| 1. |
- Hägg, Sara, et al.
(författare)
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Molecular Phenotypes of Coronary Artery Disease : The Stockholm Atherosclerosis Gene Expression (STAGE) Study
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- BACKGROUNDBy offering a comprehensive view of the molecular underpinnings of pathology, high-dimensional data have the potential to revolutionize the diagnosis and management of complex disorders such as coronary artery disease (CAD). To identify molecular phenotypes of CAD, we performed multi organ gene expression profiling of subjects enrolled in the Stockholm Atherosclerosis Gene Expression (STAGE) study.METHODSAtherosclerotic and unaffected arterial wall, liver, skeletal muscle, and mediastinal fat biopsies were obtained during coronary artery bypass grafting from 114 well-characterized CAD patients. RNA samples were isolated, and 278 transcription profiles were obtained using Affymetrix HG-U133_Plus_2 GeneChips.RESULTSThe most prominent molecular phenotype of the CAD patients was represented by 733 genes in mediastinal fat, which were involved in extracellular matrix organization, response to stress and regulation of programmed cell death. Other aspects of this phenotype were shared with liver (e.g., oxidoreductase activity), skeletal muscle (insulin-like growth factor binding), and atherosclerotic arterial wall (cell motility and adhesion, fatty acid metabolism). In addition, the activity of 400 genes exclusively in mediastinal fat was associated with the extent of coronary stenosis and atherosclerosis. Immune-cell activation in mediastinal fat defined CAD patients with poor blood glucose control and prolonged hospitalization.CONCLUSIONSThe molecular phenotype of mediastinal fat appears to be central in CAD and should be useful for early identification of CAD risk.
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| 2. |
- Moubah, Reda, et al.
(författare)
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Origin of the anomalous temperature dependence of coercivity in soft ferromagnets
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 116:5
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Tidskriftsartikel (refereegranskat)abstract
- We report on the origin of the anomalous temperature dependence of coercivity observed in some soft ferromagnets by studying the magnetic and electronic properties of FeZr films doped using ion implantation by H, He, B, C, and N. The anomalous increase of the coercivity with temperature was observed only in the C- and B-doped samples. Using x-ray photoelectron spectroscopy, we show that the anomalous behavior of the coercivity coincides with the occurrence of an electron charge transfer for those implanted samples. The origin of the anomaly is discussed in terms of (i) magnetic softness, (ii) nature of the Fe-C and -B covalent bonds, and (iii) large charge transfer.
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| 3. |
- Moubah, Reda, et al.
(författare)
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Soft Room-Temperature Ferromagnetism of Carbon-Implanted Amorphous Fe93Zr7 Films
- 2013
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Ingår i: APPL PHYS EXPRESS. - : Japan Society of Applied Physics. - 1882-0778. ; 6:5, s. 053001-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the effect of carbon implantation on the structural, electronic, and magnetic properties of Fe93Zr7 (FeZr) amorphous films. Extended X-ray absorption fine structure measurements on (FeZr)(100-x)C-x (x = 0, 5.5, and 11) indicate the incorporation of carbon in the FeZr matrix, with an increase of the Fe-Fe distance by implanting carbon. X-ray photoelectron spectroscopy measurements reveal the creation of Fe-C bonds after implantation. A significant enhancement of the Curie temperature and decrease of the coercivity are observed in the carbon-implanted films. Moreover, the non collinear ferromagnetism of the as-grown FeZr film diminishes upon carbon implantation.
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| 4. |
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| 5. |
- Razpet, A., et al.
(författare)
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Fabrication of high-density ordered nanoarrays in silicon dioxide by MeV ion track lithography
- 2005
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 97:4
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembled nanoporous alumina films were employed as masks for MeV ion track lithography. Films with thickness of 2 mum and pore diameters of 30 and 70 nm were attached to thermally grown SiO2 covered with a thin gold layer. The samples were aligned with respect to the beam by detecting backscattered He+ ions with the initial energy of 2 MeV. The ordered pattern of the porous alumina films was successfully transferred into SiO2 after irradiation with a 4 MeV Cl2+ beam at fluence of 10(14) ions/cm(2), followed by chemical etching in a 5% HF solution.
