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Sample records for polycrystalline nanowires simulations

  1. Micromagnetic simulation and the angular dependence of coercivity and remanence for array of polycrystalline nickel nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Fuentes, G.P.; Holanda, J. [Departamento de Física, Universidade Federal de Pernambuco, Recife, PE 50670-901 (Brazil); Guerra, Y.; Silva, D.B.O.; Farias, B.V.M. [Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, Recife, PE 50670-901 (Brazil); Padrón-Hernández, E., E-mail: padron@df.ufpe.br [Departamento de Física, Universidade Federal de Pernambuco, Recife, PE 50670-901 (Brazil); Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, Recife, PE 50670-901 (Brazil)

    2017-02-01

    We present here our experimental results for the preparation and characterization of nanowires of nickel and the analysis of the angular dependence of coercivity and remanence using experimental data and micromagnetic simulation. The fabrication was made by using aluminum oxide membranes as templates and deposited nickel by an electrochemical route. The magnetic measurements showed that coercivity and remanence are dependent of the angle of application of the external magnetic field. Our results are different than that expected for the coherent, vortex and transversal modes of the reversion for the magnetic moments. According to the transmission electron microscopy analysis we can see that our nanowires have not a perfect cylindrical format. That is why we have used the ellipsoids chain model for better understanding the real structure of wires and its relation with the magnetic behavior. In order to generate theoretical results for this configuration we have made micromagnetic simulation using Nmag code. Our numerical results for the realistic distances are in correspondence with the magnetic measurements and we can see that there are contradictions if we assume the transverse reversal mode. Then, we can conclude that structure of nanowires should be taken into account to understand the discrepancies reported in the literature for the reversion mechanism in arrays of nickel nanowires. - Highlights: • We present answers for the problem of angular dependence for the coercivity and remanence. • Experimental and theoretical results confirmed the great importance of the real structure. • Micromagnetic calculations confirmed the importance of the real structure.

  2. Oxygen deficiency in MoO{sub 3} polycrystalline nanowires and nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Varlec, Ana, E-mail: ana.varlec@ijs.si [Condensed Matter Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Arčon, Denis [Condensed Matter Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Faculty of Mathematics and Physics, University of Ljubljana, Jadranska cesta 19, SI-1000 Ljubljana (Slovenia); Škapin, Srečo D. [Advanced Materials Department, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Remškar, Maja [Condensed Matter Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia)

    2016-02-15

    We report on the synthesis of polycrystalline molybdenum oxide (MoO{sub 3}) nanowires via oxidation of molybdenum-sulfur-iodine (Mo{sub 6}S{sub 2}I{sub 8}) nanowires. This unique synthesis route results in an interesting morphology comprising porous nanowires and nanotubes. We found the nanowires to have the orthorhombic MoO{sub 3} structure. The structure is slightly oxygen deficient which results in the appearance of a new resonant Raman band (1004 cm{sup −1}) and paramagnetic defects (Mo{sup 5+}) of both the point and crystallographic shear plane nature. - Highlights: • Polycrystalline MoO{sub 3} nanowires were obtained via oxidation of Mo{sub 6}S{sub 2}I{sub 8} nanowires. • Nanowires are porous and tubular with either filled or empty interior. • Nanowires are slightly oxygen deficient which leads to a new Raman band.

  3. Numerical simulation of large deformation polycrystalline plasticity

    International Nuclear Information System (INIS)

    Inal, K.; Neale, K.W.; Wu, P.D.; MacEwen, S.R.

    2000-01-01

    A finite element model based on crystal plasticity has been developed to simulate the stress-strain response of sheet metal specimens in uniaxial tension. Each material point in the sheet is considered to be a polycrystalline aggregate of FCC grains. The Taylor theory of crystal plasticity is assumed. The numerical analysis incorporates parallel computing features enabling simulations of realistic models with large number of grains. Simulations have been carried out for the AA3004-H19 aluminium alloy and the results are compared with experimental data. (author)

  4. 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.

  5. Synthesis of polycrystalline Co{sub 3}O{sub 4} nanowires with excellent ammonium perchlorate catalytic decomposition property

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Hai [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Lv, Baoliang, E-mail: lbl604@sxicc.ac.cn [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); Wu, Dong; Xu, Yao [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)

    2014-12-15

    Graphical abstract: Co{sub 3}O{sub 4} nanowires with excellent ammonium perchlorate catalytic decomposition property were synthesized via a methanamide-assisted hydrolysis and subsequent dissolution–recrystallization process in the presence of methanamide. - Abstract: Co{sub 3}O{sub 4} nanowires, with the length of tens of micrometers and the width of several hundred nanometers, were produced by a hydrothermal treatment and a post-anneal process. X-ray diffraction (XRD) result showed that the Co{sub 3}O{sub 4} nanowires belong to cubic crystal system. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) analysis indicated that the Co{sub 3}O{sub 4} nanowires, composed by single crystalline nanoparticles, were of polycrystalline nature. On the basis of time-dependent experiments, methanamide-assisted hydrolysis and subsequent dissolution–recrystallization process were used to explain the precursors' formation process of the polycrystalline Co{sub 3}O{sub 4} nanowires. The TGA experiments showed that the as-obtained Co{sub 3}O{sub 4} nanowires can catalyze the thermal decomposition of ammonium perchlorate (AP) effectively.

  6. Micromagnetic simulations of cylindrical magnetic nanowires

    KAUST Repository

    Ivanov, Yurii P.; Chubykalo-Fesenko, O.

    2015-01-01

    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

  7. Deep Drawing Simulations With Different Polycrystalline Models

    Science.gov (United States)

    Duchêne, Laurent; de Montleau, Pierre; Bouvier, Salima; Habraken, Anne Marie

    2004-06-01

    The goal of this research is to study the anisotropic material behavior during forming processes, represented by both complex yield loci and kinematic-isotropic hardening models. A first part of this paper describes the main concepts of the `Stress-strain interpolation' model that has been implemented in the non-linear finite element code Lagamine. This model consists of a local description of the yield locus based on the texture of the material through the full constraints Taylor's model. The texture evolution due to plastic deformations is computed throughout the FEM simulations. This `local yield locus' approach was initially linked to the classical isotropic Swift hardening law. Recently, a more complex hardening model was implemented: the physically-based microstructural model of Teodosiu. It takes into account intergranular heterogeneity due to the evolution of dislocation structures, that affects isotropic and kinematic hardening. The influence of the hardening model is compared to the influence of the texture evolution thanks to deep drawing simulations.

  8. Micromechanical simulation of Uranium dioxide polycrystalline aggregate behaviour under irradiation

    International Nuclear Information System (INIS)

    Pacull, J.

    2011-02-01

    In pressurized water nuclear power reactor (PWR), the fuel rod is made of dioxide of uranium (UO 2 ) pellet stacked in a metallic cladding. A multi scale and multi-physic approaches are needed for the simulation of fuel behavior under irradiation. The main phenomena to take into account are thermomechanical behavior of the fuel rod and chemical-physic behavior of the fission products. These last years one of the scientific issue to improve the simulation is to take into account the multi-physic coupling problem at the microscopic scale. The objective of this ph-D study is to contribute to this multi-scale approach. The present work concerns the micro-mechanical behavior of a polycrystalline aggregate of UO 2 . Mean field and full field approaches are considered. For the former and the later a self consistent homogenization technique and a periodic Finite Element model base on the 3D Voronoi pattern are respectively used. Fuel visco-plasticity is introduced in the model at the scale of a single grain by taking into account specific dislocation slip systems of UO 2 . A cohesive zone model has also been developed and implemented to simulate grain boundary sliding and intergranular crack opening. The effective homogenous behaviour of a Representative Volume Element (RVE) is fitted with experimental data coming from mechanical tests on a single pellet. Local behavior is also analyzed in order to evaluate the model capacity to assess micro-mechanical state. In particular, intra and inter granular stress gradient are discussed. A first validation of the local behavior assessment is proposed through the simulation of intergranular crack opening measured in a compressive creep test of a single fuel pellet. Concerning the impact of the microstructure on the fuel behavior under irradiation, a RVE simulation with a representative transient loading of a fuel rod during a power ramp test is achieved. The impact of local stress and strain heterogeneities on the multi

  9. Simulation study of dielectrophoretic assembly of nanowire between electrode pairs

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Quan, E-mail: taq3@pitt.edu; Lan, Fei; Jiang, Minlin [University of Pittsburgh, The Department of Electrical and Computer Engineering (United States); Wei, Fanan [Chinese Academy of Sciences, State Key Laboratory of Robotics, Shenyang Institute of Automation (China); Li, Guangyong, E-mail: gul6@pitt.edu [University of Pittsburgh, The Department of Electrical and Computer Engineering (United States)

    2015-07-15

    Dielectrophoresis (DEP) of rod-shaped nanostructures is attractive because of its exceptional capability to fabricate nanowire-based electronic devices. This efficient manipulation method, however, has a common side effect of assembling a certain number of nanowires at undesired positions. It is therefore essential to understand the underlying physics of DEP of nanowires in order to better guide the assembly. In this work, we propose theoretical methods to characterize the dielectrophoretic force and torque as well as the hydrodynamic drag force and torque on the nanowire (typical length: 10 μm). The trajectory of the nanowire is then simulated based on rigid body dynamics. The nanowire is predicted to either bridge the electrodes or attach on the surface of one electrode. A neighborhood in which the nanowire is more likely to bridge electrodes is found, which is conducive to successful assembly. The simulation study in this work provides us not only a better understanding of the underlying physics but also practical guidance on nanowire assembly by DEP.

  10. Atomistic simulations of the yielding of gold nanowires

    International Nuclear Information System (INIS)

    Diao Jiankuai; Gall, Ken; Dunn, Martin L.; Zimmerman, Jonathan A.

    2006-01-01

    We performed atomistic simulations to study the effect of free surfaces on the yielding of gold nanowires. Tensile surface stresses on the surfaces of the nanowires cause them to contract along the length with respect to the bulk face-centered cubic lattice and induce compressive stress in the interior. When the cross-sectional area of a nanowire is less than 2.45 nm x 2.45 nm, the wire yields under its surface stresses. Under external forces and surface stresses, nanowires yield via the nucleation and propagation of the {1 1 1} partial dislocations. The magnitudes of the tensile and compressive yield stress of nanowires increase and decrease, respectively, with a decrease of the wire width. The magnitude of the tensile yield stress is much larger than that of the compressive yield stress for small nanowires, while for small nanowires, tensile and compressive yield stresses have similar magnitudes. The critical resolved shear stress (RSS) by external forces depends on wire width, orientation and loading condition (tension vs. compression). However, the critical RSS in the interior of the nanowires, which is exerted by both the external force and the surface-stress-induced compressive stress, does not change significantly with wire width for same orientation and same loading condition, and can thus serve as a 'local' criterion. This local criterion is invoked to explain the observed size dependence of yield behavior and tensile/compressive yield stress asymmetry, considering surface stress effects and different slip systems active in tensile and compressive yielding

  11. Molecular dynamics simulation of thermal conductivities of superlattice nanowires

    Institute of Scientific and Technical Information of China (English)

    YANG; Juekuan(杨决宽); CHEN; Yunfei(陈云飞); YAN; Jingping(颜景平)

    2003-01-01

    Nonequilibrium molecular dynamics simulations were carried out to investigate heat transfer in superlattice nanowires. Results show that for fixed period length superlattice nanowires, the ratio of the total interfacial thermal resistance to the total thermal resistance and the effective thermal conductivities are invariant with the changes in interface numbers. Increasing the period length leads to an increase in the average interfacial thermal resistance, which indicates that the interfacial thermal resistance depends not only on the materials that constitute the alternating segments of superlattice nanowires, but also on the lattice strain throughout the segments. The modification of the lattice structure due to the lattice mismatch should be taken into account in the acoustic mismatch model. Simulation results also demonstrated the size confinement effect on the thermal conductivities for low dimensional structures, i.e. the thermal conductivities and the interfacial thermal resistance increase as the nanowire cross-sectional area increases.

  12. On the thermomechanical deformation of silver shape memory nanowires

    International Nuclear Information System (INIS)

    Park, Harold S.; Ji, Changjiang

    2006-01-01

    We present an analysis of the uniaxial thermomechanical deformation of single-crystal silver shape memory nanowires using atomistic simulations. We first demonstrate that silver nanowires can show both shape memory and pseudoelastic behavior, then perform uniaxial tensile loading of the shape memory nanowires at various deformation temperatures, strain rates and heat transfer conditions. The simulations show that the resulting mechanical response of the shape memory nanowires depends strongly upon the temperature during deformation, and can be fundamentally different from that observed in bulk polycrystalline shape memory alloys. The energy and temperature signatures of uniaxially loaded silver shape memory nanowires are correlated to the observed nanowire deformation, and are further discussed in comparison to bulk polycrystalline shape memory alloy behavior

  13. A new computer-aided simulation model for polycrystalline silicon film resistors

    Science.gov (United States)

    Ching-Yuan Wu; Weng-Dah Ken

    1983-07-01

    A general transport theory for the I-V characteristics of a polycrystalline film resistor has been derived by including the effects of carrier degeneracy, majority-carrier thermionic-diffusion across the space charge regions produced by carrier trapping in the grain boundaries, and quantum mechanical tunneling through the grain boundaries. Based on the derived transport theory, a new conduction model for the electrical resistivity of polycrystalline film resitors has been developed by incorporating the effects of carrier trapping and dopant segregation in the grain boundaries. Moreover, an empirical formula for the coefficient of the dopant-segregation effects has been proposed, which enables us to predict the dependence of the electrical resistivity of phosphorus-and arsenic-doped polycrystalline silicon films on thermal annealing temperature. Phosphorus-doped polycrystalline silicon resistors have been fabricated by using ion-implantation with doses ranged from 1.6 × 10 11 to 5 × 10 15/cm 2. The dependence of the electrical resistivity on doping concentration and temperature have been measured and shown to be in good agreement with the results of computer simulations. In addition, computer simulations for boron-and arsenic-doped polycrystalline silicon resistors have also been performed and shown to be consistent with the experimental results published by previous authors.

  14. Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition

    Science.gov (United States)

    Guillemin, Sophie; Parize, Romain; Carabetta, Joseph; Cantelli, Valentina; Albertini, David; Gautier, Brice; Brémond, Georges; Fong, Dillon D.; Renevier, Hubert; Consonni, Vincent

    2017-03-01

    The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscale-engineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol-gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 107 nano-objects both on the macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscale-engineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.

  15. Analytical simulation of RBS spectra of nanowire samples

    Energy Technology Data Exchange (ETDEWEB)

    Barradas, Nuno P., E-mail: nunoni@ctn.ist.utl.pt [Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10 ao km 139,7, 2695-066 Bobadela LRS (Portugal); García Núñez, C. [Laboratorio de Electrónica y Semiconductores, Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Redondo-Cubero, A. [Laboratorio de Electrónica y Semiconductores, Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Centro de Micro-Análisis de Materiales, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Shen, G.; Kung, P. [Department of Electrical and Computer Engineering, The University of Alabama, AL 35487 (United States); Pau, J.L. [Laboratorio de Electrónica y Semiconductores, Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid (Spain)

    2016-03-15

    Almost all, if not all, general purpose codes for analysis of Ion Beam Analysis data have been originally developed to handle laterally homogeneous samples only. This is the case of RUMP, NDF, SIMNRA, and even of the Monte Carlo code Corteo. General-purpose codes usually include only limited support for lateral inhomogeneity. In this work, we show analytical simulations of samples that consist of a layer of parallel oriented nanowires on a substrate, using a model implemented in NDF. We apply the code to real samples, made of vertical ZnO nanowires on a sapphire substrate. Two configurations of the nanowires were studied: 40 nm diameter, 4.1 μm height, 3.5% surface coverage; and 55 nm diameter, 1.1 μm height, 42% surface coverage. We discuss the accuracy and limits of applicability of the analysis.

  16. Superheating of Ag nanowires studied by molecular dynamics simulations

    International Nuclear Information System (INIS)

    Duan Wenshi; Ling Guangkong; Hong Lin; Li Hong; Liang Minghe

    2008-01-01

    The melting process of Ag nanowires was studied by molecular dynamics (MD) simulations at the atomic level. It is indicated that the Ag nanowires with Ni coating can be superheated depending on their radius and size. Also, in this paper the mechanism of superheating was analyzed and ascribed to the epitaxial Ag/Ni interface suppressing the nucleation and growth of melt. For the analysis, a thermodynamic model was constructed to describe the superheating mechanism of the Ni-coated Ag nanowires by considering the Ag/Ni interface free energy. We showed that the nucleation and growth of the Ag melt phase are both suppressed by the low energy Ag/Ni interfaces in Ni-coated Ag wires and the suppression of melt growth is crucial and plays a major role in the process of melting. The thermodynamic analysis gave a quantitative relation of superheating with the Ag wire radius and the contact angle of melting. The superheating decreased with Ag wire radius and also depended on the Ag/Ni interfacial condition. The results of the thermodynamic model were consistent with those of the MD simulations

  17. A simulation of laser energy absorption by nanowired surface

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcelos, Miguel F.S.; Ramos, Alexandre F., E-mail: miguel.vasconcelos@usp.br, E-mail: alex.ramos@usp.br [Universidade de São Paulo (USP), SP (Brazil). Escola de Artes, Ciências e Humanidades

    2017-07-01

    Despite recent advances on research about laser inertial fusion energy, to increase the portion of energy absorbed by the target's surface from lasers remains as an important challenge. The plasma formed during the initial instants of laser arrival shields the target and prevents the absorption of laser energy by the deeper layers of the material. One strategy to circumvent that effect is the construction of targets whose surfaces are populated with nanowires. The nanowired surfaces have increased absorption of laser energy and constitutes a promising pathway for enhancing laser-matter coupling. In our work we present the results of simulations aiming to investigate how target's geometrical properties might contribute for maximizing laser energy absorption by material. Simulations have been carried out using the software FLASH, a multi-physics platform developed by researchers from the University of Chicago, written in FORTRAN 90 and Python. Different tools for generating target's geometry and analysis of results were developed using Python. Our results show that a nanowired surfaces has an increased energy absorption when compared with non wired surface. The software for visualization developed in this work also allowed an analysis of the spatial dynamics of the target's temperature, electron density, ionization levels and temperature of the radiation emitted by it. (author)

  18. A simulation of laser energy absorption by nanowired surface

    International Nuclear Information System (INIS)

    Vasconcelos, Miguel F.S.; Ramos, Alexandre F.

    2017-01-01

    Despite recent advances on research about laser inertial fusion energy, to increase the portion of energy absorbed by the target's surface from lasers remains as an important challenge. The plasma formed during the initial instants of laser arrival shields the target and prevents the absorption of laser energy by the deeper layers of the material. One strategy to circumvent that effect is the construction of targets whose surfaces are populated with nanowires. The nanowired surfaces have increased absorption of laser energy and constitutes a promising pathway for enhancing laser-matter coupling. In our work we present the results of simulations aiming to investigate how target's geometrical properties might contribute for maximizing laser energy absorption by material. Simulations have been carried out using the software FLASH, a multi-physics platform developed by researchers from the University of Chicago, written in FORTRAN 90 and Python. Different tools for generating target's geometry and analysis of results were developed using Python. Our results show that a nanowired surfaces has an increased energy absorption when compared with non wired surface. The software for visualization developed in this work also allowed an analysis of the spatial dynamics of the target's temperature, electron density, ionization levels and temperature of the radiation emitted by it. (author)

  19. Proper Generalized Decomposition (PGD) for the numerical simulation of polycrystalline aggregates under cyclic loading

    Science.gov (United States)

    Nasri, Mohamed Aziz; Robert, Camille; Ammar, Amine; El Arem, Saber; Morel, Franck

    2018-02-01

    The numerical modelling of the behaviour of materials at the microstructural scale has been greatly developed over the last two decades. Unfortunately, conventional resolution methods cannot simulate polycrystalline aggregates beyond tens of loading cycles, and they do not remain quantitative due to the plasticity behaviour. This work presents the development of a numerical solver for the resolution of the Finite Element modelling of polycrystalline aggregates subjected to cyclic mechanical loading. The method is based on two concepts. The first one consists in maintaining a constant stiffness matrix. The second uses a time/space model reduction method. In order to analyse the applicability and the performance of the use of a space-time separated representation, the simulations are carried out on a three-dimensional polycrystalline aggregate under cyclic loading. Different numbers of elements per grain and two time increments per cycle are investigated. The results show a significant CPU time saving while maintaining good precision. Moreover, increasing the number of elements and the number of time increments per cycle, the model reduction method is faster than the standard solver.

  20. Three-dimensional phase-field simulation on the deformation of metallic glass nanowires

    International Nuclear Information System (INIS)

    Zhang, H.Y.; Zheng, G.P.

    2014-01-01

    Highlights: • 3D phase-field modeling is developed to investigate the deformation of MG nanowires. • The surface defects significantly affect the mechanical properties of nanowires. • Multiple shear bands are initiated from the surfaces of nanowires with D < 50 nm. - Abstract: It is very challenging to investigate the deformation mechanisms in micro- and nano-scale metallic glasses with diameters below several hundred nanometers using the atomistic simulation or the experimental approaches. In this work, we develop the fully three-dimensional phase-field model to bridge this gap and investigate the sample size effects on the deformation behaviors of metallic glass nanowires. The initial deformation defects on the surface are found to significantly affect the mechanical strength and deformation mode of nanowires. The improved ductility of metallic glass nanowires could be related with the multiple shear bands initiated from the nanowire surfaces

  1. Simulations of backgate sandwich nanowire MOSFETs with improved device performance

    International Nuclear Information System (INIS)

    Zhao Hengliang; Zhu Huilong; Zhong Jian; Ma Xiaolong; Wei Xing; Zhao Chao; Chen Dapeng; Ye Tianchun

    2014-01-01

    We propose a novel backgate sandwich nanowire MOSFET (SNFET), which offers the advantages of ETSOI (dynamic backgate voltage controllability) and nanowire FETs (good short channel effect). A backgate is used for threshold voltage (V t ) control of the SNFET. Compared with a backgate FinFET with a punch-through stop layer (PTSL), the SNFET possesses improved device performance. 3D device simulations indicate that the SNFET has a three times larger overdrive current, a ∼75% smaller off leakage current, and reduced subthreshold swing (SS) and DIBL than those of a backgate FinFET when the nanowire (NW) and the fin are of equal width. A new process flow to fabricate the backgate SNFET is also proposed in this work. Our analytical model suggests that V t control by the backgate can be attributed to the capacitances formed by the frontgate, NW, and backgate. The SNFET devices are compatible with the latest state-of-the-art high-k/metal gate CMOS technology with the unique capability of independent backgate control for nFETs and pFETs, which is promising for sub-22 nm scaling down. (semiconductor devices)

  2. Seed-mediated shape evolution of gold nanomaterials: from spherical nanoparticles to polycrystalline nanochains and single-crystalline nanowires

    International Nuclear Information System (INIS)

    Qiu Penghe; Mao Chuanbin

    2009-01-01

    We studied the kinetics of the reduction of a gold precursor (HAuCl 4 ) and the effect of the molar ratio (R) of sodium citrate, which was introduced from a seed solution, and the gold precursor on the shape evolution of gold nanomaterials in the presence of preformed 13 nm gold nanoparticles as seeds. The reduction of the gold precursor by sodium citrate was accelerated due to the presence of gold seeds. Nearly single-crystalline gold nanowires were formed at a very low R value (R = 0.16) in the presence of the seeds as a result of the oriented attachment of the growing gold nanoparticles. At a higher R value (R = 0.33), gold nanochains were formed due to the non-oriented attachment of gold nanoparticles. At a much higher R value (R = 1.32), only larger spherical gold nanoparticles grown from the seeds were found. In the absence of gold seeds, no single-crystalline nanowires were formed at the same R value. Our results indicate that the formation of the 1D nanostructures (nanochains and nanowires) at low R values is due to the attachment of gold nanoparticles along one direction, which is driven by the surface energy reduction, nanoparticle attraction, and dipole-dipole interaction between adjacent nanoparticles.

  3. Density Functional Simulation of a Breaking Nanowire

    DEFF Research Database (Denmark)

    Nakamura, A.; Brandbyge, Mads; Hansen, Lars Bruno

    1999-01-01

    to a specific number of eigenchannels. The transitions between plateaus can be abrupt in connection with structural rearrangements or extend over a few a of elongation. The interplay between conductance modes and structural deformation is discussed by means of the eigenchannel transmission probabilities.......We study the deformation and breaking of an atomic-sized sodium wire using density functional simulations. The wire deforms through sudden atomic rearrangements and smoother atomic displacements. The conductance of the wire exhibits plateaus at integer values in units of 2e(2)/h corresponding...

  4. Molecular statics simulations of buckling and yielding of gold nanowires deformed in axial compression

    International Nuclear Information System (INIS)

    Jiang, W.; Batra, R.C.

    2009-01-01

    We use molecular statics simulations with the embedded atom method potential to delineate yielding (material instability) and buckling (structural instability) in gold nanowires deformed axially in compression. It is found that both local (stacking faults) and global instabilities occur when the gold nanowire yields but only global instabilities occur when the nanowire buckles. Furthermore strong surface effects reorient the lattice structure which significantly increases Young's modulus in the axial direction and cause a nanowire of relatively small slenderness ratio (e.g., 14) to buckle. Upon complete unloading of the nanowires, the average axial stress and the total potential energy revert to their values in the reference configuration for the nanowires that buckled but not for the one that yielded.

  5. Title: Using Alignment and 2D Network Simulations to Study Charge Transport Through Doped ZnO Nanowire Thin Film Electrodes

    KAUST Repository

    Phadke, Sujay; Lee, Jung-Yong; West, Jack; Peumans, Peter; Salleo, Alberto

    2011-01-01

    of magnitude lower than the single nanowire resistance. Simulations suggest that the conductivity of such thin film devices could be further enhanced by using longer nanowires. Solution processed Gallium doped ZnO nanowires are aligned on substrates using

  6. Synthesis of naturally cross-linked polycrystalline ZrO2 hollow nanowires using butterfly as templates

    International Nuclear Information System (INIS)

    Chen Yu; Gu Jiajun; Zhu Shenmin; Su Huilan; Zhang Di; Feng Chuanliang; Zhuang Leyan

    2012-01-01

    Highlights: ► Naturally cross-linked ZrO 2 nanotubes with ∼2.4 μm in length, ∼35 nm in diameter and ∼12 nm in wall thickness was synthesized via the selection of suitable butterfly bio-templates followed by heat processing. ► The contractions, which are main defects of the former hard-template method based on butterflies, are well controlled with the help of the surface tension effect. ► The achieved hollow ZrO 2 nanowires suggest a new optional approach that uses bio-templates in fabricating and designing nano systems. - Abstract: Butterfly wing skeleton is a widely used hard-template in recent years for fabricating photonic crystal structures. However, the smallest construction units for the most species of butterflies are commonly larger than ∼50 nm, which greatly hinders their applications in designing much smaller functional parts down to real “nano scale”. This work indicates, however, that hollow ZrO 2 nanowires with ∼2.4 μm in length, ∼35 nm in diameter and ∼12 nm in wall thickness can be synthesized via the selection of suitable butterfly bio-templates followed by heat processing. Especially, the successful fabrication of these naturally cross-linked ZrO 2 nanotubes suggests a new optional approach in fabricating assembled nano systems.

  7. Synthesis of naturally cross-linked polycrystalline ZrO{sub 2} hollow nanowires using butterfly as templates

    Energy Technology Data Exchange (ETDEWEB)

    Chen Yu, E-mail: chenyu_8323@csu.edu.cn [School of Physics Science and Electronics Central South University, Changsha, Hunan 410083 (China); Gu Jiajun, E-mail: gujiajun@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhu Shenmin; Su Huilan [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhang Di, E-mail: zhangdi@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China); Feng Chuanliang [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhuang Leyan [Measurement Center of Anti-Counterfeiting Technical Products, Shanghai (China)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Naturally cross-linked ZrO{sub 2} nanotubes with {approx}2.4 {mu}m in length, {approx}35 nm in diameter and {approx}12 nm in wall thickness was synthesized via the selection of suitable butterfly bio-templates followed by heat processing. Black-Right-Pointing-Pointer The contractions, which are main defects of the former hard-template method based on butterflies, are well controlled with the help of the surface tension effect. Black-Right-Pointing-Pointer The achieved hollow ZrO{sub 2} nanowires suggest a new optional approach that uses bio-templates in fabricating and designing nano systems. - Abstract: Butterfly wing skeleton is a widely used hard-template in recent years for fabricating photonic crystal structures. However, the smallest construction units for the most species of butterflies are commonly larger than {approx}50 nm, which greatly hinders their applications in designing much smaller functional parts down to real 'nano scale'. This work indicates, however, that hollow ZrO{sub 2} nanowires with {approx}2.4 {mu}m in length, {approx}35 nm in diameter and {approx}12 nm in wall thickness can be synthesized via the selection of suitable butterfly bio-templates followed by heat processing. Especially, the successful fabrication of these naturally cross-linked ZrO{sub 2} nanotubes suggests a new optional approach in fabricating assembled nano systems.

  8. A molecular dynamics simulation study of irradiation induced defects in gold nanowire

    Science.gov (United States)

    Liu, Wenqiang; Chen, Piheng; Qiu, Ruizhi; Khan, Maaz; Liu, Jie; Hou, Mingdong; Duan, Jinglai

    2017-08-01

    Displacement cascade in gold nanowires was studied using molecular dynamics computer simulations. Primary knock-on atoms (PKAs) with different kinetic energies were initiated either at the surface or at the center of the nanowires. We found three kinds of defects that were induced by the cascade, including point defects, stacking faults and crater at the surface. The starting points of PKAs influence the number of residual point defects, and this consequently affect the boundary of anti-radiation window which was proposed by calculation of diffusion of point defects to the free surface of nanowires. Formation of stacking faults that expanded the whole cross-section of gold nanowires was observed when the PKA's kinetic energy was higher than 5 keV. Increasing the PKA's kinetic energy up to more than 10 keV may lead to the formation of crater at the surface of nanowires due to microexplosion of hot atoms. At this energy, PKAs started from the center of nanowires can also result in the creation of crater because length of cascade region is comparable to diameter of nanowires. Both the two factors, namely initial positions of PKAs as well as the craters induced by higher energy irradiation, would influence the ability of radiation resistance of metal nanowires.

  9. FDTD simulation of trapping nanowires with linearly polarized and radially polarized optical tweezers.

    Science.gov (United States)

    Li, Jing; Wu, Xiaoping

    2011-10-10

    In this paper a model of the trapping force on nanowires is built by three dimensional finite-difference time-domain (FDTD) and Maxwell stress tensor methods, and the tightly focused laser beam is expressed by spherical vector wave functions (VSWFs). The trapping capacities on nanoscale-diameter nanowires are discussed in terms of a strongly focused linearly polarized beam and radially polarized beam. Simulation results demonstrate that the radially polarized beam has higher trapping efficiency on nanowires with higher refractive indices than linearly polarized beam.

  10. Performance analysis and simulation of vertical gallium nitride nanowire transistors

    Science.gov (United States)

    Witzigmann, Bernd; Yu, Feng; Frank, Kristian; Strempel, Klaas; Fatahilah, Muhammad Fahlesa; Schumacher, Hans Werner; Wasisto, Hutomo Suryo; Römer, Friedhard; Waag, Andreas

    2018-06-01

    Gallium nitride (GaN) nanowire transistors are analyzed using hydrodynamic simulation. Both p-body and n-body devices are compared in terms of threshold voltage, saturation behavior and transconductance. The calculations are calibrated using experimental data. The threshold voltage can be tuned from enhancement to depletion mode with wire doping. Surface states cause a shift of threshold voltage and saturation current. The saturation current depends on the gate design, with a composite gate acting as field plate in the p-body device. He joined Bell Laboratories, Murray Hill, NJ, as a Technical Staff Member. In October 2001, he joined the Optical Access and Transport Division, Agere Systems, Alhambra, CA. In 2004, he was appointed an Assistant Professor at ETH Zurich,. Since 2008, at the University of Kassel, Kassel, Germany, and he has been a Professor the Head of the Computational Electronics and Photonics Group, and co-director of CINSaT since 2010. His research interests include computational optoelectronics, process and device design of semiconductor photonic devices, microwave components, and electromagnetics modeling for nanophotonics. Dr. Witzigmann is a senior member of the SPIE and IEEE.

  11. Dislocation-induced stress in polycrystalline materials: mesoscopic simulations in the dislocation density formalism

    Science.gov (United States)

    Berkov, D. V.; Gorn, N. L.

    2018-06-01

    In this paper we present a simple and effective numerical method which allows a fast Fourier transformation-based evaluation of stress generated by dislocations with arbitrary directions and Burgers vectors if the (site-dependent) dislocation density is known. Our method allows the evaluation of the dislocation stress using a rectangular grid with shape-anisotropic discretization cells without employing higher multipole moments of the dislocation interaction coefficients. Using the proposed method, we first simulate the stress created by relatively simple non-homogeneous distributions of vertical edge and so-called ‘mixed’ dislocations in a disk-shaped sample, which is necessary to understand the dislocation behavior in more complicated systems. The main part of our research is devoted to the stress distribution in polycrystalline layers with the dislocation density rapidly varying with the distance to the layer bottom. Considering GaN as a typical example of such systems, we investigate dislocation-induced stress for edge and mixed dislocations, having random orientations of Burgers vectors among crystal grains. We show that the rapid decay of the dislocation density leads to many highly non-trivial features of the stress distributions in such layers and study in detail the dependence of these features on the average grain size. Finally we develop an analytical approach which allows us to predict the evolution of the stress variance with the grain size and compare analytical predictions with numerical results.

  12. The fracture behavior of twinned Cu nanowires: A molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jiapeng, E-mail: sun.jiap@gmail.com [College of Mechanics and Materials, Hohai University, Nanjing 210098 (China); Fang, Liang [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, Shaanxi Province (China); Ma, Aibin, E-mail: aibin-ma@hhu.edu.cn [College of Mechanics and Materials, Hohai University, Nanjing 210098 (China); Jiang, Jinghua [College of Mechanics and Materials, Hohai University, Nanjing 210098 (China); Han, Ying [Key Laboratory of Advanced Structural Materials, Ministry of Education, Changchun University of Technology, Changchun 130012, Jilin Province (China); Chen, Huawei [Department of Applied Physics, School of Science, Xi’an Jiaotong University, Xi’an 710049, Shaanxi Province (China); Han, Jing [School of Mechanical and Electrical Engineering, China University of Mining and Technology, Xuzhou 221116, Jiangsu Province (China)

    2015-05-14

    The molecular dynamics simulations are performed to explore the fracture behavior and the ductility of the twinned Cu nanowires containing orthogonally oriented growth CTBs due to the uniaxial tensile deformation. The results reveal that, the fracture behavior and the ductility of the twinned nanowires are not related to the length of the nanowires but also intensively related to the twin boundary spacing. When the twin boundary space is changed, the twinned nanowires undergo three distinct failure modes which include ductile fracture, brittle fracture and ductile-to-brittle transition depending on the length of the nanowires. We also find a reduction in the ductility of the twinned nanowires, which is ascribed to the deformation localization induced by the Lomer dislocation and the rapid necking resulted from the twinning partial slipping. Finally, the atomic-level process that occurs during deformation until final fracture are examined in detail, and a new formation mechanism of the Lomer dislocation is observed when a 90° partial dislocation transmits across a coherent twin boundary.

  13. The fracture behavior of twinned Cu nanowires: A molecular dynamics simulation

    International Nuclear Information System (INIS)

    Sun, Jiapeng; Fang, Liang; Ma, Aibin; Jiang, Jinghua; Han, Ying; Chen, Huawei; Han, Jing

    2015-01-01

    The molecular dynamics simulations are performed to explore the fracture behavior and the ductility of the twinned Cu nanowires containing orthogonally oriented growth CTBs due to the uniaxial tensile deformation. The results reveal that, the fracture behavior and the ductility of the twinned nanowires are not related to the length of the nanowires but also intensively related to the twin boundary spacing. When the twin boundary space is changed, the twinned nanowires undergo three distinct failure modes which include ductile fracture, brittle fracture and ductile-to-brittle transition depending on the length of the nanowires. We also find a reduction in the ductility of the twinned nanowires, which is ascribed to the deformation localization induced by the Lomer dislocation and the rapid necking resulted from the twinning partial slipping. Finally, the atomic-level process that occurs during deformation until final fracture are examined in detail, and a new formation mechanism of the Lomer dislocation is observed when a 90° partial dislocation transmits across a coherent twin boundary

  14. Title: Using Alignment and 2D Network Simulations to Study Charge Transport Through Doped ZnO Nanowire Thin Film Electrodes

    KAUST Repository

    Phadke, Sujay

    2011-09-30

    Factors affecting charge transport through ZnO nanowire mat films were studied by aligning ZnO nanowires on substrates and coupling experimental measurements with 2D nanowire network simulations. Gallium doped ZnO nanowires were aligned on thermally oxidized silicon wafer by shearing a nanowire dispersion in ethanol. Sheet resistances of nanowire thin films that had current flowing parallel to nanowire alignment direction were compared to thin films that had current flowing perpendicular to nanowire alignment direction. Perpendicular devices showed ∼5 fold greater sheet resistance than parallel devices supporting the hypothesis that aligning nanowires would increase conductivity of ZnO nanowire electrodes. 2-D nanowire network simulations of thin films showed that the device sheet resistance was dominated by inter-wire contact resistance. For a given resistivity of ZnO nanowires, the thin film electrodes would have the lowest possible sheet resistance if the inter-wire contact resistance was one order of magnitude lower than the single nanowire resistance. Simulations suggest that the conductivity of such thin film devices could be further enhanced by using longer nanowires. Solution processed Gallium doped ZnO nanowires are aligned on substrates using an innovative shear coating technique. Nanowire alignment has shown improvement in ZnO nanowire transparent electrode conductivity. 2D network simulations in conjunction with electrical measurements have revealed different regimes of operation of nanowire thin films and provided a guideline for improving electrical performance of nanowire electrodes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Simulation of inter- and transgranular crack propagation in polycrystalline aggregates due to stress corrosion cracking

    International Nuclear Information System (INIS)

    Musienko, Andrey; Cailletaud, Georges

    2009-01-01

    The motivation of the study is the development of a coupled approach able to account for the interaction between environment and plasticity in a polycrystalline material. The paper recalls first the constitutive equations used to describe the behavior of the grain core and of the grain boundary (GB). The procedure that is applied to generate synthetic polycrystalline aggregates with an explicit representation of the grain boundary area by 2D or 3D finite elements is then described. The approach is applied to the modeling of iodine-assisted stress corrosion cracking (IASCC) in Zircaloy tubes used in nuclear power plants.

  16. Molecular dynamics simulation on the elastoplastic properties of copper nanowire under torsion

    Science.gov (United States)

    Yang, Yong; Li, Ying; Yang, Zailin; Zhang, Guowei; Wang, Xizhi; Liu, Jin

    2018-02-01

    Influences of different factors on the torsion properties of single crystal copper nanowire are studied by molecular dynamics method. The length, torsional rate, and temperature of the nanowire are discussed at the elastic-plastic critical point. According to the average potential energy curve and shear stress curve, the elastic-plastic critical angle is determined. Also, the dislocation at elastoplastic critical points is analyzed. The simulation results show that the single crystal copper nanowire can be strengthened by lengthening the model, decreasing the torsional rate, and lowering the temperature. Moreover, atoms move violently and dislocation is more likely to occur with a higher temperature. This work mainly describes the mechanical behavior of the model under different states.

  17. Fabrication and simulation of single crystal p-type Si nanowire using SOI technology

    International Nuclear Information System (INIS)

    Dehzangi, Arash; Larki, Farhad; Naseri, Mahmud G.; Navasery, Manizheh; Majlis, Burhanuddin Y.; Razip Wee, Mohd F.; Halimah, M.K.; Islam, Md. Shabiul; Md Ali, Sawal H.; Saion, Elias

    2015-01-01

    Highlights: • Single crystal silicon nanowire is fabricated on Si on insulator substrate, using atomic force microscope (AFM) nanolithography and KOH + IPA chemical wet etching. • Some of major parameters in fabrication process, such as writing speed and applied voltage along with KOH etching depth are investigated, and then the I–V characteristic of Si nanowires is measured. • For better understanding of the charge transmission through the nanowire, 3D-TCAD simulation is performed to simulate the Si nanowires with the same size of the fabricated ones, and variation of majority and minority carriers, hole quasi-Fermi level and generation/recombination rate are investigated. - Abstract: Si nanowires (SiNWs) as building blocks for nanostructured materials and nanoelectronics have attracted much attention due to their major role in device fabrication. In the present work a top-down fabrication approach as atomic force microscope (AFM) nanolithography was performed on Si on insulator (SOI) substrate to fabricate a single crystal p-type SiNW. To draw oxide patterns on top of the SOI substrate local anodic oxidation was carried out by AFM in contact mode. After the oxidation procedure, an optimized solution of 30 wt.% KOH with 10 vol.% IPA for wet etching at 63 °C was applied to extract the nanostructure. The fabricated SiNW had 70–85 nm full width at half maximum width, 90 nm thickness and 4 μm length. The SiNW was simulated using Sentaurus 3D software with the exact same size of the fabricated device. I–V characterization of the SiNW was measured and compared with simulation results. Using simulation results variation of carrier's concentrations, valence band edge energy and recombination generation rate for different applied voltage were investigated

  18. Fabrication and simulation of single crystal p-type Si nanowire using SOI technology

    Energy Technology Data Exchange (ETDEWEB)

    Dehzangi, Arash, E-mail: arashd53@hotmail.com [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Larki, Farhad [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Naseri, Mahmud G. [Department of Physics, Faculty of Science, Malayer University, Malayer, Hamedan (Iran, Islamic Republic of); Navasery, Manizheh [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Majlis, Burhanuddin Y.; Razip Wee, Mohd F. [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Halimah, M.K. [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Islam, Md. Shabiul; Md Ali, Sawal H. [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Saion, Elias [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia)

    2015-04-15

    Highlights: • Single crystal silicon nanowire is fabricated on Si on insulator substrate, using atomic force microscope (AFM) nanolithography and KOH + IPA chemical wet etching. • Some of major parameters in fabrication process, such as writing speed and applied voltage along with KOH etching depth are investigated, and then the I–V characteristic of Si nanowires is measured. • For better understanding of the charge transmission through the nanowire, 3D-TCAD simulation is performed to simulate the Si nanowires with the same size of the fabricated ones, and variation of majority and minority carriers, hole quasi-Fermi level and generation/recombination rate are investigated. - Abstract: Si nanowires (SiNWs) as building blocks for nanostructured materials and nanoelectronics have attracted much attention due to their major role in device fabrication. In the present work a top-down fabrication approach as atomic force microscope (AFM) nanolithography was performed on Si on insulator (SOI) substrate to fabricate a single crystal p-type SiNW. To draw oxide patterns on top of the SOI substrate local anodic oxidation was carried out by AFM in contact mode. After the oxidation procedure, an optimized solution of 30 wt.% KOH with 10 vol.% IPA for wet etching at 63 °C was applied to extract the nanostructure. The fabricated SiNW had 70–85 nm full width at half maximum width, 90 nm thickness and 4 μm length. The SiNW was simulated using Sentaurus 3D software with the exact same size of the fabricated device. I–V characterization of the SiNW was measured and compared with simulation results. Using simulation results variation of carrier's concentrations, valence band edge energy and recombination generation rate for different applied voltage were investigated.

  19. Modeling and simulation of the deposition/relaxation processes of polycrystalline diatomic structures of metallic nitride films

    Science.gov (United States)

    García, M. F.; Restrepo-Parra, E.; Riaño-Rojas, J. C.

    2015-05-01

    This work develops a model that mimics the growth of diatomic, polycrystalline thin films by artificially splitting the growth into deposition and relaxation processes including two stages: (1) a grain-based stochastic method (grains orientation randomly chosen) is considered and by means of the Kinetic Monte Carlo method employing a non-standard version, known as Constant Time Stepping, the deposition is simulated. The adsorption of adatoms is accepted or rejected depending on the neighborhood conditions; furthermore, the desorption process is not included in the simulation and (2) the Monte Carlo method combined with the metropolis algorithm is used to simulate the diffusion. The model was developed by accounting for parameters that determine the morphology of the film, such as the growth temperature, the interacting atomic species, the binding energy and the material crystal structure. The modeled samples exhibited an FCC structure with grain formation with orientations in the family planes of , and . The grain size and film roughness were analyzed. By construction, the grain size decreased, and the roughness increased, as the growth temperature increased. Although, during the growth process of real materials, the deposition and relaxation occurs simultaneously, this method may perhaps be valid to build realistic polycrystalline samples.

  20. Analysis of nanowire transistor based nitrogen dioxide gas sensor – A simulation study

    Directory of Open Access Journals (Sweden)

    Gaurav Saxena

    2015-06-01

    Full Text Available Sensors sensitivity, selectivity and stability has always been a prime design concern for gas sensors designers. Modeling and simulation of gas sensors aids the designers in improving their performance. In this paper, different routes for the modeling and simulation of a semiconducting gas sensor is presented. Subsequently, by employing one of the route, the response of Zinc Oxide nanowire transistor towards nitrogen dioxide ambient is simulated. In addition to the sensing mechanism, simulation study of gas species desorption by applying a recovery voltage is also presented.

  1. Studies on the polycrystalline silicon/SiO2 stack as front surface field for IBC solar cells by two-dimensional simulations

    International Nuclear Information System (INIS)

    Jiang Shuai; Jia Rui; Tao Ke; Hou Caixia; Sun Hengchao; Li Yongtao; Yu Zhiyong

    2017-01-01

    Interdigitated back contact (IBC) solar cells can achieve a very high efficiency due to its less optical losses. But IBC solar cells demand for high quality passivation of the front surface. In this paper, a polycrystalline silicon/SiO 2 stack structure as front surface field to passivate the front surface of IBC solar cells is proposed. The passivation quality of this structure is investigated by two dimensional simulations. Polycrystalline silicon layer and SiO 2 layer are optimized to get the best passivation quality of the IBC solar cell. Simulation results indicate that the doping level of polycrystalline silicon should be high enough to allow a very thin polycrystalline silicon layer to ensure an effective passivation and small optical losses at the same time. The thickness of SiO 2 should be neither too thin nor too thick, and the optimal thickness is 1.2 nm. Furthermore, the lateral transport properties of electrons are investigated, and the simulation results indicate that a high doping level and conductivity of polycrystalline silicon can improve the lateral transportation of electrons and then the cell performance. (paper)

  2. A MONTÉ CARLO MODEL FOR SIMULATING THE NITROGEN DIFFUSION EFFECT INTO B-LPCVD-NIDOS POLYCRYSTALLINE THIN FILMS

    Directory of Open Access Journals (Sweden)

    S ALLAG

    2012-06-01

    Full Text Available The principal objective of our current work, is to study the influence of different treatment from surface which makes it possible to improve the properties of materials by technique of beam of ions (diffusion – implantation, on the distribution of the particles in a semiconductor the prone polycrystalline Silicon of our study, largely used in micro-electronics.  The interest of this study is related to the ceaseless requirements in industry for increasingly reduced, powerful materials and with the weakest possible cost price.       We thus have, makes a nitriding in gas phase during the phase of deposit LPCVD of polycrystalline Silicon, then one made an ionic implantation with the Bore ions.  The results obtained, starting from a simulation based on the Monte Carlo method, although they are carried out with amounts much lower than the really introduced amounts, being given the limitation of the machine used, satisfied the predictions established at the beginning and encourage us to continue this study from the point of view of the use of this material in particular in varied fields.

  3. Electromigration-Induced Surface Drift and Slit Propagation in Polycrystalline Interconnects: Insights from Phase-Field Simulations

    Science.gov (United States)

    Mukherjee, Arnab; Ankit, Kumar; Selzer, Michael; Nestler, Britta

    2018-04-01

    We employ the phase-field method to assess electromigration (EM) damage in wide polycrystalline interconnects due to grain-boundary grooving. An interplay of surface and grain-boundary diffusion is shown to drastically influence the mode of progressive EM damage. Rapid atomic transport along the surface leads to shape-preserving surface drift reminiscent of Blech drift-velocity experiments. On the other hand, a comparatively faster grain-boundary transport localizes the damage, resulting in the proliferation of intergranular slits with a shape-preserving tip. At steady state, the two regimes exhibit exponents of 1 and 3 /2 , respectively, in Black's law. While surface drift obeys an inverse scaling with grain size, slits exhibit a direct relationship at small sizes, with the dependence becoming weaker at larger ones. Furthermore, we explain the influence of curvature- or EM-mediated healing fluxes running along the surface on groove replenishment. Insights derived from phase-field simulations of EM in bicrystals are extended to investigate the multiphysics of mixed-mode damage of a polycrystalline interconnect line that is characterized by a drift of small grain surfaces, slit propagation, and coarsening. The triple and quadruple junctions are identified as prominent sites of failure.

  4. Multi-material gate poly-crystalline thin film transistors: Modeling and simulation for an improved gate transport efficiency

    International Nuclear Information System (INIS)

    Sehgal, Amit; Mangla, Tina; Gupta, Mridula; Gupta, R.S.

    2008-01-01

    In this work, a two-dimensional potential distribution formulation is presented for multi-material gate poly-crystalline silicon thin film transistors. The developed formulation incorporates the effects due to traps and grain-boundaries. In short-channel devices, short-channel effects and drain-induced barrier lowering (DIBL) effect exists, and are accounted for in the analysis. The work aims at the reduction of DIBL effect and grain-boundary effects i.e. to reduce the potential barriers generated in the channel by employing gate-engineered structures. A study of work-functions and electrode lengths of multi-material gate electrode is done to suppress the potential barriers, hot electron effect and to improve the carrier transport efficiency. Green's function approach is adopted for the two-dimensional potential solution. The results obtained show a good agreement with simulated results, thus, demonstrating the validity of our model

  5. Predictive simulations and optimization of nanowire field-effect PSA sensors including screening

    KAUST Repository

    Baumgartner, Stefan; Heitzinger, Clemens; Vacic, Aleksandar; Reed, Mark A

    2013-01-01

    We apply our self-consistent PDE model for the electrical response of field-effect sensors to the 3D simulation of nanowire PSA (prostate-specific antigen) sensors. The charge concentration in the biofunctionalized boundary layer at the semiconductor-electrolyte interface is calculated using the propka algorithm, and the screening of the biomolecules by the free ions in the liquid is modeled by a sensitivity factor. This comprehensive approach yields excellent agreement with experimental current-voltage characteristics without any fitting parameters. Having verified the numerical model in this manner, we study the sensitivity of nanowire PSA sensors by changing device parameters, making it possible to optimize the devices and revealing the attributes of the optimal field-effect sensor. © 2013 IOP Publishing Ltd.

  6. Examination Of Si-Ge Heterostructure Nanowire Growth Using Monte Carlo Simulation

    International Nuclear Information System (INIS)

    Nastovjak, A. G.; Neizvestny, I. G.; Shwartz, N. L.

    2011-01-01

    The process of Si-Ge heterostructures formation in nanowires (NWs) grown by vapor-liquid-solid mechanism was investigated using Monte Carlo simulation. Dependences of catalyst drop composition on temperature, flux intensity and nanowire diameter were obtained. Periodical oscillations of drop composition near mean value were observed. Oscillation results from layer-by-layer growth at the drop-whisker interface and necessity of supersaturation onset to start new layer formation. It was demonstrated that it is impossible to grow atomically abrupt axial heterojunctions via classical vapor-liquid-solid mechanism due to gradual change of catalyst drop composition when switching the fluxes. This phenomenon is the main reason of heterojunction blurriness. Junction abruptness was found to be dependent on nanowhisker diameter: in adsorption-induced growth mode abruptness of heterojunction decreases with diameter and in diffusion-induced mode it increases.

  7. Predictive simulations and optimization of nanowire field-effect PSA sensors including screening

    KAUST Repository

    Baumgartner, Stefan

    2013-05-03

    We apply our self-consistent PDE model for the electrical response of field-effect sensors to the 3D simulation of nanowire PSA (prostate-specific antigen) sensors. The charge concentration in the biofunctionalized boundary layer at the semiconductor-electrolyte interface is calculated using the propka algorithm, and the screening of the biomolecules by the free ions in the liquid is modeled by a sensitivity factor. This comprehensive approach yields excellent agreement with experimental current-voltage characteristics without any fitting parameters. Having verified the numerical model in this manner, we study the sensitivity of nanowire PSA sensors by changing device parameters, making it possible to optimize the devices and revealing the attributes of the optimal field-effect sensor. © 2013 IOP Publishing Ltd.

  8. Simulation of Nanowires on Metal Vicinal Surfaces: Effect of Growth Parameters and Energetic Barriers

    Science.gov (United States)

    Hamouda, Ajmi B. H.; Blel, Sonia; Einstein, T. L.

    2012-02-01

    Growing one-dimensional metal structures is an important task in the investigation of the electronic and magnetic properties of new devices. We used kinetic Monte-Carlo (kMC) method to simulate the formation of nanowires of several metallic and non-metallic adatoms on Cu and Pt vicinal surfaces. We found that mono-atomic chains form on step-edges due to energetic barriers (the so-called Ehrlich-shwoebel and exchange barriers) on step-edge. Creation of perfect wires is found to depend on growth parameters and binding energies. We measure the filling ratio of nanowires for different chemical species in a wide range of temperature and flux. Perfect wires were obtained at lower deposition rate for all tested adatoms, however we notice different temperature ranges. Our results were compared with experimental ones [Gambardella et al., Surf. Sci.449, 93-103 (2000), PRB 61, 2254-2262, (2000)]. We review the role of impurities in nanostructuring of surfaces [Hamouda et al., Phys. Rev. B 83, 035423, (2011)] and discuss the effect of their energetic barriers on the obtained quality of nanowires. Our work provides experimentalists with optimum growth parameters for the creation of a uniform distribution of wires on surfaces.

  9. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wei-Ting [Department of Materials Science and Engineering, National Cheng Kung University, Tainan City 70101 Taiwan (China); Hsiao, Chun-I. [Department of Materials Science and Engineering, National Cheng Kung University, Tainan City 70101 Taiwan (China); Promotion Center for Global Materials Research, National Cheng Kung University, Tainan City 70101 Taiwan (China); Hsu, Wen-Dung, E-mail: wendung@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan City 70101 Taiwan (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan City 70101 Taiwan (China); Promotion Center for Global Materials Research, National Cheng Kung University, Tainan City 70101 Taiwan (China)

    2014-01-15

    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.

  11. Plasticity-mediated collapse and recrystallization in hollow copper nanowires: a molecular dynamics simulation

    Directory of Open Access Journals (Sweden)

    Amlan Dutta

    2016-02-01

    Full Text Available We study the thermal stability of hollow copper nanowires using molecular dynamics simulation. We find that the plasticity-mediated structural evolution leads to transformation of the initial hollow structure to a solid wire. The process involves three distinct stages, namely, collapse, recrystallization and slow recovery. We calculate the time scales associated with different stages of the evolution process. Our findings suggest a plasticity-mediated mechanism of collapse and recrystallization. This contradicts the prevailing notion of diffusion driven transport of vacancies from the interior to outer surface being responsible for collapse, which would involve much longer time scales as compared to the plasticity-based mechanism.

  12. Deformation behavior of nano-porous polycrystalline silver. Part II: Simulations

    International Nuclear Information System (INIS)

    Zabihzadeh, S.; Cugnoni, J.; Duarte, L.I.; Van Petegem, S.; Van Swygenhoven, H.

    2017-01-01

    Three-dimensional finite element simulations of nano-porous silver structures are performed to understand the correlation between the porous morphology and the mechanical behavior. The nanostructures have been obtained from ptychographic X-ray computed tomography. The simulations allow distinguishing between the interplay and role of the ligament size, the pore morphology and the porosity, and therefore provide a better comprehension of the experimental observations. We show that the proposed model has a predictive character for mechanical behavior of nano-porous silver.

  13. Simulation of thermal stress and buckling instability in Si/Ge and Ge/Si core/shell nanowires.

    Science.gov (United States)

    Das, Suvankar; Moitra, Amitava; Bhattacharya, Mishreyee; Dutta, Amlan

    2015-01-01

    The present study employs the method of atomistic simulation to estimate the thermal stress experienced by Si/Ge and Ge/Si, ultrathin, core/shell nanowires with fixed ends. The underlying technique involves the computation of Young's modulus and the linear coefficient of thermal expansion through separate simulations. These two material parameters are combined to obtain the thermal stress on the nanowires. In addition, the thermally induced stress is perceived in the context of buckling instability. The analysis provides a trade-off between the geometrical and operational parameters of the nanostructures. The proposed methodology can be extended to other materials and structures and helps with the prediction of the conditions under which a nanowire-based device might possibly fail due to elastic instability.

  14. Polycrystalline strengthening

    DEFF Research Database (Denmark)

    Hansen, Niels

    1985-01-01

    for the understanding of polycrystalline strengthening is obtained mainly from surface relief patterns and from bulk structures observed by transmission electron microscopy of thin foils. The results obtained by these methods are discussed and correlations are proposed. A number of features characterizing the deformed...... structure are summarized and the behavior of a number of metals and alloys is reviewed with emphasis on the structural changes in the interior of the grains and in the vicinity of the grain boundaries. The models for strain accommodation during deformation are discussed on the basis of the microstructures...

  15. Computer simulation of current percolation in polycrystalline high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zeimetz, B [Department of Materials Science and Interdisciplinary Research Centre in Superconductivity, Cambridge University, Pembroke Street, Cambridge (United Kingdom); Rutter, N A; Glowacki, B A; Evetts, J E [Department of Materials Science and Interdisciplinary Research Centre in Superconductivity, Cambridge University, Pembroke Street, Cambridge (United Kingdom)

    2001-09-01

    YBCO-coated conductors were modelled in a computer simulation using a resistor network concept, with the resistors representing the grain boundaries. Dissipation above the critical current, accompanied by flux penetration into the grain boundaries, was described by a linear (flux-flow) resistivity. The model allowed calculation of the combined percolation of current and magnetic flux. Current-voltage data showed scaling in agreement with percolation theory for two-dimensional systems. The influence of grain alignment and electromagnetic parameters on conductor performance was investigated. (author)

  16. Multishell structure formation in Ni nanowire under uniaxial strain along <0 0 1> crystallographic direction: A molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wang Li, E-mail: wanglihxf@sdu.edu.c [School of Mechanical and Electrical Engineering, Shandong University at Weihai, 180 Wenhuaxi Road, Weihai 264209 (China); Peng Chuanxiao [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Gong Jianhong [School of Mechanical and Electrical Engineering, Shandong University at Weihai, 180 Wenhuaxi Road, Weihai 264209 (China)

    2010-04-01

    Molecular dynamics simulations based upon embedded-atom-method potential are employed to explore the fracture behavior of Ni nanowire along <0 0 1> crystallographic direction at temperature of 300 K. We find the formation of (5,5) multishell structure (MS), which is transformed from (6,5) MS at the necking region of nanowire under the strain rate of 0.02%ps{sup -1}. A reorientation transformation from <0 0 1> to <1 1 0> is first detected before formation of (6,5) MS. The formed (5,5) MS is more stable and can be tensioned longer as lower strain rate is loaded.

