13 results on '"Bragg ptychography"'
Search Results
2. The influence of strain on image reconstruction in Bragg coherent X‐ray diffraction imaging and ptychography.
- Author
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Kim, Chan, Scholz, Markus, and Madsen, Anders
- Subjects
- *
X-ray imaging , *IMAGE reconstruction , *X-ray diffraction , *ANTIPHASE boundaries , *X-ray lasers , *FREE electron lasers , *BRAGG gratings - Abstract
A quantitative analysis of the effect of strain on phase retrieval in Bragg coherent X‐ray diffraction imaging is reported. It is shown in reconstruction simulations that the phase maps of objects with strong step‐like phase changes are more precisely retrieved than the corresponding modulus values. The simulations suggest that the reconstruction precision for both phase and modulus can be improved by employing a modulus homogenization (MH) constraint. This approach was tested on experimental data from a highly strained Fe–Al crystal which also features antiphase domain boundaries yielding characteristic π phase shifts of the (001) superlattice reflection. The impact of MH is significant and this study outlines a successful method towards imaging of strong phase objects using the next generation of coherent X‐ray sources, including X‐ray free‐electron lasers. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
3. On the use of the scattering amplitude in coherent X‐ray Bragg diffraction imaging.
- Author
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Godard, Pierre
- Subjects
- *
SCATTERING amplitude (Physics) , *X-ray diffraction , *COHERENT scattering , *DISCRETE Fourier transforms , *ELECTRON density - Abstract
Lens‐less imaging of crystals with coherent X‐ray diffraction offers some unique possibilities for strain‐field characterization. It relies on numerically retrieving the phase of the scattering amplitude from a crystal illuminated with coherent X‐rays. In practice, the algorithms encode this amplitude as a discrete Fourier transform of an effective or Bragg electron density. This short article suggests a detailed route from the classical expression of the (continuous) scattering amplitude to this discrete function. The case of a heterogeneous incident field is specifically detailed. Six assumptions are listed and quantitatively discussed when no such analysis was found in the literature. Details are provided for two of them: the fact that the structure factor varies in the vicinity of the probed reciprocal lattice vector, and the polarization factor, which is heterogeneous along the measured diffraction patterns. With progress in X‐ray sources, data acquisition and analysis, it is believed that some approximations will prove inappropriate in the near future. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
4. General approaches for shear‐correcting coordinate transformations in Bragg coherent diffraction imaging. Part II.
- Author
-
Li, P., Maddali, S., Pateras, A., Calvo-Almazan, I., Hruszkewycz, S.O., Cha, W., Chamard, V., and Allain, M.
- Subjects
- *
COORDINATE transformations , *FOURIER transforms , *DIFFRACTION patterns , *FACTOR structure , *THREE-dimensional imaging - Abstract
X‐ray Bragg coherent diffraction imaging (BCDI) has been demonstrated as a powerful 3D microscopy approach for the investigation of sub‐micrometre‐scale crystalline particles. The approach is based on the measurement of a series of coherent Bragg diffraction intensity patterns that are numerically inverted to retrieve an image of the spatial distribution of the relative phase and amplitude of the Bragg structure factor of the diffracting sample. This 3D information, which is collected through an angular rotation of the sample, is necessarily obtained in a non‐orthogonal frame in Fourier space that must be eventually reconciled. To deal with this, the approach currently favored by practitioners (detailed in Part I) is to perform the entire inversion in conjugate non‐orthogonal real‐ and Fourier‐space frames, and to transform the 3D sample image into an orthogonal frame as a post‐processing step for result analysis. In this article, which is a direct follow‐up of Part I, two different transformation strategies are demonstrated, which enable the entire inversion procedure of the measured data set to be performed in an orthogonal frame. The new approaches described here build mathematical and numerical frameworks that apply to the cases of evenly and non‐evenly sampled data along the direction of sample rotation (i.e. the rocking curve). The value of these methods is that they rely on the experimental geometry, and they incorporate significantly more information about that geometry into the design of the phase‐retrieval Fourier transformation than the strategy presented in Part I. Two important outcomes are (1) that the resulting sample image is correctly interpreted in a shear‐free frame and (2) physically realistic constraints of BCDI phase retrieval that are difficult to implement with current methods are easily incorporated. Computing scripts are also given to aid readers in the implementation of the proposed formalisms. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
5. General approaches for shear‐correcting coordinate transformations in Bragg coherent diffraction imaging. Part I.
- Author
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Maddali, S., Li, P., Pateras, A., Timbie, D., Delegan, N., Crook, A. L., Lee, H., Calvo-Almazan, I., Sheyfer, D., Cha, W., Heremans, F. J., Awschalom, D. D., Chamard, V., Allain, M., and Hruszkewycz, S. O.
