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| 2. |
- Fedorych, OM, et al.
(författare)
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Magnetic order in semiconducting, ferromagnetic Ga1-xMnxAs
- 2004
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 19:4, s. 492-493
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic resonance studies allow us to distinguish paramagnetic, ferromagnetic and ferrimagnetic phases in Ga1-xMnxAs. The transition from ferromagnet to ferrimagnet is correlated with a metal to insulator transition. The analysis of spin wave resonance spectra, which occur in the ferrimagnetic phase, allows us to estimate the magnitude and the distance dependence of exchange coupling. The experimentally evaluated long range of exchange causes an effective averaging of the fluctuation of exchange interactions. As a consequence, in the semimetallic phase both spin subsystems coherently precess forming the ferrimagnetic structure. In the insulating phase, fluctuations of the local exchange field lead to a fast decoherence of the carrier spins and only the localized Mn spins form the ferromagnetic moment.
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| 3. |
- Adell, M, et al.
(författare)
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Photoemission studies of the annealing-induced modifications of Ga0.95Mn0.05As
- 2004
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 70:12: 125204
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Tidskriftsartikel (refereegranskat)abstract
- Using angle resolved photoemission we have investigated annealing-induced changes in Ga1-xMnxAs with x=0.05. We find that the position of the Fermi energy is a function of annealing time and temperature. It is also established that the Curie temperature is strongly correlated to the separation between the Fermi level and the valence band maximum. Valence band photoemission shows that the Mn3d spectrum is modified by the annealing treatments.
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| 4. |
- Asklund, H, et al.
(författare)
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Photoemission study of GaAs (100) grown at low temperature
- 2002
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 65:11
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Tidskriftsartikel (refereegranskat)abstract
- GaAs(100) layers grown by low-temperature (LT) molecular beam epitaxy were studied by means of valence-band and core-level photoelectron spectroscopy. Small differences were found between valence-band spectra from the LT layers and corresponding layers grown at high temperature. In the Ga 3d spectra a new component was found in the LT-GaAs. The relative intensity of this component was found to be practically constant with varying probing depth. It is proposed that this component represents sites coordinated to the five-atom As clusters formed at As-Ga antisites. This interpretation implies a higher density of antisite defects in the near-surface region than typically found in the bulk.
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| 5. |
- Jiricek, P, et al.
(författare)
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Electron mean free path for GaAs(100)-c(4x4) at very low energies
- 2004
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Ingår i: Proceedings of the 22nd European Conference on Surface Science (Surface Science). - : Elsevier BV. - 0039-6028. ; 566, s. 1196-1199
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Konferensbidrag (refereegranskat)abstract
- Electron mean free path (MFP) was determined by the angular resolved photoemission in 10-40 eV energy range for GaAs(100)-c(4 x 4) by the overlayer method. The investigation was based on the attenuation of the normal photoemission intensity of the Al 2p line from the molecular-beam-epitaxy grown GaAlAs layer buried four monolayers of GaAs below the surface. The energy dependence of the MFP shows a pronounced maximum at about 30 eV which is related to the corresponding section of the electron band structure of GaAs(100). (C) 2004 Elsevier B.V. All rights reserved.
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| 6. |
- Kowalski, BJ, et al.
(författare)
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MnAs overlayer on GaN(000(1)under-bar)-(1 x 1) its growth, morphology and electronic structure
- 2004
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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. ; 105:6, s. 645-650
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Tidskriftsartikel (refereegranskat)abstract
- MnAs layer has been grown by means of MBE on the GaN(000 (1) under bar)-(1 x 1) surface. Spontaneous formation of MnAs grains with a diameter of 30-60 nm (as observed by atomic force microscopy) occurred for the layer thickness bigger than 7 ML. Ferromagnetic properties of the layer with Curie temperature higher than 330 K were detected by SQUID measurements. Electronic structure of the system was investigated in situ by resonant photoemission spectroscopy for MnAs layer thickness of 1, 2, and 8 ML. Density of the valence band states of MnAs and its changes due to the increase in the layer thickness were revealed.
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| 7. |
- Laukkanen, P, et al.
