| 1. |
- Rajewsky, N., et al.
(författare)
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LifeTime and improving European healthcare through cell-based interceptive medicine
- 2020
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 587:7834, s. 377-386
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Tidskriftsartikel (refereegranskat)abstract
- LifeTime aims to track, understand and target human cells during the onset and progression of complex diseases and their response to therapy at single-cell resolution. This mission will be implemented through the development and integration of single-cell multi-omics and imaging, artificial intelligence and patient-derived experimental disease models during progression from health to disease. Analysis of such large molecular and clinical datasets will discover molecular mechanisms, create predictive computational models of disease progression, and reveal new drug targets and therapies. Timely detection and interception of disease embedded in an ethical and patient-centered vision will be achieved through interactions across academia, hospitals, patient-associations, health data management systems and industry. Applying this strategy to key medical challenges in cancer, neurological, infectious, chronic inflammatory and cardiovascular diseases at the single-cell level will usher in cell-based interceptive medicine in Europe over the next decade.
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| 2. |
- Callaway, EM, et al.
(författare)
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A multimodal cell census and atlas of the mammalian primary motor cortex
- 2021
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 598:7879, s. 86-102
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Tidskriftsartikel (refereegranskat)abstract
- Here we report the generation of a multimodal cell census and atlas of the mammalian primary motor cortex as the initial product of the BRAIN Initiative Cell Census Network (BICCN). This was achieved by coordinated large-scale analyses of single-cell transcriptomes, chromatin accessibility, DNA methylomes, spatially resolved single-cell transcriptomes, morphological and electrophysiological properties and cellular resolution input–output mapping, integrated through cross-modal computational analysis. Our results advance the collective knowledge and understanding of brain cell-type organization1–5. First, our study reveals a unified molecular genetic landscape of cortical cell types that integrates their transcriptome, open chromatin and DNA methylation maps. Second, cross-species analysis achieves a consensus taxonomy of transcriptomic types and their hierarchical organization that is conserved from mouse to marmoset and human. Third, in situ single-cell transcriptomics provides a spatially resolved cell-type atlas of the motor cortex. Fourth, cross-modal analysis provides compelling evidence for the transcriptomic, epigenomic and gene regulatory basis of neuronal phenotypes such as their physiological and anatomical properties, demonstrating the biological validity and genomic underpinning of neuron types. We further present an extensive genetic toolset for targeting glutamatergic neuron types towards linking their molecular and developmental identity to their circuit function. Together, our results establish a unifying and mechanistic framework of neuronal cell-type organization that integrates multi-layered molecular genetic and spatial information with multi-faceted phenotypic properties.
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| 3. |
- Savage, J. E., et al.
(författare)
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Genome-wide association meta-analysis in 269,867 individuals identifies new genetic and functional links to intelligence
- 2018
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Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 50:7, s. 912-919
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Tidskriftsartikel (refereegranskat)abstract
- Intelligence is highly heritable 1 and a major determinant of human health and well-being 2 . Recent genome-wide meta-analyses have identified 24 genomic loci linked to variation in intelligence 3-7, but much about its genetic underpinnings remains to be discovered. Here, we present a large-scale genetic association study of intelligence (n = 269,867), identifying 205 associated genomic loci (190 new) and 1,016 genes (939 new) via positional mapping, expression quantitative trait locus (eQTL) mapping, chromatin interaction mapping, and gene-based association analysis. We find enrichment of genetic effects in conserved and coding regions and associations with 146 nonsynonymous exonic variants. Associated genes are strongly expressed in the brain, specifically in striatal medium spiny neurons and hippocampal pyramidal neurons. Gene set analyses implicate pathways related to nervous system development and synaptic structure. We confirm previous strong genetic correlations with multiple health-related outcomes, and Mendelian randomization analysis results suggest protective effects of intelligence for Alzheimer's disease and ADHD and bidirectional causation with pleiotropic effects for schizophrenia. These results are a major step forward in understanding the neurobiology of cognitive function as well as genetically related neurological and psychiatric disorders.
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| 4. |
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| 5. |
- Bakken, TE, et al.
(författare)
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Comparative cellular analysis of motor cortex in human, marmoset and mouse
- 2021
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 598:7879, s. 111-
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Tidskriftsartikel (refereegranskat)abstract
- The primary motor cortex (M1) is essential for voluntary fine-motor control and is functionally conserved across mammals1. Here, using high-throughput transcriptomic and epigenomic profiling of more than 450,000 single nuclei in humans, marmoset monkeys and mice, we demonstrate a broadly conserved cellular makeup of this region, with similarities that mirror evolutionary distance and are consistent between the transcriptome and epigenome. The core conserved molecular identities of neuronal and non-neuronal cell types allow us to generate a cross-species consensus classification of cell types, and to infer conserved properties of cell types across species. Despite the overall conservation, however, many species-dependent specializations are apparent, including differences in cell-type proportions, gene expression, DNA methylation and chromatin state. Few cell-type marker genes are conserved across species, revealing a short list of candidate genes and regulatory mechanisms that are responsible for conserved features of homologous cell types, such as the GABAergic chandelier cells. This consensus transcriptomic classification allows us to use patch–seq (a combination of whole-cell patch-clamp recordings, RNA sequencing and morphological characterization) to identify corticospinal Betz cells from layer 5 in non-human primates and humans, and to characterize their highly specialized physiology and anatomy. These findings highlight the robust molecular underpinnings of cell-type diversity in M1 across mammals, and point to the genes and regulatory pathways responsible for the functional identity of cell types and their species-specific adaptations.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Syväjärvi, Mikael, et al.
