33 research outputs found
Photoconductance of a submicron oxidized line in surface conductive single crystalline diamond
We report on sub-bandgap optoelectronic phenomena of hydrogen-terminated
diamond patterned with a submicron oxidized line. The line acts as an energy
barrier for the two-dimensional hole gas located below the hydrogenated diamond
surface. A photoconductive gain of the hole conductivity across the barrier is
measured for sub-bandgap illumination. The findings are consistent with
photogenerated electrons being trapped in defect levels within the barrier. We
discuss the spatial and energetic characteristics of the optoelectronic
phenomena, as well as possible photocurrent effects
Enlarged magnetic focusing radius of photoinduced ballistic currents
We exploit GaAs-based quantum point contacts as mesoscopic detectors to
analyze the ballistic flow of photogenerated electrons in a two-dimensional
electron gas at a perpendicular magnetic field. Whereas charge transport
experiments always measure the classical cyclotron radius, we show that this
changes dramatically when detecting the photoinduced non-equilibrium current in
magnetic fields. The experimentally determined radius of the trajectories
surprisingly exceeds the classical cyclotron value by far. Monte Carlo
simulations suggest electron-electron scattering as the underlying reason.Comment: pdf-file includes both main article and supplementary informatio
Analysis of IL2/IL21 Gene Variants in Cholestatic Liver Diseases Reveals an Association with Primary Sclerosing Cholangitis
Background/Aims: The chromosome 4q27 region harboring IL2 and IL21 is an established risk locus for ulcerative colitis (UC) and various other autoimmune diseases. Considering the strong coincidence of primary sclerosing cholangitis (PSC) with UC and the increased frequency of other autoimmune disorders in patients with primary biliary cirrhosis (PBC), we investigated whether genetic variation in the IL2/IL21 region may also modulate the susceptibility to these two rare cholestatic liver diseases. Methods: Four strongly UC-associated single nucleotide polymorphisms (SNPs) within the KIAA1109/TENR/IL2/IL21 linkage disequilibrium block were genotyped in 124 PBC and 41 PSC patients. Control allele frequencies from 1,487 healthy, unrelated Caucasians were available from a previous UC association study. Results: The minor alleles of all four markers were associated with a decreased susceptibility to PSC (rs13151961: p = 0.013, odds ratio (OR) 0.34; rs13119723: p = 0.023, OR 0.40; rs6822844: p = 0.031, OR 0.41; rs6840978: p = 0.043, OR 0.46). Moreover, a haplotype consisting of the four minor alleles also had a protective effect on PSC susceptibility (p = 0.0084, OR 0.28). A haplotype of the four major alleles was independently associated with PSC when excluding the patients with concomitant inflammatory bowel disease (p = 0.033, OR 4.18). Conclusion: The IL2/IL21 region may be one of the highly suggestive but so far rarely identified shared susceptibility loci for PSC and UC. Copyright (C) 2011 S. Karger AG, Base
Guided assembly of nanoparticles on electrostatically charged nanocrystalline diamond thin films
We apply atomic force microscope for local electrostatic charging of oxygen-terminated nanocrystalline diamond (NCD) thin films deposited on silicon, to induce electrostatically driven self-assembly of colloidal alumina nanoparticles into micro-patterns. Considering possible capacitive, sp2 phase and spatial uniformity factors to charging, we employ films with sub-100 nm thickness and about 60% relative sp2 phase content, probe the spatial material uniformity by Raman and electron microscopy, and repeat experiments at various positions. We demonstrate that electrostatic potential contrast on the NCD films varies between 0.1 and 1.2 V and that the contrast of more than ±1 V (as detected by Kelvin force microscopy) is able to induce self-assembly of the nanoparticles via coulombic and polarization forces. This opens prospects for applications of diamond and its unique set of properties in self-assembly of nano-devices and nano-systems
Analysis of IL12B Gene Variants in Inflammatory Bowel Disease
IL12B encodes the p40 subunit of IL-12, which is also part of IL-23. Recent genome-wide association studies identified IL12B and IL23R as susceptibility genes for inflammatory bowel disease (IBD). However, the phenotypic effects and potential gene-gene interactions of IL12B variants are largely unknow
100 Jahre Einkristallzucht aus der Schmelze: Vom Spreeknie ins Silicon Valley
Im August 1916 reichte der DeutschâPole Jan Czochralski eine Publikation ĂŒber die Wachstumsgeschwindigkeit von Metallkristallen bei der Zeitschrift fĂŒr physikalische Chemie ein. Daher wird 1916 als das Jahr der Entdeckung des CzochralskiâKristallzuchtverfahrens angesehen. Im MetallâLaboratorium der AEG, wo Czochralski zunĂ€chst arbeitete, wurden seine Forschungsarbeiten nicht gebĂŒhrend anerkannt, sodass er zur Metallbank und Metallurgischen Gesellschaft (spĂ€ter: Metallgesellschaft) nach Frankfurt wechselte, wo er bald zum Laborleiter und Oberingenieur aufstieg. In Frankfurt machte er sich mit Forschungen zu Metallen und technischen Legierungen rasch einen Namen. Die Entdeckung des CzochralskiâKristallzuchtverfahrens gehört zu den wichtigsten technologischen Erfindungen des 20. Jahrhunderts, die aber erst in dessen zweiten HĂ€lfte mit dem Aufstieg der Halbleiterindustrie ökonomische Bedeutung erlangte. Heute werden 95 % der Weltproduktion an Siliciumeinkristallen nach dem CzochralskiâVerfahren hergestellt. Der Umsatz der HalbleiterâIndustrie betrug 2015 etwa 335 Milliarden USâDollar, wobei die Kristallzucht nach dem CzochralskiâVerfahren jeweils der erste Schritt bei der Herstellung ist. Der gröĂte Teil der heute gefertigten Siliciumeinkristalle hat einen Durchmesser von 300 mm. Die industrielle Produktion von Einkristallen mit 450 mm Durchmesser scheitert bisher nicht an technologischen, sondern an ökonomischen Problemen