Kinematical x‐ray diffraction model with a new boundary condition for analysis of Bragg‐peak profiles of layered crystals

1991 ◽  
Vol 69 (9) ◽  
pp. 6406-6412 ◽  
Author(s):  
C. R. Wie ◽  
H. M. Kim
Keyword(s):  
Boundary Condition ◽  
Bragg Peak ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Model ◽  
Layered Crystals ◽  
Bragg Peak Profiles

High Resolution X-ray Diffraction for the Characterization of Semiconducting Materials

1989 ◽  
Vol 33 ◽  
pp. 1-11 ◽  
Author(s):  
B. K. Tanner
Keyword(s):  
Bragg Peak ◽  
Thin Layers ◽  
X Ray Diffraction ◽  
Semiconducting Materials ◽  
Multiple Reflections ◽  
X Ray ◽  
Analyzer Crystal ◽  
Glancing Angle ◽  
Heteroepitaxial Layers

AbstractUse of a reference crystal to condition the beam in the double-axis diffractometer permits the Bragg peak width to be reduced to the correlation of the two crystal reflecting ranges. Some recent applications of double axis diffractometry to the study of heteroepitaxial layers are discussed. The advantages of multiple reflections for beam conditioning and the four reflection DuMond monochromator are examined. Glancing incidence and exit diffractometry permits the study of very thin layers, down to a few tens of nanometres in thickness and both synchrotron radiation and skew reflections can be used to tune the glancing angle close to the critical angle. Recent applications of triple-axis diffraction, where an analyzer crystal is used after the specimen, to the study of very thin single epitaxial layers and multiquantum well structures are reviewed.

Bi-Based Superconducting Multilayers Obtained by Molecular Beam Epitaxy

1999 ◽  
Vol 13 (09n10) ◽  
pp. 991-996
Author(s):  
M. Salvato ◽  
C. Attanasio ◽  
G. Carbone ◽  
T. Di Luccio ◽  
S. L. Prischepa ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Xrd Analysis ◽  
High Energy ◽  
X Ray Diffraction ◽  
One Dimensional ◽  
X Ray ◽  
Diffraction Model ◽  
Different Thickness

High temperature superconducting multilayers have been obtained depositing Bi2Sr2CuO6+δ(2201) and ACuO2 layers, where A is Ca or Sr, by Molecular Beam Epitaxy (MBE) on MgO and SrTiO3 substrates. The samples, formed by a sequence of 2201/ACuO2 bilayers, have different thickness of ACuO2 layers while the thickness of the 2201 layers is kept constant. The surface structure of each layer has been monitored by in situ Reflection High Energy Electron Diffraction (RHEED) analysis which has confirmed a 2D nucleation growth. X-ray diffraction (XRD) analysis has been used to confirm that the layered structure has been obtained. Moreover, one-dimensional X-ray kinematic diffraction model has been developed to interpret the experimental data and to estimate the period of the multilayers. Resistive measurements have shown that the electrical properties of the samples strongly depend on the thickness of the ACuO2 layers.

scholarly journals Characterization of individual stacking faults in a wurtzite GaAs nanowire by nanobeam X-ray diffraction

2017 ◽  
Vol 24 (5) ◽  
pp. 981-990 ◽  
Author(s):  
Arman Davtyan ◽  
Sebastian Lehmann ◽  
Dominik Kriegner ◽  
Reza R. Zamani ◽  
Kimberly A. Dick ◽  
...  
Keyword(s):  
Bragg Peak ◽  
Stacking Faults ◽  
Growth Direction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Patterson Function ◽  
Transmission Electron ◽  
Gaas Nanowires ◽  
Gaas Nanowire

Coherent X-ray diffraction was used to measure the type, quantity and the relative distances between stacking faults along the growth direction of two individual wurtzite GaAs nanowires grown by metalorganic vapour epitaxy. The presented approach is based on the general property of the Patterson function, which is the autocorrelation of the electron density as well as the Fourier transformation of the diffracted intensity distribution of an object. Partial Patterson functions were extracted from the diffracted intensity measured along the [000\bar{1}] direction in the vicinity of the wurtzite 00\bar{1}\bar{5} Bragg peak. The maxima of the Patterson function encode both the distances between the fault planes and the type of the fault planes with the sensitivity of a single atomic bilayer. The positions of the fault planes are deduced from the positions and shapes of the maxima of the Patterson function and they are in excellent agreement with the positions found with transmission electron microscopy of the same nanowire.

