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1
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Shallow-Deep Instability of Donor States in Many-Valley Semiconductors

100%
Grinberg M.
Acta Physica Polonica A
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1991
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vol. 80
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issue 3
361-364
EN
The shallow-deep instability of double and single donors in multi-valley semi conductors using the model Hamiltonian is studied. The obtained results describe properly the properties of double donors (in D^{0} and D^{+} state) in Ge and single deep donors in Al_{x}Ga_{1-x}As for 0.3 < x < 0.5.
2
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Spin-Orbit Coupling in Cr^{3+} Ion in Solid State Materials

51%
Wojtowicz A. J., Grinberg M., Łempicki A.
Acta Physica Polonica A
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1991
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vol. 79
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issue 2-3
235-238
EN
In this paper we introduce a new model describing the coupling of ^{2}E and ^{4}T_{2} states of octahedrally coordinated Cr^{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^{3+} doped garnets characterized by the varying crystal field parameter 10 Dq and O_{h} symmetry of the Cr site and to the kyanite (Al_{2}O_{3}:SiO_{2}), which is the case of different Cr^{3+} sites in one material, characterized by the relatively large component of the low symmetry crystal field. The agreement with experiment is reasonable.
3
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Influence of Twinning on Local Electronic Properties of ZnSe

51%
Balcerzyk M., Grinberg M., Szatkowski J.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
890-892
EN
We have obtained ZnSe single crystals by vertical Bridgman method. The surface was examined using scanning electron microscope (SEM). As usual crystals exhibited twins, which were observed on the (110) surface. On as-grown and n-type samples we observed long (of the order of millimetres) linear structures parallel to the (111) plane which correspond to the twin plane. Our observations and measurements enabled us to estimate the electronic potential as being of the order of a few volts and extending less than 1 μm in the direction perpendicular to the twin planes.
4
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Luminescence and Luminescence Kinetics of Gd_{3}Ga_{5}O_{12} Polycrystals Doped with Cr^{3+} and Pr^{3+}

45%
Mahlik S., Kukliński B., Grinberg M., Kostyk Ł., Tsvetkova O.
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issue 1
117-121
EN
In this paper spectroscopic investigations of Gd_3Ga_5O_{12} (GGG) polycrystals, containing Cr^{3+} and intentionally doped with Pr^{3+} of concentrations 0.5, 1 and 1.5 mol% are presented. We have measured the steady state luminescence and luminescence excitation spectra, as well as the time resolved spectra and luminescence kinetics. The main goal was to investigate the excitation energy transfer from lattice to impurity and between impurities. We found that relative intensity of Cr^{3+} and GGG lattice luminescence decreased when material was doped with Pr^{3+}. On the other hand, time resolved spectroscopy and luminescence decay measurements showed that the Cr^{3+} and GGG lattice luminescence decays were independent of Pr^{3+} content. The lifetime of Pr^{3+} luminescence related to ^{1}D_{2} → ^{3}H_{4} and ^{3}P_{0} → ^{3}H_{4} transitions decreased with concentration of Pr^{3+}, which was attributed to the concentration luminescence quenching. No energy transfer between GGG lattice defects and Cr^{3+}, and Pr^{3+} ions was observed. We proposed the model of radiative recombination of electron and hole, which took place through three independent pathways: by GGG host emission that peaked at 12750 cm^{-1}, by Cr^{3+} luminescence that peaked at 15400 cm^{-1}, and by Pr^{3+} luminescence.
5
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The Influence of Synthesis Temperature on Manufacturing and Properties of SrSi2O2N2:Eu2+ Powders

39%
Pawlik T., Sopicka-Lizer M., Michalik D., Barzowska J., Szczodrowski K., Lesniewski T., Grinberg M.
Archives of Metallurgy and Materials
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2017
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vol. 62
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issue 2
6
Content available remote

Photoluminescence Kinetics of YAG Crystals Activated with Ce, and Ce and Mg

39%
Barzowska J., Kubicki A., Grinberg M., Kaczmarek S., Łuczyński Z., Wojtowicz A., Koepke C.
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vol. 95
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issue 3
395-402
EN
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^{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.
7
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Excited State Absorption and Thermoluminescence in Ce and Mg Doped Yttrium Aluminum Garnet

39%
Wiśniewski K., Koepke C., Wojtowicz A., Drozdowski W., Grinberg M., Kaczmarek S., Kisielewski J.
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vol. 95
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issue 3
403-412
EN
In this paper we report preliminary results of optical studies on Y_{3}Al_{5}O_{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.
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