  17. Measurement and simulation of anisotropic magnetoresistance in single GaAs/MnAs core/shell nanowires

    International Nuclear Information System (INIS)

    Liang, J.; Wang, J.; Cooley, B. J.; Rench, D. W.; Samarth, N.; Paul, A.; Dellas, N. S.; Mohney, S. E.; Engel-Herbert, R.

    2012-01-01

    We report four probe measurements of the low field magnetoresistance (MR) in single core/shell GaAs/MnAs nanowires (NWs) synthesized by molecular beam epitaxy, demonstrating clear signatures of anisotropic magnetoresistance that track the field-dependent magnetization. A comparison with micromagnetic simulations reveals that the principal characteristics of the magnetoresistance data can be unambiguously attributed to the nanowire segments with a zinc blende GaAs core. The direct correlation between magnetoresistance, magnetization, and crystal structure provides a powerful means of characterizing individual hybrid ferromagnet/semiconductor nanostructures.

  18. Template synthesis of indium nanowires using anodic aluminum oxide membranes.

    Science.gov (United States)

    Chen, Feng; Kitai, Adrian H

    2008-09-01

    Indium nanowires with diameters approximately 300 nm have been synthesized by a hydraulic pressure technique using anodic aluminum oxide (AAO) templates. The indium melt is injected into the AAO template and solidified to form nanostructures. The nanowires are dense, continuous and uniformly run through the entire approximately 60 microm thickness of the AAO template. X-ray diffraction (XRD) reveals that the nanowires are polycrystalline with a preferred orientation. SEM is performed to characterize the morphology of the nanowires.

  19. Molecular dynamics simulation of joining process of Ag-Au nanowires and mechanical properties of the hybrid nanojoint

    Directory of Open Access Journals (Sweden)

    Su Ding

    2015-05-01

    Full Text Available The nanojoining process of Ag-Au hybrid nanowires at 800K was comprehensively studied by virtue of molecular dynamics (MD simulation. Three kinds of configurations including end-to-end, T-like and X-like were built in the simulation aiming to understand the nanojoining mechanism. The detailed dynamic evolution of atoms, crystal structure transformation and defects development during the nanojoining processes were performed. The results indicate that there are two stages in the nanojoining process of Ag-Au nanowires which are atom diffusion and new bonds formation. Temperature is a key parameter affecting both stages ascribed to the energy supply and the optimum temperature for Ag-Au nanojoint with diameter of 4.08 nm has been discussed. The mechanical properties of the nanojoint were examined with simulation of tensile test on the end-to-end joint. It was revealed that the nanojoint was strong enough to resist fracture at the joining area.

  20. A MONTÉ CARLO MODEL FOR SIMULATING THE NITROGEN DIFFUSION EFFECT INTO B-LPCVD-NIDOS POLYCRYSTALLINE THIN FILMS

    OpenAIRE

    S ALLAG; S MERABET; M BOUKEZZATA

    2012-01-01

    The principal objective of our current work, is to study the influence of different treatment from surface which makes it possible to improve the properties of materials by technique of beam of ions (diffusion – implantation), on the distribution of the particles in a semiconductor the prone polycrystalline Silicon of our study, largely used in micro-electronics.  The interest of this study is related to the ceaseless requirements in industry for increasingly reduced, powerful materials and w...

  1. First-principles simulations of the streching and final breaking of Al nanowires: Mechanical properties and electrical conductance

    Czech Academy of Sciences Publication Activity Database

    Jelínek, Pavel; Pérez, R.; Ortega, J.; Flores, F.

    2003-01-01

    Roč. 68, č. 8 (2003), 085403/1-085403/6 ISSN 0163-1829 Grant - others:European Project(XE) HPRN-CT-2000-00154; DGI-MCyT(ES) MAT2001-0665; Consejera de Educacio de la Comunidad de Madrid(ES) 07N/0050/2001 Institutional research plan: CEZ:AV0Z1010914 Keywords : nanowires * transport properties * first principles simulations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.962, year: 2003

  2. Atomistic simulation of MgO nanowires subject to electromagnetic wave

    International Nuclear Information System (INIS)

    Wang, Xianqiao; Lee, James D

    2010-01-01

    This work is concerned with the application of atomistic field theory (AFT) in modeling and simulation of polarizable materials under an electromagnetic (EM) field. AFT enables us to express an atomic scale local property of a multi-element crystalline (which has more than one kind of atom in the unit cell) system in terms of the distortions of lattice cells and the rearrangement of atoms within the lattice cell, thereby making AFT suitable to fully reproduce both acoustic and optical branches in phonon dispersion relations. Due to the applied EM field, the inhomogeneous motions of discrete atoms in the polarizable crystal give rise to the rearrangement of microstructure and polarization. The AFT and its corresponding finite element implementation are briefly introduced. Single-crystal MgO nanowires under an EM field is modeled and simulated. The numerical results have demonstrated that AFT can serve as a tool to analyze the electromagnetic phenomena of multi-element crystal materials at micro/nano-level within a field framework

  3. Atomistic simulations of the structures of Pd-Pt bimetallic nanoparticles and nanowires

    OpenAIRE

    Yun, Kayoung; Cha, Pil-Ryung; Lee, Jaegab; Kim, Jiyoung; Nam, Ho-Seok

    2015-01-01

    Bimetallic nanoalloys such as nanoparticles and nanowires are attracting significant attention due to their vast potential applications such as in catalysis and nanoelectronics. Notably, Pd-Pt nanoparticles/nanowires are being widely recognized as catalysts and hydrogen sensors. Compared to unary systems, alloys present more structural complexity with various compositional configurations. Therefore, it is important to understand energetically preferred atomic structures of bimetallic nanoallo...

  4. Characterizing and simulation the scintillation properties of zinc oxide nanowires in AAO membrane for medical imaging applications

    International Nuclear Information System (INIS)

    Esfandi, F.; Saramad, S.; Shahmirzadi, M. Rezaei

    2017-01-01

    In this work, a new method is proposed for extracting some X-ray detection properties of ZnO nanowires electrodeposited on Anodized Aluminum Oxide (AAO) nanoporous template. The results show that the detection efficiency for 12μm thickness of zinc oxide nano scintillator at an energy of 9.8 keV, near the K-edge of ZnO (9.65 keV), is 24%. The X-rays that interact with AAO can also generate electrons that reach the nano scintillator. The scintillation events of these electrons are seen as a low energy tail in the spectrum. In addition, it is found that all the X-rays that are absorbed in 300 nm thickness of the gold layer on the top of the zinc oxide nanowires can participate in the scintillation process with an efficiency of 6%. Hence, the scintillation detection efficiency of the whole detector for 9.8 keV X-ray energy is 30%. The simulation results from Geant4 and the experimental detected photons per MeV energy deposition are also used to extract the light yield of the zinc oxide nano scintillator. The results show that the light yield of the zinc oxide nanowires deposited by the electrochemical method is approximately the same as for single crystal zinc oxide scintillator (9000). Much better spatial resolution of this nano scintillator in comparison to the bulk ones is an advantage which candidates this nano scintillator for medical imaging applications.

  5. Atomistic Simulation of the Rate-Dependent Ductile-to-Brittle Failure Transition in Bicrystalline Metal Nanowires.

    Science.gov (United States)

    Tao, Weiwei; Cao, Penghui; Park, Harold S

    2018-02-14

    The mechanical properties and plastic deformation mechanisms of metal nanowires have been studied intensely for many years. One of the important yet unresolved challenges in this field is to bridge the gap in properties and deformation mechanisms reported for slow strain rate experiments (∼10 -2 s -1 ), and high strain rate molecular dynamics (MD) simulations (∼10 8 s -1 ) such that a complete understanding of strain rate effects on mechanical deformation and plasticity can be obtained. In this work, we use long time scale atomistic modeling based on potential energy surface exploration to elucidate the atomistic mechanisms governing a strain-rate-dependent incipient plasticity and yielding transition for face centered cubic (FCC) copper and silver nanowires. The transition occurs for both metals with both pristine and rough surfaces for all computationally accessible diameters (ductile-to-brittle transition in failure mode similar to previous experimental studies on bicrystalline silver nanowires is observed, which is driven by differences in dislocation activity and grain boundary mobility as compared to the high strain rate case.

  6. Piezoresistive effect in top-down fabricated silicon nanowires

    DEFF Research Database (Denmark)

    Reck, Kasper; Richter, Jacob; Hansen, Ole

    2008-01-01

    We have designed and fabricated silicon test chips to investigate the piezoresistive properties of both crystalline and polycrystalline nanowires using a top-down approach, in order to comply with conventional fabrication techniques. The test chip consists of 5 silicon nanowires and a reference...

  7. 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.

  8. Physics and performances of III-V nanowire broken-gap heterojunction TFETs using an efficient tight-binding mode-space NEGF model enabling million-atom nanowire simulations.

    Science.gov (United States)

    Afzalian, A; Vasen, T; Ramvall, P; Shen, T-M; Wu, J; Passlack, M

    2018-06-27

    We report the capability to simulate in a quantum-mechanical atomistic fashion record-large nanowire devices, featuring several hundred to millions of atoms and a diameter up to 18.2 nm. We have employed a tight-binding mode-space NEGF technique demonstrating by far the fastest (up to 10 000  ×  faster) but accurate (error  <  1%) atomistic simulations to date. Such technique and capability opens new avenues to explore and understand the physics of nanoscale and mesoscopic devices dominated by quantum effects. In particular, our method addresses in an unprecedented way the technologically-relevant case of band-to-band tunneling (BTBT) in III-V nanowire broken-gap heterojunction tunnel-FETs (HTFETs). We demonstrate an accurate match of simulated BTBT currents to experimental measurements in a 12 nm diameter InAs NW and in an InAs/GaSb Esaki tunneling diode. We apply our TB MS simulations and report the first in-depth atomistic study of the scaling potential of III-V GAA nanowire HTFETs including the effect of electron-phonon scattering and discrete dopant impurity band tails, quantifying the benefits of this technology for low-power low-voltage CMOS applications.

  9. Diffraction by disordered polycrystalline fibers

    International Nuclear Information System (INIS)

    Stroud, W.J.; Millane, R.P.

    1995-01-01

    X-ray diffraction patterns from some polycrystalline fibers show that the constituent microcrystallites are disordered. The relationship between the crystal structure and the diffracted intensities is then quite complicated and depends on the precise kind and degree of disorder present. The effects of disorder on diffracted intensities must be included in structure determinations using diffraction data from such specimens. Theory and algorithms are developed here that allow the full diffraction pattern to be calculated for a disordered polycrystalline fiber made up of helical molecules. The model accommodates various kinds of disorder and includes the effects of finite crystallite size and cylindrical averaging of the diffracted intensities from a fiber. Simulations using these methods show how different kinds, or components, of disorder produce particular diffraction effects. General properties of disordered arrays of helical molecules and their effects on diffraction patterns are described. Implications for structure determination are discussed. (orig.)

  10. Optimization of nanowire DNA sensor sensitivity using self-consistent simulation

    KAUST Repository

    Baumgartner, S; Vasicek, M; Bulyha, A; Heitzinger, C

    2011-01-01

    In order to facilitate the rational design and the characterization of nanowire field-effect sensors, we have developed a model based on self-consistent charge-transport equations combined with interface conditions for the description of the biofunctionalized surface layer at the semiconductor/electrolyte interface. Crucial processes at the interface, such as the screening of the partial charges of the DNA strands and the influence of the angle of the DNA strands with respect to the nanowire, are computed by a Metropolis Monte Carlo algorithm for charged molecules at interfaces. In order to investigate the sensing mechanism of the device, we have computed the current-voltage characteristics, the electrostatic potential and the concentrations of electrons and holes. Very good agreement with measurements has been found and optimal device parameters have been identified. Our approach provides the capability to study the device sensitivity, which is of fundamental importance for reliable sensing. © IOP Publishing Ltd.

  11. Optimization of nanowire DNA sensor sensitivity using self-consistent simulation

    KAUST Repository

    Baumgartner, S

    2011-09-26

    In order to facilitate the rational design and the characterization of nanowire field-effect sensors, we have developed a model based on self-consistent charge-transport equations combined with interface conditions for the description of the biofunctionalized surface layer at the semiconductor/electrolyte interface. Crucial processes at the interface, such as the screening of the partial charges of the DNA strands and the influence of the angle of the DNA strands with respect to the nanowire, are computed by a Metropolis Monte Carlo algorithm for charged molecules at interfaces. In order to investigate the sensing mechanism of the device, we have computed the current-voltage characteristics, the electrostatic potential and the concentrations of electrons and holes. Very good agreement with measurements has been found and optimal device parameters have been identified. Our approach provides the capability to study the device sensitivity, which is of fundamental importance for reliable sensing. © IOP Publishing Ltd.

  12. Atomistic simulations on the axial nanowelding configuration and contact behavior between Ag nanowire and single-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Cui, Jianlei; Zhang, Jianwei; He, Xiaoqiao; Yang, Xinjun; Mei, Xuesong; Wang, Wenjun; Jiang, Gedong; Wang, Kedian; Yang, Lijun; Xie, Hui

    2017-01-01

    As for the interesting new building blocks, the Ag nanowires (AgNWs) and single-walled carbon nanotubes (SWNTs) as the interesting new building blocks are viewed as the promising candidates for the next-generation interconnects due to their most remarkable electrical, thermal, optical, mechanical, and other properties. The axial nanowelding of head-to-head style and side-to-side style is relatively simulated with the molecular dynamics method. As for the head-to-head structural style, SWNTs will move toward the AgNWs and contact with the head of AgNWs. And, the part of the Ag nanowire may be subsequently encapsulated in SWNT with the core-filling Ag atom chain as the final atomic contact configuration during nanowelding, which is related to the nanowelding temperature. When the SWNTs and AgNWs are arranged by the side-to-side contact style, the SWNTs will move along the SWNT surface and may eventually catch up with the AgNW being neck and neck. Aiming at the final axial atomic configurations and the contact behavior during nanowelding process, the related dominant mechanism is revealed in this paper.

  13. Atomistic simulations on the axial nanowelding configuration and contact behavior between Ag nanowire and single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Jianlei, E-mail: cjlxjtu@mail.xjtu.edu.cn; Zhang, Jianwei [Xi’an Jiaotong University, State Key Laboratory for Manufacturing Systems Engineering (China); He, Xiaoqiao, E-mail: bcxqhe@cityu.edu.hk [City University of Hong Kong, Department of Architecture and Civil Engineering (Hong Kong); Yang, Xinjun [Fudan University, State Key Laboratory of Surface Physics and Department of Physics (China); Mei, Xuesong; Wang, Wenjun; Jiang, Gedong; Wang, Kedian [Xi’an Jiaotong University, State Key Laboratory for Manufacturing Systems Engineering (China); Yang, Lijun; Xie, Hui [Harbin Institute of Technology, State Key Laboratory of Robotics and Systems (China)

    2017-03-15

    As for the interesting new building blocks, the Ag nanowires (AgNWs) and single-walled carbon nanotubes (SWNTs) as the interesting new building blocks are viewed as the promising candidates for the next-generation interconnects due to their most remarkable electrical, thermal, optical, mechanical, and other properties. The axial nanowelding of head-to-head style and side-to-side style is relatively simulated with the molecular dynamics method. As for the head-to-head structural style, SWNTs will move toward the AgNWs and contact with the head of AgNWs. And, the part of the Ag nanowire may be subsequently encapsulated in SWNT with the core-filling Ag atom chain as the final atomic contact configuration during nanowelding, which is related to the nanowelding temperature. When the SWNTs and AgNWs are arranged by the side-to-side contact style, the SWNTs will move along the SWNT surface and may eventually catch up with the AgNW being neck and neck. Aiming at the final axial atomic configurations and the contact behavior during nanowelding process, the related dominant mechanism is revealed in this paper.

  14. Micromechanical simulation of Uranium dioxide polycrystalline aggregate behaviour under irradiation; Modele numerique micro-mecanique d'agregat polycristallin pour le comportement des combustibles oxydes

    Energy Technology Data Exchange (ETDEWEB)

    Pacull, J.

    2011-02-15

    In pressurized water nuclear power reactor (PWR), the fuel rod is made of dioxide of uranium (UO{sub 2}) pellet stacked in a metallic cladding. A multi scale and multi-physic approaches are needed for the simulation of fuel behavior under irradiation. The main phenomena to take into account are thermomechanical behavior of the fuel rod and chemical-physic behavior of the fission products. These last years one of the scientific issue to improve the simulation is to take into account the multi-physic coupling problem at the microscopic scale. The objective of this ph-D study is to contribute to this multi-scale approach. The present work concerns the micro-mechanical behavior of a polycrystalline aggregate of UO{sub 2}. Mean field and full field approaches are considered. For the former and the later a self consistent homogenization technique and a periodic Finite Element model base on the 3D Voronoi pattern are respectively used. Fuel visco-plasticity is introduced in the model at the scale of a single grain by taking into account specific dislocation slip systems of UO{sub 2}. A cohesive zone model has also been developed and implemented to simulate grain boundary sliding and intergranular crack opening. The effective homogenous behaviour of a Representative Volume Element (RVE) is fitted with experimental data coming from mechanical tests on a single pellet. Local behavior is also analyzed in order to evaluate the model capacity to assess micro-mechanical state. In particular, intra and inter granular stress gradient are discussed. A first validation of the local behavior assessment is proposed through the simulation of intergranular crack opening measured in a compressive creep test of a single fuel pellet. Concerning the impact of the microstructure on the fuel behavior under irradiation, a RVE simulation with a representative transient loading of a fuel rod during a power ramp test is achieved. The impact of local stress and strain heterogeneities on the multi

  15. Gold nanowires and the effect of impurities

    Directory of Open Access Journals (Sweden)

    Novaes Frederico

    2006-01-01

    Full Text Available AbstractMetal nanowires and in particular gold nanowires have received a great deal of attention in the past few years. Experiments on gold nanowires have prompted theory and simulation to help answer questions posed by these studies. Here we present results of computer simulations for the formation, evolution and breaking of very thin Au nanowires. We also discuss the influence of contaminants, such as atoms and small molecules, and their effect on the structural and mechanical properties of these nanowires.

  16. Ambient template synthesis of multiferroic MnWO4 nanowires and nanowire arrays

    International Nuclear Information System (INIS)

    Zhou Hongjun; Yiu Yuen; Aronson, M.C.; Wong, Stanislaus S.

    2008-01-01

    The current report describes the systematic synthesis of polycrystalline, multiferroic MnWO 4 nanowires and nanowire arrays with controllable chemical composition and morphology, using a modified template-directed methodology under ambient room-temperature conditions. We were able to synthesize nanowires measuring 55±10, 100±20, and 260±40 nm in diameter, respectively, with lengths ranging in the microns. Extensive characterization of as-prepared samples has been performed using X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and energy-dispersive X-ray spectroscopy. Magnetic behavior in these systems was also probed. - Graphical abstract: Systematic synthesis of crystalline, multiferroic MnWO4 nanowires and nanowire arrays with controllable chemical composition and morphology, using a modified template-directed methodology under ambient room-temperature conditions

  17. Topological insulator nanowires and nanowire hetero-junctions

    Science.gov (United States)

    Deng, Haiming; Zhao, Lukas; Wade, Travis; Konczykowski, Marcin; Krusin-Elbaum, Lia

    2014-03-01

    The existing topological insulator materials (TIs) continue to present a number of challenges to complete understanding of the physics of topological spin-helical Dirac surface conduction channels, owing to a relatively large charge conduction in the bulk. One way to reduce the bulk contribution and to increase surface-to-volume ratio is by nanostructuring. Here we report on the synthesis and characterization of Sb2Te3, Bi2Te3 nanowires and nanotubes and Sb2Te3/Bi2Te3 heterojunctions electrochemically grown in porous anodic aluminum oxide (AAO) membranes with varied (from 50 to 150 nm) pore diameters. Stoichiometric rigid polycrystalline nanowires with controllable cross-sections were obtained using cell voltages in the 30 - 150 mV range. Transport measurements in up to 14 T magnetic fields applied along the nanowires show Aharonov-Bohm (A-B) quantum oscillations with periods corresponding to the nanowire diameters. All nanowires were found to exhibit sharp weak anti-localization (WAL) cusps, a characteristic signature of TIs. In addition to A-B oscillations, new quantization plateaus in magnetoresistance (MR) at low fields (< 0 . 7T) were observed. The analysis of MR as well as I - V characteristics of heterojunctions will be presented. Supported in part by NSF-DMR-1122594, NSF-DMR-1312483-MWN, and DOD-W911NF-13-1-0159.

  18. A Monte Carlo simulation study of boron profiles as-implanted into LPCVD NiDoS polycrystalline thin films

    Science.gov (United States)

    Boukezzata, M.; Ait-Kaki, A.; Temple-Boyer, P.; Scheid, E.

    2003-03-01

    This work presents a Monte Carlo simulation study of boron profiles obtained from as-implanted ions into thin films nitrogen doped silicon (NiDoS) thin films. These films are performed by LPCVD technique from Si2H6 and NH3 gas sources, four values deliberately chosen, of the ratio NH3/Si2H6 to obtain samples, differently in situ nitrogen-doped. Taking into account the effect of the codoping case, and the structure specificity of these films, an accurate Monte Carlo model based on binary collisions in a multi-atomic target was performed. Nitrogen atoms present in the target is shown to affect the boron profiles and confirms clearly a reduction penetration effect which becomes more significant at high nitrogen concentrations. Whereas, the fine-grained polysilicon structure, and thus the presence of grains (G) and grain boundaries (GB), is known to enhance the opposite phenomenon by assuming an effective role played by GB's in the scattering calculation process of the incident ions. This role is represented by the change in direction of the incident ion after interaction with GB without corresponding loss in its energy. The results obtained show an enhancement of the stopping parameter when nitrogen concentration increases, while the GB interaction remains very important. This behavior is due to a great number of GB's interactions with boron atoms which gave low deflection angles. So that, the average positions described by the sequences of trajectories took place farther than what expected with channeling effect in crystal silicon materials.

  19. Simulation the spatial resolution of an X-ray imager based on zinc oxide nanowires in anodic aluminium oxide membrane by using MCNP and OPTICS Codes

    Science.gov (United States)

    Samarin, S. N.; Saramad, S.

    2018-05-01

    The spatial resolution of a detector is a very important parameter for x-ray imaging. A bulk scintillation detector because of spreading of light inside the scintillator does't have a good spatial resolution. The nanowire scintillators because of their wave guiding behavior can prevent the spreading of light and can improve the spatial resolution of traditional scintillation detectors. The zinc oxide (ZnO) scintillator nanowire, with its simple construction by electrochemical deposition in regular hexagonal structure of Aluminum oxide membrane has many advantages. The three dimensional absorption of X-ray energy in ZnO scintillator is simulated by a Monte Carlo transport code (MCNP). The transport, attenuation and scattering of the generated photons are simulated by a general-purpose scintillator light response simulation code (OPTICS). The results are compared with a previous publication which used a simulation code of the passage of particles through matter (Geant4). The results verify that this scintillator nanowire structure has a spatial resolution less than one micrometer.

  20. Nanowire failure: long = brittle and short = ductile.

    Science.gov (United States)

    Wu, Zhaoxuan; Zhang, Yong-Wei; Jhon, Mark H; Gao, Huajian; Srolovitz, David J

    2012-02-08

    Experimental studies of the tensile behavior of metallic nanowires show a wide range of failure modes, ranging from ductile necking to brittle/localized shear failure-often in the same diameter wires. We performed large-scale molecular dynamics simulations of copper nanowires with a range of nanowire lengths and provide unequivocal evidence for a transition in nanowire failure mode with change in nanowire length. Short nanowires fail via a ductile mode with serrated stress-strain curves, while long wires exhibit extreme shear localization and abrupt failure. We developed a simple model for predicting the critical nanowire length for this failure mode transition and showed that it is in excellent agreement with both the simulation results and the extant experimental data. The present results provide a new paradigm for the design of nanoscale mechanical systems that demarcates graceful and catastrophic failure. © 2012 American Chemical Society

  1. 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...... atomic force microscopy and from polarized far-field optical microscopy for various prototypical molecules are reproduced by electrostatic and Monte Carlo calculations. Based on the crystal structure, predictions on the growth habit from other conjugated molecules become in reach....

  2. Tapering-induced enhancement of light extraction efficiency of nanowire deep ultraviolet LED by theoretical simulations

    KAUST Repository

    Lin, Ronghui; Galan, Sergio Valdes; Sun, Haiding; Hu, Yangrui; Alias, Mohd Sharizal; Janjua, Bilal; Ng, Tien Khee; Ooi, Boon S.; Li, Xiaohang

    2018-01-01

    A nanowire (NW) structure provides an alternative scheme for deep ultraviolet light emitting diodes (DUV-LEDs) that promises high material quality and better light extraction efficiency (LEE). In this report, we investigate the influence of the tapering angle of closely packed AlGaN NWs, which is found to exist naturally in molecular beam epitaxy (MBE) grown NW structures, on the LEE of NW DUV-LEDs. It is observed that, by having a small tapering angle, the vertical extraction is greatly enhanced for both transverse magnetic (TM) and transverse electric (TE) polarizations. Most notably, the vertical extraction of TM emission increased from 4.8% to 24.3%, which makes the LEE reasonably large to achieve high-performance DUV-LEDs. This is because the breaking of symmetry in the vertical direction changes the propagation of the light significantly to allow more coupling into radiation modes. Finally, we introduce errors to the NW positions to show the advantages of the tapered NW structures can be projected to random closely packed NW arrays. The results obtained in this paper can provide guidelines for designing efficient NW DUV-LEDs.

  3. Tapering-induced enhancement of light extraction efficiency of nanowire deep ultraviolet LED by theoretical simulations

    KAUST Repository

    Lin, Ronghui

    2018-04-21

    A nanowire (NW) structure provides an alternative scheme for deep ultraviolet light emitting diodes (DUV-LEDs) that promises high material quality and better light extraction efficiency (LEE). In this report, we investigate the influence of the tapering angle of closely packed AlGaN NWs, which is found to exist naturally in molecular beam epitaxy (MBE) grown NW structures, on the LEE of NW DUV-LEDs. It is observed that, by having a small tapering angle, the vertical extraction is greatly enhanced for both transverse magnetic (TM) and transverse electric (TE) polarizations. Most notably, the vertical extraction of TM emission increased from 4.8% to 24.3%, which makes the LEE reasonably large to achieve high-performance DUV-LEDs. This is because the breaking of symmetry in the vertical direction changes the propagation of the light significantly to allow more coupling into radiation modes. Finally, we introduce errors to the NW positions to show the advantages of the tapered NW structures can be projected to random closely packed NW arrays. The results obtained in this paper can provide guidelines for designing efficient NW DUV-LEDs.

  4. Simulation, optimization and testing of a novel high spatial resolution X-ray imager based on Zinc Oxide nanowires in Anodic Aluminium Oxide membrane using Geant4

    Science.gov (United States)

    Esfandi, F.; Saramad, S.

    2015-07-01

    In this work, a new generation of scintillator based X-ray imagers based on ZnO nanowires in Anodized Aluminum Oxide (AAO) nanoporous template is characterized. The optical response of ordered ZnO nanowire arrays in porous AAO template under low energy X-ray illumination is simulated by the Geant4 Monte Carlo code and compared with experimental results. The results show that for 10 keV X-ray photons, by considering the light guiding properties of zinc oxide inside the AAO template and suitable selection of detector thickness and pore diameter, the spatial resolution less than one micrometer and the detector detection efficiency of 66% are accessible. This novel nano scintillator detector can have many advantages for medical applications in the future.

  5. Simulation, optimization and testing of a novel high spatial resolution X-ray imager based on Zinc Oxide nanowires in Anodic Aluminium Oxide membrane using Geant4

    International Nuclear Information System (INIS)

    Esfandi, F.; Saramad, S.

    2015-01-01

    In this work, a new generation of scintillator based X-ray imagers based on ZnO nanowires in Anodized Aluminum Oxide (AAO) nanoporous template is characterized. The optical response of ordered ZnO nanowire arrays in porous AAO template under low energy X-ray illumination is simulated by the Geant4 Monte Carlo code and compared with experimental results. The results show that for 10 keV X-ray photons, by considering the light guiding properties of zinc oxide inside the AAO template and suitable selection of detector thickness and pore diameter, the spatial resolution less than one micrometer and the detector detection efficiency of 66% are accessible. This novel nano scintillator detector can have many advantages for medical applications in the future

  6. 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.

  7. Direct electrodeposition of metal nanowires on electrode surface

    International Nuclear Information System (INIS)

    Gambirasi, Arianna; Cattarin, Sandro; Musiani, Marco; Vazquez-Gomez, Lourdes; Verlato, Enrico

    2011-01-01

    A method for decorating the surface of disk electrodes with metal nanowires is presented. Cu and Ni nanowires with diameters from 1.0 μm to 0.2 μm are directly deposited on the electrode surface using a polycarbonate membrane filter template maintained in contact with the metal substrate by the soft homogeneous pressure of a sponge soaked with electrolyte. The morphologic and structural properties of the deposit are characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The latter shows that the head of nanowires with diameter of 0.4 μm is ordinarily polycrystalline, and that of nanowires with diameter of 0.2 μm is almost always monocrystalline for Cu and frequently also for Ni. Cyclic voltammetries and impedance investigations recorded in alkaline solutions at representative Ni electrodes decorated with nanowires provide consistent values of roughness factor, in the range 20-25.

  8. 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.)

  9. 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.)

  10. Prediction of phonon thermal transport in thin GaAs, InAs and InP nanowires by molecular dynamics simulations: influence of the interatomic potential

    Energy Technology Data Exchange (ETDEWEB)

    Carrete, J; Longo, R C; Gallego, L J, E-mail: jesus.carrete@usc.es [Departamento de Fisica de la Materia Condensada, Facultad de Fisica, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela (Spain)

    2011-05-06

    A number of different potentials are currently being used in molecular dynamics simulations of semiconductor nanostructures. Confusion can arise if an inappropriate potential is used. To illustrate this point, we performed direct molecular dynamics simulations to predict the room temperature lattice thermal conductivity {lambda} of thin GaAs, InAs and InP nanowires. In each case, simulations performed using the classical Harrison potential afforded values of {lambda} about an order of magnitude smaller than those obtained using more elaborate potentials (an Abell-Tersoff, as parameterized by Hammerschmidt et al for GaAs and InAs, and a potential of Vashishta type for InP). These results will be a warning to those wishing to use computer simulations to orient the development of quasi-one-dimensional systems as heat sinks or thermoelectric devices.

  11. 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.

  12. 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.

  13. A superconducting nanowire can be modeled by using SPICE

    Science.gov (United States)

    Berggren, Karl K.; Zhao, Qing-Yuan; Abebe, Nathnael; Chen, Minjie; Ravindran, Prasana; McCaughan, Adam; Bardin, Joseph C.

    2018-05-01

    Modeling of superconducting nanowire single-photon detectors typically requires custom simulations or finite-element analysis in one or two dimensions. Here, we demonstrate two simplified one-dimensional SPICE models of a superconducting nanowire that can quickly and efficiently describe the electrical characteristics of a superconducting nanowire. These models may be of particular use in understanding alternative architectures for nanowire detectors and readouts.

  14. Anelasticity of polycrystalline indium

    Energy Technology Data Exchange (ETDEWEB)

    Sapozhnikov, K., E-mail: k.sapozhnikov@mail.ioffe.ru [A.F.Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); Golyandin, S. [A.F.Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); Kustov, S. [Dept. de Fisica, Universitat de les Illes Balears, Cra Valldemossa km 7.5, E 07122 Palma de Mallorca (Spain)

    2009-09-15

    Mechanisms of anelasticity of polycrystalline indium have been studied over wide ranges of temperature (7-320 K) and strain amplitude (2 x 10{sup -7}-3.5 x 10{sup -4}). Measurements of the internal friction and Young's modulus have been performed by means of the piezoelectric resonant composite oscillator technique using longitudinal oscillations at frequencies of about 100 kHz. The stages of the strain amplitude dependence of the internal friction and Young's modulus defect, which can be attributed to dislocation - point defect and dislocation - dislocation interactions, have been revealed. It has been shown that thermal cycling gives rise to microplastic straining of polycrystalline indium due to the anisotropy of thermal expansion and to appearance of a 'recrystallization' internal friction maximum in the temperature spectra of amplitude-dependent anelasticity. The temperature range characterized by formation of Cottrell's atmospheres of point defects around dislocations has been determined from the acoustic data.

  15. Characterization of Nanowire Photodetectors

    Science.gov (United States)

    2016-11-28

    characterization system and picosecond pulsed laser source will be used to provide deeper insight into the fast charge carrier dynamics in the GaAsSb and...value of the current fluctuations for a particular frequency, f is the effective measurement bandwidth at the discrete frequency point, and IDS is...GaAsSb CS nanowires. The best fit of the spectra with the simulation carried out using Matlab revealed flicker noise at lower frequency having 1/f

  16. 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.

  17. Oriented epitaxial TiO2 nanowires for water splitting

    Science.gov (United States)

    Hou, Wenting; Cortez, Pablo; Wuhrer, Richard; Macartney, Sam; Bozhilov, Krassimir N.; Liu, Rong; Sheppard, Leigh R.; Kisailus, David

    2017-06-01

    Highly oriented epitaxial rutile titanium dioxide (TiO2) nanowire arrays have been hydrothermally grown on polycrystalline TiO2 templates with their orientation dependent on the underlying TiO2 grain. Both the diameter and areal density of the nanowires were tuned by controlling the precursor concentration, and the template surface energy and roughness. Nanowire tip sharpness was influenced by precursor solubility and diffusivity. A new secondary ion mass spectrometer technique has been developed to install additional nucleation sites in single crystal TiO2 templates and the effect on nanowire growth was probed. Using the acquired TiO2 nanowire synthesis knowhow, an assortment of nanowire arrays were installed upon the surface of undoped TiO2 photo-electrodes and assessed for their photo-electrochemical water splitting performance. The key result obtained was that the presence of short and dispersed nanowire arrays significantly improved the photocurrent when the illumination intensity was increased from 100 to 200 mW cm-2. This is attributed to the alignment of the homoepitaxially grown nanowires to the [001] direction, which provides the fastest charge transport in TiO2 and an improved pathway for photo-holes to find water molecules and undertake oxidation. This result lays a foundation for achieving efficient water splitting under conditions of concentrated solar illumination.

  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. Bending and tensile deformation of metallic nanowires

    International Nuclear Information System (INIS)

    McDowell, Matthew T; Leach, Austin M; Gall, Ken

    2008-01-01

    Using molecular statics simulations and the embedded atom method, a technique for bending silver nanowires and calculating Young's modulus via continuum mechanics has been developed. The measured Young's modulus values extracted from bending simulations were compared with modulus values calculated from uniaxial tension simulations for a range of nanowire sizes, orientations and geometries. Depending on axial orientation, the nanowires exhibit stiffening or softening under tension and bending as size decreases. Bending simulations typically result in a greater variation of Young's modulus values with nanowire size compared with tensile deformation, which indicates a loading-method-dependent size effect on elastic properties at sub-5 nm wire diameters. Since the axial stress is maximized at the lateral surfaces in bending, the loading-method-dependent size effect is postulated to be primarily a result of differences in nanowire surface and core elastic modulus. The divergence of Young's modulus from the bulk modulus in these simulations occurs at sizes below the range in which experiments have demonstrated a size scale effect on elastic properties of metallic nanowires. This difference indicates that other factors beyond native metallic surface properties play a role in experimentally observed nanowire elastic modulus size effects

  20. Simulation of long-wave phonon ({lambda}> b) scattering at geometric imperfections in nanowires by FDTD method

    Energy Technology Data Exchange (ETDEWEB)

    Salamatov, E.I. [Physico-Technical Institute, UrB RAS, 132 Kirov Street, Izhevsk (Russian Federation)

    2012-01-15

    Elementary acts of acoustic phonon scattering in nanowires are studied numerically by the FDTD method. The points of bifurcation of the main waveguide are considered as defects. The particularities of the reflection/transmission coefficient of phonons of different polarizations are studied as a function of the frequency and geometrical parameters of the problem. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Growth mechanism and elemental distribution of beta-Ga2O3 crystalline nanowires synthesized by cobalt-assisted chemical vapor deposition.

    Science.gov (United States)

    Wang, Hui; Lan, Yucheng; Zhang, Jiaming; Crimp, Martin A; Ren, Zhifeng

    2012-04-01

    Long beta-Ga2O3 crystalline nanowires are synthesized on patterned silicon substrates using chemical vapor deposition technique. Advanced electron microscopy indicates that the as-grown beta-Ga2O3 nanowires are consisted of poly-crystalline (Co, Ga)O tips and straight crystalline beta-Ga2O3 stems. The catalytic cobalt not only locates at the nanowire tips but diffuses into beta-Ga2O3 nanowire stems several ten nanometers. A solid diffusion growth mechanism is proposed based on the spatial elemental distribution along the beta-Ga2O3 nanowires at nanoscale.

  2. Application of polycrystalline diffusion barriers

    International Nuclear Information System (INIS)

    Tsymbal, V.A.; Kolupaev, I.N.

    2010-01-01

    Degradation of contacts of the electronic equipment at the raised temperatures is connected with active diffusion redistribution of components contact - metalized systems (CMS) and phase production on interphase borders. One of systems diffusion barriers (DB) are polycrystalline silicide a film, in particular silicides of the titan. Reception disilicide the titan (TiSi 2 ) which on the parameters is demanded for conditions of microelectronics from known silicides of system Ti-Si, is possible as a result of direct reaction of a film of the titan and a substrate of silicon, and at sedimentation of layer Ti-Si demanded stoichiometric structure. Simultaneously there is specific problem polycrystalline diffusion a barrier (PDB): the polycrystalline provides structural balance and metastability film disilicide, but leaves in it borders of grains - easy local ways of diffusion. In clause the analysis diffusion permeability polycrystalline and polyphase DB is made and recommendations for practical methods of increase of blocking properties PDB are made.

  3. Templated synthesis, characterization, and sensing application of macroscopic platinum nanowire network electrodes

    DEFF Research Database (Denmark)

    Wang, D. H.; Kou, R.; Gil, M. P.

    2005-01-01

    properties of the electrodes, such as electrochemical active area and methanol oxidation, have also been studied. Compared with conventional polycrystalline Pt electrodes, these novel nanowire network electrodes possess high electrochemical active areas and demonstrate higher current densities and a lower...... onset potential for methanol electro-oxidation. Enzymatic Pt nanowire-network-based sensors show higher sensitivity for glucose detection than that using conventional polycrystalline Pt electrode. Such macroscopic nanowire network electrodes provide ideal platforms for sensing and other device......Abstract: Novel platinum nanowire network electrodes have been fabricated through electrodeposition using mesoporous silica thin films as templates. These electrodes were characterized by X-ray diffraction, transmission electron microscope, and scanning electron microscope. The electrochemical...

  4. Excitonic terahertz photoconductivity in intrinsic semiconductor nanowires

    Science.gov (United States)

    Yan, Jie-Yun

    2018-06-01

    Excitonic terahertz photoconductivity in intrinsic semiconductor nanowires is studied. Based on the excitonic theory, the numerical method to calculate the photoconductivity spectrum in the nanowires is developed, which can simulate optical pump terahertz-probe spectroscopy measurements on real nanowires and thereby calculate the typical photoconductivity spectrum. With the help of the energetic structure deduced from the calculated linear absorption spectrum, the numerically observed shift of the resonant peak in the photoconductivity spectrum is found to result from the dominant exciton transition between excited or continuum states to the ground state, and the quantitative analysis is in good agreement with the quantum plasmon model. Besides, the dependence of the photoconductivity on the polarization of the terahertz field is also discussed. The numerical method and supporting theoretical analysis provide a new tool for experimentalists to understand the terahertz photoconductivity in intrinsic semiconductor nanowires at low temperatures or for nanowires subjected to below bandgap photoexcitation, where excitonic effects dominate.

  5. Gelcasting polycrystalline alumina

    Energy Technology Data Exchange (ETDEWEB)

    Janney, M.A. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    This work is being done as part of a CRADA with Osram-Sylvania, Inc. (OSI) OSI is a major U.S. manufacturer of high-intensity lighting. Among its products is the Lumalux{reg_sign} line of high-pressure sodium vapor arc lamps, which are used for industrial, highway, and street lighting. The key to the performance of these lamps is the polycrystalline alumina (PCA) tube that is used to contain the plasma that is formed in the electric arc. That plasma consists of ionized sodium, mercury, and xenon vapors. The key attributes of the PCA tubes are their transparency (95% total transmittance in the visible region), their refractoriness (inner wall temperature can reach 1400{degrees}C), and their chemical resistance (sodium and mercury vapor are extremely corrosive). The current efficiency of the lamps is very high, on the order of several hundred lumens / watt. (Compare - incandescent lamps -13 lumens/watt fluorescent lamps -30 lumens/watt.) Osram-Sylvania would like to explore using gelcasting to form PCA tubes for Lumalux{reg_sign} lamps, and eventually for metal halide lamps (known as quartz-halogen lamps). Osram-Sylvania, Inc. currently manufactures PCA tubes by isostatic pressing. This process works well for the shapes that they presently use. However, there are several types of tubes that are either difficult or impossible to make by isostatic pressing. It is the desire to make these new shapes and sizes of tubes that has prompted Osram-Sylvania`s interest in gelcasting. The purpose of the CRADA is to determine the feasibility of making PCA items having sufficient optical quality that they are useful in lighting applications using gelcasting.

  6. A detailed study of magnetization reversal in individual Ni nanowires

    KAUST Repository

    Vidal, Enrique Vilanova; Ivanov, Yurii P.; Mohammed, Hanan; Kosel, Jü rgen

    2015-01-01

    Magnetic nanowires have emerged as essential components for a broad range of applications. In many cases, a key property of these components is the switching field, which is studied as a function of the angle between the field and the nanowire. We found remarkable differences of up to 100% between the switching fields of different nanowires from the same fabrication batch. Our experimental results and micromagnetic simulations indicate that the nanowires exhibit a single domain behavior and that the switching mechanism includes vortex domain wall motion across the nanowire. The differences between the switching fields are attributed to different cross-sections of the nanowires, as found by electron microscopy. While a circular cross-section yields the smallest switching field values, any deviation from this shape results in an increase of the switching field. The shape of the nanowires' cross-sections is thus a critical parameter that has not been previously taken into account.

  7. A detailed study of magnetization reversal in individual Ni nanowires

    KAUST Repository

    Vidal, Enrique Vilanova

    2015-01-19

    Magnetic nanowires have emerged as essential components for a broad range of applications. In many cases, a key property of these components is the switching field, which is studied as a function of the angle between the field and the nanowire. We found remarkable differences of up to 100% between the switching fields of different nanowires from the same fabrication batch. Our experimental results and micromagnetic simulations indicate that the nanowires exhibit a single domain behavior and that the switching mechanism includes vortex domain wall motion across the nanowire. The differences between the switching fields are attributed to different cross-sections of the nanowires, as found by electron microscopy. While a circular cross-section yields the smallest switching field values, any deviation from this shape results in an increase of the switching field. The shape of the nanowires\\' cross-sections is thus a critical parameter that has not been previously taken into account.

  8. Electrical and Optical Characterization of Nanowire based Semiconductor Devices

    Science.gov (United States)

    Ayvazian, Talin

    This research project is focused on a new strategy for the creation of nanowire based semiconductor devices. The main goal is to understand and optimize the electrical and optical properties of two types of nanoscale devices; in first type lithographically patterned nanowire electrodeposition (LPNE) method has been utilized to fabricate nanowire field effect transistors (NWFET) and second type involved the development of light emitting semiconductor nanowire arrays (NWLED). Field effect transistors (NWFETs) have been prepared from arrays of polycrystalline cadmium selenide (pc-CdSe) nanowires using a back gate configuration. pc-CdSe nanowires were fabricated using the lithographically patterned nanowire electrode- position (LPNE) process on SiO2 /Si substrates. After electrodeposition, pc-CdSe nanowires were thermally annealed at 300 °C x 4 h either with or without exposure to CdCl 2 in methanol a grain growth promoter. The influence of CdCl2 treatment was to increase the mean grain diameter as determined by X-ray diffraction pattern and to convert the crystal structure from cubic to wurtzite. Transfer characteristics showed an increase of the field effect mobility (mu eff) by an order of magnitude and increase of the Ion/I off ratio by a factor of 3-4. Light emitting devices (NW-LED) based on lithographically patterned pc-CdSe nanowire arrays have been investigated. Electroluminescence (EL) spectra of CdSe nanowires under various biases exhibited broad emission spectra centered at 750 nm close to the band gap of CdSe (1.7eV). To enhance the intensity of the emitted light and the external quantum efficiency (EQE), the distance between the contacts were reduced from 5 mum to less than 1 mum which increased the efficiency by an order of magnitude. Also, increasing the annealing temperature of nanowires from 300 °C x4 h to 450 This research project is focused on a new strategy for the creation of nanowire based semiconductor devices. The main goal is to understand

  9. Angular dependence of the coercivity in arrays of ferromagnetic nanowires

    International Nuclear Information System (INIS)

    Holanda, J.; Silva, D.B.O.; Padrón-Hernández, E.

    2015-01-01

    We present a new magnetic model for polycrystalline nanowires arrays in porous anodic aluminum oxide. The principal consideration here is the crystalline structure and the morphology of the wires and them the dipolar interactions between the crystals into the wire. Other aspect here is the direct calculation of the dipolar energy for the interaction of one wire with the others in the array. The free energy density was formulated for polycrystalline nanowires arrays in order to determinate the anisotropy effective field. It was using the microstructure study by scanning and transmission electron microscopy for the estimation of the real structure of the wires. After the structural analysis we used the angular dependences for the coercivity field and for the remnant magnetization to determine the properties of the wires. All analysis were made by the theory treatment proposed by Stoner and Wohlfarth

  10. Angular dependence of the coercivity in arrays of ferromagnetic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Holanda, J. [Departamento de Física, Universidade Federal de Pernambuco, Recife 50670-901, PE (Brazil); Silva, D.B.O. [Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, Recife 50670-901, PE (Brazil); Padrón-Hernández, E., E-mail: padron@df.ufpe.br [Departamento de Física, Universidade Federal de Pernambuco, Recife 50670-901, PE (Brazil); Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, Recife 50670-901, PE (Brazil)

    2015-03-15

    We present a new magnetic model for polycrystalline nanowires arrays in porous anodic aluminum oxide. The principal consideration here is the crystalline structure and the morphology of the wires and them the dipolar interactions between the crystals into the wire. Other aspect here is the direct calculation of the dipolar energy for the interaction of one wire with the others in the array. The free energy density was formulated for polycrystalline nanowires arrays in order to determinate the anisotropy effective field. It was using the microstructure study by scanning and transmission electron microscopy for the estimation of the real structure of the wires. After the structural analysis we used the angular dependences for the coercivity field and for the remnant magnetization to determine the properties of the wires. All analysis were made by the theory treatment proposed by Stoner and Wohlfarth.

  11. Manipulation and Investigation of Uniformly-Spaced Nanowire Array on a Substrate via Dielectrophoresis and Electrostatic Interaction

    Directory of Open Access Journals (Sweden)

    U Hyeok Choi

    2018-06-01

    Full Text Available Directed-assembly of nanowires on the dielectrics-covered parallel electrode structure is capable of producing uniformly-spaced nanowire array at the electrode gap due to dielectrophoretic nanowire attraction and electrostatic nanowire repulsion. Beyond uniformly-spaced nanowire array formation, the control of spacing in the array is beneficial in that it should be the experimental basis of the precise positioning of functional nanowires on a circuit. Here, we investigate the material parameters and bias conditions to modulate the nanowire spacing in the ordered array, where the nanowire array formation is readily attained due to the electrostatic nanowire interaction. A theoretical model for the force calculation and the simulation of the induced charge in the assembled nanowire verifies that the longer nanowires on thicker dielectric layer tend to be assembled with a larger pitch due to the stronger nanowire-nanowire electrostatic repulsion, which is consistent with the experimental results. It was claimed that the stronger dielectrophoretic force is likely to attract more nanowires that are suspended in solution at the electrode gap, causing them to be less-spaced. Thus, we propose a generic mechanism, competition of dielectrophoretic and electrostatic force, to determine the nanowire pitch in an ordered array. Furthermore, this spacing-controlled nanowire array offers a way to fabricate the high-density nanodevice array without nanowire registration.

  12. Atomistic modeling of mechanical properties of polycrystalline graphene

    International Nuclear Information System (INIS)

    Mortazavi, Bohayra; Cuniberti, Gianaurelio

    2014-01-01

    We performed molecular dynamics (MD) simulations to investigate the mechanical properties of polycrystalline graphene. By constructing molecular models of ultra-fine-grained graphene structures, we studied the effect of different grain sizes of 1–10 nm on the mechanical response of graphene. We found that the elastic modulus and tensile strength of polycrystalline graphene decrease with decreasing grain size. The calculated mechanical proprieties for pristine and polycrystalline graphene sheets are found to be in agreement with experimental results in the literature. Our MD results suggest that the ultra-fine-grained graphene structures can show ultrahigh tensile strength and elastic modulus values that are very close to those of pristine graphene sheets. (papers)

  13. Atomistic modeling of mechanical properties of polycrystalline graphene.

    Science.gov (United States)

    Mortazavi, Bohayra; Cuniberti, Gianaurelio

    2014-05-30

    We performed molecular dynamics (MD) simulations to investigate the mechanical properties of polycrystalline graphene. By constructing molecular models of ultra-fine-grained graphene structures, we studied the effect of different grain sizes of 1-10 nm on the mechanical response of graphene. We found that the elastic modulus and tensile strength of polycrystalline graphene decrease with decreasing grain size. The calculated mechanical proprieties for pristine and polycrystalline graphene sheets are found to be in agreement with experimental results in the literature. Our MD results suggest that the ultra-fine-grained graphene structures can show ultrahigh tensile strength and elastic modulus values that are very close to those of pristine graphene sheets.

  14. Fabrication and magnetic characterization of Co{sub x}Pt{sub 1-x} nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Shamaila, S. [Chinese Academy of Sciences, State Key Laboratory of Magnetism, Institute of Physics, Beijing (China); University of Engineering and Technology, Advanced Physics Laboratory, Lahore (Pakistan); Sharif, R.; Riaz, S.; Han, X.F. [Chinese Academy of Sciences, State Key Laboratory of Magnetism, Institute of Physics, Beijing (China); Khaleeq-ur-Rahman, M. [University of Engineering and Technology, Advanced Physics Laboratory, Lahore (Pakistan)

    2008-08-15

    Co{sub x}Pt{sub 1-x}(x{>=}0.7) alloy nanowires are grown into self-synthesized anodic alumina templates by electrodeposition. Magnetic and magnetization properties of Co{sub x}Pt{sub 1-x} alloy nanowires are measured as functions of wire length, temperature, and field orientation. X-ray diffraction shows that as-prepared CoPt nanowires are of fcc polycrystalline structure. A crossover of easy axis of magnetization is observed from parallel to perpendicular of the nanowire axis as a function of length. The coercivity (H{sub c}) and remanent squareness (SQ) of Co{sub x}Pt{sub 1-x} nanowire arrays are derived from hysteresis loops measured at various angles ({theta}) between the field and wire axis. H{sub c}({theta}) and SQ({theta}) curves show bell-shaped or otherwise bell-shaped behavior corresponding to the easy axis of their magnetization. (orig.)

  15. 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.

  16. 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...

  17. Vertical nanowire architectures

    DEFF Research Database (Denmark)

    Vlad, A.; Mátéfl-Tempfli, M.; Piraux, L.

    2010-01-01

    Nanowires and statistics: A statistical process for reading ultradense arrays of nanostructured materials is presented (see image). The experimental realization is achieved through selective nanowire growth using porous alumina templates. The statistical patterning approach is found to provide ri...

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

    Science.gov (United States)

    Saxena, Dhruv

    -quantum well (MQW) gain regions are investigated. The TE01 mode, due to its polarisation and excellent overlap with the gain region, is predicted to lase in these nanowire heterostructures. Through gain/loss calculations, important design criteria, such as the optimal well thickness to minimise the threshold carrier density and the optimal number of QWs to minimise the threshold fluence are determined. Based on the design, MQW nanowire heterostructures containing eight uniform coaxial GaAs/AlGaAs MQWs are grown. Room-temperature lasing is demonstrated from individual nanowires at a threshold fluence that is two times lower compared to the bulk GaAs nanowire lasers. Lasing is also verified to be from TE01 mode by polarisation measurements. Lastly, a mode characterisation technique based on imaging the polarisation dependent far-field emission pattern of nanowire lasers is presented. To demonstrate this technique, InP nanowire lasers are used, because of their excellent structural characteristics. The InP nanowire lasers are designed to lase from different guided modes by varying the nanowire diameter. The experimentally obtained polarisation dependent far-field profiles match very well with numerical simulations and enable unambiguous identification of the lasing mode(s) in nanowire lasers. Overall, this thesis presents extensive modelling of nanowire lasers, which is supported by experimental results. The modelling will provide a useful reference for developing novel nanoscale lasers and improving the performance of current nanowire lasers.

  19. Magneto-transport measurements of domain wall propagation in individual multi segmented cylindrical nanowires

    KAUST Repository

    Mohammed, Hanan; Vidal, Enrique Vilanova; Ivanov, Yurii P.; Kosel, Jü rgen

    2016-01-01

    Magnetotransport measurements were performed on multisegmented Co/Ni nanowires fabricated by template-assisted electrodeposition. Individual nanowires were isolated and electrodes patterned to study their magnetization reversal process. The magnetoresistance reversal curve of the multisegmented nanowire exhibits a step in the switching field. Micromagnetic simulations of the magnetization reversal process are in agreement with the experimental findings and attribute the step at the switching field to the pinning of a domain wall at the interface of the Co/Ni nanowire.

  20. Magneto-transport measurements of domain wall propagation in individual multi segmented cylindrical nanowires

    KAUST Repository

    Mohammed, Hanan

    2016-03-01

    Magnetotransport measurements were performed on multisegmented Co/Ni nanowires fabricated by template-assisted electrodeposition. Individual nanowires were isolated and electrodes patterned to study their magnetization reversal process. The magnetoresistance reversal curve of the multisegmented nanowire exhibits a step in the switching field. Micromagnetic simulations of the magnetization reversal process are in agreement with the experimental findings and attribute the step at the switching field to the pinning of a domain wall at the interface of the Co/Ni nanowire.

  1. Permanent bending and alignment of ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Borschel, Christian; Spindler, Susann; Oertel, Michael; Ronning, Carsten [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Lerose, Damiana [MPI fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle/Saale (Germany); Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Bochmann, Arne [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Christiansen, Silke H. [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); MPI fuer die Physik des Lichts, Guenther-Scharowsky-Str. 1, 91058 Erlangen (Germany); Nietzsche, Sandor [Zentrum fuer Elektronenmikroskopie, Friedrich-Schiller-Universitaet Jena, Ziegelmuehlenweg 1, 07743 Jena (Germany)

    2011-07-01

    Ion beams can be used to bend or re-align nanowires permanently, after they have been grown. We have irradiated ZnO nanowires with ions of different species and energy, achieving bending and alignment in various directions. We study the bending of single nanowires as well as the simultaneous alignment of large ensembles of ZnO nanowires in detail. Computer simulations show that the bending is initiated by ion beam induced damage. Dislocations are identified to relax stresses and make the bending and alignment permanent and resistant against annealing procedures.

  2. 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....... The gain in the matrix is modeled by adding a negative imaginary part to the dielectric function of the semiconductor. It is found that the optical coefficients of the metamaterial depend on the gain magnitude in a non-trivial way: they can both increase and decrease with gain depending on the lattice...... constant of the metamaterial. This peculiar behavior is explained by the field redistribution between the lossy metal nanowires and the amplifying matrix material. These findings are significant for a proper design of nanowire metamaterials with low optical losses for diverse applications....

  3. Polycrystalline thin films : A review

    Energy Technology Data Exchange (ETDEWEB)

    Valvoda, V [Charles Univ., Prague (Czech Republic). Faculty of Mathematics and Physics

    1996-09-01

    Polycrystalline thin films can be described in terms of grain morphology and in terms of their packing by the Thornton`s zone model as a function of temperature of deposition and as a function of energy of deposited atoms. Grain size and preferred grain orientation (texture) can be determined by X-ray diffraction (XRD) methods. A review of XRD analytical methods of texture analysis is given with main attention paid to simple empirical functions used for texture description and for structure analysis by joint texture refinement. To illustrate the methods of detailed structure analysis of thin polycrystalline films, examples of multilayers are used with the aim to show experiments and data evaluation to determine layer thickness, periodicity, interface roughness, lattice spacing, strain and the size of diffraction coherent volumes. The methods of low angle and high angle XRD are described and discussed with respect to their complementary information content.

  4. Effect of orientation on deformation behavior of Fe nanowires: A molecular dynamics study

    Science.gov (United States)

    Sainath, G.; Srinivasan, V. S.; Choudhary, B. K.; Mathew, M. D.; Jayakumar, T.

    2014-04-01

    Molecular dynamics simulations have been carried out to study the effect of crystal orientation on tensile deformation behaviour of single crystal BCC Fe nanowires at 10 K. Two nanowires with an initial orientation of /{100} and /{111} have been chosen for this study. The simulation results show that the deformation mechanisms varied with crystal orientation. The nanowire with an initial orientation of /{100} deforms predominantly by twinning mechanism, whereas the nanowire oriented in /{111}, deforms by dislocation plasticity. In addition, the single crystal oriented in /{111} shows higher strength and elastic modulus than /{100} oriented nanowire.

