Investigations of dislocation strain fields using weak beams

Cockayne, D. J. H.; Ray, I.L.F.; Whelan, M. J.

doi:10.1080/14786436908228210

Cited by 650 publications

(144 citation statements)

References 8 publications

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“…[22]. Using the weak beam (WB) dark field (DF) TEM imaging mode [23] edge dislocations are visible in (2-420) and (2-200) reflex images, while screw dislocations are highlighted in 000-4 WBDF images. In all cases the g-3g condition was used [24].…”

Section: Methodsmentioning

confidence: 99%

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

Gries

Wassner

Vogel

et al. 2015

Journal of Applied Physics

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This version is available at https://strathprints.strath.ac.uk/54019/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. Transmission electron microscopy reveals that these effects are caused by phase separation leading to the formation of a vertically ordered rock salt/wurtzite heterostructures. To explain these observations we suggest a phase separation epitaxy model that considers this process being initiated by the formation of a cubic (Mg,Zn)Al 2 O 4 spinel layer at the interface to the sapphire substrate, acting as a planar seed for the epitaxial precipitation of rock salt-type Mg x Zn 1-x O. The equilibrium fraction x of magnesium in the resulting wurtzite (rock salt) layers is approximately 0.15 (0.85), independent of the MgO content of the as-grown layer and determined by the annealing temperature. This model is confirmed by photoluminescence analysis of the resulting layer systems after different annealing temperatures. In addition we show that the thermal annealing process 2 results in a significant reduction in the density of edge-and screw-type dislocations, providing the possibility to fabricate high quality templates for quasi-homoepitaxial growth.3

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Section: Methodsmentioning

confidence: 99%

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

Gries

Wassner

Vogel

et al. 2015

Journal of Applied Physics

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“…5), using a transmission electron microscope (TEM). TEM has proven to be a powerful tool for studying the structure and arrangement of dislocations, with seminal work laid out by Cockayne et al 6 in 1969 by the introduction of the weak beam method 6,7 .…”

mentioning

confidence: 99%

Atomic scale study of the life cycle of a dislocation in graphene from birth to annihilation

et al. 2013

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Dislocations, one of the key entities in materials science, govern the properties of any crystalline material. Thus, understanding their life cycle, from creation to annihilation via motion and interaction with other dislocations, point defects and surfaces, is of fundamental importance. Unfortunately, atomic-scale investigations of dislocation evolution in a bulk object are well beyond the spatial and temporal resolution limits of current characterization techniques. Here we overcome the experimental limits by investigating the two-dimensional graphene in an aberration-corrected transmission electron microscope, exploiting the impinging energetic electrons both to image and stimulate atomic-scale morphological changes in the material. The resulting transformations are followed in situ, atom-by-atom, showing the full life cycle of a dislocation from birth to annihilation. Our experiments, combined with atomistic simulations, reveal the evolution of dislocations in two-dimensional systems to be governed by markedly long-ranging out-of-plane buckling.

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“…For example, in scanning mode (STEM) direct imaging of the crystal lattice can be coupled with spectroscopic analysis to yield chemical information at the unit cell level. [8] In imaging mode the technique is routinely used for identification and characterisation of defect structures; [9] in diffraction mode, detailed investigations of both symmetry [10] and crystal structure [11] are possible. Precision control of sample position and tilt, coupled with rapid acquisition of digital images, has contributed strongly to the development of holographic methods for the measurement of local fields within structures, [12] and tomographic approaches to three dimensional characterisation of microstructure.…”

Section: Introductionmentioning

confidence: 99%

Determination of the Crystal Structure of a New Polymorph of Theophylline

Eddleston

Hejczyk

Bithell

et al. 2013

Chemistry A European J

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Electron diffraction offers advantages over X-ray based methods for crystal structure determination as it can be applied to sub-micron sized crystallites, and picogram quantities of material. With molecular organic species, however, crystal structure determination with electron diffraction is hindered by rapid crystal deterioration in the electron beam, limiting the amount of diffraction data that can be collected, and by the effect of dynamical scattering on reflection intensities. While automated electron diffraction tomography provides one possible solution, in this paper we demonstrate an alternative approach where a set of putative crystal structures of the compound of interest is generated using crystal structure prediction methods, and electron diffraction is used to determine which of these putative structures is in agreement with the available electron diffraction data. This approach enables the advantages of electron diffraction to be exploited, while avoiding the need to obtain large amounts of diffraction data or accurate reflection intensities. We demonstrate the methodology using the pharmaceutical compounds paracetamol, scyllo-inositol and theophylline.

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Investigations of dislocation strain fields using weak beams

Cited by 650 publications

References 8 publications

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

Atomic scale study of the life cycle of a dislocation in graphene from birth to annihilation

Determination of the Crystal Structure of a New Polymorph of Theophylline

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