Daniel Simek - Academia.edu (original) (raw)
Papers by Daniel Simek
Journal of Applied Crystallography, Aug 1, 2011
Page 1. GENETIC ALGORITHM APPLIED TO MULTILAYER STRUCTURE DETERMINATION Daniel Šimek 1 , David Ra... more Page 1. GENETIC ALGORITHM APPLIED TO MULTILAYER STRUCTURE DETERMINATION Daniel Šimek 1 , David Rafaja 1, Jiøí Kub2 1 Faculty of Mathematics and Physics, Charles University in Prague E-mail: simek@apollo ...
Journal of Applied Crystallography, Aug 1, 2006
A method of reciprocal-space mapping followed by Rietveld-type refinement of the maps has been de... more A method of reciprocal-space mapping followed by Rietveld-type refinement of the maps has been developed and tested for strongly textured thin films with fibre texture. The method is particularly useful for simultaneous analysis of stress and texture, especially in non-cubic materials. It could also be used for the analysis of other parameters, like film thickness, microstrain and domain size. Both of the extreme elastic models (Voigt/Reuss) have been adopted for the case of the fibre texture often present in thin films. The method allows estimation of residual stresses even for very strong [001] texture in hexagonal materials with angular half-widths of a few degrees. The procedure of twodimensional reciprocal-space map fitting is described in detail; simulations are presented and discussed. The method can be applied to multiphase materials, as long as the assumptions of the elastic models (Voigt/Reuss) are valid in the multiphase film. research papers 488 Daniel Simek et al. Reciprocal-space mapping
Materials Science Forum, 2004
Materials Science Forum, 2004
Thin Solid Films, 2002
High degree of ordering was observed in the SrTiO , Ba Sr TiO and BaTiO thin films grown by injec... more High degree of ordering was observed in the SrTiO , Ba Sr TiO and BaTiO thin films grown by injection metal-organic 3 0.1 0.9 3 3 chemical vapour deposition on sapphire substrates. Orientation of the Al O substrates was (0 0 1) perpendicular to the surface; 2 3 orientation of the films was (1 1 1). Atomic ordering at the interface between the substrates and the films approached locally heteroepitaxial growth. Two distinct in-plane orientations of the films were observed. The projection of the w1 0 0x direction in the cubic or cubic-like films was rotated either q30 or y308 with respect to the w1 0 0x crystallographic direction of the substrate. Still, a slight disorientation of the films from the dominant directions was observed. The in-plane disorientation of the films increased with increasing barium contents. In SrTiO , the in-plane disorientation of crystallites was 1.58, in BaTiO 3.28. The 3 3
Journal of Physics: Condensed Matter, 2002
The capabilities of small-angle x-ray scattering (SAXS) and wide-angle x-ray diffraction (XRD) to... more The capabilities of small-angle x-ray scattering (SAXS) and wide-angle x-ray diffraction (XRD) to recognize structural changes in periodic multilayers were compared on Fe/Au multilayers with different degrees of structural degradation. Experimental results have shown that both methods are equally sensitive to the multilayer degradation, i.e., to the occurrence of non-continuous interfaces, to short-circuits in the multilayer structure and to the
Journal of Physics: Condensed Matter, 2002
X-ray specular reflectivity and diffuse scattering calculated using the traditional multilayer mo... more X-ray specular reflectivity and diffuse scattering calculated using the traditional multilayer model, which assumes continuous, non-intersecting interfaces, are capable of fitting the experimental data obtained on multilayers with non-continuous interfaces. However, wrong refined electron densities and interface roughness are the consequence of an inappropriate structure model. A modification of the Parratt optical formalism combined with the application of the distorted-wave
Journal of Applied Crystallography, 2006
A method of reciprocal-space mapping followed by Rietveld-type refinement of the maps has been de... more A method of reciprocal-space mapping followed by Rietveld-type refinement of the maps has been developed and tested for strongly textured thin films with fibre texture. The method is particularly useful for simultaneous analysis of stress and texture, especially in non-cubic materials. It could also be used for the analysis of other parameters, like film thickness, microstrain and domain size. Both of the extreme elastic models (Voigt/Reuss) have been adopted for the case of the fibre texture often present in thin films. The method allows estimation of residual stresses even for very strong [001] texture in hexagonal materials with angular half-widths of a few degrees. The procedure of twodimensional reciprocal-space map fitting is described in detail; simulations are presented and discussed. The method can be applied to multiphase materials, as long as the assumptions of the elastic models (Voigt/Reuss) are valid in the multiphase film. research papers 488 Daniel Simek et al. Reciprocal-space mapping
Journal of Applied Crystallography, 2011
