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1.
Sarawuth Labuayai Vinich Promarak Santi Maensiri 《Applied Physics A: Materials Science & Processing》2009,94(4):755-761
This paper reports the synthesis and optical properties of nanocrystalline ZnO powders with crystallite sizes of 32.5 (±1.4)–43.4
(±0.4) nm prepared by a direct thermal decomposition of zinc acetate at the temperatures of 400, 500, 600, and 700°C for 4
h. The structure of the prepared samples was studied by XRD and FTIR spectroscopy, confirming the formation of wurtzite structure.
The morphology of the samples revealed by SEM was affected by the thermal decomposition temperature, causing the formations
of both nanoparticles and nanorods with different size and shape in the samples. The synthesized powders exhibited the UV
absorption below 400 nm (3.10 eV) with a well defined absorption peak at around 285 nm (4.35 eV). The estimated direct bandgaps
were obtained to be 3.19, 3.16, 3.14, and 3.13 eV for the ZnO samples thermally decomposed at 400, 500, 600, and 700°C, respectively.
All the samples exhibited room-temperature photoluminescence (PL) showing a strong UV emission band at ∼395 nm (3.14 eV),
a weak blue band at ∼420 nm (2.95 eV), a blue–green band at ∼485 nm (2.56 eV), and a very weak green band at ∼529 nm (2.35 eV).
The mechanisms responsible for photoluminescence of the samples are discussed. 相似文献
2.
Polymethyl methacrylate modified carbon nanotubes were prepared using γ radiation, and the modified carbon nanotubes exhibited
strong luminescence (∼
∼568 nm) at room temperature and an absorption peak at ∼
∼247 nm can be observed in the polymer modified samples. 相似文献
3.
M. K. Hossain Y. Kitahama G. G. Huang T. Kaneko Y. Ozaki 《Applied physics. B, Lasers and optics》2008,93(1):165-170
In this study, surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) characteristics of gold nanoaggregates
with different morphologies are examined to elucidate the correlation between SPR and SERS of the object. Nanoaggregates,
defined as random aggregates (hereafter RA), elongated aggregates (hereafter EA) and two-dimensional layered aggregates (hereafter
2DLA) are fabricated by immobilizing colloidal gold nanoparticles on glass substrates. The color variation observed in the
RA and EA samples indicates the variation in localized SPR excitations excited on the samples. The RA sample mostly shows
a broadened and shifted SPR peak centered at 570 nm in addition to another peak in the longer wavelength region (∼700 nm),
whereas in the EA sample a weak blue-shifted peak is observed near 450 nm in addition to a broadened peak centered at 570 nm
covering a trail for another one near 700 nm. In the case of the 2DLA sample, more than one SPR peaks are observed in the
longer wavelength region. The SERS observation confirms million times higher enhancement at least in Raman intensity using
the gold nanoaggregates adsorbed by dye molecules. The EA sample of gold nanoparticles shows ∼5 times higher enhancement in
Raman signal compared to that of the RA and 2DLA sample. 相似文献
4.
G. A. Kachurin S. G. Cherkova D. V. Marin A. G. Cherkov V. A. Skuratov 《Applied Physics A: Materials Science & Processing》2010,98(4):873-877
Thin SiO2 layers were implanted with 140 keV Si ions to a dose of 1017 cm−2. The samples were irradiated with 130 Mev Xe ions in the dose range of 3×1012–1014 cm−2, either directly after implantation or after pre-annealing to form the embedded Si nanocrystals. In the as-implanted layers
HREM revealed after Xe irradiations the 3–4 nm-size dark spots, whose number and size grew with increase in Xe dose. A photoluminescence
band at 660–680 nm was observed in the layers with the intensity dependent on the Xe dose. It was found that passivation with
hydrogen quenched that band and promoted emission at ∼780 nm, typical of Si nanocrystals. In spectra of pre-annealed layers
strong ∼780 nm peak was observed initially. Under Xe bombardment its intensity fell, with subsequent appearance and growth
of 660–680 nm band. The obtained results are interpreted as the emission at ∼660–680 nm belonging to the imperfect Si nanocrystals.
