@article{13528, author = {{George, B. M. and Behrends, J. and Schnegg, A. and Schulze, T. F. and Fehr, M. and Korte, L. and Rech, B. and Lips, K. and Rohrmüller, M. and Rauls, E. and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, number = {{13}}, title = {{{Atomic Structure of Interface States in Silicon Heterojunction Solar Cells}}}, doi = {{10.1103/physrevlett.110.136803}}, volume = {{110}}, year = {{2013}}, } @inbook{18475, abstract = {{The frequency-dependent dielectric function and the second-order polarizability tensor of ferroelectric LiNbO3 are calculated from first principles. The calculations are based on the electronic structure obtained from density-functional theory. The subsequent application of the GW approximation to account for quasiparticle effects and the solution of the Bethe–Salpeter equation yield a dielectric function for the stoichiometric material that slightly overestimates the absorption onset and the oscillator strength in comparison with experimental measurements. Calculations at the level of the independent-particle approximation indicate that these deficiencies are at least partially related to the neglect of intrinsic defects typical for the congruent material. The second-order polarizability calculated within the independent-particle approximation predicts strong nonlinear coefficients for photon energies above 1.5 eV. The comparison with measured data suggests that self-energy effects improve the agreement between experiment and theory. The intrinsic defects of congruent samples reduce the optical nonlinearities, in particular for the 21 and 31 tensor components, further improving the agreement with measured data.}}, author = {{Riefer, Arthur and Rohrmüller, Martin and Landmann, Marc and Sanna, Simone and Rauls, Eva and Vollmers, Nora Jenny and Hölscher, Rebecca and Witte, Matthias and Li, Yanlu and Gerstmann, Uwe and Schindlmayr, Arno and Schmidt, Wolf Gero}}, booktitle = {{High Performance Computing in Science and Engineering ‘13}}, editor = {{Nagel, Wolfgang E. and Kröner, Dietmar H. and Resch, Michael M.}}, isbn = {{978-3-319-02164-5}}, pages = {{93--104}}, publisher = {{Springer}}, title = {{{Lithium niobate dielectric function and second-order polarizability tensor from massively parallel ab initio calculations}}}, doi = {{10.1007/978-3-319-02165-2_8}}, year = {{2013}}, } @article{13820, author = {{Schmidt, Wolf Gero and Wippermann, S. and Sanna, S. and Babilon, M. and Vollmers, N. J. and Gerstmann, Uwe}}, issn = {{0370-1972}}, journal = {{physica status solidi (b)}}, number = {{2}}, pages = {{343--359}}, title = {{{In-Si(111)(4 × 1)/(8 × 2) nanowires: Electron transport, entropy, and metal-insulator transition}}}, doi = {{10.1002/pssb.201100457}}, volume = {{249}}, year = {{2012}}, } @article{13566, author = {{Hoehne, Felix and Lu, Jinming and Stegner, Andre R. and Stutzmann, Martin and Brandt, Martin S. and Rohrmüller, Martin and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, number = {{19}}, title = {{{Electrically Detected Electron-Spin-Echo Envelope Modulation: A Highly Sensitive Technique for Resolving Complex Interface Structures}}}, doi = {{10.1103/physrevlett.106.196101}}, volume = {{106}}, year = {{2011}}, } @article{13567, author = {{Konopka, A. and Greulich-Weber, S. and Dierolf, V. and Jiang, H.X. and Gerstmann, Uwe and Rauls, E. and Sanna, S. and Schmidt, Wolf Gero}}, issn = {{0925-3467}}, journal = {{Optical Materials}}, pages = {{1041--1044}}, title = {{{Microscopic structure and energy transfer of vacancy-related defect pairs with Erbium in wide-gap semiconductors}}}, doi = {{10.1016/j.optmat.2010.12.005}}, volume = {{33}}, year = {{2011}}, } @article{13574, author = {{Gerstmann, Uwe and Rohrmüller, M. and Mauri, F. and Schmidt, Wolf Gero}}, issn = {{1862-6351}}, journal = {{physica status solidi (c)}}, number = {{2}}, pages = {{157--160}}, title = {{{Ab initiog-tensor calculation for paramagnetic surface states: hydrogen adsorption at Si surfaces}}}, doi = {{10.1002/pssc.200982462}}, volume = {{7}}, year = {{2010}}, } @article{13656, author = {{Bihler, C. and Gerstmann, Uwe and Hoeb, M. and Graf, T. and Gjukic, M. and Schmidt, Wolf Gero and Stutzmann, M. and Brandt, M. S.