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1
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MBE Growth of YbTe on GaAs(100) and BaF_{2}(111) Substrates

100%
Sadowski J., Dynowska E., Kowalczyk L.
Acta Physica Polonica A
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1995
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vol. 88
|
issue 5
1028-1032
EN
The structural properties of MBE grown YbTe layers were investigated by X-ray diffraction methods and photoluminescence measurements. YbTe films were grown on the ZnTe and CdTe buffer layers crystallised on the GaAs(100) 2° off oriented substrates and on the BaF_{2}(100) substrates. In the case of GaAs substrates the two-dimensional growth mode of YbTe was observed on reflection high energy electron diffraction picture. Results of the X-ray rocking curve and photoluminescence excitation measurements indicate that the structural properties of YbTe films are comparable to the properties of the MBE grown ZnTe and CdTe layers on the GaAs(100) substrates. The measured values of the YbTe lattice constant parallel and perpendicular to the growth plane show that the 1 μm thick layers are partially strained. The full width at half maximum values of the X-ray rocking curves are the smallest (900 arc seconds) for the YbTe films crystallised on the 2 μm thick CdTe bucher layer grown on the GaAs(100) substrate. In the case of BaF_{2}(111) substrate the two-dimensional MBE growth mode of YbTe was not observed.
2
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Stimulated and Laser Emission in CdZnTe/CdMnTe Double Quantum Well Heterostructures

100%
Kowalczyk L., Karczewski G., Wojtowicz T., Kossut J.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
787-790
EN
Stimulated emission by optical excitation has been investigated in CdZnTe/CdMnTe quantum well heterostructures. Laser action has been achieved at 4.2 K and at 77 K with relatively low threshold values of the excitation intensity. Photοluminescence excitation spectra of the stimulated emission were obtained indicating that the optical gain involves exciton-exci­ton inelastic scattering.
3
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Thermally Induced Nonlinear Refraction in Cd_{1-x}Mn_{x}Te

100%
Kowalczyk L., Suchocki A., Gałązka R.
|
EN
Self-focusing of laser beams is observed in Cd_{0.5}Mn_{0.5}Te at room temperature. The far-field patterns of laser beam after passing through the cadmium manganese telluride crystal are investigated. The values of focal length as well as the absorption coefficient were measured as a function of intensity of laser radiation. From these measurements the values of nonlinear refractive index for Cd_{0.5}Mn_{0.5}Te are determined. The results indicate that the self-focusing observed in Cd_{1-x}Mn_{x}Te is due to a thermally induced change in refractive index.
4
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Magnetic Susceptibility of Pb_{1-x-y}Sn_{y}Mn_{x}Se

100%
Górska M., Anderson J. R., Kowalczyk L.
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EN
Magnetic susceptibility has been measured in Pb_{1-x-y}Sn_{y}Mn_{x}Se with x values up to 0.02 and y values up to 0.05. The measurements were carried out using a SQUID system over a temperature range from 5 to 250 K. The susceptibility followed the Curie-Weiss relation with a small paramagnetic Curie temperature that indicated a weak antiferromagnetic exchange interaction between Mn ions. We analyzed the results together with our previously published data on high-field magnetization in this material. A reasonable agreement of the exchange parameters obtained from the low-field susceptibility and high-field magnetization data was obtained.
5
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High Quality ZnSe and Zn(Se,S) Produced by Low Temperature Physical Vapour Transport

100%
Mycielski A., Szadkowski A., Kowalczyk L., Zaręba A.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
1050-1054
EN
High quality, large (25 mm in diameter) crystals of ZnSe and Zn(Se,S) were grown by low-temperature physical vapour transport method and characterized by various techniques, i.e. energy dispersive X-ray fluorescence spectrometry, double-crystal X-ray diffraction rocking curve FWHM, reflectivity measurements in the region of free exciton, electrical measurements and photoluminescence measurements for both low and high excitation densities. The measurement of the photoluminescence related to the neutral-donor-bound exciton revealed superlinear log(photoluminescence intensity) versus log(excitation intensity) dependence, which indicates stimulated emission phenomena.
6
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Self-Focusing and Optical Bistability in Cd_{1-x}Mn_{x}Te

