| 1. |
- Dziawa, P., et al.
(författare)
-
Defect Free PbTe Nanowires Grown by Molecular Beam Epitaxy on GaAs(111)B Substrates
- 2010
-
Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 10:1, s. 109-113
-
Tidskriftsartikel (refereegranskat)abstract
- The molecular beam epitaxial growth of PbTe nanowires oil GaAs(111)B substrates is reported. The growth process was based oil the Au-catalyzed vapor-liquid-solid mechanism. These nanowires grow along the [100] axis; they are perpendicular to the substrate, have tapered shapes, and have diameters of about 90 rim at the base and 60 run at the top. High resolution transmission electron microscopy pictures reveal that the PbTe nanowires have a rock-salt structure and, in contrast to the one-dimensional structures of III-V and II-VI compound semiconductors such as GaAs. InAs, or ZnTe, are free from stacking faults. A theoretical analysis of these experimental findings, which is based oil ab initio modeling of the PbTe nanowires, is also presented.
|
|
| 2. |
- Lawniczak-Jablonska, K., et al.
(författare)
-
Structural and magnetic properties of GaAs:(Mn,Ga)As granular layers
- 2011
-
Ingår i: Physica Status Solidi. B: Basic Research. - : Wiley. - 0370-1972. ; 248:7, s. 1609-1614
-
Tidskriftsartikel (refereegranskat)abstract
- Granular GaAs:(Mn,Ga)As films were prepared by annealing the Ga0.92Mn0.08As/GaAs layer grown by the MBE method at low temperature. The annealing was performed at 500 or 600 degrees C. It is commonly accepted that this processing should result in formation of cubic zinc blende or hexagonal MnAs inclusions depending on the temperature. We demonstrate that such a priory assumption is not justified. The kind of formed inclusions depends not only on the annealing temperature but also on the number of defects and Mn atoms in the substitutional and interstitial positions in as grown sample. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
|
|
| 3. |
- Lawniczak-Jablonska, K., et al.
(författare)
-
Structural and magnetic properties of nanoclusters in GaMnAs granular layers
- 2011
-
Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596. ; 184:6, s. 1530-1539
-
Tidskriftsartikel (refereegranskat)abstract
- Structural and magnetic properties of GaAs thin films with embedded nanoclusters were investigated as a function of the annealing temperature and Mn content. Surprisingly, the presence of two kinds of nanoclusters with different structure was detected in most of the samples independently of the thermal processing or Mn content. This proved that the presence of a given type of clusters cannot be assumed a priori as is reported in many papers. The fraction of Mn atoms in each kind of cluster was estimated from the extended X-ray absorption fine structure analysis. This analysis ruled out the possibility of the existence of nanoclusters containing a hypothetic MnAs cubic compound-only (Ga,Mn)As cubic and hexagonal MnAs clusters were detected. Moreover the bimodal distribution of Mn magnetic moments was found, which scales with the estimated fraction of Mn atoms in the cubic and hexagonal clusters. (C) 2011 Elsevier Inc. All rights reserved.
|
|
| 4. |
|
|
| 5. |
- Dluzewski, P., et al.
(författare)
-
TEM determination of directions of (Ga,Mn)As nanowires grown by MBE on GaAs(001) substrates
- 2009
-
Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720. ; 236:2, s. 115-118
-
Tidskriftsartikel (refereegranskat)abstract
- P>The structure of GaMnAs nanowires (NW) with nominal Mn concentration of up to 7 at% was investigated by transmission electron microscopy. The (Ga,Mn)As NW were grown on epiready GaAs(001) n-type wafers by molecular beam epitaxy. The crystal structure of the NW was determined to be zinc-blende. NW with Mn concentrations lower than 5 at% grow along the << 111 >> direction. NW with higher Mn concentrations grow along the << 110 >> direction and reveal a branching structure. The main nanowire and branches grow along the << 110 >> directions belonging to only one {111} plane.
|
|
| 6. |
- Janik, E., et al.
