共查询到20条相似文献,搜索用时 15 毫秒
1.
J.K. Jian X.L. Chen T. Xu Y.P. Xu L. Dai M. He 《Applied Physics A: Materials Science & Processing》2002,75(6):695-697
SnO2 nanowires were synthesized using a direct gas reaction route and were characterized by X-ray powder diffraction (XRD), scanning
electron microscopy (SEM), selected-area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM)
and Raman-scattering spectroscopy. XRD, SEM, SAED and HRTEM indicated that the products were tetragonal SnO2 nanowires with diameters of 10–50 nm. The nanowires were single crystal and solid inside. Dendritic nanowires were observed
for the first time. Three vibrational modes were observed in the Raman spectra of the samples.
Received: 7 January 2002 / Accepted: 11 April 2002 / Published online: 19 July 2002 相似文献
2.
J.K. Jian X.L. Chen W.J. Wang L. Dai Y.P. Xu 《Applied Physics A: Materials Science & Processing》2003,76(2):291-294
Single-crystalline SnO2 nanowires, nanobelts and nanodendrites were synthesized by a simple gas-reaction route on a large scale at 900 °C. They were
characterized by means of X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive
X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). FE-SEM images
showed that the products consisted of nanowires, nanobelts and nanodendrites that represent a novel morphology reported for
the first time. XRD, SAED and EDS indicated that they were single-crystalline tetragonal SnO2. The influence of experimental conditions on the morphologies of the products is discussed.
Received: 3 June 2002 / Accepted: 10 June 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: 86-10/82649531, E-mail: xlchen@aphy.iphy.ac.cn 相似文献
3.
Z.J. Li X.L. Chen L. Dai H.J. Li H.W. Liu H.J. Gao Y.P. Xu 《Applied Physics A: Materials Science & Processing》2003,76(1):115-118
A new form of GaN nanomaterial (nanotweezers) has been obtained by chemical vapor deposition on an etched cubic MgO (100)
plane. The nanotweezers consist of a bottom rod and two arms. The bottom rods have diameters of about 100–150 nm and lengths
of about 200–500 nm, on which two arms grow out. The bottoms of the arms are about 40–70 nm and the tops are about 15–30 nm
in diameter, and 0.8–1.5 μm in length. X-ray and electron diffractions indicate the nanotweezers are zinc blende gallium nitride.
We infer that the fabrication of the GaN nanotweezers is associated with small convex hillocks on the surface of the etched
cubic MgO (100) single-crystal substrates and that the nanotweezers grow by a growth mechanism that is similar to vapor-phase
heteroepitaxy.
Received: 23 April 2002 / Accepted: 25 April 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +86-10/8264-9531, E-mail: xlchen@aphy.iphy.ac.cn 相似文献
4.
X.S. Peng Y.W. Wang J. Zhang X.F. Wang L.X. Zhao G.W. Meng L.D. Zhang 《Applied Physics A: Materials Science & Processing》2002,74(3):437-439
In2O3 nanowires have been successfully fabricated on a large scale from indium particles by thermal evaporation at 1030 °C. The
as-synthesized products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission
electron microscopy (TEM). SEM and TEM images show that these nanowires are uniform with diameters of about 60–120 nm and
lengths of about 15–25 μm. XRD and selected-area electron diffraction analysis together indicate that these In2O3 nanowires crystallize in a cubic structure of the bixbyite Mn2O3 (I) type (also called the C-type rare-earth oxide structure). The growth mechanism of these nanowires is also discussed.
Received: 29 June 2001 / Accepted: 28 September 2001 / Published online: 20 December 2001 相似文献
5.
In this study, we demonstrate the large-scale synthesis of beta gallium oxide (β-Ga2O3) nanowires through microwave plasma chemical vapor deposition (MPCVD) of a Ga droplet in the H2O and Ar atmosphere at 600 W. Unlike the commonly used MPCVD method, the H2O, not mixture of gas, was employed to synthesize the nanowires. The ultra-long β-Ga2O3 nanowires with diameters of about 20-30 nm were several tens of micrometers long. The morphology and structure of products were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscope (HRTEM). The growth of β-Ga2O3 nanowires was controlled by vapor-solid (VS) crystal growth mechanism. 相似文献
6.
