) is investigated. Empirical fitting of the data points indicates that the etch depth of Ge{sub 1-x}Sn{sub x} is proportional to the square root of the etch time t and decreases exponentially with increasing x for a given t. In addition, X-ray photoelectron spectroscopy results show that increasing t increases the intensity of the Sn oxide peak, whereas no obvious change is observed for the Ge oxide peak. This indicates that an accumulation of Sn oxide on the Ge{sub 1-x}Sn{sub x} surface decreases the amount of Ge atoms exposed to the etchant, which accounts for the decrease in etch rate with increasing etch time. Atomic force microscopy was used to examine the surface morphologies of the Ge{sub 0.918}Sn{sub 0.082} samples. Both root-mean-square roughness and undulation periods of the Ge{sub 1-x}Sn{sub x} surface were observed to increase with increasing t. This work provides further understanding of the wet etching of Ge{sub 1-x}Sn{sub x} using APM and may be used for the fabrication of Ge{sub 1-x}Sn{sub x}-based electronic and photonic devices.

  10. a Silicon Germanium Graded Junctionless Transistor with Low off Current

    Science.gov (United States)

    Surana, Neelam; Ghosh, Bahniman; Tripathy, Ball Mukund Mani; Salimath, Akshay Kumar

    2013-02-01

    We propose a Ge/Si graded junctionless transistor (JLT) which helps to reduce the band-to-band tunneling current in off-state for highly doped double gate junctionless transistor (DGJLT). In this paper, we show that there is large band-to-band tunneling (BTBT) current in off-state of silicon-channel and germanium-channel DGJLT, which causes increase in the off-state leakage current by several orders. With the help of band-gap engineering, we found that by using Ge/Si graded channel DGJLT off-state band-to-band tunneling current can be reduced. It is also observed that there is large deviation in the off-state leakage current with variation of drain voltage for Si and Ge body DGJLT, which reduces device stability. It is found that in Ge/Si graded DGJLT variation off-state leakage current with drain voltage is controlled. In Si and Ge, DGJLT electrons from the valence band of the channel tunnel to the conduction band of drain leaves holes which causes increased hole concentration in the channel creating parasitic 'BJT'.

  11. Comparison of CDMS [100] and [111] Oriented Germanium Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Leman, S.W.; Hertel, S.A.; /MIT, MKI; Kim, P.; /SLAC; Cabrera, B.; /Stanford U., Phys. Dept.; Do Couto E.Silva, E.; /SLAC; Figueroa-Feliciano, E.; McCarthy, K.A.; /MIT, MKI; Resch, R.; /SLAC; Sadoulet, B.; Sundqvist, K.M.; /UC, Berkeley

    2012-09-14

    The Cryogenic Dark Matter Search (CDMS) utilizes large mass, 3-inch diameter x 1-inch thick target masses as particle detectors. The target is instrumented with both phonon and ionization sensors and comparison of energy in each channel provides event-by-event classification of electron and nuclear recoils. Fiducial volume is determined by the ability to obtain good phonon and ionization signal at a particular location. Due to electronic band structure in germanium, electron mass is described by an anisotropic tensor with heavy mass aligned along the symmetry axis defined by the [111] Miller index (L valley), resulting in large lateral component to the transport. The spatial distribution of electrons varies significantly for detectors which have their longitudinal axis orientations described by either the [100] or [111] Miller indices. Electric fields with large fringing component at high detector radius also affect the spatial distribution of electrons and holes. Both effects are studied in a 3 dimensional Monte Carlo and the impact on fiducial volume is discussed.

  12. Point defect states in Sb-doped germanium

    International Nuclear Information System (INIS)

    Patel, Neil S.; Monmeyran, Corentin; Agarwal, Anuradha; Kimerling, Lionel C.

    2015-01-01

    Defect states in n-type Sb-doped germanium were investigated by deep-level transient spectroscopy. Cobalt-60 gamma rays were used to generate isolated vacancies and interstitials which diffuse and react with impurities in the material to form four defect states (E 37 , E 30 , E 22 , and E 21 ) in the upper half of the bandgap. Irradiations at 77 K and 300 K as well as isothermal anneals were performed to characterize the relationships between the four observable defects. E 37 is assigned to the Sb donor-vacancy associate (E-center) and is the only vacancy containing defect giving an estimate of 2 × 10 11  cm −3  Mrad −1 for the uncorrelated vacancy-interstitial pair introduction rate. The remaining three defect states are interstitial associates and transform among one another. Conversion ratios between E 22 , E 21 , and E 30 indicate that E 22 likely contains two interstitials

  13. Nanopatterning of ultrananocrystalline diamond nanowires.

    Science.gov (United States)

    Wang, Xinpeng; Ocola, Leonidas E; Divan, Ralu S; Sumant, Anirudha V

    2012-02-24

    We report the fabrication of horizontally aligned ultrananocrystalline diamond (UNCD) nanowires (NWs) via two different approaches. First, with the top-down approach by using electron beam lithography (EBL) and reactive ion etching (RIE) with a photo resist layer as an etch mask. Using this approach, we demonstrate fabrication of 50 µm long UNCD NWs with widths as narrow as 40 nm. We further present an alternative approach to grow UNCD NWs at pre-defined positions through a selective seeding process. No RIE was needed either to etch the NWs or to remove the mask. In this case, we achieved UNCD NWs with lengths of 50 µm and smallest width of 90 nm respectively. Characterization of these nanowires by using scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that the UNCD NWs are well defined and fully released, with no indication of residual stress. Characterization using visible and ultraviolet (UV) Raman spectroscopy indicates that in both fabrication approaches, UNCD NWs maintain their intrinsic diamond structure.

  14. Controllable growth of stable germanium dioxide ultra-thin layer by means of capacitively driven radio frequency discharge

    Energy Technology Data Exchange (ETDEWEB)

    Svarnas, P., E-mail: svarnas@ece.upatras.gr [High Voltage Laboratory, Department of Electrical and Computer Engineering, University of Patras, Rion 26 504, Patras (Greece); Botzakaki, M.A. [Department of Physics, University of Patras, Rion 26 504 (Greece); Skoulatakis, G.; Kennou, S.; Ladas, S. [Surface Science Laboratory, Department of Chemical Engineering, University of Patras, Rion 26 504 (Greece); Tsamis, C. [NCSR “Demokritos”, Institute of Advanced Materials, Physicochemical Processes, Nanotechnology & Microsystems, Aghia Paraskevi 15 310, Athens (Greece); Georga, S.N.; Krontiras, C.A. [Department of Physics, University of Patras, Rion 26 504 (Greece)

    2016-01-29

    It is well recognized that native oxide of germanium is hygroscopic and water soluble, while germanium dioxide is thermally unstable and it is converted to volatile germanium oxide at approximately 400 °C. Different techniques, implementing quite complicated plasma setups, gas mixtures and substrate heating, have been used in order to grow a stable germanium oxide. In the present work a traditional “RF diode” is used for germanium oxidation by cold plasma. Following growth, X-ray photoelectron spectroscopy demonstrates that traditional capacitively driven radio frequency discharges, using molecular oxygen as sole feedstock gas, provide the possibility of germanium dioxide layer growth in a fully reproducible and controllable manner. Post treatment ex-situ analyses on day-scale periods disclose the stability of germanium oxide at room ambient conditions, offering thus the ability to grow (ex-situ) ultra-thin high-k dielectrics on top of germanium oxide layers. Atomic force microscopy excludes any morphological modification in respect to the bare germanium surface. These results suggest a simple method for a controllable and stable germanium oxide growth, and contribute to the challenge to switch to high-k dielectrics as gate insulators for high-performance metal-oxide-semiconductor field-effect transistors and to exploit in large scale the superior properties of germanium as an alternative channel material in future technology nodes. - Highlights: • Simple one-frequency reactive ion etcher develops GeO{sub 2} thin layers controllably. • The layers remain chemically stable at ambient conditions over day-scale periods. • The layers are unaffected by the ex-situ deposition of high-k dielectrics onto them. • GeO{sub 2} oxidation and high-k deposition don't affect the Ge morphology significantly. • These conditions contribute to improved Ge-based MOS structure fabrication.

  15. Ballistic transport in gold [110] nanowire

    Science.gov (United States)

    Kurui, Yoshihiko; Oshima, Yoshifumi; Okamoto, Masakuni; Takayanagi, Kunio

    2009-03-01

    Conductance of gold nanowire elongated along the [110] direction (gold [110] nanowire) was measured during many breaking procedures, while simultaneously acquiring transmission electron microscope images. The conductance histogram exhibits a series of peaks whose conductance values increased nearly in steps of the conductance quantum, G0 =2e^2/h. However thick nanowires above 10G0 showed dequantization, where the increment was only 0.9G0. The structure for each peak was determined to be either an atomic sheet or a hexagonal prism. The number of conductance channels calculated for each atomic structure by first principles theory, coincided well with the peak index in the conductance histogram. The present study shows that the [110] nanowire behave as ballistic conductors, and a conductance peak appears whenever a conductance channel is opened.

  16. Nonradiative Step Facets in Semiconductor Nanowires.

    Science.gov (United States)

    Sanchez, Ana M; Zhang, Yunyan; Tait, Edward W; Hine, Nicholas D M; Liu, Huiyun; Beanland, Richard

    2017-04-12

    One of the main advantages of nanowires for functional applications is their high perfection, which results from surface image forces that act on line defects such as dislocations, rendering them unstable and driving them out of the crystal. Here we show that there is a class of step facets that are stable in nanowires, with no long-range strain field or dislocation character. In zinc-blende semiconductors, they take the form of Σ3 (112) facets with heights constrained to be a multiple of three {111} monolayers. Density functional theory calculations show that they act as nonradiative recombination centers and have deleterious effects on nanowire properties. We present experimental observations of these defects on twin boundaries and twins that terminate inside GaAsP nanowires and find that they are indeed always multiples of three monolayers in height. Strategies to use the three-monolayer rule during growth to prevent their formation are discussed.

  17. Techniques to distinguish between electron and photon induced events using segmented germanium detectors

    Energy Technology Data Exchange (ETDEWEB)

    Kroeninger, K.