  5. Effect of the template-assisted electrodeposition parameters on the structure and magnetic properties of Co nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Kac, Malgorzata, E-mail: malgorzata.kac@ifj.edu.pl [Institute of Nuclear Physics Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Krakow (Poland); Zarzycki, Arkadiusz [Institute of Nuclear Physics Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Krakow (Poland); Kac, Slawomir [AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Krakow (Poland); Kopec, Marek; Perzanowski, Marcin; Dutkiewicz, Erazm M.; Suchanek, Katarzyna; Maximenko, Alexey; Marszalek, Marta [Institute of Nuclear Physics Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Krakow (Poland)

    2016-09-15

    Highlights: • Magnetic properties of Co nanowires in polycarbonate membranes were studied. • Electrodeposition stages were illustrated by SEM images. • Electrolyte and membrane parameters were optimized for Co nanowire fabrication. • Low temperature and potential favored nanowires with high coercivity and squareness. - Abstract: We studied the magnetic properties of Co nanowires electrodeposited in polycarbonate membranes as a function of the electrodeposition and template parameters. We showed the response of the current as a function of time, for nanowires prepared in various conditions. X-ray diffraction measurements indicate that nanowires have polycrystalline hcp structure with small addition of fcc phase. Magnetic properties analyzed by SQUID measurements suggest that easy axis of magnetization follows the nanowire axis with coercivity increasing with a decrease of nanowire diameter and length. The largest coercivity, equal to 850 Oe, was obtained for nanowires with the diameter of 30 nm and the length of 1.5 μm. We find the coercivity to be insensitive to pH value. Low electrodeposition temperature, low cathodic potential, and medium pH are the synthesis parameters most beneficial for large coercivity and/or magnetic anisotropy with easy axis along nanowires.

  6. Fabrication of multilayer nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Jasveer, E-mail: kaurjasveer89@gmail.com; Singh, Avtar; Kumar, Davinder [Department of Physics, Punjabi University Patiala, 147002, Punjab (India); Thakur, Anup; Kaur, Raminder, E-mail: raminder-k-saini@yahoo.com [Department of Basic and Applied Sciences, Punjabi University Patiala, 147002, Punjab (India)

    2016-05-06

    Multilayer nanowires were fabricated by potentiostate ectrodeposition template synthesis method into the pores of polycarbonate membrane. In present work layer by layer deposition of two different metals Ni and Cu in polycarbonate membrane having pore size of 600 nm were carried out. It is found that the growth of nanowires is not constant, it varies with deposition time. Scanning electron microscopy (SEM) is used to study the morphology of fabricated multilayer nanowires. An energy dispersive X-ray spectroscopy (EDS) results confirm the composition of multilayer nanowires. The result shows that multilayer nanowires formed is dense.

  7. Fabrication of multilayer nanowires

    International Nuclear Information System (INIS)

    Kaur, Jasveer; Singh, Avtar; Kumar, Davinder; Thakur, Anup; Kaur, Raminder

    2016-01-01

    Multilayer nanowires were fabricated by potentiostate ectrodeposition template synthesis method into the pores of polycarbonate membrane. In present work layer by layer deposition of two different metals Ni and Cu in polycarbonate membrane having pore size of 600 nm were carried out. It is found that the growth of nanowires is not constant, it varies with deposition time. Scanning electron microscopy (SEM) is used to study the morphology of fabricated multilayer nanowires. An energy dispersive X-ray spectroscopy (EDS) results confirm the composition of multilayer nanowires. The result shows that multilayer nanowires formed is dense.

  8. 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...... cells. Resonance effects between the light and nanowire causes an inherent concentration of the sunlight into the nanowires, and means that a sparse array of nanowires (less than 5% of the area) can absorb all the incoming light. The resonance effects, as well as a graded index of refraction, also traps...... the light. The concentration and light trapping means that single junction nanowire solar cells have a higher theoretical maximum efficiency than equivalent planar solar cells. We have demonstrated the built-in light concentration of nanowires, by growing, contacting and characterizing a solar cell...

  9. Growth mechanism of titanium dioxide nanowires for dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Boercker, J E; Enache-Pommer, E; Aydil, E S [Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, MN 55455 (United States)], E-mail: aydil@umn.edu

    2008-03-05

    Mesoporous films made of titanium dioxide nanowires are desirable for dye-sensitized solar cells because nanowires provide direct conduction pathways for photogenerated electrons. Anatase titanium dioxide nanowires with polycrystalline microstructure were synthesized on titanium foil using a three-step process. First, the top surface of the titanium foil was transformed to Na{sub 2}Ti{sub 2}O{sub 4}(OH){sub 2} nanotubes through hydrothermal oxidation in NaOH. Next, the Na{sub 2}Ti{sub 2}O{sub 4}(OH){sub 2} nanotubes were converted to H{sub 2}Ti{sub 2}O{sub 4}(OH){sub 2} nanotubes by ion exchange. Finally, the H{sub 2}Ti{sub 2}O{sub 4}(OH){sub 2} nanotubes were converted to polycrystalline anatase nanowires through a topotactic transformation. The film morphology evolution, crystal structure transformations and growth mechanism are described in detail. Titanium foil reacts with NaOH to form Na{sub 2}Ti{sub 2}O{sub 4}(OH){sub 2} sheets, which exfoliate and spiral into nanotubes. The Na{sub 2}Ti{sub 2}O{sub 4}(OH){sub 2} nanotubes are immersed in HCl solution to replace the Na{sup +} ions with H{sup +} ions. During the topotactic transformation of H{sub 2}Ti{sub 2}O{sub 4}(OH){sub 2} nanotubes to anatase TiO{sub 2} nanowires, the sheets made of edge bonded TiO{sub 6} octahedra in the H{sub 2}Ti{sub 2}O{sub 4}(OH){sub 2} nanotubes dehydrate and move towards each other to form anatase crystals oriented along the nanotube axis which creates a polycrystalline nanowire. These mesoporous TiO{sub 2} nanowire films were suitable for use as dye-sensitized solar cell photoanodes.

  10. Growth mechanism of titanium dioxide nanowires for dye-sensitized solar cells

    International Nuclear Information System (INIS)

    Boercker, J E; Enache-Pommer, E; Aydil, E S

    2008-01-01

    Mesoporous films made of titanium dioxide nanowires are desirable for dye-sensitized solar cells because nanowires provide direct conduction pathways for photogenerated electrons. Anatase titanium dioxide nanowires with polycrystalline microstructure were synthesized on titanium foil using a three-step process. First, the top surface of the titanium foil was transformed to Na 2 Ti 2 O 4 (OH) 2 nanotubes through hydrothermal oxidation in NaOH. Next, the Na 2 Ti 2 O 4 (OH) 2 nanotubes were converted to H 2 Ti 2 O 4 (OH) 2 nanotubes by ion exchange. Finally, the H 2 Ti 2 O 4 (OH) 2 nanotubes were converted to polycrystalline anatase nanowires through a topotactic transformation. The film morphology evolution, crystal structure transformations and growth mechanism are described in detail. Titanium foil reacts with NaOH to form Na 2 Ti 2 O 4 (OH) 2 sheets, which exfoliate and spiral into nanotubes. The Na 2 Ti 2 O 4 (OH) 2 nanotubes are immersed in HCl solution to replace the Na + ions with H + ions. During the topotactic transformation of H 2 Ti 2 O 4 (OH) 2 nanotubes to anatase TiO 2 nanowires, the sheets made of edge bonded TiO 6 octahedra in the H 2 Ti 2 O 4 (OH) 2 nanotubes dehydrate and move towards each other to form anatase crystals oriented along the nanotube axis which creates a polycrystalline nanowire. These mesoporous TiO 2 nanowire films were suitable for use as dye-sensitized solar cell photoanodes

  11. Study of the effect of varying core diameter, shell thickness and strain velocity on the tensile properties of single crystals of Cu-Ag core-shell nanowire using molecular dynamics simulations

    Science.gov (United States)

    Sarkar, Jit; Das, D. K.

    2018-01-01

    Core-shell type nanostructures show exceptional properties due to their unique structure having a central solid core of one type and an outer thin shell of another type which draw immense attention among researchers. In this study, molecular dynamics simulations are carried out on single crystals of copper-silver core-shell nanowires having wire diameter ranging from 9 to 30 nm with varying core diameter, shell thickness, and strain velocity. The tensile properties like yield strength, ultimate tensile strength, and Young's modulus are studied and correlated by varying one parameter at a time and keeping the other two parameters constant. The results obtained for a fixed wire size and different strain velocities were extrapolated to calculate the tensile properties like yield strength and Young's modulus at standard strain rate of 1 mm/min. The results show ultra-high tensile properties of copper-silver core-shell nanowires, several times than that of bulk copper and silver. These copper-silver core-shell nanowires can be used as a reinforcing agent in bulk metal matrix for developing ultra-high strength nanocomposites.

  12. Study of spin dynamics and damping on the magnetic nanowire arrays with various nanowire widths

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jaehun [Department of Physics, Inha University, Incheon, 402-751 (Korea, Republic of); Fujii, Yuya; Konioshi, Katsunori [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Yoon, Jungbum [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Kim, Nam-Hui; Jung, Jinyong [Department of Physics, Inha University, Incheon, 402-751 (Korea, Republic of); Miwa, Shinji [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Jung, Myung-Hwa [Department of Physics, Sogang University, Seoul, 121-742 (Korea, Republic of); Suzuki, Yoshishige [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); You, Chun-Yeol, E-mail: cyyou@inha.ac.kr [Department of Physics, Inha University, Incheon, 402-751 (Korea, Republic of)

    2016-07-01

    We investigate the spin dynamics including Gilbert damping in the ferromagnetic nanowire arrays. We have measured the ferromagnetic resonance of ferromagnetic nanowire arrays using vector-network analyzer ferromagnetic resonance (VNA-FMR) and analyzed the results with the micromagnetic simulations. We find excellent agreement between the experimental VNA-FMR spectra and micromagnetic simulations result for various applied magnetic fields. We find that the same tendency of the demagnetization factor for longitudinal and transverse conditions, N{sub z} (N{sub y}) increases (decreases) as increasing the nanowire width in the micromagnetic simulations while N{sub x} is almost zero value in transverse case. We also find that the Gilbert damping constant increases from 0.018 to 0.051 as the increasing nanowire width for the transverse case, while it is almost constant as 0.021 for the longitudinal case. - Highlights: • We investigate the spin dynamic properties in the ferromagnetic nanowire arrays. • The demagnetization factors have similar tendency with the prism geometry results. • The Gilbert damping constant is increased from 0.018 to 0.051 as the increasing nanowire width for the transverse. • The Gilbert damping constant is almost constant as 0.021 for the longitudinal case.

  13. Constricted nanowire with stabilized magnetic domain wall

    International Nuclear Information System (INIS)

    Sbiaa, R.; Al Bahri, M.

    2016-01-01

    Domain wall (DW)-based magnetic memory offers the possibility for increasing the storage capacity. However, stability of DW remains the major drawback of this scheme. In this letter, we propose a stepped nanowire for pinning DW in a desirable position. From micromagnetic simulation, the proposed design applied to in-plane magnetic anisotropy materials shows that by adjusting the nanowire step size and its width it is possible to stabilize DW for a desirable current density range. In contrast, only a movement of DW could be seen for conventional nanowire. An extension to a multi-stepped nanowire could be used for multi-bit per cell magnetic memory. - Highlights: • A stepped nanowire is proposed to pin domain wall in desired position. • The new structure can be made by a simple off set of two single nanowires. • The critical current for moving domain wall from one state to the other could be tuned by adjusting the geometry of the device. • The device could be used for multi-bit per cell memory by extending the steps in the device.

  14. Au nanowire junction breakup through surface atom diffusion

    Science.gov (United States)

    Vigonski, Simon; Jansson, Ville; Vlassov, Sergei; Polyakov, Boris; Baibuz, Ekaterina; Oras, Sven; Aabloo, Alvo; Djurabekova, Flyura; Zadin, Vahur

    2018-01-01

    Metallic nanowires are known to break into shorter fragments due to the Rayleigh instability mechanism. This process is strongly accelerated at elevated temperatures and can completely hinder the functioning of nanowire-based devices like e.g. transparent conductive and flexible coatings. At the same time, arranged gold nanodots have important applications in electrochemical sensors. In this paper we perform a series of annealing experiments of gold and silver nanowires and nanowire junctions at fixed temperatures 473, 673, 873 and 973 K (200 °C, 400 °C, 600 °C and 700 °C) during a time period of 10 min. We show that nanowires are especially prone to fragmentation around junctions and crossing points even at comparatively low temperatures. The fragmentation process is highly temperature dependent and the junction region breaks up at a lower temperature than a single nanowire. We develop a gold parametrization for kinetic Monte Carlo simulations and demonstrate the surface diffusion origin of the nanowire junction fragmentation. We show that nanowire fragmentation starts at the junctions with high reliability and propose that aligning nanowires in a regular grid could be used as a technique for fabricating arrays of nanodots.

  15. Microscopic and magnetic properties of template assisted electrodeposited iron nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Irshad, M. I., E-mail: imrancssp@gmail.com; Mohamed, N. M., E-mail: noranimuti-mohamed@petronas.com.my; Yar, A., E-mail: asfandyarhargan@gmail.com [Department of Fundamental & Applied Sciences, Universiti Teknologi PETRONAS, 31750 PERAK (Malaysia); Ahmad, F., E-mail: faizahmad@petronas.com.my; Abdullah, M. Z., E-mail: zaki-abdullah@petronas.com.my [Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 31750 PERAK (Malaysia)

    2015-07-22

    Nanowires of magnetic materials such as Iron, nickel, cobalt, and alloys of them are one of the most widely investigated structures because of their possible applications in high density magnetic recording media, sensor elements, and building blocks in biological transport systems. In this work, Iron nanowires have been prepared by electrodeposition technique using Anodized Aluminium Oxide (AAO) templates. The electrolyte used consisted of FeSO{sub 4.}6H{sub 2}O buffered with H{sub 3}BO{sub 3} and acidized by dilute H{sub 2}SO{sub 4}. FESEM analysis shows that the asdeposited nanowires are parallel to one another and have high aspect ratio with a reasonably high pore-filing factor. To fabricate the working electrode, a thin film of copper (∼ 220 nm thick) was coated on back side of AAO template by e-beam evaporation system to create electrical contact with the external circuit. The TEM results show that electrodeposited nanowires have diameter around 100 nm and are polycrystalline in structure. Magnetic properties show the existence of anisotropy for in and out of plane configuration. These nanowires have potential applications in magnetic data storage, catalysis and magnetic sensor applications.

  16. Synthesis of platinum nanowire networks using a soft template.

    Science.gov (United States)

    Song, Yujiang; Garcia, Robert M; Dorin, Rachel M; Wang, Haorong; Qiu, Yan; Coker, Eric N; Steen, William A; Miller, James E; Shelnutt, John A

    2007-12-01

    Platinum nanowire networks have been synthesized by chemical reduction of a platinum complex using sodium borohydride in the presence of a soft template formed by cetyltrimethylammonium bromide in a two-phase water-chloroform system. The interconnected polycrystalline nanowires possess the highest surface area (53 +/- 1 m2/g) and electroactive surface area (32.4 +/- 3.6 m2/g) reported for unsupported platinum nanomaterials; the high surface area results from the small average diameter of the nanowires (2.2 nm) and the 2-10 nm pores determined by nitrogen adsorption measurements. Synthetic control over the network was achieved simply by varying the stirring rate and reagent concentrations, in some cases leading to other types of nanostructures including wormlike platinum nanoparticles. Similarly, substitution of a palladium complex for platinum gives palladium nanowire networks. A mechanism of formation of the metal nanowire networks is proposed based on confined metal growth within a soft template consisting of a network of swollen inverse wormlike micelles.

  17. Crystallinity, Surface Morphology, and Photoelectrochemical Effects in Conical InP and InN Nanowires Grown on Silicon.

    Science.gov (United States)

    Parameshwaran, Vijay; Xu, Xiaoqing; Clemens, Bruce

    2016-08-24

    The growth conditions of two types of indium-based III-V nanowires, InP and InN, are tailored such that instead of yielding conventional wire-type morphologies, single-crystal conical structures are formed with an enlarged diameter either near the base or near the tip. By using indium droplets as a growth catalyst, combined with an excess indium supply during growth, "ice cream cone" type structures are formed with a nanowire "cone" and an indium-based "ice cream" droplet on top for both InP and InN. Surface polycrystallinity and annihilation of the catalyst tip of the conical InP nanowires are observed when the indium supply is turned off during the growth process. This growth design technique is extended to create single-crystal InN nanowires with the same morphology. Conical InN nanowires with an enlarged base are obtained through the use of an excess combined Au-In growth catalyst. Electrochemical studies of the InP nanowires on silicon demonstrate a reduction photocurrent as a proof of photovolatic behavior and provide insight as to how the observed surface polycrystallinity and the resulting interface affect these device-level properties. Additionally, a photovoltage is induced in both types of conical InN nanowires on silicon, which is not replicated in epitaxial InN thin films.

  18. 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.

  19. Acoustic emission from polycrystalline graphites

    International Nuclear Information System (INIS)

    Ioka, I.; Yoda, S.; Oku, T.; Miyamoto, Y.

    1987-01-01

    Acoustic emission was monitored from polycrystalline graphites with different microstructure (pore size and pore volume) subjected to compressive loading. The graphites used in this study comprised five brands, that is, PGX, ISEM-1, IG-11, IG-15, and ISO-88. A root mean square (RMS) voltage and event counts of acoustic emission for graphites were measured during compressive loading. The acoustic emission was measured using a computed-based data acquisition and analysis system. The graphites were first deformed up to 80 % of the average fracture stress, then unloaded and reloaded again until the fracture occured. During the first loading, the change in RMS voltage for acoustic emission was detected from the initial stage. During the unloading, the RMS voltage became zero level as soon as the applied stress was released and then gradually rose to a peak and declined. The behavior indicated that the reversed plastic deformation occured in graphites. During the second loading, the RMS voltage gently increased until the applied stress exceeded the maximum stress of the first loading; there is no Kaiser effect in the graphites. A bicrystal model could give a reasonable explanation of this results. The empirical equation between the ratio of σ AE to σ f and σ f was obtained. It is considered that the detection of microfracture by the acoustic emission technique is effective in macrofracture prediction of polycrystalline graphites. (author)

  20. 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.

  1. Thermoelectric properties of semiconductor nanowire networks

    Science.gov (United States)

    Roslyak, Oleksiy; Piryatinski, Andrei

    2016-03-01

    To examine the thermoelectric (TE) properties of a semiconductor nanowire (NW) network, we propose a theoretical approach mapping the TE network on a two-port network. In contrast to a conventional single-port (i.e., resistor) network model, our model allows for large scale calculations showing convergence of TE figure of merit, ZT, with an increasing number of junctions. Using this model, numerical simulations are performed for the Bi2Te3 branched nanowire (BNW) and Cayley tree NW (CTNW) network. We find that the phonon scattering at the network junctions plays a dominant role in enhancing the network ZT. Specifically, disordered BNW and CTNW demonstrate an order of magnitude higher ZT enhancement compared to their ordered counterparts. Formation of preferential TE pathways in CTNW makes the network effectively behave as its BNW counterpart. We provide formalism for simulating large scale nanowire networks hinged upon experimentally measurable TE parameters of a single T-junction.

  2. Process Research on Polycrystalline Silicon Material (PROPSM)

    Science.gov (United States)

    Culik, J. S.; Wrigley, C. Y.

    1985-01-01

    Results of hydrogen-passivated polycrysalline silicon solar cell research are summarized. The short-circuit current of solar cells fabricated from large-grain cast polycrystalline silicon is nearly equivalent to that of single-crystal cells, which indicates long bulk minority-carrier diffusion length. Treatments with molecular hydrogen showed no effect on large-grain cast polycrystalline silicon solar cells.

  3. Application of real space Kerker method in simulating gate-all-around nanowire transistors with realistic discrete dopants*

    International Nuclear Information System (INIS)

    Li Chang-Sheng; Ma Lei; Guo Jie-Rong

    2017-01-01

    We adopt a self-consistent real space Kerker method to prevent the divergence from charge sloshing in the simulating transistors with realistic discrete dopants in the source and drain regions. The method achieves efficient convergence by avoiding unrealistic long range charge sloshing but keeping effects from short range charge sloshing. Numerical results show that discrete dopants in the source and drain regions could have a bigger influence on the electrical variability than the usual continuous doping without considering charge sloshing. Few discrete dopants and the narrow geometry create a situation with short range Coulomb screening and oscillations of charge density in real space. The dopants induced quasi-localized defect modes in the source region experience short range oscillations in order to reach the drain end of the device. The charging of the defect modes and the oscillations of the charge density are identified by the simulation of the electron density. (paper)

  4. Towards engineered branch placement: Unreal™ match between vapour-liquid-solid glancing angle deposition nanowire growth and simulation

    International Nuclear Information System (INIS)

    Taschuk, M. T.; Tucker, R. T.; LaForge, J. M.; Beaudry, A. L.; Kupsta, M. R.; Brett, M. J.

    2013-01-01

    The vapour-liquid-solid glancing angle deposition (VLS-GLAD) process is capable of producing complex nanotree structures with control over azimuthal branch orientation and height. We have developed a thin film growth simulation including ballistic deposition, simplified surface diffusion, and droplet-mediated cubic crystal growth for the VLS-GLAD process using the Unreal TM Development Kit. The use of a commercial game engine has provided an interactive environment while allowing a custom physics implementation. Our simulation's output is verified against experimental data, including a volumetric film reconstruction produced using focused ion beam and scanning-electron microscopy (SEM), crystallographic texture, and morphological characteristics such as branch orientation. We achieve excellent morphological and texture agreement with experimental data, as well as qualitative agreement with SEM imagery. The simplified physics in our model reproduces the experimental films, indicating that the dominant role flux geometry plays in the VLS-GLAD competitive growth process responsible for azimuthally oriented branches and biaxial crystal texture evolution. The simulation's successful reproduction of experimental data indicates that it should have predictive power in designing novel VLS-GLAD structures

  5. Towards engineered branch placement: Unreal™ match between vapour-liquid-solid glancing angle deposition nanowire growth and simulation

    Science.gov (United States)

    Taschuk, M. T.; Tucker, R. T.; LaForge, J. M.; Beaudry, A. L.; Kupsta, M. R.; Brett, M. J.

    2013-12-01

    The vapour-liquid-solid glancing angle deposition (VLS-GLAD) process is capable of producing complex nanotree structures with control over azimuthal branch orientation and height. We have developed a thin film growth simulation including ballistic deposition, simplified surface diffusion, and droplet-mediated cubic crystal growth for the VLS-GLAD process using the UnrealTM Development Kit. The use of a commercial game engine has provided an interactive environment while allowing a custom physics implementation. Our simulation's output is verified against experimental data, including a volumetric film reconstruction produced using focused ion beam and scanning-electron microscopy (SEM), crystallographic texture, and morphological characteristics such as branch orientation. We achieve excellent morphological and texture agreement with experimental data, as well as qualitative agreement with SEM imagery. The simplified physics in our model reproduces the experimental films, indicating that the dominant role flux geometry plays in the VLS-GLAD competitive growth process responsible for azimuthally oriented branches and biaxial crystal texture evolution. The simulation's successful reproduction of experimental data indicates that it should have predictive power in designing novel VLS-GLAD structures.

  6. Tuning wettability of hydrogen titanate nanowire mesh by Na+ irradiation

    Science.gov (United States)

    Das, Pritam; Chatterjee, Shyamal

    2018-04-01

    Hydrogen titanate (HT) nanowires have been widely studied for remarkable properties and various potential applications. However, a handful studies are available related to ion beam induced structural changes and influence on wetting behavior of the HT nanowire surface. In this work, we exposed HT nanowires to 5 keV Na+ at an ion fluence of 1×1016 ions.cm-2. Scanning electron microscope shows that at this ion fluence nanowires are bent arbitrarily and they are welded to each other forming an interlinked network structure. Computer simulation shows that ion beam induces defect formation in the nanowires, which plays major role in such structural modifications. An interesting alteration of surface wetting property is observed due to ion irradiation. The hydrophilic pristine surface turns into hydrophobic after ion irradiation.

  7. Domain wall oscillations induced by spin torque in magnetic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Sbiaa, R., E-mail: rachid@squ.edu.om [Department of Physics, Sultan Qaboos University, P.O. Box 36, PC 123, Muscat (Oman); Chantrell, R. W. [Department of Physics, University of York, York YO10 5DD (United Kingdom)

    2015-02-07

    Using micromagnetic simulations, the effects of the non-adiabatic spin torque (β) and the geometry of nanowires on domain wall (DW) dynamics are investigated. For the case of in-plane anisotropy nanowire, it is observed that the type of DW and its dynamics depends on its dimension. For a fixed length, the critical switching current decreases almost exponentially with the width W, while the DW speed becomes faster for larger W. For the case of perpendicular anisotropy nanowire, it was observed that DW dynamics depends strongly on β. For small values of β, oscillations of DW around the center of nanowire were revealed even after the current is switched off. In addition to nanowire geometry and intrinsic material properties, β could provide a way to control DW dynamics.

  8. Piezoresistance of top-down suspended Si nanowires

    International Nuclear Information System (INIS)

    Koumela, A; Mercier, D; Dupre, C; Jourdan, G; Marcoux, C; Ollier, E; Duraffourg, L; Purcell, S T

    2011-01-01

    Measurements of the gauge factor of suspended, top-down silicon nanowires are presented. The nanowires are fabricated with a CMOS compatible process and with doping concentrations ranging from 2 x 10 20 down to 5 x 10 17 cm -3 . The extracted gauge factors are compared with results on identical non-suspended nanowires and with state-of-the-art results. An increase of the gauge factor after suspension is demonstrated. For the low doped nanowires a value of 235 is measured. Particular attention was paid throughout the experiments to distinguishing real resistance change due to strain modulation from resistance fluctuations due to charge trapping. Furthermore, a numerical model correlating surface charge density with the gauge factor is presented. Comparison of the simulations with experimental measurements shows the validity of this approach. These results contribute to a deeper understanding of the piezoresistive effect in Si nanowires.

  9. Polycrystalline Silicon: a Biocompatibility Assay

    International Nuclear Information System (INIS)

    Pecheva, E.; Fingarova, D.; Pramatarova, L.; Hikov, T.; Laquerriere, P.; Bouthors, Sylvie; Dimova-Malinovska, D.; Montgomery, P.

    2010-01-01

    Polycrystalline silicon (poly-Si) layers were functionalized through the growth of biomimetic hydroxyapatite (HA) on their surface. HA is the mineral component of bones and teeth and thus possesses excellent bioactivity and biocompatibility. MG-63 osteoblast-like cells were cultured on both HA-coated and un-coated poly-Si surfaces for 1, 3, 5 and 7 days and toxicity, proliferation and cell morphology were investigated. The results revealed that the poly-Si layers were bioactive and compatible with the osteoblast-like cells. Nevertheless, the HA coating improved the cell interactions with the poly-Si surfaces based on the cell affinity to the specific chemical composition of the bone-like HA and/or to the higher HA roughness.

  10. Anodic Aluminum Oxide Membrane-Assisted Fabrication of β-In2S3Nanowires

    Directory of Open Access Journals (Sweden)

    Chen Chih-Jung

    2009-01-01

    Full Text Available Abstract In this study, β-In2S3nanowires were first synthesized by sulfurizing the pure Indium (In nanowires in an AAO membrane. As FE-SEM results, β-In2S3nanowires are highly ordered, arranged tightly corresponding to the high porosity of the AAO membrane used. The diameter of the β-In2S3nanowires is about 60 nm with the length of about 6–8 μm. Moreover, the aspect ratio of β-In2S3nanowires is up to 117. An EDS analysis revealed the β-In2S3nanowires with an atomic ratio of nearly S/In = 1.5. X-ray diffraction and corresponding selected area electron diffraction patterns demonstrated that the β-In2S3nanowire is tetragonal polycrystalline. The direct band gap energy (Eg is 2.40 eV from the optical measurement, and it is reasonable with literature.

  11. Effects of pH on the crystallographic structure and magnetic properties of electrodeposited cobalt nanowires

    International Nuclear Information System (INIS)

    Zafar, N.; Shamaila, S.; Sharif, R.; Wali, H.; Naseem, S.; Riaz, S.; Khaleeq-ur-Rahman, M.

    2015-01-01

    Anodic aluminum oxide templates with pore diameter of 40 nm and inter pore separation of 100 nm are prepared by two step anodization in 0.3 M oxalic acid solution. These templates are used to fabricate dc-deposited Co nanowires at different pH values of acidic bath. Continuous and densely packed nanowires having length ∼8 µm are observed. The hcp configuration appeared at moderate and high pH whereas both fcc and hcp phases are observed at low pH. However the crystallinity distorted at high pH due to formation of polycrystalline structure of cobalt nanowires. Alignment of easy-axis of nanowires can be tailored by varying pH of solution. - Highlights: • Variation in the structure of dc deposited cobalt nanowires can be obtained by varying pH of acidic bath. • The hcp structure is stable at room temperature with low voltage deposition for electrodeposited Co nanowires. Co with fcc structure, is stable at temperatures above 422 °C or at pH<3 with high potential. • The hcp (100) plane is obtained with pH∼3.5 and (101) is stable at pH∼5.5 due to variation in temperature inside the pores with respect to the pH. • Alignment of easy-axis of nanowires can be tailored by varying pH of solution

  12. Anodic Aluminum Oxide Membrane-Assisted Fabrication of beta-In(2)S(3) Nanowires.

    Science.gov (United States)

    Shi, Jen-Bin; Chen, Chih-Jung; Lin, Ya-Ting; Hsu, Wen-Chia; Chen, Yu-Cheng; Wu, Po-Feng

    2009-06-06

    In this study, beta-In(2)S(3) nanowires were first synthesized by sulfurizing the pure Indium (In) nanowires in an AAO membrane. As FE-SEM results, beta-In(2)S(3) nanowires are highly ordered, arranged tightly corresponding to the high porosity of the AAO membrane used. The diameter of the beta-In(2)S(3) nanowires is about 60 nm with the length of about 6-8 mum. Moreover, the aspect ratio of beta-In(2)S(3) nanowires is up to 117. An EDS analysis revealed the beta-In(2)S(3) nanowires with an atomic ratio of nearly S/In = 1.5. X-ray diffraction and corresponding selected area electron diffraction patterns demonstrated that the beta-In(2)S(3) nanowire is tetragonal polycrystalline. The direct band gap energy (E(g)) is 2.40 eV from the optical measurement, and it is reasonable with literature.

  13. Pattern analysis of aligned nanowires in a microchannel

    International Nuclear Information System (INIS)

    Jeon, Young Jin; Kang, Hyun Wook; Ko, Seung Hwan; Sung, Hyung Jin

    2013-01-01

    An image processing method for evaluating the quality of nanowire alignment in a microchannel is described. A solution containing nanowires flowing into a microchannel will tend to deposit the nanowires on the bottom surface of the channel via near-wall shear flows. The deposited nanowires generally form complex directional structures along the direction of flow, and the physical properties of these structures depend on the structural morphology, including the alignment quality. A quantitative analysis approach to characterizing the nanowire alignment is needed to estimate the useful features of the nanowire structures. This analysis consists of several image processing methods, including ridge detection, texton analysis and autocorrelation function (ACF) calculation. The ridge detection method improved the ACF by extracting nanowire frames 1–2 pixels in width. Dilation filters were introduced to permit a comparison of the ACF results calculated from different images, regardless of the nanowire orientation. An ACF based on the FFT was then calculated over a square interrogation window. The alignment angle probability distribution was obtained using texton analysis. Monte Carlo simulations of artificially generated images were carried out, and the new algorithm was applied to images collected using two types of microscopy. (paper)

  14. Plasmonic engineering of metal-oxide nanowire heterojunctions in integrated nanowire rectification units

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Luchan; Zhou, Y. Norman, E-mail: liulei@tsinghua.edu.cn, E-mail: nzhou@uwaterloo.ca [Department of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Zou, Guisheng; Liu, Lei, E-mail: liulei@tsinghua.edu.cn, E-mail: nzhou@uwaterloo.ca [Department of Mechanical Engineering, State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Duley, Walt W. [Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

    2016-05-16

    We show that irradiation with femtosecond laser pulses can produce robust nanowire heterojunctions in coupled non-wetting metal-oxide Ag-TiO{sub 2} structures. Simulations indicate that joining arises from the effect of strong plasmonic localization in the region of the junction. Strong electric field effects occur in both Ag and TiO{sub 2} resulting in the modification of both surfaces and an increase in wettability of TiO{sub 2}, facilitating the interconnection of Ag and TiO{sub 2} nanowires. Irradiation leads to the creation of a thin layer of highly defected TiO{sub 2} in the contact region between the Ag and TiO{sub 2} nanowires. The presence of this layer allows the formation of a heterojunction and offers the possibility of engineering the electronic characteristics of interfacial structures. Rectifying junctions with single and bipolar properties have been generated in Ag-TiO{sub 2} nanowire circuits incorporating asymmetrical and symmetrical interfacial structures, respectively. This fabrication technique should be applicable for the interconnection of other heterogeneous metal-oxide nanowire components and demonstrates that femtosecond laser irradiation enables interfacial engineering for electronic applications of integrated nanowire structures.

  15. Plasmonic engineering of metal-oxide nanowire heterojunctions in integrated nanowire rectification units

    Science.gov (United States)

    Lin, Luchan; Zou, Guisheng; Liu, Lei; Duley, Walt W.; Zhou, Y. Norman

    2016-05-01

    We show that irradiation with femtosecond laser pulses can produce robust nanowire heterojunctions in coupled non-wetting metal-oxide Ag-TiO2 structures. Simulations indicate that joining arises from the effect of strong plasmonic localization in the region of the junction. Strong electric field effects occur in both Ag and TiO2 resulting in the modification of both surfaces and an increase in wettability of TiO2, facilitating the interconnection of Ag and TiO2 nanowires. Irradiation leads to the creation of a thin layer of highly defected TiO2 in the contact region between the Ag and TiO2 nanowires. The presence of this layer allows the formation of a heterojunction and offers the possibility of engineering the electronic characteristics of interfacial structures. Rectifying junctions with single and bipolar properties have been generated in Ag-TiO2 nanowire circuits incorporating asymmetrical and symmetrical interfacial structures, respectively. This fabrication technique should be applicable for the interconnection of other heterogeneous metal-oxide nanowire components and demonstrates that femtosecond laser irradiation enables interfacial engineering for electronic applications of integrated nanowire structures.

  16. 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).

  17. Functionalised Silver Nanowire Structures

    International Nuclear Information System (INIS)

    Andrew, Piers; Ilie, Adelina

    2007-01-01

    Crystalline silver nanowires 60-100 nm in diameter and tens of micrometres in length have been fabricated using a low temperature, solution synthesis technique. We explore the potential of this method to produce functional nanowire structures using two different strategies to attach active molecules to the nanowires: adsorption and displacement. Initially, as-produced silver nanowires capped with a uniaxial-growth-inducing polymer layer were functionalised by solution adsorption of a semiconducting conjugated polymer to generate fluorescent nanowire structures. The influence of nanowire surface chemistry was investigated by displacing the capping polymer with an alkanethiol self-assembled monolayer, followed by solution adsorption functionalisation. The success of molecular attachment was monitored by electron microscopy, absorption and fluorescence spectroscopy and confocal fluorescence microscopy. We examined how the optical properties of such adsorbed molecules are affected by the metallic nanowires, and observed transfer of excitation energy between dye molecules mediated by surface plasmons propagating on the nanowires. Non-contact dynamic force microscopy measurements were used to map the work-function of individual wires, revealing inhomogeneity of the polymer surface coverage

  18. Stability of Organic Nanowires

    DEFF Research Database (Denmark)

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

    2011-01-01

    The morphological stability of organic nanowires over time and under thermal load is of major importance for their use in any device. In this study the growth and stability of organic nanowires from a naphthyl end-capped thiophene grown by organic molecular beam deposition is investigated via ato...

  19. Hydrothermal growth of titania nanowires for SAW device sensing area

    Directory of Open Access Journals (Sweden)

    Zakaria Mohd Rosydi

    2017-01-01

    Full Text Available Synthesis of titania or titanium dioxide (TiO2 is attracted to energy and environmental applications. Here, the growth of nanostructure TiO2 nanowires on Si (100 substrates by using the two-step method. Different seed layers of TiO2 were deposited by spin coating and annealing, followed by the growth of TiO2 nanowires by using the hydrothermal method. The sol-gel technique was used in preparing the TiO2 solution for the thin film deposition purpose. Acetic acid, hydrochloric acid and tris (2-aminoethyl amine were used as a stabilizer to synthesize three different TiO2 seed layers. The aim of this study was to understand the role of polycrystalline size on thin film towards the diameter of nanowires grown as a sensing area in Surface Acoustic Wave (SAW Biosensor. The morphology and structure of the thin film and TiO2 nanowires were characterized using X-Ray diffraction (XRD, scanning electron microscope (SEM, field emission scanning electron microscope (FESEM and atomic force microscopy (AFM.

  20. Structural study on Ni nanowires in an anodic alumina membrane by using in situ heating extended x-ray absorption fine structure and x-ray diffraction techniques

    International Nuclear Information System (INIS)

    Cai Quan; Chen Xing; Chen Zhongjun; Wang Wei; Mo Guang; Wu Zhonghua; Zhang Junxi; Zhang Lide; Pan Wei

    2008-01-01

    Polycrystalline Ni nanowires have been prepared by electrochemical deposition in an anodic alumina membrane template with a nanopore size of about 60 nm. In situ heating extended x-ray absorption fine structure and x-ray diffraction techniques are used to probe the atomic structures. The nanowires are identified as being mixtures of nanocrystallites and amorphous phase. The nanocrystallites have the same thermal expansion coefficient, of 1.7 x 10 -5 K -1 , as Ni bulk; however, the amorphous phase has a much larger thermal expansion coefficient of 3.5 x 10 -5 K -1 . Details of the Ni nanowire structures are discussed in this paper

  1. Effects of polymer surface energy on morphology and properties of silver nanowire fabricated via nanoimprint and E-beam evaporation

    Science.gov (United States)

    Zhao, Zhi-Jun; Hwang, Soon Hyoung; Jeon, Sohee; Jung, Joo-Yun; Lee, Jihye; Choi, Dae-Geun; Choi, Jun-Hyuk; Park, Sang-Hu; Jeong, Jun-Ho

    2017-10-01

    In this paper, we demonstrate that use of different nanoimprint resins as a polymer pattern has a significant effect on the morphology of silver (Ag) nanowires deposited via an E-beam evaporator. RM-311 and Ormo-stamp resins are chosen as a polymer pattern to form a line with dimensions of width (100 nm) × space (100 nm) × height (120 nm) by using nanoimprint lithography (NIL). Their contact angles are then measured to evaluate their surface energies. In order to compare the properties of the Ag nanowires deposited on the various polymer patterns with different surface energies, hydrophobic surface treatment of the polymer pattern surface is implemented using self-assembled monolayers. In addition, gold and aluminum nanowires are fabricated for comparison with the Ag nanowires, with the differences in the nanowire morphologies being determined by the different atomic properties. The monocrystalline and polycrystalline structures of the various Ag nanowire formations are observed using transmission electron microscopy. In addition, the melting temperatures and optical properties of four kinds of Ag nanowire morphologies deposited on various polymer patterns are evaluated using a hot plate and an ultraviolet-visible (UV-vis) spectrometer, respectively. The results indicate that the morphology of the Ag nanowire determines the melting temperature and the transmission. We believe that these findings will greatly aid the development of NIL, along with physical evaporation and chemical deposition techniques, and will be widely employed in optics, biology, and surface wettability applications.

  2. High vacuum tribology of polycrystalline diamond coatings

    Indian Academy of Sciences (India)

    Polycrystalline diamond coatings; hot filament CVD; high vacuum tribology. 1. Introduction .... is a characteristic of graphite. We mark the (diamond ... coefficient of friction due to changes in substrate temperature. The average coefficient of.

  3. Electronic and magnetic properties of ultrathin rhodium nanowires

    CERN Document Server

    Wang Bao Lin; Ren-Yun; Sun Hou Qian; Chen Xiao Shuang; Zhao Ji Jun

    2003-01-01

    The structures of ultrathin rhodium nanowires are studied using empirical molecular dynamics simulations with a genetic algorithm. Helical multishell cylindrical and pentagonal packing structures are found. The electronic and magnetic properties of the rhodium nanowires are calculated using an spd tight-binding Hamiltonian in the unrestricted Hartree-Fock approximation. The average magnetic moment and electronic density of states are obtained. Our results indicate that the electronic and magnetic properties of the rhodium nanowires depend not only on the size of the wire but also on the atomic structure. In particular, centred pentagonal and hexagonal structures can be unusually ferromagnetic.

  4. Broadband absorption of semiconductor nanowire arrays for photovoltaic applications

    International Nuclear Information System (INIS)

    Huang, Ningfeng; Lin, Chenxi; Povinelli, Michelle L

    2012-01-01

    We use electromagnetic simulations to carry out a systematic study of broadband absorption in vertically-aligned semiconductor nanowire arrays for photovoltaic applications. We study six semiconductor materials that are commonly used for solar cells. We optimize the structural parameters of each nanowire array to maximize the ultimate efficiency. We plot the maximal ultimate efficiency as a function of height to determine how it approaches the perfect-absorption limit. We further show that the ultimate efficiencies of optimized nanowire arrays exceed those of equal-height thin films for all six materials and over a wide range of heights from 100 nm to 100 µm

  5. Reliability of Single Crystal Silver Nanowire-Based Systems: Stress Assisted Instabilities.

    Science.gov (United States)

    Ramachandramoorthy, Rajaprakash; Wang, Yanming; Aghaei, Amin; Richter, Gunther; Cai, Wei; Espinosa, Horacio D

    2017-05-23

    Time-dependent mechanical characterization of nanowires is critical to understand their long-term reliability in applications, such as flexible-electronics and touch screens. It is also of great importance to develop a theoretical framework for experimentation and analysis on the mechanics of nanowires under time-dependent loading conditions, such as stress-relaxation and fatigue. Here, we combine in situ scanning electron microscope (SEM)/transmission electron microscope (TEM) tests with atomistic and phase-field simulations to understand the deformation mechanisms of single crystal silver nanowires held under constant strain. We observe that the nanowires initially undergo stress-relaxation, where the stress reduces with time and saturates after some time period. The stress-relaxation process occurs due to the formation of few dislocations and stacking faults. Remarkably, after a few hours the nanowires rupture suddenly. The reason for this abrupt failure of the nanowire was identified as stress-assisted diffusion, using phase-field simulations. Under a large applied strain, diffusion leads to the amplification of nanowire surface perturbation at long wavelengths and the nanowire fails at the stress-concentrated thin cross-sectional regions. An analytical analysis on the competition between the elastic energy and the surface energy predicts a longer time to failure for thicker nanowires than thinner ones, consistent with our experimental observations. The measured time to failure of nanowires under cyclic loading conditions can also be explained in terms of this mechanism.

  6. Nanopores creation in boron and nitrogen doped polycrystalline graphene: A molecular dynamics study

    Science.gov (United States)

    Izadifar, Mohammadreza; Abadi, Rouzbeh; Nezhad Shirazi, Ali Hossein; Alajlan, Naif; Rabczuk, Timon

    2018-05-01

    In the present paper, molecular dynamic simulations have been conducted to investigate the nanopores creation on 10% of boron and nitrogen doped polycrystalline graphene by silicon and diamond nanoclusters. Two types of nanoclusters based on silicon and diamond are used to investigate their effect for the fabrication of nanopores. Therefore, three different diameter sizes of the clusters with five kinetic energies of 10, 50, 100, 300 and 500 eV/atom at four different locations in boron or nitrogen doped polycrystalline graphene nanosheets have been perused. We also study the effect of 3% and 6% of boron doped polycrystalline graphene with the best outcome from 10% of doping. Our results reveal that the diamond cluster with diameter of 2 and 2.5 nm fabricates the largest nanopore areas on boron and nitrogen doped polycrystalline graphene, respectively. Furthermore, the kinetic energies of 10 and 50 eV/atom can not fabricate nanopores in some cases for silicon and diamond clusters on boron doped polycrystalline graphene nanosheets. On the other hand, silicon and diamond clusters fabricate nanopores for all locations and all tested energies on nitrogen doped polycrystalline graphene. The area sizes of nanopores fabricated by silicon and diamond clusters with diameter of 2 and 2.5 nm are close to the actual area size of the related clusters for the kinetic energy of 300 eV/atom in all locations on boron doped polycrystalline graphene. The maximum area and the average maximum area of nanopores are fabricated by the kinetic energy of 500 eV/atom inside the grain boundary at the center of the nanosheet and in the corner of nanosheet with diameters of 2 and 3 nm for silicon and diamond clusters on boron and nitrogen doped polycrystalline graphene.

  7. Effects of surface atomistic modification on mechanical properties of gold nanowires

    International Nuclear Information System (INIS)

    Sun, Xiao-Yu; Xu, Yuanjie; Wang, Gang-Feng; Gu, Yuantong; Feng, Xi-Qiao

    2015-01-01

    Highlights: • Molecular dynamics simulations of surface modification effect of Au nanowires. • Surface modification can greatly affect the mechanical properties of nanowires. • Core–shell model is used to elucidate the effect of residual surface stress. - Abstract: Modulation of the physical and mechanical properties of nanowires is a challenging issue for their technological applications. In this paper, we investigate the effects of surface modification on the mechanical properties of gold nanowires by performing molecular dynamics simulations. It is found that by modifying a small density of silver atoms to the surface of a gold nanowire, the residual surface stress state can be altered, rendering a great improvement of its plastic yield strength. This finding is in good agreement with experimental measurements. The underlying physical mechanisms are analyzed by a core–shell nanowire model. The results are helpful for the design and optimization of advanced nanomaterial with superior mechanical properties

  8. Silicon nanowire hybrid photovoltaics

    KAUST Repository

    Garnett, Erik C.; Peters, Craig; Brongersma, Mark; Cui, Yi; McGehee, Mike

    2010-01-01

    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.

  9. 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.

  10. Size and temperature dependence of the tensile mechanical properties of zinc blende CdSe nanowires

    International Nuclear Information System (INIS)

    Fu, Bing; Chen, Na; Xie, Yiqun; Ye, Xiang; Gu, Xiao

    2013-01-01

    The effect of size and temperature on the tensile mechanical properties of zinc blende CdSe nanowires is investigated by all atoms molecular dynamic simulation. We found the ultimate tensile strength and Young's modulus will decrease as the temperature and size of the nanowire increase. The size and temperature dependence are mainly attributed to surface effect and thermally elongation effect. High reversibility of tensile behavior will make zinc blende CdSe nanowires suitable for building efficient nanodevices.

  11. Nanotubes and nanowires

    Indian Academy of Sciences (India)

    Unknown

    junction nanotubes by the pyrolysis of appropriate organic precursors. ... By making use of carbon nanotubes, nanowires of metals, metal ..... The use of activated carbon in place of ..... required for the complete removal of the carbon template.

  12. 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

  13. Domain wall propagation tuning in magnetic nanowires through geometric modulation

    Energy Technology Data Exchange (ETDEWEB)

    Arzuza, L.C.C., E-mail: luisarzuza179@gmail.com [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-859 Campinas (SP) (Brazil); Universidad de la Costa, Departamento de Ciencias Naturales y Exactas, Calle 58 No. 55-66, Barranquilla (Colombia); López-Ruiz, R. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-859 Campinas (SP) (Brazil); Salazar-Aravena, D. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-859 Campinas (SP) (Brazil); Departamento de Física, Facultad de Ciencias, Universidad de Tarapacá, 1000007 Arica (Chile); Knobel, M. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-859 Campinas (SP) (Brazil); Brazilian Nanotechnology National Laboratory, Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), 13083-970 Campinas (SP) (Brazil); Béron, F.; Pirota, K.R. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-859 Campinas (SP) (Brazil)

    2017-06-15

    Highlights: • The modulated nanowires dynamics occurs through two reversal modes. • Modulated nanowires show a change in the χ in contrast to homogeneous ones. • The FORC method reveals a non-uniform stray field due to shape modulation. - Abstract: The magnetic behavior of nickel modulated nanowires embedded in porous alumina membranes is investigated. Their diameters exhibit a sharp transition between below (35 nm) and above (52 nm) the theoretical limit for transverse and vortex domain walls. Magnetic hysteresis loops and first-order reversal curves (FORCs) were measured on several ordered nanowire arrays with different wide-narrow segment lengths ratio and compared with those from homogenous nanowires. The experimental magnetic response evidences a rather complex susceptibility behavior for nanowires with modulated diameter. Micromagnetic simulations on isolated and first-neighbors arrays of nanowires show that the domain wall structure, which depends on the segment diameter, suffers a transformation while crossing the diameter modulation, but without any pinning. The experimental array magnetic behavior can be ascribed to a heterogeneous stray field induced by the diameter modulation, yielding a stronger interaction field at the wide extremity than at the narrow one. The results evidence the possibility to control the domain wall propagation and morphology by modulating the lateral aspect of the magnetic entity.

  14. 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.

  15. Biofunctionalized Magnetic Nanowires

    KAUST Repository

    Kosel, Jü rgen; Ravasi, Timothy; Contreras Gerenas, Maria Fernanda

    2013-01-01

    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.

  16. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires

    Directory of Open Access Journals (Sweden)

    Magnus Willander

    2013-09-01

    Full Text Available Cetyltrimethyl ammonium bromide cationic (CTAB surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD, scanning electron microscopy (SEM and high resolution transmission electron microscopy (HRTEM techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS. This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

  17. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires.

    Science.gov (United States)

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

    2013-09-09

    Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS). This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

  18. Magnetoelectrolysis of Co nanowire arrays grown in a track-etched polycarbonate membrane

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Barriga, J. [Instituto de Magnetismo Aplicado (UCM-RENFE-CSIC), P.O. Box 155, 28230, Las Rozas, Madrid (Spain)]. E-mail: sbarriga@bessy.de; Lucas, M. [Technische Universitaet Berlin, Institut fuer Theoretische Physik, Hardenbergstr. 36, D-10623 Berlin (Germany); Rivero, G. [Instituto de Magnetismo Aplicado (UCM-RENFE-CSIC), P.O. Box 155, 28230, Las Rozas, Madrid (Spain); Marin, P. [Instituto de Magnetismo Aplicado (UCM-RENFE-CSIC), P.O. Box 155, 28230, Las Rozas, Madrid (Spain); Hernando, A. [Instituto de Magnetismo Aplicado (UCM-RENFE-CSIC), P.O. Box 155, 28230, Las Rozas, Madrid (Spain)

    2007-05-15

    Arrays of Cobalt nanowires with a controlled length of 6{mu}m have been fabricated by electrochemical deposition into the pores of track-etched polycarbonate membranes with a nominal pore diameter of 30nm. The magnetic properties of Co-deposited nanowires and the effects of a magnetic field applied during electrodeposition of the arrays have been studied. An enhancement of the mass deposition rate due to the presence of a 50Oe magnetic field along the nanowire axis has been observed by measuring the experimental development of the current in the electrochemical cell during the fabrication process. X-ray diffraction measurements reveal a different polycrystalline degree for each deposition configuration, indicating that the crystalline structure of the deposited material has been substantially modified. Magnetic measurements show a clear dependence of the anisotropy directions on the orientation of the magnetic field applied during the electrodeposition.

  19. Magnetoelectrolysis of Co nanowire arrays grown in a tracketched polycarbonate membrane

    Energy Technology Data Exchange (ETDEWEB)

    Radu, Florin [BESSY GmbH, Berlin (Germany); Rivero, Guillermo; Marin, Pilar; Hernando, Antonio [Instituto de Magnetismo Aplicado, Madrid (Spain); Sanchez-Barriga, J. [Instituto de Magnetismo Aplicado, Madrid (Spain); BESSY GmbH, Berlin (Germany); Lucas, M. [Inst. fuer Theoretische Physik, Technische Univ. Berlin (Germany)

    2007-07-01

    Arrays of Cobalt nanowires with a controlled length of 6{mu}m have been fabricated by electrochemical deposition into the pores of track-etched polycarbonate membranes with a nominal pore diameter of 30 nm. The magnetic properties of Co-deposited nanowires and the effects of a magnetic field applied during electrodeposition of the arrays have been studied. An enhancement of the mass deposition rate due to the presence of a 50 Oe magnetic field along the nanowire axis has been observed by measuring the experimental development of the current in the electrochemical cell during the fabrication process. X-Ray diffraction measurements reveal a different polycrystalline degree for each deposition configuration, indicating that the crystalline structure of the deposited material has been substantially modified. Magnetic measurements show a clear dependence of the anisotropy directions on the orientation of the magnetic field applied during the electrodeposition.

  20. Magnetoelectrolysis of Co nanowire arrays grown in a track-etched polycarbonate membrane

    International Nuclear Information System (INIS)

    Sanchez-Barriga, J.; Lucas, M.; Rivero, G.; Marin, P.; Hernando, A.

    2007-01-01

    Arrays of Cobalt nanowires with a controlled length of 6μm have been fabricated by electrochemical deposition into the pores of track-etched polycarbonate membranes with a nominal pore diameter of 30nm. The magnetic properties of Co-deposited nanowires and the effects of a magnetic field applied during electrodeposition of the arrays have been studied. An enhancement of the mass deposition rate due to the presence of a 50Oe magnetic field along the nanowire axis has been observed by measuring the experimental development of the current in the electrochemical cell during the fabrication process. X-ray diffraction measurements reveal a different polycrystalline degree for each deposition configuration, indicating that the crystalline structure of the deposited material has been substantially modified. Magnetic measurements show a clear dependence of the anisotropy directions on the orientation of the magnetic field applied during the electrodeposition

  1. Nanowire structures and electrical devices

    Science.gov (United States)

    Bezryadin, Alexey; Remeika, Mikas

    2010-07-06

    The present invention provides structures and devices comprising conductive segments and conductance constricting segments of a nanowire, such as metallic, superconducting or semiconducting nanowire. The present invention provides structures and devices comprising conductive nanowire segments and conductance constricting nanowire segments having accurately selected phases including crystalline and amorphous states, compositions, morphologies and physical dimensions, including selected cross sectional dimensions, shapes and lengths along the length of a nanowire. Further, the present invention provides methods of processing nanowires capable of patterning a nanowire to form a plurality of conductance constricting segments having selected positions along the length of a nanowire, including conductance constricting segments having reduced cross sectional dimensions and conductance constricting segments comprising one or more insulating materials such as metal oxides.

  2. Optical Control of Internal Electric Fields in Band Gap-Graded InGaN Nanowires

    Science.gov (United States)

    Erhard, N.; Sarwar, A. T. M. Golam; Yang, F.; McComb, D. W.; Myers, R. C.; Holleitner, A. W.

    2015-01-01

    InGaN nanowires are suitable building blocks for many future optoelectronic devices. We show that a linear grading of the indium content along the nanowire axis from GaN to InN introduces an internal electric field evoking a photocurrent. Consistent with quantitative band structure simulations we observe a sign change in the measured photocurrent as a function of photon flux. This negative differential photocurrent opens the path to a new type of nanowire-based photodetector. We demonstrate that the photocurrent response of the nanowires is as fast as 1.5 ps.

  3. Investigation on the effect of atomic defects on the breaking behaviors of gold nanowires

    International Nuclear Information System (INIS)

    Wang Fenying; Sun Wei; Wang Hongbo; Zhao Jianwei; Kiguchi, Manabu; Sun Changqing

    2012-01-01

    The mechanical properties and breaking behaviors of the [100]-oriented single-crystal gold nanowires containing a set of defect ratios have been studied at different temperatures using molecular dynamics simulations. The size of the nanowire is 10a × 10a × 30a (a stands for lattice constant, 0.408 nm for gold). The mechanical strengths of the nanowires decrease with the increasing temperature. However, the defects that enhance the local thermal energy have improved the nanowire mechanical strength under a wide range of temperature. Comparing to the single-crystal nanowire, the existence of the atomic defects extends the elastic deformation showing a larger yield strain. By summarizing 300 samples at each temperature, the statistical breaking position distribution shows that the nanowire breaking behavior is sensitive to the atomic defects when the defect ratio is 5 % at 100 K, whereas the ratio is 1 % when temperatures are 300 and 500 K.

  4. Visual Understanding of Light Absorption and Waveguiding in Standing Nanowires with 3D Fluorescence Confocal Microscopy.

    Science.gov (United States)

    Frederiksen, Rune; Tutuncuoglu, Gozde; Matteini, Federico; Martinez, Karen L; Fontcuberta I Morral, Anna; Alarcon-Llado, Esther

    2017-09-20

    Semiconductor nanowires are promising building blocks for next-generation photonics. Indirect proofs of large absorption cross sections have been reported in nanostructures with subwavelength diameters, an effect that is even more prominent in vertically standing nanowires. In this work we provide a three-dimensional map of the light around vertical GaAs nanowires standing on a substrate by using fluorescence confocal microscopy, where the strong long-range disruption of the light path along the nanowire is illustrated. We find that the actual long-distance perturbation is much larger in size than calculated extinction cross sections. While the size of the perturbation remains similar, the intensity of the interaction changes dramatically over the visible spectrum. Numerical simulations allow us to distinguish the effects of scattering and absorption in the nanowire leading to these phenomena. This work provides a visual understanding of light absorption in semiconductor nanowire structures, which is of high interest for solar energy conversion applications.

  5. Tunable Magnetic Properties of Heterogeneous Nanobrush: From Nanowire to Nanofilm

    Directory of Open Access Journals (Sweden)

    Ren Y

    2010-01-01

    Full Text Available Abstract With a bottom-up assemble technology, heterogeneous magnetic nanobrushes, consisting of Co nanowire arrays and ferromagnetic Fe70Co30 nanofilm, have been fabricated using an anodic aluminum oxide template method combining with sputtering technology. Magnetic measurement suggests that the magnetic anisotropy of nanobrush depends on the thickness of Fe70Co30 layer, and its total anisotropy originates from the competition between the shape anisotropy of nanowire arrays and nanofilm. Micromagnetic simulation result indicates that the switching field of nanobrush is 1900 Oe, while that of nanowire array is 2700 Oe. These suggest that the nanobrush film can promote the magnetization reversal processes of nanowire arrays in nanobrush.

  6. Reactive diffusion and stresses in nanowires or nanorods

    International Nuclear Information System (INIS)

    Roussel, Manuel; Erdélyi, Zoltán; Schmitz, Guido

    2017-01-01

    Heterostructured nanowires are of prime interest in nowadays technology such as field-effect transistors, field emitters, batteries and solar cells. We consider their aging behavior and developed a model focusing on reactive diffusion in core-shell nanowires. A complete set of analytical equations is presented that takes into account thermodynamic driving forces, vacancy distribution, elastic stress and its plastic relaxation. This complete description of the reactive diffusion can be used in finite element simulations to investigate diffusion processes in various geometries. In order to show clearly the interplay between the cylindrical geometry, the reactive diffusion and the stresses developing in the nanowire, we investigate the formation of an intermetallic reaction product in various core-shell geometries. Emphasis is placed on showing how it is possible to control the kinetics of the reaction by applying an axial stress to the nanowires.

