| 1. |
- Sawicki, M., et al.
(författare)
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Homogeneous and heterogeneous magnetism in (Zn,Co)O : From a random antiferromagnet to a dipolar superferromagnet by changing the growth temperature
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 88:8
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Tidskriftsartikel (refereegranskat)abstract
- A series of (Zn,Co)O layers with Co contents x up to 40% grown by atomic layer deposition have been investigated. All structures deposited at 160 degrees C show magnetic properties specific to II-VI dilute magnetic semiconductors with localized spins S = 3/2 coupled by strong but short-range antiferromagnetic interactions resulting in low-temperature spin-glass freezing for x = 0.16 and 0.4. At higher growth temperature (200 degrees C) metallic Co nanocrystals precipitate in two locations giving rise to two different magnetic responses: (i) a superparamagnetic contribution coming from volume disperse nanocrystals; (ii) a ferromagneticlike behavior brought about by nanocrystals residing at the (Zn,Co)O/substrate interface. It is shown that the dipolar coupling within the interfacial two-dimensional dense dispersion of nanocrystals is responsible for the ferromagneticlike behavior.
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| 2. |
- Bak-Misiuk, J., et al.
(författare)
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Creation of MnAs nanoclusters during processing of GaMnAs
- 2009
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Ingår i: Radiation Physics And Chemistry. - : Elsevier BV. - 0969-806X. ; 78, s. 116-119
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Konferensbidrag (refereegranskat)abstract
- GaMnAs layers on (0 0 1)-oriented GaAs substrates were grown by the molecular beam epitaxy (MBE) method. Structural properties of samples processed at up to 920 K under hydrostatic Ar pressure up to 1.1 GPa were investigated by X-ray, secondary ion mass spectroscopy and atomic force microscopy methods. The sign of strain (compressive or tensile) of the GaMnAs layers, related to a creation of MnAs nanoclusters, is found to be dependent on processing conditions and on primary structure defects, whereas it was independent of Mn concentration. An influence of the defects structure in as-grown samples on the strain state of processed GaMnAs layers is discussed. (C) 2009 Elsevier Ltd. All rights reserved.
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| 3. |
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| 4. |
- Khranovskyy, V., et al.
(författare)
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Improvement of ZnO thin film properties by application of ZnO buffer layers
- 2007
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 308:1, s. 93-98
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Tidskriftsartikel (refereegranskat)abstract
- The effect of ZnO buffer layers prepared at different temperatures on the structural, optical and morphological properties of the ZnO main layer is reported. ZnO thin films (comprising a buffer and a main layer) were deposited on (0 0 0 1) c-sapphire substrates by PEMOCVD. Two-step growth regimes were applied to realize a homoepitaxial growth on ZnO buffers: low-temperature ZnO buffer layer deposited at Ts=300 °C and the main layer at Ts=500 °C, high-temperature ZnO buffer layer deposited at Ts=500 °C and the main layer at Ts=300 °C. For comparison, a sample grown at high-temperature Ts=500 °C by one-step procedure was used. The low-temperature buffer layer has shown the most beneficial effect on the structural and morphological properties, as expressed by the narrowing of the (0 0 2) diffraction peak (FWHM=0.07°) and crystallite size enlargement. However, the surface roughness of this sample is higher then that of the sample grown by one-step procedure and this needs further considerations. The photoluminescence results seem to support a conclusion that the application of a low-temperature buffer layer among the studied temperature regimes is the most advantageous. © 2007 Elsevier B.V. All rights reserved.
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| 5. |
- Kowalik, Iwona, et al.
(författare)
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Structural and optical properties of low-temperature ZnO films grown by atomic layer deposition with diethylzinc and water precursors
- 2009
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 311:4, s. 1096-1101
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Tidskriftsartikel (refereegranskat)abstract
- We report on properties of low-temperature (LT) ZnO films grown by the atomic layer deposition method with diethylzinc (DEZn) precursor. It is shown that the ZnO thin film crystallographic orientation, quality of the surface, and optical properties depend on the main growth parameters like temperature, pulsing, and purging time and thus can be varied in controllable manner. All the presented results were obtained for ZnO layers grown at temperature between 90 and 200 degrees C. (C) 2008 Elsevier B.V. All rights reserved.
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| 6. |
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| 7. |
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| 8. |
- Wronkowska, A.A., et al.
(författare)
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Lattice absorption of Be-containing semiconductor alloys determined by spectroscopic ellipsometry
- 2008
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Ingår i: Physica Status Solidi (a) applications and materials science. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 1862-6300 .- 1862-6319. ; 205:4, s. 849-853
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Tidskriftsartikel (refereegranskat)abstract
- Lattice absorption of Zn1–x –yBex Mgy Se and Cd1–x –yBex Zny Se mixed crystals grown by a high pressure Bridgman method has been investigated by infrared spectroscopic ellipsometry in the wave number range from 230 cm–1 to 5000 cm–1. Ellipsometric spectra of Cd1–x –yBex Zny Se crystals display features in the spectral range 350–550 cm–1 associated with BeSe-type phonon modes. In the optical spectra of Zn1–x –yBex Mgy Se crystals both BeSe-type and MgSe-type lattice absorption bands are detected. The MgSe-like modes are located at approximately 300 cm–1. The frequencies and oscillator strengths of optical phonon modes depend strongly on the alloy composition
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