    2007-06-05

    Two techniques to distinguish between electron and photon induced events in germanium detectors were studied: (1) anti-coincidence requirements between the segments of segmented germanium detectors and (2) the analysis of the time structure of the detector response. An 18-fold segmented germanium prototype detector for the GERDA neutrinoless double beta-decay experiment was characterized. The rejection of photon induced events was measured for the strongest lines in {sup 60}Co, {sup 152}Eu and {sup 228}Th. An accompanying Monte Carlo simulation was performed and the results were compared to data. An overall agreement with deviations of the order of 5-10% was obtained. The expected background index of the GERDA experiment was estimated. The sensitivity of the GERDA experiment was determined. Special statistical tools were developed to correctly treat the small number of events expected. The GERDA experiment uses a cryogenic liquid as the operational medium for the germanium detectors. It was shown that germanium detectors can be reliably operated through several cooling cycles. (orig.)

  18. Biallelic and Genome Wide Association Mapping of Germanium Tolerant Loci in Rice (Oryza sativa L..

    Directory of Open Access Journals (Sweden)

    Partha Talukdar

    Full Text Available Rice plants accumulate high concentrations of silicon. Silicon has been shown to be involved in plant growth, high yield, and mitigating biotic and abiotic stresses. However, it has been demonstrated that inorganic arsenic is taken up by rice through silicon transporters under anaerobic conditions, thus the ability to efficiently take up silicon may be considered either a positive or a negative trait in rice. Germanium is an analogue of silicon that produces brown lesions in shoots and leaves, and germanium toxicity has been used to identify mutants in silicon and arsenic transport. In this study, two different genetic mapping methods were performed to determine the loci involved in germanium sensitivity in rice. Genetic mapping in the biparental cross of Bala × Azucena (an F6 population and a genome wide association (GWA study with 350 accessions from the Rice Diversity Panel 1 were conducted using 15 μM of germanic acid. This identified a number of germanium sensitive loci: some co-localised with previously identified quantitative trait loci (QTL for tissue silicon or arsenic concentration, none co-localised with Lsi1 or Lsi6, while one single nucleotide polymorphism (SNP was detected within 200 kb of Lsi2 (these are genes known to transport silicon, whose identity was discovered using germanium toxicity. However, examining candidate genes that are within the genomic region of the loci detected above reveals genes homologous to both Lsi1 and Lsi2, as well as a number of other candidate genes, which are discussed.

  19. High-performance single nanowire tunnel diodes.

    Science.gov (United States)

    Wallentin, Jesper; Persson, Johan M; Wagner, Jakob B; Samuelson, Lars; Deppert, Knut; Borgström, Magnus T

    2010-03-10

    We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27.6 at liquid helium temperature. These sub-100-nm-diameter structures are promising components for solar cells as well as electronic applications.

  20. Efficient nitrogen incorporation in ZnO nanowires.

    Science.gov (United States)

    Stehr, Jan E; Chen, Weimin M; Reddy, Nandanapalli Koteeswara; Tu, Charles W; Buyanova, Irina A

    2015-08-24

    One-dimensional ZnO nanowires (NWs) are a promising materials system for a variety of applications. Utilization of ZnO, however, requires a good understanding and control of material properties that are largely affected by intrinsic defects and contaminants. In this work we provide experimental evidence for unintentional incorporation of nitrogen in ZnO NWs grown by rapid thermal chemical vapor deposition, from electron paramagnetic resonance spectroscopy. The incorporated nitrogen atoms are concluded to mainly reside at oxygen sites (NO). The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in bulk. This implies a lower defect formation energy at the NW surface as compared with its bulk value, consistent with theoretical predictions. The revealed facilitated incorporation of nitrogen in ZnO nanostructures may be advantageous for realizing p-type conducting ZnO via N doping. The awareness of this process can also help to prevent such unintentional doping in structures with desired n-type conductivity.

  1. Germanium enrichment in supergene settings: evidence from the Cristal nonsulfide Zn prospect, Bongará district, northern Peru

    Science.gov (United States)

    Mondillo, Nicola; Arfè, Giuseppe; Herrington, Richard; Boni, Maria; Wilkinson, Clara; Mormone, Angela

    2018-02-01

    Supergene nonsulfide ores form from the weathering of sulfide mineralization. Given the geochemical affinity of Ge to Si4+ and Fe3+, weathering of Ge-bearing sulfides could potentially lead to Ge enrichments in silicate and Fe-oxy-hydroxide minerals, although bulk rock Ge concentrations in supergene nonsulfide deposits are rarely reported. Here, we present the results of an investigation into Ge concentrations and deportment in the Cristal supergene Zn nonsulfide prospect (Bongará, northern Peru), which formed from the weathering of a preexisting Mississippi Valley-type (MVT) sulfide deposit. Material examined in this study originates from drillcore recovered from oxidized Zn-rich bodies 15-20 m thick, containing 5-45 wt% Zn and Ge concentrations 100 ppm. Microanalysis and laser ablation-ICP-MS show that precursor sphalerite is rich in both Fe (mean Fe = 8.19 wt%) and Ge (mean Ge = 142 ppm). Using the mineral geothermometer GGIMFis—geothermometer for Ga, Ge, In, Mn, and Fe in sphalerite—proposed by Frenzel et al. (Ore Geol Rev 76:52-78, 2016), sphalerite trace element data from the Cristal prospect suggest a possible formation temperature ( T GGIMFis) of 225 ± 50 °C, anomalously high for a MVT deposit. Germanium concentrations measured in both goethite (mean values 100 to 229 ppm, max 511 ppm) and hemimorphite (mean values 39 to 137 ppm, max 258 ppm) are similar to concentrations measured in hypogene sphalerite. Additionally, the Ge concentrations recorded in bulk rock analyses of sphalerite-bearing and oxidized samples are also similar. A persistent warm-humid climate is interpreted for the region, resulting in the development of an oxidation zone favoring the formation of abundant Zn hydrosilicates and Fe hydroxides, both able to incorporate Ge in their crystal structure. In this scenario, Ge has been prevented from dispersion during the weathering of the Ge-bearing sulfide bodies and remains in the resultant nonsulfide ore.

  2. Growth and characterization of bismuth telluride nanowires

    International Nuclear Information System (INIS)

    Picht, Oliver

    2010-01-01

    Polycrystalline Bi 2 Te 3 nanowires are electrochemically grown in ion track-etched polycarbonate membranes. Potentiostatic growth is demonstrated in templates of various thicknesses ranging from 10 to 100 μm. The smallest observed nanowire diameters are 20 nm in thin membranes and approx. 140-180 nm in thicker membranes. The influence of the various deposition parameters on the nanowire growth rate is presented. Slower growth rates are attained by selective change of deposition potentials and lower temperatures. Nanowires synthesized at slower growth rates have shown to possess a higher degree of crystalline order and smoother surface contours. With respect to structural properties, X-ray diffraction and transmission electron microscopy verified the growth of Bi 2 Te 3 and evidenced the stability of specific properties, e.g. grain size or preferential orientation, with regard to variations in the deposition conditions. The interdependency of the fabrication parameters, i.e. temperature, deposition potential and nanochannel diameters, is demonstrated for wires grown in 30 μm thick membranes. It is visible from diffraction analysis that texture is tunable by the growth conditions but depends also on the size of the nanochannels in the template. Both (015) and (110) reflexes are observed for the nanowire arrays. Energy dispersive X-ray analysis further points out that variation of nanochannel size could lead to a change in elemental composition of the nanowires. (orig.)

  3. Growth and characterization of bismuth telluride nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Picht, Oliver

    2010-05-26

    Polycrystalline Bi{sub 2}Te{sub 3} nanowires are electrochemically grown in ion track-etched polycarbonate membranes. Potentiostatic growth is demonstrated in templates of various thicknesses ranging from 10 to 100 {mu}m. The smallest observed nanowire diameters are 20 nm in thin membranes and approx. 140-180 nm in thicker membranes. The influence of the various deposition parameters on the nanowire growth rate is presented. Slower growth rates are attained by selective change of deposition potentials and lower temperatures. Nanowires synthesized at slower growth rates have shown to possess a higher degree of crystalline order and smoother surface contours. With respect to structural properties, X-ray diffraction and transmission electron microscopy verified the growth of Bi{sub 2}Te{sub 3} and evidenced the stability of specific properties, e.g. grain size or preferential orientation, with regard to variations in the deposition conditions. The interdependency of the fabrication parameters, i.e. temperature, deposition potential and nanochannel diameters, is demonstrated for wires grown in 30 {mu}m thick membranes. It is visible from diffraction analysis that texture is tunable by the growth conditions but depends also on the size of the nanochannels in the template. Both (015) and (110) reflexes are observed for the nanowire arrays. Energy dispersive X-ray analysis further points out that variation of nanochannel size could lead to a change in elemental composition of the nanowires. (orig.)

  4. Hydrogen Generation from Photocatalytic Silver|Zinc Oxide Nanowires: Towards Multifunctional Multisegmented Nanowire Devices

    NARCIS (Netherlands)

    Maijenburg, A.W.; Rodijk, E.J.B.; Maas, M.G.; Enculescu, Monica; Blank, David H.A.; ten Elshof, Johan E.

    2011-01-01

    Photoactive nanowires: A novel photo-electrochemical nanowire diode that catalyzes the conversion of methanol and water to hydrogen under UV light is demonstrated. The wire consists of a metal and a metal oxide segment that are connected via a Schottky barrier. Other functions, such as remote-

  5. Optical haze of randomly arranged silver nanowire transparent conductive films with wide range of nanowire diameters

    Directory of Open Access Journals (Sweden)

    M. Marus

    2018-03-01

    Full Text Available The effect of the diameter of randomly arranged silver nanowires on the optical haze of silver nanowire transparent conductive films was studied. Proposed simulation model behaved similarly with the experimental results, and was used to theoretically study the optical haze of silver nanowires with diameters in the broad range from 30 nm and above. Our results show that a thickening of silver nanowires from 30 to 100 nm results in the increase of the optical haze up to 8 times, while from 100 to 500 nm the optical haze increases only up to 1.38. Moreover, silver nanowires with diameter of 500 nm possess up to 5% lower optical haze and 5% higher transmittance than 100 nm thick silver nanowires for the same 10-100 Ohm/sq sheet resistance range. Further thickening of AgNWs can match the low haze of 30 nm thick AgNWs, but at higher transmittance. The results obtained from this work allow deeper analysis of the silver nanowire transparent conductive films from the perspective of the diameter of nanowires for various optoelectronic devices.

  6. CuO nanowire/microflower/nanowire modified Cu electrode with enhanced electrochemical performance for non-enzymatic glucose sensing.

