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110 results on '"Darowski, N."'

1. Nucleation at the phase transition near 40~$^{\circ }$C in MnAs nanodisks

Author

Jenichen, B, Takagaki, Y, Ploog, K H, Darowski, N, Feyerherm, R, and Zizak, I

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

The phase transition near 40~$^{\circ }$C of both as-grown thin epitaxial MnAs films prepared by molecular beam epitaxy on GaAs(001) and nanometer-scale disks fabricated from the same films is studied. The disks are found to exhibit a pronounced hysteresis in the temperature curve of the phase composition. In contrast, supercooling and overheating take place far less in the samples of continuous layers. These phenomena are explained in terms of the necessary formation of nuclei of the other phase in each of the disks independent from each other. The influence of the elastic strains in the disks is reduced considerably.

Published
2019
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2. Exchange bias in GeMn nanocolumns: the role of surface oxidation

Author

Tardif, S., Cherifi, S., Jamet, M., Devillers, T., Barski, A., Schmitz, D., Darowski, N., Thakur, P., Cezar, J. C., Brookes, N. B., Mattana, R., and Cibert, J.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We report on the exchange biasing of self-assembled ferromagnetic GeMn nanocolumns by GeMn-oxide caps. The x-ray absorption spectroscopy analysis of this surface oxide shows a multiplet fine structure that is typical of the Mn2+ valence state in MnO. A magnetization hysteresis shift |HE|~100 Oe and a coercivity enhancement of about 70 Oe have been obtained upon cooling (300-5 K) in a magnetic field as low as 0.25 T. This exchange bias is attributed to the interface coupling between the ferromagnetic nanocolumns and the antiferromagnetic MnO-like caps. The effect enhancement is achieved by depositing a MnO layer on the GeMn nanocolumns., Comment: 7 pages, 5 figures

Published
2010
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12. In-plane strain distribution in free-standing GaAs/InGaAs/GaAs single quantum well surface nanostructures on GaAs(001)

Author

Ulyanenkov, A., Baumbach, T., Darowski, N., Pietsch, U., Wang, K.H., Forchel, A., and Wiebach, T.

Subjects
Quantum wells -- Analysis, X-ray diffractometer -- Usage, Physics
Abstract

The vertical variation of in-plane strain induced by an In0.1Ga0.9As single quantum well fixed in a free-standing wire structure on GaAs is analyzed using depth resolved x-ray grazing incidence diffraction. The basis of the theoretical investigation is the distorted wave Born approximation for grazing incidence geometry. By fitting the complete set of experimental grating truncation rods simultaneously, the structural parameters of the surface nanostructure were identified. The results are discussed.

Published
1999

14. X-ray study of lateral strain and composition modulation in an AlGaAs overlayer induced by a GaAs lateral surface grating

Author

Darowski, N., Pietsch, U., Zeimer, U., Smirnitzki, V., and Bugge, F.

Subjects
X-ray diffractometer -- Usage, Gallium arsenide semiconductors -- Research, Thin films -- Research, Strains and stresses -- Measurement, Semiconductors -- Etching, Physics
Abstract

Holographic photolithography and wet chemical etching on a negligibly misaligned GaAs(001) substrate were implemented in preparing a lateral surface grating. Scanning electron microscopy and triple-axis high resolution x-ray diffraction were then used to examine structural properties prior to and after thermal annealing. Both compositional modulation and lateral strain modulation were found within the GaAlAs overlayer.

Published
1998

17. Linear growth kinetics of nanometric silicides in Co/amorphous-Si and Co/CoSi/amorphous-Si thin films.

Author

Cserháti, C., Balogh, Z., Csik, A., Langer, G. A., Erdélyi, Z., Glodán, Gy., Katona, G. L., Beke, D. L., Zizak, I., Darowski, N., Dudzik, E., and Feyerherm, R.

Subjects
ELECTROMAGNETIC waves, COMPUTER simulation, PARTICLES (Nuclear physics), SEPARATION (Technology), SEMICONDUCTOR doping, SOLID solutions, THIN films, SOLID state electronics
Abstract

Evolution of the reaction zone on the nanoscale has been studied in bi- and multilayered Co/a-Si as well as in trilayered Co/a-CoSi/a-Si and Co/CoSi/a-Si thin film diffusion couples. The kinetics of the phase boundary movement during solid state reaction has been followed with special interest of the initial stage of the diffusion, i.e. effects happening on the nanoscale (short time, short distance). The interfacial reactions have been investigated in situ by synchrotron radiation. The formed phases were also characterized by transmission electron microscopy and resistance measurements. The effect of phase nucleation and shift of phase boundaries have been separated in order to determine the “pure” growth kinetics of the crystalline CoSi and Co2Si product phases at the very early stages. Deviations have been found from the traditional diffusion controlled parabolic phase growth. Computer simulations based on a kinetic mean field model illustrated that the diffusion asymmetry (large difference in diffusion coefficients of the materials in contact) may offer a plausible explanations for this. [ABSTRACT FROM AUTHOR]

