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Sample records for gan und zno

  1. Rare earths in GaN and ZnO studied with the PAC method; Seltene Erden in GaN und ZnO untersucht mit der PAC-Methode

    Nedelec, R.

    2007-07-01

    The present thesis deals with the implantation and annealing behaviour of two examples of large-band-gap semiconductors GaN and ZnO. The studies begin with the annealing behaviour of GaN after the implantation of {sup 172}Lu. For GaN the annealing process begins at low temperatures with the decreasing of the damping of the lattice frequency. At essentially higher temperatures finally the substitunial contribution increases. This behaviour is also observed for other probe nuclei in GaN. For ZnO the behaviour at low temperature is different. Both for {sup 172}Lu and for {sup 181}Hf the damping is already after the implantation very low. The increasement of the substitutional contribution occurs like in GaN at higher temperatures. Thereafter for GaN and ZnO PAC spectra were token up at different measurement temperatures between 25 and 873 K. For {sup 172}Lu in GaN and in ZnO a strong temperature dependence of the lattice field gradient was observed. Also for {sup 181}Hf in ZnO a strong temperature dependence is observed. For {sup 172}Lu by means of a model for the interaction of quadrupole moments of electronic shells with the nucleus a lattice field gradient of {+-}5.9.10{sup 15} Vcm{sup -2} could be determined. For {sup 172}Lu in ZnO the model yields at 293 K a lattice field gradient of +14.10{sup 15} Vcm{sup -2} respectively -13.10{sup 15} Vcm{sup -2}. The corrsponding measurement with {sup 181}Hf yields a lattice field gradient of {+-}5.7.10{sup 15} Vcm{sup -2}.

  2. Epitaxial GaN around ZnO nanopillars

    Fikry, Mohamed; Scholz, Ferdinand [Institut fuer Optoelektronik, Universitaet Ulm, Albert-Einstein-Allee 45, 89081 Ulm (Germany); Madel, Manfred; Tischer, Ingo; Thonke, Klaus [Institut fuer Quantenmaterie, Universitaet Ulm, Albert-Einstein-Allee 45, 89081 Ulm (Germany)

    2011-07-01

    We report on an investigation of the epitaxial quality of GaN layers overgrown coaxially around ZnO nanopillars. In a first step, regularly arranged ZnO nanopillars were grown using pre-patterning by e-beam lithography or self-organized hexagonal polystyrene sphere masks. Alternatively, ZnO pillars were also successfully grown on top of GaN pyramids. In a second step, GaN layers were grown around the ZnO pillars by Metal Organic Vapor Phase Epitaxy. At growth temperatures above 800 C, the ZnO pillars are dissolved by the hydrogen carrier gas leaving hollow GaN nanotubes. Characterization involved photoluminescence (PL), scanning electron microscopy and cathodoluminescence. The fair quality of the deposited GaN layers is confirmed by a sharp low temperature PL peak at 3.48 eV attributed to the donor bound exciton emission. Further peaks at 3.42 eV and 3.29 eV show the possible existence of basal plane and prismatic stacking faults.

  3. GaN and ZnO nanostructures

    Fuendling, Soenke; Soekmen, Uensal; Behrends, Arne; Al-Suleiman, Mohamed Aid Mansur; Merzsch, Stephan; Li, Shunfeng; Bakin, Andrey; Wehmann, Hergo-Heinrich; Waag, Andreas [Institut fuer Halbleitertechnik, Technische Universitaet Braunschweig, Braunschweig (Germany); Laehnemann, Jonas; Jahn, Uwe; Trampert, Achim; Riechert, Henning [Paul-Drude-Institut fuer Festkoerperelektronik, Berlin (Germany)

    2010-10-15

    GaN and ZnO are both wide band gap semiconductors with interesting properties concerning optoelectronic and sensor device applications. Due to the lack or the high costs of native substrates, alternatives like sapphire, silicon, or silicon carbide are taken, but the resulting lattice and thermal mismatches lead to increased defect densities which reduce the material quality. In contrast, nanostructures with high aspect ratio have lower defect densities as compared to layers. In this work, we give an overview on our results achieved on both ZnO as well as GaN based nanorods. ZnO nanostructures were grown by a wet chemical approach as well as by VPT on different substrates - even on flexible polymers. To compare the growth results we analyzed the structures by XRD and PL and show possible device applications. The GaN nano- and microstructures were grown by metal organic vapor phase epitaxy either in a self-organized process or by selective area growth for a better control of shape and material composition. Finally we take a look onto possible device applications, presenting our attempts, e.g., to build LEDs based on GaN nanostructures. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  4. From Stable ZnO and GaN Clusters to Novel Double Bubbles and Frameworks

    Matthew R. Farrow

    2014-05-01

    Full Text Available A bottom up approach is employed in the design of novel materials: first, gas-phase “double bubble” clusters are constructed from high symmetry, Th, 24 and 96 atom, single bubbles of ZnO and GaN. These are used to construct bulk frameworks. Upon geometry optimization—minimisation of energies and forces computed using density functional theory—the symmetry of the double bubble clusters is reduced to either C1 or C2, and the average bond lengths for the outer bubbles are 1.9 Å, whereas the average bonds for the inner bubble are larger for ZnO than for GaN; 2.0 Å and 1.9 Å, respectively. A careful analysis of the bond distributions reveals that the inter-bubble bonds are bi-modal, and that there is a greater distortion for ZnO. Similar bond distributions are found for the corresponding frameworks. The distortion of the ZnO double bubble is found to be related to the increased flexibility of the outer bubble when composed of ZnO rather than GaN, which is reflected in their bulk moduli. The energetics suggest that (ZnO12@(GaN48 is more stable both in gas phase and bulk frameworks than (ZnO12@(ZnO48 and (GaN12@(GaN48. Formation enthalpies are similar to those found for carbon fullerenes.

  5. Efficient light extraction from GaN LEDs using gold-coated ZnO nanoparticles

    Alhadidi, A.

    2015-11-01

    We experimentally demonstrate the effect of depositing gold-coated ZnO nanoparticles on the surface of GaN multi-quantum well LED structures. We show that this method can significantly increase the amount of extracted light.

  6. Hydrogen-surfactant-assisted coherent growth of GaN on ZnO substrate

    Zhang, Jingzhao; Zhang, Yiou; Tse, Kinfai; Zhu, Junyi

    2018-01-01

    Heterostructures of wurtzite based devices have attracted great research interest because of the tremendous success of GaN in light emitting diodes (LED) industry. High-quality GaN thin films on inexpensive and lattice matched ZnO substrates are both commercially and technologically desirable. Intrinsic wetting conditions, however, forbid such heterostructures as the energy of ZnO polar surfaces is much lower than that of GaN polar surfaces, resulting in 3D growth mode and poor crystal quality. Based on first-principles calculations, we propose the use of surfactant hydrogen to dramatically alter the growth mode of the heterostructures. Stable H-involved surface configurations and interfaces are investigated with the help of our newly developed modelling techniques. The temperature and chemical potential dependence of our proposed strategy, which is critical in experiments, is predicted by applying the experimental Gibbs free energy of H2. Our thermodynamic wetting condition analysis is a crucial step for the growth of GaN on ZnO, and we find that introducing H will not degrade the stability of ZnO substrate. This approach will allow the growth of high-quality GaN thin films on ZnO substrates. We believe that our new strategy may reduce the manufactory cost, improve the crystal quality, and improve the efficiency of GaN-based devices.

  7. Characteristics of threading dislocations in ZnO grown on facet-controlled epitaxial overgrown GaN templates

    Zhou, H L; Chua, S J; Chow, S Y; Pan, H; Zhu, Y W; Feng, Y P; Wang, L S; Zang, K Y; Liu, W; Tripathy, S

    2007-01-01

    Using transmission electron microscopy (TEM), the authors have investigated the behavior of threading dislocations in ZnO selectively grown on a facet-controlled epitaxial overgrown GaN template. In this case, the ZnO is grown by a vapor transport method. The TEM study in the overgrown regions shows that all the pure-edge type dislocations in ZnO are parallel toward the mask area and vertical propagation of dislocation to the ZnO surface is minimized. Using such a selective growth technique on a faceted semi-polar GaN surface, a reduction of threading dislocation density in ZnO could be achieved

  8. Arsenic in ZnO and GaN: substitutional cation or anion sites?

    Wahl, Ulrich; Rita, Elisabete; Marques, Ana Claudia; Alves, Eduardo; Carvalho Soares, José

    2007-01-01

    We have determined the lattice location of ion implanted As in ZnO and GaN by means of conversion electron emission channeling from radioactive $^{73}$As. In contrast to what one might expect from its nature as a group V element, we find that As does not occupy substitutional O sites in ZnO but in its large majority substitutional Zn sites. Arsenic in ZnO is thus an interesting example for an impurity in a semiconductor where the major impurity lattice site is determined by atomic size and electronegativity rather than its position in the periodic system. In contrast, in GaN the preference of As for substitutional cation sites is less pronounced and about half of the implanted As atoms occupy Ga and the other half N sites. Apparently, the smaller size-mismatch between As and N and the chemical similarity of both elements make it feasible that As partly substitutes for N atoms.

  9. Dominant intrinsic acceptors in GaN and ZnO

    Saarinen, K; Hautakangas, S; Tuomisto, F [Laboratory of Physics, Helsinki University of Technology, PO Box 1100, FI-02015 TKK (Finland)

    2006-09-01

    Positron annihilation measurements reveal negatively charged Ga vacancies in n-type GaN and Zn vacancies in n-type ZnO. Positron trapping at other negative defects is not observed, indicating that cation vacancies are the dominant acceptors in these materials. The vacancy concentrations are the same as the total acceptor densities determined in Hall experiments, confirming the dominant role of the vacancy defects. The Ga vacancy in GaN is found as the main compensating centre over the range of four orders of magnitude of intentional oxygen doping.

  10. Dominant intrinsic acceptors in GaN and ZnO

    Saarinen, K; Hautakangas, S; Tuomisto, F

    2006-01-01

    Positron annihilation measurements reveal negatively charged Ga vacancies in n-type GaN and Zn vacancies in n-type ZnO. Positron trapping at other negative defects is not observed, indicating that cation vacancies are the dominant acceptors in these materials. The vacancy concentrations are the same as the total acceptor densities determined in Hall experiments, confirming the dominant role of the vacancy defects. The Ga vacancy in GaN is found as the main compensating centre over the range of four orders of magnitude of intentional oxygen doping

  11. Polarity in GaN and ZnO: Theory, measurement, growth, and devices

    Zúñiga-Pérez, Jesús; Consonni, Vincent; Lymperakis, Liverios; Kong, Xiang; Trampert, Achim; Fernández-Garrido, Sergio; Brandt, Oliver; Renevier, Hubert; Keller, Stacia; Hestroffer, Karine; Wagner, Markus R.; Reparaz, Juan Sebastián; Akyol, Fatih; Rajan, Siddharth; Rennesson, Stéphanie; Palacios, Tomás; Feuillet, Guy

    2016-12-01

    The polar nature of the wurtzite crystalline structure of GaN and ZnO results in the existence of a spontaneous electric polarization within these materials and their associated alloys (Ga,Al,In)N and (Zn,Mg,Cd)O. The polarity has also important consequences on the stability of the different crystallographic surfaces, and this becomes especially important when considering epitaxial growth. Furthermore, the internal polarization fields may adversely affect the properties of optoelectronic devices but is also used as a potential advantage for advanced electronic devices. In this article, polarity-related issues in GaN and ZnO are reviewed, going from theoretical considerations to electronic and optoelectronic devices, through thin film, and nanostructure growth. The necessary theoretical background is first introduced and the stability of the cation and anion polarity surfaces is discussed. For assessing the polarity, one has to make use of specific characterization methods, which are described in detail. Subsequently, the nucleation and growth mechanisms of thin films and nanostructures, including nanowires, are presented, reviewing the specific growth conditions that allow controlling the polarity of such objects. Eventually, the demonstrated and/or expected effects of polarity on the properties and performances of optoelectronic and electronic devices are reported. The present review is intended to yield an in-depth view of some of the hot topics related to polarity in GaN and ZnO, a fast growing subject over the last decade.

  12. Defect studies in electron-irradiated ZnO and GaN

    Tuomisto, F.; Look, D.C.; Farlow, G.C.

    2007-01-01

    We present experimental results obtained with positron annihilation spectroscopy in room-temperature electron-irradiated n-type ZnO and GaN. The cation vacancies act as important compensating centers in 2 MeV electron-irradiated samples, even though their introduction rates are different by 2 orders of magnitude. In addition, negatively charged non-open volume defects that also compensate the n-type conductivity are produced together with the cation vacancies at similar introduction rates. The low introduction rates of compensating defects in ZnO demonstrate the radiation hardness of the material. Isochronal thermal annealings were performed to study the dynamics of the irradiation-induced defects. In 2 MeV electron-irradiated ZnO, all the defects introduced in the irradiation disappear already at 600 K, while 1100 K is needed in GaN. Several separate annealing stages of the defects are observed in both materials, the first at 400 K

  13. Defect studies in electron-irradiated ZnO and GaN

    Tuomisto, F. [Laboratory of Physics, Helsinki University of Technology, 02015 TKK Espoo (Finland)], E-mail: filip.tuomisto@tkk.fi; Look, D.C. [Semiconductor Research Center, Wright State University, Dayton, OH 45435 (United States); Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433 (United States); Farlow, G.C. [Physics Department, Wright State University, Dayton, OH 45435 (United States)

    2007-12-15

    We present experimental results obtained with positron annihilation spectroscopy in room-temperature electron-irradiated n-type ZnO and GaN. The cation vacancies act as important compensating centers in 2 MeV electron-irradiated samples, even though their introduction rates are different by 2 orders of magnitude. In addition, negatively charged non-open volume defects that also compensate the n-type conductivity are produced together with the cation vacancies at similar introduction rates. The low introduction rates of compensating defects in ZnO demonstrate the radiation hardness of the material. Isochronal thermal annealings were performed to study the dynamics of the irradiation-induced defects. In 2 MeV electron-irradiated ZnO, all the defects introduced in the irradiation disappear already at 600 K, while 1100 K is needed in GaN. Several separate annealing stages of the defects are observed in both materials, the first at 400 K.

  14. Tunable light extraction efficiency of GaN light emitting diodes by ZnO nanorod arrays

    Chao, C H; Lin, W H; Lin, C F; Chen, C H; Changjean, C H

    2009-01-01

    We report the influence of ZnO nanorod arrays (NRAs) on the light extraction efficiency of GaN light emitting diodes (LEDs). Our investigation indicates that the output light intensity of the device exhibits a periodic oscillation as a function of the rod length. The variation of light extraction efficiency is caused by the Fabry–Perot resonance of the film composed of the nanorods. The theoretical analysis shows a good agreement with the measurement results. Our study reveals a method to control the output light extraction efficiency of GaN LEDs via a simple solution-based synthesized ZnO NRAs

  15. Strain-free GaN thick films grown on single crystalline ZnO buffer layer with in situ lift-off technique

    Lee, S. W.; Minegishi, T.; Lee, W. H.; Goto, H.; Lee, H. J.; Lee, S. H.; Lee, Hyo-Jong; Ha, J. S.; Goto, T.; Hanada, T.; Cho, M. W.; Yao, T.

    2007-01-01

    Strain-free freestanding GaN layers were prepared by in situ lift-off process using a ZnO buffer as a sacrificing layer. Thin Zn-polar ZnO layers were deposited on c-plane sapphire substrates, which was followed by the growth of Ga-polar GaN layers both by molecular beam epitaxy (MBE). The MBE-grown GaN layer acted as a protecting layer against decomposition of the ZnO layer and as a seeding layer for GaN growth. The ZnO layer was completely in situ etched off during growth of thick GaN layers at low temperature by hydride vapor phase epitaxy. Hence freestanding GaN layers were obtained for the consecutive growth of high-temperature GaN thick layers. The lattice constants of freestanding GaN agree with those of strain-free GaN bulk. Extensive microphotoluminescence study indicates that strain-free states extend throughout the high-temperature grown GaN layers

  16. Energy Level Alignment at Aqueous GaN and ZnO Interfaces

    Hybertsen, Mark S.; Kharche, Neerav; Muckerman, James T.

    2014-03-01

    Electronic energy level alignment at semiconductor-electrolyte interfaces is fundamental to electrochemical activity. Motivated in particular by the search for new materials that can be more efficient for photocatalysis, we develop a first principles method to calculate this alignment at aqueous interfaces and demonstrate it for the specific case of non-polar GaN and ZnO interfaces with water. In the first step, density functional theory (DFT) based molecular dynamics is used to sample the physical interface structure and to evaluate the electrostatic potential step at the interface. In the second step, the GW approach is used to evaluate the reference electronic energy level separately in the bulk semiconductor (valence band edge energy) and in bulk water (the 1b1 energy level), relative to the internal electrostatic energy reference. Use of the GW approach naturally corrects for errors inherent in the use of Kohn-Sham energy eigenvalues to approximate the electronic excitation energies in each material. With this predicted interface alignment, specific redox levels in water, with potentials known relative to the 1b1 level, can then be compared to the semiconductor band edge positions. Our results will be discussed in the context of experiments in which photoexcited GaN and ZnO drive the hydrogen evolution reaction. Research carried out at Brookhaven National Laboratory under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.

  17. Effect of growth temperature on the epitaxial growth of ZnO on GaN by ALD

    Särkijärvi, Suvi; Sintonen, Sakari; Tuomisto, Filip; Bosund, Markus; Suihkonen, Sami; Lipsanen, Harri

    2014-07-01

    We report on the epitaxial growth of ZnO on GaN template by atomic layer deposition (ALD). Diethylzinc (DEZn) and water vapour (H2O) were used as precursors. The structure and the quality of the grown ZnO layers were studied with scanning electron microscope (SEM), X-ray diffraction (XRD), photoluminescence (PL) measurements and positron annihilation spectroscopy. The ZnO films were confirmed epitaxial, and the film quality was found to improve with increasing deposition temperature in the vicinity of the threshold temperature of two dimensional growth. We conclude that high quality ZnO thin films can be grown by ALD. Interestingly only separate Zn-vacancies were observed in the films, although ZnO thin films typically contain fairly high density of surface pits and vacancy clusters.

  18. Atomic layer epitaxy of ZnO for applications in molecular beam epitaxy growth of GaN and InGaN

    Godlewski, M.; Szczerbakow, A.; Ivanov, V. Yu.; Barski, A.; Goldys, E.M.

    2000-01-01

    We report the successful atomic layer epitaxy growth of thin ZnO films and their use for GaN and InGaN epitaxy. The properties of ZnO epilayers, obtained by four different procedures, are analysed, as well as of GaN and InGaN films grown on ZnO-coated Si and GaAs by MBE. (author)

  19. Epitaxial growth of M-plane GaN on ZnO micro-rods by plasma-assisted molecular beam epitaxy

    Shuo-Ting You

    2015-12-01

    Full Text Available We have studied the GaN grown on ZnO micro-rods by plasma-assisted molecular beam epitaxy. From the analyses of GaN microstructure grown on non-polar M-plane ZnO surface ( 10 1 ̄ 0 by scanning transmission electron microscope, we found that the ZnGa2O4 compound was formed at the M-plane hetero-interface, which was confirmed by polarization-dependent photoluminescence. We demonstrated that the M-plane ZnO micro-rod surface can be used as an alternative substrate to grow high quality M-plane GaN epi-layers.

  20. Heteroepitaxial Patterned Growth of Vertically Aligned and Periodically Distributed ZnO Nanowires on GaN Using Laser Interference Ablation

    Yuan, Dajun

    2010-08-23

    A simple two-step method of fabricating vertically aligned and periodically distributed ZnO nanowires on gallium nitride (GaN) substrates is described. The method combines laser interference ablation (LIA) and low temperature hydrothermal decomposition. The ZnO nanowires grow heteroepitaxially on unablated regions of GaN over areas spanning 1 cm2, with a high degree of control over size, orientation, uniformity, and periodicity. High resolution transmission electron microscopy and scanning electron microscopy are utilized to study the structural characteristics of the LIA-patterned GaN substrate in detail. These studies reveal the possible mechanism for the preferential, site-selective growth of the ZnO nanowires. The method demonstrates high application potential for wafer-scale integration into sensor arrays, piezoelectric devices, and optoelectronic devices. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Herstellung und Charakterisierung von ZnO1-xSx-Dünnschichten : Dotierung mit Wasserstoff und Einsatz in ZnO1-xSx/GaN-Heterostruktur-Leuchtdioden

    Kronenberger, Achim

    2013-01-01

    Das ternäre Materialsystem ZnO1-xSx ist für den Einsatz als Cd-freie Pufferschicht in Solarzellen, für Halbleiter-Heterostrukturen (z.B. Leuchtdioden) oder als Bandkanten-Filter interessant, da sich die energetische Lage von Valenzband-Maximum und Leitungsband-Minimum und somit ebenfalls die Energie der Bandlücke durch die Komposition beeinflussen lassen. Zusätzlich eignet es sich aufgrund der damit einhergehenden Veränderung der elektrischen und phononischen Eigenschaften als Modelsystem für...

  2. Emission channeling studies on transition-metal doped GaN and ZnO: Cation versus anion substitution

    AUTHOR|(CDS)2070176; Wahl, Ulrich; Martins Correia, Joao; Amorim, Lígia; Silva, Daniel; Decoster, Stefan; Castro Ribeiro Da Silva, Manuel; Temst, Kristiaan; Vantomme, André

    2014-01-01

    The magnetic and electric properties of impurities in semiconductors are strongly dependent on the lattice sites which they occupy. While the majority site can often be predicted based on chemical similarities with the host elements and is usually simple to confirm experimentally, minority sites are far more complicated to predict, detect and identify. We have carried out extensive beta− emission channeling studies on the lattice location of transition metal impurities in wide-gap dilute magnetic semiconductors, namely Co and Mn in GaN and ZnO, making use of radioactive 61Co and 56Mn implanted at the ISOLDE facility at CERN. In addition to the majority occupation of cation (Ga, Zn) sites, we located significant fractions (of the order of 20%) of the Co and Mn impurities in anion (N, O) sites, which are virtually unaffected by thermal annealing up to 900 °C. Here, we present the beta− emission channeling experiments on 61Co-implanted GaN. We discuss these results in the context of our recent reports of mi...

  3. Scanning tunneling microscopy and spectroscopy on GaN and InGaN surfaces; Rastertunnelmikroskopie und -spektroskopie an GaN- und InGaN-Oberflaechen

    Krueger, David

    2009-12-02

    Optelectronic devices based on gallium nitride (GaN) and indium gallium nitride (InGaN) are in the focus of research since more than 20 years and still have great potential for optical applications. In the first part of this work non-polar surfaces of GaN are investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and scanning tunneling microscopy (STM). In SEM and AFM, the (1 anti 100)- and especially the (anti 2110)-plane are quite corrugated. For the first time, the (anti 2110)-plane of GaN is atomically resolved in STM. In the second part InGaN quantum dot layers are investigated by X-ray photoelectron spectroscopy (XPS), scanning tunneling spectroscopy (STS) and STM. The STMmeasurements show the dependency of surface morphology on growth conditions in the metalorganic vapour phase epitaxy (MOVPE). Nucleation, a new MOVPE-strategy, is based on phase separations on surfaces. It is shown that locally varying density of states and bandgaps can be detected by STS, that means bandgap histograms and 2D-bandgap-mapping. (orig.)

  4. Polariton condensation phase diagram in wide-band-gap planar microcavities: GaN versus ZnO

    Jamadi, O.; Réveret, F.; Mallet, E.; Disseix, P.; Médard, F.; Mihailovic, M.; Solnyshkov, D.; Malpuech, G.; Leymarie, J.; Lafosse, X.; Bouchoule, S.; Li, F.; Leroux, M.; Semond, F.; Zuniga-Perez, J.

    2016-03-01

    The polariton condensation phase diagram is compared in GaN and ZnO microcavities grown on mesa-patterned silicon substrate. Owing to a common platform, these microcavities share similar photonic properties with large quality factors and low photonic disorder, which makes it possible to determine the optimal spot diameter and to realize a thorough phase diagram study. Both systems have been investigated under the same experimental conditions. The experimental results and the subsequent analysis reveal clearly that longitudinal optical phonons have no influence in the thermodynamic region of the condensation phase diagram, while they allow a strong (slight) decrease of the polariton lasing threshold in the trade-off zone (kinetic region). Phase diagrams are compared with numerical simulations using Boltzmann equations, and are in satisfactory agreement. A lower polariton lasing threshold has been measured at low temperature in the ZnO microcavity, as is expected due to a larger Rabi splitting. This study highlights polariton relaxation mechanisms and their importance in polariton lasing.

  5. Direct Heteroepitaxial Growth of ZnO over GaN Crystal in Aqueous Solution

    Hamada, Takahiro; Ito, Akihiro; Nagao, Nobuaki; Suzuki, Nobuyasu; Fujii, Eiji; Tsujimura, Ayumu

    2013-04-01

    We report on the structural and electrical properties of ZnO films grown on surface-treated GaN/Al2O3 substrates by chemical bath deposition. X-ray diffraction analysis indicated that the ZnO films had a single-crystalline wurtzite structure with c-axis orientation. The ZnO film exhibited n-type conduction with a carrier concentration of 6.9 ×1018 cm-3, an electron mobility of 41 cm2/(V.s), and a resistivity of 2.2 ×10-2 Ω.cm. A low specific contact resistivity of 4.3 ×10-3 Ω.cm2 was obtained at the ZnO/n-GaN interface. Additionally, the ZnO film exhibited high transparency in the visible and infrared region.

  6. Growth of c-plane ZnO on γ-LiAlO2 (1 0 0) substrate with a GaN buffer layer by plasma assisted molecular beam epitaxy

    Yan, T.; Lu, C.-Y.J.; Schuber, R.; Chang, L.; Schaadt, D.M.; Chou, M.M.C.; Ploog, K.H.; Chiang, C.-M.

    2015-01-01

    Highlights: • ZnO epilayers were grown on LiAlO 2 (1 0 0) substrate with a GaN buffer layer by MBE. • A high Zn/O flux ratio is beneficial for reducing the density of screw dislocations. • Reciprocal space maps demonstrate that the misfit strain in ZnO has been relaxed. • No interfacial layer is formed at ZnO/GaN interface using a Zn pre-exposure strategy. - Abstract: C-plane ZnO epilayers were grown on LiAlO 2 (1 0 0) substrate with a GaN buffer layer by plasma assisted molecular beam epitaxy. Both the X-ray rocking curves and the transmission electron microscopy analyses indicate that the ZnO epilayers exhibit a lower threading dislocation density (∼1 × 10 10 cm −2 ) as compared to those grown on LiAlO 2 substrate without the buffer layer. A high Zn/O flux ratio is beneficial for reducing the density of screw-type dislocations. Reciprocal space maps demonstrate that the misfit strain has been relaxed. No interfacial layer is formed at the ZnO/GaN interface by using a Zn pre-exposure strategy. The ZnO epilayers exhibit a strong near band edge emission at 3.28 eV at room temperature with a negligible green band emission

  7. Thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap semiconductors SiC, GaN, and ZnO

    Zheng Huang

    2015-09-01

    Full Text Available We have investigated the thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap(n-type semiconductors SiC, GaN, and ZnO based on first-principles calculations and Boltzmann transport theory. Our results show that the thermoelectric performance increases from 3C to 6H, 4H, and 2H structures with an increase of hexagonality for SiC. However, for GaN and ZnO, their power factors show a very weak dependence on the polytype. Detailed analysis of the thermoelectric properties with respect to temperature and carrier concentration of 4H-SiC, 2H-GaN, and 2H-ZnO shows that the figure of merit of these three compounds increases with temperature, indicating the promising potential applications of these thermoelectric materials at high temperature. The significant difference of the polytype-dependent thermoelectric properties among SiC, GaN, and ZnO might be related to the competition between covalency and ionicity in these semiconductors. Our calculations may provide a new way to enhance the thermoelectric properties of wide-band-gap semiconductors through atomic structure design, especially hexagonality design for SiC.

  8. Ferromagnetism in with Fe implanted GaN and TiO{sub 2}; Ferromagnetismus in mit Fe implantierten GaN und TiO{sub 2}

    Talut, Georg

    2009-12-15

    In the present study it was tried to create a diluted magnetic semiconductor on the basis of GaN and TiO{sub 2} by means of ion beam implantation. In most cases, by characterization of structural and magnetic properties, it was possible to prove that the ferromagnetic state is related to either spinodal decomposition or secondary phase formation. In case of Fe implanted GaN spinodal decomposition, epitaxially oriented {alpha}-Fe or {epsilon}-Fe{sub 3}N nanocrystals were found to be responsible for the ferromagnetic behavior. In addition, the formation of {gamma}-Fe clusters was observed. Similarly, in TiO{sub 2} the ferromagnetism is related to the formation of epitaxially oriented {alpha}-Fe clusters. Dependent on the process parameters during annealing experiments several various secondary phases were formed. A critical examination of the references in literature points out the significance of usage of sensitive and complementary probe techniques (like CEMS, SQUID, XRD, EXAFS), in order to be able to discuss the origin of ferromagnetism in the field of diluted magnetic semiconductors in a proper way. (orig.)

  9. Electrical transport in GaN and InN nanowires; Elektrischer Transport in GaN- und InN-Nanodraehten

    Richter, Thomas Fabian

    2008-12-19

    This thesis discusses the analysis of the electrical transport in GaN and InN nanowires at room temperature and deep temperatures. From those measurements two different transport models for those two in matter of the band banding completely different materials have been found. In the investigation of the GaN nanowires the main focus was the electrical transport in dependence of the diameter and the n-doping. With the use of IV-measurements on those MBE grown nanowires with different diameters at dark and under UV illumination as well as the decay of the persistent photocurrent, it was possible to find an for GaN untypical behaviour. The electrical transport in those wires is extremely diameter dependent. The dark current shows space charged limited current. With the help of those cognitions a diameter dependent transport model could be found. The transport phenomena in those wires is based on the diameter depending band bending at the edge of the wires caused by the Fermi level pinning inside the forbidden band. This model can be fit to the data with the three parameter doping, fermi level pinning and wire diameter. On the base of those effects a method to determine the doping concentration inside those wires without field effect measurements and contact resistance has been developed. The defect structure inside those wires has been analysed with the help of spectral photoluminescence measurements. Here several defect bands have been found and it was possible with help of several contacts on one single wire to determine different defect regions along the wire and to explain them by the lattice mismatch between nanowire and substrate. Further temperature depending measurements and investigations on Schottky contacted wires as well as on GaN wires with AlN tunnel structures complete the work on GaN. The electrical characterisation on a large scale of undoped and doped InN nanowires shows linear growth of the dark current with the diameter up to wires of around 100 nm

  10. Local lattice environment of indium in GaN, AlN, and InN; Lokale Gitterumgebung von Indium in GaN, AlN und InN

    Penner, J

    2007-12-20

    After an introduction to the physical properties of the nitrides, their preparation, and the state of studies on the implantation in the nitrides the experimental method (PAC) applied in this thesis and the data analysis are presented. The next chapter describes then the applied materials and the sample preparation. The following chapters contain the PAC measurements on the annealing behaviout of GaN, AlN, and InN after the implantation as well as dose- and temperature dependent PAC studies. Finally the most important results are summarized.

  11. Fabrication and characterization of ZnO-based nanopillars; Herstellung und Charakterisierung von ZnO basierenden Nanosaeulen

    Kling, Rainer

    2005-06-15

    The goal of this thesis was the successful growth and characterization of ZnO-based nanopillars by means of metalorganic vapor-phase epitaxy (MOVPE). It was possible to grow high quality binary ZnO nanopillars with very uniform diameters of about 50 nm and lengths of up to 5 {mu}m. Structural analysis of the material was done using HRXRD. It could be confirmed that the pillars show hexagonal symmetry, that they grow unstrained and c-axis oriented. The full width of half maximum of the (0002) rocking curves was found to be about 600 arcsec, a very small value. All this results confirm the excellent structural properties of the nanopillars. To get insight in the optical properties of the samples low-temperature photoluminescence measurements were used. The spectra were dominated by the recombination of donor-bound excitons with again very narrow full width of half maximum of under 0.4 meV and no deep level emission was detected. As no shift in the position of the spectral lines in comparison with ZnO bulk material occurred, the absence of stress could again be confirmed. On the base of the binary material, the next step was to grow doped nanostructures. For this purpose indium and gallium were used. The next step was the fabrication of vanadium doped ZnO:V-nanopillars for future applications in spintronic devices. The material was successfully grown and showed a ferromagnetic phase up to room-temperature. This was confirmed by SQUID and MFM-measurements. Finally as first step towards vertical band-gap engineering, ternary ZnMgOnanopillars were grown. (orig.)

  12. GaN Nanowire Arrays for High-Output Nanogenerators

    Huang, Chi-Te

    2010-04-07

    Three-fold symmetrically distributed GaN nanowire (NW) arrays have been epitaxially grown on GaN/sapphire substrates. The GaN NW possesses a triangular cross section enclosed by (0001), (2112), and (2112) planes, and the angle between the GaN NW and the substrate surface is ∼62°. The GaN NW arrays produce negative output voltage pulses when scanned by a conductive atomic force microscope in contact mode. The average of piezoelectric output voltage was about -20 mV, while 5-10% of the NWs had piezoelectric output voltages exceeding -(0.15-0.35) V. The GaN NW arrays are highly stable and highly tolerate to moisture in the atmosphere. The GaN NW arrays demonstrate an outstanding potential to be utilized for piezoelectric energy generation with a performance probably better than that of ZnO NWs. © 2010 American Chemical Society.

  13. Role of Short-Range Chemical Ordering in (GaN) 1–x (ZnO) x for Photodriven Oxygen Evolution

    Chen, Dennis P. [Department; Neuefeind, Joerg C. [Chemical; Koczkur, Kallum M. [Department; Bish, David L. [Department; Skrabalak, Sara E. [Department

    2017-07-21

    (GaN)1–x(ZnO)x (GZNO) is capable of visible-light driven water splitting, but its bandgap at x ≤ 0.15 (>2.7 eV) results in poor visible-light absorption. Unfortunately, methods to narrow its bandgap by incorporating higher ZnO concentrations are accompanied by extensive Urbach tailing near the absorption-edge, which is indicative of structural disorder or chemical inhomogeneities. We evaluated whether this disorder is intrinsic to the bond-length distribution in GZNO or is a result of defects introduced from the loss of Zn during nitridation. Here, the synthesis of GZNO derived from layered double hydroxide (LDH) precursors is described which minimizes Zn loss and chemical inhomogeneities and enhances visible-light absorption. The average and local atomic structures of LDH-derived GZNO were investigated using X-ray and neutron scattering and are correlated with their oxygen evolution rates. An isotope-contrasted neutron-scattering experiment was conducted in conjunction with reverse Monte Carlo (RMC) simulations. We showed that a bond-valence bias in the RMC refinements reproduces the short-range ordering (SRO) observed in structure refinements using isotope-contrasted neutron data. The findings suggest that positional disorder of cation–anion pairs in GZNO partially arises from SRO and influences local bond relaxations. Furthermore, particle-based oxygen evolution reactions (OERs) in AgNO3 solution reveal that the crystallite size of GZNO correlates more than positional disorder with oxygen evolution rate. These findings illustrate the importance of examining the local structure of multinary photocatalysts to identify dominant factors in particulate-based photodriven oxygen evolution.

  14. Synthesis and characterisation of (poly-)antimonides and N-doped ZnO; Synthese und Charakterisierung von (Poly-)antimoniden und die Darstellung von N-dotiertem ZnO

    Greiwe, Magnus Josef Benedikt

    2014-06-16

    }Sb{sub y} (M = Hf, Zr) as representatives of binary antimonides were synthesized. Through Fe and/or Ni doping superconducting Phases have been found. Furthermore binary chromium-antimonides with partial Fe or Ni substitution were prepared. Cr{sub 2}Ni{sub 0,3}Sb{sub 3,7} was tested as potential anodic material and a capacity of 98% (520 mAh.g{sup -1}) of the theoretical capacity in the 2{sup nd} cycle was measured. All compounds indicated that antimonies with a covalent bonding character are more stable against lithium intercalation than the intermetallic ones. New compounds in the quaternary system Cu-Hg-Sb-X (X = Br, I) were obtained by using the reaction conditions for the earlier (lighter) elements of the V. main group (P, As). In the new structure [Hg{sub 3}Sb{sub 2}]{sub 4}[CuX{sub 3}]{sub 4}X{sub 2} (X = Br, I) X{sub 2} a barbell of the halide is present. This structure is the first example in the system Hf-Sb-X which shows two different interpenetrated networks: [Hg{sub 3}Sb{sub 2}]{sup 2+} and [CuX{sub 3}]{sup 2-}. For the first time it has been possible to calculate the Br-Br bond length by X-ray single crystal measurements at room temperature. Another topic of this work was to test the solution combustion method (SCM) in order to gain ZnO (Wurtzit structure) with nitrogen defects at the oxygen position. Standard synthesis methods for oxonitrides require high temperature or high pressure procedures. A softer synthesis method is the solution combustion method published by Mapa and Gopinath. The results of various experiments in cooperation with Stefan Soellradl yielded no intercalation of nitrogen defects into ZnO but a new phase was found which is identified as isocyanuric acid after reprocessing.

  15. Viability and proliferation of endothelial cells upon exposure to GaN nanoparticles.

    Braniste, Tudor; Tiginyanu, Ion; Horvath, Tibor; Raevschi, Simion; Cebotari, Serghei; Lux, Marco; Haverich, Axel; Hilfiker, Andres

    2016-01-01

    Nanotechnology is a rapidly growing and promising field of interest in medicine; however, nanoparticle-cell interactions are not yet fully understood. The goal of this work was to examine the interaction between endothelial cells and gallium nitride (GaN) semiconductor nanoparticles. Cellular viability, adhesion, proliferation, and uptake of nanoparticles by endothelial cells were investigated. The effect of free GaN nanoparticles versus the effect of growing endothelial cells on GaN functionalized surfaces was examined. To functionalize surfaces with GaN, GaN nanoparticles were synthesized on a sacrificial layer of zinc oxide (ZnO) nanoparticles using hydride vapor phase epitaxy. The uptake of GaN nanoparticles by porcine endothelial cells was strongly dependent upon whether they were fixed to the substrate surface or free floating in the medium. The endothelial cells grown on surfaces functionalized with GaN nanoparticles demonstrated excellent adhesion and proliferation, suggesting good biocompatibility of the nanostructured GaN.

  16. Steps towards a GaN nanowire based light emitting diode and its integration with Si-MOS technology

    Limbach, Friederich

    2012-01-01

    In dieser Arbeit wird die Machbarkeit der Herstellung von Leuchtdioden Strukturen (LEDs) in einzelnen GaN Nanodrähten (ND) und deren Integration mit herkömmlicher Si Technologie untersucht. Hierzu wird zunächst ein generelles Verständnis des Wachstums von GaN ND erarbeitet und dargestellt. Es folgen Untersuchungen zum Einfluss von Dotierstoffen, wie z.B. Mg und Si, auf das Wachstum der ND. Dieses Wissen wird anschließend angewandt um Dotierübergänge in GaN ND herzustellen die nominell n-i-p ...

  17. Wafer-Scale High-Throughput Ordered Growth of Vertically Aligned ZnO Nanowire Arrays

    Wei, Yaguang; Wu, Wenzhuo; Guo, Rui; Yuan, Dajun; Das, Suman; Wang, Zhong Lin

    2010-01-01

    -synthesized morphology. The development of textured ZnO seed layers for replacing single crystalline GaN and ZnO substrates extends the large-scale fabrication of vertically aligned ZnO NW arrays on substrates of other materials, such as polymers, Si, and glass

  18. MOVPE gallium-nitride nanostructures fabricated on ZnO nanorod templates grown from aqueous chemical solution

    Fuendling, Soenke; Li Shunfeng; Postels, Bianca; Al-Suleiman, Mohamed; Wehmann, Hergo-Heinrich; Bakin, Andrey; Waag, Andreas, E-mail: s.fuendling@tu-bs.de [Institut fuer Halbleitertechnik, Technische Universitaet Braunschweig, 38096 Braunschweig (Germany)

    2009-11-15

    Concerning optoelectronic devices fabricated by epitaxial methods, the combination of ZnO and GaN has promising aspects regarding their good optical properties and a relatively good lattice matching between both as compared to other foreign substrates like sapphire or silicon. Moreover ZnO nanopillar arrays may serve as a template for GaN nanopillar fabrication or for high quality GaN layers by lateral overgrowth of the ZnO nanopillars. In this work, we investigate the combination of two very different growth methods - aqueous chemical low temperature growth (ACG) for the ZnO nanopillar templates on silicon substrates and metalorganic vapor phase epitaxy (MOVPE) for the GaN overgrowth - in order to show to which extent the very cost efficient ZnO templates suit the high demands of GaN MOVPE. By a combination of annealing and photoluminescence experiments we show that the properties of the heterostructures change significantly with temperature.

  19. Taevo Gans / Ene Ammer

    Ammer, Ene

    1998-01-01

    Sisearhitekt Taevo Gansist. Tudengipõlvest, selle aja projektidest, sõpruskonnast, tandemist Summatavet & Gans, Venemaa tellimustest, kaastöölistest. Üksinda Hommilkumaal vene tarbekunsti näitusega 1974. a. 1988. a. loodud perefirmast "GaDis" (omanikud Taevo, Helle Gans, Riia Oja), mis nõustab ka "Wermot" mööbli osas. "GaDise" sisekujundusprojektidest, millega Taevo ja Helle Gans tegelevad üheskoos

  20. Structure guided GANs

    Cao, Feidao; Zhao, Huaici; Liu, Pengfei

    2017-11-01

    Generative adversarial networks (GANs) has achieved success in many fields. However, there are some samples generated by many GAN-based works, whose structure is ambiguous. In this work, we propose Structure Guided GANs that introduce structural similar into GANs to overcome the problem. In order to achieve our goal, we introduce an encoder and a decoder into a generator to design a new generator and take real samples as part of the input of a generator. And we modify the loss function of the generator accordingly. By comparison with WGAN, experimental results show that our proposed method overcomes largely sample structure ambiguous and can generate higher quality samples.

  1. Z L GAN

    Z L GAN. Articles written in Sadhana. Volume 43 Issue 4 April 2018 pp 59. Effect of scale size, orientation type and dispensing method on void formation in the CUF encapsulation of BGA · AIZAT ABAS FEI CHONG NG Z L GAN M H H ISHAK M Z ABDULLAH GEAN YUEN CHONG · More Details Abstract Fulltext PDF.

  2. Fabrication of GaN epitaxial thin film on InGaZnO4 single-crystalline buffer layer

    Shinozaki, Tomomasa; Nomura, Kenji; Katase, Takayoshi; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2010-01-01

    Epitaxial (0001) films of GaN were grown on (111) YSZ substrates using single-crystalline InGaZnO 4 (sc-IGZO) lattice-matched buffer layers by molecular beam epitaxy with a NH 3 source. The epitaxial relationships are (0001) GaN //(0001) IGZO //(111) YSZ in out-of-plane and [112-bar 0] GaN //[112-bar 0] IGZO //[11-bar 0] YSZ in in-plane. This is different from those reported for GaN on many oxide crystals; the in-plane orientation of GaN crystal lattice is rotated by 30 o with respect to those of oxide substrates except for ZnO. Although these GaN films showed relatively large tilting and twisting angles, which would be due to the reaction between GaN and IGZO, the GaN films grown on the sc-IGZO buffer layers exhibited stronger band-edge photoluminescence than GaN grown on a low-temperature GaN buffer layer.

  3. Low operation voltage of GaN-based LEDs with Al-doped ZnO upper contact directly on p-type GaN without insert layer

    Chen, P. H.; Chen, Yu An; Chang, L. C.; Lai, W. C.; Kuo, Cheng Huang

    2015-07-01

    Al-doped ZnO (AZO) film was evaporated on double-side polished sapphire, p-GaN layers, n+-InGaN-GaN short-period superlattice (SPS) structures, and GaN-based light-emitting diodes (LEDs) by e-beam. The AZO film on the p-GaN layer after thermal annealing exhibited an extremely high transparency (98% at 450 nm) and a small specific contact resistance of 2.19 × 10-2 Ω cm2, which was almost the same as that of as-deposited AZO on n+-SPS structure. With 20 mA injection current, the forward voltages were 3.30 and 3.27 V, whereas the output powers were 4.32 and 4.07 mW for the LED with AZO on insert n+-SPS upper contact and the LED with AZO on p-GaN upper contact (without insert layer), respectively. The small specific contact resistance and low operation voltage of LED with AZO on p-GaN upper contact was achieved by rapid thermal annealing (RTA) process.

  4. Improvement of stoichiometry in (ZnO)1-x(GaN)x thin films grown by laser ablation

    Gopalakrishnan, N.; Shin, B.C.; Bhuvana, K.P.; Elanchezhiyan, J.; Balasubramanian, T.

    2008-01-01

    The fabrication of pure and GaN (1 mol%) doped ZnO thin films by KrF excimer laser have been addressed. The fabricated films on Si(1 1 1) substrates have been investigated by X-ray diffraction (XRD), photoluminescence (PL) and atomic force microscopy (AFM) in order to investigate the structural, optical and morphological properties, respectively. The XRD analysis shows that the full width at half maximum (FWHM) of ZnO film is found to be decreased as doped with GaN due to the improvement of the stoichiometery between Zn and O. The PL spectra reveal that the deep level emissions due to native donor defects in pure ZnO are suppressed upon doping with GaN. The images of AFM show that the RMS surface roughness of pure ZnO, 27 nm is reduced to18 nm while doped with 1 mol% GaN. The incorporation of nitrogen in the film is confirmed by glow discharge mass spectroscopy (GDMS). The improved structural, optical and morphological properties of ZnO by GaN dopant due to enhancement of stoichiometry have been discussed in detail

  5. III-nitrides on oxygen- and zinc-face ZnO substrates

    Namkoong, Gon; Burnham, Shawn; Lee, Kyoung-Keun; Trybus, Elaissa; Doolittle, W. Alan; Losurdo, Maria; Capezzuto, Pio; Bruno, Giovanni; Nemeth, Bill; Nause, Jeff

    2005-01-01

    The characteristics of III-nitrides grown on zinc- and oxygen-face ZnO by plasma-assisted molecular beam epitaxy were investigated. The reflection high-energy electron diffraction pattern indicates formation of a cubic phase at the interface between III-nitride and both Zn- and O-face ZnO. The polarity indicates that Zn-face ZnO leads to a single polarity, while O-face ZnO forms mixed polarity of III-nitrides. Furthermore, by using a vicinal ZnO substrate, the terrace-step growth of GaN was realized with a reduction by two orders of magnitude in the dislocation-related etch pit density to ∼10 8 cm -2 , while a dislocation density of ∼10 10 cm -2 was obtained on the on-axis ZnO substrates

  6. Amphoteric Be in GaN: Experimental Evidence for Switching between Substitutional and Interstitial Lattice Sites

    Tuomisto, Filip; Prozheeva, Vera; Makkonen, Ilja; Myers, Thomas H.; Bockowski, Michal; Teisseyre, Henryk

    2017-11-01

    We show that Be exhibits amphoteric behavior in GaN, involving switching between substitutional and interstitial positions in the lattice. This behavior is observed through the dominance of BeGa in the positron annihilation signals in Be-doped GaN, while the emergence of VGa at high temperatures is a consequence of the Be impurities being driven to interstitial positions. The similarity of this behavior to that found for Na and Li in ZnO suggests that this could be a universal property of light dopants substituting for heavy cations in compound semiconductors.

  7. ZnO nanowires for the modification of evanescence-field sensors and the development of novel solar cells; ZnO-Nanodraehte zur Modifizierung von Evaneszenzfeldsensoren und der Entwicklung neuartiger Solarzellen

    Boerner, Susanne

    2008-10-02

    The photoluminescence of single structures and the nanowire ensemble were analyzed and compared. This pursued in dependence on the excitation density and the sample temperature. The excitonic emission contributes essentially to the near-band-edge photoluminescence. The ZnO nanowire ensemble exhibits a laser threshold of 500 kW/cm{sup 2} at room temperature. To the photoluminescence spectra the single exciton processes were assigned. The wave-guiding properties were practically detected by means of optical microscopy and micromanipulation. While the main topic of this thesis lied in the analysis of the optical properties of the ZnO nanowires in the last part the implementation of nanostructures in hybrid solar cells was discussed and first results of the characterization of the material complex of p-conducting polymer (Clevios P) and ZnO nanowires presented.

  8. Encapsulating Quantum Dots into ZnO Nanorods for Advanced photonics and Laser Applications

    2016-10-12

    axis of a hexagonal ZnO NMR is confined by total- internal reflections according to previous theoretical and experimental studies20,21. The use of QDs...monolayer of PMMA microspheres self-assembled on the GaN substrate, (b) Microporous TiO2 ring template obtained after removing PMMA microspheres. (c...TEM allows us to qualitatively probe the internal structure of the ZnO NMRs and composite QDs and to determine QDs distribution in ZnO NMRs surface

  9. Separation and recombinatiuon of charge carriers in solar cells with a nanostructured ZnO electrode; Trennung und Rekombination von Ladungstraegern in Solarzellen mit nanostrukturierter ZnO-Elektrode

    Tornow, Julian

    2010-03-02

    The publication investigates electrodes consisting of ZnO nanorods deposited hydrothermally on conductive glass substrate (conductive glass). The electrodes are transparent to visible light and are sensitized for solar cell applications by a light-absorbing layer which in this case consists either of organometallic dye molecules (N3) or of an indium sulfide layer with a thickness of only a few nanometers. Electric contacts for the sensitized electrode are either made of a liquid electrolyte or of a perforated solid electrolyte. Methods of analysis were impedance spectroscopy, time-resolved photocurrent measurements, and time-resolved microwave photoconductivity. A high concentration of up to 10{sup 20} was found in the ZnO nanorods. The dye-sensitized solar cell showed exessively fast recombination with the oxydized dye molecules (sub-{mu}s) but a slow recombination rate with the oxydized redox ions of the electrolyte (ms). In the indium sulfide solar cells, the charges are separated at the contact with the ZnO nanorods while contact with the perforated CuSCN conductor is not charge-separating. Recombination takes place in indium sulfide, directly between the perforated conductor and ZnO, and also via the charge-separating contact with decreasing rates.

  10. Efficient room temperature hydrogen sensor based on UV-activated ZnO nano-network

    Kumar, Mohit; Kumar, Rahul; Rajamani, Saravanan; Ranwa, Sapana; Fanetti, Mattia; Valant, Matjaz; Kumar, Mahesh

    2017-09-01

    Room temperature hydrogen sensors were fabricated from Au embedded ZnO nano-networks using a 30 mW GaN ultraviolet LED. The Au-decorated ZnO nano-networks were deposited on a SiO2/Si substrate by a chemical vapour deposition process. X-ray diffraction (XRD) spectrum analysis revealed a hexagonal wurtzite structure of ZnO and presence of Au. The ZnO nanoparticles were interconnected, forming nano-network structures. Au nanoparticles were uniformly distributed on ZnO surfaces, as confirmed by FESEM imaging. Interdigitated electrodes (IDEs) were fabricated on the ZnO nano-networks using optical lithography. Sensor performances were measured with and without UV illumination, at room temperate, with concentrations of hydrogen varying from 5 ppm to 1%. The sensor response was found to be ˜21.5% under UV illumination and 0% without UV at room temperature for low hydrogen concentration of 5 ppm. The UV-photoactivated mode enhanced the adsorption of photo-induced O- and O2- ions, and the d-band electron transition from the Au nanoparticles to ZnO—which increased the chemisorbed reaction between hydrogen and oxygen. The sensor response was also measured at 150 °C (without UV illumination) and found to be ˜18% at 5 ppm. Energy efficient low cost hydrogen sensors can be designed and fabricated with the combination of GaN UV LEDs and ZnO nanostructures.

  11. Synthesis of Vertically Aligned ZnO Nano rods on Various Substrates

    Hassan, J.J.; Hassan, Z.; Abu Hassan, H.; Mahdi, M.A.

    2011-01-01

    We successfully synthesized vertically aligned ZnO nano rods on Si, GaN, Sic, Al 2 O 3 , ITO, and quartz substrates using microwave assisted chemical bath deposition (MA-CBD) method. All these types of substrates were seeded with PVA-ZnO nano composites layer prior to the nano rods growth. The effect of substrate type on the morphology of the ZnO nano rods was studied. The diameter of grown ZnO nano rods ranged from 50 nm to 200 nm. Structural quality and morphology of ZnO nano rods were determined by x-ray diffraction and scanning electron microscopy, which revealed hexagonal wurtzite structures perpendicular to the substrate along the z-axis in the direction of (002). Photoluminescence measurements of grown ZnO nano rods on all substrates exhibited high UV peak intensity. Raman scattering studies were conducted to estimate the lattice vibration modes. (author)

  12. Sport und soziale Integration

    Turan, Günes

    2012-01-01

    Sport und soziale Integration : Chancen, Probleme und Perspektiven für Städte und Kommunen ; Tagungsband der gleichnamigen Tagung am 28. und 29. Juni 2011 in Augsburg / Helmut Altenberger ... (Hrsg.). - Hamburg : Feldhaus, Ed. Czwalina, 2012. - 104 S. - (Sportwissenschaft und Sportpraxis ; 161)

  13. Crystallinity Improvement of ZnO Thin Film on Different Buffer Layers Grown by MBE

    Shao-Ying Ting

    2012-01-01

    Full Text Available The material and optical properties of ZnO thin film samples grown on different buffer layers on sapphire substrates through a two-step temperature variation growth by molecular beam epitaxy were investigated. The thin buffer layer between the ZnO layer and the sapphire substrate decreased the lattice mismatch to achieve higher quality ZnO thin film growth. A GaN buffer layer slightly increased the quality of the ZnO thin film, but the threading dislocations still stretched along the c-axis of the GaN layer. The use of MgO as the buffer layer decreased the surface roughness of the ZnO thin film by 58.8% due to the suppression of surface cracks through strain transfer of the sample. From deep level emission and rocking curve measurements it was found that the threading dislocations play a more important role than oxygen vacancies for high-quality ZnO thin film growth.

  14. Growth and characterization of nonpolar (10-10) ZnO transparent conductive oxide on semipolar (11–22) GaN-based light-emitting diodes

    Kim, Ki-Wook; Choi, Nak-Jung [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung, Gyeonggi-do, 429-839 (Korea, Republic of); Kim, Kyoung-Bo [Department of Metallurgical and Materials Engineering, Inha Technical College, Incheon, 402-752 (Korea, Republic of); Kim, Moojin [Department of Renewable Energy, Jungwon University, 85, Munmu-ro, Goesan-eup, Goesan-gun, Chungbuk, 367-805 (Korea, Republic of); Lee, Sung-Nam, E-mail: snlee@kpu.ac.kr [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung, Gyeonggi-do, 429-839 (Korea, Republic of)

    2016-05-05

    We have grown thin films of nonpolar m-plane (10-10) ZnO on a semipolar (11–22) GaN template by atomic layer deposition (ALD) at low growth temperatures (<200 °C). The surface morphology of the ZnO film is found to be an arrowhead-like structure, which is a typical surface structure of the semipolar (11–22) GaN films. On increasing the growth temperature of the ZnO films, the concentration and mobility of the charge carriers in the ZnO film are increased. However, the optical transmittance decreases with an increase in the growth temperature. Based on these results, we have fabricated semipolar (11–22) GaN-based light-emitting diodes (LEDs) with nonpolar m-plane ZnO film as a transparent conductive oxide (TCO) to improve the light extraction efficiency. In spite of a decrease in the optical transmittance, the operation voltage of semipolar (11–22) GaN-based LEDs is found to decrease with an increase in the growth temperature, which might be due to the improvements in the electrical properties and current spreading effect, resulting in an increase in the optical output power. - Highlights: • Polarity control of ZnO film grown in m-/c-sapphire and semipolar GaN template. • Achievement of high quality nonpolar m-plane ZnO flims on semipolar (11–22) GaN template. • The simultaneous improvements of carrier concentration and mobility in the nonpolar ZnO TCO flims. • Nonpolar ZnO TCO increases current spreading length and light output power of semipolar GaN-LED.

  15. Advances in Hydrogen, Carbon Dioxide, and Hydrocarbon Gas Sensor Technology Using GaN and ZnO-Based Devices

    Jenshan Lin

    2009-06-01

    Full Text Available In this paper, we review our recent results in developing gas sensors for hydrogen using various device structures, including ZnO nanowires and GaN High Electron Mobility Transistors (HEMTs. ZnO nanowires are particularly interesting because they have a large surface area to volume ratio, which will improve sensitivity, and because they operate at low current levels, will have low power requirements in a sensor module. GaN-based devices offer the advantage of the HEMT structure, high temperature operation, and simple integration with existing fabrication technology and sensing systems. Improvements in sensitivity, recoverability, and reliability are presented. Also reported are demonstrations of detection of other gases, including CO2 and C2H4 using functionalized GaN HEMTs. This is critical for the development of lab-on-a-chip type systems and can provide a significant advance towards a market-ready sensor application.

  16. Advances in Hydrogen, Carbon Dioxide, and Hydrocarbon Gas Sensor Technology Using GaN and ZnO-Based Devices.

    Anderson, Travis; Ren, Fan; Pearton, Stephen; Kang, Byoung Sam; Wang, Hung-Ta; Chang, Chih-Yang; Lin, Jenshan

    2009-01-01

    In this paper, we review our recent results in developing gas sensors for hydrogen using various device structures, including ZnO nanowires and GaN High Electron Mobility Transistors (HEMTs). ZnO nanowires are particularly interesting because they have a large surface area to volume ratio, which will improve sensitivity, and because they operate at low current levels, will have low power requirements in a sensor module. GaN-based devices offer the advantage of the HEMT structure, high temperature operation, and simple integration with existing fabrication technology and sensing systems. Improvements in sensitivity, recoverability, and reliability are presented. Also reported are demonstrations of detection of other gases, including CO(2) and C(2)H(4) using functionalized GaN HEMTs. This is critical for the development of lab-on-a-chip type systems and can provide a significant advance towards a market-ready sensor application.

  17. Electrical anisotropy properties of ZnO nanorods analyzed by conductive atomic force microscopy

    Wu Yunfeng; Yu Naisen; Liu Dongping; He Yangyang; Liu Yuanda; Liang Hongwei; Du Guotong

    2013-01-01

    Highlights: ► The electrical properties of one individual lying ZnO nanorod were performed by C-AFM measurement. ► Inhomogeneous spatial current distribution was detected. ► Current was detected along the side facets while no current was detected in the top plane for ZnO nanorod. ► The side facets were more conductive than the top facets of ZnO nanorods. - Abstract: In this study, we have prepared ZnO nanorods on cracked GaN substrates using aqueous solution method. Unique electrical characterization of one individual lying ZnO nanorod is analyzed by conductive atomic force microscopy (C-AFM). Effect of anisotropy properties on the conductivity of a single nanorod has been investigated. The current maps of ZnO nanorods have been simultaneously recorded with the topography which is gained by AFM-contact mode. The C-AFM measurement present local current–voltage (I–V) characteristics of the side facets of one individual lying nanorod, however, no current is detected on the top facets of ZnO nanorods. Measurement results indicate that the side facets are more electrically active than the top facets of ZnO nanorods due to lower Schottky barrier height of the side facets.

  18. Photoluminescence investigation of thick GaN films grown on Si substrates by hydride vapor phase epitaxy

    Yang, M.; Ahn, H. S.; Chang, J. H.; Yi, S. N.; Kim, K. H.; Kim, H.; Kim, S. W.

    2003-01-01

    The optical properties of thick GaN films grown by hydried vapor phase epitaxy (HVPE) using a low-temperature intermediate GaN buffer layer grown on a (111) Si substrate with a ZnO thin film were investigated by using photoluminescence (PL) measurement at 300 K and 77 K. The strong donor bound exciton (DBE) at 357 nm with a full width at half maximum (FWHM) of 15 meV was observed at 77 K. The value of 15 meV is extremely narrow for GaN grown on Si substrate by HVPE. An impurity-related peak was also observed at 367 nm. The origin of impurity was investigated using Auger spectroscopy.

  19. Fabrication of p-type porous GaN on silicon and epitaxial GaN

    Bilousov, Oleksandr V.; Geaney, Hugh; Carvajal, Joan J.; Zubialevich, Vitaly Z.; Parbrook, Peter J.; Giguere, A.; Drouin, D.; Diaz, Francesc; Aguilo, Magdalena; O'Dwyer, Colm

    2013-01-01

    Porous GaN layers are grown on silicon from gold or platinum catalyst seed layers, and self-catalyzed on epitaxial GaN films on sapphire. Using a Mg-based precursor, we demonstrate p-type doping of the porous GaN. Electrical measurements for p-type GaN on Si show Ohmic and Schottky behavior from gold and platinum seeded GaN, respectively. Ohmicity is attributed to the formation of a Ga2Au intermetallic. Porous p-type GaN was also achieved on epitaxial n-GaN on sapphire, and transport measurem...

  20. Temperature-dependent polarized luminescence of exciton polaritons in a ZnO film

    Toropov, A.A.; Nekrutkina, O.V.; Shubina, T.V. [Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Gruber, Th.; Kirchner, C. [Department of Semiconductor Physics, Ulm University, 89081 Ulm (Germany); Waag, A. [Institute of Semiconductor Technology, Braunschweig Technical University, 38106 Braunschweig (Germany); Karlsson, K.F.; Monemar, B. [Linkoeping University, 581 83 Linkoeping (Sweden)

    2005-02-01

    We report on the studies of linearly polarized photoluminescence (PL) in a (0001) oriented ZnO epitaxial film, grown by metal organic chemical vapor deposition on a GaN template. The emission of mixed longitudinal-transverse exciton polariton modes was observed up to 130 K that evidences polaritonic nature of the excitonic spectrum up to this elevated temperature. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Digitalisierung und Selbstbestimmung

    Bezemek, Christoph

    2017-12-01

    Full Text Available Der vorliegende Beitrag skizziert das Zusammenspiel von Digitalisierung und individueller Selbstbestimmung, stellt die Frage, welche Herausforderungen dieses Zusammenspiel birgt und diskutiert, wie ihnen begegnet werden kann.

