| 1. |
- Smith, Jennifer A, et al.
(författare)
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Genome-wide association study identifies 74 loci associated with educational attainment
- 2016
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Ingår i: Nature (London). - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 533:7604, s. 539-542
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Tidskriftsartikel (refereegranskat)abstract
- Educational attainment is strongly influenced by social and other environmental factors, but genetic factors are estimated to account for at least 20% of the variation across individuals. Here we report the results of a genome-wide association study (GWAS) for educational attainment that extends our earlier discovery sample of 101,069 individuals to 293,723 individuals, and a replication study in an independent sample of 111,349 individuals from the UK Biobank. We identify 74 genome-wide significant loci associated with the number of years of schooling completed. Single-nucleotide polymorphisms associated with educational attainment are disproportionately found in genomic regions regulating gene expression in the fetal brain. Candidate genes are preferentially expressed in neural tissue, especially during the prenatal period, and enriched for biological pathways involved in neural development. Our findings demonstrate that, even for a behavioural phenotype that is mostly environmentally determined, a well-powered GWAS identifies replicable associated genetic variants that suggest biologically relevant pathways. Because educational attainment is measured in large numbers of individuals, it will continue to be useful as a proxy phenotype in efforts to characterize the genetic influences of related phenotypes, including cognition and neuropsychiatric diseases.
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| 2. |
- Frazier-Wood, Alexis C., et al.
(författare)
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Genetic variants associated with subjective well-being, depressive symptoms, and neuroticism identified through genome-wide analyses
- 2016
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Ingår i: Nature Genetics. - : Nature Research (part of Springer Nature). - 1061-4036 .- 1546-1718. ; 48, s. 624-
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Tidskriftsartikel (refereegranskat)abstract
- Very few genetic variants have been associated with depression and neuroticism, likely because of limitations on sample size in previous studies. Subjective well-being, a phenotype that is genetically correlated with both of these traits, has not yet been studied with genome-wide data. We conducted genome-wide association studies of three phenotypes: subjective well-being (n = 298,420), depressive symptoms (n = 161,460), and neuroticism (n = 170,911). We identify 3 variants associated with subjective well-being, 2 variants associated with depressive symptoms, and 11 variants associated with neuroticism, including 2 inversion polymorphisms. The two loci associated with depressive symptoms replicate in an independent depression sample. Joint analyses that exploit the high genetic correlations between the phenotypes (vertical bar(p) over cap vertical bar approximate to 0.8) strengthen the overall credibility of the findings and allow us to identify additional variants. Across our phenotypes, loci regulating expression in central nervous system and adrenal or pancreas tissues are strongly enriched for association.
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| 3. |
- Hens, Philip, et al.
(författare)
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Defect structures at the silicon/3C-SiC interface
- 2012
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Ingår i: Materials Science Forum Vols 717 - 720. - : Trans Tech Publications Inc.. ; , s. 423-426
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Konferensbidrag (refereegranskat)abstract
- In all heteroepitaxial systems the interface between substrate and layer is a crucial point. In this work SEM and TEM studies on the interface between silicon substrate and cubic silicon carbide (3C-SiC) layers obtained by chemical vapor deposition (CVD) are presented. A clear connection between process parameters, like the design of substrate cleaning, and the heating ramp, and resulting defect structures at the substrate-layer interface could be found. Whereas the process step of etching in hot hydrogen for oxide removal is crucial for avoiding the generation of closed voids of type 2, the design of the temperature ramp-up to growth temperature during carbonization influences the interface roughness. Here a fast ramp helps to obtain a flat interface.
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| 4. |
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| 5. |
- Jokubavicius, Valdas, et al.
(författare)
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Morphological and Optical Stability in Growth of Fluorescent SiC on Low Off-Axis Substrates
- 2013
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 740-742, s. 19-22
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescent silicon carbide was grown using the fast sublimation growth process on low off-axis 6H-SiC substrates. In this case, the morphology of the epilayer and the incorporation of dopants are influenced by the Si/C ratio. Differently converted tantalum foils were introduced into the growth cell in order to change vapor phase stochiometry during the growth. Fluorescent SiC grown using fresh and fully converted tantalum foils contained morphological instabilities leading to lower room temperature photoluminescence intensity while an improved morphology and optical stability was achieved with partly converted tantalum foil. This work reflects the importance of considering the use of Ta foil in sublimation epitaxy regarding the morphological and optical stability in fluorescent silicon carbide.
