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Wyświetlanie 1-15 z 92
Tytuł:
Effect of Trisodium Citrate on the Morphology and Luminescence Properties of Hydrothermally Synthesized YVO₄ Phosphor
Autorzy:
Zhang, Sa
Liang, Yan
Gao, Xiaoyong
Powiązania:
https://bibliotekanauki.pl/articles/1398668.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.-m
61.05.cp
68.37.Hk
78.30.-j
Opis:
YVO₄ phosphors with different morphologies were synthesized by trisodium citrate (Na₃cit) surfactant-assisted hydrothermal process. Effects of molar ratio of $\text{cit}^{3-}$ to $Y^{3+}$ and pH value of reaction solution were intensively investigated on the morphologies, structures and luminescence properties of YVO₄ phosphor. The morphologies of the YVO₄ particles can be effectively controlled in strong acidic and strong alkaline environment by affecting the adsorption of $\text{cit}^{3-}$ on the (001) crystal plane of YVO₄. Strong acidic condition resulted into excessive adsorption of $\text{cit}^{3-}$ groups on the YVO₄ phosphor, which annihilated the superior luminescence of YVO₄ phosphors. On the contrary, strong alkaline condition does not result into the adsorption of $\text{cit}^{3-}$ groups. The synthesized YVO₄ phosphor without adsorption of $\text{cit}^{3-}$ groups showed superior luminescence even though the effective control of the morphology in alkaline condition is not so good as in strong acidic condition.
Źródło:
Acta Physica Polonica A; 2016, 129, 1; 79-83
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hydrothermal Synthesis and Microstructural, Optical Properties Characterization of $YVO_4$ Phosphor Powder
Autorzy:
Zhang, S.
Liang, Y.
Gao, X.
Liu, H.
Powiązania:
https://bibliotekanauki.pl/articles/1207386.pdf
Data publikacji:
2014-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.-m
42.70.Hj
78.67.-n
Opis:
The phonon energy of $YVO_4$ crystal is lower than other usual compounds of salt. So it is suitable as host material for down-conversion materials. Hydrothermal method was adopted to synthesize $YVO_4$ phosphor powder with the use of yttrium oxide and sodium vanadate as raw material. The change in the relative integral intensity of the (200) and (112) diffraction peaks indicates that macroscopic stress in the lattice obviously changes with the elevated hydrothermal reaction temperature. The $YVO_4$ phosphor powder synthesized involves a certain agglomeration of small particles. The phonon vibration in the $YVO_4$ originates mainly from the internal vibrations in the vanadium-oxygen tetrahedron, in addition to the Y-O and O-H vibrations. Due to a low phonon energy of only $2.8188 × 10^{-21} J$, $YVO_4$ helps to improve the down-conversion efficiency of rare-earth ions. A bandgap value of approximately 3.8 eV for the synthesized $YVO_4$ powders leads to good absorption properties in the ultraviolet region. Upon excitation by the 320 nm ultraviolet photon, the intrinsic emission of $YVO_4$ powders is annihilated, and a broadband emission of $VO_4^{3-}$ near 450 nm is observed at room temperature. The $YVO_4$ phosphor powder synthesized at 180C exhibits the maximum photoluminescence intensity because of its excellent crystallization.
Źródło:
Acta Physica Polonica A; 2014, 125, 1; 105-110
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stokes Shift and Band Gap Bowing in $In_xGa_{1-x}N$ (0.060 ≤ x ≤ 0.105) Grown by Metalorganic Vapour Phase Epitaxy
Autorzy:
Yildiz, A.
Dagdelen, F.
Aydogdu, Y.
Acar, S.
Lisesivdin, S.
Kasap, M.
Bosi, M.
Powiązania:
https://bibliotekanauki.pl/articles/1813499.pdf
Data publikacji:
2008-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.61.-r
78.20.-e
78.40.Fy
78.55.-m
Opis:
We presented the results of electrical and optical studies of the properties of $In_xGa_{1-x}N$ epitaxial layers (0.060≤x≤0.105) grown by metalorganic vapour phase epitaxy. Resistivity and Hall effect measurements of the samples were carried out at room temperature. Optical properties of the samples were characterized by photoluminescence and optical absorption spectroscopy. The comparison between the photoluminescence and the optical absorption measurements gives the Stokes shift. We explained the observed Stokes shift in terms of Burstein-Moss effect. The band gap versus composition plot for $In_xGa_{1-x}N$ alloys is well fitted with a bowing parameter of≈3.6 eV.
Źródło:
Acta Physica Polonica A; 2008, 113, 2; 731-739
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photoluminescence Studies of Aluminum Nitride Nanowires
Autorzy:
Yang, J.
Na, H.
Kim, H.
Kebede, M.
Choi, R.
Jeong, J.
Lee, C.