Fourier Transformation of X-Ray Rocking Curves from Interferometer Structures

1993 ◽  
Vol 37 ◽  
pp. 135-144
Author(s):  
J. M. Hudson ◽  
B. K. Tanner ◽  
R. Blunt
Keyword(s):  
Layer Thickness ◽  
Bragg Peak ◽  
Noisy Data ◽  
X Ray Diffraction ◽  
Interference Structure ◽  
X Ray ◽  
Auto Correlation ◽  
Interference Fringes ◽  
Spline Fitting ◽  
Cubic Spline Fitting

AbstractWe discuss the use of Fourier transform techniques to extract layer thickness from the interference fringes observed in high resolution X-ray diffraction rocking curves of pseudomorphic HEMT structures. The interference structure is extracted by cubic spline fitting to the extrema of the data, thereby obtaining a background envelope which is used to normalise the data. The resulting constant background is subtracted from the data and the residual Fourier transformed. Auto correlation of the residual significantly improves the result from noisy data. Satisfactory results are obtained only when the Bragg peak from the substrate is windowed out. With a limited dynamic and angular range, there is often insufficient data to separate the two closely spaced periods arising from the total layer thickness and that excluding the quantum well. The result then corresponds to the average of these two thicknesses.

Structure determination of forms I and II of phenobarbital from X-ray powder diffraction

2005 ◽  
Vol 61 (1) ◽  
pp. 80-88 ◽  
Author(s):  
Cyril Platteau ◽  
Jacques Lefebvre ◽  
Stephanie Hemon ◽  
Carsten Baehtz ◽  
Florence Danede ◽  
...  
Keyword(s):  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
Space Group ◽  
X Ray ◽  
Bragg Peak Profiles ◽  
Monte Carlo Simulated Annealing ◽  
Crystal Structural ◽  
Diffraction Patterns ◽  
Annealing Method

From pure powders of forms I and II of phenobarbital, X-ray diffraction patterns were recorded at room temperature. The starting crystal structural models were found by a Monte-Carlo simulated annealing method. The structures of the two forms were obtained through Rietveld refinements. Soft restraints were applied on bond lengths and bond angles, all H-atom positions were calculated. The cell of form I is monoclinic with the space group P21/n, Z = 12, Z′ = 3. Form II has a triclinic cell, with the space group P\bar 1, Z = 6, Z′ = 3. For both forms, the crystal cohesion is achieved by networks of N—H...O hydrogen bonds along [101]. The broadening of the Bragg peak profiles is interpreted in terms of isotropic strain effects and anisotropic size effects.

scholarly journals Irreversible Structural Transformation of five fold i-AlPdMn Quasicrystals after Ion Bombardment and Annealing

2000 ◽  
Vol 643 ◽  
Author(s):  
F. Schmithüsen ◽  
G. Cappello ◽  
S. Decossas ◽  
G. Torricelli ◽  
T.-L. Lee ◽  
...  
Keyword(s):  
High Resolution ◽  
Structural Transformation ◽  
Bragg Peak ◽  
Normal Incidence ◽  
Ion Bombardment ◽  
Sample Surface ◽  
Bulk Sample ◽  
X Ray Diffraction ◽  
Energy Position ◽  
X Ray

AbstractFive fold i-AlPdMn surface prepared under UHV by ion bombardment and annealing was so far considered to be bulk terminated. This result was substantially based on a quantitative LEED analyses [1]. Analysis of the specular rod in a X ray diffraction experiment at grazing incidence supported this result [2]. We present a new study of this surface by high resolution X ray diffraction at normal incidence. In this Bragg configuration the diffraction peak 18 – 29 for instance is at a photon energy of 2.873keV, the 72 – 116 reflection at 5.725keV. This results in an analyzed thickness of the sample surface of a few micrometers.The surface was cleaned by ion bombardment. During annealing (T≅880K), we clearly observed the progressive disappearance of the initial Bragg peak characteristic of the as cast bulk sample. Conversely a new Bragg peak grows at an energy position shifted by 1eV compared to the position of the original Bragg peak. This is a clear signature for an irreversible structural transformation which takes place on at least the micron thickness. On the transformed surface, both, a LEED pattern and a RHEED pattern, characteristic for a five fold surface were easily obtained.This high resolution experiment (the relative Bragg peak shift is 3ׁ10−4) was reproduced on samples from different initial compositions. This shows that five fold i-AlPdMn surface changes after preparation by ion bombardment and annealing at 900K on a micrometer thickness. This is not consistent with the conclusion that the surface is simply terminated by a cut of the original bulk. We conclude that a reorganization process of the quasicrystalline structure during annealing proceeds in the surface vicinity (probed depth is close to a few microns).

