Home About us Contact
|
Home About us Contact | ||
|
|
||
Solid Mechanism (solid + mechanism)
Selected AbstractsA Vapor,Liquid,Solid Mechanism for Growing 3C-SiC Single-Domain Layers on 6H-SiC(0001),ADVANCED FUNCTIONAL MATERIALS, Issue 7 2006M. Soueidan Abstract Growing device-quality 3C-SiC monocrystalline material is still an issue despite two decades of work dedicated to the subject. Using silicon as the substrate generates too many defects in the layers, owing to lattice mismatch, while it is very difficult to control the initial nucleation on an ,-SiC substrate so that 60° rotated domains are randomly formed. Herein, the elaboration of mono-orientated 3C-SiC layers on a 6H-SiC(0001) on-axis, Si face substrate using a vapor,liquid,solid mechanism is reported. This non-conventional approach for growing monocrystalline layers involves feeding a Ge,Si melt by a propane flux at a temperature ranging from 1250 to 1550,°C. We show that, by using this technique, the 3C-SiC material is almost always obtained on an hexagonal substrate, even if the crystal seed is oriented 8° off-axis. Using on-axis 6H-SiC seeds and optimal growth conditions results in the reproducible deposition of single-domain 3C-SiC layers. A mechanism is proposed to clarify some aspects of this process. [source] Electrically Addressable Hybrid Architectures of Zinc Oxide Nanowires Grown on Aligned Carbon NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Jong 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 Vapor,Liquid,Solid Mechanism for Growing 3C-SiC Single-Domain Layers on 6H-SiC(0001),ADVANCED FUNCTIONAL MATERIALS, Issue 7 2006M. Soueidan Abstract Growing device-quality 3C-SiC monocrystalline material is still an issue despite two decades of work dedicated to the subject. Using silicon as the substrate generates too many defects in the layers, owing to lattice mismatch, while it is very difficult to control the initial nucleation on an ,-SiC substrate so that 60° rotated domains are randomly formed. Herein, the elaboration of mono-orientated 3C-SiC layers on a 6H-SiC(0001) on-axis, Si face substrate using a vapor,liquid,solid mechanism is reported. This non-conventional approach for growing monocrystalline layers involves feeding a Ge,Si melt by a propane flux at a temperature ranging from 1250 to 1550,°C. We show that, by using this technique, the 3C-SiC material is almost always obtained on an hexagonal substrate, even if the crystal seed is oriented 8° off-axis. Using on-axis 6H-SiC seeds and optimal growth conditions results in the reproducible deposition of single-domain 3C-SiC layers. A mechanism is proposed to clarify some aspects of this process. [source] Silicon Nanowires: A Review on Aspects of their Growth and their Electrical PropertiesADVANCED MATERIALS, Issue 25-26 2009Volker Schmidt Abstract This paper summarizes some of the essential aspects of silicon-nanowire growth and of their electrical properties. In the first part, a brief description of the different growth techniques is given, though the general focus of this work is on chemical vapor deposition of silicon nanowires. The advantages and disadvantages of the different catalyst materials for silicon-wire growth are discussed at length. Thereafter, in the second part, three thermodynamic aspects of silicon-wire growth via the vapor,liquid,solid mechanism are presented and discussed. These are the expansion of the base of epitaxially grown Si wires, a stability criterion regarding the surface tension of the catalyst droplet, and the consequences of the Gibbs,Thomson effect for the silicon wire growth velocity. The third part is dedicated to the electrical properties of silicon nanowires. First, different silicon nanowire doping techniques are discussed. Attention is then focused on the diameter dependence of dopant ionization and the influence of interface trap states on the charge carrier density in silicon nanowires. It is concluded by a section on charge carrier mobility and mobility measurements. [source] Catalyst Metal Selection for Synthesis of Inorganic Nanowires,ADVANCED MATERIALS, Issue 14 2005P. Nguyen Growth of inorganic nanowires mediated by alternatives to gold using a vapor,liquid,solid mechanism is reported. Fifteen metals have been studied as catalysts, with several of them yielding nanowires (see Figure). The nanowire growth density is a function of melting temperature of the catalyst metals, as the catalyst material serves as the soft template for incorporation of the vapor species into the nanowire. [source] Growth and Mechanism of Network-Like Branched Si3N4 NanostructuresJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2010Zhijian Peng The high-yield synthesis of network-like branched silicon nitride (Si3N4) nanostructures by a simple template catalyst-assisted pyrolysis of a polymer precursor, perhydropolysilazane, was reported. The templates were silicon wafers deposited with Fe films of 5,20 nm in thickness. The processes simply involved thermal cross-linking of the preceramic polymer, crushing of the solidified polymer chunks into fine powder, and thermal pyrolysis of the powder under flowing high-purity nitrogen. The collected white network-like branched nanostructures are ,-Si3N4 of hexagonal phase, and their microstructures, in which the diameters of each linear part of the network-like nanostructure varied in a very wide range from tens of nanometers to hundreds of nanometers, strongly depend on the applied growth parameters, where the key factors are the heating rate and catalyst thickness for change in the diameters. It was proposed that the Si3N4 nanonetworks were formed through "metal-absorption on the surface of nanostructures" model by vapor,liquid,solid mechanism. The reaction mechanism of Si3N4 nanonetworks was also discussed. [source] Photoluminescence of Hg-doped CdS nanowiresPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2006Shao-Min Zhou Abstract Hg-doped CdS nanowires with an average diameter of ,10,15 nm and lengths up to hundreds of micrometers are fabricated by chemical vapor reaction. The as-synthesized products have a single crystal phase and grow along the ,001, direction. The growth of Hg-doped CdS nanowires is suggested for the quasi-vapor,solid mechanism (QVSM). In particular, the PL spectra show enhancing emission peaks that strongly shift to long wavelengths (up to 115 nm redshift) with Hg doping where the Hg-doped CdS nanowires are found to be responsible for the different characteristics; the PL mechanism is explained in detail. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||