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1.
Vidhika Sharma Pushpendra Kumar Jaya Shrivastava Anjana Solanki V. R. Satsangi Sahab Dass Rohit Shrivastav 《Journal of Materials Science》2011,46(11):3792-3801
Cu-incorporated nanocrystalline ZnO thin films were deposited on glass substrate by sol–gel. To a solution of zinc acetate
2-hydrate in dimethyl formamide, calculated quantities of copper acetate were added. The clear solution, obtained after 2 h
of continuous stirring, was coated on ITO plates. Pre-annealing at 250 °C was followed by sintering at 400, 500, and 600 °C.
XRD analysis revealed dominant evolution of hexagonal ZnO with a possible simultaneous growth of meta-stable cubic ZnO. AFM
and SEM analysis indicated preferential growth of nanocrystallites along c-axis. Optical characterization led to two prominent absorption thresholds in the UV region; one matching with the band gap
of bulk ZnO and the second at slightly higher energy, suggesting quantum confinement effect in nanocrystallites. Cu incorporation
influenced the two band gap energies differently. Photoelectrochemical splitting of water using 1% at. Cu–ZnO film sintered
at 600 °C resulted in 141% gain in photocurrent at zero bias. 相似文献
2.
P. P. Sahay S. Tewari R. K. Nath S. Jha M. Shamsuddin 《Journal of Materials Science》2008,43(13):4534-4540
The ac responses of the ZnO pellets have been studied by ac measurements (impedance, capacitance and phase angle) over the
temperature range 300–435 K. The ac conductivity of the ZnO pellets is observed to be proportional to ω
s
, where ω is the angular frequency and the exponent s is a temperature- and frequency-dependent parameter. Based on the existing theories of ac conduction, it has been concluded
that for low frequency region (20 Hz–2 kHz), the dominant conduction mechanism in the ZnO pellets is multihopping at all temperatures,
whereas for high frequency region (500 kHz–2 MHz), the small polaron tunneling model is the dominant mechanism in the pellets.
Activation energies for ac conduction processes are estimated to be in the range of 0.028–0.277 eV which are found to vary
with the frequency of the ac signal. These results are found to be consistent with the hopping model. The ac capacitance and
the dielectric loss tangent are found to be dependent on both frequency and temperature. Such dependences have been explained
taking into account the equivalent circuit model comprising a frequency-independent capacitive element in parallel with a
temperature-dependent resistive element, both in series with a low value resistance. Impedance spectroscopy studies show single
semicircular arcs in the complex impedance spectra at all temperatures in the range 300–435 K, with their centres lying below
the real axis at a particular angle of depression indicating a multirelaxation behaviour in the pellets. 相似文献
3.
M. Vishwas K. Narasimha Rao A. R. Phani K. V. Arjuna Gowda R. P. S. Chakradhar 《Journal of Materials Science: Materials in Electronics》2011,22(9):1415-1419
Zinc oxide (ZnO) thin films have been prepared on silicon substrates by sol–gel spin coating technique with spinning speed
of 3,000 rpm. The films were annealed at different temperatures from 200 to 500 °C and found that ZnO films exhibit different
nanostructures at different annealing temperatures. The X-ray diffraction (XRD) results showed that the ZnO films convert
from amorphous to polycrystalline phase after annealing at 400 °C. The metal oxide semiconductor (MOS) capacitors were fabricated
using ZnO films deposited on pre-cleaned silicon (100) substrates and electrical properties such as current versus voltage
(I–V) and capacitance versus voltage (C–V) characteristics were studied. The electrical resistivity decreased with increasing
annealing temperature. The oxide capacitance was measured at different annealing temperatures and different signal frequencies.
The dielectric constant and the loss factor (tanδ) were increased with increase of annealing temperature. 相似文献
4.
K. Sambath M. Saroja M. Venkatachalam K. Rajendran N. Muthukumarasamy 《Journal of Materials Science: Materials in Electronics》2012,23(2):431-436
ZnO nanostructures have been synthesized in a controlled manner by varying the pH of the precursor solution using hydrothermal
technique. The morphological changes of the prepared ZnO nanostructures have been investigated in the range of pH 5–10. Radial
hexagonal rod-like shape is formed at lower pH values of 5 and 6 whereas, flower-like shape is obtained for higher pH values
of 9 and 10. Flake-like structure is observed at moderate pH of 8. The prepared ZnO nanostructures have been characterized
using X-ray diffraction technique (XRD), energy dispersive X-ray analysis, scanning electron microscope and FTIR spectroscopy.