Powiązania:
https://bibliotekanauki.pl/articles/1505466.pdf
Data publikacji:
2011-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.-b
78.55.-m
Opis:
We report the production of AlN nanowires by the thermal heating method, for exploring their photoluminescence properties. The room-temperature photoluminescence properties were investigated with different annealing environment. While broad emissions with peaks at around 2.45 and 2.95 eV were obtained from both unannealed and annealed samples, the additional 2.1 eV peak was found from the annealed samples. We have suggested the possible emission mechanisms based on the assumption that both 2.45 eV peak and 2.1 eV peak are ascribed to the nitrogen vacancies. Annealing in N_2 environment exhibited lower intensities of 2.45 eV peak and 2.1 eV peak in comparison to those in Ar environment, presumably due to the suppression of nitrogen vacancies.
Źródło:
Acta Physica Polonica A; 2011, 119, 2; 125-127
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Competition of Radiation Processes in 6H-SiC Observed by Luminescence
Autorzy:
Wysmołek, A.
Mroziński, P.
Dwiliński, R.
Vlaskina, S.
Kamińska, M.
Powiązania:
https://bibliotekanauki.pl/articles/1873137.pdf
Data publikacji:
1995-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.-m
78.60.Kn
Opis:
We report on the results of photoluminescence and thermoluminescence measurements of various 6H-SiC crystals. At low temperature in all n-type samples two bands with maxima at 2.7 eV (blue) and 1.8 eV (orange) were detected. In the p-type material only blue band was observed. The measurements performed at a broad range of temperatures showed totally different behaviour of photoluminescence intensity of both bands. The presented results could be explained in the model assuming well established donor-acceptor pair recombination for the blue band emission and the conduction band - deep defect transition for the orange band. The proposed model was confirmed by thermoluminescence measurements of the orange band which showed peaks at 30 K, 80 K, 100 K, 150 K attributed to ionization of subsequent shallow donor levels.
Źródło:
Acta Physica Polonica A; 1995, 87, 2; 437-440
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Impact Ionization of Shallow Donors on Luminescence in GaAs
Autorzy:
Wysmołek, A.
Łusakowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1932094.pdf
Data publikacji:
1995-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.-m
72.20.Ht
Opis:
Luminescence spectra of n-type molecular beam epitaxial layer and semi-insulating liquid encapsulated Czochralski grown bulk GaAs were measured at liquid helium temperature for zero electric field and for fields which caused impact ionization of shallow donors. Application of the electric field caused a decrease in the luminescence intensity and a broadening of all observed structures. It was found that the electric field changed the luminescence spectrum of the n-type material in a different way than it did in the case of the semi-insulating one. For the n-type sample, an intensity of excitonic lines decreased much more than that of donor-acceptor lines when the electric field grew. A contrary was observed for the semi-insulating sample. An explanation of the result is proposed which takes into account an influence of ionised impurity scattering and localization in fluctuations of the electrostatic potential on the luminescence process.
Źródło:
Acta Physica Polonica A; 1995, 87, 1; 261-264
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Origin of Centres Involved in Blue and Orange Luminescence of 6H-SiC
Autorzy:
Wysmołek, A.
Baranowski, J. M.
Kamińska, M.
Powiązania:
https://bibliotekanauki.pl/articles/1934050.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.-m
78.20.-e
78.60.Kn
Opis:
We present new results of luminescence of n-type 6H-SiC crystals. We have found two shallow donors with ionization energies at 60 meV and 140 meV. We have shown that the blue luminescence is not affected by the ionization of the shallower donor and is related to deeper donor which we attribute to N at C-site. We propose that the origin of the more shallower donor at 60 meV is related to carbon vacancy. We have found that the intensity of the orange luminescence increases under infrared illumination. This result confirms that the orange luminescence is due to conduction band-deep centre transitions. We believe that deep centre responsible for the orange luminescence is the silicon vacancy.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 957-960
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New High Performance Scintillators Based on Re-Activated Insulator Materials
Autorzy:
Wojtowicz, A. J.
Powiązania:
https://bibliotekanauki.pl/articles/1945553.pdf
Data publikacji:
1996-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.90.+t
78.55.-m
61.80.Ed
29.40.-n
Opis:
In this paper we address the problem of the host-to-ion energy transfer in some RE-activated wide band gap materials excited by ionizing radiation. We argue that, despite the expected self-localization of holes, the dominant mechanism in efficient materials involves sequential trapping of both charge carriers (holes and electrons) by an activating RE-ion followed by a radiative recombination via the ion producing scintillation light. Selected experimental results are presented to illustrate how various energy transfer processes manifest themselves in the spectroscopy of scintillator materials. Experimental results combined with simple considerations are used to identify these RE-ions which are likely to act as hole or electron traps in tri- and difluorides, thus initiating the recombination sequence leading to efficient scintillation.