  7. Growth control, structure, chemical state, and photoresponse of CuO-CdS core-shell heterostructure nanowires.

    Science.gov (United States)

    El Mel, A A; Buffière, M; Bouts, N; Gautron, E; Tessier, P Y; Henzler, K; Guttmann, P; Konstantinidis, S; Bittencourt, C; Snyders, R

    2013-07-05

    The growth of single-crystal CuO nanowires by thermal annealing of copper thin films in air is studied. We show that the density, length, and diameter of the nanowires can be controlled by tuning the morphology and structure of the copper thin films deposited by DC magnetron sputtering. After identifying the optimal conditions for the growth of CuO nanowires, chemical bath deposition is employed to coat the CuO nanowires with CdS in order to form p-n nanojunction arrays. As revealed by high-resolution TEM analysis, the thickness of the polycrystalline CdS shell increases when decreasing the diameter of the CuO core for a given time of CdS deposition. Near-edge x-ray absorption fine-structure spectroscopy combined with transmission x-ray microscopy allows the chemical analysis of isolated nanowires. The absence of modification in the spectra at the Cu L and O K edges after the deposition of CdS on the CuO nanowires indicates that neither Cd nor S diffuse into the CuO phase. We further demonstrate that the core-shell nanowires exhibit the I-V characteristic of a resistor instead of a diode. The electrical behavior of the device was found to be photosensitive, since increasing the incident light intensity induces an increase in the collected electrical current.

  8. Sputtering mechanisms of polycrystalline platinum by low energy ions

    International Nuclear Information System (INIS)

    Chernysh, V.S.; Eckstein, W.; Haidarov, A.A.; Kulikauskas, V.S.; Mashkova, E.S.; Molchanov, V.A.

    1999-01-01

    The results of an experimental study and a computer simulation with the TRIM.SP code of the angular distributions of atoms sputtered from polycrystalline platinum under 1.5-9 keV He + bombardment at the normal ion incidence are presented. It has been found that angular distributions of sputtered atoms are overcosine and that their shape is practically independent of the bombarding ion species and ion energy. Good agreement between experimental results and computer simulation data was found. Computer simulations of the partial angular distributions of Pt atoms ejected due to various sputtering mechanisms for He and Ar bombardments were performed. The role of different mechanisms in the formation of angular distributions of sputtered atoms has been analyzed

  9. Static and dynamic magnetic properties of densely packed magnetic nanowire arrays

    DEFF Research Database (Denmark)

    Dmytriiev, O.; Al-Jarah, U.A.S.; Gangmei, P.

    2013-01-01

    and a continuous ferromagnetic thin film. In particular, the competition between anisotropies associated with the shape of the individual nanowires and that of the array as a whole has been studied. Measured and simulated hysteresis loops are largely anhysteretic with zero remanence, and the micromagnetic...... configuration is such that the net magnetization vanishes in directions orthogonal to the applied field. Simulations of the remanent state reveal antiferromagnetic alignment of the magnetization in adjacent nanowires and the formation of vortex flux closure structures at the ends of each nanowire....... The excitation spectra obtained from experiment and micromagnetic simulations are in qualitative agreement for magnetic fields applied both parallel and perpendicular to the axes of the nanowires. For the field parallel to the nanowire axes, there is also good quantitative agreement between experiment...

  10. The Self- and Directed Assembly of Nanowires

    Science.gov (United States)

    Smith, Benjamin David

    nanowires rapidly sedimented due to gravity onto a glass cover slip to concentrate and form a dense film. Particles and assemblies were imaged using inverted optical microscopy. We quantitatively analyzed the images and movies captured in order to track and classify particles and classify the overall arrays formed. We then correlated how particle characteristics, e.g., materials, size, segmentation, etc. changed the ordering and alignment observed. With that knowledge, we hope to be able to form new and interesting structures. We began our studies by examining the assembly of single component nanowires. Chapter 2 describes this work, in which solid Au nanowires measuring 2-7 mum in length and 290 nm in diameter self-assembled into smectic rows. By both experiment and theory, we determined that these rows formed due to a balance of electrostatic repulsions and van der Waals attractions. Final assemblies were stable for at least several days. Monte Carlo methods were used to simulate assemblies and showed structures that mirrored those experimentally observed. Simulations indicated that the smectic phase was preferred over others, i.e., nematic, when an additional small charge was added to the ends of the nanowires. Our particles have rough tips, which might create these additional electrostatic repulsions. To increase the particle and array complexity, two-component, metallic nanowire assembly was explored in Chapter 3. We examined numerous types of nanowires by changing the segment length, ratio, and material, the nanowire length, the surface coating, and the presence of small third segments. These segmented nanowires were generally Au-Ag and also ordered into smectic rows. Segmented wires arranged in rows, however, can be aligned in two possible ways with respect to a neighboring particle. The Au segments on neighboring particles can be oriented in the same direction or opposed to each other. Orientation was quantified in terms of an order parameter that took into account

  11. Hydrogen retention properties of polycrystalline tungsten and helium irradiated tungsten

    International Nuclear Information System (INIS)

    Hino, T.; Koyama, K.; Yamauchi, Y.; Hirohata, Y.

    1998-01-01

    The hydrogen retention properties of a polycrystalline tungsten and tungsten irradiated by helium ions with an energy of 5 keV were examined by using an ECR ion irradiation apparatus and a technique of thermal desorption spectroscopy, TDS. The polycrystalline tungsten was irradiated at RT with energetic hydrogen ions, with a flux of 10 15 H cm -2 and an energy of 1.7 keV up to a fluence of 5 x 10 18 H cm -2 . Subsequently, the amount of retained hydrogen was measured by TDS. The heating temperature was increased from RT to 1000 C, and the heating rate was 50 C min -1 . Below 1000 C, two distinct hydrogen desorption peaks were observed at 200 C and 400 C. The retained amount of hydrogen was observed to be five times smaller than that of graphite, but the concentration in the implantation layer was comparable with that of graphite. Also, the polycrystalline tungsten was irradiated with 5 keV helium ions up to a fluence of 1.4 x 10 18 He cm -2 , and then re-irradiated with 1.7 keV hydrogen ions. The amount of retained hydrogen in this later experiment was close to the value in the case without prior helium ion irradiation. However, the amount of hydrogen which desorbed around the low temperature peak, 200 C, was largely enhanced. The desorption amount at 200 C saturated for the helium fluence of more than 5 x 10 17 He cm -2 . The present data shows that the trapping state of hydrogen is largely changed by the helium ion irradiation. Additionally, 5 keV helium ion irradiation was conducted on a sample pre-implanted with hydrogen ions to simulate a helium ion impact desorption of hydrogen retained in tungsten. The amount of the hydrogen was reduced as much as 50%. (orig.)

  12. Graphene templated Directional Growth of an Inorganic Nanowire

    Science.gov (United States)

    2015-03-23

    14,23–25 have only formed randomly oriented or poorly aligned inorganic nanostructures. Here, we show that inorganic nanowires of gold(I) cyanide can... complex . TEM image simulation from the crystal structure The TEM image simulations are performed using MacTempas and CrystalKit. The imaging

  13. Extremal Overall Elastic Response of Polycrystalline Materials

    DEFF Research Database (Denmark)

    Bendsøe, Martin P; Lipton, Robert

    1997-01-01

    Polycrystalline materials comprised of grains obtained from a single anisotropic material are considered in the framework of linear elasticity. No assumptions on the symmetry of the polycrystal are made. We subject the material to independent external strain and stress fields with prescribed mean...

  14. EDITORIAL: Nanowires for energy Nanowires for energy

    Science.gov (United States)

    LaPierre, Ray; Sunkara, Mahendra

    2012-05-01

    This special issue of Nanotechnology focuses on studies illustrating the application of nanowires for energy including solar cells, efficient lighting and water splitting. Over the next three decades, nanotechnology will make significant contributions towards meeting the increased energy needs of the planet, now known as the TeraWatt challenge. Nanowires in particular are poised to contribute significantly in this development as presented in the review by Hiralal et al [1]. Nanowires exhibit light trapping properties that can act as a broadband anti-reflection coating to enhance the efficiency of solar cells. In this issue, Li et al [2] and Wang et al [3] present the optical properties of silicon nanowire and nanocone arrays. In addition to enhanced optical properties, core-shell nanowires also have the potential for efficient charge carrier collection across the nanowire diameter as presented in the contribution by Yu et al [4] for radial junction a-Si solar cells. Hybrid approaches that combine organic and inorganic materials also have potential for high efficiency photovoltaics. A Si-based hybrid solar cell is presented by Zhang et al [5] with a photoconversion efficiency of over 7%. The quintessential example of hybrid solar cells is the dye-sensitized solar cell (DSSC) where an organic absorber (dye) coats an inorganic material (typically a ZnO nanostructure). Herman et al [6] present a method of enhancing the efficiency of a DSSC by increasing the hetero-interfacial area with a unique hierarchical weeping willow ZnO structure. The increased surface area allows for higher dye loading, light harvesting, and reduced charge recombination through direct conduction along the ZnO branches. Another unique ZnO growth method is presented by Calestani et al [7] using a solution-free and catalyst-free approach by pulsed electron deposition (PED). Nanowires can also make more efficient use of electrical power. Light emitting diodes, for example, will eventually become the

  15. Co-percolation to tune conductive behaviour in dynamical metallic nanowire networks.

    Science.gov (United States)

    Fairfield, J A; Rocha, C G; O'Callaghan, C; Ferreira, M S; Boland, J J

    2016-11-03

    Nanowire networks act as self-healing smart materials, whose sheet resistance can be tuned via an externally applied voltage stimulus. This memristive response occurs due to modification of junction resistances to form a connectivity path across the lowest barrier junctions in the network. While most network studies have been performed on expensive noble metal nanowires like silver, networks of inexpensive nickel nanowires with a nickel oxide coating can also demonstrate resistive switching, a common feature of metal oxides with filamentary conduction. However, networks made from solely nickel nanowires have high operation voltages which prohibit large-scale material applications. Here we show, using both experiment and simulation, that a heterogeneous network of nickel and silver nanowires allows optimization of the activation voltage, as well as tuning of the conduction behavior to be either resistive switching, memristive, or a combination of both. Small percentages of silver nanowires, below the percolation threshold, induce these changes in electrical behaviour, even for low area coverage and hence very transparent films. Silver nanowires act as current concentrators, amplifying conductivity locally as shown in our computational dynamical activation framework for networks of junctions. These results demonstrate that a heterogeneous nanowire network can act as a cost-effective adaptive material with minimal use of noble metal nanowires, without losing memristive behaviour that is essential for smart sensing and neuromorphic applications.

  16. Polycrystalline CVD diamond device level modeling for particle detection applications

    Science.gov (United States)

    Morozzi, A.; Passeri, D.; Kanxheri, K.; Servoli, L.; Lagomarsino, S.; Sciortino, S.

    2016-12-01

    Diamond is a promising material whose excellent physical properties foster its use for radiation detection applications, in particular in those hostile operating environments where the silicon-based detectors behavior is limited due to the high radiation fluence. Within this framework, the application of Technology Computer Aided Design (TCAD) simulation tools is highly envisaged for the study, the optimization and the predictive analysis of sensing devices. Since the novelty of using diamond in electronics, this material is not included in the library of commercial, state-of-the-art TCAD software tools. In this work, we propose the development, the application and the validation of numerical models to simulate the electrical behavior of polycrystalline (pc)CVD diamond conceived for diamond sensors for particle detection. The model focuses on the characterization of a physically-based pcCVD diamond bandgap taking into account deep-level defects acting as recombination centers and/or trap states. While a definite picture of the polycrystalline diamond band-gap is still debated, the effect of the main parameters (e.g. trap densities, capture cross-sections, etc.) can be deeply investigated thanks to the simulated approach. The charge collection efficiency due to β -particle irradiation of diamond materials provided by different vendors and with different electrode configurations has been selected as figure of merit for the model validation. The good agreement between measurements and simulation findings, keeping the traps density as the only one fitting parameter, assesses the suitability of the TCAD modeling approach as a predictive tool for the design and the optimization of diamond-based radiation detectors.

  17. Polycrystalline CVD diamond device level modeling for particle detection applications

    International Nuclear Information System (INIS)

    Morozzi, A.; Passeri, D.; Kanxheri, K.; Servoli, L.; Lagomarsino, S.; Sciortino, S.

    2016-01-01

    Diamond is a promising material whose excellent physical properties foster its use for radiation detection applications, in particular in those hostile operating environments where the silicon-based detectors behavior is limited due to the high radiation fluence. Within this framework, the application of Technology Computer Aided Design (TCAD) simulation tools is highly envisaged for the study, the optimization and the predictive analysis of sensing devices. Since the novelty of using diamond in electronics, this material is not included in the library of commercial, state-of-the-art TCAD software tools. In this work, we propose the development, the application and the validation of numerical models to simulate the electrical behavior of polycrystalline (pc)CVD diamond conceived for diamond sensors for particle detection. The model focuses on the characterization of a physically-based pcCVD diamond bandgap taking into account deep-level defects acting as recombination centers and/or trap states. While a definite picture of the polycrystalline diamond band-gap is still debated, the effect of the main parameters (e.g. trap densities, capture cross-sections, etc.) can be deeply investigated thanks to the simulated approach. The charge collection efficiency due to β -particle irradiation of diamond materials provided by different vendors and with different electrode configurations has been selected as figure of merit for the model validation. The good agreement between measurements and simulation findings, keeping the traps density as the only one fitting parameter, assesses the suitability of the TCAD modeling approach as a predictive tool for the design and the optimization of diamond-based radiation detectors.

  18. Ni3Si2 nanowires grown in situ on Ni foam for high-performance supercapacitors

    Science.gov (United States)

    Jiang, Yizhe; Li, Zhihui; Li, Beibei; Zhang, Jinying; Niu, Chunming

    2016-07-01

    Ni3Si2 nanowires and nanoawls have grown in situ on the surface of Ni foams by a controlled low pressure chemical vapor deposition process. Structural characterization shows that the individual Ni3Si2 nanowire is single crystal covered with a thin layer (1-2 nm) of SiO2 with a diameter of ∼20-30 nm and length of ten's micrometers. Individual nanoawl with a circular cone shape is polycrystalline. Both Ni3Si2 nanowire and nanoawl samples are evaluated as potential electrode materials for supercapacitors. The nanowire electrode delivers a very high specific capacitance and excellent rate capability. A specific capacitance of 760 F g-1 is measured at current density of 0.5 A g-1, which decreases to 518 F g-1 when the current density increases to 10 A g-1. The capacitance is dominated by pseudocapacitance with a mechanism similar to that of NiO or Ni(OH)2 widely studied in the literature. An asymmetric supercapacitor fabricated by pairing Ni3Si2 nanowire electrode with an activated carbon electrode exhibits energy densities of 17.5 Wh kg-1 and 8.8 Wh kg-1 at power densites of 301 W kg-1 and 3000 W kg-1.

  19. Microdamage in polycrystalline ceramics under dynamic compression and tension

    International Nuclear Information System (INIS)

    Zhang, K.S.; Zhang, D.; Feng, R.; Wu, M.S.

    2005-01-01

    In-grain microplasticity and intergranular microdamage in polycrystalline hexagonal-structure ceramics subjected to a sequence of dynamic compression and tension are studied computationally using the Voronoi polycrystal model, by which the topological heterogeneity and material anisotropy of the crystals are simulated explicitly. The constitutive modeling considers crystal plasticity by basal slip, intergranular shear damage during compression, and intergranular mode-I cracking during tension. The model parameters are calibrated with the available shock compression and spall strength data on polycrystalline α-6H silicon carbide. The numerical results show that microplasticity is a more plausible micromechanism for the inelastic response of the material under shock compression. On the other hand, the spallation behavior of the shocked material can be well predicted by intergranular mode-I microcracking during load reversal from dynamic compression to tension. The failure process and the resulting spall strength are, however, affected strongly by the intensity of local release heterogeneity induced by heterogeneous microplasticity, and by the grain-boundary shear damage during compression

  20. Physically-based modelling of polycrystalline semiconductor devices

    International Nuclear Information System (INIS)

    Lee, S.

    2000-01-01

    Thin-film technology using polycrystalline semiconductors has been widely applied to active-matrix-addressed liquid crystal displays (AMLCDs) where thin-film transistors act as digital pixel switches. Research and development is in progress to integrate the driver circuits around the peripheral of the display, resulting in significant cost reduction of connections between rows and columns and the peripheral circuitry. For this latter application, where for instance it is important to control the greyscale voltage level delivered to the pixel, an understanding of device behaviour is required so that models can be developed for analogue circuit simulation. For this purpose, various analytical models have been developed based on that of Seto who considered the effect of monoenergetic trap states and grain boundaries in polycrystalline materials but not the contribution of the grains to the electrical properties. The principal aim of this thesis is to describe the use of a numerical device simulator (ATLAS) as a tool to investigate the physics of the trapping process involved in the device operation, which additionally takes into account the effect of multienergetic trapping levels and the contribution of the grain into the modelling. A study of the conventional analytical models is presented, and an alternative approach is introduced which takes into account the grain regions to enhance the accuracy of the analytical modelling. A physically-based discrete-grain-boundary model and characterisation method are introduced to study the effects of the multienergetic trap states on the electrical characteristics of poly-TFTs using CdSe devices as the experimental example, and the electrical parameters such as the density distribution of the trapping states are extracted. The results show excellent agreement between the simulation and experimental data. The limitations of this proposed physical model are also studied and discussed. (author)

  1. Giant exchange bias and its angular dependence in Co/CoO core-shell nanowire assemblies

    International Nuclear Information System (INIS)

    Gandha, Kinjal; Chaudhary, Rakesh P.; Mohapatra, Jeotikanta; Koymen, Ali R.; Liu, J. Ping

    2017-01-01

    The exchange-bias field (H EB ) and its angular dependence are systematically investigated in Co/CoO core-shell nanowire assemblies (∼15 nm in diameter and ∼200 nm in length) consisting of single-crystalline Co core and polycrystalline CoO shell. Giant exchange-bias field (H EB ) up to 2.4 kOe is observed below a blocking temperature (T EB ∼150 K) in the aligned Co/CoO nanowire assemblies. It is also found that there is an angular dependence between the H EB and the applied magnetization direction. The H EB showed a peak at 30° between the applied field and the nanowire aligned direction, which may be attributed to the noncollinear spin orientations at the interface between the ferromagnetic core and the antiferromagnetic shell. This behavior is quantitatively supported by an analytical calculation based on Stoner–Wohlfarth model. This study underlines the importance of the competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. - Highlights: • Giant exchange bias is observed in oriented Co/CoO core-shell nanowire assemblies. • Study of angular and temperature dependence of the exchange bias effect. • Competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. • Effect of misaligned spins in FM/AFM interface on angular dependence of exchange bias. • We explain the analytical model that accounts for experimental results.

  2. Equilibrium shapes of polycrystalline silicon nanodots

    Energy Technology Data Exchange (ETDEWEB)

    Korzec, M. D., E-mail: korzec@math.tu-berlin.de; Wagner, B., E-mail: bwagner@math.tu-berlin.de [Department of Mathematics, Technische Universität Berlin, Straße des 17. Juni 136, 10623 Berlin (Germany); Roczen, M., E-mail: maurizio.roczen@physik.hu-berlin.de [Department of Physics, Humboldt-Universität zu Berlin, Newtonstraße 15, 12489 Berlin (Germany); Schade, M., E-mail: martin.schade@physik.uni-halle.de [Zentrum für Innovationskompetenz SiLi-nano, Martin-Luther-Universität Halle-Wittenberg, Karl-Freiherr-von-Fritsch-Straße 3, 06120 Halle (Germany); Rech, B., E-mail: bernd.rech@helmholtz-berlin.de [Helmholtz-Zentrum Berlin, Institute for Silicon Photovoltaics, Kekuléstraße 5, 12489 Berlin (Germany)

    2014-02-21

    This study is concerned with the topography of nanostructures consisting of arrays of polycrystalline nanodots. Guided by transmission electron microscopy (TEM) measurements of crystalline Si (c-Si) nanodots that evolved from a “dewetting” process of an amorphous Si (a-Si) layer from a SiO{sub 2} coated substrate, we investigate appropriate formulations for the surface energy density and transitions of energy density states at grain boundaries. We introduce a new numerical minimization formulation that allows to account for adhesion energy from an underlying substrate. We demonstrate our approach first for the free standing case, where the solutions can be compared to well-known Wulff constructions, before we treat the general case for interfacial energy settings that support “partial wetting” and grain boundaries for the polycrystalline case. We then use our method to predict the morphologies of silicon nanodots.

  3. Obtaining of polycrystalline silicon for semiconductor industry

    International Nuclear Information System (INIS)

    Mukashev, F.; Nauryzbaev, M.; Kolesnikov, B.; Ivanov, Y.

    1996-01-01

    The purpose of the project is to create pilot equipment and optimize the process of obtaining polycrystalline silicon on semi-industrial level. In the past several decades, the historical experience in the developing countries has shown that one of the most promising ways to improve the economy,of a country is to establish semiconductor industry. First of all, the results can help increase defense, national security and create industrial production. The silane method, which has been traditionally' used for obtaining technical and polycrystalline silicon, is to obtain and then to pyrolyzed mono-and poly silanes. Although the traditional methods of obtaining silicon hydrides have specific advantages, such as utilizing by-products, they also have clear shortcomings, i.e. either low output of the ultimate product ( through hydrolysis of Mg 2 Si) or high contents of by-products in it or high contents of dissolving vapors (through decomposing Mg 2 Si in non-water solutions)

  4. Method for producing polycrystalline boron nitride

    International Nuclear Information System (INIS)

    Alexeevskii, V.P.; Bochko, A.V.; Dzhamarov, S.S.; Karpinos, D.M.; Karyuk, G.G.; Kolomiets, I.P.; Kurdyumov, A.V.; Pivovarov, M.S.; Frantsevich, I.N.; Yarosh, V.V.

    1975-01-01

    A mixture containing less than 50 percent of graphite-like boron nitride treated by a shock wave and highly defective wurtzite-like boron nitride obtained by a shock-wave method is compressed and heated at pressure and temperature values corresponding to the region of the phase diagram for boron nitride defined by the graphite-like compact modifications of boron nitride equilibrium line and the cubic wurtzite-like boron nitride equilibrium line. The resulting crystals of boron nitride exhibit a structure of wurtzite-like boron nitride or of both wurtzite-like and cubic boron nitride. The resulting material exhibits higher plasticity as compared with polycrystalline cubic boron nitride. Tools made of this compact polycrystalline material have a longer service life under impact loads in machining hardened steel and chilled iron. (U.S.)

  5. Effective polycrystalline sensor of ultraviolet radiation

    Directory of Open Access Journals (Sweden)

    S.Yu. Pavelets

    2017-10-01

    Full Text Available Deposition of special thin layers with high and low resistance in space charge region of surface barrier photoconverters based on the p-Cu1.8S/n-CdS structure leads to a sufficient increase in photosensitivity and decrease in dark tunneling-recombination current. Highly efficient and stable polycrystalline photoconverters of ultraviolet radiation based on polycrystalline CdS have been obtained. Electrical and photoelectric properties have been investigated, and the main operational parameters of ultraviolet sensors have been adduced. The reasons for high stability of the parameters inherent to the p-Cu1.8S/n-CdS sensors are as follows: the absence of impurity components additionally doped to the barrier structure and stability of the photocurrent photoemission component.

  6. Extremal Overall Elastic Response of Polycrystalline Materials

    DEFF Research Database (Denmark)

    Bendsøe, Martin P; Lipton, Robert

    1996-01-01

    Polycrystalline materials comprised of grains obtained froma single anisotropic material are considered in the frameworkof linear elasticity. No assumptions on the symmetry of thepolycrystal are made. We subject the material to independentexternal strain and stress fields with prescribed mean...... values.We show that the extremal overall elastic response is alwaysachieved by a configuration consisting of a single properlyoriented crystal. This result is compared to results for isotropicpolycrystals....

  7. Hydrogen solubility in polycrystalline - and nonocrystalline niobium

    International Nuclear Information System (INIS)

    Ishikawa, T.T.; Silva, J.R.G. da

    1981-01-01

    Hydrogen solubility in polycrystalline and monocrystalline niobium was measured in the range 400 0 C to 1000 0 C at one atmosphere hydrogen partial pressure. The experimental technique consists of saturation of the solvent metal with hydrogen, followed by quenching and analysis of the solid solution. It is presented solubility curves versus reciprocal of the absolute doping temperature, associated with their thermodynamical equation. (Author) [pt

  8. Characterization of electrochemically modified polycrystalline platinum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Krebs, L.C.; Ishida, Takanobu.

    1991-12-01

    The characterization of electrochemically modified polycrystalline platinum surfaces has been accomplished through the use of four major electrochemical techniques. These were chronoamperometry, chronopotentiommetry, cyclic voltammetry, and linear sweep voltammetry. A systematic study on the under-potential deposition of several transition metals has been performed. The most interesting of these were: Ag, Cu, Cd, and Pb. It was determined, by subjecting the platinum electrode surface to a single potential scan between {minus}0.24 and +1.25 V{sub SCE} while stirring the solution, that the electrocatalytic activity would be regenerated. As a consequence of this study, a much simpler method for producing ultra high purity water from acidic permanganate has been developed. This method results in water that surpasses the water produced by pyrocatalytic distillation. It has also been seen that the wettability of polycrystalline platinum surfaces is greatly dependent on the quantity of oxide present. Oxide-free platinum is hydrophobic and gives a contact angle in the range of 55 to 62 degrees. We have also modified polycrystalline platinum surface with the electrically conducting polymer poly-{rho}-phenylene. This polymer is very stable in dilute sulfuric acid solutions, even under applied oxidative potentials. It is also highly resistant to electrochemical hydrogenation. The wettability of the polymer modified platinum surface is severely dependent on the choice of supporting electrolyte chosen for the electrochemical polymerization. Tetraethylammonium tetrafluoroborate produces a film that is as hydrophobic as Teflon, whereas tetraethylammonium perchlorate produces a film that is more hydrophilic than oxide-free platinum.

  9. Characterization of electrochemically modified polycrystalline platinum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Krebs, Leonard C. [State Univ. of New York (SUNY), Stony Brook, NY (United States); Ishida, Takanobu [State Univ. of New York (SUNY), Stony Brook, NY (United States)

    1991-12-01

    The characterization of electrochemically modified polycrystalline platinum surfaces has been accomplished through the use of four major electrochemical techniques. These were chronoamperometry, chronopotentiommetry, cyclic voltammetry, and linear sweep voltammetry. A systematic study on the under-potential deposition of several transition metals has been performed. The most interesting of these were: Ag, Cu, Cd, and Pb. It was determined, by subjecting the platinum electrode surface to a single potential scan between -0.24 and +1.25 VSCE while stirring the solution, that the electrocatalytic activity would be regenerated. As a consequence of this study, a much simpler method for producing ultra high purity water from acidic permanganate has been developed. This method results in water that surpasses the water produced by pyrocatalytic distillation. It has also been seen that the wettability of polycrystalline platinum surfaces is greatly dependent on the quantity of oxide present. Oxide-free platinum is hydrophobic and gives a contact angle in the range of 55 to 62 degrees. We have also modified polycrystalline platinum surface with the electrically conducting polymer poly-ρ-phenylene. This polymer is very stable in dilute sulfuric acid solutions, even under applied oxidative potentials. It is also highly resistant to electrochemical hydrogenation. The wettability of the polymer modified platinum surface is severely dependent on the choice of supporting electrolyte chosen for the electrochemical polymerization. Tetraethylammonium tetrafluoroborate produces a film that is as hydrophobic as Teflon, whereas tetraethylammonium perchlorate produces a film that is more hydrophilic than oxide-free platinum.

  10. Electronic transport in narrow-gap semiconductor nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Bloemers, Christian

    2012-10-19

    from the field-effect measurements due to the influence of surface states. The homogeneity in transport characteristics of the InN nanowires allowed for an accurate analysis of the diameter dependence of the nanowire resistivity. The effect of donor deactivation has been found to increase the resistivity of InN nanowires with small diameters. Furthermore, a quantum confinement effect has been observed in GaAs/InAs core/shell nanowires. For very low shell thicknesses below 10 nm a drastic resistivity increase has been found. Simulations with a self consistent Schroedinger-Poisson solver confirmed the interpretation in terms of quantum confinement. A further major topic of this work has been the analysis of phase coherent transport at low temperatures. In particular, universal conductance fluctuations have been analyzed and a consistent method to determine the phase coherence length quantitatively has been developed. In addition, transport measurements on GaAs/InAs core/shell nanowires with a magnetic field applied parallel to the wire axis demonstrated Aharonov-Bohm-type conductance oscillations. An explanation in terms of coherent angular momentum quantum states in the conductive InAs shell has been developed to interpret these oscillations. To conclude, both room temperature and low temperature measurements allowed gaining insights into basic classical as well as quantum transport properties of nanowires. In the face of a future application of nanowires in quantum information processing or their use in so-called phase-based switching devices, valuable information is provided within this work. Furthermore, the room temperature results show that for application of nanowires in electronic devices, both the crystal structure and the surface conditions have to be controlled. Here, it will be inevitable for future progress to achieve a controlled passivation of the wire surfaces for defined and stable surface conditions. Furthermore, a more detailed investigation of the

  11. Electronic transport in narrow-gap semiconductor nanowires

    International Nuclear Information System (INIS)

    Bloemers, Christian

    2012-01-01

    from the field-effect measurements due to the influence of surface states. The homogeneity in transport characteristics of the InN nanowires allowed for an accurate analysis of the diameter dependence of the nanowire resistivity. The effect of donor deactivation has been found to increase the resistivity of InN nanowires with small diameters. Furthermore, a quantum confinement effect has been observed in GaAs/InAs core/shell nanowires. For very low shell thicknesses below 10 nm a drastic resistivity increase has been found. Simulations with a self consistent Schroedinger-Poisson solver confirmed the interpretation in terms of quantum confinement. A further major topic of this work has been the analysis of phase coherent transport at low temperatures. In particular, universal conductance fluctuations have been analyzed and a consistent method to determine the phase coherence length quantitatively has been developed. In addition, transport measurements on GaAs/InAs core/shell nanowires with a magnetic field applied parallel to the wire axis demonstrated Aharonov-Bohm-type conductance oscillations. An explanation in terms of coherent angular momentum quantum states in the conductive InAs shell has been developed to interpret these oscillations. To conclude, both room temperature and low temperature measurements allowed gaining insights into basic classical as well as quantum transport properties of nanowires. In the face of a future application of nanowires in quantum information processing or their use in so-called phase-based switching devices, valuable information is provided within this work. Furthermore, the room temperature results show that for application of nanowires in electronic devices, both the crystal structure and the surface conditions have to be controlled. Here, it will be inevitable for future progress to achieve a controlled passivation of the wire surfaces for defined and stable surface conditions. Furthermore, a more detailed investigation of the

  12. Influence of exchange coupling on current-driven domain wall motion in a nanowire

    International Nuclear Information System (INIS)

    Komine, Takashi; Takahashi, Kota; Murakami, Hiroshi; Sugita, Ryuji

    2010-01-01

    In this study, the effect of exchange stiffness constant on current-driven domain wall motion in nanowires with in-plane magnetic anisotropy (IMA) and perpendicular magnetic anisotropy (PMA) has been investigated using micromagnetic simulation. The critical current density in a nanowire with IMA decreases as the exchange stiffness constant decreases because the domain wall width at the upper edge of the nanowire narrows according to the decrease of the exchange stiffness constant. On the other hand, the critical current density in a nanowire with PMA slightly decreases contrary to that of IMA although the domain wall width reasonably decreases as the exchange stiffness constant decreases. The slight reduction rate of the critical current density is due to the increase of the effective hard-axis anisotropy of PMA nanowire.

  13. Finite difference discretization of semiconductor drift-diffusion equations for nanowire solar cells

    Science.gov (United States)

    Deinega, Alexei; John, Sajeev

    2012-10-01

    We introduce a finite difference discretization of semiconductor drift-diffusion equations using cylindrical partial waves. It can be applied to describe the photo-generated current in radial pn-junction nanowire solar cells. We demonstrate that the cylindrically symmetric (l=0) partial wave accurately describes the electronic response of a square lattice of silicon nanowires at normal incidence. We investigate the accuracy of our discretization scheme by using different mesh resolution along the radial direction r and compare with 3D (x, y, z) discretization. We consider both straight nanowires and nanowires with radius modulation along the vertical axis. The charge carrier generation profile inside each nanowire is calculated using an independent finite-difference time-domain simulation.

  14. 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.

  15. 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...

  16. 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...

  17. Computationally derived rules for persistence of C60 nanowires on recumbent pentacene bilayers.

    Science.gov (United States)

    Cantrell, Rebecca A; James, Christine; Clancy, Paulette

    2011-08-16

    The tendency for C(60) nanowires to persist on two monolayers of recumbent pentacene is studied using molecular dynamics (MD) simulations. A review of existing experimental literature for the tilt angle adopted by pentacene on noble metal surfaces shows that studies cover a limited range from 55° to 90°, motivating simulation studies of essentially the entire range of tilt angles (10°-90°) to predict the optimum surface tilt angle for C(60) nanowire formation. The persistence of a 1D nanowire depends sensitively on this tilt angle, the amount of initial tensile strain, and the presence of surface step edges. At room temperature, C(60) nanowires oriented along the pentacene short axes persist for several nanoseconds and are more likely to occur if they reside between, or within, pentacene rows for ϕ ≤ ∼60°. The likelihood of this persistence increases the smaller the tilt angle. Nanowires oriented along the long axes of pentacene molecules are unlikely to form. The limit of stability of nanowires was tested by raising the temperature to 400 K. Nanowires located between pentacene rows survived this temperature rise, but those located initially within pentacene rows are only stable in the range ϕ(1) = 30°-50°. Flatter pentacene surfaces, that is, tilt angles above about 60°, are subject to disorder caused by C(60) molecules "burrowing" into the pentacene surface. An initial strain of 5% applied to the C(60) nanowires significantly decreases the likelihood of nanowire persistence. In contrast, any appreciable surface roughness, even by half a monolayer in height of a third pentacene monolayer, strongly enhances the likelihood of nanowire formation due to the strong binding energy of C(60) molecules to step edges.

  18. Two-dimensional nanowires on homoepitaxial interfaces: Atomic-scale mechanism of breakdown and disintegration

    Science.gov (United States)

    Michailov, Michail; Ranguelov, Bogdan

    2018-03-01

    We present a model for hole-mediated spontaneous breakdown of ahomoepitaxial two-dimensional (2D) flat nanowire based exclusively on random, thermally-activated motion of atoms. The model suggests a consecutive three-step mechanism driving the rupture and complete disintegration of the nanowire on a crystalline surface. The breakdown scenario includes: (i) local narrowing of a part of the stripe to a monatomic chain, (ii) formation of a recoverable single vacancy or a 2D vacancy cluster that causes temporary nanowire rupture, (iii) formation of a non-recoverable 2D hole leading to permanent nanowire breakdown. These successive events in the temporal evolution of the nanowire morphology bring the nanowire stripe into an irreversible unstable state, leading to a dramatic change in its peculiar physical properties and conductivity. The atomistic simulations also reveal a strong increase of the nanowire lifetime with an enlargement of its width and open up a way for a fine atomic-scale control of the nanowire lifetime and structural, morphological and thermodynamic stability.

  19. Hole-dominated transport in InSb nanowires grown on high-quality InSb films

    Energy Technology Data Exchange (ETDEWEB)

    Algarni, Zaina; George, David; Singh, Abhay; Lin, Yuankun; Philipose, U., E-mail: usha.philipose@unt.edu [University of North Texas, Department of Physics (United States)

    2016-12-15

    We have developed an effective strategy for synthesizing p-type indium antimonide (InSb) nanowires on a thin film of InSb grown on glass substrate. The InSb films were grown by a chemical reaction between Sb{sub 2}S{sub 3} and In and were characterized by structural, compositional, and optical studies. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies reveal that the surface of the substrate is covered with a polycrystalline InSb film comprised of sub-micron sized InSb islands. Energy dispersive X-ray (EDX) results show that the film is stoichiometric InSb. The optical constants of the InSb film, characterized using a variable-angle spectroscopic ellipsometer (VASE) shows a maximum value for refractive index at 3.7 near 1.8 eV, and the extinction coefficient (k) shows a maximum value 3.3 near 4.1 eV. InSb nanowires were subsequently grown on the InSb film with 20 nm sized Au nanoparticles functioning as the metal catalyst initiating nanowire growth. The InSb nanowires with diameters in the range of 40–60 nm exhibit good crystallinity and were found to be rich in Sb. High concentrations of anions in binary semiconductors are known to introduce acceptor levels within the band gap. This un-intentional doping of the InSb nanowire resulting in hole-dominated transport in the nanowires is demonstrated by the fabrication of a p-channel nanowire field effect transistor. The hole concentration and field effect mobility are estimated to be ≈1.3 × 10{sup 17} cm{sup −3} and 1000 cm{sup 2} V{sup −1} s{sup −1}, respectively, at room temperature, values that are particularly attractive for the technological implications of utilizing p-InSb nanowires in CMOS electronics.

  20. Hole-dominated transport in InSb nanowires grown on high-quality InSb films

    Science.gov (United States)

    Algarni, Zaina; George, David; Singh, Abhay; Lin, Yuankun; Philipose, U.

    2016-12-01

    We have developed an effective strategy for synthesizing p-type indium antimonide (InSb) nanowires on a thin film of InSb grown on glass substrate. The InSb films were grown by a chemical reaction between S b 2 S 3 and I n and were characterized by structural, compositional, and optical studies. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies reveal that the surface of the substrate is covered with a polycrystalline InSb film comprised of sub-micron sized InSb islands. Energy dispersive X-ray (EDX) results show that the film is stoichiometric InSb. The optical constants of the InSb film, characterized using a variable-angle spectroscopic ellipsometer (VASE) shows a maximum value for refractive index at 3.7 near 1.8 eV, and the extinction coefficient (k) shows a maximum value 3.3 near 4.1 eV. InSb nanowires were subsequently grown on the InSb film with 20 nm sized Au nanoparticles functioning as the metal catalyst initiating nanowire growth. The InSb nanowires with diameters in the range of 40-60 nm exhibit good crystallinity and were found to be rich in Sb. High concentrations of anions in binary semiconductors are known to introduce acceptor levels within the band gap. This un-intentional doping of the InSb nanowire resulting in hole-dominated transport in the nanowires is demonstrated by the fabrication of a p-channel nanowire field effect transistor. The hole concentration and field effect mobility are estimated to be ≈1.3 × 1017 cm-3 and 1000 cm2 V-1 s-1, respectively, at room temperature, values that are particularly attractive for the technological implications of utilizing p-InSb nanowires in CMOS electronics.

  1. Opto-mechano-electrical tripling in ZnO nanowires probed by photocurrent spectroscopy in a high-resolution transmission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, C.; Golberg, D., E-mail: xuzhi@iphy.ac.cn, E-mail: golberg.dmitri@nims.go.jp [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 3050044 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai 1, Tsukuba, Ibaraki 3058577 (Japan); Xu, Z., E-mail: xuzhi@iphy.ac.cn, E-mail: golberg.dmitri@nims.go.jp [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Kvashnin, D. G. [National University of Science and Technology, MISIS, Leninskiy Prospect 4, Moscow 119049 (Russian Federation); Tang, D.-M.; Xue, Y. M.; Bando, Y. [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 3050044 (Japan); Sorokin, P. B. [National University of Science and Technology, MISIS, Leninskiy Prospect 4, Moscow 119049 (Russian Federation); Moscow Institute of Physics and Technology, Institutsky Lane 9, Dolgoprudny 141700 (Russian Federation)

    2015-08-31

    Photocurrent spectroscopy of individual free-standing ZnO nanowires inside a high-resolution transmission electron microscope (TEM) is reported. By using specially designed optical in situ TEM system capable of scanning tunneling microscopy probing paired with light illumination, opto-mechano-electrical tripling phenomenon in ZnO nanowires is demonstrated. Splitting of photocurrent spectra at around 3.3 eV under in situ TEM bending of ZnO nanowires directly corresponds to nanowire deformation and appearance of expanded and compressed nanowire sides. Theoretical simulation of a bent ZnO nanowire has an excellent agreement with the experimental data. The splitting effect could be explained by a change in the valence band structure of ZnO nanowires due to a lattice strain. The strain-induced splitting provides important clues for future flexible piezo-phototronics.

  2. 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)

  3. Harmonics Generation by Surface Plasmon Polaritons on Single Nanowires.

    Science.gov (United States)

    de Hoogh, Anouk; Opheij, Aron; Wulf, Matthias; Rotenberg, Nir; Kuipers, L

    2016-08-17

    We present experimental observations of visible wavelength second- and third-harmonic generation on single plasmonic nanowires of variable widths. We identify that near-infrared surface plasmon polaritons, which are guided along the nanowire, act as the source of the harmonics generation. We discuss the underlying mechanism of this nonlinear process, using a combination of spatially resolved measurements and numerical simulations to show that the visible harmonics are generated via a combination of both local and propagating plasmonic modes. Our results provide the first demonstration of nanoscale nonlinear optics with guided, propagating plasmonic modes on a lithographically defined chip, opening up new routes toward integrated optical circuits for information processing.

  4. 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.

  5. Novel mechanical behaviors of wurtzite CdSe nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Bing [Shanghai Normal University, Department of Physics (China); Chen, Li [MCPHS University, School of Arts and Sciences (United States); Xie, Yiqun; Feng, Jie; Ye, Xiang, E-mail: yexiang@shnu.edu.cn [Shanghai Normal University, Department of Physics (China)

    2015-09-15

    As an important semiconducting nanomaterial, CdSe nanowires have attracted much attention. Although many studies have been conducted in the electronic and optical properties of CdSe NWs, the mechanical properties of Wurtzite (WZ) CdSe nanowires remain unclear. Using molecular dynamics simulations, we have studied the tensile mechanical properties and behaviors of [0001]-oriented Wurtzite CdSe nanowires. By monitoring the stretching processes of CdSe nanowires, three distinct structures are found: the WZ wire, a body-centered tetragonal structure with four-atom rings (denoted as BCT-4), and a structure that consists of ten-atom rings with two four-atom rings (denoted as TAR-4) which is observed for the first time. Not only the elastic tensile characteristics are highly reversible under unloading, but a reverse transition between TAR-4 and BCT-4 is also observed. The stretching processes also have a strong dependence on temperature. A tubular structure similar to carbon nanotubes is observed at 150 K, a single-atom chain is formed at 300, 350 and 450 K, and a double-atom chain is found at 600 K. Our findings on tensile mechanical properties of WZ CdSe nanowires does not only provide inspiration to future study on other properties of CdSe nanomaterials but also help design and build efficient nanoscale devices.

  6. Hybrid Surface Plasmon Polariton Modes of Subwavelength Nanowire Resonators

    DEFF Research Database (Denmark)

    Filonenko, Konstantin; Duggen, Lars; Willatzen, Morten

    2015-01-01

    -localized gap plasmon mode are studied depending on the vacuum wavelength. In order to directly compare resonators, where metal and semiconductor nanowires are employed, we consider the two resonators, both including silver slab and magnesium fluoride gap region, as is shown in figure. The two compared......We perform Comsol simulations of two types of hybrid plasmonic resonator configurations, similar to those proposed for nanowire plasmonic laser in [1] and [2]. In both references the nanowire - based plasmonic resonators are studied, which overall sizes are larger than the wavelength in vacuum....... However, it is advantageous for the nanolaser to have subwavelength sizes at least in two dimensions. Therefore, we study the two configurations and the hybrid mode behavior in the case, where resonator sizes are smaller than the half of the wavelength in vacuum. First, we assume finite dimensions...

  7. Phase-Field Modeling of Polycrystalline Solidification: From Needle Crystals to Spherulites—A Review

    Science.gov (United States)

    Gránásy, László; Rátkai, László; Szállás, Attila; Korbuly, Bálint; Tóth, Gyula I.; Környei, László; Pusztai, Tamás

    2014-04-01

    Advances in the orientation-field-based phase-field (PF) models made in the past are reviewed. The models applied incorporate homogeneous and heterogeneous nucleation of growth centers and several mechanisms to form new grains at the perimeter of growing crystals, a phenomenon termed growth front nucleation. Examples for PF modeling of such complex polycrystalline structures are shown as impinging symmetric dendrites, polycrystalline growth forms (ranging from disordered dendrites to spherulitic patterns), and various eutectic structures, including spiraling two-phase dendrites. Simulations exploring possible control of solidification patterns in thin films via external fields, confined geometry, particle additives, scratching/piercing the films, etc. are also displayed. Advantages, problems, and possible solutions associated with quantitative PF simulations are discussed briefly.

  8. Effect of texture on grain boundary misorientation distributions in polycrystalline high temperature superconductors

    International Nuclear Information System (INIS)

    Goyal, A.; Specht, E.D.; Kroeger, D.M.; Mason, T.A.

    1996-01-01

    Computer simulations were performed to determine the most probable grain boundary misorientation distribution (GBMD) in model polycrystalline superconductors. GBMDs in polycrystalline superconductors can be expected to dictate the macroscopic transport critical current density, J c . Calculations were performed by simulating model polycrystals and then determining the GBMD. Such distributions were calculated for random materials having cubic, tetragonal, and orthorhombic crystal symmetry. In addition, since most high temperature superconductors are tetragonal or pseudotetragonal, the effect of macroscopic uniaxial and biaxial grain orientation texture on the GBMD was determined for tetragonal materials. It is found that macroscopic texture drastically alters the grain boundary misorientation distribution. The fraction of low angle boundaries increases significantly with uniaxial and biaxial texture. The results of this study are important in correlating the macroscopic transport J c with the measured grain orientation texture as determined by x-ray diffraction copyright 1996 American Institute of Physics

  9. Discrete Tomography and Imaging of Polycrystalline Structures

    DEFF Research Database (Denmark)

    Alpers, Andreas

    High resolution transmission electron microscopy is commonly considered as the standard application for discrete tomography. While this has yet to be technically realized, new applications with a similar flavor have emerged in materials science. In our group at Ris� DTU (Denmark's National...... Laboratory for Sustainable Energy), for instance, we study polycrystalline materials via synchrotron X-ray diffraction. Several reconstruction problems arise, most of them exhibit inherently discrete aspects. In this talk I want to give a concise mathematical introduction to some of these reconstruction...... problems. Special focus is on their relationship to classical discrete tomography. Several open mathematical questions will be mentioned along the way....

  10. Hydrogenation of polycrystalline silicon thin films

    Czech Academy of Sciences Publication Activity Database

    Honda, Shinya; Mates, Tomáš; Knížek, Karel; Ledinský, Martin; Fejfar, Antonín; Kočka, Jan; Yamazaki, T.; Uraoka, Y.; Fuyuki, T.

    2006-01-01

    Roč. 501, - (2006), s. 144-148 ISSN 0040-6090 R&D Projects: GA MŠk ME 537; GA MŽP(CZ) SM/300/1/03; GA AV ČR(CZ) IAA1010316; GA AV ČR(CZ) IAA1010413; GA ČR(CZ) GA202/03/0789 Institutional research plan: CEZ:AV0Z1010914 Keywords : polycrystalline silicon * atmospheric pressure chemical vapour deposition * hydrogen passivation * photoluminescence * Raman spectroscopy * Si-H 2 bonding * hydrogen molecules Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.666, year: 2006

  11. Field performance of a polycrystalline silicon module

    International Nuclear Information System (INIS)

    Adegboyega, G.A.; Kuku, T.A.; Salau, A.A.M.

    1985-12-01

    The field performance of a polycrystalline silicon module is reported. The recorded data include the ambient temperature, solar insolation and the module output power. The module has given efficiencies in the range of 2-4% and has demonstrated good stability over a ten month period. From the field data, equations that could be used to predict performance for various seasons of the year for this location have been developed and the fit between predicted and actual performance has been found to be quite good. (author)

  12. Creep cavitation effects in polycrystalline alumina

    International Nuclear Information System (INIS)

    Porter, J.R.; Blumenthal, W.; Evans, A.G.

    1981-01-01

    Fine grained polycrystalline alumina has been deformed in creep at high temperatures, to examine the evolution of cavities at grain boundaries. Cavities with equilibrium and crack-like morphologies have been observed, distributed nonuniformly throughout the material. The role of these cavities during creep has been described. A transition from equilibrium to crack-like morphology has been observed and correlated with a model based on the influence of the surface to boundary diffusivity ratio and the local tensile stress. The contribution of cavitation to the creep rate and total creep strain has been analyzed and excluded as the principal cause of the observed non-linear creep rate

  13. Anomalous Hall effect in polycrystalline Ni films

    KAUST Repository

    Guo, Zaibing

    2012-02-01

    We systematically studied the anomalous Hall effect in a series of polycrystalline Ni films with thickness ranging from 4 to 200 nm. It is found that both the longitudinal and anomalous Hall resistivity increased greatly as film thickness decreased. This enhancement should be related to the surface scattering. In the ultrathin films (46 nm thick), weak localization corrections to anomalous Hall conductivity were studied. The granular model, taking into account the dominated intergranular tunneling, has been employed to explain this phenomenon, which can explain the weak dependence of anomalous Hall resistivity on longitudinal resistivity as well. © 2011 Elsevier Ltd. All rights reserved.

  14. Room temperature synthesis and characterization of CdO nanowires by chemical bath deposition (CBD) method

    International Nuclear Information System (INIS)

    Dhawale, D.S.; More, A.M.; Latthe, S.S.; Rajpure, K.Y.; Lokhande, C.D.

    2008-01-01

    A chemical synthesis process for the fabrication of CdO nanowires is described. In the present work, transparent and conductive CdO films were synthesized on the glass substrate using chemical bath deposition (CBD) at room temperature. These films were annealed in air at 623 K and characterized for the structural, morphological, optical and electrical properties were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), optical and electrical resistivity. The XRD analysis showed that the as-deposited amorphous can be converted in to polycrystalline after annealing. Annealed CdO nanowires are 60-65 nm in diameter and length ranges typically from 2.5 to 3 μm. The optical properties revealed the presence of direct and indirect band gaps with energies 2.42 and 2.04 eV, respectively. Electrical resistivity measurement showed semiconducting behavior and thermoemf measurement showed n-type electrical conductivity

  15. Electrodeposition of ZnO nano-wires lattices with a controlled morphology

    International Nuclear Information System (INIS)

    Elias, J.; Tena-Zaera, R.; Katty, A.; Levy-Clement, C.

    2006-01-01

    In this work, it is shown that the electrodeposition is a changeable low cost method which allows, according to the synthesis conditions, to obtain not only plane thin layers of ZnO but different nano-structures too. In a first part, are presented the formation conditions of a compact thin layer of nanocrystalline ZnO electrodeposited on a conducing glass substrate. This layer plays a buffer layer role for the deposition of a lattice of ZnO nano-wires. The step of nano-wires nucleation is not only determined by the electrochemical parameters but by the properties of the buffer layer too as the grain sizes and its thickness. In this context, the use of an electrodeposition method in two steps allows to control the nano-wires length and diameter and their density. The morphology and the structural and optical properties of these nano-structures have been analyzed by different techniques as the scanning and transmission electron microscopy, the X-ray diffraction and the optical spectroscopy. These studies show that ZnO nano-structures are formed of monocrystalline ZnO nano-wires, presenting a great developed surface and a great optical transparency in the visible. These properties make ZnO a good material for the development of nano-structured photovoltaic cells as the extremely thin absorber cells (PV ETA) or those with dye (DSSC) which are generally prepared with porous polycrystalline TiO 2 . Its replacement by a lattice of monocrystalline ZnO nano-wires allows to reduce considerably the number of grain boundaries and in consequence to improve the transport of the electrons. The results are then promising for the PV ETA cells with ZnO nano-wires. (O.M.)

  16. Nanostructured Zn and ZnO nanowire thin films for mechanical and self-cleaning applications

    Energy Technology Data Exchange (ETDEWEB)

    Shaik, Ummar Pasha [Advanced Centre of Research in High Energy Materials, University of Hyderabad, Prof. C R Rao Road, Gachibowli, Hyderabad 500046 (India); Purkayastha, Debarun Dhar, E-mail: ddebarun@yahoo.com [Department of Physics, National Institute of Technology Nagaland, Chumukedima, Dimapur 797103 (India); Krishna, M. Ghanashyam [Advanced Centre of Research in High Energy Materials, University of Hyderabad, Prof. C R Rao Road, Gachibowli, Hyderabad 500046 (India); School of Physics, University of Hyderabad, Prof. C R Rao Road, Gachibowli, Hyderabad 500046 (India); Madhurima, V. [Department of Physics, Central University of Tamil Nadu, Thiruvarur 610004 (India)

    2015-03-01

    Highlights: • Zn metal films were deposited by thermal evaporation, on various substrates. • Upon annealing Zn there is transformation of the Zn nanosheets into ZnO nanowires. • ZnO nanowires are superhydrophobic and exhibit wetting transition on UV exposure. • ZnO will be useful in self-cleaning, mechanical and oxidation resistance surfaces. - Abstract: Nanostructured Zn metal films were deposited by thermal evaporation, on borosilicate glass, Quartz, sapphire, lanthanum aluminate and yttria stabilized zirconia substrates. The as-deposited films are nanocrystalline and show a morphology that consists of triangular nanosheets. The films are hydrophobic with contact angles between 102° and 120° with hardness and Young's modulus between 0.15–0.8 GPa and 18–300 GPa, respectively. Thermal annealing of the films at 500 °C results only in partial oxidation of Zn to ZnO, which indicates good oxidation resistance. Annealing also causes transformation of the Zn nanosheets into ZnO nanowires that are polycrystalline in nature. The ZnO nanowires are superhydrophobic with contact angles between 159° and 162°, contact angle hysteresis between 5° and 10° and exhibit a reversible superhydrophobic–hydrophilic transition under UV irradiation. The nanowires are much softer than the as-deposited Zn metal films, with hardness between 0.02 and 0.4 GPa and Young's modulus between 3 and 35 GPa. The current study thus demonstrates a simple process for fabrication of nanostructured Zn metal films followed by a one-step transformation to nanowires with properties that will be very attractive for mechanical and self-cleaning applications.

  17. Microwave dynamics of high aspect ratio superconducting nanowires studied using self-resonance

    Science.gov (United States)

    Santavicca, Daniel F.; Adams, Jesse K.; Grant, Lierd E.; McCaughan, Adam N.; Berggren, Karl K.

    2016-06-01

    We study the microwave impedance of extremely high aspect ratio (length/width ≈ 5000) superconducting niobium nitride nanowires. The nanowires are fabricated in a compact meander geometry that is in series with the center conductor of a 50 Ω coplanar waveguide transmission line. The transmission coefficient of the sample is measured up to 20 GHz. At high frequency, a peak in the transmission coefficient is seen. Numerical simulations show that this is a half-wave resonance along the length of the nanowire, where the nanowire acts as a high impedance, slow wave transmission line. This resonance sets the upper frequency limit for these nanowires as inductive elements. Fitting simulations to the measured resonance enables a precise determination of the nanowire's complex sheet impedance at the resonance frequency. The real part is a measure of dissipation, while the imaginary part is dominated by kinetic inductance. We characterize the dependence of the sheet resistance and sheet inductance on both temperature and current and compare the results to recent theoretical predictions for disordered superconductors. These results can aid in the understanding of high frequency devices based on superconducting nanowires. They may also lead to the development of novel superconducting devices such as ultra-compact resonators and slow-wave structures.

  18. High-Performance Carbon Dioxide Electrocatalytic Reduction by Easily Fabricated Large-Scale Silver Nanowire Arrays.

    Science.gov (United States)

    Luan, Chuhao; Shao, Yang; Lu, Qi; Gao, Shenghan; Huang, Kai; Wu, Hui; Yao, Kefu

    2018-05-17

    An efficient and selective catalyst is in urgent need for carbon dioxide electroreduction and silver is one of the promising candidates with affordable costs. Here we fabricated large-scale vertically standing Ag nanowire arrays with high crystallinity and electrical conductivity as carbon dioxide electroreduction catalysts by a simple nanomolding method that was usually considered not feasible for metallic crystalline materials. A great enhancement of current densities and selectivity for CO at moderate potentials was achieved. The current density for CO ( j co ) of Ag nanowire array with 200 nm in diameter was more than 2500 times larger than that of Ag foil at an overpotential of 0.49 V with an efficiency over 90%. The origin of enhanced performances are attributed to greatly increased electrochemically active surface area (ECSA) and higher intrinsic activity compared to those of polycrystalline Ag foil. More low-coordinated sites on the nanowires which can stabilize the CO 2 intermediate better are responsible for the high intrinsic activity. In addition, the impact of surface morphology that induces limited mass transportation on reaction selectivity and efficiency of nanowire arrays with different diameters was also discussed.

  19. Magnetization pinning in modulated nanowires: from topological protection to the "corkscrew" mechanism.

    Science.gov (United States)

    Fernandez-Roldan, Jose Angel; Perez Del Real, Rafael; Bran, Cristina; Vazquez, Manuel; Chubykalo-Fesenko, Oksana

    2018-03-29

    Diameter-modulated nanowires offer an important paradigm to design the magnetization response of 3D magnetic nanostructures by engineering the domain wall pinning. With the aim to understand its nature and to control the process, we analyze the magnetization response in FeCo periodically modulated polycrystalline nanowires varying the minor segment diameter. Our modelling indicates a very complex behavior with a strong dependence on the disorder distribution and an important role of topologically non-trivial magnetization structures. We demonstrate that modulated nanowires with a small diameter difference are characterized by an increased coercive field in comparison to the straight ones, which is explained by a formation of topologically protected walls formed by two 3D skyrmions with opposite chiralities. For a large diameter difference we report the occurrence of a novel pinning type called here the "corkscrew": the magnetization of the large diameter segment forms a skyrmion tube with a core position in a helical modulation along the nanowire. This structure is pinned at the constriction and in order to penetrate the narrow segments the vortex/skyrmion core size should be reduced.

  20. Influence of ammonia flow rate for improving properties of polycrystalline GaN

    Science.gov (United States)

    Ariff, A.; Ahmad, M. A.; Hassan, Z.; Zainal, N.

