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Wyszukujesz frazę "Wojtowicz, A. J." wg kryterium: Autor


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:
Some Aspects of Solid State Radioluminescence
Autorzy:
Wojtowicz, A. J.
Powiązania:
https://bibliotekanauki.pl/articles/1994522.pdf
Data publikacji:
1999-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.60.Ya
78.30.Hv
78.60.Kn
29.40.Mc
Opis:
In this paper we review results of radioluminescence studies on two scintillator materials, LuAlO$\text{}_{3}$ and YAlO$\text{}_{3}$, activated with Ce. The experiments include measurements of ther moluminescence, isothermal phosphorescence decays, scintillation light yield as function of temperature, and scintillation time profiles under gamma excitation. Experimental results are interpreted in the frame of a simple kinetic model that includes a number of electron traps. We have identified and characterized a number of deep and shallow traps and demonstrated that traps in LuAlO$\text{}_{3}$:Ce are deeper than corresponding traps in YAlO$\text{}_{3}$:Ce. Unlike deep traps which are responsible for some scintillation light loss but otherwise do not have any impact on generation of scintillation light, shallow traps are shown to actively interfere with the process of radiative recombination via Ce ions. We demonstrate that shallow traps are responsible for some as yet unexplained observations including a higher room temperature light yield of YAlO$\text{}_{3}$:Ce and its longer scintillation decay time, as well as a longer scintillation rise time in LuAlO$\text{}_{3}$:Ce.
Źródło:
Acta Physica Polonica A; 1999, 95, 1; 165-178
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermoluminescence and Scintillation Time Profiles of BaF$\text{}_{2}$:Ce
Autorzy:
Głodo, J.
Szupryczyński, P.
Wojtowicz, A. J.
Powiązania:
https://bibliotekanauki.pl/articles/1994962.pdf
Data publikacji:
1999-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.60.Kn
78.60.Ya
78.55.Hx
29.40.Mc
Opis:
In this communication we present results of measurements of low temperature thermoluminescence, isothermal decays, steady state radioluminescence yield, and scintillation time profiles at various temperatures on two scintillator materials, BaF$\text{}_{2}$:Ce and undoped BaF$\text{}_{2}$. We find that all these results can be consistently interpreted in the frame of a model that includes several relatively shallow charge traps. We have identified and characterized one particular shallow trap that causes the decay of the dominant scintillation component of BaF$\text{}_{2}$:Ce to be slower than radiative, as well as a set of others that are responsible for even slower components in the scintillation time profile of this material.
Źródło:
Acta Physica Polonica A; 1999, 95, 2; 259-268
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin-Orbit Coupling in Cr$\text{}^{3+}$ Ion in Solid State Materials
Autorzy:
Wojtowicz, A. J.
Grinberg, M.
Łempicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/1879947.pdf
Data publikacji:
1991-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Hx
Opis:
In this paper we introduce a new model describing the coupling of $\text{}^{2}$E and $\text{}^{4}$T$\text{}_{2}$ states of octahedrally coordinated Cr$\text{}^{3+}$ ion, which includes spin-orbit and electron-lattice interactions and takes into account the electronic structure of both states. The model is used to calculate doublet lifetime. We have applied this model to the series of Cr$\text{}^{3+}$ doped garnets characterized by the varying crystal field parameter 10 Dq and O$\text{}_{h}$ symmetry of the Cr site and to the kyanite (Al$\text{}_{2}$O$\text{}_{3}$:SiO$\text{}_{2}$), which is the case of different Cr$\text{}^{3+}$ sites in one material, characterized by the relatively large component of the low symmetry crystal field. The agreement with experiment is reasonable.Z
Źródło:
Acta Physica Polonica A; 1991, 79, 2-3; 235-238
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Charge Traps in Ce-Doped CaF$\text{}_{2}$ and BaF$\text{}_{2}$
Autorzy:
Drozdowski, W.
Przegiętka, K. R.
Wojtowicz, A. J.
Oczkowski, H. L.