It is concluded that electronic losses of Xe ions are mainly responsible for formation of new Si nanostructures in ion tracks,
whereas elastic losses mainly introduce radiation defects, which quench the luminescence. Changes in the spectra with growth
of Xe ion dose are accounted for by the difference in the diameters of Xe ion tracks and their displacement cascades. 相似文献
5.
A simple and flexible technique aimed to generate large-area periodic nano-dot array features on metal thin films by laser
interference lithography (LIL) has been demonstrated. In this paper, gold nano-dot arrays with a period of ∼450 nm and a dot
diameter of ∼100 nm on quartz substrates coated with a gold film of 50 nm thick were fabricated. Multiple enhanced transmission
peaks were observed in this patterned film. In addition to the characteristic peak of the gold surface plasmon resonance around
500 nm, multiple shoulder peaks that range from 550 to 700 nm were also observed in the nano-chain array structures. These
shoulder peaks disappeared after thermal annealing. It was found that the nano-dots became smaller and well-separated nano-balls
under the high temperature annealing process. These nano-structures have potential applications in solar cell, nano-lithography
and biosensing. 相似文献
6.
A. S. Manukyan A. A. Mirzakhanyan G. R. Badalyan G. H. Shirinyan E. G. Sharoyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2010,45(3):132-136
Using the solid-phase pyrolysis and chemical vapor deposition of nickel-phthalocyanine, we have fabricated ferromagnetic Ni
nanoparticles in carbon matrices. The composition, structure, morphology, and magnetic properties of samples were investigated
by means of scanning electron microscopy, energy dispersive X-ray microanalysis, X-ray diffraction technique, and ferromagnetic
resonance. It is shown that the sizes of nanoparticles can be varied from ∼10 nm to ∼500 nm depending on the temperature and
time of pyrolysis. The used method allows us to synthesize metal nanoparticles in different carbon matrices: in amorphous
carbon plates, in graphitic capsules, and in carbon nanotubes. 相似文献
7.
M. E. Sánchez-Morales G. V. Vázquez E. B. Mejía H. Márquez J. Rickards R. Trejo-Luna 《Applied physics. B, Lasers and optics》2009,94(2):215-219
In this work, we report 1064 nm laser emission in Nd:YVO4 channel waveguides fabricated by carbon implantation. Typical threshold pump powers (∼808 nm) were ≥45 mW. Maximum conversion
efficiency was 11.5% (29.6% slope efficiency), and up to 9 mW of signal was delivered. Sample lengths of 4 mm were sufficient
to completely absorb the pump power. The special spectral characteristics of this material such as broad absorption band and
superior cross sections compared to the YAG crystal makes it suitable for developing compact sources to be integrated in optoelectronic
devices. 相似文献
8.
E. M. Shishonok L. Trinkler S. V. Leonchik B. Berzinya 《Journal of Applied Spectroscopy》2008,75(4):567-575
Under high pressure and temperature conditions, we have obtained samples of thulium-activated cubic boron nitride in the form
of micropowders, ceramics, and polycrystals activated by thulium in the presence of aluminum. We studied the cathodoluminescence
(CL), photoluminescence (PL), and photoluminescence excitation spectra of the samples. In the luminescence spectra we observe
structured bands with maxima at ∼370, ∼475, ∼660, and ∼ 800 nm, assigned to electronic transitions in the triply charged thulium
ions. We have established that the most efficient method for excitation of “blue” luminescence at ∼475 nm for thulium ions
in cBN is excitation by an electron beam. The cBN samples synthesized in the presence of Al have photoluminescence spectra
with a more complex structure compared with samples not containing Al, with the band of dominant intensity at about 660 nm.
Hypothetically, this is a consequence of incorporation of thulium ions into the crystalline phases cBN and AlN, which are
equally likely to be formed during synthesis. The observed photoluminescence spectrum of the indicated samples is the superposition
of the photoluminescence spectra of the Tm3+ ions located in the crystal fields of cBN and AlN of different symmetries. The presence in the photoluminescence excitation
spectra (at 450, 490, and 660 nm) of structure, with features at wavelengths shorter than the excited photoluminescence, suggests
a nonresonant mechanism for its excitation. We have established that luminescence of Tm3+ ions is less intense than for other rare earth elements incorporated into cubic boron nitride.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 547–555, July–August, 2008. 相似文献
9.