- Subjects
- *
COORDINATE transformations , *COMPACT operators , *THREE-dimensional imaging , *DIGITAL images , *COMPUTER software , *THREE-dimensional modeling , *GEOMETRY , *CARRIER sense multiple access - Abstract
This two‐part article series provides a generalized description of the scattering geometry of Bragg coherent diffraction imaging (BCDI) experiments, the shear distortion effects inherent in the 3D image obtained from presently used methods and strategies to mitigate this distortion. Part I starts from fundamental considerations to present the general real‐space coordinate transformation required to correct this shear, in a compact operator formulation that easily lends itself to implementation with available software packages. Such a transformation, applied as a final post‐processing step following phase retrieval, is crucial for arriving at an undistorted, correctly oriented and physically meaningful image of the 3D crystalline scatterer. As the relevance of BCDI grows in the field of materials characterization, the available sparse literature that addresses the geometric theory of BCDI and the subsequent analysis methods are generalized here. This geometrical aspect, specific to coherent Bragg diffraction and absent in 2D transmission CDI experiments, gains particular importance when it comes to spatially resolved characterization of 3D crystalline materials in a reliable nondestructive manner. This series of articles describes this theory, from the diffraction in Bragg geometry to the corrections needed to obtain a properly rendered digital image of the 3D scatterer. Part I of this series provides the experimental BCDI community with the general form of the 3D real‐space distortions in the phase‐retrieved object, along with the necessary post‐retrieval correction method. Part II builds upon the geometric theory developed in Part I with the formalism to correct the shear distortions directly on an orthogonal grid within the phase‐retrieval algorithm itself, allowing more physically realistic constraints to be applied. Taken together, Parts I and II provide the X‐ray science community with a set of generalized BCDI shear‐correction techniques crucial to the final rendering of a 3D crystalline scatterer and for the development of new BCDI methods and experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
6. Measuring Three-Dimensional Strain and Structural Defects in a Single InGaAs Nanowire Using Coherent X-ray Multiangle Bragg Projection Ptychography.
- Author
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Hill, Megan O., Calvo-Almazan, Irene, Allain, Marc, Holt, Martin V., Ulvestad, Andrew, Treu, Julian, Koblmüller, Gregor, Chunyi Huang, Xiaojing Huang, Hanfei Yan, Nazaretski, Evgeny, Chu, Yong S., Stephenson, G. Brian, Chamard, Virginie, Lauhon, Lincoln J., and Hruszkewycz, Stephan O.
- Subjects
- *
STRAINS & stresses (Mechanics) , *GALLIUM arsenide , *NANOWIRES , *CRYSTAL defects , *INFRARED detectors , *SILICON , *CRYSTAL structure - Abstract
III-As nanowires are candidates for near-infrared light emitters and detectors that can be directly integrated onto silicon. However, nanoscale to microscale variations in structure, composition, and strain within a given nanowire, as well as variations between nanowires, pose challenges to correlating microstructure with device performance. In this work, we utilize coherent nanofocused X-rays to characterize stacking defects and strain in a single InGaAs nanowire supported on Si. By reconstructing diffraction patterns from the 2110 Bragg peak, we show that the lattice orientation varies along the length of the wire, while the strain field along the cross-section is largely unaffected, leaving the band structure unperturbed. Diffraction patterns from the 011-0 Bragg peak are reproducibly reconstructed to create three-dimensional images of stacking defects and associated lattice strains, revealing sharp planar boundaries between different crystal phases of wurtzite (WZ) structure that contribute to charge carrier scattering. Phase retrieval is made possible by developing multiangle Bragg projection ptychography (maBPP) to accommodate coherent nanodiffraction patterns measured at arbitrary overlapping positions at multiple angles about a Bragg peak, eliminating the need for scan registration at different angles. The penetrating nature of X-ray radiation, together with the relaxed constraints of maBPP, will enable the in operando imaging of nanowire devices. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
7. The influence of strain on image reconstruction in Bragg coherent X-ray diffraction imaging and ptychography
- Author
-
Markus Scholz, Chan Kim, and Anders Madsen
- Subjects
Diffraction ,Nuclear and High Energy Physics ,Materials science ,anti-phase domain boundary ,Superlattice ,Phase (waves) ,Bragg ptychography ,02 engineering and technology ,Iterative reconstruction ,03 medical and health sciences ,Optics ,strong phase object ,Instrumentation ,030304 developmental biology ,0303 health sciences ,Radiation ,business.industry ,021001 nanoscience & nanotechnology ,Research Papers ,Ptychography ,modulus homogenization ,Reflection (mathematics) ,X-ray crystallography ,0210 nano-technology ,business ,Phase retrieval ,coherent X-ray diffraction imaging - Abstract
A quantitative analysis of the effect of strain on image reconstruction in Bragg coherent X-ray diffraction imaging and ptychography reveals reconstruction artifacts caused by the limited spatial resolution. With the modulus homogenization constraint applied, the reconstruction artifacts are efficiently removed and an Fe–Al alloy sample with strong strain that features π phase steps due to anti-phase domain boundaries is successfully reconstructed., A quantitative analysis of the effect of strain on phase retrieval in Bragg coherent X-ray diffraction imaging is reported. It is shown in reconstruction simulations that the phase maps of objects with strong step-like phase changes are more precisely retrieved than the corresponding modulus values. The simulations suggest that the reconstruction precision for both phase and modulus can be improved by employing a modulus homogenization (MH) constraint. This approach was tested on experimental data from a highly strained Fe–Al crystal which also features antiphase domain boundaries yielding characteristic π phase shifts of the (001) superlattice reflection. The impact of MH is significant and this study outlines a successful method towards imaging of strong phase objects using the next generation of coherent X-ray sources, including X-ray free-electron lasers.