    2018-06-01

    Post-annealing treatment in ammonia ambient is widely accepted for GaN material, but less works have been done to investigate the influence of the ammonia (NH3) flow rate for reducing the N-deficiency as well as improving the quality of the material. In this work, we investigated the influence of NH3 flow rate at 1, 2, 3, and 4 slm in improving properties of a ∼1 μm thick polycrystalline GaN layer. Our simulation work suggested that the uniformity of temperature and pressure gradient of the NH3 gas did not lead to the reduction of N-deficiency of the polycrystalline GaN layer. Instead, it was found that the mitigation of the N-deficiency was strongly influenced by the fluid velocity of the NH3 gas, which had passed over the layer. Either at lower or higher fluid velocity, the chance for the active N atoms to incorporate into the GaN lattice structure was low. Therefore, the N-deficiency on the polycrystalline GaN layer could not be minimized under these conditions. As measured by EDX, the N atoms incorporation was the most effective when the NH3 flow rate at 3 slm, suggesting the flow rate significantly improved the N-deficiency of the polycrystalline GaN layer. Furthermore, it favored the formation of larger hexagonal faceted grains, with the smallest FWHM of XRD peaks from the GaN diffractions in (10 1 bar 0), (0002) and (10 1 bar 1) orientations, while allowing the polycrystalline GaN layer to show sharp and intense emissions peak of NBE in a PL spectrum.

  1. Incorporating catechol into electroactive polypyrrole nanowires on titanium to promote hydroxyapatite formation

    Directory of Open Access Journals (Sweden)

    Zhengao Wang

    2018-03-01

    Full Text Available To improve the osteointegration property of biomedical titanium, nano-architectured electroactive coating was synthesized through the electrochemical polymerization of dopamine and pyrrole. The highly binding affinity of Ca2+ to the catechol moiety of doped dopamine enabled efficient interaction between polypyrrole/polydopamine nanowires and mineral ions. The results indicate that the PPy/PDA nanowires preserved its efficient electro-activity and accelerated the hydroxyapatite deposition in a simulated body fluid. The PPy/PDA nanowires coating could be applied to promote the osteointegration of titanium implant.

  2. Piezoelectric effect in InAs/InP quantum rod nanowires grown on silicon substrate

    International Nuclear Information System (INIS)

    Anufriev, Roman; Chauvin, Nicolas; Bru-Chevallier, Catherine; Khmissi, Hammadi; Naji, Khalid; Gendry, Michel; Patriarche, Gilles

    2014-01-01

    We report on the evidence of a strain-induced piezoelectric field in wurtzite InAs/InP quantum rod nanowires. This electric field, caused by the lattice mismatch between InAs and InP, results in the quantum confined Stark effect and, as a consequence, affects the optical properties of the nanowire heterostructure. It is shown that the piezoelectric field can be screened by photogenerated carriers or removed by increasing temperature. Moreover, a dependence of the piezoelectric field on the quantum rod diameter is observed in agreement with simulations of wurtzite InAs/InP quantum rod nanowire heterostructures

  3. Investigation of functionalized silicon nanowires by self-assembled monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Hemed, Nofar Mintz [Dept. of Physical Electronics, Eng. Faculty, and the University Res. Inst. for Nano Science and Nano-Technologies, Tel-Aviv University, Ramat-Aviv 69978 (Israel); Convertino, Annalisa [Istituto per la Microelettronica e i Microsistemi C.N.R.-Area della Ricerca di Roma, via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Shacham-Diamand, Yosi [Dept. of Physical Electronics, Eng. Faculty, and the University Res. Inst. for Nano Science and Nano-Technologies, Tel-Aviv University, Ramat-Aviv 69978 (Israel); The Department of Applied Chemistry, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan)

    2016-03-30

    Graphical abstract: - Highlights: • We characterize and verify the existence of self-assembled monolayer (SAM) on silicon nanowires and α-Si:H. • We define the term “electrical coverage” and find the formula for both cases. • The SAM's electrical coverage on silicon nanowires is found to be ∼63%. • The SAM's electrical coverage on α-Si:H is found to be ∼65 ± 3%. • The amount of SAM on the SiNWs is sufficient and it can serve as a linker to biological molecules. - Abstract: The functionalization using self assembled monolayer (SAM) of silicon nanowires (SiNW) fabricated by plasma enhanced chemical vapor deposition (PECVD) is reported here. The SAM is being utilized as the first building block in the functionalization process. The morphology of the SiNW comprises a polycrystalline core wrapped by an hydrogenated amorphous silicon (α-Si:H) shell. Since most of the available methods for SAM verification and characterization are suitable only for flat substrates; therefore, in addition to the SiNW α-Si:H on flat samples were produced in the same system as the SiNWs. First we confirmed the SAM's presence on the flat α-Si:H samples using the following methods: contact angle measurement to determine the change in surface energy; atomic force microscopy (AFM) to determine uniformity and molecular coverage. Spectroscopic ellipsometry and X-ray reflectivity (XRR) were performed to measure SAM layer thickness and density. X-ray photoelectron spectroscopy (XPS) was applied to study the chemical states of the surface. Next, SiNW/SAM were tested by electrochemical impedance spectroscopy (EIS), and the results were compared to α-Si:H/SAM. The SAM electrical coverage on SiNW and α-Si:H was found to be ∼37% and ∼65 ± 3%, respectively. A model, based on transmission line theory for the nanowires is presented to explain the disparity in results between the nanowires and flat surface of the same materials.

  4. Native oxide formation on pentagonal copper nanowires: A TEM study

    Science.gov (United States)

    Hajimammadov, Rashad; Mohl, Melinda; Kordas, Krisztian

    2018-06-01

    Hydrothermally synthesized copper nanowires were allowed to oxidize in air at room temperature and 30% constant humidity for the period of 22 days. The growth of native oxide layer was followed up by high-resolution transmission electron microscopy and diffraction to reveal and understand the kinetics of the oxidation process. Copper oxides appear in the form of differently oriented crystalline phases around the metallic core as a shell-like layer (Cu2O) and as nanoscopic islands (CuO) on the top of that. Time dependent oxide thickness data suggests that oxidation follows the field-assisted growth model at the beginning of the process, as practically immediately an oxide layer of ∼2.8 nm thickness develops on the surface. However, after this initial rapid growth, the local field attenuates and the classical parabolic diffusion limited growth plays the main role in the oxidation. Because of the single crystal facets on the side surface of penta-twinned Cu nanowires, the oxidation rate in the diffusion limited regime is lower than in polycrystalline films.

  5. Final Report: Multi-Scale Analysis of Deformation and Failure in Polycrystalline Titanium Alloys Under High Strain-Rates

    Science.gov (United States)

    2015-12-28

    element simulations of polycrystalline Tita - nium alloys. Jour. Mech. Phys. Solids, 59(10):2157–2176, 2011. 5. S. Ghosh and M. Anahid. Homogenized...2013) 111 – 124. [72] P. Shade, Private communication. [73] H. Ogi, S. Kai, H. Ledbetter, R. Tarumi, M. Hirao, K. Takashima, Tita - niums high-temperature

  6. Giant 1/f noise in two-dimensional polycrystalline media

    International Nuclear Information System (INIS)

    Snarskii, A.; Bezsudnov, I.

    2008-01-01

    The behaviour of excess (1/f noise) in two-dimensional polycrystalline media is investigated. On the base of current trap model, it is shown that there exists a certain anisotropy value of conductivity tensor for polycrystalline media when the amplitude of 1/f noise becomes giant

  7. SPICE analysis of the charge division in resistive semiconductor nanowire diodes

    International Nuclear Information System (INIS)

    Guardiola, C; Money, K; Carabe, A

    2014-01-01

    In this paper we present an analysis of the charge division method in semiconductor nanowire Schottky diodes using an electrical model based on the SPICE simulation code. A semiconductor nanowire prototype that is simulated as an RC network and two readout electronic systems are modelled in order to understand its behaviour and to assess its application as a possible ionizing particle detector in clinical high-LET particle beams. We study the use of resistive charge division along the semiconductor nanowire to calculate the position of deposited charge generated by an ionizing particle as it crosses the nanodevice and to determine the minimal viable spatial resolution. Our aim is to demonstrate the charge division concept in resistive semiconductor nanowire diodes, and to subsequently understand the performance of these nanodevices as radiation sensors and address the design limitations of such an application

  8. Influence of ion irradiation induced defects on mechanical properties of copper nanowires

    International Nuclear Information System (INIS)

    Li, Weina; Sun, Lixin; Xue, Jianming; Wang, Jianxiang; Duan, Huiling

    2013-01-01

    The mechanical properties of copper nanowires irradiated with energetic ions have been investigated by using molecular dynamics simulations. The Cu ions with energies ranging from 0.2 to 8.0 keV are used in our simulation, and both the elastic properties and yields under tension and compression are analyzed. The results show that two kinds of defects, namely point defects and stacking faults, appear in the irradiated nanowires depending on the incident ion energy. The Young modulus is significantly reduced by the ion irradiation, and the reduction magnitude depends on the vacancy number, which is determined by the ion energy. Moreover, the irradiated nanowires yield at a smaller strain, compared with the unirradiated nanowire. The mechanism for these changes are also discussed

  9. 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

  10. 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

  11. Contact planarization of ensemble nanowires

    Science.gov (United States)

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

    2011-06-01

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

  12. 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.

  13. Polycrystalline Diamond Schottky Diodes and Their Applications.

    Science.gov (United States)

    Zhao, Ganming

    In this work, four-hot-filament CVD techniques for in situ boron doped diamond synthesis on silicon substrates were extensively studied. A novel tungsten filament shape and arrangement used to obtain large-area, uniform, boron doped polycrystalline diamond thin films. Both the experimental results and radiative heat transfer analysis showed that this technique improved the uniformity of the substrate temperature. XRD, Raman and SEM studies indicate that large area, uniform, high quality polycrystalline diamond films were obtained. Schottky diodes were fabricated by either sputter deposition of silver or thermal evaporation of aluminum or gold, on boron doped diamond thin films. High forward current density and a high forward-to-reverse current ratio were exhibited by silver on diamond Schottky diodes. Schottky barrier heights and the majority carrier concentrations of both aluminum and gold contacted diodes were determined from the C-V measurements. Furthermore, a novel theoretical C-V-f analysis of deep level boron doped diamond Schottky diodes was performed. The analytical results agree well with the experimental results. Compressive stress was found to have a large effect on the forward biased I-V characteristics of the diamond Schottky diodes, whereas the effect on the reverse biased characteristics was relatively small. The stress effect on the forward biased diamond Schottky diode was attributed to piezojunction and piezoresistance effects. The measured force sensitivity of the diode was as high as 0.75 V/N at 1 mA forward bias. This result shows that CVD diamond device has potential for mechanical transducer applications. The quantitative photoresponse characteristics of the diodes were studied in the spectral range of 300 -1050 nm. Semi-transparent gold contacts were used for better photoresponse. Quantum efficiency as high as 50% was obtained at 500 nm, when a reverse bias of over 1 volt was applied. The Schottky barrier heights between either gold or

  14. Mechanical properties of irradiated nanowires – A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Figueroa, Emilio [Grupo de NanoMateriales, Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla, 653 Santiago (Chile); Departamento de Física, Facultad de Ciencias Naturales, Matemática y del Medio Ambiente, Universidad Tecnológica Metropolitana, Santiago 7800002 (Chile); Tramontina, Diego [Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, 5500 Mendoza (Argentina); Instituto de Bioingeniería, Universidad de Mendoza, 5500 Mendoza (Argentina); Gutiérrez, Gonzalo, E-mail: gonzalo@fisica.ciencias.uchile.cl [Grupo de NanoMateriales, Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla, 653 Santiago (Chile); Bringa, Eduardo [Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, 5500 Mendoza (Argentina)

    2015-12-15

    In this work we study, by means of molecular dynamics simulation, the change in the mechanical properties of a gold nanowire with pre-existing radiation damage. The gold nanowire is used as a simple model for a nanofoam, made of connected nanowires. Radiation damage by keV ions leads to the formation of a stacking fault tetrahedron (SFT), and this defect leads to a reduced plastic threshold, as expected, when the nanowire is subjected to tension. We quantify dislocation and twin density during the deformation, and find that the early activation of the SFT as a dislocation source leads to reduced dislocation densities compared to the case without radiation damage. In addition, we observed a total destruction of the SFT, as opposed to a recent simulation study where it was postulated that SFTs might act as self-generating dislocation sources. The flow stress at large deformation is also found to be slightly larger for the irradiated case, in agreement with recent experiments. - Highlights: • Stacking Fault Tetrahedra (SFT) formation proceeds by cascades, containing typically a vacancy cluster and interstitials. • Applied tension leads to the destruction of the SFT, in contrast to a recently reported case of a SFT which soften the NW. • After the initial dislocation activity, strength is controlled by a few surviving dislocations.

  15. Brownian motion of tethered nanowires.

    Science.gov (United States)

    Ota, Sadao; Li, Tongcang; Li, Yimin; Ye, Ziliang; Labno, Anna; Yin, Xiaobo; Alam, Mohammad-Reza; Zhang, Xiang

    2014-05-01

    Brownian motion of slender particles near a boundary is ubiquitous in biological systems and in nanomaterial assembly, but the complex hydrodynamic interaction in those systems is still poorly understood. Here, we report experimental and computational studies of the Brownian motion of silicon nanowires tethered on a substrate. An optical interference method enabled direct observation of microscopic rotations of the slender bodies in three dimensions with high angular and temporal resolutions. This quantitative observation revealed anisotropic and angle-dependent hydrodynamic wall effects: rotational diffusivity in inclined and azimuth directions follows different power laws as a function of the length, ∼ L(-2.5) and ∼ L(-3), respectively, and is more hindered for smaller inclined angles. In parallel, we developed an implicit simulation technique that takes the complex wire-wall hydrodynamic interactions into account efficiently, the result of which agreed well with the experimentally observed angle-dependent diffusion. The demonstrated techniques provide a platform for studying the microrheology of soft condensed matters, such as colloidal and biological systems near interfaces, and exploring the optimal self-assembly conditions of nanostructures.

  16. Considerations for improved polycrystalline cuprate superconductors

    International Nuclear Information System (INIS)

    Shinde, S.L.; Shaw, T.M.

    1990-01-01

    Polycrystalline cuprate superconductors exhibit two-stage superconducting transitions, that are characteristic of granular systems. This behaviour suggests approaches involving improvements in intra and inter-grain properties in order to improve the technologically important superconducting properties such as the magnetic remanent moment and transport critical current density. This paper reports results of our studies on oxygenation, twin density control through grain size and changes in flux pinning within the YBa 2 Cu 3 O 7-δ matrix with Ag substitution under the heading of intra-grain properties and the detrimental effect of grain boundary phases and the effect of Ag substitution on grain boundary pinning under the heading of inter-grain properties

  17. Process Research of Polycrystalline Silicon Material (PROPSM)

    Science.gov (United States)

    Culik, J. S.

    1984-01-01

    An investigation was begun into the usefulness of molecular hydrogen annealing on polycrystalline solar cells. No improvement was realized even after twenty hours of hydrogenation. Thus, samples were chosen on the basis of: (1) low open circuit voltage; (2) low shunt conductance; and (3) high light generated current. These cells were hydrogenated in molecular hydrogen at 300 C. The differences between the before and after hydrogenation values are so slight as to be negligible. These cells have light generated current densities that indicate long minority carrier diffusion lengths. The open circuit voltage appears to be degraded, and quasi-neutral recombination current enhanced. Therefore, molecular hydrogen is not usful for passivating electrically active defects.

  18. Mechanical properties of porous PNZT polycrystalline ceramics

    International Nuclear Information System (INIS)

    Biswas, D.R.; Fulrath, R.M.

    1977-08-01

    Niobium-doped lead zirconate-titanate (PNZT) was used to investigate the effect of porosity on the mechanical properties of a polycrystalline ceramic. Spherical pores (110 to 150 μm diameter) were introduced by using organic materials in the initial specimen fabrication. The matrix grain size (2 to 5 μm) was kept constant. Small pores (2 to 3 μm diameter) of the order of the grain size were formed by varying the sintering conditions. The effect of porosity on strength was predicted quite well by Weibull's probabilistic approach. The Young's modulus showed a linear relationship with increase in porosity. A decrease in fracture toughness with increase in porosity was also observed. It was found that at equivalent porosities, small pore specimens gave higher strength, Young's modulus and fracture toughness compared to specimens containing large pores. Fracture surface analysis, by scanning electron microscopy, showed fracture originated either at the tensile surface or at the edge of the specimen

  19. Unexpected pressure induced ductileness tuning in sulfur doped polycrystalline nickel metal

    Directory of Open Access Journals (Sweden)

    Cheng Guo

    2018-02-01

    Full Text Available The sulfur induced embrittlement of polycrystalline nickel (Ni metal has been a long-standing mystery. It is suggested that sulfur impurity makes ductile Ni metal brittle in many industry applications due to various mechanisms, such as impurity segregation and disorder-induced melting etc. Here we report an observation that the most ductile measurement occurs at a critical sulfur doping concentration, 14 at.% at pressure from 14 GPa up to 29 GPa through texture evolution analysis. The synchrotron-based high pressure texturing measurements using radial diamond anvil cell (rDAC X-ray diffraction (XRD techniques reveal that the activities of slip systems in the polycrystalline nickel metal are affected by sulfur impurities and external pressures, giving rise to the changes in the plastic deformation of the nickel metal. Dislocation dynamics (DD simulation on dislocation density and velocity further confirms the pressure induced ductilization changes in S doped Ni metal. This observation and simulation suggests that the ductilization of the doped polycrystalline nickel metal can be optimized by engineering the sulfur concentration under pressure, shedding a light on tuning the mechanical properties of this material for better high pressure applications.

  20. Unexpected pressure induced ductileness tuning in sulfur doped polycrystalline nickel metal

    Science.gov (United States)

    Guo, Cheng; Yang, Yan; Tan, Liuxi; Lei, Jialin; Guo, Shengmin; Chen, Bin; Yan, Jinyuan; Yang, Shizhong

    2018-02-01

    The sulfur induced embrittlement of polycrystalline nickel (Ni) metal has been a long-standing mystery. It is suggested that sulfur impurity makes ductile Ni metal brittle in many industry applications due to various mechanisms, such as impurity segregation and disorder-induced melting etc. Here we report an observation that the most ductile measurement occurs at a critical sulfur doping concentration, 14 at.% at pressure from 14 GPa up to 29 GPa through texture evolution analysis. The synchrotron-based high pressure texturing measurements using radial diamond anvil cell (rDAC) X-ray diffraction (XRD) techniques reveal that the activities of slip systems in the polycrystalline nickel metal are affected by sulfur impurities and external pressures, giving rise to the changes in the plastic deformation of the nickel metal. Dislocation dynamics (DD) simulation on dislocation density and velocity further confirms the pressure induced ductilization changes in S doped Ni metal. This observation and simulation suggests that the ductilization of the doped polycrystalline nickel metal can be optimized by engineering the sulfur concentration under pressure, shedding a light on tuning the mechanical properties of this material for better high pressure applications.

  1. Two-scale characterization of deformation-induced anisotropy of polycrystalline metals

    International Nuclear Information System (INIS)

    Watanabe, Ikumu; Terada, Kenjiro

    2004-01-01

    The anisotropic macro-scale mechanical behavior of polycrystalline metals is characterized by incorporating the micro-scale constitutive model of single crystal plasticity into the two-scale modeling based on the mathematical homogenization theory. The two-scale simulations are conducted to analyze the macro-scale anisotropy induced by micro-scale plastic deformation of the polycrystalline aggregate. In the simulations, the micro-scale representative volume element (RVE) of a polycrystalline aggregate is uniformly loaded in one direction, unloaded to macroscopically zero stress in a certain stage of deformation and then re-loaded in the different directions. The last re-loading calculations provide different macro-scale responses of the RVE, which can be the appearance of material anisotropy. We then try to examine the effects of the intergranular and intragranular behaviors on the anisotropy by means of various illustrations of plastic deformation process in stead of the use of pole figures for the change of crystallographic orientations

  2. Magnetostrictive properties of polycrystalline iron cobalt films

    International Nuclear Information System (INIS)

    Cooke, M.D.

    2000-10-01

    This thesis is concerned with the magnetic properties of magnetostrictive FeCo polycrystalline alloy films produced by RF magnetron sputter deposition. The bulk material is known to have highly magnetostrictive properties, coupled with the possibility of a low anisotropy with the correct thermal treatment to allow ordering. Significant reduction in the anisotropy was found by using post depostional thermal treatment in Ar/H. It has been demonstrated that it is possible to produce FeCo films with magnetostrictive properties similar to those found in the bulk. Detailed examination showed an increased peak in the magnetostriction with composition which had not been previously viewed in the bulk materials. Initial development was also made of a novel co-depositional technique to allow magnetostrictive determination as a function of composition in a single deposition. Development was made of a technique using the Daresbury Synchrotron research facility and the XRD equipment to allow determination of the magnetostriction coefficients of polycrystalline films. This is the first time this has been achieved for thin film materials and provides exciting new possibilities for the future. A critique was made of the optical cantilever technique for determining magnetostriction. Clear consideration has to be made of rotational and frequency effects. A new analytical theory was devised which allowing determination of the cantilever deflection for similar substrate and film thickness. This is essential for development of current trends in nanotechnology. The results were then optimised for use in sensor and actuator devices providing novel results. Finally investigation was made of the possible effects of surfaces on the magnetic properties. The magnetostriction of FeCo/Ag multilayers and Ag embedded in an FeCo matrix are compared. These clearly show the influence of surface and illustrate the importance of considering the technique used to determine the magnetostriction. (author)

  3. IMPEDANCE SPECTROSCOPY OF POLYCRYSTALLINE TIN DIOXIDE FILMS

    Directory of Open Access Journals (Sweden)

    D. V. Adamchuck

    2016-01-01

    Full Text Available The aim of this work is the analysis of the influence of annealing in an inert atmosphere on the electrical properties and structure of non-stoichiometric tin dioxide films by means of impedance spectroscopy method. Non-stoichiometric tin dioxide films were fabricated by two-step oxidation of metallic tin deposited on the polycrystalline Al2O3 substrates by DC magnetron sputtering. In order to modify the structure and stoichiometric composition, the films were subjected to the high temperature annealing in argon atmosphere in temperature range 300–800 °С. AC-conductivity measurements of the films in the frequency range 20 Hz – 2 MHz were carried out. Variation in the frequency dependencies of the real and imaginary parts of the impedance of tin dioxide films was found to occur as a result of high-temperature annealing. Equivalent circuits for describing the properties of films with various structure and stoichiometric composition were proposed. Possibility of conductivity variation of the polycrystalline tin dioxide films as a result of аnnealing in an inert atmosphere was demonstrated by utilizing impedance spectroscopy. Annealing induces the recrystallization of the films, changing in their stoichiometry as well as increase of the sizes of SnO2 crystallites. Variation of electrical conductivity and structure of tin dioxide films as a result of annealing in inert atmosphere was confirmed by X-ray diffraction analysis. Analysis of the impedance diagrams of tin dioxide films was found to be a powerful tool to study their electrical properties. 

  4. 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)

  5. Tunneling magnetoresistance in Si nanowires

    KAUST Repository

    Montes Muñ oz, Enrique; Rungger, I.; Sanvito, S.; Schwingenschlö gl, Udo

    2016-01-01

    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

  6. Modeling elasto-plastic behavior of polycrystalline grain structure of steels at mesoscopic level

    International Nuclear Information System (INIS)

    Kovac, Marko; Cizelj, Leon

    2005-01-01

    The multiscale model is proposed to explicitly account for the inhomogeneous structure of polycrystalline materials. Grains and grain boundaries are modeled explicitly using Voronoi tessellation. The constitutive model of crystal grains utilizes anisotropic elasticity and crystal plasticity. Commercially available finite element code is applied to solve the boundary value problem defined at the macroscopic scale. No assumption regarding the distribution of the mesoscopic strain and stress fields is used, apart the finite element discretization. The proposed model is then used to estimate the minimum size of polycrystalline aggregate of selected reactor pressure vessel steel (22 NiMoCr 3 7), above which it can be considered macroscopically homogeneous. Elastic and rate-independent plastic deformation modes are considered. The results are validated by the experimental and simulation results from the literature

  7. Catalyst-free fabrication of novel ZnO/CuO core-Shell nanowires heterojunction: Controlled growth, structural and optoelectronic properties

    Science.gov (United States)

    Khan, Muhammad Arif; Wahab, Yussof; Muhammad, Rosnita; Tahir, Muhammad; Sakrani, Samsudi

    2018-03-01

    Development of controlled growth and vertically aligned ZnO/CuO core-shell heterojunction nanowires (NWs) with large area by a catalyst free vapor deposition and oxidation approach has been investigated. Structural characterization reveals successful fabrication of a core ZnO nanowire having single crystalline hexagonal wurtzite structure along [002] direction and CuO nanostructure shell with thickness (8-10 nm) having polycrystalline monoclinic structure. The optical property analysis suggests that the reflectance spectrum of ZnO/CuO heterostructure nanowires is decreased by 18% in the visible range, which correspondingly shows high absorption in this region as compared to pristine ZnO nanowires. The current-voltage (I-V) characteristics of core-shell heterojunction nanowires measured by conductive atomic force microscopy (C-AFM) shows excellent rectifying behavior, which indicates the characteristics of a good p-n junction. The high-resolution transmission electron microscopy (HRTEM) has confirmed the sharp junction interface between the core-shell heterojunction nanowire arrays. The valence band offset and conduction band offset at ZnO/CuO heterointerfaces are measured to be 2.4 ± 0.05 and 0.23 ± 0.005 eV respectively, using X-ray photoelectron spectroscopy (XPS) and a type-II band alignment structure is found. The results of this study contribute to the development of new advanced device heterostructures for solar energy conversion and optoelectronics applications.

  8. Synthesis of Indium Nanowires by Galvanic Displacement and Their Optical Properties

    Directory of Open Access Journals (Sweden)

    Hope Greg

    2008-01-01

    Full Text Available Abstract Single crystalline indium nanowires were prepared on Zn substrate which had been treated in concentrated sulphuric acid by galvanic displacement in the 0.002 mol L−1In2(SO43-0.002 mol L−1SeO2-0.02 mol L−1SDS-0.01 mol L−1citric acid aqueous solution. The typical diameter of indium nanowires is 30 nm and most of the nanowires are over 30 μm in length. XRD, HRTEM, SAED and structural simulation clearly demonstrate that indium nanowires are single-crystalline with the tetragonal structure, the growth direction of the nanowires is along [100] facet. The UV-Vis absorption spectra showed that indium nanowires display typical transverse resonance of SPR properties. The surfactant (SDS and the pretreatment of Zn substrate play an important role in the growth process. The mechanism of indium nanowires growth is the synergic effect of treated Zn substrate (hard template and SDS (soft template.

  9. Effect of temperature and geometric parameters on elastic properties of tungsten nanowire: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Sourav, E-mail: ssaha09@me.buet.ac.bd; Mojumder, Satyajit; Mahboob, Monon [Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka-1000 (Bangladesh); Islam, M. Zahabul [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2016-07-12

    Tungsten is a promising material and has potential use as battery anode. Tungsten nanowires are gaining attention from researchers all over the world for this wide field of application. In this paper, we investigated effect of temperature and geometric parameters (diameter and aspect ratio) on elastic properties of Tungsten nanowire. Aspect ratios (length to diameter ratio) considered are 8:1, 10:1, and 12:1 while diameter of the nanowire is varied from 1-4 nm. For 2 nm diameter sample (aspect ratio 10:1), temperature is varied (10 K ~ 1500 K) to observe elastic behavior of Tungsten nanowire under uniaxial tensile loading. EAM potential is used for molecular dynamic simulation. We applied constant strain rate of 10{sup 9} s{sup −1} to deform the nanowire. Elastic behavior is expressed through stress vs. strain plot. We also investigated the fracture mechanism of tungsten nanowire and radial distribution function. Investigation suggests peculiar behavior of Tungsten nanowire in nano-scale with double peaks in stress vs. strain diagram. Necking before final fracture suggests that actual elastic behavior of the material is successfully captured through atomistic modeling.

  10. Valence band variation in Si (110) nanowire induced by a covered insulator

    International Nuclear Information System (INIS)

    Hong-Hua, Xu; Xiao-Yan, Liu; Yu-Hui, He; Gang, Du; Ru-Qi, Han; Jin-Feng, Kang; Chun, Fan; Ai-Dong, Sun

    2010-01-01

    In this work, we investigate strain effects induced by the deposition of gate dielectrics on the valence band structures in Si (110) nanowire via the simulation of strain distribution and the calculation of a generalized 6×6k·p strained valence band. The nanowire is surrounded by the gate dielectric. Our simulation indicates that the strain of the amorphous SiO 2 insulator is negligible without considering temperature factors. On the other hand, the thermal residual strain in a nanowire with amorphous SiO 2 insulator which has negligible lattice misfit strain pushes the valence subbands upwards by chemical vapour deposition and downwards by thermal oxidation treatment. In contrast with the strain of the amorphous SiO 2 insulator, the strain of the HfO 2 gate insulator in Si (110) nanowire pushes the valence subbands upwards remarkably. The thermal residual strain by HfO 2 insulator contributes to the up-shifting tendency. Our simulation results for valence band shifting and warping in Si nanowires can provide useful guidance for further nanowire device design. (classical areas of phenomenology)

  11. Biotemplated Synthesis of PZT Nanowires

    Science.gov (United States)

    2013-11-25

    electromechanical coupling coefficient , Y is the Young’s modulus, and Ri is intrinsic resistance. The PZT nanowire- based film is taken to have negligible...robotic actuation, and bioMEMS. Lead zirconate titanate ( PZT ), in particular, has attracted significant attention, owing to its superior...electromechanical conversion performance. Yet, the ability to synthesize crystalline PZT nanowires with reproducible and well-controlled properties remains a

  12. 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

  13. CVD polycrystalline diamond. A novel neutron detector and applications

    International Nuclear Information System (INIS)

    Mongkolnavin, R.

    1998-01-01

    Chemical Vapour Deposition (CVD) Polycrystalline Diamond film has been investigated as a low noise sensor for beta particles, gammas and neutrons using High Energy Physics technologies. Its advantages and disadvantages have been explored in comparison with other particle detectors such as silicon detector and other plastic scintillators. The performance and characteristic of the diamond detector have been fully studied and discussed. These studies will lead to a better understanding of how CVD diamonds perform as a detector and how to improve their performance under various conditions. A CVD diamond detector model has been proposed which is an attempt to explain the behaviour of such an extreme detector material. A novel neutron detector is introduced as a result of these studies. A good thermal and fast neutron detector can be fabricated with CVD diamond with new topologies. This detector will perform well without degradation in a high neutron radiation environment, as diamond is known to be radiation hard. It also offers better neutrons and gammas discrimination for high gamma background applications compared to other semiconductor detectors. A full simulation of the detector has also been done using GEANT, a Monte-Carlo simulation program for particle detectors. Simulation results show that CVD diamond detectors with this novel topology can detect neutrons with great directionality. Experimental work has been done on this detector in a nuclear reactor environment and accelerator source. A novel neutron source which offers a fast pulse high-energy neutrons has also been studied. With this detector, applications in neutron spectrometer for low-Z material have been pursued with various neutron detection techniques. One of these is a low-Z material identification system. The system has been designed and simulated for contraband luggage interrogation using the detector and the novel neutron source. Also other neutron related applications have been suggested. (author)

  14. CVD polycrystalline diamond. A novel neutron detector and applications

    International Nuclear Information System (INIS)

    Mongkolnavin, R.

    1998-07-01

    Chemical Vapour Deposition (CVD) Polycrystalline Diamond film has been investigated as a low noise sensor for beta particles, gammas and neutrons using High Energy Physics technologies. Its advantages and disadvantages have been explored in comparison with other particle detectors such as silicon detector and other plastic scintillators. The performance and characteristic of the diamond detector have been fully studied and discussed. These studies will lead to a better understanding of how CVD diamonds perform as a detector and how to improve their performance under various conditions. A CVD diamond detector model has been proposed which is an attempt to explain the behaviour of such an extreme detector material. A novel neutron detector is introduced as a result of these studies. A good thermal and fast neutron detector can be fabricated with CVD diamond with new topologies. This detector will perform well without degradation in a high neutron radiation environment, as diamond is known to be radiation-hard. It also offers better neutrons and gammas discrimination for high gamma background applications compared to other semiconductor detectors. A full simulation of the detector has also been done using GEANT, a Monte Carlo simulation program for particle detectors. Simulation results show that CVD diamond detectors with this novel topology can detect neutrons with great directionality. Experimental work has been done on this detector in a nuclear reactor environment and accelerator source. A novel neutron source which offers a fast pulse high-energy neutrons has also been studied. With this detector, applications in neutron spectrometry for low-Z material have been pursued with various neutron detection techniques. One of these is a low-Z material identification system. The system has been designed and simulated for contraband luggage interrogation using the detector and the novel neutron source. (author)

  15. Arsenic implantation into polycrystalline silicon and diffusion to silicon substrate

    International Nuclear Information System (INIS)

    Tsukamoto, K.; Akasaka, Y.; Horie, K.

    1977-01-01

    Arsenic implantation into polycrystalline silicon and drive-in diffusion to silicon substrate have been investigated by MeV He + backscattering analysis and also by electrical measurements. The range distributions of arsenic implanted into polycrystalline silicon are well fitted to Gaussian distributions over the energy range 60--350 keV. The measured values of R/sub P/ and ΔR/sub P/ are about 10 and 20% larger than the theoretical predictions, respectively. The effective diffusion coefficient of arsenic implanted into polycrystalline silicon is expressed as D=0.63 exp[(-3.22 eV/kT)] and is independent of the arsenic concentration. The drive-in diffusion of arsenic from the implanted polycrystalline silicon layer into the silicon substrate is significantly affected by the diffusion atmosphere. In the N 2 atmosphere, a considerable amount of arsenic atoms diffuses outward to the ambient. The outdiffusion can be suppressed by encapsulation with Si 3 N 4 . In the oxidizing atmosphere, arsenic atoms are driven inward by growing SiO 2 due to the segregation between SiO 2 and polycrystalline silicon, and consequently the drive-in diffusion of arsenic is enhanced. At the interface between the polycrystalline silicon layer and the silicon substrate, arsenic atoms are likely to segregate at the polycrystalline silicon side

  16. Electrochemically grown rough-textured nanowires

    International Nuclear Information System (INIS)

    Tyagi, Pawan; Postetter, David; Saragnese, Daniel; Papadakis, Stergios J.; Gracias, David H.

    2010-01-01

    Nanowires with a rough surface texture show unusual electronic, optical, and chemical properties; however, there are only a few existing methods for producing these nanowires. Here, we describe two methods for growing both free standing and lithographically patterned gold (Au) nanowires with a rough surface texture. The first strategy is based on the deposition of nanowires from a silver (Ag)-Au plating solution mixture that precipitates an Ag-Au cyanide complex during electrodeposition at low current densities. This complex disperses in the plating solution, thereby altering the nanowire growth to yield a rough surface texture. These nanowires are mass produced in alumina membranes. The second strategy produces long and rough Au nanowires on lithographically patternable nickel edge templates with corrugations formed by partial etching. These rough nanowires can be easily arrayed and integrated with microscale devices.

  17. 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.

  18. Structural and tunneling properties of Si nanowires

    KAUST Repository

    Montes Muñ oz, Enrique; Gkionis, Konstantinos; Rungger, Ivan; Sanvito, Stefano; Schwingenschlö gl, Udo

    2013-01-01

    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.

  19. A silicon nanowire heater and thermometer

    Science.gov (United States)

    Zhao, Xingyan; Dan, Yaping

    2017-07-01

    In the thermal conductivity measurements of thermoelectric materials, heaters and thermometers made of the same semiconducting materials under test, forming a homogeneous system, will significantly simplify fabrication and integration. In this work, we demonstrate a high-performance heater and thermometer made of single silicon nanowires (SiNWs). The SiNWs are patterned out of a silicon-on-insulator wafer by CMOS-compatible fabrication processes. The electronic properties of the nanowires are characterized by four-probe and low temperature Hall effect measurements. The I-V curves of the nanowires are linear at small voltage bias. The temperature dependence of the nanowire resistance allows the nanowire to be used as a highly sensitive thermometer. At high voltage bias, the I-V curves of the nanowire become nonlinear due to the effect of Joule heating. The temperature of the nanowire heater can be accurately monitored by the nanowire itself as a thermometer.

  20. 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....

  1. Two-dimensional discrete dislocation models of deformation in polycrystalline thin metal films on substrates

    International Nuclear Information System (INIS)

    Hartmaier, Alexander; Buehler, Markus J.; Gao, Huajian

    2005-01-01

    The time-dependent irreversible deformation of polycrystalline thin metal films on substrates is investigated using two-dimensional discrete dislocation dynamics models incorporating essential parameters determined from atomistic studies. The work is focused on the mechanical properties of uncapped films, where diffusive processes play an important role. The simulations incorporate dislocation climb along the grain boundary as well as conservative glide. Despite of severe limitations of the two-dimensional dislocation models, the simulation results are found to largely corroborate experimental findings on different dominant deformation mechanisms at different film thicknesses

  2. 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

  3. Electrochemical synthesis of highly crystalline copper nanowires

    International Nuclear Information System (INIS)

    Kaur, Amandeep; Gupta, Tanish; Kumar, Akshay; Kumar, Sanjeev; Singh, Karamjeet; Thakur, Anup

    2015-01-01

    Copper nanowires were fabricated within the pores of anodic alumina template (AAT) by template synthesis method at pH = 2.9. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to investigate the structure, morphology and composition of fabricated nanowires. These characterizations revealed that the deposited copper nanowires were highly crystalline in nature, dense and uniform. The crystalline copper nanowires are promising in application of future nanoelectronic devices and circuits

  4. From dopyballs to nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Smalley, R E [Rice Quantum Inst. and Depts. of Chemistry and Physics, Rice Univ., Houston, TX (United States)

    1993-04-19

    Consideration of the factors involved in the production of fullerene nanotubes in carbon arcs leads to the notion that a high electric field may be the critical factor that causes the tubes to grow. This thought then leads to a suggestion that it may be possible to grow continuous fullerene fibers many centimeters in length by an electric-field-and-laser induced pyrolysis of gas phase hydrocarbons of fullerenes on the tip of the growing fiber as it extends out from its place of attachment on a high voltage needle. Use of metal- or boron-doped fullerenes (dopyballs) in such an apparatus may lead to the production of doped fullerene fiber nanowires of high strength and conductivity. (orig.)

  5. Indium Arsenide Nanowires

    DEFF Research Database (Denmark)

    Madsen, Morten Hannibal

    -ray diffraction. InAs NWs can be used in a broad range of applications, including detectors, high speed electronics and low temperature transport measurements, but in this thesis focus will be put on biological experiments on living cells. Good control of Au-assisted InAs NW growth has been achieved......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...... by a systematic study to optimize the growth conditions; first the Au deposition, then the growth temperature and finally the beam fluxes. For further control of the growth, Au droplets have been positioned with electron beam lithography and large scale arrays with a > 99 % yield have been made on 2 inch...

  6. Resonance of curved nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Calabri, L [CNR-INFM-National Research Center on nanoStructures and bioSystems at Surfaces (S3), Via Campi 213/a, 41100 Modena (Italy); Pugno, N [Department of Structural Engineering and Geotechnics, Politecnico di Torino, Turin (Italy); Ding, W [Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208-3111 (United States); Ruoff, R S [Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208-3111 (United States)

    2006-08-23

    The effects of non-ideal experimental configuration on the mechanical resonance of boron (B) nanowires (NWs) were studied to obtain the corrected value for the Young's modulus. The following effects have been theoretically considered: (i) the presence of intrinsic curvature (ii) non-ideal clamps (iii) spurious masses (iv) coating layer, and (v) large displacements. An energy-based analytical analysis was developed to treat such effects and their interactions. Here, we focus on treating the effect of the intrinsic curvature on the mechanical resonance. The analytical approach has been confirmed by numerical FEM analysis. A parallax method was used to obtain the three-dimensional geometry of the NW.

  7. Corrosion detection of nanowires by magnetic sensors

    KAUST Repository

    Kosel, Jü rgen; Amara, Selma; Ivanov, Iurii; Blanco, Mario

    2017-01-01

    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.

  8. 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.

  9. Modulation of thermal conductivity in kinked silicon nanowires: phonon interchanging and pinching effects.

    Science.gov (United States)

    Jiang, Jin-Wu; Yang, Nuo; Wang, Bing-Shen; Rabczuk, Timon

    2013-04-10

    We perform molecular dynamics simulations to investigate the reduction of the thermal conductivity by kinks in silicon nanowires. The reduction percentage can be as high as 70% at room temperature. The temperature dependence of the reduction is also calculated. By calculating phonon polarization vectors, two mechanisms are found to be responsible for the reduced thermal conductivity: (1) the interchanging effect between the longitudinal and transverse phonon modes and (2) the pinching effect, that is, a new type of localization, for the twisting and transverse phonon modes in the kinked silicon nanowires. Our work demonstrates that the phonon interchanging and pinching effects, induced by kinking, are brand-new and effective ways in modulating heat transfer in nanowires, which enables the kinked silicon nanowires to be a promising candidate for thermoelectric materials.

  10. Significant reduction of thermal conductivity in Si/Ge core-shell nanowires.

    Science.gov (United States)

    Hu, Ming; Giapis, Konstantinos P; Goicochea, Javier V; Zhang, Xiaoliang; Poulikakos, Dimos

    2011-02-09

    We report on the effect of germanium (Ge) coatings on the thermal transport properties of silicon (Si) nanowires using nonequilibrium molecular dynamics simulations. Our results show that a simple deposition of a Ge shell of only 1 to 2 unit cells in thickness on a single crystalline Si nanowire can lead to a dramatic 75% decrease in thermal conductivity at room temperature compared to an uncoated Si nanowire. By analyzing the vibrational density states of phonons and the participation ratio of each specific mode, we demonstrate that the reduction in the thermal conductivity of Si/Ge core-shell nanowire stems from the depression and localization of long-wavelength phonon modes at the Si/Ge interface and of high frequency nonpropagating diffusive modes.

  11. Characteristics of domain wall chirality and propagation in a Y-junction nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, W.-Y.; Yoon, Seungha; Kwon, J.-H. [School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of); Grünberg, P. [Gruenberg Center for Magnetic Nanomaterials, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of); Cho, B. K., E-mail: chobk@gist.ac.kr [School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of); Gruenberg Center for Magnetic Nanomaterials, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of)

    2016-01-14

    Chirality-dependent propagation of transverse wall along a nanowire was investigated using a Y-junction with spin-valve structure. It was found that the Y-junction can be used for convenient and effective electric detection of transverse domain wall chirality, especially in a nanowire with sub-200 nm width, where it is difficult to electrically detect chirality using conventional artificial defect, such as a notch, due to small resistance change. Domain wall propagation path in the Y-junction was found to be determined by the wall chirality, whether clockwise or counterclockwise. Using the Y-junction nanowire, characteristics of domain wall chirality that was nucleated in a nucleation pad, attached at the end of a nanowire, were studied and found to be in good agreement with the results of theoretical simulation.

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

    KAUST Repository

    Zhao, Chao; Ng, Tien Khee; Wei, Nini; Prabaswara, Aditya; Alias, Mohd Sharizal; Janjua, Bilal; Shen, Chao; Ooi, Boon S.

    2016-01-01

    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.

  13. 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.

  14. Recovery of hexagonal Si-IV nanowires from extreme GPa pressure

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Bennett E. [Department of Chemistry, University of Washington, Seattle, Washington 98195 (United States); Zhou, Xuezhe; Roder, Paden B. [Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195 (United States); Abramson, Evan H. [Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195 (United States); Pauzauskie, Peter J., E-mail: peterpz@uw.edu [Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195 (United States); Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)

    2016-05-14

    We use Raman spectroscopy in tandem with transmission electron microscopy and density functional theory simulations to show that extreme (GPa) pressure converts the phase of silicon nanowires from cubic (Si-I) to hexagonal (Si-IV) while preserving the nanowire's cylindrical morphology. In situ Raman scattering of the longitudinal transverse optical (LTO) mode demonstrates the high-pressure Si-I to Si-II phase transition near 9 GPa. Raman signal of the LTO phonon shows a decrease in intensity in the range of 9–14 GPa. Then, at 17 GPa, it is no longer detectable, indicating a second phase change (Si-II to Si-V) in the 14–17 GPa range. Recovery of exotic phases in individual silicon nanowires from diamond anvil cell experiments reaching 17 GPa is also shown. Raman measurements indicate Si-IV as the dominant phase in pressurized nanowires after decompression. Transmission electron microscopy and electron diffraction confirm crystalline Si-IV domains in individual nanowires. Computational electromagnetic simulations suggest that heating from the Raman laser probe is negligible and that near-hydrostatic pressure is the primary driving force for the formation of hexagonal silicon nanowires.

  15. An atomistic study of the deformation behavior of tungsten nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Shuozhi [University of California, California NanoSystems Institute, Santa Barbara, CA (United States); Su, Yanqing [University of California, Department of Mechanical Engineering, Santa Barbara, CA (United States); Chen, Dengke [Georgia Institute of Technology, GWW School of Mechanical Engineering, Atlanta, GA (United States); Li, Longlei [Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States)

    2017-12-15

    Large-scale atomistic simulations are performed to study tensile and compressive left angle 112 right angle loading of single-crystalline nanowires in body-centered cubic tungsten (W). Effects of loading mode, wire cross-sectional shape, wire size, strain rate, and crystallographic orientations of the lateral surfaces are explored. Uniaxial deformation of a W bulk single crystal is also investigated for reference. Our results reveal a strong tension-compression asymmetry in both the stress-strain response and the deformation behavior due to different yielding/failure modes: while the nanowires fail by brittle fracture under tensile loading, they yield by nucleation of dislocations from the wire surface under compressive loading. It is found that (1) nanowires have a higher strength than the bulk single crystal; (2) with a cross-sectional size larger than 10 nm, there exists a weak dependence of strength on wire size; (3) when the wire size is equal to or smaller than 10 nm, nanowires buckle under compressive loading; (4) the cross-sectional shape, strain rate, and crystallographic orientations of the lateral surfaces affect the strength and the site of defect initiation but not the overall deformation behavior. (orig.)

  16. Silicon nanowire based high brightness, pulsed relativistic electron source

    Directory of Open Access Journals (Sweden)

    Deep Sarkar

    2017-06-01

    Full Text Available We demonstrate that silicon nanowire arrays efficiently emit relativistic electron pulses under irradiation by a high-intensity, femtosecond, and near-infrared laser (∼1018 W/cm2, 25 fs, 800 nm. The nanowire array yields fluxes and charge per bunch that are 40 times higher than those emitted by an optically flat surface, in the energy range of 0.2–0.5 MeV. The flux and charge yields for the nanowires are observed to be directional in nature unlike that for planar silicon. Particle-in-cell simulations establish that such large emission is caused by the enhancement of the local electric fields around a nanowire, which consequently leads to an enhanced absorption of laser energy. We show that the high-intensity contrast (ratio of picosecond pedestal to femtosecond peak of the laser pulse (10−9 is crucial to this large yield. We extend the notion of surface local-field enhancement, normally invoked in low-order nonlinear optical processes like second harmonic generation, optical limiting, etc., to ultrahigh laser intensities. These electron pulses, expectedly femtosecond in duration, have potential application in imaging, material modification, ultrafast dynamics, terahertz generation, and fast ion sources.

  17. A multiscale coupled finite-element and phase-field framework to modeling stressed grain growth in polycrystalline thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jamshidian, M., E-mail: jamshidian@cc.iut.ac.ir [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Institute of Structural Mechanics, Bauhaus-University Weimar, Marienstrasse 15, 99423 Weimar (Germany); Thamburaja, P., E-mail: prakash.thamburaja@gmail.com [Department of Mechanical & Materials Engineering, Universiti Kebangsaan Malaysia (UKM), Bangi 43600 (Malaysia); Rabczuk, T., E-mail: timon.rabczuk@tdt.edu.vn [Division of Computational Mechanics, Ton Duc Thang University, Ho Chi Minh City (Viet Nam); Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City (Viet Nam)

    2016-12-15

    A previously-developed finite-deformation- and crystal-elasticity-based constitutive theory for stressed grain growth in cubic polycrystalline bodies has been augmented to include a description of excess surface energy and grain-growth stagnation mechanisms through the use of surface effect state variables in a thermodynamically-consistent manner. The constitutive theory was also implemented into a multiscale coupled finite-element and phase-field computational framework. With the material parameters in the constitutive theory suitably calibrated, our three-dimensional numerical simulations show that the constitutive model is able to accurately predict the experimentally-determined evolution of crystallographic texture and grain size statistics in polycrystalline copper thin films deposited on polyimide substrate and annealed at high-homologous temperatures. In particular, our numerical analyses show that the broad texture transition observed in the annealing experiments of polycrystalline thin films is caused by grain growth stagnation mechanisms. - Graphical abstract: - Highlights: • Developing a theory for stressed grain growth in polycrystalline thin films. • Implementation into a multiscale coupled finite-element and phase-field framework. • Quantitative reproduction of the experimental grain growth data by simulations. • Revealing the cause of texture transition to be due to the stagnation mechanisms.

  18. The interpretation of polycrystalline coherent inelastic neutron scattering from aluminium

    Science.gov (United States)

    Roach, Daniel L.; Ross, D. Keith; Gale, Julian D.; Taylor, Jon W.

    2013-01-01

    A new approach to the interpretation and analysis of coherent inelastic neutron scattering from polycrystals (poly-CINS) is presented. This article describes a simulation of the one-phonon coherent inelastic scattering from a lattice model of an arbitrary crystal system. The one-phonon component is characterized by sharp features, determined, for example, by boundaries of the (Q, ω) regions where one-phonon scattering is allowed. These features may be identified with the same features apparent in the measured total coherent inelastic cross section, the other components of which (multiphonon or multiple scattering) show no sharp features. The parameters of the model can then be relaxed to improve the fit between model and experiment. This method is of particular interest where no single crystals are available. To test the approach, the poly-CINS has been measured for polycrystalline aluminium using the MARI spectrometer (ISIS), because both lattice dynamical models and measured dispersion curves are available for this material. The models used include a simple Lennard-Jones model fitted to the elastic constants of this material plus a number of embedded atom method force fields. The agreement obtained suggests that the method demonstrated should be effective in developing models for other materials where single-crystal dispersion curves are not available. PMID:24282332

  19. Synthesis, characterization and structural refinement of polycrystalline uranium substituted zirconolite

    International Nuclear Information System (INIS)

    Shrivastava, O.P.; Narendra Kumar; Sharma, I.B.

    2005-01-01

    Ceramic precursors of Zirconolite (CaZrTi 2 O 7 ) family have a remarkable property of substitution Zr 4+ cationic sites. This makes them potential material for nuclear waste management in 'synroc' technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a solid phase of composition CaZr 0.95 U 0.5 Ti 2 O 7 has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium respectively. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050 degC. The polycrystalline solid phase has been characterized by its typical powder diffraction pattern. Step analysis data has been used for ab initio calculation of structural parameters. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (15). The following unit cell parameters have been calculated: a =12.4883(15), b =7.2448(5), c 11.3973(10) and β = 100.615(9)0. The structure was refined to satisfactory completion. The Rp and Rwp are found to be 7.48% and 9.74% respectively. (author)

  20. Comparisons of Fabric Strength and Development in Polycrystalline Ice at Atmospheric and Basal Hydrostatic Pressures

    Science.gov (United States)

    Breton, Daniel; Baker, Ian; Cole, David

    2013-04-01

    Understanding and predicting the flow of polycrystalline ice is crucial to ice sheet modeling and paleoclimate reconstruction from ice cores. Ice flow rates depend strongly on the fabric (i.e. the distribution of grain sizes and crystallographic orientations) which evolves over time and enhances the flow rate in the direction of applied stress. The mechanisms for fabric evolution in ice have been extensively studied at atmospheric pressures, but little work has been done to observe these processes at the high pressures experienced deep within ice sheets where long-term changes in ice rheology are expected to have significance. We conducted compressive creep tests to ~10% strain on 917 kg m-3, initially randomly-oriented polycrystalline ice specimens at 0.1 (atmospheric) and 20 MPa (simulating ~2,000 m depth) hydrostatic pressures, performing microstructural analyses on the resulting deformed specimens to characterize the evolution and strength of crystal fabric. Our microstructural analysis technique simultaneously collects grain shape and size data from Scanning Electron Microscope (SEM) micrographs and obtains crystallographic orientation data via Electron BackScatter Diffraction (EBSD). Combining these measurements allows rapid analysis of the ice fabric over large numbers of grains, yielding statistically useful numbers of grain size and orientation data. We present creep and microstructural data to demonstrate pressure-dependent effects on the mechanical and microstructural evolution of polycrystalline ice and discuss possible mechanisms for the observed differences.

  1. 3D ductile crack propagation within a polycrystalline microstructure using XFEM

    Science.gov (United States)

    Beese, Steffen; Loehnert, Stefan; Wriggers, Peter

    2018-02-01

    In this contribution we present a gradient enhanced damage based method to simulate discrete crack propagation in 3D polycrystalline microstructures. Discrete cracks are represented using the eXtended finite element method. The crack propagation criterion and the crack propagation direction for each point along the crack front line is based on the gradient enhanced damage variable. This approach requires the solution of a coupled problem for the balance of momentum and the additional global equation for the gradient enhanced damage field. To capture the discontinuity of the displacements as well as the gradient enhanced damage along the discrete crack, both fields are enriched using the XFEM in combination with level sets. Knowing the crack front velocity, level set methods are used to compute the updated crack geometry after each crack propagation step. The applied material model is a crystal plasticity model often used for polycrystalline microstructures of metals in combination with the gradient enhanced damage model. Due to the inelastic material behaviour after each discrete crack propagation step a projection of the internal variables from the old to the new crack configuration is required. Since for arbitrary crack geometries ill-conditioning of the equation system may occur due to (near) linear dependencies between standard and enriched degrees of freedom, an XFEM stabilisation technique based on a singular value decomposition of the element stiffness matrix is proposed. The performance of the presented methodology to capture crack propagation in polycrystalline microstructures is demonstrated with a number of numerical examples.

  2. Polycrystalline silicon semiconducting material by nuclear transmutation doping

    Science.gov (United States)

    Cleland, John W.; Westbrook, Russell D.; Wood, Richard F.; Young, Rosa T.

    1978-01-01

    A NTD semiconductor material comprising polycrystalline silicon having a mean grain size less than 1000 microns and containing phosphorus dispersed uniformly throughout the silicon rather than at the grain boundaries.

  3. Loss of shear strength in polycrystalline tungsten under shock compression

    International Nuclear Information System (INIS)

    Dandekar, D.P.

    1976-01-01

    A reexamination of existing data on shock compression of polycrystalline tungsten at room temperature indicates that tungsten may be an exception to the common belief that metals do not behave like elastic-isotropic solids under shock compression

  4. Deuterium transport and trapping in polycrystalline tungsten

    International Nuclear Information System (INIS)

    Anderl, R.A.; Holland, D.F.; Longhurst, G.R.; Pawelko, R.J.; Trybus, C.L.; Sellers, C.H.

    1992-01-01

    This paper reports that deuterium permeation studies for polycrystalline tungsten foil have been conducted to provide data for estimating tritium transport and trapping in tungsten-clad divertors proposed for advanced fusion-reactor concepts. Based on a detailed transmission electron microscopy (TEM) microstructural characterization of the specimen material and on analyses of permeation data measured at temperatures ranging form 610 to 823 K for unannealed and annealed tungsten foil (25 μm thick), the authors note the following key results: deuterium transport in tungsten foil is dominated by extensive trapping that varies inversely with prior anneal temperatures of the foil material, the reduction in the trapped fraction correlates with a corresponding elimination of a high density of dislocations in cell-wall structures introduced during the foil fabrication process, trapping behavior in these foils can be modelled using trap energies between 1.3 eV and 1.5 eV and trap densities ranging from 1 x 10 -5 atom fraction

  5. Thermomechanical characterization of pure polycrystalline tantalum

    International Nuclear Information System (INIS)

    Rittel, D.; Bhattacharyya, A.; Poon, B.; Zhao, J.; Ravichandran, G.

    2007-01-01

    The thermomechanical behavior of pure polycrystalline tantalum has been characterized over a wide range of strain rates, using the recently developed shear compression specimen [D. Rittel, S. Lee, G. Ravichandran, Experimental Mechanics 42 (2002) 58-64]. Dynamic experiments were carried out using a split Hopkinson pressure bar, and the specimen's temperature was monitored throughout the tests using an infrared radiometer. The results of the mechanical tests confirm previous results on pure Ta. Specifically, in addition to its significant strain rate sensitivity, it was observed that pure Ta exhibits very little strain hardening at high strain rates. The measured temperature rise in the specimen's gauge was compared to theoretical predictions which assume a total conversion of the mechanical energy into heat (β = 1) [G.I. Taylor, H. Quinney, Proceedings of the Royal Society of London, vol. A, 1934, pp. 307-326], and an excellent agreement was obtained. This result confirms the previous result of Kapoor and Nemat-Nasser [R. Kapoor, S. Nemat-Nasser, Mech. Mater. 27 (1998) 1-12], while a different experimental approach was adopted here. The assumption that β = 1 is found to be justified in this specific case by the lack of dynamic strain hardening of pure Ta. However, this assumption should be limited to non-hardening materials, to reflect the fact that strain hardening implies that part of the mechanical energy is stored into the material's microstructure

  6. Tritium diffusion in polycrystalline lithium tungstate

    International Nuclear Information System (INIS)

    Krutyakov, A.N.; Shadrin, A.A.; Saunin, E.I.; Gromov, V.V.; Shafiev, A.I.

    1984-01-01

    Using radiometric method the investigation of tritium separation from neutron irradiated (neutron flux density 1.2x10 13 n/cm 2 xs) polycrystalline Li 2 WO 4 in the temperature range 200-680 deg C has been carried out. It is established that the use of helium as gas-carrier of flow-type gas-discharge counter permits to conduct continuous stable measurements of concentrations of tritium extracted depending on its chemical state. It is shown that volume diffusion is the process, limiting tritiated particle separation rate from Li 2 WO 4 . It is found that the process of tritium volume diffusion in Li 2 WO 4 corresponds to two different mechanisms respectively in low- (200-300 deg C) and high-temperature (350-680 deg C) ranges. A supposition is made that in the low-temperature range the process of diffusion is conditioned by the dissociation of the radiation defect-tritiated particle complex, which is confirmed by the data on radiation defect annealing in Li 2 WO 4 . The value of activation energy of tritium separation process in the range 350-680 deg C, proved to be equal to 13.3 kJ/mol. Possible role of crystal structure peculiarities of Li 2 WO 4 for diffusion process is pointed out

  7. Deformation localization and cyclic strength in polycrystalline molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Sidorov, O.T.; Rakshin, A.F.; Fenyuk, M.I.