  2. Emotion, Motivation und Volition

    Ulich, Dieter

    1996-01-01

    Emotion, Motivation und Volition / D. Ulich ; V. Brandstätter ; P. M. Gollwitzer. - In: Psychologie / hrsg. von Dietrich Dörner ... - 2., überarb. und erw. Aufl. - Stuttgart u.a. : Kohlhammer, 1996. - S. 115-135

  3. Informationskompetenz und Information Literacy

    Ingold, Marianne

    2012-01-01

    Informationskompetenz ist heute als Begriff , Konzept und praktisches Tätigkeitsfeld von Bibliotheken weltweit etabliert. Entstehung, Verbreitung und Entwicklung von „Informationskompetenz“ im deutschsprachigen Raum stehen in engem Zusammenhang mit dem in den USA und international seit den 1980er Jahren diskutierten und praktisch umgesetzten Konzept der „Information Literacy“. Auch wenn die beiden Begriffe in der Regel gleichbedeutend verwendet werden, zeigt ein Vergleich der vorwiegend aus e...

  4. Romanistik und gender studies

    Susanne Schlünder

    2000-11-01

    Full Text Available Die beiden Bände bieten ein breites Spektrum von Beiträgen zur französischen, italienischen und spanischen Literaturwissenschaft. Gedankliche Grundlage der im einzelnen unterschiedlichen Ansätze und Zielsetzungen ist ein im Anschluß an Judith Butler gender-reflektierendes, diskursives Konzept von Geschlecht, dessen wissenschaftsgeschichtliche Herleitung und Perspektiven Renate Kroll einleitend darlegt. Die einzelnen Artikel beschäftigen sich zum einen mit literarischen Strategien, die Schriftstellerinnen vom Mittelalter bis zur Gegenwart erprobt haben, und hinterfragen dabei die Rolle weiblicher Autoren in Literaturgeschichte und Literaturgeschichtsschreibung. Zum anderen widmen sie sich den literarischen Inszenierungs- und Repräsentationsformen von Weiblichkeit und stellen darüber einen Bezug zur Lebenswelt der behandelten Autorinnen her.

  5. Direct evidence for As as a Zn-site impurity in ZnO

    Wahl, Ulrich; Correia, J G; Lourenço-Santana-Marques, Ana Claudia; Alves, E; Carvalho-Soares, José

    2005-01-01

    Arsenic has been reported in the literature as one of the few p-type dopants in the technologically promising II-VI semiconductor ZnO. However, there is an ongoing debate whether the p-type character is due to As simply replacing O atoms or to the formation of more complicated defect complexes, possibly involving As on Zn sites. We have determined the lattice location of implanted As in ZnO by means of conversion electron emission channeling from radioactive $^{73}$As. In contrast to what one might expect from its nature as a group V element, we find that As does not occupy substitutional O sites but in its large majority substitutional Zn sites. Arsenic in ZnO (and probably also in GaN) is thus an interesting example for an impurity in a semiconductor where the major impurity lattice site is determined by atomic size and electronegativity rather than its position in the periodic system.

  6. Fotografie und atomare Katastrophe

    Bürkner, Daniel

    2015-01-01

    Die Dissertation setzt sich mit den fotografischen Repräsentationen der Atombombenabwürfe auf Hiroshima und Nagasaki sowie der Havarie des Kernkraftwerks Tschernobyl auseinander. Dabei werden künstlerische, dokumentarische und touristische Bilder analysiert, die sich der jeweiligen Strahlenkatastrophe oftmals erst Jahre nach dem Ereignis annehmen und ikonografische oder medial-materielle Bezüge zu ihr aufweisen. Es zeigen sich zentrale Strategien, atomare Katastrophen, seien sie militäri...

  7. Versicherung und volkswirtschaftlicher Kreislauf

    Lampert, Heinz

    1982-01-01

    Versicherung und volkswirtschaftlicher Kreislauf : zur Behandlung d. Privatversicherung in d. volkswirtschaftl. Gesamtrechnung. - In: Zeitschrift für die gesamte Versicherungswissenschaft. 71. 1982. S. 189-210

  8. Milch, Milchprodukte, Analoge und Speiseeis

    Coors, Ursula

    Die Produktpalette Milch und Erzeugnisse aus Milch beinhaltet Konsummilch, die aus Milch oder Bestandteilen der Milch hergestellten Milcherzeugnisse wie Sauermilch-, Joghurt-, Kefir-, Buttermilch-, Sahne-, Kondensmilch-, Trockenmilch- und Molkenerzeugnisse, Milchmisch- und Molkenmischprodukte (Produkte mit beigegebenen Lebensmitteln), Milchzucker, Milcheiweißerzeugnisse, Milchfette und Käse.

  9. Übergewicht und Adipositas in Kindheit und Jugend

    Nitzko, Sina

    2010-01-01

    Einführend wird auf wesentliche Entwicklungsaspekte der interessierenden Lebensphasen Kindheit und Jugend eingegangen. Im Anschluss daran werden verschiedene Aspekte von Übergewicht und Adipositas in Kindheit und Jugend thematisiert. Neben der Definition und Diagnostik, wird auf Möglichkeiten der Klassifikation sowie die Epidemiologie eingegangen. Dargestellt werden darüber hinaus körperliche und psychische Folgestörungen, welche mit Adipositas assoziiert sein können. Basierend auf der...

  10. Thermodynamik grundlagen und technische anwendungen

    Baehr, Hans Dieter

    2009-01-01

    Für die aktualisierte 14. Auflage des bewährten Lehrbuchs der Technischen Thermodynamik wurde das Kapitel über Wärmekraftanlagen gründlich bearbeitet und durch einen Abschnitt zur Energiewandlung ergänzt: Die Energiebedarfsstruktur von Deutschland wird erläutert, und die möglichen Energiewandlungspfade werden diskutiert. Schwerpunkt des Buches ist die ausführliche und auch dem Anfänger verständliche Darstellung der Grundlagen der Thermodynamik mit der sorgfältigen Einführung der thermodynamischen Begriffe und den fundamentalen Bilanzgleichungen für Energie, Entropie und Exergie. Die thermodynamischen Eigenschaften reiner Fluide und fluider Gemische werden eingehend erläutert. Darauf aufbauend wird die Thermodynamik der Gemische und der chemischen Reaktionen entwickelt. Auch die thermodynamischen Aspekte wichtiger energie- und verfahrenstechnischer Anwendungen werden praxisnah behandelt: - Strömungs- und Arbeitsprozesse, - thermische Stofftrennverfahren, - Verbrennungsprozesse und Verbrennungsk...

  11. Steuern und Governance

    Eduard Müller

    2014-05-01

    Full Text Available ENGLISH: Taxation, in the modern state, has long been a mass phenomenon with an interdisciplinary outlook. On the macro level of the state, a new generation of administrative reforms has crystallized under the label “good public governance”. These reforms seek to resolve regulatory interdependence of state and non - state actors by way of cooperation and interaction. In parallel, on the micro level of businesses, “corporate governance” – voluntary compliance with legal and ethical standards – has become an increasingly important issue. With a view to tax law and tax collection, these developments open up new possibilities to raise tax compliance by means of consensual and cooperative instruments and, accordingly, address taxation as a mass phenomenon. DEUTSCH: Besteuerung ist im modernen Staat ein Massenphänomen und längst interdisziplinär ausgerichtet. Auf der Makro-Ebene des Staates hat sich unter dem Begriff Good Public Governance eine neue Generation von Staats- und Verwaltungsreformen herausgebildet, die Regelungsbeziehungen von staatlichen und nichtstaatlichen Akteuren durch Kooperationen und Interaktionen zu lösen versucht. Parallel dazu hat auf der Mikro-Ebene der Unternehmen mit dem Thema Corporate Governance die freiwillige Einhaltung von rechtlichen und ethischen Regeln an Bedeutung gewonnen. Für das Steuerrecht und den Steuervollzug resultieren aus diesen Entwicklungen neue Möglichkeiten, durch Nutzung konsens- und kooperationsorientierter Instrumente die Tax Compliance zu erhöhen und so dem Massenphänomen Besteuerung gerecht zu werden.

  12. Photoconductive GaN UV Detectors

    Baranowski, Jacek

    1999-01-01

    This report results from a contract tasking University of Warsaw as follows: The contractor will investigate the growth of GaN material using atmospheric pressure metalorganic chemical vapor deposition method (MOCVD...

  13. Osteoporose und Laktoseintoleranz

    Obermayer-Pietsch B

    2008-01-01

    Full Text Available Laktosemalabsorption oder Laktoseintoleranz ist eine symptomatische Unverträglichkeit von Milchzucker (Laktose, zumeist aufgrund einer autosomal rezessiv erblichen, irreversiblen Abnahme des Enzyms Laktase im Jugendalter, die bei etwa der Hälfte der Weltbevölkerung auftritt. Die Betroffenen meiden oft instinktiv Milch und Milchprodukte wegen der damit verbundenen Malabsorptions-Symptome. Damit scheiden diese Nahrungsmittel aber auch als Kalziumlieferanten aus und es kann zu einer Mangelversorgung des Knochens mit Kalzium und damit zu Osteoporose kommen. Da in Österreich etwa 20–25 % der Bevölkerung betroffen sind, ist diese Stoffwechselveränderung nicht zu vernachlässigen. Diagnostische und begleitende ernährungsmedizinische Maßnahmen und gegebenenfalls eine osteotrope Therapie sollten zum Erhalt der Knochenmasse eingesetzt werden.

  14. Neuausrichtung und Konsolidierung

    Grohmann, Heinz

    Mit der Wahl von Wolfgang Wetzel zum Vorsitzenden der Deutschen Statistischen Gesellschaft im Jahre 1972 begann eine 32jährige Ära, in der die praktische und die theoretische Statistik in einem ausgewogenen Verhältnis gepflegt wurden. Ein regelmäßiger vierjähriger Wechsel im Vorsitz stärkte die Gemeinschaft und die praktische wie die wissenschaftliche Arbeit gleichermaßen. Die jährlichen Hauptversammlungen behandelten gesellschaftlich aktuelle wie zukunftsorientierte Themen, und die Ausschüsse sowie weitere Veranstaltungen gaben Gelegenheit zur Förderung und Pflege einer Vielzahl von Arbeitsgebieten der Statistik. Darüber wird nicht nur in diesem Kapitel, sondern auch in den Teilen II und III des Bandes berichtet.

  15. Wafer-Scale High-Throughput Ordered Growth of Vertically Aligned ZnO Nanowire Arrays

    Wei, Yaguang

    2010-09-08

    This article presents an effective approach for patterned growth of vertically aligned ZnO nanowire (NW) arrays with high throughput and low cost at wafer scale without using cleanroom technology. Periodic hole patterns are generated using laser interference lithography on substrates coated with the photoresist SU-8. ZnO NWs are selectively grown through the holes via a low-temperature hydrothermal method without using a catalyst and with a superior control over orientation, location/density, and as-synthesized morphology. The development of textured ZnO seed layers for replacing single crystalline GaN and ZnO substrates extends the large-scale fabrication of vertically aligned ZnO NW arrays on substrates of other materials, such as polymers, Si, and glass. This combined approach demonstrates a novel method of manufacturing large-scale patterned one-dimensional nanostructures on various substrates for applications in energy harvesting, sensing, optoelectronics, and electronic devices. © 2010 American Chemical Society.

  16. Are Fe and Co implanted ZnO and III-nitride semiconductors magnetic?

    AUTHOR|(CDS)2081284; Bharuth-Ram, Krish

    The chemical nature, lattice site locations and magnetic behaviour of Fe and/or Co ions implanted in nitrides (GaN, AlN, and InN) and in ZnO have been investigated using Mössbauer spectroscopy and vibrating sample magnetometer (VSM) techniques. Mössbauer data on nitride and $^{56}$Fe pre-implanted ZnO samples were obtained from emission Mössbauer spectroscopy (eMS) measurements at the ISOLDE facility, CERN, following the implantation of radioactive $^{57}$Mn$^{*}$ which $\\beta$$^{-}$decays to the 14.4 keV Mössbauer state of $^{57}$Fe. In addition, conversion electron Mössbauer spectroscopy (CEMS) data were collected on ZnO single crystals co-implanted with $^{57}$Fe + $^{56}$Fe and $^{57}$Fe + $^{59}$Co ions in a box profile. Emission Mössbauer spectra obtained for GaN and AlN reveal magnetic structure in the ‘wings’ assigned to high spin Fe$^{3+}$ weakly coupled to the lattice showing spin-lattice relaxation effects. The observed spin-relaxation rate (τ$^{-1}$) closely follows a ${T}^{2}$ temperat...

  17. Teilchendetektoren Grundlagen und Anwendungen

    Kolanoski, Hermann

    2016-01-01

    In diesem Buch werden die experimentellen Grundlagen von Teilchendetektoren und ihre Anwendung in Experimenten beschrieben. Die Entwicklung von Detektoren ist ein wichtiger Bestandteil der Teilchen-, Astroteilchen- und Kernphysik und gehört daher zum Handwerk des Experimentalphysikers in diesen Gebieten. Dieses umfassende Werk beinhaltet den kompletten Stoff für entsprechende Master-Module in der experimentellen Teilchenphysik, geht aber im Inhalt auch darüber hinaus. Zielgruppe sind Studierende, die sich in die Materie vertiefen möchten, aber auch Lehrende und Wissenschaftler, die das Buch zum Einstieg in das wissenschaftliche Arbeiten an Detektorentwicklungen verwenden können. Zielrichtung des Buches ist, die physikalischen Grundlagen für die Detektoren und ihrer verschiedenen Ausführungen so klar wie möglich und so tiefgehend wie nötig darzustellen. Die Breite des für die Detektorentwicklung nötigen Wissens umfasst viele Bereiche der Physik und Technik, von den Wechselwirkun...

  18. Mediendidaktik und Wissensmanagement

    Gabi Reinmann-Rothmeier

    2002-10-01

    Full Text Available Mediendidaktik und Wissensmanagement – das ist auf den ersten Blick ein ungleiches Paar: Die Mediendidaktik ist eine Teildisziplin der (Medien- Pädagogik, während Wissensmanagement ein genuin wirtschaftliches Thema mit betriebswirtschaftlichen Akzenten ist. Annäherungen zwischen der Mediendidaktik und Wissensmanagement gibt es zum einen durch den sog. E-Learning-Trend seitens der Wirtschaft, der mediendidaktisches Wissen und Können auf den Plan ruft, zum anderen durch wachsendes Interesse am Thema Wissensmanagement seitens der Pädagogik. Der Beitrag beschreibt sowohl für das E-Learning als auch für das Wissensmanagement aus pädagogisch-psychologischer Sicht jeweils ein Orientierungsmodell; beide Modelle machen die Berührungspunkte zwischen Mediendidaktik und Wissensmanagement deutlich. Neben einem Überblick über wirtschaftliche Argumente für eine Verschmelzung von E-Learning und Wissensmanagement werden aufbauend auf den beiden Orientierungsmodellen theoretische und praktische Verbindungslinien zwischen E-Learning und Wissensmanagement sowie die Rolle der Mediendidaktik in dem daraus entstehenden Wechselverhältnis herausgearbeitet.

  19. The Formation and Characterization of GaN Hexagonal Pyramids

    Zhang, Shi-Ying; Xiu, Xiang-Qian; Lin, Zeng-Qin; Hua, Xue-Mei; Xie, Zi-Li; Zhang, Rong; Zheng, You-Dou

    2013-05-01

    GaN with hexagonal pyramids is fabricated using the photo-assisted electroless chemical etching method. Defective areas of the GaN substrate are selectively etched in a mixed solution of KOH and K2S2O8 under ultraviolet illumination, producing submicron-sized pyramids. Hexagonal pyramids on the etched GaN with well-defined {101¯1¯} facets and very sharp tips are formed. High-resolution x-ray diffraction shows that etched GaN with pyramids has a higher crystal quality, and micro-Raman spectra reveal a tensile stress relaxation in GaN with pyramids compared with normal GaN. The cathodoluminescence intensity of GaN after etching is significantly increased by three times, which is attributed to the reduction in the internal reflection, high-quality GaN with pyramids and the Bragg effect.

  20. A Frontal Attack on Limiting Defects in GaN

    Morkoc, Hadis

    2002-01-01

    GaN community, particularly under the leadership of Drs. Wood, Win, and Litton, recognized that it is imperative that the extended, and point defects in GaN and related materials, and the mechanisms for their formation are understood...

  1. GaN Nanowires Synthesized by Electroless Etching Method

    Najar, Adel; Anjum, Dalaver H.; Ng, Tien Khee; Ooi, Boon S.; Ben Slimane, Ahmed

    2012-01-01

    Ultra-long Gallium Nitride Nanowires is synthesized via metal-electroless etching method. The morphologies and optical properties of GaN NWs show a single crystal GaN with hexagonal Wurtzite structure and high luminescence properties.

  2. Synthetic Strategies and Applications of GaN Nanowires

    Guoquan Suo

    2014-01-01

    Full Text Available GaN is an important III-V semiconductor material with a direct band gap of 3.4 eV at 300 K. The wide direct band gap makes GaN an attractive material for various applications. GaN nanowires have demonstrated significant potential as fundamental building blocks for nanoelectronic and nanophotonic devices and also offer substantial promise for integrated nanosystems. In this paper, we provide a comprehensive review on the general synthetic strategies, characterizations, and applications of GaN nanowires. We first summarize several growth techniques of GaN nanowires. Subsequently, we discuss mechanisms involved to generate GaN nanowires from different synthetic schemes and conditions. Then we review some characterization methods of GaN nanowires. Finally, several kinds of main applications of GaN nanowires are discussed.

  3. Lessing und der Islam

    Muslim, Zahim Mohammed

    2010-01-01

    „Lessing und der Islam“ beschäftigt sich unparteiisch mit Lessings Auseinandersetzung mit dem Islam. Die Arbeit setzt sich das Ziel, den Leser und den Literaturkennern sowie der deutschen Bibliothek der Germanistik etwas von Lessings Auseinandersetzung mit dem Islam in die Hand zu geben, die bis heute als großes Modell für die interkulturelle und interreligiöse Menschheitstoleranzdebatte im Gedächtnis der deutschen Literatur vorhanden ist. Im ersten Teil widmet sich die vorliegende Arbeit de...

  4. Trauma und Terror

    Szyszkowitz, T. (Tessa)

    2007-01-01

    1. Einleitung Ausgehend von der Fragestellung, warum gerade bei Tschetschenen und Palästinensern der Selbstmordterrorismus in den letzten Jahren so populär geworden ist, analysiert die Autorin die Geschichte dieser beiden Völker. Einer der Gründe ist bisher wenig beachtet worden. Der Einfluss eines kollektiven Traumas, das als solches nicht anerkannt, behandelt und auch nicht einer politischen Lösung zugeführt wurde. 2. Geschichte der Palästinenser und Tschetschenen Im Zuge der Err...

  5. Silicon—a new substrate for GaN growth

    Unknown

    of GaN devices based on silicon is the thermal mismatch of GaN and Si, which generates cracks. In 1998, the .... Considerable research is being carried out on GaN HEMTs at present. ... by InGaN/GaN multiquantum well in MOVPE was first.

  6. Integration, Informationslogistik und Architektur

    Turowski, Klaus

    2006-01-01

    Integration, Informationslogistik und Architektur : DW2006 ; 21./22.09.2006 in Friedrichshafen, Germany / Klaus Turowski ... (Hrsg.). - Bonn : Ges. für Informatik, 2006. - 490 S. - (GI-Edition / Proceedings ; 90)

  7. Supraleitung Grundlagen und Anwendungen

    Buckel, Werner

    2004-01-01

    Seit nunmehr drei Jahrzehnten ist der "Buckel" das Referenzwerk in deutscher Sprache zum Thema Supraleitung. Immer wieder aktualisiert, hat das Lehrbuch Generationen von Studenten begleitet. In der 6., vollständig überarbeiteten Auflage wird das bewährte didaktische Konzept beibehalten, inhaltlich wurde der Band dem aktuellen Stand von Forschung und Technik angepasst. Das Autorenteam um Prof. Kleiner verzichtet auf komplizierte mathematische Herleitungen. Es baut ganz auf das bewährte Step-by-Step-Prinzip: Der Schwierigkeitsgrad wird von Kapitel zu Kapitel gesteigert. So können auch Einsteiger ohne einschlägige Vorkenntnisse dem Stoff bequem folgen. Dank seiner klaren Sprache und zahlreicher Abbildungen eignet sich der Band hervorragend als einführendes Lehrbuch - und zwar nicht nur für Physik-Studenten, sondern auch für Studierende angrenzender Natur- und Ingenieurwissenschaften. Grundlegende Eigenschaften, supraleitende Elemente, Cooper-Paarung, Thermodynamik, kritische Ströme, Josephsonkontakte...

  8. Ausbildung und Erwartungshaltung

    Knoke, Holger

    1997-09-01

    werden Geologiestudenten zeitgemäß ausgebildet? Wird in der Angewandten Geologie das gelehrt, was in Wirtschaftsunternehmen an Wissen von einem Geologen erwartet wird? Erfolgt die spezielle Ausbildung zum Hydrogeologen fundiert und umfassend? Eine Antwort auf diese Fragen kann sicherlich nicht allumfassend gegeben werden, da sie von der jeweiligen Sichtweise abhängig ist. Ein Geologieprofessor wird die Ausbildung seiner Studenten im Großen und Ganzen als zeitgemäß einstufen, eventuell hier und da Verbesserungen für möglich halten. Auffällig ist die hohe Anzahl der in den letzten Jahren bereits geänderten oder zur Änderung anstehenden Studienordnungen. Es zeigt, daß die Straffung des Studiums sowie eine zumindest teilweise neue Wichtung der Schwerpunkte notwendig war bzw. ist, wobei im allgemeinen eine höhere Stundenzahl in den Grundlagenfächern Mathematik, Physik und Chemie angesetzt wird. Betrachtet man die Gesamtstundenzahlen der alten und der reformierten Studienordnungen, kann jedoch von einer Kürzung der Pflichtstunden in den meisten Fällen nicht die Rede sein. Eine grundlegende Reform des Geologiestudiums ist zur Zeit nicht zu erkennen, eher eine Verschulung des Studienganges. Die Entwicklung scheint zur Zeit weg von der freien Kurswahl und hin zu Modulangeboten mit vorgegebenen Kursen und Reihenfolgen zu gehen. Für die Hydrogeologie-Professoren ist es sicherlich nicht einfach zu entscheiden und in ihrem Kollegenkreis durchzusetzen, was aus dem generellen geowissenschaftlichen Kursangebot für einen Hydrogeologen notwendig oder aber entbehrlich ist. Genügen die Grundlagen der Paläontologie und der Mineralogie? Kann man ganz darauf verzichten? Was erwarten Behörden und Wirtschaftsunternehmen an allgemeinen und Spezialkenntnissen? Geologische Landesämter z. B. wollen, pauschal betrachtet, Geologen alten Stils. Ist ausdrücklich ein Angewandter Geologe oder speziell ein Hydrogeologe erwünscht, soll dieser die Spezialkenntnisse zus

  9. Nationale und transnationale Vernetzung polnischer Städte und Regionen: Auf dem Weg zu einer nachhaltigen Stadt- und Regionalentwicklung

    Dorsch, Pamela

    2003-01-01

    "Die Studie 'Nationale und transnationale Vernetzung polnischer Städte und Regionen - Bedeutung für eine nachhaltige Stadt- und Regionalentwicklung' liefert einen Überblick über die Einbindung polnischer Kommunen und Wojewodschaften in allgemeine und politikfeldspezifische Netzwerke auf nationaler und transnationaler Ebene. Besondere Berücksichtigung findet hierbei die Vernetzung in Fragen von Nachhaltigkeit und des Umweltschutzes. Einführend zeigt die Studie den Prozess zunehmender Dezentral...

  10. Zwischen Freakout und Normcore

    Beate Großegger

    2017-06-01

    Full Text Available Bis Ende des 20. Jahrhunderts war Rebellion jugendkulturell ein großes Thema. Heute hat die Jugend das so genannte Establishment aus den Augen verloren; die breite Mehrheit gibt sich postheroisch, setzt auf individualitätsbezogene Werte und träumt, eingeschlossen in ihre bunten Lifestyleblasen, von einem perfekten Leben. Bezugnehmend auf aktuelle Befunde der Jugend- und Generationenforschung gibt Beate Großegger in ihrem Beitrag einen Überblick über die wichtigsten Werte- und Lifestyletrends im frühen 21. Jahrhundert und zeigt dabei, wie sehr die heutige Jugend Kind ihrer Zeit und Produkt gesellschaftlicher Rahmenbedingungen ist. Until the late 20th century rebellion was an important aspect of various youth subcultures. But today’s youth has a different mindset. The majority acts post-heroically, i.e. they rather focus on their individual, their private lifestyle than opposing against the establishment. Wrapped in their lifestyle filterbubbles, they dream of a perfect life. Based on recent youth und generation studies Beate Großegger gives an overview of the most important youth cultural trends in the fields of values and lifestyles and introduces today’s youth as a child of our times.

  11. Neue Laser und Strahlquellen - alte und neue Risiken?

    Paasch, Uwe; Schwandt, Antje; Seeber, Nikolaus

    2017-01-01

    Die Entwicklungen im Bereich dermatologischer Laser, hochenergetischer Blitzlampen, LED und neuer Energie- und Strahlquellen der letzten Jahre haben gezeigt, dass mit neuen Wellenlängen, Konzepten und Kombinationen zusätzliche, zum Teil über den ästhetischen Bereich hinaus gehende therapeutische ...

  12. Führung und Machiavellismus

    Belschak, F.D.; den Hartog, D.N.; Felfe, J.

    2015-01-01

    In diesem Beitrag wird der Zusammenhang zwischen Führung und Machiavellismus aus zwei verschiedenen Perspektiven betrachtet. Zum einen werden neuere Forschungsergebnisse referiert, wie machiavellistische Mitarbeiter auf verschiedene Führungsstile ihres Vorgestzten reagieren und so mit Hinblick auf

  13. Netzformen und VDE-Bestimmungen

    Bernstein, Herbert

    Der Verband Deutscher Elektrotechniker (VDE) hat eine Reihe von Vorschriften ausgearbeitet, die dem Schutz von Leben und Sachen beim Umgang mit elektrischer Energie dienen. Besonders wichtig sind die in den VDE-Bestimmungen 0100 und 0411 festgelegten Vorschriften.

  14. Delegation und Kooperation im Gesundheitswesen

    Rosenau, Henning

    2010-01-01

    Delegation und Kooperation im Gesundheitswesen. - In: Tıpta işbirliği ve hukuksal sorunlar = Delegation und Kooperation im Gesundheitswesen / ed.: Hakan Hakeri ... - Samsun : Adalet, 2010. - S. 7-18

  15. Performance Improvement of GaN-Based Flip-Chip White Light-Emitting Diodes with Diffused Nanorod Reflector and with ZnO Nanorod Antireflection Layer

    Hsin-Ying Lee

    2014-01-01

    Full Text Available The GaN-based flip-chip white light-emitting diodes (FCWLEDs with diffused ZnO nanorod reflector and with ZnO nanorod antireflection layer were fabricated. The ZnO nanorod array grown using an aqueous solution method was combined with Al metal to form the diffused ZnO nanorod reflector. It could avoid the blue light emitted out from the Mg-doped GaN layer of the FCWLEDs, which caused more blue light emitted out from the sapphire substrate to pump the phosphor. Moreover, the ZnO nanorod array was utilized as the antireflection layer of the FCWLEDs to reduce the total reflection loss. The light output power and the phosphor conversion efficiency of the FCWLEDs with diffused nanorod reflector and 250 nm long ZnO nanorod antireflection layer were improved from 21.15 mW to 23.90 mW and from 77.6% to 80.1% in comparison with the FCWLEDs with diffused nanorod reflector and without ZnO nanorod antireflection layer, respectively.

  16. Risiko Video- und Computerspiele? Eine Studie über Video- und Computerspielnutzung und Aggression bei 12- und 16- jährigen Jugendlichen

    Schiller, Eva-Maria; Strohmeier, Dagmar; Spiel, Christiane

    2009-01-01

    Video -und Computerspielen ist heutzutage eine beliebte Freizeitaktivität von Kindern und Jugendlichen, besonders von Jungen. Trotz der großen Vielfalt der angebotenen Video- und Computerspiele für Kinder und Jugendliche, konzentriert sich die Forschung vorwiegend auf negative Einflüsse von gewalthaltigen Video- und Computerspielen. Da nicht alle Kinder und Jugendliche ausschließlich gewalthaltige Video- und Computerspiele spielen, betrachten wir diesen Fokus in der Wissenschaft als zu eng ge...

  17. RenderGAN: Generating Realistic Labeled Data

    Leon Sixt

    2018-06-01

    Full Text Available Deep Convolutional Neuronal Networks (DCNNs are showing remarkable performance on many computer vision tasks. Due to their large parameter space, they require many labeled samples when trained in a supervised setting. The costs of annotating data manually can render the use of DCNNs infeasible. We present a novel framework called RenderGAN that can generate large amounts of realistic, labeled images by combining a 3D model and the Generative Adversarial Network framework. In our approach, image augmentations (e.g., lighting, background, and detail are learned from unlabeled data such that the generated images are strikingly realistic while preserving the labels known from the 3D model. We apply the RenderGAN framework to generate images of barcode-like markers that are attached to honeybees. Training a DCNN on data generated by the RenderGAN yields considerably better performance than training it on various baselines.

  18. Gan-Hang tectonic belt and its geologic significance

    Deng Jiarui; Zhang Zhiping.

    1989-01-01

    Gan-Hang tectonic belt is predominantly controlled by Gan-Hang fracture zone. It is mainly composed of Yongfeng-Zhuji downwarping zone, Gan-Hang volcanic activity structural belt and Gan-Hang red basin downfaulted zone. Gan-Hang fracture zone is derived from evolution and development of Shaoxing-Jiangshan deep fracture. It is mainly composed of three deep and large fracture and Fuzhou-Yongfeng large fracture. The fracture zone is a long active belt, but in each active period the geologic structural patterns intensity, depth and forming time were not same. Gan-Hang tectonic belt possesses obvious inheritance. It has always maintained the character of the relative depression or low land since the Caledonian movement. This specific structural environment is favourable for uranium mineralization. At any rate, the formation of this uranium minerogenetic zone has been experiencing a long and complicated processes which were closely associated with long activity of Gan-Hang fracture zone

  19. Piezotronic Effect in Polarity-Controlled GaN Nanowires.

    Zhao, Zhenfu; Pu, Xiong; Han, Changbao; Du, Chunhua; Li, Linxuan; Jiang, Chunyan; Hu, Weiguo; Wang, Zhong Lin

    2015-08-25

    Using high-quality and polarity-controlled GaN nanowires (NWs), we studied the piezotronic effect in crystal orientation defined wurtzite structures. By applying a normal compressive force on c-plane GaN NWs with an atomic force microscopy tip, the Schottky barrier between the Pt tip and GaN can be effectively tuned by the piezotronic effect. In contrast, the normal compressive force cannot change the electron transport characteristics in m-plane GaN NWs whose piezoelectric polarization axis is turned in the transverse direction. This observation provided solid evidence for clarifying the difference between the piezotronic effect and the piezoresistive effect. We further demonstrated a high sensitivity of the m-plane GaN piezotronic transistor to collect the transverse force. The integration of c-plane GaN and m-plane GaN indicates an overall response to an external force in any direction.

  20. Ellbogen- und Handgelenksendoprothetik beim Rheumatiker - Richtlinien und Rehabilitation

    Chochole M

    2008-01-01

    Full Text Available Die Endoprothetik an Ellbogen und Handgelenk ist seit etwa drei Jahrzehnten etabliert. An beiden Gelenken haben sich einzelne Implantate oder Designs durchgesetzt. Operationstechniken und Nachuntersuchungsergebnisse sind publiziert. Wenig ist jedoch zum Thema Nachbehandlung und Nachsorge veröffentlicht. Diese Arbeit beschäftigt sich detailliert mit der ärztlichen und therapeutischen Betreuung nach Implantation einer Ellbogen- oder Handgelenksendoprothese beim Patienten mit rheumatischer Arthritis unter Aufgliederung in Krankenhausaufenthalt, ambulanter Nachsorge sowie stationärer Rehabilitation. Dabei werden Zeitrahmen, Therapieziele und Behandlungen gesondert angeführt.

  1. Characterization of Non-Polar ZnO Layers with Positron Annihilation Spectroscopy

    Zubiaga, A.; Tuomisto, F.; Zúñiga-Pérez, J.; Muñoz-San José, V.

    2008-11-01

    We applied positron annihilation spectroscopy to study the effect of growth polarity on the vacancy defects in ZnO grown by metal-organic vapor phase deposition on sapphire. Both c-plane and a-plane ZnO layers were measured, and Zn vacancies were identified as the dominant defects detected by positrons. The results are qualitatively similar to those of earlier experiments in GaN. The Zn vacancy concentration decreases in c-plane ZnO by almost one order of magnitude (from high 1017 cm-3 to low 1017 cm-3) when the layer thickness is increased from 0.5 to 2 μm. Interestingly, in a-plane ZnO the Zn vacancy concentration is constant at a level of about 2×1017 cm-3 in all the samples with thicknesses varying from 0.6 to 2.4 μm. The anisotropy of the Doppler broadening of the annihilation radiation parallel and perpendicular to the hexagonal c-axis was also measured.

  2. Altautoverwertung zwischen Staat und Markt: Bedingungen und Potentiale zur Modernisierung von Lagerhaltung und Marketing gebrauchter Autoteile

    Lucas, Rainer

    2000-01-01

    Das Arbeitspapier diskutiert vor dem Hintergrund veränderter gesetzlicher Rahmen-und Wettbewerbsbedingungen in der Autoverwertung Ziele und Maßnahmen zurStärkung kleiner und mittelständischer Verwertungsbetriebe. Der Bereich GebrauchteAutoteile wird im Rahmen eines regionalen Fallbeispiels einer tiefergehenden Analyseunterzogen. Hieraus werden Vorschläge zur regionalen Netzwerkbildung innerhalb derBranche und neue Dienstleistungsperspektiven abgeleitet. Ein wesentliches Koope-rationsfeld ist ...

  3. Growth of InGaN multiple quantum wells and GaN eplilayer on GaN substrate

    Lee, Sung-Nam; Paek, H.S.; Son, J.K.; Sakong, T.; Yoon, E.; Nam, O.H.; Park, Y.

    2006-01-01

    We investigated that the surface morphology of GaN epilayers was significantly affected by the surface tilt orientation of GaN substrate. Surface morphologies of GaN epilayers on GaN substrates show three types: mirror, wavy, and hillock. These surface morphologies are dependent on the surface orientation of GaN substrates. It is found that the hillock morphology of GaN epilayer was formed on the GaN substrate with surface tilt orientation less than 0.1 o . As the surface tilt angle increased to 0.35 o , the surface morphology varied from hillock to wavy morphology. Above a surface tilt angle of 0.4 o , surface morphology changed to the mirror-like type morphology. Additionally, these three types of GaN surface morphology also affected the optical quality of GaN epilayers as well as InGaN multiple quantum wells on GaN substrates by non-uniform In incorporation on the different surface morphologies of GaN epilayers

  4. Rosetta und Yella

    Urs Urban

    2009-11-01

    Full Text Available L’apparition de l’homo oeconomicus marque la fin des grands récits et par là de l’ensemble social que ceux-ci avaient légitimé. En même temps cependant il entre dans les récits littéraires – et filmiques, par exemple dans Rosetta (1999 des frères Dardenne et Yella (2007 de Christian Petzold. L’article se propose de montrer comment ces derniers réussissent à mettre en scène les apories existentielles d’un sujet produit par le dispositif économique en appliquant des procédés narratifs permettant de problématiser la narration elle-même.Mit dem Auftauchen des homo oeconomicus scheint das Ende der großen Erzählungen und des von diesen legitimierten sozialen Zusammenhangs besiegelt. Genau in diesem Moment indes beginnen sich die kleinen, die literarischen und filmischen Erzählformen für den ökonomischen Menschen zu interessieren. In dem Artikel geht es darum zu zeigen, wie die Brüder Dardenne und Christian Petzold die Aporien eines vom ökonomischen Dispositiv produzierten Subjekts in ihren Filmen Rosetta (1999 und Yella (2007 erzählerisch umsetzen und dabei genau diese erzählerische Umsetzbarkeit in Frage stellen.

  5. Supraleitung Grundlagen und Anwendungen

    Buckel, Werner

    2013-01-01

    Grundlegende Konzepte und Eigenschaften von Supraleitern, die Herstellung und Entwicklung von neuen supraleitenden Materialien sowie moderne Anwendungsbereiche sind die Schwerpunktthemen des Buches. Das größte Potential zur Nutzung der Supraleitung liegt in der Energietechnik. Fast unbemerkt trägt die Einführung von Kabeln, Magneten, Transformatoren oder Lagern aus supraleitenden Materialien bei zur Effizienzsteigerung bei der Stromübertragung oder in Motoren. Durch seiner klare Sprache und zahlreiche erläuternde Abbildungen eignet sich der Band hervorragend als einführendes Lehrbuch. Der Schwierigkeitsgrad wird von Kapitel zu Kapitel gesteigert. So können auch Einsteiger ohne einschlägige Vorkenntnisse dem Stoff folgen. Dank der über 350 Literaturhinweise bekommt der Leser außerdem einen Überblick über die wichtigsten Publikationen zum Thema. Ein unverzichtbares Lehrbuch also für Physik-Studenten und Studierende der Ingenieurwissenschaften. Fachleuten in Forschung und Praxis leistet das Buch au...

  6. Implantation doping of GaN

    Zolper, J.C.

    1996-01-01

    Ion implantation has played an enabling role in the realization of many high performance photonic and electronic devices in mature semiconductor materials systems such as Si and GaAs. This can also be expected to be the case in III-Nitride based devices as the material quality continues to improve. This paper reviews the progress in ion implantation processing of the III-Nitride materials, namely, GaN, AlN, InN and their alloys. Details are presented of the successful demonstrations of implant isolation as well as n- and p-type implantation doping of GaN. Implant doping has required activation annealing at temperatures in excess of 1,000 C. The nature of the implantation induced damage and its response to annealing is addressed using Rutherford Backscattering. Finally, results are given for the first demonstration of a GaN device fabricated using ion implantation doping, a GaN junction field effect transistor (JFET)

  7. Der Nahostkonflikt und die Medien

    Carola Richter

    2014-06-01

    Full Text Available Diese Einführung in eine Themenausgabe zu den vielfältigen Rollen der Medien im Nahostkonflikt skizziert die Probleme, die sich für Medien und Journalisten als Akteure im Konflikt, Adressaten der Konfliktparteien und Anlass für Konflikt durch ihre Berichterstattung ergeben. Das Konfliktgebiet Israel und Palästina ist sowohl für Forschung über Auslandsbericht-erstattung, über transnationale Agenda Building- und Public Diplomacy-Prozesse als auch über mediensystemische Entwicklungen in Besatzer- und Besatzungsgebieten interessant. Der Artikel gibt einen Überblick über das Feld und führt dabei in die in der Themenausgabe präsentierten empirischen Studien zum Nahostkonflikt und den Medien ein.

  8. GaN Micromechanical Resonators with Meshed Metal Bottom Electrode.

    Ansari, Azadeh; Liu, Che-Yu; Lin, Chien-Chung; Kuo, Hao-Chung; Ku, Pei-Cheng; Rais-Zadeh, Mina

    2015-03-17

    This work describes a novel architecture to realize high-performance gallium nitride (GaN) bulk acoustic wave (BAW) resonators. The method is based on the growth of a thick GaN layer on a metal electrode grid. The fabrication process starts with the growth of a thin GaN buffer layer on a Si (111) substrate. The GaN buffer layer is patterned and trenches are made and refilled with sputtered tungsten (W)/silicon dioxide (SiO₂) forming passivated metal electrode grids. GaN is then regrown, nucleating from the exposed GaN seed layer and coalescing to form a thick GaN device layer. A metal electrode can be deposited and patterned on top of the GaN layer. This method enables vertical piezoelectric actuation of the GaN layer using its largest piezoelectric coefficient ( d 33 ) for thickness-mode resonance. Having a bottom electrode also results in a higher coupling coefficient, useful for the implementation of acoustic filters. Growth of GaN on Si enables releasing the device from the frontside using isotropic xenon difluoride (XeF₂) etch and therefore eliminating the need for backside lithography and etching.

  9. Die biene und ihre produkte in der kunst und im alltagsleben (Fruhchristliche und byzantinische Zeit

    Liveri Angeliki

    2010-01-01

    Full Text Available Die vorliegende Arbeit ist in zwei Teile geteilt: den kunst- und kulturhistorischen Teil. Im ersten Teil werden Darstellungen uber Bienen Bienenzucht, Honig und Wachs seit der fruhchristlichen bis zur spatbyzantinischen Zeit vorgefuhrt. Daher ist es als Beitrag in der "Ikonographie" der Biene wahrend dieser Zeit zu verstehen. Im kulturhistorischen Teil werden Informationen uber die Bienenzucht, den Handel mit Honig und Wachs sowie ihre vielfaltige Anwendung von der byzantinischen Gesellschaft an Hand der primaren Quellen, des Standes der Forschung und der archaologischen Funden erwahnt. Damit ist erwunscht ein moglichst gutes Bild der byzantinischen Bienenzucht wieder zu geben und die Nutzung der Bienenprodukte in Byzanz anschaulich zu machen.

  10. Digitalisierung und Selbstbestimmung

    Eisenberger, Iris

    2017-12-01

    Full Text Available Kurztext: Der Beitrag beleuchtet das Verhältnis von Digitalisierung und Recht. Am Beispiel der Blockchain-Technologie wird aufgezeigt, wie neue Formen und Räume der Selbstbestimmung geschaffen werden können. In distribuierten Systemen ist die Tendenz erkennbar, dass sich die rechtliche hin zu einer technologischen Steuerung verlagert. Wenn Funktionen, die für gewöhnlich der demokratisch legitimierte Gesetzgeber wahrnimmt, auf andere Systeme übergehen, führt dies zu Herausforderungen für rechtsstaatliche Demokratien. Fundamentale Fragen von Kontrolle und Machtbeschränkung iZm Digitalisierung stehen im Fokus. Der Beitrag plädiert schließlich für „legal foresight“-Forschung im Bereich neuer Technologien.

  11. GaN based nanorods for solid state lighting

    Li Shunfeng; Waag, Andreas [Institute of Semiconductor Technology, Braunschweig University of Technology, 38106 Braunschweig (Germany)

    2012-04-01

    In recent years, GaN nanorods are emerging as a very promising novel route toward devices for nano-optoelectronics and nano-photonics. In particular, core-shell light emitting devices are thought to be a breakthrough development in solid state lighting, nanorod based LEDs have many potential advantages as compared to their 2 D thin film counterparts. In this paper, we review the recent developments of GaN nanorod growth, characterization, and related device applications based on GaN nanorods. The initial work on GaN nanorod growth focused on catalyst-assisted and catalyst-free statistical growth. The growth condition and growth mechanisms were extensively investigated and discussed. Doping of GaN nanorods, especially p-doping, was found to significantly influence the morphology of GaN nanorods. The large surface of 3 D GaN nanorods induces new optical and electrical properties, which normally can be neglected in layered structures. Recently, more controlled selective area growth of GaN nanorods was realized using patterned substrates both by metalorganic chemical vapor deposition (MOCVD) and by molecular beam epitaxy (MBE). Advanced structures, for example, photonic crystals and DBRs are meanwhile integrated in GaN nanorod structures. Based on the work of growth and characterization of GaN nanorods, GaN nanoLEDs were reported by several groups with different growth and processing methods. Core/shell nanoLED structures were also demonstrated, which could be potentially useful for future high efficient LED structures. In this paper, we will discuss recent developments in GaN nanorod technology, focusing on the potential advantages, but also discussing problems and open questions, which may impose obstacles during the future development of a GaN nanorod based LED technology.

  12. GaN membrane MSM ultraviolet photodetectors

    Muller, A.; Konstantinidis, G.; Kostopoulos, A.; Dragoman, M.; Neculoiu, D.; Androulidaki, M.; Kayambaki, M.; Vasilache, D.; Buiculescu, C.; Petrini, I.

    2006-12-01

    GaN exhibits unique physical properties, which make this material very attractive for wide range of applications and among them ultraviolet detection. For the first time a MSM type UV photodetector structure was manufactured on a 2.2 μm. thick GaN membrane obtained using micromachining techniques. The low unintentionally doped GaN layer structure was grown by MOCVD on high resistivity (ρ>10kΩcm) oriented silicon wafers, 500μm thick. The epitaxially grown layers include a thin AlN layer in order to reduce the stress in the GaN layer and avoid cracking. Conventional contact lithography, e-gun Ni/Au (10nm /200nm) evaporation and lift-off techniques were used to define the interdigitated Schottky metalization on the top of the wafer. Ten digits with a width of 1μm and a length of 100μm were defined for each electrode. The distance between the digits was also 1μm. After the backside lapping of the wafer to a thickness of approximately 150μm, a 400nm thick Al layer was patterned and deposited on the backside, to be used as mask for the selective reactive ion etching of silicon. The backside mask, for the membrane formation, was patterned using double side alignment techniques and silicon was etched down to the 2.2μm thin GaN layer using SF 6 plasma. A very low dark current (30ρA at 3V) was obtained. Optical responsivity measurements were performed at 1.5V. A maximum responsivity of 18mA/W was obtained at a wavelength of 370nm. This value is very good and can be further improved using transparent contacts for the interdigitated structure.

  13. "Deutsche Kultur" und Werbung

    Schug, Alexander

    2010-01-01

    Die Arbeit präsentiert die Geschichte der modernen Wirtschaftswerbung in der ersten Hälfte des 20. Jahrhunderts und zeigt, dass Werbung trotz kultureller Barrieren die Alltagswelten der Deutschen kolonialisierte und Einfluss auf die „deutsche Kultur“ nahm. Die Arbeit zeigt, dass das Konstrukt der „deutschen Kultur“ nicht ausschließlich durch die bürgerliche Hochkultur definiert wurde, sondern zunehmend auch durch Einflüsse der Konsumkultur bestimmt war. Die Bilderwelten der Werbung prägten na...

  14. Work-Life-Balance und Frauenbiographien

    Macha, Hildegard

    2006-01-01

    Work-Life-Balance und Frauenbiographien. - In: Bildungs- und Karrierewege von Frauen / Anne Schlüter (Hrsg.). - Opladen : Budrich, 2006. - S. 17-32. - (Reihe: Frauen- und Geschlechterforschung in der Erziehungswissenschaft ; 2)

  15. Nutzerorientiertes Management von materiellen und immateriellen Informationsobjekten

    Hübsch, Chris

    2001-01-01

    Schaffung einer stabilen, erweiterbaren und skalierbaren Infrastruktur für die Bereitstellung von Diensten im Umfeld von Bibliotheken und ähnlichen wissensanbietenden Einrichtungen unter Verwendung von XML-RPC und Python.

  16. ZnO Film Photocatalysts

    Bosi Yin

    2014-01-01

    Full Text Available We have synthesized high-quality, nanoscale ultrathin ZnO films at relatively low temperature using a facile and effective hydrothermal approach. ZnO films were characterized by scanning electron microscope (SEM, X-ray diffraction (XRD, Raman spectroscopy, photoluminescence spectra (PL, and UV-vis absorption spectroscopy. The products demonstrated 95% photodegradation efficiency with Congo red (CR after 40 min irradiation. The photocatalytic degradation experiments of methyl orange (MO and eosin red also were carried out. The results indicate that the as-obtained ZnO films might be promising candidates as the excellent photocatalysts for elimination of waste water.

  17. Das IHS und die Rolle der Forschungsinstitute

    Keuschnigg, Christian

    2014-01-01

    Das Institut für Höhere Studien und wissenschaftliche Forschung (IHS) ist ein unabhängiges Forschungsinstitut und leistet Forschung und Ausbildung auf Spitzenniveau für Politik, Wirtschaft und Gesellschaft. Im Wettbewerb zwischen Universitäten und angewandten Forschungsinstituten ist das IHS einzigartig, weil es unter einem Dach Grundlagenforschung und forschungsnahe Lehre mit angewandter Forschung für die wissenschaftliche Politikberatung verbindet. Mit den drei Disziplinen Ökonomie, Soziolo...

  18. Induced defects in neutron irradiated GaN single crystals

    Park, I. W.; Koh, E. K.; Kim, Y. M.; Choh, S. H.; Park, S. S.; Kim, B. G.; Sohn, J. M.

    2005-01-01

    The local structure of defects in undoped, Si-doped, and neutron irradiated free standing GaN bulk crystals, grown by hydride vapor phase epitaxy, has been investigated by employing Raman scattering and cathodoluminescence. The GaN samples were irradiated to a dose of 2 x 10 17 neutrons in an atomic reactor at Korea Atomic Energy Research Institute. There was no appreciable change in the Raman spectra for undoped GaN samples before and after neutron irradiation. However, a forbidden transition, A 1 (TO) mode, appeared for a neutron irradiated Si-doped GaN crystal. Cathodoluminescence spectrum for the neutron irradiated Si-doped GaN crystal became much more broadened than that for the unirradiated one. The experimental results reveal the generation of defects with locally deformed structure in the wurtzite Si-doped GaN single crystal

  19. Diagrammatik und Wissensorganisation

    Sascha Freyberg

    2012-11-01

    Full Text Available EinleitungDie Formen des „Sichtbarmachens“ in der Wissenschaft reichen von „Abbildungen“ über „Modelle“ bis hin zu „Simulationen“. Sie können u.a. gezeichnet, fotografiert, geometrisch konstruiert oder durch Sensorik vermittelt, digital prozessiert werden. Ihre Funktionen erstrecken sich von der Orientierung bis hin zur (hypothetischen Voraussage und somit auch vom Überblick bis zur Evidenzsuggestion. Generell handelt es sich um vereinfachte (und vereinfachende Darstellungen von (teilweise sehr komplexen Sachverhalten, zu deren Verständnis sie beitragen sollen; daher können sie bei Lernprozessen, d.h. in der Vermittlung und auch bei der Organisation von Wissen eine wichtige Rolle spielen. Diese kommt ihnen nun nicht nur zu, weil sie – wie in den mittelalterlichen Mnemotechniken – als Gedächtnisstützen für bekannte Sachverhalte dienen. Sondern resultiert auch aus ihrem Potenzial für die Entdeckung von neuen Zusammenhängen. Der folgende Artikel diskutiert die Darstellungsform des Diagramms. Es wird hier mit dem Gedanken gespielt, dass die in der universalen Zeichentheorie von C.S. Peirce entwickelte Diagrammatik wichtige Impulse für eine Untersuchung des Zusammenhangs von Wissen und Bildlichkeit geben kann.

  20. Arbeitsgestaltung und Mitarbeiterqualifizierung

    Weiss-Oberdorfer, Werner; Hörner, Barbara; Holm, Ruth; Pirner, Evelin

    Die Wertkette gliedert ein Unternehmen in strategisch relevante Tätigkeiten, um dadurch Kostenverhalten sowie vorhandene und potenzielle Differenzierungsquellen zu verstehen. Wenn ein Unternehmen diese strategisch wichtigen Aktivitäten billiger oder besser als seine Konkurrenten erledigt, verschafft es sich einen Wettbewerbsvorteil." Michael Porter, 1985

  1. Substanzbegriff und systematik

    Lütjeharms, W.J.

    1934-01-01

    Bei der Einteilung der Organismen, welche in dieser Arbeit mir von botanischem Gesichtspunkt betrachtet wird, ist die Frage nach „wesentlichen” Merkmalen oder Einteilungsgründen von grosser Wichtigkeit. Es ist die Frage nach der Substanz (Essenz) und den akzidentellen Merkmalen. Der Substanzbegriff

  2. Stenting und technische Stentumgebung

    Hoffstetter, Marc; Pfeifer, Stefan; Schratzenstaller, Thomas; Wintermantel, Erich

    In hoch entwickelten Industrieländern stehen laut Weltgesundheitsorganisation (WHO) Herz-Kreislauf-Erkrankungen und speziell die Koronare Herzkrankheit (KHK) an erster Stelle der Todesursachen. In Deutschland betrug die Zahl der erfassten, an KHK erkrankten Personen ohne Berücksichtigung der Dunkelziffer allein im Jahre 2001 über 473.000. Die KHK war im Jahre 2003 mit 92.673 erfassten Todesfällen immer noch die häufigste Todesursache, obgleich in Deutschland die Häufigkeit der Koronarinterventionen zur Behandlung der KHK zwischen 1984 und 2003 um fast das 80fache von 2.809 auf 221.867 Eingriffe pro Jahr gestiegen ist [1]. Neben der hohen Zahl an Todesfällen haben die betroffenen Personen durch chronische Schmerzen und eingeschränkte körperliche Leistungsfähigkeit zusätzlich eine starke Beeinträchtigung der Lebensqualität [2].In Folge dessen wird die erkrankte Person häufig zum Pflegefall was neben den gesundheitlichen Aspekten auch eine sozioökonomische Komponente in Form der fehlenden Arbeitskraft und den auftretenden Pflegekosten nach sich zieht. Die Kosten für die Behandlung der KHK in Deutschland beliefen sich im Jahre 2002 laut Statistischem Bundesamt auf rund 6,9 Mrd. €. Verglichen mit ähnlichen Zahlen der USA dürfte sich der entstandene Schaden für die deutsche Volkswirtschaft im zwei- bis dreistelligen Milliardenbereich bewegen [3].

  3. Herausforderungen kleiner und mittlerer Unternehmen

    Bergmann, Lars; Crespo, Isabel

    Vielfältige externe Herausforderungen, hervorgerufen durch die Dynamik, mit der sich die wirtschaftliche, technologische, soziokulturelle sowie politische Umwelt wandelt, muss jedes Unternehmen im Laufe der Zeit bestehen (Zäpfel 2000). Diese Herausforderungen werden heute insbesondere durch eine Globalisierung der Wettbewerbssowie Nachfragestrukturen verstärkt. Immer schnellere Prozessund Produktinnovationen, kürzere Produktlebenszyklen und Entwicklungszeiten, eine rasant steigende Variantenvielfalt, Nachfrageschwankungen sowie rasante Entwicklungen der Informations- und Kommunikationstechnologien sind einige der sich schnell verändernden Rahmenbedingungen. Zudem müssen sich Unternehmen an neue Gesetze und rechtliche Rahmenbedingungen anpassen. Im Bereich der Roh- und Einsatzstoffe sind Veränderungen insbesondere durch sich verknappende Rohstoffe und Primärenergieträger und in Folge dessen durch drastische Preissteigerungen für Materialien, Hilfsstoffe, Werkzeuge etc. geprägt.

  4. Amphoteric arsenic in GaN

    Wahl, U; Araújo, J P; Rita, E; Soares, JC

    2007-01-01

    We have determined the lattice location of implanted arsenic in GaN by means of conversion electron emission channeling from radioactive $^{73}$As. We give direct evidence that As is an amphoteric impurity, thus settling the long-standing question as to whether it prefers cation or anion sites in GaN. The amphoteric character of As and the fact that As$\\scriptstyle_{Ga}\\,$ " anti-sites ” are not minority defects provide additional aspects to be taken into account for an explanantion of the so-called “ miscibility gap ” in ternary GaAs$\\scriptstyle_{1-x}$N$\\scriptstyle_{x}$ compounds, which cannot be grown with a single phase for values of $x$ in the range 0.1<${x}$< 0.99.

  5. Excitonic transitions in homoepitaxial GaN

    Martinez-Criado, G.; Cros, A.; Cantarero, A. [Materials Science Inst. and Dept. of Applied Physics, Univ. of Valencia (Spain); Miskys, C.R.; Ambacher, O.; Stutzmann, M. [Technische Univ. Muenchen, Garching (Germany). Walter-Schottky-Inst. fuer Physikalische Grundlagen der Halbleiterelektronik

    2001-11-08

    The photoluminescence spectrum of a high quality homoepitaxial GaN film has been measured as a function of temperature. As temperature increases the recombination of free excitons dominates the spectra. Their energy shift has successfully fitted in that temperature range by means of the Bose-Einstein expression instead of Varshni's relationship. Values for the parameters of both semi-empirical relations describing the energy shift are reported and compared with the literature. (orig.)

  6. Identifying individual n- and p-type ZnO nanowires by the output voltage sign of piezoelectric nanogenerator

    Lin, S S

    2009-08-18

    Based on a comparative study between the piezoelectric outputs of n-type nanowires (NWs) and n-core/p-shell NWs along with the previous study (Lu et al 2009 Nano. Lett. 9 1223), we demonstrate a one-step technique for identifying the conductivity type of individual ZnO nanowires (NWs) based on the output of a piezoelectric nanogenerator without destroying the sample. A negative piezoelectric output voltage indicates an NW is n-type and it appears after the tip scans across the center of the NW, while a positive output voltage reveals p-type conductivity and it appears before the tip scans across the central line of the NW. This atomic force microscopy based technique is reliable for statistically mapping the majority carrier type in ZnO NWs arrays. The technique may also be applied to other wurtzite semiconductors, such as GaN, CdS and ZnS. © 2009 IOP Publishing Ltd.

  7. Sorption und Verbreitung per- und polyfluorierter Chemikalien (PFAS) in Wasser und Boden

    Gellrich, Vanessa

    2014-01-01

    PFAS (= Perfluoroalkyl and Polyfluoroalkyl Substances) sind persistente organische Spurenstoffe, die weltweit in verschiedenen Umweltkompartimenten nachgewiesen werden konnten. Im Rahmen dieser Dissertation sollte die Frage geklärt werden, wie die physikalisch-chemischen Eigenschaften der PFAS - besonders ihre Sorption am Boden - ihr Verhalten und ihre Verbreitung in der Umwelt beeinflussen. Dazu wurde zunächst eine Messmethode entwickelt, optimiert und validiert, mit der 17 per- und polyf...

  8. Plazentaanatomie und -physiologie mit uteroplazentarem Kreislauf

    Engel, N.; Schreiber, J. U.; Kranke, Peter

    2017-01-01

    Die Plazenta besteht neben der Nabelschnur aus parenchymatösem Gewebe, der sog. Eihaut (Amnion) und der Zottenhaut (Chorion). Sie fungiert als Schnittstelle zwischen Mutter und Fetus und ermöglicht den physiologischen Transfer von Gasen, Nährstoffen und Metaboliten. Die Funktion der Plazenta ist als

  9. P-type doping of GaN

    Wong, R.K.

    2000-01-01

    After implantation of As, As + Be, and As + Ga into GaN and annealing for short durations at temperatures as high as 1500 C, the GaN films remained highly resistive. It was apparent from c-RBS studies that although implantation damage did not create an amorphous layer in the GaN film, annealing at 1500 C did not provide enough energy to completely recover the radiation damage. Disorder recovered significantly after annealing at temperatures up to 1500 C, but not completely. From SIMS analysis, oxygen contamination in the AIN capping layer causes oxygen diffusion into the GaN film above 1400 C. The sapphire substrate (A1203) also decomposed and oxygen penetrated into the backside of the GaN layer above 1400 C. To prevent donor-like oxygen impurities from the capping layer and the substrate from contaminating the GaN film and compensating acceptors, post-implantation annealing should be done at temperatures below 1500 C. Oxygen in the cap could be reduced by growing the AIN cap on the GaN layer after the GaN growth run or by depositing the AIN layer in a ultra high vacuum (UHV) system post-growth to minimize residual oxygen and water contamination. With longer annealing times at 1400 C or at higher temperatures with a higher quality AIN, the implantation drainage may fully recover

  10. P-type doping of GaN

    Wong, Raechelle Kimberly [Univ. of California, Berkeley, CA (United States)

    2000-04-01

    After implantation of As, As + Be, and As + Ga into GaN and annealing for short durations at temperatures as high as 1500 C, the GaN films remained highly resistive. It was apparent from c-RBS studies that although implantation damage did not create an amorphous layer in the GaN film, annealing at 1500 C did not provide enough energy to completely recover the radiation damage. Disorder recovered significantly after annealing at temperatures up to 1500 C, but not completely. From SIMS analysis, oxygen contamination in the AIN capping layer causes oxygen diffusion into the GaN film above 1400 C. The sapphire substrate (A1203) also decomposed and oxygen penetrated into the backside of the GaN layer above 1400 C. To prevent donor-like oxygen impurities from the capping layer and the substrate from contaminating the GaN film and compensating acceptors, post-implantation annealing should be done at temperatures below 1500 C. Oxygen in the cap could be reduced by growing the AIN cap on the GaN layer after the GaN growth run or by depositing the AIN layer in a ultra high vacuum (UHV) system post-growth to minimize residual oxygen and water contamination. With longer annealing times at 1400 C or at higher temperatures with a higher quality AIN, the implantation drainage may fully recover.

  11. Stage of GAN (Grupo de Analise do Nucleo) calculus methodology

    Silva, C.F. da.

