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ZnO Nanowires (zno + nanowire)

Distribution by Scientific Domains

Physics and Astronomy	50%
Polymers and Materials Science	45%

Selected Abstracts

Growth and Transfer of Monolithic Horizontal ZnO Nanowire Superstructures onto Flexible Substrates

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2010
Sheng Xu
A method of fabricating horizontally aligned ZnO nanowire (NW) arrays with full control over the width and length is demonstrated. A cross-sectional view of the NWs by transmission electron microscopy shows a "mushroom-like" structure. Novel monolithic multisegment superstructures are fabricated by making use of the lateral overgrowth. Ultralong horizontal ZnO NWs of an aspect ratio on the order of ten thousand are also demonstrated. These horizontal NWs are lifted off and transferred onto a flexible polymer substrate, which may have many great applications in horizontal ZnO NW-based nanosensor arrays, light-emitting diodes, optical gratings, integrated circuit interconnects, and high-output-power alternating-current nanogenerators. [source]

Hierarchical Shelled ZnO Structures Made of Bunched Nanowire Arrays,

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2007
P. Jiang
Abstract The size- and morphology-controlled growth of ZnO nanowire (NW) arrays is potentially of interest for the design of advanced catalysts and nanodevices. By adjusting the reaction temperature, shelled structures of ZnO made of bunched ZnO NW arrays are prepared, grown out of metallic Zn microspheres through a wet-chemical route in a closed Teflon reactor. In this process, ZnO NWs are nucleated and subsequently grown into NWs on the surfaces of the microspheres as well as in strong alkali solution under the condition of the pre-existence of zincate (ZnO22,) ions. At a higher temperature (200,°C), three different types of bunched ZnO NW or sub-micrometer rodlike (SMR) aggregates are observed. At room temperature, however, the bunched ZnO NW arrays are found only to occur on the Zn microsphere surface, while double-pyramid-shaped or rhombus-shaped ZnO particles are formed in solution. The ZnO NWs exhibit an ultrathin structure with a length of ca.,,500,nm and a diameter of ca.,10,nm. The phenomenon may be well understood by the temperature-dependent growth process involved in different nucleation sources. A growth mechanism has been proposed in which the degree of ZnO22,saturation in the reaction solution plays a key role in controlling the nucleation and growth of the ZnO NWs or SMRs as well as in oxidizing the metallic Zn microspheres. Based on this consideration, ultrathin ZnO NW cluster arrays on the Zn microspheres are successfully obtained. Raman spectroscopy and photoluminescence measurements of the ultrathin ZnO NW cluster arrays have also been performed. [source]

Single ZnO Nanowire/p-type GaN Heterojunctions for Photovoltaic Devices and UV Light-Emitting Diodes

ADVANCED MATERIALS, Issue 38 2010
Ya-Qing Bie
We fabricate heterojunctions consisting of a single n-type ZnO nanowire and a p-type GaN film. The photovoltaic effect of heterojunctions exhibits open-circuit voltages ranging from 2 to 2.7 V, and a maximum output power reaching 80 nW. Light-emitting diodes with UV electroluminescence based on the heterojunctions are demonstrated. [source]

ZnO nanowire arrays , Pattern generation, growth and applications

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2010
Margit Zacharias
Abstract ZnO nanowires and related materials are in the focus of attention for electronic, optical or sensor applications. However, size, position and arrangement control are essential conditions for the development of future nanowire based devices. Various kinds of template methods including nanosphere lithography and UV laser interference lithography are powerful tools for the preparation of the starting metal catalyst arrays and will be demonstrated and discussed. However, only if the growth mechanism and its guiding parameters are understood in detail, the template will force a pattern arranged growth of nanowires. The paper gives an overview of the various kinds of growth modes for vertical arranged nanowires. Specific experimental conditions establishing the VS or the VLS growth are discussed. In addition, insight is given why the patterning is not all the time conserved and how to overcome these obstacles. In the second part different kinds of applications are summarized. Electronic properties are discussed based on metal,semiconductor,metal devices. The influence of a core,shell nanowire structure on the optical properties is demonstrated. In addition, a simple approach for ZnO nanowire based gas sensors is discussed and shown. As a last example, the transfer of Al2O3 coated nanowires into spinel tubes is reported. [source]

Preparation of ZnO Nanowires in a Neutral Aqueous System: Concentration Effect on the Orientation Attachment Process

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2006
Ming Yang
Abstract ZnO nanowires with diameters in the range of 10 to 30 nm and lengths of ca. several micrometers are prepared with the use of ZnO nanoparticles as building blocks. The length and diameter of the ZnO nanowires can be controlled by the variation of the concentration of the nanoparticles in the orientation attachment process. A plausible mechanism for the concentration-controlled orientation attachment process is suggested. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Electro-Optical Materials: Electrically Addressable Hybrid Architectures of Zinc Oxide Nanowires Grown on Aligned Carbon Nanotubes (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2010
Mater.
Hybrid assemblies of zinc oxide (ZnO) nanowires grown on carbon nanotubes (CNTs) are presented by A. J. Hart et al. on page 2470. The foreground shows a transmission electron micrograph of an individual hybrid bundle where the ZnO nanowires extend radially from the surface of the CNTs. The background shows a scanning electron micrograph of the sidewall of a ZnO/CNT hybrid forest. Color was added using Adobe Photoshop. [source]

