Accurate determination of lattice mismatch in the epitaxial AlAs/GaAs system by high-resolution X-ray diffraction

1993 ◽  
Vol 132 (3-4) ◽  
pp. 427-434 ◽  
Author(s):  
C. Bocchi ◽  
C. Ferrari ◽  
P. Franzosi ◽  
A. Bosacchi ◽  
S. Franchi
2020 ◽  
Vol 105 (3) ◽  
pp. 353-362
Author(s):  
Katarzyna Luberda-Durnaś ◽  
Marek Szczerba ◽  
Małgorzata Lempart ◽  
Zuzanna Ciesielska ◽  
Arkadiusz Derkowski

Abstract The primary aim of this study was the accurate determination of unit-cell parameters and description of disorder in chlorites with semi-random stacking using common X-ray diffraction (XRD) data for bulk powder samples. In the case of ordered chlorite structures, comprehensive crystallographic information can be obtained based on powder XRD data. Problems arise for samples with semi-random stacking, where due to strong broadening of hkl peaks with k ≠ 3n, the determination of unit-cell parameters is demanding. In this study a complete set of information about the stacking sequences in chlorite structures was determined based on XRD pattern simulation, which included determining a fraction of layers shifted by ±1/3b, interstratification with different polytypes and 2:1 layer rotations. A carefully selected series of pure Mg-Fe tri-trioctahedral chlorites with iron content in the range from 0.1 to 3.9 atoms per half formula unit cell was used in the study. In addition, powder XRD patterns were carefully investigated for the broadening of the odd-number basal reflections to determine interstratification of 14 and 7 Å layers. These type of interstratifications were finally not found in any of the samples. This result was also confirmed by the XRD pattern simulations, assuming interstratification with R0 ordering. Based on h0l XRD reflections, all the studied chlorites were found to be the IIbb polytype with a monoclinic-shaped unit cell (β ≈ 97°). For three samples, the hkl reflections with k ≠ 3n were partially resolvable; therefore, a conventional indexing procedure was applied. Two of the chlorites were found to have a monoclinic cell (with α, γ = 90°). Nevertheless, among all the samples, the more general triclinic (pseudomonoclinic) crystal system with symmetry C1 was assumed, to calculate unit-cell parameters using Le Bail fitting. A detailed study of semi-random stacking sequences shows that simple consideration of the proportion of IIb-2 and IIb-4/6 polytypes, assuming equal content of IIb-4 and IIb-6, is not sufficient to fully model the stacking structure in chlorites. Several, more general, possible models were therefore considered. In the first approach, a parameter describing a shift into one of the ±1/3b directions (thus, the proportion of IIb-4 and IIb-6 polytypes) was refined. In the second approach, for samples with slightly distinguishable hkl reflections with k ≠ 3n, some kind of segregation of individual polytypes (IIb-2/4/6) was considered. In the third approach, a model with rotations of 2:1 layers about 0°, 120°, 240° was shown to have the lowest number of parameters to be optimized and therefore give the most reliable fits. In all of the studied samples, interstratification of different polytypes was revealed with the fraction of polytypes being different than IIbb ranging from 5 to 19%, as confirmed by fitting of h0l XRD reflections.


2003 ◽  
Vol 255 (1-2) ◽  
pp. 63-67 ◽  
Author(s):  
X.H. Zheng ◽  
H. Chen ◽  
Z.B. Yan ◽  
Y.J. Han ◽  
H.B. Yu ◽  
...  

1990 ◽  
Vol 188 ◽  
Author(s):  
Paul A. Flinn

ABSTRACTAlthough wafer curvature measurement provides a rapid and accurate determination of stress in a uniform thin film, the technique is not applicable to patterned films. To study the stress in metal lines, and the effect of passivation on that stress, it is necessary to use X-ray diffraction. To obtain the sensitivity and precision required, a generalized focusing diffractometer (GFD), that had been developed especially for work on thin films, was used in this study.The elastic strain tensors for aluminum and aluminum-silicon films and patterned lines were determined by X-ray diffraction. The corresponding stress tensors were calculated with the use of the known elastic constants of aluminum. The effect of various oxide and oxynitride passivations was investigated. Passivation over uniform metal films has very little effect, while passivation over patterned metal results in substantial triaxial tensile stress in the metal. Contrary to the conventional wisdom, high compressive stress in the passivation does not result in additional tensile stress in the metal. A possible explanation for the frequently observed deleterious effect (increased tendency for formation of cracks and voids) of highly compressive silicon nitride and silicon oxynitride passivations will be discussed.


2016 ◽  
Vol 9 (6) ◽  
pp. 061102 ◽  
Author(s):  
Yuichi Oshima ◽  
Elaheh Ahmadi ◽  
Stefan C. Badescu ◽  
Feng Wu ◽  
James S. Speck

2008 ◽  
Vol 1 ◽  
pp. 045004 ◽  
Author(s):  
Hongtao Li ◽  
Yi Luo ◽  
Lai Wang ◽  
Guangyi Xi ◽  
Yang Jiang ◽  
...  

2010 ◽  
Vol 44 (1) ◽  
pp. 184-192 ◽  
Author(s):  
Carlos Driemeier ◽  
Guilherme A. Calligaris

This work defines the crystallinity of cellulose I materials on a dry-weight basis. Theoretical and experimental developments in X-ray diffraction lead to a crystallinity determination method that is estimated to reach 1σ accuracies of better than 0.05 (crystallinity defined between 0 and 1). The method is based on Rietveld modelling, to resolve cellulose I Bragg peaks, and a standard truncated invariant integral. Corrections are derived to account for incoherent scattering, moisture content and other compositional deviations from pure cellulose. The experimental development uses X-ray diffraction in transmission fibre geometry with two-dimensional pattern Rietveld modelling, including a crystal-orientation distribution function. The crystallinities of a few commercial cellulose I materials were determined with the aim of illustrating the applicability of the method.


1993 ◽  
Vol 319 ◽  
Author(s):  
P.J. Dugdale ◽  
R.C. Pond ◽  
S.J. Barnett

AbstractThe state of deformation in epitaxial layers of InGaAs grown by MBE on GaAs substrates has been determined using high resolution X-ray diffraction. This method enables the strains and rigid body rotations which occur in the layers to be measured and these are described by means of a tensor. Layers of different thicknesses have been grown on substrates whose dislocation densities differ by three orders of magnitude in order to assess the influence of this parameter on layer relaxation through the motion of misfit dislocations to the interface. Transmission electron microscopy has also been used to provide additional information on the relaxations.


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