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7 results on '"Viktor S. Kopp"'

1. X-ray diffraction from hexagonal dislocation networks

Author

Vladimir M. Kaganer and Viktor S. Kopp

Subjects
Diffraction, Materials science, Condensed matter physics, business.industry, Monte Carlo method, Honeycomb (geometry), Condensed Matter Physics, Displacement (vector), Condensed Matter::Materials Science, Honeycomb structure, Optics, Distortion, X-ray crystallography, Dislocation, business
Abstract

We built the honeycomb networks of misfit dislocations by combining angular dislocations. Two different models of the disorder in the dislocation network are explored, the random shifts of nodes and random sources of distortion. The displacement fields of disturbed dislocation networks are used to simulate the X-ray diffraction patterns by Monte Carlo method. We find that substantial disorder is needed for random shifts to be experimentally observable as diffuse scattering. The model of random distortion sources produces comparable diffuse scattering with the dislocation network looking closer to the initial perfect structure. The diffraction patterns due to distorted honeycomb dislocation networks are compared with the ones due to triangular networks of straight dislocations. The disorder parameters of the latter networks can be chosen to produce diffraction patterns similar to the former.

Published
2014
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2. Analysis of reciprocal space maps of GaN(0001) films grown by molecular beam epitaxy

Author

Bernd Jenichen, Oliver Brandt, Vladimir M. Kaganer, and Viktor S. Kopp

Subjects
Materials science, Condensed matter physics, business.industry, Substrate (electronics), General Biochemistry, Genetics and Molecular Biology, Condensed Matter::Materials Science, Reciprocal lattice, Semiconductor, Optics, Reflection (mathematics), Perpendicular, Dislocation, business, Normal, Molecular beam epitaxy
Abstract

The reciprocal space map of a heteroepitaxial single-crystal GaN(0001) film on 6H-SiC(0001) is analyzed. The film contains a high density of threading dislocations which intersect the film parallel to the surface normal. The strain field associated with these dislocations is expected to broaden all reciprocal lattice points to discs perpendicular to the dislocation lines,i.e.parallel to the surface. Experimentally, however, the reflection is observed to be broadened also perpendicular to the surface and is rotated towards the surface normal. Using Monte Carlo simulations, it is shown that both of these features are a natural consequence of the presence of misfit dislocations at the film/substrate interface.

Published
2014
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3. X-ray diffraction study of plastic relaxation in Ge-rich SiGe virtual substrates

Author

Giovanni Capellini, Monica De Seta, Vladimir M. Kaganer, Peter Zaumseil, Viktor S. Kopp, Kopp, V, Kaganer, Vm, Capellini, Giovanni, DE SETA, Monica, and Zaumseil, P.

Subjects
Diffraction, Materials science, Strain relaxation, Condensed matter physics, Scattering, Silicon Germanium, Heterojunction, Edge (geometry), Condensed Matter Physics, Microstructure, X-ray diffraction, Electronic, Optical and Magnetic Materials, Silicon-germanium, Condensed Matter::Materials Science, chemistry.chemical_compound, chemistry, X-ray crystallography, Relaxation (physics)
Abstract

""We report on the experimental and theoretical investigation of the relaxation in Ge-rich SiGe\\\/Ge\\\/Si heterostructures. The experimental x-ray diffraction data are interpreted with the help of a model including both edge and 60 degrees misfit dislocations in the calculated x-ray scattering intensity. Our results show that highly positionally correlated edge dislocations dominate in the relaxation of the compressive strain at the Ge\\\/Si interface, while a smaller tensile strain at the SiGe\\\/Ge interfaces released by uncorrelated\\\/little correlated 60 degrees dislocations.""

Published
2012
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4. Nano-precipitates made of atomic pillars revealed by single atom detection in a Mg-Nd alloy

Author

Viktor S. Kopp, Williams Lefebvre, C. Pareige, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010302 applied physics, Materials science, Physics and Astronomy (miscellaneous), Scanning electron microscope, Precipitation (chemistry), Alloy, Analytical chemistry, 02 engineering and technology, engineering.material, 021001 nanoscience & nanotechnology, 01 natural sciences, Crystallography, Transmission electron microscopy, Metastability, 0103 physical sciences, Nano, Atom, Scanning transmission electron microscopy, engineering, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology
Abstract

International audience; We report on the atomic architecture of metastable precipitates in a model Mg-0.5 at. %Nd system. High resolution Z-contrast observations in scanning transmission electron microscopy demonstrate that a common elementary structure, made of Nd atomic pillars, is shared by precipitates involved in the early decomposition of the system. A combination of Z-contrast projections has been used to establish the accurate location of Nd atoms in the atomic pillars, therefore allowing the determination of structure and composition of precipitates. Other precipitates compositions are extrapolated by means of a quantitative analysis.The ANR (Agence Nationale pour la Recherche) is thanked for the financial support through the Programme Jeune Chercheur–Jeune Chercheuse TIPSTEM. Jörn Fiedler from Clausthal University is gratefully acknowledged for the alloy preparation.