    1987-11-01

    This Technical Note presents the stage of GAN Calculus Methodology in areas of Neutronics, Fuel Rod Performance and Fission Products Inventory. Proposals of GAN's members are presented and analyzed for each of these areas and a work schedule is established. (author)

  12. Hegel und Gorgias

    Huggler, Jørgen

    Hegel und Gorgias /Jørgen Huggler (University of Aarhus, Denmark) (huggler(at)dpu.dk) Hegels Verständnis des Sophist Gorgias von Leontinoi in den Vorlesungen über die Geschichte der Philosophie gründet auf seine eigene Interpretation der Eleaten, insbesondere Zenon. Aufgrund eigener philosophischer...... „Gründen“, einen echten Beitrag zu dieser Entwicklung des griechischen Denkens geliefert. Vor allen scheint Gorgias die dialektischen Bemühungen der Eleaten fortgesetzt zu haben. Hegels Auslegung des Gorgias kann den lauwarmen Empfang der Sophisten in den deutschen Beiträgen zur Geschichte der Philosophie...... des späten 18. Jahrhunderts (Meiners, Tiedemann, Stäudlin, Buhle und Tennemann) gegenübergestellt werden. In der Tat ist Hegels philosophisches Verständnis ausreichend, um positive Kommentare zu allen Teilen der Diskussion in Gorgias Argument „Über das Nicht-Seiende, oder Über der Natur“ zu geben...

  13. Rudolf Streinz. Meinungs- und Informationsfreiheit zwischen Ost und West / Henn-Jüri Uibopuu

    Uibopuu, Henn-Jüri, 1929-2012

    1983-01-01

    Tutvustus: Streinz, Rudolf. Meinungs- und Informationsfreiheit zwischen Ost und West : Möglichkeiten und Grenzen intersystemarer völkerrechtlicher Garantien in einem systemkonstituierenden Bereich. Ebelsbach : Rolf Gremer, 1981

  14. Zur historischen Aufarbeitung und medialen Vermittlung der Shoah in Italien und Deutschland

    Peter Kuon

    2016-03-01

    Full Text Available Claudia Müller, Patrick Ostermann und Karl-Siegbert Rehberg, Hrsg., Die Shoah in Geschichte und Erinnerung: Perspektiven medialer Vermittlung in Italien und Deutschland (Bielefeld: transcript, 2015.

  15. Polarization Raman spectroscopy of GaN nanorod bundles

    Tite, T.; Lee, C. J.; Chang, Y.-M.

    2010-01-01

    We performed polarization Raman spectroscopy on single wurtzite GaN nanorod bundles grown by plasma-assisted molecular beam epitaxy. The obtained Raman spectra were compared with those of GaN epilayer. The spectral difference between the GaN nanorod bundles and epilayer reveals the relaxation of Raman selection rules in these GaN nanorod bundles. The deviation of polarization-dependent Raman spectroscopy from the prediction of Raman selection rules is attributed to both the orientation of the crystal axis with respect to the polarization vectors of incident and scattered light and the structural defects in the merging boundary of GaN nanorods. The presence of high defect density induced by local strain at the merging boundary was further confirmed by transmission electron microscopy. The averaged defect interspacing was estimated to be around 3 nm based on the spatial correlation model.

  16. Ethik und Sicherheitstechnik. Eine Handreichung

    Ammicht-Quinn, Regina; Nagenborg, Michael Herbert; Rampp, Benjamin; Wolkenstein, Andreas F.X.; Ammicht-Quinn, Regina

    2013-01-01

    Mit dem Programm „Forschung für die zivile Sicherheit“ fördert die Bundesregierung im Rahmen der „Hightech-Strategie für Deutschland“ erstmals unmittelbar die Entwicklung von Techniken, die der Schaffung und Bewahrung von ziviler Sicherheit dienen. Bei der Erforschung und Entwicklung von

  17. Impact of GaN transition layers in the growth of GaN epitaxial layer on silicon

    Zhao Danmei; Zhao Degang; Jiang Desheng; Liu Zongshun; Zhu Jianjun; Chen Ping; Liu Wei; Li Xiang; Shi Ming

    2015-01-01

    A method for growing GaN epitaxial layer on Si (111) substrate is investigated. Due to the large lattice mismatch between GaN and AlN, GaN grown directly above an AlN buffer layer on the Si substrate turns out to be of poor quality. In this study, a GaN transition layer is grown additionally on the AlN buffer before the GaN epitaxial growth. By changing the growth conditions of the GaN transition layer, we can control the growth and merging of islands and control the transfer time from 3D to 2D growth mode. With this method, the crystalline quality of the GaN epitaxial layer can be improved and the crack density is reduced. Here, we have investigated the impact of a transition layer on the crystalline quality and stress evolution of a GaN epitaxial layer with methods of X-ray diffraction, optical microscopy and in situ reflectivity trace. With the increasing thickness of transition layer, the crack decreases and the crystalline quality is improved. But when the transition layer exceeds a critical thickness, the crystalline quality of the epilayer becomes lower and the crack density increases. (paper)

  18. Atomic force microscopy studies of homoepitaxial GaN layers grown on GaN template by laser MBE

    Choudhary, B. S. [CSIR-National Physical Laboratory, Dr K.S. Krishnan Road, New Delhi 110012 (India); Rajasthan Technical University, Rawatbhata Road, Kota 324010 (India); Singh, A.; Tyagi, P. K. [Department of Applied Physics, Delhi Technological University, Delhi 110042 (India); Tanwar, S. [Rajasthan Technical University, Rawatbhata Road, Kota 324010 (India); Kumar, M. Senthil; Kushvaha, S. S., E-mail: kushvahas@nplindia.org [CSIR-National Physical Laboratory, Dr K.S. Krishnan Road, New Delhi 110012 (India)

    2016-04-13

    We have grown homoepitaxial GaN films on metal organic chemical vapor deposition (MOCVD) grown 3.5 µm thick GaN on sapphire (0001) substrate (GaN template) using an ultra-high vacuum (UHV) laser assisted molecular beam epitaxy (LMBE) system. The GaN films were grown by laser ablating a polycrystalline solid GaN target in the presence of active r.f. nitrogen plasma. The influence of laser repetition rates (10-30 Hz) on the surface morphology of homoepitaxial GaN layers have been studied using atomic force microscopy. It was found that GaN layer grown at 10 Hz shows a smooth surface with uniform grain size compared to the rough surface with irregular shape grains obtained at 30 Hz. The variation of surface roughness of the homoepitaxial GaN layer with and without wet chemical etching has been also studied and it was observed that the roughness of the film decreased after wet etching due to the curved structure/rough surface.

  19. Bildanalyse in Medizin und Biologie

    Athelogou, Maria; Schönmeyer, Ralf; Schmidt, Günther; Schäpe, Arno; Baatz, Martin; Binnig, Gerd

    Heutzutage sind bildgebende Verfahren aus medizinischen Untersuchungen nicht mehr wegzudenken. Diverse Methoden - basierend auf dem Einsatz von Ultraschallwellen, Röntgenstrahlung, Magnetfeldern oder Lichtstrahlen - werden dabei spezifisch eingesetzt und liefern umfangreiches Datenmaterial über den Körper und sein Inneres. Anhand von Mikroskopieaufnahmen aus Biopsien können darüber hinaus Daten über die morphologische Eigenschaften von Körpergeweben gewonnen werden. Aus der Analyse all dieser unterschiedlichen Arten von Informationen und unter Konsultation weiterer klinischer Untersuchungen aus diversen medizinischen Disziplinen kann unter Berücksichtigung von Anamnesedaten ein "Gesamtbild“ des Gesundheitszustands eines Patienten erstellt werden. Durch die Flut der erzeugten Bilddaten kommt der Bildverarbeitung im Allgemeinen und der Bildanalyse im Besonderen eine immer wichtigere Rolle zu. Gerade im Bereich der Diagnoseunterstützung, der Therapieplanung und der bildgeführten Chirurgie bilden sie Schlüsseltechnologien, die den Forschritt nicht nur auf diesen Gebieten maßgeblich vorantreiben.

  20. Preparation of freestanding GaN wafer by hydride vapor phase epitaxy on porous silicon

    Wu, Xian; Li, Peng; Liang, Renrong; Xiao, Lei; Xu, Jun; Wang, Jing

    2018-05-01

    A freestanding GaN wafer was prepared on porous Si (111) substrate using hydride vapor phase epitaxy (HVPE). To avoid undesirable effects of the porous surface on the crystallinity of the GaN, a GaN seed layer was first grown on the Si (111) bare wafer. A pattern with many apertures was fabricated in the GaN seed layer using lithography and etching processes. A porous layer was formed in the Si substrate immediately adjacent to the GaN seed layer by an anodic etching process. A 500-μm-thick GaN film was then grown on the patterned GaN seed layer using HVPE. The GaN film was separated from the Si substrate through the formation of cracks in the porous layer caused by thermal mismatch stress during the cooling stage of the HVPE. Finally, the GaN film was polished to obtain a freestanding GaN wafer.

  1. [Die baltischen Lande im Zeitalter der Reformation und Konfessionalisierung. Livland, Estland, Ösel, Ingermanland, Kurland und Letgallen. Stadt, Land und Konfession 1500-1721. 2. und 3. Teil] / Anti Selart

    Selart, Anti, 1973-

    2012-01-01

    Arvustus: Die baltischen Lande im Zeitalter der Reformation und Konfessionalisierung. Livland, Estland, Ösel, Ingermanland, Kurland und Letgallen. Stadt, Land und Konfession 1500-1721. Hrsg. von Matthias Asche, Werner Buchholz, Anton Schindling. 2. und 3. Teil.

  2. Novel oxide buffer approach for GaN integration on Si(111) platform through Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3} bi-layer

    Tarnawska, Lidia

    2012-12-19

    Motivation: Preparation of GaN virtual substrates on large-scale Si wafers is intensively pursued as a cost-effective approach for high power/high frequency electronics (HEMT's etc.) and optoelectronic applications (LED, LASER). However, the growth of high quality GaN layers on Si is hampered by several difficulties mainly related to a large lattice mismatch (-17%) and a huge difference in the thermal expansion coefficient (56%). As a consequence, GaN epitaxial layers grown on Si substrates show a high number of defects (threading dislocations etc.), which severely deteriorate the overall quality of the GaN films. Additionally, due to the different thermal expansion coefficients of the substrate and the film, um-thick GaN layers crack during post-growth cooling. To solve these integration problems, different semiconducting (e.g. AlN, GaAs, ZnO, HfN) and insulating (e.g. Al{sub 2}O{sub 3}, MgO, LiGaO{sub 2}) buffer layers, separating the Si substrate from the GaN film, are applied. Goal: In this thesis, a novel buffer approach for the integration of GaN on Si is proposed and investigated. The new approach employs Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3} bilayer templates as a step-graded buffer to reduce the lattice mismatch between GaN and the Si(111) substrate. According to the bulk crystal lattices, since the Y{sub 2}O{sub 3} has an in-plane lattice misfit of -2% to Si, Sc{sub 2}O{sub 3} -7% to Y{sub 2}O{sub 3}, the lattice misfit between GaN and the substrate can be theoretically reduced by about 50% from -17% (GaN/Si) to -8% (GaN/Sc{sub 2}O{sub 3}). Experimental: The GaN/Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3}/Si(111) heterostructures are prepared in a multichamber molecular beam epitaxy system on 4 inch Si(111) wafers. In order to obtain complete information on the structural quality of the oxide buffer as well as the GaN layer, synchrotron- and laboratory-based X-ray diffraction, transmission electron microscopy and photoluminescence measurements are performed. The

  3. Energetics of Mg incorporation at GaN(0001) and GaN(0001¯) surfaces

    Sun, Qiang; Selloni, Annabella; Myers, T. H.; Doolittle, W. Alan

    2006-04-01

    By using density functional calculations in the generalized gradient approximation, we investigate the energetics of Mg adsorption and incorporation at GaN(0001) and GaN(0001¯) surfaces under various Ga and Mg coverage conditions as well as in presence of light or electron beam-induced electronic excitation. We find significant differences in Mg incorporation between Ga- and N-polar surfaces. Mg incorporation is easier at the Ga-polar surface, but high Mg coverages are found to cause important distortions which locally change the polarity from Ga to N polar. At the N-rich and moderately Ga-rich GaN(0001) surface, 0.25 ML of Mg substituting Ga in the top bilayer strongly reduce the surface diffusion barriers of Ga and N adatoms, in agreement with the surfactant effect observed in experiments. As the Mg coverage exceeds 0.5 ML, partial incorporation in the subsurface region (second bilayer) becomes favorable. A surface structure with 0.5 ML of incorporated Mg in the top bilayer and 0.25 ML in the second bilayer is found to be stable over a wide range of Ga chemical potential. At the Ga bilayer-terminated GaN(0001) surface, corresponding to Ga-rich conditions, configurations where Mg is incorporated in the interface region between the metallic Ga bilayer and the underlying GaN bilayer appear to be favored. At the N-polar surface, Mg is not incorporated under N-rich or moderately Ga-rich conditions, whereas incorporation in the adlayer may take place under Ga-rich conditions. In the presence of light or electron beam induced excitation, energy differences between Mg incorporated at the surface and in deeper layers are reduced so that the tendency toward surface segregation is also reduced.

  4. Investigation of GaN LED with Be-implanted Mg-doped GaN layer

    Huang, H.-W.; Kao, C.C.; Chu, J.T.; Kuo, H.C.; Wang, S.C.; Yu, C.C.; Lin, C.F.

    2004-01-01

    We report the electrical and optical characteristics of GaN light emitting diode (LED) with beryllium (Be) implanted Mg-doped GaN layer. The p-type layer of Be-implanted GaN LED showed a higher hole carrier concentration of 2.3 x 10 18 cm -3 and low specific contact resistance value of 2.0 x 10 -4 Ωcm 2 than as-grown p-GaN LED samples without Be-implantation. The Be-implanted GaN LEDs with InGaN/GaN MQW show slightly lower light output (about 10%) than the as-grown GaN LEDs, caused by the high RTA temperature annealing process

  5. Investigation of different mechanisms of GaN growth induced on AlN and GaN nucleation layers

    Tasco, V.; Campa, A.; Tarantini, I.; Passaseo, A.; Gonzalez-Posada, F.; Munoz, E.; Redondo-Cubero, A.; Lorenz, K.; Franco, N.

    2009-01-01

    The evolution of GaN growth on AlN and GaN nucleation layers is compared through morphological and structural analyses, including ion beam analysis. By using AlN nucleation layer grown at high temperature, improved crystalline quality is exhibited by 300 nm thin GaN epilayers. GaN (002) x-ray rocking curve as narrow as 168 arc sec and atomic-step surface morphology characterize such a thin GaN film on AlN. Defects are strongly confined into the first 50 nm of growth, whereas a fast laterally coherent growth is observed when increasing thickness, as an effect of high temperature AlN surface morphology and Ga adatom dynamics over this template

  6. Nonlinear characterization of GaN HEMT

    Chen Chi; Hao Yue; Yang Ling; Quan Si; Ma Xiaohua; Zhang Jincheng

    2010-01-01

    DC I-V output, small signal and an extensive large signal characterization (load-pull measurements) of a GaN HEMT on a SiC substrate with different gate widths of 100 μm and 1 mm have been carried out. From the small signal data, it has been found that the cutoff frequencies increase with gate width varying from 100 μm to 1mm, owing to the reduced contribution of the parasitic effect. The devices investigated with different gate widths are enough to work in the C band and X band. The large signal measurements include the load-pull measurements and power sweep measurements at the C band (5.5 GHz) and X band (8 GHz). When biasing the gate voltage in class AB and selecting the source impedance, the optimum load impedances seen from the device for output power and PAE were localized in the load-pull map. The results of a power sweep at an 8 GHz biased various drain voltage demonstrate that a GaN HEMT on a SiC substrate has good thermal conductivity and a high breakdown voltage, and the CW power density of 10.16 W/mm was obtained. From the results of the power sweep measurement at 5.5 GHz with different gate widths, the actual scaling rules and heat effect on the large periphery device were analyzed, although the effects are not serious. The measurement results and analyses prove that a GaN HEMT on a SiC substrate is an ideal candidate for high-power amplifier design.

  7. Effects of the ZnO layer on the structure and white light emission properties of a ZnS:Mn/GaN nanocomposite system.

    Wang, Cai-Feng; Hu, Bo

    2017-10-01

    ZnO films were inserted between the ZnS:Mn films and GaN substrates by pulsed laser deposition (PLD). The structure, morphology, and optical properties of the ZnS:Mn/ZnO/GaN nanocomposite systems have been investigated. X-ray diffraction results show that there are three diffraction peaks located at 28.4°, 34.4°, and 34.1°, which correspond to the β-ZnS(111), ZnO(002), and GaN(002) planes, respectively. Due to the insertion of ZnO films, the diffraction peak intensity of ZnS:Mn in ZnS:Mn/ZnO/GaN is stronger than that of ZnS:Mn in ZnS:Mn/GaN, and the full width at half-maximum is smaller. Though the transmittance of ZnS:Mn/ZnO films is slightly lower than that of ZnS:Mn films, the transmittance is still higher than 80%. Compared with ZnS:Mn/GaN, an ultraviolet (UV) emission at 387 nm (originated from the near-band emission of ZnO) and a green light emission at about 520 nm appeared in the photoluminescence (PL) spectra of ZnS:Mn/ZnO/GaN, in addition to the blue emission at 435 nm and the orange-red emission at 580 nm. The emission at 520 nm may be related to the deep-level emission from ZnO and the interface of ZnS:Mn/ZnO. The PL spectrum of ZnS:Mn/ZnO/GaN covers the visible region from the blue light to the red light (400-700 nm), and its color coordinate and color temperature are (0.3103,0.3063) and 6869 K, respectively, presenting strong white light emission.

  8. Synthese und Charakterisierung wasserfreier Seltenerdmetall-Nitrate, -Acetate und -Oxyacetate

    Heinrichs, Christina

    2013-01-01

    Durch thermische Entwässerung der Seltenerdmetall(SE)-Nitrat-Hydrate und der SE-Acetat-Hydrate im Argon-Strom/Vakuum konnten wasserfreie SE-Nitrate und SE-Nitrat-Monohydrate bzw. wasserfreie SE-Acetate erhalten werden. Es gelang zudem, SE-Oxyacetate durch thermische Zersetzung der SE-Acetate darzustellen. Des Weiteren wurde beim Erhitzen von Praseodym-Carbonat-Hydrat ein Pr-Carbonat-Hydroxid erhalten. Die Verbindungen wurden mittels Röntgenpulverdiffraktometrie und an ausgewählten Beispielen ...

  9. Determination of carrier diffusion length in GaN

    Hafiz, Shopan; Zhang, Fan; Monavarian, Morteza; Avrutin, Vitaliy; Morkoç, Hadis; Özgür, Ümit; Metzner, Sebastian; Bertram, Frank; Christen, Jürgen; Gil, Bernard

    2015-01-01

    Diffusion lengths of photo-excited carriers along the c-direction were determined from photoluminescence (PL) and cross-sectional cathodoluminescence (CL) measurements in p- and n-type GaN epitaxial layers grown on c-plane sapphire by metal-organic chemical vapor deposition. The investigated samples incorporate a 6 nm thick In0.15Ga0.85N active layer capped with either 500 nm p-GaN or 1500 nm n-GaN. The top GaN layers were etched in steps and PL from the InGaN active region and the underlying layers was monitored as a function of the top GaN thickness upon photo-generation near the surface region by above bandgap excitation. Taking into consideration the absorption in the top GaN layer as well as active and underlying layers, the diffusion lengths at 295 K and at 15 K were measured to be 93 ± 7 nm and 70 ± 7 nm for Mg-doped p-type GaN and 432 ± 30 nm and 316 ± 30 nm for unintentionally doped n-type GaN, respectively, at photogenerated carrier densities of 4.2 × 1018 cm-3 using PL spectroscopy. CL measurements of the unintentionally doped n-type GaN layer at much lower carrier densities of 1017 cm-3 revealed a longer diffusion length of 525 ± 11 nm at 6 K.

  10. Interaction of GaN epitaxial layers with atomic hydrogen

    Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G.; Namkoong, G.; Doolittle, W.A.; Brown, A.S

    2004-08-15

    GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0 0 0 1) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56 MHz) H{sub 2} plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states.

  11. Interaction of GaN epitaxial layers with atomic hydrogen

    Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G.; Namkoong, G.; Doolittle, W.A.; Brown, A.S.

    2004-01-01

    GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0 0 0 1) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56 MHz) H 2 plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states

  12. In situ synthesis and characterization of GaN nanorods through thermal decomposition of pre-grown GaN films

    Yan, P; Qin, D; An, Y K; Li, G Z; Xing, J; Liu, J J

    2008-01-01

    Herein we describe a thermal treatment route to synthesize gallium nitride (GaN) nanorods. In this method, GaN nanorods were synthesized by thermal treatment of GaN films at a temperature of 800 deg. C. The morphology and structure of GaN nanorods were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that GaN nanorods have a hexagonal wurtzite structure with diameters ranging from 30 to 50 nm. Additionally, GaN nanoplates are also founded in the products. The growth process of GaN nanostructures was investigated and a thermal decomposition mechanism was proposed. Our method provides a cost-effective route to fabricate GaN nanorods, which will benefit the fabrication of one-dimensional nanomaterials and device applications

  13. Improved InGaN/GaN quantum wells on treated GaN template with a Ga-rich GaN interlayer

    Fang, Zhilai; Shen, Xiyang; Wu, Zhengyuan; Zhang, Tong-Yi

    2015-01-01

    Treated GaN template was achieved by in situ droplet epitaxy of a Ga-rich GaN interlayer on the conventional GaN template. InGaN/GaN quantum wells (QWs) were grown on the conventional and treated GaN templates under the same growth conditions and then comprehensively characterized. The indium homogeneity in the InGaN layers and the interface sharpness between InGaN and GaN layers of the InGaN/GaN QWs on the treated GaN template were significantly improved. The emission intensity from the InGaN/GaN QWs on the treated GaN template was enhanced by 20% than that on the conventional GaN template, which was attributed to the strain reduction and the improvement in crystalline quality. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Editorial: Informationstechnische Bildung und Medienerziehung

    Annemarie Hauf-Tulodziecki

    2001-10-01

    Full Text Available Die schulische Medienerziehung bzw. die Medienbildung hat ihre derzeit hohe öffentliche Aufmerksamkeit nicht zuletzt der Tatsache zu verdanken, dass gerade die so genannten «Neuen Medien» - heute oft mit den Schlagworten «Multimedia» oder «Internet» abgekürzt - wichtige Erziehungs- und Bildungsmassnahmen erforderlich machen. In der öffentlichen Diskussion gehören inhaltliche Kurzschlüsse zur Tagesordnung: Wenn von «Medienkompetenz» die Rede ist, verbirgt sich dahinter häufig nur ein «Internetführerschein». Diese Beobachtung ärgert nicht nur Medienpädagogen, sondern auch Vertreter einer Informationstechnischen Bildung (1, da berechtigte pädagogische Ansprüche beider Gruppen wenig Beachtung finden. Mittlerweile gibt es eine Reihe von Empfehlungen von BLK und KMK zu diesem Thema, in denen zudem deutlich auf die wechselseitigen Bezüge hingewiesen werden. Die wachsende Bedeutung des Mediums Computer und die weiter zunehmende Digitalisierung traditioneller Medien erfordert sowohl für die Medienerziehung als auch für die Informatische Bildung eine Weiterentwicklung ihrer Ziele und Inhalte. Die Gesellschaft für Informatik e.V. hat 1999 in ihrer Empfehlung «Informatische Bildung und Medienerziehung» aus ihrer Perspektive dargestellt, welche Aufgaben auf die Medienerziehung zukommen, wenn auch die Informations- und Kommunikationstechnologien bzw. die computerbasierten Medien in einer angemessenen Form thematisiert werden sollen. Erste praktische Ansätze, Inhalte aus beiden Bereichen bewusst zusammenzuführen, auch unter einer gemeinsamen Fach- oder Kursbezeichnung, sind häufig additiv und orientieren sich – trotz vorhandener Überschneidungen – an den etablierten medienpädagogischen oder an den informatischen Unterrichtsprinzipien. In dem vorliegenden Themenheft wird aus einer übergeordneten, medienpädagogischen Perspektive die Frage gestellt, wie eine konsistente Weiterentwicklung der Medienerziehung unter angemessener

  15. UMA/GAN network architecture analysis

    Yang, Liang; Li, Wensheng; Deng, Chunjian; Lv, Yi

    2009-07-01

    This paper is to critically analyze the architecture of UMA which is one of Fix Mobile Convergence (FMC) solutions, and also included by the third generation partnership project(3GPP). In UMA/GAN network architecture, UMA Network Controller (UNC) is the key equipment which connects with cellular core network and mobile station (MS). UMA network could be easily integrated into the existing cellular networks without influencing mobile core network, and could provides high-quality mobile services with preferentially priced indoor voice and data usage. This helps to improve subscriber's experience. On the other hand, UMA/GAN architecture helps to integrate other radio technique into cellular network which includes WiFi, Bluetooth, and WiMax and so on. This offers the traditional mobile operators an opportunity to integrate WiMax technique into cellular network. In the end of this article, we also give an analysis of potential influence on the cellular core networks ,which is pulled by UMA network.

  16. GROSSSPRENGUN UND MIKROSEISMIK

    E. HARDTWIG

    1956-06-01

    Full Text Available Uéber die bei Sprengungen entstelienden Periodenspektren ist noch
    wenig bekannt, trotzdem in jedem Jahre Tausende von Sprengungen
    registriert werden. Die wenigen Arbeiten, die zu diesem Gegenstand erscliienen
    sind, stellen nur erste Versuche dar, den Aufbau der Spektren
    zu erklaren. Wàhrend etwa George Morris (* vorwiegend die bei
    Sprengungen si eh abspielenden Detonationsvorgànge zum Ausgangspunkt
    der Untersuchung macht, ist es bei IT. Menzel (2 die Interferenz von
    Primàrwelle und reflektierter Welle, deren Einfluss auf die Gestalt
    des Spektrums untersucht wird.

  17. GaN transistors for efficient power conversion

    Lidow, Alex; de Rooij, Michael; Reusch, David

    2014-01-01

    The first edition of GaN Transistors for Efficient Power Conversion was self-published by EPC in 2012, and is currently the only other book to discuss GaN transistor technology and specific applications for the technology. More than 1,200 copies of the first edition have been sold through Amazon or distributed to selected university professors, students and potential customers, and a simplified Chinese translation is also available. The second edition has expanded emphasis on applications for GaN transistors and design considerations. This textbook provides technical and application-focused i

  18. Acceptors in ZnO

    McCluskey, Matthew D., E-mail: mattmcc@wsu.edu; Corolewski, Caleb D.; Lv, Jinpeng; Tarun, Marianne C.; Teklemichael, Samuel T. [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States); Walter, Eric D. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Norton, M. Grant; Harrison, Kale W. [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 (United States); Ha, Su [Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164-6515 (United States)

    2015-03-21

    Zinc oxide (ZnO) has potential for a range of applications in the area of optoelectronics. The quest for p-type ZnO has focused much attention on acceptors. In this paper, Cu, N, and Li acceptor impurities are discussed. Experimental evidence indicates these point defects have acceptor levels 3.2, 1.4, and 0.8 eV above the valence-band maximum, respectively. The levels are deep because the ZnO valence band is quite low compared to conventional, non-oxide semiconductors. Using MoO{sub 2} contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peak in ZnO nanocrystals is attributed to an acceptor, which may involve a Zn vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g{sub ⊥} = 2.0015 and g{sub //} = 2.0056, along with an isotropic center at g = 2.0035.

  19. Enterprise Portals und Enterprise Application Integration - Begriffsbestimmung und Integrationskonzeptionen

    Schelp, Joachim; Winter, Robert

    2002-01-01

    Unter den Stichworten »Enterprise Portals« und »Enterprise Application Integration« werden neue Herausforderungen an die Applikationsarchitektur der Unternehmungen gestellt. Bei beiden spielt die Integration vorhandener und das Einfügen neuer Applikationen eine große Rolle. Beiden Themen ist gemein, dass sie die Diskussion bestimmter technischer Konzepte aus den vergangenen Jahren fortsetzen: Portale stellen das moderne Frontend dar, über das die verschiedenen E-Business-Konzepte umgesetzt we...

  20. Photoluminescence of Mg-doped m-plane GaN grown by MOCVD on bulk GaN substrates

    Monemar, Bo; Paskov, Plamen; Pozina, Galia; Hemmingsson, Carl; Bergman, Peder; Lindgren, David; Samuelson, Lars; Ni, Xianfeng; Morkoç, Hadis; Paskova, Tanya; Bi, Zhaoxia; Ohlsson, Jonas

    2011-01-01

    Photoluminescence (PL) properties are reported for a set of m-plane GaN films with Mg doping varied from mid 1018cm-3 to well above 1019 cm-3. The samples were grown with MOCVD at reduced pressure on low defect density m-plane bulk GaN templates. The sharp line near bandgap bound exciton (BE) spectra observed below 50 K, as well as the broader donor-acceptor pair (DAP) PL bands at 2.9 eV to 3.3 eV give evidence of several Mg related acceptors, similar to the case of c-plane GaN. The dependenc...

  1. Cyberbullying und Empathie : affektive, kognitive und medienbasierte Empathie im Kontext von Cyberbullying im Kindes- und Jugendalter

    Pfetsch, Jan; Müller, Christin R.; Ittel, Angela

    2014-01-01

    "Bei medial vermittelter Kommunikation sinkt sowohl die Hemmschwelle für aggressive Verhaltensweisen wie Cyberbullying als auch die Wahrscheinlichkeit empathischer Reaktionen. Im Fokus der vorliegenden Studie mit 979 Schülerinnen und Schülern der 4.-8. Klassen (M=12.01, SD=1.68 Jahre, 55% weiblich) stand die Frage, ob Cyberbullies geringere Ausprägungen für affektive, kognitive und medienbasierte Empathie aufweisen als Unbeteiligte. Empathie wurde im Selbst- und Peerbericht erhoben. Hypothese...

  2. Jung und Alt im Dialog

    Caroline Baetge

    2012-04-01

    Full Text Available Rezension zu: Kupser, Thomas, und Ida Pöttinger, Hrsg. 2011. Mediale Brücken: Generationen im Dialog durch aktive Medienarbeit. Gesellschaft - Altern - Medien 3. München: kopaed.

  3. Frauen in Philosophie und Wissenschaft

    Regina Harzer

    2006-03-01

    Full Text Available Der von Brigitte Doetsch herausgegebene Band präsentiert die aktuelle Feministische Philosophie und sammelt Beiträge, die Einblick geben in den gegenwärtigen Forschungsstand, wie ihn „Philosophinnen im dritten Jahrtausend“ erreicht haben. Insgesamt neun, zum Teil interdisziplinär ausgerichtete Arbeiten werden vorgestellt. Das Themenspektrum ist weit: Geschichte der Philosophie; Politische Philosophie und Naturphilosophie; Epistemologie; Biopolitik und Bioethik als Bereiche praktischer Philosophie; Forschung über Geschlechterverhältnisse. Alle Beiträge gehen zurück auf eine Vortragsreihe des Braunschweiger Zentrums für Gender Studies (www.genderzentrum.de. Leser/-innen erhalten einen guten Überblick über die aktuelle Frauenforschung aus der Sicht theoretischer und praktischer Philosophie.

  4. Gesundheit und Pflege im Alter

    Pfaff, Martin

    1989-01-01

    Gesundheit und Pflege im Alter : d. Gesundheitsreformgesetz (GRG) ; Möglichkeiten, Grenzen u. weitere Vorschläge / Martin Pfaff ; Klaus Deimer. - In: Expertengespräch "Pflege in der Familie". - Augsburg, 1989. - Getr. Zählung

  5. Surface morphology of homoepitaxial GaN grown on non- and semipolar GaN substrates

    Wernicke, Tim; Hoffmann, Veit; Netzel, Carsten; Knauer, Arne; Weyers, Markus [FBH, Berlin (Germany); Ploch, Simon; Rass, Jens [Institute of Solid State Physics, TU Berlin (Germany); Schade, Lukas; Schwarz, Ulrich [IAF, Freiburg (Germany); Kneissl, Michael [FBH, Berlin (Germany); Institute of Solid State Physics, TU Berlin (Germany)

    2010-07-01

    Recently a number of groups have reported laser diodes in the green spectral range on semi- and nonpolar GaN. Nevertheless the growth process on semipolar surfaces is not well understood. In this study 3.5 {mu} m thick MOVPE grown GaN layers on bulk m-plane, (11 anti 22), (10 anti 12), and (10 anti 11) GaN substrates were investigated. XRD rocking curves exhibit a FWHM of less than 150{sup ''}, indicating excellent crystalline quality. But the surface morphology exhibits hillocks with a height of 1 {mu}m and lateral extension of 150 {mu}m in many cases. Depending on the substrate orientation and the growth temperature different hillock shapes were observed. Morphology and luminescence data point to threading dislocations as formation sources. In QWs the hillock structure is reproduced in the emission intensity and wavelength distribution on (10 anti 11) but not on the m-plane surfaces. The hillocks could be eliminated for the semipolar planes (not for the m-plane) by increasing the reactor pressure and lowering the growth temperature. Hillock free separate confinement laser structures emitting at 405 nm feature a very homogeneous luminescence in micro-PL and show amplified spontaneous emission under high power stripe excitation. Furthermore the In incorporation was found to be highest in QWs on (10 anti 11).

  6. Editorial: Computerspiele und Videogames in formellen und informellen Bildungskontexten

    Johannes Fromme

    2008-01-01

    Full Text Available Computer- und Videospiele sind heute ein selbstverständlicher Bestandteil der Lebenswelt vieler Kinder und Jugendlicher, aber auch von (jüngeren Erwachsenen, die mit diesen neuen Medien aufgewachsen sind. Lange Zeit haben elektronische Bildschirmspiele allenfalls sporadische Beachtung gefunden. Weder in der Medienforschung oder Medienpädagogik noch in der breiteren Öffentlichkeit waren sie ein Gegenstand von breiterem Interesse.* In den letzten knapp zehn Jahren sind Video- und Computerspiele allerdings zunehmend in den Fokus der Aufmerksamkeit gerückt. Dabei sind in der massenmedial vermittelten Öffentlichkeit vor allem Amokläufe in Schulen in einen direkten Zusammenhang mit den Vorlieben (der Täter für bestimmte Computerspiele gebracht worden. Die auch von prominenten Politikern aufgegriffene These lautete, dass gewalthaltige Spiele wie der First Person Shooter «Counterstrike» ein virtuelles Trainingsprogramm für das Töten und daher als wesentliche Ursache solcher Schulmassaker anzusehen seien. Auf der Basis dieser kausalen Wirkungsannahmen bzw. der unterstellten negativen Lern- und Trainingseffekte werden seither immer wieder Forderungen nach einem Verbot solcher «Killerspiele» oder gar nach der Verbannung aller Bildschirmmedien aus den Kinderzimmern abgeleitet. Neben solcher skandalisierter Thematisierung ist aber zunehmend auch eine nüchterne wissenschaftliche Auseinandersetzung zu konstatieren. So haben sich seit Beginn des neuen Jahrtausends die «digital game studies» als interdisziplinäres Forschungsfeld etabliert. Im Jahr 2000 wurde innerhalb der Gesellschaft für Medienwissenschaft z.B. die AG Games gebildet, die sich zu einem wichtigen deutschsprachigen Forum für die wissenschaftliche Beschäftigung mit Computerspielen entwickelt hat, und im Jahr 2002 entstand die internationale Digital Games Research Association (DiGRA, die im September 2009 ihre vierte grosse Konferenz nach 2003, 2005 und 2007 durchgeführt hat

  7. Application of Generative Adversarial Networks (GANs) to jet images

    CERN. Geneva

    2017-01-01

    https://arxiv.org/abs/1701.05927 We provide a bridge between generative modeling in the Machine Learning community and simulated physical processes in High Energy Particle Physics by applying a novel Generative Adversarial Network (GAN) architecture to the production of jet images -- 2D representations of energy depositions from particles interacting with a calorimeter. We propose a simple architecture, the Location-Aware Generative Adversarial Network, that learns to produce realistic radiation patterns from simulated high energy particle collisions. The pixel intensities of GAN-generated images faithfully span over many orders of magnitude and exhibit the desired low-dimensional physical properties (i.e., jet mass, n-subjettiness, etc.). We shed light on limitations, and provide a novel empirical validation of image quality and validity of GAN-produced simulations of the natural world. This work provides a base for further explorations of GANs for use in faster simulation in High Energy Particle Physics.

  8. Professionalisierung und Doping im Sport

    Wüterich, Christoph

    2004-01-01

    Der Beitrag untersucht Zusammenhänge zwischen der zunehmenden Professionalisierung des Sports und dem Anstieg von Dopingvergehen. Er zeigt, dass im historischen Vergleich beide Phänomene nicht neu sind, dass sich die Probleme aufgrund der steigenden Bedeutung des Leistungssports aber zugespitzt haben. Ausgehend von einer juristischen und sozioökonomischen Analyse der Anreize zu Doping werden Lösungsvorschläge entwickelt. The author analyzes the interdependencies between a growing commercia...

  9. Pepsi und Coca ewige Rivallen

    POLJAKOW ANDREJ; POLJAKOW WLADIMIR

    2016-01-01

    Fast jeder kennt Pepsi und Coca. Man kann sie treffen praktisch in jedem Geschaeft. Dennoch nicht alle wissen, dass diese Firmen Erzrivallen sind und das ihre Rivallitaet sich seit Ewigkeit dauert. In meinem Artikel, welches ich in der Zusammenarbeit mit meinem Vater schrieb versuchte ich den Weg beider Firmen von der Gruendung bis heutigen Tagen zu beschreiben. Auf diesem Weg trafen sich technologische Aenderungen, Gerichtsverhandlungen, sowie geschickte Tricks. Wichtige Rolle spielt auch Ma...

  10. Tax Shield, Insolvenz und Zinsschranke

    Arnold, Sven; Lahmann, Alexander; Schwetzler, Bernhard

    2010-01-01

    Dieser Beitrag analysiert den Wertbeitrag fremdfinanzierungsbedingter Steuervorteile (Tax Shield) unter realistischen Bedingungen (keine Negativsteuer; mögliche Insolvenz) für unterschiedliche Finanzierungspolitiken. Zusätzlich wird der Effekt der sogenannten Zinsschranke auf den Wert des Tax Shield ermittelt. Die Bewertung des Tax Shield mit und ohne Zinsschranke findet im einperiodigen Fall auf der Basis von Optionspreismodellen und im mehrperiodigen Fall auf der Basis von Monte Carlo Simul...

  11. Metal-organic-vapor-phase-epitaxy and characterization of homoepitaxial ZnO-layers; Metallorganische Gasphasenepitaxie und Charakteriesierung homoepitaktischer ZnO-Schichten

    Heinze, Soeren

    2009-03-30

    layers was at the beginning very bad, but could by directed change of the growth parameters be more and more improved. By application of pure O{sub 2} as oxygen source (instead of N{sub 2}O) word-widely for the first time the homoepitactical deposition of ZnO layers in a two-dimensional growth mode succeeded. On the base of such layers attempts on the p-doping were performed with arsenic as dopant. Instead of p-type ZnO indeed an electrically insulating Zn/As/O alloy was formed. This alloy was identified as Zn{sub 3}(AlO{sub 3}){sub 2} -reinerite -. (orig.) [German] ZnO ist ein direkter Halbleiter mit einer Bandluecke von 3,37 eV und einer Exzitonenbindungsenergie von ca. 60 meV. Durch Legierung mit Cadmium oder Magnesium laesst sich die Bandluecke zwischen 2,9 eV und 4 eV variieren, was die Realisierung von z. B. Quantentopfstrukturen ermoeglicht. Deswegen ist ZnO ein aussichtsreiches Material fuer optoelektronische Anwendungen im blauen und nahen ultravioletten Spektralbereich. Trotz weltweit zahlreicher Forschungsaktivitaeten ueber die letzten Jahre konnte allerdings die Realisierung von p-Typ ZnO nicht zufriedenstellend (d. h. reproduzierbar und langzeitstabil) geloest werden. Die ZnO-Schichten dieser Arbeit wurden mittels metallorganischer Gasphasenepitaxie hergestellt. Anhand der Untersuchungen an heteroepitaktisch abgeschiedenen, undotierten Schichten, zeige ich die Grenzen der Heteroepitaxie auf. Durch die Einfuehrung eines dreistufigen Wachstumsverfahrens konnten physikalischen Eigenschaften (Morphologie, Lumineszenz, kristallografische und elektrische Eigenschaften) der obersten ZnO-Schicht deutlich verbessert werden. Dennoch konnte in Dotierversuchen kein p-Typ ZnO hergestellt werden. Hingegen wurde nachgewiesen, dass sich waehrend des Herstellungsprozesses eine elektrisch hochleitfaehige Zwischenschicht in der Naehe der Substrat/ZnO-Grenzflaeche bildet, deren Ausbildung sich bei der Heteroepitaxie nicht vermeiden laesst. Seit ca. drei Jahren sind Zn

  12. Mn doped GaN thin films and nanoparticles

    Šofer, Z.; Sedmidubský, D.; Huber, Š.; Hejtmánek, Jiří; Macková, Anna; Fiala, R.

    2012-01-01

    Roč. 9, 8-9 (2012), s. 809-824 ISSN 1475-7435 R&D Projects: GA ČR GA104/09/0621 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z10480505 Keywords : GaN nanoparticles * GaN thin films * manganese * transition metals * MOVPE * ion implantations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.087, year: 2012

  13. Neue Shandite und Parkerite. Darstellung und röntgenographische Charakterisierung

    Anusca, Irina

    2009-01-01

    Das Ziel dieser Arbeit war es, neue Verbindungen mit Shandit- und Parkeritstruktur zu darstellen und mittels röntgenographischen Methoden (Pulverdiffraktometrie und Einkristallanalyse), das thermische Verhalten durch DTA / DSC - Messungen und Elektronenmikroskopische Untersuchungen (REM, EDX) zu charakterisieren. Die vorliegende Arbeit ist wie folgt im zwei Themen gegliedert: Shandite und Parkerite. Der ersten Teil dieser Arbeit befaßt sich mit metallreichen ternären Chalkogeniden M3A2X2, ...

  14. Molekulargenetische Studie zur Verbreitung und Interaktion von PCV-2 bei Haus- und Wildschweinen

    Bronnert, Bastian Balthasar Marcel

    2014-01-01

    Im Rahmen der vorliegenden Arbeit wurden Wild- und Hausschweingewebeproben aus den Jahren 2005 bis 2008 mittels nested PCR auf das Vorkommen von PCV-2 untersucht und die positiv getesteten Proben mittels Realtime PCR quantifiziert. Zusätzlich wurden die Proben im Institut für Pathologie der Justus-Liebig-Universität histologisch und immunhistologisch untersucht (Dissertation Hohloch). Ziel war es das Vorkommen von PCV-2 und die Häufigkeit von PCV-2 assoziierter Erkankungen bei Haus- und Wilds...

  15. Vom Stabilitäts- und Wachstumsgesetz zum Wohlstands- und Nachhaltigkeitsgesetz

    Koll, Willi

    2016-01-01

    Das Stabilitäts- und Wachstumsgesetz wird bald 50 Jahre alt. Neue Herausforderungen erfordern eine Wirtschaftspolitik, die weit über die Ziele des Gesetzes hinausweist. Sie muss wirtschaftliches Wachstum und Stabilität mit den Zielen fiskalischer, sozialer und ökologischer Nachhaltigkeit auf nationaler und europäischer Ebene verbinden. Der Autor gibt einen Über blick über solche umfassenden Zielsysteme und leitet daraus ab, wie eine derart erweiterte wirtschaftspolitische Agenda in ein Wohlst...

  16. ARM MJO Investigation Experiment on Gan Island (AMIE-Gan) Science Plan

    Long, CL; Del Genio, A; Deng, M; Fu, X; Gustafson, W; Houze, R; Jakob, C; Jensen, M; Johnson, R; Liu, X; Luke, E; May, P; McFarlane, S; Minnis, P; Schumacher, C; Vogelmann, A; Wang, Y; Webster, P; Xie, S; Zhang, C

    2011-04-11

    The overarching campaign, which includes the ARM Mobile Facility 2 (AMF2) deployment in conjunction with the Dynamics of the Madden-Julian Oscillation (DYNAMO) and the Cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011 (CINDY2011) campaigns, is designed to test several current hypotheses regarding the mechanisms responsible for Madden-Julian Oscillation (MJO) initiation and propagation in the Indian Ocean area. The synergy between the proposed AMF2 deployment with DYNAMO/CINDY2011, and the corresponding funded experiment on Manus, combine for an overarching ARM MJO Investigation Experiment (AMIE) with two components: AMF2 on Gan Island in the Indian Ocean (AMIE-Gan), where the MJO initiates and starts its eastward propagation; and the ARM Manus site (AMIE-Manus), which is in the general area where the MJO usually starts to weaken in climate models. AMIE-Gan will provide measurements of particular interest to Atmospheric System Research (ASR) researchers relevant to improving the representation of MJO initiation in climate models. The framework of DYNAMO/CINDY2011 includes two proposed island-based sites and two ship-based locations forming a square pattern with sonde profiles and scanning precipitation and cloud radars at both island and ship sites. These data will be used to produce a Variational Analysis data set coinciding with the one produced for AMIE-Manus. The synergy between AMIE-Manus and AMIE-Gan will allow studies of the initiation, propagation, and evolution of the convective cloud population within the framework of the MJO. As with AMIE-Manus, AMIE-Gan/DYNAMO also includes a significant modeling component geared toward improving the representation of MJO initiation and propagation in climate and forecast models. This campaign involves the deployment of the second, marine-capable, AMF; all of the included measurement systems; and especially the scanning and vertically pointing radars. The campaign will include sonde

  17. Interconnectedness und digitale Texte

    Detlev Doherr

    2013-04-01

    Full Text Available Zusammenfassung Die multimedialen Informationsdienste im Internet werden immer umfangreicher und umfassender, wobei auch die nur in gedruckter Form vorliegenden Dokumente von den Bibliotheken digitalisiert und ins Netz gestellt werden. Über Online-Dokumentenverwaltungen oder Suchmaschinen können diese Dokumente gefunden und dann in gängigen Formaten wie z.B. PDF bereitgestellt werden. Dieser Artikel beleuchtet die Funktionsweise der Humboldt Digital Library, die seit mehr als zehn Jahren Dokumente von Alexander von Humboldt in englischer Übersetzung im Web als HDL (Humboldt Digital Library kostenfrei zur Verfügung stellt. Anders als eine digitale Bibliothek werden dabei allerdings nicht nur digitalisierte Dokumente als Scan oder PDF bereitgestellt, sondern der Text als solcher und in vernetzter Form verfügbar gemacht. Das System gleicht damit eher einem Informationssystem als einer digitalen Bibliothek, was sich auch in den verfügbaren Funktionen zur Auffindung von Texten in unterschiedlichen Versionen und Übersetzungen, Vergleichen von Absätzen verschiedener Dokumente oder der Darstellung von Bilden in ihrem Kontext widerspiegelt. Die Entwicklung von dynamischen Hyperlinks auf der Basis der einzelnen Textabsätze der Humboldt‘schen Werke in Form von Media Assets ermöglicht eine Nutzung der Programmierschnittstelle von Google Maps zur geographischen wie auch textinhaltlichen Navigation. Über den Service einer digitalen Bibliothek hinausgehend, bietet die HDL den Prototypen eines mehrdimensionalen Informationssystems, das mit dynamischen Strukturen arbeitet und umfangreiche thematische Auswertungen und Vergleiche ermöglicht. Summary The multimedia information services on Internet are becoming more and more comprehensive, even the printed documents are digitized and republished as digital Web documents by the libraries. Those digital files can be found by search engines or management tools and provided as files in usual formats as

  18. Synthesis of p-type GaN nanowires.

    Kim, Sung Wook; Park, Youn Ho; Kim, Ilsoo; Park, Tae-Eon; Kwon, Byoung Wook; Choi, Won Kook; Choi, Heon-Jin

    2013-09-21

    GaN has been utilized in optoelectronics for two decades. However, p-type doping still remains crucial for realization of high performance GaN optoelectronics. Though Mg has been used as a p-dopant, its efficiency is low due to the formation of Mg-H complexes and/or structural defects in the course of doping. As a potential alternative p-type dopant, Cu has been recognized as an acceptor impurity for GaN. Herein, we report the fabrication of Cu-doped GaN nanowires (Cu:GaN NWs) and their p-type characteristics. The NWs were grown vertically via a vapor-liquid-solid (VLS) mechanism using a Au/Ni catalyst. Electrical characterization using a nanowire-field effect transistor (NW-FET) showed that the NWs exhibited n-type characteristics. However, with further annealing, the NWs showed p-type characteristics. A homo-junction structure (consisting of annealed Cu:GaN NW/n-type GaN thin film) exhibited p-n junction characteristics. A hybrid organic light emitting diode (OLED) employing the annealed Cu:GaN NWs as a hole injection layer (HIL) also demonstrated current injected luminescence. These results suggest that Cu can be used as a p-type dopant for GaN NWs.

  19. Polarity Control of Heteroepitaxial GaN Nanowires on Diamond.

    Hetzl, Martin; Kraut, Max; Hoffmann, Theresa; Stutzmann, Martin

    2017-06-14

    Group III-nitride materials such as GaN nanowires are characterized by a spontaneous polarization within the crystal. The sign of the resulting sheet charge at the top and bottom facet of a GaN nanowire is determined by the orientation of the wurtzite bilayer of the different atomic species, called N and Ga polarity. We investigate the polarity distribution of heteroepitaxial GaN nanowires on different substrates and demonstrate polarity control of GaN nanowires on diamond. Kelvin Probe Force Microscopy is used to determine the polarity of individual selective area-grown and self-assembled nanowires over a large scale. At standard growth conditions, mixed polarity occurs for selective GaN nanowires on various substrates, namely on silicon, on sapphire and on diamond. To obtain control over the growth orientation on diamond, the substrate surface is modified by nitrogen and oxygen plasma exposure prior to growth, and the growth parameters are adjusted simultaneously. We find that the surface chemistry and the substrate temperature are the decisive factors for obtaining control of up to 93% for both polarity types, whereas the growth mode, namely selective area or self-assembled growth, does not influence the polarity distribution significantly. The experimental results are discussed by a model based on the interfacial bonds between the GaN nanowires, the termination layer, and the substrate.

  20. Gosvig und das Problem der Geschichte

    Wentzer, Thomas Schwarz

    2016-01-01

    Der Essay geht der Frage nach, wieso so viele philosophische Bücher, insbesondere innerhalb der sogenannten 'kontinentalen' Philosophie des 20. Jhs, einen Titel tragen, der durch die Struktur 'x und y' gekennzeichnet ist. Hat Heideggers 'Sein und Zeit' auch hier Schule gemacht? Wenn ja, wie so? U...... These, dass die Iteration des 'und' tatsächlich und in Kontrast zur Genetivkonstruktion der Idealisten ('Phänomenologie des Geistes') die Geschichtlichkeit im Zeitalter postsubjektivistischen Denkens reflektiert....

  1. Role of the ganSPQAB Operon in Degradation of Galactan by Bacillus subtilis.

    Watzlawick, Hildegard; Morabbi Heravi, Kambiz; Altenbuchner, Josef

    2016-10-15

    Bacillus subtilis possesses different enzymes for the utilization of plant cell wall polysaccharides. This includes a gene cluster containing galactan degradation genes (ganA and ganB), two transporter component genes (ganQ and ganP), and the sugar-binding lipoprotein-encoding gene ganS (previously known as cycB). These genes form an operon that is regulated by GanR. The degradation of galactan by B. subtilis begins with the activity of extracellular GanB. GanB is an endo-β-1,4-galactanase and is a member of glycoside hydrolase (GH) family 53. This enzyme was active on high-molecular-weight arabinose-free galactan and mainly produced galactotetraose as well as galactotriose and galactobiose. These galacto-oligosaccharides may enter the cell via the GanQP transmembrane proteins of the galactan ABC transporter. The specificity of the galactan ABC transporter depends on the sugar-binding lipoprotein, GanS. Purified GanS was shown to bind galactotetraose and galactotriose using thermal shift assay. The energy for this transport is provided by MsmX, an ATP-binding protein. The transported galacto-oligosaccharides are further degraded by GanA. GanA is a β-galactosidase that belongs to GH family 42. The GanA enzyme was able to hydrolyze short-chain β-1,4-galacto-oligosaccharides as well as synthetic β-galactopyranosides into galactose. Thermal shift assay as well as electrophoretic mobility shift assay demonstrated that galactobiose is the inducer of the galactan operon regulated by GanR. DNase I footprinting revealed that the GanR protein binds to an operator overlapping the -35 box of the σ(A)-type promoter of Pgan, which is located upstream of ganS IMPORTANCE: Bacillus subtilis is a Gram-positive soil bacterium that utilizes different types of carbohydrates, such as pectin, as carbon sources. So far, most of the pectin degradation systems and enzymes have been thoroughly studied in B. subtilis Nevertheless, the B. subtilis utilization system of galactan, which is

  2. Mensch und Maschine in Übersetzungsprozessen

    Hansen, Gyde

    2014-01-01

    gebrauchstauglich sein. In meinem empirischen Projekt zur Erforschung notwendiger Kompetenzen, zum Übersetzen, Revidieren und zum Pre- und Post-Editing, TraREdit, arbeite ich mit den Sprachen Deutsch, Dänisch und Englisch. Trotz offensichtlicher Mängel von Maschinenübersetzungen muss man erkennen, dass diese besser...

  3. Sprachvermittlung und Spracherwerb in Afrika. Deutsch nach ...

    erlernende Fremdsprache richtig und auf hohem Niveau sprechen zu lernen. Lehrende sollten alles daransetzen zu verhindern, dass die Lernenden in dieser Vereinfachungsphase stehen bleiben und ihre Sprache fossilieren. Die Bewusstmachung der Ähnlichkeiten von Zulu und. Deutsch kann dazu beitragen, indem man ...

  4. Zustand und Perspektiven der Kapitalmarktfinanzierung in Deutschland

    Beck, Thorsten; Kaserer, Christoph; Rapp, Marc Steffen

    2016-01-01

    Die Autoren haben sich im Rahmen des durch das Bundesministerium für Wirtschaft und Energie (BMWi) in Auftrag gegebenen Forschungsprojekts „Beteiligungs- und Kapitalmarktfinanzierung im deutschen Finanzsystem: Zustand und Entwicklungsperspektiven“ (Dienstleistungsprojekt I C 4 -27/14) mit dem Zus...

  5. Data Science und Analytics in Bibliotheken

    José Luis Preza

    2017-09-01

    Full Text Available Bibliotheken sind in einer priviligierten Situation: Sie verwalten riesige Mengen von Daten und Informationen. Data Science und Analytics-Methoden ermöglichen es Bibliotheken, den Inhalt, den sie verwalten, voll auszunutzen, um den Nutzern bessere Informationen, Suche und Empfehlungen zu bieten.

  6. Carbon doped ZnO: Synthesis, characterization and interpretation

    Mishra, D.K.; Mohapatra, J.; Sharma, M.K.; Chattarjee, R.; Singh, S.K.; Varma, Shikha; Behera, S.N.; Nayak, Sanjeev K.; Entel, P.

    2013-01-01

    A novel thermal plasma in-flight technique has been adopted to synthesize nanocrystalline ZnO and carbon doped nanocrystalline ZnO matrix. Transmission electron microscopy (TEM) studies on these samples show the average particle sizes to be around 32 nm for ZnO and for carbon doped ZnO. An enhancement of saturation magnetization in nanosized carbon doped ZnO matrix by a factor of 3.8 has been found in comparison to ZnO nanoparticles at room temperature. Raman measurement clearly indicates the presence of Zn–C complexes surrounded by ZnO matrix in carbon doped ZnO. This indicates that the ferromagnetic signature in carbon doped ZnO arises from the creation of defects or the development of oxy-carbon clusters, in the carbon doped ZnO system. Theoretical studies based on density functional theory also support the experimental analyses. - Highlights: ► Synthesis of nanocrystalline ZnO and carbon doped ZnO matrix by inflight thermal plasma reactor. ► Enhancement of ferromagnetism in nanosized carbon doped ZnO in comparison to ZnO nanoparticles. ► Raman measurement indicates the presence of Zn–C complexes surrounded by ZnO matrix. ► Ferromagnetic signature in carbon doped ZnO arises from the development of oxy-carbon clusters. ► DFT supports experimental evidence of ferromagnetism in C doped ZnO nanoparticles.

  7. Marktkonstitution und Regulierung der unabhängigen Film- und Fernsehproduktion : Staat, Verbände und Gewerkschaften im deutsch-britischen Vergleich

    Elbing, Sabine; Voelzkow, Helmut

    2006-01-01

    "In einem internationalen Vergleich von Deutschland und Großbritannien wird untersucht, welche Beiträge die staatliche Politik und die Wirtschafts- und Sozialpartner (Wirtschafts- und Arbeitgeberverbände sowie Gewerkschaften) zur Förderung der unabhängigen Film- und Fernsehproduktion leisten. Es wird gezeigt, dass die britische Medienpolitik die Position der unabhängigen Film- und Fernsehproduktion gegenüber den Fernsehsendern gestärkt hat. In Deutschland hat die Medienpolitik darauf verzicht...

  8. GaN Bulk Growth and Epitaxy from Ca-Ga-N Solutions, Phase I

    National Aeronautics and Space Administration — This SBIR proposal addresses the liquid phase epitaxy (LPE) of gallium nitride (GaN) films using nitrogen-enriched metal solutions. Growth of GaN from solutions...

  9. [Die baltischen Lande im Zeitalter der Reformation und Konfessionalisierung : Livland, Estland, Ösel, Ingermanland, Kurland und Lettgallen : Stadt, Land und Konfession 1500-1721. Teil 4. Hrsg. von Matthias Asche, Werner Buchholtz und Anton Schindlin

    Maasing, Madis, 1984-

    2013-01-01

    Arvustus: Die baltischen Lande im Zeitalter der Reformation und Konfessionalisierung : Livland, Estland, Ösel, Ingermanland, Kurland und Lettgallen : Stadt, Land und Konfession 1500-1721. Teil 4. (Katholisches Leben und Kirchenreform im Zeitalter der Glaubensspaltung, 72). Hrsg. von Matthias Asche, Werner Buchholtz und Anton Schindling. Verlag Aschendorff. Münster 2012

  10. High surface hole concentration p-type GaN using Mg implantation

    Long Tao; Yang Zhijian; Zhang Guoyi

    2001-01-01

    Mg ions were implanted on Mg-doped GaN grown by metalorganic chemical vapor deposition (MOCVD). The p-type GaN was achieved with high hole concentration (8.28 x 10 17 cm -3 ) conformed by Van derpauw Hall measurement after annealing at 800 degree C for 1 h. this is the first experimental report of Mg implantation on Mg-doped GaN and achieving p-type GaN with high surface hole concentration

  11. StackGAN++: Realistic Image Synthesis with Stacked Generative Adversarial Networks

    Zhang, Han; Xu, Tao; Li, Hongsheng; Zhang, Shaoting; Wang, Xiaogang; Huang, Xiaolei; Metaxas, Dimitris

    2017-01-01

    Although Generative Adversarial Networks (GANs) have shown remarkable success in various tasks, they still face challenges in generating high quality images. In this paper, we propose Stacked Generative Adversarial Networks (StackGAN) aiming at generating high-resolution photo-realistic images. First, we propose a two-stage generative adversarial network architecture, StackGAN-v1, for text-to-image synthesis. The Stage-I GAN sketches the primitive shape and colors of the object based on given...

  12. GIS und Fernerkundung für Landschaftsmonitoring und Landschaftsplanung

    Blaschke, Thomas

    2002-09-01

    Der Beitrag beleuchtet die Rolle der Geographischen Informationsverarbeitung hinsichtlich der Aufgaben in der Umweltüberwachung. Dabei wird über etablierte "sektorale" Umweltbeobachtungssysteme (Boden, Wasser, Luft) hinaus zunehmend der Bedarf an einer integrativen Betrachtung der Landschaft deutlich, insbesondere in mittleren bis kleinen Maßstäben. Wie verändern sich ganze Landschaften in Deutschland, in Europa? Welches sind Bereiche kritischer Abnahme landschaftlicher Diversität? Wie können landschaftliche Vielfalt und Eigenart erhalten beziehungsweise deren Erhalt überwacht werden? Diese und weitere Fragen drängen sich vor allem bei der Erstellung langfristiger Szenarien der Veränderung ganzer Landschaften und in der Nachhaltigkeitsdiskussion auf.

  13. doped ZnO thick film resistors

    The characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated. Thick films of pure zinc oxide were prepared by the screen printing technique. Pure zinc oxide was almost insensitive to ethanol. Thick films of Al2O3 (1 wt%) doped ZnO were observed to be highly sensitive to ...

  14. Ethik, Recht und Theologie. Reproduktionstechnologien in Polen

    Susanne Lettow

    2006-03-01

    Full Text Available Die bisherigen Debatten um Stammzellforschung, Klonen und Reproduktionstechnologien wurden in Deutschland weitgehend im nationalstaatlichen Rahmen und mit Blick auf Entwicklungen im angelsächsischen Raum geführt. Dabei sind diese Forschungsrichtungen und Technologien kein genuin „westliches“ Phänomen – immerhin wurde das erste Retortenkind in Polen bereits 1987 geboren. Heidi Hofmann lässt in ihrem Band polnische Philosoph/-innen, Jurist/-innen und Politikerinnen zu Wort kommen und öffnet den Blick dafür, dass die Art und Weise, in der Reproduktionstechnologien gesellschaftlich problematisiert werden, in Polen durch ganz andere politische, kulturelle und historische Konstellationen geprägt ist als in Deutschland.