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| 6. |
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| 7. |
- Razpet, A., et al.
(författare)
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Ion transmission and characterization of ordered nanoporous alumina
- 2004
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; B:222, s. 593-600
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Tidskriftsartikel (refereegranskat)abstract
- Ordered nanoporous alumina samples with a pore diameter of 70 nm, an array period of 100 nm and several thicknesses were considered as possible masks for pattern transfer by MeV ion lithography. A simple procedure for the sample alignment using a 2 MeV He+ beam was utilized. The energy distributions of transmitted ions as well as backscattering spectra were studied in aligned and non-aligned orientations. The best transmission, comparable to the relative surface area covered by pores, was reached for 2 mum thick samples and was independent on ion species. Although the transmission for thicker membranes was generally lower, it significantly depended on the quality of each individual sample. The presented ion beam technique can therefore be used as a tool for the characterization of porous materials. The acceptance angle for transmission through pores and the effective atomic density of samples can be obtained from the experimental data and it is shown that nanoporous alumina can be used as a mask for MeV ion lithography.
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| 8. |
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| 9. |
- Rubel, Marek, et al.
(författare)
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Metallic mirrors for plasma diagnosis in current and future reactors : tests for ITER and DEMO
- 2017
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Ingår i: Physica Scripta. - : IOP PUBLISHING LTD. - 0031-8949 .- 1402-4896. ; T170
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Tidskriftsartikel (refereegranskat)abstract
- Optical spectroscopy and imaging diagnostics in next-step fusion devices will rely on metallic mirrors. The performance of mirrors is studied in present-day tokamaks and in laboratory systems. This work deals with comprehensive tests of mirrors: (a) exposed in JET with the ITER-like wall (JET-ILW); (b) irradiated by hydrogen, helium and heavy ions to simulate transmutation effects and damage which may be induced by neutrons under reactor conditions. The emphasis has been on surface modification: deposited layers on JET mirrors from the divertor and on near-surface damage in ion-irradiated targets. Analyses performed with ion beams, microscopy and spectro-photometry techniques have revealed: (i) the formation of multiple co-deposited layers; (ii) flaking-off of the layers already in the tokamak, despite the small thickness (130-200 nm) of the granular deposits; (iii) deposition of dust particles (0.2-5 mu m, 300-400 mm(-2)) composed mainly of tungsten and nickel; (iv) that the stepwise irradiation of up to 30 dpa by heavy ions (Mo, Zr or Nb) caused only small changes in the optical performance, in some cases even improving reflectivity due to the removal of the surface oxide layer; (v) significant reflectivity degradation related to bubble formation caused by the irradiation with He and H ions.
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| 10. |
- Aberg, D., et al.
(författare)
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Nitrogen deactivation by implantation-induced defects in 4H-SiC epitaxial layers
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:19, s. 2908-2910
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Tidskriftsartikel (refereegranskat)abstract
- Ion implantation causes free charge carrier reduction due to damage in the crystalline structure. Here, nitrogen-doped 4H silicon carbide (n type) epitaxial layers have been investigated using low ion doses in order to resolve the initial stage of the charge carrier reduction. It was found that the reduction of free carriers per ion-induced vacancy increases with increasing nitrogen content. Nitrogen is suggested to be deactivated through reaction with migrating point defects, and silicon vacancies or alternatively interstitials are proposed as the most likely candidates.
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| 11. |
- Aberg, D., et al.
(författare)
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Nitrogen passivation by implantation-induced point defects in 4H-SiC epitaxial layers
- 2001
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 184:04-jan, s. 263-267
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Tidskriftsartikel (refereegranskat)abstract
- Ion implantation causes damage to the crystal lattice resulting in the loss of free charge carriers. In this study, low dose implantations using different ions and implantation doses are made to resolve the initial carrier loss in nitrogen-doped epitaxial layers. A strong dependence of compensation on nitrogen concentration is seen, showing that nitrogen is passivated by implantation-induced point defects. An activation energy of 3.2 eV for the dissociation of the passivated nitrogen center is obtained.