    Science.gov (United States)

    Li, Changli; Yamahara, Hiroyasu; Lee, Yaerim; Tabata, Hitoshi; Delaunay, Jean-Jacques

    2015-07-31

    CuO nanowire/microflower structure on Cu foil is synthesized by annealing a Cu(OH)2 nanowire/CuO microflower structure at 250 °C in air. The nanowire/microflower structure with its large surface area leads to an efficient catalysis and charge transfer in glucose detection, achieving a high sensitivity of 1943 μA mM(-1) cm(-2), a wide linear range up to 4 mM and a low detection limit of 4 μM for amperometric glucose sensing in alkaline solution. With a second consecutive growth of CuO nanowires on the microflowers, the sensitivity of the obtained CuO nanowire/microflower/nanowire structure further increases to 2424 μA mM(-1) cm(-2), benefiting from an increased number of electrochemically active sites. The enhanced electrocatalytic performance of the CuO nanowire/microflower/nanowire electrode compared to the CuO nanowire/microflower electrode, CuO nanowire electrode and CuxO film electrode provides evidence for the significant role of available surface area for electrocatalysis. The rational combination of CuO nanowire and microflower nanostructures into a nanowire supporting microflower branching nanowires structure makes it a promising composite nanostructure for use in CuO based electrochemical sensors with promising analytical properties.

  7. Nanowire assembly, e.g. for optical probes, comprises optically trapping high aspect ratio semiconductor nanowire with infrared single-beam optical trap and attaching nanowire to organic or inorganic structure

    OpenAIRE

    Pauzauskie, P.; Radenovic, A.; Trepagnier, E.; Liphardt, J.; Yang, P.

    2007-01-01

    NOVELTY - A nanowire assembly method comprises optically trapping a semiconductor nanowire with an infrared single-beam optical trap and attaching the nanowire to an organic or inorganic structure by laser fusing. The nanowire is further trapped in a fluid environment. The optical trap has a beam wavelength of 1064 nm. The nanowire has an aspect ratio greater than 100 and a diameter less than 100 (preferably less than 80) nm. The nanowire and the organic or inorganic structure form a heterost...

  8. Resistance Fluctuations in GaAs Nanowire Grids

    Directory of Open Access Journals (Sweden)

    Ivan Marasović

    2014-01-01

    Full Text Available We present a numerical study on resistance fluctuations in a series of nanowire-based grids. Each grid is made of GaAs nanowires arranged in parallel with metallic contacts crossing all nanowires perpendicularly. Electrical properties of GaAs nanowires known from previous experimental research are used as input parameters in the simulation procedure. Due to the nonhomogeneous doping, the resistivity changes along nanowire. Allowing two possible nanowire orientations (“upwards” or “downwards”, the resulting grid is partially disordered in vertical direction which causes resistance fluctuations. The system is modeled using a two-dimensional random resistor network. Transfer-matrix computation algorithm is used to calculate the total network resistance. It is found that probability density function (PDF of resistance fluctuations for a series of nanowire grids changes from Gaussian behavior towards the Bramwell-Holdsworth-Pinton distribution when both nanowire orientations are equally represented in the grid.

  9. Vertical power MOS transistor as a thermoelectric quasi-nanowire device

    Science.gov (United States)

    Roizin, Gregory; Beeri, Ofer; Peretz, Mor Mordechai; Gelbstein, Yaniv

    2016-12-01

    Nano-materials exhibit superior performance over bulk materials in a variety of applications such as direct heat to electricity thermoelectric generators (TEGs) and many more. However, a gap still exists for the integration of these nano-materials into practical applications. This study explores the feasibility of utilizing the advantages of nano-materials' thermo-electric properties, using regular bulk technology. Present-day TEGs are often applied by dedicated thermoelectric materials such as semiconductor alloys (e.g., PbTe, BiTe) whereas the standard semiconductor materials such as the doped silicon have not been widely addressed, with limited exceptions of nanowires. This study attempts to close the gap between the nano-materials' properties and the well-established bulk devices, approached for the first time by exploiting the nano-metric dimensions of the conductive channel in metal-oxide-semiconductor (MOS) structures. A significantly higher electrical current than expected from a bulk silicon device has been experimentally measured as a result of the application of a positive gate voltage and a temperature gradient between the "source" and the "drain" terminals of a commercial NMOS transistor. This finding implies on a "quasi-nanowire" behaviour of the transistor channel, which can be easily controlled by the transistor's gate voltage that is applied. This phenomenon enables a considerable improvement of silicon based TEGs, fabricated by traditional silicon technology. Four times higher ZT values (TEG quality factor) compared to conventional bulk silicon have been observed for an off-the-shelf silicon device. By optimizing the device, it is believed that even higher ZT values can be achieved.

  10. PREFACE: 2nd Workshop on Germanium Detectors and Technologies

    Science.gov (United States)

    Abt, I.; Majorovits, B.; Keller, C.; Mei, D.; Wang, G.; Wei, W.

    2015-05-01

    The 2nd workshop on Germanium (Ge) detectors and technology was held at the University of South Dakota on September 14-17th 2014, with more than 113 participants from 8 countries, 22 institutions, 15 national laboratories, and 8 companies. The participants represented the following big projects: (1) GERDA and Majorana for the search of neutrinoless double-beta decay (0νββ) (2) SuperCDMS, EDELWEISS, CDEX, and CoGeNT for search of dark matter; (3) TEXONO for sub-keV neutrino physics; (4) AGATA and GRETINA for gamma tracking; (5) AARM and others for low background radiation counting; (5) as well as PNNL and LBNL for applications of Ge detectors in homeland security. All participants have expressed a strong desire on having better understanding of Ge detector performance and advancing Ge technology for large-scale applications. The purpose of this workshop was to leverage the unique aspects of the underground laboratories in the world and the germanium (Ge) crystal growing infrastructure at the University of South Dakota (USD) by brining researchers from several institutions taking part in the Experimental Program to Stimulate Competitive Research (EPSCoR) together with key leaders from international laboratories and prestigious universities, working on the forefront of the intensity to advance underground physics focusing on the searches for dark matter, neutrinoless double-beta decay (0νββ), and neutrino properties. The goal of the workshop was to develop opportunities for EPSCoR institutions to play key roles in the planned world-class research experiments. The workshop was to integrate individual talents and existing research capabilities, from multiple disciplines and multiple institutions, to develop research collaborations, which includes EPSCor institutions from South Dakota, North Dakota, Alabama, Iowa, and South Carolina to support multi-ton scale experiments for future. The topic areas covered in the workshop were: 1) science related to Ge

  11. The MAJORANA DEMONSTRATOR: A Search for Neutrinoless Double-beta Decay of Germanium-76

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, Alexis G.; Aguayo, Estanislao; Avignone, F. T.; Zhang, C.; Back, Henning O.; Barabash, Alexander S.; Bergevin, M.; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Collar, J. I.; Combs, Dustin C.; Cooper, R. J.; Detwiler, Jason A.; Leon, Jonathan D.; Doe, Peter J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S. R.; Esterline, James H.; Fast, James E.; Fields, N.; Finnerty, P.; Fraenkle, Florian; Gehman, Victor M.; Giovanetti, G. K.; Green, M.; Guiseppe, Vincente; Gusey, K.; Hallin, A. L.; Hazama, R.; Henning, Reyco; Hime, Andrew; Hoppe, Eric W.; Horton, Mark; Howard, Stanley; Howe, Mark; Johnson, R. A.; Keeter, K.; Keillor, Martin E.; Keller, C.; Kephart, Jeremy D.; Kidd, M. F.; Knecht, A.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; LaFerriere, Brian D.; LaRoque, B. H.; Leviner, L.; Loach, J. C.; MacMullin, S.; Marino, Michael G.; Martin, R. D.; Mei, Dong-Ming; Merriman, Jason H.; Miller, M. L.; Mizouni, Leila; Nomachi, Masaharu; Orrell, John L.; Overman, Nicole R.; Phillips, D.; Poon, Alan; Perumpilly, Gopakumar; Prior, Gersende; Radford, D. C.; Rielage, Keith; Robertson, R. G. H.; Ronquest, M. C.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Sobolev, V.; Steele, David; Strain, J.; Thomas, K.; Timkin, V.; Tornow, Werner; Vanyushin, I.; Varner, R. L.; Vetter, Kai; Vorren, Kris R.; Wilkerson, J. F.; Wolfe, B. A.; Yakushev, E.; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir

    2012-09-28

    The observation of neutrinoless double-beta decay would determine whether the neutrino is a Majorana particle and provide information on the absolute scale of neutrino mass. The MAJORANA Collaboration is constructing the DEMONSTRATOR, an array of germanium detectors, to search for neutrinoless double-beta decay of 76Ge. The DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment. Operation of the DEMONSTRATOR aims to determine whether a future tonne-scale germanium experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge neutrinoless double-beta decay Q-value of 2039 keV.

  12. Normal processes of phonon-phonon scattering and thermal conductivity of germanium crystals with isotopic disorder

    CERN Document Server

    Kuleev, I G

    2001-01-01

    The effect of normal processes of the phonon-phonon scattering on the thermal conductivity of the germanium crystals with various isotopic disorder degrees is considered. The phonon pulse redistribution in the normal scattering processes both inside each oscillatory branch (the Simons mechanism) and between various phonon oscillatory branches (the Herring mechanism) is accounted for. The contributions of the longitudinal and cross-sectional phonons drift motion into the thermal conductivity are analyzed. It is shown that the pulse redistribution in the Herring relaxation mechanism leads to essential suppression of the longitudinal phonons drift motion in the isotopically pure germanium crystals. The calculations results of thermal conductivity for the Herring relaxation mechanism agree well with experimental data on the germanium crystals with various isotopic disorder degrees

  13. Use of Germanium as comparator and integral monitor of neutron flux in activation analysis

    International Nuclear Information System (INIS)

    Furnari, Juan C.; Cohen, Isaac M.; Arribere, Maria A.; Kestelman, Abraham J.

