| 1. |
- Dynowska, E., et al.
(författare)
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Structural and magnetic properties of GaSb:MnSb granular layers
- 2011
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 80:10, s. 1051-1057
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Konferensbidrag (refereegranskat)abstract
- The results of structural and magnetic characterization of GaMnSb layers grown on GaSb(0 0 1) and GaAs(1 1 1) substrates are presented. The presence of hexagonal, highly oriented MnSb inclusions embedded in GaSb matrix has been demonstrated. The lattice parameters of these inclusions were the same as those for bulk MnSb for the layers grown on GaSb(1 0 0) substrate while for the layers grown on GaAs(1 1 1) the MnSb inclusions were strained. The influence of a presence of MnSb clusters on the lattice parameter of GaSb matrix has been demonstrated. It was confirmed that in all cases the MnSb clusters exhibit a ferromagnetic: behavior at room temperature. (C) 2011 Elsevier Ltd. All rights reserved.
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| 2. |
- Lawniczak-Jablonska, K., et al.
(författare)
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Structural and magnetic properties of GaAs:(Mn,Ga)As granular layers
- 2011
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Ingår i: Physica Status Solidi. B: Basic Research. - : Wiley. - 0370-1972. ; 248:7, s. 1609-1614
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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
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| 3. |
- Lawniczak-Jablonska, K., et al.
(författare)
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Structural and magnetic properties of nanoclusters in GaMnAs granular layers
- 2011
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596. ; 184:6, s. 1530-1539
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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.
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| 4. |
- Levchenko, K., et al.
(författare)
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Magnetic and Magneto-Transport Characterization of (Ga,Mn)(Bi,As) Epitaxial Layers
- 2014
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Ingår i: Acta Physica Polonica. Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics. - 0587-4246. ; 126:5, s. 1121-1124
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Tidskriftsartikel (refereegranskat)abstract
- High-quality layers of the (Ga,Mn)(Bi,As) quaternary compound semiconductor have been grown by the low-temperature molecular-beam epitaxy technique. An effect of Si incorporation into the (Ga,Mn)As ferromagnetic semiconductor and the post-growth annealing treatment of the layers have been investigated through examination of their magnetic and magneto-transport properties. Significant enhancement of the planar Hall effect magnitude upon addition of Si into the layers is interpreted as a result of increased spin orbit coupling in the (Ga,Mn)(Bi,As) layers.
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| 5. |
- Polley, Craig, et al.
(författare)
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Observation of topological crystalline insulator surface states on (111)-oriented Pb1-xSnxSe films
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 89:7, s. 075317-
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Tidskriftsartikel (refereegranskat)abstract
- We present angle-resolved photoemission spectroscopy measurements of the surface states on in-situ grown (111) oriented films of Pb1-xSnxSe, a three-dimensional topological crystalline insulator. We observe surface states with Dirac-like dispersion at (Gamma) over bar and (M) over bar in the surface Brillouin zone, supporting recent theoretical predictions for this family of materials. We study the parallel dispersion isotropy and Dirac-point binding energy of the surface states, and perform tight-binding calculations to support our findings. The relative simplicity of the growth technique is encouraging, and suggests a clear path for future investigations into the role of strain, vicinality, and alternative surface orientations in (Pb,Sn)Se solid solutions.
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| 6. |
- Romanowski, P., et al.
(författare)
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Defect Structure of High-Temperature-Grown GaMnSb/GaSb
- 2010
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Ingår i: Acta Physica Polonica A. - 0587-4246. ; 117:2, s. 341-343
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Konferensbidrag (refereegranskat)abstract
- GaMnSb/GaSb(100) layers with embedded MnSb inclusions have been grown at 720 K using MBE technique. This paper presents the investigation of the defect structure of Ga1-xMnxSb layers with different content of manganese (up to x = 0.07). X-ray diffraction method using conventional and synchrotron radiation was applied. Dimensions and shapes of inclusions were detected by scanning electron microscopy. Depth profiles of elements were measured using secondary ion mass spectroscopy technique.
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| 7. |
- Yastrubchak, O., et al.
