Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 20

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

Recombination Processes in ZnSe:Eu

100%
Świątek K., Godlewski M.
Acta Physica Polonica A
|
1991
|
vol. 80
|
issue 3
381-384
EN
The photo-ESR and photoluminescence experiments have been performed on high-resistivity ZnSe:Eu crystals. We report the first evidence that the energy level of Eu^{2+} ground state is located within the ZnSe forbidden gap, approximately 2.1 eV below the bottom of the conduction band.
2
Content available remote

Ionization Energies of RE Ions in wide Bandgap Sulphides

100%
Świątek K., Godlewskl M.
Acta Physica Polonica A
|
1991
|
vol. 79
|
issue 2-3
247-250
EN
An analysis of rare earth (RE) energy level positions in wide bandgap sulphides is presented. It is shown that the Jörgensen's refined spin-pairing energy theory (RESPET) predicts correctly the photo-ionization (PI) energy of Sm in ZnS.
3
Content available remote

SrS:Eu and CaS:Eu Thin Films: Influence of Host Lattice on Kinetics of Europium Emission

81%
Świątek K., Godlewski M., Niinistö L., Leskelä M.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 5
769-772
EN
In this paper we report the studies of photoluminescent properties of CaS:Eu and SrS:Eu thin films containing up to 3 mole % of Eu, grown by the atomic layer epitaxy method. The energy transfer and direct intrashell excitation channels of Eu ions are examined in function of temperature.
4
Content available remote

On the Nature of Eu-Related Emissions in ZnS and CaS

81%
Świątek K., Godlewski M., Niinistö L., Leskelä M.
Acta Physica Polonica A
|
1991
|
vol. 79
|
issue 2-3
255-257
EN
The Eu-connected recombination processes in ZnS and CaS are analyzed on the basis of optical studies. A new Eu-related emission in ZnS is attributed to the recombination of an exciton bound at the Eu^{2+} center, while in CaS the emission is dominated by the direct Eu^{2+} intra-ion transition.
5
Content available remote

Recombination Processes for Deep Impurity States Degenerate with the Conduction Band

81%
Świątek K., Godlewski M., Kaliński Z., Przybylińska H.
Acta Physica Polonica A
|
1991
|
vol. 79
|
issue 2-3
243-246
EN
We report on the studies of autoionization efficiency and the relevant recombination mechanism for Eu^{2+} in Ca_{x}Cd_{1-x}F_{2} depending on the energy level position of Eu^{2+} excited states in respect to the conduction band states.
6
Content available remote

Spatial Correlation of Impurity Charges Induced by Coulomb Interactions - Application to DX Centers in GaAs

81%
Kossut J., Wilamowski Z., Dietl T., Świątek K.
Acta Physica Polonica A
|
1991
|
vol. 79
|
issue 1
49-58
EN
The electron mobility enhancement observed in heavily doped GaAs under hydrostatic pressure is interpreted in terms of spatial correlation between the donor charges within partially occupied system of impurities induced by strong inter-donor Coulomb interaction. A simple analytic theory is given for both DX^{0} and DX^{-} models of the impurity state. The mobility is shown to increase together with pressure in both models. Estimates of the energy of the DX level are strongly perturbed by the inter-donor Coulomb interactions.
7
Content available remote

Optical Properties of Al_{x}Ga_{1-x}As_{y}Sb_{1-y} Epitaxial Layers

81%
Świątek K., Piskorski M., Piotrowski T.
|
EN
Photoluminescence spectra of Al_{x}Ga_{1-x}As_{y}Sb_{1-y} layers (x = 0.2-0.5, y = 0.02-0.03) grown by liquid-phase epitaxy on GaSb substrates were studied in a wide temperature range (14-295 K). The temperature changes of energy and intensity of the layer and substrate emission were measured. Linear part of the temperature-induced energy shift of the Al_{0.20}Ga_{0.80}As_{0.02}Sb_{0.98} band-to-band emission exhibits a slope of -0.3 meV/K and -0.45 meV/K at temperatures 150 K and 295 K, respectively.
8
Content available remote

