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1.
Mingsong Wang Xiaonong Cheng Juan Yang 《Applied Physics A: Materials Science & Processing》2009,96(3):783-787
ZnO thin films were prepared by RF magnetron sputtering. The photoluminescence dependence on the growth ambient and annealing
temperatures and the atmosphere has been studied. Visible photoluminescence with blue, green, orange, and red emission bands
has been demonstrated by controlling the preparation conditions. Complete suppression of the visible emission bands was also
realized by annealing the O2-ambient-grown samples in N2 atmosphere at higher temperatures, which indicated the preparation of ZnO thin films with high optical quality. 相似文献
2.
Y. M. Azhniuk A. V. Gomonnai Y. I. Hutych V. V. Lopushansky L. A. Prots I. I. Turok D. R. T. Zahn 《Applied Physics A: Materials Science & Processing》2009,95(2):473-477
While studying the effect of thermal treatment at 625–700°C on the formation of borosilicate glass-embedded CdSe or CdSe1−x
S
x
nanocrystals, pronounced bands at 323 and 646 cm−1 were observed in the Raman spectra. They are assigned to Se2 clusters on the base of their frequency positions, widths, intensities, and resonance behavior. The precipitation of Se2 molecular clusters in borosilicate glass is shown to occur when the heat treatment temperature and/or duration are beyond
the range, most suitable for the formation of CdSe or CdSe-rich CdSe1−x
S
x
nanocrystals. 相似文献
3.
We performed time-resolved spectroscopy of ZnO quantum dots (QD), and observed exciton energy transfer and dissipation between
QD via an optical near-field interaction. Two different sizes of ZnO QD with resonant energy levels were mixed to test the
energy transfer and dissipation using time-resolved photoluminescence spectroscopy. The estimated energy transfer time was
144 ps. Furthermore, we demonstrated that the ratio of energy transfer between the resonant energy states could be controlled. 相似文献
4.
Masato Ohmukai Nobutomo Uehara Tetsuya Yamasaki Yasuo Tsutsumi 《Czechoslovak Journal of Physics》2004,54(7):781-784
We have investigated the effects of chemical etching on Raman spectra of porous silicon. The as-anodized porous silicon consisted
mainly of crystalline silicon, as indicated by the Raman spectra. The background in the spectrum was strong, indicating that
the porous silicon surface was rough due to the presence of pores. When chemical etching was performed five times, the Raman
spectrum revealed the presence of spherically shaped nanocrystalline silicon whose diameter was around 3.5 nm. Further chemical
etching, however, extinguished the nanocrystallites, in addition to smoothing the surface morphology. 相似文献
5.
A periodic array of Ga oxide islands was obtained by annealing the highly ordered Ga nano-droplets on GaAs surface at 400°C
under an oxygen atmosphere for 7 hours. These Ga oxides are a mixture of α-Ga2O3 and β-Ga2O3 confirmed by Raman spectroscopy study. Enhanced optical transmission of GaAs with such ordered Ga oxide nano-islands was
obtained. Both dielectric and dimensional confinement effects were considered in analysis of the electromagnetic characteristics
of the nanostructured materials. Finite-difference time-domain method was used to numerically study the light transmission
through the patterned Ga oxide on GaAs surface. Based on the calculated results, the light transmission enhancement is attributed
to the formation of the ordered nano Ga oxides. 相似文献
6.
Takehito Yoshida Hirokazu Toyoyama Ikurou Umezu Akira Sugimura 《Applied Physics A: Materials Science & Processing》2008,93(4):961-966
Nanostructured Ni-doped indium–tantalum–oxides (InTaO4) were synthesized by a reactive pulsed laser ablation process, aiming at the final goal of direct splitting of water under
visible sunbeam irradiation. The third harmonics beam of a Nd:YAG laser was focused onto a sintered In0.9Ni0.1TaO4−δ
target in pure oxygen background gases (0.05–1.00 Torr). Increasing the oxygen gas pressure, via thin films having nanometer-sized
strong morphologies, single-crystalline nanoparticles were synthesized in the reactive vapor phases. The nanostructured deposited
materials have the monoclinic layered wolframite-type structure of bulk InTaO4, without oxygen deficiency. 相似文献
7.