  15. Restaurierung von Seen und Renaturierung von Seeufern

    Grüneberg, Björn; Ostendorp, Wolfgang; Leßmann, Dieter; Wauer, Gerlinde; Nixdorf, Brigitte

    Süßwasserseen haben als ökosysteme und Lebensraum für Pflanzen und Tiere eine herausragende Bedeutung für die Artenvielfalt auf der Erde und prägen als Landschaftselemente unsere natürliche Umwelt. Seen fungieren als natürliche Stoffsenken, vor allem für Kohlenstoff und Nährstoffe, aber auch als Senken für in ihren Einzugsgebieten emittierte gelöste und feste Schadstoffe. Darüber hinaus ist Wasser eine wichtige Naturressource. Süßwasserseen stellen in den meisten Regionen der Erde lebenswichtige Quellen für die Versorgung mit Trinkwasser und tierischem Eiweiß (Fischfang) dar. Sie dienen als Wasserspeicher für die landwirtschaftliche und industrielle Nutzung. Auch für Erholungsaktivitäten des Menschen kommt ihnen eine große Bedeutung zu.

  16. Thermal Annealing induced relaxation of compressive strain in porous GaN structures

    Ben Slimane, Ahmed; Najar, Adel; Ng, Tien Khee; Ooi, Boon S.

    2012-01-01

    The effect of annealing on strain relaxation in porous GaN fabricated using electroless chemical etching is presented. The Raman shift of 1 cm-1 in phonon frequency of annealed porous GaN with respect to as-grown GaN corresponds to a relaxation

  17. E-Government und E-Banking: Aktueller Stand, Evaluation und Erfolgsfaktoren

    Bayer, Tobias

    2002-01-01

    Zu Max Webers Zeiten entsprach die Bürokratie noch ganz dem Vorbild des preussischen Militärs " klare Hierarchien und klare Aufgabenbereiche schlugen sich nieder in Effizienz und Effektivität. Heute ist das Bild getrübt und Worte wie "Erstarrung", "Überreglementierung" und "Verwaltungskultur" machen die Runde. Neben den gestiegenen Erwartungen der Bürger, die sich in Zeiten des E-Banking und E-Commerce nicht mehr in lange Warteschlangen einreihen wollen und auf die rigiden Öffnungszeiten der ...

  18. Personen- und Güterverkehr

    Flämig, Heike; Gertz, Carsten; Mühlhausen, Thorsten

    Im Jahr 2010 war in Deutschland der Verkehrssektor für fast 20 % der energiebedingten Treibhausgase verantwortlich. Das Klima hat sich bereits so weit verändert, dass zur Sicherung der Funktion der Verkehrssysteme auch Anpassungsmaßnahmen notwendig sind. Diese Maßnahmen müssen durch verkehrsreduzierende bzw. -beeinflussende Maßnahmen ergänzt werden. Ausgehend von den Emissionen im Verkehrssektor und möglichen Minderungen schlägt das Kapitel den Bogen zu Optionen der Anpassung an den Klimawandel, die ausführlich und konkret dargestellt werden. Besonders betrachtet werden die mannigfaltigen Gefahren der Rückkopplung sowie die vielfältigen Wechselwirungen mit anderen Themengebieten und Sektoren.

  19. The 2018 GaN power electronics roadmap

    Amano, H.; Baines, Y.; Beam, E.; Borga, Matteo; Bouchet, T.; Chalker, Paul R.; Charles, M.; Chen, Kevin J.; Chowdhury, Nadim; Chu, Rongming; De Santi, Carlo; Merlyne De Souza, Maria; Decoutere, Stefaan; Di Cioccio, L.; Eckardt, Bernd; Egawa, Takashi; Fay, P.; Freedsman, Joseph J.; Guido, L.; Häberlen, Oliver; Haynes, Geoff; Heckel, Thomas; Hemakumara, Dilini; Houston, Peter; Hu, Jie; Hua, Mengyuan; Huang, Qingyun; Huang, Alex; Jiang, Sheng; Kawai, H.; Kinzer, Dan; Kuball, Martin; Kumar, Ashwani; Boon Lee, Kean; Li, Xu; Marcon, Denis; März, Martin; McCarthy, R.; Meneghesso, Gaudenzio; Meneghini, Matteo; Morvan, E.; Nakajima, A.; Narayanan, E. M. S.; Oliver, Stephen; Palacios, Tomás; Piedra, Daniel; Plissonnier, M.; Reddy, R.; Sun, Min; Thayne, Iain; Torres, A.; Trivellin, Nicola; Unni, V.; Uren, Michael J.; Van Hove, Marleen; Wallis, David J.; Wang, J.; Xie, J.; Yagi, S.; Yang, Shu; Youtsey, C.; Yu, Ruiyang; Zanoni, Enrico; Zeltner, Stefan; Zhang, Yuhao

    2018-04-01

    Gallium nitride (GaN) is a compound semiconductor that has tremendous potential to facilitate economic growth in a semiconductor industry that is silicon-based and currently faced with diminishing returns of performance versus cost of investment. At a material level, its high electric field strength and electron mobility have already shown tremendous potential for high frequency communications and photonic applications. Advances in growth on commercially viable large area substrates are now at the point where power conversion applications of GaN are at the cusp of commercialisation. The future for building on the work described here in ways driven by specific challenges emerging from entirely new markets and applications is very exciting. This collection of GaN technology developments is therefore not itself a road map but a valuable collection of global state-of-the-art GaN research that will inform the next phase of the technology as market driven requirements evolve. First generation production devices are igniting large new markets and applications that can only be achieved using the advantages of higher speed, low specific resistivity and low saturation switching transistors. Major investments are being made by industrial companies in a wide variety of markets exploring the use of the technology in new circuit topologies, packaging solutions and system architectures that are required to achieve and optimise the system advantages offered by GaN transistors. It is this momentum that will drive priorities for the next stages of device research gathered here.

  20. Osteoporose und Genetik des Knochenstoffwechsels

    Obermayer-Pietsch B

    2002-01-01

    Full Text Available Osteoporose ist in hohem Maß genetisch determiniert. Neue Wege der molekularbiologischen Forschung haben sich in den letzten Jahren auf diesem Gebiet etabliert. "Gene mapping" mit polymorphen genetischen Markern auf der Suche nach Phänotyp-assoziierten Genen ist ein aufwendiges, aber vielversprechendes Verfahren und wird durch die Erkenntnisse des Human Genome Projects beschleunigt. So wurde jüngst u. a. das Low-density Lipoprotein 5-Gen als wichtig für den Knochenstoffwechsel identifiziert. Kandidaten-gene wie Hormonrezeptor-, Cytokin- oder Kollagen-Gene werden hinsichtlich ihrer Gen-Gen- und Gen-Umwelt- Interaktionen untersucht und erlauben neue funktionelle Einsichten in Erkrankungen des Knochenstoffwechsels. Mutationen der Kollagen-Gene sind bei einigen seltenen Erkrankungen, wie dem Osteoporose-Pseudogliom-Syndrom oder der Osteogenesis imperfecta gefunden worden, könnten aber auch für häufige Varianten von Bindegewebsstörungen wie der congenitalen Hüftdysplasie verantwortlich sein, die etwa 10 % der weiblichen kaukasischen Bevölkerung in unterschiedlichem Ausmaß betrifft. Osteoporose am Schenkelhals und erhöhte Gelenkslaxizität sowie andere generalisierte Veränderungen des Knochen- und Kollagenstoffwechsels können hier möglicherweise ebenfalls durch Störungen des Kollagen I alpha 1-Gens erklärt werden. In Summe können wir zahlreiche neue Einsichten in die Pathophysiologie des Skelettsystems erwarten, die uns auch neue Zugangswege für Diagnostik und Therapie unserer Patienten ermöglichen werden.

  1. CLILiG und Musikunterricht

    Merle Jung

    2015-10-01

    Full Text Available Der Einsatz von Musik und Liedern im Sprachunterricht ist seit der Entwicklung der kommunikativen Methoden ein beliebtes Thema in der Fremdsprachendidaktik. Musik und Sprache haben Ähnlichkeiten bei den kognitiven Verarbeitungsprozessen und der gedächtnisstützende Einfluss der Musik und ihr Nutzen für das Sprachenlernen sind allgemein bekannt. Dieser Nutzen wird aber meistens nur aus der (fremdsprachlichen Perspektive gezogen, die musikalische Erziehung der Lernenden bleibt im Hintergrund. Dabei bietet der bilinguale Musikunterricht mit der klaren Ausrichtung auf die musikalischen Ziele eine gute Möglichkeit, diese zwei Bereiche – Musik und Sprache – gleichwertig miteinander zu verbinden. Das Ziel des vorliegenden Beitrags ist es, die Vorteile des bilingualen Musikunterrichts zu erörtern und an einem Beispielmodul zum Thema Wetter im Herbst zu verdeutlichen. The use of music and songs in language teaching has been a popular topic in foreign language didactics since the development of communicative methods. Music and language have similarities in cognitive processing and the memory supporting influence of music and its beneficial effect on language learning are generally known. However, this benefit will usually be drawn only from the (foreign language perspective, the musical education of the learners remains in the background. Yet bilingual music education with a clear focus on the musical goals provides a great opportunity to connect these two areas - music and language - equally to each other. The aim of this paper is to discuss the advantages of bilingual music education and to present an example based on the bilingual module Weather in Autumn.

  2. Electronic structure and lattice properties of metastable III-(N,V) semiconductor systems; Elektronische Struktur und Kristallgittereigenschaften von metastabilen III-(N,V)-Halbleitersystemen

    Guengerich, M.

    2007-12-18

    This thesis gives an overview of these influences for Ga-V semiconductors (V=P,As,Sb). Lattice vibrations of the ternary alloys Ga(N,P), Ga(N,As) und Ga(N,Sb) are studied and analyzed with respect to the local binding of the N atoms in the host lattices. For the first time, pressure coefficients of the extended host phonons as well as of the N local vibrational modes in Ga(N,As) und Ga(N,P) are determined by Raman spectroscopy under hydrostatic pressure. The relationship between the force constant of the Ga-N bond and the bond length is determined. A central aspect of the thesis is the concentration dependence of optical transitions in Ga(N,P) and Ga(N,As), studied by spectroscopic methods. The impurity levels in both materials are determined by the spatial statistics of the N atoms. (orig.)

  3. Strategische Beschaffung: Grundlagen, Planung und Umsetzung eines integrierten Supply Management

    van Weele, A.J.; Eßig, M.

    2017-01-01

    Dieses Buch bietet – erstmalig in deutscher Übersetzung – eine umfassende und sehr anschauliche Darstellung zu Grundlagen, Planung und Umsetzung einer modernen Beschaffungsfunktion. Beschaffung und Supply Management werden dabei als wesentliches Bindeglied innerhalb des Managementsystems eines

  4. Theoriebedingte Wörterbuchform- probleme und wörterbuch ...

    zunehmend mehr neue Elemente der Wörterbuchform im Vorspann, im Wörterverzeichnis und im. Nachspann ...... tur und -architektur aufweisen und sich nur quantitativ bei den überdachten ...... modernen Printwörterbüchern. Lexikos 18: ...

  5. Emil Fahrenkamp : Bauten und Projekte für Berlin

    Jacob, B.

    2006-01-01

    Thema der vorliegenden Arbeit ist die umfassende Aufarbeitung und Dokumentation der Bauten und Projekte Emil Fahrenkamps (*1885, 1966) in Berlin und Potsdam-Babelsberg sowie die kritische Einordnung seiner Arbeiten in den Kontext der Baugeschichte des 20. Jahrhunderts. Den zentralen

  6. [Preussen und Livland im Zeichen der Reformation] / Anti Selart

    Selart, Anti, 1973-

    2015-01-01

    Arvustus: Preussen und Livland im Zeichen der Reformation. Hrsg. von Arno Mentzel-Reuters und Klaus Neitmann. (Tagungsberichte der Historischen Kommission für ost- und westpreussische Landesforschung, 28). Fibre Verlag. Osnabrück 2014

  7. Post-annealing effects on pulsed laser deposition-grown GaN thin films

    Cheng, Yu-Wen; Wu, Hao-Yu; Lin, Yu-Zhong; Lee, Cheng-Che; Lin, Ching-Fuh

    2015-01-01

    In this work, the post-annealing effects on gallium nitride (GaN) thin films grown from pulsed laser deposition (PLD) are investigated. The as-deposited GaN thin films grown from PLD are annealed at different temperatures in nitrogen ambient. Significant changes of the GaN crystal properties are observed. Raman spectroscopy is used to observe the crystallinity, the change of residual stress, and the thermal decomposition of the annealed GaN thin films. X-ray diffraction is also applied to identify the crystal phase of GaN thin films, and the surface morphology of GaN thin films annealed at different temperatures is observed by scanning electron microscopy. Through the above analyses, the GaN thin films grown by PLD undergo three stages: phase transition, stress alteration, and thermal decomposition. At a low annealing temperature, the rock salt GaN in GaN films is transformed into wurtzite. The rock salt GaN diminishes with increasing annealing temperature. At a medium annealing temperature, the residual stress of the film changes significantly from compressive strain to tensile strain. As the annealing temperature further increases, the GaN undergoes thermal decomposition and the surface becomes granular. By investigating the annealing temperature effects and controlling the optimized annealing temperature of the GaN thin films, we are able to obtain highly crystalline and strain-free GaN thin films by PLD. - Highlights: • The GaN thin film is grown on sapphire by pulsed laser deposition. • The GaN film undergoes three stages with increasing annealing temperature. • In the first stage, the film transfers from rock salt to wurtzite phase. • In the second stage, the stress in film changes from compressive to tensile. • In the final stage, the film thermally decomposes and becomes granular

  8. Alignment control and atomically-scaled heteroepitaxial interface study of GaN nanowires.

    Liu, Qingyun; Liu, Baodan; Yang, Wenjin; Yang, Bing; Zhang, Xinglai; Labbé, Christophe; Portier, Xavier; An, Vladimir; Jiang, Xin

    2017-04-20

    Well-aligned GaN nanowires are promising candidates for building high-performance optoelectronic nanodevices. In this work, we demonstrate the epitaxial growth of well-aligned GaN nanowires on a [0001]-oriented sapphire substrate in a simple catalyst-assisted chemical vapor deposition process and their alignment control. It is found that the ammonia flux plays a key role in dominating the initial nucleation of GaN nanocrystals and their orientation. Typically, significant improvement of the GaN nanowire alignment can be realized at a low NH 3 flow rate. X-ray diffraction and cross-sectional scanning electron microscopy studies further verified the preferential orientation of GaN nanowires along the [0001] direction. The growth mechanism of GaN nanowire arrays is also well studied based on cross-sectional high-resolution transmission electron microscopy (HRTEM) characterization and it is observed that GaN nanowires have good epitaxial growth on the sapphire substrate following the crystallographic relationship between (0001) GaN ∥(0001) sapphire and (101[combining macron]0) GaN ∥(112[combining macron]0) sapphire . Most importantly, periodic misfit dislocations are also experimentally observed in the interface region due to the large lattice mismatch between the GaN nanowire and the sapphire substrate, and the formation of such dislocations will favor the release of structural strain in GaN nanowires. HRTEM analysis also finds the existence of "type I" stacking faults and voids inside the GaN nanowires. Optical investigation suggests that the GaN nanowire arrays have strong emission in the UV range, suggesting their crystalline nature and chemical purity. The achievement of aligned GaN nanowires will further promote the wide applications of GaN nanostructures toward diverse high-performance optoelectronic nanodevices including nano-LEDs, photovoltaic cells, photodetectors etc.

  9. Surface morphology of homoepitaxial GaN grown on non- and semipolar GaN substrates

    Wernicke, Tim; Ploch, Simon [Institute of Solid State Physics, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Hoffmann, Veit; Knauer, Arne; Weyers, Markus [Ferdinand-Braun-Institut, Leibniz Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany); Kneissl, Michael [Institute of Solid State Physics, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Ferdinand-Braun-Institut, Leibniz Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

    2011-03-15

    GaN layers on bulk m-plane, (11 anti 22), (10 anti 12) and (10 anti 11) GaN substrates were grown by metal organic vapor phase epitaxy. XRD rocking curves have a FWHM of less than 150'', indicating excellent crystalline quality. However in many cases surface morphology exhibits hillocks with a height of 1-2 {mu}m and a lateral extension of 50-200 {mu}m whereas a smooth surface would be desirable for optoelectronic devices. The influence of growth parameters on the surface morphology was studied. The goal was, to constrain the material redistribution, that is necessary to form large hillocks. This was achieved by lowering the adatom diffusion length by a reduction of temperature and an increased reactor pressure. In the case of the (10 anti 11) and (10 anti 12) semipolar planes a reduction of the adatom diffusion length leads to a reduction of hillock density, hillock size and a smoother surface between hillocks. However, the m-plane surface does not react to a reduction of adatom mobility. Even at 890 C and 400 mbar rectangular pyramids cover the surface. In contrast to the other planes, the (11 anti 22) becomes instable, when the adatom diffusion length is reduced. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Crystallographic tilt and in-plane anisotropies of an a-plane InGaN/GaN layered structure grown by MOCVD on r-plane sapphire using a ZnO buffer

    Liu, H F; Chi, D Z; Liu, W; Guo, S

    2016-01-01

    High-resolution x-ray diffraction (HRXRD) was used to investigate the crystallographic tilts and structural anisotropies in epitaxial nonpolar a-plane InGaN/GaN grown by metal–organic chemical vapor deposition on r-plane sapphire using a ZnO buffer. The substrate had an unintentional miscut of 0.14° towards its [–4 2 2 3] axis. However, HRXRD revealed a tilt of 0.26° (0.20°) between the ZnO (GaN) (11-20) and the Al 2 O 3 (1-102) atomic planes, with the (11-20) axis of ZnO (GaN) tilted towards its c-axis, which has a difference of 163° in azimuth from that of the substrate’s miscut. Excess broadenings in the GaN/ZnO (11-20) rocking curves (RCs) were observed along its c-axis. Specific analyses revealed that partial dislocations and anisotropic in-plane strains, rather than surface-related effects, wafer curvature or stacking faults, are the dominant factors for the structural anisotropy. The orientation of the partial dislocations is most likely affected by the miscut of the substrate, e.g. via tilting of the misfit dislocation gliding planes created during island coalescences. Their Burgers vector components in the growth direction, in turn, gave rise to crystallographic tilts in the same direction as that of the excess RC-broadenings. (paper)

  11. Crystallographic tilt and in-plane anisotropies of an a-plane InGaN/GaN layered structure grown by MOCVD on r-plane sapphire using a ZnO buffer

    Liu, H. F.; Liu, W.; Guo, S.; Chi, D. Z.

    2016-03-01

    High-resolution x-ray diffraction (HRXRD) was used to investigate the crystallographic tilts and structural anisotropies in epitaxial nonpolar a-plane InGaN/GaN grown by metal-organic chemical vapor deposition on r-plane sapphire using a ZnO buffer. The substrate had an unintentional miscut of 0.14° towards its [-4 2 2 3] axis. However, HRXRD revealed a tilt of 0.26° (0.20°) between the ZnO (GaN) (11-20) and the Al2O3 (1-102) atomic planes, with the (11-20) axis of ZnO (GaN) tilted towards its c-axis, which has a difference of 163° in azimuth from that of the substrate’s miscut. Excess broadenings in the GaN/ZnO (11-20) rocking curves (RCs) were observed along its c-axis. Specific analyses revealed that partial dislocations and anisotropic in-plane strains, rather than surface-related effects, wafer curvature or stacking faults, are the dominant factors for the structural anisotropy. The orientation of the partial dislocations is most likely affected by the miscut of the substrate, e.g. via tilting of the misfit dislocation gliding planes created during island coalescences. Their Burgers vector components in the growth direction, in turn, gave rise to crystallographic tilts in the same direction as that of the excess RC-broadenings.

  12. High Voltage GaN Schottky Rectifiers

    CAO,X.A.; CHO,H.; CHU,S.N.G.; CHUO,C.-C.; CHYI,J.-I.; DANG,G.T.; HAN,JUNG; LEE,C.-M.; PEARTON,S.J.; REN,F.; WILSON,R.G.; ZHANG,A.P.

    1999-10-25

    Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V{sub RB}) up to 550V and >2000V, respectively, have been fabricated. The on-state resistance, R{sub ON}, was 6m{Omega}{center_dot} cm{sup 2} and 0.8{Omega}cm{sup 2}, respectively, producing figure-of-merit values for (V{sub RB}){sup 2}/R{sub ON} in the range 5-48 MW{center_dot}cm{sup -2}. At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and {ge}15 for the 2kV diodes. Reverse recovery times were <0.2{micro}sec for devices switched from a forward current density of {approx}500A{center_dot}cm{sup -2} to a reverse bias of 100V.

  13. Transient atomic behavior and surface kinetics of GaN

    Moseley, Michael; Billingsley, Daniel; Henderson, Walter; Trybus, Elaissa; Doolittle, W. Alan

    2009-01-01

    An in-depth model for the transient behavior of metal atoms adsorbed on the surface of GaN is developed. This model is developed by qualitatively analyzing transient reflection high energy electron diffraction (RHEED) signals, which were recorded for a variety of growth conditions of GaN grown by molecular-beam epitaxy (MBE) using metal-modulated epitaxy (MME). Details such as the initial desorption of a nitrogen adlayer and the formation of the Ga monolayer, bilayer, and droplets are monitored using RHEED and related to Ga flux and shutter cycles. The suggested model increases the understanding of the surface kinetics of GaN, provides an indirect method of monitoring the kinetic evolution of these surfaces, and introduces a novel method of in situ growth rate determination.

  14. Transient atomic behavior and surface kinetics of GaN

    Moseley, Michael; Billingsley, Daniel; Henderson, Walter; Trybus, Elaissa; Doolittle, W. Alan

    2009-07-01

    An in-depth model for the transient behavior of metal atoms adsorbed on the surface of GaN is developed. This model is developed by qualitatively analyzing transient reflection high energy electron diffraction (RHEED) signals, which were recorded for a variety of growth conditions of GaN grown by molecular-beam epitaxy (MBE) using metal-modulated epitaxy (MME). Details such as the initial desorption of a nitrogen adlayer and the formation of the Ga monolayer, bilayer, and droplets are monitored using RHEED and related to Ga flux and shutter cycles. The suggested model increases the understanding of the surface kinetics of GaN, provides an indirect method of monitoring the kinetic evolution of these surfaces, and introduces a novel method of in situ growth rate determination.

  15. Optical and Structural Characterizations of GaN Nano structures

    Shekari, L.; Abu Hassan, H.; Thahab, S.M.

    2011-01-01

    We have grown wurtzite GaN nano wires (NWs) on polished silicon (Si) either with or without Au as catalyst, using commercial GaN powder by thermal evaporation in an atmosphere of argon (Ar) gas. Structural and optical characterizations were performed using high resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), photoluminescence (PL) and energy-dispersive X-ray spectroscopy (EDX) spectroscopy. Results indicate that the nano wires are of single-crystal hexagonal GaN and the nano wires on Si with Au catalyst are more oriented than those without Au catalyst; and using catalyst make the NWs grow much faster and quite well-ordered. The compositional quality of the grown nano wires on the substrates are mostly same, however the nano wires on the Au coated silicon are of low density, while the nano wires on the Si are of high density. (author)

  16. Studies on electronic structure of GaN(0001) surface

    Xie Chang Kun; Xu Fa Qiang; Deng Rui; Liu Feng; Yibulaxin, K

    2002-01-01

    An electronic structure investigation on GaN(0001) is reported. The authors employ a full-potential linearized augmented plane-wave (FPLAPW) approach to calculate the partial density of state, which is in agreement with previous experimental results. The effects of the Ga3d semi-core levels on the electronic structure of GaN are discussed. The valence-electronic structure of the wurtzite GaN(0001) surface is investigated using synchrotron radiation excited angle-resolved photoemission spectroscopy. The bulk bands dispersion along GAMMA A direction in the Brillouin zones is measured using normal-emission spectra by changing photon-energy. The band structure derived from authors' experimental data is compared well with the results of authors' FPLAPW calculation. Furthermore, off-normal emission spectra are also measured along the GAMMA K and GAMMA M directions. Two surface states are identified, and their dispersions are characterized

  17. High-Sensitivity GaN Microchemical Sensors

    Son, Kyung-ah; Yang, Baohua; Liao, Anna; Moon, Jeongsun; Prokopuk, Nicholas

    2009-01-01

    Systematic studies have been performed on the sensitivity of GaN HEMT (high electron mobility transistor) sensors using various gate electrode designs and operational parameters. The results here show that a higher sensitivity can be achieved with a larger W/L ratio (W = gate width, L = gate length) at a given D (D = source-drain distance), and multi-finger gate electrodes offer a higher sensitivity than a one-finger gate electrode. In terms of operating conditions, sensor sensitivity is strongly dependent on transconductance of the sensor. The highest sensitivity can be achieved at the gate voltage where the slope of the transconductance curve is the largest. This work provides critical information about how the gate electrode of a GaN HEMT, which has been identified as the most sensitive among GaN microsensors, needs to be designed, and what operation parameters should be used for high sensitivity detection.

  18. Benefits and Drawbacks of A High Frequency Gan Zvzcps Converter

    Blanes J. M.

    2017-01-01

    Full Text Available This paper presents the benefits and drawbacks of replacing the traditional Si Mosfets transistors with enhancement mode GaN transistors in a Half-Bridge Zero Voltage and Zero Current Switching Power Switching (ZVZCPS converter. This type of converters is usually used as Electronic Power Converters (EPC for telecommunication satellites travelling-wave tube amplifiers (TWTAs. In this study, firstly the converter is theoretically analysed, obtaining its operation, losses and efficiency equations. From these equations, optimizations maps based on the main system parameters are obtained. These optimization maps are the key to quantify the potential benefits of GaN transistors in this type of converters. Theoretical results show that using GaN transistors, the frequency of the converter can be pushed from 125kHz to 830kHz without sacrificing the converter efficiency. This frequency increase is directly related to reduction on the EPC size and weight.

  19. Mg doping and its effect on the semipolar GaN(1122) growth kinetics

    Lahourcade, L.; Wirthmueller, A.; Monroy, E.; Pernot, J.; Chauvat, M. P.; Ruterana, P.; Laufer, A.; Eickhoff, M.

    2009-01-01

    We report the effect of Mg doping on the growth kinetics of semipolar GaN(1122) synthesized by plasma-assisted molecular-beam epitaxy. Mg tends to segregate on the surface, inhibiting the formation of the self-regulated Ga film which is used as a surfactant for the growth of undoped and Si-doped GaN(1122). We observe an enhancement of Mg incorporation in GaN(1122) compared to GaN(0001). Typical structural defects or polarity inversion domains found in Mg-doped GaN(0001) were not observed for the semipolar films investigated in the present study.

  20. Conductivity based on selective etch for GaN devices and applications thereof

    Zhang, Yu; Sun, Qian; Han, Jung

    2015-12-08

    This invention relates to methods of generating NP gallium nitride (GaN) across large areas (>1 cm.sup.2) with controlled pore diameters, pore density, and porosity. Also disclosed are methods of generating novel optoelectronic devices based on porous GaN. Additionally a layer transfer scheme to separate and create free-standing crystalline GaN thin layers is disclosed that enables a new device manufacturing paradigm involving substrate recycling. Other disclosed embodiments of this invention relate to fabrication of GaN based nanocrystals and the use of NP GaN electrodes for electrolysis, water splitting, or photosynthetic process applications.

  1. A DFT study on NEA GaN photocathode with an ultrathin n-type Si-doped GaN cap layer

    Xia, Sihao; Liu, Lei; Kong, Yike; Diao, Yu

    2016-10-01

    Due to the drawbacks of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, a new-type NEA GaN photocathodes with heterojunction surface dispense with Cs activation are proposed. This structure can be obtained through the coverage of an ultrathin n-type Si-doped GaN cap layer on the p-type Mg-doped GaN emission layer. The influences of the cap layer on the photocathode are calculated using DFT. This study indicates that the n-type cap layer can promote the photoemission characteristics of GaN photocathode and demonstrates the probability of the preparation of a NEA GaN photocathode with an n-type cap layer.

  2. [Geisteswissenschaft und Publizistik im Baltikum des 19. und frühen 20. Jahrhunderts] / Manfred von Boetticher

    Boetticher, Manfred von, 1947-

    2012-01-01

    Arvustus: Geisteswissenschaft und Publizistik im Baltikum des 19. und frühen 20. Jahrhunderts (Schriften der Baltischen Historischen Kommission, 17; Baltische Biographische Forschungen, 1). Hrsg. von Norbert Angermann, Wilhelm Lenz und Konrad Maier. (Berlin: LIT-Varlag, 2011)

  3. Entwicklung und Anwendung neuer NMR-Methoden: Orientierungsmedien zur Strukturbestimmung mit anisotropen Parametern und Metabonomics

    Büchler, Silke

    2014-01-01

    Das Ziel dieser Arbeit war die Entwicklung und Anwendung neuer Orientierungsmedien zur Strukturbestimmung mit anisotropen Parametern, sowie die Etablierung von Metabonomics-Studien an Flüssigzellkulturen und Reispflanzen.

  4. Klimaanpassung in Land- und Forstwirtschaft: Ergebnisse eines Workshops der Ressortforschungsinstitute FLI, JKI und Thünen-Institut

    Schimmelpfennig, Sonja; Heidecke, Claudia; Beer, Holger; Bittner, Florian; Klages, Susanne; Krengel, Sandra; Lange, Stefan

    2018-01-01

    Das Working Paper stellt die Ergebnisse einer Umfrage und eines Workshops zusammen, die von Wissenschaftlern und Wissenschaftlerinnen der Ressortforschungsinstitute Thünen-Institut, Julius Kühn-Institut (JKI) und Friedrich-Loeffler-Institut (FLI) im Herbst 2016 zusammengetragen und diskutiert worden sind. Ziel des Workshops und der Umfrage war, den Stand des Wissens zu Klimaanpassungsthemen in der Ressortforschung des BMEL und die zukünftigen Herausforderungen einer Anpassung an den Klimawand...

  5. Geschmackspapillendichte und Geschmackswahrnehmung bei Jugendlichen mit Essstörungen und einer gesunden Kontrollgruppe

    Kaltenhofer, Alice

    2009-01-01

    Fragestellung Die Schmeckwahrnehmung wird u.a. über Lernprozesse, kognitive Vorgänge, genetische und biochemische Faktoren reguliert. Ess- und Diätverhalten werden durch sie beeinflusst. Den anatomisch und physiologisch ersten Abschnitt der Schmeckwahrnehmung bilden die fungiformen Geschmackspapillen. In den Geschmackspapillen liegen die Geschmacksknopsen, mit deren Hilfe die Schmeckstoffe aufgenommen und in Form von Aktionspotentialen zum Thalamus, dem limbischen System,dem Gyrus postzentral...

  6. Kontrolle des Verwaltungsrates : eine Untersuchung der internen und externen Kontrollinstitutionen, -instrumente und -mechanismen

    Reust, Dominik

    2014-01-01

    Eine wichtige Erkenntnis dieser Arbeit ist, dass eine effiziente und effektive Kontrolle des Verwaltungsrates nur über das Zusammenspiel der internen körperschaftlichen Kontrollinstitutionen und -instrumente mit den externen Kontrollinstitutionen und Kontrollmechanismen des Marktes erreicht wird. Die Vorschriften der VegüV betreffend transparente Entschädigungspolitik und unabhängige Stimmrechtsvertreter sowie die in der Aktienrechtsrevision angestrebte Stärkung der Informations-, Mitwirk...

  7. Recht und Rechtssystem als globale Struktur und Medium der Verhaltensorientierung / Raul Narits

    Narits, Raul, 1952-

    2008-01-01

    Äratr.: Multiple Modernität, Globalisierung der Rechtsordnung und Kommunikationsstruktur der Rechtssysteme : Internationales Symposium zur Theorie der Rechtskommunikation an der Universität Tartu im April 2006 ; II. Sonderheft Estland. Berlin, 2008, lk. 219-238. - (Rechtstheorie : Zeitschrift für Logik und Juristische Methodenlehre, Rechtsinformatik, Kommunikationsforschung, Normen- und Handlungstheorie, Soziologie und Philosophie des Rechts ; Bd. 38, 2007, H. 2/3)

  8. Das Sabbatjahr für Lehrerinnen und Lehrer: Wer profitiert und in welcher Form?

    Rothland, Martin

    2013-01-01

    Das Sabbatjahr für Lehrerinnen und Lehrer wird programmatisch als Maßnahme der Belastungsreduktion, der Regeneration sowie der Ressourcenstärkung diskutiert. Empirische Belege für die erwarteten Effekte finden sich jedoch kaum. Im Rahmen einer Längsschnittstudie mit drei Erhebungszeitpunkten vor, während und nach dem Sabbatjahr werden die Entwicklung der Belastungswahrnehmung, des Gesundheitszustands und allgemeiner sowie arbeitsbezogener Emotionen (Berufs- und Lebenszufriedenheit) auf der Ba...

  9. Referenzmodelle im Mobile Business: Analyse und Entwicklung neuer Rollen, Szenarien und Geschäftsmodelle

    Hufenbach, Yvonne

    2016-01-01

    Das digitale Zeitalter ist charakterisiert durch sich stetig wandelnde Märkte, Techniken und wirtschaftliche Voraussetzungen. Klassische Wertschöpfungsketten brechen auf und wandeln sich zu Wertschöpfungsnetzen. Dabei findet eine Neuzuordnung zwischen Wertschöpfungstätigkeiten und Marktteilnehmern statt. Diese digitale Welt ist zudem durch hohe Interdependenzen wirtschaftlicher, informationstechnischer und rechtlicher Fragestellungen gekennzeichnet. Vor diesem Hintergrund verfolgt die Arb...

  10. The influence of Fe doping on the surface topography of GaN epitaxial material

    Cui Lei; Yin Haibo; Jiang Lijuan; Wang Quan; Feng Chun; Xiao Hongling; Wang Cuimei; Wang Xiaoliang; Gong Jiamin; Zhang Bo; Li Baiquan; Wang Zhanguo

    2015-01-01

    Fe doping is an effective method to obtain high resistivity GaN epitaxial material. But in some cases, Fe doping could result in serious deterioration of the GaN material surface topography, which will affect the electrical properties of two dimensional electron gas (2DEG) in HEMT device. In this paper, the influence of Fe doping on the surface topography of GaN epitaxial material is studied. The results of experiments indicate that the surface topography of Fe-doped GaN epitaxial material can be effectively improved and the resistivity could be increased after increasing the growth rate of GaN materials. The GaN material with good surface topography can be manufactured when the Fe doping concentration is 9 × 10 19 cm −3 . High resistivity GaN epitaxial material which is 1 × 10 9 Ω·cm is achieved. (paper)

  11. The origin of the residual conductivity of GaN films on ferroelectric materials

    Lee, Kyoung-Keun; Cai, Zhuhua; Ziemer, Katherine; Doolittle, William Alan

    2009-08-01

    In this paper, the origin of the conductivity of GaN films grown on ferroelectric materials was investigated using XPS, AES, and XRD analysis tools. Depth profiles confirmed the existence of impurities in the GaN film originating from the substrates. Bonding energy analysis from XPS and AES verified that oxygen impurities from the substrates were the dominant origin of the conductivity of the GaN film. Furthermore, Ga-rich GaN films have a greater chance of enhancing diffusion of lithium oxide from the substrates, resulting in more substrate phase separation and a wider inter-mixed region confirmed by XRD. Therefore, the direct GaN film growth on ferroelectric materials causes impurity diffusion from the substrates, resulting in highly conductive GaN films. Future work needs to develop non-conductive buffer layers for impurity suppression in order to obtain highly resistive GaN films.

  12. GaN epitaxial layers grown on multilayer graphene by MOCVD

    Li, Tianbao; Liu, Chenyang; Zhang, Zhe; Yu, Bin; Dong, Hailiang; Jia, Wei; Jia, Zhigang; Yu, Chunyan; Gan, Lin; Xu, Bingshe

    2018-04-01

    In this study, GaN epitaxial layers were successfully deposited on a multilayer graphene (MLG) by using metal-organic chemical vapor deposition (MOCVD). Highly crystalline orientations of the GaN films were confirmed through electron backscatter diffraction (EBSD). An epitaxial relationship between GaN films and MLG is unambiguously established by transmission electron microscope (TEM) analysis. The Raman spectra was used to analyze the internal stress of GaN films, and the spectrum shows residual tensile stress in the GaN films. Moreover, the results of the TEM analysis and Raman spectra indicate that the high quality of the MLG substrate is maintained even after the growth of the GaN film. This high-quality MLG makes it possible to easily remove epitaxial layers from the supporting substrate by micro-mechanical exfoliation technology. This work can aid in the development of transferable devices using GaN films.

  13. Arbeitszeitflexibilisierung in der westdeutschen Metall- und Elektroindustrie und die Verbandsstrategien - Eine vergleichende Analyse der arbeitszeitpolitischen Strategien des Arbeitgeberverbandes Gesamtmetall und der Industriegewerkschaft Metall

    Altun, Ufuk

    2005-01-01

    Arbeitszeitpolitik und Arbeitszeitgestaltung haben seit dem Tarifkompromiss im Jahre 1984 in der Metall-, und Elektroindustrie in der politischen und wissenschaftlichen Diskussion einen immensen Bedeutungszuwachs erfahren. Die Forderungen nach einer flexibleren Arbeitszeitgestaltung haben zeitgleich sowohl aus der Globalisierungsdiskussion und der Debatte um die Wettbewerbsfähigkeit des "Wirtschaftsstandorts Deutschland" heraus wie auch aus beschäftigungspolitischen Gründen neuen Auftrieb bek...

  14. Osteopetrose - aktuelle Diagnostik und Therapie

    Schulz AS

    2008-01-01

    Full Text Available Unter dem Begriff Osteopetrose wird eine heterogene Gruppe von Krankheiten zusammengefasst, die durch eine pathologisch vermehrte Knochenmasse charakterisiert ist. Diese Osteosklerose basiert in den meisten Fällen auf einem Defekt in der Knochenresorption durch Osteoklasten. Beim Menschen können mehrere Typen unterschieden und nach dem Vererbungsmodus, dem Manifestationsalter, der Schwere der klinischen Symptomatik und nach assoziierten Symptomen klassifiziert werden. Hauptformen sind die infantile "maligne" autosomal rezessive Osteopetrose (ARO, intermediäre autosomal rezessive Formen (IARO und milder verlaufende autosomal dominante Subtypen (ADO. In den letzten Jahren konnten mehrere zur Osteopetrose führende Genveränderungen identifiziert werden. Alle diese Genveränderungen bei humaner Osteopetrose betreffen Proteine, die an der Differenzierung oder Funktion der Osteoklasten beteiligt sind. Da die Osteoklasten sich aus der hämatopoietischen Stammzelle differenzieren, ist die hämatopoietische Stammzelltransplantation eine kurative Therapieoption bei schweren Osteopetroseformen. Allerdings ist diese Therapie mit erheblichen Risiken verbunden. Darüber hinaus sind bestimmte Subtypen der Osteopetrose mit schweren neurologischen Veränderungen assoziiert, die durch eine Stammzelltransplantation nicht positiv beeinflusst werden können. Ein genaues Verständnis der Pathogenese der humanen Osteopetrose ist daher wichtig für die Wahl der richtigen Therapie und gewährt darüber hinaus einen tieferen Einblick in die Physiologie and andere Pathologien des Knochens.

  15. Natur und Moderne um 1900

    , nordeuropäischen Vergleich widmen sich die Beiträge den medialen Repräsentationen von Natur (in Literatur, Philosophie, Film, Foto) ebenso wie der Kolonisierung des Raumes (in Tourismus, Reisen, Sport, Natur- und Heimatschutz). Der Band bietet damit auch Impulse für die neuen theoretisch-methodischen Ansätze der...

  16. ZnO nanocrystals and allied materials

    Okada, Tatsuo

    2014-01-01

    ZnO has been the central theme of research in the past decade due to its various applications in band gap engineering, and textile and biomedical industries. In nanostructured form, it offers ample opportunities to realize tunable optical and optoelectronic properties and it was also termed as a potential material to realize room temperature ferromagnetism. This book presents 17 high-quality contributory chapters on ZnO related systems written by experts in this field. These chapters will help researchers to understand and explore the varied physical properties to envisage device applications of ZnO in thin film, heterostructure and nanostructure forms.

  17. Catalyst growth of single crystal aligned ZnO nanorods on ZnO thin films

    Zhao, Dongxu; Andreazza, Caroline; Andreazza, Pascal [Centre de Recherche sur la Matiere Divisee, CNRS-Universite d' Orleans, 1b rue de la Ferollerie, 45071 Orleans cedex 2 (France)

    2005-02-01

    One dimensional ZnO nanorods were successfully fabricated on Si substrates via a simple physical vapor-phase transport method at 950 C. A ZnO shell covered Au/Zn alloy is assumed as the nucleation site, then ZnO nanorods grow following a vapor-solid (VS) process. In order to guide the nanorod growth a c-axis oriented ZnO thin film and Au catalyst were first deposited on Si (100) surface. SEM images show nanorods grown on this substrate are vertical to the substrate surface. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. In vitro-Permeationsstudien von hydrophilen und lipophilen Arzneistoffen an okularen Geweben und Zellkulturen

    Scholz, Martina

    2003-01-01

    Da die Arzneistoffpermeation durch okulare Gewebe einen entscheidenden Einfluss auf die Heilung vieler Augenleiden hat, wurde die in vitro-Permeation hydrophiler und lipophiler Arzneistoffe durch okulare Gewebe und Zellkulturen in dieser Arbeit untersucht. Die Dissertation befasst sich vorrangig mit der Permeation des hydrophilen Modellarzneistoffs Pilocarpinhydrochlorid (P-HCl) durch isolierte Schweinecornea (SC), Schweinesklera, Kaninchenkonjunktiva und corneale bzw. konjunktivale Kan...

  19. Philologie im Horizont der Geschichtlichkeit von Sprache und Text: zum Tagungsband von Wulf Oesterreicher und Maria Selig

    Olaf Müller

    2016-03-01

    Full Text Available Wulf Oesterreicher und Maria Selig, Hrsg., Geschichtlichkeit von Sprache und Text: Philologien – Disziplingenese – Wissenschaftshistoriographie (Paderborn: Wilhelm Fink, 2014, 332 S.

  20. Zoophilie in Zoologie und Roman: Sex und Liebe zwischen Mensch und Tier bei Plutarch, Plinius dem Älteren, Aelian und Apuleius

    Judith Hindermann

    2011-09-01

    Full Text Available Die Bedeutung von Zoophilie in der antiken Literatur wurde bislang – mit Ausnahme des Mythos – kaum untersucht. Überblickt man die überlieferten literarischen Texte, fällt auf, dass Zoophilie ausserhalb des Mythos vor allem in zwei literarischen Gattungen auftritt : Einerseits in den zoologischen Schriften von Plutarch, Plinius dem Älteren und Aelian, andererseits im antiken Roman, d.h. in den Metamorphosen des Apuleius und im pseudo-lukianischen Onos. In diesem Beitrag soll untersucht werden, welche Funktion Zoophilie in den beiden literarischen Gattungen hat und wie die Autoren die sexuelle Praktik bewerten, die weder nach griechischem noch römischen Recht strafbar war. Da Vorstellungen über Tiere eng mit Gender und Geschlechterhierarchien verbunden sind, soll insbesondere die Frage berücksichtigt werden, inwiefern männliche und weibliche Verhaltens- und Rollenzuschreibungen bei der Darstellung zoophiler Akte wirksam werden.

  1. Recht und soziales Kapital im Wohlfahrtsstaat

    Karstedt, Susanne

    1997-01-01

    'Das Konzept des sozialen Kapitals spielt eine zentrale Rolle in der Diskussion um den Um- und Abbau des Wohlfahrtsstaates. Zerstört der Wohlfahrtsstaat soziales Kapital? Können staatliche Sozialleistungen durch das soziale Kapital in Familien, Nachbarschaften und Gemeinden umstandslos ersetzt werden, und individuelle Rechtsansprüche als Forderungen an diese sozialen Netzwerke zurückverwiesen werden? Kann die angestrebte 'Verantwortungsgesellschaft' (Etzioni) die Leistungen übernehmen, mit de...

  2. Variationen und ihre Kompensation in CMOS Digitalschaltungen

    Baumann, Thomas

    2010-01-01

    Variationen bei der Herstellung und während des Betriebs von CMOS Schaltungen beeinflussen deren Geschwindigkeit und erschweren die Verifikation der in der Spezifikation zugesicherten Eigenschaften. In dieser Arbeit wird eine abstraktionsebenenübergreifende Vorgehensweise zur Abschätzung des Einflusses von Prozess- und betriebsbedingten Umgebungsvariationen auf die Geschwindigkeit einer Schaltung vorgestellt. Neben Untersuchungen der Laufzeitsensitivität in low-power CMOS Technologien von...

  3. Von Medien, Übertragungen und Automaten

    Alessandro Barberi

    2013-12-01

    Full Text Available Im Zuge der Debatten zum Medialen Habitus wurde vielfach betont, dass die >Theorie der Praxispraxeologischen Medientheorie< des Medialen Habitus avant la lettre gesprochen werden kann. Dieser Artikel untersucht – ausgehend von den Debatten zur "Medienkompetenz" – wie Bourdieu Sprache, Sprechen und Diskurs, sowie Akteure, Felder und Habitus als Medien begreift und betont dabei die Nützlichkeit der Bourdieuschen Bildungssoziologie im Rahmen einer sozialwissenschaftlichen Grundlegung der Medienpädagogik.

  4. Verletzungen und Fehlbeanspruchungen im leistungsorientierten Rudersport

    Bussian, Marc Robert

    2004-01-01

    Die Stellung der Breitensportart Rudern als gesundheitsfördernde Sportform ist in der Literatur gleichlautend positiv beschrieben. Im leistungsorientierten Rudersport müssen neben den Verletzungen und Fehlbeanspruchungen der eigentlichen Sportart die unabdingbaren Nebentrainingsformen berücksichtigt werden. In den neunziger Jahren vollzog sich ein trainingsmethodischer Wandel, die Einführung eines erschwinglichen Rudersimulators und eine technische Weiterentwicklung im Boots- und Ruderbau. Ei...

  5. Pflege und Beruf: ungleiche Chancen der Vereinbarkeit

    Keck, Wolfgang

    2011-01-01

    Die Vereinbarkeit von Beruf und Pflege wird in der Öffentlichkeit zu wenig thematisiert. Pflegende in einkommensschwachen Familien können sich keine zusätzlichen Pflegedienste leisten und müssen häufiger Einschnitte im Beruf in Kauf nehmen. Beschäftigte in unteren Hierarchieebenen können Beruf und Pflege nur schwer vereinbaren, da sie flexible Arbeitszeitregelungen seltener nutzen können.

  6. Polnische qualitative Soziologie: Entwicklung und Hauptthemen

    Konecki, Krzysztof T.; Kacperczyk, Anna M.; Marciniak, Lukasz T.

    2005-01-01

    In dem vorliegenden Beitrag wird die Entwicklung der qualitativen Soziologie in Polen rekonstruiert, indem deren wesentliche intellektuelle Wurzeln und einige Hauptthemen der polnischen Soziologie vorgestellt werden. Romantizismus und die induktive Methode sind essenzielle Elemente für die Entwicklung der Disziplin in Polen gewesen und Charakteristika ihrer Besonderheit. Die Bedeutung von Florian ZNANIECKI für die Entstehung der polnischen qualitativen Soziologie wird gewürdigt. URN: urn:n...

  7. Bedeutung von Umwelt- und Organismusfaktoren bei Autoaggressionen

    Rohmann, Ulrich H.; Elbing, Ulrich; Hartmann, Hellmut

    1988-01-01

    In der vorliegenden Arbeit werden übergeordnete Hypothesen zu autoaggressiven Verhaltensweisen formuliert, wobei prozeßhafte Abläufe von umweltbezogenen und organischen Variablen angenommen werden. Eine solche dynamische Beziehung hat ihre Bedeutung sowohl für verursachende als auch aufrechterhaltende Faktoren. In einer Querschnittuntersuchung lassen sich Korrelationen von Tageszeit- und Tätigkeitscharakteristiken (umweltbezogene Variablen) zur Autoaggressionshäufigkeit und Pulsfrequenz (Orga...

  8. Rechtspopulistische Einstellungen in Ost- und Westdeutschland

    Beate Küpper

    2017-12-01

    Full Text Available Während sich die Mehrheit der Deutschen für Demokratie, Vielfalt und Gleichwertigkeit positioniert, sind zugleich rechtspopulistische Einstellungen lauter geworden. Der Beitrag berichtet über Befunde der Mitte-Studie der Friedrich-Ebert-Stiftung 2016 zu der Verbreitung rechtspopulistischer und rechtsextreme Einstellungen, wirft einen besonderen Blick auf potentielle Wähler_innen der AfD und diskutiert am Ende mögliche Erklärungen für die gefundenen Unterschiede zwischen Ost- und Westdeutschen.

  9. Improved crystal quality of a-plane GaN with high- temperature 3-dimensional GaN buffer layers deposited by using metal-organic chemical vapor deposition

    Park, Sung Hyun; Moon, Dae Young; Kim, Bum Ho; Kim, Dong Uk; Chang, Ho Jun; Jeon, Heon Su; Yoon, Eui Joon; Joo, Ki Su; You, Duck Jae; Nanishi, Yasushi

    2012-01-01

    a-plane GaN on r-plane sapphire substrates suffers from high density defects and rough surfaces. To obtain pit-free a-plane GaN by metal-organic chemical vapor deposition, we intentionally grew high-temperature (HT) 3-dimensional (3D) GaN buffer layers on a GaN nucleation layer. The effects of the HT 3D GaN buffer layers on crystal quality and the surface morphology of a-plane GaN were studied. The insertion of a 3D GaN buffer layer with an optimum thickness was found to be an effective method to obtain pit-free a-plane GaN with improved crystalline quality on r-plane sapphire substrates. An a-plane GaN light emitting diode (LED) at an emission wavelength around 480 nm with negligible peak shift was successfully fabricated.

  10. Thermal quenching of the yellow luminescence in GaN

    Reshchikov, M. A.; Albarakati, N. M.; Monavarian, M.; Avrutin, V.; Morkoç, H.

    2018-04-01

    We observed varying thermal quenching behavior of the yellow luminescence band near 2.2 eV in different GaN samples. In spite of the different behavior, the yellow band in all the samples is caused by the same defect—the YL1 center. In conductive n-type GaN, the YL1 band quenches with exponential law, and the Arrhenius plot reveals an ionization energy of ˜0.9 eV for the YL1 center. In semi-insulating GaN, an abrupt and tunable quenching of the YL1 band is observed, where the apparent activation energy in the Arrhenius plot is not related to the ionization energy of the defect. In this case, the ionization energy can be found by analyzing the shift of the characteristic temperature of PL quenching with excitation intensity. We conclude that only one defect, namely, the YL1 center, is responsible for the yellow band in undoped and doped GaN samples grown by different techniques.

  11. Taevo Gans : särama pandud postmodernism / Kadi Viljak

    Viljak, Kadi

    2004-01-01

    Viking Window ASi büroo ja ekspositsioonisaal 1979. a. Jüri Okase projekteeritud endises Paide KEKi remontmehaanikatöökoja hoones Mäos. Sisearhitekt Taevo Gans, kelle projekteeritud on ka ettevõtte juhi töölaud. T. Gansi kommentaarid. Ill.: 6 värv. sisevaadet

  12. Optical Properties and Lasing in GaN

    Song, J

    2001-01-01

    .... In the second article. femtosecond pump-probe transmission spectroscopy was used to study the nonequilibrium carrier dynamics in a GaN thin film at 10 K with carrier densities ranging from 4 x 10(exp 17) to 10(exp 19)/cu cm...

  13. Intrinsic defects in ZnO varistors

    Mahan, G.D.

    1983-01-01

    Theoretical calculations are presented for equilibrium concentrations of zinc and oxygen vacancies in ZnO. Results are presented at the sintering temperature, and also at room temperature. Theoretical calculations of reaction constants show that the intrinsic donor is the oxygen vacancy, rather than the zinc interstitial. The depletion of vacancies in the surface region, as the ZnO is cooled from the sintering temperature, is also calculated. Homojunction effects which are caused by such depletion are shown to be small

  14. Gallium adsorption on (0001) GaN surfaces

    Adelmann, Christoph; Brault, Julien; Mula, Guido; Daudin, Bruno; Lymperakis, Liverios; Neugebauer, Joerg

    2003-01-01

    We study the adsorption behavior of Ga on (0001) GaN surfaces combining experimental specular reflection high-energy electron diffraction with theoretical investigations in the framework of a kinetic model for adsorption and ab initio calculations of energy parameters. Based on the experimental results we find that for substrate temperatures and Ga fluxes typically used in molecular-beam epitaxy of GaN, finite equilibrium Ga surface coverages can be obtained. The measurement of a Ga/GaN adsorption isotherm allows the quantification of the equilibrium Ga surface coverage as a function of the impinging Ga flux. In particular, we show that a large range of Ga fluxes exists, where 2.5±0.2 monolayers (in terms of the GaN surface site density) of Ga are adsorbed on the GaN surface. We further demonstrate that the structure of this adsorbed Ga film is in good agreement with the laterally contracted Ga bilayer model predicted to be most stable for strongly Ga-rich surfaces [Northrup et al., Phys. Rev. B 61, 9932 (2000)]. For lower Ga fluxes, a discontinuous transition to Ga monolayer equilibrium coverage is found, followed by a continuous decrease towards zero coverage; for higher Ga fluxes, Ga droplet formation is found, similar to what has been observed during Ga-rich GaN growth. The boundary fluxes limiting the region of 2.5 monolayers equilibrium Ga adsorption have been measured as a function of the GaN substrate temperature giving rise to a Ga/GaN adsorption phase diagram. The temperature dependence is discussed within an ab initio based growth model for adsorption taking into account the nucleation of Ga clusters. This model consistently explains recent contradictory results of the activation energy describing the critical Ga flux for the onset of Ga droplet formation during Ga-rich GaN growth [Heying et al., J. Appl. Phys. 88, 1855 (2000); Adelmann et al., J. Appl. Phys. 91, 9638 (2002).

  15. Editorial 01/2013 Normen und Normierungen

    Christian Swertz

    2013-03-01

    Full Text Available Auf unterschiedlichsten Ebenen werden die Diskussionen und Forschungen der Medienpädagogik von normativ aufgeladenen Begriffen durchzogen: so, wenn es um Standards in der Medienbildung geht, wenn beispielsweise diskutiert wird, welche Inhalte in welcher Form vermittelt werden sollen; so auch wenn zur Debatte steht, wie Medienpädagogik institutionalisiert werden sollte und welche Voraussetzungen gegeben sein müssen, um einen geplanten Bildungsprozess zu lenken oder anzuleiten.Derartige Norm(ierungen wurden bereits mit der Konzeptualisierung des Begriffs Medienkompetenz und im Blick auf die Emanzipation des Menschen kritisch beleuchtet, womit auch Kritik an gesellschaftlichen Herrschafts- und Machtstrukturen verbunden war. Die Orientierung an der sozialwissenschaftlich verstandenen Emanzipation des Menschen ist allerdings in anderen pädagogischen Disziplinen durchaus umstritten. Gleichzeitig ist zu beobachten, dass die gesellschaftskritische Perspektive im medienpädagogischen Diskurs über die Orientierung von Medienkompetenz und Medienbildung eine immer geringere Rolle spielt. Deshalb hat sich die Redaktion der MEDIENIMPULSE entschlossen, dem Thema Normen und Normierungen eine eigene Ausgabe zu widmen.Dabei sollten folgende Fragen behandelt werden:Wie sieht es mit Norm(ierungen im Bereich der Mediendidaktik aus? Wie sind die mit aktuellen Medienkompetenz- und Medienbildungsbegriffen verbundenen Normen epistemologisch und (medientheoretisch abgestützt? Wie lassen sich – nur scheinbar paradox formuliert – wissenschaftlich begründbare medienpädagogische Normen finden, die sich den genannten Normierungen widersetzen und entziehen? Inwiefern führt die Einführung von Laptopklassen oder Smartboards im schulischen Bereich oder die Gestaltung von Videospielprojekten in der außerschulischen Medienbildung zu einer unreflektierten Sozialdisziplinierung, die als illegitime Form(atierung des Menschen verstanden werden kann? Der Schwerpunktteil

  16. Medienpädagogik und die Digitale Gesellschaft im Spannungsfeld von Regulierung und Teilhabe

    Stefan Iske

    2014-12-01

    Full Text Available Vor 25 Jahren stellte Tim Berners-Lee sein Konzept eines World Wide Web (WWW vor und legte damit einen der bedeutendsten Grundsteine der digitalen Vernetzung. Was ursprünglich zum Austausch von Informationen und Daten unter Forschenden entworfen wurde, hat sich zu einem umfassenden Kultur- und Bildungsraum entwickelt und ist ein universaler und zentraler Dienst des Internet geworden. Dieser gegenwärtige Status des Internet und des World Wide Web ist der vorläufige Zwischenstand einer historischen Entwicklung, der sowohl Transformationen und Veränderungen als auch Konstanten zugrunde liegen. Nicht erst zum diesjährigen Geburtstag des World Wide Web wird deutlich, dass durch digitale und vernetzte Technologien zentrale Kategorien wie Bildung, Erziehung und Sozialisation berührt werden. Beispielhaft kann auf die aktuellen Debatten über Regulierungsmechanismen im Internet wie auch auf die Enthüllungen Edward Snowdens hingewiesen werden. Aus dem Vorangehenden lassen sich medienpädagogische Fragestellungen ableiten, die zum Beispiel die Handlungsautonomie von Subjekten sowie Möglichkeitsräume der Mitgestaltung von und Teilhabe an Gesellschaft (Winter 2012, Swertz 2014 thematisieren. Zudem sind es Fragen der Mediensozialisation und der Konstruktion von Identität in digital vernetzten Räumen (Jörissen/Marotzki 2008, die sowohl bei der Theoriebildung als auch im Rahmen medienpädagogischer Praxis eine hohe Relevanz besitzen.

  17. Steueroasen und Regulierungsoasen – Auswirkungen auf die Stabilität des Finanzmarkts und politische Implikationen

    Michaela Schmidt

    2012-12-01

    Full Text Available In diesem Beitrag wird dargelegt, dass Steuer- und Regulierungsoasen nicht nur Steuerausfälle und Kapitalflucht ermöglichen, sondern auch eine Hauptursache für die Finanzkrise 2007/2008 waren und weiterhin die Stabilität des Finanzmarkts gefährden. Sie haben den Boden bereitet für das Aufkommen nicht regulierter Finanzinstitutionen, sogenannter Schattenbanken. Regulierungsoasen ermöglichen Finanzmarktakteuren eine Umgehung von Regulierungs- und Aufsichtsvorschriften und heizen den Wettbewerb um niedrige Regulierungsvorschriften maßgeblich an. Jeder Schritt zu einer finanzpolitischen Re-Regulierung von Steuer- und Regulierungsoasen sowie Schattenbanken ist ein aktiver Schritt zur Krisenvorbeugung und damit zum Schutz der ArbeitnehmerInnen vor den gewaltigen volkswirtschaftlichen Kosten von Finanzkrisen.

  18. Mg doping of GaN by molecular beam epitaxy

    Lieten, R R; Buchowicz, G; Dubon, O; Motsnyi, V; Zhang, L; Cheng, K; Leys, M; Degroote, S; Borghs, G

    2011-01-01

    We present a systematic study on the influence of growth conditions on the incorporation and activation of Mg in GaN layers grown by plasma-assisted molecular beam epitaxy. We show that high quality p-type GaN layers can be obtained on GaN-on-silicon templates. The Mg incorporation and the electrical properties have been investigated as a function of growth temperature, Ga : N flux ratio and Mg : Ga flux ratio. It was found that the incorporation of Mg and the electrical properties are highly sensitive to the Ga : N flux ratio. The highest hole mobility and lowest resistivity were achieved for slightly Ga-rich conditions. In addition to an optimal Ga : N ratio, an optimum Mg : Ga flux ratio was also observed at around 1%. We observed a clear Mg flux window for p-type doping of GaN : 0.31% 17 cm -3 and a mobility of 15 cm 2 V -1 s -1 . Temperature-dependent Hall effect measurements indicate an acceptor depth in these samples of 100 meV for a hole concentration of 5.5 x 10 17 cm -3 . The corresponding Mg concentration is 5 x 10 19 cm -3 , indicating approximately 1% activation at room temperature. In addition to continuous growth of Mg-doped GaN layers we also investigated different modulated growth procedures. We show that a modulated growth procedure has only limited influence on Mg doping at a growth temperature of 800 deg. or higher. This result is thus in contrast to previously reported GaN : Mg doping at much lower growth temperatures of 500 deg. C.

  19. Growth and characterization of Fe nanostructures on GaN

    Honda, Yuya; Hayakawa, Satoko; Hasegawa, Shigehiko; Asahi, Hajime

    2009-01-01

    We have investigated the growth of Fe nanostructures on GaN(0 0 0 1) substrates at room temperature using reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), and superconducting quantum interference device magnetometer. Initially, a ring RHEED pattern appears, indicating the growth of polycrystalline α-Fe. At around 0.5 nm deposition, the surface displays a transmission pattern from α-Fe films with the epitaxial relationship of Fe(1 1 0)//GaN(0 0 0 1) and Fe[1 -1 1]//GaN[1 1 -2 0] (Kurdjumov-Sachs (KS) orientational relationship). Further deposition to 1 nm results in the appearance of a new spot pattern together with the pattern from domains with the KS orientation relationship. The newly observed pattern shows that Fe layers are formed with the epitaxial relationship of Fe(1 1 0)//GaN(0 0 0 1) and Fe[0 0 1]//GaN[1 1 -2 0] (Nishiyama-Wasserman (NW) orientational relationship). From STM images for Fe layers with the KS and NW orientational relationships, it can be seen that Fe layers with the KS relationship consist of round-shaped Fe nanodots with below 7 nm in average diameter. These nanodots coalesce to form nanodots elongating along the Fe[1 0 0] direction, and they have the KS orientational relationship. Elongated Fe nanodots with the NW relationship show ferromagnetism while round-shaped Fe nanodots with the KS relationship show super-paramagnetic behavior. We will discuss their magnetic properties in connection with the change in crystalline configurations of nanodots.