    1997-01-01

    The possibility of using germanium as monitor of the thermal and epithermal components of the neutron flux, and comparator in parametric activation analysis, is discussed. The advantages and drawbacks associated to the use of this element are commented on, and the comparison with zirconium, in terms of the determination relative error, is performed. The utilisation of germanium as integral flux monitor, including the fast component of the neutron spectrum, is also discussed. Data corresponding to measurements of k 0 factor for the most relevant gamma transitions from Ge-75 and Be-77 are presented, as well as the results of the reference material analysis, employing germanium as flux monitor and comparator in a simultaneous way. (author). 8 refs., 3 figs., 2 tabs

  14. [Subacute and subchronic oral toxicity of beta-bis carboxyethyl sesquioxide of germanium in the rat].

    Science.gov (United States)

    Anger, F; Anger, J P; Guillou, L; Sado, P A; Papillon, A

    1991-12-01

    After a brief recall of toxicological data about germanium compounds, the authors relate subacute and subchronic oral toxicities of beta bis carboxyethyl-germanium sesquioxide in rats. During 28 days and six months, male and female animals have received 1 mg/kg/day. No particular toxic symptoms, no behaviour trouble except a small decrease of body weight, in male rats, at the end of the 6-month experimentation, were observed. A light decrease of erythropoiesis and a general stimulation of cellular metabolism has been noticed after 28 days. The only marked effect was a moderate renal deficiency characterized by a tubular disease with presence of cylinders, swelling of tubulus cells and floculus amounts after 6 months. Germanium urinary excretion was constant and linked to the received dose. Six months later, no preferential accumulation in organs was observed.

  15. Germanium field-effect transistor made from a high-purity substrate

    International Nuclear Information System (INIS)

    Hansen, W.L.; Goulding, F.S.; Haller, E.E.

    1978-11-01

    Field effect transistors have been fabricated on high-purity germanium substrates using low-temperature technology. The aim of this work is to preserve the low density of trapping centers in high-quality starting material by low-temperature ( 0 C) processing. The use of germanium promises to eliminate some of the traps which cause generation-recombination noise in silicon field-effect transistors (FET's) at low temperatures. Typically, the transconductance (g/sub m/) in the germanium FET's is 10 mA/V and the gate leakage can be less than 10 -12 A. Present devices exhibit a large 1/f noise component and most of this noise must be eliminated if they are to be competitive with silicon FET's commonly used in high-resolution nuclear spectrometers

  16. Classification of 3-3 transitions in neonlike germanium in laser-produced plasma

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, G. (Inst. of Laser Engineering, Osaka Univ., Osaka (Japan)); Kato, Y. (Inst. of Laser Engineering, Osaka Univ., Osaka (Japan)); Daido, H. (Inst. of Laser Engineering, Osaka Univ., Osaka (Japan)); Kodama, R. (Inst. of Laser Engineering, Osaka Univ., Osaka (Japan)); Murai, K. (Inst. of Laser Engineering, Osaka Univ., Osaka (Japan)); Nakai, S. (Inst. of Laser Engineering, Osaka Univ., Osaka (Japan))

    1994-11-01

    Classification of 3-3 transitions in neonlike germanium in laser-produced plasma has been made. The spectra have been observed in the range of 185-290 A using a high resolving power ([lambda]/[Delta][lambda][proportional to]13000) grazing-incidence spectrometer in XUV laser experiment. A total of 21 lines (including five lasing lines) have been classified as transitions between the 2s[sup 2] 2p[sup 5] 3s, 3p, 3d or 2s 2p[sup 6] 3p, 3d and sodiumlike germanium configurations. The identified transitions have been used to derive energy levels of 2s[sup 2] 2p[sup 5] 3l in neonlike germanium. The experimental results have been compared with theoretical predictions from Dirac-Fock (MCDF) calculations. (orig.)

  17. Two-Dimensional Spatial Imaging of Charge Transport in Germanium Crystals at Cryogenic Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Moffatt, Robert [Stanford Univ., CA (United States)

    2016-03-01

    In this dissertation, I describe a novel apparatus for studying the transport of charge in semiconductors at cryogenic temperatures. The motivation to conduct this experiment originated from an asymmetry observed between the behavior of electrons and holes in the germanium detector crystals used by the Cryogenic Dark Matter Search (CDMS). This asymmetry is a consequence of the anisotropic propagation of electrons in germanium at cryogenic temperatures. To better model our detectors, we incorporated this effect into our Monte Carlo simulations of charge transport. The purpose of the experiment described in this dissertation is to test those models in detail. Our measurements have allowed us to discover a shortcoming in our most recent Monte Carlo simulations of electrons in germanium. This discovery would not have been possible without the measurement of the full, two-dimensional charge distribution, which our experimental apparatus has allowed for the first time at cryogenic temperatures.

  18. Impurity diffusion, point defect engineering, and surface/interface passivation in germanium

    KAUST Repository

    Chroneos, Alexander I.

    2012-01-26

    In recent years germanium has been emerging as a mainstream material that could have important applications in the microelectronics industry. The principle aim of this study is to review investigations of the diffusion of technologically important p- and n-type dopants as well as surface and interface passivation issues in germanium. The diffusion of impurities in germanium is interrelated to the formation of clusters whenever possible, and possibilities for point defect engineering are discussed in view of recent results. The importance of electrically active defects on the Ge surface and interfaces is addressed considering strategies to suppress them and to passivate the surfaces/interfaces, bearing in mind their importance for advanced devices. © 2012 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Improved proton CT imaging using a bismuth germanium oxide scintillator

    Science.gov (United States)

    Tanaka, Sodai; Nishio, Teiji; Tsuneda, Masato; Matsushita, Keiichiro; Kabuki, Shigeto; Uesaka, Mitsuru

    2018-02-01

    Range uncertainty is among the most formidable challenges associated with the treatment planning of proton therapy. Proton imaging, which includes proton radiography and proton computed tomography (pCT), is a useful verification tool. We have developed a pCT detection system that uses a thick bismuth germanium oxide (BGO) scintillator and a CCD camera. The current method is based on a previous detection system that used a plastic scintillator, and implements improved image processing techniques. In the new system, the scintillation light intensity is integrated along the proton beam path by the BGO scintillator, and acquired as a two-dimensional distribution with the CCD camera. The range of a penetrating proton is derived from the integrated light intensity using a light-to-range conversion table, and a pCT image can be reconstructed. The proton range in the BGO scintillator is shorter than in the plastic scintillator, so errors due to extended proton ranges can be reduced. To demonstrate the feasibility of the pCT system, an experiment was performed using a 70 MeV proton beam created by the AVF930 cyclotron at the National Institute of Radiological Sciences. The accuracy of the light-to-range conversion table, which is susceptible to errors due to its spatial dependence, was investigated, and the errors in the acquired pixel values were less than 0.5 mm. Images of various materials were acquired, and the pixel-value errors were within 3.1%, which represents an improvement over previous results. We also obtained a pCT image of an edible chicken piece, the first of its kind for a biological material, and internal structures approximately one millimeter in size were clearly observed. This pCT imaging system is fast and simple, and based on these findings, we anticipate that we can acquire 200 MeV pCT images using the BGO scintillator system.

  20. Electronic and magnetic properties of perfect and defected germanium nanoribbons

    International Nuclear Information System (INIS)

    Pang Qing; Zhang Yan; Zhang Jianmin; Ji, Vincent; Xu Kewei

    2011-01-01

    Highlights: · Perfect AGeNRs are NM semiconductor with three-branch band gaps and decaying profiles. · Perfect ZGeNRs are AFM semiconductor with a decreasing band gap as width increases. · The band gap of AGeNRs can be tuned by mono- or di-vacancy at different positions. · Metallization can be realized in ZGeNRs by mono- or di-vacancy at different positions. · Magnetic properties of ZGeNRs depend closely upon the vacancy positions. - Abstract: The electronic and magnetic properties of both perfect and defected germanium nanoribbons (GeNRs) are investigated by using projector-augmented wave method based on density-functional theory. All the GeNRs with different edge shapes (armchair or zigzag) and widths are cut from the buckled Ge hexagonal sheet which is found to be semi-metallic as the planar graphene sheet. The results show that the perfect armchair GeNRs are nonmagnetic semiconductors and their band gaps exhibit three branches with decaying profiles, while the perfect zigzag GeNRs show the stable antiferromagnetic semiconducting ground state and their band gaps monotonously decrease with increasing ribbon width. These properties of the GeNRs are similar to graphene nanoribbons and should be important for designing new functional Ge-based nanodevices. The effects of the monovacancy or divacancy on the electronic and magnetic properties of the GeNRs are also considered. We found that the band gap of armchair GeNRs can be easily tuned by a monovancancy or divacancy at different positions, which provides a way of band gap engineering of armchair GeNRs for actual applications. Different from the defected armchair GeNRs, the metallization can be realized in zigzag GeNRs by a monovacancy or a divacancy, however, their magnetic properties depend closely upon the vacancy positions.

  1. Timing of gamma rays in coaxial germanium detector systems

    International Nuclear Information System (INIS)

    El-Ibiary, M.Y.

    1979-01-01

    A study is reported on the timing uncertainty in gamma ray coaxial germanium detector systems. The work deals with the zero cross over method which is widely used to reduce the dependence of the instant of timing on the radiation energy absorbed and on the position within the detector at which absorption takes place. It is found that the amplitude risetime compensated (ARC) method gives, under normal conditions, the best resolution at a specific energy. For higher energies, the resolution improves and there is no shift of the mean instant of timing. The method is therefore well suited for wide energy coverage. The parameters involved in implementing an ARC system for optimum performance at a specific energy are identified in terms of the preamplifier noise level and risetime. A trade off can be made between the resolutions at high and at low energies. The time resolution attained is given by means of a series of charts which use normalized dimensionless variables for ready application to any given case. Lithium compensated Ge detectors which normally operate under conditions of velocity saturation of the charge carriers by applying sufficient bias voltage create an electric field in excess of 1 kV/cm throughout the depleted region. High purity Ge detectors where velocity saturation may not be reached within certain parts of the depleted region are studied. Special attention is given to the probability of pulses being incorrectly timed because of their slow rise or small magnitude. Such incorrect timing is energy-dependent and results in a noticeable distortion of the timing spectrum that relates to a wide energy range. Limitations on system parameters to keep the probability of incorrect timing below a specified fraction are given

  2. Systematic Uncertainties in High-Rate Germanium Data

    Energy Technology Data Exchange (ETDEWEB)

    Gilbert, Andrew J.; Fast, James E.; Fulsom, Bryan G.; Pitts, William K.; VanDevender, Brent A.; Wood, Lynn S.