Źródło:
Acta Physica Polonica A; 1996, 90, 1; 215-222
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Luminescence and Scintillation Properties of Ce$\text{}_{x}$La$\text{}_{1-x}$F$\text{}_{3}$ Monocrystals
Autorzy:
Wojtowicz, A.
Balcerzyk, M.
Lempicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/1929799.pdf
Data publikacji:
1993-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.90.+t
78.55.-m
61.80.Ed
29.40.-n
Opis:
In this communication we present our results concerning luminescence and scintillation properties of mixed cerium-lanthanum trifluoride monocrystals, Ce$\text{}_{x}$La$\text{}_{1-x}$F$\text{}_{3}$. The luminescence, luminescence excitation spectra and decays are complex, indicating the presence of Ce$\text{}^{3+}$ ions in regular and parasitic "perturbed" sites. The efficient energy transfer from regular Ce$\text{}^{3+}$ ions (emitting at 286 and 303 nm) to "perturbed" Ce$\text{}^{3+}$ ions (emitting at 340 nm) and the lack of the fast energy migration between Ce$\text{}^{3+}$ ions are responsible for non-exponential decays of the short-wavelength emission and a relatively long rise-time of the long-wavelength emission. The short-wavelength emission decays are described by the Inokuti-Hirayama model of statistically distributed donors and acceptors. Our estimates of oscillator strengths, at 13.1 × 10$\text{}^{-3}$ for Ce$\text{}^{3+}$, and 13.5 × 10$\text{}^{-3}$ for Ce$\text{}^{3+}$$\text{}_{per}$, confirm that the d-f transition on the Ce$\text{}^{3+}$ ion in a different site must be responsible for the long-wavelength emission. Calculations of the Ce-Ce and Ce-Ce$\text{}_{per}$ energy transfer rates give 7.7 × 10$\text{}^{5}$ s$\text{}^{-1}$ and 1.56 × 10$\text{}^{9}$ s$\text{}^{-1}$. The concentration of "perturbers" in good CeF$\text{}_{3}$ samples has been reduced down to about 0.11%. It is likely that the constant and significant progress made by crystal growers (Optovac Inc.) may eventually produce a superior material for applications in high energy and nuclear physics.
Źródło:
Acta Physica Polonica A; 1993, 84, 5; 963-968
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Physics of Solid-State Laser Materials
Autorzy:
Wojtowicz, A.
Powiązania:
https://bibliotekanauki.pl/articles/1888052.pdf
Data publikacji:
1991-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.55.Rz
78.50.-w
78.55.-m
Opis:
A survey of the physical properties of solid state materials activated with d$\text{}^{2}$, d$\text{}^{3}$ and d$\text{}^{8}$ transition metal ions is presented in the context of tunable laser operation. An emphasis is put on common characteristics of all three systems, like a strong electron-phonon coupling and similar electronic structures. The conditions necessary to obtain a tunable operation and to avoid an overlap of the excited state absorption and emission are formulated. It is shown that the d$\text{}^{3}$ configuration system has the largest range of allowed values of the crystal field parameter 10Dq.
Źródło:
Acta Physica Polonica A; 1991, 80, 2; 193-205
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Excited State Absorption and Thermoluminescence in Ce and Mg Doped Yttrium Aluminum Garnet
Autorzy:
Wiśniewski, K.
Koepke, Cz.
Wojtowicz, A. J.
Drozdowski, W.
Grinberg, M.
Kaczmarek, S. M.
Kisielewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/2007834.pdf
Data publikacji:
1999-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Hx
78.55.-m
78.60.Kn
73.50.Gr
29.40.Mc
78.20.-e
78.20.Wc
78.40.-q
Opis:
In this paper we report preliminary results of optical studies on Y$\text{}_{3}$Al$\text{}_{5}$O$\text{}_{12}$ (YAG) crystals codoped with Ce and Mg. By using measurements of luminescence, absorption, and luminescence excitation spectra we demonstrate that although the basic features introduced to the YAG host by the Ce-doping remain intact, the Mg-codoping imposes some significant changes on other properties of the material. These changes are potentially important for laser and/or scintillator applications of YAG:Ce and are due, most likely, to modifications of defect populations in the material. We characterize them by using the techniques of thermoluminescence and excited state absorption under excimer laser pumping. These techniques, interestingly, yield results that seem inconsistent. While the thermoluminescence signal of the Mg-doped sample is strongly reduced, suggesting that trap concentrations in the presence of Mg are suppressed, the excited state absorption signal, which we also relate to the traps, is higher. We offer a tentative explanation of this contradiction between the two experiments that involves a massive transfer of electrons from the Mg-related defects to the excited state absorption centers caused by the excimer pump itself.
Źródło:
Acta Physica Polonica A; 1999, 95, 3; 403-412
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spectroscopy and Thermoluminescence of LuAlO$\text{}_{3}$:Ce
Autorzy:
Wiśniewski, D.