XRD results show that the prepared ZnO nanostructures exhibit hexagonal wurtzite structure. The growth mechanism suggests
that the supersaturation of the precursor results in various nucleation habits, which induce the formation of ZnO nanostructures
with different morphologies. UV–Vis spectroscopy and photoluminescence were applied to study the optical properties. The photoluminescence
spectrum demonstrated two emission bands, a near band edge emission in the UV region and a strong deep band emission in the
visible region. The change in pH from 5 to 10 results in band gap variations of 3.47–3.97 eV and blue-shift in the peak emission
of visible PL from 560 to 460 nm. 相似文献
5.
We report growth of ZnO nanorods by low temperature (<100°C) solution growth method. The substrates (Si, glass and fused Quartz)
were seeded by pre-coating with ZnO nanoparticles (4–7 nm diameter) prepared by chemical precipitation route. Nanorods were
grown on the seeded substrate in aqueous solution of Zinc Nitrate and Hexamethylenetetramine (HMT). The growth process lasts
for up to 8 h and at the maximum time of growth, the nanorods have a width of ∼230–250 nm and length of ∼1.5–1.6 μm. The growth
process after some initial growth (<2 h) preserves the aspect ratio and leads to about 90% texturing along the (002) direction.
The growth of the nanorods was studied with time and observed growth data suggests a two-stage growth process. The nanorods
have a well-defined hexagonal morphology and have a Wurtzite structure. The nanorods were characterized by different techniques
and have a band gap of 3.25 eV. 相似文献
6.
Rizwan Wahab Young-Soon Kim Kyeongseop Lee Hyung-Shik Shin 《Journal of Materials Science》2010,45(11):2967-2973
This article presents, the fabrication of perfectly hexagonal zinc oxide nanorods performed via solution process using zinc
nitrate hexahydrate (Zn(NO3)2·6H2O) and hexamethylenetetramine (HMT) at various concentrations of i.e. 1 × 10−3 to 10 × 10−2 M in 50 mL distilled water and refluxed at 100 °C for 1 h. We used HMT because it acts as a template for the nucleation and
growth of zinc oxide nanorods, and it also works as a surfactant for the zinc oxide structures. The X-ray diffraction patterns
clearly reveal that the grown product is pure zinc oxide. The diameters and lengths of the synthesized nanorods lie in the
range of 200–800 nm and 2–4 μm, respectively as observed from the field emission scanning electron microscopy (FESEM). The
morphological observation was also confirmed by the transmission electron microscopy (TEM) and clearly consistent with the
FESEM observations. The chemical composition was analyzed by the FTIR spectroscopy, and it shows the ZnO band at 405 cm−1. On the basis of these observations, the growth mechanism of ZnO nanostructures was also proposed. 相似文献
7.
Shao-Hwa Hu Yi-Chuan Chen Chyi-Ching Hwang Cheng-Hsiung Peng Dah-Chuan Gong 《Journal of Materials Science》2010,45(19):5309-5317
Nanocrystalline ZnO particles were synthesized from an aqueous solution composed of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and urea (H2NCONH2). A precipitating precursor, basic zinc carbonate (Zn5(CO3)2(OH)6), was first formed by hydrothermally treating the solution at 120 °C for 2–4 h. Nanocrystalline ZnO particles were then obtained
by calcining the precursors at 350–650 °C for 0.5–2 h. The synthesis products were characterized using thermogravimetry–differential
scanning calorimetry–mass spectrometry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy
and photoluminescence techniques. Based on the experimental results, a possible reaction mechanism for the ZnO formation was
proposed. The effects of experimental parameters (namely, the hydrothermal treatment time, the calcination time, and the calcination
temperature) on the characteristics of the resulting ZnO products (i.e., the crystalline size and the photoluminescence properties)
were analyzed by the Taguchi method to attain the optimum synthesis conditions. By using the appropriate parameters derived
from this method, we verified that the optimized synthesis provided a yield of ~70% and that the resulting ZnO particles possessed
the characteristics of a ~25 nm crystalline size and a satisfactory photoluminescence property. 相似文献
8.