Published
2008
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18. X-ray measurements with micro- and nanoresolution at BESSY RID F-1396-2011 RID A-4661-2010

Author

Gupta A, Darowski N, Zizak I, Schumacher G, Erko A., MENEGHINI, CARLO, Gupta, A, Darowski, N, Zizak, I, Meneghini, Carlo, Schumacher, G, and Erko, A.

Abstract

Capabilities of the KMC-2 beamline at BESSY for spatially resolved X-ray measurements with micro- and nanometer resolution have been reviewed. A combination of experimental methods of X-ray fluorescence analysis and extended X-ray absorption fine spectroscopy with X-ray standing waves technique was applied for the depth profiling ofSi/W/Si layers with sub-nanometer resolution. The investigated layers were placed into the waveguide structure formed by two Au films to increase sensitivity and accuracy of the measurements. In-depth resolution on the order of I nm for the structure measurements has been obtained. (c) 2007 Elsevier B.V All rights reserved.

Published
2007

20. Strain relaxation in periodic arrays of Si/SiGe quantum wires determined by coplanar high-resolution X-Ray diffraction and grazing incidence diffraction

Author

Zhuang, Y., Lübbert, D., Pietsch, U., Darowski, N., Bauer, G., and Publica

Subjects
strain, x-ray diffraction, high resolution, Si/SiGe
Abstract

Elastic relaxation in dry-etched periodic wires fabricated from molecular beam epitaxy grown Si/SiGe multilayers was studied by coplanar and grazing incidence (GID) high-resolution x-ray diffraction. The inhomogeneous strain distribution in the wires was calculated by the finite element method, which provided the input data for simulations of the scattered intensities using kinematical diffraction theory used for comparison with measured reciprocal space maps. A fabrication-induced layer covering the wire surfaces, modifies the strain distribution. Using GID, the geometrical shape of the wires and their in-plane strain can be determined independently of each other.

Published
1999

21. In-plane strain and strain relaxation in laterally patterned periodic arrays of protect (Si/SiGe) quantum wires and dot arrays

Author

Darowski, N., Pietsch, U., Zhuang, Y., Zerlauth, S., Bauer, G., Lübbert, D., Baumbach, T., and Publica

Abstract

The depth dependent strain relaxion in photolithographically defined and reactive ion etched Si/SiGe quantum wire and dot arrays is determined by high resolution grazing incidence x-ray diffraction. The laterally periodic structures were aligned along two orthogonal [110] and [110] directions on the (001) surface. By recording reciprocal space maps around the (220) and (220) reciprocal lattice points, the shape and in-plane strain could be determined independently of each other. Using triple axis diffractometry and changing the effective penetration depth of the x-ray radiation between 5 and 300 nm the strain relaxation in the wires and dots could be determined depth resolved.

Published
1998

24. Exchange bias in GeMn nanocolumns: The role of surface oxidation

Author

Tardif, S., primary, Cherifi, S., additional, Jamet, M., additional, Devillers, T., additional, Barski, A., additional, Schmitz, D., additional, Darowski, N., additional, Thakur, P., additional, Cezar, J. C., additional, Brookes, N. B., additional, Mattana, R., additional, and Cibert, J., additional

Published
2010
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50. Nucleation at the phase transition near 40 °C in MnAs nanodisks.

Author

Jenichen, B., Takagaki, Y., Ploog, K. H., Darowski, N., Feyerherm, R., and Zizak, I.

Subjects
NUCLEATION, PHASE transitions, SOLID state electronics, OPTICAL disks, MOLECULAR beam epitaxy, NANOSTRUCTURED materials, SPINTRONICS
Abstract

The phase transition near 40 °C of both as-grown thin epitaxial MnAs films prepared by molecular beam epitaxy on GaAs(001) and nanometer-scale disks fabricated from the same films is studied. The disks are found to exhibit a pronounced hysteresis in the temperature curve of the phase composition. In contrast, supercooling and overheating take place far less in the samples of continuous layers. These phenomena are explained in terms of the necessary formation of nuclei of the other phase in each of the disks independent from each other. The influence of the elastic strains in the disks is reduced considerably. [ABSTRACT FROM AUTHOR]

Published
2006
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