  20. Growth of vertically aligned ZnO nanorods using textured ZnO films

    Meléndrez Manuel

    2011-01-01

    Full Text Available Abstract A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100 substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells. PACS 61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.

  1. Synthesis of 1-D ZnO nanorods and polypyrrole/1-D ZnO ...

    1-D ZnO nanorods and PPy/1-D ZnO nanocomposites were prepared by the surfactant-assisted precipitation and in situ polymerization method, respectively. The synthesized nanorods and nanocomposites were characterized by UV–Vis spectrophotometer, Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction ...

  2. Photoluminescence of Mg-doped m-plane GaN grown by MOCVD on bulk GaN substrates

    Monemar, Bo [Department of Physics, Chemistry and Biology, Linkoeping University, 581 83 Linkoeping (Sweden); Solid State Physics-The Nanometer Structure Consortium, Lund University, Box 118, 221 00 Lund (Sweden); Paskov, Plamen; Pozina, Galia; Hemmingsson, Carl; Bergman, Peder [Department of Physics, Chemistry and Biology, Linkoeping University, 581 83 Linkoeping (Sweden); Lindgren, David; Samuelson, Lars [Solid State Physics-The Nanometer Structure Consortium, Lund University, Box 118, 221 00 Lund (Sweden); Ni, Xianfeng; Morkoc, Hadis [Department of Electrical and Computer Engineering, Virginia Commonwealth University, Richmond, Virginia 23284-3072 (United States); Paskova, Tanya [Kyma Technologies Inc., Raleigh, North Carolina 27617 (United States); Bi, Zhaoxia; Ohlsson, Jonas [Glo AB, Ideon Science Park, Scheelevaegen 17, 223 70 Lund (Sweden)

    2011-07-15

    Photoluminescence (PL) properties are reported for a set of m-plane GaN films with Mg doping varied from mid 10{sup 18} cm{sup -3} to above 10{sup 20} cm{sup -3}. The samples were grown with MOCVD at reduced pressure on low defect density bulk GaN templates. The sharp line near bandgap bound exciton (BE) spectra observed below 50 K, as well as the broader donor-acceptor pair (DAP) PL bands at 2.9-3.3 eV give evidence of several Mg related acceptors, similar to the case of c-plane GaN. The dependence of the BE spectra on excitation intensity as well as the transient decay behaviour demonstrate acoustic phonon assisted transfer between the acceptor BE states. The lower energy donor-acceptor pair spectra suggest the presence of deep acceptors, in addition to the two main shallower ones at about 0.23 eV. Similar spectra from Mg-doped GaN nanowires (NWs) grown by MOCVD are also briefly discussed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Erfahrungen an der Schnittstelle von Medienarbeit und Praxisforschung

    Peter Holzwarth

    2007-11-01

    Full Text Available Der Beitrag reflektiert die Verbindung von praktischer Medienarbeit und Forschung am Beispiel eines internationalen EU-Forschungsprojekts zum Thema Medien und Migration. Neben didaktischen Prinzipien und Konzepten für die aktive Medienarbeit im Forschungskontext geht es um die Kooperation von medienpädagogischer Begleitung (MB und wissenschaftlicher Begleitung (WB sowie um deren spezifische Kompetenzen.

  4. Leitung und Kooperation in wissenschaftlichen Bibliotheken Berlins - eine empirische Untersuchung

    Paul, Gerhard

    1998-01-01

    Die vorliegende Arbeit greift ein im bibliotheks- und IuK-wissenschaftlichen sowie im fachprofessionellen Diskurs bisher weitgehend vernachlässigtes, aber immer bedeutsameres Thema auf: das vertikale soziale Geschehen in der Arbeitsorganisation ?wissenschaftliche Bibliothek". Die Absicht der Untersuchung lag darin, einen Zusammenhang zwischen dem Interaktionsverhalten der Leitungspersonen einerseits und der Mobilisierung von Leistungs- und Innovationspotentialen bei den Mitarbeiterinnen und M...

  5. [Sascha Möbius. Das Gedähtnis der Reichsstadt. Unruhen und Kriege in der lübeckischen Chronistik und Kriege und Erinnerungskultur des späten mittelalters und der frühen Neuzeit

    Hormuth, Dennis

    2012-01-01

    Arvustus: Sascha Möbius. Das Gedähtnis der Reichsstadt. Unruhen und Kriege in der lübeckischen Chronistik und Kriege und Erinnerungskultur des späten mittelalters und der frühen Neuzeit. (Göttingen, 2011)

  6. Large electron capture-cross-section of the major nonradiative recombination centers in Mg-doped GaN epilayers grown on a GaN substrate

    Chichibu, S. F.; Shima, K.; Kojima, K.; Takashima, S.; Edo, M.; Ueno, K.; Ishibashi, S.; Uedono, A.

    2018-05-01

    Complementary time-resolved photoluminescence and positron annihilation measurements were carried out at room temperature on Mg-doped p-type GaN homoepitaxial films for identifying the origin and estimating the electron capture-cross-section ( σ n ) of the major nonradiative recombination centers (NRCs). To eliminate any influence by threading dislocations, free-standing GaN substrates were used. In Mg-doped p-type GaN, defect complexes composed of a Ga-vacancy (VGa) and multiple N-vacancies (VNs), namely, VGa(VN)2 [or even VGa(VN)3], are identified as the major intrinsic NRCs. Different from the case of 4H-SiC, atomic structures of intrinsic NRCs in p-type and n-type GaN are different: VGaVN divacancies are the major NRCs in n-type GaN. The σ n value approximately the middle of 10-13 cm2 is obtained for VGa(VN)n, which is larger than the hole capture-cross-section (σp = 7 × 10-14 cm2) of VGaVN in n-type GaN. Combined with larger thermal velocity of an electron, minority carrier lifetime in Mg-doped GaN becomes much shorter than that of n-type GaN.

  7. Nachhaltiger Lebensmittelkonsum gestern, heute und morgen

    Aschemann-Witzel, Jessica

    2013-01-01

    Die Weltgemeinschaft sieht sich mit steigendem Bevölkerungswachstum und Zielkonflikten der Nutzung von Land und Agrarrohstoffen konfrontiert. Dies wirft die Frage auf, wie nachhaltiger Lebensmittelkonsum in der Zukunft auszusehen hat. Der Beitrag diskutiert die Frage aus Sicht der Konsumverhaltens...

  8. Ruhende Flüssigkeiten und Gase

    Heintze, Joachim

    Das mechanische Verhalten von Flüssigkeiten und Gasen ist dadurch gekennzeichnet, dass sie keine statische Schubfestigkeit besitzen, andernfalls würden sie nicht beginnen, zu fließen. In ruhenden Flüssigkeiten und Gasen können daher keine Schubspannungen bestehen:

  9. Handlung und Kommunikation als Grundbegriffe der Soziologie

    Martens, W.P.M.; Albert, H.; Greshoff, R.; Schützeichel, R.

    2010-01-01

    Handlung und Kommunikation gelten in der Soziologie manchmal als alternative, konkurrierende Grundbegriffe für die Beschreibung und Erklärung sozialer Zusammenhänge (siehe u.a. Luhmann 1984; 1990; Schneider 1994; Stichweh 2000; Greshoff 1999; Schwinn 2001; Albert et. al. 2003). Eine Soziologie,

  10. Die Gestalten und das Gestalten der Welt

    Ierna, Carlo; Höfer, Ulf; Valent, Juta

    2017-01-01

    In seiner Kosmogonie bespricht Ehrenfels den Ursprung, die Entwicklung, und das endgültige Schicksal des Universums: die Gestalt der Welt. Einerseits ist sie ein Kosmos, ein Geschöpf des Ordnungsprinzips, andererseits ein Chaos, als Resultat des Prinzips des Zufalls und der Entropie. Diese beiden

  11. Systeme im Einsatz. Lernmanagement, Kompetenzmanagement und PLE

    Kalz, Marco; Schön, Sandra; Lindner, Martin; Roth, Detlev; Baumgartner, Peter

    2011-01-01

    Kalz, M., Schön, S., Lindner, M., Roth, D., & Baumgartner, P. (2011). Systeme im Einsatz. Lernmanagement, Kompetenzmanagement und PLE. In M. Ebner, & S. Schön (Eds.), L3T - Lerhbuch für Lernen und Lehren mit Technologie (pp. 111-118). Graz, Austria: Uni Graz. Available at

  12. Schottky contacts to polar and nonpolar n-type GaN

    Kim, Hogyoung [Hanbat National University, Daejeon (Korea, Republic of); Phark, Soohyon [Max-Planck-Institut fur Mikrostrukturphysik, Halle (Germany); Song, Keunman [Korea Advanced Nano Fab Center, Suwon (Korea, Republic of); Kim, Dongwook [Ewha Woman' s University, Seoul (Korea, Republic of)

    2012-01-15

    Using the current-voltage measurements, we observed the barrier heights of c-plane GaN in Pt and Au Schottky contacts to be higher than those of a-plane GaN. However, the barrier height of c-plane GaN was lower than that of a-plane GaN in the Ti Schottky contacts. The N/Ga ratio calculated by integrating the X-ray photoelectron spectroscopy (XPS) spectra of Ga 3d and N 1s core levels showed that c-plane GaN induced more Ga vacancies near the interface than a-plane GaN in the Ti Schottky contacts, reducing the effective barrier height through an enhancement of the tunneling probability.

  13. Chemical lift-off of (11-22) semipolar GaN using periodic triangular cavities

    Jeon, Dae-Woo; Lee, Seung-Jae; Jeong, Tak; Baek, Jong Hyeob; Park, Jae-Woo; Jang, Lee-Woon; Kim, Myoung; Lee, In-Hwan; Ju, Jin-Woo

    2012-01-01

    Chemical lift-off of (11-22) semipolar GaN using triangular cavities was investigated. The (11-22) semipolar GaN was grown using epitaxial lateral overgrowth by metal-organic chemical vapor deposition on m-plane sapphire, in such a way as to keep N terminated surface of c-plane GaN exposed in the cavities. After regrowing 300 μm thick (11-22) semipolar GaN by hydride vapor phase epitaxy for a free-standing (11-22) semipolar GaN substrate, the triangular cavities of the templates were chemically etched in molten KOH. The (000-2) plane in the triangular cavities can be etched in the [0002] direction with the high lateral etching rate of 196 μm/min. The resulting free-standing (11-22) semipolar GaN substrate was confirmed to be strain-free by the Raman analysis.

  14. Red shift of near band edge emission in cerium implanted GaN

    Majid, Abdul; Ali, Akbar

    2009-01-01

    Rare earth (RE) doping in GaN is a promising technology to control the optical properties. However, there are no reports on doping of cerium (Ce) into GaN, which is a very unique RE element. In this paper, we performed photoluminescence (PL) and optical transmission measurements on Ce-doped GaN for the first time. A significant red shift of about 120 meV was observed in the PL peak position of the donor bound excitons. This red shift of near band emission was corroborated by the red shift of the absorption edge related to GaN in the optical transmission measurements. This observation is attributed to the band gap narrowing in GaN heavily doped with Ce. The activation energy of the Ce-related shallow donor is found to be 21.9 meV in GaN.

  15. Understanding the Room Temperature Ferromagnetism in GaN Nanowires with Pd Doping

    Manna, S; De, S K

    2011-01-01

    We report the first synthesis and characterization of 4d transition metal palladium-doped GaN nanowires (NWs). Room temperature ferromagnetism has been observed in high quality Vapor Liquid Solid (VLS) epitaxy grown undoped n-type GaN nanowires. It was proposed that this type of magnetism is due to defects which are not observed in Bulk GaN because of large formation energy of defects in bulk GaN. Here we have successfully doped 4d transition metal Pd in GaN NWs. We find fairly strong and long-range ferromagnetic coupling between Pd substituted for Ga in GaN . The results suggest that 4d metals such as Pd may also be considered as candidates for ferromagnetic dopants in semiconductors.

  16. Red shift of near band edge emission in cerium implanted GaN

    Majid, Abdul; Ali, Akbar, E-mail: abdulmajid40@yahoo.co, E-mail: akbar@qau.edu.p [Advance Materials Physics Laboratory, Physics Department, Quaid-i-Azam University, Islamabad (Pakistan)

    2009-02-21

    Rare earth (RE) doping in GaN is a promising technology to control the optical properties. However, there are no reports on doping of cerium (Ce) into GaN, which is a very unique RE element. In this paper, we performed photoluminescence (PL) and optical transmission measurements on Ce-doped GaN for the first time. A significant red shift of about 120 meV was observed in the PL peak position of the donor bound excitons. This red shift of near band emission was corroborated by the red shift of the absorption edge related to GaN in the optical transmission measurements. This observation is attributed to the band gap narrowing in GaN heavily doped with Ce. The activation energy of the Ce-related shallow donor is found to be 21.9 meV in GaN.

  17. Growth of GaN micro/nanolaser arrays by chemical vapor deposition.

    Liu, Haitao; Zhang, Hanlu; Dong, Lin; Zhang, Yingjiu; Pan, Caofeng

    2016-09-02

    Optically pumped ultraviolet lasing at room temperature based on GaN microwire arrays with Fabry-Perot cavities is demonstrated. GaN microwires have been grown perpendicularly on c-GaN/sapphire substrates through simple catalyst-free chemical vapor deposition. The GaN microwires are [0001] oriented single-crystal structures with hexagonal cross sections, each with a diameter of ∼1 μm and a length of ∼15 μm. A possible growth mechanism of the vertical GaN microwire arrays is proposed. Furthermore, we report room-temperature lasing in optically pumped GaN microwire arrays based on the Fabry-Perot cavity. Photoluminescence spectra exhibit lasing typically at 372 nm with an excitation threshold of 410 kW cm(-2). The result indicates that these aligned GaN microwire arrays may offer promising prospects for ultraviolet-emitting micro/nanodevices.

  18. Morphology engineering of ZnO nanostructures for high performance supercapacitors: enhanced electrochemistry of ZnO nanocones compared to ZnO nanowires

    He, Xiaoli; Yoo, Joung Eun; Lee, Min Ho; Bae, Joonho

    2017-06-01

    In this work, the morphology of ZnO nanostructures is engineered to demonstrate enhanced supercapacitor characteristics of ZnO nanocones (NCs) compared to ZnO nanowires (NWs). ZnO NCs are obtained by chemically etching ZnO NWs. Electrochemical characteristics of ZnO NCs and NWs are extensively investigated to demonstrate morphology dependent capacitive performance of one dimensional ZnO nanostructures. Cyclic voltammetry measurements on these two kinds of electrodes in a three-electrode cell confirms that ZnO NCs exhibit a high specific capacitance of 378.5 F g-1 at a scan rate of 20 mV s-1, which is almost twice that of ZnO NWs (191.5 F g-1). The charge-discharge and electrochemical impedance spectroscopy measurements also clearly result in enhanced capacitive performance of NCs as evidenced by higher specific capacitances and lower internal resistance. Asymmetric supercapacitors are fabricated using activated carbon (AC) as the negative electrode and ZnO NWs and NCs as positive electrodes. The ZnO NC⫽AC can deliver a maximum specific capacitance of 126 F g-1 at a current density of 1.33 A g-1 with an energy density of 25.2 W h kg-1 at the power density of 896.44 W kg-1. In contrast, ZnO NW⫽AC displays 63% of the capacitance obtained from the ZnO NC⫽AC supercapacitor. The enhanced performance of NCs is attributed to the higher surface area of ZnO nanostructures after the morphology is altered from NWs to NCs.

  19. Schaulust und Horror Soziokulturelle - Perspektiven auf PEEPING TOM

    Thomas Ballhausen

    2010-09-01

    Full Text Available Die Geschichte des Kinos und des Films ist mindestens ebenso sehr eine Geschichte des Schreckens (und der damit verbundenen Schaulust wie sie eine Geschichte des Dokumentarischen zu sein scheint. Es sind die außergewöhnlichen Körper und deren Bewegungen, die das Publikum zu allen Zeiten faszinierten, schockierten und zum Schauen und Sehen lockten. Besonders das Genre des Horrorfilms ist mit diesem zentralen Aspekt des Kinos besonders deutlich verbunden.

  20. Quantitative Analyse und Visualisierung der Herzfunktionen

    Sauer, Anne; Schwarz, Tobias; Engel, Nicole; Seitel, Mathias; Kenngott, Hannes; Mohrhardt, Carsten; Loßnitzer, Dirk; Giannitsis, Evangelos; Katus, Hugo A.; Meinzer, Hans-Peter

    Die computergestützte bildbasierte Analyse der Herzfunktionen ist mittlerweile Standard in der Kardiologie. Die verfügbaren Produkte erfordern meist ein hohes Maß an Benutzerinteraktion und somit einen erhöhten Zeitaufwand. In dieser Arbeit wird ein Ansatz vorgestellt, der dem Kardiologen eine größtenteils automatische Analyse der Herzfunktionen mittels MRT-Bilddaten ermöglicht und damit Zeitersparnis schafft. Hierbei werden alle relevanten herzphysiologsichen Parameter berechnet und mithilfe von Diagrammen und Graphen visualisiert. Diese Berechnungen werden evaluiert, indem die ermittelten Werte mit manuell vermessenen verglichen werden. Der hierbei berechnete mittlere Fehler liegt mit 2,85 mm für die Wanddicke und 1,61 mm für die Wanddickenzunahme immer noch im Bereich einer Pixelgrösse der verwendeten Bilder.

  1. Sowjetunion und Völkerrecht 1962-1973 / Henn-Jüri Uibopuu

    Uibopuu, Henn-Jüri, 1929-2012

    1980-01-01

    Tutvustus: Sowjetunion und Völkerrecht 1962-1973 : Bibliographie und analyse / hrsg. Boris Meissner, Dietrich Frenzke und Erika Chilicki. Köln : Wissenschaft und Politik, 1979 [t.p. incorrectly: 1977

  2. Vertical GaN Devices for Power Electronics in Extreme Environments

    2016-03-31

    Vertical GaN Devices for Power Electronics in Extreme Environments Isik C. Kizilyalli (1), Robert J. Kaplar (2), O. Aktas (1), A. M. Armstrong (2...electronics applications. In this paper vertical p-n diodes and transistors fabricated on pseudo bulk low defect density (104 to 106 cm-2) GaN substrates are...discussed. Homoepitaxial MOCVD growth of GaN on its native substrate and being able to control doping has allowed the realization of vertical

  3. Thermal Annealing induced relaxation of compressive strain in porous GaN structures

    Ben Slimane, Ahmed

    2012-01-01

    The effect of annealing on strain relaxation in porous GaN fabricated using electroless chemical etching is presented. The Raman shift of 1 cm-1 in phonon frequency of annealed porous GaN with respect to as-grown GaN corresponds to a relaxation of compressive strain by 0.41 ± 0.04 GPa. The strain relief promises a marked reduction in threading dislocation for subsequent epitaxial growth.

  4. Integrated GaN photonic circuits on silicon (100) for second harmonic generation

    Xiong, Chi; Pernice, Wolfram; Ryu, Kevin K.; Schuck, Carsten; Fong, King Y.; Palacios, Tomas; Tang, Hong X.

    2014-01-01

    We demonstrate second order optical nonlinearity in a silicon architecture through heterogeneous integration of single-crystalline gallium nitride (GaN) on silicon (100) substrates. By engineering GaN microrings for dual resonance around 1560 nm and 780 nm, we achieve efficient, tunable second harmonic generation at 780 nm. The \\{chi}(2) nonlinear susceptibility is measured to be as high as 16 plus minus 7 pm/V. Because GaN has a wideband transparency window covering ultraviolet, visible and ...

  5. Adsorption property of volatile molecules on ZnO nanowires ...

    7

    Keywords: ZnO; interaction; ammonia; band structure; density of states. 1. 2. 3 .... Virtual NanoLab [18] software was utilized to construct the ZnO nanowires with 24 Zn ..... But in reality, the ZnO NWs shows a better response (80.2) towards NH3.

  6. Bewegung bei Vorschulkindern: Empfehlungen und Wirklichkeit

    Graf C

    2011-01-01

    Full Text Available Bewegung und körperliche Aktivität spielen insbesondere in der ganzheitlichen Entwicklung von Kindern eine wichtige Rolle. Heutzutage ist der kindliche Lebensstil allerdings von Bewegungsarmut und der Nutzung audiovisueller Medien geprägt. Bereits Kindergartenkinder sind überwiegend inaktiv bzw. verbringen viel Zeit mit Fernsehen. Eine mögliche Folge von mangelnder Bewegung können motorische Defizite darstellen. In eigenen Kollektiven schneiden mindestens 45 % der Kinder unterdurchschnittlich in den motorischen Hauptbeanspruchungsformen Koordination, Kraft und Schnelligkeit ab. Inwiefern sich dies langfristig auf die gesunde körperliche, aber auch geistige und emotionale Entwicklung der Kinder auswirkt, kann derzeit noch nicht beantwortet werden. Sicherlich unterstützen aber motorische Defizite ein Meidungsverhalten und den weiteren Rückzug aus der Bewegung sowie die Entwicklung von Übergewicht und Adipositas. Allgemein wird für Kinder in dieser Altersgruppe mindestens 2 Stunden tägliche Bewegungszeit sowie eine Reduktion der Fernsehzeit auf maximal 30 Min. empfohlen. Um diese Ziele zu erreichen bzw. zu unterstützen, sind effektive präventive Programme in den verschiedenen Lebensräumen der Kinder, Kindergärten, aber auch pädiatrischen Praxen etc. vonnöten. Bislang ist kein gesundheitsförderlicher/ präventiver „Königsweg“ bekannt, insbesondere nicht für Risikofamilien mit einem geringen sozioökonomischen Status und/oder Migrationshintergrund. Wichtig erscheinen aber die Förderung der intersektoralen Zusammenarbeit und ein Schwerpunkt in der Planung und Umsetzung auf Qualitätssicherung und Projektmanagement, um auch nachhaltig die Gesundheit der Kinder zu unterstützen.

  7. Lateral epitaxial overgrowth of GaN on a patterned GaN-on-silicon substrate by molecular beam epitaxy

    Wang, Yongjin; Hu, Fangren; Hane, Kazuhiro

    2011-01-01

    We report here the lateral epitaxial overgrowth (LEO) of GaN on a patterned GaN-on-silicon substrate by molecular beam epitaxy (MBE) growth with radio frequency nitrogen plasma as a gas source. Two kinds of GaN nanostructures are defined by electron beam lithography and realized on a GaN substrate by fast atom beam etching. The epitaxial growth of GaN by MBE is performed on the prepared GaN template, and the selective growth of GaN takes place with the assistance of GaN nanostructures. The LEO of GaN produces novel GaN epitaxial structures which are dependent on the shape and the size of the processed GaN nanostructures. Periodic GaN hexagonal pyramids are generated inside the air holes, and GaN epitaxial strips with triangular section are formed in the grating region. This work provides a promising way for producing novel GaN-based devices by the LEO of GaN using the MBE technique

  8. Der Einfluss von sozialer Ungleichheit und kulturellen Unterschieden auf die Wahrnehmung von finanziellen und Arbeitsplatzrisiken: Überlegungen zur Risikogesellschaft

    Abbott, David; Quilgars, Deborah; Jones, Anwen

    2006-01-01

    Der vorliegende Artikel beruht auf Daten einer Studie, die sich mit der Frage beschäftigt, wie verschiedene soziale und kulturelle Gruppen die Risiken von Einkommens- und Arbeitsplatzverlust wahrnehmen und darauf reagieren. Autoren wie LASH, DOUGLAS und LUPTON betonten die Bedeutung von Gruppenzugehörigkeit und sozialen Kategorien für die Strukturierung der Reaktionsweisen auf verschiedene Risikoarten. Sie sprechen daher lieber von Risikokulturen als von der Risikogesellschaft. Trotzdem erken...

  9. Mechanical, Thermodynamic and Electronic Properties of Wurtzite and Zinc-Blende GaN Crystals

    Luan, Xinghe; Feng, Chuang; Yang, Daoguo; Zhang, Guoqi

    2017-01-01

    For the limitation of experimental methods in crystal characterization, in this study, the mechanical, thermodynamic and electronic properties of wurtzite and zinc-blende GaN crystals were investigated by first-principles calculations based on density functional theory. Firstly, bulk moduli, shear moduli, elastic moduli and Poisson’s ratios of the two GaN polycrystals were calculated using Voigt and Hill approximations, and the results show wurtzite GaN has larger shear and elastic moduli and exhibits more obvious brittleness. Moreover, both wurtzite and zinc-blende GaN monocrystals present obvious mechanical anisotropic behavior. For wurtzite GaN monocrystal, the maximum and minimum elastic moduli are located at orientations [001] and , respectively, while they are in the orientations and for zinc-blende GaN monocrystal, respectively. Compared to the elastic modulus, the shear moduli of the two GaN monocrystals have completely opposite direction dependences. However, different from elastic and shear moduli, the bulk moduli of the two monocrystals are nearly isotropic, especially for the zinc-blende GaN. Besides, in the wurtzite GaN, Poisson’s ratios at the planes containing [001] axis are anisotropic, and the maximum value is 0.31 which is located at the directions vertical to [001] axis. For zinc-blende GaN, Poisson’s ratios at planes (100) and (111) are isotropic, while the Poisson’s ratio at plane (110) exhibits dramatically anisotropic phenomenon. Additionally, the calculated Debye temperatures of wurtzite and zinc-blende GaN are 641.8 and 620.2 K, respectively. At 300 K, the calculated heat capacities of wurtzite and zinc-blende are 33.6 and 33.5 J mol−1 K−1, respectively. Finally, the band gap is located at the G point for the two crystals, and the band gaps of wurtzite and zinc-blende GaN are 3.62 eV and 3.06 eV, respectively. At the G point, the lowest energy of conduction band in the wurtzite GaN is larger, resulting in a wider band gap

  10. High surface hole concentration p-type GaN using Mg implantation

    Long Tao; Zhang Guo Yi

    2001-01-01

    Mg ions were implanted on Mg-doped GaN grown by metalorganic chemical vapor deposition (MOCVD). The p-type GaN was achieved with high hole concentration (8.28 x 10 sup 1 sup 7 cm sup - sup 3) conformed by Van derpauw Hall measurement after annealing at 800 degree C for 1 h. this is the first experimental report of Mg implantation on Mg-doped GaN and achieving p-type GaN with high surface hole concentration

  11. Optical properties of Mg doped p-type GaN nanowires

    Patsha, Avinash; Pandian, Ramanathaswamy; Dhara, S.; Tyagi, A. K.

    2015-06-01

    Mg doped p-type GaN nanowires are grown using chemical vapor deposition technique in vapor-liquid-solid (VLS) process. Morphological and structural studies confirm the VLS growth process of nanowires and wurtzite phase of GaN. We report the optical properties of Mg doped p-type GaN nanowires. Low temperature photoluminescence studies on as-grown and post-growth annealed samples reveal the successful incorporation of Mg dopants. The as-grwon and annealed samples show passivation and activation of Mg dopants, respectively, in GaN nanowires.

  12. The feasibility of tunable p-type Mg doping in a GaN monolayer nanosheet

    Xia, Congxin; Peng, Yuting; Wei, Shuyi; Jia, Yu

    2013-01-01

    Based on density functional theory, the electronic structures, formation energy and transition energy level of a p-type Mg-doped GaN nanosheet are investigated. Numerical results show that the transition energy level decreases monotonously with increasing Mg doping concentration in Mg-doped GaN nanosheet systems, which is lower than that of the Mg-doped bulk GaN case. Moreover, the formation energy calculations indicate that Mg-doped GaN nanosheet structures can be realized under N-rich experimental growth conditions

  13. Mechanical, Thermodynamic and Electronic Properties of Wurtzite and Zinc-Blende GaN Crystals

    Hongbo Qin

    2017-12-01

    Full Text Available For the limitation of experimental methods in crystal characterization, in this study, the mechanical, thermodynamic and electronic properties of wurtzite and zinc-blende GaN crystals were investigated by first-principles calculations based on density functional theory. Firstly, bulk moduli, shear moduli, elastic moduli and Poisson’s ratios of the two GaN polycrystals were calculated using Voigt and Hill approximations, and the results show wurtzite GaN has larger shear and elastic moduli and exhibits more obvious brittleness. Moreover, both wurtzite and zinc-blende GaN monocrystals present obvious mechanical anisotropic behavior. For wurtzite GaN monocrystal, the maximum and minimum elastic moduli are located at orientations [001] and <111>, respectively, while they are in the orientations <111> and <100> for zinc-blende GaN monocrystal, respectively. Compared to the elastic modulus, the shear moduli of the two GaN monocrystals have completely opposite direction dependences. However, different from elastic and shear moduli, the bulk moduli of the two monocrystals are nearly isotropic, especially for the zinc-blende GaN. Besides, in the wurtzite GaN, Poisson’s ratios at the planes containing [001] axis are anisotropic, and the maximum value is 0.31 which is located at the directions vertical to [001] axis. For zinc-blende GaN, Poisson’s ratios at planes (100 and (111 are isotropic, while the Poisson’s ratio at plane (110 exhibits dramatically anisotropic phenomenon. Additionally, the calculated Debye temperatures of wurtzite and zinc-blende GaN are 641.8 and 620.2 K, respectively. At 300 K, the calculated heat capacities of wurtzite and zinc-blende are 33.6 and 33.5 J mol−1 K−1, respectively. Finally, the band gap is located at the G point for the two crystals, and the band gaps of wurtzite and zinc-blende GaN are 3.62 eV and 3.06 eV, respectively. At the G point, the lowest energy of conduction band in the wurtzite GaN is larger

  14. Direct growth of freestanding GaN on C-face SiC by HVPE.

    Tian, Yuan; Shao, Yongliang; Wu, Yongzhong; Hao, Xiaopeng; Zhang, Lei; Dai, Yuanbin; Huo, Qin

    2015-06-02

    In this work, high quality GaN crystal was successfully grown on C-face 6H-SiC by HVPE using a two steps growth process. Due to the small interaction stress between the GaN and the SiC substrate, the GaN was self-separated from the SiC substrate even with a small thickness of about 100 μm. Moreover, the SiC substrate was excellent without damage after the whole process so that it can be repeatedly used in the GaN growth. Hot phosphoric acid etching (at 240 °C for 30 min) was employed to identify the polarity of the GaN layer. According to the etching results, the obtained layer was Ga-polar GaN. High-resolution X-ray diffraction (HRXRD) and electron backscatter diffraction (EBSD) were done to characterize the quality of the freestanding GaN. The Raman measurements showed that the freestanding GaN film grown on the C-face 6H-SiC was stress-free. The optical properties of the freestanding GaN layer were determined by photoluminescence (PL) spectra.

  15. Mechanical, Thermodynamic and Electronic Properties of Wurtzite and Zinc-Blende GaN Crystals.

    Qin, Hongbo; Luan, Xinghe; Feng, Chuang; Yang, Daoguo; Zhang, Guoqi

    2017-12-12

    For the limitation of experimental methods in crystal characterization, in this study, the mechanical, thermodynamic and electronic properties of wurtzite and zinc-blende GaN crystals were investigated by first-principles calculations based on density functional theory. Firstly, bulk moduli, shear moduli, elastic moduli and Poisson's ratios of the two GaN polycrystals were calculated using Voigt and Hill approximations, and the results show wurtzite GaN has larger shear and elastic moduli and exhibits more obvious brittleness. Moreover, both wurtzite and zinc-blende GaN monocrystals present obvious mechanical anisotropic behavior. For wurtzite GaN monocrystal, the maximum and minimum elastic moduli are located at orientations [001] and , respectively, while they are in the orientations and for zinc-blende GaN monocrystal, respectively. Compared to the elastic modulus, the shear moduli of the two GaN monocrystals have completely opposite direction dependences. However, different from elastic and shear moduli, the bulk moduli of the two monocrystals are nearly isotropic, especially for the zinc-blende GaN. Besides, in the wurtzite GaN, Poisson's ratios at the planes containing [001] axis are anisotropic, and the maximum value is 0.31 which is located at the directions vertical to [001] axis. For zinc-blende GaN, Poisson's ratios at planes (100) and (111) are isotropic, while the Poisson's ratio at plane (110) exhibits dramatically anisotropic phenomenon. Additionally, the calculated Debye temperatures of wurtzite and zinc-blende GaN are 641.8 and 620.2 K, respectively. At 300 K, the calculated heat capacities of wurtzite and zinc-blende are 33.6 and 33.5 J mol -1 K -1 , respectively. Finally, the band gap is located at the G point for the two crystals, and the band gaps of wurtzite and zinc-blende GaN are 3.62 eV and 3.06 eV, respectively. At the G point, the lowest energy of conduction band in the wurtzite GaN is larger, resulting in a wider band gap. Densities of

  16. Dislocation-induced nanoparticle decoration on a GaN nanowire.

    Yang, Bing; Yuan, Fang; Liu, Qingyun; Huang, Nan; Qiu, Jianhang; Staedler, Thorsten; Liu, Baodan; Jiang, Xin

    2015-02-04

    GaN nanowires with homoepitaxial decorated GaN nanoparticles on their surface along the radial direction have been synthesized by means of a chemical vapor deposition method. The growth of GaN nanowires is catalyzed by Au particles via the vapor-liquid-solid (VLS) mechanism. Screw dislocations are generated along the radial direction of the nanowires under slight Zn doping. In contrast to the metal-catalyst-assisted VLS growth, GaN nanoparticles are found to prefer to nucleate and grow at these dislocation sites. High-resolution transmission electron microscopy (HRTEM) analysis demonstrates that the GaN nanoparticles possess two types of epitaxial orientation with respect to the corresponding GaN nanowire: (I) [1̅21̅0]np//[1̅21̅0]nw, (0001)np//(0001)nw; (II) [1̅21̅3]np//[12̅10]nw, (101̅0)np//(101̅0)nw. An increased Ga signal in the energy-dispersive spectroscopy (EDS) profile lines of the nanowires suggests GaN nanoparticle growth at the edge surface of the wires. All the crystallographic results confirm the importance of the dislocations with respect to the homoepitaxial growth of the GaN nanoparticles. Here, screw dislocations situated on the (0001) plane provide the self-step source to enable nucleation of the GaN nanoparticles.

  17. Synthesis and Raman scattering of GaN nanorings, nanoribbons and nanowires

    Li, Z.J. [Academia Sinica, Beijing, BJ (China). Inst. of Physics; Northwestern Polytechnical Univ., Xian, SN (China). Dept. of Materials Science and Engineering; Chen, X.L.; Tu, Q.Y.; Yang, Z.; Xu, Y.P.; Hu, B.Q. [Academia Sinica, Beijing, BJ (China). Inst. of Physics; Li, H.J. [Northwestern Polytechnical Univ., Xian, SN (China). Dept. of Materials Science and Engineering

    2001-05-01

    Low-dimensional GaN materials, including nanorings, nanoribbons and smooth nanowires have been synthesized by reacting gallium and ammonia using Ag particles as a catalyst on the substrate of MgO single crystals. They were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). EDX, XRD indicated that the low-dimensional nanomaterials were wurtzite GaN. New features are found in Raman scatterings for these low-dimensional GaN materials, which are different from the previous observations of GaN materials. (orig.)

  18. Optical and field emission properties of layer-structure GaN nanowires

    Cui, Zhen [Science School, Xi’an University of Technology, Xi’an 710048 (China); School of automation and Information Engineering, Xi’an University of Technology, Xi’an 710048 (China); Li, Enling, E-mail: Lienling@xaut.edu.cn [Science School, Xi’an University of Technology, Xi’an 710048 (China); Shi, Wei; Ma, Deming [Science School, Xi’an University of Technology, Xi’an 710048 (China)

    2014-08-15

    Highlights: • The layer-structure GaN nanowires with hexagonal-shaped cross-sections are produced via a process based on the CVD method. • The diameter of the layer-structure GaN nanowire gradually decreases from ∼500 nm to ∼200 nm along the wire axis. • The layer-structure GaN nanowire film possesses good field emission property. - Abstract: A layer-structure gallium nitride (GaN) nanowires, grown on Pt-coated n-type Si (1 1 1) substrate, have been synthesized using chemical vapor deposition (CVD). The results show: (1) SEM indicates that the geometry structure is layer-structure. HRTEM indicates that GaN nanowire’s preferential growth direction is along [0 0 1] direction. (2) The room temperature PL emission spectrum of the layer-structure GaN nanowires has a peak at 375 nm, which proves that GaN nanowires have potential application in light-emitting nano-devices. (3) Field-emission measurements show that the layer-structure GaN nanowires film has a low turn-on field of 4.39 V/μm (at room temperature), which is sufficient for electron emission devices, field emission displays and vacuum nano-electronic devices. The growth mechanism for GaN nanowires has also been discussed briefly.

  19. Site-selective spectroscopy of Er in GaN

    Dierolf, V.; Sandmann, C.; Zavada, J.; Chow, P.; Hertog, B.

    2004-01-01

    We investigated different Er 3+ defect sites found in Er-doped GaN layers by site-selective combined excitation-emission spectroscopy and studied the role of these sites in different direct and multistep excitation schemes. The layers were grown by molecular beam epitaxy and were 200 nm thick. Two majority sites were found along with several minority sites. The sites strongly differ in excitation and energy transfer efficiencies as well as branching ratios during relaxation. For this reason, relative emission intensities from these sites depend strongly on emission and excitation. The sites were identified for several transitions and a comprehensive list of energy levels has been compiled. One of the minority sites appears strongly under ultraviolet excitation above the GaN band gap suggesting that this site is an excellent trap for excitation energy of electron-hole pairs

  20. Study of Charge Carrier Transport in GaN Sensors

    Gaubas, Eugenijus; Ceponis, Tomas; Kuokstis, Edmundas; Meskauskaite, Dovile; Pavlov, Jevgenij; Reklaitis, Ignas

    2016-01-01

    Capacitor and Schottky diode sensors were fabricated on GaN material grown by hydride vapor phase epitaxy and metal-organic chemical vapor deposition techniques using plasma etching and metal deposition. The operational characteristics of these devices have been investigated by profiling current transients and by comparing the experimental regimes of the perpendicular and parallel injection of excess carrier domains. Profiling of the carrier injection location allows for the separation of the bipolar and the monopolar charge drift components. Carrier mobility values attributed to the hydride vapor phase epitaxy (HVPE) GaN material have been estimated as μe = 1000 ± 200 cm2/Vs for electrons, and μh = 400 ± 80 cm2/Vs for holes, respectively. Current transients under injection of the localized and bulk packets of excess carriers have been examined in order to determine the surface charge formation and polarization effects. PMID:28773418

  1. Structural and Magnetic Properties of Sm Implanted GaN

    Li-Juan, Jiang; Xiao-Liang, Wang; Hong-Ling, Xiao; Zhan-Guo, Wang; Chun, Feng; Ming-Lan, Zhang; Jian, Tang

    2009-01-01

    The structural and magnetic properties of Sm ion-implanted GaN with different Sm concentrations are investigated. XRD results do not show any peaks associated with second phase formation. Magnetic investigations performed by superconducting quantum interference device reveal ferromagnetic behavior with an ordering temperature above room temperature in all the implanted samples, while the effective magnetic moment per Sm obtained from saturation magnetization gives a much higher value than the atomic moment of Sm. These results could be explained by the phenomenological model proposed by Dhar et al. [Phys. Rev. Lett. 94(2005)037205, Phys. Rev. B 72(2005)245203] in terms of a long-range spin polarization of the GaN matrix by the Sm atoms. (condensed matter: electronicstructure, electrical, magnetic, and opticalproperties)

  2. Electron beam irradiation effect on GaN HEMT

    Lou Yinhong; Guo Hongxia; Zhang Keying; Wang Yuanming; Zhang Fengqi

    2011-01-01

    In this work, GaN HEMTs (High Electron Mobility Transistor) were irradiated by 0.8 and 1.2 MeV electron beams, and the irradiation effects were investigated. The results show that the device damage caused by 0.8 MeV electrons is more serious than that by 1.2 MeV electrons. Saturation drain current increase and threshold voltage negative shift are due to trapped positive charge from ionization in the AlGaN layer and N, Ga vacancy from non-ionizing energy loss in the GaN layer. Electron traps and trapped positive charges from non-ionizing in the AlGaN layer act as trap-assisted-tunneling centers that increase the gate leakage current.(authors)

  3. Ein überfälliger Dialog. Wie Frauen- und Geschlechterforschung und Soziologie miteinander ins Gespräch kommen können

    Heike Kahlert

    2007-03-01

    Full Text Available Die Monographie von Brigitte Aulenbacher zum Zusammenhang von Rationalisierung, Geschlecht und Gesellschaft ist in gegenstandsbezogener und methodologischer Hinsicht ambitioniert, überzeugend und lesenswert. Die Studie stellt eine solide, manchmal auch etwas zu weitschweifige und detailreiche Grundlage für weiterführende Diskussionen zwischen der (sozialwissenschaftlichen Frauen- und Geschlechterforschung und der Soziologie, genauer der Gesellschaftstheorie in zeitdiagnostischer Perspektive, Arbeits-, Industrie-, Organisations- und Techniksoziologie, dar.

  4. Ion beam synthesis and characterization of large area 3C-SiC pseudo substrates for homo- and heteroepitaxy; Ionenstrahlsynthese und Charakterisierung grossflaechiger 3C-SiC-Pseudosubstrate fuer die Homo- und Heteroepitaxie

    Haeberlen, Maik

    2006-12-15

    In this work, large area epitaxial 3C-SiC films on Si(100) and Si(111) were formed by ion beam synthesis and subsequently characterized for their structural and crystalline properties. These SiC/Si structures are meant to be used as SiC pseudosubstrates for the homo- and heteroepitaxial growth of other compound semiconductors. The suitability of these pseudosubstrates for this purpose was tested using various epitaxial systems and thin film growth methods. For this the homoepitaxial growth of 3C-SiC employing C{sub 60}-MBE and the heteroepitaxial growth of hexagonal GaN films grown by MOCVD and IBAMBA was studied in detail. The comparison of the structural and crystalline properties with data from literature enabled a qualified judgement of the potential of the 3C-SiC pseudosubstrates as an alternative substrate for the epitaxial growth of such films. These new 3C-SiC pseudosubstrates also enabled studies of other little known epitaxial systems: For the first time hexagonal ZnO films on (111) oriented pseudosubstrates were grown using PLD. The method if IBAMBE enabled the growth of cubic GaN layers on (100)-oriented pseudosubstrates. (orig.)

  5. Room Temperature Ultralow Threshold GaN Nanowire Polariton Laser

    Das, Ayan

    2011-08-01

    We report ultralow threshold polariton lasing from a single GaN nanowire strongly coupled to a large-area dielectric microcavity. The threshold carrier density is 3 orders of magnitude lower than that of photon lasing observed in the same device, and 2 orders of magnitude lower than any existing room-temperature polariton devices. Spectral, polarization, and coherence properties of the emission were measured to confirm polariton lasing. © 2011 American Physical Society.

  6. High sensitivity hydrogen sensors based on GaN

    Yatskiv, Roman; Grym, Jan; Žďánský, Karel

    2012-01-01

    Roč. 7, č. 9 (2012), s. 1661-1663 ISSN 1610-1642. [16th International Semiconducting and Insulating Materials Conference (SIMC-XVI). Stockholm, 19.06.2011-23.06.2011] R&D Projects: GA MŠk(CZ) OC10021 Institutional support: RVO:67985882 Keywords : Pt nanoparticles * Graphite based Schottky diodes * Hydrogen sensor * GaN Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  7. Investigation on the Solubility of GaN in Supercritical Ammonia Containing Acidic, Neutral, and Some Basic Mineralizers

    Ehrentraut, Dirk

    2009-01-01

    ... material due to the superior structural quality over HVPE GaN. In order to hold up with the progress, not at least provide a scientific platform, the solubility of GaN in supercritical ammonia (NH3...

  8. Electrical characterization of ZnO nanorods

    Schlenker, E.; Bakin, A.; Postels, B.; Mofor, A.C.; Wehmann, H.H.; Waag, A. [Institute of Semiconductor Technology, Technical University Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Weimann, T.; Hinze, P. [Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig (Germany)

    2007-05-15

    Zinc oxide (ZnO) nanorods were grown by a wet chemical approach and by vapor phase transport. To explore the electrical properties of individual nanostructures current-voltage (I-V) characteristics were obtained by using an atomic force microscope (AFM) with a conductive tip or by detaching the nanorods from the growth substrate, transferring them to an isolating substrate and contacting them with evaporated Ti/Au electrodes patterned by electron-beam lithography. The AFM-approach only yields a Schottky diode behavior, while the Ti/Au forms ohmic contacts to the ZnO. For the latter method the obtained I-V curves reveal a resistivity of the nanorods in the order of 10{sup -5} {omega} cm which is unusually low for undoped ZnO. We therefore assume the existence of a highly conductive surface channel. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Photoluminescence measurements of ZnO heterostructures

    Adachi, Yutaka; Sakaguchi, Isao; Ohashi, Naoki; Haneda, Hajime; Ryoken, Haruki; Takenaka, Tadashi

    2003-01-01

    ZnO thin films were grown on TbAlO 3 single crystal substrates by pulsed laser deposition. In photoluminescence (PL) measurements, strong emissions from TbAlO 3 were observed with the emission from ZnO when the film thickness was less than 100 nm. The relationship between the ZnO film thickness and the emission intensity from TbAlO 3 was investigated in order to determine the penetration depth of excitation light. Information on the heterostructures ranging from the surface to a depth of 300 nm was obtained by PL measurements in this study, and the absorption coefficient for a wavelength of 325 nm was estimated to be 1.31x10 5 cm -1 . (author)

  10. Investigation on thermodynamics of ion-slicing of GaN and heterogeneously integrating high-quality GaN films on CMOS compatible Si(100) substrates.

    Huang, Kai; Jia, Qi; You, Tiangui; Zhang, Runchun; Lin, Jiajie; Zhang, Shibin; Zhou, Min; Zhang, Bo; Yu, Wenjie; Ou, Xin; Wang, Xi

    2017-11-08

    Die-to-wafer heterogeneous integration of single-crystalline GaN film with CMOS compatible Si(100) substrate using the ion-cutting technique has been demonstrated. The thermodynamics of GaN surface blistering is in-situ investigated via a thermal-stage optical microscopy, which indicates that the large activation energy (2.5 eV) and low H ions utilization ratio (~6%) might result in the extremely high H fluence required for the ion-slicing of GaN. The crystalline quality, surface topography and the microstructure of the GaN films are characterized in detail. The full width at half maximum (FWHM) for GaN (002) X-ray rocking curves is as low as 163 arcsec, corresponding to a density of threading dislocation of 5 × 10 7  cm -2 . Different evolution of the implantation-induced damage was observed and a relationship between the damage evolution and implantation-induced damage is demonstrated. This work would be beneficial to understand the mechanism of ion-slicing of GaN and to provide a platform for the hybrid integration of GaN devices with standard Si CMOS process.

  11. Photoluminescence properties of Co-doped ZnO nanocrystals

    Lommens, P.; Smet, P.F.; De Mello Donega, C.

    2006-01-01

    We performed photoluminescence experiments on colloidal, Co -doped ZnO nanocrystals in order to study the electronic properties of Co in a ZnO host. Room temperature measurements showed, next to the ZnO exciton and trap emission, an additional emission related to the Co dopant. The spectral...... position and width of this emission does not depend on particle size or Co concentration. At 8 K, a series of ZnO bulk phonon replicas appear on the Co-emission band. We conclude that Co ions are strongly localized in the ZnO host, making the formation of a Co d-band unlikely. Magnetic measurements...

  12. Metal contacts on ZnSe and GaN

    Duxstad, Kristin Joy [Univ. of California, Berkeley, CA (United States). Materials Science and Mineral Engineering

    1997-05-01

    Recently, considerable interest has been focused on the development of blue light emitting materials and devices. The focus has been on GaN and ZnSe, direct band gap semiconductors with bands gaps of 3.4 and 2.6 eV, respectively. To have efficient, reliable devices it is necessary to have thermally and electrically stable Ohmic contacts. This requires knowledge of the metal-semiconductor reaction behavior. To date few studies have investigated this behavior. Much information has accumulated over the years on the behavior of metals on Si and GaAs. This thesis provides new knowledge for the more ionic wide band gap semiconductors. The initial reaction temperatures, first phases formed, and phase stability of Pt, Pd, and Ni on both semiconductors were investigated. The reactions of these metals on ZnSe and GaN are discussed in detail and correlated with predicted behavior. In addition, comparisons are made between these highly ionic semiconductors and Si and GaAs. The trends observed here should also be applicable to other II-VI and III-Nitride semiconductor systems, while the information on phase formation and stability should be useful in the development of contacts for ZnSe and GaN devices.

  13. Dopant Adsorption and Incorporation at Irradiated GaN Surfaces

    Sun, Qiang; Selloni, Annabella; Myers, Thomas; Doolittle, W. Alan

    2006-03-01

    Mg and O are two of the common dopants in GaN, but, in spite of extensive investigation, the atomic scale understanding of their adsorption and incorporation is still incomplete. In particular, high-energy electron irradiation, such as occurring during RHEED, has been reported to have an important effect on the incorporation of these impurities, but no study has addressed the detailed mechanisms of this effect yet. Here we use DFT calculations to study the adsorption and incorporation of Mg and O at the Ga- and N-polar GaN surfaces under various Ga, Mg and O coverage conditions as well as in presence of light or electron beam-induced electronic excitation. We find that the adsorption and incorporation of the two impurities have opposite surface polarity dependence: substitutional Mg prefers to incorporate at the GaN(0001) surface, while O prefers to adsorb and incorporate at the N-polar surface. In addition, our results indicate that in presence of light irradiation the tendency of Mg to surface-segregate is reduced. The O adsorption energy on the N-polar surface is also significantly reduced, consistent with the experimental observation of a much smaller concentration of oxygen in the irradiated samples.

  14. Rare earth point defects in GaN

    Sanna, S.

    2007-12-14

    In this work we investigate rare earth doped GaN, by means of theoretical simulations. The huge unit cells necessary to model the experimental system, where dilute amount of rare earth ions are used, are handled with the charge self consistent density-functional based-tight binding (SCC-DFTB) calculational scheme. The method has been extended to include LDA+U and simplified self interaction corrected (SIC)-like potentials for the simulation of systems with localised and strongly correlated electrons. A set of tight-binding parameters has been created to model the interaction of GaN with some dopants, including a selection of lanthanide ions interesting due to their optical or magnetic properties (Pr, Eu, Gd, Er and Tm). The f-electrons were treated as valence electrons. A qualitatively correct description of the band gap is crucial for the simulation of rare earth doped GaN, because the luminescence intensity of the implanted samples depends on the size of the host band gap and because the rare earths could introduce charge transition levels near the conduction band. In this work these levels are calculated with the Slater-Janak (SJ) transition state model, which allows an approximate calculation of the charge transition levels by analysing the Kohn-Sham eigenvalues of the DFT. (orig.)

  15. Dislocation core structures in Si-doped GaN

    Rhode, S. L.; Fu, W. Y.; Sahonta, S.-L.; Kappers, M. J.; Humphreys, C. J.; Horton, M. K.; Pennycook, T. J.; Dusane, R. O.; Moram, M. A.

    2015-01-01

    Aberration-corrected scanning transmission electron microscopy was used to investigate the core structures of threading dislocations in plan-view geometry of GaN films with a range of Si-doping levels and dislocation densities ranging between (5 ± 1) × 10 8  and (10 ± 1) × 10 9  cm −2 . All a-type (edge) dislocation core structures in all samples formed 5/7-atom ring core structures, whereas all (a + c)-type (mixed) dislocations formed either double 5/6-atom, dissociated 7/4/8/4/9-atom, or dissociated 7/4/8/4/8/4/9-atom core structures. This shows that Si-doping does not affect threading dislocation core structures in GaN. However, electron beam damage at 300 keV produces 4-atom ring structures for (a + c)-type cores in Si-doped GaN

  16. Dislocation core structures in Si-doped GaN

    Rhode, S. L., E-mail: srhode@imperial.ac.uk; Fu, W. Y.; Sahonta, S.-L.; Kappers, M. J.; Humphreys, C. J. [Department of Materials Science and Metallurgy, University of Cambridge, Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Horton, M. K. [Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Pennycook, T. J. [SuperSTEM, STFC Daresbury Laboratories, Warrington WA4 4AD (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Dusane, R. O. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076 (India); Moram, M. A. [Department of Materials Science and Metallurgy, University of Cambridge, Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)

    2015-12-14

    Aberration-corrected scanning transmission electron microscopy was used to investigate the core structures of threading dislocations in plan-view geometry of GaN films with a range of Si-doping levels and dislocation densities ranging between (5 ± 1) × 10{sup 8} and (10 ± 1) × 10{sup 9} cm{sup −2}. All a-type (edge) dislocation core structures in all samples formed 5/7-atom ring core structures, whereas all (a + c)-type (mixed) dislocations formed either double 5/6-atom, dissociated 7/4/8/4/9-atom, or dissociated 7/4/8/4/8/4/9-atom core structures. This shows that Si-doping does not affect threading dislocation core structures in GaN. However, electron beam damage at 300 keV produces 4-atom ring structures for (a + c)-type cores in Si-doped GaN.

  17. Radiation sensors based on GaN microwires

    Verheij, D.; Peres, M.; Cardoso, S.; Alves, L. C.; Alves, E.; Durand, C.; Eymery, J.; Lorenz, K.

    2018-05-01

    GaN microwires were shown to possess promising characteristics as building blocks for radiation resistant particle detectors. They were grown by metal organic vapour phase epitaxy with diameters between 1 and 2 μm and lengths around 20 μm. Devices were fabricated by depositing gold contacts at the extremities of the wires using photolithography. The response of these single wire radiation sensors was then studied under irradiation with 2 MeV protons. Severe degradation of the majority of devices only sets in for fluences above protons cm‑2 revealing good radiation resistance. During proton irradiation, a clear albeit small current gain was observed with a corresponding decay time below 1 s. Photoconductivity measurements upon irradiation with UV light were carried out before and after the proton irradiation. Despite a relatively low gain, attributed to significant dark currents caused by a high dopant concentration, fast response times of a few seconds were achieved comparable to state-of-the-art GaN nanowire photodetectors. Irradiation and subsequent annealing resulted in an overall improvement of the devices regarding their response to UV radiation. The photocurrent gain increased compared to the values that were obtained prior to the irradiation, without compromising the decay times. The results indicate the possibility of using GaN microwires not only as UV detectors, but also as particle detectors.

  18. High temperature refractive indices of GaN

    Liu, C.; Stepanov, S.; Gott, A.; Shields, P.A.; Zhirnov, E.; Wang, W.N. [Department of Physics, University of Bath, Bath, BA2 7AY (United Kingdom); Steimetz, E.; Zettler, J.T. [LayTec, Helmholtzstr. 13-14, 10587 Berlin (Germany)

    2006-06-15

    Undoped GaN (u-GaN) films were grown by low pressure metalorganic vapour phase epitaxy (LP-MOVPE) on sapphire substrates. In situ optical monitoring was applied to the growth process either using a LayTec EpiR-DA TT spectroscopic reflectometer or Filmetrics F30. Refractive indices of u-GaN films at 1060 C were obtained in a spectral range from 370-900 nm. A peak at 412{+-}5 nm in refractive index spectra was observed, which most likely corresponds to the band-gap of hexagonal GaN at a temperature of 1060 C. Refractive indices below this band-gap are fitted well to the first-order Sellmeier formula. As an example of the applications of the refractive indices, the effective film thicknesses of GaN during the resumption from 3 dimensional (3D) to 2 dimensional (2D) growth have been calculated from the spectra recorded by a LayTec system using the optical constants obtained. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Bakteriochlorophyllvorstufen und Pigment-Protein-Komplexe in Rhodospirillum rubrum ST3 und GN11

    Hammel, Jörg U.

    2006-01-01

    In der vorliegenden Arbeit wurden zwei Mutanten des Alpha-Proteobakteriums Rhodospirillum rubrum untersucht, die im Bakteriochlorophyll-Biosyntheseweg unterbrochen sind, um einen Beitrag zum genaueren Verständnis der Biosynthese dieser Moleküle und der einzelnen daran beteiligten Schritte zu liefern. Von den beiden Stämmen ST3 und GN11 wurden die ins Kulturmedium ausgeschiedenen Pigmente aufgereinigt und spektroskopisch analysiert. Ebenfalls wurden sowohl von ST3, als auch von GN11 die in int...

  20. Computerspielgewalt und Aggression: Längsschnittliche Untersuchung von Selektions- und Wirkungseffekten

    Staude-Müller, Frithjof

    2011-01-01

    Auf Grundlage sozialkognitiver Aggressionsmodelle wurde die Beziehung zwischen Computerspielgewohnheiten und der Aggressionsneigung sowie Verzerrungen in der sozialen Informationsverarbeitung untersucht. Dazu wurden 499 Schüler/innen weiterführender Schulen (6.-8. Kl. Gymnasium, Haupt- und Realschule) in zwei Erhebungen mit einem Intervall von einem Jahr befragt. Mit hierarchischen Regressionsanalysen wurden Wirkungs- und Selektionseffekte geprüft, wobei relevante Drittvariablen (Monitoring u...

  1. Zu den Grundlagen der visuellen Soziologie: Wahrnehmen und Sehen, Beobachten und Betrachten

    Bachleitner, Reinhard; Weichbold, Martin

    2015-01-01

    In diesem Beitrag werden die visuellen Modi des Wahrnehmens – das Sehen, Beobachten und Betrachten – in ihrem Wesen skizziert, und die doppelte Theorieabhängigkeit von Wahrnehmungsprozessen wird thematisiert. Dabei zeigt sich, dass mehrere offene methodologische und erkenntnistheoretische Fragen durch die Differenzierung des Wahrnehmungsvorgangs in drei Stufen (reines Sehen, kognitive Repräsentation, Transformation des Perzepts in Worte) sowie die Differenzierung der Wahrnehmungsmodi in jewei...

  2. Intermediale Synchronisation zwischen Volltext und Film und ihre Realisierung in Hybrideditionen

    Bülow, Gilles

    2017-01-01

    Diese Arbeit behandelt die theoretische Erfassung und prototypische Erzeugung komplexer Musterdokumente mit synchronisiertem »Volltext« und »Bewegtbild«. Dabei werden wesentliche Randbedingungen für die Dokumentengliederung ermittelt. Diese Randbedingungen erlauben es dann, unterhalb der Plattformebene (des »reinen« Buchs und des »reinen« Films) neue multimediale Hybrideditionen auf Basis elektronischer Publikationsformate als Ausgabeplattform »sinnvoll« zu generieren. Empirisch wird der F...

  3. Die Kunst des Intavolierens: Gebundenheit und Freiheit

    Ring, Johannes

    2003-12-01

    Full Text Available A big part of 16th century keyboard repertory was intabulated vocal music; arrangements of motets, sets of masses and chansons. Marcant and sometimes little known examples show the different functions of intabulations: repertoire for the organists (liturgical function, music of delight and pedagogical functions. As a part of Ars Organistum intabulations were the basis of professional musical studies, learning to improvise organ music and to compose music. Masters like H. Scheidemann, the both Gabrielis, J. de Lublin, P. Philips, the both Cabezóns, some English and French anonym composers demonstrate that intabulations are much more than keyboard reductions - artful arrangements with their own life and character on the way to artful paraphrases. The intentions of the composers / arrangers in connection with the possibilities of the keyboard instruments definite the character and the step of transforming a vocal set in a (new piece of keyboard music.

    [de] Ein großer Teil des Musikrepertoires für Tasteninstrumente im 16. Jahrhundert bestand aus intavolierter Vokalmusik - Bearbeitungen von Motetten, Messsätzen und Chansons. Markante und teilweise wenig bekannte Beispiele zeigen verschiedene Funktionen der Intavolierungen. Zu nennen sind das Organistenrepertoire (liturgisches Umfeld, die Musik zur Erbauung und Unterhaltung und die pädagogische Funktion. Als Bestandteil der Ars Organistum waren Intavolierungen wichtig um professionell das Improvisieren von Musik und das Komponieren zu erlernen. Exemplarisch dokumentieren besonders H. Scheidemann, die beiden Gabrielis, J. de Lublin, P. Philips, die beiden Cabezóns und einige anonyme Komponisten aus England und Frankreich, dass ihre Kunst des Intavolierens weit über den Übertragungsmodus hinausgeht, bis hin zum virtuosen Arrangement und zur kunstvollen Paraphrase. Die Intentionen der Komponisten in Verbindung mit den Möglichkeiten der Tasteninstrumente pr

  4. Kommunikation und Lernen in partizipativen kulturellen und medialen Räumen

    Elke Zobl

    2012-12-01

    Full Text Available Eine der interessantesten Transformationen in der Jugendkultur seit den 1990er-Jahren ist die steigende Zahl vor allem an Mädchen und jungen Frauen, die zu aktiven kulturellen Produzentinnen wurden. In diesem Artikel wird argumentiert, dass sie mit ihren eigenen kulturellen Produktionen und Netzwerken neue soziale und mediale Räume öffnen, die durch eine partizipative Kultur, selbst-organisiertes Lernen in informellen Kontexten und lokale, transnationale und virtuelle Vernetzung und Kommunikation geprägt sind. Ziel dieses Artikels ist es, das Kommunizieren und Lernen in partizipativen kulturellen (bzw. sozialen und medialen Räumen am Beispiel queer-feministischer Festivals – sogenannter „Ladyfeste“ – darzustellen und ihre Bedeutung in (medien-pädagogischen Kontexten zu diskutieren.One of the most interesting transformations in youth culture since the 1990s is the growing number of girls and young women as active cultural producers. By creating their own cultural productions and networks, this article argues, that they open up new cultural (i. e. social and media spaces which are characterized by a participatory culture, self-organised learning and local, transnational and virtual networks and communication. Taking the example of queer-feminist festivals (so called “Ladyfests”, the aim of this article is to discuss communication and learning in participatory cultural and media spaces and their meaning in the context of (media-pedagogy.

