scholarly journals Three-wave X-ray diffraction in distorted epitaxial structures

2013 ◽  
Vol 46 (4) ◽  
pp. 861-867 ◽  
Author(s):  
Reginald Kyutt ◽  
Mikhail Scheglov
Keyword(s):  
Reciprocal Lattice ◽  
Lattice Points ◽  
Angular Width ◽  
X Ray Diffraction ◽  
Structural Perfection ◽  
Multiple Diffraction ◽  
X Ray ◽  
Highly Sensitive ◽  
Integrated Intensities ◽  
Scanning Geometry

Three-wave diffraction has been measured for a set of GaN, AlN, AlGaN and ZnO epitaxial layers grown on c-sapphire. A Renninger scan for the primary forbidden 0001 reflection was used. For each of the three-wave combinations, θ-scan curves were measured. The intensity and angular width of both φ- and θ-scan three-wave peaks were analyzed. The experimental data were used to determine properties of the multiple diffraction pattern in highly distorted layers. It is shown that the FWHM of θ scans is highly sensitive to the structural perfection and strongly depends on the type of three-wave combination. The narrowest peaks are observed for multiple combinations with the largest l index of the secondary hkl reflection. An influence of the type of the dislocation structure on the θ-scan broadening was revealed. These experimental facts are interpreted by considering the scanning geometry in the reciprocal space and taking into account the disc-shaped reciprocal-lattice points. The total integrated intensities of all the three-wave combinations were determined and their ratios were found to be in only a qualitative agreement with the theory. For AlGaN layers, the presence of the nonzero 0001 reflection was revealed, in contrast to AlN and GaN films.

Protein crystals can be incommensurately modulated

2008 ◽  
Vol 41 (3) ◽  
pp. 600-605 ◽  
Author(s):  
Jeffrey J. Lovelace ◽  
Cameron R. Murphy ◽  
Lee Daniels ◽  
Kartik Narayan ◽  
Clarence E. Schutt ◽  
...  
Keyword(s):  
Diffraction Pattern ◽  
Reciprocal Lattice ◽  
Lattice Points ◽  
Chemical Crosslinking ◽  
X Ray Diffraction ◽  
X Ray ◽  
Periodic State ◽  
Orientation Matrix ◽  
Aperiodic Crystals ◽  
Future Work

For a normal periodic crystal, the X-ray diffraction pattern can be described by an orientation matrix and a set of three integers that indicate the reciprocal lattice points. Those integers determine the spacing along the reciprocal lattice directions. In aperiodic crystals, the diffraction pattern is modulated and the standard periodic main reflections are surrounded by satellite reflections. The successful indexing and refinement of the main unit cell andqvector usingTWINSOLVE, developed by Svensson [(2003). Lund University, Sweden], are reported here for an incommensurately modulated, aperiodic crystal of a profilin:actin complex. The indexing showed that the modulation is along thebdirection in the crystal, which corresponds to an `actin ribbon' formed by the crystal lattice. Interestingly, the transition to the aperiodic state was shown to be reversible and the diffraction pattern returned to the periodic state during data collection. It is likely that the protein underwent a conformational change that affected the neighbouring profilin:actin molecules in such a way as to produce the observed modulation in the diffraction pattern. Future work will aim to trap the incommensurately modulated crystal state, for example using cryocooling or chemical crosslinking, thus allowing complete X-ray data to be collected.

High Resolution X-ray Diffraction of GaN Grown on Sapphire Substrates

1996 ◽  
Vol 449 ◽  
Author(s):  
A. Saxler ◽  
M. A. Capano ◽  
W. C. Mitchel ◽  
P. Kung ◽  
X. Zhang ◽  
...  
Keyword(s):  
Metalorganic Chemical Vapor Deposition ◽  
Reciprocal Lattice ◽  
Chemical Vapor ◽  
Lattice Points ◽  
Structural Quality ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sapphire Substrates ◽  
Primary Mechanism

ABSTRACTX-ray rocking curves are frequently used to assess the structural quality of GaN thin films. In order to understand the information given by the line shape, we need to know the primary mechanism by which the curves are broadened. The GaN films used in this study were grown by low pressure metalorganic chemical vapor deposition (MOCVD) on (00•1) sapphire substrates. GaN films with both broad and very narrow (open detector linewidth of 40 arcseconds for the (00•2) GaN reflection) rocking curves are examined in this work. Reciprocal space maps of both symmetric and asymmetric reciprocal lattice points are used to determine that the cause of the broadening of GaN rocking curves is a limited in-plane coherence length.

