| 1. |
- Adell, Johan, et al.
(författare)
-
Formation of epitaxial MnBi layers on (Ga,Mn)As
- 2009
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121 .- 2469-9950 .- 2469-9969. ; 80:7
-
Tidskriftsartikel (refereegranskat)abstract
- The initial growth of MnBi on MnAs-terminated (GaMn)As is studied by means of synchrotron-based photoelectron spectroscopy. From analysis of surface core-level shifts we conclude that a continued epitaxial MnBi layer is formed, in which the MnAs/MnBi interface occurs between As and Bi atomic planes. The well-defined 1×2 surface reconstruction of the MnAs surface is preserved for up to 2 ML of MnBi before clear surface degradation occurs. The MnBi layer appears to be free from intermixed As.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Laukkanen, P., et al.
(författare)
-
A comparative study of clean and Bi-stabilized InP(100)(2 x 4) surfaces by the core-level photoelectron spectroscopy
- 2007
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 601, s. 3395-
-
Tidskriftsartikel (refereegranskat)abstract
- The bismuth-stabilized (2 x 4)-reconstructed InP(100) surface [Bi/InP(100)(2 x 4)] has been studied by synchrotron-radiation core-level photoelectron spectroscopy. The spectra are compared with previous core-level data obtained on a clean InP(100)(2 x 4) surface. The findings support that the P 2p surface-core-level shift (SCLS) of the clean InP(100)(2 x 4), which has higher kinetic energy than the bulk emission, arises from the third-layer P atoms and that the second P 2p SCLS, which has lower kinetic energy than the bulk, arises from the top-layer P atoms. Similar In 4d SCLSs are found on the clean and Bi-stabilized InP(100)(2 x 4) surfaces, indicating that these shifts contain contributions of the In atoms that lie in the second and/or fourth layers. In addition to this, the results improve our understanding of the atomic structure of the Bi/InP(100)(2 x 4) surface and lead to refined surface models which include Bi-Bi and Bi-P dimers. (C) 2007 Elsevier B.V. All rights reserved.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Adell, Martin, et al.
(författare)
-
Postgrowth annealing of (Ga,Mn) As under As capping: An alternative way to increase T-C
- 2005
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 86, s. 112501-
-
Tidskriftsartikel (refereegranskat)abstract
- In situ postgrowth annealing of (Ga,Mn)As layers under As capping is adequate for achieving high Curie temperatures (T-C) in a similar way as ex situ annealing in air or in N-2 atmosphere practiced earlier. Thus, the first efforts give an increase of T-C from 68 to 145 K after 2 h annealing at 180 degrees C. These data, in combination with lattice parameter determinations and photoemission results, show that the As capping acts as an efficient sink for diffusing Mn interstitials.
|
|
| 8. |
|
|
| 9. |
- Adell, Martin, 1976
(författare)
-
Preparation and Characterization of the Magnetic Semiconductor (GaMn)As
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The diluted ferromagnetic semiconductor (GaMn)As has been grown by low temperature molecular beam epitaxy and the effects of post growth treatments on the electronic, magnetic and structural properties have been studied. In situ low temperature annealing of (GaMn)As layers has been performed. A clear correlation between annealing temperature and the Fermi level position of the annealed layers is found by photoelectron spectroscopy. The Curie temperature is also seen to depend on the position of the Fermi level as is expected from mean field Zener model according to which it is predicted that TC∝p1/3, where p is the density of of holes in the magnetic layer.After these first annealing experiments in vacuum, much of the efforts have been devoted to an alternative method of heat treatments utilizing an amorphous arsenic capping layer as an effective sink for diffusing Mn interstitial (MnI) atoms. These MnI defects are known to act as double donors and to form antiferromagnetically coupled complexes with the substitutional Mn (MnGa) atoms and thereby causing a deterioration of the ferromagnetic state. Thus, by removing MnI by the present annealing procedure TC and the saturation magnetization are found to be considerably enhanced after only short heat treatments, ~3h, at low temperatures, ~180ºC. This short annealing time is also found to give optimal improvement of the magnetic state of the (GaMn)As layers independently of layer thickness.Several different techniques have been used to characterize the modifications of (GaMn)As layers annealed under As-capping. XRD and Hall effect measurements have given direct evidences for that MnI defects are effectively removed from the (GaMn)As and that this process primarily occurs at a time scale of only a few hours after which the rate of change is considerably slowed down. The surface reaction between the diffusing Mn atoms and arsenic from the capping layer has also been thoroughly investigated by several synchrotron radiation based spectroscopic techniques as well as by microscopy such as AFM and MFM. It is found that the number of available defects, i.e. primarily the (GaMn)As layer thickness, determines the character of the annealed surface. Upon annealing, initially a monolayer of epitaxial MnAs will be formed at the (GaMn)As/As-caping interface as the MnI reach the interface. Further out diffusion of MnI will also occur after the formation of this MnAs layer and will result in self organized quantum dots at the (GaMn)As surface. However, this process is much slower than the initial reaction forming the continuous MnAs layer. Keywords: UPS, XAS, Magnetic Semiconductor, (GaMn)As.