    2016-10-06

    For many nuclear material safeguards inspections, spectroscopic gamma detectors are required which can achieve high event rates (in excess of 10^6 s^-1) while maintaining very good energy resolution for discrimination of neighboring gamma signatures in complex backgrounds. Such spectra can be useful for non-destructive assay (NDA) of spent nuclear fuel with long cooling times, which contains many potentially useful low-rate gamma lines, e.g., Cs-134, in the presence of a few dominating gamma lines, such as Cs-137. Detectors in use typically sacrifice energy resolution for count rate, e.g., LaBr3, or visa versa, e.g., CdZnTe. In contrast, we anticipate that beginning with a detector with high energy resolution, e.g., high-purity germanium (HPGe), and adapting the data acquisition for high throughput will be able to achieve the goals of the ideal detector. In this work, we present quantification of Cs-134 and Cs-137 activities, useful for fuel burn-up quantification, in fuel that has been cooling for 22.3 years. A segmented, planar HPGe detector is used for this inspection, which has been adapted for a high-rate throughput in excess of 500k counts/s. Using a very-high-statistic spectrum of 2.4*10^11 counts, isotope activities can be determined with very low statistical uncertainty. However, it is determined that systematic uncertainties dominate in such a data set, e.g., the uncertainty in the pulse line shape. This spectrum offers a unique opportunity to quantify this uncertainty and subsequently determine required counting times for given precision on values of interest.

  3. Detached Solidification of Germanium-Silicon Crystals on the ISS

    Science.gov (United States)

    Volz, M. P.; Mazuruk, K.; Croell, A.

    2016-01-01

    A series of Ge(sub 1-x) Si(sub x) crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. The primary objective of the research is to determine the influence of containment on the processing-induced defects and impurity incorporation in germanium-silicon alloy crystals. A comparison will be made between crystals grown by the normal and "detached" Bridgman methods and the ground-based float zone technique. Crystals grown without being in contact with a container have superior quality to otherwise similar crystals grown in direct contact with a container, especially with respect to impurity incorporation, formation of dislocations, and residual stress in crystals. "Detached" or "dewetted" Bridgman growth is similar to regular Bridgman growth in that most of the melt is in contact with the crucible wall, but the crystal is separated from the wall by a small gap, typically of the order of 10-100 microns. Long duration reduced gravity is essential to test the proposed theory of detached growth. Detached growth requires the establishment of a meniscus between the crystal and the ampoule wall. The existence of this meniscus depends on the ratio of the strength of gravity to capillary forces. On Earth, this ratio is large and stable detached growth can only be obtained over limited conditions. Crystals grown detached on the ground exhibited superior structural quality as evidenced by measurements of etch pit density, synchrotron white beam X-ray topography and double axis X-ray diffraction.

  4. Long-range magnetostatic interactions in arrays of nanowires

    CERN Document Server

    Raposo, V; González, J M; Vázquez, M

    2000-01-01

    Experimental measurements and micromagnetic simulations of the hysteresis loops of arrays of cobalt nanowires are compared here. Arrays of cobalt nanowires (200 nm in diameter) were electrodeposited into the pores of alumina membranes (thickness 60 mu m). Their hysteresis loops along the axial direction of nanowires were measured using vibrating sample magnetometry. Micromagnetic simulations were performed considering dipolar interaction between nanowires leading to similar hysteresis loops as those obtained experimentally.

  5. Probing strain in bent semiconductor nanowires with Raman spectroscopy.

    Science.gov (United States)

    Chen, Jianing; Conache, Gabriela; Pistol, Mats-Erik; Gray, Struan M; Borgström, Magnus T; Xu, Hongxing; Xu, H Q; Samuelson, Lars; Håkanson, Ulf

    2010-04-14

    We present a noninvasive optical method to determine the local strain in individual semiconductor nanowires. InP nanowires were intentionally bent with an atomic force microscope and variations in the optical phonon frequency along the wires were mapped using Raman spectroscopy. Sections of the nanowires with a high curvature showed significantly broadened phonon lines. These observations together with deformation potential theory show that compressive and tensile strain inside the nanowires is the physical origin of the observed phonon energy variations.

  6. Understanding InP Nanowire Array Solar Cell Performance by Nanoprobe-Enabled Single Nanowire Measurements.

    Science.gov (United States)

    Otnes, Gaute; Barrigón, Enrique; Sundvall, Christian; Svensson, K Erik; Heurlin, Magnus; Siefer, Gerald; Samuelson, Lars; Åberg, Ingvar; Borgström, Magnus T

    2018-04-27

    III-V solar cells in the nanowire geometry might hold significant synthesis-cost and device-design advantages as compared to thin films and have shown impressive performance improvements in recent years. To continue this development there is a need for characterization techniques giving quick and reliable feedback for growth development. Further, characterization techniques which can improve understanding of the link between nanowire growth conditions, subsequent processing, and solar cell performance are desired. Here, we present the use of a nanoprobe system inside a scanning electron microscope to efficiently contact single nanowires and characterize them in terms of key parameters for solar cell performance. Specifically, we study single as-grown InP nanowires and use electron beam induced current characterization to understand the charge carrier collection properties, and dark current-voltage characteristics to understand the diode recombination characteristics. By correlating the single nanowire measurements to performance of fully processed nanowire array solar cells, we identify how the performance limiting parameters are related to growth and/or processing conditions. We use this understanding to achieve a more than 7-fold improvement in efficiency of our InP nanowire solar cells, grown from a different seed particle pattern than previously reported from our group. The best cell shows a certified efficiency of 15.0%; the highest reported value for a bottom-up synthesized InP nanowire solar cell. We believe the presented approach have significant potential to speed-up the development of nanowire solar cells, as well as other nanowire-based electronic/optoelectronic devices.

  7. Coexistence in even-even nuclei with emphasis on the germanium isotopes

    International Nuclear Information System (INIS)

    Carchidi, M.A.V.

    1985-01-01

    No simple model to date can explain in a self-consistent way the results of direct transfer data and BE2 electromagnetic rates in the germanium isotopes. The simplest models use a two-state interaction for describing the ground state and first excited O + state. In all cases, these models can account for some of the data, but they are in drastic conflict with other experimental measurements. In this thesis, it is shown that a two-state model can consistently account for two-neutron and alpha transfer O + 2 /g.s. cross-section ratio data in the germanium region (ie. zinc, germanium, and selenium), proton occupation number data in the ground states of the even stable zinc, germanium, and selenium isotopes, and BE2 transition rates in isotopes of germanium and zinc. In addition the author can account for most of the one-neutron and two-neutron transfer O + 2 /g.s. and (9/2 + 2 )/(9/2 + 1 ) cross-section ratio data in the odd-mass germanium isotopes. In this generalized two-state model (called Rerg1), the author makes as few assumptions as possible about the nature of the basis states; rather the author allows the experimental data to dictate the properties of the basis-state overlaps. In this sense, the author has learned much about the basis states and has a useful tool for constructing them. The author also shows that the Rerg1 model can quantitatively account for all two-neutron O + 2 /g.s. cross-section ratio data in all even-even nuclei from calcium to uranium

  8. Multiresidue determination of pesticides from aquatic media using polyaniline nanowires network as highly efficient sorbent for microextraction in packed syringe

    Energy Technology Data Exchange (ETDEWEB)

    Bagheri, Habib, E-mail: bagheri@sharif.edu [Environmental and Bio-Analytical Laboratories, Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran (Iran, Islamic Republic of); Alipour, Noshin; Ayazi, Zahra [Environmental and Bio-Analytical Laboratories, Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran (Iran, Islamic Republic of)

    2012-08-31

    Graphical abstract: Polyaniline nanowires network was prepared using soft template technique and used as sorbent of microextraction in packed syringe for the multiresidue determination of selected analytes from triazine, organochlrorine and organophosphorous pesticides in aqueous samples. Highlights: Black-Right-Pointing-Pointer Polyaniline nanowires network was synthesized using soft template method. Black-Right-Pointing-Pointer The presence of micelles was an important parameter in shaping the growing polymer. Black-Right-Pointing-Pointer The synthesized nanowires showed higher extraction capability in comparison with the bulk polymer. - Abstract: A simple, rapid and sensitive method based on microextraction in packed syringe (MEPS), in combination with gas chromatography-mass spectrometry (GC-MS) was developed. Polyaniline (PANI) nanowires network was synthesized and used as sorbent of MEPS for the multiresidue determination of selected analytes from triazine, organochlrorine and organophosphorous pesticides in aqueous samples. The PANI nanowires network was prepared using soft template technique and its characterization was studied by scanning electron microscopy (SEM). The presence of micelles in this methodology showed to be an important parameter in shaping the growing polymer. Hexadecyltrimethylammonium bromide (HTAB) was used as structure directing agent in PANI preparation procedure and this was led to the formation of nanowires with diameters ranging from 35 nm to 45 nm. The synthesized PANI nanowires network showed higher extraction capability in comparison with the bulk PANI. Important parameters influencing the extraction and desorption processes including desorption solvent, elution volume, draw-eject cycles of sample, draw-eject mode, pH effect and amount of sorbent were optimized. Limits of detection were in the range of 0.07-0.3 ng mL{sup -1} using time scheduled selected ion monitoring (SIM) mode. The linearity of method was in the range from 0

  9. Multiresidue determination of pesticides from aquatic media using polyaniline nanowires network as highly efficient sorbent for microextraction in packed syringe

    International Nuclear Information System (INIS)

    Bagheri, Habib; Alipour, Noshin; Ayazi, Zahra

    2012-01-01

    Graphical abstract: Polyaniline nanowires network was prepared using soft template technique and used as sorbent of microextraction in packed syringe for the multiresidue determination of selected analytes from triazine, organochlrorine and organophosphorous pesticides in aqueous samples. Highlights: ► Polyaniline nanowires network was synthesized using soft template method. ► The presence of micelles was an important parameter in shaping the growing polymer. ► The synthesized nanowires showed higher extraction capability in comparison with the bulk polymer. - Abstract: A simple, rapid and sensitive method based on microextraction in packed syringe (MEPS), in combination with gas chromatography–mass spectrometry (GC–MS) was developed. Polyaniline (PANI) nanowires network was synthesized and used as sorbent of MEPS for the multiresidue determination of selected analytes from triazine, organochlrorine and organophosphorous pesticides in aqueous samples. The PANI nanowires network was prepared using soft template technique and its characterization was studied by scanning electron microscopy (SEM). The presence of micelles in this methodology showed to be an important parameter in shaping the growing polymer. Hexadecyltrimethylammonium bromide (HTAB) was used as structure directing agent in PANI preparation procedure and this was led to the formation of nanowires with diameters ranging from 35 nm to 45 nm. The synthesized PANI nanowires network showed higher extraction capability in comparison with the bulk PANI. Important parameters influencing the extraction and desorption processes including desorption solvent, elution volume, draw–eject cycles of sample, draw–eject mode, pH effect and amount of sorbent were optimized. Limits of detection were in the range of 0.07–0.3 ng mL −1 using time scheduled selected ion monitoring (SIM) mode. The linearity of method was in the range from 0.5–200 ng mL −1 to 0.2–1000 ng mL −1 . The method precision

  10. Controlled growth of single nanowires within a supported alumina template

    DEFF Research Database (Denmark)

    Vlad, A.; Mátéfi-Tempfli, M.; Faniel, S.