High-resolution x-ray diffraction study of In0.25Ga0.75Sb/InAs superlattice

1999 ◽  
Vol 14 (5) ◽  
pp. 1744-1751 ◽  
Author(s):  
A. Vigliante ◽  
H. Homma ◽  
J. T. Zborowski ◽  
T. D. Golding ◽  
S. C. Moss
Keyword(s):  
High Resolution ◽  
Structural Parameters ◽  
Reciprocal Lattice ◽  
Lattice Points ◽  
Diffuse Interface ◽  
X Ray Diffraction ◽  
Group V ◽  
X Ray ◽  
Strained Layer Superlattice ◽  
Ir Detection

An In0.25Ga0.75Sb/InAs strained-layer superlattice, grown by molecular-beam epitaxy (MBE) on a GaSb[001] substrate, has been characterized by four-circle x-ray diffractometry. This system, proposed by Maliot and Smith for ir detection application, is challenging because of the two group V species and the likelihood of cross-incorporation of the different elements during growth, leading possibly to interdiffusion and thus, to a more diffuse interface. High-resolution x-ray diffraction (XRD) profiles were obtained about several reciprocal lattice points in order to extract a reliable set of structural parameters. The profiles were then successfully modeled by computer simulation. The presence of many sharp higher-order satellite reflections in the XRD profiles is a measure of the high quality of the superlattices. The normal and lateral structural coherence was also measured and will be discussed.

Structural Characterization of Reactive Ion Etched Semiconductor Nanostructures Using X-Ray Reciprocal Space Mapping

1995 ◽  
Vol 406 ◽  
Author(s):  
G. Bauer ◽  
A. A. Darhuber ◽  
V. Holy
Keyword(s):  
Quantum Dot ◽  
Reciprocal Lattice ◽  
Space Mapping ◽  
Reciprocal Space ◽  
Lattice Points ◽  
Scanning Electron Micrographs ◽  
X Ray Diffraction ◽  
Reciprocal Space Mapping ◽  
Entire Volume ◽  
X Ray

AbstractWe have studied GaAs/AlAs periodic quantum dot arrays using high resolution x-ray diffraction (reciprocal space mapping) around the (004) and (113) reciprocal lattice points. From the distribution of the diffracted intensities we deduced the average strain status of the dots. From the numerical simulations it is evident that random elastic strain fields are present, which extend through almost the entire volume of the quantum dot. The simulations of the x-ray measurements revealed that the crystalline part of the dots is considerably smaller as scanning electron micrographs would indicate.

Determination of dispersion and polarization of thermal plane waves in crystals

1971 ◽  
Vol 134 (3-4) ◽  
Author(s):  
P. L. La Fleur
Keyword(s):  
Intensity Distribution ◽  
Phonon Scattering ◽  
Reciprocal Lattice ◽  
Plane Waves ◽  
Lattice Points ◽  
X Ray Diffraction ◽  
Diffraction Intensity ◽  
Reciprocal Lattice Point ◽  
X Ray

AbstractThe dispersion of the thermal plane waves (phonons) in crystals can be determined from the x-ray diffraction intensity distribution around a reciprocal lattice point. In the method presented here no higher-order phonon-scattering corrections are necessary. It is shown furthermore that polarizations and dispersion of the phonons can be determined from the intensity distributions around six properly chosen reciprocal lattice points.

Structural Characterization of Reactive Ion Etched Semiconductor Nanostructures Using X-Ray Reciprocal Space Mapping

1995 ◽  
Vol 405 ◽  
Author(s):  
G. Bauer ◽  
A. A. Darhuber ◽  
V. Holy
Keyword(s):  
Quantum Dot ◽  
Reciprocal Lattice ◽  
Space Mapping ◽  
Reciprocal Space ◽  
Lattice Points ◽  
Scanning Electron Micrographs ◽  
X Ray Diffraction ◽  
Reciprocal Space Mapping ◽  
Entire Volume ◽  
X Ray

AbstractWe have studied GaAs/AlAs periodic quantum dot arrays using high resolution x-ray diffraction (reciprocal space mapping) around the (004) and (113) reciprocal lattice points. From the distribution of the diffracted intensities we deduced the average strain status of the dots. From the numerical simulations it is evident that random elastic strain fields are present, which extend through almost the entire volume of the quantum dot. The simulations of the x-ray measurements revealed that the crystalline part of the dots is considerably smaller as scanning electron micrographs would indicate.