|
|
| 10. |
|
|
| 11. |
- Eriksson, Jenny, 1975-, et al.
(författare)
-
Intressent- och behovsanalys för resvaneundersökningar : resultat från intervjuer och enkätundersökning
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I Sverige genomförs en nationell resvaneundersökning med viss regelbundenhet med Trafikanalys som ansvarig myndighet. Undersökningen har problem med bortfall, täckning, kostnader och uppgiftslämnarbörda. Ett projekt pågår som syftar till att utveckla nya metoder för att samla in data om personers mobilitet. Projektet är indelat i fem arbetspaket, varav detta arbete är ett. Syftet är att utföra en intressent- och behovsanalys avseende framtida resvaneundersökningar. I detta ingår att identifiera syften och frågeställningar som resvaneundersökningar ska kunna hantera och besvara.Det genomfördes 20 telefonintervjuer och utskick av webbenkät till 142 personer (svar från 81 personer, svarsfrekvens 57 procent). Intressenterna delades in i tre olika grupper: offentlig sektor, forskningsorganisation och övriga aktörer. Tillsammans med egna erfarenheter har en analys gjorts av vad som efterfrågas från den nationella resvaneundersökningen. Frågeställningar som centrala för användare av resvaneundersökningar är val av färdsätt, resans ärende samt mått på hur resvanorna förändras över tid och hur olika grupper reser. För detta behövs både uppgifter om individen och resorna. Utöver detta önskar man bra data på kommunal nivå eller lägre. Dock kan Trafikanalys i nuläget inte erbjuda den möjligheten, men här finns det möjlighet för kommuner, regioner och andra aktörer att välja ett extraurval från den befintliga nationella resvaneundersökningen.
|
|
| 12. |
- Eriksson, Johan, 1979-, et al.
(författare)
-
Origin of a surface state above the Fermi level on Ge(001) and Si(001) studied by temperature-dependent ARPES and LEED
- 2008
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 77:L8, s. 085406-1-085406-5
-
Tidskriftsartikel (refereegranskat)abstract
- Variable temperature photoemission studies in the literature have revealed the presence of a surface state above the Fermi level on clean Ge(001). We present photoemission and low energy electron diffraction results from Ge(001) obtained between 185 and 760 K. Our measurements show a peak above the Fermi level with a maximum intensity at a sample temperature of around 625 K. At higher temperatures, we observe a gradual decrease in the intensity. Angle resolved spectra show that the surface state has a k̅ ∥ dependence and is therefore not attributed to defects. Very similar results were obtained on both an intrinsic (30 Ω cm) and a 10 m Ω cm n-type sample. The overall appearance of the spectral feature is found to be quite insensitive to sample preparation. Low energy electron diffraction investigations show how the sharp c(4×2) pattern becomes streaky and finally turns into a 2×1 pattern. The onset of the structure above the Fermi level takes place just before all c(4×2) streaks have disappeared which corresponds to a temperature of around 470 K. On Si(001), we also observe photoemission intensity above the Fermi level. It is weaker than on Ge(001) and appears at higher temperature. We find that the emission above the Fermi level can be explained by thermal occupation of the π* band derived from a 2×1 ordering of asymmetric dimers on the surface.
|
|
| 13. |
- Glover, C. J., et al.
(författare)
-
Stationary and dispersive features in resonant inelastic soft X-ray scattering at the Ge 3p resonances
- 2009
-
Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 173:2-3, s. 103-107
-
Tidskriftsartikel (refereegranskat)abstract
- Resonant inelastic soft X-ray scattering at the 3p resonances in crystalline Ge is presented. Both stationary and dispersive features are observed in a wide energy range above as well as below the ionization limits. These observations are in agreement with theoretical predictions based on a two-step model where the initially excited electron has no influence on the emission step. Excess population of states in the conduction band is found, and discussed in terms of attosecond electron dynamics. (c) 2009 Elsevier B.V. All rights reserved.