    2006-01-01

    A simple technique for fabricating single nanowires with well-defined position is presented. The process implies the use of a silicon nitride mask for selective electrochemical growth of the nanowires in a porous alumina template. We show that this method allows the realization of complex nanowire...

  11. nanowires via electrochemical method and its investigations as a ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. The special behaviour of nanowires with respect to electrical conductivity makes them suitable for sensing application. In this paper, we present a copper–ferrous (CuFe) nanowires based sensor for detection of chemicals. CuFe nanowires were synthesized by template-assisted electrochemical method.

  12. Nanowires: properties, applications and synthesis via porous anodic ...

    Indian Academy of Sciences (India)

    Moreover, periodic arrays of magnetic nanowires hold high potential for recording media application. Nanowires are also potential candidates for sensor and bio-medical applications. In the present article, the physical and chemical properties of nanowires along with their probable applications in different fields have been ...

  13. Nanowires: properties, applications and synthesis via porous anodic ...

    Indian Academy of Sciences (India)

    TECS

    Abstract. Quasi one-dimensional nanowires possess unique electrical, electronic, thermoelectrical, optical, magnetic and chemical properties, which are different from that of their parent counterpart. The physical properties of nanowires are influenced by the morphology of the nanowires, diameter dependent band gap,.

  14. Microbial nanowires and methods of making and using

    Energy Technology Data Exchange (ETDEWEB)

    Reguera, Gemma; Cologgi, Dena; Worden, Robert Mark; Castro-Forero, Angelines A.; Steidl, Rebecca

    2017-03-21

    Electrically conductive nanowires, and genetically or chemically modified production and use of such nanowires with altered conductive, adhesive, coupling or other properties are described. The disclosed nanowires are used as device or device components or may be adapted for soluble metal remediation.

  15. Nanowires: properties, applications and synthesis via porous anodic ...

    Indian Academy of Sciences (India)

    Quasi one-dimensional nanowires possess unique electrical, electronic, thermoelectrical, optical, magnetic and chemical properties, which are different from that of their parent counterpart. The physical properties of nanowires are influenced by the morphology of the nanowires, diameter dependent band gap, carrier ...

  16. Precise characterization of self-catalyzed III-V nanowire heterostructures via optical second harmonic generation

    Science.gov (United States)

    Yu, Ying; Wang, Jing; Wei, Yu-Ming; Zhou, Zhang-Kai; Ni, Hai-Qiao; Niu, Zhi-Chuan; Wang, Xue-Hua; Yu, Si-Yuan

    2017-09-01

    We demonstrate the utility of optical second harmonic generation (SHG) polarimetry to perform structural characterization of self-assembled zinc-blende/wurtzite III-V nanowire heterostructures. By analyzing four anisotropic SHG polarimetric patterns, we distinguish between wurtzite (WZ), zinc-blende (ZB) and ZB/WZ mixing III-V semiconducting crystal structures in nanowire systems. By neglecting the surface contributions and treating the bulk crystal within the quasi-static approximation, we can well explain the optical SHG polarimetry from the NWs with diameter from 200-600 nm. We show that the optical in-coupling and out-coupling coefficients arising from depolarization field can determine the polarization of the SHG. We also demonstrate micro-photoluminescence of GaAs quantum dots in related ZB and ZB/WZ mixing sections of core-shell NW structure, in agreement with the SHG polarimetry results. The ability to perform in situ SHG-based crystallographic study of semiconducting single and multi-crystalline nanowire heterostructures will be useful in displaying structure-property relationships of nanodevices.

  17. The fingerprint of Te-rich and stoichiometric Bi2Te3 nanowires by Raman spectroscopy

    Science.gov (United States)

    Rodríguez-Fernández, Carlos; Manzano, Cristina V.; Romero, Aldo H.; Martín, Jaime; Martín-González, Marisol; Morais de Lima, Mauricio, Jr.; Cantarero, Andrés

    2016-02-01

    We unambiguously show that the signature of Te-rich bismuth telluride is the appearance of three new peaks in the Raman spectra of Bi2Te3, located at 88, 117 and 137 cm-1. For this purpose, we have grown stoichiometric Bi2Te3 nanowires as well as Te-rich nanowires. The absence of these peaks in stoichiometric nanowires, even in those with the smallest diameter, shows that they are not related to confinement effects or the lack of inversion symmetry, as stated in the literature, but to the existence of Te clusters. These Te clusters have been found in non-stoichiometric samples by high resolution electron microscopy, while they are absent in stoichiometric samples. The Raman spectra of the latter corresponds to the one for bulk Bi2Te3. The intensity of these Raman peaks are clearly correlated to the Te content. In order to ensure statistically meaningful results, we have investigated several regions from every sample.

  18. Synthesis of tris(8-hydroxyquinoline) aluminum (Alq3) nanowires under different conditions

    Science.gov (United States)

    Ng, A. M. C.; Tong, W. Y.; Djurisic, A. B.; Leung, Y. H.; Cheung, C. H.; Lui, H. F.; Surya, C.; Chan, W. K.

    2005-10-01

    Tris(8-hydroxyquinoline) aluminum (Alq3) is one of the most commonly used electron transporting and luminescent materials for organic light emitting diodes (OLEDs). It is thermally and morphologically stable to evaporate into thin films and it is a good green emitter. Due to its importance in OLEDs, the properties of Alq3 have been extensively studied. Most of the studies, however, were concentrated on the single crystals, powder or thin films of Alq3. Recently, synthesis of Alq3 nanostructures, such as nanoparticles and nanowires, has been reported. Nanostructures have been attracting increasing attention because they may have new optical, electronic, magnetic, and mechanical properties compared with those of bulk materials. In this work, we reported synthesis of Alq3 nanowires by heating Alq3 powder in a gas flow. The nanowires were grown on glass substrates which were located in the downstream. The obtained nanostructures were characterized by scanning electron microscopy (SEM) and photoluminescence (PL). The effect of substrate temperatures, fabrication system geometry (i.e. source to substrate distance), the choice of gas, and gas flow rate on the resulting nanostructures were investigated. It is found that the synthesis conditions had significant effect on the morphologies of the resulting nanostructures, but the PL showed no significant dependence on the morphology.

  19. Second harmonic generation on self-assembled GaAs/Au nanowires with thickness gradient

    Science.gov (United States)

    Belardini, A.; Leahu, G.; Centini, M.; Li Voti, R.; Fazio, E.; Sibilia, C.; Repetto, D.; Buatier de Mongeot, F.

    2017-05-01

    Here we investigated the SH generation at the wavelength of 400 nm (pump laser at 800 nm, 120 fs pulses) of a "metasurface" composed by an alternation of GaAs nano-grooves and Au nanowires capping portions of flat GaAs. The nano-grooves depth and the Au nanowires thickness gradually vary across the sample. The samples are obtained by ion bombardment at glancing angle on a 150 nm Au mask evaporated on a GaAs plane wafer. The irradiation process erodes anisotropically the surface, creating Au nanowires and, at high ion dose, grooves in the underlying GaAs substrate (pattern transfer). The SHG measurements are performed for different pump linear polarization angle at different positions on the "metasurface" in order to explore the regions with optimal conditions for SHG efficiency. The pump polarization angle is scanned by rotating a half-wave retarder plate. While the output SH signal in reflection is analyzed by setting the polarizer in `s' or `p' configuration in front of the detector. The best polarization condition for SHG is obtained in the configuration where the pump and second harmonic fields are both `p' polarized, and the experiments show a SH polarization dependence of the same symmetry of bulk GaAs. Thus, the presence of gold contributes only as field localization effect, but do not contributes directly as SH generator.

  20. A study on the forms of existence of germanium in uranium-bearing coals of Bangmai basin of Yunnan

    International Nuclear Information System (INIS)

    Zhang Shuling; Wang Shuying; Yin Jinshuang

    1988-07-01

    The Bangmai basin is an asymmetrical intermontane synclinal basin with a Hercynian-Yenshan granitic body (γ 3 3 -γ 5 2 ) as its basement. Its overlying strata are made up of the N 1 of coal-bearing clastic rocks of Neogene period. Germanium ore mostly occur within the N 1 2 coal-seam. Uranium, germanium-bearing coals are mainly lignites of low grade in coalation and belong to semidurain, semiclarain, duroclarain and clarodurain. In order to probe into the forms of existence of germanium in coal, six kinds of analytical methods (electronic probe analysis, separation of heavy liquid, grain-size analysis, electric osmosis, chemical extraction and grade-extraction) have been adopted. A simulated test of humic complex germanium in the laboratory was carried out. According to infrared spectral analysis, it is found that 1700 cm -1 wavecrest almost disappears, 1250 cm -1 peak weakens and 1600 cm -1 peak strengthens, 1400 cm -1 peak slightly strengthens. No doubt, these illustrate the formatiion of humic germanium complex. Afterward, through differential thermal analysis and measurement of pH variation of media, it futher proves the presence of humic germanium complex. It is considered that the forms of existence of germanium in uranium-bearing coals mainly are: (1) In close chemical combination with organic matter, usually in the form of humic germanium complex and germanium organic compound; (2) In the state of adsorption, germanium is adsorbed by some organic matter, clay minerals and limonite etc.; (3) A very rare part occurring as isomorphous form

  1. A complete physical germanium-on-silicon quantum dot self-assembly process.

    Science.gov (United States)

    Alkhatib, Amro; Nayfeh, Ammar

    2013-01-01

    Achieving quantum dot self-assembly at precise pre-defined locations is of vital interest. In this work, a novel physical method for producing germanium quantum dots on silicon using nanoindentation to pre-define nucleation sites is described. Self-assembly of ordered ~10 nm height germanium quantum dot arrays on silicon substrates is achieved. Due to the inherent simplicity and elegance of the proposed method, the results describe an attractive technique to manufacture semiconductor quantum dot structures for future quantum electronic and photonic applications.

