High Resolution X-ray Diffraction from Epitaxial Gallium Nitride Films

1996 ◽  
Vol 449 ◽  
Author(s):  
T. Lafford ◽  
N. Loxley ◽  
BK Tanner
Keyword(s):  
Gallium Nitride ◽  
High Resolution ◽  
Reciprocal Lattice ◽  
Wide Distribution ◽  
Reciprocal Lattice Vector ◽  
Mosaic Structure ◽  
X Ray Diffraction ◽  
Lattice Vector ◽  
Instrument Function ◽  
X Ray

ABSTRACTThe width of double axis X-ray rocking curves of epitaxial GaN layers is shown to be critically dependent on the width of the detector aperture. We show that triple axis diffraction measurements using a crystal analyser before the detector enables the instrument function to be defined and the tilt and dilation distributions separated. All GaN samples examined showed a mosaic structure of misoriented sub-grains with little dilation within the mosaic blocks. In reciprocal space maps this was revealed as a wide distribution of intensity in a direction perpendicular to the reciprocal lattice vector.

Determination by high-resolution X-ray diffraction of shape, size and lateral separation of buried empty channels in silicon-on-nothing architectures

2007 ◽  
Vol 40 (2) ◽  
pp. 338-343 ◽  
Author(s):  
Marco Servidori
Keyword(s):  
High Resolution ◽  
Lattice Point ◽  
Reciprocal Lattice ◽  
Reciprocal Lattice Vector ◽  
X Ray Diffraction ◽  
Lattice Vector ◽  
Reciprocal Lattice Point ◽  
One Dimensional ◽  
X Ray ◽  
Planar Array

High-resolution multi-crystal X-ray diffraction was employed to characterize silicon-on-nothing samples made by a one-dimensional periodic planar array of buried empty channels. When the channels are normal to the scattering plane, under the constraint of lattice continuity from the perfect substrate to the surface, this periodic array gives rise to a well defined Fraunhofer diffraction in a scan crossing a selected reciprocal lattice point and normal to the reciprocal lattice vector (transverse or ω scan). In a longitudinal scan (ω/2θ scan crossing the reciprocal lattice point and parallel to the reciprocal lattice vector) interference fringes are observed. By analysis of the ω scan and numerical fit of the ω/2θ scan, the period of the buried empty channels and their shape, size and lateral gap were easily determined, thanks to the high-resolution optics used for the measurements.

scholarly journals Applications of dynamical theory of X-ray diffraction by perfect crystals to reciprocal space mapping

2017 ◽  
Vol 50 (5) ◽  
pp. 1256-1266 ◽  
Author(s):  
Vasily I. Punegov ◽  
Konstantin M. Pavlov ◽  
Andrey V. Karpov ◽  
Nikolai N. Faleev
Keyword(s):  
Reciprocal Lattice ◽  
Dynamical Theory ◽  
Two Dimensional ◽  
Instrumental Function ◽  
X Ray Diffraction ◽  
Reciprocal Space Mapping ◽  
Lattice Vector ◽  
Reflected Waves ◽  
X Ray ◽  
Special Case

The classical dynamical theory of X-ray diffraction is expanded to the special case of transversely restricted wavefronts of the incident and reflected waves. This approach allows one to simulate the two-dimensional coherently scattered intensity distribution centred around a particular reciprocal lattice vector in the so-called triple-crystal diffraction scheme. The effect of the diffractometer's instrumental function on X-ray diffraction data was studied.

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.

Investigation of local stress fields: Finite element modelling and High Resolution X-Ray Diffraction

2005 ◽  
Vol 875 ◽  
Author(s):  
A. Loubens ◽  
C. Rivero ◽  
Ph. Boivin ◽  
B. Charlet ◽  
R. Fortunier ◽  
...  
Keyword(s):  
Finite Element ◽  
High Resolution ◽  
Reciprocal Lattice ◽  
Stress Gradient ◽  
Local Stress ◽  
Reciprocal Space ◽  
Silicon On Insulator ◽  
Stress Fields ◽  
X Ray Diffraction ◽  
X Ray