Plastic deformation of highly alloyed austenitic transformation-induced plasticity (TRIP) steels ... more Plastic deformation of highly alloyed austenitic transformation-induced plasticity (TRIP) steels with low stacking fault energy leads typically to the formation of "-martensite within the original austenite. The "-martensite is often described as a phase having a hexagonal close-packed crystal structure. In this contribution, an alternative structure model is presented that describes "-martensite embedded in the austenitic matrix via clustering of stacking faults in austenite. The applicability of the model was tested on experimental X-ray diffraction data measured on a CrMnNi TRIP steel after 15% compression. The model of clustered stacking faults was implemented in the DIFFaX routine; the faulted austenite and "-martensite were represented by different stacking fault arrangements. The probabilities of the respective stacking fault arrangements were obtained from fitting the simulated X-ray diffraction patterns to the experimental data. The reliability of the model was proven by scanning and transmission electron microscopy. For visualization of the clusters of stacking faults, the scanning electron microscopy employed electron channelling contrast imaging and electron backscatter diffraction. research papers J. Appl. Cryst. (2011). 44, 779-787 Stefan Martin et al. Stacking fault model of "-martensite 785
Ferroelectrics, 2008
ABSTRACT Optical properties of Ba 0.25 Sr 0.75 TiO 3 thin films fabricated by pulsed laser deposi... more ABSTRACT Optical properties of Ba 0.25 Sr 0.75 TiO 3 thin films fabricated by pulsed laser deposition (PLD) have been investigated using variable angle spectroscopic ellipsometry (VASE) and near-normal spectroscopic reflectivity (NNSR). The measurements were carried out from 5 K to 450 K in the spectral range 1–6 eV by VASE, and in the range 1–12 eV by NNSR at the room temperature. Both types of the experimental data (VASE and NNSR) were simultaneously fitted to obtain the optical functions (e.g. complex refractive index, dielectric function) and thicknesses of the films. To determine the optical response functions and parameters of the material we used several models to fit the experimental data. The Cauchy-Urbach formula was applied in the transparent spectral range and the direct fit procedure and the Cody-Lorentz model were applied around and beyond absorption edge. In the entire spectral range the reflectivity spectra were analyzed by Kramers-Kronig analysis. The behavior of the refractive index obtained in this way was studied and some anomalies were found. The x-ray diffraction was used for a study of sample texture. Some correlation with the optical study was found. The optimal deposition temperature can be found from both studies.
Acta Crystallographica Section A Foundations of Crystallography, 2002
Acta Crystallographica Section A Foundations of Crystallography, 2005
Med Sci Sport Exercise, 2010
Journal of Applied Crystallography, Aug 1, 2011
Page 1. GENETIC ALGORITHM APPLIED TO MULTILAYER STRUCTURE DETERMINATION Daniel Šimek 1 , David Ra... more Page 1. GENETIC ALGORITHM APPLIED TO MULTILAYER STRUCTURE DETERMINATION Daniel Šimek 1 , David Rafaja 1, Jiøí Kub2 1 Faculty of Mathematics and Physics, Charles University in Prague E-mail: simek@apollo ...
Journal of Applied Crystallography, Aug 1, 2006
A method of reciprocal-space mapping followed by Rietveld-type refinement of the maps has been de... more A method of reciprocal-space mapping followed by Rietveld-type refinement of the maps has been developed and tested for strongly textured thin films with fibre texture. The method is particularly useful for simultaneous analysis of stress and texture, especially in non-cubic materials. It could also be used for the analysis of other parameters, like film thickness, microstrain and domain size. Both of the extreme elastic models (Voigt/Reuss) have been adopted for the case of the fibre texture often present in thin films. The method allows estimation of residual stresses even for very strong [001] texture in hexagonal materials with angular half-widths of a few degrees. The procedure of twodimensional reciprocal-space map fitting is described in detail; simulations are presented and discussed. The method can be applied to multiphase materials, as long as the assumptions of the elastic models (Voigt/Reuss) are valid in the multiphase film. research papers 488 Daniel Simek et al. Reciprocal-space mapping
Materials Science Forum, 2004
Materials Science Forum, 2004
Thin Solid Films, 2002
High degree of ordering was observed in the SrTiO , Ba Sr TiO and BaTiO thin films grown by injec... more High degree of ordering was observed in the SrTiO , Ba Sr TiO and BaTiO thin films grown by injection metal-organic 3 0.1 0.9 3 3 chemical vapour deposition on sapphire substrates. Orientation of the Al O substrates was (0 0 1) perpendicular to the surface; 2 3 orientation of the films was (1 1 1). Atomic ordering at the interface between the substrates and the films approached locally heteroepitaxial growth. Two distinct in-plane orientations of the films were observed. The projection of the w1 0 0x direction in the cubic or cubic-like films was rotated either q30 or y308 with respect to the w1 0 0x crystallographic direction of the substrate. Still, a slight disorientation of the films from the dominant directions was observed. The in-plane disorientation of the films increased with increasing barium contents. In SrTiO , the in-plane disorientation of crystallites was 1.58, in BaTiO 3.28. The 3 3
Journal of Physics: Condensed Matter, 2002