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| 12. |
- Akner, Gunnar, 1953-, et al.
(författare)
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Vi står gärna bakom en utfallsbaserad vård
- 2017
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Ingår i: Dagens Samhälle. - 1652-6511.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Jörgen Nordenström försöker få det till att vår kritik av värdebaserad vård egentligen handlar om att vi vill ha mer resurser. Han har helt missuppfattat oss, skriver 26 specialistläkare i en replik.
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| 13. |
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| 14. |
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| 15. |
- Alfieri, G., et al.
(författare)
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Defect energy levels in hydrogen-implanted and electron-irradiated n-type 4H silicon carbide
- 2005
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 98:11
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Tidskriftsartikel (refereegranskat)abstract
- Using deep level transient spectroscopy (DLTS), we have studied the energy position and thermal stability of deep levels in nitrogen doped 4H-SiC epitaxial layers after 1.2 MeV proton implantation and 15 MeV electron irradiation. Isochronal annealing was performed at temperatures from 100 to 1200 degrees C in steps of 50 degrees C. The DLTS measurements, which were carried out in the temperature range from 120 to 630 K after each annealing step, reveal the presence of ten electron traps located in the energy range of 0.45-1.6 eV below the conduction band edge (E-c). Of these ten levels, three traps at 0.69, 0.73, and 1.03 eV below E-c, respectively, are observed only after proton implantation. Dose dependence and depth profiling studies of these levels have been performed. Comparing the experimental data with computer simulations of the implantation and defects profiles, it is suggested that these three new levels, not previously reported in the literature, are hydrogen related. In particular, the E-c-0.73 eV level displays a very narrow depth distribution, confined within the implantation profile, and it originates most likely from a defect involving only one H atom.
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| 16. |
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| 17. |
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| 18. |
- Audren, A., et al.
(författare)
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Damage recovery in the oxygen sublattice of ZnO by post-implantation annealing
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 272, s. 418-421
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Tidskriftsartikel (refereegranskat)abstract
- Hydrothermally grown zinc oxide bulk samples were implanted with 200 key-Co ions with a fluence of 4.5 x 10(16) cm(-2) and then annealed in air during 30 min at different temperatures up to 900 degrees C. After the implantation and each annealing step, the samples were analyzed using the nuclear reaction O-16(alpha,alpha)O-16 at 3.045 MeV He in random and channeling directions to follow the annealing of the disorder profile in the O sublattice. For comparison, the disorder in the Zn sublattice was also observed by Rutherford backscattering spectrometry (RBS) in random and channeling directions. The results reveal that the disorder created during the Co implantation is slightly higher in the O sublattice than in the Zn sublattice. The disorder recovery induced by the thermal treatments, starts at 500 degrees C in the O sublattice and at 700 degrees C in the Zn sublattice. Although, the most part of the disorder recovery occurs between 700 and 800 degrees C in both sublattices.
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| 19. |
- Audren, A., et al.
(författare)
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Damage recovery in ZnO by post-implantation annealing
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 268:11-12, s. 1842-1846
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- ZnO bulk samples were implanted with 200 key-Co ions at room temperature with two fluences, 1 x 10(16) and 8 x 10(16) cm(-2), and then annealed in air for 30 min at different temperatures up to 900 degrees C. After the implantation and each annealing step, the samples were analyzed by Rutherford backscattering spectrometry (RBS) in random and channeling directions to follow the evolution of the disorder profile. The RBS spectra reveal that disorder is created during implantation in proportion to the Co fluence. The thermal treatments induce a disorder recovery, which is however, not complete after annealing at 900 degrees C, where about 15% of the damage remains. To study the Co profile evolution during annealing, the samples were, in addition to RBS, characterized by secondary ion mass spectrometry (SIMS). The results show that Co diffusion starts at 800 degrees C, but also that a very different behavior is seen for Co concentrations below and above the solubility limit. (C) 2010 Elsevier B.V. All rights reserved.