AbstractThe influence of local stress fields on the electrical properties of Si-based nanostructures is of increasing concern. The experimental evaluation of stresses at the required scale (few nanometres) remains, however, a very challenging task. We propose a non destructive X-ray diffraction technique for local strain measurements using a laboratory radiation source. This technique provides an alternative route to micro diffraction experiments. High resolution X-ray diffraction is used to analyse the diffraction from the periodic strain field induced in silicon by a periodic array. We analyzed arrays of Si3N4 lines (thickness: 149 nm, width: 145 nm, pitch: 169 nm) on silicon, and arrays of single crystal Si lines (period: 0.6 micrometers, width: period/2, thickness: 50 nm) etched in SOI (Silicon On Insulator) and capped with SiO2 and Si3N4. Reciprocal space maps were performed around the Si substrate diffraction lines. A Bartels 4 reflections Ge 220 monochromator was used in combination with a 3 reflections Ge 220 analyser. X ray diffraction rocking curves performed on Si 004 and Si 224 reveal distinct superlattice peaks whose spacing is related to the in-plane periodicity. Reciprocal space maps reveal particular intensity distributions caused by the stress gradient in the transverse and perpendicular directions of the lines. Reciprocal space maps obtained by High Resolution X-Ray Diffraction are compared with maps calculated from displacement fields derived from finite element modeling. Very clear superlattice peaks are, however, observed around the bulk Silicon substrate reciprocal lattice nodes, which indicates a great sensitivity of this method to elastic stresses. The influence of the lines aspect ratio on the reciprocal space maps has been studied both experimentally and through modelling.

Comparative Study of 3C-GaN Grown on Semi-Insulating 3C-SiC/Si(100) Substrates

2009 ◽  
Vol 615-617 ◽  
pp. 943-946 ◽  
Author(s):  
Elena Tschumak ◽  
Katja Tonisch ◽  
Jörg Pezoldt ◽  
Donat J. As
Keyword(s):  
Residual Stress ◽  
Gallium Nitride ◽  
High Resolution ◽  
Silicon Substrates ◽  
Full Width ◽  
Half Maximum ◽  
X Ray Diffraction ◽  
Grown Layer ◽  
X Ray ◽  
Cubic Gan

Cubic gallium nitride epitaxial layers grown on differently carbonized silicon substrates were studied by high resolution X-ray diffraction. In the case of cubic GaN layers with equal layer thickness an improvement of the layer quality in terms of full width of the half maximum can be achieved by using higher carbonization temperatures. The higher crystalline quality led to an in¬crease of the residual stress in the grown layer. An increase in the thickness of the cubic Gallium Nitride allows to improve the crystallinity and to reduce the residual stress.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

Kinematical and Dynamical CBED Pattern Models: Increasing the Accuracy of the Unit-Cell Parameter Measurements Based on CBED Patterns

1990 ◽  
Vol 48 (2) ◽  
pp. 540-541
Author(s):  
I.N. Yadhikov ◽  
S.K. Maksimov
Keyword(s):  
Reciprocal Lattice ◽  
Unit Cell ◽  
Reciprocal Lattice Vector ◽  
Unit Cell Parameters ◽  
Lattice Vector ◽  
Cell Parameters ◽  
Accuracy Of Measurements ◽  
The Difference ◽  
Image Position ◽  
Convergent Beam

Convergent beam electron diffraction (CBED) is widely used as a microanalysis tool. By the relative position of HOLZ-lines (Higher Order Laue Zone) in CBED-patterns one can determine the unit cell parameters with a high accuracy up to 0.1%. For this purpose, maps of HOLZ-lines are simulated with the help of a computer so that the best matching of maps with experimental CBED-pattern should be reached. In maps, HOLZ-lines are approximated, as a rule, by straight lines. The actual HOLZ-lines, however, are different from the straights. If we decrease accelerating voltage, the difference is increased and, thus, the accuracy of the unit cell parameters determination by the method becomes lower.To improve the accuracy of measurements it is necessary to give up the HOLZ-lines substitution by the straights. According to the kinematical theory a HOLZ-line is merely a fragment of ellipse arc described by the parametric equationwith arc corresponding to change of β parameter from -90° to +90°, wherevector, h - the distance between Laue zones, g - the value of the reciprocal lattice vector, g‖ - the value of the reciprocal lattice vector projection on zero Laue zone.

Tubulin structure at intermediate resolution

1995 ◽  
Vol 53 ◽  
pp. 852-853
Author(s):  
K. H. Downing ◽  
S. G. Wolf ◽  
E. Nogales
Keyword(s):  
High Resolution ◽  
Structural Data ◽  
Therapeutic Drug ◽  
Zinc Ions ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Negative Stain ◽  
Functional Mechanisms ◽  
Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

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