100%
Kowalczyk L., Suchocki A., Gałązka R.
Acta Physica Polonica A
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1993
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vol. 84
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issue 3
519-522
EN
Thermally induced self-focusing of laser beam and optical bistability in CdMnTe at room temperature has been investigated. Photothermal focal length as a function of intensity of laser radiation has been measured in Cd_{1-x}Mn_{x}Te for 0.3 ≤ x ≤ 0.6. The time-dependence of the transmitted power for various laser intensities has been investigated and the switching from the transparent to dark state has been observed. For the first time the optical bistable characteristic has been measured in CdMnTe. The results indicate that CdMnTe is a suitable material for cavityless, large contrast, thermally induced absorptive bistable operation in visible region.
7
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Kerr Effect Investigations of Magnetic Interlayer Interactions in EuS-PbS Multilayers

76%
Kowalczyk L., Chernyshova M., Story T., Ha J., Voloubev V., Sipatov A.
Acta Physica Polonica A
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2001
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vol. 100
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issue 3
357-363
EN
Kerr magnetometry was employed to study the temperature dependence of magnetization and magnetic hysteresis loops in ferromagnetic EuS-PbS semiconductor multilayers in the temperature range T=3-35 K at low magnetic fields H≤150 Oe. For EuS-PbS/KCl(100) structures with ultrathin non-magnetic PbS spacer of 1~nm, we observed a maximum on the temperature dependence of magnetization at low fields H≤30 Oe. For higher fields, we found for these structures a regular mean-field-like increase in magnetization with decreasing temperature. The same regular behavior was also found for EuS-PbS/KCl structures with thicker PbS spacer, as well as for all EuS-PbS/BaF_2(111) multilayers independently of spacer thickness. For qualitative interpretation of these findings, we consider two magnetic contributions to the total energy of EuS-PbS multilayers: the Zeeman energy and the antiferromagnetic interlayer exchange coupling between ferromagnetic EuS layers via diamagnetic PbS spacer.
8
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MBE Growth and Properties of ZnYbTe Layers

76%
Sadowski J., Szamota-Sadowska K., Świątek K., Kowalczyk L., Abounadi A., Rajira A.
Acta Physica Polonica A
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1996
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vol. 90
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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.
9
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Stimulated Emission in Zn(Se,S) Single Crystals

76%
Kowalczyk L., Mycielski A., Szadkowski A., Testelin C., Rigaux C., Menant M.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
871-874
EN
Two different types of optically pumped stimulated emission were observed at 1.8 K in the high quality Zn(Se,S) crystals grown by low temperature physical vapour transport. One type, occurring at moderate excitation levels, is ascribed to the recombination of excitons localized because of chemical disorder in the two-anion mixed crystal. The other type, occurring at high excitation levels, is related to the inelastic exciton-exciton scattering.
10
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Luminescence Decay in Deep Quantum Wells CdTe/Cd_{0.5}Mn_{0.5}Te at Room Temperature

64%
Kowalczyk L., Fancey S., Buller G. S., Massa J. S., Kutrowski M., Janik E., Karczewski G., Wojtowicz T., Zakrzewski A. K., Kossut J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
508-513
EN
Time-resolved photoluminescence was used to study exciton recombi­nation in deep CdTe/Cd_{0.5}Mn_{0.5}Te single quantum well. The width of the investigated well was 100 A. The study was performed at room temperature. The lifetime of the exciton determined in this work has a value comparable to that observed in shallow CdTe/Cd_{0.85}Mn_{0.15}Te quantum wells. A strong enhancement of the photoluminescence decay time with increasing intensity of the exciting laser beam is observed which is indicative of saturation of the non-radiative recombination centers.
11
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Magnetic Properties of EuS/Co Multilayers on KCl and BaF₂ Substrates

64%
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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vol. 114
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issue 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.
12
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A Photoluminescence Study in PbS-EuS Superlattices

64%
Kowalczyk L., Sadowski J., Gałązka R., Stachow-Wójcik A., Sipatov A., Volobuev V., Smirnov V., Dugaev V.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
397-400
EN
Investigations of the photoluminescence of PbS-EuS superlattices deposited on (111)BaF_{2} substrates are presented. Quantum-size and deformation effects in photoluminescence spectra are observed. The strain-induced gap shift and valence-band offset is determined from experimental results. A strong stimulated photoluminescence with relatively low threshold was observed. It was found that the photocarriers generated in EuS barrier strongly affect the population of PbS subbands.
13
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Magnetization Studies of Antiferromagnetic Interlayer Coupling in EuS-SrS Semiconductor Multilayers

