| 1. |
- 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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| 2. |
- Agui, A., et al.
(författare)
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Direct observation of interface effects of thin AlAs(100) layers buried in GaAs
- 2000
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 166:1-4, s. 309-312
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Tidskriftsartikel (refereegranskat)abstract
- A study of the electronic structure of ultrathin AlAs layers buried in GaAs(100) and their interfaces is presented. Al L2,3 soft-X-ray-emission (SXE) spectra from the AlAs layers were measured. The spectra show distinct thickness-dependent features, which are reproduced using ab initio calculations.
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| 3. |
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| 4. |
- Mankefors, S., et al.
(författare)
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Theoretical investigation of the thickness dependence of soft-x-ray emission from thin AlAs(100) layers buried in GaAs
- 2000
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 61:8, s. 5540-5545
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Tidskriftsartikel (refereegranskat)abstract
- Ultrathin AlAs(100) layers of 1-, 2-, and 5-ML thickness buried in GaAs are investigated by ab initio calculations. Unique experimental soft-x-ray emission spectra are explained in terms of interface effects and changes with layer thickness are found in the density of states. Only the central layer in the 5-ML geometry is bulklike. A valence-band offset of 0.53 eV is also found for this structure, while no offset exists in the 1- and 2-ML cases. Very good agreement is achieved between theory and experiment.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Agui, A, et al.
(författare)
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Direct observation of interface effects of thin AlAs(100) layers buried in GaAs
- 2000
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Ingår i: APPLIED SURFACE SCIENCE. - : ELSEVIER SCIENCE BV. - 0169-4332. ; 166:1-4, s. 309-312
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Tidskriftsartikel (refereegranskat)abstract
- A study of the electronic structure of ultrathin AlAs layers buried in GaAs(100) and their interfaces is presented. Al L-2,L-3 soft-X-ray-emission (SXE) spectra from the AlAs layers were measured. The spectra show distinct thickness-dependent features, wh
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| 9. |
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| 10. |
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| 11. |
- Mathieu, R., Sørensen, B.S., Sadowski, J., Södervall, U., Kanski, J., Svedlindh, P., Lindelof, P.E., Hrabovsky, D. and Vanelle, E.
(författare)
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Magnetization of ultrathin (Ga,Mn)As layers
- 2003
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Ingår i: Phys. Rev. B 68, 184421 (2003)..
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Tidskriftsartikel (refereegranskat)
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| 12. |
- 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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| 13. |
- Mikkelsen, Anders, et al.
(författare)
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A study of the surface structure and composition of annealed Ga0.96Mn0.04As(100)
- 2004
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Ingår i: Applied Surface Science. - 1873-5584. ; 222:1-4, s. 23-32
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Tidskriftsartikel (refereegranskat)abstract
- The surface structure and chemical composition of annealed Ga0.96Mn0.04As(1 0 0) have been studied by scanning tunneling microscopy (STM), auger electron spectroscopy (AES) and low energy electron diffraction (LEED). The samples were As capped and subsequently transferred in-air from the MBE system to the STM chamber. After annealing to 600 K it is found that the Mn segregates to the surface and forms a compound, which is stable up to annealing temperatures of 790 K. For annealing temperatures above 825 K a well-ordered phase exists signified by a LEED pattern consisting of a superposition of a (1 x 6) and a (4 x 2) pattern. LEED and STM measurements demonstrate that the surface is dominated by (1 x 6) domains coexisting with small patches of (4 x 2) domains. By comparing the STM images of the high temperature phase found on Ga0.96Mn0.04As(1 0 0) with the high temperature phases found on ordinary GaAs(1 0 0), we demonstrate differences between annealed Ga0.96Mn0.04As(1 0 0) and GaAs(1 0 0) in both surface morphology and atomic structure. We argue that the Ga0.96Mn0.04As surface is more As rich than the GaAs surface prepared in a similar fashion. Reasons for these differences are discussed.
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| 14. |
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| 15. |
- 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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| 16. |
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| 17. |
- 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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| 18. |
- Kowalski, BJ, et al.
(författare)
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Surface states on GaN(000(1)over-bar)(1x1) - an angle-resolved photoemission study
- 2002
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Ingår i: Surface Science. - 0039-6028. ; 507, s. 186-191
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of angle-resolved photoemission studies on the (0 0 0 (1) over bar) (N-polar) surface of bulk gallium nitride crystals. The bulk and surface band Structure was investigated along Gamma-A and Gamma-K-M directions on the surface with (1 x 1) symmetry. The sets of spectra were obtained in normal and off-normal emission for the surface prepared by Ar+ ion sputtering and annealing and for the same surface enriched with Ga under molecular beam epitaxy conditions. The bulk and surface related features were identified by analysis of the acquired experimental data and by comparison with the results of band structure Calculations.
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| 19. |
- Mathieu, R, et al.
(författare)
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Magnetization of ultrathin (Ga,Mn)As layers
- 2003
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 68:18: 184421
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Tidskriftsartikel (refereegranskat)abstract
- Kerr rotation and superconducting quantum interference device magnetometry measurements were performed on ultrathin (Ga0.95Mn0.05)As layers. The thinner layers (below 250 A) exhibit magnetic properties different than those of thicker ones, associated with different microstructure, and some degree of inhomogeneity. The temperature dependence of the field-cooled magnetization of the layers is recorded after successive low temperature annealings. While the Curie temperature of the thicker layer (250 A) is nearly unchanged, the critical temperature of the thinner layers is enhanced by more than 23 K after two annealings. Secondary ion mass spectrometry experiments on similar layers show that Mn is displaced upon annealing. The results are discussed considering a possible segregation of substitutional and interstitial Mn atoms at the surface of the (Ga,Mn)As layers.
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| 20. |
- Mikkelsen, Anders, et al.
(författare)
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Defect structure of Ga1-xMnxAs: A cross-sectional scanning tunneling microscopy study
- 2004
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 70:8
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the atomic scale structure of molecular beam epitaxy grown Ga1-xMnxAs compounds with various Mn concentrations by cross-sectional scanning tunneling microscopy and first principles calculations. Only bright protrusions close to the top layer As atoms are directly correlated with the bulk Mn concentration. Atomically resolved filled and empty states images of this defect are compared to images derived from first principles calculations. We identify the Mn related defect as substitutional Mn in the second layer Ga site. Surprisingly no substitutional Mn is observed in the top-most Ga layer. The experimental results are consistent with the energetics of our first principles total energy calculations.
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| 21. |
- Suchodolskis, Arturas, et al.
(författare)
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Photoemission studies of Mg and Rb layers on Zn(0001)
- 2004
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 137-40, s. 189-192
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the clean Zn(0 0 0 1) surface is studied by angle resolved photoemission. An earlier detected surface state at the surface Brillouin zone centre is confirmed and a new surface state is found at the surface Brilluoin zone boundary. The surface electronic structure of Zn is found to be similar to the that of Cd. Evaporation of thin films of Mg and Rb onto the Zn(0 0 0 1) surface quenches the emission from both surface states and reduces the intensity of the bulk related structures.
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