    1983-06-01

    Conditions of deformation localization and its interrelation with cyclic strength in polycrystalline molybdenum were investigated. A fatigue failure of polycrystalline molybdenum after rolling and in an embrittled state reached by recrystallization annealing under cyclic bending at room temperature takes place under nonuniform distribution of microplastic strain resulting in a temperature rise in separate sections of more than 314 K. More intensive structural changes take place in molybdenum after rolling than in recrystallized state.

  8. Ballistic superconductivity in semiconductor nanowires

    Science.gov (United States)

    Zhang, Hao; Gül, Önder; Conesa-Boj, Sonia; Nowak, Michał P.; Wimmer, Michael; Zuo, Kun; Mourik, Vincent; de Vries, Folkert K.; van Veen, Jasper; de Moor, Michiel W. A.; Bommer, Jouri D. S.; van Woerkom, David J.; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P.A.M.; Quintero-Pérez, Marina; Cassidy, Maja C.; Koelling, Sebastian; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P.

    2017-01-01

    Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices. PMID:28681843

  9. 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.

  10. 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.

  11. Diameter-dependent coloration of silver nanowires

    International Nuclear Information System (INIS)

    Stewart, Mindy S; Qiu Chao; Jiang Chaoyang; Kattumenu, Ramesh; Singamaneni, Srikanth

    2011-01-01

    Silver nanowires were synthesized with a green method and characterized with microscopic and diffractometric methods. The correlation between the colors of the nanowires deposited on a solid substrate and their diameters was explored. Silver nanowires that appear similar in color in the optical micrographs have very similar diameters as determined by atomic force microscopy. We have summarized the diameter-dependent coloration for these silver nanowires. An optical interference model was applied to explain such correlation. In addition, microreflectance spectra were obtained from individual nanowires and the observed spectra can be explained with the optical interference theory. This work provides a cheap, quick and simple screening method for studying the diameter distribution of silver nanowires, as well as the diameter variations of individual silver nanowires, without complicated sample preparation.

  12. Giant exchange bias and its angular dependence in Co/CoO core-shell nanowire assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Gandha, Kinjal; Chaudhary, Rakesh P.; Mohapatra, Jeotikanta; Koymen, Ali R.; Liu, J. Ping, E-mail: pliu@uta.edu

    2017-07-12

    The exchange-bias field (H{sub EB}) and its angular dependence are systematically investigated in Co/CoO core-shell nanowire assemblies (∼15 nm in diameter and ∼200 nm in length) consisting of single-crystalline Co core and polycrystalline CoO shell. Giant exchange-bias field (H{sub EB}) up to 2.4 kOe is observed below a blocking temperature (T{sub EB} ∼150 K) in the aligned Co/CoO nanowire assemblies. It is also found that there is an angular dependence between the H{sub EB} and the applied magnetization direction. The H{sub EB} showed a peak at 30° between the applied field and the nanowire aligned direction, which may be attributed to the noncollinear spin orientations at the interface between the ferromagnetic core and the antiferromagnetic shell. This behavior is quantitatively supported by an analytical calculation based on Stoner–Wohlfarth model. This study underlines the importance of the competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. - Highlights: • Giant exchange bias is observed in oriented Co/CoO core-shell nanowire assemblies. • Study of angular and temperature dependence of the exchange bias effect. • Competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. • Effect of misaligned spins in FM/AFM interface on angular dependence of exchange bias. • We explain the analytical model that accounts for experimental results.

  13. 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.

  14. 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

  15. Growth and properties of In(Ga)As nanowires on silicon

    International Nuclear Information System (INIS)

    Hertenberger, Simon

    2012-01-01

    by TEM and XRD analysis revealing a disordered wurtzite (WZ) structure with stacking faults occurring every few monolayers to nanometers for InAs nanowires grown under different As/In ratios. However, the nanowire growth temperature is found to influence the crystal structure more significantly, such that longer phase pure WZ segments up to lengths of >10 nm are observed for elevated growth temperatures (≥530 C). Furthermore, InAs nanowire ensembles with different diameter (40-135 nm) are investigated by low-temperature PL spectroscopy. The nanowires show relatively strong emission efficiency, characteristic red-shift with temperature and low-temperature band-edge energy position of ∝0.41 eV for thick nanowires. Reduction in nanowire diameter yields a characteristic blue-shift which is related to quantum confinement effects as confirmed by simulations. The good control about In(Ga)As nanowire growth on Si and the obtained understanding of important physical properties as discussed in this thesis provide a valuable basis for the development of effective high-quality nanowire-based devices.

  16. Growth and properties of In(Ga)As nanowires on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hertenberger, Simon

    2012-10-15

    microstructure are investigated by TEM and XRD analysis revealing a disordered wurtzite (WZ) structure with stacking faults occurring every few monolayers to nanometers for InAs nanowires grown under different As/In ratios. However, the nanowire growth temperature is found to influence the crystal structure more significantly, such that longer phase pure WZ segments up to lengths of >10 nm are observed for elevated growth temperatures (≥530 C). Furthermore, InAs nanowire ensembles with different diameter (40-135 nm) are investigated by low-temperature PL spectroscopy. The nanowires show relatively strong emission efficiency, characteristic red-shift with temperature and low-temperature band-edge energy position of ∝0.41 eV for thick nanowires. Reduction in nanowire diameter yields a characteristic blue-shift which is related to quantum confinement effects as confirmed by simulations. The good control about In(Ga)As nanowire growth on Si and the obtained understanding of important physical properties as discussed in this thesis provide a valuable basis for the development of effective high-quality nanowire-based devices.

  17. pH-Dependent Toxicity of High Aspect Ratio ZnO Nanowires in Macrophages Due to Intracellular Dissolution

    KAUST Repository

    H. Müller, Karin

    2010-11-23

    High-aspect ratio ZnO nanowires have become one of the most promising products in the nanosciences within the past few years with a multitude of applications at the interface of optics and electronics. The interaction of zinc with cells and organisms is complex, with both deficiency and excess causing severe effects. The emerging significance of zinc for many cellular processes makes it imperative to investigate the biological safety of ZnO nanowires in order to guarantee their safe economic exploitation. In this study, ZnO nanowires were found to be toxic to human monocyte macrophages (HMMs) at similar concentrations as ZnCl2. Confocal microscopy on live cells confirmed a rise in intracellular Zn2+ concentrations prior to cell death. In vitro, ZnO nanowires dissolved very rapidly in a simulated body fluid of lysosomal pH, whereas they were comparatively stable at extracellular pH. Bright-field transmission electron microscopy (TEM) showed a rapid macrophage uptake of ZnO nanowire aggregates by phagocytosis. Nanowire dissolution occurred within membrane-bound compartments, triggered by the acidic pH of the lysosomes. ZnO nanowire dissolution was confirmed by scanning electron microscopy/energy-dispersive X-ray spectrometry. Deposition of electron-dense material throughout the ZnO nanowire structures observed by TEM could indicate adsorption of cellular components onto the wires or localized zinc-induced protein precipitation. Our study demonstrates that ZnO nanowire toxicity in HMMs is due to pH-triggered, intracellular release of ionic Zn2+ rather than the high-aspect nature of the wires. Cell death had features of necrosis as well as apoptosis, with mitochondria displaying severe structural changes. The implications of these findings for the application of ZnO nanowires are discussed. © 2010 American Chemical Society.

  18. Thermal desorption of deuterium from polycrystalline nickel pre-implanted with helium

    International Nuclear Information System (INIS)

    Shi, S.Q.; Abramov, E.; Thompson, D.A.

    1990-01-01

    The thermal desorption technique has been used to study the trapping of deuterium atoms in high-purity polycrystalline nickel pre-implanted with helium for 1 x 10 19 to 5 x 10 20 ions/m 2 . The effect of post-implantation annealing at 703 K and 923 K on the desorption behavior was investigated. Measured values of the total amount of detrapped deuterium (Q T ) and helium concentration were used in a computer simulation of the desorption curve. It was found that the simulation using one or two discrete trap energies resulted in an inadequate fit between the simulated and the measured data. Both experimental and simulation results are explained using a stress-field trapping model. The effective binding energy, E b eff , was estimated to be in the range of 0.4-0.6 eV. Deuterium charging was found to stimulate a release of helium at a relatively low temperature

  19. Is the molecular statics method suitable for the study of nanomaterials? A study case of nanowires

    International Nuclear Information System (INIS)

    Chang, I-L; Chen, Y-C

    2007-01-01

    Both molecular statics and molecular dynamics methods were employed to study the mechanical properties of copper nanowires. The size effect on both elastic and plastic properties of square cross-sectional nanowire was examined and compared systematically using two molecular approaches. It was found consistently from both molecular methods that the elastic and plastic properties of nanowires depend on the lateral size of nanowires. As the lateral size of nanowires decreases, the values of Young's modulus decrease and dislocation nucleation stresses increase. However, it was shown that the dislocation nucleation stress would be significantly influenced by the axial periodic length of the nanowire model using the molecular statics method while molecular dynamics simulations at two distinct temperatures (0.01 and 300 K) did not show the same dependence. It was concluded that molecular statics as an energy minimization numerical scheme is quite insensitive to the instability of atomic structure especially without thermal fluctuation and might not be a suitable tool for studying the behaviour of nanomaterials beyond the elastic limit

  20. Study of transmission function and electronic transport in one dimensional silver nanowire: Ab-initio method using density functional theory (DFT)

    Science.gov (United States)

    Thakur, Anil; Kashyap, Rajinder

    2018-05-01

    Single nanowire electrode devices have their application in variety of fields which vary from information technology to solar energy. Silver nanowires, made in an aqueous chemical reduction process, can be reacted with gold salt to create bimetallic nanowires. Silver nanowire can be used as electrodes in batteries and have many other applications. In this paper we investigated structural and electronic transport properties of Ag nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Ag nanowire have been studied theoretically. First of all an optimized geometry for Ag 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 respectively. 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. Bulk properties of Ag are in agreement with experimental values which make the study of electronic and transport properties in silver nanowires interesting because they are promising materials as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Ag nano wire reveals that silver nanowire can be used as an electrode device.

  1. Zeeman perturbed nuclear quadrupole spin echo envelope modulations for spin 3/2 nuclei in polycrystalline specimens

    Science.gov (United States)

    Ramachandran, R.; Narasimhan, P. T.

    The results of theoretical and experimental studies of Zeeman-perturbed nuclear quadrupole spin echo envelope modulations (ZSEEM) for spin 3/2 nuclei in polycrystalline specimens are presented. The response of the Zeeman-perturbed spin ensemble to resonant two pulse excitations has been calculated using the density matrix formalism. The theoretical calculation assumes a parallel orientation of the external r.f. and static Zeeman fields and an arbitrary orientation of these fields to the principal axes system of the electric field gradient. A numerical powder averaging procedure has been adopted to simulate the response of the polycrystalline specimens. Using a coherent pulsed nuclear quadrupole resonance spectrometer the ZSEEM patterns of the 35Cl nuclei have been recorded in polycrystalline specimens of potassium chlorate, barium chlorate, mercuric chloride (two sites) and antimony trichloride (two sites) using the π/2-τ-π/2 sequence. The theoretical and experimental ZSEEM patterns have been compared. In the case of mercuric chloride, the experimental 35Cl ZSEEM patterns are found to be nearly identical for the two sites and correspond to a near-zero value of the asymmetry parameter, η, of the electric field gradient tensor. The difference in the η values for the two 35Cl sites (η ˜0·06 and η˜0·16) in antimony trichloride is clearly reflected in the experimental and theoretical ZSEEM patterns. The present study indicates the feasibility of evaluating η for spin 3/2 nuclei in polycrystalline specimens from ZSEEM investigations.

  2. Ion Beam Synthesis of Ge Nanowires. rev. ed.

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, T.

    2001-01-01

    The formation of Ge nanowires in V-grooves has been studied experimentally as well as theoretically. As substrate oxide covered Si V-grooves were used formed by anisotropic etching of (001)Si wafers and subsequent oxidation of their surface. Implantation of 1 x 10{sup 17} Ge{sup +}cm{sup -2} at 70 keV was carried out into the oxide layer covering the V-grooves. Ion irradiation induces shape changes of the V-grooves, which are captured in a novel continuum model of surface evolution. It describes theoretically the effects of sputtering, redeposition of sputtered atoms, and swelling. Thereby, the time evolution of the target surface is determined by a nonlinear integro-differential equation, which was solved numerically for the V-groove geometry. A very good agreement is achieved for the predicted surface shape and the shape observed in XTEM images. Surprisingly, the model predicts material (Si, O, Ge) transport into the V-groove bottom which also suggests an Ge accumulation there proven by STEM-EDX investigations. In this Ge rich bottom region, subsequent annealing in N{sub 2} atmosphere results in the formation of a nanowire by coalescence of Ge precipitates shown by XTEM images. The process of phase separation during the nanowire growth was studied by means of kinetic 3D lattice Monte-Carlo simulations. These simulations also indicate the disintegration of continuous wires into droplets mediated by thermal fluctuations. Energy considerations have identified a fragmentation threshold and a lower boundary for the droplet radii which were confirmed by the Monte Carlo simulation. The here given results indicate the possibility of achieving nanowires being several nanometers wide by further growth optimizations as well as chains of equally spaced clusters with nearly uniform diameter. (orig.)

  3. Plasmonic Properties of Vertically Aligned Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Hua Qi

    2012-01-01

    Full Text Available Nanowires (NWs/Ag sheath composites were produced to investigate plasmonic coupling between vertically aligned NWs for surface-enhanced Raman scattering (SERS applications. In this investigation, two types of vertical NW arrays were studied; those of ZnO NWs grown on nanosphere lithography patterned sapphire substrate via vapor-liquid-solid (VLS mechanism and Si NW arrays produced by wet chemical etching. Both types of vertical NW arrays were coated with a thin layer of silver by electroless silver plating for SERS enhancement studies. The experimental results show extremely strong SERS signals due to plasmonic coupling between the NWs, which was verified by COMSOL electric field simulations. We also compared the SERS enhancement intensity of aligned and random ZnO NWs, indicating that the aligned NWs show much stronger and repeatable SERS signal than those grown in nonaligned geometries.

  4. Quantum optics with nanowires (Conference Presentation)

    Science.gov (United States)

    Zwiller, Val

    2017-02-01

    Nanowires offer new opportunities for nanoscale quantum optics; the quantum dot geometry in semiconducting nanowires as well as the material composition and environment can be engineered with unprecedented freedom to improve the light extraction efficiency. Quantum dots in nanowires are shown to be efficient single photon sources, in addition because of the very small fine structure splitting, we demonstrate the generation of entangled pairs of photons from a nanowire. By doping a nanowire and making ohmic contacts on both sides, a nanowire light emitting diode can be obtained with a single quantum dot as the active region. Under forward bias, this will act as an electrically pumped source of single photons. Under reverse bias, an avalanche effect can multiply photocurrent and enables the detection of single photons. Another type of nanowire under study in our group is superconducting nanowires for single photon detection, reaching efficiencies, time resolution and dark counts beyond currently available detectors. We will discuss our first attempts at combining semiconducting nanowire based single photon emitters and superconducting nanowire single photon detectors on a chip to realize integrated quantum circuits.

  5. Polycrystalline Mg2Si thin films: A theoretical investigation of their electronic transport properties

    International Nuclear Information System (INIS)

    Balout, H.; Boulet, P.; Record, M.-C.

    2015-01-01

    The electronic structures and thermoelectric properties of a polycrystalline Mg 2 Si thin film have been investigated by first-principle density-functional theory (DFT) and Boltzmann transport theory calculations within the constant-relaxation time approximation. The polycrystalline thin film has been simulated by assembling three types of slabs each having the orientation (001), (110) or (111) with a thickness of about 18 Å. The effect of applying the relaxation procedure to the thin film induces disorder in the structure that has been ascertained by calculating radial distribution functions. For the calculations of the thermoelectric properties, the energy gap has been fixed at the experimental value of 0.74 eV. The thermoelectric properties, namely the Seebeck coefficient, the electrical conductivity and the power factor, have been determined at three temperatures of 350 K, 600 K and 900 K with respect to both the energy levels and the p-type and n-type doping levels. The best Seebeck coefficient is obtained at 350 K: the S yy component of the tensor amounts to about ±1000 μV K −1 , depending on the type of charge carriers. However, the electrical conductivity is much too small which results in low values of the figure of merit ZT. Structure–property relationship correlations based on directional radial distribution functions allow us to tentatively draw some explanations regarding the anisotropy of the electrical conductivity. Finally, the low ZT values obtained for the polycrystalline Mg 2 Si thin film are paralleled with those recently reported in the literature for bulk chalcogenide glasses. - Graphical abstract: Structure of the polycrystalline thin film of Mg 2 Si. - Author-Highlights: • Polycrystalline Mg 2 Si film has been modelled by DFT approach. • Thermoelectric properties have been evaluated by semi-classical Boltzmann theory. • The structure was found to be slightly disordered after relaxation. • The highest value of Seebeck

  6. 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...

  7. 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.

  8. 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.

  9. Biotemplated synthesis of PZT nanowires.

    Science.gov (United States)

    Cung, Kellye; Han, Booyeon J; Nguyen, Thanh D; Mao, Sheng; Yeh, Yao-Wen; Xu, Shiyou; Naik, Rajesh R; Poirier, Gerald; Yao, Nan; Purohit, Prashant K; McAlpine, Michael C

    2013-01-01

    Piezoelectric nanowires are an important class of smart materials for next-generation applications including energy harvesting, robotic actuation, and bioMEMS. Lead zirconate titanate (PZT), in particular, has attracted significant attention, owing to its superior electromechanical conversion performance. Yet, the ability to synthesize crystalline PZT nanowires with well-controlled properties remains a challenge. Applications of common nanosynthesis methods to PZT are hampered by issues such as slow kinetics, lack of suitable catalysts, and harsh reaction conditions. Here we report a versatile biomimetic method, in which biotemplates are used to define PZT nanostructures, allowing for rational control over composition and crystallinity. Specifically, stoichiometric PZT nanowires were synthesized using both polysaccharide (alginate) and bacteriophage templates. The wires possessed measured piezoelectric constants of up to 132 pm/V after poling, among the highest reported for PZT nanomaterials. Further, integrated devices can generate up to 0.820 μW/cm(2) of power. These results suggest that biotemplated piezoelectric nanowires are attractive candidates for stimuli-responsive nanosensors, adaptive nanoactuators, and nanoscale energy harvesters.

  10. Nanowire-based gas sensors

    NARCIS (Netherlands)

    Chen, X.; Wong, C.K.Y.; Yuan, C.A.; Zhang, G.

    2013-01-01

    Gas sensors fabricated with nanowires as the detecting elements are powerful due to their many improved characteristics such as high surface-to-volume ratios, ultrasensitivity, higher selectivity, low power consumption, and fast response. This paper gives an overview on the recent process of the

  11. Direct observation of current-induced motion of a 3D vortex domain wall in cylindrical nanowires

    KAUST Repository

    Ivanov, Yurii P.

    2017-05-08

    The current-induced dynamics of 3D magnetic vortex domain walls in cylindrical Co/Ni nanowires are revealed experimentally using Lorentz microscopy and theoretically using micromagnetic simulations. We demonstrate that a spin-polarized electric current can control the reversible motion of 3D vortex domain walls, which travel with a velocity of a few hundred meters per second. This finding is a key step in establishing fast, high-density memory devices based on vertical arrays of cylindrical magnetic nanowires.

  12. Direct observation of current-induced motion of a 3D vortex domain wall in cylindrical nanowires

    KAUST Repository

    Ivanov, Yurii P.; Chuvilin, Andrey; Lopatin, Sergei; Mohammed, Hanan; Kosel, Jü rgen

    2017-01-01

    The current-induced dynamics of 3D magnetic vortex domain walls in cylindrical Co/Ni nanowires are revealed experimentally using Lorentz microscopy and theoretically using micromagnetic simulations. We demonstrate that a spin-polarized electric current can control the reversible motion of 3D vortex domain walls, which travel with a velocity of a few hundred meters per second. This finding is a key step in establishing fast, high-density memory devices based on vertical arrays of cylindrical magnetic nanowires.

  13. Brittle-to-Ductile Transition in Metallic Glass Nanowires.

    Science.gov (United States)

    Şopu, D; Foroughi, A; Stoica, M; Eckert, J

    2016-07-13

    When reducing the size of metallic glass samples down to the nanoscale regime, experimental studies on the plasticity under uniaxial tension show a wide range of failure modes ranging from brittle to ductile ones. Simulations on the deformation behavior of nanoscaled metallic glasses report an unusual extended strain softening and are not able to reproduce the brittle-like fracture deformation as found in experiments. Using large-scale molecular dynamics simulations we provide an atomistic understanding of the deformation mechanisms of metallic glass nanowires and differentiate the extrinsic size effects and aspect ratio contribution to plasticity. A model for predicting the critical nanowire aspect ratio for the ductile-to-brittle transition is developed. Furthermore, the structure of brittle nanowires can be tuned to a softer phase characterized by a defective short-range order and an excess free volume upon systematic structural rejuvenation, leading to enhanced tensile ductility. The presented results shed light on the fundamental deformation mechanisms of nanoscaled metallic glasses and demarcate ductile and catastrophic failure.

  14. Nanojoining of crossed Ag nanowires: a molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Jianlei, E-mail: cjlxjtu@mail.xjtu.edu.cn; Wang, Xuewen; Barayavuga, Theogene; Mei, Xuesong; Wang, Wenjun [Xi’an Jiaotong University, State Key Laboratory for Manufacturing Systems Engineering (China); He, Xiaoqiao, E-mail: bcxqhe@cityu.edu.hk [City University of Hong Kong, Department of Architecture and Civil Engineering (Hong Kong)

    2016-07-15

    Ag nanowires are considered to be the promising candidates for future electronic circuit owing to the excellent electrical and thermal properties, with the miniaturization of electronics devices into nanometer scale. Though interconnect technology between Ag nanowires (Ag NWs) is essential for nanofunctional devices, it lacks sufficient experimental data. Besides, the determination of Ag NW interconnection configuration is experimentally difficult to do for lacking the sufficient investigation of atomic configuration evolution during nanojoining process. So the nanojoining between the crossed Ag NWs with the same diameter of 2 nm and different lengths was performed by molecular dynamics simulation to explain the unclear nanojoining mechanism based on thermal effect. As the simulation results present, when the nanojoining temperature is relatively high, though the Ag NWs are connected with the interpenetration effect of Ag atoms at the crossed nanojunction area, the nanostructures of Ag NWs have been seriously deformed with shorter length and larger diameter, showing relatively more obvious melting characteristics based on the chaotic atomic structures. If the temperature is reduced to 300 K as cold welding, the crossed Ag NWs can be partially contacted with the partial mixture of Ag atoms, and the interstices always exist between the Si surface and the upper Ag nanowire. In addition, the obvious dislocation phenomenon will appear and evolve as time goes on. Consequently, the dominant mechanism was revealed for providing a fundamental understanding of how ‘hot’ and ‘cold’ welding technology affects the atomic contact configuration, respectively.

  15. Understanding magnetotransport signatures in networks of connected permalloy nanowires

    Science.gov (United States)

    Le, B. L.; Park, J.; Sklenar, J.; Chern, G.-W.; Nisoli, C.; Watts, J. D.; Manno, M.; Rench, D. W.; Samarth, N.; Leighton, C.; Schiffer, P.

    2017-02-01

    The change in electrical resistance associated with the application of an external magnetic field is known as the magnetoresistance (MR). The measured MR is quite complex in the class of connected networks of single-domain ferromagnetic nanowires, known as "artificial spin ice," due to the geometrically induced collective behavior of the nanowire moments. We have conducted a thorough experimental study of the MR of a connected honeycomb artificial spin ice, and we present a simulation methodology for understanding the detailed behavior of this complex correlated magnetic system. Our results demonstrate that the behavior, even at low magnetic fields, can be well described only by including significant contributions from the vertices at which the legs meet, opening the door to new geometrically induced MR phenomena.

  16. Self-Assembled InAs Nanowires as Optical Reflectors

    Directory of Open Access Journals (Sweden)

    Francesco Floris

    2017-11-01

    Full Text Available Subwavelength nanostructured surfaces are realized with self-assembled vertically-aligned InAs nanowires, and their functionalities as optical reflectors are investigated. In our system, polarization-resolved specular reflectance displays strong modulations as a function of incident photon energy and angle. An effective-medium model allows one to rationalize the experimental findings in the long wavelength regime, whereas numerical simulations fully reproduce the experimental outcomes in the entire frequency range. The impact of the refractive index of the medium surrounding the nanostructure assembly on the reflectance was estimated. In view of the present results, sensing schemes compatible with microfluidic technologies and routes to innovative nanowire-based optical elements are discussed.

  17. Ultra compact triplexing filters based on SOI nanowire AWGs

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Jiashun; An Junming; Zhao Lei; Song Shijiao; Wang Liangliang; Li Jianguang; Wang Hongjie; Wu Yuanda; Hu Xiongwei, E-mail: junming@red.semi.ac.cn [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2011-04-15

    An ultra compact triplexing filter was designed based on a silicon on insulator (SOI) nanowire arrayed waveguide grating (AWG) for fiber-to-the-home FTTH. The simulation results revealed that the design performed well in the sense of having a good triplexing function. The designed SOI nanowire AWGs were fabricated using ultraviolet lithography and induced coupler plasma etching. The experimental results showed that the crosstalk was less than -15 dB, and the 3 dB-bandwidth was 11.04 nm. The peak wavelength output from ports a, c, and b were 1455, 1510 and 1300 nm, respectively, which deviated from our original expectations. The deviation of the wavelength is mainly caused by 45 nm width deviation of the arrayed waveguides during the course of the fabrication process and partly caused by material dispersion. (semiconductor devices)

  18. Ultra compact triplexing filters based on SOI nanowire AWGs

    International Nuclear Information System (INIS)

    Zhang Jiashun; An Junming; Zhao Lei; Song Shijiao; Wang Liangliang; Li Jianguang; Wang Hongjie; Wu Yuanda; Hu Xiongwei

    2011-01-01

    An ultra compact triplexing filter was designed based on a silicon on insulator (SOI) nanowire arrayed waveguide grating (AWG) for fiber-to-the-home FTTH. The simulation results revealed that the design performed well in the sense of having a good triplexing function. The designed SOI nanowire AWGs were fabricated using ultraviolet lithography and induced coupler plasma etching. The experimental results showed that the crosstalk was less than -15 dB, and the 3 dB-bandwidth was 11.04 nm. The peak wavelength output from ports a, c, and b were 1455, 1510 and 1300 nm, respectively, which deviated from our original expectations. The deviation of the wavelength is mainly caused by 45 nm width deviation of the arrayed waveguides during the course of the fabrication process and partly caused by material dispersion. (semiconductor devices)

  19. Ultra compact triplexing filters based on SOI nanowire AWGs

    Science.gov (United States)

    Jiashun, Zhang; Junming, An; Lei, Zhao; Shijiao, Song; Liangliang, Wang; Jianguang, Li; Hongjie, Wang; Yuanda, Wu; Xiongwei, Hu

    2011-04-01

    An ultra compact triplexing filter was designed based on a silicon on insulator (SOI) nanowire arrayed waveguide grating (AWG) for fiber-to-the-home FTTH. The simulation results revealed that the design performed well in the sense of having a good triplexing function. The designed SOI nanowire AWGs were fabricated using ultraviolet lithography and induced coupler plasma etching. The experimental results showed that the crosstalk was less than -15 dB, and the 3 dB-bandwidth was 11.04 nm. The peak wavelength output from ports a, c, and b were 1455, 1510 and 1300 nm, respectively, which deviated from our original expectations. The deviation of the wavelength is mainly caused by 45 nm width deviation of the arrayed waveguides during the course of the fabrication process and partly caused by material dispersion.

  20. Measurements of light absorption efficiency in InSb nanowires

    Directory of Open Access Journals (Sweden)

    A. Jurgilaitis

    2014-01-01

    Full Text Available We report on measurements of the light absorption efficiency of InSb nanowires. The absorbed 70 fs light pulse generates carriers, which equilibrate with the lattice via electron-phonon coupling. The increase in lattice temperature is manifested as a strain that can be measured with X-ray diffraction. The diffracted X-ray signal from the excited sample was measured using a streak camera. The amount of absorbed light was deduced by comparing X-ray diffraction measurements with simulations. It was found that 3.0(6% of the radiation incident on the sample was absorbed by the nanowires, which cover 2.5% of the sample.

  1. Suppression of tunneling leakage current in junctionless nanowire transistors

    International Nuclear Information System (INIS)

    Lou, Haijun; Li, Dan; Dong, Yan; Lin, Xinnan; He, Jin; Yang, Shengqi; Chan, Mansun

    2013-01-01

    In this paper, the characteristics of tunneling leakage current for the dual-material gate junctionless nanowire transistor (DMG-JNT) are investigated by three-dimensional numerical simulations and compared with conventional junctionless nanowire transistor (JNT). The suppression of the tunneling leakage current on the JNT by introducing an energy band step with the DMG structure is verified and presented for the first time. The effects of channel length on the DMG-JNT and the JNT are also studied. Results showed that the tunneling leakage current of the DMG-JNT is two orders smaller than that of the JNT, and further, the DMG-JNT exhibits superior scaling capability. Two key design parameters of the DMG-JNT, control gate ratio (Ra) and work function difference (δW), have been optimized and the optimal ranges of Ra and δW are pointed out. (paper)

  2. Suppression of tunneling leakage current in junctionless nanowire transistors

    Science.gov (United States)

    Lou, Haijun; Li, Dan; Dong, Yan; Lin, Xinnan; He, Jin; Yang, Shengqi; Chan, Mansun

    2013-12-01

    In this paper, the characteristics of tunneling leakage current for the dual-material gate junctionless nanowire transistor (DMG-JNT) are investigated by three-dimensional numerical simulations and compared with conventional junctionless nanowire transistor (JNT). The suppression of the tunneling leakage current on the JNT by introducing an energy band step with the DMG structure is verified and presented for the first time. The effects of channel length on the DMG-JNT and the JNT are also studied. Results showed that the tunneling leakage current of the DMG-JNT is two orders smaller than that of the JNT, and further, the DMG-JNT exhibits superior scaling capability. Two key design parameters of the DMG-JNT, control gate ratio (Ra) and work function difference (δW), have been optimized and the optimal ranges of Ra and δW are pointed out.

  3. Methodology for studying strain inhomogeneities in polycrystalline thin films during in situ thermal loading using coherent x-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Vaxelaire, N; Labat, S; Thomas, O [Aix-Marseille University, IM2NP, FST avenue Escadrille Normandie Niemen, F-13397 Marseille Cedex (France); Proudhon, H; Forest, S [MINES ParisTech, Centre des materiaux, CNRS UMR 7633, BP 87, 91003 Evry Cedex (France); Kirchlechner, C; Keckes, J [Erich Schmid Institute for Material Science, Austrian Academy of Science and Institute of Metal Physics, University of Leoben, Jahnstrasse 12, 8700 Leoben (Austria); Jacques, V; Ravy, S [Synchrotron SOLEIL, L' Orme des merisiers, Saint-Aubin BP 48, 91192 Gif-sur-Yvette Cedex (France)], E-mail: nicolas.vaxelaire@univ-cezanne.fr

    2010-03-15

    Coherent x-ray diffraction is used to investigate the mechanical properties of a single grain within a polycrystalline thin film in situ during a thermal cycle. Both the experimental approach and finite element simulation are described. Coherent diffraction from a single grain has been monitored in situ at different temperatures. This experiment offers unique perspectives for the study of the mechanical properties of nano-objects.

  4. Methodology for studying strain inhomogeneities in polycrystalline thin films during in situ thermal loading using coherent x-ray diffraction

    International Nuclear Information System (INIS)

    Vaxelaire, N; Labat, S; Thomas, O; Proudhon, H; Forest, S; Kirchlechner, C; Keckes, J; Jacques, V; Ravy, S

    2010-01-01

    Coherent x-ray diffraction is used to investigate the mechanical properties of a single grain within a polycrystalline thin film in situ during a thermal cycle. Both the experimental approach and finite element simulation are described. Coherent diffraction from a single grain has been monitored in situ at different temperatures. This experiment offers unique perspectives for the study of the mechanical properties of nano-objects.

  5. 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.

  6. Polycrystalline Materials as a Cold Neutron and Gamma Radiation Filter

    International Nuclear Information System (INIS)

    Habib, N.

    2009-01-01

    The total neutron cross-section of polycrystalline beryllium, graphite and iron has been calculated beyond their cut-off wavelength using a general formula. The computer Cold Filter code was developed in order to provide the required calculations. The code also permits the calculation of attenuation of reactor gamma radiation, The calculated neutron transmissions through polycrystalline Be graphite and iron at different temperatures were compared with the experimental data measured at the ETRR-1 reactor using two TOF spectrometers. An overall agreement is obtained between the formula fits and experimental data at different temperatures. A feasibility study is carried on using polycrystalline Be, graphite and iron an efficient filter for cold neutrons and gamma radiation.

  7. Spin-wave propagation spectrum in magnetization-modulated cylindrical nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhi-xiong; Wang, Meng-ning; Nie, Yao-zhuang; Wang, Dao-wei; Xia, Qing-lin [School of Physics and Electronics, Central South University, Changsha 410083 (China); Tang, Wei [School of Physics and Electronics, Central South University, Changsha 410083 (China); Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Zeng, Zhong-ming [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Guo, Guang-hua, E-mail: guogh@mail.csu.edu.cn [School of Physics and Electronics, Central South University, Changsha 410083 (China)

    2016-09-15

    Spin-wave propagation in periodic magnetization-modulated cylindrical nanowires is studied by micromagnetic simulation. Spin wave scattering at the interface of two magnetization segments causes a spin-wave band structure, which can be effectively tuned by changing either the magnetization modulation level or the period of the cylindrical nanowire magnonic crystal. The bandgap width is oscillating with either the period or magnetization modulation due to the oscillating variation of the spin wave transmission coefficient through the interface of the two magnetization segments. Analytical calculation based on band theory is used to account for the micromagnetic simulation results. - Highlights: • A magnetization-modulated cylindrical nanowire magnonic crystal is proposed. • Propagating characteristics of spin waves in such magnonic crystal are studied. • Spin-wave spectra can be manipulated by changing modulation level and period.

  8. Angular dependence of the magnetic properties of permalloy and nickel nanowires as a function of their diameters

    Science.gov (United States)

    Raviolo, Sofía; Tejo, Felipe; Bajales, Noelia; Escrig, Juan

    2018-01-01

    In this paper we have compared the angular dependence of the magnetic properties of permalloy (Ni80Fe20) and nickel nanowires by means of micromagnetic simulations. For each material we have chosen two diameters, 40 and 100 nm. Permalloy nanowires with smaller diameters (d = 40 nm) exhibit greater coercivity than nickel nanowires, regardless of the angle at which the external magnetic field is applied. In addition, both Py and Ni nanowires exhibit the same remanence values. However, the nanowires of larger diameters (d = 100 nm) exhibit a more complex behavior, noting that for small angles, nickel nanowires are those that now exhibit a greater coercivity in comparison to those of permalloy. The magnetization reversal modes vary as a function of the angle at which the external field is applied. When the field is applied parallel to the wire axis, it reverts through nucleation and propagation of domain walls, whereas when the field is applied perpendicular to the axis, it reverts by a pseudo-coherent rotation. These results may provide a guide to control the magnetic properties of nanowires for use in potential applications.

  9. New software to model energy dispersive X-ray diffraction in polycrystalline materials

    Energy Technology Data Exchange (ETDEWEB)

    Ghammraoui, B., E-mail: bahaa.ghammraoui@cea.fr [CEA-Leti, MINATEC Campus, 17 rue des Martyrs, F 38054 Grenoble, Cedex 9 (France); Tabary, J. [CEA-Leti, MINATEC Campus, 17 rue des Martyrs, F 38054 Grenoble, Cedex 9 (France); Pouget, S. [CEA-INAC Sciences de la matieres, 17 rue des Martyrs, F 38054 Grenoble, Cedex 9 (France); Paulus, C.; Moulin, V.; Verger, L. [CEA-Leti, MINATEC Campus, 17 rue des Martyrs, F 38054 Grenoble, Cedex 9 (France); Duvauchelle, Ph. [CNDRI-Insa Lyon, Universite de Lyon, F-69621, Villeurbanne Cedex (France)

    2012-02-01

    Detection of illicit materials, such as explosives or drugs, within mixed samples is a major issue, both for general security and as part of forensic analyses. In this paper, we describe a new code simulating energy dispersive X-ray diffraction patterns in polycrystalline materials. This program, SinFullscat, models diffraction of any object in any diffractometer system taking all physical phenomena, including amorphous background, into account. Many system parameters can be tuned: geometry, collimators (slit and cylindrical), sample properties, X-ray source and detector energy resolution. Good agreement between simulations and experimental data was obtained. Simulations using explosive materials indicated that parameters such as the diffraction angle or the energy resolution of the detector have a significant impact on the diffraction signature of the material inspected. This software will be a convenient tool to test many diffractometer configurations, providing information on the one that best restores the spectral diffraction signature of the materials of interest.

  10. Angular distributions of particles sputtered from polycrystalline platinum by low-energy ions

    International Nuclear Information System (INIS)

    Chernysh, V.S.; Eckstein, W.; Haidarov, A.A.; Kulikauskas, V.S.; Mashkova, E.S.; Molchanov, V.A.

    2000-01-01

    The results of an experimental study and a computer simulation with the TRIM.SP code of the angular distributions of atoms sputtered from polycrystalline platinum under 3-9 keV Ne + bombardment at normal ion incidence are presented. It was found that angular distributions of sputtered atoms are overcosine and that their shape is practically independent of an ion energy. Comparison with the previously obtained data for He + and Ar + ions have shown that the shape of the angular distribution does not depend on the bombarding ion species. Good agreement between experimental results and computer simulation data was found. Computer simulations of the partial angular distributions of Pt atoms ejected due to various sputtering mechanisms for Ne ion bombardment were performed and the comparison with corresponding data for He and Ar bombarding was made. The role of different mechanisms in the formation of angular distributions of sputtered atoms has been analyzed

  11. Nucleation and growth of polycrystalline SiC

    DEFF Research Database (Denmark)

    Kaiser, M.; Schimmel, S.; Jokubavicius, V.

    2014-01-01

    The nucleation and bulk growth of polycrystalline SiC in a 2 inch PVT setup using isostatic and pyrolytic graphite as substrates was studied. Textured nucleation occurs under near-thermal equilibrium conditions at the initial growth stage with hexagonal platelet shaped crystallites of 4H, 6H and 15......R polytypes. It is found that pyrolytic graphite results in enhanced texturing of the nucleating gas species. Reducing the pressure leads to growth of the crystallites until a closed polycrystalline SiC layer containing voids with a rough surface is developed. Bulk growth was conducted at 35 mbar Ar...

  12. Hall measurements and grain-size effects in polycrystalline silicon

    International Nuclear Information System (INIS)

    Ghosh, A.K.; Rose, A.; Maruska, H.P.; Eustace, D.J.; Feng, T.

    1980-01-01

    The effects of grain size on Hall measurements in polycrystalline silicon are analyzed and interpreted, with some modifications, using the model proposed by Bube. This modified model predicts that the measured effective Hall voltage is composed of components originating from the bulk and space-charge regions. For materials with large grain sizes, the carrier concentration is independent of the intergrain boundary barrier, whereas the mobility is dependent on it. However, for small grains, both the carrier density and mobility depend on the barrier. These predictions are consistent with experimental results of mm-size Wacker and μm-size neutron-transmutation-doped polycrystalline silicon

  13. Spectral response of a polycrystalline silicon solar cell

    International Nuclear Information System (INIS)

    Ba, B.; Kane, M.

    1994-10-01

    A theoretical study of the spectral response of a polycrystalline silicon n-p junction solar cell is presented. The case of a fibrously oriented grain structure, involving grain boundary recombination velocity and grain size effects is discussed. The contribution of the base region on the internal quantum efficiency Q int is computed for different grain sizes and grain boundary recombination velocities in order to examine their influence. Suggestions are also made for the determination of base diffusion length in polycrystalline silicon solar cells using the spectral response method. (author). 15 refs, 4 figs

  14. Software optimization for electrical conductivity imaging in polycrystalline diamond cutters

    Energy Technology Data Exchange (ETDEWEB)

    Bogdanov, G.; Ludwig, R. [Department of Electrical and Computer Engineering, Worcester Polytechnic Institute, 100 Institute Rd, Worcester, MA 01609 (United States); Wiggins, J.; Bertagnolli, K. [US Synthetic, 1260 South 1600 West, Orem, UT 84058 (United States)

    2014-02-18

    We previously reported on an electrical conductivity imaging instrument developed for measurements on polycrystalline diamond cutters. These cylindrical cutters for oil and gas drilling feature a thick polycrystalline diamond layer on a tungsten carbide substrate. The instrument uses electrical impedance tomography to profile the conductivity in the diamond table. Conductivity images must be acquired quickly, on the order of 5 sec per cutter, to be useful in the manufacturing process. This paper reports on successful efforts to optimize the conductivity reconstruction routine, porting major portions of it to NVIDIA GPUs, including a custom CUDA kernel for Jacobian computation.

  15. Development of surface relief on polycrystalline metals due to sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Voitsenya, V.S. [IPP NSC KIPT, 61108 Kharkov (Ukraine); Balden, M. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching (Germany); Bardamid, A.F. [Taras Shevchenko National University, 01033 Kiev (Ukraine); Bondarenko, V.N. [IPP NSC KIPT, 61108 Kharkov (Ukraine); Davis, J.W., E-mail: jwdavis@starfire.utias.utoronto.ca [University of Toronto Institute for Aerospace Studies, 4925 Dufferin St., Toronto, ON, Canada M3H5T6 (Canada); Konovalov, V.G.; Ryzhkov, I.V.; Skoryk, O.O.; Solodovchenko, S.I. [IPP NSC KIPT, 61108 Kharkov (Ukraine); Zhang-jian, Zhou [University of Science and Technology Beijing, Beijing 100 083 (China)

    2013-05-01

    The characteristics of surface microrelief that appear in sputtering experiments with polycrystalline metals of various grain sizes have been studied. Specimens with grain sizes varying from 30–70 nm in the case of crystallized amorphous alloys, to 1–3 μm for technical tungsten grade and 10–100 μm for recrystallized tungsten were investigated. A model is proposed for the development of roughness on polycrystalline metals which is based on the dependence of sputtering rate on crystal orientation. The results of the modeling are in good agreement with experiments showing that the length scale of roughness is much larger than the grain size.

  16. Laser induced single-crystal transition in polycrystalline silicon

    International Nuclear Information System (INIS)

    Vitali, G.; Bertolotti, M.; Foti, G.; Rimini, E.

    1978-01-01

    Transition to single crystal of polycrystalline Si material underlying a Si crystal substrate of 100 orientation was obtained via laser irradiation. The changes in the structure were analyzed by reflection high energy electron diffraction and by channeling effect technique using 2.0 MeV He Rutherford scattering. The power density required to induce the transition in a 4500 A thick polycrystalline layer is about 70 MW/cm 2 (50ns). The corresponding amorphous to single transition has a threshold of about 45 MW/cm 2 . (orig.) 891 HPOE [de

  17. 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)].

  18. 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.

  19. Electrical limit of silver nanowire electrodes: Direct measurement of the nanowire junction resistance

    KAUST Repository

    Selzer, Franz; Floresca, Carlo; Kneppe, David; Bormann, Ludwig; Sachse, Christoph; Weiß , Nelli; Eychmü ller, Alexander; Amassian, Aram; Mü ller-Meskamp, Lars; Leo, Karl

    2016-01-01

    We measure basic network parameters of silvernanowire (AgNW) networks commonly used as transparent conductingelectrodes in organic optoelectronic devices. By means of four point probing with nanoprobes, the wire-to-wire junction resistance and the resistance of single nanowires are measured. The resistanceRNW of a single nanowire shows a value of RNW=(4.96±0.18) Ω/μm. The junction resistanceRJ differs for annealed and non-annealed NW networks, exhibiting values of RJ=(25.2±1.9) Ω (annealed) and RJ=(529±239) Ω (non-annealed), respectively. Our simulation achieves a good agreement between the measured network parameters and the sheet resistanceRS of the entire network. Extrapolating RJ to zero, our study show that we are close to the electrical limit of the conductivity of our AgNW system: We obtain a possible RS reduction by only ≈20% (common RS≈10 Ω/sq). Therefore, we expect further performance improvements in AgNW systems mainly by increasing NW length or by utilizing novel network geometries.

  20. Electrical limit of silver nanowire electrodes: Direct measurement of the nanowire junction resistance

    KAUST Repository

    Selzer, Franz

    2016-04-19

    We measure basic network parameters of silvernanowire (AgNW) networks commonly used as transparent conductingelectrodes in organic optoelectronic devices. By means of four point probing with nanoprobes, the wire-to-wire junction resistance and the resistance of single nanowires are measured. The resistanceRNW of a single nanowire shows a value of RNW=(4.96±0.18) Ω/μm. The junction resistanceRJ differs for annealed and non-annealed NW networks, exhibiting values of RJ=(25.2±1.9) Ω (annealed) and RJ=(529±239) Ω (non-annealed), respectively. Our simulation achieves a good agreement between the measured network parameters and the sheet resistanceRS of the entire network. Extrapolating RJ to zero, our study show that we are close to the electrical limit of the conductivity of our AgNW system: We obtain a possible RS reduction by only ≈20% (common RS≈10 Ω/sq). Therefore, we expect further performance improvements in AgNW systems mainly by increasing NW length or by utilizing novel network geometries.

  1. X-ray diffraction analysis of InAs nanowires

    International Nuclear Information System (INIS)

    Davydok, Anton

    2013-01-01

    Si substrate. MBE provides the opportunity to combine a group III-V material with nearly any semiconductor substrate independent from lattice mismatch. Vertically aligned nanowire ensembles were studied performing X-ray diffraction experiments in different scattering geometries. Considering the nanowires are composed by structural units of zinc-blende and wurtzite the latter one was found to be affected by a high density of stacking faults already at nanowires with short growth time. The stacking faults density was estimated by Monte-Carlo simulations based on model of ensemble average. A strong signal of unique zinc-blende reflection was observed as well. Coherent X-ray diffraction experiments with the use of a nano-focus setup have shown 'bar-code' patterning due to stacking fault arrangement within the nanowire. The found highly defective structure cannot be attributed to wurtzite or zinc-blende phases alone. Also parasitic islands were found on the samples surfaces and characterized as pure zinc-blende objects.

  2. The three-dimensional microstructure of polycrystalline materials unravelled by synchrotron light

    DEFF Research Database (Denmark)

    Ludwig, W.; King, A.; Herbig, M.

    2011-01-01

    The three-dimensional microstructure of polycrystalline materials unravelled by synchrotron light Synchrotron radiation X-ray imaging and diffraction techniques offer new possibilities for non-destructive bulk characterization of polycrystalline materials. Minute changes in electron density (diff...

  3. Functionalization of silicon nanowire surfaces with metal-organic frameworks

    KAUST Repository

    Liu, Nian

    2011-12-28

    Metal-organic frameworks (MOFs) and silicon nanowires (SiNWs) have been extensively studied due to their unique properties; MOFs have high porosity and specific surface area with well-defined nanoporous structure, while SiNWs have valuable one-dimensional electronic properties. Integration of the two materials into one composite could synergistically combine the advantages of both materials and lead to new applications. We report the first example of a MOF synthesized on surface-modified SiNWs. The synthesis of polycrystalline MOF-199 (also known as HKUST-1) on SiNWs was performed at room temperature using a step-by-step (SBS) approach, and X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy elemental mapping were used to characterize the material. Matching of the SiNW surface functional groups with the MOF organic linker coordinating groups was found to be critical for the growth. Additionally, the MOF morphology can by tuned by changing the soaking time, synthesis temperature and precursor solution concentration. This SiNW/MOF hybrid structure opens new avenues for rational design of materials with novel functionalities. © 2011 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

  4. PREFACE: Synthesis and integration of nanowires

    Science.gov (United States)

    Samuelson, L.

    2006-06-01

    The field of semiconductor nanowires has attracted much attention in recent years, from the areas of basic materials science, advanced characterization and technology, as well as from the perspective of the applications of nanowires. Research on large-sized whiskers and wires had already begun in the 1960s with the pioneering work of Wagner, as well as by other researchers. It was, however, in the early 1990s that Kenji Hiruma at Hitachi Central Research Laboratories in Japan first succeeded in developing methods for the growth of nanowires with dimensions on the scale of 10-100 nm, thereby initiating the field of growth and applications of nanowires, with a strong emphasis on epitaxial nucleation of nanowires on a single-crystalline substrate. Starting from the mid-1990s, the field developed very rapidly with the number of papers on the subject growing from ten per year to several thousand papers on the subject published annually today, although with a rather generous definition of the concept of nanowires. With this rapid development we have seen many new and different approaches to the growth of nanowires, technological advances leading to a more well-controlled formation of nanowires, new innovative methods for the characterization of structures, as well as a wealth of approaches towards the use of nanowires in electronics, photonics and sensor applications. This issue contains contributions from many different laboratories, each adding significant detail to the development of the field of research. The contributions cover issues such as basic growth, advanced characterization and technology, and application of nanowires. I would like to acknowledge the shared responsibilities for this special issue of Nanotechnology on the synthesis and integration of nanowires with my co-Editors, S Tong Lee and M Sunkara, as well as the highly professional support from Dr Nina Couzin, Dr Ian Forbes and the Nanotechnology team from the Institute of Physics Publishing.

  5. Observations of Fabric Development in Polycrystalline Ice at Basal Pressures: Methods and Initial Results

    Science.gov (United States)

    Breton, D. J.; Baker, I.; Cole, D. M.

    2012-12-01

    Understanding and predicting the flow of polycrystalline ice is crucial to ice sheet modeling and paleoclimate reconstruction from ice cores. Ice flow rates depend strongly on the fabric (i.e. the distribution of grain sizes and crystallographic orientations) which evolves over time and enhances the flow rate in the direction of applied stress. The mechanisms for fabric evolution in ice have been extensively studied at atmospheric pressures, but little work has been done to observe these processes at the high pressures experienced deep within ice sheets where long-term changes in ice rheology are expected to have significance. We conducted compressive creep tests on a 917 kg m-3 polycrystalline ice specimen at 20 MPa hydrostatic pressure, thus simulating ~2,000 m depth. Initial specimen grain orientations were random, typical grain diameters were 1.2 mm, and the applied creep stress was 0.3 MPa. Subsequent microstructural analyses on the deformed specimen and a similarly prepared, undeformed specimen allowed characterization of crystal fabric evolution under pressure. Our microstructural analysis technique simultaneously collected grain shape and size data from Scanning Electron Microscope (SEM) micrographs and obtained crystallographic orientation data via Electron BackScatter Diffraction (EBSD). Combining these measurements allows rapid analysis of the ice fabric over large numbers of grains, yielding statistically useful numbers of grain size and full c- and a-axis grain orientation data. The combined creep and microstructural data demonstrate pressure-dependent effects on the mechanical and microstructural evolution of polycrystalline ice. We discuss possible mechanisms for the observed phenomena, and future directions for hydrostatic creep testing.

  6. Analysis of twelve-month degradation in three polycrystalline photovoltaic modules

    Science.gov (United States)

    Lai, T.; Potter, B. G.; Simmons-Potter, K.

    2016-09-01

    Polycrystalline silicon photovoltaic (PV) modules have the advantage of lower manufacturing cost as compared to their monocrystalline counterparts, but generally exhibit both lower initial module efficiencies and more significant early-stage efficiency degradation than do similar monocrystalline PV modules. For both technologies, noticeable deterioration in power conversion efficiency typically occurs over the first two years of usage. Estimating PV lifetime by examining the performance degradation behavior under given environmental conditions is, therefore, one of continual goals for experimental research and economic analysis. In the present work, accelerated lifecycle testing (ALT) on three polycrystalline PV technologies was performed in a full-scale, industrial-standard environmental chamber equipped with single-sun irradiance capability, providing an illumination uniformity of 98% over a 2 x 1.6m area. In order to investigate environmental aging effects, timedependent PV performance (I-V characteristic) was evaluated over a recurring, compressed day-night cycle, which simulated local daily solar insolation for the southwestern United States, followed by dark (night) periods. During a total test time of just under 4 months that corresponded to a year equivalent exposure on a fielded module, the temperature and humidity varied in ranges from 3°C to 40°C and 5% to 85% based on annual weather profiles for Tucson, AZ. Removing the temperature de-rating effect that was clearly seen in the data enabled the computation of normalized efficiency degradation with time and environmental exposure. Results confirm the impact of environmental conditions on the module long-term performance. Overall, more than 2% efficiency degradation in the first year of usage was observed for all thee polycrystalline Si solar modules. The average 5-year degradation of each PV technology was estimated based on their determined degradation rates.

  7. Electrical Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide

    Science.gov (United States)

    2014-07-14

    Lou, Sina Najmaei, Matin Amani, Matthew L. Chin, Zheng Se. TASK NUMBER Liu Sf. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAMES AND ADDRESSES 8...Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide Sina Najmaei,t.§ Matin Ama ni,M Matthew L. Chin,* Zhe ng liu/ ·"·v: A. Gle n

  8. Electroreduction of CO on Polycrystalline Copper at Low Overpotentials

    DEFF Research Database (Denmark)

    Bertheussen, Erlend; Vagn Hogg, Thomas; Abghoui, Younes

    2018-01-01

    C uis the only monometallic electrocatalyst to produce highly reduced products from CO2 selectively because of its intermediate binding of CO. We investigate the performance of polycrystalline Cu for the electroreduction of CO in alkaline media (0.1 M KOH) at low overpotentials (−0.4 to −0.6 V vs...

  9. A study of ultrasonic velocity and attenuation on polycrystalline Ni ...

    Indian Academy of Sciences (India)

    Unknown

    tion of Fe3O4 particles at 800°C. Industrial grade particles of Ni and Zn oxides were ..... domain wall movements, which leads to electronic migrations: this can ... properties of polycrystalline Mn–Zn Ferrites, Ph.D. Thesis,. Osmania University ...

  10. Influence of hydrogen on high cycle fatigue of polycrystalline vanadium

    International Nuclear Information System (INIS)

    Chung, D.W.; Lee, K.S.; Stoloff, N.S.

    1977-02-01

    The room temperature fatigue behavior of several polycrystalline V-H 2 alloys is described. Hydrogen extends the life of unnotched vanadium but has a deleterious effect in notched materials. Crack propagation data are correlated with tensile yield stress and cyclic strain hardening data

  11. MOLECULAR DOCKING AND DYNAMICS STUDIES ON THE PROTEIN-PROTEIN INTERACTIONS OF ELECTRICALLY ACTIVE PILIN NANOWIRES OF GEOBACTER SULFURREDUCENS.

    Directory of Open Access Journals (Sweden)

    D. Jeya Sundara Sharmila1 *

    2017-06-01

    Full Text Available Molecular interactions are key aspects in biological recognitions applicable in nano/micro systems. Bacterial nanowires are pilus filament based structures that can conduct electrons. The transport of electron is proposed to be facilitated by filamentous fibers made up of polymeric assemblies of proteins called pilin. Geobacter sulfurreducens is capable of delivering electrons through extracellular electron transport (EET by employing conductive nanowires, which are pilin proteins composed of type IV subunit PilA. Protein-protein interactions play an important role in the stabilization of the pilin nanowire assembly complex and it contains transmembrane (TM domain. In current study, protein-protein docking and multiple molecular dynamic (MD simulations were performed to understand the binding mode of pilin nanowires. The MD result explains the conformational behavior and folding of pilin nanowires in water environment in different time scale duration 20, 5, 5, 10 and 20ns (total of 60ns. Direct hydrogen bonds and water mediated hydrogen bonds that play a crucial role during the simulation were investigated. The conformational state, folding, end-toend distance profile and hydrogen bonding behavior had indicated that the Geobacter sulfurreducens pilin nanowires have electrical conductivity properties.

  12. 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.

  13. Selective growth of gallium nitride nanowires by femtosecond laser patterning

    Energy Technology Data Exchange (ETDEWEB)

    Ng, D.K.T. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Data Storage Institute, Agency for Science, Technology and Research, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore); Hong, M.H. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Data Storage Institute, Agency for Science, Technology and Research, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore)], E-mail: HONG_Minghui@dsi.a-star.edu.sg; Tan, L.S. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Zhou, Y. [Data Storage Institute, Agency for Science, Technology and Research, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore); Department of Mechanical Engineering, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Chen, G.X. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore)

    2008-01-31

    We report on gallium nitride (GaN) nanowires grown using pulsed laser ablation, adopting the vapor-liquid-solid (VLS) growth mechanism. The GaN nanowires are obtained based on the principle that a catalyst is required to initiate the nanowires growth. Locations of the GaN nanowires are patterned using femtosecond laser and focused ion beam. Scanning electron microscopy (SEM) is used to characterize the nanowires. This patterning of GaN nanowires will enable selective growth of nanowires and bottom-up assembly of integrated electronic and photonic devices.

  14. Nanowire sensors and arrays for chemical/biomolecule detection

    Science.gov (United States)

    Yun, Minhee; Lee, Choonsup; Vasquez, Richard P.; Ramanathan, K.; Bangar, M. A.; Chen, W.; Mulchandan, A.; Myung, N. V.

    2005-01-01

    We report electrochemical growth of single nanowire based sensors using e-beam patterned electrolyte channels, potentially enabling the controlled fabrication of individually addressable high density arrays. The electrodeposition technique results in nanowires with controlled dimensions, positions, alignments, and chemical compositions. Using this technique, we have fabricated single palladium nanowires with diameters ranging between 75 nm and 300 nm and conducting polymer nanowires (polypyrrole and polyaniline) with diameters between 100 nm and 200 nm. Using these single nanowires, we have successfully demonstrated gas sensing with Pd nanowires and pH sensing with polypirrole nanowires.

  15. Selective growth of gallium nitride nanowires by femtosecond laser patterning

    International Nuclear Information System (INIS)

    Ng, D.K.T.; Hong, M.H.; Tan, L.S.; Zhou, Y.; Chen, G.X.