- Published
- 2021
8. General approaches for shear-correcting coordinate transformations in Bragg coherent diffraction imaging. Part I
- Author
-
S. Maddali, P. Li, A. Pateras, D. Timbie, N. Delegan, A. L. Crook, H. Lee, I. Calvo-Almazan, D. Sheyfer, W. Cha, F. J. Heremans, D. D. Awschalom, V. Chamard, M. Allain, S. O. Hruszkewycz, Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA, Argonne National Laboratory [Lemont] (ANL), Coherent Optical Microscopy and X-rays (COMiX), Institut FRESNEL (FRESNEL), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), University of Chicago, Centre for Water Research (CWR), The University of Western Australia (UWA), X-ray Science Division (XSD), European Project: 724881,H2020,3D-BioMat(2017), and Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)
- Subjects
phase retrieval ,0303 health sciences ,Bragg coherent diffraction imaging ,coordinate transformation ,Bragg ptychography ,02 engineering and technology ,021001 nanoscience & nanotechnology ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,conjugate spaces ,scattering geometry ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,shear correction ,0210 nano-technology ,030304 developmental biology - Abstract
International audience; This two-part article series provides a generalized description of the scattering geometry of Bragg coherent diffraction imaging (BCDI) experiments, the shear distortion effects inherent in the 3D image obtained from presently used methods and strategies to mitigate this distortion. Part I starts from fundamental considerations to present the general real-space coordinate transformation required to correct this shear, in a compact operator formulation that easily lends itself to implementation with available software packages. Such a transformation, applied as a final post-processing step following phase retrieval, is crucial for arriving at an undistorted, correctly oriented and physically meaningful image of the 3D crystalline scatterer. As the relevance of BCDI grows in the field of materials characterization, the available sparse literature that addresses the geometric theory of BCDI and the subsequent analysis methods are generalized here. This geometrical aspect, specific to coherent Bragg diffraction and absent in 2D transmission CDI experiments, gains particular importance when it comes to spatially resolved characterization of 3D crystalline materials in a reliable nondestructive manner. This series of articles describes this theory, from the diffraction in Bragg geometry to the corrections needed to obtain a properly rendered digital image of the 3D scatterer. Part I of this series provides the experimental BCDI community with the general form of the 3D real-space distortions in the phase-retrieved object, along with the necessary post-retrieval correction method. Part II builds upon the geometric theory developed in Part I with the formalism to correct the shear distortions directly on an orthogonal grid within the phase-retrieval algorithm itself, allowing more physically realistic constraints to be applied. Taken together, Parts I and II provide the X-ray science community with a set of generalized BCDI shear-correction techniques crucial to the final rendering of a 3D crystalline scatterer and for the development of new BCDI methods and experiments.
