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1.
Room-temperature ferromagnetism was observed in Zn 0.9Co 0.1O nanorods with diameters and lengths of ∼100–200 nm and ∼200–1000 nm, respectively. Nanorods were synthesized by a simple
sol–gel method using metal acetylacetonate powders of Zn and Co and poly(vinyl alcohol) gel. The XRD, FT-IR and SAED analyses
indicated that the nanorods calcined at 873–1073 K have the pure ZnO wurtzite structure without any significant change in
the structure affected by Co substitution. Optical absorption measurements showed absorption bands indicating the presence
of Co 2+ in substitution of Zn 2+. The specific magnetization of the nanorods appeared to increase with a decrease in the lattice constant c of the wurtzite unit cell with the highest value being at 873 K calcination temperature. This magnetic behavior is similar
to that of Zn 0.9Co 0.1O nanoparticles prepared by polymerizable precursor method. We suggest that this behavior might be related to hexagonal c-axis being favorable direction of magnetization in Co-doped ZnO and the 873 K (energy of 75 meV) being close to the exciton/donor
binding energy of ZnO. 相似文献
2.
S-graphene quantum dots (GQDs), N-GQDs, P-GQDs, and Cl-GQDs are prepared by a solution chemistry method and further incorporated with Zn xCd 1−xSe by one-step hydrothermal method. In the previous study, Zn xCd 1−xSe reached the optimal photoelectric performances at the Zn/Cd ratio of 0.9:0.1, so the Zn 0.9Cd 0.1Se were combined with doped GQDs (D-GQDs) to form Zn 0.9Cd 0.1Se/doped-GQDs. The influence of GQDs doped with different elements on the photoelectric properties of Zn 0.9Cd 0.1Se composites is discussed. Compared with pristine Zn 0.9Cd 0.1Se, Zn 0.9Cd 0.1Se/Cl-GQDs, and Zn 0.9Cd 0.1Se/P-GQDs can improve the photocurrent response and current intensity, therein, Zn 0.9Cd 0.1Se/Cl-GQDs reaches the lowest interfacial charge transfer resistance and the highest photocurrent response of 5.48 × 10 −6 A cm −2. Mott–Schottky analysis shows that the fitting slope of Zn 0.9Cd 0.1Se/Cl-GQDs composites is significantly lower than that of Zn 0.9Cd 0.1Se/GQDs with other doped elements. The results indicate that Zn 0.9Cd 0.1Se/Cl-GQDs composites has the largest carrier density, which is beneficial to charge conduction. 相似文献
3.
将生长得到的Cd 0.9Zn 0.1Te晶体在Cd气氛下及不同的温度条件下进行了退火处理. 借助已建立的退火处理过程中Cd 1-xZn xTe晶体材料电阻率及导电类型变化和扩散杂质的扩散系数之间关系的模型,结合实验数据,获得了1073K,973K和873K下Cd在Cd 0.9Zn 0.1Te晶体中的扩散系数,并估算了其激活能. 通过使用获得的扩散系数,研究了在不同温度及饱和Cd气氛下,退火时间对Cd 0.9Zn 0.1Te晶体电阻率分布及导电类型等的变化的影响. 相似文献
4.
Thin films of Zn 1−x
Cd
x
S (0.1 ≤ x ≤ 0.5) were prepared by using pulsed laser ablation technique on corning glass substrates. Phase transition from cubic to
hexagonal in Zn 1−x
Cd
x
S films is determined by X-ray diffraction analysis. We observed a lowering in the phase transition temperature with increase
in the cadmium concentration. Transmission electron microscopy suggests the crystalline nature of thin films with average
particle size of 15 nm. The grown Zn 1−x
Cd
x
S samples show the high peak intensity ratio of the near band edge emission to the defect center luminescence even at room
temperature, which indicates the small concentration of complex defects in the samples. Photoluminescence measurement show
stoichiometric dependence of the energy band gap and is found to have quadratic dependence on x. 相似文献
5.
Cd 0.9−xZn 0.1Cu xS (0≤ x≤0.06) nanoparticles were successfully synthesized by a conventional chemical co-precipitation method at room temperature. Crystalline phases and optical absorption of the nanoparticles have been studied by X-ray diffraction (XRD) and UV–visible spectrophotometer. XRD confirms the phase singularity of the synthesized material, which also confirmed the formation of Cd–Zn–Cu–S alloy nanocrystals rather than separate nucleation or phase formation. Elemental composition was examined by the energy dispersive X-ray analysis and the microstructure was examined by scanning electron microscope. The blue shift of absorption edge below Cu=2% is responsible for dominance of Cu + while at higher Cu concentration dominated Cu 2+, d–d transition may exist. It is suggested that the addition of third metal ion (Cu 2+/Cu +) is an effective way to improve the optical property and stability of the Cd 0.9Zn 0.1S solid solutions. When Cu is introduced, stretching of Cd–Zn–Cu–S bond is shifted lower wave number side from 678 cm −1 (Cu=0%) to 671 cm −1 (Cu=6%) due to the presence of Cu in Cd–Zn–S lattice and also the size effect. The variation in blue band emission peak from 456 nm (∼2.72 eV) to 482 nm (∼2.58 eV) by Cu-doping is corresponding to the inter-band radiation combination of photo-generated electrons and holes. Intensity of red band emission centered at 656 nm significantly increased up to Cu=4%; beyond 4% it is decreased due to the quenching of Cu concentration. 相似文献
6.