B. P. Aduev D. R. Nurmukhametov A. V. Puzynin 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(3):452-456
The temperature dependence of the probability of the explosion of pentaerythritol tetranitrate (PETN) with an admixture of
NiC particles (0.3 wt %) initiated by laser pulses (1064 nm, 20 ns) was studied over the temperature range 295–450 K. At 295–350
K, a weak temperature dependence was observed. The determining contribution to explosion initiation was made by the absorption
of laser radiation by nanoparticles. The threshold of explosive decomposition at 295 K decreased by ∼40 times compared with
samples free of NiC nanoparticles. Over the temperature range 400–450 K, the threshold of the explosive decomposition of samples
containing NiC nanoparticles decreased with the activation energy ∼0.4 eV. A decrease in the threshold of explosive decomposition
with a ∼0.4 eV activation energy over the temperature range 340–440 K was also observed for laser action on PETN samples not
containing NiC. A hypothesis was suggested according to which the absorption of a light quantum caused the transfer of an
electron from the valence band of the crystal to a level in the forbidden band with subsequent thermal positive ion dissociation
to the carbocation and NO3 radical. 相似文献
10.
S.W. Liu J. Xu D. Guzun G.J. Salamo C.L. Chen Y. Lin Min Xiao 《Applied physics. B, Lasers and optics》2006,82(3):443-447
Highly epitaxial Ba0.6Sr0.4TiO3 (BST) ferroelectric thin films were fabricated on (001) MgOsubstrates by pulsed laser deposition. The nonlinear optical absorption
coefficients (β) and refraction indices (γ) of the BST thin films on (001) MgO substrates were investigated using the single
beam Z-scan technique with femtosecond laser pulses at the wavelengths of 790 nm and 395 nm, respectively, at room temperature.
The nonlinear absorption coefficients of BST thin films were measured to be ∼0.087 cm/GW and ∼0.77 cm/GW at 790 nm and 395 nm,
respectively. The nonlinear refraction indices of BST thin films exhibit a strong dispersion from a positive value of 6.1×10-5 cm2/GW at 790 nm to a negative value of -4.0×10-5 cm2/GW at 395 nm near band gap. The dispersion of γ is roughly consistent with Sheik-Bahae’s theory for the bound electronic
nonlinear refraction resulting from the two-photon resonance. These results show that the BST film is a promising material
as a candidate for nonlinear optical applications.
PACS 42.70.Mp; 78.20.-e; 81.05.-t 相似文献
11.
N. Rajeswari Yogamalar A. Chandra Bose 《Applied Physics A: Materials Science & Processing》2011,103(1):33-42
Nanopowders of pure and lithium-doped semiconducting ZnO (Zn1−x
Li
x
O, where x= 0, 0.01, 0.03, 0.06, 0.09 and 0.15 in atomic percent (at.%)) are prepared by PEG-assisted low-temperature hydrothermal method.
The average crystallite size is calculated using Debye–Scherrer formula and corrected for strain-induced broadening by Williamson–Hall
(W–H) plot. The peak shift in XRD and the lattice constant of ZnO as a function of unit cell composition are predicted by
Vegard’s law. The evolution of ZnO nanostructures from rod-shaped to particle nature is observed from TEM images and the influence
of dopant on the morphology is investigated. The optical absorption measurement marks an indication that the incorporation
of lithium ion into the lattice of ZnO widens the optical band gap energy from ∼2.60 to ∼3.20 eV. The near band edge (NBE)
emission peak centered at ∼3.10 eV is considered to be the dominant emission peak in the PL spectra. Blue emission peak is
not observed in doped ZnO, thus promoting defect-free nanoparticles. The Burstein–Moss shift serves as a qualitative tool
to analyze the widening of the optical band gap and to study the shape of the NBE luminescence in doped ZnO nanopowders. FT-IR
spectra are used to identify the strong metal–oxide (Zn–O) interaction. 相似文献
12.