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| 20. |
- Ayedh, H. M., et al.
(författare)
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Carbon vacancy control in p(+)-n silicon carbide diodes for high voltage bipolar applications
- 2021
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 54:45
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Tidskriftsartikel (refereegranskat)abstract
- Controlling the carbon vacancy (V-C) in silicon carbide (SiC) is one of the major remaining bottleneck in manufacturing of high voltage SiC bipolar devices, because V-C provokes recombination levels in the bandgap, offensively reducing the charge carrier lifetime. In literature, prominent V-C evolutions have been measured by capacitance spectroscopy employing Schottky diodes, however the trade-offs occurring in the p(+)-n diodes received much less attention. In the present work, applying similar methodology, we showed that V-C is re-generated to its unacceptably high equilibrium level at similar to 2 x10(13) V-C cm(-3) by 1800 degrees C anneals required for the implanted acceptor activation in the p(+)-n components. Nevertheless, we have also demonstrated that the V-C eliminating by thermodynamic equilibrium anneals at 1500 degrees C employing carbon-cap can be readily integrated into the p(+)-n components fabrication resulting in <= 10(11) V-C cm(-3), potentially paving the way towards the realization of the high voltage SiC bipolar devices.
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| 21. |
- Ayedh, H. M., et al.
(författare)
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Controlling the carbon vacancy concentration in 4H-SiC subjected to high temperature treatment
- 2016
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Ingår i: 16th International Conference on Silicon Carbide and Related Materials, ICSCRM 2015. - : Trans Tech Publications. - 9783035710427 ; , s. 414-417
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Konferensbidrag (refereegranskat)abstract
- The carbon vacancy (VC) is the major charge carrier lifetime limiting-defect in 4H-SiC epitaxial layers and it is readily formed during elevated heat treatments. Here we describe two ways for controlling the VC concentration in 4H-SiC epi-layer using different annealing procedures. One set of samples was subjected to high temperature processing at 1950 °C for 3 min, but then different cooling rates were applied. A significant reduction of the VC concentration was demonstrated by the slow cooling rate. In addition, elimination of the VC’s was also established by annealing a sample, containing high VC concentration, at 1500 °C for a sufficiently long time. Both procedures clearly demonstrate the need for maintaining thermodynamic equilibrium during cooling.
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| 22. |
- Ayedh, H. M., et al.
(författare)
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Controlling the carbon vacancy in 4H-SiC by thermal processing
- 2018
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Ingår i: ECS Transactions. - : Electrochemical Society Inc.. - 1938-6737 .- 1938-5862. ; , s. 91-97
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Konferensbidrag (refereegranskat)abstract
- The carbon vacancy (Vc) is perhaps the most prominent point defect in silicon carbide (SiC) and it is an efficient charge carrier lifetime killer in high-purity epitaxial layers of 4H-SÌC. The Vc concentration needs to be controlled and minimized for optimum materials and device performance, and an approach based on post-growth thermal processing under C-rich ambient conditions is presented. It utilizes thermodynamic equilibration and after heat treatment at 1500 °C for 1 h, the Vc concentration is shown to be reduced by a factor-25 relative to that in as-grown state-of-the-art epi-layers. Concurrently, a considerable enhancement of the carrier lifetime occurs throughout the whole of >40 urn thick epi-layers.
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| 23. |
- Ayedh, H. M., et al.
