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Boukortt A.,University of Mostaganem | Boukortt A.,University Djilali Liabes | Berrah S.,University Djilali Liabes | Berrah S.,University of Abderrahmane Mira de Bejaia | And 2 more authors.
Physica B: Condensed Matter

We present the results of density functional calculations to study the optical properties of the technologically important Zn1-xCdxSySe1- y quaternary alloy, using the full potential linearized augmented plane wave method within the local-density approximation LDA. Our calculations were performed to evaluate the dielectric function real and imaginary parts, and the loss function of the II-VI semiconductor alloy. Also the refractive index, reflectivity, optical conductivity, and absorption coefficient are all studied. The results are compared with calculated optical properties of binary alloys and the theoretical predictions are confirmed by the available experimental data. Our results show the possibility of material design to optimize the cladding active region in index guided lasers. © 2009 Elsevier B.V. All rights reserved. Source

Muller Ch.,Institute Materiaux | Deleruyelle D.,Institute Materiaux | Muller R.,IMEC | Thomas M.,University of Toulon | And 3 more authors.
Solid-State Electronics

The present paper deals with the bipolar resistive switching of memory elements based on metal-organic complex CuTCNQ (copper-7,7',8,8'- tetracyanoquinodimethane) nanowires grown on a dedicated HfO2 oxide switching layer. Switching characteristics are explored either at millimeter scale on pad-size devices or at nanoscale by using conductive atomic force microscopy. Whatever the investigation scales, the basic memory characteristics appear to be controlled by copper ionic transport within a switching layer. This latter corresponds to either HfO2 layer in pad-size devices or nanogap formed at nanoscale between the atomic force microscopy conductive tip and CuTCNQ surface. Depending upon the observation scale, the switching layer (either HfO2 oxide or nanogap) acts as a matrix in which copper conductive bridges are formed and dissolved thanks to redox processes controlled in alternating applied bias voltages. © 2010 Elsevier Ltd. All rights reserved. Source

Holder M.G.,TU Dresden | Jesche A.,Max Planck Institute for Chemical Physics of Solids | Lombardo P.,Institute Materiaux | Hayn R.,Institute Materiaux | And 8 more authors.
Physical Review B - Condensed Matter and Materials Physics

Angle-resolved photoelectron spectroscopy, supplemented by theoretical calculations has been applied to study the electronic structure of heavy-fermion material CeFePO, a homologue to the Fe-based high-temperature superconductors, and CeFeAs 0.7P 0.3O, where the applied chemical pressure results in a ferromagnetic order of the 4f moments. A comparative analysis reveals characteristic differences in the Fe-derived band structure for these materials, implying a rather different hybridization of valence electrons to the localized 4f orbitals. In particular, our results suggest that the ferromagnetism of Ce moments in CeFeAs 0.7P 0.3O is mediated mainly by Fe 3d xz/yz orbitals, while the Kondo screening in CeFePO is instead due to a strong interaction of Fe 3d 3z2-r2 orbitals. © 2012 American Physical Society. Source

Holder M.G.,TU Dresden | Jesche A.,Max Planck Institute for Chemical Physics of Solids | Lombardo P.,Institute Materiaux | Hayn R.,Institute Materiaux | And 11 more authors.
Physical Review Letters

As a homologue to the new, Fe-based type of high-temperature superconductors, the electronic structure of the heavy-fermion compound CeFePO was studied by means of angle-resolved resonant photoemission. It was experimentally found-and later on confirmed by local-density approximation (LDA) as well as dynamical mean-field theory (DMFT) calculations-that the Ce 4f states hybridize to the Fe 3d states of d3z2-r2 symmetry near the Fermi level that discloses their participation in the occurring electron-correlation phenomena and provides insight into mechanism of superconductivity in oxopnictides. © 2010 The American Physical Society. Source

Micard G.,University of Konstanz | Hahn G.,University of Konstanz | Terheiden B.,University of Konstanz | Chrastina D.,Polytechnic of Milan | And 9 more authors.
Physica Status Solidi (C) Current Topics in Solid State Physics

p-doped hydrogenated nanocrystalline silicon (p-nc-Si:H) is one of the most critical layers in thin film silicon solar cells. LEPECVD is a new technique for the growth of nc-Si at high growth rate without compromising the layer quality, using a dense but low energy plasma. Thin p-nc-Si:H layers are grown on glass and ZnO:Al coated glass and their structural and electrical properties are investigated as a function of the silane dilution (d) and of the doping ratio (DR). The influence of the substrate on the structural properties is investigated and discussed. The incubation layer is clearly observed on both substrate types and its thickness is estimated. LEPECVD distinguishes itself from other high growth rate methods by a very low impurity distribution coefficient to obtain a comparable conductivity and boron density. The conduction path is shown to be dependent on the density of boron in the layer while a significant decrease of conductivity at high DR is not observed in the studied range. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA. Source

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