Rare-Earth Excitation Mechanism in Wide Band Gap H-VI Compounds

71%
Karpińska K., Świątek K., Godlewski M., Niinistö L., Leskelä M.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 5
959-962
EN
The excitation mechanism of rare-earth emission in Eu and Ce doped CaS and SrS is studied. It is proposed that the Eu and probably also Ce emission is induced by the photoionization transition of the rare-earth ion, which is followed by the carrier trapping via the excited state of the ion. At increased temperatures the efficiency of excitation is reduced. We explain this effect by the carrier emission from the excited core state of the rare-earth ion to the continuum of the conduction (valence) band states. It is also suggested that the charge transfer state of the rare-earth ion may act as the intermediate state in the carrier trapping.
9
Content available remote

Optical Detection of Cyclotron Resonance in Serpentine Superlattice Quantum-Wire Arrays

71%
Świątek K., Weman H., Miller M., Petroff P., Merz J.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 3
583-586
EN
We report low-temperature studies of microwave-induced cyclotron resonance of photo-generated carriers in (Al,Ga)As serpentine superlattice quantum-wire arrays. The geometric size of the parabolic-crescent cross-section of the quantum wires was of the order of 100 Å × 50 Å, depending on the angle of the vicinal substrate and the amount of parabolic curvature. Comparing the obtained spectra, we estimate the relative degree of carrier confinement in the ordered AlGaAs structure.
10
Publication available in full text mode
Content available

Magnetic Properties of Short Period InGaMnAs/InGaAs Superlattices

62%
Sadowski J., Mathieu R., Svedlindh P., Kanski J., Karlsteen M., Świątek K., Domagała J.
|
|
issue 4-5
687-694
EN
We have observed a paramagnetic-to-ferromagnetic phase transition in short period InGaMnAs/InGaAs superlattices. The thicknesses of magnetic InGaMnAs layers in the structures studied was chosen to be 4 or 8 molecular layers (12Å or 24Å). The non-magnetic InGaAs spacer layers are 12Å thick. The composition (In content) in InGaMnAs and InGaAs was chosen in such a way that magnetic layers were: deep potential wells, high potential barriers, or shallow potential wells. For superlattices with 8 monolayer thick InGaMnAs magnetic layers and 4 monolayer thick InGaAs non-magnetic spacers the temperatures of paramagnetic-to-ferromagnetic phase transition do not depend on the band offsets between InGaMnAs and InGaAs adjusted by the In content.
11
Content available remote

MBE Growth and Properties of GaMnAs(100) Films

62%
Sadowski J., Domagała J., Bąk- Misiuk J., Świątek K., Kanski J., Ilver L., Oscarsson H.
Acta Physica Polonica A
|
1998
|
vol. 94
|
issue 3
509-513
EN
We present here the results of measurements of structural and electronic properties of GaMnAs - a new diluted magnetic semiconductor system. This ternary III-V-Mn compound with the Mn content as high as 7% was obtained for the first time (by means of molecular beam epitaxial growth) by Ohno, Munekata et al. and the studies of its properties are not completed until now. We did the high resolution X-ray diffraction investigations and photoemission measurements of the samples with Mn content varied from about 0.1% up to 5%. The crystalline perfection of the ternary GaMnAs compound is very high - full width at half maximum of GaMnAs (400) Bragg reflections are of order of 50 arcseconds and the layers are fully strained to the GaAs(100) substrate. In photoemission experiments we traced the contribution of Mn 3d states to the band structure of GaMnAs ternary compound.
12
Content available remote

Co^{2+} Ions in ZnS_{x}Se_{1-x}:Co - ESR and Optical Studies

62%
Świątek K., Surkova T., Sienkiewicz A., Zakrzewski A., Godlewski M., Giriat W.
Acta Physica Polonica A
|
1998
|
vol. 94
|
issue 3
593-596
EN
The electron spin resonance of Co^{2+} ions in ZnS_{x}Se_{1-x}:Co mixed crystals was measured at temperature of 3 K and microwave frequency of 9.47 GHz. Trigonal Co_{Zn}^{2+}-S center in the ZnS_{0.001}Se_{0.999}:Co crystal was identified and parameters of relevant spin Hamiltonian were determined. Influence of alloy disorder in the anion sublattice on the Co_{Zn}^{2+} ground and first excited states is briefly discussed.
13
Content available remote