(författare)
-
ZnTe nanowires grown on GaAs(100) substrates by molecular beam epitaxy
- 2006
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:13
-
Tidskriftsartikel (refereegranskat)abstract
- ZnTe nanowires with an average diameter of about 30 nm and lengths above 1 mu m were grown on GaAs(100) substrate by molecular beam epitaxy. The growth process was based on the Au-catalyzed vapor-liquid-solid mechanism. A thin gold layer (3-20 angstrom thick) annealed in high vacuum prior to the nanowire growth was used as a source of catalytic nanoparticles. The nanowires are inclined about 55 degrees to the (100) substrate surface normal. They have a zinc-blende crystal structure and their growth axis is < 111 >.
|
|
| 7. |
- Kowalik, Iwona, et al.
(författare)
-
Structural and optical properties of low-temperature ZnO films grown by atomic layer deposition with diethylzinc and water precursors
- 2009
-
Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 311:4, s. 1096-1101
-
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.
|
|
| 8. |
- Kwiatkowski, A., et al.
(författare)
-
Magnetic properties of MnAs nanocrystals embedded in GaAs
- 2009
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 321:18, s. 2788-2791
-
Tidskriftsartikel (refereegranskat)abstract
- A phenomenological model for explaining the magnetic properties of MnAs nanocrystals embedded in GaAs is proposed. It is shown that experimental data of DC magnetization as a function of temperature, obtained according to zero-field-cooled and field-cooled protocols, can be understood assuming a transition of the system from a low temperature state in which very slow dynamics is observed(frozen state) to a high-temperature state in which dynamics is fast(quasi superparamagnetic state). (C) 2009 Elsevier B. V. All rights reserved.
|
|
| 9. |
- Kwiatkowski, A., et al.
(författare)
-
MnAs Nanocrystals Embedded in GaAs
- 2008
-
Ingår i: ACTA PHYSICA POLONICA A. - 0587-4246. ; 114:5, s. 1207-1211
-
Konferensbidrag (refereegranskat)abstract
- Magnetic properties of MnAs nanocrystals embedded in GaAs are analyzed in the frame of phenomenological model proposed by Sasaki for ferritin superparamagnets. Our calculations explain qualitatively experimental data of magnetization versus temperature; obtained according to zero-field-cooled and field-cooled protocols. They show dynamics of magnetization of MnAs nanocrystals in range of temperature from 10 K to 320 K. There is transition from state in which very slow dynamics is observed (frozen state) to state in which dynamics is fast (quasi-superparamagnetic state).
|
|
| 10. |
- Lawniczak-Jablonska, K., et al.
(författare)
-
The source of room temperature ferromagnetism in granular GaMnAs layers with zinc blende clusters
- 2011
-
Ingår i: Physica Status Solidi. Rapid Research Letters. - : Wiley. - 1862-6254. ; 5:2, s. 62-64
-
Tidskriftsartikel (refereegranskat)abstract
- Granular GaAs:(Mn,Ga) As films were prepared by annealing the Ga0.985Mn0.015As/GaAs layers at 500 degrees C or 600 degrees C. It is commonly accepted that this processing should result in the formation of cubic or hexagonal MnAs clusters, respectively. We demonstrate that such a priori assumption is not justified. If in the as grown sample there are not many defects with the interstitial Mn atoms, only small cubic clusters can be formed even after annealing at 600 degrees C. Moreover, in a sample containing solely cubic GaMnAs clusters, the Mn ions are ferro-magnetically coupled at room temperature. This fact was explained by the existence of GaMnAs solid solution in the clusters, with content of Mn close to 20% (higher than ever found in the layers) as was confirmed by experiment and theory. Extended X-ray absorption spectroscopy studies excluded the possibility of formation of the hypothetic zinc blende MnAs clusters. Not more than one Mn atom was detected in the second shell around central Mn atom. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
|
|
| 11. |
- Sawicki, M., et al.
(författare)
-
Homogeneous and heterogeneous magnetism in (Zn,Co)O : From a random antiferromagnet to a dipolar superferromagnet by changing the growth temperature
- 2013
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 88:8
-
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.
|
|