(författare)
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Fluorescent SiC as a new material for white LEDs
- 2012
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Ingår i: Physica scripta. T. - 0281-1847 .- 0031-8949 .- 1402-4896. ; T148, s. 014002-
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Tidskriftsartikel (refereegranskat)abstract
- Current III–V-based white light-emitting diodes (LEDs) are available. However, their yellow phosphor converter is not efficient at high currents and includes rare-earth metals, which are becoming scarce. In this paper, we present the growth of a fluorescent silicon carbide material that is obtained by nitrogen and boron doping and that acts as a converter using a semiconductor. The luminescence is obtained at room temperature, and shows a broad luminescence band characteristic of donor-to-acceptor pair recombination. Photoluminescence intensities and carrier lifetimes reflect a sensitivity to nitrogen and boron concentrations. For an LED device, the growth needs to apply low-off-axis substrates. We show by ultra-high-resolution analytical transmission electron microscopy using aberration-corrected electrons that the growth mechanism can be stable and that there is a perfect epitaxial relation from the low-off-axis substrate and the doped layer even when there is step-bunching.
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| 12. |
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| 13. |
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| 14. |
- Achtziger, N, et al.
(författare)
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Formation of passivated layers in p-type SiC by low energy ion implantation of hydrogen
- 2000
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS - 1999 PTS, 1 & 2. ; , s. 933-936
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Konferensbidrag (refereegranskat)abstract
- The mobility of hydrogen and its passivating effect on accepters in p-type SiC is investigated. Hydrogen (isotope H-1 or H-2 alternatively) is implanted at temperatures between 300 K and 680 K with low energy (300 eV per atom) in order to minimize implantation damage. The depth profiles of 2H and of passivated accepters correspond closely. Up to 500 K, a fully passivated layer with a well defined thickness is formed. Its depth ton the order of 1 micrometer) is investigated as a function of doping level and hydrogen fluence. At higher temperatures, the incorporation drastically increases, but the electrical passivation is partial only. Qualitative explanations are given.
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| 15. |
- Achtziger, N, et al.
(författare)
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Hydrogen passivation of silicon carbide by low-energy ion implantation
- 1998
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 73, s. 945-947
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Tidskriftsartikel (refereegranskat)abstract
- implantation of deuterium is performed to investigate the mobility and passivating effect of hydrogen in epitaxial alpha-SiC (polytypes 4H and 6H). To avoid excessive damage and the resulting trapping of hydrogen, the implantation is performed with low energy (600 eV H-2(2)+). The H-2 depth profile is analyzed by secondary ion mass spectrometry. Electrical properties are measured by capacitance-voltage profiling and admittance spectroscopy. In p-type SIG, hydrogen diffuses on a mu m scale even at room temperature and effectively passivates accepters. In n-type SiC, the incorporation of H is suppressed and no passivation is detected. (C) 1998 American Institute of Physics.
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| 16. |
- Achtziger, N, et al.
(författare)
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Mobility passivating effect and thermal stability of hydrogen in silicon carbide
- 1998
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Ingår i: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 210, s. 395-399
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Tidskriftsartikel (refereegranskat)abstract
- The diffusion and passivating effect of hydrogen (isotope H-2) in epitaxial p-type SiC is studied by secondary ion mass spectrometry and capacitance-voltage profiling on Schottky diodes. The incorporation of hydrogen is achieved by low-energy ion implantation. The influence of implantation energy, temperature and subsequent annealing is presented. Annealing experiments with an electric field applied reveal a reactivation of passivated accepters and a H+ ion drift at a surprisingly low temperature of 530 K.
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| 17. |
- Grivickas, V., et al.
(författare)
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Carrier lifetimes and influence of in-grown defects in N-B Co-doped 6H-SiC
- 2014
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Ingår i: IOP Conference Series. - : Institute of Physics Publishing (IOPP). ; 56:1, s. 012004-
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Konferensbidrag (refereegranskat)abstract
- The thick N-B co-doped epilayers were grown by the fast sublimation growth method and the depth-resolved carrier lifetimes have been investigated by means of the free-carrier absorption (FCA) decay under perpendicular probe-pump measurement geometry. In some samples, we optically reveal in-grown carbon inclusions and polycrystalline defects of substantial concentration and show that these defects slow down excess carrier lifetime and prevent donor-acceptor pair photo luminescence (DAP PL). A pronounced electron lifetime reduction when injection level approaches the doping level was observed. It is caused by diffusion driven non-radiative recombination. However, the influence of surface recombination is small and insignificant at 300 K.
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| 18. |
- Hallén, Anders, et al.