  2. A Complete Physical Germanium-on-Silicon Quantum Dot Self-Assembly Process

    Science.gov (United States)

    Alkhatib, Amro; Nayfeh, Ammar

    2013-06-01

    Achieving quantum dot self-assembly at precise pre-defined locations is of vital interest. In this work, a novel physical method for producing germanium quantum dots on silicon using nanoindentation to pre-define nucleation sites is described. Self-assembly of ordered ~10 nm height germanium quantum dot arrays on silicon substrates is achieved. Due to the inherent simplicity and elegance of the proposed method, the results describe an attractive technique to manufacture semiconductor quantum dot structures for future quantum electronic and photonic applications.

  3. Segmentation of the Outer Contact on P-Type Coaxial Germanium Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Hull, Ethan L.; Pehl, Richard H.; Lathrop, James R.; Martin, Gregory N.; Mashburn, R. B.; Miley, Harry S.; Aalseth, Craig E.; Hossbach, Todd W.

    2006-09-21

    Germanium detector arrays are needed for low-level counting facilities. The practical applications of such user facilities include characterization of low-level radioactive samples. In addition, the same detector arrays can also perform important fundamental physics measurements including the search for rare events like neutrino-less double-beta decay. Coaxial germanium detectors having segmented outer contacts will provide the next level of sensitivity improvement in low background measurements. The segmented outer detector contact allows performance of advanced pulse shape analysis measurements that provide additional background reduction. Currently, n-type (reverse electrode) germanium coaxial detectors are used whenever a segmented coaxial detector is needed because the outer boron (electron barrier) contact is thin and can be segmented. Coaxial detectors fabricated from p-type germanium cost less, have better resolution, and are larger than n-type coaxial detectors. However, it is difficult to reliably segment p-type coaxial detectors because thick (~1 mm) lithium-diffused (hole barrier) contacts are the standard outside contact for p-type coaxial detectors. During this Phase 1 Small Business Innovation Research (SBIR) we have researched the possibility of using amorphous germanium contacts as a thin outer contact of p-type coaxial detectors that can be segmented. We have developed amorphous germanium contacts that provide a very high hole barrier on small planar detectors. These easily segmented amorphous germanium contacts have been demonstrated to withstand several thousand volts/cm electric fields with no measurable leakage current (<1 pA) from charge injection over the hole barrier. We have also demonstrated that the contact can be sputter deposited around and over the curved outside surface of a small p-type coaxial detector. The amorphous contact has shown good rectification properties on the outside of a small p-type coaxial detector. These encouraging

  4. Hot Carrier Trapping in High-Purity and Doped Germanium Crystals at Millikelvin Temperatures

    Science.gov (United States)

    Piro, M.-C.; Broniatowski, A.; Marnieros, S.; Dumoulin, L.; Olivieri, E.

    2014-09-01

    A new set of experimental data is presented for the mean drift lengths and the drift velocities of hot electrons and holes as a function of the electric field in ultra-pure and in lightly doped (n- and p-type) germanium single crystals at mK temperatures. Measurements are made in the field range between 0.1 and 15 V/cm, typical for the operation of cryogenic germanium detectors for dark matter search. The analysis of the experimental data strongly suggests that the dominant trapping centers are the dopant species in the neutral state.

  5. Optimization of the Transport Shield for Neutrinoless Double Beta-decay Enriched Germanium

    Energy Technology Data Exchange (ETDEWEB)

    Aguayo Navarrete, Estanislao; Kouzes, Richard T.; Orrell, John L.; Reid, Douglas J.; Fast, James E.

    2012-04-15

    This document presents results of an investigation of the material and geometry choice for the transport shield of germanium, the active detector material used in 76Ge neutrinoless double beta decay searches. The objective of this work is to select the optimal material and geometry to minimize cosmogenic production of radioactive isotopes in the germanium material. The design of such a shield is based on the calculation of the cosmogenic production rate of isotopes that are known to cause interfering backgrounds in 76Ge neutrinoless double beta decay searches.

  6. GIOVE: a new detector setup for high sensitivity germanium spectroscopy at shallow depth

    International Nuclear Information System (INIS)

    Heusser, G.; Weber, M.; Hakenmüller, J.; Laubenstein, M.; Lindner, M.; Maneschg, W.; Simgen, H.; Stolzenburg, D.; Strecker, H.

    2015-01-01

    We report on the development and construction of the high-purity germanium spectrometer setup GIOVE (Germanium Inner Outer VEto), recently built and now operated at the shallow underground laboratory of the Max-Planck-Institut für Kernphysik, Heidelberg. Particular attention was paid to the design of a novel passive and active shield, aiming at efficient rejection of environmental and muon induced radiation backgrounds. The achieved sensitivity level of ≤100 μBq kg -1 for primordial radionuclides from U and Th in typical γ ray sample screening measurements is unique among instruments located at comparably shallow depths and can compete with instruments at far deeper underground sites

  7. Gold-mask technique for fabricating segmented-electrode germanium detectors

    International Nuclear Information System (INIS)

    Luke, P.N.

    1984-01-01

    A simple gold-mask technique has been developed for use in the fabrication of germanium nuclear radiation detectors. A layer of gold deposited over the contacts of the detectors acts as masks for chemical etching and surface treatments. It also serves as a reliable, low resistance electrical connection to the underlying germanium contact. This technique greatly facilitates the fabrication of a wide variety of segmented-electrode planar and coaxial detectors. Examples of these detectors with applications in medical imaging, gamma-ray astronomy and high-energy physics are presented

  8. Silicon nanowires in polymer nanocomposites for photovoltaic hybrid thin films

    International Nuclear Information System (INIS)

    Ben Dkhil, S.; Bourguiga, R.; Davenas, J.; Cornu, D.

    2012-01-01

    Highlights: ► Hybrid solar cells based on blends of poly(N-vinylcarbazole) and silicon nanowires have been fabricated. ► We have investigated the charge transfer between PVK and SiNWs by the way of the quenching of the PVK photoluminescence. ► The relation between the morphology of the composite thin films and the charge transfer between SiNWs and PVK has been examined. ► We have investigated the effects of SiNWs concentration on the photovoltaic characteristics leading to the optimization of a critical SiNWs concentration. - Abstract: Hybrid thin films combining the high optical absorption of a semiconducting polymer film and the electronic properties of silicon fillers have been investigated in the perspective of the development of low cost solar cells. Bulk heterojunction photovoltaic materials based on blends of a semiconductor polymer poly(N-vinylcarbazole) (PVK) as electron donor and silicon nanowires (SiNWs) as electron acceptor have been studied. Composite PVK/SiNWs films were cast from a common solvent mixture. UV–visible spectrometry and photoluminescence of the composites have been studied as a function of the SiNWs concentration. Photoluminescence spectroscopy (PL) shows the existence of a critical SiNWs concentration of about 10 wt % for PL quenching corresponding to the most efficient charge pair separation. The photovoltaic (PV) effect has been studied under illumination. The optimum open-circuit voltage V oc and short-circuit current density J sc are obtained for 10 wt % SiNWs whereas a degradation of these parameters is observed at higher SiNWs concentrations. These results are correlated to the formation of aggregates in the composite leading to recombination of the photogenerated charge pairs competing with the dissociation mechanism.

  9. Silicon nanowires in polymer nanocomposites for photovoltaic hybrid thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ben Dkhil, S., E-mail: sadok.bendekhil@gmail.com [Laboratoire Physique des Materiaux, Structures et Proprietes Groupe Physique des Composants et Dispositifs Nanometriques, 7021 Jarzouna, Bizerte (Tunisia); Ingenierie des Materiaux Polymeres, IMP, UMR CNRS 5223, Universite Claude Bernard - Lyon 1, 15, boulevard Latarjet, 69622 Villeurbanne (France); Bourguiga, R. [Laboratoire Physique des Materiaux, Structures et Proprietes Groupe Physique des Composants et Dispositifs Nanometriques, 7021 Jarzouna, Bizerte (Tunisia); Davenas, J. [Ingenierie des Materiaux Polymeres, IMP, UMR CNRS 5223, Universite Claude Bernard - Lyon 1, 15, boulevard Latarjet, 69622 Villeurbanne (France); Cornu, D. [Institut Europeen des Membranes, UMR CNRS 5635, Ecole Nationale superieure de Chimie, Universite de Montpellier, 1919 route de Mende, F34000 Montpellier (France)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Hybrid solar cells based on blends of poly(N-vinylcarbazole) and silicon nanowires have been fabricated. Black-Right-Pointing-Pointer We have investigated the charge transfer between PVK and SiNWs by the way of the quenching of the PVK photoluminescence. Black-Right-Pointing-Pointer The relation between the morphology of the composite thin films and the charge transfer between SiNWs and PVK has been examined. Black-Right-Pointing-Pointer We have investigated the effects of SiNWs concentration on the photovoltaic characteristics leading to the optimization of a critical SiNWs concentration. - Abstract: Hybrid thin films combining the high optical absorption of a semiconducting polymer film and the electronic properties of silicon fillers have been investigated in the perspective of the development of low cost solar cells. Bulk heterojunction photovoltaic materials based on blends of a semiconductor polymer poly(N-vinylcarbazole) (PVK) as electron donor and silicon nanowires (SiNWs) as electron acceptor have been studied. Composite PVK/SiNWs films were cast from a common solvent mixture. UV-visible spectrometry and photoluminescence of the composites have been studied as a function of the SiNWs concentration. Photoluminescence spectroscopy (PL) shows the existence of a critical SiNWs concentration of about 10 wt % for PL quenching corresponding to the most efficient charge pair separation. The photovoltaic (PV) effect has been studied under illumination. The optimum open-circuit voltage V{sub oc} and short-circuit current density J{sub sc} are obtained for 10 wt % SiNWs whereas a degradation of these parameters is observed at higher SiNWs concentrations. These results are correlated to the formation of aggregates in the composite leading to recombination of the photogenerated charge pairs competing with the dissociation mechanism.