(författare)
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Electronic and structural analysis of Sb-induced GaAs(100)(2x4) and (2x8) surfaces
- 2004
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 69:20
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Tidskriftsartikel (refereegranskat)abstract
- Electronic and structural properties of Sb-induced GaAs(100)(2x4) and (2x8) surfaces are studied by means of core-level and valence-band photoelectron spectroscopy utilizing synchrotron radiation and scanning tunneling microscopy. Combining these results and showing good consistency among them, we demonstrate that the Sb/GaAs(100)(2x4) surface is well compatible with the delta structural model, which includes one Sb dimer in both the first and third atomic layers and two second-layer Ga dimers per unit cell (i.e., the Sb coverage of 0.5 ML), giving experimental support to generality of the delta-type model for III-V(100)(2x4) surfaces, proposed previously on the basis of ab-initio calculations. Deconvolution of the Sb 4d core-level spectrum from the (2x4) surface shows two components, which are tentatively connected to two inequivalent Sb-dimer sites in the delta unit cell. Angle-resolved valence-band photoelectron spectroscopy reveals Sb-induced surface-derived states at near 0.4 and 0.6 eV below the valence-band maximum (VBM) for the Sb/GaAs(100)(2x4) surface, which have not been found in earlier measurements. These two surface-derived features mapped along symmetry lines of the surface Brillouin zone are identified with previous electronic-structure calculations. The results are also compared to band-structure measurements of the As/GaAs(100)(2x4) surface found in the literature. For the Sb/GaAs(100)(2x8) surface, we propose a structural model which, in contrast to the recent model, obeys the electron counting rule and consists of Sb dimers in three atomic layers, showing the Sb coverage of 1.25 ML for the (2x8) surface. The Sb 4d core-level spectrum from this surface exhibits three components, which are discussed within the determined structural model. The valence-band measurements of the (2x8) surface propose a new Sb-induced surface state at near 0.5 eV below the VBM.
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| 8. |
- Mathieu, R., Svedlindh, P., Sadowski, J., Swiatek, K., Karlsteen, M., Kanski, J., Ilver, L.
(författare)
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Ferromagnetism and interlayer exchange coupling in short period (Ga,Mn)As/GaAs superlattices
- 2002
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Ingår i: Appl. Phys. Lett. 81, 3013.
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Tidskriftsartikel (refereegranskat)
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| 9. |
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| 10. |
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| 11. |
- Sadowski, J., et al.
(författare)
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Structural and magnetic properties of molecular beam epitaxy grown GaMnAs layers
- 2000
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 18:3, s. 1697-1700
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Tidskriftsartikel (refereegranskat)abstract
- GaMnAs layers with Mn contents from 0.05% to 7% were grown by low temperature molecular beam epitaxy. At substrate temperatures lower than 300 degrees C and in this composition range a uniform ternary GaMnAs compound can be grown without MnAs precipitation. Reflection high energy electron diffraction intensity oscillations recorded during GaMnAs growth were used to calibrate the composition of the GaMnAs films with high accuracy (better than 0.1%). Films containing more than 1% Mn exhibit a ferromagnetic phase transition with Curie temperatures from a few up to 70 K depending on the composition and other growth parameters. In contrast to previous reports we have observed this transition also in the case of layers grown at very low substrate temperatures (below 300 degrees C).
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| 12. |
- Szuszkiewicz, W, et al.
(författare)
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Short-period GaMnAs/GaAs superlattices: Optical and magnetic characterization
- 2003
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Ingår i: Journal of Superconductivity (Proceedings of the PASPS Conference held July 2002 in Würzburg, Germany). - 1572-9605 .- 0896-1107. ; 16:1, s. 209-212
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Konferensbidrag (refereegranskat)abstract
- Superlattices with magnetic layers containing from 8 to 16 GaMnAs monolayers corresponding to the mixed crystal composition between 5 and 6% of Mn and from 4 to 10 GaAs monolayers were grown by the low temperature MBE technique and characterized by Raman scattering. Folded acoustic phonons were observed for all superlattices in the Raman scattering spectra. The interlayer exchange coupling, found previously by the wide-angle neutron diffraction in selected superlattices was investigated by the spin-polarized neutron reflectometry. It was always of ferromagnetic type, no trace of antiferromagnetic coupling was found.
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| 13. |
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| 14. |
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