@article{4198, abstract = {{Three-dimensional (3D) photonic crystal exhibit direction-selective transmission with respect to the center frequency of the stop gap. As a model system, the stop gap of a 3D fcc inverted-opal photonic crystal is studied in the microwave regime in detail using 3D polyamide models. The difference in the direction-selective transmittance between crystals grown in two different high symmetry directions is experimentally shown and compared to numerical simulations.}}, author = {{Üpping, J. and Miclea, P.T. and Wehrspohn, R.B. and Baumgarten, T. and Greulich-Weber, Siegmund}}, issn = {{1569-4410}}, journal = {{Photonics and Nanostructures - Fundamentals and Applications}}, number = {{2}}, pages = {{102--106}}, publisher = {{Elsevier BV}}, title = {{{Direction-selective optical transmission of 3D fcc photonic crystals in the microwave regime}}}, doi = {{10.1016/j.photonics.2009.11.002}}, volume = {{8}}, year = {{2009}}, } @article{4219, abstract = {{The solar cell concept presented here is based on 3C-SiC nano- or microwires and conju¬gated polymers. Therefore the silicon carbide wires are fabricated by a sol-gel route including a car-bothermal reduction step, allowing growth with predetermined uniform diameters between 0.1 and 2μm and lengths up to several centimetres. The design of our photovoltaic device is therein based on a p-i-n structure, well known e.g. from silicon photovoltaics, involving an intrinsic semiconduc¬tor as the central photoactive layer, sandwiched between two complementary doped wide-bandgap semiconductors giving the driving force for charge separation. In our case the 3C-SiC microwires act as the electron acceptor and simultaneously as carrier material for all involved components of the photovoltaic element. }}, author = {{Greulich-Weber, Siegmund and Zöller, M. and Friedel, B.}}, issn = {{1662-9752}}, journal = {{Materials Science Forum}}, pages = {{239--242}}, publisher = {{Trans Tech Publications}}, title = {{{Textile Solar Cells Based on SiC Microwires}}}, doi = {{10.4028/www.scientific.net/msf.615-617.239}}, volume = {{615-617}}, year = {{2009}}, } @article{4220, abstract = {{We report on constructive methods providing a large range of high purity porous SiC products. All methods are based on modified sol-gel processes combined with carbothermal re¬duction. We obtain monodisperse regular pores of well defined diameters by using carbon sphere templates which are removed after SiC infiltration. A different way is a sol-gel based conversion of graphite bodies into SiC, which transfers the porosity from the graphite matrix into the final SiC product. Thus a large variety of porosity features are available, originating either from natural poro¬sity of graphite or from priorly created nano-/ microstructures in the carbonaceous base material. Whereas all our pristine porous sol-gel derived silicon carbide products are semi-insulating, doping is possible, during the growth to modifiy the electrical and optical properties. }}, author = {{Greulich-Weber, Siegmund and Friedel, B.}}, issn = {{1662-9752}}, journal = {{Materials Science Forum}}, pages = {{637--640}}, publisher = {{Trans Tech Publications}}, title = {{{Bottom-Up Routes to Porous Silicon Carbide}}}, doi = {{10.4028/www.scientific.net/msf.615-617.637}}, volume = {{615-617}}, year = {{2009}}, } @article{4225, abstract = {{EPR and ESE in nitrogen doped 4H- and 6H-SiC show besides the well known triplet lines of 14N on quasi-cubic (Nc,k) and hexagonal (Nc,h) sites additional lines (Nx) of comparatively low intensity providing half the hf splitting of Nc,k. Frequently re-interpreted as spin-forbidden lines, arising from Nc,k pairs and triads or resulting from hopping conductivity, only recently the theoretical calculation of the corresponding g-tensors lead to a tentative model of distant NC donor pairs on inequivalent lattice sites which are coupled to S = 1 assuming a fine-structure splitting too small to be observed in the EPR and ESE experiments. In this work, we present ESE nutation measurements confirming S = 1 for the Nx center. Analysing the nutation frequencies in comparison with that of the Nc,k (S = 1/2) spectrum as well as the line width of ESE and EPR spectra we obtain a rough estimate between 5×104 cm-1 and 50×104 cm-1 for the fine-structure splitting demonstrating efficient spin-coupling between nitrogen donors in 4H-SiC.