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1
Content available remote Nonstandard Absorption on Donors in Uniformly Doped II-VI 0D Structures
100%
Karpierz K. , Szot M. , Grynberg M.
Acta Physica Polonica A
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2007
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tom 112
|
nr 2
237-241
EN
The new approach to the understanding of intrashallow donor transition in the reduced dimensionality systems is presented. The magnetospectroscopy experiments done on the CdTe/CdMgTe quantum well based samples, uniformly n-doped, show indications that the surprising lack of spectral sensitivity on applied photon energy can be understood as a result of sample response coming from its different regions. This "non spectroscopic" behaviour (in a sense of the Zeeman splitting) is a consequence of the properties of systems with reduced dimensionality where variety of centre locations in the structure results in continuous density of states available for absorption.
2
Content available remote New materials for thermoelectric generators based on PbTe-MnTe and PbTe-CdTe semiconductor alloys and nanocomposites
75%
Story T. , Dybko K. , Dziawa P. , Mycielski A. , Szczerbakow A. , Szot M.
Biuletyn Polskiego Stowarzyszenia Wodoru i Ogniw Paliwowych
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2011
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nr 6
64-69
EN
New trends in the field of thermoelectrics are discussed for PbTe-based semiconductor thermoelectric materials exhibiting density of states engineering effects strongly enhancing thermoelectric power (PbMnTe) and spontaneous formation of nano-scale two-phase crystal structures (PbTeCdTe) – technologically scalable realization of electron crystal - phonon glass concept of new thermoelectric materials.
3
Content available The Nature of Potential Fluctuations in the MBE CdTe/CdMgTe Quantum Well in a Magnetic Field: Experiment and Theory
75%
Szot M. , Karpierz K. , Avetisyan A. , Djotyan A. , Kossut J. , Grynberg M.
Acta Physica Polonica A
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2006
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tom 110
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nr 3
379-387
EN
Far infrared photoconductivity spectra of CdTe/Cd_{0.8}Mg_{0.2}Te quantum well uniformly n-type doped with iodine in barriers and in the well were investigated as a function of the magnetic field. The spectra were recorded for several fixed far infrared photon energies and peaks corresponding to intra donor transitions were observed. The magnetic field at which the peaks were observed was the same for all far infrared photon energies used. This is interpreted as an evidence of the presence of fluctuations of the electrostatic potential - quantum dots which reduce the dimensionality of the potential in which a shallow donor is placed. A characteristic size of the fluctuations was found to be of 23-25 nm and 30-40 nm. Theoretical calculations show a nonmonotonic dependence of the electron binding energy on the donor centre in such quantum dot, as a function of magnetic field. This explains why the position of experimentally observed peak is insensitive to far infrared photon energy used. Temperature evolution of spectra and the theoretical model proposed, indicate similarities between fluctuations in the two-dimensional structure investigated and fluctuations in bulk systems.
4
Content available Interlayer Exchange Coupling in Semiconductor EuS-PbS Ferromagnetic Wedge Multilayers
63%
Kowalczyk L. , Wrotek S. , Dziawa P. , Osinniy V. , Szot M. , Story T. , Sipatov A. , Volobuev V. , Fedorov A.
Acta Physica Polonica A
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2006
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tom 110
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nr 2
225-231
EN
Antiferromagnetic interlayer coupling between ferromagnetic layers of EuS via nonmagnetic PbS spacer layer was experimentally studied in EuS-PbS wedge multilayers grown on KCl (001) substrates with EuS thickness of 6 nm and PbS thickness varying in the wedges in the range 0.3-6 nm (i.e. n=1-20 monolayers). Measurements of magnetic hysteresis loops of EuS-PbS multilayers performed in the temperature range 5-30 K by superconducting (SQUID) and magneto-optical magnetometers revealed a rapid increase in saturation magnetic field in multilayers with PbS spacer thinner than about 1.5 nm. It shows a monotonic increase in interlayer coupling strength with a decreasing PbS spacer thickness, in qualitative agreement with 1/2^n dependence predicted theoretically for semiconductor magnetic superlattices.
5
Content available remote Magnetization Studies of Antiferromagnetic Interlayer Coupling in EuS-SrS Semiconductor Multilayers
63%
Samburskaya T. , Sipatov A. , Volobuev V. , Dziawa P. , Knoff W. , Kowalczyk L. , Szot M. , Story T.
Acta Physica Polonica A
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2013
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tom 124
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nr 1
133-136
EN
Temperature and magnetic field dependence of magnetization of EuS-SrS multilayers grown epitaxially on KCl (001) substrate is experimentally studied by superconducting magnetometry technique. In these lattice-matched semiconductor heterostructures EuS layers are ferromagnetic quantum wells whereas SrS layers are nonmagnetic spacer barriers. The multilayers composed of EuS layers with thickness 3.5-5 nm and SrS layers (thickness 0.5-10 nm) exhibit ferromagnetic transition at 17 K. In the multilayers with ultrathin SrS spacers (0.5-1 nm) a nonmonotonic temperature dependence of magnetization as well as a characteristic switching in magnetic hysteresis loops is observed. These experimental findings are explained considering antiferromagnetic interlayer coupling between ferromagnetic EuS layers via nonmagnetic SrS spacers. The strength of this coupling is determined based on model magnetization calculations.
6
Content available remote Magnetic Properties of EuS/Co Multilayers on KCl and BaF₂ Substrates
63%
Szot M. , Kowalczyk L. , Story T. , Domukhovski V. , Knoff W. , Gas K. , Volobuev V. , Sipatov A. , Fedorov A.