The multi-walled carbon nanotubes (MWCNTs) wrapped with hexagonal wurtzite Zn
x
Cd 1−x
S nanoparticles with a uniform and small diameter have been prepared to form Zn
x
Cd 1−x
S–MWCNT heterostructures by microwave-assisted route using Zn(Ac) 2, Cd(NO 3) 2, and thioacetamide as the reactants . The heterostructures have been characterized by X-ray powder diffraction, scanning and transmission electron microscopy,
high-resolution transmission electron microscopy, photoluminescence (PL) and PL excited lifetime. Despite the analogous size
and configuration, the Zn
x
Cd 1−x
S–MWCNT ( x = 0, 0.2, 0.5, 0.8, 1) with different Zn concentration exhibit composition-dependent absorption properties in the visible
zone. The PL peak positions of Zn
x
Cd 1−x
S–MWCNT change gradually from ZnS–MWCNT to CdS–MWCNT. The Zn
x
Cd 1−x
S–MWCNT shows different photocatalytic activity towards the photodegradation of fuchsin acid under visible light illumination,
photocatalytic activity of the Zn
x
Cd 1−x
S–MWCNT decreases gradually with the increase in the Zn concentration, the Zn 0.2Cd 0.8S–MWCNT possessed the best photocatalytic activity. After recycling thrice, the photocatalysts still have about 85% efficiency. 相似文献
7.
Eu 3+-doped Cd 1−x
Zn
x
S (0 ≤ x ≤ 0.5) quantum dots (QDs) have been synthesized using wet chemical precipitation method. X-ray diffraction and transmission
electron microscope have been used for the crystallographic and morphological characterization of synthesized nanomaterials.
In order to understand the spectral characteristics of doped QDs, N 2-laser induced time resolved spectra have been recorded. Excited state lifetime values for dichromatic emission (red and violet)
attributed to 5D 0 → 7F J ( J = 1, 2) transitions of Eu 3+ and host lattice transitions have been calculated from the recorded luminescence decay curves. Decay time dependence on the
dopant concentration (0.01–10 at. wt% of Cd 2+) has been studied in detail. 相似文献
8.
We present the results of experimental studies of the optical properties of cobalt-doped Cd
x
H 1−x
Se (x = 0.18) single crystals with cobalt ion concentrations of NCo = 5·10 18, 5·10 19, and 1·10 20 cm −3 at T = 90 K and 300 K. The composition (x = 0.18) of the Cd
x
Hg 1−x
Se solid solution was selected so that the hypothetical resonance level is found on the bottom of the conduction band. We
show that the cobalt ions in the mercury selenide can form a resonance donor level only for cobalt concentrations N Co < 5·10 18 cm −3. For N Co ∼ 5·10 18 cm −3, the cobalt ions substitute for mercury atoms, forming a solid solution and leading to an increase in the bandgap width and
a change in the physical properties. The solubility of cobalt in the HgSe lattice can be greater than 5%–10%.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 73–77, January–February, 2007. 相似文献
9.
ZnFe 2O 4 bulk material shows a normal-spinel structure and a closely defined composition at Zn 2+/Fe 3+ ≅ 0.5. However, the composition of zinc ferrite, prepared as nanoparticles, can be varied in a broad range without losing
the single-phase spinel structure. In this article, structural mechanisms enabling this non-stoichiometry were studied using
the X-ray absorption fine structure (EXAFS) in combination with X-ray diffractometry (XRD), transmission electron microscopy
(TEM), and magnetic measurements. Nanoparticles with a narrow size distribution were synthesized using co-precipitation in
water-in-oil microemulsions. First, the structure of the stoichiometric zinc-ferrite nanoparticles was studied in dependence
of their size and the annealing temperature. EXAFS analysis showed that the degree of inversion x (as defined in the compound formula (Zn 1 − x
Fe
x
)[Fe 2 − x
Zn
x
]O 4, with round and square brackets representing the tetrahedral and octahedral sites, respectively) increased with decreasing
nanoparticles size. The structure of the stoichiometric nanoparticles and the nanoparticles of comparable size displaying
Zn/Fe ratio of 0.2 (Fe-rich) and 0.7 (Zn-rich) were then compared. Analysis showed that the non-stoichiometry is structurally
compensated predominantly in the core of the nanoparticle by the adjusted distribution of Zn and Fe ions over the two sublattices
of the spinel structure. 相似文献
10.