}}, author = {{Savchenko, D.V. and Pöppl, Andreas and Kalabukhova, Ekaterina N. and Greulich-Weber, Siegmund and Rauls, Eva and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{1662-9752}}, journal = {{Materials Science Forum}}, pages = {{343--346}}, publisher = {{Trans Tech Publications}}, title = {{{Spin-Coupling in Heavily Nitrogen-Doped 4H-SiC}}}, doi = {{10.4028/www.scientific.net/msf.615-617.343}}, volume = {{615-617}}, year = {{2009}}, } @article{4226, abstract = {{In non-annealed 6H-SiC samples that were electron irradiated at low temperature, a new EPR signal due to a S =1 defect center with exceptionally large zero-field splitting (D= +652104cm1,E=8104cm1) has been observed under illumination. A positive sign of D demonstrates that the spin–orbit contribution to the zero-field splitting exceeds by far that of the spin–spin interaction. A principal axis of the fine-structure tilted by 59 1 against the crystal c -axis as well as the exceptionally high zero-field splitting D can be qualitatively understood by the occurrence of additional close-lying defect levels in defect clusters resulting in comparatively large second-order spin–orbit coupling. A tentative assignment to vacancy clusters is supported by the observed annealing behavior.}}, author = {{Scholle, A. and Greulich-Weber, S. and Rauls, E. and Schmidt, W.G. and Gerstmann, U.}}, issn = {{0921-4526}}, journal = {{Physica B: Condensed Matter}}, number = {{23-24}}, pages = {{4742--4744}}, publisher = {{Elsevier BV}}, title = {{{Vacancy clusters created via room temperature irradiation in 6H-SiC}}}, doi = {{10.1016/j.physb.2009.08.123}}, volume = {{404}}, year = {{2009}}, } @inproceedings{4228, abstract = {{The issues and challenges of growing GaN-based structures on large area Si substrates have been studied. These include Si slip resulting from large temperature non-uniformities and cracking due to differential thermal expansion. Using an AlN nucleation layer in conjunction with an AlGaN buffer layer for stress management, and together with the interactive use of real time in-situ optical monitoring it was possible to realise flat, crack-free and uniform GaN and LED structures on 6-inch Si (111) substrates. The EL performance of processed LED devices was also studied on-wafer, giving good EL characteristics including a forward bias voltage of ~3.5 V at 20 mA from a 500 μm x 500 μm device.}}, author = {{Zhu, D. and McAleese, C. and McLaughlin, K. K. and Häberlen, M. and Salcianu, C. O. and Thrush, E. J. and Kappers, M. J. and Phillips, W. A. and Lane, P. and Wallis, D. J. and Martin, T. and Astles, M. and Thomas, S. and Pakes, A. and Heuken, M. and Humphreys, C. J.}}, booktitle = {{Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XIII}}, editor = {{Streubel, Klaus P. and Jeon, Heonsu and Tu, Li-Wei}}, location = {{San Jose, California (USA)}}, publisher = {{SPIE}}, title = {{{GaN-based LEDs grown on 6-inch diameter Si (111) substrates by MOVPE}}}, doi = {{10.1117/12.814919}}, volume = {{7231}}, year = {{2009}}, } @inproceedings{4231, author = {{Lindner, Jörg}}, location = {{ Universidad Autónoma de Madrid (Spain)}}, title = {{{Characterisation of nanostructured materials for electronic and photonic information processing}}}, year = {{2009}}, } @inproceedings{4232, author = {{Lindner, Jörg}}, location = {{Bad Karlshafen (Germany)}}, title = {{{Ion Implantation: Fundamental Aspects and Recent Applications}}}, year = {{2009}}, } @inproceedings{4233, author = {{Lindner, Jörg}}, location = {{Bochum (Germany)}}, title = {{{Ionenstrahlmodifikation kleiner Oberflächenbereiche mittels selbstorganisierter Nanomasken}}}, year = {{2009}}, } @inproceedings{4234, author = {{Reichardt, F. and Weinl, M. and Gogel, D. and Wätje, K. and Wixforth, A. and Stritzker, B. and Lindner, Jörg}}, location = {{Straßburg (France)}}, title = {{{Synthesis of 2D-Nanostructured ZnO Thin Films using Nanosphere Lithography and Sputter Deposition}}}, year = {{2009}}, } @article{16111, author = {{Heim, B. and Elser, D. and Bartley, Tim and Sabuncu, M. and Wittmann, C. and Sych, D. and Marquardt, C. and Leuchs, G.