Hiroyo Segawa Hideaki Sakurai Reiko Izumi Toshiharu Hayashi Tetsuji Yano Shuichi Shibata 《Journal of Materials Science》2011,46(10):3537-3543
Transparent zinc oxide (ZnO) films were coated on seed layers prepared by the sol–gel method by chemical solution deposition
method. Firstly, seed layers were prepared from zinc acetate and monoethanolamine, 2-methoxyethanol by the sol–gel method
on a silicon substrate or a slide glass. Next, the substrate coated with a seed layer was immersed in zinc nitride solution
with hexamethylenetetramine, and ZnO films were obtained. The transmittance of the ZnO films depended on the morphology and
crystallinity of the seed layers. When the seed layer were dried on a hot plate, the seed layer had flat surface and transparent
ZnO film could be obtained on the seed layers dried at temperatures above 200 °C. When the seed layer was prepared from zinc
acetate dihydrate dried in a petri dish, the seed layer were smooth without cracks and the transparent ZnO films were obtained
at temperature below 100 °C. 相似文献
9.
A. Bandyopadhyay A. K. Deb K. Mukhopadhyay S. K. Roy P. K. Chakrabarti 《Journal of Materials Science》2012,47(5):2284-2293
Tb3+-doped zinc oxide was prepared by the co-precipitation method. The as-dried sample was annealed at 80, 300, 500, 700, and
1000 °C. Rietveld analysis of the X-ray diffraction patterns of the samples annealed up to 300 °C showed that all the Tb3+ ions were entered in the ZnO lattice. But a fraction of Tb3+ ions could not enter in the ZnO lattice above 300 °C and this fraction increases with the increase of annealing temperature.
The crystallite size and the internal strain due to substitution of bigger size R-ions in the ZnO lattice of the samples were
estimated by using the Hall–Williamson plot. Results extracted from high resolution transmission electron microscopy are in
agreement with those obtained from the XRD analysis. Magnetic susceptibility (χ) in the range of 300–14 K and magnetization
as a function of magnetic field in the range of 300–5 K of the sample annealed at 80 °C were measured by Faraday and SQUID
magnetometers, respectively. Values of χ in the paramagnetic region were analyzed by invoking the crystal field interaction
of the Tb3+ ions with its diamagnetic neighbors. Paramagnetic to ferromagnetic phase transition has been observed at low temperature
and the saturation magnetization measured at 5 K is quite high compared to the pristine sample. 相似文献
10.
The microstructure and growth behavior for vertically aligned Zinc oxide (ZnO) nanowires, synthesized on a ZnO thin film template
by pulsed-laser deposition (PLD), is reported. The nanowire growth proceeds without any metal catalyst for nucleation, although
an epitaxial ZnO thin film template is necessary in order to achieve uniform alignment. Nanowire growth at argon or oxygen
background pressures of 500-mTorr results in nanowire diameters as small as 50–90 nm, with diameters largely determined by
growth pressure and temperature. Room temperature photoluminescence show both near-band-edge and deep-level emission. The
deep-level emission is believed caused by oxygen vancancies formed during growth. 相似文献
11.
Xiaojing Yu Xiaoqin Xu Dalai Jin Sali Miao Naiyan Wang Kuihong Yao 《Inorganic Materials》2011,47(1):41-44
ZnO short rods with large yield have been synthesized by a simple chemical solution deposition method at a low temperature
of 80°C. Polymethyl methacrylate was used as the structure-directing agent in the formation of the rod-like ZnO crystals.
X-ray powder diffraction and field emission scanning electron microscopy were used to characterize the obtained product. The
results showed that the as-prepared ZnO crystals were rod-like, which have fairly uniform diameter of around 0.5 ∼ 2 μm and
length of 4 ∼ 6 μm. A possible formation mechanism of the ZnO rods has been considered. 相似文献
12.
Yulong Zhang Ye Yang Junhua Zhao Ruiqin Tan Weiyan Wang Ping Cui Weijie Song 《Journal of Materials Science》2011,46(3):774-780
Aluminum-doped zinc oxide nanopowders were prepared using a surfactant assisted complex sol–gel method, and were characterized
using inductively coupled plasma, X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy, X-ray
photoelectron spectroscopy, and UV–Vis spectroscopy. Al was effectively doped into the ZnO matrix with concentrations up to
6.00 atomic ratio percents (at.%). X-ray diffraction results revealed that all of the nanoparticles had a pure hexagonal wurtzite
structure free of any impurities when annealing temperature was below 1273 K. The optical band gap of the nanopowders, which
was affected by the Al-doping concentration, reached a maximum of 3.43 eV when ZnO was doped with 4.00 at.% Al. The effect
of post-annealing temperature and vacuum conditions on the resistivities of the Al-doped ZnO nanoparticles was also investigated.