    2008-01-01

    We report on gallium nitride (GaN) nanowires grown using pulsed laser ablation, adopting the vapor-liquid-solid (VLS) growth mechanism. The GaN nanowires are obtained based on the principle that a catalyst is required to initiate the nanowires growth. Locations of the GaN nanowires are patterned using femtosecond laser and focused ion beam. Scanning electron microscopy (SEM) is used to characterize the nanowires. This patterning of GaN nanowires will enable selective growth of nanowires and bottom-up assembly of integrated electronic and photonic devices

  16. Enhanced photovoltaic performance of an inclined nanowire array solar cell.

    Science.gov (United States)

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

    2015-11-30

    An innovative solar cell based on inclined p-i-n nanowire array is designed and analyzed. The results show that the inclined geometry can sufficiently increase the conversion efficiency of solar cells by enhancing the absorption of light in the active region. By tuning the nanowire array density, nanowire diameter, nanowire length, as well as the proportion of intrinsic region of the inclined nanowire solar cell, a remarkable efficiency in excess of 16% can be obtained in GaAs. Similar results have been obtained in InP and Si nanowire solar cells, demonstrating the universality of the performance enhancement of inclined nanowire arrays.

  17. Electrochemically synthesized amorphous and crystalline nanowires: dissimilar nanomechanical behavior in comparison with homologous flat films

    Science.gov (United States)

    Zeeshan, M. A.; Esqué-de Los Ojos, D.; Castro-Hartmann, P.; Guerrero, M.; Nogués, J.; Suriñach, S.; Baró, M. D.; Nelson, B. J.; Pané, S.; Pellicer, E.; Sort, J.

    2016-01-01

    The effects of constrained sample dimensions on the mechanical behavior of crystalline materials have been extensively investigated. However, there is no clear understanding of these effects in nano-sized amorphous samples. Herein, nanoindentation together with finite element simulations are used to compare the properties of crystalline and glassy CoNi(Re)P electrodeposited nanowires (φ ~ 100 nm) with films (3 μm thick) of analogous composition and structure. The results reveal that amorphous nanowires exhibit a larger hardness, lower Young's modulus and higher plasticity index than glassy films. Conversely, the very large hardness and higher Young's modulus of crystalline nanowires are accompanied by a decrease in plasticity with respect to the homologous crystalline films. Remarkably, proper interpretation of the mechanical properties of the nanowires requires taking the curved geometry of the indented surface and sink-in effects into account. These findings are of high relevance for optimizing the performance of new, mechanically-robust, nanoscale materials for increasingly complex miniaturized devices.The effects of constrained sample dimensions on the mechanical behavior of crystalline materials have been extensively investigated. However, there is no clear understanding of these effects in nano-sized amorphous samples. Herein, nanoindentation together with finite element simulations are used to compare the properties of crystalline and glassy CoNi(Re)P electrodeposited nanowires (φ ~ 100 nm) with films (3 μm thick) of analogous composition and structure. The results reveal that amorphous nanowires exhibit a larger hardness, lower Young's modulus and higher plasticity index than glassy films. Conversely, the very large hardness and higher Young's modulus of crystalline nanowires are accompanied by a decrease in plasticity with respect to the homologous crystalline films. Remarkably, proper interpretation of the mechanical properties of the nanowires

  18. Threshold switching uniformity in In2Se3 nanowire-based phase change memory

    International Nuclear Information System (INIS)

    Chen Jian; Du Gang; Liu Xiao-Yan

    2015-01-01

    The uniformity of threshold voltage and threshold current in the In 2 Se 3 nanowire-based phase change memory (PCM) devices is investigated. Based on the trap-limited transport model, amorphous layer thickness, trap density, and trap depth are considered to clarify their influences upon the threshold voltage and threshold current through simulations. (paper)

  19. 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.

  20. Nanowire sensor, sensor array, and method for making the same

    Science.gov (United States)

    Yun, Minhee (Inventor); Myung, Nosang (Inventor); Vasquez, Richard (Inventor); Homer, Margie (Inventor); Ryan, Margaret (Inventor); Yen, Shiao-Pin (Inventor); Fleurial, Jean-Pierre (Inventor); Bugga, Ratnakumar (Inventor); Choi, Daniel (Inventor); Goddard, William (Inventor)

    2012-01-01

    The present invention relates to a nanowire sensor and method for forming the same. More specifically, the nanowire sensor comprises at least one nanowire formed on a substrate, with a sensor receptor disposed on a surface of the nanowire, thereby forming a receptor-coated nanowire. The nanowire sensor can be arranged as a sensor sub-unit comprising a plurality of homogeneously receptor-coated nanowires. A plurality of sensor subunits can be formed to collectively comprise a nanowire sensor array. Each sensor subunit in the nanowire sensor array can be formed to sense a different stimulus, allowing a user to sense a plurality of stimuli. Additionally, each sensor subunit can be formed to sense the same stimuli through different aspects of the stimulus. The sensor array is fabricated through a variety of techniques, such as by creating nanopores on a substrate and electrodepositing nanowires within the nanopores.

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

    KAUST Repository

    Mohammed, Hanan; Corte-Leon, H.; Ivanov, Yurii P.; Moreno, J. A.; Kazakova, O.; Kosel, Jü rgen

    2017-01-01

    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.

  2. Study on the Effect of Diamond Grain Size on Wear of Polycrystalline Diamond Compact Cutter

    Science.gov (United States)

    Abdul-Rani, A. M.; Che Sidid, Adib Akmal Bin; Adzis, Azri Hamim Ab

    2018-03-01

    Drilling operation is one of the most crucial step in oil and gas industry as it proves the availability of oil and gas under the ground. Polycrystalline Diamond Compact (PDC) bit is a type of bit which is gaining popularity due to its high Rate of Penetration (ROP). However, PDC bit can easily wear off especially when drilling hard rock. The purpose of this study is to identify the relationship between the grain sizes of the diamond and wear rate of the PDC cutter using simulation-based study with FEA software (ABAQUS). The wear rates of a PDC cutter with a different diamond grain sizes were calculated from simulated cuttings of cutters against granite. The result of this study shows that the smaller the diamond grain size, the higher the wear resistivity of PDC cutter.

  3. Thermal characterization of polycrystalline diamond thin film heat spreaders grown on GaN HEMTs

    Science.gov (United States)

    Zhou, Yan; Ramaneti, Rajesh; Anaya, Julian; Korneychuk, Svetlana; Derluyn, Joff; Sun, Huarui; Pomeroy, James; Verbeeck, Johan; Haenen, Ken; Kuball, Martin

    2017-07-01

    Polycrystalline diamond (PCD) was grown onto high-k dielectric passivated AlGaN/GaN-on-Si high electron mobility transistor (HEMT) structures, with film thicknesses ranging from 155 to 1000 nm. Transient thermoreflectance results were combined with device thermal simulations to investigate the heat spreading benefit of the diamond layer. The observed thermal conductivity (κDia) of PCD films is one-to-two orders of magnitude lower than that of bulk PCD and exhibits a strong layer thickness dependence, which is attributed to the grain size evolution. The films exhibit a weak temperature dependence of κDia in the measured 25-225 °C range. Device simulation using the experimental κDia and thermal boundary resistance values predicts at best a 15% reduction in peak temperature when the source-drain opening of a passivated AlGaN/GaN-on-Si HEMT is overgrown with PCD.

  4. Electron Transport Properties of Ge nanowires

    Science.gov (United States)

    Hanrath, Tobias; Khondaker, Saiful I.; Yao, Zhen; Korgel, Brian A.

    2003-03-01

    Electron Transport Properties of Ge nanowires Tobias Hanrath*, Saiful I. Khondaker, Zhen Yao, Brian A. Korgel* *Dept. of Chemical Engineering, Dept. of Physics, Texas Materials Institute, and Center for Nano- and Molecular Science and Technology University of Texas at Austin, Austin, Texas 78712-1062 e-mail: korgel@mail.che.utexas.edu Germanium (Ge) nanowires with diameters ranging from 6 to 50 nm and several micrometer in length were grown via a supercritical fluid-liquid-solid synthesis. Parallel electron energy loss spectroscopy (PEELS) was employed to study the band structure and electron density in the Ge nanowires. The observed increase in plasmon peak energy and peak width with decreasing nanowire diameter is attributed to quantum confinement effects. For electrical characterization, Ge nanowires were deposited onto a patterned Si/SiO2 substrate. E-beam lithography was then used to form electrode contacts to individual nanowires. The influence of nanowire diameter, surface chemistry and crystallographic defects on electron transport properties were investigated and the comparison of Ge nanowire conductivity with respect to bulk, intrinsic Ge will be presented.

  5. 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)

  6. Epitaxy of advanced nanowire quantum devices

    NARCIS (Netherlands)

    Gazibegovic, S.; Car, D.; Zhang, H.; Balk, S.C.; Logan, J.A.; De Moor, M.W.A.; Cassidy, M.C.; Schmits, R.; Xu, D.; Wang, G.; Krogstrup, P.; Op Het Veld, R.L.M.; Zuo, K.; Vos, Y.; Shen, J.; Bouman, D.; Shojaei, B.; Pennachio, D.; Lee, J.S.; van Veldhoven, P.J.; Koelling, S.; Verheijen, M.A.; Kouwenhoven, L.P.; Palmstrøm, C.J.; Bakkers, E.P.A.M.

    2017-01-01

    Semiconductor nanowires are ideal for realizing various low-dimensional quantum devices. In particular, topological phases of matter hosting non-Abelian quasiparticles (such as anyons) can emerge when a semiconductor nanowire with strong spin-orbit coupling is brought into contact with a

  7. 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...

  8. 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 ...

  9. 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.

  10. Microstructural effects on the magnetic and magneto-transport properties of electrodeposited Ni nanowire arrays

    International Nuclear Information System (INIS)

    Chen, Shu-Fang; Wei, Hao Han; Liu, Chuan-Pu; Hsu, C Y; Huang, J C A

    2010-01-01

    The magnetic and magneto-transport properties of Ni nanowire (NW) arrays, fabricated by electrodeposition in anodic-aluminum-oxide (AAO) templates, have been investigated. The AAO pores have diameters ranging from 35 to 75 nm, and the crystallinity of the Ni NW arrays could change from poly-crystalline to single-crystalline with the [111] and [110] orientations based on the electrodeposition potential. Notably, double switching magnetization loops and double-peaked magnetoresistance curves were observed in [110]-oriented NWs. The crystalline orientation of the Ni NW arrays is found to influence the corresponding magnetic and magneto-transport properties significantly. These magnetic behaviors are dominated by the competition between the magneto-crystalline and shape anisotropy.

  11. Controlling the plasmonic surface waves of metallic nanowires by transformation optics

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yichao; Yuan, Jun; Yin, Ge; Ma, Yungui, E-mail: yungui@zju.edu.cn [State Key Laboratory of Modern Optical Instrumentation, Centre for Optical and Electromagnetic Research, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310058 (China); He, Sailing [State Key Laboratory of Modern Optical Instrumentation, Centre for Optical and Electromagnetic Research, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310058 (China); Department of Electromagnetic Engineering, School of Electrical Engineering, Royal Institute of Technology, S-100 44 Stockholm (Sweden)

    2015-07-06

    In this letter, we introduce the technique of using transformation optics to manipulate the mode states of surface plasmonic waves of metallic nanowire waveguides. As examples we apply this technique to design two optical components: a three-dimensional (3D) electromagnetic mode rotator and a mode convertor. The rotator can rotate the polarization state of the surface wave around plasmonic nanowires by arbitrarily desired angles, and the convertor can transform the surface wave modes from one to another. Full-wave simulation is performed to verify the design and efficiency of our devices. Their potential application in photonic circuits is envisioned.

  12. Transformation of bulk alloys to oxide nanowires

    Science.gov (United States)

    Lei, Danni; Benson, Jim; Magasinski, Alexandre; Berdichevsky, Gene; Yushin, Gleb

    2017-01-01

    One dimensional (1D) nanostructures offer prospects for enhancing the electrical, thermal, and mechanical properties of a broad range of functional materials and composites, but their synthesis methods are typically elaborate and expensive. We demonstrate a direct transformation of bulk materials into nanowires under ambient conditions without the use of catalysts or any external stimuli. The nanowires form via minimization of strain energy at the boundary of a chemical reaction front. We show the transformation of multimicrometer-sized particles of aluminum or magnesium alloys into alkoxide nanowires of tunable dimensions, which are converted into oxide nanowires upon heating in air. Fabricated separators based on aluminum oxide nanowires enhanced the safety and rate capabilities of lithium-ion batteries. The reported approach allows ultralow-cost scalable synthesis of 1D materials and membranes.

  13. Nanowire-decorated microscale metallic electrodes

    DEFF Research Database (Denmark)

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

    2008-01-01

    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...... 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......-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....

  14. 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.

  15. Preparation and Characterization of Tin Oxide Nanowires

    Directory of Open Access Journals (Sweden)

    A. Kabiri

    2013-12-01

    Full Text Available The aim of this research is preparation of SnO2 nanowires by means of Thermal chemical reaction vapor transport deposition (TCRVTD method from SnO powders. The morphology, chemical composition and microstructure properties of the nanowires are characterized using field emission scanning electron microscope (FE-SEM, EDS, and XRD. The XRD diffraction patterns reveal that the SnO2 nanowires have been grown in the form of tetragonal crystal structures with the lattice parameter of a=b=0.440 nm, and c=0.370 nm. The SEM images reveal that SnO2 nanowires have successfully been grown on the Si substrate. The EDS patterns show that only elements of Sn, O and Au are detected. Prior to the VLS process the substrate is coated by a thin layer of Au. The diameter of nanowires is measured to be something between 20-100 nm.

  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. 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.

  18. GaAs nanowire array solar cells with axial p-i-n junctions.

    Science.gov (United States)

    Yao, Maoqing; Huang, Ningfeng; Cong, Sen; Chi, Chun-Yung; Seyedi, M Ashkan; Lin, Yen-Ting; Cao, Yu; Povinelli, Michelle L; Dapkus, P Daniel; Zhou, Chongwu

    2014-06-11

    Because of unique structural, optical, and electrical properties, solar cells based on semiconductor nanowires are a rapidly evolving scientific enterprise. Various approaches employing III-V nanowires have emerged, among which GaAs, especially, is under intense research and development. Most reported GaAs nanowire solar cells form p-n junctions in the radial direction; however, nanowires using axial junction may enable the attainment of high open circuit voltage (Voc) and integration into multijunction solar cells. Here, we report GaAs nanowire solar cells with axial p-i-n junctions that achieve 7.58% efficiency. Simulations show that axial junctions are more tolerant to doping variation than radial junctions and lead to higher Voc under certain conditions. We further study the effect of wire diameter and junction depth using electrical characterization and cathodoluminescence. The results show that large diameter and shallow junctions are essential for a high extraction efficiency. Our approach opens up great opportunity for future low-cost, high-efficiency photovoltaics.

  19. Magnetic properties of mosaic nanocomposites composed of nickel and cobalt nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Castillo-Sepúlveda, S.; Corona, R.M. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Altbir, D. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), 9170124 Santiago (Chile); Escrig, J., E-mail: juan.escrig@usach.cl [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), 9170124 Santiago (Chile)

    2016-10-15

    Mosaic nanocomposites composed of nickel and cobalt nanowires arranged in different configurations were investigated using Monte Carlo simulations and a simple model that considers single-domain structures including length corrections due to the shape anisotropy. Our results showed that for an ordered array both the coercivity and the remanence decrease linearly as a function of the concentration of nickel nanowires. Besides, we obtained that the magnetic properties of an array of a certain hard magnetic material (cobalt) will not change, unless we have more than 50% of nanowires of other soft magnetic material (nickel) in the array. In principle the second material could be other soft magnetic material, but could also be a nonmagnetic material or could even be a situation in which some of the pore arrays were not filled by electrodeposition. Therefore, our results allow us to predict the behavior of magnetic mosaic nanocomposites that are promising candidates for functional electrodes, sensors, and model catalysts. - Highlights: • Mosaic nanocomposites composed of magnetic nanowires were investigated. • Magnetic properties can be adjusted by varying the concentration of nanowires. • Our results allow us to predict the behavior of magnetic mosaic nanocomposites.

  20. Low-temperature-cured highly conductive composite of Ag nanowires and polyvinyl alcohol

    International Nuclear Information System (INIS)

    He Song; Zhang Xiang; Yang Bingchu; Xu Xiaomei; Chen Hui; Zhou Conghua

    2017-01-01

    Flexible conductive films were fabricated from a low-temperature-cured, highly conductive composite of silver nanowires (as conducting filler) and polyvinyl alcohol (PVA, as binder). Sheet resistance of 0.12 Ω/sq, conductivity of 2.63×10 4 S/cm, and contact resistance of 1.0 Ω/cm 2 were measured in the films, along with excellent resistance to scratching and good flexibility, making them suitable electrical contact materials for flexible optoelectronic devices. Effects of curing temperature, curing duration, film thickness, and nanowire length on the film’s electrical properties were studied. Due to the abundance of hydroxyl groups on its molecular chains, the addition of PVA improves the film’s flexibility and resistance to scratching. Increased nanowire density and nanowire length benefit film conductance. Monte Carlo simulation was used to further explore the impact of these two parameters on the conductivity. It was observed that longer nanowires produce a higher length-ratio of conducting routes in the networks, giving better film conductivity. (paper)

  1. Influence factors of the inter-nanowire thermal contact resistance in the stacked nanowires

    Science.gov (United States)

    Wu, Dongxu; Huang, Congliang; Zhong, Jinxin; Lin, Zizhen

    2018-05-01

    The inter-nanowire thermal contact resistance is important for tuning the thermal conductivity of a nanocomposite for thermoelectric applications. In this paper, the stacked copper nanowires are applied for studying the thermal contact resistance. The stacked copper nanowires are firstly made by the cold-pressing method, and then the nanowire stacks are treated by sintering treatment. With the effect of the volumetric fraction of nanowires in the stack and the influence of the sintering-temperature on the thermal contact resistance discussed, results show that: The thermal conductivity of the 150-nm copper nanowires can be enlarged almost 2 times with the volumetric fraction increased from 32 to 56% because of the enlarged contact-area and contact number of a copper nanowire. When the sintering temperature increases from 293 to 673 K, the thermal conductivity of the stacked 300-nm nanowires could be enlarged almost 2.5 times by the sintering treatment, because of the improved lattice property of the contact zone. In conclusion, application of a high volumetric fraction or/and a sintering-treatment are effectivity to tune the inter-nanowire thermal contact resistance, and thus to tailor the thermal conductivity of a nanowire network or stack.

  2. Mechanical behavior enhancement of ZnO nanowire by embedding different nanowires

    Directory of Open Access Journals (Sweden)

    Ali Vazinishayan

    2018-06-01

    Full Text Available In this work, we employed commercial finite element modeling (FEM software package ABAQUS to analyze mechanical properties of ZnO nanowire before and after embedding with different kinds of nanowires, having different materials and cross-section models such as Au (circular, Ag (pentagonal and Si (rectangular using three point bending technique. The length and diameter of the ZnO nanowire were measured to be 12,280 nm and 103.2 nm, respectively. In addition, Au, Ag and Si nanowires were considered to have the length of 12,280 nm and the diameter of 27 nm. It was found that after embedding Si nanowire with rectangular cross-section into the ZnO nanowire, the distribution of Von Misses stresses criterion, displacement and strain were decreased than the other nanowires embedded. The highest stiffness, the elastic deformation and the high strength against brittle failure have been made by Si nanowire comparison to the Au and Ag nanowires, respectively. Keywords: Nanowires, Material effects, Mechanical properties, Brittle failure

  3. ON current enhancement of nanowire Schottky barrier tunnel field effect transistors

    Science.gov (United States)

    Takei, Kohei; Hashimoto, Shuichiro; Sun, Jing; Zhang, Xu; Asada, Shuhei; Xu, Taiyu; Matsukawa, Takashi; Masahara, Meishoku; Watanabe, Takanobu

    2016-04-01

    Silicon nanowire Schottky barrier tunnel field effect transistors (NW-SBTFETs) are promising structures for high performance devices. In this study, we fabricated NW-SBTFETs to investigate the effect of nanowire structure on the device characteristics. The NW-SBTFETs were operated with a backgate bias, and the experimental results demonstrate that the ON current density is enhanced by narrowing the width of the nanowire. We confirmed using the Fowler-Nordheim plot that the drain current in the ON state mainly comprises the quantum tunneling component through the Schottky barrier. Comparison with a technology computer aided design (TCAD) simulation revealed that the enhancement is attributed to the electric field concentration at the corners of cross-section of the NW. The study findings suggest an effective approach to securing the ON current by Schottky barrier width modulation.

  4. Modulated Magnetic Nanowires for Controlling Domain Wall Motion: Toward 3D Magnetic Memories

    KAUST Repository

    Ivanov, Yurii P.; Chuvilin, Andrey; Lopatin, Sergei; Kosel, Jü rgen

    2016-01-01

    Cylindrical magnetic nanowires are attractive materials for next generation data storage devices owing to the theoretically achievable high domain wall velocity and their efficient fabrication in highly dense arrays. In order to obtain control over domain wall motion, reliable and well-defined pinning sites are required. Here, we show that modulated nanowires consisting of alternating nickel and cobalt sections facilitate efficient domain wall pinning at the interfaces of those sections. By combining electron holography with micromagnetic simulations, the pinning effect can be explained by the interaction of the stray fields generated at the interface and the domain wall. Utilizing a modified differential phase contrast imaging, we visualized the pinned domain wall with a high resolution, revealing its three-dimensional vortex structure with the previously predicted Bloch point at its center. These findings suggest the potential of modulated nanowires for the development of high-density, three-dimensional data storage devices. © 2016 American Chemical Society.

  5. Co/Au multisegmented nanowires: a 3D array of magnetostatically coupled nanopillars

    KAUST Repository

    Bran, C.; Ivanov, Yurii P.; Kosel, Jü rgen; Chubykalo-Fesenko, O.; Vazquez, M.

    2017-01-01

    Arrays of multisegmented Co/Au nanowires with designed segment lengths and diameters have been prepared by electrodeposition into aluminum oxide templates. The high quality of the Co/Au interface and the crystallographic structure of Co segments have determined by high-resolution transmission electron microscopy. Magnetic hysteresis loop measurements show larger coercivity and squareness of multisegmented nanowires as compared to single segment Co nanowires. The complementary micromagnetic simulations are in good agreement with the experimental results, confirming that the magnetic behavior is defined mainly by magnetostatic coupling between different segments. The proposed structure constitutes an innovative route towards a 3D array of synchronized magnetic nano-oscillators with large potential in nanoelectronics.

  6. Dynamics of vortex domain walls in ferromagnetic nanowires - A possible method for chirality manipulation

    Science.gov (United States)

    Li, Y.; Lu, Z.; Chen, C.; Cheng, M.; Yin, H.; Wang, W.; Li, C.; Liu, Y.; Xiong, R.; Shi, J.

    2018-06-01

    The dynamic behaviors of vortex domain walls (VDWs) in ferromagnetic nanowires driven by a magnetic field above Walker breakdown field (Hw) were investigated using micromagnetic simulation. It was found when nanowire has proper geometrical dimensions, the VDW may oscillate in a chirality invariant mode or a chirality switching mode depending on applied field and damping constant. At fixed damping constant, the oscillation mode can be controlled by applied field - with the increase of applied field, the oscillation of VDW change from a chirality invariant mode to a variant one. As the oscillation of VDW changes from chirality invariant regime to chirality switching regime, the oscillation frequency and amplification will undergo an abnormal change, which may offer a fingerprint for the switch of oscillation mode. Our finding proposes a simple way to control the chirality of a VDW by properly manipulating nanowire geometry and applied field, which may have important applications in VDW-based devices.

  7. Young's Modulus of Wurtzite and Zinc Blende InP Nanowires.

    Science.gov (United States)

    Dunaevskiy, Mikhail; Geydt, Pavel; Lähderanta, Erkki; Alekseev, Prokhor; Haggrén, Tuomas; Kakko, Joona-Pekko; Jiang, Hua; Lipsanen, Harri

    2017-06-14

    The Young's modulus of thin conical InP nanowires with either wurtzite or mixed "zinc blende/wurtzite" structures was measured. It has been shown that the value of Young's modulus obtained for wurtzite InP nanowires (E [0001] = 130 ± 30 GPa) was similar to the theoretically predicted value for the wurtzite InP material (E [0001] = 120 ± 10 GPa). The Young's modulus of mixed "zinc blende/wurtzite" InP nanowires (E [111] = 65 ± 10 GPa) appeared to be 40% less than the theoretically predicted value for the zinc blende InP material (E [111] = 110 GPa). An advanced method for measuring the Young's modulus of thin and flexible nanostructures is proposed. It consists of measuring the flexibility (the inverse of stiffness) profiles 1/k(x) by the scanning probe microscopy with precise control of loading force in nanonewton range followed by simulations.

  8. Optoelectronic properties of p-diamond/n-GaN nanowire heterojunctions

    International Nuclear Information System (INIS)

    Schuster, Fabian; Hetzl, Martin; Weiszer, Saskia; Garrido, Jose A.; Stutzmann, Martin; Wolfer, Marco; Nebel, Christoph E.; Kato, Hiromitsu

    2015-01-01

    In this work, nanodiodes comprised of n-GaN nanowires on p-diamond substrates are investigated. The electric transport properties are discussed on the basis of simulations and determined experimentally for individual p-diamond/n-GaN nanodiodes by applying conductive atomic force microscopy. For low doping concentrations, a high rectification ratio is observed. The fabrication of a prototype nanoLED device on the basis of ensemble nanowire contacts is presented, showing simultaneous electroluminescence in the UV and the green spectral range which can be ascribed to hole injection into the n-GaN nanowires and electron injection into the p-diamond, respectively. In addition, the operation and heat distribution of the nanoLED device are visualized by active thermographic imaging

  9. Co/Au multisegmented nanowires: a 3D array of magnetostatically coupled nanopillars

    KAUST Repository

    Bran, C.

    2017-01-31

    Arrays of multisegmented Co/Au nanowires with designed segment lengths and diameters have been prepared by electrodeposition into aluminum oxide templates. The high quality of the Co/Au interface and the crystallographic structure of Co segments have determined by high-resolution transmission electron microscopy. Magnetic hysteresis loop measurements show larger coercivity and squareness of multisegmented nanowires as compared to single segment Co nanowires. The complementary micromagnetic simulations are in good agreement with the experimental results, confirming that the magnetic behavior is defined mainly by magnetostatic coupling between different segments. The proposed structure constitutes an innovative route towards a 3D array of synchronized magnetic nano-oscillators with large potential in nanoelectronics.

  10. Modulated Magnetic Nanowires for Controlling Domain Wall Motion: Toward 3D Magnetic Memories

    KAUST Repository

    Ivanov, Yurii P.

    2016-05-03

    Cylindrical magnetic nanowires are attractive materials for next generation data storage devices owing to the theoretically achievable high domain wall velocity and their efficient fabrication in highly dense arrays. In order to obtain control over domain wall motion, reliable and well-defined pinning sites are required. Here, we show that modulated nanowires consisting of alternating nickel and cobalt sections facilitate efficient domain wall pinning at the interfaces of those sections. By combining electron holography with micromagnetic simulations, the pinning effect can be explained by the interaction of the stray fields generated at the interface and the domain wall. Utilizing a modified differential phase contrast imaging, we visualized the pinned domain wall with a high resolution, revealing its three-dimensional vortex structure with the previously predicted Bloch point at its center. These findings suggest the potential of modulated nanowires for the development of high-density, three-dimensional data storage devices. © 2016 American Chemical Society.

  11. Hydrogen passivation of polycrystalline Si thin film solar cells

    International Nuclear Information System (INIS)

    Gorka, Benjamin

    2010-01-01

    Hydrogen passivation is a key process step in the fabrication of polycrystalline Si (poly-Si) thin film solar cells. In this work a parallel plate rf plasma setup was used for the hydrogen passivation treatment. The main topics that have been investigated are (i) the role of plasma parameters (like hydrogen pressure, electrode gap and plasma power), (ii) the dynamics of the hydrogen treatment and (iii) passivation of poly-Si with different material properties. Passivation was characterized by measuring the open-circuit voltage V OC of poly-Si reference samples. Optimum passivation conditions were found by measurements of the breakdown voltage V brk of the plasma for different pressures p and electrode gaps d. For each pressure, the best passivation was achieved at a gap d that corresponded to the minimum in V brk . Plasma simulations were carried out, which indicate that best V OC corresponds to a minimum in ion energy. V OC was not improved by a larger H flux. Investigations of the passivation dynamic showed that a plasma treatment in the lower temperature range (≤400 C) is slow and takes several hours for the V OC to saturate. Fast passivation can be successfully achieved at elevated temperatures around 500 C to 600 C with a plateau time of 10 min. It was found that prolonged hydrogenation leads to a loss in V OC , which is less pronounced within the observed optimum temperature range (500 C-600 C). Electron beam evaporation has been investigated as an alternative method to fabricate poly-Si absorbers. The material properties have been tuned by alteration of substrate temperature T dep =200-700 C and were characterized by Raman, ESR and V OC measurements. Largest grains were obtained after solid phase crystallization (SPC) of a-Si, deposited in the temperature range of 300 C. The defect concentration of Si dangling bonds was lowered by passivation by about one order of magnitude. The lowest dangling bond concentration of 2.5.10 16 cm -3 after passivation was

  12. Simulations

    CERN Document Server

    Ngada, Narcisse

    2015-06-15

    The complexity and cost of building and running high-power electrical systems make the use of simulations unavoidable. The simulations available today provide great understanding about how systems really operate. This paper helps the reader to gain an insight into simulation in the field of power converters for particle accelerators. Starting with the definition and basic principles of simulation, two simulation types, as well as their leading tools, are presented: analog and numerical simulations. Some practical applications of each simulation type are also considered. The final conclusion then summarizes the main important items to keep in mind before opting for a simulation tool or before performing a simulation.

  13. A model-reduction approach to the micromechanical analysis of polycrystalline materials

    Science.gov (United States)

    Michel, Jean-Claude; Suquet, Pierre

    2016-03-01

    The present study is devoted to the extension to polycrystals of a model-reduction technique introduced by the authors, called the nonuniform transformation field analysis (NTFA). This new reduced model is obtained in two steps. First the local fields of internal variables are decomposed on a reduced basis of modes as in the NTFA. Second the dissipation potential of the phases is replaced by its tangent second-order (TSO) expansion. The reduced evolution equations of the model can be entirely expressed in terms of quantities which can be pre-computed once for all. Roughly speaking, these pre-computed quantities depend only on the average and fluctuations per phase of the modes and of the associated stress fields. The accuracy of the new NTFA-TSO model is assessed by comparison with full-field simulations on two specific applications, creep of polycrystalline ice and response of polycrystalline copper to a cyclic tension-compression test. The new reduced evolution equations is faster than the full-field computations by two orders of magnitude in the two examples.

  14. Thermal expansion behavior study of Co nanowire array with in situ x-ray diffraction and x-ray absorption fine structure techniques

    Science.gov (United States)

    Mo, Guang; Cai, Quan; Jiang, Longsheng; Wang, Wei; Zhang, Kunhao; Cheng, Weidong; Xing, Xueqing; Chen, Zhongjun; Wu, Zhonghua

    2008-10-01

    In situ x-ray diffraction and x-ray absorption fine structure techniques were used to study the structural change of ordered Co nanowire array with temperature. The results show that the Co nanowires are polycrystalline with hexagonal close packed structure without phase change up until 700 °C. A nonlinear thermal expansion behavior has been found and can be well described by a quadratic equation with the first-order thermal expansion coefficient of 4.3×10-6/°C and the second-order thermal expansion coefficient of 5.9×10-9/°C. The mechanism of this nonlinear thermal expansion behavior is discussed.

  15. Electrodeposition of ZnO nano-wires lattices with a controlled morphology; Electrodepot de reseaux de nanofils de ZnO a morphologie controlee

    Energy Technology Data Exchange (ETDEWEB)

    Elias, J.; Tena-Zaera, R.; Katty, A.; Levy-Clement, C. [Centre National de la Recherche Scientifique (CNRS), Lab. de Chimie Metallurgique des Terres Rares, UPR 209, 94 - Thiais (France)

    2006-07-01

    In this work, it is shown that the electrodeposition is a changeable low cost method which allows, according to the synthesis conditions, to obtain not only plane thin layers of ZnO but different nano-structures too. In a first part, are presented the formation conditions of a compact thin layer of nanocrystalline ZnO electrodeposited on a conducing glass substrate. This layer plays a buffer layer role for the deposition of a lattice of ZnO nano-wires. The step of nano-wires nucleation is not only determined by the electrochemical parameters but by the properties of the buffer layer too as the grain sizes and its thickness. In this context, the use of an electrodeposition method in two steps allows to control the nano-wires length and diameter and their density. The morphology and the structural and optical properties of these nano-structures have been analyzed by different techniques as the scanning and transmission electron microscopy, the X-ray diffraction and the optical spectroscopy. These studies show that ZnO nano-structures are formed of monocrystalline ZnO nano-wires, presenting a great developed surface and a great optical transparency in the visible. These properties make ZnO a good material for the development of nano-structured photovoltaic cells as the extremely thin absorber cells (PV ETA) or those with dye (DSSC) which are generally prepared with porous polycrystalline TiO{sub 2}. Its replacement by a lattice of monocrystalline ZnO nano-wires allows to reduce considerably the number of grain boundaries and in consequence to improve the transport of the electrons. The results are then promising for the PV ETA cells with ZnO nano-wires. (O.M.)

  16. Lab-in-a-drop: controlled self-assembly of CdSe/ZnS quantum dots and quantum rods into polycrystalline nanostructures with desired optical properties

    International Nuclear Information System (INIS)

    Sukhanova, Alyona; Volkov, Yuri; Rogach, Andrey L; Baranov, Alexander V; Susha, Andrei S; Klinov, Dmitriy; Oleinikov, Vladimir; Cohen, Jacques H M; Nabiev, Igor

    2007-01-01

    Among the different nanometre-scale building blocks, colloidal nanocrystals are of special interest in construction of ordered assemblies to be used in optoelectronics, photonics and biosensing. It is important that the nanocrystal properties essential to allow the arrangement process, including their size, shape, surface protection, stabilization and charge, can be controlled along with the electronic structure of each nanocrystal. Here, we describe an operation of the 'lab-in-a-drop', droplets of the aqueous solutions of the water-solubilized CdSe/ZnS core/shell nanocrystal quantum dots and quantum rods, in which a variety of nanostructures with desired properties may be produced. We show that, upon incubation and controlled evaporation of the solvent from the aqueous droplets of nanocrystals, one may produce either nanowires or polycrystalline dendrites of different morphologies and dimensions, depending on the nanocrystal shape and on the very narrow concentration and temperature specific ranges. Hence, the operation of this 'lab-in-a-drop' is controlled by external parameters providing the fluorescent nanostructures of desired size and morphology. Although a majority of the results presented here were obtained with CdSe/ZnS quantum dots and rods, similar polycrystalline patterns may be produced in the aqueous suspensions of other nanocrystals

  17. Electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes: FFT-impedance spectroscopy of the growth process and magnetic properties.

    Science.gov (United States)

    Gerngross, Mark-Daniel; Carstensen, Jürgen; Föll, Helmut

    2014-01-01

    The electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes has been investigated by fast Fourier transform-impedance spectroscopy (FFT-IS) in the frequency range from 75 Hz to 18.5 kHz. The impedance data could be fitted very well using an electric circuit equivalent model with a series resistance connected in series to a simple resistor-capacitor (RC) element and a Maxwell element. Based on the impedance data, the Co deposition in ultra-high aspect ratio InP membranes can be divided into two different Co deposition processes. The corresponding share of each process on the overall Co deposition can be determined directly from the transfer resistances of the two processes. The impedance data clearly show the beneficial impact of boric acid on the Co deposition and also indicate a diffusion limitation of boric acid in ultra-high aspect ratio InP membranes. The grown Co nanowires are polycrystalline with a very small grain size. They show a narrow hysteresis loop with a preferential orientation of the easy magnetization direction along the long nanowire axis due to the arising shape anisotropy of the Co nanowires.

  18. Robust mode space approach for atomistic modeling of realistically large nanowire transistors

    Science.gov (United States)

    Huang, Jun Z.; Ilatikhameneh, Hesameddin; Povolotskyi, Michael; Klimeck, Gerhard

    2018-01-01

    Nanoelectronic transistors have reached 3D length scales in which the number of atoms is countable. Truly atomistic device representations are needed to capture the essential functionalities of the devices. Atomistic quantum transport simulations of realistically extended devices are, however, computationally very demanding. The widely used mode space (MS) approach can significantly reduce the numerical cost, but a good MS basis is usually very hard to obtain for atomistic full-band models. In this work, a robust and parallel algorithm is developed to optimize the MS basis for atomistic nanowires. This enables engineering-level, reliable tight binding non-equilibrium Green's function simulation of nanowire metal-oxide-semiconductor field-effect transistor (MOSFET) with a realistic cross section of 10 nm × 10 nm using a small computer cluster. This approach is applied to compare the performance of InGaAs and Si nanowire n-type MOSFETs (nMOSFETs) with various channel lengths and cross sections. Simulation results with full-band accuracy indicate that InGaAs nanowire nMOSFETs have no drive current advantage over their Si counterparts for cross sections up to about 10 nm × 10 nm.

  19. Optimised quantum hacking of superconducting nanowire single-photon detectors.

    Science.gov (United States)

    Tanner, Michael G; Makarov, Vadim; Hadfield, Robert H

    2014-03-24

    We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack.

  20. Observation of plastic deformation in freestanding single crystal Au nanowires

    International Nuclear Information System (INIS)

    Lee, Dongyun; Zhao Manhong; Wei Xiaoding; Chen Xi; Jun, Seong C.; Hone, James; Herbert, Erik G.; Oliver, Warren C.; Kysar, Jeffrey W.

    2006-01-01

    Freestanding single crystal nanowires of gold were fabricated from a single grain of pure gold leaf by standard lithographic techniques, with center section of 7 μm in length, 250 nm in width, and 100 nm in thickness. The ends remained anchored to a silicon substrate. The specimens were deflected via nanoindenter until plastic deformation was achieved. Nonlocalized and localized plastic deformations were observed. The resulting force-displacement curves were simulated using continuum single crystal plasticity. A set of material parameters which closely reproduce the experimental results suggests that the initial critical resolved shear stress was as high as 135 MPa

  1. Optimised quantum hacking of superconducting nanowire single-photon detectors

    Science.gov (United States)

    Tanner, Michael G.; Makarov, Vadim; Hadfield, Robert H.

    2014-03-01

    We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack.

  2. Artificial cilia of magnetically tagged polymer nanowires for biomimetic mechanosensing

    International Nuclear Information System (INIS)

    Schroeder, P; Schotter, J; Shoshi, A; Eggeling, M; Brückl, H; Bethge, O; Hütten, A

    2011-01-01

    Polymeric nanowires of polypyrrole have been implemented as artificial cilia on giant-magneto-resistive multilayer sensors for a biomimetic sensing approach. The arrays were tagged with a magnetic material, the stray field of which changes relative to the underlying sensor as a consequence of mechanical stimuli which are delivered by a piezoactuator. The principle resembles balance sensing in mammals. Measurements of the sensor output voltage suggest a proof of concept at frequencies of around 190 kHz and a tag thickness of ∼300 nm. Characterization was performed by scanning electron microscopy and magnetic force microscopy. Micromagnetic and finite-element simulations were conducted to assess basic sensing aspects.

  3. Tandem Solar Cells Using GaAs Nanowires on Si: Design, Fabrication, and Observation of Voltage Addition.

    Science.gov (United States)

    Yao, Maoqing; Cong, Sen; Arab, Shermin; Huang, Ningfeng; Povinelli, Michelle L; Cronin, Stephen B; Dapkus, P Daniel; Zhou, Chongwu

    2015-11-11

    Multijunction solar cells provide us a viable approach to achieve efficiencies higher than the Shockley-Queisser limit. Due to their unique optical, electrical, and crystallographic features, semiconductor nanowires are good candidates to achieve monolithic integration of solar cell materials that are not lattice-matched. Here, we report the first realization of nanowire-on-Si tandem cells with the observation of voltage addition of the GaAs nanowire top cell and the Si bottom cell with an open circuit voltage of 0.956 V and an efficiency of 11.4%. Our simulation showed that the current-matching condition plays an important role in the overall efficiency. Furthermore, we characterized GaAs nanowire arrays grown on lattice-mismatched Si substrates and estimated the carrier density using photoluminescence. A low-resistance connecting junction was obtained using n(+)-GaAs/p(+)-Si heterojunction. Finally, we demonstrated tandem solar cells based on top GaAs nanowire array solar cells grown on bottom planar Si solar cells. The reported nanowire-on-Si tandem cell opens up great opportunities for high-efficiency, low-cost multijunction solar cells.

  4. Thermodynamic model for grain boundary effects on hydrogen solubility, diffusivity and permeability in poly-crystalline tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Oda, Takuji, E-mail: oda@snu.ac.kr

    2016-11-15

    Highlights: • A thermodynamic model to simulate grain boundary effects on hydrogen behaviors in poly-crystalline W was established. • With this model, the effective solubility, diffusivity and permeability of hydrogen are calculated as a function of grain size. • Grain boundary significantly change the hydrogen behaviors in poly-crystalline W up to around 1000 K. - Abstract: A thermodynamic model to evaluate effects of grain boundary (GB) on hydrogen behaviors in poly-crystalline tungsten is established. With this model, the effective solubility, diffusivity and permeability of hydrogen in tungsten equilibrated with surrounding H{sub 2} gas can be calculated as a function of grain size, temperature and H{sub 2} partial pressure. By setting 1.0 eV to the binding energy of hydrogen to GBs and 0.4 eV to the diffusion barrier of hydrogen along GBs, the model reasonably reproduces some experimental data on the effective diffusivity and permeability. Comparisons between calculation results by the model and available experimental data show that GBs significantly affect the hydrogen behaviors up to around 1000 K or higher in practical materials. Therefore, the effects of GBs need to be considered in analysis of experimental results, for which the present model can be utilized, and in prediction of tritium inventory and leakage in fusion reactors.

  5. Zero and low coefficient of thermal expansion polycrystalline oxides

    International Nuclear Information System (INIS)

    Skaggs, S.R.

    1977-09-01

    Polycrystalline oxide systems with zero to low coefficient of thermal expansion (CTE) investigated by the author include hafnia-titania and hafnia. The CTE for 30 to 40 mol% TiO 2 in HfO 2 is less than or equal to 1 x 10 -6 / 0 C, while for other compositions in the range 25 to 60 mol% it is approximately 4 x 10 -6 / 0 C. An investigation of the CTE of 99.999% HfO 2 yielded a value of 4.6 x 10 -6 / 0 C from room temperature to 1000 0 C. Correlation with data on HfO 2 by other investigators shows a definite relationship between the CTE and the amount of ZrO 2 present. Data are listed for comparison of the CTE of several other polycrystalline oxides investigated by Holcombe at Oak Ridge

  6. Zero and low coefficient of thermal expansion polycrystalline oxides

    International Nuclear Information System (INIS)

    Skaggs, S.R.

    1977-01-01

    Polycrystalline oxide systems with zero to low coefficient of thermal expansion (CTE) investigated by the author include hafnia-titania and hafnia. The CTE for 30 to 40 mol percent TiO 2 in HfO 2 is less than or equal to 1 x 10 -6 / 0 C, while for other compositions in the range 25 to 60 mol percent approximately 4 x 10 -6 / 0 C. An investigation of the CTE of 99.999 percent HfO 2 yielded a value of 4.6 x 10 -6 / 0 C from room temperature to 1000 0 C. Correlation with data on HfO 2 by other investigators shows a definite relationship between the CTE and the amount of ZrO 2 present. Data are listed for comparison of the CTE of several other polycrystalline oxides investigated by Holcombe at Oak Ridge

  7. Surface Potential of Polycrystalline Hematite in Aqueous Medium

    Directory of Open Access Journals (Sweden)

    Tajana Preočanin

    2011-01-01

    Full Text Available The surface potential of polycrystalline hematite in aqueous sodium perchlorate environment as a function of pH was examined. Surface potential of hematite was obtained from measured electrode potential of a nonporous polycrystalline hematite electrode. Acidic solution was titrated with base, and the backward titration with acid was performed. Substantial hysteresis was obtained which enabled location of the point of zero potential and equilibrium values of surface potentials. The theoretical interpretation of the equilibrium data was performed by applying the surface complexation model and the thermodynamic equilibrium constants for the first and the second step of surface protonation was obtained as logK1∘=11.3;logK2∘=2.8.

  8. Inelastic x-ray scattering from polycrystalline materials

    International Nuclear Information System (INIS)

    Fischer, I.

    2008-09-01

    Inelastic X-ray scattering (IXS) is a tool to determine the phonon dispersion along high symmetry directions in single crystals. However, novel materials and crystals under extreme conditions are often only available in form of polycrystalline samples. Thus the investigation is limited to orientation-averaged properties. To overcome these limitations, a methodology to extract the single crystal phonon dispersion from polycrystalline materials was developed. The approach consists of recording IXS spectra over a large momentum transfer region and confront them with a Born - von Karman model calculation. A least-square refinement of the model IXS spectra then provides the single crystal dispersion scheme. In this work the method is developed on the test case Be. Further studies were performed on more and more complex systems, in order to explore the limitations. This novel application of IXS promises to be a valuable tool in cases where single crystalline materials are not available. (author)

  9. Ultrathin polycrystalline 6,13-Bis(triisopropylsilylethynyl)-pentacene films

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Min-Cherl; Zhang, Dongrong; Nikiforov, Gueorgui O.; Lee, Michael V.; Qi, Yabing, E-mail: Yabing.Qi@oist.jp [Energy Materials and Surface Sciences Unit (EMSS), Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1 Tancha, Onna-son, Okinawa 904-0495 (Japan); Joo Shin, Tae; Ahn, Docheon; Lee, Han-Koo; Baik, Jaeyoon; Shin, Hyun-Joon [Pohang Accelerator Laboratory, POSTECH, Pohang 790-784 (Korea, Republic of)

    2015-03-15

    Ultrathin (<6 nm) polycrystalline films of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-P) are deposited with a two-step spin-coating process. The influence of spin-coating conditions on morphology of the resulting film was examined by atomic force microscopy. Film thickness and RMS surface roughness were in the range of 4.0–6.1 and 0.6–1.1 nm, respectively, except for small holes. Polycrystalline structure was confirmed by grazing incidence x-ray diffraction measurements. Near-edge x-ray absorption fine structure measurements suggested that the plane through aromatic rings of TIPS-P molecules was perpendicular to the substrate surface.

  10. Epitaxy of advanced nanowire quantum devices

    Science.gov (United States)

    Gazibegovic, Sasa; Car, Diana; Zhang, Hao; Balk, Stijn C.; Logan, John A.; de Moor, Michiel W. A.; Cassidy, Maja C.; Schmits, Rudi; Xu, Di; Wang, Guanzhong; Krogstrup, Peter; Op Het Veld, Roy L. M.; Zuo, Kun; Vos, Yoram; Shen, Jie; Bouman, Daniël; Shojaei, Borzoyeh; Pennachio, Daniel; Lee, Joon Sue; van Veldhoven, Petrus J.; Koelling, Sebastian; Verheijen, Marcel A.; Kouwenhoven, Leo P.; Palmstrøm, Chris J.; Bakkers, Erik P. A. M.

    2017-08-01

    Semiconductor nanowires are ideal for realizing various low-dimensional quantum devices. In particular, topological phases of matter hosting non-Abelian quasiparticles (such as anyons) can emerge when a semiconductor nanowire with strong spin-orbit coupling is brought into contact with a superconductor. To exploit the potential of non-Abelian anyons—which are key elements of topological quantum computing—fully, they need to be exchanged in a well-controlled braiding operation. Essential hardware for braiding is a network of crystalline nanowires coupled to superconducting islands. Here we demonstrate a technique for generic bottom-up synthesis of complex quantum devices with a special focus on nanowire networks with a predefined number of superconducting islands. Structural analysis confirms the high crystalline quality of the nanowire junctions, as well as an epitaxial superconductor-semiconductor interface. Quantum transport measurements of nanowire ‘hashtags’ reveal Aharonov-Bohm and weak-antilocalization effects, indicating a phase-coherent system with strong spin-orbit coupling. In addition, a proximity-induced hard superconducting gap (with vanishing sub-gap conductance) is demonstrated in these hybrid superconductor-semiconductor nanowires, highlighting the successful materials development necessary for a first braiding experiment. Our approach opens up new avenues for the realization of epitaxial three-dimensional quantum architectures which have the potential to become key components of various quantum devices.

  11. Platinum boride nanowires: Synthesis and characterization

    International Nuclear Information System (INIS)

    Ding Zhanhui; Qiu Lixia; Zhang Jian; Yao Bin; Cui Tian; Guan Weiming; Zheng Weitao; Wang Wenquan; Zhao Xudong; Liu Xiaoyang

    2012-01-01

    Highlights: ► Platinum boride nanowires have been synthesized via the direct current arc discharge method. ► XRD, TEM and SAED indicate that the nanowires are single-crystal PtB. ► Two broad photoluminescence emission peaks at about 586 nm and 626 nm have been observed in the PL spectroscopy of PtB nanowires. - Abstract: Platinum boride (PtB) nanowires have been successfully fabricated with direct current arc discharge method using a milled mixture of platinum (Pt) and boron nitride (BN) powders. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the compositions, morphology, and structures of the samples. The results show that PtB nanowires are 30–50 nm thick and 20–30 μm long. TEM and selected area electron diffraction (SAED) patterns identify that the PtB nanowires are single-crystalline in nature. A growth mechanism based on vapor–liquid–solid (VLS) process is proposed for the formation of nanowires.

  12. Catalytic growth of carbon nanowires on composite diamond/silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Sellam, Amine [Université de Lorraine, Institut Jean Lamour, Département CP2S (UMR CNRS 7198), Parc de Saurupt, F-54042 Nancy Cedex (France); Miska, Patrice [Université de Lorraine, Institut Jean Lamour, Département P2M (UMR CNRS 7198), Parc de Saurupt, F-54042 Nancy Cedex (France); Ghanbaja, Jaafar [Université de Lorraine, Institut Jean Lamour, Département CP2S (UMR CNRS 7198), Parc de Saurupt, F-54042 Nancy Cedex (France); Barrat, Silvère, E-mail: Silvere.Barrat@ijl.nancy-universite.fr [Université de Lorraine, Institut Jean Lamour, Département CP2S (UMR CNRS 7198), Parc de Saurupt, F-54042 Nancy Cedex (France)

    2014-01-01

    Polycrystalline diamond (PCD) films and carbon nanowires (CNWs) provide individually highly attractive properties for science and technology applications. The possibility of carbon composite materials made from a combination of these materials remains a potential approach widely discussed in literature but modestly investigated. We report in this work an early attempt to explore this opportunity in the light of some specific experimental considerations. Carbon nanowires (CNWs) are grown at low temperature without the conventional use of external hydrocarbon vapor source on silicon substrates partially covered by a thin film of coalesced micrometric CVD diamond. Composite substrates constituted by PCD on silicon were first cleaned with H{sub 2} plasma then used for the PVD deposition of 5 nm Ni thin films. Then, samples were heat treated in a CVD reactor at 580 °C in the presence of pure H{sub 2} pressure of 60 hPa at different annealing times. Comparative effect of annealing time on the dewetting of Ni thin films and the subsequent CNWs growth process was considered in this work using systematic observations by SEM. Possible mechanisms underlying CNWs growth in pure H{sub 2} gas were proposed. The nature and structure of these CNWs have been investigated by TEM microscopy and by Raman spectroscopy on the sample showing the highest CNWs density.

  13. Effect of hydrogen passivation on polycrystalline silicon thin films

    Czech Academy of Sciences Publication Activity Database

    Honda, Shinya; Mates, Tomáš; Ledinský, Martin; Oswald, Jiří; Fejfar, Antonín; Kočka, Jan; Yamazaki, T.; Uraoka, Y.; Fuyuki, T.

    2005-01-01

    Roč. 487, - (2005), s. 152-156 ISSN 0040-6090 R&D Projects: GA AV ČR(CZ) IAA1010316; GA AV ČR(CZ) IAA1010413; GA ČR(CZ) GD202/05/H003 Institutional research plan: CEZ:AV0Z10100521 Keywords : hydrogen passivation * polycrystalline silicon * photoluminescence * Raman spectroscopy * Si-H 2 * hydrogen molecules Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.569, year: 2005

  14. Formation of photovoltaic modules based on polycrystalline solar cells

    OpenAIRE

    L. A. Dobrzański; A. Drygała; A. Januszka

    2009-01-01

    Purpose: The main aim of the paper is formation of photovoltaic modules and analysis of their main electric parameters.Design/methodology/approach: Photovoltaic modules were produced from four polycrystalline silicon solar cells, that were cut and next joined in series. Soft soldering technique and copper-tin strip were used for joining cells.Findings: In order to provide useful power for any application, the individual solar cells must be connected together to give the appropriate current an...

  15. Polycrystalline diamond film UV detectors for excimer lasers

    International Nuclear Information System (INIS)

    Ralchenko, V G; Savel'ev, A V; Konov, Vitalii I; Mazzeo, G; Spaziani, F; Conte, G; Polyakov, V I

    2006-01-01

    Photoresistive metal-semiconductor-metal detectors based on polycrystalline diamond films are fabricated for recording cw and pulsed UV radiation. The detectors have a high spectral selectivity (the UV-to-VIS response ratio is ∼10 5 ) and a temporal resolution of the order of 10 9 s. 'Solar-blind' photostable diamond detectors are promising for applications in UV lithography, laser micromachining, medicine, and space research. (letters)

  16. Ferromagnetic clusters in polycrystalline BaCoO3

    International Nuclear Information System (INIS)

    Botta, P.M.; Pardo, V.; Calle, C. de la; Baldomir, D.; Alonso, J.A.; Rivas, J.

    2007-01-01

    Polycrystalline BaCoO 3 was synthesized by a citrate technique using thermal treatments at high oxygen pressure. Magnetic susceptibility measurements on the compound were carried out under AC conditions. The magnetic properties of the material at low temperatures were found to be determined by the appearance of nanoscale ferromagnetic (FM) regions and not by a true magnetic phase transition. These clusters have a mean size of about 1 nm in diameter and obey an Arrhenius-like thermal relaxation

  17. Mechanical behavior enhancement of ZnO nanowire by embedding different nanowires

    Science.gov (United States)

    Vazinishayan, Ali; Yang, Shuming; Lambada, Dasaradha Rao; Wang, Yiming

    2018-06-01

    In this work, we employed commercial finite element modeling (FEM) software package ABAQUS to analyze mechanical properties of ZnO nanowire before and after embedding with different kinds of nanowires, having different materials and cross-section models such as Au (circular), Ag (pentagonal) and Si (rectangular) using three point bending technique. The length and diameter of the ZnO nanowire were measured to be 12,280 nm and 103.2 nm, respectively. In addition, Au, Ag and Si nanowires were considered to have the length of 12,280 nm and the diameter of 27 nm. It was found that after embedding Si nanowire with rectangular cross-section into the ZnO nanowire, the distribution of Von Misses stresses criterion, displacement and strain were decreased than the other nanowires embedded. The highest stiffness, the elastic deformation and the high strength against brittle failure have been made by Si nanowire comparison to the Au and Ag nanowires, respectively.

  18. Synthesis of Oxidation-Resistant Cupronickel Nanowires for Transparent Conducting Nanowire Networks

    Energy Technology Data Exchange (ETDEWEB)

    Rathmall, Aaron [Duke University; Nguyen, Minh [Duke University; Wiley, Benjamin J [Duke University

    2012-01-01

    Nanowires of copper can be coated from liquids to create flexible, transparent conducting films that can potentially replace the dominant transparent conductor, indium tin oxide, in displays, solar cells, organic light-emitting diodes, and electrochromic windows. One issue with these nanowire films is that copper is prone to oxidation. It was hypothesized that the resistance to oxidation could be improved by coating copper nanowires with nickel. This work demonstrates a method for synthesizing copper nanowires with nickel shells as well as the properties of cupronickel nanowires in transparent conducting films. Time- and temperature-dependent sheet resistance measurements indicate that the sheet resistance of copper and silver nanowire films will double after 3 and 36 months at room temperature, respectively. In contrast, the sheet resistance of cupronickel nanowires containing 20 mol % nickel will double in about 400 years. Coating copper nanowires to a ratio of 2:1 Cu:Ni gave them a neutral gray color, making them more suitable for use in displays and electrochromic windows. These properties, and the fact that copper and nickel are 1000 times more abundant than indium or silver, make cupronickel nanowires a promising alternative for the sustainable, efficient production of transparent conductors.

  19. 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.

  20. Mesoscopic approach to modeling elastic-plastic polycrystalline material behaviour

    International Nuclear Information System (INIS)

    Kovac, M.; Cizelj, L.

    2001-01-01

    Extreme loadings during severe accident conditions might cause failure or rupture of the pressure boundary of a reactor coolant system. Reliable estimation of the extreme deformations can be crucial to determine the consequences of such an accident. One of important drawbacks of classical continuum mechanics is idealization of inhomogenous microstructure of materials. This paper discusses the mesoscopic approach to modeling the elastic-plastic behavior of a polycrystalline material. The main idea is to divide the continuum (e.g., polycrystalline aggregate) into a set of sub-continua (grains). The overall properties of the polycrystalline aggregate are therefore determined by the number of grains in the aggregate and properties of randomly shaped and oriented grains. The random grain structure is modeled with Voronoi tessellation and random orientations of crystal lattices are assumed. The elastic behavior of monocrystal grains is assumed to be anisotropic. Crystal plasticity is used to describe plastic response of monocrystal grains. Finite element method is used to obtain numerical solutions of strain and stress fields. The analysis is limited to two-dimensional models.(author)

  1. Physics of grain boundaries in polycrystalline photovoltaic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Yanfa, E-mail: yanfa.yan@utoledo.edu; Yin, Wan-Jian; Wu, Yelong; Shi, Tingting; Paudel, Naba R. [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Ohio 43606 (United States); Li, Chen [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Poplawsky, Jonathan [The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Wang, Zhiwei [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Ohio 43606 (United States); National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Moseley, John; Guthrey, Harvey; Moutinho, Helio; Al-Jassim, Mowafak M. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Pennycook, Stephen J. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States)

    2015-03-21

    Thin-film solar cells based on polycrystalline Cu(In,Ga)Se{sub 2} (CIGS) and CdTe photovoltaic semiconductors have reached remarkable laboratory efficiencies. It is surprising that these thin-film polycrystalline solar cells can reach such high efficiencies despite containing a high density of grain boundaries (GBs), which would seem likely to be nonradiative recombination centers for photo-generated carriers. In this paper, we review our atomistic theoretical understanding of the physics of grain boundaries in CIGS and CdTe absorbers. We show that intrinsic GBs with dislocation cores exhibit deep gap states in both CIGS and CdTe. However, in each solar cell device, the GBs can be chemically modified to improve their photovoltaic properties. In CIGS cells, GBs are found to be Cu-rich and contain O impurities. Density-functional theory calculations reveal that such chemical changes within GBs can remove most of the unwanted gap states. In CdTe cells, GBs are found to contain a high concentration of Cl atoms. Cl atoms donate electrons, creating n-type GBs between p-type CdTe grains, forming local p-n-p junctions along GBs. This leads to enhanced current collections. Therefore, chemical modification of GBs allows for high efficiency polycrystalline CIGS and CdTe thin-film solar cells.