(författare)
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Passivation of SiC device surfaces by aluminum oxide
- 2014
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Ingår i: IOP Conference Series. - 1757-8981 .- 1757-899X. ; 56:1, s. 012007-
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Tidskriftsartikel (refereegranskat)abstract
- A steady improvement in material quality and process technology has made electronic silicon carbide devices commercially available. Both rectifying and switched devices can today be purchased from several vendors. This successful SiC development over the last 25 years can also be utilized for other types of devices, such as light emitting and photovoltaic devices, however, there are still critical problems related to material properties and reliability that need to be addressed. This contribution will focus on surface passivation of SiC devices. This issue is of utmost importance for further development of SiC MOSFETs, which so far has been limited by reliability and low charge carrier surface mobilities. Also bipolar devices, such as BJTs, LEDs, or PV devices will benefit from more efficient and reliable surface passivation techniques in order to maintain long charge carrier lifetimes. Silicon carbide material enables the devices to operate at higher electric fields, higher temperatures and in more radiation dense applications than silicon devices. To be able to utilize the full potential of the SiC material, it is therefore necessary to develop passivation layers that can sustain these more demanding operation conditions. In this presentation it will also be shown that passivation layers of Al2O3 deposited by atomic layer deposition have shown superior radiation hardness properties compared to traditional SiO2-based passivation layers.
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| 19. |
- Janson, M., et al.
(författare)
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Dissociation of deuterium-defect complexes in ion-implanted epitaxial 4H-SiC
- 1998
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Ingår i: Materials Research Society Symposium - Proceedings. - San Francisco, CA, USA. ; , s. 439-444
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Konferensbidrag (refereegranskat)abstract
- Epitaxial layers of low doped 4H-SiC are implanted with 20 keV 2H+ ions to a dose of 1×1015 cm-2. The samples are subsequently annealed at temperatures ranging from 1040 to 1135 °C. Secondary ion mass spectrometry is used to obtain the concentration versus depth profiles of the atomic deuterium in the samples. It is found that the concentration of implanted deuterium decreases rapidly in the samples as a function of anneal time. The experimental data are explained by a model where the deuterium migrates rapidly and becomes trapped and de-trapped at implantation-induced defects which exhibit a slightly shallower depth distribution than the implanted deuterium ions. Computer simulations using this model, in which the damage profile is taken from Monte Carlo simulations and the surface is treated as a perfect sink for the diffusing deuterium atoms, are performed with good results compared to the experimental data. The complexes are tentatively identified as carbon-deuterium at a Si-vacancy and a dissociation energy (ED) of approximately 4.9 eV is extracted for the deuterium-vacancy complexes.
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| 20. |
- Janson, M S, et al.
(författare)
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Channeled implants in 6H silicon carbide
- 2000
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS - 1999 PTS, 1 & 2. ; , s. 889-892
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Konferensbidrag (refereegranskat)abstract
- Implants of MeV B-11, Al-27 and Ga-69 into the <0001> channel of 6H-SiC have been performed and concentration versus depth profiles have been obtained utilizing secondary ion mass spectrometry (SIMS). The experiment shows that the deepest channeled Ga ions reach a depth of 6.6 mum, which is 4 times deeper than the projected range of a random angle implantation, while the deepest channeled B ions only exceed the random projected range by 40%. Measurements at several implantation fluences show that implantation induced damage quench the deep channeling at fluences around 2 and 10x10(13) cm(-2) for Al and Ga, respectively, while only a minor fluence dependence is found in the B implants at fluences up to 2.6x10(14) cm(-2). The ion mass dependence of these effects is explained by the electronic to nuclear stopping ratios. Monte Carlo simulations of the channeling implants have also been performed and good agreements are found between simulations and experimental data.
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| 21. |
- Janson, M S, et al.
(författare)
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Diffusion of dopants and impurities in device structures of SiC, SiGe and Si
- 2001
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Ingår i: DIFFUSIONS IN MATERIALS. ; , s. 597-609
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Konferensbidrag (refereegranskat)abstract
- Silicon Carbide (SiC) has a high thermal stability and for most elements temperatures in excess of 2000 degreesC are anticipated to reach reasonable diffusivities (greater than or equal to 10(-13) cm(2)/s). We demonstrate, however, that light elements, like hydrogen and lithium, exhibit a considerable mobility already at less than or equal to 400 degreesC, Technologically, the principal interest in these light elements arises because of their ability to electrically passivate shallow acceptors and donors as well as deep level defects in common semiconductors (SiC, Si, GaAs). Indeed, for both hydrogen and lithium the diffusion kinetics is shown to be strongly affected by trapping and de-trapping at boron impurities in the SiC layers. Evidence is also provided that hydrogen migrates as a positively charged ion in p-type SiC. Furthermore, similar to that in crystalline silicon, transient enhanced diffusion of ion-implanted boron is observed in SiC. The initial boron diffusivity during postimplant annealing at 1600 degreesC is enhanced by more than two orders of magnitude compared to equilibrium conditions. For Silicon Germanium (SiGe) diffusion of the n-type dopants Sb and P is studied. Comparing results from strained and relaxed SiGe layers annealed under inert and oxidizing conditions it is unambiguously shown that the diffusion of Sb is almost exclusively mediated by vacancies. On the other hand, P diffusion is predominantly assisted by Si self-interstitials and in this case compositional and strain effects in the SiGe layers are competing.