A.S. Zeng M.J. Zheng L. Ma W.Z. Shen 《Applied Physics A: Materials Science & Processing》2006,84(3):317-321
The GaAs granular films have been prepared by electrochemical anodic etching of n-GaAs in HCl electrolyte at different etching temperatures. The microstructure and optical properties of the films were investigated by micro-Raman spectrum, atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy. Raman spectra reveal marked redshift and broadening, which could be explained by phonon confinement model. Results show the GaAs nanocrystalline films have formed during the anodic etching process under certain chemical conditions. Two “infrared” PL bands at ∼860 nm and ∼920 nm and a strongly enhanced visible PL band envelope around 550 nm were observed in the film prepared at etching temperature of 50 °C. The “green” PL band envelope is attributed to both quantum confinement in GaAs nanocrystals and PL of Ga2O3 and As2O3. The results reveal that the energy band structure of GaAs granular films is closely related to the etching temperatures. PACS 81.07.Bc; 78.30.Fs; 78.55.Cr 相似文献
13.
H. Kim G. P. Kushto R. C. Y. Auyeung A. Piqué 《Applied Physics A: Materials Science & Processing》2008,93(2):521-526
Fluorine-doped tin oxide (FTO) thin films have been investigated as an alternative to indium tin oxide anodes in organic photovoltaic
devices. The structural, electrical, and optical properties of the FTO films grown by pulsed laser deposition were studied
as a function of oxygen deposition pressure. For 400 nm thick FTO films deposited at 300°C and 6.7 Pa of oxygen, an electrical
resistivity of 5×10−4 Ω-cm, sheet resistance of 12.5 Ω/□, average transmittance of 87% in the visible range, and optical band gap of 4.25 eV were obtained. Organic photovoltaic (OPV)
cells based on poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric acid methyl ester bulk heterojunctions were prepared on FTO/glass electrodes and the device performance was investigated as a function of FTO
film thickness. OPV cells fabricated on the optimum FTO anodes (∼300–600 nm thick) exhibited power conversion efficiencies
of ∼3%, which is comparable to the same device made on commercial ITO/glass electrodes (3.4%). 相似文献
14.
Distributed feedback (DFB) lasing in permanent volume transmission gratings formed in a laser dye-doped organic–inorganic
nanocomposite has been investigated. DFB laser cavities were fabricated using one-step two-beam holographic exposure of Pyrromethene
567 (PM567) doped photopolymerizable acrylate monomers containing inorganic (LaPO4) nanoparticles. Compared to the formulation previously utilized, the material composition presented provides longer lifetime
of the laser. Spectral and polarization properties, input–output and stability characteristics of the laser output have been
investigated by varying the material composition and the patterning parameters. DFB lasing emission of the second and the
third diffraction orders has been demonstrated. The spectral linewidth of ∼0.08 nm has been observed at a pump energy threshold
of about 0.2 μJ/pulse for the second-order DFB lasing when pumped with 532 nm 500 ps laser pulses. Spectral tuning of the
lasing output over ∼56 and ∼7 nm was obtained by varying the grating period and the content of inorganic nanoparticles in
the polymer matrix, respectively. 相似文献
15.
Ultraviolet broadband light spanning 337–405 nm was produced in a single-mode optical fiber primarily by stimulated Raman scattering. Pulses of 4 ns duration at 337 nm were coupled into a 50 m long ultraviolet-grade fiber featuring single-mode operation in the 320–450 nm range. Significant spectral broadening was achieved with pulses of only ∼10 W peak power. Our experiments demonstrate the potential for a source with ∼104 times the spectral radiance of a quartz tungsten halogen lamp, which is currently used for many applications in this wavelength range. PACS 42.65.Ky; 42.81.Wg 相似文献
16.
Spectral characteristics of flutamide drug have been studied in various solvents and β-cyclodextrin (β-CD). The inclusion
complex of flutamide with β-CD is analysed by UV-visible, fluorimetry, FT-IR, 1H NMR, SEM, DSC and AM1 methods. In all solvents,
flutamide exhibits a dual fluorescence. The longer wavelength emission (A band ∼380 nm) is due to intramolecular charge transfer
state (ICT) and the shorter wavelength emission (B band ∼285 nm) originates from a locally excited state. In β-CD, the increase
in the fluorescence intensity of ‘A’ band indicates ICT emission enhanced in the β-CD medium. β-CD studies shows isopropyl
group is present in the interior part of the β-CD cavity whereas amino and CF3 groups are present in the outside of the β-CD cavity. A mechanism is proposed to explain the 1:1 inclusion process. 相似文献
17.