Drozdowski, W.
Wojtowicz, A.
Lempicki, A.
Dorenbos, P.
de Haas, J. T. M.
van Eijk, C. W. E.
Bos, A. J. J.
Powiązania:
https://bibliotekanauki.pl/articles/1945649.pdf
Data publikacji:
1996-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.90.+t
78.55.-m
61.80.Ed
29.40.-n
Opis:
The present status of the LuAlO$\text{}_{3}$:Ce scintillator is reviewed. Scintillation mechanism of this material is based on capture by Ce$\text{}^{3+}$ of holes and then electrons from their respective bands. Results of spectroscopic and thermoluminescence experiments are presented to support this model.
Źródło:
Acta Physica Polonica A; 1996, 90, 2; 377-384
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Light-Induced Tautomerization in Porphyrin Isomers
Autorzy:
Waluk, J.
Powiązania:
https://bibliotekanauki.pl/articles/1993612.pdf
Data publikacji:
1999-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.20.-t
33.50.-j
78.55.-m
78.60.-b
Opis:
Double proton tautomerization occurring in porphyrin and its structural isomers represents a special case of a chemical transformation in which the substrate and the product are form ally the same. The methods used for the investigation of this kind of processes are based on polarized spectroscopy and high-resolution techniques, such as matrix isolation. Their combined use results in obtaining information pertinent to the mechanism of proton transfer, regarding e.g., the values of proton transfer rates, structure of the tautomeric forms or the shape of the potential energy surfaces. In addition, these procedures provide a way of obtaining spectral, photophysical and structural data that would be otherwise difficult to gain. The examples include determination of transition moment directions, assignment of electronic and vibrational states, elucidation of the character of the substitutional replacement of the rare gas matrix atoms by the chromophore, and the analysis of the nature of the symmetry lowering due to the matrix cage.
Źródło:
Acta Physica Polonica A; 1999, 95, 1; 49-62
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetic Roughening and Material Optical Properties Influence on Van der Waals/Casimir Forces
Autorzy:
van Zwol, P.
Palasantzas, G.
Powiązania:
https://bibliotekanauki.pl/articles/1539079.pdf
Data publikacji:
2010-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.55.Jk
68.37.Ps
85.85.+j
78.68.+m
68.55.-a
47.55.nb
Opis:
Atomic force microscopy measurements and force theory calculations using the Lifshitz theory show that van der Waals/Casimir dispersive forces have a strong dependence on surface roughness and material optical properties. It is found that at separations below 100 nm the roughness effect is manifested through a strong deviation from the normal scaling of the force with separation distance. Moreover, knowledge of precise optical properties of metals is shown to be very important for accurate force predictions rather than referring to idealized defect free material models. Finally, we compare the van der Waals/Casimir forces to capillary adhesive forces in order to illustrate their significance in stiction problems.
Źródło:
Acta Physica Polonica A; 2010, 117, 2; 379-383
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparative Spectroscopic Study of the Dy$\text{}^{3+}$ Doped Double Chloride and Double Fluoride Crystals for Telecommunication Amplifiers and IR Lasers
Autorzy:
Tkachuk, A.
Ivanova, S.
Isaenko, L.
Yelisseyev, A.
Payne, Steve
Solarz, R.
Nostrand, M.
Page, R.
Payne, Stephen
Powiązania:
https://bibliotekanauki.pl/articles/1995823.pdf
Data publikacji:
1999-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.-m
Opis:
In this work we studied spectroscopic characteristics of potassium-lead double-chloride, and lithium-yttrium double-fluoride crystals doped with dysprosium. Objects of research were KPb$\text{}_{2}$Cl$\text{}_{5}$:Dy$\text{}^{3+}$, and LiYF$\text{}_{4}$ (YLF):Dy$\text{}^{3+}$ crystals grown by the Bridgman-Stockbarger technique. We obtained the effective distribution coefficients K$\text{}_{Dy}$=0.95 for LiYF$\text{}_{4}$ :Dy$\text{}^{3+}$, and K$\text{}_{Dy}$=1 for KPb$\text{}_{2}$Cl$\text{}_{5}$:Dy$\text{}^{3+}$. Optical spectra were studied, intensity parameters were determined by the Judd-Ofelt method, and radiative probabilities and branching ratio were calculated. The conclusion was made that the studied crystals can be considered as promising new active media for laser diode pumped solid state lasers. The YLF:Dy$\text{}^{3+}$ crystals are perspective for laser action near 3 mm, and the KPb$\text{}_{2}$Cl$\text{}_{5}$ :Dy$\text{}^{3+}$ for multiwavelength IR lasers, and for 1.3 mm laser diode pumped telecommunication amplifiers.
Źródło:
Acta Physica Polonica A; 1999, 95, 3; 381-394
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 92

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