Z. Xie Y. Lu H. Wei J. Yan P. Wang H. Ming 《Applied physics. B, Lasers and optics》2009,95(4):751-755
A broad spectral surface enhanced Raman scattering sensor is developed using the solid core holey photonic crystal fiber with
silver nanoparticles cluster. This SERS probe offers an operational excitation wavelength range overlaying visible light and
near infrared light. The PCF SERS sensing is demonstrated in the detection of the 4-Mercaptobenzoic acid (10−6 M) solution with 514.5 and 785 nm excitation. In this structure of PCF sensor, the related analysis shows that leakage modes
also make an important contribution in the SERS activity not only by the evanescent field way. 相似文献
8.
Photoluminescence and Raman scattering of Cu-doped ZnO films prepared by magnetron sputtering 总被引:2,自引:0,他引:2
X.B. Wang 《Applied Surface Science》2007,253(16):6905-6909
The Cu-doped ZnO films were prepared by direct current reactive magnetron sputtering using a zinc target with various Cu-chips attached. The influences of Cu-doping on the microstructure, photoluminescence, and Raman scattering of ZnO films were systematically investigated. The results indicate that ZnO films doped with moderate Cu dopant (2.0-4.4 at.%) can obtain wurtzite structure with strong c-axis orientation. The near band edge (NBE) emission of ZnO film can be enhanced by Cu dopant with a concentration of 2.0 at.% and quench quickly with further increase of doping concentration. Two additional modes at about 230 and 575 cm−1, which could be induced by Cu dopant, can be observed in Raman spectra of the Cu-doped ZnO films. 相似文献
9.
N. Rakov L. A. Gómez D. J. Rátiva G. S. Maciel 《Applied physics. B, Lasers and optics》2009,94(2):199-202
Upconversion (UC) emission in thulium (Tm3+) and neodymium (Nd3+) co-doped aluminum oxide ceramic powders prepared by combustion synthesis was investigated at room temperature using a continuous
wave laser operating at 800 nm. Our sample containing Tm3+ (1 wt.%) did not show any UC emission but our sample co-doped with Tm3+ and Nd3+ in 1:2 wt.% proportion presented blue (∼480 nm) UC intensity more than one order of magnitude larger than our sample co-doped
with Tm3+ and Nd3+ in 1:1 wt.% proportion. X-ray diffraction data showed the presence of α-Al2O3 and REAlO3 (RE=Tm or Nd) crystalline phases in co-doped powders, while the singly doped powder has only α-Al2O3 phase. Our results show that the UC emission efficiency of Tm3+ and the host crystalline structure can be tailored by manipulating the Nd3+ doping concentration. 相似文献
10.
R. S. De Oliveira J. A. C. De Paiva M. A. B. De Araujo A. S. B. Sombra 《Il Nuovo Cimento D》1998,20(2):209-220
Summary Iron molybdenum phosphate glasses [xMoO3 · (0.6 -x)P2O5 · 0.4Li2O] :yFe2O3 with 0 ≤x ≤ 0.6 andy = 0.03 (mol%) prepared in ambient atmosphere using the melt quenching technique were studied by using DC electrical conductivity,57Fe M?ssbauer and infrared spectroscopies. The DC conductivity depends on the MoO3 concentrationx. It was observed that, with increasingx, the ratio Fe2+ /(Fe3+ + Fe2+) and the DC conductivity increase. Infrared spectroscopy and X-ray powder diffraction indicate that a Li2 MoO4 crystalline phase is present for high MoO3 content samples (x = 0.5, 0.6).
This work was partly sponsored by FINEP, CNPq (Brazilian agencies) and UECE (Universidade Estadual do Cearà). 相似文献
11.
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
12.