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
- Kowalik, I. A., et al.
(författare)
-
MnAs dots grown on GaN( 000(1)over-bar)-(1x1) surface
- 2007
-
Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969 .- 1098-0121. ; 75:23, s. 11-
-
Tidskriftsartikel (refereegranskat)abstract
- MnAs has been grown by means of MBE on the GaN(000 (1) over bar)-(1x1) surface. Two options of initiating the crystal growth were applied: (a) a regular MBE procedure (manganese and arsenic were delivered simultaneously) and (b) subsequent deposition of manganese and arsenic layers. It was shown that spontaneous formation of MnAs dots with the surface density of 1x10(11) cm(-2) and 2.5x10(11) cm(-2), respectively (as observed by atomic force microscopy), occurred for the layer thickness higher than 5 ML. Electronic structure of the MnAs/GaN systems was studied by resonant photoemission spectroscopy. That led to determination of the Mn 3d-related contribution to the total density of states distribution of MnAs. It has been proven that the electronic structures of the MnAs dots grown by the two procedures differ markedly. One corresponds to metallic, ferromagnetic NiAs-type MnAs, the other is similar to that reported for half-metallic zinc-blende MnAs. Both systems behave superparamagnetically (as revealed by magnetization measurements), but with both the blocking temperatures and the intradot Curie temperatures substantially different. The intradot Curie temperature is about 260 K for the former system while markedly higher than room temperature for the latter one. Relations between growth process, electronic structure, and other properties of the studied systems are discussed. Possible mechanisms of half-metallic MnAs formation on GaN are considered.
|
|
| 17. |
- Kuzmin, M., et al.
(författare)
-
Atomic and electronic structure of the Yb/Ge(111)-(3x2) surface studied by high-resolution photoelectron spectroscopy
- 2007
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 75
-
Tidskriftsartikel (refereegranskat)abstract
- Using high-resolution synchrotron-radiation photoelectron spectroscopy and low-energy electron diffraction, we have studied the electronic and structural properties of the Yb-induced Ge(111)-(3x2) reconstruction with a 1/6 monolayer coverage. We found these properties to be similar in many respects to those of the metal-induced Si(111) and Ge(111) reconstructions described previously in terms of the honeycomb chain-channel (HCC) structure. In particular, the Yb/Ge(111)-(3x2) is revealed to have a semiconducting character, the Yb atoms are divalent, and the surface states observed for the Yb/Ge(111) closely resemble those of the Na/Ge(111)-(3x1) in the literature. The Ge 3d core-level analysis, however, shows that the Ge 3d spectra from Yb/Ge(111)-(3x2) drastically differ from corresponding spectra of other Si and Ge HCC reconstructions. An atomic model, based on the general HCC geometry, is proposed for the Yb/Ge(111)-(3x2) surface. In this model, the important structural aspects are a buckling of the Ge = Ge double bond in the top, HCC-reconstructed layer plus a strong rearrangement of the second-layer atoms.
|
|
| 18. |
|
|
| 19. |
- Ottenklev, Fredrik, et al.
(författare)
-
Non-monotonic evolution of surface roughness in a stainless steel during cold deformation
- 2021
-
Ingår i: Materials Science and Engineering A. - : Elsevier BV. - 0921-5093. ; 799
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, polished and unpolished sheet samples of austenitic stainless steel 316L were tensile strained to investigate the evolution of surface roughness based on Sa- and Ra characteristics. In polished steel sheets, surface roughness increases with the increase of true strain up to a maximum of e = 0.14. Thereafter, roughness decreases until e = 0.26 for approximately 25%, and then becomes independent on strain. The highest roughness levels are found to be localised primarily around surface grain boundaries. The roughness-strain correlation can be explained by grain rotation and cross-slip. Unpolished sheets demonstrate near-linear relationship between tensile strain and surface roughening due to the presence of an oxide layer. The layer has a thickness of approximately 1 μm with a morphology resembling the microstructure in the substrate. When strained, it appears to show two roughness components. First one is a shortwave component originating at the oxide grain boundaries, which is believed to be produced by the rotation of underlying grains. The second one is a longwave component, which is generated by the fracture of oxide layer due to lower ductility. The slope of roughness – true strain relationship is found to be also grain orientation-dependent.
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
|
|
| 23. |
|
|