And the lowest volume resistivity (1.2 Ω cm) was achieved by annealing the Al-doped ZnO nanoparticles in a vacuum at 1173 K
for 2 h. 相似文献
13.
Ag/ZnO nanoparticles can be obtained via photocatalytic reduction of silver nitrate at ZnO nanorods when a solution of AgNO3 and nanorods ZnO suspended in ethyleneglycol is exposed to daylight. The mean size of the deposited sphere like Ag particles
is about 5 nm. However, some of the particles can be as large as 20 nm. The ZnO nanorods were pre-prepared by basic precipitation
from zinc acetate di-hydrate in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide. They are
about 50–300 nm in length and 10–50 nm in width. Transmission electron microscopy (TEM), energy-dispersive X-ray analysis
(EDS), X-ray powder diffraction (XRD), UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence
(PL) were used to characterize the resulting Ag/ZnO nanocomposites. 相似文献
14.
Yuanjie Li Xiaofen Hu Zilong Liu Jiangbo Ren 《Journal of Materials Science: Materials in Electronics》2012,23(2):408-412
Amorphous In–Ga–ZnO thin films were deposited on quartz glass substrate at room temperature utilizing radio frequency magnetron sputtering
technique. Sputtering power and oxygen flow rate effects on the physical properties of the In–Ga–ZnO films were systematically investigated. It is shown the film deposition rate and the conductivity of the In–Ga–ZnO films increased with the sputtering power. The as-grown In–Ga–ZnO films deposited at 500 W exhibited the Hall mobility of 17.7 cm2/Vs. Average optical transmittance of the In–Ga–ZnO films is greater than 80% in the visible wavelength. The extracted optical band gap of the In–Ga–ZnO films increased from 3.06 to 3.46 eV with increasing the sputtering power. The electrical properties of the In–Ga–ZnO films are greatly dependent on the O2/Ar gas flow ratio and post-growth annealing process. Increasing oxygen flow rate converted the In–Ga–ZnO films from semiconducting to semi-insulating, but the resistivity of the films was significantly reduced after being annealed
in vacuum. Both the as-grown and annealed In–Ga–ZnO films show n-type electrical conductivity. 相似文献
15.
E. Çadırlı U. Böyük S. Engin H. Kaya N. Maraşlı M. Arı 《Journal of Materials Science: Materials in Electronics》2010,21(5):468-474
Sn–3 wt% Cu hypereutectic alloy was directionally solidified upward with different growth rates (2.24–133.33 μm/s) at a constant
temperature gradient (4.24 K/mm) and with different temperature gradients (4.24–8.09 K/mm) at a constant growth rate (7.64 μm/s)
in the Bridgman-type growth apparatus. The measurements of microhardness of directionally solidified samples were obtained
by using a microhardness test device. The dependence of microhardness HV on the growth rate (V) and temperature gradient (G) were analyzed. According to these results, it has been found that with the increasing the values of V and G the value of HV increases. Variations of electrical resistivity (ρ) and electrical conductivity (σ) for casting samples with
the temperature in the range of 300–500 K were also measured by using a standard dc four-point probe technique. The variation
of Lorenz coefficient with the temperature for Sn–3 wt% Cu hypereutectic alloy was determined by using the measured values
of electrical and thermal conductivities. The enthalpy of fusion for same alloy was determined by means of differential scanning
calorimeter from heating trace during the transformation from eutectic liquid to eutectic solid. 相似文献
16.
Muzafar A. Kanjwal Nasser A. M. Barakat Faheem A. Sheikh Dae Kwang Park Hak Yong Kim 《Journal of Materials Science》2010,45(14):3833-3840
In this study, nanofiber mats consisting of two potential metal oxides were produced by electrospinning technique. An aqueous
solution of zinc acetate dihydrate and germanium isopropoxide was mixed with polyvinyl alcohol solution to prepare a sol–gel
that was electrospun at 20 kV. The obtained nanofiber mats were dried under a vacuum at 80 °C for 24 h and then calcined in
air at different temperatures and soaking times. Physiochemical characterizations have affirmed that nanofibers composed of
zinc oxide-germanium dioxide (ZnO–GeO2) can be prepared by calcination at different temperatures. Scanning electron microscopy (SEM), transmission electron microscopy
(TEM), and the Brunauer–Emmett–Teller (BET) technique were employed to characterize the as-spun nanofibers and the calcined
product. The specific surface area of the calcined product decreased with increases in temperature. X-ray powder diffractometery
(XRD) analysis was used to study the chemical composition and the crystallographic structure. The optical properties of the
as-prepared ZnO–GeO2 nanofibers were also studied. 相似文献
17.
