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1.
Thin films of ZnWO4 and CdWO4 were prepared by spray pyrolysis and the structural, optical, and luminescence properties were investigated. Both ZnWO4 and CdWO4 thin films showed a broad blue-green emission band. The broad band of ZnWO4 films was centered at 495 nm (2.51 eV) consisted of three bands at 444 nm (2.80 eV), 495 nm (2.51 eV) and 540 nm (2.30 eV). The broad band of CdWO4 films at 495 nm (2.51 eV) could be decomposed to three bands at 444 nm (2.80 eV), 495 nm (2.51 eV) and 545 nm (2.28 eV). These results are consistent with emission from the WO66− molecular complex. The luminance and efficiency for ZnWO4 film at 5 kV and 57 μA/cm2 were 48 cd/m2 and 0.22 lm/w, respectively, and for CdWO4 film the values were 420 cd/m2 and 1.9 lm/w. 相似文献
2.
It is established that doping of CdS polycrystalline films with alkaline metals (Li, Na, K, Cs) results in an increase of
luminescence intensity by 3–5 times compared with pure films. This increase is accounted for by the placement of alkaline-metal
ions in V
Cd
2−
cation vacancies, which are nonradiative recombination centers in these films. From the dependences of the luminsecence intensity
of the doped films on the synthesis conditions (deposition temperature, concentration of doping impurities, type of doping
metal), the parameters that ensure the maximum luminescence intensity of the films are determined as Tdep ≈ 450°C and CMe = 1·10−5 at %. The luminescence intensity decreases by 1–3% upon exposure of the films to UV light (λmax = 365 nm, I = 1021 quanta·sec·cm−1) for several hours. This is indicative of the stability of these films against UV radiation.
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Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 362–366, May–June, 2007. 相似文献
3.
We have studied photoluminescence and thermoluminescence (PL and TL) in CaGa2Se4:Eu crystals in the temperature range 77–400 K. We have established that broadband photoluminescence with maximum at 571 nm
is due to intracenter transitions 4f6 5d–4f7 (8S7/2) of the Eu2+ ions. From the temperature dependence of the intensity (log I–103/T), we determined the activation energy (E
a = 0.04 eV) for thermal quenching of photoluminescence. From the thermoluminescence spectra, we determined the trap depths:
0.31, 0.44, 0.53, 0.59 eV. The lifetime of the excited state 4f6 5d of the Eu2+ ions in the CaGa2Se4 crystal found from the luminescence decay kinetics is 3.8 μsec.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 112–116, January–February, 2009. 相似文献
4.
Yu. V. Zorenko A. S. Voloshinovskii G. M. Stryganyuk I. V. Konstankevych 《Optics and Spectroscopy》2004,96(1):70-76
The nature of intrinsic emission bands of yttrium orthoaluminate in the UV spectral region at max=220 nm (5.63 eV) and 330 nm (4.13 eV) is studied on the basis of the luminescence of single crystals and single-crystal films of YAlO3 and Ce: YAlO3 excited by synchrotron radiation sources with an energy of 3–25 eV at 9 and 300 K. The single crystals and single-crystal films were obtained, respectively, from solution and solution-melt by liquid-phase epitaxy and are characterized by considerably different concentrations of substitutional and vacancy defects. It is found that only the luminescence band at 300 nm, which has the decay time τ=4.1 ns and is excited in a band shifted from the range of interband transitions by 0.25 eV, has exciton-like character. The luminescence band at 220 nm with τ=0.1 µs at 9K, which is observed only for YAlO3 single crystals and is absent in the luminescence of single-crystal films, is associated with antisite defects of the Y Al 3+ type, which are a specific type of cationic isoelectronic impurities. It is shown that the phosphors based on single-crystal films of YAlO3 have a simpler scintillation decay kinetics than their bulk analogues due to the absence of channels of excitation energy dissipation associated with the antisite defects of Y Al 3+ type and vacancy defects. 相似文献
5.
Guoxin Zhang Sefei Yang Lan Zhang Haiying Zhang Yongxian Wang 《Applied Surface Science》2010,257(1):302-718
Aqueous CdWO4 QDs were synthesized by the reaction of CdCl2 and Na2WO4 in the presence of mercaptoacetic acid (TGA) as capping reagent. The crystal morphology, particle size and its distribution of as-prepared products were characterized by transmission electron microscopy (TEM, SAED) atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), and photon correlation spectroscopy (PCS), respectively. Qualitative assays for functional groups on the QDs’ surface were measured by fourier transform infrared spectroscopy (FTIR). Photoluminescence properties of QDs were studied by photoluminescence spectroscopy (PL). The results showed that the single QD with diameter of about 8 ± 2 nm was single-crystal. The particle size distribution of QDs was normal. Infrared absorption bands of carboxylic group on the surface of CdWO4 QDs were observed around 1610-1550 cm−1 (nonsymmetrical vibration of -COO−) and 1400 cm−1 (symmetric vibration of C-O). With reaction-time going, PL peak position shifted from 498 to 549 nm and intensity of PL increased first and then decreased. PL peak position of QDs was blue-shift compared with 570 nm WO66− luminescence center of bulk CdWO4. 相似文献
6.