Device grade quantum dots (QDs) require QDs ensembles to retain their original superior optical properties as in solution. QDs with thick shells are proven effective in suppressing the inter-dot interaction and preserving the emission properties for QDs solids. However, lattice strain–induced defects may form as the shell grows thicker, resulting in a notable photoluminescence quenching. Herein, a well-type Cd xZn 1−xS/CdSe/Cd yZn 1−yS QDs is proposed, where ternary alloys CdZnS are adopted to match the lattice parameter of intermediate CdSe by separately adjusting the x and y parameters. The resultant thick-shell Cd 0.5Zn 0.5S/CdSe/Cd 0.73Zn 0.27S QDs reveal nonblinking properties with a high PL QY of 99% in solution and 87% in film. The optimized quantum dot light-emitting diodes (QLEDs) exhibit a luminance of 31547.5 cd m −2 at the external quantum efficiency maximum of 21.2% under a bias of 4.0 V. The shell thickness shows great impact on the degradation of the devices. The T 50 lifetime of the QLEDs with 11.2 nm QDs reaches 251 493 h, which is much higher than that of 6.5 and 8.4 nm QDs counterparts. The performances of the well-type thick-shell QLEDs are comparable to state-of-the-art devices, suggesting that this type of QDs is a promising candidate for efficient optoelectronic devices. 相似文献
11.
For microcrystals of Zn 0.6Cd 0.4S with adsorbed molecules of a number of organic dyes, we have observed sensitized anti-Stokes luminescence excited by radiation
with wavelengths in the range 610–750 nm and flux density 10 14–10 15 photons/cm 2·sec. The positions of the bands in the excitation spectra for such luminescence match those of the absorption spectra for
the adsorbed dye molecules, which is evidence in favor of a cooperative mechanism for its appearance. We have shown that enhancement
of the anti-Stokes luminescence is possible when silver atoms and few-atom clusters appear on the Zn 0.6Cd 0.4S surface in addition to the dye molecules. We hypothesize that its excitation in the latter case occurs as a result of two-photon
optical transitions. These transitions occur sequentially, with transfer of an electron or the electronic excitation energy
from the dye molecules to silver atoms and few-atom clusters adsorbed on the surface of Zn 0.6Cd 0.4S, creating deep localized states in the bandgap with photoionization energies 1.80–2.00 eV.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 617–621, September–October, 2007. 相似文献
12.
Here, we present the effect of different Zn contents on the structural, morphological, and optical properties of CdXZn1-XS thin films deposited by electrodeposition method on stainless steel and indium-doped tin oxide (ITO) glass substrates. Electrosynthesized CdXZn1-XS thin films are characterized by using X-ray diffraction (XRD), UV-Vis spectrophotometer, field emission scanning electron microscope (FE-SEM), and surface wettability analysis. XRD pattern reveals that the CdXZn1-XS thin films are polycrystalline in nature with hexagonal crystal structure. FE-SEM micrograph displays that these CdXZn1-XS thin films exhibit the different sizes of sphere-like nanostructures by varying the X value. The optical absorption study indicates that drastic variation in band gap energy of CdXZn1-XS thin films. In advance photovoltaic measurements, CdXZn1-XS thin films are to be studied by forming the photoelectrochemical (PEC) cell having CdXZn1-XS/0.5 M (Na2SO3)/C configuration. The efficiency values of CdXZn1-XS are found to be 0.2, 0.35, 0.32, 0.25, and 0.23 % respectively at X content. 相似文献
13.
Diluted magnetic semiconductor (DMS) nanoparticles of Sn 1−x
Er
x
O 2 ( x = 0.0, 0.02, 0.04, and 0.1) were prepared by sol–gel method. The X-ray diffraction patterns showed SnO 2 rutile structure for all samples with no impurity peaks. The decrease in crystallite size with Er concentration was confirmed
from TEM measurements (from 12 to 4 nm). The UV–Visible absorption spectra of Er-doped SnO 2 nanoparticles showed blue shift in band gap compared to undoped SnO 2. The electron spin resonance analysis of Er-doped SnO 2 nanoparticles indicate Er 3+ in a rutile lattice and also decrease in intensity with Er concentration above x = 0.02. Temperature-dependent magnetization studies and the inverse susceptibility curves indicated increased antiferromagnetic
interaction with Er concentration. 相似文献
14.