  5. PHP und MySQL der Web-Baukasten fur Einsteiger und Individualisten

    Damaschke, Giesbert

    2015-01-01

    Sie haben schon eigene Webseiten gebaut und mochten diese nun mit Funktionen ausstatten, fur die Sie PHP und MySQL benotigen? Giesbert Damaschke zeigt Ihnen in diesem Buch, wie Sie das schaffen. Schritt fur Schritt erlernen Sie die benotigten Programmier- und Datenbankgrundlagen - immer im Rahmen von typischen dynamischen Anwendungen. So erheben und speichern Sie zum Beispiel mit Formularen Kontaktdaten, prufen Benutzereingaben, erstellen Menus, richten einen Besucherzahler ein, verschicken E-Mails mit PHP oder entwickeln sogar einen eigenen Blog. Alle Codebeispiele werden ausfuhrlich erklart,

  6. Wirkungen eines Bifidojoghurts mit Laktulose und eines konventionellen Joghurts auf Darmphysiologie und bakterielle Metaboliten als Risikomodulatoren der Kolonkarzinogenese sowie Darmflora und Blutlipide bei gesunden Erwachsenen

    Gerlach, Stefanie

    2007-01-01

    Hintergrund: Probiotische und synbiotische Milchprodukte zählen zu den "funktionellen Lebensmitteln", denen im Vergleich zu herkömmlichen Produkten ein gesundheitsfördernder Zusatznutzen zugeschrieben wird. Dabei wird diskutiert, ob die Gesundheit bereits gesunder Personen noch optimierbar ist, ob und in welcher Weise die Darmflora gezielt "günstig" modifiziert werden kann und/oder ob diese Manipulation zu messbaren gesundheitsfördernden Veränderungen metabolischer und systemischer Biomarker ...

  7. Editorial: Theoriebildung in Mediendidaktik und Wissensmanagement

    Michael Kerres

    2002-10-01

    Full Text Available Das Internet trägt massgeblich zur Entstehung einer neuen Lern- und Wissenskultur bei und ist mittlerweile Gegenstand einer ganzen Reihe von Projekten in der Erziehungswissenschaft. So wird zum Beispiel der Frage nachgegangen, welche Möglichkeiten der Strukturierung und Gestaltung von Lernmaterialien am besten geeignet sind, um Lernprozesse anzuregen, wie die interpersonale Kommunikation im Internet durch didaktische Gestaltungsmassnahmen gefördert werden können oder wie die entfernte Betreuung von Lernenden über das Netz funktioniert. Zunehmend wird dabei auch der Übergang bedeutsam zwischen didaktisch aufbereiteten Lernangeboten, wie sie die Mediendidaktik traditionell beschäftigt, und dem Austausch von nicht didaktisch aufbereiteten Informationen in Organisationen, wie es im Bereich des Wissensmanagements diskutiert wird. In diesen Projekten werden vielfach Detailfragen behandelt, und isoliert, ohne Bezug zu grundlegenden Theoriefragen untersucht. Es mangelt an einer genuin mediendidaktischen Theoriediskussion, die einen übergreifenden Bezugsrahmen aus erziehungswissenschaftlicher Perspektive liefert. In der Vergangenheit ist die Mediendidaktik von Seiten einer «kritischen» Medienpädagogik zeitweise skeptisch beäugt und in ihrer Existenz grundlegend infrage gestellt worden. In der aktuellen Diskussion wird gerne auf lerntheoretische Ansätze zurückgegriffen, die Lernen als aktiven Vorgang der individuellen und kooperativen Wissenskonstruktion begreifen. Doch Wissens- und Lerntheorien ersetzen keine mediendidaktische Modell- und Theoriebildung, die Perspektiven für eine Gestaltung zukünftiger Lernwelten liefert und dabei zum Beispiel sowohl bildungstheoretische Überlegungen als auch Konzepte des instructional design einbezieht. In dem ersten Teil dieser Ausgabe geht es um theoretische Perspektiven der Mediendidaktik. So diskutiert der Artikel von Michael Kerres und Claudia de Witt den Beitrag der Positionen von Behaviorismus

  8. Symmetriebrechung und Emergenz in der Kosmologie.

    Mainzer, K.

    Seit der Antike wird der Aufbau des Universums mit einfachen und regulären (symmetrischen) Grundstrukturen verbunden. Diese Annahme liegt selbst noch den Standardmodellen der relativistischen Kosmologie zugrunde. Demgegenüber läßt sich die Emergenz neuer Strukturen von den Elementarteilchen über Moleküle bis zu den komplexen Systemen des Lebens als Symmetriebrechung verstehen. Symmetriebrechung und strukturelle Komplexität bestimmen die kosmische Evolution. Damit zeichnet sich ein fachübergreifendes Forschungsprogramm von Physik, Chemie und Biologie ab, in dem die Evolution des Universums untersucht werden kann.

  9. Die Ware Buch und die Philologie

    Bernhard Hurch

    2017-10-01

    Full Text Available Die im 19. Jahrhundert sich verändernden Produktionsbedingungen für Druckwerke (Buchdruck, Satz, Papier, Bindung wirkten katalysierend auf die Fachkonstitution und Institutionalisierung der Philologien. Hier steht der tatsächliche Buchmarkt im Vordergrund der Darstellung, das Käuferpublikum und die Voraussetzungen des Vertriebs. Dazu gehören auch die Rezension als entstehende Textsorte und die rasch arbeitenden Rezensionsorgane. F.-R. Hausmann wurde in den letzten Jahren unentbehrlicher Mitarbeiter dieses im Rahmen des Grazer Schuchardt-Projekts "Netzwerk des Wissens" angesiedelten Ansatzes.

  10. Fluchen und Flamen, um ein Mann zu sein? Die Verknüpfung von Geschlecht und Sprache durch Vorurteile

    Nicola Döring

    2001-11-01

    Full Text Available Die hier besprochene Monographie der Linguistin Anja Gottburgsen beschäftigt sich theoretisch und empirisch mit sprachbezogenen Geschlechterstereotypen, also mit unseren Vorstellungen darüber, ob und wie Männer und Frauen jeweils in spezifischer und distinkter Weise sprachlich kommunizieren. Im Theorieteil der Arbeit wird der aktuelle Stand der soziolinguistischen und sozialpsychologischen Diskussion zu Geschlecht, Sprachverhalten und Stereotypisierung kritisch referiert und die Bedeutung von sprachbezogenen Geschlechterstereotypen erläutert. Im empirischen Teil berichtet die Autorin die Ergebnisse von drei Fragebogen-Studien mit deutschsprachigen Studierenden. Es zeigt sich, dass bei Studierenden unabhängig von Geschlecht und Geschlechtsrollenorientierung stereotype Vorstellungen über das sprachliche Verhalten von Männern und Frauen verbreitet sind.

  11. Enhanced field emission of ZnO nanoneedle arrays via solution etching at room temperature

    Ma, Huanming; Qin, Zhiwei; Wang, Zaide

    2017-01-01

    ZnO nanoneedle arrays (ZnO nns) were synthesized by a facile two-step solution-phase method based on the etching of pre-synthesized ZnO nanowire arrays (ZnO nws) with flat ends at room temperature. Field emission measurement results showed that the turn-on electronic fields of ZnO nns and nws wer...

  12. Control of strain in GaN by a combination of H2 and N2 carrier gases

    Yamaguchi, Shigeo; Kariya, Michihiko; Kosaki, Masayoshi; Yukawa, Yohei; Nitta, Shugo; Amano, Hiroshi; Akasaki, Isamu

    2001-01-01

    We study the effect of a combination of N 2 and H 2 carrier gases on the residual strain and crystalline properties of GaN, and we propose its application to the improvement of crystalline quality of GaN/Al 0.17 Ga 0.83 N multiple quantum well (MQW) structures. GaN was grown with H 2 or N 2 carrier gas (H 2 - or N 2 - GaN) on an AlN low-temperature-deposited buffer layer. A (0001) sapphire substrate was used. N 2 - GaN was grown on H 2 - GaN. The total thickness was set to be 1.5 μm, and the ratio of N 2 - GaN thickness to the total thickness, x, ranged from 0 to 1. With increasing x, the tensile stress in GaN increased. Photoluminescence intensity at room temperature was much enhanced. Moreover, the crystalline quality of GaN/Al 0.17 Ga 0.83 N MQW was much higher when the MQW was grown with N 2 on H 2 - GaN than when it was grown with H 2 on H 2 - GaN. These results were due to the achievement of control of strain in GaN using a combination of N 2 - GaN and H 2 - GaN. [copyright] 2001 American Institute of Physics

  13. Synthesis, optical properties and residual strain effect of GaN nanowires generated via metal-assisted photochemical electroless etching

    Najar, Adel; Shafa, Muhammad; Anjum, Dalaver H.

    2017-01-01

    Herein, we report on the studies of GaN nanowires (GaN NWs) prepared via a metal-assisted photochemical electroless etching method with Pt as the catalyst. It has been found that etching time greatly influences the growth of GaN NWs. The density

  14. Si Complies with GaN to Overcome Thermal Mismatches for the Heteroepitaxy of Thick GaN on Si.

    Tanaka, Atsunori; Choi, Woojin; Chen, Renjie; Dayeh, Shadi A

    2017-10-01

    Heteroepitaxial growth of lattice mismatched materials has advanced through the epitaxy of thin coherently strained layers, the strain sharing in virtual and nanoscale substrates, and the growth of thick films with intermediate strain-relaxed buffer layers. However, the thermal mismatch is not completely resolved in highly mismatched systems such as in GaN-on-Si. Here, geometrical effects and surface faceting to dilate thermal stresses at the surface of selectively grown epitaxial GaN layers on Si are exploited. The growth of thick (19 µm), crack-free, and pure GaN layers on Si with the lowest threading dislocation density of 1.1 × 10 7 cm -2 achieved to date in GaN-on-Si is demonstrated. With these advances, the first vertical GaN metal-insulator-semiconductor field-effect transistors on Si substrates with low leakage currents and high on/off ratios paving the way for a cost-effective high power device paradigm on an Si CMOS platform are demonstrated. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. [Das Bild und die Wahrnehmung der Stadt und der städtischen Gesellschaft im Hanseraum im Mittelalter und in der frühen Neuzeit] / Juhan Kreem

    Kreem, Juhan

    2009-01-01

    Arvustus: Das Bild und die Wahrnehmung der Stadt und der städtischen Gesellschaft im Hanseraum im Mittelalter und in der frühen Neuzeit. hrsg. v. Roman Czaja. Torun, 2004. Torunis 2002. aastal toimunud konverentsi materjalid. Projekti "Pilt ja linn" raames ilmunud publikatsioonide loendit saab näha aadressil http://www.historiaurbium.org/english/attivita_images_en.html.

  16. Structural and magnetic investigation of dilute magnetic semiconductors based on GaN and ZnO

    Kammermeier, Tom

    2010-01-19

    The two wide band gap dilute magnetic semiconductors (DMS) Gd:GaN and Co:ZnO are among the most favored materials for spintronic applications. Despite intense research efforts during the last years, the origin of the magnetic order is still under debate. This work reports structural and magnetic investigations on these DMS materials employing several complementary techniques. The X-ray linear dichroism (XLD) has been used to gain element-specific insight into the local structure of dopants and cations. X-ray diffraction (XRD) was used to probe the global structural properties. Magnetic characterization by superconducting quantum interference device (SQUID) has been complemented by electron spin resonance (ESR) and X-ray magnetic circular dichroism (XMCD). Gd:GaN samples were fabricated by focused-ion-beam (FIB) implantation and molecular beam epitaxy (MBE). Room temperature ferromagnetic-like behavior as found for some of our samples by SQUID could not be reliably reproduced. Instead XMCD measurements at the Gd L{sub 3}-edge reveal paramagnetic behavior of the dopant. Additionally a possible magnetic polarization of Ga atoms of the host crystal is shown to be too small to explain the total magnetization of these samples. In some samples the formation of Gd and GdN clusters was evidenced by ESR measurements but it can only account for low temperature ferromagnetic-like behavior. Intrinsic room temperature ferromagnetism of this material as seen by SQUID cannot be confirmed by any other technique - neither ESR nor XMCD. Co:ZnO samples used for this work were predominantly grown by reactive magnetron sputtering (RMS). As shown by XLD analysis, 95% of the Co atoms are incorporated on substitutional Zn-sites in samples of best structural quality. These samples consistently show paramagnetic behavior as found by SQUID, XMCD and ESR. RMS growth of Co:ZnO with reduced oxygen partial pressure yields a magnetic behavior known from ferromagnetic nanoclusters. The X-ray absorption near edge spectroscopy (XANES) and XMCD at the Co K-edge support an increased fraction of Co atoms with metallic character in these samples. A reduced XLD signal indicates less substitutional Co-atoms. These samples were subject to annealing procedures either conducted under O{sub 2} atmosphere or high vacuum (HV) conditions. While the latter strongly enhances ferromagnetic-like properties, they vanish upon O{sub 2} annealing. XANES and XLD analyses show that non-substitutional Co atoms are oxidized to Co{sub 3}O{sub 4} by annealing in an O{sub 2} atmosphere, whereas HV annealing increases the fraction of a metallic Co phase. ESR measurements consistently show signatures of superparamagnetic ensembles at elevated temperatures (>60 K) and isotropic spectra of blocked magnetic moments of nanoparticles at low temperatures. Samples of high structural quality, i.e. with a large fraction of substitutional Co, are inert to annealing procedures. (orig.)

  17. Diagnostik und Therapie der kutanen Androgenisierung im klimakterischen Übergang sowie in der Peri- und Postmenopause: Hirsutismus und Alopezie

    Geisthövel F

    2012-01-01

    Full Text Available Die weibliche Androgenisierung umfasst ein weites Spektrum an heterogenen Dysfunktionen und Erkrankungen. Um die Therapieprinzipien des Hirsutismus sowie der Alopecia androgenetica während des klimakterischen Übergangs („menopausal transition“ [MT] und der Peri-/Postmenopause zu erfassen, ist es sinnvoll, sich auf eine Gruppe von androgenisierten Patientinnen zu beschränken, bei der die Haut pathogenetisch im Fokus liegt. Solch eine klar definierte Patientengruppe, die „funktionell kutane Androgenisierung“ (FCA, kann meist schon über die Diagnostikebene 1 (Screening-Ebene unseres Klassifikations-Algorithmus diagnostiziert werden. Der Ferriman-Gallwey-Index bzw. eine modifizierte Sinclair-Scale dienen zur Gradeinteilung von Hirsutismus bzw. Alopezie. Die ausgeprägte endokrine Dynamik während der MT ist hormondiagnostisch zu beachten. Wachsepilation und Lasertherapie sind vielfältig eingesetzte topischmechanische bzw. -physikalische Therapieverfahren. Eine topische Behandlung des Hirsutismus kann auch mit Eflornithin-Creme durchgeführt werden, die den Effekt einer Lasertherapie unterstützt. Minoxidil-Lösung gilt als Mittel der ersten Wahl bei der topischen Therapie der Alopecia androgenetica. Steroidale Präparate, welche aus der kontrazeptiven Kombination von Ethinylestradiol und antiandrogenen Gestagenen (AA bestehen, sind therapeutische Prinzipien bei androgenisierten Patientinnen in der MT, sie sind hingegen in der Postmenopause kontraindiziert. Die orale Einnahme von Spironolacton und/oder Finasterid, beides nicht-steroidale Antiandrogene, ist während der MT unter sicherer Kontrazeption und jene von Spironolacton für die Alopezie in der Postmenopause gut geeignet. Die Einnahme von Kombinationsprapäraten, welche die nicht-kontrazeptiven natürlichen Östrogene und AA enthalten, sind für die Behandlung der FCA bei Patientinnen indiziert, die zusätzlich unter klimakterischen und peri-/postmenopausalen Störungen leiden

  18. Barrier characteristics of Pt/Ru Schottky contacts on n-type GaN ...

    Pt/Ru Schottky rectifiers; n-type GaN; temperature–dependent electrical properties; inhomogeneous barrier heights .... a 2 μm thick Si-doped GaN films which were grown by .... ted values of ap using (9) for two Gaussian distributions of bar-.

  19. Hole-induced d"0 ferromagnetism enhanced by Na-doping in GaN

    Zhang, Yong; Li, Feng

    2017-01-01

    The d"0 ferromagnetism in wurtzite GaN is investigated by the first-principle calculations. It is found that spontaneous magnetization occurs if sufficient holes are injected in GaN. Both Ga vacancy and Na doping can introduce holes into GaN. However, Ga vacancy has a high formation energy, and is thus unlikely to occur in a significant concentration. In contrast, Na doping has relatively low formation energy. Under N-rich growth condition, Na doping with a sufficient concentration can be achieved, which can induce half-metallic ferromagnetism in GaN. Moreover, the estimated Curie temperature of Na-doped GaN is well above the room temperature. - Highlights: • Hole-induced ferromagnetism in GaN is confirmed. • Both Ga Vacancy and Na-doping can introduce hole into GaN. • The concentration of Ga vacancy is too low to induce detectable ferromagnetism. • Na-doped GaN is a possible ferromagnet with a high curie-temperature.

  20. Luminescence evolution of porous GaN thin films prepared via UV-assisted electrochemical etching

    Cheah, S.F.; Lee, S.C.; Ng, S.S.; Yam, F.K.; Abu Hassan, H.; Hassan, Z.

    2015-01-01

    Porous gallium nitride (GaN) thin films with different surface morphologies and free carriers properties were fabricated from Si-doped GaN thin films using ultra-violet assisted electrochemical etching approach under various etching voltages. Fluctuation of luminescence signals was observed in the photoluminescence spectra of porous GaN thin films. Taking advantage of the spectral sensitivity of infrared attenuated total reflection spectroscopy on semiconductor materials, roles of free carriers and porous structure in controlling luminescence properties of GaN were investigated thoroughly. The results revealed that enhancement in luminescence signal is not always attained upon porosification. Although porosification is correlated to the luminescence enhancement, however, free carrier is the primary factor to enhance luminescence intensity. Due to unavoidable significant reduction of free carriers from Si-doped GaN in the porosification process, control of etching depth (i.e., thickness of porous layer formed from the Si-doped layer) is critical in fabricating porous GaN thin film with enhanced luminescence response. - Highlights: • Various pore morphologies with free carrier properties are produced by Si-doped GaN. • Free carriers are important to control the luminescence signal of porous GaN. • Enhancement of luminescence signal relies on the pore depth of Si-doped layer

  1. Synthesis and cathodoluminescence of Sb/P co-doped GaN nanowires

    Wang, Zaien; Liu, Baodan; Yuan, Fang; Hu, Tao; Zhang, Guifeng; Dierre, Benjamin; Hirosaki, Naoto; Sekiguchi, Takashi; Jiang, Xin

    2014-01-01

    Sb/P co-doped Gallium Nitride (GaN) nanowires were synthesized via a simple chemical vapor deposition (CVD) process by heating Ga 2 O 3 and Sb powders in NH 3 atmosphere. Scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDS) measurements confirmed the as-synthesized products were Sb/P co-doped GaN nanowires with rough morphology and hexagonal wurtzite structure. Room temperature cathodoluminescence (CL) demonstrated that an obvious band shift of GaN nanowires can be observed due to Sb/P co-doping. Possible explanation for the growth and luminescence mechanism of Sb/P co-doped GaN nanowires was discussed. Highlight: • Sb/P co-doped GaN nanowires were synthesized through a well-designed multi-channel chemical vapor deposition (CVD) process. • Sb/P co-doping leads to the crystallinity deterioration of GaN nanowires. • Sb/P co-doping caused the red-shift of GaN nanowires band-gap in UV range. • Compared with Sb doping, P atoms are more easy to incorporate into the GaN lattice

  2. Structural effects of field emission from GaN nanofilms on SiC substrates

    Chen, Cheng-Cheng; Wang, Ru-Zhi, E-mail: wrz@bjut.edu.cn; Zhu, Man-Kang; Yan, Hui [College of Materials Science and Engineering, Beijing University of Technology, 100 Pingleyuan, Chaoyang District, Beijing 100124 (China); Liu, Peng [Department of Physics Tsinghua University, Tsinghua-Foxconn Nanotechnology Research Center, Beijing 100084 (China); Wang, Bi-Ben [College of Chemistry and Chemical Engineering, Chongqing University of Technology, Chongqing 400054 (China)

    2014-04-21

    GaN nanofilms (NFs) with different structures are grown on SiC substrates by pulsed laser deposition under different conditions. The synthesized GaN NFs are studied by X-ray diffraction, field-emission (FE) scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The GaN NFs are composed of diversified GaN nanoparticles with a diameter of 9–38 nm, thickness of 10–50 nm, and roughness of 0.22–13.03 nm. FE from the GaN NFs is structure dependent, which is explained by stress changing the band gap of the NFs. By structure modulation, the turn-on field of GaN NFs can be as low as 0.66 V/μm at a current density of 1 μA/cm{sup 2}, with a current density of up to 1.1 mA/cm{sup 2} at a field of 4.18 V/μm. Fowler-Nordheim curves of some samples contain multiple straight lines, which originate from the structural change and diversification of GaN nanoparticles under an applied field. Overall, our results suggest that GaN NFs with excellent FE properties can be prepared on SiC substrates, which provides a new route to fabricate high-efficiency FE nanodevices.

  3. GaN and LED structures grown on pre-patterned silicon pillar arrays

    Li, Shunfeng; Fuendling, Soenke; Soekmen, Uensal; Merzsch, Stephan; Neumann, Richard; Peiner, Erwin; Wehmann, Hergo-Heinrich; Waag, Andreas [Institut fuer Halbleitertechnik, TU Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Hinze, Peter; Weimann, Thomas [Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig (Germany); Jahn, Uwe; Trampert, Achim; Riechert, Henning [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvoigteiplatz 5-7, 10117 Berlin (Germany)

    2010-01-15

    GaN nanorods (or nanowires) have attracted great interest in a variety of applications, e.g. high-efficiency light emitting diodes, monolithic white light emission and optical interconnection due to their superior properties. In contrast to the mostly investigated self-assembled growth of GaN nanorods, we performed GaN nanorod growth by pre-patterning of the Si substrates. The pattern was transferred to Si substrates by photolithography and cryo-temperature inductively-coupled plasma etching. These Si templates then were used for further GaN nanorod growth by metal-organic vapour phase epitaxy (MOVPE). The low temperature AlN nucleation layer had to be optimized since it differs from its 2D layer counterpart on the surface area and orientations. We found a strong influence of diffusion processes, i.e. the GaN grown on top of the Si nanopillars can deplete the GaN around the Si pillars. Transmission electron microscopy measurements demonstrated clearly that the threading dislocations bend to the side facets of the pyramidal GaN nanostructures and terminate. Cathodoluminescence measurements reveal a difference of In composition and/or thickness of InGaN quantum wells on the different facets of the pyramidal GaN nanostructures. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Selective area growth of GaN rod structures by MOVPE: Dependence on growth conditions

    Li, Shunfeng; Fuendling, Soenke; Wang, Xue; Erenburg, Milena; Al-Suleiman, Mohamed Aid Mansur; Wei, Jiandong; Wehmann, Hergo-Heinrich; Waag, Andreas [Institut fuer Halbleitertechnik, TU Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Bergbauer, Werner [Institut fuer Halbleitertechnik, TU Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Osram Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg (Germany); Strassburg, Martin [Osram Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg (Germany)

    2011-07-15

    Selective area growth of GaN nanorods by metalorganic vapor phase epitaxy is highly demanding for novel applications in nano-optoelectronic and nanophotonics. Recently, we report the successful selective area growth of GaN nanorods in a continuous-flow mode. In this work, as examples, we show the morphology dependence of GaN rods with {mu}m or sub-{mu}m in diameters on growth conditions. Firstly, we found that the nitridation time is critical for the growth, with an optimum from 90 to 180 seconds. This leads to more homogeneous N-polar GaN rods growth. A higher temperature during GaN rod growth tends to increase the aspect ratio of the GaN rods. This is due to the enhanced surface diffusion of growth species. The V/III ratio is also an important parameter for the GaN rod growth. Its increase causes reduction of the aspect ratio of GaN rods, which could be explained by the relatively lower growth rate on (000-1) N-polar top surface than it on {l_brace}1-100{r_brace} m-planes by supplying more NH{sub 3} (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Gadolinium-Based GaN for Neutron Detection with Gamma Discrimination

    2016-06-01

    Gadolinium-Based GaN for Neutron Detection with Gamma Discrimination Distribution Statement A. Approved for public release; distribution is...Final Technical Report BRBAA08-Per5-Y-1-2-0030 Title: “Gadolinium-Based GaN for Neutron Detection with Gamma Discrimination ” Grant...Analysis  .............................................................................................  23   6.   Gamma-ray Discrimination

  6. TEM characterization of catalyst- and mask-free grown GaN nanorods

    Schowalter, M; Aschenbrenner, T; Kruse, C; Hommel, D; Rosenauer, A

    2010-01-01

    Catalyst- and mask-free grown GaN nanorods have been investigated using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and energy filtered transmission electron microscopy (EFTEM). The nanorods were grown on nitridated r-plane sapphire substrates in a molecular beam epitaxy reactor. We investigated samples directly after the nitridation and after the overgrowth of the structure with GaN. High resolution transmission electron microscopy (HRTEM) and EFTEM revealed that AlN islands have formed due to nitridation. After overgrowth, the AlN islands could not be observed any more, neither by EFTEM nor by Z-contrast imaging. Instead, a smooth layer consisting of AlGaN was found. The investigation of the overgrown sample revealed that an a-plane GaN layer and GaN nanorods on top of the a-plane GaN have formed. The nanorods reduced from top of the a-plane GaN towards the a-plane GaN/sapphire interface suggesting that the nanorods originate at the AlN islands found after nitridation. However, this could not be shown unambiguously. The number of threading dislocations in the nanorods was very low. The analysis of the epitaxial relationship to the a-plane GaN showed that the nanorods grew along the [000-1] direction, and the [1-100] direction of the rods was parallel to the [0001] direction of the a-plane GaN.

  7. Electronic and Optical Properties of Two-Dimensional GaN from First-Principles.

    Sanders, Nocona; Bayerl, Dylan; Shi, Guangsha; Mengle, Kelsey A; Kioupakis, Emmanouil

    2017-12-13

    Gallium nitride (GaN) is an important commercial semiconductor for solid-state lighting applications. Atomically thin GaN, a recently synthesized two-dimensional material, is of particular interest because the extreme quantum confinement enables additional control of its light-emitting properties. We performed first-principles calculations based on density functional and many-body perturbation theory to investigate the electronic, optical, and excitonic properties of monolayer and bilayer two-dimensional (2D) GaN as a function of strain. Our results demonstrate that light emission from monolayer 2D GaN is blueshifted into the deep ultraviolet range, which is promising for sterilization and water-purification applications. Light emission from bilayer 2D GaN occurs at a similar wavelength to its bulk counterpart due to the cancellation of the effect of quantum confinement on the optical gap by the quantum-confined Stark shift. Polarized light emission at room temperature is possible via uniaxial in-plane strain, which is desirable for energy-efficient display applications. We compare the electronic and optical properties of freestanding two-dimensional GaN to atomically thin GaN wells embedded within AlN barriers in order to understand how the functional properties are influenced by the presence of barriers. Our results provide microscopic understanding of the electronic and optical characteristics of GaN at the few-layer regime.

  8. Conduction, reverse conduction and switching characteristics of GaN E-HEMT

    Sørensen, Charlie; Lindblad Fogsgaard, Martin; Christiansen, Michael Noe

    2015-01-01

    In this paper switching and conduction characterization of the GS66508P-E03 650V enhancement mode gallium nitride (GaN) transistor is described. GaN transistors are leading edge technology and as so, their characteristics are less than well documented. The switching characteristics are found using...

  9. The investigation of stress in freestanding GaN crystals grown from Si substrates by HVPE.

    Lee, Moonsang; Mikulik, Dmitry; Yang, Mino; Park, Sungsoo

    2017-08-17

    We investigate the stress evolution of 400 µm-thick freestanding GaN crystals grown from Si substrates by hydride vapour phase epitaxy (HVPE) and the in situ removal of Si substrates. The stress generated in growing GaN can be tuned by varying the thickness of the MOCVD AlGaN/AlN buffer layers. Micro Raman analysis shows the presence of slight tensile stress in the freestanding GaN crystals and no stress accumulation in HVPE GaN layers during the growth. Additionally, it is demonstrated that the residual tensile stress in HVPE GaN is caused only by elastic stress arising from the crystal quality difference between Ga- and N-face GaN. TEM analysis revealed that the dislocations in freestanding GaN crystals have high inclination angles that are attributed to the stress relaxation of the crystals. We believe that the understanding and characterization on the structural properties of the freestanding GaN crystals will help us to use these crystals for high-performance opto-electronic devices.

  10. Struktur und Dynamik in der Netzwerkanalyse

    Trier, M.; Stegbauer, C.; Häußling, R.

    2010-01-01

    Die Methodik der sozialen Netzwerkanalyse (SNA) ist auf die quantitative Untersuchung von strukturellen Mustern in Graphen ausgerichtet. Die Analyse arbeitet gegenwärtig meist mit Daten aus einer einmaligen und kumulierten Erhebung der Netzwerkstruktur zu einem bestimmten Zeitpunkt. Diese

  11. Satellitenbewegung, band III: Natiirliche und gesteuerte bewegung.

    Jochim, E. F.

    2014-12-01

    Im dritten Band der Satellitenbewegung werden in fortlaufender Nummerierung einige für Untersuchungen der Bewegung der künstlichen Satelliten wichtige Grundlagen der Astrodynamik mit ausführlichen mathematischen Formelsystemen behandelt. Dazu zählen die unterschiedlichen Aspekte der Bewegung der natürlichen Himmelskörper, die Steuerung und Kontrolle von künstlichen Objekten, und insbesondere die für eine Satellitenbahnanalyse wichtigen physikalischen Beeinflussungen einer Satellitenbewegung. Mathematisch entscheidend ist die Wahl geeigneter Bahnparameter, die ein bestimmtes Bewegungsproblem widerspruchsfrei und singularitätenfrei zu behandeln gestatten. Für die Behandlung routinemäßiger Aufgabenstellungen der Satellitenbewegung, in erster Linie einer präzisen Bahnbestimmung und Bahnverbesserung, kann auf eine Fülle von lehrbuchartigen Monographien verwiesen werden, so dass diese Problematik in der vorliegenden Arbeit nur angedeutet werden soll.

  12. Riots ‒ Anmerkungen zu Begriff und Konzept

    Dieter Rucht

    2016-05-01

    Full Text Available Ausgehend von sozialwissenschaftlichen Befunden werden zunächst ältere massenpsychologische Deutungen von riots zurückgewiesen. Die überwiegende Mehrzahl der im riot Aufbegehrenden entspricht nicht dem Typus entfremdeter und verängstigter Einzeltäter_innen. Zweitens benennt der Beitrag eine Reihe von Bedingungen für das Zustandekommen von riots. Drittens wird der Begriff ‚riot‘ in formaler Hinsicht näher bestimmt und einerseits von moderateren Formen des Protests, andererseits von geplanter und organisierter Gewalt (z. B. Terrorismus abgegrenzt. Abschließend wird die Frage des politischen Gehalts von riots und deren normativen Grundlagen erörtert.

  13. Lattice-Symmetry-Driven Epitaxy of Hierarchical GaN Nanotripods

    Wang, Ping

    2017-01-18

    Lattice-symmetry-driven epitaxy of hierarchical GaN nanotripods is demonstrated. The nanotripods emerge on the top of hexagonal GaN nanowires, which are selectively grown on pillar-patterned GaN templates using molecular beam epitaxy. High-resolution transmission electron microscopy confirms that two kinds of lattice-symmetry, wurtzite (wz) and zinc-blende (zb), coexist in the GaN nanotripods. Periodical transformation between wz and zb drives the epitaxy of the hierarchical nanotripods with N-polarity. The zb-GaN is formed by the poor diffusion of adatoms, and it can be suppressed by improving the ability of the Ga adatoms to migrate as the growth temperature increased. This controllable epitaxy of hierarchical GaN nanotripods allows quantum dots to be located at the phase junctions of the nanotripods and nanowires, suggesting a new recipe for multichannel quantum devices.

  14. Positron annihilation study of Pd contacts on impurity-doped GaN

    Lee, Jong-Lam; Kim, Jong Kyu; Weber, Marc H.; Lynn, Kelvin G.

    2001-01-01

    Pd contacts on both n-type and p-type GaN were studied using positron annihilation spectroscopy, and the results were used to interpret the role of Ga vacancies on the band bending below the contacts. The concentration of Ga vacancy in Si-doped GaN was higher than that in the Mg-doped one. In Si-doped GaN, implanted positrons were annihilated at the nearer surface region and the interface of Pd/n-type GaN was detected by positrons clearly shifted toward the surface of Pd. This suggests that Ga vacancies could act as an interface state, pinning the Fermi level at the interface of Pd with GaN, leading to the production of a negative electric field below the interface. [copyright] 2001 American Institute of Physics

  15. Secondary ion mass spectrometry analysis of In-doped p-type GaN films

    Chiou, C.Y.; Wang, C.C.; Ling, Y.C.; Chiang, C.I.

    2003-01-01

    SIMS was used to investigate the isoelectronic In-doped p-type GaN films. The growth rate of the p-type GaN film decreased with increasing Mg and In doping. The Mg saturation in GaN was 3.55x10 19 atoms/cm 3 . The role of In as surfactant was evaluated by varying In concentrations and it was observed that the surface appeared smooth with increasing In incorporation. The Mg solubility in p-type GaN improved to 0.0025% molar ratio of the GaN with In incorporation. The In concentration results observed in neutron activation analysis (NAA) were found to be higher by a factor of 2.88 than that observed in SIMS and can be attributed to the difference in sensitivity of the two techniques. Good linearity in the results was observed from both techniques

  16. Prospects for the application of GaN power devices in hybrid electric vehicle drive systems

    Su, Ming; Chen, Chingchi; Rajan, Siddharth

    2013-01-01

    GaN, a wide bandgap semiconductor successfully implemented in optical and high-speed electronic devices, has gained momentum in recent years for power electronics applications. Along with rapid progress in material and device processing technologies, high-voltage transistors over 600 V have been reported by a number of teams worldwide. These advances make GaN highly attractive for the growing market of electrified vehicles, which currently employ bipolar silicon devices in the 600–1200 V class for the traction inverter. However, to capture this billion-dollar power market, GaN has to compete with existing IGBT products and deliver higher performance at comparable or lower cost. This paper reviews key achievements made by the GaN semiconductor industry, requirements of the automotive electric drive system and remaining challenges for GaN power devices to fit in the inverter application of hybrid vehicles. (invited review)

  17. Prospects for the application of GaN power devices in hybrid electric vehicle drive systems

    Su, Ming; Chen, Chingchi; Rajan, Siddharth

    2013-07-01

    GaN, a wide bandgap semiconductor successfully implemented in optical and high-speed electronic devices, has gained momentum in recent years for power electronics applications. Along with rapid progress in material and device processing technologies, high-voltage transistors over 600 V have been reported by a number of teams worldwide. These advances make GaN highly attractive for the growing market of electrified vehicles, which currently employ bipolar silicon devices in the 600-1200 V class for the traction inverter. However, to capture this billion-dollar power market, GaN has to compete with existing IGBT products and deliver higher performance at comparable or lower cost. This paper reviews key achievements made by the GaN semiconductor industry, requirements of the automotive electric drive system and remaining challenges for GaN power devices to fit in the inverter application of hybrid vehicles.

  18. Spin injection in epitaxial MnGa(111)/GaN(0001) heterostructures

    Zube, Christian; Malindretos, Joerg; Watschke, Lars; Zamani, Reza R.; Disterheft, David; Ulbrich, Rainer G.; Rizzi, Angela; Iza, Michael; Keller, Stacia; DenBaars, Steven P.

    2018-01-01

    Ferromagnetic MnGa(111) layers were grown on GaN(0001) by molecular beam epitaxy. MnGa/GaN Schottky diodes with a doping level of around n = 7 × 1018 cm-3 were fabricated to achieve single step tunneling across the metal/semiconductor junction. Below the GaN layer, a thin InGaN quantum well served as optical spin detector ("spin-LED"). For electron spin injection from MnGa into GaN and subsequent spin transport through a 45 nm (70 nm) thick GaN layer, we observe a circular polarization of 0.3% (0.2%) in the electroluminescence at 80 K. Interface mixing, spin polarization losses during electrical transport in the GaN layer, and spin relaxation in the InGaN quantum well are discussed in relation with the low value of the optically detected spin polarization.

  19. A density functional theory study of the TMG adsorption on the GaN surface

    Ptasinska, Maria; Soltys, Jakub; Piechota, Jacek [Interdisciplinary Centre for Materials Modelling, University of Warsaw, ul. Pawinskiego 5a, 02-106 Warszawa (Poland); Krukowski, Stanislaw [Interdisciplinary Centre for Materials Modelling, University of Warsaw, ul. Pawinskiego 5a, 02-106 Warszawa (Poland); Institute of High Pressure Physics, Polish Academy of Sciences, ul. Sokolowska 29/37, 01-142 Warsaw (Poland)

    2011-07-01

    TMG (trimetylogallium) and NH{sub 3} (ammonia) are widely used reactants in the metal organic chemical vapor deposition (MOCVD) technique used in the growth of the GaN thin films. We have recently examined theoretically, with the help of the density functional theory (DFT), TMG adsorption on the GaN(0001) surface in order to study formation of bonds between Ga and N. Dangling bonds on the GaN(0001) surface were saturated with the hydrogen atoms. The slab polarization, which is due to the dangling bonds present on the GaN(0001) surface, and energy of the system in the vicinity of TMG was computed for different distances between the surface atoms and TMG. We also studied TMG diffusion on the GaN surface. As a result, the energy path for diffusion from Top N to Hollow was obtained.

  20. [Die baltischen Lande im Zeitalter der Reformation und Konfessionalisierung : Livland, Estland, Ösel, Ingermanland, Kurland und Lettgallen. Stadt, Land und Konfession 1500-1721. Teil 1.] / Jürgen Beyer

    Beyer, Jürgen, 1965-

    2010-01-01

    Arvustus: Die baltischen Lande im Zeitalter der Reformation und Konfessionalisierung. Livland, Estland, Ösel, Ingermanland, Kurland und Lettgallen. Stadt, Land und Konfession 1500-1721. Teil 1. (Münster : Aschendorff, 2009)

  1. Matthias Asche, Werner Buchholz, Anton Schindling (Hrsg.): Die baltischen Lande im Zeitalter der Reformation und Konfessionalisierung. Livland, Estland, Ösel, Ingermanland, Kurland und Lettgallen. Stadt, Land und Konfession 1500-1721. Tl. 2, Münste

    Wittram, Heinrich, 1931-

    2011-01-01

    Arvustus: Die baltischen Lande im Zeitalter der Reformation und Konfessionalisierung : Livland, Estland, Ösel, Ingermanland, Kurland und Lettgallen : Stadt, Land und Konfession 1500-1721. Teil 2. Münster, 2010

  2. Benjamin Ortmeyer: Mythos und Pathos statt Logos und Ethos, Zu den Publikationen führender Erziehungswissenschaftler in der NS-Zeit: Eduard Spranger, Herman Nohl, Erich Weniger und Peter Petersen, Weinheim / Basel: Beltz 2009 [Rezension

    Zimmer, Hasko

    2010-01-01

    Rezension von: Benjamin Ortmeyer: Mythos und Pathos statt Logos und Ethos, Zu den Publikationen führender Erziehungswissenschaftler in der NS-Zeit: Eduard Spranger, Herman Nohl, Erich Weniger und Peter Petersen, Weinheim / Basel: Beltz 2009, 606 S.

  3. The humanities and innovation; Geisteswissenschaften und Innovationen

    Meyer-Krahmer, F.; Lange, S. [eds.] [Fraunhofer-Institut fuer Systemtechnik und Innovationsforschung (ISI), Karlsruhe (Germany)

    1999-07-01

    The book discusses the concept and process of innovation from the perspective of linguistics, historical sciences, and philosophy. Inter-disciplinary relations become evident when it comes to research into human consciousness and behaviour, dealing with language and texts, or the growing significance of the historical sciences with respect to topical developments in technology and the economy. The cross-disciplinary discourse between the various disciplines of the humanities, natural sciences, technology and the social sciences, and between science, industry and public administration has revealed a new playing field for cross-disciplinary dialogue and cooperative action that may be rewarding. The book discusses aspects such as the innovative potential of the humanities, or their possible contributions to innovation, their capabilities to generate innovative changes in the way of thinking, to prepare the ground for innovation, strengthen innovative abilities, and on the other hand to hold aloof and keep a watchful eye on innovation. (orig./CB) [German] Das Buch beschaeftigt sich mit Innovationen aus sprachwissenschaftlicher, historischer und philosophischer Sicht. Querbezuege werden deutlich, wenn es um die Erforschung von Bewusstsein und Verhalten, dem Umgang mit Sprache und Texten oder die wachsende Bedeutung der historischen Wissenschaften fuer die aktuelle technologische und wirtschaftliche Entwicklung geht. Das Gespraech ueber Fachgrenzen hinweg zwischen den verschiedenen Disziplinen der Geisteswissenschaften, der Natur-, Technik- und Sozialwissenschaften und zwischen Wissenschaft, Industrie und oeffentlicher Verwaltung hat Aufgaben deutlich gemacht, die die Zusammenarbeit lohnen. In diesem Band wird diskutiert, welches Innovationspotential die Geisteswissenschaften bieten, wie diese zu Innovationen beitragen, Innovationen im Denken hervorbringen, Vorarbeiten fuer Innovationen leisten, die Innovationsfaehigkeit staerken und die kritische Distanz zu Innovationen

  4. Neue Technologien und Erziehung/Bildung

    Norbert Meder

    2015-03-01

    Full Text Available Es wird gezeigt, dass Computertechnologie zur pädagogischen Aufgabe wird, weil es sich um eine Kulturtechnik handelt. Ausgehend vom Begriff der Bildung als Ausbildung eines Verhältnisses zu mir selbst, zu anderen und zur Welt wird Computertechnologie als Problemlösungsautomat, Sprachentwicklungsmaschine, Simulationsmaschine, Kommunikationsmaschine, Bildschirmgestaltungsmaschine, Schlüsselloch und Superzeichenmaschine analysiert. Die Analyse zeigt, daß Computertechnologie ein neues Bildungsideal erforderlich macht: Den Sprachspieler. Der Sprachspieler kennt sein doppelt reflexives Verhältnis zu sich selbst, zu anderen und zur Welt und beherrscht so das Spiel mit der Sprache zur Ausübung von Macht und Gewalt in der Informationsgesellschaft. Der Text geht in folgenden Schritten vor: Zunächst werden mit den Begriffen "Kulturtechnik" und "Bildung" die Prinzipien der Analyse bestimmt. Anschließend wird eine Sachanalyse der Computertechnologie durchgeführt und die gefundenen Eigenschaften jeweils in Relation zum Kulturtechnik- und Bildungsbegriff gesetzt. Computer technology becomes a challenge for education if it is understood as a cultural technology. Starting with the term bildung as the formation of relations to my self, to others and the world, computer technology is analysed as problem solving machine, language development machine, simulation machine, communication machine, screen design machine, keyhole, and super sign machine. It is shown, that computertechnology reqiures a new ideal for bildung: the language player. The language player knows his double reflective relation to his self, to others and the world and thus rules the game with language that is used to excercise power and force in the information society. The text argues in the following steps: At first the principles of the analyses are defined with the terms cultural technology and bildung. Susequently, computer technology is analysed. The identified qualities are finally

  5. Medien als Lernform und die Trimediale Redaktion

    Wolf Hilzensauer

    2015-01-01

    Full Text Available Der vorliegende Artikel beschreibt ein Konzept für eine handlungsorientierte Medienpädagogik im Bildungsbereich. Im Mittelpunkt steht dabei die SO!-Campusredaktion, die als Methode für expansives Lernen die Möglichkeit bietet, unabhängig von Thema oder Medium die Verantwortung für den Lernprozess in die Hände der Lernenden zu legen. Der Dokumentation von Reflexion über den Lernprozess wird dabei eine besondere Bedeutung zugesprochen. Gleichzeitig werden unterschiedliche mediale Gestaltungsmöglichkeiten (Audio/Radio, Video/Fernsehen und Zeitung – sowohl als Print- als auch als Onlinemedium vorgestellt, die durch das Konzept BYOD – bring your own device – auch einfach und niederschwellig im Bildungskontext umsetzbar sind. Dadurch ergeben sich innovative Möglichkeiten, einen Lernprozess sichtbar zu machen und gleichzeitig eine Grundlage für eine alternative Leistungsbeurteilung anzubieten. Die SO!-Campusredaktion wird derzeit an der Pädagogischen Hochschule Salzburg in Kooperation mit dem Communitysender FS1 und der Radiofabrik entwickelt und erprobt. Community Medien nehmen als MedienpartnerInnen eine bedeutende Stellung ein: Durch ihren offenen Zugang zu Know How und Equipment sowie durch die Möglichkeit, Medienproduktionen über die verfügbaren Distibutionskanäle (Radiofrequenz oder Sendeplatz einer breiten Bevölkerung zugänglich zu machen, gewinnt die Medienpädagogik einen wichtigen Mehrwert in ihrer schulischen und außerschulischen Arbeit. (Dieser Artikel knüpft an den Artikel "BYOD, Smartphonefilme und webbasierte Videoschnittprogramme" der Medienimpulse, Ausgabe 2/2014, an.

  6. Polen, Deutschland, die EU und Russland

    Wilkiewicz, Zbigniew

    2009-01-01

    Besonders seit dem EU-Beitritt Polens ist es um die deutsch-polnischen Beziehungen nicht besonders gut bestellt. In den vergangenen Jahren hat man sich in erster Linie an bilateralen Konflikten abgearbeitet und keine gemeinsame Europapolitik betrieben. Im Beitrag wird diese Entwicklung rekonstruiert und danach gefragt, ob es angesichts einer solchen Entwicklung Aussichten auf die Wiederherstellung der deutsch-polnischen Interessengemeinschaft gibt oder die Interessen beider Staaten so stark d...

  7. Professionelle Literaturrecherche und -verwaltung im Web [Praxisbericht

    Schaffert, Sandra

    2007-01-01

    In diesem Beitrag werden Hinweise für eine professionelle Literaturrecherche und -verwaltung im World Wide Web gegeben. Dazu werden für die pädagogische Ausbildung und Forschung einschlägige Literaturdatenbanken genannt, insbesondere solche, die kostenlos zu nutzen sind. Außerdem werden Tipps für clevere Recherchen sowie eine kurze Übersicht über Web-Werkzeuge zur Verwaltung von bibliografischen Angaben gegeben. (DIPF/Orig.)

  8. Ontologische und epistemologische Grundlagen qualitative Forschung

    Vasilachis de Gialdino, Irene

    2009-01-01

    Dieser Beitrag zielt auf das Herzstück qualitativer Forschung, indem gezeigt wird, dass es – aus der Perspektive einer Epistemologie des "gewussten" Subjekts – erforderlich ist, zunächst deren ontologische und dann deren epistemologische Grundlagen neu zu überdenken. Hierzu zeichne ich in einem ersten Schritt den Weg von einer Epistemologie des "bewussten" Subjekts hin zu einer Epistemologie des "gewussten" Subjekts nach, die ich als neuen (und nicht exklusiven) Weg des Wissens vorschlage. Da...

  9. Generation Y: Arbeitsbezogene Erwartungen und affektives Commitment

    Giry, Nathalie

    2016-01-01

    Die Erwartungen der Generation Y zu kennen, ist wichtig für Unternehmen, die Leistungsträger aus dieser Generation langfristig binden wollen. Die affektive Bindung der Generation Y gegenüber einer Organisation, der Zusammenhang zwischen der Erfüllung arbeitsbezogener Erwartungen und affektivem Commitment sowie der Fluktuationsneigung der Generation Y werden empirisch überprüft. Die Generation Y hat hohe Erwartungen an Unternehmenswerte und Unternehmenskultur. Es wurden Zusammenhänge zwischen ...

  10. Climate and transportation; Klima und Verkehr

    Fabian, P. [Muenchen Univ. (Germany). Lehrstuhl fuer Bioklimatologie und Immissionsforschung

    1996-06-01

    This short contribution discusses emissions of the transportation sector, i.e. the global problem of carbon dioxide emissions and the regional ecological problem of nitric oxide, VOC and CO photosmog emissions. Reduction strategies are discussed. (RHM) [Deutsch] Im vorliegenden, kurzen Beitrag wird auf die Emissionen des Verkehrs, die Emissionen von CO{sub 2} - ein globales Klimaproblem - sowie die Emission von NO{sub x}, VOCs und CO-Photosmog als regionals Umwelt- und Klimaproblem eingegangen. Abschliessend werden Reduktionsstrategien dieskutiert. (RHM)

  11. Entscheidungsprozesse und Partizipation in der Stadtentwicklung Dresdens

    Schmidt-Lerm, Susanne

    2010-01-01

    Untersucht wurde die Auseinandersetzung um das Autobahnbauvorhaben A 17 Dresden - Prag zwischen 1990 und 1995 als ein Beispiel der Stadtentwicklung Dresdens. Seit 1935 als Reichsautobahn ins Sudetenland geplant, sollte dieses Verkehrsprojekt nach 1990 als „Lückenschluß im europäischen Autobahnnetz“ umgesetzt werden. Angesichts des hohen Konfliktpotentials erlangte der Fall überregionale Aufmerksamkeit und Beispielcharakter für die neuen Bundesländer. Die Kontroverse gipfelte im ersten Bürgere...

  12. Kolloide in externen elektrischen und magnetischen Feldern

    Zhao, Jinyu

    2011-01-01

    Kolloide spielen eine wichtige Rolle in der Forschung. In vielen Anwendungsgebieten, beispielsweise Optik, Mikro- und Nanoelektronik, Mikrofluidik, Automobilindustrie, Mineralölindustrie, dienen sie sowohl als Testsubstanzen als auch "Werkzeug", um grundlegende Vorgänge zu erforschen. In der Grundlagenforschung dienen kolloidale Suspensionen als Modelle für atomare und molekulare Systeme. In der vorliegenden Arbeit habe ich Suspensionen aus festen Kolloiden (auch als Partikel bezeichnet) in e...

  13. Kurz zum Klima: Schiefergas und Fracking

    Triebswetter, Ursula; Lippelt, Jana

    2012-01-01

    Das Verfahren zur Gewinnung von Erdgas aus wenig durchlässigem Gestein, das in den USA erfundene und dort bereits weit verbreitete »Hydraulic Fracturing«, kurz Fracking, ist aus Umweltgründen umstritten. Der Beitrag skizziert zunächst die Technologie des Fracking, umreißt dann die weltweiten Lagerstätten und beschreibt die umweltpolitische Problematik. Abschließend wird die aktuelle Situation in Deutschland dargestellt.

  14. Reducing ZnO nanoparticles toxicity through silica coating

    Sing Ling Chia

    2016-10-01

    Full Text Available ZnO NPs have good antimicrobial activity that can be utilized as agents to prevent harmful microorganism growth in food. However, the use of ZnO NPs as food additive is limited by the perceived high toxicity of ZnO NPs in many earlier toxicity studies. In this study, surface modification by silica coating was used to reduce the toxicity of ZnO NPs by significantly reducing the dissolution of the core ZnO NPs. To more accurately recapitulate the scenario of ingested ZnO NPs, we tested our as synthesized ZnO NPs in ingestion fluids (synthetic saliva and synthetic gastric juice to determine the possible forms of ZnO NPs in digestive system before exposing the products to colorectal cell lines. The results showed that silica coating is highly effective in reducing toxicity of ZnO NPs through prevention of the dissociation of ZnO NPs to zinc ions in both neutral and acidic condition. The silica coating however did not alter the desired antimicrobial activity of ZnO NPs to E. coli and S. aureus. Thus, silica coating offered a potential solution to improve the biocompatibility of ZnO NPs for applications such as antimicrobial agent in foods or food related products like food packaging. Nevertheless, caution remains that high concentration of silica coated ZnO NPs can still induce undesirable cytotoxicity to mammalian gut cells. This study indicated that upstream safer-by-design philosophy in nanotechnology can be very helpful in a product development.

  15. Kinetic-limited etching of magnesium doping nitrogen polar GaN in potassium hydroxide solution

    Jiang, Junyan; Zhang, Yuantao; Chi, Chen; Yang, Fan; Li, Pengchong; Zhao, Degang; Zhang, Baolin; Du, Guotong

    2016-01-01

    Graphical abstract: - Highlights: • Effects of Mg doping on wet etching of N-polar GaN are illustrated and analysed. • Etching process model of Mg-doped N-polar GaN in KOH solution is purposed. • It is found that Mg doping can induce tensile strain in N-polar GaN film. • N-polar p-GaN film with a hole concentration of 2.4 × 10"1"7 cm"−"3 is obtained. - Abstract: KOH based wet etchings were performed on both undoped and Mg-doped N-polar GaN films grown by metal-organic chemical vapor deposition. It is found that the etching rate for Mg-doped N-polar GaN gets slow obviously compared with undoped N-polar GaN. X-ray photoelectron spectroscopy analysis proved that Mg oxide formed on N-polar GaN surface is insoluble in KOH solution so that kinetic-limited etching occurs as the etching process goes on. The etching process model of Mg-doped N-polar GaN in KOH solution is tentatively purposed using a simplified ideal atomic configuration. Raman spectroscopy analysis reveals that Mg doping can induce tensile strain in N-polar GaN films. Meanwhile, p-type N-polar GaN film with a hole concentration of 2.4 × 10"1"7 cm"−"3 was obtained by optimizing bis-cyclopentadienyl magnesium flow rates.

  16. Kinetic-limited etching of magnesium doping nitrogen polar GaN in potassium hydroxide solution

    Jiang, Junyan; Zhang, Yuantao; Chi, Chen; Yang, Fan; Li, Pengchong [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Zhao, Degang [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Science, PO Box 912, Beijing 100083 (China); Zhang, Baolin; Du, Guotong [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China)

    2016-01-01

    Graphical abstract: - Highlights: • Effects of Mg doping on wet etching of N-polar GaN are illustrated and analysed. • Etching process model of Mg-doped N-polar GaN in KOH solution is purposed. • It is found that Mg doping can induce tensile strain in N-polar GaN film. • N-polar p-GaN film with a hole concentration of 2.4 × 10{sup 17} cm{sup −3} is obtained. - Abstract: KOH based wet etchings were performed on both undoped and Mg-doped N-polar GaN films grown by metal-organic chemical vapor deposition. It is found that the etching rate for Mg-doped N-polar GaN gets slow obviously compared with undoped N-polar GaN. X-ray photoelectron spectroscopy analysis proved that Mg oxide formed on N-polar GaN surface is insoluble in KOH solution so that kinetic-limited etching occurs as the etching process goes on. The etching process model of Mg-doped N-polar GaN in KOH solution is tentatively purposed using a simplified ideal atomic configuration. Raman spectroscopy analysis reveals that Mg doping can induce tensile strain in N-polar GaN films. Meanwhile, p-type N-polar GaN film with a hole concentration of 2.4 × 10{sup 17} cm{sup −3} was obtained by optimizing bis-cyclopentadienyl magnesium flow rates.

  17. Crystal Structures of GaN Nanodots by Nitrogen Plasma Treatment on Ga Metal Droplets

    Yang-Zhe Su

    2018-06-01

    Full Text Available Gallium nitride (GaN is one of important functional materials for optoelectronics and electronics. GaN exists both in equilibrium wurtzite and metastable zinc-blende structural phases. The zinc-blende GaN has superior electronic and optical properties over wurtzite one. In this report, GaN nanodots can be fabricated by Ga metal droplets in ultra-high vacuum and then nitridation by nitrogen plasma. The size, shape, density, and crystal structure of GaN nanodots can be characterized by transmission electron microscopy. The growth parameters, such as pre-nitridation treatment on Si surface, substrate temperature, and plasma nitridation time, affect the crystal structure of GaN nanodots. Higher thermal energy could provide the driving force for the phase transformation of GaN nanodots from zinc-blende to wurtzite structures. Metastable zinc-blende GaN nanodots can be synthesized by the surface modification of Si (111 by nitrogen plasma, i.e., the pre-nitridation treatment is done at a lower growth temperature. This is because the pre-nitridation process can provide a nitrogen-terminal surface for the following Ga droplet formation and a nitrogen-rich condition for the formation of GaN nanodots during droplet epitaxy. The pre-nitridation of Si substrates, the formation of a thin SiNx layer, could inhibit the phase transformation of GaN nanodots from zinc-blende to wurtzite phases. The pre-nitridation treatment also affects the dot size, density, and surface roughness of samples.

  18. Computational study of GaAs1-xNx and GaN1-yAsy alloys and arsenic impurities in GaN

    Laaksonen, K; Komsa, H-P; Arola, E; Rantala, T T; Nieminen, R M

    2006-01-01

    We have studied the structural and electronic properties of As-rich GaAs 1-x N x and N-rich GaN 1-y As y alloys in a large composition range using first-principles methods. We have systematically investigated the effect of the impurity atom configuration near both GaAs and GaN sides of the concentration range on the total energies, lattice constants and bandgaps. The N (As) atoms, replacing substitutionally As (N) atoms in GaAs (GaN), cause the surrounding Ga atoms to relax inwards (outwards), making the Ga-N (Ga-As) bond length about 15% shorter (longer) than the corresponding Ga-As (Ga-N) bond length in GaAs (GaN). The total energies of the relaxed alloy supercells and the bandgaps experience large fluctuations within different configurations and these fluctuations grow stronger if the impurity concentration is increased. Substituting As atoms with N in GaAs induces modifications near the conduction band minimum, while substituting N atoms with As in GaN modifies the states near the valence band maximum. Both lead to bandgap reduction, which is at first rapid but later slows down. The relative size of the fluctuations is much larger in the case of GaAs 1-x N x alloys. We have also looked into the question of which substitutional site (Ga or N) As occupies in GaN. We find that under Ga-rich conditions arsenic prefers the substitutional N site over the Ga site within a large range of Fermi level values

  19. RANK und RANKL - Vom Knochen zum Mammakarzinom

    Sigl V

    2012-01-01

    Full Text Available RANK („Receptor Activator of NF-κB“ und sein Ligand RANKL sind Schlüsselmoleküle im Knochenmetabolismus und spielen eine essenzielle Rolle in der Entstehung von pathologischen Knochenveränderungen. Die Deregulation des RANK/RANKL-Systems ist zum Beispiel ein Hauptgrund für das Auftreten von postmenopausaler Osteoporose bei Frauen. Eine weitere wesentliche Funktion von RANK und RANKL liegt in der Entwicklung von milchsekretierenden Drüsen während der Schwangerschaft. Dabei regulieren Sexualhormone, wie zum Beispiel Progesteron, die Expression von RANKL und induzieren dadurch die Proliferation von epithelialen Zellen der Brust. Seit Längerem war schon bekannt, dass RANK und RANKL in der Metastasenbildung von Brustkrebszellen im Knochengewebe beteiligt sind. Wir konnten nun das RANK/RANKLSystem auch als essenziellen Mechanismus in der Entstehung von hormonellem Brustkrebs identifizieren. In diesem Beitrag werden wir daher den neuesten Erkenntnissen besondere Aufmerksamkeit schenken und diese kritisch in Bezug auf Brustkrebsentwicklung betrachten.

  20. Finanzkrise, Sozialkrise und ungleiche Entwicklung in Südkorea und Thailand

    Schmidt, Johannes Dragsbæk

    2008-01-01

    Zehn Jahre ist es inzwischen her, dass die Finanzkrisen in Südostasien, Russland und Lateinamerika die Weltwirtschaft erschütterten. Angesichts dieses "Jubiläums" und der aktuellen US-Finanzkrise ist es Zeit für eine Bestandsaufnahme: Lektionen gelernt? Drei Fragestellungen stehen im Mittelpunkt...

  1. Methoden der Kommunikations- und Mediengeschichte: die Wechselwirkung unterschiedlicher Verfahren als Spezifikum der Kommunikations- und Mediengeschichte

    Hemels, J.; Averbeck-Lietz, S.; Klein, P.; Meyen, M.

    2009-01-01

    Dieser Beitrag verfolgt zwei Ziele: Einerseits wird beabsichtigt, nicht his-torisch geschulte Kommunikationswissenschaftler mit Grundlagen und Praxis kommunikationswissenschaftlicher Forschung vertraut zu ma-chen. Andererseits wird für ein Zusammenspiel zwischen führenden For-schungsansätzen und

  2. Alexander Kratochvil. Aufbruch und Rückkehr: Ukrainische und tschechische Prosa im Zeichen der Postmoderne.

    Marko Pavlyshyn

    2015-01-01

    Full Text Available Alexander Kratochvil. Aufbruch und Rückkehr: Ukrainische und tschechische Prosa im Zeichen der Postmoderne. [Venturing Forth and Coming Back: Ukrainian and Czech Prose in the Context of Postmodernity.] Berlin: Kulturverlag Kadmos, 2013. 311 pp. Bibliography. Index. Paper.