(författare)
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Effect of low-temperature annealing on the electronic- and band-structures of (Ga,Mn) As epitaxial layers
- 2014
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Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 115:1
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Tidskriftsartikel (refereegranskat)abstract
- The effect of outdiffusion of Mn interstitials from (Ga,Mn) As epitaxial layers, caused by post-growth low-temperature annealing, on their electronic- and band-structure properties has been investigated by modulation photoreflectance (PR) spectroscopy. The annealing-induced changes in structural and magnetic properties of the layers were examined with high-resolution X-ray diffractometry and superconducting quantum interference device magnetometry, respectively. They confirmed an outdiffusion of Mn interstitials from the layers and an enhancement in their hole concentration, which were more efficient for the layer covered with a Sb cap acting as a sink for diffusing Mn interstitials. The PR results demonstrating a decrease in the band-gap-transition energy in the as-grown (Ga,Mn) As layers, with respect to that in the reference GaAs one, are interpreted by assuming a merging of the Mn-related impurity band with the GaAs valence band. Whereas an increase in the band-gap-transition energy caused by the annealing treatment of the (Ga,Mn) As layers is interpreted as a result of annealing-induced enhancement of the free-hole concentration and the Fermi level location within the valence band. The experimental results are consistent with the valence-band origin of itinerant holes mediating ferromagnetic ordering in (Ga,Mn) As, in agreement with the Zener model for ferromagnetic semiconductors. (C) 2014 AIP Publishing LLC.
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| 8. |
- Yastrubchak, O., et al.
(författare)
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Ferromagnetism and the electronic band structure in (Ga,Mn)(Bi,As) epitaxial layers
- 2014
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:7
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Tidskriftsartikel (refereegranskat)abstract
- Impact of Bi incorporation into (Ga,Mn)As layers on their electronic-and band-structures as well as their magnetic and structural properties has been studied. Homogenous (Ga,Mn)(Bi,As) layers of high structural perfection have been grown by the low-temperature molecular-beam epitaxy technique. Post-growth annealing treatment of the layers results in an improvement of their structural and magnetic properties and an increase in the hole concentration in the layers. The modulation photoreflectance spectroscopy results are consistent with the valence-band model of hole-mediated ferromagnetism in the layers. This material combines the properties of (Ga,Mn)As and Ga(Bi,As) ternary compounds and offers the possibility of tuning its electrical and magnetic properties by controlling the alloy composition. (C) 2014 AIP Publishing LLC.
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| 9. |
- Yastrubchak, O., et al.
(författare)
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Ion-Implantation Control of Ferromagnetism in (Ga,Mn)As Epitaxial Layers
- 2010
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Ingår i: Journal Of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 39:6, s. 794-798
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Konferensbidrag (refereegranskat)abstract
- Epitaxial layers of (Ga,Mn)As ferromagnetic semiconductor have been subjected to low-energy ion implantation by applying a very low fluence of either chemically active, oxygen ions or inactive ions of neon noble gas. Several complementary characterization techniques have been used with the aim of studying the effect of ion implantation on the layer properties. Investigation of their electrical and magnetic properties revealed that implantation with either O or Ne ions completely suppressed both the conductivity and ferromagnetism in the layers. On the other hand, Raman spectroscopy measurements evidenced that O ion implantation influenced optical properties of the layers noticeably stronger than did Ne ion implantation. Moreover, structural modifications of the layers caused by ion implantation were investigated using high-resolution x-ray diffraction technique. A mechanism responsible for ion-implantation-induced suppression of the conductivity and ferromagnetism in (Ga,Mn)As layers, which could be applied as a method for tailoring nanostructures in the layers, is discussed in terms of defects created in the layers by the two implanted elements.
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| 10. |
- Yastrubchak, O., et al.
(författare)
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Photoreflectance study of the fundamental optical properties of (Ga,Mn) As epitaxial films
- 2011
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 83:24
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Tidskriftsartikel (refereegranskat)abstract
- Fundamental optical properties of thin films of the (Ga,Mn) As diluted ferromagnetic semiconductor with low (1%-2%) and high (4%-6%) Mn content and of a reference GaAs film, grown by low-temperature molecular-beam epitaxy, have been investigated by photoreflectance (PR) spectroscopy. In addition, the films were subjected to complementary characterization by means of superconducting quantum interference device magnetometry, Raman spectroscopy, and high-resolution x-ray diffractometry. Thorough full-line-shape analysis of the PR spectra, which enabled determination of the E-0 electronic transition in (Ga,Mn) As, revealed significant differences between the energy band structures in the vicinity of the Gamma point of the Brillouin zone in the investigated (Ga,Mn) As films. In view of the experimental results obtained, the evolution of the valence band structure in (Ga,Mn) As with increasing Mn content is discussed, pointing to a merging of the Mn-related impurity band with the host GaAs valence band for high Mn content.
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