Long silicon nanowires (SiNWs) grown by laser ablation or by thermal evaporation of monoxide source materials are primarily
oriented in the <112> direction, and some in the <110> direction, but rarely in the <100> or <111> directions. We propose
a model to explain these SiNW growth directional features. The model consists of two parts. Part one is concerned with mechanism-based
criteria and part two with applying these criteria to explain the experimental results. Four criteria are considered: (i)
the stability of a Si atom occupying a surface site; (ii) the Si {111} surface stability in the presence of oxygen; (iii)
the stepped Si {111} surface layer lateral growth process; and (iv) the effect of dislocations in providing perpetuating {111}
steps to facilitate SiNW growth. Analyses of SiNW growth in accordance with these criteria showed that <112> and <110> are
the preferred SiNW growth directions, and that <111> and <100> are not.
Received: 12 November 2001 / Accepted: 20 November 2001 / Published online: 23 January 2002 相似文献
7.
In this study, beta-gallium oxide (β-Ga2O3) nanowires, nanobelts, nanosheets, and nanograsses were synthesized through microwave plasma of liquid phase gallium containing H2O in Ar atmosphere using silicon as the substrate. The nanowires with diameters of about 20-30 nm were several tens of microns long and the nanobelts with thickness of about 20-30 nm were tens to hundreds of microns long. The morphology and structure of products were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and X-ray diffraction (XRD). These results showed that multiple nucleation and growth of β-Ga2O3 nanostructures could easily occur directly out of liquid gallium exposed to appropriate H2O and Ar in the gas phase. The growth process of β-Ga2O3 nanostructures may be dominated by VS (vapor-solid) mechanism. 相似文献
8.
ZnO rod arrays/CuSCN heterojunctions are fabricated by depositing ZnO rod arrays films using two-step chemical bath deposition (CBD) and CuSCN thin films using successive ionic layer adsorption and reaction (SILAR) on ITO substrate successively. The structures and morphologies of ZnO films and CuSCN films, analyzed by X-ray diffraction (XRD) spectroscopy and metallurgical microscope, show that ZnO films are hexagonal wurtzite structure and consisted of vertical polycrystalline rods with diameter of 1 μm, CuSCN films are β-phase structure and consisted of elongated grains with length of 3 μm. Current–voltage (I–V) measurements of ZnO/CuSCN heterojunctions show good diode characteristics with rectification ratio about 48.3 at 3 V. The forward conduction is, respectively, determined by carrier recombination in the space charge region, defect-assisted tunneling and exponential distribution trap-assisted space charge limited current mechanism with the increase of forward voltage. Also, a band diagram of ZnO/CuSCN heterojunctions has been proposed to explain the transport mechanism. 相似文献
9.
K. Elihn F. Otten M. Boman P. Heszler F.E. Kruis H. Fissan J.-O. Carlsson 《Applied Physics A: Materials Science & Processing》2001,72(1):29-34
Iron-containing nanoparticles were made by laser-assisted (ArF excimer laser, λ=193 nm) photolytic dissociation of ferrocene
(Fe(C5H5)2 or FeCp2) in argon and an oxygen/argon gas mixture. The particle-size distributions were obtained on-line by using differential mobility
analysers (DMAs) and were found to be log-normal with a geometric standard deviation of 1.85. In argon, particle sizes between
3 and 100 nm were generated. The volumes of these particles were found to increase linearly with the increased repetition
rate, fluence and beam size of the laser. These observations are explained on the basis of the residence-time approach model.
Received: 23 November 1999 / Accepted: 19 September 2000 / Published online: 22 November 2000 相似文献
10.
S. Gu R. Zhang Y. Shi Y. Zheng L. Zhang T.F. Kuech 《Applied Physics A: Materials Science & Processing》2002,74(4):537-540
The initial stages and subsequent growth of GaN on sapphire using ZnO buffer layers is reported for the hydride vapor phase
epitaxy technique. A high gas-phase supersaturation in the growth ambient was used to favor a rapid initial growth on the
substrate. A subsequent growth step was employed under conditions that favor a high lateral growth rate in order to promote
the coalescence of the initial islands and provide optimal material properties. The specific gas-phase mole fractions of the
GaCl and NH3 at the growth front control both the vertical and lateral growth rates. The use of a two-step growth process in the GaN growth
leads to a controlled morphology and improved material properties for GaN materials when grown with a ZnO buffer layer. An
optimized set of growth conditions, utilizing this two-step process, was found to also improve the growth directly on sapphire
without a ZnO buffer layer.
