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ZnO Crystals (zno + crystal)

Distribution by Scientific Domains

Physics and Astronomy	57%
Polymers and Materials Science	28%

Selected Abstracts

Growing ZnO Crystals on Magnetite Nanoparticles

CHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2004
Rachel Turgeman
Abstract We report herein on the oriented growth of ZnO crystals on magnetite nanoparticles. The ZnO crystals were grown by hydrolyzing a supersaturated aqueous solution of zinc nitrate. The seeds for the growth were magnetite nanoparticles with a diameter of 5.7 nm and a narrow size distribution. Hollowed ZnO hexagons of 0.15 ,m width and 0.5 ,m length filled with Fe3O4 particles were obtained. HR-TEM (high-resolution transmission electron microscopy) and selected-area EDS (energy-dispersive spectroscopy) show that the nanoparticles are homogenously spread in the ZnO tubes. Zeta potential measurements were employed to understand the relationship between the nanoparticles and the oriented growth of the ZnO crystals. The results show that the surfactants induced the directional growth of the ZnO crystals. [source]

Growth of ZnO single crystals by an induced nucleation from a high temperature solution of the ZnO-PbF2 system

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2007
Xinhua Li
Abstract To grow ZnO single crystals from a high temperature solution of the ZnO-PbF2 system, a gas cooling system was assembled at the bottom of the crucible to induce nucleation in the initial growth stage. The growth experiments were carried out in a homemade vertical Bridgman furnace and Pt crucible of 28 mm in diameter was used. The furnace temperature was set to 1100°C and the flow rate of the oxygen gas was optimized as 3.0 l/min. ZnO crystal up to 5,8mm in the thickness was obtained with the lowering rate of 0.3 mm/h. XRD patterns showed that the as-grown crystal was pure ZnO Wurtzite phase. The impurity ions were analyzed by the glow discharge mass spectroscopy (GDMS) as 390.0 ppm and 40.0 ppm for Pb2+ and F - , respectively. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Preparation and Electric Properties of Dense Nanocrystalline Zinc Oxide Ceramics

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2002
Lian Gao
This communication reports on the preparation and electric properties of dense nanocrystalline ZnO ceramics. By spark plasma sintering, nanocrystalline (,100 nm) ZnO ceramics with a high density of 98.5% were obtained at a very low temperature of 550°C. Electric property measurement revealed a novel conduction nonlinearity in the sample sintered at 500°C. This phenomenon is due to the nanometerization of ZnO crystal and the grain boundary layer with an amorphous interfacial layer. [source]

Synthesis of ZnO whiskers with different aspect ratios by a facile solution route

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2008
Juan Xie
Abstract Monodispersed zinc oxide (ZnO) whiskers with different aspect ratios were successfully prepared via a simple solution route at low temperature. It is found that the diameter and aspect ratio of ZnO whiskers depend critically on the structure and type of ionic surfactant added in the reaction solution. To further understand the effect of the surfactants on the formation process of ZnO whiskers, concentration measurements of Zn(II) remaining in the solution as well as scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analyses of the solid product have been made at regular intervals throughout the reaction with and without the surfactants. A possible formation process has been reasonably suggested based on these systematic experimental results. It is believed that anion surfactants are capable of slowing down the nucleation and growth rate of ZnO crystallite, which is favorable for the anisotropic growth habit of ZnO crystal to form needle-like whiskers. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Growth of ZnO crystals by vapour transport: Some ways to act on physical properties

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2006
R. Tena-Zaera
Abstract Nowadays, the growth of ZnO by vapor transport in silica ampoules is generally made in presence of graphite. As it has been already shown, this means that the growth process is carried out in presence of a Zn excess. In order to control that and act, as a consequence, on the physical properties of crystals we have performed a systematic study of the growth process in a wide range of Zn excess compositions using well defined experimental conditions. As a preliminary characterization, optical absorption and electrical properties have been analyzed at room temperature. The results show how some physical properties of as-grown ZnO crystals can be changed in a controlled way by an adequate combination of different growth conditions such as graphite covering of inner ampoule walls, thermal difference between source material and crystallization zone and additional gas (composition and pressure). In this frame some post-growth annealing processes can be avoided reducing the time and cost of processes. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [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]

A microwave-assisted process for coating polymer and glass surfaces with semiconducting ZnO submicron particles