- Published
- 2020
9. General approaches for shear-correcting coordinate transformations in Bragg coherent diffraction imaging. Part II
- Author
-
Nazar Delegan, Stephan O. Hruszkewycz, Hope Lee, Siddharth Maddali, Marc Allain, Irene Calvo-Almazán, Virginie Chamard, D. Timbie, David D. Awschalom, Wonsuk Cha, F. J. Heremans, Peng Li, A. Crook, Anastasios Pateras, Dina Sheyfer, Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA, Argonne National Laboratory [Lemont] (ANL), Coherent Optical Microscopy and X-rays (COMiX), Institut FRESNEL (FRESNEL), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), X-ray Science Division (XSD), European Project: 724881,H2020,3D-BioMat(2017), and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Diffraction ,Fourier synthesis ,[PHYS]Physics [physics] ,Bragg coherent diffraction imaging ,Computer science ,Coordinate system ,non-orthogonal Fourier sampling ,Bragg's law ,coordinate transformation ,Bragg ptychography ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Grid ,01 natural sciences ,Coherent diffraction imaging ,General Biochemistry, Genetics and Molecular Biology ,Digital image ,Geometric group theory ,0103 physical sciences ,Statistical physics ,010306 general physics ,0210 nano-technology ,Phase retrieval ,shear correction - Abstract
X-ray Bragg coherent diffraction imaging (BCDI) has been demonstrated as a powerful 3D microscopy approach for the investigation of sub-micrometre-scale crystalline particles. The approach is based on the measurement of a series of coherent Bragg diffraction intensity patterns that are numerically inverted to retrieve an image of the spatial distribution of the relative phase and amplitude of the Bragg structure factor of the diffracting sample. This 3D information, which is collected through an angular rotation of the sample, is necessarily obtained in a non-orthogonal frame in Fourier space that must be eventually reconciled. To deal with this, the approach currently favored by practitioners (detailed in Part I) is to perform the entire inversion in conjugate non-orthogonal real- and Fourier-space frames, and to transform the 3D sample image into an orthogonal frame as a post-processing step for result analysis. In this article, which is a direct follow-up of Part I, two different transformation strategies are demonstrated, which enable the entire inversion procedure of the measured data set to be performed in an orthogonal frame. The new approaches described here build mathematical and numerical frameworks that apply to the cases of evenly and non-evenly sampled data along the direction of sample rotation (i.e. the rocking curve). The value of these methods is that they rely on the experimental geometry, and they incorporate significantly more information about that geometry into the design of the phase-retrieval Fourier transformation than the strategy presented in Part I. Two important outcomes are (1) that the resulting sample image is correctly interpreted in a shear-free frame and (2) physically realistic constraints of BCDI phase retrieval that are difficult to implement with current methods are easily incorporated. Computing scripts are also given to aid readers in the implementation of the proposed formalisms.
- Published
- 2020
10. X-ray Bragg Ptychography on a Single InGaN/GaN Core-Shell Nanowire
- Published
- 2017
11. Microscopie quantitative tri-dimensionnelle de nanostructures cristallines
- Author
-
Pateras, Anastasios I., Coherent Optical Microscopy and X-rays (COMiX), Institut FRESNEL (FRESNEL), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Aix-Marseille Université, Karlsruhe Institut für Technologie (KIT), Virginie Chamard, Marc Allain, Tilo Baumbach, Pateras, Anastasios, and Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)
- Subjects
Couches minces ,[PHYS.PHYS.PHYS-INS-DET] Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det] ,imagerie de deformation crystalline ,thin film strain imaging ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Bragg ptychography ,[PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det] ,three dimensional ,[PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,ptychographie Bragg ,3D - Abstract
Ptychography is a coherent diffraction imaging technique which aims in retrieving the lost phase from intensity-only far-field measurements. The versatility of the approach has proved an important asset for 3D mapping of different physical quantities, like the electron density of micrometer-sized specimens with resolution in the 10 - 100nm range. In this work, we explored the possibility to push further the current limits of 3D Bragg ptychography, by addressing the case of an extended InP/InGaAs nanostructured thin film, bonded on a silicon wafer. The experiment was performed at the ID13 beamline at ESRF, with a monochromatic beam focused down to 100nm. 2D intensity patterns were acquired at several incidence angles in the vicinity of the InP (004) Bragg peak, stacking up a three dimensional dataset. Numerical analysis of the given problem was performed beforehand in order to optimize the inversion strategy and study the possibility of introducing additional physical constraints through regularization approaches. Inversions of the dataset were done using a ptychographical gradient-based optimization phase retrieval algorithm. The developed strategy was applied on the experimental data which led to the retrieval of a