Acta Physica Polonica A
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2008
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tom 114
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nr 5
1397-1402
EN
Magnetic and structural properties of EuS/Co multilayers were studied by magnetic optical Kerr effect and SQUID magnetometry techniques and by X-ray diffraction method. The multilayers containing monocrystalline, ferromagnetic EuS layer (thickness 35-55 Å) and metallic Co layer (thickness 40-250 Å), were grown on KCl (001) and BaF₂ (111) substrates using high vacuum deposition technique employing electron guns for Co and EuS. All investigated EuS/Co multilayers exhibit ferromagnetic properties at room temperature due to Co layer with the ferromagnetic transition in EuS layer clearly marked upon cooling below 16 K. In EuS/Co/EuS trilayers grown on KCl substrate the antiferromagnetic alignment of magnetization vectors of Co and EuS layers was experimentally observed as a characteristic low field plateau on magnetization hysteresis loops and a decrease in multilayer magnetization below 16 K. In Co/EuS bilayers the characteristic temperature dependent shift of magnetization loops was found due to exchange bias effect attributed to the CoO/Co interface formed by the oxidation of the top Co layer.
7
Content available remote Effect of Misfit Strain in (Ga,Mn)(Bi,As) Epitaxial Layers on Their Magnetic and Magneto-Transport Properties
63%
Levchenko K. , Andrearczyk T. , Domagała J. , Sadowski J. , Kowalczyk L. , Szot M. , Figielski T. , Wosiński T.
Acta Physica Polonica A
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2016
|
tom 129
|
nr 1a
A-90-A-93
EN
Effect of misfit strain in the layers of (Ga,Mn)(Bi,As) quaternary diluted magnetic semiconductor, epitaxially grown on either GaAs substrate or (In,Ga)As buffer, on their magnetic and magneto-transport properties has been investigated. High-resolution X-ray diffraction, applied to characterize the structural quality and misfit strain in the layers, proved that the layers were fully strained to the GaAs substrate or (In,Ga)As buffer under compressive or tensile strain, respectively. Ferromagnetic Curie temperature and magneto-crystalline anisotropy of the layers have been examined by using magneto-optical Kerr effect magnetometry and low-temperature magneto-transport measurements. Post-growth annealing treatment of the layers has been shown to enhance the hole concentration and the Curie temperature in the layers.
8
Content available remote Experimental and Theoretical Analysis οf PbTe-CdTe Solid Solution Grown by Physical Vapour Transport Method
51%
Szot M. , Szczerbakow A. , Dybko K. , Kowalczyk L. , Smajek E. , Domukhovski V. , Łusakowska E. , Dziawa P. , Mycielski A. , Story T. , Bukała M. , Galicka M. , Sankowski P. , Buczko R. , Kacman P.
Acta Physica Polonica A
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2009
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tom 116
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nr 5
959-961
EN
Bulk monocrystals of Pb_{1-x}Cd_{x}Te, with the Cd content x up to 0.11, were grown by physical vapour transport method. The structural, electrical and optical properties of these ternary crystals were studied experimentally and theoretically. All investigated samples exhibit rock-salt structure and high crystal quality, which was confirmed by X-ray rocking curve width parameter of about 100 arcsec. The decrease of the lattice parameter with increasing Cd content x was found experimentally, in agreement with ab initio calculations. The band structures of Pb_{1-x}Cd_{x}Te mixed crystals for x values up to 0.2 were calculated using tight binding approach. The calculated band gap in the L-point increases with the Cd content in qualitative agreement with photoluminescence measurements in the infrared. For all studied Pb_{1-x}Cd_{x}Te samples, the Hall effect and electrical conductivity measurements, performed in the temperature range from 4 to 300 K, revealed p-type conductivity.
9
Content available remote Magnetic Properties of EuS-SrS Semiconductor Multilayer Structures
51%
Szot M. , Kowalczyk L. , Deptuła P. , Domukhovski V. , Osinniy V. , Smajek E. , Szczerbakow A. , Sipatov A. , Volobuev V. , Fedorov A. , Story T.
Acta Physica Polonica A
|
2007
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tom 112
|
nr 2
419-424
EN
Magnetic and structural properties of EuS-SrS semiconductor multilayers were studied by SQUID and magneto-optical Kerr effect magnetometry techniques and by X-ray diffraction method. The multilayers composed of monocrystalline, lattice matched ferromagnetic EuS layers (thickness 35-50Å) and nonmagnetic SrS spacer layers (thickness 45-100Å) were grown epitaxially on KCl (001) substrates with PbS buffer layer. Ferromagnetic transition in EuS-SrS multilayers was found at the Curie temperature T_c=17 K. The multilayers exhibit only weak in-plane magnetic anisotropy with [110] easy magnetization axis. Coercive field of EuS-SrS multilayers shows a linear increase with decreasing temperature. Magneto-optical mapping of magnetic hysteresis loops of the multilayers revealed good spatial homogeneity of their magnetic properties.
10
Content available remote Epitaxial Growth and Optical Properties of PbTe/CdTe Semiconductor Heterostructures
51%
Szot M. , Kowalczyk L. , Smajek E. , Domukhovski V. , Domagała J. , Łusakowska E. , Taliashvili B. , Dziawa P. , Knoff W. , Wiater M. , Wojtowicz T. , Story T.
Acta Physica Polonica A
|
2008
|
tom 114
|
nr 5
1391-1396
EN
Growth optimization, optical and structural properties of PbTe/CdTe multilayers grown by molecular beam epitaxy on GaAs (001) as well as on BaF_2 (111) substrates is reported. An intense photoluminescence in the mid-infrared region is observed from PbTe quantum wells excited with 1.17 eV pulsed YAG:Nd laser. The energy of the emission peak shows blue shift with decreasing PbTe well width and has a positive temperature coefficient. The influence of thermal annealing on photoluminescence spectra of PbTe/CdTe multilayers grown on BaF_2 substrate is discussed.
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