The properties of ZnO quantum dots (QDs) synthesized by the sol-gel process are reported. The primary focus is on investigating the origin of the visible emission from ZnO QDs by the annealing process. The X-ray diffraction results show that ZnO QDs have hexagonal wurtzite structure and the QD diameter estimated from Debye-Scherrer formula is 8.9 nm, which has a good agreement with the results from transmission electron microscopy images and the theoretical calculation based on the Potential Morphing Method. The room-temperature photoluminescence spectra reveal that the ultraviolet excitation band has a red shift. Meanwhile, the main band of the visible emission shifts to the green luminescence band from the yellow luminescence one with the increase of the annealing temperature. A lot of oxygen atoms enter into Zn vacancies and form oxygen antisites with increasing temperature. That is probably the reason for the change of the visible emission band. 相似文献
13.
Christian Fauteux My Ali El Khakani Joseph Pegna Daniel Therriault 《Applied Physics A: Materials Science & Processing》2009,94(4):819-829
ZnO nanorods, nanoneedles, nanoparticles, and nanoballs were synthesized on fused quartz substrates upon irradiation of a
droplet of methanolic zinc acetate dihydrate solution by an infrared (IR) continuous wave CO2 laser for a few seconds. The addition of monoethanolamine and water to the solution improved the alignment of the nanorods
and had a significant effect on the volume and morphology of the deposits. An increase of the zinc acetate concentration was
found to lead to an increase of the thickness and area covered by the initial ZnO seed layer on which the nanostructures grew.
By investigating the crystal structure of the deposits using X-ray and electron diffraction, we were able to show that the
nanorods grow along the c axis with a high crystalline quality. Raman and photoluminescence spectroscopy confirmed the high quality of the grown ZnO
nanostructures. As a matter of fact, their photoluminescence spectra are dominated by an intense UV emission around 390 nm. 相似文献
14.
Shili Hou Huibing Mao Jiqing Wang Ziqiang Zhu Weiping Jing 《Applied Physics A: Materials Science & Processing》2009,94(4):795-797
Cadmium sulfide (CdS) quantum dots (QDs) prepared by a convenient chemical method have been characterized using absorption,
fluorescence, and photoluminescence excitation techniques. The photoluminescence excitation studies show that there is an
electron transfer from the surface adsorbate (thiourea) to CdS QDs in aqueous solution. The excitation band with peak maximum
at 5.8 eV is assigned to the electronic transitions in the chemisorbed thiourea, whereas the excitation band between 3.45
and 3.7 eV corresponds to the band-to-band transition within the nanocrystalline CdS host. The absorption spectroscopy of
the CdS QD solutions shows a strong absorption peak which is generated from thiourea. The band-edge fluorescence of the CdS
QDs has also been investigated. It is shown that the fluorescence property of the CdS QDs can be enhanced by adding cadmium
chloride (CdCl2) solution. 相似文献
15.
V. ?vr?ek T. Sasaki R. Katoh Y. Shimizu N. Koshizaki 《Applied physics. B, Lasers and optics》2009,94(1):133-139
Blue luminescent colloidal silicon nanocrystals (Si-ncs) were synthesized at room temperature by nanosecond pulsed laser ablation
of a single-crystal silicon target in de-ionized water. Irregular Si-nc fragments obtained by laser ablation are stabilized
into regularly shaped, spherical, and well-separated aggregates during the aging process in water. Aging in de-ionized water
for several weeks improved the photoluminescence (PL) intensity. At least two weeks of aging are necessary for observation
of broad blue room temperature PL with a maximum centered at 420 nm. Detailed structural analysis revealed that agglomerates
after aging for several months contain Si-ncs with irregular shape smaller than the quantum confinement limit (<5 nm). These
blue luminescent Si-ncs dispersed in de-ionized water exhibited a PL decay time of 6 ns, which is much faster than that of
Si-ncs prepared in traditional ways (usually on the order of microseconds). The oxidized Si-ncs with quantum confinement effects
are responsible for a PL band around 400 nm visible to the naked eye at room temperature. 相似文献
16.