Received: 8 November 2001 / Accepted: 14 November 2001 / Published online: 11 February 2002 相似文献
11.
Dandan Wang Jinghai Yang Guozhong Xing Lili Yang Ming Gao Tom Wu 《Journal of luminescence》2009,129(9):996-22735
Single-crystalline ZnO nanowires (NWs) were synthesized by a facile vapor transport method. The good orientation and high crystal quality were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) measurements. Excitation-power-dependence photoluminescence spectra of ZnO NWs show that the UV emission displayed an evident blueshift with increasing excitation power and the corresponding energy shift might be as large as 10 meV. This anomalous phenomenon correlates to the band bending level caused by the surface built-in electric field due to the existence of substantial oxygen vacancies. By increasing the excitation power, the enhanced neutralization effect near the surface will reduce the built-in electric field and lead to a reduction of band bending which triggers the blueshift of the UV emission. 相似文献
12.
2 laser-induced pyrolysis of silane in a flow reactor, based on scattering of He-Ne laser light by a particulate in the reaction
flame. The scattering and extinction measurements have been used to measure nucleation and growth kinetics of silicon powders
within the reaction zone. The experience gained by this technique allowed synthesis of silicon particles with a wide size
range.
Received: 29 April 1998/Accepted: 30 April 1998 相似文献
13.
Centimetre-long ZnO fibres are synthesized by vapour transportation via thermal evaporation of ZnO powders. The growth process is carried out in a graphite crucible, in which ZnO powder is loaded as the source material, and a silicon wafer is positioned on the top of the crucible as the growth substrate. During the growth process, the source temperature is kept at 800℃ and the substrate temperature is kept at 600℃. Typical growth time to obtain centimetre-long ZnO fibres is 5-10 hours. Scanning electron microscopy (SEM), x-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) measurement results show that ZnO fibres are single crystalline with high crystalline quality and very low defects concentration. 相似文献
14.
F. Kokai K. Takahashi D. Kasuya A. Nakayama Y. Koga M. Yudasaka S. Iijima 《Applied Physics A: Materials Science & Processing》2003,77(1):69-71
Polyhedral graphite (PG) particles have been synthesized by CO2 laser vaporization of graphite in high-pressure Ar gas (8×105 Pa). Faceted PG particles, ranging in size from 110 to 500 nm, have a turbostratic structure. The yield of PG is more than
90%. This synthesis is based on the condensation of hot carbon species confined by an Ar-gas atmosphere.
Received: 22 January 2003 / Accepted: 24 January 2003 / Published online: 11 April 2003
RID="*"
ID="*"Corresponding author. Fax: +81-59/231-9471, E-mail: kokai@chem.mie-u.ac.jp Permanent address: Chemistry Department for
Materials, Mie University, 1515 Kamihama, Tsu, Mie 514-8507, Japan 相似文献
15.
Effect of Crucibles on Qualities of Self-Seeded Aluminium Nitride Crystals Grown by Sublimation
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Self-seeded aluminium nitride (AlN) crystals are grown in tungsten and hot pressed boron nitride (HPBN) crucibles with different shapes by a sublimation method. The qualities of the AlN crystals are characterized by high-resolution transmission electronic microscopy (HRTEM), scanning electron microscopy (SEM) and Micro-Rarnan spectroscopy. The results indicate that the better quality crystals can be collected in conical tungsten crucible. 相似文献
16.
Hong Jin Fan Roland Scholz Florian M. Kolb Margit Zacharias Ulrich Gösele 《Solid State Communications》2004,130(8):517-521
We report the growth mechanism and structural properties of micrometer sized ZnO cages which were synthesized directly from Zn vapor deposition and oxidation. The ZnO microcages exhibit a hexagonal or spherical shape with partly or completely open surfaces and hollow interiors. The growth process of the microcages includes the deposition of Zn polyhedral particles, top face breaking of the Zn particles and Zn sublimation, and subsequent reaction to ZnO. By controlling the various growth stages, we obtained information on the growth mechanism of the ZnO cages, which appears to be different from a mechanism reported previously. The chemical composition and crystalline structure were studied using energy dispersive X-ray spectroscopy and transmission electron microscopy, respectively. The room-temperature photoluminescence spectrum indicates a large quantity of oxygen-vacancy related defects within the wall of the ZnO cages. 相似文献
17.