The Deformation Mechanisms of TWIP Steels (Fe-Mn-C) Viewed by X-Ray Diffraction

2007 ◽  
Vol 130 ◽  
pp. 53-56 ◽  
Author(s):  
J.L. Collet ◽  
Françoise Bley ◽  
Alexis Deschamps ◽  
H. de Monestrol ◽  
Jean François Berar ◽  
...  
Keyword(s):  
Ccd Camera ◽  
European Synchrotron Radiation Facility ◽  
Austenitic Steels ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bragg Peak Profiles ◽  
Twip Steels ◽  
State Position ◽  
Position Shift ◽  
Extensive Deformation

Fully austenitic steels of the Fe-Mn-C system can show extensive deformation twinning (TWIP effect). The deformed microstructure of such steels has been analysed using X-ray diffraction at the European Synchrotron Radiation Facility (ESRF). The experimental diffractograms, recorded using a 2D CCD camera, are analysed in terms of Bragg peak profiles (broadening and asymmetry) and position (shift from the reference [undeformed state] position) leading to an estimation of dislocation and stacking faults densities.

scholarly journals ELECTRON MICROSCOPE STUDIES ON THE HAEMOGLOBIN MOLECULES

1961 ◽  
Vol 10 (1) ◽  
pp. 113-120 ◽  
Author(s):  
S. N. Chatterjee ◽  
P. Sadhukhan ◽  
J. B. Chatterjea
Keyword(s):  
Electron Microscope ◽  
Satisfactory Agreement ◽  
Human Subjects ◽  
Average Height ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
X Ray ◽  
Diffraction Model ◽  
Normal Human ◽  
The Individual

Haemoglobin molecules isolated from normal human subjects have been directly micrographed under the electron microscope following in general Hall's technique. The average height (h) and the widths along (w11) and perpendicular (w⊥) to the shadow direction of the molecules have been measured as 56.5 ± 6.6 A, 122.7 ± 15 A, and 120.9 ± 20 A, respectively. The exaggeration in the molecular widths due to the deposition of metal cap ranges between 60 to 70 A. The probable resolution of the substructure of the molecule, e.g., presence of "holes" and dimples, in the present electron microscopic evidence has been discussed. The electron microscopic results on the size of the individual haemoglobin molecules are in satisfactory agreement with the recent x-ray diffraction model of Perutz and his associates for horse haemoglobin.

A STUDY OF MACROCRYSTALLINE PEDOGENIC CARBONATES USING SUBMICROSCOPIC TECHNIQUES

1981 ◽  
Vol 61 (2) ◽  
pp. 261-272 ◽  
Author(s):  
A. R. MERMUT ◽  
R. J. ST. ARNAUD
Keyword(s):  
Electron Probe ◽  
Size Range ◽  
X Ray Diffraction ◽  
Pedogenic Carbonate ◽  
X Ray ◽  
Pedogenic Carbonates ◽  
Layered Crystals ◽  
Magnesium Calcite ◽  
Sem Analyses

Calcitic plasmic fabric, grain calcans, neocalcitans and carbonatic glaebules with diffuse boundary were studied in situ, in soils by electron probe and SEM analyses. The occurrence of pedogenic magnesium-bearing calcite, previously detected by a shift of X-ray diffraction spacing on bulk samples, was verified by electron probes analyses on purely pedogenic carbonatic sites. This made it possible to understand further the nature of carbonates and to differentiate pure calcite from magnesium-bearing calcite. Common types of microcrystalline pedogenic carbonates included elongated, equidimensional, rod-shaped, and layered crystals. Equidimensional crystals were common in calcite, whereas elongated and rod types occurring sometimes as bundles of coalescing fibres were found to be magnesium calcite. Most visible pedogenic carbonate crystals in the soils studies had a diameter of 0.3–1.0 μm. This size range may be important in establishing relative levels of secondary carbonates in soils. Phosphorus values for studied features were higher than in the entire soil and arc evidence of precipitation of this element with pedogenic carbonates.

Improved Kematical X-Ray Rocking Cjrve Analyses

1990 ◽  
Vol 208 ◽  
Author(s):  
H. M. Kim ◽  
C. R. Wie
Keyword(s):  
Boundary Condition ◽  
Diffraction Theory ◽  
X Ray Diffraction ◽  
Device Structure ◽  
X Ray ◽  
Superlattice Peak ◽  
Kinematical Model ◽  
Shift Effect ◽  
Strained Quantum Well ◽  
Good Agreement

ABSTRACTA new boundary condition is used in the kinematical x-ray diffraction model analysis of rocking curves. The boundary condition is the dynamical reflection amplitude instead of the previously used dynamical intensity for the substrate. It is shown that this boundary condition properly accounts for the angular shift effect in the Bragg peak profile of very thin epitaxial layers and in the 0th-order superlattice peak. We present experimental and simulated rocking curves for various samples. The simulation was performed by using the dynamical diffraction theory, the kinematical model with the new amplitude boundary condition, and the kinematical model with the old intensity boundary condition. We also analyzed the strained resonant tunneling device structure and single strained quantum well samples by x-ray interference technique. Our x-ray interference results showed a good agreement with the nominal values for both experimental and simulated rocking curves.

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