The capabilities of small-angle x-ray scattering (SAXS) and wide-angle x-ray diffraction (XRD) to... more The capabilities of small-angle x-ray scattering (SAXS) and wide-angle x-ray diffraction (XRD) to recognize structural changes in periodic multilayers were compared on Fe/Au multilayers with different degrees of structural degradation. Experimental results have shown that both methods are equally sensitive to the multilayer degradation, i.e., to the occurrence of non-continuous interfaces, to short-circuits in the multilayer structure and to the
Journal of Physics: Condensed Matter, 2002
X-ray specular reflectivity and diffuse scattering calculated using the traditional multilayer mo... more X-ray specular reflectivity and diffuse scattering calculated using the traditional multilayer model, which assumes continuous, non-intersecting interfaces, are capable of fitting the experimental data obtained on multilayers with non-continuous interfaces. However, wrong refined electron densities and interface roughness are the consequence of an inappropriate structure model. A modification of the Parratt optical formalism combined with the application of the distorted-wave
Journal of Applied Crystallography, 2006
A method of reciprocal-space mapping followed by Rietveld-type refinement of the maps has been de... more A method of reciprocal-space mapping followed by Rietveld-type refinement of the maps has been developed and tested for strongly textured thin films with fibre texture. The method is particularly useful for simultaneous analysis of stress and texture, especially in non-cubic materials. It could also be used for the analysis of other parameters, like film thickness, microstrain and domain size. Both of the extreme elastic models (Voigt/Reuss) have been adopted for the case of the fibre texture often present in thin films. The method allows estimation of residual stresses even for very strong [001] texture in hexagonal materials with angular half-widths of a few degrees. The procedure of twodimensional reciprocal-space map fitting is described in detail; simulations are presented and discussed. The method can be applied to multiphase materials, as long as the assumptions of the elastic models (Voigt/Reuss) are valid in the multiphase film. research papers 488 Daniel Simek et al. Reciprocal-space mapping
Journal of Applied Crystallography, 2011
Plastic deformation of highly alloyed austenitic transformation-induced plasticity (TRIP) steels ... more Plastic deformation of highly alloyed austenitic transformation-induced plasticity (TRIP) steels with low stacking fault energy leads typically to the formation of "-martensite within the original austenite. The "-martensite is often described as a phase having a hexagonal close-packed crystal structure. In this contribution, an alternative structure model is presented that describes "-martensite embedded in the austenitic matrix via clustering of stacking faults in austenite. The applicability of the model was tested on experimental X-ray diffraction data measured on a CrMnNi TRIP steel after 15% compression. The model of clustered stacking faults was implemented in the DIFFaX routine; the faulted austenite and "-martensite were represented by different stacking fault arrangements. The probabilities of the respective stacking fault arrangements were obtained from fitting the simulated X-ray diffraction patterns to the experimental data. The reliability of the model was proven by scanning and transmission electron microscopy. For visualization of the clusters of stacking faults, the scanning electron microscopy employed electron channelling contrast imaging and electron backscatter diffraction. research papers J. Appl. Cryst. (2011). 44, 779-787 Stefan Martin et al. Stacking fault model of "-martensite 785
Ferroelectrics, 2008
ABSTRACT Optical properties of Ba 0.25 Sr 0.75 TiO 3 thin films fabricated by pulsed laser deposi... more ABSTRACT Optical properties of Ba 0.25 Sr 0.75 TiO 3 thin films fabricated by pulsed laser deposition (PLD) have been investigated using variable angle spectroscopic ellipsometry (VASE) and near-normal spectroscopic reflectivity (NNSR). The measurements were carried out from 5 K to 450 K in the spectral range 1–6 eV by VASE, and in the range 1–12 eV by NNSR at the room temperature. Both types of the experimental data (VASE and NNSR) were simultaneously fitted to obtain the optical functions (e.g. complex refractive index, dielectric function) and thicknesses of the films. To determine the optical response functions and parameters of the material we used several models to fit the experimental data. The Cauchy-Urbach formula was applied in the transparent spectral range and the direct fit procedure and the Cody-Lorentz model were applied around and beyond absorption edge. In the entire spectral range the reflectivity spectra were analyzed by Kramers-Kronig analysis. The behavior of the refractive index obtained in this way was studied and some anomalies were found. The x-ray diffraction was used for a study of sample texture. Some correlation with the optical study was found. The optimal deposition temperature can be found from both studies.
Acta Crystallographica Section A Foundations of Crystallography, 2002
Acta Crystallographica Section A Foundations of Crystallography, 2005
Med Sci Sport Exercise, 2010