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| 22. |
- Janson, M S, et al.
(författare)
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Range distributions of implanted ions in silicon carbide
- 2002
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2001, PTS 1 AND 2, PROCEEDINGS. ; , s. 779-782
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Konferensbidrag (refereegranskat)abstract
- The first four distribution moments (R-P, DeltaR(p), gamma and beta) of 113 experimental single energy ion implantations into silicon carbide (SiC) have been assembled to form the base for an empirical ion implantation simulator using Pearson frequency functions. The studied ions are H-1, H-2, Li-7, B-11, N-14, O-11, Al-27, P-31, and As-75, and the implantation energies range from 0.5 keV to 4 MeV. Thirty-nine of these implantations have been implanted, measured, and analyzed in the present study while the remaining implantation data were gathered from the literature. Furthermore, 16 additional implantations were simulated - using a new Binary Collision Approximation (BCA) code for crystalline materials - to fill up the missing energies for ions with limited experimental data. The extracted range data are presented as tabulated fitting constants to analytical functions of the distribution moments versus implantation energy.
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| 23. |
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| 24. |
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| 25. |
- Laube, M., et al.
(författare)
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Electrical activation of high concentrations of N+ and P+ ions implanted into 4H-SiC
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:1, s. 549-554
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Tidskriftsartikel (refereegranskat)abstract
- Comparative Hall effect investigations are conducted on N- and P-implanted as well as on (N+P)-coimplanted 4H-SiC epilayers. Box profiles with three different mean concentrations ranging from 2.5x10(18) to 3x10(20) cm(-3) to a depth of 0.8 mum are implanted at 500 degreesC into the (0001)-face of the initially p-type (Al-doped) epilayers. Postimplantation anneals at 1700 degreesC for 30 min are conducted to electrically activate the implanted N+ and P+ ions. Our systematic Hall effect investigations demonstrate that there is a critical donor concentration of (2-5)x10(19) cm(-3). Below this value, N- and P-donors result in comparable sheet resistances. The critical concentration represents an upper limit for electrically active N donors, while P donors can be activated at concentrations above 10(20) cm(-3). This high concentration of electrically active P donors is responsible for the observed low sheet resistance of 35 Omega/square, which is about one order of magnitude lower than the minimum sheet resistance achieved by N implantation.
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| 26. |
- Linnarsson, M K, et al.
(författare)
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Aluminum and boron diffusion in 4H-SiC
- 2003
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Ingår i: SILICON CARBIDE 2002-MATERIALS, PROCESSING AND DEVICES. ; , s. 291-301
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Konferensbidrag (refereegranskat)abstract
- A brief survey is given of some recent result of boron diffusion in low doped n-type (intrinsic) and p-type 4H-SiC. Aluminum diffusion and solubility limit in 4H-SiC are also discussed. Ion implantation of boron has been performed in epitaxial material to form a diffusion source but also epitaxial 4H-SiC structures, with heavily boron or aluminum doped layers prepared by vapor phase epitaxy have been studied. Heat treatments have been made at temperatures ranging from 1100 to 2050degreesC for 5 minutes up to 64 h. Secondary ion mass spectrometry has been utilized for analysis. For boron diffusion in acceptor doped 4H-SiC, 4x10(19) Al atoms/cm(3), an activation energy of 5.3 eV has been determined and a strong dependence on Al content for the diffusion coefficient is revealed. Transient enhanced diffusion of ion-implanted boron in intrinsic 4H-SiC samples is discussed. Solubility limits of similar to1x10(20) Al/cm(3) (1700degreesC) and <1x10(20) B/cm(3) (1900degreesC) have been deduced.
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| 27. |
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| 28. |
- Linnarsson, M K, et al.
(författare)
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Deuterium incorporation in acceptor doped epitaxial layers of 6H-SiC
- 1998
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Ingår i: SILICON CARBIDE, III-NITRIDES AND RELATED MATERIALS, PTS 1 AND 2. ; , s. 761-764
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Konferensbidrag (refereegranskat)abstract
- Deuterium is introduced in boron doped epitaxial layers of 6H-SiC by implantation of 30 keV H-2(+) ions in order to form a diffusion source. The samples were subsequently annealed in vacuum at 700 degrees C/16h, 800 degrees C/4h and 900 degrees C/4h. Using depth profiling by secondary ion mass spectrometry (SIMS), the distributions of deuterium at different levels of boron doping are studied. The deuterium concentration correlates with the boron concentration and at a level of similar to 10(18) cm(-3) a ratio H-2/B-11 larger than 0.5 is obtained. From capacitance-voltage (CV) measurements a decrease in the electrical carrier concentration by 50% is revealed after deuterium diffusion at 800 degrees C/4h. At 900 degrees C passivation of the boron accepters ceases but the H-2 atoms are still confined to the boron-doped regions and display no long range migration.