}}, issn = {{1098-0121}}, journal = {{Physical Review B}}, number = {{20}}, title = {{{Manganese-hydrogen complexes inGa1−xMnxN}}}, doi = {{10.1103/physrevb.80.205205}}, volume = {{80}}, year = {{2010}}, } @article{13837, abstract = {{In non-annealed 6H-SiC samples that were electron irradiated at room temperature, a new EPR signal due to a S=1 defect center with exceptionally large zero-field splitting (D = +652•10-4 cm-1) 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° 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 coup¬ling. A tentative assignment to vacancy clusters is supported by the observed annealing behavior. }}, author = {{Scholle, Andreas and Greulich-Weber, Siegmund and Rauls, Eva and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{1662-9752}}, journal = {{Materials Science Forum}}, pages = {{403--406}}, title = {{{Fine Structure of Triplet Centers in Room Temperature Irradiated 6H-SiC}}}, doi = {{10.4028/www.scientific.net/msf.645-648.403}}, volume = {{645-648}}, year = {{2010}}, } @article{13835, author = {{Scholle, A. and Greulich-Weber, S. and As, Donat Josef and Mietze, Ch. and Son, N. T. and Hemmingsson, C. and Monemar, B. and Janzén, E. and Gerstmann, Uwe and Sanna, S. and Rauls, E. and Schmidt, Wolf Gero}}, issn = {{0370-1972}}, journal = {{physica status solidi (b)}}, number = {{7}}, pages = {{1728--1731}}, title = {{{Magnetic characterization of conductance electrons in GaN}}}, doi = {{10.1002/pssb.200983582}}, volume = {{247}}, year = {{2010}}, } @article{13583, author = {{Scholle, A. and Greulich-Weber, S. and Rauls, E. and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{0921-4526}}, journal = {{Physica B: Condensed Matter}}, pages = {{4742--4744}}, title = {{{Vacancy clusters created via room temperature irradiation in 6H-SiC}}}, doi = {{10.1016/j.physb.2009.08.123}}, volume = {{404}}, year = {{2009}}, } @article{13657, author = {{Sanna, Simone and Schmidt, Wolf Gero and Frauenheim, Th. and Gerstmann, Uwe}}, issn = {{1098-0121}}, journal = {{Physical Review B}}, number = {{10}}, title = {{{Rare-earth defect pairs in GaN: LDA+U calculations}}}, doi = {{10.1103/physrevb.80.104120}}, volume = {{80}}, year = {{2009}}, } @article{13802, author = {{Giannozzi, Paolo and Baroni, Stefano and Bonini, Nicola and Calandra, Matteo and Car, Roberto and Cavazzoni, Carlo and Ceresoli, Davide and Chiarotti, Guido L and Cococcioni, Matteo and Dabo, Ismaila and Dal Corso, Andrea and de Gironcoli, Stefano and Fabris, Stefano and Fratesi, Guido and Gebauer, Ralph and Gerstmann, Uwe and Gougoussis, Christos and Kokalj, Anton and Lazzeri, Michele and Martin-Samos, Layla and Marzari, Nicola and Mauri, Francesco and Mazzarello, Riccardo and Paolini, Stefano and Pasquarello, Alfredo and Paulatto, Lorenzo and Sbraccia, Carlo and Scandolo, Sandro and Sclauzero, Gabriele and Seitsonen, Ari P and Smogunov, Alexander and Umari, Paolo and Wentzcovitch, Renata M}}, issn = {{0953-8984}}, journal = {{Journal of Physics: Condensed Matter}}, number = {{39}}, title = {{{QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials}}}, doi = {{10.1088/0953-8984/21/39/395502}}, volume = {{21}}, year = {{2009}}, } @article{13844, 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-forbid¬den lines, arising from Nc,k pairs and triads or resulting from hopping conductivity, only re¬cent¬ly 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-struc¬ture splitting too small to be observed in the EPR and ESE experiments. In this work, we pre¬sent 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}}, title = {{{Spin-Coupling in Heavily Nitrogen-Doped 4H-SiC}}}, doi = {{10.4028/www.scientific.net/msf.615-617.343}}, volume = {{615-617}}, year = {{2009}}, }