Results are presented of the first measurements of infrared reflection spectra of Zn 1−x
Cd xSe films ( x=0–0.55; 1) grown on a GaAs substrate by molecular-beam epitaxy. It is shown by a mathematical analysis of the experimental
spectra that the investigated Zn 1−x
Cd xSe alloy system manifests a unimodal rearrangement of its vibrational spectrum as the composition is varied.
Fiz. Tverd. Tela (St. Petersburg) 41, 982–985 (June 1999) 相似文献
15.
ZnO and Zn 0.9Cu 0.1O nanoparticles were synthesized by the sonochemical method. Structural and morphological properties of the synthesized nanoparticles were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX). The results revealed the formation of ZnO and Zn 0.9Cu 0.1O nanoparticles in wurtzite phase with average crystallite diameter of 30–40 nm calculated from Debye–Scherrer equation. Moreover, the ethanol vapor sensing properties of ZnO and Zn 0.9Cu 0.1O nanoparticles were investigated at different operating temperatures and they were compared with commercial ZnO microparticles. Comparative results demonstrated that Zn 0.9Cu 0.1O nanoparticles exhibit highest and fastest response to 250 ppm of ethanol at 300 °C. Results on response/recovery time, sensing mechanism, conductance variation and thermodynamics/kinetics of ethanol sensing is also studied and discussed. 相似文献
16.
Cd1-x ZnxS nanocrystals are prepared by a co-precipitation method with different atomic fractions of Zn.The texture,structural transformation and optical properties with increasing x value in Cd1-x ZnxS are studied with scanning electron microscopy,electron diffraction patterning,and absorption spectra respectively.Quantum confinement in a strained CdS/Cd1-xZnxS related nanodot with various Zn content values is investigated theoretically.Binding energies on exciton bound CdS/CdxZn1-xS quantum dot are computed,with consideration of the internal electric field induced by the spontaneous and piezoelectric polarizations,and thereby the interband emission energy is calculated as a function of the dot radius.The optical band gap from the UV absorption spectrum is compared with the interband emission energy computed theoretically.Our results show that the average diameter of composite nanoparticles ranges from 3 nm to 6 nm.The X-ray diffraction pattern shows that all the peaks shift towards the higher diffracting angles with an increase in Zn content.The lattice constant gradually decreases as the Zn content increases.The strong absorption edge shifts towards the lower wavelength region and hence the band gap of the films increases as the Zn content increases.The values of the absorption edge are found to shift towards the shorter wave length region and hence the direct band gap energy varies from 2.5 eV for the CdS film and 3.5 eV for the ZnS film.Our numerical results are in good agreement with the experimental results. 相似文献
17.
Cd 1−x
Zn
x
S/ p-GaAs heterojunctions for solar cell applications have been prepared by growing single crystal Cd 1−x
Zn
x
S epitaxial layers on (111)GaAs substrates through a vapour phase chemical transport method using the close-spaced geometry
and H 2 as a transport agent. Electrical and photovoltaic properties of the heterojunctions have been investigated and discussed
in connection with the main features of the growth technique. AM1 power conversion efficiencies up to 6.2% have been measured
and possible improvements have been examined. 相似文献
18.
Thin films of Cd
y
Zn 1 − y
O and Mg
x
Zn 1 − x
O ( y = 0−0.35, x = 0−0.45) ternary alloys have been grown by pulsed laser deposition onto sapphire substrates. The record solubility limits
of Cd ( y = 0.3) and Mg ( x = 0.35) have been achieved in hexagonal zinc oxide. The mismatch of the lattice parameters a of Cd 0.2Zn 0.8O and Mg 0.35Zn 0.65O does not exceed 1%; in this case, the band gap discontinuity is 1.3 eV. The surface roughness of the films does not exceed
2.5 nm at x = 0−0.27 and y = 0−0.20. 相似文献
19.
We report a numerical simulation of the conduction and valence band edges of
Cd 1-xZn xS nanocrystallites using a one — dimensional potential
model. Electron — hole pairs are assumed to be confined in nanospheres of
finite barrier heights. Optical absorption measurements are used to fit the
bandgap of the Cd 1-xZn xS nanocrystal material. A theoretical
analysis is also made to calculate the energy location of bound excitons and
the oscillator strength of interband transitions as a function of zinc
composition. The aim of the latter study is to investigate the optical
behavior of Cd 1-xZn xS nanocrystals. An attempt to explain all the
results is presented. 相似文献
20.
X-ray detectors made of CdTe crystals with a p- n junction obtained by diffusion of In into p-CdTe are investigated. The basic characteristics of such a detector are studied for the first time. It is found that the
device is highly sensitive to X rays at a low bias voltage (to −50 V) and the X-ray effective energy in the range 28–72 keV.
It is shown that photovoltaic detectors based on CdTe with p- n junctions are superior to Cd 0.9Zn 0.1Te ones. 相似文献
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