M. P. Lumb D. J. Farrell E. M. Clarke M. J. Damzen R. Murray 《Applied physics. B, Lasers and optics》2009,94(3):393-398
We have designed and grown a resonant, low-finesse quantum-dot saturable absorber mirror and subsequently modified the important
parameters using chemical etching. The modulation depth and saturation fluence at the design wavelength of 1064 nm were modified
by etching the sample to tune the cavity resonance. The device properties were characterised using normal incidence spectroscopic
reflectivity measurements, intensity dependent reflectivity measurements and modelled using a transfer matrix approach. The
saturable absorber mirror was used to facilitate self-starting, passively mode locked pulses in a neodymium vanadate laser
operating at 1064 nm. The etching was found to affect the duration of the pulses, leading to temporal width tuning over a
range of 94 ps. The shortest pulse duration of 84 ps was achieved for the cavity resonance close to 1064 nm, with an output
power of 3 W. This method is an effective technique for post-growth engineering of the properties of semiconductor saturable
absorber mirrors (SESAMs) with nanometre precision. 相似文献
17.
The influence of surface effects on the temperature dependent photoluminescence (PL) spectra from individual ZnO nanowires has been studied. It is found that the surface effects of the nanowire are very important in both ultraviolet (UV) and visible emission. We propose a new luminescence mechanism based on the recombination related to oxygen vacancies to explain the temperature dependent visible emission, which is significantly influenced by the carrier depletion and band bending caused by surface effects. In addition, the observed attenuation of UV emission with increasing temperature is ascribed to the decreasing depletion region and the increasing surface states related nonradiative recombination. 相似文献
18.
D. Valerini A. P. Caricato M. Lomascolo F. Romano A. Taurino T. Tunno M. Martino 《Applied Physics A: Materials Science & Processing》2008,93(3):729-733
We report the use of PLD to grow different ZnO nanostructures. Very different film morphologies have been observed using different
laser wavelengths to ablate the target. The influence of substrate temperature and oxygen background pressure on the film
morphology has been investigated too. Smooth and rough films, hexagonal pyramids and columns have been obtained by using a
KrF excimer laser (248 nm) for the target ablation, while hexagonal hierarchical structures and pencils have been obtained
by using ArF (193 nm). Photoluminescence and X-ray diffraction measurements revealed the good quality of the samples, in particular
of those deposited using the ArF laser beam. 相似文献
19.
N. Halder R. Rashmi S. Chakrabarti C. R. Stanley Miriam Herrera Nigel D. Browning 《Applied Physics A: Materials Science & Processing》2009,95(3):713-720
We investigate the effect of in situ annealing during growth pause on the morphological and optical properties of self-assembled InAs/GaAs quantum dots (QDs).
The islands were grown at different growth rates and having different monolayer coverage. The results were explained on the
basis of atomic force microscopy (AFM) and photo-luminescence (PL) measurements. The studies show the occurrence of ripening-like
phenomenon, observed in strained semiconductor system. Agglomeration of the self-assembled QDs takes place during dot pause
leading to an equilibrium size distribution. The PL properties of the QDs are affected by the Indium desorption from the surface
of the QDs during dot pause annealing at high growth temperature (520°C) subsiding the effect of the narrowing of the dot
size distribution with growth pause. The samples having high monolayer coverage (3.4 ML) and grown at a slower growth rate
(0.032 ML s−1) manifested two different QD families. Among the islands the smaller are coherent defect-free in nature, whereas the larger
dots are plastically relaxed and hence optically inactive. Indium desorption from the island surface during the in situ annealing and inhomogeneous morphology as the dots agglomerate during the growth pause, also affects the PL emission from
these dot assemblies. 相似文献
20.
Shoubin Xue Xing Zhang Ru Huang Huizhao Zhuang 《Applied Physics A: Materials Science & Processing》2009,94(2):287-291
ZnO thin films were first prepared on Si(111) substrates using a radio frequency magnetron sputtering system. Then the as-grown
ZnO films were annealed in oxygen ambient at temperatures of 700, 800, 900, and 1000°C , respectively. The morphologies of
ZnO films were studied by an atom force microscope (AFM). Subsequently, GaN epilayers about 500 nm thick were deposited on
the ZnO buffer layers. The GaN/ZnO films were annealed in NH3 ambient at 900°C. The microstructure, morphology and optical properties of GaN films were studied by x-ray diffraction (XRD),
AFM, scanning electron microscopy (SEM) and photoluminescence (PL). The results are shown, their properties having been investigated
particularly as a function of the ZnO layers. For better growth of the GaN films, the optimal annealing temperature of the
ZnO buffer layers was 900°C. 相似文献