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1

Raman Spectroscopy of Co-Doped ZnO Bulk Crystals

100%

Szuszkiewicz W., Morhange J., Gołacki Z., Łusakowski A., Schumm M., Geurts J.

Acta Physica Polonica A

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2007

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vol. 112

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issue 2

363-368

EN

Low-temperature Raman spectra of a bulk mixed crystal Zn_{1-x}Co_xO (x = 0.016) are shown and analyzed. Besides the common modes of the ZnO host lattice, electronic transitions related to the presence of Co^{2+} ions at the Zn sites are observed. In spite of the low Co concentration the presence of collective excitations corresponding to Co and CoO precipitates is also revealed.

2

Magnons in Cubic MBE-Grown A_{1-x}Mn_{x}Te Layers (A = Cd, Zn, Mg)

84%

Szuszkiewicz W., Hennion B., Jouanne M., Morhange J., Dynowska E., Janik E., Wojtowicz T., Zieliński M., Furdyna J.

Acta Physica Polonica A

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1998

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vol. 94

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issue 3

583-587

EN

One-magnon excitations in MBE-grown A_{1-x}Mn_{x}Te layers (where A = Cd, Zn, Mg and x>0.7) were investigated by means of the Raman scattering measurements at low temperatures (≈20 K). The composition dependence of the anisotropy energy - as extracted from these measurements - is discussed. Further, the elastic neutron scattering measurements were performed in layers of cubic MnTe, which constitute the end point material of the ternary alloys series. Abundance of variously oriented antiferromagnetic domains in MnTe layers as a function of temperature was studied. We confirm occurrence of a pronounced magnetostriction effect.

3

Optical Studies of Non-Magnetic Spacer in Thin Fe/Si Multilayers

84%

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).

4

Low-Frequency Raman Spectrum οf Bulk Zn_{0.984}Co_{0.016}O Crystal

84%

Szuszkiewicz W., Łusakowski A., Morhange J., Gołacki Z., Arciszewska M., Brodowska B., Kanehisa M., Klepka M., Dobrowolski W.

Acta Physica Polonica A

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2009

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vol. 116

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issue 1

103-106

EN

The influence of possible presence of Co^{2+} ion pairs in a bulk Zn_{1-x}Co_{x}O mixed crystal on the low-frequency part of the Raman spectrum is discussed. Two effects can be taken into account in the theoretical considerations when analyzing the energy level scheme corresponding to Co ions. The first is a local lattice deformation in the vicinity of Co^{2+} ion due to a presence of the second ion, smaller than the host ZnO lattice cation. Such deformation creates a trigonal field, which can only slightly modify the energy levels of Co^{2+} ion. The second effect, which results from an antiferromagnetic superexchange interaction between two Co^{2+} ions is responsible for a new set of energy levels. The Raman data taken at low temperature on the sample corresponding to the composition x = 0.016 demonstrated the presence of two structures at about 6 cm^{-1} and 13 cm^{-1}. These structures may be interpreted as electronic transitions between the ground state and the first excited state of a single Co^{2+} ion in the substitution site of ZnO lattice and as a similar transition for Co^{2+} ion pair, respectively.

5

Interlayer Exchange Coupling in Short Period GaMnAs/GaAs Superlattices

84%

Szuszkiewicz W., Dynowska E., Hennion B., Ott F., Jouanne M., Morhange J., Karlsteen M., Sadowski J.

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EN

The low dimensional structures containing III-V ferromagnetic semiconductors were intensively investigated in the last few years because of the variety of their potential applications. The aim of the present work was to study the interlayer exchange coupling in the short period GaMnAs/GaAs superlattices containing 16 or 8 GaMnAs monolayers. Samples with the magnetic layers corresponding to the mixed crystal composition with 5% or 6% of Mn were grown by MBE technique and characterized by both high-resolution X-ray diffraction and Raman scattering methods. Folded acoustic phonons were observed for the first time for this particular quantum system in the Raman scattering spectra. The interlayer exchange coupling in selected superlattices was investigated by both elastic neutron scattering (diffraction) and polarized neutron reflectivity measurements. Presence of the smooth interfaces and the stability of the superlattice period were confirmed by neutron reflectometry data. Ferromagnetic correlation of the magnetization vector in subsequent GaMnAs magnetic layers was demonstrated by both experimental methods.

6

Elastic Properties of Zinc Blende MnTe

68%

Djemia P., Roussigné Y., Stashkevich A., Szuszkiewicz W., Gonzalez Szwacki N., Dynowska E., Janik E., Kowalski B., Karczewski G., Bogusławski P., Jouanne M., Morhange J.