A theoretical model for the growth of single-wall carbon nanotubes produced by metal-catalyzed decomposition of hydrocarbons
and fullerenes is presented. The growth process is treated as a thermodynamic equilibrium between carbon in the gas phase
and carbon in the nanotube. The minimum possible nanotube diameters based on several published experimental conditions are
calculated by combining the free energy of the reaction with an equation derived from elastic theory. The model predicts the
possibility of generating nanotubes with extremely small diameters that are smaller than in the corresponding experiments.
Received: 18 July 2001 / Accepted: 19 November 2001 / Published online: 4 March 2002 相似文献
18.
Fabrication, morphology and structural characterization of ordered single-crystal Ag nanowires 总被引:1,自引:0,他引:1
J. Zhang X. Wang X. Peng L. Zhang 《Applied Physics A: Materials Science & Processing》2002,75(4):485-488
Highly aligned Ag nanowires have been synthesized by dc electrodeposition within a hexagonal close-packed nanochannel anodic
aluminum oxide template. The pore diameter varies from 20 nm to 50 nm depending on the anodization voltage and temperature
for the two types of aqueous solutions, sulphuric and oxalic acids, respectively. The size and morphology of the Ag nanowire
arrays were measured by scanning electron microscopy and transmission electron microscopy. The images indicate that the highly
aligned Ag nanowires grow in the uniform nanochannels of the anodic alumina template and that the size of the nanowires depends
on the size of the nanochannels. X-ray diffraction, selected area electron diffraction pattern and high-resolution transmission
electron microscopy images show that the Ag nanowires are single-crystal. The temperature coefficient of resistivity (temperature
range from 4.2 K to 300 K) of the Ag nanowire arrays decreases with decreasing diameter of the nanowires.
Received: 5 November 2001 / Revised version: 12 March 2002 / Published online: 6 June 2002 相似文献
19.
H.S. Roh Y.C. Kang H.D. Park S.B. Park 《Applied Physics A: Materials Science & Processing》2003,76(2):241-245
Y2O3:Eu phosphor particles were prepared by large-scale spray pyrolysis. The morphological control of Y2O3:Eu particles in spray pyrolysis was attempted by adding polymeric precursors to the spray solution. The effect of composition
and amount of polymeric precursors on the morphology, crystallinity and photoluminescence characteristics of Y2O3:Eu particles was investigated. Particles prepared from a solution containing polyethylene glycol (PEG) with an average molecular
weight of 200 had a hollow structure, while those prepared from solutions containing adequate amounts of citric acid (CA)
and PEG had a spherical shape, filled morphology and clean surfaces after post-treatment at high temperature. Y2O3:Eu particles prepared from an aqueous solution with no polymeric precursors had a hollow structure and rough surfaces after
post-treatment. The phosphor particles prepared from solutions with inadequate amounts of CA and/or PEG also had hollow and/or
fragmented structures. The particles prepared from the solution containing 0.3 M CA and 0.3 M PEG had the highest photoluminescence
emission intensity, which was 56% higher than that of the particles prepared from aqueous solution without polymeric precursors.
Received: 22 March 2002 / Accepted: 26 March 2002 / Published online: 5 July 2002
RID="*"
ID="*"Corresponding author. Fax: +82-42/861-4245, E-mail: yckang@pado.krict.re.kr 相似文献
20.
Fabrication of bamboo-shaped GaN nanorods 总被引:1,自引:0,他引:1
H. Li J.Y. Li M. He X.L. Chen Z. Zhang 《Applied Physics A: Materials Science & Processing》2002,74(4):561-562
Bamboo-shaped GaN nanorods were formed through a simple sublimation method. They were characterized by means of X-ray powder
diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected-area
electron diffraction (SAED). The TEM image showed that the nanorods were bamboo-like. XRD, HRTEM and SAED patterns indicated
that the nanorods were single-crystal wurtzite GaN.
Received: 8 January 2001 / Accepted: 28 April 2001 / Published online: 20 December 2001 相似文献