complex-valued 3D image. The result exhibits the high crystallinity quality of the sample with the expected values of thickness and lattice mismatch, nevertheless, small local lattice tilts have been observed - in the order of 0.02°- and confirmed by numerical modeling. This result demonstrates the high sensitivity of the technique, as well as its exciting perspectives for imaging complex organic and inorganic nanostructured materials., La ptychographie est une technique d’imagerie par diffraction cohérente qui vise à récupérer la phase perdue, uniquement par des mesures d’intensité en champ lointain. Cette technique permet l’imagerie des champs de déformation dans des cristaux périodiques avec des résolutions sous-faisceau. Dans ce travail, la ptychographie de Bragg en 3D est utilisée pour étudier les propriétés d’une couche cristalline nanostructurée de InP/InGaAs collée sur un substrat de silicium. L’expérience a été réalisée sur la ligne ID13 de l’ESRF, avec un faisceau monochromatique concentré à 100nm. Les intensités 2D ont été acquises avec plusieurs angles d’incidence dans le voisinage du pic de Bragg InP (004), empilant un jeu de données tridimensionnelles. L’analyse numérique du problème donné a été effectuée à l’avance afin d’optimiser la stratégie d’inversion et d’étudier la possibilité d’introduire des contraintes physiques supplémentaires basées sur des approches de régularisation. L’inversion de l’ensemble des données a été effectuée en utilisant un algorithme ptychographique de reconstruction de phase. L’image 3D récupérée représente la haute qualité cristalline de l’échantillon, avec les valeurs de l’épaisseur et du désaccord de maille attendus en moyenne. Néanmoins, de petites inclinaisons locales de mailles ont été observées - de l’ordre de 0.02°- et confirmées par modélisation numérique. Les résultats démontrent la sensibilité de la technique, ainsi que ses perspectives passionnantes pour l’imagerie des matériaux organiques et inorganiques nanostructurés complexes.
- Published
- 2015
12. Nondestructive three-dimensional imaging of crystal strain and rotations in an extended bonded semiconductor heterostructure
- Author
-
Manfred Burghammer, Pierre Godard, Marc Allain, Anastasios Pateras, Konstantinos Pantzas, Ludovic Largeau, Virginie Chamard, Gilles Patriarche, Anne Talneau, A. A. Minkevich, Coherent Optical Microscopy and X-rays (COMiX), Institut FRESNEL (FRESNEL), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Karlsruhe Institute of Technology (KIT), Laboratoire de photonique et de nanostructures (LPN), Centre National de la Recherche Scientifique (CNRS), European Synchrotron Radiation Facility (ESRF), ANR-10-EQPX-0050,TEMPOS,Microscopie electronique en transmission sur le plateau Palaiseau Orsay Saclay(2010), European Project, and Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)
- Subjects
[PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics] ,Materials science ,Silicon ,business.industry ,semiconductor heterostructures ,chemistry.chemical_element ,Physics::Optics ,Observable ,Heterojunction ,Bragg ptychography ,Condensed Matter Physics ,Ptychography ,PACS: 61.05.cp, 68.37.Yz, 42.30.Rx, 61.46.-w ,Electronic, Optical and Magnetic Materials ,Optics ,Semiconductor ,chemistry ,X-ray crystallography ,[SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic ,Sample preparation ,[SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics ,Phase retrieval ,business ,[SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing - Abstract
International audience; We report the 3D mapping of strain and tilts of crystal planes in an extended InP nanostructured layer bonded onto silicon, measured without sample preparation. Our approach takes advantages of 3D x-ray Bragg ptychography combined to an optimized inversion process. The excellent agreement with the sample nominal structure validates the reconstruction while the evidence of spatial fluctuations hardly observable by other means, underlines the specificities of Bragg ptychography.
- Published
- 2015
13. X-ray Bragg Ptychography on a Single InGaN/GaN Core-Shell Nanowire.
- Author
-
Dzhigaev D, Stankevič T, Bi Z, Lazarev S, Rose M, Shabalin A, Reinhardt J, Mikkelsen A, Samuelson L, Falkenberg G, Feidenhans'l R, and Vartanyants IA
- Abstract
The future of solid-state lighting can be potentially driven by applications of InGaN/GaN core-shell nanowires. These heterostructures provide the possibility for fine-tuning of functional properties by controlling a strain state between mismatched layers. We present a nondestructive study of a single 400 nm-thick InGaN/GaN core-shell nanowire using two-dimensional (2D) X-ray Bragg ptychography (XBP) with a nanofocused X-ray beam. The XBP reconstruction enabled the determination of a detailed three-dimensional (3D) distribution of the strain in the particular nanowire using a model based on finite element method. We observed the strain induced by the lattice mismatch between the GaN core and InGaN shell to be in the range from -0.1% to 0.15% for an In concentration of 30%. The maximum value of the strain component normal to the facets was concentrated at the transition region between the main part of the nanowire and the GaN tip. In addition, a variation in misfit strain relaxation between the axial growth and in-plane directions was revealed.
- Published
- 2017
- Full Text
- View/download PDF
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