E. Çadırlı U. Böyük S. Engin H. Kaya N. Maraşlı K. Keşlioğlu A. Ülgen 《Journal of Materials Science: Materials in Electronics》2010,21(6):608-618
Sn–3 wt% Cu hypereutectic alloy was prepared in a graphite crucible under the vacuum atmosphere. The samples were directionally
solidified upwards under argon atmosphere with different temperature gradients (G = 4.24–8.09 K/mm) at a constant growth rate
(V = 7.64 μm/s) and with different growth rates (V = 2.24–133.33 μm/s) at a constant temperature gradient (G = 4.24 K/mm)
by using a Bridgman type directional solidification apparatus. The microstructure of directional solidified Sn–3 wt% Cu alloy
seems to be rod eutectic structure. The influence of the growth rate (V) and temperature gradient (G) on the rod spacing (λ)
and undercooling (ΔT) were analysed. The values of λ2V, λ2G, ΔTλ, ΔTV−0.5 and ΔTG−0.5 were determined by using the Jackson–Hunt eutectic theory. The dependence of microhardness (HV) on the rod spacing (λ) was
analyzed. According to present results, it has been found that the value of HV increases with the increasing the value of
λ. 相似文献
18.
S. Mridha M. Dutta Durga Basak 《Journal of Materials Science: Materials in Electronics》2009,20(Z1):376-379
A series of n-ZnO/p-Si thin film heterojunctions have been fabricated by a low cost sol–gel technique for different ZnO film thicknesses and
the dark as well as photo current–voltage (I–V) characteristics have been investigated in details. The heterojunction with ZnO thickness of 0.46 μm shows the best diode
characteristics in terms of rectification ratio, I
F/I
R = 5.7 × 103 at 5 V and reverse leakage current density, J
R = 7.6 × 10−5 A cm−2 at −5 V. From the photo I–V curves and wavelength dependent photocurrent of the heterojunctions, it is found that the junction with 0.46 μm ZnO thickness
shows the highest sensitivity towards both UV and visible lights. 相似文献
19.
Wang H Wingett D Engelhard MH Feris K Reddy KM Turner P Layne J Hanley C Bell J Tenne D Wang C Punnoose A 《Journal of materials science. Materials in medicine》2009,20(1):11-22
Fluorescein isothiocyanate (FITC)-encapsulated SiO2 core-shell particles with a nanoscale ZnO finishing layer have been synthesized for the first time as multifunctional “smart”
nanostructures. Detailed characterization studies confirmed the formation of an outer ZnO layer on the SiO2–FITC core. These ~200 nm sized particles showed promise toward cell imaging and cellular uptake studies using the bacterium
Escherichia coli and Jurkat cancer cells, respectively. The FITC encapsulated ZnO particles demonstrated excellent selectivity in preferentially
killing Jurkat cancer cells with minimal toxicity to normal primary immune cells (18% and 75% viability remaining, respectively,
after exposure to 60 μg/ml) and inhibited the growth of both gram-positive and gram-negative bacteria at concentrations ≥250–500 μg/ml
(for Staphylococcus aureus and Escherichia coli, respectively). These results indicate that the novel FITC encapsulated multifunctional particles with nanoscale ZnO surface
layer can be used as smart nanostructures for particle tracking, cell imaging, antibacterial treatments and cancer therapy. 相似文献
20.
Haiming Zhang Yujie Li Guofeng Hu Bo Gao Yanjun Zhu 《Journal of Materials Science: Materials in Electronics》2010,21(11):1164-1167
Large-scale ZnO tetrapods have been fabricated on silicon substrate by a simple thermal evaporation method at 700 °C without
vapor transportation and characterized by FESEM, XRD, Micro-Raman, and PL, respectively. FESEM images indicate that the length
of tetrapod arm is about 3–4 μm, and the diameter of the tip is about 50 nm. XRD and Raman spectrum reveal that ZnO tetrapods
are highly pure hexagonal wurtzite structure. The PL spectrum indicates that the ZnO tetrapods have strong green emission
at 510 nm. 相似文献