}}, issn = {{0946-2171}}, journal = {{Applied Physics B}}, pages = {{635--640}}, title = {{{Atmospheric channel characteristics for quantum communication with continuous polarization variables}}}, doi = {{10.1007/s00340-009-3838-8}}, year = {{2009}}, } @article{3094, abstract = {{We demonstrate for the first time the feasibility of free space quantum key distribution with continuous variables under real atmospheric conditions. More specifically, we transmit coherent polarization states over a 100 m free space channel on the roof of our institute's building. In our scheme, signal and local oscillator (LO) are combined in a single spatial mode, which auto-compensates atmospheric fluctuations and results in an excellent interference. Furthermore, the LO acts as a spatial and spectral filter, thus allowing unrestrained daylight operation.}}, author = {{Elser, D. and Bartley, Tim and Heim, B. and Wittmann, Ch and Sych, D. and Leuchs, G.}}, issn = {{1367-2630}}, journal = {{New Journal of Physics}}, number = {{4}}, pages = {{045014}}, title = {{{Feasibility of free space quantum key distribution with coherent polarization states}}}, year = {{2009}}, } @inproceedings{4218, abstract = {{In this work we focus on the fabrication of ohmic contacts and of Schottky barrier devices (SBD) on non-polar cubic GaN epilayers grown by molecular beam epitaxy (MBE). A Ti/Al/Ni/Au metallization was used for ohmic contacts and the contact resistance was measured by transmission line measurements (TLM). Ni, Pd, Ag and NiSi Schottky barrier devices 300 µm in diameter were fabricated by thermal evaporation using contact lithography on cubic GaN epilayers. The current-voltage (I-V) and the capacity-voltage (C-V) characteristics were studied at room temperature in detail. A clear rectifying behavior was measured in all SBDs. In the Ni and Ag SBDs an abnormal large leakage current under reverse bias was observed. Isochronal thermal annealing of these Ni and Ag based SBDs at 200°C in air improved the reverse characteristics by up to three orders of magnitude. This is in contrast to the Pd contacts, where the as grown contact showed already good performance and thermal annealing had nearly no influence on the I-V characteristics. For all SBDs the magnitude of the reverse current is generally larger than that expected due to thermionic emission and an exponential increase of the reverse current is observed with increasing reverse voltage. In-depth analysis of the I-V characteristic showed that a thin surface barrier is formed at the metal semiconductor interface and that crystal defects like dislocations may be the reasons for the discrepancy between experimental data and thermionic emission theory. }}, author = {{As, Donat J. and Tschumak, Elena and Laubenstein, Irina and Kemper, Ricarda M. and Lischka, Klaus}}, booktitle = {{Materials Research Society Symposium Proceedings}}, pages = {{3--8}}, publisher = {{Materials Research Society}}, title = {{{Schottky and Ohmic Contacts on Non-Polar Cubic GaN Epilayers}}}, doi = {{10.1557/proc-1108-a01-02}}, volume = {{1108}}, year = {{2009}}, } @article{29678, author = {{Ksenzov, D. and Grigorian, S. and Hendel, S. and Bienert, F. and Sacher, Marc and Heinzmann, U. and Pietsch, U.}}, issn = {{1862-6300}}, journal = {{physica status solidi (a)}}, keywords = {{Materials Chemistry, Electrical and Electronic Engineering, Surfaces, Coatings and Films, Surfaces and Interfaces, Condensed Matter Physics, Electronic, Optical and Magnetic Materials}}, number = {{8}}, pages = {{1875--1879}}, publisher = {{Wiley}}, title = {{{Reflection of femtosecond pulses from soft X-ray free-electron laser by periodical multilayers}}}, doi = {{10.1002/pssa.200881585}}, volume = {{206}}, year = {{2009}}, } @article{40201, author = {{Andersen, U.L. and Leuchs, G. and Silberhorn, Christine}}, issn = {{1863-8880}}, journal = {{Laser & Photonics Reviews}}, keywords = {{Condensed Matter Physics, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials}}, number = {{3}}, pages = {{337--354}}, publisher = {{Wiley}}, title = {{{Continuous-variable quantum information processing}}}, doi = {{10.1002/lpor.200910010}}, volume = {{4}}, year = {{2009}}, } @inproceedings{44108, author = {{Meier, Torsten and Zhang, Tianhao and Kuznetsova, Irina and Yang, Lijun and Bristow, Alan D and Dai, Xingcan and Li, Xiaoqin and Thomas, P. and Mukamel, S. and Mirin, Richard P. and Cundiff, S.T.