  3. Ab initio investigations of the strontium gallium nitride ternaries Sr 3GaN3 and Sr6GaN5: Promising materials for optoelectronic

    Goumri-Said, Souraya

    2013-05-31

    Sr3GaN3 and Sr6GaN5 could be promising potential materials for applications in the microelectronics, optoelectronics and coating materials areas of research. We studied in detail their structural, elastic, electronic, optical as well as the vibrational properties, by means of density functional theory framework. Both of these ternaries are semiconductors, where Sr3GaN3 exhibits a small indirect gap whereas Sr6GaN5 has a large direct gap. Indeed, their optical properties are reported for radiation up to 40 eV. Charge densities contours, Hirshfeld and Mulliken populations, are reported to investigate the role of each element in the bonding. From the mechanical properties calculation, it is found that Sr6GaN5 is harder than Sr3GaN3, and the latter is more anisotropic than the former. The phonon dispersion relation, density of phonon states and the vibrational stability are reported from the density functional perturbation theory calculations. © 2013 IOP Publishing Ltd.

  4. Review: Michael Kerres & Reinhard Keil-Slawik (Hrsg.) (2005). Hochschulen im digitalen Zeitalter: Innovationspotenziale und Strukturwandel

    Hoidn, Sabine

    2008-01-01

    In dem vorliegenden Kongressband setzen sich fünfunddreißig internationale Expertinnen und Experten aus Wissenschaft und Praxis mit Möglichkeiten und Rahmenbedingungen des Einsatzes von Informations- und Kommunikationstechnologien in Hochschulen auseinander. Die Beiträge adressieren aktuelle und zukünftige Herausforderungen, denen sich Hochschulen zu stellen haben, und präsentieren einen bunten Strauß an (bisher) erfolgreichen Projekten und Praxiserfahrungen. Infolge knapper werdender Ressour...

  5. Aussteigen aus dem Rechtsextremismus: Foto-Praxis, bildwissenschaftliche Analyse und Ausstellungsarbeit als Methoden individueller Reflexion und des wissenschaftlichen und (sozialpädagogischen Kompetenzerwerbs

    Ulrike Pilarczyk

    2013-06-01

    Full Text Available Der Beitrag zeigt die medienpädagogischen und bildwissenschaftlichen Dimensionen eines zeitlich und thematisch gestaffelten Projektes auf. Ausgangspunkt war das in den Jahren 2009/10 von der Organisation EXIT-Deutschland in Berlin mit Aussteigern/-innen aus der rechtsextremen Szene initiierte Fotoprojekt «Lebensbilder». Die im Rahmen biografisch orientierter, medien- und sozialpädagogischer Fallarbeit entstandenen Fotos wurden als Prozess individueller Bilderzeugung und als Mittel zur Reflexion der jeweiligen Lebenssituation der Aussteiger(innen verstanden und eingesetzt. Eine Ausstellung schloss diese erste Phase des hier beschriebenen Projektes ab. Dem Wunsch folgend, die praktischen Erfahrungen aus der Arbeit mit Fotos wissenschaftlich überprüfen zu lassen, wurden in den Jahren 2011 und 2012 mit Studierenden am erziehungswissenschaftlichen Institut der TU Braunschweig die «Lebensbilder» zunächst einer wissenschaftlichen Bildanalyse unterzogen und anschliessend in einem gestalterisch-interpretativen Projekt durch die Studierenden zu einer Ausstellung weiterentwickelt.

  6. Die Werte der Wertvermittler - Berufliches Rollenselbstverständnis und Weltanschauung von Journalistinnen und Journalisten

    Andy Kaltenbrunner

    2010-09-01

    Full Text Available Der Beitrag analysiert professionelles Selbstverständnis, Weltanschauungen und ethische Überzeugungen von Journalistinnen und Journalisten in Österreich. Auf Basis aktueller Befragungen und Studien wird die Grundstruktur des journalistischen Wertesystems skizziert und der Zusammenhang mit täglicher Berichterstattung. Der Beitrag diskutiert mögliche Konsequenzen für Zukunft des Journalismus und Qualität der Öffentlichkeit. The article focuses on the professional values, political views and ethical beliefs of Austrian journalists. Based on recent surveys we outline the basic structure of the journalistic value system in Austria and the interdependence of these values and actual reporting and we discuss possible consequences for the future of journalism as a profession and for the quality of the public sphere.

  7. Hinkelbeinchen und "little chicken's leg": deutsche und amerikanische Idiome als kommunikative Textsorten-Problematik

    Martin Wierschin

    1998-12-01

    Full Text Available Als Marin Luther 1522 seine Übersetzung des Neuen Testaments nach der griechischen Edition des Erasmus von Rotterdam abschloß, hatte er dabei zwar mit größtem Sprachgefühl nicht nur dem deutschen, sondem auch dem idiomatischen 'logos' des Griechischen "auf das Maul" gesehen. Aber er mußte in seinem "Sendbrief vom Dolmetschen" 1530 dennoch zugeben, daß selbst er - zusammen mit seinen beiden Assistenten Melanchthon und Aurogallus - sehr oft zwei bis vier Wochen lang nach einem einzigen idiomatisch treffenden Wort zu suchen hatte. Damit wird von einem eminenten Kronzeugen, nämlich vom Schöpfer des protestantischen 'Hausbuches' Lutherbibel und vom eigentlichen Begründer einer einheitlichen deutschen Schrift­ sprache, samt ihrer sprach- und literargeschichtlich wirkungsmächtigen Idiomatik, die Schwierigkeit und Problematik idiomatischer Äquivalenzen und Transferenzen zwischen den Einzelsprachen verbürgt.

  8. Neue Medien in der Lehrerausbildung. Zu angemessenen (und unangemessenen Zielen und Inhalten des Lehramtsstudiums

    Sigrid Blömeke

    2003-01-01

    Full Text Available In vier Schritten wird dem Verhältnis von Lehrerausbildung und neuen Medien nachgegangen. Zunächst werden grundsätzliche medienpädagogische Aufgaben der Lehrerausbildung herausgearbeitet, bevor das Ausbildungsprofil ihrer ersten und zweiten Phase in den Blick genommen wird. Ausgangspunkt der Theoriebildung sind professions- und institutionentheoretische Ansätze, die auf die neuen Medien bezogen werden; Konkretisierungen erfolgen an Beispielen aus der Germanistik, der Anglistik, der Geschichte und der Mathematik. Anschliessend wird der Erwerb medienpädagogischer Kompetenz durch zukünftige Lehrerinnen und Lehrer von dem Erwerb basaler Medienkompetenz als eines Elements von Allgemeinbildung abgegrenzt. Zum Schluss werden Konsequenzen für die strukturelle Gestaltung der Lehrerausbildung gezogen.

  9. ZnO quantum dots–decorated ZnO nanowires for the enhancement of antibacterial and photocatalytic performances

    Wu, Jyh Ming; Tsay, Li-Yi

    2015-01-01

    We demonstrate highly antibacterial activities for killing off Staphylococcus aureus and Escherichia coli using ZnO nanowires decorated with ZnO quantum dots (so-called ZnO QDs/NWs) under visible-light irradiation and dark conditions. The average size of the ZnO QDs is in the range of 3–5 nm; these were uniformly dispersed on the ZnO nanowires’ surface to form the ZnO QDs/NWs. A significant blue-shift effect was observed using photoluminescence (PL) spectra. The size of the ZnO QDs is strongly dependent on the material’s synthesis time. The ZnO QDs/NWs exhibited an excellent photocatalytic activity under visible-light irradiation. The ZnO QDs’ active sites (i.e. the O–H bond and Zn"2"+) accelerate the photogenerated-carrier migration from the QDs to the NWs. As a consequence, the electrons reacted with the dissolved oxygen to form oxygen ions and produced hydroperoxyl radicals to enhance photocatalytic activity. The antibacterial activities (as indicated by R-factor-inhibiting activity) of the ZnO QDs/NWs for killing off Staphylococcus aureus and Escherichia coli is around 4.9 and 5.5 under visible-light irradiation and dark conditions, respectively. The hydroxyl radicals served as an efficient oxidized agent for decomposing the organic dye and microorganism species. The antibacterial activities of the ZnO QDs/NWs in the dark may be attributed to the Zn"2"+ ions that were released from the ZnO QDs and infused into the microbial solution against the growth of bacteria thus disrupting the microorganism. The highly antibacterial and photocatalytic activity of the ZnO QDs/NWs can be well implanted on a screen window, thus offering a promising solution to inhibit the spread of germs under visible-light and dark conditions. (paper)

  10. Role of Ga vacancies in enhancing the leakage current of GaN Schottky barrier ultraviolet photodetectors

    De-Gang, Zhao; Shuang, Zhang; Wen-Bao, Liu; De-Sheng, Jiang; Jian-Jun, Zhu; Zong-Shun, Liu; Hui, Wang; Shu-Ming, Zhang; Hui, Yang; Xiao-Peng, Hao; Long, Wei

    2010-01-01

    The leakage current of GaN Schottky barrier ultraviolet photodetectors is investigated. It is found that the photodetectors adopting undoped GaN instead of lightly Si-doped GaN as an active layer show a much lower leakage current even when they have a higher dislocation density. It is also found that the density of Ga vacancies in undoped GaN is much lower than in Si-doped GaN. The Ga vacancies may enhance tunneling and reduce effective Schottky barrier height, leading to an increase of leakage current. It suggests that when undoped GaN is used as the active layer, it is necessary to reduce the leakage current of GaN Schottky barrier ultraviolet photodetector. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  11. Studie: Die Generation Y und deren organisatorische Implikationen

    Klein, Helmut

    2016-01-01

    Die vorliegende Studie betrifft die Gen. Y und ihre spezifischen Anforderungen an die Unternehmensorganisation. Im Ergebnis einer durchgeführten Befragung ist festzuhalten, dass die Gen. Y die Kernkompetenzen eines Managers verstärkt einfordert und eine hohe Betreuungsintensität verlangt. Dies hat Auswirkungen auf die Führungsspanne, Planung und Kontrolle von Aufgaben, die Gestaltung der vertikalen und horizontalen Prozesse sowie die Zusammensetzung von Teamarbeitsformen. Projektarbeit sowie ...

  12. Beginn und Dosisanpassung einer intensivierten konventionellen Insulintherapie (ICT beim Erwachsenen

    Lohr R

    2012-01-01

    Full Text Available Eine intensivierte Insulintherapie (ICT ist die Behandlung der Wahl bei Diabetes mellitus Typ 1 und auch bei vielen Menschen mit insulinpflichtigem Typ-2-Diabetes. Bei Therapiebeginn müssen individuell Insuline ausgewählt und die richtige Dosierung festgelegt werden. Im weiteren Verlauf ist dann die Anpassung der Insulintherapie an besondere Alltagssituationen wie Sport oder akute Erkrankungen vorrangig. Eine gute Patientenschulung und eine gute Zusammenarbeit zwischen Betroffenem und Behandlerteam sind entscheidend, um diese komplizierte Therapie erfolgreich umzusetzen.

  13. Informationsdesign von Bildungsportalen : Struktur und Aufbau netzbasierter Bildungsressourcen

    Panke, Stefanie

    2009-01-01

    Sowohl Unternehmen als auch Bildungseinrichtungen, Verlage, politische Organisationen, Verbände, Interessengruppen und Privatpersonen nutzen das Internet, um Informationen zu verbreiten. Die Varianz an Akteuren, Adressaten und Botschaften spiegelt sich wider in einem wachsenden Spektrum an Web-Genres: Suchmaschine, E-Commerce-Auftritt und Online-Zeitung teilen sich die Aufmerksamkeit der Leser unter anderem mit privaten Weblogs und kollaborativen Wissenssammlungen wie der Enzyklopädie Wikiped...

  14. Molekulare Systematik und Evolution der Spezies der Familie Arthrodermataceae (Dermatophyten)

    Gräser, Yvonne

    2002-01-01

    Dermatophyten sind keratinophile Pilze, d.h. sie besiedeln und infizieren die Haut und ihre Anhangsgebilde (Haare, Nägel) bei Mensch und Tier. Die derzeit häufigsten durch Dermatophyten hervorgerufenen Infektionen sind die Onychomykose, Tinea pedis, Tinea capitis und Tinea corporis. Da Antimykotika nicht bei alle Erregern von Dermatophytosen gleich wirksam sind, sollte im Vordergrund einer Behandlung zunächst die korrekte Erregerdifferenzierung stehen. Konventionell erfolgt diese Differenzier...

  15. Spurenstoffuntersuchungen zur Bildung und Ausbreitung von Wassermassen im subpolaren Nordatlantik

    Hildebrandt, Hauke

    2001-01-01

    In der vorliegenden Arbeit wurde ein umfangreicher Spurenstoffdatensatz aus dem subpolaren Nordatlantik erstellt und ausgewertet, der Tritium-, Helium- und Neon- sowie O-18-Messungen umfaßt. Das Hauptaugenmerk galt dabei der Bildung und Ausbreitung der tiefen Wassermassen und deren Variabilität auf Zeitskalen von einigen Jahren. Anhand von Tracermittelwerten, die mit Hilfe eines optimierten Interpolationsverfahrens gewonnen wurden, konnte gezeigt werden, daß die konvektive Neubildung de...

  16. Aufgabenbezogene Differenzierung und Entwicklung des verbalen Selbstkonzepts im Anfangsunterricht

    Lipowsky, Frank; Kastens, Claudia; Lotz, Miriam; Faust, Gabriele

    2011-01-01

    Die vorliegende Studie untersucht, wie sich aufgabenbezogene Differenzierung im Deutschunterricht auf die Entwicklung des verbalen Selbstkonzepts von Erst- und Zweitklässlern (Lesen und Schreiben) auswirkt. Die untersuchte Stichprobe setzt sich aus 735 Schülern des ersten Schuljahres zusammen, die 38 Klassen an staatlichen und privaten Grundschulen besuchen und die bis zum Ende des zweiten Schuljahres in ihrer Entwicklung untersucht wurden. Die Ergebnisse zeigen sowohl einen indirekten als au...

  17. Märkte und Macht der Internetkonzerne: Konzentration - Konkurrenz - Innovationsstrategien

    Dolata, Ulrich

    2014-01-01

    In diesem Aufsatz, der auf einer systematischen Auswertung von Geschäftsberichten, Dokumenten, verfügbarem empirischem Material, Literatur und Presseberichten basiert, werden die Konzentrationsprozesse auf den wesentlichen Internetmärkten so- wie die Expansions- und Innovationsstrategien der fünf führenden Konzerne Google, Facebook, Apple, Amazon und Microsoft analysiert. Die Befunde, die der Text vorstellt, sind von einer Dezentralisierung der Markt- und Demokratisierung der Innovationsproze...

  18. Arbeitszeiten von Professorinnen und Professoren in Deutschland 2016

    Weihs, Claus; Hernández Rodríguez, Tanja; Doeckel, Maximilian; Marty, Christoph; Wormer, Holger

    2018-01-01

    In dieser Studie werden belastbare Prognoseintervalle der wöchentlichen Gesamtarbeitszeit von Universitätsprofessorinnen und -professoren aus Daten einer Umfrage aus dem Jahre 2016 und a-priori Informationen aus früheren Studien bestimmt. Neben der Gesamtarbeitszeit werden auch Teilarbeitszeiten zum Beispiel für Lehre und Forschung ermittelt. Die Ergebnisse von frequentistischer und Bayesianischer Analyse werden verglichen. Aus den gültigen Fragebögen von aktiven Vollzeit arbeitenden Universi...

  19. Umfrageforschung: Entscheidungsgrundlage für Politik und Wissenschaft

    2011-01-01

    "Der vorliegende Tagungsband dokumentiert die Beiträge der wissenschaftlichen Tagung 'Umfrageforschung - Entscheidungsgrundlage für Politik und Wissenschaft', die am 30. Juni und 1. Juli 2011 gemeinsam vom Statistischen Bundesamt, dem ADM Arbeitskreis Deutscher Markt- und Sozialforschungsinstitute e.V. und der Arbeitsgemeinschaft Sozialwissenschaftlicher Institute e.V. (ASI) in Wiesbaden durchgeführt wurde." (Autorenreferat). Inhaltsverzeichnis: Christian König, Matthias Stahl, Erich Wiegand:...

  20. Reputationsorientiertes Themen- und Issues-Management : Konzeption, Regelbetrieb, Weiterentwicklung

    Fahrenbach, Christian

    2011-01-01

    Die Dissertation untersucht, wie Organisationen ein reputationsorientiertes Themen- und Issues-Management aufbauen, betreiben und weiterentwickeln können. Dazu wird das operative Modell des Issues Managements mit dem strategischen Zielkonstrukt Reputation verbunden. Zu Beginn der Arbeit beschreiben zwei Theorie-Kapitel ausführlich Relevanz und die Steuerung von Reputation und im Issues Management. Auf dieser Basis wird ein praxisorientiertes integriertes Modell entwickelt. Es beschreibt da...

  1. Thermal stability study of Cr/Au contact formed on n-type Ga-polar GaN, N-polar GaN, and wet-etched N-polar GaN surfaces

    Choi, Yunju; Kim, Yangsoo; Ahn, Kwang-Soon; Kim, Hyunsoo

    2014-01-01

    Highlights: • The Cr/Au contact on n-type Ga-polar (0 0 0 1) GaN, N-polar (0 0 0 −1) GaN, and wet-etched N-polar GaN were investigated. • Thermal annealing led to a significant degradation of contact formed on N-polar n-GaN samples. • Contact degradation was shown to be closely related to the increase in the electrical resistivity of n-GaN. • Out-diffusion of Ga and N atoms was clearly observed in N-polar samples. - Abstract: The electrical characteristics and thermal stability of a Cr/Au contact formed on n-type Ga-polar (0 0 0 1) GaN, N-polar GaN, and wet-etched N-polar GaN were investigated. As-deposited Cr/Au showed a nearly ohmic contact behavior for all samples, i.e., the specific contact resistance was 3.2 × 10 −3 , 4.3 × 10 −4 , and 1.1 × 10 −3 Ω cm 2 for the Ga-polar, flat N-polar, and roughened N-polar samples, respectively. However, thermal annealing performed at 250 °C for 1 min in a N 2 ambient led to a significant degradation of contact, i.e., the contact resistance increased by 186, 3260, and 2030% after annealing for Ga-polar, flat N-polar, and roughened N-polar samples, respectively. This could be due to the different disruption degree of Cr/Au and GaN interface after annealing, i.e., the insignificant interfacial reaction occurred in the Ga-polar sample, while out-diffusion of Ga and N atoms was clearly observed in N-polar samples

  2. Thermal stability study of Cr/Au contact formed on n-type Ga-polar GaN, N-polar GaN, and wet-etched N-polar GaN surfaces

    Choi, Yunju [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Suncheon Center, Korea Basic Science Institute, Suncheon 540-742 (Korea, Republic of); Kim, Yangsoo [Suncheon Center, Korea Basic Science Institute, Suncheon 540-742 (Korea, Republic of); Ahn, Kwang-Soon, E-mail: kstheory@ynu.ac.kr [School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 712-749 (Korea, Republic of); Kim, Hyunsoo, E-mail: hskim7@jbnu.ac.kr [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2014-10-30

    Highlights: • The Cr/Au contact on n-type Ga-polar (0 0 0 1) GaN, N-polar (0 0 0 −1) GaN, and wet-etched N-polar GaN were investigated. • Thermal annealing led to a significant degradation of contact formed on N-polar n-GaN samples. • Contact degradation was shown to be closely related to the increase in the electrical resistivity of n-GaN. • Out-diffusion of Ga and N atoms was clearly observed in N-polar samples. - Abstract: The electrical characteristics and thermal stability of a Cr/Au contact formed on n-type Ga-polar (0 0 0 1) GaN, N-polar GaN, and wet-etched N-polar GaN were investigated. As-deposited Cr/Au showed a nearly ohmic contact behavior for all samples, i.e., the specific contact resistance was 3.2 × 10{sup −3}, 4.3 × 10{sup −4}, and 1.1 × 10{sup −3} Ω cm{sup 2} for the Ga-polar, flat N-polar, and roughened N-polar samples, respectively. However, thermal annealing performed at 250 °C for 1 min in a N{sub 2} ambient led to a significant degradation of contact, i.e., the contact resistance increased by 186, 3260, and 2030% after annealing for Ga-polar, flat N-polar, and roughened N-polar samples, respectively. This could be due to the different disruption degree of Cr/Au and GaN interface after annealing, i.e., the insignificant interfacial reaction occurred in the Ga-polar sample, while out-diffusion of Ga and N atoms was clearly observed in N-polar samples.

  3. GaN Nanowire Devices: Fabrication and Characterization

    Scott, Reum

    The development of microelectronics in the last 25 years has been characterized by an exponential increase of the bit density in integrated circuits (ICs) with time. Scaling solid-state devices improves cost, performance, and power; as such, it is of particular interest for companies, who gain a market advantage with the latest technology. As a result, the microelectronics industry has driven transistor feature size scaling from 10 μm to ~30 nm during the past 40 years. This trend has persisted for 40 years due to optimization, new processing techniques, device structures, and materials. But when noting processor speeds from the 1970's to 2009 and then again in 2010, the implication would be that the trend has ceased. To address the challenge of shrinking the integrated circuit (IC), current research is centered on identifying new materials and devices that can supplement and/or potentially supplant it. Bottom-up methods tailor nanoscale building blocks---atoms, molecules, quantum dots, and nanowires (NWs)---to be used to overcome these limitations. The Group IIIA nitrides (InN, AlN, and GaN) possess appealing properties such as a direct band gap spanning the whole solar spectrum, high saturation velocity, and high breakdown electric field. As a result nanostructures and nanodevices made from GaN and related nitrides are suitable candidates for efficient nanoscale UV/ visible light emitters, detectors, and gas sensors. To produce devices with such small structures new fabrication methods must be implemented. Devices composed of GaN nanowires were fabricated using photolithography and electron beam lithography. The IV characteristics of these devices were noted under different illuminations and the current tripled from 4.8*10-7 A to 1.59*10 -6 A under UV light which persisted for at least 5hrs.

  4. Die Landschaft in der Geschichte, in der Kultur, in der Kunts und in der Stadtplanung: theoretische Annahmen und Erfahrungen

    Mario Coletta

    2013-01-01

    Full Text Available Das vorgeschlagene Thema hat das Ziel, dem Konzept der Landschaft eine neue Definition zu geben. Sie soll nicht nur als Umhuellung des staedtischen und laendlichen Territoriums gesehen werden, das besiedelt und produktiv ist, zivilisiet und natuerlich belassen, sondern wie ein lebender Koerper, wenn auch nicht bei bester Gesundheit, der trotz seines Altes noch den vielen Veraenderungen standhaelt. Veraenderungen durch Naturkatatrophen herforgerufen, und besonders durch die vielen Wunden die das Werk der Menschen ihm zugefuegt hat. Als lebendes Wesen leidet die Landschaft und freut sich in guten Zeiten, kleidert sich lieber arm, aber schicklich, als reich und anmassend: Zeuge guter und schlechter Haushaltsfuehrung, jedoch Erbe einer Geschichte die sie erhebt, die Geschichte, Literatur, Ausdruecke der Kunts, kreative Planung beseelt hat. All das ist zusammengefasst in dem Wort "Kultur", die es verdient hat, erworben zu werden, vertieft und den naeschsten Generationen weitergegeben, moeglicherweise noch bereichert von dem, das die heutige Kultur ausarbeiten kann, auch auf dem Weg der Stadtplanung.

  5. Photoluminescence enhancement from GaN by beryllium doping

    García-Gutiérrez, R.; Ramos-Carrazco, A.; Berman-Mendoza, D.; Hirata, G. A.; Contreras, O. E.; Barboza-Flores, M.

    2016-10-01

    High quality Be-doped (Be = 0.19 at.%) GaN powder has been grown by reacting high purity Ga diluted alloys (Be-Ga) with ultra high purity ammonia in a horizontal quartz tube reactor at 1200 °C. An initial low-temperature treatment to dissolve ammonia into the Ga melt produced GaN powders with 100% reaction efficiency. Doping was achieved by dissolving beryllium into the gallium metal. The powders synthesized by this method regularly consist of two particle size distributions: large hollow columns with lengths between 5 and 10 μm and small platelets in a range of diameters among 1 and 3 μm. The GaN:Be powders present a high quality polycrystalline profile with preferential growth on the [10 1 bar 1] plane, observed by means of X-ray diffraction. The three characteristics growth planes of the GaN crystalline phase were found by using high resolution TEM microscopy. The optical enhancing of the emission in the GaN powder is attributed to defects created with the beryllium doping. The room temperature photoluminescence emission spectra of GaN:Be powders, revealed the presence of beryllium on a shoulder peak at 3.39 eV and an unusual Y6 emission at 3.32eV related to surface donor-acceptor pairs. Also, a donor-acceptor-pair transition at 3.17 eV and a phonon replica transition at 3.1 eV were observed at low temperature (10 K). The well-known yellow luminescence band coming from defects was observed in both spectra at room and low temperature. Cathodoluminescence emission from GaN:Be powders presents two main peaks associated with an ultraviolet band emission and the yellow emission known from defects. To study the trapping levels related with the defects formed in the GaN:Be, thermoluminescence glow curves were obtained using UV and β radiation in the range of 50 and 150 °C.

  6. Structural properties of Ne implanted GaN

    Majid, A; Zhu, J J; Liu, W; Lu, G J; Liu, W B; Zhang, L Q; Liu, Z S; Wang, H; Zhao, D G; Zhang, S M; Jiang, D S; Wang, Y T; Yang, H [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, PO Box 912, Beijing 100083 (China); Ali, A; Israr, M [Advance Materials Physics Laboratory, Physics Department, Quaid-i-Azam University, Islamabad (Pakistan)], E-mail: abdulmajid40@yahoo.com

    2008-03-15

    We report a study on the micro-structural changes in GaN due to neon ion implantation using the x-ray diffraction and Raman scattering techniques. An implantation dose of 10{sup 14} cm{sup -2} was found unable to produce lattice deformation observable by Raman measurements. For higher doses of implantation several disorder activated Raman scattering centers were observed which corroborate the literature. A new dose dependent feature has been recorded at 1595 cm{sup -1} for higher implantation doses which is suggested to be the vibrational mode of microcavities produced in the lattice.

  7. Structural properties of Ne implanted GaN

    Majid, A; Zhu, J J; Liu, W; Lu, G J; Liu, W B; Zhang, L Q; Liu, Z S; Wang, H; Zhao, D G; Zhang, S M; Jiang, D S; Wang, Y T; Yang, H; Ali, A; Israr, M

    2008-01-01

    We report a study on the micro-structural changes in GaN due to neon ion implantation using the x-ray diffraction and Raman scattering techniques. An implantation dose of 10 14 cm -2 was found unable to produce lattice deformation observable by Raman measurements. For higher doses of implantation several disorder activated Raman scattering centers were observed which corroborate the literature. A new dose dependent feature has been recorded at 1595 cm -1 for higher implantation doses which is suggested to be the vibrational mode of microcavities produced in the lattice

  8. GaN polarity determination by photoelectron diffraction

    Romanyuk, Olexandr; Jiříček, Petr; Paskova, T.; Bieloshapka, Igor; Bartoš, Igor

    2013-01-01

    Roč. 103, č. 9 (2013), "091601-1"-"091601-4" ISSN 0003-6951 R&D Projects: GA ČR(CZ) GBP108/12/G108 Grant - others:AV ČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : GaN * photoelectron diffraction * wurtzite * surface polarity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.515, year: 2013 http://apl.aip.org/resource/1/applab/v103/i9/p091601_s1?isAuthorized=no

  9. Characterisation of Cs ion implanted GaN by DLTS

    Ngoepe, P. N. M.; Meyer, W. E.; Auret, F. D.; Omotoso, E.; Hlatshwayo, T. T.; Diale, M.

    2018-04-01

    Deep level transient spectroscopy (DLTS) was used to characterise Cs implanted GaN grown by hydride vapour phase epitaxy (HVPE). This implantation was done at room temperature using energy of 360 keV to a fluence of 10-11 cm-2. A defect with activation energy of 0.19 eV below the conduction band and an apparent capture cross section of 1.1 × 10-15 cm2 was induced. This defect has previously been observed after rare earth element (Eu, Er and Pr) implantation. It has also been reported after electron, proton and He ion implantation.

  10. Transport mechanisms in Schottky diodes realized on GaN

    Amor, Sarrah; Ahaitouf, Ali; Ahaitouf, Abdelaziz; Salvestrini, Jean Paul; Ougazzaden, Abdellah

    2017-03-01

    This work is focused on the conducted transport mechanisms involved on devices based in gallium nitride GaN and its alloys. With considering all conduction mechanisms of current, its possible to understanded these transport phenomena. Thanks to this methodology the current-voltage characteristics of structures with unusual behaviour are further understood and explain. Actually, the barrier height (SBH) is a complex problem since it depends on several parameters like the quality of the metal-semiconductor interface. This study is particularly interesting as solar cells are made on this material and their qualification is closely linked to their transport properties.

  11. Shape dependent electronic properties of wurzite GaN nanowire

    Srivastava, Pankaj, E-mail: pankajs@iiitm.ac.in; Kumar, Avaneesh, E-mail: avaneeshk7@ymail.com; Sharma, Varun, E-mail: sunny2013@gmail.com [Nanomaterials Research Group, ABV-Indian Institute of Information Technology and Management (IIITM), Gwalior-474015 (India); Jaiswal, Neeraj K., E-mail: neerajkumar.phd@gmail.com [Discipline of Physics, PDPM-Indian Institute of Information Technology, Design and Manufacturing (IIITDM), Jabalpur-482005 (India)

    2016-05-06

    In the present work, energetic stability and electronic behavior of triangular and square shaped wurzite GaN NW oriented along [1100] and [11 2 0] direction has been investigated by employing ab-initio DFT calculation. Structural analysis suggests that triangular shaped NW undergoes strong surface reconstruction compared to square shaped NW. However, binding energy reveals that square shaped NW is energetically more feasible than triangular NW. Further, from electronic band structure we observe that both structures are metallic with higher metallicity for triangular shaped NW.

  12. Game-Review: Trilogie Mass Effect 1, 2 und 3

    Karl H. Stingeder

    2013-03-01

    Full Text Available Karl Stingeder hat als Spieletester die Science Fiction Trilogie Mass Effect (1,2 und 3 rezensiert. Er berichtet von der inneren Vielfalt und dem spannenden Gameplay. Tauchen Sie ein in eine Welt, die ihnen eine lange Spielzeit garantiert und genießen Sie die Pracht dieser Kunstwerke.

  13. Klare Regeln - effiziente und effektive FMEA-Anwendung

    Schloske, Alexander

    2014-01-01

    Der Vortrag beschreibt klare Regeln zur effizienten und effektiven FMEA-Anwendung. - Denkmodelle für die verschiedenen FMEA-Arten (System-FMEA, Konstruktions-FMEA, Prozess-FMEA) - Anwendungsbereiche und FMEA-Planung - Strukturierung von FMEAs - Funktionen, Produktmerkmale und Prozessmerkmale - Risikoanalyse - Maßnahmendefinition - Risikobewertung - Präsentation von FMEAs - FMEA als "lebendes Dokument".

  14. Der Heilige Geist und die Realisierung des Glaubens in der ...

    29. Juli 2016 ... der Sprache bis hin zu den kulturellen und religiösen. Zeichensystemen, muss von dem Einzelnen empfangen und angeeignet werden. Kommunikation, auch die religiöse, verwirklicht sich ausschließlich in der Spannung von geschichtlicher Abhängigkeit und Transformation der überlieferten Gehalte im ...

  15. Die Inquisition und ihre Wahrnehmung im Alten Reich

    Alexandra Kohlhöfer

    2013-01-01

    Full Text Available Rezension von: Tribunal der Barbaren? Deutschland und die Inquisition in der Frühen Neuzeit, hg. von Albrecht Burckhardt und Gerd Schwerhoff unter Mitwirkung von Dieter R. Bauer (Konflikte und Kultur – Historische Perspektiven 25, Konstanz, München: UVK-Verl.-Ges. 2012, 450 S., ISBN 978-3-86764-371-9

  16. Biologisch-dynamische Forschung zwischen "wissenschaftlicher Weltsicht" und "Ideologie"

    Eysel, Georg

    2002-01-01

    Der Beitrag zeigt den Konflikt zwischen "wertefreier" Wissenschaft und "ganzheitlicher" Forschung auf. Ein Zusammenspiel bio-dynamischer Forschung und der Anthroposophie mit anderen Disziplinen könnte einen Beitrag zu einem neuen Wissenschaftsbegriff mit umfassender Weltanschauung leisten. Dialog, Verständnis, Toleranz, Offenheit, kritisches Hinterfragen und Mut zur sinnvollen Anpassung sind dafür notwendige Schritte.

  17. Anmerkungen zur Methode einer theologischen Wirtschafts- und Sozialethik

    Mack, Elke

    2002-01-01

    "Moderne theologische Wirtschafts- und Sozialethik sollte im Rahmen der wissenschaftstheoretischen Schritte 'Analyse, Synthese, Operationalisierung' erfolgen. Die christliche Wirtschafts- und Sozialethik erfüllt bei diesem Zuschnitt den Anspruch einer modernen theologischen Gerechtigkeitstheorie, die erstens ihr hermeneutisches Vorverständnis hinreichend klärt und analytisch an Problemstellungen herangeht, die zweitens auf der Basis eines hypothetischen Konsenses aller Betroffener zu normativ...

  18. Die Verbesserung von Tiergesundheit und Wohlergehen der Tiere in Maststierbetrieben

    Kirchner, Marlene

    2015-01-01

    europäisches Forschungsprojekt, das die Integration des Tierwohlergehens in die Nahrungsqualitätskette zum Thema hatte. Das Projekt trug den Bedenken der Gesellschaft und Wünschen des Marktes Rechnung und entwickelte zuverlässige Systeme für die Kontrolle landwirtschaftlicher Betriebe und die...

  19. Konflikt und Kooperation bei der Wassernutzung in Mittelasien

    Wegerich, K.

    2009-01-01

    In Mittelasien sind Mensch, Natur und Wirtschaft auf das Wasser zweier Flusssysteme angewiesen: des Syr Darja im Norden und des Amu Darja im Süden. Beide Ströme sind in hohem Maße zur Stromgewinnung und landwirtschaftlichen Bewässerung erschlossen. Die Nutzung des Wassers birgt erhebliches Potential

  20. Blogs und Journalismus – Konkurrenz oder Ergänzung? – Das Verhältnis von Blogs und Journalismus in Deutschland

    Saskia Leidinger

    2015-12-01

    Full Text Available Mit der Frage, ob „Blogs und Journalismus - Konkurrenz oder Ergänzung“ sind, beschäftigt sich Saskia Leidinger in dem gleichnamigen Essay über „das Verhältnis von Blogs und Journalismus in Deutschland“. In vergleichender Perspektive richtet die Autorin ihr Hauptaugenmerk auf die Arbeitsweise sowie die Eigen- und Fremdwahrnehmung von Bloggern und Journalisten, um Gemeinsamkeiten und Unterschiede herauszustellen und ihre je spezifische Funktion innerhalb der der heutigen Informationsgesellschaft einzugrenzen.

  1. Admittance spectroscopy of spray-pyrolyzed ZnO film

    Kavasoglu, Nese; Kavasoglu, A. Sertap

    2008-01-01

    A ZnO film was deposited using the spray pyrolysis method. The admittance spectroscopy method was used to establish the contributions to electrical behavior from grains, grain boundaries, and electrodes of film. Proper equivalent electrical circuit of a ZnO film composed of a single parallel resistor, capacitor, and inductor network connected with a series resistance was proposed. Moreover, we displayed metal-semiconductor transition (MST) in the ZnO film via admittance spectroscopy

  2. Room temperature ferromagnetism in Cu doped ZnO

    Ali, Nasir; Singh, Budhi; Khan, Zaheer Ahmed; Ghosh, Subhasis

    2018-05-01

    We report the room temperature ferromagnetism in 2% Cu doped ZnO films grown by RF magnetron sputtering in different argon and oxygen partial pressure. X-ray photoelectron spectroscopy was used to ascertain the oxidation states of Cu in ZnO. The presence of defects within Cu-doped ZnO films can be revealed by electron paramagnetic resonance. It has been observed that saturated magnetic moment increase as we increase the zinc vacancies during deposition.

  3. Rasterelektronenmikroskopische und immunhistochemische Untersuchungen am Eileiter vom Schwein während Zyklus und Trächtigkeit

    Mayer, Judith

    2008-01-01

    In der vorliegenden Arbeit wurden zum einen mit Hilfe des Rasterelektronenmikroskops die morphologischen Veränderungen des Eileiterepithels und zum anderen die Expression hypophysärer wachstums- und proliferationsfördernder Hormone und ihrer Rezeptoren immunhistochemisch und mit der Reverse Transkriptase (RT)-PCR sowohl im Verlauf des Zyklus als auch der Trächtigkeit analysiert. Hierfür wurden, von 24 Schweinen der Deutschen Landrasse, die drei Abschnitte des Eileiters (Infundibulum, Ampulle,...

  4. Effect of High-Temperature Annealing on Yellow and Blue Luminescence of Undoped GaN

    Chai Xu-Zhao; Zhou Dong; Liu Bin; Xie Zi-Li; Han Ping; Xiu Xiang-Qian; Chen Peng; Lu Hai; Zhang Rong; Zheng You-Dou

    2015-01-01

    The effect of high-temperature annealing on the yellow and blue luminescence of the undoped GaN is investigated by photoluminescence (PL) and x-ray photoelectron spectroscopy (XPS). It is found that the band-edge emission in the GaN apparently increases, and the yellow luminescence (YL) and blue luminescence (BL) bands dramatically decrease after annealing at 700°C. At the annealing temperature higher than 900°C, the YL and BL intensities show an enhancement for the nitrogen annealed GaN. This fact should be attributed to the increment of the Ga and N vacancies in the GaN decomposition. However, the integrated PL intensity of the oxygen annealed GaN decreases at the temperature ranging from 900°C to 1000°C. This results from the capture of many photo-generated holes by high-density surface states. XPS characterization confirms that the high-density surface states mainly originate from the incorporation of oxygen atoms into GaN at the high annealing temperature, and even induces the 0.34eV increment of the upward band bending for the oxygen annealed GaN at 1000°C. (paper)

  5. Growth on nonpolar and semipolar GaN: The substrate dilemma

    Wernicke, T.; Weyers, M. [Ferdinand-Braun-Institute, Berlin (Germany); Kneissl, M. [Ferdinand-Braun-Institute, Berlin (Germany); Institute of Solid State Physics, TU Berlin (Germany)

    2009-07-01

    Growth of nonpolar and semipolar GaN is very promising for achieving green laser diodes (LDs). However, the choice of the substrate is a difficult one: Heteroepitaxial growth on sapphire, SiC, LiAlO{sub 2} yields GaN films with a poor surface quality and high defect densities. On the other hand non- and semipolar bulk GaN substrates provide excellent crystal quality, but are so far only available in very small sizes. In this paper hetero- and homoepitaxial growth is compared. For all heteroepitaxially grown semi- and nonpolar GaN layers threading dislocations (TD) and basal plane stacking faults (BSF) can be found. There are four possible mechanisms for the generation of BSF: Growth of the N-polar basal plane, formation during nucleation at substrate steps, formation at the coalescence front of differently stacked nucleation islands, and generation at planar defects occurring in m-plane GaN on LiAlO{sub 2}. BSF induce surface roughening and are associated with partial dislocations causing nonradiative recombination. Thus they affect the performance of devices. We show that BSFs and TDs can be reduced by epitaxial lateral overgrowth resulting in several micrometer wide defect free areas. However, for LEDs larger defect-free areas are required. GaN layers grown on bulk GaN substrates exhibit a high crystal quality, but show in many cases long-range surface structures with a height of {approx}1{mu}m.

  6. Determination of carrier diffusion length in p- and n-type GaN

    Hafiz, Shopan; Metzner, Sebastian; Zhang, Fan; Monavarian, Morteza; Avrutin, Vitaliy; Morkoç, Hadis; Karbaum, Christopher; Bertram, Frank; Christen, Jürgen; Gil, Bernard; Özgür, Ümit

    2014-03-01

    Diffusion lengths of photo-excited carriers along the c-direction were determined from photoluminescence (PL) measurements in p- and n-type GaN epitaxial layers grown on c-plane sapphire by metal-organic chemical vapor deposition. The investigated samples incorporate a 6 nm thick In0.15Ga0.85N active layer capped with either 500 nm p- GaN or 1300 nm n-GaN. The top GaN layers were etched in steps and PL from the InGaN active region and the underlying layers was monitored as a function of the top GaN thickness upon photogeneration near the surface region by above bandgap excitation. Taking into consideration the absorption in the active and underlying layers, the diffusion lengths at 295 K and at 15 K were measured to be about 92 ± 7 nm and 68 ± 7 nm for Mg-doped p-type GaN and 432 ± 30 nm and 316 ± 30 nm for unintentionally doped n-type GaN, respectively. Cross-sectional cathodoluminescence line-scan measurement was performed on a separate sample and the diffusion length in n-type GaN was measured to be 280 nm.

  7. Kinetic-limited etching of magnesium doping nitrogen polar GaN in potassium hydroxide solution

    Jiang, Junyan; Zhang, Yuantao; Chi, Chen; Yang, Fan; Li, Pengchong; Zhao, Degang; Zhang, Baolin; Du, Guotong

    2016-01-01

    KOH based wet etchings were performed on both undoped and Mg-doped N-polar GaN films grown by metal-organic chemical vapor deposition. It is found that the etching rate for Mg-doped N-polar GaN gets slow obviously compared with undoped N-polar GaN. X-ray photoelectron spectroscopy analysis proved that Mg oxide formed on N-polar GaN surface is insoluble in KOH solution so that kinetic-limited etching occurs as the etching process goes on. The etching process model of Mg-doped N-polar GaN in KOH solution is tentatively purposed using a simplified ideal atomic configuration. Raman spectroscopy analysis reveals that Mg doping can induce tensile strain in N-polar GaN films. Meanwhile, p-type N-polar GaN film with a hole concentration of 2.4 ÿ 1017 cm⿿3 was obtained by optimizing bis-cyclopentadienyl magnesium flow rates.

  8. Theoretical study for heterojunction surface of NEA GaN photocathode dispensed with Cs activation

    Xia, Sihao; Liu, Lei; Wang, Honggang; Wang, Meishan; Kong, Yike

    2016-09-01

    For the disadvantages of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, new-type NEA GaN photocathodes with heterojunction surface dispensed with Cs activation are investigated based on first-principle study with density functional theory. Through the growth of an ultrathin n-type GaN cap layer on p-type GaN emission layer, a p-n heterojunction is formed on the surface. According to the calculation results, it is found that Si atoms tend to replace Ga atoms to result in an n-type doped cap layer which contributes to the decreasing of work function. After the growth of n-type GaN cap layer, the atom structure near the p-type emission layer is changed while that away from the surface has no obvious variations. By analyzing the E-Mulliken charge distribution of emission surface with and without cap layer, it is found that the positive charge of Ga and Mg atoms in the emission layer decrease caused by the cap layer, while the negative charge of N atom increases. The conduction band moves downwards after the growth of cap layer. Si atom produces donor levels around the valence band maximum. The absorption coefficient of GaN emission layer decreases and the reflectivity increases caused by n-type GaN cap layer.

  9. Defect formation and magnetic properties of Co-doped GaN crystal and nanowire

    Shi, Li-Bin; Liu, Jing-Jing; Fei, Ying

    2013-01-01

    Theoretical calculation based on density functional theory (DFT) and generalized gradient approximation (GGA) has been carried out in studying defect formation and magnetic properties of Co doped GaN crystal and nanowire (NW). Co does not exhibit site preference in GaN crystal. However, Co occupies preferably surface sites in GaN NW. Transition level of the defect is also investigated in GaN crystal. We also find that Co Ga (S) in NW does not produce spin polarization and Co Ga (B) produces spontaneous spin polarization. Ferromagnetic (FM) and antiferromagnetic (AFM) couplings are analyzed by six different configurations. The results show that AFM coupling is more stable than FM coupling for Co doped GaN crystal. It is also found from Co doped GaN NW calculation that the system remains FM stability for majority of the configurations. Magnetic properties in Co doped GaN crystal can be mediated by N and Ga vacancies. The FM and AFM stability can be explained by Co 3d energy level coupling

  10. Theoretical investigation of electronic, magnetic and optical properties of Fe doped GaN thin films

    Salmani, E.; Mounkachi, O.; Ez-Zahraouy, H.; Benyoussef, A.; Hamedoun, M.; Hlil, E.K.

    2013-01-01

    Highlights: •Magnetic and optical properties Fe-doped GaN thin films are studied using DFT. •The band gaps of GaN thin films are larger than the one of the bulk. •The layer thickness and acceptor defect can switch the magnetic ordering. -- Abstract: Using first principles calculations based on spin-polarized density functional theory, the magnetic and optical properties of GaN and Fe-doped GaN thin films with and without acceptor defect is studied. The band structure calculations show that the band gaps of GaN thin films with 2, 4 and 6 layers are larger than the one of the bulk with wurtzite structure and decreases with increasing the film thickness. In Fe doped GaN thin films, we show that layer of thickness and acceptor defect can switch the magnetic ordering from disorder local moment (DLM) to ferromagnetic (FM) order. Without acceptor defect Fe doped GaN exhibits spin glass phase in 4 layers form and ferromagnetic state for 2 layers form of the thin films, while it exhibits ferromagnetic phase with acceptor defect such as vacancies defect for 2 and 4 layers. In the FM ordering, the thin films is half-metallic and is therefore ideal for spin application. The different energy between ferromagnetic state and disorder local moment state was evaluated. Moreover, the optical absorption spectra obtained by ab initio calculations confirm the ferromagnetic stability based on the charge state of magnetic impurities

  11. Polarity analysis of GaN nanorods by photo-assisted Kelvin probe force microscopy

    Wei, Jiandong; Neumann, Richard; Wang, Xue; Li, Shunfeng; Fuendling, Soenke; Merzsch, Stephan; Al-Suleiman, Mohamed A.M.; Soekmen, Uensal; Wehmann, Hergo-H.; Waag, Andreas [Institut fuer Halbleitertechnik, TU Braunschweig (Germany)

    2011-07-15

    Polarity dependence (N-polar (000-1) and Ga-polar (0001)) of surface photovoltage of epitaxially grown, vertically aligned GaN nanorods has been investigated by photo-assisted Kelvin probe force microscopy (KPFM). Commercial GaN substrates with known polarities are taken as reference samples. The polarity of GaN substrates can be well distinguished by the change in surface photovoltage upon UV illumination in air ambient. These different behaviors of Ga- and N-polar surfaces are attributed to the polarity-related surface-bound charges and photochemical reactivity. GaN nanorods were grown on patterned SiO{sub 2}/sapphire templates by metal-organic vapor phase epitaxy (MOVPE). In order to analyze the bottom surface of the grown GaN nanorods, a technique known from high power electronics and joining techniques is applied to remove the substrate. The top and bottom surfaces of the GaN nanorods are identified to be N-polar and Ga-polar according to the KPFM results, respectively. Our experiments demonstrate that KPFM is a simple and suitable method capable to identify the polarity of GaN nanorods. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Nanoscratch Characterization of GaN Epilayers on c- and a-Axis Sapphire Substrates

    Wen Hua-Chiang

    2010-01-01

    Full Text Available Abstract In this study, we used metal organic chemical vapor deposition to form gallium nitride (GaN epilayers on c- and a-axis sapphire substrates and then used the nanoscratch technique and atomic force microscopy (AFM to determine the nanotribological behavior and deformation characteristics of the GaN epilayers, respectively. The AFM morphological studies revealed that pile-up phenomena occurred on both sides of the scratches formed on the GaN epilayers. It is suggested that cracking dominates in the case of GaN epilayers while ploughing during the process of scratching; the appearances of the scratched surfaces were significantly different for the GaN epilayers on the c- and a-axis sapphire substrates. In addition, compared to the c-axis substrate, we obtained higher values of the coefficient of friction (μ and deeper penetration of the scratches on the GaN a-axis sapphire sample when we set the ramped force at 4,000 μN. This discrepancy suggests that GaN epilayers grown on c-axis sapphire have higher shear resistances than those formed on a-axis sapphire. The occurrence of pile-up events indicates that the generation and motion of individual dislocation, which we measured under the sites of critical brittle transitions of the scratch track, resulted in ductile and/or brittle properties as a result of the deformed and strain-hardened lattice structure.

  13. Design and simulation of GaN based Schottky betavoltaic nuclear micro-battery

    San, Haisheng; Yao, Shulin; Wang, Xiang; Cheng, Zaijun; Chen, Xuyuan

    2013-01-01

    The current paper presents a theoretical analysis of Ni-63 nuclear micro-battery based on a wide-band gap semiconductor GaN thin-film covered with thin Ni/Au films to form Schottky barrier for carrier separation. The total energy deposition in GaN was calculated using Monte Carlo methods by taking into account the full beta spectral energy, which provided an optimal design on Schottky barrier width. The calculated results show that an 8 μm thick Schottky barrier can collect about 95% of the incident beta particle energy. Considering the actual limitations of current GaN growth technique, a Fe-doped compensation technique by MOCVD method can be used to realize the n-type GaN with a carrier concentration of 1×10 15 cm −3 , by which a GaN based Schottky betavoltaic micro-battery can achieve an energy conversion efficiency of 2.25% based on the theoretical calculations of semiconductor device physics. - Highlights: • Ni-63 is employed as the pure beta radioisotope source. • The Schottky junction betavoltaic battery is based on the wide-band gap semiconductor GaN. • The total energy deposition of incident beta particles in GaN was simulated by the Monte Carlo method. • A Fe-doped compensation technique is suggested to increase the energy conversion efficiency

  14. Heteroepitaxial growth of basal plane stacking fault free a-plane GaN

    Wieneke, Matthias; Hempel, Thomas; Noltemeyer, Martin; Witte, Hartmut; Dadgar, Armin; Blaesing, Juergen; Christen, Juergen; Krost, Alois [Otto-von-Guericke Universitaet Magdeburg, FNW/IEP, Magdeburg (Germany)

    2010-07-01

    Growth of light emitting quantum-wells based on a-plane GaN is a possibility to reduce or even to avoid polarization correlated luminescence red shift and reduction of radiative recombination efficiency. But until now heteroepitaxially grown a-plane GaN films are characterized by a poor crystalline quality expressed by a high density of basal plane stacking faults (BSF) and partial dislocations. We present Si doped a-plane GaN films grown on r-plane sapphire substrates by metal organic vapor phase epitaxy using high temperature AlGaN nucleation layers. FE-SEM images revealed three dimensionally grown GaN crystallites sized up to tenth micrometer in the basal plane and a few tenth micrometers along the c-axes. Though, the full width at half maxima of the X-ray diffraction {omega}-scans of the in-plane GaN(1 anti 100) and GaN(0002) Bragg reflections exhibited a very high crystal quality. Furthermore, luminescence spectra were dominated by near band gap emission, while there was no separated peak of the basal plane stacking fault. In summary we present heteroepitaxially grown a-plane GaN without an evidence of basal plane stacking faults in X-ray diffraction measurements and luminescence spectra.

  15. High-quality GaN epitaxially grown on Si substrate with serpentine channels

    Wei, Tiantian; Zong, Hua; Jiang, Shengxiang; Yang, Yue; Liao, Hui; Xie, Yahong; Wang, Wenjie; Li, Junze; Tang, Jun; Hu, Xiaodong

    2018-06-01

    A novel serpentine-channeled mask was introduced to Si substrate for low-dislocation GaN epitaxial growth and the fully coalesced GaN film on the masked Si substrate was achieved for the first time. Compared with the epitaxial lateral overgrowth (ELOG) growth method, this innovative mask only requires one-step epitaxial growth of GaN which has only one high-dislocation region per mask opening. This new growth method can effectively reduce dislocation density, thus improving the quality of GaN significantly. High-quality GaN with low dislocation density ∼2.4 × 107 cm-2 was obtained, which accounted for about eighty percent of the GaN film in area. This innovative technique is promising for the growth of high-quality GaN templates and the subsequent fabrication of high-performance GaN-based devices like transistors, laser diodes (LDs), and light-emitting diodes (LEDs) on Si substrate.

  16. Krieg und Literatur War and Literature

    Elfi N. Theis

    2007-03-01

    Full Text Available Schreiben gegen Krieg und Gewalt heißt der Band 19 der Schriften-Reihe des Erich-Maria-Remarque-Archivs, in dem es um Ingeborg Bachmann und die deutschsprachige Literatur 1945-1980 geht. Der Band enthält die Beiträge zu einem Symposion, das am 14.-15. Januar 2005 an der Universität Nottingham stattgefunden hat. Im Mittelpunkt stand die Frage, welche Strategien im Umgang mit Nationalsozialismus, Holocaust, zweitem Weltkrieg, Kaltem Krieg oder Vietnamkrieg und auch dem deutschen Kolonialismus bei Bachmann und anderen deutschsprachigen Autoren zu finden sind. Anlass zur Tagung war die in Wien und Salzburg konzipierte Ausstellung Schreiben gegen den Krieg: Ingeborg Bachmann, 1926-1973. In insgesamt dreizehn Beiträgen wird im vorliegenden Band die literarische Auseinandersetzung mit dem Thema Gewalt und Krieg beleuchtet.Volume 19 of the series published by the Erich-Maria-Remarque Archive is entitled “Writing against War and Violence” (“Schreiben gegen Krieg und Gewalt” and approaches Ingeborg Bachmann and German language literature from 1945 to 1980. The volume contains contributions based on a symposium that took place at the University of Nottingham on January 14-15, 2005. Central to the symposium was the question as to which strategies Bachmann and other German language authors utilized in their approach to National Socialism, the Holocaust, the Second World War, the Cold War, or the Vietnam War, as well as German colonialism. The impetus for the conference was the exhibition Writing Against the War: Ingeborg Bachmann, 1926-1973 conceived in Vienna and Salzburg. In the volume at hand, thirteen contributions in total illuminate literary confrontations with the themes of war and violence.

  17. Optical Properties of ZnO Nanoparticles Capped with Polymers

    Atsushi Noguchi

    2011-06-01

    Full Text Available Optical properties of ZnO nanoparticles capped with polymers were investigated. Polyethylene glycol (PEG and polyvinyl pyrrolidone (PVP were used as capping reagents. ZnO nanoparticles were synthesized by the sol-gel method. Fluorescence and absorption spectra were measured. When we varied the timing of the addition of the polymer to the ZnO nanoparticle solution, the optical properties were drastically changed. When PEG was added to the solution before the synthesis of ZnO nanoparticles, the fluorescence intensity increased. At the same time, the total particle size increased, which indicated that PEG molecules had capped the ZnO nanoparticles. The capping led to surface passivation, which increased fluorescence intensity. However, when PEG was added to the solution after the synthesis of ZnO nanoparticles, the fluorescence and particle size did not change. When PVP was added to the solution before the synthesis of ZnO nanoparticles, aggregation of nanoparticles occurred. When PVP was added to the solution after the synthesis of ZnO nanoparticles, fluorescence and particle size increased. This improvement of optical properties is advantageous to the practical usage of ZnO nanoparticles, such as bioimaging

  18. Preparation of ZnO nanocrystals via ultrasonic irradiation

    Qian, D.; Jiang, Jianzhong; Hansen, P. L.

    2003-01-01

    A simple and rapid process has been developed for the preparation of nanometer-sized ZnO crystals via ultrasonic irradiation, by which pure ZnO nanocrystals with an average size of 6 nm and narrow size distribution can be synthesized in a short time and without using any solvents for the precipit......A simple and rapid process has been developed for the preparation of nanometer-sized ZnO crystals via ultrasonic irradiation, by which pure ZnO nanocrystals with an average size of 6 nm and narrow size distribution can be synthesized in a short time and without using any solvents...

  19. [Geisteswissenschaften und Publizistik im Baltikum des 19. und frühen 20. Jahrhunderts] / Gert von Pistohlkors

    Pistohlkors, Gert von, 1935-

    2013-01-01

    Arvustus: Geisteswissenschaften und Publizistik im Baltikum des 19. und frühen 20. Jahrhunderts. Hrsg. von Norbert Angermann, Wilhelm Lenz und Konrad Maier. (Schriften der Baltischen Historischen Kommission, Bd. 17; Baltische Biographische Forschungen, Bd. 1.) Lit. Münster 2011

  20. Kommunikationsprobleme zwischen deutschen Expatriates und Chinesen in der wirtschaftlichen Zusammenarbeit -- Empirische Erfahrungen und Analyse der Einflußfaktoren

    Shi, Hongxia

    2003-01-01

    Die vorliegende Arbeit untersucht die empirischen Erfahrungen und die Einflußfaktoren der Kommunikationsprobleme der deutschen Expatriates und Chinesen in der wirtschaftlichen Zusammenarbeit. Die Untersuchung basiert auf einem Datenmaterial, das aus 86 Interviewgesprächen mit Betroffenen besteht. Zentrale Fragestellungen der vorliegenden Arbeit sind: 1. Mit welchen Kommunikationsproblemen werden die befragten deutschen Expatriates und Chinesen in ihrer interkulturellen Kommunikation miteinand...

  1. [Glanz und Elend - Mythos und Wirklichkeit der Herrenhäuser im Baltikum] / Karsten Brüggemann

    Brüggemann, Karsten, 1965-

    2014-01-01

    Arvustus: Glanz und Elend - Mythos und Wirklichkeit der Herrenhäuser im Baltikum. Hrsg. von Ilse von zur Mühlen im Auftrag der Carl-Schirren-Gesellschaft e.V. und des Ostpreußischen Landesmuseums Lüneburg. Kunstverlag Josef Fink. Lindenberg im Allgäu 2012

  2. Wie schneiden Sie ab?: Studie über Kontroll- und Prüfungsaktivitäten bei mittelgrossen Unternehmen, Spitälern und Hochschulen in der Schweiz

    Ruud, T F; Isufi, S; Friebe, P; Stebler, W; Seheri, F; Emmenegger, M

    2008-01-01

    Kontroll- und Prüfungsaktivitäten unterstützen den Verwaltungsrat und die Geschäftsleitung bei der Steuerung und Kontrolle des Unternehmens. Bei mittelgrossen Unternehmen ist aufgrund der begrenzten personellen und finanziellen Ressourcen ein effektiver und effizienter Einsatz dieser Aktivitäten unerlässlich. Auch bei Spitälern und Hochschulen gewinnen Kontroll- und Prüfungsaktivitäten infolge erhöhter Wettbewerbsintensität und steigenden Kostendrucks sowie zunehmender Unabhängigkeit diese...

  3. Bewältigungsstrategien der Oberwalliser Primarlehrpersonen und Massnahmen der Gesundheitsförderung an Oberwalliser Primarschulen bei Stress und Burnout

    Imhof, Barbara; Mattig, Astrid

    2009-01-01

    Die vorliegende Studie befasst sich mit der Gesundheitsförderung bei Stress und Burnout an den Oberwalliser Primarschulen und der Bewältigungsstrategien der Oberwalliser Primarlehrpersonen bei Stress und Burnout. Der theoretische Teil befasst sich mit Stress und Burnout und der Bewältigung von Stress und Burnout. Verschiedene Aspekte des Lehrerberufs werden näher angeschaut und es werden mögliche Massnahmen der Gesundheitsförderung bei Stress und Burnout aufgeführt. Die Untersuchung zeigt, da...

  4. Ga vacancy induced ferromagnetism enhancement and electronic structures of RE-doped GaN

    Zhong Guohua; Zhang Kang; He Fan; Ma Xuhang; Lu Lanlan; Liu Zhuang; Yang Chunlei

    2012-01-01

    Because of their possible applications in spintronic and optoelectronic devices, GaN dilute magnetic semiconductors (DMSs) doped by rare-earth (RE) elements have attracted much attention since the high Curie temperature was obtained in RE-doped GaN DMSs and a colossal magnetic moment was observed in the Gd-doped GaN thin film. We have systemically studied the GaN DMSs doped by RE elements (La, Ce-Yb) using the full-potential linearized augmented plane wave method within the framework of density functional theory and adding the considerations of the electronic correlation and the spin-orbital coupling effects. We have studied the electronic structures of DMSs, especially for the contribution from f electrons. The origin of magnetism, magnetic interaction and the possible mechanism of the colossal magnetic moment were explored. We found that, for materials containing f electrons, electronic correlation was usually strong and the spin-orbital coupling was sometimes crucial in determining the magnetic ground state. It was found that GaN doped by La was non-magnetic. GaN doped by Ce, Nd, Pm, Eu, Gd, Tb and Tm are stabilized at antiferromagnetic phase, while GaN doped by other RE elements show strong ferromagnetism which is suitable materials for spintronic devices. Moreover, we have identified that the observed large enhancement of magnetic moment in GaN is mainly caused by Ga vacancies (3.0μB per Ga vacancy), instead of the spin polarization by magnetic ions or originating from N vacancies. Various defects, such as substitutional Mg for Ga, O for N under the RE doping were found to bring a reduction of ferromagnetism. In addition, intermediate bands were observed in some systems of GaN:RE and GaN with intrinsic defects, which possibly opens the potential application of RE-doped semiconductors in the third generation high efficiency photovoltaic devices.