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| 29. |
- Linnarsson, M K, et al.
(författare)
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Diffusion of light elements in 4H-and 6H-SiC
- 1999
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Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 61-2, s. 275-280
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Tidskriftsartikel (refereegranskat)abstract
- Deuterium and lithium were introduced in p-type SiC by implantation of 20 keV H-2(+) or 30 keV Li-7(+) ions in order to form a diffusion source. The samples were subsequently annealed in vacuum in the temperature range 400-700 degrees C for 0.25 to 16 h. Secondary ion mass spectrometry (SIMS) was used to measure the deuterium and the lithium distribution after heat treatments. Both deuterium and lithium readily decorate the bombardment-induced defects in the vicinity of the ion implantation profile and they are also trapped, most likely by residual boron impurities, during diffusion into the bulk. An effective diffusion coefficient, reflecting the dissociation of trapped lithium, with an activation energy of 2.1 eV is extracted for lithium diffusion in p-type 6H SIG. Furthermore, a capture radius for trapping (most likely by boron) of deuterium is estimated as 10 Angstrom. (C) 1999 Elsevier Science S.A. All rights reserved.
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| 30. |
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| 31. |
- Linnarsson, M K, et al.
(författare)
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Incorporation of hydrogen (H-1 and H-2) into 4H-SiC during epitaxial growth
- 2002
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2001, PTS 1 AND 2, PROCEEDINGS. ; , s. 565-568
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Konferensbidrag (refereegranskat)abstract
- The hydrogen depth distribution in 4H-SiC after epitaxial growth at 1600 degreesC has been studied in detail with secondary ion mass spectrometry. Both H-1 and H-2 have been employed as carrier gas to trace the origin of the incorporated hydrogen. In particular the substrate as a prospective hydrogen source has been considered. After growth H-2 is detected throughout the whole substrate (similar to400 mum) and a considerable quantity remains after annealing at 1500 degreesC for 15 minutes.
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| 32. |
- Linnarsson, M.K., et al.
(författare)
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Self-diffusion of 12C and 13C in intrinsic 4H-SiC
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 95:12, s. 8469-8471
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Tidskriftsartikel (refereegranskat)abstract
- The study of self-diffusion of carbon (12C and 13C) in low-doped (intrinsic) 4H-SiC using secondary ion mass spectroscopy (SIMS) was presented. A two layer 13C enriched structure with 13C/12C ratios of 0.01 and 0.1, respectively, was prepared by using vapor phase epitaxy. The subsequent anneals were carried out in Ar atmosphere in a rf heated furnace between 2100 and 2350°C for 15 min-40 h. A small variation in the enriched 13C concentration and in the layer thickness over the wafer was also presented.
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| 33. |
- Monakhov, E. V., et al.
(författare)
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Boron distribution in silicon after excimer laser annealing with multiple pulses
- 2005
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 124, s. 228-231
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Tidskriftsartikel (refereegranskat)abstract
- We have studied B re-distribution in Si after excimer laser annealing (ELA) with multiple laser pulses. B was implanted using both B and BF2 ions with energies from 1 to 20 keV and doses of 1 x 10(14) and 1 x 10(15) cm(-2). ELA with the number of pulses from 1 to 100 was performed in vacuum with the sample kept at room temperature and 450 degrees C. Independently of the implantation parameters and the ELA conditions used, a peak in the B concentration is observed near the maximum melting depth after 10 pulses of ELA. A detailed study has revealed that B accumulates at the maximum melt depth gradually with the number of ELA pulses. An increase in the carrier concentration at the maximum melt depth is observed after ELA with 100 pulses. No structural defects have been detected by transmission electron microscopy in the region of the B accumulation.
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| 34. |
- Monakhov, E. V., et al.
(författare)
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Boron distribution in silicon after multiple pulse excimer laser annealing
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 87:8
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Tidskriftsartikel (refereegranskat)abstract
- We have studied B redistribution in Si after excimer laser annealing (ELA) with multiple laser pulses. B was implanted with energies of 1 and 10 keV and doses of 1x10(14) and 1x10(15) cm(-2). ELA with the number of pulses from 1 to 100 was performed at room temperature and 450 degrees C in vacuum. Irrespective of the implantation parameters and the ELA conditions used, a pile-up in the B concentration is observed near the maximum melting depth after ten pulses of ELA. Moreover, a detailed study has revealed that B accumulates at the maximum melt depth gradually with the number of ELA pulses. Besides, an increase in the carrier concentration is observed at the maximum melt depth, suggesting electrical activity of the accumulated B. Formation of Si-B complexes and vacancy accumulation during multiple ELA are discussed as possible mechanisms for the B build-up.
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| 35. |
- Monakhov, E. V., et al.