Powiązania:
https://bibliotekanauki.pl/articles/1994795.pdf
Data publikacji:
1999-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.60.Kn
73.50.Gr
29.40.Mc
Opis:
Thermoluminescence of CaF$\text{}_{2}$:Ce, BaF$\text{}_{2}$, and BaF$\text{}_{2}$:Ce irradiated at room temperature is reported. X-ray induced emission spectra of the samples show that both excitonic (due to e$\text{}^{-}$+V$\text{}_{K}$ recombination) and Ce$\text{}^{3+}$ d-f luminescence may contribute to thermoluminescence signal. The simple Randall-Wilkins model is used to deconvolute glow curves into seven to eight first-order peaks. Parameters of all traps are calculated and correlations between peaks in the curves of the examined materials are discussed.
Źródło:
Acta Physica Polonica A; 1999, 95, 2; 251-258
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photoluminescence Kinetics of YAG Crystals Activated with Ce, and Ce and Mg
Autorzy:
Barzowska, J.
Kubicki, A.
Grinberg, M.
Kaczmarek, S.
Łuczyński, Z.
Wojtowicz, A. J.
Koepke, Cz.
Powiązania:
https://bibliotekanauki.pl/articles/1995826.pdf
Data publikacji:
1999-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.-i
78.47.+p
78.55.-m
Opis:
A basic spectroscopic measurements of luminescence, absorption, luminescence excitation spectra and emission kinetic measurements on YAG crystals activated with cerium and magnesium are presented. We report that the Ce$\text{}^{3+}$ luminescence decay constant, at 65 ns, is independent of Ce concentrations (from 0.05 to 0.2%) and that it does not change with the presence or absence of the Mg co-dopant. Nevertheless, we find that under pulsed laser excitation at 290 nm the rise time in Ce luminescence time profiles is effectively shorter in the Mg co-doped samples.
Źródło:
Acta Physica Polonica A; 1999, 95, 3; 395-402
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:
High Mobility 2D Electron Gas in CdTe/CdMgTe Heterostructures
Autorzy:
Karczewski, G.
Jaroszyński, J.
Kutrowski, M.
Barcz, A.
Wojtowicz, T.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1968126.pdf
Data publikacji:
1997-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.40.Hm
Opis:
We report on iodine doping of molecular beam epitaxy (MBE)-grown Cd(Mn)Te quasi-bulk films and modulation-doped CdTe/Cd$\text{}_{1-y}$Mg$\text{}_{y}$Te two-dimensional (2D) single quantum well structures. Modulation doping with iodine of CdTe/Cd$\text{}_{1-y}$Mg$\text{}_{y}$Te structures resulted in fabrication of a 2D electron gas with mobility exceeding 10$\text{}^{5}$ cm$\text{}^{2}$/(V s). This is the highest mobility reported in wide-gap II-VI materials.
Źródło:
Acta Physica Polonica A; 1997, 92, 4; 829-832
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetization Dynamics of a (Cd,Mn)Te Quantum Well in Pulsed Magnetic Field
Autorzy:
Kobak, J.
Goryca, M.
Kossacki, P.
Golnik, A.
Karczewski, G.
Wojtowicz, T.
Gaj, J.
Powiązania:
https://bibliotekanauki.pl/articles/1791344.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
71.70.Gm
78.55.Et
75.75.-c
Opis:
In this paper we present studies of magnetization relaxation in a (Cd,Mn)Te quantum well containing 3.2% of Mn, after a pulse of magnetic field. The relaxation was found to be very fast, with dominant component faster than 10 ns. Upon application of static magnetic field the relaxation does not slow down, in contrast with the behavior of very diluted quantum wells or bulk material.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 907-908
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non-Ohmic Conductivity of High Resistivity CdTe
Autorzy:
Łusakowski, J.
Szczytkowski, J.
Szadkowski, K.
Kamińska, E.
Piotrowska, A.
Karczewski, G.
Wojtowicz, T.
Powiązania:
https://bibliotekanauki.pl/articles/1933850.pdf
Data publikacji:
1995-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.-r
Opis:
Conductivity measurements were carried out at room temperature on samples of nominally undoped Bridgman, bulk crystals and MBE-grown layers of CdTe. The samples were equipped with indium contacts which made it possible to determine the voltage distribution along the path of the current flow. The results show that for both types of CdTe almost all of the applied voltage drops in the vicinity of the positively biased contact. The resistance of the samples was shown not to depend on the distance between the pads. The results agree with predictions of model of current injection into semiconductors with deep traps.
Źródło:
Acta Physica Polonica A; 1995, 88, 4; 803-806
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal Desorption of Krypton Implanted into Silicon
Autorzy:
Turek, M.
Droździel, A.
Wójtowicz, A.