O. V. Ovchinnikov A. B. Evlev M. A. Efimova V. G. Klyuev A. N. Latyshev A. N. Utekhin A. M. Kholkina 《Journal of Applied Spectroscopy》2005,72(6):809-813
An anti-Stokes luminescence band with λmax = 515 nm of microcrystals of solid AgCl0.95I0.05 solutions excited by a radiation flux of density 1013–1015 quanta/cm2·sec in the range 600–800 nm at 77 K was detected. It is shown that the intensity of this luminescence and the frequency of
its excitation depend on the prior UV-irradiation of samples. Analysis of the stimulated-photoluminescence spectra and the
anti-Stokes luminescence excitation spectra of the indicated microcrystals has shown that to the centers of anti-Stokes luminescence
excitation correspond local levels in the forbidden band of the crystals. These states are apparently due to the atomic and
molecular disperse silver particles that can be inherent in character or formed as a result of a low-temperature photochemical
process.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 738–742, November–December, 2005. 相似文献
7.
A. P. Losev S. M. Bachilo D. I. Volkovich Yu. S. Avlasevich K. N. Solov’yov 《Journal of Applied Spectroscopy》1997,64(1):62-71
Photoinduced electron transfer (PET) in a Pd-porphyrin-quinone complex (Pd-P-Q) was investigated using the flash photolysis
method in microsecond and picosecond range and by luminescence. The investigations were performed for toluene solutions. Intramolecular
PETs in the lower excited singlet state (kCT=1.7·1010 sec−1) and in the triplet state (kCT=2.5·108sec−1) were observed. For a quantum yield of the triplet state that is close to 1 in Pd-porphyrin (Pd-P) this yield is equal to
0.4 in Pd-P-Q. This decrease is the result of PET in the excited state and, possibly, in an unrelaxed triplet state. Triplet
Pd-P-Q molecules were efficiently quenched by unexcited molecules, and this process is related to intermolecular charge transfer.
This electron transfer is likely to occur from the Pd-P protion of an excited molecule to the quinone protion of an unexcited
molecule in the collisional complex (Pd-P-Q)2. Charged radicals, formed once the collisional complex is transferred and separated, have a wide absorption band with a maximum
of about 960 nm. The average lifetime of the radicals was about 2 msec.
Institute of Molecular and Atomic Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No 1 pp. 61–70, January–February, 1997. 相似文献
8.
O. V. Ovchinnikov E. A. Kosyakova M. S. Smirnov A. B. Evlev V. G. Klyuev A. N. Latyshev A. N. Utekhin 《Journal of Applied Spectroscopy》2007,74(5):681-686
For microcrystals of Zn0.6Cd0.4S 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 1014–1015 photons/cm2·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 Zn0.6Cd0.4S 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 Zn0.6Cd0.4S, creating deep localized states in the bandgap with photoionization energies 1.80–2.00 eV.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 617–621, September–October, 2007. 相似文献
9.
S. N. Ivanov E. Yu. Loktionov Yu. S. Protasov Yu. Yu. Protasov 《Journal of Applied Spectroscopy》2009,76(5):738-742
We describe an optical diagnostics module and the instrumental and methodological features of ultrahigh vacuum experiments
investigating the optical characteristics of condensed media in the short-wavelength (hv ~ 3.5–25 eV) range of the spectrum of probing synchrotron radiation. We give a brief presentation of the results of an experimental
determination of the spectral dependence of the luminescence quantum yield and the luminescence excitation spectrum of ablatable
polymer dielectrics on the Kurchatov synchrotron radiation source at values of the probing radiation power density (I
0 ~ 1012 photons/cm2∙sec) that are below threshold for extended surface vaporization and a surface temperature of the condensed targets equal
to 77–300 K. 相似文献
10.