(författare)
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Excimer laser annealing of B and BF2 implanted Si
- 2005
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 124, s. 232-234
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Tidskriftsartikel (refereegranskat)abstract
- We have performed a comparative study of B re-distribution and electrical activation after excimer laser annealing (ELA) of B and BF2 implanted Si. Chemical B concentration and electrical activation profiles were measured by secondary ion mass spectrometry (SIMS) and spreading resistance profiling (SRP), respectively. SIMS data demonstrate that the presence of F does not influence significantly the re-distribution of B during ELA. A dramatic contrast, however, can be observed in the electrical activation of the dopant in the B and BF2 implanted samples. While almost 100% electrical activation of B occurs in the B implanted samples, only 20-50% of the dopant can be activated by ELA in the BF2 implanted sample. Possible mechanisms causing the deactivation of B in the BF2 implanted samples after ELA are discussed.
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| 36. |
- Monakhov, E. V., et al.
(författare)
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The effect of excimer laser pretreatment on diffusion and activation of boron implanted in silicon
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 87:19
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the effect of excimer laser annealing (ELA) on transient enhanced diffusion (TED) and activation of boron implanted in Si during subsequent rapid thermal annealing (RTA). It is observed that ELA with partial melting of the implanted region causes reduction of TED in the region that remains solid during ELA, where the diffusion length of boron is reduced by a factor of similar to 4 as compared to the as-implanted sample. This is attributed to several mechanisms such as liquid-state annealing of a fraction of the implantation induced defects, introduction of excess vacancies during ELA, and solid-state annealing of the defects beyond the maximum melting depth by the heat wave propagating into the Si wafer. The ELA pretreatment provides a substantially improved electrical activation of boron during subsequent RTA.
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| 37. |
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| 38. |
- Ou, H., et al.
(författare)
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Fluorescent SiC for white light-emitting diodes
- 2012
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Ingår i: Asia Commun. Photonics Conf.. - Washington, D.C. : OSA.
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Konferensbidrag (refereegranskat)abstract
- The strong photoluminescence from f-SiC was achieved after the optimization of the B and N concentrations. Surface nanostructures were successfully applied to enhance the extraction efficiency. f-SiC is a promising wavelength convertor for white LEDs.
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| 39. |
- Rozenblatt-Rosen, O., et al.
(författare)
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Building a high-quality Human Cell Atlas
- 2021
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Ingår i: Nature Biotechnology. - : Nature Research. - 1087-0156 .- 1546-1696. ; 39:2, s. 149-153
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Tidskriftsartikel (refereegranskat)
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| 40. |
- Suvanam, Sethu Saveda, et al.
(författare)
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4H-silicon carbide-dielectric interface recombination analysis using free carrier absorption
- 2015
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 117:10
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, an alternative method to characterize the interface between 4H polytype of Silicon Carbide (4H-SiC) and passivating dielectric layers is established. The studies are made on dielectric-semiconductor test structures using Al2O3 as dielectric on 4H-SiC n-type epitaxial layers. Samples with different pre-and post-dielectric deposition preparations have been fabricated on epilayers of varying thicknesses. Effective lifetimes (tau(eff)) of all the samples were measured by an optical pump-probe method utilizing free carrier absorption (FCA) to analyse the influence of the 4H-SiC/dielectric interface on charge carrier recombination. The relative contribution to tau(eff) from the surfaces increases with decreasing epilayer thickness, and by analysing the data in combination with numerical modelling, it is possible to extract values of the surface recombination velocities (SRVs) for interfaces prepared in different ways. For instance, it is found that SRV for a standard cleaning procedure is 2 x 10(6) cm/s compared to a more elaborate RCA process, yielding a more than 50 times lower value of 3.5 x 10(4) cm/s. Furthermore, the density of interface traps (D-it) is extracted from capacitance-voltage (CV) measurements using the Terman method and a comparison is made between the SRV extracted from FCA measurements and D(it)s extracted from CV measurements on the same structures fabricated with metal contacts. It is observed that the SRV increase scales linearly with the increase in Dit. The strong qualitative correlation between FCA and CV data shows that FCA is a useful characterization technique, which can also yield more quantitative information about the charge carrier dynamics at the interface.
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| 41. |
- Svensson, B G, et al.
(författare)
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SIMS analysis of epitaxial layers for power- and micro-electronics
- 1998
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 136, s. 1034-1039
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Tidskriftsartikel (refereegranskat)abstract
- This paper gives an overview of recent secondary ion mass spectrometry (SIMS) studies of impurities and dopants in epitaxial layers of silicon and 6H silicon carbide (SiC). Detection limits in the 10(12) cm(-3) range are demonstrated for transition metal impurities like Ti in SiC. Hydrogen is found to be mobile in SiC at temperatures in excess of 600 degrees C despite strong trapping by defects and dopant atoms, and the effective diffusion coefficient exhibits an activation energy of similar to 3.5 eV. In epitaxially grown Si layers, containing Ge delta distributions, profile broadening and shift during sputtering by Ar+ ions are accurately described by recoil mixing. For O-2(divided by) ions oxide formation and surface swelling must also be considered. Further, at elevated sample temperature Ge is found to segregate out of the SiO2 surface layer formed during oxygen bombardment, consistent with a larger heat of oxide formation for Ge than Si and a high enough mobility in SiO2. (C) 1998 Elsevier Science B.V.
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| 42. |
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| 43. |
- Yakimova, R, et al.