Electrically Addressable Hybrid Architectures of Zinc Oxide Nanowires Grown on Aligned Carbon Nanotubes

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2010
Jong G. Ok
Abstract The fabrication and characterization of hybrid architectures of ZnO nanowires (ZNWs) grown on organized carbon nanotubes (CNTs), by a two-step chemical vapor deposition (CVD) process involving CNT growth from a hydrocarbon source followed by ZNW growth using a Zn metal source, is reported. The ZNWs grow uniformly and radially from individual CNTs and CNT bundles, and the aligned morphology of the CNTs is not disturbed by the ZNW growth process. The nucleation and growth of ZnO crystals on CNTs are analyzed in relation to the classical vapor,solid mechanism. Importantly, the CNTs make uniform and distributed electrical contact to the ZNWs, with up to a 1000-fold yield advantage over conventional ZNW growth on a flat substrate. Hybrid ZNW/CNT sheets are fabricated by scalable CVD, rolling, and printing methods; and their electrical properties, which are governed by transport through the anisotropic CNT network, are characterized. Functional interaction between the ZNWs and CNTs is demonstrated by photoconductive behavior and photocurrent generation of the hybrid material under UV illumination. There is significant future opportunity to extend these processing methods to fabricate other functional oxides on CNTs, and to build devices that harness the attractive properties of ZNWs and CNTs with high volumetric efficiency over large areas. [source]

Increased Interface Strength in Carbon Fiber Composites through a ZnO Nanowire Interphase

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2009
Yirong Lin
Abstract One of the most important factors in the design of a fiber reinforced composite is the quality of the fiber/matrix interface. Recently carbon nanotubes and silicon carbide whiskers have been used to enhance the interfacial properties of composites; however, the high growth temperature degrade the fiber strength and significantly reduce the composite's in-plane properties. Here, a novel method for enhancing the fiber/matrix interfacial strength that does not degrade the mechanical properties of the fiber is demonstrated. The composite is fabricated using low-temperature solution-based growth of ZnO nanowires on the surface of the reinforcing fiber. Experimental testing shows the growth does not adversely affect fiber strength, interfacial shear strength can be significantly increased by 113%, and the lamina shear strength and modulus can be increased by 37.8% and 38.8%, respectively. This novel interface could also provide embedded functionality through the piezoelectric and semiconductive properties of ZnO. [source]

Observation of a 2D Electron Gas and the Tuning of the Electrical Conductance of ZnO Nanowires by Controllable Surface Band-Bending

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2009
Youfan Hu
Abstract Direct experimental evidence for the existence of a 2D electron gas in devices based on ZnO nanowires (NWs) is presented. A two-channel core/shell model is proposed for the interpretation of the temperature-dependent current,voltage (I,V) characteristics of the ZnO NW, where a mixed metallic,semiconducting behavior is observed. The experimental results are quantitatively analyzed using a weak-localization theory, and suggest that the NW is composed of a "bulk" semiconducting core with a metallic surface accumulation layer, which is basically a 2D electron gas in which the electron,phonon inelastic scattering is much weaker than the electron,electron inelastic scattering. A series of I,V measurements on a single NW device are carried out by alternating the atmosphere (vacuum, H2, vacuum, O2), and a reversible change in the conductance from metallic to semiconducting is achieved, indicating the surface accumulation layer is likely hydroxide-induced. Such results strongly support the two-channel model and demonstrate the controllable tuning of the ZnO NW electrical behavior via surface band-bending. [source]

Electronic and Mechanical Coupling in Bent ZnO Nanowires

ADVANCED MATERIALS, Issue 48 2009
Xiaobing Han
A red shift of the exciton of ZnO nanowires is efficiently produced by bending strain, as demonstrated by a low-temperature (81,K) cathodoluminescence (CL) study of ZnO nanowires bent into L- or S-shapes. The figure shows a nanowire (Fig. a) with the positions of CL measurements marked. The corresponding CL spectra,revealing a peak shift and broadening in the region of the bend,are shown in Figure b. [source]

Energy Harvesting Using Piezoelectric Nanowires,A Correspondence on "Energy Harvesting Using Nanowires?"