Hrant Yeritsyan Vachagan Harutiunian Volodia Gevorkyan Norair Grigoryan Eleonora Hakhverdyan Sergey Nikoghosyan Aram Sahakyan Rudolf Gevorgyan Hakob Sargisyan Yeghis Keheyan 《Central European Journal of Physics》2005,3(4):623-635
Infrared (IR) absorption and luminescence in chemically and radiation-modified natural Armenian Zeolite (clinoptilolite) samples
have been studied. The luminescence was studied in 390–450 nm and 620–710 nm wavelength bands, and the IR measurements were
carried out in the 400–5400 cm−1 range. It is shown that the luminescence intensity depends on the content of pure clinoptilolite in the samples and, probably
on the distribution of “passive” luminescence centers over Si and Al sites that became “active” under radiation or chemical
treatment. The samples of electron irradiated clinoptilolite have higher luminescence intensity than the chemically and thermally
treated ones. A decrease in the intensity of IR absorption bands at 3550 cm−1 and 3650 cm−1 was found after irradiation. 相似文献
11.
Spectra of x-ray radiation-induced absorption of SrCl2−Ce crystals in the region of 340–830 nm under the effect of selective irradiation in the induced-absorption bands by both
conventional and laser sources are investigated. It is established that irradiation of sufficient intensity causes irreversible
photochemical transformations of PC, PC+, and Ce2+ color centers their destruction, and restoration of the transparency of the crystals.
To whom correspondence should be addressed.
I. Franko Lvov State University, 8, Kirill and Mefodii Str., Lvov, 290005, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 66, No. 5, pp. 666–668, September–October, 1999. 相似文献
12.
Results of investigations of spectroscopic properties of Ca3Ga2Ge4O14 single crystals activated with Sm3+ ions are reported. It is shown that Sm3+ ions in Ca3Ga2Ge4O14 form a type of activator quasicenter whose nature is associated with disordering of the matrix.
I. Franko Lvov State University, 50, Dragomanov St., Lvov, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol.
65, No. 2, pp. 296–298, March–April, 1998. 相似文献
13.
T. Caruso C. Lenardi T. Mazza A. Policicchio R.G. Agostino E. Colavita K.C. Prince P. Piseri P. Milani 《Surface science》2007,601(13):2688-2691
Nanostructured titanium dioxide (ns-TiO2) films were grown by supersonic cluster beam deposition method. Transmission electron microscopy demonstrated that films are mainly composed by TiO2 nanocrystals embedded in an amorphous TiO2 phase while their electronic structure was studied by photoemission spectroscopy. The cluster assembled ns-TiO2 films are expected to exhibit several structural and chemical defects owing to the large surface to volume ratio of the deposited clusters. Ultraviolet photoemission spectra (hv = 50 eV) from the valence band unveil the presence of a restrained amount of surface Ti 3d defect states in the band gap, whereas Ti 2p core level X-ray photoelectron (hv = 630 eV) spectra do not manifestly disclose these defects. 相似文献
14.
Cheng-Fu Yang Hong-Hsin Huang Cheng-Yi Chen Ping-Chih Huang Chien-Chen Diao 《Applied Physics A: Materials Science & Processing》2009,94(1):117-122
In this study, two different thin films, TiO2 thin film and TiO2–W–TiO2 multi-layer thin films (W, tungsten), are prepared by RF magnetron sputtering onto glass substrates. The crystal structure,
morphology, and transmittance of TiO2 and TiO2–W–TiO2 multi-layer thin films are investigated by X-ray diffraction, SEM, and UV-Vis spectrometer, respectively. The amorphous,
rutile, and anatase TiO2 phases are observed in the TiO2 thin film and in the TiO2–W–TiO2 multi-layer thin films. The deposition of tungsten as the inter-layer will have large effect on the transmittance and phase
ratios of rutile and anatase phases in the TiO2–W–TiO2 multi-layer thin films. The crystal intensities of amorous TiO2 will decrease as the tungsten is used as the middle layer in the multi-layer structure. The band gap energy values of TiO2 thin film and TiO2–W–TiO2 multi-layer thin films are evaluated from (αhν)1/2 versus energy plots, and the calculated results show that the energy gap decreases from 3.21 eV (TiO2 thin film) to 3.08∼3.03 EV (TiO2–W–TiO2 multi-layer thin films). 相似文献
15.
P. Leyral F. Litty S. Loualiche A. Nouailhat G. Guillot 《Solid State Communications》1981,38(4):333-336
Comparison between the excitation spectra of luminescence (ESL) of the 0.57 eV band (typical of p or SI materials) and of the 0.62 eV band (typical of n samples) with the photoionization cross-sections σ0n(hv) and σ0p(hv) of the chronium level leads us to attribute unambiguously these luminescence transitions to the (Cr3+?Cr2+) center in chromium doped GaAs. 相似文献
16.