Structure, Surface Morphology and Optical Properties of Thin Films of ZnS and CdS Grown by Atomic Layer Epitaxy

62%
Szczerbakow A., Godlewski M., Dynowska E., Ivanov V., Świątek K., Goldys E., Phillips M.
Acta Physica Polonica A
|
1998
|
vol. 94
|
issue 3
579-582
EN
In this communication we report successful growth of monocrystalline cubic ZnS and monocrystalline and polycrystalline cubic and wurtzite films of CdS by atomic layer epitaxy. Structural and optical properties of these films are analysed. ZnS (and CdS/ZnS) films grown on GaAs substrate are cubic. Atomic layer epitaxy grown films provide several advantages over ZnS and CdS materials grown by other techniques, especially compared to bulk material, which is grown at higher temperatures. First results for ZnS/CdS/ZnS quantum well structures are also discussed.
14
Content available remote

MBE Growth and Properties of ZnYbTe Layers

62%
Sadowski J., Szamota-Sadowska K., Świątek K., Kowalczyk L., Abounadi A., Rajira A.
Acta Physica Polonica A
|
1996
|
vol. 90
|
issue 5
1060-1064
EN
The MBE grown ZnYbTe layers were characterized by X-ray diffraction, photoluminescence and reflectivity measurements. The MBE growth conditions allowing to obtain monocrystalline ZnYbTe layers were found to be metal-rich (MBE growth with excess of Zn flux). In optical measurements (photoluminescence, reflectivity), both transitions connected with ternary ZnYbTe compound and with Yb^{3+} ions were detected. The quality of ZnYbTe layers with Yb content of 3% and 1% is inferior to the quality of pure ZnTe MBE layers, which is clearly seen in the results of photoluminescence and reflectivity measurements. In the ZnYbTe layers with 3% Yb, exhibiting monocrystalline character in reflection high-energy electron diffraction and X-ray diffraction measurements, optical transitions characteristic of pure YbTe were detected. In ZnYbTe layers with 1% Yb, no transitions connected with YbTe were observed.
15
Content available remote

Optically Detected Magnetic Resonance Studies of Cd_{1-x}Mn_{x}Te (x=0.095, 0.007)

62%
Godlewski M., Świątek K., Gałązka R., Monemar B., van Loosdrecht P., Wittlin A., Perenboom J.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 3
539-542
EN
The dominant mechanism responsible for the optical detection of the Mn^{2+} magnetic resonance in Cd_{1-x}Mn_{x}Te (x = 0.095, 0.007) is explained. By either change of the external magnetic field or by setting the conditions for the Mn^{2+} magnetic resonance, we could change the relative efficiencies of the two competing excitonic recombination processes. By lowering magnetization at the magnetic resonance, recombination via the acceptor bound exciton channel, which is mainly nonradiative, is enhanced. Then, a large up to 50% decrease in the total photoluminescence efficiency was observed in the optically detected magnetic resonance experiment. Such observation allows for verification of the large efficiency of the Auger-type transition responsible for the nonradiative decay of the acceptor bound exciton.
16
Content available remote

Optically Detected Cyclotron Resonance Studies of CdMnTe/CdTe Multiquantum Wells and CdMgTe/CdMnTe Superlattices

62%
Godlewski M., Świątek K., Harris C. I., Bergman J. P., Monemar B., Waag A.
Acta Physica Polonica A
|
1995
|
vol. 87
|
issue 1
213-216
EN
The results of photoluminescence, time resolved photoluminescence (de­cay times), optically detected cyclotron and magnetic resonances investiga­tions of CdMnTe/CdTe multiquantum wells and CdMgTe/CdMnTe super-lattices are presented. The role of defects and quantum well width fluctua­tions in recombination processes of 2D carriers is discussed.
17
Publication available in full text mode
Content available

Origin of Ultrafast Component of Photoluminescence Decay in Nanostructures Doped with Transition Metal or Rare-Earth Ions