ADVANCED MATERIALS, Issue 13 2009
by Alexe et al.
A response to the questions raised by Alexe et al. concerning nanowire-based nanogenerators is presented. Evidence is given about the existence and detection of a piezoelectric potential in ZnO nanowires. The role played by the piezoelectric potential is to overcome the threshold voltage at the Pt,ZnO junction, while the observed output signal of ,10,mV is the difference in Fermi levels between the two electrodes. The measurement system used by Alexe et al. is questioned, as is their model. [source]

Vapor,Solid,Solid Growth Mechanism Driven by Epitaxial Match between Solid AuZn Alloy Catalyst Particles and ZnO Nanowires at Low Temperatures,

ADVANCED MATERIALS, Issue 8 2008
Leonardo C. Campos
A comprehensive explanation for the precise mechanism of ZnO nanowire growth at low temperatures (T,<,400,°C) is presented. Experimental data and theoretical considerations evidence that ZnO nanowires originate from solid ,-AuZn catalyst particles. A model is proposed to describe such growth. An original feature of the model concerns the formation of nanowire, which occurs via preferential oxidation of specific ,-AuZn surfaces induced by epitaxial-like growth mechanism. [source]

Dynamic fatigue studies of ZnO nanowires by in-situ transmission electron microscopy

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7-8 2009
Zhiyuan Gao
Abstract The fatigue behavior of ceramic ZnO nanowires (NWs) has been investigated under resonance cyclic loading conditions using in-situ transmission electron microscopy (TEM). After mechanical deformation at the resonance frequency at a vibration angle of 5.2° for 35 billion cycles, no failure or any defect generations have been found. We believe that the dislocation-free nature of NWs and the large surface-to-volume ratio contribute to the NWs' ability to undergo deformation without fatigue or fracture, proving their durability and toughness for nanogenerators and nanopiezotronics. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Light emission from different ZnO junctions and nanostructures

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009
M. Willander
Abstract We will discuss our experimental results for optical spectra produced by hole-injection from different p-type organic and inorganic materials into n-type ZnO nanowires. The influence of different growth techniques and conditions on the nanowires and their emission spectral characteristics will then be analyzed and discussed. The latest findings on the mixture of the green emission band responsible for visible light emission from ZnO and the blue light emission from the organic polymer will be presented. Different high brightness light emitting diodes (HB-LEDs) from our grown ZnO nanowires are demonstrated. The p-type multi layer organic structures contain PEDOT:PSS as hole injectors combined with a hole transporting layer, and in some structures, a final top electron blocking/hole barrier stepping layer is placed. The purpose of this layer is to adjust the hole and electron emission from the corresponding junction side to optimize the LED performance. Structural scanning electron microscopy (SEM), electrical (I ,V characteristics), photoluminescence (PL) and electroluminescence (EL) characteristics of these devices are displayed. Theoretically, we study the superfluidity of a two-dimensional system of excitonic polaritons in an optical microcavity with an embedded quantum well. Using the effective low-energy action for thermodynamic phase fluctuations, we obtain an expression for the analogue of the superfluid density in the system in terms of the "current,current" correlation function. The Kosterlits,Thouless transition temperature to the superfluid state as a function of the controlling parameters is calculated. Two methods are considered for producing traps for a polariton system in an optical microcavity. The behaviour of a two-component Bose condensate of photons and excitons is analyzed theoretically for both types of the trap. The Bose condensate is described by the coupled system of equations of the Gross,Pitaevskii type. The approximate wave functions and the spatial profiles of coupled photon and exciton condensates are obtained. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

ZnO nanowire arrays , Pattern generation, growth and applications

Nanowire,quantum-dot,polymer solar cell

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2008
A. Nadarajah
Abstract We report first results on a new solar cell structure which incorporates n-type ZnO nanowires, an undoped CdSe layer, obtained from quantum dot precursors, and a p-type polymer layer as the main components. In the fabrication process the quantum dot layer is converted to a conformal ,30 nm thick polycrystalline film. The fabrication of the cell occurs in lab air at temperatures below 100 °C. Several intermittent annealing steps raise the energy conversion efficiency to approximately 1%. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Optical properties of single ZnO nanowires

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2006
L. Wischmeier
Abstract The optical properties of single ZnO nanowires with diameters <200 nm are analyzed. A comparison of the photoluminescence properties of the as-grown ensemble and of an individual nanowire is given. The temperature dependence of the individual nanowire photoluminescence shows the same behavior as that of bulk material due to the wire diameter being very large compared to the exciton Bohr radius of ZnO. Furthermore, high excitation-density measurements performed on an individual nanowire are presented in which a sharp line is observed resulting from resonator effects inside the wire. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

ZnO nanowires: chemical growth, electrodeposition, and application to intracellular nano-sensors

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008
M. Willander
Abstract In this paper we present our results on growth, characterization, and nano-devices based on ZnO nano-structures. The ZnO nano-structures were grown by mainly two methods, the catalytic Vapor Liquid Solid (VLS) and the low temperature chemical growth. We show that by multiple coating combined with low temperature chemical growth, well aligned with size controlled ZnO nanowires on silicon substrates can be achieved. The dissolution, due to its important on the stability of ZnO nano-structures in aqueous medium, is then discussed and some preliminary experimental results are shown. Basic Optical characteristics of ZnO nano-rods are briefly discussed. Finally, electrochemical intracellular nano-sensors based on ZnO nano-wires are demonstrated as efficient nano-sensors for monitoring the human cell activity with minute pH changes. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]