(författare)
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Elimination of carbon vacancies in 4H-SiC employing thermodynamic equilibrium conditions at moderate temperatures
- 2015
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 107:25
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Tidskriftsartikel (refereegranskat)abstract
- The carbon vacancy (VC) is a major point defect in high-purity 4H-SiC epitaxial layers limiting the minority charge carrier lifetime. In layers grown by chemical vapor deposition techniques, the VC concentration is typically in the range of 1012cm-3, and after device processing at temperatures approaching 2000 °C, it can be enhanced by several orders of magnitude. In the present study, both as-grown layers and a high-temperature processed one have been annealed at 1500 °C and the VC concentration is demonstrated to be strongly reduced, exhibiting a value of only a few times 1011cm-3 as determined by deep-level transient spectroscopy measurements. The value is reached already after annealing times on the order of 1 h and is evidenced to reflect thermodynamic equilibrium under C-rich ambient conditions. The physical processes controlling the kinetics for establishment of the VC equilibrium are estimated to have an activation energy below ∼3 eV and both in-diffusion of carbon interstitials and out-diffusion of VC’s are discussed as candidates. This concept of VC elimination is flexible and readily integrated in a materials and device processing sequence.
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| 24. |
- Ayedh, H. M., et al.
(författare)
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Elimination of carbon vacancies in 4H-SiC epi-layers by near-surface ion implantation : Influence of the ion species
- 2015
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 118:17
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Tidskriftsartikel (refereegranskat)abstract
- The carbon vacancy (VC) is a prevailing point defect in high-purity 4H-SiC epitaxial layers, and it plays a decisive role in controlling the charge carrier lifetime. One concept of reducing the VC-concentration is based on carbon self-ion implantation in a near surface layer followed by thermal annealing. This leads to injection of carbon interstitials (Ci's) and annihilation of VC's in the epi-layer "bulk". Here, we show that the excess of C atoms introduced by the self-ion implantation plays a negligible role in the VC annihilation. Actually, employing normalized implantation conditions with respect to displaced C atoms, other heavier ions like Al and Si are found to be more efficient in annihilating VC's. Concentrations of VC below ∼2 × 1011 cm-3 can be reached already after annealing at 1400 °C, as monitored by deep-level transient spectroscopy. This corresponds to a reduction in the VC-concentration by about a factor of 40 relative to the as-grown state of the epi-layers studied. The negligible role of the implanted species itself can be understood from simulation results showing that the concentration of displaced C atoms exceeds the concentration of implanted species by two to three orders of magnitude. The higher efficiency for Al and Si ions is attributed to the generation of collision cascades with a sufficiently high energy density to promote Ci-clustering and reduce dynamic defect annealing. These Ci-related clusters will subsequently dissolve during the post-implant annealing giving rise to enhanced Ci injection. However, at annealing temperatures above 1500 °C, thermodynamic equilibrium conditions start to apply for the VC-concentration, which limit the net effect of the Ci injection, and a competition between the two processes occurs.
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| 25. |
- Ayedh, H. M., et al.
(författare)
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Formation and annihilation of carbon vacancies in 4H-SiC
- 2016
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Ingår i: 16th International Conference on Silicon Carbide and Related Materials, ICSCRM 2015. - : Trans Tech Publications. - 9783035710427 ; , s. 331-336
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Konferensbidrag (refereegranskat)abstract
- The carbon vacancy (VC) is a major point defect in high-purity 4H-SiC epitaxial layers limiting the minority charge carrier lifetime. In layers grown by chemical vapor deposition techniques, the VC concentration is typically in the range of 1012 cm-3 and after device processing at temperatures approaching 2000 °C, it can be enhanced by several orders of magnitude. In the present contribution, we show that the cooling rate after high-temperature processing has a profound influence on the resulting VC concentration where a slow rate promotes elimination of VC. Further, isochronal annealing of as-grown and as-oxidized epi-layers protected by a carbon-cap was undertaken between 800 °C and 1600 °C. The results reveal that thermodynamic equilibrium of VC is established rather rapidly at moderate temperatures, reaching a VC concentration of only a few times 1011 cm-3 after 40 min at 1500 °C. Hence, the concept of eliminating VC’s by annealing at moderate temperatures under C-rich equilibrium conditions shows great promise and enables reannealing of high-temperature processed wafers, in contrast to the procedures commonly used today to eliminate VC. In-diffusion of carbon interstitials and out-diffusion of VC’s are discussed as the kinetics processes establishing the thermodynamic equilibrium.
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