Filiks, J.
Pyszniak, K.
Mączka, D.
Yuschkevich, Y.
Powiązania:
https://bibliotekanauki.pl/articles/1030211.pdf
Data publikacji:
2017-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.43.Vx
61.72.uf
Opis:
The thermal desorption spectrometry studies of krypton implanted Si samples are presented. Implantations (with the fluence 2×10¹⁶ cm¯²) were done with the energies 100, 150, and 200 keV. Additionally, a 200 keV and 100 keV Kr⁺G double implantation was performed. A sudden Kr release was observed in the ≈1100-1400 K range, most probably coming from the gas bubbles in cavities. The desorption activation energy varies from 2.5 eV (100 keV) to 0.8 (200 keV). The peak splitting suggests existence of two kinds of cavities trapping the implanted noble gas. Two Kr releases are observed for the 200 and 100 keV double-implanted samples. The peak shift of the release corresponding to 100 keV implantation could be a result of both introduced disorder and higher effective Kr concentration. The desorption activation energy is risen to ≈3.2 eV for both releases.
Źródło:
Acta Physica Polonica A; 2017, 132, 2; 249-253
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Deep Electron Traps in CdTe:In Films Grown by Molecular Beam Epitaxy
Autorzy:
Żakrzewski, A. K.
Dobaczewski, L.
Karczewski, G.
Wojtowicz, T.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1934051.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.55.Ln
73.61.Ga
Opis:
N-type indium doped CdTe grown on n$\text{}^{+}$-GaAs by molecular beam epitaxy has been studied by the standard deep level transient spectroscopy and the isothermal Laplace-transform deep level transient spectroscopy. It was found that the Cd/Te flux ratio strongly influences the deep level transient spectroscopy results. The unusual temperature dependence of the electron emission rate in films grown at nearly stoichiometric conditions may point out that the observed defect is resonant with the conduction band.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 961-964
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:
Nonradiative Recombination Processes in (CdTe,CdCrTe)/CdMgTe Quantum Well Structures
Autorzy:
Godlewski, M.
Ivanov, V.
Zakrzewski, A. J.
Wojtowicz, T.
Karczewski, G.
Kossut, J.
Bergman, J. P.
Monemar, B.
Powiązania:
https://bibliotekanauki.pl/articles/1968108.pdf
Data publikacji:
1997-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.60.-p
76.70.Hb
Opis:
Photoluminescence transitions in (CdTe,CdCrTe)/CdMgTe structure grown by molecular beam epitaxy are studied. Photoluminescence investigations show a very strong reduction of the photoluminescence intensity from chromium doped quantum wells. We explain this fact by a very efficient nonradiative recombination in the chromium-doped quantum wells. The present results indicate that the Auger-type energy transfer from excitons to chromium ions is responsible for the photoluminescence deactivation. The efficiency of this process is evaluated.
Źródło:
Acta Physica Polonica A; 1997, 92, 4; 781-784
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal Desorption of Helium from Defected Silicon
Autorzy:
Turek, M.
Droździel, A.
Pyszniak, K.
Wójtowicz, A.
Mączka, D.
Yuschkevich, Y.
Vaganov, Y.
Żuk, J.
Powiązania:
https://bibliotekanauki.pl/articles/1402210.pdf
Data publikacji:
2015-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.43.Vx
61.72.uf
Opis:
The thermal desorption spectroscopy measurements of He implanted silicon samples are reported. The He implantation energy was 90 keV (at 45° tilt) while the fluence was 10¹⁶ cm¯². Additionally, the influence of Si pre-implantation (fluences in the range 10¹⁴-10¹⁶ cm¯², E=260 keV) was under investigation. The He releases from both interstitials/vacancies (β peak) and cavities (α peak or rather band consisting probably of at least two peaks) were observed. The α peak disappears for the pre-implantation fluences larger than 10¹⁵ cm¯², while β peak becomes broader and shifts toward higher temperatures. The thermal desorption spectra were collected using heating ramp rates in the range 0.3-0.7 K/s. Desorption activation energy of the β peak for different pre-implantation fluences was found using the Redhead analysis of the β peak shift. It varies from 0.97 eV for the sample that was not pre-implanted up to 1.3 eV for the sample pre-implanted with the fluence 10¹⁶ cm¯².
Źródło:
Acta Physica Polonica A; 2015, 128, 5; 849-852
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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