64%
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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vol. 124
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issue 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.
14
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Effect of Misfit Strain in (Ga,Mn)(Bi,As) Epitaxial Layers on Their Magnetic and Magneto-Transport Properties

64%
Levchenko K., Andrearczyk T., Domagała J., Sadowski J., Kowalczyk L., Szot M., Figielski T., Wosiński T.
Acta Physica Polonica A
|
2016
|
vol. 129
|
issue 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.
15
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PVT-Grown Single Crystals of Cd_{1-x}Zn_{x}Te (x ≤ 0.25) and ZnTe as Substrates for Epitaxy

64%
Mycielski A., Szadkowski A., Łusakowska E., Kowalczyk L., Domagała J., Bąk-Misiuk J., Wilamowski Z., Witkowska B.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
441-445
EN
The process of growth of single crystals of Cd_{1-x}Zn_{x}Te (x ≤ 0.25) and ZnTe by physical vapour transport has been optimized and the twin-free single crystals with a very good crystal structure and low density of dislocations are grown as substrates for MBE and other techniques of epitaxy. Characterization of the crystals is described.
16
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Content available

Temperature Dependence of Antiferromagnetic Interlayer Exchange Coupling in EuS-PbS Multilayers

64%
Chernyshova M., Kowalczyk L., Baran M., Szczerbakow A., Story T., Smits C., Filip A., Swagten H., de Jonge W., Sipatov A.
Acta Physica Polonica A
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2004
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vol. 105
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issue 6
599-605
EN
Antiferromagnetic interlayer exchange coupling in semiconductor EuS-PbS-EuS ferromagnetic trilayers grown on PbS (001) substrates with ultrathin (0.6-1.2 nm) nonmagnetic PbS spacers is studied by SQUID magnetometry and model calculations. Analysis of the experimentally observed magnetic field and temperature dependence of the magnetization of EuS-PbS structures reveals a rapid decrease in the interlayer coupling energy with increasing temperature indicating a temperature dependence of the microscopic coupling mechanism acting in these all-semiconductor ferromagnetic/nonmagnetic multilayers.
17
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Optical Studies of Non-Magnetic Spacer in Thin Fe/Si Multilayers

64%
Szuszkiewicz W., Jouanne M., Morhange J., Chernyshova M., Kowalczyk L., Łusakowska E., Wandziuk P., Luciński T.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
891-896
EN
Structures containing magnetic metallic layers attract a lot of attention because of their possible applications in the area of spintronics. The hybrid structures compatible with the Si crystal lattice parameter are of special interest. In this work the short-period Fe/Si multilayers were grown by the sputtering onto (001)-oriented Si substrate and investigated by various techniques. After the deposition, all multilayers were characterized by atomic force microscopy. The goal of the present paper was to determine the chemical composition of thin layer created at the interface in Fe/Si multilayers due to the Fe diffusion into Si, as well as to analyze the phenomena, which take place in this area. The results of the optical characterization by the Raman scattering were correlated with the magnetic properties of investigated structures (determined by means of the Kerr rotation).
18
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Transmission Second Harmonic Generation in Cd_{1-x}Mn_{x}Te at 1.064 µm

64%
Koziarska B., Kowalczyk L., Suchocki A., Wojtowicz T., Zakrzewski A., Karczewski G., Janik E., Kossut J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
423-426
EN
Second harmonic generation, created by nanosecond Nd : YAG laser pulses at 1.064 µm with relatively low intensity in Cd_{1-x}Mn_{x}Te bulk crystals and thin layers was measured in transmission geometry. The effect practically occurs in a very thin surface layer of the material and it is used as a rela­tively straightforward method of layer quality characterization. It is shown that the angular dependence of the second harmonic generation intensity in thin layers of CdTe with good crystallographic (and optical) quality agrees very well with the theory in contrary to the samples with some distortions from the ideal structure which exhibits large distortions from the theory.
19
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Interlayer Exchange Coupling in Semiconductor EuS-PbS Ferromagnetic Wedge Multilayers

64%
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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vol. 110
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issue 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.
20
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Epitaxial Growth and Optical Properties of PbTe/CdTe Semiconductor Heterostructures

53%
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
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2008
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vol. 114
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issue 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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