Formation of Epitaxial Graphene Layers on 6H-SiC Induced by Electron Beam Irradiation

Device PhysicsIt is observed that the epitaxial graphene layers form on the surface of a 6H-SiC substrate by electron beam irradiation. The electron beam (e-beam) is irradiated by using a commercial electron beam evaporator with acceleration voltage 8kV in high vacuum environment. Raman spectrum measurements show all relevant peaks (D, G, 2D) clearly, confirming the formation of graphene layers. The structural analysis is confirmed by using TEM (Transmission Electron Microscopy). The result of formed graphene layers thickness measurement is verified 7 ~ 8 layers of graphene. It is checked out that thickness of 1 layer is approximately 0.32 nm. The elemental composition of the epitaxial graphene layer is measured with AES (Auger Electron Spectroscopy) and XPS (X-ray Photoelectron Spectroscopy). The sheet resistance of the epitaxial graphene layer which is measured by forming CTLM (Circular Transmission Line Model) patterns on the irradiated 6H-SiC surface is found to decrease at least 1000 times, compared with the original 6H-SiC substrate. The sheet resistance and contact resistance of graphene layer are 6.7 k??/??? and 0.18 k?? respectively. Also, the quality of the graphene layer in terms of Raman spectrum and sheet resistance is found to be improved noticeably as the electron fluence (e/cm2) is increased by making the irradiation time longer.ope

Dependence of spontaneous polarization on stacking sequence in SiC revealed by local Schottky barrier height variations over a partially formed 8H-SiC layer on a 4H-SiC substrate

Ballistic electron emission microscopy was used to measure the increase of local Schottky barrier (compared to the surrounding 4H-SiC area) over a partial 8H-SiC layer that is the surface-exposed tail of an 8H stacking fault inclusion extending from 4H substrate. This local increase is believed to be due to polarization charge induced at the interface of partial 8H layer and underlying 4H host, resulting from the spontaneous polarization (SP) difference between SiC regions with different bilayer stacking. This is a direct experimental probe of the dependence of SP in SiC on local stacking sequence by measuring carrier transport.open1

The genetic architecture of type 2 diabetes

The genetic architecture of common traits, including the number, frequency, and effect sizes of inherited variants that contribute to individual risk, has been long debated. Genome-wide association studies have identified scores of common variants associated with type 2 diabetes, but in aggregate, these explain only a fraction of heritability. To test the hypothesis that lower-frequency variants explain much of the remainder, the GoT2D and T2D-GENES consortia performed whole genome sequencing in 2,657 Europeans with and without diabetes, and exome sequencing in a total of 12,940 subjects from five ancestral groups. To increase statistical power, we expanded sample size via genotyping and imputation in a further 111,548 subjects. Variants associated with type 2 diabetes after sequencing were overwhelmingly common and most fell within regions previously identified by genome-wide association studies. Comprehensive enumeration of sequence variation is necessary to identify functional alleles that provide important clues to disease pathophysiology, but large-scale sequencing does not support a major role for lower-frequency variants in predisposition to type 2 diabetes

Electron Transport through Nano-aperture in Ferroelectric Thin Film of Metal/Insulator(Stack of Ferroelectric and Non-ferroelectric)/Metal Junction

The electron energy band profile through a nm-scale circular aperture in ferroelectric thin film of metal/insulator(stack of ferroelectric and non-ferroelectric)/metal junction was calculated by performing finite-element electrostatic modeling. It is found that the energy band profile through the circular aperture alters significantly near the boundary of aperture depending on the polarization direction of ferroelectric thin film. The energy band profile shows pinch-off when the interface bound charge at Ferroelectric/Non-ferroelectric interface is negative while it shows a valley-like shape when the interface bound charge is positive. The change of the energy band profile depending on ferroelectric polarization was confirmed to result in a drastic change of electron tunneling probability through the non-ferroelectric insulating film inside the circular aperture by using WKB method. It is believed that this switching of electron tunneling resistance through the circular aperture opens a way to develop non-volatile ferroelectric memory devices using non-destructive read-out

Erratum: Sequence data and association statistics from 12,940 type 2 diabetes cases and controls.

This corrects the article DOI: 10.1038/sdata.2017.179

Sequence data and association statistics from 12,940 type 2 diabetes cases and controls.

To investigate the genetic basis of type 2 diabetes (T2D) to high resolution, the GoT2D and T2D-GENES consortia catalogued variation from whole-genome sequencing of 2,657 European individuals and exome sequencing of 12,940 individuals of multiple ancestries. Over 27M SNPs, indels, and structural variants were identified, including 99% of low-frequency (minor allele frequency [MAF] 0.1-5%) non-coding variants in the whole-genome sequenced individuals and 99.7% of low-frequency coding variants in the whole-exome sequenced individuals. Each variant was tested for association with T2D in the sequenced individuals, and, to increase power, most were tested in larger numbers of individuals (>80% of low-frequency coding variants in ~82 K Europeans via the exome chip, and ~90% of low-frequency non-coding variants in ~44 K Europeans via genotype imputation). The variants, genotypes, and association statistics from these analyses provide the largest reference to date of human genetic information relevant to T2D, for use in activities such as T2D-focused genotype imputation, functional characterization of variants or genes, and other novel analyses to detect associations between sequence variation and T2D

Data Descriptor : Sequence data and association statistics from 12,940 type 2 diabetes cases and controls

To investigate the genetic basis of type 2 diabetes (T2D) to high resolution, the GoT2D and T2D-GENES consortia catalogued variation from whole-genome sequencing of 2,657 European individuals and exome sequencing of 12,940 individuals of multiple ancestries. Over 27M SNPs, indels, and structural variants were identified, including 99% of low-frequency (minor allele frequency [MAF] 0.1-5%) non-coding variants in the whole-genome sequenced individuals and 99.7% of low-frequency coding variants in the whole-exome sequenced individuals. Each variant was tested for association with T2D in the sequenced individuals, and, to increase power, most were tested in larger numbers of individuals (&gt; 80% of low-frequency coding variants in similar to ~82 K Europeans via the exome chip, and similar to ~90% of low-frequency non-coding variants in similar to ~44 K Europeans via genotype imputation). The variants, genotypes, and association statistics from these analyses provide the largest reference to date of human genetic information relevant to T2D, for use in activities such as T2D-focused genotype imputation, functional characterization of variants or genes, and other novel analyses to detect associations between sequence variation and T2D.Erratum in: Scientific Data, volume 5, Article number: 180002, 2018Doi:10.1038/sdata.2018.2</p