}}, booktitle = {{Ultrafast Phenomena XVI: Proceedings of the 16th International Conference, Palazzo dei Congressi Stresa, Italy, June 9--13, 2008}}, location = {{Palazzo dei Congressi Stresa, Italy}}, pages = {{247--249}}, publisher = {{Springer Berlin Heidelberg}}, title = {{{Ultrafast Coherent Interactions in Quantum Wells Studied by Two-Dimensional Fourier Transform Spectroscopy}}}, year = {{2009}}, } @article{44107, abstract = {{We demonstrate a technique for the generation and detection of electron currents at surfaces on a femtosecond time scale with a contact-free experimental setup based on a combination of coherent control and photoemission spectroscopy. We have applied this technique for electrons excited into image-potential states on a Cu(100) surface that form a free-electron-like band in the direction parallel to the surface. The photogeneration of currents is described by optical Bloch equations for a multiband model. By incorporating field-induced interband and intersubband transitions together with intraband accelerations into the model, the observed phase dependence of the population and of the current can be reproduced.}}, author = {{Meier, Torsten and Güdde, Jens and Rohleder, M. and Koch, S.W. and Höfer, Ulrich}}, journal = {{physica status solidi c}}, number = {{2}}, pages = {{461--465}}, publisher = {{WILEY‐VCH Verlag}}, title = {{{Generation and time‐resolved detection of coherently controlled electric currents at surfaces}}}, doi = {{10.1002/pssc.200880350}}, volume = {{6}}, year = {{2009}}, } @inproceedings{4179, abstract = {{We numerically investigate Whispering Gallery Modes (WGM) in a subwavelength microdisk resonator [1] embedded in an uniaxial anisotropic liquid crystal environment. It is shown that the WGMs have anticrossing behavior when modes of different radial mode order M or azimuthal order N approach each other spectrally. }}, author = {{Förstner, Jens and Declair, S. and Meier, Cedrik and Meier, Torsten}}, booktitle = {{Theoretical and Computational Nanophotonics Tacona-Photonics}}, keywords = {{tet_topic_microdisk}}, location = {{Tacona}}, number = {{1}}, pages = {{60--62}}, title = {{{Anticrossing of Whispering Gallery Modes in Microdisk Resonators Embedded in a Liquid Crystal}}}, doi = {{10.1063/1.3253921}}, volume = {{1176}}, year = {{2009}}, } @inproceedings{44069, abstract = {{Recently it has been shown experimentally that it is possible to coherently control nano-optical excitations by using sophisticated shaped laser pulses. In this work a similar technique is used to theoretically investigate a hybrid nanostructure which consists of a metal aperture and a quantum wire. It is shown that one can concentrate the optically excited electron density at an arbitrary position due to wave packet dynamics by chosing particular frequency components and phases of the chirped laser pulse. The optimization process is performed with a genetic algorithm which is linked to a 3D-FDTD solver.}}, author = {{Meier, Torsten and Reichelt, Matthias}}, booktitle = {{DPG Spring meeting 2009}}, issn = {{0420-0195}}, location = {{Dresden, Germany}}, number = {{5}}, title = {{{Coherent control in hybrid metal-semiconductor nanostructures}}}, volume = {{44}}, year = {{2009}}, } @article{23481, abstract = {{A one-dimensional semiconductor nanostructure is locally excited through a metal aperture. It is shown that the electron density can be coherently localized at desired spatial and temporal positions by using nontrivially shaped laser pulses. To obtain the optimized laser field, Bloch equations for a tight-binding model system are solved together with a genetic pulse-shaping algorithm. Full three-dimensional finite-difference time-domain (FDTD) simulations of the Maxwell–Bloch equations confirm the predicted coherent spatiotemporal control.}}, author = {{Reichelt, Matthias and Meier, Torsten}}, issn = {{0146-9592}}, journal = {{Optics Letters}}, number = {{19}}, pages = {{2900--2902}}, title = {{{Shaping the spatiotemporal dynamics of the electron density in a hybrid metal-semiconductor nanostructure}}}, doi = {{10.1364/ol.34.002900}}, volume = {{34}}, year = {{2009}}, }