Published
2012
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5. X-ray diffraction from nonperiodic layered structures with correlations: analytical calculation and experiment on mixed Aurivillius films

Author

Viktor S. Kopp, Vladimir M. Kaganer, Albert Kwasniewski, T. Remmele, F. Waidick, Jutta Schwarzkopf, and Martin Schmidbauer

Subjects
Diffraction, Models, Molecular, Titanium, Materials science, biology, Molecular Structure, Stacking, chemistry.chemical_element, Membranes, Artificial, biology.organism_classification, Crystallography, X-Ray, Molecular physics, Bismuth, Aurivillius, Sodium bismuth titanate, Crystallography, chemistry.chemical_compound, chemistry, Structural Biology, X-ray crystallography, Thin film, Perovskite (structure)
Abstract

X-ray diffraction from films consisting of layers with different thicknesses, structures and chemical contents is analysed. The disorder is described by probabilities for different sequences of layers. Closed analytical expressions for the diffracted X-ray intensity are obtained when the layers form a stationary Markov chain. The proposed model is applied to the diffraction data from epitaxial sodium bismuth titanate thin films with Aurivillius structure possessing such one-dimensional disorder. In this case, the disorder is caused by a random stacking of three and four perovskite units separated by bismuth oxide interlayers. The results of analytical calculations are in good agreement with the experimental data and indicate that the incorporation of sodium in the Bi(4)Ti(3)O(12) phase causes the formation of a fourth perovskite unit.

Published
2011

6. Determination of the Mg-Rich Phase Boundary of the Binary Mg-Nd Phase Diagram by Means of Atom Probe Tomography

Author

C. Pareige, Viktor S. Kopp, Williams Lefebvre, Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Work (thermodynamics), Phase boundary, Thermodynamics, Binary number, 02 engineering and technology, Atom probe, Assessment, 01 natural sciences, law.invention, Experimental phase equilibria, law, 0103 physical sciences, Materials Chemistry, Binary system, CALPHAD, Phase diagram, 010302 applied physics, Solid solubility, Chemistry, Metals and Alloys, Equilibriumdiagram, 021001 nanoscience & nanotechnology, Condensed Matter Physics, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology, Composition
Abstract

International audience; The present paper relates the investigation of the Mg-rich side of the binary Mg-Nd phase diagram by means of Atom Probe Tomography (APT). The solid solubility of Nd in Mg at the temperatures 400, 480, 520 A degrees C has been measured. The results of the current investigation demonstrate that the solid solubility of Nd in Mg is much larger than is usually supposed and presented in more recent Mg-Nd phase diagrams. The data presented in this work can be used for further thermodynamic calculations in order to interpolate the phase boundary between temperature points.

Published
2011
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7. X-ray determination of threading dislocation densities in GaN/Al2O3(0001) films grown by metalorganic vapor phase epitaxy

Author

Nikolay Cherkashin, Vladimir M. Kaganer, M. V. Baidakova, W. V. Lundin, Andrey E. Nikolaev, Elena V. Verkhovtceva, M. A. Yagovkina, Viktor S. Kopp, Paul-Drude-Institut für Festkörperelektronik (PDI), A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Centre d'élaboration de matériaux et d'études structurales (CEMES), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010302 applied physics, Diffraction, Materials science, Condensed matter physics, Scattering, Wide-bandgap semiconductor, General Physics and Astronomy, 02 engineering and technology, 021001 nanoscience & nanotechnology, Epitaxy, 01 natural sciences, Condensed Matter::Materials Science, Reciprocal lattice, Crystallography, 0103 physical sciences, X-ray crystallography, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Thin film, Dislocation, 0210 nano-technology
Abstract

cited By 13; International audience; Densities of a- and a+c-type threading dislocations for a series of GaN films grown in different modes by metalorganic vapor phase epitaxy are determined from the x-ray diffraction profiles in skew geometry. The reciprocal space maps are also studied. Theory of x-ray scattering from crystals with dislocations is extended in order to take into account contribution from both threading and misfit dislocations. The broadening of the reciprocal space maps along the surface normal and the rotation of the intensity distribution ellipse is attributed to misfit dislocations at the interface. We find that the presence of a sharp AlN/GaN interface leads to an ordering of misfit dislocations and reduces strain inhomogeneity in GaN films.

Published
2014
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