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009
Alexander Irzh
Abstract A new method for coating glass slides with ZnO particles with an average size of 200 nm is proposed in the current article. The coating was performed under microwave radiation. Two main morphologies are found for the ZnO crystals that are deposited on glass slides. The first morphology is that of a very dense coating of ZnO hexagonal rods growing perpendicular to the glass surface. The second is the growth of ZnO flower-like particles. In addition to coating the glass by ZnO particles, we also report on coating other polymers [poly(methyl methacrylate) plate, polycarbonate beads, Nylon 6,6 beads, and polypropylene beads) by ZnO. The morphology obtained for ZnO coated on polymers is different from that detected for coating ZnO on glass. The unorganized coating of ZnO rods on polymers has been observed. The coated glass slides were characterized by X-ray diffraction, volumetric titration, EDS, scanning electron microscope, and optical measurements (DRS and transmittance spectroscopy). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

Bioinspired Mineralization of Inorganics from Aqueous Media Controlled by Synthetic Polymers

MACROMOLECULAR BIOSCIENCE, Issue 2 2007
Katarzyna Gorna
Abstract The formation of inorganic structures in nature is commonly controlled by biogenic macromolecules. The understanding of mineralization phenomena and the nucleation and growth mechanisms involved is still a challenge in science but also of great industrial interest. This article focuses on the formation and mineralization of two archetypical inorganic materials: zinc oxide and amorphous calcium carbonate (ACC). Zinc oxide is selected as a model compound to investigate the role that polymers play in mineralization. Most of the effort has been devoted to the investigation of the effects of double-hydrophilic block and graft copolymers. Recent work has demonstrated that latex particles synthesized by miniemulsion polymerization, properly functionalized by various chemical groups, have similar effects to conventional block copolymers and are excellently suited for morphology control of ZnO crystals. Latex particles might serve as analogues of natural proteins in biomineralization. The second example presented, ACC, addresses the issue of whether this amorphous phase is an intermediate in the biomineralization of calcite, vaterite, or aragonite. Conditions under which amorphous calcium carbonate can be obtained as nanometer-sized spheres as a consequence of a liquid,liquid phase segregation are presented. Addition of specific block copolymers allows control of the particle size from the micrometer to the submicrometer length scale. The physical properties of novel materials synthesized from concentrated solution and their potential applications as a filler of polymers are also discussed. [source]

Observation of Zn vacancies in ZnO grown by chemical vapor transport

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2006
F. Tuomisto
Abstract We have used positron annihilation spectroscopy to study the vacancy defects in ZnO crystals grown by both the conventional and contactless chemical vapor transport (CVT and CCVT). Our results show that Zn vacancies or Zn vacancy related defects are present in as-grown ZnO, irrespective of the growth method. Zn vacancies are observed in CVT-grown undoped ZnO and (Zn,Mn)O. The Zn vacancies present in undoped CCVT-ZnO are the dominant negatively charged point defect in the material. Doping the material with As introduces also Zn vacancy-related defect complexes with larger open volume. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Feature Article: Bound exciton and donor,acceptor pair recombinations in ZnO

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2004
B. K. Meyer
The article [1] features the current state of knowledge on the optical properties of excitonic and donor,acceptor pair recombination in bulk n-ZnO, as revealed by recent photo- and cathodoluminescence measurements. The cover picture is a photograph showing an unusual look at the green luminescence of rod-shaped ZnO crystals under ultraviolet excitation. The first author, Bruno K. Meyer, is professor of physics at the Justus Liebig University of Giessen. His scientific interests include synthesis of semiconductor oxides by chemical vapour deposition and magnetron sputtering, in particular with respect to doping issues, materials science of electro- and thermochromic materials, recombination phenomena and defect characterization by magnetic resonance. This issue also contains an Editor's Choice on "Evolution of molecular ordering and phase transitions in C60/C70 solid solutions" by Gabriela Rueda-Morales and Jaime Ortiz-López [2]. [source]

Role of excitons in the excitation of deep-level emission in ZnO crystals

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010
V. I. Kushnirenko
Abstract In undoped ZnO crystals, photoluminescence excitation (PLE) spectra of deep-level green and orange PL bands as well as photocurrent (PC) spectra were measured at 77 and 290 K. Some PLE and PC peaks whose energy positions coincided with that of free exciton and its excited states were observed, the intensity of PL and PC excited in these peaks being higher than under excitation by band-to-band light. At the same time, a sharp minimum was found in PLE and PC spectra at the position of donor-bound exciton. Obtained results were accounted for by the interaction of excitons with lattice defects. A number of longer wavelength PLE and PC peaks whose energy positions coincided in fact with that of the first, second and third phonon replicas of free exciton were also observed. The origin of these peaks is discussed. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]