Acta Physica Polonica A

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2004

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vol. 106

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issue 2

239-247

EN

The Brillouin light scattering was used to investigate elastic properties of the zinc blende, MBE-grown MnTe layer that was deposited on a (001) GaAs substrate covered by CdTe buffer layer. The three elastic constants of the zinc blende MnTe, namely c_{11}, c_{12}, and c_{44}, were directly determined for the first time from the frequency of the Rayleigh mode, of the pseudo-surface mode, and of the shear horizontal bulk mode traveling parallel to the layer surface. The value of c_{11} was checked using the frequency of longitudinal bulk waves propagating at different angles from the normal of the layer plane. This value was also independently determined by results of the folding of acoustic phonons, observed for MnTe/CdTe superlattices by the Raman scattering. Finally, the bulk modulus given by the formula B=(c_{11}+2c_{12})/3 was determined for zinc blende MnTe by ab initio calculations making use of the density functional theory and atomic pseudopotentials; spin polarization of MnTe was taken into account. A satisfactory agreement between theoretical and experimental values was obtained.

7

Morphology and Selected Properties of Core/Shell ZnTe-Based Nanowire Structures Containing ZnO

68%

Gas K., Janik E., Zaleszczyk W., Pasternak I., Dynowska E., Fronc K., Kolkovsky V., Kret S., Morhange J., Reszka A., Wiater M., Caliebe W., Karczewski G., Kowalski B., Szuszkiewicz W., Wojtowicz T.

Acta Physica Polonica A

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2011

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vol. 119

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issue 5

612-614

EN

We report on an approach to fabricate ZnTe-based core/shell radial heterostructures containing ZnO, as well as on some of their physical properties. The molecular beam epitaxy grown ZnTe nanowires constituted the core of the investigated structures and the ZnO shells were obtained by thermal oxidation of ZnTe NWs. The influence of the parameters characterizing the oxidation process on selected properties of core/shell NWs were examined. Scanning electron microscopy revealed changes of the NWs morphology for various conditions of the oxidation process. X-ray diffraction, high resolution transmission electron microscopy, and Raman scattering measurements were applied to reveal the presence of ZnTe single crystal core and polycrystalline ZnO-shell of investigated structure.

8

Physical Properties of ZnCoO Tetrapods and Nanofibers

68%

Gas K., Fronc K., Dziawa P., Knoff W., Wojciechowski T., Zaleszczyk W., Baranowska-Korczyc A., Morhange J., Paszkowicz W., Elbaum D., Karczewski G., Wojtowicz T., Szuszkiewicz W.

Acta Physica Polonica A

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2009

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vol. 116

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issue 5

868-870

EN

In this paper the physical properties of two types of Co-doped ZnO nanostructures: tetrapods and nanofibers grown by a rapid thermal evaporation process and prepared by the electrospinning technique, respectively, were investigated and analyzed. Surface morphology of the samples was examined using scanning electron microscopy. X-ray diffraction measurements showed hexagonal wurtzite crystal structure of both types of investigated nanostructures. Both X-ray diffraction and Raman scattering data confirmed high phase purity of the samples. The magnetic properties studied with the use of the SQUID magnetometer confirmed a presence of ferromagnetic order in analyzed nanostructures. The observed photoluminescence spectra exhibited two groups of lines. The first one, in the ultraviolet spectral range, is due to the optical transitions close to ZnO band gap, the second one in the red region is most probably related to the Co^{2+} d-d internal transitions. The influence of native defects on the optical properties is also shown and discussed. All results reported here lead us to the conclusion that in the mixed crystal nanostructures obtained, a fraction of the Zn^{2+} ions is substituted by Co^{2+} ions.

9

Growth and Properties of ZnMnTe Nanowires

61%

Zaleszczyk W., Janik E., Presz A., Szuszkiewicz W., Morhange J., Dłużewski P., Kret S., Kirmse H., Neumann W., Dynowska E., Domagała J., Caliebe W., Aleszkiewicz M., Pacuski W., Golnik A., Kossacki P., Baczewski L., Petroutchik A., Karczewski G., Wojtowicz T.

Acta Physica Polonica A

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2007

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vol. 112

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issue 2

351-356

EN

Catalytically enhanced growth of ZnMnTe diluted magnetic semiconductor nanowires by molecular beam epitaxy is reported. The growth is based on the vapor-liquid-solid mechanism and was performed on (001) and (011)-oriented GaAs substrates from elemental sources. X-ray diffractometry, scanning and transmission electron microscopy, atomic force microscopy, photoluminescence spectroscopy, and Raman scattering were performed to determine the structure of nanowires, their chemical composition, and morphology. These studies revealed that the obtained ZnMnTe nanowires possess zinc-blende structure, have an average diameter of about 30 nm, typical length between 1 and 2μm and that Mn^{2+} ions were incorporated into substitutional sites of the ZnTe crystal lattice.

Refine search results

Raman Spectroscopy of Co-Doped ZnO Bulk Crystals

Magnons in Cubic MBE-Grown A_{1-x}Mn_{x}Te Layers (A = Cd, Zn, Mg)

Optical Studies of Non-Magnetic Spacer in Thin Fe/Si Multilayers

Low-Frequency Raman Spectrum οf Bulk Zn_{0.984}Co_{0.016}O Crystal

Interlayer Exchange Coupling in Short Period GaMnAs/GaAs Superlattices

Elastic Properties of Zinc Blende MnTe

Morphology and Selected Properties of Core/Shell ZnTe-Based Nanowire Structures Containing ZnO

Physical Properties of ZnCoO Tetrapods and Nanofibers

Growth and Properties of ZnMnTe Nanowires