Dislocation structures and mechanical behaviour of Ge single crystals deformed by compression

Nyilas, K.; Dupas, Corinne; Kruml, Tomáš; Zsoldos, L.; Ungár, Tamás; Martin, J.L.

doi:10.1016/j.msea.2004.01.087

Cited by 9 publications

(12 citation statements)

References 5 publications

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“…Monochromatic synchrotron diffraction experiments on single grains in bulk polycrystalline specimens have shown that RCB occurs along the Debye-Scherrer lines, where, at the same time, the radial broadening is by orders of magnitude smaller, indicating that RCB is mainly caused by rotation or tilting of subgrains. This also indicates that the subgrains created by plastic deformation are rotated or tilted with rather small changes of their average lattice constants (Nyilas et al, 2004;Jakobsen et al, 2006;Levine et al, 2006;Jakobsen et al, 2007;Ungá r et al, 2014). Following up on this evidence, we apply the method of polar decomposition (Higham, 1986) to separate the effect of deformation into stretching and rigid-body rotation, which finally allows the decomposition of diffraction peak broadening into line profiles and rocking curves, parallel and perpendicular to the diffraction vectors, respectively.…”

Section: Introductionmentioning

confidence: 95%

“…Equations 48and (50) can be considered as the fundamental expressions for RCB. Experimental evidence shows that RCs can disintegrate into more than one or several subpeaks (Barabash et al, 2003;Nyilas et al, 2004;Levine et al, 2006;Jakobsen et al, 2007). In such cases, one single mean-squarerotation value may not be sufficient for fully characterizing the shape of RCs.…”

Section: Rocking-curve Broadeningmentioning

confidence: 99%

“…RCs and LPs of the 331 reflection were measured on Ge single crystals oriented for single slip and compression deformed at 850 K (Nyilas et al, 2004(Nyilas et al, , 2010. The imagingplate micrographs and the reciprocal-space mapping image are shown in Fig.…”

Section: Compression-deformed Ge Single Crystalsmentioning

confidence: 99%

“…There is ample evidence in the literature that peak broadening of defect crystals is anisotropic around the fundamental Bragg positions in reciprocal space (cf. Wilkens et al, 1987;Jakobsen et al, 2006;Nyilas et al, 2004;Levine et al, 2006;Tamura, 2014). It is a general experience that RCs are substantially broader than line profiles (LPs).…”

Section: Introductionmentioning

confidence: 99%

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A common theory of line broadening and rocking curves

2015

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X-ray diffraction peak broadening is discussed in terms of line broadening and rocking-curve broadening in a novel theoretical description. The nonlocal strain tensor is factorized by using the method of polar decomposition instead of the more conventional separation into symmetrical and antisymmetrical components. A number of X-ray line-broadening and rocking-curve experiments on the same single crystals or individual grains in bulk polycrystals prove that plastic deformation produces strained subgrains mutually rotated by rigid-body rotations. The novel theoretical description appropriately accounts for the rigidbody rotation and strain at the same time and provides straightforward separation of the two effects of line and rocking-curve broadening in the radial and normal directions of the diffraction vector. The mathematical results are discussed in terms of experiments of X-ray diffraction, Laue asterism and electron backscatter diffraction. From the experimental results it is shown that the simultaneous evaluation of line and rocking-curve broadening provides qualitative information about the redundant and geometrically necessary character of dislocations, not available if only one or the other is accessible.

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Section: Introductionmentioning

confidence: 95%

Section: Rocking-curve Broadeningmentioning

confidence: 99%

Section: Compression-deformed Ge Single Crystalsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A common theory of line broadening and rocking curves

2015

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“…A critical point is the possibility of growing crystals with a well defined mosaicity, or with a well defined dislocation density. High quality, dislocation free germanium crystals are now available so that a given degree of mosaicity should be intentionally obtained during the growth [8][9] or by appropriate post growth treatment [10][11][12] . Germanium crystals with mosaic spread between 0.2 and 1.5 degrees could be obtained 9 by using plastic deformation at high temperature but the control to a good accuracy of this parameter is still difficult, especially in the mosaicity range between 1' to a few tens of arcseconds.…”

Section: Introductionmentioning

confidence: 99%

Mosaic GaAs crystals for hard x-ray astronomy

2008

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Recently the design of a Laue lens with field of view of 30 arcseconds and for x-rays in the energy range from 100 keV to 1 MeV has been proposed in which mosaic crystals are used as focussing elements. The proper mosaic angular spread is chosen as a compromise between intensity and energy resolution of the Laue lens. In the present work we consider the use of GaAs crystals as optical elements for hard x-ray astronomy. GaAs crystals have essentially the same electron density and lattice spacing as germanium, and are characterized by spontaneous formation of "cellular structures" with dislocations distribution at the boundaries between perfect zones of the crystal. Because of the presence of cellular structures Czochralsky grown GaAs show a natural degree of mosaicity. Several GaAs ingots grown by liquid encapsulating Czochralsky technique have been characterized by high resolution xray diffraction. Bragg diffraction profiles have been measured along ingot axes and diameters of doped, undoped or stoichiometry deviated GaAs crystals. Full width at half maximum values ranging from 15 to 40 arcseconds depending on the position were measured close to the proposed 30 arcsecond mosaicity required for the Laue lens. Appropriate growth conditions allow the control of the dislocation density and the modification of cellular structure responsible of the crystal mosaicity so that the possibility of obtaining crystals with a given degree of mosaicity by tuning the LEC growth conditions is proposed.

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Characterization of nanocrystalline materials by X-ray line profile analysis

Ungár

2006

J Mater Sci

168

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Dislocation structures and mechanical behaviour of Ge single crystals deformed by compression

Cited by 9 publications

References 5 publications

A common theory of line broadening and rocking curves

A common theory of line broadening and rocking curves

Mosaic GaAs crystals for hard x-ray astronomy

Characterization of nanocrystalline materials by X-ray line profile analysis

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