(författare)
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Silicon carbide grown by liquid phase epitaxy in microgravity
- 1998
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Ingår i: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 13, s. 1812-1815
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Tidskriftsartikel (refereegranskat)abstract
- 6H and 4H polytype silicon carbide (SiC) layers have been grown on ground and under microgravity conditions by liquid phase epitaxy (LPE) from a solution of SiC in Si-Se solvent at 1750 degrees C. The effects of gravity on the growth parameters and material characteristiques have been studied. The growth rate, Sc incorporation, and the structural defects are modified in reduced gravity conditions, while the polytype reproduction of the substrate is not affected. The results obtained are intriguing as to further experiments providing objects for carrier lifetime measurements.
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| 44. |
- Yohannes, DA, et al.
(författare)
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Effects of In Vivo Gluten Challenge on PBMC Gene Expression Profiles in Diet Treated Celiac Disease
- 2020
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Ingår i: Frontiers in immunology. - : Frontiers Media SA. - 1664-3224. ; 11, s. 594243-
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Tidskriftsartikel (refereegranskat)abstract
- The pathological mechanisms that lead to the onset and reactivation of celiac disease (CD) remain largely unknown. While gluten free diet (GFD) improves the intestinal damage and associated clinical symptoms in majority of cases, it falls short of providing full recovery. Additionally, late or misdiagnosis is also common as CD presents with a wide range of symptoms. Clear understanding of CD pathogenesis is thus critical to address both diagnostic and treatment concerns. We aimed to study the molecular impact of short gluten exposure in GFD treated CD patients, as well as identify biological pathways that remain altered constitutively in CD regardless of treatment. Using RNAseq profiling of PBMC samples collected from treated CD patients and gluten challenged patient and healthy controls, we explored the peripheral transcriptome in CD patients following a short gluten exposure. Short gluten exposure of just three days was enough to alter the genome-wide PBMC transcriptome of patients. Pathway analysis revealed gluten-induced upregulation of mainly immune response related pathways, both innate and adaptive, in CD patients. We evaluated the perturbation of biological pathways in sample-specific manner. Compared to gluten exposed healthy controls, pathways related to tight junction, olfactory transduction, metabolism of unsaturated fatty acids (such as arachidonic acid), metabolism of amino acids (such as cysteine and glutamate), and microbial infection were constitutively altered in CD patients regardless of treatment, while GFD treatment appears to mostly normalize immune response pathways to “healthy” state. Upstream regulator prediction analysis using differentially expressed genes identified constitutively activated regulators relatively proximal to previously reported CD associated loci, particularly SMARCA4 on 19p13.2 and CSF2 on 5q31. We also found constitutively upregulated genes in CD that are in CD associated genetic loci such as MEF2BNB-MEF2B (BORCS8-MEF2B) on 19p13.11 and CSTB on 21q22.3. RNAseq revealed strong effects of short oral gluten challenge on whole PBMC fraction and constitutively altered pathways in CD PBMC suggesting important factors other than gluten in CD pathogenesis.
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| 45. |
- Aberg, D, et al.
(författare)
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Ultra-shallow thermal donor formation in oxygen-containing ambient
- 1998
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Ingår i: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 210, s. 527-532
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Tidskriftsartikel (refereegranskat)abstract
- Czochralski-grown phosphorus-doped (approximate to 2 x 10(14) cm(-3)) silicon wafers have been annealed in nitrogen, wet nitrogen, argon, oxygen, and vacuum ambients at 470 degrees C for times up to 500 h. Sample characterization was made with capacitance-voltage, four-point probe, DLTS, thermally stimulated capacitance, admittance spectroscopy, secondary ion-mass spectrometry, and Fourier transform infrared spectroscopy. This study finds a strong relation between the previously reported ultra-shallow thermal donors (USTDs) and shallow thermal donors (STDs), and it is shown that the net concentration of thermally formed donors is independent on annealing ambient within the experimental accuracy. It was found that the majority of formed donors for long anneals consisted of either STDs or USTDs, however, it was found that oxygen-containing ambient is indispensable for forming USTDs.
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| 46. |
- Aberg, D, et al.
(författare)
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Ultrashallow thermal donor formation in silicon by annealing in ambient oxygen
- 1999
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Ingår i: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 85, s. 8054-8059
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Tidskriftsartikel (refereegranskat)abstract
- Czochralski-grown silicon wafers doped with phosphorus (similar to 10(14) cm(-3)) have been annealed in nitrogen, wet nitrogen, oxygen, argon, and vacuum ambients at 470 degrees C for times up to 500 h. Sample characterization was made using predominantly electrical techniques such as admittance spectroscopy and thermally stimulated capacitance measurements but also secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy were employed. In all samples, an increasing concentration of free carrier electrons is observed with increasing annealing time, reaching a maximum of similar to 10(16) cm(-3) at 100 h. For durations in excess of 100 h gradual decrease of the free electron concentration takes place except for the samples treated in wet nitrogen and oxygen atmospheres, which display donors stable even after 200 h. These stable centers are found to have shallower donor level positions in the energy band gap (similar to 25 meV below the conduction band edge E-c) than those of the centers formed in vacuum, argon, and nitrogen atmospheres (similar to 35 meV below E-c). The latter centers are associated with the well-established shallow thermal donors (STDs) while the origin of the former ones, which are labeled ultrashallow thermal donors (USTDs) is less known. However, on the basis of a wealth of experimental results we show that the USTDs are most likely perturbated STDs modified through interaction with fast-in diffusing oxygen species, possibly oxygen dimers. Further, comparison between the electrical data and the SIMS measurements reveals unambiguously that neither the STD nor the USTD centers involve nitrogen, in contrast to recent suggestions in the literature. (C) 1999 American Institute of Physics. [S0021-8979(99)06512-3].