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| 6. |
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| 7. |
- Jokubavicius, Valdas, et al.
(författare)
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Single Domain 3C-SiC Growth on Off-Oriented 4H-SiC Substrates
- 2015
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 15:6, s. 2940-2947
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the formation of structural defects in thick (∼1 mm) cubic silicon carbide (3C-SiC) layers grown on off-oriented 4H-SiC substrates via a lateral enlargement mechanism using different growth conditions. A two-step growth process based on this technique was developed, which provides a trade-off between the growth rate and the number of defects in the 3C-SiC layers. Moreover, we demonstrated that the two-step growth process combined with a geometrically controlled lateral enlargement mechanism allows the formation of a single 3C-SiC domain which enlarges and completely covers the substrate surface. High crystalline quality of the grown 3C-SiC layers is confirmed using high resolution X-ray diffraction and low temperature photoluminescence measurements.
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| 8. |
- Lin, Li, et al.
(författare)
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An adhesive bonding approach by hydrogen silsesquioxane for silicon carbide-based LED applications
- 2019
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Ingår i: Materials Science in Semiconductor Processing. - : ELSEVIER SCI LTD. - 1369-8001 .- 1873-4081. ; 91
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Tidskriftsartikel (refereegranskat)abstract
- We report an adhesive bonding approach using hydrogen silsesquioxane (HSQ) for silicon carbide (SiC) samples. A hybrid light-emitting diode (LED) was successfully fabricated through bonding a near-ultraviolet (NUV) LED grown on a commercial 4H-SiC substrate to a free-standing boron-nitrogen co-doped fluorescent-SiC epi-layer. The bonding quality and the electrical performance of the hybrid LED device were characterized. Neither voids nor defects were observed which indicates a good bonding quality of the proposed HSQ approach. A strong warm white emission was successfully obtained from the hybrid LED through an electric current injection of 30 mA.
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| 9. |
- Ou, Haiyan, et al.
(författare)
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Advances in wide bandgap SiC for optoelectronics
- 2014
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Ingår i: European Physical Journal B. - : Springer Science and Business Media LLC. - 1434-6028 .- 1434-6036. ; 87:3, s. 58-
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Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide (SiC) has played a key role in power electronics thanks to its unique physical properties like wide bandgap, high breakdown field, etc. During the past decade, SiC is also becoming more and more active in optoelectronics thanks to the progress in materials growth and nanofabrication. This paper will review the advances in fluorescent SiC for white light-emitting diodes, covering the polycrystalline doped SiC source material growth, single crystalline epitaxy growth of fluorescent SiC, and nanofabrication of SiC to enhance the extraction efficiency for fluorescent SiC based white LEDs.
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| 10. |
- Ou, Yiyu, et al.
(författare)
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Broadband and omnidirectional light harvesting enhancement of fluorescent SiC
- 2012
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 20:7, s. 7575-7579
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, antireflective sub-wavelength structures have been fabricated on fluorescent 6H-SiC to enhance the white light extraction efficiency by using the reactive-ion etching method. Broadband and omnidirectional antireflection characteristics show that 6H-SiC with antireflective sub-wavelength structures suppress the average surface reflection significantly from 20.5 % to 1.01 % over a wide spectral range of 390-784 nm. The luminescence intensity of the fluorescent 6H-SiC could be enhanced in the whole emission angle range. It maintains an enhancement larger than 91 % up to the incident angle of 70 degrees, while the largest enhancement of 115.4 % could be obtained at 16 degrees. The antireflective sub-wavelength structures on fluorescent 6H-SiC could also preserve the luminescence spectral profile at a large emission angle by eliminating the Fabry-Perot microcavity interference effect.
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