  10. Impedance Analysis of Silicon Nanowire Lithium Ion Battery Anodes

    KAUST Repository

    Ruffo, Riccardo

    2009-07-02

    The impedance behavior of silicon nanowire electrodes has been investigated to understand the electrochemical process kinetics that influences the performance when used as a high-capacity anode in a lithium ion battery. The ac response was measured by using impedance spectroscopy in equilibrium conditions at different lithium compositions and during several cycles of charge and discharge in a half cell vs. metallic lithium. The impedance analysis shows the contribution of both surface resistance and solid state diffusion through the bulk of the nanowires. The surface process is dominated by a solid electrolyte layer (SEI) consisting of an inner, inorganic insoluble part and several organic compounds at the outer interface, as seen by XPS analysis. The surface resistivity, which seems to be correlated with the Coulombic efficiency of the electrode, grows at very high lithium contents due to an increase in the inorganic SEI thickness. We estimate the diffusion coefficient of about 2 × 10 -10 cm 2/s for lithium diffusion in silicon. A large increase in the electrode impedance was observed at very low lithium compositions, probably due to a different mechanism for lithium diffusion inside the wires. Restricting the discharge voltage to 0.7 V prevents this large impedance and improves the electrode lifetime. Cells cycled between 0.07 and 0.70 V vs. metallic lithium at a current density of 0.84 A/g (C/5) showed good Coulombic efficiency (about 99%) and maintained a capacity of about 2000 mAh/g after 80 cycles. © 2009 American Chemical Society.

  11. Single nanowire resistive nano-heater for highly localized thermo-chemical reactions: localized hierarchical heterojunction nanowire growth.

    Science.gov (United States)

    Yeo, Junyeob; Kim, Gunho; Hong, Sukjoon; Lee, Jinhwan; Kwon, Jinhyeong; Lee, Habeom; Park, Heeseung; Manoroktul, Wanit; Lee, Ming-Tsang; Lee, Bong Jae; Grigoropoulos, Costas P; Ko, Seung Hwan

    2014-12-29

    A single nanowire resistive nano-heater (RNH) is fabricated, and it is demonstrated that the RNH can induce highly localized temperature fields, which can trigger highly localized thermo-chemical reactions to grow hierarchical nanowires directly at the desired specific spot such as ZnO nanowire branch growth on a single Ag nanowire. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Designed Quasi-1D Potential Structures Realized in Compositionally Graded InAs1-xPx Nanowires.

    Science.gov (United States)

    Nylund, Gustav; Storm, Kristian; Lehmann, Sebastian; Capasso, Federico; Samuelson, Lars

    2016-02-10

    III-V semiconductor heterostructures are important components of many solid-state optoelectronic devices, but the ability to control and tune the electrical and optical properties of these structures in conventional device geometries is fundamentally limited by the bulk dimensionality and the inability to accommodate lattice-mismatched material combinations. Here we demonstrate how semiconductor nanowires may enable the creation of arbitrarily shaped one-dimensional potential structures for new types of designed device functionality. We describe the controlled growth of stepwise compositionally graded InAs1-xPx heterostructures defined along the axes of InAs nanowires, and we show that nanowires with sawtooth-shaped composition profiles behave as near-ideal unipolar diodes with ratchet-like rectification of the electron transport through the nanowires, in excellent agreement with simulations. This new type of designed quasi-1D potential structure represents a significant advance in band gap engineering and may enable fundamental studies of low-dimensional hot-carrier dynamics, in addition to constituting a platform for implementing novel electronic and optoelectronic device concepts.

  13. Quantification of nanowire uptake by live cells

    KAUST Repository

    Margineanu, Michael B.

    2015-05-01

    Nanostructures fabricated by different methods have become increasingly important for various applications at the cellular level. In order to understand how these nanostructures “behave” and for studying their internalization kinetics, several attempts have been made at tagging and investigating their interaction with living cells. In this study, magnetic iron nanowires with an iron oxide layer are coated with (3-Aminopropyl)triethoxysilane (APTES), and subsequently labeled with a fluorogenic pH-dependent dye pHrodo™ Red, covalently bound to the aminosilane surface. Time-lapse live imaging of human colon carcinoma HCT 116 cells interacting with the labeled iron nanowires is performed for 24 hours. As the pHrodo™ Red conjugated nanowires are non-fluorescent outside the cells but fluoresce brightly inside, internalized nanowires are distinguished from non-internalized ones and their behavior inside the cells can be tracked for the respective time length. A machine learning-based computational framework dedicated to automatic analysis of live cell imaging data, Cell Cognition, is adapted and used to classify cells with internalized and non-internalized nanowires and subsequently determine the uptake percentage by cells at different time points. An uptake of 85 % by HCT 116 cells is observed after 24 hours incubation at NW-to-cell ratios of 200. While the approach of using pHrodo™ Red for internalization studies is not novel in the literature, this study reports for the first time the utilization of a machine-learning based time-resolved automatic analysis pipeline for quantification of nanowire uptake by cells. This pipeline has also been used for comparison studies with nickel nanowires coated with APTES and labeled with pHrodo™ Red, and another cell line derived from the cervix carcinoma, HeLa. It has thus the potential to be used for studying the interaction of different types of nanostructures with potentially any live cell types.

  14. Modelling of bulk superconductor magnetization

    International Nuclear Information System (INIS)

    Ainslie, M D; Fujishiro, H

    2015-01-01

    This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE = rare earth or Y) and MgB 2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialization stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarized with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet–superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets. Finally, the use of hollow bulk cylinders/tubes for shielding is analysed. (topical review)

  15. Modelling of bulk superconductor magnetization

    Science.gov (United States)

    Ainslie, M. D.; Fujishiro, H.

    2015-05-01

    This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE = rare earth or Y) and MgB2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialization stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarized with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet-superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets. Finally, the use of hollow bulk cylinders/tubes for shielding is analysed.

  16. Unveiling polytype transformation assisted growth mechanism in boron carbide nanowires

    Science.gov (United States)

    Song, Ningning; Li, Xiaodong

    2018-01-01

    We demonstrate direct evidence that the lattice distortion, induced by boron carbide (BxCy) stoichiometry, assists the growth of boron carbide nanowires. The transformation between different polytypic boron carbide phases lowers the energy barrier for boron diffusion, promoting boron migration in the nanowire growth. An atomistic mass transport model has been established to explain such volume-diffusion-induced nanowire growth which cannot be explained by the conventional surface diffusion model alone. These findings significantly advance our understanding of nanowire growth processes and mass transport mechanisms and provide new guidelines for the design of nanowire-structured devices.

  17. Gold nanocluster distribution on faceted and kinked Si nanowires

    International Nuclear Information System (INIS)

    Boukhicha, Rym; Vincent, Laetitia; Renard, Charles; Gardès, Cyrille; Yam, Vy; Fossard, Frédéric; Patriarche, Gilles; Jabeen, Fauzia; Bouchier, Daniel

    2012-01-01

    Si nanowires were grown on (111) substrates by ultra high vacuum chemical vapor deposition using the Au-catalyzed vapor–liquid–solid (VLS) technique. Depending on the growth temperature, the nanowires can be straight in the direction or kinked towards . We present a transmission electron microscopy investigation of the Si nanowires. Results exhibit the relationship between the morphology of nanowires and the distribution of gold on sidewalls bounding the nanowires. The distribution of Au nanoclusters is used as a probe to investigate the growth mechanisms of the VLS process. Our observations are consistent with the model of nucleation and step flow related to the oscillatory behavior of the catalyst droplet.

  18. Conducting Polyaniline Nanowire and Its Applications in Chemiresistive Sensing.

    Science.gov (United States)

    Song, Edward; Choi, Jin-Woo

    2013-08-07

    One dimensional polyaniline nanowire is an electrically conducting polymer that can be used as an active layer for sensors whose conductivity change can be used to detect chemical or biological species. In this review, the basic properties of polyaniline nanowires including chemical structures, redox chemistry, and method of synthesis are discussed. A comprehensive literature survey on chemiresistive/conductometric sensors based on polyaniline nanowires is presented and recent developments in polyaniline nanowire-based sensors are summarized. Finally, the current limitations and the future prospect of polyaniline nanowires are discussed.

  19. Properties of Ni and Ni–Fe nanowires electrochemically deposited into a porous alumina template

    Directory of Open Access Journals (Sweden)

    Alla I. Vorobjova

    2016-11-01

    Full Text Available The comparative analysis of the electrochemical deposition of Ni and Ni–Fe nanowires (NWs into ordered porous alumina templates is presented. The method developed allows for obtaining NWs of 50 ± 5 nm in diameter and 25 μm in length, i.e., with an aspect ratio of 500. XRD data demonstrate the polycrystalline nature of Ni and Ni–Fe in a face-centered cubic close-packed lattice. Both fabricated materials, Ni and Ni–Fe, have shown ferromagnetic properties. The specific magnetization value of Ni–Fe NWs in the alumina template is higher than that of the Ni sample and bulk Ni, also the Curie temperature of the Ni–Fe sample (790 K is higher than that of the Ni sample one or bulk Ni.

  20. Bundled tungsten oxide nanowires under thermal processing

    International Nuclear Information System (INIS)

    Sun Shibin; Zhao Yimin; Xia Yongde; Zhu Yanqiu; Zou Zengda; Min Guanghui

    2008-01-01

    Ultra-thin W 18 O 49 nanowires were initially obtained by a simple solvothermal method using tungsten chloride and cyclohexanol as precursors. Thermal processing of the resulting bundled nanowires has been carried out in air in a tube furnace. The morphology and phase transformation behavior of the as-synthesized nanowires as a function of annealing temperature have been characterized by x-ray diffraction and electron microscopy. The nanostructured bundles underwent a series of morphological evolution with increased annealing temperature, becoming straighter, larger in diameter, and smaller in aspect ratio, eventually becoming irregular particles with size up to 5 μm. At 500 deg. C, the monoclinic W 18 O 49 was completely transformed to monoclinic WO 3 phase, which remains stable at high processing temperature. After thermal processing at 400 deg. C and 450 deg. C, the specific surface areas of the resulting nanowires dropped to 110 m 2 g -1 and 66 m 2 g -1 respectively, compared with that of 151 m 2 g -1 for the as-prepared sample. This study may shed light on the understanding of the geometrical and structural evolution occurring in nanowires whose working environment may involve severe temperature variations