Ajay KaushalNitin Choudhary Navjot KaurDavinder Kaur 《Applied Surface Science》2011,257(21):8937-8944
Pure VO2 and VO2-WO3 composite thin films were grown on quartz substrate by pulsed laser deposition (PLD) technique. The influence of varying WO3 molar concentration in the range from x = 0.0 to x = 0.4 on structural, electrical and optical properties of VO2-WO3 nanocomposite thin films has been systematically investigated. X-ray diffraction studies reveal the single crystalline monoclinic VO2 phase (m-VO2) up to 10% of WO3 content whereas both m-VO2 as well as h-WO3 (hexagonal WO3) phases were present at higher WO3 content (0.2 ≤ x ≤ 0.4). Optical transmittance spectra of the films showed blue shift in the absorption edge with increase in WO3 content. Temperature dependence of resistivity (R-T) measurements indicates significant variation in metal-insulator transition temperature, width of the hysteresis, and shape of the hysteresis curve. Cyclic Voltammetry measurements were performed on VO2-WO3 thin films. A direct correlation between V/W ratio and structure-property relationship was established. The present investigations reveal that doping of WO3 in VO2 is effective to increase the optical transmittance and to reduce the semiconductor to metal phase transition temperature close to room temperature. 相似文献
17.
β-γ-γ directional correlation studies for the cascades (i)β-rays ofE
max=0.12 MeV,γ-rays of 557 keV andγ-rays of 53 keV and (ii)β-rays ofE
max=0.21 MeV,γ-rays of 444 keV andγ-rays of 53 keV have been made. The triple correlation functionsW(θ) were obtained to beW(θ)=1+(−0.153±0.031)P
2(cosθ)+(0.004±0.035)P
4(cosθ) forβ-rays ofE
max 0.12 MeV→557→53 keV cascade andW(θ)=1+(0.163±0.042)P
2(cosθ)+(−0.035±0.058)P
4(cosθ) forβ rays ofE
max=0.21 MeV→444 keV→53 keV cascade.
Spins and parities of the 650, 537 and 93 keV levels of103Rh are deduced by triple angular correlation and the internal conversion coefficient studies. Multipolarities of the transitions
are also determined. 相似文献
18.
Variation-after-projection (VAP) calculations in conjunction with Hartree-Bogoliubov (HB) ansatz have been carried out for
A=100−108 molybdenum (Mo) isotopes. In this framework, the yrast spectra with J
max
π
≥10+, B(E2) transition probabilities, quadrupole (β2) and hexadecapole (β4) deformation parameters, moment of inertia (I) and square of cranking frequency (ω2) for even-even Mo isotopes have been obtained. The results of the calculation give an indication that it is important to
include the hexadecapole-hexadecapole component of the two-body interaction for obtaining various nuclear structure quantities
in these Mo isotopes. 相似文献
19.
O. V. Ovchinnikov E. A. Kosyakova L. Yu. Leonova M. S. Smirnov A. B. Evlev A. N. Latyshev A. N. Utekhin 《Russian Physics Journal》2008,51(3):244-250
The sensitized anti-Stokes luminescence excited by radiation with wavelengths from 610 to 750 nm and flux densities of 1014–1015 quanta/(cm2·s) is detected for microcrystals of Zn
0.6
Cd
0.4
S solid solutions with adsorbed organic malachite green and methylene blue dye molecules. The position of its excitation spectra
coincides with that of the absorption spectra of adsorbed dye molecules, which suggests the cooperative mechanism of its occurrence.
The possibility of amplification of the anti-Stokes luminescence by means of adsorption of silver atoms and few-atomic silver
clusters, in addition to the dye molecules, on the Zn
0.6
Cd
0.4
S surface is investigated. It is assumed that in the latter case, the anti-Stokes luminescence is excited as a result of two-quantum
optical transitions with electron or electron excitation energy transfer from the dye molecules adsorbed on the Zn
0.6
Cd
0.4
S surface to silver atoms and few-atomic silver clusters creating deep local states with photoionization energies of 1.8–2.0
eV in the gap.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 21–26, March, 2008. 相似文献
20.
Spatially separated defects created by photons with energies 6–8 eV in alkali-earth fluoride crystals doped with cerium are
investigated with the help of thermoluminescence. Measuring the spectra of creation of Vk and H peaks of thermostimulated luminescence inBaF
2:Ce3+. we demonstrate that photons with energies higher than 6eV induce H centers (self-trapped holes captured by interstitialF ions), whereas the formation of self-trapped holes begins on exposure to photons with energies greater than 7 eV. The influence
of photoionization on theCe
3+ luminescence inBaF
2, SrF2, CaF2, andCeF
3 crystals is investigated in the range of photon energies 4–8 eV. An exponentialCe
3+-emisson decay was observed for excitation energy lying in the range 4–6 eV. Slow and fast decay components were observed
under excitation by photons with energies higher than 6 eV. We believe that the slow and fast components are due to the tunnel
recombination of trapped electrons with hole centers.
A. P. Vinogradov Institute of Geochemistry of the Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya
Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 43–49, March, 2000. 相似文献