  5. Ab initio-based approach to reconstruction, adsorption and incorporation on GaN surfaces

    Ito, T; Akiyama, T; Nakamura, K

    2012-01-01

    Reconstruction, adsorption and incorporation on various GaN surfaces are systematically investigated using an ab initio-based approach that predicts the surface phase diagram as functions of temperature and beam-equivalent pressure (BEP). The calculated results for GaN surface reconstructions with polar (0 0 0 1), nonpolar (1 1 −2 0), semipolar (1 −1 0 1) and semipolar (1 1 −2 2) orientations imply that reconstructions on GaN surfaces with Ga adlayers generally appear on the polar and the semipolar surfaces, while the stable ideal surface without Ga adsorption is found on the nonpolar GaN(1 1 −2 0) surface because it satisfies the electron counting rule. The hydrogen adsorption on GaN(0 0 0 1) and GaN(1 1 −2 0) realizes several surface structures forming N–H and Ga–NH 2 bonds on their surfaces that depend on temperature and Ga BEP during metal-organic vapor-phase epitaxy (MOVPE). In contrast, the stable structures due to hydrogen adsorption on the semipolar GaN(1 −1 0 1) and GaN(1 1 −2 2) surfaces are not varied over the wide range of temperature and Ga BEP. This implies that the hydrogen adsorbed stable structures are expected to emerge on the semipolar surfaces during MOVPE regardless of the growth conditions. Furthermore, we clarify that Mg incorporation on GaN(1 −1 0 1) surfaces is enhanced by hydrogen adsorption consistent with experimental findings

  6. Soziologische Wissenskulturen zwischen individualisierter Inspiration und prozeduraler Legitimation. Zur Entwicklung qualitativer und interpretativer Sozialforschung in der deutschen und französischen Soziologie seit den 1960er Jahren

    Reiner Keller

    2016-01-01

    Full Text Available Wie wissen Soziologinnen und Soziologen, was sie wissen? Trotz der Internationalisierung der Soziologie bestehen nach wie vor starke sprachräumliche Unterschiede in der soziologischen Wissensproduktion, in eingesetzten Theorien, Methoden und Fragestellungen. Der nachfolgende Beitrag erläutert die Entwicklung und Ausprägung der Unterschiedlichkeit soziologischer Wissenskulturen im Hinblick auf den Einsatz qualitativer bzw. interpretativer Ansätze seit den 1960er Jahren in Deutschland und Frankreich. Er stützt sich auf ein von uns 2012-2014 geleitetes Forschungsprojekt und dessen empirische Grundlagen: Dokumentenanalysen und Interviews. Wissenskulturen werden als die Arten und Weisen der Produktion und Legitimation von (hier: soziologischem Wissen verstanden. Diesbezüglich lässt sich von der Erkenntnisproduktion als dem zentralen Handlungsproblem soziologischen Forschens sprechen. Während für die französischsprachige Soziologie diagnostisch von einer Lösung dieses Erkenntnisproblems durch die den Forschenden zugeschriebenen Kompetenzen und Inspirationen ausgegangen werden kann, schiebt sich im deutschsprachigen Raume eine prozedurale Legitimation durch Verfahren in den Vordergrund. Der Beitrag rekonstruiert exemplarisch die Ausgangssituation dieser Entwicklungen um die Wende zu den 1960er Jahren und bettet sie in die weitere Entfaltung der jeweiligen Soziologien ein. Er will damit zur gegenwärtigen Entwicklung einer reflexiven Soziologie beitragen. URN: http://nbn-resolving.de/urn:nbn:de:0114-fqs1601145

  7. Sodium doping in ZnO crystals

    Parmar, N. S.; Lynn, K. G.

    2015-01-01

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1-3.5) × 1017 cm-3. Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a NaZn level at ˜(220-270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4-5) orders of magnitude at room temperature.

  8. Sodium doping in ZnO crystals

    Parmar, N. S.; Lynn, K. G.

    2015-01-01

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1–3.5) × 10 17  cm −3 . Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a Na Zn level at ∼(220–270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4–5) orders of magnitude at room temperature

  9. Sodium doping in ZnO crystals

    Parmar, N. S., E-mail: nparmar@wsu.edu; Lynn, K. G. [Center for Materials Research, Washington State University, Pullman, Washington 99164-2711 (United States)

    2015-01-12

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1–3.5) × 10{sup 17 }cm{sup −3}. Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a Na{sub Zn} level at ∼(220–270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4–5) orders of magnitude at room temperature.

  10. Magneto-ballistic transport in GaN nanowires

    Santoruvo, Giovanni; Allain, Adrien; Ovchinnikov, Dmitry; Matioli, Elison

    2016-01-01

    The ballistic filtering property of nanoscale crosses was used to investigate the effect of perpendicular magnetic fields on the ballistic transport of electrons on wide band-gap GaN heterostructures. The straight scattering-less trajectory of electrons was modified by a perpendicular magnetic field which produced a strong non-linear behavior in the measured output voltage of the ballistic filters and allowed the observation of semi-classical and quantum effects, such as quenching of the Hall resistance and manifestation of the last plateau, in excellent agreement with the theoretical predictions. A large measured phase coherence length of 190 nm allowed the observation of universal quantum fluctuations and weak localization of electrons due to quantum interference up to ∼25 K. This work also reveals the prospect of wide band-gap GaN semiconductors as a platform for basic transport and quantum studies, whose properties allow the investigation of ballistic transport and quantum phenomena at much larger voltages and temperatures than in other semiconductors.

  11. Magneto-ballistic transport in GaN nanowires

    Santoruvo, Giovanni, E-mail: giovanni.santoruvo@epfl.ch; Allain, Adrien; Ovchinnikov, Dmitry; Matioli, Elison, E-mail: elison.matioli@epfl.ch [Ecole Polytechnique Fédérale de Lausanne (EPFL), CH 1015 Lausanne (Switzerland)

    2016-09-05

    The ballistic filtering property of nanoscale crosses was used to investigate the effect of perpendicular magnetic fields on the ballistic transport of electrons on wide band-gap GaN heterostructures. The straight scattering-less trajectory of electrons was modified by a perpendicular magnetic field which produced a strong non-linear behavior in the measured output voltage of the ballistic filters and allowed the observation of semi-classical and quantum effects, such as quenching of the Hall resistance and manifestation of the last plateau, in excellent agreement with the theoretical predictions. A large measured phase coherence length of 190 nm allowed the observation of universal quantum fluctuations and weak localization of electrons due to quantum interference up to ∼25 K. This work also reveals the prospect of wide band-gap GaN semiconductors as a platform for basic transport and quantum studies, whose properties allow the investigation of ballistic transport and quantum phenomena at much larger voltages and temperatures than in other semiconductors.

  12. Size dictated thermal conductivity of GaN

    Beechem, Thomas E.; McDonald, Anthony E.; Fuller, Elliot J.; Talin, A. Alec; Rost, Christina M.; Maria, Jon-Paul; Gaskins, John T.; Hopkins, Patrick E.; Allerman, Andrew A.

    2016-09-01

    The thermal conductivity of n- and p-type doped gallium nitride (GaN) epilayers having thicknesses of 3-4 μm was investigated using time domain thermoreflectance. Despite possessing carrier concentrations ranging across 3 decades (1015-1018 cm-3), n-type layers exhibit a nearly constant thermal conductivity of 180 W/mK. The thermal conductivity of p-type epilayers, in contrast, reduces from 160 to 110 W/mK with increased doping. These trends—and their overall reduction relative to bulk—are explained leveraging established scattering models where it is shown that, while the decrease in p-type layers is partly due to the increased impurity levels evolving from its doping, size effects play a primary role in limiting the thermal conductivity of GaN layers tens of microns thick. Device layers, even of pristine quality, will therefore exhibit thermal conductivities less than the bulk value of 240 W/mK owing to their finite thickness.

  13. Radiotracer Spectroscopy on Group II Acceptors in GaN

    2002-01-01

    The semiconductor GaN is already used for the production of high power light emitting diodes in the blue and UV spectral range. But the $\\rho$-type doping, which is usually obtained by Mg doping, is still inefficient due to compensation and passivation effects caused by defects present in the material. It is theoretically predicted, that Be is a more promising candidate for $\\rho$-doping with a lower ionization energy of 60meV. It is our goal to investigate the electrical and optical properties of Be- and Mg-related defects in GaN to clarify the problem of compensation and passivation. The used methods are standard spectroscopic methods in semiconductor physics which are improved by using radioactive isotopes. The radioactive decay of $^{7}$Be and $^{28}$Mg is used to clearly correlate different signals with Be or Mg related defects. We intend to use the spectroscopic techniques Deep Level Transient Spectroscopy (DLTS), Thermal Admittance Spectroscopy (TAS), photoluminescence (PL) and additionally Hall-effect...

  14. Atomic layer deposition of GaN at low temperatures

    Ozgit, Cagla; Donmez, Inci; Alevli, Mustafa; Biyikli, Necmi [UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey)

    2012-01-15

    The authors report on the self-limiting growth of GaN thin films at low temperatures. Films were deposited on Si substrates by plasma-enhanced atomic layer deposition using trimethylgallium (TMG) and ammonia (NH{sub 3}) as the group-III and -V precursors, respectively. GaN deposition rate saturated at 185 deg. C for NH{sub 3} doses starting from 90 s. Atomic layer deposition temperature window was observed from 185 to {approx}385 deg. C. Deposition rate, which is constant at {approx}0.51 A/cycle within the temperature range of 250 - 350 deg. C, increased slightly as the temperature decreased to 185 deg. C. In the bulk film, concentrations of Ga, N, and O were constant at {approx}36.6, {approx}43.9, and {approx}19.5 at. %, respectively. C was detected only at the surface and no C impurities were found in the bulk film. High oxygen concentration in films was attributed to the oxygen impurities present in group-V precursor. High-resolution transmission electron microscopy studies revealed a microstructure consisting of small crystallites dispersed in an amorphous matrix.

  15. Electronic Transport Mechanism for Schottky Diodes Formed by Au/HVPE a-Plane GaN Templates Grown via In Situ GaN Nanodot Formation

    Moonsang Lee

    2018-06-01

    Full Text Available We investigate the electrical characteristics of Schottky contacts for an Au/hydride vapor phase epitaxy (HVPE a-plane GaN template grown via in situ GaN nanodot formation. Although the Schottky diodes present excellent rectifying characteristics, their Schottky barrier height and ideality factor are highly dependent upon temperature variation. The relationship between the barrier height, ideality factor, and conventional Richardson plot reveals that the Schottky diodes exhibit an inhomogeneous barrier height, attributed to the interface states between the metal and a-plane GaN film and to point defects within the a-plane GaN layers grown via in situ nanodot formation. Also, we confirm that the current transport mechanism of HVPE a-plane GaN Schottky diodes grown via in situ nanodot formation prefers a thermionic field emission model rather than a thermionic emission (TE one, implying that Poole–Frenkel emission dominates the conduction mechanism over the entire range of measured temperatures. The deep-level transient spectroscopy (DLTS results prove the presence of noninteracting point-defect-assisted tunneling, which plays an important role in the transport mechanism. These electrical characteristics indicate that this method possesses a great throughput advantage for various applications, compared with Schottky contact to a-plane GaN grown using other methods. We expect that HVPE a-plane GaN Schottky diodes supported by in situ nanodot formation will open further opportunities for the development of nonpolar GaN-based high-performance devices.

  16. Highly c-axis oriented growth of GaN film on sapphire (0001 by laser molecular beam epitaxy using HVPE grown GaN bulk target

    S. S. Kushvaha

    2013-09-01

    Full Text Available Growth temperature dependant surface morphology and crystalline properties of the epitaxial GaN layers grown on pre-nitridated sapphire (0001 substrates by laser molecular beam epitaxy (LMBE were investigated in the range of 500–750 °C. The grown GaN films were characterized using high resolution x-ray diffraction, atomic force microscopy (AFM, micro-Raman spectroscopy, and secondary ion mass spectroscopy (SIMS. The x-ray rocking curve full width at a half maximum (FWHM value for (0002 reflection dramatically decreased from 1582 arc sec to 153 arc sec when the growth temperature was increased from 500 °C to 600 °C and the value further decreased with increase of growth temperature up to 720 °C. A highly c-axis oriented GaN epitaxial film was obtained at 720 °C with a (0002 plane rocking curve FWHM value as low as 102 arc sec. From AFM studies, it is observed that the GaN grain size also increased with increasing growth temperature and flat, large lateral grains of size 200-300 nm was obtained for the film grown at 720 °C. The micro-Raman spectroscopy studies also exhibited the high-quality wurtzite nature of GaN film grown on sapphire at 720 °C. The SIMS measurements revealed a non-traceable amount of background oxygen impurity in the grown GaN films. The results show that the growth temperature strongly influences the surface morphology and crystalline quality of the epitaxial GaN films on sapphire grown by LMBE.

  17. "Tabula Sinvs Venetici" von W. Barents und ihre Geschichtilische und Geographische Bedeutung

    Mithad Kozličić

    1999-06-01

    Full Text Available In der wissenschaftlichen Literatur sind zwei Varianten der Seekarte der Adria vom niederländischen Seefahrer und Polarforscher Willem Barents (1550-1597 bekannt. Die erste, in diesem Aufsatz als K-1 bezeichnete Karte, wurde in Amsterdam 1595 hergestellt und gedruckt. Sie hatte anfänglich eine praktisch-navigatorische Funktion. Die zweite, K-2, ins Jahr 1595 datierte (1637-1662 Karte, wurde als geostrategische Karte der Adria und der südlichen Teile Europas ausgenützt. An den adriatischen Nordküsten, besonders in ihrem Hinterland, geschahen mit dem Durchbruch der Türken seit der Hälfte des 16. Jahrhunderts wichtige militärische und politische Änderungen. In den “Atlanten” des Niederländers Jan (Johann; Joannes Janssonius (1588-1664 fehlte gerade solch eine Karte, die auch mehrmals in Amsterdam gedruckt wurde, aber zwischen 1637 und 1662. Die K-1 von Barents, deren Druckplatte Janssonius zur Verfügung hatte, konnte diese Funktion befriedigen. Deswegen machte Janssonius nur die nötigen dem darstellenden Standard der ersten Hälfte des 17. Jahrhunderts entsprechenden Änderungen, und als solche wurde sie gedruckt. Die K-2 verlor ihre ursprüngliche praktisch-navigatorische Funktion und wurde eine Karte von geostrategischer Bedeutung. Mit diesen Grundfragen befaßt sich dieser Aufsatz.

  18. [Vilis Kolms. Das Rigaer Gesangbuch und die kirchenordnung von 1530]/ Dennis Hortmuth

    Hormuth, Dennis

    2012-01-01

    Arvustus: .Vilis Kolms. Das Rigaer Gesangbuch und die kirchenordnung von 1530. In: Die baltischen Lande im Zeitalter der Reformation und Konfessionaliesierung. Livland, Estland, Ösel, Ingermanland, Kurland und Lettgallen. Stadt, Land und Konfession 1500-1721. Teil 2 (=Katholisches Leben und Kirchenreform im Zeitalter der Glaubensspaltung 70). Münster, 2010. S. 175-190

  19. Modification of GaN(0001) growth kinetics by Mg doping

    Monroy, E.; Andreev, T.; Holliger, P.; Bellet-Amalric, E.; Shibata, T.; Tanaka, M.; Daudin, B.

    2004-01-01

    We have studied the effect of Mg doping on the surface kinetics of GaN during growth by plasma-assisted molecular-beam epitaxy. Mg tends to segregate on the surface of GaN, inhibiting the formation of the self-regulated Ga film which is used as a surfactant for the growth of undoped and Si-doped GaN. The growth window is hence significantly reduced. Higher growth temperatures lead to an enhancement of Mg segregation and an improvement of the surface morphology

  20. Redshift of A 1(longitudinal optical) mode for GaN crystals under strong electric field

    Gu, Hong; Wu, Kaijie; Zheng, Shunan; Shi, Lin; Zhang, Min; Liu, Zhenghui; Liu, Xinke; Wang, Jianfeng; Zhou, Taofei; Xu, Ke

    2018-01-01

    We investigated the property of GaN crystals under a strong electric field. The Raman spectra of GaN were measured using an ultraviolet laser, and a remarkable redshift of the A 1(LO) mode was observed. The role of the surface depletion layer was discussed, and the interrelation between the electric field and phonons was revealed. First-principles calculations indicated that, in particular, the phonons that vibrate along the [0001] direction are strongly influenced by the electric field. This effect was confirmed by a surface photovoltage experiment. The results revealed the origin of the redshift and presented the phonon property of GaN under a strong electric field.

  1. Photoassisted Kelvin probe force microscopy at GaN surfaces: The role of polarity

    Wei, J. D.; Li, S. F.; Atamuratov, A.; Wehmann, H.-H.; Waag, A.

    2010-10-01

    The behavior of GaN surfaces during photoassisted Kelvin probe force microscopy is demonstrated to be strongly dependant on surface polarity. The surface photovoltage of GaN surfaces illuminated with above-band gap light is analyzed as a function of time and light intensity. Distinct differences between Ga-polar and N-polar surfaces could be identified, attributed to photoinduced chemisorption of oxygen during illumination. These differences can be used for a contactless, nondestructive, and easy-performable analysis of the polarity of GaN surfaces.

  2. Electron holography studies of the charge on dislocations in GaN

    Cherns, D.; Jiao, C.G.; Mokhtari, H. [H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Cai, J.; Ponce, F.A. [Department of Physics and Astronomy, Arizona State University, Tempe, AZ85287 (United States)

    2002-12-01

    The measurement of charge on dislocations in GaN by electron holography is described. Recent results are presented showing that edge dislocations in n-doped GaN are highly negatively charged, whereas those in p-doped GaN are positively charged. It is shown that the results are consistent with a model which assumes Fermi level pinning at dislocation states about 2.5 V below the conduction band edge. The application of electron holography to screw dislocations, and the dependence of the observations on the dislocation core structure, are also discussed. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

  3. Real time ellipsometry for monitoring plasma-assisted epitaxial growth of GaN

    Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR and INSTM UdR Bari, via Orabona, 4, 70126 Bari (Italy); Losurdo, Maria [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR and INSTM UdR Bari, via Orabona, 4, 70126 Bari (Italy)]. E-mail: maria.losurdo@ba.imip.cnr.it; Giangregorio, Maria M. [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR and INSTM UdR Bari, via Orabona, 4, 70126 Bari (Italy); Capezzuto, Pio [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR and INSTM UdR Bari, via Orabona, 4, 70126 Bari (Italy); Brown, April S. [Department of Electrical and Computer Engineering, Duke University, 128 Hudson Hall, Durham, NC (United States); Kim, Tong-Ho [Department of Electrical and Computer Engineering, Duke University, 128 Hudson Hall, Durham, NC (United States); Choi, Soojeong [Department of Electrical and Computer Engineering, Duke University, 128 Hudson Hall, Durham, NC (United States)

    2006-10-31

    GaN is grown on Si-face 4H-SiC(0 0 0 1) substrates using remote plasma-assisted methods including metalorganic chemical vapour deposition (RP-MOCVD) and molecular beam epitaxy (MBE). Real time spectroscopic ellipsometry is used for monitoring all the steps of substrate pre-treatments and the heteroepitaxial growth of GaN on SiC. Our characterization emphasis is on understanding the nucleation mechanism and the GaN growth mode, which depend on the SiC surface preparation.

  4. Preparation, structural and optical characterization of ZnO, ZnO: Al nanopowder

    Mohan, R. Raj [Department of ECE, Gojan School of Business and Technology, Chennai (India); Rajendran, K. [Department of Electronics, Government Arts College for Women, Ramanathapuram, TN (India); Sambath, K. [Department of ECS, Sri Krishna Arts and Science College, Coimbatore, TN (India)

    2014-01-28

    In this paper, ZnO and ZnO:Al nanopowders have been synthesized by low cost hydrothermal method. Zinc nitrate, hexamethylenetetramine (HMT) and aluminium nitrate are used as precursors for ZnO and AZO with different molar ratios. The structural and optical characterization of doped and un-doped ZnO powders have been investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDAX), photoluminescence (PL) and ultra violet visible (UV-Vis) absorption studies. The SEM results show that the hydrothermal synthesis can be used to obtain nanoparticles with different morphology. It is observed that the grain size of the AZO nanoparticles increased with increasing of Al concentration. The PL measurement of AZO shows that broad range of green emission around 550nm with high intensity. The green emission resulted mainly because of intrinsic defects.

  5. Improving ultraviolet photodetection of ZnO nanorods by Cr doped ZnO encapsulation process

    Safa, S.; Mokhtari, S.; Khayatian, A.; Azimirad, R.

    2018-04-01

    Encapsulated ZnO nanorods (NRs) with different Cr concentration (0-4.5 at.%) were prepared in two different steps. First, ZnO NRs were grown by hydrothermal method. Then, they were encapsulated by dip coating method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, and ultraviolet (UV)-visible spectrophotometer analyses. XRD analysis proved that Cr incorporated into the ZnO structure successfully. Based on optical analysis, band gap changes in the range of 2.74-3.84 eV. Finally, UV responses of all samples were deeply investigated. It revealed 0.5 at.% Cr doped sample had the most photocurrent (0.75 mA) and photoresponsivity (0.8 A/W) of all which were about three times greater than photocurrent and photoresponsivity of the undoped sample.

  6. Photoluminescence lineshape of ZnO

    Bruno Ullrich

    2014-12-01

    Full Text Available The merger of the absorption coefficient dispersion, retrieved from transmission by the modified Urbach rule introduced by Ullrich and Bouchenaki [Jpn. J. Appl. Phys. 30, L1285, 1991], with the extended Roosbroeck-Shockley relation reveals that the optical absorption in ZnO distinctively determines the photoluminescence lineshape. Additionally, the ab initio principles employed enable the accurate determination of the carrier lifetime without further specific probing techniques.

  7. Spin noise spectroscopy of ZnO

    Horn, H.; Berski, F.; Balocchi, A.; Marie, X.; Mansur-Al-Suleiman, M.; Bakin, A.; Waag, A.; Hübner, J.; Oestreich, M.

    2013-12-01

    We investigate the thermal equilibrium dynamics of electron spins bound to donors in nanoporous ZnO by optical spin noise spectroscopy. The spin noise spectra reveal two noise contributions: A weak spin noise signal from undisturbed localized donor electrons with a dephasing time of 24 ns due to hyperfine interaction and a strong spin noise signal with a spin dephasing time of 5 ns which we attribute to localized donor electrons which interact with lattice defects.

  8. Spin noise spectroscopy of ZnO

    Horn, H.; Berski, F.; Hübner, J.; Oestreich, M. [Institute for Solid State Physics, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover (Germany); Balocchi, A.; Marie, X. [INSA-CNRS-UPS, LPCNO, Université de Toulouse, 135 Av. de Rangueil, 31077 Toulouse (France); Mansur-Al-Suleiman, M.; Bakin, A.; Waag, A. [Institute of Semiconductor Technology, Technische Universität Braunschweig, Hans-Sommer-Straße 66, 38106 Braunschweig (Germany)

    2013-12-04

    We investigate the thermal equilibrium dynamics of electron spins bound to donors in nanoporous ZnO by optical spin noise spectroscopy. The spin noise spectra reveal two noise contributions: A weak spin noise signal from undisturbed localized donor electrons with a dephasing time of 24 ns due to hyperfine interaction and a strong spin noise signal with a spin dephasing time of 5 ns which we attribute to localized donor electrons which interact with lattice defects.

  9. Diffuser Haarausfall und klinische Endokrinologie: Neue Erkenntnisse

    Liptak J

    2013-01-01

    Full Text Available Diffuser Haarausfall ist ein häufiges Krankheitsbild in der täglichen Praxis, dessen Diagnostik allerdings oft eine Herausforderung darstellt. In den vergangenen 10 Jahren wurden große Fortschritte in der Erforschung der Effekte diverser Hormone erzielt. In murinen Haarfollikeln wird Corticoliberin (Corticotropin-releasing Hormone [CRH] mit einem Peak in der Anagenphase (Wachstumsphase exprimiert. Ein stressinduziert erhöhter CRH-Spiegel kann durch Aktivierung von Mastzellen zu erhöhtem Haarverlust führen. Melatonin wird ebenfalls im Haarfollikel exprimiert und wirkt dort auf unterschiedliche Rezeptoren. Besonders der nukleäre Retinoic Acid Receptor-(RAR- Related Orphan-Receptor alpha (RORα scheint regulatorisch auf haarzyklusabhängige Prozesse zu wirken und wird auch abhängig vom Haarzyklus exprimiert. Melatonin greift zudem in androgen- und östrogenvermittelte Signaltransduktionswege ein. Eine topische Anwendung von Melatonin kann zu einer Zunahme der Anagenhaare führen. Auch Leptin wird im Haarfollikel exprimiert und beeinflusst Haarwachstum und Hautregeneration durch Aktivierung von STAT3. Bei Mäusen konnte durch Leptin die Anagenphase induziert werden. Über den Zusammenhang zwischen androgenetischer Alopezie und Metabolischem Syndrom wurden zahlreiche widersprüchliche Daten veröffentlicht. Zuletzt wies eine große koreanische Studie eine positive Assoziation der Krankheitsbilder bei Frauen nach, jedoch nicht bei Männern. Prolaktin induziert den verfrühten Übergang zur Katagenphase, senkt die Proliferationsrate der Keratinozyten im Haarfollikel und steigert deren Apoptoserate. Eine zu Haarausfall führende Hyperprolaktinämie kann unter anderem durch diverse Medikamente, insbesondere typische und atypische Neuroleptika, hervorgerufen werden. Zahlreiche Studien an Mäusen konnten belegen, dass der Vitamin-D-Rezeptor (VDR eng mit dem Haarwachstum assoziiert ist. Dieser scheint den Haarzyklus unabhängig von seinen Liganden

  10. Big Data in kleinen und mittleren Unternehmen: Eine empirische Bestandsaufnahme

    Vossen, Gottfried; Lechtenbörger, Jens; Fekete, David

    2015-01-01

    Dieser Bericht untersucht das Potential von Big Data in und für kleine und mittlere Unternehmen (KMU). Dafür werden mittels einer Umfrage, Fokus-Interviews und zusätzlichen Recherchen die Potentiale und Herausforderungen bei Big Data untersucht, welche für KMU zu Tragen kommen. Der Begriff Big Data selbst wird genauer betrachtet und es wird erklärt, welche Dimensionen abseits schierer Größe ebenfalls dazu zählen, wie etwa Vielfalt oder Schnelligkeit der Daten. Weiter wird mit eingängigen Prax...

  11. Von Nischen und Infrastrukturen - Herausforderungen und neue Ansätze politischer Technologien

    Felix Stalder

    2011-06-01

    Full Text Available Neue Technologien aus dem aktivistischen Umfeld bieten radikale Alternativen zu kultureller Nischenbildung und zentralisierten Web 2.0-Infrastrukturen. Die sozialen und politischen Realitäten der Digitalisierung und Vernetzung sind heute von zwei konstitutiven, aber grundsätzlich unterschiedlichen, ja teilweise sogar entgegengesetzten Dynamiken geprägt. Beide stellen den Medienaktivismus vor neue Herausforderungen. Zum einen können wir ein Aufblühen neuer kultureller Nischen und horizontaler Organisationsformen beobachten. Zum anderen erleben wir gleichzeitig eine enorme Zentralisierung und Konzentration auf der Ebene der Plattformen, welche einen grossen Teil der infrastrukturellen Grundlage des Wachstum der Nischen und neuen Kooperationsmuster darstellen. Nachdem der Aufbau alternativer Infrastrukturen – Zeitschriften, TV Kanäle und Internetplattformen – in den ersten 30 Jahren medienaktivistischer Projekte eine grosse Rolle gespielt hat (Stalder 2008 sind diese Fragen in den letzten 10 Jahren etwas in den Hintergrund getreten. Denn die Komplexität der Infrastrukturen nahm stetig zu, was es immer aufwendiger machte, sie zu betreiben und die neuen, offene Plattformen, wie sie für Web 2.0 typisch sind, stellten allen - scheinbar ohne Einschränkungen - mächtige Werkzeuge zu Verfügung. Warum eine eigene Plattform betreiben, wenn grosse professionelle Anbieter das besser, sicherer und kostenfrei anbieten? Heute sind die Probleme dieser Entwicklungen aber deutlich zu erkennen. Im Folgenden werden die Herausforderungen dieser Nischenbildung, die dunkle Seite der zentralisierten Infrastrukturen sowie die darauf reagierenden, neue Entwürfe für de-zentrale Infrastrukturen skizziert.

  12. Boltzmann und das Ende des mechanistischen Weltbildes

    Renn, Jürgen

    2007-01-01

    Der Wissenschaftshistoriker und Physiker Jürgen Renn untersucht die Rolle des österreichischen Physikers und Philosophen Ludwig Boltzmann (18441906) bei der Entwicklung der modernen Physik. Boltzmann war einer der letzen Vertreter des mechanistischen Weltbildes und stand somit am Ende eines Zeitalters. Renn porträtiert den Wissenschaftler aber als einen Pionier der modernen Physik, dessen Beschäftigung mit den inneren Spannungen der klassischen Physik ihn visionär zukünftige Fragestellungen aufgreifen ließ. So befasste sich Boltzmann etwa mit den Grenzproblemen zwischen Mechanik und Thermodynamik, die ihn zur Entwicklung immer raffinierterer Instrumente der statistischen Physik antrieb, die schließlich zu Schlüsselinstrumenten der modernen Physik wurden. Boltzmanns Werk steht somit am Übergang vom mechanistischen Weltbild zur Relativitäts- und Quantentheorie. Der Aussage des viel bekannteren Physikers Albert Einstein, dass Fantasie wichtiger sei als Wissen, hält Jürgen Renn im Hinblick auf Leben ...

  13. Kontinuierliche Wanddickenbestimmung und Visualisierung des linken Herzventrikels

    Dornheim, Lars; Hahn, Peter; Oeltze, Steffen; Preim, Bernhard; Tönnies, Klaus D.

    Zur Bestimmung von Defekten in der Herztätigkeit kann die Veränderung der Wanddicke des linken Ventrikels in zeitlichen MRTAufnahmesequenzen gemessen werden. Derzeit werden für diese Bestimmung im allgemeinen nur die aufwändig manuell erstellte Segmentierungen der Endsystole und Enddiastole benutzt. Wir stellen ein bis auf die Startpunktinitialisierung automatisches Verfahren zur Bestimmung der Wanddicke des linken Ventrikels und ihrer Veränderung vor, das auf einer vollständigen Segmentierung der Herzwand in allen Zeitschritten durch ein dynamisches dreidimensionales Formmodell (Stabiles Feder-Masse-Modell) basiert. Dieses Modell nutzt bei der Segmentierung neben der Grauwertinformation eines Zeitschrittes auch die Segmentierungen der anderen Zeitschritte und ist so aufgebaut, dass die Wanddicken direkt gemessen und visualisiert werden können. Auf diese Weise werden die lokalen Wanddickenextrema über den gesamten Aufnahmezeitraum detektiert, auch wenn sie nicht in die Endsystole bzw. -diastole fallen. Das Verfahren wurde auf sechs 4D-Kardio-MRT-Datensätzen evaluiert und stellte sich als sehr robust bzgl. der einzig nötigen Interaktion heraus.

  14. Schule und Bildung im Prozess der Globalisierung

    Jürgen Oelkers

    2000-05-01

    Full Text Available Der Autor erörtert die Auswirkungen der Globalisierung auf Schulen, Lern- und Lehrarrangements sowie die künftige Rolle der Bildung innerhalb der vernetzten, entgrenzten Lebensräume. Dabei geht er der Frage nach, welche Rolle die Schule als traditionell ortsgebundene Einrichtung hinsichtlich der Vorbereitung auf einen globalem Arbeitsmarkt mit seinen Unsicherheiten einnehmen kann. Zunächst beschreibt er allgemeine Tendenzen der Individualisierung und Flexiblisierung von Arbeitsbedingungen, um Konsequenzen für die Kindheit abzuleiten (Zeit der Eltern als knappes Gut, Kommerzialisierung. In einem zweiten Schritt verdeutlicht er, welche Auswirkungen die neuen Medien Internet und Computer für das Lernen haben (Ungebundenheit hinsichtlich Ort, Zeit, damit verknüpft die Unverlässlichkeit von Quellen. In einem letzten Schritt charakterisiert er die Konsequenzen der Globalisierung für die Bildung und die Schule (internationale Standards in den drei großen Wirtschaftsräumen, Notwendigkeit der Vermittlung von Wissen zur Strukturierung und Bewertung von Informationen.

  15. Nudges, Recht und Politik: Institutionelle Implikationen

    Lepenies Robert

    2016-07-01

    Full Text Available In diesem Beitrag argumentieren wir, dass eine umfassende Implementierung sogenannter Nudges weitreichende Auswirkungen für rechtliche und politische Institutionen hat. Die wissenschaftliche Diskussion zu Nudges ist derzeit hauptsächlich von philosophischen Theorien geprägt, die im Kern einen individualistischen Ansatz vertreten. Unsere Analyse bezieht sich auf die Art und Weise, in der sich Anhänger des Nudging neuster Erkenntnisse aus den Verhaltenswissenschaften bedienen – immer in der Absicht, diese für effektives Regieren einzusetzen. Wir unterstreichen, dass die meisten Nudges, die derzeit entweder diskutiert werden oder bereits implementiert sind, nicht Teil eines Rechtssystems sind und keinen normativen Charakter haben. Dazu unterscheiden wir zwischen zwei Idealtypen, um menschliches Verhalten zu beeinflussen, die wir als normativ bzw. instrumentell bezeichnen. Diese Idealtypen stehen für verschiedene Weisen, in denen öffentliche Regeln strukturiert werden können; sie erlauben uns, die institutionellen Implikationen von Nudges zu verstehen und zu bewerten. Hier betonen wir den Wert des Rechts als Absicherung gegenüber den möglichen schädlichen Konsequenzen von in der Politik und Regierungsführung eingesetzten Nudges. Unser Beitrag schließt mit Reaktionen auf einige Einwände, die unsere Vorschläge bereits erhalten haben.

  16. MOCVD growth of GaN layer on InN interlayer and relaxation of residual strain

    Lee, Keon-Hun; Park, Sung Hyun; Kim, Jong Hack; Kim, Nam Hyuk; Kim, Min Hwa [Department of Materials Science and Engineering, Seoul National University, Seoul, 151-742 (Korea, Republic of); Na, Hyunseok [Department of Advanced Materials Science and Engineering, Daejin University, Pocheon, 487-711 (Korea, Republic of); Yoon, Euijoon, E-mail: eyoon@snu.ac.k [Department of Materials Science and Engineering, Seoul National University, Seoul, 151-742 (Korea, Republic of); Department of Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Suwon 433-270 (Korea, Republic of)

    2010-09-01

    100 nm InN layer was grown on sapphire c-plane using a metal-organic chemical vapor deposition (MOCVD) system. Low temperature (LT) GaN layer was grown on InN layer to protect InN layer from direct exposure to hydrogen flow during high temperature (HT) GaN growth and/or abrupt decomposition. Subsequently, thick HT GaN layer (2.5 {mu}m thick) was grown at 1000 {sup o}C on LT GaN/InN/sapphire template. Microstructure of epilayer-substrate interface was investigated by transmission electron microscopy (TEM). From the high angle annular dark field TEM image, the growth of columnar structured LT GaN and HT GaN with good crystallinity was observed. Though thickness of InN interlayer is assumed to be about 100 nm based on growth rate, it was not clearly shown in TEM image due to the InN decomposition. The lattice parameters of GaN layers were measured by XRD measurement, which shows that InN interlayer reduces the compressive strain in GaN layer. The relaxation of compressive strain in GaN layer was also confirmed by photoluminescence (PL) measurement. As shown in the PL spectra, red shift of GaN band edge peak was observed, which indicates the reduction of compressive strain in GaN epilayer.

  17. Ultrasonic synthesis of fern-like ZnO nanoleaves and their enhanced photocatalytic activity

    Ma, Qing Lan; Xiong, Rui; Zhai, Bao-gai; Huang, Yuan Ming

    2015-01-01

    Graphical abstract: - Highlights: • Fern-like ZnO nanoleaves were synthesized by ultrasonicating Zn microcrystals in water. • A fern-like ZnO nanoleaf is a self-assembly of ZnO nanoplates along one ZnO nanorod. • Fern-like ZnO nanoleaves exhibit enhanced photocatalytic activity than ZnO nanocrystals. • The branched hierarchical structures are responsible for the enhanced photocatalytic activity. - Abstract: Two-dimensional fern-like ZnO nanoleaves were synthesized by ultrasonicating zinc microcrystals in water. The morphology, crystal structure, optical property and photocatalytic activity of the fern-like ZnO nanoleaves were characterized with scanning electron microscopy, X-ray diffraction, transmission electron microscopy, photoluminescence spectroscopy and ultraviolet–visible spectroscopy, respectively. It is found that one fern-like ZnO nanoleaf is composed of one ZnO nanorod as the central trunk and a number of ZnO nanoplates as the side branches in opposite pairs along the central ZnO nanorod. The central ZnO nanorod in the fern-like nanoleaves is about 1 μm long while the side-branching ZnO nanoplates are about 100 nm long and 20 nm wide. Further analysis has revealed that ZnO nanocrystals are the building blocks of the central ZnO nanorod and the side-branching ZnO nanoplates. Under identical conditions, fern-like ZnO nanoleaves exhibit higher photocatalytic activity in photodegrading methyl orange in aqueous solution than spherical ZnO nanocrystals. The first-order photocatalytic rate constant of the fern-like ZnO nanoleaves is about four times as large as that of the ZnO nanoparticles. The branched architecture of the hierarchical nanoleaves is suggested be responsible for the enhanced photocatalytic activity of the fern-like ZnO nanoleaves

  18. Kunst und Revolution.John Berger und der sowjetische Bildhauer Ernst Neiswestni

    Artinger, Kai

    2011-01-01

    John Berger war einer der einflussreichsten Kunstkritiker der Linken in den 1950er Jahren in Großbritannien. Er spielte eine zentrale Rolle in den Diskursen über die Situation der Kunst und ihre Zukunft. Bezeichnend für sein Kunstverständnis war es, ausgetretene Pfade zu verlassen und den herrschenden Kanon zu ignorieren. Daher erfasste sein Blick auch die osteuropäische Kunst. Seit 1953 besucht er mehrfach die UdSSR und die DDR. Als unabhängiger Marxist lehnte sich Berger an den Strategien...

  19. Lew Kopelew - der Schriftsteller und Wissenschaftler, der Freund der Menschen und Verfechter ihrer Grundrechte

    Keller, Werner

    2010-01-01

    Unsere Erwartung war anders als sonst – freudig, doch nicht frei von Erregung und leiser Furcht: Wird man im Kreml das gegebene Wort halten und nach einem Jahr die Rückkehr in die russische Heimat erlauben? Als Gast Heinrich Bölls kam Lew Kopelew im November 1980 nach Deutschland. In der Bonner Wohnung des Slawisten Wolfgang Kasack konnte ich mich ihm wenige Tage später vorstellen: Er war groß, von beeindruckender Physiognomie – nicht nur durch den Prophetenbart –, allerdings fast bleich und ...

  20. Gedenken, Geschichte und Versöhnung in Südafrika und Zimbabwe

    Marx, Christoph

    2006-01-01

    'Die Gesellschaft Südafrikas hat sich nach der Überwindung der Apartheid mit der Einrichtung einer Wahrheits- und Versöhnungskommission auf eine wichtige öffentliche Debatte über ihre Vergangenheit eingelassen. Der Kontext dieser Debatte und die Vorgabe, dass die Beschäftigung mit der Vergangenheit in die Bildung einer neuen Nation münden solle, führten indes dazu, dass sich neue Formen von Inklusion und Exklusion entwickelten. Da Identität nur über die Betonung von Differenz möglich ist, läs...

  1. Anodized ZnO nanostructures for photoelectrochemical water splitting

    Huang, Mao-Chia [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Wang, TsingHai [Department of Biomedical Engineering and Environment Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Wu, Bin-Jui [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Lin, Jing-Chie, E-mail: jclin4046@gmail.com [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Wu, Ching-Chen [Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu 310, Taiwan (China)

    2016-01-01

    Highlights: • ZnO nanostructures were synthesized by electrochemical anodic process. • The parameter of ZnO nanostructure was anodic potential. • The model of growth of ZnO nanostructure was investigated. - Abstract: Zinc oxide (ZnO) nanostructures were fabricated on the polished zinc foil by anodic deposition in an alkaline solution containing 1.0 M NaOH and 0.25 M Zn(NO{sub 3}){sub 2}. Potentiostatic anodization was conducted at two potentials (−0.7 V in the passive region and −1.0 V in the active region vs. SCE) which are higher than the open circuit potential (−1.03 V vs. SCE) and as-obtained ZnO nanostrcutures were investigated focusing on their structural, optical, electrical and photoelectrochemical (PEC) characteristics. All samples were confirmed ZnO by X-ray photoelectron spectroscopy and Raman spectra. Observations in the SEM images clearly showed that ZnO nanostructures prepared at −0.7 V vs. SCE were composed of nanowires at while those obtained at −1.0 V vs. SCE possessed nanosheets morphology. Result from transmission electron microscope and X-ray diffraction patterns suggested that the ZnO nanowires belonged to single crystalline with a preferred orientation of (0 0 2) whereas the ZnO nanosheets were polycrystalline. Following PEC experiments indicated that ZnO nanowires had higher photocurrent density of 0.32 mA/cm{sup 2} at 0.5 V vs. SCE under 100 mW/cm{sup 2} illumination. This value was about 1.9 times higher than that of ZnO nanosheets. Observed higher photocurrent was likely due to the single crystalline, preferred (0 0 2) orientation, higher carrier concentration and lower charge transfer resistance.

  2. Aggregation und Management von Metadaten im Kontext von Europeana

    Gerda Koch

    2017-09-01

    Full Text Available Mit dem In-Beziehung-Setzen und Verlinken von Daten im Internet wird der Weg zur Umsetzung des semantischen Webs geebnet. Erst die semantische Verbindung von heterogenen Datenbeständen ermöglicht übergreifende Suchvorgänge und späteres „Machine Learning“. Im Artikel werden die Aktivitäten der Europäischen Digitalen Bibliothek im Bereich des Metadatenmanagements und der semantischen Verlinkung von Daten skizziert. Dabei wird einerseits ein kurzer Überblick zu aktuellen Forschungsschwerpunkten und Umsetzungsstrategien gegeben, und darüber hinaus werden einzelne Projekte und maßgeschneiderte Serviceangebote für naturhistorische Daten, regionale Kultureinrichtungen und Audiosammlungen beschrieben.

  3. Islam, Migration und Integration: Konflikte jugendlicher Migranten mit islamischem Hintergrund

    Ilhan Kizilhan

    2008-04-01

    Full Text Available Der Islam mit seinen verschiedenen Verhaltensweisen und Verboten spielt direkt oder indirekt immer noch eine wichtige Rolle im alltäglichen Leben vieler Migranten. Religiöse Vorschriften zeichnen sich dadurch aus, dass ihrer Achtung nicht juristisch, sondern durch sozialen Druck Nachdruck verliehen wird (Verwandtschaft, religiöse Lehrer, islamische Gemeinde, religiöse Vereine etc. und dass ihre Missachtung mit Folgen in Form von Ausgrenzung, Missachtung und Diskriminierung einhergeht. Die kulturellen Vorstellungen der ersten Generation unterscheiden sich auf Grund der unterschiedlichen Biografien von denen der zweiten und dritten durch den Grad der Verwurzelung in der kulturellen Identität und der Verbundenheit mit traditionellen Wertvorstellungen. Fehlende Integrationskonzepte, Ausgrenzung im Migrationsland auf der einen und weltweite staatliche und halbstaatliche Konflikte im Namen des Islams bis hin zum Terrorismus auf der anderen Seite haben einen erheblichen Einfluss auf den Integrationsgrad von jugendlichen Migranten im Aufnahmeland.

  4. Geschichtsbezogene und rechtspolitische Polonica im Bücherbestand Gottfried Lengnichs

    Iwona Imańska

    2017-11-01

    Full Text Available Gottfried Lengnich, der Historiker und Syndikus der Stadt Danzig aus dem 18. Jahrhundert, hinterließ eine Büchersammlung mit über viertausend Büchern, die nach seinem Tode in zwei Auktionen im Juli und November 1774 versteigert werden sollten. Die Auktionskataloge befinden sich in der Staatsbibliothek zu Berlin – Stiftung Preußischer Kulturbesitz und sind auch online zugänglich. Wegen wissenschaftlicher Interessen Lengnichs befanden sich in seiner Bibliothek ca. 600 Polonica-Drucke, die meisten davon waren Abhandlungen im Themenfeld Geschichte, Recht und Politik. Die Analyse dieses Fragments des Bücherbestands Lengnichs bewies, dass der Syndikus eine perfekte Arbeitswerkstatt für sich schuf, indem er die Werke der meisten wichtigsten polnischen und fremden Autoren, die über die Geschichte und die Gesetzgebung Polens und Preußens schrieben, sammelte.

  5. Hexagonal (wurtzite) GaN inclusions as a defect in cubic (zinc-blende) GaN

    Zainal, N.; Novikov, S.V.; Akimov, A.V.; Staddon, C.R.; Foxon, C.T.; Kent, A.J.

    2012-01-01

    The dependence of the hexagonal fraction with thickness in MBE-grown bulk cubic (c-) GaN epilayer is presented in this paper. A number of c-GaN epilayers with different thicknesses were characterized via PL and XRD measurements. From the PL spectra, the signal due to h-GaN inclusions increases as the thickness of the c-GaN increases. On the contrary, in the XRD diffractogram, c-GaN shows a dominant signal at all thicknesses, and only a weak peak at ∼35° is observed in the diffractogram, implying the existence of a small amount of h-GaN in the c-GaN layer. The best quality of c-GaN is observed in the first 10 μm of GaN on the top of GaAs substrate. Even though the hexagonal content increases with the thickness, the average content remains below 20% in c-GaN layers up to 50 μm thick. The surface morphology of thick c-GaN is also presented.

  6. Growth of β-Ga2O3 and GaN nanowires on GaN for photoelectrochemical hydrogen generation

    Hwang, Jih-Shang; Liu, Tai-Yan; Chen, Han-Wei; Chattopadhyay, Surjit; Hsu, Geng-Ming; Basilio, Antonio M; Hsu, Yu-Kuei; Tu, Wen-Hsun; Lin, Yan-Gu; Chen, Kuei-Hsien; Li, Chien-Cheng; Wang, Sheng-Bo; Chen, Hsin-Yi; Chen, Li-Chyong

    2013-01-01

    Enhanced photoelectrochemical (PEC) performances of Ga 2 O 3 and GaN nanowires (NWs) grown in situ from GaN were demonstrated. The PEC conversion efficiencies of Ga 2 O 3 and GaN NWs have been shown to be 0.906% and 1.09% respectively, in contrast to their 0.581% GaN thin film counterpart under similar experimental conditions. A low crystallinity buffer layer between the grown NWs and the substrate was found to be detrimental to the PEC performance, but the layer can be avoided at suitable growth conditions. A band bending at the surface of the GaN NWs generates an electric field that drives the photogenerated electrons and holes away from each other, preventing recombination, and was found to be responsible for the enhanced PEC performance. The enhanced PEC efficiency of the Ga 2 O 3 NWs is aided by the optical absorption through a defect band centered 3.3 eV above the valence band of Ga 2 O 3 . These findings are believed to have opened up possibilities for enabling visible absorption, either by tailoring ion doping into wide bandgap Ga 2 O 3 NWs, or by incorporation of indium to form InGaN NWs. (paper)

  7. Growth of β-Ga2O3 and GaN nanowires on GaN for photoelectrochemical hydrogen generation.

    Hwang, Jih-Shang; Liu, Tai-Yan; Chattopadhyay, Surjit; Hsu, Geng-Ming; Basilio, Antonio M; Chen, Han-Wei; Hsu, Yu-Kuei; Tu, Wen-Hsun; Lin, Yan-Gu; Chen, Kuei-Hsien; Li, Chien-Cheng; Wang, Sheng-Bo; Chen, Hsin-Yi; Chen, Li-Chyong

    2013-02-08

    Enhanced photoelectrochemical (PEC) performances of Ga(2)O(3) and GaN nanowires (NWs) grown in situ from GaN were demonstrated. The PEC conversion efficiencies of Ga(2)O(3) and GaN NWs have been shown to be 0.906% and 1.09% respectively, in contrast to their 0.581% GaN thin film counterpart under similar experimental conditions. A low crystallinity buffer layer between the grown NWs and the substrate was found to be detrimental to the PEC performance, but the layer can be avoided at suitable growth conditions. A band bending at the surface of the GaN NWs generates an electric field that drives the photogenerated electrons and holes away from each other, preventing recombination, and was found to be responsible for the enhanced PEC performance. The enhanced PEC efficiency of the Ga(2)O(3) NWs is aided by the optical absorption through a defect band centered 3.3 eV above the valence band of Ga(2)O(3). These findings are believed to have opened up possibilities for enabling visible absorption, either by tailoring ion doping into wide bandgap Ga(2)O(3) NWs, or by incorporation of indium to form InGaN NWs.

  8. Ultralow threading dislocation density in GaN epilayer on near-strain-free GaN compliant buffer layer and its applications in hetero-epitaxial LEDs.

    Shih, Huan-Yu; Shiojiri, Makoto; Chen, Ching-Hsiang; Yu, Sheng-Fu; Ko, Chung-Ting; Yang, Jer-Ren; Lin, Ray-Ming; Chen, Miin-Jang

    2015-09-02

    High threading dislocation (TD) density in GaN-based devices is a long unresolved problem because of the large lattice mismatch between GaN and the substrate, which causes a major obstacle for the further improvement of next-generation high-efficiency solid-state lighting and high-power electronics. Here, we report InGaN/GaN LEDs with ultralow TD density and improved efficiency on a sapphire substrate, on which a near strain-free GaN compliant buffer layer was grown by remote plasma atomic layer deposition. This "compliant" buffer layer is capable of relaxing strain due to the absorption of misfit dislocations in a region within ~10 nm from the interface, leading to a high-quality overlying GaN epilayer with an unusual TD density as low as 2.2 × 10(5) cm(-2). In addition, this GaN compliant buffer layer exhibits excellent uniformity up to a 6" wafer, revealing a promising means to realize large-area GaN hetero-epitaxy for efficient LEDs and high-power transistors.

  9. Einleitung: Jahrbuch Medienpädagogik 5. Evaluation und Analyse

    Ben Bachmair

    2017-09-01

    Full Text Available Evaluationsmethoden für E-Learning, Forschungsmethoden zur Mediennutzung und zur Analyse von Medienkulturen sind Gegenstand dieses Jahrbuchs Medienpädagogik. Dabei reicht das Spektrum der Medien von Fernsehen über Video bis zum Internet. Die Auswahl dieses Themenschwerpunkts kommt dabei nicht von ungefähr. Zum einen hat wissenschaftliche Medienforschung bereits eine lange Tradition und ist in vielen Disziplinen etabliert. Forschungsmethoden lieferten der medienpädagogischen Praxis empirisch fundierte Ergebnisse und Instrumente. Forschungsdesigns und Methodologien wurden entwickelt, um Mediennutzungsverhalten und Medienwirkungen zu erklären, Evaluationsmethoden eingesetzt, um Lernprozesse zu beurteilen. Zum anderen gewinnen Qualitätssicherung und Leistungsmessungen im Bildungssystem generell immer mehr an Bedeutung. In den Ergebnissen aktueller Evaluationen zeigen sich Bestrebungen nach Qualität von Bildungs- und Lernprozessen. Empirische Forschung kommt die Aufgabe zu medienpädagogische Wirkungsgrade und Zielerreichung zu überprüfen und zu kontrollieren. Quantitative Forschungsmethoden ermöglichen es Mediennutzungsverhalten bestimmter Zielgruppen in Wechselwirkung mit Programmstrukturen und -inhalten zu ermitteln. Nutzungsmuster von Medienangeboten – vor allem bei Kindern und Jugendlichen – sind auch bei der Entwicklung medienpädagogischer Ansätze wichtig. Qualitative Medienforschung dient als Planungsinstrument für medienpädagogische Konzeptionen sowie für medienpädagogische Praxis und hilft bei der Entwicklung neuer, mehr als bisher an inhaltlichen Kriterien orientierter Angebote eingesetzt werden. Eine der zentralen Fragestellungen war und ist dabei, mit welchen kognitiven und ästhetischen Vermittlungsformen die Inhalte einer Sendung am besten kommuniziert werden können. Dies ist zugleich eine der Grundfragen im Hinblick auf den Medieneinsatz in pädagogisch orientierten Lernprozessen (vgl. Dichanz 1998.

  10. Climate protection and competition; Klimaschutz und Wettbewerb

    Diekmann, M. [Stadtwerke Braunschweig GmbH (Germany)

    1998-06-01

    Discussions on energy-related matters have recently been dominated above all by the two issues climate protection and the introduction of competition. The public utility Stadtwerke Braunschweig GmbH and its subsidiaries Braunschweiger Versorgungs-AG and Braunschweiger Verkehrs-AG have committed themselves to the cause of climate protection. The ongoing implementation of the utility`s energy supply concept is making a substantial contribution to energy conservation and air pollution control. [Deutsch] Die Diskussionen zum Thema Energie werden in der letzten Zeit im wesentlichen von zwei Themen beherrscht: Klimaschutz und Einfuehrung von Wettbewerb. Die Stadtwerke Braunschweig GmbH mit ihren Tochtergesellschaften Braunschweiger Versorgungs-AG und Braunschweiger Verkehrs-AG engagieren sich im Klimaschutz. Die fortlaufende Umsetzung des Energieversorgungskonzepts der Stadtwerke traegt wesentlich zur Energieeinsparung und zur Reduzierung von Schadstoff-Emissionen bei. (orig./MSK)

  11. Grundlage und Bedeutung der operativen Endometriosetherapie

    Schweppe KW

    2009-01-01

    Full Text Available Die Endometriose wird invasiv durch Laparoskopie und bioptische Sicherung diagnostiziert, sodass es nahe liegt, dass sich die chirurgische Therapie in gleicher Narkose anschließt. Unterschiedliche Wachstumsformen der Endometriose einerseits (kleinherdig-peritoneal, zystisch-ovariell oder tief infiltrierend und unterschiedliche Therapieziele andererseits (Schmerzfreiheit, Tumorbeseitigung, Schwangerschaft erfordern einen individuellen Behandlungsplan, der auch das Alter der Patientin mitberücksichtigt. Medikamentöse Therapieoptionen spielen additiv zum primär operativen Vorgehen eine Rolle, wobei oft symptomatische Maßnahmen bei dieser chronischen, rezidivierenden Krankheit ausreichen. Endoskopische Operationstechniken sind heute Standard. Unterschiede in Erfolgs- und Rezidivraten sind bisher für die verschiedenen Techniken nicht durch randomisierte Studien belegt.

  12. [Die baltischen Lande im Zeitalter der Reformation und Konfessionalisierung. Livland, Estland, Ösel, Ingermanland, Kurland und Lettgallen. Stadt, Land und Konfession 1500-1721. Teil I] / Heinrich Wittram

    Wittram, Heinrich, 1931-

    2011-01-01

    Arvustus : Die baltischen Lande im Zeitalter der Reformation und Konfessionalisierung. Livland, Estland, Ösel, Ingermanland, Kurland und Lettgallen. Stadt, Land und Konfession 1500-1721. Teil I. Münster : Aschendorff, 2009. (Katholisches Leben und Kirchenreform im Zeitalter der Glaubensspaltung, 69)

  13. [Christofer Herrmann. Kloster und Burg - die architektur des Deutschens Ordens im Pressen und Livland. In : Glaube, Macht und Pracht. GeistlicheGemeinschaften des Ostseeraums im Zeitalter der Backsteingotik] / Dennis Hortmuth

    Hortmuth, Dennis

    2011-01-01

    Arvustus: Christofer Herrmann. Kloster und Burg - die Architektur des Deutschen Ordens in Preussen und Livland. In : Glaube, Macht und Pracht. GeistlicheGemeinschaften des Ostseeraums im Zeitalter der Backsteingotik (=Archäologie und Geschichte im Ostseeraum; Archaeology and History of the Baltic 6) Rahden : Verlag Marie Leidorf, 2009. S. 209-219. Saksa Ordu arhitektuurist Preisi- ja Liivimaal

  14. [St. Petersburg und Livland - und die Entwicklung der estnischen Literatur : Anton Schiefner (1817-1879) und Friedrich R. Kreutzwald (1803-1882) im Briefwechsel (1853-1879)] / Felix Köther

    Köther, Felix

    2015-01-01

    Arvustus: St. Petersburg und Livland - und die Entwicklung der estnischen Literatur : Anton Schiefner (1817-1879) und Friedrich R. Kreutzwald (1803-1882) im Briefwechsel (1853-1879) / bearbeitet von Hartmut Walravens. Wiesbaden : Harrassowitz, 2013. (Orientalistik-Bibliographien und Dokumentationen ; Bd. 22)

  15. Design of Low Inductance Switching Power Cell for GaN HEMT Based Inverter

    Gurpinar, Emre; Iannuzzo, Francesco; Yang, Yongheng

    2018-01-01

    . The design of gate drivers for the GaN HEMT devices is presented. Parasitic inductance and resistance of the proposed design are extracted with finite element analysis and discussed. Common-mode behaviours based on the SPICE model of the converter are analyzed. Experimental results on the designed 3L......In this paper, an ultra-low inductance power cell is designed for a three-Level Active Neutral Point Clamped (3LANPC) based on 650 V gallium nitride (GaN) HEMT devices. The 3L-ANPC topology with GaN HEMT devices and the selected modulation scheme suitable for wide-bandgap (WBG) devices...... are presented. The commutation loops, which mainly contribute to voltage overshoots and increase of switching losses, are discussed. The ultra-low inductance power cell design based on a four-layer Printed Circuit Board (PCB) with the aim to maximize the switching performance of GaN HEMTs is explained...

  16. GaN nano-membrane for optoelectronic and electronic device applications

    Ooi, Boon S.

    2014-01-01

    The ~25nm thick threading dislocation free GaN nanomembrane was prepared using ultraviolet electroless chemical etching method offering the possibility of flexible integration of (Al,In,Ga)N optoelectronic and electronic devices.

  17. 380 keV proton irradiation effects on photoluminescence of Eu-doped GaN

    Okada, Hiroshi; Nakanishi, Yasuo; Wakahara, Akihiro; Yoshida, Akira; Ohshima, Takeshi

    2008-01-01

    The effect of 380 keV proton irradiation on the photoluminescence (PL) properties has been investigated for undoped and Eu-doped GaN. As the proton irradiation exceeds 1x10 13 cm -2 , a drastic decrease of PL intensity of the near band-edge emission of undoped GaN was observed. On the other hand, for Eu-doped GaN, the PL emission corresponding to the 5 D 0 → 7 F 2 transition in Eu 3+ kept the initial PL intensity after the proton irradiation up to 1x10 14 cm -2 . Present results, together with our previous report on electron irradiation results, suggest that Eu-doped GaN is a strong candidate for light emitting devices in high irradiation environment

  18. The GaN trench gate MOSFET with floating islands: High breakdown voltage and improved BFOM

    Shen, Lingyan; Müller, Stephan; Cheng, Xinhong; Zhang, Dongliang; Zheng, Li; Xu, Dawei; Yu, Yuehui; Meissner, Elke; Erlbacher, Tobias

    2018-02-01

    A novel GaN trench gate (TG) MOSFET with P-type floating islands (FLI) in drift region, which can suppress the electric field peak at bottom of gate trench during the blocking state and prevent premature breakdown in gate oxide, is proposed and investigated by TCAD simulations. The influence of thickness, position, doping concentration and length of the FLI on breakdown voltage (BV) and specific on-resistance (Ron_sp) is studied, providing useful guidelines for design of this new type of device. Using optimized parameters for the FLI, GaN FLI TG-MOSFET obtains a BV as high as 2464 V with a Ron_sp of 3.0 mΩ cm2. Compared to the conventional GaN TG-MOSFET with the same structure parameters, the Baliga figure of merit (BFOM) is enhanced by 150%, getting closer to theoretical limit for GaN devices.

  19. Electronic structure and optical properties of Al and Mg co-doped GaN

    Ji Yan-Jun; Du Yu-Jie; Wang Mei-Shan

    2013-01-01

    The electronic structure and optical properties of Al and Mg co-doped GaN are calculated from first principles using density function theory with the plane-wave ultrasoft pseudopotential method. The results show that the optimal form of p-type GaN is obtained with an appropriate Al:Mg co-doping ratio rather than with only Mg doping. Al doping weakens the interaction between Ga and N, resulting in the Ga 4s states moving to a high energy region and the system band gap widening. The optical properties of the co-doped system are calculated and compared with those of undoped GaN. The dielectric function of the co-doped system is anisotropic in the low energy region. The static refractive index and reflectivity increase, and absorption coefficient decreases. This provides the theoretical foundation for the design and application of Al—Mg co-doped GaN photoelectric materials

  20. Above room-temperature ferromagnetism of Mn delta-doped GaN nanorods

    Lin, Y. T.; Wadekar, P. V.; Kao, H. S.; Chen, T. H.; Chen, Q. Y.; Tu, L. W.; Huang, H. C.; Ho, N. J.

    2014-01-01

    One-dimensional nitride based diluted magnetic semiconductors were grown by plasma-assisted molecular beam epitaxy. Delta-doping technique was adopted to dope GaN nanorods with Mn. The structural and magnetic properties were investigated. The GaMnN nanorods with a single crystalline structure and with Ga sites substituted by Mn atoms were verified by high-resolution x-ray diffraction and Raman scattering, respectively. Secondary phases were not observed by high-resolution x-ray diffraction and high-resolution transmission electron microscopy. In addition, the magnetic hysteresis curves show that the Mn delta-doped GaN nanorods are ferromagnetic above room temperature. The magnetization with magnetic field perpendicular to GaN c-axis saturates easier than the one with field parallel to GaN c-axis