Many studies have been done on low energy (1–200 keV) and high dose (1016–1017) implantation of Mn in GaAs. This study is an attempt to incorporate Mn ions in GaAs through implantation of 1 MeV Mn+1 ions in semi-insulating GaAs substrates at doses of 3×1015/cm2 and subsequent annealing. This was done to find out if any alloy of Mn–Ga–As, or binary compounds of Mn–Ga or Mn–As form
due to annealing of Mn+1 ions implanted in GaAs substrates. High Resolution XRD (HRXRD) performed before annealing shows a possibility of Ga–Mn–As
alloy formation, and after annealing at 800°C, except for GaAs main peaks no other phase peaks were detected. Scanning electron
microscopy (SEM) shows nanostructures of various dimensions which are thought to be formed due to the defects generated due
to implantation. Fourier Transform Infrared (FTIR) study shows the shift in bandgap due to Mn doping. Raman spectroscopy shows
the red shift in LO and TO peak positions of GaAs after annealing, which indicates the presence of disorder and damage due
to implantation. Resistivity measurement shows a thermally activated semiconductor character of charge conduction with an
activation energy of 51 meV and this activation may have occurred through the transitions from impurity band to valence band.
Large positive (∼25%) magnetoresistance and a mixture of ferromagnetic and paramagnetic behavior obtained in the magnetization
measurement indicate the presence of ferromagnetic MnAs nanoclusters embedded in paramagnetic GaAs:Mn matrix. 相似文献
18.
Uniform self-organized grating is fabricated by scanning of a single femtosecond laser on ZF6 glass. The scanning electron
microscope and atom force microscope results show that the period and tooth length of the uniform coarse grating are ∼750 nm
and ∼20 μm, respectively. The period of the grating is independent of pulse number, neighboring dots intervals, and laser
powers, whereas the uniformity of the grating is largely determined by the above three factors. 相似文献
19.
Good and adhesive semiconducting films of ZnO (∼ 100–1100 nm) were deposited over planar borosilicate glass by spray pyrolysis
and dip & dry method. The films were characterized by X-ray diffraction and optical absorption measurements. The band gap
of these films were found to be 3.21 eV and the films were randomly oriented having average crystallite sizes of 20 to 25
nm.
Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003. 相似文献
20.
Flat layered structure and improved photoluminescence emission from porous silicon microcavities formed by pulsed anodic etching 总被引:2,自引:0,他引:2
Z.H. Xiong L.S. Liao X.M. Ding S.H. Xu Y. Liu L.L. Gu F.G. Tao S.T. Lee X.Y. Hou 《Applied Physics A: Materials Science & Processing》2002,74(6):807-811
Single-mode, highly directional and stable photoluminescence (PL) emission has been achieved from porous silicon microcavities
(PSMs) fabricated by pulsed electrochemical etching. The full width at half maximum (FWHM) of the narrow PL peak available
from a freshly etched PSM is about 9 nm. The emission concentrates in a cone of 10° around the normal of the sample, with
a further reduced FWHM of ∼5.6 nm under angle-resolved measurements. Only the resonant peak is present in such angle-resolved
PL spectra. No peak broadening is found upon exposure of the freshly prepared PSM to a He-Cd laser beam, and the peak becomes
somewhat narrower (∼5.4 nm) after the PSM has been stored in an ambient environment for two weeks. At optimized etching parameters,
even a 4-nm FWHM is achievable for the freshly etched PSM. In addition, scanning electron microscopy (SEM) plane-view images
reveal that the single layer porous Si formed by pulsed current etching is more uniform and flatter than that formed by direct
current (dc) etching, demonstrated by the well-distributed circular pores with small size in the former in comparison with
the irregular interlinking pores in the latter. The SEM cross-section images show the existence of oriented Si columns of
10 nm diameter along the etching direction within the active layer, good reproducibility and flat interfaces. It is thus concluded
that pulsed current etching is superior to dc etching in obtaining flat interfaces within the distributed Bragg reflectors
because of its minor lateral etching.
Received: 7 March 2001 / Accepted: 23 July 2001 / Published online: 30 October 2001 相似文献