Interference phenomena observed by X-ray diffraction in nanocrystalline thin films

2004 ◽  
Vol 37 (4) ◽  
pp. 613-620 ◽  
Author(s):  
David Rafaja ◽  
Volker Klemm ◽  
Gerhard Schreiber ◽  
Michael Knapp ◽  
Radomír Kužel
Keyword(s):  
Thin Films ◽  
Reciprocal Lattice ◽  
Preferred Orientation ◽  
Lattice Points ◽  
Partial Coherence ◽  
Diffraction Line ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nanocrystalline Thin Films

An increase of the X-ray diffraction line broadening with increasing diffraction angle was observed experimentally in nanocrystalline thin films. Such a change of the line width is usually related to the microstrain in the sample, which, however, contradicts the assumptions that the microstrain is relatively low in nanocrystalline materials and that the line broadening is caused mainly by small crystallite size. For nanocrystalline thin films, the observed changes in the diffraction line broadening are explained by a partial coherence of adjacent crystallites, which is stronger at low diffraction angles than at high diffraction angles. Furthermore, it is found that the degree of coherence of the adjacent crystallites depends on their size and preferred orientation. Smaller crystallites show better coherence, because the corresponding reciprocal-lattice points are broadened compared with those related to large crystallites. A strong preferred orientation improves further the coherence of the adjacent crystallites. Theoretical results are confirmed by experimental data obtained on nanocrystalline (Ti,Al)N thin films using a combination of glancing-angle X-ray diffraction, high-resolution transmission electron microscopy and X-ray texture analysis.

Crystal truncation rod X-ray scattering: exact dynamical calculation

2008 ◽  
Vol 41 (1) ◽  
pp. 18-26 ◽  
Author(s):  
Václav Holý ◽  
Paul F. Fewster
Keyword(s):  
Reciprocal Lattice ◽  
Dynamical Theory ◽  
Lattice Points ◽  
Space Distribution ◽  
Matrix Formalism ◽  
X Ray ◽  
Transmission Coefficients ◽  
X Ray Scattering ◽  
Crystal Truncation Rod ◽  
Scattering Geometry

A new method is presented for a calculation of the reciprocal-space distribution of X-ray diffracted intensity along a crystal truncation rod. In contrast to usual kinematical or dynamical approaches, the method is correct both in the reciprocal-lattice points and between them. In the method, the crystal is divided into a sequence of very thin slabs parallel to the surface; in contrast to the well known Darwin dynamical theory, the electron density in the slabs is constant along the surface normal. The diffracted intensity is calculated by a matrix formalism based on the Fresnel reflection and transmission coefficients. The method is applicable for any polarization of the primary beam and also in a non-coplanar scattering geometry.

scholarly journals High-resolution characterization of the forbidden Si 200 and Si 222 reflections

2015 ◽  
Vol 48 (2) ◽  
pp. 528-532 ◽  
Author(s):  
Peter Zaumseil
Keyword(s):  
High Resolution ◽  
Angular Range ◽  
Angular Divergence ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
Diffraction Plane ◽  
X Ray ◽  
Sample Orientation ◽  
Plane Sample

The occurrence of the basis-forbidden Si 200 and Si 222 reflections in specular X-ray diffraction ω–2Θ scans is investigated in detail as a function of the in-plane sample orientation Φ. This is done for two different diffractometer types with low and high angular divergence perpendicular to the diffraction plane. It is shown that the reflections appear for well defined conditions as a result of multiple diffraction, and not only do the obtained peaks vary in intensity but additional features like shoulders or even subpeaks may occur within a 2Θ range of about ±2.5°. This has important consequences for the detection and verification of layer peaks in the corresponding angular range.

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