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| 47. |
- Bathen, M. E., et al.
(författare)
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Influence of carbon cap on self-diffusion in silicon carbide
- 2020
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Ingår i: Crystals. - : MDPI AG. - 2073-4352. ; 10:9, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Self-diffusion of carbon (12C and13C) and silicon (28Si and30Si) in 4H silicon carbide has been investigated by utilizing a structure containing an isotope purified 4H-28Si12C epitaxial layer grown on an n-type (0001) 4H-SiC substrate, and finally covered by a carbon capping layer (C-cap). The13C and30Si isotope profiles were monitored using secondary ion mass spectrometry (SIMS) following successive heat treatments performed at 2300–2450◦C in Ar atmosphere using an inductively heated furnace. The30Si profiles show little redistribution within the studied temperature range, with the extracted diffusion lengths for Si being within the error bar for surface roughening during annealing, as determined by profilometer measurements. On the other hand, a significant diffusion of13C was observed into the isotope purified layer from both the substrate and the C-cap. A diffusivity of D = 8.3 × 106 e−10.4/kBT cm2/s for13C was extracted, in contrast to previous findings that yielded lower both pre-factors and activation energies for C self-diffusion in SiC. The discrepancy between the present measurements and previous theoretical and experimental works is ascribed to the presence of the C-cap, which is responsible for continuous injection of C interstitials during annealing, and thereby suppressing the vacancy mediated diffusion.
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| 48. |
- Doyle, J. P., et al.
(författare)
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Characterization of deep level defects in 4H and 6H SiC via DLTS, SIMS and MeV e-beam irradiation
- 1996
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Ingår i: III-nitride, SiC and diamond materials for electronic devices. ; , s. 519-524
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Konferensbidrag (refereegranskat)abstract
- Electrically active defects in both 4H and 6H polytypes of SiC have been observed through the use of deep level transient spectroscopy (DLTS). Schottky contacts were grown by VPE with doping concentrations, the epitaxial layer having a doping concentration in the range of 10 exp 14/cu cm to 10 exp 17/cu cm. Numerous levels have been found in the as-grown n-type 6H-SiC samples, and SIMS and MeV electron irradiation have been employed to correlate the defect levels to impurities or structural defects. In contrast, only a single level is observed in the as-grown 4H-SiC samples.
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| 49. |
- Doyle, J P, et al.
(författare)
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Observation of near-surface electrically active defects in n-type 6H-SiC
- 1998
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 83, s. 3649-3651
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Tidskriftsartikel (refereegranskat)abstract
- In n-type 6H-SiC epitaxial layers grown by vapor phase epitaxy, we find that in contrast to the majority of the epitaxial layer, where electrically active defects are observed with a concentration less than 1 X 10(-13) cm(-3), a region near the front surface contains defects with concentrations approaching 10(14) cm(-3). A relationship between the near-surface defects and metallic impurities is suggested by a Ti concentration of 1 X 10(16) cm(-3) in this region. The high concentration of near surface defects is found to significantly reduce the carrier lifetime. (C) 1998 American Institute of Physics. [S0021-8979(98)03007-2].
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| 50. |
- Forsberg, Urban, 1971-, et al.
(författare)
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Aluminum doping of epitaxial Silicon Carbide
- 2003
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Ingår i: Journal of Crystal Growth. - : ScienceDirect. - 0022-0248 .- 1873-5002. ; 253:1-4, s. 340-350
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Tidskriftsartikel (refereegranskat)abstract
- Intentional doping of aluminum in 4H and 6H SiC has been performed using a hot-wall CVD reactor. The dependence of aluminum incorporation on temperature, pressure, C/Si ratio, growth rate, and TMA flow has been investigated. The aluminum incorporation showed to be polarity dependent. The high aluminum incorporation on the Si-face is closely related to the carbon coverage on the SiC surface. Changes in process parameters changes the effective C/Si ratio close to the SiC surface. Increased growth rate and C/Si ratio increases the aluminum incorporation on the Si-face. Diffusion limited incorporation occurs at high growth rate. Reduced pressure increases the effective C/Si ratio, and at low growth rate, the aluminum incorporation increases initially, levels off at a critical pressure, and continues to decrease below the critical pressure. The aluminum incorporation showed to be constant in a temperature range of 50°C. The highest atomic concentration of aluminum observed in this study was 3×1017 and 8×1018 cm−3 in Si and C-face, respectively.
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