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Freiburg, Germany

The Fraunhofer Society is a German research organization with 67 institutes spread throughout Germany, each focusing on different fields of applied science . It employs around 23,000 people, mainly scientists and engineers, with an annual research budget of about €1.7 billion. Some basic funding for the Fraunhofer Society is provided by the state , but more than 70% of the funding is earned through contract work, either for government-sponsored projects or from industry.It is named after Joseph von Fraunhofer who, as a scientist, an engineer, and an entrepreneur, is said to have superbly exemplified the goals of the society.The organization has seven centers in the United States, under the name “Fraunhofer USA”, and three in Asia. In October 2010, Fraunhofer announced that it would open its first research center in South America.Fraunhofer UK Research Ltd was established along with the Fraunhofer Centre for Applied Photonics, in Glasgow, Scotland, in March 2012. Wikipedia.

Szunerits S.,Lille University of Science and Technology | Nebel C.E.,Fraunhofer Institute for Applied Solid State Physics | Hamers R.J.,University of Wisconsin - Madison
MRS Bulletin | Year: 2014

Recent advances in biotechnology have fueled a need for well-defined, highly stable interfaces modified with a variety of biomolecules. Diamond is a particularly attractive material for biological applications because of its chemical stability and good biocompatibility. Since diamond can be made conductive by doping, it is also of interest for a variety of electrically based biological sensing applications that achieve improved performance through selective biological modification. Recent developments of diamond growth by chemical vapor deposition have enabled the preparation of large-area synthetic diamond films on different substrates at a reasonable cost. An as-grown diamond film is terminated by hydrogen on the surface and shows hydrophobic wetting characteristics, besides chemical inertness. This has created problems for attachment of many biomolecules that are inherently hydrophilic. The challenge to make diamond useful for in vivo applications thus lies in covalently linking biomolecules to such surfaces. Several breakthroughs have been accomplished over the last decade, and attaching biomolecules to diamond in a controlled and reproducible way can nowadays be achieved in several different manners and is the focus of this article. © Materials Research Society 2014. Source

Williams O.A.,Fraunhofer Institute for Applied Solid State Physics
Diamond and Related Materials | Year: 2011

Diamond properties are significantly affected by crystallite size. High surface to volume fractions result in enhanced disorder, sp 2 bonding, hydrogen content and scattering of electrons and phonons. Most of these properties are common to all low dimensional materials, but the addition of carbon allotropes introduces sp 2 bonding, a significant disadvantage over systems such as amorphous silicon. Increased sp 2 bonding results in enhanced disorder, a significantly more complex density of states within the bandgap, reduction of Young's modulus, increased optical absorption etc. At sizes below 10 nm, many diamond particle and film properties deviate substantially from that of bulk diamond, mostly due not only to the contribution of sp 2 bonding, but also at the extreme low dimensions due to size effects. Despite these drawbacks, nano-diamond films and particles are powerful systems for a variety of applications and the study of fundamental science. Knowledge of the fundamental properties of these materials allows a far greater exploitation of their attributes for specific applications. This review attempts to guide the reader between the various nanocrystalline diamond forms and applications, with a particular focus on thin films grown by chemical vapour deposition. © 2011 Elsevier B.V. All rights reserved. Source

Scheibenzuber W.G.,Fraunhofer Institute for Applied Solid State Physics | Schwarz U.T.,Albert Ludwigs University of Freiburg
Physica Status Solidi (B) Basic Research | Year: 2011

We investigate the influence of polarization switching on the optical gain of semipolar InGaN quantum wells (QWs) depending on indium content and charge carrier concentration using self-consistent 6×6 k·p-band structure calculations. The semipolar planes considered here are the $(11\bar {2}2)$- and the $(20\bar {2}1)$-plane. In contrast to the $(20\bar {2}1)$-plane, the dominant polarization of the optical gain in a QW on the $(11\bar {2}2)$-plane can depend on both the indium content and the charge carrier concentration, as reported from experiments. These effects are explained by a detailed analysis of the wave function composition of the topmost valence bands in a semipolar QW. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Rath P.,Karlsruhe Institute of Technology | Khasminskaya S.,Karlsruhe Institute of Technology | Nebel C.,Fraunhofer Institute for Applied Solid State Physics | Wild C.,Fraunhofer Institute for Applied Solid State Physics | And 2 more authors.
Nature Communications | Year: 2013

Diamond offers unique material advantages for the realization of micro- and nanomechanical resonators because of its high Young's modulus, compatibility with harsh environments and superior thermal properties. At the same time, the wide electronic bandgap of 5.45 eV makes diamond a suitable material for integrated optics because of broadband transparency and the absence of free-carrier absorption commonly encountered in silicon photonics. Here we take advantage of both to engineer full-scale optomechanical circuits in diamond thin films. We show that polycrystalline diamond films fabricated by chemical vapour deposition provide a convenient wafer-scale substrate for the realization of high-quality nanophotonic devices. Using free-standing nanomechanical resonators embedded in on-chip Mach-Zehnder interferometers, we demonstrate efficient optomechanical transduction via gradient optical forces. Fabricated diamond resonators reproducibly show high mechanical quality factors up to 11,200. Our low cost, wideband, carrier-free photonic circuits hold promise for all-optical sensing and optomechanical signal processing at ultra-high frequencies. © 2013 Macmillan Publishers Limited. All rights reserved. Source

Keller B.G.,Free University of Berlin | Kobitski A.,Fraunhofer Institute for Applied Solid State Physics | Jaschke A.,University of Heidelberg | Nienhaus G.U.,Fraunhofer Institute for Applied Solid State Physics | And 2 more authors.
Journal of the American Chemical Society | Year: 2014

We have developed a hidden Markov model and optimization procedure for photon-based single-molecule FRET data, which takes into account the trace-dependent background intensities. This analysis technique reveals an unprecedented amount of detail in the folding kinetics of the Diels-Alderase ribozyme. We find a multitude of extended (low-FRET) and compact (high-FRET) states. Five states were consistently and independently identified in two FRET constructs and at three Mg2+ concentrations. Structures generally tend to become more compact upon addition of Mg2+. Some compact structures are observed to significantly depend on Mg2+ concentration, suggesting a tertiary fold stabilized by Mg2+ ions. One compact structure was observed to be Mg2+-independent, consistent with stabilization by tertiary Watson-Crick base pairing found in the folded Diels-Alderase structure. A hierarchy of time scales was discovered, including dynamics of 10 ms or faster, likely due to tertiary structure fluctuations, and slow dynamics on the seconds time scale, presumably associated with significant changes in secondary structure. The folding pathways proceed through a series of intermediate secondary structures. There exist both compact pathways and more complex ones, which display tertiary unfolding, then secondary refolding, and, subsequently, again tertiary refolding. © 2014 American Chemical Society. Source

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