  2. Polycrystalline silicon availability for photovoltaic and semiconductor industries

    Science.gov (United States)

    Ferber, R. R.; Costogue, E. N.; Pellin, R.

    1982-01-01

    Markets, applications, and production techniques for Siemens process-produced polycrystalline silicon are surveyed. It is noted that as of 1982 a total of six Si materials suppliers were servicing a worldwide total of over 1000 manufacturers of Si-based devices. Besides solar cells, the Si wafers are employed for thyristors, rectifiers, bipolar power transistors, and discrete components for control systems. An estimated 3890 metric tons of semiconductor-grade polycrystalline Si will be used in 1982, and 6200 metric tons by 1985. Although the amount is expected to nearly triple between 1982-89, research is being carried out on the formation of thin films and ribbons for solar cells, thereby eliminating the waste produced in slicing Czolchralski-grown crystals. The free-world Si production in 1982 is estimated to be 3050 metric tons. Various new technologies for the formation of polycrystalline Si at lower costs and with less waste are considered. New entries into the industrial Si formation field are projected to produce a 2000 metric ton excess by 1988.

  3. Polycrystalline diamond detectors with three-dimensional electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Lagomarsino, S., E-mail: lagomarsino@fi.infn.it [University of Florence, Department of Physics, Via Sansone 1, 50019 Sesto Fiorentino (Italy); INFN Firenze, Via B. Rossi 1, 50019 Sesto Fiorentino (Italy); Bellini, M. [INO-CNR Firenze, Largo E. Fermi 6, 50125 Firenze (Italy); Brianzi, M. [INFN Firenze, Via B. Rossi 1, 50019 Sesto Fiorentino (Italy); Carzino, R. [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia, Genova, Via Morego 30, 16163 Genova (Italy); Cindro, V. [Joseph Stefan Institute, Jamova Cesta 39, 1000 Ljubljana (Slovenia); Corsi, C. [University of Florence, Department of Physics, Via Sansone 1, 50019 Sesto Fiorentino (Italy); LENS Firenze, Via N. Carrara 1, 50019 Sesto Fiorentino (Italy); Morozzi, A.; Passeri, D. [INFN Perugia, Perugia (Italy); Università degli Studi di Perugia, Dipartimento di Ingegneria, via G. Duranti 93, 06125 Perugia (Italy); Sciortino, S. [University of Florence, Department of Physics, Via Sansone 1, 50019 Sesto Fiorentino (Italy); INFN Firenze, Via B. Rossi 1, 50019 Sesto Fiorentino (Italy); Servoli, L. [INFN Perugia, Perugia (Italy)

    2015-10-01

    The three-dimensional concept in diamond detectors has been applied, so far, to high quality single-crystal material, in order to test this technology in the best available conditions. However, its application to polycrystalline chemical vapor deposited diamond could be desirable for two reasons: first, the short inter-electrode distance of three-dimensional detectors should improve the intrinsically lower collection efficiency of polycrystalline diamond, and second, at high levels of radiation damage the performances of the poly-crystal material are not expected to be much lower than those of the single crystal one. We report on the fabrication and test of three-dimensional polycrystalline diamond detectors with several inter-electrode distances, and we demonstrate that their collection efficiency is equal or higher than that obtained with conventional planar detectors fabricated with the same material. - Highlights: • Pulsed laser fabrication of polycristalline diamond detectors with 3D electrodes. • Measurement of the charge collection efficiency (CCE) under beta irradiation. • Comparation between the CCE of 3D and conventional planar diamond sensors. • A rationale for the behavior of three-dimensional and planar sensors is given.

  4. 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...

  5. Room temperature synthesis and photocatalytic property of AgO/Ag2Mo2O7 heterojunction nanowires

    International Nuclear Information System (INIS)

    Hashim, Muhammad; Hu, Chenguo; Wang, Xue; Wan, Buyong; Xu, Jing

    2012-01-01

    Graphical abstract: The AgO nanoparticles are attached on the surface of the Ag 2 Mo 2 O 7 nanowires to form a heterojunction structure. The AgO nanoparticles start embedding into the nanowires with increasing reaction temperature or time. Highlights: ► AgO/Ag 2 Mo 2 O 7 heterojunction NWs were synthesized at room temperature for the first time. ► AgO particles embed into the Ag 2 Mo 2 O 7 NWs with increase in reaction time and temperature. ► The heterojunction NWs display much better photocatalytic activity than the none-heterojunction NWs. ► The catalytic mechanism was proposed. -- Abstract: AgO/Ag 2 Mo 2 O 7 heterojunction nanowires were synthesized at temperatures of 25 °C, 50 °C, 80 °C, and 110 °C, under magnetic stirring in solution reaction. The catalytic activity of AgO/Ag 2 Mo 2 O 7 nanowires was evaluated by the degradation of Rhodmine B dye under the irradiation of the simulated sunlight. The synthesized samples were characterized by X-ray diffractometer, energy dispersive spectrometry, X-ray photoelectron spectrometer, scanning electron microscopy, and transmission electron microscopy. The results show that the AgO nanoparticles are attached on the surface of the Ag 2 Mo 2 O 7 nanowires to form a heterojunction structure. The length of the nanowires is up to 10 μm and the size of the AgO nanoparticles is 10–20 nm. The length of nanowires increases with increasing reaction time and temperature while the AgO particles are gradually embedded into the nanowires. The photocatalytic activity is greatly improved for the AgO/Ag 2 Mo 2 O 7 heterojunction nanowires compared with that of the pure Ag 2 Mo 2 O 7 nanowires, indicating a remarkable role of AgO particles on the Ag 2 Mo 2 O 7 nanowires in the photodegradation.

  6. Semiconductor Nanowires: What's Next?

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Peidong; Yan, Ruoxue; Fardy, Melissa

    2010-04-28

    In this perspective, we take a critical look at the research progress within the nanowire community for the past decade. We discuss issues on the discovery of fundamentally new phenomena versus performance benchmarking for many of the nanowire applications. We also notice that both the bottom-up and top-down approaches have played important roles in advancing our fundamental understanding of this new class of nanostructures. Finally we attempt to look into the future and offer our personal opinions on what the future trends will be in nanowire research.

  7. 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

  8. Perspectives of single cast nanowires technology

    International Nuclear Information System (INIS)

    Ioisher, Anatolii; Badinter, Efim; Postolache, Vitalie; Leporda, Nicolae; Tiginyanu, Ion; Monaico, Eduard

    2011-01-01

    The paper is dedicated to production potential of glass-coated cast nanowire with metal-, semimetal- and semiconductor-based cores by means of Taylor-Ulitovsky method. Criteria of melted core-formative material penetration into a drawing capillary were analyzed. Theoretical preconditions of the reduction of cast microwire diameter up to nano-dimensions of core are reviewed and an improved method of cast nanowire manufacturing is proposed. Correctness of conclusions was experimentally proved and laboratory samples of micro- and nano-wires with core diameter of about 200-300 nanometers were produced, even in case of materials with poor adhesion.

  9. Silicon nanowire-based solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Stelzner, Th; Pietsch, M; Andrae, G; Falk, F; Ose, E; Christiansen, S [Institute of Photonic Technology, Albert-Einstein-Strasse 9, D-07745 Jena (Germany)], E-mail: thomas.stelzner@ipht-jena.de

    2008-07-23

    The fabrication of silicon nanowire-based solar cells on silicon wafers and on multicrystalline silicon thin films on glass is described. The nanowires show a strong broadband optical absorption, which makes them an interesting candidate to serve as an absorber in solar cells. The operation of a solar cell is demonstrated with n-doped nanowires grown on a p-doped silicon wafer. From a partially illuminated area of 0.6 cm{sup 2} open-circuit voltages in the range of 230-280 mV and a short-circuit current density of 2 mA cm{sup -2} were obtained.

  10. Silicon nanowire-based solar cells

    International Nuclear Information System (INIS)

    Stelzner, Th; Pietsch, M; Andrae, G; Falk, F; Ose, E; Christiansen, S

    2008-01-01

    The fabrication of silicon nanowire-based solar cells on silicon wafers and on multicrystalline silicon thin films on glass is described. The nanowires show a strong broadband optical absorption, which makes them an interesting candidate to serve as an absorber in solar cells. The operation of a solar cell is demonstrated with n-doped nanowires grown on a p-doped silicon wafer. From a partially illuminated area of 0.6 cm 2 open-circuit voltages in the range of 230-280 mV and a short-circuit current density of 2 mA cm -2 were obtained

  11. Electrospinning synthesis of superconducting BSCCO nanowires

    International Nuclear Information System (INIS)

    Duarte, Edgar A.; Quintero, Pedro A.; Meisel, Mark W.; Nino, Juan C.

    2013-01-01

    Highlights: •Bi 2 Sr 2 CaCu 2 O 8+x nanowires 150 nm to 250 nm thick are synthesized using the electrospinning. •Bi 2 Sr 2 CaCu 2 O 8+x nanowires are obtained after a heat treatment at 850 °C. •Bi 2 Sr 2 CaCu 2 O 8+x nanowires show a T c = 78.7 K consistent with bulk superconductor behavior. -- Abstract: This paper presents the synthesis and characterization of Bi 2 Sr 2 CaCu 2 O 8+x superconducting nanowires. Bi 2 Sr 2 CaCu 2 O 8+x nanowires with a T c = 78.7 K are synthesized using the electrospinning process employing sol–gel precursors. A sol–gel methodology is used to obtain a homogeneous PVP solution containing Bi, Sr, Ca, and Cu acetates. Mats of randomly oriented nanowires and aligned nanowires are also collected. After a heat treatment at 850 °C in ambient atmosphere using heating rates of 100 and 400 °C/h, fully crystallized Bi 2 Sr 2 CaCu 2 O 8+x nanowires are obtained. The morphology, microstructure, and crystal structure of these nanowires are then examined to reveal a rectangular morphology having typical wire thickness in the range of 150–250 nm, and a wire width between 400 and 600 nm. DC magnetization studies are conducted to investigate the critical transition temperature (T c ) of Bi 2 Sr 2 CaCu 2 O 8+x nanowires and to compare their magnetic properties to those of bulk Bi 2 Sr 2 CaCu 2 O 8+x powder. The T c for the commercial powder is observed at 78.6 K, and that of the obtained nanowires at 78.7 K. These results point to the superconducting nature of Bi 2 Sr 2 CaCu 2 O 8+x nanowires, and the potential of the electrospinning process for the synthesis of this superconductor material

  12. Deformation behaviour of body centered cubic Fe nanowires under tensile and compressive loading

    OpenAIRE

    Sainath, G.; Choudhary, B. K.; Jayakumar, T.

    2014-01-01

    Molecular Dynamics (MD) simulations have been carried out to investigate the deformation behaviour of /{111} body centered cubic (BCC) Fe nanowires under tensile and compressive loading. An embedded atom method (EAM) potential was used to describe the interatomic interactions. The simulations were carried out at 10 K with a constant strain rate of $1\\times10^{8}$ $s^{-1}$. The results indicate a significant differences in deformation mechanisms under tensile and compressive loading. Under ten...

  13. Enhanced ionic conductivity of AgI nanowires/AAO composites fabricated by a simple approach

    International Nuclear Information System (INIS)

    Liu Lifeng; Alexe, Marin; Lee, Woo; Goesele, Ulrich; Lee, Seung-Woo; Li Jingbo; Rao Guanghui; Zhou Weiya; Lee, Jae-Jong

    2008-01-01

    AgI nanowires/anodic aluminum oxide (AgI NWs/AAO) composites have been fabricated by a simple approach, which involves the thermal melting of AgI powders on the surface of the AAO membrane, followed by the infiltration of the molten AgI inside the nanochannels. As-prepared AgI nanowires have corrugated outer surfaces and are polycrystalline according to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. X-ray diffraction (XRD) shows that a considerable amount of 7H polytype AgI exists in the composites, which is supposed to arise from the interfacial interactions between the embedded AgI and the alumina. AC conductivity measurements for the AgI nanowires/AAO composites exhibit a notable conductivity enhancement by three orders of magnitude at room temperature compared with that of pristine bulk AgI. Furthermore, a large conductivity hysteresis and abnormal conductivity transitions were observed in the temperature-dependent conductivity measurements, from which an ionic conductivity as high as 8.0 x 10 2 Ω -1 cm -1 was obtained at around 70 deg. C upon cooling. The differential scanning calorimetry (DSC) result demonstrates a similar phase transition behavior as that found in the AC conductivity measurements. The enhanced ionic conductivity, as well as the abnormal phase transitions, can be explained in terms of the existence of the highly conducting 7H polytype AgI and the formation of well-defined conduction paths in the composites.

  14. Enhanced ionic conductivity of AgI nanowires/AAO composites fabricated by a simple approach.

    Science.gov (United States)

    Liu, Li-Feng; Lee, Seung-Woo; Li, Jing-Bo; Alexe, Marin; Rao, Guang-Hui; Zhou, Wei-Ya; Lee, Jae-Jong; Lee, Woo; Gösele, Ulrich

    2008-12-10

    AgI nanowires/anodic aluminum oxide (AgI NWs/AAO) composites have been fabricated by a simple approach, which involves the thermal melting of AgI powders on the surface of the AAO membrane, followed by the infiltration of the molten AgI inside the nanochannels. As-prepared AgI nanowires have corrugated outer surfaces and are polycrystalline according to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. X-ray diffraction (XRD) shows that a considerable amount of 7H polytype AgI exists in the composites, which is supposed to arise from the interfacial interactions between the embedded AgI and the alumina. AC conductivity measurements for the AgI nanowires/AAO composites exhibit a notable conductivity enhancement by three orders of magnitude at room temperature compared with that of pristine bulk AgI. Furthermore, a large conductivity hysteresis and abnormal conductivity transitions were observed in the temperature-dependent conductivity measurements, from which an ionic conductivity as high as 8.0 × 10(2) Ω(-1) cm(-1) was obtained at around 70 °C upon cooling. The differential scanning calorimetry (DSC) result demonstrates a similar phase transition behavior as that found in the AC conductivity measurements. The enhanced ionic conductivity, as well as the abnormal phase transitions, can be explained in terms of the existence of the highly conducting 7H polytype AgI and the formation of well-defined conduction paths in the composites.

  15. Template-based fabrication of nanowire-nanotube hybrid arrays

    International Nuclear Information System (INIS)

    Ye Zuxin; Liu Haidong; Schultz, Isabel; Wu Wenhao; Naugle, D G; Lyuksyutov, I

    2008-01-01

    The fabrication and structure characterization of ordered nanowire-nanotube hybrid arrays embedded in porous anodic aluminum oxide (AAO) membranes are reported. Arrays of TiO 2 nanotubes were first deposited into the pores of AAO membranes by a sol-gel technique. Co nanowires were then electrochemically deposited into the TiO 2 nanotubes to form the nanowire-nanotube hybrid arrays. Scanning electron microscopy and transmission electron microscopy measurements showed a high nanowire filling factor and a clean interface between the Co nanowire and the TiO 2 nanotube. Application of these hybrids to the fabrication of ordered nanowire arrays with highly controllable geometric parameters is discussed

  16. Biofunctionalization of zinc oxide nanowires for DNA sensory applications

    Directory of Open Access Journals (Sweden)

    Rudolph Bettina

    2011-01-01

    Full Text Available Abstract We report on the biofunctionalization of zinc oxide nanowires for the attachment of DNA target molecules on the nanowire surface. With the organosilane glycidyloxypropyltrimethoxysilane acting as a bifunctional linker, amino-modified capture molecule oligonucleotides have been immobilized on the nanowire surface. The dye-marked DNA molecules were detected via fluorescence microscopy, and our results reveal a successful attachment of DNA capture molecules onto the nanowire surface. The electrical field effect induced by the negatively charged attached DNA molecules should be able to control the electrical properties of the nanowires and gives way to a ZnO nanowire-based biosensing device.

  17. THE INFLUENCE OF SUNLIGHT AND WIND ON THE POLYCRYSTALLINE SILICON MODULES

    Directory of Open Access Journals (Sweden)

    Piotr Lichograj

    2016-12-01

    Full Text Available Changing conditions have a significant impact on the efficiency and durability of photovoltaic cells. On photovoltaic modules have also influence such external factors as temperature of the module, which changes during the long exposure to light radiation, wind, pollution and the frequency of rainfall. Parameters of PV modules provided by the manufacturers differ significantly from the results achieved under natural conditions. This work presents the laboratory study on the impact of temperature of the polycrystalline silicon module to the change of generated voltage tested with no load. Research confirms the correlation of temperature increase during the long exposure to light radiation with a voltage drop. At the same time simulation of wind causes the cooling of the module and increase the voltage circuit. Further development of research on the effects of environmental conditions will allow for accurate placement optimization of photovoltaic farms.

  18. Micromachined single-level nonplanar polycrystalline SiGe thermal microemitters for infrared dynamic scene projection

    Science.gov (United States)

    Malyutenko, V. K.; Malyutenko, O. Yu.; Leonov, V.; Van Hoof, C.

    2009-05-01

    The technology for self-supported membraneless polycrystalline SiGe thermal microemitters, their design, and performance are presented. The 128-element arrays with a fill factor of 88% and a 2.5-μm-thick resonant cavity have been grown by low-pressure chemical vapor deposition and fabricated using surface micromachining technology. The 200-nm-thick 60×60 μm2 emitting pixels enforced with a U-shape profile pattern demonstrate a thermal time constant of 2-7 ms and an apparent temperature of 700 K in the 3-5 and 8-12 μm atmospheric transparency windows. The application of the devices to the infrared dynamic scene simulation and their benefit over conventional planar membrane-supported emitters are discussed.

  19. Non-destructive identification of unknown minor phases in polycrystalline bulk alloys using three-dimensional X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yiming, E-mail: yangyiming1988@outlook.com [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xu, Liang [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Yudan; Du, Guohao [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Yang, Sam [Commonwealth Scientific and Industrial Research Organization, Melbourne, VIC 3168 (Australia); Xiao, Tiqiao, E-mail: tqxiao@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

    2017-02-15

    Minor phases make considerable contributions to the mechanical and physical properties of metals and alloys. Unfortunately, it is difficult to identify unknown minor phases in a bulk polycrystalline material using conventional metallographic methods. Here, a non-destructive method based on three-dimensional X-ray diffraction (3DXRD) is developed to solve this problem. Simulation results demonstrate that this method is simultaneously able to identify minor phase grains and reveal their positions, orientations and sizes within bulk alloys. According to systematic simulations, the 3DXRD method is practicable for an extensive sample set, including polycrystalline alloys with hexagonal, orthorhombic and cubic minor phases. Experiments were also conducted to confirm the simulation results. The results for a bulk sample of aluminum alloy AA6061 show that the crystal grains of an unexpected γ-Fe (austenite) phase can be identified, three-dimensionally and nondestructively. Therefore, we conclude that the 3DXRD method is a powerful tool for the identification of unknown minor phases in bulk alloys belonging to a variety of crystal systems. This method also has the potential to be used for in situ observations of the effects of minor phases on the crystallographic behaviors of alloys. - Highlights: •A method based on 3DXRD is developed for identification of unknown minor phase. •Grain position, orientation and size, is simultaneously acquired. •A systematic simulation demonstrated the applicability of the proposed method. •Experimental results on a AA6061 sample confirmed the practicability of the method.

  20. Enhanced Photon Extraction from a Nanowire Quantum Dot Using a Bottom-Up Photonic Shell

    Science.gov (United States)

    Jeannin, Mathieu; Cremel, Thibault; Häyrynen, Teppo; Gregersen, Niels; Bellet-Amalric, Edith; Nogues, Gilles; Kheng, Kuntheak

    2017-11-01

    Semiconductor nanowires offer the possibility to grow high-quality quantum-dot heterostructures, and, in particular, CdSe quantum dots inserted in ZnSe nanowires have demonstrated the ability to emit single photons up to room temperature. In this paper, we demonstrate a bottom-up approach to fabricate a photonic fiberlike structure around such nanowire quantum dots by depositing an oxide shell using atomic-layer deposition. Simulations suggest that the intensity collected in our NA =0.6 microscope objective can be increased by a factor 7 with respect to the bare nanowire case. Combining microphotoluminescence, decay time measurements, and numerical simulations, we obtain a fourfold increase in the collected photoluminescence from the quantum dot. We show that this improvement is due to an increase of the quantum-dot emission rate and a redirection of the emitted light. Our ex situ fabrication technique allows a precise and reproducible fabrication on a large scale. Its improved extraction efficiency is compared to state-of-the-art top-down devices.

  1. High-performance silicon nanowire bipolar phototransistors

    Science.gov (United States)

    Tan, Siew Li; Zhao, Xingyan; Chen, Kaixiang; Crozier, Kenneth B.; Dan, Yaping

    2016-07-01

    Silicon nanowires (SiNWs) have emerged as sensitive absorbing materials for photodetection at wavelengths ranging from ultraviolet (UV) to the near infrared. Most of the reports on SiNW photodetectors are based on photoconductor, photodiode, or field-effect transistor device structures. These SiNW devices each have their own advantages and trade-offs in optical gain, response time, operating voltage, and dark current noise. Here, we report on the experimental realization of single SiNW bipolar phototransistors on silicon-on-insulator substrates. Our SiNW devices are based on bipolar transistor structures with an optically injected base region and are fabricated using CMOS-compatible processes. The experimentally measured optoelectronic characteristics of the SiNW phototransistors are in good agreement with simulation results. The SiNW phototransistors exhibit significantly enhanced response to UV and visible light, compared with typical Si p-i-n photodiodes. The near infrared responsivities of the SiNW phototransistors are comparable to those of Si avalanche photodiodes but are achieved at much lower operating voltages. Compared with other reported SiNW photodetectors as well as conventional bulk Si photodiodes and phototransistors, the SiNW phototransistors in this work demonstrate the combined advantages of high gain, high photoresponse, low dark current, and low operating voltage.

  2. Silicon nanowire hot carrier electroluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Plessis, M. du, E-mail: monuko@up.ac.za; Joubert, T.-H.

    2016-08-31

    Avalanche electroluminescence from silicon pn junctions has been known for many years. However, the internal quantum efficiencies of these devices are quite low due to the indirect band gap nature of the semiconductor material. In this study we have used reach-through biasing and SOI (silicon-on-insulator) thin film structures to improve the internal power efficiency and the external light extraction efficiency. Both continuous silicon thin film pn junctions and parallel nanowire pn junctions were manufactured using a custom SOI technology. The pn junctions are operated in the reach-through mode of operation, thus increasing the average electric field within the fully depleted region. Experimental results of the emission spectrum indicate that the most dominant photon generating mechanism is due to intraband hot carrier relaxation processes. It was found that the SOI nanowire light source external power efficiency is at least an order of magnitude better than the comparable bulk CMOS (Complementary Metal Oxide Semiconductor) light source. - Highlights: • We investigate effect of electric field on silicon avalanche electroluminescence. • With reach-through pn junctions the current and carrier densities are kept constant. • Higher electric fields increase short wavelength radiation. • Higher electric fields decrease long wavelength radiation. • The effect of the electric field indicates intraband transitions as main mechanism.

  3. 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.

  4. Quantification of nanowire uptake by live cells

    KAUST Repository

    Margineanu, Michael B.

    2015-01-01

    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 p

  5. Electrical conductivity measurements of bacterial nanowires from Pseudomonas aeruginosa

    International Nuclear Information System (INIS)

    Maruthupandy, Muthusamy; Anand, Muthusamy; Beevi, Akbar Sait Hameedha; Priya, Radhakrishnan Jeeva; Maduraiveeran, Govindhan

    2015-01-01

    The extracellular appendages of bacteria (flagella) that transfer electrons to electrodes are called bacterial nanowires. This study focuses on the isolation and separation of nanowires that are attached via Pseudomonas aeruginosa bacterial culture. The size and roughness of separated nanowires were measured using transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively. The obtained bacterial nanowires indicated a clear image of bacterial nanowires measuring 16 nm in diameter. The formation of bacterial nanowires was confirmed by microscopic studies (AFM and TEM) and the conductivity nature of bacterial nanowire was investigated by electrochemical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which are nondestructive voltammetry techniques, suggest that bacterial nanowires could be the source of electrons—which may be used in various applications, for example, microbial fuel cells, biosensors, organic solar cells, and bioelectronic devices. Routine analysis of electron transfer between bacterial nanowires and the electrode was performed, providing insight into the extracellular electron transfer (EET) to the electrode. CV revealed the catalytic electron transferability of bacterial nanowires and electrodes and showed excellent redox activities. CV and EIS studies showed that bacterial nanowires can charge the surface by producing and storing sufficient electrons, behave as a capacitor, and have features consistent with EET. Finally, electrochemical studies confirmed the development of bacterial nanowires with EET. This study suggests that bacterial nanowires can be used to fabricate biomolecular sensors and nanoelectronic devices. (paper)

  6. Silver Nanowire Arrays : Fabrication and Applications

    OpenAIRE

    Feng, Yuyi

    2016-01-01

    Nanowire arrays have increasingly received attention for their use in a variety of applications such as surface-enhanced Raman scattering (SERS), plasmonic sensing, and electrodes for photoelectric devices. However, until now, large scale fabrication of device-suitable metallic nanowire arrays on supporting substrates has seen very limited success. This thesis describes my work rst on the development of a novel successful processing route for the fabrication of uniform noble metallic (e.g. A...

  7. Optical Properties of Rotationally Twinned Nanowire Superlattices

    DEFF Research Database (Denmark)

    Bao, Jiming; Bell, David C.; Capasso, Federico

    2008-01-01

    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...... a heterostructure in a chemically homogeneous nanowire material and alter in a major way its optical properties opens new possibilities for band-structure engineering....

  8. Plasmonic Waveguide-Integrated Nanowire Laser

    DEFF Research Database (Denmark)

    Bermudez-Urena, Esteban; Tutuncuoglu, Gozde; Cuerda, Javier

    2017-01-01

    technologies. Despite significant advances in their fundamental aspects, the integration within scalable photonic circuitry remains challenging. Here we report on the realization of hybrid photonic devices consisting of nanowire lasers integrated with wafer-scale lithographically designed V-groove plasmonic......Next-generation optoelectronic devices and photonic circuitry will have to incorporate on-chip compatible nanolaser sources. Semiconductor nanowire lasers have emerged as strong candidates for integrated systems with applications ranging from ultrasensitive sensing to data communication...

  9. Electrodeposition of rhenium-tin nanowires

    International Nuclear Information System (INIS)

    Naor-Pomerantz, Adi; Eliaz, Noam; Gileadi, Eliezer

    2011-01-01

    Highlights: → Rhenium-tin nanowires were formed electrochemically, without using a template. → The nanowires consisted of a crystalline-Sn-core/amorphous-Re-shell structure. → The effects of bath composition and operating conditions were investigated. → A mechanism is suggested for the formation of the core/shell structure. → The nanowires may be attractive for a variety of applications. - Abstract: Rhenium (Re) is a refractory metal which exhibits an extraordinary combination of properties. Thus, nanowires and other nanostructures of Re-alloys may possess unique properties resulting from both Re chemistry and the nanometer scale, and become attractive for a variety of applications, such as in catalysis, photovoltaic cells, and microelectronics. Rhenium-tin coatings, consisting of nanowires with a core/shell structure, were electrodeposited on copper substrates under galvanostatic or potentiostatic conditions. The effects of bath composition and operating conditions were investigated, and the chemistry and structure of the coatings were studied by a variety of analytical tools. A Re-content as high as 77 at.% or a Faradaic efficiency as high as 46% were attained. Ranges of Sn-to-Re in the plating bath, applied current density and applied potential, within which the nanowires could be formed, were determined. A mechanism was suggested, according to which Sn nanowires were first grown on top of Sn micro-particles, and then the Sn nanowires reduced the perrhenate chemically, thus forming a core made of crystalline Sn-rich phase, and a shell made of amorphous Re-rich phase. The absence of mutual solubility of Re and Sn may be the driving force for this phase separation.

  10. Andreev molecules in semiconductor nanowire double quantum dots.

    Science.gov (United States)

    Su, Zhaoen; Tacla, Alexandre B; Hocevar, Moïra; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Daley, Andrew J; Pekker, David; Frolov, Sergey M

    2017-09-19

    Chains of quantum dots coupled to superconductors are promising for the realization of the Kitaev model of a topological superconductor. While individual superconducting quantum dots have been explored, control of longer chains requires understanding of interdot coupling. Here, double quantum dots are defined by gate voltages in indium antimonide nanowires. High transparency superconducting niobium titanium nitride contacts are made to each of the dots in order to induce superconductivity, as well as probe electron transport. Andreev bound states induced on each of dots hybridize to define Andreev molecular states. The evolution of these states is studied as a function of charge parity on the dots, and in magnetic field. The experiments are found in agreement with a numerical model.Quantum dots in a nanowire are one possible approach to creating a solid-state quantum simulator. Here, the authors demonstrate the coupling of electronic states in a double quantum dot to form Andreev molecule states; a potential building block for longer chains suitable for quantum simulation.

  11. Size-dependent elastic moduli and vibrational properties of fivefold twinned copper nanowires

    Science.gov (United States)

    Zheng, Y. G.; Zhao, Y. T.; Ye, H. F.; Zhang, H. W.

    2014-08-01

    Based on atomistic simulations, the elastic moduli and vibration behaviors of fivefold twinned copper nanowires are investigated in this paper. Simulation results show that the elastic (i.e., Young’s and shear) moduli exhibit size dependence due to the surface effect. The effective Young’s modulus is found to decrease slightly whereas the effective shear modulus increases slightly with the increase in the wire radius. Both moduli tend to approach certain values at a larger radius and can be suitably described by core-shell composite structure models. Furthermore, we show by comparing simulation results and continuum predictions that, provided the effective Young’s and shear moduli are used, classic elastic theory can be applied to describe the small-amplitude vibration of fivefold twinned copper nanowires. Moreover, for the transverse vibration, the Timoshenko beam model is more suitable because shear deformation becomes apparent.

  12. Size-dependent elastic moduli and vibrational properties of fivefold twinned copper nanowires

    International Nuclear Information System (INIS)

    Zheng, Y G; Zhao, Y T; Ye, H F; Zhang, H W

    2014-01-01

    Based on atomistic simulations, the elastic moduli and vibration behaviors of fivefold twinned copper nanowires are investigated in this paper. Simulation results show that the elastic (i.e., Young’s and shear) moduli exhibit size dependence due to the surface effect. The effective Young’s modulus is found to decrease slightly whereas the effective shear modulus increases slightly with the increase in the wire radius. Both moduli tend to approach certain values at a larger radius and can be suitably described by core-shell composite structure models. Furthermore, we show by comparing simulation results and continuum predictions that, provided the effective Young’s and shear moduli are used, classic elastic theory can be applied to describe the small-amplitude vibration of fivefold twinned copper nanowires. Moreover, for the transverse vibration, the Timoshenko beam model is more suitable because shear deformation becomes apparent. (paper)

  13. Hydrogen passivation of polycrystalline Si thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Gorka, Benjamin

    2010-12-15

    Hydrogen passivation is a key process step in the fabrication of polycrystalline Si (poly-Si) thin film solar cells. In this work a parallel plate rf plasma setup was used for the hydrogen passivation treatment. The main topics that have been investigated are (i) the role of plasma parameters (like hydrogen pressure, electrode gap and plasma power), (ii) the dynamics of the hydrogen treatment and (iii) passivation of poly-Si with different material properties. Passivation was characterized by measuring the open-circuit voltage V{sub OC} of poly-Si reference samples. Optimum passivation conditions were found by measurements of the breakdown voltage V{sub brk} of the plasma for different pressures p and electrode gaps d. For each pressure, the best passivation was achieved at a gap d that corresponded to the minimum in V{sub brk}. Plasma simulations were carried out, which indicate that best V{sub OC} corresponds to a minimum in ion energy. V{sub OC} was not improved by a larger H flux. Investigations of the passivation dynamic showed that a plasma treatment in the lower temperature range ({<=}400 C) is slow and takes several hours for the V{sub OC} to saturate. Fast passivation can be successfully achieved at elevated temperatures around 500 C to 600 C with a plateau time of 10 min. It was found that prolonged hydrogenation leads to a loss in V{sub OC}, which is less pronounced within the observed optimum temperature range (500 C-600 C). Electron beam evaporation has been investigated as an alternative method to fabricate poly-Si absorbers. The material properties have been tuned by alteration of substrate temperature T{sub dep}=200-700 C and were characterized by Raman, ESR and V{sub OC} measurements. Largest grains were obtained after solid phase crystallization (SPC) of a-Si, deposited in the temperature range of 300 C. The defect concentration of Si dangling bonds was lowered by passivation by about one order of magnitude. The lowest dangling bond concentration

  14. A finite element analysis of the effects of geometrical shape on the elastic properties of chemical vapor deposited diamond nanowire

    Directory of Open Access Journals (Sweden)

    Garuma Abdisa Denu

    2017-01-01

    Full Text Available We report the effect of geometrical shape of diamond nanowire on its mechanical properties. Finite element modeling using COMSOL Multiphysics software is used to simulate various diamond nanowire with circular, square, rectangular, hexagonal and triangular cross-sections. A bending test under concentrated load applied at one of the free ends is simulated using FEM. The force response of the nanowire under different loading is studied for the various cross-sections. The dimensions of each cross-section is chosen so that material properties such as Young’s modulus can be kept constant for comparison in all the cross-sections. It is found out that the bending capability of a triangular nanowire is higher compared to other cross-sections due to its lowest second moment. Circular and hexagonal cross-section show highest stiffness. The study of mechanical property of diamond nanowires is useful for optimal nanomechanical designs where the effect of cross-section has to be taken into account.

  15. Additional compound semiconductor nanowires for photonics

    Science.gov (United States)

    Ishikawa, F.

    2016-02-01

    GaAs related compound semiconductor heterostructures are one of the most developed materials for photonics. Those have realized various photonic devices with high efficiency, e. g., lasers, electro-optical modulators, and solar cells. To extend the functions of the materials system, diluted nitride and bismide has been paid attention over the past decade. They can largely decrease the band gap of the alloys, providing the greater tunability of band gap and strain status, eventually suppressing the non-radiative Auger recombinations. On the other hand, selective oxidation for AlGaAs is a vital technique for vertical surface emitting lasers. That enables precisely controlled oxides in the system, enabling the optical and electrical confinement, heat transfer, and mechanical robustness. We introduce the above functions into GaAs nanowires. GaAs/GaAsN core-shell nanowires showed clear redshift of the emitting wavelength toward infrared regime. Further, the introduction of N elongated the carrier lifetime at room temperature indicating the passivation of non-radiative surface recombinations. GaAs/GaAsBi nanowire shows the redshift with metamorphic surface morphology. Selective and whole oxidations of GaAs/AlGaAs core-shell nanowires produce semiconductor/oxide composite GaAs/AlGaOx and oxide GaOx/AlGaOx core-shell nanowires, respectively. Possibly sourced from nano-particle species, the oxide shell shows white luminescence. Those property should extend the functions of the nanowires for their application to photonics.

  16. Reversal modes in asymmetric Ni nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Leighton, B.; Pereira, A. [Departamento de Fisica, Universidad de Santiago de Chile (USACH), Avda. Ecuador 3493, 917-0124 Santiago (Chile); Escrig, J., E-mail: jescrigm@gmail.com [Departamento de Fisica, Universidad de Santiago de Chile (USACH), Avda. Ecuador 3493, 917-0124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Avda. Ecuador 3493, 917-0124 Santiago (Chile)

    2012-11-15

    We have investigated the evolution of the magnetization reversal mechanism in asymmetric Ni nanowires as a function of their geometry. Circular nanowires are found to reverse their magnetization by the propagation of a vortex domain wall, while in very asymmetric nanowires the reversal is driven by the propagation of a transverse domain wall. The effect of shape asymmetry of the wire on coercivity and remanence is also studied. Angular dependence of the remanence and coercivity is also addressed. Tailoring the magnetization reversal mechanism in asymmetric nanowires can be useful for magnetic logic and race-track memory, both of which are based on the displacement of magnetic domain walls. Finally, an alternative method to detect the presence of magnetic drops is proposed. - Highlights: Black-Right-Pointing-Pointer Asymmetry strongly modifies the magnetic behavior of a wire. Black-Right-Pointing-Pointer Very asymmetric nanowires reverse their magnetization by a transverse domain wall. Black-Right-Pointing-Pointer An alternative method to detect the presence of magnetic drops is proposed. Black-Right-Pointing-Pointer Tailoring the reversal mode in asymmetric nanowires can be useful for potential applications.

  17. A numerical study of the influence of feeding polycrystalline silicon granules on melt temperature in the continuous Czochralski process

    Science.gov (United States)

    Ono, Naoki; Kida, Michio; Arai, Yoshiaki; Sahira, Kensho

    1993-09-01

    Temperature change was simulated using a solid body rotating melt model when solid polycrystalline silicon granules were supplied to a melt in a double-crucible method. Only heat conduction was considered in the analysis. The influence of the crucible rotation rates and of the initial temperature of the supplied silicon was investigated systematically and quantitatively. The influence of the crucible rotation rate was stronger than expected, which suggests that the crucible rotation rate cannot be lowered too much because of the possibility of the melt solidifying between the inner and outer crucibles.

  18. Theory and modeling of microstructural evolution in polycrystalline materials: Solute segregation, grain growth and phase transformations

    Science.gov (United States)

    Ma, Ning

    2005-11-01

    To accurately predict microstructure evolution and, hence, to synthesis metal and ceramic alloys with desirable properties involves many fundamental as well as practical issues. In the present study, novel theoretical and phase field approaches have been developed to address some of these issues including solute drag and segregation transition at grain boundaries and dislocations, grain growth in systems of anisotropic boundary properties, and precipitate microstructure development in polycrystalline materials. The segregation model has allowed for the prediction of a first-order segregation transition, which could be related to the sharp transition of solute concentration of grain boundary as a function of temperature. The incorporating of interfacial energy and mobility as functions of misorientation and inclination in the phase field model has allowed for the study of concurrent grain growth and texture evolution. The simulation results were analyzed using the concept of local grain boundary energy density, which simplified significantly the development of governing equations for texture controlled grain growth in Ti-6Al-4V. Quantitative phase field modeling techniques have been developed by incorporating thermodynamic and diffusivity databases. The models have been validated against DICTRA simulations in simple 1D problems and applied to simulate realistic microstructural evolutions in Ti-6Al-4V, including grain boundary a and globular a growth and sideplate development under both isothermal aging and continuous cooling conditions. The simulation predictions agree well with experimental observations.

  19. Palladium assisted silver transport in polycrystalline SiC

    Energy Technology Data Exchange (ETDEWEB)

    Neethling, J.H., E-mail: Jan.Neethling@nmmu.ac.za [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); O' Connell, J.H.; Olivier, E.J. [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa)

    2012-10-15

    The transport of silver in polycrystalline 3C-SiC and hexagonal 6H-SiC has been investigated by annealing the SiC samples in contact with a Pd-Ag compound at temperatures of 800 and 1000 Degree-Sign C and times of 24 and 67 h. The Pd was added in an attempt to improve the low wetting of SiC by Ag and further because Pd is produced in measurable concentrations in coated particles during reactor operation. Pd is also known to coalesce at the IPyC-SiC interface and to chemically attack the SiC layer. SEM, TEM and EDS were used to show that the Ag penetrates polycrystalline SiC along grain boundaries together with Pd. It is suggested that Ag transport in SiC takes place along grain boundaries in the form of moving nodules consisting of a Ag-Pd mixture. It is assumed that the nodules move along grain boundaries by dissolving the SiC at the leading edge followed by the reprecipitation of SiC at the trailing edge. Since the solubility of Cs in Ag and Pd is extremely low, it is unlikely that Cs will penetrate the SiC together with the Ag-Pd compound if present at the IPyC-SiC interface. If it is assumed that the dominant transport mechanism of Ag in intact polycrystalline SiC is indeed the Pd assisted mechanism, then the stabilization of Pd (and other metallic fission products) in the kernel could be a way of mitigating Ag release from TRISO-coated particles.

  20. Palladium assisted silver transport in polycrystalline SiC

    International Nuclear Information System (INIS)

    Neethling, J.H.; O’Connell, J.H.; Olivier, E.J.

    2012-01-01

    The transport of silver in polycrystalline 3C-SiC and hexagonal 6H-SiC has been investigated by annealing the SiC samples in contact with a Pd–Ag compound at temperatures of 800 and 1000 °C and times of 24 and 67 h. The Pd was added in an attempt to improve the low wetting of SiC by Ag and further because Pd is produced in measurable concentrations in coated particles during reactor operation. Pd is also known to coalesce at the IPyC–SiC interface and to chemically attack the SiC layer. SEM, TEM and EDS were used to show that the Ag penetrates polycrystalline SiC along grain boundaries together with Pd. It is suggested that Ag transport in SiC takes place along grain boundaries in the form of moving nodules consisting of a Ag–Pd mixture. It is assumed that the nodules move along grain boundaries by dissolving the SiC at the leading edge followed by the reprecipitation of SiC at the trailing edge. Since the solubility of Cs in Ag and Pd is extremely low, it is unlikely that Cs will penetrate the SiC together with the Ag–Pd compound if present at the IPyC–SiC interface. If it is assumed that the dominant transport mechanism of Ag in intact polycrystalline SiC is indeed the Pd assisted mechanism, then the stabilization of Pd (and other metallic fission products) in the kernel could be a way of mitigating Ag release from TRISO-coated particles.

  1. Influence of copper foil polycrystalline structure on graphene anisotropic etching

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Kamal P. [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Mahyavanshi, Rakesh D. [Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Tanemura, Masaki [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2017-01-30

    Graphical abstract: Hexagonal hole formation with anisotropic etching independent of the stripes and wrinkles in the synthesized graphene. We also observed variation in etched pattern of the graphene depending on the base Cu grain orientations, attributing to difference in nucleation and growth process. - Highlights: • Reveal the influence of copper polycrystalline structure on anisotropic etching of graphene. • Hexagonal hole formation with etching is observed to be independent of stripes and wrinkles in graphene. • Variation in etched pattern of graphene depending on the base Cu grain is confirmed. • This finding will help to understand the nature of microscopic etched pattern in graphene. - Abstract: Anisotropic etching of graphene and other two dimensional materials is an important tool to understand the growth process as well as enabling fabrication of various well-defined structures. Here, we reveal the influence of copper foil polycrystalline structure on anisotropic etching process of as-synthesized graphene. Graphene crystals were synthesized on the polycrystalline Cu foil by a low-pressure chemical vapor deposition (LPCVD) system. Microscopic analysis shows difference in shape, size and stripes alignment of graphene crystals with dissimilar nucleation within closure vicinity of neighboring Cu grains. Post-growth etching of such graphene crystals also significantly affected by the crystallographic nature of Cu grains as observed by the field emission scanning electron microscope (FE-SEM) and electron back scattered diffraction (EBSD) analysis. Hexagonal hole formation with anisotropic etching is observed to be independent of the stripes and wrinkles in the synthesized graphene. We also observed variation in etched pattern of the graphene depending on the base Cu grain orientations, attributing to difference in nucleation and growth process. The findings can facilitate to understand the nature of microscopic etched pattern depending on metal

  2. Influence of copper foil polycrystalline structure on graphene anisotropic etching

    International Nuclear Information System (INIS)

    Sharma, Kamal P.; Mahyavanshi, Rakesh D.; Kalita, Golap; Tanemura, Masaki

    2017-01-01

    Graphical abstract: Hexagonal hole formation with anisotropic etching independent of the stripes and wrinkles in the synthesized graphene. We also observed variation in etched pattern of the graphene depending on the base Cu grain orientations, attributing to difference in nucleation and growth process. - Highlights: • Reveal the influence of copper polycrystalline structure on anisotropic etching of graphene. • Hexagonal hole formation with etching is observed to be independent of stripes and wrinkles in graphene. • Variation in etched pattern of graphene depending on the base Cu grain is confirmed. • This finding will help to understand the nature of microscopic etched pattern in graphene. - Abstract: Anisotropic etching of graphene and other two dimensional materials is an important tool to understand the growth process as well as enabling fabrication of various well-defined structures. Here, we reveal the influence of copper foil polycrystalline structure on anisotropic etching process of as-synthesized graphene. Graphene crystals were synthesized on the polycrystalline Cu foil by a low-pressure chemical vapor deposition (LPCVD) system. Microscopic analysis shows difference in shape, size and stripes alignment of graphene crystals with dissimilar nucleation within closure vicinity of neighboring Cu grains. Post-growth etching of such graphene crystals also significantly affected by the crystallographic nature of Cu grains as observed by the field emission scanning electron microscope (FE-SEM) and electron back scattered diffraction (EBSD) analysis. Hexagonal hole formation with anisotropic etching is observed to be independent of the stripes and wrinkles in the synthesized graphene. We also observed variation in etched pattern of the graphene depending on the base Cu grain orientations, attributing to difference in nucleation and growth process. The findings can facilitate to understand the nature of microscopic etched pattern depending on metal

  3. Synthesis and characterization of Au incorporated Alq3 nanowires

    Science.gov (United States)

    Khan, Mohammad Bilal; Ahmad, Sultan; Parwaz, M.; Rahul, Khan, Zishan H.

    2018-05-01

    We report the synthesis and characterization of pure and Au incorporated Alq3 nanowires. These nanowires are synthesized using thermal vapor transport method. The luminescence intensity of Au incorporated Alq3 nanowires are recorded to be higher than that of pure Alq3 nanowires, which is found to increase with the increase in Au concentration. Fluorescence quenching is also observed when Au concentration is increased beyond the certain limit.

  4. 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

    2018-05-09

    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.

  5. Trace diffusion of different nuclear reactions products in polycrystalline tantalum

    International Nuclear Information System (INIS)

    Beyer, G.J.; Fromm, W.D.; Novgorodov, A.F.

    1976-07-01

    Measurements of the lattice diffusion coefficients for carrier free isotopes of Hf, Lu, Yb, Tm, Tb, Gd, Eu, Ba, Cs, Y, Sr, Rb and As in polycrystalline tantalum were made over the temperature range 1700 Fsub(As)>Fsub(lanthanides)>Fsub(Sr)>Fsub(Ba)>Fsub(Hf)>Fsub(Rb)>Fsub(Cs). The data indicate, that the Arrhenius relation was obeyed over the entire temperature range. Within the lanthanide-group no differences in the diffusion velocities could be detected, this fact points to a diffusion mechanism of Me 3+ -ions of lanthanides, Me 2+ -ions of earth alkaline elements and Me + -ions of alkaline elements. (author)

  6. Progress and issues in polycrystalline thin-film PV technologies

    Energy Technology Data Exchange (ETDEWEB)

    Zweibel, K.; Ullal, H.S.; Roedern, B. von [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    Substantial progress has occurred in polycrystalline thin-film photovoltaic technologies in the past 18 months. However, the transition to first-time manufacturing is still under way, and technical problems continue. This paper focuses on the promise and the problems of the copper indium diselenide and cadmium telluride technologies, with an emphasis on continued R&D needs for the near-term transition to manufacturing and for next-generation improvements. In addition, it highlights the joint R&D efforts being performed in the U.S. Department of Energy/National Renewable Energy Laboratory Thin-Film Photovoltaic Partnership Program.

  7. Compensation for thermally induced birefringence in polycrystalline ceramic active elements

    International Nuclear Information System (INIS)

    Kagan, M A; Khazanov, E A

    2003-01-01

    Polycrystalline ceramics differ significantly from single crystals in that the crystallographic axes (and hence of the axes of thermally induced birefringence) are oriented randomly in each granule of the ceramic. The quaternion formalism is employed to calculate the depolarisation in the ceramics and the efficiency of its compensation. The obtained analytic expressions are in good agreement with the numerical relations. It is shown that the larger the ratio of the sample length to the granule size, the closer the properties of the ceramics to those of a single crystal with the [111] orientation (in particular, the uncompensated depolarisation is inversely proportional to this ratio). (active media)

  8. Modeling chemisorption kinetics of carbon monoxide on polycrystalline platinum

    Energy Technology Data Exchange (ETDEWEB)

    Donnelly, R.G.; Modell, M.; Baddour, R.F.

    1978-04-01

    Seven distinct desorption surface states of carbon monoxide on polycrystalline platinum were detected by deconvoluting temperature-programed desorption spectra of 4-100% carbon monoxide monolayer coverage. The adstates had fixed activation energies of desorption (22.5-32.6 kcal/mole) over the entire coverage range. Rates of formation and populations were derived. The chemisorption was modeled by a Hinshelwood-type expression which allowed for site creation and suggested that adsorbed molecules are sufficiently mobile during desorption heating to fill ordered states of minimum energy and that chemisorption into these states is noncompetitive and determined by the surface. Spectra, diagrams, graphs, tables, and 49 references.

  9. Laser beam machining of polycrystalline diamond for cutting tool manufacturing

    Science.gov (United States)

    Wyszyński, Dominik; Ostrowski, Robert; Zwolak, Marek; Bryk, Witold

    2017-10-01

    The paper concerns application of DPSS Nd: YAG 532nm pulse laser source for machining of polycrystalline WC based diamond inserts (PCD). The goal of the research was to determine optimal laser cutting parameters for cutting tool shaping. Basic criteria to reach the goal was cutting edge quality (minimalization of finishing operations), material removal rate (time and cost efficiency), choice of laser beam characteristics (polarization, power, focused beam diameter). The research was planned and realised and analysed according to design of experiment rules (DOE). The analysis of the cutting edge was prepared with use of Alicona Infinite Focus measurement system.

  10. Rotary Ultrasonic Machining of Poly-Crystalline Cubic Boron Nitride

    Directory of Open Access Journals (Sweden)

    Kuruc Marcel

    2014-12-01

    Full Text Available Poly-crystalline cubic boron nitride (PCBN is one of the hardest material. Generally, so hard materials could not be machined by conventional machining methods. Therefore, for this purpose, advanced machining methods have been designed. Rotary ultrasonic machining (RUM is included among them. RUM is based on abrasive removing mechanism of ultrasonic vibrating diamond particles, which are bonded on active part of rotating tool. It is suitable especially for machining hard and brittle materials (such as glass and ceramics. This contribution investigates this advanced machining method during machining of PCBN.

  11. New deformation model of grain boundary strengthening in polycrystalline metals

    International Nuclear Information System (INIS)

    Trefilov, V.I.; Moiseev, V.F.; Pechkovskij, Eh.P.

    1988-01-01

    A new model explaining grain boundary strengthening in polycrystalline metals and alloys by strain hardening due to localization of plastic deformation in narrow bands near grain boundaries is suggested. Occurrence of localized deformation is caused by different flow stresses in grains of different orientation. A new model takes into account the active role of stress concentrator, independence of the strengthening coefficient on deformation, influence of segregations. Successful use of the model suggested for explanation of rhenium effect in molybdenum and tungsten is alloys pointed out

  12. An acoustic emission study of plastic deformation in polycrystalline aluminium

    Science.gov (United States)

    Bill, R. C.; Frederick, J. R.; Felbeck, D. K.

    1979-01-01

    Acoustic emission experiments were performed on polycrystalline and single crystal 99.99% aluminum while undergoing tensile deformation. It was found that acoustic emission counts as a function of grain size showed a maximum value at a particular grain size. Furthermore, the slip area associated with this particular grain size corresponded to the threshold level of detectability of single dislocation slip events. The rate of decline in acoustic emission activity as grain size is increased beyond the peak value suggests that grain boundary associated dislocation sources are giving rise to the bulk of the detected acoustic emissions.

  13. An electrical conductivity inspection methodology of polycrystalline diamond cutters

    Science.gov (United States)

    Bogdanov, G.; Wiggins, J.; Bertagnolli, K.; Ludwig, R.

    2012-05-01

    The polycrystalline diamond cutter (PDC) is widely used in oil and gas drilling operations. It is manufactured by sintering diamond powder onto a tungsten carbide substrate at 6 GPa and 1500 C. During sintering, molten cobalt from the substrate infiltrates the diamond table. The residual metal content correlates with cutter performance. We present an instrument that employs electrical impedance tomography capable of imaging the 3D metal content distribution in the diamond table. These images can be used to predict cutter performance as well as detect flaws.

  14. High energy argon ion irradiations of polycrystalline iron

    International Nuclear Information System (INIS)

    Dunlop, A.; Lesueur, D.; Lorenzelli, N.; Boulanger, L.

    1986-09-01

    We present here the results of our recent irradiations of polycrystalline iron targets with very energetic (1.76 GeV) Ar ions. The targets consist of piles of thin iron samples, the total thickness of each target being somewhat greater than the theoretical range (450 μm) of the ions. We can thus separate the phenomena which occur at different average energies of the ions and study during the slowing-down process: the different types of induced nuclear reactions. They allow us to determine the experimental range of the ions, the defect profiles in the targets, the structure of the displacement cascades (electron microscopy) and their stability

  15. Complex strain paths in polycrystalline copper: microstructural aspects

    Directory of Open Access Journals (Sweden)

    M.F. Vieira

    1999-07-01

    Full Text Available Microstructural aspects of polycrystalline copper sheets subjected to complex strain paths were analysed in this work. Dislocation structures developed during the strain paths (rolling and tension and the evolution of this microstructure during reloading have been studied. The active slip systems developed in each strain path were used to explain the microstructural evolution. The heterogeneous surface deformation observed on polished tensile specimens prestrained in rolling was also analysed. The structural aspects are related with the mechanical behaviour of the material, namely with the increase in yield stress in reloading, the work hardening evolution and the premature occurrence of plastic instability for some prestrain values.

  16. Study of GaN nanowires converted from β-Ga2O3 and photoconduction in a single nanowire

    Science.gov (United States)

    Kumar, Mukesh; Kumar, Sudheer; Chauhan, Neha; Sakthi Kumar, D.; Kumar, Vikram; Singh, R.

    2017-08-01

    The formation of GaN nanowires from β-Ga2O3 nanowires and photoconduction in a fabricated single GaN nanowire device has been studied. Wurtzite phase GaN were formed from monoclinic β-Ga2O3 nanowires with or without catalyst particles at their tips. The formation of faceted nanostructures from catalyst droplets presented on a nanowire tip has been discussed. The nucleation of GaN phases in β-Ga2O3 nanowires and their subsequent growth due to interfacial strain energy has been examined using a high resolution transmission electron microscope. The high quality of the converted GaN nanowire is confirmed by fabricating single nanowire photoconducting devices which showed ultra high responsivity under ultra-violet illumination.

  17. 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 ...

  18. 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...

  19. Semiconductor Nanowires and Nanotubes for Energy Conversion

    Science.gov (United States)

    Fardy, Melissa Anne

    In recent years semiconductor nanowires and nanotubes have garnered increased attention for their unique properties. With their nanoscale dimensions comes high surface area and quantum confinement, promising enhancements in a wide range of applications. 1-dimensional nanostructures are especially attractive for energy conversion applications where photons, phonons, and electrons come into play. Since the bohr exciton radius and phonon and electron mean free paths are on the same length scales as nanowire diameters, optical, thermal, and electrical properties can be tuned by simple nanowire size adjustments. In addition, the high surface area inherent to nanowires and nanotubes lends them towards efficient charge separation and superior catalytic performance. In thermoelectric power generation, the nanoscale wire diameter can effectively scatter phonons, promoting reductions in thermal conductivity and enhancements in the thermoelectric figure of merit. To that end, single-crystalline arrays of PbS, PbSe, and PbTe nanowires have been synthesized by a chemical vapor transport approach. The electrical and thermal transport properties of the nanowires were characterized to investigate their potential as thermoelectric materials. Compared to bulk, the lead chalcogenide nanowires exhibit reduced thermal conductivity below 100 K by up to 3 orders of magnitude, suggesting that they may be promising thermoelectric materials. Smaller diameters and increased surface roughness are expected to give additional enhancements. The solution-phase synthesis of PbSe nanowires via oriented attachment of nanoparticles enables facile surface engineering and diameter control. Branched PbSe nanowires synthesized by this approach showed near degenerately doped charge carrier concentrations. Compared to the bulk, the PbSe nanowires exhibited a similar Seebeck coefficient and a significant reduction in thermal conductivity in the temperature range 20 K to 300 K. Thermal annealing of the Pb

  20. Probing the Statistical Validity of the Ductile-to-Brittle Transition in Metallic Nanowires Using GPU Computing.

    Science.gov (United States)

    French, William R; Pervaje, Amulya K; Santos, Andrew P; Iacovella, Christopher R; Cummings, Peter T

    2013-12-10

    We perform a large-scale statistical analysis (>2000 independent simulations) of the elongation and rupture of gold nanowires, probing the validity and scope of the recently proposed ductile-to-brittle transition that occurs with increasing nanowire length [Wu et al. Nano Lett. 2012, 12, 910-914]. To facilitate a high-throughput simulation approach, we implement the second-moment approximation to the tight-binding (TB-SMA) potential within HOOMD-Blue, a molecular dynamics package which runs on massively parallel graphics processing units (GPUs). In a statistical sense, we find that the nanowires obey the ductile-to-brittle model quite well; however, we observe several unexpected features from the simulations that build on our understanding of the ductile-to-brittle transition. First, occasional failure behavior is observed that qualitatively differs from that predicted by the model prediction; this is attributed to stochastic thermal motion of the Au atoms and occurs at temperatures as low as 10 K. In addition, we also find that the ductile-to-brittle model, which was developed using classical dislocation theory, holds for nanowires as small as 3 nm in diameter. Finally, we demonstrate that the nanowire critical length is higher at 298 K relative to 10 K, a result that is not predicted by the ductile-to-brittle model. These results offer practical design strategies for adjusting nanowire failure and structure and also demonstrate that GPU computing is an excellent tool for studies requiring a large number of independent trajectories in order to fully characterize a system's behavior.