52%
Godlewski M., Yatsunenko S., Ivanov V., Khachapuridze A., Świątek K., Goldys E., Phillips M., Klar P., Heimbrodt W.
|
EN
Bulk samples, layers, quantum well, and quantum dot structures of II-Mn-VI samples all show coexistence of slow and fast components of Mn^{2+} photoluminescence decay. Thus, fast photoluminescence decay cannot be related to low dimensionality of a host material. This also means that the model of the so-called quantum confined atom is incorrect. Based on the results of time-resolved photoluminescence and optically detected magnetic resonance investigations we relate the observed lifetime decrease in Mn^{2+} intra-shell transition to spin dependent magnetic interactions between localized spins of Mn^{2+} ions and between Mn^{2+} ions and spins/magnetic moments of free carriers. The latter mechanism is enhanced in nanostructures.
18
Content available remote

Electrical, Magnetic, and Structural Properties of Sn_{1-x}Mn_{x}Te Layers Grown by Molecular Beam Epitaxy

52%
Nadolny A., Sadowski J., Story T., Dobrowolski W., Arciszewska M., Świątek K., Kachniarz J., Adamczewska J.
Acta Physica Polonica A
|
1998
|
vol. 94
|
issue 3
449-453
EN
Layers of Sn_{1-x}Mn_{x}Te (x ≤ 0.1) with thickness 0.2-2 μm were grown by molecular beam epitaxy on BaF_{2} substrates with a 0.01-1 μm thick SnTe buffer layer. Both SnTe and Sn_{1-x}Mn_{x}Te layers show metallic p-type conductivity with conducting hole concentrations (at T=77 K) p_{77}=7×10^{19} -2×10^{21} cm^{-3}. The layers grown under the conditions of an extra Te flux have a high carrier concentration and exhibit ferromagnetic phase transition at T_{C} ≤ 7 K. The layers grown with no (or very low) additional Te flux show low carrier concentrations (below 10^{20} cm^{-3}) and remain paramagnetic in the temperature range studied T=4.5÷70 K.
19
Publication available in full text mode
Content available

Magnetic, Structural, and Optical Properties of Low Temperature ZnMnO Grown by Atomic Layer Epitaxy

42%
Wójcik A., Kiecana M., Kopalko K., Godlewski M., Guziewicz E., Yatsunenko S., Łusakowska E., Minikayev R., Paszkowicz W., Świątek K., Wilamowski Z., Sawicki M., Dietl T.
Acta Physica Polonica A
|
2005
|
vol. 108
|
issue 5
915-921
EN
Magnetic, structural, and optical properties of ZnMnO films grown with atomic layer epitaxy are discussed. Atomic layer epitaxy films were grown at low temperature using organic zinc and manganese precursors. From magnetometry and electron spin resonance investigations we conclude that lowering of a growth temperature significantly limits formation of Mn precipitates and inclusions of different foreign phases of manganese oxides to ZnMnO host.
20
Content available remote

Ferromagnetic Transition in Ge_{1-x}Mn_{x}Te Layers

42%
Knoff W., Domukhovski V., Dybko K., Dziawa P., Jakieła R., Łusakowska E., Reszka A., Świątek K., Taliashvili B., Story T., Szałowski K., Balcerzak T.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue 5
904-906
EN
Ferromagnetic transition temperature in thin layers of diluted magnetic (semimagnetic) semiconductor Ge_{1-x}Mn_{x}Te was studied experimentally by SQUID magnetometry method and analyzed theoretically for a model Ising-type diluted magnetic system with Ruderman-Kittel-Kasuya-Yosida indirect exchange interaction. The key features of the experimentally observed dependence of the Curie temperature on Mn content (x ≤ 0.12) and conducting hole concentration p = (1-10) × 10^{21} cm^{-3} were reproduced theoretically for realistic valence band and crystal lattice parameters of p-Ge_{1-x}Mn_{x}Te taking into account short carrier mean free path encountered in this material and Ruderman-Kittel-Kasuya-Yosida mechanism with both delta-like and diffused character of spatial dependence of the exchange coupling between magnetic ions and free carriers.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.